An approach to the synthesis of polyoxometalate encapsulating different kinds of oxoanions as heteroions: bisphosphitopyrophosphatotriacontamolybdate [(HPO3)2(P2O7)Mo30O90]8-.

A yellow [(HPO3)2(P2O7)Mo30O90]8− anion was prepared as a tetrapropylammonium (Pr4N+) salt from a 50 mM MoVI−2 mM P2O74−−4 mM HPO32−−0.95 M HCl−60% (v/v) CH3CN system at ambient temperature. The (Pr4N)8[(HPO3)2(P2O7)Mo30O90] salt crystallized in the orthorhombic space group Pnma (No. 62), with a = 30.827(2) A, b = 22.8060(15) A, c = 30.928(2) A, V = 21743(3) A3, and Z = 4. The structure contained a (P2O7)Mo12O42 fragment derived from the removal of each corner-shared Mo3O13 unit in a polar position from a [(P2O7)Mo18O54]4− structure, and each side of the (P2O7)Mo12O42 fragment was capped by a B-type (HPO3)Mo9O24 unit. The [(HPO3)2(P2O7)Mo30O90]8− anion was characterized by voltammetry and IR, UV−vis, and 31P NMR spectroscopy. Unlike the Keggin and Dawson anions and the parent [(P2O7)Mo18O54]4− anion, the [(HPO3)2(P2O7)Mo30O90]8− anion exhibited two-electron redox waves in CH3CN with and without acid.