Anion binding properties of a hollow PdL-cage

Abstract

The hollow [PdL][BArF]2complex1of 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)2coordination environment (12A). These species bind further to the coordinating anions in the order Cl−> N3−> Br−> I−> AcO−withKa1 : 1≤ 414 M−1. With relatively non-coordinating anions1remains intact and displays 1 : 2 binding behaviour dominated by the 1 : 1 stoichiometry in the order NO3−(∼105M−1) » ClO4−and BF4−(∼103M−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.