Synthesis and Crystal Structures of the First Stable Mononuclear

Dec 2, 2008 - The first stable dihydrogermyl(hydrido) platinum(II) complex cis-(Ph3P)2Pt(H)(GeH2Trip) was synthesized by the oxidative addition reacti...
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Organometallics 2009, 28, 534–538

Synthesis and Crystal Structures of the First Stable Mononuclear Dihydrogermyl(hydrido) Platinum(II) Complexes Norio Nakata, Shun Fukazawa, and Akihiko Ishii* Department of Chemistry, Graduate School of Science and Engineering, Saitama UniVersity, Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan ReceiVed August 20, 2008

The first stable dihydrogermyl(hydrido) platinum(II) complex cis-(Ph3P)2Pt(H)(GeH2Trip) (2) was synthesized by the oxidative addition reaction of an overcrowded trihydrogermane, TripGeH3 (1, Trip ) 9-triptycyl), with (Ph3P)2Pt(η2-C2H4) in toluene. The reaction of 1 with (dppe)PtCl2 in the presence of NaBH4 afforded the corresponding hydrido complex (dppe)Pt(H)(GeH2Trip) (3) together with bis(germyl) platinum(II) complex (dppe)Pt(GeH2Trip)2 (4). In addition, the ligand exchange reaction of complex 2 with free Cy2PCH2CH2PCy2 in toluene resulted in the formation of (dcpe)Pt(H)(GeH2Trip) (5) in moderate yield. The structures of complexes 2-5 were fully determined on the basis of their NMR and IR spectra and elemental analyses. Moreover, the low-temperature X-ray crystallography of 2, 3, and 5 revealed that the platinum center has a distorted square-planar environment, probably due to the steric requirement of the cis-coordinated phosphine ligands and the bulky 9-triptycyl group on the germanium atom. Furthermore, the thermal rearrangement of bis(germyl) complex 4 in toluene at 60 °C gave digermyl(hydrido) complex (dppe)Pt(H)[Ge(HTrip)GeH2Trip] (6) in high yield without irreversible reductive elimination of tetrahydrodigermane. Introduction Oxidative additions of Si-H bonds to the metal center of low-valent transition metal complexes have been proposed as the key elementary steps to generate active intermediates for catalytic reactions such as hydrosilylation.1 While many reactions of hydrosilanes with platinum(0) complexes affording mono(silyl), bis(silyl), and silyl-bridged multinuclear platinum complexes2,3 have been reported so far, the reactivity of Ge-H bonds toward platinum(0) complexes has been investigated for only a few cases of tertiary and secondary hydrogermanes.4-6 Recently, Braddock-Wilking et al. have described the syntheses * To whom correspondence should be addressed. E-mail: ishiiaki@ chem.saitama-u.ac.jp. (1) (a) Marciniec, B. ComprehensiVe Handbook on Hydrosilylation; Pergamon Press: Oxford, 1992. (b) Ojima, I.; Li, Z.; Zhu, J. Recent Advances in Hydrosilylation and Related Reactions. In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley and Sons: New York, 1998; p 1687. (2) For recent reviews, see: (a) Eisen, M. S. In The Chemistry of Organic Silicon Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: New York, 1998; Vol. 2,Part 3, Chapter 35. (b) Ogino, H.; Tobita, H. AdV. Organomet. Chem. 1998, 42, 223–290. (c) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175–292. (d) Osakada, K.; Tanabe, M. Bull. Chem. Soc. Jpn. 2005, 78, 1887–1898. (e) Shimada, S.; Tanaka, M. Coord. Chem. ReV. 2006, 250, 991–1011. (3) For recent works on (silyl) platinum complexes, see: (a) BraddockWilking, J.; Corey, J. Y.; Trankler, K. A.; Xu, H.; French, L. M.; Praingam, N.; White, C.; Rath, N. P. Organometallics 2006, 25, 2859–2871. (b) Shimada, S.; Li, Y.-H.; Rao, M. L. N.; Tanaka, M. Organometallics 2006, 25, 3796–3798. (c) Braddock-Wilking, J.; Corey, J. Y.; French, L. M.; Choi, E.; Speedie, V. J.; Rutherford, M. F.; Yao, S.; Xu, H.; Rath, N. P. Organometallics 2006, 25, 3974–3988. (d) Tanabe, M.; Ito, D.; Osakada, K. Organometallics 2007, 26, 459–462. (e) Arii, H.; Takahashi, M.; Noda, A.; Nanjo, M.; Mochida, K. Organometallics 2008, 27, 1929–1935. (f) Tanabe, M.; Ito, D.; Osakada, K. Organometallics 2008, 27, 2258–2267. (4) (a) Braddock-Wilking, J.; Corey, J. Y.; White, C.; Xu, H.; Rath, N. P. Organometallics 2005, 24, 4113–4115. (b) White, C. P.; BraddockWilking, J.; Corey, J. Y.; Xu, H.; Redekop, E.; Sedinkin, S.; Rath, N. P. Organometallics 2007, 26, 1996–2004. (5) Tanabe, M.; Ishikawa, N.; Osakada, K. Organometallics 2006, 25, 796–798.

