Dynamisches Verhalten dimerer 1,3,2,4λ2-Diazasilastannetidine und -plumbetidine in Lösung — eine Multikern-NMR-Studie/Dynamic Behaviour of Dimeric 1,2,3,4λ2-Diazasilastannetidines and -plumbetidines in Solution — a Multinuclear NMR Study

1989 ◽  
Vol 44 (3) ◽  
pp. 288-292 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Klaus Horchler ◽  
Hong Zhou ◽  
Michael Veith
Keyword(s):  
Low Temperature ◽  
Dynamic Process ◽  
Room Temperature ◽  
Dynamic Behaviour ◽  
The Other ◽  
Multinuclear Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
Intramolecular Process

1,3-Diisopropyl-2,2-dimethyl-1,3,2,4λ2-diazasilastannetidine (1b) and -plumbetidine (2b) are dimeric [(1b)2, (2b)2] in solution. At room temperature the structure of (1b)2 is fluxional. The dynamic behaviour is interpreted - on the basis of 1H. 13C, 29Si and 119Sn NMR data - as an intramolecular process in which the four-membered rings keep their identity. Such a process involves either concerted opening of the two coordinative Sn - N bonds and mutual slippage of the two rings, or consecutive cleavage of one of the coordinative Sn - N bonds and rotation about the other one. At room temperature the dimer (2b)2 is in equilibrium with its monomer 2b, whereas at low temperature the dynamic process corresponds to that established for (1b)2. In solutions which contain a mixture of the dimers (1b)2 and (2b)2, the presence of the mixed dimer 1b/2b can be proved unambiguously by consistent 29Si, 119Sn and 207Pb NMR data.

scholarly journals A multinuclear NMR study of some cyclic phosphonic diamides

1994 ◽  
Vol 12 (1) ◽  
pp. 31-34
Author(s):  
Wojciech Bocian ◽  
Lech Stefaniak ◽  
Graham A. Webb
Keyword(s):  
Molecular Structure ◽  
Chemical Shifts ◽  
Multinuclear Nmr ◽  
Nmr Data ◽  
Nmr Study ◽  
Sensitive Parameters

1H,13C,15N and31p NMR data are presented for four cyclic phosphonic diamides. In tenns of useful structural infonnation it is found that the31p chemical shifts and1J(31P_15N) couplings are the most sensitive parameters to variations in molecular structure.

Low-temperature phases of dicalcium barium hexakis(propanoate)

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Jan Fábry ◽  
Michal Dušek
Keyword(s):  
Low Temperature ◽  
Phase I ◽  
Room Temperature ◽  
High Temperature Phase ◽  
The Other ◽  
Phase Iii ◽  
Temperature Phase ◽  
Acta Cryst ◽  
Carboxylate Groups ◽  
Structure Determinations

The structure determinations of phases (II) and (III) of barium dicalcium hexakis(propanoate) {or poly[hexa-μ4-propanoato-bariumdicalcium], [BaCa2(C3H5O2)6] n } are reported at 240 and 130 K, respectively [phase (I) was determined previously by Stadnicka & Glazer (1980). Acta Cryst. B36, 2977–2985; our structure determination of phase (I) at room temperature is included in the supporting information]. In the high-temperature phase, the Ba2+ cation is surrounded by six carboxylate groups in bidentate bridging modes. In the low-temperature phases, five carboxylate groups act in bidentate bridging modes and one acts in a monodentate bridging mode around Ba2+. The Ca2+ cations are surrounded by six carboxylate O atoms in a trigonal antiprism in all the structures. The Ba2+ and Ca2+ cations are underbonded and significantly overbonded, respectively, in all the phases. The bonding of the Ba2+ cation increases slightly at the cost of the bonding of Ca2+ cations during cooling to the low-temperature phases. The phase transitions during cooling are accompanied by ordering of the ethyl chains. In room-temperature phase (I), all six ethyl chains are positionally disordered over two positions in the crossed mode, with additional splitting of the ethyl α- and β-C atoms. In phase (II), on the other hand, there are three disordered ethyl chains, one with positionally disordered ethyl α- and β-C atoms, and the other two with positionally disordered ethyl β-C atoms only, and in the lowest-temperature phase (III) there are four ordered ethyl chains and two disordered ethyl chains with positionally disordered ethyl β-C atoms only.

scholarly journals 23Na NMR Study of NASICON-type Compounds, Na1+xScxTi2–x(PO4)3

2000 ◽  
Vol 55 (1-2) ◽  
pp. 348-352 ◽  
Author(s):  
Hirotsugu Masui ◽  
Takahiro Ueda ◽  
Keisuke Miyakubo ◽  
Taro Eguchi ◽  
Nobuo Nakamura
Keyword(s):  
Nmr Spectroscopy ◽  
Axial Symmetry ◽  
Room Temperature ◽  
Chemical Exchange ◽  
The Other ◽  
Special Position ◽  
Nasicon Type ◽  
Nmr Study ◽  
Low Symmetry ◽  
23Na Nmr

