Chalcogen Bonding between Tetravalent SF₄ and Amines

Abstract

The N···S chalcogen bond between SF4 and a series of alkyl and arylamines is examined via ab initio calculations. This bond is a strong one, with a binding energy that varies from a minimum of 7 kcal/mol for NH3 to 14 kcal/mol for trimethylamine. Its strength derives in large measure from charge transfer from the N lone pair into the σ*(SF) antibonding orbitals involving the two equatorial F atoms, one of which is disposed directly opposite the N atom. Decomposition of the total interaction energy reveals that the induction energy constitutes more than half of the total attraction. The positive region of the molecular electrostatic potential of SF4 that lies directly opposite the equatorial F atoms is attracted to the N lone pair, but the magnitude of this negative region on each amine is a poor predictor of the binding energy. The shortness and strength of the N···S bond in the dimethylamine···SF4 complex suggest it may better be described as a weak covalent bond.

Halogen, Chalcogen, and Pnicogen Bonding Involving Hypervalent Atoms

“…The authors found monomer rearrangements similar to those described here, with comparable deformation energies, which were directly linked to a strengthening of the relevant σ‐holes. Previous calculations of the S⋅⋅⋅N chalcogen bond involving SF 4 and a series of N bases found chalcogen bond energies comparable to that in Table . Also confirmed there was the NBO charge transfer into peripheral S−F antibonding orbitals.…”

“…Even when the valency is extended to five, as in the case of XF 5 , its square‐pyramidal shape allows a path of a base to the central X atom that is not obstructed by the surrounding substituents. In the case of a hypervalent chalcogen atom, the see‐saw shape of SF 4 likewise presents little in the way of a steric obstacle to formation of a S⋅⋅⋅N chalcogen bond, nor is this a problem in a YO 2 X 2 bonding situation with Y a chalcogen atom, nor for SO 3 . There has been some study of hypervalent pnicogens (Z), specifically in the case of four substituents as in ZOF 2 X, ZOF 3 , and ZH 2 FO but little was described concerning any geometrical changes in the monomer required to accommodate the base, nor the energetic consequence of any such distortion.…”

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

“…But the question arises as to whether a tetrel atom, within a tetravalent covalent bonding situation, is limited to only a single such bond. [25,[55][56][57][58][59][60] There has been a certain amount of consideration of the general topic of hypervalent pnicogen, halogen, and even aerogen atoms [9,[61][62][63][64][65][66][67][68][69][70][71][72][73][74] but not in the context of tetrel atoms, which have their own unique electronic and spatial issues. The theoretical literature to date has little to say on this issue.…”

Complexes of O=C=S with Nitrogen Bases: Chalcogen Bonds, Tetrel Bonds, and Other Secondary Interactions

“…The first of these is the halogen bond, which arises when a Group 17 atom acts as an acid and accepts a pair of electrons from a base . Chalcogen bonds arise when a Group 16 atom is the electron‐pair acceptor, pnictogen bonds involve Group 15 atoms, and tetrel bonds Group 14 . Recently, Legon and Resnati, et al.…”