Crystal and molecular structures of cadmium(II) nitrate complexes with triamines: 1,5-diamino-3-azapentane, 1,6-diamino-3-azahexane and 1,7-diamino-4-azaheptane

The following new complexes of Cd(II) nitrate with triamines have been prepared and characterized: [Cd(NH2(CH2)(2)NH-(CH2)(2)NH2)(2)](NO3)(2) (1), [Cd(NH2(CH2)(2)NH(CH2)(3)NH2)(2)](NO3)(2) (2) and [Cd(NH2(CH2)(3)NH(CH2)(3)NH2)(2)](NO3)(2) (3). Their structures have been determined by a single-crystal X-ray diffraction method. Because of the instability of the crystals 2 and 3 at room temperature, all complexes were examined at 100 K. In the complexes investigated all nitrogen atoms of the triamines coordinate the Cd(II) atom. All data sets showed {N6}-coordinated complexes. The stoichiometry of the complexes in the solid state is always 1:2, although the crystals were grown from solutions with different concentration ratios of the components (Cd-triamine: 1: 1, 1:2 or 1:3). The Cd(II) atom of complex 1 is sandwiched between two triamines related by a twofold axis. Complexes 2 and 3 are characterized by a distorted octahedral coordination. The conclusions obtained correspond to the solution structures obtained from NMR, IR as well as equilibrium studies. (C) 2002 Elsevier Science Ltd. All rights reserved.