1972 Volume 45 Issue 7 Pages 2129-2137
New cobalt(III) complexes containing optically active (RR and SS) and meso(RS) 2,4-pentanediamine (2,4-ptn) have been synthesized. [Co(RR-2,4-ptn)3]3+ gives two diastereoisomers, prismatic crystals with (−)546 rotation and needle-like crystals with (+)546 rotation. The former is produced much more than the latter. The conformations of the RR- (or SS-) and RS-2,4-pentanediamine chelate of the complexes were assigned to λ- (or δ-) twist and chair form, respectively, from comparison of their PMR spectra with those of the corresponding tetra-acetato complexes. [Co(RS-2,4-ptn)3]3+ seems to have fac structure with respect to the coordination of the amino groups adjacent to the R- and S-carbon atoms. The circular dichroism spectra of mono and trans-bis-(RR-2,4-ptn) complexes in the first band region are essentially the same as those of the corresponding R-propylenediamine complexes. The circular dichroism spectra of (+)546- and (−)546-[Co(RR-2,4-ptn)3]3+ and (−)546-[Co(RS-2,4-ptn)3]3+ are very different from those of the triscobalt(III) complexes of R-propylenediamine and trimethylenediamine. Such differences have been discussed with reference to the stereochemistry of six-membered chelate complexes.
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