Establishing the NO oxidation state in complexes [Cl5(NO)M]n−, M = Ru or Ir, through experiments and DFT calculations

Abstract

Predominantly NO-centered reduction was observed by EPR and IR spectroelectrochemistry to occur reversibly at low temperatures for [Cl₅Ir(NO)]⁻. In contrast, the [Cl₅Ru(NO)]²⁻ ion was found to undergo only irreversible reduction but reversible oxidation to a ruthenium(III) species at −40°C. DFT calculations were used to establish the electronic structures and to rationalise the different stabilities. The calculations also reveal orientation-dependent energies and EPR properties between staggered and eclipsed conformations.