A first preliminary report on the crystal structure of a hydrated salt formulated as [Ge(taci)2]Cl4·13H2O (taci is 1,3,5-triamino-1,3,5-trideoxy-cis-inositol) appeared more than 20 years ago [Ghisletta (1994). PhD thesis, ETH Zürich. Switzerland]. At that time it was not possible to discriminate unambiguously between the positions of some of the chloride ions and water O atoms, and disorder was thus postulated. In a new determination, a conclusive scheme of hydrogen bonding proves to be a particularly appealing aspect of the structure. Single crystals of the title compound, C12H30GeN6O6(4+)·4Cl(-)·6H2O or [Ge(taci)2]2Cl8·12H2O, were grown from an aqueous solution by slow evaporation of the solvent. The two [Ge(taci)2](4+) cations exhibit a double-adamantane-type structure with exclusive O-atom coordination and approximate D3d symmetry. The taci ligands adopt a zwitterionic form with deprotonated hydroxy groups and protonated amino groups. Both cations are hydrogen bonded to six water molecules. The structure of the hydration shell of the two cations is, however, slightly different. The {[Ge(taci)2]·6H2O}(4+) aggregates are interlinked in all three dimensions by further hydrogen bonds of the types N-H...Cl...H-N, N-H...O(H)2...H-N, (Ge)O...H-O(H)...H-N, N-H...O(H)-H...Cl...H-N, (Ge)O...H-O-H...Cl...H-N, N-H...O(H)-H...Cl...H-(H)O...H-N, (Ge)O...H-O-H...Cl...H-(H)O...H-N and Ge(O)...H-O-H...Cl...H-O-H...O(Ge).
Keywords: GeIV complex; cis-inositol; crystal structure; graph-set analysis; hydrogen bonding; taci.