Tetra- and pentamanganese(II) macrocyclic complexes with bridging carboxylate groups: product control by pretreatment of manganese acetate solutions

Abstract

Transmetallation of [Ba(H 2L)(H 2O) 2](ClO 4) 2 with manganese(II) acetate tetrahydrate in methanol can yield either the pentamanganese(II) complex [Mn 5(L) 2(CH 3OO) 2(ClO 4) 2](ClO 4) 2 ( 1) or the tetramanganese(II) complex [Mn 2(L)(CH 3OO)] 2(ClO 4) 2 ( 2), where H 2L is a macrocyclic ligand formed by a [2 + 2] condensation of 2,6-diacetylpyridine and 1,3-diaminopropan-2-ol. Both complexes have been characterized by X-ray crystallography; 1·2H 2O, monoclinic, P2 1 c a = 13.032(4), b = 20.677(5), c = 14.113(5) A ̊ , β = 108.13(2)° ; 2·5H 2O·2dmf (dmf = N,N-dimethylformamide), monoclinic, C2/c, a = 32.026(7), b = 14.623(6), c = 16.464(5) A ̊ , β = 118.11(2)° . Once formed, the complexes are stable in solution and are not interconvertible. The identity of the complex formed depends on the treatment of the methanolic manganese(II) acetate solution before addition to the barium complex but not on the conditions of the transmetallation reaction. Transmetallation reactions using manganese(II) formate yielded only the tetramanganese complex [Mn 2(L)(HCOO)] 2(ClO 4) 2 ( 3), this was also characterized crystallographically; 3·H 2O·2dmf, monoclinic, C2/c, a = 27.057(8), b = 14.793(5), c = 16.126(4) A ̊ , β = 97.56(2)° . Both the tetramanganese(II) complexes 2 and 3 contain Mn 4(alkoxide) 4 cubane cores.