UI4(1,4-dioxane)2, [UCl4(1,4-dioxane)] 2, and UI3(1,4-dioxane)1.5: Stable and versatile starting materials for low- and high-valent uranium chemistry

Article abstract of DOI:10.1021/om200093q

The uranium(III) and uranium(IV) iodide complexes UI₃(1,4- dioxane)_1.5 and UI₄(1,4-dioxane)₂ have been easily prepared in high yield by reacting uranium turnings with a 1,4-dioxane solution of iodine under mild

Full text of DOI:10.1021/om200093q

ARTICLE
pubs.acs.org/Organometallics
UI4(1,4-dioxane)2, [UCl4(1,4-dioxane)]2, and UI3(1,4-dioxane)1.5:
Stable and Versatile Starting Materials for Low- and High-Valent
Uranium Chemistry
Marisa J. Monreal, Robert K. Thomson, Thibault Cantat, Nicholas E. Travia, Brian L. Scott, and
Jaqueline L. Kiplinger*
Los Alamos National Laboratory, Mail Stop J-514, Los Alamos, New Mexico 87545, United States
S Supporting Information
b
ABSTRACT: The uranium(III) and uranium(IV) iodide complexes UI3(1,4-dioxane)1.5 and
UI4(1,4-dioxane)2 have been easily prepared in high yield by reacting uranium turnings with a
1,4-dioxane solution of iodine under mild conditions. The two complexes exhibit outstanding
thermal stability and are excellent precursors to a variety of uranium(III), uranium(IV), and
uranium(VI) alkoxide, amide, organometallic, and halide compounds, including a safe, room-
temperature synthesis of [UCl4(1,4-dioxane)]2, which is a useful synthetic alternative to
UCl4.
’ INTRODUCTION
limited thermal stability or contain unsaturated ligands that are
incompatible with strong nucleophiles.16-20
Uranium molecular chemistry has become a valuable tool for
understanding the behavior and properties of the light actinides
in a variety of applications ranging from environmental and aque-
ous processing to advanced materials for nuclear fuel cycles.1,2
Inexpensive, easy, and safe access to a wide range of uranium
halide starting materials is vital for continued developments in
the field.
An important advance to the field was recently provided by
Arnold and co-workers, who demonstrated that sonication of
uranium turnings with iodine in diethyl ether gives UI3 or
UI4(OEt2)2, depending on the stoichiometry.21 In related work,
Hayton and co-workers reported that UH3 could be used to
access UI4(OEt2)2 in high yields by oxidation with iodine; similar
oxidations with silver reagents afforded UX4(DME)2 (X = Br, Cl,
OTf).22 However, UH3 must be prepared by reaction of uranium
metal with 1 atm hydrogen at 225 °C, and both of these
UI4(OEt2)2 synthetic routes require special equipment or ma-
terials that are not available at all institutions.
Recently, we discovered that ThCl4(1,4-dioxane)2 could be
prepared under mild conditions from ThCl4(H2O)4, HCl, and
Me3SiCl in 1,4-dioxane.23 A useful attribute of 1,4-dioxane is that
unlike THF it does not readily undergo ring-opening. Addition-
ally, it is a weak donor ligand and is easily displaced by stronger
donor ligands such as 1,2-dimethoxyethane (DME) and THF to
access ThCl4(DME)2 and ThCl4(THF)3.5, respectively. Herein, we
show that 1,4-dioxane can also be used to prepare two new
uranium(III) and uranium(IV) iodide synthons, UI3(1,4-dioxane)1.5
and UI4(1,4-dioxane)2. Of particular note is that these complexes are
stable above ambient temperature and are useful precursors to a
variety of alkoxide, amide, organometallic, and halide compounds,
including a safe, room-temperature synthesis of [UCl4(1,4-diox-
ane)]2, which is a practical synthetic alternative to UCl4.
To date, UI3(THF)43,4 and UCl45-9 have served as the most
popular starting materials for synthetic uranium(III) and
uranium(IV) chemistry. However, difficulties exist with the
syntheses of both compounds. For example, the preparation of
UCl4 requires high temperature (140-700 °C) combinations of
uranium oxides (UO2, UO3, or U3O8) and chlorinating reagents
(CCl4, S2Cl2, or Cl2CdC(Cl)-CCl3).5-9 From this collection,
the method of choice for the synthesis of UCl4 has been the
reaction of UO3 2H2O (or U3O8) with hot (190 °C) hexa-
3
chloropropene, a highly toxic chemical, and special precautions
must be taken to avoid uncontrolled radical reactions.9 Another
high-temperature route requires heating UH3 with NH4Cl at
300 °C for 30 h to initially generate (NH4)2UCl6, which is then
heated at 350 °C under high vacuum to ultimately give UCl4.10
The synthesis of UI3(THF)4 needs to be performed in the pre-
sence of HgI2 at temperatures slightly below 10 °C and is usually
low-yielding because of the formation of unwanted byproducts
caused by the ring-opening of THF. In addition, UI3(THF)4 is
thermally sensitive and must be stored at low temperature.4
Efforts to circumvent these issues with UI3(THF)4 and UCl4
have appeared in modern accounts that focus on the develop-
ment of new uranium(III) and uranium(IV) halide starting
materials. For instance, syntheses of bare UI3 have been devel-
oped, but they necessitate harsh conditions and/or the use of
special equipment.11-15 Reports of Lewis base adducts of UI4
have also appeared, but many of these compounds also possess
’ RESULTS AND DISCUSSION
Reaction of uranium turnings with 2.05 equiv of iodine in 1,4-
dioxane at room temperature for 7 days affords the uranium(IV)
Received: February 1, 2011
Published: March 21, 2011
r
2011 American Chemical Society
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Scheme 1a
Figure 1. Molecular structure of UI4(1,4-dioxane)2 (1) with thermal
ellipsoids projected at the 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond distances (Å) and angles (deg):
U(1)-I(1), 2.9637(11); U(1)-I(2), 2.9588(10); U(1)-O(1),
2.333(6); I(1)-U(1)-I(2), 90.31(3); I(1)-U(1)-O(1), 89.53(15);
I(2)-U(1)-O(1), 89.74(16); O(1)-U(1)-O(10), 179.999(1).
complex UI4(1,4-dioxane)2 (1) as a red-orange solid in 95% iso-
lated yield (eq 1). Shorter reaction times (18 h) can be achieved
with mild heat (50 °C). Importantly, the synthesis of 1 can be
easily performed on multigram scales and does not require the
purification of iodine by sublimation or the activation of the
uranium turnings by sonication or HgI2.
