La6Br10Fe: a La6Fe octahedron with a mixed M6X12/M6X8 type environment

The title compound was synthesized from La, LaBr3, and Fe under Ar atmosphere at 800 degrees C. It crystallizes in space group P4(1) (No. 76) with lattice constants a = 8.255(1) A and c = 30.033(6) A. The structure features an isolated Fe-centered La 6 octahedron with all corners, 9 of its 12 edges, and 3 of its 8 triangular faces coordinated, bridged, or capped by Br atoms. The La6Fe octahedron is significantly distorted, and the La coordination by Br atoms deviates from the common close-packing arrangements found in other reduced rare earth metal halides. Band structure, bonding, and physical properties of the compound have been investigated.