Inorganic Chemistry, Vol.35, No.2, 467-471, 1996
Dipicolylamine Complexes of Copper(II) - 2 Different Coordination Geometries in the Same Unit-Cell of Cu(Dipica)(2)(BF4)(2)
Bright blue Cu(Dipica)(2)(BF4)(2) crystallizes in the monoclinic space group P2(1)/n, with unit cell parameters a 23.406(6) Angstrom, b = 9.338(2) Angstrom, c = 25.573(7) Angstrom, beta = 95.39(2)degrees, and Z = 8. The structure was solved by conventional Patterson and Fourier methods. The R and R(w) values for 5282 observed reflections were 7.06% and 9.10% respectively. Two structurally different complex cations are present in the same unit cell, one hexacoordinate and the other pentacoordinate. In the hexacoordinate cation, the two tridentate bis(2’-picolyl)amine Ligands are trans-facially coordinated with two pyridine nitrogens and the two secondary amine nitrogens situated on four positions in a plane [Cu-N-pyr = 2.189(6), 2.146(6) Angstrom; Cu-N-sat 2.207(6), 2.201(5) Angstrom]. The remaining two pyridine nitrogens constitute the axis [Cu-N-pyr 2.035(5), 2.038(5) Angstrom] in an equatorially expanded pseudooctahedral geometry. The pentacoordinate cation possesses a square-pyramidal configuration, the two secondary nitrogens being mutually cis, with one Dipica equatorially tridentate [Cu-N-pyr 2.044(5), 2.027(5) Angstrom, Cu-N-sat = 1.995(5) Angstrom]. The other Dipica functions as a bidentate ligand, with one of the pyridine nitrogens occupying the equator [Cu-N-pyr = 1.986(5) Angstrom] and the aliphatic nitrogen defining the axial copper position [Cu-N-sat = 2.344(5) Angstrom]. Its second pyridine is uncoordinated but hydrogen-bonded to the coordinated NH of the other ligand. Solution properties offer no clear distinction between the two cation stereochemistries. The ternary chelates [Cu(Dipica)(Acac)]ClO4 and [Cu(Dipica)(Bipy)](ClO4)(2) are also described.
Keywords:CRYSTAL-STRUCTURES;MOLECULAR-STRUCTURES;ELECTRONIC-PROPERTIES;LIGANDS;IMIDAZOLE;CHLORIDE;ION;STEREOCHEMISTRY;PERCHLORATE;ZINC(II)