Discovery of a Neutral 40-Pd II -Oxo Molecular Disk, [Pd 40 O 24 (OH) 16 {(CH 3 ) 2 AsO 2 } 16 ]: Synthesis, Structural Characterization, and Catalytic Studies
Résumé
We report on the synthesis and structural characterization of the giant discrete and neutral molecular disk, [Pd40O24(OH)16{(CH3)2AsO2}16] (Pd40), 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. Pd40, which is the largest 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] 4or [GeW12O40] 4-. 1 H and 13 C NMR as well as 1H-DOSY NMR studies indicate that Pd40 is stable in aqueous solution, which is also confirmed by ESI-MS studies. Pd40 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.
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