Synthesis of Li₂PtH₆ using high pressure: Completion of the homologous series A₂PtH₆ (A=alkali metal)

Li₂PtH₆, the missing member of the complex transition metal hydride series A₂PtH₆ (A=alkali metal), was prepared by reacting mixtures of LiH and Pt in the presence of BH ₃NH₃ as hydrogen source at pressures above 8 GPa. According to powder X-ray diffraction analysis, Li₂PtH₆ is isostructural to its heavier homologues and crystallizes in the cubic K ₂PtCl₆ structure (space group Fm3̄m, a=6.7681(3), Z=4). However, PtH₆^2- octahedral complexes in Li ₂PtH₆ approach each other closely and its structure may likewise be regarded as a defective perovskite structure where half of the octahedrally coordinated atoms (cations) are missing. The IR spectrum of Li ₂PtH₆ reveals the PtH T_1u stretch and bend at 1840 and 889 cm^-1, respectively.