Cs-symmetric hafnocene complexes for synthesis of syndiotactic polypropene

Three new Cs-symmetric ansa-hafnocene complexes such as dichloro[η10-2,4-cyclopentadienyl-1-ylidenebis(4-methyldiphenyl-methylen)[2,7-bis(1,1-di-methylethyl)-9H-fluorene-9-ylidene]]hafnium (2) were synthesized which produce partiell syndiotactic polypropylenes with very high molecular weights. The influence of the methyl and methoxy substitution in the bridge was studied on the activity, tacticity, and molar mass. The hafnocene–MAO catalysts (1–4) were active up to polymerisation temperatures of 90 °C and produces 55 000 kg polymer in 1 h by 1 mol of hafnocene. The molecular weight of the obtained elastic polypropylene reaches 2.2 million g mol−1.