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Updated: Jan 19, 2026

Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy
Published on: February 20, 2020
New Insights in Frustrated Lewis Pair Chemistry with Azides
Devin H A Boom1, Andrew R Jupp1, Martin Nieger2
1Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1090 GD, Amsterdam, The Netherlands.
Abstract:
The geminal frustrated Lewis pair (FLP) tBu2 PCH2 BPh2 (1) reacts with phenyl-, mesityl-, and tert-butyl azide affording, respectively, six, five, and four-membered rings as isolable products. DFT calculations revealed that the formation of all products proceeds via the six-membered ring structure, which is thermally stable with an N-phenyl group, but rearranges when sterically more encumbered Mes-N3 and tBu-N3 are used. The reaction of 1 with Me3 Si-N3 is believed to follow the same course, yet subsequent N2 elimination occurs to afford a four-membered heterocycle (5), which can be considered as a formal FLP-trimethylsilylnitrene adduct. Compound 5 reacts with hydrochloric acid or tetramethylammonium fluoride and showed frustrated Lewis pair reactivity towards phenylisocyanate.
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