The copper ion is utilized in a number of important transformations in homogeneous catalysis, and is a key component of catalytic transformations in the production of commodity chemicals and pharmaceuticals. It has been proposed that a key intermediate in these transformations are high-valent organocopper(III) species, which are proposed to be highly reactive intermediates that readily undergo reductive eliminations, resulting in C-C bond formation and a subsequent copper(I) species. For example, (Cu(CH3)4)- yields a mixture of products (including ethane), while (Cu(CF3)3R)- species cleanly yield R-CF3 and (Cu(CF3)2)–. This can be contrasted with (Cu(CF3)4)-, which is room temperature stable, and inert towards formal reductive elimination. These observations, coupled with recent reports by Lancaster and co-workers1,2 casting doubt on the existence of physical 3d8 copper(III) has prompted us to investigate formal reductive eliminations from (CuR4)- (R = CH3 or CF3) through the lens of valence bond (VB) theory. Using breathing orbital VB calculations, which were benchmarked to CCSD(T) calculations extrapolated to the basis set limit, we will propose that these eliminations are not reductive in any physical sense, and instead can be thought of as an admixture of C-C radical coupling and Lewis acid/base reactivity with no major charge shift between metal and alkyl fragment. Furthermore, the physical reason for the inertness of (Cu(CF3)4)- vs (Cu(CH3)n(CF3)m)- will be explored.

Are Reductive Eliminations from Organocopper Species Reductive? A Valence Bond Study of (CuR4)– (R = CH3 or CF3)

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.