Distortion, interaction, and conceptual DFT perspectives of MO4-alkene (M = Os, Re, Tc, Mn) cycloadditions.

TLDR: Distortion/interaction and absolutely localized energy decomposition analyses provide new insights into why the (3 + 2) pathway is highly preferred over the (2 + 1) pathway, the origin of rate enhancement from ligated base, and reactivity differences between OsO (4), ReO(4)(-), TcO(-), and MnO( 4)(-).

Abstract: The reaction pathways (including the transition states) of ethylene addition to osmium tetroxide (OsO4, and amine ligated), rhenate (ReO4−), technetate (TcO4−), and permanganate (MnO4−) have been studied by qualitative and quantitative analyses. Distortion/interaction and absolutely localized energy decomposition analyses provide new insights into why the (3 + 2) pathway is highly preferred over the (2 + 2) pathway, the origin of rate enhancement from ligated base, and reactivity differences between OsO4, ReO4−, TcO4−, and MnO4−. The (2 + 2) transition state has a much larger barrier than the (3 + 2) transition state because (1) the Os−O bond is stretched significantly resulting in a larger distortion energy (ΔEd⧧) value and (2) the transition state interaction energy (ΔEi⧧) is destabilizing due to large exchange repulsions overwhelming stabilizing charge-transfer terms. Base ligation lowers osmium tetroxide and ethylene distortion energies due to the ground-state O−Os−O angle being predistorted from 110°...