Ligand Exchange of Diplatinum Complexes with Bridging Silyl Ligands Involving Si−H Bond Cleavage and Formation

Abstract

Reactions of excess H2SiEt2 and H2SiHex2 with [Pt(PCy3)2] at room temperature form mononuclear cis-hydrido(silyl)platinum complexes, cis-[Pt(H)(SiHR2)(PCy3)2] (1: R = Et, 2: R = Hex), which are converted into diplatinum complexes with bridging dialkylsilyl ligands, [{Pt(PCy3)}2(µ-η2-HSiR2)2] (3: R = Et, 4: R = Hex), upon heating at 80 °C. Complex 3 reacts with excess H2SiPhMe and H2SiPh2 to afford dinuclear complexes [{Pt(PCy3)}2(µ-η2-HSiPhR)2] (5: R = Me, 6: R = Ph) via exchange of the bridging silyl ligands. An equimolar reaction of H2SiPh2 with 3 yields a mixture of diplatinum complexes [{Pt(PCy3)}2(µ-η2-HSiEt2)(µ-η2-HSiPh2)] (7) and [{Pt(PCy3)}2(µ-η2:η2-H2SiEt2)(µ-SiPh2)] (8). Use of D2SiPh2 in the reaction results in distribution of deuterium in the diethylsilyl and diphenylsilyl ligands of 7, the diethylsilane ligand of 8, and the diphenylsilyl ligand of 6. Complex 6 undergoes exchange of the phosphine ligands with dmpe (1,2-bis(dimethylphosphino)ethane) and with dppe (1,2-bis(diphenylphosphino)ethane) to afford diplatinum complexes with bridging silylene ligands and the chelating diphosphine ligands, [{Pt(dmpe)}2(µ-SiPh2)2] (9) and [{Pt(dppe)}2(µ-SiPh2)2] (10). Short contact between the two Si atoms (2.718(2) and 2.646(2) Å) suggests a weak Si···Si interaction.