Chalcogen-Centered Spirocyclic Mixed-Metal Carbonyl Complexes:  Synthesis and Molecular Structures of (CO)₈(μ-PCy₂)Re₂(μ₄-E)Fe₂(μ-ER)(CO)₆ and [(CO)₈(μ-PCy₂)Re₂(μ₄-E)Fe₂(CO)₆]₂(μ₄-E₂) (E = S, Se, Te; R = Organic Residue)

When NEt₄[Re₂(μ-PCy₂)(CO)₈] (1) was reacted with Fe₂(μ-E₂)(CO)₆ (E = S, Se, Te) in THF, the salts NEt₄[(CO)₈(μ-PCy₂)Re₂(μ₄-E)Fe₂(μ-E)(CO)₆] (E = S (2a), Se (2b), Te (2c)) were formed. Their spirocyclic anions were trapped with MeI, giving the spirocyclic complexes (CO)₈(μ-PCy₂)Re₂(μ₄-E)Fe₂(μ-EMe)(CO)₆ (E = S (3a), Se (3b), Te (3c)). Their molecular structures were confirmed by single-crystal X-ray analysis. The anions of 2a−c are sensitive to oxidation. On crystallization in the presence of oxygen the corresponding dichalcogenides [(CO)₈(μ-PCy₂)Re₂(μ₄-E)Fe₂(CO)₆]₂(μ₄-E₂) (E = S (4a), Se (4b), Te (4c)) were obtained in good yield. Their molecular structures were confirmed by single-crystal X-ray analysis. 2a was also trapped with CF₃COOH, giving (CO)₈(μ-PCy₂)Re₂(μ-S₄)Fe₂(μ-SH)(CO)₆ (5). The latter can be expanded by SH oxidative addition of its μ-SH function to Os₃(CO)₁₁(NCMe), giving the mixed-metal carbonyl complex (CO)₈(μ-PCy₂)Re₂(μ₄-S)Fe₂(CO)₆(μ₃-S)Os₃(μ-H)(CO)₁₁ (6). The framework of 6 could be derived from X-ray diffraction data. However, these data were insufficient for complete solution of the molecular structure, but spectroscopic data and elemental analysis of 6 are in accordance with the proposed molecular structure.