2232 Organometallics, Vol. 28, No. 7, 2009
Xiao et al.
(s), 1593 (s), 1460 (s), 1421 (s), 1388 (m), 1316 (m), 1278 (m),
1153 (m), 1006 (w), 992 (m), 825 (w), 747 (m), 671 (s). Anal.
Calcd for C17H15N3O2 (309.32): C, 66.01; H, 4.89; N, 13.58. Found:
C, 65.94; H, 4.85; N, 13.64.
6.92 (s, 2H, Ar), 2.31 (s, 3H, CH3), 2.30 (s, 3H, CH3), 2.03 (s, 6H,
CH3). 13C NMR (75 MHz, CDCl3, TMS): δ 166.5, 155.9, 150.6,
147.1, 145.9, 144.4, 137.7, 133.7, 132.4, 128.5, 125.1, 124.0, 122.8,
122.5, 122.1, 120.1, 111.2, 20.7, 17.9, 16.5. IR (KBr; cm-1): 3446
(w), 3000 (w), 2962 (w), 2913 (m), 1647 (vs), 1592 (s), 1570 (vs),
1490 (w), 1460 (s), 1420 (m), 1385 (m), 1362 (m), 1308 (m), 1279
(m), 1215 (s), 1147 (m), 1121 (s), 1011 (m), 992 (w), 856 (s), 824
(m), 789 (w), 767 (w), 745 (vs). Anal. Calcd for C23H22N4 (354.45):
C, 77.94; H, 6.26; N, 15.81. Found: C, 77.95; H, 6.31; N, 15.72.
4.3. Synthesis of Tridentate Ligands L1-L6: (E)-2,6-Di-
methyl-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyridin-2-yl)eth-
ylidene)benzenamine (L1). A mixture of 2-acetyl-6-(1H-2-
benzimidazolyl)pyridine (474 mg, 2 mmol), 2,6-dimethylaniline
(302 mg, 2.5 mmol), and a catalytic amount of p-toluenesulfonic
acid dissolved in toluene (25 mL) was refluxed for 24 h. After
solvent evaporation, the crude product was purified by column
chromatography on basic Al2O3 with petroleum ether/ethyl acetate
(E)-2,6-Dichloro-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyridin-
2-yl)ethylidene)benzenamine (L5). Using a similar procedure to
that for the synthesis of L1, with silicic acid tetraethyl ester
employed as solvent instead of toluene, L5 was obtained as a white
(v/v ) 3:1) as eluent to afford the product as a light yellow powder
1
1
powder in 31.6% yield. Mp: 160-162 °C. H NMR (300 MHz,
in 68.3% yield. Mp: 194-195 °C. H NMR (300 MHz, CDCl ,
3
CDCl3, TMS): δ 10.39 (brs, 1H, NH), 8.56 (d, 1H, J ) 7.6 Hz,
Py), 8.45 (d, 1H, J ) 7.8 Hz, Py), 8.02(t, 1H, J ) 7.8 Hz, Py),
7.88 (s, 1H, Ar), 7.58 (s, 1H, Ar), 7.38 (m, 4H, Ar), 7.03 (t, 1H, J
) 8.0 Hz, Ar), 2.43(s, 3H, CH3). 13C NMR (75 MHz, CDCl3, TMS):
δ 170.7, 155.2, 150.5, 147.4, 145.5, 144.6, 138.1, 133.8, 128.4,
124.7, 124.6, 124.3, 123.3, 123.1, 120.4, 111.4, 17.9. IR (KBr;
cm-1): 3441 (w), 3054 (w), 2957 (w), 1650 (vs), 1623 (w), 1594
(m), 1570 (m), 1462 (vs), 1434 (vs), 1422 (vs), 1388 (w), 1367
(m), 1320 (s), 1279 (m), 1224 (vs), 1150 (w), 1134 (m), 1074 (m),
1009 (w), 974 (m), 824 (m), 745 (vs). Anal. Calcd for C20H14Cl2N4
(381.26): C, 63.01; H, 3.70; N, 14.70. Found: C, 63.08; H, 3.75;
N, 14.58.
