DFT-studies of cis- and trans-[Rh(CO)₂X₂]⁺ (X = PH₃, PF₃, PC1₃, PBr₃ PI₃ or P(CH₃)₃) and oxidative addition of CH₃I to them

We have performed B3LYB density functional calculations for oxidative addition of CH₃I to [Rh(CO)₂X₂]⁺ (X = PH₃, PF₃, PCl₃, PBr₃, PI₃ or P(CH₃)₃). This species is similar to the catalyst used in industrially important Monsanto process. Our goal is to see if the catalytic process could be enhanced by modifying the ligands. We have taken a set of phophine ligands and calculated the oxidative addition of methyl iodide to both the cis - and trans-forms of the modified catalysts. In our calculations, we found concerted mechanisms for the oxidative additions studied. Our results show that the activation parameters of the oxidative additions have a clear correlation to the ligand type and ligand size. With PCl₃ and PBr₃, our results show lower activation parameters than for the experimentally observed cis-[Rh(CO)₂I₂]^-.