A NiII complex supported by an iminophosphorane ONP ligand: synthesis and catalytic CC and CO bond hydrosilylation

Abstract

An original ONP iminophosphorane ligand was synthesised and coordinated to [NiX₂(DME)] (X = Cl, Br). The corresponding complexes (2X, X = Cl, Br) were isolated and characterised among others by multinuclear NMR spectroscopy and X-ray crystallography. The collected data suggest that different geometries coexist in solution at room temperature. 2Cl proved to be an efficient hydrosilylation catalyst able to perform at a loading of 1 mol% in the presence of one equivalent of SiH₂Ph₂ and 1 mol% of ^tBuOK, with the reduction of CC and CO bonds in high yield in 1 h for most substrates. Moreover, the selective conversion of the CO bond to a silylether linkage was observed for nine enones. Therefore, 2Cl presents a rather unique catalytic behaviour compared to previously described Ni catalysts. Both experimental and theoretical investigations regarding the mechanism suggest the involvement of a Ni–H complex. The computed mechanism presents a highest-lying transition state at only 19.0 kcal mol⁻¹ and shows that the reaction is driven by favorable thermodynamics.