Nr. Sangeetha et al., Copper(II)-activated transformation of azomethine to imidate: synthetic and structural studies, POLYHEDRON, 19(28), 2000, pp. 2713-2717
The Schiff base 2-pyridine-carboxaldehyde 4-dimethylaminobenzoylhydrazone (
HL, 1) was prepared by reacting 2-pyridine-carboxaldehyde and 4-dimethylami
nobenzoylhydrazine in a 1:1 molar ratio in methanol. Reaction of HL (1) wit
h Cu(O2CCH3)(2).H2O (in a 1:1 molar ratio) in methanol afforded a dinuclear
copper(II) complex, [Cu-2(mu -O2CCH3)(2)L'(S)]. 2H(2)O (2). The azomethine
functionality (-CH=N-) of 1 is converted to imidate (-C(OMe)=N-) in the co
mplexed ligand L'(-). Molecular structures of both 1 and 2 were determined
by X-ray crystallographic studies. The dinuclear molecule of 2 is centrosym
metric and contains two monoatomic bridging acetate groups. Each copper(II)
centre is in a square-pyramidal N2O3 coordination sphere. The ligand, L'(-
) coordinates the metal ion via the pyridine-N, the imidate-N, and the depr
otonated amide-O atoms. One of the acetate oxygen atoms completes the N2O2
square-plane. The oxygen of the symmetry-related acetate fills the apical c
oordination site. Structural parameters are consistent with both copper ion
s being in a +2 oxidation state. The room temperature magnetic moment is 1.
89 mu (B) (per Cu). In powder phase the complex displays an axial EPR spect
rum at 298 K. The complex is nonconducting in methanol solution. The electr
onic spectrum shows a ligand field absorption at 680 nm and charge transfer
bands in the range 426-215 nm. (C) 2000 Elsevier Science B.V. All rights r
eserved.