Si–H Bond Activation of a Primary Silane with a Pt(0) Complex: Synthesis and Structures of Mononuclear (Hydrido)(dihydrosilyl) Platinum(II) Complexes

A hydrido platinum(II) complex with a dihydrosilyl ligand, [cis-PtH(SiH2Trip)(PPh3)2] (2) was prepared by oxidative addition of an overcrowded primary silane, TripSiH3 (1, Trip = 9-triptycyl) with [Pt(η-C2H4)(PPh3)2] in toluene. The ligand-exchange reactions of complex 2 with free phosphine ligands resulted in the formation of a series of (hydrido)(dihydrosilyl) complexes (3–5). Thus, the replacement of two PPh3 ligands in 2 with a bidentate bis(phosphine) ligand such as DPPF [1,2-bis(diphenylphosphino)ferrocene] or DCPE [1,2-bis(dicyclohexylphosphino)ethane] gave the corresponding complexes [PtH(SiH2Trip)(L-L)] (3: L-L = dppf, 4: L-L = dcpe). In contrast, the ligand-exchange reaction of 2 with an excess amount of PMe3 in toluene quantitatively produced [PtH(SiH2Trip)(PMe3)(PPh3)] (5), where the PMe3 ligand is adopting trans to the hydrido ligand. 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, which is probably due to the steric requirement of the cis-coordinated phosphine ligands and the bulky 9-triptycyl group on the silicon atom.