Synthesis of Coordinatively Unsaturated Tetravalent Actinide Complexes with η5 Coordination of Pyrrole

Article abstract of DOI:10.1021/acs.inorgchem.5b02853

The synthesis of new actinide complexes utilizing bridged α-alkyl-pyrrolyl ligands is presented. Lithiation of the ligands followed by treatment with 1 equiv of actinide tetrachloride (uranium or thorium) produces the desired complex in good yield. X-ray diffraction studies reveal unique η⁵:η⁵ coordination of the pyrrolyl moieties; when the nonsterically demanding methylated ligand is used, rapid addition of the lithiated ligand solution to the metal precursor forms a bis-ligated complex that reveals η⁵:η¹ coordination as determined by crystallographic analysis.

Full text of DOI:10.1021/acs.inorgchem.5b02853

Article
pubs.acs.org/IC
Synthesis of Coordinatively Unsaturated Tetravalent Actinide
Complexes with η5 Coordination of Pyrrole
Rami J. Batrice, Natalia Fridman, and Moris S. Eisen*
Schulich Faculty of Chemistry, Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, Technion
City, 3200008 Israel
S
* Supporting Information
ABSTRACT: The synthesis of new actinide complexes utilizing bridged α-
alkyl-pyrrolyl ligands is presented. Lithiation of the ligands followed by
treatment with 1 equiv of actinide tetrachloride (uranium or thorium)
produces the desired complex in good yield. X-ray diffraction studies reveal
unique η5:η5 coordination of the pyrrolyl moieties; when the nonsterically
demanding methylated ligand is used, rapid addition of the lithiated ligand
solution to the metal precursor forms a bis-ligated complex that reveals η5:η1
coordination as determined by crystallographic analysis.
examples in which these side reactions are absent are mainly seen
in early transition metal chemistry, and studies of such complexes
elucidate the highly electrophilic nature of the metal and steric
environment that are required to yield the pentahapto pyrrolyl-
metal moiety.51,52 Although studies of actinide-pyrrolyl com-
plexes date as far back as 1974 with Marks’ preparation of
tetrakis(2,5-dimethylpyrrolyl)uranium(IV),53 it is only in the
past decade that pyrrolyl ligands have been reintroduced into
actinide chemistry and the focus of continued investigation.54 In
the first of these studies, Boncella et al. revealed a UVI center
coordinated to a bridged dipyrrolylmethane (dpm) ligand. Salt
metathesis of the dipotassium ligand with U(NtBu)2I2(THF)2
yielded the η1:η1-bound ligand; when the 1,9-bis(arylated) ligand
is employed using similar reaction conditions, the coordination
mode of the ligand is found to favor the π-coordinated η5:η5 motif
(Scheme 1).55
INTRODUCTION
■
The actinide metallocenes have long been the cornerstone of 5f-
block coordination chemistry. Since the earliest reports of
cyclopentadienyl-actinide complexes,1−4 this class of complexes
has drawn the attention of numerous studies focusing on the
preparation of various Cp analogues,5−12 as well as their
reactivity in diverse stoichiometric13−21 and catalytic reac-
tions.8,11,22−35 One of the most attractive features of the
pentamethylcyclopentadienyl (Cp*) ligands in particular is the
considerable thermal stability that they impart upon the resulting
organoactinide complex;36 however, despite this, relatively little
work has been done exploring similar ligands containing
heteroatoms within the ring structure. Of the possibilities,
pyrrole emerges as the most suitable substitute for Cp* largely
owing to its isoelectronic properties. As compared to other
common heterocycles, pyrrole is highly susceptible to facile
deprotonation to generate a monoanionic species because of the
acidity of the N−H proton (pKa = 23.0 in DMSO),37 in contrast
to other protic heterocycles; moreover, the electronegativity of
the nitrogen in competition with the π-system of the heterocycle
results in a considerable resonance stabilization energy of 29.6
kcal mol−1.38 The combination of these factors suggests that
pyrrole possesses the capacity to form an aromatic system
capable of forming a pentahapto coordination pattern to a metal
center, similar to that seen in cyclopentadienyl ligands.
In addition, Cloke and co-workers have unveiled a trivalent
uranium complex displaying η5 coordination of 2,3,4,5-
tetramethylpyrrole.56 By the salt metathesis reaction of the
dipotassium salts of a substituted cyclooctatetraene and the
potassium salt of tetramethylpyrrole with uranium(III) iodide, a
Scheme 1. Synthesis of U(VI)-Dipyrrolylmethane Complexes
While pyrrole is widely used in coordination complexes
incorporating virtually all metals of the transition block, most of
these show pyrrole to be bound in an η1 fashion, directly forming
a nitrogen−metal bond.39−47 Interestingly, there are still many
examples of η5-bound pyrrole in transition metal chemistry;
however, it is often seen that such ligation is vulnerable to
substitution reaction or haptotropic shifts.48−50 The selected
Received: December 13, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
bimetallic complex bearing π-coordination of both ligands is
formed, which upon solvation with THF yields the monometallic
complex (Scheme 2).
series of uranium(IV) and thorium(IV) ansa-bridged dipyrrolyl
complexes that inherently incorporate coordinative unsaturation
of the metal sphere, making subsequent functionalization or
reactivity studies of the metal complex readily achievable. Herein,
we report the synthesis of 1,9-dialkyl-dipyrrolylmethane ligands
Scheme 2. Synthesis of the Uranium(III) Mixed-Sandwich
Complex
t
(H2dpmR; R = Me, Bu, or Ad), the methyl analogue being
prepared according to previously reported methods, and the
synthesis of the corresponding organoactinides by salt metathesis
with the dilithiated ligands. The formed complexes are studied by
spectroscopic and crystallographic techniques and reveal unusual
pentahapto coordination of the pyrrolic fragment of the ligand.
We demonstrate the suitability of the dpmR motif to stabilize the
U(IV) or Th(IV) center with a preference of forming an ansa-
bridged structure analogous to cyclopentadienyl systems.
Investigation of the bond lengths reveals differences in the
electronic nature of the pyrrole that show promise for future
functionalization and reactivity studies.
