Structure of the 18-crown-6 complex with ammonium hexafluorosilicate and water

Abstract

The crystalline host–guest type complex [(18-crown-6ċNH4)2][SiF6]ċ4H2Ohas been obtained as the result of the interaction of SiF4ċ2NH3 with 18-crown-6 (18C6) in an aqueous medium. Crystal data: monoclinic, space groupC 2 c, a=26.541(2), b=8.363(2), c=20.469(2) Å, β = 122.43(1)°and Z=4. The final R-value is 0.070 for 3253 reflections with I ≥ 2σ(I).The crystals consist of the complex [NH4ċ18C6]+ cations, [SiF6]2-anions and water molecules. The ammonium cation is hydrogen bonded by three of its H-atoms to the crown ether oxygen atoms with N(1) ċO separations2.923(5)–2.940(5) Å and by the fourth H-atom to the fluorine atom of thehexafluorosilicate anion, the N(1)ċF(4) distance being 2.797(6) Å.The conformation of the macrocycle and the hydrogen-bond geometry in thecomplex cation closely resemble those in related adducts between 18-crown-6and ammonium salts. All crystal components are connected via a system of hydrogen bonds into a ribbon alongthe b axis in the unit cell.