Organometallic Nickel(III) Complexes Relevant to Cross-Coupling and Carbon–Heteroatom Bond Formation Reactions

Nickel
complexes have been widely employed as catalysts in C–C
and C–heteroatom bond formation reactions. In addition to Ni(0)
and Ni­(II) intermediates, several Ni-catalyzed reactions are proposed
to also involve odd-electron Ni­(I) and Ni­(III) oxidation states. We
report herein the isolation, structural and spectroscopic characterization,
and organometallic reactivity of Ni­(III) complexes containing aryl
and alkyl ligands. These Ni­(III) species undergo transmetalation and/or
reductive elimination reactions to form new C–C or C–heteroatom
bonds and are also competent catalysts for Kumada and Negishi cross-coupling
reactions. Overall, these results provide strong evidence for the
direct involvement of organometallic Ni­(III) species in cross-coupling
reactions and oxidatively induced C–heteroatom bond formation
reactions.