Anion binding properties of a hollow PdL-cage.

Abstract

The hollow [PdL][BArF]2 complex 1 of a tetra-pyridyl (py) ligand (L) has a [Pd(py)4]2+ coordination environment. Addition of coordinating anions resulted in the formation of a neutral species with Pd(py)2(anion)2 coordination environment (12A). These species bind further to the coordinating anions in the order Cl− > N3− > Br− > I− > AcO− with Ka1 : 1 ≤ 414 M−1. With relatively non-coordinating anions 1 remains intact and displays 1 : 2 binding behaviour dominated by the 1 : 1 stoichiometry in the order NO3− (∼105 M−1) » ClO4− and BF4− (∼103 M−1). As evidenced by crystal structure data, DFT calculations and {1H–19F}-HOESY NMR with BF4−, the anions are bound by charge assisted [C–H]+···anion interactions.