Cj. Campbell et al., GLYCINE COUPLED TO A BIS(IMIDAZOLE) - A TETRADENTATE LIGAND RENDERINGDINUCLEAR COPPER(II) COMPOUNDS THROUGH LIGAND SHARING, Journal of the Chemical Society. Dalton transactions, (16), 1998, pp. 2703-2706
The tetradentate ligand (carboxymethylamino)bis(imidazole-2-yl)methane
(Hglyim), obtained through the reaction of glycine with bis(imidazol-
2-yl)nitromethane, rendered several dinuclear copper(II) compounds, vi
z. [Cu-2(glyim)(2)Cl-2]. 6H(2)O 1, [Cu-2(glyim)(2)Br-2]. 5H(2)O 2, [Cu
-2(glyim)(2)Cl(H2O)][CF3SO3]. 2H(2)O 3 and [Cu-2(glyim)(2)Cl(H2O)][ClO
4]. 2H(2)O 4. The single crystal structure of 1 was determined. It con
sists of [Cu-2(glyim)(2)Cl-2] units and several, mostly disordered, wa
ter molecules. The ligands and the anions are grouped in dimers of for
mula [Cu-2(glyim(-))(2)(Cl-)(2)] in which the two copper(II) ions are
entangled by two ligands. Each copper is in a square pyramidal N3OCl e
nvironment with the chloride ion occupying the apical position. Two of
the co-ordinating nitrogens are from the imidazole groups of one liga
nd, while an amine nitrogen and a carboxyl oxygen are donated by the o
ther ligand. This 2+2 ligand-sharing arrangement imposes a rather shor
t distance on the two copper(II) ions, i.e. 3.249(2), 3.357(2) and 3.3
73(2) Angstrom. A well resolved EPR spectrum of 10(-3) M 3 in MeOH was
obtained at 77 K with g(eff) values for H-z1, H-xy1, H-z2 and H-xy2 a
t 2.69, 2.26, 1.89 and 1.86 respectively, an A(parallel to) value of 8
7 G and a half-field signal at g = 4.24, indicating the preservation o
f the dinuclearity in solution (D = 0.047 cm(-1)). At concentrations o
f 10(-4) M and lower the dinuclear signals break down and the complex
decomposes into monomeric species (g(parallel to) = 2.27 and g(perpend
icular to) = 2.10).