Catalytic Transmetalation of Alkoxychromium(0) Carbenes to Late Transition Metals:  Self-Dimerization and Cyclopropanation Reactions

• Published in: Organometallics Vol. 23; no. 21; pp. 5021 - 5029
• Main Authors: del Amo, Juan C, Mancheño, María J, Gómez-Gallego, Mar, Sierra, Miguel A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.10.2004
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om049455d

A systematic study of the transfer of the carbene ligand from [pentacarbonylalkoxychromium(0)]carbene complexes catalyzed by Ni and Cu catalysts is reported. The results obtained indicate that Ni and Cu catalysts are not as effective as palladium to promote the carbene self-dimerization process. Ni catalysts are the less efficient in these reactions, while Cu catalysts are of intermediate reactivity. In the presence of electron-deficient olefins, cyclopropanation products or γ-ketoesters can be selectively formed by choosing the adequate Ni or Cu catalyst, while Pd catalysts are ineffective in these processes. Cyclopropanes are better formed with Ni(PPh3)4, Ni(COD)2, or Cu(0) and electron-poor olefins at room temperature, whereas γ-ketoesters are the exclusive products with Ni-Raney or Zn(0)/CuCl in stoichiometric reactions. The transmetalation from Cr to the late transition metal to form a new metal-carbene complex is the key step of these reactions and is strongly dependent on the nucleophilicity of the catalyst used.