Structures and properties of di-μ-oxo dimanganese(IV) complexes with bidentate Schiff bases, N-alkyl-substituted-salicylideneamine

Abstract

Novel di-μ-oxo dimanganese(IV) complexes, [MnIV(N–R–X-sal)2(μ-O)]2, with bidentate Schiff base ligands, N-alkyl-substituted-salicylideneamine, N–R–X-salH [R=CH3 (Me), C2H5 (Et), n-C3H7 (Pr), n-C4H9 (Bu), n-C6H13 (Hx), n-C8H17 (Oct), n-C10H21 (Dec), n-C12H25 (Dod), or n-C18H37 (Octd) and X=H or 5,6-benzo], have been prepared by their reaction with potassium permanganate (KMnO4) in MeCN, while stirring at room temperature. These complexes were characterized by spectroscopy, magnetic susceptibility, thermal analysis and X-ray crystallography. The structures consist of a MnIV2(μ-O)2 core with a Mn–Mn separation of 2.731(4) Å for [MnIV(N–Me-sal)2(μ-O)]2, 1, 2.769(2) Å for [MnIV(N-Et-sal)2(μ-O)]2, 2, 2.780(2) Å for [MnIV(N–Hx-sal)2(μ-O)]2, 5, 2.780(2) Å for MnIV(N-Dec-sal)2(μ-O)]2, 7, and 2.756(3) Å for [MnIV(N–Me-5,6-benzo-sal)2(μ-O)]2, 10. The complex 1 is the first di-μ-oxo dimanganese(IV) complex having asymmetrical form in which two manganese ions adopt different configurations each other. Moreover, the complexes 5 and 7 are found to exhibit the longest one among all of the Mn–Mn separation observed for the structurally characterized Mn2(μ-O)2 complexes prior to this work. The antiferromagnetic exchange interaction has been found to be J=−83 and −188 cm−1 for 1 and 7, respectively.