Synthesis and reactivity of the imido analogues of the uranyl ion

Article abstract of DOI:10.1021/ja0629155

Addition of 1.5 equiv of I₂ to a THF solution of UI ₃(THF)₄, containing either 6 equiv of ^tBuNH₂ or 2 equiv of RNH₂ (R = Ph, 3,5-(CF ₃)₂C₆H₃, 2,6-(ⁱPr) ₂C₆H₃) and 4 equiv of NEt₃, generates orange solutions containing U(N^tBu)₂I ₂(THF)₂ (1) or U(NAr)₂I₂(THF) ₃ (Ar = Ph, 2; 3,5-(CF₃)₂C₆H ₃, 3; 2,6-(ⁱPr)₂C₆H₃, 4), respectively, all of which can be isolated in good yields. Alternatively, 1 can be prepared by reaction of uranium metal with 3 equiv of I₂ and 6 equiv of ^tBuNH₂, also in good yield. Complexes 1-4 have been characterized by X-ray crystallography, and each of these complexes exhibits linear N-U-N linkages and short U-N bonds. Using density functional theory simulations of complexes 1 and 2, two triple bonds between the metal center and the nitrogen ligands were identified. Complexes 1 and 2 readily react with neutral Lewis bases such as pyridine or Ph₃PO to form U(NR)₂I₂(L)₂ (R = ^tBu, L = py, 5; Ph₃PO, 7; R = Ph, L = py, 6; Ph₃PO, 8), and with PMe ₃ to form U(NR)₂I₂(THF)(PMe₃) ₂ (R = ^tBu, 9; Ph, 10). The solid-state molecular structures of 5, 7, and 9 have been determined by X-ray crystallography, and these complexes, like their parent compounds, exhibit linear N-U-N angles and short U-N bonds. Complexes 1 and 2 also react with AgOTf in CH ₂CI₂, forming U(NR)₂(OTf)₂(THF) ₃ (R = ^tBu, 11; Ph, 12) after recrystallization from THF. Crystals of 12 grown from CH₂CI₂ were found to contain a dimer, [U(NPh)₂(OTf)₂(THF)₂]₂, a complex possessing bridging triflate groups.

Full text of DOI:10.1021/ja0629155

Published on Web 07/25/2006
Synthesis and Reactivity of the Imido Analogues of the
Uranyl Ion
Trevor W. Hayton,† James M. Boncella,*,† Brian L. Scott,† Enrique R. Batista,‡ and
P. Jeffrey Hay‡
Contribution from the Chemistry DiVision, Los Alamos National Laboratory, MS J514, and
Theoretical DiVision, Los Alamos National Laboratory, MS B268,
Los Alamos, New Mexico 87545
Received May 4, 2006; E-mail: boncella@lanl.gov
Abstract: Addition of 1.5 equiv of I2 to a THF solution of UI3(THF)4, containing either 6 equiv of tBuNH2 or
2 equiv of RNH2 (R ) Ph, 3,5-(CF3)2C6H3, 2,6-(iPr)2C6H3) and 4 equiv of NEt3, generates orange solutions
containing U(NtBu)2I2(THF)2 (1) or U(NAr)2I2(THF)3 (Ar ) Ph, 2; 3,5-(CF3)2C6H3, 3; 2,6-(iPr)2C6H3, 4),
respectively, all of which can be isolated in good yields. Alternatively, 1 can be prepared by reaction of
t
uranium metal with 3 equiv of I2 and 6 equiv of BuNH2, also in good yield. Complexes 1-4 have been
characterized by X-ray crystallography, and each of these complexes exhibits linear N-U-N linkages and
short U-N bonds. Using density functional theory simulations of complexes 1 and 2, two triple bonds
between the metal center and the nitrogen ligands were identified. Complexes 1 and 2 readily react with
t
neutral Lewis bases such as pyridine or Ph3PO to form U(NR)2I2(L)2 (R ) Bu, L ) py, 5; Ph3PO, 7; R )
t
Ph, L ) py, 6; Ph3PO, 8), and with PMe3 to form U(NR)2I2(THF)(PMe3)2 (R ) Bu, 9; Ph, 10). The solid-
state molecular structures of 5, 7, and 9 have been determined by X-ray crystallography, and these
complexes, like their parent compounds, exhibit linear N-U-N angles and short U-N bonds. Complexes
t
1 and 2 also react with AgOTf in CH2Cl2, forming U(NR)2(OTf)2(THF)3 (R ) Bu, 11; Ph, 12) after
recrystallization from THF. Crystals of 12 grown from CH2Cl2 were found to contain a dimer, [U(NPh)2-
(OTf)2(THF)2]2, a complex possessing bridging triflate groups.
1,3-(SiMe3)2C5H3, R ) H).9,10 The presence of a uranium-
Introduction
nitrogen multiple bond in these complexes suggests that there
Since the discovery of the first uranium imido complex over
20 years ago by Andersen and co-workers,1 the chemistry of
this functional group has been the focus of many actinide
chemists. The research inspired by this initial discovery has led
to the synthesis of a variety of uranium imido complexes in
which the metal varies in oxidation state from +4 to +6. For
instance, Andersen was also able to synthesize U(NSiMe3)-
(N{SiMe3}2)3,2 while Burns and co-workers have isolated Cp*2-
U(NR)2 (R ) Ph, adamantyl),3-5 Cp*2U(O)(N-2,6-(iPr)2C6H3),6
and Cp*2U(N-2,4,6-(tBu)3C6H2).4 In addition, several hetero-
atom-substituted imido complexes are known for uranium, such
as Cp3U(NPPh3) and Cp*2U(NSPh2)2.7,8 Bridging imido ligands
are also known for uranium, as in the case of the U(IV)
compounds [(Cp′)2U(µ-NR)]2 (Cp′ ) MeCp, R ) Ph; Cp′ )
may be a significant covalent interaction between the metal and
the nitrogen atom. Such covalency challenges the conventional
wisdom that the bonding in actinide compounds is primarily
ionic in nature and does not involve a significant contribution
from the valence 5f and 6d orbitals on the metal center.
The obvious similarity between the oxo ligand and the imido
group has made the synthesis of an imido analogue of the uranyl
ion highly desirable. Uranyl (UO22+) is the most prevalent
functional unit in the chemistry of U(VI) and has been known
for more than 150 years.11 With the advent of nuclear energy
and the use of uranium oxide as a reactor fuel, the chemistry of
the uranyl ion has played an essential role in the processing of
uranium ore, nuclear fuel, and waste.12 The linear arrangement
of the oxo ligands, extremely short U-O bonds, and high
thermal and chemical stability reflect some of the unique
properties of this moiety.13
† Chemistry Division.
‡ Theoretical Division.
(1) Brennan, J. G.; Andersen, R. A. J. Am. Chem. Soc. 1985, 107, 514-
Recently, we discovered a simple, general, high-yield pro-
cedure for the synthesis of a family of bis(imido) uranium(VI)
diiodide complexes, the imido analogues of the uranyl ion.14
516.
(2) Zalkin, A.; Brennan, J. G.; Andersen, R. A. Acta Crystallogr., Sect. C 1988,
44, 1553-1554.
(3) Arney, D. S. J.; Burns, C. J.; Smith, D. C. J. Am. Chem. Soc. 1992, 114,
10068-10069.
(4) Arney, D. S. J.; Burns, C. J. J. Am. Chem. Soc. 1995, 117, 9448-9460.
(5) Warner, B. P.; Scott, B. L.; Burns, C. J. Angew. Chem., Int. Ed. 1998, 37,
959-960.
(9) Brennan, J. G.; Andersen, R. A.; Zalkin, A. J. Am. Chem. Soc. 1988, 110,
4554-4558.
(10) Zi, G.; Blosch, L. L.; Jia, L.; Andersen, R. A. Organometallics 2005, 24,
4602-4612.
(6) Arney, D. S. J.; Burns, C. J. J. Am. Chem. Soc. 1993, 115, 9840-9841.
(7) Cramer, R. E.; Edelmann, F.; Mori, A. L.; Roth, S.; Gilje, J. W.; Tatsumi,
K.; Nakamura, A. Organometallics 1988, 7, 841-849.
(8) Ariyaratne, K. A. N. S.; Cramer, R. E.; Gilje, J. W. Organometallics 2002,
21, 5799-5802.
(11) Comyns, A. E. Chem. ReV. 1960, 60, 115-146.
(12) Katz, J. J.; Seaborg, G. T.; Morss, L. R. The Chemistry of the Actinide
Elements, 2nd ed.; Chapman and Hall: New York, 1986; Vol. 1.
(13) Denning, R. G. Struct. Bonding 1992, 79, 215-276.
9
10.1021/ja0629155 CCC: $33.50 © 2006 American Chemical Society
J. AM. CHEM. SOC. 2006, 128, 10549-10559
10549

A R T I C L E S
Hayton et al.
The ability to obtain these complexes presents a unique
opportunity to expand the chemistry of U(VI) and to study the
trans disposition of two imido ligands, an arrangement that is
exceedingly rare. In addition, the ease of synthesis of the bis-
(imido) complexes makes them attractive as starting materials
for the isolation of a variety of new derivatives.
triethylamine, a bis(imido) complex could be made in high yield.
Thus, addition of 1.5 equiv of I2 to a THF solution of UI3-
(THF)4, ArNH2 (2 equiv), and NEt3 (4 equiv) generates orange-
brown solutions containing U(NAr)2I2(THF)3 (Ar ) Ph, 2; 3,5-
(CF3)2C6H3, 3; 2,6-(iPr)2C6H3, 4) (eq 2). The methodology
outlined in eq 2 appears to be readily adaptable to the synthesis
of a large number of imido complexes, simply by changing the
primary amine. Indeed, complex 1 can also be made from UI3-
(THF)4 in high yield.
