Defects Engineering on Ceria and C-C Coupling Reactions Using [Au11(PPh3)7I3] Nanocluster: A Combined Experimental and Theoretical Study.

Ligand protected atom-precise gold-based catalysts have been utilized in many essential chemical processes, but their mechanism and the fate of the catalyst during reaction are still unrevealed. Atom-precise cluster without ligands are thus highly desirable to maximize atom efficiency, but making these in solution phase is challenging. In this scenario, catalysts with dispersion on oxide support are highly desirable to understand the role of metal core during catalytic reaction. Here, we report the synthesis of Au11(PPh3)7I3 cluster that consists of an incomplete icosahedron core. During its impregnation process on CeO2 support, all of the ligands were removed from the kernel and the Au11 kernel fits into the defects of ceria (embedded onto the oxygen vacancy of ceria (111) plane). This Au11@CeO2 has high atom efficiency and catalytic activity for Ullmann-type C-C homocoupling reactions for electron rich substrates. Density functional theory calculations showed that hexagonal arrangements of Au11 kernel on (111) plane of CeO2 is the most stable one. Theoretical calculations also proved that the atop gold atom has more favorable interaction with phenyl iodide than the second layer gold atoms of the Au11@CeO2. This demonstrated that the present catalyst mimics the single-atom catalyst-like behavior in facilitating the coupling reactions.