Synthesis and oxidation study of the simplest binuclear metallocene compound of osmium, biosmocene

• Biosmocene was synthesized by Ullmann coupling reaction of iodoosmocene.
• Biosmocenium-I triiodide salt was obtained by reaction of biosmocene and I2.
• The intramolecular electron transfer reaction between OsII and Os IV was observed.
• The activation energy of the electron transfer reaction was determined.
• The Os–I bond was larger than the Ru–I bond.

Selective mono-lithiation method of bis(cyclopentadienyl)osmium(II) (osmocene) was established. Iodoosmocene(C5H4I)Os(C5H5) (OcI), which is the first monohalogenated product of osmocene, was prepared by the reaction of lithioosmocene with I2. Ullmann coupling reaction of iodoosmoene allowed to prepare biosmocene(C5H5)Os(μ2-η5:η5-C10H8)Os(C5H5) (OcOc). OcOc reacted with I2, giving mixed-valence biosmocenium salt [(C5H5)OsII(μ2-η5:η5-C10H8) (C5H5)OsIVI]I3(A). The structure of A was determined by single crystal X-ray structural analysis. The intramolecular electron transfer reaction between OsII and Os IV was observed by using 1H NMR spectroscopy, accompanied by the exchange of I− anion between the two units. The activation energy of the electron transfer reaction was estimated and the value was larger than that of binuclear ruthenocenium salt [(C5H5)RuII(μ2-η5:η5-C10H8) (C5H5)RuIVI]I3(B).

Ullmann coupling reaction of iodoosmoene allowed to prepare biosmocene (OcOc). OcOc reacted with I2, giving mixed-valence biosmocenium salt [(C5H5)OsII(μ2-η5:η5-C10H8) (C5H5)OsIVI]I3. The intramolecular electron transfer reaction between OsII and Os IV was observed by using 1H NMR spectroscopy, accompanied by the exchange of I− anion between the two units.Figure optionsDownload as PowerPoint slide