Synthesis, structure, and reactivity of the sterically crowded complex (C5Me4SiMe3)3U

Article abstract of DOI:10.1002/zaac.201000225

The unusual chemistry obtainable from sterically crowded (C ₅R₅)₃M complexes has been explored with M = U and (C₅Me₄SiMe₃)^1-, a ligand that has independently provided unexpected uranium chemistry. (C₅Me ₄SiMe₃)₂UMe₂ (1), is reduced by potassium to generate the "ate" salt (C₅Me ₄SiMe₃)₂UMe₂K (2), which reacts with [HNEt₃][BPh₄] to yield the cationic species [(C ₅Me₄SiMe₃)₂U][BPh₄] (3). KC₅Me₄SiMe₃ reacts with 3 in benzene to form (C₅Me₄SiMe₃)₃U, (4). The structure of 4 shows that the displacement of the methyl groups from the cyclopentadienyl ring planes, a useful indicator of steric crowding, is the largest ever observed in a (C₅R₅)₃M complex. The reactivity of 4 is consistent with this structural indicator in that it engages in THF ring opening to form (C₅Me₄SiMe₃)₂UO[(CH ₂)₄(C₅Me₄SiMe₃)](THF).

Full text of DOI:10.1002/zaac.201000225

ARTICLE
DOI: 10.1002/zaac.201000225
Synthesis, Structure, and Reactivity of the Sterically Crowded Complex
(C5Me4SiMe3)3U
Nathan A. Siladke,[a] Joseph W. Ziller,[a] and William J. Evans*[a]
In Memory of Professor Herbert Schumann
Keywords: Cyclopentadienyl ligands; Metallocenes; THF ring-opening; Steric crowding; Uranium
Abstract. The unusual chemistry obtainable from sterically crowded (4). The structure of 4 shows that the displacement of the methyl
(C5R5)3M complexes has been explored with
M = U and groups from the cyclopentadienyl ring planes, a useful indicator of
(C5Me4SiMe3)1–, a ligand that has independently provided unexpected steric crowding, is the largest ever observed in a (C5R5)3M complex.
uranium chemistry. (C5Me4SiMe3)2UMe2 (1), is reduced by potassium The reactivity of 4 is consistent with this structural indicator in that it
to generate the “ate” salt (C5Me4SiMe3)2UMe2K (2), which reacts with engages in THF ring opening to form (C5Me4SiMe3)2UO-
[HNEt3][BPh4] to yield the cationic species [(C5Me4SiMe3)2U][BPh4] [(CH2)4(C5Me4SiMe3)](THF).
(3). KC5Me4SiMe3 reacts with 3 in benzene to form (C5Me4SiMe3)3U,
Introduction
This paper explores the effects of combining the
(2)
(C5Me4SiMe3)1– ligand with steric crowding in a tris(peralkyl-
cyclopentadienyl) uranium complex. Recent studies of the
(C5Me4SiMe3)1– ligand attached to uranium have led to unu-
sual C–H activation reactivity as shown in Equation (1) [1].
Specifically, in contrast to (C5Me5)2UMe2 [2], which has a
half-life of 16 h at 100 °C, (C5Me4SiMe3)2UMe2 (1) under-
goes two C–H bond activation reactions to form the bis(teth-
ered alkyl) complex (η5-C5Me4SiMe2CH2-κ,C)2U.
As part of the exploration of the uranium chemistry of the
(C5Me4SiMe3)1– ligand, the synthesis of the tris(ligand) com-
plex (C5Me4SiMe3)3U was pursued. Sterically crowded
tris(peralkylcyclopentadienyl) complexes, (C5R5)3M, have their
own unusual chemistry in that the normally inert peralkylcy-
clopentadienyl ligand becomes activated to engage in reduc-
tion, insertion, ring-opening, substitution, and sigma bond me-
tathesis reactivity [4]. Recently, it was also found that
(C5Me5)1– could participate in C–H activation chemistry when
the synthesis of an extremely crowded complex was attempted
[Equation (3)] [5].