Until our recent report, the closest imido analogues to the
uranyl ion were the bent, bis(imido) complexes synthesized by
Burns and co-workers (A), and the zwitterionic phosphoriminato
complex synthesized by Denning et al. (B)15,16 and studied using
electronic structure calculations by Kaltsoyannis.17 In the case
of the bent bis(imido) complexes, the bulky pentamethylcyclo-
pentadienyl ancillary ligands provide a significant degree of
kinetic stabilization that limits the reactivity of the UdN bond.
Furthermore, the acute NdUdN angle leads to a different
bonding interaction between the metal center and the N-R
groups relative to a complex with a linear NdUdN arrange-
ment. The phosphoriminato complexes, while preserving the
linear NdUdN structure of uranyl, have a significant contribu-
tion from a resonance form that is best described as having a
U-N single bond. Thus, neither A nor B duplicates the
combination of structural and electronic properties that a true
imido analogue of the uranyl ion would have.
Complex 1 is an orange, moisture-sensitive crystalline solid,
which is soluble in THF and toluene. The H NMR spectrum
1
of 1 displays resonances for both THF ligands and tert-butyl
groups, in a 1:1 ratio. Complexes 2 and 3 are red-brown
crystalline solids with solubility properties similar to those of
1
1. The H NMR spectrum of 2 exhibits resonances for three
equivalent THF ligands and two equivalent phenyl moieties,
while complex 3 also exhibits resonances in its 1H NMR
spectrum consistent with the presence of three equivalent THF
ligands and two imido groups. In addition, its 19F NMR spectrum
consists of a single peak at -64.0 ppm. Broad resonances for
three equivalent THF ligands, as well as resonances for four
equivalent isopropyl groups, are observed in the 1H NMR
spectrum of 4 at room temperature.
The chemically equivalent THF ligands of 2, 3, and 4 contrast
with their solid-state molecular structures (vide infra), suggesting
exchange of the two types of THF ligands. Rapid exchange
between free and coordinated THF was confirmed when THF
was added to NMR samples of 2. In the presence of excess
THF, the THF resonances of 2 are shifted from 4.38 and 1.41
ppm to the values anticipated for free THF (3.57 and 1.40 ppm),
suggesting exchange of coordinated and uncoordinated THF
molecules. Given the facile exchange of THF, it is likely that
two types of THF ligands can exchange similarly, via a
dissociative mechanism.
In this report, we describe the synthesis of four complexes
with the general formula U(NR)2I2(THF)x (x ) 2, 3), and the
reactivity of these complexes with a variety of Lewis bases,
and AgOTf. The nature of the chemical bonding between the
uranium center and the nitrogen ligands was studied using ab
initio density functional calculations and is described in detail.
Results and Discussion
Synthesis of Uranium Bis(imido) Complexes. The reaction
of uranium turnings with I2 (3 equiv) and tert-butylamine (6
equiv) in THF quickly results in metal dissolution and the
formation of an orange solution (eq 1). Recrystallization of the
resulting orange material from a toluene/hexanes solution
provides U(NtBu)2I2(THF)2 (1) in high yield.
The IR spectra of complexes 1 and 2 show strong vibrations
at 1170 and 1270 cm-1, respectively, which are in the region
expected for a trans imido complex.18 The UV/vis spectra of 1
and 2 each display two intense, broad maxima. For 1, the
absorption bands occur at 291 nm (ꢀ ) 3500 L mol-1 cm-1
)
and 353 nm (ꢀ ) 2200 L mol-1 cm-1), whereas for 2 they are
observed at 291 nm (ꢀ ) 7900 L mol-1 cm-1) and 352 nm (ꢀ
) 1900 L mol-1 cm-1). The vibronic coupling fine-structure
often seen in uranyl UV/vis spectra is not observed for 1 and
2. The lack of fine structure is understandable given that the
U-N stretching modes are coupled with other vibrational modes
of the substituents of the imido ligands.
(14) Hayton, T. W.; Boncella, J. M.; Palmer, P. D.; Scott, B. L.; Batista, E. R.;
Hay, P. J. Science 2005, 310, 1941-1943.
(15) Brown, D. R.; Denning, R. G. Inorg. Chem. 1996, 35, 6158-6163.
(16) Brown, D. R.; Denning, R. G.; Jones, R. H. Chem. Commun. 1994, 2601-
2602.
(17) Kaltsoyannis, N. Inorg. Chem. 2000, 39, 6009-6017.
(18) Li, Z.-Y.; Huang, J.-S.; Chan, M. C.-W.; Cheung, K.-K.; Che, C.-M. Inorg.
Chem. 1997, 36, 3064-3071.
Replacing tert-butylamine with aniline in eq 1 does not
provide any tractable products. However, by using UI3(THF)4
as the uranium source, and by adding a strong base such as
9
10550 J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006

Synthesis of the Imido Analogues of the Uranyl Ion
A R T I C L E S
Figure 2. Solid-state molecular structure of U(NPh)2I2(THF)3 (2). Selected
bond lengths (Å) and angles (deg): U1-N1 ) 1.866(2), U1-N2 ) 1.859-
(2), U1-O1 ) 2.418(2), U1-O2 ) 2.452(2), U1-O3 ) 2.4632(2), U1-
I1 ) 3.1378(3), U1-I2 ) 3.1207(2), N1-U1-N2 ) 177.42(9), U1-N1-
C7 ) 176.2(2), U1-N2-C1 ) 177.7(2).
Figure 1. Solid-state molecular structures of U(NtBu)2I2(THF)2 (1) and
U(NtBu)2I2(THF)3 (1a) with 50% probability ellipsoids shown. Selected
bond lengths (Å) and angles (deg) for 1: U1-N1 ) 1.848(4), U1-N2 )
1.840(4), U1-O1 ) 2.429(4), U1-O2 ) 2.401(3), U1-I1 ) 3.0571(4),
U1-I2 ) 3.0502(4), N1-U1-N2 ) 175.4(2), U1-N1-C1 ) 167.7(3),
U1-N2-C5 ) 168.9(4). Selected bond lengths (Å) and angles (deg) for
1a: U1-N1 ) 1.855(2), U1-O1 ) 2.490(2), U1-O2 ) 2.534(2), U1-I1
) 3.1371(2), N1-U1-N1* ) 175.6(1), U1-N1-C7 ) 166.3(2).
The solid-state molecular structures for 1, 2, 3, and 4 have
all been determined. Large X-ray quality crystals of 1 were
grown by layering hexanes onto a THF solution of 1 at room
temperature, and the structure of complex 1 is shown in Figure
1a. In addition, we have also isolated a second species from
cold THF solutions of 1, U(NtBu)2I2(THF)3 (1a), as shown in
Figure 1b. Complex 1 exhibits an octahedral geometry, while
1a exhibits pentagonal bipyramidal coordination. Both geom-
etries are common for the uranyl ion. The two linear imido
ligands in 1 exhibit a trans geometry (N1-U1-N2 ) 175.4-
(2)°) and short U-N bonds (U1-N1 ) 1.848(4) Å, U1-N2 )
1.840(4) Å). The bis(imido) unit in 1a is nearly identical (U1-
N1 ) 1.855(2) Å, N1-U1-N1* ) 175.6(1)°). The U-I bond
lengths in 1 and 1a are U1-I1 ) 3.0571(4) Å and U1-I2 )
3.0502(4) Å, and U1-I1 ) 3.1371(2) Å, respectively.
Like 1a, complex 2 also exhibits a pentagonal bipyramidal
geometry; however, in this instance the third THF ligand
coordinates between the two iodide ligands (Figure 2). Complex
2 also exhibits trans, linear imido ligands and short U-N bonds
(U1-N1 ) 1.866(2) Å, U1-N2 ) 1.859(2) Å, N1-U1-N2
) 177.42(9)°). The other metrical parameters of 2 are similar
to those of 1 and 1a.
Figure 3. Solid-state molecular structure of U(N{C6H3-3,5-(CF3)2})2I2-
(THF)3 (3). Selected bond lengths (Å) and angles (deg): U2-N3 ) 1.86-
(1), U2-N4 ) 1.89(1), U2-O5 ) 2.42(1), U2-O4 ) 2.43(1), U2-O6 )
2.45(1), U2-I3 ) 3.126(1), U2-I4 ) 3.115(1), N3-U2-N4 ) 176.8(4),
C37-N4-U2 ) 169.1(9), C29-N3-U2 ) 168.1(9).
unit, and the solid-state molecular structure of one molecule is
shown in Figure 3. Its bis(imido) framework is similar to that
of 2, with nearly identical U-N bond lengths (U2-N3 ) 1.86-
(1) Å, U2-N4 ) 1.89(1) Å), and a linear N-U-N angle (N3-
U2-N4 ) 176.8(4)°). Furthermore, the U-O and U-I bond
lengths of 3 are comparable to those observed in 2. Thus, it
appears that the electron-withdrawing CF3 groups in 3 do not
have an appreciable effect on the bonding in the bis(imido)
framework.
Complex 4 crystallizes in the monoclinic space group P21/c
as the THF solvate 4‚THF. Its solid-state molecular structure
is shown in Figure 4. The bis(imido) framework in 4 is nearly
identical to that seen in 2 and 3. It exhibits short U-N bonds
(U1-N1 ) 1.886(3) Å, U1-N2 ) 1.888(3) Å) and a linear
N-U-N angle (N1-U1-N2 ) 169.3(1)°). Unlike those
complexes though, the coordination sphere of complex 4 is
notably distorted from an ideal pentagonal bipyramidal geom-
etry. Looking down the O1-U1 vector (Figure 4b) shows a
significant displacement of two THF ligands out of the I1-
Complex 3 was found to crystallize in the orthorhombic space
group Pbc21 with two independent molecules in the asymmetric
9
J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006 10551

A R T I C L E S
Hayton et al.
