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- ItemCobalt pincer complexes for catalytic reduction of nitriles to primary amines(London : RSC Publ., 2019) Schneekönig, Jacob; Tannert, Bianca; Hornke, Helen; Beller, Matthias; Junge, KathrinVarious cobalt pincer type complexes 1-6 were applied for the catalytic hydrogenation of nitriles to amines. Among these, catalyst 4 is the most efficient, allowing the reduction of aromatic as well as aliphatic nitriles in moderate to excellent yields. © 2019 The Royal Society of Chemistry.
- ItemMetal–ligand cooperative activation of nitriles by a ruthenium complex with a de-aromatized PNN pincer ligand(London : Soc., 2016) Eijsink, Linda E.; Perdriau, Sébastien C. P.; de Vries, Johannes G.; Otten, EdwinThe pincer complex (PNN)RuH(CO), with a de-aromatized pyridine in the ligand backbone, is shown to react with nitriles in a metal–ligand cooperative manner. This leads to the formation of a series of complexes with new Ru–N(nitrile) and C(ligand)–C(nitrile) bonds. The initial nitrile cycloaddition products, the ketimido complexes 3, have a Brønsted basic (nitrile-derived) Ru–N fragment. This is able to deprotonate a CH2 side-arm of the pincer ligand to give ketimine complexes (4) with a de-aromatized pyridine backbone. Alternatively, the presence of a CH2 group adjacent to the nitrile functionality can lead to tautomerization to an enamido complex (5). Variable-temperature NMR studies and DFT calculations provide insight in the relative stability of these compounds and highlight the importance of their facile interconversion in the context of subsequent nitrile transformations.
- ItemFacile synthesis of supported Ru-Triphos catalysts for continuous flow application in selective nitrile reduction(Cambridge : RSC, 2019) Konrath, Robert; Heutz, Frank J.L.; Steinfeldt, Norbert; Rockstroh, Nils; Kamer, Paul C.J.The selective catalytic hydrogenation of nitriles represents an important but challenging transformation for many homogeneous and heterogeneous catalysts. Herein, we report the efficient and modular solid-phase synthesis of immobilized Triphos-type ligands in very high yields, involving only minimal work-up procedures. The corresponding supported ruthenium-Triphos catalysts are tested in the hydrogenation of various nitriles. Under mild conditions and without the requirement of additives, the tunable supported catalyst library provides selective access to both primary amines and secondary imines. Moreover, the first application of a Triphos-type catalyst in a continuous flow process is presented demonstrating high catalyst life-time over at least 195 hours without significant activity loss. © 2019 The Royal Society of Chemistry.
- ItemCobalt-based nanoparticles prepared from MOF-carbon templates as efficient hydrogenation catalysts(Cambridge : RSC, 2018) Murugesan, Kathiravan; Senthamarai, Thirusangumurugan; Sohail, Manzar; Alshammari, Ahmad S.; Pohl, Marga-Martina; Beller, Matthias; Jagadeesh, Rajenahally V.The development of efficient and selective nanostructured catalysts for industrially relevant hydrogenation reactions continues to be an actual goal of chemical research. In particular, the hydrogenation of nitriles and nitroarenes is of importance for the production of primary amines, which constitute essential feedstocks and key intermediates for advanced chemicals, life science molecules and materials. Herein, we report the preparation of graphene shell encapsulated Co3O4- and Co-nanoparticles supported on carbon by the template synthesis of cobalt-terephthalic acid MOF on carbon and subsequent pyrolysis. The resulting nanoparticles create stable and reusable catalysts for selective hydrogenation of functionalized and structurally diverse aromatic, heterocyclic and aliphatic nitriles, and as well as nitro compounds to primary amines (>65 examples). The synthetic and practical utility of this novel non-noble metal-based hydrogenation protocol is demonstrated by upscaling several reactions to multigram-scale and recycling of the catalyst.
- ItemCarboxylated nitrile butadiene rubber/hybrid filler composites(São Carlos : Universidade Federal de São Carlos, 2012) Mousa, A.; Heinrich, G.; Simon, F.; Wagenknecht, U.; Stöckelhuber, K.-W.; Dweiri, R.The surface properties of the OSW and NLS are measured with the dynamic contact-angle technique. The x-ray photoelectron spectroscopy (XPS) of the OSW reveals that the OSW possesses various reactive functional groups namely hydroxyl groups (OH). Hybrid filler from NLS and OSW were incorporated into carboxylated nitrile rubber (XNBR) to produce XNBR hybrid composites. The reaction of OH groups from the OSW with COOH of the XNBR is checked by attenuated total reflectance spectra (ATR-IR) of the composites. The degree of curing ΔM (maximum torque-minimum torque) as a function of hybrid filler as derived from moving die rheometer (MDR) is reported. The stress-strain behavior of the hybrid composites as well as the dynamic mechanical thermal analysis (DMTA) is studied. Bonding quality and dispersion of the hybrid filler with and in XNBR are examined using scanning-transmission electron microscopy (STEM in SEM).
