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991.
Combining diaryl-calixarenyl phosphines with [Ni(cod)(2)] resulted in highly active Kumada-Tamao-Corriu cross-coupling catalysts. With one of the ligands, TOFs up to 439,000 mol(ArBr) mol(Ni)(-1) h(-1) were observed in the reaction of 1-bromonaphthalene with PhMgBr. The systems were also found to be active at room temperature with aryl chlorides. 相似文献
992.
Bourdreux Y Lemétais A Urban D Beau JM 《Chemical communications (Cambridge, England)》2011,47(7):2146-2148
Tandem catalysis by using iron(III) chloride hexahydrate leads to carbohydrate building blocks displaying an orthogonal protecting group pattern as illustrated by the regioselective protection of trehalose and maltose disaccharides. 相似文献
993.
Stephan Dominique Andres Winfried Hochstättler Christiane Schallück 《Discrete Applied Mathematics》2011,159(16):1660-1665
We prove that the game chromatic index of n-wheels is n for n≥6. 相似文献
994.
Reaction of 4′-(3-pyridyl)-2,2′:6′,2′′-terpyridine (pyterpy) with Cu(hfacac)2 (hfacac = hexafluoroacetylacetonate) led to the formation of the novel compound [Cu3(hfacac)4(μ-pyterpy)2][Cu(hfacac)3]2 (1). The structure is composed of a trinuclear [Cu3(hfacac)4(μ-pyterpy)2]2+ cation and two [Cu(hfacac)3]− anionic species. The cation consists of a chain of three CuII atoms connected by bridging pyterpy ligands. The [Cu(hfacac)3]− anions have the hfacac ligands coordinated in their usual chelating manner through their carbonyl O donors. Besides the coulombian forces, the ionic species are fixed by C-H?O, C-H?F, F?F and a variety of unusual inter-ion C-F?π interactions that control the packing motif. These π-interactions involve the terpyridine groups from the pyterpy ligand and the five-membered rings of the chelating hexafluoroacetylacetonate anions. 相似文献
995.
Sophie Fournier Cyril Cugnet Alain Vallat Charles H. Devillers Yoann Rousselin Marek M. Kubicki Dominique Lucas Yves Mugnier Pierre D. Harvey 《Journal of Cluster Science》2010,21(4):837-856
Abstract
The reactivity of the trinuclear palladium cluster [Pd3(dppm)3(CO)] n+ (dppm = bis(diphenylphosphinomethane); n = 2, 1) towards F− was investigated by electrochemical and spectroscopic methods. The reaction depends on the charge of the cluster. The chemical reduction of the cluster dication is observed in the presence of F− generating the paramagnetic monocationic cluster. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) provided evidence for the radical F• as an intermediate. In a similar manner to the dication, the monocationic cluster [Pd3(dppm)3(CO)]+ is also reduced, but in a slower process, by the F− ion to produce [Pd3(dppm)3(CO)]0. Additionally, the alkyne cluster adducts [Pd3(dppm)3(CO)(RCCR)] n+ (n = 2, 1; R = CO2Me) are also reactive towards F−. Particularly, the dication adduct leads to a metastable fluoride adduct [Pd3(dppm)3(CO)(RCCR)(F)]+. The electroreductive behavior of this adduct involves electron-transfer steps and F− exchange equilibriums, for which digital simulation enables the extraction of the thermodynamic parameters (standard potentials and equilibrium constants). Concurrently, the monocation adduct [Pd3(dppm)3(CO)(RCCR)]+ with F−, leads to a disproponation generating 0.5 equiv. of [Pd3(dppm)3(CO)(RCCR)(F)]+ and 0.5 equiv. of [Pd3(dppm)3(CO)(RCCR)]0. The former slowly evolves to [Pd3(dppm)3(RCCR)(F)]+, which was described by X-ray diffraction method. 相似文献996.
We study the problem where a robot has to pick up items of different sizes which are stored along a corridor. A natural requirement is that the items have to be collected in decreasing order of their sizes. We deal with various systems according to the location of the Entry/Exit station where the robot unloads the collected items after each trip along the corridor. The links of these systems with generalized coloring problems and other applications such that train shunting and pallet loading problems are discussed and related results are obtained. We conclude with several open questions on the topic. 相似文献
997.
Valore A Balordi M Colombo A Dragonetti C Righetto S Roberto D Ugo R Benincori T Rampinini G Sannicolò F Demartin F 《Dalton transactions (Cambridge, England : 2003)》2010,39(42):10314-10318
Various Ru(II) complexes with substituted 1,10-phenanthroline or 4,5-diazafluorene are characterized by a good to very large second order NLO response, as determined by EFISH. Among these complexes, [Ru(9-fulleriden-4,5-diazafluorene)(PPh(3))(2)Cl(2)] is particularly appealing due to its huge second-order NLO response and its transparency to the second harmonic generation. The structure of cis-Cl,trans-PPh(3)-[Ru(5-NO(2)-1,10-phen)(PPh(3))(2)Cl(2))] was determined by single-crystal X-ray diffraction. 相似文献
998.
999.
Spagnoli S Block D Botzung-Appert E Colombier I Baldeck PL Ibanez A Corval A 《The journal of physical chemistry. B》2005,109(18):8587-8591
Spectroscopic and kinetic properties of a new photochromic medium, consisting of nanocrystals of spyropyran molecules (1,3-dihydro-1,3,3,5',6',pentamethyl-spiro[2H-indole-2,2'-[2H]pyrano [3,2-b]pyridinium] iodide) embedded in an organo-silicate sol-gel film, are presented and compared to microcrystals obtained by slow evaporation of a solvent. High photoconversion efficiencies for both kinds of crystals have been observed. In microcrystals, the photomerocyanine form absorbs at 570 nm with a fading rate of 5 h, in nanocrystals the photomerocyanine form absorbs at 535 nm with a fading rate of 41 h. Therefore, the crystalline structure of nanocrystals is different from the microcrystal one. 相似文献
1000.
A vriable step size control algorithm for the weak approximation of stochastic differential equations is introduced. The algorithm
is based on embedded Runge–Kutta methods which yield two approximations of different orders with a negligible additional computational
effort. The difference of these two approximations is used as an estimator for the local error of the less precise approximation.
Some numerical results are presented to illustrate the effectiveness of the introduced step size control method.
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