SYNTHESIS AND PROPERTIES OF ISOSTRUCTURAL TRANSITION-METAL (COPPER, NICKEL, COBALT, AND IRON) COMPOUNDS WITH 7,7',8,8'-TETRACYANOQUINODIMETHANIDE(1-) IN AN UNUSUAL MONODENTATE COORDINATION MODE - CRYSTAL-STRUCTURE OF BIS(3,5-BIS(PYRIDIN-2-YL)-4-AMINO-1,2,4-TRIAZOLE)BIS(7,7',8,8'-TETRACYANOQUINODIMETHANIDO)COPPER(II)

The synthesis and properties of compounds M(abpt)2(TCNQ)2, with M = Cu, Ni, Co, and Fe, abpt = 3,5-bis(pyridin-2-yl)-4-amino-1,2,4-triazole, and TCNQ = 7,7',8,8'-tetracyanoquinodimethane, are described. The complexes exhibit very similar spectroscopical and electrical properties. The four compounds appear to be isostructural according to their IR spectra and X-ray powder diffraction data. The crystal structure of CuC48H28N20 has been solved. It crystallizes in the triclinic space group, P1BAR with a = 9.194 (1) angstrom, b = 9.761 (2) angstrom, c = 12.235 (2) angstrom, alpha = 68.29 (1)-degree, beta = 86.72 (1)-degree, gamma = 81.80 (1)-degree, V = 1009.7 (3) angstrom3, and Z = 1. Heavy-atom techniques were used, and the structure was refined by least-squares methods to a residual R value of 0.052 for 1957 reflections. The copper(II) atom is elongated octahedrally, surrounded by four nitrogens of two symmetry-related abpt ligands (Cu-N = 1.987(5) and 2.046(5) angstrom) and by two axial, monodentately coordinating TCNQ- anions (Cu-N = 2.442 (5) angstrom). The intermolecular TCNQ units form eclipsed dimers, with their mean planes at a close distance of 3.22 angstrom. At room temperature, all four compounds behave virtually as insulators (sigma(300 K) = 10(-7)-10(-10) S cm-1).