2 - (1h-imidazole -2 -) Methyl-cyclopentadienyl Ligand And Its Complexes Synthesis Research

Synthesis and structural characterization of organometallic compounds containing N-donor ligands remain an area of a special interest in organometallic chemistry during the past twenty years. This interest is due to their rich structural diversity, along with their potential applications in industrial catalytic systems, biochemical systems, and material science.Recently, our group have synthesized two novel bidentate ligands, (cyclopenta-1,3-dien-2-yl)-2,2-diphenylmethyl-lH-imidazole (la) and (cyclopenta-1,3-dien-2-yl)-2-phenylmethyl-lH-imidazole (1b), and both of them have been already introduced as ligands for the further development of the Group 4 metal complexes derived from them.In the present work, the synthetic routines and related techniques concerning preparation of 6-phenylfulvene (a key prercursor) and ligand lb have been considerably improved.For instance, we have demonstrated that complete and thorough exclusion of air and moisture during the 6-phenylfulvene preparation along with application of the column chromatography instead of formerly used distillation under reduced pressure incredibly improves the yield of the target fulvene.The synthetic routines for ligand lb were also essentially improved. Thus, at the final purification step which follows acidic hydrolysis and neutralization, ligand lb was precipitated as a light yellow solid from the solution. After filtration, washing and drying, ligand lb was pure enough to be used in further procedures. This improvement nearly doubled the chemical yield of lb comparatively to earlier observed.Treatment of ligand la with Ti(NEt2)4 in toluene at 100℃afforded 2-[(η5-cyclopentadienyl)(diphenyl)methyl]-1H-imidazolido-κN]bis(N,N-diethylamido)titani-um(IV) (2a). Molecular structure of 2a has been established by an X-ray diffraction analysis and 1H NMR spectroscopy.Similarly, for the preparation of complexes (3a,3b), ligands la and lb were used to react with Zr(NEt2)4 respectively in toluene. Full purification and exhaustive characterization of these complexes appeared to be not a trivial task and is still in progress.