Inorganic Chemistry
ARTICLE
uranium, an observation which is further highlighted by the fact
that the reductant in the process, Iꢀ, is a relatively mild reducing
agent. In addition, the formation of U(OSiMe3)2I2(bipy)2 from
uranyl parallels the synthesis of UX4(MeCN)4 (X = Cl, Br, I),
reported by Ephritikhine and co-workers,3 and it is likely that
[U(OSiMe3)2I4]ꢀ and U(OSiMe3)2I2(bipy)2 are analogous to
the intermediates generated along the pathway to UX4(MeCN)4.
Ultimately, the observed redox chemistry reveals the importance
of functionalizing the uranyl oxo ligands to access the 4þ state,
an observation which may have implications for the bioremedia-
tion of uranyl in the environment or the separation of uranyl in
spent nuclear waste.
7.23 (s, 2H, aryl CH), 8.09 (s, 2H, aryl CH), 12.32 (s, 1H, NH).
13C{1H} NMR (C6D6, 25 °C, 125 MHz): δ 32.1 (Me), 54.0 (CMe),
96.0 (γ-C), 128.0, 128.7, 128.8, 129.0, 129.1, 131.1, 138.8, 141.4, 166.8
(β-CN), 188.1 (β-CO). EIþ MS: m/z 279. UVꢀvis (CH2Cl2, 6.4 ꢁ
10ꢀ5 M): 355 nm (ε = 11600 L molꢀ1 cmꢀ1).
tBuNC(Ph)CHC(Ph)OSiMe3. To a Et2O solution (3 mL) of
tBuNHC(Ph)CHC(Ph)O (53 mg, 0.19 mmol) was added NaN-
(SiMe3)2 (35 mg, 0.19 mmol). The solution immediately turned pale
pink. Me3SiCl (50 μL, 0.39 mmol) was then added to the reaction
mixture, and the solution underwent a color change to yellow. After 2 h
of stirring, the solution was filtered through a Celite column (0.5 cm
ꢁ2.0 cm) supported on glass wool, and all volatiles were removed in vacuo
to provide a yellow oil. The product was extracted into hexanes (3 mL) and
refiltered through a Celite column (0.5 cm ꢁ2.0 cm) supported on glass
wool. The volatiles were removed in vacuo to give a yellow oil (54 mg, 81%
yield). 1H NMR (C6D6, 25 °C, 500 MHz): δ ꢀ0.16 (s, 9H, SiMe), 1.56 (s,
9H, Me), 6.16 (s, 1H, γ-CH), 6.92 ꢀ 7.42 (s, 6H, aryl CH), 7.56 (s, 2H,
arylCH), 8.12 (s, 2H, aryl CH). 13C{1H} NMR (C6D6, 25 °C, 125 MHz):
δ 1.0 (SiMe), 31.3 (Me), 35.5 (CMe), 107.3 (γ-C), 126.6, 129.0, 129.2,
129.3, 129.5, 139.5, 142.8, 152.6 (β-CN), 160.5 (β-CO). One aryl CH
resonance was not observed. EIþ MS: m/z 351.
’ EXPERIMENTAL SECTION
General Procedures. All reactions and subsequent manipulations
were performed under anaerobic and anhydrous conditions under either
high vacuum or an atmosphere of nitrogen or argon. THF, hexanes,
Et2O, and toluene were dried using a Vacuum Atmospheres DRI-SOLV
solvent purification system. CH2Cl2 and CD2Cl2 were dried over 3 Å
molecular sieves for 24 h before use. C6D6 was dried over activated 4 Å
molecular sieves for 24 h before use. UO2(N{SiMe3}2)2(THF)2 was
synthesized according to the previously reported procedure.40 UO2-
(Aracnac)2 (Ar = 3,5-tBu2C6H3) was also synthesized according to the
previously reported procedure.8 This complex exhibits a νsym(UdO) at
812 cmꢀ1 (see Supporting Information, Figure S7). All other reagents
were purchased from commercial suppliers and used as received.
NMR spectra were recorded on a Varian UNITY INOVA 400 or
Varian UNITY INOVA 500 spectrometer. 1H and 13C{1H} NMR
spectra were referenced to external SiMe4 using the residual protio
solvent peaks as internal standards (1H NMR experiments) or the
characteristic resonances of the solvent nuclei (13C NMR experiments).
31P{1H} NMR spectra were referenced to external 85% H3PO4. IR
spectra were recorded on a Mattson Genesis FTIR spectrometer. Raman
spectra were recorded on a Nicolet 6700 FTIR spectrometer with a NXR
FT Raman Module. UVꢀvis/NIR experiments were performed on a
UV-3600 Shimadzu spectrophotometer. Magnetic moments were de-
termined using the Evans’ method.22 Elemental analyses were per-
formed by the Micro-Mass Facility at the University of California,
Berkeley.
