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Title: Formation Mechanism of NF 4 + Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids

Authors:
ORCiD logo [1];  [1];  [2];  [2]
  1. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles CA 90089-1661 USA
  2. Department of Chemistry, The University of Alabama, Tuscaloosa AL 35487 USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1378796
Grant/Contract Number:
FG02-03ER15481
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Angewandte Chemie
Additional Journal Information:
Journal Volume: 129; Journal Issue: 27; Related Information: CHORUS Timestamp: 2017-10-20 17:26:25; Journal ID: ISSN 0044-8249
Publisher:
German Chemical Society
Country of Publication:
Germany
Language:
English

Citation Formats

Christe, Karl O., Haiges, Ralf, Vasiliu, Monica, and Dixon, David A. Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids. Germany: N. p., 2017. Web. doi:10.1002/ange.201701784.
Christe, Karl O., Haiges, Ralf, Vasiliu, Monica, & Dixon, David A. Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids. Germany. doi:10.1002/ange.201701784.
Christe, Karl O., Haiges, Ralf, Vasiliu, Monica, and Dixon, David A. Thu . "Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids". Germany. doi:10.1002/ange.201701784.
@article{osti_1378796,
title = {Formation Mechanism of NF4+ Salts and Extraordinary Enhancement of the Oxidizing Power of Fluorine by Strong Lewis Acids},
author = {Christe, Karl O. and Haiges, Ralf and Vasiliu, Monica and Dixon, David A.},
abstractNote = {},
doi = {10.1002/ange.201701784},
journal = {Angewandte Chemie},
number = 27,
volume = 129,
place = {Germany},
year = {Thu May 04 00:00:00 EDT 2017},
month = {Thu May 04 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1002/ange.201701784

