Facile syntheses of unsolvated Ul3 and tetramethylcyclopentadienyl uranium halides

Article abstract of DOI:10.1021/ic0482685

In the course of comparing the reaction chemistry of (C₅Me ₅)₃U, 1, and its slightly less crowded analogue (C ₅Me₅H)₃U, 2, new syntheses of Ul₃, (C₅Me₄H)₃U, (C₅Me₄H) ₃UCl, 3, and (C₅Me₅)₃UCl, 4, have been developed. Additionally, (C₅Me₅H)₃Ul, 5, and (C₅Me₄H)₂UCl₂, 6, have been identified for the first time. A facile synthesis of unsolvated Ul₃ is reported that proceeds in high yield with inexpensive equipment from iodine and hot uranium turnings. Both Ul₃ and Ul₃(THF) ₄ react with KC₅Me₄H in toluene to make unsolvated C₅Me₄H)₃U in higher yield than in previous reports that involve reduction of tetravalent (C₅Me ₄H)₃UCl, 3. A more atom-efficient synthesis of complex 3 is also reported that proceeds from reduction of t-BuCl, PhCl, or HgCl ₂ by 2. Similarly, (C₅Me₄H)₃U reacts with Phi or Hgl₂ to generate (C₅Me₄H) ₃Ul. These studies also provided a basis to improve the synthesis of (C₅Me₅)₃UCl from 1 by employing t-BuCl or HgCl₂ as the halide source. Like (C₅Me₅)UCl, the (C₅Me₄H)₃UCl complex reacts with HgCl ₂ to form (C₅Me₅H)₂ and (C ₅Me₄H)₂UCl₂, 6, but unlike (C ₅Me₅)₃UX (X = Cl or l), the less substituted (C₅Me₄H)₃UX complexes do not reduce t-BuCl or PhX. The synthesis of 6 from (C₅Me₄H)MgCl·THF and UCl₄ is also included.

Full text of DOI:10.1021/ic0482685

Inorg. Chem. 2005, 44, 3993−4000
Facile Syntheses of Unsolvated UI and Tetramethylcyclopentadienyl
3
Uranium Halides
William J. Evans,*,† Stosh A. Kozimor,† Joseph W. Ziller,† Anatolii A. Fagin,‡ and
Mikhail N. Bochkarev*,‡
Department of Chemistry, UniVersity of California, IrVine, California 92697-2025, and
RazuVaeV Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49,
603950 Nizhny NoVgorod, Russia
Received December 9, 2004
In the course of comparing the reaction chemistry of (C
Me H) U, 2, new syntheses of UI , (C Me H) U, (C Me H)
Additionally, (C Me H) UI, 5, and (C Me H) UCl , 6, have been identified for the first time. A facile synthesis of
unsolvated UI is reported that proceeds in high yield with inexpensive equipment from iodine and hot uranium
turnings. Both UI and UI (THF) react with KC Me H in toluene to make unsolvated (C Me H) U in higher yield
than in previous reports that involve reduction of tetravalent (C Me H) UCl, 3. A more atom-efficient synthesis of
complex 3 is also reported that proceeds from reduction of t-BuCl, PhCl, or HgCl by 2. Similarly, (C Me H)
reacts with PhI or HgI to generate (C Me H) UI. These studies also provided a basis to improve the synthesis of
Me UCl from 1 by employing t-BuCl or HgCl
reacts with HgCl to form (C Me H) and (C Me
Me H)
also included.
5
Me
5
)
3
U, 1, and its slightly less crowded analogue
(C
5
4
3
3
5
4
3
5
4
3
UCl, 3, and (C
5
Me UCl, 4, have been developed.
5 3
)
5
4
3
5
4
2
2
3
3
3
4
5
4
5
4
3
5
4
3
2
5
4
3
U
2
5
4
3
(
C
5
5
)
3
2
as the halide source. Like (C
H) UCl , 6, but unlike (C Me
UX complexes do not reduce t-BuCl or PhX. The synthesis of 6 from (C
5
Me
UX (X
5
)
3
UCl, the (C
Cl or I), the less substituted
Me H)MgCl THF and UCl is
5 4 3
Me H) UCl complex
2
5
4
2
5
4
2
2
5
5
)
3
)
5
(C
5
4
3
4
‚
4
3 4
(THF)
.13,14
Introduction
the discovery of a convenient synthesis of UI
This precursor can be prepared from amalgamated uranium
Historically, the chemistry of U(IV) has been more heavily
studied than that of U(III).1-5 One practical reason for this
difference is that the tetravalent chloride, UCl
1
3-15
and iodine in THF
and is currently a starting material
8
,16-27
for many U(III) syntheses.
4
, is a more
useful precursor than the corresponding trivalent compound,
(
9) Andersen, R. A. Inorg. Chem. 1979, 18, 1507.
10) Moody, D. C.; Pennenman, R. A.; Salazar, K. V. Inorg. Chem. 1979,
8, 208.
6
-12
UCl
3
.
One of the breakthroughs in U(III) chemistry was
(
1
*
To whom correspondence should be addressed. E-mail: wevans@uci.edu.
(11) Moody, D. C.; Zozulin, A. J.; Salazar, K. V. Inorg. Chem. 1982, 21,
3856.
(12) Moody, D. C.; Odom, J. D. J. Inorg. Chem. 1979, 41, 533.
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1989, 28, 1771.
Fax: (+1)-949-824-2210 (W.J.E.). E-mail: mboch@imoc.sinn.ru. Fax:
(
+7)8312-661-497 (M.N.B.).
†
University of California.
Razuvaev Institute of Organometallic Chemistry.
‡
(
1) Marks, T. J. Prog. Inorg. Chem. 1979, 25, 223.
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G.; Zwick, B. D. Inorg. Chem. 1994, 33, 2248.
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J. B.; Abney, K. D. Inorg. Chem. 1996, 35, 1425.
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(
2) Marks, T. J.; Ernst, R. D. In ComprehensiVe Organometallic Chem-
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Oxford, 1982; Chapter 21, p 211.
(
3) Edelmann, F. T. ComprehensiVe Organometallic Chemistry II; Wilkin-
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Chapter 2, p 131.
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20, 2552.
(5) Seyferth, D. Organometallics 2004, 23, 3562.
(
6) Hermann, J. A.; Suttle, J. F.; Hoekstra, H. R. Inorg. Synth. 1957, 5,
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2001, 26,
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Synth. 1974, 15, 243.
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1
0.1021/ic0482685 CCC: $30.25
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 11, 2005 3993
Published on Web 04/28/2005

Evans et al.
In some investigations, however, unsolvated UI
ferred. For example, Cloke and Hitchcock needed unsolvated
UI for the synthesis of an unsolvated pentalene complex,
Me (1,4-i-Pr Si) ], that showed interesting reac-
tion chemistry with dinitrogen. Unsolvated UI
be preferred in systems in which U(III) complexes ring-open
3
is pre-
(C
5
Me
4
H)
3
U, 2.46,47 Although both complexes crystallize with
a trigonal arrangement of cyclopentadienyl ring centroids
around the metal, 1 has slightly longer U-C bond distances
than 2, which apparently leads to different chemistry. Hence,
both 1 and 2 form CO adducts,
retains its trigonal arrangement of cyclopentadienyl rings,
3
(C
5
5
)U[C10H
4
3
2
28
43,46,47
43
3
would also
5 5 3
but (C Me ) U(CO)
2
9
46,47
THF. Indeed, the formation of oily green residues presumed
to arise from THF ring opening complicates the synthesis
whereas (C
5 4 3
Me H) U(CO) becomes more tetrahedral.
