A substance containing ytterbium while performing a catalytic function is referred to as an ytterbium catalyst. Ytterbium is a soft silver-white metal that is one of the lanthanide elements. It is easily oxidized and is slowly corroded in the air. Ytterbium is mainly found in ionic rare earth ore, xenotime and black gold ore whose common valences are +2 and +3, and the valence of ytterbium in most ytterbium catalysts is +3.
Ytterbium catalysts have excellent catalytic properties and therefore have a wide range of applications in the field of organic catalysis and environmental protection.
- Mannich reaction: The Mannich reaction is an important type of organic reaction for the synthesis of nitrogenous compounds. The products of Mannich reaction are widely used not only in medicines, pesticides, dyes, coatings, explosives, etc., but also as important intermediates for the synthesis of physiologically active molecules in natural products. However, the conditions of the Mannich reaction are relatively strict and usually require the catalysis of a strong protonic acid. Some ytterbium compounds (such as ytterbium trichloride) have strong Lewis acidity and can be used as a catalyst for the Mannich reaction. For example, ytterbium trichloride with higher Lewis acidity as a Lewis acid type catalyst can catalyze the "one-pot" Mannich reaction of aromatic amines, aromatic aldehydes and cyclopentanone. In addition, the metal ytterbium can also be combined with a ligand to form a coordination compound. These coordination compounds also have Lewis acidity and can also be used as a catalyst for the Mannich reaction. Moreover, by changing the coordination environment, structure, activity, selectivity of the Lewis acid ytterbium catalyst, this kind of catalyst can be finely tuned to better catalyze the Mannich reaction.
Figure 1. Ytterbium catalyst-catalyzed Mannich reaction
- Biginelli-type condensation reaction: Dihydropyrimidinone and its derivatives are a class of compounds with important biological activities, and have wide applications in antiviral, antitumor, anti-inflammatory and bactericidal. The Biginelli-type condensation reaction is a common method for the synthesis of dihydropyrimidinone and its derivatives. The rare earth trichloride has a good catalytic effect on the Biginelli-type condensation reaction, and the ytterbium trichloride is often used as the Biginelli-type condensation reaction catalyst. For example, ytterbium trichloride can catalyze the Biginelli-type condensation reaction of benzaldehyde, urea, and cyclopentanone. Furthermore, under the catalysis of Yb(OTf)3, the aromatic aldehyde can undergo a Biginelli-type condensation reaction with a cyclic ketone to form an α,α'-disubstituted benzylmethylenecycloalkanone.
Figure 2. Ytterbium catalyst-catalyzed Biginelli-type condensation reaction
- Nitration reaction: Nitration reaction, especially the nitration reaction of aromatic hydrocarbons, has long been one of the most important and widely studied organic chemical reactions. Its product aromatic nitrates are widely used in the industrial production of pesticides, pharmaceuticals, dyes, chemical fiber and rubber. The lanthanum triflate metal salt has good catalytic activity for nitration reaction, among which Yb(OTf)3 has the best catalytic activity and can be used as a catalyst for nitration reaction. For example, Yb(OTf)3 can be used as a catalyst to catalyze the nitration of toluene.
Figure 3. Ytterbium catalyst-catalyzed nitration reaction
- Other reactions: In addition to the above reactions, ytterbium catalysts can catalyze many other types of organic reactions, including Friedel-Crafts acylation, benzylation and cyclohexylation of aromatic hydrocarbons, Knoevenagel reaction, Ene reaction, and the like. For example, Yb(OTf)3 can catalyze the acylation of aromatic hydrocarbons to form aryl ketones. Besides, under the catalysis of Yb(OTf)3, the active methylene compound and various aldehydes can undergo Knoevenagel reaction without any solvent, thereby producing the corresponding substituted olefin derivative.
- Environmental protection: Due to its high concentration, high toxicity and low level of biodegradation, pharmaceutical wastewater has become one of the most important sources of pollution in environmental waters. Advanced oxidation technology provides a practical way to deal with the treatment of wastewater. The ytterbium catalyst can not only complex the organic compounds in the wastewater, but also accelerate the decomposition of ozone to produce hydroxyl radicals with stronger oxidizing ability, thereby removing organic matter in the sewage. Therefore, ytterbium rhodium catalysts are often used in advanced oxidation techniques. For example, when using advanced oxidation technology to treat chemical pharmaceutical wastewater, the core-shell magnetic rare earth catalyst (Fe3O4@SiO2@Yb2O3) can be used to catalyze the degradation of the main pollutants benzotriazole and guaiacol.
- Imamura, Hayao. (2002), “Selective dimerization of ethene over lanthanide catalysts deposited from Eu or Yb metal solutions in liquid ammonia.” Chemistry Letters (2002), (7), 744-745.
- Imamura, Hayao. (1995), “Cyclization of ethyne and propyne over lanthanide catalysts deposited from Eu or Yb metal solutions in liquid ammonia.” Chemistry Letters (3), 215-16.
- Keim, Wilhelm (1991), “Rare earth catalysts in carbon-carbon linkage of olefins. I. Ytterbium catalyzed linear oligomerization of ethylene.” Catalysis Letters (1991), 10(3-4), 233-8.
※ Please kindly note that our services are for research use only.