Selective and Efficient Olefin Epoxidation by Robust Magnetic Mo Nanocatalysts

Abstract

Iron oxide magnetic nanoparticles were synthesized with different sizes (11 and 30 nm). Subsequently they were shelled with a silica layer allowing grafting of an organic phosphine ligand that coordinated to the [MoI2(CO)3] organometallic core. The silica layer was prepared by the Stöber method using either mechanical (both 11 and 30 nm nanoparticles) or ultrasound (30 nm only) stirring. The latter nanoparticles once coated with silica were obtained with less aggregation, which was beneficial for the final material holding the organometallic moiety. The Mo loadings were found to be 0.20, 0.18, and 0.34 mmolMo·g−1 for MNP30-Si-phos-Mo,MNP11-Si-phos-Mo, and MNP30-Sius-phos-Mo, respectively, with the ligand-to-metal ratio reaching 4.6, 4.8, and 3.2, by the same order, confirming coordination of the Mo moieties to two phos ligands. Structural characterization obtained from powder X-ray diffraction (XRD), scanning electron microscopy (SEM)/ transmission electron microscopy (TEM) analysis, and Fourier-transform infrared (FTIR) spectroscopy data confirmed the successful synthesis of all nanomaterials. Olefin epoxidation of several substrates catalyzed by these organometallic nano-hybrid materials using tert-butyl hydroperoxide (tbhp) as oxidant, achieved very good results. Extensive testing of the catalysts showed that they are highly active, selective, recyclable, and efficient concerning oxidant consumption.

Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

“…Beyond that, research also devotes effort to determining the most suitable oxygen source (ideally dioxygen, but also organic peroxides or hydrogen peroxide), physical conditions (pressure and temperature), and the solvent [14][15][16][17]. Solvent choice is usually screened in terms of striking a balance between activity and selectivity, with the ultimate choice being made, eventually, from a sustainability point of view [18,19]. Across research on the development of efficient systems for the catalytic oxidation of olefins (Scheme 1 showing possible oxidation products), several physical parameters are usually tuned.…”

Synthesis, thermal evolution and magnetic investigations of SBA-15 silica functionalized with anchored iron phosphonate molecules

“…From many variable nanostructures, the greatest advantage is the gaining of nanoparticles, whose remediation-related capabilities include their small size (1-100 nm), providing features that cannot be achieved by bulk materials. Enormous large surface areas and high surface reactivity, in combination with magnetic and strong catalytic properties typically observed for iron or iron oxides, [2][3][4][5][6][7] can be considered effective reductants and catalysts for the transformation of such environmental contaminants as chlorinated organic compounds as well as anions (for example, NO 3 − , Cr 3 O 3 2− ), heavy metals (for example, Ni 2+ , Hg 2+ ), radionuclides (for example, UO 2 2+ ) and metal ions [8][9][10]. Magnetic properties ensure the immobilization of metals on the nanoparticles' surface, including Cr, Hg, As [11].…”

Substrate-Solvent Crosstalk – Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

“…Beyond that, research also devotes effort to find the most suitable oxygen source (ideally dioxygen, but also organic peroxides or hydrogen peroxide), physical conditions (pressure and temperature) and the solvent [14][15][16][17]. Solvent choice is usually screened in terms of finding a sweet spot in the activity/selectivity balance, with the ultimate choice being made, eventually, from a sustainability point of view [18,19]. However, little attention has been devoted to assessing what specific phenomena rule the differences observed in a given process when the solvent is changed.…”