Discovery and Supramolecular Interactions of Neutral Palladium‐Oxo Clusters Pd 16 and Pd 24

We report on the synthesis, structure, and physicochemical characterization of the first three examples of neutral palladium‐oxo clusters (POCs). The 16‐palladium(II)‐oxo cluster [Pd16O24(OH)8((CH3)2As)8] (Pd16) comprises a cyclic palladium‐oxo unit capped by eight dimethylarsinate groups. The chloro‐derivative [Pd16Na2O26(OH)3 Cl3 ((CH3)2 As)8] (Pd16Cl) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24‐palladium(II)‐oxo cluster [Pd24O44(OH)8((CH3)2As)16] (Pd24) can be considered as a bicapped derivative of Pd16 with a tetra‐palladium‐oxo unit grafted on either side. The three compounds were fully characterized 1) in the solid state by single‐crystal and powder XRD, IR, TGA, and solid‐state 1H and 13C NMR spectroscopy, 2) in solution by 1H, 13C NMR and 1H DOSY spectroscopic methods, and 3) in the gas phase by electrospray ionization mass spectrometry (ESI‐MS).
The first three examples of neutral palladium‐oxo clusters (POCs), Pd16, Pd16Cl, and Pd24, were prepared by simple open‐pot, room‐temperature reactions of palladium(II) salts in sodium dimethylarsinate aqueous solutions. The dimethylarsinate capping groups act as bidentate, monoanionic ligands for the various palladium‐oxo cores. The three POCs were fully characterized in the solid, solution, and gaseous states by a multitude of physicochemical techniques.