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1.
The molecular structures of SiH3N3 and (SiH3)2 NCN have been determined by electron diffraction : SiH3N3 has a non-linear SiN3 skeleton, and (SiH3)2 NCN is a carbodiimide with SiNCN Si probably linear. A new model is proposed which rationalises the observed geometry of a number of molecular pseudohalides. 相似文献
3.
The structures of four isomeric forms of the model “silylenoid” SiH2LiF have been investigated by ab initio molecular orbital theory. The two most stable forms are suggested to be the SiH2Li+F? ion pair and the H2Si : FLi complex, analogous to the similar structures previously found for carbenoids. Two further species, a H2Si : LiF complex and the “classical” (tetrahedral) SiH2LiF, are also local minima on the potential energy surface, but are higher in energy. 相似文献
4.
The time-resolved laser magnetic resonance (LMR) method has been applied to kinetic measurements for the first time. An intracavity spectrometer based on a CO2 laser with resonant modulation of the magnetic field and with phase-sensitive detection of the signal has been used. Kinetic curves of generation and disappearance of CI atoms and SiH3 radicals were obtained in the pulse photolysis of a mixture of S2Cl2 + SiH4 under the fourth harmonic of a Nd laser (265 nm, 0.5 mJ, 12.5 Hz) at a total pressure of 520–980 Pa (he as diluent) and a temperature of 326 K. The reagent concentrations were: [S2Cl2 = (2.0?10.2)×1014 cm?3, [SiH4 = (2.4?17.4)×1013 cm?3. To remove the transition saturation, 5.3×1015 cm?3 CCl4 was introduced into the reactor. The fraction of dissociated S2Cl2 was 1‰ Rate constants of the reactions (I) Cl+S2Cl2 → products, (II) Cl+SiH4 → HCl+SiH3 and a preliminary rate constant of the reaction (III) SiH3 + S2Cl2 → products were obtained: k1 ≤ (4.3±1.2)×10?12 cm3/s, k2 = (2.3±0.5)×10?10 cm3/s, k3 = (2.4±0.5)×10?11 cm3/s. At a signal-to-noise ratio of 1:1, 1000 pulses and a 12 cm long detection zone the sensitivity to Cl atoms and to SiH3 radicals was 4×1010 cm?3 and = 1011 cm?3, respectively. The time resolution of the method was 4 μs. The method is shown to be promising for kinetic investigations and experiments on fast processes. 相似文献
5.
The first band in the vacuum ultraviolet photoelectron spectrum of the silyl radical, corresponding to the process SiH3 (X 1A′1) ← SiH3(X 2A1), has been observed with HeI radiation. Extensive vibrational fine structure associated with the SiH3+ deformation vibration was observed in this band and analysis of the structure gave a value of ω = 820 = 40 cm-1 for the out-of-plane deformation mode in the ion. The vertical and adiabatic ionization energies were measured as 8.74 = 0.01 eV and 8.14 ± 0.01 eV respectively and use of the latter value together with the established heat of formation of the silyl radical allows an improved heat of formation of SiH3-. ΔH2980 (SiH3-) to be derived as 980 ± 7 kJ mol?1. 相似文献
6.
采用密度泛函理论B3LYP方法研究了SiH2自由基与HNCO的反应机理, 并在B3LYP/6-311++G**水平上对反应物、中间体、过渡态进行了全几何参数优化, 通过频率分析和内禀反应坐标(IRC)确定了中间体和过渡态. 为了得到更精确的能量值, 又用QCISD(T)/6-311++G**方法计算了在B3LYP/6-311++G**水平优化后的各个驻点的相对能量. 计算结果表明SiH2自由基与HNCO的反应有五条反应通道, 其中顺式反应通道SiH2+HNCO→IM3→ TS4→IM5→TS5→IM6→SiH2NH+CO反应能垒最低, 为主反应通道. 相似文献
7.
Paul von Ragué Schleyer Yitzhak Apeloig Dorit Arad Brian T. Luke John A. Pople 《Chemical physics letters》1983,95(6):477-482
Differences between SiH+5 and CH+5 are more significant than the similarities. The proton affinity of SiH4 exceeds than of CH4 by ≈25 kcal/mol. but the heat of hydrogenation of SiH+3 is smaller than that of CH+3 by nearly the same amount. Like CH+5 the C5 structures of SiH+5 are preferred, but SiH+5 is best regarded as a weaker SiH+3—H2 complex. D3h, C2v, and C4v forms are much higher in energy and SiH+5 should not undergo hydrogen scrambling (pseudorotation) readily, as does CH+5 The neutral BH5 is only weakly bound toward loss H2, and the D3h. C2v, and C4v forms are also high in energy. The contral-atom electronegativities, C+ > B > Si+, control this behavior. The electronegativities also determine the ability to bear positive charges. Thermodynamically. SiH+5 and SiH+3 are more stable than CH+5 and CH+3, respectively; hydride transfer occurs from SiH4 to CH+3 and proton transfer from CH+5 to SiH4. 相似文献
8.
