Synthesis, structure and catalytic behaviour in oxidation of cyclohexene of K₄H₂[SiW₅Mo₆M(H ₂O)O₃₉]-xH₂O (M=Mn²⁺, Co ²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd ²⁺)

A series of the title complexes were synthesised. The general molecular formula K₄H₂[SiW_sMo₆M(H ₂O)O₃₉]-xH₂O denoted as MW₅ (M=Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn ²⁺, Cd²⁺) was determined by means of chemical analysis and thermoanalysis. IR-spectra, UV-spectra, XPS-spectra, and thermal decomposition were systematically investigated. The crystal structure of K ₄H₂[SiW₅Mo₆Mn(H₂O)O ₃₉]-22H₂O was determined. The compounds were studied in oxidation of cyclohexene with 30% hydrogen peroxide as oxidant, which indicated that these transition-metal-substituted polyoxometalates were more effective than their corresponding parent compounds.