Chiral metal complexes 43. Cobalt (III) complexes of novel asymmetric tetradentate and pentadentate aminopolypicolyl ligands

The syntheses of the two novel chiral amines, N,N′-di(2-picolyl)-1R, 3S-diamino-1,2,2,-trimethylcyclopentane) (R,S-pictmcp) and 3S-di-(2-picolyl)-amino-N-(2-picolyl)hexahydroazepine (S-ahazterpy), and their complexes with Co(III) are reported. Coordination of the tetradentate R,S-pictmcp is shown to be highly stereoselective, with only the Δ-ß isomer of [Co(R,S-pictmcp)CO₃]ClO₄·2H₂O being isolated. Assignment of stereochemistry was made using a combination of CD and NMR techniques. In the preparation of [Co(S-ahazterpy)ClO₄)₂·2H₂O, containing the pentadentate polyamine, a single isomer (trans-equatorial was obtained. The yield, however, was low, and no inference is made to the extent of any stereoselectivity in this case. CD and NMR data are presented for both species and discssed in relation to assigned stereochemistries.