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111.
Structural and electrochemical characterization of 1,3-bis-(4-methylphenyl)imidazolium chloride 总被引:1,自引:0,他引:1
The structure of 1,3-bis(4-methylphenyl)imidazolium chloride was determined and compared to its related imidazole-based carbene. The important structural difference is the greater N2–C2–N3 angle in the salt (109.6°) than in the carbene (101.2°). An electrochemical investigation of the salt revealed a single reduction at –2.32 V in the forward scan and two oxidations at –0.89 and –0.54 V following scan reversal. 相似文献
112.
113.
C.R. Fuller 《Journal of sound and vibration》1981,75(2):207-228
The transmission of flexural type waves through various discontinuities in the walls of cylindrical shells is investigated. Theoretical curves of transmission loss are obtained for different circumferential wavenumbers and wave types, as functions of frequency. Material stiffness and extensional phase speed, together with the relationship between radial vibration amplitude and total wave power of propagation, are important factors which are found to strongly influence wave transmission through discontinuities. Some practical results useful for predicting the performance of typical pipe isolators (in vacuo) are obtained. 相似文献
114.
115.
The bonding in closo-boron hydrides, BnH2?n (where n = 5–12), is considered to be the sum of all possible n(n ? 1)/2 boron-boron interactions. The bonding energy u between any pair of boron atoms is taken to depend only upon the internuclear distance d, and to be given by u = 1/d2 ? 1/d. This scheme can be used to rationalize details of molecular geometry and also allows the relative importance of various intramolecular rearrangement pathways to be assessed. This method is compared with alternative approaches to treating the bonding in these molecules. 相似文献
116.
The copper(II) carboxylate-promoted intramolecular carboamination reactions of variously substituted gamma-alkenyl amides have been investigated. These oxidative cyclization reactions efficiently provide polycyclic lactams, useful intermediates in nitrogen heterocycle synthesis, in good to excellent yields. The efficiency of the carboamination process is dependent upon the structure of the amide backbone as well as the nitrogen substituent. 相似文献
117.
Monteux C Kirkwood J Xu H Jung E Fuller GG 《Physical chemistry chemical physics : PCCP》2007,9(48):6344-6350
The mechanical response of particle-laden fluid interfaces is determined by measuring the internal pressures of particle-coated drops as a function of the drop volume. The particle monolayers undergoing compression-expansion cycles exhibit three distinct states: fluid state, jammed state, and buckled state. The P-V curves are compared to the surface pressure isotherms Pi-A that are measured using a Langmuir trough and a Wilhelmy plate on a flat water-decane interface covered with the same particles. We find that in the fluid and jammed states, the water drop in decane can be described by the Young-Laplace equation. Therefore in these relatively low compression states, the bulk pressure measurements can be used to deduce the interfacial tension of the droplets and yield similar surface pressure isotherms to the ones measured with the Wilhelmy plate. In the buckled state, the internal pressure of the drop yields a zero value, which is consistent with the zero interfacial tension measured with the Wilhelmy plate. Moreover we find that the compressibility in the jammed state does not depend on the particle size. 相似文献
118.
Reacting 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [{PhP(Se)(μ-Se)}2], Woollins’ reagent, with an equivalent of aromatic diol in refluxing toluene afforded 10-membered phosphorus-selenium heterocycles 1 and 2 with an O-P(Se)-Se-Se-P(Se)-O linkage. Two equivalents of aromatic diol and Woollins’ reagent in refluxing toluene gave seven-membered phosphorus-selenium heterocycles 3 and 4 with an O-P(Se)-O linkage together with 10-membered phosphorus-selenium heterocycles 1 and 2. It was also found that the diphosphorus species O-P(Se)-Se-Se-P(Se)-O rings 1 and 2 could be readily ring contracted into the monophosphorus rings 3 and 4 in almost quantitative yields via further reaction with another equivalent of corresponding aromatic diol. One representative X-ray structure is reported. 相似文献
119.