A recent study by Arnold et al. utilized pyrrolic macrocyclic
ligands bound to a uranium(IV) center. With this considerably
electrophilic metal center (5f26d0), the pyrrolyl moieties of the
ligand bind in a pentahapto manner; however, reduction of the
uranium center using potassium-graphite provides a more
electron rich metal and results in isomerization of the ligand
coordination mode to an η1:η1 configuration (Scheme 3).57
RESULTS AND DISCUSSION
■
Ligand Synthesis. The methylated dipyrrolylmethane
ligand (H2dpmMe) was prepared according to previously
reported methods. Beginning from H2dpm, Vilsmeier−Haack
formylation62 selectively formed the 1,9-bisformyl-dipyrrolyl-
methane in 90% isolated yield. Successive Wolff−Kishner
reduction63 yielded the target ligand in 96% yield after workup
(Scheme 4).
Scheme 3. Synthesis of the U(IV) Pyrrolyl-Macrocyclic
Complex and Its Subsequent Reduction to a U(III) Analogue
To prepare the tert-butyl and 1-adamantyl derivatives of the
H2dpm ligand, a dissimilar synthetic protocol was employed. The
2-alkylpyrroles were prepared by Friedel−Crafts alkylation
according to published methods;64,65 using the α-substituted
pyrroles, acid-catalyzed condensation was achieved in dichloro-
methane with 2,2-dimethoxypropane (DMP) and pyridinium p-
toluenesulfonate (PPTS) as the acid source, yielding the desired
ligands after column chromatography on silica gel with an eluent
of 5% ethyl acetate in hexane (eq 1).
The ability to form pentahapto pyrrolyl bonding to an actinide
center was further demonstrated by Gambarotta and co-workers
with the preparation of a [(-CH2-]4-calix[4]tetrapyrrolyl
uranium complex and a uranium(III) polypyrrolide complex.58,59
The polypyrrolides displayed η5 coordination of two of the four
pyrroles present, and retention of a solvated potassium or lithium
counterion; however, more impressive was the catalytic behavior
exhibited by these complexes, showing C−H bond activation,
solvent deoxygenation and fragmentation, polysilanol depoly-
merization, and dinitrogen cleavage.59,60 In addition, it has been
shown that reduction of a thorium(IV) bis-pyrrolide complex
using potassium metal in a coordinating solvent results in the
formation of a thorium(III) center displaying η5:η5 coordination
to the pyrrolic moieties.61
Although the investigation of pyrrolyl-actinides is limited,
these studies show extraordinary behavior and provide insight
into the influences of the ligand substitution and metal center,
which facilitate the divergent coordination modes of the pyrrolic
moiety. The six-electron donation to the metal center achieved
through the π-bonding interactions of pyrrole would be expected
to stabilize the metal in a manner similar to cyclopentadienyl
ligation. Inspired by this, we have pursued the preparation of a
Synthesis of (dpmR)nAn(IV) Complexes. The ligands were
n
deprotonated in situ using 2 equiv of 1.6 M BuLi to yield the
dilithium salt (Li2dpmR). The reaction between the dilithiated
ligand solution and an equimolar amount of actinide
tetrachloride (UCl4 or ThCl4·3THF) was performed in THF
at ambient temperature for up to 2 days or 12 h, respectively.
After workup and filtration through Celite to remove the LiCl
generated, samples were recrystallized in either a toluene
solution or a mixture of toluene and ethyl ether, furnishing
structures 1−4 (Table 1). Each of the complexes showed the
retention of solvated lithium ions, similar to the molecular
structure seen for previous actinide polypyrrolide complexes.59
Conversely, the structures can be considered as bonding of a
Scheme 4. Synthesis of 1,9-Dimethyl(dipyrrolylmethane)
B
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 1. Crystal Data and Structure Analysis Results
1
2
3
4
formula
fw
C34H48Cl2Li2N4O2Th
861.58
C28H40Cl4Li2N2O3Th
840.34
C34H48Cl2Li2N4O2U
867.57
C31H48Cl4Li2N2O3U
890.42
space group
a (Å)
monoclinic, C2/c
20.753(4)
10.150(6)
17.081(3)
90
triclinic, P1
monoclinic, P21/c
17.3080(8)
11.5880(5)
17.456(1)
90
triclinic, P1
̅
̅
8.745(18)
9.35(4)
15.89(5)
74.50(3)
76.40(4)
67.87(6)
1147(7)
2
10.2600(3)
11.2090(3)
17.8490(6)
96.878(1)
99.668(1)
110.1340(16)
1864.61(10)
2
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
98.180(13)
90
97.7620(17)
90
3561(2)
4
3469.0(3)
4
radiation (Kα, Å)
T (K)
0.71073
200
0.71073
200
0.71073
0.71073
200
200
D
calcd (g cm−3
)
1.607
2.433
1.661
1.586
μcalcd (cm−1
R1, wR2
GOF
)
4.372
7.010
4.869
4.670
0.0295, 0.0746
1.094
0.0775, 0.1950
1.032
0.0598, 0.1458
1.034
0.0683, 0.1857
1.222
Figure 1. Solid state structure of 1 (thermal ellipsoids are drawn at 50% probability). (a) Full molecular structure and (b) condensed structure showing
only the ligand binding mode with hydrogen atoms removed for the sake of clarity. (c) Molecular structure of 1 with coordinated THF molecules
removed for the sake of clarity. Selected bond distances (angstroms) and angles (degrees): Th1−N1, 2.748(3); Th1−C1, 2.778(2); Th1−C2, 2.915(3);
Th1−C3, 2.956(3); Th1−C4, 2.876(2); Th1−N2, 2.516(7); Th1−[η5-C4N]cent, 2.601(5); Th1−Cl1, 2.816(7); [η5-C4N]cent−Th1−N2, 85.83(8);
Cl1−Th1−Cl1, 170.25(4).
lithium pyrrolide to the actinide center with accompanying
chloride ion and stabilizing solvent.
The molecular structure obtained shows a highly symmetric
metal complex with each dpmMe ligand bound in an η1:η5 fashion
and 2 equiv of lithium chloride and two molecules of THF.
Several interesting features are apparent in this structure, one of
the most notable being the bond lengths to the atoms of the η5-
pyrrole; the ring structure is found to be disposed with the
nitrogen atom of the π-bound heterocycle closer to the thorium
metal center at a distance of 2.748(3) Å, with the carbon atoms
growing more distant from the α- to β-carbons up to a length of
2.956(3) Å, and a centroid distance of 2.601(5) Å. Via
comparison of the Th−N bond distances between two nitrogens
of the bridged pyrrols, the pentahapto pyrrole nitrogen is found
to be 0.232 Å farther from the metal center than from the η1
pyrrole (Th1−N2, 2.516 Å), a reasonable observation given the
strong σ-donation that is absent from the η5 heterocycle. The
In the reaction of the actinide precursors with Li2dpmMe, it is
seen with the thorium analogue that rapid addition of the ligand
solution results in a mixture of mono- and bis-dpmMe complexes.
