Dalton Transactions
Page 4 of 10
DOI: 10.1039/C5DT00575B
was stirred for
5
min before 7.5 mL (100 mmol) of
then sodium triacetoxyborohydride (2.12 g, 10 mmol) in
dimethylformamide was added. The solution was further stirred 60 methanol (5 mL) was dropwise added to the resulting solution
for 1 h at −78 oC and then allowed to warm slowly to room
temperature. Then, 25 mL HCl (12 mol L−1) were added before
another 1 h’s stirring. The pH of the mixture was then adjusted to
10 with NaOH (aq., 40%) and extracted with dichloromethane (3
under stirring. After the solution was stirred for 2 days at room
temperature, it was acidified by adding HCl (2 mol L−1) and then
evaporated to dryness under reduced pressure. The residue was
dissolved in saturated aqueous Na2CO3 solution (25 mL) and
5
× 60 mL). All organic extracts were combined and dried with 65 extracted with CHCl3 (3 × 50 mL). The combined extracts were
Na2SO4. After evaporation of the solvents, a yellow oily liquid
dried over anhydrous Na2SO4 and filtered. A light yellow oily
liquid (1.14 g, 43%) was collected by column chromatography
(eluent: EA−EtOH−Et3N = 5 : 1 : 0.1). 1H NMR (400 MHz,
CDCl3): δ10.90 (s, 1H, OH), 8.54 (d, J = 4.8 Hz, 1H, Py), 7.60
70 (td, J = 7.7, 1.6 Hz, 1H, Py), 7.21 – 7.13 (m, 3H, 2Py, Ph), 7.06
(d, J = 7.4 Hz, 1H, Ph), 6.91 – 6.86 (m, 2H, Ph, Im), 6.76 (dd, J =
7.3, 6.8 Hz, 1H, Ph), 6.71 (s, 1H, Im), 3.85 (s, 2H, CH2), 3.72 (s,
4H, 2CH2), 3.38 (s, 3H, CH3).
(5.33 g, 97%) was collected by silica gel flash chromatography
1
10 (eluent: ethyl acetate, EA). H NMR (400 MHz, CDCl3): δ 9.78
(s, 1H, CHO), 7.23 (s, 1H, Im), 7.07 (s, 1H, Im), 3.98 (s, 3H,
CH3).
2.3.2 Preparation of bis(pyridin-2-ylmethyl) amine (B). 2ꢀ
Aminomethylpyridine (2.5 mL, 26 mmol) in methanol (20 mL)
15 was dropwise added to 2ꢀpyridinecarboxaldehyde (2.7 mL, 26
mmol) in methanol (40 mL). After being stirred overnight,
Ligand HL3 as a white solid (2.73 g, 87%) was analogously
NaBH4 (2.42 g, 63.76 mmol) was slowly added and the mixture 75 synthesized by using the procedure employed for the preparation
was further stirred for another day before being concentrated to
dryness to give a residue to which water (60 mL) was added. The
20 pH of the resultant solution was adjusted to 7 by HCl (2 mol L−1)
followed by extraction with CH2Cl2 (3 × 100 mL). The organic
of HL2 but using 3ꢀtertꢀbutylꢀ2ꢀhydroxybenzaldehyde as the
aldehyde and sodium cyanoborohydride as the reducing agent. 1H
NMR (400 MHz, CDCl3): δ 10.78 (s, 1H, OH), 8.53 (d, J = 4.8
Hz, 1H, Py), 7.56 (td, J = 7.7, 1.6 Hz, 1H, Py), 7.22 – 7.16 (m,
phases were combined and dried with MgSO4. After evaporation 80 1H, Py), 7.15 – 7.07 (m, 2H, Py), 6.91 (d, J = 6.5 Hz, 1H, Py),
of the solvents, a yellow oily liquid (3.32 g, 54%) was collected
by silica gel flash chromatography (eluent: EA−EtOH−Et3N = 5 :
25 1 : 0.1). H NMR (400 MHz, CDCl3): δ 8.47 (d, J = 4.7 Hz, 2H,
6.82 (d, J = 0.9 Hz, 1H, Im), 6.68 (dd, J = 14.3, 6.8 Hz, 2H, Py,
Im), 3.81 (s, 2H, CH2), 3.71 (s, 4H, 2CH2), 3.32 (s, 3H, CH3),
1.41 (s, 9H, 3CH3).
1
Py), 7.55 (t, J = 7.6 Hz, 2H, Py), 7.28 (s, 2H, Py), 7.14 – 6.98 (m,
2H, Py), 3.90 (s, 4H, CH2), 2.86 (s, 1H, NH).
