Two-dimensional composition diagram of the Al(OH)3-dien-HFaq.-ethanol system: Evidence of a new tetrahedral (Al4F18)6− polyanion

Six domains appear in the 2D composition diagram of the Al(OH)3-dien-HFaq.-ethanol system at 190 °C and [Al3+] = 1 mol L−1 under microwave heating. Four organic–inorganic fluorides crystallise: [H3dien]·(AlF6) (P21/c, Z = 4), [H3dien]2·(AlF5(H2O))3·2H2O (P21/n, Z = 4), [H3dien]·(AlF6)·2H2O, which was previously known, and [H3dien]2·(Al4F18) (C2/c, Z = 4). A new (Al4F18)6− polyanion, which results from the tetrahedral association of four AlF6 octahedra linked by corners, is evidenced in [H3dien]2·(Al4F18).