The rate constants for the addition of radicals CCl3CH2·CHR (R = Ph,CO2Me,CONC4H8) to some unsaturated compounds

The rate constants for the addition of radicals CCl₃CH₂ ^·CHR to unsaturated compounds CH₂=CHR (R = Ph, CO₂Me, CONC₄H₈) and to CH₂=CMeCO₂Me were determined at 22 °C by ESR spectroscopy.     

Chlorination of charged buckyballs: reactions of C60x+ cations (x = 1–3) with Cl2, CCl4, CDCl3, CH2Cl2, and CH3Cl

The chlorination of singly and multiply charged C₆₀ cations has been investigated with the selected-ion flow tube technique. Observations are reported for the reactions of C₆₀^·+, C₆₀²⁺ and C₆₀^·3+ with Cl₂, CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl at room temperature (295 ± 2 K) in helium at a total pressure of 0.35 ± 0.02 Torr. C₆₀^·+ and C₆₀²⁺ were observed not to chlorinate, or react in any other way, with these five molecules. Chlorine also did not react with C₆₀^·3+, but bimolecular chloride transfer and electron transfer reactions, reactions that result in charge reduction/charge separation, were observed to occur with CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl. Chloride transfer was the predominant channel seen with CCl₄, CDCl₃ and CH₂Cl₂ while electron transfer dominates the reaction with CH₃Cl. These results are consistent with trends in chloride affinity and ionization energy. The reluctant chlorination of the first two charge states of C₆₀ is attributed to the energy required to distort the carbon cage upon bond formation, while the observed chloride transfer to C₆₀^·3+ is attributed to the greater electrostatic interactions with this ion.     

Synthesis and structure of [Re3S3.7Br4.3(PPh3)3]·0.5CH2Cl2

One of the products of the reaction between Re₃S₇Br₇ and PPh₃ has been isolated in crystalline state and characterized by single crystal X-ray diffraction (XRD), mass-spectrometry, and EPR spectroscopy. The crystalline phase obtained is a co-crystallization product of two cluster complexes: [Re₃(μ₃-S)₂(μ-S)₂(μ-Br)Br₃(PPh₃)₃] (1a) an [Re₃(μ₃-S)₂(μ-S)(μ-Br)₂Br₃(PPh₃)₃] (1b). The ratio 1a:1b in the investigated single crystal sample is ～7:3.     

Conformational preferences of RCH2CH2CN (R = CH3, F, Cl) cyanides and their corresponding isocyanides

The structure and relative stability of the different conformers of RCH₂CH₂CN (R = CH₃, F, Cl) cyanides and their corresponding isocyanides have been investigated through the use of high-level ab initio G4 theory as well as B3LYP/aug-cc-pVQZ and M06/aug-cc-pVQZ density functional theory calculations. This theoretical survey ratifies that the gauche conformer of butyronitrile is slightly more stable than the anti one, so that in the gas phase and at room temperature this compound should exist as a mixture of 57 % of the former and 43 % of the latter. Similar stability trends are predicted for the corresponding isocyanide isomer. Conversely, when the terminal methyl group of butyronitrile (or its isocyanide isomer) is replaced by F or Cl, the stability trends are reversed and the anti conformer becomes slightly more stable than the gauche one. These changes in relative stabilities could be traced through an analysis of the reduced density gradient which shows the existence of a stabilizing interaction between the terminal methyl group and the cyano (or isocyano) group in butyronitrile (or its isocyanide isomer), which becomes repulsive when this methyl group is replaced by F or Cl.     

POSSIBLE HYDRIDE AND METHIDE TRANSFER REACTIONS: REACTIONS OF Fe(CO)4R−(R = H,CH3) AND W(CO)5R− (R = H,CH3, Cl,Br, I) WITH METAL CARBONYL CATIONS

Abstract

Reactions of metal carbonyl cations (M(CO)₆ ⁺, M = Mn, Re) with hydride-, methide- or halide-containing metal carbonyl anions (Fe(CO)₄R^?, R = H, Me; W(CO)₅R^?, R = H, Me, Cl, Br, I) produce products that indicate several mechanisms are operative. Reactions of the halo-tungsten complexes produce neutral, solvated tungsten complexes, W(CO)₅(CH₃CN) and W(CO)₄(CH₃CN)₂ and M(CO)₅X in a reaction that appears to be initiated by decomposition of W(CO)₅X^?. In contrast, the tungsten hydride and methide complexes react, predominantly, by transfer of the hydride or methide to a carbonyl of the cation at a much faster rate. The iron hydride and methide complexes react by iron-based nucleophilicity involving a two-electron process.     

