CRYSTAL AND MOLECULAR STRUCTURE OF THIO-P-TOLUOYLDISULFIDOBIS(DITHIO-P-TOLUATO)IRON(3)

The crystal and molecular structure of thio-p-toluoyldisulfidobis(dithio-p-toluato)iron(III), Fe(CH3-C6H4CS3)(CH3C6H4CS2)2, Fe(TTD)(DTT)2, has been determined by a three-dimensional X-ray crystallographic analysis. The compound crystallizes as dark violet prisms in space group P21/c with unit cell dimensions a = 18.23 (2), b = 7.64 (1), c = 24.12 (2) Å, β = 125.4 (1)°. The density of 1.43 g/cm3 calculated for four molecules per unit cell agrees well with the observed density of 1.42 ± 0.01 g/cm3. From approximately 1225 independent nonzero reflections estimated visually from Weissenberg photographs, the structure was solved by the use of conventional Patterson, Fourier, and least-squares refinement techniques to a final value of the discrepancy index, R, of 0.085. The geometry about the iron atom consists of a distorted octahedron of sulfur atoms contributed by two essentially equivalent bidentate dithioacid ligands and a third bidentate ligand containing an extra sulfur atom to form the structural grouping I, shown in the text. The average of four Fe-S distances in the four-membered rings is 2.32 ± 0.02 Å whereas the two Fe-S distances in the five-membered ring are 2.18 and 2.24 ± 0.01 Å, respectively. These differences may be understood in terms of simple ring constraint and valence-bond resonance arguments. The S-S distance in the five-membered chelate ring is 2.09 ± 0.01 Å. An analysis of the geometry reveals some evidence for electron derealization between the iron atom and the ligand molecules. A brief discussion of the possible relevance of this work to nonheme iron protein systems is set forth. © 1969, American Chemical Society. All rights reserved.