ELECTROCHEMICAL REDUCTION PATHWAYS OF THE RHODOCENIUM ION - DIMERIZATION AND REDUCTION OF RHODOCENE

The electrochemical reduction of the rhodocenium ion, Cp2Rh+, and its dicarbollide analogue, [(B9C2Hu)2Rh]-, has been studied in nonaqueous solvents by dc and ac polarography, cyclic voltammetry, and controlled potential coulometry. The starting Rh(III) complexes can both be reduced in two separate one-electron processes to Rh(II) and Rh(I) compounds which are very reactive. Cp2Rh has a lifetime of about 2 s at room temperature but can be stabilized by performing the electrolysis at low temperatures. Rhodocene decomposes by dimerizing to form [Cp2Rh]2, which can be isolated in good yield by electrolysis of Cp2Rh+ solutions. Evidence is presented for the transient existence of the rhodocene anion, and comparison to the reduction of Cp2Co+ is made. © 1979, American Chemical Society. All rights reserved.