High-pressure synthesis and crystal structure of Sr2MgH6

Sr2MgH6 has been prepared by subjecting binary SrH2 and MgH2 in a 2:1 molar ratio by solid state reaction at T=870 K under quasi-hydrostatic pressure of 35 kbar during 200 minutes, and investigated by neutron powder diffracti on on its deuteride. It crystallises with the K2GeF6-type structure (space group P (3) over bar m 1, Z=1; cell parameters at 293 K for the hydride a=5 .5610(6), c=4.1708(5) Angstrom, V=111.7 Angstrom(3), and the deuteride a=5. 5458(2), c=4.1630(2) Angstrom, V=110.9 Angstrom(3)). Magnesium has a nearly octahedral deuterium coordination with bond distances Mg-D=2.03 Angstrom, and strontium a twinned cuboctahedral deuterium coordination with bond dist ances in the range Sr-D=2.50-2.78 Angstrom. It decomposes at about 650 K an d 5 bar deuterium pressure into SrD2 and Mg. (C) 1999 Elsevier Science S.A. All rights reserved.