Evidence of 13 hybrid fluoroaluminates in the composition space diagram of the Al(OH)3–tren–HF–ethanol system

Thirteen phases are now evidenced in the composition space diagram of the Al(OH)3–tren–HF–ethanol system at 190 °C. Solvothermal syntheses are performed under microwave heating. Six new organic–inorganic fluorides crystallise and their structures are determined: (H3O)·[H4tren]2·(AlF6)3·6H2O (P-1, Z = 2), [H3tren]2·(AlF5(H2O))3·8H2O (C2/c, Z = 8), [H3tren]4·(AlF6)2·(Al2F11)·(F)·10H2O (P21/n, Z = 2), [H3tren]2·(Al4F18)·3.5H2O (P63, Z = 2), [H3tren]2·(Al4F18) (P-1, Z = 1), and [H3tren]4·(Al8F35)·(OH)·H2O (P-1, Z = 1). The existence domains are approximately located for all phases. Tren amine is tetraprotonated at high HF concentration, otherwise it is triprotonated. A protonated water cluster, H3O+(H2O)6, appears in (H3O)·[H4tren]2·(AlF6)3·6H2O while a new Al4F18 unit, found in [H3tren]2·(Al4F18), is evidenced; it results from corner and edge sharing association of four AlF6 octahedra. Finally, the structure of [H3tren]4·(Al8F35)·(OH)·H2O revealed the largest known fluoroaluminate polyanion, built from eight vertex sharing AlF6 octahedra, (Al8F35)11−.