10.1002/chem.202000047
Chemistry - A European Journal
FULL PAPER
characterized by NMR; otherwise, the data were collected from
hydrochloride salt.
2,6-diflourophenylhydrazine. Yield: 2.38 g (61%). 1H NMR (CDCl3, 400
MHz): δ(ppm) = 6.78-6.68 (m, 3H, m-Ph and p-Ph), 5.30 (br.s., 1H, NH),
3.93 (br.s., 2H, NH2). 13C NMR (DMSO-d6, 101 MHz): δ(ppm) =153.73 (q,
a
(C23H13Cl4N5O2): C 51.81, H, 2.46, N 13.13; Found: C, 51.44, H, 2.89, N
12.79.
LiPr. Yield: 377 mg (67%). 1H NMR (DMSO-d6, 600 MHz): δ(ppm) = 1.14
3
i
3
i
(t, 24H, JH,H = 7.1 Hz, Pr-CH3), 2.25 (sept, 4H, JH,H = 7.1 Hz, Pr-CH),
3
6.16 (s, 2H, pyraz-CH), 7.32 (d, 4H, JH,H = 7.8 Hz, m-Ph-H), 7.48 (t, 2H,
3JH,H = 7.8 Hz, p-Ph-H), 7.75-7.77 (m, 3H, Py), 11.30 (s, 2H, OH, D2O-
exchangeable). 13C NMR (DMSO-d6, 101 MHz): δ(ppm) = 155.16 (s, 5-
pyraz), 152.44 (s, 2-Py), 150.82 (s, 3-pyraz), 147.27 (s, 2-Ph), 137.90 (s,
4-Py), 134.44 (s, 1-Ph), 130.16 (s, 4-Ph), 123.82 (s, 3-Ph), 117.89 (s, 3-
Py), 84.41 (s, 4-pyraz), 28.52 (s, iPr-CH), 24.16 (s, iPr-CH3), 23.82 (s, iPr-
CH3) (Fig. S21). Anal. Calc. for (C35H41N5O2): C, 74.57, H, 7.33, N, 12.42;
Found: C, 73.98, H, 7.10, N, 12.13.
3
2
1JC,F = 242.4 Hz, JC,F = 6.6 Hz, 2-Ph), 128.52 (t, JC,F = 12.7 Hz, 1-Ph),
4
120.46 (t, JC,F = 7.2 Hz, 4-Ph), 111.58 (q, 2JC,F = 15.9 Hz, 4JC,F = 7.1 Hz,
3-Ph) (Fig. S13). Anal. Calc. for (C6H5F2N): C, 55.82, H, 3.90, N, 10.85;
Found: C, 55.67, H, 3.81, N, 10.74.
2,6-dichlorophenylhydrazine. Yield: 2.71 g (51%).1H NMR (CDCl3, 300
MHz): δ(ppm) = 7.24 (d, 3JH,H = 8.3 Hz, 2H, m-Ph), 6.88 (t, 3JH,H = 8.3 Hz,
1H, p-Ph), 5.56 (br.s., 1H, NH), 3.94 (br.s., 2H, NH2). 13C NMR (DMSO-d6,
50 MHz): δ(ppm) = 129.09 (s, 3-Ph), 128,87 (s, 2-Ph), 126.80 (s, 1-Ph),
123.92 (s, 4-Ph) (Fig. S14). Anal. Calc. for (C6H5Cl2N): C, 44.48, H, 3.11,
N, 8.65; Found: C, 44.33, H, 3.01, N, 8.47.
2,6-dimethylphenylhydrazine hydrochloride. Yield: 3.05 g (59%). 1H
NMR (DMSO-d6, 300 MHz): δ(ppm) = 9.65 (s, 3H, NH2 HCl), 7.04 (s, 3H,
Ph), 4.27 (br.s, 1H, NH), 2.34 (s, 6H, 2CH3). 13C NMR (DMSO-d6, 50
MHz): δ(ppm) = 140.84 (s, 1-Ph), 135.34 (s, 2-Ph), 129.05 (s, 3-Ph), 127.5
(s, 4-Ph), 17.99 (s, 2CH3) (Fig. S15). Anal. Calc. for (C8H12ClN): C, 60.95,
H, 7.67, N, 8.89; Found: C, 60.79, H, 7.55, N, 8.77.
