Extending the Library of Boron Bases: A Contribution from Theory

In recent years, the isolation of nucleophilic boron bases led to a paradigm shift in boron chemistry which prompted us to perform computational studies on a series of bis­(carbene) borylene complexes. The structure and electronic properties of these complexes have been studied, and all of them were found to possess strong donor ability as evident from high values of calculated pKa and proton affinities (244–300 kcal mol–1). The ability to form strong donor–acceptor bond between the boron and carbene center, together with the high thermodynamic stability of the complexes, render them as a promising class of ligands for use in transition metal based systems. The comparable bond dissociation energies of hitherto unknown acyclic (3A–5A, 8A, 15A, 18A, 19A, and 21A) and cyclic borylenes (2C–5C, 9C, 10C, and 15C) to that of the synthetically accessible borylenes (2A, 7A, 9A, and 16A) indicate the likelihood of isolation of these hitherto unknown borylenes.