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111.
Preparation, Properties, and Reaction Behaviour of 2-(Dimethylaminomethyl)phenyl- and 8-(Dimethylamino)naphthylsubstituted Lithium Hydridosilylamides – Formation of Silanimines by Elimination of Lithium Hydride The hydridosilylamines Ar(R)Si(H)–NHR′ ( 2 a : Ar = 2-Me2NCH2C6H4, R = Me, R′ = CMe3; 2 b : Ar = 2-Me2NCH2C6H4, R = Ph, R′ = CMe3; 2 c : Ar = 2-Me2NCH2C6H4, R = Me, R′ = SiMe3; 2 d : Ar = 8-Me2NC10H6, R = Me, R′ = CMe3; 2 e : Ar = 8-Me2NC10H6, R = Ph, R′ = CMe3; 2 f : Ar = 8-Me2NC10H6, R = Me, R′ = SiMe3) have been synthesized from the appropriate chlorosilanes Ar(R)SiHCl either by reaction with the stoichiometric amount of Me3CNHLi ( 2 a , 2 b , 2 d , 2 e ) or by coammonolysis in liquid NH3 with chlorotrimethylsilane in molar ratio 1 : 3 ( 2 c , 2 f ). Treatment of 2 a–2 f with n-butyllithium in equimolar ratio in n-hexane resulted in the lithiumhydridosilylamides Ar(R)Si(H)–N(Li)R′ 3 a–3 f . The frequencies of the Si–H stretching vibration and 29Si–1H coupling constants in the amides are smaller than in the analogous amines indicating a higher hydride character for the hydrogen atom of the Si–H group in the amides compared to the amines. Results of NMR spectroscopic studies point to the existence of a (Me2)N → Si coordination bond in the 8-(dimethylamino)naphthyl-substituted amines and amides. The amides 3 a–3 c are stable under refluxing in m-xylene. At the same conditions 3 d and 3 e eliminate LiH and the silanimines 8-Me2NC10H6(R)Si=NCMe3 ( 4 d : R = Me, 4 e : R = Ph) are formed. The amides 3 a–3 d und 3 f react with chlorotrimethylsilane in THF to give the corresponding N-substitution products Ar(R)Si(H)–N(SiMe3)R′ 6 a–6 d and 6 f in good yields. 4 d is formed as a byproduct in the reaction of 3 d with chlorotrimethylsilane. In n-hexane and m-xylene these amides are little reactive opposite to chlorotrimethylsilane. 6 a–6 d and 6 f are obtained in very small amounts. In the case of 3 d besides the N-substitution product 6 d the silanimine 4 d is obtained. In contrast to chlorotrimethylsilane the amides 3 a and 3 f react well with chlorodimethylsilane in m-xylene producing 2-Me2NCH2C6H4(H) SiMe–N(SiHMe2)CMe3 ( 7 a ) and 8-Me2NC10H6(H)SiMe–N(SiHMe2)SiMe3 ( 7 f ). 相似文献
112.
We propose a solution to the η -problem in supergravity (SUGRA) hybrid inflation using a Nambu–Goldstone-like shift symmetry within a new class of models. The flatness of the tree-level inflaton potential is ensured by shift symmetry invariance of the Kähler potential, while a small symmetry breaking term in the superpotential gives rise to a slope of the potential at loop-level. In the proposed class of inflation models, potentially dangerous couplings between the inflaton and the moduli sector are avoided. We also discuss under which conditions the predicted spectral index can be in agreement with the best-fit-value of the latest WMAP observation ns∼0.96, corresponding to a hilltop-type inflaton potential at loop-level. 相似文献
113.
Stefan Antusch Mar Bastero-Gil Koushik Dutta Steve F. King Philipp M. Kostka 《Physics letters. [Part B]》2009
We propose the introduction of a Heisenberg symmetry of the Kähler potential to solve the problems with chaotic inflation in supergravity, as a viable alternative to the use of shift symmetry. The slope of the inflaton potential emerges from a small Heisenberg symmetry breaking term in the superpotential. The modulus field of the Heisenberg symmetry is stabilized and made heavy with the help of the large vacuum energy density during inflation. The observable predictions are indistinguishable from those of typical chaotic inflation models, however the form of the inflationary superpotential considered here may be interpreted in terms of sneutrino inflation arising from certain classes of string theory. 相似文献
114.
We show that the principal order ideal of an element w in the Bruhat order on involutions in a symmetric group is a Boolean lattice if and only if w avoids the patterns 4321, 45312 and 456123. Similar criteria for signed permutations are also stated. Involutions with this
property are enumerated with respect to natural statistics. In this context, a bijective correspondence with certain Motzkin
paths is demonstrated.
