Reactivity of UI4(OEt2)2 with phenols: Probing the chemistry of the U-I bond

Article abstract of DOI:10.1039/b823002a

Solutions of UI₄(OEt₂)₂ in Et₂O were found to deposit orange crystals of [H(OEt₂) ₂][UI₅(OEt₂)] (1) upon standing at room temperature. The proton in the cation of 1 mo

Full text of DOI:10.1039/b823002a

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Reactivity of UI4(OEt2)2 with phenols: probing the chemistry of the U–I bond†
David D. Schnaars, Guang Wu and Trevor W. Hayton*
Received 23rd December 2008, Accepted 11th February 2009
First published as an Advance Article on the web 12th March 2009
DOI: 10.1039/b823002a
Solutions of UI4(OEt2)2 in Et2O were found to deposit orange crystals of [H(OEt2)2][UI5(OEt2)] (1)
upon standing at room temperature. The proton in the cation of 1 most likely originates from the
surface of the glass vial in which the solution was stored. Reactions of UI4(OEt2)2 with 1 equiv. of
ArOH in toluene, followed by addition of THF, provides UI3(OAr)(THF)x (Ar = Ph, x = 3, 2;
Ar = 2,6-Ph2C6H3, x = 2, 3). UI4(OEt2)2 also reacts with 2 equiv. of ArOH (Ar = Ph, 4-tBuC6H4,
2,6-Me2C6H3, C6F5) in toluene, followed by addition of THF, to generate UI2(OC6H5)2(THF)3 (4),
UI2(O-4-tBuC6H4)2(THF)3 (5), UI2(O-2,6-Me2C6H3)2(THF)3 (6) and UI2(OC6F5)2(THF)3 (7), in
moderate yields. Complete conversion to the products requires the use of a dynamic vacuum to remove
the HI generated upon addition of the phenol.
Introduction
Results
The lack of a commercially available uranium halide, the typ-
ical starting point for most organometallic uranium chemistry,
requires that any uranium halide or pseudo-halide synthon be
synthesized ‘in-house’. The most popular access point for synthetic
U(IV) chemistry is undoubtedly UCl4, which is simple to prepare
and can be isolated in good yields.1,2 However, the ability of the
chloride ligands to readily form “ate” complexes3–11 has made the
discovery of a simple, high-yielding route to its bromo or iodo
congeners of considerable interest.12,13 In this regard, the recent
development of two low-temperature and high-yielding routes
to UI4(OEt2)2,14,15 is potentially of great benefit to the synthetic
actinide community.
The development of a new synthon can have a major impact in
an area. This is well illustrated by the synthesis of UI3(THF)4,16
which spurred a major expansion of U(III) chemistry,17 as this
reagent has several advantages, including ease of preparation and
high solubility in organic solvents, over the previous alternative,
UCl3.18–21 It is possible that UI4(OEt2)2, which is also easy to
prepare and soluble in Et2O and toluene, will have a similar impact.
However, its utility for synthesis can not be adequately judged until
preliminary reactivity studies are completed.
UI4(OEt2)2 is stable indefinitely in the solid state at -25 ◦C, however
it slowly decomposes at room temperature to an intractable tan
powder. When allowed to stand at room temperature, cherry-
red Et2O solutions of UI4(OEt2)2 turn orange over the course
of 24 h, concomitant with the deposition of orange needles. An
X-ray crystallographic analysis of this material has shown it to
be [H(OEt2)2][UI5(OEt2)] (1) (Fig. 1), the result of HI addition
to UI4(OEt2)2. Complex 1 crystallizes in the orthorhombic space
group Pnna and consists of discrete cation–anion pairs. The
[UI5(OEt2)]- anion exhibits octahedral coordination around the
uranium(IV) center with bond angles of I2–U1–I2* = 178.70(5)◦
and I3–U1–I3* = 174.14(7)◦. The U–I bond lengths in 1 range
˚
from 2.964(2)–2.998(1) A, while the U1–O1 bond length is
˚
2.43(1) A. The cation portion of the complex consists of a proton
coordinated to two diethyl ether molecules. The proton could not
be observed in the electron density map, but the distance between
In this contribution, we report the first reactivity study of this
new, and potentially important, U(IV) synthon. Here, we present
the synthesis of several uranium(IV) phenoxide complexes by direct
protonation of a U–I bond in UI4(OEt2)2 with a variety of phenols.
