The Ligand Chemistry of Tellurium

Coordirtarion C&u&~ Reuieq 42 (1982) 133-244 Elsevier Scientific Publishing Company, Amsterdam-Printed in The Netherlands

I33

THE L~~A~~ CHEMISTRY OF TELLURIUM

CONTENTS

A. B*

c. ID. E.

Iutrod~c~on. ................................................. Tellurium-an overview of its chemistry ..............................

(i) Oxidation states of tellurium ................................. (ii) Te(II) and Te(IV) as Lewis acids. ..............................

A survey of teliturium iigands and synthesis of metal-teliurium bonds ” _ . . f _ . _ _ . Synthesis of or~~otelIu~um hgands ................................. Transition metal complexes with tellurium ligands .......................

(i) Zn,Cd,Hg.........._.....~...~._......_.............._ . (ii) Cu.A~.Au......................_......~........~_~ .....

(iii) Ni,Pd,Pt ............................................... (iv) Co,Rh,Ir .............................................. fv) Fe,Ru,Us.........................~....._ ..............

(vi) Mn,Tc,Re.......................~ ...................... {vii) Cr,Mo.W ..............................................

(viii) V,Nb,Ta......................................_ ......... (ix) Ti.Zr.Hf........................_......_.__._._.._~ .... (x) tanthankies and actinkiea ...................................

References _._______ ___...._ _ __..._.~,____.._.____I_____l_tll_ _ _ _ Noteaddedinproof _. . . _ _. _. __ _._. . _. . . . . . . . . . . -.. . . . _. . .*. . . . . . . .

ABBREXIATIONS

VCP 7r-c&q Ph C,H, p-talyl ~-433, -C,H, Me CH; Et C,H, n-Pr n-C,H, Zl-BU Xl-C,H, R alkyl Ar aryl

134 135 135 135 136 140 146 146 157 162 185 I90 20g 216 225 227 228 228 239

134

DMF N, N-dimethylformamide DMSO dimethyl sulfoxide THF tetrahydrofuran DCE 1 ,Zdichloroethane tu thiourea etu ethylenethiourea SU selenourea esu ethyieneselenourea fod 1,1,~,2,2,3,3-heptafluorooctane-4,6-dionate PPN ~~~PPh~~~] +

A. INTRCHXJCTION

Although the coordination chemistry of Iigands containing heavier group

VA donor atoms [1,2] as we11 as sulfur [3--9f and selenium [3,3,f5] ligands has been widely investigated, the analogous chemistry of tellurium ligands is relatively unexplored [3,15- 131, This has probably been due to the lack of commercial availability of a wide variety of organotellurium ligands, in contrast to, for example, organophosphines, as well as to the generally heId belief that organutellurium compounds are extremely toxic and air sensitive. This misconception can probably be traced historically to the early work in this area by Chatt and coworkers fI4-Da] dealing with Pd(If) and Pt(I1) complexes with diethyl telluride and di(n-propyl) telluride. These latter materials are indeed foul-smelling, air-sensitive liquids. The diary1 derivatives, with the exception of the liquid TePh,, are air-stable solids. Indeed, air-stable dialkyl derivatives are obtained with suffi~~e~t~y fong aIky1 chains (e.g., Te(n-C,,H,,), is an air-stable white solid; m-p. 45OC [l l]).

In the past few years, however, considerably increased interest in organotellurium chemistry is evidenced by the number of pubhcations [ 11,123 and patents [23b] in this area. This latter work is related to the use of organotel- ~uri~rn compounds in thermally processed photographic elements. The facile chemical reduction of such compounds at elevated temperatures (i-e., fOU-- 175*C) in both stoichiometric and catalytic modes has resulted in the formulation of a wide variety of nonsilver imaging processes using tellurium chemistry [23b]- The synthetic methodology now exists to prepare a wide variety of organotellurium Iigands f 11,12],

Indeed, in the past few years an increasing number of papers have appeared describing transition metal complexes with organotellurium ligands. This trend can be expected to accelerate as organotellurium synthetic methodology becomes familiar to the practising coordination chemist. Compari- son of the properties of such complexes with those of the Iarge number of complexes with orga~o~hosp~nes f&2], for example, may lead to usefut

135

applications for such complexes. This review is intended to promote interest in this relatively unexplored area of &and chemistry.

B. TELLURIUM-AN OVERVIEW OF ITS CHEMISTRY

(i) Ox-id&ion states of t,-Aiuriunt

Tellurium exhibits an exceptionally wide variety of formal oxidation states. Its common oxidation states are 2 - (Te”- [24]), 1 - (Tei- [24,25], Te- f26j), 2 + (Te(S,X)3; X = NR, f27-291, COR f27,30-321) 4 + (TeCI.. TeO, [33,34]), and 6 + (TeF, 133,343). A number of polynuclear species with fractional formal oxidation states have been reported: Z/3 - (Tei- ) [35]. l/4 + (Teif ) [36,37], l/3 + (Tei’ ) [36-383, l/2 -i- (Tei+ ) [36-401. and 2/3 + (Te:” ) [41]. T rivalent compounds, [Et,N],[Te(mnt),Cl] (mnt = 1.2- dicyanoethylene-1,2-dithiolate) [42] and ~2-biphenylyl)~Te~i~ 1431, and several monovalent compounds (i.e., Te:+ [36,38,393) have also been repotted.

The 2- state is readily accessible by the reduction of the metal in aqueous solution by a variety of reducing agents or by sodium in liquid ammonia [24,44]. This oxidation state is very susceptible to aerial oxidation to the metal, and solutions of Te(‘- ), which are useful reagents in organotef- iurium chemistry, are generally prepared in situ. The 6 + state is accessible only with strong oxidizing agents (e.g_, Fz, permanganate. chloric acid) (33.34). The two most common oxidation states in tellurium chemistry are the 2 -i- and 4 + states. Most tellurium compounds in these oxidation states can be conveniently prepared from Te metal (in some cases with intermediate reduction to Te’-), TeCl., or TeO,.

(ii) Te(lI) and Te(I V) us Lewis acids

The coordination chemistry of Te(II) as a Lewis acid has been the subject of relatively little detailed investigation with respect to the synthesis and properties of these materials, although several crystal structures of Te(I1) complexes with monodentate and bidentate sulfur ligands [27,30,31] have been reported (e.g., fTeL,Xz] [45,46], [TeL,]X, [27,30,31,47,48], [L,Te(p-

L),TeL, I 4+ [49] where L = thiourea or setenourea and X = halide, pseudo- halide; and Te&X)I? where X = COR [27,30-321, CNR, [27-291, P(OR); [27,5OJ). Indeed, the coordination chemistry of Te(I1) is generally restricted to halo ligands and ligands with sulfur or selenium donor atoms (e.g., thioureas, selenoureas, SCN, l,l-dithio ligands). The crystal structures of a number of the complexes with l,l-dithio ligands have shown the presence of intermolecular Te-S interactions to give pseudo five-coordinate complexes 1271. A recent paper [51] reported the crystal structure of the first five-

137

[102]. In addition to the use of dialkyl ~103,104] and diary1 [102-1051 tellurides as ligands, Hieber and co-workers introduced the use of diary1 ditellurides (ArTeTeAr) as reagents to form bridging Mfp-TeAr),M Iinkages via oxidative addition reactions E 102,106]

Fe,(CO),, + 3 Te,( p-MeO-C,H,)l -,

3(0C),Fe(p-Te( p-MeO-C,H,)),Fe(CO), + 6 CO (~WO~l

Baddley and co-workers [ 107,108] later demonstrated that a terminal M-TeAr bond could be formed by analogous reactions, the dimeric comptexes with the bridging bonding mode being formed under more forcing conditions

[rCpFe(CO),j, + Te,Phz~nCpFe(CO),TePhc~l~;~~,~ 1

aCp(C0) Fe( p-TePh), Fe(C0) zCp (2)1107l

An interesting complex incorporating both terminal and bridging aryl tellurol ligands was recently reported by Chia and McWhinnie Cl091

=&-+6 A(\r f’dCpP~3Jq -t ArZTez __L

AC., p-EtO-cCgH,

Ph3P, ,Te\ ,leAr

(3) 2 - thlenyl A rT/‘*\

2 / ‘*\PPh 3

In addition to the use of diarylditellurides to form M( p-TeAr),M linkages [102,106-l 141, recent work has shown that ArTeCOAr’ [I 151 (eqn. 4) and ArTeMPh, (M = Ge, Sn. Pb) (eqns. 5, 6) [I 16-I 191 derivatives are useful reagents for the formation of such linkages.

PdCl,(NCPh), + PhTeCOPh c?? [Pd(TePh),l,, (4X1 151

CuCI + Ph,SnTePh CHzN [CuTePh] ,* (5)[ 116,117]

PdCI,(NCPh), + Ph,GeTePh =y’ [Pd(TePh)?] ,, (6)[1191

Two examples have been reported in which such bridging units (i.e.. p-TePh) are formed under forcing conditions using TePh? [ 102,120].

A variety of complexes containing both bridge M( p-TeAr),M linkages [I 17,121] (e.g., eqn. 7) and terminal M-TeAr bonds [ 113,122- 1251 (e.g., eqns. 8-10) have been prepared by metathetical reactions in which a ditelluride is initially cleaved with a reducing agent to generate ArTe -

Naf TePh- + CuCl EtzH [CuTePh] ,1

T NaBH,/NaOH

PhTeTePh

(7)[1171

138

[ rrCpNi( P(n-Bu),),] + Cl - + NaTePh + rrCpNi(P(n-Bu),)TePh

-t- P(n-Bu), + NaCl 1W221

~Cp~Zrcl~ + 2 PhTeLi -+ rr Cp, Zr(TePh), -!- 2 LiCl WD23f ? Te(O)/cther

PhLi

Hg(TePh), + iPh,Pl+ [TePh]-T2F [PPh,j + [Hg(TePh),f - WELL31

Dimeric complexes containing TePh- bridging ligands have also been prepared by use of a mercury reagent f126]

3Wt0flC YrcD*~<“=r~<No =Cp,M(TePh), + l/2 Hg[Fe(CO),NO], - Te ,_ (1 I)[1261

Ph

M=fc. t.x NO M=Nb.Lm CO

A Te-Sn cleavage reaction with the formation of a telhu-ol bridged dimer occurred in the reaction of Te(SnMe,), with bromopentacarbonylman- ganese( I) [ 1271

(12)[127!

Complexes with diary1 ditellurides (HgfH) [87,I 14a,f.28], Cu(I) [I t6,117,129], U(V) [130a], and Re(f) f130b]) and dialkyl diteliurides (Cu(i) [ 1161) in which the Te-Te bond remains intact have also been reported.

Most of the reported transition metal complexes with tellurium ligands involve the above ligand types, although a few examples with tellurium heteroeycles flU2,131- 1351 as well as with tigands containing Te-E bonds fE = Ge 11361, Sn [127,f36,137], Pb [i36], P [238a,c], As fl38a]) as well as cluster compounds incorporating tellurium f 102,139- 1481 have been reported (see Fig. 1). The first tellurocarbonyl complex [149a] (i.e., OsCl, - (CO)KTeXPPh&), complexes with a tellurourea-type ligand (M(CO),L (M = Cr, Mo, W), ci.s-Mn(Br)(CO),L; L = Te=~NEtCH,CH,NEt [138b]) and HTe - (i.e., CS‘[M(CO)STeH] -, M = Cr; C f = PPN i. ; M = W; C c = AsPhz [149b]) have al&o been recently reported.

Although a large number of coordination complexes of the pseudohalides (XCN - ; X=0 [IS%1901, S [188,189,191,192], Se [188,189,192]) have been reported, to date no transition metal tellurocyanates have been described. The simple alkali metal tellurocyanates can be prepared in nonaqueous solvents (e.g., MeCN, acetone, DMSO) by reacting MCN (M = Na, K) with

139

Ti c [I261 a [I231

Zr El [I231

Hf

w

Nb t [I 261 d [I241

Ta 0 0~1

CT a [149b] h [I%. 1371

i WI k [uag

0 [Mb]

P 04Sb 1 CQl49b

MO cGO8.1251 d[lOB. 1241 k[lJac]

0 CL#bJ

W d [I241 h [X.137]

0 [USad

P c149ld qtf49bI

Mn 0 [1o2*1 b [102,105] c i

t 102.1511 1271

i WI D [I3Ebf

TC

Re

0 103, I521

b(w) C#Ob] i 0277

Fe b[l02] C[lO2.Kl6.IY

mr.112.w 126.153]

dbo?] il321 n[l39-1461

OS 1 C149al

m P49J

co e [I261 m [IO21 i OUbl

Rh 0 &55-1571 b [Ml] c [I201

Ir D [Is31

Ni

Pd 0 [l3,Wza

160-168~ b [Kr9,9,167

169-171~

Pt D [14,15 I&

Zl-2k 160-164:

b m9J?l,l74 f n Sbl

tlCwS1

b[l7l, ISO] c [ll6,ll7,ll9] e[ll6.11?] f [~,l16.117,

1291 9 CWl7J

[I%1

I. Transition metal complexes with tellurium ligands: (a) complex with with diary1 telluride; with bridging Te(atyI)-; (d) complex with

with bridging Te(alkyl)-; (f) complex with with dia~kyiditellu~de; with terminal Te(MR,), (M=Ge.Sn. Pb): (i)

complex with TeSnMe, ; fi) complex with tellurium heterocycle: (k) complex with (CF,)?ETeMe (E=P, As); (1) complex with tellurocarbonyl (M-CTe); (mf tellurium incorpo- rated in cluster compound: (n) complex with bridging TeMe, ligand: (0) complex with

(p)complex with terminal TeH -; (q) complex with bridging TeH -. * The complex Mn(CO),(Te(n-Bu),)Cl was proposed as an intermediate in the catalytic conversion of Mn(CO),Cl into [Mn(CO),Cl], in the presence of the telluride in refluxing ether. but no didkyl telluride complex of Mn has been isolated. ** A compIex involving this linkage has

been proposed as an intermediate in the conversion of ArTeCl 3 and Ar,TeCl z derivatives into the corresponding carboxylic acids by Ni(CO), in DMF.

tellurium, but such solutions deposit the starting materials on evaporation of the soivent 11931. However, salts of tellurocyanate with bulky cations have been isolated (i.e., Et,N + [194], Me,N + [ 1951, AsPhi [ 195J, PPN + [196]), and the crystal structure of PPN[TeCN] has been reported [ 1971.

An analogous situation exists for the trialkyl phosphine tellurides. A series of (alkyl),PTe derivatives C198-2 101 have been prepared by reaction of the

phosphines with tellurium in nonaqueous solvents. However, unlike the analogs with the lower chalcogens (R,PX; X = 0 [Zl 1 J, S [212,213], Se

[ 10,213]), no coordination complexes with these rather unstable derivatives have been reported_

Thus, tellurium ligand chemistry still offers a vast area of interesting synthetic organometallic chemistry as well as coordination chemistry involving studies of new tellurium-metal linkages and fundamental studies of the ligand properties of tellurium bases,

In much of the early work in this area, complexes with tellurium ligands were prepared merely as supplementary examples, the main emphasis being on complexes with group VA ligands, especially organophosphines. In the past few years, however, there has been renewed interest in all the above areas as well as some efforts to understand the fundamental ligand properties of organotellurium compounds. “‘Te NMR [168,214] and MCissbauer spectroscopy [ 1 I$a,b,t I7,171,215-2181 have provided useful information on the properties of tellurium ligands, and the first crystal structure determinations of metal complexes with organotellurium ligands have recently been reported (i.e., t~atzs-Pd(SCN),(Te(CH1CH.CH7SifCH,),),), [13], [PPh,][Hg(TePh),] [187], [Cr(CO)5(Te=&NEtCHICH,NEt)] [138b], cis- frrCpCOFe(p-Te( p-EtO-C6H4))2FeCO&Zp] [ 114b], and Re,( p-Br},( Et- Te,Ph,)(CU), fl3Obj. In the sections that follow, coordination complexes with or~anotel~u~um ligands will be described according to the central metal

and the Te ligand type. At present, complexes with tellurium ligands have been reported for 24 elements (Fig. 1).

D. SYNTHESIS OF ORGANOTELLURIUM LIGANDS

Irgolic [ 11,12,24] has discussed the synthetic aspects of organotellurium chemistry in several reviews and a monograph. Therefore, only some general aspects of the synthesis of organotellurium ligands will be discussed here, and the reader is referred to the above references for detailed procedures for specific compounds.

The organic chemistry of tellurium has been the subject of study for more than 140 years, the first organometallic compound, Tel+, having been prepared in 1840 by Wahler [219]. After this initial work, the area remained relatively dormant until the work of Lederer in 1910- 1920 and Morgan and Drew in the t92Us. (See ref. I I for a summary of this early work.) Since 1960

has been and coordination

complexes with tellurium ligands [ 135. The two most generally useful for organotellurium

syntheses are TeCi, and tellurium 3). Reactions

141

Ar2Te rt reduction

Ar~RC12 ArTeAr’

R$iZ

I

T I &W3iOIl

ArTeTeAr -ArTeCls Ar’H

&%gCl * ArAt‘TeCI,

(RTeTeR) reduction A

R,TeCt, +--- RTeC13 * RHgCl

&I (Ad w-k$z)

Fig. 2. The USC of TeCl, in organotcliurium synthesis.

with aromatics 12211, olefins [222,223], and a wide variety of organomet~~~ic reagents 12241, both aromatic and aliphatic, can be used to prepare organotellurium derivatives (Fig. 2).

Diaikyl tellurides can be prepared starting from TeCi, by reactions with alkyd mercuric chlorides [2X3, acetylenes [226]. oXefins or ketones (e.g.. MeCOPh [227], acetylacetone derivatives [228--2321) followed by reduction

ArTeTeAr

Fig. 3. The use of Tefo) in organutellurium synthesis.

I42

of the initially formed (alkyl),TeCI, derivatives. However, reactions with TeCI, are most commonly used to prepare the aryl derivatives

ArH 122 1,237-2391

ArH/AKJl 3 [233]

TeCl, + > ArTeCI, (13)

ArHgCl [224,225,238]

Ar, Hg [224,234]

MAr, (M = Sn [235], Pb [236])

Activated aromatics (e.g., PhOMe, PhNMe?) [221] readily condense with TeC14, and nonactivated aromatics such as benzene itself react in the presence of AlCl, [233]. Of the organometallic reagents that have been used in reactions with TeCl, (eqn. 13), the aryl mercuric chlorides are the generally most useful for the preparation of both symmetrical ligands (TeAr,) and unsymmetrical derivatives (TeArAr’), the latter ligands being prepared by sequential reactions with TeCl, and the isolated Cl,TeAr derivative. Such mercury reagents incorporating a wide variety of functional groups can be readily prepared by Grignard reactions (HgCl, + ArMgBr) or more conveniently by the diazo method (decomposition of the double salts

~ArN,I/[HgCl,l by Cu(O) in acetone or alcohol) [240,241]. Diary1 tellurides have also been prepared by reaction of TeCl, with aryl

Grignard [241,242] and lithium [243,244] reagents. These reactions are generally carried out with excess organometallic reagent under forcing conditions to decompose the unstable intermediate tetraaryl tellurium derivative [245].

The aryl tellurium trichlorides, which are readily isolated from reactions with TeCl, (eqn. 13), can be easily reduced to diary1 ditellurides [237]. These, in- turn, are very useful reagents for the synthesis of a wide variety of symmetrical and unsymmetrical diorganotellurides (Fig. 4). They are also useful reagents for the formation of terminal metal-TeAr and bridge metal (p-TeAr), metal linkages by direct or indirect routes (Fig. 5). Under forcing conditions, the trichlorides are converted to dichlorides by reaction with a second mole of organic or organometallic reagent, These derivatives can then be easily reduced to the corresponding diary1 tellurides (eqn. 13).

Alkyl derivatives of tellurium * are generally most conveniently prepared starting from Te(0) via reduction to Tez- or Te”- followed by alkylation (Fig: 3). WBhler’s [219] original synthesis of diethyl telluride in 1840 involved reacting potassium telluride with ethyl sulfate. He prepared the potassium telluride by reducing tellurium metal with the carbonaceous residue obtained

* TeMe,, TeEt, and Te(n-Bu), are commercially available.

143

ArTeAr’

t redrtm

AFTa%’

ArTeR

RTeAr

ArTeR

Fig. 4. Synthesis of symmetrical and unsymmctricztl diorgnnotcllurides from dinryfditclluridcs.

Fig. 5. Generation of ArTe - ligands from diary1 diteKsrides.

144

by the thermal decomposition of potassium hydrogen D-tar&ate at red heat until the carbon monoxide evolution had ceased. However, the reduction of tellurium to Te’- can be carried out more conveniently in aqueous base with a variety of reducing agents (e.g., sodium formaldehyde suffoxylate (Ronga- lite-C) [246,248,269,270], sodium dithionite 12711, sodium bisuffite f272f. thiourea dioxide 127 1,272], and potassium borohydride EI33).

Reaction of the aqueous Te’- solution (Rongahte-C and borohydride being the most common reducing agents here) with an alkyl halide in a suitable solvent such as methanol gives facile alkylation to the dialkyl telluride (Fig. 3) Alternatively, if the alkyl halide is not stable under such highly alkaline conditions, a suspension of sodium telluride in an organic solvent such as methanol or DMF is used, the telluride being formed by the sodium reduction of telhu-ium in liquid ammonia followed by evaporation of the ammonia and addition of an appropriate organic solvent [44,273-2751,

Bergman and Engman [276] have recently reported a phase-transfer method for the alkylation of sodium telluride. Reaction of a toluene solution of phthaloyl chloride with an aqueous solution of Na,Te, generated by N&H, reduction of tellurium metal, with tetrabutylammonium hydrogen sulfate as the phase-transfer catalyst, gave telluraphthalic anhydride [276a]:

(14)

This method may have more general utility in the synthesis of dialkyl tellurides, which are unstable at the high pH used in the conventionat methods in aqueous solution 1133.

The same authors have also reported 12771 a convenient one-step synthesis of symmetrical dialkyl selenides by reacting selenium metal with the appropriate tetraalkyl ammonium borohydride in toluene

2 R,N * BH, f Se + R,Se + H, -t R,NBH, 05)

Here the ammonium salt functions as both the reducing agent [Se(O) * Se’-] and the alkylating agent. With Te(O), only tetrabutylammonium borohydride was a strong enough reducing agent to give the dialkyl telluride [277].

