Pd/Cu₂O/CuO as Active Sites on the Cyclometalated Pd(II)/Cu(II) Nanosheet: Active Centre Formation, Synergistic and Catalytic Mechanism

Abstract

A key to understand relationships between structure and activity is help for rational designing high active catalytic films. In this research, a new bi‐cyclometallic ferrocene imine Pd(II)/Cu(II) catalytic monolayer supported on graphene oxide (GO@Fcl−Pd/Cu) was fabricated, which exhibited a higher activity (TOF=1.48×106 h−1) in Suzuki coupling reaction. Enhanced higher activity was related to the in situ formed Pd/ Cu2O (CuO) active centre on the surface during catalysis. Fe in ferrocene had the redox ability for making Pd0 more stability, meaning that Fe3+ was electron withdraw or donor during catalytic process, which could tune the electronic properties of the Pd and Cu in one complex and improve their electronic transferring to boost the activity. CuO/Cu2O could make Pd0 more negative and stability. Ensemble synergistic effect, including the metals, metal oxide, ligand and GO could be described as that the electron transferred from GO via ferrocene to Pd or via Cu(II) to Pd made more negative, improving the oxidative addition. Meanwhile, aryl boronic acid adsorbed on the vicinal Cu(II), Cu2O and CuO around Pd0 synergetic reaction easily with the Pd intermediate to form next intermediate.

Pd/Co3O4–Pd/PdO formed in situ on the surface of the self-assembly ferrocenylimine Pd(ii)/Co(ii) monolayer for catalyzing the Suzuki cross-coupling reaction—formation, synergistic effect, and catalytic mechanism

“…In the case of the spin-coated film mobilized on the surface of the silicon wafer ( Si/APTES-Fcl-Pd 0.1 Co 0.9 ) (entry 9), a lower yield was obtained due to the irregular orientation of the catalyst molecular in the film, which could improve the effective collision between substrates and active sites to enhance the activity. 57–79 When the catalyst was linked on the surface of the silicon wafer by self-assembly ( Si@APTES-Fcl-Pd 0.1 Co 0.9 ), the catalytic activity was relatively lower than that of GO@APTES-Fcl-Pd 0.1 Co 0.9 (entry 7), reflecting the excellent function of GO. The results above suggested the effects of orientation, preparation method, and a proper ligand and support for the catalytic activity.…”

“…In situ ReactIR has been widely used because of its efficient and convenient detection means to accurately monitor the catalytic process. 64,70,74,78 GO@APTES-Fcl-Pd 0.1 Co 0.9 and (PhCN) 2 PdCl 2 /CoCl 2 ·6H 2 O were used to catalyze the reaction, and the monitored 3D spectrum showed a great difference for the two catalytic processes (Fig. S14a and b, ESI†).…”

“…103 We speculated that the real multi-active centers contained Pd, Pd/PdO, and Pd/Co 3 O 4 . 31,64,70,74,78,100–105…”

“…57–62 Previous studies on ligands, the molecular structure of the surface, metal combination, and carrier with the synergy between metals to develop the higher active catalysts have been our effort directions. 14,60–79…”

Fabrication and Catalytic Property of an Ordered Terpyridine Pd(II)/Ni(II) Catalytic Monolayer for Suzuki Coupling Reactions

“…Bi-organometallic catalytic monolayer exhibits higher activity than the mono-organometallic catalytic monolayer because of the synergistic effect existing on the catalytic surface, such as the electron distribution of active species. Moreover, active metals or nonactive metals in active sites simultaneously joined in the catalytic process, as described in Scheme 3 [63][64][65][66]. The results indicated that the morphology, catalyst orientation, ligand design, support selection, the rational combination of different metals, and the ratio of multi-metals were crucial factors for achieving a highly active and stable catalyst.…”