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31.
Babij C Farrar DH Koshevoy IO Poë AJ Tunik SP 《Dalton transactions (Cambridge, England : 2003)》2005,(1):116-122
Reactions of the halides X- (X- = chloride, bromide or iodide) with the substituted cluster Rh6(CO)15(PPh3) in oxygen-free chloroform lead to [Rh5(CO)14(PPh3)]-, Rh(CO)2(PPh3)2X and [Rh(CO)2X2]- in the molar ratios 2:1: approximately 13. Oxidation by the solvent is assumed to lead to most of the Rh(I) product, and the stoichiometry for reactions with I- can be defined as 4Rh6(CO)15(PPh3) + 27I- + 12CHCl3 --> 2[Rh5(CO)14(PPh3)]- + Rh(CO)2(PPh3)2I + 13[Rh(CO)2I2]- + 6C2H2Cl4 + 4CO + 12Cl-. This can be rationalized quite simply with the aid of a few generally justifiable assumptions. Rate constants for reactions with bromide increase to a limiting value with increasing [Br-] in a way that shows that breaking of one Rh-Rh bond, with an unusual closo to nido structural change, is rate determining. This opening of the cluster might be spontaneous or solvent induced. To complete the reaction, the bromide has to compete with the reverse nido to closo change. The same closo to nido change is also a major rate determining step for reactions with P(OPh)3 in oxygen-free solutions, and for reactions with bromide in oxygenated solutions in the presence of trifluoroacetic and some other acids. The limiting rates increase slightly with increasing basicity of the ligands P(p-XC6H4)3 along the series X = F3C, Cl, F, H and MeO. Activation parameters for these reactions are reported. 相似文献
32.
[reaction: see text]. We have previously described a diastereofacially selective 1,3-dipolar cycloaddition reaction of isomünchnones with vinyl ethers. While adapting this methodology for solid phase synthesis, we discovered a chemoselective and self-promoted linker aminolysis that provides liberated product in high purity, at a significantly enhanced rate. Herein we describe the implementation of a chiral auxiliary as a solid-phase linker, the detailed investigation of its unique aminolysis, and the utility of this cleavage within a chemical diversity format. 相似文献
33.
V. S. Bogdanov S. V. Baranin A. Dib I. P. Yakovlev V. A. Dorokhov 《Russian Chemical Bulletin》1992,41(9):1693-1699
Mono- and binuclear boron chelates have been synthesized by the action of butylthiodibutylborane on the ethyl esters of 4-[N-(R-pyrid-2-yl)carbamoyl]-3-amino-2-cyanobuten-2-ic acids (codimers of N-(R-pyrid-2-yl) amides and the ethyl ester of cyanoacetic acid). Complexes of this type can exist in solution in the form of two tautomers: acetamide acid derivatives or the corresponding ketene N,O-acetals.N. D. Zelinski Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2162–2170, September, 1992. 相似文献
34.
Burford N Cameron TS Clyburne JA Eichele K Robertson KN Sereda S Wasylishen RE Whitla WA 《Inorganic chemistry》1996,35(19):5460-5467
The phosphadiazonium cation [MesNP](+) reacts quantitatively with the fluorenylide anion, MesNH(2), and MesOH (Mes = 2,4,6-tri-tert-butylphenyl), resulting in formal insertion of the N-P moiety into the H-Y (Y = C, N, O) bonds. Specifically, reaction of MesNPCl with fluorenyllithium gives the aminofluorenylidenephosphine [crystal data: C(31)H(38)NP, monoclinic, P2(1)/c, a = 9.568(8) ?, b = 24.25(2) ?, c = 11.77(1) ?, beta = 101.38(8) degrees, Z = 4]. Similarly, reaction of [MesNP][GaCl(4)] with MesNH(2) gives the diaminophosphenium salt [MesN(H)PN(H)Mes][GaCl(4)] [crystal data: C(36)H(60)Cl(4)GaN(2)P, monoclinic, C2/c, a = 24.921(2) ?, b = 10.198(4) ?, c = 16.445(2) ?, beta = 93.32(1) degrees, Z = 4], and reaction with MesOH gives the first example of an aminooxyphosphenium salt [MesN(H)POMes][GaCl(4)]. It is proposed that the reactions involve nucleophilic attack at phosphorus followed by a 1,3-hydrogen migration from Y to N. Experimental evidence for the formation of sigma-complex intermediates is provided by the isolation of [MesNP-PPh(3)][SO(3)CF(3)] [crystal data: C(37)H(44)F(3)NO(3)P(2)S, triclinic, P&onemacr;, a = 10.663(1) ?, b = 19.439(1) ?, c = 10.502(1) ?, alpha = 103.100(7) degrees, beta = 113.311(7) degrees, gamma = 93.401(7) degrees, Z = 2]. As part of the unequivocal characterization of the aminooxyphosphenium salt, detailed solid-state (31)P NMR studies and GIAO calculations on the phosphenium cations have been performed. Contrary to popular belief, the phosphorus shielding in dicoordinate cations is not caused by the positive charge but results from efficient mixing between the phosphorus lone pair and pi orbitals. 相似文献
35.