(1)
The latter complex has become an effective platform to gen-
erate many new types of tethered uranium metallocenes, e.g.
Equation (2) [1, 3].
(3)
* Prof. Dr. W. J. Evans
Because the (C5Me4SiMe3)1– ligand has reactive C–H bonds,
as indicated in Equation (1), it was possible that the reaction
of KC5Me4SiMe3 with [(C5Me4SiMe3)2U][BPh4] could lead to
C–H activation rather than (C5Me4SiMe3)3U. On the other
hand, (C5Me4SiMe3)3La had been made in an analogous way
without any complicating metalation [Equation (4)] [6].
Fax: +1-949-824-2210
E-Mail: wevans@uci.edu
[a] Department of Chemistry
University of California
Irvine, California, 92697-2025, USA
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201000225 or from the
author.
View this journal online at
wileyonlinelibrary.com
Z. Anorg. Allg. Chem. 2010, 636, 2347–2351
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2347

N. A. Siladke, J. W. Ziller, W. J. Evans
ARTICLE
powder (246 mg, 90 %). 1H NMR (C6D6): δ = –4.37 (s, 18 H,
C5Me4SiMe3), 2.88 (s, 12 H, C5Me4SiMe3), 6.56 (s, 12 H,
C5Me4SiMe3) ppm. Only the ring methyl and trimethylsilyl resonances
(4)
were located in the 1H NMR spectrum. IR: ν = 3052 (s), 2953 (s),
˜
2907 (s), 1591 (s), 1431 (s), 1317 (w), 1240 (vs), 1030 (w), 884 (w),
837 (vs), 747 (s), 701 (vs) cm–1. C48H62BSi2U (944.03): calcd. C
61.07, H 6.62; found C 57.87, H 5.97. Repeated analysis of this com-
pound gave incomplete combustion as is sometimes observed with f
element complexes [3, 10]. The 1.24 H:C ratio found is close to the
1.30 ratio calculated.
To explore these two synthetic options and to make uranium
vs. lanthanum comparisons, the synthesis of (C5Me4SiMe3)3U
was examined. This has led to the most crowded (C5R5)3M
complex structurally characterized to date. The reactivity of
the complex was preliminarily examined to see if it would
effect ring opening of THF, a reaction well characterized for
lanthanides by Schumann and co-workers [7].
(C5Me4SiMe3)3U (4): In a glovebox free of coordinating solvents,
KC5Me4SiMe3 (150 mg, 0.63 mmol) was added to a stirred brown so-
lution of 3 (390 mg, 0.42 mmol) in toluene (15 mL). After the brown
solution was stirred for 12 h, it was centrifuged to remove insoluble
material and the solvent was removed under vacuum to yield 4 as a
brown microcrystalline solid (324 mg, 95 %). X-ray quality crystals
Experimental Section
1
of 4 were grown from a concentrated hexane solution at –35 °C. H
The syntheses and manipulations described below were conducted un-
der argon with rigorous exclusion of air and water using glovebox,
Schlenk, and vacuum-line techniques. All reactions were performed at
room temperature unless otherwise noted. Solvents were dried by pas-
sage through columns containing Q-5 and 4A molecular sieves.
[D6]Benzene and [D8]THF were dried with sodium-potassium alloy,
degassed using three freeze-pump-thaw cycles, and vacuum transferred
before use. (C5Me4SiMe3)2UMe2 (1) [1], and [HNEt3][BPh4] [8] were
prepared as previously reported. KC5Me4SiMe3 was prepared accord-
ing to the procedure reported for KC5Me5 [9]. Potassium metal in oil
was purchased from Aldrich, washed with hexanes to remove the oil,
and dried under vacuum before use. NMR spectra were recorded with
a Bruker DRX 500 MHz spectrometer at 25 °C. Infrared spectra were
recorded as KBr pellets with a Varian 1000 FT-IR spectrometer. Ele-
mental analysis was performed with a Perkin–Elmer 2400 CHN analy-
zer.
