Dinickel(II), dizinc(II) and dilead(II) complexes of a pyridazine-containing Schiff-base macrocycle

The study of the mid-late first row transition metal co-ordination chemistry of the pyridazine-containing Schiff-base macrocycle L1 [derived from the (2 + 2) condensation of 3,6-diformylpyridazine and 1,3-diaminopropane] has been completed. Transmetallation reactions of [Pb2(4 + 4)](ClO4)4 (1) under appropriate conditions have led to the formation of the following complexes, [Ni2L1(NCS)2(SCN)2] (3), [{Pb2L1}2(μ3-OH)2](ClO4)6 (4), and [Zn2L1(CH3CN)4](ClO4)4 (5 · 4CH3CN), all of which have been structurally characterised. The analogous triflate salt of 5, [Zn2L1](CF3SO3)4 (6), can only be obtained by template reaction, as transmetallation of 1 with Zn(CF3SO3)2 · 6H2O gave 5, albeit in reduced yield. Attempts to synthesise pure [Fe2L1(CH3CN)4](ClO4)4 (7) using the transmetallation procedure, from either [Pb2(4 + 4)](ClO4)4 or [Zn2L1(CH3CN)4](ClO4)4, were unsuccessful. The electrochemical studies carried out on [Zn2L1](ClO4)4 (5) revealed multiple reduction processes and associated oxidations, but no processes corresponding to oxidation of 5.