Evolution of guanazolium fluoroaluminates within the composition-space diagram and with the temperature
Résumé
The 2D composition-space diagram of the Al(OH)3−Am2TAZ−HFaq−ethanol system is established under microwave heating at 190 °C for [Al3+] = 1 mol·L−1. Four new fluoroaluminates are evidenced when the [HF]/[Am2TAZ] ratio is increased in the starting solution, and the dimensionality of the inorganic frameworks is increased from 0D in [HAm2TAZ]2·(AlF5(H2O))·2H2O (Pc, Z = 2), to 1D in [HAm2TAZ]2·(AlF5) and [HAm2TAZ]2·(Al2F8) (Fdd2, Z = 8), and to 2D in [HAm2TAZ]2·(Al5F17) (Imm2, Z = 2). This evolution is partially paralleled by the thermal decomposition of [HAm2TAZ]2·(AlF5(H2O))·2H2O; on heating, this hydrate gives [HAm2TAZ]2·(AlF5) at 100−150 °C and [HAm2TAZ]2·(Al2F8) at 180 °C; the loss and simultaneous decomposition of [HAm2TAZ]F leave a solid residue of polymeric paracyanogen (CN)2n that is further decomposed and hydrolyzed into HCN and HNCO by atmospheric water traces. NMR 19F spectroscopy of [HAm2TAZ]2·(AlF5) is in agreement with the crystallographic determination, and the 27Al spectrum demonstrates that a significant F−/OH− substitution is excluded.