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  On the mechanism of olefin polymerisation with titanium β-diketonato complexes. A model density functional study

Bühl, M., & Mauschick, F. T. (2002). On the mechanism of olefin polymerisation with titanium β-diketonato complexes. A model density functional study. Journal of Organometallic Chemistry, 648(1-2), 126-133. doi:10.1016/S0022-328X(01)01448-6.

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 Creators:
Bühl, M.1, Author           
Mauschick, F. T.2, Author           
Affiliations:
1Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445590              
2Research Group Bühl, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445601              

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Free keywords: olefin polymerisation; titanium beta-diketonato complex; density functional study
 Abstract: According to density functional calculations (BP86/AEI + ZPE level) for a model system with L = HC(O)CHC(O)H, cationic titanium complexes of the type L2TiR+ (R = growing alkyl chain) can be viable intermediates in the homogeneous olefin polymerisation catalysed by titanium beta-diketonato complexes. As with the related cationic metallocenes. olefin insertion in beta- and alpha-agostic intermediates is a facile process. Little activation for chain propagation is computed on the potential energy surface, 2.9 kcal mol(-1) (incl. ZPE), but this value is raised to 15.8 kcal mol(-1) on the free energy surface at 298 K. The main portion of this total barrier stems from the entropic destabilisation of the intermediate olefin pi-complexes. Chain termination via P-H transfer requires significantly higher activation, consistent with the observation of olefin polymerisation, rather than oligomerisation. Electron-withdrawing substituents at the diketonate ligand are predicted to lower the barrier for chain propagation by as much as 4.5 or 5.4 kcal mol(-1) for L = F3CC(O)CHC(O)CF3 (hfac) or NCC(O)CHC(O)CN. respectively. Thus, hfac complexes should produce highly active catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.

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Language(s): eng - English
 Dates: 2002-04-01
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 20112
DOI: 10.1016/S0022-328X(01)01448-6
ISI: 000175170100017
 Degree: -

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Title: Journal of Organometallic Chemistry
  Alternative Title : J. Organomet. Chem.
Source Genre: Journal
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Pages: - Volume / Issue: 648 (1-2) Sequence Number: - Start / End Page: 126 - 133 Identifier: ISSN: 0022-328X