Meiere, S. H.; Ding, F.; Friedman, L.; Sabat, M.; Harman, W. D. Dihapto Coordination of Carboxylic Acid Derivatives with an Asymmetric Rhenium π-Base: A New Mechanism for Amide Isomerization?. J. Am. Chem. Soc. 2002, 124, 13506-13512.
Abstract
The asymmetric π basic metal fragment {TpRe(CO)(MeIm)} (Tp = hydridotris(pyrazolyl)borate, MeIm = 1-methylimidazole) forms thermally stable complexes with ethyl acetate, acetic anhydride, N-methylsuccinimide, N-acetylpyrrole, and N-methylmaleimide in which the metal binds a carbonyl group in a π fashion. In all cases a single diastereomer is observed, indicating that one enantioface of the carbonyl is selectively coordinated. X-ray and NMR data for the compound TpRe(CO)(MeIm)(η2-N-methylsuccinimide) indicate that metal coordination effectively removes the π interaction between the bound carbonyl and the nitrogen of the succinimide ring.
