Thiols, Sulfur, Selenium, and Tellurium Compounds

The red complex found in reaction of cysteine with [Fe(CN)sNO] is a 1 1 complex as in equation (7) in which cysteine RSH is bound to the 

NO ligand with a stability constant of 145 at 25°C and 1.5 M ionic strength. The complex decays to [Fe(CN)5NO] and 5RSSR with a rate constant of 1.8 x 10 s but is subject to equilibria involving loss or attack by CN . A purple vanadium(IV) complex has been detected as a product in the vanadium(V) oxidation of cysteine.It is thought to be a bis-cysteine adduct. Acid decomposition of [(en)2Co(SCH2CH2NH2)] is first order in the complex, independent of [H ], with a rate constant of 2.10 x 10 s  

Oxidation of 2-thiouracil by [FeCphenjs] is first order in each reagent and proceeds at a rate of 4.14 s at 25 C and pH 2.3. However, 

Under anaerobic conditions, the copper(III)-tetraglycine complex, [Cu(H 3G4)] , oxidizes SO3 to SO3 in two one-electron steps (10) and (11). The SO3 formed subsequently hydrolyzes to sulfate with a rate 

The oxygen-bound sulfate complex [Co(tren)(OH2)OS02] is formed by reaction of [Co(tren)(OH2)OH] with SO3 and undergoes internal electron transfer to give cobalt(II) and SO4 with a rate constant 1.0 X 10 s at 25 C and pH less than 5.4. Activation parameters are MI 24 kcal moF and AS 8.2 cal moF. At higher pH a bis-sulfite complex which is not subject to internal redox is formed. Infrared evidence points to both S and O binding in this species. 

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