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 Co^II, Ni^II, Cu^II, and Zn^II 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 Cu^II 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 Fe^II→ Fe^III 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.