Di-palladium Complexes with Urea-containing Ligands as Anion Receptors

A series of di-palladium complexes with thiolato ligands containing urea groups for hydrogen bonding have been prepared. Three of these complexes have been structurally characterised by X-ray crystallography showing some interesting supramolecular interactions between the metal complexes and counter-anions. ³¹P NMR solution studies have been carried out to gain some insight into the different conformations of the complexes in solution. To support the experimental findings, computational studies have been performed demonstrating the preference for one of the two conformers in the presence of the appropriate solvent and anion. The anion-binding properties of two of these metallo-receptors have been studied by ¹H NMR spectroscopy. Binding constants (in DMSO) between the receptors and specific anions (e.g., [H₂PO₄]^– ) are in the order of 10e³.