Examination of Drago's EB and CB Parameters for Phosphines through the Quantitative Analysis of Ligand Effects (QALE)

Comparison of pairs of physiochemical properties of phosphines and their complexes demonstrates that, in general, at least four independent stereoelectronic parameters are in general required to describe the variations in these properties. Consequently, any two-parameter model such as Drago's E/C model will have limited use in correlation analyses involving phosphines. The QALE analysis of EB and CB shows that these parameters are linear combinations of the QALE parameters χ and θ, with a small contribution from Ear. Thus, successful application of the E/C model will be restricted to the situation where the property being analyzed depends primarily on χ and θ.