Fe (III) complexes of a bis-benzimidazolyl diamide ligand: Spectral and Catalytic studies

A new tetradentate bis benzimidaozlyl diamide ligand N,N′-Bis (benzimidazol-2-yl-methyl)-hexane-1,6-dicarboxamide (GBSA) has been synthesized and utilized to prepare new Fe(III) complexes with exogenous anionic ligand X = Cl− and NO3−. Isomer shift values are in the range found for Iron in the +3 oxidation state while Quadrupole Splitting indicates large distortion from a six coordinate geometry, a finding supported by low temperature EPR work. The E1/2 values are found to be quite cathodic indicating stability of the Iron (III) complexes. The oxidation of alcohols was investigated using [Fe(GBSA)Cl3] as the catalyst with TBHP as an alternate source of oxygen. The respective carbonyl products have been isolated and characterized by 1H NMR, electronic spectroscopy, mass and IR spectral studies.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Tetradentate ligand N,N′-Bis (benzimidazol-2-yl-methyl)-hexane-1,6dicarboxamide is synthesized. ► Iron (III) complexes of the above ligand have been characterized by EPR and Mössbauer spectroscopy. ► The complexes are axially distorted and larger the distortion, more anodic the E1/2. ► Catalytic Oxidation of alcohols using [Fe(GBSA)Cl3] and TBHP has been carried out. ► The catalytic activity has been found to be in the range of 37–45%.