排序方式: 共有32条查询结果,搜索用时 15 毫秒
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E. Ya. Misochko A. V. Akimov A. A. Masitov D. V. Korchagin S. M. Aldoshin S. E. Boganov K. N. Shavrin V. D. Gvozdev M. P. Egorov O. M. Nefedov 《Russian Chemical Bulletin》2011,60(11):2180-2187
The ESR spectrum of the first representative of highly conjugated triplet ethynylvinylcarbenes, 5-methylhexa-1,2,4-triene-1,3-diyl (1), was recorded in solid argon matrix. The zero-field splitting (ZFS) parameters of carbene 1 (D = 0.5054±0.0006 cm?1 and E = 0.0045±0.0002 cm?1) determined from the experimental ESR spectrum are in between the corresponding parameters of ethynylcarbene C3H2 (2) and vinylcarbene C3H4 (3): D(3) < D(1) < D(2) and E(2) < E(1) < E(3). Quantum chemical calculations of the ZFS parameters of 1, 2, and 3 have been carried out for the first time using two DFT-based approaches, RODFT and UDFT. An analysis of the experimental and theoretical ZFS parameters shows that carbene 1 is characterized by a greater extent of delocalization of the spin density of unpaired electrons than carbenes 2 and 3. The characteristic structural fragments of carbene 1 possess the principal features of the electronic structure of both ethynylcarbene (2) and vinylcarbene (3), respectively. Magnetic spin-spin interactions are identical in carbenes 1 and 2. The dominant contribution to D in 1 and 2 results from the one-center spin-spin interactions on carbon atoms in the propynylidene group, which are subjected to strong spin polarization. 相似文献
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S. E. Boganov M. P. Egorov V. I. Faustov I. V. Krylov O. M. Nefedov R. Becerra R. Walsh 《Russian Chemical Bulletin》2005,54(3):483-511
The results of time resolved gas phase studies of labile germylenes (GeH2 and GeMe2) and dimethylstannylene (SnMe2) reactions reported to date are considered together with data of quantum-chemical investigations of the potential energy surfaces of these systems. Reaction mechanisms are discussed. A comparison of reactivity in the series of carbene analogs, ER2 (E = Si, Ge, Sn, R = H, Me), is made.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 477–505, March, 2005. 相似文献
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Becerra R Boganov SE Egorov MP Faustov VI Krylova IV Nefedov OM Promyslov VM Walsh R 《The journal of physical chemistry. A》2008,112(5):849-857
Time-resolved studies of silylene, SiH2, and dimethylsilylene, SiMe2, generated by the 193 nm laser flash photolysis of appropriate precursor molecules have been carried out to obtain rate constants for their bimolecular reactions with dimethylgermane, Me2GeH2, in the gas phase. SiMe2 + Me2GeH2 was studied at five temperatures in the range 299-555 K. Problems of substrate UV absorption at 193 nm at temperatures above 400 K meant that only three temperatures could be used reliably for rate constant measurement. These rate constants gave the Arrhenius parameters log(A/cm3 molecule(-1) s(-1)) = -13.25 +/- 0.16 and E(a) = -(5.01 +/- 1.01) kJ mol(-1). Only room temperature studies of SiH2 were carried out. These gave values of (4.05 +/- 0.06) x 10(-10) cm3 molecule(-1) s(-1) (SiH2 + Me2GeH2 at 295 K) and also (4.41 +/- 0.07) x 10(-10) cm3 molecule(-1) s(-1) (SiH2 + MeGeH3 at 296 K). Rate constant comparisons show the surprising result that SiMe2 reacts 12.5 times slower with Me2GeH2 than with Me2SiH2. Quantum chemical calculations (G2(MP2,SVP)//B3LYP level) of the model Si-H and Ge-H insertion processes of SiMe2 with SiH4/MeSiH3 and GeH4/MeGeH3 support these findings and show that the lower reactivity of SiMe2 with Ge-H bonds is caused by a higher secondary barrier for rearrangement of the initially formed complexes. Full details of the structures of intermediate complexes and the discussion of their stabilities are given in the paper. Other, related, comparisons of silylene reactivity are also presented. 相似文献
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Complexes (1:1) between difluorostannylene and benzene, chlorobenzene, and toluene as well as the (PhH)2·SnF2 complex were obtained and characterized by matrix IR spectroscopy. The capability of carbene analogs to form labile complexes
with aromatics was demonstrated for the first time taking SnF2 as an example.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 97–102, January, 1999. 相似文献
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V. N. Khabashesku S. E. Boganov K. N. Kudin J. L. Margrave J. Michl O. M. Nefedov 《Russian Chemical Bulletin》1999,48(11):2003-2015
The recent advances in spectroscopic and quantum-chemical studies of carbene-to-olefin isomerization of carbene analogs of
Group 14 elements are discussed. Primary attention is devoted to the use of matrix isolation spectroscopy, whose successful
combination with modern calculation techniques has resulted in the first spectroscopic characterization of a number of novel
short-lived silylenes and germylenes and their structural isomers with unsaturated Si=C, Ge=C, and Si=O bonds.
Based on invited lecture given by Professor Dr. V. N. Khabashesku at the Sixth International Conference on Chemistry of Carbenes
and Related Intermediates (May 28–30, 1998, St. Petersburg, Russia).
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2027–2039, November, 1999. 相似文献