Intramolecular Rearrangements of >Si(O–C·=O)(CH2–CH3) and >Si(CH2–CH·–CH3)(CH2–CH3) Radicals

Using ESR and IR spectroscopy, the structures of >Si(O–C^·=O)(CH₂–CH₃) (1) and >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) (2) radicals were deciphered. The directions and kinetic parameters of reactions of intramolecular rearrangements in these radicals were determined. The reactions of hydrogen atom abstraction in radical (1) from the CH₂ and CH₃ groups were studied. It was found that the endothermic reaction of hydrogen atom abstraction from the methyl group occurs at a higher rate than the exothermic reaction with the methylene group. The differences are determined by changes in the size of a cyclic transition state. Based on the experimental data, the strengths of separate C–H bonds in surface fragments are compared. The rearrangement >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) >Si(C^·(CH₃)₂)(CH₂–CH₃) was discovered and its mechanism was determined. One of its steps is the skeletal isomerization Si- (2)- _. (1)Si- (1)- _. (2). Experimental data are analyzed using the results of quantum-chemical calculations of model systems.     

Geometric shielding corrections for calculation of electron scattering by CO2, C2H2, CHCl3, CH2Cl2, CH3Cl,CHF3, CH2F2 and CH3F at 30–5000 eV

Taking into account the changes of the geometric shielding effect in a molecule as the incident electron energy varies, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using the new additivity rule, the total cross sections of electron scattering by CO₂, C₂H₂, CHCl₃, CH₂Cl₂, CH₃Cl, CHF₃, CH₂F₂ and CH₃F are calculated at the Hartree–Fork level at 30–5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, especially above 100 eV.     

反常蓝移单电子锂键Y…Li-CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]体系的结构与性质

在密度泛函理论B3LYP/6-311++G(d,p)及MP2/6-311++G(d,p)水平上研究了单电子锂键复合物Y…Li—CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]的结构与性质. 结果表明, 三种单电子锂键复合物H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III)和(H3C)3C…Li—CH3(IV)单电子锂键强度依II(-26.7 kJ·mol-1)相似文献   

Ab initio study of Eu3+–L (L=H2O,H2S,NH2CH3, S(CH3)2, imidazole) complexes

The ground states and binding energies of Eu³⁺–L (L=H₂O,H₂S,NH₂CH₃,S(CH₃)₂, imidazole) complexes has been determined using ab initio techniques. The binding is mostly electrostatic as expected. The empty f orbital is different for the S compounds, being a π-like orbital, while for the O and N containing ligands it is a σ-like orbital. However, the range in the binding energies for the different f holes is small.     

Synthesis,characterization and reactions of the transition metal halogenoalkyl carbocation complexes [Cp(CO)2M{η2-CH2CH(CH2)nX}]PF6 (n = 1–8, 10, M = Fe; n = 3, 4 M = Ru; X = Br,I)

The halogenoalkyl complexes [Cp(CO)₂M{(CH₂)_nX}] (n = 3–10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph₃CPF₆ in dry CH₂Cl₂ to give the corresponding carbocation complexes [Cp(CO)₂M{η²-(CH₂CH(CH₂)_n?2X}]PF₆ in high yields. NMR evidence indicates that the metals form metallacyclopropane type structures with the carbocation ligand. The reactions of some of the cationic complexes with NaI, PPh₃, Na[Cp(CO)₂Fe] and Et₃N are discussed. NaI and Na[Cp(CO)₂Fe] displace the halogeno-olefin, while PPh₃ adds at the β-CH^δ+ giving the unstable phosphonium adducts [Cp(CO)₂Fe{CH₂CH(PPh₃)(CH₂)_n?2X}]PF₆ which decompose to the halogeno-olefins and the cationic PPh₃ complex [Cp(CO)₂Fe(PPh₃)]⁺. Et₃N causes allylic deprotonation forming internal olefin complexes of the type [Cp(CO)₂Fe{CH₂CHCH(CH₂)_n?3X}]PF₆.     

Complexes [Ni2(μ-OH2)(μ-O2CCH(CH3)2)2L2–4((CH3)2CHCO2)2]: Synthesis,Structure, and Mass Spectrometric Studies

Russian Journal of Coordination Chemistry - Three new binuclear aqua-bridged nickel(II) 2-methylpropionate complexes [Ni2(μ-OH2)(μ-O2CCH(CH3)2)2L2–4((CH3)2CHCO2)2] (L is...     

