Structural study of bonding in halogeno ruthenium complexes: Application to ruthenium nitrosyls

The halogeno nitrosyl ruthenium complexes are studied using their structural characteristics as basis. The structures of K₂RuNOX₅ (X=Cl, Br, I) have been determined or redetermined. The study of the bond lengths Ru-Cl is, in a first part, placed in the general frame of the chlorocomplexes of ruthenium having and+ type ligands. The comparison points to a lengthening of the Ru-Cl_axial bond in [RuNOCl₅]^2–, which is opposite to the trans shortening effect up to now considered. A second part deals with the deformation of the octahedral coordination of the ruthenium atom. In [RuNOX₅]^2–, the distance from the ruthenium to the equatorial plane varies with the position ofX in the spectrochemical series. The role of thed_xy orbital in the geometry of these ions is discussed.