Olefin metathesis catalyst systems based on molybdenum halides and organosilicon compounds

Article abstract of DOI:10.1134/S0965544116020067

The catalytic activity of heterogeneous catalytic systems based on molybdenum halides immobilized onto the silica gel surface in combination with organosilicon cocatalysts has been studied in a model reaction of hexene-1 metathesis at 27 and 50°C. It has been established that quite active catalysts are formed when using 1,1,3,3-tetramethyl-1,3-disilacyclobutane or triethylsilane as cocatalysts. Tetramethylsilane has exhibited no marked activity, while tetramethyltin has turned out to be the most effective cocatalyst. Possible routes of formation of active centers have been proposed for organosilicon cocatalysts.

Full text of DOI:10.1134/S0965544116020067

ISSN 0965ꢀ5441, Petroleum Chemistry, 2016, Vol. 56, No. 2, pp. 121–124. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © V.I. Bykov, B.A. Belyaev, T.A. Butenko, E.Sh. Finkel’shtein, 2016, published in Neftekhimiya, 2016, Vol. 56, No. 2, pp. 140–143.
Olefin Metathesis Catalyst Systems Based on Molybdenum Halides
and Organosilicon Compounds
V. I. Bykov, B. A. Belyaev, T. A. Butenko, and E. Sh. Finkel’shtein
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia
eꢀmail: bykov@ips.ac.ru
Received January 15, 2015
Abstract—The catalytic activity of heterogeneous catalytic systems based on molybdenum halides immobiꢀ
lized onto the silica gel surface in combination with organosilicon cocatalysts has been studied in a model
reaction of hexeneꢀ1 metathesis at 27 and 50°C. It has been established that quite active catalysts are formed
when using 1,1,3,3ꢀtetramethylꢀ1,3ꢀdisilacyclobutane or triethylsilane as cocatalysts. Tetramethylsilane has
exhibited no marked activity, while tetramethyltin has turned out to be the most effective cocatalyst. Possible
routes of formation of active centers have been proposed for organosilicon cocatalysts.
Keywords: olefin metathesis, organosilicon compounds, heterogeneous catalysts
DOI: 10.1134/S0965544116020067
Olefin metathesis is of interest for modern petroꢀ eneꢀ1 and a cocatalyst, selected from 1,1,3,3ꢀtetramꢀ
leum chemistry and fine organic synthesis. Several ethylꢀ1,3ꢀdisilacyclobutane, triethylsilane, and tetꢀ
industrial processes have been implemented on the ramethylsilane, were loaded into the dropping funnel.
basis of this reaction [1], and also effective syntheses of All the operations were performed in a flow of dried
natural compounds, in particular, insect pheromones argon of the special purity grade. The volumetric data
have been developed [2–4].
were confirmed by determining the concentration of
deceneꢀ5 in the catalyzate using GLC analysis.
Heterogeneous catalytic systems possess a number
of technological advantages as compared to homogeꢀ
neous catalytic systems, in particular, they open
opportunities to carry out the process in the absence of
solvent and to take catalystꢀfree samples, thereby
allowing their easy analysis by gas–liquid chromatogꢀ
raphy (GLC) and thus monitoring chemoselectivity
and stereoselectivity during the course of the reaction
At a defined conversion of hexeneꢀ1, the catalyzate
was separated from the catalyst, and a new portion of
hexeneꢀ1 equal to the previous portion was added to
the partially deactivated catalyst. The procedure was
repeated two–five times.
The purity of initial hexeneꢀ1 and the cocatalysts
was monitoring using GLC analysis on an LKhMꢀ
8MD chromatograph equipped with a flame ionizaꢀ
[5]. Earlier, we studied the kinetics of ꢀolefin metꢀ
α
athesis in the presence of twoꢀ and threeꢀcomponent
heterogeneous catalytic systems on the basis of MoCl5
or МоOСl4 immobilized onto the silica gel surface [6–
8] in combination with tetramethyltin (Me4Sn).
In this paper, we report data on the activity and staꢀ
bility of catalysts in combination with organosilicon
compounds in a model reaction of hexeneꢀ1 metatheꢀ
sis. Apparently, the search for sufficiently active orgaꢀ
nosilicon cocatalysts that are less toxic than organotin
compounds is a reasonable and relevant task.
×
0.2
mm quartz capillary
tion detector (FID) (50 m
column coated with the SKTFP or the SEꢀ30 stationꢀ
Н
ary phase, and 2 as the carrier gas). The analyses were
performed in the linear temperature programming
12°
mode ( C/min). Electron ionization mass spectra
(70 eV) were recorded on a Finnigan MAT 95 XL 70
instrument. All the reactions, as well as the preparaꢀ
tion of reactants (reagent grade hexeneꢀ1,
Novocherkassk plant), were performed in the atmoꢀ
LiAlH
4, Na, or
2 as a drying agent. The purity of initial hexeneꢀ1
sphere of specialꢀpurity argon using
CaH
and cocatalysts was 98–99% according to GLC data.
EXPERIMENTAL
Hexeneꢀ1 metathesis was carried out in a thermoꢀ
stated glass reactor equipped with a magnetic stirrer, a
dropping funnel, a reflux condenser, and a gas burette
for measuring the volume of ethylene evolving during
RESULTS AND DISCUSSION
The metathesis of hexeneꢀ1, like that of all other αꢀ
the reaction. A weighed amount of the catalyst was olefins, proceeds in accordance with the stoichiometꢀ
charged into the reactor, and certain amounts of hexꢀ ric equation of formation of one symmetric olefin
121

