Organophosphoryl polyoxotungstate derivatives [gamma-SiW10O36(RPO)(2)](4-) (R = H (1), Et (2), n-Bu (3), t-Bu (4), C2H4COOH (5), Ph (6)) have been obtained by reaction of the divacant [gamma-SiW10O36](8-) anion with organophosphonic acids RPO(OH)(2) in acetonitrile. These new heteropolyanions have been characterized by elemental analysis, infrared spectroscopy, multinuclear (H-1, Si-29, P-31, and W-183) NMR, and X-ray crystallography. Crystals of (NBu4)(2)(NEt4)H[gamma-SiW10O36(C6H5PO)(2)] (anion 6) are monoclinic, space group P2(1), with lattice constants a = 16.489(4) Angstrom, b = 14.016(3) Angstrom, c = 18.542(8) Angstrom, beta = 91.30(3)degrees and Z = 2. The hybrid anion has a structure of virtual C-2v symmetry with two phenylphosphonate groups grafted to the surface of the divacant tungstosilicate. W-183 and P-31 NMR spectra of NBu4 salts in DMF solution agree with the solid-state structure and the virtual C-2v symmetry.