- Pnictogen-hydride activation by (silox)3Ta (silox = tBu3SiO); Attempts to circumvent the constraints of orbital symmetry in N2 activation
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Activation of N2 by (silox)3Ta (1, silox = tBu3SiO) to afford (silox)3Ta=N-N=Ta(silox) 3 (12-N2) does not occur despite ΔG°cald = -55.6 kcal/mol because of constraints of orbital symmetry, prompting efforts at an independent synthesis that included a study of REH2 activation (E = N, P, As). Oxidative addition of REH 2 to 1 afforded (silox)3HTaEHR (2-NHR, R = H, Me, nBu, C6H4-p-X (X = H, Me, NMe2); 2-PHR, R = H, Ph; 2-AsHR, R = H, Ph), which underwent 1,2-H2- elimination to form (silox)3Ta=NR (1=NR; R = H, Me, nBu, C6H4-p-X (X = H (X-ray), Me, NMe2, CF 3)), (silox)3Ta=PR (1=PR; R = H, Ph), and (silox) 3Ta=AsR (1=AsR; R = H, Ph). Kinetics revealed NH bond-breaking as critical, and As > N > P rates for (silox)3HTaEHPh (2-EHPh) were attributed to (1) ΔG°calc(N) calc(P) ~ ΔG°calc(As); (2) similar fractional reaction coordinates (RCs), but with RC shorter for N P~As. Calculations of the pnictidenes aided interpretation of UV-vis spectra. Addition of H2NNH2 or H2N-N(cNC2H3Me) to 1 afforded 1=NH, obviating these routes to 12-N2, and formation of (silox)3MeTaNHNH2 (4-NHNH2) and (silox) 3MeTaNH(-cNCHMeCH2) (4-NH(azir)) occurred upon exposure to (silox)3Ta=CH2 (1=CH2). Thermolyses of 4-NHNH2 and 4-NH(azir) yielded [(silox)2TaMe](μ- NαHNβ)(μ-NγHN δH)[Ta(silox)2] (5) and [(silox)3MeTa] (μ-η2-N,N: η1-C-NHNHCH2CH 2CH2)[Ta(κ-O,C-OSitBu2CMe 2CH2)(silox)2] (7, X-ray), respectively. (silox)3Ta=CPPh3 (1=CPPh3, X-ray) was a byproduct from Ph3PCH2 treatment of 1 to give 1=CH 2. Addition of Na(silox) to [(THF)2Cl3Ta] 2(μ-N2) led to [(silox)2ClTa](μ-N 2) (8-Cl), and via subsequent methylation, [(silox) 2MeTa]2(μ-N2) (8-Me); both dimers were thermally stable. Orbital symmetry requirements for N2 capture by 1 and pertinent calculations are given.
- Hulley, Elliott B.,Bonanno, Jeffrey B.,Wolczanski, Peter T.,Cundari, Thomas R.,Lobkovsky, Emil B.
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p. 8524 - 8544
(2010/12/18)
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- Synthesis of volatile inorganic hydrides by electrochemical method
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Published data and results of our investigations on the problem of electrochemical synthesis of arsenic, phosphorus, and germanium hydrides are generalized. The results of the developments of the physicochemical bases of arsine synthesis by electrochemical reduction of arsenic acid, phosphine by reduction of white phosphorus in organic solvents, and monogermane by reduction of germanate in basic conditions are reported. The current yield of hydrides is 95, 90, and 40%, respectively. The promising guidelines of the practical use of electrochemical methods of the synthesis of the hydrides in the manufacture of semiconductor materials for microelectronics, optics, and laser engineering are discussed. The development of an arsine generator attracts considerable interest, which can serve as a basis for an aggregative continuous apparatus used in complex flow charts of manufacture of semiconductor materials.
- Turygin,Tomilov,Berezkin, M. Yu.,Fedorov
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p. 1459 - 1478
(2011/02/28)
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- GASEOUS DIELECTRICS WITH LOW GLOBAL WARMING POTENTIALS
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A dielectric gaseous compound which exhibits the following properties: a boiling point in the range between about ?20° C. to about ?273° C.; non-ozone depleting; a GWP less than about 22,200; chemical stability, as measured by a negative standard enthalpy of formation (dHf0); a toxicity level such that when the dielectric gas leaks, the effective diluted concentration does not exceed its PEL; and a dielectric strength greater than air.
