Tetrabutylammonium tetrathioperrhenate

Adapted from the method by Wei et al.[4] and Goodman et al.,[5] sulfur (0.25 g, 7.8 mmol) was added to 10 mL of yellow 40 % ammonium sulfide solution. Tetra-n-butylammonium bromide (0.50 g, 1.6 mmol) was added, and the yellow solution turned red. Ammonium perrhenate (0.50 g, 1.8 mmol) was added, and the pH was checked to be ~ 9. The vessel was sealed with a septum fitted with a syringe for pressure-relief, and the mixture was stirred overnight. In 10 minutes, the red solution turned orange; it turned brown after a further 15 minutes. Overnight, a purple suspension in a yellow solution was obtained.

The residue was filtered off, washed with water, a small amount of methanol, and diethyl ether, and dried in vacuo. The infrared spectrum showed a band at 485 cm-1, attributed to Re=S, in agreement with the literature value.[5] ESI MS detected both cation and anion, with the appropriate isotopic patterns.

In air and light, the solid compound turned from purple to brown over several weeks. Where necessary, the compound was purified by dissolving in acetonitrile, filtering through a plug of Celite to remove large amounts of a brown-black residue, and drying in vacuo to regain the purple solid.[5]

Yield: 900 mg, > 95 %. IR (KBr pellet): 2960, m; 1467, s; 737, m; 485, vs (Re=S). ESI MS m/z (%): 242.3 [NnBu4]+ (100); 315.2 [ReS4]- (100).