Anion/Naphthalenediimide Interactions in a Pd(II)-Based Tetrameric Metallocycle

A tetrameric metallocycle [Pd(dppp)(DPNDI)]₄·8TfO consisting of four dppp-capped Pd(II) corners (dppp = 1,3-bis(diphenylphosphonium)propane) and four linear π-acidic N,N′-di(4-pyridyl)-1,4,5,8-naphthalene diimine (DPNDI) ligands has been synthesized, and its single-crystal structure has been elucidated for the first time. The crystal structure of the metallocycle revealed anion-π, lone-pair-π, and CH···anion interactions between electron-deficient DPNDI ligands and TfO^- counterions and provided valuable insights into its anion recognition and metathesis capabilities. The ¹H, ¹⁹F, and ³¹P NMR studies demonstrated that in noncoordinating solvents, such as nitromethane and dichloromethane, the [Pd(dppp)(DPNDI)]₄ ⁸⁺ metallocycle underwent anion exchange in a single-crystal to single-crystal fashion without any structural changes. However, the metallocycle experienced slow dissociation in a polar solvent DMSO, which could be reversed easily by thermal treatment.