Chlorine bond distances in ClF and Cl2 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 +/- 0.11 Angstrom and 1.55 +/- 0.07 Angstrom, respectively. The ClF molecule with a non-zero dipole moment interacts more strongly and closely with B than C12 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 Angstrom), pointing to the importance of multipole moments in intermolecular interaction, in this case the quadrupole moment of Cl-2. (C) 2003 Elsevier B.V. All rights reserved.