4853-56-9Relevant articles and documents
Nelson et al.
, p. 399 (1968)
Synthesis, Characterization, and Photocatalytic Application of Type-II CdS/Bi2W2O9 Heterojunction Nanomaterials towards Aerobic Oxidation of Amines to Imines
Bhoi, Yagna Prakash,Mishra, Braja G.
, p. 2648 - 2658 (2018)
A series of new type-II CdS/Bi2W2O9 heterojunction nanomaterials is prepared by a two stage process. Initially, phase-pure Bi2W2O9, with orthorhombic crystalline structure, is prepared by a facile combustion-synthesis route. The combustion-synthesized Bi2W2O9 is subsequently modified by CdS nanoparticles using a hydrothermal route. The CdS/Bi2W2O9 heterojunctions are characterized using XRD, XPS, FTIR spectroscopy, UV/Vis DRS, PL, and FESEM and HRTEM studies. The occurrence of ultrafine CdS nanoparticles, with diameters of 8–15 nm, well-dispersed over BWO plates, is inferred from microscopic characterization studies. The two crystalline phases exhibit microscopic close contact across grain boundaries, facilitating the transfer of excitons. The heterojunction materials exhibit improved visible-light absorption, enhanced charge-carrier separation, and suitable band-alignment characteristics of a type-II heterojunction. The CdS/Bi2W2O9 heterojunctions are evaluated as visible-light-active photocatalysts for the aerobic oxidation of amines to imines. Structurally and functionally diverse amine molecules are oxidized to the corresponding imines, with excellent selectivity, in a short span of time.
Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant
Li, Rong-Jian,Ling, Chun,Lv, Wen-Rui,Deng, Wei,Yao, Zi-Jian
, p. 5153 - 5162 (2021/05/04)
Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.
Site-specific catalytic activities to facilitate solvent-free aerobic oxidation of cyclohexylamine to cyclohexanone oxime over highly efficient Nb-modified SBA-15 catalysts
Ding, Wei,Mao, Liqiu,Peng, Haoyu,Yin, Dulin,Zhong, Wenzhou
, p. 3409 - 3422 (2020/06/09)
The development of highly active and selective heterogeneous catalysts for efficient oxidation of cyclohexylamine to cyclohexanone oxime is a challenge associated with the highly sensitive nitrogen center of cyclohexylamine. In this work, dispersed Nb oxide supported on SBA-15 catalysts are disclosed to efficiently catalyze the selective oxidation of cyclohexylamine with high conversion (>75%) and selectivity (>84%) to cyclohexanone oxime by O2without any addition of solvent (TOF = 469.8 h?1, based on the molar amount of Nb sites). The role of the active-site structure identity in dictating the site-specific catalytic activities is probed with the help of different reaction and control conditions and multiple spectroscopy methods. Complementary to the experimental results, further poisoning tests (with KSCN or dehydroxylation reagents) and DFT computational studies clearly unveil that the surface exposed active centers toward activation of the reactants are quite different: the surface -OH groups can catch the NH2group from cyclohexylamine by forming a hydrogen bond and lead to a more facile cyclohexylamine oxidation to desired products, while the monomeric or oligomeric Nb sites with a highly distorted structure play a key role in the dissociation of O2molecules beneficial for insertion of active oxygen species into cyclohexylamine. These catalysts exhibit not only satisfactory recyclability for cyclohexylamine oxidation but also efficiently catalyze the aerobic oxidation of a wide range of amines under solvent-free conditions.
Air-Stable Half-Sandwich Iridium Complexes as Aerobic Oxidation Catalysts for Imine Synthesis
Deng, Wei,Fan, Xiao-Nan,Ou, Hui-Dan,Yao, Zi-Jian
supporting information, (2020/04/02)
Several N,O-coordinate half-sandwich iridium complexes, 1-5, containing constrained bulky β-enaminoketonato ligands were prepared and clearly characterized. Single-crystal X-ray diffraction characterization of these complexes indicates that the iridium center adopts a distorted octahedral geometry. Complexes 1-5 showed good catalytic efficiency in the oxidative homocoupling of primary amines, dehydrogenation of secondary amines, and the oxidative cross-coupling of amines and alcohols, which furnished various types of imines in good yields and high selectivities using O2 as an oxidant under mild conditions. No distinctive substituent effects of the iridium catalysts were observed in these reactions. The diverse catalytic activity, broad substrate scope, mild reaction conditions, and high yields of the products made this catalytic system attractive in industrial processes.