This method negates the need to first generate the alkali metal
salt of the phenol, as required in previous syntheses of uranium
phenoxides.11,22–24 It also eliminates the possibility of forming “ate”
complexes, which are normally undesirable. While iodide ligands
are less likely than other halides to form “ate” complexes, a few
iodide “ate” complexes are known for the highly electropositive f
elements.4,25–28
Fig. 1 ORTEP diagram of [H(OEt2)2][UI5(OEt2)] (1) with 50% prob-
˚
ability ellipsoids being shown. Selected bond lengths (A) and angles
(◦): U1–I1 = 2.964(2), U1–I2 = 2.998(1), U1–I3 = 2.984(1), U1–O1 =
2.43(1), I1–U1–I2 = 90.65(3), I1–U1–I3 = 92.93(3), I1–U1–O1 = 180.0,
I2–U1–I3 = 90.71(3), I2–U1–I2* = 178.70(5), I2–U1–O1 = 89.35(3),
I3–U1–I3* = 174.14(7), I3–U1–O1 = 87.07(3).
Department of Chemistry and Biochemistry, University of California Santa
Barbara, Santa Barbara, CA 93106. E-mail: hayton@chem.ucsb.edu
† CCDC reference numbers 715605–715610. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b823002a
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˚
as the toluene solvate, 2·C7H8. Its solid-state molecular structure
is shown in Fig. 2. Complex 2 exhibits a pentagonal bipyramidal
geometry in the solid-state, with the phenoxide ligand and one
iodide ligand occupying the axial sites. The U–O(phenoxide) bond
the two oxygen atoms (O2–O3 = 2.48 A), is comparable to the
O–O distances observed for this cation in previous examples.29–32
The formulation of complex 1 as a uranium(V) iodide was also
considered. However, we believe this possibility is unlikely, in part
◦
˚
because UI5 is unknown.33 In addition, the U–I bond lengths in 1
length is 2.01(1) A, while the U1–O1–C1 bond angle is 172(1) .
14
˚
˚
The U–I bond distances (av. U–I = 3.08 A) are typical of other
match well with that reported for UI4(OEt2)2 (U–I = 2.964(1) A).
U(IV) iodides,34 while the U–O(THF) bond lengths (av. 2.43 A) are
˚
The formation of 1 from UI4(OEt2)2 most likely occurs via
protonation of a U–I bond by a hydroxyl group on the glass
surface, generating a molecule of HI. The HI can then react with
an intact molecule of UI4(OEt2)2 to generate complex 1 (eqn (1)).
To demonstrate the involvement of glass in the formation of 1, a
solution of UI4(OEt2)2 was partitioned into two vials, one glass
and one PTFE, and both vials were stored at room temperature.
After 48 h, the solution in the glass vial contained orange needles
and an orange solution consistent with the formation of 1, whereas
the solution in the PTFE vial was unchanged (as confirmed by 1H
NMR spectroscopy). Attempts to further characterize complex 1
were complicated by its low solubility in non-coordinating solvents
and its reactivity with donor solvents, such as THF and MeCN.
also similar to other tetrahydrofuran complexes of uranium.24,35
(1)
Fig. 2 ORTEP diagram of UI3(OC6H5)(THF)3 (2·C7H8) with 50% prob-
◦
˚
ability ellipsoids being shown. Selected bond lengths (A) and angles ( ):
U1–O1 = 2.01(1), U1–O2 = 2.47(1), U1–O3 = 2.42(1), U1–O4 = 2.41(1),
U1–I1 = 3.018(2), U1–I2 = 3.108(2), U1–I3 = 3.099(2), U1–O1–C1 =
172(1), O1–U1–I1 179.0(4).
Given the striking reactivity of UI4(OEt2)2 with glass, we have
explored the reactivity of this complex with other protic substrates.
For instance, addition of 1 equiv. of phenol to a cherry-red
toluene solution of UI4(OEt2)2 results in a colour change to
orange. Upon application of a dynamic vacuum this solution
becomes cloudy. The addition of excess THF, and recrystallization
from toluene–hexanes provides air- and moisture-sensitive green
crystals of UI3(OC6H5)(THF)3 (2) in a 41% yield (Scheme 1).
Similarly, reaction of UI4(OEt2)2 with 2,6-Ph2C6H3OH under
identical conditions provides UI3(O-2,6-Ph2C6H3)(THF)2 (3), also
in a moderate yield.
