A mild protocol to generate uranium(IV) mixed-ligand metallocene complexes using copper(I) iodide

Article abstract of DOI:10.1021/om800622g

Reaction of the trivalent uranium complexes (C₅Me ₅)₂UI(THF) (1), (C₅Me₅) ₂U[N(SiMe₃)₂] (3), (C₅Me ₅)₂U(NPh₂)(THF) (4), and (C₅Me ₅)₂U(O-2,6-ⁱPr₂-C₆H ₃)(THF) (5) with copper(I) iodide affords the corresponding tetravalent uranium diiodide, amide iodide, and aryloxide iodide complexes (C₅Me₅)₂UI₂ (2), (C ₅Me₅)₂U[N(SiMe₃)₂](I) (6), (C₅Me₅)₂U(NPh₂)(I) (7) and (C₅Me₅)₂U(O-2,6-ⁱPr ₂-C₆H₃)(I) (8), respectively. This protocol was also extended to the synthesis of the alkyl iodide complex ~(C ₅Me₅)₂U(CHPh₂)(I) (10). The isolation of complex 10 from the in situ generated trivalent uranium alkyl complex (C₅Me₅)₂U(CHPh₂)(THF) (9) illustrates the synthetic value of this oxidation procedure in those situations where the uranium(III) metallocene complex cannot be isolated or is unstable. Overoxidation and ligand redistribution are not observed with this Cu-based U^III → U^IV oxidation procedure. Attempted functionalization of the U^IV amide iodide complex (C ₅Me₅)₂U[N(SiMe₃)₂](I) (6) with Me₂Mg afforded the novel azametallacycle (C₅Me ₅)₂U[η²(N,C)-CH₂SiMe ₂N(SiMe₃)] (12) by intramolecular C - H activation and liberation of methane. Reaction between (C₅Me₅) ₂U(NPh₂)(I) (7) and Me₂Mg afforded a mixture of the products (C₅Me₅)₂U(NPh₂)(Me) (13), (C₅Me₅)₂UMe₂ (14), and ~(C₅Me₅)₂U(NPh₂)₂ (15) at room temperature; heating the mixture smoothly furnished the azametallacycle ~(C₅Me₅)₂U[η²(N,C)-(o-C ₆H₄)NPh] (16). Similarly, reaction between 14 and HNPh₂ at 100 °C produced the azametallacycle 16 by aminolysis and subsequent intramolecular C - H activation.

Full text of DOI:10.1021/om800622g

Organometallics 2008, 27, 5371–5378
5371
A Mild Protocol To Generate Uranium(IV) Mixed-Ligand
Metallocene Complexes using Copper(I) Iodide
Christopher R. Graves, Eric J. Schelter, Thibault Cantat, Brian L. Scott, and
Jaqueline L. Kiplinger*
Los Alamos National Laboratory, Los Alamos, New Mexico 87545
ReceiVed July 2, 2008
Reaction of the trivalent uranium complexes (C5Me5)2UI(THF) (1), (C5Me5)2U[N(SiMe3)2] (3),
(C5Me5)2U(NPh2)(THF) (4), and (C5Me5)2U(O-2,6-iPr2-C6H3)(THF) (5) with copper(I) iodide affords the
corresponding tetravalent uranium diiodide, amide iodide, and aryloxide iodide complexes (C5Me5)2UI2
(2), (C5Me5)2U[N(SiMe3)2](I) (6), (C5Me5)2U(NPh2)(I) (7) and (C5Me5)2U(O-2,6-iPr2-C6H3)(I) (8),
respectively. This protocol was also extended to the synthesis of the alkyl iodide complex
(C5Me5)2U(CHPh2)(I) (10). The isolation of complex 10 from the in situ generated trivalent uranium
alkyl complex (C5Me5)2U(CHPh2)(THF) (9) illustrates the synthetic value of this oxidation procedure in
those situations where the uranium(III) metallocene complex cannot be isolated or is unstable.
Overoxidation and ligand redistribution are not observed with this Cu-based UIII f UIV oxidation
procedure. Attempted functionalization of the UIV amide iodide complex (C5Me5)2U[N(SiMe3)2](I) (6)
with Me2Mg afforded the novel azametallacycle (C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] (12) by
intramolecular C-H activation and liberation of methane. Reaction between (C5Me5)2U(NPh2)(I) (7)
and Me2Mg afforded a mixture of the products (C5Me5)2U(NPh2)(Me) (13), (C5Me5)2UMe2 (14), and
(C5Me5)2U(NPh2)2 (15) at room temperature; heating the mixture smoothly furnished the azametallacycle
(C5Me5)2U[η2(N,C)-(o-C6H4)NPh] (16). Similarly, reaction between 14 and HNPh2 at 100 °C produced
the azametallacycle 16 by aminolysis and subsequent intramolecular C-H activation.
C5H2)2U(OSiMe3)(X) (X ) Cl, Br, I, CN, OTf, N3),10 (4)
reactionof1equivofPh3C-X(X)Cl,OTf)with(C5Me5)2UMe2,6,7
and (5) salt metathesis between 1 equiv of an alkali-metal salt
and the dichloride complex (C5Me5)2UCl2.1,11 While the third
route is synthetically limited to oxo compounds, the first, fourth,
and fifth procedures are often difficult to control and lead to
mixtures of products. Recently, we discovered that UIV-imido
complexes could be oxidized and functionalized with copper(I)
halides to give the corresponding pentavalent systems (eq 1).12,13
Based on our interest in the synthesis, reactivity, and electronic
structure of actinide complexes,13-21 we were prompted to
explore the use of this Cu-based oxidative functionalization
Introduction
Mixed-ligand metallocene complexes of the type
(C5Me5)2U(X)(Y) (where X ) halogen, triflate; Y ) alkyl,
amide, alkoxide/aryloxide, phosphide) have played an important
role in the development of organometallic actinide chemistry,
serving as convenient starting materials for the preparation of
uranium complexes with various functional groups such as
hydrides,1 pyrazolates,2 imides,3,4 phosphinidenes,5 hydrazon-
ates,6 and ketimides.7 However, access to this class of molecules
is currently limited to very specific reaction chemistries such
as (1) redistribution reactions between the dihalide
((C5Me5)2UCl2) and dimethyl ((C5Me5)2UMe2) or diphosphide
complexes ((C5Me5)2U(PR2)2),1,8 (2) protonolysis of (C5Me5)2-
UMe2 or (C5Me5)2U(Me)Cl with amines/alcohols/phosphines,1,8,9
(3) addition of Me3SiX (X ) Cl, Br, I, CN, OTf, N3) across
the U-O bond in (1,2,4-tBu3-C5H2)2UdO to give (1,2,4-tBu3-
(8) Cendrowski-Guillaume, S. M.; Ephritikhine, M. J. Organomet. Chem.
