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1.
Synthesis,Solid‐State NMR Characterization,and Application for Hydrogenation Reactions of a Novel Wilkinson’s‐Type Immobilized Catalyst
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Safaa Abdulhussain Dr. Hergen Breitzke Dr. Tomasz Ratajczyk Dr. Anna Grünberg Mohamad Srour Danjela Arnaut Heiko Weidler Ulrike Kunz Prof. Dr. Hans Joachim Kleebe Dr. Ute Bommerich Prof. Dr. Johannes Bernarding Dr. Torsten Gutmann Prof. Dr. Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1159-1166
Silica nanoparticles (SiNPs) were chosen as a solid support material for the immobilization of a new Wilkinson’s‐type catalyst. In a first step, polymer molecules (poly(triphenylphosphine)ethylene (PTPPE); 4‐diphenylphosphine styrene as monomer) were grafted onto the silica nanoparticles by surface‐initiated photoinferter‐mediated polymerization (SI‐PIMP). The catalyst was then created by binding rhodium (Rh) to the polymer side chains, with RhCl3 ? x H2O as a precursor. The triphenylphosphine units and rhodium as RhI provide an environment to form Wilkinson’s catalyst‐like structures. Employing multinuclear (31P, 29Si, and 13C) solid‐state NMR spectroscopy (SSNMR), the structure of the catalyst bound to the polymer and the intermediates of the grafting reaction have been characterized. Finally, first applications of this catalyst in hydrogenation reactions employing para‐enriched hydrogen gas (PHIP experiments) and an assessment of its leaching properties are presented. 相似文献
2.
Natural Abundance 15N NMR by Dynamic Nuclear Polarization: Fast Analysis of Binding Sites of a Novel Amine‐Carboxyl‐Linked Immobilized Dirhodium Catalyst
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Torsten Gutmann Jiquan Liu Niels Rothermel Yeping Xu Eva Jaumann Mayke Werner Hergen Breitzke Snorri T. Sigurdsson Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3798-3805
A novel heterogeneous dirhodium catalyst has been synthesized. This stable catalyst is constructed from dirhodium acetate dimer (Rh2(OAc)4) units, which are covalently linked to amine‐ and carboxyl‐bifunctionalized mesoporous silica (SBA‐15?NH2?COOH). It shows good efficiency in catalyzing the cyclopropanation reaction of styrene and ethyl diazoacetate (EDA) forming cis‐ and trans‐1‐ethoxycarbonyl‐2‐phenylcyclopropane. To characterize the structure of this catalyst and to confirm the successful immobilization, heteronuclear solid‐state NMR experiments have been performed. The high application potential of dynamic nuclear polarization (DNP) NMR for the analysis of binding sites in this novel catalyst is demonstrated. Signal‐enhanced 13C CP MAS and 15N CP MAS techniques have been employed to detect different carboxyl and amine binding sites in natural abundance on a fast time scale. The interpretation of the experimental chemical shift values for different binding sites has been corroborated by quantum chemical calculations on dirhodium model complexes. 相似文献
3.
Ken Motokura Dr. Satoka Tanaka Dr. Mizuki Tada Dr. Yasuhiro Iwasawa Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10871-10879
We report the first tunable bifunctional surface of silica–alumina‐supported tertiary amines (SA–NEt2) active for catalytic 1,4‐addition reactions of nitroalkanes and thiols to electron‐deficient alkenes. The 1,4‐addition reaction of nitroalkanes to electron‐deficient alkenes is one of the most useful carbon–carbon bond‐forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA‐supported amine (SA–NEt2) catalyst enabled selective formation of a double‐alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA–NEt2 catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA–NEt2 catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron‐deficient alkenes. The solid‐state magic‐angle spinning (MAS) NMR spectroscopic analyses, including variable‐contact‐time 13C cross‐polarization (CP)/MAS NMR spectroscopy, revealed that acid–base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid–base interactions. 相似文献
4.