In
addition, complex 1 displays several types of reactions not
reported for 2: sterically induced reduction reactions via a
C Me /C Me redox couple, formation of an isolable end-
5 5 5 5
on dinitrogen complex, ring opening of THF, and
cyclopentadienyl displacement reactions via ionic salt me-
tathesis.
of UI
iodine, and the reaction must be carried out below 10 °C.
Previously, unsolvated UI has been prepared by reduction
of UI
with Zn at 870 K in sealed silica vessels.30,31 Recently,
Cloke and Hitchcock showed that UI could be prepared at
70 °C from U turnings and HgI , eq 1, in a manner similar
to the synthesis of LnI
described by Corbett.32
3 4
(THF) from amalgamated uranium turnings and
1
4
1-
41
2
9
29
3
4
4
5
3
1-
3
2
Samples of (C Me H) U for these comparative (C Me )
versus (C Me H) studies were originally prepared by Na-
5 4
5
4
3
5
5
1-
3
(
C
10
H
8
) reduction of (C
5
Me
To obtain (C
4
H)
3
UCl, a precursor that requires
Me H) U faster and
2
U + 3HgI f 2UI + 3Hg
(1)
46,47
2
3
a multistep synthesis.
5
4
3
in a more uranium-efficient method, a synthetic route from
UI has been developed. Exploration of the reactivity of (C -
We report here that unsolvated UI
3
can be made directly
3
5
from uranium and iodine without the use of mercury in any
form. This preparation uses the method recently employed
4 3
Me H) U with alkyl and aryl halides for comparison with
(C Me ) U reactions has led to a more atom-efficient
5
5 3
4
6-48
to make highly reactive divalent lanthanide diiodides by
synthesis of (C Me H) UCl,
3, the former precursor of
5
4
3
direct reaction of the elements.3
3-39
Not only is this route
(C Me H) U, as well as the first synthesis and structural
5
4
3
mercury-free, but it can be carried out in a few hours with
5 4 3
characterization of (C Me H) UI, 5. These studies also
rather inexpensive equipment. In addition, solvation of UI
to form the popular trivalent starting material UI (THF)
proceeds smoothly. The route to UI (THF)
more efficient than previously reported syntheses
in terms of overall yield and in terms of uranium waste
generated.
3
5 4 2 2
resulted in the isolation of (C Me H) UCl , 6, the analogue
3
4
of a valuable starting material in pentamethylcyclopenta-
1-5,49-51
3
4
reported here is
5 5 2 2
dienyl uranium chemistry, namely (C Me ) UCl .
1
3-15
both
Experimental Section
General Experimental. The complexes described here are
extremely air- and moisture-sensitive. The syntheses and manipula-
tions of these compounds were conducted with rigorous exclusion
of air and water by Schlenk, vacuum line, and glovebox techniques.
Except where noted, all glovebox manipulations were carried out
in an argon-filled glovebox that was free of coordinating solvents.
THF, benzene, toluene, and hexanes were saturated with Ar and
This alternative synthesis of UI
3
was developed as part of
Me U,
vis- a` -vis the slightly less crowded complex
our examination of the reaction chemistry of (C
5
5 3
)
2
9,40-45
1
,
(
(
(
(
23) Monteiro, B.; Roitershtein, D.; Ferreira, H.; Ascenso, J. R.; Martins,
A. M.; Domingos, Aˆ .; Marques, N. Inorg. Chem. 2003, 42, 4223.
24) Berthet, J.-C.; Nierlich, M.; Ephritikhine, M. Chem. Commun. 2004,
passed through a GlassContour column.52 Benzene-d
Isotope Laboratories) was distilled over a NaK alloy and benzophe-
none. C Me (Aldrich) was distilled at 140 °C as a colorless
870.
6
(Cambridge
25) Karmazin, L.; Mazzanti, M.; Bezombes, J.-P.; Gateau, C.; P e´ caut, J.
Inorg. Chem. 2004, 3, 5147.
5
4 2
H
26) Maria, L.; Campello, M. P.; Domingos, Aˆ .; Santos, I.; Andersen, R.
liquid and dried over Type 4 activated molecular sieves. PhCl, PhI,
J. Chem. Soc., Dalton Trans. 1999, 2015.
(
(
(
27) Dro z˘ d z˘ y n´ ski, J.; Preez, J. G. H. Inorg. Chim. Acta 1994, 218, 203.
28) Cloke, F. G. N.; Hitchcock, P. B. J. Am. Chem. Soc. 2002, 124, 9352.
29) Evans, W. J.; Kozimor, S. A.; Ziller, J. W. J. Am. Chem. Soc. 2003,
and t-BuCl (Aldrich) were dried over Type 4 activated molecular
sieves. Benzene-d , C Me H , PhCl, PhI, and t-BuCl were all
6 5 4 2
1
25, 14264.
30) Levy, J. H.; Taylor, J. C.; Wilson, P. W. Acta Crystallogr., Sect. B
975, B31, 880.
(
(43) Evans, W. J.; Kozimor, S. A.; Nyce, G. W.; Ziller, J. W. J. Am. Chem.
Soc. 2003, 125, 13831.
1
(
(
(
(
(
31) Zachariasen, W. H. Acta Crystallogr. 1948, 1, 265.
32) Corbett, J. D. Inorg. Synth. 1983, 22, 31.
33) Bochkarev, M. N.; Fagin, A. A. Russ. Chem. Bull. 1999, 48, 1187.
34) Bochkarev, M. N.; Fagin, A. A. Chem.sEur. J. 1999, 5, 2990.
35) Katkova, M. A.; Fukin, G. K.; Fagin, A. A.; Bochkarev, M. N. J.
Organomet. Chem. 2003, 682, 218.
(44) Evans, W. J.; Kozimor, S. A.; Ziller, J. W. Polyhedron 2004, 23, 2689.
(45) Evans, W. J.; Kozimor, S. A.; Ziller, J. W.; Kaltsoyannis, N. J. Am.
Chem. Soc. 126, 2004, 14533.
(46) Parry, J.; Carmona, E.; Coles, S.; Hursthouse, M. J. Am. Chem. Soc.
1995, 117, 2649.
(47) Conejo, M. D.; Parry, J. S.; Carmona, E.; Schultz, M.; Brennan, J.
G.; Beshouri, S. M.; Andersen, R. A.; Rogers, R. D.; Coles, S.;
Hursthouse, M. Chem.sEur. J. 1999, 5, 3000.
(36) Bochkarev, M. N.; Khoroshenkov, G. V.; Schumann, H.; Dechert, S.
J. Am. Chem. Soc. 2003, 125, 2894.
(
37) Balashova, T. V.; Khoroshenkov, G. V.; Kusyanev, D. M.; Eremenko,
I. L.; Aleksandrov, G. G.; Fukin, G. K.; Bochkarev, M. N. Russ. Chem.
Bull. Int. Ed. 2004, 53, 825.
