New ternary and quaternary metal hydrides with K2PtCl6-type structures
摘要:
The ternary alkaline earth transition metal hydrides Ca2FeH6, Sr2FeH6, Eu2FeH6, Mg2RuH6, Mg2OsH6 and Ca2OsH6 were synthesized from metal mixtures at 450-500-degrees-C and 70-130 bar H-2 pressure. They crystallize with the f.c.c. K2PtCl6 structure type and contain octahedral [TH6]4- (T = Fe, Ru, Os) hydride complexes with bond distances [T-D] = 1.618(5) angstrom (Ca1.98Mg0.02FeD6), 1.673(4) angstrom (Mg2RuD6), 1.682(2) angstrom (Mg2OsD6) and 1.728(5) angstrom (Ca1.92Mg0.08OsD6) as refined from neutron powder diffraction of magnesium-containing deuterides. In systems containing two alkaline earth elements quaternary hydrides with primitive cubic structures are formed in which the alkaline earth atoms are ordered. Preliminary neutron data on iron-based CaMgFeD6 and nickel-based CaMgNiD4 confirm the presence of octahedral [FeD6]4- and tetrahedral [NiD4]4- complexes respectively.