Dinuclear chelates of acyclic and cyclic tridentate Schiff bases derived from sterically hindered o-aminophenols. A new type of reactivity of tridentate ligands under electrosynthesis conditions

Abstract

The chemical and electrochemical synthesis of cobalt(II), nickel(II), and copper(II) com plexes based on sterically hindered tridentate Schiff bases obtained by the coupling of 2 amino 4,6 di tert butylphenol with salicylaldehyde derivatives (H 2 L, H 2 L´) was performed. The re sulting dinuclear complexes were characterized by elemental analysis, IR spectroscopy, and magnetochemical measurements in the 300-2 K temperature range. The structures of the dinuclear nickel(II) and copper(II) complexes with the composition Ni 2 L 2 •2AcOH•2MeOH and Cu 2 L 2 , respectively, were established by X ray diffraction. The copper chelates are charac terized by the presence of antiferromagnetic exchange interactions. The mononuclear copper(II) complexes (DMSO)bis[2 (5,7 di tert butyl 4 hydroxybenzoxazol 2 yl)phenolato]copper(II) and (DMF) 2 bis[2 (5,7 di tert butyl 4 hydroxybenzoxazol 2 yl)phenolato]copper(II) were iso lated upon electrochemical dissolution of copper(0) and were structurally characterized.Tridentate Schiff bases prepared from various alde hydes (X = NTs, O, or S) and o substituted anilines (Y = NHR, O, or S), have attracted considerable inter est 1-20 because they can be used for the synthesis of metal complexes with different compositions and structures (Scheme 1).In addition, the possible use of complexes of tridentate Schiff bases derived from sterically hindered o amino phenols and their sulfur analogs in the catalysis, 21-23 the design of magnetic 24-27 and optical materials, 28,29 and the asymmetric synthesis 30 have been extensively in vestigated.The main aims of the present study were the synthesis of dinuclear cobalt(II), nickel(II), and copper(II) complex es of azomethines derived from sterically hindered o ami nophenol, investigation into their physicochemical prop