The molecular structure of bis(ethyl thioxanthato)-μ-bis(ethyl thioxanthato)-μ′-bis(ethylthio)-diiron(III), [Fe(SC2H5)-(S2CSC2H5)2]2, has been determined in a single-crystal X-ray diffraction study. The complex crystallizes in the monoclinic system, space group p21/c, with a = 12.193 (5) Å, b = 8.469 (4) Å, c = 19.82 (1) A, and β = 130.11 (5)°. The density of 1.657 (1) g/cm3 calculated on the basis of two dimeric formulas per unit cell is in agreement with the measured density of 1.64 ± 0.01 g/cm3. The structure was solved using ~1350 independent, statistically significant reflections collected on a full-circle automated diffractometer. Refinement of all atoms including several of the hydrogen atoms led to a final value of the discrepancy index, R1, of 0.048. The molecular structuee consists of centrosymmetric dimers in which two ethyl mercaptide and two ethylthioxanthate groups function as bridging ligands and two more nonbridging ethylthioxanthate ligands complete the distorted octahedral coordination polyhedra around the two iron atoms. The iron-iron distance of 2.618 (2) Å is 0.39 Å shorter than the S … S bite of the bridging thioxanthate ligand. This result, together with the small Fe-S-Fe angle of 72.35 (7)° at the bridging sulfur atoms, provides direct structural proof for metal-metal bonding. Average values for the three chemically distinct types of iron-sulfur bonds in the molecule are 2.218 (2) Å for the bridging mercaptide ligands, 2.287 (2) Å for the bridging thioxanthate ligands, and 2.338 (4) Å for the terminal thioxanthate ligands. From the observed carbon-sulfur distances it is concluded that resonance form VII (see text) contributes significantly (~20%) to the electronic structure of the coordinated thioxanthate groups.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry