Vinyl Iodide Homocoupling Catalyzed by Platinum(II) Iodo Complexes: A DFT Study

The energy profile for vinyl iodide (RI) electrophile C(sp²)–C(sp²) homocoupling catalyzed by platinum(II) iodo complexes has been theoretically evaluated by the DFT method using the hybrid meta exchange-correlation functional M06 and the LANL2DZ basis set in the Gaussian09 software package. The reaction mechanism proposed earlier on the basis of experimental data was confirmed, consisting of the sequence of the following steps: R^I oxidative addition to Pt^II to form the intermediate compound RPt^IV— reduction of the latter by iodide ions into RPt^II—RI oxidative addition to form R₂Pt^IV—reductive elimination to yield the final butadiene-1,3. The highest activation barrier was found for the oxidative addition of the second vinyl iodide molecule, which is consistent with the experimental fact that the overall catalytic reaction rate is limited by just this step.