The reduction of tellurium metal in ethanol with NaBH, has also been reported 1278-2831.

Here the reduction product formed in situ was formulated as NaHTe

145

(although the selenium analog is well known [284,283]. this species is not we11 characterized: the only well-documented tellurol derivatives are the very unstable CH,TeH [2%,287a] and PhTeH [287b]).

Another usefuI route to alkyd tellurides involves reacting tellurium powder at high temperature with an alkyI iodide, the resuhing Te(aIkyl), I1 E252.2531 derivative being readily reduced to the diaikyl telluride [2i4]. The yields in such reactions are generally rather low, although use of tellurium generated in a metal atom reactor has been reported to give improved yields [253]. Ziolo and Gunther [251] recentIy reported a convenient modification of this general method in which tehurium powder is refluxed in a high-boiling solvent (e.g., 2-methoxyethanol) in the presence of a large excess of NaI and an alkyd halide (eqn. 17)

,/-\_/=H2=L 2-methoxyethqnol _/%/\

II I + e-x. No1 + Te l ._/,*\ A * II I

v_//-\_ / Tel, (17)[2511

CHzCI

,/**,/ CH2Br

II I I

EH,-/EtOH

N2H.,/EtOH

tiq. NH3 _/‘**/’

2Na + Te p NazTe c II I MeOH 12751 l \,4-\,

>Te (18)

The particular derivative prepared by this new route, 1.1 -diiodo-3,4-benzo- I-

telluracyclopentane, is a convenient precursor to the Te(II) heterocycle 1,3-dihydrobenzo[c]telIurophene, which has also been prepared [275] by alkylation of Na,Te formed from the reaction of the elements in liquid ammonia (eqn. 18). This synthetic method may have more general utility in organotellurium chemistry.

The heterocyclic chemistry of tellurium has been the subject of considerable recent interest, a number of new ring-closure reactions having been developed [220]. Most of the tellurium heterocycles that have been used as Iigands, however, can be prepared by the general reactions described above.

-A SW%?0 -I* WOf + ICH2CU2CHZCH21 -

/

Y_,!

tetturocyclopentone lHg(II) ComPtex)

(19) [133]

phenoxotetiurine (Mn(I)complexl[lO2]

t20)[288]

146

PA CClCHpCH,120 $ No,Te - i I

. (21 )[246]

X

1-Oxa-4-teIturacyClohexone IAgffI complex) [134,1353

dibenrotelluroPhene tAgt1) compteX> [135]

Tellurophene itself has been prepared by a variety of routes [ 111, and its chemistry has been reviewed [290,291]. A recently reported route provides this heterocycle in good yield from readily available starting materials (2921.

NozTe t TIDngO,~~_c,~~C-C-C-CSIMe, Etoti

- iY-7 123)[292]

-\ /- Te

I I

TeIO) Cr(O).Pdt!.IJ.Fe(OI complexes: I13.2) CO: [154 b]

E. TRANSITION METAL COMPLEXES WITH TELLURIUM LIGANDS

(i) Zn, Cd, Hg

Zn, Cd No well-dharacterized complexes of Zn or Cd with organotellurides have

been reported_ Coates f182] claimed that dimethyl telluride forms a complex with cadmium iodide, but no details were given. However, cadmium complexes with Te(EEt,), (E = Ge, Sn) have been prepared and characterized

El851 Cd(Ge(CGF5)~),+nTeiEEt~)z4Cd(Ge(C,F)3)2(Te(EEt,),)ll (24)

E = Ge, B = 1; E = Sn, n = 1, 2. The air-sensitive, colorless complexes, which

I47

are soluble in common organic solvents, were prepared by reaction of the components in toluene, concentration of the reaction solution, and dilution with hexane. The difficulty in forming 2: 1 compiexes with these Te ligands has been attributed to both steric and electronic factors (i.eY decreased d donor properties of the Te as a result of Te - E c&r-_P?T interactions).

e Dialkyi Muride complexes, Several complexes having the composition HgX,(TeR,) (Table I) have been prepared by reacting the telluride with the

TABLE I

Cd and Hg compfc?ces with tellurium ligands

Mp. (“C) Ref.

Cd compIexes

Cd(C,F,),(Te(ceEt,),) Cd(C~~)~(Te(S~Et~)~) CdtC,F,),(Te(SnEt,)1),

IO4- 106 185 dec. ~85 185 dec. V80 185

Hg complexes

(a) Dialkyl telfuride tomplexes

fHgCl,TeEtzJl HgCl ,TeMe, ’ HgBr,TeMe, ’ HgI,TeMe, a [HgCI,Te(n-B&j, HgCIJe(n-C,H,,), a Hg3r,Te(n-C&,,)1a HgI,Te(n-C&I,,),” Me2TeBr,Hg12 Me,TeI z HgBr, [Me,TeI,],HgPh,h

(b) DiaryI telluride complexes

HgCl ,TePh 1- 5 EtOH HgCl ,TePh 7 HgJ3rzTePh 1 HgI ,TePh 2 HgCI J+e( o- tolyX), Hgf ,Te{ u-tolyl) 7 HgBrzTe(cr-tolyl)z HgCIzTe( p-toly1)2*6 EtOH HgCI,Te(p-tolyl),.3 EtOH

HgBr,Te( p-talyl), HgI,TeQ-tolyl):!

179 (dec.) 160-161 (dec.) 107 (sl. dec.) 97-98

88

127-128 127-128

130 89 160-161 89 148 90 146 87 212 188 142-143 90 199-200 90 135-136 89 132-133 89 85 90 65 90

186 84-86 85. 86 85, 86

186 88 88 88

ll4a f14a 114a

f48

M.p. (“C) Ref.

I-igC1l-Tf$o-EtO-C,H,l, HgBr,Tc( o-EtO-C,H,f~ HgI,Te(uEsO-C,H,f, HgCI,Te( a-naphthyl), HgBr,Te( a-naphthyl), HgI~Tc(~-naphth~~)~ HgCI,Te(nr-NeO-C,H,)-r HgBr~T~~~j-t-MeO-C,f3;,):! HgI 2Te( r&vN&C,H, I1 H&t zTef at-Me-C&H, ),*6 EtOH HgBr,Te( nr-MC-C,H, jz H~I,T~(~~-Mc--C~H~)~ IlgCI,Tf( p-EtO-C,H,), WgBr,Te( p-Et%-C,H,), HgI,Tefp-Et@-C,H,), HgCI,Te(p-MeO-C,H,)3 HgBr,Tc( p-Me@-C,H,), HgI,Te(p-MeO-C,H,)2 H~CI,T~(U-M~O-C$-I~)~ HgBr,Te( o-Me@-C&H, I3 Hgi,Te( u-Me@-C,H,), HgClzTe{2.4-Me: -C&I,), HgBr,Te(2,4-Me,-C,H3)lt HgI,Te(2.4-MC,-C,H,), HgCt~Te(2,5-Me,-C,H,), HgBr~Te~2.~-Me~-C~H~)~ W~r,Tc(2,S-Ne,-C,H3);

(~1 Complexes with u~symmet~~~ diary1 :eI~u~des

HgI ,TePh( o- tolyl) HgC12TePh{ p-tolyi) ~g~r~TeP~~ p-tolyl) HgI,TePh( p-tolyl)

(d) Complexes with alkyI aryl telhtrides

HgBrJeMePh

(e) Complexes with diatyl ditellurides

Yellow-HgI,TezPhl (HgCl&I-e,t p-EtO+,H,), (HgCI~),Te,fp-MeO-C,W,)z Yellow-HgBrzTe,( p-EtO-C,H,), Bro~vn-HgBr~Te~(p-EtO-C6Hq)t Yctlow-HgIzTez( p-EtO-C,H,), Brown-HgX,Tel(p-EtO-C~Ei,),

174-175 160-161

90 1X7-188

178-179 152-153 89

I IS (desf 122 flfi-117 53

tS@-ISI

IS- 156 123- 124 90

77-78

63 I43- M4

84 w-8 I

I06 99

107-108

179-180 i69-I70 166-167

96 96 96 97 97 97 94

94 94 92 ‘31 92

toa

100 loo 9x 98 98 95

95 95

93

93 93

93

93 93

133-134 91

54

74

101

99 99

99

124 87

IOI-102 tt0--1’12

114-115 120-122 10% I 10

202-204 12% 126

87 114a 114a I14a I I&l 1 f4a I Ma

149

TABLE I (continued)

M.p. (“C) Ref.

(f) Hg complexes with ttIIuro1 Iigands

Hg(TePh), HgTe( p-EtO-C,H,), [PPh,lHg(TeW, [Ph,Pl,Hg,(TePh),, PhTeHgCl p-EtO-C,H,TeHgCI Te heterocycles

Ill 110-112 1143 130 (dec.) 113. 1x7

113 dcc. 390 121 160-161 Ii&l

146- 147 133

a These complexes itre presumably haIo-bridged dimers as are the TeEt, and Tqn-Ru), complexes on the basis of their far-IR spectra. ’ Probable structure is a tclfuronium Salt ([MelTePh],[HgI, J) anaiogous to the methyl analog f294].

appropriate mercuric salt in water, ethanol, or acetone. These derivatives were used as a means of characterizing the organotellurium products formed by the photolysis of acetophenone 1871 and acetone [86] in the presence of a tellurium mirror (Le., HgX ?TeMe,. HgX ,TePh ?, HgX z MeTePh and HgI,Tez Phi were isolated in the former case and HgX,TeMe, (X = CI, I) in the latter study). The facile formation of such insoluble mercuric halide complexes has been used as a means of characterizing liquid dialkyl tellurides (i.e., HgX,TeMe2 [84-871, X = Cl, Br, I; HgX,Te(n-C,H, ,)? [SS]).

Reaction of di-n-amyl telluride with an equimolar amount of HgCl, in acetone gave a precipitate containing two components, which could not be separated [88]. Mercuric iodide gave, on concentration of the reaction solution, a viscous residue which could not be crystallized but ‘from which the telluride was regenerated by thermolysis [88]_ Mercuric bromide, however, gave a precipitate of the 1: 1 adduct, which was recrystallized from acetone [SSJ.

The adducts HgX, - TeMe, (X = Cl, Br, acetone solutions of the two components, in quantitative yields [SS]. They can be slowly liberate TeM+ in air [85).

I) were prepared by reacting cold the adducts rapidly precipitating recrystallized from acetone but

The formation of HgC12 - TeMe, by trapping the volatile product resulting from the action of various molds on potassium tellurite with a solution of mercuric chloride in concentrated HCI (Biginelli’s solution) has also been described 1841.

The related derivatives I-IgC12TeRz (R = Et, n-Bu), prepared by reacting

150

ethanol solutions of mercuric chloride with the appropriate dialkyl telluride, have been formulated as chloro bridged dimers on the basis of their far-IR spectra f 186]. Presumably the other HgX, - TeR, derivatives are also dimeric for polymeric, as proposed for HgXzTeArz derivatives on the basis of their Mijssbauer spectra f I l4a3).

Dance and Jones [I 14a] have reported the synthesis and characterization of a variety of organotellurium-mercury(I1) complexes. Reaction of cy- MelTeIT with HgBr, in ethanol gave a 1: 1 adduct as yellow needles. This adduct was shown to be a weak molecular complex between the products of an anion exchange reaction_ Me,TeBr, - Hg12, on the basis of “‘Te M&s- bauer spectroscopy (the adduct had parameters similar to those of Me,TeBr?) and Raman sqectroscopy ( vTc_Hr = 168, 147 cm- ’ ). The complex decomposed on standing to give HgI, and a-M%TeBr,. The p-rc_Br values, which are about 20 cm-’ lower in the complex vs. Eu-Me,TeBr,. were interpreted in terms of appreciable Hg - - - Br interactions in the adduct rather than

I-Ig* - - Te interaction. The same adduct was formed by the reaction of a-Me,TeBr, and KgI, in ethanol. The complex completely dissociated in benzene, precluding a molecular weight determination-

The above observations suggested the use of mercuric halides to effect anion exchange in dialkyl telIurium diiodides. Indeed, refluxing cw-Me,TeI, with HgBr, in a solvent in which ar-Me,TeBr, is soluble but Hg12 is insoluble (e.g., CHCl,) 11 a owed essentially quantita&e conversion to ar-Me,TeBr, after filtration of the insoluble red HgIz and evaporation of the filtrate [f f4a].

An analogous adduct between ar-MsTeIz and HgCl, could nut be isolated, but reaction of the two compounds in refluxing chloroform did result in quantitative anion exchange [ll4a]. Diphenyl mercury forms adducts with ar-R,TeI; (R= Me, Et) [114a] with the composition HgPh,- 2R,Te12, the complexes readily precipitating from chloroform solutions. Dance and Jones [I 14a] have studied the methyl derivative by a variety of physical techniques and formulated it as a telluronium salt (i-e., [PhMe,TelZI-Igf. or fPhMe,Te’ I-],- HgI,): *“Te Massbauer p arameters indicate tellurium atoms in essentially a trigonal environment; conductivity shows a 2/l electrolyte in DMF; the mass spectrum indicates phenyl transfer to tellurium has occyrred; 13C NMR confirms a Te-Ph group by the observation of a doublet (Jw~~_u~ = 17 1.6 Hz) for the aromatic carbon bonded to the tellurium; the Raman spectrum shows pTcMe = 533 cm-‘, pTe_ph = 248, 262 cm-‘, VT+] = 125 cm-‘.

The mercuric chloride adduct of ~yclotellurobutane was isolated as white

* Tw5 forms of Me,TeI, have been established by single-crystal X-ray diffraction studies. the true dialkyl tellurium diiodide (a-form) 1293) and the telluronium sah @$Te] *IMeTe&] - (&form) [294].

crystals when alcohol solutions of the components were mixed fl33]_ The telluride was released on warming the complex in aqueous Na0I-I f 1331.

D&z@ fe~~~~~~~~ co~@exes, Lederer fS9-1011 prepared a number of crystalline complexes of mercuric halides with diary1 tellurides (HgX2TeAr,; X = Cl, Br, I) as a routine method of characterizing the diary1 t&n-ides he prepared by reaction of Grignard reagents with “TeXZ” ]l I] (see Table I)_ The chloride complexes were generally prepared by simply shaking an aqueous solution of HgCl, with an ethereal solution of the telluride. Ethanol or acetone was generally used for the fo~atio~ of the bromo and iodo complexes. No structural characterization of derivatives of this type was reported until the recent work of Dance and Jones f 1 f4a]. The complexes HgXZTeArZ (Ar = Ph, p-EtO-C&H,; X =r Cl, Br, 1) have been formulated on the basis of Mijssbauer spectroscopy (parameters characteristic of telluronium salts such as Ph,Te + Cl - ; a = 0.35 mm s - I ; A = 5.83 mm s - ’ ), IR

spectroscopy, and Raman spectroscopy as polymeric species containing fArZTe c -HgX]X - units linked through bridging halide groups to give infinite chains [I 14a]. The Raman spectra of these complexes (e.g., ~1rr~_~~ = 100-140 cm-‘) suggest that the strength of the zig-Te interaction increases with increasing etectronegativity of the halogen (Ph?TeHgX,: X = Cl. 133 cm-“; X = Br, 124 cm-‘: X = I. 118 cm-‘).

Piary! dW”frcride cotttp!exes. The first report [IS?] of a diary1 ditelluride complex involved the use of mercuric iodide to complex the products resulting from the photolysis of acetophenone in the presence of a tellurium mirror (the products were TePh,, TeMe,, PhTeMe and Ph,Te,). The complex with diphenyldite~luride was reported to be a yellow solid which became orange at 86YZ, began to sinter and darken at 9ZQC, was almost black at 96”C, and melted to a russet-colored liquid at IOI-102°C. This melting behavior was reported to be the same as that of an authentic sample of the diphenylditellu~de mercuric iodide complex, although no synthetic details or other physicaf data Fur the complex were reported fW]_ Dance and Jones [I 14a7 have prepared three general types of mercuric halide complexes with diarylditellurides by reaction of the components in ethanol, characterization being by ‘“$Te Miissbauer and far-IR spectroscopy. The type of complex isolated depends on the s~oi~hiometry of the reaction and the mercuric halide used. Reaction of ArzTe, (Ar =p-MeO-C,H,. p-Et@-C,H,) and HgCl, (I : 2 molar ratio) in hot ethanol followed by coofing gave yellow products formulated on the basis of elemental analysis as ArTeHgCl,, The lz5Te Mijssbauer spectra of these complexes indicate that there is only one type of Te present and that it is trigonafly coordinated, These complexes were formulated as Ar2Te2(HgCt 7 )-, , analogous or~anos~lfide complexes

- - having been reported tl14a].

Yellow complexes of she type ( p-EtO-C,H,),Te, - HgX, (X = Br, I) were isolated by the reaction of the ditelluride with the mercuric halide (1: 2 molar ratio) in warm ethanol [114a]. The Mlissbauer spectra of these yellow complexes indicate a similar Te environment as in the above HgCl, complexes. With a 1: t molar ratio, complexes were obtained whose lZsTe Massbauer spectra indicated that the Te atoms are two-coordinate and that all Te sites are equivalent, thereby suggesting that the diarylditelluride is weakly complexed in such adducts.

Although cleavage of Te-Te bonds in reactions of diarylditellurides with transition metal substrates to give bridging or terminal TeAr - iigands is an established reaction for these derivatives (Fig. 5). they can also coordinate tu metals with this bond intact.

Indeed, the first crystal structure has recently been reported for a diarylditelluride complex, (OC),Re( p-Br),( p-Te, Ph,)Re(CO), [ 130b], related complexes with bridging S,Phz [295a], &Me, f295b], Se,Ph 1 [296a], and Z&Me, f296b] as welf as the parent St- (2971 and Se:- f298.2993 ligands ha\ring been described previously. Complexes with $-S3 (e.g., Ru($-

S,)(CO),(PPh,), [3001) and #-Se, (e-g., Os( q”-Se,)(CO)2(PPh,), [301]) chelating ligands have also been reported recently.

A qd teh-d ccmpte_xes_ The first derivative incorporating an Hg-TeAr Iinkage (PhTeHgCl) was reported by Lederer [IZI], who reacted HgCl, with a solution of “HTePh” (obtained by cleavage of Te,Ph, with Na in ethanol followed by acidification of the NaTePh solution and ether extraction). The analog, p-EtO-C,H,TeHgCl, was prepared by refluxing a solution of equimolar amounts of Hg(Te( p-EtO-C,H,))l_ and HgCl, [l 14a]_ .

MetaIlic mercury reacts with Te, Arz (Ar = Ph [ 11 I], p-Eta-C,H, f 114a]) in benzene at room temperature to give Hg(TeAr), derivatives whose insolu- bility in organic solvents suggests that they are polymeric materials with bridging ArTe- ligands. This type of oxidative addition reaction is analogous to that previously described flU9] for the reaction of Pd/PPh,), with Te,Ar, (Ar = 2-thienyl, p-Et@-C,H,) to give [Pd(PPh,)TeAr( p-TeAr)fl (eqn. 3). Complex mercuric phenyltellurol complexes were prepared by reaction of NaTePh with Hg(TePh), [ 1131

The tetraphenylphosphonium salt is solubIe in THF and CHCI,, insoluble in petroleum ether, benzene, ethanol and ether, and air stable in the solid state for several weeks. The tris complex can be readily formed in liquid ammonia

153

by the above reaction, but attempts to react the former complex with another equivalent of Ph,PTePh in CWCl, to give I-%g(TePh)i- gave instead Hg,(TePh):, v the Ph,P i- salt being isolated as orange-red crystals.

A trigonaf planar (D,,) structure fur the ~~~(TePh)~~ - anion, proposed on the basis of a detailed study of its far-IR and Raman spectra (Te-zig vibrations; v, = 120 cm-i (Raman); vW = 148, 13’7 cm-’ (XR) [I 131) was subsequently confirmed by a single-crystal X-ray diffraction study of [Ph~~~~Hg(TePh)~~ [187] (Fig.6). The complex has an ionic structure with distances between Te and ,EIg atoms of adjacent Hg(TePh), units being generally longer than 10 A, The three TePh- Iigands in the anion are coordinated in a propeller-like arrangement about the central fig atom in an approximate planar HgT% unit. The analogous thio- and selenophenolate complexes are believed to be trigonal pyramidal, this being one of the few reported three-coordinate trigonal planar I-Ig(II) complexes_ The structure of fPh4 P]~~~g~(TePh~ t, f is unknown.

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D&y1 t&&& c~~rp~exczs Several complexes of cuprous halides with TeAr, (Ar = Ph, p-tolyl, p-CH$&-Cf,H,, and p-EtO-C,H,) have been reported by McWhinnie and Rattanaphani [ 1801. The complexes, prepared by addition of alcohol solutions of the telluride to aqueous solutions of the halide dissolved in 1 M hydrohalic acid (HCl, HBr) or saturated KI solutions, were obtained with the indicated stoichiometries (Table2f regardless of the metal:ligand ratio used in the reaction, This is in marked contrast to analogous phosphine systems, which give a wide range of stoichiometries. depending on reaction conditions (e.g., GuX(PR,),,: n = I ]302], 2 [303]. 3 [304,305]; Cu,Cl,(PPh,), ]304-3061). The moderately high conductivities of these complexes in acetonitrile (61-77 ohm- ’ cm2 mol - 1 vs. values of 120-160 for 1: 1 electrolytes) was attributed to solvolysis reactions involving molecular complexes rather than the presence of double salts (i.e., ICuI-,I]CuX,]; n = 2, 4) on the basis of the z+~_~ bands in their far-IR spectra. This conclusion is supported by measurements of molar conductivities of these solutions as a function of the square root of concentration, which show behavior typical of weak rather than strong electrolytes. Indeed, acetonitrile is known to function as a stabilizing ligand for Cu(I) [30?,308). The most common structure found for these complexes involves dimers with two bridging halide ligands (i.e., (TeAr,),Cu(p-X),Cu(TeAr,),; X = Cl, Br: Ar= Ph, p-tolyl, X = I, Ar = Ph), the Cu( I) assuming its -characteristic tetrahedral geometry [309]. A wide variety of G(I) halide f304-306f and thiocyanate 13101 complexes have been shown to have such dimeric structures. This formulation is supported by their far-IR spectra, two bridge Cu-X-Cu stretching vibrations typically occurring at lower energies than expected for singlet terminal Cu-X vibrations ]3 I 1-3 141. The 2: I complex of CuI with Te( p-tolyl), exhibited an anomalous X-ray powder pattern, and, its far-IR spectrum had a ZQ.~~ at 163 cm-‘, a value typical of a terminal Cu-I bond (31 l-314]. This complex, therefore, has been tentatively assigned a monomeric structure with trigonal planar Cu(I), a stereochemistry which has been we11 established by several single-crystal X-ray diffraction studies (e.g., [CuCI(SPMe3)]s, [CU(SPM~)~]CIO,, [Cutu,Ci] [315]).

