The complex [Et(4)N](2)[(WO2)-O-VI(mnt)(2)] (1), [Et(4)N](2)[(WO)-O-IV(mnt)(2)] (2), and [Et(4)N](2)[(WO)-O-VI(S-2)(mnt)2] (3) (mnt(2-) = 1,2-dicyanoethylenedithiolate) have been synthesized as possible models for the tungsten cofactor of inactive red tungsten protein (RTP) and the active aldehyde ferredoxin oxidoreductase (AOR) of the hyperthermophilic archaeon Pyrococcus furiosus. The [Ph(4)P](+) salt of the complex anion of 1 . 2H(2)O crystallizes in space group Pbcn, with a = 20.526(3) Angstrom, b = 15.791(3) Angstrom, c = 17.641(3) Angstrom, and Z = 4. The (WO2S4)-O-VI core of [Ph(4)P](2)[(WO2)-O-VI(mnt)(2)]. 2H(2)O has distorted octahedral geometry with cis dioxo groups. 2 crystallizes in space group P2(1)2(1)2, with a = 14.78(3) Angstrom, b = 30.08(2) Angstrom, c = 7.37(4) Angstrom, and Z = 4. The complex anion of 2 has a distorted square-pyramidal structure with an axial W=O bond. 3 crystallizes in space group P2(1)/a, with a = 12.238(3) Angstrom, b = 18.873(2) Angstrom, c = 15.026(2) Angstrom, beta = 102.84(2)degrees, and Z = 4. The anion of 3 with a terminal oxo group and a dihapto disulfido ligand in an adjacent position is the first example of a seven-coordinate W(VI) species with bis-dithiolene coordination.