Single crystals of 3 were grown from toluene–hexanes, where
it crystallizes in the monoclinic space group C2/c (Fig. 3). In
contrast to 2, complex 3 exhibits an octahedral structure in
the solid state. Presumably, the extra steric bulk of the 2,6-
diphenylphenoxide precludes the coordination of three THF
ligands to the uranium center. Like 2, complex 3 exhibits a short
Scheme 1
1
The H NMR spectra of 2 and 3 are both consistent with the
incorporation of the aryl alcohol. For instance, the 1H NMR
spectrum of 2 in C6D6 exhibits signals at 76.9 ppm, 39.2 ppm
and 28.1 ppm, assignable to the ortho, meta, and para hydrogen
nuclei of the phenyl ring, respectively; while the signals attributable
to the THF ligands are observed at -18.1 ppm and -27.3 ppm as
broad singlets.
Single crystals of 2 suitable for X-ray diffraction analysis were
grown from toluene–hexanes solutions stored at -25 ◦C for several
days. Complex 2 crystallizes in the orthorhombic space group Pbca
Fig. 3 ORTEP diagram of UI3(O–2,6-Ph2C6H3)(THF)2 (3) with 50%
˚
probability ellipsoids being shown. Selected bond lengths (A) and angles
(◦): U1–O1 = 2.088(7), U1–O2 = 2.378(6), U1–O3 = 2.382(6), U1–I1 =
3.013(1), U1–I2 = 3.021(1), U1–I3 = 3.014(1), U1–O1–C1 = 170.9(6),
O1–U1–I3 = 178.2(2).
3682 | Dalton Trans., 2009, 3681–3687
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˚
U–O(phenoxide) distance (U1–O1 = 2.088(7) A) and a nearly
linear U1–O1–C1 angle (170.9(6)◦). It also exhibits comparable
˚
˚
U–I (av. 3.02 A) and U–O(THF) distances (U1–O2 = 2.378(6) A
˚
and U1–O3 = 2.382(6) A).
The exchange of two iodide ligands in UI4(OEt2)2 by protona-
tion is also possible. For instance, addition of 2 equiv. of phenol
to a toluene solution of UI4(OEt2)2, followed by application of a
dynamic vacuum, and addition of excess THF, results in the forma-
tion of UI2(OC6H5)2(THF)3 (4) in a 67% yield (Scheme 1). Several
other uranium(IV) bis(phenoxide) complexes can be synthesized in
an identical manner. Thus, UI2(O-4-tBuC6H4)2(THF)3 (5), UI2(O-
2,6-Me2C6H3)2(THF)3 (6), and UI2(OC6F5)2(THF)3 (7) can also
be isolated in moderate yields (Scheme 1). Again, the application
of a dynamic vacuum is essential for driving the reaction to
completion.
Fig. 4 ORTEP diagram of UI2(O-4-tBuC6H4)2(THF)3 (5) with 50%
probability ellipsoids being shown.
Complexes 4–7 can also be isolated by addition of 2 equiv.
of NEt3 to the reaction mixture, negating the requirement of
a dynamic vacuum. However, when synthesized in this man-
ner the uranium complexes are invariably contaminated with
[NEt3H]I, and the resulting yields are much lower. In addition,
the comproportionation reaction of complex 4 with UI4(OEt2)2
in CD2Cl2 quickly yields complex 2. Attempts to make U(OPh)3I
and U(OPh)4 by reacting UI4(OEt2)2 with 3 and 4 equiv. of phenol,
respectively, yield only complex 4 in both cases.
The 1H NMR spectra for compounds 4, 5, 6, and 7 are consistent
with the proposed formulations. For instance, the 1H NMR
spectrum of 4 in C6D6 exhibits signals at 93.8 ppm, 46.8 ppm
and 33.4 ppm, assignable to the ortho, meta, and para hydrogen
nuclei of the phenyl ring, respectively. These chemical shifts are
similar to those observed for 2. The 1H NMR spectra for 5 and 6
also exhibited paramagnetically-shifted resonances for the protons
on the phenoxide ligands, while for complex 7 the 19F{ H} NMR
1
Fig. 5 ORTEP diagram of UI2(O-2,6-Me2C6H3)2(THF)3 (6·2THF) with
spectrum in C6D6 contains three singlets at -33.8 ppm, -71.6 ppm
and -86.5 ppm, corresponding to the ortho, meta, and para fluorine
nuclei, respectively.