of hydrido(germyl) complex cis-(Ph3P)2Pt(H)(GeHMes2) and symmetrical dinuclear complex [(Ph3P)Pt(µ-η2-H-GePh2)]2 by the reactions of the corresponding secondary hydrogermanes with (Ph3P)2Pt(η2-C2H4) and their characterization.4 Osakada et al. also have reported that the reaction of Ph2GeH2 with (Cy3P)2Pt afforded the corresponding cis- and trans-(Cy3P)2Pt(H)(GeHPh2) as the kinetic and thermodynamic products.5 In the reactions of tertiary hydrogermanes such as (HPh2Ge)2(SiMe2)n (n ) 1, 2) with (Ph3P)2Pt(η2-C2H4), Mochida et al. have reported an unexpected formation of germylene-bridged dinuclear complex [(Ph3P)Pt]2(µ-GePh2)2 through the corresponding germasilaplatinacycles.6 Quite recently, they have also reported that the reactions of primary hydrogermane MesGeH3 with (Ph3P)2Pt(η2C2H4) produced unsymmetrical diplatinum complex [(Ph3P)3Pt2(µη2- H-GeHMes)2], symmetrical diplatinum complex [(Ph3P)Pt(µη2-H-GeHMes)]2, and bis(germyl)platinum complex cis-(Ph3P)2Pt(GeH2Mes)2, respectively.7 However, there are no structural characterizations of dihydrogermyl(hydrido) platinum(II) complexes, which are anticipated as the initial products in the Ge-H bond activation reactions of primary hydrogermanes with platinum(0) complexes. Meanwhile, we have recently succeeded in the first isolation of stable hydrido(selenolato) platinum(II) complex cis-(Ph3P)2Pt(H)(SeTrip)8 using a bulky substituent, the 9-triptycyl group (Trip ) 9-triptycyl).9 On the basis of this result, we envisioned (6) Usui, Y.; Hosotani, S.; Ogawa, A.; Nanjo, M.; Mochida, K. Organometallics 2005, 24, 4337–4339. (7) Arii, H.; Nanjo, M.; Mochida, K. Organometallics 2008, 27, 4147– 4151. (8) Ishii, A.; Nakata, N.; Uchiumi, R.; Murakami, K. Angew. Chem., Int. Ed. 2008, 47, 2661–2664. (9) For applications of the Trip group, see: (a) Ishii, A.; Matsubayashi, S.; Takahashi, T.; Nakayama, J. J. Org. Chem. 1999, 64, 1084–1084. (b) Ishii, A.; Takahashi, T.; Nakayama, J. Heteroat. Chem. 2001, 12, 198– 203. (c) Ishii, A.; Takahashi, T.; Tawata, A.; Furukawa, A.; Oshida, H.; Nakayama, J. Chem. Commun. 2002, 2810–2811. (d) Ishii, A.; Mori, Y.; Uchiumi, R. Heteroat. Chem. 2005, 16, 525–528.

10.1021/om800809n CCC: $40.75  2009 American Chemical Society Publication on Web 12/02/2008

Stable Mononuclear Dihydrogermyl(hydrido) Pt(II) Complexes

Organometallics, Vol. 28, No. 2, 2009 535

Scheme 1

that the introduction of the 9-triptycyl group onto a germanium atom that should coordinate to a platinum center would be useful for the preparation of novel classes of germyl(hydrido) complexes. Herein, we present the synthesis, characterization, and properties of the first stable dihydrogermyl(hydrido) platinum(II) complexes, having Ph3P, dppe [bis(1,2-diphenylphosphino)ethane], and dcpe [bis(1,2-dicyclohexylphosphino)ethane] ligands by the reactions of an overcrowded primary germane, TripGeH3 (1), with platinum(0) complexes or ligand exchange reaction of a dihydrogermyl(hydrido) platinum(II) complex.

