Discrimination of σ‐Bond Metathesis Pathways in H/D Exchange Reactions on [(SiO)3ZrH]: A Density Functional Theory Study
10.1002/cphc.200200495
Crossref journal-article
Wiley
ChemPhysChem (311)
Abstract

AbstractThe mechanism of the H/D exchange reaction in alkane/hydrogen mixtures on silica‐supported zirconium hydride was investigated by a modelling study using density functional theory (DFT) calculations. The electronic activation enthalpy (ΔH${^{\ne }_{\rm elec}}$) for the CH bond activation step (TS3) was calculated to be around 92 kJ mol−1, whereas it would be 258 kJ mol−1 for a direct exchange process (TS1, also called the kite TS). These data clearly speak in favour of the former as a mechanism for CH bond scrambling. Moreover, the calculated enthalpy of activation (ΔH${^{\ne }_{{\rm elec}}}$) for H/D exchange in H2/D2 mixtures (TS2) is 33.5 kJ mol−1, which shows that this reaction is much faster than the H/D scrambling in alkane/H2 mixtures, as shown experimentally. Additionally, the calculated activation entropies (For TS1–4, ΔS${^{\ne }_{{\rm tot}}}$ ranges between −129 and −174 J mol−1 K−1) are very negative. Although the calculated activation entropies are also in full agreement with experimental data (ΔS${^{\ne }_{{\rm exp}}}$=−113 J mol−1 K−1), overall, the calculated activation enthalpies are much higher than the experimental ones. This suggests that the actual catalyst is probably more electrophilic than the model chosen for the calculations.

Bibliography

Copéret, C., Grouiller, A., Basset, J., & Chermette, H. (2003). Discrimination of σ‐Bond Metathesis Pathways in H/D Exchange Reactions on [(SiO)3ZrH]: A Density Functional Theory Study. ChemPhysChem, 4(6), 608–611. Portico.

Authors 4
  1. Christophe Copéret (first)
  2. Annie Grouiller (additional)
  3. Jean‐Marie Basset (additional)
  4. Henry Chermette (additional)
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Dates
Type When
Created 21 years, 2 months ago (June 28, 2004, 5:03 p.m.)
Deposited 1 year, 10 months ago (Oct. 9, 2023, 4:07 p.m.)
Indexed 1 year, 8 months ago (Dec. 13, 2023, 9:05 a.m.)
Issued 22 years, 3 months ago (June 6, 2003)
Published 22 years, 3 months ago (June 6, 2003)
Published Online 22 years, 3 months ago (June 6, 2003)
Published Print 22 years, 2 months ago (June 16, 2003)
Funders 0

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@article{Cop_ret_2003, title={Discrimination of σ‐Bond Metathesis Pathways in H/D Exchange Reactions on [(SiO)3ZrH]: A Density Functional Theory Study}, volume={4}, ISSN={1439-7641}, url={http://dx.doi.org/10.1002/cphc.200200495}, DOI={10.1002/cphc.200200495}, number={6}, journal={ChemPhysChem}, publisher={Wiley}, author={Copéret, Christophe and Grouiller, Annie and Basset, Jean‐Marie and Chermette, Henry}, year={2003}, month=jun, pages={608–611} }