III

77-2394

EDWARDS, Robert Charles, 1949- SYNTHESES AND CHARACTERIZATION OF CHROMIUM COMPLEXES WITH TETRAAZA MACROCYCLIC LIGANDS.

The Ohio State U n ive rs ity , Ph.D., 1976 Chemistry, inorganic

Xerox University M icrofilms, Ann Arbor, M ichigan 48106

SYNTHESES AND CHARACTERIZATION OF CHROMIUM COMPLEXES

WITH TETRAAZA MACROCYCLIC LIGANDS

DISSERTATION

P resen ted in P a r tia l F u lfillm en t of the R equ irem ents fo r the

D egree D octor of Philosophy in the G raduate School of

The Ohio State U niversity

By

R o b ert C h arles E dw ards, B .S .

The Ohio S tate U niversity 1976

Reading C om m ittee:

P ro fe s so r D aryle H. Busch P ro fe s so r Devon W. M eek P ro fe s so r Eugene P . Schram

Approved by

AdvisedD epartm ent of C hem istry

To D ebra and M arie

& # 5J: a j: % # # #

ACKNOWLEDGEMENTS

I would like to acknowledge the help given to m e by fellow graduate s tu d en ts ,

p o s t-d o c to ra l fellow s in D r. B u sch 's group, and the s ta ff in the D epartm ent of

C hem istry . I want to esp ec ia lly thank P ro fe s so r D aryle H„ Busch fo r h is guidance

and understanding,,

iii

CURRICULUM VITAE

M arch 2, 1949 ................. . . . ................................................. .... B orn , M arion, Ohio

1971.................................................. ...................... .......................... B .S . , H eidelberg CollegeTiffin , Ohio

1971-1974........................................................................................ Teaching A ssocia te ,D ept, of C hem istry , The Ohio State U niversity , Colum bus, Ohio

1974-197 5 ................................................................................. A llied -C hem ical FellowThe Ohio State U niversity , Colum bus, Ohio

1975-1976 . ................... . .............. R esea rch A ssocia te ,D ept, of C h em istry , The Ohio State U niversity , Colum bus, Ohio

1976....................... ............................................................................P h . D . , The Ohio StateU niversity , Colum bus, Ohio

PUBLICATIONS

R o b ert C . Edw ards and D aryle H. B usch, "S yn thesis and P ro p e rtie s of Chrom ium (I), (III), and (IV) C o m p lex es" , A m erican C hem ical Society C entennial M eeting,New Y ork C ity , New Y ork, A p ril, 1976, A b s tr. INOR-153.

FIELD O F STUDY

M ajor F ield : C hem istry

Specialization—Inorganic C oordination C hem istryP ro fe s so r D aryle H. Busch, adv ise r

iv

TABLE OF CONTENTS

Page.

A cknow ledgem ents........................................... ................. . . . . . . . . . . ..... .......... iii

C u rricu lu m V itae . ........................ . . . . . . . . . . . . . . . . . . . . . .iv

L is t of T a b le s .............................................................................................................................. vii

L is t of F ig u re s ......................................................................................................................... x

In tro d u c tio n , ........................ 1

E x p e rim e n ta l. ............... .19

P h y sica l ^ M e a s u r e m e n t s . . . . . . c o . o . . . . . . . . . . . . . . 0 . 00 . 0 . . 0 . 0 0 . . . . . . . . 19S yn theses.............................................................................................................................. 21

R esu lts and D isc u ss io n . ........... 37

P re p a ra tio n of [Cr(Me2[ l4 ]te traenatoN 4)(py)2]P F G, [Cr(Me2[i5 ]- te traenatoN 4) (py)2]P F G> [Cr(Me2[ l6 ]te traenatoN 4)(py)2]P F G, and[Cr(M e4[l4 ]tetraenatoN 4)(py)2]PF6o ........................ 37P re p a ra tio n of [Cr(Me2[Z]tetraenatoN 4)(L)2]P F 6 (Z = 14, 15, o r 16) and [Cr(M e4[l4 ]te traenatoN 4)(L)2]P F G (L = dim ethylform am ide,1-m ethylim idazole, th iocyanate, or cyanide). ................................40C h arac te riza tio n of [Cr(Me2[Z]tetraenatoN 4)(L)2jP F G (Z = 14, 15, o r 16) and [Cr(M e4[l4 ]te traenatoN 4)(L)2]PFG (L = pyrid ine , dim ethylform a­m ide, and 1-m ethylim idazole) ....................................................... 43C h arac te riza tio n of Cr(M e2[Z]tetraenatoN 4)(NCS)(py), Cr(M e4[l4 ]- te traenatoN 4)(NCS)(py), and Cr(M e2[Z]tetraenatoN 4)CN (Z = 14, 15,o r 1 6 ) .............. 57O xidation and O ther R eactions of the Chromium!HI) C om plexes............... .63P re p a ra tio n of Cr(M e2[Z]tetraenatoN 4)(CGH5)(py) (Z = 14, 15, or 16)and Cr(M e2[14]tetraenatoN 4) (L)(py) (L = Me or n-Bu) 67C h arac te riza tio n of Cr(M e2[Z]tetraenatoN 4)(C6H5)(py) (Z = 14, 15,o r 16) and Cr(M e2[l4 ]te traenatoN 4)(L)(py) (L = CH3 o r n -B u)......................... 68E lec tro n ic Spectra of the Chromium!HI) C om plexes........ .................... .75E le c tro c h e m is try of the Chromium(III) C o m p lex es . ............. 86ESR S pectra of the Chromium(IU) C o m p lex es . ............. 91P re p a ra tio n of [Cr(Me2[l4 ]tetraenatoN 4) (CGH5)]X (X = I o r SCN)...................100

v

TABLE OF CONTENTS

Page

C h arac te riza tio n of [Cr(Me2[i4 ]tetraenatoN 4)(C6H5)]X (X = I andSCN) ............................................... io iP re p a ra tio n of Cr(M e2[l4 ]tetraenatoN 4)(NO) and [Cr(Me6[i4 ]-4, il-d ie n e N 4)(NO)(N02)]P F G.................... . . . . . . . . . . . ................ 112C h arac te riza tio n of Cr(M e2[i4 ]tetraenatoN 4)(NO) and[Cr(Mee[i4j4 , ll-d ie n e N 4)(N 0)(N 02)]P F s.................... 113Syntheses and C h arac te riza tio n of Chromium(Il) and (III)Com plexes with MeG[l4]4, ll-d ie n e N 4„ ....................... „ ...............123P rep a ra tio n of the Chrom ium (II) and Chromium(III) C om plexes0 ...........123C h arac te riza tio n of the Chromium(H) and Chromium(IU)C omplexe s . ........................................................................................................................124

AppendlXo . . . . . . . . . . • o . . . o a o . . . . « o o o . . . « o * . . . . . . . a . . a o o . o . . e . . . . . . . . . 133

BeferenCeSo 138

vi

LIST O F TABLES

Page

Table 1. A nalytical D ata fo r the C om plexes, [Cr(Me [Z jte traen a to N ^-(L)2]P F 6 ................................................................................* . . . . . . ...................... 44

Table 2 . Selected In fra red A bsorptions of the C om plexes,[Cr(Me [Z jtetraenatoN ^lL ^ ]P F G . . . . . . : ............................... 48

Table 3. P hysical P ro p e r tie s of the C om plexes, [Cr(Me [Z Jte traenato-N4)(L)2]P F 6. . ............................................. * 49

Table 4. T em p era tu re Dependence of the M agnetic Susceptib ility of[Cr(M e2{44]tetraenatoN4)(py)2]PF6o 51

Table 5. T em p era tu re Dependence of the M agnetic Susceptib ility of[C r (Me2115] te t r aenatoN4) (py) 2] P F 6 ...............................................................................52

Table 6 . T em p era tu re Dependence of the M agnetic Susceptib ility of[Cr(M e2[ l6 ]te traenatoN 4)(py)2]PFG...............................................................................53

Table 7. T em p era tu re Dependence of the M agnetic Susceptib ility of[Cr(M e4[l4 ]te traenatoN 4)(py)2]PFg ........... 54

Table 8 . M agnetic M om ents and W eiss C onstants C alculated fro m the V ariab le T em p era tu re M agnetic Susceptib ility Data of the B is- physica l C om plexes...................... 56

Table 9. A nalytical D ata fo r the C om plexes, Cr(M e [Z jte traenatoN ^-(A)(B). .......................................... ? .......................................... 58

Table 10. Selected In frared A bsorption Bands of the C om plexes,Cr(M e [Z ]tetraenatoN 4)(A )(B ). .................... 61

x

Table 11. P hysical P ro p e r tie s of the C om plexes, Cr(M e [Z jte traen ato -N4)(A)(B)........................................................................................X. .....................................62

Table 12. A nalytical Data fo r the Com plexes with A ryl and Alkyl L ig a n d s .. . 69

vii

Page

Table 13. Selected In fra red A bsorptions fo r the Com plexes with A ryland Alkyl L igands................................................................. ..................................... 72

Table 14. P hysical P ro p e rtie s of the Com plexes with Alkyl and A rylL ig a n d s ............................ 74

Table 15. C om parison of C alculated and O bserved S pectral BandP o sitio n s of Chrom ium (HI)—Ethylene diam ine Com plexes. „ . . . . . . . . . . . . . 7 8

Table 16. E lec tro n ic S pectra l D ata fo r Chromium(HI) Complexes with;the L igands Me6[i4]aneN 4 and Me6[i4]4, ll-d ien eN 4 .................79

Table 17. E lec tro n ic S pectra l D ata fo r the C om plexes, [Cr(Me [Z]-te traenatoN 4)(L)2]PF 6........................................................................... X.........................80

Table 18. E lec tro n ic S pectra l D ata fo r the Com plexes, Cr(Me [Z]-te traenatoN ^ (A) (B).................................................... .X. ..........................81

Table 19. E lec tro n ic S pectra l D ata fo r the C om plexes, Cr(M e2[Z]-te traenatoN 4) (R) (py). ........................................ 82

Table 20. E lec tro ch em ica l D ata fo r the C om plexes, [Cr(Me [Z]-te traenatoN 4) (L)2]P F e............... 87

Table 21. E lec tro ch em ica l D ata fo r the C om plexes, Cr(M ex [Z]-te traenatoN ^ (A) (B) ...................................................................................88

Table 22. E lec tro ch em ica l D ata for the Com plexes, Cr(M e2[Z]-te traenatoN 4) (R) (py) ........... 89

Table 23. P hysica l P ro p e rtie s of the Chromium(IV) C o m p lex es . .................108

Table 24. E lec tro n ic S pectra l D ata fo r the Chromium(IV) C o m p lex es ...........108

Table 25. A nalytical D ata for the C hrom ium (I) N itrosyl C om plexes................116

Table 26. P h y sica l P ro p e rtie s of the Chromium(l) N itrosyl C o m p le x e s .. . . 116

Table 27. E lec tro n ic S pectra l D ata fo r the Chromium(I) N itrosy lC o m p lex es ............................. 116

v iii

Page

Table 28. A nalytical Data fo r the Chromium(II) Com plexes withMe6[l4]4 , ll-d ie n e N 4 . ..................................................................................................... 125

Table 29. P hysica l P ro p e r tie s of the Com plexes with Me6[l4]4, ii-d ie n e N 4. . 126

Table 30. E lec tro ch em ical D ata fo r the Cliromium(Il) C om plexes.........................127

Table 31. E lec tro n ic S p ectra l D ata fo r the Chromium(II) Com plexes withMe6[l4]4 , il-d ie n e N 4 ....................... ...............................................................................128

Table 32. P hysica l P ro p e r tie s of the C om plexes, [Cr(Me6[l4]4, 11-diene-N ^X glPFg. ........................................ 130

Table 33. A nalytical D ata fo r the C om plexes, [Cr(Me6[l4 ]4 ,1 1 -d ien eN ^ -X2]P F g. ............................................ .................. ................. .. 131

Table 34. E lec tro n ic S p ec tra l D ata fo r the Com plexes, [Cr(Mee[ l4 ]4 ,11-dieneN4)X ]PF6................................................................................................ ................... 132

ix

LIST OF FIGURES

Page

F igure 1. In fra red S pectrum of [Cr(M e2[ i4 ]te traenatoN 4)(py)2]P F G.................. 45

F igu re 2 . In fra red S pectrum of [Cr(M e2[l4 ]te traenatoN 4)(dmf)2]P F G. .............. 46

F igu re 3. In fra red S pectrum of [Gr(Me4[l4 ]te traenatoN 4)(M e-Im )2]P F 6. ........... 47

F ig u re 4 . V ariation of 1/ xm with T em p era tu re fo r:#» - [C r (Me4 [ 14 JtetraenatoN 4) (py) 2 ]PFG;& - [C r(M e2 [ 14 JtetraenatoN 4) (py) 2 ]PFg;® -[C r(M e2[l5 ]te traenatoN 4)(py)2]P F 6; and^ -[C r(M e2[ l6 ]te traenatoN 4)(py)2]P F e. ...................................... . . .................. . .. 55

F igu re 5. In fra re d S pectrum of Cr(M e2f l6 ]tetraenatoN 4)(NCS)(py)..................... 59

F igure 6 . In fra red S pectrum of Cr(M e2[ l 5 ]tetraenatoN 4) C N . ......... 60

F igu re 7. In fra red S pectrum of Cr(M e2[l4 ]te traenatoN 4)(C6H5)(py).................... 70

F igu re 8 . In fra red S pectrum of Cr(M e2[l4 ]te traenatoN 4) (CH3) (py). . . . . . . . . . . 7 1

F igu re 9. T e rm Splitting D iagram fo r a d3 M etal Ion in andS y m m etrie s .......................................................................................................................... 76

F igure 10. E lec tro n ic S pectra o f : -----[Cr(Me2[ l4 ]tetraenatoN 4)(M e-Im )2J-P F e; • ° • [Cr(M e4[l4 ]te traenatoN 4)(M e-Im )2]P F s ; -• [Cr(Me2[l5 ]te t- raenatoN 4)(M e-Im )2]P F 6; [Cr(M e2[l6]te traenatoN 4)(M e-Im )]PF6. . . . . 8 3

F igu re 11. E lec tro n ic S pectra o f : -----[Cr(Me2[i5 ]te traenatoN 4)(py)2]PFG; [Cr(Me2[ l 5 ]te traenatoN 4) (dmf)2]P F 6; • * 0 tCr(M e2[l5 ]te traenatoN 4) -(M e-Im )2]P F G; Cr(M e2[l5 ]te traenatoN 4)(NCS)(py); and-• -• Cr(M e2[l5 ]te traenatoN 4)CN............................................................................ 85

F igure 12. Energy L evels of a d3 Ion in T etragonal Sym m etry ............................. 92

F igu re 13. ESR S pectra of: A, [Cr(Me4[l4 ]te traenatoN 4)(py)2]PFG;B, [Cr(M e2[ l6 ]te traenatoN 4)(py)2]P F G; C, [Cr(Me2[ l4 ]te traen a to - N4)(py)2]PFg; D, [Cr(Me2[l5 ]te traenatoN 4)(py)2]PFG........................................... 95

Page

F igu re 14. ESR S pectra of:A , [Cr(Me2[i5]tetraenatoN,j) (M e-Im)2]PFG;B, [Cr(Me2[ i4 ]tetraenatoN 4)(M e-Im )2]P F 6;C , [C r (Me4 [l4 ]tetraenatoN 4) (Me -Ini) 2 ] P F 6;D, [Cr(M e2[ l6 ]tetraenatoN 4)(M e-Im )2]P F 6 .............. . ............ 96

F ig u re 15. ESR S pectra of :A , [Cr(M e2[ i 6 ]te traenatoN 4) (dmf)2]PFG;B , [Cr(M e2 [i4 ]tetraenatoN it) (dmf)2]P F G;C , [Cr(M e2 [i5 ]tetraenatoN 4) (dmf)2]P F G;D, [Cr(M e4[14]tetraenatoN 4)(dmf)2]P F G ................. 97

F igu re 16. ESR S pectra of:A , Cr(M e4[ i4 ]tetraenatoN 4) (NCS)(py);B, Cr(M e2[ i6 ]tetraenatoN 4) (NCS) (py);C, Cr(M e2[i4]tetraenatoN 4)(NCS)(py) ;D, Cr(M e2[i5]tetraenatoN 4)(NCS)(py);....................................................... 98

F igu re 17. ESR S pectra of:A, Cr(M e2[l4 ]tetraenatoN 4)CN;B, Cr(M e2[l5 ]tetraenatoN 4)CN;C, Cr(M e2[ l6 ]tetraenatoN 4)C N ..................... 99

F ig u re 18. In fra red Spectrum of [Cr(Me2[l4]tetraenatoN 4)(CGH5) ] I . . . . . . . . . 102

F ig u re 19. In frared Spectrum of [Cr(Me2[i4 jte traenatoN 4)(CGH5)]SCN 104

F ig u re 20 . E lec tron ic Spectrum of [Cr(Me2[l4 ]tetraenatoN 4)(CGH5)]I: Mull; CH3N02 S o l 'n . ........ 106

F igure 21. E lec tro n ic Spectrum of [Cr(Me2[l4 jte traenatoN 4)(CGH5)]SCN: Mull; CH2N 02 S o l'n ............... 107

F igu re 22. ESR Spectrum of (Cr(M e2[l4]tetraenatoN 4)(CGH5)]I. .............. 110

F ig u re 23. In frared Spectrum of Cr(M e2[ l4 jte traenatoN 4)NO...............................114

F ig u re 24. In fra red Spectrum of [Cr(MeG[l4]4, ll-d ien eN ^ (NO)(N02)]P F G. . 115

F ig u re 25. ESR Spectrum of C r(M e2[l4]tetraenatoN 4)NO„. . . . . . . . . . . . . . . . . 117

xi

Page

F igure 26. ESR Spectrum of [Cr(M eG[i4]4 , li-d ie n e N 4)(NO)(N02)JP F 6................118

F igure 27. Schem atic M olecular O rb ita l D iagram fo r the Chromium(l)N itrosy l C om plexes................................................................................... . ...................<.120

F igu re 28. O rtep Drawing of [Cr(MeG[i4]4, ii-d ie n e N 4)(N0 )(N0 2)]P F 6.............. 121

F igure 29. X -ray C rysta llograph ic Bond D istances fo r [Cr(MeG[ l4 ]4 ,11-dieneN4) (NO) (NOz) ] P F G ................................ . ................................. . 122

F igu re 30. D iagram of the D ry T ra in .............................................................................. 135

F igure 31. D iagram of the F u rn ac e ...................................... . ........................... . . . . . . 136

F igu re 32. W iring D iagram fo r the Sw itches„..................... 137

x ii

INTRODUCTION

D uring the la s t ten to fifteen y e a rs th e re has been a g re a t deal of in te re s t

in the syn thesis and study of m eta l com plexes containing m acrocyclic ligands . 1-4

These m etal com plexes a re re la te d s tru c tu ra lly to im portan t n a tu ra l p roducts,

such as heme p ro te in s , ch lorophyll, and v itam in B 12. Many of these m acrocyclic

ligand coinplexes exhibit unusual p ro p e rtie s ( e . g . , they can contain m etal ions in

unusual oxidation sta tes) due to the s te r ic and e lec tro n ic c o n stra in ts im posed on

the m eta l ion by the ligand. In addition to the b iochem ical im plications these

re su lts have led to a g re a te r understanding of the ch em istry of m eta l ions in

g en era l and a re of fundam ental significance to the understanding of m etal ion

c a ta ly s is .

Although some m acrocyclic ligands have been re p o rte d with e th e r5’G or

th ioe ther d o n o rs , 7-9 the v as t m a jo rity of th ese com plexes have ligands with

only n itrogen donor a to m s. T hese te tra a z a m acro cy cles have proven to be

very v e rsa tile a s they can be co n s tru c ted to in co rpo ra te a wide v a rie ty of

fe a tu re s , such a s vary ing rin g s ize , degree of unsaturation , type and num ber of

substituen ts, and ch arg e . M ost of the te tra a z a m acrocyclic ligands produced

have 14-m em bered rin g s because in som e c a se s ligands with ring s ize s of 13,

15, and 16 m em bers a re m ore d ifficu lt to syn thesize and com m only the 14-m em ­

b e red cyclic ligands a re the m ost effective a t coordination. D espite the long

known n a tu ra l anionic ligands ( e . g . , the porphyrin and c o rr in ligands) re la tiv e ly

few synthetic m acrocyclic ligands b earin g negative ch arg es have been rep o rted

until recen tly .

The bulk of the e a r ly s tu d ies 'o n m etal com plexes having te tra a z a m acrocyclic

ligands w ere done with the m eta l ions of iro n , cobalt, and n ickel. Since the

p rep a ra tio n and study of n ickel com plexes is not p a r tic u la rly difficult and iron

and cobalt com plexes with m acro cy c les a re d irec tly re la te d to b iological sy stem s1

2

the use of th ese m etal ions fo r e a r ly study w as e n tire ly log ical. A s a d ire c t

r e s u l t of the r ic h ch em istry d isp layed by these iro n , cobalt, and n ickel com plexes,

these stud ies have been expanded to include many o ther tran sitio n m etal ions in

re c e n t y e a rs .

To fu rth e r extend the ch em istry of m eta l com plexes with m acrocyclic ligands,

i t is app ropria te to syn thesize and c h a ra c te r iz e a s e r ie s of m acrocyclic com p­

lex es having m acrocycles w ith d ifferen t ring s ize s and negative ch arg es and

having a m eta l ion whose m acrocyclic com plexes a re unknown o r have rece iv ed

li t t le p rev ious atten tion . This th esis is concerned with the syn thesis and study

of a num ber of chrom ium com plexes with te tra a z a m acrocyclic ligands. It

a ttem p ts to add to the p rev ious w ork done by S p era ti10 with chromium(H) mid

(III) com plexes containing the ligands of s tru c tu re s I and II. The m ajo r po rtion

of th is th esis is devoted to the p rep a ra tio n and p ro p e rtie s of a new group of

chrom ium com plexes.w ith the ligands shown in s tru c tu re s JH-VI.

I II

III IV

3

Investigations of m eta l com plexes with these m acrocycles and o ther s tru c tu ra lly

s im ila r sp ec ies have dem onstra ted that in a basic environm ent the m acro cy cles

lose two rin g pro tons becom ing dianionic in natu re upon coord ination to m etal ions.

With m etal ions in the d ipositive oxidation sta te these ligands fo rm n eu tra l p lanar

com plexes as shown in s tru c tu re s VII-X . 11-18 M ost of these com plexes p o sse ss

MIT Y

i

M il Y

V II V III

4

MU

Ph

i — i

IX X

x = "(c h 2)2- =y

X= -(C H 2)r , Y= -(C H 2)3=

X= - (c h 2)3- =Y

re la tiv e ly facile oxidation po ten tia ls which allow them to undergo ligand oxidative

dehydrogenation reac tio n s o r m eta l ion oxidation . 15 >1G ,l8 ,19

Since tlie axial s ite s of the chromium(II]) com plexes w ith ligands III-VI

p roved to be lab ile to ligand substitu tion re a c tio n s , a num ber of deriva tives w ere

produced and ch a ra c te r ise d having n eu tra l o r anionic ax ial ligands. T herm ally

stab le a ry l and alkyl d eriv a tiv es w ere a lso syn thesized v ia ax ia l ligand substitu tion

and ch a rac te r iz e d . E lec tro ch em ica l investigations of these d eriv a tiv es led d irec tly

to the production and c h a ra c te r iz a tio n of the f i r s t chromium(IV) com plexes having

a chelating ligand. In addition, the reac tio n of sodium n itr i te w ith one of the

chrom ium (ffl) d eriv a tiv es afforded a chrom ium (I), n itro sy l com plex.

In g en era l, the coordination ch em istry of chrom ium is dom inated by the d i-

and trip o sitiv e oxidation s ta te s , although num erous compounds a re known having

the oxidation s ta te s of 0 through VI. A la rg e var iety of ligands fo rm com plexes

5

with chromium(U) and (III) bu t since the am ine com plexes a re c lose ly re la te d to

those with te tra a z a m acrocyclic ligands, they a re of specia l in te re s t. In co m p ari­

son to m any of the tra n s itio n m etal ions the p rep a ra tio n of chromium(D) and (III)

am ine com plexes is not t r iv ia l . 20 Chromium(H) is ea s ily oxidized by m olecu lar

oxygen; th e re fo re , com plexes having chrom ium in th is oxidation s ta te m ust be

p re p a re d in an oxygen-free environm ent. Chromium(III) is v e ry a ir -s ta b le but

its in e r tn e ss tow ard ligand substitu tion reac tio n s is a genuine handicap. Also

chrom ium ions in both oxidation s ta te s a re known to read ily fo rm chromium(HI)

hydroxo- o r oxo-bridged sp ec ies in b as ic aqueous so lu tion . 20

In sp ite of these d ifficu lties, many am ine com plexes of chromium(II) and (HI)

have been p re p a re d . Using hydrated chromium(D) s a lts , alcoholic so lven ts, and

an in e r t a tm o sp h ere , chromium(H) com plexes with the ligands p y rid in e , 21

a c e to n itr ile , 22 ethylene d iam ine , 23 diethylene tr ia m in e , 24 2 , 2 '-b ip y r id y l , 25 and

i , iO -phenanthroline25 have been p rep a re d . A ll of these com plexes a re a i r - s e n s i ­

tive and, in m ost c a s e s , they have sp ec tra l and m agnetic p ro p e rtie s which a re

c h a ra c te r is t ic of h igh-sp in chrom ium (D ). The m agnetic m om ents of the com plexes

C r dienX2 w here X is Cl~, B r , o r I- a re 4 .2 8 -4 .3 8 B .M . which a re w ell below

the sp in-only value a t room tem p era tu re of 4 .9 0 B .M . These low m agnetic

m om ents a re believed to r e s u lt from the halide bridged , b inuclear s tru c tu re

shown in s tru c tu re XI in which th e re is in te rac tio n betw een the chrom ium io n s . 24

C l

C r

C lC t

X I

6

The t r is -2 ,2 '-b ip y r id y l and t r i s - 1 , iO -phenanthroline diacido com plexes a re assum ed

to be low -sp in a s they have m agnetic m om ents of 2„77-3 .24 B .M . indicating two

im paired e le c tro n s . 25

A wide v a rie ty of am ine com plexes with chromium(IH) have been p re p a re d . 20

They include com plexes having m onoam ines, d iam ines, tr ia m in es , and te tra m in es

in various num bers and com binations. Several m ethods w ere used to p re p a re

these am ine com plexes, such a s the reac tio n of anhydrous chrom ium (ni) sa lts with

anhydrous am ines, the reac tio n of CrX3Cl3 (X = py, dmf, dm so, thf) with am ines,

the re ac tio n of diperoxochrom ium (IV) am ines with ac ids, and the oxidation of the

co rresponding chromium(U) com plexes . 20 The physical and chem ical p ro p e rtie s of

the chrom ium (III) am ine com plexes a re not unusual. They a re stable and unreactive

and have effective m agnetic m om ents of 3. 5 -4 .1 B .M . which ag ree g en era lly with

the spin-only value for th ree unpaired e lec tro n s of 3 .8 7 B .M . 20

The f i r s t rep o rted chrom ium com plexes containing m acrocyclic ligands w ere

those fo rm ed with d e riv a tiv es of the porphine r in g (s tru c tu re XII) and with

phthalocyanine (s tru c tu re XIII). The reac tio n of chromium(III) ace ta te with

p h thalon itrile a t 270° C afforded the sublim able p roduct phthalocyanine-chrom ium -

(IB) hydroxide. Using th is com plex a s a s ta rtin g m a te r ia l, a num ber of o c tahed ra l

X II X III

7

chromium(ID) deriva tives w ere p rep a red along with fo u r- and s ix -coo rd ina te

chromium(IJ) com plexes. The chromium(IU) com plexes had typical m agnetic

m om ents of 3 .6 9 -4 .0 6 B .M . The m agnetic m om ents fo r the chromium(U)

com plexes w ere considerab ly low er than the spin-only value for h igh-sp in

chromium(D) indicating th a t m e ta l-m e ta l in te rac tio n may occur in the p lan ar

com plex and that e lec tro n p a irin g takes p lace in the six -coo rd ina te com plex,

re su ltin g in two unpaired e le c tro n s . 26

Several chrom ium com plexes with p o rphyrin s have been p re p a red and

ch a ra c te r iz e d . 27-32 The p rep a ra tio n of these chrom ium p o rp h y rin s involves

reac tio n s of Cr(CO ) 6 o r C rC l2 with the porphyrin ligand in high boiling so lvents,

such as decalin , n -decane, o r d im ethylform am ide. Depending on the reac tio n

conditions, e ith e r chrom ium (II) o r chromium(IIT) d eriva tives can be obtained.

