Tetrabutylammonium salts of tritransition-metal-substituted A-α-tungstogermanate: Halogen-free and single-component catalysts for the coupling reaction of carbon dioxide and epichlorohydrin

The green synthesis of chloropropylene carbonate via the coupling reaction of carbon dioxide and epichlorohydrin had been achieved using halogen-free and single-component catalysts tetrabutylammonium salts of tritransition-metal-substituted A-α-tungstogermanate [(n-C4H9)4N]3H7GeW9M3(H2O)3O37 (M = CuII, NiII, CoII and MnII) without any solvent. The catalytic activity was significantly depended on the transition metal introduced in polyoxometalates. [(n-C4H9)4N]3H7GeW9Mn3(H2O)3O37 exhibited the highest catalytic activity with 94.9% conversion for epichlorohydrin and 98% selectivity for chloropropylene carbonate in 3 h. Plausible mechanism was proposed based on the results.