High-valent manganese in polyoxotungstates—II. Oxidation of the tetramanganese heteropolyanion [Mn 4(H 2O) 2(PW 9O 34) 2] 10−

Abstract

Oxidation of the heteropolyanion [Mn 4 II(H 2O) 2(PW 9O 34) 2] 10− ( 0) with potassium persulphate yielded mixed valence Mn II,III products reproducibly isolated as the green potassium salt of [Mn 4(H 2O) 2(PW 9O 34) 2] 9− ( 1) and the brown potassium-caesium salt of [Mn 4(OH) 2(PW 9O 34) 2] 9− ( 2). Coulometric and single crystal X-ray structure analysis revealed that 1 and 2 are one- and three-electron oxidized derivatives of 0 and are isostructural with 0. Slight metrical variations 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. The magnetic susceptibility of 1 between 2 and 300 K shows Curie-Weiss law behaviour, θ = −27.35 K, without the maximum for χ at T ≈ 16 K previously observed for 0.