ORGANOMETALLIC CHALCOGEN COMPLEXES .16. PREPARATION AND STRUCTURAL CHARACTERIZATION OF CO4(PI-C5H5)4S6 . A NEW MODE OF TRANSITION METAL BONDING FOR A DISULFIDE GROUP

The reaction of elemental sulfur with Co(π-C5H6)(CO)2 has resulted in the synthesis of a new kind of organometallic sulfur complex, Co4(π-C5H5S5. This air-stable, relatively insoluble compound was shown to be diamagnetic from its nmr spectrum which revealed four separate, equivalent resonances characteristic of four nonequivalent cyclopentadienyl rings. Its stereochemical characterization as a tetranuclear cobalt complex was ascertained from a three-dimensional X-ray diffraction study carried out on a crystal of stoichiometry Co4(π-C5H5)4-S6 1/2CHCl3. This solvated crystal contains eight formula species in a monoclinic unit cell of symmetry P21/c and dimensions a = 25.618 ± 0.010 Å, b = 10.604 ± 0.004 Å, c = 19.295 =± 0.008 Å, ² = 105° 43ʹ ± 04ʹ. The structure, determined by the application of the Hauptman-Karle symbolic addition method, was refined by rigid-body isotropic least squares of the automatically collected diffractometry data to an unweighted R1 discrepancy index of 11.7%. The molecular structure consists of a distorted tetrahedral array of C5H5Co units interconnected by two triply bridging disulfide S2 groups and two triply bridging sulfur atoms located above the four triangular faces of the distorted tetrahedron of nonbonding cobalt atoms. This molecular complex supplies a heretofore “missing link” in organometallic chemistry in its exemplification of an S2 ligand covalently coordinated as a four-electron donor with three metal atoms. The one crystallographically independent chloroform molecule is closely associated by presumed hydrogen bonding with only one of the two crystallographically independent Co4(π-C5H5)4S6 molecules. The detailed molecular features are compared with those of related molecular complexes. © 1969, American Chemical Society. All rights reserved.