Synthesis,crystal structure,and properties of hybrid-3D copper tetraphosphonate: [Cu3((HO3PCH2)2N–CH2C6H4CH2–N(CH2PO3H)2)(H2O)4] n

The new copper(II) tetraphosphonate, [Cu₃(HO₃PCH₂)₂N–CH₂C₆H₄CH₂–N(CH₂PO₃H)₂)(H₂O)₄] _n (1) was hydrothermally synthesized from the reaction of Cu(NO₃)₂ and (H₂O₃PCH₂)₂N–CH₂C₆H₄CH₂–N(CH₂PO₃H₂)₂, (H₈L). Compound 1 was structurally characterized by means of X-ray single crystal diffraction. The structure of 1 showed a 3D structure constructed from two types of Cu(II) and chelating and bridging modes of (HO₃PCH₂)₂N–CH₂C₆H₄CH₂–N(CH₂PO₃H)₂, and features a (4⁴.6¹⁰.8) topological network. The 3D compound is further stabilized by hydrogen bonds. UV–Vis diffuse reflectance and infrared spectroscopy as well as elemental analysis of compound 1 are also presented.     

Iodination of B12H11OC(O)CH2–3, B12H11OH2–, and B12H11SCN2–

Reactions of iodination of monosubstituted derivatives of B₁₂H₁₁X^2–anion (X = OC(O)CH₃, OH, SCN) were studied. The reactions were shown to proceed smoothly to give B₁₂H₁₀(OC(O)CH₃)I^2–((carboxy)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), B₁₂H₁₀(OH)I^2–((hydroxo)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), and B₁₂H₁₀(SCN)I^2–((thiocyanato)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion) in high yields, irrespective of the solvent used (benzene, H₂O–ROH, where R = C₂H₅, CH₂CH₂CH₃).¹     

(CH2)2O, (CH2)2S与双卤分子间卤键的理论研究

运用量子化学密度泛函B3LYP方法, 采用6-311＋＋G(d,p)及aug-cc-pVDZ基组, 通过CP校正的几何梯度优化对(CH2)2O和(CH2)2S与双卤分子XY (XY＝Cl2, Br2, ClF, BrF, BrCl)形成的卤键复合物的几何构型、振动频率和相互作用能等进行了研究. 利用电子密度拓扑分析理论方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, (CH2)2O和(CH2)2S与双卤分子间的卤键介于共价键与离子键之间, 偏于静电作用成分为主. 形成卤键后, 双卤分子的键长增加, 振动频率减小, 原子积分性质发生改变. 卤键键长的变化、键能的强弱、键鞍点处的电子密度值与双卤分子的电负性有关.     

Theoretical prediction regarding structural and thermodynamical characteristics of stable CH3PO2 isomers and unimolecular decomposition mechanisms of species CH3P(O)2, CH3O?PO,and CH2P(O)OH

The detailed isomerization and dissociation reaction potential energy profile of the CH₃PO₂ system was established at the UCCSD(T)/6‐311++G(3df,2p)//UB3LYP/6‐311++G(d,p) level of theory. Seventy minimum isomers were located and connected by 93 optimized interconversion transition states. Furthermore, 32 isomers with high kinetic stability were predicted to be possible candidates for further experimental detection. The bonding nature of the suggested stable isomers was analyzed while their molecular properties including heats of formation, adiabatic ionization potentials, and adiabatic electronic affinities were calculated at the G2, G2(MP2), G3, and CBS‐Q levels. Based on the isomerization and dissociation potential energy surface, possible unimolecular decomposition mechanisms and pathways of the low‐lying molecules CH₃P(?O)₂, CH₃O? P?O, and CH₂?P(?O)OH were discussed. Furthermore, the transition state theory rate constants of the primary unimolecular dissociation channels were also calculated. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

Relative permittivity increments for {xCH3OH + (1 − x)CH3OCH2(CH2OCH2)3CH2OCH3} fromT = 283.15 K toT = 323.15 K

Relative permittivities of { CH₃OH  +  CH₃OCH₂(CH₂OCH₂)₃CH₂OCH₃(2,5,8,11,14-pentaoxapentadecane, tegdme)} at temperatures from 283.15 K to 323.15 K and atmospheric pressure, were measured over the whole composition range. Experimental relative permittivities were fitted by a polynomial function in mole fraction. Values of relative permittivity were measured using a HP4284A precision LCR Meter together with the measuring cell HP16452A at 1 MHz. Relative permittivity increments were determined from experimental data and fitted to a variable-degree polynomial function. Different theoretical models were used to predict the permittivity of this mixture. The predictions are better when the volume change on mixing is considered.     