T su tsu i and cow orkers p rep a re d m eso -porphyrin -IX -d im ethy lesterchrom ium (Il)

which is rep o rted to be square p lan ar in die so lid -s ta te . This compound has a

so lid -s ta te m agnetic m om ent of 2 .84 B. M. and a solution m om ent of 5.19 B .M .

The so lid -s ta te m agnetic m om ent indicates in te rac tio n betw een m etal c e n te rs

re su ltin g in e le c tro n p a irin g but th is in te rac tio n is destroyed when the com plex

is in solution and a m agnetic m om ent co n sis ten t with h igh-sp in chrom ium ! II)

r e s u l ts .

F le isc h e r and cow orkers29-31 p rep a red se v e ra l chromium(III) porphyrin

com plexes and studied the ax ial substitu tion reac tio n s of chromium(III) te t r a -

(p-sulfonatophenyl)porphine in d e ta il. The m agnetic m om ent of 3 .87 B .M . for

th is com plex ag rees with the assigned oxidation s ta te . R ates fo r the rep lacem en t

of axial w ater m olecules by CN , F , and py w ere found to be 103-104 f a s te r than

ra te s p rev iously determ ined fo r o th er chromium(HI) com plexes. T here is

assum ed to be extensive e lec tro n delocalization in th is com plex which re su lts

from the rr-bonding between the ligand t t * o rb ita ls and the m etal dyz and dxz

o rb ita ls . By th is m echanism e lec tro n density is tra n s fe rre d from the e lec tro n

r ic h dianionic porphyrin to the chrom ium ion, thereby malting the com plex

lab ile tow ard substitu tion.

Furhop and cow orkers32 have studied the e le c tro c h e m is try of octaethy lpor-

phinatochrom ium (IH ) hydroxide in b u ty ro n itrile using a SCE re fe ren ce e lec tro d e .

The oxidations that occur a t 1.22 volts and 0 .99 volts have been assigned to ligand

oxidations and the cathodic p ro c e ss a t -1 .3 5 volts has been assigned to a ligand

reduction . Although oxidations of chromium(HI) a re very r a re ly observed e le c tro -

chem ically , an oxidation talcing place a t 0 .79 volts was assigned to the chrom ium (Itt)-

chromium(IV) couple. The cathodic p ro c e ss observed a t -1 .1 4 vo lts was desig ­

nated a s the chrom ium (III) to chromium(D) reduction .

S p era ti syn thesized both chromium(U) and chrom ium (III) com plexes with the

ligands Me6[l4]aneN 4 (s tru c tu re H) and Me6[14]4,11-dieneN ,^10̂ (s tru c tu re 1), while

Tobe and F erguson 33 p re p a red only chromium(ILO com plexes with cyclam ([l4 ]ane-

N4, s tru c tu re XIV). W orking in a dry box with an in e r t a tm osphere , the chromium(IJ)

com plexes with Me6 [l4]aneN 4 and Me6[l4]4, ll-d ie n e N 4 w ere p rep a red by the

XIV

reac tio n of the ace to n itr ile adducts of the chromium(D) halides with the ligands

in ethanol so lu tions. The reac tio n with the sa tu ra ted ligand produced only

t r a n s - dihalide com plexes while the diene ligand fo rm ed five-coord inate com plexes

having only one axial halide. O ther chrom ium (II) d eriv a tiv es w ere p rep a red by

m e ta th esis of die halide com plexes.

Although these chrom ium (II) com plexes a re a ir -s e n s itiv e in both solution

and the so lid -s ta te , solid sam ples of the com plexes containing the diene ligand

9

can be exposed to a ir fo r a sh o rt tim e w ithout noticeable oxidation. The so lid -

s ta te m agnetic m om ents fo r these com plexes indicate that the chromium(II) is

h igh-sp in in n a tu re , as the m om ents deviate only slightly fro m the spin-only

value of 4 .90 B. M. The conductivity data support the six coordination of the

sa tu ra te d com plexes and the five coordination of the diene com plexes. Five

coordination is r a r e fo r chrom ium (II) com plexes as the only o ther rep o rted

exam ples a re com plexes containing the tripod ligands tr is (2 -d im ethylam inoethyl)-

am ine , 34 t r i s ( 2 -diphenylphosphinoethyl)am ine, and b is(2 -diethylam inoethyl)-

(2-diphenylphosphinoethyl)am ine . 35 The e lec tro n ic sp ec tra of these m acrocyclic

com plexes have been assigned using the c ry s ta l fie ld model fo r te tragonal high-

spin d4 sy stem s.

A num ber of chromium(Hl) com plexes w ere a lso p rep a re d with these two

m acrocyclic ligands. W orking on the benchtop, halogens w ere used to oxidize

the app rop ria te chromium(H) com plex. M etathesis was then used to p re p a re

o ther d eriv a tiv es that did not contain halide ligands. All of these chrom ium (lll)

com plexes w ere found to be quite s tab le , being high-sp in , s ix -coo rd ina te species

with te tragonal s tru c tu re s . M agnetic suscep tib ility m easu rem en ts confirm ed the

tr ip o s itiv e oxidation s ta te fo r these com plexes. The e lec tron ic sp ec tra w ere

a ssig n ed fo r these com plexes on the b as is of the c ry s ta l f ie ld m odel fo r te tragonal

d3 sy s tem s.

Since the p rep ara tio n of the f i r s t pu re cr-bonded organochrom ium compound,

[CeH5C H 2C r ( H 20 ) 5]2+, by Anet and Leblanc in 1 9 5 7 ,36 a num ber of com plexes

which have alkyl or a ry l groups covalently bonded to chromium!ID or (III) have

been p re p a re d and c h a ra c te r iz e d . 37’ 38 However, no organochrom ium com plex

has p rev iously been p re p a re d containing a m acrocyclic ligand.

The in te rac tio n of c e r ta in organom etallic compounds and chrom ium (n) or

chromium(HD halides in e th e re a l so lvents lead s to the corresponding solvated

cr-bonded organochrom ium (in) and (H) compounds provided p a r tic u la r attention

is paid to solvent, tem p e ra tu re , and s to ich iom etry of the reac tio n . By varying

reac tio n conditions, i t is possib le to produce organochrom ium compounds having

10

from one to th re e alkyl o r a ry l groups and varying am ounts and types of solvation.

The m ost convenient and perhaps c lean es t rou te to cr-bonded organochrom ium

compounds is by the action of organom agnesium halides on chrom ium halides in

te trah y d ro fu ran o r diethyl e th e r (equations 1-5).

t h fRMgX + C rC l3(THF)3 - R C rC l2(THF)3 (1)

R = m ethy l , 39 p - to ly l , 40 benzy l , 39 and o th ers

THF2 RMgX + C rC l3(THF) 3 R2CrCl(THF) (2)

R = benzyl , 40 e th y l , 38 m ethyl3,8 p ropy l , 38 and o thers

THF3RMgX + C rC l3(THF)3 - R3Cr(TH F )3 (3)

R = phenyl, 41 benzy l , 40 a - and ^-naphthyl, 42 m ethyl43 and o th ers

THFRM gBr + C rC l2 =* RCrBr(TH F) (4)

IT - 1-naphthyl, 44 l-(2-m ethylnaphthyl) , 44 and o th e rs

RM gBr + C rC l2 E t 2 ° R2Cr(TH F ) 3 o r [R2C r ]2 (5)

R = m esity l , 44 o-m ethoxyphenyl, 45 phenyl, 48 and o th ers

The te trah y d ro fu ran of solvation in these com plexes m ay be d isplaced by

pyi-idine, 2 ,2 '-b ip y r id y l, o r 1 ,10-phenanthroline. These n itrogen donor ligands

a re known to stab ilize ca rb o n -m eta l cr-bonds38 and th is has p e rm itted the iso lation

of o therw ise unstable organochrom ium species (equations 6 and 7).

CGH5CH2C rC l2(THF) c 6H5CIi2C rC l2(py)3 (6)

CgH5M gBr + C rB r2(THF) 2 TH E /blPy (c 6H5)2Cr(bipy ) 2 (7)

i i

The reac tio n betw een t r ia r y l - o r tria lky la lum inum compounds and chrom ium -

(III) ch loride in te trah y d ro fu ran re su lts in only one organ ic group being introduced37

(equation 8).

R = phenyl, 37 m ethy l , 47 e thy l , 47 p ro p y l , 47 and o th e rs

R eactions of organolith ium and organosodium compounds w ith chromium(II)

and chromium(III) sa lts can lead to the fo rm ation of lith ium o r sodium poly(organo)-

chrom ate com plexes of the type M3Cr(III)Rg, M2Cr(III)R5, MCr(IH)R4, and M Cr(II)-

R3 (M = Li o r Na). However, the specific p roducts fo rm ed in these reac tio n s

depend c r itic a lly upon the n a tu re of the o rgan ic group in the o rganom etallic reagen t,

the s to ich iom etry of the re a g e n ts , the ligands asso c ia ted with the final product, and

the so lvent em ployed fo r the reac tio n (equations 9-12).

RgAl + C rC l3(THF)3THF R C rC l2(THF)3 (8)

6 LiR + C rC l3 E- ^ ° Li3 [CrReHEtjjO]

R = p h en y l , 38 p - to ly l , 38 m ethy l , 38 and o th ers

(9)

5NaCgH5 + CrCl; Ei 2 0 Na2[Cr(C6H5)5][E t20]3(48) ( 10)

4Li(2-CH 3OC6H4) + C rC l3 E^ ° L i[C r(2 -CH30 C6H4)4][Et2 0 ]3(38̂ (11)

8 CH3Li + 2C rC l2 E-^ ° [Li2Cr(CH3)4]2[Et2 0 ]nTHF

Li4 [(CII3)4C r - Cr(CH3)4][THF]4(49) (12)

In some ca se s organolith ium reag en ts give n e u t r a l com plexes (equation 13).49

’ ( g j C t f C I * , ) , - CrCl3(THF)3 E3 ° d3)

12

Another in te re s tin g ro u te to organochrom ium species is based on the reac tio n

of chromium(I]) s a lts with c e r ta in o rgan ic halides36’ 50 (equation 14).

2C r2+ + RC1 H4 ° [RCr(H20 )5]2+ (14)

R = CgH5CH2, 2-CH3C6H,tCH2, and o th ers

A m odification of th is m ethod (equation 15) has been used to p rep a re the c ry s ta l­

line m onoorganochrom ium com pounds R C rC l2(py)3̂ 51̂ (R = benzyl, o -c h lo ro -

benzyl, and p -ch lo ro b en zy l).

CgH5CH2C1 + 2C rC l2(py) 2 C6H5CH2C rC l2(py)3 (15)

O rganochrom ium compounds d iffer m arked ly in th e ir s ta b ilitie s . The w ater

soluble spec ies [RCr(H20 )5]2+ a re sensitive to oxygen and have not been iso la ted

as so lid s . The m ajo rity of the iso la tab le organochrom ium compounds a re se n s i­

tive to both oxygen and p ro tic so lvents although th e re a re som e ( e . g . , [(C6H5)2-

Cr(bipy)2)+] th a t a re stab le in a ir and w a te r . 38 T he ir th erm al s ta b ilitie s a lso

vary depending upon the type and num ber of organo groups p re se n t. B roadly

speaking, the com plexes having a ry l groups ( e . g . , (CGH5)3Cr(TH F )3 and 4-CH3-

CGH4C rC l2(THF)3) a re m ore stab le than sp ec ies having alkyl g roups38 ( e . g . ,

(CgH5CH2)3C r(THF) 3 and (CH3CH2)3Cr(TH F)3) .

O rganochrom ium compounds undergo a v a rie ty of reac tio n s in which the

chrom ium ion ac ts as a coord ination cen te r o r as cen ter fo r hydrogen tra n s fe r .

A ll of the known cr-bonded organochrom ium compounds re a c t with m ercu ric

ch loride to give quantita tively the o rg an o m ercu ric halide and a chromium(HD

sp e c ie s . 38 T hese sp ec ies r e a c t with oxygen, iodine, andw ater, as w ell as

th erm a lly re su ltin g in the hom olytic o r he tero ly tic cleavage of the ch rom ium -

carbon bond; th e re fo re , they can se rv e as so u rces of ra d ic a ls o r carban ions.

T he ir reac tio n s with a lkenes, alkynes, and ketones have been investigated .

A cetylenes re a c t with tris(o rgano)chrom ium compounds to produce products

13

form ed from one, two, o r th ree acety len ic units and one o r two of the organic

groups o rig ina lly bonded to chrom ium (equation 16) . 52 The reac tio n s with

enolizable ketones yield a ry l o r alkyl ca rb in o ls form ed by the tra n s fe r of one of

the organic g roups bonded to chrom ium to com plexed ketone and p roducts form ed

from one of the groups bonded to chrom ium and two m olecules of ketone (equation

17).53 P o lym ers or addition p roducts a re obtained when olefins re a c t with these

chrom ium com pounds . 38 A ryl chrom ium compounds a re known to undergo

rea rra n g em e n ts to fo rm n -a renech rom ium com plexes . 37’ 38 T h is th e s is will

re p o r t the syn thesis and p ro p e rtie s of the f i r s t organochrom ium (IH) com plexes

with m acrocyclic ligands.

Although the ch em istry of chrom ium is cen tered around the d i- and tr ip o s i-

tive oxidation s ta te s , com plexes containing chromium(I) and (IV) a re known. The

m o st common chrom ium (I) spec ies a re the ■p-bis(arene) chrom ium (I) compounds

which a re fo rm ed by oxidizing the n -b is(arene) chromium(O) com pounds . 38 These

compounds a re a i r - and w a te r-s tab le and fo rm sa lts with a v a rie ty of anions.

The ESR sp e c tra of r-b is (a ren e ) chrom ium (i) compounds show g values of slightly

le s s than 2 and have m agnetic m om ents of 1 .7 0 -1 .8 0 B .M . which indicate a low-

spin d5 e lec tro n configuration.

The t r i s ( 2 , 2 '-b ipyridyl)chrom ium (I) com plex (s tru c tu re XV) has been synthe­

sized and c h a ra c te r iz e d . 54’ 55 I t has a m agnetic m om ent of 2. 05 B .M . and a solu­

tion ESR sp ec tru m showing a g value of 1.9971.

(C6H5)3C r(TH F )3 + CH3GeCCH3C

C

H

CH3

( 16)

(C6II5)3Cr(TH F )3 + (17)

14

XV

The o ther w ell-know n chrom ium (I) com plexes a re n itro sy l d eriv a tiv es.

S everal com plexes having the C rN 02+ m oiety have been iso la ted and ch a rac te rize d ,

e . g . , [Cr(CN)5(NO)J3- , [Cr(NH3)5(NO)]2+, [Cr(H20)5(NO)]2+ , and [Cr(Cl)(NO)

(d ia rs ) 2]+. 5G_G0 The coordination of an NO+ group to chrom ium has been accom plished

using NO, N 02", N 03~, and NH2OH. The n itro sy l com plexes a re a ll a ir -s ta b le

so lid s exhibiting N -0 in fra red absorp tions a t 1645-1747 cm -1, which a re co n sis ten t

with the NO+ form ulation of the n itro sy l ligand. The m agnetic m om ents range from

1.70 B .M . to 2 .3 0 B .M . indicating the p resen ce of one unpaired e lec tro n and a

low -sp in d5 e lec tro n configuration.

The room tem p era tu re solution ESR sp ec tra of these compounds have g values

slightly low er than 2 and in m ost ca se s show 53C r hyperfine and 14N superhyperfine

sp litting . The low tem p era tu re , frozen solution sp e c tra appear ax ially sy m m etric

with g ^ la rg e r than . 59~62

15

G ray and cow orkers have rep o rted m o lecu lar o rb ita l calcu lations fo r

[Cr(CN)5(NO)]3_ which re su lted in an energy level d iagram with the low est-ly ing

unoccupied level being derived m ainly from the n itro sy l antibonding o rb ita l.

The e lec tro n ic sp ec tra fo r the com plexes with CN" and NH3 ligands have been

assigned using the re su lts of these m olecu lar o rb ita l ca lcu la tions. 59, 63,64,65

The c ry s ta l s tru c tu re of [Cr(CN)5(NO) ]3- was determ ined by E nem ark and

c o w o rk e rs . 66 The m olecule has a C r-N distance of 1.71 A, an N-O distance of

1.21 A, and a C r-N -O angle of 176°.

To th is date only two chrom ium n itro sy l com plexes w ith m acrocyclic ligands

have been rep o rted . The reac tio n of n itr ic oxide with chrom ium (II) phthalocyanine

is re p o rte d to give a n itro sy l com plex bu t v e ry little data has been offered in

support of th is c la im . 67 W ayland and cow orkers have re c e n tly p re p a re d n itro sy l-

tetraphenylporphyrinchrom ium (l) (CrTPP(NO)) by the reac tio n of n itr ic oxide with

e ith e r te traphenylporphyrinchrom ium (II) o r tetraphenylporphyrinchrom ium (ni)

m ethox ide .68 CrTPP(NO) can be iso la ted a s a re d so lid having a N -O s tre tch in g

frequency a t 1700 cm -1. The ESR spectrum of the com plex in fro zen solution is

an iso trop ic with g ^ > gjj while the room tem p era tu re spec trum is iso tro p ic and

com plicated by n itro g e n -14 superhyperfine sp litting from both n itr ic oxide and

porphyrin p ju ro le n itrogens. CrTPP(NO) behaves a s a low -spin d5 sp ec ies with

the ESR g values indicating that the odd e lec tro n is in the m olecu lar o rb ita l

derived from the chrom ium d o rb ita l.xy

The p rep a ra tio n and p ro p e rtie s of two chrom ium (I) n itro sy l com plexes with

d iffe ren t te tra a z a m acrocyclic ligands w ill be p re se n te d and d iscu ssed . The

c ry s ta l s tru c tu re of the chrom ium (I) n itro sy l com plex with a diene m acrocyclic

ligand [Cr(M e6[l4]4, il-d ien eN 4)(N 02)(N 0)]P F 6 has been p erfo rm ed by D r. Dennis

W ester.

Although sev era l organochrom ium (IV) com plexes have been rep o rted recen tly ,

compounds with chrom ium in the te trap o sitiv e oxidation s ta te a re uncom m on.

The halides a re rep o rted and C rF 4 has been iso la ted while C rC l4 and C rB r4 e x is t

only as gaseous m a te r ia ls . 69 The com plex m ixed oxides M4CrO e, M3C r 0 5, and

16

M2C r0 4 (M = Sr o r Ba) 70 and the K, Rb, and Cs s a lts of C rF 62“ a re known. 69

Several a ir -s e n s itiv e dialkylam ides have been p re p a re d bu t only the p iperid ina to

derivative (s tru c tu re XVI) w as iso la ted as a so lid m a te r ia l . 71

X V I

A few Cr(OR )4 compounds (R = t-B u , CMe2E t, CMeEl^, CEt3 , and SiEt3) have

been synthesized and found to be re la tiv e ly stab le due to the absence of a-CH

bonds . 12,73 The predom inant m ethod used fo r m aking these compounds was the

reac tio n of the te r t ia ry alcohol o r trie th y ls ilan o l with Cr(N Et2)4, which re su lts in

a co lor change from g reen to blue and the lib e ra tio n of d iethylam ine. These a i r -

sensitive compounds a re royal blue in co lo r and a ll of them a re liquids except fo r

C r(0 -t-B u )4 which is a low m elting so lid . The e lec tro n ic sp ec tra of these com ­

pounds d isplayed sev era l bands which w ere p rov isionally assigned based on

te tra h e d ra l sym m etry . The m agnetic m om ents fo r the chromium(IV) alkoxides

a re close to the spin-only value of 2 .83 B„M. fo r a d2 sy stem . A weak peak

assignable to the p a ren t ion was found (m /e = 344 fo r C r(0 -t-B u )4+) in the m ass

spectrum of C r(0-t~B u)4.

A ttem pts to p rep a re p r im a ry o r secondary alkoxides led to the oxidation of

the ligand and form ation of the chromium(Hl) alkoxide. S im ila rly , a ttem pts to

synthesize chromium(IV) compounds in h igher coordination s ta te s by exchange

reac tio n s with chelating ligands ( e . g . , acety lacetone and hexafluoroacetylacetone)

consis ten tly led to redox reac tio n s and the fo rm ation of t r is -c h e la te s of chrom ium (ID ).

17

The p rev iously m entioned chromium(IV) compounds a ll contain a heteroatom

bonded to chrom ium bu t recen tly a num ber of chromium(IV) compounds have been

p re p a re d which have carbon bonded to chrom ium and a re te tra h e d ra l in s tru c tu re .

Compounds have been p re p a re d and iso la ted containing the alkyl groups Me*

CH2CPh3, CH2CMe2Ph, CH2CMe3, CH2SiMe3, i-cam phy l, i-n o rb o rn y l, and t -

bu ty l . 74-77 The s ta b ilitie s of these compounds have been a ttrib u ted to the

absence of hydrogen atom s on the carbon be ta to the m etal c e n te r . 76 ,78 ,79

This obviates two of the low -energy fragm entation ro u tes c h a ra c te r is tic of

CT-bonded alkyl tra n s itio n m eta l com pounds; i . e . , concerted /3-m e ta l-h y d rid e

elim ination (equation 18) and /2-hydrogen ab strac tio n (equation 19).

R - CH - CH, RCH = CH, + MH (18)I I

H M

R - CH - CH?I J

H M/

r '

R - CII = CIi2 + R'H + M (19)

In addition to the two fragm entation ro u te s m entioned above and sim ple

hom olytic bond cleavage, th e re a re a v a rie ty of o ther low -energy fragm entation

ro u te s w hereby the carbon to m eta l bond m ay be destroyed . T here a re th ree ways

in which these low -energy pa ths m ay be blocked thereby stab iliz ing the a-bonded

alkyl chrom ium com pound . 38 Alkyl groups can be used which lack hydrogen or

o ther read ily tra n s fe rra b le groups on the carbon atom /? to the m eta l. The co o rd i­

nation s ite s on the m etal cen te r which a re req u ired fo r the m eta l-hydride

elim ination p ro c e ss can be blocked with some suitable ligand, e . g . , 2 , 2 '-b ip y rid y l.

F inally , the geom etry of the m olecule can be a lte red so th a t not only a re there no

coordination s ite s on the m etal cen te r availab le fo r partic ip a tio n in the m e ta l-

hydride elim ination p ro cess but a lso that the bulk of the organic groups a re such

18

a s to p rev en t both concerted /3-hydrogen ab strac tio n and /3-m e ta l-h y d rid e

elim ination .IV

The sp ec ies C r (R) 4 w ere p re p a red e ith e r by the in te rac tio n of G rignard

o r lith ium reag en ts with C rC l3(THF) 3 o r by an exchange re a c tio n betw een

lith ium reag en ts and chromium(IV) t-butoxide. In the syn theses using the C rC l3-

(THF )3 and G rignard o r lith ium reag en ts the chrom ium !Ill) is oxidized to

chrom ium !Ill) v ia a d isproportionation reac tio n o r by a ir ox idation . 74-77

Depending on the type of organic group coordinated to the m e ta l, the

p ro p e rtie s of these compounds v a ry . Some a re c ry s ta llin e , a ir -s ta b le so lids

( e .g . , C r( i-n o rb o rn y l) 4 and Cr(CH2CPh3)4) while o th e rs a re unstable liquids

( e .g . , Cr(CH3)4 and Cr(n-B u)4) . These compounds have m agnetic m om ents of

2 .6 -3 .0 B. M. which co rrespond to two unpaired e lec tro n s a s is expected fo r

chrom ium (IV ). T heir e lec tro n ic and variab le tem p era tu re ESR sp e c tra have

been investigated and d iscussed in te rm s of th e ir te tra h e d ra l configu ra tions . 76 >77 »80 »81

T his data indicates that these compounds p o sse ss slightly d is to rte d te tra h e d ra l

s tru c tu re s . M ass sp ec tro m etry has been used to c h a ra c te r iz e te tra !a lk y l)ch ro -

mium(IV) compounds and, of the compounds studied , C r(i-cam p h y l)4,

C r(l-n o rb o rn y l)4, and Cr(neopentyl)4 showed peaks a t m /e values co rresponding

to the te tra a lk y ls . 74, 75 A p re lim in a ry re p o rt of a single c ry s ta l X -ray s tru c tu re

an a ly s is confirm s the te tra h e d ra l a r ra y of the organic ligands in Cr(CH2C(CH3)2-

c gh 5) 4. 82

The syn thesis and ch arac te riza tio n of the f i r s t chromium(IV) com plexes with

a chelating ligand and a n o n -te trah ed ra l configuration w ill be p re sen ted and

d iscu ssed in th is th esis .

EXPERIMENTAL

P hysical M easurem ents

NMR S pectra . — V arian A -60 and A-60A sp ec tro m e te rs w ere used to

perfo rm a ll nm r m easurem ents,, To de term ine the probe tem p era tu re of the

in stru m en ts, a ca lib ra tion curve based on the chem ical sh ift of m ethanol was

used. All chem ical sh ifts w ere determ ined using ex te rn a l te tram eth y ls ilan e

(TMS) as the re fe re n c e . A ir-se n s itiv e sam ples w ere p rep a red in a glove box

and sealed with tigh t-fitting caps which w ere then w rapped with p a ra film . The

sp ec tra of the sam ples w ere im m ediately reco rd ed upon rem oval of the sam ples

from the glove box.

E lec tron ic S pectra. — Both v isib le and n ea r in fra red sp e c tra w ere obtained

using a C ary Model 14R reco rd in g spectropho tom eter. The p re p a ra tio n of a i r -

sensitive sam ples was accom plished in a glove box by f i r s t weighing the sam ples

on a Cahn Model RTL E lec trobalance and then p rep arin g solutions using vo lum etric

fla sk s . These sam ples w ere loaded into one cm . m atching q u artz ce lls and

tightly sealed with teflon s to p p ers . A fter rem oval of these sam ples fro m the

glove box, th e ir sp e c tra w ere im m ediately reco rd ed . S o lid -sta te sp e c tra w ere

obtained from m ulls p rep a red hi the glove box using f ilte r pap er im pregnated with

H alocarbon 25-55 g rea se .

In frared S pectra . — In frared sp e c tra w ere acquired with P e rk in -E lm e r

Model 337 and Model 457 reco rd ing spectropho tom eters using Nujol m ulls

between po tassium brom ide p la tes . Mulls of a ir -s e n s itiv e com plexes w ere

p repared hi a glove box and th e ir sp ec tra w ere reco rd ed d irec tly upon rem oval

from the box.

