Chiral metal complexes 44. Enantiomeric discrimination in ternary cobalt(III) complexes of N,N′-dimethyl-N,N′-di(2-picolyl)-1S,2S-diaminocyclohexane and α-amino acids; including the crystal structure of the S-prolinato complex

Ronald R. Fenton, Frederick S. Stephens, Robert S. Vagg*, Peter A. Williams

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

When the C2-symmetrical complex Λ-α[Co(S,S-picchxcMe2Cl2]+ (S,S-picchxnMe2 is N,N′-dimethyl-N,N′-di(2-picolyl)-1S,2S-diaminocyclohexane) is reacted with the α-amino acids proline (proH), alanine (alaH) or 2-amino-2-methylpropandioic acid (AMMAH2), the two chloride ions are replaced by the O,N-bidentates with retention of configuration at the metal centre. The steric environment generated by the metal complex is shown to enantiospecifically discriminate in favour of S-proline from a racemic mixture due to the steric requirements of this amino acid. With the less bulky alanine and AMMAH2 ligands there is no enantiomeric preference observed upon their coordination. When the mixed diastereoisomeric Λ-α-[Co(S,S-piccchxnMe2) (AMMAH)]2+ precursors are decarboxylated under warm acidic conditions, neither hand of alanine is found to predominate in the product. The crystal structure of the Λ-α-[Co(S,S-picchxnMe2) (S-pro)] (ClO4)2· H2O salt of the sole S-prolinate product was determined by X-ray diffraction methods. Crystal data: C25H28N5O11Cl2Co is orthorhombic, space group P212121, with a = 11.082(3), b = 13.838(4), c = 19.387(5) A ̊ and Z = 4. The structure was refined by least-squares methods to R = 0.033 for 2672 diffractometer data. The Co atom is six-coordinate with the N4-tetradentate and the O,N-bidentate amino acidate comprising the octahedral coordination sphere. The average CoN(pyridine) and Coz.sbnd;N(tert-amine) distance are 1.96 and 2.00 Å, respectively.

Original languageEnglish
Pages (from-to)109-115
Number of pages7
JournalInorganica Chimica Acta
Volume236
Issue number1-2
DOIs
Publication statusPublished - 1995

Keywords

  • amino acid complexes
  • chiral metal complexes
  • cobalt complexes
  • crystal structures

Fingerprint

Dive into the research topics of 'Chiral metal complexes 44. Enantiomeric discrimination in ternary cobalt(III) complexes of <i>N,N′</i>-dimethyl-<i>N,N′</i>-di(2-picolyl)-1S,2S-diaminocyclohexane and α-amino acids; including the crystal structure of the S-prolinato complex'. Together they form a unique fingerprint.

Cite this