The ligand (i-Pr)2PCH2(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO2CF3) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes (P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)2PCH2(oxazoline)}]2(OTf)2 (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]2 to be characterized by X-ray crystallography.
Résumé
Le ligand (i-Pr)2PCH2(oxazoline) (1a), de type donneur P,N, réagit avec [PdClMe(COD)] pour former le complexe plan carré méthylpalladium(II) [PdClMe(P,N)] (P,N = 1a) (2a), à partir duquel le complexe [PdMe(P,N)OTf] (OTf = OSO2CF3) (3a) a été obtenu par abstraction de chlorure à l'aide de AgOTf. Les complexes alkyles (P,N = 1a) (5a, R = H; 7a, R = C(O)OMe), ont été isolés lors des premières étapes d'insertion de CO/éthylène ou de CO/acrylate de méthyle, respectivement, dans la liaison Pd–Me de 3a, et caractérisés par méthodes spectroscopiques. Les complexes 2a, 3a et 7a ont été complètement caractérisés par diffraction des rayons X sur monocristal. Le complexe 7a est un exemple encore rare de produit d'insertion par étapes de CO/acrylate de méthyle qui ait été caractérisé structuralement. Ces complexes sont pertinents pour la copolymérisation alternée d'oléfines et de monoxyde de carbone catalysée par les complexes du palladium. En outre, le complexe dinucléaire centrosymétrique trans-[Pd(μ-Cl){(i-Pr)2PCH2(oxazoline)}]2(OTf)2 (6) a été obtenu et caractérisé par diffraction des rayons X; il s'agit du premier complexe dinucléaire de type [Pd(μ-Cl)(P,N)]2 à être caractérisé par diffraction des rayons X. 相似文献
A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of
cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace
metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of
the 13 participants were 0.3186 mg kg−1 (RSD = 11.3%) and 1.650 mg kg−1 (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique
for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users.
The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest
metrological IDMS approach gave a better precision than other routine calibration methods. 相似文献
Raman spectroscopy has been sued to study the antimony containing mineral roméite Ca2Sb2O6(OH,F,O) from three different origins. Roméite is a calcium antimonate mineral of the pyrochlore group. An intense Raman band at ～518 cm?1 for roméite is assigned to the SbO ν1 symmetric stretching mode and the band at 466 cm?1 to the SbO ν3 antisymmetric stretching mode. The Raman band at 303 cm?1 is attributed to the OSbO bending mode. Some variation in band positions is observed and is attributed to the variation in composition between the three mineral samples. 相似文献
Mathematical modeling via the fast Padé transform (FPT) is applied according to experimental NMR data encoded from (a) normal,
non-infiltrated breast tissue, (b) benign pathology (fibroadenoma) and (c) malignant breast tissue. At a partial signal length
NP = 1500, the FPT provided exact reconstruction of all the input spectral parameters for the time signals corresponding to
the normal, benign as well as to the malignant lesions. The converged parametric results remained stable at longer signal
lengths. The Padé absorption spectra yielded unequivocal resolution of all the extracted physical metabolites, even of those
that were nearly completely overlapping (phosphocholine and phosphoethanolamine at 3.22 ppm). The capacity of the FPT to resolve
and precisely quantify the physical resonances as encountered in normal versus benign versus malignant breast is demonstrated.
In particular, the FPT unambiguously delineated and quantified diagnostically important metabolites such as lactate, as well
as choline, phosphocholine and glycerophosphocholine that are very closely overlapping and may represent MR-retrievable molecular
markers of breast cancer. This was achieved by the FPT without any fitting or numerical integration of peak areas. We conclude
that these advantages of the FPT could be of definite benefit for breast cancer diagnostics via NMR and that this line of
investigation should continue with encoded data from benign and malignant breast tissue, in vitro and in vivo. We anticipate
that Padé-optimized MRS will reduce the false positive rates of MR-based modalities and further improve their sensitivity.
Once this is achieved, and given that MR entails no ionizing radiation, new possibilities for screening/early detection open
up, especially for risk groups, e.g. Padé-optimized MRS could be used with greater surveillance frequency among younger women
with high breast cancer risk. 相似文献
Influence of the synthesis medium on the saponite crystallisation: formation mechanism in acidic and basic media. The present work is relative to the hydrothermal synthesis of saponite, a clay mineral having the following chemical formula per half unit cell : MxMg3 (Si4–xAlx)O10(OH,F)2, 0.2 < x < 1.20, where M is an hydrated exchangeable cation and x is the layer charge. Syntheses were performed in fluorine medium in the pH range 1 to 12. Two mechanisms can be proposed: in acidic medium, tetrahedral polysilicic acid incorporate Al3+ cations and, in basic medium, silica polycondensation occurs around a [Mg(OH)2] brucite-like layer. To cite this article: M. Jaber, J. Miéhé-Brendlé, C. R. Chimie 8 (2005). 相似文献
The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin–wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol?1 · K?1. 相似文献