Dr. Fu Chen Dr. Guibin Ma Dr. Guy M. Bernard Prof. Roderick E. Wasylishen Prof. Ronald G. Cavell Dr. Robert McDonald Dr. Michael J. Ferguson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2826-2838
Several 1:1 adducts of gallium trihalides with triarylphosphines, X3Ga(PR3) (X=Cl, Br, and I; PR3=triarylphosphine ligand), were investigated by using solid‐state 69/71Ga and 31P NMR spectroscopy at different magnetic‐field strengths. The 69/71Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the 71Ga quadrupolar coupling constants (CQ(71Ga)) range from approximately 0.9 to 11.0 MHz . The spans of the gallium magnetic shielding tensors for these complexes, δ11?δ33, range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for InIII–phosphine complexes. This experimental trend, attributed to spin‐orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of CQ(69/71Ga) for some of the adducts were determined from the analysis of the 31P NMR spectra acquired with magic angle spinning (MAS). The 1J(69/71Ga,31P) and ΔJ(69/71Ga, 31P) values, as well as their signs, were also determined; values of 1J(71Ga,31P) range from approximately 380 to 1590 Hz. Values of 1J(69/71Ga,31P) and ΔJ(69/71Ga,31P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi‐contact and spin‐dipolar Fermi‐contact mechanisms make important contributions to the 1J(69/71Ga,31P) tensors. The 31P NMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single‐crystal X‐ray diffraction data for Br3Ga[P(p‐Anis)3] and I3Ga[P(p‐Anis)3] were obtained. 相似文献
5.
Enhanced Formaldehyde‐Vapor Adsorption Capacity of Polymeric Amine‐Incorporated Aminosilicas
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Dr. Akihiro Nomura Prof. Dr. Christopher W. Jones 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6381-6390
Airborne formaldehyde, which is a highly problematic volatile organic compound (VOC) pollutant, is adsorbed by polymeric amine‐incorporated silicas (aminosilicas), and the factors that affect the adsorption performance are systematically investigated. Three different types of polymeric amines 1) poly(ethyleneimine) branched (PEIBR); 2) poly(ethyleneimine) linear (PEILI); and 3) poly(allylamine) (PAA) are impregnated into two types of porous silicas [SBA‐15 and mesocellular foam (MCF) silicas] with systematic changes of the amine loadings. The adsorption results demonstrate that the adsorption capacity increases along with the amine loading until the polymeric amines completely fill the silica pores. This results in the MCF silica, which has a larger pore volume and hence can accommodate more polymeric amine before completely filling the pore, giving materials that adsorb more formaldehyde, with the largest adsorption capacity, q, of up to 5.7 mmolHCHO g?1 among the samples studied herein. Of the three different types of polymers, PAA, comprised of 100 % primary amines, showed the highest amine efficiency μ (mmolHCHO/mmolN) for capturing formaldehyde. The chemical structures of the adsorbed formaldehyde are analyzed by 13C cross‐polarization magic‐angle spinning (CP‐MAS) NMR, and it is demonstrated that the adsorbed formaldehyde is chemically attached to the aminosilica surface, forming hemiaminal and imine species. Because the chemical adsorption of formaldehyde forms covalent bonds, it is not desorbed from the aminosilicas below 130 °C based on temperature‐programed‐desorption (TPD) analysis. The high formaldehyde‐adsorption capacity and stability of the trapped formaldehyde on the amine surface in this study reveal the potential utility of aminosilicas as formaldehyde abatement materials. 相似文献
6.
Gisbert Großmann Gisela Ohms Kerstin Krüger Konstantin Karaghiosoff Klaus Eckstein Josef Hahn Andreas Hopp Olga L. Malkina Peter Hrobarik 《无机化学与普通化学杂志》2001,627(6):1269-1278
Diselenadiphosphetane Diselenides and Triselenadiphospholane Diselenides – Synthesis and Characterization by 31P and 77Se Solid‐State NMR Spectroscopy 1,3‐Diselena‐2,4‐diphosphetane‐2,4‐diselenides (RPSe2)2 with R = Me, Et, t‐Bu, Ph, 4‐Me2NC6H4, 4‐MeOC6H4 have been synthesized by different methods. The insoluble compounds were investigated by 31P and 77Se solid‐state NMR and the purity of the compounds has been checked by their CP MAS sideband NMR spectra. The structure of the investigated compounds has been confirmed by the isotropic and anisotropic values of the chemical shifts and the 1JP–Se coupling constants. In addition, two new 1,2,4‐triselena‐3,5‐diphospholane‐3,5‐diselenides, (RPSe2)2Se (R = Me, Et), formed under similar synthesis conditions, were investigated. Their structure was derived from the 77Se satellites of 31P solution spectra and from solid‐state spectra. For (t‐BuPSe2)2 the experimentally obtained principal values of phosphorus and selenium shielding tensors are compared with values from IGLO calculations (HF und SOS DFPT). The calculated orientations of the principal axes are discussed. 相似文献
7.
