Chemistry Letters Vol.34, No.8 (2005)
1097
Table 1. Dechlorination of DDT catalyzed by hydrophobic
a
not decomposed even after the 4th Run which was confirmed
by MALDI-TOF-MS.
vitamin B12
In conclusion, the dechlorination of DDT was carried out in
an ionic liquid in the presence of a catalytic amount of hydropho-
bic vitamin B12 and a Ru photosensitizer under irradiation of
visible light. The recycled use of hydrophobic vitamin B12 in
an ionic liquid was demonstrated for the first time.
Cl
Cl
Cl
Cl
Cl
Cl
H
Cl Cl
Vis light
Cl
+
Cl
in ionic liquid
Cl
Cl
Cl
Cl
Cl
DDT
DDD
TTDB (Z/E)
Yields/%c
The present work was supported by a Grant-in-Aid for
Scientific Research on Priority Areas (417) from the Ministry
of Education, Culture, Sports, Science and Technology (MEXT)
of Japan and a Grant-in-Aid for Scientific Research from the
Japan Society for the Promotion of Science (JSPS).
Vis. Conversion
light of DDT/%b
99ꢄ
Entry B12 [RuII(bpy)3]2þ
TTDB TTDB
(Z)
DDD
(E)
1d
2
3d
4e
5f
86
trace
9
6
1
ꢂ
ꢄ1
10
—
trace
—
—
trace
—
ꢂ
4
trace
1
trace
References and Notes
—
—
1
2
3
Special issues on recoverable catalysts and reagents can be
found in Chem. Rev., 102, 3215 (2002).
H. Shimakoshi, M. Tokunaga, K. Kuroiwa, N. Kimizuka,
and Y. Hisaeda, Chem. Commun., 2004, 50.
T. Welton, Chem. Rev., 99, 2071 (1999); T. Itoh, N. Ouchi,
S. Hayase, and Y. Nishimura, Chem. Lett., 32, 654 (2003); Y.
Shen, T. Tajima, M. Atobe, and T. Fuchigami, Electrochem-
istry, 72, 849 (2004); J. Dupont, R. F. de Souza, and P. A. Z.
Suarez, Chem. Rev., 102, 3667 (2002).
aDechlorination reactions were carried out under N2 atmosphere with irra-
diation of 500-W tungsten lamp for 3 h. Initial concentration: [Cob(II)-
7C1ester]ClO4, 5:0 ꢂ 10ꢁ4 M; DDT, 4:0 ꢂ 10ꢁ2 M; [Ru(II)(bpy)3]Cl2,
2:5 ꢂ 10ꢁ2 M; triethanolamine, 5:0 ꢂ 10ꢁ1 M, solvent: [bmim][PF6]–
CH3CN (3:7 v/v). bConversion was estimated by the recovery of DDT.
cProducts were analyzed by NMR, HPLC, and GC-MS. dA small amount
of DDE (1,1-bis(4-chlorophenyl)-2,2-dichloroethylene) was formed. eIn
f
the absence of triethanolamine. The reaction was carried out in the pres-
ence of [CH3I], 4:0 ꢂ 10ꢁ1 M.
4
5
6
Y. Murakami, Y. Hisaeda, and A. Kajihara, Bull. Chem. Soc.
Jpn., 56, 3642 (1983).
H. Shimakoshi, M. Tokunaga, T. Baba, and Y. Hisaeda,
Chem. Commun., 2004, 1806.
Table 1, and which also showed the supernucleophilic Co(I) spe-
cies is formed as a reactive intermediate. Dehalogenation of an-
other organic halide such as 1,1-bis(4-methoxyphenyl)-2,2,2-tri-
chloroethane (methoxychlore) also efficiently proceeded, and a
monodechlorinated product, 1,1-bis(4-methoxyphenyl)-2,2-di-
chloroethane, was obtained as a major product.
After the reaction, CH3CN was removed by evaporation and
the resulting precipitation10 was filtered off; then to the obtained
filtrate were added Et2O and H2O. Three layers, Et2O, H2O, and
[bmim][PF6], were clearly separated. Dechlorinated products
such as DDD, etc. were extracted in Et2O and hydrophobic vita-
min B12, [Cob(II)7C1ester]þ remained in the ionic liquid,
[bmim][PF6]. The recovery of hydrophobic vitamin B12 in an
ionic liquid was over 90% based on UV–vis and MS analysis.
