Discovery of a Neutral 40-Pd^II-Oxo Molecular Disk, [Pd₄₀O₂₄(OH)₁₆{(CH₃)₂AsO₂}₁₆]: Synthesis, Structural...

We report on the synthesis and structural characterization of a giant, discrete, and neutral molecular disk, [Pd₄₀O₂₄(OH)₁₆{(CH₃)₂AsO₂}₁₆] (Pd), comprising a 40-palladium-oxo core that is capped by 16 dimethylarsinate moieties, resulting in a palladium-oxo cluster (POC) with a diameter of ∼2 nm. Pd, which is the largest known neutral Pd-based oxo cluster, can be isolated either as a discrete species or constituting a 3D H-bonded organic-inorganic framework (HOIF) with a 12-tungstate Keggin ion, [SiW₁₂O₄₀]^4- or [GeW₁₂O₄₀]^4-. ¹H and ¹³C NMR as well as ¹H-DOSY NMR studies indicate that Pd is stable in aqueous solution, which is also confirmed by ESI-MS studies. Pd was also immobilized on a mesoporous support (SBA15) followed by the generation of size-controlled Pd nanoparticles (diameter ∼2-6 nm, as based on HR-TEM), leading to an effective heterogeneous hydrogenation catalyst for the transformation of various arenes to saturated carbocycles.