NMR (C6D6): δ = –16.7 (s, 27 H, C5Me4SiMe3), –3.80 (s, 18 H,
C Me SiMe ), 14.6 (s, 18 H, C Me SiMe ) ppm. IR: ν = 2952 (s),
˜
5
4
3
5
4
3
2899 (s), 2084 (w), 1429 (m), 1321 (m 1248s), 1207 (w), 1016 (m),
839 (vs), 753 (m), 748 (m), 717 (m) cm–1. C36H63Si3U (818.18): calcd.
C 52.85, H 7.76; found C 52.91, H 7.56.
(C5Me4SiMe3)2UO[(CH2)4(C5Me4SiMe3)](THF): In a glovebox con-
taining coordinating solvents, excess THF (5 mL) was added to 4
(10 mg, 0.012 mmol) resulting in a green solution. The solvent was
removed under vacuum yielding a tacky green solid. The 1H NMR
spectrum in C6D6 contained resonances expected for the THF ring
opened product: δ = –8.18 (s, 12 H, C5Me4SiMe3), –7.00 (s, 18 H,
C5Me4SiMe3), –5.59 (s, 12 H, C5Me4SiMe3), –0.028 (s, 9 H, SiMe3),
1.82 (s, 6 H, C5Me4SiMe3), 1.91 (s, 6 H, C5Me4SiMe3), 2.00 (s, 2 H,
CH2), 2.36 (s, 2 H, CH2), 2.83 (s, 2 H, CH2), 3.32 (s, 2 H, CH2), 4.38
(m, THF), 6.80 (m, THF) (half height line widths ranged from 2 to
300 Hz) ppm. Similarly, in a stoichiometric reaction, THF (2.1 μL,
0.026 mmol) was added to 4 (11 mg, 0.013 mmol) in C6D6 (1 mL).
1
1
Syntheses
The H NMR spectrum was recorded, which gave the same H NMR
spectroscopic data as above.
(C5Me4SiMe3)2UMe2K (2): An orange solution of 1 (240 mg,
0.36 mmol) in toluene (15 mL) was added to a vial of toluene (5 mL)
that contained a smear of potassium metal (14 mg, 0.37 mmol). This
mixture was allowed to stir for 4 d with periodic scraping (twice per
day) of the potassium metal from the vial walls. The resulting green
suspension was centrifuged and the soluble portion discarded. The
solid was washed three times with toluene and dried under vacuum to
yield 2 as a green-gray powder (200 mg, 80 %). 1H NMR ([D8]THF):
δ = –13.9 (s, 12 H, C5Me4SiMe3), –12.5 (s, 12 H, C5Me4SiMe3), –3.92
(s, 18 H, C5Me4SiMe3) ppm. Only the ring methyl and trimethylsilyl
resonances were located in the 1H NMR spectrum of this paramagnetic
Crystallographic Data
CCDC-778886 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif
Supporting Information (see footnote on the first page of this article):
X-ray Data Collection, Structure Solution and Refinement for
(C5Me4SiMe3)3U (4). NMR spectra of the elemental analysis samples
for 2 and 3.
complex. IR: ν = 2949 (s), 2899 (s), 1583 (w), 1444 (w), 1389 (w),
˜
1319 (m), 1247 (s), 1127 (w), 1017 (w), 833 (vs), 749 (s) cm–1.
C26H48KSi2U (693.96): calcd. C 44.88, H 6.95; found C 43.55, H 6.75.
Repeated analysis of this compound gave incomplete combustion as is
sometimes observed with f element complexes [3, 10]. The 1.86 H:C
ratio found matches the 1.86 ratio calculated.