2,6-diethylphenylhydrazine hydrochloride. Yield: 2.71 g (45%). 1H
NMR (DMSO-d6, 300 MHz): δ(ppm) = 7.23-7.1 (m, 3H, Ph), 2.55 (q, 4H,
3JH,H = 8.3 Hz, 2CH2), 1.09 (t, 6H, 3JH,H = 8.3 Hz, 2CH3). 13C NMR (DMSO-
d6, 50 MHz): δ(ppm) = 130.87 (s, 1-Ph), 127.81 (s, 2-Ph), 126.82 (s, 3-Ph),
119.91 (s, 4-Ph), 23.38 (s, CH2), 14.89 (s, CH3) (Fig. S16). Anal. Calc. for
(C10H16ClN): C, 64.68, H, 8.68, N, 7.54; Found: C, 64.49, H, 8.54, N, 7.34.
2,6-diisopropylphenylhydrazine hydrochloride. Yield: 2.95 g (43%). 1H
NMR (DMSO-d6, 400 MHz): δ(ppm) = 9.73 (s, 3H, NH2 HCl), 7.30-7.14 (m,
3H, m-Ph and p-Ph), 3.24 (sept, 2H, 3JH,H =6.6 Hz), 1.15 (d, 12H, 3JH,H =6.6
Hz). 13C NMR (DMSO-d6, 150 MHz): δ(ppm) = 141.98 (s, 1-Ph), 128.41
(s, 2-Ph), 128.85 (s, 3-Ph), 124.63 (s, 4-Ph), 27.53 (s, CH), 24.04 (s, CH3)
(Fig. S17). Anal. Calc. for (C12H20ClN): C, 67.43, H, 9.43, N, 6.55; Found:
C, 67.25, H, 9.29, N, 6.35.
General procedure for synthesis of ligands LF, LCl and LiPr. A mixture
of diethyl 3,3'-(pyridine-2,6-diyl)bis(3-oxopropanoate) (0.307 g, 1 mmol)
and an appropriate arylhydrazine (2.3 mmol) was dissolved in 10 mL of
acetic acid to produce an orange solution. After its heating under reflux for
8 h, a light-yellow precipitate was formed. A precipitate was filtered,
washed with acetic acid, then with water, and dried under vacuum. The
product was used without further purification.
LF. Yield: 350 mg (75%). 1H NMR (DMSO-d6, 400 MHz): δ(ppm) = 6.26 (s,
2H, pyraz-CH), 7.37-7.40 (m, 4H, m-Ph-H), 7.63-7.68 (m, 2H, p-Ph-H),
7.84-7.90 (m, 3H, Py). 13C NMR (DMSO-d6, 101 MHz): δ(ppm) = 158.19
(q, 1JC,F = 252,2 Hz, 4JC,F = 3,3 Hz, 2-Ph), 155.49 (s, 5- pyraz), 151.92 (s,
2-Py), 150.94 (s, 3-pyraz), 137.97 (s, 4-Py), 131.74 (t, 3JC,F = 9,9 Hz, 4-Ph),
118.58 (s, 3-Py), 115.10 (t, 2JC,F = 16,0 Hz, 1-Ph), 112.98 (q, 2JC,F = 18.98
Hz, 4JC,F = 3.2 Hz, 3-Ph), 84.75 (s, 4- pyraz). 19F NMR (DMSO-d6, 376
MHz): δ(ppm) = −118.96 (s, 4F, PhF2) (Figs S18-19). Anal. Calc. for
(C23H13F4N5O2): C, 59.11, H, 2.80, N, 14.98; Found: C, 59.18, H, 2.63, N,
14.81.
LCl. Yield: 351 mg (66%). 1H NMR (DMSO-d6, 400 MHz): δ(ppm) = 6.19 (s,
2H, pyraz-CH), 7.61 (t, 2H, 3JH,H = 8.2 Hz, p-Ph-H), 7.72 (d, 4H, 3JH,H = 8.2
Hz, m-Ph-H), 7.80-7.82 (m, 3H, Py). 13C NMR (DMSO-d6, 101 MHz):
δ(ppm) = 155.21 (s, 5-pyraz), 152.11 (s, 2-Py), 151.63 (s, 3-pyraz), 137.95
(s, 4-Py), 134.95 (s, 3-Ph), 133.88 (s, 2-Ph), 132.45 (s, 1-Ph), 129.39 (s,
4-Ph), 118.68 (s, 3-Py), 84.94 (s, 4-pyraz) (Fig. S20). Anal. Calc. for
General procedure for synthesis of ligands LMe and LEt. A mixture of
diethyl 3,3'-(pyridine-2,6-diyl)bis(3-oxopropanoate) (0.307 g, 1 mmol) and
an appropriate arylhydrazine (2.3 mmol) was dissolved in 10 mL of acetic
acid to produce an orange solution. After heating under reflux for 16 h, the
reaction mixture was cooled to r.t. and poured over 50 mL of crushed ice.
