Compounds of Cobalt(III) With trans-6,13-Diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane

Abstract

Compounds are described of cobalt(III) with the macrocycle trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane ( diam ) of the types [Co(diam-N₆)]³⁺, with diam in octahedral coordination, with the primary amino substituents coordinated trans; [Co(diam-N₅)X]^2,3+ and [Co(diamH-N₅)X]^3,4+, with diam in square pyramidal pentacoordination , with a ligand X,X-coordinated trans to the primary amino substituent and with the non-coordinated amino substituent neutral or monoprotonated, respectively; and trans-[Co(diamH-N₄)X₂]²⁺ and trans-[Co(diamH₂-N₄)X₂]³⁺, with diam in planar tetracoordination, with trans ligands X-, and with one or both amino groups protonated , respectively. The diam and [Co(H₂O)₆](ClO₄)₂ in water exposed to the air react to sequentially form [Co( diam )]²⁺, trans-[{Co(diam-N₅)}₂(O₂)]⁴⁺, trans-[Co(diam-N₅)(OH)]²⁺ and [Co(diam-N₆)]³⁺ cations. The μ- peroxo or hydroxo compounds can be used to prepare other N₅-cations including [Co(diamH-N₅)(H₂O)]⁴⁺, [Co(diamH-N₅) Cl ]³⁺ and [Co(diam-N₅) Cl ]²⁺. [Co(diamH₂-N₄)]⁴⁺ formed by reduction of [Co(diam-N₆]³⁺ with zinc amalgam in hydrochloric acid reoxidizes in air to form trans-[Co(diamH₂-N₄)Cl₂]³⁺ and a [Co(diamH-N₅) Cl ]²⁺ cation isomeric with that obtained from the hydroxo compound. The N₄-tetra- and N₅-penta-coordinated forms are stable in acid solution, but in base convert sequentially into the N₆-hexacoordinated form in equilibrium with trans-[Co(diam-N₅)(OH)]²⁺. Preparations, spectroscopic properties, and interconversion reactions of compounds of these cations, and some bromo, thiocyanato and acetato analogues are reported.