Theoretical studies on the reactions OH + CH3COCCl2 X (X = F, Cl, Br)

Theoretical investigations are carried out on the title reactions by means of the direct dynamics method. The optimized geometries, frequencies and minimum energy path are obtained at the MP2/6-31 + G(d,p) level, and energetic information is further refined at the MC-QCISD (single-point) level. The rate constants for both reactions are calculated by the improved canonical variational transition state theory with the small-curvature tunneling correction in a wide temperature range 200–3,000 K. The theoretical rate constant is in good agreement with the available experimental data. Furthermore, the effects of different halogen substitution on the rate constants are also discussed.     

Synthesis and Structure of Acetonitrile Solvates of Copper(II) Monofluoroacetate and Silver(I) Trifluoroacetate, [Cu2(CH2FCOO)4· 2CH3CN](CH3CN) and Ag3(CF3COO)3(CH3CN)2

Compounds [Cu₂(CH₂FCOO)₄· 2CH₃CN](CH₃CN) (I) and Ag₃(CF₃COO)₃(CH₃CN)₂(II) were synthesized and studied by X-ray structural analysis. Crystals Iare monoclinic, space group C2/c, a= 27.854(6), b= 8.286(2), c= 19.428(4) Å, = 106.82(3)°, V= 4292(2) ų, Z= 8, R ₁= 0.0426; crystals IIare triclinic, space group , a= 8.676(2), b= 9.819(2), c= 11.961(2) Å, = 95.27(3), = 109.59(3)°, = 104.60(3)°, V= 911.4(3) ų, Z= 2, R ₁= 0.0252. Structure Iis composed of the structural units (lanterns) typical of copper(II) carboxylates. The presence of an additional acetonitrile molecule noncoordinated by the copper atoms makes it possible to consider compound Ias a lattice clathrate. Structure IIhas no analogs among the silver carboxylates. It simultaneously contains silver atoms with coordination numbers varying from 2 to 4.     

Characterization of [Re2Cl3(μ-dppm)2(NCCH3)2][Cl] and [Re2Cl3(μ-dppm)2(NCC6H5)2][Cl]·2CH2Cl2 by X-ray Crystallographic and Two-Dimensional NMR Spectroscopic Techniques

The complex Re₂Cl₆(P-n-Bu₃)₂ prepared in situ reacts with CH₃CN to form a blue-green solution. Addition of the chelating phosphine bis(diphenylphosphino)methane (dppm) results in the formation of the complex [Re₂Cl₃(-dppm)₂(NCCH₃)₂][Cl] (1) upon heating. The two acetonitrile molecules adopt a trans geometry on the rhenium center with the axially coordinated chlorine. The analogous trans benzonitrile species [Re₂Cl₃(-dppm)₂(NCC₆H₅)₂][Cl]·2CH₂Cl₂ (2) is synthesized under the same reaction conditions. The coupling constants of the AABB ³¹P{¹H} NMR spectra of the compounds were elucidated from ³¹P–³¹P homonuclear J-resolved NMR experiments. Additional characterization methods include ³¹P{¹H} NMR spectroscopy, UV-vis spectroscopy, and X-ray crystallography.     

