Inorganic Chemistry
Article
C41H59BrN2: C, 74.63; H, 9.01; N, 4.25. Found: C, 74.25; H, 9.11; N,
4.31.
7.39−7.24 (m, 10 H, Ar-H), 6.77 (s, 2 H, Ar-H-BI), 6.04 (s, 4 H,
NCH2Ar), 4.72 (t, J = 2.8 Hz, 2 H, COD-CH), 2.90 (t, J = 2.8 Hz, 2
H, COD-CH), 2.21−2.11 (m, 2 H, COD-CH2), 2.16 (s, 6 H, Ar−
CH3-BI), 2.01−1.95 (m, 2 H, COD-CH2), 1.74−1.68 (m, 2 H, COD-
CH2), 1.58−1.48 (m, 2 H, COD-CH2). 13C NMR (100.6 MHz,
CDCl3, TMS, 25 °C, ppm): δ = 191.7 (Ir-Ccarbene), 136.6 (Ar-C), 133.9
(Ar-C), 131.9 (Ar-C), 129.0 (Ar-C), 127.9 (Ar-C), 127.3 (Ar-C), 111.8
(Ar-C), 87.0 (COD-CH), 53.1 (NCH2Ar), 52.6 (COD-CH), 33.6
(COD-CH2), 29.5 (COD-CH2), 20.4 (Ar-CH3−BI). Anal. Calc. for
C31H34ClN2Ir: C, 56.22; H, 5.17; N, 4.23. Found: C, 56.31; H, 5.13;
N, 4.19.
1,3-Dibenzyl(5,6-dimethyl)benzimidazolium bromide (3). A
mixture of 5,6-dimethyl-1-H-benzimidazole (340 mg, 5 mmol) and
K2CO3 (760 g, 11 mmol) was suspended in CH3CN (10 mL) and
stirred at ambient temperature for 1 h. Benzyl bromide (855 mg, 5
mmol) was then added to the suspension. The reaction mixture was
stirred under reflux conditions for 24 h. The solution was filtered-off,
and the solvent was removed under reduced pressure. The resulting
crude product was dissolved in toluene (15 mL), and a second portion
of benzyl bromide (855 mg, 5 mmol) was added and stirred at reflux
conditions for 24 h. The white solid that separated out after cooling to
room temperature was filtered off and washed with diethyl ether (2 ×
20 mL) and dried under reduced pressure (1.90 g, 93%). Mp: 205−
Chloro(dicarbonyl)[1,3-bis(2,4,6-triisopropylbenzyl)imidazol-2-
ylidene] Iridium(I) (1b). Complex 1a (83.7 mg, 0.1 mmol) was
dissolved in CH2Cl2 (5 mL) and carbon monoxide was bubbled
through the solution for 30 min. Color of the solution changed from
yellow to pale yellow. The solution was concentrated ca. 1 mL and
pentane (5 mL) was added. The pale yellow solid that separated out
was filtered and washed with pentane and dried under reduced
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206 °C. H NMR (400 MHz, CDCl3, TMS, 25 °C, ppm): δ = 11.72
(s, 1 H, NCHN+), 7.50−7.48 (m, 4 H, Ar-H), 7.39−7.33 (m, 6 H, Ar-
H), 7.30 (s, 2 H, Ar-H-BI), 5.81 (s, 4 H, NCH2Ar), 2.33 (s, 6 H, Ar−
CH3-BI), 13C NMR (100.6 MHz, CDCl3, TMS, 25 °C, ppm): δ =
142.2 (NCHN+), 137.7 (Ar-C), 133.0 (Ar-C), 130.1 (Ar-C), 129.6
(Ar-C), 129.4 (Ar-C), 128.4 (Ar-C), 113.5 (Ar-C), 51.5 (NCH2Ar),
20.9. Anal. Calc. for C23H23BrN2: C, 67.82; H, 5.69; N, 6.88. Found:
C, 67.68; H, 5.73; N, 6.81.
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pressure (72 mg, 92%). IR (CH2Cl2): νCO = 2068, 1985 cm−1. H
NMR (400 MHz, CDCl3, TMS, 25 °C, ppm): δ = 7.17 (s, 4 H, Ar-H),
6.23 (s, 2 H, NCHCHN), 5.54 (d, J = 14.8 Hz, 2 H, NCH2Ar), 5.31
(d, J = 14.8 Hz, 2 H, NCH2Ar), 3.10−3.02 (m, 4 H, ArCH(CH3)2),
2.85−2.78 (m, 2 H, ArCH(CH3)2), 1.17 (d, J = 6.8 Hz, 24 H,
ArCH(CH3)2), 1.02 (d, J = 6.8 Hz, 12 H, ArCH(CH3)2). 13C NMR
(100.6 MHz, CDCl3, TMS, 25 °C, ppm): δ = 181.9 (Ir-CO), 173.3
(Ir-Ccarbene), 168.2 (Ir-CO), 150.4 (Ar-C), 148.9 (Ar-C), 125.3 (Ar-C),
121.9 (NHCCHN),), 119.8 (Ar-C), 48.0 (NCH2Ar), 34.5 (ArCH-
(CH3)2), 29.9 (ArCH(CH3)2), 24.5 (ArCH(CH3)2), 24.2 (ArCH-
(CH3)2), 24.1 (ArCH(CH3)2).
