Synthesis and structure of biphenylferrocenes
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 3, March, 2003
613
methanol (100 mL) was added dropwise with stirring to a boiling
mixture of 4,4´ꢀdinitrobiphenyl (9.00 g, 0.037 mol), toluene
(50 mL), and methanol (200 mL) during 30 min. The reaction
mixture was refluxed with stirring for 3.5 h, a yellow precipitate
was separated, and the remaining redꢀorange solution was conꢀ
centrated on a rotary evaporator. The product was obtained as
an orange powder in a yield of 5.69 g. After recrystallization
from ethanol (300 mL), 4ꢀaminoꢀ4´ꢀnitrobiphenyl was obtained
in a yield of 4.90 g (63%) as orange crystals, m.p. 191—201 °C
(cf. lit. data9: m.p. 201—203 °C).
diethyl ether from a solution in acetonitrile. Found (%): C, 53.34;
H, 2.57; N, 14.09. C13H8BF4N3. Calculated (%): C, 53.29;
H, 2.75; N, 14.34.
4ꢀBromoꢀ4´ꢀferrocenylbiphenyl (2a). 4´ꢀBromoꢀ4ꢀbiphenylꢀ
diazonium tetrafluoroborate (9.09 g, 0.026 mol) was added
portionwise with stirring to a solution of ferrocene (8.37 g,
0.045 mol) in a mixture of 1,2ꢀdichloroethane (50 mL), glacial
acetic acid (200 mL), and trifluoroacetic acid (15 mL). The
diazonium salt was added at ~20 °C during 1 h, after which the
reaction mixture was stirred for 4 h and kept at ~20 °C for 12 h.
Then water (350 mL) and chloroform (150 mL) were added.
The organic layer was separated and the aqueous layer was exꢀ
tracted with chloroform (50 mL). The combined organic phases
were washed with a solution of ascorbic acid and water until the
reaction mixture became neutral, dried with sodium sulfate, and
filtered. The solvent was removed on a rotary evaporator. The
residue (~12 g) was chromatographed on a column (l 50 cm,
d 2.5 cm) with aluminum oxide. A mixture of ferrocene and
4ꢀbromobiphenyl was eluted with light petroleum, after which
virtually pure 4ꢀbromoꢀ4´ꢀferrocenylbiphenyl was eluted with a
1 : 3 benzene—light petroleum mixture in a yield of 1.16 g (first
portion) and then 4ꢀbromoꢀ4´ꢀferrocenylbiphenyl weakly conꢀ
taminated with an impurity (second portion) was eluted with
benzene in a yield of 3.40 g. Repeated chromatography of the
first portion on a column (l 15 cm, d 2.5 cm) with aluminum
oxide afforded 4ꢀbromoꢀ4´ꢀferrocenylbiphenyl in a yield of 0.93 g
as orange pearly plateletꢀlike crystals, m.p. 202—204 °C. The
second portion of the product was chromatographed three times
on a column (l 20 cm, d 2.5 cm) to obtain 4ꢀbromoꢀ4´ꢀ
ferrocenylbiphenyl in a yield of 2.60 g, m.p. 202—204 °C. The
total yield of 4ꢀbromoꢀ4´ꢀferrocenylbiphenyl was 3.53 g (32%).
Found (%): C, 63.37; H, 4.11; Br, 19.04. C22H17BrFe. Calcuꢀ
lated (%): C, 63.35; H, 4.11; Br, 19.16. 1H NMR, δ: 4.05 (s,
5 H, C5H5); 4.33 (m, 2 H, C(7)H, C(8)H); 4.66 (m, 2 H,
C(6)H, C(9)H); 7.45—7.54 (m, 8 H, Ar).
