Issue 28, 2022

Evidence for the encounter complex in frustrated Lewis pair chemistry

Abstract

Frustrated Lewis Pairs (FLPs) are combinations of bulky Lewis acids and bases that can carry out small-molecule activation and catalysis. Mechanistically, the reaction of the acid, base and substrate involves the collision of three distinct molecules, and so the pre-association of the acid and base to form an encounter complex has been proposed. This article will examine the evidence for the formation of this encounter complex, focusing on the archetypal main-group combinations P(tBu)3/B(C6F5)3 and PMes3/B(C6F5)3 (Mes = mesityl), and includes quantum chemical calculations, molecular dynamics simulations, NMR spectroscopic measurements and neutron scattering. Furthermore, the recent discovery that the associated acid and base can absorb a photon to promote single-electron transfer has enabled the encounter complex to also be studied by UV-Vis spectroscopy, EPR spectroscopy, transient absorption spectroscopy, and resonance Raman spectroscopy. These data all support the notion that the encounter complex is only weakly held together and in low concentration in solution. The insights that these studies provide underpin the exciting transformations that can be promoted by FLPs. Finally, some observations and unanswered questions are provided to prompt further study in this field.

Graphical abstract: Evidence for the encounter complex in frustrated Lewis pair chemistry

Article information

Article type
Frontier
Submitted
01 mar 2022
Accepted
05 apr 2022
First published
06 apr 2022
This article is Open Access
Creative Commons BY license

Dalton Trans., 2022,51, 10681-10689

Evidence for the encounter complex in frustrated Lewis pair chemistry

A. R. Jupp, Dalton Trans., 2022, 51, 10681 DOI: 10.1039/D2DT00655C

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