The Nature of Conformational Polymorphism in the Crystals of Ph3Sb(O2CCH2–CH=CH2)2

Russian Journal of Coordination Chemistry - Crystallization of the Ph3Sb(O2CCH2?CH=CH2)2 complex upon fast solvent (benzene) evaporation gives monoclinic crystals (I), whereas in the case of...     

Reaction of sterically congested NHC–Zn(CH2CH3)2 with substituted phenols leading to zincate complexes

We report the reaction of a sterically congested NHC–Zn(CH₂CH₃)₂ Lewis adduct (1) prepared through reaction of an equimolar ratio of 1,3-di-tert-butylimidazol-2-ylidene and diethyl zinc, with various substituted phenols (4-tert-butyl-phenol, 2,6-di-tert-butyl-4-methyl phenol, and 1-bromo-4,6-di-tert-butyl phenol). The NHC–Zn dative bond was cleaved in each of the reactions with the substituted phenols to afford the corresponding ionic complexes of imidazolium cation and aryloxo-zincate, [{(4-CMe₃C₆H₄O)₂Zn(μ-OC₆H₄-4-CMe₃)}₂{(1,3-(CMe₃)_2-ImCH}₂] (2), [{(2,6-(CMe₃)₂-4-Me-C₆H₃O)₂}Zn{(1,3-(CMe₃)_2-ImCH}] (3), and [{(1-Br-3,5-(CMe₃)₂C₆H₂O)₂}_2-Zn{(1,3-(CMe₃)_2-ImCH}] (4), where 1,3-(CMe₃)_2-ImCH) is imidazolium carbocation. The molecular structures of 1–4 were established by X-ray diffraction analyses and from the solid-state structures of 2–4, it was confirmed that, in all the compounds, zinc ions are coordinated through substituted phenolate groups.     

Synthesis,crystal structure,and luminescence of a new coordination polymer, {[Cd9(IDC)2(HIDC)6(Bipy)4] · 2N(CH3)(CH2CH3)2 · 2DMF} n

A new cadmium coordination polymer based on imidazole-4,5-dicarboxylic acid (H₃IDC) and 4,4′-bipyridine (Bipy), {[Cd₉(IDC)₂(HIDC)₆(Bipy)₄] · 2N(CH₃)(CH₂CH₃)₂ · 2DMF} _n , has been synthesized under solvothermal conditions and characterized by energy dispersive X-ray spectroscopy, elemental analysis, FT-IR spectroscopy, thermal analysis, and single crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group Pnnm with a = 20.530(2) Å, b = 15.5957(14) Å, c = 16.3846(15) Å, α = β = γ = 90°, V = 5245.9(9) ų, and Z = 2. The complex exhibits a 3-D structure with channels along the c-axis, in which the free N,N-dimethylformamide and methyl-diethyl-amine molecules are located. The thermal behavior and luminescence of this complex have also been studied in the solid state.     

Synthesis, crystal structure, magnetic property and thermal studies of [Ni(CH(3)COO)2·(NH2CH2Ph)4

[Ni(CH(3)COO)(2)·(NH(2)CH(2)Ph)(4)] complex was synthesized using benzylamine and nickel acetate. The molecular structure of this complex was obtained by single crystal X-ray diffraction and characterized by elemental analysis, IR spectrometry and thermal analysis. The complex crystallized in the monoclinic space group P2(1)/n with cell parameters a=11.234(4)?, b=6.459(2)?, c=22.647(8)?, α=90.00, β=91.149(4)°, γ=90.00, V=1642.8(10)?(3), Z=2. The structure has been solved by direct methods and refined to R(1)=0.0876 for 6377 observed reflections I>2σ(I). Magnetic studies for complex show the data over the whole temperature range 5-300 K are well fitted to the Curie-Weiss law with C=1.03 cm(3) K mol(-1) and θ=-1.38 K. This fitting indicates antiferromagnetic interaction between the Ni ions and the metal center exhibits distorted octahedral coordination geometries. The thermal analysis was carried out to understand the thermal stability of the title complex.     

第一过渡系金属离子和CH,CH2,CH3配合物的从头算研究

利用从头算方法 ,以赝势基组 (LANL2DZ)研究了第一过渡系金属离子M (Sc 到Zn )和CH ,CH2 ,CH3 的配合物的构型和成键特征 .MCH 和MCH 2 分别为线型和共平面构型 ,并带有明显的叁键或双键特征 ,但这些多重键多是“不完整”的 .计算所得的CM ,CM ,CM 键解离能 ,多数与实验值接近 ,且从Sc到Zn均表现出类似的周期性变化趋势