Syntheses and Structures of Octamethylmetallocenes of Osmium
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The reaction of sodium hexachloroosmate(IV) hydrate with five equivalents of tetramethylcyclopentadiene (C5Me4H2) in refluxing ethanol yielded the novel coordination compound bis(tetramethylcyclopentadienyl)chloroosmocinium(IV) hexachloroosmate, [(η 5-C5Me4H)2OsCl]2[OsCl6] (1). Compound 1 has been characterized by NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The cationic complex of 1 [(η 5-C5Me4H)2OsCl]+, adopts a bent geometry with a ring centroid-osmium-ring centroid angle of 146.2° and an eclipsed conformation of its two tetramethylcyclopentadienyl rings. The addition of zinc powder to sodium hexachloroosmate(IV) hydrate and five equivalents of tetramethylcyclopentadiene in refluxing ethanol produced the known compound, bis(tetramethylcyclopentadienyl)osmium, (η 5-C5Me4H)2Os (2). The crystal structure of 2 has been determined and it reveals an eclipsed arrangement of the tetramethylcyclopentadienyl rings in the solid state. The average Os–Cring bond length in octamethylosmocene 2 (2.187 Å) is in accordance with corresponding bond lengths in osmocene, (η 5-C5H5)2Os (2.19 Å) and decamethylosmocene, (η 5-C5Me5)2Os (2.18 Å).
KeywordsOctamethylosmocene Bis(tetramethylcyclopentadienyl)osmium Osmium Tetramethylcyclopentadiene Octamethylmetallocene
This article is dedicated in memoriam to Professor Dwight A. Sweigart. This research was supported by an award from Research Corporation for Science Advancement (Award # 20904), the M.J. Murdock Charitable Trust (A.W.A. and E.N.F.), the Peach Foundation (E.M.O.) and Seattle University. RDP thanks the NSF and the College of William and Mary for the purchase of the X-ray equipment.
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