Comparison between Tetrel Bonded Complexes Stabilized by σ and π Hole Interactions

Abstract

The σ-hole tetrel bonds formed by a tetravalent molecule are compared with those involving a π-hole above the tetrel atom in a trivalent bonding situation. The former are modeled by TH4, TH3F, and TH2F2 (T = Si, Ge, Sn) and the latter by TH2=CH2, THF=CH2, and TF2=CH2, all paired with NH3 as Lewis base. The latter π-bonded complexes are considerably more strongly bound, despite the near equivalence of the σ and π-hole intensities. The larger binding energies of the π-dimers are attributed to greater electrostatic attraction and orbital interaction. Each progressive replacement of H by F increases the strength of the tetrel bond, whether σ or π. The magnitudes of the maxima of the molecular electrostatic potential in the two types of systems are not good indicators of either the interaction energy or even the full Coulombic energy. The geometry of the Lewis acid is significantly distorted by the formation of the dimer, more so in the case of the σ-bonded complexes, and this deformation intensifies the σ and π holes.

Hexacoordinated Tetrel‐Bonded Complexes between TF4 (T=Si, Ge, Sn, Pb) and NCH: Competition between σ‐ and π‐Holes

“…[25,26,38,98,99] Previous studies have confirmed the trend that the tetrel bond grows stronger as T becomes larger, [30,32,33,47,100] but that the effect levels off between Sn and Pb. However, there are a few works dealing with tetravalent Sn and Pb, and the noncovalent bonds they form with various bases.…”

“…However, there are a few works dealing with tetravalent Sn and Pb, and the noncovalent bonds they form with various bases. [25,26,38,98,99] Previous studies have confirmed the trend that the tetrel bond grows stronger as T becomes larger, [30,32,33,47,100] but that the effect levels off between Sn and Pb. [45,101] An earlier work [45,102] supports the result noted here that the deformation energy induced within the Lewis acid molecule by formation of a tetrel bonded complex drops as the central tetrel atom grows in size.…”

Ability of IR and NMR Spectral Data to Distinguish between a Tetrel Bond and a Hydrogen Bond

“…In the case of the C atom, its ability to engage in a TB has typically been amplified by adding a number of electron-withdrawing substituents like F [27][28][29] rather than considering a CH3 group itself. Our own lab has contributed to the current understanding of tetrel bonding as well [30][31][32][33][34][35] including the issue of steric crowding 26,36 and the manner in which such interactions might be used to design an effective selective anion receptor [37][38][39][40] . In sum, like their noncovalent bonding counterparts, TBs are strengthened by electron-withdrawing substituents whose polarization induces a more positively charged central atom.…”

Quantification of &sigma;&ndash;Holes and Their Use as a Descriptor for the Theoretical Calculation of p<em>K</em>a Values for Carboxylic Acids

“…Such interactions are similar to those observed for elements in groups 15 and 16, which are termed pnictogen and chalcogen bonds, respectively. The formation of these non-covalent interactions stems from a similar origin as halogen bonds, via the presence of σ-holes [3][4][5], a localized region of positive electrostatic potential on the surface of the group 17 atom and opposite to the internuclear axis of a covalent σ bond, hence σ-holes. Therefore, tetrel bonds belong to a broader kind of directional non-covalent electrostatic interactions like halogen [6][7][8], chalcogen [9,10], and pnicogen bonds [11].…”

“…Unsaturated carbon species can also form tetrel-bonds involving their π electron density with various electron rich donors such as CO, CS [49] and OCS with nitrogen bases [50][51][52], σ-π bonded complexes [4,53], π-σ-hole [54] bonded complexes and cation-π interactions [55], and π electrons bearing carbon compounds with potential applications for CO2 capture [56][57][58].…”