Stereo-electronic descriptors

Quantum-chemical methods (Dewar and Thiel, 1977 Dewar et al, 1985 Stewart, 1989) may be applied to obtain a large variety of stereo-electronic descriptors such as ionization potential, polarizability, electron affinity, dipole moment, charge densities, HOMO- and LUMO-energies or atomic charges using semi-empirical or ab initio calculations (Table 1.4). 

Figure 6.9 Descriptors calculated for phosphines in the irons-Rh (PR3)2(CO)CI catalyst a the deformation coordinate S4 is employed as steric measure b stereo-electronic map showingthe distribution of the various PR3 ligands.

The stereo descriptor u denotes that two chirality centres are present the configuration of which is unlike. One of these chirality centres is due to the unshared electron pair on the substituted pyramidal sulfur atom. The unshared electron pair is given the lowest priority in determining the configuration. 

---