STEPWISE ACTIVATION OF SIGMA-THIENYL LIGANDS AT DI-TUNGSTEN CENTERS

The attachment of sigma-2-thienyl and sigma-2-benzothienyl ligands (bu t not sigma-3-thiophenyl ligands) to W2(6+) containing centres leads t o the stepwise opening of the five-membered ring to generate, in the p resence of tert-butyl alcohol, a novel thiolato-mu-alkylidyne metalloc ycle in W2(OBut)5(mu-SC4H4)(eta1-2-SC4H3), which has been structurally characterized; the intermediate W2(OBut)4(mu-SC4H3)(eta1-2-SC4H3), wh ich contains a bridging thiolato-vinylidene metallocycle has been char acterized by NMR spectroscopy.