1999, 577, 161–166.
(9) Peters, R. G.; Scott, B. L.; Burns, C. J. Acta Crystallogr. 1999, C55,
1482–1483.
(10) Zi, G.; Jia, L.; Werkema, E. L.; Walter, M. D.; Gottfriedsen, J. P.;
Andersen, R. A. Organometallics 2005, 24, 4251–4264.
(11) Hall, S. W.; Huffman, J. C.; Miller, M. M.; Avens, L. R.; Burns,
C. J.; Sattelberger, A. P.; Arney, D. S. J.; England, A. F. Organometallics
1993, 12, 752–758.
(12) Graves, C. R.; Scott, B. L.; Morris, D. E.; Kiplinger, J. L. J. Am.
Chem. Soc. 2007, 129, 11914–11915.
(13) Graves, C. R.; Yang, P.; Kozimor, S. A.; Vaughn, A. E.; Clark,
D. L.; Conradson, S. D.; Schelter, E. J.; Scott, B. L.; Thompson, J. D.;
Hay, P. J.; Morris, D. E.; Kiplinger, J. L. J. Am. Chem. Soc. 2008, 130,
5272–5285.
(14) Schelter, E. J.; Yang, P.; Scott, B. L.; Da Re, R. E.; Jantunen, K. C.;
Martin, R. L.; Hay, P. J.; Morris, D. E.; Kiplinger, J. L. J. Am. Chem. Soc.
2007, 129, 5139–5152.
* To whom correspondence should be addressed. E-mail: kiplinger@
lanl.gov.
(1) Fagan, P. J.; Manriquez, J. M.; Maatta, E. A.; Seyam, A. M.; Marks,
T. J. J. Am. Chem. Soc. 1981, 103, 6650–6667.
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9460.
(4) Arney, D. S. J.; Burns, C. J.; Smith, D. C. J. Am. Chem. Soc. 1992,
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(5) Arney, D. S. J.; Schnabel, R. C.; Scott, B. C.; Burns, C. J. J. Am.
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(6) Kiplinger, J. L.; John, K. D.; Morris, D. E.; Scott, B. L.; Burns,
C. J. Organometallics 2002, 21, 4306–4308.
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14, 7782–7790.
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10.1021/om800622g CCC: $40.75
2008 American Chemical Society
Publication on Web 09/20/2008

5372 Organometallics, Vol. 27, No. 20, 2008
GraVes et al.
chemistry as a new and versatile method for accessing mixed-
ligand UIV metallocene systems.
Herein, we describe our investigations and report the synthesis
and characterization of (C5Me5)2U(I)(X) (X ) I, N(SiMe3)2,
NPh2, O-2,6-iPr2-C6H3, CHPh2) from the reaction of copper(I)
iodide with the corresponding UIII precursor complexes. Im-
portantly, we demonstrate that overoxidation and ligand redis-
tribution are not observed with this Cu-based UIII f UIV
oxidation procedure. While the mixed amide iodide complexes
(C5Me5)2U(I)(X) (X ) N(SiMe3)2, NPh2) are quite stable, the
corresponding amide methyl derivatives (C5Me5)2U(Me)(X) (X
) N(SiMe3)2, NPh2) undergo intramolecular C-H activation
chemistry to afford methane and the novel azametallacycles
(C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] and (C5Me5)2U[η2(N,C)-
(o-C6H4)NPh], respectively. The preparation and characterization
of these azametallacycle complexes are also reported in this
paper.
Figure 1. Molecular structure of complex 2 with thermal ellipsoids
projected at the 50% probability level. Hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): U(1)-I(1)
) 2.9807(9), U(1)-I(2) ) 2.9868(9); I(1)-U(1)-I(2) ) 95.96(2).
parameters are presented in Table 1. At 2.9807(9) and 2.9868(9)
Å and 95.96(2)°, the respective U-I bond distances and I-U-I
angle observed in 2 are comparable to those reported for the
structurally similar base-free complex [1,3-(SiMe3)2-C5H3]2UI2:
U-I ) 2.953(2), 2.954(2) Å, I-U-I ) 105.40(8)°.26 As would
be expected, the U-I bond distances in the base-free systems
are on average slightly shorter when contrasted with structurally
related adduct and anion complexes (e.g. (C5Me5)2UI2(NtCMe),
U-I ) 3.0536(13), 3.0920(12) Å and I-U-I ) 80.13(3)°;22
(C5Me5)2UI2(NtCtBu), U-I ) 3.0707(8), 3.0732(8) Å and
I-U-I ) 83.29(2)°;22 (C5Me5)2UI2(NtCPh), U-I ) 2.942(3),
3.092(2) Å and I-U-I ) 83.16(7)°;25 [(C5Me5)2UI2]-, U-Iave
) 3.1038(14) Å27) which possess a more electron-rich uranium
metal center.
Results and Discussion
As a starting point, the oxidation of (C5Me5)2UI(THF) (1)
with copper(I) iodide to give (C5Me5)2UI2 (2) was performed
(eq 2). Complex 2 was obtained in 75% isolated yield as a dark
red solid, signifying that the UIV/UIII redox couple is accessible
to oxidative functionalization chemistry with copper halides.
Importantly, 2 was the only observed organometallic product
and other compounds resulting from overoxidation or ligand
redistribution were not observed. This synthetic protocol is an
attractive alternative to current literature procedures for the
synthesis of 2, which is most readily prepared by the halogen
exchange reaction between (C5Me5)2UCl2 and either Me3SiI22,23
or BI3;24 oxidation of (C5Me5)2UCl(THF) with I2 or alkyl iodides
also gives (C5Me5)2UI2,24 and the benzonitrile adduct
(C5Me5)2UI2(NtCPh) has also been prepared from the reaction
of UI4(NtCPh)4 with (C5Me5)MgCl(THF).25
Under conditions identical with those employed for the
synthesis of 2, the UIII complexes (C5Me5)2U[N(SiMe3)2] (3),
(C5Me5)2U(NPh2)(THF) (4), and (C5Me5)2U(O-2,6-iPr2-
C6H3)(THF) (5) were all smoothly oxidized with copper(I)
iodide to afford the corresponding UIV amide iodide
((C5Me5)2U[N(SiMe3)2](I) (6) and (C5Me5)2U(NPh2)(I) (7)) and
UIV aryloxide iodide ((C5Me5)2U(O-2,6-iPr2-C6H3)(I) (8)) com-
plexes (Scheme 1).28Again, overoxidation and ligand redistribu-
tion were not evident in these systems. Following workup by
filtration through Celite and crystallization, 6-8 were repro-
ducibly isolated as analytically pure solids and characterized
1
by a combination of H NMR, elemental, and mass spectro-
metric analyses and X-ray crystallography.
