Rate constants for the coupled two-electron/halide transfer self-exchange reactions of [Cp2MX]+ with Cp2M (M = Ru, Os; X = Cl, Br) have been measured in CD3CN at 298 K by 2D NMR spectroscopic techniques. Including data for the iodo complexes, the rates vary over 6 orders of magnitude depending on the metal and the halide, with the relative orderings I > Br > Cl and Ru > Os. The relative reactant state free energies for the ruthenium complexes have been determined from halide substitution equilibria and indicate that the reactant state energy ordering is Cl < Br < I. From these data and the free energies of activation for the self-exchange reactions, the relative transition state energies have been determined. A reaction coordinate and orbital correlation is proposed which rationalizes the observed data.

[Cp2RuCl]PF6 reacts with benzylruthenocene in acetonitrile with a 1:1 stoichiometry to produce Cp2Ru and phenylruthenocenyl methylium cation. Similar hydride abstraction reactivity has also been observed with diruthenocenylmethane, ethylruthenocene, and benzylferrocene. The complexes [Cp2MX]+ (M = Ru, Os; X = Cl, Br, I) also react with leuco crystal violet and leuco malachite green to give the corresponding carbenium ions but do not exhibit any detectable reactivity with triphenylmethane, cycloheptatriene, or xanthene. On the basis of these observations, the pK R + values for the [Cp2MX]+ species are estimated to be between +4.7 and +6.9.