Polyhedron 28 (2009) 2313–2320

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Polyhedron

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Synthesis and characterization of new bis(diphenylphosphino)aniline ligandsand their complexes: X-ray crystal structure of palladium(II) and platinum(II)complexes, and application of palladium(II) complexes as pre-catalysts in Heckand Suzuki cross-coupling reactions

Murat Aydemir a, Feyyaz Durap a, Akın Baysal a,*, Osman Akba a, Bahattin Gümgüm a, Saim Özkar b,Leyla Tatar Yıldırım c

a Dicle University, Department of Chemistry, TR-21280 Diyarbakır, Turkeyb Middle East Technical University, Department of Chemistry, TR-06531 Ankara, Turkeyc Hacettepe University, Department of Engineering Physics, Beytepe, TR-06800 Ankara, Turkey

a r t i c l e i n f o a b s t r a c t

Article history:Received 9 March 2009Accepted 10 April 2009Available online 4 May 2009

Keywords:AminophosphineComplexesCrystal structuresCatalysisHeck reactionSuzuki coupling

0277-5387/$ - see front matter � 2009 Elsevier Ltd. Adoi:10.1016/j.poly.2009.04.033

* Corresponding author. Tel.: +90 412 2488550x31E-mail address: akinb@dicle.edu.tr (A. Baysal).

Two new bis(diphenylphosphino)isopropylphenylamines, (PPh2)2N-C6H4-CH(CH3)2, having the isopropylsubstituent at the carbon atom 2 (1) or 4 (2), were prepared by the aminolysis of chlorodiphenylphos-phine with isopropyl substituted aniline at the ortho- or para-position, respectively, under anaerobic con-ditions. Oxidation of 1 and 2 with either aqueous hydrogen peroxide, elemental sulfur or grey selenium inthf gave the corresponding oxides, sulfides and selenides (Ph2P@E)2N-C6H4-CH(CH3)2, where E = O, S orSe, respectively. The palladium and platinum complexes [M{(Ph2P)2N-C6H4-CH(CH3)2}Cl2] (M = Pd, Pt)and the copper complex [Cu{(Ph2P)2N-C6H4-CH(CH3)2}2]PF6 were isolated from the reaction of thebis(phosphino)anilines with MCl2(cod) or [Cu(CH3CN)4]PF6, respectively. The new compounds were char-acterized by NMR, IR spectroscopy and elemental analysis. Furthermore, the solid-state structures of tworepresentative complexes were determined using single crystal X-ray diffraction analysis. The com-pounds of palladium (1d) and platinum (1e), both mononuclear complexes, crystallize in the monoclinicP21/c space group. In both compounds the metal ion has a distorted square–planar coordination geome-try. The structural properties of complexes 1d and 1e in the solid state are very similar. The palladiumcomplexes were also tested for their catalytic activities in C–C coupling reactions.

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1. Introduction

Tertiary phosphines have long been used in the design and syn-thesis of transition metal complexes with catalytic properties [1–3], especially with late transition metals like nickel, rhodium,ruthenium, palladium and platinum [4] that can be used as highlyactive catalysts in industrially important reactions such as allylicalkylation [5–8], amination [9–11], the Heck reaction [12–20], Su-zuki coupling [21–25], hydroformylation [26–29], and hydrogena-tion of olefins [30–33]. In particular, palladium complexescontaining phosphine ligands serve as highly active catalysts forthe straightforward formation of carbon–carbon bonds [34–37].Compounds containing phosphorus–nitrogen direct bonds havebeen known for many years and their chemistry has been of con-siderable interest because of their applications in increasingly di-verse fields [38,39]. The applications of chelatingbis(phosphino)amine ligands is widespread in organometallic

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chemistry and in homogeneous catalysis as these ligands can beused for fine tuning the activity and selectivity of the catalyst[40]. A variety of PNP and related diphosphine ligands, speciallyin combination with Cr(III) compounds, were reported to be veryactive and efficient catalysts for ethylene tri- and tetramerization[41–44]. Bis(phosphino)amines display their versatility by exhibit-ing different coordination behavior when the donor–acceptorproperties are altered by incorporating a substituent at the ligandbackbone [45]. Synthesis and coordination chemistry of bis(phos-phino)anilines have also been studied in some detail [46,47]. Ithas been shown that coordination of bis(phosphino)anilines totransition metal ions occurs mainly via the phosphorus centersdue to the low basicity of the amine nitrogen, attributable to theP–N p interaction between the phosphorus dp and nitrogen pporbitals [48].

Herein, we report the synthesis of two new bis(diphenylphos-phino)anilines by the aminolysis of chlorodiphenylphosphine withisopropyl substituted aniline at the ortho- or para-positions and thecorresponding oxides, sulfides and selenides as well as their com-plexes with selected transition metal ions (Cu+, Pd2+ and Pt2+). The

2314 M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320

compounds were isolated from the reaction mixture by crystalliza-tion and fully characterized using elemental analysis, FT-IR, multi-nuclear NMR spectroscopy. The solid-state structures of two of theproducts were established by single crystal X-ray diffraction anal-yses. We also report on the catalytic activities of the palladium(II)complexes as pre-catalysts in the Heck and Suzuki couplingreactions.

