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Reaction between Silicon Difluoride and 3,3,3-trifluorpropyne
No full text[[abstract]]Silicon difluoride has been found to undergo a wide variety of reactions a t low temperatures. In reactions with alkenes and alkynes the products identified are usually consistent with a mechanism involving attack of biradicals .SiFz(SiFz),SiFz. (n = 0, 1, 2, etc.) on the carbon-carbon multiple bond in the unsaturated molecule. In many of the reactions a rearrangement involving the shift of a hydrogen atom is also observed, giving chain rather than cyclic products. In this note we report the results of the reaction between silicon difluoride and trifluoropropyne, which was studied since the possibilities for rearrangement might have been more limited than in the case of nonfluorinated alkynes.[[fileno]]2010311010002[[department]]化學
Photochemical Preparation of Transition-Metal Carbonyl Compounds with 1,1,2,2-Tetrafluoro-1,2-disilacyclobutenes as Ligands
No full text[[abstract]]Organometallic compounds involving a five-membered disilametallacyclic structure are conveniently prepared by photochemical reactions between 1,1,2,2-tetrafluoro- 1,2-disilacyclobutene and transition-metal carbonyls (M = Mo, Fe, Mn, and Co). The reaction mechanism can be rationalized as an initial dissociation of M-CO followed by oxidative addition of the Si-Si bonds to the coordinatively unsaturated metal carbonyl species. Some intermediates, the olefin complexes, can be isolated and converted to the disilametallacyclic compounds by further irradiation.[[fileno]]2010311010020[[department]]化學
Reactions of Difluorosilylene with Isonitriles
No full text[[abstract]]The reactions of difluorosilylene with some isocyanides R-N=C (R=CH3, C2H5, t-C4H9) are studiedin the gas phase and by cocondensation method. The results show, for the first time in the study of SiF2chemistry, that the mechanisms in gas phase experiments and cocondensation experiments are essentiallythe same. The reactions can be rationalized by an initial attack of difluorosilylene on the carbon end ofisocyanides to generate alkyl radicals which lead to the formation of various gas products and polymeriza-tions. In the cocondensation reaction of methyl isocyanide, chemiluminescence and isomerization areobserved accompanying the formation of large amount of methane. A plausible reaction mechanism isproposed and compared with other possible reaction pathways. The unusually rapid reactions betweendifluorosilylene and isonitriles are severely inhibited by the presence of oxygen.[[fileno]]2010311010024[[department]]化學
Alcoholysis of (2-methoxycarbonyl)ethyltin compounds
No full text[[abstract]]Under acid or base catalysis, di(2-alkoxycarbonylethyl)tin dichlorides of various R groups, (ROCOCH2CH2)2SnCl2, can be prepared conveniently in high yield by alcoholysis of (CH3OCOCH2CH2)2SnCl2 in various alcohols, ROH (R = C2H5, C4H9, iso-C4H9, C5H11, C6H5CH2, C4H9CH(C2H5)CH2). When excess acid or base is present in the aqueous solution, (ROCOCH2CH2)2SnCl2 eliminate ROH and precipitate as C6H8O4Sn regardless of the R group. C6H8O4Sn can be converted into various (ROCOCH2CH2)2SnCl2 derivatives on dissolving in alcoholic HCl solutions.[[fileno]]2010311010032[[department]]化學
Polygon Building Block Route to sp2 Carbon Based Materials
No full text[[abstract]]Pentagonal- and hexogonal-shaped building block precursors provide a novel, high-yield method for the preparation of carbon onions and nanosized graphite particles. A reaction of hexachlorocyclopentadiene (C5Cl6) with sodium (see Figure) offers carbon onions with 8-50 spherical and elliptical shells. The same reaction with hexachlorobenzene (C6Cl6) results in a mixture of graphite crystallites.[[fileno]]2010311010064[[department]]化學
Preparation and Characterization of Volatile Alkaline-Earth Metal Complexes with Multiple Coordinated Aminoalkoxide Ligands
