Relatively few high-valent transition metal oxide fluoride cations are known. OsO3F +, OsO2F3 + and — Analytical Chemistry Chemistry Question
Stabilization of high-valent transition metal ions
Relatively few high-valent transition metal oxide fluoride cations are known. OsO3F +, OsO2F3 + and µ-F(OsO2F3)2+ are some of these, where µ-F indicates the F– ion bridging the two Os units. In a recent study (Inorg. Chem. 2010, 49, 271) the [OsO2F3][Sb2F11] salt has been synthesized by dissolving solid cis-OsO2F4 in liquid SbF5, which is a strong Lewis acid, at 25 °C, followed by removal of excess SbF5 under vacuum at 0 °C. The crystal structure of [OsO2F3][Sb2F11] determined by XRD reveals the existence of OsO2F3 + cation and fluoride bridged Sb2F11 – anion. Under dynamic vacuum at 0 °C, the orange, crystalline [OsO2F3][Sb2F11] loses SbF5, yielding [µ-F(OsO2F3)2][Sb2F11] salt. In both salts osmium is six-coordinate in solid state, but in liquid SbF5 solution, both 19F-NMR and Raman data are consistent with the presence of five-coordinate osmium in the trigonal bipyramidal OsO2F3 + cation.
Write balanced chemical equations for the formation of [OsO2F3][Sb2F11] and [µ-F(OsO2F3)2] [Sb2F11].
Model Answer
cis-OsO2F4(s) + 2 SbF5(l) → [OsO2F3][Sb2F11](s)
2 [OsO2F3][Sb2F11](s) → [µ-F(OsO2F3)2] [Sb2F11](s) + 2 SbF5(g)
Draw all the possible geometrical isomers of trigonal bipyramidal OsO2F3 + cation.
What is the oxidation number of Os in the OsO2F3 + and µ-F(OsO2F3)2+ cations?
Model Answer
VIII in the OsO2F3 + cation.
VIII in the [µ-F(OsO2F3)2] + cation.
When we assume a free rotation around Os-F(bridging) bond, µ-F(OsO2F3)2 + cation complex can be represented as a mononuclear octahedral complex of osmium, [OsO2F3X]+, where X = F-OsO2F3. Assuming that X is a monodentate ligand, draw all possible geometrical isomers of [OsO2F3X]+ complex ion. Is there any optical isomer of [OsO2F3X]+ ?
Model Answer
No optical isomers.