(48) Cloke, G. F. N.; Hawkes, S. A.; Hitchcock, P. B.; Scott, P.
Organometallics 1994, 13, 2895.
(49) Manriquez, J. M.; Fagan, P. J.; Marks, T. J. J. Am. Chem. Soc. 1978,
100, 3939.
(50) Fagan, P. J.; Manriquez, J. M.; Maata, E. A.; Seyam, A. M.; Marks,
T. J. J. Am. Chem. Soc. 1981, 103, 6650.
(
38) Bochkarev, M. N. Coord. Chem. ReV. 2004, 248, 835.
(
39) Evans, W. J.; Allen, N. T.; Workman, P. S.; Meyer, J. C. Inorg. Chem.
2003, 42, 3097.
(
(
(
40) Evans, W. J.; Forrestal, K. J.; Ziller, J. W. Angew. Chem., Int. Ed.
Engl. 1997, 36, 774.
41) Evans, W. J.; Nyce, G. W.; Ziller, J. W. Angew. Chem., Int. Ed. 2000,
(51) Spirlet, M. R.; Rebizant, J.; Apostolidis, C. Acta Crystallogr., Sect C
1992, C48, 2135.
(52) THF and diethyl ether were dried over activated alumina and sieves.
Toluene and n-hexanes were dried over Q-5 and molecular
sieves. For more information on the drying system, see www.
glasscontour.com.
39, 240.
42) Evans, W. J.; Nyce, G. W.; Johnston, M. A.; Ziller, J. W. J. Am. Chem.
Soc. 2000, 122, 12019.
3994 Inorganic Chemistry, Vol. 44, No. 11, 2005

Facile Syntheses of UnsolWated Uranium Halides
3 2
degassed by three freeze-pump-thaw cycles. KN(SiMe ) (Ald-
rich) was crystallized from toluene and washed with hexane before
-
5
use. HgCl
2
and HgI
2
(Aldrich) were dried under vacuum (2 × 10
Torr). i-PrMgCl (Aldrich) was obtained as a 2 M solution in diethyl
ether and used as received. Uranium turnings, submerged in mineral
oil (Manufacturing Science Corporation, Oak Ridge, Tennessee)
were cut with tin snips into small pieces to ensure uniform heating.
Caution: uranium turnings can spark! To remove the mineral oil,
the turnings were washed with hexane followed by acetone and
then H
procedures.14 (C
described. NMR experiments were conducted with Bruker 400 or
00 MHz spectrometers. IR samples were analyzed as thin films
2
O. The turnings were then cleaned according to the literature
53
6
5
5 3 4
Me ) U and UCl were prepared as previously
5
54
from benzene using an ASI ReactIR1000. Elemental analyses were
provided by Analytische Laboratorien, Lindlar, Germany.
KC
toluene (10 mL) was added to a solution of KN(SiMe
.010 mmol) in toluene (10 mL). The reaction mixture was stirred
5
Me
4
H. A solution of C
5
Me
H
4 2
(0.98 g, 0.008 mmol) in
3 2
)
(1.955 g,
0
for 12 h, the solution was centrifuged, and the insoluble yellow/
white solids were washed with toluene until all of the yellow
contaminant was removed. White KC
obtained after drying under a vacuum.
Me H)MgCl‚THF. A solution of C
5
Me
5
H (1.183 g, 92%) was
(C
5
4
5
Me (629 mg, 5.2
4 2
H
mmol) in toluene (50 mL) was cannulated into a Schlenk flask
equipped with a condenser containing gelatinous i-PrMgCl made
by removal of the solvent from i-PrMgCl (2.6 mL, 5.2 mmol) in
diethyl ether. The reaction mixture was lowered into an oil bath at
Figure 1. Apparatus used to make the UI3.
dried under a vacuum. The flask was filled with argon, the Tygon
tubing was clamped shut with its surgical clamp, and the assembly
was detached from the Schlenk line and weighed (1.350 g of U,
100 °C, and white solids immediately precipitated. After 4 h, the
flask was cooled to room temperature and the solvent was removed
under a vacuum. THF was added to the flask in a glovebox, and
the THF insoluble solids were removed by centrifugation. The
solvent was removed from the slightly yellow THF solution by
rotary evaporation, leaving a pale yellow solid. The solid was
0.0056 mol).
Using standard Schlenk methods under Ar, the U-containing flask
1 was attached to the glass tee that was connected to the Schlenk
#
line as depicted in Figure 1. An inert atmosphere was established
in the apparatus. Under a strong flow of argon, flask #2 was replaced
with a glass stopper while it was quickly charged with finely ground
washed once with toluene, and (C
was isolated as a white solid after being dried under a vacuum. H
NMR (C ): δ 5.7 (s, 1H, C Me H), 3.6 (s, 4H, THF), 2.3 (s,
H), 2.1 (s, 6H, C Me H), 1.3 (t, br, 4H, THF).
H) . In a flask wrapped in aluminum foil, HgCl
.125 mmol) and KC Me H (41 mg, 0.226 mmol) were stirred in
5 4
Me H)MgCl‚THF (995 mg, 76%)
1
2
I (1.848 g, 0.0784 mol). Flask #2 was then reattached to the
D
6 6
5
5
apparatus in place of the glass stopper. By using clamp #2 to
oscillate between dynamic and static vacuum, the iodide was cooled
with a liquid-nitrogen bath and degassed by three freeze-pump-
thaw cycles.
With clamp #2 closed and the iodine flask #2 under a static
vacuum, clamp #1 was removed, exposing the U turnings to a
dynamic vacuum. The turnings were heated with a natural gas/
oxygen torch, taking care to keep the temperature below the melting
point of the glass while the vacuum gauge on the Schlenk line was
used to monitor the uranium for outgassing. The uranium turnings
both outgassed and blackened upon heating. When no further
outgassing was observed, clamps #1 and #3 were closed while the
uranium containing vessel, flask #1, was kept hot. Clamp #2 was
5
6H, C Me
5
5
4
(C
5
Me
4
2
2
(34 mg,
0
5
4
toluene (10 mL) for 12 h. A pale yellow solution was separated
from a yellow insoluble oil, a white precipitate, and a small amount
of Hg metal. The solvent was removed from the pale yellow solution
by rotary evaporation, and (C
5
Me
solid (30 mg, 99%). H NMR: δ 6.10 (s), 6.01 (s), 5.97 (s), 5.83
d), 5.69 (d), 1.99 (s), 1.89 (s), 1.82 (d), 1.80 (d), 1.80 (s), 1.78 (s),
.73(d), 1.69 (t), 1.66 (s,br), 1.63 (s,br), 1.60 (t), 1.59 (m), 1.57
s,br), 1.51 (s,br), 1.21 (s), 1.18 (d), 1.16 (s), 1.15 (s), 1.13 (d),
.11 (s). GC-MS m/z: 242.3.
