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81.
Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C6H5)4][SnF3] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)5SnF3]? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)5THF only one pure triiodostannidometalate(O) Complex, [N(C2H5)4][Cr(CO)5SnJ3], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)5SnClX2]? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX2-insertion reactions of the [M(CO)5Cl]? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes. 相似文献
82.
The protonation and deprotonation rates of the coordinated amide group in the Cu2+ complexes with Nα-(2-pyridyl-methyl)-glycinamide (I) and Nα-(2-pyridyl-methyl)-glycineethylamide (II) have been studied by stopped flow techniques. It is shown that the rate determining step of the formation of the complex with the deprotonated amide group is given by the rate of water dissociation from Cu2+. Weaker bases than OH? or stronger acids than water can react by a different path, in which the proton transfer and/or the rotation from the O-co-ordinated into the N-co-ordinated form and vice versa is rate determining. 相似文献
83.
A multi-analyte method without any pre-treatment steps using reversed-phase liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was developed and applied for the determination of 20 primary aromatic amines (PAA) associated with polyurethane (PUR) products or azo-colours. The method was validated in-house for water and 3% acetic acid food simulants using spiked migrates from plastic laminates. Detection limits ranged from 0.27 to 3 microg amine/L food simulants, and RSD values of within-laboratory reproducibility at the 2 microg PAA/L level ranged from 3.9 to 19%. PAA migration from plastic laminates and black nylon cooking utensils were determined with the method, and high levels of 4,4'-methylenedianiline and aniline were found in migrates from about half of the tested cooking utensils. The method fulfils present legislative demands in the EU for screening and verification of PAA migration from food contact materials. 相似文献
84.
85.
Lee D Pervushin K Bischof D Braun M Thöny-Meyer L 《Journal of the American Chemical Society》2005,127(11):3716-3717
The heme chaperone CcmE is essential for the delivery of heme to c-type cytochromes. It forms an unusual transient, yet covalent, bond between an essential histidine, H130, and heme. We report on the discovery of the chemical structure of this bond solved by NMR, where the heme vinyl is cross-linked at the beta carbon to the Ndelta1 of H130. As this type of heme linkage has not been described previously in any cytochrome or hemoprotein, it represents a novel type of heme-histidine complex. 相似文献
86.
Thermolysis of the enyne-carbodiimides 7 having the central carbon-carbon double bond incorporated as part of the cyclopentene ring favors the formation of the corresponding N,4-didehydro-2-(phenylamino)pyridine intermediates, either as the sigma,pi-biradicals 8 or as the zwitterions 8', for subsequent synthetic elaborations. By placing appropriate substituents at the acetylenic terminus, a variety of the intramolecular decay routes are available for the initially formed sigma,pi-biradicals/zwitterions, leading to the 5,6-dihydrobenzo[c][1,8]naphthyridine 21, the 1,2,3,4-tetrahydro[1,8]naphthyridine 24 and related compounds 25 and 26, the 5,6-dihydrobenz[f]isoquinoline 28, and the benzofuro[3,2-c]pyridine 30. Surprisingly, the use of the dimethylamino group of the 2-(dimethylamino)phenyl substituent to capture the carbocationic center in the zwitterion 8e' furnished the 5H-pyrido[4,3-b]indole 32 in only 14% yield. The majority of the products were the 1H-pyrrolo[2,3-b]quinolines 34 and 35, isolated in 48 and 7% yields, respectively. However, it was possible to redirect the reaction toward 32 by conducting thermolysis of the enyne-carbodiimide 7e in the presence of 5 equiv of dimethylphenylsilyl chloride. Under this reaction condition, the 2-pyridone imine 37 was isolated in 86% yield, which on exposure to silica gel was converted to 32 in essentially quantitative yield. Thermolysis of the enyne-carbodiimide 42 having a methoxymethyl substituent at the acetylenic terminus led to the formation of 46' as a pyridine analogue of ortho-quinone methide imine. An intramolecular hetero-Diels-Alder reaction of 46' then furnished the tetrahydro[1,8]naphthyridino[2,1-c][1,4]benzoxazine 47. 相似文献
87.
Microwave—optical double resonance experiments have been carried out on the 4o1 band of the 1A21A1 system of thioformaldehyde (H2CS). More than 100 microwave and radiofrequency transitions have been observed in the 1A2 excited state. Many of these transitions are magnetically sensitive. Some of the excited state levels are perturbed by triplet levels and others by high vibrational levels of the ground state. 相似文献
88.
G. J. De Jong U. A. Th. Brinkman 《Journal of Radioanalytical and Nuclear Chemistry》1977,35(1):223-232
For the system liquid anion-exchanger—Cr(III)−NCS−, an investigation has been made of the dependence of the percentage extraction of Cr(III) on parameters such as standing
time of the Cr(III)−NCS− solution, temperature, pH and type of exchanger. Quantitative extraction of e.g. 4·10−4 M Cr(III) by 0.1M Aliquat in CCl4 is easily achieved at room temperature, using 4.75M KNCS−0.05N HCl as aqueous phase. At high Cr(III) concentrations, the
complex anion present in the organic phase is Cr(NCS)
6
3−
; when working with dilute metal ion solutions, the species extracted is Cr(NCS)4 (H2O)
2
−
. Separations of mixtures containing 10−2−10−4 M Co(II), Ni(II) and Cr(III) have successfully been accomplished. 相似文献
89.
On Calcium Bromated and Iodates – Crystal Structure, X-Ray, IR and Raman Spectroscopical and Thermoanalytical Investigations The phase relationships (and both decomposition and disproportionation)of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-Ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO3)2 · 6 H2O oF 216, the isotypic Ca(BrO3)2 · H2O and Ca(IO3)2 · H2O mP 48, Ca(IO3)2 I (Lautarit) mP 36, Ca(IO3)2 II and Ca(BrO3)2. The Crystal structure of Ca(IO3)2 · H2O (brüggenite) (space group P21/c, Z = 4) has been determined by single crystal X-ray diffraction (MoKα). The final R value for 3888 reflections with Io > 3σ1 is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO3–ions as well as the strengths of H-bonds present in the respective hydrates. 相似文献
90.
The reaction of [SiMe2(C5H4)2][(C5Me5)ZrMe2]2 with H2S at 110°C proceeds with the formation of [SiMe2(C5H4)2][(C5Me5)Zr(-S)]2]2. The molecular structure of this dinuclear zirconocenophane compound features a non-planar four-membered Zr2(-S)2
2 ring with two symmetrically-bridging sulfido groups. The bridging dimethylsilyl-bridged bis(cyclopentadienyl) ligand adopts a skewed orientation to accommodate the long Zr ... Zr separation of 3.611(1) Å. This compound crystallizes in the centrosymmetric space group P1 with refined lattice parameters ofa = 10.905(1) Å,b = 10.939(2) Å,c = 14.621(2) Å, = 106.32(1)°, = 91.25(1)°, = 111.25(1)°,V = 1545.1(8) Å3, calc. = 1.512g/cm3,Z=2. Full-matrix refinement converged with final discrepancy indices of R(F
o = 0.045 andR(F
o) = 0.079 with GOF= 1.60 for 4403 data withF
o > 3(F
o).This paper is dedicated to Professor Larry Dahl, a valued friend and mentor, on the occasion of his 65th birthday and in recognition of his significant fundamental contributions to the field of metal cluster chemistry. May the Goddess Fortuna continue to bring distinction and honor to him and his research endeavors. 相似文献