ELECTROCHEMICAL STUDIES OF MN(3)HGM (M=MO, W, MN, FE OR CO) AND MN3AUCLUSTER ANIONS

The electrochemical behaviour of compounds of the type (PPh(4))[Mn-3(C O)(12)(mu(3)-H)(mu-Hgm)][m = Mo(CO)(3)Cp (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)(mu(3)-H)}Hg-2](2-) (6), [{Mn-3(CO)(12)(mu(3) -H>Au}(2)(dppe)](2-) (7) and -3(CO)(12)(mu(3)-H)Au}(n)(triphos)(AuCl)( 3-n)](n-) [n=1(8), 2(9), 3(10)] has been investigated at Pt (or Au) el ectrodes in CH2Cl2 or THF by means of cyclic voltammetry and coulometr y. All the compounds undergo a quasi-reversible oxidation and an irrev ersible reduction. The electrons involved in both oxidation and reduct ion are delocalized mainly onto the metal fragments, Mn3Hg and Mn3Au, 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 interac tion has been observed between the metal units through the triphosphin e.