19

20

M a g n e t i c S uscep tib ilities . — S o lid -sta te m agnetic su scep tib ilitie s w ere

m easu red by the F arad ay method83 a t room tem p era tu re under a helium p re ssu re

of 35 mm using a Cahn e lec trobalance and a V arian e lec trom agnet operating a t a

c u rre n t of 3. 5 am ps. F o r m agnetic su scep tib ilitie s in the tem p era tu re range

90-350° K, the technique and appara tus used w ere as d escrib ed in the l i te ra tu r e . 83

Solution su scep tib ilitie s w ere m easu red by the Evans m ethod84 using V arian

A-60 and A-60A sp e c tro m e te rs . The sam ples w ere p rep a red in the glove box

em ploying the Cahn e lec trobalance to accu ra te ly determ ine the m ass of the

sam ples and vo lum etric fla sk s to make up the solutions. Solvents com m only used

for th is type of m easu rem en t w ere ch loroform , a c e to n itr ile , n itrom ethane, and

acetone.

F o r both so lid -s ta te and solution su scep tib ilitie s diam agnetic co rrec tio n s

w ere made using P a s c a l 's c o n s ta n ts . 85

C onductiv ities. — Conductance m easu rem en ts w ere made with an in d u stria l

In strum ents Model RC 16B conductivity b rid g e . The conductance ce ll was the

Sproule type having a ce ll constant of 0 .100 cm -1. The sam ple solutions w ere

p rep ared in the glove box u tilizing the Calm electrobalance and vo lum etric f la sk s .

The m easu rem en ts w ere c a r r ie d out in the glove box on 1.0 x 10-3 M solutions a t

room tem p era tu i’e and a t 1000 cps. N itrom ethane and ace to n itrile w ere commonly

used as solvents fo r these m easu rem en ts .

M ass S pectra . — The m ass sp e c tra w ere obtained by M r. R ichard W eisenberger

of th is D epartm ent em ploying an MS-9 sp ec tro m ete r a t an ionizing potential of

70 eV.

E lem ental A nalyses. — E lem ental ana lyses w ere perfo rm ed by G albraith

and Schwarzkopf L a b o ra to rie s . N itrogen analyses fo r m ost of the com plexes

w ere done by the author o r by M r. Wayne Scham m el of th is D epartm ent using a

Model 29 Colem an N itrogen A nalyzer.

21

ESR S pectra . — The e s r sp e c tra w ere obtained using a V arian V4500-10A

sp e c tro m e te r operating on the X band a t a frequency of approxim ately 9300 MHz.

Since the instrum en t was equipped with a dual cavity, the fre e ra d ic a l diphenyl-

p iera lhyd razy l (g = 2.0037) was p laced in the r e a r cavity and used as a re fe ren ce

for a ll m easu rem en ts . Sam ples having concentrations approxim ately i0 -2 - 10“ 3 M

in com plex and containing a sm all am ount of te tra -n -bu ty lam m onium te tra flu o ro -

b o ra te86 w ere p rep a red in the glove box, placed in quartz c e lls s toppered with

ground g la ss jo in ts , and frozen with liquid n itrogen im m ediately upon rem oval

from th e glove box. In o rd e r to m aintain the sam ples a t a constan t tem p era tu re

while th e ir sp ec tra w ere being reco rd ed , the ce ll was placed in a sm all q u artz

dew ar containing liquid n itrogen which was then in se rted into the fro n t cavity of

the in stru m en t.

E lec tro ch em is try . — Polarography and cyclic vo ltam m etry w ere p erfo rm ed

by M iss Kathy H olter of th is D epartm ent and in some cases by the au thor using

an Indiana Instrum ent and Chem ical C orporation C ontrolled P o ten tia l and

D erivative V oltam m eter Model ORNL-1988A. The cu rren t-p o ten tia l cu rv es w ere

reco rd ed on a H ew lett-P ackard /M oseley D ivision X-Y re c o rd e r . The p o la ro -

g raphic ce ll was a th ree com partm ent H-type ce ll utilizing a ro ta tin g platinum

w ire working e lectrode and a re fe re n ce e lec trode consisting of a s ilv e r w ire

im m ersed in a 0 .1 M ace to n itrile solution of s ilv e r n itra te . A ll m easu rem en ts

w ere c a r r ie d out in a Vacuum A tm ospheres Dry Lab using ace to n itrile a s the

solvent and te tra-n-bu ty lam m onium te tra fluo roborate as the supporting e le c tro ­

ly te.

Syntheses

G eneral P ro c ed u re s . — U nless otherw ise indicated a ll m anipulations

involving chromium(II) sa lts and m etal com plexes w ere c a r r ie d out in a Vacuum

A tm ospheres Dry Lab equipped with a rec ircu la tio n and pu rifica tio n system

which is la te r d escribed in deta il.

22

M ate ria ls . — Only reag en t g rade chem icals and so lven ts w ere em ployed

in ca rry in g out syntheses and obtaining physical m easu rem en ts . The solvents

used in the glove box w ere d ried and degassed before they w ere taken into the

dry box. A ceton itrile , diethyl e th e r , ethanol, m ethanol, te trahydro fu ran , and

benzene w ere refluxed fo r a t le a s t one hour over calcium hydride before being

d is tilled under n itrogen. C hloroform , dim ethylform am ide, n itrom ethane, and

acetone w ere s to red sev era l days over Linde m olecu lar s iev es and then

d istilled under n itrogen. A fter being s to red over po tassium hydroxide for

sev e ra l days pyridine and trie thy lam ine w ere d is tilled under n itrogen . Chrom ium

m etal, 9.9$ and 140 m esh, and alkyl and a ry l lith ium reag en ts w ere purchased

from Alfa Inorganics, B everly , M assachuse tts .

Tetraaquochrom ium (II) ch lo ride , CrCl? • 4 H?Q. — Following the method

of Lux and Illm an , 87 th is chrom ium (Il) s a lt was p re p a red on the benchtop under

a b lanket of n itrogen. To a fla sk containing 10.4 g (0 .2 mole) of v ery pure

chrom ium m etal was added 100 m l of 2 0 $ hydrochloric acid under a n itrogen

s tre am . The fla sk was w arm ed and s t i r re d under a purge of n itrogen until a ll

of the m etal d issolved. A fter the volume of the blue solution was reduced to

n ea r d ry n ess under vacuum , the f la sk was taken into the glove box. Upon the

addition of acetone to the fla sk the blue c ry s ta ls w ere co llected by filtra tio n ,

w ashed with acetone and diethyl e th e r , and d ried under vacuum .

Hexaaquochromium(D) b rom ide, CrBr? • 6H?Q and Hexaaquochromium(II)

iodide, CrL> • 6H?Q. — These chromium(H) s a lts w ere p rep a red a s in the

p reced ing procedure using the ap p rop ria te acid .

Chromium(II) ace ta te , CrA c2. — Again following the method of Lux and

Illm an , 87 on the benchtop under n itrogen hydrated chromium(U) ace ta te was

p rep ared from a w ater solution of chromium(II) chloride by the addition of

sodium ace ta te . A fter tra n sfe rr in g the fla sk containing the re d chromium(H)

acetate to the glove box, the re d m a te ria l w as co llected by f iltra tio n and w ashed

with ethanol and e th e r . The chrom ium (n) ace ta te was p laced in a tube equipped

23

with a vacuum stopcock, rem oved from the dry box, and heated under vacuum

a t approxim ately 200° C overn ight causing the b rig h t red solid to becom e light

orange in c o lo r . The tube w as taken into the dry box w here the anhydrous

chromium(II) ace ta te was w ashed with ethanol and diethyl e th e r and d ried under

vacuum .

B is(pyridine)chrom ium (H ) ch lo ride , CrCl? • 2py. — T his g reen chromium(II)

s a lt w as p rep ared by a m ethod s im ila r to th a t of Holah and F a c k le r . 20 An

ex cess of pyrid ine w as added to a hot ethanolic solution of C rC l2 • 4H20 resu ltin g

in the fo rm ation of a ligh t g reen p rec ip ita te . The g reen solid w as co llected by

filtra tio n , w ashed with ethanol and diethyl e th e r , and d ried under vacuum .

Hexakis(pyridine)chromium(H> brom ide, C rBr? • 6py and hexakis(p.yridine)-

chromium(II) iodide, CrI? • Gpy. — These two chromium(U) halides w ere

p rep ared according to the above p rocedure em ploying the app rop ria te hydrated

chromium(IJ) halide.

Tetrakis(pyrid ine)chrom ium (II) trifluorom ethylsu lfonate , Cr(CF^SO^)9 • 4py. —

To a s lu r ry of 4 .0 g (11.1 mmol) of [Cr(Ac)2]2 in 50 m l of ace to n itrile was added

dropw ise an ex cess of trifluorom ethanesu lfon ic acid. As the acid was added,

the fum es w ere rem oved by vacuum . The b rig h t blue solution was f ilte re d and

then the volume reduced to n ea r d ry n ess . The addition of 30 m l of diethyl e ther

caused the p rec ip ita tio n of a b rig h t blue so lid . This blue solid was collected by

filtra tio n and w ashed with diethyl e th e r . To a hot s tir r in g solution of the above

blue so lid in ethanol was slow ly added approxim ately 20 m l of p y rid ine . A fter

the solution cooled to room tem p era tu re , the blue c ry sta llin e p roduct was

collected by filtra tio n , w ashed with ethanol and diethyl e th e r , and d ried under

vacuum . The product was re c ry sta llized from pyridine and ethanol. Based on

chrom ous ace ta te , the y ield w as 81^. Anal. C alcd. fo r C r(C F 3S03) 2 • 4py:

C, 39.65; H, 3 .05 ; N, 8 .4 2 . Found: C, 39.37; H, 3 .11 ; N, 8 .31 .

24

tra n s-[(5 ,1 4 -D im e th y l-1 ,4 ,8 > li- te tra a z a c .y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -te tra e -

nato)bis( pyridine) chrom ium (II])]hexafluorophosphate, [Cr(Me?[14]tetraenatoN^)~

(py)?]PFR. — To a solvent m ix ture containing 50 m l of ace to n itrile and 10 m l of

pyrid ine was added 5.12 g (0.01 mol) of H2[Me2 [ l4 ]te traeneN 4](PFg)215 and 2 .81 g

(0 .01 mol) of C rC l2 • 2py. When the m ix tu re w as heated and s t i r r e d the ligand

s a lt d isso lved but the chromium(II) s a lt did not. To th is w arm s tir r in g solution

was added dropw ise 4 .04 g (0.04 mol) of trie th y lam in e causing the solution to

tu rn a b rig h t g reen co lo r. The solution was refluxed fo r 30 m in and then allowed

to cool to room tem p era tu re . The g reen solution was f ilte re d to rem ove the

insoluble white sa lts and any unreacted chrom ium (II) sa lt. The volum e was

reduced under vacuum to approxim ately 10 m l, a f te r which 40 m l of ethanol was

added to the hot s tir r in g solution resu ltin g in the fo rm ation of g reen c ry s ta ls .

A fter the solution had cooled to room te m p e ra tu re , the g reen c ry s ta ls w ere

co llected by filtra tio n , washed with ethanol and diethyl e th e r , and d ried under

vacuum . This complex was re c ry s ta ll iz e d by f i r s t d issolving the com plex in

pyrid ine and filte ring and then causing it to c ry s ta lliz e by adding ethanol. Yields

obtained ranged from 50-60$ based on the ligand sa lt.

tra n s-[(7 , 13-D im eth .y l-l,4, 8 , 1 2 -te traazacy c lo p en tad eca -4 ,6 ,1 2 ,1 4 -te tra e -

nato)bis(pyridine) chrom ium ( ttljJhexafluorophosphate, [Cr(Me?[ 15]te traenatoN t1) -

(py),]PFfi. — The procedure fo r th is com plex w as the sam e a s the preced ing

one except tha t 5.26 g (0.01 mol) of H2[Me2[ l 5]te traeneN 4](PF6)215 w as the ligand

s a lt u sed . The c ry sta llin e product w as dark brow n in co lo r and the yields

obtained w ere 45-55$ based on the ligand s a lt .

tra n s-[(2 ,1 2 -D im e th y l-l, 5, 9 , 1 3 -te traazacy c lo h ex ad eca-l, 3, 9 ,1 1 -

tetraenato)bis(pyridine)chrom ium (U D ]hexafluorophosphate, [Cr(M e7[ l6 ] te tra e -

natoN^)(py)c>]PFfi. — This com plex was p re p a red by a p ro ced u re s im ila r to the

one used for the above com plex except in th is case 5.40 g (0.01 mole) of

H2[Me2[ l6 ]tetraeneN 4](PF6) 10 was used as the ligand so u rce . A lso the solvent

volum e was reduced to approxim ately 5 m l before the addition of the ethanol.

25

The com plex was orange in co lor and typical y ields w ere 35-45$ based on the

ligand sa lt.

tran s-[(5 , 7 ,1 2 ,1 4 -T e tra m e th y l- l ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

te tr aenato) b i s( pyr idine) ch r om ium (III) ]hexafluor ophosphate, [C r (Me,t [ 14 ]te t r aenatoN ̂-

(py)2]P F R. — To a so lvent m ix tu re consisting of 50 m l of ace to n itr ile and 10 m l

of pyridine was added 3 .1 g (0.0125 mol) of Me4 [l4 jte traeneN 417 and 3 .51 g (0.0125

mol) of C rC l2 • 2py. S tirr in g and heating the solution caused it to becom e green

in co lo r. A fter refluxing the g reen solution fo r 15 m in, 4 .08 g (0.025 mol) of

NH4P F g was added to the hot so lution with s tir r in g . The solution was f ilte re d and

the volume was reduced under vacuum to 10 m l. Then 40 m l of ethanol w ere

added to th is hot solution. When the solution cooled, the g reen c ry s ta ls w ere

co llected by filtra tio n , w ashed w ith ethanol and diethyl e th e r , and d ried under

vacuum . This com plex w as re c ry s ta ll iz e d by disso lv ing it in a m inim um am ount

of pyridine and then adding ethanol to cause the product to c ry s ta lliz e . Y ields

obtained w ere 70-85$ based on the ligand.

tra n s-[(5 ,1 4 -D im e th y l-1 ,4 , 8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -te tra e -

nato)bis(dim ethylform am ide)chrom ium (III)]hexafluorophosphate, [Cr(M e?[l4j-

te traenatoN 4)(dmf)?]PFR. — To 50 m l of d im ethylform am ide was added 2 .0 g

(3.49 mmol) of [Cr(Me2[i4 ]te traenatoN 4)(py)2]P F 6. The volume of th is solution

was reduced under vacuum to n e a r d ry n ess re su ltin g in rem oval from the com plex

the low er boiling pyrid ine and leaving only dim ethylform am ide as a possib le

ax ial ligand. As the pyridine w as rem oved , the co lor of the solution changed

from green-brow n to re d -o ra n g e . To th is hot solution (about 5 ml) 50 m l of

ethanol was added w ith s tir r in g . T his re su lted in the p rec ip ita tion of a re d -

orange solid which was co llec ted by f iltra tio n a fte r the solution had cooled

to room tem p era tu re . This so lid w as w ashed with ethanol and diethyl e th e r and

d ried under vacuum . The compound w as re c ry s ta lliz e d by dissolving i t in a

m inim um am ount of d im ethylform am ide, f ilte rin g the solution, and then adding

ethanol causing the p roduct to p rec ip ita te . The y ield was 82$ based on the

s ta r tin g com plex.

26

tra n s-[(7 , 13-D im ethy l-1 ,4 , 8 , l2 -te tra a za cy c lo p en ta d e c a -4 ,6 ,1 2 ,1 4 -te tra e -

nato)bis(dim ethylform am ide)chrom ium (H I)]hexafluorophosphate, [Cr(Me9[l5 ]-

te traenatoN 4)(dmf) ;]P F R. — The above p rocedure was em ployed to p rep a re this

com plex s ta rtin g with [Cr(M e2[ i5 ]te traenatoN 4)(py)2]PF6. The y ield of th is orange

com plex was 65$ based on 2 .0 g (3 .4 mmol) of s ta rtin g com plex.

tra n s -[(2 ,1 2 -D im e th y l- l, 5, 9 , 1 3 -te traazacy c lo h ex ad eca-l, 3, 9 , 1 1 - te tra e -

nato)bis( dim ethylform am ide) chrom ium (H I)]hexafluorophosphate, [Cr(M e?[ l6 ]~

te traenatoH d (dmf) 9]PFR. — T his orange com plex was p re p a red in the sam e

m anner as the p receding com plex. Based on 1. 5 g (2. 5 mmol) of [Cr(Me2[ l6]-

te traenatoN 4)(py)2]P F G, the yield was 55$.

tra n s-[(5 , 7 ,1 2 ,1 4 -T e tra m e th y l~ l,4 ,8, l l- te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

tetraenato)b is(d im ethylform am ide)chrom ium (n])]hexafluorophosphate, [Cr(Me^~

[i 4 jtetraenatoN ,1) (dmf),] P F R. — The p rep a ra tio n of this orange com plex was

s im ila r to the p rep a ra tio n of the above com plex. Em ploying 1 .0 g (1.66 mmol)

of [Cr(Me4[l4 ]tetraenatoN 4)(py)2]P F G, the y ield was 82$ based on that com plex.

tra n s-[(5 , 14-D im ethy l-1 ,4 , 8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -te tra e -

nato)bis( l-m ethylim idazole)chrom ium (H I)]hexafluorophosphate, [Cr(Me9[l4]~

te t r ae natoISh) (Me - Im) 9 ] P FR. — A pproxim ately 0 .5 m l of 1-m ethylim idazole was

added to a s tir r in g solution of 1 .0 g (1.74 mmol) of [Cr(M e2[l4]tetraenatoN 4)(py)2]-

PFg in 50 m l of acetone. Im m ediately following th is addition, the co lor of the

solution turned from g reen to re d indicating rep lacem en t of the ax ial pyrid ine by

1-m ethy lim idazo les. The volum e was reduced to 15 ml under vacuum and 30 ml of

ethanol was added. Upon again reducing the volume to 15 m l, re d c ry s ta ls

w ere produced. The p roduct was co llected by filtra tio n , washed with sev e ra l

po rtions of ethanol and diethyl e th e r , and d ried under vacuum . This product was

re c ry s ta ll iz e d by dissolving i t in acetone and then adding ethanol causing the

p roduct to c ry s ta lliz e . B ased on the s ta rtin g com plex, the y ield w as 79$.

27

tr a n s - [ ( 7 ,13-D im e th y l-1 ,4 ,8 , l2 - te tra az ac y c lo p e n tad e c a -4 ,6 ,1 2 ,1 4 -te tra e -

nato)bis( 1 -m ethylim idazole)chrom ium ( HI) jhexailuorophosphate, [Cr(M e?[15]-

tetraenatoINh) (M e-Im )?]P F ft. — This re d com plex was p re p a re d in the sam e

m anner as the preceding com plex. B ased on 1 .5 g (2.55 mmol) of [Cr(M e2[l5 ]-

tetraenatoN 4) (py)2]PF6, the y ield w as 89$.

tra n s -[(2 ,1 2 -D im e th y l- l, 5, 9 , 1 3 -te traazacy c lo h ex ad eca-l, 3 , 9 , 11-tetraenato)-

b is(l-m ethylim idazole)chrom ium (III) Jhexailuorophosphate, [Cr(Me?{l6 ]te traen a to -

N4)(M e-Im )9]PFR. — T his orange com plex w as synthesized using the sam e

procedure as fo r the above com plex. The yield w as 92$ s ta r tin g with 1. 5 g

(2. 5 mmol) of [Cr(M e2[ l6 ]te traenatoN 4)(py)2]P F e.

tra n s-[(5 , 7 ,1 2 ,1 4 -T e tra m e th y l- l ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

te traenato)b is( l-m ethylim idazole)chrom ium (III) Jhexafluorophosphate, [Cr(Me^ [14]-

tetraenatoN^) (M e-Im)9]P F R. — The syn thesis of th is re d com plex was the sam e

as the one described p rev iously . The y ield was 79$ based on 1.0 g (1.66 mmol)

of [Cr(Me4[l4]tetraenatoN 4)(py)2]P F 6„

tra n s-T h io cy an a to (5 ,1 4 -d im eth y l-1 ,4 ,8 , l l- te tra a z a c y c lo te tra d e c a -4 , 6 ,1 1 , -

l3 -te traenato )py rid inech rom ium (IlI), C r(M e?[l4]tetraenatoN 4)(NCS)(p.y). — To a

s tir r in g solution of 3 .0 g (5.23 mmol) of [Cr(M e2[i4 ]tetraenatoN 4)(py)2]PF 6 in 50

m l of ace to n itrile was added 0 .5 g (49.4 mmol) of NaSCN. After the g reen solution

was heated to reflux , the volume was reduced under vacuum to 10 m l re su ltin g

in the form ation of d ark g reen c ry s ta ls . Upon adding 40 m l of ethanol to insure

p rec ip ita tio n of a ll the com plex and cooling to room tem p era tu re , the p roduct

w as co llec ted by filtra tio n , w ashed with ethanol and diethyl e th e r , and d ried

under vacuum . The com plex was re c ry s ta ll iz e d by dissolving i t in a m inim um

am ount of hot pyridine and then adding ethanol causing the p roduct to p rec ip ita te .

The yield was 94$ based on the s ta r tin g com plex.

28

trans-T h iocyanato (7 , l3 -d im e th y l- l ,4 ,8 , l2 -te tra az ac y c lo p e n tad e c a -4 ,6 ,12 , -

l4 -te traenato )py rid ineeh rom ium (U I), Cr(M e9[l5]tetraenatoN /i)(NCS)(py). — The

p ro ced u re fo r making th is d ark brow n com plex was s im ila r to the one used above.

Since the so lubility of th is com plex in ace to n itrile is substan tia l, the volum e of

the solution was reduced to 20 m l a f te r the addition of the ethanol in o rd e r to

rem ove m ost of the ace to n itr ile . Using 1 .5 g (2.56 mmol) of [Cr(Me2[ l5 ] te tra e -

natoN,i)(py)2]P F 6, the yield was 84$,

trans-T h ioc .yanato (2 ,12-d im e th y l-1, 5 , 9 , 1 3 -te traazacy c lo h ex ad eca-l, 3 ,9 ,1 1 -

tetraenato)pyrid ineehrom ium (IU ), Cr(M e?[ l6 ]tetraenatoN^)(NCS)(py). — The

p rep ara tio n of th is orange com plex was the sam e as that used fo r the preceding}

com plex. S tarting with 1 .5 g (2 .5 mmol) of [Cr(Me2[ l 6 ]te traenatoN 4)(py)2]P F 6,

the yield w as 83$.

tra n s-T h io c .y an a to (5 ,7 ,12, l4 - te t r a m e th y l - l ,4 ,8 , 11-te traazac .yclo te tradeca-

4 ,6 ,1 1 , l 3 -te traenato )pyrid inechrom ium (III), C r(MeA[14]te tra e n a to N J(NCS)(p.y). —

The p rocedure for producing th is g reen com plex w as the sam e as that used fo r

the above com plex. B ased on 1.0 g (1.66 mmol) of [Cr(Me4[ l4 ]tetraenatoN 4)(py)2]-

P F G, the y ield w as 83$,

C .yano(5,14-dim ethyl-1 ,4 ,8 , ll- te tra a z a c y c lo te tra d e c a -4 , 6 ,1 1 ,1 3 -te traenato )-

chi-omium(IU), Cr(M e2[l4 ]tetraenatoN 4)CN. — To 50 m l of m ethanol w ere added

0 .2 g (4 .1 mmol) of NaCN and a solution containing 1.0 g (1.74 mmol) of [Cr(Me2-

[ l4 ]te traenatoN 4)(py)2]P F 6 d isso lved hi 10 m l of ace to n itr ile . T his solution was

refluxed fo r one hour and then f ilte re d . The volume was reduced under vacuum

to 10 m l and after adding 50 m l of d im ethylform am ide the volume was again reduced

to 10 m l producing a g reen p rec ip ita te . A sm all portion of ethanol was added to

the solution and the g reen powder w as co llected by filtra tio n , w ashed with ethanol

and diethyl e th e r , and d ried under vacuum . F o r purification the com plex was d is ­

solved hi a m inim um am ount of hot pyrid ine . A fter the solution was f ilte re d , 50 m l

of dim ethylform am ide w ere added and the volume reduced under vacuum until

the solid p rec ip ita ted . The yield based on th e s ta rtin g com plex w as 77$.

29

C yano(7 ,13-d im e th y l-1 ,4 ,8 , l2 -te traazacy c lo p en tad eca-4 , 6 ,1 2 ,1 4 -te t-

raenato)chrom ium (III), Cr(M e?[l5]tetraenatoN )1)CNo — The syn thesis of th is

g reen com plex was the sam e as fo r the p reced ing com plex. Using 1 .0 g

(1 .7 mmol) of [Cr(Me2[l5 ]tetraenatoN 4)(py)2]P F 6, the yield was 75^.

30

C yano(2 ,12-d im e th y l-1 ,5 ,9 , 1 3 -te traazacy c lo h ex ad eca-l, 3 , 9 , 1 1 -te traenato )-

chrom ium (III), Cr(M e9[ l 6 ]te traenatoN ;1)CN. — This orange com plex was p rep ared

using the sam e procedure as fo r the above com plex. The y ield was 50$ using

1.5 g (2 .5 mmol) of [Cr(M e2[ l 6 ]te traenatoN 4)(py)2]P F 8.

tran s-P h en y l(5 , 1 4 -d im ethy l-1 ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

te traenato )py rid inech rom ium (n i), [Cr(M e9[l4]tetraenatoN ^)(CRHR)(py). — To a

s lu r ry of 1.45 g (2.53 mmol) of [Cr(M e2[ l4 ]te traenatoN 4)(py)2]P F 6 hi 50 m l of

te trahydro fu ran was added an ex cess of phenyllithium reag en t (Alfa Inorganics,

2 M in 70:30 benzene :diethyl e th e r) . As the addition of the phenyllithium reag en t

proceeded , the solution tu rned red -b ro w n hi co lor and som e of the lavender

product s ta r te d to p rec ip ita te . A fter the solution was heated to red isso lv e a ll of

the product and f ilte re d , 25 m l of ethanol w ere added and the volume w as reduced

under vacuum to 20 m l. The lavender c ry s ta ls w ere co llected by filtra tio n , w ashed

with ethanol and diethyl e th e r , and d ried under vacuum . This com plex was

re c ry s ta lliz e d by f i r s t d isso lv ing it in a m inim um am ount of hot benzene, f ilte rin g

the solution, and then adding ethanol causing the p roduct to c ry s ta lliz e . The y ield

was 79$ based on the s ta rtin g com plex.

tran s-P h en y l(7 , l3 -d im e th y l- l ,4 ,8 , l2 - te tra a za cy c lo p en ta d e ca -4 ,6 ,1 2 ,1 4 -

te traenato)pyridm echrom ium (III), Cr(M e?[l5]tetraenatoN 4)(CKHR)(py). — This

red com plex was p rep ared in the sam e m anner as the p rev ious com plex. The

yield was 88$ s ta rtin g with 2 .5 g (4.26 mmol) of [Cr(M e2[ l 5 ]tetraenatoN 4)(py)2jP F G.

tra n s -P h e n y l(2 ,12-d im e th y l-1, 5 , 9 , 1 3 -te traazacy c lo h ex ad eca-l, 3 ,9 ,1 1 -

te traenato)pyrid inechrom ium (IIl), Cr(M e?[f6 ]tetraenatoN^)(CRHR)(p,y). — This

orange com plex was synthesized using a p rocedure s im ila r to tha t used fo r the

above com plex. A fter adding the ethanol the volum e was reduced to approxi­

m ately 5 ml since th is com plex has good solubility in ethanol. The com plex was

re c ry s ta lliz e d from diethyl e th e r . The yield w as 62$ based on 1. 5 g (2. 5 mmol) of

[C r (Me2 [ i 6 ] te t r aenatoN4) (py) 2 ] P F G.