a Reagents and conditions: (i) Et2O, rt, 1 h, 71% yield; (ii) 4 equiv HCl
(4.0 M/1,4-dioxane), 1,4-dioxane, rt, 10 min, 86% yield; (iii) (1) 2.2 equiv
TMEDA, toluene, rt, 18 h; (2) 5 equiv HCl (4.0 M/1,4-dioxane), rt, 4 h;
(3) 5 equiv TMEDA, rt, 1 h, 91% yield; (iv) [K2(OEt2)2]fc[NSi(tBu)Me2]2,
THF, -35 °Cfrt, 1 h, 61% yield; (v) 4 equiv K[N(SiMe3)2], toluene,
110 °C, 15 h, 70% yield; (vi) 4.1 equiv K(O-2,6-tBu2C6H3), THF, rt, 12
h, 64% yield; (vii) 2 equiv K(C5Me5), toluene, 110 °C, 18 h, 65% yield.
undergoes rapid ring-opening of THF.18 The diethyl ether
complex UI4(Et2O)2 (2) is also thermally sensitive and under-
goes loss of diethyl ether above room temperature.21,22,25
Furthermore, UI4(Et2O)2 (2) reacts with the surface of glass
vials to yield [H(OEt2)2][UI5(OEt2)].25 In contrast, UI4(1,4-
dioxane)2 (1) is stable in 1,4-dioxane or toluene solution for 12 h
at 80 °C without degradation and can be stored at room tem-
perature under an inert atmosphere for at least two weeks. We
attribute this greater stability to not only the higher boiling point
of 1,4-dioxane, which limits loss of the coordinating ligand,26 but
also the lower susceptibility of coordinated 1,4-dioxane toward
metal-mediated nucleophilic attack.
As outlined in Scheme 1, UI4(1,4-dioxane)2 (1) is an excellent
synthetic precursor to a wide range of U(IV) alkoxide, amide,
organometallic, and halide complexes. Substitution of the 1,4-
dioxane ligands by diethyl ether occurs by dissolving complex 1
in diethyl ether, to give UI4(OEt2)2 (2)21 in 71% isolated yield.
This observation highlights the relative donor strength of diethyl
ether versus 1,4-dioxane toward uranium(IV) and indicates that
UI4(1,4-dioxane)2 (1) should be a useful U(IV) starting material.
Indeed, reaction of UI4(1,4-dioxane)2 (1) with anhydrous HCl
(4.0 M/1,4-dioxane) smoothly converts 1 to the chloride-bridged
uranium dimer complex [UCl4(1,4-dioxane)]2 (3). Complex 3 is
insoluble in 1,4-dioxane and precipitates from the reaction
mixture, granting a simple workup and 86% isolated yield. Likewise,
treatment of complex 1 with N,N0-tetramethylethylenediamine
(TMEDA), followed by anhydrous HCl (4.0 M/1,4-dioxane),
gives the known UCl4(TMEDA)2 (4)27 in 91% yield. Salt metath-
esis chemistry provides access to amide, alkoxide, and organometallic
compounds, as illustrated by the synthesis of fc[NSi(tBu)Me2]2UI2-
(THF) (5),28 [(Me3Si)2N]2U[κ2-(C,N)-CH2Si(Me)2N(SiMe3)]
(6),29,30 U(O-2,6-tBu2C6H3)4 (7),31-33 and (C5Me5)2UI2 (8).34-36
As typified by the syntheses of complexes 5 and 8, UI4(1,4-
dioxane)2 (1) provides a more efficient and atom-economical
way to access uranium(IV) iodide compounds. For example,
1
Complex 1 was fully characterized by a combination of H
NMR spectroscopy, elemental analysis, and X-ray crystallogra-
phy. The H NMR spectrum of 1 at ambient temperature in
C6D6 is simple and exhibits a broad singlet at δ 3.32 ppm, which
is consistent with reversible coordination of the 1,4-dioxane to
the uranium metal center.
1
Dark red, X-ray quality crystals of UI4(1,4-dioxane)2 (1)
were obtained from a toluene/1,4-dioxane (90:10) solution
at -30 °C. The molecular structure of 1 is presented in Figure 1
and features octahedral geometry about the U(IV) metal center
with trans-bound 1,4-dioxane molecules and four equatorial
iodide ligands. There is an inversion center at uranium, and no
deviation of the iodide ligands from the equatorial plane is
observed. The U-I bond distances of 2.9637(11) and
2.9588(10) Å lie at the short end of the range observed for the
handful of structurally characterized Lewis base adducts of UI4
(e.g., UI4(NtCPh)4, U-I = 3.027(1) Å;20 UI4(py)3, U-I =
2.9558(4)-3.0438(4) Å;19 UI4[OdC(NMe2)2]4, U-I =
2.996(3), 3.027(3) Å;16 UI4(Et2O)2, U-I = 2.9614(6) Å).21
Presumably, this is due to the weaker donor strength of 1,4-dioxane.
To the best of our knowledge, complex 1 represents the first
structurally characterized 1,4-dioxane complex of an actinide ion.
Consistent with the weaker donor strength of 1,4-dioxane, the U-
O bond length of 2.333(6) Å is comparable to those observed for
the diethyl ether complex UI4(Et2O)2 (2) (2.366(8) Å)21 and
much longer than those reported for the N,N,N0,N0-tetramethylurea
complex UI4[OdC(NMe2)2]4 (2.20(3), 2.17(3) Å).16
UI4(1,4-dioxane)2 (1) exhibits significantly increased thermal
stability compared to the related UI4(THF)4 and UI4(Et2O)2
(2) systems. In fact, due to its thermal instability, UI4(THF)4
cannot be isolated.18,24 However, it can be generated in situ at
room temperature from UI4(NtCMe)4 in THF solution but
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Scheme 2a
sublimation or the activation of the uranium turnings by sonication
or HgI2. As such, this synthetic route to 10 represents a significant
improvement over the synthesis of UI3(THF)4 (11),3,4 which is
prone to decomposition of the intermediate UI4(THF)4 by ring-
opening of coordinated THF at room temperature.4,18
It is interesting that the analogous synthesis in diethyl ether
affords the adduct-free complex UI321 and demonstrates the rela-
tive donor strength of diethyl ether versus 1,4-dioxane toward
uranium(III). In contrast to UI4(1,4-dioxane)2 (1), the 1,4-
dioxane ligands in 10 are not displaced by diethyl ether.
