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  • Neutralization-reionization mass spectrometry  (8)
  • Transition-metal ions  (4)
  • Rate constants  (3)
  • 1
    ISSN: 1434-193X
    Keywords: Neutralization-reionization mass spectrometry ; Density functional theory ; Oxyallyl ; Ketocarbenes ; Methoxy vinylidene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five different anionic [C3, H4, O]·- isomers, i.e. the radical anions of acrolein, acetyl carbene, formyl methyl carbene, methoxy vinylidene, and oxyallyl are generated in an ion beam mass spectrometer and subjected to neutralization-reionization (NR) mass spectrometric experiments including neutral and ion decomposition difference (NIDD) mass spectrometry; the latter allows for the examination of the neutrals′ unimolecular reactivity. Further, the anionic, the singlet and triplet neutral, and the cationic [C3, H4, O]·-/0/·+ potential-energy surfaces are calculated at the B3LYP-6-311++G(d, p) level of theory. For some species, notably the singlet state of oxyallyl, the theoretical treatment is complemented by G2, CASSCF, and MR-CI calculations. Theory and experiment are in good agreement in that at the neutral stage (i) acrolein does not react within the μsec timescale, (ii) acetyl and formyl methyl carbenes isomerize to methyl ketene, (iii) methoxy vinylidene rearranges to methoxy acetylene, (iv) singlet 1A1 oxyallyl undergoes ring closure to cyclopropanone, and (v) triplet 3B2 oxyallyl may have a lifetime sufficient to survive a NR experiment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 983-987 
    ISSN: 1434-1948
    Keywords: Telluroles ; Neutralization-reionization mass spectrometry ; DFT calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,2-Dichloro-1,3-dichalcogena-2-telluroles of sulfur and selenium, C6H4[XTe(Cl)2Y] with X, Y = S, Se, serve as precursors to generate the cation radicals of 1,3-dichalcogena-2-telluroles C6H4[XTeY]+• as well as the corresponding neutral counterparts by means of neutralization-reionization mass spectrometry. These neutral 2-telluroles are intrinsically stable for at least 1 μs in the gas phase. The most abundant fragmentation channel at the neutral and cationic stages is due to loss of atomic tellurium to afford the corresponding benzo-1,2-dichalcogena-cyclobutenes. For the latter, partial isomerization to the related dichalcogena-ortho-quinones is indicated by the mass-spectrometric fragmentation pattern.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1583-1586 
    ISSN: 0009-2940
    Keywords: Transition-metal ions ; Bond activation, CH and CC ; Olefine activation ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanistic details (i.e. β-versus γ-hydrogen transfer) of transition-metal ion induced generation of propene from metastable ion complexes of 1,7-octadiene with M+=Cr+, Fe+, Ni+ are strongly affected by the nature of M+. For Cr+ the major reaction involves the transfer of an allylically activated hydrogen atom to M+ (γ-H transfer), followed by coupling of this hydrogen with the C3H5 unit (Scheme 3: 8 → 9→ 11 → C3H6). The hydrogen transfer 9→ 11 is preceded by substantial exchange reactions. A minor path for M+=Cr+ corresponds to the more traditional β-hydrogen transfer 9→ 10. This process, however, represents the major route for propene loss induced by M+ = Fe+, Ni+.
    Additional Material: 1 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 2069-2071 
    ISSN: 0009-2940
    Keywords: Interstellar chemistry ; Polycarbon disulfides ; Neutralization-reionization mass spectrometry ; Beam experiments ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds are generated and characterized in the gas phase by tandem mass spectrometry (neutralization-reionization mass spectrometry); it is demonstrated that both even and odd-numbered polycarbon disulfides S(Cn)S(n = 2-6) are stable species. The elusiveness of the even-numbered analogues (n = 2, 4, 6) in the condensed phase must be due to facile intermolecular reactions.
