Noncovalent Bonds between Tetrel Atoms

Abstract

The pairing of TFH3 with a TH2CH3− anion, where T represents tetrel atoms C, Si, Ge, Sn, Pb, results in a strong direct interaction between the two T atoms. The interaction energy is sensitive to the nature of the two T atoms but can be as large as 90 kcal/mol. The noncovalent bond strength rises quickly as the basic T atom of the anion becomes smaller, or as the Lewis acid T grows larger, although there is less sensitivity to the latter atom. The electrostatic component makes up some 55–70 % of the total attraction energy. This term is well accounted for by simple combination of the maximum and minimum values of the molecular electrostatic potential of the Lewis acid and base units, respectively. The complexation induces a rearrangement in the TFH3 molecule from tetrahedral to trigonal pyramidal. The associated deformation energy reduces the exothermicity of the complexation reaction. Electron density shift patterns reveal a density loss on the basic T atom, along with accompanying increases on the acidic T and its attached F atom.

Competition between Inter and Intramolecular Tetrel Bonds: Theoretical Studies Complemented by CSD Survey

“…Consequently, complexes with CN − are characterized by E int values exceeding 70 kcal/mol, whereas the weak HCN complexes do not rise above 10 kcal/mol. Equally strong TBs were reported by us for TH 3 F monomers paired with CH 3 CH 2 − anion (E int above 80 kcal/mol) [14b] . On the other hand, much weaker bonds were noted by An and Han examining complexes of TH 3 F (T=C, Si, Ge) with pyridine and its alkali derivatives.…”

Competition between a Tetrel and Halogen Bond to a Common Lewis Acid

“…This same sort of insensitivity occurs also when a phenyl substituent is placed on the tetrel atom 86 or when bound to an anion. 84 It was only when monomer deformations were added that the resulting binding energies displayed the expected Si < Ge < Sn trend. These deformations become progressively more important as the substituents on the tetrel atom become bulkier, 82,86 for example, CF 3 , isobutyl, or phenyl groups, and are typically of greater magnitude for the smaller T atoms.…”

“…The stretches that occur in the covalent bond to the tetrel atom are a common feature of these sorts of bonds, 81−83 especially for the strong TBs with anions. 84 The halogen bond is more diverse in this respect, either stretching 65 or contracting depending on circumstances.…”

Molecular Electrostatic Potential and Noncovalent Interactions in Derivatives of Group 8 Elements

“…While the geometry around osmium remains essentially tetrahedral (e.g., O‐Os‐O angles in 2 a span the range 101.5–117.7°), it becomes somewhat similar to a trigonal bipyramid, the incoming N or O atom occupying an apical position. A similar deformation from tetrahedral towards trigonal bipyramidal geometry is observed on formation of σ‐hole interactions involving tetravalent elements of group 14 [4, 34] . An elongation of the covalent bond opposite to the incoming nucleophile is common for σ‐hole interactions, [3, 4] and is usually rationalized as a consequence of the LP→σ* charge transfer.…”

“…A similar deformation from tetrahedral towards trigonal bipyramidal geometry is observed on formation of shole interactions involving tetravalent elements of group 14. [4,34] An elongation of the covalent bond opposite to the incoming nucleophile is common for s-hole interactions, [3,4] and is usually rationalized as a consequence of the LP!s* charge transfer. Such elongation is observed also in 2 a-c, e.g., in 2 b the OsÀO bond opposite to the Os•••N OmB is 171.2 pm while the mean value of the three other Os À O bonds is 169.2 pm and the mean Os À O bond in pure OsO 4 is 169.7 pm.…”