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

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

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

12 Citations (Scopus)
213 Downloads (Pure)

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 languageEnglish
Pages (from-to)123-133
Number of pages11
JournalNature Catalysis
Volume2
Issue number2
Early online date31 Dec 2018
DOIs
Publication statusPublished - 1 Feb 2019

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