50% probability ellipsoids being shown.
1
2
The U–O(phenoxide) bond lengths for 5, 6·2THF and 7· THF
Complex 5 crystallizes in the orthorhombic space group Pbca,
while complex 6 crystallizes in the monoclinic space group C2/c,
as the THF solvate 6·2THF, and 7 crystallizes in the monoclinic
are nearly identical. For instance, complex 5 exhibits U–
˚
˚
O(phenoxide) bond lengths of 2.051(8) A and 2.084(8) A, complex
˚
6 exhibits a U–O(phenoxide) bond length of 2.092(8) A, and
1
˚
space group P21/c, as the THF solvate 7· THF. The solid-state
in complex 7 the U–O(phenoxide) bond lengths are 2.114(7) A
2
1
˚
molecular structures for 5, 6·2THF, and 7· THF are shown in
and 2.125(6) A. In addition, the U–O–C bond angles of the
2
Fig. 4, 5 and 6, respectively. Selected bond length and angles for
phenoxide ligands are nearly linear. For example, in complex
5 the U–O–C angles are U1–O1–C1 = 176.9(8)◦ and U1–O2–
C11 = 166.1(8)◦. These metrical parameters are similar to other
U(IV) phenoxide complexes.35,36 For instance, UI2(OAr)2(THF)
(Ar = 2,6-tBu2C6H3) exhibits U–O(phenoxide) bond lengths of
1
2
5, 6·2THF and 7· THF can be found in Table 1. All three of
these compounds adopt similar distorted pentagonal bipyramidal
geometries, with the two phenoxide ligands exhibiting a trans
disposition.
◦
1
2
˚
Table 1 Selected bond lengths (A) and angles ( ) for 5, 6·2THF and 7· THF
1
2
5
6·2THF
U1–I1
7· THF
U1–I1
U1–I2
U1–O1
U1–O2
U1–O3
U1–O4
U1–O5
3.145(1)
3.143(1)
2.051(8)
2.084(8)
2.443(9)
2.47(1)
3.1326(8)
2.092(8)
2.521(7)
2.47(1)
U1–I1
U1–I2
U1–O1
U1–O2
U1–O3
U1–O4
U1–O5
3.0918(9)
3.0914(9)
2.114(7)
2.125(6)
2.449(6)
2.486(6)
2.398(6)
174.4(2)
176.0(6)
173.8(6)
U1–O1
U1–O2
2.499(9)
U1–O3
O1–U1–O2
U1–O1–C1
U1–O12–C11
173.5(3)
176.9(8)
166.2(8)
O1–U1–O1*
U1–O1–C1
168.2(4)
176.8(6)
O1–U1–O2
U1–O1–C1
U1–O2–C7
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iodide-metal charge transfer.38 The observed red-shift can be
rationalized by invoking a larger crystal field splitting upon
coordination of increasingly electron rich phenoxide ligands. This
subsequently raises the energy of the metal-based orbitals involved
in the LMCT.
Discussion
Both theoretical and experimental thermochemical data shows
that U–I bonds are amongst the weakest bonds known for
uranium,39–41 while U–O bonds are amongst the strongest.39,42,43
The reactivity observed for UI4(OEt2)2 can be explained within
this context as the reaction is driven by the formation of a strong
U–O bond, which can overcome the unfavourable pKa of HI.
A similar protonation is also observed during the reaction of
uranium metal with iodine in isopropanol. This reaction results
in the isolation of [UI2(OiPr)2(HOiPr)2]2, which is presumably
formed via a solvated UI4 complex.38 In addition, UI4(THF)x
(generated in situ) is known to rapidly ring-open THF, producing
UI2(OCH2CH2CH2CH2I)2(THF)x, again demonstrating the sensi-
tivity of the U–I bond and the oxophilicity of the uranium center.44
Several other UI4 complexes have also been reported, but they do
not exhibit such reactive U–I bonds. Typically these complexes
contain better donor ligands, such as MeCN or PhCN,12,13,45–50 sug-
gesting that the electron poor uranium center in UI4(OEt2)2 also
plays a role in the U–I bond reactivity. Interestingly, UI4(MeCN)4
has been previously used to make uranium aryloxides, including
U(OAr)4 and U(OAr)2I2(THF) (Ar = 2,6-tBu2C6H3),11 but these
syntheses follow the traditional metathetical protocol.
