738 JOURNAL OF CHEMICAL RESEARCH 2016
1
699, 629; H NMR (400 MHz, DMSO-d6): 9.91 (s, 2H, H2-imidazole),
CDCl3): 8.79 (m, 4H, Hα-Py), 7.68–7.61 (m, 6H, Hγ-Py, Ar), 7.21 (m, 4H,
Hβ-Py), 7.02 (s, 4H, Ph), 6.93 (d, J = 2.0 Hz, 2H, H5-imidazole), 6.86 (d,
J = 2.0 Hz, 2H, H4-imidazole), 6.03 (s, 4H, CH2), 2.37 (s, 6H, CH3), 2.32 (s,
12 H, CH3); 13C NMR (100 MHz, CDCl3): 152.6, 150.5, 139.2, 137.5,
136.3, 135.8, 134.8, 129.8, 129.3, 125.0, 124.3, 121.5, 55.4, 21.2, 19.9;
Anal. calcd for C42H46Br4N6Pd2: C, 43.21; H, 3.97; N, 7.20; found: C,
43.06; H, 3.89; N, 7.27%.
8.18 (d, J = 1.8 Hz, 2H, H5-imidazole), 8.13 (d, J = 1.8 Hz, 2H, H4-imidazole),
7.63–7.45 (m, 10H, Ph), 5.63 (s, 4H, CH2), 2.20 [m, 4H, CH(CH3)3],
1.12 (d, J = 3.2 Hz, 12H, CH3), 1.11 (d, J = 3.2 Hz, 12H, CH3); 13C NMR
(100 MHz, DMSO-d6): 145.4, 138.6, 136.0, 132.0, 130.9, 129.2, 125.9,
124.9, 123.9, 52.4, 28.6, 24.3, 24.0; Anal. calcd for C38H48Br2N4: C,
63.34; H, 6.71; N, 7.77; found: C, 63.55; H, 6.64; N, 7.84%.
1,1’-[1,4-Phenylenebis(methylene)]bis(4-phenyl-4H-1,2,4-triazol-
Complex 3c: Pale yellow solid; yield 75%; IR (νmax, cm–1) KBr: 3149,
3114, 3093, 2963, 2932, 1603, 1466, 1406, 1355, 1287, 1250, 1216,
1180, 1069, 958, 815, 755, 727, 693, 643; 1H NMR (400 MHz, CDCl3):
8.74 (m, 4H, Hα-Py), 7.67–7.44 (m, 8H, Hγ-Py, Hβ-Py, Ph), 7.30–7.18 (m,
8H, Ph), 6.94 (m, 4H, H5-imidazole, H4-imidazole), 6.04 (s, 4H, CH2), 2.87 (m,
4H, CH2CH3), 2.51 (m, 4H, CH2CH3), 1.18 (t, J = 7.6 Hz, 12H, CH3);
13C NMR (100 MHz, CDCl3): 152.5, 151.2, 142.3, 137.5, 135.80, 135.75,
129.92, 129.88, 126.4, 125.5, 124.3, 121.2, 55.4, 25.5, 15.0; Anal. calcd
for C44H48Br4N6Pd2: C, 44.28; H, 4.05; N, 7.04; found: C, 44.06; H,
4.12; N, 7.12%.
1-ium) dibromide (2a): White solid; yield 87%; m.p. > 300 °C; IR (νmax
,
cm–1) KBr: 3003, 2973, 1593, 1495, 1593, 1373, 1226, 1209, 1185, 1023,
843, 766, 752, 688, 634, 518; 1H NMR (400 MHz, DMSO-d6): 11.06 (s,
2H, H5-triazole), 9.79 (s, 2H, H3-triazole), 7.86–7.83 (m, 4H, Ph), 7.73–7.60
(m, 10H, Ph), 5.74 (s, 4H, CH2); 13C NMR (100 MHz, DMSO-d6):
143.8, 142.5, 134.2, 132.6, 131.0, 130.7, 129.9, 123.0, 55.0; Anal. calcd
for C24H22Br2N6: C, 52.01; H, 4.00; N, 15.16; found: C, 51.86; H, 4.05;
N, 15.27%.
