title: Oxidative C-C Bond Formation Reactivity of Organometallic Ni(II), Ni(III), and Ni(IV) Complexes.
abstract: The use of the tridentate ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) and the cyclic alkyl/aryl C-donor ligand -CH2CMe2-o-C6H4- (cycloneophyl) allows for the synthesis of isolable organometallic NiII, NiIII, and NiIVcomplexes. Surprisingly, the five-coordinate NiIIIcomplex is stable both in solution and the solid state, and exhibits limited C-C bond formation reactivity. Oxidation by one electron of this NiIIIspecies generates a six-coordinate NiIVcomplex, with an acetonitrile molecule bound to Ni. Interestingly, illumination of the NiIVcomplex with blue LEDs results in rapid formation of the cyclic C-C product at room temperature. This reactivity has important implications for the recently developed dual Ni/photoredox catalytic systems proposed to involve high-valent organometallic Ni intermediates. Additional reactivity studies show the corresponding NiIIspecies undergoes oxidative addition with alkyl halides, as well as rapid oxidation by O2, to generate detectable NiIIIand/or NiIVintermediates and followed by C-C bond formation.
authors.affiliation: Department of Chemistry, Washington University , One Brookings Drive, St. Louis, Missouri 63130-4899, United States.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Watson
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri-St. Louis , One University Boulevard, St. Louis, Missouri 63121-4400, United States.
authors.forename: Nigam P
authors.initials: NP
authors.lastname: Rath
authors.affiliation: Department of Chemistry, Washington University , One Brookings Drive, St. Louis, Missouri 63130-4899, United States.
authors.forename: Liviu M
authors.identifier: 0000-0003-0584-9508
authors.initials: LM
authors.lastname: Mirica