Synthesis and structure of dilead(II) and dimanganese(II) complexes of macrocycles derived from 3,6-diformylpyridazine

Abstract

An improved synthesis of 3,6-diformylpyridazine I has been elaborated. The macrocyclic complexes Pb₂L¹(ClO₄)₄1 and [Pb₂L²][ClO₄]₄2 were prepared from this precursor, 1,3-diaminopropane and lead(II) perchlorate in 1 : 1 : 1 and 2 : 2 : 1 ratios respectively. The ability of lead(II) perchlorate to template the formation of the two macrocycle ring sizes, L¹=(2 + 2) and L²=(4 + 4), simply by alteration of the reagent ratio is unprecedented. Transmetallation of 1 or 2 with manganese(II) perchlorate and an excess of sodium thiocyanate led to the formation of [Mn₂L¹(NCS)₄]3. Single-crystal X-ray analyses of 2 and 3 revealed that on transmetallation a ring contraction, (4 + 4) to (2 + 2), occurs. The two manganese(II) ions have irregular geometries and are inequivalent; one is six- whilst the other is seven-co-ordinate. Unusual single-atom > NCS bridging of the manganese ions occurs.