Many bis(imido) complexes are known for the transition
metals. For instance, several group 6 bis(imido) complexes of
the type M(NR)2Cl2L2 (where M is Mo or W, and L is a neutral
Lewis base) are known.28-30 In each of these derivatives, the
imido functionalities are in a cis arrangement with respect to
each other. The trans arrangement of the imido ligands is quite
rare18,31-33 and has only been observed when the substituents
on the imido ligands and the co-ligands are quite bulky (as in
Os(N-2,6-(iPr)2C6H3)2(PMe2Ph)2),31 or when the co-ligand is a
porphyrin (as in Os(NtBu)2(tetrakis(4-clorophenyl)porphyri-
nato).18,34,35 For comparison, in Os(N-2,6-(iPr)2C6H3)2(PMe2-
Ph)2, the Os-N bond length is 1.790(6) Å.33
The oxidation of uranium metal with I2 in organic solvents
generally leads to either U(III)- or U(IV)-containing products.36-38
The isolation or observation of a U(VI) species is unprecedented
under those conditions. Interestingly, neither UI6 nor UI5 is
known to exist, and UI4 slowly disproportionates to UI3 and
I2.39 Thus, the formation of the U-N multiple bonds plays a
significant role in providing a thermodynamic driving force over
and above the oxidizing power of I2 to facilitate this reaction.
The strength of the U-N interactions in 1-4 is also consistent
with the short U-N bond lengths that are observed in the solid
state. In addition, the competency of UI3(THF)4 as a uranium
source in the formation of U(NR)2I2(THF)x (x ) 2, 3) suggests
that other U(III), and possibly U(IV), coordination complexes
could also be precursors to a bis(imido) species. Interestingly,
under no circumstance do we observe a reaction between UI3-
(THF)4 and the primary amine, even in the presence of NEt3.
As such, it is likely that uranium must be oxidized to U(IV)
before the amine can react with the metal complex. In this
Figure 4. Solid-state molecular structure of U(N{C6H3-2,6-(iPr)2})2I2-
(THF)3‚THF (4‚THF). Selected bond lengths (Å) and angles (deg): U1-
N1 ) 1.886(3), U1-N2 ) 1.888(3), U1-O1 ) 2.431(3), U1-O2 )
2.541(3), U1-O3 ) 2.530(3), N1-U1-N2 ) 169.3(1), N1-U1-O3 )
110.2(1), N2-U1-O2 ) 109.6(1), C1-N1-U1 ) 176.9(3), C13-N2-
U1 ) 174.5(3).
t
regard, the U(IV) tris(amide) complex [U(NHtBu)3(NH2 Bu)3]+
has been isolated by Ephritikhine and co-workers,40 and this
species or a similar complex represents a possible intermediate
in the formation of complex 1 from uranium metal. Finally,
when eq 1 is performed with an excess of uranium metal the
only product isolated is 1, and unreacted metal remains in the
reaction flask.
U1-I2 plane. This is also exemplified by the N-U-O angles,
which deviate from the expected 90° (N1-U1-O3 ) 110.2-
(1)°, N2-U1-O2 ) 109.6(1)°). This deviation is no doubt
caused by the bulky isopropyl groups on the phenyl ring.
The U-N bonds in 1, 2, 3, and 4 are significantly shorter
than the U-N bonds reported for [PPh4][UOCl4(NSPh2)] and
[PPh4][UOCl4(NPPh3)] (1.920(3) and 1.912(3) Å, respec-
tively).19 They are also much shorter than those observed in
other uranium imido species, for example, Cp*2U(NPh)2 (U-N
) 1.952(7) Å),3 Cp*2U(NAd)2 (av. U-N ) 1.95 Å),5 and
U(NSiMe3)(N{SiMe3}2)3 (U-N ) 1.910(6) Å),2 but are com-
parable to the U-N bond in U[N(SiMe3)2]3(NSiMe3)(F) (U-N
) 1.85(2) Å).20 A number of uranyl iodide complexes have also
been structurally characterized,21-24 and they exhibit U-I
metrical parameters similar to those of complexes 1-4. The
U-O bond lengths in 1, 2, 3, and 4 are comparable to the U-O
distances in related uranyl THF complexes.25-27
Analysis of the Chemical Bonding. The chemical bonding
in uranium imido complexes was analyzed using density
(26) Rebizant, J.; Van den Bossche, G.; Spirlet, M. R.; Goffart, J. Acta
Crystallogr., Sect. C 1987, 43, 1298-1300.
(27) Wilkerson, M. P.; Burns, C. J.; Paine, R. T.; Scott, B. L. Inorg. Chem.
1999, 38, 4156-4158.
(28) del Rio, D.; Montilla, F.; Pastor, A.; Galindo, A.; Monge, A.; Gutie´rrez-
Puebla, E. J. Chem. Soc., Dalton Trans. 2000, 2433-2437.
(29) Danopoulos, A. A.; Wilkinson, G.; Hussain-Bates, B.; Hursthouse, M. B.
J. Chem. Soc., Dalton Trans. 1990, 2753-2761.
(30) Ashcroft, B. R.; Bradley, D. C.; Clark, G. R.; Errington, J.; Nielson, A. J.;
Rickard, C. E. F. 1987, 170-171.
(31) Anhaus, J. T.; Kee, T. P.; Schofield, M. H.; Schrock, R. R. J. Am. Chem.
Soc. 1990, 112, 1642-1643.
(32) Danopoulos, A. A.; Wilkinson, G.; Hussain-Bates, B.; Hursthouse, M. B.
Polyhedron 1992, 11, 2961-2964.
(33) Schofield, M. H.; Kee, T. P.; Anhaus, J. T.; Schrock, R. R.; Johnson, K.
H.; Davis, W. M. Inorg. Chem. 1991, 30, 3595-3604.
(34) Smieja, J. A.; Omberg, K. M.; Breneman, G. L. Inorg. Chem. 1994, 33,
614-616.
(19) Williams, V. C.; Mu¨ller, M.; Leech, M. A.; Denning, R. G.; Green, M. L.
H. Inorg. Chem. 2000, 39, 2538-2541.
(35) Smieja, J. A.; Shirzad, K.; Roy, M.; Kittilstved, K.; Twamley, B. Inorg.
Chim. Acta 2002, 335, 141-146.
(20) Burns, C. J.; Smith, W. H.; Huffman, J. C.; Sattelberger, A. P. J. Am. Chem.
Soc. 1990, 112, 3237-3239.
(36) Avens, L. R.; Bott, S. G.; Clark, D. L.; Sattelberger, A. P.; Watkin, J. G.;
Zwick, B. D. Inorg. Chem. 1994, 33, 2248-2256.
(21) Crawford, M.-J.; Ellern, A.; Karaghiosoff, K.; Mayer, P.; No¨th, H.; Suter,
M. Inorg. Chem. 2004, 43, 7120-7126.
(37) Enriquez, A. E.; Scott, B. L.; Neu, M. P. Inorg. Chem. 2005, 44, 7403-
7413.
(22) Crawford, M.-J.; Ellern, A.; No¨th, H.; Suter, M. J. Am. Chem. Soc. 2003,
125, 11778-11779.
(38) Evans, W. J.; Kozimor, S. A.; Ziller, J. W.; Fagin, A. A.; Bochkarev, M.
N. Inorg. Chem. 2005, 44, 3993-4000.
(23) Berthet, J.-C.; Nierlich, M.; Ephritikhine, M. Chem. Commun. 2004, 870-
871.
(39) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. AdVanced
Inorganic Chemistry, 6th ed.; John Wiley & Sons: New York, 1999; pp
1146-1147.
(24) Crawford, M.-J.; Mayer, P. Inorg. Chem. 2005, 44, 5547-5549.
(25) Charpin, P.; Lance, M.; Nierlich, M.; Vigner, D. C. B. Acta Crystallogr.,
Sect. C 1987, 43, 1832-1833.
(40) Wang, J. X.; Dash, A. K.; Kapon, M.; Berthet, J.-C.; Ephritikhine, M.;
Eisen, M. S. Chem.-Eur. J. 2002, 8, 5384-5396.
9
10552 J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006

Synthesis of the Imido Analogues of the Uranyl Ion
A R T I C L E S
a
Table 1. Mulliken Populations and Orbital Energies for the Six Molecular Orbitals Involved in the U-N Bonds of U(NMe)2I2(THF)2
U
Na
Nb
ꢀ
[eV]
s
p
d
f
total
type
total
total
HOMO-6
HOMO-7
HOMO-8
HOMO-9
HOMO-12
HOMO-21
-7.129
-7.193
-7.314
-7.528
-8.665
-11.394
0.000
0.017
0.000
0.000
0.000
0.006
0.005
0.002
0.026
0.000
0.079
0.001
0.012
0.025
0.131
0.240
0.080
0.101
0.320
0.272
0.232
0.002
0.243
0.019
0.337
0.316
0.389
0.242
0.402
0.127
fπ
fπ
0.238
0.218
0.254
0.254
0.195
0.193
0.243
0.248
0.203
0.263
0.198
0.197
fσ + dπ
dπ
fσ
dσ
a The populations are given in fractions of an electron. The type of uranium atomic orbital involved in each of the bonding molecular orbitals is identified
in the “type” column.
functional calculations on complexes 1 and 2 with four and five
equatorial ligands, respectively. In all cases, the B3LYP hybrid
density functional was used.41 For the sake of reducing the
computational cost, in complex 1 we used a model system that
replaced the tBu groups in the ligands with methyl groups. The
similarities in the bonding analysis between U(NMe)2I2(THF)2
and 2 and the closeness in the predicted and experimental bond
distances indicate that this simplification did not affect the U-N
bonding.
Figure 5. Isomers of U(NMe)2I2(THF)2 and 2 studied by DFT.
To validate the computational methodology, the structures
of U(NMe)2I2(THF)2 and complex 2 were optimized and
compared to the experimental ones. For U(NMe)2I2(THF)2, the
calculated U-N distances (1.844 Å) and U-I distances (3.058
Å) were found to be within 0.005 Å of the observed measure-
ments of complex 1. For complex 2, the predicted U-N
distances (1.860 Å) and U-I distances (3.197 Å) are also within
0.005 Å of the experimental values. Similarly, the calculated
N-U-N angles were within 2° of the experimental values
(173.5° for U(NMe)2I2(THF)2 and 175.7° for complex 2). This
is in good agreement with the experimental measurements
considering that the molecules were optimized in isolation and,
in the case of U(NMe)2I2(THF)2, the ligands were slightly
simplified.
