Preparation and crystal structure of the Isotypic Carbides Ln 4 Ni 2 C 5 (Ln = Er, Tm, Yb and Lu)

The title compounds were prepared from the elemental components in a lithium flux. Their crystal structure was determined for the ytterbium compound from single‐crystal X‐ray data. It is orthorhombic, Pmm2, a = 352.88(6) pm, b = 1 143.0(3) pm, c = 366.16(6) pm, Z = 1, R = 0.020 for 1 261 structure factors and 29 variable parameters. The structure may be viewed as an intergrowth of slabs consisting of the CeNiC 2 and the ScC (NaCl type) structures. It thus contains C 2 pairs with a CC distance of 138(1) pm and isolated carbon atoms. Together with the nickel atoms the C 2 pairs form one‐dimensionally infinite building elements [Ni 2 C 4 ] n . The fifth carbon atom is octahedrally coordinated by ytterbium atoms. Accordingly the compound may be rationalized to a first approximation with the formula (Yb 3+ ) 4 [Ni 2 C 4 8− ]C 4− . Yb 4 Ni 2 C 5 shows Curie‐Weiss behaviour with a magnetic moment of μ exp = 4.44 μ B per ytterbium atom in good agreement with the theoretical moment of μ eff = 4.53 μ B for Yb 3+ .