Synthesis and Crystal Structures of Cs2MgD4 and Cs3MgD5.

Abstract The title compounds were prepared by sintering stoichiometric mixtures of the binary deuterides in an autoclave under 65 bar pressure at 625 K. Neutron powder diffraction reveals a β-K 2 SO 4 type structure for Cs 2 MgD 4 (space group Pnma , a =8.5988(4), b =6.6234(3), c =11.5988(5) A) and a Cs 3 CoCl 5 type structure for Cs 3 MgD 5 (space group I 4/ mcm , a =8.4022(2), c =12.6951(4) A). In both deuterides magnesium is tetrahedrally coordinated by deuterium. The Mg–D bond distances (1.82–1.88 A in Cs 2 MgD 4 and 1.84 A in Cs 3 MgD 5 ) are longer by 0.02 A, on the average, than those in the corresponding rubidium analogues.