Quantum chemistry calculations and experimental investigations of the unimolecular dissociation step of the molecular radical cation of tetramethylsilane losing a methyl radical to give the m/z 73 trimethyl silyl cation have been carried out. There is an apparent lack of an ion/neutral complex in the minimum energy reaction pathway, where in quaternary carbon compounds there is evidence of such complexes. It is suggested that at interfragment separation distances at which an ion/neutral complex would be expected the electrostatic interactions are “swamped” by the strength of the conventional covalent bonding interactions which are an order of magnitude greater than in the quaternary carbon systems at similar separations.
Get full access to this article
View all access options for this article.
References
1.
RylanderP.N.MeyersonS.J., J. Amer. Chem. Soc.78, 5799 (1956).
2.
HammerumS., in Fundamentals of Gas Phase Ion Chemistry, Ed by JenningsK.R., Kluwer, Dordrecht, NATO ASI Series C, 379–393, (1991).
HeinrichN.ShwarzH., in Ion and Cluster Ion Spectroscopy and Structure, Ed. by MaierJ.P., Elsevier, Amsterdam, p. 329 (1989).
10.
BeveridgeW., Techniques for the Study of the Ion Chemistry of Group IV Quaternary Cations. PhD Thesis, Heriot-Watt Univeristy, Edinburgh (1993).
11.
BeveridgeW.JohnsonC.A.F.ParkerJ.E., 17th Meeting of the British Mass Spectrometry Society.University of Nottingham, Abstracts p. 40–41 (1989).
12.
JohnsonC.A.F.ParkerJ.E.HunterJ.A.BeveridgeW., 18th Meeting of the British Mass Spectrometry Society.University College London, Abstracts p. 132–133 (1990).
13.
BeveridgeW.GariochI.W.HunterJ.A.JohnsonC.A.F.ParkerJ.E., 18th Meeting of the British Mass Spectrometry Society.University College London, Abstracts p. 16–17 (1990).
14.
BeveridgeW.GariochI.W.HunterJ.A.JohnsonC.A.F.ParkerJ.E., Org. Mass Spectrom.26, 416 (1991).
15.
BeveridgeW.HunterJ.A.JohnsonC.A.F.ParkerJ.E., Org. Mass Spectrom.27, 543 (1992).
16.
Eight Peak Index of Mass Spectra, 2nd Edition. Mass Spectral Data Centre, Aldermaston (1974).
17.
DibelerV.H., J. Research of National Bureau of Standards49, 235 (1952).
18.
BeveridgeW., Quaternary Radical Cations of Carbon and Silicon—a Combined Mass Spectrometry/Quantum Chemical Study. BSc Dissertation, Heriot-Watt University, Edinburgh (1989).
19.
ShinS.K.CordermanR.R.BeauchampJ.L., Int. J. Mass Spectrom. Ion Proc.101, 257 (1990).
20.
JohnsonC.P.LangerA., J. Phys. Chem.61, 1010 (1957).
21.
HunterJ.A.JohnsonC.A.F.McGillI.J.M.ParkerJ.E.SmithG.P., J. Chem. Soc., Faraday Trans.2, 83, 2025 (1987).
22.
FrischM.BinkleyJ.S.SchlegelH.B.RaghavachariK.MartinR.StewartJ.J.P.BrobowiczF.W.DefreesD.SeegerR.WhitesideR.FoxD.FluderE.PopleJ.A., GAUSSIAN86, Release C. Carnegie-Mellon Quantum Chemistry Publishing Unit, Pittsburgh, PA (1984).
23.
FrischM.J.Head-GordonM.TrucksG.W.ForesmanJ.B.SchlegelH.B.RaghavachariK.RobbM.BinkleyJ.S.GonzalezC.DefreesD.J.FoxD.J.WhitesideR.A.SeegerR.NeliusC.F.BakerJ.MartinR.L.KahnL.R.StewartJ.J.P.TopiolS.PopleJ.A., GAUSSIAN90, Revision H. Gaussian Inc., Pittsburgh, PA (1990).
24.
HehreW. J.RadomL.von R. SchleyerP.PopleJ.A., Ab Initio Molecular Orbital Theory.Wiley-Interscience, New York, p. 66 (1986).
25.
EvansS.GreenJ.C.JpachimP.J.OrchardA.F.TurnerD.W.MaierJ.P., J. Chem. Soc. Farad. Trans.2, 68, 905 (1972).
26.
KimuraK.KatsumataS.AchibaY.YamazakiT.IwataS., Handbook of the He I Photoelectron Spectra of Organic Molecules.Japan Scientific Societies Press, Tokyo, p. 257 (1981).
27.
PopleJ.A., Molecular Ions, Geometric and Electronic Structures, Ed by BerkowitzJ.GroenieveldK.-O., Plenum Press, New York, NATO ASI Series B, Physics, vol. 90, p. 287 (1983).
28.
RosenstockH.M.DraxlK.SteinerB.W.HerronJ.T., “Energetics of Gaseous Ions”, J. Phys. Chem. Ref. Data6, Suppl. No. 1 (1977).
29.
GroenwoldG.S.GrossM.J.BurseyM.M.JonesP.R., J. Organometal. Chem.255, 165 (1982).
30.
HolznagelC.M.BakhtiarR.JacobsonD.B., J. Amer. Soc. Mass Spectrom.2, 278 (1991).
31.
CottonF.A.WilkinsonG., Advanced Inorganic Chemistry, A Comprehensive Text, 4th Edition. Wiley, New York, p. 1280 (1980), and references contained therein.
