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Rationalization of the mechanism of in situ Pd(0) formation for cross-coupling reactions from novel unsymmetrical pincer palladacycles using DFT calculations

journal contribution
posted on 2023-06-09, 05:26 authored by Sarote Boonseng, Gavin W Roffe, Msugh Targema, John SpencerJohn Spencer, Hazel CoxHazel Cox
Density functional theory (DFT) is used to determine the mechanism for Pd(0) generation from pincer palladacycle pre-catalysts. The elucidated mechanisms comprise two key steps, transmetallation and reductive elimination. It is found that the presence of a base in the pre-catalyst activation step serves to significantly lower the Gibbs free energy barrier of the transmetallation step and the Gibbs free energy of the overall pre-catalyst activation. The DFT results are used to rationalize the catalytic activity of a number of pincer palladacycles in the Suzuki-Miyaura coupling of sterically demanding and electronically deactivated aryl bromides with 2-tolyboronic acid. A strong correlation exists between the Gibbs free energy barrier of the transmetallation step and/or overall pre-catalyst activation energy and the percentage conversions of the Suzuki- Miyaura coupling in the presence of the novel pre-catalysts. The data presented suggest that the slow, controlled release of the “true, active catalyst,” Pd(0), from the pincer palladacycle pre-catalysts provides the optimum reaction conditions and may be achieved by a high transmetallation energy barrier or overall pre-catalyst activation energy or both.

History

Publication status

  • Published

File Version

  • Accepted version

Journal

Journal of Organometallic Chemistry

ISSN

0022-328X

Publisher

Elsevier

Volume

845

Page range

71-81

Department affiliated with

  • Chemistry Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2017-03-13

First Open Access (FOA) Date

2018-03-01

First Compliant Deposit (FCD) Date

2017-03-12

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