Accurate ab initio potential energy surface, thermochemistry, and dynamics of the Cl(2P, 2P(3/2) + CH4 → HCl + CH3 and H + CH3Cl reactions

We report a high-quality, ab initio, full-dimensional global potential energy surface (PES) for the Cl((2)P, (2)P(3/2)) + CH(4) reaction, which describes both the abstraction (HCl + CH(3)) and substitution (H + CH(3)Cl) channels. The analytical PES is a least-squares fit, using a basis of permutationally invariant polynomials, to roughly 16,000 ab initio energy points, obtained by an efficient composite method, including counterpoise and spin-orbit corrections for the entrance channel. This composite method is shown to provide accuracy almost equal to all-electron CCSD(T)/aug-cc-pCVQZ results, but at much lower computational cost. Details of the PES, as well as additional high-level benchmark characterization of structures and energetics are reported. The PES has classical barrier heights of 2650 and 15,060 cm(-1) (relative to Cl((2)P(3/2)) + CH(4)(eq)), respectively, for the abstraction and substitution reactions, in good agreement with the corresponding new computed benchmark values, 2670 and 14,720 cm(-1). The PES also accurately describes the potential wells in the entrance and exit channels for the abstraction reaction. Quasiclassical trajectory calculations using the PES show that (a) the inclusion of the spin-orbit corrections in the PES decreases the cross sections by a factor of 1.5-2.5 at low collision energies (E(coll)); (b) at E(coll) ≈ 13,000 cm(-1) the substitution channel opens and the H/HCl ratio increases rapidly with E(coll); (c) the maximum impact parameter (b(max)) for the abstraction reaction is ~6 bohr; whereas b(max) is only ~2 bohr for the substitution; (d) the HCl and CH(3) products are mainly in the vibrational ground state even at very high E(coll); and (e) the HCl rotational distributions are cold, in excellent agreement with experiment at E(coll) = 1280 cm(-1).     

[C5H4C(CH3)2CH2CH=CH2]Sm(OH)Cl·2MgCl2·4THF的晶体结构分析

用Ｘ－射线晶体结构衍射法测定了［Ｃ５Ｈ４Ｃ（ＣＨ３）２ＣＨ２ＣＨ＝ＣＨ２］Ｓｍ（ＯＨ）Ｃｌ·２ＭｇＣｌ２·４ＴＨＦ的晶体结构。它属三斜晶系,空间群为Ｐ＾－１,ａ＝１０．７７３（２）,ｂ＝１２．８３６（３）,ｃ＝１５．４７８（３）Ａ,ａ＝１１１．４６（３）,β＝１０７．７１（３）,γ＝９２．５４（３）°,Ｖ＝１８６８（１）Ａ＾３,Ｍｒ＝８２７．９１,Ｄｘ＝１．４７２ｇ／ｃｍ＾３,μ＝２．０００６ｍｍ     

DUAL BEHAVIOR OF ACETONITRILE IN A NEW CADMIUM CYANIDE CLATHRATE: CRYSTAL STRUCTURE OF Cd(CH3CN)2Cd(CN)4·2CH3CN

Abstract

We report a new crystal structure of the title clathrate containing tetrahedral and octahedral Cd atoms in a ratio of 1:1. The preparation of the compound is similar to that of the cristobalite-like clathrate Cd(CN)₂·G, where all Cd atoms are tetrahedral. The new inclusion compound crystallizes in the monoclinic space group C2/c, a = 12.337(4), b = 11.964(3), c = 13.594(3) Å, β = 108.60(2)°, Z = 4, R = 0.034 for 1631 reflections. The three-dimensional host framework is built of alternate linkages between the tetrahedral Cd atom of the tetracyanocadmate and the octahedral Cd atom similar to that of the Hofmann-Td and the en-Td types. In the new clathrate dual behavior of acetonitrile, one as a unidentate ligand in the three-dimensional host framework and the other as the guest in the cage-like cavity, has been demonstrated.     

多吡唑烷配体与(CH3CN)2Mo(Cl)(CO)3(GeCl3)取代反应的研究

通过多吡唑烷配体与(CH3CN)2Mo(Cl)(CO)3(GeCl3)中乙腈配体的取代反应,合成了含多吡唑烷配体的Mo-Ge双核金属化合物.多吡唑烷配体环上3,5位取代基的立体位阻以及4位取代基的电子效应均影响其配位能力.通过元素分析、1H NMR、IR和MS谱表征了所有新化合物的分子结构.     

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.     

