Nanoparticle Supported, Magnetically Recoverable Oxodiperoxo Molybdenum Complexes: Efficient Catalysts for Selective Epoxidation Reactions

Heterogenous Epoxidation of Isobutene Selectively Enabled by MoSe2 in Hexafluoroisopropanol (HFIP)

Herein, a high selective epoxidation of isobutene was achieved by heterogeneously dispersed MoSe2 with tert-butyl hydroperoxide (TBHP), which further showed versatile substrate scopes and well-retained activity among recycling tests. A rational mechanism is proposed based on extensive control experiments and electron paramagnetic resonance spectroscopy, surprisingly unveiling the metal-oxo and radical mediated pathways dramatically accelerated by hydrogen bonds of hexafluoroisopropanol (HFIP).

Excellent Pd-Loaded Magnetic Nanocatalyst on Multicarboxyl and Boronic Acid Biligands

An effective palladium nanocatalyst (Fe3O4@SiO2-FPBA-DTPA-Pd) was proposed and prepared, which was immobilized on magnetic silica with ethylenediamine pentaacetic acid and formylphenylboronic acid as biligands. A series of characterizations showed that Fe3O4@SiO2-FPBA-DTPA-Pd was 5-15 nm and contained 1.44 mmol/g Pd2+/Pd0. It was stable below 232.7 °C, and its saturation magnetization value was 21.17 emu/g which was easily recycled by a magnet. Its catalytic ability was evaluated through 7 Suzuki reactions and 15 Heck reactions. Results showed that the yields of 14 reactions catalyzed by Fe3O4@SiO2-FPBA-DTPA-Pd were more than 90%, while were better than those of the other two immobilized Pd catalysts on a single diethyltriamine pentaacetic acid (DTPA) group or boronic acid group. Moreover, Fe3O4@SiO2-FPBA-DTPA-Pd showed good reusability in both Suzuki and Heck reactions. In two model Suzuki and Heck reactions, after seven cycles, its yields were still above 95% without significant loss, which exceeded those of many reported catalysts; therefore, it has great potential in future large-scale industrial production.

Selective and Efficient Olefin Epoxidation by Robust Magnetic Mo Nanocatalysts

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.

Heterogeneous catalysis with an organic–inorganic hybrid based on MoO3 chains decorated with 2,2′-biimidazole ligands

Polymeric [MoO₃(2,2′-biimidazole)]·H₂O outperforms other one-dimensional MoO₃-ligand hybrid materials as a heterogeneous and recyclable catalyst for (bio)olefin epoxidation and sulfoxidation.

Ionic Liquids Based on Oxidoperoxido-Molybdenum(VI) Complexes with a Chelating Picolinate Ligand for Catalytic Epoxidation

Ionic oxidoperoxido-molybdenum(VI) complexes of the type [Cat][MoO(O2)2(pic)], with pic = N,O-chelated picolinate ligand and Cat = monocation, were prepared in high yields (82–95%) from the precursor complex [H3O][MoO(O2)2(pic)] via [H]+ cation exchange for 1-ethyl-3-methylimidazolium [EMIM]+, 1-butyl-3-methylimidazolium [BMIM]+, 1-octyl-3-methylimidazolium [OMIM]+, N-cetylpyridinium [C16Py]+, and N-methyl-N,N,N-trioctylammonium [Aliquat]+. The structure and purity of the ionic compounds were assessed by 1H and 13C NMR, FT-IR, and elemental analysis (C, H, N), and the electrochemical properties were studied by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The [Cat][MoO(O2)2(pic)] compounds showed promising catalytic epoxidation activity based on the model reaction of cis-cyclooctene with tert-butyl hydroperoxide as oxidant. The type of cation influenced the physical state of the compound and the catalytic performance.

