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DOI: 10.1055/a-1928-4902
Enhancement of London Dispersion in Frustrated Lewis Pairs: Towards a Crystalline Encounter Complex
This work was supported by the Council for Chemical Sciences of the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (The Netherlands Organization for Scientific Research, NWO/CW) by a VIDI grant (J.C.S.), the Nationale Wetenschapsagenda (Dutch Research Agenda, NWA) Idea Generator grant (J.C.S.), and by a postdoc fellowship (C.H.) of the Deutscher Akademischer Austauschdienst (German Academic Exchange Service, DAAD). The X-ray diffractometer was financed by NWO.
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Abstract
The encounter complex, i.e., the pre-organized assembly consisting of a Lewis acid and a Lewis base, is a fundamental concept in frustrated Lewis pair (FLP) chemistry. However, this donor–acceptor complex is challenging to study due to its transient nature. Here, we present a combined theoretical and experimental investigation on the potential isolation of an encounter complex enabled by enhancement of London dispersion forces between a sterically encumbered Lewis acid and base pair. Guided by computational analyses, the FLP originating from the bulky triarylamine N(3,5-tBu2C6H3)3 and the novel triarylborane B(3,5-tBu2C6H3)3 was investigated, leading to the isolation of a 1:1 co-crystal of both FLP components.
Key words
frustrated Lewis pairs - encounter complex - London dispersion forces - Lewis acid - Lewis baseSupporting Information
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article is available online at https://doi.org/10.1055/a-1928-4902.
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Publication History
Received: 15 July 2022
Accepted after revision: 19 August 2022
Accepted Manuscript online:
22 August 2022
Article published online:
11 October 2022
© 2022. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by/4.0/)
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- 23 Synthesis of N(3,5-tBu2C6H3)3/B(3,5-tBu2C6H3)3 N(3,5-tBu2C6H3)3 (10 mg, 0.017 mmol) and B(3,5-tBu2C6H3)3 (10 mg, 0.017 mmol) were dissolved in toluene-d 8 (0.5 mL). Storage of the solution at –30 °C overnight afforded colorless crystals of N(3,5-tBu2C6H3)3/B(3,5-tBu2C6H3)3. Yield: 16 mg (0.014 mmol, 80%); mp 224 °C. IR (neat): ν = 2951, 2902, 2866, 1582, 1495, 1476, 1461, 1447, 1426, 1413, 1391, 1361, 1307, 1246, 1221, 1204, 1130, 1038, 1008, 993, 924, 896, 886, 865, 822, 727, 720, 711, 694, 671, 539, 463 cm–1. 1H NMR (500 MHz, C6D6): δ 8.03 (s, 3 H, p-CH), 7.86 (s, 6 H, o-CH), 7.46 (s, 3 H, p-CH), 7.27 (s, 6 H, o-CH), 1.32 (s, 54 H, tBu), 1.23 (s, 54 H, tBu).