2. Results and discussion

2.1. Synthesis and characterization

N,N-bis(diphenylphosphino)isopropylanilines (PPh2)2N-C6H4-CH(CH3)2, having the isopropyl substituent at the carbon 2 (1) or4 (2) were easily prepared from the reaction of o-H2N-C6H4-CH(CH3)2 or p-H2N-C6H4-CH(CH3)2, respectively, with two equiva-lents of chlorodiphenylphosphine in the presence of triethylaminein thf solution at 0 �C (Scheme 1). Although the existence of com-pound 1 has been reported by Killian et al., neither the experimen-tal procedure for the preparation nor characterization data isavailable [49]. Hence, the synthesis and full characterization ofcompound 1 will be reported herein for the first time. Compounds1 and 2 were isolated as white solids in high yields (87% and 85%,respectively) under anaerobic conditions. Attempts to prepare N,N-bis(diphenylphosphino)-2,6-diisopropylaniline did not succeed,may be due to the steric repulsion between the two isopropylgroups and phenyl rings of the phosphine.

In the 1H NMR spectra, both 1 and 2 show multiplets for thearomatic H-atoms in the regions 6.75–7.53 and 6.58–7.39 ppm,respectively. The CH signal of the isopropyl group is at 2.99 ppmfor 1 and 2.76 ppm for 2. The methyl groups of the isopropyl sub-stituent give doublets at 0.75 and 1.15 ppm for 1 and 2, respec-tively. The 31P–{1H} NMR spectra of 1 and 2 show a single

Scheme 1. Syntheses of N,N-bis(diphenylphosphino)isopropylanilines by the aminolysioxidation of 1 and 2 with aqueous H2O2 (1a, 2a), elemental sulfur (1b, 2b) and grey sel

Scheme 2. Reactions of aminophosphines 1 and 2 with

resonance at 62.2 and 68.5 ppm, respectively, in line with the val-ues previously observed for similar compounds [50,51]. The 13CNMR spectra of the compounds give four signals for the phenyl car-bon atoms, two signals for the isopropyl groups, and six or four sig-nals for the aniline ring in 1 or 2, respectively.

Oxidation of 1 and 2 with aqueous hydrogen peroxide or ele-mental sulfur or selenium in thf gave the corresponding oxides(1a, 2a), sulfides (1b, 2b), and selenides (1c, 2c), respectively(Scheme 1).

Oxidation of both 1 and 2 using aqueous H2O2 was very rapideven at ambient temperature. However, the reaction with elemen-tal sulfur or selenium had to be carried out at elevated tempera-tures, as expected because elemental sulfur and selenium areweaker oxidizing agents than hydrogen peroxide, especially to-wards phosphorus atoms with bulky phenyl groups [52–55]. The31P–{1H} NMR spectra display one singlet for each of 1a and 2a(23.9 and 24.2 ppm) and 1b and 2b (68.5 and 68.9 ppm), suggest-ing that the two phosphorus atoms are chemically equivalent inthese compounds. The 31P NMR signals of 1c and 2c are also sing-lets, but they are accompanied by selenium satellites at 67.8 ppm(1J(31P–77Se) = 787 Hz) and 67.3 ppm (1J(31P–77Se) = 792 Hz),respectively.

In the reaction of [M(cod)Cl2] (M = Pd, Pt; cod = 1,5-cyclooctadi-ene) with one equivalent of 1 or 2 in thf solution, cod is replaced byN,N-bis(diphenylphosphino)isopropylaniline as a bidentate ligand,yielding the respective [M{(Ph2P)2N-C6H4-CH(CH3)2}Cl2] com-plexes 1d, 2d, 1e, 2e (M = Pd, Pt, respectively). The reaction of[Cu(CH3CN)4]PF6 with two equivalents of 1 or 2 gives the expectedcomplexes [Cu{(Ph2P)2N-C6H4-CH(CH3)2}2]PF6 1f or 2f, respec-tively. Both reactions are summarized in Scheme 2. The 31P–{1H}NMR spectra of 1d and 2d exhibit a single resonance at 37.9 and38.5 ppm, respectively, which are within the range expected forstructurally similar complexes [56–58]. The phosphorus reso-

s reaction of H2N-C6H4-CH(CH3)2 with Ph2PCl (1: 2-CH(CH3)2; 2: 4-CH(CH3)2) andenium (1c, 2c).

[M(cod)Cl2] (M = Pd, Pt) and [Cu(CH3CN)4]PF6 in thf.

Table 1Crystal data and experimental details of the structural analysis of dichloro{N,N-bis(diphenylphosphino)-2-isopropyl aniline}palladium(II) (1d) and dichloro{N,N-bis(diphen-ylphosphino)-2-isopropyl aniline}platinum(II) (1e).

1d 1e

Empirical formula [(Ph2P)2N-(C6H4)-2-CH(CH3)2PdCl2]�(C2H5)2O [(Ph2P)2N-(C6H4)-2-CH(CH3)2PtCl2]�(C2H5)2OFormula weight 754.97 843.63Crystal system monoclinic monoclinicSpace group P21/c P21/cUnit cell dimensionsa (Å) 12.1266(10) 12.170(2)b (Å) 14.028(2) 14.167(5)c (Å) 21.617(2) 21.552(2)b (�) 101.744(7) 101.610(11)Volume (Å3) 3600.3(7) 3639.7(15)Z 4 4Dcalc (Mg/m3) 1.393 1.539Absorption coefficient (mm�1) 0.782 4.119F(0 0 0) 1552 1680h, k, l ranges �14 ? 15, �17 ? 0, �26 ? 0 �14 ? 15, �17 ? 0, �26 ? 0Reflections collected/unique 7483–7284 [Rint = 0.0356] 7580/7377 [Rint = 0.0432]Refinement on F2 w = 1/[r2F2

