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.

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► 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%.