Molecular structure of mononuclear azido- and dicyanamido-Cu(II) complexes

A new series of mononuclear azido- and dicyanamido-Cu(II) complexes, [Cu(L)(N3)]ClO4 where L = pdpa {N-(2-aminopropyl)-N,N-bis(2-pyridylmethyl)amine}, Me3tren {tris(N-methyl-2-aminoethyl)amine} and Me6trien (1,1,4,7,10,10-hexamethyltriethylenetetraamine) and Cu(L)(C2N3)2 with L = pmedien (N,N,N′,N″,N″-pentamethyldiethylenetriamine) and Me2dpt (N,N-dimethyldipropyltriamine) were synthesized and structurally characterized by electronic and IR spectroscopy as well as by X-ray. Single crystal X-ray diffraction analysis of the complexes [Cu(pdpa)(N3)]ClO4 (1), [Cu(Me3tren)(N3)]ClO4 (2) and [Cu(pmedien)(C2N3)2] (3) reveals their monomeric nature. The structures of the complexes 1 and 2 derived from the blocking tripod tetraamines pdpa and Me3tren consist of isolated [Cu(L)(N3)]+ cations and ClO4− counter ions. The copper centers are penta-coordinated by the four N of the amine ligands with the monodentate azido ligand occupying the apical site in distorted trigonal bipyramidal (TBP) geometry. Complex 1 exhibits π–π stacking interaction between the pyridyl groups. In the neutral complex 3, where the blocking ligand, pmedien is a linear tridentate amine the penta-coordinate geometry of the complex was achieved by the three planar amine-N and two terminal nitrile-N atoms from the two dicyanamide groups; one N in the basal position from the first dicyanamido group and one N at the apical position from the second group. The coordination polyhedron around the copper center may be described as an axially elongated square pyramidal (SP). The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers.