ON THE EPR-SPECTRA OF IRON(III) SPIN-EQUILIBRIUM COMPOUNDS

The postulate of a limiting resonance structure involving low-spin iro n(II) and an unpaired electron on a radical ligand for the spin-equili bria iron(III) tris(dithiocarbamates), Fe(S2CNR2)3, is disproved as a result of the observation of a structured line in the g = 2 region of the EPR spectrum of Fe(S2COEt)3, ascribed to an impurity [Fe(NO)(S2COE t)2]. A similar signal in the spectra of the dithiocarbamates is assig ned to [Fe(NO)(S2CNR2)2]. Evidence for unequivocal assignment of signa ls for separate isomers in the EPR spectra of a spin-equilibrium compo und, Fe(Ph.CS.CH.CO.Ph)3, is presented.