Permethylated Cyclodextrins with Thiol Groups as Stabilizing Agents for Catalytic Water-Soluble Platinum Nanoparticles

In this study, water-soluble colloidal platinum nanoparticles (Pt NPs) have been stabilized with novel thiolated cyclodextrins (CD-SH) and their catalytic performance has been investigated. We varied the size of the CD cycle (α-CD/β-CD), the degree of thiolation (one or two thiol groups per CD), and the CD/Pt molar ratio (0.5; 0.2; 0.1; 0.05) to find the best performing water-soluble, air-stable hydrogenation catalyst. An organometallic approach for the Pt NP synthesis resulted in the formation of small well-dispersed NPs of 1–2 nm in size, as shown by TEM. XPS analysis confirmed the formation of a Pt−S interaction, rationalizing the strong NP stabilization by a small quantity of CD-SH, while preserving the NP catalytic properties. Only 0.1 equivalent of CD-SH was enough to obtain a promising hydrogenation activity with preserved stability of the colloidal dispersion. Performing catalysis in biphasic conditions allowed simple separation of the products and reuse of the catalyst five times without deactivation.