Cuprous iodide was also anomalous in its reactions with TePh, and Tefp-Et&C&H,),, I : 1 complexes being obtained. Of the three possible structures for such complexes [linear two-coordinate (e.g., [Cu(CN),] - [3 161); tetrameric cubane structure (e.g., [CuI(AsEt,)], [317]); or dimeric trigonal planar with two halo bridges (e.g., [CUCI(P(C,H,,),)]~ [302]), the last formulation was favored on the basis of the occurrence of strong vcttI bands at I61 and I I I em-” for the TePh, complex. The IR data for CuI(T~ p-Et0

-C,H,),) did not allow a structural formulation of this complex. A Mossbauer study [ 17 1] of a series of complexes of several metals with

Te( p-EtO-C,H,), indicated that this Iigand functions primarily as a u donor, using its lone p electron pair with the following order of Lewis acidity established from the measured quadrupole splittings: Hg(I1) > Pt( II) > Pd( II) > Cu(1).

Diaryi- and dialkylditelluride complexes. Complexes of cuprous halides with diaryldite11urides (CuXArzTe,; X = CI, Br; Ar = Ph, p-EtO-C,H,) have been prepared by addition of an equimolar amount of Ar,Te, in ether solution to an acetonitrile solution of the cuprous hafide (in a nitrogen atmosphere), orange to red precipitates of the complexes being obtained on cooling the reaction sohttions [I 16,117]. The formulation of these complexes as ditelluride complexes with the Te-Te bond intact is based on their color (characteristic of the free diteilurides, poiymeric TcAr- bridged species resulting from Te-Te cleavage generally giving dark brown materials) and the assignment of a vTc_rc absorption for CuCl(Te,Ph2) at 170 cm-’ in its far-IR spectrum. This latter absorption is apparently enhanced by coordination, the corresponding band for the free diteiluride occurring at 167 cm- ’ in its Raman spectrum. The occurrence of a z+~_~, at 230 cm-’ in the far-IR [ 116,117] indicates the presence of bridging rather than terminal chloro ligands. Coordination of both Te atoms of the ditehuride ligands in these complexes is supported by their “‘Te Mossbauer spectra, which both give good computer fits for one quadrupole doublet [116,117]. The chemical isomer shifts (8) are a11 the same within experimentai error and are similar to the values for the free ditellurides, indicating that no significant change in hybridization at Te has occurred on coordination_ The quadrupole splitting values were also all very similar but Iowered vs. the free ditellurides,

Fig. 7. Proposed structure for diorga~oditeil~~de complexes with cuprous halides.

I59

indicating coordination of the p-lone pair, resulting in a lowering of the p orbital imbalance. Comparison of these quadrupole splittings with those of W&II) complexes ((EtO-C,H,),Te,HgX,; X = Cl, Br; A = 8.9-9.5 mm SC%-’ for the Cu(1) complexes vs. 5.1 mm set - ’ for the Hg( II) complexes) indicates that Hg(II) has greater Lewis acidity than Cu(I) with respect to this ditelluride ligand. On the basis of the above spectroscopic data, polymeric structures have been proposed for these complexes (Fig. 7). Attempts to obtain single crystals of these complexes for a definitive X-ray diffraction study resulted in decomposition.

Complexes of dial-amino~henyl~ditelluride with CuCl and CuCl z have also been reported [63,129]. This new ditefluride was prepared by borohydride reduction of the novel o-metallated derivative, (2-phenylazophenyl-C.N’)- tellurium(l1) chloride

l /-** Ph ii I

Te!CI~ -TizGz

C,,H9N,TeCl, N,$% L

f.J la._,’

Mea4 II I

~N\te -Cl Ph

Reaction of an ethereal solution of di-2-aminophenyl ditelluride with an acetonitrile solution of CuCl under nitrogen gave a brown 1: 1 complex [63,129]. Unlike the other reported complexes of cuprous halides with ditellurides [ 116,l f7], this product could be recrystallized from acetonitrile. The molar conductivity of the compiex in acetonitrile indicated a 1: 1

&GtrOlyte, and its IR spectrum in the Pm.r region (Table 2) supports coordination of one of the amino functions of the ditelluride. The complex was formulated as fCu((o-NH, -C,H,),Te,),]fCuCl,], the cation containing two bidentate ditelluride ligands and tetrahedral Cu( I).

An analogous reaction with anhydrous CuCl, also gave a 1: i complex [63,129]. This complex, however, has not been well characterized (it gives a molar conductivity of 65 ohm-’ cm’ mol - ’ in acetonitrile and has a very broad absorption peaking at 3240 cm-’ in the vNH region). The I stoic~omet~

Several analogous derivatives with dialkylditellurides have also been prepared [Te, R, ]CuX (R = Et, n-Bu, n-C,H, 1 ; X = Cl, Br) [ 116,117] and have been assigned structures similar to the aryl derivatives on the basis of their Miissbauer spectra (Table 2) and color.

ilt$- nrtd alk~$relitwof catlzpie.ves. Highly insoluble and presumably polymeric tellurol complexes, CuTeR (R = Et. n-Bu, n-C5H,, ) and CuTeAr (Ar = Ph, p-EtO-C,H,). h ave been prepared by the following two routes [ 116.117]

Ar,Te, i- NaBI-I, 1 M NnOH/EtOH

- (27) (RJe,)

ArTeSnPh, -i- CuCl Et 20/MKN

- (RTeSnPh,) (%%%j

The similarity of the Mossbauer isomer shifts for these complexes with those observed for diorganotellurides and ArTeSnPh, suggests that the Te bridges two copper atoms and has a coordination number of three. In a structure in which the Te bridged three copper atoms and has a coordination number of four, considerable rehybridizati~n at the tellurium would be expected, resulting in significant removal of s electron density corresponding to one of the localized nonbonding electron pairs and a resulting large shift in the chemical isomer shift vs. TeRz derivatives.

Ag ~~~~~ky~ rel&-ide conrpie_-ues. The Ag(I) complexes AgI(TeMe,). and (Agf), TeMe, have been reported by Coates [ 1823. Addition of TeMez in acetone to a solution of AgI in concentrated aqueous KI (2/l molar ratio] gave a white precipitate of AgI - 2 TeMe, which was recrystallized from acetone with some decomposition (m-p. 73-74*C; white sohd). The complex smelb strongly of TeMe,, and the l&and can be quantitatively removed by heating at 180°C under vacuum- Addition of a solution of AgNO, to an acetone solution of the complex gives a heavy yellow precipitate of AgI, leading to the sugges- tion of the formulation [Ag(TeMe,),] + I -. However, a far-IR study or a

single-crystal X-ray diffraction an&is of this compound is necessary to establish its actual structure. A related compound, AgCl- 2PPh, [318], was recently shown by single-crystal X-ray diffraction to be a chloro-bridged dimer, the coordination polyhedron around the silver being a distorted tetrahedron. Phosphine complexes with AgI generally form tetrameric complexes with bridging iodo ligands (e.g., [Agf - PEt,], f319], [AgI - PPh,], [320,32 l]).

The complex (AgI), - TeMe, (m-p- 137- 138YZ, dec_ to black liquid) pre-

cipitates on addition of an acetone solution of TeMe, to a solution of AgI in concentrated aqueous KI (1:2 molar ratio) [182]. It is insoluble in water. alcohol, acetone and benzene and loses TeMe, qua~titativeIy on heating at 18W’C under vacuum_

The formation constants of Ag( I) complexes with the water-soluble ligands X(CH,CH,CO,H), (X = 0, S, Se, Te) have been measured potentiometri- tally, a stability order Te > Se z=- S Z+ 0 being found [ 18 11.

Complexes of AgBr with Te(rr-B~)~, Te(CH,CH,CN),. PhTeEt. PhTeCOEt, PhTeCOPh and (Z-naphthyl)Te(CH,Ph), having the general formula (AgBr),TeR,, were reported in a recent patent [ l35] which describes their use as light-sensitive compositions in photothermographic elements.

These complexes were prepared by adding a solution of AgBr dissolved in aqueous KBr to an acetone solution of the ligand (a I:2 molar ratio of ligand to AgBr was used). No spectroscopic data relating to the structure of these complexes were reported. Their photoelectron spectra. however, were recorded and showed that the tellurium binding energy increased by ca. 0.7-0.9 eV in the Ag(1) complexes vs. the free ligands ft35]. Presumably the complexes are dimeric with bridging telluride ligands, a bridging bonding mode for TeMe, having been previously proposed on the basis of NMR data for the complexes ~Bu~N)~[X~Pt~~-TeM~~)PtX~] (X = CL Br) f176]_

DiaryI fehride camplexes. The first examples of diary1 telIuride complexes of Ag(I) were recently reported in patents [ 134,135] which describe their

synthesis and use in photothermographi~ imaging elements. Complexes of the type (AgX),Arz (X = Br; Ar =p-MeO-C,H, r134.1351; o-Me-C,H, [ 1351; 2-naphthyl [ 1351; p-Me,N-C&I-I, [ 1351; (Ph){ p-tolyl) [ 1353; (Ph)( p-Br -C,H,) [ 135] and X = Cl, 1; Ar = Ph [ 135]) have been reported. These complexes presumably have the same structures as the alkyl analogs [135]. As observed for the dialkyl telluride derivatives the ESCA spectra of these complexes showed an increase of ca. 0.7-0.8 eV in the teiiurium binding energy upon coordination to A&l) [ 135]_

Tel&ium Itererocyc!es. Complexes of the formula (AgX),L (L = I-0x+4-

telluracyclohexane, X = NO, [ 1343, Br [ 1341; L = dibenzotellurophene, X = Br 11351) were prepared by the method used for the above alkyd and aryl telluride complexes (i.e., addition of an aqueous soIution of AgNO, or AgBrt to an acetone solution of the ligand). The ESCA data for these complexes showed the typicai increase in Te binding energy of 0.6-0.9 eV vs. the free Iigand [135]. No other data, other than elemental analysis, were reported for these compiexes.

Although Ag(i) salts form a wide variety of complexes with phosphines (i.e., AgL,$X; X =I: anionic Iigand, n = i -3 or noncoordinating counteranion,

162

Au The formation constant of AuBrTeMe, was measured by potentiometric

titration of Au(MeCN)’ in acetonitrile (K= 7.6 X lo”), although the product was not isolated fl83], The following stability order was found from a series of titrations: Me>S < Me,Se -=z Ph,Sb -= PhNC - Ph,As ( Me,Te < MeCN - Ph,P< Ph,MeP< PhMeiP.

The reaction of an ethanol solution of TePh, with aqueous AuCl, was reported to cause precipitation of a grey chloroaurate complex (m-p. 154- IS6*C), but no other detaiIs were reported [184& Indeed, the proposed oxidation state of the gold, Au(fII), is questionable, since phosphines are known to reduce Au(W) readily to Au(I) with stabilization of the lower oxidation state by complexation with excess of the l&and (e.g.. AuPPh,Cl [322], AuP(OPh),Cl 13231). Analogous chemistry is reasonable for diorganotellurides, facile oxidation to TeRIX, (X = CL Br, 1) by oxidants such as halogens and transition metal chlorides being characteristic reactions of such derivatives [‘I I]. The synthesis of transition metal complexes of diorganotet- h.nides by such Iigand reduction processes, well established for Au(I) [ 1 S&323], Rh(1) [ 1201 and Cu(I) [3 IO] chemistry using phosphorus and sulfur ligands, is an area that remains to be explored.

Ni Only one paper [122] has described the synthesis of wetl-characterized Ni

compounds with organotel~urium ligands. The compounds 7rCpNi(P{n- Bu)3)(Te-X-C,HJ (X =p-UMe; p-Me, H, p-C& tn-CFs) have been prepared by metathetical reactions

[7rCpNifP(n-Bu),),]CCI- +NaTe(X-C,H,) 3

zCpNi(P(n-Bu),)(Te-X-C,H,) + NaCl -f P(n-Bu), (29)

These complexes, which are stable in the solid state under an inert atmosphere and moderately stable in air, are solubIe in benzene and hexane but react with CH,C17 and CCI, to give the complex nCpNiP(n-Bu),Cl. They react with methyl-iodide in benzene solution to give =CpNiP(n-Bu),I and MeTeX-C, f-f,. The ’ H NMR spectra of the complexes show a signal at T 8.3-9.5 ppm due to the phosphine iigand and a sharp singlet at ca, 4.9 ppm due to the cyclopentadienyl protons, the position of the latter resonance showing a linear relationship with the value of the Hammett constant of the substituent in the -X-C,H, ligand. Comparison of these NMR results with those of the corresponding S and Se analogs indicates that the order of transmission of polar effects of the X substituent through the Ni-E (E = S,

t63

Se, Te) bonds to influence the electron density in the PCP ring is S < Se < Te (P’ - 17.9, - 18.7 and - 19.3, respectively).

The reaction of Ni(CO), with TePh, gave only thermal deccrmposition with deposition of Te(0) and I%(O) [ 19i]. Bergman and Engman f 153f have

reported the synthesis of carboxyfic acids by the reaction of Ni(CQ), with aryl tellurium chIorides in DMF

ArTeCl, + 2 Ni(CO),(” ~Z~~~c’ ArCO, H + NiGI Z + NiTe + 7 CO -t HCI ::

ArzTeCl Z + Ni(CO), “) Dh~71’0Ct 2 ArCO, H + NiTe + 2 CO + 2 HCI (17) 2 If,0 (31)

A mechanism invotving the oxidative addition of the ~on~ponents of ArTeCI folIowed by CO insertion has been proposed for this transformation. In contrast to the analogous reactions with aryl mercuric chlorides, which give exclusively the diary1 ketones, this procedure gives predominantly the carboxylic acid with only small amounts of the diary1 ketones as side products. The facile synthesis of ArTeCf, derivatives with a wide range of functional groups suggests that rhis chemistry may have considerable utility in organic synthesis.

Pd

Diuikyf tellrrride conzppfeses. The first monomeric Pd{II) complex with a dialkyl telturide (i.e., PdCI,(TeEt,),) was prepared in f957 by Chatt and Venanzi [I91 by reacting an aqueous solution of (NH,)?PdCt, with TeEt,. The chloro-bridged dimeric analog of this complex and the Te(n-Pr)> derivative were also prepared in this work by the reaction of Na,PdCI, with one equivalent of the telluride in ethanol. Alternatively. the dimers can be prepared by reaction of equivalent amounts of Na, PdCl. and PdCl zfTeR, ): in ethanol.

Subsequent studies reported the far-IR [164,166j, Raman 11641. ‘H NMR [162,163,166,172,173], UV-visibie [166] spectra and dipole moments in benzene [I 641 of the complexes Pd(TeEt,),X, (X = Cl, Br, I).

The chloro and bromo monomeric c&piexes were prepared by shaking an ethanol solution of the teffuride with an aqueous solution of K3 PdX, (X = Ci, Br), and the iodo complex was prepared by a metathetical reaction between the chforo complex and KI in acetone or ethanol.

The range for the ypd_-rc vibrations was reported as 13% I57 cm- ’ [ 1661, a range somewhat Iower than that reported for the TeMez analogs [ 1601. The complex PdCl,(TeEt,), has two vprt_cI bands in its solid-state IR spectrum indicative of cis geometry, but the bromo and iodo complexes both give one

Pd(S

CN

),(T

eEt 2

I2

TeE

t ,C

IPd(

@l)

;PdC

ITeE

tz

Tc(

n-Pr

),C

IPd(

pCl)

,PdC

lTc(

n-Pr

),

PdT

eEt,(

pipe

ridi

ne)C

l z

h

Tru

wPd

(SC

N),

(Te(

CH

zSiM

c,),

),

Tru

ns-P

dClz

(Tc(

CH

,CH

zCH

,SiM

cj),

),

Tru

wPd

(TcE

t,),P

hCl

Tru

wPd

(TcE

t,),P

hI

Tru

wPd

(TcE

tz).

& o

-1ol

yl)B

r T

ruw

Pd(T

cE(,

),(

p-to

lyl)

I

M-p

. X7-

89°C

B

lack

tH

NM

R

p(bc

nzcn

c)=

I .Y

D

IJ,,,

,_~ (P

hCI s

oln)

= 1

60 cm

- ’ (

Ram

an)

M-p

. 35-

3X”C

M

,p.

I IO

- 125

°C (d

cc.)

D

ark

red-

brow

n M

ap. I

3 I .

5- 1

32°C

(dcc

.)

Dar

k re

d-br

own

I’N

,I =32

49 a

n-

’

A ,,

,,,(h

cxiln

c)=

340

nm

(c

350)

f’

Ntt =

3345

. 32

x0 c

ttt-’

“N

tI =

3359

, 32

% c

ttt -’

M

-p. Y

9’C

I’

~+,_

~~

(sol

id)=

34X

cm

- ’

M.p

. 14

3°C

)‘

CN

(mul

l)=

210

7 (s

p),

(CH

CI,

) 21

22 (s

p). 2

095

(sh)

cm

- i

A=

2,8X

IO

“ M-l

cm

-?

M.p

. 70°

C

~~~~

~~~~

(s

olid

)=35

2 cm

A”

M.p

. 64’

C

I’(~

t,!

(nltt

ll)=

2 1

06 (S

p),

(CH

CI,

) 21

13 c

m-

’ A

=3.

2X ]

OJ M

-l

cm-?

M

.p.

101°

C

~~~~

~~~~

~ (n

iull)

=Z

XS.

305

, (C

H$Z

lz)

348

cm-’

M

.p. X

X-9

2°C

M

W (

bcnz

cnc)

=6O

X (6

34 ta

lc.)

M

.pa 3

2-33

°C;

I’ ,,J

_cI i

mul

l)=

2X

I cm

‘ I

M.p

. X7-

90°C

M

.p. 9

7- 1

02V

M

.p. 8

7’C

M

W (~

~cnz

cnc)

=6~

2 (6Y

6 tal

c.)

164

163,

166

16

4 16

4 I6

7 I9

19

l&20

21

20

20

I3

I3

I3

13

16X

I65

I65

165

165

I65

TA

BL

E 3

(co

ntin

ued)

Mis

c. d

ata

Ref

.

7iw

rs-P

d(T

eEt,)

2( p

-Cl-

C,H

,)C

i

T/w

s-Pd

(TeE

t,)z(

/I

-F-C

,H,)

B~

~~u}

~~-P

d(T

eEt~

)~Ph

(S~N

)

(b)

Dia

ry1

tellu

ride

com

plex

es

~~~~

-Pd~

l &re

Ph 2

)?

M,p

. 97-

100

aC

MW

(bc

nzcn

c)=6

57 (

627

caic

.)

VI’

&])

r (111u11)= 165 Clll" I

M,p

. 69-

71 “

C

MW

(bcn

zcnc

)=bX

9 (7

12 c

ais,

) yM

_lfr

(mul

l)=

160

cm-’

k

Map

. 99-

106

YZ

M

W (b

enzc

nc)=

619 (

625 t

alc.

) vl

Jd_e

I (mul

l)=2

81 cm

* ’

M,p

. I1

2-12

4’C

(dc

c.)

MW

{bcn

zenc

)=64

1 (66

9 ta

lc.)

M

+p.

1 IO

-1 IY

C

MW

~bc

nz~r

l~~ =

64X

(652

cc\

Ic.)

M.p

. 164

T

z+d_

cI (m

ull)

=350

(s) c

m-

I,

h,(1

0w3

M, D

MF)

=3S

ohm

-’ c

m””

moi

”“’

X,,,

,(C

~H,)

=24

.81 c

m-’

(~=

58,0

00)

Up.

l%

I°C

A

M (l

o-”

M, D

MF)

=81

oh

m”’

cm

? m

oi -I

M

.p, 2

2%22

7OC

M

-p, 2

30-2

32Y

M

,p. 2

45-2

45°C

M

.p.

l68-

169

Y.Z

M

ap. 1

60- 1

62O

C

Mp.

55O

C (d

cc.)

R

ed m

elt

at 9

OT

165

165

I65

I65

165

165

109,

167

10

9

109

167

167

167

167

167

t67

~r~~

f~-P

dBr*

(Te(

p-

EtO

-C,H

,),)

,

(c) C

ompl

exes

with

ary

l tel

hrol

lig

ands

(Pd(

TeP

h),)

,, [P

d(PP

h,)(

Te-

PEtO

-C,H

&-T

e-PE

tO-C

,H,)

]l’

[Pd(

PPh,

)(T

e-2-

thie

nyl)

(pT

c-2-

thie

nyl)

],

’

(d) H

eter

ocyc

lic lig

ands

cis-

PdCL

,

trofIS

- Pd

Cl2

M.p

, 125

°C

AM

( 10e

J M

, DM

F)=

3,2

ohm

-’ c

m’ m

ol-’

cp

d_cI

(mul

l)=3

5I c

m-

I 6=

0,31

mm

see

-‘;

A=

7.61

mm

scc-

’ M

,p, 1

05°C

A

, ( 1

0 -3

M, D

MF)

= 8

9 oh

m-

’ cm

’ mol

-- ’

Y

PJ_

l), (m

ull)

= 2

75 cm

-’ ’

S=O

.29 m

m S

W “‘

I; A

=6,

78 m

m se

e-’

M,p

, 117

’C

A,

(IO

-” M

, DM

F)=

3,3

ohm

-’ c

m? t

nol-

* ’ D

ark

brow

n M

ap, 1

45°C

A

, (I

O-”

M, D

MF)

=2.

3 oh

m-’

cm

! mol

-’

Dar

k br

own

M.p

. I3O

’C (d

cc,)

I’

p&.c

’,

= 3

03, 2

87 cm

”’

I

Red

-bro

wn

M,p

. 130

°C (d

cc,)

I’

~‘,_

‘., = 3

59, 2

98,2

70 cm

- ’

Red

-bro

wn

Red

-bro

wn

l’j“

l_C

I = 3

54 cm

- ’

109

171

109

171

115,

119

10

9

109

132

132

132

TA

BL

E 3

~co

nt~~

ucd)

%

Mis

t, da

ta

Rcf

,

Pt c

ompl

exes

(a)

Dia

lkyl

tel

lu~d

~ co

mpi

exe~

Cis

-PtC

I,(T

eMc,

),

Pate

-yel

low

solid

v~

,_~~

(sol

id)=

303

, 283

cm

” i

+,_

‘,‘t

(sol

id)=

187

, 156

cm-

’ L

ight

-bro

wn

solid

~~

~~~~

~~

~su~

id) = 2

45 (s

) cm

- I

Lig

ht-b

row

n so

lid

YpX

_j

(sol

id)=

147

cm-

’ (v

sg

Jls&

_ils

~r

= -1

553

Hz

Jlur

pci3

iT, =

-

IOf2

2 Hz

JLU

Jf*,

_‘lS

~I

=-4

0QN

z Jl

usp,

..‘?5

Tu

= 5923 Hz

Jlus

,‘,_

“s~v

=

50

88 H

z

‘H N

MR

@cc

Sec

tion

E~j

ii))

M.p

, 12

6-12

7*C

Y

~,_~

~ (sol

id)=

302

, 282

cm

”‘“!