0 + 20.0701P)2 + 0.0000P], P = (F20 + 2F2

c )/3 w = 1/[r2F20 + 20.0447P)2 + 2.3P = (F2

0 + 2F2c )/3

Parameters/restrains 400/3 401/1Goodness of fit (GOF) on F2 0.99 1.025R indices [I > 2r(I)] R1 = 0.0432, wR2 = 0.1046 R1 = 0.0315, wR2 = 0.0764R indices [all data] R1 = 0.1023, wR2 = 0.1237 R1 = 0.0572, wR2 = 0.0839(D/r)max 0.001 0.002Largest difference in peak and hole (e/Å3) 0.865 and �0.508 1.39 and �1.674

M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320 2315

nances of 1d and 2d are shifted to lower frequencies by ca. 24 and30 ppm, respectively, compared to the free ligands. The 31P–{1H}NMR spectra of complexes 1e and 2e show a singlet at d 23.6and 20.5 ppm, respectively, accompanied by platinum satellites.The large 1J(135Pt–31P) coupling constants of 3325 and 3310 Hzfor 1e and 2e, respectively, are indicative of a cis arrangement ofphosphines around a platinum(II) center [59]. The 31P–{1H} NMRchemical shifts of 1f and 2f are also within the expected range,89.4 and 87.6 ppm, respectively, for structurally similar complexes[43,54,60,61]. The phosphorus resonances of complexes 1f and 2fshow a coordination shift to higher frequencies by ca. 27 and19 ppm, respectively, compared to those of the free ligands.

Single crystals of [Pd{(Ph2P)2N-C6H4-2-CH(CH3)2}Cl2] (1d) and[Pt{(Ph2P)2N-C6H4-2-CH(CH3)2}Cl2] (1e) suitable for X-ray diffrac-tion studies were obtained by slow diffusion of diethylether intoa solution of the complexes in dichloromethane. Both complexeswere crystallized as 1:1 solvent adducts and the crystallographicdata of [Pd{(Ph2P)2N-C6H4-2-CH(CH3)2}Cl2]�(C2H5)2O and[Pt{(Ph2P)2N-C6H4-2-CH(CH3)2}Cl2]�(C2H5)2O are listed in Tables 1and 2 for 1d and 1e. A perspective view of the molecules is givenin Fig. 1.

These two crystal structures are isomorphous. The key bondlengths and angles of complexes 1d and 1e in the solid state arevery similar, with minimal structural differences due to the reloca-

Table 2Selected bond lengths (Å) and bond angles (�) for the solid state structure of 1d and1e. M = Pd and Pt, respectively.

1d 1e 1d 1e

M–P1 2.2045(11) 2.1925(12) P1–M–P2 71.93(4) 72.52(4)M–P2 2.2068(10) 2.1936(12) Cl1–M–Cl2 96.96(5) 92.92(5)M–Cl1 2.3600(11) 2.3462(13) P1–M–Cl1 167.26(4) 97.15(5)M–Cl2 2.3553(11) 2.3510(13) P1–M–Cl2 95.37(4) 169.76(5)P1–N 1.722(3) 1.719(4) P2–M–Cl1 95.62(4) 169.55(5)P2–N 1.710(3) 1.724(4) P2–M–Cl2 167.14(4) 97.36(5)P1–C1 1.797(4) 1.799(5) P1–N–P2 98.02(16) 97.82(17)P1–C7 1.794(5) 1.808(5) M–P1–N 94.68(11) 94.71(12)P2–C13 1.795(4) 1.798(5) M–P2–N 94.96(11) 94.53(12)P2–C19 1.799(4) 1.809(4) C25–N–P1 126.2(3) 126.6(3)P1���P2 2.5908(14) 2.5942(16) C25–N–P2 127.6(3) 127.5(3)N–C25 1.459(5) 1.454(5)

tion of the isopropyl groups. The coordination geometry aroundthe Pd and Pt atoms is distorted square–planar, involving two Pand two Cl atoms. In the coordination environment, the Pd–Pand Pt–P bond lengths are 2.2045(11)–2.2068(10) and2.1925(12)–2.1936(12) Å, respectively. The Pd–Cl and Pt–Cl coor-dination bond lengths are 2.3600(11)–2.3553(11) and2.3462(13)–2.3510(13) Å, respectively. The coordination bondlengths of the Pt atom are slightly smaller than the Pd atom. Thepalladium(II) complex 1d and the platinum(II) complex 1e havecoordination angles around the Pd and Pt atoms in the range71.93(4)–96.96(5)� and 72.52(4)–97.36(5)�, respectively. Despitethe difference of the two metal atoms, the P–Pd–P angle and P–Pt–P angles are close to each other (71.93(4)� and 72.52(4)�,respectively). The fact that these angles are much smaller thanthe ideal value of 90� in a regular square planar geometry can beattributed to the strain in the diphosphine ligands: the bite dis-tance in these ligands is obviously small. Indeed, the P1���P2 dis-tances are 2.5908(14) Å for Pd complex and 2.5942(16) Å for Ptcomplex. The Pd and Pt atoms are at distance of 0.0538(3) and

Fig. 1. ORTEP drawing of the compounds 1d and 1e with the atomic numberingscheme. H atoms have been omitted for clarity, where M = Pd and Pt, respectively.

Table 3Dihedral angles between defined planes of the compounds 1d and 1e.

