filtered and the filtrate was kept for 2 days in an open beaker
for slow evaporation. Yellow, needle-shaped crystals, precipi-
tated during this time, were collected by filtration, washed with
hexane and dried at room temperature. Yield: 0.233 g (97%).
Anal calcd (found): C, 74.67 (75.02); H, 6.27 (6.16); N, 5.81
(5.79)%. Mp: 115–116ꢄ C. IR (KBr, cmꢁ1): 3214, 1626, 1577,
1491, 1458, 1383, 1273, 1211, 1153, 1118, 1062, 916, 857,
806, 754, 692, 636, 520, 457. UV/Vis [CH3CN; lmax/nm (e)]:
214 (29 060), 255 (14 180), 315 (4290). 1H NMR (200 MHz,
CDCl3): d 3.95 (d, J ¼ 6.12 Hz, 2H, CH2), 4.49 (t, J ¼ 6.49
Hz, 1H, CH), 6.864–7.008 (m, 2H, Ar), 7.269–7.403 (m, 7H,
Ar), 8.5 (s, 1H). 13C NMR (200 MHz, CDCl3): d 67.62,
75.69, 117.08, 118.89, 127.16, 127.90, 128.86, 131.82, 132.72,
139.39, 166.27. [a]2D5 ¼ ꢁ122 (c 0.04, MeOH).
resin. Unit cell dimensions were determined from several accu-
rately centered reflections using XSCANS program.8 Scans
were of the o type. Three standard reflections measured after
every 97 reflections exhibited no significant loss of intensity.
The data were corrected for Lorentz polarization effects and
absorption. Additional details of the data collection and
refinement are collected in Table 1.z
The compound crystallized in the chiral monoclinic space
group C2 with four molecules in the unit cell. The structure
was solved by direct methods and refined by least-squares tech-
niques adopting the full-matrix weighted least-squares scheme,
wꢁ1 ¼ s2Fo2 þ (0.0341P)2 þ 0.53P, where P ¼ (Fo2 þ 2Fc2)/3,
on F2 using SHELXS-97 and SHELXL-97 programs, respec-
tively.9 All atoms were located in the difference maps during
successive cycles of least-squares refinement. The sites of the
non-hydrogen atoms were refined anisotropically, whereas
those of the hydrogen atoms were refined isotropically. The
absolute configuration for the compound molecule was
successfully determined by refining the Flack parameter
[0.028(15)].10 The final Fourier difference synthesis showed
1. To a methanolic solution (15 mL) of ligand H2L (0.241 g,
1 mmol) was added Mn(CH3COO)2ꢀ4H2O (0.245 g, 1 mmol).
The mixture was allowed to stir at room temperature in air
for 3 h. The resulting dark brown solution was evaporated
to dryness using rotary vapor and vacuum pump. The solid,
thus obtained, was dissolved in dichloromethane, washed twice
with water, once with brine solution (using a separating fun-
nel) and dried over anhydrous Na2SO4 . The resulting dark
brown solution, on slow evaporation, gave a brown microcrys-
talline solid of 1. Yield: 0.198 g (74.15%). X-Ray quality crys-
tals of 1 were grown from ethanol by the slow evaporation
method. Anal calcd (found): C, 67.54 (67.16); H, 4.91 (4.83);
N, 5.25 (5.33)%. IR (KBr, cmꢁ1): 1616, 1535, 1440, 1312,
1200, 1148, 1022, 943, 897, 802, 756, 700, 640, 611, 579, 540,
457. UV/Vis [CH3CN; lmax/nm (e)]: 210 sh, 240 (44 640),
340 sh, 410 sh, 550 sh. FAB-MS (3-nitrobenzyl alcohol) m/z:
535. Conductivity (CH3CN, 10ꢁ3 M solution): 1.7 mho cm2
molꢁ1, consistent with a neutral compound.
ꢁ3
˚
minimum and maximum peaks of ꢁ0.153 and þ0.112 e A
.
