PREPARATION OF BIS(ETA(6)-2-R-BENZO[B]THIOPHENE)-CHROMIUM AND BIS(ETA(6)-2-R-BENZO[B]THIOPHENE)-MOLYBDENUM (R=H, ME, SIME(3)) SANDWICH COMPLEXES VIA METAL VAPOR SYNTHESIS - CRYSTAL-STRUCTURE OF [CR(ETA(6)-2-MEC8H5S)(2)]

Co-condensation of chromium atoms with benzo[b]thiophene, 2-methylbenz o[b]thiophene or 2-trimethylsilylbenzo[b]thiophene at 77 K yields the sandwich complexes [Cr(eta(6)-C8H6S)(2)] (1), [Cr(eta(6)-2-MeC(8)H(5)S )(2)] (2) and [Cr(eta(6)-2-SiMe(3)C(8)H(5)S)(2)] (3). The molybdenum c omplex [Mo(eta(6)-2-MeC(8)H(5)S)(2)] (4) was prepared analogously. Com plexes 1, 2 and 4 exist as a mixture of diastereoisomers as indicated by H-1 and C-13 NMR spectroscopy, with mesomeric and racemic forms pre sent in the ratios 1:1 for 1 and 1:2 for 2 and 4. The mesomeric form o f complex 2 was also studied by single-crystal X-ray diffraction which confirmed eta(6)-ligation of the arene function of both 2-methylbenzo [b]thiophene rings.