Assessing Phosphine-Chalcogen Bond Energetics from Calculations

Phosphine chalcogenides are useful reagents in chalcogen atom transfer reactions and nanocrystal syntheses. Understanding the strength and electronic structure of these bonds is key to optimizing their use, but a limited number of experimental and computational studies probe these issues. Using density functional theory (DFT), we computationally screen multiple series of trisubstituted phosphine chalcogenide molecules with a variety of phosphorus substituents and examine how these affect the strength of the phosphorus-chalcogen bond. DFT provides valuable data on these compounds including PE bond dissociation energies, P-E bond order, Lowdin charge on phosphorus and chalcogen atoms, and molecular geometries. Experimentally monitoring the P-31 and Se-77 NMR chemical shifts and published Hammett constants provides good estimates and confirmation of the relative magnitude of electronic shielding around these nuclei and confirms the predictive value of the computational results.