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- Electrochemical reduction of As(III) in acid media
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Measurements of the cathode potentials of different electrode materials in the galvanostatic electrolysis of As2O3 solutions in sulfuric acid indicate that the Pb cathode ensures the most stable negative potential, favorable for AsH3 formation. Preparative electrolyses confirm stability of the arsine yield in a series of experiments. The current efficiency for arsine on the Pb cathode is 60-70%. The byproduct of this process is As0, with a current efficiency of about 2%. We have designed and tested an electrolyzer with improved hydrodynamics, which makes it possible to avoid the formation of dead zones and to prevent the cathode chamber from being clogged.
- Smirnov,Turygin,Shalashova,Khudenko,Tomilov
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- Laser spectroscopy and dynamics of the jet-cooled AsH2 free radical
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The A2A1-X2B1 electronic transition of the jet-cooled AsH2 free radical has been studied by laser-induced fluorescence (LIF), wavelength-resolved emission, and fluorescence lifetime measurements. The radical was produced by a pulsed electric discharge through a mixture of arsine (AsH3) and high pressure argon at the exit of a pulsed valve. Nine vibronic bands wereidentified by LIF spectroscopy in the 505-400 nm region, including a lo ng progression in the bending mode and two bands (101 and 101201) involving the excited state As-H symmetric stretch. Single vibronic level emission spectra showed similar activity in the bending and symmetric stretching frequencies of the ground state. High-resolution spectra of the 000 band exhibited large spin splittings and small, resolved arsenic hyperfine splittings, due to a substantial Fermi contact interaction in the excited state. The rotational constants obtained in the analysis gave effective molecular structures of r″0 = 1.5183(1) ?, θ″0=90.75(1) ° and r′0=1.4830(1) ?, θ′0= 123.10(2)°. The excited state fluorescence lifetimes vary dramatically with rovibronicstate, from a single value of 1.4 μs to many with lifetimes less tha n 10 ns, behavior which the authors interpret as signaling the onset of a predissociative process near the zero-point level of the ground state.
- He, Sheng-Gui,Clouthier, Dennis J.
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- Spectrophotometric determination of arsenic via nanogold formation in micellar medium
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Colloidal gold nanoparticles are formed in aqueous anionic micellar medium by the quantitative reduction of chloroauric acid (HAuCl4) by arsine (AsH3) gas produced from arsenic bearing sample water. The absorbance of the pink gold sol (λmax at 530 nm) is a measure of arsenic concentration present in the sample. Both, As(III) and As(V) either present individually or in mixture could be determined. The molar absorptivity is 6.1×103 lit mol-1 cm-1 and the Sandell sensitivity is 1.28×10-2 μg cm-2. The gold particles, as observed from the transmission electron microscopy analysis, are spherical in nature, the average size being 14±5 nm. The linear dynamic range (LDR) for the arsenic determination is 0-0.5 ppm (0-6.67×10 -6 M). The limit of detection (LOD) is 0.005 ppm. The 95% confidence limit for 0.2 ppm of arsenic is 0.207±0.007 ppm (for 10 replicates). The relative standard deviation (RSD) is 2+/Fe3+, Ca2+/Mg 2+, PO4-3, SiO3-2, NO3-, Cl-, SO4-2, humic acid, common herbicides/pesticides like 2,4-D, endosulfan, atrazine, etc. and can be applied for the determination of total arsenic concentration in real water samples. The results are in good agreement with the SDDC method. The toxic and volatile organic solvents used for silver diethyldithiocarbamate method could be avoided in this method and hence it is safer, much easier and more reproducible.
- Pal, Anjali,Maji, Sanjoy Kumar
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p. 1178 - 1182
(2007/10/03)
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- Electrochemical preparation of H2S and H2Se
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H2S and H2Se have been electrolytically prepared by electrolysis in aqueous H2SO4 solutions of composite cathodes made of S or Se and graphite. The efficiencies depended strongly on the electrolyte composition, in particular on the acid concentration and presence of K+. Faradaic efficiencies of 80% were obtained in dilute (0.05 M) acid, and this increased to 100% with added K2SO4. The efficiencies dropped drastically in concentrated acid (>a few moles). H 2Te and AsH3 generation were also briefly studied for comparison. The mechanisms of hydride formation are discussed. Both the reaction of nascent hydrogen with the free element and direct reduction of the element are considered. The latter is believed to be the dominant mechanism.