    Additional Material: 2 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1481-1483 
    ISSN: 0009-2940
    Keywords: Interstellar chemistry ; Polycarbon nitride radicals ; Neutralization-reionization mass spectrometry ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title radicals, thought to be of prime importance in the genesis of interstellar organic molecules, are accessible in the gas phase by neutralization of the corresponding CnN+ ions (n = 2-5) using tandem mass spectrometry methods (neutralization-reionization mass spectrometry). Collision-induced dissociation reactions of mass-selected CnN+ are in keeping with the connectivity of a “carbon rod” bearing a nitrogen atom at one terminus.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2817-2819 
    ISSN: 0009-2940
    Keywords: Transition-metal ions ; Metathesis, gas-phase ; Bond activation, CH and CC ; Ion cyclotron resonance mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In contrast to the reactions of “bare” Fe+ with 1,7-octadiene (1), the chemistry of Fe(CH2)+ with 1 represents a “textbook” example for a gas-phase metathesis process to generate in a clean fashion Fe(C2H4)+. Similarly, for the formation of Fe(C6H6)+ a mechanism is suggested which is in keeping with the experimental findings. In contrast, the reactions of Fe(CH2)+ with 1 leading to Fe(C3H4)+ and Fe(C4H6)+ are so complex that a coherent description is not yet possible.
    Additional Material: 1 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2353-2355 
    ISSN: 0009-2940
    Keywords: Ylides ; Distonic ions ; Neutralization-reionization mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The recently described (Maier et al.[2]) title compound is not only viable in an argon matrix (10 K) but is also accessible in the gas phase. Electron impact ionization of (CH3)3CCX2NC (X = H, D) gives rise to HCNCX2+, which can be successfully neutralized in a beam experiment.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 141-147 
    ISSN: 0009-2940
    Keywords: Bond activation, C  -  H, C  -  C ; Transition-metal ions ; Neighbouring group participation ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metastable-ion mass spectra of Fe+ complexes of alkanedinitriles NC(CH2)nCN (n = 1 - 10) exhibit six types of reactions: (1) Loss of the intact ligand to regenerate bare Fe+ as the exclusive (n = 1) or major reaction (n = 2) for the lower homologues; (2) generation of nitriles H(CH2)mCN with m = 0 - 6; (3) formation of unsaturated nitriles CH2 = CH(CH2)mCN with m = 0 - 4; (4) production of C2H4; (5) dehydrogenation, and (6) expulsion of the radicals C2H5 and CH2CN+. The branching ratios of these competing processes are governed by the chain length (CH2)n separating the two CN groups. Mechanistic insight is provided by the study of isotopomers. A comparison of the present data with the previously described behaviour of RCN/Fe+ complexes (R = alkyl) leaves no doubt that for the α,ω-alkanedinitriles it is the Fe+-mediated interaction of the two functional groups which controls the gas-phase chemistry of these organometallic systems. For example, results are presented demonstrating inter alia that losses of H2 and C2H4 proceed by completely different pathways when dinitriles serve as precursors, and either reaction is affected by neighbouring group participation. In distinct contrast, for RCN/Fe+ complexes (R = alkyl) the existing data point to common intermediates.
    Additional Material: 4 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 279-283 
    ISSN: 0009-2940
    Keywords: Interstellar chemistry ; Heterocumulenes ; Neutralization-reionization mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isomeric [C2,N,O2]+ ions OCNCO+, OCCNO+, and NCCO2- have been generated and structurally characterized on the basis of their collisional activation, charge reversal, and neutralization-reionization mass spectra. The open-shell neutrals formed in the neutralization step undergo facile unimolecular decomposition. A recovery signal is obtained only for OCCNO.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2499-2503 
    ISSN: 0009-2940
    Keywords: Bond activation ; Oxygen atom transfer ; Iron oxenoid chemistry ; Rate constants ; Ion cyclotron resonance mass spectrometry ; Ligand effects ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The presence of a benzene ligand in Fe(C6H6)O+ (1) has a profound effect on the gas-phase reactivity of FeO+. While the latter oxide is known to act as an efficient C-H/C-C bond-activation reagent, the ligated species 1 is entirely unreactive in that respect. However, 1 serves as an excellent reagent for transferring oxygen to various olefins. In addition, it is demonstrated that the ligand substitution Fe-(C6H6)O+ + X → Fe(X)O+ + 6H6) follows two principally different pathways. For X = C6D6 and C5H5N the traditional direct substitution process with attack at the metal centre is operative. However, for X = olefins it is argued that the olefin will not initially attack the metal center; rather, the reaction commences by coordinating the olefin X to the oxygen atom of Fe6H6)O+. The resulting intermediate (6H6)Fe(OX)+ will then fall apart either to separated Fe(OX)+/6H6) or to Fe(6H6)+/OX, thus bringing about an epoxidation of the olefin rather than ketone formation.
    Additional Material: 1 Ill.
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