Redox reactions of metallocenes with tungsten and molybdenum hexafluoride
Abstract
Tungsten and molybdenum hexafluoride react in acetonitrile with a series of metallocenes to give coloured salts. Oxidation of iodo-, bromo- and 1,1′-dibromo-ferrocene with both hexafluorides resulted in the formation of 1 : 1 halogenoferrocenium hexafluoro-tungstate(V) and -molybdate(V) compounds, [Fe(η-C5H5)(η-C5H4Br)][MF6], [Fe(η-C5H5)(η-C5H4I)][MF6] and [Fe(η-C5H4Br)2][MF6](M = W or Mo). Cobaltocene reduced MoF6 in a two-electron step to give a 2 : 1 adduct, [Co(η-C5H5)2·2MeCN]2[MoF6], while with WF6 the 1 : 1 product [Co(η-C5H5)2·2MeCN][WF6] was formed. The redox reactions involving metallocenes and the hexafluorides are in agreement with the thermodynamic stabilities of their oxidation states found by electrochemical methods. The electrode potentials obtained for the metallocene hexafluorometalates consist of the two one-electron reduction steps for [MF6]0/–/2–(M = W or Mo) and the reversible one-electron steps for the metallocene–metallocenium couples.