Similar to UI3(THF)4 (11) and related compounds, the for-
mation of complex 10 initially involves the generation of a
uranium(IV) intermediate, UI4(1,4-dioxane)2 (1), which ap-
pears as a red suspension within a few hours and is later reduced
to blue-violet UI3(1,4-dioxane)1.5 (10). This was confirmed by
the reaction of UI4(1,4-dioxane)2 (1) with uranium turnings in
1,4-dioxane at room temperature, which quantitatively gives
UI3(1,4-dioxane)1.5 (10) (eq 3).
a Reagents and conditions: (i) 2 equiv (C5Me5)MgCl(THF), toluene,
110 °C, 15 h, 70% yield; (ii) 4.3 equiv K(O-2,6-tBu2C6H3), toluene, 70 °C,
15 h, 65% yield; (iii) 4 equiv Na[N(SiMe3)2], toluene, 110 °C, 15 h,
80% yield.
while complex 5 has been synthesized by a disproportionation
reaction that takes place over 16 h upon mixing UI3(THF)4 with
[K2(OEt2)2]fc[NSi(tBu)Me2]2,28 the reaction between UI4(1,4-
dioxane)2 (1) and [K2(OEt2)2]fc[NSi(tBu)Me2]2 affords com-
plex 5 in 1 h. Moreover, the primary routes to complex 8 have
involved multistep syntheses starting from either UCl4 or UI3-
(THF)4 and culminating with a halogen exchange reaction bet-
ween (C5Me5)2UCl2 and Me3SiI34,35 or by oxidation of
(C5Me5)2UI(THF) with CuI2,36 respectively. Using UI4(1,4-
dioxane)2 (1) and 2 equiv of K(C5Me5), complex 8 can be easily
prepared in one step in 65% isolated yield.
Since complex 10 is only slightly soluble in 1,4-dioxane and is
insoluble in noncoordinating solvents (such as diethyl ether,
benzene, toluene, or hexane), this precluded characterization by
NMR spectroscopy and X-ray crystallography. However, the
identity of the complex was unequivocally established by H, C, I,
and U elemental analyses, ligand displacement by coordinating
solvents (THF or pyridine), and reaction chemistry. On the basis
of our recent work with ThCl4(1,4-dioxane)2, it is likely that the
poor solubility of UI3(1,4-dioxane)1.5 (10) is due to an extended
polymeric structure with bridging 1,4-dioxane ligands.23
UI3(1,4-dioxane)1.5 (10) is a versatile reagent for low- and
high-valent uranium chemistry, as it displays a wide range of
reactivity, which is summarized in Scheme 3. The 1,4-dioxane
ligands in complex 10 are readily displaced by other strong
donors such as THF or pyridine to quantitatively access the
known complexes UI3(THF)4 (11)3 and UI3(py)4 (12),4 respec-
tively. Interestingly, the bidentate ligand DME is not able to
displace the coordinated 1,4-dioxane from 10 to form the known
adduct UI3(DME)2, even when heated to 75 °C for 2 h. The
aryloxide and homoleptic amide complexes U(OAr)3(THF)
(Ar = 2,6-tBu2C6H3 (13);38 2,6-iPr2C6H3 (14)39) and U[N-
(SiMe3)2]3 (15)3,4,21,40,41 are obtained in good yields by salt
metathesis using 3 equiv of K(OAr) and Na[N(SiMe3)2], respec-
tively. Similarly, the monoiodide complexes (C5Me4R)2-
UI(THF) (R = Me (16),42 Et (17)43) can be synthesized in
high yield by reacting 10 with 2 equiv of K(C5Me4R) (R = Me,
Et). Finally, complex 10 reacts with tert-butylamine and iodine in
THF, followed by Ph3PdO in toluene, to give the linear
bis(imido) uranium(VI) complex 18 in 46% isolated yield.44
This shows that the reactivity of UI3(1,4-dioxane)1.5 (10) is not
limited to trivalent uranium and underscores its broad utility as a
starting material for inorganic and organometallic uranium
chemistry.
The high-yielding room-temperature synthesis of [UCl4(1,4-
dioxane)]2 (3) deserves additional comment, as it represents a
considerable advance over the existing preparative routes to
UCl4. As noted above, the method of choice for the synthesis
of UCl4 has been the high-temperature (190 °C) radi-
cal reaction between UO3 2H2O (or U3O8) and hexachloro-
3
propene.5,9 From a synthetic standpoint, complex 3 is equivalent
to UCl4 (Scheme 2), which makes it potentially a more appealing
starting material. For example, 1/2[UCl4(1,4-dioxane)]2 (3)
reacts with 2 equiv of (C5Me5)MgCl(THF) to give the known
dichloride complex (C5Me5)2UCl2 (9).37 Likewise, reaction of
1/2[UCl4(1,4-dioxane)]2 (3) with 4 equiv of K[O-2,6-tBu2-
C6H3] or Na[N(SiMe3)2] correspondingly gives U(O-
2,6-tBu2C6H3)4 (7)31,33 and [(Me3Si)2N]2U[κ2-(C,N)-CH2Si-
(Me)2N(SiMe3)] (6).29,30
The straightforward synthesis, stability, and favorable proper-
ties of UI4(1,4-dioxane)2 (1) and [UCl4(1,4-dioxane)]2 (3)
prompted us to investigate the use of 1,4-dioxane as a supporting
ligand for trivalent uranium. As given in eq 2, reaction of uranium
turnings with 1.35 equiv of iodine in 1,4-dioxane at room tempe-
rature for 18 h affords the new uranium(III) complex UI3(1,4-
dioxane)1.5 (10) as a blue-violet solid in 99% isolated yield.
Complex 10 is remarkably robust and can also be prepared at
80 °C in comparable yields. As with complex 1, the synthesis of
UI3(1,4-dioxane)1.5 (10) can be easily performed on multigram
scales and does not require the purification of iodine by
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Scheme 3a
stored over activated 4 Å molecular sieves prior to use. Benzene-d6
(Aldrich), toluene-d8 (Aldrich), and tetrahydrofuran-d8 (Cambridge
Isotope Laboratories) were purified by storage over activated 4 Å mole-
cular sieves or sodium metal prior to use. 238U turnings were obtained
from Los Alamos National Laboratory and cleaned as described below.
Iodine was purchased from Aldrich and used as received. [K2(OEt2)2]fc-
[NSi(tBu)Me2]2 and K(C5Me4Et)43 were prepared according to
45
literature procedures.
Caution! Depleted uranium (primary isotope 238U) is a weak R-emitter
(4.197 MeV) with a half-life of 4.47 ꢀ 109 years; manipulations and
reactions should be carried out in monitored fume hoods or in an inert
atmosphere drybox in a radiation laboratory equipped with R- and β-
counting equipment.
Oxide-Free Uranium Metal Turnings. This is a modification of
a literature procedure.4 Oxide-coated depleted uranium turnings (20 g)
were immersed in 100 mL of concentrated nitric acid to remove the
oxide coating. The turnings were mixed and swirled in the nitric acid.
The reaction of nitric acid with uranium metal was accompanied by the
evolution of heat and brown NO2 gas as the metal turnings lost the black
oxide coating. The nitric acid was carefully decanted from the turnings.