UO2(tBuacnac)2 (1). To a Et2O solution (3 mL) of BuNHC-
t
(Ph)=CHC(Ph)O (80 mg, 0.287 mmol) was added UO2(N-
{SiMe3}2)2(THF)2 (104 mg, 0.141 mmol). The solution immediately
turned orange, concomitant with the deposition of orange solid. After 24
h of stirring, the supernatant was decanted off, and the orange powder
was washed with Et2O (2 ꢁ 5 mL) and dried in vacuo (78 mg, 67%
yield). Analytically pure material was grown from a solution of dichlor-
omethane and hexane. Anal. Calcd for UO4N2C38H40 2CH2Cl2: C,
3
1
48.21; H, 4.45; N, 2.81 Found: C, 49.16; H, 4.34; N, 3.05. H NMR
(C6D6, 25 °C, 500 MHz): δ 1.73 (s, 18H, Me), 5.81 (s, 2H, γ-CH), 6.99
(br s, 6H, aryl CH), 7.11 ꢀ 7.18 (br s, 4H, aryl CH), 7.20 (br s, 6H, aryl
CH), 8.17 (br s, 4H, aryl CH). 13C{1H} NMR (CD2Cl2, 25 °C, 125
MHz): δ 33.6 (Me), 102.9 (γ-C), 127.6, 127.9, 128.4, 129.0, 130.6,
131.1, 139.7, 146.5, 171.8 (β-CN), 173.4 (β-CO). The (CMe) reso-
nance was not observed. UVꢀvis (CH2Cl2, 3.1 ꢁ 10ꢀ5 M): 343 nm (ε =
18900 L molꢀ1 cmꢀ1). IR (KBr pellet, cmꢀ1): 1608(m), 1588(s),
1562(s), 1481(s), 1459(s), 1396(w), 1383(m), 1367(m), 1341(s),
1303(w), 1276(m), 1241(w), 1227(m), 1197(s), 1135(w), 1077(w),
1059(m), 1027(m), 1003(w), 973(w), 907(s, νasym(UdO)), 857(w),
815(w), 758(s), 705(s), 694(s), 626(w), 594(w), 554(m), 532(m),
502(m). Raman (cmꢀ1): 823 (s, νsym(UdO)).
[Ph3PI][U(OSiMe3)2I4] (2). To an orange suspension of 1 (135 mg,
0.163 mmol) in toluene (3 mL) was added Me3SiI (240 μL, 1.90 mmol).
The solution immediately turned deep red. After stirring for 60 min, the
solution was filtered through a Celite column (0.5 cm ꢁ2.0 cm)
supported on glass wool. Triphenylphosphine (44 mg, 0.17 mmol)
was then added to the reaction mixture. After 15 min of stirring the
deposition of black microcrystalline material was observed. The solid
was isolated and extracted into dichloromethane (3 mL). Storage of
this solution at ꢀ25 °C for 24 h resulted in the deposition of black
crystals suitable for X-ray analysis (85 mg, 40% yield). The reaction
can also be performed in the presence of 0.5 equiv of Ph3P; however,
the isolated yield is slightly reduced (34%). Anal. Calcd for
UO2C24H33Si2P1I5: C, 21.95; H, 2.53; N, 0.00. Found: C, 22.43;
H, 2.20; N, <0.2. 1H NMR (CD2Cl2, 25 °C, 500 MHz): δ 2.17
(s, 18H, Me), 4.03 (s, 18H, Me), 7.38 (q, 6H, JHH = 7.7 Hz, ortho
CH), 7.61 (br s, 6H, meta CH), 7.77 (t, 3H, JHH = 7.1 Hz, para CH).
31P{1H} NMR: (CD2Cl2, 25 °C, 202 MHz): δ 11.6 (br s). UVꢀ
vis/NIR (CH2Cl2, 4.5 ꢁ 10ꢀ3 M): 1102 nm (ε = 10 L molꢀ1
cmꢀ1), 1478 nm (ε=6.6 Lmolꢀ1 cmꢀ1), 1570 nm (ε=11Lmolꢀ1 cmꢀ1),
1664 nm (ε = 4.0 L molꢀ1 cmꢀ1). IR (KBr pellet, cmꢀ1): 1480(w),
1437(m), 1367(w), 1351(w), 1252(s), 1164(m), 1125(s), 1102(s),
1067(s), 997(m), 924(m), 851(s), 812(s), 756(s), 725(s), 689(s),
Cyclic Voltammetry Measurements. CV experiments were
performed with a CH Instruments 600c Potentiostat, and the data were
processed using CHI software (version 6.29). All experiments were
performed in a glovebox using a 20 mL glass vial as the cell. The working
electrode consisted of a platinum disk embedded in glass (2 mm
diameter), the counter electrode was a platinum wire, and the reference
electrode consisted of AgCl plated on Ag wire. Solutions employed
during CV studies were typically 1 mM in the metal complex and 0.1 M
in [Bu4N][PF6]. All potentials are reported versus the [Cp2Fe]0/þ
couple. For all trials, ip,a/ip,c = 1 for the [Cp2Fe]0/þ couple, while ip,c
√
increased linearly with the square root of the scan rate (i.e., v). Redox
couples which exhibited behavior similar to the [Cp2Fe]0/þ couple were
thus considered reversible.
tBuNHC(Ph)=CHC(Ph)O. To a yellow solution of diphenylpropy-
none (1.0972 g, 0.0053 mol) in toluene (20 mL) was added tert-
butylamine (6.0 mL, 0.057 mol) and Zn(OTf)2 (200 mg, 0.55 mmol).
After heating to reflux for 48 h, the volatiles were removed in vacuo to
provide a pale yellow solid. This material was extracted into Et2O
(20 mL) and filtered through a Celite column (0.5 cm ꢁ2.0 cm)
supported on glass wool. The volatiles were removed in vacuo to give a
pale yellow solid which was washed with hexane (3 ꢁ 5 mL). 1.2833 g,
86% yield. 1H NMR (C6D6, 25 °C, 500 MHz): δ 1.00 (s, 9H, Me), 5.82
(s, 1H, γ-CH), 7.07 (br s, 3H, aryl CH), 7.10 ꢀ 7.20 (m, 3H, aryl CH),
5110
dx.doi.org/10.1021/ic200387n |Inorg. Chem. 2011, 50, 5105–5112