Addition of halogens and interhalogens on palladacyclopentadienyl complexes stabilized by pyridyl−thioether N−S spectator ligands

We have studied from the experimental and theoretical point of view the oxidative addition of halogens (I2 and Br2) and interhalogens (ICl and IBr) on palladiumcyclopentadienyl complexes bearing heteroditopic pyridyl−thioether spectator ligands. Addition of I2 or of a stoichiometric amount of Br2 to a CDCl3 solution of the starting palladacyclopentadienyl complexes yields the expected palladium−σ−butadienyl derivatives. The bromide derivative in the presence of a further excess of Br2 gives the wanted dibromo−(E, E)−σ−butadienyl and the pyridylthioether palladium(II) dibromide species. The rates of these reactions have been determined. When the interhalogens are used as oxidizing agents the thermodynamically hampered species is formed at first. Only in the case of the reaction of IBr is the formation of the energetically hampered derivative followed by partial isomerization to the most stable complex. The rate of isomerization and the related equilibrium constant between isomers have been measured. On the basis of the experimental evidence and the computational approach we have proposed a plausible energetic path yielding the first formed unexpected species. Finally, the solid state structures of two reaction products were resolved and reported.