Copper(II), nickel(II), cobalt(II) and zinc(II) complexes of the 22-membered hexa-aza macrocycle 1,4,7,16,19,22-hexa-aza[9.9]metacyclophane (L) have been prepared and characterised. The crystal structure of a copper(II) chloro complex has been determined. The complex exists in two forms, one form (Type 1) with an inversion centre has both copper atoms in essentially square pyramidal stereochemistry with an N 3 Cl 2 donor set and a Cu...Cu distance of 5.82 9. The other form (Type II) has one square pyramidal copper with an N 3 Cl 2 donor set and one planar copper with an N 3 Cl donor set. The Type II Cu...Cu distance is 6.13 9. The structure is best described as [Cu 2 LCl 4 ] 0 . 5 .[Cu 2 LCl 3 ]ClO 4 .dmf (dmf=N,N-dimethylformamide). The copper(II) complex catalyses the hydrolysis of the phosphotriester 2,4-dinitrophenyldiethylphosphate to give diethyl phosphate and the mechanism of the reaction is discussed.