However, either of these products can be formed selectively by
the addition of 2 equiv of the ligand solution to ThCl4·3THF to
yield Li2(dpmMe)2ThCl2·2THF (1), or slow addition of 1 equiv
of the ligand to a cooled solution of thorium tetrachloride (−35
°C) to yield Li2(dpmMe)ThCl4·3THF (2). Single crystals of these
complexes were prepared from saturated THF solutions layered
with n-hexane at −35 °C in a nitrogen-filled glovebox. The X-ray
diffraction pattern from the bis complex (1) revealed the
molecular structure shown in Figure 1.
C
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. Variable-temperature NMR spectra of [(dpmMe)2ThCl2][Li2(THF)2] with the pyrrolic region shown. Coalescence is observed at 80 °C.
Figure 3. Solid state structure of 2 (thermal ellipsoids are drawn at 50% probability). (a) Full molecular structure and (b) condensed structure showing
only the ligand binding mode with hydrogen atoms removed for the sake of clarity. (c) Molecular structure of 2 with coordinated THF molecules
removed for the sake of clarity. Selected bond distances (angstroms) and angles (degrees): Th1−N1, 2.446(1); Th1−C2, 2.713(1); Th1−C3, 2.782(2);
Th1−C4, 2.742(2); Th1−C5, 2.522(9); Th1−N2, 2.258(2); Th1−C9, 2.341(1); Th1−C10, 2.560(1); Th1−C11, 2.631(1); Th1−C12, 2.533(1);
Th1−Cl1, 2.428(8); Th1−Cl2, 2.478(6); Th1−Cl3, 2.543(8); Th1−Cl4, 2.269(8); Th1−[η5-C4N]cent(ave), 2.265(2); [η5-C4N1]cent−Th1−[η5-
C4N2]cent, 105.66(2); Cl1−Th1−Cl2, 84.3(2); Cl3−Th1−Cl4, 82.8(1); Cl1−Th1−Cl3, 164.4(1); Cl1−Th1−Cl4, 86.5(2); Cl2−Th1−Cl3, 82.7(1);
Cl2−Th1−Cl4, 80.2(1).
geometry of the resultant molecule is arranged with the two
chloride moieties in a trans configuration (Cl−Th−Cl, 170.38°),
and the pentahapto pyrrols cis to each other ([η5-C4N]cent−Th−
[η5-C4N]cent) at an angle of 112.09°. Line-shape analysis of the
in an η5:η5 fashion (Figure 3), resembling the previously reported
ansa-bridged metallocenes.10
Similar to the structure of complex 1, the pyrrole rings in 2 are
found to be disposed with the π-bound nitrogen closer to the
thorium center; however, the bond distances from the actinide
center to the pyrrole centroid (2.265 Å) are significantly shorter
than those of the bis-ligated complex (1) and in fact are shorter
than the Th−Cp*cent bond distance (2.53 Å),66 suggesting higher
covalency to dpmMe and the possibility of augmented thermal
stability. It is worth noting that the difference in bond lengths
between the two thorium−nitrogen bonds is 0.188 Å; however,
the proton NMR signals for the pyrrolic hydrogens are found to
be degenerate for this complex in solution. This indicates that the
asymmetry seems to be a structural phenomenon arising from
the solid state structure that is lost upon dissolution at ambient
1
pyrrolic proton signals in H NMR spectrum shows that the
ligand isomerizes between the η5 and η1 modes of coordination
with an enthalpic barrier of 20.1(1) kcal mol−1, and coalescence
occurs at 80 °C (Figure 2). The entropy calculated by the
exchange rates of these peaks was found to be 7.3(4) eu,
suggesting that the ligand isomerization occurs by decoordina-
tion/coordination rather than by a highly ordered twisting
mechanism.
Conversely, the molecular structure of 2, prepared by the slow
addition of a Li2dpmMe solution to a cooled solution of ThCl4·
3THF, revealed a single ligand coordinated to the thorium center
D
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 4. Solid state structure of 3 (thermal ellipsoids are drawn at 50% probability). (a) Full molecular structure and (b) condensed structure showing
only the ligand binding mode with hydrogen atoms removed for the sake of clarity. (c) Molecular structure of 3 with coordinated THF molecules
removed for the sake of clarity. Selected bond distances (angstroms) and angles (degrees): U1−N1, 2.436(8); U1−N2, 2.731(9); U1−C10, 2.84(1);
U1−C11, 2.90(1); U1−C12, 2.85(1); U1−C13, 2.73(1); U1−[η5-C4N2]cent, 2.547(9); U1−N3, 2.462(9); U1−N4, 2.715(9); U1−C27, 2.84(1); U1−
C28, 2.91(1); U1−C29, 2.88(1); U1−C30, 2.73(1); U1−[η5-C4N4]cent, 2.553(9); U1−Cl1, 2.751(3); U1−Cl2, 2.742(3); [η5-C4N2]cent−U1−N1,
86.19(3); [η5-C4N4]cent−U1−N3, 85.44(7); [η5-C4N2]cent−U1−[η5-C4N4]cent, 111.46(8); Cl1−U1−Cl2, 170.3(1).
temperature, likely arising from the rapid thermal motion of the
thorium center within the binding pocket of the bidentate ligand.
Via comparison of the thorium−centroid bond lengths to those
found for the thorium(III) bis-pyrrolides presented by
Gambarotta et al.,61 one can assume that the higher electro-
philicity of the thorium(IV) center leads to a stronger bonding
interaction to the heterocycle. Seeing the markedly short Li2−
Cl2 bond length [1.859(2) Å], we can consider the structure as
retaining 1 equiv of lithium chloride rather than forming an
anionic actinide complex. The lithium−pyrrole bonds [1.72(2)
and 1.79(1) Å] are significantly shorter than those seen for
previous actinide pyrrolides (2.05 Å),59 also suggesting the
presence of a lithium pyrrolide moiety rather than a lithium ion
balancing an anionic complex.
given the aforementioned low solubility of UCl4, the
tBu
monoligated complex of the formula Li2(dpm )UCl4·3THF
(4) is produced selectively (Figure 5).
