Structure of ammonium decachloro-μ-oxodiosmate(IV) (NH4) 4[Os2OCl10] and its behavior in solutions

The structure of (NH4)4[OS2OCl 10] has been determined by X-ray diffraction. The crystals are tetragonal, space group I4/mmm, a = 7.292(1) Å, c = 17.157(3) Å, Z = 2. The binuclear anion has D 4h symmetry; the osmium atom is coordinated to five chlorine atoms and the oxygen atom. The Os-O distances are 1.8242(5) Å; Os-Cleqv, 2.3743(18) Å; Os-Clax, 2.335(3) Å; the Cl1OsCl2 angle is 86.84(4). The anion has been established spectrophotometrically to remain structurally unchanged in freshly prepared aqueous and hydrochloric acid solutions. Slow aquation with retention of a binuclear structure occurs with time in 1 and 6 M HCl. At 75 or 90 C, the process is faster with the disrupture of the Os-O-Os bond and the formation [OsCl6]2- ions in 6 M HCl and a mixture of [OsCl6]2- and [Os(H2O)Cl 5]- ions in 1 M HCl. © 2013 Pleiades Publishing, Ltd.