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31.
32.
Dr. Kevin Schwedtmann Michael Quest Dr. Benedikt J. Guddorf Jan Keuter Dr. Alexander Hepp Dr. Milica Feldt Jörn Droste Prof. Dr. Michael Ryan Hansen Dr. Felicitas Lips 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17361-17368
The bicyclic amido-substituted silicon(I) ring compound Si4{N(SiMe3)Mes}4 2 (Mes=Mesityl=2,4,6-Me3C6H2) features enhanced zwitterionic character and different reactivity from the analogous compound Si4{N(SiMe3)Dipp}4 1 (Dipp=2,6-iPr2C6H3) due to the smaller mesityl substituents. In a reaction with the N-heterocyclic carbene NHC (1,3,4,5-tetramethyl-imidazol-2-ylidene), we observe adduct formation to give Si4{N(SiMe3)Mes}4 ⋅ NHC ( 3 ). This adduct reacts further with the Lewis acid BH3 to yield the Lewis acid–base complex Si4{N(SiMe3)Mes}4 ⋅ NHC ⋅ BH3 ( 4 ). Coordination of AlBr3 to 2 leads to the adduct 5 . Calculated proton affinities and fluoride ion affinities reveal highly Lewis basic and very weak Lewis acidic character of the low-valent silicon atoms in 1 and 2 . This is confirmed by protonation of 1 and 2 with Brookharts acid yielding 6 and 7 . Reaction with diphenylacetylene only occurs at 111 °C with 2 in toluene and is accompanied by fragmentation of 2 to afford the silacyclopropene 8 and the trisilanorbornadiene species 9 . 相似文献
33.
Droste S Schellenträger M Constapel M Gäb S Lorenz M Brockmann KJ Benter T Lubda D Schmitz OJ 《Electrophoresis》2005,26(21):4098-4103
We describe the successful coupling of CEC and capillary HPLC with the recently developed atmospheric-pressure laser ionization (APLI) method. APLI is suitable for selectively and sensitively ionizing nonpolar aromatic compounds at ambient pressure for subsequent mass-selective detection. The polycyclic aromatic hydrocarbons used as analytes are first separated either by CEC on a silica-based monolithic column or by capillary HPLC. The eluent, along with a sheath flow, is volatilized by microelectrospray and then selectively ionized by excimer laser (KrF*) radiation via two-photon excitation. A QTOF-MS is used as mass-selective detector. This interface combination makes soft ionization of thermally labile nonpolar aromatic analytes possible. 相似文献
34.
E. M. Limanski M. Piepenbrink E. Droste K. Burgemeister B. Krebs 《Journal of Cluster Science》2002,13(3):369-379
Two novel examples of sandwich type heteropolyanions were synthesized and characterized by X-ray crystal structure and elemental analysis as well as infrared spectroscopy. Na13[H3Cu4(H2O)2(CuW9O34)2]39H2O (1) and Na9K[Fe4(H2O)2(FeW9O34)2]32H2O (2) were prepared in aqueous solution by reaction of sodium tungstate with FeIII and CuII cations, respectively. 1 crystallizes in the monoclinic space group P21/n (a=13.054(3) Å, b=17.729(4) Å, c=20.998(4) Å, =93.50(3)°), while 2 is triclinic, space group P¯1 (a=12.316(2) Å, b=13.716(3) Å, c=14.925(3) Å, =99.36(3)°, =104.21(3)°, =101.55(3)°). Each anion consists of two [XW9O34]
n– moieties (X=FeIII, n=11 (1) and CuII, n=12 (2)) which can be described as -B-isomers of the defect Keggin anion. These units are linked via a belt of four FeIIIO6 or CuIIO6 groups. Two transition metal atoms fill their octahedral coordination sphere with one additional water ligand. 相似文献
35.
We consider endomorphism monoids of graphs. It is well-known that any monoid can be represented as the endomorphism monoid M of some graph Γ with countably many colors. We give a new proof of this theorem such that the isomorphism between the endomorphism monoid $\mathop{\rm End}\nolimits (\Gamma)We consider endomorphism monoids of graphs. It is well-known that any monoid can be represented as the endomorphism monoid
M of some graph Γ with countably many colors. We give a new proof of this theorem such that the isomorphism between the endomorphism
monoid
and M is absolute, i.e.
holds in any generic extension of the given universe of set theory. This is true if and only if |M|,|Γ| are smaller than the first Erdős cardinal (which is known to be strongly inaccessible). We will encode Shelah’s absolutely
rigid family of trees (Isr. J. Math. 42(3), 177–226, 1982) into Γ. The main result will be used to construct fields with prescribed absolute endomorphism monoids, see G?bel and Pokutta
(Shelah’s absolutely rigid trees and absolutely rigid fields, in preparation).
This work was supported by the project No. I-706-54.6/2001 of the German-Israeli Foundation for Scientific Research & Development
and a fellowship within the Postdoc-Programme of the German Academic Exchange Service (DAAD). 相似文献
36.
A. A. Pasternak E. O. Podsvirova R. M. Lieder S. Chmel W. Gast Ts. Venkova H. M. Jäger L. Mihailescu G. de Angelis D. R. Napoli A. Gadea D. Bazzacco R. Menegazzo S. Lunardi W. Urban Ch. Droste T. Morek T. Rzaca-Urban G. Duchêne A. Dewald 《The European Physical Journal A - Hadrons and Nuclei》2005,23(2):191-196
Lifetimes have been measured for dipole bands in 142Gd using DSAM. The deduced B(M1) and B(E2) values as well as B(M1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (Shears mechanism with Principal Axis Cranking) models. The dipole bands DB1 to DB4 can be interpreted as magnetic rotational bands. 相似文献
37.
Manfred Droste 《Order》1985,2(3):291-319
Using combinatorial and model-theoretic means, we examine the structure of normal subgroup lattices N(A()) of 2-transitive automorphism groups A() of infinite linearly ordered sets (, ). Certain natural sublattices of N(A()) are shown to be Stone algebras, and several first order properties of their dense and dually dense elements are characterized within the Dedekind-completion
of (, ). As a consequence, A() has either precisely 5 or at least 221 (even maximal) normal subgroups, and various other group- and lattice-theoretic results follow. 相似文献
38.
39.
In 1963, W. Charles Holland proved that every lattice-ordered group can be embedded in the lattice-ordered group of all order-preserving
permutations of a totally ordered set. In this article we examine the context and proof of this result and survey some of
the many consequences of the ideas involved in this important theorem. 相似文献
40.
Siegel Miles G. Shuker Athony J. Droste Christine A. Hahn Patrick J. Jesudason Cynthia D. McDonald III John H. Matthews Donald P. Rito Christopher J. Thorpe Andrew J. 《Molecular diversity》1997,3(2):113-116
A library of potential agonists and antagonists for adrenergic receptors was prepared using high-throughput solution-phase
parallel synthesis. Traditional solution-phase reductive amination reactions followed by rapid purification by ion exchange
chromatography yielded products with near-analytical purity. An array of ketones and amines, arranged in an 8 × 12 matrix,
were combined to form 96 individual compounds.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献