Mixed cobalt(III) complexes with aromatic amino acids and diamine. Part II. Synthesis and configuration of (1,2-diaminoethane)Bis(L-Tyrosinato)-cobalt(III)complex diastereomers. The crystal structure of the Δ-C 1 -Cis(O) diastereomer
Résumé
In the reaction of trans-[CoCl 2 (en) 2 ] + with L-tyrosine all six theoretically possible diastereomers of the (1,2-diaminoethane)bis(L-tyrosinato) cobalt(III) complex were formed. The following five were isolated Λ-trans(O); and Λ- and Δ-C 2 -cis(O) and Λ- and Δ-C 1 -cis(O) diastereomers, while the Δ-trans(O) diastereomer was only detected in the corresponding eluate. Separation of the obtained diastereomers was performed by chromatography on a Dowex 1 x 4 column. Characterization of the isolated diastereomers was carried out by means of elemental analysis, electronic absorption, circular dichroic, 1 H and 13 CNMR spectra, and by x-ray crystal structure analysis in the case of the Δ-C 1 -cis(O) diastereomer. We established the general rule of preference of diasteromers formation in complexes of [Co(L-aa) 2 diamine] + (L-aa=L-amino acid anion; diamine=1,2-diaminoethane or 1,3-diaminopropane) type.