Mixed-valence gold bis(diselenolene) complex turning metallic under pressure

While oxidation of d(8) anionic gold bis(dithiolene) complexes most often affords the corresponding neutral radical single-component conductor, an original gold bis(diselenolene) complex isolated as a Ph4P+ salt affords upon electrocrystallization a mixed-valence 1 : 2 salt, [Ph4P][Au(Me-thiazds)(2)](2) (Me-thiazds: 2-methyl-1,3-thiazoline-2-thione-4,5-diselenolate). This salt exhibits a rare charge alternation associated with the simultaneous presence of both cis and trans isomers of the gold complex in the conducting layers. The salt is semiconducting (sigma(RT) = 3 x 10(-2) S cm(-1), E-act = 0.137 eV) but, in contrast with other 1 : 2 gold bis(dithiolene) salts, turns metallic under pressure (>10 GPa). [Ph4P][Au(Me-thiazds)(2)](2) is thus the first metallic, fully characterized, 1 : 2 mixed-valence gold complex, opening the door for the preparation of highly conducting solids of this type.

Automated summary

Electrocrystallization of an original gold bis(diselenolene) complex yields a mixed-valence 1:2 salt with rare charge alternation, containing both cis and trans isomers of the gold complex in the conducting layers. The salt is semiconducting at room temperature but turns metallic under pressure, making it the first fully characterized 1:2 mixed-valence gold complex with potential for highly conducting solids.