Results and Discussion The reaction of TripGeH3 (1)10 with (Ph3P)2Pt(η2-C2H4) in toluene at room temperature proceeded efficiently to form cis(Ph3P)2Pt(H)(GeH2Trip) (2) in 99% yield as colorless crystals (Scheme 1). In the 1H NMR spectrum of 2, characteristic signals due to the platinum hydride were observed as a doublet of doublets around δ -3.23 (2JP-H ) 168, 18, 1JPt-H ) 894 Hz). The Ge-H protons appeared as a multiplet signal at 4.43 ppm. The 31P{1H} NMR spectrum for 2 showed two nonequivalent doublet signals (2JP-P ) 13 Hz) at δ 31.2 and 31.6 with similar 195Pt-31P coupling constants, 2317 and 2252 Hz. The former signal is assigned to the phosphorus trans to the platinum hydride on the basis of NMR data reported for cis-(Ph3P)2Pt(H)(GeHMes2) [δ 29.5 (1JPt-P ) 2350 Hz), 33.3 (1JPt-P ) 2137 Hz)].4b In the IR spectrum for 2, the Ge-H and Pt-H stretching vibrations were observed at 1953 and 2063 cm-1, respectively. Complex 2 is thermally stable in the solid state (mp 127 °C) or in solution, and no dimerization or disossiation of phosphine ligands was observed. The molecular structure of 2 was confirmed unambiguously by X-ray analysis, as depicted in Figure 1. The X-ray crystallographic analysis of 2 revealed that the platinum center has a distorted square-planar environment, probably due to the steric requirement of the cis-coordinated PPh3 ligands and the bulky 9-triptycyl group on the germanium atom. The Pt-Ge bond length [2.4135(7) Å] is slightly shorter than those of previously reported mononuclear germyl(hydrido) platinum(II) complexes, cis-(Ph3P)2Pt(H)(GeHMes2) [2.4285(5) Å],4b cis(Ph3P)2Pt(H)(GePh3) [2.4400(4) Å],11 and cis-(Ph3P)2Pt(H)(GeHMesGeH2Mes) [2.4348(8) Å].7 Both of the Pt-P bond lengths [Pt1-P1 2.3030(16), Pt1-P2 2.2941(16) Å] are almost the same, indicating that the trans influence of the germanium atom is close to that of the hydride in this complex. As part of a program geared to exploring the synthesis of new types of dihydrogermyl(hydrido) platinum(II) complexes, we next focused our attention on the bidentate phosphine ligands such as dppe and dcpe. Thus, the reaction of 1 with 1 equiv with (dppe)Pt, which was generated in situ by the reduction of (dppe)PtCl2 with an excess amount of NaBH4 in ethanol,12 afforded the corresponding dihydrogermyl(hydrido) complex (dppe)Pt(H)(GeH2Trip) (3) together with bis(germyl) complex (dppe)Pt(GeH2Trip)2 (4) in 36% and 16% yields, respectively, while the reaction of 1 with a half-equivalent of (dppe)Pt in (10) Brynda, M.; Geoffroy, M.; Bernardinelli, G. Chem. Commun. 1999, 961–962. (11) Habereder, T.; No¨th, H. Appl. Organomet. Chem. 2003, 17, 525– 538.

Figure 1. ORTEP drawing of cis-(Ph3P)2Pt(H)(GeH2Trip) (2) (30% thermal ellipsoids, three CH2Cl2 molecules and hydrogen atoms except H1, H2, and H3 were omitted for clarity). Selected bond lengths (Å): Pt1-Ge1 ) 2.4135 (7), Pt1-P1 ) 2.3030(16), Pt1-P2 ) 2.2941(16), Pt1-H1 ) 1.64(7), Ge1-C1 ) 1.998(6). Selected bond angles (deg): P1-Pt1-P2 ) 100.93(6), Ge1-Pt1-P1 ) 96.97(6), Ge1-Pt1-H1 ) 77(3), P2-Pt1-H1 ) 85(3), Ge1-Pt1-P2 ) 162.04(4), P1-Pt1-H1 ) 174(3). Scheme 2

