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

DOI: 10.1038/s41929-018-0197-z

Authors: Antonis M. Messinis (University of Bristol) , Stephen L. J. Luckham (University of Bristol) , Peter P. Wells (University of Southampton; Diamond Light Source; UK Catalysis Hub, Research Complex at Harwell) , Diego Gianolio (Diamond Light Source) , Emma K. Gibson (UK Catalysis Hub, Research Complex at Harwell; University of Glasgow) , Harry M. O’brien (University of Bristol) , Hazel A. Sparkes (University of Bristol) , Sean A. Davis (University of Bristol) , June Callison (UK Catalysis Hub, Research Complex at Harwell; University College London) , David Elorriaga (University of Bristol) , Oscar Hernandez-fajardo (University of Bristol) , Robin B. Bedford (University of Bristol)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Catalysis , VOL 2 , PAGES 123 - 133

State: Published (Approved)
Published: December 2018
Diamond Proposal Number(s): 15151

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.

Journal Keywords: Catalytic mechanisms; Coordination chemistry; Homogeneous catalysis; Organometallic chemistry

Subject Areas: Chemistry


Instruments: B18-Core EXAFS