Elimination Of HCl Research Articles

Competitive Activation of CH and CX Bonds in Reactions of Pt+ with CH3X (X=F,Cl): Experiment and Theory

The reactions of Pt(+) with CH(3)X (X=F, Cl) are studied experimentally by employing an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer and theoretically by density functional theory. Dehydrogenation and HX elimination are found to be the primary reaction channels in the remarkably different ratios of 95:5 and 60:40 in the fast reactions of Pt(+) with CH(3)F and CH(3)Cl, respectively. The observed kinetics are consistent with quantum chemistry calculations, which indicate that both channels in the reaction with CH(3)F are exothermic with ground-state Pt(+)((2)D), but that HF elimination is prohibited kinetically because of a transition state that lies above the reactant entrance. The observed HF-elimination channel is attributed to a slow reaction of CH(3)F with excited-state Pt(+)((4)F) for which calculations predict a small barrier. The calculations also show that both the HCl-elimination and dehydrogenation channels observed with CH(3)Cl are thermodynamically and kinetically allowed, although the state-specific product distributions could not be ascertained experimentally. Further CH(3)F addition is observed with the primary products to produce PtCH(2) (+)(CH(3)F)(1,2) and PtCHF(+)(CH(3)F)(1,2). With CH(3)Cl, sequential HCl elimination is observed with PtCH(2) (+) to form PtC(n)H(2) (n) (+) with n=2, 3, which then add CH(3)Cl sequentially to form PtC(2)H(4) (+)(CH(3)Cl)(1-3) and PtC(3)H(6) (+)(CH(3)Cl)(1,2). Also, sequential addition is observed for PtCHCl(+) to form PtCHCl(+)(CH(3)Cl)(1,2).

Dehydrochlorination of Intermediates in the Production of Vinyl Chloride over Lanthanum Oxide-Based Catalysts

Lanthanum oxide-based catalysts are active in the elimination of HCl from C2H5Cl, 1,2-C2H4Cl2 and 1,1,2-C2H3Cl3 leading to the formation of their respective chlorinated ethenes. An oxygen-rich catalytic surface may form CO, CO2 and C2HCl as side products, whereas with chlorine-rich catalytic surfaces a stable product distribution is achieved with 100% selectivity towards the formation of ethenes, such as the valuable C2H3Cl intermediate.

Performance of CaO and MgO for the hot gas clean up in gasification of a chlorine-containing (RDF) feedstock

Calcined limestone (CaO) and calcined dolomite (CaO·MgO) were tested at bench scale to study their usefulness in cleaning hot raw gas from a fluidized bed gasifier of a synthetic or simulated refuse-derived fuel (RDF) with a high (3wt%) content in chlorine. In the gas cleaning reactor two main reactions occurred simultaneously: the elimination of HCl and the elimination of tar by steam reforming. The elimination of HCl formed CaCl2 and MgCl2 with melting points below the high (above 800°C) temperatures required for the simultaneous tar elimination reaction. So, the CaO-based particles progressively melted and the catalytic gas cleaning reactor became a compact, agglomerated or glued, cake. Therefore, the life and usefulness of the CaO-based solids used was very low. Nevertheless, and to further avoid these problems, some positive guidelines for future research are proposed here.

Molecular mechanisms in the pyrolysis of unsaturated chlorinated hydrocarbons

Laser-induced pyrolysis of small chlorinated hydrocarbons at temperatures where radical processes are likely to be unimportant has provided clear evidence for direct low-energy molecular reactions between acetylenes and chlorinated acetylenes or ethylenes. High-level ab initio calculations of possible pathways have shown that these reactions proceed via two routes. Direct bimolecular reaction accompanied by HCl elimination leads to diacetylenes or vinylacetylenes, respectively, while carbene molecular adducts, followed by Cl or H migrations to yield three- or four-membered rings and ring-opening, lead to vinylacetylenes or butadienes, respectively. Analogues of these processes are likely to be central to the growth of larger molecules in such systems.

