Experimental
(S,S )-1,2-Bis(1-methylbenzimidazol-2-yl)-1,2-ethanediol (SS-
). N-Methyl-1,2-phenylenediamine [5 ml (97%), 42.7 mmol]
and (ϩ) tartaric acid (3.21 g, 21.3 mmol) were dissolved in
0 ml 4 M hydrochloric acid. The solution was heated to reflux
for 24 hours. After cooling, a blue compound (the chloride salt
of the protonated ligand) crystallised from the black solution.
The crystals were filtered and redissolved in 150 ml water
and 150 ml ethanol. After adding active carbon the solution
was heated to reflux for 2 hours. The colourless solution was
neutralised with conc. ammonia and the white precipitate was
filtered. Recrystallisation was difficult due to the low solubility
of the compound. To recrystallise 0.265 g of 2 a volume of
2
Physical measurements
5
Potentiometric titrations were carried out in 1 : 1 water–ethanol
mixtures. In a typical experiment ligand (0.2 mmol), metal (0.1
mmol) and HCl (0.5 mmol) were dissolved in a volume of 40
ml, with ionic strength adjusted to 0.1 M with sodium chloride.
The solutions were titrated with NaOH (0.1 M) with a Mettler
DL70 titrator at 22 ЊC in a nitrogen atmosphere. The pH data
were fitted to the equilibrium model with a local version of the
1
8
TITFIT program allowing the dissociation constant for water
to vary to allow for the non-aqueous solvent. The protonation
constants log (β ) and log (β ) were determined to be 5.01(4)
5
00 ml (4 : 1 ethanol–water) was necessary. An alternative is to
10
1
10
2
dissolve the product in water–ethanol (230 ml–150 ml) and
conc. HCl (53 ml) and to heat to reflux in the presence of active
carbon. After cooling, the protonated ligand crystallises. The
precipitate is filtered and redissolved in 200 ml water and 200 ml
ethanol. The hot solution is neutralised slowly by sodium
hydroxide (5 M). The solution with the white precipitate was
allowed to cool and then filtered. The precipitate of (S,S )-
and 8.79(6) for 1 and 4.46(6) and 8.50(9) for 2. Electronic spec-
tra were recorded using a Perkin-Elmer Lambda 900 UV/VIS/
NIR spectrometer, CD spectra using a Jasco J-715 spectro-
polarimeter and infra-red spectra as KBr pastilles using a
Perkin-Elmer Spectrum One spectrometer. NMR spectra were
recorded on a Varian Gemini instrument, at 300 MHz for pro-
13
tons and 75.44 MHz for C. Reflectivity spectra were recorded
using a Perkin-Elmer Lambda 900 UV/VIS/NIR spectrometer
equipped with an integration sphere of diameter 60 mm. The
white standard was PTFE. Samples were prepared in a 1 mm
cell after mixing the compound with magnesium oxide (∼10%
compound). Baseline correction was performed by measuring
the spectrum of pure magnesium oxide. Magnetic susceptibility
data were collected with a Quantum Design SQUID magnet-
ometer (XL5S) operating in the temperature range 300–2 K
1
,2-bis(1-methylbenzimidazol-2-yl)-1,2-ethanediol (SS-2) was
dried in a oven at 90 ЊC for several hours; (3.98 g, 58%) (Found:
C, 66.89; H, 5.66; N, 17.35. C N O H requires C, 67.10; H,
18
4
2
18
Ϫ4
5
1
2
1
.59; N, 17.38%); UV (T = 22 ЊC/3.14 × 10 M/DMSO/l =
mm) λmax/nm (ε/dm mol cm ) 248 (16100), 258 (15200),
73 (14400), 279 (15800), 287 (13400); CD (T = 22 ЊC/3.14 ×
3 Ϫ1 Ϫ1
Ϫ4
3
Ϫ1
Ϫ1
0
M/DMSO/l = 1 mm) λmax/nm (∆ε/dm mol cm ) 251
(
0.521), 264 (Ϫ1.520), 274 (Ϫ1.231), 290 (0.865); IR (KBr)
Ϫ1
19
ν/cm 3097w, 2850w, 1614s, 1589m, 1481m, 1397s, 1345m,
with a field of 1000 Gauss. Pascal’s constants were used for
the diamagnetic corrections. The experimental data for χT were
fitted to the equation
1
8
329m, 1310s, 1281s, 1243s, 1145s, 1108s, 1075s, 1002s, 911s,
73m, 845m, 799m, 767s, 731m, 657m, 576m, 536s, 445m, 380s;
NMR [DMSO-d ] δH (300 MHz) 7.45 (m, arom. H, 4H),
6
7
3
.10 (m, arom. H, 4H), 6.09 (m, OH, 2H), 5.44 (m, CH, 2H),
.91 (s, CH , 6H); δ (75.44 MHz) 154.90 (C᎐N), 142.19 (arom.
3
C
C), 136.14 (arom. C), 122.66 (arom. C), 121.89 (arom. C),
19.52 (arom. C), 110.65 (arom. C), 67.92 (CH), 30.55 (CH );
MS (EI 70 eV): m/z = 323 (M ), 304, 275, 162, 92, 77. Solubility:
1
3
3
where x = ϪJ/kT. The r.m.s. error on the fit was 0.014 cm
mol K.
ϩ
Ϫ1
insoluble in most organic solvents and H O, weakly soluble in
2
DMSO, hot ethanol, hot methanol. The enantiomeric ligand
RR-2 was prepared by a similar route.
Synthesis of the ligands
(
R,R)-1,2-Bis(1H-benzimidazol-2-yl)-1,2-ethanediol (RR-1).