Plane 1 Plane 2 Dihedral angle (�) 1d Dihedral angle (�) 1e

P1/M/P2 Cl1/M/Cl2 3.69(5) 2.31(4)P1/M/P2 P1/N/P2 6.6(2) 6.7(2)A B 61.3(2) 59.9(2)C D 64.2(2) 64.9(2)E F 77.1(1) 77.1(1)

Notes: Planes A–F are involving the atoms as given (Fig. 2): A: C1/C2/C3/C4/C5/C6,B: C7/C8/C9/C10/C11/C12, C: C13/C14/C15/C16/C17/C18, D: C19/C20/C21/C22/C23/C24, E: C25/C26/C27/C28/C29/C30, F: Pt/P1/N/P2. M = Pd, Pt.

2316 M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320

0.0341(3) Å, respectively from the basal plane defined by theatoms Cl1, Cl2, P1, P2.

The P–N bond distances of palladium complex 1d [1.722(3) and1.710(3) Å] are very similar to those of platinum complex 1e[1.724(4) and 1.719(4) Å]. They are within the expected ranges incomparison to similar structures [52–54,58]. The aromatic ringsin the molecules, as expected, have the usual bond lengths andangles.

It is interesting to note that compounds 1d and 1e crystallizedunder similar conditions, both forming 1:1 adduct with solventmolecules. To get information about the conformation of the com-plexes 1d and 1e, dihedral angles between the neighboring squareplanes in the molecule were calculated with PARST [62]. Some dihe-dral angles between the planes around the coordination sphereand phenyl rings (Fig. 2) are given in Table 3. The title moleculeis not planar but the phenyl rings are essentially planar.

2.2. The Heck coupling reactions

The palladium complexes 1d and 2d were tested as catalysts inone of the most important C–C bond forming processes in syn-thetic organic chemistry, known as the Heck reaction, the palla-dium-catalyzed coupling of aryl/vinyl halides with olefins[63,64]. After optimizing the reaction conditions, we carried outthe coupling reactions of several substrates with styrene. We foundthat the use of 0.01 mmol of palladium complexes (1d and 2d)with two equivalents of K2CO3 in dioxane at 85 �C led to the bestconversion. A control experiment indicated that the couplingreaction does not occur in the absence of 1d or 2d. Under theseoptimum conditions, a wide range of arylbromides bearingelectron-donating or electron-withdrawing groups (p-bromoaceto-phenone, p-bromobenzaldehyde, p-bromobenzene, p-bromoani-sole and p-bromotoluene) react with styrene giving the coupledproducts in high yields (Table 4).

2.3. The Suzuki coupling reactions

The palladium complexes 1d and 2d were tested as catalysts inthe Suzuki reaction of aryl/vinyl halides with boronic acid, which isone of the most efficient methods for C–C bond formation [65]. Fol-lowing optimization experiments, we found that the use of0.01 mmol of the palladium complexes (1d and 2d) with Cs2CO3

as the base at 75 �C in dioxane appeared to provide the highestyield. We initially tested the catalytic activity of the complexes(1d and 2d) for the coupling of p-bromoacetophenone with phen-ylboronic acid and the control experiments showed that the cou-pling reaction does not occur in the absence of the catalyst.Under these conditions, p-bromoacetophenone, p-bromobenzalde-hyde, p-bromobenzene, p-bromoanisole and p-bromotoluene react

Fig. 2. Conformation of the compounds 1d and 1e.

cleanly with phenylboronic acid giving high yields of the products(Table 5).

3. Experimental

All reactions and manipulations were performed under argonatmosphere using standard Schlenk techniques unless otherwisestated. Ph2PCl, 2-isopropylaniline and 4-isopropylaniline werepurchased from Fluka and were used as received. Solvents weredried using the appropriate reagents and distilled prior to use.The starting materials [MCl2(cod)] (M = Pd, Pt, cod = 1,5-cyclo-octadiene) [66,67] and [Cu(CH3CN)4]PF6 [68] were preparedaccording to the literature procedures. Infrared spectra wererecorded from KBr pellets in the range 4000–400 cm�1 on aMattson 1000 ATI UNICAM FT-IR spectrometer. NMR spectra wererecorded on a Bruker AC 400 spectrometer (400.1 MHz for 1H,100.6 MHz for 13C, and 162.0 MHz 31P). Microanalysis wascarried out on a Fisons EA 1108 CHNS-O instrument. GC analyseswere performed on a HP 6890 N Gas Chromatograph equippedwith a capillary column (5% biphenyl, 95% dimethylsiloxane)(30 m � 0.32 mm � 0.25 lm).

3.1. General procedure for the synthesis of N,N-bis(diphenylphosphino)isopropylanilines [(Ph2P)2N-(C6H4)-CH(CH3)2] (1, 2)

Ph2PCl (1.63 g, 7.40 mmol) was added slowly to a solution of 2-or 4-isopropylaniline (0.50 g, 3.70 mmol) and Et3N (0.75 g,7.40 mmol) in thf (20 mL) at 0 �C. The resulting white suspensionwas stirred for 1 h and precipitated triethylamine hydrochloridewas removed by filtration through a sintered Schlenk tube. Thesolution was evaporated to dryness under reduced pressure andwhite solids of 1 or 2 were obtained.

3.1.1. N, N-bis(diphenylphosphino)-2-isopropylaniline [(Ph2P)2N-(C6H4)-2-CH(CH3)2] (1)

Yield: 1.62 g, 87%; M.p. 129–131 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.75–7.53(m, 24H, Ar–H), 2.99(m, 1H,CH(CH3)2, 0.75(d, 3J(H–H) = 6.4 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 146.3, 139.7, 134.9, 132.5,131.4, 130.5, 128.5, 127.8, 126.6, 125.8 (Carm); 27.5 (–CH(CH3)2);23.6 (–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 62.2 (s); IR (KBr pellet, m cm�1): 901 (PNP), 1432 (PPh);Elemental Anal. Calc. for C33H31NP2: C, 78.71; H, 6.21; N, 2.78.Found: C, 78.46; H, 5.97; N, 2.59%.