At the minimum energy structure the vibrational frequencies
were calculated and the strong active infrared peaks from
experiment identified with the calculated peaks at 1229 cm-1
for U(NMe)2I2(THF)2 and 1326 cm-1 for complex 2. The
calculated frequencies appear shifted by the order of 70 cm-1
from those determined by experiment, which corresponds to
the expected error of DFT for this type of calculation.42 This
identification shows that the active IR modes correspond to the
N-U vibrational mode coupled out of phase with the N-C
stretch mode, coupling which is expected given the closeness
in mass of the nitrogen and carbon atoms.
A series of isomers of U(NMe)2I2(THF)2 and complex 2 were
also studied to quantify the energy landscape for the different
possible configurations of the ligands (Figure 5). For U(NMe)2I2-
(THF)2, the configuration with the two THF ligands in a trans
arrangement was studied (C), as well as two configurations
containing cis imido ligands, D and E. Complex C was found
to have essentially the same energy as the experimentally
observed isomer, while D and E were found to be 14.7 and
16.5 kcal/mol higher, respectively, demonstrating a profound
energetic preference for the trans imido geometry. This energy
landscape is similar to that of the uranyl-hydroxo species UO2-
(OH)4 where the cis uranyl is 19 kcal/mol higher than the trans
Figure 6. Decomposition of the first bonding orbital (HOMO-6) between
the metal center and the nitrogen ligands. This decomposition clearly shows
the molecular orbital as consisting of a 5fπ atomic orbital of the uranium
forming a covalent π bond with an antibonding π orbital on the imido
ligands.
species.43 For complex 2, a second isomer (F) was found to be
essentially isoenergetic with the observed isomer. This species,
with all three THF ligands confined to one-half of the equatorial
plane, bears resemblance to complex 1a.
The nature of the chemical bonding between the metal center
and the imido ligands was analyzed for U(NMe)2I2(THF)2 and
2 from the charge distribution and molecular orbitals, as
determined by the DFT calculations. Overall, there are six
orbitals with strong interactions between the uranium center and
the nitrogen ligands, indicating the presence of two triple bonds
analogous to the U-O bonds in the uranyl ion. Each of these
six orbitals contains a strong admixture of either 5f or 6d
character on the uranium, according to Mulliken population
analysis. Table 1 shows the Mulliken decomposition for each
of these six molecular orbitals involved in the U-N bonding.
Because the highest six occupied molecular orbitals correspond
to the lone pair 5p electrons of the iodide ligands, the first U-N
bonding orbitals are HOMO-6 and HOMO-7. In these two
molecular orbitals, the uranium participates in the bonding via
the 5fπ electrons (Figure 6). The uranium 5f contributions to
these MOs are 32% and 27%, respectively. In HOMO-8, the
metal uses both 5fσ (23%) and 6dπ (13%), while the metal
contribution to HOMO-9 is all 6dπ in character (24%). In these
four orbitals, the nitrogen contributions range from 20% to 24%.
The remaining two U-N bonding orbitals were identified as
HOMO-12, with a uranium component composed of 5fσ (24%),
(41) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
(42) Staroverov, V. N.; Scuseria, G. E.; Tao, J.; Perdew, J. P. J. Chem. Phys.
2003, 119, 12129-12137.
(43) Schreckenbach, G.; Hay, P. J.; Martin, R. L. Inorg. Chem. 1998, 37, 4442-
4451.
9
J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006 10553

A R T I C L E S
Hayton et al.
Table 2. Electronic Population of the Valence Uranium Atomic
Orbitals for U(NMe)2I2(THF)2, U(NPh)2I2(THF)3 (2), and UO22+, As
Determined by Mulliken and Natural Bond Orbital Analysisa
2+
U(NMe)2I2(THF)2
2
UO2
Mulliken
NBO
Mulliken
NBO
Mulliken
NBO
7s
7p
6d
5f
6p
qU
0.133
0.000
2.016
2.633
5.737
+1.50
0.265
0.007
1.802
2.855
6.000b
0.126
0.000
1.945
2.545
5.652
+1.73
0.260
0.004
1.704
2.808
6.000b
-0.073
0.000
1.249
2.449
5.650
+2.73
0.035
0.010
0.992
2.494
6.000b
+1.27
+1.41
+2.84
a The final row shows total valence charge (qU) on uranium. For the
2+
sake of comparing UO2 to complexes 1 and 2, the oxygen atoms were
placed 1.84 Å from the uranium center. b The NBO analysis puts the 6p
electrons in the core.
Scheme 1
Figure 7. Solid-state molecular structure of U(NtBu)2I2(py)2 (5). Selected
bond lengths (Å) and angles (deg): U1-N1 ) 1.835(2), U1-N2 ) 2.538-
(2), U1-I1 ) 3.0652(2), N1-U1-N1* ) 180.0(1), C1-N1-U1 ) 174.5-
(2).
valence populations in the table are obtained by subtracting the
“core” 5s25p65d106s26p6 configurations. While the populations
in U(NMe)2I2(THF)2 and 2 are similar, the bonding in the uranyl
ion shows more ionic character.
Reactivity Studies. Preliminary reactivity studies have shown
that complexes 1 and 2 readily react with Lewis bases. For
instance, addition of pyridine to toluene solutions of 1 provides
U(NtBu)2I2(py)2 (5) in 74% yield (Scheme 1). U(NPh)2I2(py)3
(6) can be generated in an analogous fashion. Complex 5 is an
orange crystalline solid that is soluble in THF and toluene, while
6 is a brown microcrystalline solid that is insoluble in toluene,
poorly soluble in THF, but quite soluble in CH2Cl2.
The solid-state molecular structure of 5 was determined by
X-ray crystallography. Complex 5 crystallizes in the monoclinic
space group P21/c, and its ORTEP diagram is shown in Figure
7. In contrast to 1, complex 5 has trans-iodide and trans-THF
ligands. This observation supports the theoretical calculations,
which suggested that the trans-iodide isomer of U(NMe)2I2-
(THF)2 was only slightly higher in energy than the cis-iodide
isomer. The metrical parameters of the two tert-butylimido
ligands are similar to those of 1, while the comparable uranyl
complex, UO2I2(py)3, is also known.23
Addition of 2 equiv of Ph3PO to 1 and 2 generates
U(NtBu)2I2(Ph3PO)2 (7) and U(NPh)2I2(Ph3PO)2 (8), respectively
(eq 3). Both 7 and 8 are insoluble in toluene, poorly soluble in
THF, and soluble in CH2Cl2. The 31P{1H} NMR spectra of 7
and 8 each exhibit a single peak at 45.5 and 49.9 ppm,
respectively.
mixed in with 8% 6d and 8% pσ, and HOMO-21, where the
uranium contribution is 6dσ (10% participation). Overall, we
can say that the U-N bonding orbitals in U(NMe)2I2(THF)2
2+
are of the same type as those of the UO2 fragment, which
has six bonding orbitals, σg, σu, two πu, and two πg,44 although
the ordering is different. This difference in order is an indication
that the “pushing-from-below” mechanism proposed for uranyl
does not exert a strong influence in the present case due perhaps
to a smaller involvement of the uranium 6p orbital in the binding
MOs.
In each orbital, the uranium contribution is large, indicating
a strong covalent interaction. This is consistent with the Mulliken
population analysis, which assigns an effective total charge on
uranium of +1.50 (Table 2). In contrast, for a completely ionic
description the formal charge on U(VI) would be +6. Further-
more, the natural bond orbital (NBO) analysis assigns an ef-
fective total charge of +1.27. For comparison, an NBO analysis
of the uranyl ion assigns a higher charge on uranium (+2.84),
indicating a more ionic interaction. These conclusions are in
agreement with those of Kaltsoyannis,17 who carried out an
extensive analysis of the six bonding orbitals in the naked UN2
and U(NPR3)24+ fragments and found that the U-N bonds were
more covalent than the analogous U-O interactions in uranyl.
Table 2 shows the total population on uranium for s, p, d,
and f electrons explicitly treated in the 60e- core potential. The
X-ray suitable crystals of 7 were grown from CH2Cl2/hexanes,
and its solid-state molecular structure is shown in Figure 8.
Consistent with the other bis(imido) complexes presented here,
(44) Pepper, M.; Bursten, B. E. Chem. ReV. 1991, 91, 719-741.
9
10554 J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006

Synthesis of the Imido Analogues of the Uranyl Ion
A R T I C L E S
Figure 8. Solid-state molecular structure of U(NtBu)2I2(Ph3PO)2 (7).
Selected bond lengths (Å) and angles (deg): U1-N1 ) 1.840(3), U1-N2
) 1.839(3), U1-O1 ) 2.358(3), U1-O2 ) 2.317(3), U1-I1 ) 3.0928-
(4), U1-I2 ) 3.0832(4), N1-U1-N2 ) 177.8(2), C5-N2-U1 ) 171.5-
(3), C1-N1-U1 ) 170.4(3).
Figure 9. Solid-state molecular structure of U(NtBu)2I2(PMe3)2(THF) (9).
Selected bond lengths (Å) and angles (deg): U1-N1 ) 1.833(6), U1-N2
) 1.823(5), U1-O1 ) 2.492(4), U1-I1 ) 3.1402(7), U1-I2 ) 3.1204-
(6), U1-P1 ) 3.075(3), U1-P2 ) 3.042(2), N1-U1-N2 ) 177.8(3), C5-
N1-U1 ) 172.7(6), C1-N2-U1 ) 176.3(6).
