Synthesis and crystal structure of pentavalent uranyl complexes. the remarkable stability of UO2X (X = I, SO3CF3) in non-aqueous solutions

Article abstract of DOI:10.1039/b820659g

The reaction of [UO₂I₂(THF)₃] with KC ₅R₅ (R = H, Me) or K₂C₈H₈ in pyridine gave crystals of [{UO₂(py)₅}{KI ₂(py)₂}]_∞<

Full text of DOI:10.1039/b820659g

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis and crystal structure of pentavalent uranyl complexes. The
remarkable stability of UO2X (X = I, SO3CF3) in non-aqueous solutions†
Jean-Claude Berthet,* Ge´rald Siffredi, Pierre Thue´ry and Michel Ephritikhine*
Received 26th November 2008, Accepted 29th January 2009
First published as an Advance Article on the web 24th February 2009
DOI: 10.1039/b820659g
The reaction of [UO2I2(THF)3] with KC5R5 (R = H, Me) or K2C8H8 in pyridine gave crystals of
[{UO2(py)5}{KI2(py)2}]• (1), which were desolvated under vacuum into pulverulent [UO2(py)2.2KI2] (2).
Similar reactions with [UO2(OTf)2] afforded [UO2(py)2.3K(OTf)2] (3) as a powder and crystals of
[{UO2(py)5} {K3(OTf)5}·py]• (4·py), which were also obtained together with crystals of
[{UO2(py)5}22{K(OTf)2(py)2}][OTf]·py (5·py) by treating [UO2(OTf)2] with KC4Me4P. Crystals of 6·py,
the thallium analogue of 5·py, were isolated from the reaction of [UO2(OTf)2] and TlC5H5. Treatment of
[UO2I2(THF)3] with LiCH2SiMe3 in pyridine afforded crystals of [{UO2(py)5}{LiI(py)2}][I] (7) while
[UO2(OTf)2] reacted with the alkyllithium reagent in acetonitrile to give crystals of
[{UO2(py)5}{Li2(OTf)3}]• (8) in pyridine. The crystal structures of 1, 4·py, 5·py, 6·py, 7 and 8 revealed
=
the presence of U O→M interactions (M = Li, K, Tl), and the rich diversity of these structures, from
dinuclear (7) to 3D polymeric (4), is related to the distinct coordination numbers of the M+ ion and
=
ligation modes of the bridging iodide and triflate ligands as well as the presence of U O→M
interactions. The mononuclear complexes [UO2(OTf)(THF)n] (9) and [UO2(OTf)(Et2O)0.5] (10) were
respectively obtained by reaction of [UO2(OTf)2] with KC5R5 in THF or LiCH2SiMe3 in Et2O, and were
transformed into [UO2(OTf)(py)2] (11) in pyridine. Treatment of [UO2I2(THF)3] with TlC5H5 in
pyridine afforded crystals of [UO2(py)5][I]·py (12·py) which were desolvated under vacuum into the
powder of [UO2I(py)2.5] (14). The same reaction in THF gave [UO2I(THF)2.7] (13) in powder form.
Crystals of [UO2(CyMe4BTBP)(py)][OTf]·1.5py (15·1.5py) and the powder of [UO2I(CyMe4BTBP)]
(16) were obtained by treating [UO2(CyMeBTBP)X2] (X = OTf, I) with KC5Me5 or TlC5H5,
respectively. The uranyl(V) chloride and nitrate compounds [UO2Cl(py)3] (17) and [UO2(NO3)(py)3] (18)
were prepared by reaction of the uranyl(VI) precursors with TlC5H5 in pyridine; complex 18 was also
obtained by treating 13 with TlNO3. Crystals of the neutral mononuclear complex [UO2(OTf)(py)4] (19)
were isolated from reaction of [UO2(OTf)2] with Me3SiC5H5 in acetonitrile. Similar reaction with
[UO2Cl2(THF)2]2 in pyridine gave crystals of [UO2Cl2(py)3]. The crystal structures of 12·py, 15·1.5py
and 19 were determined; the structure of 15 was compared with that of the uranyl(VI) counterpart. All
the uranyl(V) compounds are remarkably stable in pyridine solution; the IR absorption at 816 cm-1 is
+
=
attributed to the nasym(U O) of the ubiquitous [UO2(py)5] species.
exceptions which could be obtained from high-valent precursors.5
The uranium(VI) chemistry is dominated by the uranyl ion
[UO2]2+, which is a remarkably stable moiety with an unusual
linear structure. The strong oxophilicity of this ion was an
obstacle to the isolation of anhydrous starting materials required
for organometallic syntheses. It is only recently that practical
routes to such uranyl species, [UO2(OTf)2] (OTf = OSO2CF3)6
and [UO2X2(THF)3] (X = Cl,7 I8), have been designed. From
these precursors were obtained the first stable uranyl compounds
containing U–C bonds, i.e. the bis-iminophosphorane complex
Introduction
Recent years have witnessed a fast growing interest in organoura-
nium chemistry.1 The low-valent U(III) and U(IV) complexes, in
particular those of the tris and bis(pentamethylcyclopentadienyl)2
and mono and bis(cyclooctatetraene) series,3 were found to
display unsuspected chemical behaviour. The discovery of novel
reactions and structures are an incitement to further experimental
and theoretical investigations in f element chemistry, especially
for a better understanding of the nature of the metal–ligand
bonding.In contrast, organouranium compounds in their highest
oxidation state (+5 and +6) are still quite uncommon, although
attracting a deeper attention. These were most generally prepared
by oxidation of low-valent uranium compounds,4 with a few
3
[UO2Cl(h -CH{Ph2PNSiMe3}2)]2 and its derivatives,9 the cyanido
compound [UO2(CN)5][NEt4]3,10 and a few N-heterocyclic carbene
complexes.11 The synthesis of uranyl alkyl compounds remains a
challenging goal, while first attempts at their preparation date
back to the middle of the XIX century.12 The lack of success
in the isolation of alkyl or cyclopentadienyl complexes of uranyl
was related to the instability of the U–C bond toward hydrolysis
and/or reduction processes leading to unidentified brown-orange
U(IV) species.13
CEA, IRAMIS, Service de Chimie Mole´culaire, CNRS URA 331,
CEA/Saclay, 91191, Gif-sur-Yvette, France. E-mail: jean-claude.berthet@
cea.fr, michel.ephritikhine@cea.fr
† CCDC reference numbers 711336–711344. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b820659g
3478 | Dalton Trans., 2009, 3478–3494
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Recently, we prepared the first cyclopentadienyl uranyl
complex [UO2(C5Me5)(CN)3][NR4]2 by oxidation of the U(IV)
linear pentacyanido metallocene [U(C5Me5)2(CN)5][NR4]2 with
pyridine oxide.14 This result prompted us to take another look
at the reactions of UO2X2 (X = OTf, I, Cl, NO3) and their
Lewis base adducts with the cyclopentadienyl and cycloocta-
precursors. However, all these compounds showed limited stability
toward disproportionation in solution, while Ikeda et al. reported
that some electrochemically generated, but not isolated, U(V)
species like [UO2(dbm)(DMSO)]- and [UO2(salophen)(DMSO)]-
(salophen
=
N,N¢-disalicylidene-ortho-phenylenediaminate)
were quite stable in DMSO.24 Here, we report on the synthesis
and characterization of uranyl(V) complexes obtained by
reduction of UO2X2 (X = I, OTf, Cl, NO3) with alkyl or
cyclopentadienyl anions in organic solution. Depending on
the nature of X, the solvent, the reducing agent and its metal
salt, a variety of complexes, neutral or cationic, with distinct
structures, from mononuclear to heteronuclear 3D polymeric,
have been obtained. These complexes were found to be quite
stable in organic solution. The X-ray crystal structures of
[UO2(py)4(OTf)], [UO2(py)5][I], [UO2(CyMe4BTBP)(py)][OTf]
-
tetraene anions, C5R5 (R = H, Me) and C8H82-. These reactions
did not afford the U(VI) organometallic compounds but involved
a one electron transfer to give the corresponding pentavalent
uranyl(V) compounds. Thus, we found a convenient access
to stable complexes of the [UO2]+ ion.15 Because of its rapid
disproportionation into [UO2]2+ and U4+ in aqueous solutions,16
the [UO2]+ ion was for a long time an elusive species, in contrast
to the other actinyl(V) ions [AnO2]+ (An = Np, Pu, Am). Suitable
[UO2]+ complexes were highly desirable for the study of the
fundamental properties of the [AnO2]+ compounds17 which
have important implications in nuclear fuel processing, waste
treatment and environmental remediation.18 The first uranyl(V)
compound to have been crystallographically characterized,
[UO2(OPPh3)4][OTf], was obtained serendipitously during the
crystallization of its U(VI) parent.19 This result gave clear
evidence that such complexes of the [UO2]+ ion could be
isolated in anhydrous conditions and stabilized by the choice
of appropriate ligands and media. During the last two years,
pentavalent uranyl(V) compounds were reproducibly synthesized
and isolated by using such anhydrous and anaerobic experimental
conditions. The 1D polymeric complex [{UO2(py)5}{KI2(py)2}]•,
that we described in our preliminary communication,15 was
prepared by Mazzanti et al. by following a distinct route via
the oxidation of [UI3(THF)3],20 and was transformed into the
tetrameric and dimeric derivatives [{UO2(dbm)2}4{K6(py)10]2+
and [UO2(dbm)2K(18-crown-6)]2 (dbmH = dibenzoylmethane).21
The mononuclear uranyl(V) b-diketiminate complexes
(CyMe4BTBP
1,2,4-triazin-3-yl)-2,2¢-bipyridine),
[{UO2(py)5}2{M(OTf)2(py)2}][OTf] (M = K, Tl), [{UO2(py)5}2-
{K3(OTf)5}·py]• and [{UO2(py)5}{Li2(OTf)3}]• are described.
=
6,6¢-bis-(3,3,6,6-tetramethyl-cyclohexane-
[{UO2(py)5}{LiI(py)2}][I],
Results
= =
Polynuclear uranyl(V) complexes with O U O→M interactions
(M = Li, K, Tl)
The syntheses of the complexes are summarized in Scheme 1.
KC5R5, K2C8H8, KC4Me4P and TlC5R5 as the reducing agents.
Treatment of [UO2I2(THF)3] with 1 mol equivalent of KC5R5
(R = H, Me) or 0.5 mol equivalent of K2C8H8 in pyridine
reproducibly led to an orange suspension, which was stable for
many days at 20 ◦C. The clear solution obtained by heating under
reflux deposited thin orange needles of [{UO2(py)5}{KI2(py)2}]•
(1) upon cooling down at room temperature. The 1D polymeric
crystal structure of 1 has already been described and will not be
further commented; it consists of infinite chains where [UO2(py)5]+
cations are linked by the oxo groups with the [KI2(py)2]- anionic
[UO2(Ar2nacnac)(Ph2MePO)2] [Ar2nacnac
=
(2,6-iPr2C6H3)-
NC(Me)CHC(Me)N(2,6-iPr2C6H3)]22 and [UO2(Ar2nacnac)-
(RCOCHCOR)]- (R = Me, Ph, CF3)23 were synthesized by
Hayton and Wu by reduction of the corresponding uranyl(VI)
=
Scheme 1 Synthesis of the uranyl(V) complexes with U O→M interactions. All reactions are in pyridine.
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fragments.15 Such O U O→M interactions are well documented
in uranyl(VI) and neptunyl(V) chemistry,25,26 and reflect the Lewis
basicity of the axial oxygen atoms. In view of the lower positive
charge on the metal centre and consequently the greater electron
density on the oxygen atoms, the [UO2]+ moiety is expected to have
a more pronounced basicity than its [UO2]2+ analogue.
=
=
the polymeric compound [{UO2(py)5}2{K3(OTf)5}·py]• (4·py)
(Table 1).
Crystals of 4·py were also obtained from the reaction of
[UO2(OTf)2] and the potassium salt of the phospholyl anion
KC5Me4P, together with orange crystals of the trinuclear complex
[{UO2(py)5}2{K(OTf)2(py)2}][OTf]·py (5·py). As in the case of
reactions with KC5R5 (R = H, Me) and K2C8H8, no organoura-
nium complex was detected by 1H NMR during the synthesis of 4
and 5. Similar treatment of [UO2(OTf)2] with TlC5H5 in pyridine
rapidly afforded a brown solution without precipitation of TlOTf,
which displays good solubility in organic solvents. Attempts
at crystallization by slow diffusion of pentane into the crude
reaction mixture afforded dark-orange crystals of the trinuclear
compound [{UO2(py)5}2{Tl(OTf)2(py)2}][OTf]·py (6·py), which
are isomorphous with the potassium analogue 5·py (Table 2).
A view of the asymmetric unit of 4 is shown in Fig. 1a while
selected bond distances and angles are listed in Table 1. The
pentagonal bipyramidal UO2(py)5 units are linked to K(OTf)3
The bright orange compound 1 was found to desolvate under
vacuum into an ochre powder, which analyses as [UO2(py)2.2KI2]
(2). Diffusion of diethyl ether into a pyridine solution of 2 gave
back orange crystals of 1. An orange powder was also formed when
uranyl iodide was reacted with K(Hg) in pyridine but separation
of the product from the residual mercury was difficult.
The 1H NMR spectra of the reaction mixtures of [UO2I2(THF)3]
27
and KC5R5 (R = H, Me) showed the formation of C5H6-nDn or
(C5Me5)2,28 resulting from hydrogen abstraction or coupling of the
C5R5∑ radical; reduction of the uranyl(VI) compound with K2C8H8
gave free cyclooctatetraene. These observations clearly indicate
-
2-
that the C5R5 and C8H8 anions act as the reducing agents.
