Synthesis and characterisation of manganese(III) unsymmetrical Schiff-base complexes: a unique example of a cocrystallised manganese(III) unsymmetrical Schiff-base complex, and a symmetric Schiff-base complex arising from rearrangement of the former

Abstract

Some manganese(III) complexes with unsymmetrical Schiff bases have been prepared and characterised. The ligands were prepared by condensation of 7-amino-4-methyl-5-azahept-3-en-2-one with salicylaldehyde, 2-hydroxyacetophenone or substituted salicylaldehydes (5-chloro, 5-methoxy, 3-ethoxy or 3,5-dibromo). On reaction with manganese(II) perchlorate in air, manganese(III) Schiff-base complexes are obtained. The crystal structures of two of these have been determined, one being cocrystallised with [{Mn(salen)(H₂O)}₂][ClO₄]₂ containing the symmetrical salen ligand [N,N′-ethane-1,2-diylbis-(salicylideneiminate)]. Unlike the dimeric structures previously found for similar complexes, the two structures are monomeric with octahedral MnN₂O₄ co-ordination spheres.