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

✍ Scribed by Paola Antoniotti; Roberto Rabezzana; Francesca Turco; Stefano Borocci; Maria Giordani; Felice Grandinetti

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 380 KB
• Volume: 43
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1404

✦ Synopsis

Abstract

The ion–molecule reactions occurring in GeH~4~/NF~3~, GeH~4~/SF~6~, and GeH~4~/SiF~4~ gaseous mixtures have been investigated by ion trap mass spectrometry and ab initio calculations. While the NF~x~^+^ (x = 1–3) react with GeH~4~ mainly by the exothermic charge transfer, the open‐shell Ge^+^ and GeH~2~^+^ undergo the efficient F‐atom abstraction from NF~3~ and form GeF^+^ and FGeH~2~^+^ 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NF~2~^+^ and H~2~GeFNF~2~^+^, their subsequent crossing to the significantly more stable isomers FGeNF~2~^+^ and FGeH~2~NF~2~^+^, and the eventual dissociation of these ions into GeF^+^ (or FGeH~2~^+^) and NF~2~. The closed‐shell GeH^+^ and GeH~3~^+^ are instead much less reactive towards NF~3~, 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 from NF~3~ to SF~6~ and SiF~4~, the average strength of the MF bond increases from 70 to 79 and 142 kcal mol^−1^, and in fact the only process observed by reacting GeH~n~^+^ (n = 0–3) with SF~6~ and SiF~4~ is the little efficient F‐atom abstraction from SF~6~ 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 CH~3~F. Additionally observed processes include in particular the conceivable formation of the elusive thiohypofluorous acid FSH from the reaction between SF^+^ and GeH~4~. Copyright © 2008 John Wiley & Sons, Ltd.