Hydrogen-Sulfur Bonds

Thiols (RSH) cleave a( the sulfur-hydrogen bond on irradiation, and this allows the preparation of sulfides by subsequent radical addition to an alkene (5.62). Hydrogen sulfide behaves in the same way (5.631, and long-chain thiols are made commercially for use as modifiers in emulsion polymerization. 

The ruthenium benzyne complex previously discussed is an excellent entryway into. activation of oxygen- and sulfur-hydrogen bonds. Reactions proceed cleanly under mild conditions ... 

Thiols are good hydrogen donors toward carbon-centered radicals (Eq. 1) the relatively low dissociation energy of the sulfur-hydrogen bond [T> (MeS-H) =... 

The tertiary structure of many proteins is strengthened by sulfur-sulfur covalent bonds called disulfide linkages. The amino acid cysteine contains a sulfur-hydrogen bond. Two cysteines in a protein can form a disulfide linkage, which stabilizes the protein structure much like a cross-link strengthens a polymer s stracture. Many other noncovalent intermolecular forces contribute to the stability of the tertiary structure of a protein, as shown in Figure 22.6. 

Taking the order of magnitude, these results are, of course, not surprising considering that a sulfur-hydrogen bond in thiols is generally weaker by up to about 20 kcal mol" (ca. 85 kJ moE ) than a carbon-hydrogen bond. An even faster H-atom abstraction is achieved by hydroxyl radicals which occurs with rate constants of several 10 M s [13], reaction (2) ... 

The sulfur-hydrogen bond addition to alkynes represents a convenient access to vinyl sulfides. Nolan, Beletskaya and co-workers reported a new selective hydrothiolation process induced by homogeneous NHC-Ni complexes." They showed that [(IMes)Ni(Cp)Cl] was effective in catalyzing the reaction of terminal alkynes and various aryl thiols (Equation (10.10)). The process was found highly selective and the classical transfer of two thioaryl groups did not... 

The addition of sulfur-hydrogen bonds to alkynes (hydrothiolation) is a valuable and popular approach to the synthesis of vinyl sulfides [23], Some of the earliest reports of this chemistry involved the use of molybdenum [77] and palladium complexes [78]. While discussions of the challenges encountered when trying to design an effective cross-coupling reactions often focus on concerns about reactivity and substrate scope, hydroelementation reactions introduce further complications due to regio- and stereoselectivity issues, hi many... 

Early examples were restricted to the insertion into sulfur-hydrogen bonds (214-216). For example, addition of phenylisothiocyanate to [Au(SH)2] affords the bis(dithiocarbamate) complex [Au(S2CNHPh)2] (216). More recently, Shaver and co-workers (217) demonstrated a similar insertion into the sulfur-silicon bond of [CpRu(PPh3)2(SSi-i-Pr3)], yielding unusual silicon-substituted dithiocarbamate ligands (Eq. 35). 

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