The nitric acid washing was repeated two more times until the turnings
displayed a shiny, metallic surface. Residual acid was removed by rinsing
the turnings three times with copious amounts of deionized water. The
resulting shiny turnings were then rinsed three times (3 ꢀ 100 mL) with
acetone to remove water. The turnings were then transferred into the
drybox antechamber, where the residual acetone was removed under
reduced pressure.
a Reagents and conditions: (i) THF, rt, 1 h, 98% yield; (ii) pyridine, rt,
4 h, 89% yield; (iii) 3 equiv KOAr (Ar = 2,6-tBu2C6H3, 2,6-iPr2C6H3),
THF, rt, 1 h, 81-82% yield; (iv) 3 equiv Na[N(SiMe3)2], THF, rt, 1 h,
73% yield; (v) 2 equiv K(C5Me4R) (R = Me, Et), THF, rt, 18 h, 67-75%
yield; (vi) (1) 6.8 equiv tBuNH2, 1.5 equiv I2, THF, rt, 10 min; (2) 2.3
equiv Ph3PdO, rt, 15 h, 46% yield.
’ CONCLUSIONS
We have developed simple, safe, inexpensive, and high-yield-
ing solution routes to UI4(1,4-dioxane)2 and UI3(1,4-diox-
ane)1.5, which possess exceptional thermal stability and are
easy to prepare on a large scale. Furthermore, they are excellent
starting materials to a wide range of uranium(III), uranium(IV),
and uranium(VI) alkoxide, amide, organometallic, and halide
compounds, including a safe, room-temperature synthesis of
[UCl4(1,4-dioxane)]2, which has proved to be a useful synthetic
alternative to UCl4. We anticipate that these three new uranium
compounds will become important reagents in synthetic actinide
chemistry and enable future progress in uranium materials
science and nuclear fuel cycle research.
Synthesis of K(C5Me5). This is a modification of a literature proce-
dure46 and is similar to that reported for K(C5Me4H)14 and K-
(C5Me4Et):43 A 250 mL side arm flask equipped with a magnetic stir
bar was charged with K[N(SiMe3)2] (18.3 g, 91.8 mmol) and Et2O
(125 mL). The resulting slurry was stirred at room temperature. To this
stirring suspension was added C5Me5H (15.0 g, 110 mmol) dropwise by
pipet over 10 min. The solution became increasingly cloudy, and the
white suspension was stirred for 15 h at room temperature. The reaction
mixture was filtered through a medium-porosity fritted filter to collect an
off-white powder, which was washed with Et2O (20 mL) and dried
under reduced pressure to give K(C5Me5) as an off-white powder (16.0
1
g, 91.8 mmol, 100%). H NMR (THF-d8, 298 K): δ 1.93 (s, 15H,
C5Me5).
Synthesis of K(OAr) (Ar = 2,6-tBu2C6H3, 2,6-iPr2C6H3). This
is a modification of a literature procedure.32,47 The syntheses of K(O-
2,6-tBu2C6H3) and K(O-2,6-iPr2C6H3) are analogous, and the prepara-
tion of K(O-2,6-tBu2C6H3) is given as a representative example: A
125 mL side arm flask equipped with a magnetic stir bar was charged
with 2,6-di-tert-butylphenol (2.00 g, 9.69 mmol) and THF (30 mL). To
this clear, colorless stirring solution was added K[N(SiMe3)2] (1.61 g,
8.08 mmol) as a solid, generating a pale yellow solution. The resulting
solution was stirred at room temperature for 15 h, after which time the
volatiles were removed under reduced pressure. The resulting pale pink
solid was washed with pentane (25 mL), collected by filtration through a
medium-porosity fritted filter, and dried under reduced pressure to afford
K(O-2,6-tBu2C6H3) as a white solid (1.96 g, 8.04 mmol, 99%). 1H NMR
(THF-d8, 298 K): δ 6.72 (d, 2H, m-Ar-CH), 5.77 (t, 1H, p-Ar-CH), 1.38
(s, 18H, C-CH3). K(O-2,6-iPr2C6H3): 1H NMR (THF-d8, 298 K): δ 6.69
(d, J = 7 Hz, 2H, m-Ar-CH), 6.07 (t, J = 7 Hz, 1H, p-Ar-CH), 3.51 (sept,
J = 7 Hz, 2H, CHMe2), 1.12 (d, J = 6 Hz, 12H, CH(CH3)2).
’ EXPERIMENTAL SECTION
General Synthetic Considerations. Unless otherwise noted, all
reactions and manipulations were performed at 20 °C in a recirculating
Vacuum Atmospheres NEXUS model inert atmosphere (N2) drybox
equipped with a 40CFM Dual Purifier NI-Train. Glassware was dried
overnight at 150 °C before use. All NMR spectra were obtained using a
1
Bruker Avance 300 MHz spectrometer. Chemical shifts for H NMR
spectra were referenced to solvent impurities. Elemental analyses were
performed at the University of California, Berkeley Microanalytical
Facility, Columbia Analytical Services (Tucson, AZ), or Midwest
Microlab, LLC (Indianapolis, IN).
Note: Heating can be performed inside a ventilation hood using oil
baths and thick-walled Schlenk tubes equipped with Teflon valves. However,
we found it more convenient to heat reactions inside the glovebox using an
IKA RCT Basic stirring hot plate equipped with an ETS-D5 thermocouple
and ChemGlass reaction PIE-BLOCK hardware, which have a drilled
thermowell for insertion of an electronic contact, thermometer.
Materials. Unless otherwise noted, reagents were purchased from
commercial suppliers and used without further purification. Celite
(Aldrich), alumina (Brockman I, Aldrich), and 4 Å molecular sieves
(Aldrich) were dried under dynamic vacuum at 250 °C for 48 h prior to
use. All solvents (Aldrich) were purchased anhydrous and were dried
over KH for 48 h, passed through a column of activated alumina, and
Synthesis of UI4(1,4-dioxane)2 (1). Method A: Room Tem-
perature. A 20 mL scintillation vial was charged with a stir bar, uranium
turnings (1.02 g, 4.28 mmol), iodine (2.23 g, 8.78 mmol), and 1,4-
dioxane (10 mL). The reaction mixture was vigorously stirred for 7 days
at room temperature to give a thick brick-red suspension. The reaction
mixture was filtered over a medium-porosity fritted filter to collect a red-
orange solid. The solid was washed with a 1:1 mixture of hexane and the
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noncoordinating ether TMS2O (3 ꢀ 15 mL) and dried under reduced
pressure to give UI4(1,4-dioxane)2 (1) as a red-orange solid (3.75 g, 4.06
mmol, 95%). Anal. Calcd for C8H16I4O4U (mol wt 921.86): C, 10.42; H,
1.75; I, 55.06. Found: C, 11.08; H, 1.70; I, 50.0. 1H NMR (C6D6, 298 K):
δ 3.31 (br s, ν1/2 = 69 Hz, 16H, CH2).
