Structural characterization of five-coordinate copper(II), nickel(II), and cobalt(II) thiocyanato complexes derived from bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)amine

The reaction of M(ClO4)2·6H2O with NH4NCS in presence of the organic sterically hindered bis(2-(di-3,5-dimethyl-1-pyrazolyl)ethyl)amine (bedmpza) afforded the five-coordinate mononuclear dithiocyanato–M(II) complexes [M(bedmpza)(NCS)2]·xMeOH (1: M = Cu2+, x = 0; 2: M = Ni2+, x = 0; 3: M = Co2+, x = 0.84). The compounds which proved to be non-electrolytes were characterized by IR and UV–Vis spectroscopy and their molecular structures were determined by single-crystal X-ray crystallography. In these complexes, the five-coordinate geometry was achieved by the three N-donors of the ligand bedmpza and two N atoms of the terminal thiocyanato ligands. The Cu(II) complex exists in two polymorphs 1-I and 1-II: an intermediate five-coordinate geometry with the two thiocyanato ligands are arranged as cisoid in 1-I and distorted square pyramidal geometry with the thiocyanato ligands are in transoid orientation in 1-II. Although the later geometry was also observed in the nickel complex 2, distorted trigonal bipyramidal geometry was found in 3. Each complex forms hydrogen bonds of type N–H⋯S from the secondary amine N(3) donor atoms to the adjacent terminal S(1) acceptor atoms of the thiocyanate group. The thermal behavior of the two polymorphs 1-I and 1-II were similar and no significant differences were observed between the two complexes.

The five coordinate complexes [M(bedmpza)(NCS)2], where M = Cu(II), Ni(II), and Co(II) and bedmpza = bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)amine, were synthesized and characterized by spectroscopic techniques. The molecular structures of the complexes were determined by X-ray crystallography.Figure optionsDownload as PowerPoint slideHighlights
► Five coordinate copper(II), nickel(II), and cobalt(II) complexes.
► Spectroscopic characterization of mononuclear thiocyanato complexes.
► Molecular structures of the complexes.