- ItemTriangular Monometallic Cyanide Cluster Entrapped in Carbon Cage with Geometry-Dependent Molecular Magnetism(Washington, DC : ACS Publications, 2016) Liu, Fupin; Gao, Cong-Li; Deng, Qingming; Zhu, Xianjun; Kostanyan, Aram; Westerström, Rasmus; Wang, Song; Tan, Yuan-Zhi; Tao, Jun; Xie, Su-Yuan; Popov, Alexey A.; Greber, Thomas; Yang, ShangfengClusterfullerenes are capable of entrapping a variety of metal clusters within carbon cage, for which the entrapped metal cluster generally keeps its geometric structure (e.g., bond distance and angle) upon changing the isomeric structure of fullerene cage, and whether the properties of the entrapped metal cluster is geometry-dependent remains unclear. Herein we report an unusual triangular monometallic cluster entrapped in fullerene cage by isolating several novel terbium cyanide clusterfullerenes (TbNC@C82) with different cage isomeric structures. Upon varying the isomeric structure of C82 cage from C2(5) to Cs(6) and to C2v(9), the entrapped triangular TbNC cluster exhibits significant distortions as evidenced by the changes of Tb–C(N) and C–N bond distances and variation of the Tb–C(N)–N(C) angle by up to 20°, revealing that the geometric structure of the entrapped triangular TbNC cluster is variable. All three TbNC@C82 molecules are found to be single-ion magnets, and the change of the geometric structure of TbNC cluster directly leads to the alternation of the magnetic relaxation time of the corresponding TbNC@C82 clusterfullerene.
- ItemHydration of nitriles using a metal-ligand cooperative ruthenium pincer catalyst(Cambridge : RSC, 2019) Guo, Beibei; de Vries, Johannes G.; Otten, EdwinNitrile hydration provides access to amides that are important structural elements in organic chemistry. Here we report catalytic nitrile hydration using ruthenium catalysts based on a pincer scaffold with a dearomatized pyridine backbone. These complexes catalyze the nucleophilic addition of H2O to a wide variety of aliphatic and (hetero)aromatic nitriles in tBuOH as solvent. Reactions occur under mild conditions (room temperature) in the absence of additives. A mechanism for nitrile hydration is proposed that is initiated by metal-ligand cooperative binding of the nitrile. This journal is © The Royal Society of Chemistry.
- ItemTrimethylsilyl Pseudohalide Adducts of GaCl3 and B(C6F5)3(Weinheim : Wiley-VCH, 2021) Bläsing, Kevin; Bresien, Jonas; Maurer, Steffen; Schulz, Axel; Villinger, AlexanderMe3Si−X (X=CN, N3, OCN, and SCN) was treated with the Lewis acids GaCl3 and B(C6F5)3 in toluene yielding the desired adducts Me3Si−X→GaCl3 and Me3Si−X→B(C6F5)3. All synthesized adducts were isolated and completely characterized including single crystal structure elucidations. The different structures, thermodynamics of formation and charge transfer effects are discussed on the basis of experimental and theoretical data.
- ItemHexacyanidosilicates with Functionalized Imidazolium Counterions(Weinheim : Wiley-VCH, 2020) Harloff, Jörg; Laatz, Karoline Charlotte; Lerch, Swantje; Schulz, Axel; Stoer, Philip; Strassner, Thomas; Villinger, AlexanderFunctionalized imidazolium cations were combined with the hexacyanidosilicate anion, [Si(CN)6]2–, by salt metathesis reactions with K2[Si(CN)6], yielding novel ionic compounds of the general formula [R–Ph(nBu)Im]2[Si(CN)6] {R = 2-Me (1), 4-Me (2), 2,4,6-Me = Mes (3), 2-MeO (4), 2,4-F (5), 4-Br (6); Im = imidazolium}. All synthesized imidazolium hexacyanidosilicates decompose upon thermal treatment above 95 °C (96 – 164 °C). Furthermore, the hexa-borane-adduct [Mes(nBu)Im]2{Si[(CN)B(C6F5)3]6}·6CH2Cl2 (7), which is thermally stable up to 215 °C, was obtained from the reaction of 3 with Lewis acidic B(C6F5)3. In CH3CN solution, decomposition of the hexaadduct to the Lewis-acid-base adduct CH3CN–B(C6F5)3 and [(C6F5)3B·(µ-CN)·B(C6F5)3]– was observed. All synthesized compounds were isolated in good yields and were completely characterized including single crystal structure elucidations. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.