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871.
872.
Senthil Subramaniam Mond F. Guo Tanmayi Bathena Michel Gray Xiao Zhang Abraham Martinez Libor Kovarik Konstantinos A. Goulas Karthikeyan K. Ramasamy 《Angewandte Chemie (International ed. in English)》2020,59(34):14550-14557
Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C5+ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd‐promoted ZnO‐ZrO2 catalyst. The sequence of reaction steps involved in the C5+ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross‐aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C5+ ketones and the stability of the catalyst. A yield of >70 % to C5+ ketones was achieved over a 0.1 % Pd‐ZnO‐ZrO2 mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation. 相似文献
873.
Geminally Diaurated Aryls Bridged by Semirigid Phosphine Pillars: Syntheses and Electronic Structure 下载免费PDF全文
Amberle R. Browne Dr. Nihal Deligonul Bryce L. Anderson Prof. Arnold L. Rheingold Prof. Thomas G. Gray 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17552-17564
Geminally diaurated μ2‐aryl complexes have been prepared where gold(I) centers were bridged by the semirigid diphosphine ligands bis(2‐diphenylphosphinophenyl)ether (DPEphos) and 4,6‐bis(diphenylphosphanyl)dibenzo[b,d]furan (DBFphos). Diaurated complexes were synthesized in ligand redistribution reactions of the corresponding di‐gold dichlorides with di‐gold diaryls (six of them new) and silver(I) salts. Diaurated complexes were isolated as salts of the minimally coordinating anions SbF6? and ReO4?. Efforts to prepare salts of the tetraarylborate [B(3,5‐(CF3)2C6H3)4]? led to transmetalation from boron, with crystallization of the fluorinated aryl complex. The new complexes were characterized by multinuclear NMR, absorption and emission spectroscopies, 77 K emission lifetimes, and by combustion analysis; three are crystallographically characterized. Structures of geminally diaurated aryl ligands are compared to those of mono‐aurated analogues. Both crystal structures and density‐functional theory calculations indicate slight but observable disruptions of aryl ligand aromaticity by geminal di‐gold binding. An intermolecular aurophilic interaction in one structurally authenticated complex was examined computationally. 相似文献
874.
Syntheses of novel 3-ethynyl (8), 3-vinyl (10) and 3-acetoxy (13)-2′-deoxy-3-deazauridine analogs starting from the protected 2′-deoxy-3-deazauridine derivative 4 are described. 相似文献
875.
Simon M. Harwood Kenneth J. Toyne John W. Goodby Michael Parsley George W. Gray 《Liquid crystals》2013,40(4):443-449
The syntheses of seven esters of cholest-5-ene-3beta-carboxylic acid are reported and the melting points, transition temperatures and mesophase morphologies of the esters are compared with those of the isomeric 3beta-cholesterol compounds which have the ester link reversed. For the examples reported, the cholest-5-ene-3beta-carboxlates always have significantly lower melting points, but the differences in clearing temperatures for the two series of esters are usually much less. Several of the new compounds give an increased chiral nematic phase range and an intense selective reflection of light. They therefore represent a novel type of chiral nematic material for use in thermochromic applications. 相似文献
876.
Xi Yin Steven A. Warren Yung‐Tin Pan Kai‐Chieh Tsao Dr. Danielle L. Gray Dr. Jeffery Bertke Prof.Dr. Hong Yang 《Angewandte Chemie (International ed. in English)》2014,53(51):14087-14091
A new motif for infinite metal atom wires with tunable compositions and properties is developed based on the connection between metal paddlewheel and square planar complex moieties. Two infinite Pd chain compounds, [Pd4(CO)4(OAc)4Pd(acac)2] 1 and [Pd4(CO)4(TFA)4Pd(acac)2] 2 , and an infinite Pd? Pt heterometallic chain compound, [Pd4(CO)4(OAc)4Pt(acac)2] 3 , are identified by single‐crystal X‐ray diffraction analysis. In these new structures, the paddlewheel moiety is a Pd four‐membered ring coordinated by bridging carboxylic ligands and μ2 carbonyl ligands. The planar moiety is either Pd(acac)2 or Pt(acac)2 (acac=acetylacetonate). These moieties are connected by metallophilic interactions. The results showed that these one‐dimensional metal wire compounds have photoluminescent properties that are tunable by changing ligands and metal ions. 3 can also serve as a single source precursor for making Pd4Pt bimetallic nanostructures with precise control of metal composition. 相似文献
877.
Dr. Alasdair P. M. Robertson B.Sc. Paul A. Gray Prof. Neil Burford 《Angewandte Chemie (International ed. in English)》2014,53(24):6050-6069
Pnictine derivatives can behave as both 2e? donors (Lewis bases) and 2e? acceptors (Lewis acids). As prototypical ligands in the coordination chemistry of transition metals, amines and phosphines also form complexes with p‐block Lewis acids, including a variety of pnictogen‐centered acceptors. The inherent Lewis acidity of pnictogen centers can be enhanced by the introduction of a cationic charge, and this feature has been exploited in recent years in the development of compounds resulting from coordinate Pn–Pn and Pn–Pn′ interactions. These compounds offer the unusual opportunity for homoatomic coordinate bonding and the development of complexes that possess a lone pair of electrons at the acceptor center. This Review presents new directions in the systematic extension of coordination chemistry from the transition series into the p‐block. 相似文献
878.
Erich Müller Otto Wahle W. D. Treadwell S. Janett M. Blumenthal J. Herzog W. S. Hendrixson L. M. Verbeck William T. Hall Carl E. Carlson G. L. Kelley M. G. Spencer C. B. Illingworth T. Gray D. Chervet Robert Müller Fr. Hölz W. Knaus Fr. Planíszig K. Prett R. Hönig und A. Konetschnigg 《Fresenius' Journal of Analytical Chemistry》1924,65(3-4):140-153
Ohne Zusammenfassung 相似文献
879.
880.
In an attempt to prepare stable dispersions of cellulose nanocrystals in dipolar aprotic solvents, dilute aqueous suspensions
of cellulose nanocrystals were prepared by sulfuric acid hydrolysis of cotton. The aqueous suspensions were freeze-dried,
and then sonicated in the solvent of interest. Dispersions of 1 and 3% w/v concentration were prepared in polar organic solvents
DMSO and DMF. The dispersions showed flow birefringence. The redispersion was incomplete, and there was some evidence for
aggregation in the suspensions. A small amount of water appeared to be critical to suspension stability. Birefringent cellulose
films were prepared from the dispersions by drying under vacuum and at ambient conditions. 相似文献