N-Heterocyclic Carbenes (NHC) Derived from Imidazo[1,5-a]pyridines
1
3
1
(
1
1
(
1
s, 3H, C5 CH
3
). C NMR (75 MHz, DMSO-d
34.68 (CH, C3), 129.26 (Cq, C9), 129.02 (CH, C8), 120.37 (CH, C1),
16.04 (CH, C6), 111.32 (CH, C7), 35.12 (CH3, N2 CH ), 18.09
) ppm. FT-IR (ATR, ν, cm ): 3114, 3091, 3074, 1941,
6
, δ, ppm): 135.57 (Cq, C5),
dichloromethane–n-hexane–acetonitrile
mixture.
H
NMR
(300 MHz, CDCl -d, δ, ppm): 8.44 (dddd, J = 7.3, 1.1, 1.0, 1.0 Hz, 1H,
H5), 7.51–7.28 (m, 2H, overlapping signals for H8, H1), 6.91 (ddd,
J = 9.3, 6.6, 1.1 Hz, 1H, H7), 6.84–6.63 (m, 1H, H6), 4.48 (q,
3
3
À1
CH
3
C5 CH
3
13
812, 1785, 1676, 1578, 1541, 1449, 1385, 1348, 1327, 1266, 1212,
J = 7.3 Hz, 2H, N2 CH
2
Me), 1.59 (t, J = 7.3 Hz, 3H, N2 CH
2
CH
3
).
C
1
186, 1146, 1068, 1033, 783, 735, 617. (+) MS (ESI): m/z (%): 147
NMR (75 MHz, CDCl -d, δ, ppm): 161.83 (Ccarbene, C3), 130.35 (CH,
C5), 127.41 (Cq, C9), 123.46 (CH, C8), 117.27 (CH, C1), 114.07 (CH,
3
À +
(
100) [(M À I ) ]. Anal. Calcd for C
9
H
11IN
2
(%): C, 39.44; H, 4.05; N,
1
0.22. Found (%): C, 39.78; H, 3.98; N, 10.18.
-(2-Hydroxyethyl)imidazo[1,5-a]pyridin-2-ium iodide (11)
C H IN O). Starting materials: 2-iodoethanol (0.9 ml, 11.51 mmol)
C6), 109.81 (CH, C7), 47.77 (CH2, N2 CH Me), 16.79 (CH ,
2
3
À1
2
N2 CH CH ) ppm. FT-IR (ATR, ν, cm ): 3204, 3156, 3115, 2979,
2 3
(
2929, 2851, 1922, 1783, 1749, 1649, 1558, 1523, 1462, 1443, 1411,
1334, 1305, 1242, 1167, 1063, 980, 926, 799, 747, 730, 641. MS (EI):
9
11
2
and 2 (250 mg, 2.11 mmol). Yield 0.4 g (1.37 mmol, 65%); colourless
solid. H NMR (300 MHz, DMSO-d , δ, ppm): 9.75 (s, 1H, H3), 8.64 (d,
J = 7.1 Hz, 1H, H5), 8.27 (s, 1H, H1), 7.91 (d, J = 9.5 Hz, 1H, H8), 7.41–
1
37
35
À
m/z (%): 380 (28) [M( Cl)], 378 (100) [M( Cl)], 343 (60) [M À Cl ],
6
314 (38), 118 (77), 117 (30). Anal. Calcd for C H N AuCl (%): C,
9
10 2
7
1
.13 (m, 2H, overlapping signals for H6, H7), 5.22 (d, J = 5.4 Hz,
H OH), 4.64–4.49 (m, 2H, N2 CH CH OH), 3.86 (t, J = 5.2 Hz, 2H,
28.55; H, 2.66; N, 7.40. Found (%): C, 28.84; H, 2.77; N, 7.68.