UI . UI was prepared in an apparatus comprised of simple 20
4 2
H) was isolated as a white waxy
1
(
1
(
1
3
3
opened, a small amount of I
2
was shaken into the tee, and clamp
mL Schlenk tubes whose necks were typically 10 cm long. These
Schlenk tubes were connected by pieces of Tygon tubing, 5 cm in
length, whose openings were controlled by surgical clamps as shown
in Figure 1. This provided a flexible apparatus that allowed a grease-
free addition of solids to the hot reaction tube. The uranium turnings,
cleaned as described above, were transferred into the Schlenk tube
labeled flask #1. Flask #1, the Tygon tube to which it was attached,
and its surgical clamp had all been preweighed. Flask #1 was
attached to a Schlenk line with Tygon tubing, and the turnings were
#
2 was closed. Clamp #1 was quickly opened and closed so that
2
only small portions of I fell into flask #1. The contents of the
tube glowed red, and heating continued. Caution: It is important
that a high temperature is maintained in the bottom of flask #1
and that the I
2
addition is slow. If the flask is not hot enough or
will sublime in the top of
too much I is added at one time, the I
2
2
the flask rather than react. This can cause increased pressure that
ruptures the apparatus at the weakest point, the Tygon tube
connection to the tee.
Iodine was added repeatedly in small portions as described above.
(
53) Evans, W. J.; Nyce, G. W.; Forrestal, K. J.; Ziller, J. W. Organo-
metallics 2002, 21, 1050.
When all of the I
had stopped, heating ceased and flask #1 was slowly cooled to room
temperature. The flask containing the UI and unreacted uranium
2
was added and the glowing in the reaction tube
(54) Evans, W. J.; Johnston, M. A.; Clark, R. D.; Ziller, J. W. Inorg. Chem.
2000, 39, 3421.
3
Inorganic Chemistry, Vol. 44, No. 11, 2005 3995

Evans et al.
metal was lowered into a liquid-nitrogen bath, and the vessel was
exposed to a dynamic vacuum by removing clamps #1 and #3. The
pressure change was monitored to determine if noncondensable
gases were present. Clamp #3 was subsequently closed and clamp
C
6
D
6
(1 mL) in an NMR tube. A color change to red occurred
1
upon addition of the aryl halide, and the H NMR spectrum
indicated quantitative formation of the previously characterized
(C Me H) UCl
46-48
5
4
3
6 5 2
as well as resonances consistent with (C H ) .
#
2 was opened, isolating the entire apparatus under a static vacuum.
The iodine-containing tube was gently heated with the torch, and
any remaining I was sublimed under a vacuum into flask #1.
5 4 3
(C Me H) UCl shows no sign of reactivity with an additional
equivalent of C H Cl after 12 h at 65 °C or after 24 h in neat C H -
6
5
6
5
2
Cl at room temperature.
Me H) UI, 5, from HgI
synthesis of 3 from HgCl , (C Me
was reacted with HgI (32 mg, 0.070 mmol) in toluene (10 mL) to
form a red solution. (C Me H) UI (91 mg, 88%) was isolated as a
red powder. X-ray quality crystals of (C Me H) UI were obtained
from saturated solutions in toluene at -35 °C. H NMR (C
Clamps #2 and #1 were closed, and flask #1 was slowly warmed
to room temperature. Flask #1 was heated until its contents seemed
to melt. After it appeared that all of the I had reacted and there
2
was no further glowing in flask #1, the flask was cooled to room
temperature and sealed under a vacuum. The flask was then lowered
into a liquid-nitrogen bath, and the UI
(C
5
4
3
2
. As described above for the
H) U (87.3 mg, 0.145 mmol)
2
5
4
3
2
5
4
3
5
4
3
3
was knocked off of the
1
H ,
6 6
walls of the flask by carefully tapping the cold flask with a rubber
hose. The tube was brought into an argon-filled glovebox that was
2
9
98 K): δ 37.9 (s, 9H, C
H, C Me H), -7.9 (s, 3H, C
): 2961m, 2922m, 2856m, 1602w, 1451w,
413w, 1382w, 1262s, 1089s, 1019s, 864m, 799s, 698m, 675m
5
Me
4
H), 16.5 (s, 9H, C
5
Me
4
H), 13.2 (s,
5
4
5
Me H), -36.3 (s, 9H, C
4
5
Me H). IR
5
free of coordinating solvents and broken open. UI
a dark purple powder (3.084 g, 89%; based on uranium). Anal.
Calcd for UI : U, 38.5; I, 61.5. Found: U, 38.8; I, 61.3. In the
event that the reaction does not go to completion, uranium metal
will be present in excess. The UI can be easily separated from
3
was isolated as
6 6
(thin film from C H
1
3
-1
cm . Anal. Calcd for C27
7.43. Found: C, 43.77; H, 5.32; U, 33.46; I, 17.94.
Me H) UI, 5, from C I. As described above for the
synthesis of 3 from C Cl, C I (2.0 µL, 0.018 mmol) was
reacted with (C Me H) U (11.0 mg, 0.018 mmol) in C (1 mL)
to form a red solution. After 2 h, the H NMR spectrum indicated
quantitative conversion to (C Me H) UI as well as resonances
consistent with (C . (C Me H) UI shows no sign of reactivity
with an additional equivalent of C I, even after 12 h at 65 °C,
and is stable in neat C I.
(C Me H) UCl , 6, from HgCl
12 mg, 0.019) in toluene (2 mL) was added to HgCl
H39UI: C, 44.53; H, 5.36; U, 32.69; I,
1
3
(C
5
4
3
6 5
H
any unreacted residual metal as the THF solvate, UI
extraction with THF.
3 4
(THF) , by
H
6 5
6 5
H
5
4
3
6 6
D
(C Me
5
4
H)
3
U, 1, from UI
3
. Toluene (15 mL) was added to an
(34.9
1
intimate mixture of KC
5
Me H (28.9 mg, 0.180 mmol) and UI
4
3
5
4
3
mg, 0.056 mmol) and stirred for 24 h. White and black solids were
removed from the green-brown solution by centrifugation. Upon
removal of the solvent by rotary evaporation, the previously
characterized (C
green-brown powder. The H NMR spectrum and the unit cell
H
6 5
)
2
5
4
3
6 5
H
6 5
H
4
6,47
5
Me
4
H)
3
U
(24 mg, 71%) was isolated as a
1
5
4
2
2
2 5 4 3
. A solution of (C Me H) UCl
(
2
(3 mg, 0.010
parameters obtained from crystals grown in toluene at -35 °C
matched literature values.46,47
mmol) in a flask that had been wrapped with tape to exclude light.
After the reaction was stirred for 12 h, a gray solid was removed
by centrifugation. The solvent was removed by rotary evaporation,
(C
5
Me
that contained coordinating solvents, UI
dissolving UI in THF followed by centrifugation and then removal
of the solvent by rotary evaporation. A purple suspension of UI
4 3
H) U, 1, from UI
3
(THF)
4
. In a nitrogen-filled glovebox
3
(THF) was prepared by
4
leaving a red powder that was subsequently washed with (Me
Si) O. The red washings were discarded, the red powder was dried
under a vacuum, and (C Me H) UCl (9 mg, 82%) was isolated. A
common contaminant in this reaction is unreacted (C Me H) UCl.
