Density functional study of S(N) 2 substitution reactions for CH(3) Cl + CX(1) X(2•-) (X(1) X(2) = HH, HF, HCl, HBr, HI, FF, ClCl, BrBr, and II)

A systematic investigation on the S_N2 displacement reactions of nine carbene radical anions toward the substrate CH₃Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6‐31+G (d, p)/relativistic effective core potential (RECP), 6‐311++G (d, p)/RECP, and aug‐cc‐pVTZ/RECP. The studied models are CX¹X^2?? + CH₃Cl → X²X¹CH₃C^? + Cl^?, with CX¹X^2?? = CH₂^??, CHF^??, CHCl^??, CHBr^??, CHI^??, CF₂^??, CCl₂^??, CBr₂^??, and CI₂^??. The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH₂^?? should be a strongest base among the anion‐containing species (CX¹X^2??) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the S_N2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back‐S_N2 pathway is much more preferred than the front‐S_N2 one in terms of the energy gaps [ΔE(front)?ΔE(back)], steric demand, NBO population analysis. Thus, the back‐S_N2 reaction was discussed in detail. On the one hand, based on the energy barriers (ΔE and ΔE) analysis, we have strongly affirmed that the stabilization of back attacking transition states (b‐TSs) presents increase in the order: b‐TS‐CI₂ < b‐TS‐CBr₂ < b‐TS‐CCl₂ < b‐TS‐CHI < b‐TS‐CHBr < b‐TS‐CHCl < b‐TS‐CF₂ < b‐TS‐CHF < b‐TS‐CH₂. On the other hand, depended on discussions of the correlations of ΔE with influence factors (PA, IE, bond order, and ΔE), we have explored how and to what extent they affect the reactions. Moreover, we have predicted that the less size of substitution (α‐atom) required for the gas‐phase reaction with α‐nucleophile is related to the α‐effect and estimated that the reaction with the stronger PA nucleophile, holding the lighter substituted atom, corresponds to the greater exothermicity given out from reactants to products. © 2012 Wiley Periodicals, Inc. J Comput Chem, 2012     

Pressure-induced formation of molecular B2X4(μ-X)2 (X = Cl, Br, I) species

Boron(III) halides (BX(3), where X = F, Cl, Br, I) at ambient pressure conditions exist as strictly monomeric, trigonal-planar molecules. Using correlated ab initio calculations, the three heavier halides (X = Cl, Br, I) are shown to possess B(2)X(4)(μ-X)(2) local minima, isostructural with the diborane molecule. The calculated dissociation barrier of the B(2)I(4)(μ-I)(2) species [≈14 kJ/mol with CCSD(T)/cc-pVTZ] may be high enough to allow cryogenic isolation. The remaining dimer structures are more labile, with dissociation barriers of less than 6 kJ/mol. All three dimer species may be stabilized by application of external pressure. Periodic density functional theory calculations predict a new dimer-based P1 solid, which becomes more stable than the P6(3)/m monomer-derived solids at 5 (X = I) to 15 (X = Cl) GPa. Metadynamics simulations suggest that B(2)X(4)(μ-X)(2)-based solids are the kinetically preferred product of pressurization of the P6(3)/m solid.     

[Pd(en)2Pd(en)2X2]4+n(X=Cl,Br,I)链的畸变研究

对一维卤桥过渡金属化合物〔Ｐｄ（ｅｎ）２Ｐｄ（ｅｎ）２Ｘ２〕ｎ＾４＋（Ｘ＝Ｃｌ,Ｂｒ,Ｉ）应用量子化学从头算及ＥＨＴ能带计算进行了研究,发现Ｐｅｉｅｒｌｓ畸变的产生及程度取决于填充轨道能量的降低与核间及电子间相互作用。     

Torsional potentials and conformational structures in the halogen substituted molecules HOCCH2X,HOCCHX2, XOCCH2X,XOCCHX2, XH2CCOCH3, X2HCCOCH3, (XH2C)2CO, (X2HC)2CO,and (X3C)2CO (X = Cl,Br) as determined by molecular-mechanics calculations

Parameter values of the non-blonded atom⋯atom interaction Br⋯OC have been established from gas-phase data. Conformational energies, structures, torsional barrier heights and torsional force constants of the title compounds have been estimated. For BrOCCH₂Br, (Cl₃C)₂CO and (ClH₂C)₂CO the calculated results are compared with gas-phase observations. It is suggested that hexachloroacetone ought to be reinvestigated by electron diffraction.     

