A Nanospheric Polyhydrido Copper Cluster of Elongated Triangular Orthobicupola Array: Liberation of H₂ from Solar Energy

An unprecedented air-stable, nanospheric polyhydrido copper cluster, [Cu₂₀H₁₁(S₂P­(OⁱPr)₂)₉] (1_H), which is the first example of an elongated triangular orthobicupola array of Cu atoms having C_3h symmetry, was synthesized and characterized. Its composition was primarily determined by electrospray ionization mass spectrometry, and it was fully characterized by ¹H, ²H, and ³¹P NMR spectroscopy and single-crystal X-ray diffraction (XRD). The structure of complex 1_H can be expressed in terms of a trigonal-bipyramidal [Cu₂H₅]^3– unit anchored within an elongated triangular orthobicupola containing 18 Cu atoms, which is further stabilized by 18 S atoms from nine dithiophosphate ligands and six capping hydrides. The positions of the 11 hydrides revealed by low temperature XRD were supported by a density functional theory investigation on the simplified model [Cu₂₀H₁₁(S₂PH₂)₉] with C_3h symmetry. 1_H is capable of releasing H₂ gas upon irradiation with sunlight, under mild thermal conditions (65 °C), or in the presence of acids at room temperature.