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The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling

The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling
The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling
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 31P 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.
2520-1158
123–133
Messinis, Antonis M.
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Luckham, Stephen L.J.
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Wells, Peter P.
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Gianolio, Diego
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Gibson, Emma K.
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O'Brien, Harry M.
eca61e1d-a6db-40ef-872d-db0a68556bcd
Sparkes, Hazel A.
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Davis, Sean A.
b4bf65bc-72be-437f-a711-d6dafad5f3d1
Callison, June
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Elorriaga, David
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Hernandez-Fajardo, Oscar
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Bedford, Robin B.
42532c45-cb80-48cd-9e93-8c2d5059eabe
Messinis, Antonis M.
b31968a0-b45b-4882-b816-303378b5d484
Luckham, Stephen L.J.
90193d96-88df-4f43-b294-6a8113431b52
Wells, Peter P.
bc4fdc2d-a490-41bf-86cc-400edecf2266
Gianolio, Diego
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Gibson, Emma K.
738c74e4-ab68-42fe-bda8-9d4a43669b31
O'Brien, Harry M.
eca61e1d-a6db-40ef-872d-db0a68556bcd
Sparkes, Hazel A.
9066ec9b-6904-49ac-b650-04d4b5424b73
Davis, Sean A.
b4bf65bc-72be-437f-a711-d6dafad5f3d1
Callison, June
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Elorriaga, David
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Hernandez-Fajardo, Oscar
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Bedford, Robin B.
42532c45-cb80-48cd-9e93-8c2d5059eabe

Messinis, Antonis M., Luckham, Stephen L.J., Wells, Peter P., Gianolio, Diego, Gibson, Emma K., O'Brien, Harry M., Sparkes, Hazel A., Davis, Sean A., Callison, June, Elorriaga, David, Hernandez-Fajardo, Oscar and Bedford, Robin B. (2019) The highly surprising behaviour of diphosphine ligands in iron-catalysed Negishi cross-coupling. Nature Catalysis, 2 (2), 123–133. (doi:10.1038/s41929-018-0197-z).

Record type: Article

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 31P 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.

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Accepted/In Press date: 9 November 2018
e-pub ahead of print date: 31 December 2018
Published date: February 2019

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Local EPrints ID: 427349
URI: http://eprints.soton.ac.uk/id/eprint/427349
ISSN: 2520-1158
PURE UUID: d6c11ce7-3300-4732-9b6f-d501c5e9033f
ORCID for Peter P. Wells: ORCID iD orcid.org/0000-0002-0859-9172

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Date deposited: 14 Jan 2019 17:30
Last modified: 16 Mar 2024 07:28

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Contributors

Author: Antonis M. Messinis
Author: Stephen L.J. Luckham
Author: Peter P. Wells ORCID iD
Author: Diego Gianolio
Author: Emma K. Gibson
Author: Harry M. O'Brien
Author: Hazel A. Sparkes
Author: Sean A. Davis
Author: June Callison
Author: David Elorriaga
Author: Oscar Hernandez-Fajardo
Author: Robin B. Bedford

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