(3

10,3

04,2

82 c

m-

‘)

M.p

. f2

6- 1

2Y’C

p-

2,3

D

(6,O

D)

Var

iabl

e-tc

mp,

‘H

NM

R

M,p

. 12

5- t2

7YI

(127

-128

Y$

Bro

wn-

yclI

ow so

lid

Pi,+

(sol

id)=

217,

208

cm

-”

218,

210

cm-’

(P

hCI s

oln.

) 203

cm

-’

~Ram

an)

~~b~

~cne

) = I

.9 D

V

atia

b~c.

~cm

p. ‘H

NM

R

. .

. . . . _

_ ..,_

(

160

160

I60

176

176

176

176

176

177

177

23

164

I64

164

174

162,

163

, 172

, 173

23

16

4

23

164

164

I64

162,

163

, 172

, 173

I69

F

170

c-3-Y ca -

Cis

-PtC

l,(T

e( p-

EtO

-C,H

,),)

z 6=

0,35

mm

see

-‘;

A=

6.63

mm

see

-’

171

‘I’r

ans-

PtB

rz(T

e(

pEtO

-C,H

,)&

M

.p, 1

50°C

10

9

’ t=

ter

min

al P

d-ha

loge

n st

retc

hing

vibr

atio

n; b

=bri

dge

Pd-h

alog

en-P

d st

retc

hing

vib

ratio

n. h

Com

plex

es no

t is

olat

ed: I

R s

pect

ra o

f so

lutio

ns ob

tain

ed b

y di

ssol

ving

Pd&

14(T

eR,)

, an

d th

e am

ine i

n C

CI,

(I :

2 m

olar

ratio

). ’

See e

qn, 3

for

the

str

uctu

re o

f th

is d

imer

. (’

Com

plex

was

pre

pare

d by

met

athe

tical

reac

tion

betw

een t

he c

orre

spon

ding

brom

o co

mpl

ex an

d K

SCN

, but

no

data

are

rep

orte

d fo

r th

e th

iocy

anat

e com

plex

, The

not

atjo

u (C

NS)

for

the

tl~oc

yana

tc @

and

impl

ies a

n un

know

n bo

ndin

g m

ode

for

this

am

bide

ntat

e lig

and,

’ A

C

HzC

l, so

lutio

n co

ntai

ning

[N(n

-Bu)

,]Pt

(CN

S),T

eMe,

was

obt

aine

d by

equ

ilibr

atio

n of

Pt(C

NS)

l(T

cMcz

)l w

ith [N

(n-B

u),]

,Pt(

SCN

),. ’

T

he re

actio

n bet

wee

n Pt,C

I,(T

eEt,)

, an

d py

ridi

ne w

as ca

rrie

d out

by

addi

ng a

CH

,Cl,

solu

tion

of p

yrid

ine t

o a

very

dilu

te so

lutio

n of

the

dim

er t

o av

oid

the

form

atio

n of

PtC

lz(p

y~di

ne)~

and

PtC

l*(T

eEt~

)z, s

Thi

s co

mpl

ex, p

repa

red

by r

eact

ing

~-Pt

Cl~

(NC

Ph)~

with

2

equi

vale

nts o

f Te(

p-E

tO-t

&H

,),,

was

form

ulat

ed as

the

mm

is

omer

on t

he b

asis

of

its s

olub

ility

in b

enze

ne an

d th

e ob

serv

atio

n of

one

F r

,_ot

band

[ 109

). The

repo

rted

valu

e of

the

~~~~

~~~

band

is, h

owev

er, m

ore c

hara

cter

istic

of a

cis

com

plex

[ 168

1, The

ben

zene

solu

bilit

y may

be

the

resu

lt of

a c

is~

~ru

~~

jsom

eriz

at~o

n upon

djs

solu

tion,

a ph

enom

enon

obse

rved

for ~

i~-P

tCl,(

Tc(

CH

,CH

?Ph)

2)1 11

683.

172

band characteristic of mms geometry [ 1641 (see TabIe 3). AIt three complexes exist exclusively as the trays isomers in benzene solution, on the basis of dipole moment measurements (ea. 1.8 D) [ 1641,

The far-IR spectrum of PdI,(TeMe,),. prepared by addition of TeMe, to aqueous K, PdI,, supports a rrarzs configuration for this complex. Similar reactions with PdXG- (X = Ct, Br) gave the halo-bridged dimeric complexes [ 1601. Variable-temperature NMR studies have been reported for the complexes PdX,(EEt,), (X = Cl, Br, I; E = S. Se. Te) [162.163,172.173]. The complexes al1 have coalescence temperatures which have been associated with a rapid inversion of configuration at the pyramidal chatcogen ff72,173f atom (Le., truns-PdX;(TeEt , j7: X = Cl, 30°C; X = Br, 5 I “C; X = ii, 18°C). Since Pd, unlike Pt. has no-observable magnetic nuclei (i.e., IY5Pt, 33% natural abundance, I = l/2), precluding the observation of a metal-H coupling, the unequivocal assignment of the phenomenon associated with these spectroscopic parameters was not possible for these complexes (e.g.. the spectra of the PtX,(EEt,)? complexes showed Pt-I-I coupling above and below the coalescence temperatures, precluding an intermolecular ligand- exchange process). Indeed, the rather wide variation of coalescence temperatures observed for the Pd complexes as a function of the halide lig:and suggests that some process other than chalcogen inversion is operative; i.e., for the series PtX,(EEt& (E= S, Se. Te) the variation in the coalescence temperatures for the three halides in a set of complexes with a given chalcogen ligand is (5°C.

The variable-temperature spectrum of PdBr,(TeEt.), in the presence of free TeEt2 ( K 10 mole 5% of TeEt, relative to complex) also gave one coalescence temperature, lower than that observed in the absence of free l&and {-K - lO*C vs. t5 1°C for the complex alone) 11631. The failure to observe two distinct coalescence temperatures in the spectra of the PdBr,(TeEt ,), /TeEtl system (as observed in the spectra of UCIIIS- PdX,(SEt,);,X = Cl, Br, and trans-PtCl,(SeEt,),, X = Cl, Br, in the pres- . - ence of the respective free figand) precluded the assignment of the coalescence phenomenon for the pure compIex to an inversion process. It was suggested that the variable-temperature spectral data may be compatible with both inversion and exchange processes in the PdBrz(TeEt,), system, the former simply being slower than the latter 11631.

The chloro bridges in the dimerie complexes can be cleaved by amines to give the monomeric Pd~TeR~)(amine)Cl~ complexes (amine = piperidin~* n-octytamine, ~-to~uidine) [20]. Infrared studies have shown that such mixed complexes rearrange in Ccl, solution to give PdCIz(amine)z and PdCll(TeEt,), [18J.

Infrared itidies of the Pd(TeRz)(amine)Ci, complexes (Le., the vNH of the coordinated amine) were interpreted to suggest that the effects trans-

173

mitted from the Te Iigands (as weill as ofher arsine, stibine, amine, sulfide and selenide hgands) across the Pd atom to the N-H bond are mainly electrostatic [20].

The anomalous properties of the phosphine complexes were explained by v-bonding invofving d-Y,. (or c& hybrid) orbitals of the metat with vacant low-energy orbitals of suitable symmetry in the phosphine (in view of recent rest&s [324,325], this behavior can be attributed to more efficient u overlap in the phosphine complexes compared to the other Iigands. the latter showing a linear correlation of vNtI with electronegativity of the donor atom)_ The observation that the yNr.+ frequencies in the Pd( II) complexes are generaIIy 15-20 cm- 1 higher than in the Pt(Ii) analogs is consistent with weaker acceptor properties of Pd(II) vs. Pt(I1).

The complexes PdXI(TeR,), (X = Cl, SCN; R = CH1SiMe3, CH,CH,CH,SiMe,) were recently-prepared and characterized by IR and NMR spectroscopy (13J. The presence of only one ypJ_cI band in the far-IR spectra of the chloro compIexes (Le., 348 cm- ’ ‘* respectively), supports a as tt-uzs S-bonded species the basis the position and intensity of their v<.~ bands. The appearance of low-energy shoulders of these complexes in CHCI, solution to result from of small amount of tis isomer

in the ‘H NMR spectra these thiocyanate compfexes the presence the shift

of the thiocyanate 18.1 117.6 both upfield ionic in complexes) Pd-SCN

in solution The proposed the of evidence been for tt.ails-Pd(SCN)2(TelCH1-

CH,CH,SiMe,),), 1131 fFig.8) by a single-crystal X-ray diffraction study. The complex PdCI,(Te(CH,CH,Ph),), has been formmated as the cis isomer in the solid state (~r,~_~, = 285: 505 cm-‘) with complete isomeriza- tion occurring on dissolution in CHC1, or toluene (350 cm - ’ IR; 305 cm - ’

Raman) [ 1681, A series of Organopa~~adium~II~ compounds, rr-urts-Pd(TeEt L! )z ArX (X =

Cl, Ar = J&I-C,H,; X = Br, Ar = Ph, o-tolyl, mesityi, o-CL-C,H,. p-Cl-- C,H,; X = I, Ar = Ph, p-tolyl) have been prepared from rr-ans-Pd(TeEt?), X, and the appropriate Grignard reagent, the yields being generally low [ 1651. Aryi lithium reagents in these reactions reduced the complexes to Pd(0) even at -WC, and the reactions with MeMgX fX = Br, I) gave only recovered starting materiaIs. CompIexes of the type Pd(TeR&Ar, were not obtained even though excess Crignard reagent was used in the reactions (analogous Pt(TeR.), At-, complexes are known) [ 1751. Molecular weights determined _ _ osmometrically confirmed monomeric structures for these compounds, TOWS

Fig. 8. Moiccuiar structure of rru,r~-~d(SCN),(Te(CHICH,CX-X,SiM~~),),. Rcpmduccd with . __ permission from Inorg. Chtm., t 8 (I 979) 2696.

configurations were proposed for the compfexes, as expected from the geometry of the starting materials, on the basis of the VP&or bands in their far-IR spectra.. The rather low values of the ~r~_~i vibrations (Table3) are characteristic of halogen ligands frans to an organic Iigand. Except for the p-Cl and p-F-C611, derivatives, which are relativeiy stable, the complexes slowly decompose to Pd(0) at room temperature in solution and even in the solid state. The stability of a homologous series increased in the order Cl ( Br ( I. In general electron-withdrawing substituents in the para position of the aromatic ring give complexes of enhanced stability vs_ analogs with ~I~ctron-donating substituents, and the ability of EEt, fE = S, Se, Te)

175

ligands to stabilize such organopalladium compounds increases in the OFdeF

SEtl ( SeEt, ( TeEtl. Illustrative of the above considerations, Pd(SeEt,)- (p-Y-C,H,)X (X = Cl, Br; Y = F, Cl) derivatives were isolated, but attempts to prepare p-tolyl derivatives resulted in deposition of Pd(O), and with TeEt. the very unstable Pd(TeEt.),I( p-tolyl) complex was isolated.

The stability order has been related-to the increasing polarizability of the donor atoms going down group VIA and metal - ligand 1~ bonding. Al- though a bonding between Pd and sulfur (in thioethers) has been reported to be insignificant 13261, such 7~ bonding involving the filled 4d orbitals of I’d(U) and the empty 4J and 5d orbit& of Se and Te respectively seems to be important (with Pd-Te 3 Pd-Se) [327].

Diavf tekrk& curnpkez Relatively few Pd(l[l) complexes with diary1 tellurides have been reported (Table 3) [ IO9,167,169,170.17 11. the most detailed study having been reported by Chia and M~Whinnie {tO9]. The complexes PdX,fTeAr, )-, (X = Cl, Br; AF = Ph, p-EtU-C,H,) were prepared by reaction of Pddli(NCPh), with the telluride ( f : 2 molar ratio) in benzene, the bromo complexes being obtained by a subsequent metathetical reaction with KBr [109]. The high sol~bility of the complexes in benzene together with the observation of only one v~+~~,~,~,” band in the solid-state far-iR spectra of the complexes was cited as evidence for t~atts geometries in these complexes. The solution structures of these complexes have not been studied. Conduc- tivity measurements in DMF indicate considerable dissociation of the halo ligand in the bromo complexes (Table3). These authors also reported that PdC12(NCPh)2 did not react with Te,ArZ (Ar==p-EtO-C&H,, 2-thienyl). A ‘“‘Te Mijssbauer study [ 17 I] of some metal complexes with Tef p-EtO- C,H,), indicated the following order of Lewis acidity towards this base: Hg(Ii) > Pt( If) > Pdf II) s Cu( I).

The complexes PdX,(TeAr,), (X = Cl, Ar = Ph. p-tolyl, p-MeO-C,H,. CGFs; X = SCN -, Ar = Ph. p--MeO-C,H,, p-C,F;-,,) have also been reported f167J, cis geometries for the chloro complexes and trutrs structures for the thiocyanates being suggested by IR evidence_ The only other description of diary1 telluride complexes of Pd(II) involved the use of TePh, in an analytical scheme for the determination of palladium based on the formation of PdCl,(TePh,),, which could be readily extracted into a benzene phase and dethroned spectrophotometrically at 400 nm [ 169,170f. The proposed Pd(I I) complex, however, was not actually isolated and characterized.

Al@ tekr@i con?pIe,ues_ Interesting complexes containing both bridging and terminal TeAr - (Ar = EtO-C,H,, 2-thienyl) Iigands have been prepared by oxidative addition reactions between Pd(PPh3), and the corresponding ditelluride [ 1091 feqn. 3).

176

Molecular weight determinations have confirmed dimeric structures for these brown complexes [ 109]*, and their conductivities in DMF are typical of nonelectrolytes_

Polymeric species of the composition (Pd(TePh)L!),, have been prepared by the reaction of PdCl 1( NCPh), with PhTeCUPh [ 1151 (eqn. 4) or PhTeGePh, [ 1 I q (eqn. 6).

Te heterocycles. Monomeric (A) and dimeric (B) complexes were obtained from the reaction of Na,PdCl, and tellurophene in methanol at 40-50°C fl32f_

,.=. Cl

‘I FL\ A_ I -=-\ /““xc,/ pd,cl I ,fe

.1=b i=d

n e

(70% yield) (27% ytetd)

The formulation of the complexes was based on elemental analysis and their far-IR spectra fTable3). The two products were separated by their solubility differences in acetone and CHCI,. Reaction of a suspension of the dimeric complex in CHCl, with excess tellurophene gave the monomer (A). Al- though it was claimed that the assignments of the v~~_~, bands for these two complexes were made by comparison with the spectra of the corresponding bromo complexes, no data on these latter two complexes were given. Reaction of Na,PdCl. in methanol with tetra~hlorotellurophene gave a monomeric complex formulated as tru,zs-PdCl,(TeC,Cl.)l on the basis of elemental analysis and the occurrence of only one vpd_ci band in the far-IR spectrum (Table 3). The larger truns effect of tetrachlorotellurophene vs. tellurophene, reflected in the formation of the ~rnrrs complex in the former case and the cis complex in the latter case, has been rationalized on the basis of increased ?z-acceptor property of the chioro-substituted l&and_

Pt ~~ff~~y~ te~kkkx The first reported coordination complex with an organotef- lurium ligand was described by Fritzmann [1’78] in 1915 (i.e., cis- PtCl,(Te(CH,Ph),),). This compound, which was prepared by the reaction of ai aqueous sol&i& of K.Ptkl, with an alcohol-sol&ion of the ligand Ot-

* The authors report that molecular weight determit~ations in benzene were obtaintzd vapor pressure osmometry. but no specific data are given.

by

17s

present. Infrared, Raman and ‘H NMR data support tray configurations in solution for the bromo and iodo complexes [ 1641. For a series of MX,(ER,), complexes. the tendency towards forming the tl*ar?s isomers in solution follows the orders Pd > Pt, Te > Se > S, and I =>- Br r Cl. The complete characterization of such complexes, therefore, requires careful measurement of their far-IR spectra in both solid and solution states, Raman f164f and NMR spectroscopy ( I l-3 [ I64], rrtjTe 11681) and dipole moment m~as~rern~~ts [ 164.1741 being useful su~?~en~~~t~ry structural probes.

Cross and co-workers [ 162,163,172,173] have used variable-temperature ‘H NMR spectroscopy to study inversion of ~o~fignratio~ at S, Se and Te in the complexes MfEEt,),X, (M= Pd. Pt; X = Cl, Br, I; E = S, Se. Te) as well as exchange processes in solutions of these complexes containing excess EEt2. In studies of the complexes in the absence of excess iigand below the coalescence temperature (i-e., PtX,(TeEt,),: X =t CL IO7*C; X = Br. 110°C; X = I, 105”C), the methylene protons are diastereatupic, forming part of an ABM,Y (Y =“‘Pt, 33% abundant, I= l/2) spectrum with ““Pt satellites. whereas above the coalescence temperatures the methylene protons appear equivatent (A,M,Y) [162,163.172.173].

For the SEt, and SeEt, complexes, the retention of the fr~~~_t~ in the spectra above the coalescence t~rnp~~tur~s precludes a disso~~ative mechanism. a fast inversion af configuration at the pyramidal chalcogen atom on the NMR time-scale being unequivocally proposed for the spectral changes [ 172,173],* The coalescence temperatures indicate that the ease of inversion is S > Se >Te and Pt > Pd. The increasing barrier to inversion for the complexes as one goes down the chalcogen elements [ 172,173] resembles the situation for the pyramidal group VA compounds [328.3293. For the TeEt, complexes, however, a ligand dissociation-recombination process could not be unequivocally ruled out, since no Pt-H coupling could be observed in the spectra above the coalescence temperature [172,173].. However, the solvent and concentration independence of the coalescence temperatures, the reversi- bility of the temperature variation of the NMR spectra, and the similarity of the coalescence temperatures for the different halides of the Pt(TeEt ,&X7 series are all consistent with lone pair inversion at the tellurium atom iaiher than a fast ligaud-exchange process being responsible for the observed spectroscopic changes. Variable-temperature NMR studies of the complex Pt(TeEt &( p-tolyl), were, however, unequivocally consistent with a facile inversion of configuration at the pyramidal tellurium atom, since the spectra over the temperature range studied (ambient to -57OC) retained Pt-H coupling (an A,M,Y system; J’IPs~+I~ = 29 Hz) [ 173]. No line broadening of the methylene resonance was observed down to - 57”C, setting this temperature as an upper limit for the inversion process. On the basis of the ability of strsngly tr*arrs activating aryl groups to similarly markedly increase the rate

I79

of inversion at sulfur 13301, the complex Pt(TeEt,),( p-tolyl), was assigned a cis configuration.

The variable-temperature ‘H NMR spectrum of PtI,(TeEt,),* in the presence of free TeEt I! indicated that very rapid exchange occurs between free and coordinated telluride [l62.163]. In the analogous system PtXI(SeEt,), (X = CI, Br), two distinct coalescence temperatures were observed, a lower-temperature coalescence unaffected by the presence of free SeEt, and a higher-temperature coalescence involving both free and coordinated ligand, but the PtIz(TeEt ?)? -TeEt 1 system showed only one eoales- cence, involving both free and coordinated teifuride [ 162, I63]_ The temperature of this coafescence was considerably lower than that observed in the absence of free telluride, the introduction of even the smallest measurable amount of TeEt, lowering the coalescence temperature so much that it could not be observed [263]_ The addition of only a trace amount of TeEt, allowed observation of a coalescence at ca. - 10°C (vs. + 119°C in the absence of added TeEt 1) [ 1631. No lusPt--‘H coupling was observed above the coafescence temperature. It was not possible, therefore, to rule out unequivocally an associative-dissociative process being responsible for the coalescence in the absence of free l&and [172,173] as in the cases of some of the SEt z and SeEt 1 complexes, where two distinct coalescence temperatures were observed in the presence of free ligand [163]. Comparison of the various chalcogen &and systems indicates that the ease of exchange between free and coordinated tigand has the order TeEt, s SeEt z > SEt z and Pd > Pt f 1631.

The dimeric complexes Pt,Cl,(TeR,), (R = Et, n-Pr) [ 141 were prepared by reacting equivalent amounts of NaiPiCI, and &-PtCl,(TeR,), in absolute. ethanol at room temperature, Since the simple dialkyl tefluride complexes isomerize spontaneously, the bridged complexes can be prepared directly by reacting equivalent amounts of TeR, and Na,PdCI, in ethanol. The following order of stabilities was established for dimeric complexes of formula A [14]: PR, - R2S > AsR, > amines > R,Te > SbR, > R,Se.

The reaction of the chloro-bridged dimers in acetone with nmines was also studied by Chatt and Venanzi fl5].

L y_/Cr~pt/Cf L

‘IT’ Cl

a’ ‘a/ ‘L f2at-n _ /\

Cl am

* Infrared and Raman measurements support a truris configuration for this compIcx in the solid state. and dipoIe moment determinations in benzene support ;1 WUNS gcomctq in this solvent [164]_ The variable-temperature study. however. was done in CH2Cl ,/CHCI, [ 1631.