OXO (X=Cl,Br)与X (2P3/2)反应机理的理论研究

用密度泛函B3LYP/6-311+G^**和高级电子相关的组态相互作用QCISD(T)/6-311+G^**方法研究了OXO与X(²P_3/2)双自由基反应的微观机理.研究结果表明:该反应存在两个反应通道,产物分别为XO和X₂+O₂.由于形成产物XO的活化势垒较低,因而是主要反应通道,这与实验观察到的结果是一致的.而形成X₂+O₂的通道从动力学上看是不利的.     

C70X2(X=H,F, Cl)的稳定性和电子光谱

用INDO方法研究C70H2四种异构体的稳定性, 表明其最稳定异构体为1, 9-C70H2和7, 8-C70H2, 两者能量差为16.3KJ.mol^-^1, 与实验值及ab initio计算值接近; 光谱计算表明, 其特征吸收峰与实验值一致。在此基础上预测C70F2和C70Cl2的稳定性和电子光谱, 表明C70F2四种异构体的稳定性顺序与C70H2一致, 而C70Cl2则以21, 42-异构体最为稳定。二者的电子光谱与C70H2极其相似只是在500nm以上有细微差别。     

Structures and bonding situation of Pb2X2 (X?=?H, F, Cl, Br and I)

Quantum chemical calculations using DFT (BP86) and ab initio methods (MP2, MP4 and CCSD(T)) have been carried out for the title compounds. The nature of the Pb?CPb interactions has been investigated with an energy decomposition analysis. The energy minimum structures of the halogen substituted Pb₂X₂ molecules possess a doubly bridged butterfly geometry A like the parent system Pb₂H₂. The unusual geometry can be explained with the interactions between PbX fragments in the X ²?? ground state which leads to one Pb?CPb electron-sharing ?? bond and two donor?Cacceptor bonds between the Pb?CX bonds as donor and vacant p(??) AOs of Pb. The energy difference between the equilibrium form A and the linear structure XPb??PbX (E) which is a second-order saddle point is much higher when X is a halogen atom than for X?=?H. This is because the a ⁴??^?????X ²?? excitation energies of PbX (X?=?F?CI) are higher than for PbH. The structural isomers B, D1, D2, E, F1, F2 and G of Pb₂X₂ are no minima on the potential energy surface.     

金属簇X (X=Pt-Au, Au-Au)负载在(3×2) TiO2(110)完整表面上的覆盖度效应

采用自旋极化密度泛函和广义梯度近似的方法并结合周期平板模型,探讨了不同覆盖度(θ)下双金属簇X (X=Pt-Au, Au-Au)在(3×2)TiO2(110)完整表面上的吸附行为.另外,在本文给出的所有覆盖度模式下(θ=1/6-1 ML),我们仅研究其基态构型.计算结果表明:当θ<1/2 ML时,金属簇X在TiO2(110)表面上吸附能随覆盖度的增加而增加;当θ>1/2 ML时,除了饱和覆盖度下,吸附能随覆盖度的增加而减小;当θ=1/2 ML时,吸附能最大.即使Pt-Au/TiO2体系的吸附能比Au-Au/TiO2体系的小,但相对于Au-Au簇, Pt-Au簇更容易在TiO2(110)表面上形成双金属单分子层.在半覆盖和全覆盖下, X簇的峰与TiO2的峰在-3.0 eV到费米能级之间产生明显重叠,表明簇与底物之间存在化学作用.且当覆盖度小时, X-TiO2相互作用是成簇的主要因素;随着覆盖度的增大, X-X原子间相互作用就逐渐变成了成簇的主要动力     

Mixed Amidohalotantalates [Ta(NMe2)3X3]– (X = F,Cl)

Russian Journal of Coordination Chemistry - The anionic tantalum complex (ItBuH)[Ta(NMe2)3Cl3] (I) is synthesized by the reaction of [Ta(NMe2)3Cl2]2 with N-heterocyclic carbene ItBu and is isolated...     

