Mass spectrometric studies on the decomposition of trialkylgallium on gaas surfaces

The thermal decomposition of trimethylgallium [(CH₃)₃Ga] and triethylgallium [(C₂H₅)₃Ga] on gallium arsenide (GaAs) surfaces was studied under an ultra-high vacuum using mass spectrometry. It was observed that the decomposition process of (CH₃)₃Ga and (C₂H₅)₃Ga depends on the arsenic coverage of the substrate surface. On a (100)-oriented surface, increasing the arsenic coverage basically enhances the decomposition of (CH₃)₃Ga and (C₂H₅)₃Ga to gallium atoms above 350 and 300°C, respectively. The decomposition of (CH₃)₃Ga proceeds by emitting CH₃ radicals. On a surface with low arsenic coverage, the decomposition of (CH₃)₃Ga is imperfect and fewer than three methyl groups of alkylgallium are desorbed. On a (111)B-oriented surface, however, an increase in the surface arsenic coverage suppresses the decomposition of alkylgallium, which is different from the case for a (100) surface.     

CH3SO3裂解反应的机理和热力学性质

在G3XMP2//B3LYP/6-311+G(3df,2p)水平上对CH₃SO₃裂解反应的机理进行了研究, 获得了6 条通道(10 条路径), 并构建了其势能剖面. 同时采用单分子反应理论计算了各个通道在温度200-3000 K区间的速率常数. 研究结果表明, 在计算温度范围内, CH₃SO₃裂解反应的主产物为P1(CH₃+SO₃), 产物P2(CH₃O+SO₂)和P3(HCHO+HOSO)仅在温度大于3000 K时对总产物有贡献, 而产物P4(CHSO₂+H₂O), P5(CH₂SO₃+H)和P6(CHSO₃+H₂)贡献相对较少. 将裂解反应总的速率常数拟合为k_total=1.40×10¹²T^0.15exp(7831.58/T). 此外, 根据统计热力学原理, 预测了所有物种的生成焓(D_fH^Θ_{298 K}, D_fH_{0 K}), 熵(S^Θ_{298 K})和热容(C_p, 298-2000 K), 计算的结果与实验值较接近.     

Thermal decomposition of organo-bielemental vanadium compounds Cp2V(ER3) (ER3 - GeEt3, SnEt3, CH2SiMe3 SeGeEt3)

The thermal decompositon of a number of organo-bielemental vanadium compounds with the general formula Cp₂V(ER₃) (ER₃ - GeEt₃, SnEt₃, CH₂SiMe₃, SeGeEt₃) has been investigated in solids and in solution. The main decomposition products of Cp₂V(SnEt₃) are vanadocene and hexaethyldistannane. Et₃GeH, Et₃GeCp, Cp₂V and CpV(C₅H₄GeEt₃) are formed from Cp₂V (GeET₃) decomposition. Isolated CpV(C₅H₄GeEt₃) is characterized by IR and mass spectra. The decomposition of Cp₂V(CH₂SiMe₃) is accompanied by Me₄Si, Cp₂V and CpV-(C₅H₄CH₂SiMe₃) formation, the latter is identified from the mass spectrum. Triethylgermane, vanadocene, and a diselenide of vanadium are isolated on decomposition of Cp₂V(SeGeEt₃). Based upon the experimental data, mechanisms for the decompositon are proposed.     

反式2-甲基-2-丁烯酸甲酯与臭氧反应机理的计算研究

采用G3B3方法构建反式2-甲基-2-丁烯酸甲酯与O3反应体系以及后续Criegee自由基有、无水分子参与下异构化反应的势能面剖面.结果表明,反式2-甲基-2-丁烯酸甲酯与O3反应首先生成一个稳定的五元环中间体,此中间体按断键位置不同后续裂解反应存在两条路径,分别生成产物P1(CH3CHOO+CH3OC(O)C(CH3)O)和P2(CH3CHO+CH3OC(O)C(CH3)OO).利用经典过渡态理论(TST)并结合Wigner矫正模型计算了200-1200 K温度区间内标题反应的速率常数kTST/W.计算结果显示,294 K时,该反应速率常数为7.55×10-18cm3molecule-1s-1,与Bernard等对类似反应所测实验值非常接近.生成的Criegee自由基(CH3CHOO和CH3OC(O)C(CH3)OO)可分别与水分子发生α-加成及β-氢迁移反应,其中Criegee自由基与水的α-加成反应较其与水的β-氢迁移反应具有优势.另外与无水分子参与CH3CHOO和CH3OC(O)C(CH3)OO异构化反应相比,水分子的参与使得异构化反应较为容易进行.     

