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Spectroscopic and Reactivity Studies of Platinum−Silicon Monomers and Dimers

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posted on 22.05.2006, 00:00 by Janet Braddock-Wilking, Joyce Y. Corey, Kevin A. Trankler, Huan Xu, Lisa M. French, Ngamjit Praingam, Colin White, Nigam P. Rath
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.