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Jean-Marc Mörsdorf, Hubert Wadepohl, Joachim Ballmann
The central phosphorus atom of a novel hydroxyl-functionalized triarylphosphane was shown to reversibly insert into one of the molecule's O-H bonds, which forms the basis for a tautomeric λ3 /λ5 -phosphane equilibrium. For the first time, this equilibrium was detected for a λ3 -triarylphosphane and the underlying dynamic process was elucidated by NMR spectroscopy. On the basis of reactivity studies, a nucleophilic character was assigned to the minor species present in solution, the λ3 -phosphane. Upon methylation, for example, the λ3 -form was selectively removed from the equilibrium and converted to the corresponding phosphonium salt...
February 19, 2019: Inorganic Chemistry
Seoung-Bum Son, Lei Cao, Taeho Yoon, Arthur Cresce, Simon E Hafner, Jun Liu, Markus Groner, Kang Xu, Chunmei Ban
Silicon (Si) has been well recognized as a promising candidate to replace graphite because of its earth abundance and high-capacity storage, but its large volume changes upon lithiation/delithiation and the consequential material fracturing, loss of electrical contact, and over-consumption of the electrolyte prevent its full application. As a countermeasure for rapid capacity decay, a composite electrode of graphite and Si has been adopted by accommodating Si nanoparticles in a graphite matrix. Such an approach, which involves two materials that interact electrochemically with lithium in the electrode, necessitates an analytical methodology to determine the individual electrochemical behavior of each active material...
February 6, 2019: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Emilie Molina, Mélody Mathonnat, Jason Richard, Patrick Lacroix-Desmazes, Martin In, Philippe Dieudonné, Thomas Cacciaguerra, Corine Gérardin, Nathalie Marcotte
Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)- b -poly(acrylic acid) (PEO- b -PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium...
2019: Beilstein Journal of Nanotechnology
Hsiang-Jung Wu, Kota Tanabe, Hiroki Nagai, Mitsunobu Sato
Photo-induced super-hydrophilic thin films were fabricated on a quartz glass substrate by ultraviolet (UV) irradiation of a molecular precursor film at room temperature. A molecular precursor film exhibiting high solubility to both ethanol and water was obtained by spin-coating a solution involving a Ti(IV) complex; this complex was prepared by the reaction of Ti(IV) alkoxide with butylammonium hydrogen oxalate and hydrogen peroxide in ethanol. Transparent and well-adhered amorphous thin films of 160⁻170 nm thickness were obtained by weak UV irradiation (4 mW·cm-2 at 254 nm) of the precursor films for over 4 h at room temperature...
January 23, 2019: Materials
Boris Colin, Olivier Lavastre, Stephane Fouquay, Guillaume Michaud, Frederic Simon, Jean-Michel Brusson
In this work, a high-throughput screening (HTS) method was used to discover new efficient catalysts to substitute organotin compounds (DBTDL) for the cross-linking of silyl-modified polymers (SMPs). We report here on the use of our HTS method to investigate a library of alkoxide/oxime systems with different metal/ligand (M/L) ratios. Among the 156 candidates tested, 40 interesting hits were detected. Then, the cross-linking times for the better hits were measured on the SMP. Some of these seem to be more efficient than DBTDL and exhibit a good stability during storage in cartridges...
January 24, 2019: ACS Combinatorial Science
Mitsutaka Takeda, Atsuhisa Mitsui, Kazunori Nagao, Hirohisa Ohmiya
The copper-catalyzed reductive coupling of two different carbonyl compounds has been achieved. The reaction of aromatic aldehydes and arylketones with a silylboronate in the presence of a catalytic amount of CuCl-N-heterocyclic carbene (NHC) complex and a stoichiometric amount of alkoxide base yielded cross-coupled 1,2-diol derivatives. A reaction pathway is proposed that involves the catalytic formation of a nucleophilic a-silyloxybenzylcopper(I) species from the aromatic aldehyde and its subsequent coupling with the arylketone...
January 17, 2019: Journal of the American Chemical Society
André Santos Fernandes, Philippe Maitre, Thiago Carita Correra
The Katsuki-Sharpless epoxidation reaction is one of the most recognized chiral catalytic reactions, allowing for chiral epoxides to be used as starting materials for a series of synthetic pathways. The complete understanding of this reaction mechanism depends on the identification and description of species formed from Ti(IV) alkoxides and alkyl tartrates precatalysts. Despite previous reports on the nature of a bimetallic catalyst based on IR spectroscopy and NMR analysis, some debate remains. Therefore, we carried out mass spectrometry analysis by direct extraction of the ions from the reaction media by ESI(-)-FT-ICR and evaluated the observed ions by CID and IRMPD experiments...
