Structure and redox properties of the molybdenum(IV) metal cluster K5[Mo3S4(CN)9].7H2O

Abstract

The anionic molybdenum(IV) cluster [Mo3S4(CN)9]5- has been subjected to X-ray crystal structure analysis. The potassium salt crystallized in the triclinic space group P1, a 10.634(1), b 11.888(3), c 24.892(2) �, α 89.56(2), β 79.86(1), γ 76.53(2)�, Z 4. The three MoIV atoms in each unit of approximately CSL3v symmetry are situated at the corners of an equilateral triangle with Mo-Mo distance 2.765(7) �. There are three S2- ligands bridging between pairs of Mo atoms, and a unique S2- ligand located uniformly above the plane of the equilateral triangle. Distorted octahedral coordination of each MoIV is completed by three CN- ligands to each of the three metal centres. The ion is structurally similar to the [MO3S(S2)6]2- precursor, and to [Mo3O4X9]n- analogues. In dimethyl sulfoxide, the cluster is irreversibly reduced in a single step near -2 V (v. saturated calomel electrode), but exhibits a quasi-reversible oxidation at + 0.51 V. On the coulometric time scale, the complex is irreversibly oxidized to MoV monomer.