TMS): δ 10.42 (brs, 1H, NH), 8.54 (d, 1H, J ) 7.8 Hz, Py), 8.52
(t, 1H, J ) 7.6 Hz, Py), 8.44(t, 1H, J ) 7.8, Py), 7.99 (d, 1H, J )
7.8 Hz, Ar), 7.56 (d, 1H, J ) 7.6 Hz, Ar), 7.35 (m, 2H, Ar), 7.11
(d, 2H, J ) 7.5 Hz, Ar), 6.98 (t, 1H, J ) 7.4 Hz, Ar), 2.31 (s, 3H,
CH3), 2.06 (s, 6H, CH3). 13C NMR (75 MHz, CDCl3, TMS): δ
166.5, 156.1, 150.8, 148.7, 147.3, 144.6, 137.9, 133.8, 128.1, 125.5,
124.2, 123.4, 123.0, 122.8, 122.3, 120.3, 111.4, 18.1, 16.8. IR (KBr;
cm-1): 3447 (w), 3066 (m), 2953 (m), 2922 (m), 1648 (vs), 1592
(s), 1569 (s), 1464 (vs), 1420 (vs), 1385 (w), 1318 (s), 1278 (w),
1206 (s), 1125 (m), 1092 (w), 993 (w), 823 (w), 767 (m), 744 (vs).
Anal. Calcd for C22H20N4 (340.42): C, 77.62; H, 5.92; N, 16.46.
Found: C, 77.59; H, 5.95; N, 16.42.
(E)-2,6-Dibromo-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyridin-
2-yl)ethylidene)benzenamine (L6). Using the same procedure as
for the synthesis of L5, L6 was obtained as a white powder in
28.5% yield. Mp: 113-114 °C. 1H NMR (300 MHz, CDCl3, TMS):
δ 10.58 (brs, 1H, NH), 8.57(d, 1H, J ) 7.8 Hz, Py), 8.46 (d, 1H,
J ) 7.8 Hz, Py), 8.00 (t, 1H, J ) 7.9 Hz, Py), 7.89 (t, 1H, J ) 5.0
Hz, Ar), 7.58 (m, 3H, Ar), 7.34 (m, 2H, Ar), 6.88 (t, 1H, J ) 8.0
Hz, Ar), 2.40 (s, 3H, CH3). 13C NMR (75 MHz, CDCl3, TMS): δ
170.5, 155.2, 150.6, 148.0, 147.5, 144.6, 138.1, 138.0, 133.9, 132.1,
129.2, 128.4, 125.6, 125.4, 124.3, 123.4, 123.1, 123.0, 120.4, 113.6,
111.4, 17.9. IR (KBr; cm-1): 3405 (m), 3054 (m), 1648 (vs), 1620
(w), 1593 (m), 1569 (m), 1462 (s), 1422 (vs), 1389 (w), 1366 (m),
1318 (s), 1221 (vs), 1196 (w), 1149 (w), 1074 (m), 1008 (w), 993
(w), 822 (m), 756 (w), 742 (vs). Anal. Calcd for C20H14Br2N4
(470.16): C, 51.09; H, 3.00; N, 11.92. Found: C, 51.06; H, 3.04;
N, 11.88.
(E)-2,6-Diethyl-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyridin-2-
yl)ethylidene)benzenamine (L2). Using the same procedure as for
the synthesis of L1, L2 was obtained as a light yellow powder in
61.5% yield. Mp: 235-236 °C. 1H NMR (300 MHz, CDCl3, TMS):
δ 10.46 (brs, 1H, NH), 8.54 (d, 1H, J ) 7.8 Hz, Py), 8.45 (d, 1H,
J ) 8.1 Hz, Py), 8.00 (t, 1H, J ) 7.8 Hz, Py), 7.89 (m, 1H, Ar),
7.57 (d, 1H, J ) 6.0 Hz, Ar), 7.27 (m, 2H, Ar), 7.14 (d, 2H, J )
8.1 Hz, Ar), 7.08 (m, 1H, Ar), 2.56 (q, 4H, J ) 7.5 Hz, CH2), 2.31
(s, 3H, CH3), 1.15 (t, 6H, J ) 7.5 Hz, CH3). 13C NMR (75 MHz,
CDCl3, TMS): δ 166.3, 156.0, 150.8, 147.7, 147.3, 144.6, 138.0,
133.9, 131.2, 126.1, 124.2, 123.6, 122.7, 122.3, 120.3, 111.5, 24.7,
17.1, 13.9. IR (KBr; cm-1): 3449 (w), 3060 (w), 2964 (s), 2931
(m), 2872 (w), 1650 (vs), 1591 (vs), 1569 (vs), 1462 (vs), 1421
(vs), 1386 (w), 1364 (m), 1318 (s), 1279 (m), 1239 (w), 1226 (w),
1197 (m), 1127 (m), 1010 (w), 993 (m), 823 (m), 781 (m), 745
(vs). Anal. Calcd for C24H24N4 (368.47): C, 78.23; H, 6.57; N, 15.21.
Found: C, 78.25; H, 6.59; N, 15.15.
4.4. Synthesis of Tridentate Iron Complexes Fe1-Fe6. The
complexes Fe1-Fe6 were synthesized by the reaction of
FeCl2 · 4H2O with the corresponding ligands in ethanol. A typical
synthetic procedure for Fe1 can be described as follows: The ligand
L1 (71 mg, 0.21 mmol) and FeCl2 · 4H2O (79.5 mg, 0.20 mmol)
were added to a Schlenk tube, followed by the addition of freshly
distilled ethanol (5 mL) with rapid stirring at room temperature.
