Synthesis, Structure and Hydrolytic Properties of a Family of New Zn Complexes Containing Hexaazamacrocyclic Ligands

The synthesis, structure and spectroscopic properties of a family of Zn complexes containing a dinucleating hexaazamacrocyclic ligand (L) and anionic ligands (X) of general formula [Zn 2 (X) 4− n (L)] n + ( 1 − 8 ; L = H2p, H3p, Me2p, Me2m, Me3p, Me3m; X = Cl, n = 0; X = NO 3 , n = 2) have been investigated. The solid‐state structural characterisation has been performed by means of X‐ray diffraction analysis for complexes 3 , 5 , 7·1/3CH 2 Cl 2 and 8 . The Zn complexes 5 , 7·1/3CH 2 Cl 2 and 8 containing chloride ligands present a distorted N 2 Cl 2 tetrahedral coordination with two non‐coordinated N atoms of the macrocyclic ligand. On the other hand, complex 3 , which contains nitrate ligands, displays an N 3 O 2 pentacoordination with all the N atoms of the macrocyclic ligand bonded to the metal centres. The different factors governing the relative Zn−Zn disposition are discussed. NMR spectroscopy in solution reveals the presence of fluxional behaviour and a completely different structural arrangement than in the solid state. In particular, evidence for the formation and breaking of Zn−N bonds involving all the macrocyclic ligand aminic N atoms is obtained for the chloride complexes 2 and 4 − 8 . Finally, complexes 1 , 3 , 5 and 7 hydrolyse p ‐nitrophenyl acetate (NA) with second‐order rate constants ranging from 0.045 to 0.193 M −1 s −1 , thus manifesting the influence of the ligands over the hydrolytic activity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)