A Baker-Figgis isomer of conventional sandwich polyoxometalates.: H2Na14[FeIII2(NaOH2)2(P2W15O56)2], a diiron catalyst for catalytic H2O2-based epoxidation

A new structural type of sandwich polyoxometalate has been synthesized and characterized. The X-ray structure of this diiron complex, [Fe-2(III)(NaOH2)(2)-(P2W15O56)(2)] reveals that the junction between the central unit (Fe2Na2) and the trivacant POM units is rotated 60 degrees from that observed in all other known sandwich POMs of this type. The tetra-n-butylammonium salt is an effective catalyst for the H2O2-based epoxidation of alkenes.