Notes. Dicopper(II) complexes of an N6O2 macrocycle and seven-co-ordinate manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and zinc(II) complexes of its N5O2 open-chain precursor

The syntheses, via metal-ion (Mg2+, Ca2+, or Ba2+) template methods followed by transmetallation, of the complexes [ML1]X2(M = MnII, FeII, CoII, NiII, CuII, or ZnII; X = ClO4– or BPh4–) of the potentially septidentate ligand L1 formed by condensation of 1 mol of 2,6-diacetylpyridine with 2 mol of 3-oxapentane-1,5-diamine is described. The collective evidence of the properties (magnetic and spectroscopic) of the complexes indicates a seven-co-ordinate (pentagonal-bipyramidal) structure. Ring closure, via a transamination mechanism, of L1 in BaL1(ClO4)2 leads to the complex BaL2(ClO4)2·3H2O containing the 24-membered N6O2 macrocyclic ligand L2. The single Ba2+ in this complex may be replaced by two copper(II) ions to afford the binuclear complex Cu2L2(ClO4)4·H2O which on treatment with imidazole (Him) gives Cu2L2(im)(ClO4)3·H2O containing an imidazolate bridge between the antiferromagnetically coupled metal centres.