7471-05-8Relevant articles and documents
Efficient Cp?Ir Catalysts with Imidazoline Ligands for CO2 Hydrogenation
Xu, Shaoan,Onishi, Naoya,Tsurusaki, Akihiro,Manaka, Yuichi,Wang, Wan-Hui,Muckerman, James T.,Fujita, Etsuko,Himeda, Yuichiro
, p. 5591 - 5594 (2015)
We report newly developed iridium catalysts with electron-donating imidazoline moieties as ligands for the hydrogenation of CO2 to formate in aqueous solution. Interestingly, these new complexes promote CO2 hydrogenation much more effectively than their imidazole analogues and exhibit a turnover frequency (TOF) of 1290 h-1 for the bisimidazoline complex compared to that of 20 h-1 for the bisimidazole complex at 1 MPa and 50 C. In addition, the hydrogenation proceeds smoothly even under atmospheric pressure at room temperature. The TOF of 43 h-1 for the bisimidazoline complex is comparable to that of a dinuclear complex (70 h-1, highest TOF reported) [Nat. Chem. 2012, 4, 383], which incorporates proton-responsive ligands with pendent-OH groups in the second coordination sphere. The catalytic activity of the complex with an N-methylated imidazoline moiety is much the same as that of the corresponding pyridylimidazoline analogue. This result and the UV/Vis titrations of the imidazoline complexes indicate that the high activity is not attributable to the deprotonation of NH on the imidazoline under the reaction conditions. A novel complex having imidazoline ligands shows much higher catalytic activity for CO2 hydrogenation than the conventional complex having imidazole ligands. The change from a double bond in imidazole to a single bond in imidazoline leads to a 60-fold increase in the catalytic activity.
Hydrogen production from formic acid catalyzed by a phosphine free manganese complex: Investigation and mechanistic insights
Léval, Alexander,Agapova, Anastasiya,Steinlechner, Christoph,Alberico, Elisabetta,Junge, Henrik,Beller, Matthias
supporting information, p. 913 - 920 (2020/02/27)
Formic acid dehydrogenation (FAD) is considered as a promising process in the context of hydrogen storage. Its low toxicity, availability and convenient handling make FA attractive as a potential hydrogen carrier. To date, most promising catalysts have been based on noble metals, such as ruthenium and iridium. Efficient non-noble metal systems like iron were designed but manganese remains relatively unexplored for this transformation. In this work, we present a panel of phosphine free manganese catalysts which showed activity and stability in formic acid dehydrogenation. The most promising results were obtained with Mn(pyridine-imidazoline)(CO)3Br yielding >14 l of the H2/CO2 mixture and proved to be stable for more than 3 days. Additionally, this study provides insights into the mechanism of formic acid dehydrogenation. Kinetic experiments, Kinetic Isotopic Effect (KIE), in situ observations, NMR labeling experiments and pH monitoring allow us to propose a catalytic cycle for this transformation.
Thermally triggered solid-state single-crystal-to-single-crystal structural transformation accompanies property changes
Li, Quan-Quan,Ren, Chun-Yan,Huang, Yang-Yang,Li, Jian-Li,Liu, Ping,Liu, Bin,Liu, Yang,Wang, Yao-Yu
supporting information, p. 4703 - 4711 (2015/03/18)
The 1D complex [(CuL0.5H2O)·H2O]n (1) (H4 L = 2,2′-bipyridine-3,3′ ,6,6′-tetracarboxylic acid) undergoes an irreversible thermally triggered single-crystal-to-single-crystal (SCSC) transformation to produce the 3D anhydrous complex [CuL0.5]n (2). This SCSC structural transformation was confirmed by single-crystal X-ray diffraction analysis, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) patterns, variable-temperature powder X-ray diffraction (VT-PXRD) patterns, and IR spectroscopy. Structural analyses reveal that in complex 2, though the initial 1D chain is still retained as in complex 1, accompanied with the Cu-bound H2O removed and new O(carboxyl)-Cu bond forming, the coordination geometries around the CuII ions vary from a distorted trigonal bipyramid to a distorted square pyramid. With the drastic structural transition, significant property changes are observed. Magnetic analyses show prominent changes from antiferromagnetism to weak ferromagnetism due to the new formed Cu1-O-C-O-Cu4 bridge. The catalytic results demonstrate that, even though both solid-state materials present high catalytic activity for the synthesis of 2-imidazolines derivatives and can be reused, the activation temperature of complex 1 is higher than that of complex 2. In addition, a possible pathway for the SCSC structural transformations is proposed.
