Metal-Involving Bifurcated Halogen Bonding C–Br···η2(Cl–Pt)

The complexes trans-[PtCl2(NCNR2)2] (R2 = Me2 1, Et2 2, (CH2)4 3) were cocrystallized with CBr4 in CHCl3 (1 and 3) or in MeNO2 (2) forming adducts 1·CHCl3·CBr4, 2·2CBr4, and 3·2CBr4, respectively. In two out of three adducts, viz. 1·CHCl3·CBr4 and 2·2CBr4, unique Br3C–Br···η2(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.