Tetraplatinum cluster complexes bearing hydrophilic anchors as precursors for γ-Al2O3-supported platinum nanoparticles

Abstract

Tetraplatinum cluster complexes bearing hydrophilic anchors, [Pt₄(μ-OCOCH₃)₄(μ-OCOC₆H₄OH-4)₄] (2a), [Pt₄(μ-OCOCH₃)₄(μ-OCOC₆H₄B(OH)₂-4)₄] (2b), and [Pt₄(μ-OCOCH₃)₄(μ-OCOC₆H₄NH₂-4)₄] (2c), were successfully prepared by a selective substitution reaction of four in-plane acetates of [Pt₄(μ-OCOCH₃)₈] (1) with the corresponding p-substituted benzoic acids. Solid-state structure determination of 2a revealed the 3D network structure through intermolecular hydrogen bonding between the hydroxy group of the p-hydroxybenzoate ligand and the oxygen atom of the carboxylate ligand of 2a. UV-vis analysis of 2a–c in CH₃CN or CH₃CN–H₂O in the presence of γ-Al₂O₃ clearly indicated the adsorption efficiency of these platinum clusters on γ-Al₂O₃: 2a bearing a hydroxyl group and 2b bearing a B(OH)₂ group were effectively deposited onto γ-Al₂O₃ from CH₃CN solution, whereas less than 40% of 1 and 2c were chemically adsorbed onto γ-Al₂O₃. Highly dispersed and very small platinum nanoparticles (less than 1 nm) on γ-Al₂O₃ were obtained by thermal treatment of Pt₄-deposited γ-Al₂O₃ at 500 °C.