The effects of substituents on the reductive elimination of difluoromethylated hydrazones from small bite-angle PdII molecular catalyst: A DFT study

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We report herein computational insights concerning the electronic effects of the substituents on the reductive elimination of difluoroalkylated hydrazones from a small bite-angle PdII molecular catalyst. The DFT results revealed that hydrazones with substituted electron-withdrawing (EW) groups (e.g. p-NO2) can notably exhibit a depreciation in the activation energy barrier (ΔG‡). According to the DFT-calculated ΔG‡, the Hammett analysis revealed an excellent correlation (R2 = 0.98) with a reaction constant (ρ) of + 2.34 indicative of an enhanced accumulation of negative charge density at the transition state (TS). Natural bond orbital (NBO) charge analysis of the corresponding TS suggests distinguishable nucleophilic and electrophilic characteristics for selected atoms at the reaction center. Hence, the NBO analysis revealed an electronic transition of the type lp(C1) → σ*(PdII-C2) for EW = NO2 with stabilizing energy E(2) of 143 kcal/mol indicative of more stabilized TS that is well in line with the ΔG‡ and NBO analyses.