7.16 (2 H, s, aromatic 4/6H of m-xylyl ring), 4.95 (2 H, s,
PhCH2O), 4.68 (4 H, s, CH2OH) and 2.33 (3 H, s, CH3).
4-(Benzyloxy)-2,6-bis(chloromethyl)toluene. To a solution
of 4-(benzyloxy)-2,6-bis(hydroxymethyl)toluene (5 g, 0.019
mol) in CH2Cl2 (100 cm3), was added dropwise SOCl2 (17 g,
0.014 mol). After stirring for 3 h the solution was evaporated to
dryness under a gentle stream of dinitrogen. After addition of
CH2Cl2 (50 cm3) the solution was again evaporated to dryness
(5.66 g, 98%). Found: C, 65.14; H, 5.40. Calc. for C16H16Cl2O:
C, 65.09; H, 5.42%. GC mass spectrum: m/z 294 (30%); calc.
for C16H16Cl2O Ϫ H 294. 1H NMR (400 MHz, CDCl3, 298 K):
δ 7.52–7.34 (5 H, m, aromatic protons of PhCH2O), 7.23 (2 H,
s, aromatic 4/6 H of m-xylyl ring), 5.08 (2 H, s, PhCH2O), 4.62
(4 H, s, CH2Cl) and 2.34 (3 H, s, CH3).
4-(Benzyloxy)-2,6-bis(pyrazol-1-ylmethyl)toluene. Sodium
hydride (1.73 g, 0.072 mol) was suspended in dmf (40 cm3) and
pyrazole (1.844 g, 0.27 mol) added, under a dry dinitrogen
atmosphere. The mixture was then stirred for 1 h. To this was
added dropwise 4-(benzyloxy)-2,6-bis(chloromethyl)toluene
(4 g, 0.14 mol) in dmf (25 cm3). The resulting mixture was
magnetically stirred for 4 d at ≈25 ЊC. Addition of water (15
cm3) followed by solvent evaporation under reduced pressure
afforded a slurry, to which was added an aqueous 10% NaOH
solution (25 cm3). The protected ligand was extracted with
CH2Cl2 (40 cm3) and the organic layer washed with water,
followed by drying over anhydrous Na2SO4. Solvent removal
to one-third under reduced pressure afforded a yellow oil, to
which n-hexane (15 cm3) was added to give a brownish white
product (3.51 g, 72%). Found: C, 73.82; H, 6.20; N, 15.71. Calc.
for C22H22N4O: C, 73.74; H, 6.15; N, 15.64%. GC mass spec-
trum: m/z 355 (25%); calc. for C22H22N4O Ϫ 3H 355. 1H NMR
(400 MHz, CDCl3, 298 K): δ 7.54–7.26 (7 H, m, aromatic
protons of PhCH2O and 3/5-pyrazole protons), 6.81 (2 H, s, 4/6-
protons of m-xylyl ring), 6.26 (2 H, t, pyrazole 4-H proton),
5.32 (4 H, s, CH2N2C3H3), 4.76 (2 H, s, OCH2Ph) and 2.20 (3 H,
s, CH3).
over anhydrous Na2SO4. Solvent removal to one-third of its
original volume, under reduced pressure, afforded a yellow oil,
to which n-hexane (≈20 cm3) was added to give a brownish
white product (2.3 g, 96%). Found: C, 75.40; H, 7.30; N, 13.43.
Calc. for C26H30N4O: C, 75.36; H, 7.25; N, 13.53%. GC mass
spectrum: m/z 415 (6%); calc. for C26H30N4O ϩ H 415. 1H
NMR (400 MHz, CDCl3, 298 K): δ 7.43 (5 H, s, aromatic pro-
tons), 6.38 (2 H, s, aromatic protons), 5.84 (2 H, s, pyrazole 4-H
protons), 5.21 (4 H, s, CH2N2C3HMe2), 4.71 (2 H, s, OCH2Ph),
2.25 (6 H, s, CH3), 2.14 (3 H, s, CH3) and 2.06 (6 H, s, CH3).
HLЈ. 4-(Benzyloxy)-2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)-
toluene (2.3 g, 5.6 mmol) was refluxed with concentrated HBr
(25 cm3) and water (38 cm3) for 10 h. The reaction mixture was
then cooled to room temperature and neutralised to pH 7 with
an aqueous NaOH solution (10 mol dmϪ3). The HLЈ was then
extracted with CH2Cl2 (30 cm3) and the organic layer dried over
anhydrous Na2SO4. The organic extract was concentrated to
one-fifth of its initial volume and addition of n-hexane (≈10
cm3) resulted in precipitation of a white solid. It was filtered
off, washed with n-hexane and air-dried (1.7 g, 92%). Found:
C, 70.40; H, 7.51; N, 17.32. Calc. for C19H24N4O: C, 70.37; H,
7.41; N, 17.28%. GC mass spectrum: m/z 327 (4%); calc. for
1
C19H24N4O ϩ 3H 327. H NMR (400 MHz, CDCl3, 298 K):
δ 6.70 (2 H, s, aromatic protons), 5.82 (2 H, s, pyrazole 4-H
protons), 5.15 (4 H, s, CH2N2C3HMe2), 2.24 (6 H, s, CH3), 2.22
(6 H, s, CH3) and 2.07 (3 H, s, CH3).
