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Pentalanthanum ethenide(4‐) digermanide(4‐), La 5 (C 2 )Ge 2
Author(s) -
Carrillo–Cabrera Wilder,
Čurda Jan,
Peters Karl,
Kohout Miroslav,
von Schnering Hans Georg
Publication year - 2004
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200400190
Subject(s) - octahedron , crystallography , crystal structure , metal , yield (engineering) , covalent bond , materials science , chemistry , trigonal crystal system , metallurgy , organic chemistry
La 5 (C 2 )Ge 2 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 of La 5 (C 2 )Ge 2 (space group Pbam , a = 8.873Å, b = 12.946Å, c = 4.273Å; Z = 2; R gt ( F ) = 0.069, R w ( F 2 ) = 0.147) is an arrangement of condensed La 9 3‐fold capped trigonal prisms and La 6 octahedra, centered by Ge atoms and C 2 dumbbells, respectively ( d (Ge‐La) = 3.173 ‐ 3.887Å; d (C‐La) = 2.42Å ( end‐on ) and 2.83Å ( side‐on ); d (C‐C) = 1.34Å). The structure differs from the La 2 SnS 5 structure with covalent S—S bonds only by the replacement of the Sn atoms by C 2 dumbbells: La 2 SnS 5 = S 5 (Sn)La 2 ≙ La 5 (C 2 )Ge 2 . The anionic chains of edge‐condensed octahedra ∞ 1 [SnS 4/2 S 2 ] 4‐ are replaced by ∞ 1 [(C 2 )La 4/2 La 2 ] chains, containing remarkable piles of alternating C 2 and La 2 pairs ( d (La‐La) = 3.438Å) with side‐on coordination along the c axis. The formal oxidation states La 3+ , Ge 4‐ , C 2 4‐ yield in an excess of three electrons per formula unit. The source of rest electron density of about 2.5 e·Å ‐3 is analyzed and discussed. The calculated band structure indicates metallic behavior.