Issue 17, 2023

Planar bismuth triamides: a tunable platform for main group Lewis acidity and polymerization catalysis

Abstract

Geometric deformation in main group compounds can be used to elicit unique properties including strong Lewis acidity. Here we report on a family of planar bismuth(III) complexes (cf. typically pyramidal structure for such compounds), which show a geometric Lewis acidity that can be further tuned by varying the steric and electronic features of the triamide ligand employed. The structural dynamism of the planar bismuth complexes was probed in both the solid and solution phase, revealing at least three distinct modes of intermolecular association. A modified Gutmann–Beckett method was used to assess their electrophilicity by employing trimethylphosphine sulfide in addition to triethylphosphine oxide as probes, providing insights into the preference for binding hard or soft substrates. Experimental binding studies were complemented by a computational assessment of the affinities and dissection of the latter into their intrinsic bond strength and deformation energy components. The results show comparable Lewis acidity to triarylboranes, with the added ability to bind two bases simultaneously, and reduced discrimination against soft substrates. We also study the catalytic efficacy of these complexes in the ring opening polymerization of cyclic esters ε-caprolactone and rac-lactide. The polymers obtained show excellent dispersity values and high molecular weights with low catalyst loadings used. The complexes retain their performance under industrially relevant conditions, suggesting they may be useful as less toxic alternatives to tin catalysts in the production of medical grade materials. Collectively, these results establish planar bismuth complexes as not only a novel neutral platform for main group Lewis acidity, but also a potentially valuable one for catalysis.

Graphical abstract: Planar bismuth triamides: a tunable platform for main group Lewis acidity and polymerization catalysis

Supplementary files

Article information

Article type
Edge Article
Submitted
17 Feb 2023
Accepted
14 Mar 2023
First published
06 Apr 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 4549-4563

Planar bismuth triamides: a tunable platform for main group Lewis acidity and polymerization catalysis

T. J. Hannah, W. M. McCarvell, T. Kirsch, J. Bedard, T. Hynes, J. Mayho, K. L. Bamford, C. W. Vos, C. M. Kozak, T. George, J. D. Masuda and S. S. Chitnis, Chem. Sci., 2023, 14, 4549 DOI: 10.1039/D3SC00917C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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