TWO BINUCLEAR MANGANESE(III) COMPLEXES CONTAINING BRIDGING KETONIC OXYGEN ATOM. Shi-Xiong Liu* and Yun-Long Feng, Department of Chemistry, Fuzhou University, Fuzhou, Fujian 350002, China
Two binuclear manganese(III) complexes containing bridging ketonic oxygen atom have been characterized by X-ray crystallography. They are [Mn2(bzacen)2(MeOH)2](ClO4)2 (1) and [Mn2(bzacen)2(MeOH)2] (ClO4)2*2H2O (2), where bzacen2- is N,N'-ethylenebis(1-phenyl-3-imino-1-butanonato). These Schiff base compounds crystallize in Space group P 21/n for (1) and P bca for (2). Coordination geometry around Mn atoms in these two complexes is a distorted octahedron with an equatorial plane N2O2 from the bzacen2- , while the axial sites are occupied by two oxygen atoms of methanol molecules. The very strong axial elongation has unusually found in a few complexes, for example, Mn-O(axial) bond being 2.493 Å in (1) and 2.448(8) Å in (2). The [Mn2(bzacen)2(MeOH)2]2+ cation in these complexes is a centrosymmetric dimer in which two Mn(III) atoms are joined by two ketonic oxygen atoms (Mn-O: 1.908 and 2.448Å for (1); 1.910 and 2.493Å for (2)). Therefore, Mn2O2 cores in the dimers being a parallelogram with Mn...Mn separation (3.387Å for (1) and 3.355Å for (2)) and Mn-O-Mn angles (99.7deg. for (1) and 100.0deg. for (2)). It was reported in Mn Schiff base complexes that the bridging oxygen atoms were from the u2-O2- anion, u2-phenoxy, and u2-alkoxo. To our knowledge, the two structures are the first structure containing bridging ketonic oxygen atom in Mn Schiff base complexes.