Cyclopropanation / Copper / N ligands / Macrocycles / Supported catalysts Cu I and Cu II complexes of cyclic and open-chain polyaza has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements suggest the compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate.
formation of oligomeric species. Some of the chiral ligands lead to small enantiomeric excesses. Open-chain ligands can In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the easily be supported on organic polymers and their complexes can be used as catalysts. Furthermore, cyclic and acyclic structure of the ligand, e.g. amine-amides are more efficient than polyamines, and on the oxidation state of copper, Cu II complexes can be supported on clays by cation exchange and the solids obtained tend to promote the reaction with a being more active than Cu I . Given that Cu I is the active species, these changes of behavior must be related to the decrease in the trans/cis ratio. stabilities of the complexes. The nature of the counterion also Given the presence of nitrogen atoms related by the sym-Universidad de Zaragoza -C.S.I.C., respect to its disproportionation into Cu II and Cu 0 . [10] We E-50009 Zaragoza, Spain prepared its Cu I complex in situ and used it as a catalyst