186983-16-4Relevant articles and documents
The structural and electronic promoting effect of nitrogen-doped carbon nanotubes on supported Pd nanoparticles for selective olefin hydrogenation
Chen, Peirong,Chew, Ly May,Kostka, Aleksander,Muhler, Martin,Xia, Wei
, p. 1964 - 1971 (2013)
A high-performance Pd catalyst for selective olefin hydrogenation was synthesized by supporting Pd nanoparticles on nitrogen-doped carbon nanotubes (NCNTs). X-ray diffraction, hydrogen chemisorption, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize Pd supported on NCNTs and nitrogen-free oxygen-functionalized CNTs (OCNTs). The Pd nanoparticles were stabilized on NCNTs with narrower size distribution compared with OCNTs. The XPS analysis revealed that the nitrogen functional groups favor the reduction of Pd on CNTs suggesting an electronic promoter effect. The Pd/NCNT catalyst showed extraordinary catalytic performance in terms of activity, selectivity and stability in the selective hydrogenation of cyclooctadiene, which is related to the structural and electronic promoting effect of the NCNT support.
A promoting effect of dilution of Pd sites due to gold surface segregation under reaction conditions on supported Pd-Au catalysts for the selective hydrogenation of 1,5-cyclooctadiene
Concepción, Patricia,García, Saray,Hernández-Garrido, Juan Carlos,Calvino, Jose Juan,Corma, Avelino
, p. 213 - 221 (2015)
Restructuration of AuPd/CeO2 catalysts is observed during 1,5-cyclooctadiene hydrogenation, with gold surface segregation in which gold acts as a diluent of Pd surface sites. The composition of the catalyst influences the catalytic behavior, an
Synthesis, Characterization, and Catalytic Properties of Iridium Pincer Complexes Containing NH Linkers
Leveson-Gower, Reuben B.,Webb, Paul B.,Cordes, David B.,Slawin, Alexandra M. Z.,Smith, David M.,Tooze, Robert P.,Liu, Jianke
, p. 30 - 39 (2018/01/17)
A series of tert-butyl-substituted pincer ligands based on 1,3-diaminobenzene and 3-aminophenol scaffolds, tBu4PXCYP (1e, X = Y = NH; 1f, X = NH; Y = O) and the corresponding iridium hydridochloro complexes (tBu4PXCYP)IrHCl (2e, X = Y = NH; 2f, X = NH; Y = O) were prepared with moderate yields and high purity and were fully characterized by 1H and 31P NMR spectroscopy. Unsymmetrical hybrid pincer ligands R2PNCOPtBu2 (1g, R = isopropyl; 1h, R = cyclohexyl) were prepared conveniently in high yield via a one-pot procedure by judiciously choosing reaction conditions and base; the corresponding iridium hydrido chloro complexes iPr2PNCOPtBu2IrHCl (2g) and Cy2PNCOPtBu2IrHCl (2h) were synthesized by the reaction of [IrCl(COE)2]2 with ligands. X-ray crystallography reveals that these iridium pincer complexes adopt similar square-pyramidal geometries and exhibit strong intermolecular hydrogen bonding between the NH linker and chloride ions of the adjacent iridium complex in the solid state. 1H NMR chemical shifts of tert-butyl based pincer ligated iridium hydrides move downfield when the electronegativity of the linker between the benzene backbone and phosphine moiety increases for 2a, 2e, 2f, and 2b. Accordingly the corresponding iridium pincer carbonyl complexes (tBu4PXCYP)Ir(CO), 3a, 3e, 3f, and 3b show a blue shift in the CO stretching frequency. The activities of iridium complexes containing NH linkers were briefly examined for transfer dehydrogenation from cyclooctane to tert-butylethylene; (iPr2PNCOPtBu2)IrHCl (2g) exhibits the highest activity among all tested iridium pincer complexes, including the most studied (tBu4PCP)IrHCl (2a) and (tBu4POCOP)IrHCl (2b). The enhanced catalytic activity could be related to combined electronic and steric effects of the NH/O hybrid linker and different alkyl groups at phosphorus. This new class of iridium pincer complexes could have great implications in catalytic transformation of polar compounds due to the strong hydrogen-bond-donating ability of the NH linker.
An electron poor iridium pincer complex for catalytic alkane dehydrogenation
Kovalenko, Oleksandr O.,Wendt, Ola F.
, p. 15963 - 15969 (2016/10/22)
A novel electron deficient 4,6-bis(trifluoromethyl)-1,3-phenylene diphosphinite ligand 4 was developed and synthesized. Reaction of Ir precursors with ligand 4 gave chloro(hydride) pincer complex 5, which demonstrated a higher TON in alkane dehydrogenation reactions compared to similar phosphinite based pre-catalysts. The formation of cyclooctene (COE) and tert-butylethylene adducts of the 14e catalysts was also studied and the COE adduct is implicated as the resting state of the catalyst. All compounds were characterized by NMR spectroscopy and, in addition, the molecular structures of key complexes were confirmed by X-ray analysis.
