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Issue 25, 2013
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Zirconium and hafnium Salalen complexes in isospecific polymerisation of propylene

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Abstract

The activity of dibenzylzirconium and dibenzylhafnium Salalen complexes in polymerisation of propylene with MAO as a cocatalyst is described. Three Salalen ligand precursors combining a bulky alkyl group (1-adamantyl) on the imine-side phenol and electron withdrawing halo groups of different sizes on the amine-side phenol were explored. All metal complexes were obtained as single diastereomers. An X-ray crystallographic structure of a hafnium complex of an additional ligand carrying the combination of tert-butyl and chloro substituted phenolates, 4-Hf, revealed a facmer wrapping of the Salalen ligand around the metal centre. All complexes led to active catalysts in propylene polymerisation and to isotactic polypropylene of high regioregularity. The zirconium complexes led to polypropylene having molecular weights of Mw = 132 000–200 000 and isotacticities of [mmmm] = 65.7–75.0%. The hafnium complexes led to polypropylene of higher molecular weights of Mw = 375 000–520 000 and higher stereoregularities of [mmmm] = 80.6–89.3%, the highest isotacticity obtained with 3-Hf.

Graphical abstract: Zirconium and hafnium Salalen complexes in isospecific polymerisation of propylene

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Publication details

The article was received on 03 Jan 2013, accepted on 19 Feb 2013 and first published on 20 Feb 2013


Article type: Paper
DOI: 10.1039/C3DT00024A
Citation: Dalton Trans., 2013,42, 9096-9103
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    Zirconium and hafnium Salalen complexes in isospecific polymerisation of propylene

    K. Press, V. Venditto, I. Goldberg and M. Kol, Dalton Trans., 2013, 42, 9096
    DOI: 10.1039/C3DT00024A

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