L. H. Simons, J. J. Lagowski / Tetrahedron Letters 43 (2002) 1771–1773
1773
Acknowledgements
produced very selectively and is present in a concentra-
tion equivalent to 22% of theory.
We wish to thank the Robert A. Welch Foundation for
its generous financial support of this work.
4. Preparation of uranocene (U(COT)2)
UCl4 is prepared by the reaction of hexachloropropene
with anhydrous UO3.1a,9 The green product is washed
with CCL4 and vacuum dried for 21 h at 165–170°C
before storing in the dry box. When examined by
electron-impact mass spectrometry, UCl4 exhibits the
molecular ion at m/e 380, along with successive loss of
Cl at m/e 345, 308, 273. Uranium is seen in the vapor
phase at m/e 238. The yield of UCl4 is about 93%.
References
1. (a) Streitwieser, A., Jr.; Muller-Westerhoff, U.; Sonnich-
sen, G.; Mares, F.; Morrell, D. G.; Hodgson, K. O.;
Harmon, C. A. J. Am. Chem. Soc. 1973, 95, 8644–8649;
(b) Lyttle, M. H.; Streitwieser, A.; Miller, J. J. J. Org.
Chem. 1989, 54, 2331–2335; (c) Fray, G. I.; Saxton, R. G.
The Chemistry of Cyclooctatetraene and Its Derivatives;
Cambridge University Press: Cambridge, 1978; pp. 172–
189; (d) Gorman, C. B.; Ginsburg, E. J.; Grubbs, R. H.
J. Am. Chem. Soc. 1993, 115, 1397–1409.
2. (a) Evans, W. J.; Wink, D. J.; Wayda, A. L.; Little, D. A.
J. Org. Chem. 1981, 46, 3925–3928; (b) Evans, W. J.;
Wayda, A. L.; Chang, C.-W.; Cwirla, W. M. J. Am.
Chem. Soc. 1978, 100, 333–334.
3. (a) Simons, L. H.; Lagowski, J. J. J. Org. Chem. 1978, 43,
3247–3248; (b) Simons, L. H.; Lagowski, J. J. In Funda-
mental Research in Homogeneous Catalysis; Ishii, Y.;
Tsutsui, M., Eds. Reaction of alkynes with transition
metal atoms. Plenum: New York, 1978; Vol. 2, pp. 73–80;
(c) Simons, L. H.; Lagowski, J. J. J. Organomet. Chem.
1983, 249, 195–203.
4. Holy, N. L. Chem. Rev. 1974, 74, 243–277.
5. Bates, R. B.; McCombs, D. A. Tetrahedron Lett. 1969,
10, 977–978.
In the dry box, 1.95 g (10.7 mol) K2COT and a
glass-encased stir bar are placed in a 70 mm OD
Schlenck storage tube equipped with a J. Young Teflon
stopcock and a male 24/40 joint. UCl4 (2.02 g, 5.3
mmol) is weighed into a 500 mL Schlenck flask. At the
vacuum-nitrogen line, 100 mL of THF is cannula-trans-
ferred onto the K2COT producing a dark brown solu-
tion. The K2COT solution is stirred and chilled in a
−35°C slush bath. THF (75 mL) is cannula-transferred
onto the UCl4, producing a murky, green liquid, which
is then cannula-transferred, in one portion, into the
stirring, chilled K2COT solution. The reaction mixture
quickly becomes dark green throughout and is stirred
for 3 h in the range of −33 to −39°C under N2 on a
mercury bubbler. The reaction mixture is stirred
overnight as the slush bath warms to room tempera-
ture. THF is removed by vacuum transfer, leaving fine,
green solids. The solids are washed with ether to
remove organic impurities, then, vacuum dried at 50°C
and transferred into the dry box where 3.112 g fine,
green solids are weighed. A 559 mg portion of the green
powder is placed in a short-path sublimation device. On
the vacuum line, the green powder is sublimed for 2 h
at 211°C and 3×10−3 torr to produce 43 mg of a dark
green sublimate on the water-cooled cold finger. This
corresponds to a 12% isolated yield of uranocene,
which is characterized by NMR10 and mass spectrome-
try.11 In the proton NMR, at 300 K, a broad peak is
observed at −36.4 ppm, which corresponds well to the
temperature-dependent NMR spectra reported by Edel-
stein et al.12 The carbon NMR, at 300 K, shows a
broad peak at 297.1 ppm, which is in excellent agree-
ment with the value of 297 ppm indicated by Stre-
itwieser et al.13
6. Shriver, D. F.; Drezdzon, M. A. The Manipulation of
Air-Sensitive Compounds, 2nd ed.; John Wiley: New
York, 1986; pp. 1–128.
7. NMR data for K2C8H8: 1H NMR (500 MHz, THF-d8,
referenced to THF-d8 peak at 1.73 ppm) 5.74 ppm. 13C
NMR (125 MHz, THF-d8, referenced to THF-d8 peak at
25.3 ppm) 90.3 ppm.
8. Mass spectral data for K2C8H8: Electron impact: m/e
182, 104, 78. Chemical ionization (positive mode): m/e
182, 105. High resolution calcd for C8H8K2: 181.990016.
Found: 181.991086.
9. Hermann, J. A.; Suttle, J. F. Inorg. Synth. 1957, 5,
143–145.
1
10. NMR data for U(C8H8)2: H NMR (500 MHz, THF-d8,
300 K, referenced to THF-d8 peak at 1.73 ppm) −36.4
ppm. 13C NMR (125 MHz, THF-d8, 300 K, referenced to
THF-d8 peak at 25.3 ppm) 297.1 ppm.
11. Mass spectral data for U(C8H8)2: Electron impact: m/e
446, 342, 104. Chemical ionization (positive mode): m/e
447, 105. High resolution calcd for C16H16U: 446.175986.
Found: 446.175329.
12. Edelstein, N.; Lamar, G. N.; Mares, F.; Streitwieser, A.,
Jr. Chem. Phys. Lett. 1971, 8, 399–402.
In summary, a new naphthalene radical anion mediated
preparation of COT dianion from 1,5-COD is
described. COT is prepared by oxidation of K2COT
with air and iodine. Reaction of K2COT with UCl4 in
THF produces uranocene. Further reactions of COT
dianion will be reported elsewhere.
13. Luke, W. D.; Berryhill, S. R.; Streitwieser, A., Jr. Inorg.
Chem. 1981, 20, 3086–3089.