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1.
2.
N.M.R. Investigation of Methylphosphonium Chloride The n.m.r. spectra of [CH3PH3]Cl in aqueous hydrochloric acid as solvent and of [OP(CH3) (OCH2CH2Cl)OCH2? ]2 in C6D6 und CD2Cl2 are described. 31P n.m.r. resonances with a line width at half height of 55 Hz are found for the H2O? HCl solutions of [CH3PH3]Cl in the solid state at 183 K. 相似文献
3.
2-Substituted secondary alcohol o-DPPB esters (o-DPPB=ortho-diphenylphosphanylbenzoyl) have been prepared and their o-DPPB-directed diastereoselective hydroformylation examined. It was found that the diastereoselectivity increased as a function of the steric demand of the substituents both at the stereogenic center and in the alkene 2-position. Hydrolytic cleavage of the o-DPPB group afforded-via the lactols 29-the corresponding lactones 30, the relative configurations of the vicinal stereogenic centers of which were ascertainable by 2D-NOESY spectroscopy. In addition, a crystal structure analysis of the hydroformylation product 2 d provided further confirmation of the relative configuration. Replacement of the ester carbonyl group of the o-DPPB by a methylene unit resulted in significantly worse diastereoselectivity in the course of the hydroformylation (34-->35), which indicates a decisive role for the ester carbonyl function. All the experimental observations were combined in a model of the origin of the 1,2-asymmetric induction during the title reaction. The key feature is the consideration of diastereomeric trigonal-bipyramidal rhodium-hydrido-olefin complexes I and II, capable on the basis of the Hammond postulate of acting as good models for the transition states of the selectivity-determining hydrometalation step. Investigation of these complexes by force-field methods indicated good correlation between theoretically predicted and experimentally determined diastereoselectivities. 相似文献
4.
5.
Synthesis of the Stannatetraphospholanes (tBuP)4SnR2 (R = tBu, nBu, C6H5) and (tBuP)4Sn(Cl)nBu Molecular and Crystal Structure of (tBuP)4Sn(tBu)2 The reaction of the diphosphide K2[tBuP-(tBuP)2-PtBu] 4 with the halogenostannanes (tBu)2SnCl2, (nBu)2SnCl2, (C6H5)2SnCl2 or nBuSnCl3 in a molar ratio of 1 : 1 leads via a [4 + 1]-cyclocondensation reaction to the stannatetraphospholanes (tBuP)4SnR2 3 b–3 d and (tBuP)4Sn(Cl)nBu 3 e , respectively, with the binary 5-membered P4Sn ring system. 3 b was characterized by a single crystal structure analysis; the 5-membered ring exists in a planar conformation. The compounds 3 b–3 e were identified by NMR and also by mass spectroscopy; the 31P{1H}-NMR spectra of 3 b–3 d showed an AA′MM′ (AA′MM′X), 3 e on the other hand an ABCD (ABCDX) spin system. 相似文献
6.
E. Träbert P. H. Heckmann H. v. Buttlar 《Zeitschrift für Physik A Hadrons and Nuclei》1977,281(4):333-339
Electronically excited states of Si ions are created by passing a 20 MeV Si5+ beam through a thin carbon foil. The EUV-radiation (λ=13–61 nm) emitted by the beam is analyzed using a grazing-incidence spectrometer. From the decay curves, lifetimes of 24 low lying levels in Si VIII to Si XII and of the 4f and 5g levels of Si XI and Si XII are derived. Cascades from doubly excited states turn out to be an important contribution to the radiation observed. The lifetime values of this work are compared to theoretical data mainly of Wiese, Sinanoλu and Dankwort/Trefftz. Most experimental values agree with at least one of the theoretical values. The decay time 560 ps of the 2s2p 3 3 D 3 0 state of Si IX is clearly longer than the theoretical prediction (highest value 455 ps by Sinanoglu). 相似文献
7.
Ekkehard Fluck Manfred Spahn Gernot Heckmann Horst Borrmann Axel Obermeyer 《Heteroatom Chemistry》1991,2(5):593-599
1,1,3,3 - Tetrakis(dimethylamino) - 1λ5,3λ5 - diphosphete, 1 , reacts with cyanoformic acid methyl ester to form two isomers of the title compound 2 . Properties, NMR, mass, and IR spectra of 2 , as well as the molecular and crystal structure of the E isomer of 2 , are described and discussed. 相似文献
8.
9.
W. Nitsche P. H. Heckmann E. Träbert H. v.Buttlar 《Zeitschrift für Physik A Hadrons and Nuclei》1981,299(4):301-306
Ratios of initial populations of foil-excited hydrogen-like ions of He, B, C, N and O have been measured. Combined with earlier results for H obtained by Tielert they show aZ-dependence of the population process and indicate a velocity dependence as well. For the population of thenp-levels (n=2–5) of He+ ann-dependence ∞n ?(3.6±0.4) has been observed. 相似文献
10.
J. Barrau J.C. Brabant M. Brousseau J. Collet M. Heckmann H. Maareff 《Solid State Communications》1975,16(9):1079-1082
The microwave absorption technique was used to measure the transient free carrier density following an electric injection in silicon at 4°K. The experiment agrees with the idea that droplets are obtained by free carrier condensation directly, without a preliminary formation of free excitons.1 An Auger recombination process in droplets explains the observed kinetics; parameters are measured. 相似文献