Concerted Oxidative Addition of Diaryliodine(III) Reagents to a Pincer-Palladium(II) Substrate: A Computational Analysis

Density functional theory applied in a mechanistic study of the oxidation of pincer complex Pd^II(mer-NCN)(K¹-O₂CPh) (NCN = 2,6-(dimethylaminomethyl)phenyl-N,C,N) by diphenyliodine(III) triflate, in the presence of the widely used bicarbonate base as an additive/reagent in organic synthesis, indicates that concerted oxidative addition by Ph₂I(OCO₂H) is preferred over a Ph⁺ transfer mechanism to initially form octahedral PhPd^IV(mer-NCN)(K¹-O₂CPh){I(Ph)(···OCO₂H)-I}. Interaction of bicarbonate with the iodine center has little effect on the d_z² orbital interaction with the σ* I-Ph orbital required for the concerted transition state but does destabilize the Ph⁺ transfer mechanism, which requires a later transition state with a much weaker interaction with bicarbonate.