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),], where M = Ni, Pd, and Cu. The crystals are composed of discrete molecular units, of composition Mz(dpt)4, which have a syn-syn structure analogous to that of copper(11) 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) A 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 'f. The unit cell parameters in the order of a, b, c, a, p, and y are 10.d p t )~. 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@), palladium(~~) and copper(11) compounds respectively, converging with R values 0.13 (isotropic), 0.056 (anisotropic) and 0.069 (isotropic) respectively.
The structure of the complex Lcu2Cl2,6H2O (where LH2 is the tetra-Schiff base macrocycle formed as the condensation product of propane-1,3-diamine and 2-hydroxy-5-methylisophthal- aldehyde in the mole ratio 2: 2) was determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, a 7.720(1), b 17.079(1), c 11.171(1) � and β 91.50(1)�, with two molecules per unit cell. It has proved difficult to resolve the ambiguity between the three possible space groups (C2, Cm, and C2/m) and the initial model has been refined in each using a full-matrix least-squares method. The space group C2/m seems the most likely and the structure is described in it; R 0.049 for the 1369 independent reflections measured using counter methods. The structure analysis has confirmed the anticipated cyclic structure of the ligand with the two copper atoms held together in a binuclear arrangement by the planar N4O2 donor set; the Cu.. .Cu distance is 3.133(1)�. Each copper atom has a distorted square-pyramidal environment with the apical position of each being occupied by a chlorine atom; the two chlorine atoms are on the opposite sides of the macrocycle. The water molecules are not coordinated, but form an extensive system of hydrogen bonding throughout the crystal with discrete binuclear molecules of the LCu2Cl2 complex.
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