Dissertation

|6.1 Synthesis of the Organic Ligands|
6.1.11 Attempted Synthesis of the triethylborane adduct of
1,3-dibenzyl-1H-imidazo[4,5-f][1,10]phenanthroline-2-ylidene - bbipBEt 3
For the synthesis, 0.41 ml of a 1 M solution of HLiB(Et) 3 were added to a stirred solution of
100 mg bbip in 20 ml of dry tetrahydrofuran under argon atmosphere at -80°C. Upon addition
a darkening of the solution toward yellow was observed. The temperature was raised to room
temperature within 12 hours after the reaction time of 20 minutes at -80°C. After removal of
the solvent and dying under high vacuum 1 H-NMR spectra were recorded in dry chloroform-d
and dry acetonitrile-d 3 . It was observed that the formed product is not sensitive to air. According
to the obtained NMR-spectra it could be concluded that the hydrogenated product was formed.
Indicators are signals for the A-, B-, C-protons which refer to the symmetric ligand, a signal which
refers to the D-position with an peak area of two protons at 4.7 ppm and the missing characteristic
triplet and quartet signals for the ethyl groups at ∼1 ppm.
9
N
N
10
11
6 4
5
CH 2
N
N
CH 2
H
H
Ar
2
Ar
1
H-NMR (CDCl 3 , 400 MHz): δ = 8.97 (d, 2H (6/9) , 3 J = 3.6Hz), 8.35 (dd,
2H (4/11) , 3 J = 8.3 Hz, 4 J = 1.0 Hz), 7.62 (dd, 2H (5/10) , 3 J = 4.5 Hz, 3 J = 8.3 Hz),
7.31 (m, 10H (Ar)) , 4.76 (s, 2H (2)) , 4.25 (d, 2H (CH2 ), 2 J = 23.7 Hz), 4.19 (d,
2H (CH2 ), 2 J = 26.0 Hz) ppm. 1 H-NMR (CD 3 OD, 400 MHz): δ = 8.91 (dd,
1H (6/9) , 3 J = 4.4Hz, 4 J = 1.6 Hz), 8.36 (dd, 2H (4/11) , 3 J = 8.3 Hz, 4 J = 1.6 Hz),
7.64 (dd, 2H (5/10) , 3 J = 8.3 Hz, 3 J = 4.3 Hz), 7.29 (m, 6H (Ar)) , 7.20 (m, 4H (Ar)) , 4.69 (s, 2H (2)) , 4.13 (s,
4H (CH2 )) ppm.
6.1.12 1-Ethyl-1H-imidazo[4,5-f][1,10]phenanthroline - eip
Under argon atmosphere 1.3 g (5.9 mmol) of ip and 260 mg (6.49 mmol) of sodium hydride (60%
in paraffin) were suspended in 50 ml of dry DMF as described in method L2. After stirring
and sonicating for 30 min the imidazolide anion was completely dissolved and no further gas
evolution was observed. Then 440 µl (5.9 mmol) of bromoethane were added and the solution
was stirred for three more hours at room temperature. After the reaction time the solvent was
removed completely under vacuum and the residue was redissolved in chloroform and washed
with water. The combined organic phases were dried over Na 2 SO 4 . After removal of the solvent
the crude product was purified by column chromatography using chloroform and silica gel 60 as
phase system. Yield: 1.43 g (5.8 mmol, 98%) of a colorless solid.
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