The increased stability of UI4(OEt2)2 solutions when stored in
PTFE strongly suggests that glass is the source of the proton in the
hydronium counterion of complex 1. This type of reactivity is rare,
but not unprecedented. Several f element complexes are known to
react with glass. For instance, [(C5Me5)2Ln][(m-Ph)2BPh2] (where
Ln = La, Ce, and Pr) can abstract an oxygen from the glass surface,
generating [(C5Me5)2Ln]2(m-O).51
The dynamic vacuum required to synthesize complexes 2–
7 (Scheme 1) is probably necessary to remove HI from the
reaction mixture. This synthetic method reduces the possibility
of forming “ate” complexes during metathesis, an often unwanted
reaction pathway that is common for the f elements.4,5,8,11 There
are several previous examples in transition metal chemistry,52 and
the actinides,38,53 of direct protonation of a metal-halide bond to
form a metal alkoxide and HX.
1
2
Fig. 6 ORTEP diagram of UI2(OC6F5)2(THF)3 (7· THF) with 50%
probability ellipsoids being shown.
◦
˚
˚
2.073(9) A and 2.080(8) A, and U-O–C bond angles of 172.6(8)
and 166.2(8)◦,35 while the U–O bond length in U(OAr)4 is
36
˚
2.135(4) A.
Given the similarity of the U–O(phenoxide) bond lengths in
5, 6·2THF and 7· THF, we are unable to draw any conclusions
1
2
from the crystallographic data about variation in the phenoxide
bonding interaction as a function of the aryl ring. However, the
absorption spectra for complexes 4, 6 and 7 do exhibit changes
depending on the aryl ring substituents. In Et2O, these compounds
produce similar UV-vis spectra (Fig. 7). In particular, complex 7
(Ar = C6F5) exhibits a well-defined peak at 362 nm (e = 4200 L
mol-1 cm-1). Notably, this feature is successively red-shifted as the
phenoxide ligand becomes more electron donating.37 For instance,
this peak is observed at 369 nm (e = 3260 L mol-1 cm-1) and 378 nm
(e = 4430 L mol-1 cm-1) for complexes 4 (Ar = Ph) and 6 (Ar =
2,6-Me2C6H3), respectively. Complex 5 (Ar = 4-tBuC6H4) does
not follow this trend: its absorption is observed at 370 nm (e =
4230 L mol-1 cm-1), but based on pKa it should be closer to that
observed for 6.
Summary
UI4(OEt2)2 has proven to be an incredibly reactive U(IV) syn-
thon as shown by its ability to deprotonate glass to form
[H(OEt2)2][UI5(OEt2)]. We have demonstrated that this potent
reactivity can be productively harnessed through our syntheses
of UI3(OAr)(THF)x (Ar = Ph, x = 3; Ar = 2,6-Ph2C6H3, x = 2)
and UI2(OAr)2(THF)3 (Ar = Ph, 4-tBu-C6H4, 2,6-Me2C6H3, C6F5)
directly from UI4(OEt2)2 and ArOH. This procedure eliminates
the requirement of first making the alkali metal salt of the phenol.
It also simplifies the reaction work-up, as no salt byproduct is
generated. This represents a potential advantage that UI4(OEt2)2
has over other U(IV) halides. It is likely that UI4(OEt2)2 will be an
Fig. 7 Absorption spectra of 4 (0.19 mM), 5 (0.20 mM), 6 (0.22 mM),
and 7 (0.24 mM). All spectra recorded in Et2O.
Given the similarity of the bands observed for complexes 4–7
with those observed for UI4(OEt2)2 (both in terms of location and
intensity), we attribute these features to an iodide–metal LMCT.14
A similar feature in UI2(OiPr)2(HOiPr)x was also assigned to
3684 | Dalton Trans., 2009, 3681–3687
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extremely useful reagent for future synthetic studies with uranium,
and we are continuing to explore the reactivity of this complex.
30.52, H 2.85. 1H NMR (400 MHz, 25 ◦C, C6D6): d 40.26 (s, 2H,
meta CH), 33.82 (s, 4H, ortho CH), 27.79 (t, 1H, JCH = 7.4 Hz,
para CH), -5.09 (s, 4H, meta CH), -17.51 (s, 8H, b-THF), -58.80
(s, 8H, a-THF). The resonance attributable to the 2 para hydrogen
atoms of the aryloxide was not found.