Comment on “1,1,2,2-Tetrachloroethane Reactions with OH-, Cr(II), Granular Iron, and a Copper−Iron Bimetal: Insights from Product Formation and Associated Carbon Isotope Fractionation”

Despite widespread implementation of zero-valent iron remediation schemes, the manner and order of chemical bond cleavage in iron-mediated organohalide transformations remains imperfectly understood. We present insights from carbon isotope fractionation for the dehalogenation of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) and 1,1,1-trichloroethane (1,1,1-TCA) by various reactants. Elimination of HCl by OH- gave isotope fractionation in 1,1,2,2-TeCA of e = −25.6‰, KIEC = 1.02 to 1.03 per carbon center, consistent with a concerted (E2) mechanism. In contrast, 1,1,1-TCA reduction by Cr(II), Fe(0), and Cu-plated iron (Cu/Fe) resulted in e = −13.6‰ to −15.8‰ indicating the initial involvement of a single C−Cl bond (KIEC ≈ 1.03). 1,1,2,2-TeCA reduction by Cr(II), Fe(0), and Cu/Fe yielded e = −18.7‰, −19.3‰, and −17.0‰, respectively. In the two latter cases, depletion of the minor product TCE by 26‰ indicated its formation via nonreductive dehydrohalogenation. The major 1,1,2,2-TeCA reduction products, cis- and tra...

Experimental and theoretical study on the kinetics and mechanism of thermal decomposition of 1,2-dichloroethane

The kinetics and mechanism for the thermal decomposition of 1,2-dichloroethane (EDC) was studied in a flow system over the temperature range of 849–1064 K and pressure range of 10–300 Torr under homogeneous conditions in a tubular quartz reactor. Gas chromatography was used to measure the concentration of products. Four-center HCl elimination was found to be the most important channel in this system. Minor products such as methane, ethylene, acetylene, chloroethane, and chloroprene were identified. Ab initio calculations at the DFT, CASMP2, and QCISD(T) levels of theory were carried out to investigate the mechanism of this system and to calculate necessary parameters to compute the rate constants of different steps. Dependence of formation of vinyl chloride on the total pressure is measured, experimentally.

Insights into Mechanistic Photodissociation of Acetyl Chloride by ab Initio Calculations and Molecular Dynamics Simulations

The potential energy surfaces of dissociation and elimination reactions for CH(3)COCl in the ground (S0) and first excited singlet (S1) states have been mapped with the different ab inito calculations. Mechanistic photodissociation of CH(3)COCl has been characterized through the intrinsic reaction coordinate and ab initio molecular dynamics calculations. The alpha-C-C bond cleavage along the S1 pathway leads to the fragments of COCl((2)A' ') and CH(3) ((2)A') in an excited electronic state and a high barrier exists on the pathway. This channel is inaccessible in energy upon photoexcitation of the CH(3)COCl molecules at 236 nm. The S1 alpha-C-Cl bond cleavage yields the Cl((2)P) and CH(3)CO(X(2)A') fragments in the ground state and there is very small or no barrier on the pathway. The S1 alpha-C-Cl bond cleavage proceeds in a time scale of picosecond in the gas phase, followed by CH(3)CO decomposition to CH(3) and CO. The barrier to the C-Cl bond cleavage on the S1 surface is significantly increased by effects of the argon matrix. The S1 alpha-C-Cl bond cleavage in the argon matrix becomes inaccessible in energy upon photoexcitation of CH(3)COCl at 266 nm. In this case, the excited CH(3)COCl(S1) molecules cannot undergo the C-Cl bond cleavage in a short period. The internal conversion from S1 to S0 becomes the dominant process for the CH(3)COCl(S1) molecules in the condensed phase. As a result, the direct HCl elimination in the ground state becomes the exclusive channel upon 266 nm photodissociation of CH(3)COCl in the argon matrix at 11 K.

Oxovanadium(V) Tetrathiacalix[4]arene Complexes and Their Activity as Oxidation Catalysts

