Organoarsonates Enable Single-Site Condensation of Hexalacunary {P₂W₁₂} Polyoxotungstates

A systematic study of the condensation reactions of arylarsonic-functionalized [alpha-P2W12O48](14-) units in acidic aqueous media identified that the specific presence of an amino group in the ortho position of the phenyl rings induces a dimerization process that allowed isolation of discrete dimeric polyanions [(o-H2N-C6H4-AsO3)(4)P4W24O85](14-) (1) with an unprecedented polyoxometalate skeleton characterized by two seminal {P2W12} groups joined via a single W-O-W bridge. At the same time, addition of divalent transition metal ions (Mn-II, Co-II, and Ni-II) in the reaction mixture directed a condensation process on a completely different pathway resulting in one-dimensional (1D) coordination polymers based on V-shaped [{M(H2O)(4)}P4W24O92(C6H6AsNO)(2)](14-) polyanions (M = Mn-II (2), Co-II (3), and Ni-II (4)). All polyanions were isolated as hydrated mixed potassium/dimethylammonium salts and thoroughly characterized in the solid state. P-31 NMR studies showed that the discrete cluster 1 is comparatively stable in 1 M LiCl aqueous solution and thus represents a potential precursor for subsequent reactions.