Abstract: | Ba3Cu2Al2F16 is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P21 (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with Fo/σ(Fo) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated (AlF5)2]∞4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra AlF6], linked by two vertices and distanced by a. The second one, formulated Cu2AlF11]∞4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra CuF6], linked by edges, which form infinite chains interconnected by three vertices of isolated AlF6] octahedra. The stacking sequence of the sheets is (A, B, B)∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba3Cu2Al2F16 is closely related to that of Ba4Cu2Al3F21. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries. |