H2C(X)- X•••X- (X = CI, Br) Halogen Bonding of Dihalomethanes

The dihalomethane-halide H2C(X)-X center dot center dot center dot X- (X = Cl, Br) halogen bonding was detected in a series of the cis [PdX(CNCy){C(NHCy)=NHC6H2Me2TH2}] X center dot CH2X2 (X = Cl, Br) associates by single-crystal XRD followed by DFT calculations. Although ESP calculations demonstrated that the a-hole of dichloromethane is the smallest among all halo methane solvents (the maximum electrostatic potential is only 2.6 kcal/mol), the theoretical DFT calculations followed by Bader's QTAIM analysis (MO6/DZP-DICH level of theory) confirmed the H2C(X)-X center dot center dot center dot X- halogen bond in both the solid-state and gas-phase optimized geometries. The estimated bonding energy in H2C(X)-X center dot center dot center dot X- is in the 1.9-2.8 kcal/mol range.