Scheme 3

toluene produced only complex 4 in 77% yield (Scheme 2). The formation of bis(germyl) complex 4 was verified by the reaction of 3 with 1 in toluene at room temperature for 3 days to give a 1:1 mixture of 3 and 4 (judged from 1H NMR). By sharp contrast, complex 2 did not react with 1 under similar conditions, indicating that the steric hindrance due to a tiedback dppe ligand is smaller than that due to two Ph3P ligands. On the other hand, dihydrogermyl(hydrido) platinum(II) complex (dcpe)Pt(H)(GeH2Trip) (5) was synthesized by the ligand exchange reaction of complex 2 with free dcpe in toluene at ambient temperature in 63% isolated yield (Scheme 3). The structures of 3-5 were confirmed by NMR and IR spectroscopies and elemental analyses. In the 1H NMR spectrum of (12) The generation of (dppe)Pt species was identified by 1H and P{1H} NMR spectra. 1H NMR (400 MHz, C6D6): δ 2.12 (br s, 4 H), 6.90-6.98 (m, 12 H), 7.53 (br s, 8 H). 31P{1H} NMR (162 MHz, C6D6): δ 31.2 (s, 1JP-Pt ) 3729 Hz). These NMR results are obviously different from those of the related hydrido-(dppe)Pt complexes [(dppe)PtH]2 [31P{1H} NMR: δ 70.9 (s, 1JP-Pt ) 2201 Hz)],13a [(dppe)2Pt2H2] [31P{1H} NMR: δ68.1 (s, 1JP-Pt ) 2201 Hz)],13b and [(dppe)3Pt3H3]+ [31P{1H} NMR: δ82.2 (s, 1JP-Pt ) 2834 Hz)]. 13b 31

536 Organometallics, Vol. 28, No. 2, 2009

Nakata et al. Scheme 4

Figure 2. ORTEP drawing of (dppe)Pt(H)(GeH2Trip) (3) (30% thermal ellipsoids, a CH2Cl2 molecule and hydrogen atoms except H1, H2, and H3 were omitted for clarity). Selected bond lengths (Å): Pt1-Ge1 ) 2.4207(7), Pt1-P1 ) 2.2867(15), Pt1-P2 ) 2.2534(16), Pt1-H1 ) 1.61(8), Ge1-C1 ) 2.001(6). Selected bond angles (deg): P1-Pt1-P2 ) 86.06(6), Ge1-Pt1-P1 ) 103.61(4), Ge1-Pt1-H1 ) 80(2), P2-Pt1-H1 ) 91(2), Ge1-Pt1-P2 ) 169.89(4), P1-Pt1-H1 ) 177(2).

Figure 3. ORTEP drawing of (dcpe)Pt(H)(GeH2Trip) (5) (30% thermal ellipsoids, two CH2Cl2, a toluene molecule, and hydrogen atoms except H1, H2, and H3 were omitted for clarity). Selected bond lengths (Å): Pt1-Ge1 ) 2.4162(4), Pt1-P1 ) 2.2875(9), Pt1-P2 ) 2.2635(10), Pt1-H1 ) 1.55(4), Ge1-C1 ) 2.017(3). Selected bond angles (deg): P1-Pt1-P2 ) 87.63(3), Ge1-Pt1-P1 ) 99.63(3), Ge1-Pt1-H1 ) 84.0(16), P2-Pt1-H1 ) 88.9(16), Ge1-Pt1-P2 ) 171.95(3), P1-Pt1-H1 ) 175.3(15).

3 and 5, the hydride resonated as a doublet of doublets at δ -0.58 (2JP-H ) 180, 10, 1JPt-H ) 1034 Hz) for 3 and -0.85 (2JP-H ) 172, 12, 1JPt-H ) 956 Hz) for 5, which are shifted downfield relative to that of complex 2. The 31P{1H} NMR spectra exhibited two singlets with 195Pt satellites at δ 54.1 (1JPt-P ) 1802 Hz) and 61.3 (1JPt-P ) 2144 Hz) for 3 and δ 69.4 (1JPt-P ) 1793 Hz) and 83.2 (1JPt-P ) 2161 Hz) for 5, which were assigned to the phosphorus atoms lying trans to a hydride and a germyl ligand, respectively. By contrast, the 31P{1H} NMR chemical shift of 4 was δ 55.1 (1JPt-P ) 2027 Hz). The molecular structures of 3 and 5 are determined by X-ray crystallography, as shown in Figures 2 and 3. Distortions from square-planar geometry at the platinum centers were observed, similarly to the case of 2, which were due to the steric repulsion between dppe or dcpe ligands and each 9-triptycyl group. The Pt-Ge bond lengths [2.4212(5) Å for 3, 2.4162(4) Å for 5] are relatively similar to that observed in complex 2. The Pt1-P1

