A comparative synthetic and structural study of µ-oxo and µ-sulphido derivatives of N,N′-ethylenebis(acetylacetoneiminato)iron(III), including the synthesis and structural characterization of the parent compound

Abstract

The synthesis of [{ Fe(acen)}₂](1)[acen =N,N′-ethylenebis(acetylacetoneiminate) dianion, µ_eff.= 4.84] was performed by treating anhydrous FeCl₂·1.5thf with H₂acen in the presence of Na(OMe). Complex (1) has a monomeric structure in solution (M= 288 in C₆H₆) but is dimeric in the solid state as shown by an X-ray analysis. It has good solubility in organic solvents. Iron(II) achieves five-co-ordination either through dimerization or by binding of a molecule of solvent, e.g. pyridine, to form [Fe(acen)(py)](2). Complex (1) undergoes one-electron oxidation by molecular oxygen and elemental sulphur to form the corresponding iron(III) derivatives [{Fe-(acen)}₂(µ-O)](3) and [{Fe(acen)}₂(µ-S)](4) respectively. In complexes (3) and (4) the two d⁵ high-spin configurations are strongly antiferromagnetic [µ_eff.= 1.80 at 290 K for (3) and 2.16 at 293 K for (4)]. X-Ray analysis of (3) and (4) has allowed a comparison of the most significant parameters associated with the Fe–X–Fe backbone [Fe–O 1.775(13), Fe–S 2.210(3) and 2.204(2)Å; Fe–O–Fe 150.7(13), Fe–S–Fe 120.8(1)°].