The structure reveals a distorted octahedral geometry with
both pyrrole rings maintaining the previously seen η5
coordination mode. Upon comparison to the average bond
length of the uranium−pyrrole centroid (2.566 Å), the lengths
are found to be longer than the uranium−centroid bond in
bis(pentamethylcyclopentadienyl)uranium dichloride (2.47 Å);
however, they are found to be remarkably similar to the centroid
lengths seen in previous pentahaptic pyrrolyl−uranium moieties
(2.55 Å).58 Additionally, the observed bond lengths reveal a high
level of symmetry, particularly evident in the uranium−nitrogen
and −carbon bond lengths of the pyrrolic moieties. Although
crystal structures of the other (dpmR)uranium complexes would
aid in a systematic study of the effects of alkyl substitution,
unfortunately attempts to form single crystals of the 1-adamantyl
analogue have thus far been unsuccessful. However, examining
the data obtained thus far would suggest that the sterically
encumbering tert-butyl groups create additional crowding about
the metal center that forces the pyrrole rings to be situated farther
from the uranium atom.
During the salt metathesis reaction of Li2dpmMe with UCl4, the
limited solubility of the uranium precursor, even in ethereal
solvent, proved to be problematic for the desired synthesis. After
workup and crystallization, the molecular structure found by X-
ray diffraction revealed a bis-ligated complex of the formula
Li2(dpmMe)2UCl2·2THF (3) (Figure 4). No indication of the
monoligated complex is found, informing us that the chloride
displacement by the lithiated ligand occurs more rapidly than the
dissolution of uranium tetrachloride as the reagent is consumed.
The structure is seen to be isomorphous with complex 1 with
only slightly longer bond lengths, consistent with the smaller
ionic radius of U(IV) compared to that of Th(IV).67
Although attempts to crystallize the samples prepared with the
thorium analogue bearing dpmtBu or dpmAd provided only
1
clusters of crystals, H NMR spectroscopy and combustion
analysis were useful in proposing the nature of the complexes
obtained. In both thorium complexes bound to either the tert-
butyl- or 1-adamantyl-substituted ligands, similar chemical shifts
and splitting patterns are seen for the pyrrolic protons, as well as
chemical shifts consistent with coordinated THF molecules,
suggesting that according to the previously seen structures and
their respective spectra, these compounds are isostructural to
Using larger alkyl substituents on the dpm backbone was
studied to sterically crowd the actinide center sufficiently to form
the target monoligated complex. Similar salt metathesis reactions
were performed with H2dpmtBu and H2dpmAd with both actinide
precursors, and single crystals isolated from the reaction of
Li2dpmtBu with UCl4. The molecular structure revealed that even
E
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 5. Solid state structure of 4 (thermal ellipsoids are drawn at 50% probability). (a) Full molecular structure and (b) condensed structure showing
only the ligand binding mode with hydrogen atoms removed for the sake of clarity. (c) Molecular structure of 4 with coordinated THF molecules
removed for the sake of clarity. Selected bond distances (angstroms) and angles (degrees): U1−N1, 2.753(3); U1−C5, 2.946(8); U1−C6, 2.959(5);
U1−C7, 2.831(7); U1−C8, 2.687(1); U1−N2, 2.749(6); U1−C12, 2.711(1); U1−C13, 2.810(1); U1−C14, 2.904(5); U1−C15, 2.928(2); U1−Cl1,
2.663(7); U1−Cl2, 2.721(6); U1−Cl3, 2.724(2); U1−Cl4, 2.702(9); U1−[η5-C4N]cent(ave), 2.566(3); [η5-C4N1]cent−U1−[η5-C4N2]cent, 101.31(3);
Cl1−U1−Cl2, 162.15(1); Cl3−U1−Cl4, 76.37(4); Cl1−U1−Cl3, 81.93(9); Cl1−U1−Cl4, 80.71(4); Cl2−U1−Cl3, 84.79(1); Cl2−U1−Cl4,
84.62(1).
complex 1. In addition, the elemental analyses showed percent
compositions of carbon, hydrogen, and nitrogen consistent with
the proposed molecular formulas, further supporting formation
of the desired compounds; while these data are useful in
proposing the aforementioned structures, further analysis,
namely, single-crystal diffraction studies, is needed to definitively
identify the molecular structure of these compounds.
EXPERIMENTAL SECTION
■
Materials and Methods. All manipulations of air-sensitive
materials were performed with the rigorous exclusion of oxygen and
moisture in flamed Schlenk-type glassware or J-Young Teflon valve-
sealed NMR tubes on a dual-manifold Schlenk line interfaced with a
high-vacuum (10−5 Torr) line, or in a nitrogen-filled Innovative
Technologies glovebox with a medium-capacity recirculator (1−2 ppm
of O2). Argon and nitrogen were purified by passage through a MnO
oxygen-removal column and a Davison 4 Å molecular sieve column.
Hydrocarbon solvents benzene-d6 (Cambridge Isotopes), toluene-d8
(Cambridge Isotopes), toluene (Bio-Lab), THF (Bio-Lab), and diethyl
ether (BioLab) were distilled under vacuum from Na/K alloy or purified
by passage through an activated alumina column under a nitrogen
atmosphere. Pyrrole was purified by distillation on a rotary evaporator
CONCLUSIONS
■
A set of actinide-dipyrrolylmethane complexes have been
prepared and show the unusual η5 coordination of pyrrole.
When methyl groups are introduced at positions 1 and 9 of the
ligand, a mono- or bis-ligated complex may be obtained
selectively for the thorium complex by salt metathesis with the
dilithiated ligand. Conversely, the analogous reaction performed
with UCl4 generated only the bis(dpmMe) complex because of
the low solubility of the uranium precursor. The 1,9-di-tert-
butyldipyrrolylmethane was additionally reacted with uranium
tetrachloride after lithiation and, after crystal structure
determination, showed that the use of larger alkyl groups favored
the formation of the mono(dpm) complex. The coordinative
unsaturated monoligated complexes show the structural
potential to serve as possible precatalysts for future organic
transformations. Functionalization and reactivity studies are
currently under investigation in our group.
and then dried by refluxing over CaH2 and distilling. UCl4,68 ThCl4·
62
2DME,69 H2dpmMe
,
2-tert-butylpyrrole,64 and 2-adamantylpyrrole
were prepared according to previously reported methods.65 ThCl4·
3THF was prepared by passage of carbon tetrachloride vapor under a
stream of helium over thoria in a tube furnace heated to 750 °C, followed
by heating of the ThCl4 produced in THF and precipitation with n-
hexane.
NMR spectra of crude reaction mixtures were recorded on a Bruker
Avance 300, Bruker Avance III 400, or Bruker Avance 500 spectrometer.