Experimental
General
UI2(OC6H5)2(THF)3 (4). The synthesis required UI4(OEt2)2
(30.0 mg, 0.034 mmol), and phenol (6.3 mg, 0.067 mmol) in
toluene (3 mL). Total yield: 20.1 mg, 67% yield. Crystals of 4 turn
opaque and pale green-yellow when dried in vacuo. Anal. calcd for
UI2O5C24H34: C 32.23, H 3.83. Anal. calcd for UI2O4C20H26 (i.e.
UI2(OC6H5)2(THF)2): C 29.21, H 3.19. Found: C 28.77, H 3.27. 1H
NMR (400 MHz, 25 ◦C, C6D6): d 93.80 (s, 4H, ortho CH), 46.75
(s, 4H, meta CH), 33.35 (s, 2H, para CH), -21.76 (s, 12H, b-THF),
-28.25 (s, 12H, a-THF). UV-vis (Et2O, 0.19 ¥ 10-3 M): 303 nm
(sh, e = 4840 L mol-1 cm-1), 369 nm (e = 3260 L mol-1 cm-1).
Allreactions andsubsequentmanipulations were performedunder
anaerobic and anhydrous conditions either under high vacuum or
an atmosphere of nitrogen or argon. THF, hexanes, diethyl ether
and toluene were dried by passage over activated molecular sieves
using a Vacuum Atmospheres solvent purification system. C6D6
and CD2Cl2 were dried over activated 4 A and 3 A molecular sieves
respectively for 24 h before use. Uranium metal was obtained from
Los Alamos National Laboratory, and UI4(OEt2)2 was prepared
using the published procedure.14 All other reagents were obtained
from commercial sources and used as received.
NMR spectra were recorded on a Varian INOVA 400 spec-
trometer. 1H NMR spectra are referenced to external SiMe4 using
the residual protio solvent peaks as internal standards. 19F NMR
spectra were referenced to external 0.05% a,a,a-trifluorotoluene
in C6D6. UV-vis experiments were performed on a JASCO V-570
UV-Vis-NIR spectrometer. Elemental analyses were performed by
Desert Analytics in Tucson, AZ or the Microanalytical Laboratory
at UC Berkeley.
˚
˚
UI2(O-4-tBuC6H4)2(THF)3 (5). The synthesis required
UI4(OEt2)2 (30.0 mg, 0.034 mmol) and 4-tert-butylphenol
(10.1 mg, 0.067 mmol) in toluene (2 mL). Total yield: 11.1 mg,
33% yield. Crystals of 5 turn opaque and pink when dried in
vacuo. Anal. calcd for UI2O5C32H50: C 38.18, H 5.01. Anal. calcd
for UI2O3C24H34 (i.e. UI2(O-4-tBuC6H4)2(THF)): C 33.43, H 3.97.
Found: C 33.13, H 3.95. H NMR (400 MHz, 25 ◦C, C6D6): d
1
93.15 (s, 4H, ortho CH), 47.58 (s, 4H, meta CH), 17.54 (s, 18H,
tBu), -27.05 (s, 12H, b-THF), -35.92 (s, 12H, a-THF). UV-vis
(Et2O, 0.20 ¥ 10-3 M): 300 nm (sh, e = 7080 L mol-1 cm-1), 370 nm
(e = 4230 L mol-1 cm-1).
[H(OEt2)2][UI5(OEt2)] (1). A 20 mL glass vial was charged
with a magnetic stir bar, UI4(OEt2)2 (102 mg, 0.11 mmol), and Et2O
(7 mL). The resulting cherry-red solution was filtered through a
column of Celite supported on glass wool (0.5 cm ¥ 2 cm). The
filtrate was stored at room temperature for several days producing
an orange solution and an orange crystalline solid. The solid
was isolated and dried in vacuo to provide orange crystals of 1
(19.6 mg, 16% yield). Complex 1 has proven to be insoluble in non-
coordinating solvents, such as Et2O, toluene and CH2Cl2, limiting
the amount of characterization data that could be collected. Anal.
calcd for UI5O3C12H31: C 13.15, H 2.85. Found: C 11.10, H 2.52.
Crystals of 1 turn opaque when dried in vacuo.
