Organometallics
Article
1-(2,6-Diisopropylphenyl)-3-[(p-tolylsulfinyl)methyl]-1H-imi-
dazol-3-ium Bromide (3b). 1-(2,6-Diisopropylphenyl)imidazole
(1b; 137 mg, 0.6 mmol) was used as the starting material, and the
reaction mixture was irradiated for 6 h, affording 3b (216 mg) in 78%
yield as a hygroscopic off-white solid: mp 157−159 °C; 1H NMR (300
MHz, CDCl3) δ 9.67 (s, 1H), 8.00 (s, 1H), 7.70 (AA′BB′ system, 2H),
7.53 (t, J = 7.8 Hz, 1H), 7.36 (AA′BB′ system, 2H), 7.26 (t, J = 7.8 Hz,
2H), 7.01 (t, J = 1.8 Hz, 1H), 6.89 (d, J = 13.9 Hz, 1H), 6.12 (d, J =
13.9 Hz, 1H), 2.39 (s, 3H), 2.27 (q, J = 6.7 Hz, 1H), 2.04 (q, J = 6.7
Hz, 1H), 1.29 (d, J = 6.8 Hz, 3H), 1.14 (d, J = 6.8 Hz, 3H), 1.12 (d, J
= 6.8 Hz, 3H), 1.09 (d, J = 6.8 Hz, 3H) ppm; 13C NMR (75 MHz,
CDCl3) δ 145.5, 145.2, 142.7, 137.8, 134.4, 132.2, 130.5 (2C), 129.8,
125.0, (2C), 124.9, 124.8, 124.3, 123.2, 66.7, 28.7, 28.6, 24.6, 24.4,
24.4, 24.2, 21.6 ppm; HRMS (FAB+) m/z [M − Br]+ calcd for
C23H29N2OS 381.2001, found 381.1998.
21.6 ppm (Ccarbene not observed); HRMS (ESI+) m/z [M − AgBr2]+
calcd for C46H56N4S2O2Ag [M − AgBr2]+ 869.2892, found 869.2895.
Bis{1-methyl-3-[(p-tolylsulfinyl)methyl]imidazol-2-ylidene}-
silver(I) Dibromoargentate (4c). 1-Methyl-3-[(p-tolylsulfinyl)-
methyl]-1H-imidazolium bromide (3c; 32 mg, 0.1 mmol) was used
as the starting material, and the reaction mixture afforded the silver
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complex 4c (42 mg) in 95% yield as a white solid. H NMR (300
MHz, acetonitrile-d3) δ 7.39 (AA′BB′ system, 2H), 7.33 (AA′BB′
system, 2H), 7.10 (d, J = 1.8 Hz, 1H), 7.05 (d, J = 1.8 Hz, 1H), 5.38
(d, J = 13.3 Hz, 1H), 5.15 (d, J = 13.3 Hz, 1H), 3.74 (s, 3H), 2.38 (s,
3H) ppm; 13C NMR (76 MHz, acetonitrile-d3) δ 184.1, 143.7, 138.0,
131.3 (2C), 125.5 (2C), 123.7, 123.5, 72.2, 39.4, 21.6 ppm; HRMS
(ESI+) m/z [M − AgBr2]+ calcd for C24H28N4S2O2Ag 575.0699,
found 575.0698; MS (ESI−) calcd for AgBr2 [M] 266.74.
Bis{1-tert-butyl-3-[(p-tolylsulfinyl)methyl]imidazol-2-
ylidene}silver(I) Dibromoargentate (4d). 1-tert-Butyl-3-[(p-
tolylsulfinyl)methyl]-1H-imidazolium bromide (3d; 36 mg, 0.1
mmol) was used as the starting material, and the reaction mixture
afforded the silver complex 4d (46 mg) in 91% yield as a yellowish
solid. 1H NMR (300 MHz, acetonitrile-d3) δ 7.31 (br s, 4H), 7.28 (d, J
= 2.0 Hz, 1H), 7.08 (d, J = 2.0 Hz, 1H), 5.41 (d, J = 13.4 Hz, 1H), 5.28
(d, J = 13.4 Hz, 1H), 2.36 (s, 3H), 1.60 (s, 9H) ppm; 13C NMR (76
MHz, acetonitrile-d3) δ 181.3, 143.5, 137.6, 131.4 (2C), 125.3 (2C),
122.2, 120.3, 73.0, 58.9, 31.9 (3C), 21.5 ppm; HRMS (ESI+) m/z [M
− AgBr2]+ calcd for C30H40N4S2O2Ag 661.1636, found 661.1628.
General Procedure for the Synthesis of Sulfinyl-NHC−Pd
Complexes 5a−d. In a vial were added 1-substituted 3-[(p-
tolylsulfinyl)methyl]-1H-imidazol-3-ium bromides 3a−d (0.30 mmol,
1.0 equiv), Ag2O (70 mg, 0.30 mmol, 1.0 equiv), and MeCN (2 mL).