Chemical shifts for 1H and 13C NMR are referenced to internal protio
solvent and reported relative to tetramethylsilane. J values are reported
for 1H NMR coupling constants in Hertz. Known products were
compared to previously reported data. Elemental analyses were
performed on a Thermo Scientific Flash 2000 CHNS OEA instrument.
Synthetic Procedures. Synthesis of 5,5′-(Propane-2,2-diyl)bis[2-
(tert-butyl)pyrrole] (H2dpmtBu). 2-tert-Butylpyrrole (3.6 g, 29.7 mmol)
F
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
and evaporation, yielding 577 mg of a dark red solid occurring from
coordination of 2 equiv of ligand (69%): 1H NMR (300 MHz, C6D6) δ
20.77 (s, 6H), 20.44 (s, 6H), 15.17 (s, 2H), 4.16 (s, 18H), 1.73 (s, 2H),
1.48 (s, 18H), −1.15 (s, 2H), −1.60 (s, 6H), −5.55 (s, 6H), −8.84 (s,
6H), −31.84 (s, 2H), −33.91 (s, 6H). 13C NMR is silent except for THF
resonances. Anal. Calcd for C34H48Cl2Li2N4O2U: C, 47.07; H, 5.58; N,
6.46. Found: C, 47.55; H, 6.08; N, 6.27.
was dissolved in 100 mL of DCM, and 1.8 mL of 2,2-dimethoxypropane
(14.8 mmol) was added to the solution. The solution was sparged with
dinitrogen for 5 min, and then 750 mg of PPTS was added (3.0 mmol)
and the solution stirred at room temperature for 6 h, resulting in a rapid
color change of the solution to orange. The solution was then passed
through a plug of Celite and the filtrate evaporated, and the solids were
purified by column chromatography on silica gel with a 5% solution of
ethyl acetate in hexane to yield 1.8 g of an orange waxy solid as the
desired product (43%): 1H NMR (400 MHz, CDCl3) δ 7.49 (bs, 2H,
NH), 5.97 (t, J = 3.0 Hz, 2H, pyrrole CH), 5.84 (t, J = 3.0 Hz, 2H, pyrrole
CH), 1.63 (s, 6H, CH3), 1.23 [s, 18H, C(CH3)3]; 13C NMR (101 MHz,
CDCl3) δ 141.22, 137.78, 103.20, 101.79, 35.80, 31.41, 30.59, 29.71; mp
58−60 °C; HRMS (APCI) [M + H]* observed m/z 287.2479, calcd for
C19H31N2 m/z 287.2487. Anal. Calcd for C19H30N2: C, 79.66; H, 10.56;
N, 9.78. Found: C, 79.45; H, 10.46; N, 10.09.
Synthesis of Li2(η5:η5-dpmMe)ThCl4·3THF (2). An ethyl ether solution
of the ligand (288 mg, 1.42 mmol) was cooled to −35 °C, followed by
the addition of 2 equiv of nBuLi as a 1.6 M solution in hexane (1.78 mL,
2.85 mmol). The solution was warmed to room temperature and stirred
for 2 h. A second solution of ThCl4·3THF (840 mg, 1.42 mmol) in THF
was prepared, and both solutions were cooled to −35 °C, followed by
the slow addition of the ligand solution to the thorium solution. The
mixture was warmed to room temperature and stirred overnight. The
solution was evaporated to dryness and dissolved in a mixture of toluene
and ethyl ether, followed by filtration and evaporation, yielding 869 mg
of a beige solid (77%): 1H NMR (300 MHz, C6D6) δ 6.90 (d, J = 2.5 Hz,
2H, pyrrole CH), 6.62 (d, J = 2.5 Hz, 2H, pyrrole CH), 3.59 (t, J = 6.5
Hz, 12H, THF CH2), 2.86 (s, 6H, CH3), 1.71 (s, 6H, CH3), 1.33−1.21
(m, 12H, THF CH2); 13C NMR (126 MHz, C6D6) δ 146.62 (C), 145.80
(C), 120.13 (CH), 119.13 (CH), 68.14 (CH2), 25.54 (CH2), 24.26
(CH3), 18.56 (CH3). Anal. Calcd for C25H40Cl4Li2N2O3Th: C, 37.33; H,
5.01; N, 3.48. Found: C, 37.18; H, 4.90; N, 3.37.
Synthesis of 5,5′-(Propane-2,2-diyl)bis[2-(1-adamantyl)pyrrole]
(H2dpmAd). A 500 mL Schlenk flask was loaded with 9.4 g (46.7
Synthesis of Li2(η5:η5-dpmtBu)UCl4·3THF (4). A THF solution of the
ligand (201 mg, 702 μmol) was cooled to −35 °C, followed by the
addition of 2 equiv of nBuLi as a 1.6 M solution in hexane (877 μL, 1.40
mmol). The solution was warmed to room temperature and stirred for 2
h. A second solution of UCl4 (267 mg, 702 μmol) in THF was prepared,
and both solutions were cooled to −35 °C, followed by the slow addition
of the ligand solution to the uranium solution. The mixture was warmed
to room temperature and stirred for 3 days. The solution was then
evaporated to dryness and dissolved in toluene, followed by filtration
and evaporation, yielding 408 mg of a dark red solid (66%): 1H NMR
(300 MHz, C6D6) δ 19.17 (s, 1H), 18.78 (s, 1H), 16.67 (s, 6H), 15.86 (s,
1H), 14.41 (s, 1H), 13.54 (s, 1H), 7.16 (s, 7H), 1.61 (s, 3H), 1.33 (s,
2H), 1.06 (s, 7H), 0.98 (s, 1H), −9.89 (s, 18H), −13.41 (s, 3H). 13C
NMR was silent. Anal. Calcd for C31H52Cl4Li2N2O3U: C, 41.63; H, 5.86;
N, 3.13. Found: C, 42.05; H, 6.14; N, 2.79.
mmol) of 2-(1-adamantyl)pyrrole, 250 mL of DCM, and 2.8 mL of 2,2-
dimethoxypropane (22.9 mmol). The solution was sparged with
nitrogen for 5 min, and then 1.17 g of PPTS (4.7 mmol) was added
in one portion. The reaction mixture was stirred at room temperature for
24 h, then filtered through a plug of Celite, and dried under vacuum. The
solids were purified by column chromatography on silica gel with a 5%
solution of ethyl acetate in hexane to yield 7.95 g of an orange oil that
1
solidified upon standing (79%): H NMR (400 MHz, CDCl3) δ 7.53
(bs, 2H, NH), 5.96 (t, J = 3.0 Hz, 2H, pyrrole CH), 5.81 (t, J = 3.0 Hz,
2H, pyrrole CH), 2.02 (bs, 12H, adamantyl CH2), 1.81 (d, J = 2.2 Hz,
12H, adamantyl CH2), 1.72 (q, J = 12.2 Hz, 6H, adamantyl CH), 1.61 (s,
6H, CH3); 13C NMR (101 MHz, CDCl3) δ 141.98, 137.44, 103.20,
101.09, 42.94, 36.89, 35.82, 33.30, 29.75, 28.67; mp 121−123 °C;
HRMS (APCI) [M + H]* observed m/z 443.3430, calcd for C31H43N2
m/z 443.3426. Anal. Calcd for C31H42N2: C, 84.11; H, 9.56; N, 6.33.
