Heterogeneous electron-transfer kinetics for some multiply bonded dirhenium complexes

Abstract

Standard electrochemical rate constants kexob have been measured for the two sequential one-electron oxidations of triply-bonded dirhenium(II) complexes Re2X4(PR3)4, where X = Cl or Br, and PR3 = a monodentate tertiary phosphine, and also for allied complexes in methylene chloride, acetonitrile, and N,N-dimethylformamide at platinum electrodes. The objective is to explore the possible dependence of kexob upon the known differences in the structural changes accompanying electron transfer. Although significant and even substantial variations in kexob were observed for closely related redox couples, the reactivity trends appear to be chiefly a consequence of differences in electrostatic work terms at the metal/solution interface. Comparisons are made with recent results for mononuclear organometallic redox couples.