Unexpected effect of the ring on the extent of Si⋯H interligand interactions in half-sandwich silyl hydrides of ruthenium

Abstract

This paper reports preparation of new silyl hydride complexes of ruthenium supported by the Cp/PR₃ ligand set. It is shown that the easiest and most general route to these complexes is provided by the thermal reaction of [RuCp(PR₃)(H)₃] with hydrosilanes. Complexes [RuCp(PR₃)(H)₂(SiMe₂Cl)] exhibit Interligand Hypervalent Interactions (IHI) between the hydride and silyl ligands. Comparison of the X-ray structures of complexes [RuCp(PPrⁱ₃)(H)₂(SiMe₂Cl)], [RuCp(PPhPrⁱ₂)(H)₂(SiMe₂Cl)], and [RuCp(PPh₃)(H)₂(SiMe₂Cl)] shows that the IHI weakens with the decreasing electron-releasing ability of the phosphine. Comparison of the X-ray structure of [RuCp(PPh₃)(H)₂(SiMe₂Cl)] with the structure of the previously reported complex [RuCp*(PPh₃)(H)₂(SiMe₂Cl)] reveals that the lack of IHI in the latter compound is due to unfavourable steric interactions between the bulkier Cp* ring and the SiMe₂Cl group.