- Bastide, Stephane,Huegel, Paul,Levy-Clement, Claude,Hodes, Gary
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- Synthesis and TG/DTA study on two new metallo(VI)-arsenato(V) heteropolyacids containing vanadium(V)
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An improved method for the synthesis of two heteropolyacids of the same type: H5[AsMo10V2O40]· 13H2O and H5[AsW10V2O40] ·16H2O was elaborated. Th
- Fodor,Ghizdavu,?uteu,Caraban
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p. 153 - 158
(2008/10/09)
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- Etching AlAs with HF for epitaxial lift-off applications
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The epitaxial lift-off process allows the separation of a thin layer of III/V material from the substrate by selective etching of an intermediate AlAs layer with HF In a theory proposed for this process, it was assumed that for every mole of AIAs dissolved three moles of H2 gas are formed. In order to verify this assumption the reaction mechanism and stoichiometry were investigated in the present work. The solid, solution and gaseous reaction products of the etch process have been examined by a number of techniques, It was found that aluminum fluoride is formed, both in the solid form as well as in solution. Furthermore, instead of H2 arsine (AsH3) is formed in the etch process. Some oxygen-related arsenic compounds like AsO, AsOH, and AsO2 have also been detected with gas chromatography/mass spectroscopy. The presence of oxygen in the etching environment accelerates the etching process, while a total absence of oxygen resulted in the process coming to a premature halt. It is argued that, in the absence of oxygen, the etching surface is stabilized, possibly by the sparingly soluble A1F3 or by solid arsenic.
- Voncken,Schermer,Van Niftrik,Bauhuis,Mulder,Larsen,Peters,De Bruin,Klaassen,Kelly
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p. G347-G352
(2008/10/09)
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- Electrochemical preparation of arsenic and its compounds
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Electrochemical processes are used to recover elemental arsenic from NaH2AsO3 solutions, oxidize As2O3 suspensions to arsenic acid, and reduce arsenic acid to arsine. The electrolysis conditions are optimized for obtaining elemental arsenic: 0.8-0.9 M NaH 2AsO3, 0.03-0.05 A/cm2, 20-25°C. The introduction of tetraalkylammonium salts containing C9-C12 substituents, e.g., trimethylcetylammonium bromide, is shown to stabilize the current efficiency in terms of As at a level of 45-50%. The current efficiency of copper cathodes attains 89% in 1-2 M H3AsO4 solutions at a current density of 0.2 A/cm2. In the electrosynthesis of arsenic acid, quantitative substance and current yields are achieved in 2-3 M HCl solutions. Low-waste processes are proposed for preparing arsenic, H 3AsO4, and As2O5 from As 2O3. The resulting arsenic is suitable for producing high-purity (99.9999%) material. The physicochemical processes underlying arsine generation are examined, and a bench-scale electrochemical arsine generator is described which can be used in the manufacturing of semiconductor materials.
- Smetanin,Smirnov,Chernykh,Turygin,Khudenko,Fedorov,Tomilov
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- Submillimeter-wave spectrum of the AsH2 radical in the 2B1 ground electronic state
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The pure rotational spectrum of the AsH2 radical in its 2B1 ground electronic state was observed for the first time by microwave spectroscopy. The AsH2 radical was generated in a free-space cell by dc-glow discharge of a mixture of H2 and O2 gases over arsenic powder. Fifty-five fine and hyperfine components of six rotational transitions were measured in the frequency region of 304-374 GHz, and were analyzed by least-squares methods. Molecular constants, including the rotational constants, the centrifugal distortion constants, the spin-rotation coupling constant incorporating the centrifugal distortion term, and the hyperfine coupling constants associated with the arsenic and hydrogen nuclei, were precisely determined. The bonding in AsH2 was discussed on the basis of the hyperfine coupling constants, first determined in the present study.
- Fujiwara, Hideo,Kobayashi, Kaori,Ozeki, Hiroyuki,Saito, Shuji
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p. 5351 - 5355
(2007/10/03)
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- Submillimetre-wave spectra of AsH and AsD radicals in the X3∑- electronic state
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Rotational lines of AsH and AsD radicals in their X 3∑- ground state have been observed in the submillimetre-wave region for the first time. The AsH radical was generated by de-glow discharge in pure AsH3 gas, and the AsD radical was generated by the reaction of arsenic powder with a mixture of D2 and O2 gases in a de-glow discharge. Three rotational transitions of AsH with hyperfine structure (N,J = 0,1-1,0 2,1-1,1 3,2-2,2) were measured in the frequency region 120-338 GHz, and five transitions (N,J = 0,1-1,0 2,1-1,0 2,2-1,1 4,3-3,3 5,4-4,4) of AsD in the region 173-440 GHz. The molecular constants, including the rotational constants, the spin-rotation coupling constant with the centrifugal distortion term and hyperfine coupling constants associated with the arsenic, hydrogen and deuterium nuclei, were precisely determined by least-squares fitting to the observed spectral lines. Using the results of both AsH and AsD, the Born-Oppenheimer equilibrium bond length was derived, where the adiabatic correction was taken into account: reBO = 1.522 370 (86) A.