31

(5, 1 4 -D im e th y l-1 ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,13 -te traenato )-

n itro sy lch rom ium (]), Cr(M e9[ l4 ]te traen a to IS b )N O .— To 50 m l of m ethanol

w ere added 2 .0 g (3.49 mmol) of [Cr(Me2[l4 ]tetraenatoN 4)(py)2]P F 6 and 0. 5 g

(7 .25 mmol) of sodium n itr ite . A fter the m ixture was refluxed fo r one hour,

the volum e was reduced to d ry n ess under vacuum and the so lid was then ex trac ted

with hot benzene. The g reen benzene solution was f ilte re d and the volume

reduced to 10 m l under vacuum . A fter adding 50 m l of ethanol to the solution,

the volume w as again reduced to io ml causing the g reen solid to p rec ip ita te .

The com plex w as co llected by filtra tio n , w ashed with ethanol and diethyl e th e r,

and d ried under vacuum . The compound was re c ry s ta lliz e d by dissolving it in a

m inim um am ount of hot benzene, f ilte rin g the solution, and adding ethanol causing

the com plex to p rec ip ita te . B ased on the s ta rtin g com plex, the y ield w as 48$.

trans-M ethy l( 5 , 1 4 -d im eth y l-l, 4 , 8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

te traenato)pyrid inechrom ium (III), C r (Me? [ 14]tetraenatoN.i) (CHa) (p.y). — To a

solution consisting of 1 .5 g (2.62 mmol) of [Cr(M e2[ i4 ]tetraenatoN 4) (py)2]P F 6 in

50 ml of pyrid ine was added an ex cess of methyllithium reag en t (Alfa Inorganics,

1.3 M in diethyl e th e r). The addition of the m ethyllithium reag en t caused the

co lor of the solution to change from b rig h t g reen to dark brow n. A fter the solution

was s t i r re d fo r 15 m inutes, the g reen c ry sta llin e com plex was co llected by

filtra tio n , w ashed with a sm all portion of pyridine and a lib e ra l am ount of e th e r,

and d ried under vacuum . The com plex was re c ry s ta lliz e d from a m inim um amount

of hot benzene. The yield w as 78$ based on the s ta rtin g m ate ria l.

tran s-n -B u ty l(5 , l4 -d im e th y l- l ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,1 3 -

te traenato)pyrid inechrom ium (ID ), Cr(M e9[l4 ]tetraenatoN /1)(CH^(CH?)^)(py). — This

green com plex was synthesized using the sam e method as above. In th is syn thesis

ex cess n-buty llith ium (Alfa Inorgan ics, 2 M in hexane) was em ployed as the alkyl

so u rce . B ased on 1.45 g (2.53 mmol) of [Cr(Me2[l4]tetraenatoN 4)(py)2jP F G, the

yield was .

32

[P h en y l(5 ,1 4 -d im e th y l-l,4 ,8 , l l- te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,13 -te traen a to )-

chi-omium(IV)]iodide, [Cr(M e2[l4 jte traenatoN /t)(CfiHQ jl. — A te trah y d ro fu ran

solution of 0 .35 g (1.38 mmol) of iodine was added slowly to a hot s t i r r in g solution

containing 1.2 g (2.82 mmol) of Cr(M e2[l4 ]tetraenatoN 4)(C6H5)(py) in 50 m l of

te trah y d ro fu ran . As the addition of the iodine solution proceeded , the solution

becam e d ark g reen in co lor and solid began to p rec ip ita te . A fter the solution

cooled to room tem p era tu re , the dark g reen ish -b row n c ry s ta ls w ere co llec ted

by filtra tio n , w ashed with te trah y d ro fu ran and diethyl e th e r , and d ried under

vacuum . F o r p u rifica tion the com plex w as passed through a colum n of cellu lose

15 cm long using ethanol a s the eluan t. The yield was 8 6 % based on the s ta rtin g

com plex.

[P h en y l(5 ,1 4 -d im e th y l-l,4, 8 , l l - te tra a z a c y c lo te tra d e c a -4 ,6 ,1 1 ,13 -te traen a to )-

chrom ium (IV )]thiocyanate, [Cr(Me? [MJtetraenatoISb)(CfiHfl)]SCN. — To a solution

com posed of 0 .5 g (1 .05 mmol) of [Cr(M e2[l4]tetraenatoN 4)(CGH5)]I d isso lved in

50 ml of ethanol was added 0 .25 g (3.09 mmol) of NaSCN. The solution w as s t i r re d

until g reen c ry s ta ls fo rm ed and p rec ip ita ted . These c ry s ta ls w ere co llec ted by

filtra tio n , w ashed with ethanol and diethyl e th e r, and d ried under a vacuum . B ased

on the s ta rtin g com plex, the y ield was 82%.

[Chloro(5, 7, 7 ,1 2 ,1 4 , l4 -h e x a m e th y l- l ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,11-

diene)chrom ium (II)]hexafluorophosphate, [Cr(MeR[14]4, l l-d ie n e N JC l ]PFfi . — To

a s lu r ry of Me6[l4]4, ll-d ie n e N 4 • 2CF3S03H88 (2 .9 g, 5 .0 mmol) and C rC l2 • 2py

(2.81 g, 5 .0 mmol) in 50 m l of ethanol was added an excess of trie thy lam ine causing

the solution to becom e brown in co lo r. A fter being brought to reflux the solution

was f ilte red and 3 .0 g (18.4 mmol) of NII4P F G was added to the hot s t i r r in g solution.

As the solution cooled.to room tem p era tu re with s tir r in g , the red -b ro w n p roduct

p rec ip ita ted . The com plex w as co llected by filtra tio n , washed with ethanol and

diethyl e th e r , and dried under vacuum . It w as re c ry s ta lliz e d by d isso lv ing i t in a

m inim um of ace to n itr ile , f ilte r in g the solution, and then adding ethanol until the

p ro d u c t p rec ip ita ted . B ased on the ligand sa lt, the y ields w ere 65-88%.

33

[Bromo(5, 7 ,7 ,1 2 ,1 4 , l4 -h e x a m e th y l- l ,4 ,8 , l l - te tr a a z a c y c lo te tr a d e c a -4 ,11-

diene)chrom ium (II) jhexafluorophosphate, [Cr(MeR[1 4 ]4 ,ll-d ie n e N JB rjP F e and

[Iodo(5,7 ,7 ,1 2 ,1 4 ,1 4 -h ex am eth y l-1 ,4 ,8 , l l- te tra a z a c y c lo te tra d e c a -4 ,1 1 -d ie n e )-

chromium(H) jhexafluorophosphate, [Cr(MeR[l4]4, ll-d ien eN ^IjP F fi. — These

two i’ed-brow n com plexes w ere p re p a re d by the above m ethod using C rB r2 • 6py

and C rl2 • 6py as the m etal so u rc e s . The y ields w ere 6 6 jo and 6 8 $ resp ec tiv e ly ,

based on the ligand sa lt.

[Thjocyanato(5,7 ,7 ,1 2 ,1 4 , i4 -h e x a m e th y l- l ,4 ,8 ,1 1 - te tra a z a c y c lo te tra d e c a -

4 ,1 1-diene)chrom ium (II)Jhexafluorophosphate, [Cr(MeR[l4 j4 , ll-dieneN ,i)N CS]PFR. —

To a s lu r ry of 1.25 g (2.44 mmol) of [Cr(M eG[l4]4, ll-d ien eN ^C ljP F g in 50 m l of

hot e th a io l was added 0 .4 g (4.93 mmol) of NaSCN. The brow n solution was

refluxed for 5 m in and then f ilte re d . The volume was reduced under vacuum until

the brown product p rec ip ita ted . T t was co llected by filtra tio n , washed with

e th a io l and diethyl e th e r , and d ried under vacuum . The com plex was re c ry s ta lliz e d

from e th a io l. The yield w as 68f0 based on the s ta rtin g com plex.

[P y rid in e(5 ,7 ,7 , 12,14, l4 -h e x a m e th y l- l ,4 ,8 , l l - te tra a z a c y c lo te tra d e c a -4 ,11-

diene)chrom ium (II)Jhexafluorophosphate, [Cr(MeR[14]4, li-d ieneN .4)py j(P F fi)?. — To

50 m l of ethanol containing 5.8 g (10 mmol) of Me6[l4]4, ll-d ie n e N /1 • 2CF3S03H

a id 6 . 7 g (10 mmol) of C r(C F 3S03)2 • 4py w as added an excess of trie thy lam ine

causing the solution to tu rn brow n. The solution was refluxed fo r a sh o rt tim e and

then f ilte re d hot. To the hot f il tra te w as added 5 .0 g (31 mmol) of NH4P F 6 and the

solution was again brought to re flu x . The brown solution w as allowed to cool with

s tir r in g resu ltin g in the p rec ip ita tio n of a brow n product. The com plex was

co llected by filtra tio n , w ashed with e th a io l a id diethyl e th e r , and d ried under

vacuum . The com plex was re c ry s ta lliz e d by dissolving it in a m inim um amount

of hot pyrid ine, f ilte rin g the hot solution, a id then adding e th a io l to cause

c ry sta lliza tio n . The yield was 83$ based on the ligand sa lt.

34

[N itro (5 ,7, 7 ,1 2 ,1 4 ,1 4 -h ex am eth y l-l,4 ,8 , l l - te tr a a z a c y c lo te tr a d e c a -4 ,11-

d iene)n itrosy lchrom ium (3) Jhexafluorophosphate, [Cr(MeK[14j4, ll-d ieneN /)(N O )-

(NO?)]P F fi. — To a solution consisting of 1 .0 g (1.43 mmol) of [Cr(M ee[ i4 j4 ,11-

dieneN4)pyJ(PF6)2 d isso lved in a m ix ture of 35 m l of ace to n itrile and 15 m l of

ethanol was added 0 .25 g (3.62 mmol) of sodium n itr ite . The solution w as s t i r re d

fo r 30 min a t room tem p era tu re and then f ilte re d . A fter the volum e had been

reduced under vacuum to 10 m l, 30 m l of ethanol w ere added and the volume was

again reduced until the g reen p roduct c ry s ta llized . The com plex was co llec ted

by filtra tio n , w ashed with diethyl e th er and ethanol, and d ried under vacuum .

It was re c ry s ta lliz e d by dissolving it in a m inim um am ount of ace to n itrile ,

f ilte rin g the solution, and then adding ethanol to cause the product to p rec ip ita te .

The y ield was 43$ based on the s ta rtin g com plex. The halogen com plexes could

also be used to p rep are the com plex.

[Dichloro(5, 7 ,7 ,1 2 ,1 4 ,1 4 -h ex am eth y l-l,4 ,8 , l l - te tr a a z a c y c lo te tr a d e c a -4 ,11-

diene)chrom ium (H I)Jhexafluorophosphate, [Cr(MeR[ l4 ]4 ,11 -dieneN JC 19]P F R and

[Dibromo(5, 7, 7 ,1 2 ,1 4 ,1 4 -h ex am e th y l-l,4 ,8 , l l - te tr a a z a c y c lo te tr a d e c a -4 ,11-

diene)chrom ium (III) jhexafluorophosphate, [C r(M e Jl4 ]4 ,11-dieneISh)Br9 ] P F fi. —

A sealed v ia l containing the chromium(U) com plex was rem oved from the glove

box and disso lved under n itrogen in 50 ml of ace to n itrile . When a slig h t ex cess

of the appropria te halogen (Cl2 o r B r2) was introduced to the brow n solution, the

co lor of the solution im m ediately changed indicating oxidation of the m etal ion.

A la rg e ex cess of am m onium hexafluorophosphate was added to th is solution.

The solution volume was reduced under vacuum to about 10 m l and then 80 m l of

ethanol was added. The volum e of the solution was again reduced until the

p roduct c ry s ta lliz e d . The com plex was co llected by filtra tio n , w ashed with

w ate r, ethanol, and diethyl e th e r , and d ried under vacuum . Both com plexes

w ere re c ry s ta lliz e d by d issolving them in a m inim um am ount of ace to n itr ile ,

f ilte rin g the solution, and then adding ethanol causing the com plexes to c ry s ta lliz e .

The y ie lds fo r the purple d ichloro com plex and the pink dibrom o com plex w ere

60-80$ based on the s ta rtin g com plex.

35

[D icyano(5,7, 7 ,1 2 ,1 4 ,14 -hexam ethy l-l, 4 , 8 , 1 1 -te traazacy c lo te trad eca -

4-, ll-d iene)chrom ium (III)]hexafluorophosphate, [Cr(Mefi[l4]4, ll-d ie n e N 4)(CN)?]-

P F (; and [D ithiocyanato{5,7, 7 ,1 2 ,1 4 ,1 4 -h e x am e th y l-l,4 , 8 , 1 1 - te tra az ac y c lo te tra -

deca-4 , ll-d iene)chrom ium (III) jhexafluorophosphate, [Cr(Mefi[l4]4 , ll-d ie n e N A)-

(NCS)?]PFfi. — To 100 m l of w ater w ere added 2 m m ol of [Cr(M e6[ l4 ]4 ,11-

dieneN4)Cl2]P F G and 6 m m ol of NaSCN o r NaCN. T his w as heated on a steam

bath fo r 30 m in resu ltin g in the d isso lu tion of the s ta r tin g com plex and a co lor

change of purp le to o range. A la rg e ex cess of am m onium hexafluorophosphate

was added to the hot solution and as the solution cooled to room tem p e ra tu re ,

the product c ry s ta llized . It was co llected by filtra tio n , w ashed with w ater,

ethanol, and diethyl e th e r , and d ried under vacuum . The com plexes w ere

re c ry s ta lliz e d by dissolving them in a m inim um am ount of ace to n itr ile , f ilte rin g

the solution, and adding ethanol causing them to p rec ip ita te . The yields of the

yellow cyanide and orange thiocyanate com plexes w ere 35-50$ based on the

s ta r tin g com plex.

D i(chloro or b rom o)(m eso-5 , 5, 7 ,1 2 ,1 2 ,1 4 -h e x am e th y l-l,4 , 8 , 1 1 -te tra a za -

c.yclote trad e cane) chrom ium (Il), Cr(M eR[l4 ]aneN/i)X9, ( X - Cl o r B r). — These

com plexes w ere p rep a red using the. method of S p e ra ti . 10

B is(th iocyanato)(m eso-5, 5 ,7 ,1 2 ,1 2 ,1 4 -h ex am eth y l-l,4 , 8 , 11-tetraazac.yclo-

tetradecane)chrom ium (II), Cr(M eR[!4]aneN,i)(NCS)2. — To 1.0 g (2.45 mmol) of

Cr(M e6[ l4 janeN4)C l2 d isso lved hi 50 m l of ethanol was added 0 .4 g (4.94 mmol)

of NaSCN. The solution was s t i r re d and heated causing the co lor of the solution

to change from blue to pink. A fter the solution had cooled to room tem p era tu re ,

the pink com plex was co llec ted by filtra tio n , w ashed with ethanol and diethyl

e th e r, and d ried imder vacuum . The yield was 88$ based on the s ta r tin g m a te r ia l.

36

[B is(ace to n itrile )(m eso -5 > 5 ,7 ,1 2 ,1 2 ,14 -hexam ethy l-l, 4 , 8 , 1 1 -te tra az a -

cyclo tetradecane)chrom ium (II)jhexafluorophosphate, [Cr(M eJl4]aneN,d (CIljCN)?]-

(P F k)?. — To a solution of 1 .0 g (2 .04 mmol) of [Cr(Me6[ l4 janeN4)(CH3CN)2]C1210

in 50 ml of ace to n itrile w as added 2 . 5 g (15,3 mmol) of NH4P F 6. A fter the volume

of the solution had been reduced to 15 m l, 40 m l of ethanol w ere added and the

volum e was again reduced resu ltin g in the p rec ip ita tio n of the pink p roduct.

The p roduct was co llected by filtra tio n , washed with ethanol and diethyl e th e r,

and d ried under vacuum . The yield based on the s ta rtin g com plex w as 84^.

RESULTS AND DISCUSSION

Syntheses and C h arac te riza tio n of Chromium(IIi) Com plexes with M e?[l4 ]te traene-

Nd, Me?[l5]te traeneN ii, M e?[l6 ]tetraeneN A> and Me/t[l4 ]te traeneN A.

P rep a ra tio n of [Cr(M e7[l4]tetraenatoN f))(py)9]PF(;, [C iiM e?[l5 jte ti-aenatoN ^-

(py)?]PFR, [Cr(M e9[ l6 ]te traenatoN A)(p.y)?]PFR, and [Cr(MeA[14]tetraenatoN ft)(p,y)9]-

P F Ro — Several methods can be used to p rep a re the com plexes XVII-XX. Since

the m ethods involve the use of a ir -se n s itiv e chromium(II) s a lts as s ta rtin g

p ;

X V II

+

PR:

CrH

+

PPC

X V III

+

PFo

PR.

XIX

37XX

38

m a te r ia ls , a ll of the p rep a ra tio n s w ere c a r r ie d out in a glove box under a n itrogen

a tm o sp h ere . Although chrom ium com plexes have been syn thesized em ploying

chrom ium sp ecies in the oxidation s ta te s of 0, II, and III, chromium(H) s ta rtin g

m a te ria ls w ere selected because of th e ir re ac tiv ity . Chromium(II) is known to be

very lab ile to ligand substitu tion reac tio n s while chrom ium (III) is substitu tion

in e rt. When the ra te constan ts fo r the exchange of w ater m olecu les from the

f i r s t coordination sphere of the m etal ions is considered , the m agnitude of the

difference in th e ir reac tiv ity becom es read ily apparen t. The ra te constan t fo r

chromium(H) is 7 x 109 s e c -1 while the ra te constan t fo r chrom ium (IIl) is 3 x 10~6

se c -1 . 89 Since m acrocyclic ligands a re known to coordinate m ore slowly by a few

o rd e rs of magnitude than s im ila r open chained lig an d s , 90 i t would seem that a

labile m etal ion is n ecessa ry to in sure com plexation within a reasonab le tim e

p eriod .

These com plexes w ere f i r s t p rep a red by refluxing anhydrous chrom ium (Il)

ace ta te and H2[Me2[Z]tetraeneN 4](P F 6)2 (Z = 14, 15, o r 16) in pyrid ine overnight

with e ith e r the acetate o r the pyrid ine deprotonating the ligand s a lts . This

method proved to be u nsa tisfac to ry as the p roducts w ere produced in low yields

and an excessive reac tio n tim e was re q u ire d . The ligand s a lts and C r(C F 3S03) 2 °

4py w ere found to re a c t read ily in hot pyridine upon adding trie th y lam in e to depro-

tonate the ligand sa lts . This method re su lte d in good y ie lds of highly c ry sta llin e

products in re la tiv e ly sh o rt tim e s . The p re fe r re d m ethod fo r the p rep a ra tio n of

these com plexes was the reac tio n of the ligand s a lts , C rC l2 * 2py, and tr ie th y l­

am ine in a refluxing solvent m ix ture of pyrid ine and ac e to n itr ile (equation 20 ).

*Cr \ P F 6(20)Y (PFe)2 + xsE%NC rC l2 • 2py +

Py

39

R = H o r C H g , X = -(CH2)2- = Y

R = H, X = -(CH2)2- , Y = -(CH2)3-

R = H, X = -(CH2)3- = Y

This reac tio n gave sligh tly low er y ields and le s s pu re p roducts than the prev ious

reac tio n but th is chrom ium (II) s ta rtin g m a te ria l was much e a s ie r to obtain.

Com plexes XVII-XX w ere iso lated as th e ir hexafluorophosphate sa lts by

reducing the volume of the reac tio n m ix ture to n ea r d ry n ess and then adding a

copious am ount of ethanol to induce c ry s ta lliza tio n . These com plexes w ere

re c ry s ta ll iz e d by d isso lv ing them in a m inim um am ount of pyrid ine and inducing

c ry sta lliza tio n by adding ethanol. They can a lso be pu rified by disso lv ing them

in pyrid ine and then passing the solutions through a 10-15 cm length colum n of

n eu tra l alum ina. All m anipulations m ust be p erfo rm ed in an in e r t a tm osphere.

In view of the conditions used fo r p rep arin g these com plexes, i t is unusual

that they contain chrom ium in the trip o sitiv e oxidation s ta te . C alderazzo e t al

have p rep a red tris(N -m ethylsalicylideneim inato)chrom ium (II3) by the reac tio n of

hexacarbonylchrom ium and N -m ethylsalicy lideneim ine in refluxing toluene for

6 .5 h o u rs . 91 T su tsu i and cow orkers allowed hexacarbonylchrom ium and m eso -

p o rp h y rin -IX -d im eth y lester to re a c t in refluxing decalin fo r 1 .5 hours obtaining

m esoporphyrin-IX -d im ethy lesterchrom ium (II) . 28 Since both of these com plexes

w ere p rep ared under n itrogen , i t was postu lated that the acid ic p ro tons on the

ligands w ere responsib le fo r the oxidation of the chrom ium . The m acrocyclic

ligands a re re la te d to the N -m ethy lsalicy lideneim ine and the porphyrin in that

they too have acid ic p ro to n s; th e re fo re , it seem s likely that th ese pro tons

im m ediately oxidize the in itia lly form ed chromium(II) com plex giving the

chromium(HI) com plex th a t is subsequently iso la ted . In addition, when the

com plexation reac tio n was c a r r ie d out a t room tem p era tu re , gas evolution was

observed indicating that the p ro tons do indeed a c t as the oxidizing agent and a re

reduced to hydrogen.

40

P rep a ra tio n of [Cr(Me?[Z]tetraenatoN A)(L)9]P F fi (Z = 14, 15, o r 16) and

[CrCMe^ [l4]tetraenatoN /t) (L)9]P F (; (L - dim eth.ylform am ide, 1-m ethylim idazole,

thiocyanate, or cyanide). — As has been p rev iously d iscu ssed , chromium(IQ)

com plexes a re considered to be re la tiv e ly substitu tion in e r t but the chromium(II])

com plexes, XVII-XX, w ere found to read ily undergo ax ial ligand substitu tion .

F le isc h e r and cow orkers found th a t the axial s ite s of the chromium(IH) com plex

w ith te tra(p-sulfonatophenyl)porphine, XXI, w ere substitu tionally la b i le .29’30

R eaction ra te s w ere m easu red fo r the rep lacem en t of axially coordinated w ater

X X I

•scy

m olecules by fluoride , cyanide, and pyrid ine. These r a te s w ere found to be

103-104 fa s te r than substitu tion r a te s of chrom ium (IIt) com plexes th a t did not

contain porphyrin ligands. This enhanced reac tiv ity is thought to be a re su lt of

extensive n-bonding betw een the d and d m etal o rb ita ls and the r r porphyrinyz xzo rb ita ls . This rr-bonding allows significant e lec tro n delocalization which re su lts

in g rea tly enhanced e lec tro n density on the chrom ium (M ) and th is , in tu rn ,

enhances the substitu tion lab ility of that m eta l containing sp ec ies . Since the

chromium(III) com plexes, XVII-XX, a re s tru c tu ra lly s im ila r to the chromium(HI)

tetra(p-sulfonatophenyl)porphyrin com plexes, these com plexes should a lso

involve extensive n -in te rac tio n which would r e s u lt in lab ilization of groups in the

ax ial s ite s .

41

Making use of the lab ility of the axial pyrid ine ligands, a num ber of sim ple

d eriv a tiv es w ere p rep a red in the d ry box utilizing re la tiv e ly m ild conditions.

Employing m eta th esis re a c tio n s , com plexes w ere iso lated containing 1-m ethyl­

im idazole, d im ethylform am ide, th iocyanate, and cyanide a s ax ial ligands (equa­

tions 21-23). The b is- l-m e th y lim id az o le d eriv a tiv es w ere p rep a red by adding an

excess of 1-m ethylim idazole to acetone so lutions of the re sp e c tiv e b is-p y rid in e

com plexes in a m inim um am ount of acetone and adding ethanol to induce c ry s ta l­

lization.

XVH-XX + L

L = M e-Im or dmf

XVII-XX + NaSCN S 5 lC.»

XVII-XIX + NaCNMe OH &

NCS

X X II

N

x x i n

X X IV

(21)

(22)

(23)

To p rep a re the dim ethylform am ide d e riv a tiv e s , the re sp ec tiv e b is-p y rid in e

com plexes w ere d isso lved in dim ethylform am ide (equation 21). A fter the volum es

of the solutions w ere reduced to n ea r d ry n ess , ethanol w as added p rec ip ita ting

the cationic com plexes as th e ir hexafluorophosphate s a lts , A la rg e volum e of

dim ethylform am ide was used to guaran tee the rem oval of a ll the pyridine from

the reac tio n solutions when die volum e was reduced under vacuum . Since pyridine

is a s tro n g e r donor than d im ethylform am ide, m ix tu res of the s ta rtin g com plex and

the d es ired derivative w ill be obtained if a ll the pyridine is n<?t rem oved from

the reac tion solution. T hese com plexes w ere re c ry s ta ll iz e d by dissolving them

in a m inim um volume of d im ethylform am ide and adding ethanol to cause p re c ip i­

tation , D im ethylform am ide so lu tions of these com plexes can also be p assed through

a 10-15 cm length alum ina colum n.

42

Adding ex cess NaSCN to ace to n itr ile solutions of the cationic b is-p y rid in e

com plexes re su lte d in the fo rm ation of n eu tra l thiocyanate com plexes with one

thiocyanate rep lacing one of the ax ial pyrid ine ligands (equation 22). The th io­

cyanate com plexes w ith the 14-m em bered m acrocycles a re not very soluble in

ace to n itrile and they c ry s ta lliz e upon fo rm ation . The d eriv a tiv es with the 15-

and 16-m em bered m acro cy c les have b e tte r solubility; th e re fo re , i t is n ecessa ry

to reduce the volume of the ace to n itr ile so lu tions and add ethanol to iso la te the

c ry sta llin e p ro d u c ts . T hese com plexes w ere re c ry s ta ll iz e d from e th an o l-p y ri-

dine m ix tu res . Since th e ir so lubility was not good in cold pyrid ine, they w ere

not subjected to chrom atography on alum ina.

The cyanide d eriv a tiv es w ere p re p a re d by refluxing m ethanol solutions

containing the pyrid ine com plexes d isso lved in ace to n itrile and ex cess NaCN

(equation 23). Extended reflux is n e c e ssa ry because n e ither the pyridine

com plex nor the NaCN a re v ery soluble in m ethanol. The volume of the reac tio n

solutions w as reduced to n ea r d ry n ess , d im ethylform am ide was added, and the

volume was again reduced until the p roduct p rec ip ita ted . T hese com plexes a re

ex trem ely soluble in a v a rie ty of solvents when any pyrid ine is p re se n t and

ex trem ely insoluble when i t is absen t. T h e re fo re , the addition of the dim ethyl­

form am ide and the subsequent volum e reduction is req u ired to in su re the rem oval

of the pyridine and to allow solid products to be iso la ted . The cyanide deriva tives

a re n eu tra l com plexes which have a cyanide m olecule in one ax ial coordination site

but, unlike the thiocyanate com plexes, they do not have a pyridine m olecule in the

o ther s ite . These com plexes can a lso be p rep a red by the reac tio n of the

dim ethylform am ide derivative with NaCN in m ethanol. As no pyridine is p re se n t,

the cyanide com plex p re c ip ita te s im m ediately upon form ation . They w ere

re c ry s ta lliz e d by d isso lv ing them in a m inim um of pyrid ine , adding a la rge

quantity of d im ethylform am ide, and reducing the volume until the com plexes

p rec ip ita ted . P yrid ine solutions of these com plexes can be p assed through

alum ina colum ns (10-15 cm in length) fo r fu rth e r purification .

