Quantitative insights into noncovalent interactions involving halogen and tetrel bonds in 2,4,6-trimethylpyrylium tetrafluoroborate

Abstract

The crystal and molecular structure of an organic salt, in which a 2,4,6-trimethylpyrylium cation forms a salt with a tetrafluoroborate anion, namely, 2,4,6-trimethylpyrylium tetrafluoroborate, C8H11O+·BF4 −, has been experimentally realized. The compound crystallizes in the orthorhombic centrosymmetric space group Pnma. The crystal packing is stabilized via a subtle interplay of [F3—B—F]−...O+—C fluorine/oxygen-centred halogen/chalcogen bonds and Cδ+...Fδ− tetrel-bonded contacts. Although the O centre has a formal charge of +1, the estimation of the partial negative charges on O is in accordance with electronegativity considerations. Hirshfeld surface analysis, which also includes an analysis of the three-dimensional deformation density, along with molecular electrostatic potential (MESP) calculations, provides quantitative insights into the nature of the intermolecular interactions. The topological analysis of the electron-density distribution has been performed using AIMAll and TOPOND, and unequivocally establishes the bonding character associated with the different noncovalent interactions. In addition, NBO analysis and polarizability calculations using PolaBer render deeper physical insights into the electronic characteristics of these noncovalent interactions.

Halogen bonds, chalcogen bonds, pnictogen bonds, tetrel bonds and other σ-hole interactions: a snapshot of current progress

“…The analysis of the interactions is supported by Hirshfeld surfaces, fingerprint plots and energy framework calculations (Spackman & Jayatilaka, 2009;Spackman et al, 2021), the latter indicating that the observed chalcogen bonds make a larger electrostatic contribution to the lattice energy than the C-X� � �X halogen bonds. Chopra, Hathwar and co-workers report the structure of the organic salt 2,4,6-trimethylpyrylium tetrafluoroborate, C 5 H 2 Me 3 O + •BF 4 À , and present an extensive computational analysis of the short intermolecular contacts to provide a description of the interaction type (Mandal et al, 2022). Among the interactions indicated by the topological analysis of the calculated electron density and accompanying distributed atomic polarizability calculations are B-F� � �O interactions.…”

Transition from covalent to noncovalent bonding between tetrel atoms

“…But there are caveats here as well. Unlike the majority of tetrel bonds in the literature, [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] the stability of these systems is predicated on an overall charge, whether positive or negative. Secondly, one sees a coulombic interaction more nuanced than the classical contact between a positive s or p-hole on one unit and a negative region on the partner molecule.…”