Characterization, Reactivity, and Potential Catalytic Intermediacy of a Cyclometalated Tri-tert-butylphosphine Palladium Acetate Complex

Palladium acetate and tri-tert-butylphosphine react at room temperature via C–H activation of a tert-butyl group to form the novel palladium(II) complex [(PtBu3)Pd(CH2C(CH3)2PtBu2)(OAc)]. This cyclometalated complex can be reduced to Pd(PtBu3)2 by either heat or hydrogen, but is resistant to reduction by alkoxide bases and amines. As a result of the existence of this cyclometalated complex, the production of catalytically active palladium(0) species generated in situ from Pd(OAc)2 and tri-tert-butylphosphine is diminished, as evident by the catalytic inactivity of this complex. Additionally, datively bound tri-tert-butylphosphine is easily displaced by amines and less basic phosphines to form a series of novel cyclometalated palladium(II) complexes.