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

A series of new lanthanide-containing peroxoisopolyoxotungstates, KNa[H{Ln(WO)(HO)[WO(O)]}]·105HO [Ln = Ce (1), Nd (2), Sm (3), Tb (4), Er (5)], have been successfully synthesized and structurally characterized. All polyanions [Ln(WO)(HO){WO(O)}] are isostructural and consist of a central [Ln(WO)(HO)] cluster surrounded by four peripheral [WO(O)] 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.