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

Abstract

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.

Mechanistic insights into Ag+induced size-growth from [Au6(DPPP)4]2+to [Au7(DPPP)4]2+clusters

“…[26][27][28] Nevertheless, the reported mechanistic study mainly focus on the metal ion-induced alloying/assembly, while the mechanistic details on the ion "catalyzed" size conversion of nanoclusters (Ag + induced [Au 6 (dppp) 4 ] 2+ to [Au 7 (dppp) 4 ] 3+ and Cu 2+ induced Au 25 (PET) 18 → Au 44 (PET) 18 ) 18,23 have been largely unknown. Intrigued by the fantastic foreign metal effect [29][30][31] , we sought to perform a detailed mechanistic study on the Ag + induced reaction of [Au 6 (dppp) 4 ] 2+ → [Au 7 (dppp) 4 ] 3+ with density functional theory (DFT) calculations. According to Konishi's experiments, 18 [Au 6 (dppp) 4 ] 2+ transformed into [Au 7 (dppp) 4 ] 3+ within one minute after 5 molars equivalent AgBF 4 is added.…”

“…Intrigued by the fantastic foreign metal effect, [29][30][31] we sought to perform a detailed mechanistic study on the Ag + induced reaction of [Au 6 (dppp) 4 ] 2+ / [Au 7 (dppp) 4 ] 3+ with density functional theory (DFT) calculations. According to Konishi's experiments, 18 [Au 6 (dppp) 4 ] 2+ transformed into [Au 7 (dppp) 4 ] 3+ within one minute aer 5 molars equivalent AgBF 4 was added.…”

Incorporating Au11 nanoclusters on MoS2 nanosheet edges for promoting the hydrogen evolution reaction at the interface

“…The synthesis and characterization of atomically precise [Au 11 (PPh 3 ) 7 I 3 ] NCs and ultrathin MoS 2 nanosheets were followed from previous reports. 48,49 Preparation of 0.5%-Au 11 @MoS 2 nanocomposites 50 mg of MoS 2 nanosheets were dispersed in dichloromethane and sonicated for ∼ 30 min to obtain a well-dispersed suspension. Then, 0.5 mL of dichloromethane containing 1 mg of [Au 11 (PPh 3 ) 7 I 3 ] NCs was added dropwise to the suspension.…”

“…In this scenario, a recent study from our group has shown that impregnation of an [Au 11 (PPh 3 ) 7 I 3 ] NC on CeO 2 removed all the ligands leaving behind a bare Au 11 core on the oxide support. 48 This Au 11 @CeO 2 has high atom efficiency and has been demonstrated to be a catalyst that mimics the singleatom-catalyst-like behavior in facilitating Ullman-type C-C homocoupling reactions. So herein, we have employed Au 11 (PPh 3 ) 7 I 3 NCs as an HER catalyst by incorporating them onto MoS 2 nanosheets.…”

A Review of State of the Art in Phosphine Ligated Gold Clusters and Application in Catalysis

“…[ 387 ] Additionally, defects are found to be beneficial for trapping and encapsulating clusters. [ 200 ] The survival of unaggregated clusters on supports is critical for maintaining high catalytic activity as severe aggregation leads to decreased activity. Au 25 (PPh 3 ) 10 (SR) 5 Cl 2 encapsulated in microporous silica displays strong resistance against aggregation after calcination at 500 °C.…”