Abstract

The electrochemical behavior of binuclear ruthenium(II) complexes of the type [{(arene)RuCl2}2] where arene = benzene (1), toluene (2), p-cymene (3) and hexamethylbenzene, (HMB) (4), have been studied by cyclic voltammetry, coulometry and voltammetry with rotating disk and ring-disk electrodes. These compounds undergo electrochemical quasi-reversible reduction in dimethylsulphoxide (DMSO) and acetonitrile (MeCN). The ruthenium(I) species formed react in a very fast chemical reaction (EC mechanisms), although the rate constants of electrochemical and chemical processes are different for the arenes studied. Conditional rate constants (k) and charge transfer coefficients (a ) for the cathodic reactions were determined by rotating disk techniques, and the kinetic collection efficiency (Nk) was determined with a rotating ring-disk electrode. On the other hand, the binuclear complexes 1 and 2 are quasi-reversibly oxidized in MeCN solution in two electron steps yielding binuclear Ru(III) species, while complex 3 is partially oxidized to give a mixture of products, and complex 4 generates a very unstable species, which chemically returns to the starting reduced complex