This Cu-based oxidative platform also provided a useful entry
to an uranium alkyl iodide complex. As shown in Scheme 2,
the complex (C5Me5)2U(CHPh2)(THF) (9), prepared in situ from
1 and KCHPh2, was treated with excess CuI to give
(22) Maynadie, J.; Berthet, J.-C.; Thuery, P.; Ephritikhine, M. Orga-
nometallics 2006, 25, 5603–5611.
(23) Maynadie, J.; Berthet, J.-C.; Thuery, P.; Ephritikhine, M. J. Am.
Chem. Soc. 2006, 128, 1082–1083.
(24) Finke, R. G.; Hirose, Y.; Gaughan, G. J. Chem. Soc., Chem.
Commun. 1981, 232–234.
Single crystals of 2 suitable for X-ray diffraction were grown
from a concentrated tetrahydrofuran solution at -30 °C. The
thermal ellipsoid representation of the base-free complex
(C5Me5)2UI2 (2) is shown in Figure 1, and the crystallographic
(25) Enriquez, A. E.; Scott, B. L.; Neu, M. P. Inorg. Chem. 2005, 44,
7403–7413.
(18) Jantunen, K. C.; Burns, C. J.; Castro-Rodriguez, I.; Da Re, R. E.;
Golden, J. T.; Morris, D. E.; Scott, B. L.; Taw, F. L.; Kiplinger, J. L.
Organometallics 2004, 23, 4682–4692.
(19) Jantunen, K. C.; Scott, B. L.; Kiplinger, J. L. J. Alloys Compd.
2007, 444-445, 363–368.
(20) Pool, J. A.; Scott, B. L.; Kiplinger, J. L. J. Am. Chem. Soc. 2005,
127, 1338–1339.
(26) Blake, P. C.; Lappert, M. F.; Taylor, R. G.; Atwood, J. L.; Hunter,
W. E.; Zhang, H. J. Chem. Soc., Dalton Trans. 1995, 3335–3341.
(27) Mehdoui, T.; Berthet, J.-C.; Thuery, P.; Salmon, L.; Riviere, E.;
Ephritikhine, M. Chem. Eur. J. 2005, 11, 6994–7006.
(28) Copper(I) chloride was also effective as an oxidant for the synthesis
of (C5Me5)2U[N(SiMe3)2](Cl) and (C5Me5)2U(NPh2)(Cl) from
(C5Me5)2U[N(SiMe3)2] (3) and (C5Me5)2U(NPh2)(THF) (4), respectively,
showing the generality of this Cu-based oxidative functionalization platform.
(21) Pool, J. A.; Scott, B. L.; Kiplinger, J. L. Chem. Commun. 2005,
2591–2593.

Uranium(IV) Mixed-Ligand Metallocene Complexes
Organometallics, Vol. 27, No. 20, 2008 5373
Table 1. Crystallographic Experimental Parameters for 2, 6, 8, 12, and 16
2
6
8
12
16
formula
a (Å)
b (Å)
C20H30I2U
8.5406(16)
16.293(3)
15.827(3)
90.00
98.717(2)
90.00
2176.9(7)
4
C
27.5H51.5INSiU
C32H47IOU
16.5602(17)
18.6484(19)
19.595(2)
90
C26H48NSi2U
8.753(3)
15.573(5)
11.017(3)
90
110.857(5)
90
1403.2(7)
2
C32H44NU
9.2465(9)
10.8850(11)
13.7791(14)
86.5926(14)
80.0815(14)
80.0828(15)
1345.1(2)
2
9.760(2)
17.856(4)
18.371(4)
95.73(3)
100.47(3)
93.31(3)
3122.9(11)
4
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
90
90
6051.3(11)
8
Z
formula wt (g/mol)
space group
T (K)
762.27
P21/n
120(1)
0.710 73
2.326
10.291
0.0476
0.1401
1.194
817.30
P1
141(2)
0.710 73
1.738
812.63
P212121
120(1)
0.710 73
1.784
668.86
P21/m
120(1)
0.710 73
1.583
680.71
P1
120(1)
0.710 73
1.681
j
j
λ (Å)
Dcalcd (g cm-3
)
µ (mm-1
)
6.279
6.407
5.882
6.054
R1 (I > 2σ(I))
wR2 (all data)
GOF (F2)
0.0264
0.0496
0.983
0.0359
0.0739
1.029
0.0787
0.2123
1.539
0.0374
0.0875
0.826
Scheme 1. Synthetic Routes for Tetravalent Uranium Mixed-
Ligand Metallocene Amide Iodide and Aryloxide Iodide
Complexes
Figure 2. Molecular structure of one of the molecules found in the
unit cell for complex 6 with thermal ellipsoids projected at the 50%
probability level. Hydrogen atoms are omitted for clarity. Selected
bond distances (Å) and angles (deg): U(1)-N(1) ) 2.288(3),
U(1)-I(1) ) 3.0253(9), Si(1)-C(21) ) 1.866(4), Si(1)-C(22) )
1.874(4), Si(1)-C(23) ) 1.881(4), Si(2)-C(24) ) 1.890(4),
Si(2)-C(25) ) 1.886(4), Si(2)-C(26) ) 1.886(4), U(1)-C(25) )
3.280(4); N(1)-U(1)-I(1) ) 93.41(8), U(1)-N(1)-Si(1) )
130.26(15), U(1)-N(1)-Si(2) ) 113.80(14), N(1)-Si(2)-N(1) )
108.35(15), N(1)-U(1)-C(25) ) 61.2(1), U(1)-C(25)-Si(2)
) 76.8(1). Bond distances for the other molecule present in the
unit cell can be found in the Supporting Information.
(C5Me5)2U(CHPh2)(I) (10) in 89% isolated yield over two steps.
Although the intermediate UIII-alkyl complex 9 was not
isolated, analysis of the reaction mixture by 1H NMR revealed
a sharp signal at δ -3.30 ppm, corresponding to the C5Me5
ligand protons. The trivalent amide and aryloxide starting
materials 3-5 display similar C5Me5 ligand proton reso-
nances.29-32 The Ar-H resonances in 9 were not observed at
room temperature. Since overoxidation and ligand redistribution
are not detected in the high-yield formation of complex 10 from
9, this reaction sequence is noteworthy, as it nicely demonstrates
how the Cu-based oxidation chemistry can be valuable in those
situations where the uranium(III) metallocene complex cannot
be isolated or is unstable, thereby dramatically expanding its
utility.
sponding to the C5Me5 ligand protons and paramagnetically
shifted resonances for the other protons in the compounds.