- Fujiwara, Hideo,Kobayashi, Kaori,Ozeki, Hiroyuki
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p. 1045 - 1051
(2007/10/03)
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- Ba11KX7O2 (X = P, AS): Two novel zintl phases with infinite chains of oxygen centered Ba6 octahedra, isolated X3- and dimeric X24- anions
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Reactions of BaX (X = P, As) with Ba, K and BaO in tantalum tubes at 900-1000°C yielded black, very air-and moisture-sensitive crystals of Ba11KP7O2 and isotypic Ba11KAs7O2 which were characterized by EDX and X-ray diffraction (orthorhombic, Fddd, Z = 8; a = 1069.9(1), b = 1514.3(2), c = 3164.6(4) pm and a = 1087.8(2), b = 1542.3(2), c = 3232.4(4) pm, respectively). The structure contains infinite zigzag chains, 1∞[Ba4Ba2/2O], of oxygen-centered, corner-sharing Ba6 octahedra along [100]. They are connected by linear strings built of alternating isolated X atoms and X2 dimers to form layers parallel to (001). While the isolated X atoms are surrounded by eight Ba forming a distorted cube, the X2 dimers center a Ba12 polyhedron which is comprised of a pair of face-sharing Ba square antiprisms. This results in a cube-antiprism-antiprism-cube sequence of face-sharing Ba polyhedra. Additional X atoms function as spacers between the layers and connect them along [001]. Two atom positions are statistically occupied by Ba and K, and the formula may be written as Ba2+11K+X3-5(X 2)4-O2-2 according to the Zintl-Klemm concept.
- Lulei, Michael
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p. 1796 - 1802
(2008/10/09)
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- Reduction of Oxygen Compounds of Vanadium(V), Chromium(VI), and Manganese(VII) by Phosphine and Arsine in the Presence of Halide Ions: Assessment of Activation Parameters
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Halide ions (X(-)=Cl(-), Br(-), I(-)) significantly accelerate the PH3 and AsH3 (EH3) oxidation in acid solutions to phosphorus and arsenic acids by oxygen compounds of vanadium(V), chromium(VI), and manganese(VII). The reaction rate increases with an increase of the concentrations of these reagents, catalysts, or hydrogen ions, as well as upon replacement of Cl(-) by Br(-) or I(-) ions, of PH3 by AsH3, and of vanadium(V) by Cr(VI) or Mn(VII). The kinetic methods with the use of free-radical inhibitors showed that the reaction proceeds through the formation of halophosphine or haloarsine metal complexes and the inner-sphere interaction of EH3 molecules with the halide ions, promoting two-electron redox decomposition of the intermediate, reduction of the metal ions, and formation ofhalophosphine or haloarsine (EH2X). The latter compounds are halogenate d in a similar way to phosphorus and arsenic halides (MX3), which hydrolyze to the corresponding acids. The total energy of the intermediate as a function of the EH3 deflection angle from the equilibrium position toward the halide ion, a potential barrier emerges, which is used as an index of reaction ability. The barrier value correlates with the activationand kinetic parameters of the reactions. This value decreases upon the substitution of Cl(-) by Br(-) or I(-) ions; PH3, by AsH3; and vanadium( V), by Cr(VI) or Mn(VII).
- Dorfman, Ya. A.,Polimbetova, G. S.,Doroshkevich, D. M.
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p. 636 - 644
(2008/10/08)
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- IR Spectrum of the AsH Radical in its X3Σ- State, recorded by Laser Magnetic Resonance
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The IR spectrum of AsH in its ground 3Σ- state has been recorded using CO laser magnetic resonance (LMR).Several molecular parameters of AsH have been determined for the first time.In particular, arsenic nuclear hyperfine structure h
- Hensel, Kristine D.,Hughes, Rebecca A.,Brown, John M.
