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Updated: Aug 19, 2025

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
Threshold photoelectron spectroscopy of trimethylborane and its pyrolysis products
Domenik Schleier1, Marius Gerlach1, Dorothee Schaffner1
1Institute for Physical and Theoretical Chemistry, University of Würzburg, 97074, Würzburg, Germany. ingo.fischer@uni-wuerzburg.de.
Abstract:
Trimethylborane (TMB) and its chemistry upon pyrolysis have been investigated by threshold photoelectron spectroscopy. TMB shows an unstructured spectrum and its adiabatic ionization energy (IEad) has been determined to be 9.93 ± 0.1 eV. Dissociative photoionization induces a methyl radical loss in TMB and the barrier to dissociation in the cation is measured to be 0.65 ± 0.1 eV. Upon pyrolysis methane loss dominates, leading to C2H5B, which can exist in five different isomeric structures. Quantum chemical calculations were used to investigate possible methane loss mechanisms as well as the isomerization pathways on the C2H5B potential energy surface. Through isomer-selective photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) the two isomers CH3BCH2 and CH3CHBH were identified by their ms-TPE spectra and IEad values of 8.55 ± 0.02 eV and 8.73 ± 0.02 eV were determined, respectively. A second channel leading to the loss of ethene from TMB forms CH2BH, which exhibits an IEad value of 9.37 ± 0.03 eV. The reaction mechanism in the literature needs to be expanded by an additional methane loss from the intermediately formed ethyl methyl borane.
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