The high-valent uranium iodide complexes being generally less
stable than the other halide (Cl, Br) or pseudo halide (OTf) con-
geners, the synthesis and isolation of more uranyl(V) derivatives
involving different counter anions were anticipated. Replacing
[UO2I2(THF)3] with [UO2(OTf)2] in its reactions with KC5R5 and
K2C8H8 in pyridine gave a clear brown-orange solution, which
deposited a brown powder upon addition of diethyl ether. The
latter turned beige when dried under vacuum and the elemental
analyses are in agreement with the formula [UO2(py)2.3K(OTf)2]
(3), the triflate analogue of 2. Crystallization of the crude reaction
mixture from pyridine-diethyl ether afforded orange crystals of
=
=
=
fragments via one (U1 O1) or two (O3 U2 O4) oxo groups, and
1
2
K1 and K2 are bridged by a m-k :k triflate ligand. Each potassium
atom is linked to two symmetry related atoms via bridging OTf
ligands, so that the K atoms are the knots of a three dimensional
network (Fig. 1b). While K1 and K2 are connected to three K
atoms, K3 is linked to two K atoms, one of its OTf ligands
being terminal and monodentate. A view of the cation of 5 is
shown in Fig. 2; selected bond distances and angles are listed in
Table 2. The complex is built up of two [UO2(py)5]+ units which are
-
=
attached to a [K(OTf)2(py)2] fragment via a U O→K interaction.
Complexes 4, 5 and 6 are unique examples of pentavalent
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) in [{UO2(py)5}2{K3(OTf)5}·py]• (4·py)
˚
Bond lengths/A
U(1)–O(1)
U(1)–O(2)
U(2)–O(3)
U(2)–O(4)
<U–O(yl)>
U(1)–N(1)
U(1)–N(2)
U(1)–N(3)
1.855(8)
1.816(8)
1.823(8)
1.844(8)
1.83(1)
2.614(10)
2.608(9)
2.622(8)
U(1)–N(4)
U(1)–N(5)
<U(1)–N>
U(2)–N(6)
U(2)–N(7)
U(2)–N(8)
U(2)–N(9)
U(2)–N(10)
2.615(10)
2.617(7)
2.615(9)
2.606(11)
2.638(10)
2.591(10)
2.607(10)
2.588(11)
<U(2)–N>
K(1)–O(1)
K(2)–O(3)
K(3)–O(4)
K(1)–O(5)
K(1)–O(6¢)
K(1)–O(7¢)
K(1)–O(8)
2.61(2)
K(2)–O(9)
3.07(3)
2.611(9)
2.655(9)
2.672(9)
2.684(10)
2.773(10)
2.826(10)
2.802(12)
K(2)–O(10)
K(2)–O(12)
K(2)–O(13¢¢)
K(3)–O(14)
K(3)–O(15)
K(3)–O(16#)
K(3)–O(17)
2.791(18)
2.897(13)
2.612(12)
2.797(18)
3.18(2)
2.642(16)
2.787(11)
Bond angles/◦
O(1)–U(1)–O(2)
N(1)–U(1)–N(2)
N(2)–U(1)–N(3)
N(3)–U(1)–N(4)
N(4)–U(1)–N(5)
N(5)–U(1)–N(1)
O(3)–U(2)–O(4)
N(6)–U(2)–N(7)
N(7)–U(2)–N(8)
N(8)–U(2)–N(9)
N(9)–U(2)–N(10)
N(10)–U(2)–N(6)
U(1)–O(1)–K(1)
U(2)–O(3)–K(2)
U(2)–O(4)–K(3)
179.6(4)
O(1)–K(1)–O(5)
O(1)–K(1)–O(6¢)
O(1)–K(1)–O(7¢)
O(1)–K(1)–O(8)
O(6¢)–K(1)–O(7¢)
O(3)–K(2)–O(9)
O(3)–K(2)–O(10)
O(3)–K(2)–O(11)
O(3)–K(2)–O(12)
O(3)–K(2)–O(13¢¢)
O(9)–K(2)–O(10)
O(11)–K(2)–O(12)
O(4)–K(3)–O(14)
O(4)–K(3)–O(15)
O(4)–K(3)–O(16#)
O(4)–K(3)–O(17)
O(14)–K(3)–O(15)
94.3(3)
133.0(3)
88.9(3)
80.4(3)
51.1(3)
85.9(4)
123.5(4)
137.2(3)
87.4(3)
98.6(4)
44.8(3)
50.3(3)
127.8(4)
84.2(3)
110.4(5)
90.3(3)
47.3(4)
69.3(3)
72.0(3)
76.9(3)
72.5(3)
70.7(3)
178.7(4)
75.6(3)
69.4(3)
69.1(3)
69.5(3)
76.4(3)
173.1(4)
177.0(5)
168.0(4)
Symmetry codes: ¢ = 1 - x, y + 1/2, 1 - z; ¢¢ = -x, y + 1/2, 1 - z; # = -x, y - 1/2, -z.
3480 | Dalton Trans., 2009, 3478–3494
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Fig. 2 View of the cation in complex 5. Displacement ellipsoids are drawn
at the 30% probability level. Hydrogen atoms are omitted.
1
1
1
1
1
Me2phen)4(m2-k :k -OTf)2(m3-k :k :k -OTf)2]29 and 2.678(2) A in
˚
[K2(phen)4(k -OTf)2].30 In the structure of 6, the Tl–O and Tl–N
distances are larger, by a mean value of 0.1 A, than the correspond-
1
˚
ing K–O and K–N distances in 5, in agreement with the variation
in the radii of the K+ and Tl+ ions (Table 2).31
LiCH2SiMe3 as the reducing agent. The stabilizing effect of
the polarizable a-silicon atom confers to the CH2SiMe3 group a
major utility for the synthesis of stable alkyl complexes. This group
permitted to isolate unique examples of monocyclooctatetraene
uranium alkyl compounds, [U(C8H8)(CH2SiMe3)2(hmpa)] and
[Li(THF)3][U(C8H8)(CH2SiMe3)3], while other alkyl derivatives
were found to decompose into [U(C8H8)2].32 For this reason, reac-
tions of UO2X2 (X = I, OTf) and LiCH2SiMe3 were considered.
After 24 h at room temperature, slow diffusion of pen-
Fig. 1 (a) View of complex 4. Displacement ellipsoids are drawn at the
30% probability level. Hydrogen atoms are omitted. Symmetry codes: ¢ =
1 - x, y + 1/2, 1 - z; ¢¢ = -x, y + 1/2, 1 - z; # = -x, y - 1/2, -z. (b) View
of the three-dimensional assembly. The fluorine and carbon atoms of the
triflate ligands are omitted. Atoms are represented as spheres of arbitrary
radii.
tane into
a red-brown solution of a 1 : 1 mixture of
[UO2I2(THF)3] and LiCH2SiMe3 in pyridine led to the formation
of dark orange crystals of the pentavalent uranyl compound
[{UO2(py)5}{LiI(py)2}][I] (7). Treatment of [UO2(OTf)2] with
1 mol equivalent of the alkyl lithium in acetonitrile readily gave
a dark brown solution; after evaporation, crystallisation of the
residue from pyridine-pentane afforded light green crystals of
[{UO2(py)5}{Li2(OTf)3}]• (8). Crystals of 7 and 8 were also
obtained from the reaction of the corresponding uranyl(VI) species
and LiC5Me5.
uranyl derivatives involving both terminal and bridging oxo
groups of the [UO2]+ moiety. The terminal U O bond lengths
=
˚
˚
˚
of 1.816(8) A in 4 and 1.826(3) A and 1.825(3) A in 5 can be
compared with those measured in the mononuclear complexes
[UO2(Ar2nacnac)(Ph2MePO)2]22 and [UO2(Ar2nacnac)(dbm)]-,23
˚
=
which vary from 1.79(1) to 1.828(4) A. These U O distances
=
seem slightly shorter than those involved in U O→K interactions
Views of the cation of 7 and the 1D polymer 8 are shown in
Fig. 3 and 4, respectively, while selected bond lengths and angles
of both complexes are listed in Table 3. The dinuclear compound
7 is the simplest example of a pentavalent uranyl complex with
˚
˚
which average 1.842(1), 1.84(2) A and 1.835(5) A in 1, 4 and
5, respectively. The mean U O distance (total) of 1.83(1) A in
4 and 5 is identical to that of 1.843(2) A in 1. These values
˚
=
˚
˚
=
are larger by ca. 0.05–0.1 A than those reported for uranyl(VI)
a single U O→M interaction. The bridging U–O1 and terminal
compounds. The U–N distances of the [UO2(py)5]+ moieties in 1,
4 and 5 are very close to one another with mean values in the
U–O2 bonds are surprisingly very long and short, with lengths
˚
of 1.881(9) and 1.750(10) A, respectively, while the average U–N
˚
˚
range 2.60(1)–2.62(1) A. The K–O(oxo) distances in 4 average
2.64(3) A and are significantly smaller than those of 2.757(2) and
2.80(1) A in 5 and 1, respectively; this difference likely reflects
the more electropositive charge of the K(OTf)3 fragment, by com-
distance of 2.61(2) A is similar to those in complexes in 1, 4 and
˚
˚
5. However, these U–O distances should be considered with some
suspicion since the O1 and O2 atoms are affected by rather small
thermal parameters by comparison with the U atom, possibly
reflecting not well corrected absorption effects.
parison with the more electron rich KX2(py)2 fragments (X = I,
OTf), leading to stronger U O→K interactions in 4. The average
The infinite chains of 8 consist of [UO2(py)5]+ units attached
=
1
1
˚
K–O(OTf) distances of 2.8(2) and 2.68(2) A in 4 and 5, respectively,
via the two oxo groups to the lithium atoms of [Li2(m2-k :k -
can be compared with those of 2.8(1) A in [K4(MeOH)2(2,9-
OTf)3]- fragments. The geometrical parameters of the uranyl
˚
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©

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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) in [{UO2(py)5}2{M(OTf)2(py)2}][OTf]·py (M = K, 5·py or Tl, 6·py); the values for the Tl derivative
are in brackets
˚
Bond lengths/A
U(1)–O(1)
U(1)–O(2)
U(2)–O(3)
U(2)–O(4)
<U–O(yl)>
1.839(3)
[1.836(4)]
1.826(3)
[1.828(4)]
1.831(3)
[1.833(4)]
1.825(3)
[1.829(4)]
1.830(5)
[1.831(3)]
U(1)–N(1)
U(1)–N(2)
U(1)–N(3)
U(1)–N(4)
U(1)–N(5)
<U(1)–N>
2.606(5)
[2.601(5)]
2.650(5)
[2.632(5)]
2.618(4)
[2.623(5)]
2.620(5)
[2.618(5)]
2.600(5)
[2.611(5)]
2.62(2)
U(2)–N(6)
U(2)–N(7)
U(2)–N(8)
U(2)–N(9)
U(2)–N(10)
<U(2)–N>
2.619(4)
[2.605(5)]
2.623(4)
[2.623(5)]
2.594(4)
[2.581(5)]
2.609(4)
[2.606(5)]
2.590(5)
[2.588(5)]
2.61(1)
M–O(1)
M–O(3)
M–O(5)
M–O(8)
M–N(11)
M–N(12)
2.759(3)
[2.839(4)]
2.756(3)
[2.801(4)]
2.669(4)
[2.804(4)]
2.703(4)
[2.890(5)]
2.953(5)
[2.989(6)]
2.953(5)
[3.076(5)]
[2.61(1)]
[2.60(1)]
Bond angles/◦
O(1)–U(1)–O(2)
N(1)–U(1)–N(2)
N(2)–U(1)–N(3)
N(3)–U(1)–N(4)
N(4)–U(1)–N(5)
N(5)–U(1)–N(1)
O(3)–U(2)–O(4)
N(7)–U(2)–N(8)
N(8)–U(2)–N(9)
N(9)–U(2)–N(10)
177.67(17)
N(10)–U(2)–N(6)
70.72(14)
[71.37(15)]
166.3(2)
[164.2(2)]
175.44(19)
[176.2(2)]
175.42(12)
[174.18(11)]
157.46(15)
[148.76(15)]
171.71(15)
[172.29(15)]
83.21(15)
[80.33(14)]
104.99(15)
[107.25(14)]
79.97(14)
[177.92(18)]
70.92(15)
[70.94(16)]
67.69(14)
[67.68(15)]
71.95(13)
[72.54(14)]
77.17(14)
[76.91(15)]
72.94(14)
[72.61(15)]
179.37(17)
[179.74(19)]
73.23(14)
[73.21(16)]
75.20(13)
[74.87(15)]
72.53(14)
[71.99(15)]
U(1)–O(1)–M
U(2)–O(3)–M
O(1)–M–O(3)
O(5)–M–O(8)
N(11)–M–N(12)
O(5)–M–N(11)
O(5)–M–N(12)
O(8)–M–N(11)
O(8)–M–N(12)
[73.82(16)]
91.80(15)
[98.52(16)]
1
1
4}2] (X = Cl, Br)33 and 1.95(1) A in [(LiL)2(m2-k :k -OTf)2] [L =
˚
(MeOCH2CH2)2O].34
Mononuclear uranyl(V) compounds
The preparation of soluble [UO2X(L)n] compounds (L = THF,
Et2O, py), which would be more convenient starting materials
for the development of uranyl(V) chemistry than the poly-
heteronuclear [UO2(py)nMX2] complexes (M = K, Li, Tl), was
desirable. The elimination of MX salt from compounds 1–8 was
endeavoured either by changing the solvent, THF or diethyl ether
in place of pyridine, and/or by replacing the lithium or potassium
cyclopentadienyl reagents MC5R5 with thallium derivatives, which
generally give insoluble TlX salts (X = halide) in metathesis
reactions. The syntheses of the complexes are summarized in
Scheme 2.
KC5R5, LiCH2SiMe3 and TlC5H5 as the reducing agents. Treat-
ment of [UO2(OTf)2] or [UO2I2(THF)3] with 1 mol equivalent of
KC5R5 (R = H, Me) in THF led to the immediate formation of
a brown solution and a precipitate of KX; C5H6-nDn or (C5Me5)2
Fig. 3 View of the cation in complex 7. Displacement ellipsoids are drawn
at the 30% probability level. Hydrogen atoms are omitted.