X-ray quality crystals of (C Me H) UCl readily form overnight
from hot toluene solutions slowly cooled to -35 °C. H NMR
(C , 298 K): δ 47.0 (s, 12H, C Me H), -16.4 (s, 12H, C Me H),
55.1(s, 2H, C Me H). IR (thin film from C ): 2961m, 2926m,
856m, 1586vw, 1382w, 1258s, 1089s, 1019s, 864w, 795s, 698w
3
-
3
2
3
-
5
4
2
2
(THF)
4
(472 mg, 0.520 mmol) in toluene (10 mL) was added to
H (250 mg, 1.560 mmol). The mixture was stirred for 12
5
4
3
KC
5
Me
4
5
4
2
2
h, and the color slowly changed to green-brown. White insoluble
solids were removed by centrifugation, and the previously char-
acterized (C Me H)
spectroscopy, was isolated as a green-brown powder upon removal
of the solvent by rotary evaporation. Crystals obtained from
saturated solutions of (C
identical unit cell parameters as those in the literature.
Me H) UCl, 3, from t-BuCl. t-BuCl (7.6 µL, 0.068 mmol)
was added to (C Me H) U (41 mg, 0.068 mmol) in toluene (10
1
U (288 mg, 92%), identified by 1H NMR
D
6 6
5
5
5
5
5 4 3
-
5
4
6 6
H
2
-
1
2
cm . Anal. Calcd for C18H26Cl U: C, 39.21; H, 4.71; Cl, 12.86;
5 4 3
Me H) U in toluene at -35 °C had
4
6,47
U, 43.17. Found: C, 39.12; H, 4.69; Cl, 12.69; U, 43.02. When
1
this reaction was followed by H NMR spectroscopy, resonances
(C
5
4
3
consistent with (C
5
Me
4
H)
2
were observed.
5
4
3
(C
5
Me H) UCl
4
2
2
, 6, from (C
5
Me H)MgCl‚THF. In a nitrogen-
4
mL). The solution immediately changed to red. After the solution
had been stirred for 12 h, the solvent and any organic products
that had formed during the reaction were removed by rotary
filled glovebox that contained coordinating solvents, toluene (50
mL) was added to a Schlenk flask that contained an intimate mixture
UCl4
6-48
was isolated as a red powder
of (C Me H)MgCl‚THF (8.601 g, 0.034 mol) and UCl (6.352 g,
evaporation, and (C
5
Me
4
H)
3
5
4
4
1
0.017 mol). The Schlenk flask was equipped with a condenser,
attached to a Schlenk line, and heated at 100 °C. The mixture
immediately turned cherry red. After 48 h, the solvent was removed
under a vacuum, the reaction flask was brought into an argon-filled
glovebox, and benzene (125 mL) was added. A white insoluble
solid was removed from the red solution by filtration. The extraction
process was repeated (three times), the extracted fractions were
combined into a Schlenk flask, and the flask was attached to a
vacuum line. The solvent was removed under a vacuum to give
(48 mg, 100%). The H NMR spectrum in toluene-d
8
matched
Me H),
4
6-48 1
literature values.
H NMR (C
6
D
6
): δ 33.6 (s, 9H, C
5
4
-
10.9 (s, 9H, C
Me H), -34.9 (s, 9H, C
Me H) UCl, 3, from HgCl
mg, 0.077 mmol) in toluene (7 mL) was added to HgCl
.037 mmol) in a flask that had been wrapped with tape to exclude
5
Me
4
H), 9.7 (s, 9H, C
5
Me
4
H), -1.9 (s, 3H, C
5
-
4
5
Me H).
4
(C
5
4
3
2
. A solution of (C
5
Me
4
H)
3
U (46
2
(10 mg,
0
light. After the solution had been stirred for 12 h, gray insoluble
solids were removed by centrifugation and the solvent was removed
by rotary evaporation. (C
powder (48 mg, 98% yield).
Me H) UCl, 3, from C
was added to a solution of (C
6-48
5 4 2 2
(C Me H) UCl (7.118 g, 78%) as a red solid.
5
Me
4
H)
3
UCl4
was isolated as a red
(C Me ) UCl, 4, from t-BuCl. As described above for the
5
5 3
(C
5
4
3
6 5
H
Cl. C Cl (1.3 µL, 0.013 mmol)
6
H
5
synthesis of 3 from t-BuCl, (C
5 5 3
Me ) U (150 mg, 0.233 mmol) was
5
Me H) U (7.7 mg, 0.013 mmol) in
4
3
reacted with t-BuCl (28 µL, 0.244) to form a red solution. After
3996 Inorganic Chemistry, Vol. 44, No. 11, 2005

Facile Syntheses of UnsolWated Uranium Halides
Table 1. Crystal Data and Structure Refinement for (C5Me4H)3UI, 5,
and (C5Me4H)2UCl2, 6
from a difference Fourier map and refined (x, y, z and Uiso). At
convergence, wR2 ) 0.0292 and GOF ) 1.136 for 80 variables
refined against 1184 data points (0.76 Å resolution). As a
comparison for refinement on F, R1 ) 0.0121 for those 1166 data
points with I > 2.0σ(I).
5
6
empirical formula
fw
cryst syst
space group
a (Å)
C27H39IU
728.51
cubic
C18H26Cl2U
551.32
orthorhombic
Cmcm
17.7866(16)
6.7022(6)
15.6540(14)
90
90
90
1866.1(3)
4
I 4h 3d
Results
21.4984(10)
21.4984(10)
21.4984(10)
90
b (Å)
c (Å)
3 3
Synthesis of UI . Unsolvated UI can be made directly
from uranium turnings and iodine according to eq 2 in a
three-component apparatus, as shown in Figure 1.
R (deg)
â (deg)
γ (deg)
90
90
9936.2(8)
16
3
vol(Å )
2U + 3I f 2UI
(2)
2
3
Z
λ(Å)
0.710 73
1.948
7.788 mm
1.163
0.0184
0.0467
0.710 73
1.962
8.977 mm
1.136
0.0121
0.0292
3
Short lengths of Tygon tubing whose openings are controlled
by surgical pinch clamps provide a flexible arrangement in
which solid iodine can be slowly transferred, in a grease-
free environment, to a hot reaction vessel that contains the
uranium. Small amounts of iodine are added repeatedly to
the uranium turnings, which are heated with a torch. An
amber glow emanates from the reaction vessel as the uranium
is oxidized by iodine. The method generates multigram
densitycalcd (mg/m )
abs coeff
-
1
-1
2
GOF on F
a
R [I > 2σ(I)]: R1
b
R (all data): wR2
the solution was stirred for 3 h, the previously characterized (C
Me
UCl42 was isolated as a red powder (143 mg, 90%).
X-ray Data Collection, Structure Determination, and Refine-
ment. (C Me H) UI, 5. A dark red/ruby color crystal of ap-
5
-
5 3
)
5
4
3
quantities of unsolvated UI
from a procedure that can be completed within hours.
Synthesis of (C Me H) U, 2. (C Me H) U can be prepared
directly from unsolvated UI , eq 3, or from the THF solvate
UI (THF)
3
in high yield in powder form
proximate dimensions 0.16 × 0.22 × 0.24 mm was mounted on a
glass fiber and transferred to a Bruker CCD platform diffractometer.
The SMART55 program package was used for determination of the
5
4
3
5
4
3
unit-cell parameters and for data collection (25 s/frame scan time
for a sphere of diffraction data). The raw frame data was processed
using SAINT56 and SADABS to yield the reflection data file.
