Recent advances in boron-centered ligands and their transition metal complexes

Compounds containing boron in the formal oxidation state of +III are well known and are classic examples of Lewis acids. In turn, these simple electron lone pair acceptors have seen limited use as ligands towards transition metals. Nevertheless, compounds with subvalent boron in different bonding arrangements act as strong sigma-donors, pi-donors and acceptors, making them versatile ligands for transition metal centers. Boron-centered ligands form transition metal complexes through a variety of binding modes, which impart unique and unexpected properties to the resulting complexes. This review provides an account of the latest advances in boron-centered transition metal chemistry from our research group with a particular focus on their syntheses, structural features, electronic properties and reactivity. The ligands reviewed include borylenes, diborenes, diborynes, and boron-containing heterocycles. (C) 2018 Published by Elsevier B.V.