Mn(III) based binapthyl Schiff base complex hetrogenized over organo-modified SBA-15: Synthesis, characterization and catalytic application
A heterogenized organocatalyst was synthesized by the covalent anchoring of the complex chloro (S,S)(−)[N-3-tert-butyl-5-chloromethyl salicylidene]-N′-[3′,5′-di-tert-butyl salicylidene] 1,1′-binapthyl-2,2′-diamine manganese(III) over modified mesoporous surface of SBA-15 through the reactive 3-aminopropyl trimethoxysilane (3-APTMS) group. The surface properties of the functionalized catalyst were analyzed by a series of characterization techniques such as elemental analysis, XRD, N2 sorption measurement isotherm, FT-IR, TGA–DTA, XPS, and solid state 13C NMR. The XRD and N2 sorption measurement, UV reflectance and CP MAS NMR spectroscopy (13C and 29Si) of the catalyst confirmed the structural integrity of the mesoporous hosts and the spectroscopic characterization technique proved the successful anchoring of the metal complex over the modified mesoporous support. The screening of the catalyst Mn(III)-L-SBA-15 and neat Mn(III)-L complexes was done in the oxidation reaction of thioanisole (methyl phenyl sulfide) by using TBHP as an oxidant. Mn(III)-L-SBA-15 catalyst shows higher activities and turnover number (TON) and exhibit enhanced enantiomeric excess comparable to homogeneous catalyst [Mn(III)-L]. [Mn(III)-L-SBA-15] catalyst was found more active than homogeneous catalyst [Mn(III)-L]; Moreover bulkier alkene like 1,2-dihydronapthalene was also efficiently epoxidised with the synthesized supported catalyst.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (177 K)Download as PowerPoint slideHighlight► The synthesis of mesoporous SBA-15 was carried out hydrothermally under the autogeneous pressure in an autoclave. ► Surface modification of SBA-15 was achieved by a post synthesis grafting method. ► Neat Mn(III)-L complex and Mn(III)-L-SBA-15 were applied for sulfoxidation of thioanisole.
Journal: Applied Catalysis A: General - Volumes 439–440, 10 October 2012, Pages 101–110