High-spin iron(II) chelate complexes with β-diketonate and Schiff base ligands: Mössbauer and electronic spectra

Abstract

A number of high-spin iron(II) chelate complexes with some bidentate monoanionic ligands (β-diketonates, salicylaldehydate, and N-alkylsalicylideneiminates) and the quadridentate dianion NN′-ethylenebis(salicylideneiminate), and its analogues, has been studied by means of Mössbauer and electronic spectroscopy. In all the complexes the iron atom is probably six-co-ordinate because of intermolecular interactions, even in complexes of the quadridentate ligands. The isomer shifts mainly depend on the nature of the ligand atoms bound directly to the iron. For a series of closely related complexes, a linear relation has been observed between isomer shifts and quadrupole splittings. From an analysis of the temperature dependence of the quadrupole splitting, it may be inferred that the complexes studied undergo large axial distortion. This conclusion also rationalizes the relatively narrow range (2·0–2·9 mm s^–1) of quadrupole splittings observed.