Uranocene
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| Uranocene | |
|---|---|
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| Systematic name | bis(η8-cyclooctatetraenyl)uranium(IV) |
| Other names | uranium cyclooctatetraenyl |
| Molecular formula | C16H16U U(C8H8)2 |
| Molar mass | 446.33 g mol−1 |
| Appearance | green[1] |
| Density | ? g/cm3 |
| Solubility (water) | ? g/l |
| Melting point | ? °C |
| Boiling point | ? °C |
| CAS number | ? |
| Disclaimer and references | |
Uranocene U(C8H8)2 is the most notable cyclooctatetraenide of the f elements, and one of the first organouranium compounds to be synthesized. Uranocene is a member of the actinocenes, a group of metallocenes incorporating elements from the actinide series. It is the most studied bis[8]annulene-metal system.
Contents |
[edit] Synthesis
Uranocene was first prepared by the reaction of uranium tetrachloride and dipotassium cyclooctatetraene, viz.
- 2K + C8H8 → K2(C8H8)
- 2K2(C8H8) + UCl4 → U(C8H8)2 + 4KCl.[2]
[edit] Physical and chemical properties
Uranocene is paramagnetic, pyrophoric, and stable to hydrolysis. The η8-cyclooctatetraenyl groups are planar, as expected for a ring containing 10 π-electrons, and are mutually parallel to each other, forming a sandwich containing the uranium atom. In the solid state, the rings are eclipsed, conferring D8h symmetry on the uranocene molecule. In solution the rings rotate with a low energy barrier.
[edit] Uranium-COT bond
The nature of the uranium-cyclooctatetraenyl bond is the subject of continuing research and debate [3]. UV-PES indicates the bonding in uranocene has contributions from 5f and 6d orbitals.
[edit] Analogous compounds
Some examples of analogous compounds of the form M(C8H8)2 exist for M = (Nd, Tb, Pu, Pa, Np, Th, and Yb). Extensions include the air-stable derivative U(C8H4Ph4)2 and the cycloheptatrienyl species [U(C7H7)2]−.[4]
[edit] References
- ^ A. Streitwieser and U. Müller-Westerhoff, Bis(cyclooctatetraenyl)uranium (uranocene). A new class of sandwich complexes that utilize atomic f orbitals, J. Am. Chem. Soc. 90, 7364, 1968.
- ^ J.S. Hager et al., Raman under nitrogen. The high-resolution Raman spectroscopy of crystalline uranocene, thorocene, and ferrocene, J. Chem. Phys., Vol. 120, no 6., pp. 2708-2718, 2004
- ^ http://www.radiochemistry.org/periodictable/la_series/A12.html
- ^ Seyferth, D. "Uranocene. The First Member of a New Class of Organometallic Derivatives of the f Elements" Organometallics 2004, volume 23, pages 3562-3583
[edit] Other reading materials
- The f elements, Nikolas Kaltsoyannis and Peter Scott. ISBN 0-19-850467-5
- Chemistry of the Elements, N. N. Greenwood and A. Earnshaw. ISBN 0-08-022057-6