7 has short U-N bonds (U1-N1 ) 1.840(3) Å, U1-N2 )
1.839(3) Å) and a linear N-U-N angle (177.8(2)°), while the
U-O bond lengths in 7 (U1-O1 ) 2.358(3) Å, U1-O2 )
2.317(3) Å) are comparable to those seen in the uranyl analogue,
UO2I2(Ph3PO)2.21
uranium phosphine complexes are either U(III) or U(IV), making
complexes 9 and 10 the first known phosphine complexes of
U(VI).
The previous paragraphs have demonstrated that the THF
ligands in 1 and 2 are readily replaced with other Lewis bases.
In addition to this, the iodide ligands in both 1 and 2 can undergo
metathesis reactions. For instance, reaction of 1 with 2 equiv
of AgOTf in CH2Cl2, followed by crystallization from THF/
hexanes, provides U(NtBu)2(OTf)2(THF)3 (11) in moderate
yields, while reaction of 2 with 2 equiv of AgOTf in CH2Cl2,
and subsequent crystallization from CH2Cl2/THF/hexanes, gives
U(NPh)2(OTf)2(THF)3 (12) (eq 5).
The bis(imido) uranium fragment is also capable of binding
PMe3. Thus, addition of PMe3 to 1 and 2 provides the isostruc-
tural complexes U(NtBu)2I2(PMe3)2(THF) (9) and U(NPh)2I2-
(PMe3)2(THF) (10), respectively (eq 4).
Complex 9 is an orange crystalline solid, while 10 is dark
brown. The 31P{1H} NMR spectrum of 9 consists of a broad
singlet at 42.1 ppm (fwhm ) 900 Hz) at room temperature,
while that of 10 appears at 68.2 ppm (fwhm ) 480 Hz). The
uranyl ion is not known to bind phosphines, so the isolation of
9 and 10 indicates that there are significant electronic differences
between our bis(imido) complexes and uranyl. This suggests
that the [U(NR)2]2+ fragment is a much softer Lewis acid than
the uranyl ion, which is consistent with the DFT calculations
on the two species.
Given the rarity of uranium-phosphine complexes, the solid-
state molecular structure of 9 was determined by X-ray
crystallography. Complex 9 was found to crystallize in the
tetragonal space group P-421/c, and its solid-state molecular
structure is shown in Figure 9. The metrical parameters of the
bis(imido) fragment are comparable to those of 5 and 7 (U1-
N1 ) 1.833(6) Å, U1-N2 ) 1.823(5) Å, N1-U1-N2 ) 177.8-
(3)°), while the U-P distances in 9 (U1-P1 ) 3.075(3) Å,
U1-P2 ) 3.042(2) Å) are comparable to the U-P bond lengths
in other uranium phosphine complexes.45 Only one other
trimethylphosphine complex of uranium has been structurally
characterized (MeCp)3U(PMe3), and it has a slightly shorter
U-P bond length of 2.972(6) Å.46 All previously characterized
The 1H NMR spectrum of 11 in THF-d8 exhibits a singlet at
0.23 ppm, confirming the presence of a tert-butyl imido ligand,
while the 19F NMR spectrum exhibits a single peak at -79.3
ppm, confirming the presence of the triflate ligand. Complex
11 crystallizes in the orthorhombic space group Pbc21;47
however, one triflate ligand is badly disordered and could not
be effectively modeled. The X-ray data do confirm the proposed
connectivity though, which is isostructural with 1a.
The 1H NMR spectrum of 12 in CD2Cl2 exhibits several broad
resonances at room temperature. Cooling a CD2Cl2 solution of
12 to -40 °C provides a spectrum with much sharper reso-
1
nances. By H NMR, complex 12 contains three THF ligands
in two different environments, in addition to two phenyl groups.
Only one resonance is observed in the 19F NMR spectrum, at
(45) Edwards, P. G.; Andersen, R. A.; Zalkin, A. J. Am. Chem. Soc. 1981, 103,
7792-7794.
(46) Brennan, J. G.; Zalkin, A. Acta Crystallogr., Sect. C 1985, 41, 1038-
1040.
(47) Crystal data for U(NtBu)2(OTf)2(THF)3 (11): orthorhombic, Pbc21, a )
11.946(5) Å, b ) 16.145(6) Å, c ) 17.315(7) Å, V ) 3340(2) Å3, Z ) 8.
9
J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006 10555

A R T I C L E S
Hayton et al.
proven to be excellent starting materials for the synthesis of
new uranium imido complexes as the THF ligands in 1 and 2
are readily displaced by addition of donor ligands. Furthermore,
the isolation of complexes 11 and 12 also demonstrates that
the iodide ligands in 1 and 2 can undergo metathesis. This raises
the possibility of synthesizing alkoxide, amide, and alkyl
complexes containing the bis(imido) moiety.
Experimental Section
General. All reactions and subsequent manipulations were performed
under anaerobic and anhydrous conditions under either high vacuum
or an atmosphere of helium or argon. Hexanes, THF, and toluene were
dried by passage over activated alumina. C6D6 and tert-butylamine were
dried over activated 4 Å molecular sieves for 24 h before use. Aniline
was distilled from CaH2, while NEt3 was distilled from Na/benzophe-
none. UI3(THF)4 was synthesized by the published procedure.36 All
other reagents were purchased from commercial suppliers and used as
received.
NMR spectra were recorded on a Bruker AVA300. 1H and 13C{1H}
NMR spectra were referenced to the residual protio solvent peaks as
internal standards (1H NMR experiments) or the characteristic reso-
nances of the solvent nuclei (13C NMR experiments) and are reported
relative to TMS. IR spectra were obtained on a Nicolet Magna-IR 560
spectrometer, while UV-vis spectra were recorded on a Varian Cary
6000i. Elemental analyses were performed at the UC Berkeley
Microanalytical Facility, on a Perkin-Elmer Series II 2400 CHNS
analyzer.
U(NtBu)2I2(THF)2. Method A. To a stirring THF solution (10 mL)
containing uranium metal turnings (0.303 g, 1.27 mmol) and tert-
butylamine (0.614 g, 8.40 mmol) was added I2 (0.970 g, 3.82 mmol).
After 2 h, the metal was consumed and the volatiles were removed in
vacuo to give an orange powder. This material was washed with hexanes
(10 mL) and then dissolved in toluene (15 mL). The resulting orange
solution was filtered through a Celite column, and the column was
rinsed with another aliquot of toluene (10 mL). The combined filtrates
were layered with hexanes (15 mL), and this solution was stored at
-32 °C for 24 h, resulting in the precipitation of red crystals, which
were collected by decanting the supernatant. Another crop of crystals
was harvested from the mother liquor, giving a total of 0.674 g, 68%
yield. Anal. Calcd for C16H34UI2N2O2: C, 24.69; H, 4.40; N, 3.60.
Found: C, 24.64; H, 4.27; N, 3.52. 1H NMR (C6D6, 25 °C, 300 MHz):
δ 0.66 (s, 18H), 1.54 (br s, 8H), 4.56 (br s, 8H). 13C{1H} NMR (C6D6,
25 °C, 75 MHz): δ 26.1 (OCH2CH2), 35.9 (CH3), 74.3 (OCH2CH2),
77.1 (CMe3). IR (Nujol mull): 861 (m), 924 (w), 1010 (m), 1080 (s),
1110 (m), 1170 (s), 1220 (m), 1290 (w). UV/vis (THF, 1.2 × 10-5
M): 291 nm (ꢀ ) 3500 L mol-1 cm-1), and 353 nm (ꢀ ) 2200 L
mol-1 cm-1).
Method B. To a purple solution of UI3(THF)4 (0.480 g, 0.53 mmol)
and tert-butylamine (0.264 g, 3.62 mmol) in THF (10 mL) was added
I2 (0.204 g, 0.81 mmol). The solution, which quickly turned orange-
red, was vigorously shaken. After 10 min, the volatiles were removed
in vacuo and the resulting red oil was dissolved in toluene (10 mL).
This solution was filtered though a Celite column supported on glass
wool. The Celite column was rinsed with more toluene (5 mL), and
the combined filtrates were layered with an equal volume of hexanes
and stored at -32 °C for 72 h, resulting in the precipitation of red
crystals, which were collected by decanting the supernatant. 0.362 g,
87% yield.
Figure 10. Solid-state molecular structure of [U(NPh)2(OTf)2(THF)2]2‚
2CH2Cl2. CH2Cl2 molecules omitted for clarity. Selected bond lengths (Å)
and angles (deg): U1-N1 ) 1.849(3), U1-N2 ) 1.847(3), U1-O6 )
2.393(3), U1-O2 ) 2.400(3), U1-O1 ) 2.434(3), U1-O3 ) 2.459(3),
U1-O4 ) 2.463(3), N1-U1-N2 ) 177.7(2), C1-N1-U1 ) 172.2(3),
C7-N2-U1 ) 175.2(3).
-79.0 ppm. Given this, there are two possible arrangements of
the THF ligands: one in which all three THF ligands occupy
one-half of the equatorial plane (as in 1a), or one in which the
third THF ligand occupies the site between the two iodide
ligands (as in 2). Because the low-temperature NMR data cannot
rule out either isomer, the structure of 12 has been determined
by X-ray crystallography.
X-ray quality crystals of 12 were grown slowly from a CH2-
Cl2/hexanes solution at -35 °C. Under these conditions, 12 was
found to crystallize in the monoclinic space group P21/n as a
dimer. Its solid-state molecular structure is shown in Figure 10.
Like the other structurally characterized bis(imido) complexes,
[U(NPh)2(OTf)2(THF)2]2‚2CH2Cl2 exhibits a trans arrangement
of the two imido groups and short U-N bonds (U1-N1 )
1.849(3) Å, U1-N2 ) 1.847(3) Å). Of the two triflate ligands,
the nonbridging triflate has a shorter U-O contact (U1-O6 )
2.393(3) Å) than the bridging triflate (O3 ) 2.459(3) Å, U1-
O4 ) 2.463(3) Å). The solid-state molecular structure contrasts
with the analytical data, which suggest that 12 is a monomer
(that is, a tris(THF) adduct) when it is isolated from solutions
containing THF. In support of this, the NMR data are wholly
consistent with the presence of three THF ligands. However,
in THF-deficient environments, it can exist as a dimer, at least
in the solid state.
