Solid-state structures of the covalent hydrides germane and stannane

The low-temperature crystal structures of perdeuterogermane (m.p. 108 K) and perdeuterostannane (m.p. 123 K) are reported. The structures have been characterized from low-temperature (5 K) high-resolution neutron powder diffraction experiments following sample preparation using in situ gas-condensation techniques. GeD4 crystallizes in an ortho-rhombic structure, space group P212121, with one molecule in the asymmetric unit, and with an average Ge - D bond length of 1.517 (3) Å. The SnD4 structure is monoclinic (space group C2/c), and the molecule is located on a twofold rotation axis with an average Sn - D bond length of 1.706 (3) Å. The crystal structures are discussed in relation to those of other tetrahedral molecules of group IV hydrides at low temperature, and evidence is presented that the crystal structure of silane, below 38 K, is isostructural with germane.