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 m ethods. The R and R(w) values for 5282 observed reflections were 7.06% and 9.10% respectively. Two structurally different complex cations ar e present in the same unit cell, one hexacoordinate and the other pent acoordinate. In the hexacoordinate cation, the two tridentate bis(2'-p icolyl)amine Ligands are trans-facially coordinated with two pyridine nitrogens and the two secondary amine nitrogens situated on four posit ions in a plane [Cu-N-pyr = 2.189(6), 2.146(6) Angstrom; Cu-N-sat 2.20 7(6), 2.201(5) Angstrom]. The remaining two pyridine nitrogens constit ute the axis [Cu-N-pyr 2.035(5), 2.038(5) Angstrom] in an equatorially expanded pseudooctahedral geometry. The pentacoordinate cation posses ses a square-pyramidal configuration, the two secondary nitrogens bein g mutually cis, with one Dipica equatorially tridentate [Cu-N-pyr 2.04 4(5), 2.027(5) Angstrom, Cu-N-sat = 1.995(5) Angstrom]. The other Dipi ca functions as a bidentate ligand, with one of the pyridine nitrogens occupying the equator [Cu-N-pyr = 1.986(5) Angstrom] and the aliphati c nitrogen defining the axial copper position [Cu-N-sat = 2.344(5) Ang strom]. Its second pyridine is uncoordinated but hydrogen-bonded to th e coordinated NH of the other ligand. Solution properties offer no cle ar distinction between the two cation stereochemistries. The ternary c helates [Cu(Dipica)(Acac)]ClO4 and [Cu(Dipica)(Bipy)](ClO4)(2) are als o described.