Xy. Zhang et al., HIGH-VALENT MANGANESE IN POLYOXOTUNGSTATES .3. DIMANGANESE COMPLEXES OF GAMMA-KEGGIN ANIONS, Inorganic chemistry, 35(1), 1996, pp. 30-34
Dimanganese-substituted gamma-Keggin heteropoly tungstates have been s
ynthesized by reaction of the lacunary species gamma-[(SiO4)W10O32](8-
) with appropriate mixtures of Mn-II and MnO4-. The crystal structure
of [(CH3)(3)(C6H5)N](4)[(SiO4)(W10Mn2O36H6)-O-III]. H2O (anion 1) was
determined by X-ray diffraction. Crystallographic data: space group P
(1) over bar, a = 12.951(3) Angstrom, b = 14.429(3) Angstrom, c = 20.3
47(4) Angstrom, alpha = 81.95(3)degrees, beta = 88.92(3)degrees, gamma
= 67.48(3)degrees, V = 3475.2(13) Angstrom(3), and Z = 2. The final R
value is 7.29% for 15861 reflections with I > 2 sigma(I). The anion h
as the anticipated gamma-Keggin structure with virtual C-2v symmetry.
The two Mn cations occupy adjacent, edge-shared octahedra with bridgin
g hydroxo and terminal aqua ligands. Anion 1 can be oxidized and reduc
ed to the corresponding (MnMnIV)-Mn-III (2) and Mn-2(II) (3) species r
espectively. The magnetic susceptibility of 1 between 2 and 300 K indi
cates that the Mn-III cations are antiferromagnetically coupled, with
J = -17.0 cm(-1) and g = 1.965. No simple magnetic behavior was observ
ed for 2 or 3.