The Mössbauer spectra and structure of some 1,2-dithiolene complexes of iron

Abstract

The Mössbauer spectra of 32 iron dithiolene complexes have been measured at 77°K and at a higher temperature, usually 295°K. The structural implications of the observed chemical isomer shifts and quadrupole splittings are discussed. The variations of these parameters in several isostructural series of complexes as the nature of the ligand is systematically varied or as the charge state of the species is altered are interpreted in terms of the detailed electronic bonding. The complexes are unusual in that changes in the dithiolene ligand which are several atoms removed from the iron atom frequently have a marked influence on the quadrupole splitting whilst leaving the chemical isomer shift virtually unaltered. The tetrachlorobenzene-1,2-dithiolato-complexes [Fe{S₂C₆CI₄}₂]₂^2– and [Fe py {S₂C₆CI₄}₂]^– have the largest quadrupole splitting yet reported for low-spin Fe^III compounds (3·02 mm. sec.^–1).