Three-dimensional Hydrogen Bonding Network in the Structures of (Dimethylcyanamide)cobalt(II) Complexes

Abstract

Two complexes trans-[Co(NCNMe2)2(H2O)4]X2•2H2O ([1]X2•2H2O; X = Cl, Br) were prepared by the reaction of CoX2•6H2O with 2 equiv of NCNMe2 in methanol and isolated in excellent (98%) yields. The complexes were characterized by elemental analyses (C, H, N), high resolution ESI, IR spectroscopies, and their molecular structures were determined by a single-crystal X-ray diffraction. In [1]X2•2H2O, the hydrogen bonding between the counterions X– and both ligated and crystallization water molecules responsible for the formation of a 3D-network. Based on quantum chemical DFT calculations and topological analysis of the electron density distribution within the formalism of Bader's theory (AIM method) these interactions can be classified as weak (HO–H•••X–, X–•••H–OH, and HO–H•••X– contacts, 2.5–3.5 kcal/mol) and moderate (HO–H•••OH2 contacts, 5.7–6.3 kcal/mol) strength hydrogen bonds mainly due to electrostatics.