Samarium is a chemical element with a chemical symbol of Sm and an atomic number of 62. It belongs to the lanthanide element and is preferentially present in nature in the form of trivalent strontium salts. It is quite stable in dry air and forms an oxide film on the surface in the humid air. It is soluble in acid and insoluble in water. It can be used as a neutron absorber, photovoltaic equipment and alloys. In addition, samarium compounds are also useful as catalysts for a large number of chemical reactions. The main samarium catalysts are samarium iodide and samarium oxide. They can be used in quite a number of different reactions, such as Michael, Diels-Alder and Michael-aldol reactions, methane coupling reactions and so on.
- Catalytic decomposition of NO: Some researchers have used the co-precipitation method to prepare different amounts of Sm-doped manganese-based catalysts with manganese acetate as precursors, and studied the effect of Sm-doped catalysts on NO catalytic conversion ability. The results show that the structure and morphology of manganese oxide are changed due to the embedding of the samarium. The trivalent samarium replaces the tetravalent manganese, and due to the charge compensation, an anion vacancy is formed in the catalyst, causing defects. The increase in surface defects increases the active site and promotes the progress of the catalytic reaction.
- Catalytic synthesis of dibutyl oxalate: Some researchers have used microwave irradiation technology to synthesize dibutyl oxalate with nano-oxidized samarium as an esterification catalyst. The effects of microwave radiation power, microwave irradiation time, catalyst dosage and the molar ratio of alkyd on esterification reaction were investigated. The results show that the nano-oxidized samarium catalyst shows good catalytic performance in the synthesis of dibutyl oxalate. Moreover, the method has the advantages of simple operation, fast reaction rate and energy saving.
- Catalytic epoxide rearrangement reaction: SmI2 can effectively convert the terminal epoxide to methyl ketone when studying the deoxidation of epoxide by diiodinated samarium.
Figure 1. SmI2 catalytic epoxide rearrangement reaction.
- Catalytic epoxide ring opening reaction: SmI2 can catalyze the ring opening reaction of different nucleophiles to epoxide at room temperature. The yield of the product ranges from medium to high, and the reaction shows different regioselectivity depending on the nucleophile. For example, in the ring opening reaction of trimethylsilyl azide to epoxy styrene, the nucleophile selectively attacks the larger side of the ternary oxygen ring steric hindrance, the ratio of the product 1 and the product 2 is 10:90. When the nucleophilic reagent is trimethylsilyl, the probability of attack of nucleophiles from different sides of the oxygen ring is relatively close, the selectivity of the reaction is decreased, and the product 1 is still a dominant product.
Figure 2. SmI2 catalytic epoxide ring opening reaction.
- Catalytic photocatalytic reaction: TiO2 photocatalysts with different Sm doping amount by sol-gel method and applied them to the degradation experiment of methylene blue. The results show that when the calcination temperature is 500 °C, the Sm3+ doping amount is 1.2%, and the catalyst dosage is 1.5 g/L, the catalytic performance is the best.
- Prand, J, Menoret, G., Kagan, H. B.(1985). “Selective catalyzed-rearrangement of terminal epoxides to methyl ketones”. J Organomet.Chem. 285,449.
- Van de Weghe, P. Collin. (1995). “Ring opening reactions of epoxides catalyzed by samarium iodides”. Tetrahedron Lett .36,1649.
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