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- ItemNi-In Synergy in CO2Hydrogenation to Methanol(Washington, DC : ACS Publications, 2021) Zhu, Jiadong; Cannizzaro, Francesco; Liu, Liang; Zhang, Hao; Kosinov, Nikolay; Filot, Ivo A.W.; Rabeah, Jabor; Brückner, Angelika; Hensen, Emiel J.M.Indium oxide (In2O3) is a promising catalyst for selective CH3OH synthesis from CO2but displays insufficient activity at low reaction temperatures. By screening a range of promoters (Co, Ni, Cu, and Pd) in combination with In2O3using flame spray pyrolysis (FSP) synthesis, Ni is identified as the most suitable first-row transition-metal promoter with similar performance as Pd-In2O3. NiO-In2O3was optimized by varying the Ni/In ratio using FSP. The resulting catalysts including In2O3and NiO end members have similar high specific surface areas and morphology. The main products of CO2hydrogenation are CH3OH and CO with CH4being only observed at high NiO loading (≥75 wt %). The highest CH3OH rate (∼0.25 gMeOH/(gcath), 250 °C, and 30 bar) is obtained for a NiO loading of 6 wt %. Characterization of the as-prepared catalysts reveals a strong interaction between Ni cations and In2O3at low NiO loading (≤6 wt %). H2-TPR points to a higher surface density of oxygen vacancy (Ov) due to Ni substitution. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electron paramagnetic resonance analysis of the used catalysts suggest that Ni cations can be reduced to Ni as single atoms and very small clusters during CO2hydrogenation. Supportive density functional theory calculations indicate that Ni promotion of CH3OH synthesis from CO2is mainly due to low-barrier H2dissociation on the reduced Ni surface species, facilitating hydrogenation of adsorbed CO2on Ov © 2021 The Authors. Published by American Chemical Society
- ItemA General and Highly Selective Palladium-Catalyzed Hydroamidation of 1,3-Diynes(Weinheim : Wiley-VCH, 2021) Liu, Jiawang; Schneider, Carolin; Yang, Ji; Wei, Zhihong; Jiao, Haijun; Franke, Robert; Jackstell, Ralf; Beller, MatthiasA chemo-, regio-, and stereoselective mono-hydroamidation of (un)symmetrical 1,3-diynes is described. Key for the success of this novel transformation is the utilization of an advanced palladium catalyst system with the specific ligand Neolephos. The synthetic value of this general approach to synthetically useful α-alkynyl-α, β-unsaturated amides is showcased by diversification of several structurally complex molecules and marketed drugs. Control experiments and density-functional theory (M06L-SMD) computations also suggest the crucial role of the substrate in controlling the regioselectivity of unsymmetrical 1,3-diynes. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemAmbient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core-Shell Catalyst(Weinheim : Wiley-VCH, 2021) Gao, Jie; Ma, Rui; Feng, Lu; Liu, Yuefeng; Jackstell, Ralf; Jagadeesh, Rajenahally V.; Beller, MatthiasA general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemAzadiphosphaindane-1,3-diyls: A Class of Resonance-Stabilized Biradicals(Weinheim : Wiley-VCH, 2021) Bresien, Jonas; Michalik, Dirk; Schulz, Axel; Villinger, Alexander; Zander, EdgarConversion of 1,2-bis(dichlorophosphino)benzene with sterically demanding primary amines led to the formation of 1,3-dichloro-2-aza-1,3-diphosphaindanes of the type C6H4(μ-PCl)2N-R. Reduction yielded the corresponding 2-aza-1,3-diphosphaindane-1,3-diyls (1), which can be described as phosphorus-centered singlet biradical(oid)s. Their stability depends on the size of the substituent R: While derivatives with R=Dmp (2,6-dimethylphenyl) or Ter (2,6-dimesitylphenyl) underwent oligomerization, the derivative with very bulky R=tBuBhp (2,6-bis(benzhydryl)-4-tert-butylphenyl) was stable with respect to oligomerization in its monomeric form. Oligomerization involved activation of the fused benzene ring by a second equivalent of the monomeric biradical and can be regarded as formal [2+2] (poly)addition reaction. Calculations indicate that the biradical character in 1 is comparable with literature-known P-centered biradicals. Ring-current calculations show aromaticity within the entire ring system of 1. © 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemColor Tuning of Electrochromic TiO2Nanofibrous Layers Loaded with Metal and Metal Oxide Nanoparticles for Smart Colored Windows(Washington, DC : ACS Publications, 2021) Eyovge, Cavit; Deenen, Cristian S.; Ruiz-Zepeda, Francisco; Bartling, Stephan; Smirnov, Yury; Morales-Masis, Monica; Susarrey-Arce, Arturo; Gardeniers, HanCo-axial electrospinning was applied for the structuring of non-woven webs of TiO2 nanofibers loaded with Ag, Au, and CuO nanoparticles. The composite layers were tested in an electrochromic half-cell assembly. A clear correlation between the nanoparticle composition and electrochromic effect in the nanofibrous composite is observed: TiO2 loaded with Ag reveals a black-brown color, Au shows a dark-blue color, and CuO shows a dark-green color. For electrochromic applications, the Au/TiO2 layer is the most promising choice, with a color modulation time of 6 s, transmittance modulation of 40%, coloration efficiency of 20 cm2/C, areal capacitance of 300 F/cm2, and cyclic stability of over 1000 cycles in an 18 h period. In this study, an unexplored path for the rational design of TiO2-based electrochromic device is offered with unique color-switching and optical efficiency gained by the fibrous layer. It is also foreseen that co-axial electrospinning can be an alternative nanofabrication technique for smart colored windows. © 2021 The Authors. Published by American Chemical Society.
