Metal complexes (Co3+, Fe3+, Mn3+) of the quinquedentate salen analogue, 2-methyl-4-benzylthio-N,N′-butane-1,2-diylbis(salicylideneimine): crystal structures and sulphur co-ordination effects

Abstract

Three metal complexes, [Co(L)(Him)]PF₆(Him = imidazole), [Fe(L)Cl], and [Mn(L)(CH₃OH)]BPh₄, were obtained using a quinquedentate salen analogue with a pendant sulphur capable of axial co-ordination, 2-methyl-4-benzylthio-N,N′-butane-1,2-diylbis(salicylideneimine)(H₂L), and their structures and properties were examined with regard to the axial co-ordination of the pendant sulphur. A six-co-ordinate structure with the imidazole and the pendant sulphur at the axial sites was inferred for [Co(L)(Him)] PF₆ from the electronic specta and electrochemical behaviour. The structure of [Fe(L)Cl] was determined by single-crystal X-ray crystallography. The configuration around the metal is a distorted square pyramid with the chloride ion at the axial site; the pendant sulphur is not co-ordinated to the metal ion. The co-ordination geometry of [Mn(L)(CH₃OH)]BPh₄ is pseudo-octahedral, with a short Mn–O(methanol) bond [2.246(3)Å] and a long Mn–S bond [2.798(1)Å], The electronic spectrum in dichloromethane was characterized by an absorption near 27.3 × 10³ cm^–1, which was tentatively assigned to a charge-transfer transition from the co-ordinated sulphur to the manganese(III) ion.