Coordination chemistry of 1,4-bis-carboxymethylcyclam, H2(1,4-bcc)

Abstract

Zinc metal reduction of the cobalt(III) complex [Co(1,4-bcc)]⁺ (1,4-bcc = 1,4-bis-carboxymethylcyclam) produces the corresponding cobalt(II) complex which crystallises as the coordination polymer {[Co(1,4-bcc)]ZnCl₂}_n. A method has been developed for removal of the cobalt(III) ion from [Co(1,4-bcc)]⁺ and isolation of the free ligand as its hydrochloride salt, H₂(1,4-bcc)·4HCl. This has been used for the preparation of new metal complexes, and the syntheses and characterisation of the copper(II), nickel(II), zinc(II) and chromium(III) complexes containing the 1,4-bcc ligand are described. X-Ray crystal structures of {[Co(1,4-bcc)]ZnCl₂}_n·2.5H₂O, {[Cu(1,4-bcc)]CuCl₂}_n·0.25MeOH·H₂O and [Cu(1,4-bcc)H]ClO₄ show the complexes to have the trans(O) geometry of the 1,4-bcc ligand, while the structure of [Cr(1,4-bcc)H_0.5](ClO₄)_1.5·EtOH exhibits the cis(O) configuration.