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# A Selected Ion Flow Tube Study of the Reactions of Several Cations with the Group 6B Hexafluorides SF6, SeF6, and TeF6

Jarvis, G. K. and Kennedy, R. A. and Mayhew, C. A. and Tuckett, R. P. (2000) A Selected Ion Flow Tube Study of the Reactions of Several Cations with the Group 6B Hexafluorides SF6, SeF6, and TeF6. The Journal of Physical Chemistry A, 104 (46). pp. 10766-10776. ISSN 1089-5639

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URL of Published Version: http://dx.doi.org/10.1021/jp002120z

Identification Number/DOI: doi:10.1021/jp002120z

The first investigation of the ion chemistry of SeF$$_6$$ and TeF$$_6$$ is presented. Using a selected ion flow tube, the thermal rate coefficients and ion product distributions have been determined at 300 K for the reactions of fourteen atomic and molecular cations, namely H$$_3$$O$$^+$$, CF$$_3^+$$, CF$$^+$$, CF$$_2^+$$, H$$_2$$O$$^+$$, N$$_2$$O$$^+$$, O$$^+$$, CO$$_2^+$$, CO$$^+$$, N$$^+$$, N$$_2^+$$, Ar$$^+$$, F$$^+$$ and Ne$$^+$$ (in order of increasing recombination energy), with SeF$$_6$$ and TeF$$_6$$. The results are compared with those from the reactions of these ions with SF$$_6$$, for which the reactions with CF$$^+$$, CF$$_2^+$$, N$$_2$$O$$^+$$ and F$$^+$$ are reported for the first time. Several distinct processes are observed amongst the large number of reactions studied, including dissociative charge transfer, and F$$^-$$, F, F$$_2^-$$ and F$$_2$$ abstraction from the neutral reactant molecule to the reagent ion. The dissociative charge transfer channels are discussed in relation to vacuum ultraviolet photoelectron and threshold photoelectron-photoion coincidence spectra of XF$$_6$$ (X = S, Se, and Te). For reagent ions whose recombination energies lie between the first dissociative ionisation limit, XF$$_6$$ $$\rightarrow$$ XF$$_5^+$$ + F + e$$^-$$, and the onset of ionisation of the XF$$_6$$ molecule, the results suggest that if dissociative charge transfer occurs, it proceeds via an intimate encounter. For those reagent ions whose recombination energies are greater than the onset of ionisation, long-range electron transfer may occur depending on whether certain physical factors apply, for example non-zero Franck-Condon overlap. From the reaction kinetics, limits for the heats of formation of SeF$$_4$$, SeF$$_5$$, TeF$$_4$$ and TeF$$_5$$ at 298 K have been obtained; $$\Delta_f$$H$$^o$$(SeF$$_4$$) < -369 kJ mol$$^{-1}$$, $$\Delta_f$$H$$^o$$(SeF$$_5$$) < -621 kJ mol$$^{-1}$$, $$\Delta_f$$H$$^o$$(TeF$$_4$$) > -570 kJ mol$$^{-1}$$, and $$\Delta_f$$H$$^o$$(TeF$$_5$$) < -822 kJ mol$$^{-1}$$.

Type of Work: Article 2000 (Publication) Schools (1998 to 2008) > School of Chemical Sciences School of Chemistry, School of Physics QD ChemistryQC Physics University of Birmingham American Chemical Society 732 YES

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