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1.
Phosphonium Salts with Hydrogen Dihalide Anions HCl2?, HBr2?, HI2?, or HBrCl? Phosphonium hydrogen dihalides [R3PR′][XHY] (X = Y = Cl, Br, I; X = Br, Y = Cl) resp. [R3PH]HBr2 are obtained as extremely hydrolyzable crystals by reaction of phosphonium halides or tertiary phosphanes with hydrogen halide. According to IR spectroscopic results the solid compounds mostly contain anions [XHX]? with symmetric hydrogen bonds. In solution 1H NMR measurements show a slight (X = Cl, Br) or considerable (X = I) dissociation according to HX2? ? X? + HX. On heating the solid compounds decompose with formation of hydrogen halide and [R3PR′]X or [R3PH]X. In this process the hydrogen bromidechlorides [R3PR′][BrHCl] exclusively eliminate HCl. NMR studies (1H und 31P) with solutions containing [R3PH]HBr2 (R = phenyl, 1-naphtyl) or HBr and Ph3P in varying molar ratios show that a fast proton exchange between the competing Lewis bases R3P and Br? exists.  相似文献   

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The structures and energies of the electronic ground states of the FeS0/?, FeS20/?, Fe2S20/?, Fe3S40/?, and Fe4S40/? neutral and anionic clusters have been computed systematically with nine computational methods in combination with seven basis sets. The computed adiabatic electronic affinities (AEA) have been compared with available experimental data. Most reasonable agreements between theory and experiment have been found for both hybrid B3LYP and B3PW91 functionals in conjugation with 6‐311+G* and QZVP basis sets. Detailed comparisons between the available experimental and computed AEA data at the B3LYP/6‐311+G* level identified the electronic ground state of 5Δ for FeS, 4Δ for FeS?, 5B2 for FeS2, 6A1 for FeS2?, 1A1 for Fe2S2, 8A′ for Fe2S2?, 5A′′ for Fe3S4, 6A′′ for Fe3S4?, 1A1 for Fe4S4, and 1A2 for Fe4S4?. In addition, Fe2S2, Fe3S4, Fe3S4?, Fe4S4, and Fe4S4? are antiferromagnetic at the B3LYP/6‐311+G* level. The magnetic properties are discussed on the basis of natural bond orbital analysis.  相似文献   

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A stingray pattern is adopted by Ba2Ag8S7. Crystals of this compound were grown in a two-electrode chemical cell from a BaS3/ethylenediamine solution. In the pseudo-one-dimensional structure columns of 1[Ag8S7] (shown in the picture) are stacked head-to-tail to create voids where the barium atoms reside. The coexistence of S2− and S22− indicates a reductive decomposition [Eq. (1)].  相似文献   

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Are the ‘Textbook Anions’ O2?, [CO3]2?, and [SO4]2? Fictitious? Experimental second electron affinities are still unknown for the title anions. It will be shown by means of quantum chemical ab initio calculations that these dianions are unstable with respect to spontaneous ionization. They all must be designated as non-existent.  相似文献   

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A procedure to calculate the quantum mechanical transition probability of a unimolecular primary chemical process, A?A + e? is investigated for the circumstance where A? and A have different numbers of vibrational and rotational degrees of freedom (one is linear, the other not). A procedure is introduced to deal with the coupling between the vibrational and rotational motions. The proposed method was applied to calculating the lifetimes of CO2˙? and N2O˙? in the gas phase. The geometry optimizations and frequency calculations for CO2, CO2˙?, N2O, and N2O˙? are performed at HF, MP2, and QCISD(T) levels with 6-31G* or 6–31+G* basis sets, in order to obtain reliable geometric and spectroscopic information on these systems. Lifetimes are calculated for several of the lower vibrational–rotational states of the anions, as well as for the Boltzmann distribution of states at 298 K. The lifetime of the lowest vibrational–rotational state of CO2˙?, is 1.03 × 10?4 s, and of the lowest vibrational state with rotational levels weighted by Boltzmann distribution at 298 K, 1.50 × 10?4 s. These values are in good agreement with the experimental number, 9.0 ± 2.0 × 10?5 s, and support the experimental evidence that CO2˙? was formed in its ground vibrational level by the techniques used. The lifetime of CO2˙? calculated with Boltzmann distribution over its vibrational and rotational levels at 298 K, is 1.51 × 10?5 s. There are no direct measurements of the lifetime of N2O˙?, but it was estimated to be greater than 10?4 s from experimental evidence. The predicted lifetimes of N2O˙?, at its lowest vibrational–rotational state (0 K) and lowest vibrational state with rotational levels weighted by the Boltzmann distribution at 298 K, are 238 and 19.1 s, respectively. The lifetime of N2O˙? at thermal equilibrium at 298 K is 6.66 × 10?2 s, indicating that electron loss from the excited vibrational states of N2O˙? is significant. This study represents the first theoretical investigation of CO2˙? and N2O˙? lifetimes. © 1994 John Wiley & Sons, Inc.  相似文献   

