Organophosphoryl derivatives of trivacant tungstophosphates of general formula α-A-[PW9O34(RPO)2]5-:: synthesis and structure determination by multinuclear magnetic resonance spectroscopy (31P, 183W)

In the presence of (NBu4Br)-Br-n acting as phase-transfer reagent, organophosphonic acids RPO(OH)(2) reacted in acetonitrile with the trivacant tungstophosphate sodium salt beta-A-Na-8[HPW9O34]. 24H(2)O to give hybrid organophosphoryl polyoxotungstate derivatives alpha-A-[NBu4n](3)Na-2[PW9O34(RPO)(2)] (R = Et 1, Bu-n 2, Bu-t 3, allyl 4 or Ph 5) in satisfactory yield (> 65%). The structure of the hybrid anions has been inferred from spectroscopic data, especially from multinuclear ((31)p, W-183) NMR studies. In particular, the five-line (1:2:2:2:2) W-183 spectrum indicates a lowering of the symmetry of the tungstophosphate framework from C-3v to C-s. According to spectroscopic observations and chemical analyses, the hybrid anion consists of an alpha-A-[PW9O34] framework on which are grafted two RPO groups through P-O-W bridges. This structure displays two nucleophilic oxygen atoms at the polyoxotungstate surface and thus remains unsaturated.