Reactivity and stability of a ring-expanded N-heterocyclic carbene copper(I) boryl imidinate

Charman, Rex S. C. and Horsley Downie, Thomas M. and Jerome, Thomas H. and Mahon, Mary F. and Liptrot, David J. (2022) Reactivity and stability of a ring-expanded N-heterocyclic carbene copper(I) boryl imidinate. Inorganics, 10 (9). 135. ISSN 2304-6740 (https://doi.org/10.3390/inorganics10090135)

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Abstract

Frustrated Lewis pairs (FLPs) have evolved from a revolutionary concept to widely applied catalysts. We recently reported the ring-expanded N-heterocyclic carbene supported copper(I) boryliminomethanide, (6-Dipp)CuC(=NtBu)Bpin and noted it reacted with heterocumulenes in a fashion reminiscent of FLPs. We thus set out to explore its reactivity with a range of other substrates known to react with FLPs. This was undertaken by a series of synthetic studies using NMR spectroscopy, mass spectrometry, IR spectroscopy, and single crystal X-ray crystallography. (6-Dipp)CuC(=NtBu)Bpin was investigated for its reactivity towards water, hydrogen, and phenylacetylene. Its solution stability was also explored. Upon heating, (6-Dipp)CuC(=NtBu)Bpin decomposed to (6-Dipp)CuCN, which was characterised by SC-XRD and NMR spectroscopy, and pinBtBu. Although no reaction was observed with hydrogen, (6-Dipp)CuC(=NtBu)Bpin reacted with water to form (6-Dipp)CuC(=N(H)tBu)B(OH)pin, which was structurally characterised. In contrast to its FLP-reminiscent heterolytic cleavage reactivity towards water, (6-Dipp)CuC(=NtBu)Bpin acted as a Brønsted base towards phenyl acetylene generating (6-Dipp)CuCCPh, which was characterised by SC-XRD, IR, and NMR spectroscopy, and HC(=NtBu)Bpin

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