No full text[[abstract]]The aminoalkoxide complexes Sr(amak)2 (1) and Ba(amak)2 (2) were prepared by treatment of a multiply-chelating fluorinated aminoalcohol ligand HOC(CF3)2CH2N(CH2CH2OMe)2, (amak)H, with the Group 2 metal reagents Sr(OPri)2 and BaH2 respectively. Single crystal X-ray diffraction studies indicate that complex 1 possesses an 8-coordinate distorted bicapped octahedral geometry with all O and N atoms coordinated to the central Sr cation. However, complex 2 adopts a unique 10-coordinate bicapped square antiprismatic structure, of which the coordination number is increased by two fluorine-to-barium dative interactions. Variable temperature 19F NMR studies show the existence of two inter-convertible isomers in solution and their possible molecular structures are proposed according to their structures in the solid-state. Preliminary investigation suggests that these complexes are good CVD source reagents for depositing SrF2 and BaF2 thin films.[[fileno]]2010311010065[[department]]化學
Rational Color Tuning and Luminescent Properties of Functionalized Boron-Containing 2-Pyridyl Pyrrolide Complexes
No full text[[abstract]]Three systematically functionalized pyrrolide ligands were prepared via the coupling of methyl vinyl ketone and the respective carbaldehyde reagents, followed by treatment of the pre-formed dicarbonyl compounds with (NH4)(2)CO3 in order to generate the required pyrrole fragment. These ligands readily reacted with the boron reagent BPh3 to afford the complexes [(pyro)BPh2] (2a), [(noro)BPh2] (2b), and [(xaro)BPh2] (2c), where (pyro)H, (noro)H, and (xaro)H represents the 2-pyridyl, 2-quinolinyl, and 2-quinoxalinyl pyrrole groups, respectively. Complexes 2a-2c give stable solutions in air, and show strong photoluminescence with emission peak maxima located at 490 nm, 510 nm, and 575 nm, respectively. Calculations based upon time-dependent density function theory (TDDFT) show that the S-1 state in these complexes is attributed to an allowed (pi-symmetry) -> pi* (pi-symmetry) transition located at the chelating pyrrolide moieties. Electroluminescence (EL) devices based on 2c were fabricated. The EL emission from 2c as the host-emitter, with the emission peak maximum shifted to 580 nm, was observed when BCP was used as the hole blocking material. This device produces saturated red-orange light-emission at an onset voltage of 8 V and a maximum brightness of 5000 cd m(-2) at a driving voltage of 15 V, the external quantum yield is estimated to be 0.5 %.[[fileno]]2010311010083[[department]]化學
Cooperative Jahn-Teller Effect in Dysprosium Antimonide
No full text[[abstract]]We have analyzed the recent magneto-thermal and elastic data on dysprosium antimonide. Within the framework of the molecular field approximation we fit the data by using a model Hamiltonian which contains besides the crystal field term, bilinear and biquadratic pair interactions and a strain coupling of the lattice to the magnetic ions. The softening of the elastic constant (1/2)(C11-C12) above the transition at 9.5°K is due to a strain coupling. This coupling dominates over the remaining biquadratic pair interactions of comparable magnitudes but opposite signs. We determine the bilinear coupling by fitting the magneto-thermal data below the ordering temperature. We find that in DySb the biquadratic coupling is as important as the bilinear.[[fileno]]2010111030002[[department]]物理
Migdal-Kadanof Renormalization for the Exchange Interaction Model
No full text[[abstract]]The Migdal-Kadanoff (MK) renormalization group transformation is derived for the spin-S exchange interaction model. Both the standard MK approach and a modified MK method are used to determine critical temperatures of the model for various spin values.[[fileno]]2010111010034[[department]]物理
Fuzzy Logic and the Resolution Principle
No full text[[abstract]]The relationship between fuzzy logic and two-valued logic in the context of the first order predicate calctflus is discussed. It is proved that if every clause in a set of clauses is somethblg more than a "half-truth" and the most reliable clause has truth-value a and the most unreliable clause has truth-value b, then we are guaranteed that all the logical con- sequences obtained by repeatedly applying the resolution principle will have truth-value between a and b. The significance of this theorem is also discussed.[[fileno]]2030256010003[[department]]資訊工程學