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A Theoretical Study of Structure and Reactivity of Titanium Chlorides

  • C. Martinsky
  • C. Minot
Part of the Progress in Theoretical Chemistry and Physics book series (PTCP, volume 7)

Abstract

The study of various TiLn species (L=Cl, H, CH3) is a prerequisite for understanding the mechanism of the Ziegler-Natta reaction. The oxidation state of the titanium chloride active sites in the heterogeneous catalyst remains uncertain. The aim of this study is to provide better comprehension of the bonding in TiCln compounds and to compare their reactivity toward simple reactants in order to help investigating adsorption and catalysis. From DFT-GGA calculations we show that the increase in coordination of titanium shortens the TiCl bond, increasing their covalent component. The TiCl bond remains, however, very ionic and very strong. On the contrary, the TiH and TiC bonds are rather weak; this allows the titanium complexes to loose such ligands and thus form hydrocarbons. TiCl3 structures have unusual geometries that do not obey the Valence-Shell Electron-Pair Rules. Such deviations can be understood in terms of molecular orbital analysis. We also provide a topological description of the Electron Localisation Function (ELF) that explains the arrangement of the H atoms in terms of the ligand field around the titanium atom. Lewis bases and Cl radicals react at the Ti centre, TiCl3 being the most reactive structure. Lewis acids and H and CH3 radicals react with the ligand, initiating their abstraction; then, the products remain in high spin states.

Keywords

High Spin State Titanium Atom Electron Localisation Function Titanium Hydride Titanium Chloride 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • C. Martinsky
    • 1
  • C. Minot
    • 1
  1. 1.Laboratoire de Chimie Théorique, UMR 7616 CNRS, Boîte 137, Tour 23-22Université P. et M. CurieParis Cedex O5France

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