Spectroscopic characterization of lanthanum-mediated dehydrogenation and C-C bond coupling of ethylene

Sudesh Kumari, Wenjin Cao, Yuchen Zhang, Mourad Roudjane, Dong Sheng Yang

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19 Scopus citations


La(C2H2) and La(C4H6) are observed from the reaction of laser-vaporized La atoms with ethylene molecules by photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization spectroscopy. La(C2H2) is identified as a metallacyclopropene and La(C4H6) as a metallacyclopentene. The three-membered ring is formed by concerted H2 elimination and the five-membered cycle by dehydrogenation and C-C bond coupling. Both metallacycles prefer a doublet ground state with a La 6s-based unpaired electron. Ionization of the neutral doublet state of either complex produces a singlet ion state by removing the La-based electron. The ionization allows accurate measurements of the adiabatic ionization energy of the neutral doublet state and metal-ligand and ligand-based vibrational frequencies of the neutral and ionic states. Although the La atom is in a formal oxidation state of +2, the ionization energies of these metal-hydrocarbon cycles are lower than that of the neutral La atom. Deuteration has a small effect on the ionization energies of the two cyclic radicals but distinctive effects on their vibrational frequencies.

Original languageEnglish
Pages (from-to)4482-4489
Number of pages8
JournalJournal of Physical Chemistry A
Issue number26
StatePublished - Jul 7 2016

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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