Stereochemistry of alkylthioiron carbonyls and isovalent cyclopentadienylcobalt and benzeneiron derivatives

Density functional calculations on the Fe2(CO)6(μ-SR)2, Co2(η5-C5H5)2(μ-SR)2, and Fe2(η6-C6H6)2(μ-SR)2 systems (R = CH3, CF3) predict butterfly structures with a non-planar central M2S2 unit containing one M-M bond for the “body” of the butterfly and four M-S bonds at the edges of the “wings” of the butterfly. In every case the lowest energy structures are those with the two RS groups oriented in opposite directions. The nature of the RS substituents has no significant effect on the relative energies of the isomers.