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 [Pb-2(4+4)](ClO4)(4) (1) under appropriate conditions have led to the formation of the following complexes, [Ni(2)L1(NCS)(2)(SCN)(2)] (3), [{Pb(2)L1}(2)(mu(3)-OH)(2)](ClO4)(6) (4), and [Zn(2)L1(CH3CN)(4)](ClO4)(4\)(5.4CH(3)CN), all of which have been structurally characterised. The analogous triflate salt of 5, [Zn(2)L1](CF3SO3)(4) (6), can only be obtained by template reaction, as transmetallation of 1 with Zn(CF3SO3)(2).6H(2)O gave 5, albeit in reduced yield. Attempts to synthesise pure [Fe(2)L1(CH3CN)(4)](ClO4)(4) (7) using the transmetallation procedure, from either [Pb-2(4+4)](ClO4)(4) or [Zn(2)L1(CH3CN)(4)](ClO4)(4), were unsuccessful. The electrochemical studies carried out on [Zn(2)L1](ClO4)(4) (5) revealed multiple reduction processes and associated oxidations, but no processes corresponding to oxidation of 5. (C) 2004 Elsevier B.V. All rights reserved.