Method B: 50 °C. A 50 mL round-bottom flask was charged with a
large stir bar, uranium turnings (2.13 g, 8.94 mmol), iodine (4.65 g, 18.3
mmol), and 1,4-dioxane (12 mL). The reaction mixture was vigorously
stirred for 18 h at 50 °C, using a thermocouple-equipped IKA stirring hot
plate, yielding a brick-red suspension. The reaction mixture was cooled
to room temperature and filtered over a medium-porosity fritted filter to
collect a red-orange solid. The solid was washed with a 1:1 mixture of
hexane and the noncoordinating ether TMS2O (3 ꢀ 15 mL) and dried
under reduced pressure to give UI4(1,4-dioxane)2 (1) as a red-orange
solid (7.94 g, 8.61 mmol, 96%).
[K2(OEt2)2]fc[NSi(tBu)Me2]2 was added to it dropwise with stirring.
The reaction mixture was allowed to warm to room temperature while
stirring for 1 h. The volatiles were removed under reduced pressure. The
resulting brown solid was extracted into toluene (∼40 mL) and filtered
through a Celite-padded coarse-porosity fritted filter. The Celite plug
was rinsed until the washings were colorless. The filtrate was collected,
and the volatiles were removed under reduced pressure. The extraction,
filtration, and drying were repeated. The dried solid was scraped from
the flask walls, transferred to a medium-porosity fritted filter, washed
with hexane (∼40 mL) until the filtrate was nearly clear, and dried under
reduced pressure, giving fc[NSi(tBu)Me2]2UI2(THF) (5) as a brown
solid (1.21 g, 1.21 mmol, 61%). The 1H NMR spectrum was consistent
with the data previously reported for complex 5.28 1H NMR (C6D6, 298
K): δ 56.6 (s, 12H, SiCH3), 40.5 (s, 18H, SiC-CH3), -20.3 (m, 4H,
C5H4), -26.1 (s, 4H, THF-CH2), -41.0 (m, 4H, C5H4), -74.0 (s, 4H,
THF-CH2).
Synthesis of UI4(Et2O)2 (2). A 20 mL scintillation vial was charged
with a stir bar, UI4(1,4-dioxane)2 (1) (0.101 g, 0.110 mmol), and diethyl
ether (15 mL). The reaction mixture was stirred for 1 h at room
temperature and then concentrated to ∼3 mL. Pentane (10 mL) was
added, resulting in precipitation of a red solid. The solid was collected by
filtration on a medium-porosity fritted filter and dried under reduced
pressure to give UI4(Et2O)2 (2) as a red solid (0.069 g, 0.078 mmol,
71%). The 1H NMR spectrum collected in C6D6 was consistent with the
data previously reported for complex 2.21 1H NMR (C6D6, 298 K):
δ -10.53 (s, 6H, O(CH2CH3)2), -22.54 (s, 4H, O(CH2CH3)2).
Synthesis of [UCl4(1,4-dioxane)]2 (3). A 125 mL side arm flask
was charged with a stir bar, UI4(1,4-dioxane)2 (1) (1.50 g, 1.63 mmol),
and 1,4-dioxane (35 mL). To this suspension was added HCl (4 M/1,4-
dioxane, 2 mL, 8 mmol) over 1 min. Initially, the red-orange suspension
clears up and turns dark red. Additional HCl causes the rapid formation
of a yellow precipitate. The reaction mixture was vigorously stirred for 10
min at room temperature to give a yellow precipitate. The yellow solid
was collected by filtration over a medium-porosity fritted filter, washed
sequentially with 1,4-dioxane (5 mL) and hexane (2 ꢀ 15 mL), and
dried thoroughly under reduced pressure. The product changed color
from yellow to orange while drying, to give [UCl4(1,4-dioxane)]2 (3) as
an orange solid (0.655 g, 0.700 mmol, 86%). Anal. Calcd for
C8H16Cl8O4U2 (mol wt 935.89): C, 10.27; H, 1.72. Found: C, 9.90;
H, 1.39. 1H NMR (C6D6, 298 K): δ 1.25 (br s, 16H, CH2). Note: This
compound has poor solubility in C6D6, and the chemical shift of the
product can vary between δ 1.25 and 1.75 depending on the concentra-
tion and temperature.
Synthesis of UCl4(TMEDA)2 (4). A 20 mL scintillation vial was
charged with a stir bar, UI4(1,4-dioxane)2 (1) (0.194 g, 0.211 mmol),
and toluene (10 mL). TMEDA (0.0538 g, 0.463 mmol) was added to the
resulting solution, and the reaction was stirred for 18 h at room
temperature to give an orange precipitate (UI4(TMEDA)2). Excess
HCl (4 M/1,4-dioxane, 0.26 mL, 1.0 mmol) was added to the suspen-
sion, and the reaction mixture was stirred at room temperature for 4 h.
Next, TMEDA (0.1226 g, 1.055 mmol) was added to the reaction
mixture, which was stirred for 1 h to give a light green precipitate. The
volatiles were then removed under reduced pressure to give UCl4-
(TMEDA)2 (4) as a light green solid (0.118 g, 0.192 mmol, 91%). The
1H NMR spectrum collected in toluene-d8 was consistent with the
data previously reported for complex 4.27 1H NMR (toluene-d8, 298 K):
δ 6.56 (br s, 12H, N(CH3)2), -6.79 (br s, 12H, N(CH3)2), -34.8 (s, 4H,
CH2), -60.6 (s, 4H, CH2).
Synthesis of [(Me3Si)2N]2U[K2-(C,N)-CH2Si(Me)2N(SiMe3)]
(6). Method A: From UI4(1,4-dioxane)2. A 250 mL Schlenk flask was
charged with a stir bar, UI4(1,4-dioxane)2 (1) (2.03 g, 2.20 mmol),
K[N(SiMe3)2] (1.76 g, 8.81 mmol), and toluene (100 mL). The resul-
ting yellow-orange suspension was transferred to a ventilation hood and
heated in a 110 °C oil bath with stirring. After 15 h, the flask was cooled
to room temperature, the stoppers were secured with electrical tape, and
the flask was brought into an inert atmosphere drybox. The volatiles
were then removed under reduced pressure to give a yellow residue,
which was extracted into hexane (50 mL) and filtered through a Celite-
padded medium-porosity fritted filter to remove salt byproducts. The
Celite plug was washed with hexane (∼10 mL) until the washings went
colorless. The filtrate was collected, and the volatiles were removed
under reduced pressure to give [(Me3Si)2N]2U[κ2-(C,N)-CH2Si(Me)2-
N(SiMe3)] (6) as a waxy yellow solid (1.10 g, 1.53 mmol, 70%). The 1H
NMR spectrum collected in C6D6 was consistent with the data previously
reported for complex 6.30 1H NMR (C6D6, 298 K): δ 11.3 (s, 6H,
Si(CH3)2), 9.7 (s, 9H, Si(CH3)3), -13.1 (s, 36H, N[Si(CH3)3]2), -117.7
(s, 2H, U-CH2).
