292-64-8Relevant academic research and scientific papers
Solid-State Chemistry of Molecular Metal Oxide Clusters. Ortho Metalation and Hydrogen Transport in 3PW12O40 Probed by 31P NMR Long-Range Deuterium Isotope Effects
Siedle, A. R.,Newmark, R. A.
, p. 2058 - 2062 (1989)
Deuterium isotope effects on 31P shielding that are large relative to the accuracy with which they can be measured are reported.In (Ph3P)2IrH2(dmf)2+, substitution of one 2H for 1H at the IR-H or at the ortho position in the Ph3P ligand leads to two- and three-bond isotope shifts of +0.094 and -0.110 ppm, respectively, with the effect being defined as 2H form)-δ(1H form)>.The ortho-deuterium effects on 31P for Ph3P, Ph3PO, Ph3PMe+I-, and (Ph3P)2Ir(C8H12)+ are -0.110, -0.096, -0.035, and -0.077 ppm, respectively.These long-range isotope effects are used to demonstrate a thermally activated, solid-state exchange of deuterium between iridium and only in the ortho positions of the Ph3P ligands in 3PW12O40.There occurs, additionally, an intermolecular hydrogen-deuterium exchange process.Slow exchange with c-C6D12 leads to incorporation of the deuterium label in the Ph3P rings.
Transformation of a Norbornadiene Unit to Ethylenylcyclopentene Requiring Cooperation between Boron and Rhodium Centers
Coles, Simon J.,Da Costa, Rosenildo C.,Guwy, Alan J.,Iannetelli, Angelo,Owen, Gareth R.,Tizzard, Graham J.
, p. 1976 - 1988 (2020)
The synthesis of the lithium salt of a bis-substituted borohydride anion containing a phenyl substituent and a 2-mercaptopyridyl unit (mp) is reported herein. This salt has been used as a pro-ligand for the synthesis of rhodium(I) complex, [Rh{κ3-H,H,S-H2B(Ph)(mp)}(NBD)] (1) (where NBD = 2,5-norbornadiene). The new boron-based ligand coordinates to the rhodium center via the thione donor and the two B-H bonds of the BPhH2 unit, with a dihydroborate motif. Reaction of complex 1 with two equivalents of triphenylphosphine leads to an unprecedented rearrangement and transfer of the former norbornadiene ligand to the boron center. The transformation occurs via an initial hydride migration from boron to rhodium center followed by a hydroboration of one of the double bonds. Finally, a ring-opening process occurs involving both boron and rhodium centers leading to an unusual boron-bound ethylenylcyclopentene unit. The product of this reaction was confirmed as [Rh{η1-S,η2-B,C-B(Ph)(CHCH2(C5H7)(mp)}(PPh3)2] (2). The net result of these transformations is the incorporation of the two hydrogen atoms from the secondary borohydride ligand [BPhH2(mp)]- into the former norbornadiene unit. The end point positions of these hydrogen atoms were confirmed by deuterium labeling experiments. Complex 2 was further reacted with carbon monoxide to generate [Rh{η1-S,η2-B,C-B(Ph)(CHCH2(C5H7)(mp)}(CO)(PPh3)] (3) via ligand substitution. The new ligand and the three complexes, 1, 2, and 3, have been characterized by spectroscopic techniques as well as by X-ray crystallography. Detailed characterization of 2 and 3 revealed an unusual η2-B,C coordination mode within these complexes. Further studies have demonstrated that complexes 2 and 3 react with hydrogen gas (or dimethylamine borane as a source of H2) to generate the hydrogen addition products involving the unprecedented activation of the Rh-η2-B,C motif. Complexes 2 and 3 were further found to be active catalysts for the hydrogenation of olefins and the dehydrogenation of dimethylamine borane.
In situ formed "weakly ligated/labile ligand" iridium(0) nanoparticles and aggregates as catalysts for the complete hydrogenation of neat benzene at room temperature and mild pressures
Bayram, Ercan,Zahmakiran, Mehmet,Oezkar, Saim,Finke, Richard G.
