Cobalt(III) complexes of N,N′-bis(2(S)-aminopropyl)-1(R),2(R)-trans-1,2-diaminocyclohexane

A novel optically active tetraamine ligand possessing four asymmetric centers, N,N′-bis(2(S)-aminopropyl-1(R),2(R)-trans-1,2-diaminocyclohexane (SRRS-apchxn) and its cobalt(III) complexes, [Co(SRRS-apchxn)X₂]ⁿ⁺ (X=Cl-, H₂O, X₂ = CO₃^2-) have been synthesized. This ligand has coordinated stereospecifically to the cobalt(III) ion to give only the Λ-uns-cis-(SS) isomer. A trans dichloro complex has been obtained via the stereospecific isomerization of Λ-uns-cis-(SS)-[Co(SRRS-apchxn)Cl₂]⁺ to trans-(SS)-[Co(SRRS-apchxn)Cl₂]⁺ in CH₃OH-HCl medium. Ligand and complexes have been characterized by electronic absorption, ¹H NMR, CD spectra, and also by elemental analysis. It is of interest that this is one of the few Co^III(N₄)X₂ type complex preparations, which produces such an uns-cis isomer with stereospecificity.