Results and discussion
Synthesis of H2L and manganese complex 1
The enantiopure ligand H2L is prepared in quantitative yield in
a Schiff base condensation reaction (shown in Scheme 1) of 1
equiv of (S)-(þ)-2-phenylglycinol with 1 equiv of salicylalde-
hyde in methanol.
Reaction of Mn(II) acetate and the optically pure ligand H2L
IV
afforded the neutral and optically active complex [Mn L2], 1,
in good yield. Compound 1 was characterized by different phy-
sical techniques including CV, EPR and CD studies. Remark-
ably, oxidation of the manganese(II) center directly to the
Epoxidation studies
IV
manganese(IV) species [Mn L2] proceeds easily in the presence
(E)-Stilbene catalyzed by 1. (E)-Stilbene (0.1 g, 0.55 mmol)
and iodosobenzene (0.244 g, 1.1 mmol) were added to a solu-
tion of 1 (0.016 g, 30 mmol) in acetonitrile (5 mL) at room tem-
perature. After stirring for 12 h, the mixture was concentrated
under vacuum and purified with column chromatography
(SiO2 , hexane–ethyl acetate 1:0 to 19:1) to give stilbene oxide
as colorless crystals. Yield: 0.040 g (37%). The product was
identified as (E)-stilbene oxide by comparing its NMR spec-
trum (d ꢂ3.85 in CDCl3) with that of reported (E)-stilbene
oxide7 (see also Electronic supplementary information).
of air, indicating that the tridentate ligand L2ꢁ containing two
Oꢁ donors effectively stabilizes an enigmatic Mn(IV) oxidation
state. Stabilization of Mn(IV) species by similar ligands/pheno-
late oxygens has been previously reported.6(l)
Selected IR data for the complex 1 are given in the
Experimental section. The IR band that conveys important
Table 1 Crystallographic data for 1
Empirical formula
FW
C30H26MnN2O4
533.47
Monoclinic
C2
Styrene catalyzed by 1. Styrene (0.114 g, 1.1 mmol) and
iodosobenzene (0.49 g, 2.23 mmol) were added to a solution
of 1 (0.032 g, 60 mmol) in acetonitrile (5 mL) and stirred at
room temperature under nitrogen atmosphere. After comple-
tion of the reaction, the solvent was removed under vacuum
and the residue was treated with Et2O (6 ꢅ 5 mL). The Et2O
washings were combined together and concentrated to a small
volume. Bromobenzene (0.075 g) was added as an internal
standard and the volume was made up to 10 mL. The resulting
solution was analyzed by gas chromatography and the product
was identified as styrene oxide by comparing the retention time
with that of the authentic sample (see Electronic supplemen-
tary information). Yield: 0.070 g (53%). Both epoxidation
products, (E)-stilbene oxide and styrene oxide, were found to
be racemic mixtures, as evidenced by polarimetric studies.
Crystal system
Space group
˚
l/A
0.71073
23.052(7)
8.9826(8)
12.684(3)
107.504(12)
2504.8(10)
4
˚
a/A
˚
b/A
˚
c/A
b/ꢄ
U/A
3
˚
Z
m/mmꢁ1
0.567
25
T/ꢄC
Independent reflections
Rint
2637
0.0138
2552
Obs reflections [F > 4s(F)]
a
R1 [F > 4s(F)]
wR2
0.0236
0.0622
1
b
X-Ray crystallography
a
b
2
2
2
2
2
2
R1 ¼ SkFo| ꢁ |Fck/S|Fo|. wR2 ¼ [S{w(Fo ꢁ Fc ) }/S{w(Fo) }] .
X-Ray diffraction data were collected at room temperature
ꢄ
IV
(25 C) for [Mn L2] on a Siemens P4 diffractometer equipped
with a molybdenum tube and a graphite monochromator. A
dark brown crystal of approximate dimensions 0.62 ꢅ
0.50 ꢅ 0.42 mm3 was mounted on a glass fiber using epoxy
suppdata/nj/b3/b315658c/ for crystallographic data in .cif or other
electronic format.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
736
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 7 3 5 – 7 3 9