Apparent two-dimensional behavior of TiO2 nanotubes revealed by light absorption and luminescence 总被引:1,自引:0,他引:1
Bavykin DV Gordeev SN Moskalenko AV Lapkin AA Walsh FC 《The journal of physical chemistry. B》2005,109(18):8565-8569
Optical absorption and photoluminescence (PL) properties of colloidal TiO(2) nanotubes, produced by the alkali hydrothermal method, were studied at room temperature in the range 300-700 nm. Nanotubes having an internal diameter in the range 2.5-5 nm have very similar optical properties, in contrast to the expected behavior for quasi-1-D systems. This is explained by the complete thermal smearing of all 1-D effects, due to the large effective mass of charge carriers in TiO(2), resulting in an apparent 2-D behavior of TiO(2) nanotubes. 相似文献
36.
UV absorption spectra of acetyl fluoride-h3 and -d3 (CH3COF and CD3COF) molecules in the region of S1S0 electronic transitions are investigated. The origins (00
0 or 140±
0) of these transitions are observed at 39912 and 39904 cm–1, respectively, and some of the fundamental frequencies of these molecules in the s0 and S1 states are determined. In particular, the systems of torsion and inversion (out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h3 molecule in the S1 state are estimated by the theoretical simulation of the rotational contours of the 00
0 (140±
0) band. These data are used to evaluate the potential barriers to internal rotation in the S0 and S1 states, which were found to be 360 and 560 cm–1 for acetyl fluoride-h3 and 380 and 770 cm–1 for acetyl fluoride-d3, respectively, as well as the potential barriers to inversion in the S1 states, which were found to be 2090 and 2370 cm–1 for acetyl fluoride-h3 and acetyl fluoride-d3, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1964, November, 1994.In conclusion, the authors would like to acknowledge T. S. Kuznetsova for the synthesis and purification of the AF samples.The research presented here was supported in part by the International Science Foundation under grant No. MJ 1000. 相似文献
37.
A. V. Yakovlev A. I. Finaenov S. L. Zabud’kov E. V. Yakovleva 《Russian Journal of Applied Chemistry》2006,79(11):1741-1751
Results obtained in synthesis of thermally expanded graphite by chemical and electrochemical methods with sulfuric and nitric acids are summarized. The possibility of controlling the properties of thermally expanded graphite compounds in electrochemical synthesis is demonstrated. The existing and promising application areas of thermally expanded graphite are analyzed. 相似文献
38.
Krivovichev SV Kahlenberg V Tananaev IG Kaindl R Mersdorf E Myasoedov BF 《Journal of the American Chemical Society》2005,127(4):1072-1073
A first amine-templated uranyl selenate based upon highly porous uranyl selenate nanotubules, (C4H12N)14[(UO2)10(SeO4)17(H2O)], has been prepared in the room-temperature reaction of uranyl nitrate, butylamine, and H2SeO4 in aqueous solution. The structure consists of nanometer-scale tubular [(UO2)10(SeO4)17(H2O)]14- units packed in a hexagonal-type fashion. The tubules have elliptical cross section with outer dimensions of 25 x 23 A = 2.5 x 2.3 nm. The internal free crystallographic diameter of the tubules is 12.6 A = 1.26 nm, which is comparable to the effective pore size in large-pore zeolites. This finding demonstrates the possibility of nanostructures for actinides in higher oxidation states and opens up a new area of research and exploration. 相似文献
39.
A.B. Zolotoy O.A. Dyachenko L.O. Atovmyan I.P. Yakovlev V.O. Reichsfeld 《Journal of organometallic chemistry》1980,190(3):267-276
The structure of 5-ethyl-5,10-dihydro-10,10-diphenylphenazasiline has been determined from three-dimensional X-ray data collected by counter methods. The compound in the monoclinic space group P21/b with a 10.782(5), b 22.642(9), c 8.830(4) Å and γ 74°41′(2). The observed and calculated densities (Z = 4) are 1.22 and 1.21 g cm-3, respectively. Anisotropic(Si, N, C)-isotropic block-diagonal least squares refinement gave a conventional R factor of 3.9% for 1871 reflections with I>2σ(I). The central six-membered ring of the tricyclic system adopts a boat conformation; the dihedral angle between the benzo-group planes is 157.3°. The CSiC angle in the heterocycle is 101.1(1)°; the mean SiC bond length is 1.850(2) Å (in the cycle) and 1.862(2) Å (with Ph group). The nitrogen atom is displaced 0.05 Å from the plane of the adjacent carbon atoms; the sum of the angle about N is 359.7°. 相似文献
40.
Yu. V. Yakovlev N. N. Dogadkin O. I. Kutchinskaja 《Journal of Radioanalytical and Nuclear Chemistry》1975,28(1-2):201-207
A calculation method of self-shielding coefficients of interesting elements in samples of any forms is given for the neutron
activation analysis of cadmium and its compounds. The determination of ten elements in cadmium telluride using radiochemical
separation and γ spectrometry is described.
相似文献