, p. 12455 - 12464 (2010)
"Weakly ligated/labile ligand" nanoparticles, that is nanoparticles where only weakly coordinated ligands plus the desired catalytic reactants are present, are of fundamental interest. Described herein is a catalyst system for benzene hydrogenation to cyclohexane consisting of "weakly ligated/labile ligand" Ir(0) nanoparticles and aggregates plus dry-HCl formed in situ from commercially available [(1,5-COD)IrCl]2 plus 40 ± 1 psig (～2.7 atm) H2 at 22 ± 0.1 °C. Multiple control and other experiments reveal the following points: (i) that this catalyst system is quite active with a TOF (turnover frequency) of 25 h-1 and TTO (total turnovers) of 5250; (ii) that the BF 4- and PF6- iridium salt precursors, [(1,5-COD)Ir(CH3CN)2]BF4 and [(1,5-COD)Ir(CH3CN)2]PF6, yield inferior catalysts; (iii) that iridium black with or without added, preformed HCl cannot achieve the TOF of 25 h-1 of the in situ formed Ir(0)/dry-HCl catalyst. However and importantly, CS2 poisoning experiments yield the same activity per active iridium atom for both the Ir(0)/dry-HCl and Ir black/no-HCl catalysts (12.5 h-1 Ir1-), but reveal that the Ir(0)/dry-HCl system is 10-fold more dispersed compared to the Ir(0) black catalyst. The simple but important and key result is that "weakly ligated/labile ligand" Ir(0) nanoparticles and aggregates have been made in situ as demonstrated by the fact that they have identical, per exposed Ir(0) activity within experimental error to Ir(0) black and that they have no possible ligands other than those desired for the catalysis (benzene and H2) plus the at best poor ligand HCl. As expected, the in situ catalyst is poorly stabilized, exhibiting only 60% of its initial activity in a second run of benzene hydrogenation and resulting in bulk metal precipitation. However, stabilization of the Ir(0) nanoparticles with a ca. 2-fold higher catalytic activity and somewhat longer lifetime for the complete hydrogenation of benzene was accomplished by supporting the Ir(0) nanoparticles onto zeolite-Y (TOF of 47h-1 and 8600 TTOunder otherwise identical conditions). Also reported is the interesting result that Cl- (present as Proton Sponge ·H+Cl-) completely poisons benzene hydrogenation catalysis, but not the easier cyclohexene hydrogenation catalysis under otherwise the same conditions, results that suggest different active sites for these ostensibly related hydrogenation reaction. The results suggest that synthetic routes to "weakly ligated/labile ligand" nanoparticles exhibiting improved catalytic performance is an important goal worthy of additional effort. 2010 American Chemical Society.
The two-step chemical vapor deposition of Pd(allyl)Cp as an atom-efficient route to synthesize highly dispersed palladium nanoparticles on carbon nanofibers
Liang, Changhai,Xia, Wei,Soltani-Ahmadi, Hamideh,Schlueter, Oliver,Fischer, Roland A.,Muhler, Martin
, p. 282 - 284 (2005)
Highly dispersed palladium nanoparticles supported on carbon nanoflbers, which show high catalytic activity and stability in the hydrogenation of cyclooctene, were synthesized by the two-step metal organic chemical vapor deposition (MOCVD) of allylcyclopentadienylpalladium (Pd(allyl)Cp) as precursor at atmospheric pressure.
Pd Nanoparticles supported on MIL-101: An efficient recyclable catalyst in oxidation and hydrogenation reactions
Bhattacharjee, Samiran,Kim, Jun,Ahn, Wha-Seung
, p. 2546 - 2552 (2014)
Pd nanoparticles supported on the chromium terephthalate metal organic framework MIL-101 (Pd/MIL-101) in different loadings (0.9 and 4.5 wt%) have been successfully prepared through a simple Pd-acetate adsorption and reduction in acetone, and tested as catalyst for selected liquid phase oxidation and hydrogenation reactions. The materials were characterized by XRD, N2 adsorption-desorption isotherm, TEM, SEM-EDX and ICP analysis. The parent MIL-101 structure was found well preserved after formation of Pd nanoparticles and after catalytic reaction runs. The present catalyst afforded good activity and selectivity for the oxidation of benzyl alcohol to benzaldehyde with 85% conversion and 97% selectivity using air (1 atm) at 85 °C after 14 h. The catalyst also showed good activity in the hydrogenation of the C C bond in alkenes to corresponding alkanes and also benzaldehyde to benzyl alcohol at room temperature using H2 (1 atm). Rigorous test results confirmed that Pd-nanoparticles supported on MIL-101 are responsible for the catalytic reactions occurred. Pd/MIL-101 was reusable several times without losing the structural integrity and initial activity, and demonstrated significantly higher catalytic activities than those by a commercial Pd catalyst supported on activated carbon. Copyright
Synthesis, characterisation, and catalytic properties of halloysite-supported metal nanoparticles
Jaine, Jacob. E.,Mucalo, Michael. R.