1,1’-[1,4-Phenylenebis(methylene)]bis(4-mesityl-4H-1,2,4-triazol-
1-ium) dibromide (2b): White solid; yield 88%; m.p. 256–257 °C; IR
(νmax, cm–1) KBr: 2997, 2751, 1607, 1558, 1522, 1437, 1376, 1193, 1153,
1091, 1036, 983, 860, 733, 680, 581; 1H NMR (400 MHz, DMSO-d6):
10.99 (s, 2H, H5-triazole), 9.55 (s, 2H, H3-triazole), 7.62 (s, 4H, Ph), 7.18
(s, 4H, Ph), 5.81 (s, 4H, CH2), 2.34 (s, 6H, CH3), 2.09 (s, 12H, CH3);
13C NMR (100 MHz, DMSO-d6): 146.2, 144.5, 141.5, 134.8, 134.3,
130.0, 129.9, 128.4, 55.2, 21.1, 17.7; Anal. calcd for C30H34Br2N6: C,
56.44; H, 5.37; N, 13.16; found: C, 56.61; H, 5.44; N, 13.21%.
1,1’-[1,4-Phenylenebis(methylene)]bis[4-(2,6-diethylphenyl)-
4H-1,2,4-triazol-1-ium] dibromide (2c): White solid; yield 85%;
m.p. 285–286 °C; IR (νmax, cm–1) KBr: 3067, 2971, 2876, 2779, 1589,
1557, 1462, 1379, 1197, 1162, 1110, 1060, 820, 777, 753, 727, 680;
1H NMR (400 MHz, DMSO-d6): 11.13 (s, 2H, H5-triazole), 9.68 (s, 2H,
H3-triazole), 7.65–7.42 (m, 10H, Ph), 5.86 (s, 4H, CH2), 2.33 (q, J = 7.6 Hz,
8H, CH2CH3), 1.06 (t, J = 7.6 Hz, 12H, CH3); 13C NMR (100 MHz,
DMSO-d6): 146.4, 144.7, 140.9, 134.4, 132.3, 129.9, 129.5, 127.7, 55.3,
23.8, 14.8; Anal. calcd for C32H38Br2N6: C, 57.67; H, 5.75; N, 12.61;
found: C, 57.43; H, 5.81; N, 12.56%.
Complex 3d: Pale yellow solid; yield 73%; IR (νmax, cm–1) KBr: 3160,
3125, 2967, 2928, 2866, 1518, 1447, 1417, 1363, 1304, 1229, 1218, 1075,
959, 803, 758, 694, 641 cm-1. 1H NMR (400 MHz, CDCl3): 8.79 (m, 4H,
Hα-Py), 7.69-7.62 (m, 6H, Hγ-Py, Hβ-Py, Ph), 7.52-7.20 (m, 10H), 6.94 (d,
J = 2.0 Hz, 2H, H5-imidazole), 6.92 (d, J = 2.0 Hz, 2H, H4-imidazole), 6.10 (s,
4H, CH2), 3.05 (m, 4H, CH2CH3), 1.43 (d, J = 6.8 Hz, 12H, CH3), 1.04
(d, J = 6.8 Hz, 12H, CH3). 13C NMR (100 MHz, CDCl3): 152.5, 151.4,
147.1, 137.6, 135.7, 134.4, 130.3, 130.0, 126.5, 124.3, 124.1, 120.7, 55.7,
28.6, 26.6, 23.4. Anal. calc. for C48H56Br4N6Pd2 (1249.45 g mol–1): C,
46.14; H, 4.52; N, 6.73; found: C, 45.06; H, 4.45; N, 6.81%.