Method B: From [UCl4(1,4-dioxane)]2. A 100 mL round-bottom flask
was charged with a stir bar, [UCl4(1,4-dioxane)]2 (3) (0.250 g, 0.267
mmol), Na[N(SiMe3)2] (0.462 g, 2.52 mmol), and toluene (45 mL).
The flask was sealed, and the resulting yellow suspension was stirred for
15 h at 110 °C, using a thermocouple-equipped IKA stirring hot plate.
The flask was then cooled to room temperature, and the volatiles were
removed under reduced pressure to give a yellow residue, which was
extracted into hexane (25 mL) and filtered through a Celite-padded
medium-porosity fritted filter to remove salt byproducts. The Celite plug
was washed with hexane (∼10 mL) until the washings went colorless.
The filtrate was collected, and the volatiles were removed under reduced
pressure to give [(Me3Si)2N]2U[κ2-(C,N)-CH2Si(Me)2N(SiMe3)] (6)
as a waxy yellow solid (0.309 g, 0.431 mmol, 80%).
Synthesis of U(O-2,6-tBu2C6H3)4 (7). Method A: From UI4(1,4-
dioxane)2. A 20 mL scintillation vial was charged with a stir bar, UI4(1,4-
dioxane)2 (1) (0.112 g, 0.121 mmol), K(O-2,6-tBu2C6H3) (0.121 g,
0.495 mmol), and THF (5 mL). The resulting yellow suspension was
stirred for 12 h at rt. The volatiles were removed under reduced pressure.
The residue was dissolved in toluene (5 mL) and filtered through a
Celite-padded coarse-porosity fritted filter. The orange filtrate was
collected, and the volatiles were removed under reduced pressure to
give an orange solid residue. The residue was then extracted with hexane
(5 mL) and filtered through a Celite-padded medium-porosity fritted
filter. The filtrate was collected, and the volatiles were removed under
reduced pressure to give U(O-2,6-tBu2C6H3)4 (7) as a dark yellow solid
(0.082 g, 0.0774 mmol, 64%). The 1H NMR spectrum collected in C6D6
Synthesis of fc[NSi(tBu)Me2]2UI2(THF) (5). A 20 mL scintilla-
tion vial was charged with [K2(OEt2)2]fc[NSi(tBu)Me2]2 (1.33 g, 1.99
mmol) and THF (20 mL). A second 20 mL scintillation vial was charged
with UI4(1,4-dioxane)2 (1) (1.84 g, 1.99 mmol) and THF (20 mL).
Both solutions were cooled at -35 °C for at least 30 min. The cooled
THF solution of UI4(1,4-dioxane)2 (1) was transferred to a 100 mL
round-bottom flask containing a stir bar, and the cooled THF solution of
was consistent with the data previously reported for complex 7.31,32 1
H
NMR (C6D6, 298 K): δ 10.6 (d, 8H, m-Ar-CH), 8.4 (t, 4H, p-Ar-CH),
-0.96 (br s, 72H, C-CH3).
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Method B: From [UCl4(1,4-dioxane)]2. A 20 mL scintillation vial was
charged with a stir bar, [UCl4(1,4-dioxane)]2 (3) (0.0520 g, 0.0556
mmol), K[O-2,6-tBu2C6H3] (0.118 g, 0.484 mmol), and toluene
(10 mL). The reaction mixture was stirred for 15 h at 70 °C, using a
thermocouple-equipped IKA stirring hot plate. The resulting yellow
suspension was filtered through a Celite-padded coarse-porosity fritted
filter. The volatiles were removed under reduced pressure to give a
yellow-orange crystalline solid, which was extracted with hexane
(20 mL) and filtered through a Celite-padded medium-porosity frit.
The filtrate was collected, and the volatiles were removed under reduced
pressure to give U(O-2,6-tBu2C6H3)4 (7) as a dark yellow solid (0.0764
g, 0.0722 mmol, 65% yield).
Synthesis of (C5Me5)2UI2 (8). A 125 mL side arm flask equipped
with a magnetic stir bar was charged with K(C5Me5) (0.427 g, 2.45
mmol), UI4(1,4-dioxane)2 (1) (1.13 g, 1.23 mmol), and toluene (35 mL).
The reaction mixture was stirred for 18 h at 110 °C using a thermocouple-
equipped IKA stirring hot plate. The resulting red-brown suspension was
filteredthroughaCelite-paddedcoarse-porosityfrittedfilter, andtheCelite
plug was washed with toluene (20 mL) until the washings went colorless.
Excess solvent was removed under reduced pressure. The red-brown
residue was extracted into hexane (50 mL) and filtered through a Celite-
padded coarse-porosity fritted filter, and the Celite plug was washed with
hexane (50 mL) until the washings went colorless. The volatiles were
removed under reduced pressure to give (C5Me5)2UI2 (8) as a waxy red-
brownsolid(0.605 g, 0.797mmol, 65%). The1HNMRspectrumcollected
in C6D6 was consistent with the data previously reported for complex
8.34-36 1H NMR (C6D6, 298 K): δ 17.9 (s, 30H, C5Me5).
precipitate a blue-violet solid. The solid was isolated by filtration through
a coarse-porosity fritted filter, being careful to leave unreacted uranium
turnings behind. The solid was dried under reduced pressure to give
UI3(1,4-dioxane)1.5 (10) as a blue-violet solid (5.77 g, 7.68 mmol, 79%).
Synthesis of UI3(THF)4 (11). A 20 mL scintillation vial was
charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (0.346 g, 0.461 mmol),
and THF (10 mL) to give a clear blue solution. The solution was stirred
for 1 h at room temperature. The volatiles were then removed under
reduced pressure to give UI3(THF)4 (11) as a dark blue solid (0.410 g,
0.452 mmol, 98%). The 1H NMR spectrum collected in toluene-d8 was
consistent with the data previously reported for complex 11.4 1H NMR
(toluene-d8, 298 K): δ 10.78 (br s, 4H, THF-CH2), 6.16 (br s, 4H, THF-
CH2).