January 10, 2019: Journal of Physical Chemistry. A
He Dong, Ying Zheng, P Hu
Furfural conversion via hydrodeoxygenation pathways on the Ru/Co3O4 surface is thoroughly investigated using density functional theory calculations. All feasible steps are identified. It is found that an oxygen vacancy is necessary to be generated in the form of water for the subsequent hydrodeoxygenation of furfural. The furfural adsorbs at oxygen vacancy sites in an η2(C-O) pattern. The hydrodeoxygenation product, 2-methylfuran, is yielded via the hydrogenation of furfural into furyl-CH2O alkoxide intermediate, followed by C-O cleavage, and finally the hydrogenation of the unsaturated furyl-CH2 species...
January 8, 2019: Physical Chemistry Chemical Physics: PCCP
Luis M Martínez-Prieto, Pilar Palma, Juan Cámpora
Monomeric alkoxo complexes of the type [(iPrPCP)M-OR] (M = Ni or Pd; R = Me, Et, CH2CH2OH; iPrPCP = 2,6-bis(diisopropylphosphino)phenyl) react rapidly with CO2 to afford the corresponding alkylcarbonates [(iPrPCP)M-OCOOR]. We have investigated the reactions of these compounds as models for key steps of catalytic synthesis of organic carbonates from alcohols and CO2. The MOCO-OR linkage is kinetically labile, and readily exchanges the OR group with water or other alcohols (R'OH), to afford equilibrium mixtures containing ROH and [(iPrPCP)M-OCOOH] (bicarbonate) or [(iPrPCP)M-OCOOR'], respectively...
January 4, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
Eddie L Myers, Michael J Palte, Ronald T Raines
The identification and understanding of structure-activity relationships is vital for rational catalyst design. A kinetic study of the hydrogen-deuterium exchange reaction of cyclohexanone in aqueous solution, as catalyzed by proline derivatives, has revealed valuable structure-activity relationships. In phosphate-buffered solution, cis-4-fluoroproline is more active than the trans isomer, a distinction that appears to originate from a destabilizing interaction between the fluorine atom and phosphate anion during general acid catalyzed dehydration of the carbinolamine intermediate...
January 2, 2019: Journal of Organic Chemistry
Yanmei Wen, Chunmei Deng, Jianying Xie, Xinhuang Kang
Diboron reagents have been traditionally regarded as "Lewis acids", which can react with simple Lewis base to create a significant nucleophilic character in one of boryl moieties. In particular, bis(pinacolato)diboron (B₂pin₂) reacts with simple Lewis bases, such as N -heterocyclic carbenes (NHCs), phosphines and alkoxides. This review focuses on the application of trivalent nucleophilic boryl synthon in the selective preparation of organoboron compounds, mainly through metal-free catalytic diboration and the β-boration reactions of alkynes and alkenes...
December 28, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Alexander A Vinogradov, Dmitrii M Roitershtein, Mikhail E Minyaev, Konstantin A Lyssenko, Ilya E Nifant'ev
The title compound, [Al2 La2 (C20 H15 O2 )4 (CH3 )6 (CH3 O)2 ]·4CH3 C6 H5 or [{La(Ph3 CCOO)2 (Me3 AlOMe)}2 ]·4CH3 C6 H5 , was formed in a reaction between lanthanum tris-(tetra-methyl-aluminate) and tri-phenyl-acetic acid (1:1) with unintended partial oxidation. The tri-phenyl-acetate ligand exhibits μ2 -κ1 O :κ1 O ' bridging and μ2 -κ2 O , O ':κ1 O semi-bridging coordination modes, forming a dimeric La2 (μ-OCO)4 core. The semi-bridging tri-phenyl-acetate group provides additional bonding with an La3+ cation via the π-system of one of its phenyl rings...
December 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Yidong Liu, Song Liu, Dongmei Li, Nan Zhang, Lei Peng, Jun Ao, Choong Eui Song, Yu Lan, Hailong Yan
The development and characterization of enantioselective catalytic kinetic resolution of allylic alcohols through asymmetric isomerization with chiral BINOL derivatives-based alkoxides as bifunctional Brønsted base catalyst were described in the study. A number of chiral BINOL derivatives-based alkoxides were synthesized and their structure-enantioselectivity correlation study in asymmetric isomerization identified a promising chiral Brønsted base catalyst, which afforded various chiral secondary allylic alcohols (ee up to 99%, s factor up to >200)...
December 18, 2018: Journal of the American Chemical Society
Eric Steffensmeier, Matthew T Swann, Kenneth M Nicholas
The oxo-vanadium-catalyzed redox disproportionation of activated alcohols (oxidation-reductive coupling, Ox-RC) produces carbonyl compounds and hydrocarbon dimers. A mechanistic study of this novel reaction is reported herein. Following our initial disclosure, new findings include the following: (1) The [(salimin)VO2 ]- -catalyzed Ox-RC of Ph2 CHOH in the presence of fluorene affords the products of H-atom abstraction and all possible hydrocarbon dimers. (2) Electronic substituent effects on the relative rates of Ox-RC with respect to 4-X-BnOH reactants and Bu4 N[(Y-salimin)VO2 ] catalysts (1a-c) reveal (a) a correlation of the oxidation rate of X-BnOH reactants with the radical σ parameter and (b) correlation of the oxidation rate for (Y-salimin)VO2 - with the standard Hammett σ parameter...