New deoxygenative transformations; reactions of (CO)4Fe[Si(CH3)3]2 with acyclic ethers

The reaction of cis-(CO)₄Fe[Si(CH₃)₃]₂ (I) with CH₃OSi(CH₃)₃ and C₆H₅CH₂-OSi(CH₃)₃ at 80°C affords good yields of [(CH₃)₃Si]₂O and the deoxygenation products RSi(CH₃)₃ (R = CH₃, C₆H₅CH₂). These reactions are proposed to occur via (CO)₄Fe(R)Si(CH₃)₃ intermediates. This is supported by the observed formation of cis-(CO)₄Fe(CH₃)Si(CH₃)₃ (II) during the more rapid reaction of I with (CH₃)₂O; subsequent (CH₃)₄Si elimination occurs. With (C₆H₅CH₂)₂O, I reacts at 80°C to yield C₆H₅CH₂Si(CH₃)₃ and C₆H₅CH₂OSi(CH₃)₃ as primary products. With C₆H₅CH₂OCH₃, I effects regioselective benzyl---oxygen bond cleavage.     

Preparation and Electrical Properties of Lnx(SiO4)6O(1.5x?12) (Ln: Nd, La) with Apatite Structure

In this study, Ln_x(SiO₄)₆O_(1.5x–12) (Ln: Nd, La) materials as electrolytes for solid oxide fuel cells (SOFC) were prepared by the sol-gel process. It has been reported that the apatite structure of Ln_x(SiO₄)₆O_(1.5x–12) shows higher ionic conductivity than yttrium-stabilized zirconium oxide at the working temperature of the SOFC. Ln₁₀(SiO₄)₆O₃ is a major component of the Ln_x(SiO₄)₆O_(1.5x–12) system. Ln₁₀(SiO₄)₆O₃ consists of Ln_9.33(SiO₄)₆O₂ and a small amount of Ln₂SiO₅. It has been proposed that the ionic conductivity of Ln_x(SiO₄)₆O_(1.5x–12) decreases with increasing Ln₂SiO₅ with non-apatite structure. The object of the present study was to bring about this decrease by generating Ln₂SiO₅ in the system.Precursor solutions for synthesis of the powder were prepared using tetraethoxysilane (Si(OC₂H₅)₄) and neodymium acetate monohydrate (Nd(CH₃COO)₃·H₂O) or lanthanum acetate monohydrate (La (CH₃COO)₃·H₂O) as raw materials and acetic acid (CH₃COOH), 2-methoxyethanol (C₂H₅OCH₂CH₂OH), and triethanolamine (N(CH₂CH₂OH)₃) as solvents. To obtain the powder, the solution was dried and heat-treated at 600 °C for 2 h. Disks made from the powder were heat-treated at temperatures between 1100 and 1500 °C for 10 h. The results of an XRD investigation indicate that almost all diffraction peaks of these samples could be assigned to Ln_9.33(SiO₄)₆O₂. The sample with x = 10.00 included a small amount of Ln₂SiO₅. The ionic conductivity of this latter sample was higher than that of other samples with similar values of x (x = 9.33 and 10.67).     

Preparation and characterization of M(CH3)5 (M = Nb or Ta) and Ta(CH2C6H5)5 and evidence for decomposition by α-hydrogen atom abstraction

The preparations of Nb(CH₃)₅, Ta(CH₃)₅, and Ta(CH₂C₆H₅)₅ are reported in detail. The M(CH₃)₅ complexes decompose autocatalytically to give 3.4 ± 0.1 mol of methane and a non-hyclrolyzable residue with approximate composition MC_1–5H while Ta(CH₂C₆H₅)₅ decomposes in a non-autocatalytic manner to give ca. 2.6 mol of toluene per Ta. Decomposition of Nb(CD₃)₅ gave 96% CD₄ in diethyl ether while the toluene produced on decomposition of Ta(CD₂C₆H₅)₅ was at least 90%-d₃. An observed kinetic deuterium isotope effect of 2–3 in each case is evidence that an α-CH(D) bond is broken in a slow step of the decomposition. It is postulated that M(CH₃)₅ and Ta(CH₂C₆H₅)₅ decompose primarily by α-hydrogen atom abstraction though almost certainly in a complex, possibly intermolecular fashion in the case of M(CH₃)₅. In neither case (R = CH₃ or CH₂C₆H₅) was there evidence for significant homolytic cleavage of the metalcarbon bond to give free alkyl radicals.     

