Li5OCl3 and Li3OCl: Two Remarkably Different Lithium Oxide Chlorides

Yellow to red, transparent single crystals of the lithium oxide chloride Li5OCl3 were obtained as main product from a solid-state reaction between Li3N and oxygen-contaminated lithium (covered by a Li[OH] crust) with YbCl3 and carbon in silica-jacketed, arc-welded niobium ampoules originally designed to yield Yb[CN2]. Li5OCl3 adopts the crystal structure of Cs3CoCl5 (= Cs3Cl[CoCl4]) according to Cl3Li[OLi4] with the tetragonal space group I4/mcm (no. 140) and the cell parameters a = 685.28(3) pm and c = 1093.23(5) pm for Z = 4. Hence, it contains isolated [OLi4]2+ tetrahedra in a LiCl matrix it thus can be compared with other alkali- and alkaline-earth metal oxide chlorides. Its unconventional color might be due to the fact that small parts of O2 are substituted with isoelectronic imide anions ([NH]2). Additionally cubic perovskite-type Li3OCl with corner-sharing [OLi6]4+ octahedra according to $\rm boolean AND{3}_{\infty}${[OLi6/2]Cl} could be obtained during attempts to synthesize Li5OCl3 from Li2O and LiCl as colorless powder and its lattice parameter for the space group Pm$\rm boolean AND{3}_{\infty}$m (no. 221) was determined to a = 390.70(4) pm (Z = 1) by means of X-ray powder diffraction.