Probing selective bond activation in alkylamines: Lanthanum-mediated C-H and N-H bond activation studied by mati spectroscopy

Nyambo, Silver

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https://hdl.handle.net/2142/100763 Copy

Description

Title

Probing selective bond activation in alkylamines: Lanthanum-mediated C-H and N-H bond activation studied by mati spectroscopy

Author(s)

Nyambo, Silver

Contributor(s)

• Yang, Dong-Sheng
• Zhang, Yuchen

Issue Date

2018-06-22

Keyword(s)

Metal containing

Abstract

In this work, La atom reactions with small alkylamines R − NH2 and H2N − (CH2)n − NH2 (n=2, 3, 4) are carried out in a laser-ablation supersonic molecular beam source. Reaction products are observed with photoionization time-offlight mass spectrometry and characterized by mass-analyzed threshold ionization (MATI) spectroscopy and DFT calculations. These reactions proceed via an exothermic H2 loss from the ligand and form a metal complex. The R − NH2 ligands favor the formation of acyclic metal complexes where La atom is doubly bonded to the N atom, whereas the H2N − (CH2)n − NH2 ligands prefer the formation of cyclic metal complexes where La atom is bonded to both N atoms. The reaction between La atom and CH3NH2 produces LaNCH3 in two low-energy isomeric forms: an acyclic C3v structure and a three -membered Cs ring. The C3v isomer is formed by concerted elimination of two H atoms from the NH2 group, whereas the Cs ring is formed by H atom elimination from both the alpha C and NH2 group. Both isomers prefer a doublet ground state with a La 6s1 -based electron configuration and a singlet ionic state by removing the 6s electron. The C3v structure is calculated to be more stable than the Cs isomer but has a slightly lower adiabatic ionization energy (40022 (5) cm−1 ) than the ring isomer (40399 (5) cm−1 ) as measured from the MATI spectra. The MATI spectrum of the C3v isomer is dominated by the origin band and La-Ligand and C-N stretching vibronic bands. The MATI signal of the Cs isomer is very weak and is only 10% of the C3v MATI signal. This observation confirms that the C3v isomer is more stable and its formation is more favorable than the Cs ring.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100763

DOI

10.15278/isms.2018.FB01

Copyright and License Information

Copyright 2018 Silver Nyambo

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