With the aim of modeling reactive moieties and relevant intermediates on the surfaces of vanadium oxide based catalysts during oxygenation/dehydrogenation of organic substrates, mono- and dinuclear vanadium oxo complexes of doubly deprotonated p-tert-butylated tetrathiacalix[4]arene (H4TC) have been synthesized and characterized: PPh4[(H2TC)VOCl(2)] (1) and (PPh4)2[{(H2TC)V(O)(mu-O)}2] (2). According to the NMR spectra of the dissolved complexes they both retain the structures adopted in the crystalline state, as revealed by single-crystal X-ray crystallography. Compounds 1 and 2 were tested as catalysts for the oxidation of alcohols with O(2) at 80 degrees C. Both 1 and 2 efficiently catalyze the oxidation of benzyl alcohol, crotyl alcohol, 1-phenyl-1-propanol, and fluorenol, and in most cases dinuclear complex 2 is more active than mononuclear complex 1. Moreover, the two thiacalixarene complexes 1 and 2 are in many instances more active than oxovanadium(V) complexes containing "classical" calixarene ligands tested previously. Complexes 1 and 2 also show significant activity in the oxidation of dihydroanthracene. Further investigations led to the conclusion that 1 acts as precatalyst that is converted to the active species PPh4[(TC)V==O] (3) at 80 degrees C by double intramolecular HCl elimination. For complex 2, the results of mechanistic investigations indicated that the oxidation chemistry takes place at the bridging oxo ligands and that the two vanadium centers cooperate during the process. The intermediate (PPh4)2[{H2TCV(O)}2(mu-OH)(mu-OC13H9)] (4) was isolated and characterized, also with respect to its reactivity, and the results afforded a mechanistic proposal for a reasonable catalytic cycle. The implications which these findings gathered in solution may have for oxidation mechanisms on the surfaces of V-based heterogeneous catalysts are discussed.

Photodissociation Pathways of 1,1-Dichloroacetone

We present a comprehensive investigation of the dissociation dynamics following photoexcitation of 1,1-dichloroacetone (CH(3)COCHCl(2)) at 193 nm. Two major dissociation channels are observed: cleavage of a C-Cl bond to form CH(3)C(O)CHCl + Cl and elimination of HCl. The branching between these reaction channels is roughly 9:1. The recoil kinetic energy distributions for both C-Cl fission and HCl elimination are bimodal. The former suggests that some of the radicals are formed in an excited electronic state. A portion of the CH(3)C(O)CHCl photoproducts undergo secondary dissociation to give CH(3) + C(O)CHCl. Photoelimination of Cl(2) is not a significant product channel. A primary C-C bond fission channel to give CH(3)CO + CHCl(2) may be present, but this signal may also be due to a secondary dissociation. Data from photofragment translational spectroscopy with electron impact and photoionization detection, velocity map ion imaging, and UV-visible absorption spectroscopy are presented, along with G3//B3LYP calculations of the bond dissociation energetics.

Formation of polychlorinated diphenyl ethers from condensation of chlorophenols with chlorobenzenes

Polychlorinated diphenyl ethers (PCDEs), which are among the members of persistent organic pollutants, and PCDEs have been determined in a number of environmental samples. The main possible sources are the technical production of chlorinated phenols and all processes of incomplete combustion. PCDEs were observed in the fly ash from a municipal waste incinerator (MWI). It was speculated that the condensation of chlorophenols with chlorobenzenes occurred via PCDEs to form polychlorinated dibenzofurans (PCDFs). Nevertheless, PCDEs formation from condensation of chlorophenols with chlorobenzenes has not been confirmed by experimental observation. The objective of this paper is to investigate the formation mechanism of PCDEs from the condensation of chlorophenols with chlorobenzenes. The results are expected to be helpful in understanding the formation of PCDEs and in controlling and abating PCDEs emissions from MWI. The pyrolysis of pentachlorophenol (PCP) and/or polychlorobenzenes (PCBz) was carried out in a sealed glass tube. The reaction products were extracted and purified with K2CO3 solution. The samples were concentrated and then cleaned up on an alumina column. GC/MS was used for identification and quantification of reaction products. The results showed that the pyrolysis of hexachlorobenzene (HCB) at 340 degrees C for 6 h led to the formation of decachlorodiphenyl ether (DCDE) (2.41 microg/mg) and octachlorodibenzo-p-dioxins (OCDD) (0.24 micropg/mg), while the pyrolysis of PCP yielded DCDE (13.08 microg/mg) and OCDD (180.13 microg/mg). In addition, the amount of DCDE formation from the pyrolysis of the mixture of PCP and HCB was 4.65 times higher than the total amount of DCDE formation from the pyrolysis of HCB and PCP, respectively. This indicated that PCP and HCB were prone to condensation and formation of DCDE. DCDE was the main congener of PCDEs from condensation of PCP with HCB at 340, 400 and 450 degrees C. A small amount of nonachlorodiphenyl ether (NCDE) was formed by dechlorination reaction at 450 degrees C. The condensation of PCP with 1,2,4,5-tetrachlorobenzene (Cl4Bz) formed 2,2',3,4,4',5,5',6-octachlorodiphenyl ether (OCDE). Small amounts of heptachlorodiphenyl ether (HpCDE) and hexachlorodiphenyl ether (HxCDE) were detected at 450 degrees C. Meanwhile, polychlorinated dibenzo-p-dioxins (PCDDs) and PCDFs were detected from the condensation of PCP and PCBz. Experimental studies clarified the behavior of the formation of PCDEs from condensation of polychlorophenols and PCBz. The condensation of polychlorophenols with PCBz formed PCDEs through elimination of HCl between polychlorophenols and PCBz molecules. Another pathway of PCDEs formation was elimination of H2O between two polychlorophenol molecules. In addition, dechlorination processes had caused the specific homologous pattern of PCDEs under higher temperatures.