Complex 4a: : Light yellow solid; yield 76%; IR (νmax, cm–1) KBr:
3137, 3051, 1605, 1531, 1498, 1472, 1445, 1351, 1324, 1259, 1225, 1212,
1
1174, 1070, 1017, 986, 851, 758, 692, 652, 559; H NMR (400 MHz,
CDCl3): 8.86 (m, 4H, Hα-Py), 8.16 (s, 2H, H3-triazole), 7.99–7.55 (m, 16H,
Hγ-Py, Hβ-Py, Ph), 7.29 (m, 4H, Ph), 6.03 (s, 4H, CH2); 13C NMR (100
MHz, CDCl3): 157.2, 152.6, 143.0, 138.0, 135.9, 134.5, 130.1, 129.9,
129.6, 126.1, 124.6, 56.8; Anal. calcd for C34H30Br4N8Pd2: C, 37.70; H,
2.79; N, 10.35; found: C, 37.56; H, 2.82; N, 10.40%.
1,1’-[1,4-Phenylenebis(methylene)]bis[4-(2,6-diisopropylphenyl)-
4H-1,2,4-triazol-1-ium] dibromide (2d): White solid; yield 83%; m.p.
265–266 °C; IR (νmax, cm–1) KBr: 3067, 2965, 2739, 1554, 1460, 1369,
Complex 4b: : Light yellow solid; yield 82%; IR (νmax, cm–1) KBr:
3125, 3026, 2917, 2858, 1603, 1530, 1519, 1466, 1447, 1365, 1312, 1215,
1164, 1066, 1038, 1017, 985, 945, 855, 782, 757, 697, 645, 585; 1H NMR
(400 MHz, CDCl3): 8.81 (m, 4H, Hα-Py), 7.90 (s, 2H, H3-triazole), 7.74 (s,
4H, Ph), 7.68 (m, 2H, Hγ-Py), 7.28 (m, 4H, Hβ-Py), 7.06 (s, 4H, Ph), 6.15 (s,
4H, CH2), 2.40 (s, 6H, CH3), 2.33 (s, 12H, CH3); 13C NMR (100 MHz,
CDCl3): 157.9, 152.7, 144.9, 140.2, 137.8, 136.1, 134.9, 131.1, 129.8,
129.6, 124.4, 57.3, 21.2, 19.9; Anal. calcd for C40H42Br4N8Pd2: C, 41.16;
H, 3.63; N, 9.60; found: C, 40.98; H, 3.57; N, 9.68%.
1
1358, 1300, 1191, 1088, 1001, 938, 813, 762, 718, 685, 554; H NMR
(400 MHz, DMSO-d6): 11.37 (s, 2H, H5-triazole), 9.79 (s, 2H, H3-triazole),
7.70–7.49 (m, 10H, Ph), 5.90 (s, 4H, CH2), 2.29 [m, 4H, CH(CH3)3],
1.15 (d, J = 6.8 Hz, 12H, CH3), 1.11 (d, J = 6.8 Hz, 12H, CH3); 13C NMR
(100 MHz, DMSO-d6): 146.7, 145.6, 144.9, 134.5, 132.7, 129.9, 127.7,
125.2, 55.3, 28.5, 24.08, 24.05; Anal. calcd for C36H46Br2N6: C, 59.84;
H, 6.42; N, 11.63; found: C, 59.61; H, 6.49; N, 11.72%.
Complex 4c: Light yellow solid; yield 80%; IR (νmax, cm–1) KBr:
2970, 2933, 2875, 1602, 1533, 1459, 1447, 1356, 1308, 1216, 1070, 1017,
Synthesis of di-NHC dipalladium complexes (3 and 4); general
procedure
1
983, 864, 812, 787, 758, 700; H NMR (400 MHz, CDCl3): 8.77 (m,
4H, Hα-Py), 7.95 (s, 2H, H3-triazole), 7.76 (s, 4H, Ar), 7.66 (m, 2H, Hγ-Py),
7.52–7.22 (m, 10H, Ph, Hβ-Py), 6.14 (s, 4H, CH2), 2.85 (m, 4H, CH2CH3),
2.46 (m, 4H, CH2CH3), 1.29 (t, J = 7.6 Hz, 12H, CH3); 13C NMR (100
MHz, CDCl3): 158.3, 152.7, 145.0, 142.1, 137.8, 134.9, 132.2, 130.7,
129.9, 126.6, 124.4, 57.3, 25.3, 14.8; Anal. calcd for C42H46Br4N8Pd2: C,
42.20; H, 3.88; N, 9.37; found: C, 42.09; H, 3.92; N, 9.43%.
