Water-Soluble Copper(I) Hydroxide Catalyst and Its Formation in Ligand-Free Suzuki-Miyaura Cross-Coupling Reactions

Copper has emerged as an alternative metal for metal-catalyzed cross-coupling reactions due to its low cost, readily availability, and low toxicity. This article reports a water-soluble active molecular catalyst and its formation in the ligand-free Suzuki-Miyaura (SM) cross-coupling reactions with copper iodide as the precatalyst in aqueous solutions. The SM coupling is homogeneous in nature, and the molecular catalyst is Cu(OH) in its singlet electronic state as identified by experimental and computational UV-vis absorption spectroscopy. The Cu(OH) catalyst is generated through the leaching of oval-shaped Cu2O nanoparticles, which are characterized with X-ray Auger electron spectroscopy, Xray absorption spectroscopy, and transmission electron microscopy. The soluble Cu(OH) species is stable for at least 4 weeks under ambient conditions.