Reactions of TiCl4 and ZrCl4 with IOCN

On Hexagonal Perovskites with Cationic Vacancies. V. Structure Determination on H? Ba₂Lu_2/3 □ _1/3WO₆ — a Novel Rhombohedral Stacking Polytype with 18 Layers Compounds of type Ba₂B□_1/3W^VIO₆ with B^III ? Gd—Lu, Y are polymorphic They crystallize in a cubic 1:1 ordered perovskite structure and in a new rhombohedral perovskite stacking polytype of 18 L respectively. By intensity calculations out of the three possible stacking sequences (4)(2), (5)(1) and (3)1(1)1 (all space group R3 m) the sequence (5)(1) can be selected. For H? Ba₂Lu_2/3□_1/3WO₆ the refined R′ factor is 14.1%. The structure contains groups of three octahedra connected with another by common faces which are linked with each other by three corner sharing octahedra. In the block of three face sharing octahedra the central octahedral lattice site is vacant, the two outer positions are occupied by tungsten atoms. According to this distribution a direct contact of occupied face sharing octahedra is absent.