Electrochemical oxidation and reduction of Rh[Ph2PC(S)NR]3 (R = Ph, Me), Rh[Me2NC(S)NPh]3 and Rh[Bu2NC(S)S]3. Generation of rhodium(I) species and their reaction with carbon monoxide

Abstract

Abstract Cyclic voltammetry and pulse polarography show that under nitrogen, the complexes Rh[Ph 2 PC(S)NR] 3 (R = Ph, Me), Rh[Me 2 NC(S)NPh] 3 and Rh[Bu 2 NC(S)S] are chemically irreversibly oxidised in a one-electron process. Upon oxidation of Rh[Bu 2 NC(S)S] 3 , the dimeric species Rh 2 [Bu 2 NC(S)S] + 5 is most probably formed. Introduction of CO has no influence on the cyclic voltammograms. Under nitrogen the complexes Rh[Ph 2 PC(S)NR] 3 and Rh[Bu 2 NC(S)S] 3 are chemically irreversibly reduced in a two-electron process, yielding Rh(I)-species. The reduced product is oxidised in a one-electron step, probably resulting in an unstable Rh(II)-complex. For Rh[Ph 2 PC(S)NR] 3 no splitting off of a ligand is observed, whereas under CO one phosphino ligand is displaced by CO after the electrochemical reduction. Even under nitrogen Rh[Bu 2 NC(S)S] 3 displays liberation of dithiocarbamate upon reduction. Under CO the two-electron reduction at the same low potential is immediately followed by substitution of the ligand with CO and further reduction to presumably [Rh(CO) 4 ] − . The is supported by the considerable increase of the oxidation-wave of the free [Bu 2 NC(S)S] − ligand and the observation that the complex Rh(CO) 2 [Et 2 NC(S)S] is reduced at a lower potential.