Organometallics
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(400 MHz, C6D6, 293 K): −108.23 (s, 2H, CH(CH3)2); −43.6 (s, 6H,
NC(CH3)), −18.44 (s, 2H, CH Ar), −14.00 (s, 6H, CH(CH3)2), −8.53
(s, 2H, CH(CH3)2), −8.09 (s, 6H, CH(CH3)2), −6.94 (s, 2H, CH Ar),
−2.27 (s, 6H, C5(CH3)4H), −0.63 (s, 2H, CH Ar), 1.36 (s, 6H,
C5(CH3)4H), 7.02 (s, 1H, C5(CH3)4H), 20.43 (s, 6H, CH(CH3)2),
36.10 (s, 6H, CH(CH3)2), 58.63 (s, 4H, C4H8O), 125.48 (s, 4H,
C4H8O). IR (Nujol, KBr, cm−1): 1591 (s), 1267 (s), 1183 (m), 1122 (s),
1043 (m), 937 (m), 765 (m), 523 (m). Anal. Calcd for C41H61N2OYb:
C, 63.82; H, 7.96; N 3.63; Yb, 22.44. Found: C, 63.41; H, 7.80; N, 3.23;
Yb 22.59. 6: IR (Nujol, KBr, cm−1) 1326 (m), 1149 (s), 1019 (m), 969
(m), 608 (m). Anal. Calcd for C29H37Yb: C, 64.85; H, 6.90; Yb, 27.43.
Found: C, 64.49; H, 7.15; Yb, 27.59.
auxiliary electrode, and a saturated silver chloride electrode was used as
the reference electrode. The potential of the Fc/Fc+ redox couple in our
experimental conditions is +0.53 V.
Crystal Structure Determination of 3−9. X-ray diffraction
intensity data for compounds 3−9 were collected on Bruker Smart
APEX-II (3) and Bruker Smart APEX (4, 5HT, 6−9) diffractometers
with graphite monochromated Mo−Kα radiation (λ = 0.71073 Å) using
ω scans. The structures were solved by direct methods and were refined
on F2 using the SHELXTL package.23 All non-hydrogen atoms were
found from Fourier syntheses of electron density and were refined
anisotropically. All hydrogen atoms were placed in calculated positions
and were refined in the riding model with Uiso(H) = 1.2 Ueq (Uiso(H) =
1.5 Ueq for the hydrogen atoms in CH3 groups) of their parent atoms.
SADABS24 was used to perform area-detector scaling and absorption
corrections.
A crystal of 5LT was glued under an inert gas atmosphere on a
MiTeGenMicroMount, mounted on a Huber 4-circle diffractometer
equipped with a 4K-Displex closed-cycle helium cryostat and was cooled
to 9(1) K. Preliminary examination and final data collection were carried
out with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å)
generated from a Bruker FR 591 rotating anode running at 50 kV and
60 mA. Intensity data were collected employing a MAR345 IP Detector
and 1° φ-scans with a detector-to-sample distance of 160 mm.
The systematic pseudo-merohedrically twining of the crystals of
5LT afforded an empirical absorption correction using the program
TWINABS25 (Tmin = 0.3195, Tmax = 0.4305) for a total of 58 914
reflections and 15 169 unique reflections (Rint = 0.0214). For the
refinements, a HKLF5 formatted data file with 29 621 reflections was
used. Subsequent full-matrix least-squares refinements against F2 were
carried out using the SHELXL97 program.26 All non-hydrogen atoms
were found from Fourier syntheses of electron density and were refined
anisotropically. All hydrogen atoms were placed in geometrically idealized
positions and treated as riding with Uiso(H) = 1.2 Ueq (Uiso(H) = 1.5 Ueq
for the hydrogen atoms in CH3 groups) of their parent atoms. Due to
strong correlation between the parameters of the two crystallographically
independent molecules in the unit cell, it was necessary to restrain the
displacement parameters of seven atoms to be isotropic. A batch scaling
factor was introduced to describe the twin volume fractions, resulting in a
0.6813/0.3187 ratio for the volume of domains 1 and 2, respectively. Low
values of completeness (90.8% for θ = 26° and 85.6% for θ = 25°) are
explained by poor quality of the crystal specimen.
Crystal data and details of data collection and structure refinement
for the different compounds are given in Table S1 (Supporting
Information). Main crystallographic data (excluding structure factors)
are available as Supporting Information, as CIF files. CCDC-1024539
(3), 1024540 (4), 1024541 (5LT), 1024542 (5HT), 1031761 (6),
1024543 (7), 1024544 (8), and 1024545 (9) contain the supplementary
crystallographic data for this paper; crystallographic data for 1 and 2
were previously published7 as CCDC-607546 (1) and 607547 (2).
Magnetic Measurements. Magnetic susceptibility data were
collected with a Quantum Design MPMS-XL SQUID magnetometer
working between 1.8 and 350.0 K with the magnetic field up to 7 T.
The samples were prepared in a glow box and kept in an anaerobic
atmosphere. The magnetic data were corrected for the sample holder,
and the diamagnetic contributions were calculated from the Pascal’s
constants.27
Synthesis of (Me3Si)2Yb(DAD4iPr2Me)(dme) (7). A solution of
DAD4iPr2Me (0.80 g, 1.98 mmol) in thf (20 mL) was added to Na
shavings (0.09 g, 3.96 mmol), and the reaction mixture was stirred at
room temperature for 3 days until complete dissolution of the metal.
