Conservation of [(C2H4NH3)3N]2·(ZrF7)2·H2O layers during the topotactic dehydration of [(C2H4NH3)3N]2·(ZrF7)2·9H2O

Tren amine cations [(C2H4NH3)3N]3+ and zirconate or tantalate anions adopt a ternary symmetry in two hydrates, [H3tren]2·(ZrF7)2·9H2O and [H3tren]6·(ZrF7)2·(TaOF6)4·3H2O, which crystallise in R32 space group with aH = 8.871 (2) Å, cH = 38.16 (1) Å and aH = 8.758 (2) Å, cH = 30.112 (9) Å, respectively. Similar [H3tren]2·(MX7)2·H2O (M = Zr, Ta; X = F, O) sheets are found in both structures; they are separated by a water layer (Ow(2)–Ow(3)) in [H3tren]2·(ZrF7)2·9H2O. Dehydration of [H3tren]2·(ZrF7)2·9H2O starts at room temperature and ends at 90 °C to give [H3tren]2·(ZrF7)2·H2O. [H3tren]2·(ZrF7)2·H2O layers remain probably unchanged during this dehydration and the existence of one intermediate [H3tren]2·(ZrF7)2·3H2O hydrate is assumed. Ow(1) molecules are tightly hydrogen bonded with –NH3+ groups and decomposition of [H3tren]2·(ZrF7)2·H2O occurs from 210 °C to 500 °C to give successively [H3tren]2·(ZrF6)·(Zr2F12) (285 °C), an intermediate unknown phase (320 °C) and ZrF4.