Mn(III)‐salan/graphene oxide/magnetite nanocomposite as a highly selective catalyst for aerobic epoxidation of olefins

Abstract

A nanocomposite was synthesized using carbon-coated Fe 3 O 4 nanoparticle-decorated reduced graphene oxide as a convenient and efficient supporting material for grafting of a manganese-reduced Schiff base (salan) complex via covalent attachment. The nanocomposite was characterized using X-ray diffraction, Fourier transform infrared and diffuse reflectance UV-visible spectroscopies, inductively coupled plasma atomic emission spectrometry and scanning electron microscopy. It was evaluated as a catalyst for the aerobic epoxidation of olefins in acetonitrile in combination with a sacrificial co-reductant (isobutyraldehyde). The catalytic performance of the heterogeneous system of the Mn-salan complex is superior to that of the homogeneous one. The catalyst activity strongly depends on the reaction temperature and nature of the solvent. The epoxide yield increases with the nucleophilic character of the olefin. The nanocomposite performs well as an epoxidation catalyst for electron-rich and conjugated olefins. It can be recovered from the reaction medium by magnetic decantation and reused, maintaining good catalytic activity.

Hydrophobic and Superhydrophobic Bio-Based Nano-Magnetic Epoxy Composites as Organic Coating of Steel

“…The rough spherical surfaces of both HPHI ( Figure 4b) and DCHI (Figure 4c) confirm the higher capability of DCHI to embed more magnetite inside the sphere or on their surfaces more than HPHI [34]. This was attributed to greater pi interactions of olefinic and phenyl groups of DCHI ( Figure 4c) with magnetite NPs [35]. HR-TEM micrographs of HPHI-Fe 3 O 4 ( Figure 5a) and DCHI-Fe 3 O 4 (Figure 5b) confirm that the magnetite NPs were dispersed inside spherical morphologies.…”

Recent Advancements in Graphene‐Based Supports of Metal Complexes/Oxides for Epoxidation of Alkenes

“…The catalytic activity and yield of epoxides on the nanocomposite catalyst under the optimized conditions was investigated . There was no distinct effect of the steric properties on the reactivity of the olefins.…”

“…There was no distinct effect of the steric properties on the reactivity of the olefins. The epoxide yield is enhanced with increasing nucleophilicity of the olefin . We studied the epoxidation of various substrates over various kinds of catalysts (VO IV T, VO IV G, MoO 2 VI T, and MoO 2 VI G), and found that the conversion of different substrates followed the order geraniol>cyclooctene>styrene>1‐octene, which was related to electron density and hindrance effects.…”

“…Hosseini‐Monfared et al. reported a possible mechanism for olefin epoxidation on a supported manganese catalyst . The Mn–salen‐mediated epoxidation of olefins with O 2 / i PrCHO proceeds via an acylperoxo–Mn complex .…”

Epoxidation of cyclohexene with H2O2 over efficient water‐tolerant heterogeneous catalysts composed of mono‐substituted phosphotungstic acid on co‐functionalized SBA‐15

“…Nevertheless, two major side reactions, allylic oxidation and epoxide ring‐opening, can considerably occur in epoxidation of cyclohexene, resulting in cyclohexene epoxidation to epoxide becoming difficult . Great efforts have been made in the development of new active and selective catalysts for cyclohexene/olefins epoxidation to circumvent the above‐mentioned side reactions and facilitate the formation of the desired product …”