This article is largely based on results from the second author’s M.Sc. thesis [15]. 相似文献
115.
J. Zavadil P. Kostka J. Pedlikova K. Zdansky M. Kubliha V. Labas J. Kaluzny 《Journal of Non》2009,355(37-42):2083-2087
Chalcogenide bulk glasses Ge20Se80−xTex for x(0,15) have been prepared by systematic replacement of Se by Te. Selected glasses have been doped with Ho, Er and Pr, and samples have been characterized by transmission spectroscopy, measurements of dc electrical conductivity and low-temperature photoluminescence. Absorption coefficients have been derived from measured transmittance and estimated reflectance. Arrhenius plots of dc electrical conductivity, in the measured temperature range 300–460 K, are characterized by single activation energies roughly equal to the half of the optical gap. Activation energies deduced from Arrhenius plots reveal a systematic decrease with increasing Te content. Similarly, both absorption and low-temperature photoluminescence spectra reveal shifts of absorption edge and/or dominant luminescence band to longer wavelength due to Te → Se substitution. Samples doped with Ho and Er exhibit a strong luminescence at 1200 and 1540 nm due to 5I6 → 5I8 and 4I13/2 → 4I15/2 transitions of Ho3+ and Er3+ ions, respectively. Pr doped samples exhibit only a relatively weak luminescence peak at 1590 nm, which we tentatively assign to 3F3 → 3H4 transition of Pr3+ ions. Absorption of the base glass luminescence at 1460 and 1520 nm has been observed at low temperature on samples doped with Pr and Er, respectively. 相似文献
116.
Svenja Werkmeister Steffen Fleischer Dr. Kathrin Junge Prof. Dr. Matthias Beller 《化学:亚洲杂志》2012,7(11):2562-2568
The first asymmetric hydrogenation/transfer hydrogenation of imines to amines using zinc(II) triflate in combination with chiral ligands is described. The monodentate binaphthophosphepine ligand ( 3g ) provided the highest enantioselectivities. Using different imines, the corresponding amines were obtained in moderate yields and enantioselectivities. 相似文献
117.
118.
The aim of a more precise knowledge about molecular structures and the nature of chemical bonds is the driving force behind the development of numerous experimental methods and theories. Recent soft X-ray based techniques provide novel opportunities for tackling the structure and the dynamics of chemical and biochemical systems in solution. In our research group we are developing experimental methods for mapping the electronic structure and dynamics of molecular systems in solution during bond-building and breaking using soft X-ray absorption and emission spectroscopy. The combination of such recent developments with conventional spectroscopy as well as theoretical modeling allows us to address open questions about hydrogen bonds, thermodynamics and active centers of biological systems. Based on the core-hole clock and pump-probe spectroscopy dynamics on the time scale from sub-femtoseconds up to picoseconds can be revealed. 相似文献
119.
K Butsch A Klein S Nitsche K Stirnat JR Hawkett EJ McInnes M Bauer 《Dalton transactions (Cambridge, England : 2003)》2012,41(37):11464-11475
The new copper complex [Cu(triaz)(2)] (Htriaz = 2,4-di-(tert-butyl)-6-(5-chloro-2H-benzo[d][1,2,3]triazol-2-yl)phenol) was investigated in detail by single crystal XRD, EPR-, UV/Vis-absorption-, CV-, and spectroelectrochemistry. The oxidised species [Cu(triaz)(2)](+) was characterised by UV/Vis spectroelectrochemistry and contains a phenoxyl-radical bound to Cu(ii). This quite stable species was chemically generated by two different methods: aerial oxidation of a Cu(i) precursor in the presence of Htriaz (and base) or from [Cu(triaz)(2)] by adding a Cu(ii) salt (disproportionation). The efficiency for the latter reaction has been studied by UV/Vis spectroscopy, XAS and catalytic test reactions (oxidation of benzyl alcohol). 相似文献
120.
Novel catalytic reductions of tertiary and secondary phosphine oxides to phosphines have been developed. Using tetramethyldisiloxane (TMDS) as a mild reducing agent in the presence of copper complexes, PO bonds are selectively reduced in the presence of other reducible functional groups (FGs) such as ketones, esters, and olefins. Based on this transformation, an efficient one pot reduction/phosphination domino sequence allows for the synthesis of a variety of functionalized aromatic and aliphatic phosphines in good yields. 相似文献