Diverse Catalytic Applications of Phosphine Oxide-Based Metal Complexes

Phosphine oxides are an interesting class of compounds possessing tetracoordinate and pentavalent phosphorus atoms and have been employed in a wide range of applications including reagents in organic synthesis, metal extractants, flame retardants, pharmaceuticals, and bioactivity studies. Among all, the degree of basicity of phosphoryl oxygen driven by the nature of substituents influences the electronic properties of the central metal in a complex toward the diversified catalytic processes. Further, the presence of heteroatoms adjacent to the central phosphorus atom enhances the nucleophilicity of the phosphoryl oxygen atom. In view of this, the present review covers the past two decades of remarkable catalytic versatility of P=O-based metal complexes and describes the governing factors influencing the structural properties and the resultant coordination behavior. Interestingly, some of the P=O bond distances of metal complexes are either longer or shorter compared to their free ligands, indicating the catalytic activity. These complexes can effectively catalyze a wide range of chemical reactions including polymerizations, C-C and Si-C bond activations, oxidation, reduction, hydroformylation, hydrophosphination, hydrogenation and cyclization reactions. Furthermore, this review emphasizes the impact of substituents, solvents, additives, light, and temperature on the catalytic efficiency. This review draft uncovers the interesting coordination properties and catalytic applications of various phosphine oxide ligands bound with d-block and f-block metal salts. The factors influencing the catalytic properties are discussed. These complexes catalyze a wide range of chemical reactions including polymerizations, C-C and Si-C bond activations, hydroformylation, hydrophosphination, hydrogenation and cyclization reactions. image