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21.
Spontaneous Nef reaction of primary and secondary 3-aryl-2-(diethoxyphosphoryl)-4-nitroalkanoic acids has been observed for the first time. The reaction provides a general and effective, highly diastereoselective synthesis of 3-(diethoxyphosphoryl)-1-hydroxysuccinimides and 2-(diethoxyphosphoryl)-4-oxoalkanoic acids. 相似文献
22.
Photoelectron spectroscopic investigations indicate that (i) monocyclic diaziridines prefer a trans-conformation of the nitrogen-lone pairs, and (ii) the interaction between these is comparable to that exhibited by open-chain analogues, i.e. alkyl-substituted hydrazines. The chemical experience concerning the particular case of ? NH? NH? →? N?N? oxidation of diaziridines can therefore not be accounted for by a prevailing unfavorable ‘lone pair’ interaction. Thermochemical as well as entropy arguments may serve as an explanation. A rather unsatisfactory agreement between predictions from various theoretical procedures and experimental results for the ionization potentials of ‘lone pair’ MO electrons is noted. 相似文献
23.
Guillena G Rodríguez G Albrecht M van Koten G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(23):5368-5376
Arylplatinum(II) complexes have been covalently bonded to the N and C termini and to the alpha-carbon of various amino acid derivatives. These organometallic-functionalized amino acid compounds can be converted into the corresponding free amino acids under both basic and acidic conditions; this demonstrates the excellent stability properties of these biomolecules. Due to the NMR activity displayed by the 195Pt nucleus (natural abundance 33.8%, I = 1/2) these compounds are functional bio-markers. Furthermore, the ability of the arylplatinum functional group to bind SO2 gas, selectively and reversibly as indicated by changes in the spectroscopic properties (1H, 13C, 195Pt NMR and UV spectra) of these compounds, allows for the potential use of these complexes as in vitro biosensors. 相似文献
24.
H. Meier E. Zimmerhackl W. Albrecht D. Bösche W. Hecker P. Menge A. Ruckdeschel E. Unger G. Zeitler 《Mikrochimica acta》1970,58(3):553-563
Zusammenfassung Die hochspannungselektrophoretische Wanderung der Halogenokomplexe der Platinmetalle und einer Reihe weiterer anorganischer Ionen wird mit Nitrilotriessigsäure und Äthylendiamintetraessigsäure als Elektrolyt in Abhängigkeit von verschiedenen Versuchsparametern (Elektrolytkonzentration,ph-Wert und Substanzmenge) untersucht. Die Wanderungsgeschwindigkeiten der verschiedenen Metallionen bzw.-komplexe zeigen charakteristische Abstufungen, die sich mit den für die hochspannungselektrophoretische Wanderung gültigen Gesetzmäßigkeiten erklären lassen. Beispielsweise beobachtet man eine Abnahme der Beweglichkeit bei Ersatz von Chlorid- durch Bromidionen (Masseneinfluß), Auswirkungen der vomph bzw. der Elektrolytkonzentration abhängigen unterschiedlichen Komplexierungen zwei- und dreiwertiger Ionen, Einflüsse der auf Hydrolyse zurückgehenden Änderungen der Ligandenzusammensetzung sowie Unterschiede der Wanderungsgeschwindigkeiten als Folge der Komplexierung mit NTE oder AeDTE.Durch die unter bestimmten Bedingungen erreichbare Abstufung der Beweglichkeiten können verschiedene Gemische, unter anderem auch die Chlorokomplexe der meisten Platinmetalle in der Reihenfolge Ir > Os Pt > Rh Pd > Ru (> Rh), getrennt werden. NTE ist dabei für Trennungen besser als AeDTE geeignet.
The high tension electrophoretic separation of inorganic ions with special reference to the platinum metals. I
Summary The high tension electrophoretic migration of the halogeno complexes of the platinum metals and several other inorganic ions was investigated with nitrilotriacetic acid and ethylenediaminetetraacetic acid as electrolytes in relation to the various experimental parameters (electrolyte concentration,ph-value, and amount of substance). The migration velocities of the various metal ions or complexes exhibit characteristic gradations that may be explained on the basis of the regularities that are valid for the high tension electrophoretic migration. Instances are: a decrease was observed in the mobility when chloride was replaced by bromide ions (mass effect), influence of different complexing of di- and trivalent ions that are related to changes in theph or electrolyte concentration, or influences of the changes due to hydrolysis in the composition of the ligands or alterations in the migration rates resulting from complexing with nitrolotriacetic acid or EDTA.The gradation of the mobility obtained under certain conditions are employed as the basis of a procedure for separating various mixtures, including also the chloro complexes of most of the platinum metals in the succession Ir > Os Pt > Rh Pd > Ru (> Rh). It has been found that NTE is better for separations than EDTA.相似文献
25.
J. Hladký S. NĚmeček M. Novák A. Prokeš J. Votruba K. -F. Albrecht A. Meyer M. Sachwitz B. N. Guskov V. G. Krivokhizhin M. F. Likhachev I. A. Savin G. Vesztergombi 《Czechoslovak Journal of Physics》1977,27(11):1210-1218
Results of the first elastic K
S
o
regeneration experiment on carbon, using magnetic spark chamber spectrometer, are presented in the beam momentum interval 10p50 GeV/c. The d ifferentia cross section d/dt is reconstructed in the range 0·0025–t0·02 (GeV/c)2 and its slopeB is found to be momentum independent with an average valueB=(65±11) (GeV/c)–2. The results are in agreement with the calculations using the coherent production model. 相似文献
26.
