Titanium complexes supported by imidazo[1,5-a]pyridine-containing pyrrolyl ligand as catalysts for hydroamination and polymerization reactions, and as an antitumor reagent

Abstract

A new imidazo[1,5-a]pyridine-containing pyrrolyl ligand HL (HL = 3-(1H-pyrrol-2-yl)imidazo[1,5-a]pyridine) was synthesized and employed in the organometallic chemistry of titanium. The syntheses, structures, catalytic properties and antitumor activity of three titanium complexes supported by HL are reported. Reactions of Ti(NMe₂)₄ and Ti(NEt₂)₄ with 2 equivalents of HL, led to the production of titanium bisamido complexes TiL₂(NMe₂)₂ (1) and TiL₂(NEt₂)₂ (2), respectively. Treatment of Ti(OⁱPr)₄ with 2 equivalents of HL resulted in the formation of TiL₂(OⁱPr)₂ (3). All complexes were characterized by elemental analyses and NMR studies. The solid-state structures of 2 and 3 were further established by single X-ray crystallography. The titanium bisamido complexes 1 and 2 are shown to be good pre-catalysts for the hydroamination of alkynes. Complex 1 was found to be an active catalyst for the ring-opening polymerization of ε-caprolactone. The cytotoxicity activities of 3 towards the tumor cells HCT-116, PC3 and MCF-7 were measured. Complex 3 exhibited good antitumor properties.