Cu₂₈H₂₀: a peculiar chiral nanocluster with an exposed Cu atom and 13 surface hydrides

Reported herein is a racemate of a chiral nanocluster [Cu₂₈H₂₀(S₂P(OiPr)₂)₉]^-, which has a tetrahedral Cu₄ core embedded in a peculiar Cu₂₄ shell. The Cu₂₈H₂₀ framework conforms to idealized C₃ symmetry. The positions of the hydrides were determined by a combinatorial use of ²H NMR and SC-XRD, revealing four different coordination modes: face-capping μ₃-H, butterfly μ₄'-H, tetrahedral μ₄-H, and square-pyramidal μ₅-H. These coordination modes were authenticated by DFT calculations. Simple empirical rules were developed for assigning the H NMR spectra. One exposed Cu atom from the Cu₄ core and 13 exposed surface hydrides are easily accessible and thus may have catalytic functions.