Inorganic Chemistry
Article
N-(4-Methylphenyl)benzenethioamide (C). Synthesized as pre-
viously reported.36
stirring, resulting in a brick red suspension that was stirred overnight.
The reaction mixture was taken to dryness on a rotary evaporator
giving a reddish solid. Saturated aqueous sodium bicarbonate was
added to the solid with stirring until bubbles stopped forming (∼80
mL), and then the product was extracted with CH2Cl2 (5 × 80 mL).
The combined organic fractions were filtered to remove a brown solid
impurity (Caution! Toxic selenium residues must be disposed of
appropriately). The filtrate was washed with saturated NaCl (100
mL), and the resulting organic fraction was dried over MgSO4 then
taken to dryness, giving a dark brown oil (2.0 g). The oil was dried
under high vacuum for 8 h, to give the desired product as a brown
crystalline solid (1.9 g, 61% from 4-methyl pyrimidine). C7H8N2O2 (M
= 152.15 g mol−1): calcd C 55.26, H 5.30, N 18.41; found: C 54.71, H
5.34, N 17.98%. 1H NMR (400 MHz, CDCl3): δ (ppm) = 9.42 (s, 1H,
H1), 9.00 (d, 3J = 5.1 Hz, H2), 8.03 (dd, J = 1.4, 4.8 Hz, 1H, H3), 4.51
(q, 3J = 7.2 Hz, 2H, −CH2), 1.46 (t, 3J = 7.2 Hz, 3H, CH3). 13C NMR
(126 MHz, d6-DMSO): δ (ppm) = 164.0, 159.2, 159.0, 154.9, 120.9,
62.8, 14.2. ESI-MS m/z: 175.0487 ([Na(C7H8N2O2)]+ calcd
175.0484). IR (ATR) ν, cm−1: 3317, 2983, 1723, 1387, 1309, 1188,
1133, 999, 834, 703.
Ethyl N-(4-Methylphenyl)benzenethiocarboximido-thioate. Syn-
thesized as previously reported.36
4-(4-Methylphenyl)-3-(2-pyrimidinyl)-5-phenyl-1,2,4-triazole
( L 2 p y r i m i d i n e ) . C r u d e e t h y l N - ( 4 - m e t h y l p h e n y l ) -
benzenecarboximidothioate (0.8 g, 3 mmol) and pyrimidine-2-
carbohydrazide (0.4 g, 3 mmol) were dissolved in 1-butanol (30
mL) and refluxed for 3 d. The reaction mixture was taken to dryness
under reduced pressure to give a brown solid (1.3 g). Column
chromatography of the crude solid (silica, 10% CH3OH in CHCl3)
gave the ligand L2pyrimidine as a yellow solid (0.7 g), which was found to
1
be impure by H NMR. Recrystallization of this solid from toluene
gave analytically clean L2pyrimidine as a pale yellow solid (0.4 g, 40%).
C19H15N5 (M = 313.36 g mol−1): calcd C 72.83, H 4.82, N 22.35%;
1
found C 72.55, H 4.75, N 22.08%. H NMR (400 MHz, CDCl3): δ
(ppm) = 8.71 (d, J = 4.9 Hz, 2H, H1 and H3), 7.48 (d, J = 7.1 Hz, 2H,
H8), 7.37 (m, J = 7.3, 1H, H10), 7.30 (m, J = 7.7, 2H, H9), 7.24 (m, J =
4.9 Hz, 1H, H2), 7.18 (d, J = 8.1 Hz, 2H, H12), 7.11 (d, J = 8.3 Hz, 2H,
H13), 2.41 (s, 3H, H15). 13C NMR (101 MHz, CDCl3): δ (ppm) =
157.3 (C1 and C3), 156.3 (C6), 155.8 (C5), 152.9 (C4), 139.5 (C14),
133.0 (C11), 129.96 (C10), 129.94 (2 × C12), 129.0 (2 × C8), 128.5 (2
× C9), 127.7 (2 × C13),126.6 (C7), 120.8 (C2), 21.4 (methyl C15).
Pyrimidine-4-carbohydrazide (B). Caution! Hydrazine hydrate is
potentially explosive. Perform the reaction behind a blast screen in a fume
hood. Dispose of hydrazine hydrate residues appropriately. 80%
Hydrazine hydrate (4 mL, 4.1 g, 80 mmol) was added to a solution
of ethyl pyrimidine-4-carboxylate (1.9 g, 10 mmol) in ethanol (7 mL).
