Inorganic Chemistry
Article
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30.1, 17.2, 10.2, 7.4, 6.7, 0.9, −0.1, −9.2, −12.4, −13.6, −31.7 (all
broad singlets). IR (KBr solution cell, benzene): 3389 cm−1. UV−vis
(C6H6) λmax, nm (ε): 501 (197), 607 (49), 669 (58). Evans’ method
(C6D6): 5.77 μB. Anal. Calcd for C60H69CuMnN4P4: C, 66.20; H, 6.39;
N, 5.15. Found: C, 66.12; H, 6.43; N, 5.23.
Hz, 12H, Ar-H), 6.95 (t, JHH = 7.2 Hz, 6H, Ar-H), 3.31 (bs, 3H, Pr−
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CH), 2.89 (bs, 3H, -NH), 0.82 (d, JHH = 6.0 Hz, 18H, Pr−CH3).
13C{1H} NMR (100.53 MHz, C6D6), δ 136.7, 132.7, 128.8 (s), 46.0 (s,
iPr-CH), 25.7 (s, iPr-CH3) ppm. 31P{1H} NMR (161.84 MHz, C6D6),
δ 31.0 ppm. IR (KBr solution cell, THF): 3294 cm−1. Anal. Calcd for
C45H51CuIN3P3: C, 58.92; H, 5.60; N, 4.58. Found: C, 58.69; H, 5.95;
N, 4.49.
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[Fe(iPrNPPh2)3Cu(iPrNHPPh2)] (2). A solution of PrNHPPh2
(0.243 g, 1.00 mmol) in THF (5 mL) was cooled to −78 °C. To
this, nBuLi (0.630 mL, 1.6 M in hexanes, 1.0 mmol) was added
dropwise over 10 min. The resulting pale yellow solution was warmed
[Cu(PPh2NHiPr)3][PF6]. A solution of [ICu(PPh2NHiPr)3] (160
mg, 0.18 mmol) in THF (5 mL) was cooled to −32 °C, and this was
added to a THF (5 mL) solution of TlPF6 (61 mg, 0.18 mmol). The
resulting solution was warmed to room temperature and stirred for 1
h. Solid TlI was removed via filtration, and all volatiles were removed
from the filtrate in vacuo. The remaining colorless material was washed
with pentane (2 × 2 mL) to obtain 5 as an analytically pure crystalline
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to room temperature and stirred for 2 h to form PrNLiPPh2 in situ.
The mixture was then cooled again to −78 °C, and FeCl2 (32 mg, 0.25
mmol) in cold THF (3 mL) was added dropwise over 5 min. The
reaction mixture was gradually warmed to room temperature and
stirred for 10 min. To the resulting mixture, solid CuI (48 mg, 0.25
mmol) was added, and the mixture was continuously stirred for 12 h.
The insoluble materials were removed via filtration, and all volatiles
were subsequently removed in vacuo. The remaining crude olive green
material was extracted with Et2O (3 × 2 mL). Upon standing at room
temperature, the concentrated Et2O solution of 2 yielded analytically
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solid (160 mg, 98%). H NMR (400 MHz, C6D6): δ 7.27 (bs, 12H,
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Ar-H), 7.05−6.97 (m, 18H, Ar-H), 3.15 (bs, 3H, Pr−CH), 2.90 (bs,
3H, -NH), 0.87 (d, JHH = 6.0 Hz, 18H, Pr−CH3). 13C{1H} NMR
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(100.53 MHz, C6D6): δ 135.5 (bm), 132.9 (b), 130.2 (s), 128.9 (s),
46.9 (s, Pr-CH), 25.9 (s, Pr-CH3). 31P{1H} NMR (161.84 MHz,
C6D6): δ 36.6 (s), −141.9 (sept, JPF = 718 Hz). 19F{1H} NMR (376.11
MHz, C6D6): δ 82.5 (d, JFP = 718 Hz). IR (KBr solution cell, THF):
3379, 3274 cm−1. Anal. Calcd for C45H54CuN3P4F6: C, 57.60; H, 5.80;
N, 4.48. Found: C, 57.66; H, 5.89; N, 4.51.
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pure olive green blocks of 2 (230 mg, 85%). H NMR (400 MHz,
C6D6): δ 29.8, 17.2, 10.3, 7.2, 6.0, 1.1, 0.0, −9.2, −12.4, −13.9 (all
broad singlets). IR (KBr solution cell, benzene): 3366 cm−1. UV−vis
(C6H6) λmax, nm (ε): 495 (367), 671 (107). Evans’ method (C6D6):
4.98 μB. Anal. Calcd for C60H69CuFeN4P4: C, 66.14; H, 6.38; N, 5.14.
Found: C, 66.24; H, 6.45; N, 5.09.
Electrochemistry. CV measurements were carried out in a
glovebox under a dinitrogen atmosphere in a one-compartment cell
using a CH Instruments electrochemical analyzer. A glassy carbon
electrode and platinum wire were used as the working and auxiliary
electrodes, respectively. The reference electrode was Ag/AgNO3 in
THF. Solutions of electrolyte (0.40 M [nBu4N][PF6] in THF) and
analyte (2 mM) were also prepared in the glovebox. All potentials are
reported versus an internal ferrocene/ferrocenium reference.