Bernd Wirsam 《Chemical physics letters》1973,18(4):578-580
SCF and CI calculations for the silicon-hydrogen compounds SiH3, SiH+3 and SiH? with D3h and C3v geometries are carried out f 相似文献
9.
Mean amplitudes and shrinkages are calculated from spectroscopic data for SiH3NCO, SiD3NCO, SiH3NCS and SiD3NCS. The lowest frequency (ν10) in each of the molecules is uncertain, and its influence on the calculated amplitude parameters is investigated. The results are compared with electron diffraction studies. 相似文献
10.
The gas phase reactions of Ge(3P0,1) and Si(3PJ) with O2, NO and N2O have been studied in a flow tube system at 350 K. Atomic Ge and Si were produced by flowing GeH4 and SiH4 through a hollow cathode discharge. The subsequent disappearance of the Ge and Si atoms was followed with atomic absorption spectroscopy. Rate constants were determined for the reactions at 4 and 5 torr pressures. 相似文献
11.
The laser-induced fluorescence of the SiH2 radical was observed in the photolysis of phenylsilane by an ArF excimer laser in the 550–650 nm range. The apparent fluorescence lifetime is 60 ± 5 ns at 580.1 nm. The bending vibrational spacing in the ground state was found to be 990 ± 20 cm?1 from the dispersed fluorescence spectrum. 相似文献
12.
Ab initio HF and Cl calculations were performed to determine the equilibrium geometry of SiH?5 and SiH?3, the barrier for internal rotation (SiH?5) and inversion (SiH?3) and the stability of SiH?5 and further to study the effect of electron correlation on reaction energies. The gaussian-type basis included d and f functions on Si and a p set on II. The D3h structures of SiH?5 is lower in energy than the C4v structure by 2.9(3.2) kcal/mol (corresponding HF results in parentheses). SiH?3 has C3v structure, the inner-ion barrier computed is 26.2 (27.3) kcal/mol. SiH?5 turns out to be stable with respect to SiH4 + H? by 20.3 (13.8) kcal/mol, but it is unstable with respect to SiH?3 ← H2 by 6.3 (5.6) kcal/mol. These results show that electron correlation has a small effect on barriers of inversion (SiH?3) or pseudorotation (SiH?5), but may have a pronounced effect on reaction energies even if all systems involved have closed shells. The correlation energy contributions are analyzed in terms of intrapair and interpair terms in order to get a better understanding of the influence of correlation on reaction and activation energies. 相似文献
13.
An electron diffraction analysis of the molecular structures of 1,1,1,3,3,3-hexachloro-1,3-disilapropane and octachloro-1,3-disilapropane has been carried out. Deviations from the staggered conformation are indicated. The data may be approximated by models with C2 symmetry and a small tilt of the SiCl3 groups. The main bond lengths (rg) and bond angles obtained for (SiCl3)2 CH2 are: SiCl, 202.7(4); SiC, 186.6(6); CH, 109.8(24) pm, ClSiCl, 107.9(1); SiCSi, 118.3(7)°; and for (SiCl3)2CCl2: SiCl, 202.0(4); SiC, 190.2(9); CCl, 179.6(9) pm; ClSiCl, 109.5(1); SiCSi, 120.6(9); ClCCl, 110.9(16); SiCCl, 106.3(3)°. 相似文献
14.
Tunneling spectra of Al2O3/—SiHx, MgO/—SiHx, Al2O3/—SiDx, and Al2O3/—SiHx + NCS? are reported. Analysis of the vibrational spectra observed from isotopic substitution of the barriers obtained by deposition of a thin film of SiO onto alumina and magnesia indicate that the supported species is —SiH. The Al2O3/—SiH barrier can be used as a support for studying inorganic ions by IETS. 相似文献
15.
The interaction between S2 molecule and SiHx (x=1, 2, 3) in porous silicon is investigated using the B3LYP method of density functional theory with the lanl2dz basis set. The model of porous silicon doped with CH3,Si-O-Si and OH species is built. By analyzing the binding energy and electronic transfer, we conclude that the interaction of S2 molecule with SiHx (x=1, 2, 3) is much stronger than the interaction of S2 molecule with CH3 and OH, as S2 molecule is located in different sites of the model. Using the transition state theory, we study the Si2H6+S2→H3SiH2SiS+HS reaction, and the reaction energy barrier is 50.2 kJ/mol, which indicates that the reaction is easy to occur. 相似文献
16.
