The bis-phenyltin-substituted, lone-pair-containing tungstoarsenate [(C6H5Sn)(2)AS(2)W(19)O(67)(H2O)](8-) (1) has been synthesized and characterized by multinuclear NMR, IR, and elemental analysis. Single-crystal X-ray analysis was carried out on (NH4)(7)Na[(C6H5Sn)(2)AS(2)W(19)O(67)(H2O)].17.5H(2)O (NH4-1), which crystallizes in the monoclinic system, space group P2(1)/c, with a = 18.3127(17) Angstrom, b = 24.403(2) Angstrom, c = 22.965(2) Angstrom, beta = 106.223(2)degrees, and Z = 4. Polyanion 1 consists of two B-alpha-((AsW9O33)-W-III) Keggin moieties linked via a WO(H2O) fragment and two SnC6H5 groups leading to a sandwich-type structure with nominal C-2v symmetry. Polyanion 1 is stable in solution as indicated by the expected 6-line pattern (4:4:4:4:2:1) in W-183 NMR and the expected Sn-119, C-13, and H-1 NMR spectra. Synthesis of 1 was accomplished by reaction of C6H5SnCl3 and K-14[AS(2)W(19)O(67)(H2O)] in a 2:1 molar ratio in aqueous acidic medium (pH 2). In the solid-state structure of NH4-1, neighboring polyanions are wealkly bound via W-O-Na bonds leading to chains which interact with each other via the phenyl rings resulting in a 2-D assembly.