Gas‐phase reactions of XH 3 + (X = C, Si, Ge) with NF 3 : a comparative investigation on the detailed mechanistic aspects

The gas‐phase reaction of CH 3 + with NF 3 was investigated by ion trap mass spectrometry (ITMS). The observed products include NF 2 + and CH 2 F + . Under the same experimental conditions, SiH 3 + reacts with NF 3 and forms up to six ionic products, namely (in order of decreasing efficiency) NF 2 + , SiH 2 F + , SiHF 2 + , SiF + , SiHF + , and NHF + . The GeH 3 + cation is instead totally unreactive toward NF 3 . The different reactivity of XH 3 + (X = C, Si, Ge) toward NF 3 has been rationalized by ab initio calculations performed at the MP2 and coupled cluster level of theory. In the reaction of both CH 3 + and SiH 3 + , the kinetically relevant intermediate is the fluorine‐coordinated isomer H 3 X‐F‐NF 2 + (X = C, Si). This species forms from the exoergic attack of XH 3 + to one of the F atoms of NF 3 and undergoes dissociation and isomerization processes which eventually result in the experimentally observed products. The nitrogen‐coordinated isomers H 3 X‐NF 3 + (X = C, Si) were located as minimum‐energy structures but do not play an active role in the reaction mechanism. The inertness of GeH 3 + toward NF 3 is also explained by the endoergic character of the dissociation processes involving the H 3 Ge‐F‐NF 2 + isomer. Copyright © 2009 John Wiley & Sons, Ltd.