Results and Discussion
Synthesis
[(C5Me4SiMe3)2U][BPh4] (3): [HNEt3][BPh4] (250 mg, 0.58 mmol)
was added to a stirred green suspension of 2 (200 mg, 0.3 mmol) in
benzene (15 mL). After 5 min, the solution began to turn dark brown
and was allowed to stir for an additional 12 h. The solution was centri-
fuged to remove insoluble material, and the solvent was removed under
vacuum to yield a tacky brown powder. This solid was dissolved in
methylcyclohexane (15 mL) and centrifuged to remove insoluble ma-
The synthesis of (C5Me4SiMe3)3U was pursued in analogy
to the synthesis of (C5Me5)3U [11]. (C5Me4SiMe3)2UMe2 (1),
is reduced by potassium to make the U3+ “ate” salt,
(C5Me4SiMe3)2UMe2K (2), as a green-gray solid [Equation
(5)]. Complex 2 was characterized by NMR and IR spectro-
terial. The solvent was under vacuum removed to yield 3 as a brown scopy and by elemental analysis.
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The Sterically Crowded Complex (C5Me4SiMe3)3U
(5)
Complex 2 is an example of a rather small class of trivalent
uranium alkyl complexes [11, 12] and its formation via Equa-
tion (5) is directly analogous to the synthesis of
1
(C5Me5)2UMe2K [11]. The H NMR spectrum of 2 contained
only resonances for the ring methyl and trimethylsilyl groups,
whereas resonances for the methyl groups directly attached to
paramagnetic uranium were not located. Similarly, methyl res-
onances were not located in the spectrum of (C5Me5)2UMe2K
[11].
The reaction of 2 with two equiv. of [HEt3N][BPh4] gener-
ates the U3+ cation [(C5Me4SiMe3)2U][BPh4], 3, as a brown
solid [Equation (6)].
(6)
Figure 1. Thermal ellipsoid plot of (C5Me4SiMe3)3U (4), drawn to the
50 % probability level with hydrogen atoms excluded for clarity.
Complex 3 was also characterized by NMR and IR spectro-
scopy and by elemental analysis. The synthesis of 3 via Equa-
tion (6) is directly analogous to the formation of
[(C5Me5)2U][BPh4], and the NMR spectra are also similar in
that resonances for the [BPh4]1– anion were not observed [11].
The reaction of 3 with KC5Me4SiMe3, the analog of Equa-
tion (3) and Equation (4) above, leads to formation of the
tris(cyclopentadienyl) product (C5Me4SiMe3)3U (4) as a brown
solid [Equation (7)].
Table 1. X-ray data collection parameters for (C5Me4SiMe3)3U (4).
Empirical formula
Formula weight
Temperature /K
Crystal system
Space group
a /Å
C36H63Si3U (4)
818.16
148(2)
triclinic
¯
P1
10.2024(7)
12.2156(8)
15.9301(11)
81.4802(7)
73.9260(7)
71.8350(7)
1808.5(2)
2
b /Å
c /Å
α /°
β /°
γ /°
(7)
Volume /Å3
Z
ρcalcd. /Mg·m–3
μ /mm–1
1.502
4.610
R1a) [I ≥2.0σ(I)]
0.0167
Complex 4 was characterized by NMR and IR spectroscopy
wR2b) (all data)
0.0420
2
and elemental analysis, and was definitively identified by X-
1
ray crystallography (Figure 1). The H NMR spectrum con-
a) R1 = Σ||Fo|–|Fc||/Σ|Fo|, b) wR2 = [Σ [w(Fo –Fc ) ]/Σ[w(Fo ) ]]1/2
2 2
2 2
tains a single set of ligand resonances at –16.7, –3.80, and
14.6 ppm with ratios of 27:18:18, indicating that the three
(C5Me4SiMe3)1– rings are equivalent in solution. Details on the
X-ray data collection parameters are given in Table 1.
(C5Me5)3M complexes [14], are compared between 4 and 5 in
Table 3.
