Reactions of [(CO)₃Mn(η⁵-Thi)]⁺ (Thi = thiophene or 2,5-dimethylthiophene) with nucleophiles

The η⁵-thiophene complexes, [(CO)₃Mn(η⁵-T)]⁺ (1) and [(CO)₃Mn(η⁵-2,5-Me₂T)]⁺ (2), react with LiCuR₂ (R = Me or Ph) by adding R^- to the sulfur atom of the thiophene, which gives the η⁴-thiophene complexes, (CO)₃Mn(η⁴-T·R) and (CO)₃Mn(η⁴-2,5-Me₂T·R). An X-ray study of (CO)₃Mn(η-T·C₆H₅) (6) shows the η⁴-T·C₆H₅ ligand to be coordinated to the manganese through the four thiophene carbon atoms, while the sulfur bearing the phenyl group is bent away from the metal. The structure of 6 supports previous suggestions that the sulfur in η⁵-thiophene complexes is an electrophilic center. Reactions of 1 or 2 with RS^-, CH₃O^-, or ^-CH(CO₂CH₃)₂ nucleophiles result in the displacement of thiophene with the formation of [(CO)₄Mn(μ-SR)]₂ or Mn₂(CO)₁₀. The structure of [(CO)₄Mn(μ-SC₆H₄CH₃-P)] ₂ (9), established by X-ray studies, is also reported.