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21.
IR studies of SnF2 and hept-1-yne codeposited in an argon matrix at 12 K has revealed new bands at 540, 565, 1011, 2088 and 3256 cm–1, assigned to the formation of a complex between SnF2 and the alkyne. Quantum chemical AM1 and PM3 calculations confirm this assignment to the -complex of SnF2 and the triple bond of hept-1-yne, and show that the complex forms without an activation barrier. The energy of the formation of the complex according to AM1 and PM3 calculations is 7.4 and 9.1 kcal/mol, respectively. The calculations indicate that the product of the cycloaddition of SnF2 to a triple bond, stannyrene, is significantly less stable than the -complex.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 54–56, January, 1994. 相似文献
22.
A new set of parameters for the magnesium atom has been developed within the MNDO method. In contrast to previously published parameters, the new parameters correctly describe molecules with different chemical natures: magnesium halides, organomagnesium compounds and the recently found small magnesium clusters Mg
n
(n=2-8). The average errors in the calculated heats of formation and bond lengths of magnesium compounds, including clusters are: 10.7 kcal/mol and 0.167 Å, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1384–1388, August, 1994. 相似文献
23.
Thermal isomerization of acetylnitrene: a quantum-chemical study 总被引:1,自引:0,他引:1
The electronic structure and pathways of thermal isomerization of formylnitrene and acetylnitrene were studied by the B3LYP/6-311G(d,p) density functional method and ab initio G2(MP2,SVP) computational procedure using the geometries obtained from B3LYP calculations. According to G2 calculations, both nitrenes have singlet ground states while the energies of the corresponding triplet states are 2.8 and 5.7 kcal mol–1 higher. For acetylnitrene, the activation barrier to the nitrene isocyanate isomerization was estimated at 28.9 kcal mol–1 (G2). Calculations revealed no pathway for single-step isomerization of nitrene into cyanate in both systems. The formation of methyl cyanate from isocyanate is thermodynamically unfavorable (E = 26.5 kcal mol–1) and requires a high activation barrier (89.4 kcal mol–1) should be overcome. Based on the results obtained, the pathways of transformation of nitrene formed in thermal decomposition of acetyl azide (Curtius rearrangement) were analyzed. 相似文献
24.
S. E. Boganov V. I. Faustov M. P. Egorov O. M. Nefedov 《Russian Chemical Bulletin》1998,47(6):1054-1060
Complexes of difluorostannylene with dinitrogen of composition 1∶1 and 1∶2 were stabilized in Ar matrix (12 K) and characterized
by IR spectra. The bands at 588, 565, and 583, 557 cm−1, respectively, were assigned to these complexes. Potential energy surfaces of the systems SnF2+N2 and SnF2+2N2 were studied by theab initio MP2/3-21G(d2)//HF/3-21G(d2) method using the basis set including polarization functions at Sn, F, and N atoms. Equilibrium
structures of the complexes haveC
s andC
2v symmetry and correspond to coordination of lone electron pairs of nitrogen molecules with vacant p-AO of the carbenic center.
The calculated complexation energies are equal to 4.6 and 8.9 kcal mol−1, respectively. Based on results of quantum-chemical calculations an interpretation of the IR spectra of the complexes was
given and it was shown that cycloaddition of SnF2 to a triple N≡N bond with formation ofcyclo-SnF2N2 is energetically unfavorable. The absorption band belonging to SiF4·N2 complex in Ar matrix was detected and assigned.
Dedicated to the memory of Academician M. E. Vol'pin timed to his 75th birthday.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1087–1093, June, 1998. 相似文献
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Corrections of orders α5 and α6 to the superfine ground-state structure of the muonic hydrogen atom were calculated. The calculations took into account the effects of the structure of the nucleus on one-and two-loop Feynman amplitudes with the help of the electromagnetic form factors of the proton and the modification of the superfine part of the Breit potential caused by the electronic polarization of the vacuum. The total splitting of the 1S state is 182.725 meV; this value can be used as a reliable estimate in conducting a corresponding experiment with an accuracy of 30 ppm. 相似文献
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