1
moieties are identical to those previously described. The average
were detected by H NMR. In the case of the uranyl triflate, the
˚
Li–O(oxo) and Li–O(OTf) distances of 1.88(1) and 1.93(2) A can
reaction was carried out on a preparative scale; the product was
extracted with a THF-toluene mixture and, after precipitation
˚
be compared with those of 1.892(2) A in [{UO2X4}{Li(12-crown-
3482 | Dalton Trans., 2009, 3478–3494
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◦
˚
Table 3 Selected bond lengths (A) and angles ( ) in [{UO2(py)5}{LiI(py)2}][I] (7) and [{UO2(py)5}{Li2(OTf)3}]• (8)
7
U–O(1)
1.881(9)
1.750(10)
2.589(8)
U–N(2)
U–N(3)
U–N(4)
179.6(3)
72.2(3)
72.8(2)
73.4(2)
70.8(3)
71.0(2)
174.3(6)
2.589(9)
2.652(8)
2.595(10)
U–N(5)
<U–N>
Li–O(1)
O(1)–Li–N(6)
O(1)–Li–N(7)
O(1)–Li–I(1)
N(6)–Li–N(7)
N(6)–Li–I(1)
N(7)–Li–I(1)
2.619(9)
2.61(2)
1.90(2)
Li–I(1)
2.87(2)
2.16(2)
2.04(2)
U–O(2)
U–N(1)
Li–N(6)
Li–N(7)
109.6(10)
108.1(9)
111.1(9)
113.7(10)
103.2(7)
111.1(9)
O(1)–U–O(2)
N(1)–U–N(2)
N(2)–U–N(3)
N(3)–U–N(4)
N(4)–U–N(5)
N(5)–U–N(1)
U–O(1)–Li
8
U(1)–O(1)
1.839(3)
1.840(2)
1.8395(5)
1.837(2)
1.838(2)
1.8375(5)
2.587(3)
2.595(3)
2.584(3)
U(1)–N(4)
U(1)–N(5)
<U(1)–N>
U(2)–N(6)
U(2)–N(7)
U(2)–N(8)
U(2)–N(9)
U(2)–N(10)
< U(2)–N >
178.16(11)
178.82(12)
73.97(9)
71.74(10)
72.42(10)
71.53(9)
70.48(9)
73.60(9)
2.600(3)
2.576(3)
2.588(8)
2.603(3)
2.598(3)
2.578(3)
2.591(3)
2.587(3)
2.591(8)
Li(1)–O(1)
Li(1)–O(5)
Li(1)–O(8)
Li(1)–O(11)
Li(2)–O(2)
Li(2)–O(14)
Li(2)–O(17)
Li(2)–O(20)
1.904(7)
1.894(7)
1.947(7)
1.904(7)
1.881(6)
1.954(7)
1.945(7)
1.946(7)
Li(3)–O(3)
Li(3)–O(21)
Li(3)–O(15)
Li(3)–O(18)
Li(4)–O(4)
Li(4)–O(6¢¢)
Li(4)–O(9¢¢)
Li(4)–O(12¢¢)
1.875(7)
1.913(7)
1.939(7)
1.958(7)
1.871(7)
1.932(7)
1.906(7)
1.928(7)
U(1)–O(2)
<U(1)–O>
U(2)–O(4)
U(2)–O(3)
<U(2)–O>
U(1)–N(1)
U(1)–N(2)
U(1)–N(3)
O(1)–U(1)–O(2)
O(3)–U(2)–O(4)
N(1)–U(1)–N(2)
N(2)–U(1)–N(3)
N(3)–U(1)–N(4)
N(4)–U(1)–N(5)
N(5)–U(1)–N(1)
N(6)–U(2)–N(7)
N(7)–U(2)–N(8)
N(8)–U(2)–N(9)
N(9)–U(2)–N(10)
N(10)–U(2)–N(6)
U(1)–O(1)–Li(1)
U(1)–O(2)–Li(2)
U(2)–O(3)–Li(3)
U(2)–O(4)–Li(4)
O(1)–Li(1)–O(5)
O(1)–Li(1)–O(8)
O(1)–Li(1)–O(11)
O(2)–Li(2)–O(14)
O(2)–Li(2)–O(17)
O(2)–Li(2)–O(20)
O(3)–Li(3)–O(15)
O(3)–Li(3)–O(18)
O(3)–Li(3)–O(21)
O(4)–Li(4)–O(6¢¢)
O(4)–Li(4)–O(9¢¢)
O(4)–Li(4)–O(12¢¢)
173.0(3)
175.4(3)
102.8(3)
106.7(3)
105.5(3)
104.9(3)
107.4(3)
107.2(3)
107.8(3)
107.2(3)
107.6(3)
104.3(3)
105.1(3)
110.4(3)
72.07(9)
74.29(9)
70.74(10)
69.65(9)
178.2(3)
176.2(2)
Symmetry code: ¢¢ = x - 1, y, z.
Fig. 4 View of the polymeric arrangement in complex 8. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms are omitted.
Symmetry codes: ¢ = x + 1, y, z; ¢¢ = x - 1, y, z.
with pentane, isolated as a beige powder which analyzes as
[UO2(OTf)(THF)n] (9) (n = 1.5 or 2) in 84% yield.
While reaction of [UO2(OTf)2] and TlC5H5 in pyridine gave
the trinuclear compound 6·py, slow diffusion of pentane into
a 1 : 1 mixture of [UO2I2(THF)3] and TlC5H5 in pyridine led
to the precipitation of a yellow powder of thallium iodide and
the formation of dark-orange crystals of [UO2(py)5][I]·py (12·py).
The same reaction in THF afforded, after elimination of TlI by
filtration and addition of pentane, a brown product which was
dried under vacuum to give a powder analyzing as [UO2I(THF)2.7]
(13) in 95% yield. Evaporation of a pyridine solution of 12 or
Another route to a [UO2(OTf)(L)n] compound was considered
by reacting [UO2(OTf)2] and 1 mol equivalent of LiCH2SiMe3
in diethyl ether, and a pale brown powder analyzing as
[UO2(OTf)(Et2O)0.5] (10) was thus obtained in 80% yield. Com-
plexes 9 and 10 are soluble in pyridine, and evaporation of the
solution led to an ochre powder of the adduct [UO2(OTf)(py)2]
(11).
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Fig. 5 View of the cation in complex 12. Displacement ellipsoids are
drawn at the 30% probability level. Hydrogen atoms are omitted.
discrete ion pairs, following pyridine substitution of the iodide
ligand.
Scheme 2 Synthesis of the mononuclear uranyl(V) complexes.
Attempts at growing crystals of other [UO2(L)n][X] or
[UO2X(L)n] complexes (L = THF, MeCN, pyridine) by crystalliza-
tion of the powders of [UO2(OTf)(THF)n] (9), [UO2(OTf)(Et2O)0.5]
(10), [UO2(OTf)(py)2] (11) or [UO2I(THF)2.7] (13) in the corre-
sponding solvent have been unsuccessful. However, addition of
KC5Me5 into a 1 : 1 mixture of [UO2(OTf)2] and CyMe4BTBP37
in pyridine led to the formation of dark brown-green crystals of
the mononuclear compound [UO2(CyMe4BTBP)(py)][OTf]·1.5py
(15·1.5py). The brown iodide derivative [UO2I(CyMe4BTBP)] (16)
was isolated similarly, in 92% yield, from the treatment in THF of
[UO2I2(THF)3] and CyMe4BTBP with TlC5H5.
13 gave a brown powder which analyzes as [UO2I(py)2.5] (14).
Addition of excess KI into pyridine solutions of the mononuclear
compounds 9–14 led to brown-orange solutions which deposited
orange needles of the 1D polymer 1 after some days.
A view of the cation of 12 is shown in Fig. 5, selected
bond distances and angles being listed in Table 4. This complex
represents, after [UO2(OPPh3)4]+,19 a new example of a structurally
characterized [UO2(L)n]+ ion. The structural parameters of the
pentagonal bipyramidal complex, in particular the mean U–O
+
˚
distance of 1.83(1) A, are similar to those of the [UO2(py)5] units
The crystal structure of 15 can be compared with that of
the corresponding uranyl(VI) compound [UO2(CyMe4BTBP)-
(py)][OTf]2,38 thus providing a new pair of crystallographically
characterized penta- and hexavalent uranyl complexes differing
in the polynuclear compounds 1 and 4–8. It is noteworthy
that, in contrast to the crystals of [UI3(py)4],35 [UI4(py)3]36 and
[UO2I2(py)3],8 those of the uranyl(V) iodide 12 are composed of
◦
˚
Table 4 Selected bond lengths (A) and angles ( ) in [UO2(py)5][I]·py (12·py), [UO2(CyMe4BTBP)(py)][OTf]·1.5py (15·1.5py) and [UO2(OTf)(py)4] (19)
12·py
U–O(1)
1.839(4)
1.823(5)
1.831(8)
U–N(1)
U–N(2)
<U–N>
179.5(2)
72.11(18)
72.78(18)
2.609(6)
2.589(6)
2.61(1)
U–N(3)
U–N(4)
2.609(6)
2.620(6)
U–N(5)
2.623(6)
2.533(4)
2.590(5)
U–O(2)
<U–O>
O(1)–U–O(2)
N(2)–U–N(3)
N(4)–U–N(5)
15·1.5py
N(1)–U–N(2)
N(3)–U–N(4)
N(1)–U–N(5)
72.03(18)
70.92(19)
73.82(17)
U–O(1)
1.816(4)
1.822(4)
1.819(3)
U–N(1)
U–N(2)
<U–N(BTBP)>
178.25(13)
63.14(12)
83.62(14)
2.562(4)
2.606(4)
2.58(2)
U–N(3)
U–N(4)
2.611(4)
2.570(4)
U–N(9)
U–O(2)
<U–O>
O(1)–U–O(2)
N(2)–U–N(3)
N(1)–U–N(9)
19
N(1)–U–N(2)
N(3)–U–N(4)
N(4)–U–N(9)
62.48(12)
62.76(12)
88.05(14)
U–O(1)
1.831(6)
U–O(2)
2.525(8)
U–N(1)
<U–N>
2.605(6)
2.59(1)
U–N(2)
O(1)–U–O(1¢)
N(2)–U–N(2¢)
177.3(3)
71.0(2)
N(1)–U–N(2)
N(1)–U–O(2)
69.76(19)
74.85(14)
Symmetry code: ¢ = -x, y, 1.5 - z.
3484 | Dalton Trans., 2009, 3478–3494
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only by their electronic charge, after the [UO2(OPPh3)4]n+ (n = 1,
2)19 and [UO2(Ar2nacnac)(dbm)]n- (n = 0, 1) couples.23 However,
the metrical parameters of the uranyl moieties in the mixed
b-diketiminate/b-diketonate complexes are indistinguishable be-
cause of the low precision of the structure of the U(V) compound.
Crystals of 15·1.5py are composed of discrete cation-anion pairs;
a view of the cation is shown in Fig. 6 and selected bond
distances and angles are presented in Table 4. The U(V) and U(VI)
complexes adopt the same pentagonal bipyramidal configuration.
In 15, the equatorial plane defined by the N1, N2, N3, N4
planar ligand as well as the size of the metal ions. Distinct Ln–Nl
and Ln–Nc distances were also noticed in the series of lanthanide
complexes [Ln(Et4BTBP)(NO3)3] (Ln = La–Lu), where the ratio
Ln–Nc/Ln–Nl varies with Ln, being > 1 for the largest lanthanides
(La–Eu), and < 1 for the heaviest elements (Dy–Yb).40 The
˚
˚
U–N(py) distance of 2.533(4) A in 15 is 0.03 A larger than that
in the U(VI) analogue. This short U–N(py) bond, by comparison
+
˚
with those of the [UO2(py)5] cation [2.59(1)–2.61(1) A], could be
related to the stronger Lewis acidity of the uranyl moiety induced
by the weak s-donating capacity of the BTBP ligand.
˚
and N9 atoms (rms deviation of 0.035 A) is perpendicular to
The synthesis of uranyl(V) complexes with chloride or nitrate
counter ions was attempted with the aim to structurally charac-
terize a mononuclear [UO2X(L)n] or [UO2(L)n][X] species (X =
Cl, NO3). Two distinct routes to such compounds, either from
uranyl(VI) or uranyl(V) precursors, were considered. Treatment of
[UO2Cl2(THF)2]2 or [UO2(NO3)2(MeCN)] with 1 mol equivalent
of TlC5H5 in pyridine led to the precipitation of TlCl or TlNO3
and formation of C5H6 resulting from abstraction of a H atom
the almost linear UO2 fragment and forms a dihedral angle of
2.60(14)◦ with the planar CyMe4BTBP ligand (rms deviation of
˚
0.117 A for the aromatic rings). The average U–O and U–N(BTBP)
˚
˚
distances of 1.819(3) and 2.58(2) A are ca. 0.07 A larger than the
corresponding distances in the U(VI) analogue. This lengthening
=
of the U O bond, which is identical to that observed between
the [UO2(OPPh3)4]n+ (n = 1, 2) complexes, can be compared
∑
2+
˚
with the variation of 0.03 A in the radii of the [UO2] and
of a THF molecule by the C5H5 radical. After usual work-up,
[UO2]+ ions,31 and with the difference of 0.1 A between the U O
the brown powder of [UO2Cl(py)3] (17) was obtained in 89% yield.
The nitrate analogue [UO2(NO3)(py)3] (18) was isolated as a brown
powder in 96% yield from the reaction of the uranyl(V) iodide
[UO2I(THF)2.7] (13) with TlNO3. Crystallization of 17 and 18 did
not afford crystals suitable for X-ray diffraction analysis.
