Binuclear gold phosphine complexes as single-source precursors for CO oxidation catalysts: insights into the formation of surface-stabilized Au particles

We herein present a systematic study on the application of atomically precise binuclear gold phosphine complexes as precursors for supported Au catalysts tested in CO oxidation. Utilizing a plethora of complementary analytical techniques, such as powder X-ray diffraction, transmission electron microscopy imaging, in situ and operando X-ray absorption spectroscopy as well as diffuse reflectance infrared Fourier transformed spectroscopy, we found that minor changes in the ligand arrangement of molecular Au phosphine complexes as precursors result in significantly different activation behaviors of alumina supported Au catalysts under reaction conditions. Specifically, the use of two POP-based ligands within the molecular Au precursor [Au2(µ2-POP)2]OTf2 (POP = tetraphenylphosphoxane) creates a P-containing binding pocket, which not only enhances the thermal stability of the Au particles but also affects their electronic properties. Conversely, employing a supported dppe-based gold complex [Au2(µ2-dppe)2]OTf2 (dppe = diphenylphosphinoethane) decreases the CO oxidation activity, due to the blockage of active sites. This work provides detailed insights into the ligand decomposition of molecular gold phosphine complexes under reaction conditions and paves the way for the targeted use of molecular transition metal complexes as precursors in synthesizing surface-stabilized nanoparticles.