868
M.R. Rao et al. / Journal of Organometallic Chemistry 695 (2010) 863–869
(
SHELXS-97) [12] and refined using full-matrix least-squares meth-
pound was subjected to silica gel column chromatography using
ods on F2 using SHELXL-97 [13].
of petroleum ether/dichloromethane (80:20) and afforded 1 as
blue solid in 70% yield (46 mg). 1H NMR (400 MHz, CDCl3, d in
ppm): 2.47 (s, 3H; CH3), 4.34–4.37 (m, 7H; Fc), 4.67 (s, 2H; Fc),
6.53 (m, 1H; Py), 6.63 (d, 3J(H, H) = 3.98 Hz, 1H; Py), 6.90 (m, 2H;
Py), 7.32 (d, 3J(H, H) = 7.6 Hz, 2H; Ar), 7.44 (d, 3J(H, H) = 7.94 Hz,
2H; Ar); 7.94 (s, 1H; Py), 19F NMR (CDCl3): ꢀ146.3 [q, J(B, F)]; MAL-
5.1.1. 3-Bromo-4,4-difluoro-8-(4-tolyl)-4-bora-3a,4a-diaza-s-
indacene (5)
This compound was prepared in sequence of steps in one pot
reaction. Meso-(p-tolyl)-dipyrromethane 10 (500 mg, 2.12 mmol)
was treated with one equivalent of N-bromosuccinimide
(377 mg, 2.12 mmol) in dry THF (50 mL) at ꢀ78 °C under nitrogen
for 1 h. The reaction mixture was warmed to room temperature
and DDQ (483 mg, 2.12 mmol) in THF was added dropwise over
10 min. The solvent was removed on rotary evaporator under vac-
uum. The crude compound was subjected to flash column chroma-
tography using CH2Cl2, concentrated on rotary evaporator,
dissolved in CH2Cl2, neutralized with triethylamine (10.49 mL,
75.4 mmol) and treated with BF3ꢁEt2O (13.44 mL, 107.0 mmol) at
room temperature for additional 1 h. The reaction mixture was
washed successively with 0.1 M NaOH solution and water. The or-
ganic layers were combined, dried over Na2SO4, filtered, and evap-
orated. The TLC analysis of crude compound showed three spots;
the first minor spot corresponding to unsubstituted boron-dipyrro-
methene, the second major spot corresponding to the required 3-
bromo derivative of BODIPY 5 and the last minor spot correspond-
ing to 3,5-dibromo substituted boron-dipyrromethenes. The crude
compound was subjected to silica gel column chromatography and
the required 3-bromo derivative of BODIPY 5 was collected as sec-
ond band using of petroleum ether/dichloromethane (90:10). The
solvent was removed on rotary evaporator under vacuo and affor-
ded pure 5 as purple powder (457 mg, 60% yield). 1H NMR
(400 MHz, CDCl3, d in ppm): 2.47 (s, 3H; CH3), 6.53 (m, 2H; Py),
6.57 (m, 2H; Py), 6.84 (d, 3J(H, H) = 4.28 Hz, 2H; py), 6.93 (d, 3J(H,
H) = 3.70 Hz, 2H; py), 7.38 (d, 3J(H, H) = 7.95 Hz, 2H; Ar), 7.44 (d,
3J(H, H) = 7.95 Hz, 2H; Ar); ES-MS: (C16H13BBrF2N2) 341.09
[M+ꢀF]; CHN calc.: C-53.23, H-3.35, N-7.76, Obsd. C-53.58, H-
3.99, N-7.70.
DI-TOF: (C28H27BF2N2Fe) 474.1[M+ꢀF], UV–vis (in toluene, kmax
/
nm, log e
/molꢀ1 dm3 cmꢀ1): 531 (4.67), 613br (4.19); CHN calc.:
C-68.61, H-4.32, N-5.72, Obsd. C-53.58, H-3.77, N-7.72.
5.1.4. 3,5-bis(ferrocenylethynyl)-4,4-difluoro-8-(4-tolyl)-4-bora-
3a,4a-diaza-s-indacene (2)
Samples of compound 6 (50 mg, 113
cene (24 mg, 113 mol), were coupled in the presence of CuI
(2.1 mg, 11.3 mol), and Pd(PPh3)2Cl2 (4.8 mg, 6.78 mol) in tolu-
lmol) and ethynylferro-
l
l
l
ene/triethylamine at 60 °C for 6 h under inert atmosphere. Column
chromatographic purification on silica gel using petroleum ether/
dichloromethane (70:30) afforded 2 as violet solid (51 mg, 65%).
1H NMR (400 MHz, CDCl3, d in ppm): 2.46 (s, 3H; CH3), 4.35–4.38
(m, 7H; Fc), 4.69 (s, 2H; Fc), 6.63 (d, 3J(H, H) = 4.28 Hz, 1H; Py),
6.84 (d, 3J(H, H) = 4.28 Hz, 1H; Py), 7.32 (d, 3J(H, H) = 7.94 Hz, 2H;
Ar), 7.42 (d, 3J(H, H) = 7.94 Hz, 2H; Ar); 19F NMR (CDCl3): ꢀ146.5
[q, J(B, F)]; 13C NMR (100 MHz, CDCl3, 25 °C): 21.6, 70.1, 70.7,
72.4, 80.4, 103.6, 123.5, 127.8, 129.2, 129.8, 130.4, 130.7, 131.6,
135.3, 136.6, 140.7; MALDI-TOF: (C40H29BF2N2Fe2) 698.1 [M+1]+;
UV–vis (in toluene, kmax/nm, log e
/molꢀ1 dm3 cmꢀ1): 558 (4.42),
680br (4.31); CHN calc.: C-68.95, H-4.66, N-3.92, Obsd. C-68.58,
H-4.01, N-3.99.
