ONE-STEP CLOSER TO STRUCTURAL MODELS FOR HDS CATALYSTS - THIENYL-OXO COMPLEXES OF RE(V)

The present investigation focuses on thiophene derivatives of oxometal centers with low d-electron counts. Treatment of a THF slurry of ReOC l3(PPh(3))(2) with thienyllithium reagents afforded Li(THF)(n)ReO(thie nyl)(4) where thienyl is 2-C4H3S, 2-MeC(4)H(2), 2-C8H5S (benzothienyl) , and 2-C12H7S (dibenzothienyl). In contrast to the previously reporte d low-valent derivatives these species are reactive toward protic and oxidizing reagents. Electrochemical studies demonstrate that these Re- V complexes undergo oxidation at mild potentials. Crystallographic ana lyses of Li(THF)(3)ReO(C4H3S)(4) and Li(THF)(4)ReO(C8H5S)(4) indicate a square pyramidal Re center with the four thienyl ligands tilted in a pinwheel arrangement. Studies on Re(2-C4H3S)(CO)(5) reveal that it is stable toward hydrolysis.