Renouard et al.
dihydrochloride (0.2 g, 1.0 mmol). The solution turned yellow and
then formed a precipitate, which was stirred at 60 °C for 12 h.
After cooling to room temperature (25 °C), the solution was treated
with aqueous sodium carbonate. The precipitate was filtered and
washed with methanol to yield the title compound as a pale yellow
powder (170 mg, 67%). 1H NMR (DMSO-d6, δ ppm, J Hz): 9.28
(2H, d, H3,3′, J ) 1.4); 8.86 (2H, d, H5,5′, J ) 1.4); 7.75 (4H, m,
Ar-H); 7.31 (4H, m, Ar-H); 4.07 (6H, s, CH3).
(4) 4′,4′′-Diethoxycarbonyl-2,2′:6′,2′′:6′′,2′′′-quaterpyridine
(L4). Tetrahydrofuran (20 mL) was added to a mixture of NiBr2-
(PPh3)2 (100 mg, 0.144 mmol), zinc (120 mg, 1.89 mmol), and
tetraethylammonium iodide (Et4NI, 60 mg, 0.233 mmol) under
nitrogen at room temperature. The resulting green color of the
solution changed gradually to dark red. Ethyl-6-bromo-2,2′-
bipyridine-4′-carboxylic ester (70 mg, 0.23 mmol)20 was separately
dissolved in THF and added to the above solution by syringe. After
stirring for 16 h at 50 °C, the mixture was poured into 2 M aqueous
ammonia solution (60 mL). To the resulting mixture was added
chloroform (100 mL). The organic layer was separated, and the
aqueous phase was extracted with chloroform (3 × 30 mL). The
combined organic phases were washed with water (5 × 50 mL)
and saturated NaCl solution (50 mL). The organic layer was dried
(MgSO4), and solvent was removed. To the resulting residue was
added concentrated hydrochloric acid (20 mL), and then, the
material was extracted with dichloromethane (3 × 30 mL). The
aqueous phase was cautiously neutralized with solid sodium
carbonate. After extraction with dichloromethane (4 × 40 mL), the
combined organic phases were dried (MgSO4) and the solvent was
removed. Compound L4 was then purified on silica gel with 3/2
dichloromethane/hexane. Yield: 30 mg (58%). 1H NMR (CDCl3):
δ 9.16 (2H, d, J ) 1.50, H3′); 9.03 (2H, d, J ) 1.50, H5′); 8.75
(2H, m, H6); 8.71 (2H, md, J ) 7.80, H3); 7.92 (2H, ddd, J )
8.30, J ) 7.80, J ) 1.95, H4); 7.39 (2H, ddd, J ) 8.30, J ) 7.80,
J ) 1.95, H5); 4.52 (4H, q, J ) 6.90, CH2); 1.50 (6H, t, J ) 6.90,
CH3).
Anal. Found: C, 60.28; H, 4.65; N, 15.36%. Calcd for
C28H20N6O4‚3H2O: C, 60.21; H, 4.69; N, 15.04%.
(2) Synthesis of 4,4′′′-Bis(tert-butyl)-4′,4′′-bis[p-(methoxy-
carbonyl)phenyl]-2,2′:6′,2′′:6′′,2′′′-quaterpyridine (L2). (2.1)
1,6-Bis[p-(methoxycarbonyl)phenyl]hexa-1,5-diene-3,4-dione.
Piperidine (0.5 mL, 5 mmol) and acetic acid (0.3 mL, 5 mmol)
were added to a stirred solution of methyl 4-formylbenzoate (1.55
g, 9 mmol) and 2,3-butanedione (0.4 mL, 4.5 mmol) in methanol
(15 mL). The mixture was refluxed for 6 h, during which bright
orange crystals started to form. After cooling to room temperature,
the crystals were filtered and washed with methanol to yield the
title compound (0.42 g, 25%). 1H NMR (DMSO-d6, δ ppm, J Hz):
8.03 (4H, d, Ar-H, J ) 8.0); 7.95 (4H, d, Ar-H, J ) 8.0); 7.84
(2H, d, dCH, J ) 16.0); 7.50 (2H, d, dCH, J ) 16.0); 3.88 (6H,
s, CH3).
