The Phosphate-Bridged Pentapalladium(II)-Containing 18-Tungsto-4-Phosphate [Pd ₅ O ₂ (HPO ₄ ) ₂ (PW ₉ O ₃₄ ) ₂ ] ^16– : Synthesis and Physicochemical Properties

High Resolution Image Download MS PowerPoint Slide The pentapalladium(II)-containing 18-tungsto-4-phosphate [Pd 5 O 2 (HPO 4 ) 2 (PW 9 O 34 ) 2 ] 16– ( Pd 5 ) has been synthesized in a simple one-pot procedure reacting Pd 2+ ions with the trilacunary precursor [ A -α-PW 9 O 34 ] 9– at room temperature in aqueous dimethylarsinate buffer with some free phosphate ions. The polyanion Pd 5 comprises a [Pd 5 O 2 (HPO 4 ) 2 ] 2+ assembly sandwiched between two [ A -α-PW 9 O 34 ] 9– units, and it was isolated as a hydrated sodium salt, Na 16 [Pd 5 O 2 (HPO 4 ) 2 (PW 9 O 34 ) 2 ]·25H 2 O ( Na-Pd 5 ), which was characterized in the solid state by single-crystal XRD, FT-IR, TGA, and elemental analysis. In solution, Na-Pd 5 was characterized by 31 P NMR, ESI-MS, UV–vis, and small- and wide-angle X-ray scattering (SWAXS). Furthermore, Na-Pd 5 was employed as a precatalyst immobilized on SBA-15-apts for the hydrogenation of o -xylene, which showed excellent activity and recyclability.