A simple method for the determination of the Tolman electronic parameter of different phosphorus containing ligands, by means of the average local ionization energy

Abstract

The average local ionization energy (I(r)) was tested as a theoretical descriptor of the Tolman electronic parameter (TEP) for a set of monodentate phosphines and phosphites. Results indicated that this magnitude correlates with the experimental TEP, which could be explained in terms of the HSAB principle of Pearson. This function represents a simple, reliable, and fast option to measure the electronic contribution of these type of compounds. The performance of the electrostatic potential (V(r)) was also studied for these molecules. Comparison of I(r) with the experimental basicity showed that this magnitude, as well as the experimental TEP correlate with the reported pKb values, which in both cases are poor. A simple methodology to measure the Tolman cone angle from the mapping of the I(r) function over the van der Waals isocontour is also described.