3.1.2. N, N-bis(diphenylphosphino)-4-isopropylaniline [(Ph2P)2N-(C6H4)-4-CH(CH3)2] (2)

Yield: 1.58 g, 85%; M.p. 103–105 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.58–7.39(m, 24H, Ar–H), 2.76(m, 1H,CH(CH3)2, 1.15(d, 3J(H–H) = 7.2 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 145.8, 139.6, 133.3, 131.3,128.9, 128.5, 127.9, 126.2 (Carm); 33.5 (–CH(CH3)2); 24.0(–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%

Table 4The Heck coupling reactions of aryl bromides with styrenea.

Br R+1d or 2d (0.01 mmol)

K2CO3, Dioxane, 85 oC R

Entry R Catalyst Yield (%)b TOF (h�1)

1 COCH3 1d 95.42 63.62 COCH3 2d 93.25 62.23 CHO 1d 97.12 64.84 CHO 2d 94.08 62.75 H 1d 88.77 59.26 H 2d 74.93 49.97 OCH3 1d 69.28 46.28 OCH3 2d 57.95 38.69 CH3 1d 76.53 51.010 CH3 2d 69.26 46.2

a Reaction conditions: 1.0 mmol of R-C6H4Br-p, 1.5 mmol of styrene, 2.0 mmol K2CO3, 0.01 mmol Pd complex, dioxane (3 mL).b Purity of compounds was checked by NMR and yields are based on aryl bromide, all reactions were monitored by GC, temperature 85 �C, 1.5 h. TOF = (mol product/mol

Cat) x h�1.

Table 5The Suzuki coupling reactions of aryl bromides with phenylboronic acida.

B(OH)2 Br R+1d or 2d (0.01 mmol)

Cs2CO3, Dioxane, 75 oC

R

Entry R Catalyst Yield (%)b TOF (h�1)c

1 COCH3 1d 94.06 94.12 COCH3 2d 91.72 91.73 CHO 1d 98.46 98.54 CHO 2d 95.12 95.15 H 1d 85.80 85.86 H 2d 88.35 88.47 OCH3 1d 70.45 70.58 OCH3 2d 67.08 67.19 CH3 1d 73.57 73.610 CH3 2d 61.79 61.8

a Reaction conditions: 1.0 mmol of R-C6H4Br-p, 1.5 mmol of phenylboronic acid, 2.0 mmol Cs2CO3, 0.01 mmol Pd complex, dioxane (3 mL).b Purity of compounds was checked by NMR and yields are based on aryl bromide, all reactions were monitored by GC, temperature 75 �C, 1 h.c TOF = (mol product/mol Cat) x h�1.

M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320 2317

H3PO4): 68.5 (s); IR (KBr pellet, m cm�1): 906 (PNP), 1438 (PPh);Elemental Anal. Calc. for C33H31NP2: C, 78.71; H, 6.21; N, 2.78.Found: C, 78.62; H, 6.02; N, 2.64%.

3.2. General procedure for the synthesis of the chalcogenides

3.2.1. N,N-bis(diphenyloxophosphino)isopropylanilines [(Ph2P(O))2N-(C6H4)-CH(CH3)2] (1a, 2a)

A thf solution (10 mL) of N,N-bis(diphenylphosphino)isopropylaniline (0.20 g, 0.40 mmol) and aqueous H2O2 (30% w/w, 0.08 mL)was stirred for 2 h at room temperature. The solution was filteredthrough Celite to remove a small amount of insoluble material. Thefiltrate was concentrated in vacuo to ca. 1–2 mL and addition of n-hexane (10 mL) gave 1a and 2a as white solids which were col-lected by suction filtration.

3.2.2. N,N-bis(diphenyloxophosphino)-2-isopropylaniline[(Ph2P(O))2N-(C6H4)-2-CH(CH3)2] (1a)

Yield: 0.16 g, 75%; M.p. 202–204 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.98–7.71(m, 24H, Ar–H), 3.59(m, 1H,CH(CH3)2), 0.65(d, 3J(H–H) = 6.4 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 149.2, 134.6, 134.2, 133.1,

132.6, 132.2, 131.9, 128.3, 127.7, 125.9 (Carm); 27.8 (–CH(CH3)2);23.9 (–CH(CH3)2). 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 23.9 (s); IR (KBr pellet, m cm�1): 908 (PNP), 1448 (PPh),1216 (PO); Elemental Anal. Calc. for C33H31NO2P2: C, 74.01; H,5.83; N, 2.62. Found: C, 73.81; H, 5.72; N, 2.46%.

3.2.3. N,N-bis(diphenyloxophosphino)-4-isopropylaniline[(Ph2P(O))2N-(C6H4)-4-CH(CH3)2] (2a)

Yield: 0.18 g, 85%; M.p. 124–126 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.97–7.81(m, 24H, Ar–H), 3.56(m, 1H,CH(CH3)2), 0.75(s, 6H, –CH(CH3)2); 13C NMR (100 MHz, [D]CHCl3,25 �C, TMS): 149.3, 134.1, 133.2, 132.6, 131.6, 128.5, 127.8, 125.6(Carm); 27.8 (–CH(CH3)2); 24.1 (–CH(CH3)2); 31P–{1H} NMR(162 MHz, [D]CHCl3, 25 �C, 85% H3PO4): 24.2 (s); IR (KBr pellet, mcm�1): 910 (PNP), 1446 (PPh), 1199 (PO); Elemental Anal. Calc.for C33H31NO2P2: C, 74.01; H, 5.83; N, 2.62. Found: C, 73.67; H,5.48; N, 2.43%.