Subsequent calculations were carried out using the SHELXTL58
program. The diffraction symmetry was 4/mmm, and the systematic
absences were consistent with the tetragonal space group I 4h 3d,
which was later determined to be correct.
3
3
4
, eq 4, in high yield.
57
UI + 3KC Me H
8 (C Me H) U + 3KI
(3)
3
5
4
5
4
2
3
toluene
UI (THF) + 3KC Me H toluene8 (C
Me
2
H)
U + 3KI +
4THF (4)
In the past, 2 was synthesized by reduction of (C Me H) -
3
4
5
4
5
4
3
The structure was solved using the uranium coordinates from
the isomorphous uranium chloride complex and refined on F by
2
full-matrix least-squares techniques (see Table 1 for crystallographic
data and structure refinement). The analytical scattering factors59
for neutral atoms were used throughout the analysis. Hydrogen atom
H(5) was located from a difference Fourier map and refined (x, y,
z and Uiso). The methyl hydrogen atoms were included using a riding
model. At convergence, wR2 ) 0.0467 and GOF ) 1.163 for 92
variables refined against 2074 data points. As a comparison for
refinement on F, R1 ) 0.0184 for those 1885 data points with I >
5
4
3
4
6,47
UCl with sodium naphthalenide in THF.
H (M ) K46,47 or Li ) and
was, in turn, made from MC Me
5 4 3
(C Me H) UCl
48
5
4
UCl
uranium oxides.
4
, which was obtained from hexachloropropene and
6-8
A representative multistep synthesis is
shown in Scheme 1. The new routes to complex 2, eqs 3
and 4, are advantageous over the previous syntheses, Scheme
1, because (C Me H) U can be made more directly and in
5 4 3
2
.0σ(I). The absolute structure was assigned by refinement of the
Flack parameter.
6
0
higher yield. In addition, 2 can be made with rigorous
exclusion of coordinating solvents, like THF, if desirable,
eq 3.
5 4 2 2
(C Me H) UCl , 6. A red crystal of approximate dimensions 0.08
×
0.14 × 0.24 mm was handled as described above for 5. The
diffraction symmetry was mmm, and the systematic absences were
consistent with the orthorhombic space group Cmcm, which was
later determined to be correct. The structure was solved by direct
Synthesis of (C Me H) UCl, 3, and (C Me ) UCl, 4.
5
4
3
5
5 3
Both (C Me H) U and (C Me ) U react with alkyl, aryl, and
5
4
3
5
5 3
2
methods and refined on F by full-matrix least-squares techniques
mercuric chlorides to form the corresponding tris(cyclopen-
tadienyl) uranium chlorides, eq 5 and 6 (R ) Me or H; R′
(
see Table 1). The analytical scattering factors59 for neutral atoms
were used throughout the analysis. Hydrogen atoms were located
)
Ph or t-Bu). In the (C
5 4 3
Me R) U reaction with PhCl, the
(
C
5
Me R) UCl complex is formed quantitatively. The major
4
3
(
(
(
(
(
55) SMART Software User’s Guide, version 5.1; Bruker Analytical X-ray
1
Systems, Inc.: Madison, WI, 1999.
56) SAINT Software User’s Guide, version 6.0; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1999.
57) Sheldrick, G. M. SADABS, version 2.05; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
58) Sheldrick, G. M. SHELXTL, version 6.12; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
59) International Tables for X-ray Crystallography; Wilson, A. J. C., Ed.;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.
organic product identified by H NMR spectroscopy was
Scheme 1
(60) Flack, H. D. Acta Crystallogr., Sect. A 1983, A39, 876.
Inorganic Chemistry, Vol. 44, No. 11, 2005 3997

Evans et al.
Table 2. Selected Bond Distances (Å) and Angles (deg) for
(C5Me4H)3UI, 5, and (C5Me4H)2UCl2, 6
Complex 5
Complex 6
U(1)-I(1)
U(1)-C(1)
U(1)-C(2)
U(1)-C(3)
U(1)-C(4)
U(1)-C(5)
U(1)-Cnt
3.0338(5) U(1)-Cl(1)
2.5909(7)
2.646(3)
2.6861(18)
2.7470(19)
2.767(4)
2.901(4)
2.882(4)
2.755(4)
2.669(4)
2.524
U(1)-C(1)
U(1)-C(2)
U(1)-C(3)
Cl(1)-U(1)-Cl(1A)
U(1)-Cnt
Cnt-U(1)-Cnt
Cnt-U(1)-Cl(1)
99.79(3)
2.418
133.1
Cnt-U(2)-Cnt 117.5
Cnt-U(1)-I(1) 99.2
104.8
of the structurally similar (C
5
Me
4
H)
and THF ) complexes. For example, the
H NMR spectrum of (C Me H) UCl has four methyl
resonances at δ ) 33.6, 10.9, 9.7, and -34.9 ppm. In
3 5 4 3
UCl and (C Me H) -
4
6,47
29
UL (L ) CO
1
5
4
3
1
5
contrast, the H NMR spectrum of the parent molecule, (C -
U, displays only two methyl resonances.4
6,47
Me
4 3
H)
Complex 5 is stable at 70 °C in C
6 6
D
and does not react
Figure 2. Thermal ellipsoid plot of (C5Me4H)3UI, 5, drawn at the 50%
probability level.
with coordinating solvents such as THF or ether. It is also
stable in neat PhI.
biphenyl.42,61,62 To obtain pure (C
5 4 3
Me R) UCl, the organic
byproducts must be separated in an extraction step that results
in decreased yields. Hence, when compared to PhCl, the
Structure of (C
phous with the chloride analogue (C
ring centroid)-U-I and 117.5° (ring centroid)-U-(ring
centroid) angles in 3 give it a distorted-tetrahedral geometry
5
Me
4
H)
3
UI, 5. (C
5
Me
4
H)
3
UI is isomor-
48
5
Me
4
H)
3
UCl. The 99.2°
(
HgCl
Me
organic byproducts, respectively, can be easily separated.
2
or t-BuCl reagents are superior in the synthesis of
4
8
similar to that found in (C
5
Me
4
H)
Me
-p-OMe, or THF ) complexes (Table 2). Complex
cannot be compared with the pentamethyl analogue (C
3
UCl and other crystal-
(C
5
4
3
R) UCl complexes because the Hg and volatile
4 3
H)
UL (L ) CO,4
6,47
lographically characterized (C
5
47
29
6 4
CNC H
5
5
-
4
2
Me
5
)
3
UI because this reactive species has not yet been
Me H) UI is structur-
ally different from crystallographically characterized (C
characterized by X-ray diffraction. (C
5
4
3
5
-
-
4
3
29
42
5 3 5 5 3 2 5 5 3 5 5
Me ) U(CO), (C Me ) U(N ), (C Me ) UF, (C Me )
3
4
2
63
UCl, and (C
maintain a trigonal arrangement around the metal center with
20° (ring centroid)-An-(ring centroid) angles. The fourth
5 5 3
Me ) ThH complexes whose ring centroids
1
ligand in each case is located on the 3-fold axis perpendicular
to the trigonal plane with a 90° (ring centroid)-An-(fourth
ligand) angle.
