pi-Arene complexes. Part 12. Synthesis of chromiumtricarbonyl complexes ofquinoline and N-methylindoles and selected metallation reactions

The lithiation of indole, using a slight excess of n-butyl lithium in THF, followed by methylation and reaction with [Cr(CO)(6)] in refluxing dibutyl ether, resulted in the formation of [Cr(eta (6)-N-methylindole)(CO)(3)] (1a ) and [Cr(eta (6)-N-methyl-2-methyl-2-methylindole)(CO)(3)] (1b). In contra st, lithiation of quinoline in THF, silylation and the subsequent reaction with [Cr(CO)(6)] under similar reaction conditions, afforded [Cr(eta (6)-N- trimethylsilyl-2-butyl-1,2-dihydroquinoline)(CO)(3)] (2) and [Cr(eta (6)-{2 -butyl 1,2,3,4-tetrahydroquinoline})(CO)(3)] (3). The formation of [Cr(eta (6)-2,2'-bis{N-methylindolyl})(CO)(3)] (4) implied lithiation at the 2-posi tion of 1a. However, metallation at the 7-position was also indicated durin g the same reaction. In the presence of [Mn(CO)(5)Br], product 4 and the tr ansmetallation product [Cr(eta (6)-{7-(N-methylindolyl)Mn(CO)(5)})(CO)(3)] (5) were isolated. Reaction with titanocene dichloride gave [Cr(eta (6)-{2- (N-methylindolyl)TiCp2Cl})(CO)(3)] (6), which slowly converted into [TiCp2{ Cr(eta (6)-2-(N-methylindolyl) (CO)(3)}(2)] (7). (C) 2000 Elsevier Science B.V. All rights reserved.