˚
=
bond lengths in [UO2(CO3)3]5- and [UO2(CO3)3]4-, as measured
by EXAFS.39 It is noteworthy that the U O bond lengths in 15
=
and its uranyl(VI) analogue correspond nicely to those calculated in
+
2+
˚
˚
[UO2(H2O)5] (1.810 A) and [UO2(H2O)5] (1.756 A) using density
functional theory and relativistic effective core potentials.17a These
calculations also indicated that the elongation of the equatorial U–
O(H2O) bonds would be larger than that of the axial U–O(oxo)
bonds when passing from the U(VI) to the U(V) compound. If
Me3SiC5R5 as the reducing agent. Since reactions of UO2X2
(X = Cl, I, OTf, NO3) with MC5R5 (M = Li, K, Tl; R =
H, Me) gave invariably uranyl(V) complexes, other routes to
cyclopentadienyl uranyl(VI) compounds, precluding the use of
such a difference was observed with the [UO2(OPPh3)4]n+ (n =
V
-
˚
1, 2) complexes, where the U –O(OPPh3) distances are 0.14 A
the reducing anion C5R5 , have been devised. Burns et al.
larger than the UVI–O(OPPh3) distances, the similar lengthening
of both the U–N(BTBP) bonds and U–O(oxo) bonds in 15 is
likely related to the limited size of the cavity of the polydentate
nitrogen ligand. The U–N1 and U–N4 distances of the lateral
attempted to introduce a C5Me5 group in a uranyl species by
protonolysis of the [U]–NR2 bond of the amide compound
[Na(THF)2]2[UO2{N(SiMe3)2}4] with C5Me5H.41 This reaction led
to the successful protonation of one of the silylamido ligand,
as shown by the formation of HN(SiMe3)2, but afforded the
trisamido derivative [Na(THF)2][UO2{N(SiMe3)2}3], following
elimination of NaC5Me5. Another approach is the treatment of a
metal halide MX with a silylated cyclopentadiene Me3SiC5R5 for
giving MC5R5 and Me3SiX. This metathetical exchange reaction
was successfully applied in d and f element chemistry,42 in
particular for the synthesis of the U(IV) polynuclear compound
[U3(C5H5)6Cl5][U2(C5H5)2Cl7] from UCl4 and Me3SiC5H5.42a
Reactions of UO2X2 (X = Cl, I, OTf) and Me3SiC5R5 (R =
H, Me) led to complicated mixtures of unidentified reduced
products and did not afford cyclopentadienyl uranyl complexes
nor represent interesting synthetic routes to uranyl(V) com-
pounds. Treatment of [UO2(OTf)2] with 1 or 2 mol equivalents
of Me3SiC5H5 in acetonitrile-d3 gave a green-yellow solution
containing free cyclopentadiene; after heating, a brown powder
was deposited from the green solution. Dissolution in pyridine-d5
˚
˚
triazine groups (U–Nl) average 2.566(4) A and are 0.04 A smaller
˚
than the mean U–Nc distance of 2.608(2) A between the metal
and the N2 and N3 atoms of the central pyridyl units. This trend,
already observed in the U(VI) counterpart,38 does not reflect the
distinct Lewis basicities of the Nc and Nl atoms since a stronger
interaction of the Lewis acidic group [UO2]2+ would be expected
with the stronger s-donating nitrogen atoms of the central pyridyl
groups. It can rather be ascribed to the cavity size of the rigid and
1
gave a clear solution the H NMR spectrum of which showed
signals of unidentified paramagnetic species at d 72, 61 and
48 ppm. Similar reactions of [UO2I2(THF)3] or [UO2Cl2(THF)2]2
with Me3SiC5R5 (R = H, Me) also afforded, at room temperature,
mixtures of unidentified complexes; the NMR spectra exhibit
signals in the d 50–60 ppm region. These spectra, which are similar
to those of mixtures of UX4 (X = Cl, OTf) and NaOSiMe3 (see
Experimental), strongly suggest that uranium(IV) complexes with
OSiMe3 ligands were formed. These UIV–OSiMe3 species would
Fig. 6 View of the cation in complex 15. Displacement ellipsoids are
drawn at the 30% probability level. Hydrogen atoms are omitted.
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◦
˚
Table 5 Selected bond lengths (A) and angles ( ) in [UO2Cl2(py)3]
˚
Bond lengths/A
U–O(1)
U–O(2)
1.767(3)
1.764(3)
U–N(1)
U–N(2)
2.561(4)
2.588(4)
U–N(3)
<U–N>
2.563(4)
2.57(1)
U–Cl(1)
U–Cl(2)
2.7338(12)
2.6926(12)
Bond angles/◦
O(1)–U–O(2)
N(1)–U–Cl(1)
N(1)–U–Cl(2)
177.36(14)
74.77(9)
73.74(9)
N(2)–U–N(3)
N(2)–U–Cl(1)
N(3)–U–Cl(2)
66.36(12)
74.45(9)
74.41(9)
result from the reductive silylation of the uranyl oxo groups, a
process which was recently illustrated with the formation of the
uranium(V) compound [UO(OSiMe3)(THF)(M2I2)(L)] (M = Fe,
Zn; H4L = polypyrrolic macrocycle) from [UO2(THF)(H2L)].43
However, during one attempt at crystallization of the crude
reaction mixture containing [UO2Cl2(THF)2]2 and Me3SiC5H5 in
pyridine-Et2O, crystals of [UO2Cl2(py)3] were obtained (Table 5).
Attempts to isolate any product from these reactions of UO2X2
and Me3SiC5R5 were unsuccessful, except in the case of X = OTf
and R = H, where crystallization of the reaction mixture from
pyridine-pentane gave a few red crystals of [UO2(OTf)(py)4] (19)
together with yellow crystals of [UO2(OTf)2(py)3]. These results
indicate that Me3SiC5R5 is able to reduce uranyl(VI) complexes, as
it is the case with the Me3SiX reagents which are efficient in the
reduction of [UO2I2(THF)3] or [UO2(OTf)2] into the uranium(IV)
derivatives [UX4(MeCN)4] (X = Cl, Br, I).44
˚
triflate ligand. The U–O(oxo) bond length of 1.831(6) A is quite
identical to those measured in the [UO2(py)5]+ cations and can
be compared with that of 1.82(1) A in the octahedral compound
[UO2(Ar2nacnac)(Ph2MePO)2];22 this distance is expectedly larger
than that of 1.745(2) A in [UO2(OTf)2(py)3]. The U–O(OTf)
and mean U–N distances of 2.525(8) and 2.59(1) A are 0.14
and 0.06 A larger than in the uranyl(VI) complex (2.38(1) and
˚
6
˚
˚
˚
˚
2.53(1) A), respectively. The mean U–N(py) distance in 19 is
similar to those found in the [UO2(py)5]+ cation in the variety
˚
of complexes described here [2.58–2.61 A] and close to that
determined in the U(VI) complex [UO2Cl2(py)3] [2.57(1) A]. It
must be underlined that the difference between the equatorial U–O
distances in the U(V)/U(VI) counterparts is much more important
than that between the U–N distances. Thus, the variation of 0.14 A
in the mean U–O(OTf) distances of 19 and [UO2(OTf)2(py)3] is
identical to that measured in the mean U–O(OPPh3) distances in
the [UO2(OPPh3)4]n+ compounds.
˚
˚
Complex 19 is, after [UO2(Ar2nacnac)(Ph2MePO)2], a novel
example of a neutral mononuclear complex of uranyl(V) to have
been crystallographically characterized. A view of 19 is shown
in Fig. 7, while selected bond distances and angles are listed in
Table 4. The uranium atom is found in the classical pentagonal
bipyramidal configuration, with the linear UO2 fragment perpen-
dicular to the equatorial plane defined by four nitrogen atoms of
the pyridine ligands and one oxygen atom of the monodentate
Infrared spectra of the complexes
The IR spectra of the uranyl(V) complexes in Nujol mulls exhibit
medium to strong peaks in the 800–850 cm-1 region, corresponding
=
to the asymmetric stretch nasym(U O); these frequencies are expect-
edly lower than those of 905–980 cm-1 observed for the uranyl(VI)
compounds, in agreement with the more electron-rich 5f1 species
=
=
and the longer U O bonds. In particular, the nasym(U O) of
801 cm-1 for [UO2I(CyMe4BTBP)] (16) is 144 cm-1 lower than that
observed for the parent cationic uranyl(VI) complex.38 This value
is at the upper limit of the range of the differences between the
=
n
asym(U O) for penta- and hexavalent uranyl complexes differing
only by their electronic charge, which vary from 58 cm-1 for
[UO2(Ar2nacnac)(CF3COCHCOCF3)]n- (n = 0, 1)23 to 131 cm-1
for [UO2(dbm)2(dmso)]n- (n = 0, 1).24c A decrease of 145 cm-1
=
was also observed in the wave number of the nasym(Np O) with
the reduction of [NpO2]2+ into [NpO2]+ in aqueous solution.45
=
=
The nasym(U O) values are in the range of the nasym(Np O) in
neptunyl(V) compounds;26c,45 for example, this value is 826 cm-1
for [NpO2(OPPh3)4][ReO4].46 The uranyl(V) absorption bands are
broader than those of uranyl(VI). This feature was explained by the
lower bending frequency for the [UO2]+ ion, which is of the order
of kT298, leading to thermal excitation of a large proportion of the
ions to excited states of the bending vibration, thus broadening
the absorption maximum.45
=
Variations in the
nasym(U O) of the [UO2XLn] and
Fig. 7 View of complex 19. Displacement ellipsoids are drawn at the 30%
probability level. Hydrogen atoms are omitted. Only one position of the
disordered atoms is represented. Symmetry code: ¢ = -x, y, 1.5 - z.
[UO2(py)nMX2] species (X = I, OTf, Cl; L = py, THF, Et2O; M =
K, Li, Tl) in Nujol mulls are difficult to interpret because of the
3486 | Dalton Trans., 2009, 3478–3494
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Fig. 8 IR spectra of the uranyl(VI) compounds in pyridine solution.
Fig. 9 IR spectra of the uranyl(V) compounds in pyridine solution.
undetermined coordination of the uranyl moiety in the desolvated
compounds, with likely the presence of bridging iodide and triflate
greater electron donating ability of the chloride ligand, giving a
-1
=
more electron-rich complex, as seen by the nasym(U O) of 924 cm ,
=
=
ligands in various ligation modes and U O→M or U O→U
which is lower than those of the other uranyl(VI) compounds.
interactions. The IR spectra of the uranyl(V) and (VI) compounds
=
in pyridine are shown in Fig. 8 and 9, respectively. The nasym(U O)
Discussion
for the [UO2X2(py)3] (X = I, Cl, OTf) and [UO2(NO3)2(py)2]
complexes, which range from 924–934 cm-1, decrease in the order
OTf > NO3 ~ I > Cl, reflecting the increasing electron donating
Reactions of uranyl(VI) complexes with the alkali metal and thal-
lium salts of the C5R5 , C8H8 , C4Me4P- and Me3SiCH2 anions
do not afford organometallic compounds but represent convenient
routes to pentavalent uranyl complexes, which proved stable with
respect to disproportionation, in contrast to what is observed in
aqueous solutions. These results further point up the necessary
use of strictly anhydrous and anaerobic experimental conditions
for the development of this uranyl chemistry. The only other
examples of controlled [UO2]2+ → [UO2]+ chemical reduction
leading to stable and isolated compounds are given by the synthesis
of the b-diketiminate complexes [UO2(Ar2nacnac)(Ph2MePO)2]22
and [UO2(Ar2nacnac)(RCOCHCOR)]- (R = Me, Ph, CF3)23 by
treatment of the uranyl(VI) precursors with [Co(C5R5)2]. It was
previously observed that reactions of [UO2Cl2] with a variety
of alkyllithium and Grignard reagents in organic solvents gave
brown-orange solutions of unidentified compounds, presumably
-
-
-
capacity of X. The uranyl(V) iodide and triflate complexes exhibit
-1
=
a nasym(U O) of 816 cm , except those of general formula
=
[UO2(OTf)Ln] (L = py, THF, Et2O) which display a nasym(U O)
of 812 cm-1. These two absorption bands can be respectively
attributed to [UO2(py)5]+, in view of the ubiquity of this cation
=
in the crystals of compounds with X = I and/or U O→MX
interactions (X = I, OTf), and to [UO2(OTf)(py)4] (19), which
crystallized from pyridine.
The IR spectra in pyridine of the uranyl(V) chloride and nitrate
[UO2X(py)3] [X = Cl (17) or NO3 (18)] display broad bands at
ca. 810 cm-1 (Fig. 10 and 11). However, the peak at 924 cm-1
indicates that the uranyl(V) chloride is contaminated with its
U(VI) precursor. This easier UV → UVI oxidation for X = Cl by
comparison with X = I, OTf and NO3, could be related to the
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Fig. 10 IR spectra of the uranyl(V) nitrate in pyridine solution. Pink curve: from the in situ reaction of UO2(NO3)2 + TlC5H5. Blue curve: from the in
situ reaction of UO2I2 + TlC5H5 + TlNO3.
Fig. 11 IR spectra of the uranyl(V) chloride in pyridine solution.
unstable UO2R2 species which decompose into UO2 with elimina-
tion of the R–R coupling product or a mixture of the alkane RH
and alkene R(–H) molecules; the possible involvement of uranyl(V)
complexes in these reactions was not considered.13
[UO2(py)2.2KI2] (1) or [UO2(OTf)(Et2O)0.5] (10). These compounds
are likely polymeric in the solid state, their structure being ensured
=
by bridging iodide or triflate ligands and U O→M interactions.
The involvement of the [UO2]+ ion in such so-called cation–cation
With the exception of [UO2(OTf)(py)4] (19) and the BTBP
adduct 15, all the pentavalent uranyl complexes crystallograph-
ically characterized in this work contain the cationic [UO2(py)5]+
interactions, via one or two oxo groups, is clearly favored by the
=
Lewis basicity of the U O oxygen atoms.
