Synthesis and structure of mononuclear and binuclear zinc(II) compartmental macrocyclic complexes

The structures of four neutral binuclear ZnII complexes of the Schiff-base macrocycles formed by the [2+2] template condensation of 2,6-diformyl-4-methylphenol with 1,2-diaminoethane: [H2L1], 1,3diaminopropane: [H2L2], 1,4-diaminobutane: [H2L3] and 2,6-diacetyl-4-methylphenol with 1,2diaminoethane: [H2L4] have been determined. The complexes [Zn2(L1)(OAc)2]·2CHCl3, [Zn2(L2)(OAc)2]· 2CHCl3 and [Zn2(L4)Cl2] each contain two five coordinate ZnII centres with each metal ion bound to the N2O2 donor set of the macrocyclic ligand and to an anion molecule. Two different coordination environments are observed in [Zn2(L3)(mu-OAc)(OAc)]·CHCl3 which contains both a five- and a sixcoordinate ZnII centre, with one acetate bridging two metal ions and a monodentate acetate bound to the six-coordinate ZnII ion. Significantly, the reaction of pre-formed macrocyclic ligands [H4L2](PF6)2 and [H4L4](PF6)2 with Zn(OAc)2·2H2O affords [Zn2(L2)(mu-OAc)](PF6)·MeCN and [Zn(H2L4)(MeCN)](PF6)2, respectively. The former shows two five-coordinate ZnII centres in which an acetate bridges both metal ions. In the latter complex the macrocyclic ligand binds only one five-coordinate ZnII ion with a molecule of MeCN bound at an apical position.