Using the reagents bis(tetrahydrofuran)tetrachloro niobium, tetraethylammonium hexacarbonyl niobium, and bis(mesitylene) niobium, new organoniobium complexes were prepared, and data from 1H NMR spectra, IR spectra, mass spectrometry experiments, and X-ray diffraction studies are presented. Reactions of Cr(CO)3([Eta]6-BT), in which the Cr is [Pi]-coordinated to the benzene ring of benzo[b]thiophene (BT), with CP'(CO)2Re(THF), where Cp'= [Eta]5-C5H5 or C5Me5, give the products CP'(CO)2Re([Eta]2:[Eta]6-[Mu]2-BT)Cr(CO)3 in which the Cr remains coordinated to the benzene ring and Re is bound to the C(2)=C(3) double bond.
An X-ray diffraction study of Cp(CO)2Re([Eta]2:[Eta]6-[Mu]2-BT)Cr(CO)3 (3) provides details of the geometry. This structure contrasts with that of the CP'(CO)2Re(BT) complexes that exist as mixtures of isomers in which the BT is coordinated to the Re through either the double bond (2,3-[Eta]2) or the sulfur ([Eta]1 (S)). Thus, the electron-withdrawing Cr(CO)3 group in 3 stabilizes the 2,3-[Eta]2 mode of BT coordination to the CP'(CO)2Re fragment. Implications of these results for catalytic hydrodesulfurization of BT are discussed. Crystal data for 3: triclinic, space group P [line above 1], a=6.716(2), b= 11.651(2), c= 11.956(2) Å, [Alpha]=70.20(2), [Beta]=74.84(2), [Gamma]=89.90(2) 0, Z=2