X@(HAINH)_(12)和X(HAINH)_(12)(X=F~-,Cl~-,Br~-,O~(2-),S~(2-),Se~(2-))复合物的结构和稳定性

用DFT的B3LYP方法在6-31G(d)基组的水平上,对闭式多面体簇合物(HA1NH)12及其内含式X@(HA1NH)12外接式X(HA1NH)12(X=F-,Cl-,Br-,O2-,S2-,Se2-)复合物的结构进行了构型优化和能量计算,并讨论了几何构型、自然键轨道(NBO)、振动频率、能量参数及NMR数据与结构的关系,最后得到复合物结构的稳定性信息,具有Th对称性的X@(HA1NH)12(X=F-,Cl-,Br-,S2-,Se2-)复合物和具有C3对称性的O2-@(HA1NH)12复合物为内含式的基态结构,从能量角度分析,内含式复合物比外接式复合物的结构稳定.     

Synthese,Kernresonanzspektren und Schwingungsspektren der Hexamethyltrisilane und Pentamethyltrisilane (XMe2Si)2SiMe2 und (XMe2Si)2SiMeX (XH,F, Cl,Br, I,Ph, OMe)

The syntheses, IR, Raman and ²⁹Si spectra of the title compounds are reported. SiSi force constants, calculated with the aid of normal coordinate analyses, are compared with ²⁹Si²⁹Si coupling constants.     

CH2X(X=H,F,Cl)与臭氧反应机理的量子化学研究

用量子化学UMP2方法,在6-311++G**基组水平上研究了CH2X(X=H,F,Cl)与臭氧反应机理,全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型,在UQCISD(T)/6-311++G**水平上计算了它们的能量,并对它们进行了振动分析,以确定中间体和过渡态的真实性.从CH2X(X=H,F,Cl)与O3的反应机理的研究结果看,它们与O3反应的活性都比较强,相对而言,活性大小顺序为CH2F＞CH3＞CH2Cl,也就是说,CH2F自由基与臭氧间的反应活性最强,对大气臭氧的损耗将是最大的.同时研究还发现CH2X(X=H,F,Cl)系列自由基与O3的反应都是强放热反应.     

Au(II)化合物[Au(CH_2)_2PH_2]_2X_2(X=F,Cl,Br,I)的量子化学理论研究

采用从头计算HF,MP2方法和密度泛函理论,对Au(II)系列化合物[Au(CH2)2PH2]2X2(X=F,Cl,Br,I)的几何结构、电子结构和振动频率进行了研究.研究表明Au的5d和6s电子参与Au—Au以及Au—X之间的成键.Au—Au,Au—X键强烈的电子相关作用使HF方法不适于该体系的研究,BP86和B3LYP两种泛函给出较大的Au—Au和Au—X键长,而MP2方法和局域的密度泛函方法则给出了合理的结构参数.局域密度泛函方法计算得到的Au—Au键和Au—X键振动频率也与实验数据符合较好.还运用含时密度泛函理论计算了[Au(CH2)2PH2]2X2的电子激发能,对分子在紫外-可见光谱范围内的电子跃迁进行了分析,考察了卤素配体对激发能的影响,并结合分子轨道能级的变化对此给予了解释.     