1
,2-Phenylenediamine (10.00 g, 92.5 mmol) and (Ϫ) tartaric
Synthesis of the complexes
acid (6.94 g, 46.3 mmol) were dissolved in 200 ml 4 M hydro-
chloric acid. The solution was heated to reflux for 24 hours. On
cooling, green crystals of the chloride salt of the protonated
ligand formed. The crystals were filtered and dissolved in 200
ml water and treated with activated carbon under reflux for
CAUTION! Perchlorate salts of organic ligands are potentially
explosive. Only small amounts should be used and suitable
20
protective measures should be taken.
Rac-bis[1,2-bis(1H-benzimidazol-2-yl)-1,2-ethanediol]-
2
hours. Neutralisation with concentrated ammonia gave a
nickel(II) dinitrate, rac-[Ni(RR,SS-1) ](NO ) (C H OH) . A
2
3
2
2
5
2
white voluminous precipitate. The precipitate, was filtered and
recrystallised from a water–ethanol mixture (200 ml–200 ml)
to give colourless needles or plates of (RR)-1,2-bis(1H-benz-
imidazol-2-yl)-1,2-ethanediol (RR-1) (3.41 g, 25%) (Found: C,
mixture of Ni(NO ) ؒ6H O (0.0291 g, 0.1 mmol), RR-1
3 2 2
(0.0294 g, 0.1 mmol) and SS-1 (0.0294 g, 0.1 mmol) was dis-
solved in 2.5 ml ethanol and 0.25 ml water. Slow evaporation of
half of the solvent led within a week to blue prismatic crystals.
The solution was filtered and the crystals washed with water
and dried in air (0.0661 g, 77%); (Found: C, 49.7; H, 4.5; N,
16.53. C H N O ؒNi(NO ) ؒCH CH OH requires C, 50.1; H,
6
3.23; H, 4.95; N, 18.13. C H N O ؒ0.5H O requires C, 63.35;
16 14 4 2 2
Ϫ4
H, 4.99; N, 18.48%); UV (T = 22 ЊC/3.14 × 10 M/DMSO/l =
3
Ϫ1
Ϫ1
1
2
mm) λmax/nm (ε/dm mol cm ) 250 (13100), 278 (18300),
32
28
8
4
3
2
3
2
Ϫ4
3
83 (17400); CD (T = 22 ЊC/3.14 × 10 M/DMSO/l = 1 mm)
4.7; N, 16.2%; UV (T = 22 ЊC/0.029 M/DMSO) λmax/nm (ε/dm
Ϫ1 Ϫ1
3
Ϫ1
Ϫ1
λmax/nm (∆ε/dm mol cm ): 248 (0.704), 261 (Ϫ0.072), 281
mol cm ) 993 (6), 594 (12), 376(18); Reflectivity in MgO
Ϫ1
Ϫ1
(
Ϫ0.140), 288 (Ϫ0.220); IR (KBr) ν/cm 3200br, 3385s, 3330m,
λmin/nm 993; IR (KBr) ν/cm 3206br s, 1765m, 1623s, 1594s,
3
1
8
058m, 1620m, 1590m, 1527m, 1483m, 1454s, 1430w, 1307m,
272w, 1226m, 1205m, 1111m, 1086s, 1059m, 1030s, 997m,
99m, 844m, 796m, 763s, 738m, 613m, 439m, 360m; NMR
1549m, 1532m, 1416br s, 1274m, 1149s, 1119s, 1067m, 1037m,
1004s, 986s, 924s, 908s, 879s, 822s, 810s, 765s, 740m, 633s, 620s,
577m, 510m, 483s, 453s, 437s, 426s; ES-MS (DMSO) : m/z (%)
2ϩ
2ϩ
[DMSO-d ] δ (300 MHz) 12.33 (br s, NH, 2H), 7.49 (m, arom.
362.3 (100) [Ni(1) (DMSO)] , 323.3 (74) [Ni(1) ] , 401.3 (56)
2 2
2ϩ ϩ
6
H
H, 4H), 7.12 (m, arom. H, 4H), 5.92 (d, OH, 2H, J = 5 Hz), 5.28
[Ni(1) (DMSO) ] , 295.1 (45) [(1)H] , 429.1 (22) [Ni(1 Ϫ
2 2
ϩ 2ϩ
(
(
d, CH, 2H, J = 5 Hz); δ (75.44 MHz) 156.29 (C᎐N), 143.82
arom. C), 134.73 (arom. C), 122.18 (arom. C), 121.60 (arom.
H)] (DMSO), 440.2 (13) [Ni(1) (DMSO) ] , 645.1 (13)
C
2
3
ϩ
[Ni(1) (ϪH)] .
2
C), 119.04 (arom. C), 112.09 (arom. C), 71.60 (CH); MS (EI 70
eV) m/z 294 (M ), 148, 119, 65. Solubility: soluble in DMSO,
DMF; poorly soluble in ethanol and methanol, insoluble in
ϩ
Bis[bis[(R,R)-1,2-bis(1-methylbenzimidazol-2-yl)-1,2-ethane-
diol]nickel(II) diperchlorate, [Ni(RR-2)(RR-2-H)] (ClO ) (C H -
2
4
2
2
5
H O, CH CN. The enantiomeric ligand SS-1 was prepared by a
similar route.
OH) . A mixture of Ni(ClO ) ؒ6H O (0.0366 g, 0.1 mmol) and
2
3
3
4
2
2
RR-2 (0.0644 g, 0.2 mmol) was dissolved in 25 ml ethanol to
J. Chem. Soc., Dalton Trans., 2002, 3899–3905 3903