Synthesis of UI3(py)4 (12). A 20 mL scintillation vial was charged
with a stir bar, UI3(1,4-dioxane)1.5 (10) (0.338 g, 0.450 mmol), and
pyridine (10 mL) to give a blue-black solution. The solution was stirred
for 4 h at room temperature. The volatiles were then removed under
reduced pressure to give UI3(py)4 (12) as a black microcrystalline solid
(0.376 g, 0.402 mmol, 89%). The 1H NMR spectrum collected in C6D6
was consistent with the data previously reported for complex 12.4 1
H
NMR (C6D6, 298 K): δ 18.17 (br s, py-CH), 14.88 (br s, py-CH), 11.46
(br s, py-CH).
Synthesis of U(O-2,6-tBu2C6H3)3(THF) (13). A 20 mL scintilla-
tion vial was charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (0.240 g,
0.320 mmol), and THF (5 mL). With stirring, a THF (5 mL) solution of
K(O-2,6-tBu2C6H3) (0.234 g, 0.960 mmol) was added to the THF
solution of UI3(1,4-dioxane)1.5 (10), and the reaction mixture was
stirred for 1 h at room temperature. The volatiles were then removed
under reduced pressure. The resulting solid was then extracted into
pentane (10 mL) and filtered through a Celite-padded pipet filter. The
filtrate was collected, and the volatiles were removed under reduced
pressure to give U(O-2,6-tBu2C6H3)3(THF) (13) as a brown solid
(0.239 g, 0.258 mmol, 81%). The 1H NMR spectrum collected in C6D6
Synthesis of (C5Me5)2UCl2 (9). A 125 mL side arm flask equipped
with a magnetic stir bar was charged with (C5Me5)MgCl(THF) (0.740
g, 2.77 mmol), [UCl4(1,4-dioxane)]2 (3) (0.648 g, 0.692 mmol), and
toluene (55 mL). To this solution was added 1,4-dioxane (2 mL), and
the reaction mixture was capped and stirred for 15 h at 110 °C using a
thermocouple-equipped IKA stirring hot plate. The resulting red
suspension was filtered through a Celite-padded coarse-porosity fritted
filter, and the Celite plug was washed with toluene (35 mL) until the
washings went colorless. The volatiles were removed under reduced
pressure. The red residue was extracted into hexane (50 mL) and filtered
through a Celite-padded coarse-porosity fritted filter, and the Celite plug
was washed with hexane (50 mL) until the washings went colorless. The
filtrate was collected, and the volatiles were removed under reduced
pressure to give (C5Me5)2UCl2 (9) as a red crystalline solid (0.560 g,
was consistent with the data previously reported for complex 13.38 1
H
NMR (C6D6, 298 K): δ 16.07 (s, 6H, m-Ar-CH), 13.37 (s, 3H, p-Ar-
CH), -1.61 (br s, 54H, C-CH3), -16.32 (br s, 4H, THF-CH2), -39.71
(br s, 4H, THF-CH2).
Synthesis of U(O-2,6-iPr2C6H3)3(THF) (14). A 20 mL scintilla-
tion vial was charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (0.324 g,
0.431 mmol), and THF (5 mL). A solution of K(O-2,6-iPr2C6H3)
(0.280 g, 1.29 mmol) in THF (5 mL) was added with stirring. The
resulting reaction mixture was stirred for 1 h at room temperature. The
reaction mixture was filtered through a Celite-padded coarse-porosity
fritted filter, and the Celite plug was rinsed with THF (3 ꢀ 2 mL). The
volatiles were removed under reduced pressure. The resulting solid was
extracted into toluene (10 mL) and filtered through a Celite-padded
pipet filter. The filtrate was collected, and the volatiles were removed
under reduced pressure to give U(O-2,6-iPr2C6H3)3(THF) (14) as a
brown solid (0.297 g, 0.352 mmol, 82%). The 1H NMR spectrum collec-
1
0.964 mmol, 70%). The H NMR spectrum collected in C6D6 was
consistent with the data previously reported for complex 9.37 1H NMR
(C6D6, 298 K): δ 13.5 (s, 30H, C5Me5).
Synthesis of UI3(1,4-dioxane)1.5 (10). Method A: Room Tem-
perature. A 20 mL scintillation vial was charged with a stir bar, uranium
turnings (2.50 g, 10.5 mmol), iodine (3.60 g, 14.2 mmol), and dioxane
(10 mL). The reaction was vigorously stirred for 18 h at room
temperature, during which time the reaction mixture changed color
from red to a blue-violet suspension. The reaction mixture was filtered
through a medium-porosity fritted filter to collect the blue-violet solid.
During the solid collection, care was taken to leave behind any unreacted
uranium turnings. The solid was washed with diethyl ether (∼20 mL)
and dried under reduced pressure to give UI3(1,4-dioxane)1.5 (10) as a
blue-violet solid (7.05 g, 9.38 mmol, 99%). Anal. Calcd for C6H12I3O3U
(mol wt 750.90): C, 9.60; H, 1.61; I, 50.70; U, 31.70. Found: C, 11.06; H,
1.70; I, 50.4; U, 28.7.
Method B: 80 °C. A 50 mL thick-walled Schlenk tube sealed with a
Teflon valve and equipped with a magnetic stir was charged with
uranium turnings (2.58 g, 10.8 mmol), iodine (3.71 g, 14.6 mmol),
and 1,4-dioxane (12 mL). The reaction mixture was vigorously stirred in
an 80 °C oil bath for 18 h. The flask was cooled to room temperature and
brought into a drybox. The blue-violet suspension was concentrated to a
thick sludge under reduced pressure, and Et2O (10 mL) was added to
ted in C6D6 was consistent with the formation of complex 14.38,39 1
H
NMR (C6D6, 298 K): δ 11.23 (s, 6H, m-Ar-CH), 9.47 (s, 3H, p-Ar-CH),
1.06 (s, 6H, iPr-CH), -1.39 (s, 36H, iPr-CH3), -3.31 (br s, 4H, THF-
CH2), -6.06 (br s, 4H, THF-CH2).
Synthesis of U[N(SiMe3)2]3 (15). A 125 mL side arm flask was
charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (1.00 g, 1.33 mmol),
Na[N(SiMe3)2] (0.733 g, 4.00 mmol), and THF (45 mL). The resulting
cloudy purple suspension was stirred for 1 h at room temperature. The
solution was filtered through a Celite-padded medium-porosity fritted
filter, and the volatiles were removed under reduced pressure. The red-
purple residue was extracted into pentane (50 mL) and filtered through a
Celite-padded medium-porosity fritted filter. The filtrate was collected,
and the volatiles were removed under reduced pressure to give U[N-
(SiMe3)2]3 (15) as a red-purple powder (0.700 g, 0.970 mmol, 73%).
The 1H NMR spectrum collected in C6D6 was consistent with the data
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Organometallics
ARTICLE
previously reported for complex 15.40,41 1H NMR (C6D6, 298 K): δ
-11.4 (s, 54H, SiMe3).