35Cl Nqr spectroscopy of the [PO2Cl2]− and POCl3 groups in Me(PO2Cl2)2·2D (Me = Mg,Ca, Mn; D = POCl3,CH3COOC2H5,CH3COCH3)

³⁵Cl NQR spectra of dichlorophosphates Me(PO₂Cl₂)₂ · 2D (Me = Mg, Ca, Mn; D = CH₃COOC₂H₅, CH₃COCH₃, POCl₃) are studied in the temperature range 77 ? T (K) ? 305. It is shown that the three compounds with CH₃COOC₂H₅ as donor are isomorphic at 77 K, the crystal structure of Mn(PO₂Cl₂)₂· 2CH₃COOC₂H₅. The structure of Mg(PO₂Cl₂)_2^?· 2CH₃COCH₃ and of Mg(PO₂Cl₂)₂ · 2POCl₃ probably consists of infinite chains as found for Mn(PO₂Cl₂)₂· 2CH₃COOC₂H₅. Mg(PO₂Cl₂)₂· 2CH₃COOC₂H₅ shows phase transformations and a complicated dynamical behaviour leading to strong deviations from a Bayertype NQR function v = f(T). The donor capacity of POCl₃ in Mg(PO₂Cl₂)₂· 2POCl₃ is comparable with the donor strength in AsCl₃ · POCl₃ · A d_π-p_π overlap of the P-O bond influences the P-Cl bond.     

An ab initio molecular orbital study of the trimethylgallium-arsine adduct: (CH3)3Ga:AsH3

The structure, harmonic frequencies, and binding energy of the trimethylgallium-arsine adduct, (CH₃)₃Ga: AsH₃, have been computed using ab initio molecular orbital methods, and, where possible, compared with experimental results. The structures and frequencies of the precursors trimethylgallium and arsine are perturbed to only a small extent upon adduct formation. The binding energy of (CH₃)₃Ga: AsH₃ is found to be 5.2 kcal/mol lower than that for H₃Ga:AsH₃ at the MP2/HUZSP^*//RHF/HUZSP^* level of computation.     

A first methodical approach to salts with unsymmetrical fluorophenyl(pentafluorophenyl)difluoroiodonium(V) cations [Rf(RF)IF2] (Rf=x-FC6H4, x=2, 3, 4; RF=C6F5)

A promising approach to the unknown type of [Ar′(Ar)IF₂]X salts is offered. x-FC₆H₄IF₄ (x=2, 3, 4) reacts with C₆F₅BF₂ in CH₂Cl₂ and forms [x-FC₆H₄(C₆F₅)IF₂][BF₄] salts in good yields. For [4-FC₆H₄(C₆F₅)IF₂][BF₄] the fluoro-oxidizer property is shown in reactions with weakly reducing agents like E(C₆F₅)₃ (E=P, As, Sb, Bi) and ArI (Ar=4-FC₆H₄, C₆F₅). The fluorine/aryl substitution method is also applied to the synthesis of [(4-FC₆H₄)₂IF₂][BF₄], an example with two identical aryl groups in the difluoroiodonium(V) moiety.     

Bond energies and thermal decomposition of [Pt(X)(CH3)(P(C2H5)3)2] complexes

The thermal decomposition of the complexes trans-[Pt(X)(CH₃)L₂] (L  P(C₂H₅)₃; X  Cl, Br, I, CN) in decalin at 170 and 200°C affords methane platinum metal and [Pt(X)₂L₂]. The kinetics of the decomposition of the complexes were determined by monitoring the appearance of methane by GLC. The observed first-order rate constant was found to be independent on the nature of the ligand X. The thermal decomposition of the trideuteriomethyl complexes [Pt(X)(CD₃)L₂] (X  I, CN) in decalin-d₁₈ at 170 and 200°C was studied by GLC/MS. The thermolysis affords CD₃H and CD₄ in ratios which are independent of the nature of X and of the temperature used. The mass spectra of the complexes were also examined. A relative scale of platinum-to-methyl bond dissociation energies has been established by measuring the appearance potential of the fragment ion [Pt(X)L₂]⁺ and the ionization energies in the series [Pt(X)(CH₃)L₂]. Ionization potentials and PtCH₃ bond energies show a clear dependence on the nature of X which is not reflected in corresponding changes in the decomposition rates.     