=
=
The diversity of structures of the complexes with O U O→M
interactions (M = Li, K), from the simplest dinuclear compound
7 to the 3D coordination polymer 4, is obviously related to
˚
moiety. The average U–O distance of 1.82–1.83 A in this species is
similar to that measured in the few other uranyl(V) complexes and
the variety of neptunyl(V) compounds,26c,45 being 0.07 A larger
˚
=
the basicity of the U O oxygen atoms, but also the distinct
than the typical U–O distance in uranyl(VI) compounds. This
coordination numbers of the Li+ and K+ ions, and the distinct
ligation modes of the triflate and iodide ligands. Depending on
the nature of the solvent, M+ and the counterion X-, it is likely
that the complexes of the [UO2]+ ion may exist under various forms
as revealed by the crystallization of both the polymeric compound
4 and the trinuclear complex 5 from the same solution. However,
crystallization of 5 and 6, whereas the iodide analogue 1 is a 1D
polymer in the solid state, is difficult to explain.
=
lengthening goes together with the decrease of the nasym(U O)
-1
=
by ca. 110 cm , reflecting the weakening of the U O bond due to
the reduced charge on the metal ion and the destabilizing effect of
the single 5f electron. Uranyl(V) complexes will therefore exhibit,
by comparison with the U(VI) counterparts, a weaker Lewis acidic
character of the metal centre and a stronger Lewis basicity of
the oxo goups. This difference explains why uranyl(V) complexes
are so easily desolvated under vacuum, leading to the forma-
tion of apparently coordinatively unsaturated compounds like
There is no significant difference between the two U–O distances
=
=
of the O U O→M fragments (M = K, Tl) in complexes 4–6, while
3488 | Dalton Trans., 2009, 3478–3494
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in uranyl(VI) complexes like [Na(THF)2][UO2{N(SiMe3)2}3]41 and
alkoxides where the presence of cation–cation interactions led to
[Na(THF)2(PhCN)0.5][UO2(NCN)3] [NCN = PhC(NSiMe3)2],47
the formation of aggregates or induced unusual reactivity of the
25g
˚
=
U O bond.
the bridging U–O(Na) bond is 0.03
A
longer than the
U–O(terminal) bond. The lengthening of the An–O(bridging)
versus An–O(terminal) bond in cation–cation complexes of nep-
Conclusion
=
tunyl(V) and uranyl(VI) with An O→An interactions is typi-
Whereas [U(NR)2]2+, an imido analogue of the uranyl ion,
readily gives the stable organouranium(VI) U(NR)2(C5R5)2 and
UI(NR)2(C5R5) derivatives in its reaction with the C5R5 anion
˚
˚
cally equal to 0.04 A and as large as 0.1 A in the trimeric
complex [UO2(CF3COCHCOCF3)2]3.48 In the tetrameric complex
of pentavalent uranyl [{UO2(dbm)2}4{K6(py)10}]2+, which exhibit
-
(R = H, Me),5b treatment of the uranyl(VI) compounds [UO2X2]
(X = I, Cl, OTf, NO3) with the alkali metal salts of a variety
of organometallic anions such as KC5R5 (R = H, Me), TlC5H5,
KC4Me4P, K2C8H8 and LiCH2SiMe3 or the neutral silane molecule
Me3SiC5R5 (R = H, Me) permit the convenient and efficient
chemical reduction of the [UO2]2+ ion into stable pentavalent
uranyl(V) complexes, which are potential precursors for further
developments in uranium(V) chemistry. Reactions of [UO2X2] with
the neutral silane molecules Me3SiC5R5 (R = H, Me) do not
represent a synthetic route to cyclopentadienyl uranyl complexes
or [UO2]+ compounds.
=
=
K←O U O→U fragments, the mean U–O(K) distances of
˚
˚
1.82(1) A is similar to that measured in 4–6, but is 0.11 A
smaller than the U–O distance for the oxo group coordinated
to a vicinal uranyl moiety.21 These observations would indicate
that in pentavalent as well as in hexavalent uranyl complexes
=
=
with O U O→M interactions, the U–O bond lengths are less
unsymmetrical with M = alkali metal than with M = U in di- or
oligomeric complexes.
While various heteronuclear uranyl(V) complexes with an
=
=
O U O→M interaction (M = Li, K, Tl) were characterized,
no such homonuclear compound with M = UO2 was identi-
fied. This is perhaps not surprising in view of the remarkable
stability, in the solid state or in solution, of all the uranyl(V)
compounds isolated in this work, since it was demonstrated that
the formation of such inner-sphere cation–cation ([UO2]+/[UO2]+)
complexes is likely responsible for the disproportionation of
pentavalent uranyl into UIV and UVI species.16,49 The sole uranyl(V)
The distinct coordination numbers of the metal ion in the
reducing agents (M = Li, K, Tl), the various ligation modes of
the bridging iodide and triflate ligands and the involvement of the
=
=
uranyl fragment in O U O→M interactions led to a rich diversity
in the crystal structures of the uranyl(V) complexes, from mononu-
clear compounds to heteronuclear 3D polymers. The dinuclear
compound [{UO2(py)5}{LiI(py)2}][I] (7) is a unique example of a
=
=
complex exhibiting an O U O→UO2 interaction in the solid
state is the electron-rich species [{UO2(dbm)2}4{K6(py)10}]2+,
which retains its tetrameric structure in pyridine solution
where it rapidly decomposes, and which is transformed in
DMSO into a more stable monomeric species.21 The bulky
Ar2nacnac ligand, which provides steric protection along the
=
=
pentavalent uranyl complex with a single O U O→M interaction,
while [UO2(py)5][I] (12) and [UO2(OTf)(py)4] (19) are the simplest
mononuclear uranyl(V) compounds to have been isolated and
characterized.
The remarkable stability towards disproportionation of all these
uranyl(V) complexes in pyridine solution, where the [UO2(py)5]+
ion appears to be an ubiquitous entity, and the stability of
[UO2X(THF)n] (X = I, OTf) in THF, likely related to the absence
=
=
uranyl equatorial plane and also along the O U O axis, was
used to stabilize the [UO2]+ ion against disproportionation by
blocking its dimerization via cation–cation interaction. How-
ever, the isolated compounds [UO2(Ar2nacnac)(Ph2MePO)2] and
[UO2(Ar2nacnac)(RCOCHCOR)]- (R = Me, Ph, CF3) were found
to decompose in CH2Cl2 or THF, likely following ligand exchange
reactions with the solvent.22,23 The stability in pyridine solution
of the uranyl(V) complexes presented here could be related to
the strong U–py interaction in the electron-poor [UO2(py)5]+
and [UO2(py)5(OTf)] species, preventing ligand dissociation and
formation of a dimeric cation–cation complex. In these com-
pounds, the uranyl oxo groups are apparently insufficiently basic
to compete with the pyridine solvent of the [UO2(py)5]+ moiety
while they can bind to the Li+ or K+ ions which certainly
display weaker M–py+ interaction. Furthermore, the synthesis and
relative stability of the iodide and triflate uranyl(V) complexes
[UO2X(THF)n] 9 and 13 in THF demonstrate that bulky or
strongly coordinating ligands are not prerequisite to the stability
of the [UO2]+ ion. It seems patent that the electron richness of the
uranyl(V) complexes has a major influence on their reactivity. By
comparison with the aforementioned complexes which are anionic
and/or contain the strongly electron-donating b-diketiminate and
b-diketonate ligands, the uranyl(V) compounds under study have
a lesser electron density and their stability could be related to
their lesser propensity to both ligand dissociation and dispropor-
=
=
of a cation–cation O U O→UO2 interaction, clearly show that
pentavalent uranyl compounds can be isolated from various
organic media and not only, as generally believed, with a restricted
choice of suitably bulky equatorial ligands. Such convenient access
to [UO2]+ species would induce further developments in the
chemistry of uranium(V) and favour better understanding of the
chemical behaviour of the stable but highly radioactive [AnO2]+
ions (An = Np, Pu, Am).
Experimental
All experiments were carried out under ultra high purity argon
atmosphere with rigorous exclusion of air and water (less than
2 ppm oxygen and water), using standard Schlenk-vessel and
vacuum-line techniques or in a glove box. Solvents were thor-
oughly dried and deoxygenated by standard methods and distilled
immediately before use. Deuterated acetonitrile, THF and pyridine
(Eurisotop) were distilled over NaH and acetonitrile was then
stored over 3 A molecular sieves. The H NMR spectra, given
1
˚
for a temperature of 23 ◦C, were recorded on a Bruker DPX 200
instrument and were referenced internally using the residual protio
solvent resonances relative to tetramethylsilane (d 0 ppm). The IR
spectra of the complexes in pyridine solution or in Nujol mulls
between KBr round cell windows were recorded on a Perkin-Elmer
=
=
tionation via a O U O→UO2 intermediate. Such an electronic
effect is reminiscent of that found in the electron-rich uranyl(VI)
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FT-IR 1725X spectrometer. Elemental analyses were performed
by Analytische Laboratorien at Lindlar (Germany).
F 14.44%) IR (Nujol) n/cm-1: 1637 w, 1603 s, 1260 (broad, vs),
1208 s, 1177 s, 1069 m, 1033 vs, 927 w, 890 m, 793 s shoulder [nasym
UCl4,50 U(OTf)4,51 [UO2(OTf)2],6 [UO2I2(THF)3],8 [UO2Cl2-
(THF)2]27 and [UO2(NO3)2(MeCN)]52 were prepared as previously
described. MC5Me5 (M = Li, K) and KC5H5 were prepared by
treating C5Me5H or freshly distilled C5H6 (Aldrich) with Li in
Et2O or KH in THF at room temperature. K2C8H8,53 KC4Me4P,54
TlC5H555 and Me3SiC5H556 were obtained as previously described;
Me3SiC5Me5 (Aldrich) was degassed and dried over molecular
sieves under argon, NaOSiMe3 (Aldrich) was used after drying
under vacuum. The solution of LiCH2SiMe3 (1.0 M in pentane,
Aldrich) was evaporated to dryness to give a white powder which
was stored under argon.
(U O)], 757 vs, 701 s, 636 vs, 581 m, 518 m. IR (pyridine) n/cm :
-1
=
=
816 s [nasym (U O)].
(b) An NMR tube was charged with [UO2(OTf)2] (10.0 mg,
0.017 mmol) and KC5Me5 (3.1 mg, 0.017 mmol) in pyridine-d5
(0.3 mL). After 10 h at 20 ◦C, the spectrum showed the formation
of (C5Me5)2.
[{UO2(py)5}2{K3(OTf)5}·py]• (4·py). (a) An NMR tube was
charged with [UO2(OTf)2] (10.0 mg, 17.6 mmol) and KC5R5 (R =
H: 1.8 mg, 17.6 mmol; R = Me: 2.5 mg, 17.6 mmol) in pyridine
◦
(0.4 mL). After 24 h at 20 C, pentane (1 mL) was added to the
brown solution, leading to the formation of orange crystals of
4·py.
Synthesis
(b) An NMR tube was charged with [UO2(OTf)2] (7.9 mg,
14.0 mmol) and KC4Me4P (2.5 mg, 14.0 mmol) in pyridine (0.4 mL).
After 24 h at 100 ◦C, the brown solution was cooled to room
temperature and addition of pentane (1.5 mL) led to the formation
of orange crystals of 4·py.
[{UO2(py)5}{KI2(py)2}]• (1). An NMR tube was charged with
[UO2I2(THF)3] (10.0 mg, 13.5 mmol) and KC5R5 (R = H: 2.26 mg,
13.5 mmol; R = Me: 3.1 mg, 13.5 mmol) in pyridine-d5 (0.4 mL).
The reaction mixture was heated at 100 ◦C for 2 h and thin orange
needles of 1 suitable for X-ray diffraction were deposited in a
few hours upon cooling to room temperature. The 1H NMR
spectrum of the solution showed the formation of C5H6-nDn or
(C5Me5)2. d (C5D5N, 23 ◦C) for C5H6:6.63 (br, CH, 2H), 6.49 (br,
CH, 2H), 2.92 (br, CH2, 2H), for (C5Me5)2:1.74 (s, 6H), 1.68 (s, 6H),
1.14 (s, 3H). The same reaction with K2C8H8 (0.5 mol equivalent)
in place of KC5R5 also gave crystals of 1 and the NMR spectrum
showed the formation of C8H8 characterized by a singlet at d
5.8 ppm.
[{UO2(py)5}2{M(OTf)2(py)2}][OTf]·py (M = K, 5·py; M =
Tl, 6·py). (a) An NMR tube was charged with [UO2(OTf)2]
(10.0 mg, 17.6 mmol) and KC4Me4P (3.1 mg, 17.6 mmol) in THF
(0.4 mL). After 30 min at room temperature, the brown solution
was evaporated to dryness. The residue was dissolved in pyridine
(0.4 mL) affording a clear orange solution in which pentane
(1.5 mL) was slowly diffused. Large orange crystals of 5·py were
obtained after 5 d at 20 ◦C, together with orange crystals of 4·py.
(b) An NMR tube was charged with [UO2(OTf)2] (10.0 mg,
17.6 mmol) and TlC5H5 (4.7 mg, 17.6 mmol) in pyridine (0.5 mL).
The tube was immersed in an ultrasound bath (80 W, 40 kHz)
for 24 h. Slow diffusion of pentane (1.5 mL) into the dark brown
solution gave dark orange crystals of 6·py (7.8 mg, 40%).
[UO2(py)2.2KI2] (2). (a) Pyridine (15 mL) was condensed at
-70 ◦C under vacuum into a 50 mL round bottom flask containing
[UO2I2(THF)3] (250 mg, 0.33 mmol) and KC5Me5 (59 mg,
0.33 mmol). The orange suspension was stirred for 2 h at room
temperature and after condensation of THF (5 mL), the orange
powder was filtered off. During drying under vacuum (20 h at
23 ◦C), the colour of the powder turned from bright orange to
ochre (200 mg, 80%). (Found: C 18.03, H 1.48; N 4.24; I 34.66.
