The synthesis, and properties of Fe/Mo/S clusters with MoFe 3S 4 cubane subunits, Mo bound bidentate oxalate ligands and terminal or bridging cyanide ligands. Structural characterization of (Et 4N) 3[(C 2O 4)(CN)MoFe 3S 4Cl 3] and (Et 4N) 5{[C 2O 4)MoFe 3S 4Cl 2] 2(μ-CN)(μ-S)}

Abstract

The reaction of (Et 4N) 3[(C 2O 4)MoFe 3S 4Cl 4] ( I) with (Et 4N)CN affords [(C 2O 4)(CN)MoFe 3S 4Cl 3] 3− ( IV) in nearly quantitative yields. The reaction of I with 0.5 eq. of (Et 4N)CN and 0.5 eq. of a source of S 2− affords the doubly-bridged double-cubane {[(C 2O 4)MoFe 3S 4Cl 2] 2(μ 2-CN)(μ 2-S)} 5− ( V) in ≈30% yield. Single crystal X-ray structures were determined for IV and V. The mean FeFe, FeS and FeCl bond distances in IV at 2.713(3), 2.270(5) and 2.214(5) Å, are typical for MoFe 3S 4 cubane-like structures. The MoC(N) and CN bond lengths are found at 2.19(2) and 1.04(2) Å, respectively. The pentaanion in V consists of two doubly-bridged cubane subunits bridged by μ 2-CN − ligand through the Mo atoms and a μ s-S 2− through two Fe atoms. The Mo⋯Mo and Fe⋯Fe(intercube) distances and the Feμ 2-SFe angle are found at 5.267(4), 3.443(7) and 104.1(4)°. The spectroscopic and electrochemical features of IV and V are discussed.