Mechanisms of ethyne oxidation catalyzed by LMnO₃ (L = O^-, Cl, NPH₃, CH₃, and Cp): a density functional theory study

The mechanisms of LMnO₃ (L = O^-, Cl, NPH₃, CH₃, and Cp)-catalyzed oxidation of ethyne has been studied on the singlet and triplet hypersurfaces at the M06/6-311G(d) level of theory. For the first step, the [3 + 2] pathways to the formation of the metalla-2,5-dioxol-3-ene intermediate are kinetically and thermodynamically the most favored pathways in all the complexes studied; it is favored over the [2 + 2] addition pathways to the metallaoxetene intermediate. The formation of the oxirene precursor that could give the oxirene the reported key intermediates in the ozonolysis of alkynes would most likely result from the oxidation of ethyne by MnO₃Cl on the triplet potential energy surface (PES). [3 + 2] versus [2 + 1] addition of MnO₃Cl with ethyne at the M06/6-311G(d) level of theory.