DEHYDROGENATION AND C-H BOND INSERTION OF PROPENE: La($\eta^2$-C$_3$H$_4$) AND HLa($\eta^3$-C$_3$H$_5$)

Abstract

Dehydrogenation and C-H bond insertion are observed in the reaction of laser-ablated La atoms with propene (C$_3$H$_6$) in a pulsed molecular beam source. Several dehydrogenated and inserted products are identified by the time-of-flight mass spectrometry. La(C$_3$H$_4$) formed from H$_2$ elimination and HLa(C$_3$H$_5$) formed by C-H bond insertion are characterized by pulsed-field-ionization electron and ion spectroscopy, in combination with density functional theory. Two isomers of La(C$_3$H$_4$) are identified from 1,2- and 1,3-dehydrogenation. The adiabatic ionization energies of 1,2- and 1,3-dehydrogenated isomers are measured to be 40506(5) and 40941(5) cm$^{-1}$, respectively. For the inserted product HLa(C$_3$H$_5$), La atom is bound to the allyl radical in a three-fold binding mode ($\eta^3$). It is observed that the ionization energy of the HLa($\eta^3$-C$_3$H$_5$) insertion complex (41130(5) cm$^{-1}$) is close to that of the 1,3-dehydrogented La($\eta^2$-C$_3$H$_4$) species.