Summary
In this contribution, we have described the synthesis of several
complexes with the general formula U(NR)2I2(THF)x (R ) alkyl,
aryl; x ) 2, 3). Their successful synthesis leads us to believe
that many different bis(imido) complexes could be synthesized
via eq 2, and we are trying to extend this methodology to new
bis(imido) complexes with bulky substituents attached to the
nitrogen. This will allow exceptional steric and electronic control
of reactivity at the metal center through the variation of the
imido substituents. The DFT calculations show that the U-N
interaction is a triple bond and is similar to U-O interaction in
U(NPh)2I2(THF)3. I2 (0.372 g, 1.47 mmol) was added to a purple
solution of UI3(THF)4 (0.898 g, 0.99 mmol), aniline (0.194 g, 2.09
mmol), and NEt3 (0.509 g, 5.03 mmol) dissolved in THF (15 mL).
The solution turned orange-red, and a white crystalline precipitate
quickly formed. The solution was shaken for 10 min at which point it
was stored at -35 °C for 2 h. The cold solution was filtered through
a Celite column, and the white solid was rinsed with several aliquots
the UO22+. The uranium atomic orbitals involved in these bonds
2+
are the 5fσ, 5fπ, 6dπ, and 6dσ, which is also the case in UO2
.
However, the bonding in the bis(imido) fragment is more
covalent in character. In addition, complexes 1 and 2 have
9
10556 J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006

Synthesis of the Imido Analogues of the Uranyl Ion
A R T I C L E S
of toluene (50 mL total). The volume of the combined filtrates was
reduced in vacuo, and the solution was then layered with an equal
volume of hexanes. The flask was then stored at -35 °C for 72 h,
resulting in the precipitation of red-brown crystals, which were collected
by decanting off the supernatant. 0.742 g, 84% yield. Anal. Calcd for
C24H34UI2N2O3: C, 32.38; H, 3.85; N, 3.15. Found: C, 31.45; H, 3.88;
N, 3.15. 1H NMR (C6D6, 25 °C, 300 MHz): δ 1.41 (m, 12H,
OCH2CH2), 4.38 (m, 12H, OCH2CH2), 5.73 (t, JHH ) 7.4 Hz, 2H, para
C-H), 6.20 (d, JHH ) 7.5 Hz, 4H, ortho C-H), 7.00 (t, JHH ) 7.8 Hz,
4H, meta C-H). 13C{1H} NMR (C6D6, 25 °C, 75 MHz): δ 26.2
(OCH2CH2), 70.9 (OCH2CH2), 125.9 (meta C), 128.9 (para C), 130.3
(ortho C), 153.7 (ipso C). IR (Nujol mull): 768 (m), 866 (m), 910
(w), 920 (w), 962 (m), 999 (w), 1020 (m), 1060 (w), 1170 (w), 1270
(br s), 1300 (w), 1340 (w), 1380 (m). UV/vis (THF, 6.8 × 10-6 M):
291 nm (ꢀ ) 7900 L mol-1 cm-1), and 352 nm (ꢀ ) 1900 L mol-1
cm-1).
yield). Anal. Calcd for C18H28UI2N4: C, 27.29; H, 3.56; N, 7.07.
Found: C, 27.29; H, 3.79; N, 6.94. H NMR (THF-d8, 25 °C, 300
MHz): δ 0.49 (s, 18H, CMe3), 7.43 (t, 4H, JHH ) 12 Hz, CH), 7.79 (t,
2H, JHH ) 8 Hz, CH), 8.93 (br, 4H, CH). 13C{1H} NMR (THF-d8, 25
°C, 75 MHz): δ 35.7 (CMe3), 77.0 (CMe3), 124.9 (CH), 137.4 (CH),
151.1 (CH).
1
U(NPh)2I2(py)3. To a Et2O (2 mL) and toluene (2 mL) solution of
U(NPh)2I2(THF)3 (0.0796 g, 0.09 mmol) was added pyridine (0.149 g,
1.89 mmol). The vial was then stored at -35 °C for 24 h, resulting in
the precipitation of red-brown crystals, which were collected by
decanting off the supernatant (0.0413 g, 51%). Anal. Calcd for C27H25-
UI2N5: C, 35.58; H, 2.76; N, 7.68. Found: C, 34.20; H, 2.69; N, 7.28.
1H NMR (THF-d8, 25 °C, 300 MHz): δ 5.74 (d, 4H, JHH ) 7 Hz,
imido ortho CH), 5.82 (t, 2H, JHH ) 7 Hz, imido para CH), 6.96 (t,
4H, JHH ) 8 Hz, imido meta CH), 7.31 (m, 6H, py meta CH), 7.71 (t,
3H, JHH ) 8 Hz, py para CH), 8.63 (d, 6H, JHH ) 4 Hz, py ortho CH).
13C{1H} NMR (THF-d8, 25 °C, 75 MHz): δ 124.6 (py meta CH), 125.8
(imido meta CH), 128.5 (imido para CH), 130.5 (imido ortho CH),
136.8 (py para CH), 151.1 (py ortho CH), 153.7 (imido ipso C).
U(NtBu)2I2(Ph3PO)2. To an orange solution of U(NtBu)2I2(THF)2
(0.0661 g, 0.08 mmol) in toluene (5 mL) was added Ph3PO (0.0496 g,
0.18 mmol), also dissolved in toluene (2 mL). After 2 h, large orange
crystals had been deposited in the vial, and the supernatant was almost
colorless. The crystals were isolated by decanting the solvent (0.0728
g, 72% yield). Anal. Calcd for C44H48UI2N2O2P2: C, 44.39; H, 4.06;
U(N-3,5-(CF3)2C6H3)2I2(THF)3. To a purple solution of UI3(THF)4
(0.212 g, 0.23 mmol), NEt3 (0.168 g, 1.7 mmol), and 3,5-(CF3)2C6H3-
NH2 (0.132 g, 0.58 mmol) in THF (5 mL) was added I2 (0.0885 g,
0.35 mmol). The solution turned deep red, and a white crystalline
precipitate quickly formed. After 10 min, the volume of the solution
was reduced in vacuo to 2 mL, and the solution was stored at -35 °C
for 2 h. The cold solution was filtered through a Celite column, and
the white solid was rinsed with several aliquots of toluene (5 mL total).
The volume of the combined filtrates was reduced in vacuo, and the
solution was then layered with an equal volume of hexanes. The vial
was then stored at -35 °C for 24 h, resulting in the precipitation of
more white crystals. This solution was filtered through a Celite column,
the volume was reduced to 2 mL in vacuo, and more hexanes were
layered on top of the filtrate. Storing this vial at -35 °C for 24 h resulted
in the deposition of red crystals (0.184 g, 68% yield). Anal. Calcd for
C28H30F12I2N2O3U: C, 28.93; H, 2.60; N, 2.41. Found: C, 28.65; H,
1
N, 2.35. Found: C, 44.58; H, 4.0; N, 2.24. H NMR (CD2Cl2, 25 °C,
300 MHz): δ 0.01 (s, 18H, CMe3), 7.66 (m, 18H, CH), 8.39 (m, 12H,
CH). 31P{1H} NMR (CD2Cl2, 25 °C, 121 MHz): δ 45.5. 13C{1H} NMR
(CD2Cl2, 25 °C, 75 MHz): δ 34.9 (CMe3), 64.4 (CMe3), 129.2 (d, JCP
) 14 Hz, CH), 133.6 (s, CH), 134.1 (d, JCP ) 11 Hz, CH).
U(NPh)2I2(Ph3PO)2‚C7H8. To a brown-orange solution of U(NPh)2I2-
(THF)3 (0.0823 g, 0.09 mmol) in toluene (5 mL) was added Ph3PO
(0.0530 g, 0.19 mmol), also dissolved in toluene (2 mL). After 5 min,
black crystals had begun to form. The vial was stored at -35 °C for
24 h, resulting in the further precipitation of crystals, which were
collected by decanting the supernatant (0.0698 g, 57% yield). Anal.
Calcd for C48H40UI2N2O2P2‚C7H8: C, 49.94; H, 3.66; N, 2.13. Found:
C, 49.86; H, 3.48; N, 2.08. 1H NMR (CD2Cl2, 25 °C, 300 MHz): 5.17
(d, 4H, JHH ) 8 Hz, imido ortho CH), 5.69 (t, 2H, JHH ) 7 Hz, imido
para CH), 6.94 (t, 4H, JHH ) 8 Hz, imido meta CH), 7.40 (m, 12H,
meta CH), 7.60 (t, 6H, JHH ) 8 Hz, para CH), 8.09 (dd, 12H, JHH ) 8
Hz, JHP ) 13 Hz, ortho CH). 31P{1H} NMR (CD2Cl2, 25 °C, 121
MHz): δ 49.9. 13C{1H} NMR (CD2Cl2, 25 °C, 75 MHz): δ 125.5
(imido meta CH), 127.4 (imido para CH), 129.9 (s, JCP ) 13 Hz, meta
CH), 130.2 (d, JCP ) 14 Hz, ispo C), 130.4 (imido ortho CH), 134.4
(para CH), 134.5 (d, JCP ) 11 Hz, ortho CH), 153.0 (imido ipso C).