The vial was protected from the light, and the reaction mixture was
stirred at room temperature for 5 h. Then, the reaction mixture was
filtered through a Celite pad, the pad was rinsed with MeCN (1 mL),
and PdCl2(MeCN)2 (78 mg, 0.30 mmol, 1 equiv) was added to the
filtrate. The reaction mixture was stirred for 16 h at room temperature
and filtered through a Celite pad. The filtrate was evaporated under
reduced pressure, and the residue was dissolved in CH2Cl2. The
suspension was filtered again through a Celite pad, and the solvent was
evaporated under vacuum. Finally, the residue was washed with Et2O
and dried under vacuum, affording the pure complexes. If necessary,
further purification was performed by recrystallization in CH2Cl2/
Et2O.
1-Methyl-3-[(p-tolylsulfinyl)methyl]-1H-imidazol-3-ium Bro-
mide (3c). 1-Methylimidazole (1c; 49 mg, 0.6 mmol) was used as the
starting material, and the reaction mixture was irradiated for 10 h,
affording 3c (123 mg) in 65% yield as a hygroscopic off-white solid:
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mp 160−162 °C; H NMR (300 MHz, CDCl3) δ 9.68 (s, 1H), 7.56
(AA′BB′ system, 2H), 7.49 (t, J = 1.4 Hz, 1H), 7.45 (t, J = 1.4 Hz,
1H), 7.31 (AA′BB′ system, 2H), 6.14 (d, J = 13.4 Hz, 1H), 5.84 (d, J =
13.4 Hz, 1H), 4.00 (s, 3H), 2.38 (s, 3H) ppm; 13C NMR (75 MHz,
CDCl3) δ 143.1, 137.6, 135.1, 130.5 (2C), 124.7 (2C), 123.6, 122.8,
68.1, 37.1, 21.6 ppm; HRMS (FAB+) m/z [M − Br]+ calcd for
C12H15N2OS 235.0901, found 235.0905.
1-tert-Butyl-3-[(p-tolylsulfinyl)methyl]-1H-imidazol-3-ium
Bromide (3d). 1-tert-Butylimidazole (1d; 75 mg, 0.6 mmol) was used
as the starting material, and the reaction mixture was irradiated for 10
h, affording 3d (169 mg) in 79% yield as an off-white solid: mp 164−
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166 °C; H NMR (300 MHz, CDCl3) δ 9.91 (s, 1H), 7.54 (AA′BB′
system, 2H), 7.53−7.50 (m, 1H), 7.41 (t, J = 1.9 Hz, 1H), 7.29
(AA′BB′ system, 2H), 6.09 (d, J = 13.3 Hz, 1H), 5.84 (d, J = 13.3 Hz,
1H), 2.34 (s, 3H), 1.52 (s, 9H) ppm; 13C NMR (76 MHz, CDCl3) δ
142.7, 135.6, 134.8, 130.3 (2C), 124.7 (2C), 123.6, 118.6, 67.6, 60.7,
29.9 (3C), 21.4 ppm; HRMS (FAB+) m/z [M − Br]+ calcd for
C15H21N2OS [M − Br]+ 277.1375, found 277.1379.
General Procedure for the Synthesis of Sulfinyl-NHC−Ag
Complexes 4a−d. In a vial were added 1-substituted 3-[(p-
tolylsulfinyl)methyl]-1H-imidazol-3-ium bromides 3 (0.1 mmol, 1.0
equiv), Ag2O (23 mg, 0.1 mmol, 1.0 equiv), and MeCN (1 mL). The
vial was protected from the light, and the reaction mixture was stirred
at room temperature for 5 h. Then, the reaction mixture was filtered
through a Celite pad and the filtrate was evaporated under reduced
pressure, affording the Ag complexes 4a−d, which were used in the
next step without further purification.
Chloro{1-mesityl-3-[(p-tolylsulfinyl)methyl]imidazol-2-
ylidene}palladium(II) (5a). 1-Mesityl-3-[(p-tolylsulfinyl)methyl]-
1H-imidazol-3-ium bromide (3a; 126 mg, 0.30 mmol) was used as
the starting material, and the reaction afforded the Pd complex 5a (141
1
mg) in 91% yield as a crystalline yellow solid: mp 218 °C dec; H
NMR (300 MHz, acetonitrile-d3) δ 7.74 (AA′BB′ system, 2H), 7.44
(AA′BB′ system, 2H), 7.11−7.03 (m, 3H), 6.98 (d, J = 1.9 Hz, 1H),
5.62 (d, J = 7.7 Hz, 1H), 2.44 (s, 3H), 2.38 (s, 3H), 2.17 (s, 3H), 2.13
(s, 3H) ppm; 13C NMR (76 MHz, acetonitrile-d3) δ 150.0, 144.0,
140.6, 139.2, 137.2, 137.1, 135.6, 131.2 (2C), 130.0, 130.0, 125.9,
125.7 (2C), 124.6, 73.7, 21.6, 21.2, 19.1 (2C) ppm; HRMS (ESI+) m/
z [M − Cl − MeCN]+ calcd for C20H22ClN2OSPd 481.0168, found
481.0194. Anal. Calcd for C22H26Cl2N3OPdS: C, 47.37; H, 4.70; N,
7.53; S, 5.75. Found: C, 47.48; H, 4.49; N, 7.42; S, 6.05.
