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Stereoselectivity in Reactions of Metal Complexes. Part XV. Structure and stability of chiral cobalt(III) complexes with pentadentate ligands

✍ Scribed by Klaus Bernauer; Helen Stoeckli-Evans; Deirdre Hugi-Cleary; Hermann J. Hilgers; Habib Abd-el-Khalek; Joëlle Porret; Jean-Jacques Sauvain

Publisher
John Wiley and Sons
Year
1992
Tongue
German
Weight
685 KB
Volume
75
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

The syntheses and characterization of four new linear pentadentate ligands and their Co^III^ complexes are described: N,N′‐[(pyridine‐2,6‐diy)bis(methylene)]bis[sarcosine] (sarmp), N,N′‐[(pyridine‐2,6‐diyl)bis(methylene)]bis[(R)‐ or (S)‐proline] ((R,R)‐ or (S,S)‐promp), N,N′‐[(pyridine‐2,6‐diyl)bis(methylene)]bis[N‐(methyl)‐(R)‐ or (S)‐alanine] ((R,R)‐ or (S,S)‐malmp); 2,2′‐[pyridine‐2,6‐diyl]bis[(S)‐ or rac‐N‐(acetic acid)pyrrolidine] ((S,S)‐ or rac‐bapap). The complexes were characterized and, with but one exception, complex formation is stereospecific: Δ‐exo‐(R,R) (or Λ‐exo‐(S,S)) for promp and Λ‐(R,R) (or Δ‐(S,S)) for bapap. The exception is [Co((R,R)‐ or (S,S)‐malmp)H~2~O]ClO~4~ for which two forms are obtained, to which Λ‐endo‐(R,R) (or Δ‐endo‐(S,S)) and, tentatively, Δ‐unsymmetric‐(R,R)‐ (or Λ‐unsymmetric‐(S,S)‐) configurations are assigned. X‐Ray crystal structures are presented for the complexes [Co(sarmp)H~2~O]ClO~4~, [Co((S,S)‐promp)H~2~O]ClO~4~, [Co(rac‐bapap)H~2~O]ClO~4~ and endo‐[Co(rac‐malmp)H~2~O]ClO~4~. Ligand acid dissociation and Co^II^ and Fe^II^ complex‐formation constants are reported.

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