Chloro(2-benzylimidazo[1,5-a]pyridin-3-ylidene)gold(I) (14)
(C H N AuCl). Compound 9 (0.1 g, 0.347 mmol) in CH Cl was
2
2
1
3
N2 CH CH ). C NMR (75 MHz, DMSO-d , δ, ppm): 129.04 (CH,
2
2
6
14 12
2
2
2
C3), 126.66 (CH, C5), 124.42 (Cq, C9), 124.02 (CH, C8), 118.18 (CH,
treated with Ag O (0.04 g, 0.173 mmol) with stirring for 5 h. AuCl
2
C1), 117.33 (CH, C6), 113.68 (CH, C7), 59.64 (CH , N2 CH CH OH),
(SMe ) (0.1 g, 0.347 mmol) was added and the reaction was stirred
for another 10 h. The product was purified using a celite column
2
2
2
2
À1
5
3
1
2.97(CH , N2 CH CH ). FT-IR (ATR, ν, cm ): 3284, 3138, 3114,
084, 2979, 1654, 1541, 1460, 1421, 1350, 1330, 1307, 1145, 1126,
2
2
2
(281 nm particle size). Yield 0.065 g (0.145 mmol, 42%); dark green
1
083, 1063, 945, 882, 797, 754, 662, 639. MS (EI): m/z (%): 163
solid. H NMR (300 MHz, CDCl -d, δ, ppm): 8.49 (dddd, J = 7.3, 1.1,
3
À
(100) [(M À I )]. Anal. Calcd for C H IN O (%): C 37.26; H, 3.82; N,
1.0, 1.0 Hz, 1H, H3), 7.90 (s, 1H, H5), 7.38–7.26 (m, 5H, overlapping
9
11
2
9.66. Found (%): C, 37.63; H, 3.59; N, 9.42.
2
signals for N2 CH Ph), 7.18–7.16 (m, 1H, H8), 6.90 (ddd, J = 9.4,
6
.6, 1.1 Hz, 1H, H7), 6.69. (ddd, J = 7.3, 6.6, 1.2 Hz, 1H, H6), 5.60 (s,
13
2 6
N2 CH Ph). C NMR (75 MHz, DMSO-d , δ, ppm): 162.57 (Ccarbene,
General Procedure for Synthesis of Gold(I)–NHC Complexes
12–16)
C3), 134.64 (CPhenyl, C2′), 130.67 (CH, C5), 129.15 (CPhenylH, 2C, over-
lapping signals for C4′, C6′), 128.99 (Cq, C9), 128.28 (CPhenylH, 2C,
overlapping signals for C3′, C7′), 127.51 (CPhenylH, C5′), 123.73 (CH,
(
The respective imidazo[1,5-a]pyridin-2-ium halide salts (1 equiv.)
–11 were suspended in dry dichloromethane and treated with
Ag O (0.5 equiv.) with stirring for 5 h at ambient temperature in
the dark. AuCl(SMe ) (1 equiv.) was added and the mixture was
7
2
C8), 117.28 (CH, C1), 114.24 (CH, C6), 110.18 (CH, C7), 56.44 (CH ,
À1
2
2
N2 CH Ph, C1′). FT-IR (ATR, ν, cm ): 3207, 3145, 3086, 3032, 2929,
2
2852, 1650, 1525, 1494, 1454, 1394, 1364, 1343, 1322, 1248, 1206,
stirred for another 10 h. The obtained suspension was filtered
through celite (281 nm particle size), and the solvent was removed
under reduced pressure to afford the desired products.
1079, 1062, 987, 847, 754, 711, 649. MS (EI): m/z (%): 442 (10) [M
37
35
À
( Cl)], 440 (25) [M( Cl)], 405 (5) [M À Cl ], 314 (12), 207 (52), 208
+
12 2
(12), 91 (100) [Bn ]. Anal. Calcd for C14H N AuCl (%): C, 38.16; H,
Chloro(2-methylimidazo[1,5-a]pyridin-3-ylidene)gold(I) (12)
2.74; N, 6.36. Found (%): C, 37.42; H, 2.68; N, 6.51.
