Affinity of Telluronium Chalcogen Bond Donors for Lewis Bases in Solution: A Critical Experimental‐Theoretical Joint Study

Abstract

AbstractTelluronium salts [Ar2MeTe]X were synthesized, and their Lewis acidic properties towards a number of Lewis bases were addressed in solution by physical and theoretical means. Structural X‐ray diffraction analysis of 21 different salts revealed the electrophilicity of the Te centers in their interactions with anions. Telluroniums’ propensity to form Lewis pairs was investigated with OPPh3. Diffusion‐ordered NMR spectroscopy suggested that telluroniums can bind up to three OPPh3 molecules. Isotherm titration calorimetry showed that the related heats of association in 1,2‐dichloroethane depend on the electronic properties of the substituents of the aryl moiety and on the nature of the counterion. The enthalpies of first association of OPPh3 span −0.5 to −5 kcal mol−1. Study of the affinity of telluroniums for OPPh3 by state‐of‐the‐art DFT and ab‐initio methods revealed the dominant Coulombic and dispersion interactions as well as an entropic effect favoring association in solution. Intermolecular orbital interactions between [Ar2MeTe]+ cations and OPPh3 are deemed insufficient on their own to ensure the cohesion of [Ar2MeTe ⋅ Bn]+ complexes in solution (B=Lewis base). Comparison of Grimme's and Tkatchenko's DFT‐D4/MBD‐vdW thermodynamics of formation of higher [Ar2MeTe ⋅ Bn]+ complexes revealed significant molecular size‐dependent divergence of the two methodologies, with MBD yielding better agreement with experiment.