3.2.4. N,N-bis(diphenylthiophosphino)isopropylanilines [(Ph2P(S))2N-(C6H4)-CH(CH3)2] (1b, 2b)

To a solution of 1 or 2 (0.20 g, 0.40 mmol) in thf (10 mL), S8

(0.025 g, 0.80 mmol) was added and this mixture was refluxed

2318 M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320

for 4 h. The solution was filtered through Celite while hot to re-move a small amount of insoluble material. The filtrate was con-centrated in vacuo to ca. 1–2 mL and addition of n-hexane(15 mL) gave 1b and 2b as light yellow solids which were collectedby suction filtration.

3.2.5. N,N-bis(diphenylthiophosphino)-2-isopropylaniline[(Ph2P(S))2N-(C6H4)-2-CH(CH3)2] (1b)

Yield: 0.17 g, 75%; M.p. 149–151 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.90–8.05(m, 24H, Ar–H), 3.54(m, 1H,CH(CH3)2), 0.69(d, 3J(H–H) = 6.8 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 151.0, 136.5, 134.7, 134.0,133.7, 132.2, 131.3, 128.4, 127.4, 125.0 (Carm); 28.3 (–CH(CH3)2);24.6 (–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 68.5 (s); IR (KBr pellet, m cm�1): 905 (PNP), 1440 (PPh),650 (PS); Elemental Anal. Calc. for C33H31NS2P2: C, 69.82; H, 5.50;N, 2.47. Found: C, 69.61; H, 5.31; N, 2.38%.

3.2.6. N,N-bis(diphenylthiophosphino)-4-isopropylaniline[(Ph2P(S))2N-(C6H4)-4-CH(CH3)2] (2b)

Yield: 0.19 g, 84%: M.p. 189–191 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.72–8.10(m, 24H, Ar–H), 2.59(m, 1H,CH(CH3)2), 0.99(s, 6H, –CH(CH3)2); 13C NMR (100 MHz, [D]CHCl3,25 �C, TMS): 147.8, 136.1, 133.6, 132.9, 132.4, 131.3, 127.5, 125.9(Carm); 33.4 (–CH(CH3)2); 23.7 (–CH(CH3)2); 31P–{1H} NMR(162 MHz, [D]CHCl3, 25 �C, 85% H3PO4): 68.9 (s); IR (KBr pellet, mcm�1): 906 (PNP), 1446 (PPh), 694 (PS); Elemental Anal. Calc. forC33H31NS2P2: C, 69.82; H, 5.50; N, 2.47. Found: C, 69.68; H, 5.36;N, 2.36%.

3.2.7. N,N-bis(diphenylselenophosphino)isopropylanilines[(Ph2P(Se))2N-(C6H4)-CH(CH3)2] (1c, 2c)

Grey Se (0.063 g, 0.8 mmol) was added to a solution of 1 or 2(0.20 g, 0.40 mmol) in thf (10 mL) and this mixture was refluxedfor 1 h. The solution was filtered through Celite while hot to re-move a small amount of insoluble material. The filtrate was con-centrated in vacuo to ca. 1–2 mL and addition of n-hexane(15 mL) gave 1c and 2c as light yellow solids which were collectedby suction filtration.

3.2.8. N,N-bis(diphenylselenophosphino)-2-isopropylaniline[(Ph2P(Se))2N-(C6H4)-2-CH(CH3)2 ] (1c)

Yield: 0.21 g, 80%; M.p. 240–242 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.88–8.04(m, 24H, Ar–H), 3.53(m, 1H,CH(CH3)2), 0.70(d, 3J(H–H) = 6.8 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 151.2, 136.8, 134.6, 134.4,132.8, 131.6, 130.5, 127.8, 127.5, 125.0 (Carm); 28.4 (–CH(CH3)2);24.9 (–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 67.8, J(PSe) = 786.6 Hz; IR (KBr pellet, m cm�1): 891(PNP), 1438 (PPh), 563 (PSe); Elemental Anal. Calc. forC33H31NSe2P2: C, 59.92; H, 4.72; N, 2.12. Found: C, 59.62; H,4.43; N, 2.01%.

3.2.9. N,N-bis(diphenylselenophosphino)-4-isopropylaniline[(Ph2P(Se))2N-(C6H4)-4-CH(CH3)2] (2c)

Yield: 0.22 g, 84%: M.p. >300 �C (dec.); 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.71–8.15(m, 24H, Ar–H), 2.60(m, 1H,CH(CH3)2), 1.00(d, 3J(H–H) = 6.8 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 147.6, 136.0, 134.3, 133.4,132.8, 131.4, 127.5, 125.9 (Carm); 33.4 (–CH(CH3)2); 23.6(–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 67.3, J(PSe) = 792 Hz; IR (KBr pellet, m cm�1): 917(PNP), 1446 (PPh), 542 (PSe); Elemental Anal. Cal. forC33H31NSe2P2: C, 59.92; H, 4.72; N, 2.12. Found: C, 59.72; H,4.57; N, 1.98%.

