摘要:
By precipitation with ethylene diamine (en) from a hydrofluoric acid solution of aluminium enH(2)(H3O)[AlF6] is formed. It crystallizes in the orthorhombic space group Pnma, a = 1084.9(1), b = 1079.4(1), c = 682.0(1) pm, R = 0.032. H3O+ cations and [AlF6](3-) anions are connected via strong H bonds to layers which are further linked to a 3 D network by H bonds from the enH(2)(2+) cations. By recrystallization from water or precipitation from a less acid solution enH(2)[AlF5(H2O)] is formed, which crystallizes monoclinic in the space group P2(1) (a = 660.0(1), b = 563.5(1), c = 994.4(2) pm, beta = 98.44(3)degrees, R = 0.029). The [AlF5(H2O)](2-) anions are linked by strong O-H ... F bonding to form 'einer-double chains' interconnected again via the enH(2)(2+) cations to a 3 D framework. Thermoanalytical investigations show that enH(2)[AlF5(H2O)], by loss of water above 150 degrees C, as well as enH(2)(H3O)[AlF6], by loss of water and if above 120 degrees C, transform to enH(2)AlF(5). The subsequent decomposition goes over NH4+ containing intermediates towards beta-AlF3. Before decomposition the oxonium fluoroaluminate reveals a reversible phase transition at 99 degrees C.