Comparisons of the structures should take into account dif-
ferences in radial size of the metals. The only Shannon radius
Structure of 4
Complex 4 is not isomorphous with (C5Me4SiMe3)3La (5), given for U3+ is for hexacoordination [15]. Comparing this
which was crystallized with a molecule of toluene in the lattice 1.025 Å value with the six coordinate radius of La3+, 1.032 Å,
[6]. Comparisons of complexes 4 and 5 as well as (C5Me5)3U suggests that the nonacoordinate radius of U3+ should be
[13] and (C5Me5)3La [6] are given in Table 2.
slightly smaller than that of La3+. Despite this slight difference,
The deviations of the silicon and methyl carbon atoms from the U-(C5Me5 ring centroid) distance in the pentamethylcyclo-
the cyclopentadienyl ring planes, the metric parameter that has pentadienyl analog, (C5Me5)3U, is 2.581 Å, compared to
been consistently used to evaluate steric crowding in 2.642 Å in (C5Me5)3La, and each of the three crystallographi-
Z. Anorg. Allg. Chem. 2010, 2347–2351
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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N. A. Siladke, J. W. Ziller, W. J. Evans
Table 2. Bond lengths /Å and angles /° for (C5Me4SiMe3)3U (4), (C5Me5)3U [13], (C5Me4SiMe3)3La (5) [6], and (C5Me5)3La [6].
ARTICLE
4
(C5Me5)3U
5
(C5Me5)3La
U–C(1)
2.968(2)
2.926(2)
2.939(2)
2.903(2)
2.905(2)
2.947(2)
2.897(2)
2.853(2)
2.848(2)
2.861(2)
2.889(2)
2.886(2)
2.906(2)
2.916(2)
2.857(2)
2.666
U–C(1)
U–C(2)
U–C(3)
U–Cnt
2.940(4)
2.840(3)
2.813(3)
2.581
La–C(1)
3.029(2)
2.962(2)
2.941(2)
2.940(2)
2.957(2)
3.018(2)
2.986(2)
2.923(2)
2.890(2)
2.906(2)
2.988(2)
2.952(2)
2.948(2)
2.925(2)
2.925(2)
2.706
La–C(1)
La–C(2)
La–C(3)
La–Cnt
2.975(3)
2.896(2)
2.873(2)
2.642
U–C(2)
La–C(2)
U–C(3)
La–C(3)
U–C(4)
La–C(4)
U–C(5)
Cnt–U–Cnt
120.0
La–C(5)
Cnt-La–Cnt
120.0
U–C(13)
La–C(13)
La–C(14)
La–C(15)
La–C(16)
La–C(17)
La–C(25)
La–C(26)
La–C(27)
La–C(28)
La–C(29)
La–Cnt(1)
La–Cnt(2)
La–Cnt(3)
La–C(24)
La–C(35)
U–C(14)
U–C(15)
U–C(16)
U–C(17)
U–C(25)
U–C(26)
U–C(27)
U–C(28)
U–C(29)
U–Cnt(1)
U–Cnt(2)
U–Cnt(3)
U–C(24)
2.615
2.685
2.625
2.687
3.561
3.42
U–C(35)
3.830
4.10
Cnt(1)–U–Cnt(2)
Cnt(1)–U–Cnt(3)
Cnt(2)–U–Cnt(3)
120.8
Cnt(1)–La–Cnt(2) 120.3
Cnt(1)–La–Cnt(3) 119.5
Cnt(2)–La–Cnt(3) 119.7
0.542
120.9
118.0
Max. methyl displace- 0.563
ment from ring (Å)
0.51
0.501
Table 3. Deviations /Å from the C5Me4R plane of the α-C (or Si) for
each alkyl or silyl substituent for (C5Me4SiMe3)3U (4) and
(C5Me4SiMe3)3La (5).