Hydrocarbon solutions of Mo2(O—t-Bu)6 and PF3 (2 equiv) yield Mo4F4(O—t-Bu)8, I, and PF2(O—t-Bu). Compound I contains a bisphenoid of molybdenum atoms with two short MoMo distances, 2.26 Å, and four long MoMo distances, 3.75 Å, corresponding to localized MoMo triple bonding and non-bonding distances, respectively. The tetranuclear compound may be viewed as a dimer, [Mo2(μ2-F)2(O-t-Bu)4]2, and addition of PMe3 to hydrocarbon solutions of I yields Mo2F2(O—t-Bu)4(PMe3)2, II, which contains an unbridged MoMo triple bond of distance 2.27 Å. Each molybdenum atom is coordinated to two oxygen atoms, one fluorine atom and the phosphorus atom of the PMe3 ligand in a roughly square planar manner. The overall central Mo2O4F2P2 skeleton has C2 symmetry and NMR studies (1H, 19F and 31P) are consistent with the maintenance of this type of structure in solution. Infrared and electronic absorption spectral data are reported. These are the first compounds containing fluorine ligands attached to the (MoMo)6+ unit. 相似文献
17.
The calculation of the molecular orbital parameters of the σ-bonding square-planar Cu(NH3)2+4 cation in Cu(NH3)4PtCl4 is reported, involving metal—ligand and ligand—ligand overlap integrals. In order to obtain a reasonable correlation of the magnetic g- and A-values and the electronic transition energies it is necessary to use a Cu+ wavefunction to represent the radially expanded Cu2+ wavefunction in this complex. 相似文献
18.
James A. Kaduk Arthur T. Poulos James A. Ibers 《Journal of organometallic chemistry》1977,127(2):245-260
The structure of (η3-allyl)carbonylchlorobis(dimethylphenylphosphine)-iridium(III) hexafluorophosphate, [Ir(η3-C3H5)Cl(CO)(P(CH3)2(C6H5))2][PF6], has been determined from three-dimensional X-ray data to add support for a proposed mechanism of the oxidative addition of allyl halides to IrX(CO)(PR3)2 (X = halide). The compound crystallizes in space group C52h-P21/c with four formula units in a cell of dimensions a = 11.027(1), b = 12.230(2), c = 19.447(5) Å, and β = 103.16(2)0. Least-squares refinement of the structure has led to a value of the conventional R index (on F) of 0.066 for the 3018 independent reflections having F20>3—(F20). The crystal structure consists of discrete, monomericions. The hexafluorophosphate anion is disordered. The coordination geometry around the iridium atom may be described as octahedral, with the chloro ligand trans to the carbonyl group and each phosphorus atom trans to a terminal carbon of the allyl group. Structural parameters: Ir—P = 2.366(4), 2.347(3);Ir—Cl = 2.389(3); Ir—C(allyl) = 2.28(1), 2.24(1),2.25(1); Ir—C (carbonyl) = 1.85(1) Å; P—Ir—P = 105.7(1); C(terminal)—Ir—C(terminal) = 66.2(8); C—C—C = 125(2)o. The allyl group makes an angle of 126o with the P—Ir—P plane. Correlations between geometric structure and number of d electrons are noted among several M—C3H5-complexes, and are interpreted in the light of theoretical models of the M—C3H5- bond. 相似文献
19.
The microwave spectrum of trimethyl silyl isocyanate has been investigated in the region 26.5–40 GHz. The spectrum belonging to the ground vibrational state is characteristic of a symmetric top indicating that the equilibrium configuration of the SiNCO chain is either linear or very nearly so. The ground state B0 value is 1203.83 MHz which is consistent with the structure observed for SiH3NCO. The ground state transitions are accompanied by many vibrational satellites belonging to the lowest bending mode whose frequency was estimated to be 64 ± 15 cm−1. These results are consistent with electron diffraction results from which the SiNC angle is deduced to be ≈ 150°. 相似文献
20.
The infrared multiple photon excitation of SiH2Cl2, under collision-free and collisional conditions, via its v2(a1) SiH2 bending fundamental resulted in dissociation and in an ultraviolet luminescence. The photodissociative products were found to be H2 and SiCl2 while the luminescence was shown to arise from a spontaneous one-photon radiative decay from electronically excited SiCl2(1B1 → 1A1). The radiative lifetime of this transition has been measured as 4.5 μs and the collisional quenching rate of SiCl2(1B1 → 1A1) by SiH2Cl2 as 2.6 × 106 s?1 Torr?1. The reaction mechanism leading to product formation as well as models for populating the electronic state of the fragment are proposed and discussed in conjunction with present multiple photon dissociation theory. 相似文献