Optically active complexes of Schiff bases. Part 3. Complexes of iron(III) with quadridentate Schiff bases derived from salicylaldehyde

Abstract

Five-co-ordinate complexes of iron(III) have been prepared with quadridentate Schiff-base ligands obtained by the condensation of 2 mol of salicylaldehyde with 1 mol of a C-substituted diamine. They are neutral high-spin iron(III) species which in some cases can crystallize as dimers. depending on the solvent of crystallization and the natures of the apical anionic ligand. the substituents in the benzene ring of the salicylaldehyde. and the diamine. A new criterion of distinguishing between mono- and di-merit structures, based on i.r. spectroscopy, is presented. In only one case, with the cyanide ligand, have anionic low-spin species been obtained. The factors favouring the addition of a base to five-co-ordinate complexes to form six-co-ordinate adducts are discussed, together with the conformational aspects of the quadridentate Schiff-base ligand.