Modulated Lanthanum Chains in the Crystal Structure of La3.65[Ru(C2)3

Abstract

AbstractLanthanum ruthenium carbide La3.65[Ru(C2)3] crystallizes hexagonal (P63/m) with a = 887.9(2) pm and c = 1606.8(6) pm, V = 1096.8(4)·106 nm3, and Z = 6. The crystal structure contains trigonal‐planar Ru(C2)3 groups and lanthanum atoms, which form a partial structure of the chemical composition La3Ru(C2)3. Additional lanthanum atoms occupy hexagonal channels built by those carbon atoms of the C2 ligands, which are non‐bonded to the central ruthenium atoms. The distribution of these lanthanum atoms along the c axis results in a threefold superstructure, which was refined as a commensurate modulated structure (P63/m (00g)s0, q = (0, 0, {}^1/{}_3)). Harmonic occupational and displacive modulation functions were used for the structure refinement. The structure converged to R1 = 4.9 % for all data (R1 = 2.6 % for the main reflections, R1 = 11.1 % for the 1st order satellite reflections). A small homogeneity range for this phase is predicted by total energy calculations using the PAW‐GGA method (VASP). Chemical bonding analysis reveals that the C2 pairs are best described as acetylide C22– units.