Reactivity of a new family of diamido-diamine cyclam-based zirconium complexes in ethylene polymerization

Compounds of general formula [(*Bn(2)Cyclam)ZrCl(2)] (*Bn = 4-(t)BuC(6)H(4)CH(2), (4) and 4-CF(3)C(6)H(4)CH(2), ( 5)) were synthesised using Zr(CH(2)SiMe(3))(2)Cl(2)(Et(2)O)(2) and the corresponding ligand precursors 1,8-(4-(t)butylbenzyl)-1,4,8,11-tetraazacyclotetradecane (H(2)(4-(t)BuBn)(2)Cyclam), (4a), and 1,8-(4-trifluoromethylbenzyl)-1,4,8, 11-tetraazacyclotetradecane (H(2)(4-CF(3)Bn)(2)Cyclam), (5a). Complexes 4 and 5, in addition to other [(*Bn(2)Cyclam)ZrCl(2)] compounds previously described by some of us (*Bn = PhCH(2), ( 1), 3,5-Me(2)C(6)H(3)CH(2), (2) and 3,5-(t)Bu(2)C(6)H(3)CH(2), (3)) were tested in the polymerization of ethylene in the presence of MAO. System 4/MAO presents the highest activity ( 2790 g PE molZr(-1) h(-1) atm(-1)). The polymers formed are slight to moderately branched polyethylenes with a percentage of branching ranging between 1.2% and 3.3%. The melting points obtained by differential scanning calorimetry (DSC) ranging from 128 to 140 degrees C, are consistent with rather high average molecular weight polymers with crystallinity close to 50%. (C) 2010 Elsevier B. V. All rights reserved.