Selective Catalytic Oxidation of Benzyl Alcohol by MoO2 Nanoparticles

Selective oxidation of benzyl alcohol to benzaldehyde was carried out with MoO2 nanoparticles (MoO2 NPs). MoO2 NPs were synthesized by two different approaches and characterized by several techniques. The synthesis was done by a hydrothermal procedure using ethylenediamine and either Fe2O3 or hydroquinone. In the latter case, an additional calcination step under N2 was performed to eliminate passivating agents at the surface of the nanoparticles. The synthesized nanocatalysts showed similar catalytic properties, being efficient catalysts in the oxidation of benzyl alcohol. High substrate conversion and product selectivity were achieved under all tested conditions. Studies were conducted using two different oxidants: tert-butyl hydroperoxide and hydrogen peroxide, in our continuous effort to obtain more efficient catalysts for more sustainable catalytic processes. When H2O2 was used as the oxidant, 94% yield was achieved with 100% selectivity for benzaldehyde, which was a very promising result to undergo other studies with this system. Moreover, to elucidate some aspects of the reaction mechanism, a study was conducted, and it was possible to conclude that the reaction undergoes, to some extent, through a radical mechanism with both oxidants.

Catalytic epoxidation of olefins in liquid phase over manganese based magnetic nanoparticles

Epoxidation of olefins stands out as a crucial class of reactions and is of great interest in academic research and industry due to the production of various important fine chemicals and intermediates. Manganese complexes have the potential to catalyze the epoxidation of olefins with high efficiency. Magnetic nanocatalysts have attracted significant attention for immobilizing homogeneous transition metal complexes. Easy separation by external magnetic fields, nontoxicity, and a core shell structure are the main advantages of magnetic nanocatalysts over other heterogeneous catalysts. The method of functionalizing magnetic nanoparticles and of anchoring homogeneous metal complexes has significant effects on catalytic performance. Therefore, a critical review of recent research progress on manganese complexes' immobilization on magnetic nanoparticles for liquid phase olefin epoxidation is necessary. In this work, magnetic nanoparticles are categorized according to their preparation procedures and structures. The physical/chemical properties, catalytic performance for olefin epoxidation, reusability and plausible reaction mechanisms will be discussed, in an attempt to unravel the structure-function relationship and to guide the future study of MNPs' design for olefin epoxidations.

Recent Advances in Facile Liquid Phase Epoxidation of Light Olefins over Heterogeneous Molybdenum Catalysts

Molybdenum complexes are versatile and efficient for liquid phase olefin epoxidation reactions. Rational design of catalysts is critical to achieve high atom efficiency during epoxidation processes. Although liquid phase epoxidation has been a popular topic for decades, three key issues, (a) rational control of morphology of molybdenum nanoparticles, (b) manipulating metal-support interaction and (c) altering electronic configuration at molybdenum center remains unsolved in this area. Therefore, in this paper, we have critically revised recent research progress on heterogeneous molybdenum catalysts for facile liquid phase olefin epoxidation in terms of catalyst synthesis, surface characterization, catalytic performance and structure-function relationship. Furthermore, plausible reaction mechanisms will be systematically discussed with the aim to provide insights into fundamental understanding on novel epoxidation chemistry.

MoO2 Formed on Mesoporous Graphene Oxide: Efficient and Stable Catalyst for Epoxidation of Olefins

A novel mesoporous MoO2 composite supported on graphene oxide (m-MoO2/GO) has been designed and applied as an efficient epoxidation catalyst. The m-MoO2/GO composite was characterised by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmet–Teller surface area analysis, field emission scanning electron microscopy, and transmission electron microscopy. Compared with pure mesoporous MoO2 (m-MoO2) and amorphous MoO2-graphene oxide (a-MoO2/GO), m-MoO2/GO exhibits the best catalytic activity. The conversion and selectivity for cyclooctene are both over 99 % in 6 h. Remarkably, the mesoporous structure in m-MoO2/GO which derives from SiO2 nanospheres endows the catalyst better catalytic performance for long chain olefins: the conversion of methyl oleate can be as high as 82 %. Such a robust catalyst can be easily recycled and reused five times without significant loss of catalytic activity. This novel catalyst is promising in the synthesis of epoxides with a long carbon chain or large ring size.

Development of the catalytic reactivity of an oxo–peroxo Mo(vi) Schiff base complex supported on supermagnetic nanoparticles as a reusable green nanocatalyst for selective epoxidation of olefins

A novel ancillary branch coated oxo–peroxo Mo(vi)tetradentate Schiff base complex on superparamagnetic nanoparticles as an epoxidation catalyst.

