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 superatom 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 [PtHAg19(dtp/desp)(12)] (dtp = S2P((OPr)-Pr-n)(2), 1; dsep = Se2P((OPr)-Pr-i)(2), 2) describe a central platinum hydride (PtH) unit encapsulated within a distorted Ag-12 icosahedron, the resulting (PtH)@Ag-12 core being stabilized by an outer sphere made up of 7 capping silver atoms and 12 dichalcogenolates. Solid-state structures of 1 and 2 differ somewhat in the spatial configuration of their outer spheres, resulting in overall different symmetries, C-1 and C-3, respectively. Whereas the multi-NMR spectra of 2 in solution at 173 K reveal that the structure of C-3 symmetry is the predominant one, H-1 and Pt-195 NMR spectra of 1 at the same temperature disclose the presence of isomers of both C-1 and C-3 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-12](5+) kernel can be viewed as a closed-shell superatomic core, the mu(4)-hydride electron contributing to its eight-electron count. On the other hand, the 1s(H) orbital contributes only moderately to the superatomic orbitals, being mainly involved in the building of a Pt-H bonding electron pair with the 5d(z)(2)(Pt) orbital.

Automated summary

Recent research has found that the encapsulated hydride in hydride-doped noble metal nanoclusters is part of the superatom core, but its precise location has not been experimentally determined. In this study, the position of a four-coordinated hydride in a hydride-doped eight-electron platinum/silver alloy nanocluster was determined for the first time using neutron diffraction.