F+ and F鈭?/sup> Affinities of Simple NxFy and OxFy Compounds

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• 作者：Daniel J. Grant ; Tsang-Hsiu Wang ; Monica Vasiliu ; David A. Dixon ; Karl O. Christe
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：March 7, 2011
• 年：2011
• 卷：50
• 期：5
• 页码：1914-1925
• 全文大小：942K
• 年卷期：v.50,no.5(March 7, 2011)
• ISSN：1520-510X

文摘

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral and ionic N_xF_y and O_xF_y systems using coupled cluster theory with single and double excitations and including a perturbative triples correction (CCSD(T)) method with correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. To achieve near chemical accuracy (卤1 kcal/mol), three corrections to the electronic energy were added to the frozen core CCSD(T)/CBS binding energies: corrections for core鈭抳alence, scalar relativistic, and first order atomic spin鈭抩rbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory where possible. The calculated heats of formation are in good agreement with the available experimental values, except for FOOF because of the neglect of higher order correlation corrections. The F⁺ affinity in the N_xF_y series increases from N₂ to N₂F₄ by 63 kcal/mol, while that in the O₂F_y series decreases by 18 kcal/mol from O₂ to O₂F₂. Neither N₂ nor N₂F₄ is predicted to bind F^{鈭?/sup>, and N₂F₂ is a very weak Lewis acid with an F鈭?/sup> affinity of about 10 kcal/mol for either the cis or trans isomer. The low F鈭?/sup> affinities of the nitrogen fluorides explain why, in spite of the fact that many stable nitrogen fluoride cations are known, no nitrogen fluoride anions have been isolated so far. For example, the F鈭?/sup> affinity of NF is predicted to be only 12.5 kcal/mol which explains the numerous experimental failures to prepare NF₂鈭?/sup> salts from the well-known strong acid HNF₂. The F鈭?/sup> affinity of O₂ is predicted to have a small positive value and increases for O₂F₂ by 23 kcal/mol, indicating that the O₂F₃鈭?/sup> anion might be marginally stable at subambient temperatures. The calculated adiabatic ionization potentials and electron affinities are in good agreement with experiment considering that many of the experimental values are for vertical processes.}