Found: C, 84.38; H, 9.31; N, 6.31.
Synthesis of Li2(η5:η5-dpmtBu)ThCl4·3THF. A solution of H2dpmtBu
(327 mg, 1.14 mmol) in THF (3 mL) was cooled to −35 °C, and then
1.463 mL of a 1.6 M nBuLi solution was added at the reduced
temperature. The solution was warmed to room temperature, stirred for
3 h, and then added to a cooled (−35 °C) solution of ThCl4·2DME (632
mg, 1.14 mmol) in THF. The reaction mixture was warmed to room
temperature and stirred for 8 h, followed by removal of solvent in vacuo.
The residue was dissolved in toluene, filtered through a plug of Celite,
Synthesis of Li2(η5:η1-dpmMe)2ThCl2·2THF (1). A THF solution of the
ligand (170 mg, 840 μmol) was cooled to −35 °C, followed by the
addition of 2 equiv of nBuLi as a 1.6 M solution in hexane (1.05 mL, 1.68
mmol). The solution was warmed to room temperature and stirred for 2
h. A second solution of ThCl4·3THF (248 mg, 420 μmol) in THF was
prepared, and both solutions were cooled to −35 °C, followed by the
rapid addition of the ligand solution to the thorium solution. The
mixture was warmed to room temperature and stirred overnight. The
solution was then evaporated to dryness and dissolved in toluene,
followed by filtration and evaporation, yielding 299 mg of a beige solid
(84%): 1H NMR (300 MHz, C6D6) δ 7.31 (d, J = 2.7 Hz, 2H, η5-pyrrole
CH), 6.21 (d, J = 2.8 Hz, 2H, η5-pyrrole CH), 6.18 (d, J = 2.7 Hz, 2H, η1-
pyrrole CH), 6.01 (dd, J = 2.8, 0.7 Hz, 2H, η1-pyrrole CH), 3.59 (t, J =
6.5 Hz, 12H, THF CH2), 2.58 (s, 6H, CH3), 2.34 (s, 6H, CH3), 2.25 (s,
6H, CH3), 1.66 (s, 6H, CH3), 1.33−1.21 (m, 12H, THF CH2); 13C
NMR (126 MHz, C6D6) δ 156.82 (C), 150.42 (C), 145.12 (C), 138.71
(C), 121.91 (CH), 117.49 (CH), 108.27 (CH), 105.52 (CH), 68.14
(CH2), 39.33 (C), 34.82 (CH3), 30.20 (CH3), 25.54 (CH2), 18.18
(CH3), 16.63 (CH3). Anal. Calcd for C34H48Cl2Li2N4O2Th: C, 47.40; H,
5.62; N, 6.50. Found: C, 47.02; H, 5.97; N, 6.88.
1
and evaporated, yielding 730 mg of a light orange powder (73%): H
NMR (500 MHz, C6D6) δ 7.15 (m, 2H, pyrrole CH), 6.83 (m, 2H,
pyrrole CH), 3.63 (bs, 12H, THF CH2), 2.80 (s, 6H, CH3), 1.67 [s, 18H,
C(CH3)3], 1.36 (s, 12H, THF CH2); 13C NMR (126 MHz, C6D6) δ
164.24 (C), 142.18 (C), 122.67 (CH), 116.41 (CH), 69.80 (C), 68.19
(CH2), 59.30 (C), 25.22 (CH2), 23.42 (CH3), 21.07 (CH3). Anal. Calcd
for C31H52Cl4Li2N2O3Th: C, 41.91; H, 5.90; N, 3.15. Found: C, 42.26;
H, 5.85; N, 2.82.
Synthesis of Li2(η5:η5-dpmAd)ThCl4·3THF. A solution of 490 mg of
H2dpmAd (1.107 mmol) in 4 mL of THF was cooled to −35 °C,
followed by the addition of 2 equiv of nBuLi as a 1.6 M solution in hexane
(1.384 mL, 2.214 mmol). The solution was warmed to room
temperature, stirred for 3 h, and then added to a cooled solution
(−35 °C) of 613 mg (1.107 mmol) of ThCl4·2DME dissolved in THF.
The reaction mixture was warmed to room temperature and stirred
overnight, at which point the volatiles were removed under vacuum. The
residue was dissolved in a mixture of ethyl ether and toluene, then
filtered through a plug of Celite, and evaporated under vacuum to yield
644 mg of a pale orange powder (56%): 1H NMR (500 MHz, C6D6) δ
6.23 (t, J = 3.0 Hz, 2H, pyrrole CH), 6.06 (t, J = 3.0 Hz, 2H, pyrrole CH),
3.61 (bs, 12H, THF CH2), 1.87−1.82 (m, 12H, adamantyl CH2), 1.73
(d, J = 2.4 Hz, 12H, adamantyl CH2), 1.66 (s, 6H, CH3), 1.58 (bs, 6H,
Synthesis of Li2(η5:η1-dpmMe)2UCl2·2THF (3). A THF solution of the
ligand (198 mg, 979 μmol) was cooled to −35 °C, followed by the
addition of 2 equiv of nBuLi as a 1.6 M solution in hexane (1.22 mL, 1.96
mmol). The solution was warmed to room temperature and stirred for 2
h. A second solution of UCl4 (372 mg, 979 μmol) in THF was prepared,
and both solutions were cooled to −35 °C, followed by the slow addition
of the ligand solution to the uranium solution. The mixture was warmed
to room temperature and stirred for 3 days. The solution was then
evaporated to dryness and dissolved in toluene, followed by filtration
G
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
adamantyl CH), 1.39 (bs, 12H, THF CH2); 13C NMR (126 MHz,
C6D6) δ 141.18 (C), 136.91 (C), 103.78 (CH), 101.93 (CH), 70.64
(CH2), 58.93 (C), 42.66 (C), 36.53 (CH), 29.73 (CH), 28.52 (CH2),
25.31 (CH2), 13.94 (CH3). Anal. Calcd for C43H64Cl4Li2N2O3Th: C,
49.44; H, 6.18; N, 2.68. Found: C, 49.18; H, 5.92; N, 2.60.
