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-C1-Cis(O) diastereomer

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: A-trans(O); and A- and Δ-C 2 -cis(O) and A- 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 1 3 C NMR 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.