Mixed-chalcogenide, mixed-metal carbonyl clusters. Synthesis and characterization of Cp₂Mo₂Fe₂(μ₄-Te)(μ₃-E)(μ₃-E')(CO)₆ (E, E' = Te; E = S, E' = Te; E, E' = S; E = S, E' = Se), Cp₂Mo₂Fe₂(μ₃-Te)(μ₃-E)(CO)₇, and Cp₂Mo₂Fe_(μ3-E)(CO)₇ (E = S, Te)

Abstract

Reflux of a benzene solution of Fe₃STe(CO)₉ and Cp₂Mo₂(CO)₆ yielded the new cluster Cp₂Mo₂Fe₂STe(CO)₇ (6) as the major product and the following clusters in smaller amounts: Cp₂Mo₂Fe₂Te₃(CO)₆ (1), Cp₂Mo₂Fe₂STe₂(CO)₆ (2), Cp₂Mo₂Fe₂S₂Te(CO)₆ (3), Cp₂Mo₂FeTe(CO)₇ (4), Cp₂Mo₂FeS(CO)₇ (5), and Cp₂Mo₂Fe₂Te₂(CO)₇ (7). The new cluster 3 was formed in good yield when a benzene solution of 6 was refluxed with sulfur powder. Similarly, 2 was obtained when a benzene solution of 6 was refluxed with tellurium powder. A new cluster with three different chalcogen ligands, Cp₂Mo₂Fe₂SSeTe(CO)₆ (8), was obtained when a benzene solution of 6 was refluxed in the presence of selenium powder. Structures of 1-4, 6, and 8 were established by crystallographic methods. The structures of 1-3 and 8 consist of Mo₂Fe₂ butterfly cores with a μ₄-Te atom and two μ₃-chalcogen atoms (1, Te and Te; 2, S and Te; 3, S and S; 8, S and Se) capping the two Mo₂Fe faces. Each Mo atom has a Cp ligand, and each Fe atom has three terminally bonded carbonyl groups. The structure of 4 conists of a Mo₂FeTe tetrahedron with each Mo possessing a Cp ligand and two terminally bonded carbonyl groups and the Fe atom having three terminal carbonyl groups attached to it. The structure of 6 consists of a Mo₂Fe₂ tetrahedron. One Mo₂Fe face is capped by a μ₃-S ligand and the other by a μ₃-Te atom. The Fe?Fe bond is bridged by a carbonyl group; there are two terminally bonded carbonyl groups attached to each Fe atom. A semitriply bridging carbonyl group is attached to one Mo atom. The other Mo atom has one terminal carbonyl group. Each Mo atom has one Cp ligand attached to it.