4ꢀNitroꢀ4´ꢀferrocenylbiphenyl (2b). 4´ꢀNitroꢀ4ꢀbiphenylꢀ
diazonium tetrafluoroborate (4.4 g, 0.014 mol) was added
portionwise with stirring to a solution of ferrocene (3.9 g,
0.021 mol) in a mixture of 1,2ꢀdichloroethane (17 mL), glacial
acetic acid (110 mL), and trifluoroacetic acid (24 mL) at ~20 °C
during 30 min. The reaction mixture was stirred at ~20 °C for
6 h. The mixture gradually turned darkꢀcherry and a cherryꢀ
colored precipitate formed. Then the reaction mixture was kept
without stirring at 4 °C for 18 h, after which water (200 mL) and
chloroform (150 mL) were added. The organic layer was sepaꢀ
rated and the aqueous layer was extracted with chloroform
(150 mL). The combined organic solutions were washed with
water until the mixture became neutral, dried with sodium sulꢀ
fate, and filtered. The solvent was removed on a rotary evaporaꢀ
tor. The crude product, which was obtained as a darkꢀred powꢀ
der in a yield of 5.5 g, was divided into two equal portions. Each
portion was chromatographed on a column (l 20 cm, d 2.9 cm)
with aluminum oxide. Ferrocene was eluted with light petroꢀ
leum. Three fractions, viz., 4ꢀnitrobiphenyl, 4ꢀnitroꢀ4´ꢀferroꢀ
cenylbiphenyl with a small impurity of 4ꢀnitrobiphenyl, and
pure 4ꢀnitroꢀ4´ꢀferrocenylbiphenyl, were eluted with a 1 : 2
light petroleum—chloroform mixture. 4ꢀNitrobiphenyl was exꢀ
tracted from the second fraction with two portions of boiling
light petroleum (2×10 mL). From two portions, 4ꢀnitroꢀ4´ꢀ
ferrocenylbiphenyl was obtained in a yield of 2.2 g (41%) as
4ꢀAminoꢀ4´ꢀcyanobiphenyl (3c). A solution of 90% sodium
hydrosulfide monohydrate (1.90 g, 0.023 mol) in water (15 mL)
was added dropwise with stirring to a boiling suspension of
4ꢀnitroꢀ4´ꢀcyanobiphenyl (2.70 g, 0.012 mol) in methanol
(110 mL) during 15 min. The reaction mixture was refluxed with
stirring for 6 h, during which 4´ꢀcyanoꢀ4ꢀnitrobiphenyl was comꢀ
pletely dissolved. The methanolic solution was concentrated on
a rotary evaporator and the residue was treated with water
(150 mL). The precipitate of the amine that formed was filtered
off, washed on a filter with water (4×25 mL), and dried in air.
The product was purified by chromatography on a column
(l 20 cm, d 2.5 cm) with aluminum oxide. 4ꢀAminoꢀ4´ꢀ
cyanobiphenyl was eluted with chloroform in a yield of 1.95 g
(83%), m.p. 180—184 °C (cf. lit. data7: m.p. 182—184 °C).
4´ꢀNitroꢀ4ꢀbiphenyldiazonium tetrafluoroborate (1b). Hydroꢀ
chloric acid (36%; 15 mL) was added to a suspension of 4ꢀaminoꢀ
4´ꢀnitrobiphenyl (3.83 g, 0.018 mol) in water (120 mL). The
reaction mixture was cooled with ice to 2 °C and then a solution
of sodium nitrite (1.44 g, 0.021 mol) in water (16 mL) was added
dropwise with stirring during 15 min. The reaction mixture was
stirred at 2—4 °C for 30 min and then a solution of ammonium
tetrafluoroborate (2.20 g, 0.021 mol) in water (15 mL) was added,
after which the reaction mixture turned paleꢀpink and solidified.
Then the mixture was kept with periodic stirring at 3—4 °C for
40 min. The precipitate that formed was filtered off, washed on a
filter with cold water (2×35 mL) and ether (2×30 mL), and dried
in air. 4´ꢀNitroꢀ4ꢀbiphenyldiazonium tetrafluoroborate was obꢀ
tained as a paleꢀpink powder (t.decomp. >125—127 °C) in a
yield of 4.90 g (87%). The precipitation with diethyl ether from
a solution in acetonitrile afforded pure 4´ꢀnitroꢀ4ꢀbiphenylꢀ
diazonium tetrafluoroborate. Found (%): C, 46.03; H, 2.42;
N, 13.54. C12H8BF4N3O2. Calculated (%): C, 46.05; H, 2.58;
N, 13.42.
4´ꢀBromoꢀ4ꢀbiphenyldiazonium tetrafluoroborate (1a). The
synthesis was carried out analogously to the synthesis of 4´ꢀnitroꢀ
4ꢀbiphenyldiazonium tetrafluoroborate. 4´ꢀBromoꢀ4ꢀbiphenylꢀ
diazonium tetrafluoroborate was prepared from 4ꢀaminoꢀ4´ꢀ
bromobiphenyl (6.0 g) in a yield of 7.37 g (88%) as a yellow
powder, t.decomp. >128 °C. Pure 4´ꢀbromoꢀ4ꢀbiphenyldiꢀ
azonium tetrafluoroborate was obtained by precipitation with
diethyl ether from a solution in acetonitrile. Found (%): C, 41.29;
H, 2.09; N, 7.87. C12H8BBrF4N2. Calculated (%): C, 41.55;
H, 2.32; N, 8.07.
4´ꢀCyanoꢀ4ꢀbiphenyldiazonium tetrafluoroborate (1c). The
synthesis was carried out analogously to the synthesis of 4´ꢀnitroꢀ
4ꢀbiphenyldiazonium tetrafluoroborate. 4´ꢀCyanoꢀ4ꢀbiphenylꢀ
diazonium tetrafluoroborate was prepared from 4ꢀaminoꢀ4´ꢀ
cyanobiphenyl (2.91 g) in a yield of 3.75 g (85%) as a yellow
powder, t.decomp. >129—131 °C. Pure 4´ꢀcyanoꢀ4ꢀbiphenyldiꢀ
azonium tetrafluoroborate was obtained by precipitation with