Short X···N Halogen Bonds With Hexamethylenetetraamine as the Acceptor

Abstract

Hexamethylenetetramine (HMTA) and N-haloimides form two types of short (imide)X···N and X–X···N (X = Br, I) halogen bonds. Nucleophilic substitution or ligand-exchange reaction on the peripheral X of X–X···N with the chloride of N-chlorosuccinimide lead to Cl–X···N halogen-bonded complexes. The 1:1 complexation of HMTA and ICl manifests the shortest I···N halogen bond [2.272(5) Å] yet reported for an HMTA acceptor. Two halogen-bonded organic frameworks are prepared using 1:4 molar ratio of HMTA and N-bromosuccinimide, each with a distinct channel shape, one possessing oval and the other square grid. The variations in channel shapes are due to tridentate and tetradentate (imide)Br···N coordination modes of HMTA. Density Functional Theory (DFT) studies are performed to gain insights into (imide)X···N interaction strengths (ΔEint). The calculated ΔEint values for (imide)Br···N (−11.2 to −12.5 kcal/mol) are smaller than the values for (imide)I···N (−8.4 to −29.0 kcal/mol). The DFT additivity analysis of (imide)Br···N motifs demonstrates Br···N interaction strength gradually decreasing from 1:1 to 1:3 HMTA:N-bromosuccinimide complexes. Exceptionally similar charge density values ρ(r) for N–I covalent bond and I···N non-covalent bond of a (saccharin)N–I···N motif signify the covalent character for I···N halogen bonding.

A π–Cu(II)−π Complex as an Extremely Active Catalyst for Enantioselective α-Halogenation of N-Acyl-3,5-dimethylpyrazoles

“…Inspired by this development, we envisioned that chiral π–Cu­(II) catalysts could also promote other halogenation reactions. However, chlorination and bromination were suppressed under the same conditions due to undesired halogen bonding between 2,6-lutidine and X + reagents (X = Cl, Br) (see the Supporting Information for details) . This may be one of the reasons the development of catalytic enantioselective chlorination and bromination is more difficult than that of enantioselective fluorination.…”

Tetraruthenium Macrocycles with Laterally Extended Bis(alkenyl)quinoxaline Ligands and Their F4TCNQ•− Salts

“…The reversible formation and degradation of oligonuclear complexes along the way to the thermodynamically most stable metallamacrocyclic or cage structure are highlighted by the selective transformation of intermittently formed tetra-or hexaruthenium metallamacrocycles into larger octa-or smaller tetraruthenium ones on prolonged warming, which is strongly accelerated in the presence of an excess of the respective carboxylate ligand [18][19][20]. Similar phenomena en route to supramolecular coordination compounds (SCCs) and interconversions between different types of defined metallamacrocyclic or cage architectures that originate from reversible ligand binding were also described for other complex/ligand combinations [21][22][23][24][25][26][27][28][29][30]. Herein we report on two new tetraruthenium macrocycles, Ru4-5 and Ru4-6, that result from the electron-rich diruthenium building block Ru2-3.…”

The Pnictogen Bond, Together with Other Non-Covalent Interactions, in the Rational Design of One-, Two- and Three-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite Semiconducting Materials, and Beyond

“…The pnictogen bonds appear as N···I contacts in Figure 17 a,b, and as N···Br contacts in Figure 17 c,d. The N···I and N···Br contacts, respectively, in Figure 17 a,c,d are longer than the N···I contacts in Figure 17 b, which are exceptionally short, suggesting a significant degree of covalency [ 132 , 133 , 134 , 135 ].…”