Although only the chloro-bridged complex was investigated for the TeEt, dimer. the above equi~~br~um was increasingly in favor of the bridged species in the order C1 C Br < I (i.e.. with (P(n-Pr).l)lPt,X, as the substrate)_ As generally observed for these halo-bridled dimers_ the monomer obtained from the reaction with the amine has the $rnz~ configuration for the TeEt, derivative. The complexes with dialkyl tellurides tend to disproportionate

t-(TeEt,)(p-Me-C,H,--NH,)PtCl, -(TeEt,),PtCl, +

( p-Me-C,H,--NH,)lPtCt, (32)

The monomeric complexes with amines can be recrystallized from light petroIeum and are nonelectrolytes in nitrobenzene. Their solubiiity in carbon tetrachloride and ether suggests a tl’a#zs configuration. In a subsequent study [13f_ the position and intensity of the N-H stretching frequencies in a series of these amine complexes were measured, and a stability order for the ligands was proposed (e.g., 4-alkylpyridines, pipe&dine, R,S, R,Se. R,Te. AsR,, PR,. SbR,, P(OR),, CIH,). The ligands to the left of trial- kytphosphines were proposed to function solely as 0: donors, whereas the phosphines and those ligands to the right were proposed to act as both tf donors and = acceptors of Pt d electron density (see refs. 324, 325 for recent discussions of the bonding of organophosphines in transition metal com- pIexes). The assignment of dialkyi tellurides as solely CI donors (with a ~‘zrfxs effect order: SEt, -K SeEt, < TeEt,) is consistent with the available data, but no detailed studies have been reported addressing the bonding properties of these donors.

A related study aimed at distinguishing inductive from mesumeric effects was also reported by Chatt and Westiand [22] using ‘H NMR spectroscopy to study the monomeric trutr~ complexes obtained by cleavage of the halo-bridled complexes Pr$Zl,L, (L = alkyi-phosphines, -arsines, -stibines, -sulfides, -selenides, and -telhtrides) with pyridine. The pyridine Iigand was chosen as a detector because the Ir-electron system of the ring can interact with the d orbitals on the metal atom, which may be engaged in the rr bonding to the Iigand in the cram position. For the z~~~~~-PtCl~(pyridine~L complexes, the constancy of the P-proton shifts relative to free pyridine was interpreted as indicating that inductive and mesomeric effects are probably balanced and smaI1 at this position. The small shifts observed for the coordinated pyridine ligand in these complexes, however, preeiuded any meaningful conclusions about the bonding. A study of the electronic spectra of a series of trans-PtCI,(piperidine)L complexes [213 gave the following order of ligand field splittings: P(OMe), > P(n-Pr), 2 piperidine > As(n-Pr), > SEt, > SeEt, > TeEt,.

A series of aryl platfnum complexes containing diethyf tetluride were

prepared by reaction of the aryi Grignard reagent and cis-PtCl,(TeEt ,), [175a], the aryI bromo derivatives PtAr(TeEt>),Br (Ar = Ph, mesityl) be&g obtained when I :4 and I:2 molar ratios, respectively, of Pt complex to Grignard reagent were used. A similar reaction with o-toiyl magnesium chloride (I:2 molar ratio of Pt complex to Grignard) gave Pt(TeEt 2)7(u- tolYl)l, which was assigned a tram geometry on the basis of its dipole moment (2.48 D) in benzene solution. The bromo ligands in these complexes can be replaced metathetically by chloride (LiCl/MeOH). A tr~rts configuration was assigned tu the Pt(TeEtI),CIAr complexes on the basis of their low ~r+~r values, characteristic of halo ligands mm to a strong activating group. The derivative Pt(TeEt 7 ),( p-tolyl),, prepared From Ptl: ,(TeEt 7 I1 and p-tolyl lithium in ether, was as&&ed a cis configuration, and the complex obtained by recrystallization of this initial product from ~vater/methanol was assigned a trams configuration [193]_ The S-sulfinato complex. tram- Pt(TeEt,),(PhSO,)Cl, was prepared by SO, insertion into the Pt-C bond of the phenyr derivative [ 175b].

The series of complexes PtX,(TeMel), (X = Cl, Br, I) were prepared and their IR and Raman spectra recorded f X60,161]. The chloro complex was assigned a c-is configuration in the basis of its solubiiity properties and the observation of two ~~~~~~ stretching frequencies (Table 3) [it%]. characteristic of C,, symmetry. The bromo and iodo complexes, however, were assigned frnrzs configurations [160f. The increasing tendency for the stability of the tram isomer in complexes PtX,L, in going from X = Cl to Br to I is well established. For the bromo complex, however, the correspondence of the far-IR and Raman bands suggests that the complex has no center of symmetry (i.e., has cis configuration}, but the solubility properties and the observation of onfy one ~~~~~~ vibration (i.e., 13;lh symmetry) are both consistent with a tram structure [ 1601. Calculations of the platinum- chalcogen force constants (i.e., kp,+. = 2.2. lips_= = 1.4. kpl_-r.c = 2.1 mdyne A- ‘) indicate a bond-strength order Pt-S > Pt-Se ( Pt-Te [ 16Uf. Since the bond strength would be expected to decrease with decreasing difference in the electronegativity between Pt and the donor atom, going down group Vf, it was suggested that considerable IZ bonding must be involved in the Pt-Te bond (e.g., calculations of the Pt-halogen force constants give the expected trend; kpt_Ct = 2.3, kPt_Br = 2.0, and kPc_l = f -7 mdyne A- ’ )_ Evidence for the w-bonding ability of dialkyl tellurides was further suggested by the following observations: (1) only the cis isomer of PtClz(TeMe, ), could be prepared and (2) studies of the relative bond moments of the $t-chalcogen bonds suggest an order S KI Se < Te.

A detailed study of the IR spectra in the 4~~0-40~ cm-’ region of TeMe, and MX,(TeMe- I7 (M = Pd, Pt; X = Ci, Br, I) c.ompfexes showed only slight . - changes in the internal modes of the telluride ligand on complexation,

although careful analysis of the spectra in the CM, rocking region allowed differentiation of ci.s and tram isomers of these square planar complexes [ I6 I]. The values of ‘J~t+s~r~ for n-Bu.N[PtX,TeMe,] (X = Cl, Br, I) and ~n-Bu~N]~~X~Pt~~-T~Me~~PtX~] (X = Cl, Br) have been obtained by heteronuclear INDOR spectroscopy and direct Fourier-transform ilsTe NMR spectroscopy, respectively [ 1761. The coupling constants (Table 3) decrease markedly in the order CI > Br > I, with the values for the former monomeric complexes being much less than those for the latter dimeric complexes. The observed J values are much smaller than those observed in the phosphine analogs, and the percent decrease from Cf through Br to I is much greater than in any previously reported series 1176). The unusually small coupling constants in the Pt-Te monomeric complexes compared to the phosphine analogs have been attributed to the presence of nonbonding electrons on the teilurium. indeed, the couphng constants for the dimeric complexes in which both Ione. pairs of the bridging telfurium figand are involved in bonding are much targer and similar to those in PtCI 3PMe3 [I 761.

The monomeric 1331-3333 (eqn. 33) and dimeric [334] dimethyl telluride complexes were prepared by the routes previously described for the dimethyl sulfide analogs (eqn. 34,351:

MezTe\pfc~\p{cc lTeM, + 2R4NCc

=%R? - R,NfPtCtjCTeMez,]

z (33) [x31 -3331

7c R,N%r + RsN[%rzPt Pt8rzj

‘5/ Me,

acetone

&N (Pt8r, CSMe,)] +

CH,Cl, - (R4N12( BrxPt W- SMe,,Pt8r,]

Pm*

IlOO%.)

c35>f3341

Although attempted metathetical replacement of the chloride ligands in ~N~n-Bu~~]~Pt~~~TeMe~] with KSCN in acetone resufted in dispfacement of the telluride Iigand, solutions of [N(n-Bu)q J[Pt(CNS),TeMe,f were obtained by equilibration of [N(n-Bu),],[Pt(SCN), ] with [Pt(CNS),(TeMe, j7 ] in CH,Cl, 11771. The neutral complex, Pt(CNS)~tTeMe~)~ [177], was prepared by a metathetical reaction between the corresponding chioride [I601 and KSCN in acetone, but no data have been reported for this complex. The thiocyanate isomers present in this CH,CI, solution were identified by

‘H-{ r9sPt) INDOR spectroscopy [177]. The following isomers were found (along with their relative proportions):

U.0) co.31 (004) (0.006)

rCMf?)=7.75 7.76. 7.60 7.66

5&$& = 336 HZ 35.7 HZ al. 35 HZ

‘h5 Pt-“N = 367=SHr co. 450 Hz

The number of N-bonded thiocyanate ligands in a given isomer was deduced from the multiplicity of the “N coupling pattern in the rH-(rysPt) INDOR spectrum, and the specific assignments of the mixed complexes were made, assuming a regular upfield shift of the methyl resonances when S- is replaced by N-bonded thiocyanate in the position cif to the telluride tigand and a rather larger shift for the rrans position f177J These results were compared with simifar measurements with complexes containing other neutral Iigands having N, P, As, Sb, S and Se donor atoms, the general conclusions being that N-bonding is favored when the neutral figand contains a tight donor atom, when the tram ligand has a high rrarts influence, or when a cis tigand is bulky [ 1771.

The complex PtC12(Te(CH2CH,Ph),),, prepared by reaction of the telluride ligand with aqueous KIPtCI,, was shown by IR and Raman spectroscopy to have the cis confjguration in the solid state ~~~~~~~ = 305, 290 cm-‘)

Fig. 9. lSTe NMR and F&AR spectra of PtC1,(Te(CW,CH2Ph)l)1 in CH,CIz. Reproduced with permission from J. Organomet. Chem., 209 ( 198 1) C4 1 -

initial product in the case of Pt(I1) complexes with organotellurium ligands

K,PtCl. -l- 2 TePh, - cis-PtCl,(TePht), (34)[1743

~~~~?~-Pt~l~~N~Ph~~ i- 2 Te( p-EtO-C, H, lz -

fmns-Pfcf,(Te(p-Efu-c~H~),), (37)f1091 - _

(iv) Co, RJI, Zr

The only report in the literature of an organotelluri~m complex with Co describes the synthesis of ~Cp~Nb(~-TePh)~Co(C~)~ [ 1261 by the reaction of vCp,Nb(TePh), [I241 with Hg(Co(C0),)2). An analogous derivative could not be obtained using =CpzTi(TePh), [ 1261. The complex is stable under nitrogen, but DMSO solutions immediatefy decompose in air. Its diamagnetism suggests the presence of a Nb-Co bond. A preliminary note [154b] reported ESR evidence for coordination of tellurophene to a square planar Co(II) complex with a Schiff base, N, ~‘-u-phenyIenebis(sali- cylideneaminat~)cobalt( II), but no product was isolated.

The reaction of TePh2 with Coz(CO), in benzene at room temperature gave the paramagnetic, highly insoluble black crystatline complex [CozTe(CO),],, [102], This complex has high aerial and thermal stability.

The mixed cluster compound FeCo,(CO),Te has been prepared in 30% yield by the reaction, in stoichiometric amounts, of Go,(CO), and Fe,(CO),, with TeEt, [ 1411. The structure of this brown, air-stable compound has been shown by single-crystal X-ray diffraction to involve a tetrahedral FeCozTe cluster system formed by the symmetrical coordination of an apical Te atom to a basal FeCo,(CO), fragment containing three M(CO), groups at the corners of an equilateral triangle and linked to one another by metal-metal bonds [141]. Although the cluster compounds CoJ(CO),X (X = S, Se) ff41,335] have been prepared by the reaction of Co,(CO), with a variety of sulfur substrates and H,Se respectively, attempts to prepare the Te analog were unsuccessful [ I4 I 1.

Rh The complex [RbCO(TeEt,),Cl] has been prepared by the reaction of

ERWo),clL , with TeEt 2 in pentane at room temperature [ 1561, This brown- yellow complex has a viu+cI band at 299 cm-’ [ f56f, a value characteristic of a chlorine trapls to a CO Iigand in a Rh(1) complex [336]. The complex readily undergoes oxidative addition reactions with a variety of substrates

(Cl,, Br2, I,, HCI, Mef; PhSU,Cl; Table4) to give tram octahedral Rh(III) complexes [ 1561. The complex. RhMeCO(TeEt &Cl1 readily undergoes CO

TABL

E 4

Ga,

Rh,

Ir c

art

tplc

xes

M.p

. (“C

) Ph

ysic

al d

ata

_ ~

. _

_.

Co

com

plex

es

~Cp~

Nb(

~-T

ePh)

~Ca(

~~)~

~C~z

Tev

J),l,

, Fe

Co$

?&T

e

157-

160

30

64-7

5 (d

cc.)

>30

(de

c,)

62-6

5

71-7

8 (d

a)

120-

123

(dec

.)

>89

(de

@

v,,=

l859

, 19

11 cm

-’

126

7(C

p)=

4,73

(s)

, 4.9

9 (s

), 5

.31

(s)

+Ph

)=2,

45-2

A5

(m)

vco=

2068

(s

), 2

027,

199

4, 1

859,

184

1, 1

810 c

m-’

10

2 B

row

n, a

ir-s

tabl

e so

lid

I41

Sin&

-cry

stal

X

-ray

dif

frac

tion

k+.N

=22

20 (

s) c

m-’

vc

o =

205

9 (s

) cm

- i

vcN

r22i

0 (m

) cm

-’

q.0

= 2

022

(s)

cm-

I

vco

= 1

955 f

vs)

cm”

f v&

C)

- 29

9 (s

) cm

- ’

vco

~206

0 (s

) cm

-’

vI+c

I =

332

(s)

cm*

’ vc

o ~2

056

(vs)

cm

-’

~~~,

_~~=

314 (s

) cm

-”

q.

~204

3 (s

) cm

-’

vRc_

cf =32

8 (s

) cm

- t

vca

~203

0 (m

) cm

-l

vRl,_

cl ~3

21 (

m)

cm-

I IJ

~~ = 2

060

(vs)

cm

- ’

vCO

fa~c

,yl~

=

I7

t 3 (

vs) c

m-

’ vc

o =

206

4 (v

s) c

m-

1 I’,

+~

~ =

320

(s),

292

(vs)

cm

-’

156

156

156

156

156

156

156

157

L57

mer

-RhC

l,(T

eMez

),

6(“‘

“Rh)

=31

79 p

pm i’

Jl

?“~e

_lf”

a,,:

TeM

e, l

wru

to

TcM

e, -

I- 7 1

Hz;

TcM

e, /

I’U

/IS to

Cl

-I- 9

4 H

z S(

““R

h)=

2567

pp

m”

Jl?l

@Ja

,,:

TeM

c, t

rutts

to

TcM

c,

t 70

Hz;

TcM

c, t

rm

to B

r t

93H

z S(

“‘3R

h)=

135

2 pp

m”

155

mer

-RhI

,(T

eMe&

RhC

l,(T

ePh,

),

197-

199

RhC

l,CO

(TeP

h,),

16

3-16

5

Rh(

TeP

h),

RhC

l(C

O)(

TeP

h,),

15

8-15

9

Rh

CI(

TeP

hJ,

(Ph,

Te)

,Rh(

@I)

zRh(

TeP

h2),

RhC

OC

IBr,

(TeP

h,),

RhC

OC

I( SC

N),

(TcP

h? )

?

RhC

l,TeP

h(T

cPh,

),

>50

(dec

.)

=.X

5 (dc

c.)

> I

25 (

dec.

)

136-

138

> I

I5 (

dcc.

)

TeM

e, m

m

to T

cMc,

+66

Hz;

T

cMc,

~K

UIS

to I

t 69

Hz

MW

(DtiE

) = 9

20 (t

alc.

iO

55)

MW

(DC

E)=

780

(tal

c, 8

01)

vco

= 2

080

cm-

’ D

ark-

brow

n so

lid

Cho

cola

te-b

row

n so

lid

vco

= 2

040

cm-

I;

MW

(DC

E)=

710

(tal

c. 7

30)

Bro

wn

solid

vc

o =

206

0 cm

- ’

vcN

=21

35 c

m-’

M

W(D

CE

) = 7

05 (t

alc.

736

) R

ed s

olid

M

W(D

CE

)=61

4 (t

alc.

9X

9)

Red

sol

id

MW

(DC

E)=

6X4

(tal

c. 7

02)

Red

sol

id

vco

= 2

060

cm -

’ M

W(D

CE

) = X

50 (t

alc.

X90

) R

ed s

olid

vc

.0 = 2

070

cm-

’

MW

(DC

E) =

940

(cel

c. 9

X4)

R

ed-b

row

n so

lid

I’co

= 2

0x0

cm--

’

1’C

.N =21

40 c

m-

MW

(DC

E) =

X00

(tal

c. X

46)

Dar

k-re

d so

lid

MW

(DC

E)=

905

(tal

c. 9

42)

155

155

120

120

120

120

120

120

I20

I20

120

120

I20

5

E

TA

BL

E 4

(con

tinue

d)

M.p

. (“C

l Ph

ysic

al da

ta

RcT

.

Red

solid

“C

o = 2

050 c

m . ’

12

0

Ir c

ompl

cxcs

[Ir(

CO

),T

cEt,C

I],,

184-

198 (

dcc.

) V

c.()

=

201

x (v

s), I

’)W

(1

11) c

m

. ’

158

n

In p

pm to

the

high

freq

uenc

y of

the

rcso

nanc

c frc

qucn

cy co

rrw

rd t

n D

p~l~

~rjz

ing il~

~gl~

~ti~

fi

eld s

uch

thrr

t SiM

L; gi

ves a

pro

ton

r~s~

n~n~

c of

exa

ctly

100

MH

z.

189

insertion into the Rh-Me bond in CH,Ci, to give RhCO(TeEt,)$OMeClI. A subsequent study f 1571 extended the substrates which can add to RhCOfTeEt,),CI to include tetracyanoetbylene (TCNE) and fumaronitrile (FMN) (Table 4).

Reaction of rhodium trichforide hydrate with excess TePh? in ethanoi under reflux gave ~Ph~Te)~~Cl~ [XXI]. In contrast, although the analogous reaction under mild conditions with a stoichiometric amount of PPh, allowed the isolation of (PPh,),RhCI, [337], the use of excess phosphine reduced the metal to Rh(1) and (PPh,)3RhCl was isolated f3383. The latter complex {Wilkinson’s catalyst) is an active catalyst for the hydroformylation and hydrogenation of olefins under mild conditions 13393. One of the diphenyl telluride ligands of this complex can be displaced by CO under mild conditions

Rh(II1) complexes with terminal and bridging TePh- ligands have also been prepared by the following routes [ 1201

3fS q_ CH,O RhCI,-3 H,O+TePh, --+

rcnU.K 24 h RhCl ,TePh(TePhl )?

EtOH 1 CO/hcnzcnt:

RhCl,COTePh(TePh,)l

RhCl, - 3 H,O + TePh, 404; “4. CW20/KOH

--* EtOH/rcflux 30 min

Rh(TePh),

(39)

(40)

Analogous reactions with PPh, give RhtPPh~)~~l~CO) [340] and Rh( PPh,),(CO)H f3413, respectively. The complex (TePh z )z RhCl was, however, prepared by a substitution reaction with a labile Rh(1) ethylene complex [ 1201

[(CHI= CHz)zRhCl]z + excess TePh, rz (TePh, f,RhCl (41)

The reactivity of this complex is significantly different from that of the PPh, analog [ 1201

Rh(TePh,),Ci Rh(PPh,),Cl

4CO- Mixture of carbonylated (PPh,),(CO)RhCl (42) products 1338,341 J

- 1950-2040 cm-‘ ’

+cs, - z!?h>e& RhCl] z (PPh,)zKS)RhCl (43) W21

+ F,CeCCF, - [(PhzTe),R.hCl], (~h,P)Z(F,CC=CCF#_hCl (44) [3431

+C,H,,CHO -* [(Ph,Te)zRhC1], (PPh,),(CO)RhCl (45) E34Il

190

Carbonyiation of (Ph?Te),RhCl gave a mixture of products [1203, and the PPh, analog gave the monosubstituted product, which is inert to further CO substitution [338,341], A variety of other substrates which readily replace PPh, gave the chloro-bridged dimer, [(PhZTe)tR.hCl],, in reactions with the diphenyl telluride analog (eqns, 42-45). Methyl iodide oxidativefy added to the (PhZTe),RhCi to give (Ph,Te),RhClMeI. (PPh,),RhCl reacted similarly but gave a methyl iodide adduct (PPh,),RhCl(Me)I - Me1 [343]. The dimer [( Ph ,Te), RhCI] 2 was also obtained by simple recrystallization of (Ph ,Te):, RhCl.

Diphenyl tehuride [120] (like triphenyl phosphine 53441 and TeEt 7f156]) reacts with @h(CO),Clfz to give the monomeric substituted product

[Rh(CO)zCi], i- 4 TePhLt”znc (Ph~Te)~~(C~)Cl

This derivative undergoes oxidative addition reactions with halogens and thiocyanogen (Table41 but not with methyl iodide. In contrast, the PPh, analog does not oxidatively add bromine. A further difference in reactivity between the TePh, and TeEt, complexes was noted in the inactivity of ~Ph~T~~~~~~O)Cl(Me~I to CO insertion into the Rh-CH, bond fl20], a facile reaction for the TeEtz analog [156], The chloro ligand in RhC1(CO)(TePh,fz cannot be simply replaced metathetically by thiocyanate as in the PPh, analog; instead, a thiocyanate-bridged dinner is formed, (OC)TePh,Rh(~-SCN)2RhTePh,(CO) [120].

The ‘OJR.h chemical shifts of the complexes mer-RhX,(TeMe,), (X = Cl. Br, I) have been obtained by iH-(‘03Rh) INDOR measurements [I%]. The vatues of t

J+-e_s~3Rh were relativefy insensitive to changes in the halide ligand, in contrast to the unusually large changes observed in ‘J~+.~_ws~~ in analogous platinum complexes [345]. The complexes RhX,(TeMe?), (X = Cl, Br) can readily be prepared by shaking an ethanol solution of RhCl, - 3 H,O with TeMe, for several hours, the iodo compIex being prepared by metathetical reaction of the chloro complex with KI in acetone [346],

The onIy reported Ir complex with an organotellurium ligand is Ir(CO)ZTeEtzCl, prepared by reacting [IrCOCl],, with the telluride [I%] (Table 4).

