Organoarsonate Functionalization of Heteropolyoxotungstates.

Functionalization of the {PW} polyoxotungstate (POT) archetype with aromatic organoarsonates results in the first homometallic {PW} derivatives, with the general formula [(RAsO)PWO] [R = CH (1) or p-(HN)CH (2)]. Short As-O bonds here induce unusual bending of the otherwise rigid {PW} macrocycle, breaking its D symmetry. The obtained species also represent the first lacunary POTs functionalized with organoarsonates and can potentially act as polyoxometalate precursors themselves. We elaborate solution stability in different aqueous media using H and P NMR spectroscopy and possible pathways for subsequent transformations in aqueous solutions of the functionalized polyanions. Recrystallization of the K/Li/dimethylammonium salt of 2 from 4 M LiCl solution yielded a further functionalized POT, [(HNCHAsO)PWOH{WO(HO)}] (3), revealing dissociation of the organoarsonate fragments in slightly acidic aqueous solutions followed by their rearrangement within the inner POT cavity.