Preparation and properties of oxometallate complexes with sulfur-rich dithiolate ligands, [M(O)(C8H4S8)2]2− (M=V(IV) and Mo(IV)) salts, and high electrical conductivity of their oxidized species

Penta-coordinate oxometallate complexes with sulfur-rich dithiolate ligands, [NEt4]2[V(O)(C8H4S8)2], [N-methylpyridinium]2[V(O)(C8H4S8)2], and [NEt4]2[Mo(O)(C8H4S8)2] (C8H4S82−=2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithiolate(2-)), were prepared by reactions of V(O)(acac)2 (acacH=acetylacetone) or [pyridinium]2[Mo(O)Cl5] with Na2C8H4S8 in ethanol in the presence of NEt4Cl or N-methylpyridinium iodide. They exhibited oxidation potentials at −0.27±0.14 V (vs. SCE), and were reacted with iodine, 7,7,8,8-tetracyano-p-quinodimethane or the decamethylferrocenium cation in benzonitrile to afford oxidized species, [V(O)(C8H4S8)2], [NEt4]0.2[V(O)(C8H4S8)2], [NEt4]0.3[Mo(O)(C8H4S8)2], and [Fe(C5Me5)2]0.05[Mo(O)(C8H4S8)2], and a reaction of suspension of powdered [N-methylpyridinium]2[V(O)(C8H4S8)2] with an excess amount of iodine in hexane gave [N-methylpyridinium]2[V(O)(C8H4S8)2](I3)2. In the oxidized species occurred the C8H4S8 ligand-centered oxidation. They exhibited electrical conductivities of 0.11–5.5 S cm−1 measured for compacted pellets at room temperature. The electronic states of the oxovanadium(IV) and oxomolybdenum(IV) complexes and their oxidized species are discussed on the basis of electronic absorption, powder reflectance, IR and ESR spectra.