Nature of halogen bond adducts of carbones with XCF3 (X = Cl, Br, I) species

Quantum chemical calculations have been utilized to study the covalent character of halogen bonding in addition complexes of trifluorohalomethanes XCF3 (X = Cl, Br, I) with well-studied electron-pair-donor divalent C(0) compounds C(NHC)(2), NHC-C-CO, NHC-C-PH3 and PPh3-C-CO [NHC =N-heterocyclic carbene, (CHNH)(2)C]. The geometries of the complexes in which the dicoordinated carbon molecules bind as ligands to one and two XCF3 moieties, respectively, have been optimized to analyze the strength and nature of bond formation using energy decomposition analysis and natural bond orbital calculations. Addition of one XCF3 to the carbones occurs through the lone pair having a orbital character in the plane of the L -> C <- L' bond, while the addition of a subsequent XCF3 leads to the carbone acquiring a tetrahedral geometry. The bond dissociation energy (BDE) for removing ICF3 from one of the carbone adducts is higher than for ClCF3 or BrCF3, while the BDE for the second XCF3 is clearly less than for the first dissociation. Even though electrostatic interactions are known to dominate in halogen bonding, we find considerable contributions from orbital and dispersion interactions. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Quantum chemical calculations were used to study the covalent character of halogen bonding in addition complexes of trifluorohalomethanes with electron-pair-donor divalent compounds. The study found differences in the addition of XCF3 molecules and bond dissociation energies, indicating significant contributions from orbital and dispersion interactions in addition to electrostatic interactions in halogen bonding.