Reactions of the iridathiabenzene complex Cp*Ir(2,5-dimethylthiophene) with Co₂(CO)₈, Co₄(CO)₁₂, and (η⁶-C₆H₃Me₃)Co ₄(CO)₉

With the goal of preparing an η⁶-iridathiabenzene complex of Co₄(CO)₁₂, the ring-opened iridathiabenzene complex Cp*Ir(C,S-2,5-Me₂T) (1), where 2,5-Me₂T is 2,5-dimethylthiophene, was reacted with Co₄(CO)₁₂, Co₂(CO)₈, and (η⁶-C₆H₃Me₃)Co ₄(CO)₉. Only in the reaction of (η⁶-C⁶H³Me³)Co ⁴(CO)⁹ under mild conditions (35-40 °C) was the η⁶-iridathiabenzene cluster [η⁶-Cp*Ir(C,S-2,5-Me₂T)]Co₄(CO) ₉ (7) obtained. At higher temperatures, the reaction yielded Cp*Ir(η⁴-2,5-Me₂T·Co₄(CO) ₁₁) (6), in which the 2,5-Me₂T ligand is coordinated through its diene to the Ir and through its sulfur to a Co of the cluster. Reactions of Co₄(CO)₁₂ and Co₂(CO)₈ with 1 yielded Cp*Ir(η⁴-2,5-Me₂T·Co₄(CO) ₁₁) (2), an isomer of 6, which converts to the desulfurized linear tetranuclear cluster [Cp*Ir(C(Me)=CHCH=C(Me))(μ-CO)₂Co]₂ (3); this species contains bridging iridacyclopentadiene units. Cluster 3 has a structure with a Co₂(μ-CO)₂ core and Cp*Ir(C(Me)=CHCH=C(Me))(CO) (4) end groups. In fact, 3 can be prepared from Co₂(CO)₈ and 4. Molecular structures of 2-4 are reported, together with a discussion of pathways that lead to their formation.