Albrecht M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(19):3485-3489
Dinuclear triple-stranded helicates or meso-helicates are formed by self-assembly of linear ligand strands with appropriate metal ions. Very often this self-assembly proceeds with high diastereoselectivity leading either to the helicate or the meso-helicate. The stereoselectivity of the self-assembly process can be influenced by different factors such as the rigidity of the ligand (-->helicate), the number of methylene units in the alkyl spacers (even number of CH2 units --> helicate; odd number --> meso-helicate), template effects, or chiral substituents. 相似文献
27.
28.
Reactions of Ferrocenol and 1,1′-Ferrocendiol with Cyclotriphosphazenes, P3N3F6 and P3N3Cl6 The hexahalogeno-cyclotriphosphazenes, P3N3X6 (X ? F ( 1 a ), Cl ( 1 b )), react with ferrocenol (FcOH) in a molar ratio 1 : 1 to give the ferrocenoxy derivatives, FcO[P3N3X5] (X ? F ( 3 a ), Cl ( 3 b )); in an analogous manner the tetrameric ring P4N4Cl8 ( 2 b ) is converted to FcO[P4N4Cl7] ( 4 b ). 1 Abkürzungen: Fc = Ferrocenyl, (C5H5)Fe(C5H4?); fc = 1,1′-ferrocendiyl, Fe(C5H4?)2; rc = 1,1′-ruthenocendiyl, Ru(C5H4?)2. Fluorphosphazene werden mit a , Chlorphosphazene mit b gekennzeichnet. With 1,1′-ferrocenediol, (fc(OH) 2 ), the cyclo triphosphazenes react in a molar ratio 1 : 1 to produce fcO 2 [P 3 N 3 X 4 ] (X ? F ( 5 a ), Cl ( 5 b )). According to the x-ray structure analysis, the 1,1′-ferrocenediolato group in 5 a , b is bound to two different phosphorus atoms. On the contrary, the 1,1′-ferrocenedithiolato- and 1,1′-ferrocenediselenolato units in fcS 2 [P 3 N 3 X 5 ] (X ? F ( 6 a ), Cl ( 6 b )) and fcSe 2 [P 3 N 3 X 5 ] (X ? F ( 7 a ), Cl ( 7 b )) are attached to only one phosphorus atom, and spirocyclic 1,3-dichalcogena-2-phospha-[3]ferrocenophanes are formed. All new products have been characterized on the basis of their 1 H, 13 C and 31 P NMR as well as EI mass spectra. The molecular structures of 5 a , b and 6 a have been determined by x-ray structure analyses. 相似文献
29.
William L. Albrecht Winton D. Jones F. William Sweet 《Journal of heterocyclic chemistry》1978,15(2):209-215
The reaction of cyclic-α-haloketones with 5-subslituted-4-amino-4H-1,2,4-triazole-3-lhiols gave s-triãzolocycloalkylhydrothiadiazines and s-triazolobenzocycloalkylthiadiazines. Reduetion of the 5,5a-imine bond of the s-triazoloeycloalkylthiadiazines gave s-triazolocycloalkylhydrothia-diazines. 相似文献
30.
Albrecht M Mirtschin S de Groot M Janser I Runsink J Raabe G Kogej M Schalley CA Fröhlich R 《Journal of the American Chemical Society》2005,127(29):10371-10387
The ligands 4-7-H(2) were used in coordination studies with titanium(IV) and gallium(III) ions to obtain dimeric complexes Li(4)[(4-7)(6)Ti(2)] and Li(6)[(4/5a)(6)Ga(2)]. The X-ray crystal structures of Li(4)[(4)(6)Ti(2)], Li(4)[(5b)(6)Ti(2)], and Li(4)[(7a)(6)Ti(2)] could be obtained. While these complexes are triply lithium-bridged dimers in the solid state, a monomer/dimer equilibrium is observed in solution by NMR spectroscopy and ESI FT-ICR MS. The stability of the dimer is enhanced by high negative charges (Ti(IV) versus Ga(III)) of the monomers, when the carbonyl units are good donors (aldehydes versus ketones and esters), when the solvent does not efficiently solvate the bridging lithium ions (DMSO versus acetone), and when sterical hindrance is minimized (methyl versus primary and secondary carbon substituents). The dimer is thermodynamically favored by enthalpy as well as entropy. ESI FT-ICR mass spectrometry provides detailed insight into the mechanisms with which monomeric triscatecholate complexes as well as single catechol ligands exchange in the dimers. Tandem mass spectrometric experiments in the gas phase show the dimers to decompose either in a symmetric (Ti) or in an unsymmetric (Ga) fashion when collisionally activated. The differences between the Ti and Ga complexes can be attributed to different electronic properties and a charge-controlled reactivity of the ions in the gas phase. The complexes represent an excellent example for hierarchical self-assembly, in which two different noncovalent interactions of well balanced strengths bring together eleven individual components into one well-defined aggregate. 相似文献