Vibrational properties of PbCO3 · PbX2 (X = Cl,Br)

The i.r. and Raman spectra of PbX₂ · PbCO₃ (X = Cl, Br) have been recorded. The symmetry of the Raman peaks have been assigned on the basis of the data collected on a natural single crystal of phosgenite (X = Cl). The factor group and site group analysis has been discussed in relation to the experimental data.     

Structure of a new binuclear complex of tungsten [W2S4Cl2(dppe)2]·2CH3CN

Journal of Structural Chemistry - In the reaction of (Et4N)2[W2S4Cl4] with 1,2-bis(diphenylphosphino)ethane in acetonitrile a new binuclear complex of tungsten(V) [W2S4Cl2(dppe)2]·2CH3CN is...     

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.     

Rate constants for reactions O(3P) + X2 → OX + X (X = Br,I) determined by an RRKM-type statistical algorithm employing Monte Carlo simulation

Thermal and crossed molecular beam experiments have independently given information on the reactions O(³P) + Br₂ → OBr + Br and O(³P) + I₂ → OI + I, which proceed through long-lived reaction complexes. Our previously described statistical RRKM-type simulation algorithm is now modified to calculate detailed and macroscopic rate constants for these reactions. Good agreement is found with the experimental thermal rate constant for O + I₂, while reasonable results are found for O + Br₂ when a potential energy barrier with a height of 4.2 kJ/mol is included in the entrance channel. A somewhat larger energy barrier may be needed to reach good agreement with experiments. Angular momentum restrictions are shown to considerably lower the rate constants for these reactions. It is demonstrated that the detailed reaction model largely influences the energy dependence of the detailed rate constants, and also that extrapolations to other temperatures for thermal rate constants depend strongly on the potential energy model used.     

(CH3NH3)AuX4⋅H2O (X=Cl,Br) and (CH3NH3)AuCl4: Low-Band Gap Lead-Free Layered Gold Halide Perovskite Materials

Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic–inorganic perovskite-type halides based on gold (Au), (CH₃NH₃)AuBr₄⋅H₂O ( 1 ), (CH₃NH₃)AuCl₄⋅H₂O ( 2 ), and (CH₃NH₃)AuCl₄ ( 3 ). Hydrated compounds 1 and 2 crystallize in a brand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX₆ building blocks. In contrast, the novel crystal structure of the solvent-free compound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge- and corner-shared AuCl₆ octahedra. The use of Au metal instead of Pb results in unprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show a weak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halides as alternatives for Pb-based halides for optoelectronic applications.     

Heats of reaction of HMo(CO)3C5H5 with CCl4 and CBr4 and of NaMo(CO)3C5H5 with I2 and CH3. Solution thermochemical study of the MoX bond for X = H,Cl, Br,I and CH3

The heats of reaction of HMo(CO)₃C₅H₅ with CX₄ (X = Cl, Br) producing XMo(CO)₃C₅H₅ have been measured by solution calorimetry and are −31.8±0.9 and −34.4±2.0 kcal/mole, respectively. The heats of reaction of NaMo(CO)₃C₅H₅ with I₂ and CH₃I producing IMo(CO)₃C₅H₅ and H₃CMo(CO)₃C₅H₅ are −32.3± 1.3 and −7.7± 0.3 kcal/mole. Oxidation with Br₂CCl₄ yielding Br₃Mo(CO)₂C₅H₅ was measured for the following complexes: (C₅H₅(CO)₃Mo)₂, (−92.0±1.0 kcal/mole), BrMo(CO)₃C₅H₅ (−24.9± 2.0 kcal/mole) and HMo(CO)₃C₅H₅ (−60.7± 2.0 kcal/mole). These and other data are used to calculate the Mo–X bond strength for X = H, Cl, Br, I, and CH₃. These bond strength estimates are compared to those reported for X₂Mo(C₅H₅)₂. Iodination of H₃CMo(CO)₃C₅H₅, reported in the literature to yield CH₃I and IMo(CO)₃C₅H₅, actually produces CH₃C(O)I and I₃Mo(CO)₂C₅H₅.