Chiral metal complexes. 49. Structural studies of ternary Co(III) complexes of N,N′-di (2S-pyrrolidin-2-yl)-1S, 2S-diaminocyclohexane and α-aminoacids

Ternary complexes of the type Δ-β_1,2-[Co(S,S,S,S,-pychxn)(aa)]²⁺ where S,S,S,S-pychxn is N,N′-di(2S-pyrrolidin-2-yl)-1S,2S-diaminocyclohexane and aa is an aminoacidate (glyH = glycine, alaH = alanine) have been synthesized and structurally characterized. Δ-β₁-[Co(S,S,S,S-pychxn)-(gly)](ClO₄) ₂ 2H₂O is orthorhombic, space group P2₁2₁2₁, with a = 10.133(2), b = 14.418(2), c = 19.646(5) Å and Z = 4. The structure was refined to R = 0.065 and R_w = 0.072 for 2224 reflections with I >3σ(I) Δ-β₂-[Co(S,S,S,S-pychxn) (R-ala)](ClO₄)₂.2H₂O is orthorhombic, space group P2₁2₁2₁, with a = 10.933(4), b = 13.667(2), c = 18.853(3) Å, and Z = 4. This structure was refined to R = 0.040 and R_w = 0.033 for 2221 reflections with I > 3σ(I). Both complex structures are analogous in that the coordination of the tetradentate is identical with both nitrogen atoms of coordinated pyrrolidyl groups adopting S absolute configurations; the two internal nitrogen atoms have opposite configurations with that at the fold of the tetradentate being R. While S,S,S,S-pychxn is not absolutely stereospecific with respect to its coordination with Co(III) it is markedly more so than its congener S,R,R,S,-pychxn. The structural study benchmarks stereochemistries adopted by this class of compound with respect to further studies.