A yellow precipitate was filtered, washed with water and dried under high
vacuum. For purification, the yellowish solid was dissolved in a minimum
amount of hot ethanol, and water was added by small portions to this
solution until a precipitate appeared. The mixture was then stored for 12 h
at −10 °C. A precipitate was filtered and dried in high vacuum.
1
LMe. Yield: 333 mg (74%). H NMR (DMSO-d6, 600 MHz): δ(ppm) = 2.06
(s, 12 H, CH3), 6.20 (s, 2H, pyraz-CH), 7.22 (d, 4H, 3JH,H = 7.5 Hz, m-Ph-
3
H), 7.32 (t, 2H, JH,H = 7.5 Hz, p-Ph-H), 7.78 (br.s, 3H, Py), 11.27 (s, 2H,
OH, D2O-exchangeable). 13C NMR (DMSO-d6, 101 MHz): δ(ppm) =
154.39 (s, 5-pyraz), 152.21 (s, 2-Py), 151.10 (s, 3-pyraz), 137.48 (s, 4-Py),
136.88 (s, 1-Ph), 136.82 (s, 3-Ph), 129.36 (s, 4-Ph), 128.37 (s, 2-Ph),
117.96 (s, 3-Py), 84.81 (s, 4-pyraz), 17.67 (s, CH3) (Fig. S22). Anal. Calc.
for (C27H25N5O2): C, 71.82, H, 5.58, N, 15.51; Found: C, 15.09, H, 70.38,
N, 5.67.
LEt. Yield: 395 mg (78%). 1H NMR (DMSO-d6, 600 MHz): δ(ppm) = 1.07 (t,
12H, 3JH,H = 7.4 Hz, CH3), 2.36 (sept, 8H, 3JH,H = 7.4 Hz, CH2), 6.18 (s, 2H,
pyraz-CH), 7.25 (d, 4H, 3JH,H = 7.6 Hz, m-Ph-H), 7.4 (t, 2H, 3JH,H = 7.6 Hz,
p-Ph-H), 7.76 (s, 3H, Py), 11.27 (s, 2H, OH, D2O-exchangeable). 13C NMR
(DMSO-d6, 101 MHz): δ(ppm) = 154.65 (s, 5-pyraz), 152.31 (s, 2-Py),
150.85 (s, 3-pyraz), 142.72 (s, 3-Ph), 137.39 (s, 4-Py), 135.79 (s, 1-Ph),
129.77 (s, 4-Ph), 126.83 (s, 2-Ph), 117.75 (s, 3-Py), 84.43 (s, 4-pyraz),
24.43 (s, CH2), 15.11 (s, CH3) (Fig. S23). Anal. Calc. for (C31H33N5O2): C,
73.35, H, 6.55, N, 13.80; Found: C, 73.84, H, 6.96, N, 12.55.
General procedure for synthesis of complexes [Fe(L)2](ClO4)2, L = LF,
LCl, LMe and LEt. In a 5 ml one-necked flask, iron(II) perchlorate
hexahydrate (0.036 g, 0.1 mmol) and an appropriate ligand (0.2 mmol)
were mixed in 3 ml of acetonitrile and stirred for 3 h. Volatiles were
removed under vacuum. For further purification, the solid residue was
dissolved in a minimum amount of THF, and hexane was added by small
portions until a precipitate appeared. The mixture was then stored for 12 h
at −10 °C. The yellow precipitate was filtered and dried under high vacuum
for 4 h at r. t.
Perchlorate salts are potential explosives, so they must be handled with
care!
[Fe(LF)2](ClO4)2. Yield: 101 mg (85%). 1H NMR (CD3CN, 600 MHz):
δ(ppm) = 9.58 (br.s, 8H, m-Ph-H), 13.01 (br.s, 4H, p-Ph-H), 17.01 (br.s,
4H, OH), 29.38 (br.s, 2H, p-Py-H), 57.54 (br.s, 4H, pyraz-CH), 63.58 (br.s,
4H, m-Py-H) (Fig. S9). Anal. Calc. for (C46H26Cl2F8FeN10O12): C, 46.45, H,
2.20, N, 11.78; Found: C, 45.80, H, 2.85, N, 11.89.
[Fe(LCl)2](ClO4)2. Yield: 120 mg (91%). 1H NMR (CD3CN, 600 MHz):
δ(ppm) = 9.15 (br.s, 8H, m-Ph-H), 11.09 (br.s, 4H, p-Ph-H), 13.38 (br.s,
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