Understanding Electronic Ligand Perturbation over Successive Metal-Based Redox Potentials in Mononuclear Ruthenium–Aqua Complexes

A family of new ruthenium complexes containing a combination of polypyridyl and carbene ligands has been prepared and characterized from structural, spectroscopic, and redox viewpoints both experimentally and computationally. Interestingly, a correlation between ΔE1/2, defined as the difference between E1/2(RuIV/III) and E1/2(RuIII/II), and the activity and selectivity of some catalytic oxidation processes has been clearly established. A density functional theory study on the synthesized species has been carried out revealing a correlation between the number of carbene ligands and ΔE1/2, and consequently with the RuIII disproportionation. The reactivity of these complexes has been tested with regard to the electrocatalytic oxidation of benzyl alcohol.Support from MINECO (CTQ2010-21497, CTQ2011-26440, CTQ2010-21532-C02-01, CTQ2009-08328, and CTQ2011-23121), “Torres y Quevedo” contract (X.S.) and Consolider Ingenio 2010 (CSD2006-0003) are gratefully acknowledge