title: Electrochemical synthesis and structural and physical characterization of one- and two-electron-reduced forms of [SMo12O40]2-.
abstract: Isolation of a soluble [NHex4]+ salt has allowed a detailed electrochemical study of the anion alpha-[SMo12O40]2- to be undertaken. Four reversible one-electron-reduction processes are observed in CH2Cl2 solution. Controlled potential electrolysis led to isolation of tetraalkylammonium salts of the one-electron-reduced anion alpha-[SMo12O40]3- and the two-electron-reduced anion alpha-[SMo12O40].4- [SMo12O40]3- is stable to disproportionation in dry solvents (Kdis = 10(-7.4). EPR and magnetic susceptibility data indicate that [SMo12O40]3- is a simple paramagnet (S = 1/2) while [SMo12O40]4- is paramagnetic with the mu eff values decreasing at low temperatures. Solutions of the two-electron-reduced species are EPR silent, but microcrystalline powders show very weak signals. The crystal structure of alpha-[NBu4]3[SMo12O40] has been determined (triclinic P1; a = 13.840(3) A; b = 15.587(4) A; c = 19.370(3) A; alpha = 94.82(2) degrees; beta = 93.10(1) degrees; gamma = 91.05(2) degrees; Z = 2). There is disorder around the C2 axis of the central SO4(2-) tetrahedron. In the presence of aqueous HClO4 (0.045 M) in thf/H2O or MeCN/H2O (98/2 v/v), [SMo12O40]2- exhibits five two-electron-reduction processes. Under these conditions, [SMo12O40]3- protonates and disproportionates into [SMo12O40]2- and the (2e-, 2H+)-reduced anion [H2SMo12O40]2-.
authors.affiliation: Department of Chemistry, PO Box 23, Monash University, Victoria 3800, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Vu
authors.forename: A M
authors.initials: AM
authors.lastname: Bond
authors.forename: D C
authors.initials: DC
authors.lastname: Hockless
authors.forename: B
authors.initials: B
authors.lastname: Moubaraki
authors.forename: K S
authors.initials: KS
authors.lastname: Murray
authors.forename: G
authors.initials: G
authors.lastname: Lazarev
authors.forename: A G
authors.initials: AG
authors.lastname: Wedd