{RuNO}6vs. co-ligand oxidation: two non-innocent groups in one ruthenium nitrosyl complex

Abstract

Recently, a new {RuNO}⁶ complex, [Ru(L)(PPh₃)(NO)(Cl)]²⁺ (where L = 1-phenyl-1-(pyridin-2-yl)-2-(pyridin-2-ylmethylene)hydrazine), was reported which exhibits a one-electron quasireversible oxidation. The oxidized product, [Ru(L)(PPh₃)(NO)(Cl)]³⁺, was isolated and proposed to be a highly unusual {RuNO}⁵ complex. In this paper, we investigate the electronic structure of both of these ruthenium complexes by DFT calculations and find that the oxidized species is best described as a {RuNO}⁶ complex with a co-ligand radical. [Ru(L)(PPh₃)(NO)(Cl)]²⁺ is therefore oxidized to [Ru(L^+˙)(PPh₃)(NO)(Cl)]³⁺, i.e. this is an interesting example of a complex with two non-innocent ligands simultaneously bound to a ruthenium center.