xantphos

Xantphos is a bidentate diphosphine ligand with a rigid xanthene backbone, formally named 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene. The two phosphine donors occupy the 4 and 5 positions on the xanthene framework, giving a notably wide bite angle when bound to a metal center. This structural feature distinguishes xantphos from many other ligands and influences catalytic geometry and reactivity.

The ligand’s large bite angle, combined with its rigid, bulky framework, stabilizes metal complexes and can favor catalytic steps such as reductive elimination and migratory insertion in various transformations. The phenyl substituents on phosphorus add steric bulk, contributing to catalyst longevity and substrate compatibility in several reactions. Xantphos is typically used as a coordinating ligand in homogeneous catalysis and forms stable complexes with metals such as palladium and rhodium.

Synthesis of xantphos typically involves functionalization of the xanthene backbone to introduce two phosphine-bearing groups, commonly by coupling or lithiation strategies followed by reaction with chlorophosphine reagents. The ligand is commercially available and can be prepared in laboratory settings through established organophosphorus coupling methods.

Applications include promotion of hydroformylation and related hydrofunctionalization reactions using rhodium or related metals, where the wide bite angle can improve activity and selectivity. It is also employed in various palladium-catalyzed cross-coupling reactions, such as carbon–carbon bond-forming processes, where the ligand’s geometry can influence turnover and outcomes. Xantphos serves as a versatile, general-purpose ligand in many workflows involving homogeneous catalysis, often providing robust performance across a range of substrates.