C O M M U N I C A T I O N S
from crystal-field splitting of the ground (2F5/2) and excited (2F7/2
)
spin-orbit manifolds. The relatively minor shifts in these near-IR
bands for 3 versus 4 reflect minor differences in the crystal-field
perturbation for the two imide ligands. Notably, the energetic
proximity of these bands for 3 and 4 versus those for the octahedral
halide systems suggests that the spin-orbit coupling is comparable
(∼2000 cm-1) in all these systems.12
In conclusion, we have discovered a general and versatile Cu-
(I)-based oxidation procedure that enables facile access to pen-
tavalent organouranium complexes. Work focused on elucidating
the electronic structure and bonding of these 5f1 derivatives, in
addition to extending this chemistry to other copper reagents and
uranium oxidation states, is currently underway in our laboratory.
Figure 2. Molecular structure of complex 6 with thermal ellipsoids at the
50% probability level. Selected bond distances (Å) and angles (°): U(1)-
S(1) 2.7230(13), U(1)-N(1) 1.976(4), N(1)-C(27) 1.398(6), S(1)-C(21)
1.775(5), U(1)-C5Me5(cent) 2.457(4), 2.466(4), N(1)-U(1)-S(1) 103.35-
(12), C(27)-N(1)-U(1) 171.6(3), U(1)-S(1)-C(21) 131.08(17), C5-
Me5(cent)-U(1)-C5Me5(cent) 136.2(2).
Acknowledgment. For financial support of this work, we
acknowledge LANL (Director’s PD Fellowship to C.R.G.), the
LANL G. T. Seaborg Institute (PD Fellowship to C.R.G.), the
Division of Chemical Sciences, Office of Basic Energy Sciences,
Heavy Element Chemistry program, and the LANL LDRD program.
We thank Drs. Eric J. Schelter and Jacqueline M. Veauthier (LANL)
for helpful discussions.
Supporting Information Available: Full experimental and char-
acterization details, and crystallographic data (PDF, CIF) for 3-6. This
References
Figure 3. Cyclic voltammogram for (C5Me5)2U(dN-2,6-iPr2-C6H3)(I) 4
at a Pt electrode in 0.1 M [Bu4N][B(C6F5)4]/THF at a scan rate of 200
mV/s.
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(7) See Supporting Information.
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N, 2.019(6), U-N-C, 167.4(6): Brennan, J. G.; Andersen, R. A. J. Am.
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Figure 4. Room temperature electronic absorption spectral data for
complexes 3 (red line) and 4 (blue line) in toluene-d8 solution.
as a result of the metal-imide linkage and the added electron
density at the uranium center from the ancillary anionic ligand (e.g.,
iodide).
These stable U(V) systems provide an opportunity to interrogate
the electronic structure of 5f1 actinide complexes. The UV-visible
region of these spectra (Figure 4, top) is dominated by broad,
relatively intense bands ascribed principally to πUdN-to-nonbonding
metal (5f) orbital transitions similar to those seen in early transition-
metal imido complexes.11 Additional narrow, relatively weak bands
in the near-IR region (Figure 4, bottom) arise from intraconfigu-
ration (f-f) transitions associated with the 5f1 valence electronic
structure. These bands are comparable in energy and structure to
those reported for U(V) halides in much higher symmetry environ-
ments.12 They are assigned to vibronic components of the Γ7f Γ7′
electronic transition, where the ground and excited states derive
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