Electrochemistry of Ru 2Cp′ 2(CO) 4 and Ru 2Cp 2(CO) 3(PMe 3) and the estimation of Ru 2(μ-H) bond dissociation enthalpies

Abstract

The oxidation potentials for a series of diruthenium compounds have been measured. The heat of protonation (−Δ H MHM) and oxidation potentials ( E 1/2) for a series of Ru 2Cp′ 2(CO) 4 (Cp′=Cp 2, Cp* 2, C 5H 4CH 2C 5H 4, (C 5H 4CH 2) 2, (C 9H 7) 2, C 10H 8, (HBpz 3) 2) compounds and Ru 2Cp 2(CO) 3(PMe 3) were used to estimate the homolytic RuHRu bond dissociation enthalpy (BDEs) using a thermochemical cycle. Poor correlation between −Δ H MHM and E 1/2 was observed, as anticipated, due to the effects of the bridging carbonyls on the heats of protonation. There is a correlation between the oxidation potentials and the average ν CO bands for the protonated dimers as both are a measurement of the donor ability of the ligands. The calculated BDE values were also compared with values obtained for mononuclear ruthenium compounds.