Diethylphenylphosphine is primarily used as a ligand in coordination chemistry and catalysis. It plays a significant role in the synthesis of organometallic compounds, particularly in the formation of metal complexes that are utilized in various catalytic processes. Its application is notable in homogeneous catalysis, where it aids in facilitating reactions such as hydrogenation, hydroformylation, and cross-coupling reactions. Additionally, it is employed in the development of phosphine-based catalysts, which are essential in organic synthesis for creating complex molecules. Its stability and electron-donating properties make it a valuable component in research and industrial applications involving transition metal catalysis.