The resulting dark-red solution was filtered and added slowly to a
solution of (1.98 mmol) ((Me3Si)2N)YbCl2(THF)n, which was
obtained in situ from YbCl3 (0.55 g, 1.98 mmol) and NaN(SiMe3)2
(0.36 g, 1.98 mmol) in thf (15 mL) (60 °C, 72 h). The reaction mixture
was stirred at room temperature for 2 days (20 °C). The resulting
brownish-green solution was filtered, the volatiles were evaporated in
vacuum, the resulting solid residue was extracted with toluene (25 mL),
and the extracts were filtered. Toluene was then evaporated in vacuum.
Recrystallization of the solid residue from a DME−hexane (1:3) mixture
(20 °C) afforded 7 as blue green crystals (0.72 g, 44%). IR (Nujol,
KBr, cm−1): 1583 (s), 1252 (s), 1202 (s), 1120 (m), 1091 (m), 1043
(m), 826 (m), 763 (m), 670 (m). Anal. Calcd for C38H68N3O2Si2Yb: C,
55.06; H, 8.21; N, 5.07; Yb, 20.89; found: C, 55.83; H, 8.01; N, 5.99; Yb,
21.07.
Synthesis of (tBuO)Yb(DAD4iPr2Me)(dme) (8). A solution of
DAD4iPr2Me (0.88 g, 2.18 mmol) in THF (20 mL) was added to an
excess of Na shavings (0.10 g, 4.36 mmol), and the reaction mixture was
stirred at room temperature for 3 days until complete dissolution of the
metal. The resulting dark-red solution was filtered and added slowly to
a solution of (2.18 mmol) (tBuO)YbCl2(THF)n, which was obtained
in situ from YbCl3 (0.61 g, 2.18 mmol) and tBuOK (0.24 g, 2.18 mmol)
in THF (15 mL) (60 °C, 72 h). The reaction mixture was stirred at room
temperature for 2 days (20 °C). The resulting brownish-green solution
was filtered, the solvent was evaporated in vacuum, the resulting solid
residue was extracted with toluene (25 mL), and the extracts were
filtered. Toluene was then evaporated in vacuum. Recrystallization of
the solid residue from a DME−hexane (1:4) mixture (20 °C) afforded 8
as blue green crystals (0.93 g, 58%). IR (Nujol, KBr, cm−1):1589 (s),
1269 (s), 1210 (s), 1197 (m), 1148 (m), 1088 (s), 1029 (m), 825 (m),
793 (m), 752 (m), 696 (m), 553 (m). Anal. Calcd for C36H59N2O3Yb:
C, 58.31; H, 7.96; N, 3.78; Yb, 23.36; found: C, 57.95; H, 8.09; N, 3.99;
Yb 23.83.
Synthesis of {Li(thf)3}{Yb[4iPr2MeDAD][N(SiMe3)2](μ-Cl)} (9). A
solution of 4iPr2MeDAD (0.57 g, 1.41 mmol) in THF (20 mL) was added
to Li shavings (0.02 g, 2.82 mmol), and the reaction mixture was stirred
at room temperature for 3 days until complete dissolution of the metal.
The resulting dark-red solution was filtered and added slowly to a
solution of (1.41 mmol) [(Me3Si)2N]YbCl2(THF)n, which was obtained
in situ from YbCl3 (0.39 g, 1.41 mmol) and LiN(SiMe3)2(Et2O) (0.34 g,
1.41 mmol) in THF (15 mL) (60 °C, 72 h). The reaction mixture was
stirred at room temperature for 2 days. The solvent was evaporated in
vacuum, and the resulting solid residue was extracted with toluene
(25 mL). Recrystallization from a THF−hexane mixture afforded 9 as
blue green crystals (0.59 g, 42%). IR (Nujol, KBr, cm−1):1586 (s),
1249(s), 1115(s), 1038(s), 937 (m), 887 (m), 773 (m), 728 (m), 561
(s), 527 (s). Anal. Calcd for C46H83ClLiN3O3Si2Yb: C, 55.32; H, 8.32;
N, 4.21; Yb, 17.34; found: C, 55.00; H, 8.13; N, 3.99; Yb 18.07.
Electrochemical Studies. Electrochemical studies were carried out
using an IPC-Win digital potentiostat/galvanostat connected to a PC.
Voltammograms were recorded by cyclic voltammetry (CV) at a
stationary Pt disk electrode (d = 3.2 mm) at different potential scan rates
in DMF using a 0.05 M n-Bu4NBF4 solution as the supporting elec-
trolyte at 20 °C in a 10 mL electrochemical cell. Oxygen was removed
from the cell by purging with dry argon. Platinum wire served as the
ASSOCIATED CONTENT
■
S
* Supporting Information
CV curves, molecular structure, table of crystallographic data and
structure refinement details, IR spectra, UV/vis spectra, and 1H
NMR spectra. This material is available free of charge via the
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Organometallics 2015, 34, 1177−1185