Adducts xanthate structures

No binary xanthate structures of manganese, technetium, or rhenium have been reported. Indeed, there are relatively few crystal structures known with only a single manganese structure (two polymorphs), two phosphine adducts of technetium and three structures containing rhenium, two of which are dinuclear. 

A variety of cobalt xanthate structures are available in the literature, including four binary xanthates and a large range of phosphine adducts. By contrast, only one rhodium structure is known and no structure is yet available containing iridium. 

Of the transition metals, the nickel triad has been the most studied in terms of xanthate structures, especially nickel xanthates. Thus, binary xanthate structures are known for all elements with no less than 15 binary nickel xanthate structures known and these aggregate in the solid state in six distinct supramolecular architectures. There is also a rich diversity of adducts as well as mixed-ligand complexes, in particular for nickel. 

A wide range of structural motifs are found for the copper-triad xanthates, ranging from monomeric species to layer structures. This variety of structures can be ascribed to the flexible coordination modes adopted by the xanthate ligands in this group, in particular for the copper and silver xanthates. However, there is a dearth of binary xanthate structures with only two available for copper and one each for silver and gold. The paucity of data can be ascribed directly to the inability to obtain suitable crystals for structure determination. Phosphine adducts are known for all three elements of this group and in the case of both copper and silver, mixed-metal species are also known. 

The addition of silyl radicals to thiocarbonyl derivatives is a facile process leading to a-silylthio adducts (Reaction 5.37). This elementary reaction is the initial step of the radical chain deoxygenation of alcohols or Barton McCombie reaction (see Section 4.3.3 for more details). However, rate constants for the formation of these adducts are limited to the value for the reaction of (TMS)3Si radical with the xanthate c-C6HuOC(S)SMe (Table 5.3), a reaction that is also found to be reversible [15]. Structural information on the a-silylthio adducts as well as some kinetic data for the decay reactions of these species have been obtained by EPR spectroscopy [9,72]. 

Another method that provides chlorides from alcohols with retention of configuration involves conversion to a xanthate ester, followed by reaction with sulfuryl chloride. This method is thought to involve collapse of a chlorinated adduct of the xanthate ester. The reaction is useful for secondary alcohols, including stoically hindered structures.8... 

There is a rich structural chemistry in the Lewis base adducts of the nickel xanthates so that a variety of coordination geometries are found as well as... 

Structural Data for Nickel Xanthate Adducts of the General Formula Ni(S2COR)2(NnN)... 

Three phosphine adducts are known for the mercury xanthates and each structure reveals that the aggregation observed in the parent compounds no longer persists. 

The Pb- -S mediated chains observed in the structure of polymeric Pb(S2COEt)2 are disrupted upon the addition of base. The immediate coordination geometry about the lead atom in the adduct Pb(S2CO—i-Pr)2(py) (231) is shown in Fig. 145(a). The lead atom is coordinated by the pyridine nitrogen atom and two xanthate ligands, one that forms asymmetric Pb—SI and Pb—S2 distances of 2.72(2) and 3.06(2) A, and one that forms symmetric bonds of... 

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