[Ag(NH3)2]Ag(OsO3N)2:: a new nitridoosmate(VIII)

Dark brown single crystals of [Ag(NH3)(2)]Ag(OsO3N)(2) were obtained from the reaction of Ag2CO3, OsO4, and NH3 in aqueous solution. The crystal structure was solved in the monoclinic space group C2/m, with the following unit-cell dimensions: a = 1962.5(3); b = 633.1 (1), c = 812.6(l) pm, beta = 96.71 (1)degrees. The final reliability factor was R = 0.0256 for 1034 reflections with I > 2sigma(I). Linear [Ag(NH3)(2)](+) ions are present oriented perpendicular to the [010] direction, leading to short Ag+-Ag+ distances of 316 pm. A second type of Ag+ ions in the crystal structure present coordination number "6 + 1" and are surrounded by oxygen and nitrogen atoms of the nitridoosmate groups. Within the first of the two crystallographically distinguishable anions one can clearly differentiate between oxygen and nitrogen atoms while the second one exhibits a N/O disorder over two positions. The infrared spectrum of [Ag(NH3)(2)]Ag(OsO3N)(2) shows the typical absorptions which can be attributed to the complex anions and the NH3 ligands. (C) 2004 Elsevier Inc. All rights reserved.