Complexes of Guanidinium Ion (NH2)3C+ with Super Lewis Acidic XH4+ (X = B and Al): Comparison with XH3 Complexes and Protonated and Methylated Guanidinium Dications

In a recent publication, Suresh and Koga suggested that the molecular electrostatic potential minimum (Vmin) could be used as a quantitative measure of the "a donating power" of substituted phosphorus(III) ligands. In support of this assertion, they showed linear correlations between a number of physicochemical properties and Vmin. Our examination of the analyses of the sets of experimental data used to support this assertion shows unequivocally that the variations in the properties cannot be described by a single parameter. Therefore, the utility of Vmin as a measure of the "(sigma) donating power" of substituted phosphorus(III) ligands remains unsubstantiated.