HIGH-VALENT MANGANESE IN POLYOXOTUNGSTATES .2. OXIDATION OF THE TETRAMANGANESE HETEROPOLYANION [MN-4(H2O)(2)(PW9O34)(2)](10-)

Oxidation of the heteropolyanion [Mn-4(II)(H2O)(2)(PW0O34)(2)](10-) (0 ) with potassium persulphate yielded mixed valence Mn-II,Mn-III produc ts reproducibly isolated as the green potassium salt of [Mn-4(H2O)(2)( PW9O34)(2)](9-) (1) and the brown potassium-caesium salt of [Mn-4(OH)( 2)(PW9O34)(2)](9-) (2). Coulometric and single crystal X-ray structure analysis revealed that 1 and 2 are one- and three-electron oxidized d erivatives of 0 and are isostructural with 0. Slight metrical variatio ns among 0, 1 and 2 appear in some Mn-O bond distances, which suggest that oxidation has occurred first at the aquated Mn(2) centres of 0. T he magnetic susceptibility of 1 between 2 and 300 K shows Curie-Weiss law behaviour, theta = -27.35 K, without the maximum for chi at T appr oximate to 16 K previously observed for 0.