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

A series of new lanthanide-containing peroxoisopolyoxotungstates, K6 Na4 [H32 {Ln4 (WO4 )(H2 O)16 [W7 O22 (O2 )2 ]4 }3 ]·105H2 O [Ln = CeIII (1), NdIII (2), SmIII (3), TbIII (4), ErIII (5)], have been successfully synthesized and structurally characterized. All polyanions [Ln(WO4 )(H2 O)16 {W7 O22 (O2 )2 }4 ]14- are isostructural and consist of a central [Ln(WO4 )(H2 O)16 ]10+ cluster surrounded by four peripheral [W7 O22 (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.