Vibronic transitions and spin–orbit coupling of three-membered metallacycles formed by lanthanide-mediated dehydrogenation of dimethylamine

Abstract

Metal-mediated N–H and C–H bond activation of aliphatic amines is an effective strategy for synthesizing biologically important molecules. Ln (Ln = La and Ce) atom reactions with dimethylamine are carried out in a pulsed-laser vaporization supersonic molecular beam source. A series of dehydrogenation species are observed with time-of-flight mass spectrometry, and the dehydrogenated Ln-containing species in the formula Ln(CH2NCH3) are characterized by single-photon mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and multiconfiguration self-consistent field and quasi-degenerate perturbation theory for the Ce species. The MATI spectrum of La(CH2NCH3) consists of a single vibronic band system, which is assigned to the ionization of the doublet ground state of N-methyl-lanthanaaziridine. The MATI spectrum of Ce(CH2NCH3) displays two vibronic band systems, which are attributed to the ionization of two-pair lowest-energy spin–orbit coupling states of N-methyl-ceraaziridine. Both metallaaziridines are three-membered metallacycles and formed by the thermodynamically and kinetically favorable concerted dehydrogenation of the amino group and one of the methyl groups.

Electronic Structure of Heteronuclear Cerium-Platinum Clusters

“…Spectroscopy of small molecule or cluster models can provide a back-door approach to understanding the fundamental electronic structure of these materials. Small clusters, , even diatomics, provide an insight into bonding and atomic-scale interactions − within the materials; they are also effective models of edges, corners, and defect sites. − …”

Probing La and Ce Excited-State Reactivity with Resonant Two-Photon Ionization Spectroscopy

“…27−34 The presence of the 4f electrons and stronger spin−orbit coupling makes the lanthanides different from d-block transition metals. 34,35 The compactness of the 4f orbitals makes the lanthanide reactions with minimal reliance on ligands and the ability to undergo rapid ligand exchange. 36,37 activations are hard to find in the literature.…”

“…More recently, lanthanide atoms in the ground electronic states have been used to activate C–C/C–H bonds of small hydrocarbons, and the activation reactions were characterized by ionization spectroscopy in the gas phase. − The presence of the 4f electrons and stronger spin–orbit coupling makes the lanthanides different from d-block transition metals. , The compactness of the 4f orbitals makes the lanthanide reactions with minimal reliance on ligands and the ability to undergo rapid ligand exchange. , Despite the recent advancement in the hydrocarbon activation by the ground-state lanthanide atoms and the unique feature of these heavy elements, reports on how their excited states would affect C–H/C bond activations are hard to find in the literature. In this work, we report the reactivity comparison of the initial and excited states of La and Ce atoms using 1-butyne (C 4 H 6 ) as a reaction substrate.…”