稀土配合物[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3的标准生成焓及热分解动力学研究

合成了高氯酸镨和咪唑(C₃H₄N₂), DL-α-丙氨酸(C₃H₇NO₂)混配配合物晶体. 经傅立叶变换红外光谱、化学分析和元素分析确定其组成为[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃. 使用具有恒温环境的溶解-反应量热计, 以2.0 mol•L^－1 HCl为量热溶剂, 在T＝(298.150±0.001) K时测定出化学反应PrCl₃•6H₂O(s)＋2C₃H₇NO₂(s)＋C₃H₄N₂(s)＋3NaClO₄(s)＝[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃(s)＋3NaCl(s)＋5H₂O(1)的标准摩尔反应焓为Δ_rH_m^ө＝(39.26±0.11) kJ•mol^－1. 根据盖斯定律, 计算出配合物的标准摩尔生成焓为Δ_fH_m^ө{[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃(s), 298.150 K}＝(－2424.2±3.3) kJ•mol^－1. 采用TG-DTG技术研究了配合物在流动高纯氮气(99.99%)气氛中的非等温热分解动力学, 运用微分法(Achar-Brindley-sharp和Kissinger法)和积分法(Satava-Sestak和Coats-Redfern法)对非等温动力学数据进行分析, 求得分解反应的表观活化能E＝108.9 kJ•mol^－1, 动力学方程式为dα/dt＝2(5.90×10⁸/3)(1－α)[－ln(1－α)]^－1exp(－108.9×10³/RT).     

Investigation of phase transitions of a pseudo-hexagonal phase of [Rh(NH3)5Cl]2[Re6S8(CN)6]·3H2O during thermal decomposition

A general motif of the crystal structure of [Rh(NH₃)₅Cl]₂[Re₆S₈(CN)₆]·3H₂O is examined, and the cluster anions are found to form a pseudo-hexagonal sublattice. The thermal decomposition of [Rh(NH₃)₅Cl]₂[Re₆S₈(CN)₆]·3H₂O is studied, and it is shown that in helium atmosphere thermolysis occurs through the formation of intermediate amorphous phases. The final product obtained at 1200°C is a disordered single-phase solid solution of Re_0.75Rh_0.25 based on the structure of rhenium. Powder X-ray diffraction data for solid solutions in the system of Rh-Re are surveyed. It is demonstrated that the data for phases prepared by the thermal decomposition of coordination compounds better match the theoretical state diagram than the experimental one. The dependence of atomic volume on the composition of solid solutions of Re_xRh_1−x is derived. Original Russian Text Copyright ? 2007 by S. A. Gromilov, K. V. Yusenko, and E. A. Shusharina __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No.5, pp.957–962, September–October, 2007.     

Preparation and properties of (η-C5H5)2ZrCl[Si(CH3)3] and (η-C5H5)2Zr[Si(CH3)3]2; trimethylsilyl group transfer from mercury to zirconium

Two silyl-zirconium compounds (η-C₅H₅)₂ZrCl[Si(CH₃)₃] (I) and (η-C₅H₅)₂-Zr[Si(CH₃)₃]₂ (II), have been prepared by the reaction of (η-C₅H₅)₂ZrCl₂ with Hg[Si(CH₃)₃]₂ in refluxing benzene. While I is unreactive toward 1-hexyne (55–60°C) and CO (350 psi), the zirconiumsilicon bond is cleaved by electrophiles such as Cl₂, HgCl₂, and AlCl₃.     

Preparation and configurational isomerism of ditertiary stibine sulfides, (C6H5)(CH3)(S)SbCH2Sb(CH3)(C6H5) and [(C6H5)(CH3)(S)Sb]2(CH2)3

Asymmetric ditertiary stibine sulfides (C₆H₅)(CH₃)(S)SbCH₂Sb(CH₃)(C₆H₅) and [(C₆H₅)(CH₃)(S)Sb]₂(CH₂)₃ have been prepared. It was found that they exist as only one of two possible diastereomers in the crystalline state. However, isomerization to the other form takes place in solution, resulting in an equilibrium mixture. A possibility of configurational lability of tertiary stibine sulfide was suggested for the first time.     

Isomorphism in the (NH4)2Th(NO3)6-K2Th(NO3)6-Rb2Th(NO3)6 system

Syntheses were developed, and compounds of composition (NH₄)_2x K_2y Rb_2z Th(NO₃)₆(x + y + z = 1) were prepared. These compounds were structurally studied using X-ray diffraction and IR spectroscopy. Incomplete miscibility in the solid phase of the title system was found, and the impossibility of existence of a hexanitratothorate complex in the (NH₄)₂Th(NO₃)₆-K₂Th(NO₃)₆ system at 298.15 K and the component molar ratio 1: 3 was demonstrated. Calorimetric standard enthalpies of formation and mixing at 298.15 K were determined. Original Russian Text ? N.G. Chernorukov, A.V. Knyazev, A.A. Sazonov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1066–1071.     

