Preparation of titanocene and zirconocene dichlorides bearing bulky 1,4-dimethyl-2,3-diphenylcyclopentadienyl ligand and their behavior in polymerization of ethylene

New metallocene dichlorides [η5-(1,4-Me2-2,3-Ph2-C5H)2TiCl2] (2), [η5-(1,4-Me2-2,3-Ph2-C5H)2ZrCl2] (3) and [η5-(1,4-Me2-2,3-Ph2-C5H)η5-(C5H5)ZrCl2] (4) were prepared from lithium salt of 1,4-dimethyl-2,3-diphenylcyclopentadiene (1) and [TiCl3(THF)3], [ZrCl4] and [η5-(C5H5)ZrCl3(DME)], respectively. Compounds 2–4 were characterized by NMR spectroscopy, EI-MS and IR spectroscopy, and the solid state structure of 3 was determined by single crystal X-ray crystallography. The catalytic systems 3/MAO and 4/MAO were almost inactive in polymerization of ethylene at 30–50 °C, however, they exhibited high activity at temperature 80 °C. The catalyst formed from 2 and excess of MAO was practically inactive at all temperatures.

Graphical abstractSynthesis of new titanocene dichloride 2 and zirconocene dichlorides 3, 4 bearing bulky 1,4-dimethyl-2,3-diphenylcyclopentadienyl ligand and their catalytic activity in polymerization of ethylene have been described. Whereas both zirconocene dichlorides 3 and 4 in combination with methylaluminoxane (MAO) exhibited only negligible activity at 30–50 °C, they were highly active at 80 °C. The 2/MAO system was found practically inactive at the same conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide