Synthesis, characterization and catalytic epoxidation properties of lanthanide-stabilized peroxoisopolytungstates

A series of new lanthanide-containing peroxoisopolyoxotungstates, K6Na4[H32{Ln4(WO4)(H2O)16[W7O22(O2)2]4}3]·105H2O [Ln = CeIII (1), NdIII (2), SmIII (3), TbIII (4), ErIII (5)], have been successfully synthesized and structurally characterized. All polyanions [LnIII4(WO4)(H2O)16{W7O22(O2)2}4]14− are isostructural and consist of a central [LnIII4(WO4)(H2O)16]10+ cluster surrounded by four peripheral [W7O22(O2)2]6− units. They could act as efficient recyclable catalysts for the epoxidation of various alkenes including different cycloalkenes, styrene derivatives, internal and long-chain alkenes. Under optimal conditions, catalyst 2 displays the best catalytic activity for the oxidation of cyclooctene with high cyclooctene conversion (98.3%) and excellent selectivity (up to 99%) and could be reused for three cycles with a negligible decrease in reactivity.