Powder‐XRD and 14N magic angle‐spinning solid‐state NMR spectroscopy of some metal nitrides
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Some metal nitrides (TiN, ZrN, InN, GaN, Ca3N2, Mg3N2, and Ge3N4) have been studied by powder X‐ray diffraction (XRD) and 14N magic angle‐spinning (MAS) solid‐state NMR spectroscopy. For Ca3N2, Mg3N2, and Ge3N4, no 14N NMR signal was observed. Low speed (νr = 2 kHz for TiN, ZrN, and GaN; νr = 1 kHz for InN) and ‘high speed’ (νr = 15 kHz for TiN; νr = 5 kHz for ZrN; νr = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder‐XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their 14N MAS solid‐state NMR spectrum matches perfectly well with the number of nitrogen‐containing phases identified by powder‐XRD. The 14N MAS solid‐state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc's arising from structural defects in the compounds studied. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
Investigation of two‐ and three‐bond carbon–hydrogen coupling constants in cinnamic acid based compounds
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Gregory K. Pierens Taracad K. Venkatachalam David C. Reutens 《Magnetic resonance in chemistry : MRC》2016,54(12):941-946
Two‐ and three‐bond coupling constants (2JHC and 3JHC) were determined for a series of 12 substituted cinnamic acids using a selective 2D inphase/antiphase (IPAP)‐single quantum multiple bond correlation (HSQMBC) and 1D proton coupled 13C NMR experiments. The coupling constants from two methods were compared and found to give very similar values. The results showed coupling constant values ranging from 1.7 to 9.7 Hz and 1.0 to 9.6 Hz for the IPAP‐HSQMBC and the direct 13C NMR experiments, respectively. The experimental values of the coupling constants were compared with discrete density functional theory (DFT) calculated values and were found to be in good agreement for the 3JHC. However, the DFT method under estimated the 2JHC coupling constants. Knowing the limitations of the measurement and calculation of these multibond coupling constants will add confidence to the assignment of conformation or stereochemical aspects of complex molecules like natural products. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
Phosphinines with pendant phenol or catechol functionalities and their gold(I) complexes were synthesised and characterised by spectroscopic data and in one case by a single‐crystal X‐ray diffraction study. Reactions of ligands or complexes with TiO2 or chloropropyl modified hexagonal mesoporous silica were then studied with the aim to immobilise ligands or complexes on the carrier by covalent tethering. 31P MAS NMR studies revealed that immobilisation on TiO2 was accompanied by complete degradation of the phosphinine moiety. Base induced coupling with chloropropyl modified silica produced a material that contained a mixture of several surface‐bound phosphorus compounds. 31P MAS NMR studies revealed that approx. 40 % of the ligand had retained its integrity whereas the remaining fraction had been converted into further, not unambiguously identified structures. 相似文献
10.
Harris E. Mason Joshua J. Hirner Wenqian Xu John B. Parise Brian L. Phillips 《Magnetic resonance in chemistry : MRC》2009,47(12):1062-1070
Pb‐containing hydroxylapatite phases synthesized under aqueous conditions were investigated by X‐ray diffraction and solid‐state nuclear magnetic resonance (NMR) techniques to determine the Pb, Ca distribution. 31P and 1H magic‐angle spinning (MAS) NMR results indicate slight shifts of the isotropic chemical shift with increased Ca content and complex lineshapes at compositions with near equal amounts of Ca and Pb. 31P{207Pb} and 1H{207Pb} rotational‐echo double resonance (REDOR) results for intermediate compositions show that resolved spectral features cannot be assigned simply in terms of local Ca, Pb configurations or coexisting phases. 207Pb MAS NMR spectra are easily obtained for these materials and contain well‐resolved resonances for crystallographically unique A1 and A2 Pb sites. Splitting of the A1 and A2 207Pb resonances for pure hydroxyl‐pyromorphite (Pb10(PO4)6(OH)2) compared to natural pyromorphite (Pb5(PO4)3Cl) suggests symmetry reduced from hexagonal. We find that 207Pb{1H} CP/MAS NMR is impractical in Pb‐rich hydroxylapatites due to fast 207Pb relaxation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
The irreversible inhibition of δ‐chymotrypsin with the enantiomerically pure, P(3)‐axially and P(3)‐equatorially X‐substituted cis‐ and trans‐configurated 2,4‐dioxa‐3‐phospha(1,5,5‐2H3)bicyclo[4.4.0]decane 3‐oxides (X=F, 2,4‐dinitrophenoxy) was monitored by 31P‐NMR spectroscopy. 1H‐Correlated 31P{2H}‐NMR spectra enabled the direct observation of the vicinal coupling (3J) between the P‐atom of the inhibitor and the CH2O moiety of Ser195 (=‘Ser195’(CH2O)), thus establishing the covalent nature of the ‘Ser195’(CH2O? P) bond in the inhibited enzyme. The stereochemical course of the phosphorylation is dependent on the structure of the inhibitor, and neat inversion, both inversion and retention, as well as neat retention of the configuration at the P‐atom was found. 相似文献
12.
