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Understanding the activation and speciation of the active species in nickel catalysis


   Department of Pure and Applied Chemistry


About the Project

Nickel-catalysed methodology often relies on the in-situ formation of an active catalyst from a nickel complex and an ancillary ligand. This can be ‘simple’ ligand exchange at a nickel(0) complex or the reduction of a nickel(II)/ligand complex to nickel(I) or nickel(0). When the ancillary ligand is an N-heterocyclic carbene (NHC), this is typically added as an azolium salt which must be deprotonated. The in-situ formation of the active catalyst is convenient for screening reaction conditions or for high-throughput experimentation, but a lack of turnover might then be the result of the active catalyst: (i) being ineffective for the transformation of interest; (ii) forming too slowly or even not forming at all; (iii) being inhibited by pre-catalyst initiation by-products; or (iv) being unstable under the reaction conditions, and therefore prone to decomposition.

This hinders attempts to understand ligand effects in a structured and data-driven manner: ligand structure will affect the rate of active catalyst formation, the speciation of the active catalyst, the rate and selectivity of the reaction of interest, and the rate at which the active catalyst decomposes. This is especially important as the use of machine learning and other data analysis techniques take an increasing role in reaction understanding and optimisation, because these require high-quality datasets. Furthermore, the use of single time-point yields makes it difficult to assess whether reaction failure is due to slow turnover, or to rapid turnover plus rapid catalyst death. This project comprises a detailed and structured analysis of the way(s) in which nickel (pre)-catalysts generate active catalysts, and how this process depends on ancillary ligand structure and reaction conditions. This will allow the confident interpretation of data from screening and optimisation studies that use these nickel (pre-)catalysts.


Funding Notes

The project is supported by GSK and the Engineering and Physical Sciences Research Council. This will include a three month placement at GSK as part of a 48 month project. Funding will cover a stipend at no less than the UKRI rate, tuition fees (for home students only), costs for conference attendance, laboratory costs, and all costs associated with a placement at GSK.

References

For details of some of our previous work in the area, please see:
Inhibition of (dppf)nickel-catalysed Suzuki-Miyaura cross-coupling reactions by α-halo-N-heterocycles. A. K. Cooper, M. E. Greaves, W. Donohoe, P. M. Burton, T. O. Ronson, A. R. Kennedy, and D. J. Nelson, Chemical Science, 2021, 12, 14074
The Effect of Added Ligands on the Reactions of [Ni(COD)(dppf)] with Alkyl Halides: Halide Abstraction may be Reversible. M. E. Greaves, T. O. Ronson, F. Maseras, and D. J. Nelson, Organometallics, 2021, 40, 1997
Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0). M. E. Greaves, T. O. Ronson, G. C. Lloyd-Jones, F. Maseras, S. Sproules, and D. J. Nelson
ACS Catalysis, 2020, 10, 10717
Aldehydes and Ketones Influence Reactivity and Selectivity in Nickel-Catalyzed Suzuki-Miyaura Reactions. A. K. Cooper, D. K. Leonard, S. Bajo, P. M. Burton, and D. J. Nelson, Chemical Science, 2020, 11, 1905
Steric effects determine the mechanisms of reactions between bis(N-heterocyclic carbene)nickel(0) complexes and aryl halides. D. J. Nelson and F. Maseras, Chemical Communications, 2018, 54, 10646
Halide Abstraction Competes with Oxidative Addition in the Reactions of Aryl Halides with [Ni(PMenPh(3-n))4]. I. Funes-Ardoiz, D. J. Nelson, and F. Maseras, Chemistry - A European Journal, 2017, 23, 16728
Oxidative Addition of Aryl Electrophiles to a Prototypical Nickel(0) Complex: Mechanism and Structure/Activity Relationships. S. Bajo, G. Laidlaw, A. R. Kennedy, S. Sproules, and D. J. Nelson, Organometallics, 2017, 36, 1662

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