(18) Kiernicki, J. J.; Newell, B. S.; Matson, E. M.; Anderson, N. H.;
Fanwick, P. E.; Shores, M. P.; Bart, S. C. Inorg. Chem. 2014, 53, 3730−
3741.
(19) Fang, B.; Ren, W.; Hou, G.; Zi, G.; Fang, D.-C.; Maron, L.; Walter,
M. D. J. Am. Chem. Soc. 2014, 136, 17249−17261.
(20) Ren, W.; Zhou, E.; Fang, B.; Zi, G.; Fang, D.-C.; Walter, M. D.
Chem. Sci. 2014, 5, 3165−3172.
(21) Ren, W.; Zhou, E.; Fang, B.; Hou, G.; Zi, G.; Fang, D.-C.; Walter,
M. D. Angew. Chem., Int. Ed. 2014, 53, 11310−11314.
(22) Andrea, T.; Barnea, E.; Eisen, M. S. J. Am. Chem. Soc. 2008, 130,
2454−2455.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b02853.
(23) Barnea, E.; Andrea, T.; Berthet, J.-C.; Ephritikhine, M.; Eisen, M.
S. Organometallics 2008, 27, 3103−3112.
(24) Barnea, E.; Moradove, D.; Berthet, J.-C.; Ephritikhine, M.; Eisen,
M. S. Organometallics 2006, 25, 320−322.
CIF file providing crystallographic data for 1 (CIF)
CIF file providing crystallographic data for 2 (CIF)
CIF file providing crystallographic data for 3 (CIF)
CIF file providing crystallographic data for 4 (CIF)
(25) Dash, A. K.; Eisen, M. S. Org. Lett. 2000, 2, 737−740.
(26) Dash, A. K.; Gourevich, I.; Wang, J. Q.; Wang, J.; Kapon, M.;
Eisen, M. S. Organometallics 2001, 20, 5084−5104.
(27) Dash, A. K.; Wang, J. Q.; Eisen, M. S. Organometallics 1999, 18,
4724−4741.
AUTHOR INFORMATION
Corresponding Author
*E-mail: chmoris@tx.technion.ac.il. Telephone: +972-4-
8292680.
■
(28) Haskel, A.; Straub, T.; Dash, A. K.; Eisen, M. S. J. Am. Chem. Soc.
1999, 121, 3014−3024.
(29) Haskel, A.; Wang, J. Q.; Straub, T.; Neyroud, T. G.; Eisen, M. S. J.
Am. Chem. Soc. 1999, 121, 3025−3034.
Notes
(30) Sharma, M.; Andrea, T.; Brookes, N. J.; Yates, B. F.; Eisen, M. S. J.
Am. Chem. Soc. 2011, 133, 1341−1356.
The authors declare no competing financial interest.
(31) Straub, T.; Haskel, A.; Eisen, M. S. J. Am. Chem. Soc. 1995, 117,
6364−6365.
ACKNOWLEDGMENTS
■
This research was supported by the Israel Science Foundation,
administered by the Israel Academy of Science and Humanities
under Contract 78/14, and by the PAZY Foundation Fund
(2015) administered by the Israel Atomic Energy Commission.
(32) Wang, J.; Gurevich, Y.; Botoshansky, M.; Eisen, M. S. J. Am. Chem.
Soc. 2006, 128, 9350−9351.
(33) Wang, J. Q.; Eisen, M. S. J. Organomet. Chem. 2003, 670, 97−107.
(34) Stubbert, B. D.; Marks, T. J. J. Am. Chem. Soc. 2007, 129, 4253−
4271.
REFERENCES
(35) Wobser, S. D.; Marks, T. J. Organometallics 2013, 32, 2517−2528.
(36) Burns, C.; Eisen, M. Organoactinide Chemistry: Synthesis and
Characterization. In The Chemistry of the Actinide and Transactinide
Elements; Morss, L., Edelstein, N., Fuger, J., Eds.; Springer: Dordrecht,
The Netherlands, 2006; pp 2799−2910.
■
(1) Fischer, E. O.; Treiber, A. Z. Naturforsch., A: Phys. Sci. 1962, 17,
276−277.
(2) Baumgartner, F.; Fischer, E. O.; Kanellakopulos, B.; Laubereau, P.
̈
Angew. Chem., Int. Ed. Engl. 1969, 8, 202−202.
(37) Bordwell, F. G.; Drucker, G. E.; Fried, H. E. J. Org. Chem. 1981,
46, 632−635.
(3) Fischer, E. O.; Hristidu, Y. Z. Naturforsch., B 1962, 17, 275−276.
(4) Baumgartner, F.; Fischer, E. O.; Kanellakopulos, B.; Laubereau, P.
̈
(38) Franklin, J. L. J. Am. Chem. Soc. 1950, 72, 4278−4280.
(39) Mathis, M.; Harsha, W.; Hanks, T. W.; Bailey, R. D.; Schimek, G.
L.; Pennington, W. T. Chem. Mater. 1998, 10, 3568−3575.
(40) Yeh, K.-N.; Barker, R. H. Inorg. Chem. 1967, 6, 830−833.
Angew. Chem., Int. Ed. Engl. 1968, 7, 634−634.
(5) Fagan, P. J.; Manriquez, J. M.; Maatta, E. A.; Seyam, A. M.; Marks,
T. J. J. Am. Chem. Soc. 1981, 103, 6650−6667.
(6) Blake, P. C.; Edelstein, N. M.; Hitchcock, P. B.; Kot, W. K.; Lappert,
M. F.; Shalimoff, G. V.; Tian, S. J. Organomet. Chem. 2001, 636, 124−
129.
(41) Muller, J.; Gaede, P.; Qiao, K. Zeitschrift fur Naturforschung B
̈
̈
2014, 49, 1645−1653.
(42) Hirano, M.; Onuki, K.; Kimura, Y.; Komiya, S. Inorg. Chim. Acta
2003, 352, 160−170.
