Skip to main content
padlock icon - secure page this page is secure

Open Access Non-Linear Effects in Asymmetric Reactions: Negative and Positive Stereoselectivity in the Formation of Homoleptic 1:2 Metal to Ligand Complexes of Chiral 1,9-Disubstituted Semicorrin Ligands

Download Article:
(PDF 507.8 kb)
The stereoselectivity of the formation of bis-chelates with the 1,9-disubstituted chiral semicorrin ligands (1S,9S)-dimethyl 5-cyanosemicorrin-1,9-dicarboxylate (1) for Co2+, Ni2+, Cu2+, and Pd2+ and with its (1S,9S)-diethyl analogue 2 for Co2+ and Cu2+ have been measured by the method of continuous variation of enantiomers, and with 1 for Zn2+ by NMR. Positive selectivities were found for Co2+, Ni2+, and Zn2+ complexes, whereas very high negative selectivities prevail in the complexes of Cu2+ and Pd2+. These results are rationalised by X-ray structural determinations of some of the corresponding complexes. The optically active Cu2+ and Pd2+ complexes show distorted square planar structures with chirality predetermined by the chirality of the ligand. Ni2+ complexes are five or hexacoordinated and exhibit a distorted tetrahedral arrangement of the four coordinated nitrogen atoms. In the optically active compound the ester moiety is coordinated by the oxygen atom of the alkoxy group and the arrangement of the two N-N chelate rings shows Δ-(S,S) chirality. Interestingly, with the racemic ligand, it is not the more stable heterochiral, but the racemic complex containing the two homochiral enantiomers which is obtained. The coordination of the ester groups occurs by the carbonyl oxygen and the chirality is opposite to the optically active compound, e.g Δ(S,S)/Δ-(R,R). The structure of the optically active zinc compound shows very weak interaction with the alkoxy group of one ester moiety of each ligand molecule and the chirality of the N-N-chelate rings is Δ-(S,S). Again, the compound obtained with the racemic ligand contains the enantiomers of the homochiral complex, the chirality of which is Δ-(R,R)/Δ-(S,S). The results are discussed with respect to the possibility to perform asymmetric amplifications of the 1:1 complexes of semicorrin ligands as enantioselective catalysts.

36 References.

No Supplementary Data.
No Article Media
No Metrics


Document Type: Research Article

Publication date: October 1, 2003

More about this publication?
  • International Journal for Chemistry and Official Membership Journal of the Swiss Chemical Society (SCS) and its Divisions

    CHIMIA, a scientific journal for chemistry in the broadest sense, is published 10 times a year and covers the interests of a wide and diverse readership. Contributions from all fields of chemistry and related areas are considered for publication in the form of Review Articles and Notes. A characteristic feature of CHIMIA are the thematic issues, each devoted to an area of great current significance.

  • Editorial Board
  • Information for Authors
  • Subscribe to this Title
  • Information for Advertisers
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more