Abstract
Iron-catalysed cross-coupling is undergoing explosive development, but mechanistic understanding lags far behind synthetic methodology. Here, we find that the activity of iron–diphosphine pre-catalysts in the Negishi coupling of benzyl halides is strongly dependent on the diphosphine, but the ligand does not appear to be coordinated to the iron during turnover. This was determined using time-resolved in operando X-ray absorption fine structure spectroscopy employing a custom-made flow cell and confirmed by 31 P NMR spectroscopy. While the diphosphine ligands tested are all able to coordinate to iron(ii), in the presence of excess zinc(ii)—as in the catalytic reaction—they coordinate predominantly to the zinc. Furthermore, combined synthetic and kinetic investigations implicate the formation of a putative mixed Fe–Zn(dpbz) species before the rate-limiting step of catalysis. These unexpected findings may not only impact the field of iron-catalysed Negishi cross-coupling, but potentially beyond to reactions catalysed by other transition metal/diphosphine complexes.
Original language | English |
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Pages (from-to) | 123-133 |
Number of pages | 11 |
Journal | Nature Catalysis |
Volume | 2 |
Issue number | 2 |
Early online date | 31 Dec 2018 |
DOIs | |
Publication status | Published - 1 Feb 2019 |
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Iron Negishi mechanistic NatCat 2018
Bedford, R. B. (Creator), University of Bristol, 23 Dec 2018
DOI: 10.5523/bris.1kp2f62x3klb02mfz2qymcmxmx, http://data.bris.ac.uk/data/dataset/1kp2f62x3klb02mfz2qymcmxmx
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Dr Sean A Davis
- School of Chemistry - Senior Lecturer
- Soft Matter, Colloids and Materials
Person: Academic , Member