Bridged (alkoxo)CoIII(salen) complexes: synthesis and structure
摘要:
The preparation and oxygenation of Co-II(salen) complexes 2a-d whose ethanediyl moieties carry an omega-hydroxyalkyl pendant arm is reported. Air oxidation of 2a gives bridged (alkoxo)Co-III(salen) complex la with a planar salen ligand. Upon aeration of 2b in MeOH, monomeric bridged complex 1b with a planar salen ligand precipitates, whereas in CH,Cl, a dimeric bridged complex 1b' with twisted-salen ligands is obtained and characterized by X-ray crystallography. Formation of a bridged (alkoxo)Coll(salen) complex upon aeration of 2c is probably followed by beta-elimination. The tert-butyl substituted oxidation product of 2d is paramagnetic in non-coordinating and diamagnetic in coordinating solvents, supporting the concept that the salen moiety of (alkoxo)Co-III(salen) complexes can have either a planar or a twisted geometry depending on the solvent and the solid state properties. (C) 2002 Elsevier Science B.V. All rights reserved.