The solution turned green immediately, and a blue precipitate was
formed. The reaction mixture was stirred for 12 h, and then the
precipitate was washed with diethyl ether twice and dried to give
the pure product as a blue powder in 87.5% yield. IR (KBr; cm-1):
3449 (m), 3065 (m), 2951 (w), 2915 (w), 1599 (vs), 1496 (m),
1473 (s), 1418 (s), 1374 (m), 1321 (s), 1274 (m), 1210 (s), 1098
(m), 1020 (w), 812 (m), 793 (w), 766 (m), 746 (s). Anal. Calcd for
C22H20Cl2FeN4 (467.17): C, 55.56; H, 4.32; N, 11.99. Found: C,
55.50; H, 4.38; N, 11.87. Data for Fe2 are as follows. Yield: 96.3%.
IR (KBr; cm-1): 3433 (m), 3066 (w), 2967 (m), 2934 (w), 1598
(vs), 1495 (w), 1475 (m), 1443 (w), 1413 (m), 1374 (m), 1321 (s),
1299 (m), 1273 (m), 1234 (w) 1202 (m), 1162 (w), 1116 (w), 812
(s), 791 (s), 766 (m), 755 (vs). Anal. Calcd for C24H24Cl2FeN4
(495.23): C, 58.21; H, 4.88; N, 11.31. Found: C, 58.15; H, 4.95;
N, 11.28. Data for Fe3 are as follows. Yield: 92.7%. IR (KBr;
cm-1): 3367 (w), 3061 (m), 2962 (s), 1595 (vs), 1496 (w), 1475
(m), 1439 (m), 1411 (s), 1370 (m), 1318 (vs), 1299 (m), 1273 (w),
1234 (w), 1200 (m), 1176 (w), 1130 (w), 1017 (w), 814 (m), 790
(E)-2,6-Diisopropyl-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyri-
din-2-yl)ethylidene)benzenamine (L3). Using the same procedure
as for the synthesis of L1, L3 was obtained as a light yellow powder
1
in 77.3% yield. Mp: 256-257 °C. H NMR (300 MHz, CDCl3,
TMS): δ 10.44 (brs, 1H, NH), 8.53 (d, 1H, J ) 7.8 Hz, Py), 8.45
(d, 1H, J ) 7.5 Hz, Py), 8.01 (t, 1H, J ) 7.8 Hz, Py), 7.88 (d, 1H,
J ) 6.1 Hz, Ar), 7.56 (d, 1H, J ) 6.1 Hz, Ar), 7.33 (m, 2H, Ar),
7.19 (m, 2H, Ar), 7.12 (m, 1H, Ar), 2.78 (m, 2H, CH), 2.33 (s,
3H, CH3), 1.18 (d, 12H, J ) 6.6 Hz, CH3). 13C NMR (75 MHz,
CDCl3, TMS): δ 166.3, 156.0, 150.8, 147.3, 146.4, 144.6, 138.0,
135.9, 133.9, 132.6, 124.2, 123.9, 123.2, 123.0, 122.7, 122.4, 120.3,
111.5, 28.5, 23.4, 23.0, 22.6, 17.5. IR (KBr; cm-1): 3460 (w), 3046
(w), 2962 (vs), 1655 (vs), 1592 (s), 1569 (vs), 1463 (vs), 1421
(vs), 1386 (s), 1340 (s), 1317 (s), 1278 (w), 1227 (m), 1191 (w),
1128 (w), 1110 (m), 992 (m), 935 (w), 824 (m), 778 (s), 745 (vs).
Anal. Calcd for C26H28N4 (396.53): C, 78.75; H, 7.12; N, 14.13.
Found: C, 78.69; H, 7.15; N, 14.09.
(E)-2,4,6-Trimethyl-N-(1-(6-(1H-benzo[d]imidazol-2-yl)pyri-
din-2-yl)ethylidene)benzenamine (L4). Using the same procedure
as for the synthesis of L1, L4 was obtained as a light yellow powder
1
in 58.2% yield. Mp: 211-212 °C. H NMR (300 MHz, CDCl3,
TMS): δ 10.45 (brs, 1H, NH), 8.53 (d, 1H, J ) 7.7 Hz, Py), 8.43
(d, 1H, J ) 7.2 Hz, Py), 8.00 (t, 1H, J ) 7.8 Hz, Py), 7.89 (t, 1H,
J ) 5.0 Hz, Ar), 7.58 (t, 1H, J ) 3.7 Hz, Ar), 7.33 (m, 2H, Ar),