Binuclear metal(II) complexes of 1,3-diphenyltriazene : The crystal and molecular structures of the nickel(II), palladium(II) and copper(II) derivatives

Abstract

The crystal and molecular structures have been determined, by single-crystal X-ray methods, for each of the isomorphous set of divalent binuclear metal derivatives of 1,3-diphenyltriazene, abbreviated as dptH, [M(dpt)₂]₂ where M = Ni, Pd, and Cu. The crystals are composed of discrete molecular units, of composition M₂(dpt)₄, which have a syn-syn structure analogous to that of copper(II) acetate monohydrate with pairs of closely separated metal atoms held together by the terminal nitrogen atoms of four ligand groups in such a way that the environment of each metal atom is almost square-planar. The interatomic distances between the pairs of metal atoms, 2.395(3), 2563(1), and 2.441(2) Ǻ for the Ni, Pd, and Cu compounds, are strongly suggestive of metal-metal bonding. The two N₄-planes are almost parallel but the two sets of coordinating nitrogen atoms are twisted markedly from the eclipsed configuration, the average angle of rotation being about 15°. Crystals of each complex are triclinic with space group P 1. The unit cell parameters in the order of a, b, c, α, β, and γ are 10.335(3), 15.84(1), 13.546(3)& 100.48(5), 94.47(2), 102.57(3)° for Ni₂(dpt)₄; 10.486(1), 15.791(2), 13.751(1)Ǻ, 99.48(1), 93.61(1), 104.37(1)° for Pd₂(dpt)₄; 10.373(3), 15.916(5), 13.612(3) Ǻ, 99.51(2), 94.85(3), 102.33(2)° for Cu₂(dpt)₄. The structure of the nickel complex was solved by the Patterson-Fourier method and the atomic parameters found for this structure were used as the basis of the structure determinations of the isomorphous copper and palladium compounds. All three structures were refined by a block-diagonal least-squares method using 3300 (photographic data) 4065 (counter) and 2753 (counter) independent non-zero terms for the nickel(II), palladium(II) and copper(II) compounds respectively, converging with R values 0.13 (isotropic), 0.056 (anisotropic) and 0.069 (isotropic) respectively.