Tetra-aza macrocyclic complexes containing a pendant amino group. Copper(<scp>II</scp>), nickel(<scp>II</scp>), and cobalt(<scp>III</scp>) 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(<scp>III</scp>) 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 kOH= 2.2 × 104 dm3 mol–1 s–1 and kaq= 3.5 × 10–5 s–1 at 25 °C and I= 0.1 mol dm–3.