Metal(III) compounds of potentially septadentate[N4O3] ligands derived from tris(2-aminoethyl)amine and substituted salicylaldehydes. Part I. Preparation of gallium, chromium, manganese, iron, and cobalt compounds, and the crystal and molecular structure of the iron compound of tris[2-(5-chloro-2-hydroxybenzylidene)ethyl]amine, [Fe(C27H24Cl3N4O3)]·3H2O

Abstract

The potentially septadentate and trianionic Schiff base ligands, prepared from tris(2-aminoethyl)amine and three moles of salicylaldehyde, react with Ga^III, Cr^III, Mn^III, Fe^III and Co^III species to form 1 : 1 neutral compounds. This paper reports a range of such compounds, prepared from substituted aldehydes (3-OMe, 3-NO_2-, 5-Cl, 5-Br, 5-OMe, and 5-NO₂) as well as the parent salicylaldehyde; details are given of their electronic spectra; some polymorphs and isomorphous series are classified from the X-ray powder diffraction patterns; and a full X-ray structural analysis of the iron(III) compound of the 5-chloro-substituted ligand is reported. Crystals of the latter were cubic with a = 22.497(1)Å, space group la3 (T_n⁷, No. 206). Data were collected by diffractometer, and the structure solved from 1 081 independent reflections by conventional Patterson and Fourier techniques; it was refined by block-diagonal least-squares to a final R of 0.060. The molecule is essentially an [Fe(O₃N₂)] octahedral species [Fe–O 1.953(6), Fe–N 2.185(7)Å], lying on a three-fold crystallographic axis. The latter passes through the iron and the other (apical) nitrogen N(1), which appears to be antibonding with respect to the metal. This nitrogen is 3.26(2)Å, from the metal atom, and almost co-planar with its three carbon-atom substituents. C–N(1)–C anglesare 117.8 (15)°; and N(1) isonly 0.2Å below the C₃plane. Thewater molecules, in the crystal, form a flattened octahedral set about the crystallographic C₃ axis, hydrogen-bonded to themselves and to the phenolic oxygens of the ligand.