Author ORCID Identifier

https://orcid.org/0000-0002-2852-4047

Date Available

12-7-2018

Year of Publication

2018

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department/School/Program

Chemistry

First Advisor

Dr. Dong-Sheng Yang

Abstract

Lanthanum-mediated bond activation reactions of small hydrocarbon molecules, including alkenes, alkynes, and alkadienes, were carried out in a laser vaporization metal cluster beam source. Time-of-flight mass spectrometry and mass-analyzed threshold ionization (MATI) spectroscopy, in combination with quantum chemical and multi-dimensional Franck-Condon factor calculations, were utilized to identify the reaction products and investigate their geometries, electronic structures, and formation mechanisms.

La-hydrocarbon association was only observed in the reaction of La with isoprene. C-H bond activation was observed in all reactions, hydrogen elimination was observed as the prominent reaction for the alkenes (2-butene, isobutene, 1-pentene, and 2-pentene), alkynes (1-butyne, 2-butyne, and 1-pentyne), and 1,4-pentadiene, and C-C bond activation was observed for the five-membered hydrocarbons (1-pentene, 2-pentene, 1-pentyne, isoprene, and 1,4-pentadiene).

The La-hydrocarbon radicals formed in these reactions had lanthanacyclic structures in various sizes, and each of the La-hydrocarbon complexes had a doublet ground state with a 6s1 La-based electron configuration. Ionization removed the 6s electron, and the resultant ion was in a singlet state. Formations of dehydrogenated products were either through a concerted hydrogen elimination process or the dehydrogenation after ligand isomerization. The C-C bond activation proceeded through La-assisted hydrogen migration, followed by C-C bond cleavage, or vice versa.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2018.503

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