First stable nitrate-encapsulated sandwich type polyoxometalate: Synthesis, structural characterization, and catalytic performance

The X-ray structure of stable Na4K5[K3Cu3(NO3)(A-α-PW9O34)2] reveals three Cu(II) ions sandwiched between two A-α-PW9O34 moieties and a nitrate monoanion which are encapsulated in the same plane as the three Cu(II) atoms. The TBA salt of [K3Cu3(PW9O34)2] 9− revealed high catalytic activity and selectivity in the liquid phase epoxidation of alkenes with aqueous H2O2.