Raman spectroscopic studies on palladium and platinum hydrido complexes

Abstract

Fm3m) and K 3 PtH 5 (P 4/mbm), are presented and discussed with respect to the influence of the different strengths of Pt-H and Pd-H bonds and of the relative volume of the reduced (per formula unit) unit cells. The 'antisymmetric' MD (M = Pt; Pd) stretching mode (species B 1g of free, square MX 4 units) decreases from 1436 to 1291 cm −1 on going from K 2 PtD 4 to Rb 2 PdD 4 . Likewise, the PtH stretch of Na 2 PtH 4 at 2026 cm −1 decreases to 2001 cm −1 for K 2 PtH 4 but increases to 2039 cm −1 for K 3 PtH 5 . The totally symmetric MH stretches (A 1g ), which are of lower intensity, are shifted by about 50 cm −1 to higher wavenumbers compared with the asymmetric stretches. The results of a group theoretical treatment of the respective site group and unit-cell group modes are given.

Stabilization of Electron-Dense Palladium−Hydrido Complexes in Solid-State Hydrides

“…The INS spectrum shows that all deformations, except one at 1280 cm -1 , are accidentally degenerate at 820 cm -1 , which explains why only two peaks are observed in the IR spectra. The proposed assignment of the INS spectrum of K 2 PdH 4 is shown in Table , which also closely corresponds to recent Raman data on the structural analogue K 2 PtH 4 . The model used for describing the normal vibrations of the square-planar PdH 4 is shown in Figure , which corresponds exactly to the local environment around the complexes in the crystal.…”

“…Such a bonding with substantial covalent contribution between hydrogen and the counterions would also nicely explain the large influence upon the vibrational modes from the distance to the counterions observed for the octahedral complexes in the solid-state hydrides A 2 TMH 6 , where A = Mg, Ca, Sr, Ba and TM = Ru, Os . This sensitivity of the strength of the TM−H bonds toward intermolecular interaction was recently commented upon also for a series of hydrides based on platinum−hydrido complexes . The bonding can in a sense be compared with the conventional stabilization of electron-dense formal low oxidation states of the central atom by distributing electron density to suitable ligand orbitals.…”

Ternary Gold Hydrides: Routes to Stable and Potentially Superconducting Compounds

“…Pd 2– and Pt 2– are also iso-valence-electronic with Au – , and form linear PdH 2 2– and PtH 2 2– ions, readily stabilized in the solid state as persistent [A] 2 PdH 2 and [A] 2 PtH 2 salts (A = alkali metal). − Several of these molecular solids show a surprising metallicity, which has been explained as arising from alkali metal s-states crossing the Fermi level. − Pursued for possible hydrogen storage , and high temperature applications, their design and synthesis is an active field of research. , …”

Alkali Metal Cation Effects in Structuring Pt, Rh, and Au Surfaces through Cathodic Corrosion

“…The presence of these species would match the suggested simultaneous importance of the corroded metal, electrolyte cations, and adsorbed hydrogen. However, ternary metal hydrides are extremely sensitive to moisture and air, , which would make them highly unstable in our working electrolyte. Interestingly, this instability is consistent with current and previous experimental results.…”