C–H bond activation over chitosan based Fe(III) and Ni(II) catalysts

Abstract

Chitosan (Cs) supported heterogeneous catalysts of Fe(III) and Ni(II) is developed by the equimolar reaction of two schiff base ligands, L₁ [Cs-HACP] and L₂ [ANI-HACP] and Metal salts {where Metal = Fe(III) and Ni(II)}with chitosan. The L₁ ligand is prepared by the reaction of chitosan (Cs) and ortho hydroxyl (HACP) acetophenone in methanol and L₂ ligand is prepared by the condensation of aniline (ANI) and ortho hydroxyl acetophenone (HACP) in solvent free condition. The prepared catalysts {M-[Cs-L₁-L₂]Cl₂} are characterized by different analytical techniques viz. scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman, UV-VIS-NIR, X-ray photoelectron spectroscopy (XPS) and computational studies. The catalytic behavior of newly synthesized catalysts are tested for the C–H activation using 70 % tert-butyl hydroperoxide (TBHP). The best results are obtained for tetralin oxidation. The order of catalytic reactivity of {M-[Cs-L₁-L₂]Cl₂}catalyst is in decreasing order: {Fe(III)-[Cs-L₁-L₂]Cl₂} > {Ni(II)-[Cs-L₁-L₂]Cl₂}. The {Fe(III)-[Cs-L₁-L₂]Cl₂} gives maximum conversion 81.99 % of tetralin with 84.50 % selectivity of tetralone (T-lone) and 6.47 % selectivity of tetralol (T-lol) after 5 h of reaction at 80 °C temperature. The chitosan based heterogeneous catalyst is easy to separate and recover. It can be recycled seven times.