Electrochemical studies of Mn 3HgM (M = Mo, W, Mn, Fe or Co) and Mn 3Au cluster anions

Abstract

The electrochemical behaviour of compounds of the type (PPh 4)[Mn 3(CO) 12( μ 3-H)(μ-Hgm)][m = Mo(CO) 3Cp( 1), W(CO) 3 Cp ( 2), Mn(CO) 5 ( 3), Fe(CO) 2 Cp ( 4) or Co(CO) 4 ( 5)] and the [PPh 4] + salts of the anions [{Mn 3(CO) 12( μ 3-H} 2Hg] 2− ( 6), [{Mn 3(CO) 12( μ 3-H)Au} 2(dppe)] 2− ( 7) and [{Mn 3(CO) 12( μ 3- H) Au} n( triphos)(AuCl) 3−n] n− [n = 1 ( 8), 2( 9), 3( 10)] has heen investigated at Pt (or Au) electrodes in CH 2Cl 2 or THF by means of cyclic voltammetry and coulometry. All the compounds undergo a quasi-reversible oxidation and an irreversible reduction. The electrons involved in both oxidation and reduction are delocalized mainly onto the metal fragments, Mn 3Hg and Mn 3Au, and the slight changes in the redox potential throughout the series of compounds are explained in terms of the nucleophilicity of the metal fragments, m. In the series of gold clusters a weak electronic interaction has been observed between the metal units through the triphosphine.