Vanadium C-scorpionate supported on mesoporous aptes-functionalized SBA-15 as catalyst for the peroxidative oxidation of benzyl alcohol

The neutral trichloro[hydrotris(1-pyrazolyl)methane]vanadium(III) [VCl3(Tpm)] (Tpm = HC(pz)(3); pz = pyrazolyl) C-scorpionate complex was immobilized on amine-functionalized mesoporous silica (aptesSBA-15) via an impregnation method forming the [VCl3(Tpm)]@aptesSBA-15 composite. The immobilization of the vanadium compound was confirmed by several characterization techniques, namely SEM/EDS, powder XRD, FT-IR/ATR, ICP and BET surface area analysis, revealing the successful incorporation of the complex, and confirming the structural and morphological preservation of the porous support and the vanadium complex. The vanadium composite was tested as heterogeneous catalyst for the peroxidative oxidation of benzyl alcohol under mild conditions and its catalytic performance was compared to that of the analogous homogeneous [VCl3(Tpm)] complex. The catalytic studies were extended to other substrates. The effect of various parameters, such as amount and type of oxidant, catalyst and additives, temperature and reaction time were investigated allowing to reach overall yields of ca. 60% and turnover numbers (TONs) up to ca. 7.6 x 10(3). The results obtained demonstrated the higher performance of the heterogeneous catalyst using much less [VCl3(Tpm)] complex under a solvent-free system. Furthermore, consecutive reaction cycles could be performed, showing its recycling capacity. Structural stability was also investigated, indicating the viability of the vanadium C-scorpionate composite as catalyst for other oxidative reactions with high industrial interest.