The reaction between [Fe-III(dmf)(6)](ClO4)(3) and the ligand S-methyl-1-phenyl-isothiosemicarbazide, H-2[L-Me], and triethylamine (1:3:6) in methanol under an argon blanketing atmosphere at elevated temperatures (reflux) yields a purple solution from which upon cooling to 20degreesC dark green crystals of [Fe-III(L-Me.)(2)(SCH3)] (1) were obtained in 15% yield. From a similar reaction mixture using FeCl3 as starting material in the solvent acetone under anaerobic conditions at -80degreesC, dark green crystals of [Fe-III (L-Me.)(2)Cl] (2) were obtained in 21% yield. The structures of complexes 1 and 2 have been determined by single-crystal X-ray crystallography at 100 K. Both complexes are five-coordinate square base pyramidal ferric species containing two N,N-coordinated, monoanionic T radicals, (L-Me.)(1-), of the parent S-methyl-1-phenyl-isothiosemicarbazide(2-) dianion in the basal positions whereas the axial position is occupied by methylthiolate in 1 and chloride in 2, respectively. The electronic structure of both species has been elucidated by their electronic spectra, magnetic properties, and X-band EPR and Mossbauer spectra. Both possess an S-t = 1/2 ground state which is attained via an antiferromagnetic coupling between the spins of an intermediate spin ferric ion (S-Fe = 3/2) and two ligand pi radical anions (S-rad = 1/2).