Synthesis of (C
HgI according to eq 7 to form (C
our knowledge, has not been previously identified in the
literature. Like (C Me H) UCl, it can also be prepared from
PhI and (C Me H) U.
5
Me
4
H)
3
UI, 5. (C
5
Me
4
H)
3
U reacts with
The 2.52 Å U-(ring centroid) distance in 5 is similar to
2
5
Me
4
H)
3
UI, 5, which, to
those in the trivalent (C
Å, as well as those in the tetravalent (C
.520 Å. The five unique U-C(C Me
a wide range, 2.699(4)-2.901(4) Å, and are very similar to
those of (C Me H)
UCl, 2.658(11)-2.911(10) Å.48 The
shortest U-C(C Me H) distance involves the H-substituted
C(5) ring carbon, whereas the longest U-C(C Me H)
distances involve the C(2) and C(3) carbons, which are
furthest from C(5). The longest U-C(C Me H) bond dis-
tances in 5 are similar to those in the sterically crowded (C
Me UCl complex, 2.780(6)-2.899(9) Å. The shorter
distances are similar to those in less crowded complexes,
for example, the 2.69(2)-2.78(3) Å U-C(C ) lengths in
UI. The 3.0338(5) Å U-I distance in 5 is similar
5
Me
4
H)
3
U parent molecule, 2.523
Me H) UCl complex,
H) distances in 5 span
5
4
3
5
4
3
2
5
4
5
4
3
5
4
3
5
4
5
4
5
4
5
-
5 3
)
To confirm the identity of 5, it was characterized by X-ray
1
diffraction, Figure 2. The H NMR spectrum of 5 in benzene-
5 5
H
d contains four methyl resonances at δ ) 37.9, 16.5, 13.2,
6
6
4
1
5 5 3
(C H )
and -36.3 ppm, which is consistent with the H NMR spectra
(
61) Finke, R. G.; Hirose, Y.; Gaughan, G. J. Chem. Soc., Chem. Commun.
981, 232.
62) Finke, R. G.; Schiraldi, D. A.; Hirose, Y. J. Am. Chem. Soc. 1981,
03, 1875.
(63) Evans, W. J.; Nyce, G. W.; Ziller, J. W. Organometallics 2001, 20,
5489.
(64) Rebizant, J.; Spirlet, M. R.; Apostolidis, C.; Kanellakopulos, B. Acta
Crystallogr., Sect. C 1991, C47, 854.
1
(
1
3998 Inorganic Chemistry, Vol. 44, No. 11, 2005

Facile Syntheses of UnsolWated Uranium Halides
4 5 4
salts. Thus, UCl reacts with (C Me H)MgCl‚THF to form
6
, eq 11.
Figure 3. Left: Thermal ellipsoid plot of (C5Me4H)2UCl2, 6, drawn at
the 50% probability level. Right: Ball-and-stick representation of (C5Me5)2-
3
5
UCl2.
Structure of (C
Me H) UCl can be compared with those of (C
; [(1,3-Me
; and [(1,2-t-Bu)
5 4 2 2 5
Me H) UCl , 6. The structure of (C -
Me
5
)
]
2
UCl
UCl
2
,5
1
9 7 3
to the 3.059(2) Å distance in (C H )
UI65 and the 3.041(1)
4
2
2
5
6
6,67
66
7
9
3
Si)
2
C
5
H
C
3
]
2
UCl
2
,
8; [(1,3-t-Bu)
2
C H
5 3
2
2
,
64
Å distance in (C
Synthesis of (C
UCl, which reacts with PhCl via sterically induced reduction
H
5 5
)
3
UI.
6
8
2
5
H
]
3 2
UCl
2
, 10. The U-(ring centroid)
5
Me R)
4
2 2 5 5 3
UCl , 6. In contrast to (C Me ) -
distance in 6 is 2.42 Å compared to 2.47, 2.44, 2.49, and
.43 Å for 7-10, respectively. The three unique U-C(C
Me H) bond lengths in 6 are 2.646(3), 2.6861(18), and
2
5
-
5
1
to make (C
less substituted (C
a solvent. However, the (C
with HgCl to form (C Me
5
Me
5
)
2
UCl
2
,
eq 8, PhCl is unreactive with the
UCl complex and can be used as
Me H) UCl complex does react
H) UCl , eq 9 and Figure 3, a
4
5
Me
4 3
H)
2.7470(19) Å, and they average 2.69(5) Å. In comparison,
7-10 have U-C bond distances that average 2.72(2),
2.72(1), 2.77(5), and 2.71(7) Å, respectively.
5
4
3
2
5
4
2
2
compound that has never before been synthesized to our
knowledge. The reaction in eq 9 generates black solids and
The (ring centroid)-U-(ring centroid) angle in 6 is 133.1°
compared to 132°, 124.85°, 128.1°, and 123.3° in 7-10,
respectively. The cyclopentadienyl rings in 6 are eclipsed
(C
5
Me
4
H)
2
, which can be removed from (C
5 4 2 2
Me H) UCl by
extraction with (Me
comparing its H NMR spectra and GC-MS data with that
3
Si) O. (C Me H) was identified by
2
5
4
2
similar to those in (C
5
Me
5
)
2
UCl
2
and [(1,2-t-Bu)
2 5
C
H
3
]
2
UCl
2
1
and in contrast to the structures of [(1,3-Me
3
Si) C H ] UCl
2 5 3 2
2
of a sample independently synthesized as shown in eq 10.
5
1,66-68
and [(1,3-t-Bu)
2
C
5 3
H ]
2
UCl
2
.
Although 6 and 7 have
1
The H NMR spectra indicate that multiple isomers of
eclipsed rings, they differ in the orientation of the rings to
5 4 2
(C Me H) are generated in both eqs 9 and 10.
2
+
the [UCl
2
]
units. As shown in Figure 3, the methyl groups
eclipse both of the chlorides in 6, whereas the methyl groups
in 7 are staggered with respect to the chlorides. This allows
the H-substituted carbon atoms, C(1) and C(1A), to be in
the most congested part of the metallocene substructure; C(1)
and C(1A) lie opposite the metallocene wedge and in the
plane defined by the ring centroids and the uranium ion. This
ring orientation is similar to that observed in rotationally
2 5 4 2 2
constrained metallocenes, such as in [Me Si(C Me ) ]UCl ‚
6
9
2
LiCl‚4(Et
The 2.5909(7) Å U-Cl distance and the 99.79(3)°
Cl(1)-U-Cl(1A) angle in 6 are similar to those in 7-10:
2
O).
5
1
66,67
2
2
9
.583(6) Å and 97.9(4)°; 2.579(2) Å and 95.3(1)°;
.577(4) Å and 91.0(2)°; and 2.591(4) Å, 2.576(4) Å, and
7.66(14)°, respectively.
6
6
6
8
Discussion
3
Unsolvated UI can be synthesized by direct reduction of
iodine by uranium turnings in simple Schlenk tubes without
the use of furnaces. This method offers advantages over other
1
3-15,28,30,31
procedures
3
in that it provides UI in high yield
via a mercury-free route using inexpensive equipment within
(65) Rebizant, J.; Spirlet, M. R.; Van Den Bossche, G.; Goffart, J. Acta
Crystallogr., Sect C 1988, C44, 1710.
