Complexes of some alkali-metal and silver salts with 1,4-dioxan

Abstract

The 1,4-dioxan (dx) complexes NaClO₄,3dx, NaBF₄,3dx and NaI,3dx have the cubic structure of AgClO₄,3dx. The metal ion is octahedrally co-ordinated by oxygen atoms from dioxan with Na–O distance 2·43—2·46 Å, identical to those found in Na(OH₂)₆ octahedral Size and shape requirements limit the anions found in complexes of this structure. The heavier alkali-metal ions are too large for the structure to be stable. The lattice energy of the parent salt is not important in selecting which alkali-metal ions form complexes with dioxan. The lattice energy of the complex is dominated by metal–dioxan ion–dipole interaction. Temperatures, enthalpies, and entopies of decomposition are reported. AgClO₄,3dx decomposes to AgClO₄,dx and thence to AgClO₄, NaClO₄,dx, and NaBF₄,3dx decompose directly to the parent salt. NaI,3dx decomposes to NaI at atmospheric pressure but NaI,2dx and NaI,dx have been characterised in vacuo. Temperatures and enthalpies of phase changes in AgClO₄, NaClO₄, NaBF₄, and NaClO₄,3dx are reported.