LiSrGe2 and LiBaGe2: One-dimensional chains of (1)(infinity)[Ge-2](3-) in an unusual conformation

Abstract

Two new isostructural intermetallic germanides, LiSrGe2 and LiBaGe2, were synthesized as single crystals from constituent elements in molten Na. They both crystallize in the space group Pnma (no. 62) with a = 7.142(1), b = 4.459(1), c= 11.550(2)angstrom, Z= 4, and a = 7.381 (1), b = 4.617(1), c= 11.837(1)angstrom, Z= 4, for LiSrGe2 and LiBaGe2, respectively. They contain one-dimensional anionic germanide chains, (1)(infinity)[Ge-2](3-), running along the a-axis. The chains are in an unusual zigzag-like conformation, with weakly alternating Ge-Ge bond lengths of 2.475(1) and 2.498(1)angstrom, and 2.473(1) and 2.525(1)angstrom, for LiSrGe2 and LiBaGe2, respectively. Extended Huckel calculations suggest that LiSrGe2 is metallic: the Fermi level lies within bands having anti-bonding character. (C) 2008 Elsevier B.V. All rights reserved.