Anisotropic repulsion in complexes B.Cl2 and B.HCl: The shape of the chlorine atom-in-a-molecule

Modelling of the repulsion potential around a Cl centre in HCl, Cl2 and ClF predicts a systematic shortening of about 1 bohr in the effective van der Waals radius for end-on approach to bare Cl compared with approach to Cl shielded by H. This is in agreement with the experimental average of 0.53(7) إ for the difference in weak-bond lengths between B.HCl and B.Cl2, and allows a consistent electrostatic picture of the bonding in both series.