Electrochemistry of Ru2Cp2′(CO)4 and Ru2Cp2(CO)3(PMe3) and the estimation of Ru2(μ-H) bond dissociation enthalpies

The oxidation potentials for a series of diruthenium compounds have been measured. The heat of protonation (-DeltaH(MHM)) and oxidation potentials (E-1/2) for a series of Ru2Cp2(CO)(4) (Cp' = Cp-2, Cp-2(*), C5H4CH2C5H4, (C5H4CH2)(2), (C9H7)(2), C10H8, (HBpz(3))(2)) compounds and Ru2Cp2(CO)(3)(PMe3) were used to estimate the homolytic Ru-H-Ru bond dissociation enthalpy (BDEs) using a thermochemical cycle. Poor correlation between - DeltaH(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 nu(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. (C) 2002 Elsevier Science B.V. All rights reserved.