This mixture was refluxed for 3 h behind a blast screen. When the
reaction solution was cooled to −18 °C in the freezer a dark yellow
precipitate appeared. The precipitate was filtered and washed with cold
ethanol (5 mL) and then air-dried for 1 h to give a brown solid (1.3 g).
The solid was recrystallized from CH3CN (20 mL) to give pure
product as a pale yellow solid (0.6 g, 36%). A second crop of clean
material was obtained from the filtrate (0.3 g, 15%). Combined yield:
0.9 g, 51%. C5H6N4O (M = 138.13 g mol−1): calcd C 43.48, H 4.38, N
ESI-MS m/z: 649.2490 ([Na(L2pyrimidine)2]+ calcd 649.2547),
,
336.1190 ([Na(L2pyrimidine)]+, calcd 336.1220), 314.1375 ([H-
(L2pyrimidine)]+, calcd 314.1400). IR (ATR) ν, cm−1: 3035, 1555,
1512, 1449, 1389, 1213, 819, 779, 692, 626, 605. UV−Vis (λ, nm and
maximum values of ε, L·mol−1·cm): 268 (16 396).
4-Methylpyrimidine. Caution! Colorless, odorless, and highly toxic
carbon monoxide gas is evolved during this reaction. Perform reaction in
well-ventilated fumehood. In a fumehood on boost, a colorless mixture
of formamide (60.0 g, 1.4 mol), ammonium chloride (3.5 g, 70 mmol),
and H2O (2 mL, 110 mmol) was heated to 180 °C in a three-necked
flask. 4,4′-Dimethoxy-2-butanone (27.0 g, 210 mmol) was then added
dropwise over the course of 3 h, during which the mixture changed
from colorless to orange to red-brown. The resulting red-brown
solution was heated at 180 °C for 2 h. After being cooled to RT, the
solution was neutralized with 0.1 mol L−1 NaOH(aq) (60 mL) and
extracted with CHCl3 (3 × 100 mL). The combined organic fractions
were dried over MgSO4 and taken to dryness yielding a thick brown oil
(18.2 g, 190 mmol, 95% based on 4,4′-dimethoxyl-butanone). C5H6N2
1
40.56%; found C 43.73, H 4.37, N 40.85%. H NMR (400 MHz, d6-
DMSO): δ (ppm) = 10.27 (br s, 1H, CONH), 9.26 (d, J = 1.3 Hz, 1H,
H1), 9.02 (d, J = 5.1 Hz, 1H, H2), 7.96 (dd, J = 5.1, 1.4 Hz, 1H, H3),
4.68 (br s, 2H, NH2). 13C NMR (d6-DMSO): δ (ppm) = 161.2, 159.9,
158.3, 156.9, 118.9. ESI-MS: m/z = 167.0393 ([C5H6N4O+Et]+ calcd
167.0933). IR (ATR) ν, cm−1: 3332, 2915, 1685, 1509, 1428, 1367,
1282, 1146, 701, 660, 572.
4-(4-Methylphenyl)-3-(4-pyrimidinyl)-5-phenyl-1,2,4-triazole
( L 4 p y r i m i d i n e ) . C r u d e e t h y l N - ( 4 - m e t h y l p h e n y l ) -
benzenecarboximidothioate (1.0 g, 40 mmol) and pyrimidine-4-
carbohydrazide (0.5 g, 4 mmol) were dissolved in 1-butanol (30
mL) and refluxed for 3 d. When the solution was cooled a pale yellow
solid precipitated out of the yellow reaction mixture. The solid was
filtered off and washed with cold butanol (10 mL) and then cold H2O
(10 mL) to remove unreacted pyrimidine-4-carbohydrazide. The solid
was then air-dried for 1 h to give analytically pure 4-(4-methylphenyl)-
3-(4-pyrimidyl)-5-phenyl-1,2,4-triazole (L4pyrimidine) (0.8 g, 68%) as a
pale yellow powder. Slow evaporation of a CH2Cl2/CH3OH (5:1)
solution of ligand L4pyrimidine yielded colorless rectangular single
crystals of L4pyrimidine suitable for X-ray diffraction. C19H15N5 (M =