Photoreaction mechanism of 2-chloropropionic acid in a low-temperature argon matrix

The photoreaction mechanism of 2-chloropropionic acid in a low-temperature argon matrix has been investigated by Fourier transform infrared spectroscopy with an aid of density-functional-theory calculations. The photoisomerization from syn to anti around the C O bond with the isomerization around the central C C bond was observed when the matrix sample was exposed to UV light ( λ > 240 nm). In the anti isomer produced in this reaction, the hydrogen atom in the carboxyl group is so close to the chlorine atom that this isomer changed to a less stable photoreaction intermediate by elimination of HCl. The photoreaction intermediate, which showed a strong C O stretching band around 1910 cm −1, was assigned by comparison with the calculated spectral pattern to methyloxiranone, a 3-membered lactone. This photoreaction mechanism was confirmed by a kinetic analysis for the absorbance changes of the reactant and intermediate bands.

Photochemical Synthesis of Polycyclic Pyrimidines Through the Acid Catalyzed Cycloaddition of 6‐Chloro‐1‐methyluracil to Methyl Substituted Benzenes.

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1,1,2,2-Tetrachloroethane Reactions with OH-, Cr(II), Granular Iron, and a Copper−Iron Bimetal: Insights from Product Formation and Associated Carbon Isotope Fractionation

Despite widespread implementation of zero-valent iron remediation schemes, the manner and order of chemical bond cleavage in iron-mediated organohalide transformations remains imperfectly understood. We present insights from carbon isotope fractionation for the dehalogenation of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) and 1,1,1-trichloroethane (1,1,1-TCA) by various reactants. Elimination of HCl by OH- gave isotope fractionation in 1,1,2,2-TeCA of Euro = -25.6 per thousand, KIE(c) = 1.02 to 1.03 per carbon center, consistentwith a concerted (E2) mechanism. In contrast, 1,1,1-TCA reduction by Cr(II), Fe(0), and Cu-plated iron (Cu/Fe) resulted in Euro = -13.6 per thousand to -15.8 per thousand indicating the initial involvement of a single C-Cl bond (KIE(c) approximately 1.03). 1,1,2,2-TeCA reduction by Cr(II), Fe(0), and Cu/Fe yielded Euro = -18.7 per thousand, -19.3 per thousand, and -17.0 per thousand, respectively. In the two latter cases, depletion of the minor product TCE by 26 per thousand indicated its formation via nonreductive dehydrohalogenation. The major 1,1,2,2-TeCA reduction products, cis- and trans-DCE, differed by 2.3 per thousand +/- 1.0 per thousand in Cr(II) systems, but were equivalent in Fe(0) and Cu/Fe systems. In contrast, the ratio of cis-DCE to trans-DCE concentration was 2.5 for reduction with Cr(II) and Fe(0), but -3.8 with Cu/Fe. Complementary isotope and concentration data therefore suggest differences in the transition state geometry and/ or reaction intermediates in each reductant system.

Four Distinctively Different Decomposition Pathways of Metastable Supermesityltellurium(IV) Trichloride

