Reaction of [(OC)2(cp)FeC(S)SFe(cp)(CO)2](cp =η5-C5H5) with dicobalt octacarbonyl; X-ray crystal structure of [Co3Fe(cp)(CO)9(CS)] containing a six-electron donor thiocarbonyl group

Abstract

The reaction between [(OC)₂(cp)FeC(S)SFe(cp)(CO)₂](cp =η⁵–C₅H₅) and [Co₂(CO)₈] produces the novel mixed-metal cluster [Co₃Fe(cp)(CO)₉(CS)] which contains a thiocarbonyl group, and the two known derivatives [Co₄(CO)₁₀S₂] and [CoFe(cp)(CO)₆]. This product distribution, which accounts for the fragmentation and desulphurization of the starting dithioester complex, may be seen as occurring via an unstable dithiocarbene intermediate. The structure of [Co₃Fe(cp)(CO)₉(CS)] has been determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group Pbca(no. 61) with cell constants a= 16.196(7), b= 12.325(3), c= 18.971(6)Å, and Z= 8. The structure has been solved from 1 292 reflections collected by counter methods, and refined by least-squares calculations to R= 0.044 (R′= 0.040). The molecule contains a triangle of Co atoms carrying an external Fe(cp)(CO)₂ fragment. The CS group, which lies parallel to the Co₃ triangle, contributes six electrons to the cluster orbitals. The carbon atom of this ligand bridges all metal atoms, while the sulphur atom is bonded only to two Co atoms. The bonding mode of the CS ligand is discussed in terms of σ and π interactions.