Immobilization of a molybdenum complex on the surface of magnetic nanoparticles for the catalytic epoxidation of olefins

A molybdenum complex was immobilized on Fe₃O₄ nanoparticles modified with chloropropyl by two routes and used as a nanocatalyst for the oxidation of alkenes.

Multifunctional Au-Fe3O4@MOF core-shell nanocomposite catalysts with controllable reactivity and magnetic recyclability

The recovery and reuse of expensive catalysts are important in both heterogeneous and homogeneous catalysis due to economic and environmental reasons. This work reports a novel multifunctional magnetic core-shell gold catalyst which can be easily prepared and shows remarkable catalytic properties in the reduction of 4-nitrophenol. The novel Au-Fe3O4@metal-organic framework (MOF) catalyst consists of a superparamagnetic Au-Fe3O4 core and a porous MOF shell with controllable thickness. Small Au nanoparticles (NPs) of 3-5 nm are mainly sandwiched between the Fe3O4 core and the porous MOF shell. Catalytic studies show that the core-shell structured Au-Fe3O4@MOF catalyst has a much higher catalytic activity than other reported Au-based catalysts toward the reduction of 4-nitrophenol. Moreover, this catalyst can be easily recycled due to the presence of the superparamagnetic core. Therefore, compared to conventional catalysts used in the reduction of 4-nitrophenol, this porous MOF-based magnetic catalyst is green, cheap and promising for industrial applications.

Magnetic nanoparticle-supported imidazole tribromide: a green, mild, recyclable and metal-free catalyst for the oxidation of sulfides to sulfoxides in the presence of aqueous hydrogen peroxide

Imidazole tribromide immobilized on magnetic nanoparticles as a bromine source was prepared and characterized by XRD, TGA, FT-IR, EDS, scanning and transmission electron microscopy, and vibrating sample magnetometer techniques.

Mo(vi) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalysts for selective oxidation of sulfides to sulfoxides

A molybdenum complex was immobilized on amino propyl and Schiff base modified magnetic nanoparticles by covalent linkage. In catalytic oxidation of sulfides, the catalysts showed similar catalytic activity but different stability and recyclability.

1-Methyl-3-(propyl-3-sulfonic acid)imidazolium triflate supported on magnetic nanoparticles: an efficient and reusable catalyst for synthesis of mono- and bis-isobenzofuran-1(3H)-ones under solvent-free conditions

An efficient procedure for the synthesis of isobenzofuran-1(3H)-one derivatives in the presence of [HSO₃PMIM]OTf–SiO₂@MNPs as a highly recyclable catalyst under solvent-free thermal conditions and MW irradiation is reported.

Enhanced catalytic activity of nanoporous Cu3(BTC)2 metal–organic framework via immobilization of oxodiperoxo molybdenum complex

A new bimetallic heterogeneous epoxidation catalyst was prepared through chemical modification of Cu₃(BTC)₂ metal–organic framework.

Efficient magnetic and recyclable SBILC (supported basic ionic liquid catalyst)-based heterogeneous organocatalysts for the asymmetric epoxidation of trans-methylcinnamate

A green heterogeneous catalytic alternative was developed for the asymmetric epoxidation of trans-methylcinnamate to (2R,3S)-phenyl glycidate.

Excellent catalytic activity of magnetically recoverable Fe3O4–graphene oxide nanocomposites prepared by a simple method

An easy-to-prepare Fe₃O₄–graphene oxide nanocomposite which works well as a reusable catalyst for A³-coupling reactions.

Immobilization of phosphomolybdic acid nanoparticles on imidazole functionalized Fe3O4@SiO2: a novel and reusable nanocatalyst for one-pot synthesis of Biginelli-type 3,4-dihydro-pyrimidine-2-(1H)-ones/thiones under solvent-free conditions

Fe₃O₄@SiO₂-imid-PMAⁿ: a novel and reusable nanocatalysts.

An immobilised Co(ii) and Ni(ii) Schiff base magnetic nanocatalyst via a click reaction: a greener approach for alcohol oxidation

A Schiff base immobilised magnetic nanocatalyst synthesized via copper catalysed alkyne azide cycloaddition (CuAAC) exhibited a strong interaction and improved yielding for oxidation of alcohols in a solventless system.