Chlorination of bis(supermesityl)ditelluride RTeTeR (R = 2,4,6-t-Bu3C6H2) with 3 equiv of sulfuryl chloride SO2Cl2 provided the intrinsically unstable supermesityltellurium(IV) trichloride RTeCl3 (1) as bright yellow crystals. Severe repulsion between the equatorial Cl atom and one tert-butyl group in an ortho position in the supermesityl ligand is the reason for the extreme reactivity of 1, which is in contrast to that of all previously known monoorganotellurium trihalides. In the solid state at room temperature, (the triclinic modification of) 1 reacts slowly under HCl elimination and intramolecular Te-C bond formation to give the bicyclic 5,7-di-tert-butyl-2-hydro-3,3-dimethylbenzo[b]tellurophene-1,1-dichloride (2), which was originally obtained as a colorless amorphous solid. On one occasion, when the solid-state reaction was allowed to occur under air conditions, compound 2 and a colorless crystalline byproduct, namely, trans-supermesityltellurium hydroxide dichloride (3), had formed, from which a few crystals were hand-selected. The formation of 3 has been tentatively rationalized by a solid-state hydrolysis of a second (monoclinic?) modification present in the bulk material of 1. In diethyl ether, THF, or carbon disulfide, a redox equilibrium exists between yellow supermesityltellurium(IV) trichloride RTeCl3 (1), deep blue supermesityltellurenyl(II) chloride RTeCl (4), and chlorine gas, which can be shifted to 4 when the reaction vessel is purged with argon to remove the chlorine gas. Compound 4 was also obtained by the reaction of RTeTeR (R = 2,4,6-t-Bu3C6H2) with 1 equiv of SO2Cl2. When a solution of 1 was stored with an excess of SO2Cl2 for a prolonged amount of time, Te-C bond cleavage occurred and [(Et2OH)2Te2Cl10].2Et2O (5) was formed. Compounds 1-5 have been characterized by X-ray crystallography.

A Grafting Study on Partially Dehydrochlorinated Poly(vinyl chloride) by Atom Transfer Radical Polymerization

HCl elimination in low ratio was first carried out from poly(vinyl chloride) to increase allylic chlorines. Partially dehydrochlorinated poly(vinyl chloride), having a macroinitiator effect, was grafted with tert‐butyl methacrylate via atom transfer radical polymerization in the presence of CuBr/2,2′‐bipyridine at 64°C in tetrahydrofuran. Original poly(vinyl chloride) was also grafted with tert‐butyl methacrylate under the same conditions to compare with that of partially dehydrochlorinated poly(vinyl chloride). The graft copolymers were characterized by elemental analysis, FTIR, 1H and 13C‐NMR, differential scanning calorimetry, and gel permeation chromatography (GPC). Thermal stabilities of the graft copolymers were investigated by thermogravimetric analysis as compared with those of the macroinitiators.

Influence of Cu2+‐organic montmorillonites on thermal decomposition and smoke emission of poly(vinyl chloride) by cone calorimetric study

AbstractCu2+‐Organic montmorillonites were prepared by modifying Na+ montmorillonite (Na+‐MMT) with silane coupling agents and cupric sulfate. PVC/organic montmorillonite composites were prepared by the melt intercalation method. Morphological structure of modified MMT and PVC/MMT was obtained by using XRD and SEM. The XRD results showed that silanes and Cu2+ were intercalated among interlayers and that modified MMT may have exfoliated dispersion in PVC. Effects of Cu2+‐organic montmorillonites on decomposition and smoke emission of poly(vinyl chloride) (PVC) in the flaming mode were investigated by using a cone calorimeter at an incident heat flux of 25 kW·m−2. Cone experimental data demonstrated that the Cu2+‐organic montmorillonites prepared were new effective smoke suppressants. They clearly promoted an early HCl elimination, crosslinking reactions, and char residue formation, based upon the decomposition parameters of mass loss, mass loss rate, and time of initial decomposition (tinitial). Cu2+‐Organic montmorillonites decreased peak heat release rate, total heat release, peak smoke production rate, total smoke production, and smoke extinction area during the flaming process. The smoke‐reducing efficiency of Cu2+‐organic montmorillonites (Cu2+‐OMMTs) was the best. However, the content of cupric ion was only 0.6–0.8% in Cu2+‐OMMTs and 0.03–0.04% in PVC composites. They may make the smoke‐reducing efficiency reach 45–50%. This result further demonstrates that Cu2+ ion is a very effective smoke suppressant for PVC. J. VINYL ADDIT. TECHNOL., 13:31–39, 2007. © 2007 Society of Plastics Engineers.

Ab initio and RRKM study of the elimination of HF and HCl from chlorofluoroethylene

Electronic structure calculations (MP2, B3LYP, and MC3BB) were performed to characterize the stationary points involved in the elimination of HX (X = F, Cl) from chlorofluoroethylene. The calculations predict 10 different HX elimination channels, being the HF elimination energetically favoured over the HCl elimination. The relative product abundances were computed as a function of the energy, using RRKM theory. At low energies, near threshold, the total HF/HCl ratio is greater than unity, but as the energy increases, the ratio becomes less than unity due to an entropic effect. This trend is in agreement with the experimental observations.

