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 P–E bond dissociation
energies, P–E bond order, Löwdin charge on phosphorus
and chalcogen atoms, and molecular geometries. Experimentally monitoring
the 31P and 77Se 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.