Ion chemistry in germane/fluorocompounds gaseousmixtures: a mass spectrometric and theoretical study

The ion–molecule reactions occurring in GeH4/NF3, GeH4/SF6, andGeH4/SiF4 gaseousmixtures have been investigated by ion trap mass spectrometry and ab initio calculations. While the NFx + (x = 1–3) react with GeH4 mainly by the exothermic charge transfer, the open-shellGe+ andGeH2 + undergo the efficient F-atom abstraction fromNF3 and formGeF+ and F–GeH2 + as the only ionic products. The mechanisms of these two processes are quite similar and involve the formation of the fluorine-coordinated complexes Ge–F–NF2 + and H2Ge–F–NF2 +, their subsequent crossing to the significantly more stable isomers FGe–NF2 + and F–GeH2–NF2 +, and the eventual dissociation of these ions into GeF+ (or F–GeH2 +) and NF2. The closedshell GeH+ and GeH3 + are instead much less reactive towards NF3, and the only observed process is the less efficient formation of GeF+ from GeH+. The theoretical investigation of this unusual H/F exchange reaction suggests the involvement of vibrationally-hot GeH+. Passing fromNF3 to SF6 and SiF4, the average strength of theM–F bond increases from 70 to 79 and 142 kcal mol−1, and in fact the only process observed by reacting GeHn + (n = 0–3) with SF6 and SiF4 is the little efficient F-atom abstraction from SF6 by Ge+. Irrespective of the experimental conditions, we did not observe any ionic product of Ge–N, Ge–S, or Ge–Si connectivity. This is in line with the previously observed exclusive formation of GeF+ from the reaction between Ge+ and C–F compounds such as CH3F. Additionally observed processes include in particular the conceivable formation of the elusive thiohypofluorous acid FSH from the reaction between SF+ and GeH4. Copyright  2008 John Wiley & Sons, Ltd.