Chloro(dicarbonyl)[1,3-bis(2,4,6-triisopropylbenzyl)-(5,6-
dimethyl)benzimidazol-2-ylidene] Iridium(I) (2b). Complex 2b was
prepared in analogy to 1b from the complex 2a (91.5 mg, 0.1 mmol).
Pale yellow solid (81 mg, 94%). IR (CH2Cl2): νCO = 2067, 1983 cm−1.
1H NMR (400 MHz, CDCl3, TMS, 25 °C, ppm): δ = 7.00 (s, 4 H, Ar-
H), 6.02 (d, J = 15.2 Hz, 2 H, NCH2Ar), 5.98 (s, 2 H, Ar-H-BI), 5.65
(d, J = 15.2 Hz, 2 H, NCH2Ar), 3.35−3.20 (m, 4 H, ArCH(CH3)2),
2.88−2.84 (m, 2 H, ArCH(CH3)2), 1.84 (s, 6 H, Ar−CH3-BI), 1.20 (d,
J = 6.8 Hz, 24 H, ArCH(CH3)2), 1.11 (d, J = 6.8 Hz, 12 H,
ArCH(CH3)2). 13C NMR (100.6 MHz, CDCl3, TMS, 25 °C, ppm): δ
= 183.2 (Ir-Ccarbene), 181.8 (Ir-CO), 168.3 (Ir-CO), 150.5 (Ar-C),
149.2 (Ar-C), 133.8 (Ar-C), 132.2 (Ar-C), 125.8 (Ar-C), 121.7 (Ar-C),
113.0 (Ar-C), 49.1 (NCH2Ar), 34.6 (ArCH(CH3)2), 30.1 (ArCH-
(CH3)2), 24.4 (ArCH(CH3)2), 24.3 (ArCH(CH3)2), 20.2 (Ar-CH3−
BI).
Chloro(μ4-1,5-cyclooctadiene)[1,3-bis(2,4,6-triisopropylbenzyl)-
imidazol-2-ylidene] Iridium(I) (1a). Under an argon atmosphere, a
mixture of 1 (291 mg, 0.5 mmol) and Ag2O (52 mg, 0.5 mmol) was
suspended in degassed CH2Cl2 (5 mL) and stirred at ambient
temperature for 1 h shielded from light. [IrCl(COD)]2 (168 mg, 0.25
mmol) was then added to the suspension, and the reaction mixture
was stirred at ambient temperature for more 12 h. The resulting
suspension was filtered over Celite. The remaining solid was washed
with CH2Cl2 (2 × 5 mL), and the solvent of the filtrate was
evaporated. The residue was purified by column chromatography on
silica gel (eluent: CH2Cl2) to give pure complex as a yellow solid (348
mg, 83%). 1H NMR (400 MHz, CDCl3, TMS, 25 °C, ppm): δ = 7.05
(s, 4 H, Ar-H), 6.15 (s, 2 H, NCHCHN), 5.91 (d, J = 14.4 Hz, 2 H,
NCH2Ar), 5.38 (d, J = 14.4 Hz, 2 H, NCH2Ar), 4.71 (t, J = 2.4 Hz, 2
H, COD-CH), 3.25 (t, J = 2.4 Hz, 2 H, COD-CH), 3.22−3.14 (m, 4
H, ArCH(CH3)2), 2.94−2.87 (m, 2 H, ArCH(CH3)2), 2.32−2.28 (m,
4 H, COD-CH2), 1.81−1.71 (m, 4 H, COD-CH2), 1.26 (d, J = 6.8 Hz,
12 H, ArCH(CH3)2), 1.22 (d, J = 6.8 Hz, 12 H, ArCH(CH3)2), 1.15
(d, J = 6.8 Hz, 12 H, ArCH(CH3)2). 13C NMR (100.6 MHz, CDCl3,
TMS, 25 °C, ppm): δ = 180.2 (Ir-Ccarbene), 149.9 (Ar-C), 149.2 (Ar-C),
125.9 (Ar-C), 121.7 (NHCCHN),), 118.4 (Ar-C), 84.6 (COD-CH),
51.8 (COD-CH), 47.0 (NCH2Ar), 34.5 (ArCH(CH3)2), 34.0 (COD-
CH2), 29.9 (COD-CH2), 29.8 (ArCH(CH3)2), 24.6 (ArCH(CH3)2),
24.3 (ArCH(CH3)2), 24.2 (ArCH(CH3)2). Anal. Calc. for
C43H64ClN2Ir: C, 61.73; H, 7.71; N, 3.35. Found: C, 61.99; H, 7.64;
N, 3.31.