C11H11I2KN2.2O2U requires C 17.93, H 1.50; N 4.34; I 34.44%).
IR (Nujol) n/cm-1: 1378 s, 1216 w, 1152 w, 1066 m, 1038 m,
[{UO2(py)5}{LiI(py)2}][I] (7). (a) An NMR tube was charged
with [UO2I2(THF)3] (10.0 mg, 13.5 mmol) in pyridine (0.4 mL) and
LiCH2SiMe3 (15.3 mg, 16.3 mmol) was added via a microsyringe.
◦
After 24 h at 20 C, the red solution was evaporated to dryness
and the red powder was washed with pentane (2 mL). The powder
was dissolved in pyridine (0.5 mL) and slow diffusion of pentane
(2 mL) into the solution led to the formation of dark orange
crystals of 7 (4.7 mg, 32%).
=
1007 m, 922 w, 797 vs [nasym (U O)], 754 s, 701 vs, 626 m. IR
(pyridine) n/cm-1: 816 s [nasym (U O)]. The same reaction with
=
1 mol equivalent of KC5H5 or 0.5 mol equivalent of K2C8H8 gave
identical results. Slow diffusion of diethyl ether into a pyridine
solution of 2 gave crystals of 1.
(b) An NMR tube was charged with [UO2I2(THF)3] (10.0 mg,
0.013 mmol) and KC5Me5 (2.3 mg, 0.013 mmol) in THF-d8
(0.5 mL) The tube was immersed in an ultrasound bath for 30 min
affording a brown solution and a white precipitate. The NMR
spectrum showed the presence of (C5Me5)2.
(b) An NMR tube was charged with [UO2I2(THF)3] (10.0 mg,
13.5 mmol) and LiC5Me5 (1.9 mg, 13.5 mmol) in pyridine-d5
(0.4 mL). After 24 h at 20 ◦C, the NMR spectrum of the red
solution showed the presence of (C5Me5)2. Slow diffusion of
pentane (2 mL) into the solution led to the formation of dark
orange crystals of 7 (5.0 mg, 34%). IR (pyridine) n/cm-1: 816 s
=
[nasym (U O)].
[{UO2(py)5}{Li2(OTf)3}]• (8). (a) An NMR tube was charged
with [UO2(OTf)2] (10.0 mg, 17.6 mmol) and LiCH2SiMe3 (16.5 mg;
17.6 mmol) in acetonitrile (0.4 mL). After stirring for 24 h at
20 ◦C, the dark brown solution was evaporated to dryness, leaving
a brown powder which was washed with pentane (2 mL). The
powder was dissolved in pyridine (0.4 mL) and slow diffusion of
pentane (2 mL) into the solution led to the formation of light green
crystals of 8 (5.9 mg, 30%).
[UO2(py)2.3K(OTf)2] (3). (a) Pyridine (20 mL) was condensed
in a 50 mL round bottom flask containing [UO2(OTf)2] (2000 mg,
3.52 mmol) and KC5Me5 (613.6 mg, 3.5 mmol). After stirring
for 15 h at room temperature, the volume of the brown orange
solution was reduced to 10 mL. Addition of diethyl ether (50 mL)
led to the precipitation of a brown powder, which was filtered
off; its colour turned beige upon drying under vacuum for 20 h
at 25 ◦C (2480 mg, 91%). (Found C 20.33, H 1.53; N 4.30; F
14.35. C12.5H11.5F6KN2.3O8S2U requires C 20.54, H 1.47; N 4.08;
(b) An NMR tube was charged with [UO2(OTf)2] (10.0 mg,
17.6 mmol) and LiC5Me5 (2.2 mg, 17,6 mmol) in pyridine-d5
3490 | Dalton Trans., 2009, 3478–3494
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(0.4 mL). After 48 h at 20 ◦C, the NMR spectrum of the red
solution showed the presence of (C5Me5)2. Slow diffusion of
pentane (2 mL) into the solution led to the formation of light
green crystals of 8 (6.9 mg, 35%). IR (pyridine) n/cm-1: 816 s [nasym
n/cm-1: 1637 w, 1602 mw, 1262 m, 1169 s, 1067 w, 1040 vs, 944
-1
=
w, 821 s [nasym (U O)], 755 m, 641 s, 518 m. IR (pyridine) n/cm :
=
812 m [nasym (U O)]. Complex 11 was similarly obtained from 9.
[UO2(py)5][I]·py (12·py). An NMR tube was charged with
[UO2I2(THF)3] (10.0 mg, 0.013 mmol) and TlC5H5 (3.6 mg,
0.013 mmol) in pyridine-d5 (0.5 mL). The mixture was stirred
in an ultrasound bath for 24 h at room temperature, affording a
dark brown solution and a yellow precipitate of TlI. The NMR
spectrum showed the presence of free C5H6-nDn. After filtration,
slow diffusion of pentane (3 mL) into the solution led to the
formation of dark-red crystals of 12·py. IR (pyridine) n/cm-1:
=
(U O)].
[UO2(OTf)(THF)n] (9). (a) n = 1.5. A flask was charged
with [UO2(OTf)2] (300 mg, 0.53 mmol) and KC5Me5 (92.0 mg,
0.53 mmol) and THF (20 mL) was condensed in it. The suspension
◦
was stirred at 20 C for 15 h, affording a brown solution with a
white precipitate of KOTf. After filtration, two extractions from
the salts with a 1.5 : 1 mixture of toluene–THF (25 mL) and
evaporation of the solvents afforded a brown powder, which was
recrystallized from a 1 : 4 mixture of THF–pentane (25 mL). The
beige powder was then dried under vacuum for 15 h at room
temperature. (233 mg, 84%). (Found C 16.32, H 2.14, F 10.44.
C7H12F3O6.5SU requires C 15.95, H 2.29, F 10.81%). IR (Nujol)
=
816 m [nasym (U O)].
[UO2I(THF)2.75] (13). THF (15 mL) was condensed in a
50 mL round bottomed flask containing [UO2I2(THF)3] (2000 mg,
2.7 mmol) and freshly sublimed TlC5H5 (728.2 mg, 2.7 mmol). The
suspension was stirred at room temperature for 15 h, affording a
brown solution and a yellow precipitate of TlI. After decantation
and slow filtration of the solution, which was repeated three times,
the volume of the solution was reduced to 5 mL and a brown
powder precipitated upon addition of pentane (15 mL). (1580 mg,
95%). (Found: C 22.41; H 3.71; I 21.35. C11H22IO4.75U requires C
22.20, H 3.72, I 21.32%). IR (Nujol) n/cm-1: 1308 s, 1261 m, 1198
n/cm-1: 1332 vs, 1236 vs, 1202 vs, 1024 vs, 947 s, 920 m, 853, 847
-1
=
vs [nasym (U O)], 681 s, 634 vs, 586 m, 513 s. IR (pyridine) n/cm :
=
812 m [nasym (U O)].
(b) n = 2. By following a procedure similar to that in (a), the
reaction of [UO2(OTf)2] (306 mg, 0.54 mmol) and KC5H5 (58.0 mg,
0.55 mmol) gave a beige powder which was dried for 10 h at 20 ◦C
(220 mg, 72%). (Found C 19.03, H 2.43, F 9.88. C9H16F3O7SU
(563.31) requires C 19.19, H 2.86, F 10.12%). IR (Nujol) n/cm-1:
=
m, 1170 m, 1075 m, 1013 vs, 921 vs, 847 s [nasym (U O)], 800 m,
634 m, 427 m. IR (pyridine) n/cm-1: 816 m [nasym (U O)].
=
=
1337 vs, 1237 s, 1202 vs, 1013 vs, 949 s, 885 w, 851 vs [nasym (U O)],
829 m, 679 m, 635 vs, 586 w, 513 m. IR (pyridine) n/cm-1: 812 m
[UO2I(py)2.5] (14). Pyridine (10 mL) was condensed in a
50 mL flask containing 13 (100 mg, 0.17 mmol). The brown
solution was stirred at room temperature for 10 min. Addition
of pentane (30 mL) induced the precipitation of a dark brown
powder of 14 (99.2 mg, 97%). (Found: C 25.83; H 2.26; I
21.18. C12.5H12.5IN2.5O2U requires C 25.23; H 2.10; I 21.36%). IR
=
[nasym (U O)].
(c) An NMR tube was charged with [UO2(OTf)2] (15.0 mg,
0.026 mmol) and KC5Me5 (4.6 mg, 0.026 mmol) in THF-d8
◦
1
(0.4 mL). After 10 h at 20 C, the H NMR spectrum showed
the signals of the dimer (C5Me5)2 (d 1.77 (s, 6H), 1.65 (s, 6H), 1.07
(s, 3H)). Evaporation of the volatiles and dissolution of the residue
in pyridine-d5 showed only the presence of the dimer (C5Me5)2.
(d) An NMR tube was charged with [UO2(OTf)2] (10.2 mg,
0.018 mmol) and KC5H5 (1.9 mg, 0.018 mmol) in THF-d8 (0.4 mL).
After 10 h at 20 ◦C, the spectrum showed the formation of
C5H6-nDn. d (C4D8O, 23 ◦C) 6.51 (br, CH, 2H), 6.38 (br, CH,
2H), 2.92 (br, CH1-n).
(pyridine) n/cm-1: 816 m [nasym (U O)]. The powder of 14 was
=
similarly obtained from 12.
[UO2(CyMe4BTBP)(py)][OTf]·1.5py (15·1.5py). An NMR
tube was charged with [UO2(OTf)2] (10.0 mg, 17.6 mmol),
CyMe4BTBP (9.38 mg, 17.6 mmol) and KC5Me5 (3.07 mg,
17.6 mmol) in pyridine-d5 (0.4 mL). After 24 h at 20 ◦C,
the spectrum of the brown solution showed the formation of
(C5Me5)2 and the disappearance of the signals corresponding to
CyMe4BTBP. Slow diffusion of pentane (3 mL) into the solution
led to the formation of brown-green crystals of 15·1.5py. Reactions
of [UO2(CyMe4BTBP)X2] (X = I, OTf) with 1 mol equivalent
of TlC5H5 in THF-d8 or MeCN-d3 afforded orange or dark red
solutions whose NMR spectra showed the signals of C5H6-nDn
and of traces of the starting uranyl(VI) compound. The NMR
spectra of 1 : 1 mixtures of [UO2X] compounds (X = I, OTf) and
CyMe4BTBP only exhibited the signals corresponding to traces of
the uranyl(VI) complexes [UO2(CyMe4BTBP)X2].
[UO2(OTf)(Et2O)0.5] (10).
A
solution of LiCH2SiMe3
(85.0 mg, 0.90 mmol) in Et2O (10 mL) was added into a
flask containing a yellow suspension of [UO2(OTf)2] (510 mg,
0.89 mmol) in Et2O (15 mL). The immediately formed brown
suspension was stirred for 90 min at 20 ◦C. After evaporation
to dryness, the product was extracted by the Soxhlet method
with diethyl ether (40 mL). The volume of the solution was
reduced to 15 mL and addition of pentane (30 mL) led to the
precipitation of a pale brown powder which turned beige after
15 h drying under vacuum at 25 ◦C (330 mg, 80%). (Found C
7.48, H 0.97. C3H5F3O5.5SU requires C 7.90, H 1.10%). IR (Nujol)
[UO2I(CyMe4BTBP)] (16). THF (30 mL) was condensed in
a 50 mL flask containing [UO2I2(THF)3] (69.3 mg, 0.094 mmol)
and CyMe4BTBP (50.1 mg, 0.094 mmol). The brown suspension
was stirred at 20 ◦C for 20 h and addition of TlC5H5 (25.2 mg,
0.094 mmol) gave rapidly a brown solution and a yellow precipitate
of TlI. After decantation and slow filtration, the volume of the
solution was reduced to 5 mL and a brown powder precipitated
upon addition of diethyl ether (20 mL). The brown solid was
filtered off, washed with a 1:4 mixture of THF and Et2O (30 mL),
n/cm-1:1309 s, 1225 vs, 1039 vs, 972 w, 799 s [nasym (U O)], 640 s,
=
516 w. IR (pyridine) n/cm-1: 812 m [nasym (U O)].
=
[UO2(OTf)(py)2] (11). Addition of pentane (15 mL) into a
red brown solution of 10 (100 mg) in pyridine (5 mL) led to the
precipitation of a brown powder. After filtration and drying under
vacuum (20 ◦C, 15 h) the ochre pyridine adduct 11 was obtained
in quantitative yield (106 mg). (Found C 23.09, H 1.77, N 4.82.
C11H10F3N2O5SU requires C 22.89, H 1.75, N 4.85%). IR (Nujol)
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Dalton Trans., 2009, 3478–3494 | 3491
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and dried under vacuum for 20 h (80.5 mg, 92%). (Found C, 41.52;
H, 4.21; N, 12.00. C32H38IN8O2U requires C, 41.25; H, 4.11; N,
12.03%). No NMR signal was detected. IR (Nujol) n/cm-1: 1600
w, 1531 w, 1261 vs, 1100 s, 1031 vs, 949 w, 903 w, 801 vs [nasym
in pyridine-d5 showed broad singlets at d 72, 61 and 57 ppm
corresponding to undefined paramagnetic compounds. Attempts
at crystallization in pyridine-Et2O led to the formation of yellow
crystals of [UO2(OTf)2(py)3] only. The same reaction with a large
excess of Me3SiC5H5 gave an orange solution in acetonitrile.
Undefined green crystals were obtained from a pyridine-pentane
mixture.
