Hydride-Containing Eight-Electron Pt/Ag Superatoms: Structure, Bonding, and Multi-NMR Studies.

Recent reports on hydride-doped noble metal nanoclusters strongly suggest that the encapsulated hydride is a part of the core, but no accurate location of the hydride could be experimentally proved, so far. We report herein a hydride-doped eight-electron platinum/silver alloy nanocluster in which the position of four-coordinated hydride was determined by neutron diffraction for the first time. X-ray structures of [PtHAg(dtp/desp)] (dtp = SP(OPr), ; dsep = SeP(OPr), ) describe a central platinum hydride (PtH) unit encapsulated within a distorted Ag icosahedron, the resulting (PtH)@Ag core being stabilized by an outer sphere made up of 7 capping silver atoms and 12 dichalcogenolates. Solid-state structures of and differ somewhat in the spatial configuration of their outer spheres, resulting in overall different symmetries, and , respectively. Whereas the multi-NMR spectra of in solution at 173 K reveal that the structure of symmetry is the predominant one, H and Pt NMR spectra of at the same temperature disclose the presence of isomers of both and symmetry. DFT calculations found both isomers to be very close in energy, supporting the fact that they co-exist in solution. They also show that the [PtH@Ag] kernel can be viewed as a closed-shell core, the μ-hydride electron contributing to its eight-electron count. On the other hand, the 1s(H) orbital contributes only moderately to the orbitals, being mainly involved in the building of a Pt-H bonding electron pair with the 5(Pt) orbital.