in 5) are clustered close to 120°. The uranium atom in 4 is
0.184 Å out of the plane of the ring centroids compared to
0.111 Å for lanthanum in 5 [6]. Each structure is also arranged
so that two of the three SiMe3 groups have two methyl groups
pointing away from the crowded center of the molecule such
that the third methyl group of those SiMe3 units points toward
the pseudo C3 axis perpendicular to the plane of the three ring
centroids. In 4, this involves methyl carbons C24 and C35,
which are located 3.56 and 3.83 Å, respectively, from uranium
(Figure 2). Both distances are within the sum of the van der
Waals radii of a methyl group (2.0 Å) [16] and uranium
(1.86 Å) [17]. The comparable distances in 5 are 3.42 and
(C5Me4SiMe3)3U (4)
(C5Me4SiMe3)3La (5)
0.563 [C6]
0.270 [C7]
0.454 [C8]
0.319 [C9]
0.694 [Si1]
0.477 [C18]
0.238 [C19]
0.278 [C20]
0.395 [C21]
–0.113 [Si2]
0.467 [C30]
0.202 [C31]
0.255 [C32]
0.418 [C33]
0.022 [Si3]
0.542 [C6]
0.236 [C7]
0.313 [C8]
0.364 [C9]
0.498 [Si1]
0.458 [C18]
0.271 [C19]
0.279 [C20]
0.369 [C21]
0.161 [Si2]
0.447 [C30]
0.190 [C31]
0.342 [C32]
0.308 [C33]
0.190 [Si3]
cally unique M–C(C5Me5) bonds is 0.035–0.060 Å shorter in
the uranium complex. A similar result is found when compar-
ing the structures of 4 and 5. The 2.615, 2.625, and 2.666 Å
U–(ring centroid) distances in 4 are all smaller than expected
when compared to the 2.685, 2.687, and 2.706 Å La–(ring cen-
troid) distances in 5, Table 2. The M–C(C5Me4SiMe3) bonds
in 4 vs. 5 are shorter by a larger range, 0.023–0.072 Å, than
the differences observed between (C5Me5)3U and (C5Me5)3La.
The overall structures of 4 and 5 are similar in that each
contains a distorted trigonal planar arrangement of cyclopen-
tadienyl ring centroids around the metal. The centroid–M–cen-
Figure 2. View of 4 showing how C24 and C35 are oriented toward
troid angles in 4 (118.0°–120.9°, like the 119.5°–120.3° angles uranium, where U1···C24 is 3.561 Å and U1···C35 is 3.830 Å.
2350
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The Sterically Crowded Complex (C5Me4SiMe3)3U
4.10 Å, i.e., only one of these distances is in the U···C range.
pentadienyl rings. Complex 4 contains the largest displacement
Complexes 4 and 5 are also similar in that the third SiMe3 from the ring plane of a methyl substituent ever observed in a
group cannot adopt this favorable arrangement and has two peralkyl (C5R5)3M complex and is more reactive with THF
methyl groups pointed in toward the center of the molecule, than its permethyl analog, (C5Me5)3U. The structure of 4 also
C10 and C11 in 4, Figure 2. This “more crowded” SiMe3 is the first example of a (C5R5)3M complex with a negative
group has the largest displacement of a substituent atom from displacement of a ring substituent. Comparison of the structure
the cyclopentadienyl ring plane in 4, 0.694 Å for Si1. In 5, the of 4 and its lanthanum analog, (C5Me4SiMe3)3La (5) shows
silicon displacement is large (0.498 Å), but not as large as the that 4 has more agostic interaction within the sum of van der
0.542 Å displacement of a methyl group on that ring. The sili- Waals radii limits and bond lengths shorter than would be ex-
con atom displacements from the ring plane for the other pected by comparison of ionic radii. This could be used as
SiMe3 groups, i.e. the ones with methyl groups oriented toward evidence that uranium is more covalent than lanthanum.
the metal, are much less for both 4 and 5. This has also been
observed, in general, with (C5Me4R)3La complexes (R = Et,
Acknowledgement
We thank National Science Foundation for support of this research and
Dr. Michael K. Takase for assistance with the X-ray crystallography.
iPr) [6]. In 4, this is taken to an extreme such that Si2, attached
to C17, actually has a negative displacement, i.e., it is bent
toward and not away from the metal atom. This is the first
example of negative displacement of an R group in a peralkyl
(C5R5)3M complex.
References
Complexes 4 and 5 are also similar in that the methyl group
with the largest displacement is found on the ring with the
longest M–(ring centroid) distance. In 4, this 0.563 Å displace-
ment for C6 is the largest ever observed in a (C5R5)3M com-
plex. Previously, the 0.542 Å value in 5 and the 0.5475 Å dis-
tance in (C5Me5)3Y [4b] were the largest found. Displacements
of 0.48 to 0.54 Å have been observed to give unusual reactiv-
ity to the (C5R5)1– rings in (C5R5)3M complexes [14].