UI2(O-2,6-Me2C6H3)2(THF)3 (6). The synthesis required
UI4(OEt2)2 (30.0 mg, 0.034 mmol) and 2,6-dimethylphenol
(8.2 mg, 0.067 mmol) in toluene (4 mL). Total yield: 18 mg, 56%
yield. Crystals of 6 become pale-green and opaque when dried in
vacuo. Anal. calcd for UI2O5C28H42: C 35.38, H 4.45. Anal. calcd
for UI2O3C20H26 (i.e. UI2(O-2,6-Me2C6H3)2(THF)): C 29.79, H
3.25. Anal. calcd for UI2O2C16H18 (i.e. UI2(O-2,6-Me2C6H3)2): C
26.18, H 2.47. Found: C 27.81, H 3.14. 1H NMR (400 MHz, 25 ◦C,
C6D6): d 42.95 (s, 4H, meta CH), 38.77 (s, 12H, CH3), 30.38 (s,
2H, para CH), -18.98 (s, 12H, b-THF), -39.62 (s, 12H, a-THF).
UV-vis (Et2O, 0.22 ¥ 10-3 M): 310 nm (sh, e = 4790 L mol-1 cm-1),
378 nm (e = 4430 L mol-1 cm-1).
Complexes 2–7 were synthesized similarly and only the synthesis
of complex 2 will be described in detail.
UI2(OC6F5)2(THF)3 (7). The synthesis required UI4(OEt2)2
(30.0 mg, 0.034 mmol) and pentafluorophenol (12.4 mg,
0.067 mmol) in toluene (2 mL). Total yield: 21 mg, 58% yield.
Crystals of 7 turn opaque and pale-green upon exposure to
vacuum. Anal. calcd for UI2O5C24F10H24: C 26.83, H 2.25. Anal.
calcd for UI2O3C16F10H8 (i.e. UI2(OC6F5)2(THF)): C 20.66, H 0.87.
UI3(OC6H5)(THF)3 (2). A 20 mL glass vial was charged with a
magnetic stir bar, UI4(OEt2)2 (32.7 mg, 0.037 mmol), and toluene
(2 mL). Addition of phenol (3.6 mg, 0.038 mmol) to the cherry
red solution resulted in a colour change to orange. The volume
of the solution was reduced in vacuo to 0.5 mL and then diluted
with toluene (1 mL), resulting in a cloudy orange solution. THF
(0.2 mL) was then added, and the resulting yellow solution was
filtered though a Celite column supported on glass wool (0.5 cm ¥
2 cm). The filtrate was layered with hexanes (3 mL) and stored
at -25 ◦C for 96 h resulting in the deposition of green crystals
(13.9 mg, 41% yield). Anal. calcd for UI3O4C18H29: C 23.29, H
3.15. Found: C 22.94, H 3.05. 1H NMR (400 MHz, 25 ◦C, C6D6):
d 76.87 (s, 2H, ortho CH), 39.15 (s, 2H, meta CH), 28.06 (s, 1H,
para CH), -18.11 (s, 12H, b-THF), -27.29 (s, 12H, a-THF).
Found: C 20.06, H 0.86. H NMR (400 MHz, 25 ◦C, C6D6): d
1
1
-20.24 (s, 12H, b-THF), -39.76 (s, 12H, a-THF) 19F{ H} NMR
(376 MHz, 25 ◦C, C6D6) d -33.84 (s, 4F, ortho CF), -71.63 (s, 4F,
meta CF), -86.54 (s, 2F, para CF). UV-vis (Et2O, 0.24 ¥ 10-3 M):
287 nm (sh, e = 8580 L mol-1 cm-1), 362 nm (e = 4200 L mol-1
cm-1).