Complex 4d: : Light yellow solid; yield 72%; IR (νmax, cm–1) KBr:
3130, 2965, 2928, 2867, 1605, 1534, 1447, 1383, 1363, 1302, 1216,
1155, 1071, 1016, 983, 803, 785, 757, 694; 1H NMR (400 MHz, CDCl3):
8.80 (m, 4H, Hα-Py), 7.95 (s, 2H, H3-triazole), 7.78 (s, 4H, Ar), 7.68 (m, 2H,
Hγ-Py), 7.55–7.35 (m, 6H, Ph), 7.26 (m, 4H, Hβ-Py), 6.18 (s, 4H, CH2), 2.96
(m, 4H, CH), 1.43 (d, J = 6.4 Hz, 12H, CH3), 1.06 (d, J = 6.8 Hz, 12H,
CH3); 13C NMR (100 MHz, CDCl3): 158.7, 152.7, 147.0, 145.5, 137.8,
134.8, 131.1, 130.7, 130.0, 124.5, 124.5, 57.5, 28.6, 26.4, 23.3; Anal.
calcd for C46H54Br4N8Pd2: C, 44.15; H, 4.35; N, 8.95; found: C, 44.32;
H, 4.39; N, 9.00%.
A mixture of bis(imidazolium) bromides or bis(triazolium) bromides
(2.0 mmol), PdCl2 (1.069 g, 4.0 mmol), NaBr (1.646 g, 16 mmol) and
K2CO3 (5.528 g, 40 mmol) was added to pyridine (30 mL) in a 50 mL
round bottom flask. The reaction mixture was heated at 85 °C for 18 h,
after which time the mixture was filtered through Celite and washed
with DCM. The solvent was removed under vacuum, and the crude
product was washed with diethyl ether (15 mL). The pure compound
was obtained as yellow solid by recrystallisation from DCM/Et2O.
Complex 3a: Pale yellow solid; yield 70%; IR (νmax, cm–1) KBr:
3174, 3142, 3064, 2927, 1602, 1519, 1498, 1445, 1421, 1404, 1352,
1
1281, 1245, 1069, 958, 762, 719, 690, 644, 551; H NMR (400 MHz,
CDCl3): 8.84 (m, 4H, Hα-Py), 8.06 (m, 4H, Hγ-Py, Ph), 7.72–7.47 (m, 12H,
Py, Ph), 7.28–7.25 (m, 4H, Ph), 7.15 (d, J = 2.0 Hz, 2H, H5-imidazole), 6.93
(d, J = 2.0 Hz, 2H, H4-imidazole), 5.92 (s, 4H, CH2); 13C NMR (100 MHz,
CDCl3): 152.5, 137.7, 135.6, 135.2, 130.0, 129.2, 128.8, 126.1, 124.5,
123.5, 122.1, 118.2, 55.1; Anal. calcd for C36H32Br4N6Pd2: C, 39.99; H,
2.98; N, 7.77; found: C, 40.23; H, 3.02; N, 7.82%.
Catalytic Heck coupling reaction; general procedure
Complex 3b: Pale yellow solid; yield 78%; IR (νmax, cm–1) KBr: 3174,
3144, 3072, 2919, 1602, 1559, 1518, 1485, 1447, 1419, 1362, 1232, 1214,
A mixture of phenylbromide (52 µL, 0.5 mmol), styrene (63 µL,
0.6 mmol), Pd catalyst (0.0025 mmol), K3PO4 (212 mg, 1.0 mmol)
and DMF (2 mL) were added to a 5 mL vial equipped with a magnetic
1
1070, 1033, 853, 758, 749, 696, 643, 588, 512; H NMR (400 MHz,