Synthesis and Characterization of Hexadentate Cobalt(III) Complexes with New edta-Type Ligands Part 5. Structure and Absolute Configuration of the trans(O5)(−)546-Isomer of Lithium (Ethylenediamine-N,N,N′-triacetato-N′-3-propionato)cobaltate(III) Monohydrate, (−)546-trans(O5)-Li[Co(ed3ap)]·H2O. Strain Analysis of [Co(edta-Type)]− Chelates in Relation to Their Octahedral Distortion

Abstract

Abstract The preparation and resolution of the two hexadentate Co(III) complexes containing unsymmetrical edta-type ligands, [Co(ed3ap)]− (A) and [Co(u-eddadp)]− (B) (ed3ap = ethylenediamine-N,N,N′-triacetate-N′-3-propionate ion; u-eddadp = ethylenediamine-N-diacetate-N′-di-3-propionate ion) have been reexamined. The X-ray data are reported for the Λ-(−)546-trans(O)5-Li[Co(ed3ap)]·H2O for which the same (Λ) absolute configuration was predicted from the CD sign pattern of the lowest energy band. The complex crystallizes in the space group P21 (#4) of the monoclinic crystal system with a = 6.523(4), b = 15.025(7), c = 7.464(3) Å, β = 105.40(4)°, and Z = 2. The conformations of the chelate rings are found to be envelope for the glycinates and skew-boat (half-chair) for the β-alaninate ring. Structural parameters and strain analysis of [Co(edta-type)]− chelates are discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD and IR (carboxylate region) spectra of complexes A and B are also discussed.