Tetra-aza macrocyclic complexes containing a pendant amino group. Copper(II), nickel(II), and cobalt(III) complexes of 5-aminomethyl-2,5,10,12-tetramethyl-1,4,8,1 1-tetra-azacyclotetradecane (L) and X-ray structural characterisation of the cobalt(III) complex [Co(L)Cl][ClO4]Cl·EtOH

Abstract

The macrocycle 5-aminomethyl-2,5,10,12-tetramethyl-1,4,8,11-tetra-azacyclotetradecane (L) containing a pendant amino group has been prepared. A variety of copper(II), nickel(II), and cobalt(III) complexes have been characterised. Octahedral [NiL(H₂O)]²⁺ complexes are readily protonated to give yellow or orange planar [Ni(HL)]³⁺ species. Analogous copper(II) complexes have also been prepared. X-ray crystallographic investigation of the complex [Co(L)Cl][ClO₄]Cl·EtOH confirms the ligand stereochemistry and establishes a trans III (2 N–H bonds up, 2 N–H bonds down) stereochemistry for the chiral NH centres. The pendant amino group acts as a donor in one of the axial sites and lies trans to the chloride ligand. Rapid base hydrolysis of the Cl^– ligand occurs with k_OH= 2.2 × 10⁴ dm³ mol^–1 s^–1 and k_aq= 3.5 × 10^–5 s^–1 at 25 °C and I= 0.1 mol dm^–3.