(NDI)Ni 2 catalysts (NDI = naphthyridine-diimine) promote cyclopropanation reactions of 1,3-dienes using (Me 3 Si)CHN 2 .Mechanistic studies reveal that ametal carbene intermediate is not part of the catalytic cycle.T he (NDI)Ni 2-(CHSiMe 3)complex was independently synthesized and found to be unreactive toward dienes.B ased on DFT models,w e propose an alternative mechanism that begins with aN i 2mediated coupling of (Me 3 Si)CHN 2 and the diene.N 2 extrusion followed by radical CÀCb ond formation generates the cyclopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.

A dinickel catalyst promotes the [2 + 2 + 1]-cycloaddition of two aldehyde equivalents and a vinylidene. The resulting methylenedioxolane products can be deprotected in one pot under acidic conditions...

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A dinickel catalyst promotes reductive cyclization reactions of 1,1-dichloroalkenes containing pendant olefins. The reactions can be conducted with a Zn reductant or electrocatalytically using a carbon working electrode. Mechanistic studies are consistent with the intermediacy of a Ni2(vinylidene) species, which adds to the alkene and generates a metallacyclic intermediate. β-Hydride elimination followed by C–H reductive elimination forms the cyclization product. The proposed dinickel metallacycle is structurally characterized and its stoichiometric conversion into product is demonstrated. Spin-polarized, unrestricted DFT calculations are used to further examine the cyclization mechanism. These calculations reveal that both nickel centers function cooperatively to mediate the key oxidative addition, migratory insertion, β-hydride elimination, and reductive elimination steps.

(NDI)Ni 2 catalysts (NDI = naphthyridine-diimine) promote cyclopropanation reactions of 1,3-dienes using (Me 3 Si)CHN 2 .Mechanistic studies reveal that ametal carbene intermediate is not part of the catalytic cycle.T he (NDI)Ni 2-(CHSiMe 3)complex was independently synthesized and found to be unreactive toward dienes.B ased on DFT models,w e propose an alternative mechanism that begins with aN i 2mediated coupling of (Me 3 Si)CHN 2 and the diene.N 2 extrusion followed by radical CÀCb ond formation generates the cyclopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.