Recent advances in transition metal-catalyzed organic transformations using hemilabile P,PO ligands

Abstract

Bisphosphine monoxides (BPMOs) represent a distinctive class of hemilabile bidentate ligands featuring a trivalent phosphine as a soft coordination site, combined with a hard coordination site in the form of P(V)O; hence, they are referred to as P,PO ligands. Despite their potential benefits, including their ability to regulate a variety of elementary steps essential in transition metal-enabled organic reactions, such as ligand exchange, isomerization, oxidative addition, migratory insertion, and reductive elimination, the P,PO ligands have not garnered significant attention compared with other hemilabile ligands and bidentate phosphine ligands in the past decades. This limited recognition is due to challenges associated with their synthesis methods and their inconspicuous presence within high-valent transition-metal/bidentate phosphine ligand catalytic systems under basic or oxygen-containing conditions. The incorporation of the P,PO ligands in transition metal-catalyzed organic reactions offers a pathway characterized by low activation energy for a diverse range of reactions. Herein, this review article provides a comprehensive overview of the utilization of the BPMO ligands in transition metal-catalyzed organic transformations from around 2004 to date, encompassing addition reactions, alkene functionalization reactions, coupling reactions, [4 + 2] cycloadditions, C–H functionalizations, and other transformations.