Stereochemistry of complexes of multidentate ligands. Part VI. Stereoselective cobalt(III) complexes of (3R)3-methyl-1,6-bis[(2S)-pyrrolidin- 2-yl]-2,5-diazahexane and (3S)3-methyl-1,6-bis[(2S)-pyrrol-idin-2-yl]-2,5-diazahexane

Abstract

The compounds (3R)3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane (L1) and (3S)3-methyl-l,6 bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane (L2) have been synthesized, together with their cobait(III) complexes, cis- and trans-[CoCl2L]+ and cis-[CoL(NO2)2]+ and cis-[CoL(C2O4)]+. The optically active quadridentate ligands co-ordinate stereospecifically in both the cis and trans complexes: in the cis geometry, L1 and L2 give stereo-specifically the Λ-cis-β and Δ-cis-β configurations, respectively; in the trans geometry, both ligands give optically active trans configurations. Electronic-absorption, circular-dichroism, and optical-rotatory-dispersionspectra are reported and used, together with chemical data, to assign the absolute configurations of the complexes.