Metal-Involving Bifurcated Halogen Bonding C-Br center dot center dot center dot eta(2)(Cl-Pt)
CRYSTAL GROWTH & DESIGN
Authors: Dabranskaya, Uladzislava; Ivanov, Daniil M.; Novikov, Alexander S.; Matveychuk, Yury, V; Bokach, Nadezhda A.; Kukushkin, Vadim Yu
Abstract
The complexes trans-[PtCl2 (NCNR2)(2)] (R-2 = Me-2 1, Et-2 2, (CH2)(4) 3) were cocrystallized with CBr4 in CHCl3 (1 and 3) or in MeNO2 (2) forming adducts 1 center dot CHCl3 center dot CBr4, 2.2CBr(4), and 3.2CBr(4), respectively. In two out of three adducts, viz. 1 center dot CHCl3 center dot CBr4 and 2.2CBr(4), unique Br3C-Br center dot center dot center dot eta(2)(Cl-Pt) metal-involving bifurcated halogen bonding was detected, by single-crystal XRD, along with other halomethane-chloride interactions. Appropriate density functional theory calculations performed by two complementary methodologies, (i) single-point "quasi-solid state" calculations with topological analysis of the electron density distribution within the framework of Bader theory (QTAIM method) and (ii) Kohn-Sham calculations with periodic boundary conditions, confirmed the existence of the bifurcated interactions and their noncovalent nature. Estimated energies of these interactions vary from 1.1 to 4.7 kcal/mol.
Mechanisms of the reactions of propane with CBr3+ cation and superelectrophilic complex CBr4+center dot AlBr3- containing a bromine-centered cationic center: a theoretical study
RUSSIAN CHEMICAL BULLETIN
Authors: Chistyakov, AL; Stankevich, IV; Gambaryan, NP; Akhrem, IS
Abstract
Fragments of the potential energy surfaces (PES) of the systems [C3H8 + CBr3+] and [C3H8 + Br2CBr+. Br2AlBr2-] were simulated by the MNDO/PM3 method. Energy minima corresponding to weakly bound adducts of propane molecule with the CBr3+ cation or neutral complex CBr3+. AlBr4- were found on the PES's of both systems. These are adducts with the coordination of a H atom of the methylene group of the propane molecule to the electrophile at the Br atom carrying the largest positive charge. As the fragments of the adducts are brought close together, the coordinated H atom migrates to the C atom of the CBr3+ fragment. The potential barriers of these migrations were found to be low for both systems. The reactions proceed without formation of cyclic intermediates or transition states typical of the Olah mechanism.
COA
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