Titanium Catalysts with Linked Indenyl Amido Ligands for Hydroamination and Hydroaminoalkylation Reactions

Titanium complexes containing a bridging indenylethylamido ligand have been synthesized and used as catalysts for hydroamination and hydroaminoalkylation reactions. All dichloro titanium complexes (eta(5):eta(1)-Ind-C2H4-NR)TiCl2 (R = i-Pr (2a), t-Bu (2b), Cy (2c), Ph (2d)), which were prepared by reacting TiCl4(Et2O)(2) with Li-2[Ind-C2H4-NR], were fully characterized by single-crystal X-ray analysis. Reaction of 2a-c with methyllithium gave the thermally sensitive corresponding dimethyl titanium complexes [eta(5):eta(1)-Ind-C2H4-N(alkyl)]TiMe2 (alkyl = i-Pr (3a), t-Bu (3b), Cy (3c)), while the N-aryl-substituted dimethyl titanium complexes [eta(5):eta(1)-Ind-C2H4-N(aryl)]-TiMe2 (aryl = Ph (3d), p-MeOC6H4 (3e)) were directly prepared by reacting Li-2[Ind-C2H4-N(aryl)] with in situ generated Cl2TiMe2. In the case of complex 3d, the molecular structure could be determined by single-crystal X-ray analysis. All dimethyl titanium complexes (eta(5):eta(1)-Ind-C2H4-NR)TiMe2 (R = i-Pr (3a), t-Bu (3b), Cy (3c), Ph (3d), p-MeOC6H4 (3e)) were finally used as precatalysts for the intermolecular hydroaminoalkylation of 1-octene (4), the intramolecular hydroamination and hydroaminoalkylation reactions of aminoalkenes, and the intermolecular hydroamination of 1-phenylpropyne (12). These experiments showed that the N substituent of the indenylethylamido ligand strongly influences the activity of the catalysts in the individual reactions.