Transition-Metal-Substituted Keggin-Type Germanotungstates for Catalytic Conversion of Carbon Dioxide to Cyclic Carbonate

The tetra-n-heptylammonium salts of transition-metal-substituted (TMS) Keggin type germanotungstates [(n-C(7)H(15))(4)N](n)GeW(11)MO(39) (M = Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+) and Zn(2+), n = 5 or 6) were found to be efficient catalysts for cyclic carbonates synthesis from epoxides and CO(2) under solvent-free and halogen-free condition. The catalytic activities were significantly influenced by the transition metal and the countercation and a plausible mechanism was proposed.