Palladium-Tin Cations Enable the Formation of Palladium-Aryl Species

A silylpalladium cationic complex was recently developed by the Gagne Lab. The complex could cleave C(sp3)-O bonds however it was not stable to air. In this work, a [(XantPhos)Pd-SnBu3][BArF24] complex was synthesized and characterized. This Pd-Sn complex was found to be stable to air. The complex was unable to complete the C(sp3/sp2)-O bond cleavage, yet it was found that it reacts with conjugated and isolated dienes to form Pd-allyl species. Additionally, the addition of electron-deficient aryl halides to the Pd-Sn complex resulted in ligand substitution to form Pd-Aryl bonds. The reactant and product in these reactions have a Pd(II) oxidation state, indicating two possible mechanisms for this reactivity. One pathway is an oxidative addition/reductive elimination, with the other being sigma-bond metathesis. Crystal structures were acquired for some of these Pd-Aryl products. The silylpalladium cationic complex was also reacted with aryl halides to compare its reactivity with the Pd-Sn complex.