In recent years, there has been increasing interest in utilising halogen bonds in organic synthesis, especially in aromatic halogenation reactions. -Halosuccinimides and 1,3-dihalo-5,5-dimethylhydantoins are popular sources of halonium ions due to their ease of handling and low toxicities. Traditionally, these -haloimides are activated by electrophiles, namely Brønsted and Lewis acids. The recent discovery of possible activation by nucleophilic Lewis base catalysts led to a paradigm shift in aromatic halogenation. Active functional motifs in Lewis base catalysts such as CS, R-S-R, Ar-S-S-Ar, SO, Ar-NH, and RNHCl form halogen bonds with the positively charged σ-hole of the halogen atoms: an essential interaction to produce halonium ions. This review highlights the evolution of the two modes of activation. Evidence of halogen bond formation from mechanistic studies of nucleophilic activation is also discussed herein.
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http://dx.doi.org/10.1039/d1ob00936b | DOI Listing |
Angew Chem Int Ed Engl
January 2025
Chang Chun Institute of Applied Chemistry Chinese Academy of Sciences, State Key Laboratory of Electroanalytical Chemistry, 5625 Renmin Street, 130022, Changchun, CHINA.
Single-atom catalysts (SACs) with high metal loadings are highly desirable but still challenging for large scale synthesis. Here we report a new technique named as dry-solid-electrochemical synthesis (DSES) for a general large-scale synthesis of SACs with high metal loadings in an energy-conservation and environment-friendly way. With it, a series of pure carbon-supported metal SACs (Platinum up to 35.
View Article and Find Full Text PDFChemistry
January 2025
Universitat Bielefeld, Chemie, Universitätsstraße 15, 33615, Bielefeld, GERMANY.
This work combines halogen and chalcogen bonding. Short, polarity directed C-X⋅⋅⋅Ch (X = Br or I, Ch = Se or Te) contacts were prepared by in situ low-temperature cocrystallization of liquid mixtures of neutral pentafluorohalogenobenzenes C6F5X and dimethyl chalco-genides Me2Ch. Solid-state structures of Me2Se and Me2Te were determined 150 and 125 years after their first description.
View Article and Find Full Text PDFChemistry
January 2025
Politecnico di Milano, Department of Chemistry, Materials, Chemical Engineer., via Mancinelli 7, 20131, Milan, ITALY.
Molecular recognition mediated by s-hole interactions is enhanced as the electrostatic potential at the σ-hole becomes increasingly positive. Traditional methods to strengthen σ-hole donor ability of atoms such as halogens often involve covalent modifications, such as, introducing electron-withdrawing substituents (neutral or positively charged) or electrochemical oxidation. Metal coordination, a relatively underexplored approach, offers a promising alternative.
View Article and Find Full Text PDFJ Phys Chem A
January 2025
Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23173, United States.
The propensities for sigma hole bonding by halogen atoms bonded to central atoms below period 2 in the periodic table remain to be systematically examined. Using iodine as our reference halogen atom, a comprehensive analysis of the tendencies for halogen and other forms of significant sigma hole bonding by simple compounds of main group atoms from H to At is accomplished. An examination of the structure and bonding of complexes formed by those iodine-substituted main group compounds and sigma donating bases (ammonia and trimethylamine) is performed to probe the viability of halogen bonding by heavy main group RM-I compounds in particular, given the historic focus on period 2.
View Article and Find Full Text PDFPhys Chem Chem Phys
January 2025
Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, Ecuador.
A theoretical description of various [AeX] (Ae = Be-Ba, X = F-I) systems, some of which have been reported in the literature to bear an unusual quadruple bond between the metal and the halogen, is provided based on both (i) the localization of the Fermi hole and (ii) the topological analysis of the one-electron density. Insights into the bond order of various [AeX] systems are inferred on the basis of the number of electrons localized in the bond basin, the topology of the Fermi hole information computed along the bond axis, and the delocalization index. The results suggest that the [AeX] molecules present a bond with attributes closer to a classical dative bond than to a multiple one, being characterized by large stabilization due to the electrostatic interaction between the polarized metal and the halogen anion.
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