New iron(III) nitrate hydrates: Fe(NO3)3•xH2O with x=4, 5 and 6

Crystals of the title compounds were grown from their hydrous melts or solutions. The crystal structure of iron(III) trinitrate hexahydrate {hexaaquairon(III) trinitrate, [Fe(H2O)6](NO3)3} is built up from [Fe(H2O)6]2+ octahedra and nitrate anions connected via hydrogen bonds. In iron(III) trinitrate pentahydrate {pentaaquanitratoiron(III) dinitrate, [Fe(NO3)(H2O)5](NO3)2}, one water molecule in the coordination octahedron of the FeIII atom is substituted by an O atom of a nitrate group. Iron(III) trinitrate tetrahydrate {triaquadinitratoiron(III) nitrate monohydrate, [Fe(NO3)2(H2O)3]NO3 center dot H2O} represents the first example of a simple iron(III) nitrate with pentagonalbipyramidal coordination geometry, where two bidentate nitrate anions and one water molecule form a pentagonal plane.