43

C h arac te riza tio n of [Cr(M e?[Z]tetraenatoN,i)(L)9]PFfl (Z = 14, 15, o r 16) and

[C r(Me,t [ 14]tetraenatoN ^)(L)? j P F R (L = pyrid ine, d im ethylform am ide, and 1-m ethyl­

im idazole) . — The six -coo rd ina te cationic chromium(III) com plexes, [Cr(Me2-

[Z]tetraenatoN 4)(L)2]P F e (Z = 14, 15, o r 16) and [Cr(Me4[l4]tetraenatoN 4)(L)2]P F G

(L = py, dmf, and M e-Im ), have been assigned s tru c tu re s XVII-XX and XXII. The

com positions of these com plexes a re co n sis ten t with the given form ulations as

shown by th e ir analy tical da ta (Table 1) „ The in fra red sp e c tra of these com plexes

indicates the p resence of the m acrocyclic ligands, the type of ax ial ligands

p re se n t, and the p resen ce of the hexafluorophosphate anion. Sample in fra red

sp e c tra a re p resen ted in F ig u res 1-3 and se lected in fra red abso rp tions fo r a ll

of the com plexes a re given in Table 2.

The in fra red sp e c tra of the chrom ium com plexes have bands o ccu rrin g in the

double bond reg ion which a re very s im ila r to those observed in the in fra red

sp e c tra of iron(II) com plexes with the sam e l ig a n d s .15 An incom plete c ry s ta l

s tru c tu re on Fe(Me6[l5]tetraenatoN 4) shows that the com plex is e ssen tia lly

s q u a re -p la n a r .92 Also, these m acrocyclic ligands have been re p o rte d to fo rm

sq u a re -p lan a r com plexes with a num ber of o ther d ivalent m eta l io n s .15-16

In view of th is evidence the m acrocyclic ligands of the chrom ium com plexes

a re assum ed to be in an e ssen tia lly p lan ar a rran g em en t around the chrom ium

m etal ion and to have two negative ch a rg es. Knowing that the chromium(III)

ion and the ligand a re in a p lan a r configuration, a ll of the m onodentate ligands

m ust th e re fo re be tra n s to. each o ther occupying coordination s ite s above and

below the plane of the r in g . The m olar conductiv ities (Table 3) of these

com plexes a re indicative of 1:1 e le c tro ly te s93 which supports the form ulation

of the com plexes as univalent cationic sp ec ies .

M agnetic suscep tib ility m easu rem en ts and ESR sp e c tra w ere used to

substan tiate that the chrom ium ion is in the trip o sitiv e oxidation s ta te . The

so lid -s ta te m agnetic m om ents of these com plexes (Table 3) range from 3. 79-

3 .97 B .M . and a re in good ag reem ent with the spin-only value of 3 .87 B .M .

for 3 unpaired e lec tro n s . Due to sp in -o rb it coupling the m agnetic moments

Table 1

A nalytical Data fo r the Com plexes, [Cr(Mex [Z]tetraenatoN 4)(L) 2 ] P F 6.Calc. <! Found %

x_ JZ_ L C H N C H N

2 14 Py 46.08 4.92 14.65 45.76 5.02 14.76

2 15 Py 47.02 5,15 14.30 47.08 5.21 14.14

2 16 Py 47.92 5.36 13.97 48.17 5.22 13.78

4 14 Py 47.92 5.36 13.97 48.01 5.45 13.95

2 14 dmf 38.51 4 .75 14.97 38.50 5.64 15.01

2 15 dmf 39.66 5.96 14.60 39.57 5.90 14.23

2 16 dmf 40.75 6.16 14.26 40.52 6.18 14.23

4 14 dmf 40.75 6.16 14.26 40.84 6.14 14.16

2 14 M e-Im 41.45 5.22 19.34 41.20 5.30 19.25

2 15 M e-Im 42.50 5.43 18.88 42.57 5.42 18.87

2 16 M e-Im 43.49 5.64 18.44 43.42 5.64 18.34

4 14 M e-Im 43.49 5.64 18.44 43.38 5.65 18.37

600 40016 00 10001200 8001400

F re q u e n c y (c m *)

F ig u r e 1. I n f r a r e d S p e c t r u m of [C r (M e 2[ l4 ] t e t r a e n a to N 4)(P y)2] P F 6.

—I__600

1_ l___1Z00

_J—

1000 4001600 8001400F re q u e n c y (c m -1 )

F ig u r e 2 . I n f r a r e d S p e c t r u m of [C r (M e 2[ l4 ] t e t r a e n a to N 4)(D m f)2]P F 6 „

C5

6001600 1200F re q u e n c y (c m ""1)

1000 80014003000

F ig u r e 3„ I n f r a r e d S p e c t r u m of [C r(M e 4[ l4 ] t e t r a e n a to N 4) (M e -Im )2]PF6.

Table 2

Selected Infrared A bsorptions of the Com plexes

x_ Z_ L Double Bond Region

2 14 py 1569, 1502

2 15 py 1574, 1510

2 16 py 1582, 1518

4 14 py 1535, 1515

2 14 dmf 1572

2 15 dmf 1580

2 16 dmf 1576

4 14 dmf 1550, 1517, 1497

2 14 M e-Im 1570, 1532, 1499

2 15 M e-Im 1585, 1535, 1510

2 16 M e-Im 1575, 1535, 1512

4 14 M e-Im 1558, 1540, 1521

a Units a re cm -1.

[Cr(Mex [Z]tetraenatoN 4) (L)2]PF6. a

L P F fi

1608 840, 560

1604 840, 560

1608 840, 560

1605 840, 560

1642 840, 560

1645 840, 560

1646 840, 560

1650 840, 560

3120 840, 560

3120 840, 560

3122 840, 560

3125 840, 560

oo

Table 3

Physical P ro p e rtie s of the Com plexes, [Cr(Mex [Z]tetraenatoN 4)(L)2]PFG„

x_ Z_ JL_ Color (B .M .) A]vi(cm2ohm

2 14 py green 3.90 80

2 15 py brown 3.83 86

2 16 py orange 3.87 82

4 14 py green 3.87 86

2 14 dmf red 3.82 89

2 15 dmf orange 3.84 82

2 16 dmf orange 3.97 87

4 14 dmf red 3.79 91

2 14 M e-Im red 3.84 75

2 15 M e-Im red 3.87 85

2 16 M e-Im orange 3.87 81

4 14 M e-Im red 3.82 95

d e te r m in e d by the F araday m ethod a t room tem p era tu re . D eterm ined a t room tem p era tu re using 1 x 10-3M CH3N 02 so lutions.

CD

50

for chromium(IH) com plexes a re expected to be reduced below the spin-only

value (|i = (1-4 A/10 Dq)fj, sp in-only). Since the sp in -o rb it coupling constant

(A.) for chromium(IQ) is sm all and p o sitiv e , the reduction in the m om ents is

ra th e r sm all, often approxim ate ly 4 $ .94 V aria tions due to such d ifficu lties as

u n certa in tie s in diam agnetic c o rrec tio n s often exceed th is value.

The m agnetic su scep tib ilitie s of the b is-p y rid in e com plexes, XVII-XX,

w ere m easu red over the tem p era tu re range from 98°K to 330°K. The data from

these m easu rem en ts is p re sen ted in T ables 4 -7 . As shown by the s tra ig h t line

g raphs in F ig u re 4, these com plexes obey the C urie-W eiss law ( V x m = C /-

(T + 9)) over the tem p era tu re range studied . M agnetic m om ents app ropria te to

the en tire tem p era tu re range can be calcu lated from the slopes of the s tra ig h t

lines from the g raphs of 1/ x m v e rsu s te m p e ra tu re . The m om ents and W eiss

constan ts (Table 8) fo r the b is-p y rid in e com plexes w ere calcu la ted from the

slopes which w ere determ ined using a le a s t sq u ares calculation .

The com plicated fro zen solution ESR sp ec tra of these com plexes a re

indicative of a chrom ium (III) ion in a te tragonal environm ent. No n itrogen or

chrom ium hyperfine sp littings w ere observed in these sp e c tra . These sp ec tra

w ill be d iscu ssed in g re a te r d e ta il in a la te r section of the th e s is .

The e lec tro n ic sp e c tra of these cationic com plexes have a la rg e num ber of

absorp tions with la rg e m o lar-ex tin c tio n coefficien ts indicating an extensive

am ount of m ixing betw een the ligand and m etal o rb ita ls . The e lec tro n ic sp ec tra

of the com plexes having 14- and 15-m em bered m acrocycles a re s im ila r in

na tu re but the sp e c tra of the com plexes with the 16-m em bered m acrocycle a re

m arkedly d ifferen t a s they p o sse ss few er bands and no bands low er in energy

than 18 kK.

P o laro g rap h ic m easu rem en ts on these com plexes show, in g en era l, two

oxidations and one reduction . One of the oxidations o ccu rs n ea r 0 .0 volts vs

Ag/AgNOg in a ce to n itr ile and th is cau ses these com plexes to be a ir -s e n s itiv e .

Both the e lec tro n ic sp e c tra and the e lec tro ch em istry of the cationic com plexes

w ill be the sub jec t of fu rth e r d iscussion .

51

Table 4

T em p era tu re Dependence of the M agnetic Susceptib ility of

[Cr(Me2[i4 ]te traenatoN 4) (py)2]P F 6. a

T(K) 1 / x m ’ H eff(B ,M *)

98.1 61.1 3 .59

134.8 79.1 3 .69

152.9 87.8 3 .74

189.3 104.3 3.81

210 .9 114.9 3.83

240 .1 129.2 3 .86

27 0 .5 144.4 3 .87

302.8 155.5 3 .95

329.6 168.1 3.96

d e te r m in e d by the F araday m ethod. ^U nits a re x iO6 cgs. d ia m a g n e tic cor-* "“6rec tio n of 335 x 10 'cgsu using P a s c a l 's constan ts .

52

Table 5

T em p era tu re Dependence of the M agnetic Susceptib ility of

[Cr(M e2[i5 ]te traenatoN 4) (py)2]P F 6. a

T (K) V x m *3’ 0 Meff

103.2 61 .9 3 .65

137.7 80 .7 3 .70

155.7 89 .7 3 .73

188.3 109.6 3 .71

213.0 121.8 3.74

242 .4 133.4 3.81

268 .5 146.9 3.82

300.2 162.1 3 .85

328.8 173.1 3 .90

aD eterm ined by the Faraday Method. Units a re x l0 6cgs. CDiamagnetic c o r ­rec tion of 347 x i0~6cgsu using P a s c a l 's constants.

53

Table 6

T em peratu re Dependence of the M agnetic Susceptib ility of

[Cr(Me2 [!6]tetraenatoN 4) (py)2]P F G. a

T (k) VXM b ’ C Ueff (B

103.8 62.4 3.65

137. 5 78.1 3.74

164.6 91.6 3.79

195.7 107.6 3.81

217.2 117.9 3.84

243.3 130.7 3.86

264 .6 141.6 3.87

303.6 159.4 3.90

329.5 171.9 3.92

d e t e r m i n e d by the F araday method. d n i t s a re x 106 cgs. d i a m a g n e t i c c o r ­rec tion of 359 x 10-Gcgsu using P a s c a l 's constants.

54

Table 7

T em p era tu re Dependence of the M agnetic Susceptib ility of

[Cr (Me4 [!4]tetraenatoN 4) (py)2|P F G. a

T(K) . / D , CX_M ..... ■ Feff (B:

101.6 63 .0 3.59

132.4 77 .4 3.70

164.2 96.8 3.68

195.2 114.1 3.70

222. 5 127.5 3.74

247.9 141.2 3 .75

273. 5 155.0 3.76

301.6 167. 5 3.79

330. 1 175.7 3.88

a D eterm ined by the Faraday Method,, Units a re x 10G cgs. CDiamagnetic c o r ­rec tion of 359 x iO-(fcgsu using P a s c a l 's constants .

55

170

160

150

140

130

120

80

70

150 200 250100 300T e m p e r a tu r e (°K)

F ig u re 4„ V a r ia t io n of 1 /x w ith T e m p e r a tu r e f o r : ® - [C r(M e 4[ 1 4 ] te tra e n a to N 4)( P y ^ ] P F ( , / ^ - [ C r ( M e 2[ 14 ] te tr a e n a to N 4)( P y)2]- P F 6s° @ - [C r (M e 2[ l5 ] te t r a e n a to N 4)(P y )2]P F 6 ; and ^ - [C r(M e 2[ l6 ]- t e t r a e n a to N 4)(P y )2]P F 6 .

56

Table 8

M agnetic M oments and W eiss C onstants C alculated from the V ariab le

T em p era tu re M agnetic Susceptib ility D ata of the B is-p y rid in e C om plexes.

Complex p. (B. M.) 8 (K)

[Cr(Me2[l4]tetraenatoN4)(py)2]PF6 4 . 17 36

[Cr(M e2[l5]tetraenatoN 4)(py)2]PF6 4 .0 3 27

[Cr(M e2[i6]tetraenatoN 4)(py)2]PFG 4 .0 6 24

[Cr(Me4[l4]tetraenatoN 4)(py)2]P F 6 3 .97 24

57

C h arac te riza tio n of Cr(M e?[Z]tetraenatoN,i)(NCS)(py), C r(M e J l4 jte tra e n a to -

N^)(NCS)(py), and Cr(M e9[Z]tetraenatoN 4)CN (Z = 14, 15, o r 16). — T hese

n eu tra l com plexes a re assigned s tru c tu re s XXIII and XXIV. As is the ca se

with the cationic com plexes, these com plexes a re assum ed to have the ligand in

an essen tia lly p lanar configuration about the m etal ion. The e lem ental analyses

for these com plexes a re given in Table 9 and they confirm the assigned fo rm ula­

tions. R epresen ta tiv e in fra re d sp e c tra a re p resen ted in F ig u res 5 and 6 and

se lec ted in fra red absorp tion bands fo r a ll of these com plexes a re rep o rted in

Table 10. In fra re d sp ec tro scopy proved v ery usefu l in estab lish ing the p resen ce

of pyrid ine in the thiocyanate com plexes and its absence in the cyanide com plexes.

E lem ental an a ly ses suggest th a t the thiocyanate com plexes a re six -coo rd ina te

and th a t the cyanide com plexes m ay be five-coord inate in the so lid -s ta te . The

n eu tra lity of these spec ies w as estab lish ed by th e ir m olar conductivity m e asu re ­

m ents (Table 11) which a re w ell below values fo r e le c tro ly te s .93

The oxidation sta te of the chrom ium ion in these com plexes w as estab lish ed

by the m agnetic su scep tib ility data in Table 11. The so lid -s ta te m agnetic

m om ents fo r the thiocyanate com plexes ag ree quite w ell with accepted values fo r

d3 m etal ions but the m om ents fo r the cyanide com plexes a re about 0 .5 B. M.

below the spin-only value of 3 .8 7 B .M . Even by taking into account experim en tal

e r r o r and sp in -o rb it coupling the m easu red m agnetic m om ents a re s ti l l too low.

The so lubility behavior of th ese com plexes and th e ir low solid s ta te m om ents im ply

that in the so lid -s ta te the cyanide com plexes a re probably po lym eric in natu re

having Cr(IH )-CN -Cr(III) b rid g es but while in solution a re s ix -coo rd ina te having

a pyrid ine ligand tra n s to the cyanide ligand. To substan tiate th is hypothesis,

solution su scep tib ility m easu rem en ts w ere p erfo rm ed on py rid ine-n itrom ethane

solutions of these com plexes. The m om ents obtained from these m easu rem en ts

(Table 11) a re much higher than the so lid -s ta te m om ents and ag ree quite w ell

with expected values fo r chromium(HI) com plexes.

Table 9

A nalytical Data for the C om plexes, Cr(M ex [Z]tetraenatoN 4)(A)(B).

Calc, j Found <%>X Z_ A_ B_ c_ _H_

2 14 NCS py 53.06 5.69

2 15 NCS py 54.14 5.98

2 16 NCS py 55.15 6.25

4 14 NCS py 55.15 6.25

2 14 CN — 52.69 6.12

2 15 CN — 54.18 6.50

2 16 CN _ — 55.54 6.84

A A J L A

20.63 53.11 5 .44 20.46

19.94 54.26 5.92 19.83

19.30 55.20 6 .37 19.24

19.30 55.34 6 .32 19.40

23.63 52.40 6 .09 23.51

22.57 53.81 6 .71 22.34

21.59 55.39 6 .68 21.45

Cl00

16002000 1800 1400 10001200 800F re q u e n c y (c m “ )

F ig u r e 5. I n f r a r e d S p ec tru m , of C r ( M e 2[ l6 ] t e t r a e n a to N 4)(N C S)(Py).

C lo

L _ _

2000_J___1800 1600 1400 1200

F re q u e n c y (cm.-1 )

I1000 800

F ig u r e 6 . I n f r a r e d S p e c t r u m of C r (M e 2[ l5 ] t e t r a e n a to N 4)CN.

Table 10clSelected Infrared A bsorption Bands of the C om plexes, Cr(M ex [Z]tetraenatoN 4)(A)(B).

X Z_ A_ B_ Double Bond Region CN m . c s

2 14 NCS py 1570, 1500 2082 1602 770

2 15 NCS py 1580, 1508 2092 1597 772

2 16 NCS py 1575, 1505 2090 1608 775

4 14 NCS py 1560, 1525 2090 1685 775

2 14 CN — 1580, 1503 2140 — —

2 15 CN — 1585, 1509 2145 . — —

2 16 CN 1582, 1515, 1493 2155 — - _____

a Units a re cm -1.

Table 11

P hysical P ro p e rtie s of the Com plexes, Cr(Me [Z]tetraenatoN |)(A )(B).X

X Z_ A_ B_ Color Ueff (B .M .)a A ]yj( cm2ohm -1m or

2 14 NCS py g reen 3.93 I2b

2 15 NCS py brown 3.80 2b

2 16 NCS py orange 3.78 9b

4 14 NCS py g reen 3.92 I2b

2 14 . CN — g reen 3.38 (3 .88)d i C

2 15 CN — green 3.39 (3 .84)d 1C

2 16 CN — orange 3.22 (3 .80)d 1C

3. bD eterm ined by the F araday method a t room tem p era tu re . D eterm ined a t room tem p era tu re on lO ^M CH3N 02 solutions.°D eterm ined a t room tem p era tu re on 10-3M pyridine solutions. D eterm ined by the Evans method a t room tem pera tu re

in CH3N 02-pyrid ine solution.

63

The frozen solution ESR s p e c tra of the thiocyanate and cyanide com plexes

a re much the sam e a s those of the cationic com plexes. The low tem p era tu re

so lid -s ta te ESR sp e c tra of the cyanide com plexes has a v e ry b ro ad intense

absorption a t about g = 2. A ll of the o th er com plexes studied gave no absorp tions

in the so lid -s ta te . This indicates the so lid -s ta te s tru c tu re of the cyanide com plex

d iffers significantly from the o th e rs . The oxidation po ten tia ls fo r the n eu tra l

com plexes a re low er than a re those of the co rresponding cationic com plexes with

the sam e m acrocycle . The e lec tron ic sp e c tra a lso re sem b le those obtained with

the cationic com plexes. The ESR sp e c tra , e lec tro ch em ica l m easu rem en ts and

e lec tron ic sp e c tra of these n eu tra l com plexes w ill be d iscu ssed la te r in m ore

de ta il.

Oxidation and Other R eactions of the Chromium(IU) C om plexes. — In view

of the low oxidation po ten tia ls exhibited by these com plexes, chem ical oxidations

w ere attem pted with a v a rie ty of oxidizing agen ts. The reac tio n of [Cr(M e2[l4 ]-

tetraenatoN,j)(py)2jP F 6 with Cl2, 0 2, and (NH4)Ce(N03)6 in a v a rie ty of solvents

produced no ch a rac te riza b le com pounds. F ro m these reac tio n s only insoluble

dark-brow n or b lack powders w ere obtained indicating th a t the m acrocycle was

probably destroyed . The le s s pow erful oxidizing agents I2 and K3Fe(CN)6 w ere

tr ie d on the sam e com plex. The K3Fe(CN)e is probably too weak an oxidizing

agent a s only s ta rtin g m a te ria l w as reco v e red from the sy stem .

The reac tio n of the g reen com plex with ex cess I2 or I3“ in refluxing p y r i­

dine re su lte d in the fo rm ation of an a ir -s e n s itiv e , dark-brow n c ry sta llin e

p roduct. The in fra red spectrum of th is com plex is s im ila r to that of the

s ta rtin g m a te ria l suggesting that the ligand is s ti l l p re se n t. The elem ental

analysis of the complex ag rees w ell with th a t calcu la ted fo r the s ta r tin g complex.

(Found C, 46.04; H, 5 .02 ; N, 14.79; C alcd. f . C, 4 6 .08 ; H, 4 .9 2 ; N, 14 .65 .)

The m olar conductance value in CH3N02 of 82 cm 2ohm -1m ol-1 is co n sis ten t with

the p resen ce of a 1:1 e le c tro ly te ,93 and the so lid -s ta te m agnetic m om ent of 3 .82

B. M. indicates that the chrom ium ion is in the .tripositive oxidation s ta te .

64

The e lec tro n ic spectrum in ace to n itr ile is as follows: 8 .3 kK (sh, 84), 14.7 (670),

19.6 (sh, 1690), 23 .3 (sh, 2330), and 29 .8 (sh, 3000). As would be expected

from the color change, th is e lec tro n ic spec trum is quite d ifferen t from th a t of

the s ta rtin g com plex. A p lausib le explanation fo r these observations is tha t the

m acrocycle has been a lte re d by oxidative dehydrogenation re su ltin g in a g re a te r

degree of unsaturation . Holm and cow orkers have rep o rted oxidative dehydrogena­

tion reac tio n s with s im ila r F e , Ni, Co, and Cu m acrocyclic co m p le x e s .19 If

indeed oxidative dehydrogenation has o ccu rred , the com plex m ay have s tru c tu re

XXV.

PR

XXV

The reac tio n s of the ckromium(IH) com plexes with n itr ic oxide and carbon

monoxide w ere investigated . No reac tio n was observed when carbon monoxide was

bubbled through an ace to n itr ile solution of [Cr(M e2[l4]te traenatoN 4)(py)2]PFe. A

reac tio n was observed when an ace to n itrile solution of the sam e com plex was

exposed to n itr ic oxide. The green solution turned brow n, but only ta r s o r

insoluble dark-brow n pow ders could be iso la ted suggesting extensive decom posi­

tion.

65

In addition to the re p o rte d d e riv a tiv es having various ax ial ligands, the

p rep a ra tio n s of o ther sim ple d e riv a tiv es such a s azide and the halides w ere

a ttem pted . The re a c tio n s of sodium azide and lithium chloride w ith [Cr(Me2[l4 ]-

tetraenatoN 4)(py)2]PF6 in v ario u s po lar so lvents re su lted only in iso la tion of the

s ta r tin g com plex. It w as suspected tha t since pyrid ine is a s trong ligand, perhaps

azide and chloride ions m ight not be s trong enough ligands to d isp lace i t . 95

T h e re fo re , these ions w ere allow ed to re a c t with [Cr(Me2[i4]te traenatoN 4)(dmf)2]-

P F G in acetone or a lcohols. Again, only the s ta rtin g com plex was iso la ted from

the reac tio n s . These re s u l ts seem to suggest that these com plexes w ill coordinate

n eu tra l ligands but w ill only coordinate s trong anionic ligands.

The com plexes [Cr(Me2[i4]tetraenatoN 4)(py)2]P F 6 and [Cr(M e2[i5 ]te traen a to -

N4)(py)2]P F G re a c t with p o tassiu m t-butoxide in diethyl e th e r o r te trah y d ro fu ran

so lvents to give brown c ry s ta llin e p ro d u c ts . T hese p roducts a re v ery a i r - s e n s i ­

tive and a re soluble in non -po la r so lven ts such as benzene, diethyl e th e r , and

te trah y d ro fu ran . This so lubility behavior and the absence of hexafluorophosphate

in th e ir in fra red sp e c tra indicate they a re probably n eu tra l compounds having a

coordinated t-butoxide in p lace of a pyrid ine as shown in s tru c tu re s XXVI and

XXVII. M ass sp e c tra l m easu rem en ts on these com plexes gave p a re n t ions a t

270 m /e fo r the com plex with the 14-m em bered ring and 284 m /e for the com plex

with the 15-m em bered rin g which in both cases corresponded to the p resen ce of

only the chrom ium atom and the m acrocycle although th e ir in fra red sp e c tra show

the p resen ce of pyrid ine . E lem ental an a ly ses obtained on these com plexes w ere

not sa tis fa c to ry but they indicate that the above form ulations a re p o ssib le .'•t-Bu

AI j

X X V I X X V II

66

A nother c la s s of reac tio n s attem pted with the chrom ium (ffl) com plexes

involved protonation of [Cr(M e2[ l4 ]te traenatoN 4)(py)2]PFg and [Cr(M e2[ i4 ] te tra e -

natoN,1)(dm f)2]PFG. T r if luorom e thane sulfonic acid was added to an ace to n itrile

solution of the b is-p y rid in e com plex and to a dim ethylform am ide solution of the

b is-d im ethy lfo rm am ide deriva tive . A pale yellow c ry sta llin e compound w as

iso la ted from the ace to n itrile solution and a light pink c ry sta llin e compound was

iso lated from the dim ethylform am ide solution. The in fra red spec trum of the

yellow com plex showed no N-H absorp tion , a huge absorp tion due to hexafluoro-

phosphate, and a C=N absorp tion , along with bands a ttribu tab le to the m acrocycle .

Since pyrid ine is a fa ir base , the acid p ro tonated the pyrid ine along with the

ligand; th e re fo re , a c e to n itr ile s becam e the ax ial ligands in place of the p y rid in es .

The sp ec tru m of the pink com plex showed no N-H absorp tion , a la rg e absorp tion

from hexafluorophosphate, and absorp tions from dim ethylform am ide and the

m acrocycle . F ro m this evidence and protonation reac tio n s of Fe(II) com plexes

with the sam e ligands15 the com plexes have been assigned the probable s tru c tu re s

XXVIII and XXIX. These com plexes did not appear to be a ir -s e n s itiv e , but i t

was ex trem ely difficult to keep them protonated as they a re ex trem ely ac id ic .

S a tisfac to ry elem ental analyses w ere not obtained fo r these com plexes because

the solvents used for re c ry s ta lliz a tio n and the exposure to the d ry box atm osphere

tended to deprotonatc the com plexes.

3 +

X X V III L= a c e to n i t r i le

XXIX Li= d im e th y lfo rm a m id e

67

P rep a ra tio n of Cr(M e?[Z]tetraenatoN^)(CnHs)(py) (Z = 14, 15, o r 16) and C r-

(Me9[l4]tetraenatoN,i)(L)(py) (L = Me o r n-B u). — E xcess phenyllithium reag en t

was added to a s lu rry of a b is-p y rid in e com plex in te trah y d ro fu ran re su ltin g in

the fo rm ation of a cr-bonded phenyl derivative th a t is soluble in te trah y d ro fu ran

(equation 24). The volume of the solution was reduced to n ea r d ry n ess and ethanol

was added to cause c ry sta lliza tio n . Since the phenyl com plex with the 16-m em -

b ered rin g has good solubility in ethanol, the volum e of th is ethanol solution was

reduced to fac ilita te p rec ip ita tio n . The addition of the ethanol not only p re c ip i­

ta ted the com plexes but a lso destroyed any ex cess phenyllithium reag en t. The

com plexes with the 14- and 15-m em bered m acrocycles w ere re c ry s ta lliz e d by

dissolving them in a m inim um amount of hot benzene, f ilte rin g the benzene solutions,

and adding ethanol. The com plex with the 16-m em bered m acrocycle w as r e c ry s ta l ­

lized from diethyl e th e r.

n-B uty l and methyl deriva tives of [Cr(Me2[ l4 ]te traenatoN 4)(py)2]P F 6 w ere p r e ­

p ared by the addition of ex cess n-buty llith ium reag en t o r m ethyllithium reag en t to

a pyrid ine solution of the com plex (equation 25). The products c ry s ta lliz ed from

the pyridine solutions and w ere collected by f iltra tio n and re c ry s ta lliz e d from a

m inim um am ount of hot benzene. The reac tio n s with the alkyllith ium reag en ts

w ere tr ie d with the b is-p y rid in e com plexes having the 15- and 16-m em bered rin g s

Eh

THF[Cr(M e2[Z]tetraenatoN 4)(py)2]PF6 + CGH5Li (24)

XXX

R

p r(M e 2[l4]tetraenatoN 4)(py)2]P F 6 + RLi ———^

R = CH3 o r n-B u

(25)

P yX X X I

68

in a v a rie ty of so lvents and under a v a rie ty of reac tio n conditions, but in each

instance no product was iso la ted . The solubility p ro p e rtie s of the 14-m em bered

ring d eriv a tiv es in pyrid ine probably fac ilita ted th e ir iso lation w hereas useful

solvent sy stem s fo r the deriv a tiv es of the o ther rin g s izes w ere not found. All

m anipulations with the a ry l and alkyl com plexes w ere p erfo rm ed in the dry box

as these spec ies proved to be the m ost a ir -s e n s itiv e group of chromium(IU)

com plexes encountered in these s tu d ies .

