A Computational Study of Chalcogen‐containing H₂X…YF and (CH₃)₂X…YF (X=O, S, Se; Y=F, Cl, H) and Pnicogen‐containing H₃X′…YF and (CH₃)₃X′…YF (X′=N, P, As) Complexes

Abstract

A computational study was undertaken for the model complexes H X…YF and (CH ) X…YF (X=O, S, Se; Y=F, Cl, H), and H X'…YF and (CH ) X'…YF (X'=N, P, As), at the MP2/6-311++G(d,p) level of theory. For H X…YF and H X'…YF, noncovalent interactions dominate the binding in order of increasing YF dipole moment, except for H As…F , and possibly H As…ClF. However, for the methyl-substituted complexes (CH ) X…YF and (CH ) X'…YF the binding is especially strong for the complexes containing F , implying significant chemical bonding between the interacting molecules. The relative stability of these complexes can be rationalized by the difference in the electronegativity of the X or X' and Y atoms.

Regular/abnormal variation in the strength and nature of the halogen bond between H2Te and the dihalogens: Prominent effect of methyl substituents

“…A similar result was found for the halogen bond formed by ClF with H 2 O and H 2 Se since the respective interaction energies were − 4.5 and − 3.8 kcal/mol . Although H 2 Z (Z = O, S, and Se) binds weakly with F 2 , their binding becomes very strong when the two H atoms are replaced by methyl groups, increasing to −45.4 kcal/mol in Me 2 Se‐F 2 . This indicates that the methyl group in the electron donor has a prominent effect on the strength of the halogen bond.…”

“…For example, Bloemink et al found that F 2 can form a halogen bond with NH 3 in their experimental study . More recently, McDowell and Buckingham performed a theoretical study of the H 3 N‐F 2 complex, for which an interaction energy of −1.2 kcal/mol at the MP2/6–311++(d,p) level was reported . This showed that the complex is stable in some environments and can be detected as a pre‐reactive intermediate in gas‐phase mixtures of fluorine and ammonia …”

“…This showed that AsH 3 has a much stronger binding ability with F 2 than does NH 3 . However, AsH 3 is bound more weakly to ClF than it is to F 2 . A possible reason is the different origin of the halogen bond formed by F 2 and by ClF since the former halogen bond has greater covalency .…”

“…Furthermore, it is of interest to compare the electron‐donating ability of the heavier group 15 or 16 atoms . The complexes of NH 3 ‐F 2 , PH 3 ‐F 2 and AsH 3 ‐F 2 were studied with infrared spectroscopy and their interaction energies were, respectively, calculated to be −1.2, −0.4 and − 40.2 kcal/mol at the MP2/6–311++G(d,p) level . This showed that AsH 3 has a much stronger binding ability with F 2 than does NH 3 .…”

Noncovalent Interactions in Complexes Involving the Cyclic C2H2X (X=O, S, Se) Molecules and the Lewis Acids YF (Y=F, Cl, Br, H)

“…A previous study of the related chalcogen‐containing H 2 X…YF and (CH 3 ) 2 X…YF (X=O, S, Se; Y=F, Cl, H) complexes found stronger binding of the F 2 complexes, vis‐à‐vis the ClF and HF analogues, despite the fact that F 2 is nonpolar . This unusual finding was rationalized by the difference in the electronegativity of the X and Y atoms .…”