bond lengths [2.2897(11) Å for 3, 2.2875(9) Å for 5] are slightly longer than the Pt1-P2 bond length [2.2546(11) Å for 3, 2.2635(10) Å for 5], suggesting the lower trans influence of the germanium atom compared to that of the hydride. Banaszak-Holl and co-workers reported thermal rearrangement of bis(germyl) complex trans-(Et3P)2Pt(GeAr2H)2 (Ar ) 3,5-(CF3)2C6H3), which was prepared by the reaction of secondary hydrogermane Ar2GeH2 with (Et3P)2PtGe[N(SiMe3)2]2, to give digermyl(hydrido) complex cis-(Et3P)2Pt(H)(GeAr2GeAr2H).14 Very recently, Mochida et al. also reported that bis(germyl) complex cis-(Ph3P)2Pt(GeH2Mes)2 was converted to digermyl(hydrido) complex cis-(Ph3P)2Pt(H)(GeHMesGeH2Mes), involving the 1,2-migration of a germyl group at room temperature.7 Thus, we examined the thermal reaction of cis-bis(germyl) derivative 4 (Scheme 4). Heating a toluene solution of 4 at 60 °C for 1 day efficiently gave the corresponding digermyl(hydrido) complex (dppe)Pt(H)[Ge(HTrip)GeH2Trip] (6) in 88% yield. The 1H NMR spectrum of 6 displayed characteristic Ge-H and Pt-H signals at δ 5.57, 5.21, and -0.37 (2JP-H ) 179, 8, 1JPt-H ) 1019 Hz), respectively. The 31P{1H} NMR spectrum of 6 showed two singlets with 195Pt satellites at δ 52.8 (1JPt-P ) 1834 Hz) and 57.3 (1JPt-P ) 2182 Hz). The formation mechanism of 6 can be explained by the formation of a germylene-platinum complex as formal platinum(IV) intermediate 7 or the reductive elimination of digermane 8 from 4, followed by an oxidative addition of the Ge-H bond in 8, to generate the (dppe)Pt complex (Scheme 5).15 Tilley has reported that 1,2-migrations in four-coordinated Pt-Si complexes to produce platinum-silylene complexes without prior ligand dissociation are not favorable and that the metal center must be unsaturated for the R-migration to be favorable.16 In our system, the dissociation of chelating dppe ligand in 4 is not likely. Therefore, the pathway via reductive elimination may be more preferable.

Conclusion The oxidative addition of an overcrowded trihydrogermane, TripGeH3 (1), to Pt(0) precursors such as (Ph3P)2Pt(η2-C2H4) or (dppe)Pt resulted in the successful isolations of dihydrogermyl(hydrido) platinum(II) complexes cis-(Ph3P)2Pt(H)(GeH2Trip) (2) or (dppe)Pt(H)(GeH2Trip) (3), respectively. Additionally, the ligand exchange reaction between complex 1 and dcpe smoothly proceeded at room temperature to give the corresponding hydrido complex (dcpe)Pt(H)(GeH2Trip), 5. The molecular structures of the hydrido complexes were revealed (13) (a) Knobler, C. B.; Kaesz, H. D.; Minghetti, G.; Bandini, A. L.; Banditelli, G.; Bonati, F. Inorg. Chem. 1983, 22, 2324–2331. (b) Carmichael, D.; Hitchcock, P. B.; Nixon, J. F.; Pidcock, A. P. J. Chem. Soc., Chem. Commun. 1988, 1554–1556. (14) Bender, J. E.; Litz, K. E.; Giarikos, D.; Wells, N. J.; BanaszakHoll, M. M.; Kampf, J. W. Chem.-Eur. J. 1997, 3, 1793–1796. (15) We confirmed the production of (digermyl) complex 6 by the oxidative addition of tetrahydrodigermane (TripH2Ge)2 with (Ph3P)2Pt(η2C2H4) in toluene (29% yield). (16) (a) Mitchell, G. P.; Tilley, T. D. Angew. Chem., Int. Ed. 1998, 37, 2524–2526. (b) Feldman, J. D.; Mitchell, G. P.; Nolte, J.-O.; Tilley, T. D. Can. J. Chem. 2003, 81, 1127–1136.

Stable Mononuclear Dihydrogermyl(hydrido) Pt(II) Complexes

Organometallics, Vol. 28, No. 2, 2009 537 Scheme 5

Table 1. Crystallographic Data and Details of Refinement for 2, 3, and 5 formula fw color cryst size/mm temp/K cryst syst space group a/Å b/Å c/Å R/deg β/deg γ/deg V/Å3 Z Dcalcd/g cm-3 no. of unique data no. of params no. of restraints R1 (I > 2σ(I)) wR2 (all data) GOF

2

3

5

C59H52Cl6GeP2Pt 1303.33 colorless 0.30 × 0.20 × 0.20 123 triclinic P1j 11.8284(9) 12.1690(9) 21.1183(16) 102.190(2) 93.663(2) 114.777(2) 2657.6(3) 2 1.629 10 351

C47H42Cl2GeP2Pt 1007.33 colorless 0.43 × 0.40 × 0.25 103 monoclinic P21/n 11.2374(4) 20.0320(7) 19.0101(7) 90 105.2000(10) 90 4129.6(3) 4 1.620 7682

C55H76Cl4GeP2Pt 1208.58 colorless 0.30 × 0.30 × 0.30 103 monoclinic P21/c 16.2932(6) 19.9960(7) 17.0506(6) 90 104.4760(10) 90 5378.7(3) 4 1.492 11 138

626 0 0.0480 0.1322 1.035

490 1 0.0329 0.0855 1.023

635 29 0.0340 0.0852 1.036

by the spectroscopic data and by X-ray crystallography. These results present the first examples of stable dihydrogermyl(hydrido) platinum(II) complexes, which are proposed as the initial products in the oxidative additions of primary trihydrogermanes to platinum(0) complexes.

