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La 6 (C 2 ) 3 Cl 4 und La 8 (C 2 ) 5 Cl 4 : Schichten und Kanäle aus La 6 (C 2 )‐Clustern

2007; Wiley; Volume: 633; Issue: 2 Linguagem: Inglês

10.1002/zaac.200600289

1521-3749

Hansjürgen Mattausch, Constantin Hoch, Chong Zheng, Arndt Simon,

Organometallic Complex Synthesis and Catalysis

Abstract La 6 (C 2 ) 3 Cl 4 and La 8 (C 2 ) 5 Cl 4 : Sheets and Channels of La 6 (C 2 )‐Clusters Single crystals of La 6 (C 2 ) 3 Cl 4 are formed from a mixture of LaCl 3 , La und C (2:7:9) at 1000 °C, those of La 8 (C 2 ) 5 Cl 4 at 975 °C (2:10:15). La 6 (C 2 ) 3 Cl 4 crystallizes in P 2 1 / c with a = 7.770(2) Å, b = 12.962(3) Å, c = 6.910(1) Å and β = 104.30(3)°, La 8 (C 2 ) 5 Cl 4 in C 2/ m with a = 22.570(4) Å, b = 3.9300(8) Å, c = 10.190(2) Å and β = 95.69(3)°. The structure of La 6 (C 2 ) 3 Cl 4 is composed of La octahedra centered by (C 2 ) groups, which are connected via common edges to form buckled sheets. These are coordinated by Cl atoms above and below the tetrahedra edges of close‐packed La atoms. This special arrangement leads to the composition La:Cl = 3:2 and to the corrugation of the layers. The structure of La 8 (C 2 ) 5 Cl 4 also contains sheets formed by (C 2 )‐centered La octahedra. These sheets are further connected by chains of La double octahedra to form tunnels, which contain the Cl atoms. Both compounds are metallic conductors, La 6 (C 2 ) 3 Cl 4 becomes superconducting at 2.5 K. Band structure calculations support the C‐C double bond assignment suggested by the C‐C distance according to ionic formulations as(La 3+ ) 6 (C 2 4− ) 3 (Cl − ) 4 2e − und (La 3+ ) 8 (C 2 4− ) 5 (Cl − ) 4 .