Synthesis, characterization and properties of two novel octanuclear heterometallic molecules consisting of two triangular molybdenum clusters bridged by oxochromium ligands: M2[Mo3O4(O2CEt)8Cr2(O2CEt)8O4Mo3] · n(HO2CEt) (M = K, n = 2; M = Li, n = 0)

Two novel octanuclear mixed-metal clusters M2[Mo3O4(O4CEt)8Cr2(O2CEt)8O4Mo3] · n(HO2CEt) [M = K, n = 2 (1); M = Li, n = 0 (2)] have been synthesized and characterized by X-ray crystallographic structure determinations. Compound 1 is soluble in EtOH and N,N′-dimethylformamide solution, while compound 2 is insoluble. Both compounds contain a novel cyclic anion formed by two triangular trinuclear molybdenum cluster anions [Mo3O4(O2CEt)8]4− and two chromium atoms as bridges connecting the two triangular molybdenum cluster anions. The potassium atom in compound I is coordinated to six oxygen atoms, including one oxygen atom from a weakly bound terminal HO2CEt ligand. The lithium atom in compound 2 is five-coordinate. The weakly bound terminal ligand is responsible for the solubility of compound 1. Cyclic voltammetry shows a quasireversible redox couple for compound 1 at −0.97/−0.75 V/SCE and an irreversible oxidation peak at −0.52 V/SCE. The EPR spectrum of compound 1 suggests strong delocalization of electrons in this compound.