Three-dimensional hydrogen bonding network in the structures of (dimethylcyanamide)cobalt(II) complexes

Two complexes trans-[Co(NCNMe2)(2)(H2O)(4)]X-2 center dot 2H(2)O ([1] X-2 center dot 2H(2)O; X = Cl, Br) were prepared by the reaction of CoX2 center dot 6H(2)O 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] X-2 center dot 2H(2)O, 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 center dot center dot center dot X, X center dot center dot center dot H-OH, and HO-H center dot center dot center dot X contacts, 2.5-3.5 kcal/mol) and moderate (HO-H center dot center dot center dot OH2 contacts, 5.7-6.3 kcal/mol) strength hydrogen bonds mainly due to electrostatics. (C) 2016 Elsevier B.V. All rights reserved.