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| Home > Publications database > Reactive MALDI mass spectrometry of saturated hydrocarbons: A theoretical study |
| Journal Article | PreJuSER-11775 |
; ;
2010
Elsevier Science
[S.l.]
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Please use a persistent id in citations: doi:10.1016/j.ijms.2010.02.012
Abstract: Recently it has been shown that the cobaltocenium cation, prepared by the laser ablation of a CoCp(CO)(2)/fullerene matrix, may react with alkanes and polyethylenes in the gas phase via a dehydrogenation reaction to produce [Co(Cp)(2)(alkadiene)](+) ions without chain scission (W.E. Wallace, Chem. Commun. 2007, 4525-4527). To better understand these experimental observations, density functional calculations were used to obtain the gas phase binding energies and molecular structures of cobaltocenium, Co(Cp)(2)(+), with 1,3-butadiene, 2,4-hexadiene, and 2,3-hexadiene. Calculations were conducted for both cis and trans molecular configurations, in both singlet and triplet electronic states, and with a variety of cyclopentadienyl hapticities. For 1,3-butadiene the 18-electron rule would predict a [Co(eta(5)-Cp)(2)(1,3-butadiene)](+), however, the lowest energy structure, [Co(eta(5)-Cp)(2)(1,3-butadiene)](+), has a higher than expected cyclopentadienyl hapticity. In this structure a distance of nearly 0.5 nm between the metal core and the butadiene ligand leads to very little electron sharing. Thus the detected ions are better described as non-covalent ion-molecule complexes. In turn, the lack of orbital overlap leads to a low enthalpy giving the cis-butadiene complex a -13.0 kJ/mol binding energy and the trans-butadiene binding a -3.8 kJ/mol binding energy. These low binding energies lead to low levels of charged alkanes in the reactive ion formation process in agreement with experimental observations. Published by Elsevier B.V.
Keyword(s): J ; Alkane (auto) ; Cobaltocene (auto) ; Dehydrogenation (auto) ; Density functional theory (auto) ; Non-covalent (auto) ; Polymer (auto)
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