Several iron carbonyl complexes with bridging (and in one case, terminal) aryl tellurol Iigands have been prepared by reaction of Fe(CCQ, Fe&O),,

191

or bCpFe(CO), I1 with diary1 ditellurides. Reaction of Fe,(W)!, with

Te,Ar, (Ar =I: Ph [l IO,1 121, C,F5 [ 1 lo], p-EtO-C,H, [102]) in refluxing petroleum ether (80-100°C) [l lo] or benzene [ 102,112] gave the dimeric complexes (OC),Fe(p-TeAr)lFe(CO),. Comparison of the vco bands of these complexes (Tables) suggests an increased +acceptor capacity of the

TeC,F,-bridged complex, as one would expect [ 1 lo]. A similar comparison of the vco bands of the dimeric. complexes (OC),Fe( p-E-C,X,)2Fe(CO), (E = S, Se, Te; X = H, F) suggests the following order of increased u-donor ability (and/or decreased +zr-acceptor capacity) of the bridging chalcogenide ligand: Te > Se > S f 1 lo].

The similarity of the IR spectrum of (OC),Fe( p-TePh), Fe(CO), to those of the p-EPh (E = S, Se) analogs suggests that all three derivatives have similar structures [ 1121. The crystal structure determination of (OC), Fe( EL- SEt&Fe(CO), [3473 has shown it to have a folded Fe,& ring with an crtzri conformation of the alkyl groups and a “bent” Fe-Fe band. The qtz isomer of this dimer has also been reported [348,349]. The complex (OC),Fe(p- TePh),Fe(CO), appears to be isomerically pure, but TLC evidence suggests that two isomers may exist for the Se analog. although only one isomer was isolated and characterized [I 12]_ The mass spectrum of (OC),Fe( FL- TePh)?Fe(CO), shows weak peaks due to the molecular ion and ions corresponding to the loss of 2-5 CO ligands, the strongest peaks being due to the Fe,Te,PhZ and Fe,Te,* fragments [ 1121. The relative abundance of the Fe,E: ions (i.e., S C Se, Te) as well as the appearance of weak peaks due to FeE’ only for the Se and Te derivatives has been suggested to indicate the following order of iron-chalcogen bond strengths: Te - Se > S [ 1121.

The reaction of Fe(CO), with TePh, gave no characterizable product [ IO21 (analogous reactions with PPh, gave Fe(CO),_,,(PPh,),, ()I= 1, 2) f350J).

The reaction of Fe,(CO),, with TePhz (1: 3 molar ratio; refluxing cyclo- hexane), however, gave ca, 25% yield of Fe(CO),TePh, [ 1021. Diphenyl teliuride also substitutes for CO in dihalotetracarbonyliron(l1) [ 1023

Fe(CO),X, + TePh, - Fe(CO),TePhzXz + CO (47) X = Br, I

Although IR spectroscopy did not allow an assignment of the structure of these complexes, presumably, on the basis of the more strongly rrans-directing effect of CO vs. the halide ligands, the TePh, ligand is cis to both halides (a cis configuration for Fe(CO),I, has been established by a dipole moment measurement [35 l])_ These substituted derivatives show considerably enhanced stability towards air and moisture vs. the parent dihalides.

Substitution by organotellurium ligands of CO in Fe(CO),(NO), has also been reported to give monomeric and dimeric complexes

Fe(NO),(CO), f TePh, et. Fe(NO)zCOTePh, + CO r t . .

(48111021

192

0 8 8 -

Fc(N

O),

(CO

)(T

cPh,

)

Fe(C

O),

TeP

hzB

rz

Fe(C

O),

TeP

h,I,

IrC

pFe(

CO

),T

ePh

Ir C

pCO

Fe(

I.L

_TeP

h), Fe

( II C

p)C

O

Cis

-aC

pCO

Fe(p

Te(

~-

E~O

-C,H

&FC

(VC

~)C

O

102-

103

Trr

rns-

(?rC

p)C

OFe

@-T

e( p-

EtO

-C,H

,)),

Fe(n

Cp)

CO

99

- 10

1

‘3

(ON

),F

e(p

-Te-

< l -OM

d2F

e(

NO

),

.=.’

66

200-

225

(dar

kens

ab

ove

150)

Red

sol

id

u~o(

C,H

,,)=

2012

cm

- I’

~~(C

~,H

,~)=

1764

, 172

7 m-’

Red

-bro

wn

crys

tals

uc

o (K

Br)

=20

16,

1957

, 192

0 cm

-”

Bla

ck-b

row

n cr

ysta

ls

qo

(KB

r)=

2088

,204

2,20

27

cm-

’

Gre

en c

ryst

als

MW

(C

HC

I,)

=43

4 (3

82 ta

lc.)

pc

o (C

,H,,)

=20

18,

1976

cm-’

‘H

NM

R (

CS,

): 4

.77

ppm

D

ark-

brow

n so

lid

MW

(CH

CI,

)=68

0 (7

07 ta

lc.)

+

o=l9

65,

1937

, 192

1 cm

“ ‘H

NM

R:

(CS)

4.

48,4

. I I

ppm

Si

ngle

-cry

stal

X-r

ay d

ilfra

ctio

n D

ark-

brow

n cr

ysta

ls

vco

(CS,

)= 1

943 (

s) c

m-’

S(

57F~

)= f0

.66

(01)

mm

s-

’ A

= 1

.64 (

01)

mm

s--

’ 6(

“‘T

c)=

$0.0

6 (0

8) m

m s

-’

A=

6,2

(I)

mm

s-’

D

ark-

brow

n so

lid

vco

(CS,

)= 1

934 (

m),

192

0 (s)

cm

-’

S(57

F~)=

-t-0

.64

(01)

mm

s ._

’ A

= 1

.68 (

01)

mm

s-’

6(

“‘T

c) =

to.

01

(08)

mm

s --

’ A

=6,

l (I

) m

m s

-’

102

102

102

107

107

I l4b

ll4b

Gre

en c

ryst

als

j~=

3.00

D

I06

Red

cry

stal

s vc

o =

204l

, 19

65, 1

938 (

sh)

cm-

’

I31

I

‘E u

l-l

E

195

3 -

c-7 % s - - % - 3s -- u -

c 8

-a

c-1 u z -

P-l

c; x z -

7

%

I

8 ‘D

8

197

c

c

TA

BL

E 5

(con

tinue

d)

M.p

. (“C

) Ph

ysic

al d

arn

ik

Ref

.

M,R

u,(C

O),

Te

135

(dcc

.)

Yel

low

sol

id

147

vco

=2

I 12

(s),

207

9 (v

s), 2

06 I

(8, s

h),

2058

(vs)

, 204

7 (s

, sh)

, 201

4 (v

s),

201 I

(s,

sh

) cm

* ’

MW

(m

ass

spcc

,)=

690

(tal

c. 6

~~

~~

) r(

brid

gc H

-)

= 2

9,70

ppm

(si

ngl

et)

mas

s spe

ctru

m: M

” ,

M ’

-II C

O (

I) =

I, 2

),

[M”-

2 ~

O]-

}~~

~H

~C

O]

fnj=

1,

2)

(Ru

&C

O),

,Tc]

’ n

=O

-4,

Ru

; pc

o =

2 I

11 (m

), 2

078

(s),

20

54 (a

),

2043

(s),

201

2 (s

),

2006

(s),

199

3 (m

), 1

987

(w)

cm

’ r~

/c=

696

(for

‘@

Ru,

““T

c)

148

148

OS c

ompl

exes

OsC

lz(C

O)C

Te(

PPhs

),

C$(

CO

),T

e,

e

221-

223

Ora

nge,

air

-sta

ble

crys

tals

;~

~o(N

u~ol

) = 2

040

cm-

’ ac

re =

104

6 cm

- i

vco

= 2

067

(s),

204

6 (s

),

2006

(s).

200

2 (s

h) c

m-

’ w

/e=

1088

(far

“‘O

S. ‘

30T

c)

149

148

a In

frar

ed d

ata:

s, s

tron

g; v

s, v

ery s

tron

g; m

, med

ium

s w, w

eak.

NM

R d

ata:

d, d

oubl

et;

dd, d

oubl

et o

f dou

blc~

s, I’ N

o da

ta w

crc r

epor

ted

for

this

com

poun

d, b

ut i

nfra

red

(vco

) an

d m

ass s

pect

ral d

ata

are

give

n in

ref

. 14

8 fo

r th

e S

and

Se a

nalo

gs.

Alth

ough

the

clus

ters

0s

3(C

O),

H,T

e an

d O

s,(C

O),

,H,T

e w

ere

also

rcp

artc

d in

ref

. 14

8 as

pro

duct

s of

the

rea

ctio

n of

OS,

(CO

),~

with

clc

mcn

tal

Te,

no

data

arc

re

port

ed f

or t

hcsc

com

poun

ds,

199

2 Fe(N0)2(CO)I + ( ---, r.l.

@N),Fe(p-Te-p-MeO-C,H,),Fe(NO), + 4 co (49)[1061

The air- and light-stable derivative Fe(NU),CUTePh, is formed under much fess vigorous conditions than required fur the substitution reaction with

PPh, [352f, The diamagnetic complex [Fe(NO),Te-p-Mea-C,H, Jz has been formulated, on the basis of its IR spectrum, as isostructural with red Roussin’s salt, [Fe(NO),SEt],. the crystal structure determination [353a] of which has shown that each Fe atom is tetrahedral@ surrounded by two bridging sulfur atoms and two nitrosyl ligands with an Fe-Fe distance of 2.72 A.

Reaction of Te,Ph, with [~KpFe(C0),j~ gave initially a monomeric complex with a terminal PhTe- ligand and, under more forcing conditions, a dimeric complex with PhTe- bridging tigands [ 107,1533

benzene [ -CpFe(C@,]z + Ph,Tez re;Uux sCpFe(COf zTePh

benzene 3_ reflux

IR lamp

~CpCOFe(lifePh),Fe~U7TCp W-8

The dimeric complex was obtained as a mixture of two isomers (TLC and ‘H

NMR (2 cyclopentadienyl signals) evidence), but the pure isomers could not be isolated. The S and Se analogs were, however, separated into two isomers by column chromatography [107]_ Five stereoisomers of such a dimer are pussibfe and for a nonplanar Fe+_ , ring each of these can exist in two conformational forms [353b]_ The formulations of the two isomers obtained in this work (Fig. I I) were based on spectroscopic evidence. The stabihties of the dimeric Se and Te compounds are considerably greater than that of the S analog. The relative stabilities of the two isomers (Fig. 11) of these dimers also differ significantly for the three chalcogens. the amount of isomer B obtained in the reactions increasing in the order Te (major product) > Se(- 25%) > S(- 1%):

A B

E qo(C&& sofn.) pcu (cm- ‘) (cm-“)

&$CS, soln,) %p (ppm) (PPm)

S” 1982, s 4.43 1953, s x937, s 4.03

Se 1975, s 4.46 1947, s 1931, s 4.02 Te 1965, m 4.48 1937, 1921 4.11

a The crystal structure of this isomer has been reported, the Fe& ring being slightly puckered (i.e., the ring is folded about a line through the Fe atoms through ca. IdOf f354j.

Ph

Ph

(A) (6)

Fig. I 1. Proposed structures of [AIp(CO)FeEPh], (E=S. Se. Tc) dimcrs.

A similar reaction with Te,( p-EtO-C,H,), [ 114b] gave a dark brown product from which two isomers were separated mechanically after recrystallization of the reaction residue from dichloromethane/hexane. Crystals of the isomer obtained in lower yield (ca. 5%) were shown by single-crystal X-ray diffraction to have the structure in which the cyclopentadienyl rings are cis with respect to the puckered Fe,Te, ring and both aromatic groups on the tellurium bridge atoms lie on the same side of the Fe,Tez ring (i.e., Fig. 11 B) [ 114b]. The four-membered FezTe, ring is folded by 17O about a line

joining the Fe atoms and is similar to the puckering of the ring in vCpCOFe( ,+SPh)2FeCOrrCp, where angles of 16” and 19” for the two independent molecules of the asymmetric unit were reported [354]. Infrared and Mijssbauer ( 57Fe and iZ5Te) data for both isomers have been reported (Table 5) [ 114b].

Two brief reports [ 131,132] of iron carbonyl complexes with tellurophene derivatives have appeared_ The reaction of tellurophene with Fe,(CO),, in boiling benzene gave, besides black Te?Fe,(CO), and the yellow ferracyclo- pentadiene complex, C,H,Fe,(CO),, a red crystalline, sublimabIe, light- sensitive complex in 18% yield [132]. This complex, which has the empirical formula C ,eH, Fe,O,Te, is monomeric in benzene and gives, on thermolysis, C,H,Fe(C0)6. Its IR spectrum is quite different from that of free tellurophene and has three terminal and no bridge I+~ bands (Table5). Its mass spectrum shows a parent ion at 459 and additional peaks at 459 - n - 28 (tt = l-4), h- w rch are generated by successive cleavage of the CO ligands. On the basis of this evidence and its NMR spectrum (Table5), a metallocycle structure was proposed for the complex (Table5). Analogous structures have been proposed for thianaphthalene [355], 2,2’-thienyl [356] and arsole [3573 iron carbonyl complexes.

The reaction of tetraphenyltellurophene with Fe,(CO),, in refluxing toluene-benzene (2 : 1) gave a red crystalline product formulated as (tetra-

201

phenytteIIurophene)FeCCO), on the basis of its f R spectrum [ I3 I]. The cluster compound FeCo,(CO),Te [I411 has been discussed in the

section on Co complexes. Several other cluster compounds incorporating Te in the framework have been reported [139- 146]_ The first such cluster compound, reported by Hieber and Gruber f139alj in 1958, was prepared in aqueous solution by telluric acid oxidation of the tetracarbonylferrate anion (the S and Se derivatives were prepared by analogous reactions)

3 [Fe(CO),]“- + 2 Teat- + 10 H -’ - Fe,Tel(CO), + 2 CO + 5 H,O (5 I) f MIOH/M~OH

Fef CU) s

The cluster is obtained as a grey-black, air-stable solid. which is stable even to dilute acids at high temperatures [139a]. The mass spectrum of this cluster shows a molecular peak followed by nine signals of equal intensity. corresponding to the successive Ioss of the nine carbonyf figands, the Fe3Tez- peak being the most intense [142]_ Loss of Fe atoms from the decarbonyfated cluster core is also observed, the foIIo\ving degradation scheme being proposed on the basis of the mass spectral data

Fe,Tez(CO), --* Fe,Tez(CO)z - FeJe2(CO),” -i- 9 - II CO -- 1

Fe>Te;+ - Fe,Te,” - FezTe ’

I Fe,’ (52)

An analysis of the intensity relations in the mass spectra of the Fe,E,(CO), (E = S, Se, Te) cfusters gave the foflowing order of Fe-C bond strengths: S < Se< Te, This order corresponds to the decrease in electronegativity going from S to Te, the increased basicity of the Te being reflected in increased covalence of the Fe-C bond [ 1421. Attempts to identify the residue obtained in the thermogravimetric analysis of Fe,Te,(CO), by X-ray diffraction were unsuccessful f 1421..

The structure of this cluster has not been reported, but Dahl et al. showed that the S [358] and Se [359] analogs contain an approximate square pyramidal Fe,E, framework with an iron atom set at the apex and alternate E and Fe atoms at the corners of the basal plane, each Fe having three terminal CO figands.

Fractional sublimation (U.1 mm Hg, 45OC, 36 h) of the crude product obtained by the method of Hieber and Gruber [ 139aJ (i.e., primarily Fe,( p3- Te),(CO),) has been reported [ 139b] to give a small amount (( 1% of total) of a black solid formulated on the basis of IR spectroscopy (Table5) and chemical reactivity as a mixture of Ft=l,( p3-Te),(CO), and Fe& ptl -Te, >fCO),.

202

Although the dimer could not be purified by adsorption chromatography, its oxidative addition product with Pt(PPh,),(C,H,) was isolated and purified chromatograph~cally. The cluster Fe3(p,-Te)l(CO), is unreactive towards the Pt(O) complex. The formation of the oxidative addition product, (CO~~Fe~(~~-Te)~Pt(PPh~~~ 1139bf, which was characterized by IR, j1 P NMR, and field desorption mass spectroscopy. was cited as evidence for the presence of Fez( p,-Te,)(CO), in the sublimate.

The variable-temperature 13C NMR spectrum of Fe,Te,(CO), (CDCI, solution) has been interpreted in terms of two discrete carbonyl exchange processes fi43j. In the first step, the carbonyls on the apical iron atom become equivalent, and in the second step. those at the basal iron atoms. At room temperature 0x11~ two resonances are observed, corresponding to the equivalent carbonyls on apical Fe(l) and the two basal iron atoms Fe(2) (Fig. 12). When the temperature is lowered to -87OC, the carbonyls on the apical iron Fe(l) remain equivalent (the solid-state structure predicts two types of carbonyls), while two resonances are observed for the carbonyls on the bass! iron atoms (three types of carbonyls on the basal iron atoms are expected for the solid-state structure). Delocalized exchange between CO groups of apical and basal iron atoms does not occur.

I I I I I

-87%

20X2ppm (41 f Cod, CC&

214.9 ppm (21:

I+--213.3 ppm (3): CC&, cob

Fig. 12. The structure and variable-temperature ‘3C NMR spectrum of Fe,Tel(CO),. Rcpra- duced tvith permission from .I. Chem. Sot., Dalton Trans., ( 1980) 46,

203

Reaction of Fe,Te,(CO), under miXd conditions with CO, P(n-Bu)s, P(OPh),, and AsPh, gave, initially, ligand addition products, FesTez(CO),L [140], but under more forcing reaction conditions mono- and disubstituted complexes were obtained for the P and As bases, FejTe(CO),_,,L,, (n = 1, 2) f 1403, In contrast, the S and Se analogs gave only the tatter two types of substitution products [ 1401. The ligand addition reaction with CO required high CO pressures (70-80 atm) to give the black, rather insoluble, and air-sensitive Fe,Te,(CO),,. In contrast, the P and As ligands readily undergo this reaction in essentially quantitative yields by reaction of the cluster with ca. 6 equivalents of the ligand in heptane at room temperature for about 1 day. These air-sensitive adducts readily revert to F%Te,fCO), in solution_ Similar reactions run at 40-50°C gave mixtures of mono- and disubstituted products, the ratio depending on reaction time, which were separated by TLC. The solid substituted derivatives, as solids or in solution, are stable in an inert atmosphere and decompose only slowly in air, but the liquid

derivatives are more unstable [ 1401. The kinetics of CO isotopic exchange and substitution reactions with the

above ligands in the clusters FeJCQ),X2 (X = S, Se, Te) follow an S,l and/or S,2 mechanism, depending on the electronegativity of X and the nucleophilicity of the ligand [ 1461, The tendency of these clusters to react via S,2 vs. S,l kinetics increases in the direction CO (: AsPh, < P(OPh), < P(n

-LW,, whereas, for the same ligand, the pattern is SC SeKTe. Increased chaicogen electronegativity (ca. Te 2-l; Se 2.4; S 2.5) f360] is reflected in increased positive charge on Fe and reduced Fe -f CO 7r back donation and an increased vco ( 3 Fe Xz(CO),: X = Te, 2048, 2027, 2007; Se, 2057, 2037, 2017; S, 2063, 2045, 2025 cm-‘) [140]. The requirement of Fe-CO bond cleavage for the S,f mechanism is consistent with the observed increased tendency for S,l substitution in the Fe,E,(CO), clusters with increasing electronegativity of the chalcogen atom [ 1461.

The variable-temperature r3C NMR spectrum of Fe,Te,(C0)9P(n-Bu),, has been reported [143], Four resonances were observed at - 90°C (two doublets corresponding to the three carbonyls on the apical iron (CC&( 1) and CO,(2), Fig. 13) and two singlets ~~orresponding to the two distinguishable types of carbonyls on the basal iron atoms (CO, and CO,,>. Raising the temperature merges the two singlets, corresponding to a rapid exchange of the carbonyls on the basal irons, while the two doublets corresponding to the apical carbonyis remain unchanged (Fig. 13). The latter behavior is in contrast to that of the parent Fe,Te,(CO),, which gives a single resonance

for all three carbonyls on the axial iron atom over the complete temperature

range studied [ 1431. These spectral results support the presence of two symmetry-equivalent

Fe(CU), groups and show that only the CO ligands bound to the unique

Fig. 13. ‘-‘C NMR and proposed for FcJTcl(CO),- Reproduced with from J_ SOL DaIton (I 9SO) 46.

apical iron atom exhibit sizable P-C coupling constants_ Two structures have been proposed [143] on the basis of these spectral data (Fig. 13): (1) two isomers of structure A in which the phosphine is coordinated to the apical iron and (2) structure B in which the phosphine bridges the two basal tellurium atoms, its interaction with the cluster being via an empty molecular orbital which has predominantly chalcogen character. The latter structure, B, is more consistent with the chemical properties of the phosphine adduct [140] (e.g., (1) with group VA ligands, the substitution of one CO occurs at only one of the basal iron atoms and (2) the stability of the adducts increases with decreasing electronegativity of the chalcogen).

The clusters Fe,(CO),ETe (E = S, Se) have been prepared by reaction of Fe(CO), in alkaline methanol solution with an equimolar mixture of sodium selenite and tellurite, respectively, at 0°C 1144,145) (e.g., eqn. 51). The mixed clusters were separated from the other products (F%(CO),Te, and Fe,(CO),E,) by thin-layer chromatography [144]. The similarity of their IR spectra (Table 5) to those of the Fe3(CO),E, (E = S {358], Se [359], Te [139a]) as we11 as the analogies in elemental formula, preparative methods and properties, suggests that these mixed clusters are isostructural with the former clusters_ Substituted derivatives of these mixed chalcogen clusters (Fe,(CO),_,,L,ETe; E = S, Se; n = 1, 2; L = AsPh,, P(OPh),) have been

prepared by reaction of the parent clusters with a large excess of the ligands (ca. 10: 1 molar ratio) in heptane or petroleum ether at 40- 100°C. the mono- and disubstituted products being isolated analytically pure by TLC followed by recrystallization [ 145). The substituted derivatives, which are generally air stable in the solid state, were obtained in 50% (n~onusubstituted) and 20% (disubstituted) yields. The disubstituted derivatives give lower qo bands compared to the monosubstituted analogs. as expected from the relative n-acceptor ability of the phosphite and arsine ligands vs. CO. Similarly, a decrease in vco is observed in a homologous series of Te. E clusters as the ele~tronegativity of the chalcogen decreases (S r Se >T’e)_ Both of these effects produce increased electron density on the iron atoms, which is then delocalized by VT back bonding into the carbonyl ligands. The substitution reactions and the CO exchange reactions follow a two-term rate law: rate = k, [compIexf + k, fcompIex][ligandf in which the relative values of k, and /cl depend on the nature of the chslcogen atoms and the ligands [146].