(7) Clark, D. L.; Sattelberger, A. P.; Bott, S. G.; Vrtis, R. N. Inorg. Chem.
1989, 28, 1771−1773.
(8) Stubbert, B. D.; Stern, C. L.; Marks, T. J. Organometallics 2003, 22,
4836−4838.
(9) Golden, J. T.; Kazul’kin, D. N.; Scott, B. L.; Voskoboynikov, A. Z.;
Burns, C. J. Organometallics 2003, 22, 3971−3973.
(10) Fendrick, C. M.; Mintz, E. A.; Schertz, L. D.; Marks, T. J.
Organometallics 1984, 3, 819−821.
(11) Wang, J.; Gurevich, Y.; Botoshansky, M.; Eisen, M. S.
Organometallics 2008, 27, 4494−4504.
(12) MacDonald, M. R.; Fieser, M. E.; Bates, J. E.; Ziller, J. W.; Furche,
F.; Evans, W. J. J. Am. Chem. Soc. 2013, 135, 13310−13313.
(13) Langeslay, R. R.; Walensky, J. R.; Ziller, J. W.; Evans, W. J. Inorg.
Chem. 2014, 53, 8455−8463.
(43) Johnson, T. J.; Arif, A. M.; Gladysz, J. A. Organometallics 1993, 12,
4728−4730.
(44) DiFranco, S. A.; Maciulis, N. A.; Staples, R. J.; Batrice, R. J.; Odom,
A. L. Inorg. Chem. 2012, 51, 1187−1200.
(45) Edema, J. J. H.; Gambarotta, S.; Meetsma, A.; Spek, A. L.;
Veldman, N. Inorg. Chem. 1991, 30, 2062−2066.
(46) Li, Y.; Turnas, A.; Ciszewski, J. T.; Odom, A. L. Inorg. Chem. 2002,
41, 6298−6306.
(47) Levine, D. S.; Tilley, T. D.; Andersen, R. A. Organometallics 2015,
34, 4647−4655.
(48) Rakowski DuBois, M.; Parker, K. G.; Ohman, C.; Noll, B. C.
Organometallics 1997, 16, 2325−2334.
(49) Heenan, D. P.; Long, C.; Montiel-Palma, V.; Perutz, R. N.; Pryce,
M. T. Organometallics 2000, 19, 3867−3873.
(14) Siladke, N. A.; Webster, C. L.; Walensky, J. R.; Takase, M. K.;
Ziller, J. W.; Grant, D. J.; Gagliardi, L.; Evans, W. J. Organometallics
2013, 32, 6522−6531.
(50) Swartz, D. L., II; Odom, A. L. Dalton Trans. 2008, 4254−4258.
(51) Tanski, J. M.; Parkin, G. Organometallics 2002, 21, 587−589.
(52) Novak, A.; Blake, A. J.; Wilson, C.; Love, J. B. Chem. Commun.
2002, 2796−2797.
(15) Webster, C. L.; Ziller, J. W.; Evans, W. J. Organometallics 2012, 31,
7191−7197.
(16) Evans, W. J.; Walensky, J. R.; Ziller, J. W.; Rheingold, A. L.
Organometallics 2009, 28, 3350−3357.
(53) Marks, T. J.; Kolb, J. R. J. Organomet. Chem. 1974, 82, C35−C39.
(54) Sessler, J. L.; Melfi, P. J.; Pantos, G. D. Coord. Chem. Rev. 2006,
250, 816−843.
(17) Webster, C. L.; Ziller, J. W.; Evans, W. J. Organometallics 2014, 33,
433−436.
H
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(55) Swartz, D. L., II; Spencer, L. P.; Scott, B. L.; Odom, A. L.;
Boncella, J. M. Dalton Trans. 2010, 39, 6841−6846.
(56) Kahan, R. J.; Cloke, F. G. N.; Roe, S. M.; Nief, F. New J. Chem.
2015, 39, 7602−7607.
(57) Arnold, P. L.; Farnaby, J. H.; White, R. C.; Kaltsoyannis, N.;
Gardiner, M. G.; Love, J. B. Chem. Sci. 2014, 5, 756−765.
(58) Korobkov, I.; Gambarotta, S.; Yap, G. P. A.; Thompson, L.; Hay,
P. J. Organometallics 2001, 20, 5440−5445.
(59) Korobkov, I.; Gambarotta, S.; Yap, G. P. A. Organometallics 2001,
20, 2552−2559.
(60) Korobkov, I.; Gambarotta, S.; Yap, G. P. A. Angew. Chem., Int. Ed.
2002, 41, 3433−3436.
(61) Korobkov, I.; Vidjayacoumar, B.; Gorelsky, S. I.; Billone, P.;
Gambarotta, S. Organometallics 2010, 29, 692−702.
(62) Beer, P. D.; Cheetham, A. G.; Drew, M. G. B.; Fox, O. D.; Hayes,
E. J.; Rolls, T. D. Dalton Trans. 2003, 603−611.
(63) Martínez-García, H.; Morales, D.; Perez, J.; Coady, D. J.;
́
Bielawski, C. W.; Gross, D. E.; Cuesta, L.; Marquez, M.; Sessler, J. L.
Organometallics 2007, 26, 6511−6514.
(64) Harman, W. H.; Harris, T. D.; Freedman, D. E.; Fong, H.; Chang,
A.; Rinehart, J. D.; Ozarowski, A.; Sougrati, M. T.; Grandjean, F.; Long,
G. J.; Long, J. R.; Chang, C. J. J. Am. Chem. Soc. 2010, 132, 18115−
18126.
(65) King, E. R.; Hennessy, E. T.; Betley, T. A. J. Am. Chem. Soc. 2011,
133, 4917−4923.
(66) Spirlet, M. R.; Rebizant, J.; Apostolidis, C.; Kanellakopulos, B.
Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1992, 48, 2135−2137.
(67) Shannon, R. D. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor.
Gen. Crystallogr. 1976, 32, 751−767.
(68) Khan, I. A.; Ahuja, H. S.; Bagnall, K. W.; Sinf, L. 43. Uranium(IV)
Chloride for Organometallic Synthesis. In Inorganic Syntheses; John
Wiley & Sons, Inc.: New York, 2007; pp 187−190.
(69) Cantat, T.; Scott, B. L.; Kiplinger, J. L. Chem. Commun. 2010, 46,
919−921.
I
DOI: 10.1021/acs.inorgchem.5b02853
Inorg. Chem. XXXX, XXX, XXX−XXX