HIGH-VALENT MANGANESE IN POLYOXOTUNGSTATES .1. MANGANESE(IV) KEGGIN DERIVATIVES

Aqueous and non-aqueous soluble salts of manganese(IV)-containing Kegg in polyoxotungstates [(XO(4))(W11MnO36H)-O-IVx](n-) (X = Si, B, and Zn ) have been prepared by chemical and electrolytic oxidation of corresp onding manganese(II) or manganese(III) anions, and have been character ized by magnetic susceptibilities, ESR and X-ray absorption near-edge spectroscopy (XANES), in addition to conventional elemental and spectr oscopic analyses. The crystal structure of dark brown K-7[(ZnO4)(W11Mn O36H)-O-IV].19H(2)O (I) was determined by X-ray diffraction and reveal s a disordered Keggin anion. Manganese EXAFS investigation of I and th e corresponding manganese(II) complex, which contains a terminal Mn-II -OH2 group, strongly indicates that I contains Mn-IV-OH (r(Mn-O) simil ar to 1.82 Angstrom) rather than Mn-IV=O.