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1.
The effects of substitution of X = C by Si or Ge in X(CH(3))(3) moieties attached to the formal double bond of 3,3-dimethylcyclopropene are examined. Regularities in observed trends of vibrational frequencies implicating the moieties containing the X atom, as the X atomic mass is increased, are extrapolated to X = Sn. The results of this extrapolation made it possible to assign the known experimental vibrational frequencies of 3,3-dimethyl-1-(trimethylstannyl)cyclopropene and 3,3-dimethyl-1,2-bis(trimethylstannyl)cyclopropene.  相似文献   

2.
Su MD 《Inorganic chemistry》2004,43(16):4846-4861
Potential energy surfaces for the abstraction reactions of dimetallenes with halocarbons have been studied using density functional theory (B3LYP). Five dimetallene species, (SiH(3))(2)X=X(SiH(3))(2), where X = C, Si, Ge, Sn, and Pb, have been chosen in this work as model reactants. The present theoretical investigations suggest that the relative dimetallenic reactivity increases in the order C=C < Si=Si < Ge=Ge < Sn=Sn < Pb=Pb. That is to say, for halocarbon abstractions there is a very clear trend toward lower activation barriers and more exothermic reactions on going from C to Pb. Moreover, for a given dimetallene, the overall barrier heights are determined to be in the order CF(4) > CCl(4) > CBr(4) > CI(4). That is, the heavier the halogen atom (Y), the more facile its abstraction from CY(4). Halogen abstraction is always predicted to be much faster than the abstraction of a CY(3) group irrespective of the dimetallene or halocarbon involved. Our model conclusions are consistent with some available experimental findings. Furthermore, both a configuration mixing model based on the work of Pross and Shaik and bonding dissociation energies can be used to rationalize the computational results. These results allow a number of predictions to be made.  相似文献   

3.
利用B3LYP和CCSD(T)(单点)方法, 研究了含Si, Ge, Sn, Pb的六原子体系[MAl5]+中各个异构体的结构及稳定性. 研究结果表明, 尽管与[CAl5]+一样也具有18个价电子, 但[MAl5]+(M=Si, Ge, Sn, Pb)体系并不存在具有平面五配位结构的异构体, 其能量的全局极小点为具有Cs对称性的蝶形异构体Int1, 这是由于中心原子M(Si, Ge, Sn, Pb)较大的体积显著破坏了[MAl5]+中平面五配位结构的稳定性所致.  相似文献   

4.
Substitution Reactions of Bis(trimethylelement)carbodiimides of Silicon and Germanium with Metal Chlorides and Dimethylmetalchlorides of Sb, Al, Ga, and In The reaction of Me3Ge? N?C?N? GeMe3 (Me?CH3) with SbCl5 in a 1 : 1 molar ratio forms dimeric Cl4SbNCNGeMe3 in high yields. The corresponding compounds (X2MNCNSiMe3)2–3 (with X?Cl, Me and M = Al, Ga), formed by reactions of X2MCl and Me3SiNCNSiMe3, are less stable and tend to condensations, eliminating Me3SiX. The carbodiimide derivates (Me2MNCNEMe3)2–3 (with E = Si, Ge) are also available in aprotic solvents from polymeric LiNCNEMe3 and Me2MCl (M = Al, Ga, In). According to the IR and Raman spectra the low associated substitution products consists of cyclic ring skeletons and asymmetric > N? C?N? EMe3 units with cyanamide conformation.  相似文献   

5.
Using the first-principles method with the generalized gradient approximation, the authors have studied the structural and electronic properties of Al(12)X(+) (X=C, Si, Ge, Sn, and Pb) clusters in detail. The ground state of Al(12)C(+) is a low symmetry C(s) structure instead of an icosahedron. However, the Si, Ge, Sn, and Pb atom doped cationic clusters favor icosahedral structures. The ground states for Al(12)Si(+) and Al(12)Ge(+) are icosahedra, while the C(5nu) structures optimized from an icosahedron with a vertex capped by a tetravalent atom have the highest binding energy for Al(12)Sn(+) and Al(12)Pb(+) clusters. The I(h) structure and the C(5nu) structure are almost degenerate for Al(12)Ge(+), whose binding energy difference is only 0.03 eV. The electronic properties are altered much by removing an electron from the neutral cluster. The binding strength of a valence electron is enhanced, while the binding energy of the cluster is reduced much. Due to the open electronic shell, the band gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are approximately 0.3 eV for the studied cationic clusters.  相似文献   

