89794-53-6Relevant articles and documents
Aluminum Metal-Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis
Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Dwivedi, Ashutosh,Manna, Kuntal
, p. 3943 - 3957 (2021/04/12)
The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal-organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon-oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.
Elucidating the reactivity of methoxyphenol positional isomers towards hydrogen-transfer reactions by ATR-IR spectroscopy of the liquid-solid interface of RANEY Ni
De Castro, Ilton Barros Daltro,Gra?a, Inês,Rodríguez-García, Laura,Kennema, Marco,Rinaldi, Roberto,Meemken, Fabian
, p. 3107 - 3114 (2018/06/29)
In the valorisation of lignin, the application of catalytic hydrogen transfer reactions (e.g. in catalytic upstream biorefining or lignin-first biorefining) has brought a renewed interest in the fundamental understanding of hydrogen-transfer processes in the defunctionalisation of lignin-derived phenolics. In this report, we address fundamental questions underlining the distinct reactivity patterns of positional isomers of guaiacol towards H-transfer reactions in the presence of RANEY Ni and 2-PrOH (solvent and H-donor). We studied the relationship between reactivity patterns of 2-, 3- and 4-methoxyphenols and their interactions at the liquid-solid interface of RANEY Ni as probed by attenuated total reflection infrared (ATR-IR) spectroscopy. Regarding the reactivity patterns, 2-methoxyphenol or guaiacol is predominantly converted into cyclohexanol through a sequence of reactions including demethoxylation of 2-methoxyphenol to phenol followed by hydrogenation of phenol to cyclohexanol. By contrast, for the conversion of the two non-lignin related positional isomers, the corresponding 3- and 4-methoxycyclohexanols are the major reaction products. The ATR-IR spectra of the liquid-solid interface of RANEY Ni revealed that the adsorbed 2-methoxyphenol assumes a parallel orientation to the catalyst surface, which allows a strong interaction between the methoxy C-O bond and the surface. Conversely, the adsorption of 3- or 4-methoxyphenol leads to a tilted surface complex in which the methoxy C-O bond establishes no interaction with the catalyst. These observations are also corroborated by a smaller activation entropy found for the conversion of 2-methoxyphenol relative to those of the other two positional isomers.
Robustly supported rhodium nanoclusters: Synthesis and application in selective hydrogenation of lignin derived phenolic compounds
Fehn, Sonja,Zaheer, Muhammad,Denner, Christine E.,Friedrich, Martin,Kempe, Rhett
, p. 9252 - 9256 (2016/11/11)
The stabilization of small rhodium nanoclusters (NCs) in a polymer derived silicon carbonitride (SiCN) matrix has been reported to generate highly robust and active solid catalysts for the selective hydrogenation of phenolic compounds. An aminopyridinato Rh complex was used to modify a preceramic polymer (HTT 1800) followed by its pyrolysis at 1100 °C to afford small Rh NCs nicely dispersed over dense SiCN ceramic. For the synthesis of porous catalysts containing Rh NCs, microphase separation (followed by pyrolysis) of a diblock copolymer of HTT 1800 with hydroxy-polyethylene (PE-OH) was used. Both catalysts exhibit high activity in the hydrogenation of substituted phenols at room temperature and under low hydrogen pressure. The catalysts remained highly active and selective for six consecutive catalytic runs.
