Hydrogen Bonds To Phosphorus Observed

Researchers have found unusual hydrogen bonds to phosphorus in three bimolecular alcohol-trimethylphosphine complexes and have measured their strengths. H-bonds do not usually form to P. In the new study, in which a hydroxyl H atom bonds with P in another compound, P bears a partial positive charge, making H-bond formation especially unlikely. The work was carried out by Henrik G. Kjaergaard and coworkers at the University of Copenhagen (J. Phys. Chem. Lett. 2014, DOI: 10.1021/jz502150d). P. G. Sennikov of the Russian Academy of Sciences, in Nizhny Novgorod, and coworkers earlier observed H bonding to P in phosphine. Kjaergaard and coworkers believe that case to be the only other experimental observations of the phenomenon. In their study, although trimethylphosphine’s P atom has partial positive charge, its electrostatic potential surface also has a negative-potential area around the lone pair, and the H-bonds form at that spot. “This work clearly shows that we cannot continue to think of charge distribution as spherical in atoms, molecules, or even ions,” Kjaergaard says.