La4[(C2)1−xGex]3, Lanthanum(III) Dicarbide(4-) Germanide(4-) Mixed Crystals: A Continuous Transition between the Cubic Structure Types cI40 (Rb4O6/Pu2C3) and cI28 (Th3P4)

✍ Scribed by Wilder Carrillo-Cabrera; Jan Curda; Karl Peters; Hans Georg von Schnering

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 406 KB
• Volume: 147
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8374

✦ Synopsis

La 4 (C 2 ) 2 Ge was obtained as a minor component from the reaction of the elements in corundum crucibles enclosed in stainless steel ampoules at 1360 K. The compound is gray with metallic luster. The crystal structure (space group I4 3d (No. 220); a ‫؍‬ 8.995(1) A s ; Z ‫؍‬ 4; R(F) ‫؍‬ 0.033, R w (F 2 ) ‫؍‬ 0.061 for 106 re-6ections (all data) with 2 max ‫؍‬ 503 measured on four-circle di4ractometer) may be described as a 3D framework of condensed La 8 dodecahedra (bisdisphenoids) centered by Ge atoms and C 2 dumbbells (d(C+C) ‫؍‬ 1.22 A s ). La 4 (C 2 ) 2 Ge and the previous reported cubic compounds La 2 C 3 H La 4 (C 2 ) 3 , 99La 5 C 1.5 Ge 3 :: HLa 4 (C 2 ) 0.60 Ge 2.40 , and La 4 Ge 3 demonstrate the existence of a large range of homogeneity La 4 [(C 2 ) 1؊x Ge x ] 3 between the yellow transparent ethenide (4-) La 2 C 3 and La 4 Ge 3 . In the series, the C 2 dumbbells are replaced by Ge atoms, corresponding with the formal charges C 4؊ 2 , Ge 4؊ , and La 3؉ . These mixed crystals (Pearson symbol cI28840) represent a continuous transition between the structure types cI40 (Rb 4 O 6 /Pu 2 C 3 ) and cI28 (Th 3 P 4 ). The results are discussed together with the general trends in the members of both structures types.