title: High-Valent Manganese in Polyoxotungstates. 3. Dimanganese Complexes of gamma-Keggin Anions.
abstract: Dimanganese-substituted gamma-Keggin heteropoly tungstates have been synthesized by reaction of the lacunary species gamma-[(SiO(4))W(10)O(32)](8)(-) with appropriate mixtures of Mn(II) and MnO(4)(-). The crystal structure of [(CH(3))(3)(C(6)H(5))N](4)[(SiO(4))W(10)Mn(III)(2)O(36)H(6)].2CH(3)CN.H(2)O (anion 1) was determined by X-ray diffraction. Crystallographic data: space group P&onemacr;, a = 12.951(3) Å, b = 14.429(3) Å, c = 20.347(4) Å, alpha = 81.95(3) degrees, beta = 88.92(3) degrees, gamma = 67.48(3) degrees, V = 3475.2(13) Å(3), and Z = 2. The final R value is 7.29% for 15861 reflections with I > 2sigma(I). The anion has the anticipated gamma-Keggin structure with virtual C(2)(v)() symmetry. The two Mn cations occupy adjacent, edge-shared octahedra with bridging hydroxo and terminal aqua ligands. Anion 1 can be oxidized and reduced to the corresponding Mn(III)Mn(IV) (2) and Mn(II)(2) (3) species respectively. The magnetic susceptibility of 1 between 2 and 300 K indicates that the Mn(III) cations are antiferromagnetically coupled, with J = -17.0 cm(-)(1) and g = 1.965. No simple magnetic behavior was observed for 2 or 3.
authors.affiliation: Department of Chemistry, Georgetown University, Washington, D.C. 20057, and Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Zhang
authors.forename: Charles J.
authors.initials: CJ
authors.lastname: O'Connor
authors.forename: Geoffrey B.
authors.initials: GB
authors.lastname: Jameson
authors.forename: Michael T.
authors.initials: MT
authors.lastname: Pope