Mallory Gobet Corinne Rondeau‐Mouro Solange Buchin Jean‐Luc Le Quéré Elisabeth Guichard Loïc Foucat Céline Moreau 《Magnetic resonance in chemistry : MRC》2010,48(4):297-303
The feasibility of solid‐state magic angle spinning (MAS) 31P nuclear magnetic resonance (NMR) spectroscopy and 23Na NMR spectroscopy to investigate both phosphates and Na+ ions distribution in semi‐hard cheeses in a non‐destructive way was studied. Two semi‐hard cheeses of known composition were made with two different salt contents. 31P Single‐pulse excitation and cross‐polarization MAS experiments allowed, for the first time, the identification and quantification of soluble and insoluble phosphates in the cheeses. The presence of a relatively ‘mobile’ fraction of colloidal phosphates was evidenced. The detection by 23Na single‐quantum NMR experiments of all the sodium ions in the cheeses was validated. The presence of a fraction of ‘bound’ sodium ions was evidenced by 23Na double‐quantum filtered NMR experiments. We demonstrated that NMR is a suitable tool to investigate both phosphates and Na+ ions distributions in cheeses. The impact of the sodium content on the various phosphorus forms distribution was discussed and results demonstrated that NMR would be an important tool for the cheese industry for the processes controls. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
Yuko Wada Kenta Iyoki Dr. Ayae Sugawara‐Narutaki Prof. Dr. Tatsuya Okubo Prof. Dr. Atsushi Shimojima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1700-1705
A new class of inorganic–organic hybrid porous materials has been synthesized by a reaction between octa(hydridosilsesquioxane) (H8Si8O12), which has a double‐four‐ring (D4R) structure, and various diols, such as 1,3‐propanediol (PD), 1,4‐cyclohexanediol (CHD), and 1,3‐adamantanediol (AD). Solid‐state 29Si magic‐angle‐spinning NMR spectroscopic analysis confirmed that most of the corner Si? H groups reacted with diols to form Si‐O‐C bonds with retention of the D4R cage. Nitrogen adsorption–desorption studies showed that the products are microporous solids with high BET surface areas (up to ≈580 m2 g?1 for CHD‐ and AD‐linked products). If n‐alkanediols are used as linkers, the surface area becomes smaller as the number of carbon atoms is increased. The thermal and hydrolytic stability of the products strongly depend on the type of diol linkers. The highest stabilities are found for the AD‐linked products, which are thermally stable up to around 400 °C and remain intact even after being soaked in water for 1 day. In contrast, the PD‐linked product is easily hydrolyzed in water to give microporous silica. These results offer a new route toward a series of silica‐based porous materials with unique structures and properties. 相似文献
14.
Direct Estimation of the Surface Location of Immobilized Functional Groups for Concerted Catalysis Using a Probe Molecule
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Hiroto Noda Dr. Ken Motokura Prof. Dr. Yusuke Wakabayashi Kaori Sasaki Dr. Hiroo Tajiri Dr. Akimitsu Miyaji Dr. Sho Yamaguchi Prof. Dr. Toshihide Baba 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5113-5117
The location of active sites during concerted catalysis by a metal complex and tertiary amine on a SiO2 surface is discussed based on the interaction between the functionalized SiO2 surface and a probe molecule, p‐formyl phenylboronic acid. The interactions of the probe molecule with the surface functionalities, diamine ligand, and tertiary amine, were analyzed by FT‐IR and solid‐state 13C and 11B MAS NMR. For the catalyst exhibiting high 1,4‐addition activity, the diamine ligand and tertiary amine base exist in closer proximity than in the catalyst with low activity. 相似文献
15.
