Synthesis and crystal structures of lithium and potassium hexanitroruthenates (II)

A procedure for preparing Li₄Ru(NO₂)₆]…12H₂O and K₄Ru(NO₂)₆] is described. We have carried out an X-ray diffraction study of polycrystals (DRON-UM1 diffractometer, R=192mm, CuK_α radiation, Ni filter) and single crystals (CAD-4 automatic diffractometer, MoK_α radiation, graphite monochromator, ω/2? scan mode). Crystal data for Li₄Ru(NO₂)₆]…12H₂O are a=11.749(9), c=16.807(12) Å, space group $I\bar 4$ , V=2320.0 ų, Z=4, d_calc=1.778 g/cm³; for K₄ Ru(NO₂)₆]: a=8.595(1) Å, α=53.23 (2)^o, space group $R\bar 3$ , V=367.0 ų, Z=1, d_calc=2.414 g/cm³. The structures are composed of Ru(NO₂)₆]^4? comple anions, alkaline metal cations, and crystallization water molecules. In both compounds, the coordination polyhedra of Ru are nearly regular octahedra formed by nitrite nitrogen atoms. The Ru-N bond lengths are 2.054–2.102 Å. The NO₂ groups have virtually the same geometric characteristics: the N?O distances are within 1.196–1.316 Å and the O?N?O angles are 112.9–117.4^o. The coordination environment of alkaline metals by oxygen atoms is discussed.