Interestingly, the 1H NMR spectrum of 6 shows three different
SiMe3 environments at δ 9.22, 4.83, and -109.70 ppm in a
3:2:1 ratio. The highly upfield resonance at δ -109.70 ppm,
which has an integration of three protons, is consistent with
restricted rotation of the SiMe3 group about one of the two N-Si
axes due to the presence of an agostic33 U · · · H-C interaction
between one of the Si-Me groups and the uranium center. This
interaction is also observed in the solid-state structural data for
complex 6 (vide infra). Agostic U · · · H-C interactions have
been previously reported for both [N(SiMe3)2]3U(S-2,6-Me2-
The 1H NMR spectra for complexes 6-8 and 10 are
consistent with those reported for other UIV metallocene
systems1,3,6,20sall four complexes have sharp signals corre-
35
C6H3)34 and (C5Me5)U[N(SiMe3)2]2 (vide infra). Complex 7
also has a highly upfield shifted Ar-H proton (δ -146.83)
(29) Graves, C. R.; Scott, B. L.; Morris, D. E.; Kiplinger, J. L.
Organometallics 2008, 27, 3335–3337.
(30) Arney, D. S. J.; Burns, C. J. J. Am. Chem. Soc. 1993, 115, 9840–
9841.
(31) Evans, W. J.; Nyce, G. W.; Forrestal, K. J.; Ziller, J. W.
Organometallics 2002, 21, 1050–1055.
(32) Fagan, P. J.; Manriquez, J. M.; Marks, T. J.; Day, C. S.; Vollmer,
S. H.; Day, V. W. Organometallics 1982, 1, 170–180.
(33) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Nat. Acad. Sci.
U.S.A. 2007, 104, 6908–6914.
(34) Clark, D. L.; Miller, M. M.; Watkin, J. G. Inorg. Chem. 1993, 32,
772–774.
(35) Avens, L. R.; Burns, C. J.; Butcher, R. J.; Clark, D. L.; Gordon,
J. C.; Schake, A. R.; Scott, B. L.; Watkin, J. G.; Zwick, B. D. Organome-
tallics 2000, 19, 451–457.

5374 Organometallics, Vol. 27, No. 20, 2008
GraVes et al.
Scheme 2. Synthetic Route for the Tetravalent Uranium Alkyl Iodide Complex (C5Me5)2U(CHPh2)(I) (10)
Scheme 3. Synthesis of the UIV Metallacycle (C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] (12)
interaction is present in the solid state. This is further supported
by the different U-N-Si geometric parameterssat 113.80(14)°
the U(1)-N(1)-Si(2) angle is significantly smaller than the
U(1)-N(1)-Si(1) angle of 130.26(15)°. Such U · · · H-C in-
teractions have been reported for other uranium systems that
possess a N(SiMe3)2 ligand.34,35,39 The (C5Me5)U[N(SiMe3)2]2
complex features two U · · · H-C interactions in the solid state,
as evidenced by close U · · · C contacts (2.86(2), 2.80(2) Å) and
decreased U-N-Si angles for the interacting (106.3(11),
101.5(9)°) versus noninteracting (134.2(12), 132.4(12)°)
groups.35 Although the U-C distances observed for
(C5Me5)U[N(SiMe3)2]2 are much shorter than those seen for 6,
the distances reported for the three agostic U · · · H-C interac-
tionsinthe[N(SiMe3)2]3U(S-2,6-Me2-C6H3)complex(3.158-3.539
Å) are much more in accord with our findings. Decreased
U-N-Si angles (109.5-117.2° versus 127.8-134.4°) were also
hallmarksfortheseU · · · H-Cinteractionsinthe[N(SiMe3)2]3U(S-
2,6-Me2-C6H3) complex.34 An agostic interaction has also been
reported for the homoleptic alkyl complex U[CH(SiMe3)2]3,
which contained a short U-C (3.09(2) Å) bond distance.39
Although neutron diffraction and theoretical studies suggest that
such agostic interactions in similar lanthanide complexes result
from ꢀ-Si-C rather than γ-C-H interactions, these conclusions
were based on significant differences in the Si-C bond
distances40 and such an interpretation cannot be made in the
present case, where the Si-C distances are all statistically
comparable.
Figure 3. Molecular structure of one of the molecules found in the
unit cell for complex 8 with thermal ellipsoids projected at the 50%
probability level. Hydrogen atoms are omitted for clarity. Selected
bond distances (Å) and angles (deg): U(1)-O(1) ) 2.114(6),
U(1)-I(1) ) 3.0366(7), O(1)-C(21) ) 1.372(10); O(1)-U(1)-I(1)
) 104.87(15), U(1)-O(1)-C(21) ) 166.6(6). Bond distances for
the other molecule present in the unit cell can be found in the
Supporting Information.
relative to the other proton signals, suggesting that an agostic
interaction may also be present in this system.
The identities of compounds 6 and 8 were confirmed by
single-crystal X-ray crystallography studies. Single crystals were
not obtained for 7 or 10, but their formulation is consistent with
1H NMR, mass spectrometric, and elemental analyses. Com-
pound 6 crystallized with two independent, but structurally
similar, molecules in the unit cell. As shown in Figure 2, the
molecule features a bent-metallocene framework with the
N(SiMe3)2 and iodide ligands contained within the metallocene
wedge. The U-Namide (2.288(3) Å) and U-I (3.0253(9) Å) bond
distances observed in 6 fall in the ranges observed for other
organometallic uranium complexes having U-Namide31,35-37 and
U-I linkages.38 The most notable feature of the N(SiMe3)2
ligand structure is the presence of a short U-C contact observed
between the uranium center and one of the methyl groups.
Corroborating the solution 1H NMR data, the U(1)-C(25)
distance of 3.280(4) Å indicates that an agostic U · · · H-C
Complex 8 also crystallized with two independent but
structurally similar complexes in the unit cell (Figure 3).
Interestingly, the geometric parameters observed for 8 are
statistically indistinguishable from those obtained for the
structurally related UV complex (C5Me5)2U(O-2,6-iPr2-
C6H3)(dO),30 with both complexes having close to linear
U-O-Caryl bond angles (166.6(6) and 169.7(5)°, respectively).
The U-O bond distance of 2.114(6) Å seen for 8 is also
comparable to that seen for (C5Me5)2U(O-2,6-iPr2-C6H3)(dO)
(2.135(5) Å) and is positioned well in the range of those
observed for other UIV aryloxide complexes (e.g. IU(O-2,6-
tBu2-C6H3)3,41 U-O ) 2.092(8), 2.102(8), 2.114(11) Å; [N(Si-
(36) Evans, W. J.; Kozimor, S. A.; Ziller, J. W. Polyhedron 2006, 25,
484–492.
