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The ligand‐exchange mechanism of solvated Be2+ cations has been studied by means of DFT calculations (RB3LYP/6‐311+G**). Ligand exchange around [BeL4]2+, where L=H2O, NH3, CO2, formaldehyde (H2CO), HCN, N2, and CO, was found to follow an associative interchange (Ia) process in all cases. The size of the activation barrier is almost independent of the type of donor atom, and depends mainly on the hybridization undergone by the donor atom. This, in turn, suggests that steric effects play a major role in solvent‐ and ligand‐exchange reactions in Be2+ systems. 相似文献
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Saalfrank RW Deutscher C Maid H Ako AM Sperner S Nakajima T Bauer W Hampel F Hess BA van Eikema Hommes NJ Puchta R Heinemann FW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(8):1899-1905
In the reaction of the N-substituted diethanolamines (H(2)L(1-3)) (1-3) with calcium hydride followed by addition of iron(III) or indium(III) chloride, the iron wheels [Fe(6)Cl(6)(L(1))(6)] (4) and [Fe(6)Cl(6)(L(2))(6)] (6) or indium wheels [In(6)Cl(6)(L(1))(6)] (5), [In(6)Cl(6)(L(2))(6)] (8) and [In(6)Cl(6)(L(3))(6)] (9) were formed in excellent yields. Exchange of the chloride ions of 6 by thiocyanate ions afforded [Fe(6)(SCN)(6)(L(2))(6)] (7). Whereas the structures of 4, 5 and 7 were determined unequivocally by single-crystal X-ray analyses, complexes 8 and 9 were characterised by NMR spectroscopy. Contrary to what is normally presumed, the scaffolds of six-membered metallic wheels are not generally rigid, but rather undergo nondissociative topomerisation processes. This was shown by variable temperature (VT) (1)H NMR spectroscopy for the indium wheel [In(6)Cl(6)(L(1))(6)] (5) and is highlighted for the enantiotopomerisation of one indium centre [ 1/6[S(6)-5]<==>[1/6[S(6)-5']]. The self-assembly of metallic wheels, starting from diethanolamine dendrons, is an efficient strategy for the convergent synthesis of metallodendrimers. 相似文献
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Peter C. Burgers Henk Hommes Johan K. Terlouw 《Journal of mass spectrometry : JMS》1979,14(10):571-573
Loss of an alkyl group X? from acetylenic alcohols HC?C? CX(OH)(CH3) and gas phase protonation of HC?C? CO? CH3 are both shown to yield stable HC?C? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}(OH)(CH3) ions. Ions of this structure are unique among all other [C4H5O]+ isomers by having m/z 43 [C2H3O]+ as base peak in both the metastable ion and collisional activation spectra. It is concluded that the composite metastable peak for formation of m/z 43 corresponds to two distinct reaction profiles which lead to the same product ion, CH3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O, and neutral, HC?CH. It is further shown that the [C4H5O]+ ions from related alcohols (like HC?C? CH(OH)(CH3)) which have an α-H atom available for isomerization into energy rich allenyl type molecular ions, consist of a second stable structure, H2C?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? C(OH)?CH2. 相似文献
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Unprecedented Strong Lewis Bases—Synthesis and Methyl Cation Affinities of Dimethylamino‐Substituted Terpyridines 下载免费PDF全文
Dr. Paul Hommes Christina Fischer Dr. Christoph Lindner Prof. Dr. Hendrik Zipse Prof. Dr. Hans‐Ulrich Reissig 《Angewandte Chemie (International ed. in English)》2014,53(29):7647-7651
A versatile method for the synthesis of functionalized 2,2′:6′,2′′‐terpyridines by assembly of the terminal pyridine rings is presented. The cyclization precursors—bis‐β‐ketoenamides—are prepared from 4‐substituted 2,6‐pyridinedicarboxylic acids and acetylacetone or its corresponding enamino ketone. Treatment with trimethylsilyl trifluoromethanesulfonate induces a twofold intramolecular condensation providing an efficient access to 4,4′′‐di‐ and 4,4′,4′′‐trifunctionalized 6,6′′‐dimethyl‐2,2′:6′,2′′‐terpyridines. Using this method, hitherto unknown 4,4′′‐bis(dimethylamino)‐ and 4,4′,4′′‐tris(dimethylamino)terpyridines have been prepared that show remarkably high calculated Lewis basicities. 相似文献
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Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI. 相似文献