[Cu2(L)2(OClO3)2] 1. To a solution of Cu(ClO4)2ؒ6H2O
(0.138 g, 0.38 mmol) in MeOH (5 cm3) was added dropwise a
mixture of HL (0.1 g, 0.38 mmol) and triethylamine (0.04 g,
0.38 mmol) in MeOH (6 cm3), under magnetic stirring. The
resulting reddish brown mixture was further stirred for 2 h at
298 K. The brown precipitate thus formed was collected by
filtration, washed with MeOH and vacuum dried. Recrystallis-
ation from MeCN–MeCO2Et (vapour diffusion) afforded a
crystalline solid suitable for structural studies. Yield = 62%.
Found: C, 42.18; H, 3.53; N, 13.19. Calc. for C15H15ClCuN4O5:
C, 41.90; H, 3.52; N, 13.03%. IR (KBr disc, selected peaks): 1110,
1070, 1055, 630 and 620 cmϪ1 (ν(ClO4)). Conductivity (MeCN,
HL. 4-(Benzyloxy)-2,6-bis(pyrazol-1-ylmethyl)toluene (3.51
g, 9.8 mmol) was refluxed with concentrated HBr (40 cm3) and
water (56 cm3) for 10 h. The reaction mixture was then cooled
to room temperature and neutralised to pH 7 with aqueous
NaOH solution (10 mol dmϪ3). The HL was then extracted with
CH2Cl2 (40 cm3) and the organic layer dried over anhydrous
Na2SO4. The organic extract was then concentrated to one-fifth
of its initial volume and addition of n-hexane (≈15 cm3)
resulted in precipitation of a white solid. It was filtered off,
washed with n-hexane and air-dried (2.8 g, 94%). Found: C,
67.14; H, 6.12; N, 21.10. Calc. for C15H16N4O: C, 67.16; H, 5.97;
N, 20.90%. GC mass spectrum: m/z 268 (55%); calc. for
≈10Ϫ3 mol dmϪ3 solution at 298 K): ΛM = 225 ΩϪ1 cm2 molϪ1
.
UV/VIS, λmax/nm (ε/dm3 molϪ1 cmϪ1): (MeCN) 668 (665), 441
(6330), 328 (sh) (3050) and 282 (11 100); (Nujol mull) 1050–
1
650 (very broad feature) and 480. H NMR (CD3CN): δ 2.11,
3.14, ≈6.00 (vbr), 7.39 (shoulder on right), 7.65 and 9.86.
[Cu2(LЈ)2(OClO3)2] 2. A similar procedure on the same scale
as that described for complex 1 was followed. To a magnetically
stirred solution of Cu(ClO4)2ؒ6H2O (0.114 g, 0.31 mmol) in
MeOH (6 cm3) was added dropwise a mixture of HLЈ (0.1 g,
0.31 mmol) and triethylamine (0.032 g, 0.31 mmol) in MeOH
(8 cm3). The reddish brown mixture formed was further stirred
for 2 h at 298 K. It was then concentrated to one-third of its
initial volume, diethyl ether (4 cm3) added and kept in a deep
freeze. After 2 h a brownish green crystalline material precipi-
tated and was collected by filtration, washed with diethyl ether
and dried in vacuo. Yield = 73%. Found: C, 46.51; H, 4.60; N,
11.40. Calc. for C19H23ClCuN4O5: C, 46.90; H, 4.70; N, 11.50%.
IR (KBr disc, selected peaks): 1120, 1090, 1065, 630 and 625
cmϪ1 (ν(ClO4)). Conductivity (CH3CN, 10Ϫ3 mol dmϪ3 solu-
tion at 298 K): ΛM = 232 ΩϪ1 cm2 molϪ1. Absorption spectrum
[λmax/nm (ε/dm3 molϪ1 cmϪ1): (in MeCN) 620 (900), 438
(5020), 330 (sh) (2740) and 280 (10 450)]; (Nujol mull) 990 (sh),
700 and 460. 1H NMR (CD3CN): δ 1.36, 2.51, 2.69, 5.02, 7.00,
7.39 and 7.88.
1
C15H16N4O 268. H NMR (400 MHz, CDCl3, 298 K): δ 7.53–
7.49 (4 H, m, pyrazole 3/5 protons), 6.92 (2 H, s, aromatic
protons of m-xylyl ring), 6.25 (2 H, t, pyrazole 4-H), 5.27 (4 H,
s, CH2N2C3H3) and 2.20 (3 H, s, CH3).13
2,6-Bis(3,5-dimethylpyrazol-1-ylmethyl)-4-methylphenol,
HLЈ. The method used to prepare this new ligand was as
described above except for 3,5-dimethylpyrazole in place of
pyrazole. The coupling reaction and final deprotection step are
described below.
4-(Benzyloxy)-2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)-
toluene. Sodium hydride (0.73 g, 0.031 mol) was suspended in
dmf (20 cm3) and 3,5-dimethylpyrazole (1.11 g, 0.115 mol)
added, under a dry dinitrogen atmosphere. The mixture
was then stirred for 1 h. To this was added dropwise 4-
(benzyloxy)-2,6-bis(chloromethyl)toluene (1.7 g, 0.058 mol) in
dmf (10 cm3). The resulting mixture was magnetically stirred
for 4 d at ≈25 ЊC. Addition of water (10 cm3) followed by sol-
vent evaporation under reduced pressure afforded a slurry,
to which was added an aqueous 10% NaOH solution (15
cm3). The protected ligand was extracted with CH2Cl2 (30 cm3)
and the organic layer washed with water, followed by drying
CAUTION: perchlorate salts of compounds containing
organic ligands are potentially explosive!
Physical measurements
Elemental analyses were obtained from either Indian Associ-
4026
J. Chem. Soc., Dalton Trans., 1999, 4025–4030