Evidence for and evaluation of fluorine–tellurium chalcogen bonding

Abstract

In the field of noncovalent interactions, chalcogen bonding (ChB) involving the tellurium atom is currently attracting much attention in supramolecular chemistry and in catalysis. However, as a prerequisite for its application, the ChB should be studied in solution to assess its formation and, if possible, to evaluate its strength. In this context, new tellurium derivatives bearing CH₂F and CF₃ groups were designed to exhibit Te⋯F ChB and were synthesized in good to high yields. In both types of compounds, Te⋯F interactions were characterized in solution by combining ¹⁹F, ¹²⁵Te and HOESY NMR techniques. These Te⋯F ChBs were shown to contribute to the overall J_Te–F coupling constants (94–170 Hz) measured in the CH₂F- and CF₃-based tellurium derivatives. Finally, a variable temperature NMR study allowed us to approximate the energy of the Te⋯F ChB, from 3 kJ mol⁻¹ for the compounds with weak Te σ-holes to 11 kJ mol⁻¹ for Te σ-holes activated by the presence of strong electron withdrawing substituents.