[Fe(iPrNPPh2)3Cu2(iPrNPPh2)]·Et2O (3). A solution of iPrNHPPh2
(0.243 g, 1.00 mmol) in THF (5 mL) was cooled to −78 °C. To this,
nBuLi (0.63 mL, 1.6 M in hexanes, 1.0 mmol) was added dropwise
over 10 min. The resulting pale yellow solution was warmed to room
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temperature and stirred for 2 h to form PrNLiPPh2 in situ. The
mixture was then cooled again to −78 °C, and FeCl2 (32 mg, 0.25
mmol) in cold THF (3 mL) was added dropwise over 5 min. The
reaction mixture was gradually warmed room temperature and stirred
for 10 min. To the resulting mixture, solid CuI (96 mg, 0.5 mmol) was
added, and the mixture was continuously stirred for 12 h. The
insoluble materials were removed via filtration, and all volatiles were
subsequently removed in vacuo. The remaining crude orange material
was extracted with Et2O (3 × 2 mL). Upon standing at room
temperature, the concentrated Et2O solution of 3 yielded analytically
pure orange blocks of 3 (260 mg, 92%). 1H NMR (400 MHz, C6D6):
δ 25.7, 16.4, 10.7, 6.9, 4.0, 3.9, −3.6, −10.9, −12.2 (bs) ppm. UV−vis
(C6H6) λmax, nm (ε): 485 (135), 671 (53). Evans’ method (C6D6):
4.89 μB. Anal. Calcd for C60H68Cu2FeN4P4: C, 62.55; H, 5.95; N, 4.86.
Found: C, 61.64; H, 5.87; N, 4.75 (Vacuum dried samples lost lattice
ether solvate).
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Mossbauer Spectroscopy. Iron-57 Mossbauer spectra were
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measured on a constant acceleration spectrometer (SEE Co,
Minneapolis, MN) with a Janis SVT-100 cryostat. Isomer shifts are
quoted relative to α-Fe foil (<25 μm thick) at room temperature. The
Fe foil standard spectrum has linewidths Γ (fwhm) of 0.292 and 0.326
mm/s for the doublets within the 4 mm/s window when measured
outside the cryostat at room temperature. A sample of 3 was prepared
using approximately 30 mg of sample suspended in paratone-N oil.
Data were analyzed using a package written by E. R. King and
modified by E. V. Eames in Igor Pro (Wavemetrics) using a simple
model consisting of Lorentzian lineshapes with optional asymmetry.
Computational Details. All calculations were performed using
Gaussian09-E.0154 for the Linux operating system. Density functional
theory calculations were carried out using a combination of Becke’s
1988 gradient-corrected exchange functional59 and Perdew’s 1986
electron correlation functional60 (BP86). For open shell systems,
unrestricted wave functions were used in energy calculations. A mixed-
basis set was employed, using the LANL2TZ(f) triple-ζ basis set with
effective core potentials for iron and copper,61−63 Gaussian09’s
internal 6-311+G(d) for atoms bonded directly to the metal centers
(nitrogen and phosphorus), and Gaussian09’s internal LANL2DZ
basis set (equivalent to D95 V64) for carbon and hydrogen. Starting
with crystallographically determined geometries as a starting point,
when available, the geometries were optimized to a minimum,
followed by analytical frequency calculations to confirm that no
imaginary frequencies were present. NBO analysis was performed
using NBO 3.1,65 as implemented by Gaussian09.
Isolation of [iPrNLiPPh2(THF)]2. The lithium amide was isolated
in a similar fashion and displays similar spectroscopic signatures to the
previously reported Et2O adduct.56 A solution of iPrNHPPh2 (243 mg,
1.00 mmol) in THF (5 mL) was cooled to −78 °C. To this solution,
nBuLi (0.63 mL, 1.6 M in hexanes, 1.0 mmol) was added dropwise
over 10 min. The resulting pale yellow solution was warmed to room
temperature and stirred for 2 h. All volatiles were removed from the
reaction mixture and washed cold pentanes (2 × 2 mL) to obtain a
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pale yellow solid (240 mg, 75%). H NMR (400 MHz, C6D6): δ 7.74
(d, JHH = 4.4 Hz, 4H, Ar-H), 7.19 (t, JHH = 7.2 Hz, 4H, Ar-H), 7.13
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(dd, JHH = 7.2 Hz, 2H, Ar-H), 3.86 (bs, 1H, Pr−CH), 3.39 (t, JHH
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6.0 Hz, 4H, THF-CH2), 1.27 (d, JHH = 6.0 Hz, 6H, iPr−CH3), 1.22 (t,
JHH = 6.0 Hz, 4H, THF-CH2). 13C{1H} NMR (100.53 MHz, C6D6), δ
133.3, 133.2, 133.1 (overlapping multiplets), 126.9 (s), 68.4 (s, THF-
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CH2), 48.8 (s, Pr-CH), 29.6 (s, Pr-CH3), 25.3 (s, THF-CH2) ppm.
31P{1H} NMR (161.84 MHz, C6D6), δ 39.7 ppm.
X-ray Crystallography. All operations were performed on a
Bruker-Nonius Kappa Apex2 diffractometer, using graphite-mono-
chromated MoKα radiation. All diffractometer manipulations,
including data collection, integration, scaling, and absorption
corrections were carried out using the Bruker Apex2 software.66
Preliminary cell constants were obtained from three sets of 12 frames.
Crystallographic parameters are provided in Supporting Information,
Table S1 and further experimental crystallographic details are
described for each compound in the Supporting Information.
[ICu(PPh2NHiPr)3] (4). Solid CuI (64 mg, 0.33 mmol) was added
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to a cold THF (5 mL) solution of PrNHPPh2 (0.243 g, 1.00 mmol).
The resulting mixture was warmed to room temperature and
continuously stirred for 12 h. The insoluble materials were removed
via filtration, and the volatiles were removed from the filtrate in vacuo.
Colorless blocks of 4 were obtained from the benzene/pentane
mixture upon recrystallization at room temperature (290 mg, 95%).
1H NMR (400 MHz, C6D6): δ 7.20 (bs, 12H, Ar-H), 7.04 (t, JHH = 6.8
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dx.doi.org/10.1021/ic202165z | Inorg. Chem. 2012, 51, 1866−1873