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81.
Michael MuehlhoferThomas Strassner Eberhardt HerdtweckWolfgang A Herrmann 《Journal of organometallic chemistry》2002,660(2):121-126
Novel bridged platinum(II) biscarbene complexes are reported: 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) (3) and 1,1′-dimethyl-3,3′-ethylene-4-diimidazolin-2,2′-diylidene platinum(II) complexes 4 are directly accessible in high yields starting from platinum halides. The one-pot synthesis obviates the need for multi-step reactions via metal precursors or free carbenes. An X-ray crystal structure of 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) dibromide (3b) confirmed the structural similarity to the known corresponding palladium complexes. Since free 1,1′-di-R-3,3′-methylene-4-diimidazolin-2,2′-diylidenes are only available in low yields this synthetic route provides an easy access to the corresponding carbene complexes. 相似文献
82.
R.?Mitchell C.?M.?CarrEmail author M.?Parfitt J.?C.?Vickerman C.?Jones 《Cellulose (London, England)》2005,12(6):629-639
The surface chemical composition of raw unscoured cotton was successfully investigated by the surface analytical techniques
X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The presence of non-cellulosic
material at the fibre surface was established and determined to be a complex mixture of fatty acids, alcohols, alkanes, esters
and glycerides. The effect of scouring and bleaching was to reduce the surface concentration of these materials but even after
aqueous processing some non-cellulosic material residue was still detected at the fibre surface. 相似文献
83.
《Surface and interface analysis : SIA》2004,36(7):654-657
The mineral chemistry of enargite surfaces and near‐surfaces prepared by fracture within an ultrahigh vacuum are investigated using XPS and synchrotron radiation XPS (SRXPS). The purpose of the study is to identify surface core‐level line positions in high‐resolution photoelectron spectra. The XPS spectra obtained using monochromatic Al Kα radiation show that there are near‐identical monosulphide line positions in S 2p spectra for the As–S and Cu–S bonds in enargite. The SRXPS spectra for sulphur are remarkably similar to the XPS spectra for sulphur, showing that there is minimal difference in the chemical environment between sulphur atoms at the surface and in the mineral matrix. The Cu 2p XPS data have only cuprous contributions and a minor surface contribution. The surface Cu contribution is observed as a high‐binding‐energy tail in the Cu 2p3/2 spectrum. The As 3d data for both XPS and SRXPS show contributions from arsenic atoms at the surface and in the bulk mineral matrix. The surface contribution is distinct and is found 1 eV below the bulk contribution. The results of the study suggest that, following fracture, the enargite surface is reorganized in such a manner that the surface is characterized by protrusions of individual arsenic atoms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
84.
85.
The molecular structure of samarium dibromide has been studied by electron diffraction at T
exp = 1250(50) K. The molecule has C2v symmetry; the internuclear distance Rg(Sm–Br) = 274.5(5) pm; g =131(6)°. The vibration frequencies were estimated from the experimental values of the mean square vibration amplitudes. 相似文献
86.
I. V. Ukrainets N. L. Bereznyakova O. V. Gorokhova A. V. Turov 《Chemistry of Heterocyclic Compounds》2007,43(11):1426-1433
The bromination of 3-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline by molecular bromine is accompanied by the closure of a five
membered furan ring and gives the corresponding 2-bromomethyl-3,9-dihydro-2H-furo[2,3-b]quinolin-4-one.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1677–1686, November, 2007. 相似文献
87.
88.
The ab initio calculation of the title compound was carried out at HF as well as DFT level of theory. The full geometry optimization of the ligand was carried out using 6-31G(d) basis set. The results obtained were correlated with the single crystal X-ray data, also reported in this paper, shows close resemblance between these two. The influence of electron correlation effects also was studied by carrying out geometry optimization at the MP2 level. The attempts were also made to ascertain the most stable tautomer of the said compound. 相似文献
89.
I. V. Ukrainets N. L. Bereznyakova G. P. Petyunin I. A. Tugaibei V. B. Rybakov V. V. Chernyshev A. V. Turov 《Chemistry of Heterocyclic Compounds》2007,43(6):729-739
An improved method for the preparation and purification of ethyl 2-hydroxy-4-oxo-4H-pyrido[1,2-a]-pyrimidine-3-carboxylates
is proposed. According to 1H and 13C NMR spectroscopic data the synthesized compounds exist in DMSO solution in the 2-hydroxy-4-oxo form while in the crystal
(at least for the case of the unsubstituted derivative) X-ray analysis shows that it occurs in the bipolar 2,4-dioxo form.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 864–876, June, 2007. 相似文献
90.
Lorenzo MalavasiPaolo Ghigna Gaetano ChiodelliGiorgio Maggi Giorgio Flor 《Journal of solid state chemistry》2002,166(1):171-176
The synthesis and structural properties of Mg1−xMn2+xO4, for 0≤x≤1 are described. Complete miscibility in the solid state exists for this system. For the material with the correct stoichiometry, i.e. MgMn2O4, the effect of temperature on the cation distribution was investigated= above 600°C the inversion degree (m) starts increasing. The electrical conductivity shows a small dependence on P(O2) which is consistent with the small oxygen non-stoichiometry determined by means of thermogravimetry. The main contribution to the transport properties arises from the inversion equilibrium. Two distinct conductivity regimes, below and above the inversion threshold, can be assumed to explain the electrical conductivity and thermoelectric power results. 相似文献