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 BH3NH3 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 K2PtCl6 structure (space group Fm3¯m, a=6.7681(3), Z=4). However, PtH62− octahedral complexes in Li2PtH6 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 Li2PtH6 reveals the Pt–H T1u stretch and bend at 1840 and 889 cm−1, respectively.