Abstract
La reaction with propene is carried out in a laser-vaporization molecular beam source. Three La-hydrocarbon radicals are characterized by mass-analyzed threshold ionization (MATI) spectroscopy. One of these radicals is methylenelanthanum [La(CH2)] (Cs), a Schrock-type metal carbene. The other two are a five-membered 1-lanthanacyclopent-3-en [La(CH2CHCHCH2)] (Cs) and a tetrahedron-like trimethylenemethanelanthanum [La(C(CH2)3)] (C3v). Adiabatic ionization energies and metal-ligand stretching and hydrocarbon-based bending frequencies of these species are measured from the MATI spectra, preferred structures and electronic states are identified by comparing the experimental measurements and spectral simulations, and reaction pathways for the formation of the metal-hydrocarbon radicals are investigated with density functional theory calculations. All three radicals prefer doublet ground electronic states with La 6s1-based valence electron configurations, and singly charged cations favor singlet states generated by the removal of the La 6s1 electron. The metal-carbene radical is formed via multi-step carbon-carbon cleavage involving metallacyclization, β-hydrogen migration, and metal insertion. The metal-carbene radical formed in the primary reaction reacts with a second propene molecule to form the five-membered-ring and tetrahedron-like isomers through distinct carbon-carbon coupling paths.
Document Type
Article
Publication Date
5-9-2017
Digital Object Identifier (DOI)
https://doi.org/10.1063/1.4982949
Funding Information
We are grateful for the financial support from the National Science Foundation Division of Chemistry (Chemical Structure, Dynamics, and Mechanisms, Grant No. CHE-1362102).
Related Content
See the supplementary material for the geometries of La(CH2), La(CH2CHCHCH2) and La(C(CH2)3), and their ion states; energies of the stationary points along the reaction coordinates for the formation of three La-hydrocarbon radicals.
Repository Citation
Hewage, Dilrukshi C.; Cao, Wenjin; Kumari, Sudesh; Silva, Ruchira; Li, Tao Hong; and Yang, Dong-Sheng, "Spectroscopy and Formation of Lanthanum-Hydrocarbon Radicals Formed by C—C Bond Cleavage and Coupling of Propene" (2017). Chemistry Faculty Publications. 112.
https://uknowledge.uky.edu/chemistry_facpub/112
Supplementary Material
Notes/Citation Information
Published in The Journal of Chemical Physics, v. 146, issue 18, 184304, p. 1-8.
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The following article appeared in The Journal of Chemical Physics, v. 146, issue 18, 184304, p. 1-8 and may be found at https://doi.org/10.1063/1.4982949.