Cu 28 H 20 : a peculiar chiral nanocluster with an exposed Cu atom and 13 surface hydrides.

Reported herein is a racemate of a chiral nanocluster [Cu 28 H 20 (S 2 P(OiPr) 2 ) 9 ] - , which has a tetrahedral Cu 4 core embedded in a peculiar Cu 24 shell. The Cu 28 H 20 framework conforms to idealized C 3 symmetry. The positions of the hydrides were determined by a combinatorial use of 2 H NMR and SC-XRD, revealing four different coordination modes: face-capping μ 3 -H, butterfly μ 4 '-H, tetrahedral μ 4 -H, and square-pyramidal μ 5 -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 Cu 4 core and 13 exposed surface hydrides are easily accessible and thus may have catalytic functions.