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排序方式: 共有282条查询结果,搜索用时 31 毫秒
1.
2.
Gordon K. Anderson Ronald J. Cross Ljubica Manojlovic-Muir Kenneth W. Muir Tihomir Solomun 《Journal of organometallic chemistry》1979,170(3):385-397
The known complex, -(η-C5H5)2Rh2(CO)2(CF3C2CF3) is formed in high yield from (η-C5H5)Rh(CO)2 and CF3FCCF3 at 100°. The less stable -isomer of the complex is obtained in low yield from the same reaction. The infrared, 1H, 19F and 13C NMR spectra of the two isomers are compared. The -isomer undergoes CO scrambling in solution at room temperature, and the variable temperature 13C NMR spectra are consistent with a pairwise bridge opening and closing mechanism. The mechanism is extended to account for the isomerization of to isomer, whihc has a half-life of 12 h at room temperature. The 13C spectrum indicates that the -isomer is static in solution at room temperature. The -isomer is reversibly protonated by protonic acids, and BF4? and PF6? salts of the protonated species can be isolated. The spectroscopic properties of these salts are consistent with protonation at one of the alkynyl-carbons, but it is not possible to distinguish between two alternative structures for the complex cation.Treatment of (η-C5H5)2Rh2(CO)2(CF3C2CF3) with (η-C5H5)Rh(CO)2 gives the trinuclear complex (η-C5H5)3Rh3(CO)(CF3C2CF3) in 80% yield. The analogoug but-2-yne complex is formed from (η-C5H5)3Rh3(CO)3 and MeCCMe. The infrared, 1H, 19F and 13C NMR spectra indicate that the hexafluorobut-2-yne complex exists in two different structural arrangements in solution. One has an edge bridging, and the other a face bridging carbonyl. The proportion of the isomers is affected by the solvent polarity. The spectra of the but-2-yne complex indicate it is fluxional at room temperature, and has a face bridging structure in solution regardless of the polarity of the solvent. Reversible protonation of the hexafluorobut-2-yne complex occurs in protonic acids, and the salt [(η-C5H5)3Rh3(CO)(CF3C2CF3)H]+[BF4]?,H2O can be isolated. The spectroscopic properties of this complex are consistent with a structure incorporating an edge-bridging carbonyl, and probably, an edge-bridging hydride ligand. 相似文献
3.
A synthesis of N-acetylcolchinol, a key intermediate in the synthesis of ZD6126, was developed. The enantiodifferentiating step required the catalytic asymmetric hydrogenation of an enamide. After screening a range of metal and ligand combinations it was found that (S,S)-iPr-FerroTANE Ru(methallyl)2 and [(S,S)-tBuFerroTANE Rh(COD)]BF4 gave both high enantioselectivity (>90% ee) and high catalyst utility (molar S/C = 1000). 相似文献
4.
The addition of R3SiCl to B(OTf)3 gives “supersilylating agents” formulated as R3SiB(OTf)3Cl. The catalytic properties of these species are similar to those of the previously-described (but less accessible) R3SiB(OTf)4. 相似文献
5.
[reaction: see text] On treatment with samarium(II) iodide, gamma,delta-unsaturated ketones undergo very different processes depending upon the nature of the reaction conditions. Employing samarium(II) iodide and MeOH, functionalized syn-cyclopentanol products are obtained stereoselectively. Mechanistic studies suggest that this cyclization occurs via a sequential reduction/intramolecular aldol reaction. With samarium(II) iodide and HMPA, products of a 4-exo-trig cyclization and of an interesting fragmentation reaction are observed. 相似文献
6.
Elina Ruiz Xuejiao Tang Yong -Ji Li Mariel M. Muir 《Journal of chemical crystallography》1993,23(10):791-794
Tetraethylammonium tribromo[2-(2-chloro-5-nitrostyryl)benzoselenazole] platinate (II), [(C2H5)4N][PtBr3(C15H9ClN2O2Se)], is monoclinic, in space groupP21/c, witha=9.496(2),b=20.321(7),c=15.166(3)Å,=100.18(1)°,V=2880(2)Å3,M
r
=928.72,Z=4,D
x
=2.141 g cm–3, (MoK)=0.71073 Å,=104.1 cm–1,F(000)=1752,T=298 K. The structure was solved by direct methods and refined toR=0.032 for 2626 unique observed reflections withI>3(I). The [Pt(nsbse)Br3)] unit has square-planar geometry about the Pt atom, with the nsbse coordinated to the Pt through the N of the selenazole ring. The ligand molecule is non-planar, with a dihedral angle of 61.6(2)° between the benzoselenazole and phenyl rings. The dihedral angles between the PtBr3 plane and the benzoselenazole and phenyl planes are 105.2(1) and 80.7(1)°, respectively. 相似文献
7.
8.
Mineral and short-chain carboxylic acid vapours and NO(x) gases were reacted with cyclohexene oxide (1,2-epoxycyclohexane) to quantitatively produce specific, thermally stable cyclohexyl derivatives. Subsequent analysis of these derivatives by gas chromatography with mass spectroscopy and flame ionisation detection afforded a multi analyte method for the assay of these gaseous acidic atmospheric species. Derivatisation was found to be quantitative for the derivatives tested and the method highly sensitive (to 0.3 mg/m3 for a 30 l sample), accurate, precise and free from apparent interferences. The technique has been applied to "acid stack gases" and a number of other acid rich atmospheres and the results obtained show good agreement with the single analyte wet chemical determinations indicating that the approach has considerable potential as a routine analytical method for measuring such atmospheric pollutants. The high specificity of the reaction mechanism and its potential for the analysis of analyte mixtures is illustrated in the assay of nitric acid and its acid anhydride, dinitrogen pentoxide. 相似文献
9.
LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301
10.
David G. Morris Kenneth W. Muir Karl S. Ryder 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(10):o615-o618
Crystals of 9‐methylfluoren‐9‐ol, C14H12O, undergo a reversible phase transition at 176 (2) K. The structure of the high‐temperature α form at 200 K is compared with that of the low‐temperature β form at 100 K. Both polymorphs crystallize in space group P with Z = 4 and contain discrete hydrogen‐bonded R(8) ring tetramers arranged around crystallographic inversion centres. The most obvious changes observed on cooling the crystals to below 176 K are an abrupt increase of ca 0.5 Å in the shortest lattice translation, and a thermal transition with ΔH = 1 kJ mol?1. 相似文献