N-chelate ruthenium carbene complexes in olefin metathesis and isomerization

Article abstract of DOI:10.1134/S1070428015070015

The catalytic activity of N-chelate ruthenium carbene complexes in the metathesis of hex-1-ene has been studied in comparison to the second generation Grubbs catalyst.

Full text of DOI:10.1134/S1070428015070015

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 7, pp. 907–909. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © N.M. Shcheglova, V.D. Kolesnik, R.V. Ashirov, E.A. Krasnokutskaya, 2015, published in Zhurnal Organicheskoi Khimii, 2015,
Vol. 51, No. 7, pp. 927–929.
N-Chelate Ruthenium Carbene Complexes
in Olefin Metathesis and Isomerization
N. M. Shcheglovaa, V. D. Kolesnika, R. V. Ashirova, and E. A. Krasnokutskayab
a SIBUR Tomskneftekhim Chemical Research and Development Center,
ul. Kuzovlevskii trakt 2, build. 270, Tomsk, 634067 Russia; P.O. Box 1548
e-mail: Sheglova2006@rambler.ru
b National Research Tomsk Polytechnic University, pr. Lenina 30, Tomsk, 634050 Russia
Received March 9, 2015
Abstract—The catalytic activity of N-chelate ruthenium carbene complexes in the metathesis of hex-1-ene has
been studied in comparison to the second generation Grubbs catalyst.
DOI: 10.1134/S1070428015070015
Olefin metathesis in the presence of ruthenium
carbene complexes has found wide application in the
synthesis of organic compounds and polymers [1]. In
some cases, the reaction is accompanied by isomeriza-
tion [2] involving double bond migration. Undesirable
isomerization may be avoided by appropriate variation
of the catalyst structure [3, 4].
activities of complexes 1 and 2 were compared with
the activity of complex 3 which is a well known
second generation Grubbs catalyst [1, 7, 8].
Scheme 1.
[Ru], 80°C
Bu
Bu
Bu
H2C
The catalytic activity of recently reported com-
plexes 1 [5] and 2 [6] containing an N-chelating ben-
zylidene ligand has been studied only in ring-opening
metathesis polymerization and ring-closing metathesis
[5, 6]. The behavior of these complexes in cross meta-
thesis was not described, and their effect on the
isomerization during metathesis was not studied; these
issues were the subjects of the present study. As model
substrate we used hex-1-ene (Scheme 1). The catalytic
The reaction was carried out either under solvent-
free conditions or in 1,2-dichloroethane in the presence
of 0.01 mol % of complex 1 or 2 at 80°C. The product
composition was determined by gas chromatography
(see table). Complex 1 turned out to be the least active
in the metathesis of hex-1-ene, but it was more selec-
tive than 3. The catalytic activity of 2 approached that
of complex 3; however, it also favored isomerization,
and the selectivity was about 30%. We failed to sup-
press isomerization and obtain pure dec-5-ene using
a chlorinated solvent [1, 9].
PCy3
N
N
Mes
Mes
Cl
The presence of an N-chelating ligand in complexes
1 and 2 is expected to endow them with higher thermal
stability compared to complex 3 [10]. In fact, these
complexes were stable on heating the reaction mixture
to 150°C. The reaction catalyzed by complex 2 gave
a mixture of C2‒C29 olefins (see figure). Analogous set
of olefins is obtained in the large-scale Shell higher
olefin process (SHOP) for the manufacture of synthetic
oils [11]; this process includes three steps: oligomer-
ization of ethylene, isomerization, and metathesis.
Each step is catalyzed by its own catalyst. The use of
complex 2 could considerably enhance the efficiency
of this process (one step instead of three).
Cl
Ru
N
Cl
Ru
N
Cl
Me
Me
Me
Me
1
2
N
N
Mes
Mes
Cl
Cl
Me
Me
Ru
PCy3
3
907

