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((OPr)-Pr-i)(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 H-1, H-2, and P-31 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 H-2 gas upon irradiation with sunlight, under mild thermal conditions (65 degrees C), or in the presence of acids at room temperature.