Nitrenium ions and trivalent boron ligands as analogues of N-heterocyclic carbenes in olefin metathesis: a computational study
We used the density functional theory to evaluate the suitability of nitrenium ions and trivalent boron ligands as analogues of N-heterocyclic carbenes in ruthenium-based metathesis catalysts. We demonstrate that these analogues induce only minor structural changes in Hoveyda-Grubbs-like precatalyst...
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Veröffentlicht in: | Dalton transactions : an international journal of inorganic chemistry 2015-01, Vol.44 (46), p.20021-20026 |
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Sprache: | eng |
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Zusammenfassung: | We used the density functional theory to evaluate the suitability of nitrenium ions and trivalent boron ligands as analogues of N-heterocyclic carbenes in ruthenium-based metathesis catalysts. We demonstrate that these analogues induce only minor structural changes in Hoveyda-Grubbs-like precatalysts, but have major impact on precatalyst initiation. Nitrenium ion-modified precatalysts are characterized by a weak Ru-N bond resulting in a relatively strong Ru-O bond and large free energy barriers for initiation, making them good candidates for efficient latent Ru-based catalysts. On the other hand the trivalent boron ligand, bearing a formal -1 charge, binds strongly to the ruthenium ion, weakening the Ru-O bond and facilitating its dissociation, to promote fast reaction initiation. We show that the calculated bond dissociation energy of the Ru-C/N/B bond may serve as an accurate indicator of the Ru-O bond strength and the rate of metathesis initiation. |
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ISSN: | 1477-9226 1477-9234 |
DOI: | 10.1039/c5dt03446a |