2H, 31P, and 1H‐magic‐angle‐spinning (MAS) solid‐state NMR spectroscopic methods were used to elucidate the interaction between sorbic acid, a widely used weak acid food preservative, and 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) bilayers under both acidic and neutral pH conditions. The linewidth broadening observed in the 31P NMR powder pattern spectra and the changes in the 31P longitudinal relaxation time (T1) indicate interaction with the phospholipid headgroup upon titration of sorbic acid or decanoic acid into DMPC bilayers over the pH range from 3.0 to 7.4. The peak intensities of sorbic acid decrease upon addition of paramagnetic Mn2+ ions in DMPC bilayers as recorded in the 1H MAS NMR spectra, suggesting that sorbic acid molecules are in close proximity with the membrane/aqueous surface. No significant 2H quadrupolar splitting (ΔνQ) changes are observed in the 2H NMR spectra of DMPC‐d54 upon titration of sorbic acid, and the change of pH has a slight effect on ΔνQ, indicating that sorbic acid has weak influence on the orientation order of the DMPC acyl chains in the fluid phase over the pH range from 3.0 to 7.4. This finding is in contrast to the results of the decanoic acid/DMPC‐d54 systems, where ΔνQ increases as the concentration of decanoic acid increases. Thus, in the membrane association process, sorbic acids are most likely interacting with the headgroups and shallowly embedded near the top of the phospholipid headgroups, rather than inserting deep into the acyl chains. Thus, antimicrobial mode of action for sorbic acid may be different from that of long‐chain fatty acids. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
16.
Sankaranarayanapillai Shylesh Dr. Alex Wagner Andreas Seifert Dr. Stefan Ernst Prof. Dr. Werner R. Thiel Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7052-7062
Acid–base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one‐step synthesis by co‐condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid‐state 29Si and 13C cross‐polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N2 adsorption–desorption analyses, and SEM imaging. The catalytic activities of the mono‐ and bifunctional mesoporous hybrid materials were evaluated in carbon–carbon coupling reactions like the nitroaldol reaction and the one‐pot deacetalization–nitroaldol and deacetalization–aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN–NNH2–SO3H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid–base activation is envisaged for the carbon–carbon coupling reactions. 相似文献
17.
Ilia B. Moroz Pierre Florian Jasmine Viger‐Gravel Christopher P. Gordon Anne Lesage Christophe Copret 《Angewandte Chemie (International ed. in English)》2020,59(37):16167-16172
A silica‐supported monomeric alkylaluminum co‐catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid‐state 27Al NMR spectroscopy augmented by computational studies, efficiently activates (nBu3P)2NiCl2 towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species—tetra‐ and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the (nBu3P)2NiCl2 complex and generate the active cationic species. 相似文献
18.
A novel fairly stable N‐trimethylsilylamino(dichloro)phosphine was prepared, in which the nitrogen atom bears a 9‐borabicyclo[3.3.1]nonyl group. The gas phase structures of various amino‐ and silylaminophosphines including a phosphenium cation and an amino(imono)phosphine were optimized at the B3LYP/6‐311+G(d,p) level of theory, and NMR parameters were calculated. Both magnitude and sign of the two‐bond coupling constants 2J(31P,N,13C) and 2J(31P,N,29Si), known to be sensitive towards the respective conformation, are well reproduced by the calculations. This also holds for 1J(31P,15N), although calculated values 1K(31P,15N) (all < 0) are slightly more negative [1J(31P,15N) more positive] than experimental values. 相似文献
19.
Hendrik E. van der Bij Dr. Luis R. Aramburo Dr. Bjørnar Arstad Dr. James J. Dynes Dr. Jian Wang Prof. Dr. Bert M. Weckhuysen 《Chemphyschem》2014,15(2):283-292
A variety of phosphated zeolite H‐ZSM‐5 samples are investigated by using a combination of Fourier transfer infrared (FTIR) spectroscopy, single pulse 27Al, 29Si, 31P, 1H‐31P cross polarization (CP), 27Al‐31P CP, and 27Al 3Q magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, scanning transmission X‐ray microscopy (STXM) and N2 physisorption. This approach leads to insights into the physicochemical processes that take place during phosphatation. Direct phosphatation of H‐ZSM‐5 promotes zeolite aggregation, as phosphorus does not penetrate deep into the zeolite material and is mostly found on and close to the outer surface of the zeolite, acting as a glue. Phosphatation of pre‐steamed H‐ZSM‐5 gives rise to the formation of a crystalline tridymite AlPO4 phase, which is found in the mesopores of dealuminated H‐ZSM‐5. Framework aluminum species interacting with phosphorus are not affected by hydrothermal treatment. Dealuminated H‐ZSM‐5, containing AlPO4, retains relatively more framework Al atoms and acid sites during hydrothermal treatment than directly phosphated H‐ZSM‐5. 相似文献
20.
The diamide exo, exo‐β‐P4S3(NHCH(Me)Ph)2 has been made in solution using enantiomerically pure or racemic PhCH(Me)NH2, and its three diastereomers characterised by complete analysis of their 31P{1H} NMR spectra.The unsymmetric diastereomer contains phosphorus atoms, made chemically non‐equivalent by the chirality of the substituents, which show a large 2J(P—P—P) coupling to each other (225.2 Hz). 相似文献