5.1.5. 4,4-Difluoro-8-(ferrocenyl)-4-bora-3a,4a-diaza-s-indacene (3)
Sample of meso-ferrocenyl dipyrromethane
7
(300 mg,
0.91 mmol) was taken in CH2Cl2 (30 mL) and oxidized with DDQ
(207 mg, 0.91 mmol) at room temperature for 1 h. Triethylamine
(4.86 mL, 36.4 mmol) followed by BF3ꢁEt2O (5.67 mL, 45.5 mmol)
was added, and continued stirring at room temperature for addi-
tional 1 h. The reaction mixture was diluted with CH2Cl2 and
washed thoroughly with 0.1 M NaOH solution and water. The or-
ganic layers were combined, dried over Na2SO4, filtered, and sol-
vent was removed on rotary evaporator under vacuum. The
resulted crude product was purified by column chromatography
on silica gel, using petroleum ether/dichloromethane (75:25) and
afforded pure compound 3 as a green powder (102 mg, 30%). 1H
NMR (400 MHz, CDCl3, d in ppm): 4.22 (s, 5H; Fc), 4.75 (m, 2H;
Fc), 4.97 (m, 2H; Fc), 6.54 (m, 2H; Py), 7.66 (m, 2H; Py); 7.85 (m,
2H; Py); 19F NMR (CDCl3): ꢀ146.2 [q, J(B, F)]; 13C NMR (100 MHz,
CDCl3, 25 °C): 72.1, 72.3, 74.2, 79.3, 117.6, 130.1, 134.9, 140.9,
151.8; MALDI-TOF: (C19H15BF2N2) 374.5 [M+]; UV–vis (in toluene,
5.1.2. 3,5-Dibromo-4,4-difluoro-8-(4-tolyl)-4-bora-3a,4a-diaza-s-
indacene (6)
This compound 6 was prepared by following the same proce-
dure mentioned for 5 using two equivalents of N-bromosuccini-
mide instead of one equivalent used for the preparation of 5. The
TLC analysis showed two spots corresponding to 3-bromo deriva-
tive of boron-dipyrromethene 5 as minor spot and the desired
3,5-dibromo derivative of BODIPY 6 as major spot. The crude com-
pound was subjected to silica gel column chromatography and the
pure compound 6 was collected as second band using of petroleum
ether/dichloromethane (85:15). The solvent was removed on ro-
tary evaporator under vacuo and afforded 6 as purple powder
(600 mg, 64%). 1H NMR (400 MHz, CDCl3, d in ppm): 2.46 (s, 3H;
CH3), 6.53 (d, 3J(H, H) = 4.28 Hz, 2H; Py), 6.82 (d, 3J(H,
H) = 4.28 Hz, 2H; Py), 7.32 (d, 3J(H, H) = 7.9 Hz, 2H; Ar), 7.38 (d,
3J(H, H) = 7.9 Hz, 2H; Ar); ES-MS: (C16H11BBr2F2N2) 421.06
[M+ꢀF]; CHN clcd: C-43.69, H-2.52, N-6.37, Obsd. C-43.60, H-
3.99, N-7.41.
kmax/nm, log e
/molꢀ1 dm3 cmꢀ1): 509 (4.88), 656br (3.72); CHN
calc.: C-60.69, H-4.02, N-7.45, Obsd. C-60.58, H-3.99, N-7.70.
5.1.6. 4,4-Difluoro-8-[4-(ferrocenylethynyl)phenyl]-4-bora-3a,4a-
diaza-s indacene (4)
Samples of meso-(4-iodophenyl) boron-dipyrromethene
8
(50 mg, 127
dry toluene/triethylamine (3:1, 20 mL) were coupled in the pres-
ence of catalytic amounts of CuI (2.4 mg, 12.7 mol) and
Pd(PPh3)2Cl2 (5.3 mg, 7.62 mol) at 50 °C for 6 h. The formation
of the desired compound was confirmed by the appearance of
new spot on TLC. The crude compound was purified by silica gel
column chromatography, and the pure compound 4 was collected
using petroleum ether/dichloromethane (80:20) as orange solid
(39 mg, 65%). 1H NMR (400 MHz, CDCl3, d in ppm): 4.27–4.30 (m,
7H; Fc), 4.55 (m, 2H; Fc), 6.56 (m, 3J(H, H) = 3.98 Hz, 2H; Py),
6.97 (d, 3J(H, H) = 3.98 Hz, 2H; Py), 7.53 (d, 3J(H, H) = 7.94 Hz, 2H;
Ar), 7.62 (d, 3J(H, H) = 8.3 Hz, 2H; Ar); 19F NMR (CDCl3): ꢀ146.2
lmol) and ethynylferrocene (26 mg, 127 lmol) in
5.1.3. 3-Ferrocenylethynyl-4,4-difluoro-8-(4-tolyl)-4-bora-3a,4a-
diaza-s-indacene (1)
l
Samples of 5 (50 mg, 138
138 mol) was dissolved in toluene/triethylamine (20 mL, 5:1)
and nitrogen was purged for 10 min. The coupling reaction was ini-
tiated by addition of catalytic amounts of CuI (2.6 mg, 13.8 mol)
and Pd(PPh3)2Cl2 (5.9 mg, 8.28 mol) and the reaction mixture
lmol) and ethynylferrocene (29 mg,
l
l
l
l
was stirred at 50 °C for 4 h. The reaction progress was followed
by TLC analysis at frequent intervals. The TLC analysis showed
the disappearance of starting materials and appearance of new
spot corresponding to the desired compound 1. The crude com-