Composition dependence of the photophysical and photocatalytic properties of (AgNbO3)1−x(NaNbO3)x solid solutions

A series of orthorhombic photocatalysts (AgNbO₃)_1−x(NaNbO₃)_x solid solutions have been synthesized by a solid-state reaction method. The composition dependence of the photophysical and photocatalytic properties of synthesized solid solutions has been investigated systematically. With an increase in the content of NaNbO₃, we found that (1) the lattice parameters decreased; (2) the Nb-O bond length in NbO₆ octahedron reduced; (3) the band gap increased; and (4) the mean particle size decreased while the Brunauer-Emmett-Teller (BET) surface area increased. Photocatalytic activities of the (AgNbO₃)_1−x(NaNbO₃)_x (0?x?0.5) samples were evaluated from gaseous 2-propanol (IPA) decomposition into acetone and CO₂ under visible-light irradiation emitted from blue-light-emitting diodes (BLEDs; light intensity: 0.01 mW cm⁻²). Among all the samples, the (AgNbO₃)_0.6(NaNbO₃)_0.4 sample showed the highest photocatalytic activity.     

Photocatalytic Dissociation of CH3OH on ZnO(0001) Surface

Photocatalysis of CH₃OH on the ZnO(0001) surface has been investigated by using temperature-programmed desorption (TPD) method with a 266 nm laser light. TPD results show that part of the CH₃OH adsorbed on ZnO(0001) surface are in molecular form, while others are dissociated. The thermal reaction products of H₂, CH₃^·, H₂O, CO, CH₂O, CO₂ and CH₃OH have been detected. Experiments with the UV laser light indicate that the irradiation can promote the dissociation of CH₃OH/CH₃O^· to form CH₂O, which can be future converted to HCOO^- during heating or illumination. The reaction between CH₃OH_Znand OH_ad can form the H₂O molecule at the Zn site. Both temperature and illumination promote the desorption of CH₃^· from CH₃O^·. The research provides a new insight into the photocatalytic reaction mechanism of CH3OH on ZnO(0001).     

Etude vibrationnelle des composes (C4H4P)Mn(CO)3 et [C4H2(CH3)2P]Mn(CO)3 et calcul du champ de force du cycle C4H4P complexe

The Raman and infrared spectra (4000200 cm^?1) of (C₄H₄P)Mn(CO)₃ and (C₄D₄P)Mn(CO)₃, and of [C₄H₂(CH₃)₂P]Mn(CO)₃ and [C₄D₂(CH₃)₂P]Mn(CO)₃ in the liquid and solid states (10–400 K) have been investigated. A complete vibrational assignment is proposed and valence force fields of the (C₅H₅) and (C₄H₄P) cycles are compared. From these results, it is clearly shown that the (C₄H₄P) rings are more electrophilic and weaker π-electron donors than (C₅H₅) rings, this is in agreement with their chemical behavior.     

Synthesis and X-ray diffraction study of R[UO2(CH3COO)3] (R = H3O+ or NH(C2H5) 3+ )

Single crystals of (H₃O)[UO₂(CH₃COO)₃] (I) and (NH(C₂H₅)₃)[UO₂(CH₃COO)₃] (II) are synthesized, and their structures are studied by X-ray crystallography. Compound I crystallizes in the tetragonal crystal system with the unit cell parameters a = 13.70640(10) ?, c = 27.5258(5) ?, V = 5171.14(11) ?³, space group I4₁/a, Z = 16, R = 0.0238. The crystals of compound II are orthorhombic with the parameters a = 13.3685(3) ?, b = 10.6990(3) ?, c = 12.2616(3) ?, V = 1753.77(8) ?³, space group Pna2₁, Z = 4, R = 0.0228. The uranium-containing structural units of crystals I and II are [UO₂(CH₃COO)₃]⁻ island mononuclear groups belonging to the A B₃⁰¹(A = UO₂²⁺, B⁰¹ = CH₃COO⁻) crystal-chemical group of uranyl complexes. [UO₂(CH₃COO)₃]⁻ complexes are linked into a three-dimensional framework by electrostatic interactions with the outer-sphere cations and by hydrogen bonds involving the hydrogen atoms of hydroxonium (I) or triethylammonium (II) with the oxygen atoms of the acetato groups.