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p. 2999 - 3004
(2007/10/03)
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- Spectroscopic observation of the b 1Σ+ -> 3Σ- transition of AsH
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Emission lines of the b1Σ+ ->3Σ- transition of AsH radicals have been detected in the fluorescence of a dc-glow-discharge of arsine in hydrogen.From measurement of line positions of the (0,0), (1,1), and (2,2) Q branches and the (0,0) P and R branches, the molecular constants of the b1Σ+ state were determined: Te = 14 178.0 cm-1, B0 = 7.2467 cm-1, D0 = 3.1528*10-4 cm-1, ωe = 2213 cm-1, ωexe = 47.5 cm-1, re = 152.937 pm.
- Arens, M.,Richter, W.
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p. 7094 - 7096
(2007/10/02)
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- Infrared Product Spectra of Arsine-Ozone Complexes, Reaction Products, and Photolysis in Solid Argon
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Codeposition of AsH3 and O3 at high dilution in argon gave a large yield of AsH3-O3 complex and a small yield of reaction products identified as cis- and trans-H2AsOH.The complex photolyzed with red light, which showed that a specific interaction within the complex markedly increased the red photodissociation probability for the O3 submolecule.The red photolysis products were H3AsO, H2AsOH, and an intermediate species tentatively identified as HAsO.Further blue and near-UV irradiations destroyed HAsO and produced HOAsO2.This AsH3 and O3 study parallels earlier PH3 work and shows that AsH3, is slightly more reactive than PH3 with O3.
- Andrews, Lester,Withnall, Robert,Moores, Brian W.
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p. 1279 - 1285
(2007/10/02)
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- Reactions of Phosphine, arsine, and Stibine with Carbonylbis(triethylphosphine)iridium(I) Halides. Part 1. Reactions in Toluene; X-Ray Crystal Structures of and 6-MeC6H4CHMe2-p)> (X=Br, Z=P; X=Cl, Z=As)
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trans- (X=Br or Cl) reacts with ZH3 (Z=P, As, or Sb) in toluene at 180 K to give .When Z=P or As, the product is monoisomeric, but with Z=Sb two isomers are formed.. (4) reacts with Cl2 to give ; with Se, is the product.Reaction with HCl at 200 K gives (1+), but as the solution is allowed to warm PH3 is displaced by Cl, and a similar reaction with H2Se leads to the formation of .Boron trifluoride does not interact with (4), but B2H6 reacts to give a BH3 adduct that is stable in solution at room temperature.Compound (4) reacts with 6-MeC6H4CHMe2-p)>2>, forming 6-MeC6H4CHMe2-p)>.Reactions of (5) are similar, except that treatment with Se leads to decomposition.The crystal structures of (5) and the complexes formed by both (4) and (5) with 6-MeC6H4CHMe2-p)>2> are reported.
- Ebsworth, E. A. V.,Gould, Robert O.,Mayo, Richard A.,Walkinshaw, Malcolm
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p. 2831 - 2838
(2007/10/02)
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- Acidity, basicity, and ion-molecule reactions of arsine in the gas phase by ion cyclotron resonance spectroscopy
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The ion-molecule reactions of arsine, both in pure form and in binary mixtures with several other molecules, have been investigated by ion cyclotron resonance spectroscopy. Reaction pathways, product distributions, and rate constants have been determined for ion-molecule reactions of both positive and, to a lesser extent, negative ions. Rate constants are determined by examining variation of ion abundance with both pressure and time, the latter experiments utilizing trapped ion techniques. Arsine fragment ions condense with neutral AsH3 to generate product ions containing two and, on further reaction, three atoms af arsenic. In the process of condensation, one or two molecules of H2 are expelled. The formation of AsH4+ occurs from AsH3+ which does not undergo condensation reactions to any significant extent. Where possible, thermochemical data have been determined, including the gas-phase acidity, PA(AsH2-) = 360 ± 10 kcal/mol, and basicity, PA(AsH3) = 175 ± 5 kcal/mol, of AsH3. Observation of gas-phase nucleophilic displacement reactions involving AsH3 as a nucleophile have allowed limits to be placed on the basicity of AsH3 toward a soft acid, CH3+. The implications of these results are discussed and the ion-molecule reactions of AsH3 are compared with those of other hydrides.
- Wyatt,Holtz,McMahon,Beauchamp
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p. 1511 - 1517
(2008/10/08)
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