, p. 251 - 258 (2019)
A facile synthetic method is reported for the immobilisation of metal nanoparticles on halloysite, an aluminosilicate material with a unique nanotubular structure. A one-step colloidal synthesis was developed, from which nine different catalysts were prepared. The materials were tested in three different catalytic hydrogenations, and the halloysite-supported catalysts were found to outperform alumina- or silica-supported catalysts prepared in the same fashion. Electron microscopy showed that the activity was closely linked to the spatial distribution of the supported metal particles, which in turn affected the shapes of certain surface-associated peaks in the infrared and nuclear magnetic resonance spectra. From this data insight is gained into the nature of the interaction between metal nanoparticles and the surfaces of these support materials.
Encapsulation of supported metal nanoparticles with an ultra-thin porous shell for size-selective reactions
Shang, Zeyu,Patel, Rajankumar L.,Evanko, Brian W.,Liang, Xinhua
, p. 10067 - 10069 (2013)
A novel nanostructured catalyst with an ultra-thin porous shell obtained from the thermal decomposition of an aluminium alkoxide film deposited by molecular layer deposition for size-selective reactions was developed. The molecular sieving capability of the porous metal oxide films was verified by examining the liquid-phase hydrogenation of n-hexene versus cis-cyclooctene. The Royal Society of Chemistry 2013.
Catalytic properties of MIL-101
Henschel, Antje,Gedrich, Kristina,Kraehnert, Ralph,Kaskel, Stefan
, p. 4192 - 4194 (2008)
A very high catalytic activity in the cyanosilylation reaction was observed for MIL-101, a chromium based metal-organic framework; moreover, MIL-101 is also a remarkably stable support for palladium in hydrogenation reactions, with significantly higher activity than e.g. palladium on activated carbon. The Royal Society of Chemistry.
A Facile and In-situ Methanol-mediated Fabrication of Low Pd Loading, High-efficiency and Size-selectivity Pd@ZIF-8 Hydrogenation Catalyst
Zhang, Fengwei,Liu, Mengmeng,Liu, Qiang,Li, Jingjing,Li, Boyang,Dong, Zhengping
, p. 2952 - 2957 (2021)
In-situ encapsulation of tiny and well-dispersed Pd nanoparticles (Pd NPs) in zeolitic imidazolate frameworks (ZIFs) was firstly achieved using a one-pot and facile methanol-mediated growth approach, in which methanol served as both solvent and a mild reductant. The microstructure, morphology, crystallinity, porosity as well as evolution process of the catalysts were determined by TEM, XRD, N2 adsorption and UV-vis spectra. Due to the complete encapsulation of such Pd NPs combined with ultrahigh surface area and uniform microporous structure of ZIF-8, the resulting Pd@ZIF-8-60 min nanocomposite exhibited more superior catalytic activity for olefins hydrogenation with TOF of 7436 h?1 and excellent size selectivity than previously reported catalysts. Furthermore, the catalyst displays excellent recyclability for 1-octene hydrogenation and without any loss of the Pd active species.
Generation and Stabilization of Small Platinum Clusters Pt12± x Inside a Metal-Organic Framework
Kratzl, Kathrin,Kratky, Tim,Günther, Sebastian,Tomanec, Ond?ej,Zbo?il, Radek,Michali?ka, Jan,Macak, Jan M.,Cokoja, Mirza,Fischer, Roland A.
, p. 13962 - 13969 (2019)
The generation and matrix stabilization of ligand-free, small platinum nanoclusters (NCs) Pt12±x is presented. The metal-organic framework-template approach is based on encapsulating CO-ligated, atom-precise Pt9 Chini clusters [{Pt3(CO)6}3]2- into the zeolitic imidazolate framework ZIF-8. The selective formation of the air-stable inclusion compound [NBu4]2[{Pt3(CO)6}4]?ZIF-8 of defined atomicity Pt12 and with Pt loadings of 1-20 wt % was monitored by UV/vis and IR spectroscopy and was confirmed by high-resolution transmission electron microscopy (HR-TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (PXRD). Thermally induced decarbonylation at 200 °C yields the composite material Ptn?ZIF-8 with a cluster atomicity n close to 12, irrespective of the Pt loading. The PtNCs retain their size even during annealing at 300 °C for 24 h and during catalytic hydrogenation of 1-hexene at 25 °C in the liquid phase. The Ptn?ZIF-8 material can conveniently be used for storing small PtNCs and their further processing. Removal of the protective ZIF-8 matrix under acidic conditions and transfer of the PtNCs to carbon substrates yields defined aggregation to small Pt nanoparticles (1.14 ± 0.35 nm, HR-TEM), which have previously shown exceptional performance in the electrocatalytic oxygen reduction reaction (ORR).