金属簇X (X=Pt-Au,Au-Au)负载在(3×2) TiO2(110)完整表面上的覆盖度效应

采用自旋极化密度泛函和广义梯度近似的方法并结合周期平板模型, 探讨了不同覆盖度(θ)下双金 属簇X (X=Pt-Au, Au-Au)在(3×2)TiO₂(110)完整表面上的吸附行为. 另外, 在本文给出的所有覆盖度模式下(θ= 1/6-1 ML), 我们仅研究其基态构型. 计算结果表明: 当θ<1/2 ML时, 金属簇X在TiO₂(110)表面上吸附能随覆盖 度的增加而增加; 当θ>1/2 ML时, 除了饱和覆盖度下, 吸附能随覆盖度的增加而减小; 当θ=1/2 ML时, 吸附能最 大. 即使Pt-Au/TiO₂体系的吸附能比Au-Au/TiO₂体系的小, 但相对于Au-Au 簇, Pt-Au 簇更容易在TiO₂(110)表 面上形成双金属单分子层. 在半覆盖和全覆盖下, X簇的峰与TiO₂的峰在-3.0 eV到费米能级之间产生明显重 叠, 表明簇与底物之间存在化学作用. 且当覆盖度小时, X-TiO₂相互作用是成簇的主要因素; 随着覆盖度的增 大, X-X原子间相互作用就逐渐变成了成簇的主要动力.     

The MNDO study of the potential energy surface for 1,5-H-migration in the radicals ĊCl2(CH2)2X(Me)2Et (X = C,Si, Ge)

The optimal geometries of the radicals Cl₂(CH₂)₂X(Me)₂Et [R¹(X)] and CHCl₂(CH₂)₂XMe₂CHMe [R²(X)] (X = C, Si, Ge) and the transition state structures for 1,5-hydrogen migration in the radical R¹(X) (R¹(X) R²(X)) are determined by use of the MNDO method with unrestricted Hartree-Fock approximation. It is found that the activation energies of these reactions increase on going from C to Si by 1.40 kcal/mole and decrease on going from Si to Ge by 0.56 kcal/mole.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No 1, pp. 98–100, January, 1993.     

Tantalocene complexes as bidentate métalloligands: (C5Me5)(C5H4X)Ta(H2)(PPh2) (C5Me5) (C5H4X)Ta(CO) (PPh2) (X = PPh2, CH2CH2NMe2)

The synthesis of new bidentate métalloligands derived from tantalocene(C₅Me₅)(C₅H₄X)Ta(H₂)(PPh₂) (X = PPh₂, 2P; X = CH₂CH₂NMe₂2N) and (C₅Me₅)(C₅H₄X)Ta(CO)(PPh₂) 4(P,N) is described. When opposed to chromium unsaturated fragments the phosphino functionalised complexes 2P and 4P act as chelating bidentate ligands affording Ta(V) (C₅Me₅)(C₅H₄PPh₂)Ta(CH₂) (μ-PPh₂)Cr(CO)₄ or Ta(III) (C₅Me₅)(C₅H₄PPh₂)Ta(CO)(μ-PPh₂)Cr(CO)₄ bimetallic complexes. The same reaction carried out starting from 2N gives rise to a μ-phosphido, μ-hydrido dibridged complex Cp*(C₅H₄CH₂CH₂NMe₂)TaH(μ-H)(μ-PPh₂)Cr(CO)₄.     

Substituent effects on the compounds CX1X2•− (X1, X2 = H, F, Cl, Br, I) from theoretical investigation

The electronic and molecular structures of mono- and dihalocarbene anions constructed by model CX¹X^2?? (X¹, X² = H, F, Cl, Br, I), as well as the corresponding carbenes CX¹X² and analogous silicon-anions SiX¹X^2??, have been studied in detail using the B3LYP, MP2, and QCISD(T) levels of theory. Our calculated findings suggest that stabilization of the compounds is associated with the size of the halogen substituent X, which is further confirmed by ionization energies, the spin density (S _d), and the second-order perturbative energies (E(2)). Besides, we have also explored the source of the anions’ proton affinity difference.     

An MP2 study on pre-reactive complexes (CH_2)_2O … XY (X,Y = H,F,Cl,Br,I)

The structures, energies, atomic chaiges and IR spectra of complexes (CH2)2O…XY (X, Y = H, F, Cl, Br, and I) have been examined by means of ab initio molecular orbital theory at the second-order level of Moller-Plesset perturbation correction. It is found that the hydrogen bond O…H-X is non-linear. The attraction between X and the H atoms in oxirane ring causes O…H-X bond bending. The hydrogen bond slighdy weakens the bond strength of C-O, and leads the bending and stretching mode of IR to shift to the red. The calculation results show that there is no evidence of a significant extent of proton transfer to give (CH2)2OH …X- in the isolated complexes.