SHCHEGLOVA et al.
Metathesis of hex-1-ene catalyzed by complexes 1–3a
908
Olefin, wt %
Conversion
of hex-1-ene, %
Fraction of dec-5-ene
in C10 alkenes, %
Catalyst
Time, h
C6
C7
C8
C9
C10
C11
1
19.0
24.0
00.2
00.7
17.0
58.0
26.4
27.1
31.3
21.9
00.2
00.6
00.7
12.2
01.8
0.1
0.1
0.6
9.6
0.7
00.3
00.6
05.6
25.6
05.4
41.4
72.2
63.9
21.0
69.7
0.0
0.1
2.1
0.3
0.5
42
74
73
69
78
99
98
3
2
85
32
b81b
a
Amount of the catalyst 0.01 mol %; temperature 80°C.
In 1,2-dichloroethane (a 2 M substrate solution).
b
It was reported previously [3] that ruthenium
environment. Probably, the ligand composition of com-
plex 1 does not allow profound isomerization of the
double bond.
carbene complexes are capable of abstracting a proton
from the allylic position (Scheme 2), which leads to
migration of the double bond. The olefins thus formed
undergo metathesis to give a mixture of new olefins,
and the latter isomerize again; as a result, the set of
olefins extends.
Thus, the catalytic activity of complexes 1 and 2 in
the cross metathesis of hex-1-ene is comparable with
the activity of the second generation Grubbs catalyst;
however the metathesis of hex-1-ene in the presence of
complex 2 is accompanied by strong isomerization
with formation of C2‒C29 olefin mixture.
Scheme 2.
[Ru]
H
R
[Ru]
CH2
CH2
CH2
R
[Ru]
R
+
EXPERIMENTAL
H
R
Me
The products were analyzed by GLC using
an Agilent 7890A gas chromatograph equipped with
a flame ionization detector (HP-1 column, 30 m).
Complexes 1–3 were synthesized according to the
procedures described in [5–7], respectively; the syn-
theses were carried out under argon in an MBraun
glove box.
R
Me
[Ru]
[Ru]
Presumably, analogous processes take place in the
presence of complex 2. The ability to induce isomer-
ization is likely to depend on the basicity of the
ruthenium complex, which is determined by the ligand
%
8
7
6
5
4
3
2
1
0
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
n
Concentrations of CnH2n olefins in the reaction mixture obtained by heating hex-1-ene in the presence of 0.01 mol % of complex 2
(40 min at 80°C and 3 h at 150°C). Lower olefins (C2‒C6) were not analyzed.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

N-CHELATE RUTHENIUM CARBENE COMPLEXES IN OLEFIN METATHESIS
909
5. Shcheglova, N.M., Kolesnik, V.D., Ashirov, R.V., and
Krasnokutskaya, E.A., Izv. Akad. Nauk, Ser. Khim.,
2015, no. 1, p. 44.
6. Afanas’ev, V.V., Nizovtsev, A.V., Dolgina, T.M., and
Bespalova, N.V., RU Patent no. 2374269, 2008; Byull.
Izobret., 2009, no. 33.
Metathesis of hex-1-ene. A solution of 0.012 mmol
of complex 1–3 in 10 g of hex-1-ene was heated at
80°C on an oil bath until the mixture no longer boiled.
The product mixture was analyzed by GLC.
REFERENCES
7. Scholl, M., Trnka, T.M., Morgan, J.P., and
Grubbs, R.H., Tetrahedron Lett., 1999, vol. 40, p. 2247.
1. Handbook of Metathesis, Grubbs, R.H., Ed., Weinheim:
8. Ritter, T., Hejl, A., Wenzel, A.G., Funk, T.W., and
Wiley-VCH, 2003, vols. 1–3.
Grubbs, R.H., Organometallics, 2006, vol. 25, p. 5740.
9. Campbell, M.J. and Johnson, J.S., J. Am. Chem. Soc.,
2. Lehman, S.E., Schwendeman, J.E., O’Donnell, P.M.,
and Wagener, K.B., Inorg. Chim. Acta, 2003, vol. 345,
p. 190.
2009, vol. 131, p. 10370.
3. Dragutan, V., Dragutan, I., Delaude, L., and Demon-
10. Grubbs, R., Hejl, A., Sanders, D., Schrodi, Y.,
Trimmer, M., and Ung, T., US Patent Appl.
no. 20050261451 A1, 2004.
ceaub, A., Coord. Chem. Rev., 2007, vol. 251, p. 765.
4. Zaja, M., Connon, S.J., Dunne, A.M., Rivard, M.,
Buschman, N., Jiricek, J., and Blechert, S., Tetrahedron,
2003, vol. 59, p. 6545.
11. Mol, J.C., J. Mol. Catal. A: Chem., 2004, vol. 213,
p. 39.
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