U(NtBu)2I2(PMe3)2(THF). To an orange solution of U(NtBu)2I2-
(THF)2 (0.0776 g, 0.10 mmol) in toluene (5 mL) was added PMe3
(0.0560 g, 0.74 mmol). The solution was then filtered through a Celite
column, and an equal volume of hexanes was layered onto the
supernatant. The vial was stored at -35 °C for 24 h, resulting in the
precipitation of crystals, which were collected by decanting off the
supernatant (0.0521 g, 61%). Anal. Calcd for C18H44I2N2OP2U: C,
25.19; H, 5.17; N, 3.26. Found: C, 25.27; H, 5.18; N, 3.37. 1H NMR
(C6D6, 25 °C, 300 MHz): δ 0.71 (s, 18H, CMe3), 1.48 (m, 22H, PMe3
and OCH2CH2), 4.09 (s, 4H, OCH2CH2). 31P{1H} NMR (C6D6, 25 °C,
121 MHz): δ 42.1 (fwhm ) 900 Hz). 13C{1H} NMR (C6D6, 25 °C, 75
MHz): δ 18.4 (br s, PMe3), 26.1 (OCH2CH2), 36.6 (CMe3), 71.5 (OCH2-
CH2), 77.4 (CMe3).
1
2.36; N, 2.55. H NMR (C6D6, 25 °C, 300 MHz): δ 0.45 (s, 12H,
OCH2CH2), 2.37 (m, 12H, OCH2CH2), 6.54 (s, 2H, para CH), 6.75 (s,
4H, ortho CH). 19F NMR (C6D6, 25 °C, 282 MHz): δ -64.0. 13C{1H}
NMR (C6D6, 25 °C, 75 MHz): δ 25.1 (OCH2CH2), 70.4 (OCH2CH2),
121.4 (para C), 126.4 (meta C), 129.8 (q, CF3, JCF ) 32 Hz), 131.1
(ortho C), 151.2 (ipso C).
U(N-2,6-(iPr)2C6H3)2I2(THF)3. To a purple solution of UI3(THF)4
(0.2344 g, 0.26 mmol), NEt3 (0.104 g, 1.03 mmol), and 2,6-(iPr)2C6H3-
NH2 (0.0986 g, 0.56 mmol) in THF (5 mL) was added I2 (0.0980 g,
0.39 mmol). The solution, which quickly turned deep red, was
vigorously shaken. No precipitate formed. The volume of the solution
was reduced by one-half in vacuo, and the solution was stored at -35
°C for 2 h, resulting in the deposition of white crystals. This solution
was then filtered through a column of Celite, layered with an equal
volume of hexanes, and stored at -35 °C for 24 h, resulting in the
deposition of brown crystals (0.046 g). Removal of all of the solvent
from the supernatant and recrystallization of the resulting solid from
toluene allowed for the isolation of three more crops of crystals (total
yield from all crops: 0.142 g, 52%). Anal. Calcd for C36H58I2N2O3U:
1
C, 40.84; H, 5.52; N, 2.65. Found: C, 39.46; H, 5.01; N, 2.69. H
NMR (CD2Cl2, 25 °C, 300 MHz): δ 1.14 (d, JHH ) 11 Hz, 24H, Me),
1.96 (br s, 12H, OCH2CH2), 3.98 (br s, 4H, CHMe2), 4.40 (br s, 12H,
OCH2CH2), 5.50 (t, JHH ) 8 Hz, 2H, para CH), 6.97 (d, JHH ) 8 Hz,
4H, meta CH). 1H NMR (THF-d8, 25 °C, 300 MHz): δ 1.26 (d, JHH
)
7 Hz, 24H, Me), 4.27 (septet, JHH ) 7, 4H, CHMe2), 5.50 (t, JHH ) 8
Hz, 2H, para CH), 7.01 (d, JHH ) 8 Hz, 4H, meta CH). 13C{1H} NMR
(THF-d8, 25 °C, 75 MHz): δ 26.8 (CHMe2), 28.1 (Me), 119.8 (meta
C), 129.3 (para C), 138.6 (ortho C), 151.4 (ipso C).
U(NtBu)2I2(py)2. To an orange solution of U(NtBu)2I2(THF)2 (0.112
g, 0.14 mmol) in toluene (5 mL) was added pyridine (0.101 g, 1.28
mmol). This solution was filtered through a Celite column and then
layered with an equal volume of hexanes. The solution was then stored
at -35 °C for 24 h, resulting in the precipitation of orange crystals,
which were collected by decanting off the supernatant (0.0846 g, 74%
U(NPh)2I2(PMe3)2(THF). To an orange-brown solution of U(NPh)2I2-
(THF)3 (0.0843 g, 0.09 mmol) in toluene (5 mL) was added PMe3 (0.060
g, 0.79 mmol). The solution was then filtered through a Celite column,
and an equal volume of hexanes was layered onto the supernatant. The
vial was stored at -35 °C for 24 h, resulting in the precipitation of
crystals, which were collected by decanting off the supernatant (0.0463
g, 54%). Anal. Calcd for C22H36I2N2OP2U: C, 29.41; H, 4.04; N, 3.12.
9
J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006 10557

A R T I C L E S
Hayton et al.
Table 3. X-ray Crystallographic Data for Complexes 1-3
crystal data
1
1a
2
3
empirical formula
crystal habit, color
crystal size (mm)
crystal system
C
16H34I2N2O2U
C22H42I2N2O3U
irregular, red
0.16 × 0.14 × 0.12
monoclinic
C2/c
2670.7(2)
11.7556(5)
13.8565(6)
17.1139(9)
90
C24H34N2I2O3U
block, red
0.30 × 0.22 × 0.12
monoclinic
P21/n
2772.0(4)
10.9867(8)
17.7376(13)
14.2243(11)
90
C28H30F12I2N2O3U
plate, red
0.22 × 0.148 × 0.01
orthorhombic
Pbc21
6899.0(8)
9.1025(6)
17.488(1)
43.339(3)
90
block, orange
0.12 × 0.08 × 0.08
monoclinic
P21/n
2373.7(2)
12.3751(7)
15.3700(8)
12.4804(7)
90
space group
volume (Å3)
a (Å)
b (Å)
c (Å)
R (°)
â (°)
90.507(1)
90
4
106.660(1)
90
4
90.070(1)
90
4
90
90
8
γ (°)
Z
formula weight (g/mol)
density (calcd) (M g/m3)
absorption coefficient (cm-1
F000
778.28
2.178
9.448
1432
874.41
2.175
8.414
1640
890.36
2.133
8.109
1656
1162.37
2.238
6.593
4336
Mo KR, 0.71073 Å
)
radiation
Mo KR, 0.71073 Å
Mo KR, 0.71073 Å
Mo KR, 0.71073 Å
data refinement
final R indicesa
R1 ) 0.029, wR2 ) 0.061
2.70 and -0.74
R1 ) 0.017, R2 ) 0.042
0.71 and -0.63
R1 ) 0.018, wR2 ) 0.042
1.03 and -0.54
R1 ) 0.034, R2 ) 0.084
1.18 and -1.12
largest diff. peak and hole (e Å-3
)
2
2
4
2
a Number of observed reflections: 1, 5822 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0215p)2 +
2
2
2
2
4
2
2.1893p]-1, p ) [Fo + 2Fc ]/3. 1a, 3075 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0215p)2]-1, p
) [Fo2 + 2Fc ]/3. 2, 6802 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo2 + (0.0188p)2 + 0.6614p]-1, p ) [Fo
2
2
2
4
2
2
2
2
4
2
2
+ 2Fc ]/3. 3, 9694 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0145p)2 + 149.7929p]-1, p ) [Fo
+
2
2Fc ]/3.
Found: C, 28.14; H, 3.79; N, 2.81. 1H NMR (C6D6, 25 °C, 300 MHz):
δ 1.55 (s, 4H, OCH2CH2), 1.61 (s, 18H, PMe3), 4.50 (s, 4H, OCH2-
CH2), 5.71 (t, JHH ) 7 Hz, 2H, para CH), 6.17 (d, JHH ) 8 Hz, 4H,
ortho CH), 7.04 (t, JHH ) 8 Hz, 4H, meta CH). 31P{1H} NMR (C6D6,
25 °C, 121 MHz): δ 68.2 (fwhm ) 480 Hz). 13C{1H} NMR (C6D6, 25
°C, 75 MHz): δ 18.5 (br s, PMe3), 26.2 (OCH2CH2), 74.2 (OCH2-
CH2), 125.8 (para CH), 129.7 (meta CH), 130.8 (ortho CH), 153.8 (ipso
CH).
(OCH2CH2), 75.2 (OCH2CH2), 76.5 (OCH2CH2), 125.1 (CH), 127.9
(CH), 129.0 (CH), 153.6 (ipso CH).
X-ray Crystallography. The data for 1, 1a, 2, 3, 4, and 5 were
collected on a Bruker X-ray diffractometer, with a D8 goniometer and
an APEX II charge-coupled-device (CCD) detector. The crystal was
cooled with a KRYO-FLEX liquid nitrogen vapor cooling device to
141 K. The instrument was equipped with a graphite monochromatized
Mo KR X-ray source (λ ) 0.71073 Å), with MonoCap X-ray source
optics. A hemisphere of data was collected using ω scans, with 5-s
frame exposures and 0.3° frame widths. Data collection and initial
indexing and cell refinement were handled using APEX II software.48
Frame integration, including Lorentz-polarization corrections, and final
cell parameter calculations were carried out using SAINT+ software.49
The data were corrected for absorption using the SADABS program.50
Decay of reflection intensity was monitored via analysis of redundant
frames.
U(NtBu)2(OTf)2(THF)3. To an orange solution of U(NtBu)2I2(THF)2
(0.192 g, 0.25 mmol) in CH2Cl2 (5 mL) was added AgOTf (0.1273 g,
0.50 mmol). After 2 h of stirring, the volatiles were removed in vacuo
and the resulting orange solid was dissolved in a mixture of THF (3
mL) and MeCN (1 mL). This solution was filtered through a Celite
column, and the column was rinsed with THF (1 mL). Hexanes (4
mL) were layered on top of the filtrate, and the vial was stored at -35
°C for 24 h, resulting in the precipitation of fine white crystals. The
orange supernatant was decanted from the crystals, and the volatiles
were removed to give an orange oil. This was dissolved in THF (1
mL), and the resulting orange solution was layer with hexanes (1 mL)
and stored at -35 °C for 7 days, resulting in the deposition of orange
blocks (0.0537 g, 24% yield). Upon application of vacuum, the orange
crystals slowly crumbled and turned opaque. Anal. Calcd for
C22H42F6N2O9S2U: C, 29.53; H, 4.73; N, 3.13. Found: C, 26.76; H,
4.16; N, 3.52 (analysis is consistent with U(NtBu)2(OTf)2(THF)2; Anal.