The structure of NASICON-type compounds, Na1+xScxTi2-x(PO4)3 (O ≤ x ≤ 2), and the dynamics of Na+ have been investigated by 23Na NMR spectroscopy. It was found that the 23Na 1D and 2D MQMAS spectra depend on the Na concentration, suggesting strongly that the Na+ ions are distributed between two crystallographically nonequivalent sites, one is a special position with axial symmetry, and the other a position of low symmetry. The chemical exchange between these different sites in the crystal takes place at room temperature, which may cause the high Na ion conduction of this material

A New Investigation of Tetrahydrofuran-Based Polyether Glycols in Urethane Elastomers

1980 ◽  
Vol 53 (5) ◽  
pp. 1032-1040 ◽  
Author(s):  
E. Pechhold ◽  
G. Pruckmayr ◽  
I. M. Robinson
Keyword(s):  
Low Temperature ◽  
Physical Properties ◽  
Room Temperature ◽  
Hydrolytic Stability ◽  
Cyclic Ether ◽  
The Other ◽  
Temperature Behavior ◽  
Oil Resistance ◽  
Soft Segments ◽  
Better Than

Abstract Random copolyether glycols with 50 mole % EO and low cyclic ether content represent novel soft segments for polyurethanes, and have some advantages over the other soft segments as shown in Table V. THF/EO copolyether glycols are easier to handle and to process because they are liquids at room temperature and exhibit lower viscosities and better diol compatibility. Physical properties of polyurethanes made from THF/EO copolyether glycols are comparable to those made from other soft segments; the hydrolytic stability and low temperature behavior are superior to polyester and polycaprolactone glycols, and solvent/oil resistance is better than PTMEG. THF/EO copolyether glycol is a replacement for PTMEG only with reformulation; it could be considered for applications which require better solvent/oil resistance or easier handling and processability.

NMR study of Ni3Al with B and C additions

1993 ◽  
Vol 8 (6) ◽  
pp. 1285-1290 ◽  
Author(s):  
T. Shinohara ◽  
T. Takasugi
Keyword(s):  
Electronic Structure ◽  
Low Temperature ◽  
Curie Temperature ◽  
Atomic Number ◽  
Knight Shift ◽  
Room Temperature ◽  
Nmr Study ◽  
Knight Shifts

NMR study has been carried out on Ni3Al with B and C additions. The 27Al-, 11B-, and 13C-spectra have been measured as a function of temperature for determining their Knight shifts. The Curie temperature and Knight shift at low temperature in Ni3Al with B and C additions decrease in the order of atomic number of additions, but the Knight shifts around room temperature are nearly the same as that of pure Ni3Al. It is suggested that the addition of B and C affects the electronic structure of Ni, and that B atoms and possibly C atoms occupy the octahedrally symmetric sites neighboring all the Ni atoms.

scholarly journals 1.1-Dimethyl-1-methoxy-1λ5phospholan und -phosphorinan: Synthese, Struktur und dynamisches Verhalten / 1,1 -Dimethyl-1-methoxy-1λ5 phospholane and -phosphorinane: Synthesis, Structure and Dynamic Behaviour

1978 ◽  
Vol 33 (5) ◽  
pp. 489-492 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Peter Holl
Keyword(s):  
Methoxy Group ◽  
Room Temperature ◽  
Dynamic Behaviour ◽  
Elevated Temperatures ◽  
Variable Temperature ◽  
Axial Position ◽  
Trigonal Bipyramidal ◽  
Nmr Study ◽  
Methoxy Groups ◽  
High Yields

The title compounds have been prepared in high yields from equimolar amounts of methanol and the ylides 1-methyl-1-methylene-phospholane and -phosphorinane, respectively. On the basis of a variable temperature 1H, 13C, and 31P NMR study the compounds have been assigned a molecular structure with a pentacovalent phosphorus atom in a trigonal bipyramidal configuration and the methoxy group in an axial position. The molecules are fluxional on the NMR time scale and rapid ligand scrambling is observed at room temperature, predominantly affecting the ring systems. At elevated temperatures an irregular, intermolecular exchange of methoxy groups and CH3P-protons is observed, which is a consequence of a retro cleavage to form ylide and methanol. This process is faster with the phosphorinane than with the phospholane.

