MAS NMR-STUDY OF THE LAYERED HOST ALPHA-VANADYL PHOSPHATE DIHYDRATE -POTENTIAL AS A SHAPE-SELECTIVE CATALYST

Two magnetic resonance methods, magic-angle spinning (MAS) NMR and EPR , were used in the characterisation of the layered phase alpha-VOPO4 . 2H(2)O, and its n-butylammonium and n-butylamine intercalates. These revealed that intercalating molecules could replace water molecules in the coordination sphere of vanadium and that this influences the rela tive stability of the different oxidation states of the transition met al. Based on these findings, alpha-VOPO4 . 2H(2)O was tested for catal ytic activity in the Diels-Alder cycloaddition of methyl vinyl ketone to cyclopentadiene. The layered phase displayed some catalytic activit y with the ratio of products indicating a degree of shape selectivity. This catalysis was shown by EPR to involve electron donation to the l ayered host, with methyl vinyl ketone being intercalated (and activate d) as a radical cation.