(2.2) N-{2-oxo-2-[2-(4-tert-butyl)pyridyl]ethyl}pyridinium
Iodide. 2-Acetyl-4-tert-butylpyridine (1.6 g, 9 mmol) was added
to a solution of iodine (5 g, 20 mmol) in anhydrous pyridine (20
mL), and the mixture was heated at 70 °C for 1 h. The dark solution
was cooled to room temperature and the solvent evaporated. To
the resulting mixture was added dichloromethane. After filtration
and evaporation, the title compound was collected as fine brownish
crystals (0.94 g, 66%). 1H NMR (CDCl3, δ ppm, J Hz): 9.01 (2H,
d, H2′,6′, J ) 6.6); 8.78 (1H, dd, H,6 J ) 5.1, 0.55); 8.28 (2H, d,
H3′,5′, J ) 6.6); 8.15 (1H, d, H4′, J ) 7.7); 8.02 (1H, dd, H3, J )
1.2, 0.55); 7.85 (1H, dd, H,5 J ) 5.1, 1.2); 6.51 (2H, s, CH2); 1.34
Anal. Found: C, 68.64; H, 5.01; N, 12.26%. Calcd for
C26H22N4O4: C, 68.71; H, 4.88; N, 12.33%.
(5) Synthesis of Ru(L1)Cl2. [Ru(p-cymene)Cl2]2 (61 mg, 0.1
mmol) was dissolved in ethanol (50 mL) by heating. To this orange
solution was added ligand L1 (100 mg, 0.2 mmol), and the mixture
was refluxed for 6 h. The black precipitate which formed was
filtered and washed with ethanol to yield the title compound as a
1
t
dark powder (120 mg, 90%). H NMR (DMSO-d6, δ ppm, J Hz):
(9H, s, Bu).
9.12 (4H, broad s, H3, H5); 8.49 (2H, d, Ha, J ) 8); 7.92 (2H, d,
Hd, J ) 7); 7.69 (4H, m, Hb, Hc); 4.10 (6H, s, CH3).
(2.3)
4,4′′′-Bis(tert-butyl)-4′,4′′-bis[p-(methoxycarbonyl)-
phenyl]-2,2′:6′,2′′:6′′,2′′′-quaterpyridine. 1,6-Bis[p-(methoxy-
carbonyl)phenyl]hexa-1,5-diene-3,4-dione (1.65 g, 4.3 mmol), N-{2-
oxo-2-[2-(4-tert-butyl)pyridyl]ethyl}pyridinium iodide (3.5 g, 9.2
mmol), and ammonium acetate (1 g, 13 mmol) were refluxed in
ethanol (25 mL) for 12 h. The mixture was cooled to room
temperature, and the precipitate which formed was filtered and
washed with ethanol to yield the title compound as a brownish
powder (0.68 g, 23%). 1H NMR (CDCl3, δ ppm, J Hz): 9.06 (2H,
Anal. Found: C, 49.08; H, 3.07; N, 11.88%. Calcd for
C28H20N6O4Cl2Ru: C, 49.66; H, 2.98; N, 12.41%.
