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)‡

Abstract

In the presence of NBuⁿ₄Br acting as phase-transfer reagent, organophosphonic acids RPO(OH)₂ reacted in acetonitrile with the trivacant tungstophosphate sodium salt β-A-Na₈[HPW₉O₃₄]·24H₂O to give hybrid organophosphoryl polyoxotungstate derivatives α-A-[NBuⁿ₄]₃Na₂[PW₉O₃₄(RPO)₂] (R = Et 1, Buⁿ 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 (³¹P, ¹⁸³W) NMR studies. In particular, the five-line (1∶2∶2∶2∶2) ¹⁸³W 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 α-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.