(37) Evans, W. J.; Kozimor, S. A.; Ziller, J. W.; Kaltsoyannis, N. J. Am.
Chem. Soc. 2004, 126, 14533–14547.
(38) For representative examples of structurally characterized organo-
metallic uranium iodide complexes, see: (a) Crawford, M. J.; Mayer, P.
Inorg. Chem. 2005, 44, 5547–5549. (b) Maynadie´, J.; Berthet, J. C.; Thue´ry,
P.; Ephritikhine, M. Organometallics 2006, 25, 5603–5611. See also ref
35.
(39) Van der Sluys, W. G.; Burns, C. J.; Sattelberger, A. P. Organo-
metallics 1989, 8, 855–857.
(40) Klooster, W. T.; Brammer, L.; Schaverien, C. J.; Budzelaar,
P. H. M. J. Am. Chem. Soc. 1999, 121, 1381–1382.
(41) Avens, L. R.; Barnhart, D. M.; Burns, C. J.; McKee, S. D.; Smith,
W. H. Inorg. Chem. 1994, 33, 4245–4254.

Uranium(IV) Mixed-Ligand Metallocene Complexes
Organometallics, Vol. 27, No. 20, 2008 5375
Scheme 4. Profile of the Reaction between (C5Me5)2U(NPh2)(I) (7) and Me2Mg
Me3)2]3U(O-2,6-tBu2-C6H3),42 U-O ) 2.145(8) Å). The U-I
bond distance of 3.0366(7) Å observed for 8 is unexceptional
and can be compared with that observed in complex 6 and other
tetravalent uranium iodide complexes.
Interestingly, attempts to alkylate (C5Me5)2U[N(SiMe3)2](I)
(6) with Me2Mg gave a mixture of products at room temperature
after 12 h.43 Although complex 6 was entirely consumed, the
major product of the reaction was the novel metallacycle
(C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] (12) (82% by 1H
NMR), not the anticipated product (C5Me5)2U[N(SiMe3)2](Me)
(11). An NMR signal at δ 8.26 ppm (18% by 1H NMR) in the
range expected for the C5Me5 ligand protons of 11 was also
observed as the minor product of the reaction. We propose that
11 is formed as an intermediate in the salt metathesis reaction
and that a subsequent intramolecular C-H activation reaction
with elimination of methane44 affords the metallacycle 12. Upon
heating at 50 °C for 12 h in toluene 12 is formed quantitatively
under indentical reaction conditions and can be obtained in 90%
isolated yield (Scheme 3).
Figure 4. Molecular structure of complex 12 with thermal ellipsoids
projected at the 50% probability level. Hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): U(1)-N(1)
) 2.221(8), U(1)-C(14) ) 2.52(2); U(1)-N(1)-Si(1) ) 136.2(5),
U(1)-N(1)-Si(2) ) 100.7(4), U(1)-C(14)-Si(2) ) 86.6(7),
N(1)-U(1)-C(14) ) 70.5(4), Si(1)-N(1)-Si(2) ) 123.1(6),
N(1)-Si(2)-C(14) ) 102.2(8).
As illustrated in Scheme 4, the reaction between
(C5Me5)2U(NPh2)(I) (7) and Me2Mg also formed a mixture of
products at room temperature.43 While the desired product
(C5Me5)2U(NPh2)(Me) (13, 25% by NMR) could be observed
diphenylamine, respectively, gives the metallacycle product 16.
A subsequent protonolysis reaction between 14 and HNPh2
followed by C-H activation accounts for the consumption of
the dialkyl complex. To confirm that this is a possibility,
(C5Me5)2UMe2 (14) was treated with 1 equiv of diphenylamine
at100°C,whichcleanlygavethemetallacycle(C5Me5)2U[η2(N,C)-
(o-C6H4)NPh] (16) as the sole organometallic product. Ad-
ditionally, heating (C5Me5)2U(NPh2)2 (15) at 100 °C also affords
the azametallacycle (C5Me5)2U[η2(N,C)-(o-C6H4)NPh] (16) and
diphenylamine.
Similar alkanolysis chemistry has been observed for the
uranium phosphide complexes (C5Me5)2U[P(SiMe3)2](Me) and
(C5Me5)2U(PPh2)(Me), with thermolysis giving the correspond-
ing phosphametallacycles (C5Me5)2U[η2(P,C)-CH2SiMe2P-
(SiMe3)] and (C5Me5)2U[η2(P,C)-(o-C6H4)PPh], respectively,
although for these systems much higher temperatures were
required.8,11 Further, this cyclometalation pathway is not
unique for these bis(pentamethylcyclopentadienyl) UIV methyl
amide and methyl phosphide mixed-ligand systems. The actinide
tris(amide) complexes [N(SiMe3)2]3AnR (An ) Th, U; R ) H,
Me) readily expel either H2 or CH4 at elevated temperatures to
give the azametallacycles [N(SiMe3)2]2An[η2(N,C)-CH2SiMe2N-
(SiMe3)] (An ) Th, U).46,47 Analogous chemistry was observed
for the homoleptic UIV amide complex U[N(SiMe3)2]4 formed
in situ between the reaction of UCl4 with 4 equiv of NaN-
1
in the reaction mixture by H NMR spectroscopy, the major
product was (C5Me5)2UMe2 (14, 50% by NMR), in addition to
another organometallic, (C5Me5)2U(NPh2)2 (15, 25% by
NMR).45 While (C5Me5)2UMe2 is a known compound,1 the
identity of (C5Me5)2U(NPh2)2 (15) was confirmed by an NMR
reaction between (C5Me5)2U(NPh2)(I) (7) and 1.2 equiv of
KNPh2, which showed a single resonance corresponding to the
C5Me5 protons at δ 11.28 ppm. In analogy to the formation of
(C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] (12), when this mix-
ture of 13, 14, and 15 was heated to 100 °C, the complex
(C5Me5)2U[η2(N,C)-(o-C6H4)NPh] (16) was formed as the sole
organometallic product. Presumably, intramolecular C-H ac-
tivation from both 13 and 15 with elimination of methane and
(42) Berg, J. M.; Clark, D. L.; Huffman, J. C.; Morris, D. E.; Sattelberger,
A. P.; Streib, W. E.; Van der Sluys, W. G.; Watkin, J. G. J. Am. Chem.
Soc. 1992, 114, 10811–10821.
(43) Excess Me2Mg was utilized to ensure complete consumption of
the uranium starting material.
(44) A peak in the 1H NMR spectrum for the reaction between
(C5Me5)2U[N(SiMe3)2](I) (6) and Me2Mg in C6D6 had a signal at δ 0.14
ppm corresponding to CH4.