The data for 7 and 12 were collected on a Bruker P4/1k-CCD
diffractometer and cooled to 203 K using a Bruker LT-2 temperature
device. The instrument was equipped with a sealed, graphite mono-
chromatized Mo KR X-ray source (λ ) 0.71073 Å). A hemisphere of
data was collected using æ scans, with 30 s frame exposures and 0.3°
frame widths. Data collection and initial indexing and cell refinement
were handled using SMART software.51 Frame integration, including
Lorentz-polarization corrections, and final cell parameter calculations
were carried out using SAINT.52 Decay of reflection intensity was
monitored via analysis of redundant frames.
1
Calcd for C18H34F6N2O8S2U: C, 26.28; H, 4.17; N, 3.41). H NMR
(THF-d8, 25 °C, 300 MHz): δ 0.23 (s, 18H, CMe3), 1.70 (m,
OCH2CH2), 3.61 (m, OCH2CH2). 19F NMR (THF-d8, 25 °C, 282
MHz): δ -79.3. 13C{1H} NMR (THF-d8, 25 °C, 75 MHz): δ 26.5
(OCH2CH2), 35.3 (CMe3), 68.4 (OCH2CH2), 81.2 (CMe3).
The structures were solved using direct methods and difference
Fourier techniques. All hydrogen atom positions were idealized and
rode on the atom they were attached to. For all compounds, the final
refinement included anisotropic temperature factors on all non-hydrogen
atoms. Structures 1, 4, and 9 had ligand disorder (tBu group for 1,
THF for 4, and PMe3 and tBu for 9) that was modeled as two one-half
occupancy positions. Lattice solvent molecules for 4 (THF) and 12
(dichloromethane) were found and refined anisotropically, with hy-
drogen atoms. Structure solution, refinement, graphics, and creation
of publication materials were performed using SHELXTL.53 A summary
U(NPh)2(OTf)2(THF)3. To an orange-brown solution of U(NPh)2I2-
(THF)3 (0.2085 g, 0.24 mmol) in CH2Cl2 (2 mL) was added AgOTf
(0.1206 g, 0.47 mmol). After 2 h of stirring, this solution was filtered
through a Celite column and the column was rinsed with THF (2 mL).
Hexanes (4 mL) were layered on top of the filtrate, and the vial was
stored at -35 °C for 24 h, resulting in the precipitation of fine maroon-
brown crystals (0.1109 g, 51% yield). Anal. Calcd for C26H34-
F6N2O9S2U: C, 33.41; H, 3.67; N, 3.00. Found: C, 33.34; H, 3.61; N,
2.98. 1H NMR (CD2Cl2, -40 °C, 300 MHz): δ 2.36 (s, 4H, OCH2CH2),
2.54 (s, 4H, OCH2CH2), 4.89 (s, 8H, OCH2CH2), 5.10 (m, 12H, ortho
(48) APEX II 1.08; Bruker AXS, Inc.: Madison, WI, 2004.
(49) SAINT+ 7.06; Bruker AXS, Inc.: Madison, WI, 2003.
(50) Sheldrick, G. M. SADABS 2.03; University of Go¨ttingen: Germany, 2001.
(51) SMART 5.054; Bruker AXS, Inc.: Madison, WI, 1996.
(52) SAINT 6.45A; Bruker AXS, Inc.: Madison, WI, 2003.
(53) SHELXTL 5.10; Bruker AXS, Inc.: Madison, WI, 1997.
CH and OCH2CH2), 5.80 (t, JHH ) 7 Hz, 2H, para CH), 7.03 (t, JHH
)
8 Hz, 4H, meta CH). 19F NMR (CD2Cl2, -40 °C, 282 MHz): δ -79.0.
13C{1H} NMR (CD2Cl2, -40 °C, 75 MHz): δ 26.6 (OCH2CH2), 26.7
9
10558 J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006

Synthesis of the Imido Analogues of the Uranyl Ion
A R T I C L E S
Table 4. X-ray Crystallographic Data for Complexes 4‚THF-9
crystal data
4
‚
THF
5
7
9
empirical formula
crystal habit, color
crystal size (mm)
crystal system
C
36H58I2N2O3U‚OC4H8
C
18H28I2N4U
C44H48N2I2O2P2U
block, orange
0.30 × 0.20 × 0.10
monoclinic
P21/c
4485.2(9)
11.792(1)
20.984(3)
18.416(2)
90
C18H44I2N2OP2U
irregular, orange
block, brown
0.14 × 0.12 × 0.08
monoclinic
P21/c
4264.5(3)
16.6844(6)
13.7864(5)
18.5403(7)
90
block, orange
0.14 × 0.11 × 0.04
monoclinic
P21/c
1197.3(2)
8.2887(7)
15.640(1)
9.7391(8)
90
0.20 × 0.12 × 0.10
tetragonal
P-421/c
5872(1)
23.516(3)
23.516
10.617(1)
90
space group
volume (Å3)
a (Å)
b (Å)
c (Å)
R (°)
â (°)
90.311(1)
90
4
108.495(1)
90
2
100.172(2)
90
4
90
90
8
γ (°)
Z
formula weight (g/mol)
density (calcd) (M g/m3)
absorption coefficient (cm-1
F000
1130.78
1.761
5.293
2200
792.27
2.198
9.365
724
1190.61
1.763
5.103
2280
858.32
1.942
7.751
3216
Mo KR, 0.71073 Å
)
radiation
Mo KR, 0.71073 Å
Mo KR, 0.71073 Å
Mo KR, 0.71073 Å
data refinement
final R indicesa
R1 ) 0.029, R2 ) 0.064
2.16 and -0.77
R1 ) 0.017, wR2 ) 0.037
0.63 and -0.47
R1 ) 0.026, wR2 ) 0.048
0.68 and -0.53
R1 ) 0.034, wR2 ) 0.075
1.49 and -0.89
largest diff. peak and hole (e Å-3
)
2
2
4
2
a Number of observed reflections: 4, 8272 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0256p)2 +
2
2
2
2
4
2
2.1000p]-1, p ) [Fo + 2Fc ]/3. 5, 2534 (Io > 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0180p)2]-1, p )
2
2
2
2
4
2
2
2
[Fo + 2Fc ]/3. 7, 6629, R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0204p)2]-1, p ) [Fo + 2Fc ]/3. 9, 5888 (Io
2
2
4
2
2
2
> 2σIo), R1 ) ∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo + (0.0285p)2]-1, p ) [Fo + 2Fc ]/3.
Table 5. X-ray Crystallographic Data for Complex 12‚2CH2Cl2
32 electrons, corresponding to the 5, 6, and 7 shells, are treated
explicitly. For the atoms in the ligands, the double-ú basis set 6-31G*
was employed. All of the calculations were carried out using the
Gaussian 03 suite of codes for quantum chemistry.56
crystal data
12‚2CH2Cl2
empirical formula
crystal habit, color
crystal size (mm)
crystal system
C44H52N4O16F12S4U‚2CH2Cl2
block, brown
0.12 × 0.08 × 0.06
monoclinic
P21/n
Acknowledgment. We are grateful to the Seaborg Institute
at Los Alamos National Laboratory for support of this work.
T.W.H. wishes to acknowledge NSERC (Canada) and the
Seaborg Institute for postdoctoral fellowships. E.R.B. and P.J.H.
were supported by the Division of Chemical Sciences, Office
of Basic Energy Sciences, U.S. Department of Energy, under
the Heavy Element Chemistry program at Los Alamos National
Laboratory. We would also like to thank Phillip D. Palmer for
help with the UV/vis measurements.
space group
volume (Å3)
3248(1)
13.224(2)
16.179(3)
15.338(3)
90
98.158(3)
90
a (Å)
b (Å)
c (Å)
R (°)
â (°)
γ (°)
Z
2
formula weight (g/mol)
density (calcd) (M g/m3)
absorption coefficient (cm-1
F000
1895.0
1.938
5.370
1824
)
radiation
Mo KR, 0.71073 Å
Supporting Information Available: Complete details of the
X-ray crystallographic studies as CIF files, geometries of the
various isomers of the model complex 1 and complex 2, and a
complete version of ref 56. This material is available free of
charge via the Internet at http://pubs.acs.org.
data refinement
final R indicesa
R1 ) 0.031, wR2 ) 0.054
0.86 and -0.86
largest diff. peak and hole (e Å-3
)
a Number of observed reflections: 12‚2CH2Cl2, 5505 (Io > 2σIo), R1 )
2
2
2
4
∑|(|Fo| - |Fc|)|/∑|Fo|, wR2 ) [∑w(|Fo| - |Fc| )2/∑wFo ]1/2, w ) [σ2Fo
2
2
+ (0.0268p)2]-1, p ) [Fo + 2Fc ]/3.
JA0629155
of relevant crystallographic data is found in Tables 3-5, and full details
of all crystallographic analyses are provided in the CIF files.
DFT Calculations. The uranium center was described using the
Stuttgart relativistic effective core potential,54,55 which places 60
electrons in the core (complete shells 1s through 4f), and the remaining
(54) Cao, X.; Dolg, M.; Stoll, H. J. Chem. Phys. 2003, 118, 487-496.
(55) Ku¨chle, W.; Dolg, M.; Stoll, H.; Preuss, H. J. J. Chem. Phys. 1994, 100,
7535-7542.
(56) Frisch, M. J.; et al. Gaussian 03, revision C.02; Gaussian, Inc.: Wallingford,
CT, 2004.
9
J. AM. CHEM. SOC. VOL. 128, NO. 32, 2006 10559