X-Ray Crystallography
UI3(O-2,6-Ph2C6H3)(THF)2 (3). The synthesis required
UI4(OEt2)2 (31.0 mg, 0.035 mmol) and 2,6-diphenylphenol
(8.5 mg, 0.035 mmol) in toluene (2 mL). Total yield: 19.0 mg,
54%. Anal. calcd for UI3O3C26H29: C 30.97, H 2.90. Found: C
The crystal structures of complexes 1, 2·C7H8, 3, 5, 6·2THF and
1
2
7· THF, were determined similarly with exceptions noted in the
following paragraph. Crystals were mounted on a glass fiber under
Paratone-N oil. Data collection was carried out using a Bruker
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Dalton Trans., 2009, 3681–3687 | 3685
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1
2
Table 2 X-Ray crystallographic data for complexes 1, 2·C7H8, 3, 5, 6·2THF and 7· THF
1
2
1
2·C7H8
3
5
6·2THF
7· THF
Empirical formula
FW/g mol-1
Crystal habit,
colour
C12H31I5O3U
1095.90
Plate, orange-red
C25H37I3O4U
1020.28
Plate, green
C26H29I3O3U
1008.22
Plate, yellow-green
C32H50I2O5U
1006.55
Plate, green
C36H58I2O7U
1094.65
Block, green
C26H28F10I2O5.5
1110.31
Block, green-blue
U
Crystal size/mm
Crystal system
Space group
0.20 ¥ 0.10 ¥ 0.05
Orthorhombic
Pnna
14.141(3)
18.184(4)
10.585(2)
90
0.20 ¥ 0.20 ¥ 0.03
Orthorhombic
Pbca
17.166(3)
12.357(2)
29.580(5)
90
0.25 ¥ 0.25 ¥ 0.06
Monoclinic
C2/c
19.332(7)
12.547(4)
24.785(9)
90
106.953(5)
90
5750(3)
8
2.329
8.890
3680
22 838
5827
0.0795
0.24 ¥ 0.18 ¥ 0.04
Orthorhombic
Pbca
23.0285(16)
13.3321(9)
23.6112(17)
90
90
90
7249.1(9)
8
1.845
0.20 ¥ 0.10 ¥ 0.06
Monoclinic
C2/c
13.6892(18)
11.8797(15)
24.995(3)
90
93.130(3)
90
4058.7(9)
4
1.791
5.562
2112
14 998
4075
0.1242
0.20 ¥ 0.20 ¥ 0.15
Monoclinic
P21/c
21.613(3)
10.9881(16)
14.154(2)
90
96.465(3)
90
3339.9(8)
4
2.208
6.799
2064
14 985
4916
0.0550
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
90
90
90
90
3
˚
V/A
2721.7(11)
4
2.674
11.640
1936
11 975
2800
0.1304
6274.7(19)
8
2.160
8.151
3760
27 765
5352
0.1400
Z
D
calcd/Mg m-3
m/mm-1
F000
6.216
3840
57 858
7636
Total no. reflections
Unique reflections
Rint
0.1855
Final R indices [I >
2s(I)]
R1 = 0.0473,
wR2 = 0.1047
1.92 and -0.88
R1 = 0.0618,
wR2 = 0.1393
2.72 and -1.34
R1 = 0.0548,
wR2 = 0.1271
5.92 and -1.78
R1 = 0.0813,
wR2 = 0.1324
3.57 and -2.14
R1 = 0.0563,
wR2 = 0.1177
2.17 and -3.35
R1 = 0.0432,
wR2 = 0.0947
2.38 and -0.87
Largest diffraction
-3
˚
peak and hole/e A
GOF
0.788
1.254
1.079
0.987
0.917
0.970
3-axis platform diffractometer with a SMART-1000 CCD detec-
tor. The instrument was equipped with a graphite monochroma-
˚
˚
set to 1.4 A, and 1.5 A, respectively. The C28–C25 bond length
˚
˚
was set to 2.3 A, while O6–C26 and O6–C27 were set to 2.2 A. The
carbon atoms were modelled with isotropic temperature factors.
In addition, C24 in complex 7 was refined isotropically. Additional
X-ray crystallographic data for complexes 1, 2·C7H8, 3, 5, 6·2THF,
˚
tized MoKa X-ray source (l = 0.71073 A). All data were collected
at 150(2) K using an Oxford nitrogen gas cryostream system. A
hemisphere of data was collected using w scans and 0.3◦ frame
widths. SMART54 was used to determine the cell parameters
and data collection. The raw frame data were processed using
SAINT.55 The empirical absorption correction was applied based
on Psi-scan or SADABS. Subsequent calculations were carried out
using SHELXTL.56 Structures were solved using Direct methods
and difference Fourier techniques. All hydrogen atom positions
were idealized, and rode on the atom of attachment, while the
final refinement included anisotropic temperature factors on all
non-hydrogen atoms. Structure solution, refinement, graphics,
and creation of publication materials were performed using
SHELXTL.
1
2
and 7· THF, can be found in Table 2.
Acknowledgements
We thank the University of California, Santa Barbara, for financial
support of this work.
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