Nanosized Bispyrazole-Based Cryptand-Stabilized Palladium(0) Nanoparticles: A Reusable Heterogeneous Catalyst for the Suzuki-Miyaura Coupling Reaction in Water.

A macrobicyclic cryptand with a long rigid cavity incorporating a chelating bispyrazole moiety in each of the three bridges was synthesized. The multiple chelating metal binding sites were utilized for the controlled synthesis and stabilization of ultrafine palladium nanoparticles (Pd NPs) of nearly ∼2 nm size. The as-synthesized Pd NPs were characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The well-dispersed cryptand-stabilized nanoparticles are found to catalyze the C-C bond-forming Suzuki-Miyaura reaction heterogeneously using water as a green solvent.