title: Mass-analyzed threshold ionization spectroscopy of lanthanum-hydrocarbon radicals formed by C-H bond activation of propene.
abstract: La(C3H4) and La(C3H6) are observed from the reaction of laser-vaporized La atoms with propene by photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization spectroscopy. Two isomers of La(C3H4) are identified as methyl-lanthanacyclopropene [La(CHCCH3)] (Cs) and lanthanacyclobutene [La(CHCHCH2)] (C1); La(C3H6) is determined to be H-La(η3-allyl) (Cs), a C-H bond inserted species. All three metal-hydrocarbon radicals prefer a doublet ground state with a La 6s-based electron configuration. Ionization of the neutral doublet state of each of these radicals produces a singlet ion state by removing the La-based 6s electron. The threshold 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. The formation of the three radicals is investigated by density functional theory computations. The inserted species is formed by La inserting into an allylic C-H bond and lanthanacyclopropene by concerted vinylic H2elimination, whereas lanthanacyclobutene involves both allylic and vinylic dehydrogenations. The inserted species is identified as an intermediate for the formation of lanthanacyclobutene.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
authors.forename: Sudesh
authors.initials: S
authors.lastname: Kumari
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
authors.forename: Wenjin
authors.identifier: 0000000228524047
authors.initials: W
authors.lastname: Cao
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
authors.forename: Dilrukshi
authors.initials: D
authors.lastname: Hewage
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
authors.forename: Ruchira
authors.initials: R
authors.lastname: Silva
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
authors.forename: Dong-Sheng
authors.identifier: 0000000198424343
authors.initials: DS
authors.lastname: Yang