Neutron Diffraction Directly Locates an Interstitial Hydride in a Ni–Ag Superatomic Nanocluster

Abstract Interstitial hydrides can modulate the electronic and geometric structures of atomically precise metal nanoclusters (NCs). Direct crystallographic localization of hydrides in heavy-metal nanoclusters remains challenging by single-crystal X-ray diffraction (SCXRD). Here, dithiophosphate-to-diselenophosphate ligand exchange produced [Ni(H)Ag19{Se2P(OiPr)2}12] (1x) and [NiAg20{Se2P(OiPr)2}12] (2). The ligand exchange enabled the growth of high-quality single crystals suitable for neutron diffraction. The neutron structure of 1x (1o) directly locates the hydride in an interstitial μ4-NiAg3 cavity, providing the first direct neutron-crystallographic localization of a Ni–H motif in a superatomic nanocluster. The result supports the metallic-hydrogen description for a first-row-transition-metal-centered superatom. Comparison with the hydride-free analogue shows hydride-induced distortion and expansion of the Ag12 core together with changes in optical response. These findings provide an experimental structural benchmark for Ni-centered hydride superatoms and establish neutron diffraction as a direct probe of interstitial hydrogen in heavy-metal nanoclusters.