The new anionic carbon sulfides C6S102- and C12S162- are described and crystallographically characterized. The C12S162- anion consists of two C6S8 units connected by an exceptionally long (2.157(12) Å) S-S bond. In solution, C12S162- exists in equilibrium with the radical C6S8-. The equilibrium constant for radical formation (293 K, THF) is 1.2 × 10-4 M, as determined by optical spectroscopy at varying concentrations. Radical formation occurs through scission of the S-S bond. On the basis of variable temperature EPR spectra, the thermodynamic parameters of this process are ΔH = +51.5 ± 0.5 kJ mol-1 and ΔS = +110 ± 3 J mol-1 K-1. C6S102- is an oxidation product of C3S52- and consists of two C3S5 units connected by an S-S bond. The S-S bond length (2.135(4) Å) is long, and the CS-SC torsion angle is unusually acute (52.1°), which is attributed to an attractive interaction between C3S2 rings. The oxidation of (Me4N)2C3S5 occurs at -0.90 V vs Fc+/Fc in MeCN, being further oxidized at -0.22 V. The similarity of the cyclic voltammogram of (Me4N)2C6S10 to that of (Me4N)2C3S5 indicates that C6S102- is the initial oxidation product of C3S52-.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry