Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Bimolecular Formation of Alkanes

Abstract

Monomeric Cu(I) alkyl complexes (NHC)Cu(R) (NHC = N-heterocyclic carbene; R = Me or Et) and (dtbpe)Cu(Me) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) have been prepared, isolated, and characterized. Single-electron oxidation of the Cu(I) alkyl complexes upon reaction with AgOTf to form putative Cu(II) intermediates of the type [(L)Cu(R)]+ (L = NHC or dtbpe, R = Me or Et) results in the rapid production of (L)Cu(X) (X = OTf) and R2. Experimental studies suggest that the reductive elimination of R2 from Cu(II) occurs through a nonradical bimolecular mechanism. Computational studies of the Cu−Cmethyl yield bond dissociation enthalpies of [(SIPr)Cu−CH3]n+ (80 kcal/mol for n = 0 {Cu(I)} and 38 kcal/mol for n = 1 {Cu(II)}).