Poly-Hydride [Au-7(I)(PPh3)(7)H-5](SbF6)(2) cluster complex: Structure, Transformation, and Electrocatalytic CO2 Reduction Properties

Hydride Au-I bonds are labile due to the mismatch in electric potential of an oxidizing metal and reducing ligand, and therefore the structure and structure-activity relationships of nanoclusters that contain them are seldom studied. Herein, we report the synthesis and characterization of [Au-7(PPh3)(7)H-5](SbF6)(2) (abbrev. Au7H52+), an Au cluster complex containing five hydride ligands, which decomposed to give [Au-8(PPh3)(7)](2+) (abbrev. Au-8(2+)) upon exposure to light (300 to 450 nm). The valence state of Au-I and H- was verified by density functional theory (DFT) calculations, NMR, UV/Vis and XPS. The two nanoclusters behaved differently in the electrocatalytic CO2 reduction reaction (CO2RR): Au7H52+ exhibited 98.2 % selectivity for H-2, whereas Au-8(2+) was selective for CO (73.5 %). Further DFT calculations showed that the H- ligand inhibited the CO2RR process compared with the electron-donor H.