Chloro{1-(2,6-diisopropylphenyl)-3-[(p-tolylsulfinyl)methyl]-
imidazol-2-ylidene}palladium(II) (5b). 1-(2,6-Diisopropylphenyl)-
3-[(p-tolylsulfinyl)methyl]-1H-imidazol-3-ium bromide (3b; 138 mg,
0.30 mmol) was used as the starting material, and the reaction afforded
the Pd complex 5b (137 mg) in 82% yield as a crystalline yellow solid:
mp 175 °C dec; 1H NMR (300 MHz, acetonitrile-d3) δ 7.74 (AA′BB′
system, 2H), 7.54 (t, J = 8.2 Hz, 1H), 7.43 (AA′BB′ system, 2H), 7.04
(dd, J = 2.1 and 9.7 Hz, 1H), 5.81 (d, J = 13.3 Hz, 1H), 5.58 (d, J =
13.3 Hz, 1H), 2.80 (q, J = 6.7 Hz, 1H), 2.54 (q, J = 6.7 Hz, 1H), 2.44
(s, 3H), 1.38 (d, J = 6.7 Hz, 3H), 1.35 (d, J = 6.7 Hz, 3H), 0.99 (d, J =
6.7 Hz, 3H), 0.97 (d, J = 6.7 Hz, 3H) ppm; 13C NMR (76 MHz,
acetonitrile-d3) δ 147.8, 147.7, 144.1, 139.0, 139.0, 135.2, 131.6, 131.2
(2C), 127.5, 126.0 (2C), 126.0, 125.1, 124.0, 73.3, 29.4, 29.3, 26.3,
26.2, 23.5, 23.3, 21.6 ppm; HRMS (ESI+) m/z [M − Cl − MeCN]+
calcd for C23H28ClN2OPdS 523.0638, found 523.0628.
Bis{1-mesityl-3-[(p-tolylsulfinyl)methyl]imidazol-2-ylidene}-
silver(I) Dibromoargentate (4a). 1-Mesityl-3-[(p-tolylsulfinyl)-
methyl]-1H-imidazolium bromide (3a; 42 mg, 0.1 mmol) was used
as the starting material, and the reaction mixture afforded the silver
complex 4a (53 mg) in a 94% yield as a yellowish solid. 1H NMR (300
MHz, acetonitrile-d3) δ 7.44 (AA′BB′ system, 2H), 7.32 (AA′BB′
system, 2H), 7.18 (d, J = 1.9 Hz, 1H), 7.00−6.93 (m, 2H), 6.98 (d, J =
1.9 Hz, 1H), 5.55 (d, J = 13.7 Hz, 1H), 5.44 (d, J = 13.7 Hz, 1H), 2.36
(s, 3H), 2.34 (s, 3H), 1.85 (s, 3H), 1.66 (s, 3H) ppm; 13C NMR (76
MHz, acetonitrile-d3) δ 184.7, 143.4, 140.2, 137.4, 136.4, 135.9, 135.6,
131.3 (2C), 130.0, 129.9, 125.6 (2C), 123.8, 123.6, 71.0, 21.6, 21.2,
17.9, 17.9 ppm; HRMS (ESI+) m/z [M − AgBr2]+ calcd for
C40H44N4S2O2Ag [M − AgBr2]+ 785.1951, found 785.1959.
Bis{1-(2,6-diisopropylphenyl)-3-[(p-tolylsulfinyl)methyl]-
imidazol-2-ylidene}silver(I) Dibromoargentate (4b). 1-(2,6-
Diisopropylphenyl)-3-[(p-tolylsulfinyl)methyl]-1H-imidazolium bro-
mide (3b; 46 mg, 0.1 mmol) was used as the starting material, and
the reaction mixture afforded the silver complex 4b (57 mg) in 93%
yield as a yellowish solid. 1H NMR (300 MHz, acetonitrile-d3) δ 7.52−
7.34 (m, 5 H), 7.32−6.98 (m, 4H), 5.60 (bs, 1H), 5.35 (d, J = 13.4 Hz,
1H), 2.39 (s, 3H), 2.25 (q, J = 6.8 Hz, 1H), 2.21−2.10 (m, 1H), 1.24−
0.89 (m, 6H), 1.10 (s, 3H), 1.08 (s, 3H) ppm; 13C NMR (76 MHz,
acetonitrile-d3) δ 146.9, 146.5, 143.5, 137.4, 135.7, 131.3 (2C), 125.4
(3C), 125.0, 125.0, 124.8, 123.8, 70.7, 28.9 (2C), 24.8, 24.6, 24.4, 24.3,
7492
dx.doi.org/10.1021/om400981x | Organometallics 2013, 32, 7487−7494