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71.
The reduction of prochiral ketones using chiral reducing reagents, prepared from lithium aluminum hydride and (-)-(1R, 2S, 3S, 5R)-10-anilinopinanediol (5) and (-)-(1R, 2S, 3S, 5R)-10-N-methylanilinopinanediol (6), affords chiral secondary alcohols in useful chemical yields (70 ~ 93%) but in low optical purity (8 ~ 33% ee). Modifiers 5 and 6 are synthesized from (lR)-(-)-β-pinene in three steps. 相似文献
72.
J. L. Gautier E. Meza E. Silva C. Lamas C. Silva 《Journal of Solid State Electrochemistry》1997,1(2):126-133
The electrochemical insertion of lithium in the spinel-type manganite with the formula ZnNi
y
Mn2–
y
O4 has been studied. The galvanostatic discharge curves show that the best performance is obtained for y = 0.25, where a tetragonal to cubic structural transformation occurs. The thermodynamics and kinetics of the process of insertion
of the lithium into the tetragonal spinel Li
x
ZnNi0.25Mn1.75O4 (x = 0.05–1.3) have been studied. The molar thermodynamic quantities, such as enthalpy, entropy and free energy determined by
EMF-T measurements, varied with the lithium concentration in the oxide structure, and a major variation was observed around
x = 0.8. The chemical diffusion coefficient of lithium in these spinels was also determined. Structural analysis, degree of
oxidation and magnetic susceptibility measurements were carried out for the lithiated oxides in order to obtain the cationic
distribution as a function of x. It has been possible to demonstrate that, upon lithium insertion, Mn4+ ions on B sites are reduced to Mn3+ and then to Mn2+. A cooperative Jahn-Teller effect is present in these spinel manganese-nickel oxides.
Received: 4 February 1997 / Accepted: 11 April 1997 相似文献
73.
F. Schaller W. Schwarz H.-D. Hausen K. W. Klinkhammer J. Weidlein 《无机化学与普通化学杂志》1997,623(9):1455-1466
Base-free Tris(trimethylsilyl)methyl Derivatives of Lithium, Aluminium, Gallium, and Indium Base-free LiR* (R*=-C(SiMe3)3) has been prepared from R*Cl and Li-metal in toluene at 85?90°C and used to synthesize the metallanes R*MMe2 with M = Al, Ga and In, respectively. The NMR (1H, 13C, 29Si) and the vibrational spectra of these trisyl compounds have been discussed. AlCl3 and LiR*(ratio 1 : 1) forms the metallate metallate Li[R*AlCl3]. The triclinic unit cell (space group P1 ) consists of a centrosymmetric assoziate, formed by four Li[R*AlCl3]- units with Al? Cl…?Li bridges, two pairs of Li-atoms differing in their chlorine-coordination and two disordered toluene molecules, inserted in the crystal lattice (R1wR2 =0,0444/0,1072). The reaction of GaCl3 with LiR* (I :1) gives the unusual sesquichloride (R*Ga(Cl1,33)Me0,67)3 in moderate yield. The X-ray structure determination shows a Ga3Cl3-skeleton with chairconformation and disordered, terminal gallium ligands (R1/wR2= 0,0646/0,2270). 相似文献
74.
Sc2Ni2In was prepared by a reaction of the elemental components in an are furnace and subsequent annealing at 1070 K. Sc2Ni2In is a Pauli paramagnet and a poor metallic conductor with a specific resistivity of 224 mΩcm at room temperature. Its crystal structure was refined from X-ray powder data: P4/mbm, a = 716.79(1) pm, c = 333.154(8) pm, Z = 2, Rwp = 0.040, and RB(I) = 0.026. Sc2Ni2In crystallizes with a ternary ordered version of the U3Si2-type structure. The nickel and indium atoms occupy [NiSc6] trigonal prisms and [InSc8] square prisms, respectively. These structural fragments are derived from the AlB2 and CsCl-type structures. Semi-empirical band structure calculations reveal Sc2Ni2In to be a nickelide, and the strongest bonding interactions are found for the Sc? Ni contacts, followed by Sc? In and Ni? In. A rigidband model suggests the existence of the isotypic phase Sc2Ni2Sb. 相似文献
75.
Reaction steps and mechanisms of the thermal dehydration of lithium metaborate dihydrate were investigated by means of thermoanalytical measurements, high temperature powder X-ray diffractometry, FT-IR spectroscopy, and microscopic observations. The first half of thermal dehydration was characterized by the melting of the sample producing viscous surface layer, the formation of bubbles on the particle surfaces, and the sudden mass-loss taking place by an opportunity of cracking and/or bursting of the bubble surface layer. The second half of the dehydration with a long-tailed mass-loss process in a wide temperature region was divided further into three distinguished reaction steps by the measurements of controlled rate thermal analysis. During the course of the thermal dehydration, four different poorly crystalline phases of intermediate hydrates were observed, in addition to an amorphous phase produced by an isothermal annealing. Just after completing the thermal dehydration, an exothermic DTA peak of the crystallization of β-LiBO2 was appeared at around 750 K. The phase transition from β-LiBO2 to α-LiBO2 was observed in the temperature range of 800-900 K, which subsequently melted by indicating a sharp endothermic DTA peak with the onset temperature at 1101.4 ± 0.6 K. 相似文献
76.
Dietmar Rahner Stefan Machill Heike Schlörb Kerstin Siury Matthias Kloss Waldfried Plieth 《Journal of Solid State Electrochemistry》1998,2(2):78-84
An overview is given of intercalation materials for both the negative and the positive electrodes of lithium batteries, including
the results of our own research. As well as lithium metal as a negative electrode, we consider insertion materials based on
aluminium alloys. In the case of the positive electrode metal-oxides based on manganese, nickel and cobalt are discussed.
Received: 27 May 1997 / Accepted: 30 July 1997 相似文献
77.
78.
Two chromogenic monoaza crown ethers were synthesized and investigated for their lithium extraction capabilities. The chromogenic monoaza 14-crown-4 compound exhibited the best selectivity for lithium over sodium; ca. 2800, with a detection limit of 0.08 ppm. 相似文献
79.
Xingang Kong Jiarui Zhang Jianfeng Huang Jiayin Li Yi Qin Ting Zhao Qi Feng 《中国化学快报》2019,30(3):771-774
SnNb2O6 and Sn2Nb2O7 nanosheets were synthetized via microwave assisted hydrothermal method, and innovatively employed as anode materials for lithium-ion battery. Compared with Sn2Nb2O7 and the previously reported pure Sn-based anode materials, the SnNb2O6 electrode exhibited outstanding cycling performance. 相似文献
80.
Jun Wang Michael G. Gardiner Brian W. Skelton 《Journal of organometallic chemistry》2005,690(1):220-227
The synthesis of 2,5-bis{(diethyl-3′-indolyl)methyl}furan by the acid catalysed condensation of 2,5-bis(diethylhydroxymethyl)furan with indole is presented. Dilithium, disodium and dipotassium derivatives are prepared by the reaction of the bis(indole) with n-BuLi, NaH and K, respectively, in the presence of various Lewis bases. The X-ray structures of 2,5-bis{(diethyl-3′-indolyl)methyl}furan and the dilithiated derivative (as a polymeric tetrahydrofuran adduct) are reported. 相似文献