Chloro(dicarbonyl)[1,3-dibenzyl-(5,6-dimethyl)benzimidazol-2-
ylidene] Iridium(I) (3b). Complex 3b was prepared in analogy to 1b
from the complex 3a (66 mg, 0.1 mmol). Pale yellow solid (58 mg,
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95%). IR (CH2Cl2): νCO = 2071, 1988 cm−1. H NMR (400 MHz,
Chloro(μ4-1,5-cyclooctadiene)[1,3-bis(2,4,6-triisopropylbenzyl)-
(5,6-dimethyl)benzimidazol-2-ylidene] Iridium(I) (2a). Complex 2a
was prepared in analogy to 1a from the salt 2 (330 mg, 0.5 mmol).
CDCl3, TMS, 25 °C, ppm): δ = 7.35−7.29 (m, 10 H, Ar-H), 6.96 (s, 2
H, Ar-H-BI), 5.99 (d, J = 15.6 Hz, 2 H, NCH2Ar), 5.76 (d, J = 15.6 Hz,
2 H, NCH2Ar), 2.22 (s, 6 H, Ar−CH3-BI). 13C NMR (100.6 MHz,
CDCl3, TMS, 25 °C, ppm): δ = 182.8 (Ir-Ccarbene), 181.4 (Ir-CO),
168.0 (Ir-CO), 135.4 (Ar-C), 133.8 (Ar-C), 133.2 (Ar-C), 129.2 (Ar-
C), 128.4 (Ar-C), 127.4 (Ar-C), 112.4 (Ar-C), 52.9 (NCH2Ar), 20.6
(Ar-CH3−BI).
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Yellow solid (371 mg, 81%). H NMR (400 MHz, CDCl3, TMS, 25
°C, ppm): δ = 7.08 (s, 4 H, Ar-H), 6.50 (d, J = 14.8 Hz, 2 H,
NCH2Ar), 5.78 (d, J = 14.8 Hz, 2 H, NCH2Ar), 5.69 (s, 2 H, Ar-H-
BI), 4.77 (t, J = 2.8 Hz, 2 H, COD-CH), 3.41−3.34 (m, 4 H,
ArCH(CH3)2), 3.18 (t, J = 2.4 Hz, 2 H, COD-CH), 2.96−2.92 (m, 2
H, ArCH(CH3)2), 2.34−2.27 (m, 4 H, COD-CH2), 1.84 (s, 6 H, Ar−
CH3-BI), 1.76−1.71 (m, 4 H, COD-CH2), 1.29 (d, J = 6.4 Hz, 24 H,
ArCH(CH3)2), 1.22 (d, J = 6.4 Hz, 12 H, ArCH(CH3)2). 13C NMR
(100.6 MHz, CDCl3, TMS, 25 °C, ppm): δ = 191.8 (Ir-Ccarbene), 150.2
(Ar-C), 134.2 (Ar-C), 130.0 (Ar-C), 126.3 (Ar-C), 121.8 (Ar-C), 112.3
(Ar-C), 85.9 (COD-CH), 51.8 (COD-CH), 48.4 (NCH2Ar), 34.7
(ArCH(CH3)2), 33.9 (COD-CH2), 30.0 (COD-CH2), 29.7 (ArCH-
(CH3)2), 24.5 (ArCH(CH3)2), 24.4 (ArCH(CH3)2), 20.0 (Ar-CH3−
BI). Anal. Calc. for C49H70ClN2Ir: C, 64.34; H, 7.71; N, 3.06. Found:
C, 64.43; H, 7.78; N, 3.09.
X-ray Diffraction Studies. Single crystal X-ray diffraction
experiments were carried out with an Agilent XCalibur X-ray
diffractometer with EOS CCD detector using Mo Kα radiation
́
(graphite crystal monochromator λ = 0.7107 Å) at room temperature.
The data collection, cell refinement, and data reduction were executed
using the CrysAlisPro19 program. Absorption corrections were based on
multiple scans.17 The structures were solved by direct methods
(SHELXS-9718) and refined by full-matrix least-squares against F2
(SHELXL-9718). All non-hydrogen atoms were refined anisotropically.
All hydrogen atoms were placed in calculated positions (C−H = 0.95−
0.99 Å) and were included in the refinement in the riding model
approximation with Uiso(H) set to 1.2−1.5Ueq(C). Disorder refine-
ment models were applied to some of the isopropyl fragments: C42A/
C42B, C43A/C43B atoms with an occupancy ratio of 0.85(1) to
0.15(1) in 1a and C40A/C40B, C41A/C41B, C50A/C50B, C51A/
Chloro(μ4-1,5-cyclooctadiene)[1,3-dibenzyl-(5,6-dimethyl)-
benzimidazol-2-ylidene] Iridium(I) (3a). Complex 3a was prepared in
analogy to 1a from the salt 3 (204 mg, 0.5 mmol). Yellow solid (292
1
mg, 88%). H NMR (400 MHz, CDCl3, TMS, 25 °C, ppm): δ =
G
dx.doi.org/10.1021/ic401626e | Inorg. Chem. XXXX, XXX, XXX−XXX