Polymerization of Ethylene by the Electrophilic Mixed Cyclopentadienylpyridylalkoxide Complexes [CpM{NC5H4(CR2O)-2}Cl2] (M = Ti, Zr, R = Ph, Pri)

The group 4 mixed-ligand compounds [CpM{NC5H4(CR2O)-2}Cl2] (M = Ti; R = Pri (1a), Ph (1b); M = Zr, R = Pri (2a), Ph (2b)) have been prepared and characterized. Single-crystal X-ray analyses reveal that 1a and 2b adopt four-legged piano-stool structures in which the cyclopentadienyl ligand is asymmetrically bonded and the pyridylalkoxide is bidentate. Toluene solutions of [CpM{NC5H4(CR2O)-2}Cl2] and methylaluminoxane catalyze the polymerization of ethylene, generating high molecular weight polymers with narrow molecular weight distributions. The activity of the titanium- and zirconium-based catalysts are comparable.