Iridium complexes featuring a tridentate SiPSi ligand: from dimeric to monomeric 14, 16 or 18-electron species.

In the solid state, the dinuclear iridium complex [μ-Cl-Ir(SiMeCH-o-CH)PPh], 1, is shown by X-ray diffraction to bear dibenzylsilylphosphine ligands in SiPSi tridentate coordination modes as well as chloride bridges. In CD solution, 1 dissociates into the 14-electron species [IrCl(SiMeCH-o-CH)PPh] prone to coordinate one or two L-type ligands such as PR (R = Cy, Ph, OEt), CO and CHCN giving rise to the corresponding mononuclear 16- or 18-electron complexes [IrCl(SiMeCH-o-CH)PPh(L)] (x = 1, 2) as evidenced by X-ray and NMR studies. The dinuclear structure is retained upon reaction with EtSiH which results in the formation of [μ-Cl,μ-H-Ir{(SiMeCH-o-CH)PPh}] with a bridging hydride.

A family of rhodium and iridium complexes with semirigid benzylsilyl phosphines: from bidentate to tetradentate coordination modes.

The synthesis of a new trisbenzylsilanephosphine P{(o-CHCH)SiMeH} (1) is shown to proceed with high yields from P(o-tolyl). Compound 1 coordinates to the Rh and Ir dimers [MCl(COD)] (M = Rh, Ir) in a tetradentate or tridentate fashion, depending on the strict exclusion of water. The dimeric compounds [ClM(SiMeCH-o-CH)P(o-CH-CHSiMeH)], 2Rh and 2Ir, feature a tetradentate coordination of the starting ligand with P and two Si atoms as well as a non-classical agostic Si-H group.

Phosphinodi(benzylsilane) PhP{(o-C6H4CH2)SiMe2H}2: a versatile "PSi2Hx" pincer-type ligand at ruthenium.

The synthesis of the new phosphinodi(benzylsilane) compound PhP{(o-C6H4CH2)SiMe2H}2 (1) is achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1 acts as a pincer-type ligand capable of adopting different coordination modes at Ru through different extents of Si-H bond activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR spectroscopy. Reaction of 1 with RuH2(H2)2(PCy3)2 (2) yields quantitatively [RuH2{[η(2)-(HSiMe2)-CH2-o-C6H4]2PPh}(PCy3)] (3), a complex stabilized by two rare high order ε-agostic Si-H bonds and involved in terminal hydride/η(2)-Si-H exchange processes.