(45) The C5Me5 resonances observed in the 1H NMR corresponding to
(C5Me5)2U(NPh2)(Me) (13), (C5Me5)2UMe2 (14), and (C5Me5)2U(NPh2)2
(15) are located at δ 8.50, 5.27, and 11.28 ppm, respectively.

5376 Organometallics, Vol. 27, No. 20, 2008
GraVes et al.
for the preparation of mixed-ligand metallocene complexes of
the type (C5Me5)2U(X)(Y) (where X ) halogen and Y ) alkyl,
amide, aryloxide, etc.). The isolation of the alkyl iodide complex
(C5Me5)2U(CHPh2)(I) (10) from the in situ generated trivalent
uranium alkyl complex (C5Me5)2U(CHPh2)(THF) (9) demon-
strates the synthetic utility of this oxidation method for those
situations where the UIII metallocene complex cannot be isolated
or is unstable. Importantly, neither overoxidation nor ligand
redistribution chemistry is observed with this Cu-based oxidative
functionalization protocol. We are presently exploring its
efficacy on an assortment of non-metallocene actinide systems.
Experimental Section
Figure 5. Molecular structure of complex 16 with thermal ellipsoids
projected at the 50% probability level. Hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (deg): U(1)-N(1)
) 2.239(5), U(1)-C(22) ) 2.342(7); U(1)-N(1)-C(21) ) 93.9(4),
U(1)-N(1)-C(21) ) 93.9(4), U(1)-N(1)-C(27) ) 142.9(4),
N(1)-U(1)-C(22) ) 62.7(2), N(1)-C(21)-C(22) ) 114.2(6).
General Considerations. Reactions and manipulations were
performed in either a recirculating Vacuum Atmospheres NEXUS
model inert-atmosphere (N2) drybox equipped with a 40CFM Dual
Purifier NI-Train or using standard Schlenk techniques. Glassware
was dried overnight at 150 °C before use. All NMR spectra were
obtained in C6D6 using a Bruker Avance 300 MHz spectrometer.
1
Chemical shifts for H NMR spectra were referenced to solvent
(SiMe3)2.48 Finally, at elevated temperatures, the thorium dialkyl
complexes (C5Me5)2Th(CH2EMe3)2 (E ) C, Si) eliminate CMe4
and SiMe4, respectively, to give the corresponding cyclometa-
lated products (C5Me5)2Th[η2(C,C)-CH2EMe2CH2].49,50
The metallacyles 12 and 16 were both characterized by single-
crystal X-ray diffraction. Thermal ellipsoid plots are shown in
Figures 4 (12) and 5 (16), and crystallographic experimental
parameters are provided in Table 1. Both complexes exhibit a
bent-metallocene framework with the newly formed metalla-
cyclic ligands contained within the metallocene wedge. The
structure of 12 is similar to that of the previously reported
phosphorus analogue (C5Me5)2U[η2(P,C)-CH2SiMe2P(SiMe3)].
The two have similar U-CH2 bond distances (2.52(2) and
2.415(20) Å, respectively) and X-U-CH2 angles (86.6(7) and
78.7(5)°, respectively). At 2.221(8) and 2.239(5) Å, the
U-Namide bond lengths observed in 12 and 16 agree well with
similar parameters obtained for other uranium amides.51
impurities. Melting points were determined with a Mel-Temp II
capillary melting point apparatus equipped with a Fluke 50S K/J
thermocouple using capillary tubes flame-sealed under nitrogen;
values are uncorrected. Mass spectrometric (MS) analyses were
obtained at the University of California, Berkeley Mass Spectrom-
etry Facility, using a VG ProSpec (EI) mass spectrometer. Elemental
analyses were performed at the University of California, Berkeley
Microanalytical Facility, on a Perkin-Elmer Series II 2400 CHNS
analyzer. X-ray data were collected using either a Bruker APEX2
or Bruker P4/CCD diffractometer. Details regarding data collection
are provided in the CIF files given in the Supporting Information.
Structural solution and refinement was achieved using the SHELXL97
program suite.52
Unless otherwise noted, reagents were purchased from com-
mercial suppliers and used without further purification. Benzene-
d6 (Aldrich) was purified by passage through activated alumina
and storage over activated 4 Å molecular sieves prior to use.
Celite (Aldrich), alumina (Brockman I, Aldrich), and 4 Å
molecular sieves (Aldrich) were dried under dynamic vacuum
at 250 °C for 48 h prior to use. All solvents (Aldrich) were
purchased anhydrous and were dried over KH for 24 h, passed
through a column of activated alumina, and stored over activated
4 Å molecular sieves prior to use. (C5Me5)2UI(THF) (1),35
(C5Me5)2U(NPh2)(THF) (4),29 (C5Me5)2U(O-2,6-iPr2-C6H3)(THF)
(5),30 (C5Me5)2UMe2 (14),1 KCHPh2,53 and Me2Mg54 were
prepared according to literature procedures.
Conclusions
Oxidative functionalization of trivalent uranium organome-
tallic complexes with copper(I) iodide provides a simple and
mild method for synthesizing the corresponding UIV iodide
complexes in good yield. This new approach works on a variety
of UIII complexes to give not only the basic UIV diiodide but
also amide iodide, aryloxide iodide, and alkyl iodide complexes,
making it an attractive synthetic alternative to the existing routes
Caution! Depleted uranium (primary isotope 238U) is a weak
R-emitter (4.197 MeV) with a half-life of 4.47 × 109 years;
manipulations and reactions should be carried out in monitored fume
hoods or in an inert-atmosphere drybox in a radiation laboratory
equipped with R- and ꢀ-counting equipment.
Synthesis of (C5Me5)2UI2 (2). A 125 mL sidearm flask
equipped with a stir bar was charged with (C5Me5)2UI(THF)
(1; 0.50 g, 0.70 mmol) and toluene (50 mL). CuI (0.67 g, 3.5
mmol) was added to the dark green solution, and the reaction
mixture was stirred at room temperature. After 12 h, the reaction
mixture was filtered through a Celite-padded coarse-porosity frit
(46) Simpson, S. J.; Turner, H. W.; Andersen, R. A. J. Am. Chem. Soc.
1979, 101, 7728–7729.
(47) Simpson, S. J.; Turner, H. W.; Andersen, R. A. Inorg. Chem. 1981,
20, 2991–2995.
(48) Dormond, A.; El Bouadili, A.; Aaliti, A.; Moise, C. J. Organomet.
Chem. 1985, 288, C1-C5.
(49) Bruno, J. W.; Marks, T. J.; Day, V. W. J. Am. Chem. Soc. 1982,
104, 7357–7360.
