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Metastable and collision‐induced fragmentation studies and thermochemistry of isomeric C 4 H 11 Si + ions and their adducts with C 4 H 12 Si silanes
Author(s) -
Hop Cornelis E. C. A.,
Saulys Dovas A.,
Gaines Donald F.,
Szulejko Jan E.,
McMahon Terrance B.
Publication year - 2000
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/1096-9888(200008)35:8<1003::aid-jms28>3.0.co;2-v
Subject(s) - chemistry , silanes , adduct , dissociation (chemistry) , mass spectrum , ion , mass spectrometry , collision induced dissociation , thermochemistry , fragmentation (computing) , deuterium , silane , photochemistry , analytical chemistry (journal) , inorganic chemistry , organic chemistry , tandem mass spectrometry , physics , chromatography , quantum mechanics , computer science , operating system
Metastable Ion (MI) and collision‐induced dissociation (CID) mass spectra for all isomeric even‐electron [C 4 H 12 Si − H] + ions were recorded and compared. Deuterium labeling experiments indicated that most precursors give rise to silylium ions. Silylium ions with two or more methyl groups are found to lose C 2 H 4 after isomerization via a straightforward hydrogen transfer to the appropriate ethylsilylium ion. Similarly, all isomeric propyl‐ and butyl‐containing silylium ions are found to lose C 2 H 4 by rearrangement preceding dissociation. In the CI source of the mass spectrometer many of the silylium ions are found to cluster with the parent neutral silane present in the source to give stable {[M − H] + +M} adduct ions. The MI and CID spectra of these adduct ions were also obtained. In the MI spectra of all adducts, except i ‐BuSiH 3 , only the starting silylium ion is observed. Under CID conditions generation of silylium ions dominates. Deuterium labeling studies show that this dissociation may be accompanied by some rearrangement, in particular for the adducts from i ‐BuSiH 3 . High‐pressure mass spectrometric clustering equilibrium measurements were also carried out to determine the enthalpies and entropies of binding of the silylium ions to the neutral silanes. These measurements yield insight into the effects of various alkyl group substitutions on the association thermochemistry in these adducts. Copyright © 2000 John Wiley & Sons, Ltd.