NiII complex supported by an iminophosphorane ONP ligand: Synthesis and catalytic C=C and C=O bonds hydrosilylation
Résumé
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 presence of one equivalent SiH2Ph2 and 1 mol % of t BuOK, the reduction of C=C and C=O bonds in high yield in 1 h for most substrates. Moreover, the selective conversion of C=O bond to 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 the favorable thermodynamics.
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