X-ray Crystallography. A crystal (0.10 ꢀ 0.08 ꢀ 0.08 mm) of
complex 1 was mounted in a nylon cryoloop using Paratone-N oil under
an argon gas flow. The data were collected on a Bruker D8 APEX II
charge-coupled-device (CCD) diffractometer with a KRYO-FLEX
liquid nitrogen vapor cooling device. The instrument was equipped
with a graphite-monochromatized Mo KR X-ray source (λ = 0.71073 Å),
with MonoCap X-ray source optics. A hemisphere of data was collected
using ω scans. Data collection and initial indexing and cell refinement
were handled using APEX II software.48 Frame integration, including
Lorentz-polarization corrections, and final cell parameter calculations
were carried out using SAINTþ software.49 The data were corrected for
absorption using the SADABS program.50 Decay of reflection intensity
was monitored by analysis of redundant frames. The structure was
solved using direct methods and difference Fourier techniques. Non-
hydrogen atoms were refined anisotropically, and hydrogen atoms were
treated as idealized contributions. Structure solution, refinement, gra-
phics, and creation of publication materials were performed using
SHELXTL.51 Additional details regarding data collection are provided
in the CIF file.
Synthesis of (C5Me5)2UI(THF) (16). A 125 mL side arm flask was
charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (3.34 g, 4.45 mmol),
and THF (80 mL). To the resulting dark blue solution was added
K(C5Me5) (2.33 g, 13.3 mmol) as a solid. The solution immediately
changed color to green. The reaction mixture was stirred for 36 h at
room temperature and filtered through a Celite-padded medium-
porosity fritted filter to remove salt byproducts. The Celite plug was
washed with THF (15 mL) until the washings went colorless. The
filtrate was collected, and the volatiles were removed under reduced
pressure. The resulting green-brown residue was extracted into toluene
(60 mL) and filtered through a Celite-padded medium-porosity fritted
filter. The filtrate was collected, and THF (10 mL) was added to the
solution. The volatiles were removed under reduced pressure to give a
green-brown residue, which was extracted into hexane (75 mL) and
filtered through a Celite-padded medium-porosity fritted filter. The
Celite plug was then washed with THF (∼10 mL) until the washings
went colorless. The dark green filtrate was collected, and the volatiles
were removed under reduced pressure to give (C5Me5)2UI(THF) (16)
as a dark green solid (2.35 g, 3.34 mmol, 75%). The 1H NMR spectrum
collected in C6D6 was consistent with the data previously reported for
complex 16.42 1H NMR (C6D6, 298 K): δ -1.1 (br s, 30H, C5Me5),
-17.4 (br s, 4H, THF-CH2), -54.7 (br s, 4H, THF-CH2).
’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic information
b
for complex 1 in CIF format. This material is available free of
Synthesis of (C5Me4Et)2UI(THF) (17). A 125 mL side arm flask
was charged with a stir bar, UI3(1,4-dioxane)1.5 (10) (1.18 g, 1.57
mmol), and THF (75 mL). To the resulting dark blue solution was
added K(C5Me4Et) (0.888 g, 4.71 mmol) as a solid. The solution
immediately changed color to green. The reaction mixture was stirred
for 15 h at room temperature and filtered through a Celite-padded
medium-porosity fritted filter to remove salt byproducts. The Celite plug
was washed with THF (15 mL) until the washings went colorless. The
filtrate was collected, and the volatiles were removed under reduced
pressure. The resulting green-brown residue was extracted into toluene
(30 mL) and filtered through a Celite-padded medium-porosity fritted
filter. The Celite plug was washed with toluene (5 mL) until the
washings went colorless. The filtrate was collected, and THF (10 mL)
was added to the solution. The volatiles were removed under reduced
pressure to give a green-brown residue, which was extracted into hexane
(35 mL) and filtered through a Celite-padded medium-porosity fritted
filter. The Celite plug was then washed with THF (∼5 mL) until the
washings went colorless. The dark green filtrate was collected, and the
volatiles were removed under reduced pressure to give (C5Me4Et)2-
UI(THF) (17) as a dark green solid (0.775 g, 1.05 mmol, 67%). The
1H NMR spectrum collected in C6D6 was consistent with the data
previously reported for complex 17.43 1H NMR (C6D6, 298 K): δ 16.85
(br s, 6H, -CH2CH3), 0.09 (br s, 4H, THF-CH2), -0.963 (br s, 4H,
THF-CH2), -3.51 (br s, 12H, -CH3), -4.01 (br s, 12H, -CH3),
-18.21 (br s, 4H, -CH2CH3).
charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: kiplinger@lanl.gov. Phone: 505-665-9553. Fax: 505-
667-9905.
’ ACKNOWLEDGMENT
For financial support of this work, we acknowledge the LANL
G. T. Seaborg Institute for Transactinium Science (Graduate
Student Fellowship to M.J.M.; PD Fellowships to R.K.T. and N.
E.T.), LANL (Director’s PD Fellowship to T.C.), the Division of
Chemical Sciences, Office of Basic Energy Science, Heavy
Element Chemistry Program, and the LANL LDRD program.
The authors thank Prof. Paula L. Diaconescu (UCLA) for a
donation of [K2(OEt2)2]fc[NSi(tBu)Me2]2. Drs. Rebecca M.
Chamberlin, David L. Clark, Stosh A. Kozimor, and David E.
Morris (all LANL) are acknowledged for helpful discussions and
for sharing unpublished results.
’ REFERENCES
Synthesis of U(dNtBu)2(I)2(OdPPh3)2 (18). A 20 mL scintilla-
tion vial was charged with UI3(1,4-dioxane)1.5 (10) (0.208 g, 0.277
mmol) and THF (5 mL). A stir bar, tBuNH2 (0.138 g, 1.89 mmol), and
I2 (0.106 g, 0.416 mmol) were added to the vial, which was then stirred
vigorously with frequent shaking for 10 min (giving U(dNtBu)2(I)2-
(THF)2-3). The volatiles were removed under reduced pressure. The
resulting solid was extracted into toluene (10 mL) and filtered through a
Celite-filter-plugged pipet. The filtrate was collected, and a solution of
Ph3P dO (0.163 g, 0.585 mmol) in toluene (5 mL) was added with
stirring. The solution was stored at room temperature for 15 h, and
U(dNtBu)2(I)2(OdPPh3)2 (18) deposited as bright red crystals
(0.143 g, 0.120 mmol, 46%). The 1H NMR spectrum collected in
CD2Cl2 was consistent with the data previously reported for complex
18.44 1H NMR (CD2Cl2, 298 K): δ 8.38 (m, 12H, o-Ar-CH), 7.61 (m,
18H, m- and p-Ar-CH), 0.00 (s, 18H, C-CH3).
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