80143-73-3Relevant articles and documents
Metal-Ligand Cooperation Facilitates Bond Activation and Catalytic Hydrogenation with Zinc Pincer Complexes
Rauch, Michael,Kar, Sayan,Kumar, Amit,Avram, Liat,Shimon, Linda J. W.,Milstein, David
supporting information, p. 14513 - 14521 (2020/10/13)
A series of PNP zinc pincer complexes capable of bond activation via aromatization/dearomatization metal-ligand cooperation (MLC) were prepared and characterized. Reversible heterolytic N-H and H-H bond activation by MLC is shown, in which hemilability of the phosphorus linkers plays a key role. Utilizing this zinc pincer system, base-free catalytic hydrogenation of imines and ketones is demonstrated. A detailed mechanistic study supported by computation implicates the key role of MLC in facilitating effective catalysis. This approach offers a new strategy for (de)hydrogenation and other catalytic transformations mediated by zinc and other main group metals.
Visible-Light Photocatalytic Synthesis of Amines from Imines via Transfer Hydrogenation Using Quantum Dots as Catalysts
Xi, Zi-Wei,Yang, Lei,Wang, Dan-Yan,Pu, Chao-Dan,Shen, Yong-Miao,Wu, Chuan-De,Peng, Xiao-Gang
, p. 11886 - 11895 (2018/09/25)
CdSe/CdS core/shell quantum dots (QDs) can be used as stable and highly active photoredox catalysts for efficient transfer hydrogenation of imines to amines with thiophenol as a hydrogen atom donor. This reaction proceeds via a proton-coupled electron transfer (PCET) from the QDs conduction band to the protonated imine followed by hydrogen atom transfer from the thiophenol to the α-aminoalkyl radical. This precious metal free transformation is easy to scale up and can be carried out by a one-pot protocol directly from aldehyde, amine, and thiophenol. Additional advantageous features of this protocol include a wide substrate scope, high yield of the amine products, extremely low catalyst loading (0.001 mol %), high turnover number (105), and the mild reaction conditions of using visible light or sun light at room temperature in neutral media.
Ruthenium(II) complexes containing lutidine-derived pincer CNC ligands: Synthesis, structure, and catalytic hydrogenation of C=N bonds
Hernández-Juárez, Martín,López-Serrano, Joaquín,Lara, Patricia,Morales-Cerón, Judith P.,Vaquero, Mónica,álvarez, Eleuterio,Salazar, Verónica,Suárez, Andrés
, p. 7540 - 7555 (2015/05/13)
Abstract A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5e(BF4) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C=N bond assisted either by the pincer ligand or a second coordinated H2 molecule. The outer limits: Facially coordinated Ru-CNC complexes, in the presence of tBuOK, are active catalysts in the hydrogenation of a series of substrates containing C=N bonds (see scheme). Intermediate species in the catalytic cycle have been studied by using NMR spectroscopy; DFT calculations support a stepwise outer-sphere mechanism for the hydrogen transfer to the C=N bond assisted by either the pincer ligand or a second coordinated H2 molecule.
