The assembling of a catalytic active copper site, in solution, followed byEXAFS

Cuprates can be used as reagents for the formation of C-C bonds in organic reactions. The structure of these cuprates under working conditions is stil l unclear. In this study we will show that EXAFS is a powerful technique to obtain the structural information of these cuprates derived from [CU3(SAr) (3)] catalysts. It will be shown that the reaction of a parent [Cu-3(SAr)(3 )] complex with a Grignard reagent (MeMgI) results in re-aggregation of the [Cu-3(SAr)(3)] structure. In the case of a threefold excess of MeMgI a str ucture [R2Cu4(SAr)(2)], including four Cu centres connected by two carbon a nd two sulfur bridges, for the newly formed aggregate is proposed. After ad ding a 6 fold excess of MeMgI to [Cu-3(SAr)(3)], Cu-Mg, Cu-C and C-S contri butions were found. For this complex a structure of the type [RCu(SAr)Mg(I) ] with bridging carbon or sulfur atoms is proposed.