Synthesis and reactivity of an aluminium n-heterocyclic aminal

Wilde, Taylor and Murphy, Fáinché and Smylie, Cooper R. T. and Kennedy, Alan R. and Weetman, Catherine E. (2024) Synthesis and reactivity of an aluminium n-heterocyclic aminal. Chemistry - An Asian Journal, 19 (5). e202301058. ISSN 1861-471X (https://doi.org/10.1002/asia.202301058)

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Abstract

Tethered N-heterocyclic carbenes (NHCs) are an emerging class of ligand, as they feature all the desirable aspects of NHCs (ease of synthesis, high tunabilty) but also enable metal-ligand cooperativity when combined with Lewis acidic metal centres due to the donor-acceptor nature of the complexes formed. Herein we report a simple ethoxy-tethered NHC for the stabilisation of Al(III) hydrides, resulting in the unexpected formation of a bicyclic N-heterocyclic aminal (1). Compound 1 behaves as a metal hydride, capable of reducing benzophenone and carbodiimide to yield compounds 2 and 3, respectively. Furthermore, we show that 1 behaves as an efficient catalyst in the dehydrocoupling of amine-boranes due to the hemilabile nature of the supporting ligand.