Dinuclear transition-metal catalysts with a direct metal-metal bond have the potential to induce novel reaction mechanisms and selectivity compared to mononuclear catalysts. Mononuclear Ni complexes, for example (bpy)Ni(COD), generally catalyze non-regioselective cyclotetramerization of alkynes. In contrast, the dinuclear (NDI)Ni2(C6H6) complex catalyzes regioselective cyclotrimerization of monosubstituted alkynes. This talk will present density-functional calculations that reveal the catalyst Ni-Ni interaction results in a unique cyclotrimerization mechanism involving spin crossover, a key dinickel migratory insertion step, and a nonclassical metallacycloheptatriene. The proposed catalytic cycle provides an explanation for alkyne cyclotrimerization regioselectivity and periselectivity preference for cyclotrimerization versus cyclotetramerization.

Computational study of dinuclear nickel catalyzed alkyne cyclotrimerization

253rd National Meeting (2017)

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