Neutral Homoleptic and Heteroleptic Organocuprates

That the natures both of the organic group and of the additional donor-solvent molecules are factors that determine the actual cuprate a egates formed is demonstrated by the structure of [Cu2Li2(CH2SiMej)4(DMS)2]n in the solid state [113] (see Fig. 1.25). In this structure, the basic framework consists of repeating central 

The solid-state structure of Cu2Li2Ph4(DMS)j is dosdy related to that observed for Cu2Li2Ph4(OEt2)2 except that one of the Hthium atoms here is now four-coordinate as a result of coordination of two DMS molecules [114]. This observation shows that even slight changes in the coordinating properties of donor solvent molecules may change the overall structure of the cuprate. 

So far, only cuprates with a 1 1 copper/lithium ratio have been considered. Treatment of phenylHthium with various substoichiometric quantities of copper bromide in DMS as solvent afforded so-called higher order cuprates, of which two were characterizable by X-ray crystallography. These have the overall stoichiometries Cu2l4Phs(DMS)4 and Cu4lisPh9(DMS)4 [114,115]. The structure of the former compound in the solid state is shown in Fig. 1.26. 

Such equilibria are governed by thermodynamics, and so the abundances of the different species in solution are dependent on their relative thermodynamic stabilities. If, however, such a mixture of spedes is applied in, for example, a conjugate addition reaction, the product formation will be controlled by kinetics, and it is most likely that Cu2Li2Me4 would be kinetically the most active spedes present. 

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