Unique stability of μ-hydroxo ligands in Pt(IV) complexes towards alkaline hydrolysis

Pt(IV)-nitrate solutions are widely used as precursors for mobile and stationary emission control catalysts for being chlorine-free but are unfit for the preparation of highly dispersed catalysts due to hydrolysis taking place after dilution and/or interaction with a basic carrier surface. The alkalization of the commercial Pt(IV)-nitrate solutions was found not to lead to light-yellow mononuclear [Pt(OH)6]2− solution because the bridged OH ligands stabilizing oligomeric Pt nitrate complexes are not cleaved even after refluxing with excess of alkali. The alkalization results in dilution-resistant polynuclear precursor solutions fit for highly dispersed Pt/Al2O3 catalyst preparation.