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排序方式: 共有1043条查询结果,搜索用时 31 毫秒
1.
Giuseppe Spedalotto Dr. Robert Gericke Marta Lovisari Dr. Erik R. Farquhar Dr. Brendan Twamley Dr. Aidan R. McDonald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11983-11990
Hydroxide-bridged high-valent oxidants have been implicated as the active oxidants in methane monooxygenases and other oxidases that employ bimetallic clusters in their active site. To understand the properties of such species, bis-μ-hydroxo-NiII2 complex ( 1 ) supported by a new dicarboxamidate ligand (N,N′-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide) was prepared. Complex 1 contained a diamond core made up of two NiII ions and two bridging hydroxide ligands. Titration of the 1 e− oxidant (NH4)2[CeIV(NO3)6] with 1 at −45 °C showed the formation of the high-valent species 2 and 3 , containing NiIINiIII and NiIII2 diamond cores, respectively, maintaining the bis-μ-hydroxide core. Both complexes were characterised using electron paramagnetic resonance, X-ray absorption, and electronic absorption spectroscopies. Density functional theory computations supported the spectroscopic assignments. Oxidation reactivity studies showed that bis-μ-hydroxide-NiIII2 3 was capable of oxidizing substrates at −45 °C at rates greater than that of the most reactive bis-μ-oxo-NiIII complexes reported to date. 相似文献
2.
Investigation of N‐Heterocyclic Carbene‐Supported Group 12 Triflates as Pre‐catalysts for Hydrosilylation/Borylation 下载免费PDF全文
Matthew M. D. Roy Dr. Michael J. Ferguson Dr. Robert McDonald Prof. Dr. Eric Rivard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18236-18246
N‐Heterocyclic carbene (NHC) complexes of Cd and Hg triflates (OTf) were prepared and their attempted conversion into rare cadmium and mercury hydrides was explored. In contrast to zinc, which forms stable [ZnH]+ complexes with NHCs, the heavier Cd and Hg congeners could not be formed; the increased instability of Cd‐H and Hg‐H units was rationalized with the aid of computations. It was also discovered that the dimeric adduct [IPr?Cd(μ‐OTf)2]2 (IPr=[(HCNDipp)2C:]; Dipp=2,6‐iPr2C6H3) is an active precatalyst for the hydrosilylation and hydroborylation of hindered aldehydes and ketones. The related zinc congener was inactive as a catalyst highlighting a distinct advantage of using heavy Group 12 metals to promote catalytic hydrosilylation/borylation. 相似文献
3.
Cover Picture: Thermal and Photolytic Transformation of NHC–B,N‐Heterocycles: Controlled Generation of Blue Fluorescent 1,3‐Azaborinine Derivatives and 1H‐Imidazo[1,2‐a]indoles by External Stimuli (Chem. Eur. J. 40/2015) 下载免费PDF全文
4.
Dr. Saurabh S. Chitnis Prof. Neil Burford Prof. Jan J. Weigand Dr. Robert McDonald 《Angewandte Chemie (International ed. in English)》2015,54(27):7828-7832
Reactions of triarylphosphines with fluoroantimony(III) triflates give phosphine antimony(III) complexes, which undergo spontaneous reductive elimination of fluorophosphonium cations. The resulting phosphine antimony(I) complexes catenate to give the first examples of cationic antimony bicyclic compounds, [(R3P)4Sb6]4+, featuring a bicyclo[3.1.0]hexastibine framework stabilized by four phosphine ligands. The unprecedented 14‐electron redox process illustrates the generality of the reductive catenation method. 相似文献
5.
