Structures, magnetic and catalytic properties of three sandwich-type silicotungstates containing tetranuclear copper(II) clusters

Three sandwich-type silicotungstates. formulated as [Cu-4(H2O)(2)(SiW9O34)(2)] 12NH(4) 22H(2)O (1), [Cu-4(H2O)(2)(SiW9O34)(2)] 12NH(4) 11H(2)P (2) and {[Cu(NH3)(4)](2)[Cu(H2O)(4)][Cu-4(H2O)(2)(SiW9O34)(2)]} 2[Cu(NH3)(4)(H2O)] 2NH(4) 6H(2)O (3), were synthesized by microwave irradiation and hydrothermal reaction Crystal structural analysis reveals that 1-3 possess the same dimeric polyoxoanions [Cu(2)StW(9)O(34) (H2O)(2)(12-) featuring tetranuclear copper(II) clusters Magnetic studies indicate that the Cu., clusters exhibit ferromagnetic coupling interactions Investigation on their catalytic activity for the oxidation of ethylbenzene suggests that catalytic activity of 1-3 is closely related to the acidity of complexes and the existence of unsaturated coordination sites in the complex