(c) An NMR tube was charged with [UO2(OTf)2] (11.5 mg,
20.4 mmol) in acetonitrile-d3 (0.3 mL) and Me3SiC5Me5 (4.9 mL,
20.4 mmol) was added via a microsyringe. After 48 h at 25 ◦C, the
green solution was evaporated to dryness and the residue dissolved
in pyridine-d5 (0.3 mL). The spectrum of the orange solution
showed signals at d 61 and 58 ppm. By using 2 mol equivalents of
Me3SiC5Me5, the spectrum exhibited a major signal at d 60 ppm
and minor peaks at d 46, 27 and 22 ppm.
=
(U O)], 638 w, 634 w.
[UO2Cl(py)3] (17). Pyridine (25 mL) was condensed in a
50 mL round bottom flask containing [UO2Cl2(THF)2]2 (200 mg,
0.41 mmol) and TlC5H5 (111 mg, 0.41 mmol). The suspension
was stirred at 20 ◦C for 4 h, leading to a brown solution and
a pale yellow precipitate of TlCl. After decantation and slow
filtration, the volume of the solution was reduced to 5 mL and a
brown powder precipitated upon addition of pentane (20 mL). The
powder was filtered off, washed with a 1 : 4 mixture of pyridine–
pentane (20 mL) and dried under vacuum during 10 h (199 mg,
89%). (Found C 32.90, H 2.95, N 7.61. C15ClH15N3O2U requires C
33.19, H 2.78, N 7.74%). IR (Nujol) n/cm-1:1264w, 1218s, 1153 m,
Reactions of [UO2I2(THF)3] or [UO2Cl2(THF)2]2 with
Me3SiC5R5 (R = H, Me). Crystals of [UO2Cl2(py)3]. (a) An NMR
tube was charged with [UO2I2(THF)3] (10.0 mg, 13.5 mmol) and
Me3SiC5H5 (2.27 mL, 13.5 mmol) in acetonitrile-d3 (0.3 mL). After
2 h at 20 ◦C, the spectrum of the red brown solution showed the
presence of C5H6-nDn and a signal at d 60.5 ppm.
=
1067 s, 1038 s, 1008 s, 905 vs, 801 s [nasym (U O)], 753 s, 697 s, 627 m,
465 s. A similar experiment was carried out in pyridine-d5 and the
NMR spectrum revealed the formation of C5H6. IR (pyridine)
n/cm-1: 924 m [nasym (UVI=O)], 812 m [nasym (UV=O)].
[UO2(NO3)(py)3] (18). (a) Pyridine (25 mL) was condensed in
a 50 mL round bottom flask containing [UO2I(THF)2.7] (200 mg,
0.34 mmol) and TlNO3 (91.1 mg, 0.34 mmol). The suspension
was stirred at 20 ◦C for 2 h, affording a brown-red solution and a
yellow precipitate of TlI. After decantation and slow filtration, the
volume of the solution was reduced to 5 mL and a brown powder
precipitated upon addition of pentane (20 mL). The powder was
filtered off, washed with a 1 : 4 mixture of pyridine–pentane
(20 mL) and dried under vacuum for 10 h (184 mg, 96%). (Found:
C 31.32, H 2.79, N 9.63. C15H15N4O5U requires C 31.64, H 2.65, N
9.84%). IR (Nujol) n/cm-1: 1269 vs, 1068 m, 1023 vs, 927 s, 884 s,
804 w, 761 s, 692 s, 630 vs, 513 m. IR (pyridine) n/cm-1: 812 m
(b) An NMR tube was charged with [UO2Cl2(THF)2]2 (10.0 mg,
0.02 mmol) and Me3SiC5H5 (3.37 mL, 0.020 mmol) in acetonitrile-
d3 (0.3 mL). After 20 h at 20 ◦C, the spectrum of the yellow solution
showed signals at d 65 and 58 ppm. The solution was evaporated
to dryness and the residue dissolved in pyridine (0.4 mL) to give
a green solution. Slow diffusion of Et2O (2 mL) into this solution
gave yellow crystals of [UO2Cl2(py)3] suitable for X-ray diffraction.
By using Me3SiC5Me5 in place of Me3SiC5H5, the NMR spectrum
showed a signal at d 54 ppm. Crystals of [UO2Cl2(py)3] were
again obtained by slow diffusion of Et2O into the pyridine
solution.
=
Reactions of UX4 (X = Cl, OTf) and NaOSiMe3. (a) An NMR
tube was charged with UCl4 (12.0 mg, 0.031 mmol) and NaOSiMe3
(6.9 mg, 0.062 mmol) in pyridine-d5 (0.4 mL). After 48 h at 110 ◦C,
the spectrum of the pale green solution showed large signals at d
56 and 0 ppm.
(b) An NMR tube was charged with U(OTf)4 (11.5 mg,
0.014 mmol) and NaOSiMe3 (3.1 mg, 0.028 mmol) in pyridine-
d5 (0.4 mL). After 48 h at 110 ◦C, the spectrum of the
brown solution showed broad signals at d 60, 27, 24, 15.5 and
0.3 ppm.
[nasym (U O)].
(b) An NMR tube was charged with [UO2(NO3)2(MeCN)]
(10.0 mg, 0.023 mmol) and KC5Me5 (4.0 mg, 0.023 mmol) or
TlC5H5 (6.2 mg, 0.023 mmol) in pyridine-d5 (0.4 mL). The yellow
solution turned brown rapidly, and a white precipitate of TlNO3
was deposited. The NMR spectra showed the formation of either
(C5Me5)2 or C5H6-nDn. The solution was filtered and evaporated
to dryness, leaving the brown powder of 18.
Reactions of [UO2(OTf)2] and Me3SiC5R5 (R = H, Me). Crystals
of [UO2(OTf)(py)4] (19). (a) An NMR tube was charged with
[UO2(OTf)2] (10.0 mg, 17.6 mmol) in acetonitrile (0.3 mL) and
Me3SiC5H5 (2.97 mL, 17.6 mmol) was added via a microsyringe.
Crystallography
◦
After 48 h at 25 C, the colour of the solution turned from light
The data were collected at 100(2) K on a Nonius Kappa-CCD
area detector diffractometer57 using graphite-monochromated Mo
yellow to green yellow. The solution was evaporated to dryness,
leaving a green yellow powder which was washed with pentane
(2 mL) and then dissolved in pyridine (0.4 mL). Slow diffusion
of pentane (2 mL) into the orange solution led to the formation
of yellow crystals of [UO2(OTf)2(py)3] together with a few red
crystals of 19. The same compound was obtained by using 2 mol
equivalents of Me3SiC5H5.
(b) An NMR tube was charged with [UO2(OTf)2] (10.0 mg,
17.6 mmol) in acetonitrile-d3 (0.3 mL) and Me3SiC5H5 (5.94 mL,
35.2 mmol) was added via a microsyringe. After 20 h refluxing,
the colour of the solution turned from light yellow to green with
a brown precipitate. The NMR spectrum of the green solution
˚
Ka radiation (l 0.71073 A). The crystals were introduced into
glass capillaries with a protecting “Paratone-N” oil (Hampton
Research) coating. The unit cell parameters were determined from
ten frames, then refined on all data. The data (combinations
of j- and w-scans giving complete data sets up to q = 25.7◦
and a minimum redundancy of 4 for 90% of the reflections)
were processed with HKL2000.58 The structures were solved
by Patterson map interpretation (8, 15·1.5py, 19) or by direct
methods (all other compounds) with SHELXS-97, expanded
by subsequent Fourier-difference synthesis and refined by full-
matrix least-squares on F2 with SHELXL-97.59 Absorption effects
3492 | Dalton Trans., 2009, 3478–3494
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Table 6 Crystal data and structure refinement details
4·py
5·py
6·py
7
8
12·py
15·1.5py
19
UO2Cl2(py)3
Chemical formula C60H55F15K3- C68H65F9-
C68H65F9N13- C35H35I2-
C28H25F9Li2- C30H30IN6-
C45.5H50.5F3- C21H20F3- C15H15Cl2-
N11O19S5U2 KN13O13S3U2 O13S3TlU2
2272.81 2054.67 2219.94
Monoclinic Orthorhombic Orthorhombic Orthorhombic Monoclinic Orthorhombic Triclinic
LiN7O2U
1084.47
N5O11S3U
1126.62
O2U
871.53
N
10.5O5SU N4O5SU
N3O2U
578.23
M/g mol-1
1151.55 735.50
Crystal system
Space group
Monoclinic Monoclinic
C2/c P21/c
¯
P1
P21
P212121
19.0805(4)
20.0091(8)
20.5906(8)
90
P212121
19.1433(5)
19.9724(5)
20.6551(7)
90
Pna21
17.1377(8)
12.3158(11)
18.5640(19)
90
P21/c
Pbca
˚
a/A
17.5189(6)
11.7341(2)
20.1579(7)
90
21.6519(4)
21.3781(6)
19.0730(5)
90
111.162(2)
90
16.5129(7)
17.2053(8)
22.4464(7)
90
90
90
12.5854(12) 13.2614(8) 11.1335(8)
14.1686(19) 12.2270(10) 13.0944(9)
14.4513(19) 15.2571(10) 13.2043(6)
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
110.201(6) 90
90
98.720(5) 112.600(4)
90 90
2445.3(3) 1777.2(2)
99.510(2)
90
90
90
90
90
98.845(8)
94.538(9)
2365.2(5)
2
90
90
3
˚
V/A
4086.9(2)
2
1.847
7861.2(5)
4
1.736
7897.2(4)
4
1.867
3918.2(6)
4
1.838
8233.1(4)
8
1.818
4.194
4344
6377.2(4)
8
1.815
6.094
3304
Z
4
4
Dc/g cm-3
1.617
3.544
1144
91 211
8946
1.998
6.785
1396
40 910
2317
2.161
9.445
1072
51 854
3363
m (Mo Ka)/mm-1
F(000)
4.343
2200
4.336
4000
6.294
4248
5.757
2044
Reflections collected 106 663
128 320
14 875
175 501
14 973
158 854
7075
264 858
15603
207 093
6034
Independent
reflections
15 426
Observed reflections 14 246
12 835
13 364
5982
12 270
4291
7820
1801
2968
[I > 2s(I)]
Rint
0.074
0.072
983
0.034
0.043
983
0.030
0.066
434
0.045
0.027
1063
0.029
0.033
361
0.043
0.093
603
0.043
0.034
176
0.036
0.048
208
0.031
Parameters refined 1034
R1 (observed
reflections)
wR2 (all data)
S
0.055
0.139
1.092
0.007(8)
-1.18
2.04
0.072
0.993
-0.009(3)
-0.99
0.82
0.064
1.014
-0.007(4)
-1.09
1.23
0.113
1.043
0.500(8)
-1.03
1.77
0.072
1.019
—
-1.28
1.13
0.095
1.091
—
-1.23
1.00
0.106
1.078
—
-1.29
1.34
0.096
1.116
—
-1.42
1.48
0.079
1.001
—
-2.09
1.38
Flack parameter
-3
˚
Drmin/e A
Drmax/e A
-3
˚
were corrected empirically with the program SCALEPACK.58 All
non-hydrogen atoms were refined with anisotropic displacement
parameters. The hydrogen atoms were introduced at calculated
positions and were treated as riding atoms with an isotropic
displacement parameter equal to 1.2 (CH, CH2) or 1.5 (CH3) times
that of the parent atom. Specific details are as follows:
Compound 4·py. One of the pyridine molecules (containing N5)
was refined as an idealized hexagon. Some restraints on bond
lengths and/or displacement parameters were applied for some
badly behaving atoms, particularly in the triflate groups.
Compound 12·py. Restraints on displacement parameters were
applied for five carbon atoms from two coordinated pyridine
molecules, seemingly affected with unresolved disorder.
Compound 15·1.5py. Restraints on bond lengths were applied
for atoms C16, C17 and C26, C27 as well as restraints on
displacement parameters for some badly behaving atoms. One
solvent pyridine molecule is disordered around a symmetry
centre.
Compound 19. The triflate ion is disordered over two equally
populated positions related by the binary axis and sharing atoms
O2 and F1; a restraint was applied on the S1–C11 bond length.
Restraints on displacement parameters were applied for some
carbon atoms of the pyridine rings and one pyridine molecule
was refined as an idealized hexagon. The large displacement
parameters of several carbon atoms of the pyridine rings, as well as
a short O4 ◊ ◊ ◊ C6 contact, likely indicate some unresolved disorder
of the pyridine molecules.
Acknowledgements
We are grateful to Dr Franc¸ois Nief (Ecole Polytechnique,
Palaiseau, France), Dr Mark Foreman (University of Reading,
U. K.) and Dr Cle´ment Hill (CEA Marcoule) for giving us samples
of KC5Me4P and CyMe4BTBP. We also thank the Direction de
l’Energie Nucle´aire of the Commissariat a` l’Energie Atomique for
its financial support.
References
1 (a) E. Barnea and M. S. Eisen, Coord. Chem. Rev., 2006, 250, 855;
(b) W. J. Evans and S. A. Kozimor, Coord. Chem. Rev., 2006, 250, 911;
(c) I. C. Rodrıguez and K. Meyer, Chem. Commun., 2006, 1353; (d) M.
Ephritikhine, Dalton Trans., 2006, 2501; (e) S. Cotton, Lanthanide
and Actinide Chemistry, John Wiley and Sons, Chichester, England,
2006; (f) M. Sharma and M. S. Eisen, Struct. Bonding, 2008, 127, 1;
(g) O. T. Summerscale and F. G. N. Cloke, Struct. Bonding, 2008, 127,
87; (h) S. C. Bart and K. Meyer, Struct. Bonding, 2008, 127, 119.
2 (a) J. Maynadie´, J. C. Berthet, P. Thue´ry and M. Ephritikhine, J. Am.
Chem. Soc., 2006, 128, 1082; (b) J. Maynadie´, N. Barros, J. C. Berthet, P.
Thue´ry, L. Maron and M. Ephritikhine, Angew. Chem., Int. Ed., 2007,
46, 2010.