Experimental Section General Procedure. All experiments were performed under an argon atmosphere unless otherwise noted. Solvents were dried by standard methods and freshly distilled prior to use. 1H, 13C{1H}, and 31P{1H} NMR spectra were recorded on a Bruker DPX-400 or DRX-400 (400, 100.7, and 162 MHz, respectively) spectrometer using CDCl3 or C6D6 as the solvent at room temperature. IR spectra were obtained on a Perkin-Elmer System 2000 FT-IR spectrometer. Elemental analyses were carried out at the Molecular Analysis and Life Science Center of Saitama University. All melting points were determined on a Mel-Temp capillary tube apparatus and are uncorrected. Preparative thin-layer chromatography (PTLC) was performed with Merck Kieselgel 60 PF254. 9-Triptycyltrihydrogermane (1)10 and (Ph3P)2Pt(η2-C2H4)17 were prepared according to the reported procedures. [cis-(Ph3P)2Pt(H)(GeH2Trip)] (2). A mixture of 1 (31.3 mg, 0.095 mmol) and (Ph3P)2Pt(η2-C2H4) (75.8 mg, 0.101 mmol) in dry toluene (3 mL) was stirred at room temperature for 1 h to form a pale yellow solution. After removal of the solvent in vacuo, the residual colorless solid was purified by washing three times with hexane (ca. 3 mL) to give 2 (100 mg, 99%) as colorless crystals. Mp: 127 °C (dec). 1H NMR (400 MHz, CDCl3): δ -3.23 (dd, 1 H, 2 JH-P(trans) ) 168, 2JH-P(cis) ) 18, 1JPt-H ) 894 Hz, Pt-H), 4.43 (m,