dm Tlgyesi Tams Farkas Mria Blint Thomas J. McDonald Virender K. Sharma 《Molecules (Basel, Switzerland)》2021,26(4)
Alternaria toxins are emerging mycotoxins whose regulation and standardization are in progress by the European Commission and the European Committee for Standardization. This paper describes a dilute and shoot approach to determine five Alternaria toxins in selected food samples using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The strategy involves sample extraction with acidified aqueous methanol, followed by a solvent change accomplished via sample evaporation and reconstitution. The quantification is based on isotope dilution, applying all corresponding isotopically labeled internal standards to compensate possible matrix effects of the analysis. The main advantages of the present method over other existing methods includes simple and effective sample preparation, as well as detection with high sensitivity. The five-fold sample dilution can decrease matrix effects, which were evaluated with both external and internal standard methods. The results demonstrated a limit of quantification lower than 1.0 µg/kg for all five analytes for the first time. The newly presented method showed acceptable accuracy (52.7–111%) when analyzing naturally contaminated and spiked standard samples at the described levels. The method was validated for tomato-based and flour samples (wheat, rye, and maize). The absolute recovery ranged from 66.7% to 91.6% (RSD < 10%). The developed method could be an alternative approach for those laboratories that exclude sample cleanup and pre-concentration of state-of-the-art instruments with enhanced sensitivity. 相似文献
6.
Hyung-gyu Jun Thomas R. Way Bjrn Lfgren Mats Landstrm Alvin C. Bailey Eddie C. Burt Timothy P. McDonald 《Journal of Terramechanics》2004,41(4):209-222
A Trelleborg Twin 421 Mark II 600/55-26.5 steel-reinforced bias-ply forwarder drive tire at inflation pressures of 100 and 240 kPa and dynamic loads of 23.9 and 40 kN was used at 5% travel reduction on a firm clay soil. Effects of dynamic load and inflation pressure on soil–tire contact pressures were determined using six pressure transducers mounted on the tire tread. Three were mounted on the face of a lug and three at corresponding locations on the undertread. Contact angles increased with decreases in inflation pressure and increases in dynamic load. Contact pressures on a lug at the edge of the tire increased as dynamic load increased. Mean and peak pressures on the undertread generally were less than those on a lug. The peak pressures on a lug occurred forward of the axle in nearly all combinations of dynamic load, inflation pressure, and pressure sensor location, and peak pressures on the undertread occurred to the rear of the axle in most of the combinations. Ratios of the peak contact pressure to the inflation pressure ranged from 0 at the edge of the undertread for three combinations of dynamic load and inflation pressure to 8.39 for the pressure sensor on a lug, near the tire centerline, when the tire was underinflated. At constant dynamic load, net traction and tractive efficiency decreased as inflation pressure increased. 相似文献
7.
Jillian S. K. Clark Michael J. Ferguson Robert McDonald Mark Stradiotto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6457-6461
Base‐metal catalysts capable of enabling the assembly of heteroatom‐dense molecules by cross‐coupling of primary heteroarylamines and (hetero)aryl chlorides, while sought‐after given the ubiquity of unsymmetrical di(hetero)arylamino fragments in pharmacophores, are unknown. Herein, we disclose the new “double cage” bisphosphine PAd2‐DalPhos ( L2 ). The derived air‐stable NiII pre‐catalyst C2 functions well at low loadings in challenging test C?N cross‐couplings with established substrates, and facilitates the first Ni‐catalyzed C?N cross‐couplings of primary five‐ or six‐membered ring heteroarylamines and activated (hetero)aryl chlorides, with synthetically useful scope that is competitive with Pd catalysis. 相似文献
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10.
Charles J. McDonald 《Journal of Dispersion Science and Technology》2013,34(3-4):365-392
The structure of a 70/30 ethyl acrylate-acrylamide latex made in a semi-continuous process with surfactant has been investigated. The molar composition and relative concentration of the polymers in the serum phase, on the surface and in the particle were characterized by coupling a filtration procedure, serum replacement, with carbon-13 NMR spectroscopy. The development of polymer in the different phases could be monitored by taking samples at timed intervals during the polymerization. Post-treatment of the latex with sodium hydroxide selectively hydrolyzed the copolymerized ethyl acrylate in the serum and on the surface. By measurement of spin lattice relaxation times it was possible to estimate surface concentration of oligomeric polymer 相似文献