Delocalization and geometries in the P-function of thiophosphinic derivatives: tautomerism and supramolecular interactions

Abstract

Model series of thiophosphinic acid derivatives were scrutinized at the B3LYP/6–311 + + G(2d,2p) level of theory, and the resulting geometries were compared with experimental crystal structure data obtained from the Cambridge Structure Database (CSD). Typical bond length and bond angle values were selected for a series of similar fragments from CSD, and mean dimensions were also calculated from the experimental data accumulated. Linking the results of theoretical calculations and the evidences of data mining allowed the reconsideration of a few past experimental models with (thio)phosphinate-anion-(thio)phosphinic acid-type associations. It seems also from this survey that thiophosphinic acid derivatives may be suitable vehicles for transgressing boundaries from a single molecule to supramolecular relations and vice versa. The study shows that a few intramolecular distances such as the P-O bond lengths both in the anionic and in the neutral forms may significantly depend on intermolecular contacts as well. The tautomerism involving the thionic acid and thiolic acid forms was studied by theoretical methods at the B3LYP/6–311 + + G(2d,2p) level of theory assuming monomolecular and different bimolecular mechanisms. The shift toward the thionic actor was supported by the kinetic and thermodynamic energetics.