16873-17-9Relevant articles and documents
Introducing Water-Network-Assisted Proton Transfer for Boosted Electrocatalytic Hydrogen Evolution with Cobalt Corrole
Li, Xialiang,Lv, Bin,Zhang, Xue-Peng,Jin, Xiaotong,Guo, Kai,Zhou, Dexia,Bian, Hongtao,Zhang, Wei,Apfel, Ulf-Peter,Cao, Rui
supporting information, (2022/01/11)
Proton transfer is vital for many biological and chemical reactions. Hydrogen-bonded water-containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown-ether-free analogues showed very small enhancement. Inhibition studies by adding 1) external 18-crown-6-ether to extract water molecules and 2) potassium ion or N-benzyl-n-butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water-containing networks.
Ammonia-Borane Dehydrogenation Catalyzed by Dual-Mode Proton-Responsive Ir-CNNHComplexes
álvarez, Eleuterio,López-Serrano, Joaquín,Ortega-Lepe, Isabel,Rendón, Nuria,Rossin, Andrea,Sánchez, Práxedes,Santos, Laura L.,Suárez, Andrés
, p. 18490 - 18502 (2021/12/01)
Metal complexes incorporating proton-responsive ligands have been proved to be superior catalysts in reactions involving the H2 molecule. In this contribution, a series of IrIII complexes based on lutidine-derived CNNH pincers containing N-heterocyclic carbene and secondary amino NHR [R = Ph (4a), tBu (4b), benzyl (4c)] donors as flanking groups have been synthesized and tested in the dehydrogenation of ammonia-borane (NH3BH3, AB) in the presence of substoichiometric amounts (2.5 equiv) of tBuOK. These preactivated derivatives are efficient catalysts in AB dehydrogenation in THF at room temperature, albeit significantly different reaction rates were observed. Thus, by using 0.4 mol% of 4a, 1.0 equiv of H2 per mole of AB was released in 8.5 min (turnover frequency (TOF50%) = 1875 h-1), while complexes 4b and 4c (0.8 mol%) exhibited lower catalytic activities (TOF50% = 55-60 h-1). 4a is currently the best performing IrIII homogeneous catalyst for AB dehydrogenation. Kinetic rate measurements show a zero-order dependence with respect to AB, and first order with the catalyst in the dehydrogenation with 4a (-d[AB]/dt = k[4a]). Conversely, the reaction with 4b is second order in AB and first order in the catalyst (-d[AB]/dt = k[4b][AB]2). Moreover, the reactions of the derivatives 4a and 4b with an excess of tBuOK (2.5 equiv) have been analyzed through NMR spectroscopy. For the former precursor, formation of the iridate 5 was observed as a result of a double deprotonation at the amine and the NHC pincer arm. In marked contrast, in the case of 4b, a monodeprotonated (at the pincer NHC-arm) species 6 is observed upon reaction with tBuOK. Complex 6 is capable of activating H2 reversibly to yield the trihydride derivative 7. Finally, DFT calculations of the first AB dehydrogenation step catalyzed by 5 has been performed at the DFT//MN15 level of theory in order to get information on the predominant metal-ligand cooperation mode.
Hydrolysis of B2pin2 over Pd/C Catalyst: High Efficiency, Mechanism, and in situ Tandem Reaction
Li, Ning,Shen, Jialu,Liu, Xiang
supporting information, p. 2797 - 2800 (2021/02/16)
A facile and effective synthesis of H2 or D2 from Pd/C catalyzed hydrolysis of B2pin2 has first been developed. Among them, B2pin2 is frequently used for borylation reaction, and has rarely been used for hydrogen evolution. The kinetic isotope effects (KIEs) and tandem reaction for diphenylacetylene and norbornene hydrogenation have confirmed both two H atoms of H2 gas are provided from H2O. This is contrary to other boron compounds hydrolysis (including NH3BH3, NaBH4), which generates H2 with only one H atom provided by water and the other one by boron compounds. Note that the hydrolysis of B2pin2 in D2O also provides an easy and useful synthesis of D2.