6.
利用从头算MP2方法和密度泛函理论B3LYP和B3PW91方法, 研究了杂硼原子簇XB6+ (X=C, Si, Ge, Sn, Pb)的结构、稳定性及化学键合情况. 对C, Si, Ge, B使用6-311+G(d)基组, 对Sn和Pb使用LANL2DZ赝势基组. 研究结果表明, 具有Cs对称性的假平面XB6+ (X=C, Si, Ge, Sn, Pb)结构是势能面上的全域极小点, 其稳定性要高于C6v对称性的锥形结构和C2对称性的假锥形结构. 在B3LYP水平上, 对这些异构体的势能面的极小点进行了自然键轨道(NBO)的分析; 对最稳定构型的最高占据分子轨道(HOMO)和最低空轨道(LUMO)能级差、分子轨道(MO)和核独立化学位移(NICS)进行了计算和讨论. 分析了杂原子和硼原子间、相邻硼原子间的键合情况, 讨论了最稳定构型的芳香性质.  相似文献   

7.
The reactions of (E)-2-diethylboryl-1-trimethylstannylbut-1-ene and (Z)-3-diethylboryl-2-trimethylstannylpent-2-ene with carbodiimides, methyl thiocyanate, thioisocyanates, and isocyanates were studied, and the products were characterized by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C and 119Sn NMR). It was found that carbodiimides bearing tert-butyl or trimethylsilyl groups at the nitrogen atoms do not react with (E)-2-boryl-1-stannylalkenes, in contrast to dicyclohexylcarbodiimide. There was also no reaction in the case of MeSCN. All other reactions proceed via a weak NB adduct formation in the initial step, followed by different rearrangements, depending on the structure of reagents as well as on the substitution pattern at the C=C bond in alkenes. New heterocycles are formed, in which the boron atom is either tricoordinated (1,2-azaborolenes, 1,2-azaborolan! es), a nd one ethyl group has been transferred to the neighbor olefinic carbon atom, or the boron atom is tetracoordinated (1,2-azaboratoles, 1,2-oxoniaboratoles), and the trimethylstannyl group has migrated to one of the heteroatoms of the heterocumulenes.  相似文献   

8.
A series of reactions of the type Y. + XH(4) --> YH + .XH(3) and Y'. + HX(CH(3))(3) --> Y'H + .X(CH(3))(3), where Y = H, CH(3); Y' = CH(3), C(CH(3))(3); and X = Si, Ge, Sn, Pb are studied using state-of-the-art ab initio electronic structure methods. Second-order M?ller-Plesset perturbation theory; the coupled-cluster singles, doubles, and perturbative triples method; and density functional theory are used with correlation-consistent basis sets (cc-pVNZ, where N = D, T, Q) and their pseudopotential analogs (cc-pVNZ-PP) to determine the transition-state geometries, activation barriers, and thermodynamic properties of these reactions. Trends in the barrier heights as a function of the group IVA atom (Si, Ge, Sn, and Pb) are examined. With respect to kinetics and thermodynamics, the use of a hydrogen attached to a group IVA element as a possible hydrogen donation tool in the mechanosynthesis of diamondoids appears feasible.  相似文献   

9.
在CCSD(T)/aug-cc-pVTZ&;CEP-121G//B3LYP/6-311+G(d)&;LANL2DZ水平上, 研究了由更高周期的Sn和Pb单掺杂Al4团簇形成的五原子含铝体系XAl4(X=Sn, Pb), 确定了体系的低能异构体, 分析了关键异构体的结构和稳定性. 研究结果表明, 与SiAl4及GeAl4的基态平面四配位Si/Ge结构所不同, 等价电子的SnAl4和PbAl4体系的基态结构不是平面四配位Sn/Pb, 而是平面四配位Al, 其中杂原子Sn/Pb采取二配位方式, 此外, Sn/Pb采取三配位方式的非平面结构的稳定性也要优于平面四配位Sn/Pb结构.  相似文献   

10.
The transition of the “ordered” anti-PbCl2 lattice in the anti-PbFCl lattice: The ternary phases ABX of the alkaline earths with main group IV elements (A = Ca, Sr, Ba; B = Mg; X = Si, Ge, Sn, Pb) The compounds CaMgX, SrMgX and BaMgX (X = Si, Ge, Sn, Pb) were synthesized and their structures determined. CaMgX and SrMgX crystallize in the “ordered” Anti-PbCl2-type and are therefore related to the binary compounds Ca2X(X = Si, Ge, Sn, Pb), which form the Anti-PbCl2-type too. The phases BaMgX build up the Anti-PbFCl-structure. The relations of these two different structures are discussed in respect to the radii of the components.  相似文献   

