Quantifying interactions in the active encounter complex of frustrated Lewis pairs.
basic_science · Level V
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- Record sourced from PubMed, PMID 40246902.
- Also identified by DOI 10.1038/s41467-025-58965-2 and PMC identifier 12006534.
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Abstract
Sustainable catalysts based on main-group elements, such as frustrated Lewis pairs (FLPs), have emerged as alternatives to precious metal systems. The initial reaction of the Lewis acid, Lewis base and small molecule (e.g. H<sub>2</sub>) is formally termolecular, but the reaction is rationalised by the pre-association of the acid and base in an encounter complex. Here we show that the charge-transfer band between P(mes)<sub>3</sub> and B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> can be analysed by supramolecular UV-vis spectroscopic techniques to provide the key thermodynamic parameter, the association constant (K<sub>a</sub>), for the active encounter complex, i.e. the pre-associated complex that is specifically in the correct orientation for small-molecule activation. We also demonstrate that a higher concentration of active encounter complex in solution leads to a faster activation of hydrogen. This method enables researchers to directly probe the complex that underpins FLP small-molecule activation and subsequent catalysis, and will aid the design of more active sustainable catalysts.