3 J. C. Berthet, P. Thue´ry and M. Ephritikhine, Organometallics, 2008,
27, 1664.
4 (a) J. G. Brennan and R. A. Andersen, J. Am. Chem. Soc., 1985, 107, 514;
(b) D. S. J. Arney and C. J. Burns, J. Am. Chem. Soc., 1993, 115, 9840;
(c) D. S. J. Arney and C. J. Burns, J. Am. Chem. Soc., 1995, 117, 9448;
(d) T. Arliguie, M. Lance, M. Nierlich, J. Vigner and M. Ephritikhine,
J. Chem. Soc., Chem. Commun., 1995, 183; (e) M. F. Lappert and D. S.
Liu, J. Organomet. Chem., 1995, 500, 203; (f) R. E. Cramer, K. A. N. S.
Ariyaratne and J. W. Gilje, Z. Anorg. Allg. Chem., 1995, 621, 1856; (g) D.
Gourier, D. Caurant, J. C. Berthet, C. Boisson and M. Ephritikhine,
Inorg. Chem., 1997, 36, 5931; (h) D. Gourier, D. Caurant, T. Arliguie
and M. Ephritikhine, J. Am. Chem. Soc., 1998, 120, 6084; (i) J. C.
Crystal data and structure refinement parameters are given in
Table 6. The molecular plots were drawn with SHELXTL59 and
Balls & Sticks.60
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View Article Online
Berthet and M. Ephritikhine, Coord. Chem. Rev., 1998, 178–180, 83;
(j) T. Arliguie, M. Fourmigue´ and M. Ephritikhine, Organometallics,
2000, 19, 109; (k) P. B. Duval, C. J. Burns, D. L. Clark, B. L. Morris,
B. L. Scott, J. D. Thompson, E. L. Werkema, L. Jia and R. A. Andersen,
Angew. Chem., Int. Ed., 2001, 40, 3358; (l) J. L. Kiplinger, D. E. Morris,
B. L. Scott and C. J. Burns, Chem. Commun., 2002, 30; (m) W. J. Evans,
S. A. Kozimor and J. W. Ziller, Chem. Commun., 2005, 4681; (n) C. R.
Graves, B. L. Scott, D. E. Morris and J. L. Kiplinger, J. Am. Chem.
Soc., 2007, 129, 11914; (o) C. R. Graves, A. E. Vaughn, E. J. Schelter,
B. L. Scott, J. D. Thompson, D. E. Morris and J. L. Kiplinger, Inorg.
Chem., 2008, 47, 11879.
5 (a) C. Boisson, J. C. Berthet, M. Lance, J. Vigner, M. Nierlich and M.
Ephritikhine, J. Chem. Soc., Dalton Trans., 1996, 947; (b) L. P. Spencer,
R. L. Gdula, T. W. Hayton, B. L. Scott and J. M. Boncella, Chem.
Commun., 2008, 4986.
6 J. C. Berthet, M. Lance, M. Nierlich and M. Ephritikhine, Eur. J. Inorg.
Chem., 2000, 1969.
Krot and M. S. Grigoriev, Russ. Chem. Rev., 2004, 73, 89; (d) M. L.
McKee and M. Swart, Inorg. Chem., 2005, 44, 6975.
27 M. A. Cooper, D. D. Elleman, C. D. Pearce and S. L. Manatt, J. Chem.
Phys., 1970, 53, 2343.
28 (a) P. Jutzi and F. Kohl, J. Organomet. Chem., 1979, 164, 141; (b) W. J.
Evans, K. J. Forrestal and J. W. Ziller, J. Am. Chem. Soc., 1998, 120,
9273.
29 J. H. N. Buttery Effendy, S. Mutrofin, N. C. Plackett, B. W. Skelton,
C. R. Whitaker and A. H. White, Z. Anorg. Allg. Chem., 2006, 632,
1809.
30 J. H. N. Buttery Effendy, S. Mutrofin, N. C. Plackett, B. W. Skelton, N.
Somers, C. R. Whitaker and A. H. White, Z. Anorg. Allg. Chem., 2006,
632, 1839.
31 (a) R. D. Shannon, Acta Crystallogr., Sect. A: Found. Crystallogr.,
1976, 32, 751; (b) E. N. Rizkalla and G. R. Choppin, in Handbook
on the Physics and Chemistry of Rare Earths. Lanthanides/Actinides:
Chemistry, ed. K. A. Gschneidner, Jr., L. Eyring, G. R. Choppin and
G. H. Lander, Elsevier Science, Amsterdam, 1994, vol. 18, p. 529.
32 J. C. Berthet, J. F. Le Mare´chal and M. Ephritikhine, J. Organomet.
Chem., 1994, 480, 155.
33 J. A. Danis, M. R. Lin, B. L. Scott, B. W. Eichhorn and W. H. Runde,
Inorg. Chem., 2001, 40, 3389.
34 W. A. Henderson, V. G. Young, N. R. Brooks and W. H. Smyrl, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun., 2002, 58, m501.
35 J. C. Berthet, P. Thue´ry and M. Ephritikhine, unpublished results.
36 J. C. Berthet, P. Thue´ry and M. Ephritikhine, Inorg. Chem., 2005, 44,
1142.
7 M. P. Wilkerson, C. J. Burns, R. T. Paine and B. L. Scott, Inorg. Chem.,
1999, 38, 4156.
8 J. C. Berthet, M. Nierlich and M. Ephritikhine, Chem. Commun., 2004,
870.
9 M. J. Sarsfield, M. Helliwell and D. Collison, Chem. Commun., 2002,
2264.
10 J. C. Berthet, P. Thue´ry and M. Ephritikhine, Chem. Commun., 2007,
604.
11 (a) W. J. Oldham, S. M. Oldham, B. L. Scott, K. D. Abney, W. H. Smith
and D. A. Costa, Chem. Commun., 2001, 1348; (b) P. L. Arnold and
S. T. Liddle, Chem. Commun., 2006, 3959; (c) S. M. Oldham, B. L. Scott
and W. J. Oldham, Appl. Organomet. Chem., 2006, 20, 39.
12 (a) W. Hallwachs and A. Schafarik, Ann. Chem., 1859, 109, 206; (b) J.
Sand and F. Singer, Justus Liebigs Ann. Chem., 1903, 329, 190.
13 A. M. Seyam, Inorg. Chim. Acta, 1982, 58, 71.
37 M. R. S. Foreman, M. J. Hudson, M. G. B. Drew, C. Hill and C. Madic,
Dalton Trans., 2006, 1645.
38 J. C. Berthet, P. Thue´ry, M. R. S. Foreman and M. Ephritikhine,
Radiochim. Acta, 2008, 96, 189.
39 T. I. Docrat, J. F. W. Mosselmans, J. M. Charnock, M. W. Whiteley,
D. Collison, F. R. Livens, C. Jones and M. J. Edmilston, Inorg. Chem.,
1999, 38, 1879.
14 J. Maynadie´, J. C. Berthet, P. Thue´ry and M. Ephritikhine, Chem.
Commun., 2007, 486.
15 J. C. Berthet, G. Siffredi, P. Thue´ry and M. Ephritikhine, Chem.
Commun., 2006, 3184.
40 M. G. B. Drew, M. R. S. Foreman, C. Hill, M. J. Hudson and C. Madic,
Inorg. Chem. Commun., 2005, 8, 239.
41 C. J. Burns, D. L. Clark, R. J. Donohoe, P. B. Duval, B. L. Scott and
C. D. Tait, Inorg. Chem, 2000, 39, 5464.
42 (a) T. Arliguie, M. Ephritikhine, M. Lance, J. Vigner and M. Nierlich,
J. Organomet. Chem., 1994, 484, 195; (b) Z. J. Tonzetich and R.
Eisenberg, Inorg. Chim. Acta, 2003, 345, 340; (c) H. Yamamoto, H.
Yasuda, K. Tatsumi, K. Lee, A. Nakamura, J. Chen, Y. Kai and N.
Kasai, Organometallics, 1989, 8, 105; (d) T. Yakamoto, H. Yasuda, A.
Nakamura, Y. Kai, N. Kanehisa and N. Kasai, J. Am. Chem. Soc., 1988,
110, 5008.
43 P. L. Arnold, D. Patel, C. Wilson and J. B. Love, Nature, 2008, 315.
44 J. C. Berthet, G. Siffredi, P. Thue´ry and M. Ephritikhine, Eur. J. Inorg.
Chem., 2007, 4017.
16 A. Ekstrom, Inorg. Chem, 1974, 13, 2237.
17 (a) P. J. Hay, R. L. Martin and G. Schreckenbach, J. Phys. Chem. A,
2000, 104, 6259; (b) S. Matsika, Z. Zhang, S. R. Brozell, J. P. Blaudeau,
Q. Wang and R. M. Pitzer, J. Phys. Chem. A, 2001, 105, 3825; (c) L.
Gagliardi, I. Grenthe and B. Roos, Inorg. Chem., 2001, 40, 2976; (d) T.
Privalov, P. Macak, B. Schimmelpfennig, E. Fromager, I. Grenthe and
U. Wahlgreen, J. Am. Chem. Soc., 2004, 126, 9801.
18 J. J. Katz, G. T. Seaborg and L. R. Morss, The Chemistry of the Actinide
Elements, 2nd edn, Chapman and Hall, New York, 1986, vols. 1 and 2.
19 J. C. Berthet, M. Nierlich and M. Ephritikhine, Angew. Chem., Int. Ed.,
2003, 42, 1952.
20 L. Natrajan, F. Burdet, J. Pe´caut and M. Mazzanti, J. Am. Chem. Soc.,
2006, 128, 7152.
21 (a) F. Burdet, J. Pe´caut and M. Mazzanti, J. Am. Chem. Soc., 2006, 128,
16512; (b) G. Nocton, P. Horeglad, J. Pe´caut and M. Mazzanti, J. Am.
Chem. Soc., 2008, 130, 16633.
22 T. W. Hayton and G. Wu, J. Am. Chem. Soc., 2008, 130, 2005.
23 T. W. Hayton and G. Wu, Inorg. Chem., 2008, 47, 7415.
24 (a) K. Mizuoka and Y. Ikeda, Inorg. Chem., 2003, 42, 3396; (b) K
Mizuoka, S. Y. Kim, M. Hasegawa, T. Hoshi, G. Uchiyama and
Y. Ikeda, Inorg. Chem., 2003, 42, 1031; (c) K. Mizuoka and Y.
Ikeda, Radiochim. Acta, 2004, 92, 631; (d) K. Mizuoka, S. Tsushima,
M. Hasegawa, T. Hoshi and Y. Ikeda, Inorg. Chem., 2005, 44,
6211.
25 (a) P. Thue´ry, Chem. Commun., 2006, 853; (b) M. J. Sarsfield and M.
Helliwell, J. Am. Chem. Soc., 2004, 126, 1036; (c) P. Thue´ry and B.
Masci, Polyhedron, 2004, 649; (d) P. Thue´ry and B. Masci, Dalton
Trans., 2003, 2411; (e) J. A. Danis, M. R. Lin, B. L. Scott, B. W.
Eichhorn and W. H. Runde, Inorg. Chem., 2001, 40, 3389; (f) M. P.
Wilkerson, C. J. Burns, H. J. Dewey, J. M. Martin, D. E. Morris, R. T.
Paine and B. L. Scott, Inorg. Chem., 2000, 39, 5277; (g) P. Thue´ry,
M. Nierlich, B. Souley, Z. Asfari and J. Vicens, J. Chem. Soc., Dalton
Trans., 1999, 2589, and references therein.
45 L. H. Jones and R. A. Penneman, J. Chem. Phys., 1953, 21, 542.
46 G. H. Jones, I. May, M. J. Sarsfield, H. M. Steele, D. Collison, M.
Helliwell and J. M. McKinney, Dalton Trans., 2004, 734.
47 M. J. Sarsfield, M. Helliwell and J. Raftery, Inorg. Chem., 2004, 43,
3170.
48 J. C. Taylor, A. Ekstrom and C. H. Randell, Inorg. Chem., 1978, 17,
3285.
49 H. Steele and R. J. Taylor, Inorg. Chem., 2007, 46, 6311.
50 J. A. Hermann and J. F. Suttle, Inorg. Synth., 1957, 5, 143.
51 J. C. Berthet, M. Lance, M. Nierlich and M. Ephritikhine, Eur. J. Inorg.
Chem., 1999, 2005.
52 J. C. Berthet, P. Thue´ry, J. P. Dognon, D. Guillaneux and M.
Ephritikhine, Inorg. Chem., 2008, 47, 6850.
53 T. M. Gilbert, R. R. Ryan and A. P. Sattelberger, Organometallics,
1988, 7, 2514.
54 P. Gradoz, D. Baudry, M. Ephritikhine, F. Nief and F. Mathey, J. Chem.
Soc., Dalton Trans., 1992, 3047.
55 E. O. Fischer, Angew. Chem., 1957, 69, 207.
56 E. W. Abel and M. O. Dunster, J. Organomet. Chem., 1971, 33, 161.
57 R. W. W. Hooft, COLLECT, Nonius BV, Delft, The Netherlands, 1998.
58 Z. Otwinowski and W. Minor, Methods Enzymol., 1997, 276, 307.
59 G. M. Sheldrick, Acta Crystallogr. Sect. A: Found. Crystallogr., 2008,
64, 112.
26 (a) C. Den Auwer, A. C. Gre´goire-Kappenstein and Ph. Moisy,
Radiochim. Acta, 2003, 91, 773; (b) T. E. Albrecht-Schmitt, P. M.
Almond and R. E. Sykora, Inorg. Chem., 2003, 42, 3788; (c) N. N.
60 T. C. Ozawa and S. J. Kang, J. Appl. Crystallogr., 2004, 37, 679.
3494 | Dalton Trans., 2009, 3478–3494
This journal is
The Royal Society of Chemistry 2009
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