Spectroscopic and Reactivity Studies of Platinum−Silicon Monomers and Dimers

Mononuclear Pt−Si-containing complexes with the general formulas (Ph₃P)₂Pt(H)(SiAr₂H) and (Ph₃P)₂Pt(SiAr₂H)₂ were produced at low temperature from the reaction of the secondary arylhydrosilanes Ph₂SiH₂, C₁₂H₈SiH₂ (silafluorene), and C₂₀H₂₄SiH₂ (3,7-di-tert-butylsilafluorene) with (Ph₃P)₂Pt(η²-C₂H₄). When solutions of the mononuclear complexes were run at low temperature and then warmed to room temperature, or when the reactions were run at room temperature or above, dinuclear Pt−Si-containing complexes were produced, [(Ph₃P)Pt(μ-η²-HSiAr₂)]₂ (Ar = Ph (4)) and [(Ph₃P)₂Pt(H)(μ-SiAr₂)(μ-η²-HSiAr₂)Pt(PPh₃)] (Ar₂ = C₁₂H₈ (8), C₂₀H₂₄ (15); both fluxional). A mechanism is proposed for the formation of the unsymmetrical dinuclear complexes (8 and 15) that involves a bimolecular reaction between two mononuclear species, (Ph₃P)₂Pt(H)(SiAr₂H) and (Ph₃P)Pt(H)(SiAr₂H). VT-NMR studies of complexes 8 and 15 illustrate that a fluxional process occurs which can be explained by elimination and recoordination of a PPh₃ ligand. Complex 15 reacted with added P(p-Tol)₃ to produce a mixture of dinuclear products consistent with the presence of both types of phosphines in the dinuclear complexes. Reaction of the dinuclear complex 8 with the mononuclear complex 16 as well as the elevated-temperature reaction between 8 and 15 will be described.