Hieber and John [104] have reported the synthesis of several rutheniu~l carbonyl complexes. Reaction of an alcoholic CO-saturated solution of ruthenium trichloride hydrate with diphenyl telluride gave a mixture of mono- and disubstituted complexes, which were separated in yields of 40% and 25%: respectively, by fractional crystallization Analogous reactions with N, P and As bases gave exclusively the disubstituted products. RuCl ,(CO), LZ [361-3641. Disubstituted complexes were also prepared by the reaction of the polymeric carbonyl halides with the telluride [104]

where X = I and L = Te(n-Bu), or TePh,; X = Br and L = TePh,. The trisubstituted derivatives were also reported to have been formed in small amounts in these reactions. However, they were not isolated but were detected by IR spectroscopy (Table5). No data other than melting points were reported for the isolated ruthenium complexes. These complexes (Table51 are generally less stable than the analogs with N and P ligands.. Unlike the latter complexes, which undergo facile halide exchange when treated with molecular halogens of stronger oxidizing power, the organotellurium ligands are cleaved from their ruthenium complexes by such treat- ment [104]

Ru(CO),TeR21, x 2 ar R=n-Bu,Ph = _

Ru(CO),X, i- 2 TeR,X, -t- I, (54)

The only other report of a monomeric Ru complex containing a teilurium

207

Fig. 14. Proposed structures of H,Ru,Te(CO),.

the polymeric products, on the basis of their IR spectra and solubility properties [ 112]_

Attempts to prepare Ru,Tel(CO), by reacting Ru,(CO),? in alkaline solution with tellurite ion (i-e_. TeO, + aqueous KOH). reaction conditions used in the synthesis of Fe,Te,(CO), [139a], gave the hydride cluster H,Ru,Te(CO), [147]. This product was obtained in only 0.5% yield after acidification of the reaction solution with 2 N IizSO, and Ccl, extraction of the resulting precipitate. The residue from the extraction was a poorly defined polymeric material containing Ru,Te and terminal CO ligands. On the basis of its spectroscopic properties (Table5), two alternative structures have been proposed for the cluster product (Fig. 14).

Lewis and co-workers [ 1481 have reported that reaction of Ru &CO) ,’ with elemental tellurium in n-octane under a CO/H, pressure of 35 atm gave a mixture of Ru,(CO),Te, and Ru,(CO),H,Te_ which was separated by thin- layer chromatography. * These workers also reported that carrying out the reaction under a pure CO pressure gave a significantly decreased yield of the hydrido cluster, but yields for these reactions are not given. Infrared data for only the hydrido cluster have been reported (Table5).

OS The only OS complex with an organotellurium ligand is the recently

reported tellurocarbonyl OsCl,(PPh,),(CO)CTe [149a]. A number of thio- and selenocarbonyl complexes are known, these ligands generally being introduced by using CE2 (E = S, [366,367], Se [368,369]), but this is the first example of a tellurocarbonyl complex, Since CTez is unknown, a novel route involving a dichlorocarbene complex was used [ 149a]

* The S and Se analogs were prepared by similar reactions [ 1481.

Tht: orange crystalline te~lur~~a~bo~y~ complex was isolated in 30% yield after cofumn chromatography and ~hara~ter~2ed by l;R spe&tros&opy (Tabte 5)_