2.3.3 Preparation of 1-methyl-1H-imidazol-2-ylmethyl-(pyrid-
2-ylmethyl)amine (C). 1ꢀMethylꢀ1Hꢀimidazoleꢀ2ꢀcarbaldehyde
30 (A) (4.71 g, 42.8 mmol) in methanol (30 mL) was dropwise
added to 2ꢀaminomethylpyridine (4.62 g, 42.8 mmol) in methanol
2.3.6 Preparation of complexes 1 and 2. Complex 1 was
85 prepared by the reaction of a solution of CuCl2·2H2O (0.34 g, 2.0
mmol) in methanol (2 mL) with ligand L1 (0.47 g, 2.0 mmol) in
methanol (3 mL). The reaction turned blue and blue precipitate
formed gradually. After being stirred at room temperature for 1 h,
the precipitate (0.64 g, 83%) was collected by filtration, washed
(50 mL). The mixture was stirred overnight and then NaBH4 90 successively with small amounts of methanol, diethyl ether (5 ×
(2.28 g, 60 mmol) was added. The solution was further stirred for
another day before being concentrated to dryness. The resultant
35 residue was dissolved in water (30 mL) and extracted with
dichloromethane (3 × 40 mL). The organic phases were combined
50 mL), and then dried in vacuo. Blue crystals of complex 1 were
obtained by recrystallization from methanol / diethyl ether.
Elemental analysis for complex 1 (C15H15Cl2CuN3·H2O, FW =
388.00), calc. (%): C, 46.22; H, 4.40; N, 10.78; Found (%): C,
and dried with MgSO4. After evaporation of the solvents, a light 95 46.32; H, 4.31; N, 10.37.
yellow oily liquid (3.45 g, 40%) was attained by column
chromatography (eluent: EA−EtOH−Et3N = 5 : 1: 0.1). H NMR
40 (400 MHz, CDCl3): δ 8.46 (d, J = 4.3 Hz, 1H, Py), 7.56 (td, J =
7.7, 1.7 Hz, 1H,Py), 7.25 (t, J = 5.8 Hz, 1H, Py), 7.08 (dd, J =
Complex 2 (0.96 g, 82%) was synthesized by using the same
1
procedure employed for the preparation of complex 1 by
replacing the ligand with ligand HL2. Elemental analysis for
complex 2 (C19H24Cl2CuN4O2·H2O, FW = 491.07), calc. (%): C,
6.9, 5.5 Hz, 1H, Py), 6.84 (s, 1H, Im), 6.73 (s, 1H, Im), 3.86 (s, 100 46.30; H, 5.32; N, 11.37. Found (%): C, 46.08; H, 4.94; N, 11.90.
2H, CH2), 3.82 (s, 2H, CH2), 3.58 (s, 3H, CH3), 3.07 (s, 1H, NH).
2.3.4 Preparation of ligand L1. To a solution of bis(pyridinꢀ2ꢀ
45 ylmethyl) amine (B) (1.90 g, 10 mmol) in THF (60 mL) was
added K2CO3 (5.52 g, 40 mmol) and propargyl bromide (0.8 mL,
2.3.7 Preparation of complexes 3 and 4. Complex 3 was
prepared by the reaction of a solution of Cu(ClO4)2·6H2O (0.75 g,
2.0 mmol) in methanol (2 mL) with ligand HL2 (0.62 g, 2.0
mmol) in methanol (3 mL) in the presence of one equivalent
10 mmol). After being stirred at room temperature for 6 h, the 105 potassium hydroxide (KOH). The solution was stirred for 1 h to
reaction was filtered. After evaporation of the solvents, a yellow
oily liquid (1.85 g, 78%) was collected by column
50 chromatography (eluent: EA−EtOH−Et3N = 5 : 1 : 0.1). 1H NMR
(400 MHz, CDCl3) δ 8.58 (d, J = 4.7 Hz, 2H, Py), 7.68 (td, J =
obtain a light blue precipitate (0.91 g, 94%), which was collected
by filtration, washed successively with small amounts of
methanol, diethyl ether (5 × 50 mL), and dried in vacuo. Blue
crystals of complex 3 were obtained by recrystallization from
7.6, 1.6 Hz, 2H, Py), 7.54 (d, J = 7.8 Hz, 2H, Py), 7.21 – 7.16 (m, 110 methanol / dichloromethane. Elemental analysis for complex 3
2H, Py), 3.94 (s, 4H,CH2), 3.45 (d, J = 2.3 Hz, 2H, CH2), 2.32 (t,
J = 2.3 Hz, 1H, CH).
55 2.3.5 Preparation of ligands HL2 and HL3. To a solution of
salicylaldehyde (1.05 g, 8.6 mmol) in methanol (25 mL) was
(C36H38N8O10Cu2Cl2·CH2Cl2, FW = 1022.02, calc. (%): C, 43.86;
H, 4.16; N, 10.77. Found (%): C, 43.88; H, 3.76; N, 10.87.
Complex 4 (0.84 g, 70%) was synthesized by using the same
procedure employed for the preparation of complex 3 by using
added
1ꢀmethylꢀ1Hꢀimidazolꢀ2ꢀylmethylꢀ(pyridꢀ2ꢀylmethyl) 115 ligand
HL3.
Elemental
analysis
for
complex
4
amine (1.73 g, 8.6 mmol) and a small amount of acetic acid. And
(C23H31N4O6CuCl·CH2Cl2, FW = 641.08), calc. (%): C, 44.80; H,
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