A Vanadium-Containing Iron−Sulfur Cluster with a V₂Fe₂S₄ Cubane-like Core. Synthesis, Structure, and Characterization of (Et₄N)[V₂Fe₂S₄(Me₂dtc)₅]

A cubane-type cluster (Et₄N)[V₂Fe₂S₄(Me₂dtc)₅] (1) has been synthesized from an assembly system VS₄^3-/FeCl₂/Me₂dtc^-/PhS^- in acetonitrile (Me₂dtc^- = dimethyldithiocarbamate). The compound 1·2CH₃CN crystallizes in the monoclinic space group P2₁/c (No. 14), with a = 12.174(3) Å, b = 22.135(4) Å, c = 19.712(5) Å, β = 105.43(2)°, V = 5120.3 ų, ρ_calcd = 1.50 g/cm³, and Z = 4. The structure was solved from 6336 unique reflections (I > 3σ(I)) and refined by a full-matrix least-squares method to R = 0.053. The cluster anion contains a cubane-like [V₂Fe₂S₄]⁴⁺ core, in which the V−V, Fe−Fe, and V−Fe(mean) distances of the V₂Fe₂ tetrahedron are 2.745(2), 2.681(1), and 2.780(6) Å, respectively. The Mössbauer effect and the structural parameters indicate that the oxidation states of the Fe and V atoms in the [V₂Fe₂S₄]⁴⁺ core are both +3. The ¹H NMR shows the paramagnetism of the cluster. The chemical shift of ⁵¹V NMR was observed at −391 ppm. The FAB-MS behavior of the cluster indicates the bond breaking of the cluster core.