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Total syntheses of (?)‐isoschizogamine and (?)‐2‐hydroxyisoschizogamine are described. The synthesis employs two asymmetric Michael additions to establish chiral centers at C7 and the quaternary carbon C20. Regioselective reduction of the methylthioiminium cation rather than the enamine generates an isoschizogamine‐type pentacyclic skeleton. Acidic hydrolysis of the isoschizogamine‐type intermediate in the absence of oxygen provides natural (?)‐isoschizogamine. Conducting the reaction in the presence of oxygen leads to a multistep oxidative hydrolysis cascade that affords unnatural (?)‐2‐hydroxyisoschizogamine.  相似文献   

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Collision-induced dissociation of the ions [ArS]?, [ArSO]? and [ArSO2]? has uncovered a rich and varied ion chemistry. The major fragmentations of [ArS]? are complex and occur without prior ring hydrogen scrambling: for example, [C6H5S]?→[C2HS]? and [HS]?; [p-CD3C6H4S]?→[C6H4S]?˙, [CD3C4S]? and [C2HS]?. In contrast, all decompositions of [C6H5CH2S]? are preceded by specific benzylic and phenyl hydrogen interchange reactions. [ArSO2]? and [ArSO2]? ions undergo rearrangement, e.g. [C6H5SO]?→[C6H5O]? and [C6H5S]?; [C6H5SO2]?→[C6H5O] ?. The ion [C6H5CH2SO]? eliminates water, this decomposition is preceded by benzylic and phenyl hydrogen exchange.  相似文献   

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A novel nitride, Sr2−yEuyB2−2xSi2+3xAl2−xN8+x (x≃ 0.12, y≃ 0.10) (distrontium europium diboron disilicon dialuminium octanitride), with the space group P2c, was synthesized from Sr3N2, EuN, Si3N4, AlN and BN under nitrogen gas pressure. The structure consists of a host framework with Sr/Eu atoms accommodated in the cavities. The host framework is constructed by the linkage of MN4 tetrahedra (M = Si, Al) and BN3 triangles, and contains substitutional disorder described by the alternative occupation of B2 or Si2N on the (0, 0, z) axis. The B2:Si2N ratio contained in an entire crystal is about 9:1.  相似文献   

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NaAg3S2, a Thioargentate Containing the Anionic Cluster [Ag6S4]2? . Dark-red octahedrally shaped crystals of NaAg3S2 could be obtained by the reaction of NaAg(CN)2 and NaCN in a stream of hydrogen sulfide at 630 K. NaAg3S2 crystallizes cubic, a=12.358(1) Å, space group Fd3 m, Z=16. The structure was determined from four-circle diffractometer data. NaAg3S2 contains the anionic cluster [Ag6S4]2?. The structure can be traced back to the spinel structure typ. An extended Hückel calculation for the cluster anion, which is considered to be isolated, shows weak bonding silver-silver interactions. NaAg3S2 is diamagnetic at room temperature.  相似文献   

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Reactions of ZnI2L2 (where L=[HC(PPh2NPh)]) with solutions of the Zintl phase K4Ge9 in liquid ammonia lead to retention of the Zn−Zn bond and formation of the anion [(η4‐Ge9)Zn−Zn(η4‐Ge9)]6−, representing the first complex with a Zn−Zn unit carrying two cluster entities. The trimeric anion [(η4‐Ge9)Zn{μ211Ge9)}Zn(η4‐Ge9)]8− forms as a side product, indicating that oxidation reactions also take place. The reaction of Zn2Cp*2 (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with K4Ge9 in ethylenediamine yielded the linear polymeric unit {[Zn[μ241Ge9)]}2− with the first head‐to‐tail arrangement of ten‐atom closo ‐clusters. All anions were obtained and structurally characterized as [A (2.2.2‐crypt)]+ salts (A =K, Rb). Copious computational analyses at a DFT‐PBE0/def2‐TZVPP/PCM level of theory confirm the experimental structures and support the stability of the two hypothetical ten vertex cluster fragments closo ‐[Ge9Zn]2− and (paramagnetic) [Ge9Zn]3−.  相似文献   

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The reaction Fe(CN)4(bpy)2? + S2O82? has been studied in aqueous micellar solutions of N‐tetradecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propanesulfonate, SB3‐14. The influence of changes in the surfactant concentration as well as in the peroxodisulfate ions concentration on kobs was investigated. Spectroscopic and conductivity measurements have given information about the distribution of both anionic reagents between the aqueous and micellar pseudophases of the SB3‐14 micellar solutions. A discussion about the adequacy of various equations based on the pseudophase model to rationalize kinetic micellar effects for anion‐anion reactions in sulfobetaine micellar solutions has been done. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 225–231, 2001  相似文献   

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