An H-Substituted Rhodium Silylene

Abstract

Divergent reactivity of organometallic rhodium(I) complexes, which led to the isolation of neutral rhodium silylenes, is described. Addition of PhRSiH₂ (R=H, Ph) to the rhodium cyclooctene complex (^iPr NNN)Rh(COE) (1-COE; ^iPr NNN=2,5-[iPr₂ P=N(4-iPrC₆ H₄ )]₂ N(C₆ H₂ )^- , COE=cyclooctene) resulted in the oxidative addition of an Si-H bond, providing rhodium(III) silyl hydride complexes (^iPr NNN)Rh(H)SiHRPh (R=H, 2-SiH₂ Ph; Ph, 2-SiHPh₂ ). When the carbonyl complex (^iPr NNN)Rh(CO) (1-CO) was treated with hydrosilanes, base-stabilized rhodium(I) silylenes κ² -N,N-(^iPr NNN)(CO)Rh=SiRPh (R=H, 3-SiHPh; Ph, 3-SiPh₂ ) were isolated and characterized using multinuclear NMR spectroscopy and X-ray crystallography. Both silylene species feature short Rh-Si bonds [2.262(1) Å, 3-SiHPh; 2.2702(7) Å, 3-SiPh₂ ] that agree well with the DFT-computed structures. The overall reaction led to a change in the ^iPr NNN ligand bonding mode (κ³ →κ² ) and loss of H₂ from PhSiRH₂ , as corroborated by deuterium labelling experiments.

Keywords: H-substituted silylene; hydrosilation catalysis; metal-ligand cooperativity; pincer ligands; rhodium.