(66) Lukens, W. W., Jr.; Beshouri, S. M.; Blosch, L. L.; Stuart, A. L.;
Andersen, R. A. Organometallics 1999, 18, 1235.
HgCl + 2KC Me H
8 (C Me H) + Hg + 2KCl
5 4 2
2
5
4
(67) Blake, P. C.; Lappert, M. F.; Taylor, R. G.; Atwood, J. L.; Hunter,
toluene
(10)
W. E.; Zhang, H. J. Chem. Soc., Dalton Trans. 1995, 3335.
(
68) Hughes, R. P.; Lomprey, J. R.; Rheingold, A. L.; Haggerty, B. S.;
Yap, G. P. A. J. Organomet. Chem. 1996, 517, 89.
69) Schnabel, C. R.; Scott, B. L.; Smith, W. H.; Burns, C. J. J. Organomet.
Chem. 1999, 591, 14.
Like other dichlorouranium metallocenes,4
9-51,66
5 4 2
(C Me H) -
(
UCl can also be made from cyclopentadienyl magnesium
2
Inorganic Chemistry, Vol. 44, No. 11, 2005 3999

Evans et al.
UCl reacts with HgCl via a
ligand exchange reaction. Because KC Me H reacts with
HgCl to form (C Me H) , transmetalation between (C
Me H) UCl and HgCl to form an unstable (C Me H) Hg
intermediate could also explain the products.
In any case, the reaction of (C Me H) UCl with HgCl
provides a useful way to generate (C Me H) UCl for the
hours. The unsolvated UI
toluene, with KC Me H to make (C
coordinating solvents. UI can also be readily converted to
the popular UI (THF) reagent
green oily contaminants.
The synthesis of (C Me
3
reacts in nonpolar solvents, like
also possible that (C
5
Me
4
H)
3
2
5
4
5
Me H) U free of
4
3
5
4
3
2
5
4
2
5
-
13,14
3
4
without the formation of
4
3
2
5
4
2
1
3,14
5
4
H)
3
U from UI
3
or UI
3
(THF)
4
is
5
4
3
2
an improvement over previous synthetic routes that were
based on reduction of tetravalent precursors originating from
5
4
2
2
first time. Syntheses of bis(cyclopentadienyl) uranium dichlo-
46-48
49,50,66-68
UCl
4
.
5
(C Me
4 3
H) U can subsequently be used to prepare
ride complexes, in general, are not straightforward.
(
(
C
C
5
Me
Me
4
H)
H)
3
UCl in quantitative yield. This synthetic route to
UCl proceeds with an 82% overall yield from the
For example, (C
5 5 2 2 4
Me ) UCl is not prepared simply from UCl
and KC Me . In practice, magnesium reagents are typically
5
5
5
4
3
uranium turnings compared to a 33% yield based on uranium
used. Because the alternative mercuric salt method, exempli-
fied in eq 9, proceeds with complexes that contain normal
bond distances, this approach may provide entrance into other
(ancillary ligand) UCl complexes that are not synthetically
2 2
available via ionic metatheses with alkali or alkaline earth
salts.
46-48
in the previous synthesis from uranium oxides.
The reductions of PhCl, t-BuCl, and HgCl by (C
to form (C Me H) UCl, eqs 6 and 7, as well as the reduction
of HgI and PhI by (C Me H) U to form (C Me H) UI, eq
, are consistent with the one-electron reduction chemistry
2
5 4 3
Me H) U
5
4
3
2
5
4
3
5
4
3
7
6
1,62,70-75
previously observed for trivalent uranium.
Me H) UI can be crystallographically characterized, whereas
the sterically more-crowded pentamethyl analogue, (C Me
UI, readily decomposes to (C Me UI at room temperature.
In contrast to their (C Me UX analogues, the (C Me H)
(C
5
-
5 4 2 2
The synthetic accessibility of (C Me H) UCl , which can
also be synthesized from (C Me H)MgCl‚THF and UCl ,
5
4
4
4
3
1
-
5
)
3
4
-
provides further opportunities to compare (C
5
Me
5
)
versus
5
2
1-
)
5 2
5 4
(C Me H) chemistry with uranium. These ligands clearly
5
5
)
3
5
4
3
-
have different chemistry in tris(cyclopentadienyl) com-
5
2
9,40-45
UX complexes do not decompose in THF or in alkyl halides
such as PhX and t-BuCl. This suggests that the reactivity of
plexes,
Me R)
the (C
5
but this may also be true with the [(C -
U]2 metallocenes. For example, the recent use of
+
4
2
-
1-
(C
5
Me
4
R)
3
UX (R ) H, Me; X ) Cl, I) complexes relates to
5
Me
4
H)1 versus (C
5 5
Me )
ligand has had a significant
76-79
the amount of steric crowding: the less sterically crowded
complexes are more stable.
impact in early transition-metal dinitrogen chemistry.
Conclusion
Interestingly, (C
Me H) UCl , eq 9, in a reaction similar to the sterically
induced reduction of HgCl by (C Me UCl to form (C
Me UCl . As in the (C Me UCl chemistry, a cyclopen-
tadienyl dimer is also observed as a byproduct. If the reaction
in eq 9 does involve a ligand-based reduction with a (C
5 4 3 2
Me H) UCl does react with HgCl to form
3
The solid-state synthesis of UI described here provides a
simple and inexpensive entrance into trivalent uranium
chemistry. Also reported here are more atom-efficient
(C
5
4
2
2
2
5
5
)
3
5
-
5
)
2
2
5
5 3
)
syntheses of (C
plexes, in turn, provide access to (C
Me H) UCl , valuable precursors for further exploration of
5
Me
4
H)
3
U and (C
5
Me
4
H)
3
UCl. These com-
5
Me
4
H) UI and (C
3
5
-
5
-
4
2
2
1-
4 5 4 2
Me H) /(C Me H) redox couple, it is the first example, to
the effect of cyclopentadienyl ring substitution on uranium
chemistry.
our knowledge, of this type of cyclopentadienyl reduction
reaction in an f element complex that contains some normal
metal-C(ring) bond distances. As noted above, the structure
Acknowledgment. We thank the U.S. National Science
Foundation, the Civilian Research and Development Founda-
tion, and the Russian Foundations (RFBR 04-03-32093; NSh
of (C
distances, similar to those in the sterically crowded (C
UCl, but it also has some more conventional bond lengths.
5
Me
4
H)
3
UCl has some long U-C(C
5
Me
4
H) bond
Me ) -
5 5 3
5
8.2003.3) for support of this research.
1
-
If (C R
5 5
) /(C
5
R
)
5 2
reductions can occur without having all
Supporting Information Available: X-ray diffraction data,
of the M-C(ring) bonds unusually long, this would sub-
stantially increase the scope of this reaction. However, it is
atomic coordinates, thermal parameters, complete bond distances
and angles, and a listing of observed and calculated structure factor
amplitudes for compounds 5 and 6 (in PDF and CIF formats).
This material is available free of charge via the Internet at
http://pubs.acs.org.
(
(
(
(
(
(
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1
756.
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4000 Inorganic Chemistry, Vol. 44, No. 11, 2005