A series of bis(dithiolene)tungsten(IV,VI) complexes derived from benzene-1,2-dithiolate (bdt) has been prepared as an synthetic approach to pterin dithiolene-bound active sites of tungstoenzymes, one example of which, a archaeal oxidoreductase, has been established crystallographically (Chan et al. Science 1995, 267, 1463). With [WIVO(bdt)2]2- (2) as the starting compound, silylation with RR‘2SiCl afforded [WIV(bdt)2(OSiRR‘2)]1- (4). Oxidation of 4 with Me3NO gave [WVIO(bdt)2(OSiRR‘2)]1- (5), also accessible by silylation of [WVIO2(bdt)2]2- (3). Reaction of 3 or 5 with Me3SiCl resulted in [WVIO(bdt)2Cl]1- (6), from which the unstable species [WVIO(bdt)2L]1- (L = ButO-, PhS-) were generated in solution. Reductive oxo transfer of 6 with L‘ = P(OEt)3 or ButNC/P(OEt)3 gave [WIV(bdt)2L‘2] (8 and 9). Sulfido complex [WVIS(bdt)2(OSiRR‘2)]1- (12) was obtained in the reaction systems 4/(PhCH2S)2S and 5/(Me3Si)2S. Structures of [WO(SPh)4]1- and [W(bdt)3]2- and eight complexes of types 4−6, 8, 9, and 12 were determined by X-ray crystallography. Complexes 4 and 5 are tungsten analogues of the desoxo Mo(IV) and monooxo Mo(VI) states of Rhodobacter sphaeroides DMSO reductase. Six types of reactivity, including oxygen atom transfer, are recognized by the synthesis and interconversion of the set of complexes. The potential biological relevance of these complexes to the structure and function of active sites in two families of tungstoenzymes is considered (RR‘2 = Me3 (4); ButMe2 (4 and 5), ButPh2 (4, 5, and 12)).

A family of new coordination vanadium(IV) compounds supported by a terminal or bridged aryl imido ligand are reported. Reaction of V(NMe(2))(4) with anilines ArNH(2), where Ar = 2,6-i-Pr(2)-C(6)H(3), 2,6-Me(2)-C(6)H(3), Ph, 2,6-Cl(2)-C(6)H(3), and C(6)F(5), afforded the diamagnetic imido-bridged complexes [V(NAr)(NMe(2))(2)](2) (1a-e). Chlorination of 1a-e with trimethylchlorosilane afforded complexes 2a-e formulated as [V(=NAr)Cl(2)(NHMe(2))(x)()](n)(). One-pot reaction of V(NMe(2))(4) with ArNH(2) in the presence of an excess of trimethylchlorosilane gave the five-coordinate compound [V(=NAr)Cl(2)(NHMe(2))(2)] (3a-e). Reaction of 3a-e with pyridine, bipyridine (bipy), or N,N,N',N'-tetramethylethylenediamine (tmeda) gave respectively the six-coordinate tris- or bis(pyridine) adducts [V(=NAr)Cl(2)(Py)(3)] (4a-e) or [V(=NAr)Cl(2)(Py)(2)(NHMe(2))] (5a), bipyridine complexes [V(=NAr)Cl(2)(bipy)(NHMe(2))] (5a-e) and [V(=NAr)Cl(2)(bipy)(Py)] (9a), and tmeda adduct [V(=NAr)Cl(2)(tmeda)(NHMe(2))] (10a). Moreover, five-coordinate complexes free of NHMe(2) ligands, such as [V(=NAr)Cl(2)(Py)(2)] (5a), [V(=NAr)Cl(2)(bipy)] (8a), and [V(=NAr)Cl(2)(tmeda)] (11a), were directly prepared starting from precursors 2a-e. All compounds were totally characterized by spectroscopic methods (IR, (1)H NMR for diamagnetic complexes, and EPR for paramagnetic complexes), elemental analysis, magnetism, and single-crystal X-ray diffraction studies for 1b, 3a, 3d, 4b, 4d, 7c, 10a, and 11a.

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