- ItemRecent Advances in Catalytic Hydrosilylations: Developments beyond Traditional Platinum Catalysts(Weinheim : Wiley-VCH, 2021) de Almeida, Leandro Duarte; Wang, Hongli; Junge, Kathrin; Cui, Xinjiang; Beller, MatthiasHydrosilylation reactions, which allow the addition of Si−H to C=C/C≡C bonds, are typically catalyzed by homogeneous noble metal catalysts (Pt, Rh, Ir, and Ru). Although excellent activity and selectivity can be obtained, the price, purification, and metal residues of these precious catalysts are problems in the silicone industry. Thus, a strong interest in more sustainable catalysts and for more economic processes exists. In this respect, recently disclosed hydrosilylations using catalysts based on earth-abundant transition metals, for example, Fe, Co, Ni, and Mn, and heterogeneous catalysts (supported nanoparticles and single-atom sites) are noteworthy. This minireview describes the recent advances in this field. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemCpCo(III) Precatalysts for [2+2+2] Cycloadditions(Basel : MDPI, 2021) Fischer, Fabian; Eder, Michael; Hapke, MarkoCatalysts applied in cobalt-catalyzed cyclotrimerizations reactions in general rely on the use of Co(I) precatalysts or the in situ generation of Co(I) catalysts from Co(II) sources by reduction in the presence of steering ligands, often by addition of less noble metals. In this paper, we report the synthesis and properties of novel stable CpCo(III) complexes as precatalysts and their exemplary evaluation for application in catalytic [2+2+2] cycloadditions. The role of phosphite neutral ligands, as well as iodide and cyanide as anionic ligands, on the reactivity of the complexes was evaluated. A modified one-pot approach to the synthesis of Cp ring-functionalized Cp’Co(III) complexes was developed. The investigations demonstrated that CpCo(III) complexes can be directly applied as catalysts in catalytic cyclotrimerizations of triynes without reducing agents as additives. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemRhodium-catalyzed borylative carbon monoxide reduction to gem-diborylmethane(Amsterdam [u.a.] : Elsevier, 2021) Xua, Jian-Xing; Wu, Fu-Peng; Wu, Xiao-FengHerein, we developed a rhodium-catalyzed reduction of CO with bis(pinacolato)diboron (B2pin2) under atmospheric pressure of CO with silane as the hydride source, gem-diborylmethane [H2C(Bpin)2] as a versatile and fundamental C1 compound can be formed. Notably, this is the first example on transition metal-catalyzed borylation of CO. © 2020 The Author(s)
- ItemPhotophysical and Electrochemical Properties of Pyrimidopteridine‐Based Organic Photoredox Catalysts(Weinheim : Wiley-VCH, 2021) Taeufer, Tobias; Argüello Cordero, Miguel A.; Petrosyan, Andranik; Surkus, Annette‐E.; Lochbrunner, Stefan; Pospech, JolaHerein we describe the synthesis and photophysical and electrochemical characterization of pyrimidopteridine-based photoredox catalysts. The pyrimidopteridines can be obtained from the corresponding N-oxides through photo-mediated oxygen atom transfer to a sacrificial acceptor molecule on gramscale. The presence of a triplet excited state was evidenced by means of transient absorption spectroscopy. Pyrimidopteridines are potent excited state oxidants with excited state reduction potentials exceeding +2.10 V vs. SCE in MeCN. The catalytic activity is illustrated in the photo-mediated oxidative annulation of 2-phenylbenzoic acid.
- ItemAvoiding Pitfalls in Comparison of Activity and Selectivity of Solid Catalysts for Electrochemical HMF Oxidation(Weinheim : Wiley-VCH, 2021) Wöllner, Sebastian; Nowak, Timothy; Zhang, Gui-Rong; Rockstroh, Nils; Ghanem, Hanadi; Rosiwal, Stefan; Brückner, Angelika; Etzold, Bastian J. M.Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. © 2021 The Authors. Published by The Chemical Society of Japan & Wiley-VCH GmbH