11.
Spectroscopical Investigations on R3MF Compounds (M = Si, Ge, Sn) The IR and RAMAN spectra of a number of R3MF compounds (M? Si, Ge, Sn) have been recorded. The frequencies of the vibrational spectra were almost completely assigned. The measurements of the IR-spectra were investigated (as for as possible) in all states of aggregations. The force of the intermolecular interactions were discussed by means of the spectroscopic data.  相似文献   

12.
The infrared andRaman spectra of theM(CH3)4 andM(CD3)4 species,M=Si, Ge, Sn and Pb, have been reinvestigated. The spectra of the mixed tetramethyl compounds (CH3)3 MCD3,M=Si, Ge, Sn and Pb, and of (CH3)2Si(CD3)2 and CH3Si(CD3)3 have been recorded in the gaseous (i.r.) and liquid states (Raman). The proposed assignment is supported by a normal coordinate analysis.
  相似文献   

13.
The infrared and Raman vibrational spectra of X3MCo(CO)4 compounds (M = Si, Ge, Sn and X = Cl, Br, I) including depolarization measurements are presented. These spectra result in complete vibrational assignments which are different from those reported previously.  相似文献   

14.
在B3LYP计算水平下,使用混合基组6-311+G(d)LANl2dz首次对含Sn,Pb的五原子平面四配位碳分子[CAl3X]和[CAl3X]-(X=Sn,Pb)两个体系(分别具有17和18价电子)的异构体结构及能量进行了量子化学计算研究,并与文献已经报道的[CAl3X]和[CAl3X]-(X=Si,Ge)作了比较.结果表明,具有平面四配位碳结构的异构体int1是能量的全局最小点.相对于17e的[CAl3X]体系来说,在得到一个电子以后形成18e的[CAl3X]-int1异构体在热力学上变得更稳定.本项研究将进一步丰富五原子平面四配位碳化学.  相似文献   

15.
16.
Compounds (4-FC6H4)3SnSEPh3 (E=C, Si, Ge, Sn, or Pb) were synthesized or generated in solution. The data on the comparative electronegativity of the Ph3E groups were obtained from the results of19F NMR spectroscopy. It was established that, except for E=C, the electronegativity changes in parallel with the absolute electronegativity of the central atom. Possible reasons for the deviation observed are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1215‐1218, June, 1997.  相似文献   

17.
The isotypic Na4XO4 (X = Si, Ti, Cr, Mn, Co, Ge, Sn, Pb) and K4XO4 (X = Ti, Cr, Mn, Ge, Zr, Sn, Hf, Pb) phases crystallize in the triclinic system. Optical and magnetic properties of the chromium, manganese, and cobalt compounds show that the transition element has a tetrahedral surrounding.  相似文献   

18.
The Group XIV tetratolyl series X(C6H4‐CH3)4 (X=C, Si, Ge, Sn, Pb) were studied by using inelastic neutron scattering to measure the low‐energy phonon spectra to directly access the methyl‐group torsional modes. The effect of increased molecular radius as a function of the size of the central atom was shown to have direct influence on the methyl dynamics, reinforced with the findings of molecular dynamics and contact surface calculations, based upon the solid‐state structures. The torsional modes in the lightest analogue were found to be predominantly intramolecular: the Si and Ge analogues have a high degree of intermolecular methyl–methyl group interactions, whilst the heaviest analogues (Sn and Pb) showed pronounced intermolecular methyl interactions with the whole phonon bath of the lattice modes.  相似文献   

19.
A new class of exceptionally stable asymmetric N‐heterocyclic germylenes, stannylenes, and plumbylenes has been successfully isolated and characterized by single‐crystal X‐ray diffraction analysis and multinuclear NMR spectroscopy. Their stability results from tetrameric supramolecular aggregation through strong intermolecular Npy→EII (E=Ge, Sn, Pb) interactions involving the nitrogen atom of a neighboring pyridine moiety. The electronic structures and stabilities of the prepared divalent derivatives of Ge, Sn, and Pb in monomeric and aggregated forms are discussed based on theoretical investigations.  相似文献   

20.
采用第一性原理密度泛函方法,在考虑极化函数的双数字(DND)基组水平上,对α-[XMo12O40]n-(X=P, Si, Ge)杂多阴离子进行了几何构型优化,得到了与X-ray晶体衍射实验结果相一致的结构参数;并在优化几何构型基础上进行了振动频率分析,首次得到了非经验计算的杂多阴离子的振动光谱,计算的频率及强度与实验结果总体上吻合得较好.对全部22个有红外活性(IR)和44个有拉曼(R)活性的频率进行了指认,并与经验方法得到的结果进行了比较,同时,对部分频率的归属加以进一步的澄清与确认.  相似文献   

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