The reaction of 0s,(CO)t2 with efementd telhrium in reffuxing n-octane gave a mixture of Os,(CO),H,Te, Os,(COf,Te,, and Os,(CO),,HzTez [148]. which was separated by thin-Iayer chromatography. The S and Se anaiogs were prepared by analogous reactions, and the molecular structure of Us,(CO),,H,Se, was established by single-crystal X-ray diffraction. fn the latter structure the four OS and two St: atoms define a distorted trigor& prism with each Se atom capping a triangufar arrangement of OS atoms and two OS-OS distances in each Qs,Se unit being nonbonded (ea. 4A). Three terminal carbonyt hgands are bonded tu each OS atom, and the t\vo hydride figands presumably edge-bridge the two fong OS-OS bonds, since the carbon@ Iigands bend away from the edges. Infrared data for Qs,(CO),Te, have been reported (Table 5).

~~~~~~~~ ~~~~z~r~~~ CUJ@WZJ. Although Wieber and Kruck reported in early work dealing with organotellurium ligands in transition metal carbonyl chemistry that a variety of substitution products could be obtained from reactions with TePh,, similar reactions with Tefn-Bu), did nbt give anafo- gous substitution products [li02f

2 Mrt(CO),Cl + 2 Te(n-Bu)13~-c _ “‘w ~(OC)JUnCI], -i- 2 CO + 2 Te(n-Bu), (56)

Although both aromatic and atiphatie o~~~~ophosph~~~ readily give sub-

209

stitution products with manganese carbonyis such as Mn,(CO),, [3?U,37I ] and Mn(CO),CI f372-3751, only the chloro-bridged dimer was obtained in the reactions with Te(n-Bu),. However, in view of the low yield (ca. 40%) of the same dimeric product obtained on heating Mn(CO)5C1 in petroleum ether (IOO- I02°C) [372], the essentially quantitative yield obtained here was rationalized in terms of a catalytic effect of the dibutyf telturide hgand, an unstable monosubstituted product being invoked as an intermediate [ 1021

2 Mn(CO),Cl -t 2 Te(n-Bu), - 2 { Mn(CO),(Te(n-Bu),)CI} + 2 CO (58)

2 { Mn(CO~~~Te(n-Bu~~~Cl f 4 [ Mn(COf,Ci], i- 2 Te( n-Bu), (59)

The difference in reaction products obtained with TePhz and Te(n-&Gl was

expIained in terms of increased metal --+ tellurium back bonding in the case of the former ligand.

DGzr@ tellrr~ine conl-pfe,ues, The first reported work dealing with organotel- furium tigands in transition metal carbonyl chemistry was reported by Hieber and Kruck [IO23 in 1962. Although the reaction of Mn,(CO),,, with dipheny1 telluride cleaved a Te-C bond in this ligand to give a dimeric product with TePh- bridges, substitution products were isolated in reactions with manganese pentacarbonyi halides

Mn(CO),X + 2 TePh, &;;;+L~ 354c Mn(~O)~(TePh~~~X . 1) X = Cl, Br, I

These reactions go readily in refluxing ether to give air- and moisture-stable

products which are nonelectrolytes. In contrast to analogous reactions {372-3751 with phosphines, arsines, and

stibines, no monosubstituted derivatives could be isolated [IOZ]. nor could more than two carbon monoxides be substituted in these reactions. Although the IR spectra of the substituted products did not allow an unequivocal assignment of their stereochemistry, it was proposed that the halide and diphenyj telluride figands are mutually cis in these complexes. A dark-green

nitrosyl complex was obtained by passing NO through these carbonyl complexes [ 1023

2 Mn(C0)3(TePhz),CI 4- 6 NO -

2 Mn(NO~~(TePh~~ 4- 6 CO + TePh, + TePh,Cl, (611

This complex was characterized only by IR spectroscopy, since it could not be isolated in pure form because its solubihty was similar to that of TePh?. Substitution reactions of Mn(CO)3(TePh,)zBr with a variety of nitrogen bases were studied by Hieber and Stanner f IOS], one or both of the tellurium

210

Iigands being replaced, depending on the nitrogen ligand used

[Mn(CO),L,]Br + TePh, L = pyrrolidine, morpholine,

rY piperidine

[Mn(CO),(TePh,),Br] 3eL [Mnl(CO),L,]Brl + 4 TePh, (62)

L = piperazine, benzidine L = hydrazobenzene,

phenylhydrazine, benzaldehyde phenyl- hydrazone

Mn,(CO),L,Brl + 4 TePh, p-aminoatobcnzcnc

+ [Mn(CO),(TePh,)( ID-H,N-C,H,--N= N-&)Br] f TePh?

Aryl tellurul co~?zpIexes. The reaction of Mn,(CO),o with TePh2 for 125 h at 125OC in p-xylene gave the orange, air-stable dimer (OC),Mn(p- TePh)?Mn(CO), [102]. Although bridging ArTe- ligands are generally introduced with a ditelluride [ 106,107,109-l l2,114a,b], a telluroester (ArTeCOAr’) [ 115], or a ArTeMAr; derivative [11&l 17,119], a similar Te-C bond cleavage with formation of PhTe- bridging ligands has been reported in the reaction of RhCl, with TePh, [120] (eqn. 40). Indeed. dimeric selenium analogs, (OC),Mn(p-SeR)IMn(CO), (R = alkyl, aryl). have been prepared from dis- elenides (eqn. 63) and R,SnSeR’ (eqn, 64) reagents

Mn(CO),H + RSeSeR - (OC),Mn(p-SeR),Mn(CO), (63) [376[3

R = CX,, C,X,, C,X,; X = H, F

Mn(CO),Cl + - p-SeR),Mn(CO),

[151] and (OC),Mn(p-Br)ZMn(CO), (the crystal structure of which has established a D,, molecular configuration [378]), indicates the compounds are isostruct- Ural.

Heterocyclic Zigands. Only one Mn complex with a heterocyclic tellurium ligand has been reported, Mn(CO),(phenoxtellurine),Cl, prepared by reacting Mn(COj,Cl with two moles of the heterocycle in ethanol at 50°C [102].

Lappert et al. [ 138b] have recently reported the first metal complexes with t

a tellurourea-type ligand (e.g., ci~-Br~OC)~Mn~Te=CN(Et)~CH~~~~Et~; see eqn. 73).

212

8 4 E” 8

8 s: -

W

213

1

E rt)

z t

I F -J

8

215

The monosubstituted complex was assigned a cis configuration on the basis of IR spectroscopy (C, symmetry; 3A’ + A”), and a similar analysis of the disubstituted derivative (three strong vco bands observed, C,: AL + AL + A”,

and a pRc-cI characteristic of a &zn~-QC-Re-Cl linkage) supported the following structure [ 1521:

TeEtp

*:G==+=e:

oc

Comparison of the vco bands for a series of analogous complexes with group VIA donor atoms led to the following order of bond strengths: Re-Se > Re- Te - Re-S z=- Re-0 [ 1521.

The reaction of M(CO),Cl (M = Mn, Re) with Te(SnMe,), in benzene or 1,Zdimethoxyethane gave the dimeric complexes (UC),M( p-TeSnMe&- M(CU),. The Mn derivative was isolated and futty characterized, but the Re comptex was rather unstable and was characterized only spectroscopically (Table 6) [ 1271.

Dimeric complexes with bridging diphenyl ditelluride ligands have been

Fig. IS- Mofecutar structure of (OC),Re(~--Br)z(tt-Ph~T~~)Re(CO),. Reproduced with permission from f. C&em. Sot., Dalton Tram_. ( 198 1) 1004.

216

prepared by the following reactions [13Ob]:

[Re,Br2(CO)h(THF)3] + Te,Ph, ‘t? r.t. [Re,Br,(CO),(TelPhz)] + THF (69)

2[Re(CUj51] f- Te,Ph, r:zE [Rezl,(CO),(Te2Phl)] t- 4 CO

A dimeric structure with bridging bromo and diphenyl ditelluride ligands, (O~)~Re~~-Br)~(~-T~~Ph~)Re(C~)~ (Fig. 15) was established for the former complex by a single-crystal X-ray diffraction study [ 130b). The presence of the Te,Ph, ligand is shown by the Te-Te separation of 2,794(5) A, the corresponding values for the sum of the covalent radii and the experimental value for Te,Ph, being 2.74 A and 2.7 12 A, respectively. The Re - - - Re non-bonding distance is 3.945(2) A. The angle of fold about the Br - - . Br vector in the Re,Br, fragment is significantly smaher here (13.2”) than for the sulfur (33*) and selenium (31”) analogs [130b]. These values can be rationalized by decreased strain of the bridge unit afforded by the larger E-E bond length.

The similarity of the IR spectra of the iodo and bromo analogs suggests they have the same structure.

Attempts to substitute TePh? in Cr(CO), failed even after 24h of heating the compounds at 125°C [191], but the z complex, tellurophene chromium tricarbonyt, was prepared in 80% yield by the following reaction [132]

(MeCN13CrK0)3 @-.

f 11 11 Eh+W z ,- 50 -60°C -0 “---* II 11 * I Cl- tea,

Te ‘Te--- (71)

The purple-red crystalline compound was soluble in benzene as a monomer and was vacuum sublimed at ca. 65°C without decomposition. The higher dipole moment of this complex vs. the thiophene analog has been attributed to the larger atomic distance of Te ( 1.37 A) vs. sulfur ( 1.04 ;i>, which would give a fengthening of the metal-ring distance, The *Ii NMR spectrum of the complex consists of two rnu~t~~~ets at 3.5 and 4.0 ppm (acetone-d,), which correspond to the AA’BB’ pattern of the free heterocycie (r 1 ,I and 2,2). A comparison of this spectrum with those of the free heterocycle and 2,5- dideuterotellurophene showed that in both cases the low-field signal is assigned to the LY protons, which are, therefore, shifted in the ?r complex to higher field than the 8 protons [ 132]- The relation and direction of the shifts of these two signals, therefore, correspond to those found with the ~hiophe~~

217

system [379], but the absolute magnitude is larger. The complexes Cr(CO),Te(EMe,)z (E = Ge [ 1361, Sn [ 136,137], Pb [ 1361)

have been prepared by substitution reactions with the photochemically generated Cr(CO), THF complex

Cr(CO), _!zF (Cr(CO),THF} TL‘(rT)z Cr(CO),Te( EMe,)? (72)

The high light sensitivity of the telIuride Iigands necessitated this two-step reaction rather than direct irradiation of the two substrates, as with the analogous selenides [ 136,137]. The complexes are quite sensitive to air and moisture and slowly decompose in the solid state even at 0°C. The IR and Raman spectra of the complexes [ l36j (Table 7) are very similar to those of the S [380] and Se (3811 analogs, a result interpreted to indicate that the three organometalIic chalcogens have similar u-donor and rrr-acceptor properties. The ‘H NMR spectra of the complexes in benzene all had a singlet main signal with JtHC_~~~~~~7Sn or JXHC_~~,Ph satellites, and in the (OC),CrTe(GeMe,j2 complex, a three-bond .!1Hcc;c_~~5Tc was also observed (Table7). The increase in the latter coupling constant from that observed in the free ligand (3.5 Hz vs. 5.5 Hz) was attributed to an increase in s character of the Ge-Te bond from chiefly p2-hybridized Te in the free Iigand to sp3-hybridized teIlurium in the complex [ 1363.

The pentacarbonyls Cr(CO),(CF,),ETeMe, (E = P, As) have also been prepared by the above indirect photochemical substitution method [138a]. The complexes were isolated as red-brown oils in 23% and 14% yields.

P dN\ I /c=Te

MtCOIS(NCMel PhMe. 20°C

c

l YN I R

f\

Et

reflux

M - cP(75%)

Mo(52%)

wc71w

(73)

:’ _YNX+

-) Cm-f3r(OC14Mn-Te=c \ ’

N/O 1 Et

R - Me&t

Scheme I

TA

BLE

I

0,

MO

, W c

otnp

lcxc

s

M.p

(‘C

l Ph

ysic

al d

ata

Ref

.

Cr

com

plex

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(CO

) Cr

i-i

3

--./ Te

> 14

5 (d

cc.)

( -4

W

D,

1

(CO

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SnM

c,),

73 (d

cc.)

[I371

85 (d

cc.)

[I361

91 (d

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101

132

136, 1

37

Purp

le-r

ed,

air-

stab

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su

blim

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*, h

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vacw

m)

Solu

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in b

cnzc

nc a

s a

mon

omer

Jlc

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196

7 (A

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1895

and

1872

(E)

cm-’

p

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)=6.

10*0

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D

X,n

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hH,2

) 415

(c 5

890)

, 212

(E 3

1,63

0),

580

(sh)

, 320

(sh)

, 260

(sh

) nm

7

(ace

tone

-~~~

)=3.

5 (m

), 4

.0 (

m)

ppm

Y

ello

w, a

ir-s

ensi

tive

crys

tals

~,o(

C~H

,~)=

2059

(w

), (R

: 20

61);

19

67 (m

) (R

: 19

70),

194

3 (s

) (R

: 19

44),

19

40 (s

) (R

: 19

38),

192

5 (m

) (R

: 19

22),

I8

98 (

w) (

R:

1890

) cm

- ’

6 (b

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C40

7.2

Hz

(bcn

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as

inte

rnal

sta

ndar

d)

JI,.,

~IIT

~~

=52

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z J1

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2064

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: 20

51),

19

74 (m

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71),

194

0 (v

s) (

R:

1943

),

1934

(vs)

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192

7 (m

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: 19

16),

19

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401

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z (b

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cry

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58 (

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1976

(w) (

R:

1971

), 1

938

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1930

),

1935

(sh)

(R

: 19

28),

193

0 (sh

) (R

: 19

24),

19

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) (R

: 18

88) c

m-

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136

136

TA

BL

E 7

(co

ntin

ued)

M,p

, (“

C)

Phys

ical

dat

a R

cf,

,I,

Mal

CO

), T

e= c

,,

Y’ 4

‘3

-. _

*I.^

a. I _

Bla

ck n

ccdb

s vc

o(C

H,C

t$=

1985

(vs)

, 19

35 (s

) cm

-’

t&K

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= 1

990 f

vs),

i 94

7 (v

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, 7.

27 (

mf

and

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(m)

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125

75

Yel

low

sol

id

vCN

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ull)

= 1

525

cm-

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t”C

)= 1

52 p

pm v

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M5

138b

Dar

k-br

own

oit

t38c

~~

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~=20

9~ (m

), 2

019

(vw

),

1990

(s, s

h),

1985

(vs)

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m-’

6

(C,D

b)=

1.

68 pp

m (

Jq,_

~tt ~

7.0

Hz)

S(

‘“F;

C,D

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-5

6.0

ppm

(J+

..Iu,

: -

66.9

Hz)

, vs.

int

erna

l C

CI,

F 6

t3’P

; C

,$)=

-i

-32.

5 pp

m (

vs. 8

5% H

3PQ

t)

212-

213

212-

214

Bro

wn

solid

‘H

NM

R (

CD

CI,

): T

4.6

6 (s

, Cp)

, T 2

.10-

2.95

(m

, Ph

) B

row

n so

lid

“H N

MR

(C

DC

I,):

7 4

.69

(s, C

pf

T 2

.3 I

(d)

and

3.02

(d)

(C&

H,)

124

124

86

Yel

low

sol

id

pCN

(mul

l)=

153

8 cm

-’ t

&tj,

),

150

ppm

vs.

TM

S

I38b

222

respectively. The (CFJ)lPTeMe complex has good thermal and light stability in the solid state and solution in the absence of oxygen, but the complex with the weaker donor (CF,),AsTeMe decomposes in solution over a few days, even with the exclusion of air and fight, The spectroscopic results (Table71 support the coordination of both the As and Te atoms in the (Cf;,),AsTeMe complex, whereas the (CF;;),PTeMe is isomerically pure and bonded through the P atom [138a].

Lappert et al. [138b] recently reported the first metal complex with a ligand incorporating a tellurourea function (see Scheme 1, page 217). These metal complexes are moderately air stable in the solid state and stable indefinitely under an inert atmosphere in the dark. They are thermally and photochemically sensitive to tellurium extrusion. The Cr complex undergoes Te extrusion at 20°C in toluene to give the corresponding carbene complex

(741

This reaction was acccferated by heat, Iight, or reaction with mercury. The crystal structure of the Cr complex has been reported [138b] (Fig. 16).

The first examples of complexes with the TeH - Iigand have recently been prepared by photochemizal (eqn. 75) and thermal (eqn. 76) substitution reactions [ 149bJ.

M (CO ),2F M (CO ), (THF ) i- CO -%&z:

(751

M=Cr. W

i

Nn 2Te

EIOH/ - 60°C

1 Na’[M(CO),TeHj- c *zr- C f [M(CO),TeHf

CC=PPN+.M=Cr c+‘= AsPh:, M=W

[PPN] [Cr(CO),Clj + NazTe’Iy [PPN] [Cr(CO),TeHl . .

(76)

These very air-sensitive complexes, which are soluble in polar soivents, were characterized by IR and ‘H NMR spectroscopy fTable7). The chromium complex was alkylated to give the neutral diethyl telluride complex [ 149b]

[PPNl [Cr(CO)5TeH] + [Et,Of [BF,] E’?r (OC),Cr(TeEt2 f (77)

The TeH - ligand can also function as a bridging group, as evidenced by the

223

. Fig. 16. Molecular structure of Cr(CO~,(T~=~NEtCH,CH2NEtf. Rcpmduccd s&n from Chcm. Commun.. (1980) 63;:

xvith pcmmis-

isolation of dinucfear comptexes from the reaction of the monomeric compfexes with the photochemically generated labile M(CO)~~THF) complexes

C +[M(CO)JTeH)] - + M(CO),(THF) -4 ‘[(OC),M(E.r-TeH)M(CO),J -

T THF M=Cr,C.“=PPN; hv/-w’C W.C+- = AsPh;

MtCO), (78)

Tetracarbonyl(norbornadiene)chromium(O) reacts with tellurobis(di-t- butylphosphane) in toluene at room temperature to give the red crystalline complex [Cr(CO),P,-I-Bu,Te] which has been assigned a CrPzTe cheiate structure on the basis of spectroscopic evidence (Le., fR, NMR (‘H, “P, “‘Te), and mass spectroscopy) [382,383].

(C,H,)Cr(CO), + Te(PR2)2 --, C,Hx + (OC)4CrpFA$:Te: (79) R = r-Bu R c)Y R

MO

The reaction of Te,Ph, with [~CpMo(C0),1, in ea. equimolar amounts gave a variety of products involving different coordination modes of the phTe_ ligand, depending on the severity of the reaction conditions [ I081

[~CpMo(CO),], + PhTeTePh ‘hcn? ~cp(CO)~~o(~r-TePh),Mo(CO)lrrCp renux $4 h

\ Wax \ &UK 5 tr [ 7KpMo(TePh),],, (80)

A third carbonyf-containing product was also detected by IR spectroscopy when the monumer was refhrxed For 12 h in tohtene, but the main product of the thermolysis was the decarbonylated polymeric f &pMo(TePh)J,, [ 1081. The highest-energy carbonyl stretching frequencies in the complex gCpMo(CO),EPh are: S, 2033 cm-‘; Se, 2026 cm-‘; Te, 2016 cm-‘; the order of “softness” of the chafcogens (Te> Se> S) being reflected in the increased bonding between MO and CO in this order_ Converseiy, the ease of thermofysis of the monomeric to dimeric complexes follows the order S > Se >Te. Although geometrical isomers are possible for the dimeric complex, the ‘H NMR spectrum of [n-CpMo(CO),TePhll showed only one kind of Cp proton [ 108J.

Complexes of the type (~Cp)~MofTeAr), have been prepared by metathetical reactions from the corresponding chloride [ 1243

~Cpl!MoCl-, f 2 ArTeMgBr - -Cp, Mo(TeAr), + 2 MgBrCl (80 (1) Ms/THF

’ (2) Te(0) Ar = Ph, p-tolyl

ArBr

These complexes react with concentrated HGI to give the starting dichloride and with Me1 to give ~rCp,Mol, (and presumably ArTeMe) [124]. Although the complexes are quite stable in the solid state, CH,Cl, solutions decompose on standing ca_ 1 day, the Se analogs being somewhat more stable ] 1243, This enhanced stability of the Se analogs is similar to that found for aCpNi(P(n-Bu),)EAr (E= Se, Te) [I221 and 7rCpIM(EAr)l (M =Ti, Zr) [ 1231 but is opposite that found for ?rCpFe(CO),EPh [107] and &pMo(C0)3EPh. [ 1081.

Reaction of PhTeLi (PhLi +Te(O) in ether) with (~‘-C,H,)MO(CO)~B~ gave the symmetricdfy double-bridged species f$ -C,H,)COMofp-

225

TePh),MoCO( #-C7H7) as black needles in 54% yield f 125j.

The complex Mo(CO),(CF,),PTeMe was prepared in 27% yield by reacting the tellurium ligand with the photochemically generated complex Mo(CO),THF 1138 c , ] analogous Cr complexes having been prepared by this route fl38a]. The complex, obtained as a dark-brown oil, was characterized by IR (vco)t NMR 0% t9F, and s* P), and mass spectroscopy (Table 7).

The tellurourea complex [(OC),Mo(Te=CN(Et)CH,CH,NEt}] has been prepared by a substitution reaction starting from Mo(CO),(NCMe) (see eqn. 73) [ 138b].

w The tungsten complexes rrCp,W(TeAr), (Ar = Ph, p-toIyI), were prepared

by metatheticaf reactions from the corresponding chlorides [ 1241

THF ?rCp,WCI, + 2 ArTeMgBr -+ rrCp,W(TeAr),

r.t. (82)

These complexes, which are moderately soiuble in CHCI,, CH,CI,, THF. acetone, DMSO, and CS, but insoluble in other organic solvents, readily react with concentrated WC1 to regenerate the starting dichloride” They also react with Me1 to give ?rCpzW12 [ 1241.

The tellurourea complex IfoC),W(Te~C7N(Et)CHzCH1NEt)f was prepared as described in eqn. 73 ft38bf. The complexes AsPh~[W~CO~~TeH] (eqn. 75) and AsPh~r(OC)~W~~-TeH~W(C~~~] (eqn. 78) were prepared by the routes used for the Cr analogs.

(oiii) V, iVb, Tu

No vanadium complexes with teIIurium ligands have been reported. although the metatheticat reaction used to prepare &Jp,VfSeAr),_ (Ar = Ph, p-tolyl: zCp2VCI, + ArTeLi) couid presumably be extended to the tellurium analogs [ 124J.

The Nb complex, =CplNb(TePh)l, has been prepared in 80% yieId by such a route fI24f. Like the MO and W analogs, this complex reacts with concentrated HCI to regenerate the dichloride and with Mef to give the diiodide [ 1243. Unlike the latter derivatives, however, &p,Nb(TePh), is very air sensitive in both the solid state and solution. Organote!lurium-bridged heteronuclear complexes have been prepared by the following routes [ 1261

+t/2= ~c~,Nbl~-TePh)~Fe(No)C0

(80%) nCp,Nb(TePh),

h

(83)

~Cp,Nb(lit_cTePh),CotCO), 3cXton~f r.t. (90%)

226

TABLES

V. Nb. Ta complexes

Complex M.p. (“C) Misc. data Ref.

TaCl,TeMe,

= Cp, Nb( p-TePh), Fe( NO)CO

I37- 142

170-171

157-160

Moss-green crystals. air-sensitive in scdid

state and solution Dark-brown solid ‘H NMR (CH&i,, -6O*C)

6=2.54 ppm As=& (TaCI,TeMe,)- G(TeMc, ) = 0.62 ppm

Bfack solid ‘H NMR (CH&12_ -60°C)

&=2.58 ppm A&=S(TnBrsTeMel)- 6(Tt?Mez) = 0.67 ppm

Brown crystzds vXo = 1623 (s) cm-’ vco = 1845 (s) cm- ’ ~~~ (ppm) = 4.64 (s).

4.83 (s), 4.90 (s). 5.07 (s). 5.25 (S). 5.31 (s)

Brown crystals vXo = 1859 (s) cm-’ vc- = 191 I (s) cm-’ @ppm) =4.73 (s).

4.99 (s). 5.3 1 (s) *

124

150

150

126

126

The complexes, which are stable under N,, have enhanced air stability in both solution and the solid state compared to the parent TCpzNb(TePh),. Their IR spectra support their formulation as p-TePh complexes with terminal CO ligands, and their ‘H NMR spectra indicate the presence of cis

and tr~ns isomers (3 and 6 Cp resanances for the Nb, Fe and Nb, Co dimers, respectively) [ 1261.

The only other reported complexes of a group VB metal with a tellurium ligand are the TaX,TeMe, (X = Cl, Br) derivatives, prepared by reacting the

pcntahalides with excess dimethyf telluride in CH,CI, [ 150f. The relative stability of a series of such adducts (TaX,EMe,; X = Cl, Br; E = 0, S, Se, Te) has been determined by ‘H NMR in CH,Cl, at -6O”C_ At room temperature, in the presence of excess ligand, the adducts showed only one signal in their ‘H NMR spectra as the result of a rapid exchange process [ISO], but at lower temperature two distinct signals are observed, that corresponding to coordinated ligand appearing at lower field than free

227

@and. Competitive equilibria between different bases for the pentahalides were also studied by NMR spectroscopy, the stability of the adduct. with EMe, (E = 0, S, Se, Te) increasing with the atomic number of the donor

atom.

The monomeric complexes &pIM(TeAr)l! (M = Ti, Ar = Ph, p-tolyl; M = Zr, Ar = Ph) have been prepared by metathetical reactions [ 1231

zCp,TiCI, -i- ArTeMgBr - =Cp?Ti(TcAr), (84) r -k(O)

ArMgBr

7rCpIZrCl, + PhTeLi -+ nCp,Zr(TePh), (I) Li/ether

’ (2)Te(O)

PhBr

(85)

Selenium analogs, v Cp,Ti( SePh), , have also been prepared from the reaction of ?rCp,TiCll with HSePh [384] in the presence of NEt, (a route not feasible for the tellurium compfex owing to the instability of tellurols) as well as by oxidative addition (mCp,Ti + Ph,Se,) [385]. The iatter route is feasible for the tellurium analog; several such exampfes of the use of diary1 ditel-

TABLE 9.

Ti, Zr. Hf complexes

Complex M-p. (“C)

~cp,Ti(TePh), 123- 126

zCp,Ti(Te-p-toiyl)I 165-167

m CpzTi( p-TePh), FefNO)l 156-157

Misc. data

Red-brown solid ‘H NMR (CS,) 74.15(s.Cp) T 2.26-2.50 and 2.72-2.98 (Ph)

Red-brown solid ‘H NMR (CS,) 74.18(s,Cp) T 2.48 (d) and 2.98 (d) (Ph) 77.59 (s. Me)

Green soiid MW (benzene) =68 I (talc. 703) vNo = 1623 (s) cm-’

“co = 1845 (s) cm-’ ‘H NMR (acetone-d,)

T 4.68 (s), 4.7 I (s), 4.83 (s), Cp 7 2.60-2.84 (m, Ph)

Ref.

123

I23

126

228

lurides as substrates in oxidative addition reactions have been reported [106,107,109-112,114].

These complexes are very air sensitive, especially in solution. Interestingly, sCp,Nb(TePh), cannot be prepared by using PhTeMgBr, the Li reagent being necessary to effect the metathesis [123]. The organotellurium-bridged heteronuclear complex qCplTi( ,u-TePh)lFe(NO), has also been prepared by a route analogous to that described above for Nb, Fe and Nb, Co dimers [ 1261

TCplTi(TePh)l + l/2 Hg[Fe(CO),NO], - =Cp,Ti( CL-TePh),FeCONO (86)

(AT) Lanrhanides arld actirzides

The only complex of the f elements containing a tellurium ligand is the violet-black diphenyl ditelluride adduct UCI,( Ph?Te,), prepared by reacting the pentachloride with Te,Ph, in a 1: 1 molar ratio in benzene [130a]. The complex, which is soluble in CHCI,, CH,CI,. MeNO, and MeCN and decomposes above 151°C, has not been characterized with respect to the bonding of the tellurium ligand.

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238

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239

NOTE ADDED IN PROOF

Several new complexes with tellurium ligands as well as additional data for some previously reported compounds have been published recently (Table 10).

The complex PtCI,(TeCI,), has been characterized in the solid state by IR and Raman spectroscopy in the 60-700 cm-’ region [386]. These data {Table IO) support a trur~s structure, TeC1. being coordinated through the chloride (e.g., PtCI,(TeCt,),) f386).

Diphenylditelluride was reported to be unreactive towards Pt(PPh,),(C2H,) [387J. Related oxidative addition reactions of Pd(PPh,), with Te,Arz (Ar =p-EtO-C,H,, 2-thienyl [109]) as well as Pt(PPh,), with Te$ p-totyi), and p-Me&C, H,TeCN [3883 have, however, been reported.

Fe

Another example of a complex with ,

Te=CN~Et)~H~CH~NEt (see eqn. 731, has been t3s91

Fe<CO15 + hexme

650c_ Fe(CO), &!$Mel

be be E3901 I

PPh3 hexonef hv 13893

f Fe(C0)3(PPh,) (W(Me)CH,CH2NMe)

!

THF,QO*C

(tf PPh3

(2) Agl3F,

[Fe(C0)2(PPh32(iN(Me)CH2CH2PIMe)leF,

Et.

20 *c

CH&t2 j

,LCH, ‘Te==c I

‘$4--CHz

the tellurourea ligand, reported by Lappert et al.

(87)

This paramagnetic Fe(I) carbene complex was not isolated, but its infrared spectrum was recorded in solution (Table 10).

The chemistry of F~.JJ.L~-T~)(CO)~ and Fe,(pJ-Te),(CO), has been further explored by Rauchfuss and co-workers f387,39 1,392].

The dimer Fe-J p, -Te,)(.CO),, a side product in the synthesis of Fe,(p-,- Te),(CX& [139b], has been isolated in solution in 4.3% yield by nonaqueous

TA

BL

E 1

0

Rec

ently

rep

orte

d co

mpl

exes

with

tel

luri

um li

gand

s

Pt c

ompl

exes

Pt

Cl,(

TeC

I,),

v,

,,(I+

CI)

=35

5 (v

s) c

m-’

(I

R);

v&

I?-C

l)=

352

(s)

cm-’

(R

) v,

,,(Pt

-TeC

1,)=

324

(m)

cm-’

(I

n);

I~#$

-T&

,)=

324

(s)

(R)

G(C

I-Pt

-Cl)

=

178 (

w) c

m-’

(IR

) 13

861

Fe c

ompl

exes

&T

&I,

-I%

-Cl,T

c)=

162

(w) c

m-.

’ (I

R)

v,,,(

Tc-

Cl)

=37

4 cm

-’

(IR

), 3

83 c

m”’

(R

); Q

Tc-

Cl)

= 17

0 cm

-’

(IR

):

&,(

CI-

Tc-

Cl)

=

175

(w)

cm-’

(R

): G

$ZI-

Tc-

Cl)

= 14

4 (m

) (I

R)

Et I

[Fe(

CO

)(PP

hJz(

Te

= C

<N

-CH

2 1 )(

CN

(Me)

CH

JH?N

Mc)

JBF,

v,

~(C

HJJ

~)=

18

61 cm

-’

N-C

H,

I Et

Fez(

pz-T

e2W

),

S(‘2

STe)

= -

733

ppm

(up

ficl

d fr

om n

eat

TcM

c,)

vco(

C,,H

,,)=

2067

, 20

28, 1

995 c

m-l

el

ectr

on-i

mpa

ct m

ass

spec

trum

: Fc

,Tc,

(CO

),

x=2-

6 (F

qTcl

=

100

% pe

ak)

Mel

, w

t. (C

,“hF

~~O

~,‘~

HT

~‘Z

’~T

~)=

537.

6499

; fo

und

537.

6500

Fe&

-Te)

#%

~&Z

,,H,~

)=20

45,2

025,

2004

cm

-’

S(“‘

Tc)

= t

1123

ppm

(do

wnf

ield

fro

m T

eMc,

)

1389

1

(39 1

I

1391

1

Fe,(

P:!-

TeC

H,P

h),(

NO

),

Mo

com

plex

es

(q7-

C,H

,)M

o(C

O},

TeP

h (~

7-~~

H~)

Mo(

~*-T

e(n-

Bu)

)~M

o(~7

-~7H

~)

R

( ~7”

C~H

7)M

o(~O

)~

i eM

e

vco(

C,H

,2)=

2104

,205

4,20

49,2

038,

2019

, 1994

, 198

4, 19

72 cm

- re

d ne

cdic

s [3

911

v,o(

C,H

,,)=

2034

s, 1

995 v

s, 1

960 s

cm-

f

’ fie

ld-d

csor

ptio

n mas

s spe

ctru

m *

mol

ecul

ar io

n a(

‘?sT

e)=

- 86

1 pp

m (

upfi

cld f

rom

nea

t TeM

e,) J

(‘“s

Tc-

“‘sP

t)=

S61

Hz

S(3’

P)=

-I- 1

9-3 p

pm (

upfi

eld

fron

t 85%

H,P

O,)

~(~

‘P-‘

~~Pt

~~28

46,4

H

z cr

ysta

l st~

ctu~

e [3

92]

1387

1

eata

ble-

tem

pera

ture

“P N

MR

(392

1 ~~

o(C

H,C

1,)=

1770

, 175

Ocm

- ‘I

i N

MR

: &=

7,2 s

&

Won

-im

pact

mas

s spe

ctru

m: M

’ ~6

46

vNo(

CH

zClz

)= 17

65, 1

745 c

m-’

el

ectr

on-i

nlpa

ct m

ass s

pect

rum

M ’

~674

1393

1

(393

1

crys

tal s

truc

ture

(Fig

. 17)

[3

95I

no d

ata

repo

rted

[3

951

red-

brow

n thc

rn~a

l~y un

stab

le cr

ysta

ls

I396

1

vco =

199

0, 19

30 cm

- ’

IJ~

~..~

=47

0 cm

_ I

~‘T

c=O

= 9

60, 7

85, 7

50, 6

95 cm

.‘ ’

T 2

.33 (

s)

242

gel permeation chromatography of the product of the reaction of K2Te0, and KHFe(CO), [391]. The complex was previously isolated, contaminated with Fe,(pCL3-Te),(CO),, by vacuum sublimation of the above reaction product and characterized by a selective oxidative addition reaction with Pt(C,H,)(PPh,), [139bf. The product of the latter reaction is (OC),Fe,(p,- Te),Pt(PPh,)l, the trimer being inert towards the Pt complex. The dimer has now been characterized by IR, mass spectrometry, and “‘Te NMR (Table 10) [391]. The solid decomposed when the chromatographic solution was evaporated under N2 or CO, impure Fe,(~3-Te),(CO),, being proposed as the product. The tZSTe chemical shifts of the dimer and Fe,(p,-Te)z(CO),, surprisingly, differ by 1856 ppm (Table 10).

The instability of Fe,(p,-Te?)(CO), was rationalized in terms of the steric strain associated with the small closed cluster incorporating the large Te atoms. Indeed, this thermally unstable dimer has been proposed as an intermediate in the synthesis of Fe,(pt,-Te),(CO), via an oxidative addition reaction of HFe(C0); across the Te-Te bond of the dimer.

Fe,(p2-Te,)(CO), -f- KCWFe(C%l- *’ Fe,(p3-TeJ2(CO)tt,

T .\wer;ll stL’ps J‘

TeOi- \ K’[HFe(CO),]- Fe&.+Te),(CO),

(88)

The proposed oxidative addition reaction of HFe(COj; is analogous to the previously reported reaction with Pt(PPh,)JC,H,) 1139bJ.

The initial decacarbonyl product is readiiy decarbonylated thermatly or chemically (with Me,NO) to give the stable nonacarbonyl. The decacarbonyl was obtained in 70% yield by a modification of Hieber and Gruber’s [ 1391 original method in which the reaction was carried out at 0°C and the thermally Iabile product was extracted into CH,Cll after acidification 13911 (rather than Soxhlet extraction with hot petroleum ether as in the original reference [ 1391).

Further details of the synthesis and properties of (CO),Fe,( p3 - Te)2Pt(PPh,), have appeared [387]. This mixed-metal cluster and the S and Se analogs were prepared in 70% yield by the previously described oxidative addition reaction [139b]. The cluster was purified by preparative TLC and characterized by NMR (3’P and IZ5Te) and IR [387] (see Table 10).

A single-crystal X-ray structural determination of (CO),Fe,(ps - Se),Pt(PPh,), 13871 has confirmed the structure proposed for these mixed- metal clusters [139bf. A single-crystal X-ray diffraction study of Fe,&- Te)z(CO),PPh, [387,392] has shown that a nido-arachno cluster rearrang-

243

ment has accompanied adduct formation (see ref. 140 and Fig. 13 for the previously proposed structures for this adduct of Fq(p3-Te),(CO), and PPh,).

The Te analog of Roussin’s red salt, fFe,(pz-Te),(NO),]‘- , has been prepared in solution and used as a reagent for the synthesis of a neutral alkylated derivative [393]

Fe,(~LZ-I)1(N0)4+LizTe-, [Fe,(pI-Te),(NO),l’-

T THF

I

PIKH,CI

Te -l- LiBEt,H

Fe,( ~+Q-l,Ph),(NW,

(89)

The neutral phenyl analog was prepared by a metathetical reaction 13931

Fe,(pZ-I)7(NO)q t Li + TePh- - F~~t~~-TePh)~(NO)~

,:;;y1

PhTeTePh

The cleavage of the P-Te bond induced by Me,SnH in the previously reported Cr(CO),(CF,),PTeMe [138a] has been studied [394]. No reaction products were isolated, but the products were characterized in toluene solution by ‘H and “F NMR

Cr(CO),(CF,),PTeMe -yc M.+S!lH

Cr(CO),(CF,),PH + Me,SnTeMe (91)

‘zCr(CO),(CF1),PSnMe, f Cr(CO),(CF,),PH (92)

The cleavage reactions of a number of complexes with coordinated R, EE’R’ (R, R’ = Me, CF,; E = P, As; E’ = S, Se, Te) derivatives were investigated in this study. The same primary products are obtained in such reactions as for the free ligands although the reaction rate is significantly decreased upon coordination.

The crystal structure of the complex q7-C7H7Mo(C0)7TePh has been reported (Fig. 17) [395]. This monomeric complex and the dimer [?I~- C,H,Mo(CO)TePh], were formed in the reaction of ~~~-C,H,MO(CO)~ Br with TePh- _ The Mo-Te bond distance (279.7 pm) is 15 pm shorter than the sum of the covalent radii, indicating a considerable double-bond character_

An analogous reaction of q7-C,H7Mo(C0)zBr and Te(n-Bu) - was reported to give the triply telluro-bridged species ( q7-C, H ,)Mo( p-Te(n- Bu))~M~~~-~~H~) 139%

The first example of TeO, insertion into a metal-carbon bond has been

244

Fig. 17. MolecuIar structure of ( q’-C,H,)Mo(C0)7TePh. Reproduced with the permission of A. Rettenmcier. K. Weidenhammer and M. Ziegler. Z. Anorg. AI&+ Chem.. 473 (1981) 91.

described [396] ??

( q’-C7H ,)Mo(CO)$X, -I- EO, - ( q’-C,H,)MO(CO)~ ES;‘”

0 E=S,Se,Te

(93)

The TeO, was generated in a metal-atom reactor (ether matrix; - 196OC) and subsequently reacted with the methyl compound at -78OC. The complex was too thermally unstable, decomposing in a few minutes at room temperature, to allow an X-ray structural investigation_ A monomeric formulation was supported by the similarity of the spectral properties (Table 10) with those of the Sanalog, for which the molecular weight was determined by osmometry. The analogous phenyl derivative gave insertion onIy with SO?.

w The compounds ?rCpW(CO),TePh and [~CpW(CO),TePh],. prepared

from &ZpW(CO),H and TqPh,, have been described in two Ph.D. theses [ 153,397J.

V

A highly insoluble and presumably polymeric compound, [aCpV(TePh)l],, prepared from &pV(CO), abd Te,Ph,, has been reported in a Ph.D. thesis [397] but no detailed publication on this material has appeared.

A review of the coordination chemistry of thioethers, selenoethers, and telluroethers has appeared recently j398f.

The Ligand Chemistry of Tellurium

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