Discovery of neutral palladium-oxo clusters Pd16 and Pd24 and their supramolecular interactions.

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 [Pd 16 O 24 (OH) 8 ((CH 3 ) 2 As) 8 ] ( Pd 16 ) comprises a cyclic palladium-oxo unit capped by eight dimethylarsinate groups. The chloro-derivative [Pd 16 Na 2 O 26 (OH) 3 Cl 3 ((CH 3 ) 2 As) 8 ] ( Pd 16 Cl ) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24-palladium(II)-oxo cluster [Pd 24 O 44 (OH) 8 ((CH 3 ) 2 As) 16 ] ( Pd 24 ) can be considered as a bicapped derivative of Pd 16 with a tetra-palladium-oxo unit grafted on either side. The three compounds were fully characterized (i) in the solid state by single-crystal and powder XRD, IR, TGA, XPS, physisorption, and solid-state 1 H and 13 C NMR, (ii) in solution by 1 H and 13 C NMR and 1 H DOSY, and (iii) in the gas phase by electrospray ionization mass spectrometry (ESI-MS).