Anionic and zwitterionic copper(I) complexes incorporating an anionic N-heterocyclic carbene decorated with a malonate backbone: synthesis, structure and catalytic applications.
The anionic malonate-derived N-heterocyclic carbenes (maloNHCs) react cleanly and rapidly with copper chloride to generate the anionic complexes of type [(maloNHC)CuCl]·Li, which crystallize in the solid state either in an oligomeric trimer arrangement or in polymeric helixes depending on the substitution pattern and the solvent. Ten zwitterionic heteroleptic Cu(I) complexes combining the anionic maloNHC and a neutral imidazol-2-ylidene are also obtained in a very selective manner and fully characterized. Whereas the anionic complexes are relatively active catalysts for the hydrosilylation of carbonyl compounds, the zwitterionic complexes reveal to be efficient and extremely robust pre-catalysts for the intramolecular cyclopropanation reaction of a diazo ester and outperform the corresponding cationic Cu(i) complexes with classical imidazol-2-ylidenes.
CNRS, Laboratoire de Chimie de Coordination, 205 route de Narbonne, F-31077 Toulouse Cedex 4, France. vincent.cesar@lcc-toulouse.fr
Vincent
V
César
Cécile
C
Barthes
Yoann C
YC
Farré
Stéphane V
SV
Cuisiat
Bernard Y
BY
Vacher
Rémy
R
Brousses
Noël
N
Lugan
Guy
G
Lavigne