Organoarsonates Enable Single-Site Condensation of Hexalacunary {P 2 W 12 } Polyoxotungstates.

A systematic study of the condensation reactions of arylarsonic-functionalized [α-P 2 W 12 O 48 ] 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 -H 2 N-C 6 H 4 -AsO 3 ) 4 P 4 W 24 O 85 ] 14- ( 1 ) with an unprecedented polyoxometalate skeleton characterized by two seminal {P 2 W 12 } 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(H 2 O) 4 }P 4 W 24 O 92 (C 6 H 6 AsNO) 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. 31 P 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.