3.3. General procedure for the synthesis of the complexes

3.3.1. Dichloro{N,N-bis(diphenylphosphino)isopropylaniline}palla-dium(II) (1d, 2d)

A solution of [PdCl2(cod)] (0.227 g, 0.795 mmol) and 1 or 2(0.40 g, 0.795 mmol) in thf (20 mL) was stirred for 2 h. Thevolume was concentrated in vacuum to ca. 1–2 mL and addi-tion of diethyl ether (15 mL) gave 1d and 2d as yellow solidswhich were collected by suction filtration and dried invacuum.

3.3.2. Dichloro{N,N-bis(diphenylphosphino)-2-isopropylaniline}palladium(II) (1d)

Yield: 0.44 g, 81%; M.p. 249–251 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.78–7.85(m, 24H, Ar–H), 2.57(m, 1H,CH(CH3)2), 0.31(d, 3J(H–H) = 6.4 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 147.4, 136.4, 134.8, 134.4,132.4, 130.6, 130.4, 129.9, 128.6, 126.6 (Carm); 28.7 (–CH(CH3)2);23.8 (–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 37.9 (s); IR (KBr pellet, m cm�1): 890 (PNP), 1438 (PPh);Elemental Anal. Calc. for C33H31NP2PdCl2: C, 58.21; H, 4.59; N,2.06. Found: C, 57.94; H, 4.43; N, 1.83%.

3.3.3. Dichloro{N,N-bis(diphenylphosphino)-4-isopropylaniline}palladium(II) (2d)

Yield: 0.48 g, 89%; M.p. 250–252 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.79–7.85(m, 24H, Ar–H), 2.58(m, 1H,CH(CH3)2), 0.3(d, 3J(H–H) = 6.0 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 147.3, 138.1, 134.8, 134.4,132.1, 130.0, 128.7, 126.6 (Carm); 28.9 (–CH(CH3)2); 23.8(–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 38.5 (s); IR (KBr pellet, m cm�1): 892 (PNP), 1447 (PPh);Elemental Anal. Calc. for C33H31NP2PdCl2: C, 58.21; H, 4.59; N,2.06. Found: C, 57.84; H, 4.37; N, 1.93%.

3.3.4. Dichloro{N,N-bis(diphenylphosphino)isopropylaniline}platinum(II) (1e, 2e)

A solution of [PtCl2(cod)] (0.298 g, 0.795 mmol) and 1 or 2(0.40 g, 0.795 mmol) in thf (20 mL) was stirred for 2 h. The volumewas concentrated in vacuum to ca. 1–2 mL and addition of diethylether (15 mL) gave 1e and 2e as white solids which were collectedby suction filtration and dried in vacuum.

3.3.5. Dichloro{N,N-bis(diphenylphosphino)-2-isopropylaniline}platinum(II) (1e)

Yield: 0.52 g, 85%; M.p. 294–296 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.75–7.81(m, 24H, Ar–H), 2.63(m, 1H,CH(CH3)2), 0.30(d, 3J(H–H) = 6.8 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 147.7, 139.3, 134.6, 134.2,132.2, 130.6, 130.2, 129.8, 127.4, 126.4 (Carm); 28.9(–CH(CH3)2); 23.8 (–CH(CH3)2); 31P–{1H} NMR (162 MHz,[D]CHCl3, 25 �C, 85% H3PO4): 23.6, J(PtP) = 3325 Hz; IR (KBr pel-let, m cm�1): 893 (PNP), 1440 (PPh); Elemental Anal. Calc. forC33H31NP2PtCl2: C, 51.51; H, 4.06; N, 1.82. Found: C, 51.24;H, 3.82; N, 1.69%.

3.3.6. Dichloro{N,N-bis(diphenylphosphino)-4-isopropylaniline}platinum(II) (2e)

Yield: 0.55 g, 90%; M.p. >250 �C (dec.); 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.40–7.81(m, 24H, Ar–H), 2.66(m, 1H,CH(CH3)2), 0.31(d, 3J(H–H) = 6.8 Hz, 6H, –CH(CH3)2); 13C NMR(100 MHz, [D]CHCl3, 25 �C, TMS): 147.0, 137.6, 134.3, 133.1,132.2, 130.1, 128.0, 126.6 (Carm); 30.8 (–CH (CH3)2); 25.6(–CH(CH3)2); 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 20.5, J(PtP): 3310 Hz; IR (KBr pellet, m cm�1): 892 (PNP),

M. Aydemir et al. / Polyhedron 28 (2009) 2313–2320 2319

1438 (PPh); Elemental Anal. Calc. for C33H31NP2PtCl2: C, 51.51; H,4.06; N, 1.82. Found: C, 51.29; H, 3.94; N, 1.73%.

3.3.7. Bis[N,N-bis(diphenylphosphino)isopropylaniline]copper(I)hexafluorophosphates (1f, 2f)

To a solution of [Cu(CH3CN)4]PF6 (0.148 g, 0.398 mmol) in thf(15 mL) was added compound 1 or 2 (0.40 g, 0.795 mmol), andthe resulting solution was stirred for 1 h. The volume was concen-trated in vacuum to ca. 1–2 mL and addition of diethyl ether(15 mL) gave 1f and 2f as white solids which were collected by suc-tion filtration and dried in vacuum.

