The first structural evidence of a polymeric Cu(II) compound with a bridging dicyanamide anion: X-ray structure, spectroscopy and magnetism of catena-[polybis(2-aminopyrimidine)copper(II)-bis(mu-dicyanamido)]

The new Cu(II) coordination compound, catena-[Cu(N(CN)(2))(2)(ampym)(2)] (i n which ampym = 2-aminopyrimidine) has been synthesized and investigated by X-ray analysis, ligand field, EPR spectroscopy and magnetic susceptibility . The first compound crystallizes in the monoclinic space group C2/c With I I = 13.579(6), b = 15.453(5), c = 7.570(7) Angstrom, beta = 92.03(5)degrees and refines to an R value of 0.0322. The geometry around the copper(II) at om is axially elongated octahedral with the basal plane formed by the nitro gen of two monodentate coordinating ligands and two (N2) nitrogens of the b ridging dicyanamide anions with distances which vary from 1.972(3) to 2.078 Angstrom forming an almost perfect square planar geometry. The apical posi tions are occupied by the other nitrogens (N3) of the bridging dicyanamide anions with a distance of 2.316(3) Angstrom. The bridging dicyanamide forms a one-dimensional polymeric chain with the other copper units. The Cu-Cu s eparation is 7.570 Angstrom. Hydrogen bonding (3.1231 Angstrom) between the hydrogen atoms of the amino nitrogen and the uncoordinated nitrogen of the ligand forming pairs of ligands stabilizes the lattice, and bridges the ch ain in 2D-sheets. A Ligand field maximum occurs at 14.3 x 10(3) cm (- 1) an d the EPR values, measured as a solid, are g(perpendicular to) = 2.08 and g (//) = 2.29. Magnetic susceptibility of the powdered sample was measured fr om 4 to 300 K. The inverse susceptibility versus temperature shows that the curve follows the Curie-Weiss law. The mu(eff) versus temperature gives a negligible rise at lower temperature and stays constant at about 1.80-1.84. The characteristic infrared vibrations for the dicyanamide anion are the n u(s) + nu(as) (C drop N), found as one strong band at 2301 cm (- 1), and th e nu(C drop N), found as two strong bands at 2254 and 2188 cm (- 1). (C) 20 00 Elsevier Science S.A. All rights reserved.