The compound Cp2Mo2FeTe2(CO)7 (Cp = η5-C5H5), 2, is formed in high yield from the reaction of Fe3Te2(CO)9 and Cp2Mo2(CO)6 in hexane under CO. The product was characterized by spectroscopic methods and its structure determined by X-ray crystallography. Compound 2 crystallizes in the P1 space group with a = 13.216 (2) Å, b = 15.962 (3) Å, c = 21.710 (5) Å, α = 100.31 (2)°, β = 104.74 (2)°, γ = 94.20 (1)°, Z = 8, and ρcalcd = 2.547 g cm-3. The structure was solved by direct methods. Blocked cascade refinement on 9947 reflections (Fo ≥ 3σFo) produced the final residuals RF = 0.0354 and RWF = 0.0394 The four molecules per asymmetric unit are quite similar, each consisting of a CpMo(CO)2 fragment bridging the Te wing tips of a Cp(CO)5MoFeTe2 butterfly. The 3.13-Å Te⋯Te distance is well within bonding distance and is proposed to be chemically significant. This interaction is discussed in the context of other nonmetal-containing cluster compounds. On the basis of these data, it is proposed that such intracluster nonmetal-nonmetal interactions can have a significant influence on the structures and reactivity of compounds in this class of clusters. The mechanism of formation of 2 is discussed in light of the recently reported compound Co2Fe2S2(CO)11. Thermolysis of 2 affords metallatetrahedrane Cp2Mo2FeTe(CO)7, Cp2Mo2Fe2Te3(CO)6, and Cp2Mo2Fe2Te2(CO)7, 3. Compound 3 crystallizes in the orthorhombic space group Pn21a with a = 13.617 Å, b = 12.939 Å, c = 12.199 Å, Z = 4°, (10)°, and ρcalcd = 2.73 g cm-3. The structure was solved by direct methods. Blocked cascade refinement on 1837 reflections (F0 > 3σF0) produced RF = 0.0256 and RWF = 0.0249. The molecule of approximately C2v symmetry consists of a tetrahedral Mo2Fe2 core with each Mo2Fe face capped by a μ3-Te atom. The Fe-Fe distance of 2.433 Å is one of the shortest known single Fe-Fe bonds. The mechanism of formation of 3 from 2 was shown to involve no scrambling of Mo moieties (Cp-labeling experiments) and proceeds optimally (60%) in the presence of 10 equiv of Fe(CO)5. Compound 2 also reacts with CpCo(CO)2 to give two isomers of Cp3Mo2CoFeTe2(CO)5. These results imply that the recently reported isomers of Cp2Mo2Fe2S2(CO)8 are formed via a five-vertex Mo2FeS2 intermediate.
ASJC Scopus subject areas
- Colloid and Surface Chemistry