(
C
8
H
8
N
2
AuCl). Compound 7 (0.1 g, 0.384 mmol) was dissolved in di-
chloromethane and treated with Ag O (0.044 g, 0.192 mmol) for 5 h
at ambient temperature in the dark. AuCl(SMe ) (0.113 g,
.384 mmol) was added, and the reaction was stirred for another
0 h. The product was purified using a celite column (281 nm par-
Chloro(2,5-dimethylimidazo[1,5-a]pyridin-3-ylidene)gold(I)
2
(15) (C
9
H
10
N
2
AuCl). Compound 10 (100 mg, 0.364 mmol) in CH
2 2
Cl
2
2
(10 ml) was treated with Ag O (42.17 mg, 0.182 mmol) with stirring
0
1
for 5 h at ambient temperature in the dark. Au(tht)Cl (116.69 mg,
0.364 mmol) was added and the mixture was stirred overnight at
ambient temperature. The product was purified using a celite col-
1
ticle size). Yield 0.065 g (0.178 mmol, 46%); colourless solid. H
NMR (600 MHz, CDCl -d, δ, ppm): 8.48 (dddd, J = 7.4, 1.1, 1.0,
umn (265 nm particle size). Yield 0.556 g (0.147 mmol, 40%);
3
1
1.0 Hz, 1H, H5), 7.33 (ddd, J = 9.3, 1.1, 1.1 Hz, 1H, H8), 7.25 (d,
colourless solid. H NMR (300 MHz, CDCl -d, δ, ppm): 7.41–7.24 (m,
3
J = 0.7 Hz, 1H, H1), 6.92 (ddd, J = 9.3, 6.5, 0.9 Hz, 1H, H7), 6.70
1H, H8), 7.39 (s, 1H, H1), 6.88 (ddd, J = 9.3, 6.6, 0.4 Hz, 1H, H7),
1
3
(ddd, J = 7.4, 6.5, 1.2 Hz, 1H, H6), 4.11 (s, 3H, N2 CH3). C NMR
6.49 (dd, J = 6.6, 1.2 Hz, 1H, H6), 4.21 (s, 3H, N2 CH ), 3.24 (s, 3H,
3
13
(
150 MHz, CDCl -d, δ, ppm): 163.11 (Ccarbene, C3), 130.37 (CH, C5),
C5 CH3). C NMR (75 MHz, CDCl -d, δ, ppm): 162.00 (Ccarbene, C3),
3
3
1
1
3
1
27.43 (Cq, C9), 123.71 (CH, C8), 117.06 (CH, C1), 114.15 (CH, C6),
134.10 (Cq, C5), 126.10 (Cq, C9), 122.64 (CH, C8), 115.34 (CH, C1),
À1
11.45 (CH, C7), 39.47 (CH , N2 CH ). FT-IR (ATR, ν, cm ): 3207,
114.78 (CH, C6), 112.15 (CH, C7), 40.37 (CH , N2 CH ) 23.23 (CH ,
3
3
3
3
3
À1
114, 3054, 2924, 2851, 1919, 1649, 1464, 1341, 1307, 1250, 1171,
C5 ;CH ). FT-IR (ATR, ν, cm ): 3206, 3064, 2929, 2817, 1653, 1472,
3
094, 991, 931, 844, 750, 728, 637. MS (EI): m/z (%): 366 (33) [M
1337, 1306, 1251, 1169, 1084, 989, 933, 844, 748, 729, 636. MS (EI):
37
35
À
37
35
À
(
Cl)], 364 (100) [M( Cl)], 330 (10), 329 (98) [M À Cl ]. Anal. Calcd
m/z (%): 380 (30) [M( Cl)], 378 (87) [M( Cl)], 342 (100) [M À Cl ],
for C H N AuCl (%): C, 26.36; H, 2.21; N, 7.68. Found (%): C, 26.20;
146 (82), 131 (35), 93 (25), 55 (28). Anal. Calcd for C H N AuCl
8
8
2
9 10 2
H, 2.49; N, 7.07.
(%): C, 28.55; H, 2.66; N, 7.40. Found (%): C, 28.76; H, 2.68; N, 7.49.
Chloro(2-ethylimidazo[1,5-a]pyridin-3-ylidene)gold(I) (13)
Bis(2-(2-hydroxyethyl)imidazo[1,5-a]pyridin-3-ylidene)gold
(
C
9
H
10
N
2
AuCl). Compound 8 (0.1 g, 0.264 mmol) was dissolved in
dichloromethane and treated with Ag O (0.030 g, 0.132 mmol) for
h at ambient temperature in the dark. AuCl(SMe ) (0.077 g,
.264 mmol) was added, and the reaction mixture was stirred for
(I) chloride (16) (C18
0.206 mmol) in CH Cl
0.103 mmol) with stirring for 5 h at ambient temperature in the
dark. AuCl(SMe ) (0.061 g, 0.206 mmol) was added and the mixture
H
20
N
4
O
2
AuCl). Compound 11 (0.06 g,
(5 ml) was treated with Ag O (0.024 g,
2
2
2
2
5
0
2
2
another 10 h. The product was purified using a celite column
281 nm particle size). Yield 0.05 g (0.132 mmol, 50%); pale yellow
solid. Single crystals suitable for X-ray measurements were grown
was stirred overnight. The product was purified using a celite col-
(
umn (265 nm particle size). Yield 0.054 g (0.097 mmol, 47%);
1
colourless solid. H NMR (600 MHz, DMSO-d
6
, δ, ppm): 8.81 (dd,
by slow diffusion of diethyl ether into a solution of 13 in a
J = 7.1, 1.0 Hz, 1H, H5), 8.55 (dd, J = 7.1, 1.1 Hz, 1H, H5′), 8.05 (d,
Appl. Organometal. Chem. 2016, 30, 581–589
Copyright © 2016 John Wiley & Sons, Ltd.
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