Flux Growth of an Intermetallic with Interstitial Fluorides via Decomposition of a Fluorocarbon.

La 15 (FeC 6 ) 4 F 2 was grown as large crystals by reacting iron in a La/Ni eutectic flux in the presence of decafluorobiphenyl (C 12 F 10 ) which acts as both a carbon and fluoride source. This mild fluorinating technique enables the isolation of an intermetallic product containing fluoride interstitials, as opposed to forming ionic metal fluorides. The compound adopts a structure in the hexagonal crystal system with space group P 6̅ which features FeC 6 units composed of a central iron atom coordinated by three ethylenide units in a trigonal planar configuration. The structure is related to the previously reported La 15 (FeC 6 ) 4 H, but with fluoride fully occupying the interstitial hydride positions, which induces partial occupancies and site splitting disorder in the adjacent layers of lanthanide ions. No supercell formation is observed.