December 7, 2018: Inorganic Chemistry
Ghafar Ali, Yang Jeong Park, Arif Hussain, Sung Oh Cho
The present work reports the formation of three-dimensional (3D) nanoflowers like morphology of iron-alkoxide via anodization of Fe-sheet in ethylene glycol (EG) electrolyte. XRD, FESEM, EDX, XPS, Raman and FTIR are applied to characterize the samples. SEM results show that the as-anodized sample is composed of 3D nanoflowers with hierarchical nanosheets beneath it. Average width of the nanoflower petal is ~ 25 nm and length is about 1 µm. The 3D nanoflowers is transformed into spherical nanoparticles (NPs) with uniform size when calcined at elevated temperature...
November 30, 2018: Nanotechnology
Tomasz Pietrzak, Iwona Justyniak, Jiwon Victoria Park, Michał Terlecki, Łukasz Kapuśniak, Janusz Lewinski
Despite decades of extensive studies on the reactivity of magnesium alkyls towards O₂, the isolation and structural characterization of discrete products of these reactions still remains a challenge. Although the formation of the most frequently encountered magnesium alkoxides via unstable alkylperoxide intermediates has commonly been accepted, the latter species have been elusive for over 100 years. Probing the oxygenation of a well-defined neo-pentylmagnesium complex stabilized by a β-diketminate ligand, (dippBDI)MgCH₂CMe₃, we report on the isolation and structure characterization of both a dimeric magnesium alkoxide [(dippBDI)Mg(µ-OCH₂CMe₃)]2 and the first example of monomeric magnesium alkylperoxide [(dippBDI)Mg(thf)OOCH₂CMe₃] (dippBDI = [(ArNCMe)₂CH]- and Ar = C₆H₃iPr₂-2,6)...
December 5, 2018: Chemistry: a European Journal
Ze Kan, Wenlong Luo, Tong Shi, Chuanzhi Wei, Binghao Han, Dejuan Zheng, Shaofeng Liu
Ring-opening polymerization (ROP) of cyclic esters/lactones by efficient catalysts is a powerful method for synthesis of biodegradable and biocompatible polyesters with well-defined structures. To develop catalytic systems that are fast, selective and controlled is a persistent effort of chemists. In this contribution, we report a binary urea/alkoxide catalytic system that could catalyze ROP of rac -LA in a fast (over 90% conversion within 1-2 min), stereoselective ( P i up to 0.93) and controlled manner, indicated by narrow MW distributions, linear relationship between the monomer conversions and M n s, end-group fidelity, and chain extension experiments...
2018: Frontiers in Chemistry
Alexandre Amormino S Gonçalves, Mietek Jaroniec
The one-pot synthesis of nanostructured ternary mixed oxides is challenging due to the heterogeneous nature of the hydrolysis and condensation processes of all metal oxide precursors. In addition, the solvents and additives used can affect these processes too. Herein, we report the effect of different solvents (ethanol, 1- and 2-propanol, or butanol) and additives (citric acid or 1,3,5-triisopropylbenzene) used on the formation of binary and ternary alumina-based oxides, NiO-Al2 O3 , NiO-TiO2 -Al2 O3 , and NiO-ZrO2 -Al2 O3 in the presence of triblock copolymer Pluronic P123 used as a soft template...
November 14, 2018: Journal of Colloid and Interface Science
Rafael O Costa, Sarah S Ferreira, Crystiane A Pereira, Jeffrey R Harmer, Christopher J Noble, Gerhard Schenk, Roberto W A Franco, Jackson A L C Resende, Peter Comba, Asha E Roberts, Christiane Fernandes, Adolfo Horn
The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2 BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)](ClO4 )·2H2 O, 1 , in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2 BPClNOL, a phenoxide and an alkoxide group...
2018: Frontiers in Chemistry
Jianrong Steve Zhou, Xiaohu Zhao, Haiyan Xu, Xiaolei Huang
asymmetric reductive amination of poorly nucleophilic sulfonamides is realized in the presence of nickel catalysts and titanium alkoxide. A wide range of enolizable ketones, including some dialkyl and biaryl ketones, were converted in one pot to sulfonamides in excellent enantiomeric excess. The method is also applicable to cyclization of sulfamates and intermolecular reductive amination of a diarylphosphinamide. Formic acid was used as a safe and economic surrogate of high-pressure hydrogen gas.
October 30, 2018: Angewandte Chemie
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