Assessing the effects of covalent, dative and halogen bonds on the electronic structure of selenoamides

Abstract

Here, the interaction between N,N-dimethyl-selenobenzoamide PhC(Se)NMe₂ (1) and various Lewis acids of different strengths, namely IC₆F₁₃(I), B(C₆F₅)₃ (B) and Me⁺, has been analysed by a combined experimental and theoretical approach. In all cases, an increase of the C–NMe₂ rotational barrier has been evidenced and quantified by ¹H-variable temperature-exchange NMR spectroscopy (VT-EXSY) in the cases of 1-I and 1-B. For B(C₆F₅)₃, the structure of the adduct has been elucidated by single crystal X-ray diffraction, allowing the lengthening of the Se–C bond (186 pm) and the consequent double characteristic of the C–NMe₂ bond (131 pm) to be measured. Computational studies (mainly natural bond orbitals and natural orbital for chemical valence analyses) gave precious insight into the effect of various Lewis acids on the electronic structure of 1. The advantages and the limitations of this new method to characterize chemical interactions are discussed.