Displacement of H 3 CB(C 6 F 5) 3 - anions from zirconocene methyl cations by neutral ligand molecules : equilibria, kinetics, and mechanisms

Schaper, Frank; Geyer, Armin; Brintzinger, Hans-Herbert

Displacement of H 3 CB(C 6 F 5) 3 - anions from zirconocene methyl cations by neutral ligand molecules : equilibria, kinetics, and mechanisms

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Datum

2002

Autor:innen

Schaper, Frank

Geyer, Armin

Brintzinger, Hans-Herbert

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Zeitschriftenartikel

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Erschienen in

Organometallics. 2002, 21(3), pp. 473-483. ISSN 0276-7333. eISSN 1520-6041. Available under: doi: 10.1021/om010671l

Zusammenfassung

The displacement of the MeB(C₆F₅)₃^- anion from seven different zirconocene methyl cations by neutral Lewis bases, such as dimethylaniline, benzyldimethylamine, and dinbutyl ether, was investigated by 1D and 2D NMR spectroscopy. Equilibrium constants for reactions with diⁿbutyl ether change by factors of less than 5 between the zirconocene contact ion pairs studied, despite substantial steric differences. Rate constants of this displacement reaction, however, change by a factor of more than 105 between Me₂Si(C₅H₄)₂ZrMe+MeB(C₆F₅)₃^-, the most "open" complex, and rac-Me₂Si(2-Me-BzInd)₂ZrMe+MeB(C₆F₅)₃^-, the most highly substituted species studied. Kinetic and stereochemical data indicate that Lewis base−anion exchange proceeds by way of an associative mechanism, which occurs without side change of the zirconium-bound methyl group. DFT calculations support an associative substitution mechanism and propose five-coordinated reaction intermediates with the Lewis base coordinated to the central coordination site.

Fachgebiet (DDC)

540 Chemie

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ISO 690

SCHAPER, Frank, Armin GEYER, Hans-Herbert BRINTZINGER, 2002. Displacement of H 3 CB(C 6 F 5) 3 - anions from zirconocene methyl cations by neutral ligand molecules : equilibria, kinetics, and mechanisms. In: Organometallics. 2002, 21(3), pp. 473-483. ISSN 0276-7333. eISSN 1520-6041. Available under: doi: 10.1021/om010671l

BibTex

@article{Schaper2002Displ-23731,
  year={2002},
  doi={10.1021/om010671l},
  title={Displacement of H 3 CB(C 6 F 5) 3 - anions from zirconocene methyl cations by neutral ligand molecules : equilibria, kinetics, and mechanisms},
  number={3},
  volume={21},
  issn={0276-7333},
  journal={Organometallics},
  pages={473--483},
  author={Schaper, Frank and Geyer, Armin and Brintzinger, Hans-Herbert}
}

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    <dcterms:abstract xml:lang="eng">The displacement of the MeB(C&lt;sub&gt;6&lt;/sub&gt;F&lt;sub&gt;5&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; anion from seven different zirconocene methyl cations by neutral Lewis bases, such as dimethylaniline, benzyldimethylamine, and dinbutyl ether, was investigated by 1D and 2D NMR spectroscopy. Equilibrium constants for reactions with di&lt;sup&gt;n&lt;/sup&gt;butyl ether change by factors of less than 5 between the zirconocene contact ion pairs studied, despite substantial steric differences. Rate constants of this displacement reaction, however, change by a factor of more than 105 between Me&lt;sub&gt;2&lt;/sub&gt;Si(C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;ZrMe+MeB(C&lt;sub&gt;6&lt;/sub&gt;F&lt;sub&gt;5&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, the most "open" complex, and rac-Me&lt;sub&gt;2&lt;/sub&gt;Si(2-Me-BzInd)&lt;sub&gt;2&lt;/sub&gt;ZrMe+MeB(C&lt;sub&gt;6&lt;/sub&gt;F&lt;sub&gt;5&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, the most highly substituted species studied. Kinetic and stereochemical data indicate that Lewis base−anion exchange proceeds by way of an associative mechanism, which occurs without side change of the zirconium-bound methyl group. DFT calculations support an associative substitution mechanism and propose five-coordinated reaction intermediates with the Lewis base coordinated to the central coordination site.</dcterms:abstract>
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