C h arac te riza tio n of Cr(M e?[ZJtetraenatoN,i)(CRHR)(py) (Z = 14, 15, o r 16) and

Cr(M e9[ l4 ]tetraenatoN d)(L)(py) (L = CH^ or n -B u ). — These com plexes with

the a ry l and alkyl ligands have been assigned s tru c tu re s XXX and XXXI. They

a re c ry sta llin e compounds containing th erm a lly stab le ch rom ium -carbon cr-bonds.

As in the other d e riv a tiv es , the m etal and m acrocycle a re in a p lan ar a rran g em en t

with the pyridine and a ry l ligands occupying the coordination positions above and

below th is p lane. The analy tical data fo r these com plexes in Table 12 indicate that

the fo rm ulations fo r the phenyl d eriv a tiv es a re c o rre c t; how ever, the analyses

for the alkyl com plexes a re not v e ry good indicating that im p u ritie s a re p re se n t.

Repeated re c ry s ta lliz a tio n s did not r e s u lt in b e tte r analy tical da ta fo r the alkyl

com plexes. The im p u ritie s p re se n t a re probably lithium compounds of some type

which have so lub ilities in benzene s im ila r to those of the com plexes. A possib le

solution to th is problem m ay be to syn thesize these alkyl com plexes using G rignard

reagen ts instead of lith ium reag en ts because they have been rep o rted to give much

c lean er p ro d u c ts . 37’ 96

The in fra red sp e c tra of these com plexes proved useful as they show the

absence of hexafluorophosphate and the p resen ce of pyrid ine, the m acrocycle , and

the a ry l and alkyl g roups. R epresen ta tive in fra re d sp ec tra of these com plexes a re

given in F ig u res 7 and 8 and se lec ted absorp tions fo r a ll of the com plexes a re

rep o rted in Table 13.

Since these com plexes a re n eu tra l, th e ir m ass sp ec tra w ere m easu red . As

no p a ren t ions w ere observed in these sp ec tra , values fo r the h ighest m olecular

Table 12

A nalytical D ata fo r the Com plexes with A ryl and Alkyl Ligands.

C omplex CCalc. %

H N CFound 4,

H N

Cr(M e2 [l4]tetraenatoN 4) (py) (Ph) 64.77 6.62 16.42 64.47 6 .8 8 16.33

C r (Me2 [ 15 ] tetraenatoN 4) (py) (Ph) 65.43 6 .8 6 15.90 65.38 6.96 15.84

Cr(M e2 [!6 ]tetraenatoN 4)(py) (Ph) 66.06 7.10 15.41 66.39 7.02 15.49

Cr(M e2[l4]tetraenatoN 4)(py)(CH3) 59.32 7.19 19.22 60.47 6.54 18.73

Cr(M e2 [l4 ]tetraenatoN 4) (py) (n-Bu) 62.05 7.93 17.23 62.16 7.43 18.54

C5to

4008001000F re q u e n c y (cm * '1)

12001600 1400

F i g u r e 7 . I n f r a r e d S p e c t r u m of C r (M e 2[ l4 ] t e t r a e n a to N 4)(C6H5) (P y )0

o

3000 1600 1400 1200 1000 F re q u e n c y { c m " 1)

800

F i g u r e 8 . I n f r a r e d S p e c t r u m of C r (M e 2[ l4 ] t e t r a e n a to N 4)(CH3)(Py)«

Table 13cL

Selected In frared A bsorptions fo r the Complexes with Alkyl and A ryl Ligands.

Complex Double Bond Region A rom atic C-H Bend Alkyl C

C r (Me2 [ 14 ] tc t r aenatoN4) (py) (Ph) 1575, 1568, 1501 1595 763, 732, 722, 713, 700 -----

C r (Me2 [ 15 ] te t r ae natoN4) (py) (Ph) 1583, 1504 1596 755, 725, 693 -----

Cr(M e2 [!6 ]tetraenatoN 4) (py) (Ph) 1576, 1511 1600 750, 738, 725, 703, 692 -----

C r(M e2 [14 ]tetraenatoN 4) (py) (CH3) 1518, 1488 1585 762, 725, 692 3028

C r (Me2 [ 14 ] te t r aenatoN4) (py) (n-Bu) 1516, 1486 1583 760, 723, 691 3025

a Units a re cm -1.

-qto

73

w eight fragm en ts a re rep o rted in Table 14 and com pared to the calcu la ted

m o lecu lar weights fo r the com plexes. F or the th ree a ry l com plexes the h ighest

m ass peak found co rresponds to the com plex with the pyrid ine ligand rem oved.

The alkyl com plexes, on the o ther hand, have high m ass peaks that a re equivalent

in m ass to the com plexes m inus the alkyl ligands. It is not su rp r is in g that

p a ren t peaks w ere not observed fo r these com plexes a t the ionizing voltages used,

but the inform ation gained from the h ighest m ass frag m en ts do help support the

assigned s tru c tu re s .

As befo re the trip o sitiv e oxidation sta te is assigned to the chrom ium ion

in these com plexes on the b a s is of m agnetic suscep tib ility m easu rem en ts (Table

14). The so lid -s ta te m agnetic m om ents of the a ry l d eriv a tiv es a re c lose to the

spin-only value for th ree unpaired e le c tro n s . Solution m om ents w ere obtained

for the alkyl com plexes because th e ir ex trem e a ir -s e n s itiv ity would no t p e rm it

the sh o rt exposure to a ir req u ired fo r a so lid -s ta te m agnetic suscep tib ility

m easu rem en t. These m agnetic m om ents a re slightly low due to e r r o r in the

m easu rem en ts and the p resen ce of the p rev iously d iscussed im p u ritie s .

The alkyl com plexes a re destroyed by alcohols and w a te r. The reac tio n s

with w ate r w ere very vigorous with definite evolution of gas which p robably was

m ethane or butane depending on the com plex used. They a lso re a c te d with HgCl2

in te trahydro fu ran which probably re su lte d in cleavage of the C r-C bond to give

the alkyl m ercu ry sp ec ies , RHgCl. The alkyl and a ry l sp ec ie s have good th erm al

s tab ilitie s which undoubtedly re su lt from the p resen ce of the dianionic te tra a z a

m acrocyclic and pyridine ligands. As d iscussed e a r l ie r , p y rid ine , 2 ,2 '~ b ipy ridy l,

and 1 , 10 -phenanthroline ligands a re known to stab ilize ch ro m iu m -carb o n

cr-bonds. 38 F o r these com plexes the m acrocyclic ligands can ac t in a s im ila r

m anner to the n itrogen donor ligands m entioned above by blocking coordination

s ite s and donating e lec tro n density to the m etal ion which helps s tab ilize the

ch rom ium -carbon cr-bonds.

Table 14

Physical P ro p e rtie s of the Com plexes with Alkyl and A ryl L igands.

Complex Color Meff

3 .S2a

C alc. Mol. Wt. H ighest M ass Found

Cr(M e2[l4]tetraenatoN 4)(py)(Ph) lavendar 426(m /e)347

C r(M e2 [15 ]tetraenatoN 4) (py) (Ph) red 3 .8 3 a 440 361°

Cr(M e2 [ l6 ]tetraenatoN 4) (py) (Ph) orange 3 .8 5 a 454 375°

Cr(M e2 [14 ItetraenatoN ^ (py) (CH3). green 3.52b 364 349d

Cr(M e2[l4]tetraenatoN 4)(py) (n-Bu) green 3.74b 406 349d

o QD eterm ined by the Faraday m ethod a t room tem p era tu re . D eterm ined by the Evans m ethod in CHC13 solvent.

C o r re s p o n d s to m /e calcu lated fo r Cr(M e2[Z]tetraenatoN 4)(P h). C orresponds to the m /e calcu lated fo r Cr(M e2[l4 ]- tetraenatoN 4) (py).

75

The oxidation po ten tia ls of these organo-chromiura(LD) com plexes a re very

cathodic explaining th e ir ex trem e sen sitiv ity to a i r although the a ry l spec ies in

the so lid -s ta te can be exposed to a ir fo r a sh o rt period of tim e without noticeable

oxidation. The e lec tro n ic and ESR sp e c tra of these com plexes a re s im ila r to

the sp e c tra observed fo r the o th er d e riv a tiv es. The polarography, e lec tro n ic

sp ec tra , and ESR sp ec tra of these a ry l and alkyl species w ill be d iscussed la te r

in conjunction with the o th er deriv a tiv es.

E lec tro n ic S pectra of the Chromium(3J]) Com plexes. — Since these

chromium(HI) com plexes with te tra a z a m acrocyclic ligands have pseudo D4h or

C.lv sym m etry , th e ir e lec tro n ic sp e c tra a re expected to show fea tu re s consisten t

with th ese configurations. The c ry s ta l fie ld theory fo r D4h com plexes including

chrom ium (ID) com plexes has been given by B allhausen . 97 O ctahedral chrom ium -

(III) com plexes should exhib it th ree tra n s itio n s , each of which, upon descending

in sym m etry to D4it , should be sp lit into two components (F igure 9). The sp lit­

ting of the bands is ex p re ssed in te rm s of two p a ra m e te rs , Ds and Dt. Making

the energy of the ground sta te (4Bjg) z e ro , the energ ies of the f i r s t four excited

s ta te s a re

E (4B2g) = 10 Dq

E (4Eg) = 10 Dq - 35/4 Dt

E (4A2g) - 10 Dq + 12B - 4Ds + 5 Dt

E (4E g') = 10 Dq + 12B + 2 Ds - 25 /4 Dt

Thus, the sp litting of the f i r s t band is 35/4 Dt and that of the second band is

CDs - 5/4 Dt. The sp litting of the f i r s t band can provide a d ire c t estim ation

of the axial ligand field s tren g th . The m agnitude of sp litting is a lso a function

of the geom etry about the m etal as tra n s com plexes a re expected to have twice

the sp litting of the corresponding c-is com plexes.

In g en era l, the d -d e lec tro n ic sp ec tru m of a chromium(III) com plex with

te tragonal sym m etry contains two, th re e , o r four absorptions with m olar

extinction coeffic ien ts of 10-100 . 98-100 The f i r s t absorption o ccu rs a t about

76

4E ,

4T\M g

\\

\

^ g

4Eg

4rpT lg

//

y "" _ _____ 4a ,/ ^ 2g

//

//

4 J P I S 4 g

4\ E g

\^ *Azg 4 b 1d

F r e e Ion 0 4 ^

F ig u re 9° T e rm . S p littin g D ia g ra m f o r a d3 M e ta l Ion in an d D4^ S y m m e tr ie s o

77

17-19 kK, the next ap p ears a t about 20-21 kK, the th ird band a t approxim ately

25 kK, and the la s t in the range 28-30 kK„ The second absorp tion is usually

observed while the fourth is alw ays ill- re so lv e d and often not detected . The

bands a re assigned to the tran sitio n s from the 4B4g ground s ta te to the excited

s ta te s 4E g, 4B2g, 4A2g, and 4Eg (4T 1g(F)) su ccess iv e ly . The tra n s itio n to the

components of the (4Tjg(P)) s ta te s a re assum ed to occur a t v e ry high en erg ies

and th e re fo re a re not observed .

The p red ic ted positions of the abso rp tions bands in the sp e c tra of te tragonal

d isubstitu ted am ine and ethylene diam ine com plexes have been calcu la ted using

appropriate Dt v a lu es . 98 Table 15 shows the calcu la ted band positions for

sev e ra l ethylenediam ine com plexes and co m p ares them w ith the observed sp ec tra

for the sam e com plexes. These sp e c tra a re of in te re s t because the ethy lene-

diam ines approxim ate the ligand fie ld s tren g th of the te tra a z a m acrocycles

studied. In addition, the t ia n s -diacido ethylenediam ine com plexes have a

geom etry s im ila r to that of the m acrocyclic ligand com plexes. S pectra l data

(Table 16) fo r the chromium(IH) com plexes w ith the ligands Me6[14]aneN4 and

Me6 |l4 ]4 , ll-d ien eN 4 provide an.even b e tte r source fo r co m p ariso n . 10

The sp ec tra l data obtained for the chrom ium (III) com plexes with the

dianionic te tra a z a m acrocyclic ligands a re shown in Tables 17-19. These

sp ec tra do not resem b le any of the p rev ious exam ples, i . e . , the ethylenediam ine

and m acrocyclic ligand com plexes, as they exh ib it num erous in tense bands between

16-30 kK with m olar extinction coefficien ts of 400 to 20, 000. The sp e c tra of the

com plexes having the 14- and 15-m em bered m acrocycles a re s im ila r to each

o ther while the sp ec tra of the com plexes with the 16-m em b ered rin g a re quite

d ifferen t. F igure 10 shows how the sp ec tra of the b is -l-m e th y lim id azo le com p­

lexes change as a function of the m acrocyclic ligand. Depending on the type of

ax ial ligands p re sen t, the sp e c tra fo r the 14- and 15-m em bered rin g s have from

two to th ree absorptions between 16-20 kK having m olar extinction coefficients

between 400-1000. The sp ec tra of the com plexes with the 16-m em bered

m acrocycle show only an ill- re so lv e d shoulder before 20 kK. Although the

78

Table 15

C om parison of C alculated and O bserved S pectra Band P ositions ofclChromium( Ill) —Ethylenediam ine C om plexes.

[Cr(en)2Cl2]+ [Cr(en)2(H20 )2]3+ [Cr(en)2(NCS)2]+A ssignm ent C alc. Obs. (e) C alc . Obs. (e) C alc. Obs. (£)

4E 17.0 17.3 (25) 19.4 19.7 (22) 19.5g 20. 7 (93)

4B2 . 21 .6 22 .1 (23) 21 .6 22 .6 (30) 21 .6

4A2o. 23 .6 25 .3 (34) 25 .8 25 .9

‘g

S2g

]g

2 7 .7 (39) 2 7 .5 (6 7 )4E„ 26 .2 27 .3 (23) 27 .0 27 .1

c lUnits a re kK.

79

Table 16

E lec tro n ic S pectral Data for Chrom ium (lll) Com plexes with the Ligands

M e J l^ a n e h h and MeR[i4]4, 11-dieneN,,.

C om plex

[Cr(M eG[l4]aneN 4)C l2]Cl

[Cr(MeG [MJaneN^ B r2]Br

[Cr(M eG[l4]aneN4)(CH3CN)2](C104)3

[Cr(M ee[l4]4, ll-d ie n eN 4)Cl2]Cl

[C r (MeG [ 14 ]4, 11 -dieneN4) B r 2 ]Br

[C r (MeG [ 14 ]4,11 -dieneN 4) (CH3C N) 2 ] - (C104)3

^ (e)

17.3 (29), 23.8 (sh , 31), 2 6 .0 (42)

16.4 (29), 23 ,9 (sh, 48), 25„8 (53)

18.7 (39), 23 .5 (sh, 52), 27 .4 (130)

17. 5 (26) , 2 5 . 1 (sh, 23), 27. 5 (58)

16.2 (28), 25 .2 (sh, 35), 27 .3 (22)

18.5 (39), 25 .0 (sh , 36), 2 7 .9 (148)

a Units a re kK.

Table 173,Electronic Spectral Data for the Complexes, [Cr(Me [Z]tetraenatoN4)(L)2]PF6.X

x . Z_ L_ Solvent V a x ^

2 14 py py 15.3(922), l6 .4 (sh ) , 20.4(5810), 21.7(4110), 23 .3(sh), 27.4(sh)

2 15 py py 16.0(820), 16 .9(sh). 21.5(5800), 22 .8(sh), 23. 0(5100),. 31. 3(16, 700)

2 16 py py 17. 5(sh), 22.6(5000), 25.3(6400), 30. 1(15,700)

4 14 py py 16.1(1000), I7 .2 (sh ), 21.2(5300), 22.5(3800), 23 .9 (sh), 27.3(sh)

2 14 dmf dmf 1 7 .5(sh), 18.5(660), I9 .8 (sh ), 21.8(9200), 23.1(6600), 24 .4 (sh ), 32.3(22,000)

2 15 dmf dmf l8 .2 (s h ) , I9 .4 (sh ), 23.1(6700), 24.3(6000), 25 .3(sh), 31.7(18,300)

2 16 dmf dmf 18. 5(sh), 26.2(12,700)

4 14 dmf dmf I8 .4 (sh ), 19.3(837), 22 .5(10 ,700), 23 .7 (sh ), 32.7(25,300)

2 14 M e-Im acetone 16.5(960), 17.8(975), I9 .2 (sh ), 21.0(8500), 22.4(6200), 23 .8 (sh ), 28.2(sh)

2 15 M e-Im acetone 17.3(850), 18.6(870), 20.0(790), 22.3(8800), 23.5(5800), 27.4(5800)

2 16 M e-Im acetone 1 8 .5(sh), 23. 5(sh), 25.8(9200)

4 14 M e-Im acetone 17.3(990), 18.5(820), 21.8(6970), 23.2(4830), 24 .6(sh), 28.6(sh)

a Units a re kK.ooo

Table 18

E lectronic Spectral Data for the Complexes, Cr(Me [Z]tetraenatoN4)(A)(B).X

X JZ_ A B Solvent a (e) max

2 14 NCS py CHClg 16„ 2(738), 17 .2(sh), 20.6(4470), 21.8(3480), 23 .3 (sh ),3 2 . (19,400)

2 15 NCS py CHC13 16.8(600), 1 7 .9(sh), I9 .0 (sh ), 21.6(3600), 23.2(3000), 25, 31 .4 (15,600)

2 16 NCS py CHClg 18. l(sh ) , 24.0(6210), 25.6(7420), 31.6(15,100)

4 14 NCS py CHC13 16.2(700), 22.4(5700), 23.7(4700), 25 .2(sh), 30.0(20,000)

2 14 CN — py 15.4(1300), 17.0(1050), 20.0(8400), 21.2(5800), 23 .0 (sh ), 27. l(sh)

2 15 CN -- py 16.3(600), 17. 5(sh), I9 .5 (sh ), 21.5(4000), 22 .8 (sh ), 26 .4 (4000), 31 .7 (13,400)

2 16 CN — py I8 .2 (sh ), 23.2(6200), 26.0(5100), 31.4(13,500)

a Units a re kK.

>

Table 19clE lec tron ic S pectra l Data for the Com plexes, Cr(M e2[Z]tetraenatoN 4)(R) (py).

z_ _R_ Solvent '''•max (s)

14 c 6h 5 CHC13 12.9(490), 17.8(400), 2 0 .2(sh), 22.2(5000), 27.3(sh)

15 C6H5 CHCI3 13.3(600), 17. 6 (sh), 22.8(5000)

16 c 6h 5 CHCI3 19. 3(sh), 25.0(7800), 26.9(12,300)

14 c h 3 CHCI3 16.4(570), 17.6(540), 20.6(4800), 21.9(3400), 27 .7 (sh ), 32.0 (17,300)

14 n-B u CHCI3 16.3(540), 17.6(510), 20.6(4500), 21.9(3700), 27 .7 (sh ), 32.0(16,500)

a Units a re kK.

00to

900C 900

8 0 0 0 - 800

/ \ • / 7 .-^ '

700

6 00 0 6 0 0 4

5005000H-<

±00^4 0 0 0

3000 300

2002000

1001000 • T ----

60040 0 500 500W a v e le n g th (nm )

F ig u re 10. E le c tr o n ic S p e c tra o f : - - - [C r(M e 2[ l4 ] te t r a e n a to N 4)(M e -Im )2] P F 6J 0 • * [C r(M e 4[1 4 ]- te t r a e n a to N 4)(M e -Im )2]PF£,; - • - • [C r(M e 2[ l5 ] te t r a e n a to N 4)(M e-Im .)2]P F 6 i —=— [C r(M e 2[ l6 ] te t r a e n a to N 4)(M e-Im .)} p p . oc

84

com plexes with the two d ifferen t 14-m em bered m acro cy c les d iffer by only two

m ethyl g roups, th e ir sp e c tra a re found to be d ifferen t indicating th a t m ethyl

substituen ts can effect the e lec tro n ic s tru c tu re su b s ta n tia lly .15 F ro m two to

four absorp tions with m olar ex tinction coefficien ts of g re a te r than 1000 occur

a t en e rg ie s h igher than 20 kK! in the sp e c tra of these com plexes w ith the 16-m em ­

bered deriva tives having few er bands than the com plexes with the 14- and 15-m em ­

bered rin g s .

The ax ial ligands p re se n t a lso r e s u l t in sp e c tra l d ifferen ces. F igu re 11

shows how the sp ec tra of the com plexes having the m acrocyclic ligand Me2[i5 ]-

te traenatoN 4 a re affected by the ax ia l ligands p re se n t. No sy stem atic changes

in the sp e c tra a re observed a s a function of the ax ial ligands but d ifferen t axial

ligands re s u l t in vary ing num bers of bands and v a ria tio n s in in tensity fo r com p­

lexes having the sam e m acro cy c lic ligand.

A ssignm ents for the ab so rp tio n s in these sp e c tra w ere not attem pted using

the theory d iscussed e a r l ie r a s a ll the bands observed a re too in tense to be

pure d -d tra n s itio n s . These sp e c tra re sem b le those rep o rted fo r m eta l com p­

lexes with the sam e15’ 16 or s im ila r m acrocyclic lig an d s18’ 19 and of chromium(JII)

com plexes with porphyrin31 and phthalocyanine26 ligands. The m acrocyclic

ligands p re se n t in these com plexes a re capable of substan tia l TT-bonding with the

m etal o rb ita ls due to the conjunction of the ligand double bonds. The m olecu lar

o rb ita ls that re su lt fro m the TT-bonding betw een the m etal and the ligand a re

low enough in energy th a t low -energy tra n s itio n s can occur betw een occupied

and unoccupied m olecu lar o rb ita ls which a re derived m ainly from e ith e r the

ligand or the m etal, i . e . , low -energy m etal to ligand tt* tra n s itio n s , ligand

rr to m eta l tra n s itio n s , o r ligand tt to ligand tt* tran s itio n s can o ccu r. Thus,

the com bination of these low -energy charge tra n s fe r p ro c e sse s and the d-d

tra n s itio n s re su lts in the ob serv ed sp e c tra fo r the chrom ium !Ill) m acrocyclic

ligand com plexes and a t th is tim e the sep ara tio n of only the d -d tran sitio n s

seem s im possib le .

8008 0 0 C

700700C

600C V 600

500 500

000 400

3000 / • < - 300

2000 200

1001000s

"— i r ~ —W a v e le n g th (nm )

F ig u re 11, E le c tr o n ic S p e c tr a o f [ C r ( M e 2[1 5 ] te tra e n a to N 4)(P y )2]PF£,;—-[C r(M e 2[ l5 ] te t r a e n a to N 4)(D m f)2- ]P F 6j— [C r(M e 2[ l5 ] te t r a e n a to N 4)(M e -Im )2]P F 6t——[C r(M e 2[ l5 ] te t r a e n a to N 4)(N C S)(Py)f an d — * —. C r(M e 2[ l5 ] te t r a e n a tN 4)C N .

ooU1

Molar

Ab

sorp

tivity

86

E le c tro c h e m is try of the Chromium(II]) C om plexes, — The e lec tro ch em ica l

behavior of these chrom ium (III) com plexes w ith the dianionic te tra a z a m acrocyclic

ligands is quite unusual. The e lec tro ch em ica l data obtained fo r these com plexes

is rep o rted in T ables 20-22. The b is-d im ethy lfo rm am ide d eriv a tiv es (Table 20)

would probably be b e tte r re p re se n te d a s b is -a c e to n itr ile d eriv a tiv es since the

da ta was obtained in ace to n itrile which is a s tro n g e r donor than dim ethylform am ide

and m ost ce rta in ly re p lac e s i t in solution. The thiocyanate (Table 21) d eriva tives

have po laro g ram s which show o ther p ro c e ss e s th a t a re not included in the tab le .

These p ro c e sse s a re a ttribu ted to the rep lacem en t of the thiocyanate ligand by a

so lvent m olecule as the sam e w aves a re p re se n t in the p o la ro g ram s of the b is -

dim ethylform am ide com plexes.

In g en era l, these chrom ium (m ) com plexes have two oxidation p ro ce sse s

and one reduction p ro c e ss . The le s s anodic oxidation p ro c e ss o ccu rs a t re la tiv e ly

low m oderate po ten tia ls and is re sp o n sib le fo r the a ir -s e n s itiv ity of these com p­

lex es . F o r the cationic and n eu tra l a ry l com plexes th is oxidation p ro c e ss is

re v e rs ib le o r q u a s i- re v e rs ib le in n a tu re a s the cyclic voltam m ogram of these

com plexes give AEp values of 50-100 m illiv o lts while fo r the o ther n eu tra l com p­

lexes th is oxidation p ro ce ss is i r re v e rs ib le . F o r a com pletely re v e rs ib le one-

e lec tro n p ro cess ae P should have a value of 60 m v .86 The o ther oxidation p ro ce ss

fo r these chromium(ffl) com plexes is alw ays ir re v e rs ib le excep t for the b is -1 -

m ethylim idazole deriv a tiv es in winch the p ro c e ss is q u a s i- re v e rs ib le . The

reduction p ro cess exhibited by these com plexes occurs a t v ery negative po ten tia ls

and is fo r the m ost p a r t ir re v e rs ib le in n a tu re .

Although oxidations of chrom ium (EI) th a t can be detected e lec tro ch em ica lly

a re ex trem ely r a re , the oxidation with the low er po ten tia l o ccu rrin g in these

chromium(III) com plexes with the dianionic te tra a z a m acrocyclic ligands is

assigned as a Cr(IH) -» Cr(IV) oxidation. A Cr(ID) - Cr(IV) oxidation o ccu rs a t

0 .79 v vs SCE in b u ty ro n itrile (about 0 .43 v vs A g/AgN03) fo r octaethy lporph i-

natochrom ium (Hl) hydrox ide .32 Iron com plexes with the sam e15 and s im ila r18

dianionic m acrocyclic ligands have v ery cathodic re v e rs ib le Fe(II) Fe(III)

x_ Z

Table 20

E lec trochem ical Data fo r the Com plexes, Oxidations

L E , /o ,a Cr(III)/Cr(IV) (AEp)

[Cr(Mex [Z ]tetraenatoN 4) (L) 2]PF6.

ci bE i /,, Ligand ( aE p) E 1 / , ,

Reductions aCr(ffl) /C r(II) (AEp)

4 14 dmf -0 .11 (70)

/

-0 .78 (HO) -1 .7 1 (irr)

2 14 dmf 0.02 (60) -0 .9 4 (irr) -1 .6 9 (240)

2 15 dmf 0.12 (100) 0 .79 (irr) -1 .8 0 (irr)

2 16 dmf 0.09 (70) 0.46 (irr) -1 .8 9 (irr)

4 14 py -0 .03 (80) 0.83 (irr) -1 .7 7 (irr)

2 14 py 0.03 (60) 0.99 (irr) -1 .6 2 (90)

2 15 py 0.13 (100) 0.80 (irr) -1 .73 (irr)

2 16 py 0.20 (180) 0.69 (irr) -1 .9 (irr)

4 14 M e-Im

c—iH•O1 (60) 0.73 (60) -2 .2 4 (irr)

2 14 M e-Im -0 .1 1 (90) 0.85 (100) -2 .1 0 (irr)

2 15 M e-Im 0.02 (90) 0.66 (irr) -2 .1 1 (irr)

2 16 M e-Im 0.05 (90) 0.49 (HO) -2 .3 0 (irr)

a bVolts vs Ag/AgNOg (0.1 M) re fe ren ce e lec tro d e , in ace ton itrile with 0 .1 M (n-Bu)4NBF4. M illivolts.

