Sulfur atom transfer reactions of tungsten(VI) and tungsten(IV) chalcogenide complexes

Abstract

The sulfur, oxygen and chlorine atom transfer reactions of thio-W(VI) and -W(IV) complexes containing monodentate and ambidentate dithiophosphinate co-ligands are examined. Systems featuring monodentate ligands are complicated by the instability of the W(IV) species; significantly and in contrast to observations in thio-Mo chemistry, thio-W(VI) complexes such as Tp*WS 2Cl fail to react with cyanide. Dithiophosphinate systems are more tractable and amenable to full description. The oxo-thio and bis(thio) complexes, Tp*WOS(S 2PPh 2- S) and Tp*WS 2(S 2PPh 2- S) [Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate] undergo sulfur atom transfer to tertiary phosphines to produce Tp*WO(S 2PPh 2- S, S ′) and Tp*WS(S 2PPh 2- S, S ′), respectively, and phosphine sulfides. The X-ray crystal structures of Tp*WS 2(S 2PPh 2) · 0.5CH 2Cl 2 and Tp*WS(S 2PPh 2) have been determined. Both complexes possess six-coordinate, distorted-octahedral tungsten centers ligated by tridentate fac-Tp*, terminal thio (W=S=2.139–2.143 Å) and mono- or bidentate dithiophosphinate ligands, respectively. The W(IV) complexes, Tp*WE(S 2PPh 2) (E=O, S), react with sulfur atom donors to produce thio-W(VI) complexes, Tp*WES(S 2PPh 2) but with oxygen atom donors to yield mixtures of Tp*WOE(S 2PPh 2) and Tp*WES{SP(O)Ph 2- S}. The latter result from oxygen atom transfer to phosphorus with concomitant sulfur atom transfer from phosphorus to tungsten. Catalytic sulfur atom transfer by thio-W complexes is demonstrated for the first time.