Studio teorico dell'attivazione dei legami C-H e C-C mediante cationi di attinidi in fase gassosa

Abstract

Density functional theory calculations were performed to study the ability of thorium (Th+, Th2+) and uranium (U+, U2+ The potential energy surfaces were explored taking into consideration different spin states. A close description of the reaction pathways leading to different reaction products is presented, and the obtained results are compared with experimental data. ) cations to activate the C-H and C-C bonds of methane, ethane and propane in the gas-phase. Th+ activates the C-H bonds of methane and ethane, in contrast, U+ is inert in both reactions. Th2+ reacts with all three alkanes, whereas U2+ reacts with C2H6 and C3H8, with product distributions different than those of Th2+ The computed potential energy profiles, which all proceed by insertion, were used to evaluate the relationship between the energetics of the bare Th . + (2+) and U+ (2+) ions and the energies for C-H and C-C bond activation. It was found that the computed energetics for insertion are entirely consistent with the empirical model which relates insertion efficiency to the energy needed to promote the An+ (2+) ion from its ground state to a prepared divalent state with two non 5f valence electrons suitable for bond formation in {C-An+ (2+)-H} and {C-An+ (2+)-C} activated intermediates.