Molecular and electronic structure of the complexes formed by the Schiff base N-(o-hydroxybenzylidene)ferroceneamine with CoII, NiII, CuII, and ZnII
Abstract
The Schiff base (HL) formed by condensation of ferrocenylamine with salicylaldehyde has been used for the preparation of complexes with CoII, NiII, CuII, and ZnII of formula [ML2]. The ligand HL is stable in the solid state and easily hydrolyzed in solution with formation of the free N-base. This hydrolysis has been studied kinetically in a water–acetone acidic medium. A single-crystal X-ray study of HL [orthorhombic, space group Pca21, a= 16.229(2), b= 5.914(1), c= 14.516(2)Å, α=β=γ= 90°, and Z= 4] indicates almost coplanarity between the chelating N–C–C–O moiety and the adjacent cyclopentadienyl ring of ferrocene, with the H atom of the hydroxyl group bridging between the N and O atoms. An X-ray study has been also carried out on the complex [CuL2[monoclinic, space group P21/c, a= 12.668(2), b= 10.422(2), c= 20.921 (3)Å;, α=γ= 90, β= 91.10(1)°, and Z= 4] in which CuII has a distorted tetrahedral environment. On the basis of the available information, i.e. X-Ray, visible spectral, and magnetic susceptibility data, all the [ML2 complexes can be assigned a tetrahedral or pseudo-tetrahedral structure. Cyclic voltammetric experiments in dimethylformamide have been performed mainly to examine the FeII→ FeIII one-electron oxidation in HL and its [ML2] complexes, and the results are compared to those previously obtained for ferrocenylamine and other monosubstituted ferrocene derivatives.