Asymmetry in Ionic Shape

Soft ligands (e.g., sulfur) can also show asymmetry of shape. The directions of approach of atoms to sulfur in a C-S—C group have been analyzed by Parthasarathy and co-workers (Rosenfield et al., 1977). They 

Studied the orientations of groups near the C-S-C group in a variety of crystal structures containing it the Cambridge Structural Database (Allen et al., 1979) was searched for this information. Not only did these investigators find that the sulfur atom appeared to have a different radius in different directions but they found that nucleophiles and electrophiles approach it from different directions (Fig. 9). 

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