Locating Interstitial Hydrides in MH₂@Cu₁₄ (M = Cu, Ag) Clusters by Single-Crystal X-ray Diffraction

Area of Science:

• Inorganic Chemistry
• Crystallography
• Materials Science

Background:

• Metal-organic frameworks and clusters are crucial in catalysis and materials science.
• Accurate structural determination of interstitial atoms, like hydrogen, presents significant challenges.
• Understanding metal-hydride interactions is key to designing new functional materials.

Purpose of the Study:

• To synthesize and characterize novel copper and silver-copper metal cage compounds.
• To accurately determine the positions of interstitial hydride atoms within these structures.
• To investigate the challenges and considerations for anisotropic refinement of hydride atoms in X-ray crystallography.

Main Methods:

• Single-crystal X-ray crystallography was employed for structural determination.
• High-quality single crystals of two new compounds, [Cu15H2(S2CNBu2)6(C≡CPh)6][CuCl2] and [AgH2Cu14{S2P(OPr)2}6(C≡CPh)6][PF6], were obtained.
• Anisotropic displacement parameters (ADPs) were refined for the interstitial hydride atoms.

Main Results:

• The precise locations of interstitial hydrides within the metal cages were successfully determined.
• Anisotropic refinement of hydride atoms was achieved, providing detailed information on their thermal motion.
• Structural analysis revealed insights into metal-metal distances and cage geometries in MH2@Cu14 compounds (M = Cu, Ag, Pd).

Conclusions:

• The study demonstrates the feasibility of accurately locating and refining interstitial hydrides using X-ray crystallography.
• Successful anisotropic refinement of hydride atoms provides valuable data for understanding metal-hydride bonding and cage dynamics.
• This work highlights critical aspects and challenges in X-ray data collection and analysis for hydrogen atoms in complex inorganic structures.