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  • The interaction of Cp{prime}{sub 2}Nb({eta}{sup 2}-CO{sub 2})CH{sub 2}SiMe{sub 3} (1; Cp{prime} = {eta}{sup 5}-MeC{sub 5}H{sub 4}) with several Lewis acids has been studied and found to result in facile decarbonylation of 1; the Nb-containing products depend markedly on the Lewis acid partner. Reaction of 1 with LiPF{sub 6} or BF{sub 3}{center_dot}Et{sub 2}O causes both decarbonylation and deoxygenation, producing [Cp{prime}{sub 2}Nb(F)CH{sub 2}SiMe{sub 3}]Z [Z = PF{sub 6}{sup -}(3), BF{sub 4}{sup -} (6)], which have been characterized spectroscopically and (for 3) by X-ray diffraction; 3 is also produced in the reaction of the oxo derivative Cp{prime}{sub 2}Nb(O)CH{sub 2}SiMe{sub 3} (2) with LiPF{submore » 6} or BF{sub 3}{center_dot}Et{sub 2}O. 1 reacts with ZnCl{sub 2} first to form an adduct, Cp{prime}{sub 2}Nb-(CO){sub 2}CH{sub 2}SiMe{sub 3}{center_dot}ZnCl{sub 2} (7), which based on IR and NMR data appears to have a novel {mu}-CO{sub 2} unit bridging Nb and Zn. Complex 7 is unstable, decomposing with CO loss to form [Cp{prime}{sub 2} Nb(CH{sub 2}SiMe{sub 3})O{center_dot}ZnCl{sub 2}]{sub 2} (8), an adduct of ZnCl{sub 2} with the oxo species 2, which has been characterized crystallographically; 8 is also produced from 2 and ZnCl{sub 2}. Reaction of 1 with HgCl{sub 2} rapidly produces an incompletely characterized product 10, which has been both decarbonylated and dealkylated. Although CdCl{sub 2} does not react with 1 under comparable conditions, Me{sub 3}SiCl reacts rapidly with 1 to produce Cp{prime}{sub 2}Nb(O) Cl (11), resulting from decarbonylation and dealkylation; the structure of 11 has been established by X-ray diffraction. 19 refs., 3 figs., 5 tabs.« less
  • We studied the emission of the fluorine (2{ital p}{sup 4}3{ital s}) {sup 2,4}{ital P}{r arrow}(2{ital p}{sup 5}) {sup 2}{ital P} resonance lines in the vacuum ultraviolet (VUV) at 95.5 and 97.5 nm, respectively, following dissociative excitation of SF{sub 6}, CF{sub 4}, NF{sub 3}, and CCl{sub 2}F{sub 2} by controlled electron impact under single collision conditions. Absolute photoemission cross sections and appearance potentials have been determined for the 95.5 nm {sup 2}{ital P}{r arrow}{sup 2}{ital P} multiplets for all four target gases. The apparent cross sections, which include cascade contribution from higher states, were measured to range from 2 to 5{times}10{supmore » {minus}18} cm{sup 2} at 200 eV impact energy. The cross sections were found to be heavily influenced by 3{ital p}{r arrow}3{ital s} cascading with contributions ranging from 30% (SF{sub 6}) to 75% (CF{sub 4}). Subtraction of the cascade contributions yielded direct cross sections of 0.5{times} 10{sup {minus}18} cm{sup 2} (CF{sub 4}), 1.4{times}10{sup {minus}18} cm{sup 2} (CCl{sub 2}F{sub 2}), 1.5{times}10{sup {minus}18} cm{sup 2} (SF{sub 6}), and 2.9{times}10{sup {minus}18} cm{sup 2} (NF{sub 3}) at 200 eV. The fluorine emissions are the result of the total fragmentation of the parent molecule for the targets SF{sub 6}, CF{sub 4}, and NF{sub 3}. A much lower appearance potential and a different energy dependence of the cross section in the case of CCl{sub 2}F{sub 2} indicates that partial fragmentation of this molecule plays a very important role. The findings for the 97.5 nm {sup 4}{ital P}{r arrow}{sup 2}{ital P} multiplet were essentially similar to those for the {sup 2}{ital P}{r arrow}{sup 2}{ital P} multiplet with the exception that accurate apparent emission cross sections could not be determined from a measurement of the 97.5 nm photon emission intensity.« less
  • High level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the third row transitionmetal hexafluorides. The electron affinities, heats of formation, first (MF₆ → MF₅ + F) and average M-F bond dissociation energies, and fluoride affinities of MF₆ (MF₆ + F⁻→ MF₇ ⁻) and MF₅ (MF₅ + F⁻→ MF₆ ⁻) were calculated. The electron affinities which are a direct measure for the oxidizer strength increase monotonically from WF₆ to AuF₆, with PtF₆ and AuF₆ being extremely powerful oxidizers. The inclusion of spin orbit corrections is necessary to obtain the correct qualitative order for the electronmore » affinities. The calculated electron affinities increase with increasing atomic number, are in good agreement with the available experimental values, and are as follows: WF₆ (3.15 eV), ReF₆ (4.58 eV), OsF₆ (5.92 eV), IrF₆ (5.99 eV), PtF₆ (7.09 eV), and AuF₆ (8.20 eV). A wide range of density functional theory exchange-correlation functionals were also evaluated, and only three gave satisfactory results. The corresponding pentafluorides are extremely strong Lewis acids, with OsF₅, IrF₅, PtF₅, and AuF₅ significantly exceeding the acidity of SbF₅. The optimized geometries of the corresponding MF₇⁻ anions for W through Ir are classical MF₇⁻ anions with M-F bonds; however, for PtF₇⁻ and AuF₇⁻ non-classical anions were found with a very weak external F-F bond between an MF₆⁻ fragment and a fluorine atom. These two anions are text book examples for “superhalogens” and can serve as F atom sources under very mild conditions, explaining the ability of PtF₆ to convert NF₃ to NF₄⁺, ClF₅ to ClF₆⁺, and Xe to XeF⁺ and why Bartlett failed to observe XePtF₆ as the reaction product of the PtF₆/Xe reaction.« less