Dinuclear complexes of MnII, CoII and ZnII triply bridged by carboxylate groups: structures, properties and catalase-like function‡

Abstract

1,3-Bis[(2-dimethylaminoethyl)iminomethyl]benzene (baib), having two isolated metal-binding sites separated by a m-xylenylene group, formed dinuclear metal(II) complexes [Mn₂(baib)(O₂CPh)₃]BPh₄·MeCN 1, [Mn₂(baib)(O₂CPh)₃(NCS)] 2, [Co₂(baib)(O₂CMe)₃]BPh₄ 3, [Co₂(baib)(O₂CPh)₃]BPh₄ 4 and [Zn₂(baib)(O₂CMe)₃]BPh₄ 5. The structure of a dimethylformamide adduct of 2, [Mn₂(baib)(O₂CPh)₃(NCS)]·dmf 2′, was determined. It has a dinuclear core bridged by two benzoate groups in the symmetric η¹:η¹ mode and one benzoate group in the asymmetric η¹:η² mode, with a Mn· · ·Mn separation of 3.501(4) Å. A thiocyanate ion co-ordinates to one Mn through its nitrogen; both manganese ions are six-co-ordinated. Complex 3 was also characterized crystallographically. The pair of cobalt ions are bridged by three acetate groups in the η¹:η¹ mode with a Co· · ·Co intermetallic separation of 3.449(2) Å. The geometry about each Co is a trigonal bipyramid. The complexes 4·MeCN (4′) and 5 have dinuclear cores essentially similar to that of 3: Co· · ·Co 3.482(2) and Zn· · ·Zn 3.4648(7) Å. The physicochemical properties of the complexes are reported together with the catalase-like function of 1–3.