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

La15(FeC6)4F2 was grown as large crystals by reacting iron in a La/Ni eutectic flux in the presence of decafluorobiphenyl (C12F10) 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 P6̅ which features FeC6 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 La15(FeC6)4H, 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.