3847-57-2Relevant articles and documents
Influence of axial ligands on diverse properties in three trinickel string complexes
Zhang, Jing,Zhu, Long-Guan
, p. 1071 - 1077 (2012)
Three new trinickel string complexes, [Ni3(dpa)4(3-nba) 2](1), [Ni3(dpa)4(4-nba)2]·(CH 3OH) (2), and [Ni3(dpa)4(3,5-dnba)2](3) where dpa- is the anion of 2,2-dipyridylamine, 3-nba- is 3-nitrobenzoate anion, 4-nba is 4-nitrobenzoate anion, and 3,5-dnba- is 3,5-dinitrobenzoate anion, were synthesized in good yield and characterized by X-ray crystallography, infrared spectra, elemental analysis, magnetic susceptibility, cyclic voltammogram (CV), UV-vis spectra, fluorescence spectra, and TG analysis. The magnetic susceptibilities suggested that the terminal Ni atoms in all three complexes are in high-spin state while the central Ni atom is in a low-spin state. The CVs of complexes 1-3 showed reversible one-electron redox waves at E1/2 = 1.1395 V for 1, 1.108 V for 2, and 1.109 V for 3 corresponding to Ni3 7+/Ni3 6+. The Ni-Ni distances in three complexes are somewhat different, indicating the axial nitrobenzoate ligands have significant effect on the structural assembly. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
Stabilities of trityl-protected substrates: The wide mechanistic spectrum of trityl ester hydrolyses
Horn, Markus,Mayr, Herbert
supporting information; experimental part, p. 7469 - 7477 (2010/09/11)
Ionization rates of para-substituted triphenylmethyl (trityl) acetates, benzoates, and para-nitrobenzoates have been determined in aqueous acetonitrile and aqueous acetone at 25 °C. Conventional and stoppedflow techniques have been used to evaluate rate constants ranging from 1.38 × 10-5 to 2.15 × 102S-1 by conductimetry and photospectrometry methods. The varying stabilities of the differently substituted tritylium ions account for a gradual change of reaction mechanism. Poorly stabilized carbocations are generated slowly by the ionization of their covalent precursors and trapped fast by water. Better stabilized carbocations are generated more rapidly and accumulate, so that ionization and trapping by water can be observed as separate steps in a single experiment. Finally, highly stabilized tritylium ions do not react with water, and only the rates of their formation could be measured. The ionization rate constants correlate linearly with Winstein's ionizing powers Y; the low slopes (0.17 + parameters is excellent for symmetrically substituted tritylium derivatives, deviations for unsymmetrically substituted systems are observed. The failing rate-equilibrium relationship between the rates of ionizations (log kion) and the stabilities of the carbocations in aqueous solution (pKR+) may be explained by the late " development of resonance between a p-amino group and the carbocationic center of the tritylium ion during the ionization process.
Kinetics and mechanism of the formation and decomposition of imidazolin-4-ones from 2-(n-benzoylamino)alkanamides in aqueous medium
Sedlak, Milos,Hanusek, Jiri,Bina, Radim,Kavalek, Jaromir,Machacek, Vladimir
, p. 1629 - 1640 (2007/10/03)
The cyclization reactions of substituted 2-(N-benzoyl-N-methyl)aminoalkanamides 1a-1g have been studied in aqueous medium. The Hammett reaction constant is ρ = 1.4 for the cyclization reactions of compounds 1a-1e in sodium hydroxide solutions. 2-[N-Methyl-N-(4-nitrobenzoyl)amino]-2-(4-nitrophenyl)propanamide (1g) is cyclized to imidazolinone 2g in aqueous amine buffers of pH 9-11.5; the reaction is subject to specific base catalysis in these media, and the rate-limiting step is the formation of a tetrahedral intermediate. In sodium hydroxide solution, the primary cyclization product is hydrolyzed to give an intermediate M which is subsequently decomposed to sodium 4-nitrobenzoate and 2-methylamino-2-(4-nitrophenyl)propanamide. At low sodium hydroxide concentration, the rate-limiting step of the opening of imidazoline ring of compound 2g is non-catalyzed decomposition of the intermediate. At higher sodium hydroxide concentrations, the other reaction path begins to make itself felt: hydroxide-ion-catalyzed decomposition of the intermediate. The dependence of observed rate constant of cyclization of compound 1f on sodium hydroxide concentration was used to determine kinetically the value of pKa = 13.5 ± 0.1. The kinetic deuterium isotope effect of cyclization of compounds 1f giving 2f (kCH / kCD = 1.7) was determined in solutions of NaOD in D2O.