This paper describes the unique catalytic activity of bimetallic Au/Pd alloy nanoclusters (NCs) for Ullmann coupling of chloroarenes in aqueous media at low temperature. The corresponding reaction cannot be achieved by monometallic Au and Pd NCs as well as their physical mixtures. On the basis of quantum chemical calculation, it was found that the crucial step to govern the unusual catalytic activity of Au/Pd is the dissociative chemisorption of ArCl, which is unlikely in the monometallic Au and Pd NCs.

An increasing number of boron‐mediated reactions have become leading synthetic tools in organic chemistry. The transition‐metal‐catalyzed oxidative coupling reactions of aryl‐ and alkylboron compounds have been intensively studied over recent decades. Palladium‐based catalysts are often used in the presence of an appropriate oxidant, and the reaction mechanism has been fully elucidated. Efficient homocoupling reactions that are catalyzed by nanosized (<2 nm) gold particles were introduced in 2004, which allow the use of oxygen as a sustainable oxidant. Besides palladium and gold, other transition metals and bimetallic combinations can also serve as excellent catalysts. This review summarizes both the seminal early work and recent developments in the area of transition‐metal‐catalyzed oxidative homocoupling reactions of organoboron compounds and discusses the mechanistic details.

An efficient method for the Ullmann coupling of chloropyridines catalyzed by poly(N-vinylpyrrolidone) (PVP)-stabilized bimetallic Au-Pd alloy nanoclusters (NCs) under ambient conditions is demonstrated. The reaction does not occur with either gold or palladium single-metal clusters alone, nor with a physical mixture of the two metals. The experimental results indicate that the inclusion of Au as a nearest heteroatom is crucial to initiate the coupling and its composition up to 50% is essential to accelerate the reaction. Unlike the conventional transition metal catalysis, 2-chloropyridine was found to be highly reactive as compared to 2-bromopyridine. From the UV-vis and ICP-AES measurements, a significant amount of leached Pd(II) was observed in the coupling with 2-bromopyridine as compared with 2-chloropyridine, indicating that the leaching process might be a crucial factor in diminishing the reactivity.