Hydrodechlorination of 1,2-dichloroethane and dichlorodifluoromethane over Ni/C catalysts: The effect of catalyst carbiding

Abstract In spite of previous reports, nickel catalysts appeared active in hydrodechlorination of 1,2-dichloroethane, producing ethylene with very high selectivity (up to 97%) at low temperatures of reaction (210–230 °C). In addition, at these temperatures, nickel deactivation by surface chloriding, observed by others, does not practically occur. The use of different nickel salts (chloride, nitrate, acetate) as catalyst precursors makes it possible to obtain different metal dispersions, reflected in variations of overall catalytic activity expressed per mass of nickel. The conditions of catalyst reduction led to a complete reduction of nickel precursor and effective removal of the counterion (Cl − or NO 3 − ). Interestingly, in the case of the chloride- and acetate-derived catalysts, the selectivity to vinyl chloride increases gradually with time on stream, at the expense of ethylene, even up to 30%. The appearance of fcc NiC x solutions ( x ≤ 0.1) and an hcp Ni 3 C phase in Ni/C catalysts used results from a massive production of ethylene, which is an efficient carbiding agent. An increasingly deeper transformation of Ni to Ni 3 C led to a higher selectivity to vinyl chloride. Alternatively, the Ni/C samples which were most selective toward ethylene (and characterized by a smaller Ni particle size) contained only tiny amounts of carbon in the form of NiC x solution. The behavior of Ni/C catalysts seems to be largely regulated by the population of surface carbon species. A higher surface carbon content (implied by a higher carbon content in Ni 3 C than in NiC x ≤ 0.1 ) creates an undeniable difficulty in removal of the second chlorine atom from 1,2-dichloroethane. It is suggested that, in such conditions, a new reaction route leading to vinyl chloride via a concerted elimination of HCl is feasible. The Ni/C catalysts subjected to CCl 2 F 2 hydrodechlorination contained even higher amounts of Ni 3 C than the analogous samples screened in the reaction of 1,2-dichloroethane.

Dimethyl Group IV Metal Complexes of the OSO-Type Ligand Bearing AlMe2Moieties

Complexes having two ancillary (tbop)2- ligands where tbopH2 = 2,2‘-thiobis{4-(1,1,3,3-tetramethylbutyl)phenol}, viz., [M(tbop-κ3O,S,O)2] (M = Ti, 1; M = Zr, 2; M = Hf, 3), have been prepared in good yields by amine or HCl elimination from tbopH2. The 1H and 13C NMR studies showed that complexes 1−3 adopt in solution mononuclear structures. Treatment of 1−3 with 2 equiv or an excess of AlMe3 generates heterometallic [M(μ-tbop-κ3O,S,O)2Me2(μ-AlMe2)2] (M = Ti, 4; M = Zr, 5; M = Hf, 6) complexes. The structures of 4−6 were confirmed by NMR spectroscopy; complexes 5 and 6 were further investigated by X-ray crystallography. These studies showed 4−6 to be trimers either in the solid state or in solution. The crystals of 5·CH2Cl2 and 6·CH2Cl2 consist of eight-coordinate dimethyl Zr or Hf centers and two AlMe2 moieties attached to oxygen atoms of the tbop ligands. The saturated coordination sphere of the metal centers in 1−6 makes them inactive in ethene polymerization.

Solvent and Ligand Effects on the Structures of Iron Halide Cations in the Gas Phase

AbstractThe effects of the oxidation state, the ligand, and the solvent on structures and energetics of cationic iron complexes are investigated by means of electrospray‐ionization mass spectrometry. Insights into the potential‐energy surfaces of FeX+, FeX2+, and XFe(OCH3)+ ions (X = F, Cl, Br, I) with a variable number of coordinated methanol molecules are obtained by means of collision experiments and complementary thermochemical considerations. It is shown that upon change of the halide ligand, the weakly solvated ions respond differentially to the increasing need for stabilization of the partial charge on the metal center. For example, whereas F2Fe(CH3OH)n+ ions tend to lose mainly HF for n = 1–3, the loss of HBr is not observed at all for Br2Fe(CH3OH)n+. Instead, the iron‐bromide cations undergo reductive loss of atomic bromine. Cl2Fe(CH3OH)n+ bears an intermediate position in that both reduction as well as elimination of HCl can occur. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)