Table 21

Elec trochem ical Data for the Complexes, Cr(Me [ZjtetraenatoNJ (A)(B).X

Oxidations Reductions

x_ Z_ A B E f / „ a Cr(IH)/Cr(IV) <AEp)b E 1/ ? , a Ligand (&Ep) E 1/9, a Cr(III)/Cr(ID (AEp)b

4 14 NCS py -0 .28 (irr) 0.50 (irr) -2 .08 (irr)

2 14 NCS py -0 .21 (irr) 0.32 (irr) -1 .98 (irr)

2 15 NCS py -0 .13 (irr) 0.45 (irr) -2 .05 (irr)

2 16 NCS py 0.0 (irr) . 0.48 (irr) -2 .27 (irr)

2 14 CN — -0 .26 (irr) 1.24 (irr) -2 .40 ( ir r )C

2 15 CN — -0 .15 (irr) 0.63 (irr) -2 .60 ( ir r )C

2 16 CN _ _ -0 .02 (irr) 0.46 (irr) -2 .40 ( ir r )C

a b eVolts vs Ag/AgN03 (0.1 M) re fe ren ce e lec tro d e , in ace ton itrile with 0 .1 M (n-Bu)4NBF4. M illivolts. Pyrid ine solu­tion of com plex added to ace to n itrile .

oooo

Table 22

E lec trochem ical D ata fo r the Com plexes, Cr(M e2[Z]tetraenatoN 4)(R)(py).

z_ R

Oxidations

Ei /?, aCr(IU)/Cr(IV) (AEp)ba . ,

E i / , , Ligand (AEp)b

Reductions

E 1/ , , aCr(IU )/Cr(II) (AEp)b

14 c gh 5 -0 .6 0 (50) 0.62 (irr) -2 .4 3 (50)

15 C6H5 -0 . 50 (50) 0 .41 (irr) - 2 .5 5 (irr)

16 c 6h5 -0 .4 2 (60) 0 .32 (irr) -----

14 c h 3 - 1 .4 5 ( ir r )° 0 .90 (irr) -2 .5 4 (irr)

14 n-B u - 1 .4 5 ( ir r )C 0 .85 (irr) -----

aV olts vs Ag/AgNOg (0 .1 M) re fe ren ce e lec tro d e , in acetonitrile. with 0 . 1 M (n-Bu)4NBF4. M illivolts. °V ery broad w aves.

\

OOCO

90

oxidationso The a lte rn a tiv e to the assignm en t of th is oxidation p ro c e ss as a

m etal ion oxidation is to assig n i t to a ligand p ro c e ss . The q u a s i- re v e rs ib le

behavior of the oxidation in m ost of the com plexes and the absence of a free

ra d ic a l signal in the ESR sp ec tru m of the e lec tro ch em ica l oxidation p roduct of

[Cr(Me2U 4]tetraenatoN 4)(py)2]P F G do not support a ligand oxidation assignm ent.

The m ost convincing evidence fo r th is p ro c e ss being a m eta l oxidation is that

the iodine oxidation of Cr(M e2[14]tetraenatoN4)(C6H5)(py) p roduces a ch a rac te rized

chromium(IV) com plex (vida in fra).

The dianionic te tra a z a m acrocyclic ligands of these com plexes physically

constra in the chromium(HI) ion and they also can donate a la rg e am ount of

e lec tro n density to the m eta l by both or- and Tr-bonding making the chromium(III)

ion e lec tro n r ic h . Both of these effects would tend to lower the oxidation potential

of the chromium(HJ) ion, thereby prom oting the o ccu rrence of h igher oxidation

s ta te s of the chrom ium com plexes with these m acrocyclic ligands. E lec tro ch e­

m ical studies of n ickel com plexes with anionic m acrocyclic ligands dem onstrated

that negative charge does p rom ote the fo rm ation of h igher oxidation s ta te s of the

com plexes and causes th e ir reductions to be m ore d ifficu lt.86

The irre v e rs ib le oxidation that o ccu rs a t m ore anodic po ten tia ls is m ost

likely a ligand oxidation p ro c e ss which involves the rem oval of an e lec tro n from

the tt system of the ligand to fo rm a f re e ra d ic a l sp ec ies . The ir re v e rs ib le

reduction p ro ce ss which ap p ears a t v e ry cathodic po ten tia ls m ay be the Cr(III) ->

Cr(Il) reduction a t -1 .1 4 v vs SCE in b u ty ro n itrile (about -1 .5 0 v vs A g/A gN Q J.

This low reduction po ten tial would be expected fo r a com plex having a negatively

charged ligand.

These chrom ium (III) com plexes exhibit changes in th e ir m etal ion and ligand

oxidation potentials which a re a function of both the ring size of the m acrocycle

and the ax ial ligands. Keeping the ax ial ligands constant, the m etal ion oxidation

potential becom es m ore positive as the ring size in c reases while the ligand oxida­

tion shows the re v e rs e behavior becom ing le s s positive . T hese tren d s can be

explained using charge density a rg u m en ts. As the ring size of the m acrocyclic

91

ligand in c re a se s , the in te rac tion betw een the m etal ion and the ligand d e c re a se s .

Thus, the la rg e r m acrocyclic ligand donates le ss e lec tro n density to the c h ro -

mium(IIl) ion than do the sm a lle r r in g s . This causes the m etal ion in the com p­

lexes with the sm a lle r rin g s to be m ore e lec tro n r ic h and th e re fo re to be m ore

eas ily oxidized. The re v e rs e trend o ccu rs when the ligand oxidation is considered

because as the ligand donates m ore e lec tro n density , it, in tu rn , becom es le ss

e lec tro n r ic h and m ore difficult to oxidize.

The o rd e r of increasing ax ial ligand donor streng th is d im ethylform am ide

(actually aceton itrile) < pyridine < 1-m ethylim idazole < thiocyanate < cyanide.

This o ra e r is re flec ted by the m etal and ligand oxidation p ro c e sse s of com plexes

having the sam e m acrocyclic ligand. In g en era l, as the donor streng th of the

ax ial ligand in c re a se s the m etal and ligand oxidations becom e m ore fac ile .

C harge density argum ents can again be invoked to explain th is behav io r. L igands

of g re a te r donor s tren g th can donate m ore e lec tro n density to a m etal ion, thereby

making the m etal ion e a s ie r to oxidize. T his in c rease in e lec tro n density on the

m etal ion is p assed on to the ligand a lso making it m ore oxidizable. It is in te re s t­

ing to note th a t the d eriv a tiv es which have the a ry l and alkyl ligands exhibit the

low est (m ost cathodic) m eta l ion oxidation po ten tia ls (Table 22), indicating that

these ligands a re m ore effective a t donating e lec tro n density than even cyanide

for these chromium(III) m acrocyclic ligand com plexes.

ESR S pectra of the Chrom ium (III) C om plexes. — Investigations of the ESR

sp e c tra of chrom ium (ni) compounds with te tragonal and low er sym m etry recen tly

have been rep o rted fo r sev e ra l s e r ie s of com plexes in the so lid -s ta te and in

frozen so lu tio n .101-106 The conventional spin-H am iltonian o p era to r fo r S = 3 /2 is

H - g.jgH S + g .,3 (H S + H S ) + D[S 2- i/3S(S+l)] +I f z z XL x x y y z

E(S 2- S 2) (26)x y

92

At ze ro m agnetic field the q u a r te t ground s ta te is sp lit into doublets sep a ra ted in

■energy by 2[D2+ 3E2]1/ 2. T hese p a ir s , which re f le c t the degeneracy of an ion

with an odd num ber of e le c tro n s , a re called K ra m e r 's doub lets . 107 The axial

z e ro -fie ld sp litting p a ra m e te r , D, m e a su re s the difference betw een the sp in-

o rb it mixing about the Z ax is and th a t about an ax is in the xy p lane. The rhom bic

z e ro -fie ld sp litting p a ra m e te r , E , m e a su re s d ifferences in the sp in -o rb it mixing

about the x and y d irec tio n s and, th e re fo re , should vanish fo r te trag o n al com p­

lexes (F igure 12).

3 /2

1 / 2

/2DS

- 1 / 2

3 /2

F ig u re 12. E n e rg y L e v e ls of a d3 Ion in T e tr a g o n a l S y m m e try .

93

The frozen solution sp e c tra of chrom ium (IIl) com plexes with appreciab le

z e ro -fie ld sp litting a re b road and have a num ber of fe a tu re s a t low fie ld . In

these frozen solution sp e c tra , in te rac tio n s of the com plex with random ly o rien ted

counterions and solvent m olecu les contribute to the w idths of absorp tion lin e s . The

in te rp re ta tio n of sp e c tra fo r random ly o rien ted spec ies is com plicated by the

fa c t that fea tu re s in addition to those a t reso n an ce positions fo r the m agnetic

fie ld along a sym m etry ax is of the system can be expected in c e rta in situations.

These include tra n s itio n s fo r which the m axim um or m inim um effective g value

does not co rresp o n d to the x, y, or z resonance position ( e .g . , a AM = 2 t ra n s i­

tion). It is a lso possib le th a t tra n s itio n s which cannot occur fo r a specific value

of hv when the m agnetic fie ld is along one or m ore sym m etry axes do occur for

in te rm ed ia te o rien ta tio n s of the m agnetic fie ld with re sp e c t to the sym m etry

axes. X, y , and z tra n s itio n s co rrespond to m axim a, m inim a, o r inflection

po in ts. F e a tu re s correspond ing to z tra n s itio n s a re ch a ra c te r is tic a lly le s s

in tense than the asso c ia ted x and y tra n s itio n s . In tensities of sp ec tra l fea tu re s

a re functions of how the absorp tion lines fo r each param agnetic com plex in the

random ly o rien ted a r ra y superim pose and the re la tiv e tra n s itio n probab ility fo r

each tran sitio n and o rien ta tio n involved . 101

In o rd e r to in te rp re t the random o rien ta tion sp e c tra of chromium(HI) com p­

lexes com puter sim ulations of the sp e c tra m ust be p erfo rm ed based on the sp in -

Ilam iltonian (equation 26). T hese calcu lations r e s u l t in g raphs showing resonance

fie ld positions a s functions of the various sp in-H am iltonian p a ra m e te rs . Using

the se g raphs p rom inen t peaks or inflections in the sp ec tra can be located which

co rresp o n d to x, y, z, o r in term ed ia te o rien ta tio n s of the s ta tic m agnetic fie ld

re la tiv e to the m o lecu lar m agnetic axes. Using th is p ro c e ss one can obtain good

e s tim a te s of the sp in-H am ilton ian p a ra m e te rs . D etailed com puter sim ulations

based on these p re lim in a ry p a ra m e te rs can then be p erfo rm ed , followed by

sm all ad justm ents of the p a ra m e te r s . 101-104

94

The frozen solution ESR sp e c tra of the chrom ium ! HI) com plexes with the

dianionic te tra a z a m acrocyclic ligands a re p resen ted in F ig u res 13-17. All

a re X -band sp e c tra of fro zen dim ethylform am ide solutions of the com plexes taken

a t liquid n itrogen te m p e ra tu re . As expected fo r chrom ium (m ) com plexes they

have num erous b road bands with many of them occurring a t low fie ld . There

seem s to be no d ra s tic change in the sp e c tra as the ax ial ligands a re v a ried but

the com plexes with the 16-m em b ered m acrocycle definitely show the b e s t

reso lu tio n .

The purpose of p resen tin g these sp ec tra is in estab lish ing that these

m acrocyclic ligand com plexes contain a chromium!ID) ion in a te tragonal

env ironm ent. No fu rth e r in te rp re ta tio n of the sp e c tra w as attem pted a s th is

would req u ire detailed com puter sim ulation of the sp ec tra . In addition, the ESR

in stru m en t used to obtain these sp e c tra would not operate above a m agnetic

fie ld s treng th of 4500 gauss; th e re fo re , som e im p o rtan t fea tu res that m ay

occur above th is fie ld s tren g th could not be detected .

^ j b - g = 2 .0036

=2 .0036

H(kG)1 2 3 4.

F ig u re 13. ESR S p e c tr a o f : A , [C r(M e 4[1 4 ] te tra e n a to N 4)(P y )2]PFe, *B, [C r(M e 2[ l 6 ] te tr a e n a to N 4)( P y )2] P F 6>°C, [C r(M e 2[1 4 ] te tra e n a to N 4)(P y )2]PF6JD, [C r(M e 2[1 5 ] te tra e n a to N 4)( P y )2] P F 6 .

96

*Tg =2. 0036

1 2 H (kG) 3 4F ig u re 14. ESR S p e c tr a of: A, [C r(M e 2[1 5 ] te tra e n a to N 4)(M .e-Irn )2]P F 6;B, [C r (M e 2[ l4 ] te t r a e n a to N 4 ) (M e -Im )2] P F 6;C, [C r(M e 4[1 4 ] te tra e n a to N 4)(M e -Im )2]PF£,;D, [C r(M e 2[ l 6 ] te tr a e n a to N 4 )(M e-lm .)2] P F 6.

97

2 H (kG)1 3 4

F ig u r e 15. ESR S p e c tr a o f: A, [C r(M e 2[ l 6 ] te tr a e n a to N 4 )(D m f)2]P F 6;B, [C r(M e 2[1 4 ] te tra e n a to N 4)(D m f)2] P F 6;C, [C r(M e 2[ l5 ] te t r a e n a to N 4 )(D m f)2]P F 6;D, [C r(M e 4[ l4 ] te t r a e n a to N 4 )(D m f)2]P F 6 .

98

H(kG)1 2 3 4

F ig u re 16. ESR S p e c tr a of: A , C r(M e4[1 4 ] te t r a e m to N 4)(NCS)(Py),*B, C r(M e 2[ l 6 ] te tr a e n a to N 4)(NCS)(Py),°C, C r(M e 2[ 1 4 ] te tra e n a to N 4)(NCS)(Py),°D, C r(M e 2[1 5 ] te tra e n a to N 4)(N C S )(P y ).

99

g = 2 . 0 0 3 6

F ig u re 17 „ ESR S p e c tr a of: A , C r(M e 2[ 14 ] te tr a e n a to N 4)CN ; B s C r(M e 2[1 5 ] te tra e n a to N 4)CN,°C , C r(M e 2[ l 6 ] te tr a e n a to N 4 )C N .

100

Syntheses and C h arac te riza tio n of the C om plexes, [Cr(M e^[l4-jtetraenatoN /i)-

(CfiHg)]X (X = I or SCN).

P rep a ra tio n of [Cr(M e9[ l4 ]te traenatoN J (CRHS)JX (X = I o r SCN). — Since

the com plex Cr(M e2[l4 ]te traenatoN 4)(C6H5)(py) p o sse sse s a highly re v e rs ib le

m etal oxidation a t a fa ir ly cathodic po ten tial, the tre a tm en t of th is com plex with

a m ild oxidizing agent should r e s u l t in the form ation-of a chromium(IV) com plex.

The s ta rtin g com plex w as disso lved in hot te trahydro fu ran and a te trahydro fu ran

solution containing one equivalent of iodine was added to the hot s tir r in g solution

of the com plex causing it to darken im m ediately . A fter the solution cooled to

room te m p era tu re , the g reen-b row n product, [Cr(Me2tl4 ]te traenatoN 4)(C6H5)]I,

c ry s ta lliz ed and was co llec ted by f iltra tio n (equation 27). T his chromium(IV)

com plex was then d isso lved in ethanol and an excess of sodium thiocyanate was

added causing the d a rk g reen com plex LCr(Me2[ i4 ]tetraenatoN 4)(C6H5)jSCN, to

The oxidation of C r(M e2[i5 ]te traenatoN 4)(C6H5)(py) was attem pted using

the sam e p rocedure with iodine as the oxidizing agent. A brow n p roduct was

obtained which contained ax ially bound pyridine and chrom ium (H I). This

compound w as not ch a rac te r iz e d fu rth e r but the p re lim in ary data indicate that

a d ifferen t type of reac tion o ccu rred .

Ph “1

Cr(M e2[l4]tetraenatoN 4)(C6H5)(py) + 1/21^ ■—

(27)

X X X II

c ry s ta lliz e (equation 28).

XXXII + NaSCNEtOH SCN (28)

101

The chromium(IV) com plexes a re a ir -s e n s itiv e with the thiocyanate derivative

being m ore a ir -s e n s itiv e than the iodide derivative and they d isso lve in such

p o la r solvents as n itrom ethane, a ce to n itr ile , and ethanol. A fter an ethanol

solution of [Cr(M e2[i4 ]te traenatoN 4) (C6H5)]I w as p assed through a 15 cm column

of ce llu lo se , an acceptable e lem ental an a ly sis w as obtained- (Calcd. $ fo r

C rC 18H23N4I: C, 45 .58 ; H, 4 .8 9 ; N, 11 .81 . Found $ : C, 45 .23 ; H, 4 .9 8 ; N,

11.60.) N eutral alum ina and s ilic a gel proved to be unsa tisfac to ry column

supports as they caused the iodide com plex to decom pose. Since alum ina, s ilic a

gel, and cellu lose caused [Cr(M e2[l4 ]tetraenatoN 4)(CGH5)]SCN to decom pose

that compound was no t successfu lly p u rified . An elem ental analysis was obtained

on the crude com plex and although i t w as u n sa tisfac to ry , it does help support the

assigned form ulation of the com plex- (Calcd- fa fo r C rC i9H23N5S: C, 56.28; H,

5 .72; N, 17.27. F o u n d e r C , 54.27; H, 5 .70 ; N, 16.80.)

C h arac te riza tio n of [Cr(Me?[l4]tetraenatoN /<)(CfiHr,)]X (X = I and SCN). —

The two chromium(IV) com plexes a re assigned s tru c tu re s XXXII and XXXIII.

The in fra red sp e c tra of these com plexes (F ig u res 18 and 19) indicate the

p resen ce of the m acrocycle , the a ry l group, and fo r the one com plex, thiocyanate.

I t is in te re s tin g to note tha t the in fra re d bands due to the double bonds in the

m acrocycle a re shifted to low er frequencies fo r the chromium(IV) com plexes.

The five-coord inate s tru c tu re fo r th ese com plexes is estab lished by the

conductivity m easu rem en ts (Table 23) in n itrom ethane which indicate that the

compounds a re 1:1 e le c tro ly te s -93 This type of s te reo ch em is try is r a r e fo r

chromium(IV) com plexes as m o st of them have d is to rted te tra h e d ra l g eo m etrie s .

The e lec tron ic solution and m ull sp e c tra fo r the chromium(IV) com plexes

a re shown in F ig u res 20 and 2 l and the sp e c tra l data is sum m arized in Table

24. These sp e c tra a re quite d ifferen t from the sp ec tra rep o rted for the

chromium(III) com plexes with the sam e m acrocyclic ligand. They contain a

la rg e num ber of in tense bands w ith se v e ra l occu rring below 15 kK. The

in ten sities of these bands im ply that they a re m ainly charge tra n s fe r in n atu re ;

I—___________ I__________________________ I____________________ I_________ t___4000 3000 2000 1500 1300

F re q u e n c y ( c m " 1)

F ig u r e 18. I n f r a r e d S p e c t r u m of [C r(M e 2[1 4 ] te t r a e n a to N 4)(C6H5)]l.

1200

J _____________ I ______________ !________________ I________ s______________________________ I1300 1000 800 600 500 400

F re q u e n c y ( c m " 1)F ig u r e 18 ( c o n t . ) . I n f r a r e d S p e c t r u m of [C r (M e 2[ l4 ] t e t r a e n a to N 4)(C6H5)]l.

oCO

I___4000

I______________________________ I_______________________________5__________________ S___________ I3000 2000 1500 1300 1200

F re q u e n c y (c m -1 )

F ig u r e 19. I n f r a r e d S p e c t r u m of [C r (M e 2[1 4 ] te t r a e n a to N 4)(C6H5)]SCN„

J - - - - - - - - - 1_ _ _ _ _ _ _ _ _ _ I _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ S_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ !1300 1000 800 600 500 400

F re q u e n c y (c m -1 )

F ig u r e 19 (co n t . ). I n f r a r e d S p e c t r u m of [C r (M e 2[1 4 ] te t r a e n a to N 4)(C6H5)]SCN.

8________ i________s________ i________ i________ i________ i________ i________ i________ ■400 600 800 1000 1200

W a v e le n g th (nm )

F ig u r e 2 0 . E le c t r o n i c S p e c t r u m of [C r(M e 2[1 4 ] te t r a e n a to N 4)(Q ,H5) ] l : - M ull; —— CH3N 0 2 S o l 'n .

oC5

IA400 600 800 1000 1200 1400

W avelength , (nm )

F ig u r e 21 . E le c t r o n ic S p e c t r u m of [C r (M e 2[1 4 ] te t r a e n a to N 4)(C6H5)]SCN: - - - - M u l l ; - “ CH3N 0 2 S o l 'n .

108

Table 23

P hysical P ro p e rtie s of the Chromium(IV) C om plexes.

Com plex Color M .)a Ajyj(cm2o h m ''1m ol_1)b

[Cr(M e2[14]tetraenatoN4)(CGH5)]I brown 2 .8 5 95

[Ci'(Me2[i4]tetraenatoN 4)(CGH5)]SCN g reen 3 .29 75

c D eterm ined by the F araday m ethod a t room tem p e ra tu re . D eterm ined using 10-3 M CH3N 02 solutions a t room tem p era tu re .

Table 24

E lec tron ic Spectral Data for the Chromium(IV) C om plexes.

Com plex Solvent

a

[Cr(M e2[ l4 ]tetraenatoN 4)(C6H5)]I CH3N 02

Mull

[Cr(M e2 [i4]tetraenatoN 4) (C6H5) ]-SCN CH3N 02

Mull

^ max.....—

1 0 .0(sh, 430), 12.8(4000), 14.7(5400),1 6 .7(sh, 3500), 2 0 .0 (sh , 1200), 2 3 .8 (sh , 3200)10.0(sh), 12 .5 , 15 .1 , I7 .2 (sh ) , 2 2 .7 (sh ), 25.0(sh)

l0 .4 (sh ,4 0 0 ), 13.0(2800), 14.8(4000),16. 7(sh, 3000), 2 2 .2 (sh , 3280), 2 3 .5 (sh, 4280)7 .7 , 13 .2 , 16 .1 , 2 0 .8(sh), 26.3(sh)

a Units a re kK.

109

th e re fo re , no assignm ents w ere attem pted,, The spec trum of [Cr(M e2ll4 ] te tra e -

natoN4)(CGH5)]I in solution is e ssen tia lly the sam e a s in the so lid -s ta te . T his

indicates that there is l ittle in te rac tio n with the iodide o r with the solvent and

confirm s five-coord ination fo r th is com plex. D ifferences a re apparen t in the

solution and m ull sp e c tra of the thiocyanate derivative dem onstra ting that the

thiocyanate does in te ra c t w ith the com plex in the so lid -s ta te .

The te trap o sitiv e oxidation s ta te of the chrom ium ion in these com plexes

is estab lish ed by ESR, m agnetic, and e lec tro ch em ica l m easu rem en ts . The

frozen solution ESR spectrum of [Cr(M e2[l4 ]te traenatoN 4)(C6H5)]I (F igure 22)

is s im ila r to the rep o rted sp e c tra of o ther chromium(IV) com pounds.77’80’81

The m agnetic m om ents fo r these com plexes (Table 23) indicate the p resen ce

of two unpaired e lec tro n s . The m agnetic m om ent of the iodide com plex ag rees

w ell w ith the spin-only value fo r a d2 system while the higher value of the thio­

cyanate derivative probably re f le c ts its im pure s ta te .

The po larogram of [Cr(M e2[l4 ]te traenatoN 4)(C6H5)JI has th re e ir re v e rs ib le

oxidations a t 0 .66 v, and -0 .1 5 v , a re v e rs ib le reduction a t -0 .5 5 v (AEp= 60 m v ),

and an ir re v e rs ib le reduction a t -2 .4 1 v a ll vs the Ag/AgNQj re fe ren ce e lec trode

in ace to n itr ile . The oxidation p ro c e sse s a t -0 .1 5 v and 0 .23 v a re due to iodide

and the oxidation a t 0 .66 v co rresp o n d s to po ten tia ls p rev iously observed for the

ligand oxidation. The re v e rs ib le reduction a t -0 .5 5 v ind icates that the c h ro -

m ium (in) ion of the s ta r tin g com plex has indeed been oxidized to chromium(IV)

as the s ta rtin g complex has a re v e rs ib le oxidation a t -0 .6 0 v.

T hese chromium(IV) com plexes with the dianionic te tra a z a m acrocyclic

ligands a re the f i r s t fully o b n rac te rized chromium(IV) com plexes having a

chelating ligand. W ilkinson and cow orkers77 rep o rted the com plex b i s ( i ,3 -

dim ethylezietetram ethyldisiloxane)chrom ium (IV ) bu t i t w as only p a r tia lly

c h a rac te rize d by its ESR and e lec tro n ic sp e c tra . The specia l fea tu res of th is

dianionic te tra a z a m acrocycle allow the ex istence of these chromium(IV)

com plexes. The encom passing na tu re of the m acrocycle and its asso c ia ted

g = 2 . 0 0 3 6

H (kG)

F ig u r e 22 . ESR S p e c t r u m of [C r (M e 2[1 4 ] te t r a e n a to N 4)(C6H5)]l.

o

i l l

kinetic in e rtn e ss p ro te c t the m eta l ion by effectively blocking coordination s ite s .

The anionic ch a ra c te r of the ligand enab les i t to s tab ilize high m etal oxidation

s ta te s by donation of e lec tro n density . The cyclic p lanar n a tu re of th is m a c ro -

cyclic ligand a lso accounts for the unique s te reo c h e m is try of these chromium(IV)

com plexes. Since the r in g cannot fold to assum e even a p seu d o -te trah ed ra l

configuration, the five-coord inate s tru c tu re r e s u lts .

112

Syntheses and C h arac te riza tio n of the C om plexes, Cr(M e?[l4]tetraenatoNJ(.NO)

and [Cr(M eR[l4 j4 , ll-dieneN ,)(NO)(NQ>)]PFR.

P re p a ra tio n of C r(M e9[l4]tetraenatoN /1)(NO) and [Cr(MeR[l4]4,11-dieneN ^)-

(NQ)(N09)]P F Ro - - The com plexes Cr(M e2[l4]tetraenatoN 4)(NO) and [Cr(Mee[i4 ]-

4 , ii-d ie n e N 4)(N 0)(N 02)]P F 6 w ere p re p a red in e ssen tia lly the sam e m anner

(equations 29 and 30) „ A la rg e ex cess of sodium n itr i te was added to alcoholic

solutions of [Cr(Me2[l4 ]te traenatoN 4)(py)2]P F 6 o r [Cr(MeG[l4]4, il-d ien eN 4)(py)]-

(P F g)2. Since n e ith e r the s ta r t in g com plexes n o r the sodium n itr ite a re v ery soluble

in the alcoholic m edia, the so lutions w ere refluxed fo r a p e rio d of tim e . The neu tra l

com plex, XXXIV, was ex trac ted w ith benzene from the re s id u e which rem ained

a fte r the reac tio n solution was taken to d ry n ess . The cationic com plex, XXXV,

was iso la ted as a hexafluorophosphate sa lt by reducing the volum e of the reac tio n

solution. A fter the re c ry s ta lliz a tio n of the n eu tra l com plex from benzene and

the cationic com plex fro m ace to n itrile -e th an o l, sa tis fac to ry elem ental analyses

(Table 25) w ere obtained fo r both com plexes. The sam e reac tion p rocedure was

used with [Cr(M e2[l5 ]te traenatoN 4)(py)2]P F 6 but only s ta r tin g com plex was

obtained.

