Synthesis, structure and computational studies of a cationic T-shaped Pd-complex

Reaction of [(cod)Pd(Me)(thf)][SbF₆] or [(cod)Pd(Me)(MeCN)][B(Ar_F)₄] (cod = 1,5-cyclooctadiene, B(Ar_F)₄ = [3,5-(F₃C)₂C₆H₃]₄B) with one or two equivalents of tBu₃P gives [(tBu₃P)₂Pd(Me)]⁺ (3) exclusively. The two sterically encumbered tBu-groups prevent solvent coordination. In addition, this formally three coordinate complex is stabilized by a γ-agostic interaction in solid state, whereas solution NMR studies confirm that this interaction is rather weak. The strength of the γ-agostic interaction was evaluated using density functional theory (DFT) calculations. Surprisingly, [(tBu₃P)₂Pd(Me)]⁺ is unreactive toward CO, H₂, C₂H₄ and norbornene.