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

• The first structurally characterized cobalt(II) complexes featuring cyanamide ligands.
• The hydrogen bonding in trans-[Co(NCNMe2)2(H2O)4]X2·2H2O (X = Cl, Br) forms a 3D-network.
• The hydrogen bonds were classified as weak and moderate strength contacts.

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.

The system of hydrogen bonding forms a 3D-network in the structures of trans-[Co(NCNMe2)2(H2O)4]X2·2H2O (X = Cl, Br).Figure optionsDownload as PowerPoint slide