It is in te re stin g to note tha t the n eu tra l com plex was p rep ared from a

chromium(III) com plex while the cationic com plex was p re p a re d from a ch rom ium -

(H) com plex. Wayland e t a l . 68 rep o rted the p rep ara tio n of CrTPP(NO) from both

[Cr(M e2[i4 ]tetraenatoN 4)(py)2]PF6 + xsN aN 02Me 01

(29)

XXXIV n q I +

[Cr(M e6[i4]4, il-d ie n e N 4)(py)](PF6)2 + xsN aN t^

113

C r^ T P P and C r^ T P P (O M e ). The p rep ara tio n of a chrom ium (l) n itro sy l species

from a chrom ium (Il) com plex can be viewed as sim ply the tra n s fe r of the NO n*

e lec tro n to the m etal. Using a chrom ium (III) com plex, however, re q u ire s another

type of m echanism which a t th is tim e is not understood.

C h arac te riza tio n of Cr(M e?[l4]tetraenatoN,i) (NO) and [Cr(MeR[l4 ]4 ,1 1 -d ien e-

N,i) (NQ)(NQ9) ]PF,;0 — The two chrom ium (I) n itro sy l com plexes a re assigned

the s tru c tu re s XXXIV and XXXV. The in fra red sp ec tra of these com plexes

(F ig u res 23 and 24) indicate the p resence of the n itro sy l groups, the m acrocycles,

and hexafluorophosphate fo r the cationic com plex. The n itro sy l absorp tions

for the n eu tra l, XXXIV, and cation ic , XXXV, com plexes a re 1620 cm -1 and

1640 cm -1, resp ec tiv e ly , which a re indicative of NO „108 The conductivity data

in Table 26 d em o n stra tes the n eu tra lity of Cr(M e2[l4]tetraenatoN 4)(NO) and the

ionic nature of [Cr(MeG[l4]4 , ll-d ieneN 4)(N 0)(N 02)]P F 6. 93 Since Cr(M e2[l4 j-

te traenatoN 4) (NO) is a n eu tra l com plex, its m ass spectrum was obtained giving a

p a re n t ion a t m /e = 300 which is the sam e as the calculated m olecu lar weight

of the com plex.

The ESR sp e c tra and m agnetic m om ents of these com plexes confirm ed the

m onopositive oxidation s ta te of the chrom ium ion. The m agnetic m om ents of

th ese chromium(I) n itro sy l com plexes in the solid sta te (Table 26) indicate the

p resen ce of one unpaired e lec tro n ; therefore, the d5 chrom ium (l) ion m ust be low-

spiiio The frozen solution ESR sp e c tra of both com plexes (F ig u res 25 and 26) show

ax ia l sym m etry with g j_ > gjj while the room tem p era tu re solution spectrum of

both com plexes have only one signal that averages gj^and gjj. No 53C r hyperfine

o r 14N superhyperfine sp litting is observed a t e ith e r room or liquid nitrogen

te m p e ra tu re s . The lo w -tem p era tu re ESR sp ec tra of these com plexes a re in

com plete ag reem ent with the lo w -tem p era tu re sp e c tra rep o rted fo r o ther clrro-

mium(I) n itro sy l com plexes59*61>62>68 but usually hyperfine o r superhyperfine

sp litting was observed in the room tem p era tu re solution sp ec tra fo r the other

com plexes.

6001600 4001200 1000 8001400F re q u e n c y (c m ” 1)

F ig u re 23 . I n f r a re d S p e c tru m of C r(M e2[ l4 ] te t r a e n a to N 4)NO.

IJ. i 1i —I__60016003000 1400 1200 1000 800

F re q u e n c y (c m -1 )

F ig u r e 24 . I n f r a r e d S p e c t r u m of [C r(M e 6[ l4 ]4 , 11 -d ie n e N 4)(NO)(NC>2) ]P F 6.

cn

116

Table 25

A nalytical Data fo r the Chrom ium (l) N itrosy l C om plexes.

C omplex CC alc . %

H N CFound 4>

H N

Cr(M e2 [l4]tetraenatoN4)(NO) 47.99 6.04 23.32 47 .74 6.01 23.38

[Cr(MeG[l4]4, ii-d ien eN 4)(NO)- (NG>)]PFe 34.75 5.83 15.19 34.94 5.87 15.28

Table 26

P hysical P ro p e rtie s of Chromium(I) N itrosy l C om plexes.

Com plex Color (B .M .)a A (cm 2ohm -1

Cr(M e2[l4]tetraenatoN 4)(NO) g reen 1 .81 < 1

[Cr(M e6[i4]4, li-d ie n e N 4)-(N0)(N02)]PF6 green 1.72 87

3- b ' D eterm ined by the F arad ay method a t room tem p era tu re . D eterm ined using 10-’M CH3N 02 solutions a t room tem p e ra tu re .

Table 270.

E lec tro n ic S pectra l Data fo r the Chromium(I) N itrosy l C om plexes.

C omplex ̂m ax ’ ^

C r (Me2 [ 14 ] tetraenatoN 4) (N O)'0 15.3(1330), 22 .2 (sh ,2 l0 0 ), 26.0(7100)32.6(16,000)

[Cr(M eG[l4 j4 , ll-d ien eN 4) -(N 0)(N 02)]P F Gc 15.4(45), 22.2(99), 27.7(340)

a Units a re kK. ^TH F solvent. CCH3CN solvent.

i 17

g =

F ig u r e 25 . ESR S p e c tr u m of C r(M e 2[1 4 ]te t r a e n a to N4)N O .

£ rcr(Me,,[14]4, H-dieneN4)(N0)(N02)]PFt.F igu re 26 . ESR Spectrum o£ [C r(M e 6l

119

A schem atic MO diagram fo r th ese chrom ium (I) n itro sy l com plexes with

m acrocyclic ligands ap p ears in F igu re 27 which focuses on the m eta l d and

n itr ic oxide n ' levels that a re the p rin c ip a l valence o rb ita ls .68’ 109 The Cr*(NO )

units a re expected to be lin ea r in o rd e r to m axim ize d r r -T T * bonding which is

co n sis ten t with the ax ially observed g te n so rs fo r these com plexes, hi analogy

to the com plex CrTPP(NO) the odd e lec tro n fo r these m acrocyclic ligand

com plexes is p laced in the d ^ m olecu lar o rb ita l since gj^> g jj.

The e lec tron ic sp e c tra l data fo r the chrom ium (I) n itro sy l com plexes are

p resen ted in Table 27. If band in ten sitie s a re not taken into account, the

s im ila r ity of these sp ec tra is s trik in g considering th a t the two com plexes have

d ifferen t coordination num bers and v e ry d ifferen t m acrocyclic ligands. This

seem s to indicate the m olecular o rb ita l schem e in F igure 27 is applicable to

both com plexes and that the n itro sy l ligand does dom inate the e lec tro n ic

configurations of chromium(I) n itro sy l com plexes. The f i r s t th ree bands

observed fo r these com plexes m ay be assigned to the 2B2g-»2A i, the 2B2 -» 2B j ,

and the 2B2 -> 2E tra n s itio n s , re sp ec tiv e ly .

D r. Dennis W ester solved the c ry s ta l s tru c tu re of [Cr(M e6[l4]4, ii-d ien eN 4) -

(N 0)(N 02)]P F 6 which unequivocally p roves the p rev iously assigned s tru c tu re .

The o rtep d iagram of th is com plex is p resen ted in F igure 28 showing that the

com plex is s ix -coord inate with ax ia l n itro sy l and n itro ligands. The N 3-C r-N 4

bond angle is 180° and th is bond axis a lso constitu tes a C2 ax is fo r the com plex

which m akes one-half of the m acrocycle equivalent to the o th e r. The chrom ium

atom is d isp laced out of the p lane of the m acrocycle tow ard the n itro sy l ligand.

A diagram of the com plex in F ig u re 29 p re se n ts p e rtin e n t bond d is tan ces. The

chrom ium -n itro sy l n itrogen bond d istance of i .6 7 9 A is very sh o rt fo r a C r-N

bond but i t is not unusual fo r m e ta l-n itro sy l co m p lex es .109 The C r-N , C -C , and

C-N bonds have no rm al lengths and the im ine function is read ily d istinguishable

having a C-N distance of 1.272 A com pared to the C-N distance of 1. 500 A for

the am ine.

(N O tT + d x z .d y z ) 3E— ± 2 \

// \

\B j (dx2- y 2)-

“ T Bl\

\

I/ - +

(d z2 + NO d) j/ 3A, /

A 1 (d z2) — }-

E (d x z , dyz)—

/ /

A /\

B2 (dxy) “ — b 2\

/

\ //\ '+ *.

dyz+ h

ZE

(dx^, dyz+N O TT )

120

(NO n )E

-H— (NO a)A j

1 E q p Z ± T -------------------" T p f r - (N O rr)E

C r ( l l ) L C r( l) L(NO) NO

F ig u re 27« S c h e m a tic M o le c u la r O rb i ta l D ia g ra m f o r th e C h ro m iu m (l) N i t ro s y l C o m p lex es ,,

121

c *

F ig u re 28„ O r te p D raw in g of [C r(M e 6[14]4 , 1 l - d ie n e N 4)(N 0 )(N 0 2) ]P F 6.

4 9 2

O

F ig u re 29 . X -R a y C r y s ta l lo g r a p h ic Bond D is ta n c e s fo r [C r(M e 6[1 4 ]4 , 11 -d ie n e N 4)(N 0 )(N 0 2) ]P F 6.

123

Syntheses and C h arac te riza tio n of Chromium(II) and Chromium(III) Com plexes

with Mefi[l4]4, ll-d ieneN ^.

P re p a ra tio n of the Chrom ium (Ip and Chromium(IH) C om plexes. — The

chrom ium (II) com plexes with MeG[14]4, il~dieneN 4, I, w ere p rep ared f i r s t and

then oxidized to yield the chrOmium(IU) com plexes. S p era ti10 in itia lly p rep ared

cationic ch loride , b rom ide, and thiocyanate chromium(II) and chromium(II])

com plexes with Me6[l4]4, ii-d ie n e N 4 and iso la ted them as p e rch lo ra te sa lts .

Since p e rc h lo ra te s a re hazardous m a te r ia ls , these com plexes w ere again p rep ared

in the p re se n t w ork as th e ir hexafluorophosphate sa lts and pyrid ine and iodide

d eriv a tiv es w ere a lso p re p a re d . Instead of using the p e rch lo ra te sa lt of the

ligand in the syn theses of the com plexes, the trifluorom ethylsu lfonate sa lt was

em ployed since com plexes with th is anion can be eas ily m etathesized to the

co rrespond ing hexafluorophosphate s . The halide com plexes w ere p rep a red using

C rC l2 ° 2py, C rB r2 - 6py, and Crl^ • 6py as the m etal so u rces . The thiocyanate

com plex was p rep a red from the ch loride derivative by m eta th esis and the p y r i­

dine com plex re su lte d fro m em ploying C r(C F3S03)2 • 4py as the m etal so u rce .

The p rep a ra tio n of a cyanide derivative was also attem pted and re su lted in an

ex trem ely a ir -s e n s itiv e g reen m a te ria l which was not ch a rac te rize d .

The chrom ium (ll) ch loride and brom ide deriva tives w ere oxidized on the

benchtop with Cl2 and B r2, re sp ec tiv e ly , to give [Cr(Mee[i4]4, ii-d ie n e N 4)Cl2]P F G

and [Cr(Me6[i4]4, ll-d ie n e N 4)B r2]P F G. The dicyanide and dithiocyanate com plexes'

w ere p rep ared by m eta th esis from [Cr(Mee[l4]4, ll-d ie n e N 4)C l2]PFG. The p r e ­

p ara tion of the cliiodo com plex of chromium(III) was attem pted but these attem pts

failed to give a ch a rac te rizab le com plex.

124

C h arac te riza tio n of the ChrQmium(II) and Chromium(III) C om plexes. — The

a ir -se n s itiv e chromium(II) com plexes with Me6[l4]4, ll-d ie n e N 4 a re f iv e -co o rd i­

nate and high-sp in as w ere those p re p a re d by S p e ra t i .10 S atisfac to ry elem ental

analyses (Table 28) fo r these com plexes indicate that th e ir fo rm ulations a re

c o rre c t. The in fra red sp e c tra of th ese com plexes show the p re sen ce of the

m acrocycle , the hexafluorophosphate anion, and pyrid ine or thiocyanate fo r

those p a r tic u la r d e riv a tiv e s . The N-H and C=N absorp tions fo r these com plexes

a re sum m arized in Table 29. The N-H s tre tch in g frequencies fo r th ese com p­

lexes occur about 100 cm -1 h igher in energy than the corresponding p erch lo ra te

d eriva tives and the C=N absorp tions a re about 20 cm -1 higher in energy . The

hexafluorophosphate d eriv a tiv es a re a lso much m ore a ir -s e n s itiv e in the so lid -

sta te than a re the p e rch lo ra te com plexes.

Since these com plexes a re ex trem ely a ir -s e n s it iv e , th e ir solution m om ents

(Table 29) w ere m easu red by the E vans method and so lid -state m easu rem en ts

w ere not attem pted . These m agnetic m om ents a re som ew hat below those

expected fo r h igh-sp in d4 configurations which may be due to experim en ta l e r ro r

or slight m eta l-m eta l in te rac tio n betw een species in solution. The conductivity

data (Table 29) is consis ten t with the assigned five coordination of these com plexes

dem onstrating tha t they a re 1:1 e le c tro ly te s .93 E lec tro ch em ica l data for these

chrom ium (II) com plexes with the diene m acrocyclic ligand 'and fo r se v e ra l

chromium(II) com plexes with MeG[i4]aneN 4, II, p rep ared p rev iously by S p era ti10

a re p resen ted in Table 30. The v e ry cathodic m eta l oxidation po ten tia ls displayed

by these com plexes a re responsib le for th e ir ex trem e a ir -s e n s itiv ity .

The e lec tro n ic sp e c tra l data fo r these com plexes a re given in Table 31.

S perati observed two d -d bands and one charge tra n s fe r band fo r the p erch lo ­

ra te com plexes but only one d-d band and one charge tra n sfe r band w ere

detected in the e lec tro n ic sp e c tra of the hexafluorophosphate com plexes.

Curve analysis of these sp e c tra m ay possib ly re so lv e another d-d band at

low er energy . Following S p e ra ti1 s reason ing , th is d -d band which occu rs a t

about 20 kK in these com plexes is assigned to the 5B4g-* 5B2g tra n s itio n .

Table 28

A nalytical D ata for the Chromium(II) Com plexes with Me6[l4]4, ll-d ien eN 4.C alc. Found €

Complex _C_ _N _C_ H_ _N_

[Cr(Mee[l4]4, ii-d ien eN 4) I]PF6 31.79 5.34 9.27 31.41 5.48 9.21

[Cr(Me6[i4]4, il-d ien eN 4)B r]P F 6 34.48 5.79 10.05 34.09 5.71 10.05

[Cr(Mee[14]4, ll-d ien eN 4)C l]PF6 37.47 6.29 1Q092 37.12 6.16 10.74

[Cr(Mee[l4]4, il-d ien eN 4)SCN]PF6 38.13 6.02

00oCO'rH 38.61 6.37 13.35

[C r (Me6 [ 14 ]4,11 -diene N4) py ](P F 6) 2 35.96 5.32 9.98 35.87 5.61 9.61

toOl

Table 29

P hysical P ro p e rtie s of the Chromium(II) Com plexes with Me6[l4]4, li-d ien eN 4.

Complex Color Meff (B .M .)a Ajvf(cm2ohm-1m ol ^ vC=N(c-m '^ VN-H^cm

[Cr(Me6[l4]4, ll-d ien eN 4)I]P F 6 brown 4.68 185 1660 3250

[Cr(Me6[l4]4, il-d ien eN 4)B r]P F 6 brown 4 .50 181 1663 3255

[Cr(Mee[l4]4, ll-d ien eN 4)C l]P F 6 brown 4 .64 172 1660 3250

[Cr(Me6[l4]4, ii-d ien eN 4)SCN]PF6 tan 4.58 167 1648 3270

[C r (Me6 [ 14 ]4,11 -diene N4) py ] (P F 6) 2 tan 4 .7 0 317 1658 3265

d e te r m in e d by the Evans m ethod in acetone solution. D eterm ined using 10 3 M aceton itrile solutions a t room tem p era ­tu re .

toCi

Table 30

E lec trochem ical Data for the Chromium(II) Com plexes. a

Complex

[Cr(Me@[l4]4, ll-d ieneN ^pyK P Fg^

[Cr(Me6[l4]4, ll-d ien eN 4)NCS]PF6

[Cr(Me6[l4]4, ll-d ien eN 4)C l]PF6

[Cr(Me6[l4]4, li-d ien eN 4)B r]P F 6

[Cr(Mes[l4]4, U -dieneN 4)I]P F 6

Cr(M e6[l4]aneN4) (NCS)2

Cr(M es[i4]aneN4)(CH3CN)2

Cr(M e6[l4]aneN4)Cl2

Cr(M e6[i5]aneN4)B r2

Oxidations

-0 .3 0 i r r

-0 .2 0 i r r , 1 .37 i r r

-0 .8 0 i r r , 0 .36 i r r

-0 .7 5 i r r , 1.01 i r r

-0 . 59 i r r , 0 .77 i r r

-0 .7 7 i r r , 0 .38 i r r , 1.83 i r r

-0 .8 6 i r r , 0 .82 i r r

-1 .3 7 re v , -0 .7 6 i r r , 0 .75 i r r

-1 .4 5 i r r , -0 .9 8 i r r , -0 .7 0 i r r0.33 i r r , 0. 61 i r r

Reductions

-2 .3 6 i r r

-2 .3 5 i r r

-2 .3 2 i r r

-2 .3 5 i r r

-2 .3 3 i r r

-2 .3 7 i r r

-1 .4 2 i r r

-2 .7 6 i r r

-2 .4 6 i r r

^Volts vs Ag/AgN03 (0.1 M) re fe ren ce e lectrode in a c e to n itr ile .

Table 31clE lectron ic S pectral Data fo r the Chromium(II) Com plexes with Me6[l4]4, ll-d ien eN 4.

Complex Solvent ^m ax’ ^

[Cr(Me6[i4]4, ll-d ien eN 4)(py)2](PF6)2 CH3CN 21.6 (sh, 65), 30 .7 (1960)

[Cr(Mee[l4]4, ll-d ien eN 4)NCS]PF6 CHgCN 20 .0 (sh, 70), 29 .6 (2200)

[Cr(Mee[i4]4, ll-d ien eN 4)C l]P F 6 CH3CN 19.5 (sh, 60), 28 .6 (1900)

[Cr(Mee[l4]4, H -dieneN 4)B rjP F 6 CHgCN 19.0 (sh, 63), 28 .6 (1600)

[Cr(Me6[l4]4, ll-d ien eN 4)I]P F 6 CHgCN 20.0 (sh, 95), 28 .6 (1950)

aUnits a re kK.

to00

129

The cationic chromium(II]) com plexes with Me6[i4]4, ll-d ie n e N 4 and the

hexafluorophosphate anion a re very unreactive and a ir -s ta b le sp ec ie s . They

a re tra n s s ix -coo rd inate com plexes having m agnetic m om ents (Table 32) that

a re consis ten t with a h igh-sp in d3 e lec tro n configuration. The conductivity

data p resen ted in Table 32 d em o n stra tes th a t they a re s ix -coo rd inate com plexes

in solution as the values co rrespond to those rep o rted fo r 1:1 e le c tro ly te s .93

In addition, the analy tical data (Table 33) fo r these com plexes show good a g re e ­

m ent with the assigned fo rm ula tions.

The N-H and C=N in fra re d abso rp tions fo r the m acrocycle in these com plexes

a re sum m arized in Table 32. In frared bands fo r the cyanide and thiocyanate

ligands a re observed in the sp ec tra of those deriva tives and hexafluorophosphate

bands appear in the sp e c tra fo r a ll the com plexes. The e lec tro n ic sp e c tra l data

fo r the chrom ium (III) com plexes appear in Table 34. The dihalo com plexes have

a typical chromiura(HI) spectrum with th ree abso rp tions. The cyanide and th io ­

cyanate com plexes, how ever, show only two bands and one band, re sp ec tiv e ly .

The o ther bands a t h igher energy a re probably obscured by the charge tra n s fe r

reg io n . Using the sam e band assignm ents as S p e ra t i ,10 the th ree bands observed

fo r the dihalo com plexes a re assigned successively to the 4B lg -* 4Eg , the

4B4g - 4B2g , and the 4B lg 4A2g tra n sitio n s (see F igure 9).

x_

CN

SCN

Cl

B r

Table 32

P hysical P ro p e rtie s of the Com plexes, [Cr(Mee[ l4 ]4 ,1 l-d ieneN 1)X2]PF6o

Color ueff (B. M .)a Am (cm2°hm “ im ° l“ 1)b VC=N VN-H (crn~̂

yellow 3.88 145 1650 3170

yellow 3 .87 149 1650 3190

purple 3 .74 148 1649 3234

pink 3 ,96 175 1660 3240

a D eterm ined by the F araday method a t room tem p era tu re . D eterm ined using 10 3M CH3CN solutions at room tem p era­tu re .

Table 33

A nalytical Data for the Com plexes, [Cr(Me6[i4]4, ii-dLeneN 4)X2]PFg.

Calc. Found 4x_ C_ H N C H N

CN 40.83 6.09 15.96 40.76 6.22 15.85

SCN 36.42 5.43 14.16 36.43 5.35 14.13

Cl 35.05 5.88 10.22 35.28 6 .07 10.05

B r 30.16 5.06 8.79 30.43 5.34 9.02

CO

Table 34

E lec tron ic Spectral Data fo r the Com plexes,

X Solvent

CN CH3CN

SCN CH3CN

Cl CH3CN

B r CH3CN

a Units a re kK.

[Cr(Mee[14]4, H -dieneN ^X ojPFg.a

^m ax1

19. 8(sh, 6), 24.5(58)

2 0 .5 (91)

17.5(26), 2 3 .9(sh, 22), 27.1(52)

18.4(32), 23 .5 (sh , 19), 26.7(44)

CODO

133

APPENDIX

D ry T ra in D escrip tion

When m anipulations involving a ir -s e n s itiv e m a te r ia ls a re c a r r ie d out inside

a glove box, i t is n e ce ssa ry to m ain tain an in e r t a tm osphere th a t is fre e from

m o istu re and oxygen. The m o st effective way to accom plish th is ta sk is through

the use of an attached dry tra in th a t continuously rem oves oxygen, m o istu re ,

and so lvents from the glove box a tm o sp h ere . Vacuum A tm ospheres of C aliforn ia

can provide such a unit that is a lm o st com pletely autom atic but the co s t of th is

co m m erc ia l unit is p roh ib itive . T h e re fo re , a unit costing approxim ately one-

fourth as m uch as the com m ercia l one w as designed and b u ilt to provide the

d es ired in e rt atm osphere p u rifica tion .

The d ry tra in in conjunction with the d ry box is a com pletely enclosed

system with the glove box a tm osphere being continuously re c irc u la te d through

the pu rifica tion system . The d ry tra in (F igure 30) co n sis ts of a blow er for

c ircu la tin g the atm osphere and a fu rnace containing oxygen rem oval ca ta ly s t and

m olecular s ieves fo r purify ing the glove box a tm osphere . The box, blow er, and

furnace a re joined by an assem b ly of 1 inch copper tubing and b a ll valves.

V alves one, two, and th ree a re 1 inch Lunkenheim er ball valves which allow

e ith e r p a r t of or the e n tire d ry tra in to be iso la ted from the glove box.

The M .D . ligh t duty blow er is b e lt driven and pow ered by a i /2 h .p .

e le c tr ic m o to r. To reduce v ib ra tion , the blow er and m otor assem bly is

mounted on a p latfo rm which is sep ara ted from the one that houses tire r e s t of

the dry tra in . A lso , the copper tubing is connected to the b low er using bellow s.

The furnace (F igure 31) is a b ra s s drum containing 10 lb s . of Ridox oxygen

rem oval ca ta ly s t sandwiched between la y e rs of Linde 13X m olecu lar sieves

(12 lb s . to tal). To heat the fu rnace , c u rre n t is p assed through a n ichrom e w ire

134

th a t is w rapped around the b ra s s d rum . A T em com eter (Therm olyne C orp .)

supplies c u r re n t to the h e a te r and a lso m onito rs the tem p era tu re of the fu rnace

v ia a therm ocoup le . The drum is w rapped with se v e ra l la y e rs of a sb esto s and

m ounted in a box filled with verm icu lite in o rd er to m inim ize heat lo s s . Following

the fu rnace is a w ater jack e t which helps cool the c ircu la tin g a tm osphere of the

d ry box.

An assem bly of 1/2 inch copper tubing, 1/2 inch Lunkenheim er b a ll valves,

and A sco solenoid valves is used to supply n itrogen and vacuum to the d ry box

during no rm al operation and reg en era tio n gas and vacuum fo r reg en e ra tio n of

the s ieves and Ridox. The p re s s u re of the box a tm osphere is con tro lled e ith e r

m anually by footsw itches o r au tom atically by a photohelic sw itch which ac tiv a tes

the n itrogen o r vacuum solenoid v a lves. The sw itches a re connected to the

solenoid valves through a th ree-w ay sw itch th a t allow s e ith e r the footsw itches o r

the photohelic to activate the solenoids. The w iring d iagram for these co n tro ls

is shown in F ig u re 32.

The s iev es and oxygen rem oval ca ta ly s t should be reg en era ted a t le a s t once

a month to in su re a good glove box a tm osphere . A fter the blow er is tu rned off,

valves 2, 3, 5, and 6 a re closed and the furnace is heated to 200-225°C which

re q u ire s about five h o u rs . When the req u ired furnace tem p era tu re is a tta ined ,

valves 5 and 6 a re opened, solenoids 3 and 4 a re activated , and a m ix tu re of 95$

N2 and 5$ H2 is p assed through the fu rnace and vented into a fume hood. A to ta l

of sixty cubic fe e t of the gas m ixture is passed through the furnace during one

hour. Then solenoids 3 and 4 a re deactivated and valve 5 is c losed . A vacuum

is connected to solenoid 4 and it is ac tivated fo r two hours to rem ove any

rem ain ing w ater o r solvent. F ina lly , solenoid 4 is deactivated , valve 6 is c losed ,

valves 2 , 3, and 5 a re opened, and the blow er is r e s ta r te d .

n 2 -®c

V aC o < -“

Nz/HzC

V ent &=■

SI

S2

S3

4̂-O ^ r

K

V6□EE

Out

VI

W a te rJ a c k e t

F u rn a c e

E CV4

V5

M .

V3

E le c t r ic M o to r

X

.In

V2

B e llo \ rs

B lo w er

Bellow ;

F ig u re 3 0 . D ia g ra m of th e D ry T r a in .

136

T h e rm o c o u p le W e ll

Ridoc£ 10 lb s

.ecxe

F ig u re 3 1 . D ia g ra m of th e F u r n a c e .

P h o to h e lic S w itch

T h re e -W a y S w itch

S2

V a c .N2F o o ts w itc h F o o ts w itc h

3 2 . W irin g D ia g r a in f o r th e S w itc h e s .

138

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