(50) Bruno, J. W.; Marks, T. J.; Day, V. W. J. Organomet. Chem. 1983,
250, 237–246.
(51) For representative U-N bond lengths for complexes containing a
uranium-amide linkage, see: (a) U[N(SiMe3)2]3, U-Namide ) 2.320(4) Å:
Stewart, J. L.; Andersen, R. A. Polyhedron 1998, 17, 953–958. (b)
(C5Me5)2U[N(SiMe3)2], U-Namide ) 2.352(2) Å: Evans, W. J.; Nyce, G.
W; Forrestal, K. J.; Ziller, J. W. Organometallics 2002, 21, 1050–1055.
(c) (C5Me5)2U[NH(2,6-Me2-C6H3)]2, U-Namide ) 2.276(6) Å: Straub, T.;
Frank, W.; Reis, G. J.; Eisen, M. S. J. Chem. Soc., Dalton Trans. 1996,
2541–2546. (d) [N(SiMe3)2]3U(dNSiMe3)(F), U-Namide ) 2.217(17)-
2.252(17) Å; [N(SiMe3)2]3U(dNC6H5)(F), U-Namide ) 2.206(7)-2.226(6)
Å: Burns, C. J.; Smith, W. H.; Huffman, J. C.; Sattelberger, A. P. J. Am.
Chem. Soc. 1990, 112, 3237–3238.
(52) (a) Bruker AXS SAINT 7.06, Integration Software; Bruker Analyti-
cal X-ray Systems, Madison, WI, 2003. (b) Sheldrick, G. M. SADABS
2.03, Program for Adsorption Correction; University of Go¨ttingen, Go¨t-
tingen, Germany, 2001. (c) Sheldrick, G. M. SHELXTL 5.10, Structure
Solution and Refinement Package; University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
(53) Schumann, H.; Freckmann, D. M. M.; Dechert, S. Organometallics
2006, 25, 2696–2699.
(54) Tobia, D.; Baranski, J.; Rickborn, B. J. Org. Chem. 1989, 54, 4253–
4256.

Uranium(IV) Mixed-Ligand Metallocene Complexes
Organometallics, Vol. 27, No. 20, 2008 5377
and the volatiles were removed from the filtrate. The residue
was extracted into hexane (50 mL) and the extract filtered
through a Celite-padded coarse-porosity frit. The filtrate was
collected, and the volatiles were removed under reduced pressure
to give 2 as a red solid (0.40 g, 0.53 mmol, 75%). Spectroscopic
characterization of 2 matched literature data.23 1H NMR (C6D6,
298 K): δ 20.34 (30H, C5Me5). X-ray-quality samples of 2 were
obtained by recrystallization from a concentrated tetrahydrofuran
solution at -30 °C.
Synthesis of (C5Me5)2U[N(SiMe3)2] (3). A 125 mL sidearm
flask equipped with a stir bar was charged with (C5Me5)2UI(THF)
(1; 1.0 g, 1.4 mmol) and toluene (50 mL). KN(SiMe3)2 (0.28 g,
1.4 mmol) was added to the dark green solution, and the reaction
mixture was stirred at room temperature. After 1 h, the reaction
mixture was filtered through a Celite-padded coarse-porosity frit
and the volatiles were removed from the filtrate. The residue
was extracted into hexane (50 mL) and the extract filtered
through a Celite-padded coarse-porosity frit. The filtrate was
collected, and the volatiles were removed under reduced pressure
to give 3 as a dark green solid (0.81 g, 1.2 mmol, 86%).
Spectroscopic characterization of 3 matched literature data.31,32
1H NMR (C6D6, 298 K): δ -5.73 (30H, C5Me5), -25.59 (18H,
SiMe3).
porosity frit. The filtrate was collected, and the volatiles were
removed under reduced pressure to give 8 as a red solid (0.49
1
g, 0.60 mmol, 91%). H NMR (C6D6, 298 K): δ 10.85 (1H, d,
J ) 8 Hz), 10.20 (1H, d, J ) 8 Hz), 9.85 (30H, C5Me5), 7.97
(1H, t, J ) 8 Hz), -5.60 (6H, CHMe2), -10.71 (6H, CHMe2),
-35.02 (1H), -40.69 (1H). Anal. Calcd for C32H47OIU (mol
wt 812.65): C, 47.30; H, 5.83. Found: C, 47.69; H, 6.01. Mp:
280-282 °C. MS (EI, 70 eV): m/z 812 (M+). X-ray-quality
samples of 8 were obtained by recrystallization from a concen-
trated hexane solution at -30 °C.
Synthesis of (C5Me5)2U(CHPh2)(I) (10). A 125 mL sidearm
flask equipped with a stir bar was charged with (C5Me5)2UI(THF)
(1; 0.25 g, 0.35 mmol) and tetrahydrofuran (50 mL). KCHPh2
(0.073 g, 0.35 mmol) was added to the dark green solution, and
the reaction mixture was stirred at room temperature. After 12 h
the reaction mixture was filtered through a Celite-padded coarse-
porosity frit and CuI (0.33 g, 1.75 mmol) was added to the
filtrate. The resulting mixture was stirred at room temperature.
After 12 h, the reaction mixture was filtered through a Celite-
padded coarse-porosity frit and the volatiles were removed from
the filtrate. The residue was extracted into hexane (50 mL) and
the extract filtered through a Celite-padded coarse-porosity
frit. The filtrate was collected, and the volatiles were removed
under reduced pressure to give 10 as a red solid (0.25 g, 0.31
mmol, 89%). 1H NMR (C6D6, 248 K): δ 33.03 (2H), 15.41 (2H),
7.80 (2H), 4.41 (30H, C5Me5), 3.42 (1H), 0.93 (2H), -1.39 (1H),
-50.01 (1H). Anal. Calcd for C33H41IU (mol wt 802.61): C,
49.38; H, 5.15. Found: C, 49.12; H, 5.35. Mp ) 97-99 °C.