Elizabeth A. Jacobs Anna Fuller Simon J. Coles Graham J. Tizzard Joseph A. Wright Simon J. Lancaster 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8647-8658
Treatment of Me2S ? B(C6F5)nH3?n (n=1 or 2) with ammonia yields the corresponding adducts. H3N ? B(C6F5)H2 dimerises in the solid state through N? H???H? B dihydrogen interactions. The adducts can be deprotonated to give lithium amidoboranes Li[NH2B(C6F5)nH3?n]. Reaction of the n=2 reagent with [Cp2ZrCl2] leads to disubstitution, but [Cp2Zr{NH2B(C6F5)2H}2] is in equilibrium with the product of β‐hydride elimination [Cp2Zr(H){NH2B(C6F5)2H}], which proves to be the major isolated solid. The analogous reaction with [Cp2HfCl2] gives a mixture of [Cp2Hf{NH2B(C6F5)2H}2] and the N? H activation product [Cp2Hf{NHB(C6F5)2H}]. [Cp2Zr{NH2B(C6F5)2H}2] ? PhMe and [Cp2Hf{NH2B(C6F5)2H}2] ? 4(thf) exhibit β‐B‐agostic chelate bonding of one of the two amidoborane ligands in the solid state. The agostic hydride is invariably coordinated to the outside of the metallocene wedge. Exceptionally, [Cp2Hf{NH2B(C6F5)2H}2] ? PhMe has a structure in which the two amidoborane ligands adopt an intermediate coordination mode, in which neither is definitively agostic. [Cp2Hf{NHB(C6F5)2H}] has a formally dianionic imidoborane ligand chelating through an agostic interaction, but the bond‐length distribution suggests a contribution from a zwitterionic amidoborane resonance structure. Treatment of the zwitterions [Cp2MMe(μ‐Me)B(C6F5)3] (M=Zr, Hf) with Li[NH2B(C6F5)nH3?n] (n=2) results in [Cp2MMe{NH2B(C6F5)2H}] complexes, for which the spectroscopic data, particularly 1J(B,H), again suggest β‐B‐agostic interactions. The reactions proceed similarly for the structurally encumbered [Cp′′2ZrMe(μ‐Me)B(C6F5)3] precursor (Cp′′=1,3‐C5H3(SiMe3)2, n=1 or 2) to give [Cp′′2ZrMe{NH2B(C6F5)nH3?n}], both of which have been structurally characterised and show chelating, agostic amidoborane coordination. In contrast, the analogous hafnium chemistry leads to the recovery of [Cp′′2HfMe2] and the formation of Li[HB(C6F5)3] through hydride abstraction. 相似文献
120.
Szczepanski J Fuller J Ekern S Vala M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(4):775-786
Neutral and anionic carbon clusters have been generated via a laser-induced graphite-based plasma and deposited in a solid argon matrix. Anionic clusters were formed from neutral clusters by using crossed electron/carbon cluster beams. Thermal annealing (to 36 K) resulted in the aggregation of the smaller carbon species, leading to the formation of long chain neutral and anionic clusters. Spectroscopic measurements in the ultraviolet, visible, near-infrared and infrared regions revealed a series of bands attributable to a homologous set of odd-numbered C5-C29 neutral clusters and even-numbered C6(-)-C36- anionic clusters. Good agreement is found for the band positions of carbon chains containing odd C15-C21 neutrals and even C6(-)-C22- anions, with species previously identified by Maier and coworkers using mass selection or laser vaporization, followed by neon matrix isolation. Resonance Raman frequencies for the neutral C17, C21 and C23 species are shown to be consistent with the above attributions. Density functional theory calculations agree well with the observed bands. It is found that certain low frequency Raman stretching frequencies decrease in a predictable way with increasing chain length. Comparison of the 0(0)0 absorption transitions of the even C18(-)-C36- anionic clusters with the 'unidentified' infrared (UIR) interstellar emission bands suggests that the electronic emission from specific long chain carbon anions may contribute to the some of the UIR bands. 相似文献