Therefore, the hydrophobic vitamin B12 is a tough and excellent
catalyst in the reaction and could be reused for the successive re-
action. The result of recycled use of hydrophobic vitamin B12
and ionic liquid in the dechlorination reaction is summarized
in Table 2.11 The reaction proceeded with almost the same
efficiency in the 4th Run. And hydrophobic vitamin B12 was
The ESR signal observed in Figure 1b is probably ascribed
to a cation radical of triethanolamine but was not analysed
further.
7
Counter anion of the [Ru(II)(bpy)3]þ is exchanged from the
ꢁ
starting Clꢁ to PF6 and the PF6 salt is not dissolved in
[bmim][PF6], thus we used CH3CN as co-solvent. The
dechlorination of DDT was carried out in [bmim][PF6]–
CH3CN(3:7 v/v) under a nitrogen atmosphere in the pres-
ence of [Cob(II)7C1ester]ClO4 with irradiation of a 500-W
tungsten lamp. Initial concentrations: cobalt complex,
5:0 ꢂ 10ꢁ4 M; DDT, 4:0 ꢂ 10ꢁ2 M; [Ru(II)(bpy)3]Cl2,
2:5 ꢂ 10ꢁ2 M; TEOA, 5:0 ꢂ 10ꢁ1 M. After the reaction,
CH3CN was removed by evaporation under reduced pressure
and 30 mL of Et2O and H2O was added to the residue. The
Et2O layer was washed with water (3 ꢂ 30 mL) and dried
with Na2SO4. And then, the filtrate was evaporated to
dryness. The products were analyzed by HPLC, NMR, and
GC-mass spectroscopies.
a
Table 2. Recycled catalysis of hydrophobic vitamin B12
Yields/%c
8
9
H. Shimakoshi, I. Aritome, M. Tokunaga, and Y. Hisaeda,
Acta Crystallgr., E60, o1470 (2004).
Conversion
of DDT/%b
Run
DDD
TTDB (Z)
TTDB (E)
Formation of Z-form of TTDB was preferred in an ionic
liquid. On the other hand, E-form of TTDB was preferably
obtained in ethanol. See Ref. 5.
1st
99ꢄ
99ꢄ
99ꢄ
99ꢄ
86
89
93
90
6
6
5
4
1
1
1
1
2nd
3rd
4th
1
10 The precipitate is [Ru(II)(bpy)3](PF6)2; H NMR (acetone-
d6, 500 MHz): ꢀ 7.57 (3H, m, bpy), 8.05 (3H, d, bpy), 8.21
(3H, td, bpy), 8.81 (3H, d, bpy), 13C NMR: ꢀ 125.2, 128.7,
138.8, 152.6, 158.0. MALDI-MS (m=z): ½M ꢁ PF6ꢃþ,
715.1. IR (KBr, ꢁ/cmꢁ1), 777 (P–F). Anal. Found: C,
41.86; H, 2.90; N, 9.77%; calcd for C30H24N6F12P2Ru1: C,
41.92; H, 2.81; N, 9.78%.
aDechlorination reactions were carried out under N2 atmosphere with
irradiation of 500-W tungsten lamp for 3 h. Initial concentration:
[Cob(II)7C1ester]ClO4, 5:0 ꢂ 10ꢁ4 M; DDT, 4:0 ꢂ 10ꢁ2 M; [Ru(II)-
(bpy)3]Cl2, 2:5 ꢂ 10ꢁ2 M; triethanolamine, 5:0 ꢂ 10ꢁ1 M, solvent:
[bmim][PF6]–CH3CN (3:7 v/v). After the 1st Run, the same amount
of DDT, [Ru(II)(bpy)3]Cl2 and triethanolamine were added at each
Run (2nd–4th). bConversion was estimated by the recovery of DDT.
cProducts were analyzed by NMR, HPLC, and GC-MS.
11 A small amount of ionic liquid was lost during the extraction
process.
Published on the web (Advance View) July 2, 2005; DOI 10.1246/cl.2005.1096