3.3.8. Bis[N,N-bis(diphenylphosphino)-2-isopropylaniline]copper(I)hexafluorophosphate (1f)

Yield: 0.41 g, 85%; M.p. 179–181 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 7.11–7.57(m, 24H, ArH), 2.60(m, 1H,CH(CH3)2), 0.10(d, 3J(H–H):6.4 Hz, 6H, –CH(CH3)2); No 13C NMRspectrum was obtained due to the low solubility of the complexin all common solvents; 31P–{1H} NMR (162 MHz, [D]CHCl3,25 �C, 85% H3PO4): 89.4, PF6:�144.3, J(PF6) = 712 Hz; IR (KBr pellet,m cm�1): 898 (PNP), 1446 (PPh); Elemental Anal. Calc. forC66H62N2P5F6Cu: C, 65.21; H, 5.14; N, 2.30. Found: C, 64.96; H,4.95; N, 2.18%.

3.3.9. Bis[N,N-bis(diphenylphosphino)-4-isopropylaniline]copper(I)hexafluorophosphate (2f)

Yield: 0.38 g, 79%; M.p. 181–183 �C; 1H NMR (400 MHz,[D]CHCl3, 25 �C, TMS): 6.77–7.52(m, 24H, ArH), 2.72(br, 1H,CH(CH3)2), 1.10(s, 6H, –CH(CH3)2); No 13C NMR spectrum wasobtained due to the low solubility of the complex in all com-mon solvents; 31P–{1H} NMR (162 MHz, [D]CHCl3, 25 �C, 85%H3PO4): 87.6, PF6: �144.3, J(PF6) = 712 Hz; IR (KBr pellet, mcm�1): 908 (PNP), 1439 (PPh); Elemental Anal. Calc. forC66H62N2P5F6Cu: C, 65.21; H, 5.14; N, 2.30. Found: C, 65.02; H,4.97; N, 2.19%.

3.4. General procedure for the Heck coupling reaction

Heck coupling reactions were conducted as follows: the bis-phosphinoamine–palladium complexes (1d or 2d) (0.01 mmol),arylbromide (1.0 mmol), styrene (1.5 mmol), K2CO3 (2.0 mmol)and 1,4-dioxane (3 mL) were placed in a Schlenk tube and the mix-ture was heated to 85 �C for 1.5 h. The progress of the reaction wasmonitored by GC. Upon completion, the mixture was cooled, andthe product extracted with ethyl acetate/hexane (1:5), filteredthrough a pad of silica gel with copious washing, concentratedand purified by flash chromatography on silica gel. The purity ofthe compounds was checked by NMR and GC, and yields are basedon arylbromide.

3.5. General procedure for the Suzuki coupling reaction

Suzuki coupling reactions were conducted as follows: the bis-phosphinoamine–palladium complexes (1d or 2d) (0.01 mmol),arylbromide (1.0 mmol), phenylboronic acid (1.5 mmol), Cs2CO3

(2.0 mmol) and 1,4-dioxane (3 mL) were placed in a smallSchlenk tube and the mixture was heated at 75 �C for 1 h. Theprogress of the reaction was monitored by GC. Upon completion,the mixture was cooled, the product extracted with ethylacetate/hexane (1:5), filtered through a pad of silica gel withcopious washing, concentrated and purified by flashchromatography on silica gel. The purity of the compoundswas checked by NMR and GC, and yields are based onarylbromide.

3.6. X-ray diffraction structure analyses

To determine the crystal structures of 1d and 1e, X-ray dif-fraction data were collected at room temperature using an En-raf-nonius CAD4 diffractometer with graphite monochromatedMo Ka radiation using the w/2h scan mode. The latticeparameters and their estimated standard deviations weredetermined from a least-squares analysis using 25 centeredreflections in the range 9.86–17.99� for the Pd complex and10.15-17.98� for the Pt complex by using CAD4 Express [69].Data reduction was carried out using XCAD 4 [70]. The struc-tures were solved by the direct method using the solutionprogram SHELXS97 and refined on F2

0 using SHELXS97 [71]. In bothcomplexes, all non-hydrogen atoms were refined, first withisotropic and then with anisotropic thermal parameters by fullmatrix least squares. The hydrogen atom of the CH group inthe 2-isopropyl aniline ligand was taken from a differenceFourier map. All other hydrogen atoms were positioned geo-metrically with C–H = 0.93, 0.97 and 0.96 Å for aromatic,methylene and methyl H, and constrained to ride on theirparent atoms, with Uiso(H) = xUeq(C), where x = 1.5 for methylH, and x = 1.2 for others H atoms. Results of the X-ray struc-ture determination are given in Tables 1–3 for 1d and 1e, andthe ORTEP [72] drawings of the molecules are shown inFig. 1.

4. Conclusion

In conclusion, two new bis(diphenylphosphino)amines andtheir oxides, sulfides and selenides have been prepared. In addi-tion, both compounds show similar coordination properties to-wards Cu, Pd and Pt. The Pd complexes exhibit high catalyticactivity in the Heck and Suzuki cross-coupling reactions. The pro-cedure for carrying out the catalytic reactions is quite simple andefficient towards various aryl bromides and does not require aninduction period. Based on these findings, it can be postulated that1d and 2d offer some distinctive advantages in the C–C couplingreactions compared to other palladium/aminophosphine systems[20,50,55,64].

5. Supplementary data

CCDC 694356 and 69455 contain the supplementary crystallo-graphic data for 1d and 1e. These data can be obtained free ofcharge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, orfrom the Cambridge Crystallographic Data Centre, 12 Union Road,Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:deposit@ccdc.cam.ac.uk.

Acknowledgements

Partial support from Turkish Academy of Sciences, Dicle Univer-sity (Project number: DÜAPK 05-FF-27) and Hacettepe University(Scientific Research Department, Project number: 04A602004)are gratefully acknowledged.

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