abstract
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.
keywords
HIGH-DENSITY POLYETHYLENES; GROUP-4 METAL-COMPLEXES; OLEFIN POLYMERIZATION; ALPHA-OLEFINS; RHEOLOGICAL PROPERTIES; LIVING POLYMERIZATION; MACROCYCLIC LIGAND; HAFNIUM COMPLEXES; DONOR LIGANDS; CATALYSTS
subject category
Chemistry
authors
Alves, LG; Antunes, MA; Matos, I; Munha, RF; Duarte, MT; Fernandes, AC; Marques, MM; Martins, AM
our authors
Rui Munhá
Post-doc FellowshipGroups
acknowledgements
The authors are grateful to Fundacao para a Ciencia e a Tecnologia, Portugal, for funding (Research Projects PPCDT/QUI/55744/2004 and PTDC/QUI/66187/2006 and Fellowships SFRH/BD/44295/2008, SFRH/BPD/26745/2006, SFRH/BPD/34659/2007 and SFRH/BD/29986/2006) and to the Portuguese NMR Network (IST-UTL Center) for providing access to the NMR facility.