Poly‐Hydride [AuI7(PPh3)7H5](SbF6)2 cluster complex: Structure, Transformation, and Electrocatalytic CO2 Reduction Properties

Hydride AuI 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 [Au7 (PPh3 )7 H5 ](SbF6 )2 (abbrev. Au7 H52+ ), an Au cluster complex containing five hydride ligands, which decomposed to give [Au8 (PPh3 )7 ]2+ (abbrev. Au82+ ) upon exposure to light (300 to 450 nm). The valence state of AuI 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 (CO2 RR): Au7 H52+ exhibited 98.2 % selectivity for H2 , whereas Au82+ was selective for CO (73.5 %). Further DFT calculations showed that the H- ligand inhibited the CO2 RR process compared with the electron-donor H.