Thermal Diffusion in Jammed Aluminum Nanopowders

2011 ◽  
Vol 121-126 ◽  
pp. 1809-1812
Author(s):  
Ching Yen Ho ◽  
C. Ma ◽  
F. M. Sui
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Transport ◽  
Surface Area ◽  
Room Temperature ◽  
Bulk Material ◽  
The Other ◽  
Insulating Material ◽  
Size Dependent ◽  
Bed Porosity

Nanoparticles show a variety of size-dependent properties due to the dramatic changes in the ratio of surface area to volume. The characteristics of nanoparticles different from the bulk material make the properties of the powders composed of these nanoparticles attract more attention. The heat transfer in the powder composed of nanoparticles is experimentally investigated in this paper. The powder is wrapped up in the slender tube made of insulating material. One end of the slender tube filled with powder is maintained at low temperature and the other end is kept at room temperature. The temperature histories at two different locations in the slender tube are recorded using thermalcouples. The results show that the heat transfer depends on the bed porosity and the thermal conductivities of the solid and the gas. The pressure on the Al powders enhances the rate of heat transport due to the decrease of the bed porosity and a small fraction of gas.

Low Temperature Multinuclear NMR Study of the Mechanism of Protonation of W(H)2Cl2(PMe2Ph)4

1995 ◽  
Vol 34 (11) ◽  
pp. 2894-2901 ◽  
Author(s):  
Helmut Rothfuss ◽  
Dmitry G. Gusev ◽  
Kenneth G. Caulton
Keyword(s):  
Low Temperature ◽  
Multinuclear Nmr ◽  
Nmr Study

A multinuclear NMR study of the cycloaddition reaction of SNSAsF6 with tert-butylphosphaacetyline (CH3)3CCP leading to the 5-tert-butyl-1,3,2,4-dithiazaphospholium cation; a preliminary account of the novel exchange of a cyclic phosphorus by nitrogen in the reaction of with azide N3− leading to 5-tert-butyl-1,3,2,4-dithiadiazolyl

1995 ◽  
Vol 73 (8) ◽  
pp. 1312-1320 ◽  
Author(s):  
Simon Parsons ◽  
Jack Passmore ◽  
Xiaoping Sun ◽  
Manfred Regitz
Keyword(s):  
Sulfur Dioxide ◽  
Low Temperature ◽  
Cycloaddition Reaction ◽  
The Novel ◽  
Multinuclear Nmr ◽  
Tert Butyl ◽  
Nmr Study ◽  
Preliminary Account ◽  
Net Replacement

The cycloaddition reaction of SNS+ (as the AsF6− salt) with 5-tert-butylphosphaacetyline (CH3)3CCP in sulfur dioxide solution at −60 °C gave [Formula: see text], the first identified example of a 1,3,2,4-dithiazaphospholium heterocycle [Formula: see text]. The cycloadduct was characterized by multinuclear NMR (1H, 13C, 14N, 15N, 31P) spectroscopy at low temperature. Reduction of 6π [Formula: see text] in situ with SbPh3 in the presence of Me4NCl led to a radical, which may be the 7π tert-butyl-1,3,2,4-dithiazaphospholyl [Formula: see text]. The reaction of 5-tert-butyl-1,3,2,4-dithiazaphospholium [Formula: see text] with azide N3− surprisingly gave the previously known 5-tert-butyl-1,3,2,4-dithiadiazolyl [Formula: see text]. The conversion of [Formula: see text] to [Formula: see text] by the net replacement of a cyclic phosphorus with nitrogen is unprecedented. Keywords: dithiazaphospholium, dithiazaphospholyl, cycloaddition, multinuclear NMR, ESR.

A topochemical rearrangement with multiple inversions of configuration

2001 ◽  
Vol 79 (8) ◽  
pp. 1272-1277 ◽  
Author(s):  
Saul Wolfe ◽  
Yih-Huang Hsieh ◽  
Raymond J Batchelor ◽  
Frederick WB Einstein ◽  
Ian D Gay
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Room Temperature ◽  
The Other ◽  
X Ray ◽  
Controlled Processes ◽  
X Ray Crystallography ◽  
Intramolecular Process ◽  
C Nmr ◽  
The Ideal

Crystalline 2-benzyloxypyridine-1-oxide rearranges slowly at room temperature to crystalline 1-benzyloxy-2-pyridone. No intermediates are detected when the process is followed by solid-state 13C NMR. The crystal structure of the pyridine-1-oxide strongly suggests that a topochemically controlled intramolecular process, in which the benzyl group migrates with retention of configuration, is not feasible. On the other hand, although somewhat disfavoured by initial solid-state O···C···O angles significantly less than the ideal 180°, intermolecular topochemically controlled processes can be envisaged that lead, with multiple inversions of configuration, either to net retention of configuration or to net inversion of configuration in the benzyl group. In contrast to the 50–80% inversion observed in solution, in the solid state only inversion is observed experimentally when chirally labelled α-deuteriobenzyloxypyridine-1-oxide is allowed to rearrange.Key words: X-ray crystallography, solid-state 13C NMR, benzyl-α-D-alcohol, 2-benzyloxypyridine-1-oxide, 1-benzyloxy-2-pyridone.

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