2 H, Ge-H), 5.28 (s, 1 H), 6.80-6.90 (m, 6 H), 7.01-7.05 (m, 6 H), 7.14-7.30 (m, 21 H), 7.45-7.49 (m, 6 H), 7.77-7.79 (d, 3 H, J ) 7.1 Hz). 13C{1H} NMR (101 MHz, CDCl3): δ 55.3, 122.7, 123.8, 126.5, 127.7, 127.8, 129.4, 129.6, 134.1, 134.1, 134.2, 134.3, 148.3, 149.8. 31P{1H} NMR (162 MHz, CDCl3): δ 31.2 (d, 2JP-P ) 13, 1JP-Pt ) 2317 Hz, trans to Ge), 31.6 (d, 2JP-P) 13, 1JP-Pt ) 2252 Hz, trans to H). IR (KBr) (ν, cm-1): 1953 (Ge-H), 2063 (Pt-H). Anal. Calcd for C56H46GeP2Pt: C, 64.13; H, 4.42. Found: C, 63.87; H, 4.32. Reaction of 1 with 1 equiv of (dppe)Pt. A solution of 1 (20.0 mg, 0.061 mmol) in dry toluene (2 mL) was added to the ethanol (2 mL) solution of (dppe)Pt, which was prepared via reduction of (dppe)PtCl2 (42.8 mg, 0.064 mmol) with NaBH4 (8.4 mg, 0.221 mmol) at room temperature for 10 min. The reaction mixture was stirred at room temperature for 3 h. The solution was filtered through Celite and rinsed with CH2Cl2. After removal of the solvent in vacuo, the residue was purified by PTLC (CH2Cl2/hexane, 1:1) to give[(dppe)Pt(H)(GeH2Trip)](3)(20.3mg,36%)and[(dppe)Pt(GeH2Trip)2] (4) (5.7 mg, 16%) as colorless crystals. 3: mp 155 °C (dec). 1 H NMR (400 MHz, CDCl3): δ -0.58 (dd, 1 H, 2JH-P(trans) ) 180, 2 JH-P(cis) ) 10, 1JPt-H ) 1034 Hz, Pt-H), 2.43 (m, 4 H), 5.02-5.26 (m, 2 H, Ge-H), 5.34 (s, 1 H), 6.83-6.93 (m, 6 H), 7.31-7.34 (m, 8 H), 7.43-7.45 (m, 6 H), 7.70-7.80 (m, 9 H), 7.89-7.91 (d, 3 H, J ) 7 Hz). 13C{1H} NMR (100.6 MHz, C6D6): δ 27.8 (dd, 1 JC-P ) 31, 2JC-P ) 17 Hz), 30.5 (dd, 1JC-P ) 32, 2JC-P ) 19 Hz), 51.1 (m, 1 C), 56.1, 123.3, 124.3, 124.3,127.5, 128.3, 128.7-128.9 (m), 130.6 (d, 4JC-P ) 2 Hz), 130.7 (d, 4JC-P ) 2 Hz), 133.0 (d, 1 JC-P ) 44 Hz), 133.0 (d, 1JC-P ) 44 Hz), 133.3-133.4 (m), 150.0, 150.8. 31P{1H} NMR (162 MHz, CDCl3): δ 54.1 (s, 1JP-Pt ) 1802 Hz, trans to H), 61.3 (s, 1JP-Pt ) 2144 Hz, trans to Ge). IR (KBr) (ν, cm-1): 1941 (Ge-H), 2032 (Pt-H). Anal. Calcd for C46H40GeP2Pt: C, 59.89; H, 4.37. Found: C, 59.53; H, 4.49. 4: mp 185 °C (dec). 1H NMR (400 MHz, CDCl3): δ 2.00-2.05 (m, 4 H), 4.86-5.05 (m, 4 H, Ge-H), 5.17 (s, 2 H), 6.48-6.52 (m, 6 H), 6.73-6.77 (m, 6 H), 7.10-7.24 (m, 18 H), 7.62-7.73 (m, 14 H). 13 C{1H} NMR (100.7 MHz, CDCl3): δ 32.0-32.5 (m, 2 C), 52.2 (dd, 3JC-P ) 5, 5 Hz, Ge-C), 55.2, 122.4, 123.6, 123.9, 127.3, 128.2 (d, 3JC-P ) 5 Hz), 128.2 (d, 3JC-P ) 5 Hz), 129.5 (d, 3JC-P ) 47 Hz), 130.9, 133.7 (d, 3JC-P ) 6 Hz), 133.8 (d, 3JC-P ) 6 Hz), 147.2, 149.4. 31P{1H} NMR (162 Hz, CDCl3): δ 55.1 (s, 3JP-Pt ) 2027 Hz). IR (KBr) (ν, cm-1): 1976 (Ge-H). Anal. Calcd for C66H54Ge2P2Pt: C, 63.45; H, 4.36. Found: C, 63.46; H, 4.47. Reaction of 1 with 0.5 equiv of (dppe)Pt. A solution of 1 (247.3 mg, 0.751 mmol) in dry toluene (5 mL) was added to the ethanol (5 mL) solution of 0.5 equiv of (dppe)Pt (0.373 mmol). The reaction mixture was stirred at room temperature for 13 h. The solution was filtered through Celite and rinsed with CH2Cl2. After removal of the solvent in vacuo, the residue was purified by PTLC (CH2Cl2/ hexane, 1:1) to give complex 4 (358.8 mg, 77%). [(dcpe)Pt(H)(GeH2Trip)] (5). A mixture of 2 (60.5 mg, 0.058 mmol) and Cy2PCH2CH2PCy2 (24.8 mg, 0.059 mmol) in dry toluene (5 mL) was stirred at room temperature for 30 min to form a clear solution. After removal of the solvent in vacuo, the residual colorless