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To test if the large methyl displacements in 4 would lead to
reactivity typical of sterically crowded (C5R5)3M complexes,
compound 4 was dissolved in THF. This reaction immediately
produced a green solution, from which a green solid can be
isolated that has the characteristic NMR spectrum of a THF
ring open product [7], in this case (C5Me4SiMe3)2UO-
[(CH2)4(C5Me4SiMe3)](THF) [Equation (8)]. To establish if
the larger methyl displacement in 4 compared to (C5Me5)3U
could lead to an increase in reactivity, 4 was also reacted with
two equiv. of THF. It has been previously reported that
(C5Me5)3U does not react with stoichiometric amounts of THF
[18]. Since complex 4 does react with stoichiometric THF, it
is more reactive than (C5Me5)3U in this regard.
[7] H. Schumann, M. Glanz, H. Hemling, F. H. Görlitz, J. Orga-
nomet. Chem. 1993, 462, 155.
[8] W. J. Evans, M. A. Johnson, J. W. Ziller, Inorg. Chem. 2000, 39,
3421.
[9] W. J. Evans, S. A. Kozimor, J. W. Ziller, N. Kaltsoyannis, J. Am.
Chem. Soc. 2004, 126, 14533.
[10] a) A. J. Gaunt, B. L. Scott, M. P. Neu, Inorg. Chem. 2006, 45,
7401; b) J. H. Melman, C. Rohde, T. J. Emge, J. G. Brennan, In-
org. Chem. 2002, 41, 28; c) D. Freedman, T. J. Emge, J. G. Bren-
nan, Inorg. Chem. 1999, 38, 4400.
[11] W. J. Evans, G. W. Nyce, K. J. Forrestal, J. W. Ziller, Organome-
tallics 2002, 21, 1050.
[12] a) S. D. Bella, G. Lanza, I. L. Fragalà, T. J. Marks, Organometal-
lics 1996, 15, 205; b) C. Villiers, M. Ephritikhine, J. Organomet.
Chem. 1990, 393, 339; c) S. D. Stults, R. A. Andersen, A. Zalkin,
J. Am. Chem. Soc. 1989, 111, 4507; I. Korobkov, S. Gambarotta,
Inorg. Chem. 2010, 49, 3409; d) W. G. Van der Sluys, C. J.
Burns, A. P. Sattelberger, Organometallics 1989, 8, 855.
[13] W. J. Evans, K. J. Forrestal, J. W. Ziller, Angew. Chem. 1997,
109, 798; Angew. Chem. Int. Ed. Engl. 1997, 36, 774.
[14] W. J. Evans, S. A. Kozimor, J. W. Ziller, Inorg. Chem. 2005, 44,
7960.
(8)
[15] R. D. Shannon, Acta Crystallogr., Sect. A 1976, 32, 751.
[16] L. Pauling, The Nature of the Chemical Bond, 3rd ed., Cornell
Univ. Press. 1960, p. 260.
Conclusions
[17] a) A. Bondi, J. Phys. Chem. 1964, 68, 441; b) http://www.webele-
ments.com.
The sequence of syntheses that takes (C5R5)2UMe2 to
(C5R5)2UMe2K to [(C5R5)2U][BPh4] to (C5R5)3U for (C5R5)1–
=
[18] W. J. Evans, S. A. Kozimor, J. W. Ziller, J. Am. Chem. Soc. 2003,
125, 14264.
(C5Me5)1– is also applicable for (C5R5)1– = (C5Me4SiMe3)1–.
Hence, (C5Me4SiMe3)3U (4) can be made without the compli-
cating C–H bond activation of the SiMe3 groups on the cyclo-
Received: May 31, 2010
Published Online: June 16, 2010
Z. Anorg. Allg. Chem. 2010, 2347–2351
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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