Comprehensive investigations on DNa⋯A (D = H/F) complexes show why ‘sodium bonding’ is not commonly observed

A comprehensive study of D-Na⋯A (D = H/F) complexes has been done using advanced ab initio and atoms in molecule (AIM) theoretical analyses. The correlation between electron density at bond critical point and binding energy gives a distinguishing feature for hydrogen bonding, different from the ‘electrostatic complexes’ formed by LiD and NaD. Moreover, the LiD/NaD dimers have both linear and anti-parallel minima, as expected for electrostatic dipole–dipole interactions. The HF dimer has a quasi-linear minimum and the anti-parallel structure is a saddle point. Clearly, characterizing hydrogen bonding as ‘nothing but electrostatic interaction between two dipoles’ is grossly in error.