(6) Synthesis of Ru(L1)(SCN)2. To a solution of complex 5 (42
mg, 6 × 10-5 mol) in DMF (35 mL) was added ammonium
thiocyanate (350 mg, 4.6 mmol) in water (15 mL). The reaction
mixture was heated at 140 °C for 3 h. The solution was allowed to
cool to room temperature. The black precipitate which formed was
filtered, washed thoroughly with water, and dried under vacuum
to yield the title compound as a dark powder (10 mg, 23%). The
resulted crude complex was further purified using a Sephadex LH-
d, H3′,5′′, J ) 1.6); 8.82 (2H, d, H5′,3′′, J ) 1.6); 8.81 (2H, d, H3,3′′′
,
J ) 1.4); 8.68 (2H, d, H6,6′′′, J ) 5.3); 8.24 (4H, d, Ar-H, J )
8.5); 8.05 (4H, d, Ar-H, J ) 8.5); 7.42 (2H, dd, H5,5′′′, J ) 5.3,
1
20 column. H NMR (DMSO-d6, δ ppm, J Hz): 9.32 (2H,s, H3);
t
1.9); 4.00 (6H, s, CH3); 1.49 (18H, s, Bu).
9.05 (2H, s, H5); 8.42 (2H, d, Ha, J ) 8.0); 7.98 (2H, d, Hd, J )
8); 7.69 (4H, broad m, Hb, Hc), 4.10 (6H, s, CH3).
Anal. Found: C, 76.53; H, 6.10; N, 8.05%. Calcd for
C44H42N4O4: C, 76.49; H, 6.12; N, 8.11%.
Anal. Found: C, 49.27; H, 2.73; N, 15.25%. Calcd for
C30H20N8O4S2Ru: C, 49.88; H, 2.79; N, 15.51%.
(3) Synthesis of 4′,4′′-bis[3,4-(dimethoxy)phenyl]-2,2′:6′,2′′:
6′′,2′′′-quaterpyridine (L3). Using the same conditions as for
compound L2, starting from 1,6-bis[3,4-(dimethoxy)phenyl]hexa-
1,5-diene-3,4-dione (1.5 g, 4. mmol) and N-[2-oxo-2-(2-pyridyl)-
ethyl]pyridinium iodide (3.5 g, 9.2 mmol), the title compound was
obtained as a pale yellow powder (475 mg, 21%). 1H NMR (CDCl3,
ppm, J Hz): 8.91 (2H, d, H3′,5′′, J ) 1.7); 8.78 (2H, m, H3,3′′′); 8.75
(2H, m, H5′,3′′); 8.71 (2H, m, H6,6′′′); 7.94 (2H, dd, H4,4′′′, J ) 7.7,
1.6); 7.55 (2H, d, Ar-H, J ) 8.3, 2.0); 7.46 (2H, d, Ar-H, J )
2.0); 7.41 (2H, dd, H5,5′′′, J ) 7.4, 1.5); 7.07 (2H, d, Ar-H, J )
8.3); 4.06 (6H, s, CH3); 4.00 (6H, s, CH3).
(7) Synthesis of Ru(L2)Cl2. Using the same conditions as for
complex 5, starting from ligand L2 (120 mg, 1.8 × 10-4 mol), the
title compound was obtained as a dark powder (130 mg, 89%). 1H
NMR (DMSO-d6, δ ppm, J Hz): 9.61 (2H, d, H6, J ) 6); 9.10
(2H, d, H3′, J ) 2); 9.01 (2H, d, H5′, J ) 2); 8.78 (2H, d, H3, J )
2); 8.36 (4H, d, Ha, J ) 8.4); 8.18 (4H, d, Hb, J ) 8.4); 7.90 (2H,
t
dd, H,5 J ) 5.7, 1.8); 3.95 (6H, s, CH3); 1.54 (18H, s, Bu).
Anal. Found: C, 59.58; H, 4.85; N, 6.42%. Calcd for C44H42N4O4-
Cl2Ru: C, 61.20; H, 4.90; N, 6.48%.
Anal. Found: C, 74.30; H, 5.35; N, 9.46%. Calcd for
C36H30N4O4: C, 74.21; H, 5.20; N, 9.61%.
(20) Fallahpour, R.-A. Synthesis 2000, 1138. (b) Iyoda, M.; Otsuka, H.;
Sato, K.; Nisato, N.; Oda, M. Bull. Chem. Soc. Jpn. 1990, 63, 80.
370 Inorganic Chemistry, Vol. 41, No. 2, 2002