313.36 g mol−1): calcd C 72.83, H 4.82, N 22.35%; found C 72.83, H
4.89, N 22.26%. 1H NMR (400 MHz, CDCl3): δ (ppm) = 8.97 (s, 1H,
H1), 8.85 (d, J = 5.1 Hz, 1H, H2), 8.22 (d, J = 4.7 Hz, 1H, H3), 7.51 (d,
J = 7.7 Hz, 2H, H8), 7.41 (t, J = 7.8 Hz, 1H, H10), 7.33 (t, J = 7.3 Hz,
2H, H9), 7.23 (d, J = 8.1 Hz, 2H, H13), 7.13 (d, J = 8.5 Hz, 2H, H12),
2.45 (s, 3H, H15). 13C NMR (126 MHz, CDCl3): δ (ppm) = 158.3
(C1), 157.7 (C2), 156.7 (C6), 154.2 (C5), 151.9 (C4), 139.8 (C14),
132.9 (C11), 130.2 (C10), 130.1 (2 × C13), 129.0 (2 × C8), 128.6 (2 ×
C9), 127.7 (2 × C12), 126.4 (C7), 120.3 (C3), 21.5 (methyl C15). ESI-
MS m/z: 649.2488 ([Na(L4pyrimidine)2]+ calcd 649.2547), 336.1175
([Na(L4pyrimidine)]+ calcd 336.1220), 314.1393 ([H(L4pyrimidine)]+ calcd
314.1400). IR (ATR) ν, cm−1: 3036, 1573, 1511, 1512, 1462, 1445,
1379, 847, 821, 776, 710, 690, 662, 604. UV−vis (λ, nm and max
values of ε, L·mol−1·cm): 284 (15 523).
1
(M = 94.10 g mol−1). H NMR (400 MHz, CDCl3): δ (ppm) = 9.03
3
3
(s, 1H, H1), 8.52 (d, J = 5.2 Hz, 1H, H2), 7.14 (d, J = 5.2 Hz, 1H,
H3), 2.48 (s, 3H, HMe). IR (ATR) ν, cm−1: 2927, 2855, 1685, 1618,
1431, 1389, 1254, 1158, 1029, 775, 636, 516.
Pyrimidine-4-carboxylic Acid. Caution! Toxic and ecotoxic elemental
selenium and selenium salts are produced during this procedure, so the
reaction must be performed in a fumehood, and the selenium residues must
be disposed of appropriately. Solid SeO2 (3.4 g, 31 mmol) was slowly
added to a light yellow solution of crude 4-methylpyrimidine (1.9 g, 20
mmol) in pyridine (20 mL). The solution was stirred for 10 min,
during which it changed to orange and then to a dark red/brown, then
heated to 80 °C for 4 h. After the resulting red suspension was cooled
to room temperature, H2O (10 mL) was added, and the suspension
was stirred for 15 min before being filtered through filter paper, and
the residue on the filter paper was washed with H2O (3 × 20 mL). The
combined filtrates were taken to dryness, giving a dark brown solid. To
azeotrope off any remaining H2O, the solid was suspended in ethanol
(50 mL) and taken to dryness, then suspended in toluene (50 mL)
and taken to dryness again. The resulting crude brown solid (2.4 g,
95%) was used in the subsequent reaction without further purification.
C5H4N2O2 (M = 124.10 g mol−1). 1H NMR (400 MHz, d6-DMSO): δ
(ppm) = 9.35 (s, 1H, H1), 9.04 (d, 3J = 5.0 Hz, 1H, H2), 7.99 (d, 3J =
5.0 Hz, 1H, H3). 13C NMR (126 MHz, d6-DMSO): δ (ppm) = 165.8,
159.9, 159.2, 156.1, 121.3. IR (ATR) ν, cm−1: 3042 (br), 1686, 1590,
1386, 1281, 1058, 1013, 872, 690.
Ethyl Pyrimidine-4-carboxylate. Crude pyrimidine-4-carboxylic
acid (2.3 g, maximum 20 mmol) was suspended in dry ethanol (30
mL), and the flask was placed in an ice bath. To this suspension
thionyl chloride (3.3 g, 2.0 mL, 30 mmol) was added dropwise under
Inorganic Synthesis. [FeII(L2pyrimidine)2(NCS)2] (1). Under nitrogen,
a pale yellow solution of L2pyrimidine (62.0 mg, 198 μmol) in 1:1
CH3OH/CHCl3 (5 mL) was added to a yellow/green solution of
L
Inorg. Chem. XXXX, XXX, XXX−XXX