.2 - [2 - (¦Ç ~ 5 - Cyclopentadienyl-yl) Ethyl]-1h-imidazole Ligands And Their Titanium (iv) Complexes Synthesis, Structure And Catalytic Activity Of The Study

Recently, a novel series of 2-(1H-imidazol-2-yl)ethyl-substituted cyclopentadienes was introduced as ligands into the further development of synthesis, structure and property of the Group 4 metals complexes.In the course of the present work, the synthetic routine and related techniques concerning the cyclopentadienes of the question has been considerably improved. Thus, 2-cyclopentadienyl-2,2-diphenylethyl-,2-cyclopentadienyl-2-phenylethyl-, and 2-cyclopentadienyl-2-methylpropyl-1H-imidazoles (2a,2c, and 2b, respectively) have been prepared by lithiation of 1-N-(diethoxymethyl)-2-methyl-1H-imidazole (1), followed by a reaction with an appropriate fulvene and subsequent mild-acidic hydrolysis. The dimer of ligand 2c which is named as rac-3,5-bis (IRS-2-phenylmethyl-1H-imidazole)-4,7-methano-1H-indene (2c')was obtained during the purification of 2c. Crystal and molecular structure of preference of 2c'has been established by X-ray diffraction analysis.Treatment of cyclopentadienes 2a and 2b with Ti(NEt2)4 in toluene at 80℃has been shown to afford formation of (2-cyclopentadienyl-2,2-diphenylethyl-1H-imidazolyl)-and (2-cyclopentadienyl-2-methylpropyl-1H-imidazolyl) bis(N,N-diethylamido)titaniums(Ⅳ) (3a and 3b). Crystal and molecular structure of 3b has been established by X-ray diffraction analysis.Treatment of complexes 3a and 3b with excess of chlorotrimethylsilane has been shown to lead to dichloro(2-cyclopentadienyl-2,2-diphenylethyl-1H-imidazolyl)-and trichloro (2-cyclopentadienyl-2-methylpropyl-l-trimethylsilyl-1H-imidazolyl)titaniums(Ⅳ) (8a and 6b', respectively). Crystal structure of complex 6b'has been established by X-ray diffraction analysis. In solutions, complex 6b'is stable only in presence of excess chlorotrimethylsilane, alternatively, it co-exists in an equilibrium with ca.15 mol.% of diichloro(2-cyclopentadienyl-2-methylpropyl-1H-imidazolyl)titanium(Ⅳ) (6b) (NMR spectroscopy data).Structures of all organic and organometallic compounds under discussion have been adequately confirmed by 1H and 13C NMR spectroscopy.Complexes 3a and 3b were used to catalyze hydroamination reaction. But they have low activity. And complexes 3b was examined its catalytic activity in respect to ethylene (co)polymerization. It turned out low activity.Complexes 6b' was examined its catalytic activity in respect to ethylene polymerization in presence of methylalumoxane (MAO; molar ratio Al:Ti 1000) under different temperature and reaction time. The tests revealed catalytic activity of the system is not changed a lot under different reaction conditions.