2 NEW MU-AZIDO NICKEL(II) UNIFORM CHAINS - SYNTHESES, STRUCTURES, AND MAGNETOSTRUCTURAL CORRELATIONS

Two new monodimensional (mu-azido)nickel(II) complexes of formulas catena-(mu-N3)[Ni(232-tet)](ClO4) (1) and catena-(mu-N3)[Ni(323-tet)](ClO4) (2) have been synthesized and characterized. 232-tet and 323-tet are the tetraamines N,N'-bis(2-aminoethyl)-1,3-propanediamine and N,N'-bis(3-aminopropyl)-1,2-ethanediamine, respectively. The crystal structures of 1 and 2 have been solved. The complex [C7H20N7Ni]n(ClO4)n (1) crystallizes in the monoclinic system, space group P2(1)/a, with fw = 360.44, a = 11.806(3) angstrom, b = 13.154(3) angstrom, c = 9.598(2) angstrom, beta = 97.90(2)-degrees, V = 1476(1) angstrom3, Z = 4, R = 0.045, and R(w) = 0.055. The complex [CgH22N7Ni]n(ClO4)n (2) crystallizes in the orthorhombic system, space group Pbca, with fw = 374.47, a = 17.151(2) angstrom, b = 16.267(2) angstrom, c = 11.478(2) angstrom, V = 3203(1) angstrom3, Z = 8, R = 0.049, and R(w) = 0.058. In both compounds the nickel atoms are placed in an octahedral environment with the mu-azido groups in trans positions. The magnetic properties of these compounds have been studied. The thermal variation of the molar susceptibility is typical of an antiferromagnetically coupled nickel(II) uniform chain displaying Haldane gap behavior. Using the Hamiltonian H = -JSIGMAS(i)S(i+1), the J values obtained were -26.9 and -62.7 cm-1 for 1 and 2, respectively. Magneto-structural correlations have been obtained in a series of analogous systems, using extended Huckel calculations.