Synthesis of (C5Me5)2U[η2(N,C)-CH2SiMe2N(SiMe3)] (12). A
150 mL thick-walled Schlenk tube equipped with Teflon valve
and a stir bar was charged with (C5Me5)2U[N(SiMe3)2](I) (6;
0.25 g, 0.31 mmol) and toluene (50 mL). Me2Mg (0.026 g, 0.47
mmol) was added as a white powder. The reaction vessel was
sealed and removed from the drybox to a fume hood, where it
was placed in a 50 °C oil bath. After 12 h, the reaction mixture
was removed from heat, cooled to room temperature, and brought
back into the drybox. The reaction mixture was filtered through
a Celite-padded coarse-porosity frit, and the volatiles were
removed from the filtrate. The residue was extracted into hexane
(50 mL) and the extract filtered through a Celite-padded coarse-
porosity frit. The filtrate was collected, and the volatiles were
removed under reduced pressure to give 12 as a red solid (0.19
g, 0.28 mmol, 90%). 1H NMR (C6D6, 298 K): δ 15.75 (6H,
SiMe2), 5.56 (2H, U-CH2Si), 1.99 (9H, SiMe3), 1.29 (30H,
C5Me5). Anal. Calcd for C26H47NSi2U (mol wt 667.86): C, 46.76;
H, 7.09; N, 2.10. Found: C, 48.11; H, 7.34; N, 1.91. Mp:
134-136 °C. MS (EI, 70 eV): m/z 667 (M+). X-ray-quality
samples of 12 were obtained by recrystallization from either a
concentrated hexane or toluene solution at -30 °C.
Synthesis of (C5Me5)2U[N(SiMe3)2](I) (6). A 125 mL sidearm
flask equipped with a stir bar was charged with (C5Me5)2U-
[N(SiMe3)2] (3; 0.5 g, 0.75 mmol) and toluene (50 mL). CuI
(0.72 g, 3.8 mmol) was added to the dark green solution, and
the reaction mixture was stirred at room temperature. After 12 h,
the reaction mixture was filtered through a Celite-padded coarse-
porosity frit and the volatiles were removed from the filtrate.
The residue was extracted into hexane (50 mL) and the extract
filtered through a Celite-padded coarse-porosity frit. The filtrate
was collected, and the volatiles were removed under reduced
1
pressure to give 6 as a red solid (0.44 g, 0.56 mmol, 74%). H
NMR (C6D6, 298 K): δ 12.84 (30H, C5Me5), 9.22 (9H, SiMe3),
4.83 (6H, SiMe2), -109.70 (3H, SiMe). Anal. Calcd for
C26H48NSi2IU (mol wt 795.77): C, 39.24; H, 6.08; N, 1.76.
Found: C, 39.25; H, 6.06; N, 1.69. Mp: 249-251 °C. MS (EI,
70 eV): m/z 794 ([M - H]+). X-ray-quality samples of 6 were
obtained by recrystallization from a concentrated hexane solution
at -30 °C.
Synthesis of (C5Me5)2U(NPh2)(I) (7). A 125 mL sidearm flask
equipped with
a stir bar was charged with (C5Me5)2-
U(NPh2)(THF) (4; 0.25 g, 0.33 mmol) and toluene (50 mL). CuI
(0.31 g, 1.6 mmol) was added to the dark green solution, and
the reaction mixture was stirred at room temperature. After 12 h,
the reaction mixture was filtered through a Celite-padded coarse-
porosity frit and the volatiles were removed from the filtrate.
The residue was extracted into hexane (50 mL) and the extract
filtered through a Celite-padded coarse-porosity frit. The filtrate
was collected, and the volatiles were removed under reduced
Synthesis of (C5Me5)2U[η2(N,C)-(o-C6H4)NPh] (16). A 150 mL
thick-walled Schlenk tube equipped with a Teflon valve and a stir
bar was charged with (C5Me5)2UMe2 (14; 0.50 g, 0.92 mmol) and
toluene (100 mL). Diphenylamine (0.16 g, 0.92 mmol) was added,
and the reaction vessel was sealed and removed from the drybox
to a fume hood, where it was placed in a 100 °C oil bath. After
12 h, the reaction mixture was removed from heat, cooled to room
temperature, and brought back into the drybox. The reaction was
filtered though a Celite-padded coarse-porosity frit, and the volatiles
were removed from the filtrate. The crude product was extracted
into hexane (50 mL), the extract was filtered through a Celite-
padded coarse-porosity frit, and the volatiles were removed under
reduced pressure to give 16 as a brown solid (0.57 g, 0.85 mmol,
1
pressure to give 7 as a red solid (0.25 g, 0.31 mmol, 92%). H
NMR (C6D6, 248 K): δ 16.93 (30H, C5Me5), 5.94 (1H, Ar-H),
5.15 (2H, Ar H), -3.54 (1H, Ar H), -5.75 (2H, Ar H), -8.44
(1H, Ar H), -8.70 (1H, Ar H), -17.28 (1H, Ar H), -146.83
(1H, Ar H). Anal. Calcd for C32H40NIU (mol wt 803.60): C,
47.83; H, 5.02; N, 1.74. Found: C, 47.47; H, 5.20; N, 1.65. Mp:
297-299 °C.
Synthesis of (C5Me5)2U(O-2,6-iPr2-C6H3)(I) (8). A 125 mL
sidearm flask equipped with a stir bar was charged with
(C5Me5)2U(O-2,6-iPr2-C6H3)(THF) (5; 0.50 g, 0.66 mmol) and
toluene (50 mL). CuI (0.63 g, 3.3 mmol) was added to the dark
green solution, and the reaction mixture was stirred at room
temperature. After 12 h, the reaction mixture was filtered through
a Celite-padded coarse-porosity frit and the volatiles were
removed from the filtrate. The residue was extracted into hexane
(50 mL) and the extract filtered through a Celite-padded coarse-
1
92%). H NMR (C6D6, 298 K): δ 15.72 (1H, d, J ) 8 Hz), 8.42
(1H, t, J ) 8 Hz), 5.06 (2, t, J ) 6 Hz), 2.92 (1H, t, J ) 6 Hz),
0.89 (30H, C5Me5), -7.91 (1H, d, J ) 7 Hz), -11.27 (2H, d, J )
8 Hz), -25.08 (1H, d, J ) 7 Hz). Anal. Calcd for C32H39NU (mol
wt 675.69): C, 56.88; H, 5.82; N, 2.07. Found: C, 56.74; H, 5.70;

5378 Organometallics, Vol. 27, No. 20, 2008
GraVes et al.
N, 2.27. Mp: 79-81 °C. MS (EI, 70 eV): m/z 675 (MH+). X-ray-
quality samples of 16 were obtained by recrystallization from a
concentrated hexane solution at -30 °C.
Office of Basic Energy Sciences, Heavy Element Chemistry
program, and the LANL Laboratory Directed Research &
Development program.
Acknowledgment. For financial support of this work, we
acknowledge the LANL (Director’s PD Fellowships to
C.R.G., T.C., and E.J.S.; Frederick Reines PD Fellowship
to E.J.S.), the LANL G. T. Seaborg Institute (PD Fellowships
to C.R.G. and E.J.S.), the Division of Chemical Sciences,
Supporting Information Available: >CIF files giving crystal-
lographic details for complexes 2, 6, 8, 12, and 16. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM800622G