International audienceHalf-sandwich N-heterocyclic carbene (NHC)-nickel complexes of the general formula [Ni(NHC)ClCp†] (Cp†=Cp, Cp*) efficiently catalyze the hydrosilylation of aldehydes and ketones at room temperature in the presence of a catalytic amount of sodium triethylborohydride and thus join the fairly exclusive club of well-defined nickel(II) catalyst precursors for the hydrosilylation of carbonyl functionalities. Of notable interest is the isolation of an intermediate nickel hydride complex that proved to be the real catalyst precursor
The in situ generated nickel hydride complex, [Ni(Mes 2 NHC)HCp], and its cationic analogue, [Ni(Mes 2 NHC)(NCMe)Cp](PF 6 ), are efficient and chemoselective pre-catalysts for the hydrosilylation of both aldimines and ketimines under mild conditions.
International audienceA series of nickel complexes (1–3)b of 1,2,4-triazole derived amido-functionalized N-heterocyclic carbene ligands were synthesized and structurally characterized. In particular, the [1-(R)-4-N-(furan-2-ylmethyl)acetamido-1,2,4-triazol-5-ylidene]2Ni [R = Et (1b), i-Pr (2b) and Bn (3b)] complexes were obtained by the direct reaction of the corresponding triazolium chloride salts (1–3)a by the treatment with NiCl2·6H2O in presence of K2CO3 as a base. The density functional theory studies performed on these complexes reveal highly polar character of the NHC–Ni σ-bonding interaction with corresponding molecular orbital having a maximum contribution (59–69%) from the NHC ligand fragments while that of a minimum contribution (4%) from the central nickel atom. The (1–3)b complexes were found to be moderately active for the catalytic borylation reactions of bromoaryl derivatives by bis(pinacolato)diboron reagent (B2pin2) in the presence of Cs2CO3 as a base at 70 °
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