Chlorine bond distances in ClF and $Cl_2$ complexes

Intermolecular distances in weakly bound complexes have been usually interpreted in terms of van der Waals radii of atoms/molecules. Recently, it has been shown that for hydrogen-bonded complexes, one could empirically define a hydrogen bond radius [J. Chem. Phys. 114 (2001) 3880]. In this Communication, a similar approach is used for analyzing the B· · ·Cl distances in B· · ·$ClF/Cl_2$ complexes, where B is the atom or center in the bonding partner. Chlorine bond radius for ClF and $Cl_2$ are determined to be 1.28 $\pm$ 0.11 $\AA$ and 1.55 $\pm$ 0.07 $\AA$ , respectively. The ClF molecule with a non-zero dipole moment interacts more strongly and closely with B than $Cl_2$ having zero dipole moment. However, the Cl bond radius in $Cl_2$ complexes is still smaller than the van der Waals radius of Cl (1.80 $\AA$ ), pointing to the importance of multipole moments in intermolecular interaction, in this case the quadrupole moment of $Cl_2.