538 Organometallics, Vol. 28, No. 2, 2009 solid was purified by PTLC (CH2Cl2/hexane, 1:2) to give complex 5 (34.3 mg, 63%) as colorless crystals. Mp: 182 °C (dec). 1H NMR (400 MHz, CDCl3): δ -0.85 (dd, 1 H, 2JH-P(trans) ) 172, 2JH-P(cis) ) 12, 1JPt-H ) 956 Hz, Pt-H), 1.16-1.37 (m, 20 H), 1.64-1.86 (m, 24 H), 2.15-2.18 (m, 2 H), 2.34-2.39 (m, 2 H), 5.25 (dd, 2 H, 2JH-H ) 15, 3JH-P(trans) ) 5, 2JPt-H ) 72 Hz, Ge-H), 5.33 (s, 1 H), 6.81-6.91 (m, 6 H), 7.30-7.32 (d, 3 H, J ) 7.0 Hz), 7.90-7.92 (d, 3 H, J ) 7.0 Hz). 13C{1H} NMR (101 MHz, CDCl3): δ 23.5 (dd, 3JC-P ) 23, 16 Hz, PCH2), 25.1 (dd, 3JC-P ) 24, 18 Hz, PCH2), 26.2 (d, 3JC-P ) 14 Hz, PCy), 26.6 (d, 3JC-P ) 13 Hz, PCy), 26.8-27.1 (m, PCy × 2), 28.8 (m, PCy), 29.1 (m, PCy), 29.6 (m, PCy), 35.1-35.8 (m, PCy × 2), 49.9, 55.4, 122.7, 123.6, 123.7, 127.1, 149.4, 150.5. 31P{1H} NMR (162 MHz, CDCl3): δ 69.4 (s, 1 JP-Pt ) 1793 Hz, trans to H), 83.2 (s, 1JP-Pt ) 2161 Hz, trans to Ge). IR (KBr) (ν, cm-1): 1929 (Ge-H), 2024 (Pt-H). Anal. Calcd for C46H64GeP2Pt: C, 58.36; H, 6.81. Found: C, 58.63; H, 6.81. {(dppe)Pt(H)[Ge(HTrip)GeH2Trip]} (6). 4 (17.9 mg, 0.014 mmol) was heated to 60 °C in toluene (3 mL) for 1 day. After removal of the solvent in vacuo, the residual colorless solid was purified by washing three times with hexane (ca. 3 mL) to give 6 (15.8 mg, 88%) as colorless crystals. Mp: 205 °C (dec). 1H NMR (400 MHz, C6D6): δ -0.37 (dd, 1 H, 2JH-P(trans) ) 179, 2JH-P(cis) ) 8, 1JPt-H ) 1019 Hz, Pt-H), 1.65 (br s, 1 H), 1.89-2.13 (m, 3 H), 5.22 (br, 1 H, Ge-H), 5.22 (s, 1 H), 5.26 (s, 1 H), 5.31-5.32 (m, 1 H, Ge-H), 5.54-5.61 (m, 1 H, Ge-H), 6.39 (dd, 3 H, J ) 7.2, J ) 7.6 Hz), 6.73 (dd, 3 H, J ) 7.2, J ) 7.6 Hz), 6.80-7.25 (m, 24 H), 7.48-7.69 (m, 8 H), 7.90 (d, J ) 7.6 Hz, 3 H), 8.27 (br s, 2 H), 9.11 (br s, 1 H). 31P{1H} NMR (162 MHz, C6D6): δ 52.8 (s, 1 JP-Pt ) 1834 Hz, trans to H), 57.3 (s, 1JP-Pt ) 2182 Hz, trans to Ge). IR (KBr) (ν, cm-1): 1934 (br), 2002 (br). Anal. Calcd for C66H54Ge2P2Pt: C, 63.45; H, 4.36. Found: C, 63.37; H, 4.34. We were unable to obtain a 13C{1H} NMR spectrum due to the poor solubility of this complex in CDCl3 or C6D6.

Nakata et al. X-ray Crystallographic Analyses of 2, 3, and 5. Colorless single crystals of 2 and 3 were grown by the slow evaporation of its saturated CH2Cl2 and hexane solution, and single crystals of 5 were grown by the slow evaporation of its saturated toluene, CH2Cl2, and hexane solution. The intensity data were collected at 123 K for 2 and 103 K for 3 and 5 on a Bruker AXS SMART diffractometer employing graphite-monochromatized Mo KR radiation (λ ) 0.71073 Å). The structures were solved by direct methods and refined by full-matrix least-squares procedures on F2 for all reflections (SHELX-97).18 Hydrogen atoms, except for the PtH hydrogen of 2 and PtH and GeH hydrogens of 3 and 5, were located by assuming ideal geometry and were included in the structure calculations without further refinement of the parameters. Crystallographic data and details of refinement for 2, 3, and 5 are summarized in Table 1.

Acknowledgment. This work was supported by a Grantin-Aid for Scientific Research (Nos. 18750026 and 19027014) from the Ministry of Education, Science, Sports, and Culture of Japan. We are grateful to Professor Kohtaro Osakada and Dr. Makoto Tanabe of Tokyo Institute of Technology for their useful discussions and suggestions. Supporting Information Available: Crystallographic data for 2, 3, and 5 as CIF files. This material is available free of charge via the Internet at http://pubs.acs.org. OM800809N (17) (a) Cook, C. D.; Jauhal, G. S. J. Am. Chem. Soc. 1968, 90, 1464– 1467. (b) Ugo, R.; Caliati, F.; LaMonica, G. Inorg. Synth. 1968, 11, 106. (18) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refinement; University of Go¨ttingen: Germany, 1997.