title: The activation of tertiary carboxamides in metal complexes: an experimental and theoretical study on the methanolysis of acylated bispicolylamine copper(II) complexes.
abstract: It is a well-established concept that the C-N bond cleavage of carboxamide functions is facilitated by the coordination of a metal ion to the carbonyl oxygen atom. In contrast, the alternative C-N bond activation by coordination of a neutral tertiary carboxamide nitrogen atom has not been studied. We present the first results on the effect of nitrogen pyramidalization in N-coordinated metal complexes on the methanolysis of tertiary carboxamide groups. An analysis of the reactions products obtained from the methanol cleavage of [(N-Acyl-bpa)Cu]2+ (bpa = N,N-bispicolylamine) complexes is presented together with experimental and high-level theoretically calculated structures. The strong effect of different anions on the amide pyramidalization and subsequent C-N-bond cleavage is evaluated. We show that dichloro complexes [(N-Acyl-bpa)CuCl2] have much less activated amide groups than the corresponding triflate species. They should therefore be less reactive. However, [(N-Acyl-bpa)CuCl2] complexes dissociate in solution to give cationic monochloro complexes [(N-Acyl-bpa)Cu(S)Cl]+ (S = solvent molecule). Theoretical calculations show that the amide pyramidalization in the monochloro complexes is equal to that in the corresponding CF3SO3- salts. Consequently, chloro and triflato complexes are cleaved with similar rates and efficiencies. Parallels to and differences in the reactivity of purely organic distorted amides are discussed.
authors.affiliation: Institute of Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstr. 1, D-91058 Erlangen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Niklas
authors.forename: Frank W
authors.initials: FW
authors.lastname: Heinemann
authors.forename: Frank
authors.initials: F
authors.lastname: Hampel
authors.forename: Tim
authors.initials: T
authors.lastname: Clark
authors.forename: Ralf
authors.initials: R
authors.lastname: Alsfasser