A theoretical view on CrO2+-mediated C–H bond activation in ethane

• DFT study of the spin-forbidden reaction CrO2+ with C2H6.
• The reactions are “two-state reactivity” reactions, one crossing point is involved.
• The probability of surface hopping between the two PESs is calculated to be small.

The gas-phase reaction of C–H bond activation in ethane by CrO2+ has been investigated using density functional theory (DFT) at the UB3LYP/6-311G(2d,p) level. Our results reveal that the activation process is actually a spin-forbidden reaction. The involved crossing point between the doublet and quartet potential energy surfaces (PES) has been discussed by two well-known methods, i.e., intrinsic reaction coordinate (IRC) approach for crossing point (CP) and Harvey’s algorithm for minimum energy crossing point (MECP). The obtained single (P1ISC = 2.48 × 10−3) and double (P1ISC = 4.95 × 10−3) passes estimated at MECP show that the intersystem crossing (ISC) occurs with a little probability. The C–H bond activation processes should proceed to be endothermic by 73.16 kJ/mol on the doublet surface without any spin change.

On the basis of Hammond postulate, this is a typical ‘two-state reactivity’ (TSR) reaction. The crossing point CP is located at s = 1.60 with the electron configuration being 2–4A. For comparison purposes, we have also used the algorithm proposed by Harvey et al. to characterize the MECP (2–4A). Total energy values of the CP and MECP are −1274.53871 and −1274.56226 a.u. at the UB3LYP/6-311G(2d,p) level, respectively. Namely, the energy of MECP is lower by 61.81 kJ/mol than CP′s.Figure optionsDownload as PowerPoint slide