Metal sulfide/thiolate complexes

Within this context, the present article concentrates on transition metal cluster complexes of cobalt, iron and manganese with mixed chalcogen/carbonyl ligand spheres obtained by reaction of simple binary metal carbonyls with alkali-metal sulfides, alkali-metal thiolates or transition-metal thiolate complexes and their selenium or tellurium counterparts. 

Although the mechanism of Equation (14) is unknown/ a four-center S2H2 transition state or a reduction coupled with proton transfer as in metalloenzymes can be envisioned. Activation of H2 could be sulfide ligand-based in certain biological and industrial catalyst systems. Heterolysis of H2 at the metal can directly be observed in thiolate complexes (Equation (16)). ... 

It is tempting to speculate whether the role of promoter HDS metals (Co, Ni) is the C-S activation of the thiophenes whereas the catalytic metal (group 6, Mo, W) would be responsible for the transfer of hydrogen to the activated substrate. This is a very likely pathway to be envisaged on metal sulfide surfaces where sulfides or thiolates bonded to two or more metal atoms are plentiful. However, this type of interaction is obviously unavailable in single-site complexes, and this could explain why ring opening is frequent but complete desulfurization is rare on mononuclear derivatives. 

Metal thiolate complexes will reduce elemental sulfur or red selenium via the oxidative elimination of RSSR. In a similar manner, metal selenolate complexes ean be used to reduce elemental selenium. The resulting E ligands favor the formation of polynuclear cluster complexes, due to the greater tendency of E (vs. RE ) to form bridging interactions between metal centers. Originally developed in the synthesis of [Fe4Se4(SPh)4], this method has been well utilized in the synthesis of a number of iron thiolate/sulfide clusters, as well as their selenide counterparts (Equation (5)). More recently, sulfur- and selenium-containing lanthanide clusters (see Section 7.2.5.5) have been synthesized by the displacement of ER from Ln(ER)3 ... 

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