122
BYKOV et al.
molecule and one ethylene molecule from two
fin molecules (reaction (1)):
α
ꢀoleꢀ
The precursor of active centers of the olefin metꢀ
athesis catalyst is molybdenum(V) chloride, which
interacts with surface hydroxyl groups of silica gel at
2 (R–CH=CH2) = R–CH=CH–R + CH2=CH2, (1)
where R = C4H9
80 С to release two HCl molecules per MoCl5 moleꢀ
°
.
cule (reaction (2)).
O H
O H
O
(2)
80°C
SiO2
SiO2
+ MoCl5
+ 2HCl.
MoCl3
O
It can be assumed that the fraction of molybdenum SiO2, with the evolution of two HCl molecules; howꢀ
atoms bound to three oxygen atoms of silica gel is quite
insignificant because this requires a temperature above
ever, an inactive sample is formed in this case.
During the interaction of Me4Sn with the precursor
of the active center (reaction (3)), dimethyl derivative
150
than 150
°
С
. If the immobilization is carried out at or higher
°
С, inactive precursors of catalytic systems for
II is formed, which decomposes via
α
ꢀН elimination
metathesis are formed. It should be noted that molybꢀ
denum(V) chloride interacts with hydroxyl groups of
to give the primary carbene active center and methane
γ
ꢀaluminum oxide at 80°C in the same manner as with (reaction (4)).
CH3
O
O
SiO2
(3)
+ 2(CH3)3SnCl.
Mo CH3
I + 2Sn(CH3)4
Cl
II
[Me2SiCH2]2) versus 63% within 16 min in the case of
Et3SiH. The catalytic system based on [Me2SiCH2]2 is
more stable than that with Et3SiH. For example, the
time to reach the conversion specified in the table is
32 min for the second portion of hexeneꢀ1, whereas
that in the case of [Me2SiCH2]2 is 13.2 min for the
O
O
II
SiO2
Mo
Cl
+ 2CH4.
CH2
(4)
III
When tetramethylsilane is used instead of tetrameꢀ third portion of hexeneꢀ1.
thyltin, no metathesis reaction occurs. only It is only
after treating the precursor with Ме4Si vapor at 110
that nonselective catalysts having low activity are
formed.
By using gas chromatography–mass spectrometry,
it was found that the only product of Et3SiH interacꢀ
°C
tion with
I is triethylchlorosilane (Et3SiCl), the
amount of which was close to two equivalents per
equivalent of molybdenum. Traces of hexane were
detected in the first portion of the catalyzate. In the
case of Et3SiH used as the cocatalyst, the formation
route for the active center can be represented by reacꢀ
When organosilicon compounds, such as 1,1,3,3ꢀ
tetramethylꢀ1,3ꢀdisilacyclobutane ([Me2SiCH2]2) or
triethylsilane (Et3SiH), are used as a cocatalyst, the
resulting catalysts are quite active. The table shows the
results of some experiments on the metathesis of hexꢀ
tions (5)–(7). First, activeꢀcenter precursor
with triethylsilane to form dihydride derivative IV
A comparison of the experimental results presented (reaction (5)), to which two molecules of hexeneꢀ1
in the table shows that a more active catalytic system is add, thus forming dihexyl derivative (reaction (6)).
formed when [Me2SiCH2]2, rather than Et3SiH, is This derivative degrades via ꢀН elimination to form a
used as the cocatalyst. Thus, a hexeneꢀ1 conversion of secondary carbene center and a hexane molecule
67% is reached within 6.2 min ( = 27 C, (reaction (7)).
I interacts
eneꢀ1 at 27 and 50°C.
V
α
Т
°
O
O
H
H
I + 2(Et3SiH)
SiO2
Mo
(5)
Cl
IV
PETROLEUM CHEMISTRY Vol. 56
No. 2
2016

OLEFIN METATHESIS CATALYST SYSTEMS
123
Dependence of hexeneꢀ1 conversion on the reaction time for various cocatalysts at 27 and 50°C
Time to reach specified conversion, min
Hexeneꢀ1
portion
number
Conversion
of hexeneꢀ1
cocatalyst
[Me2SiCH2]2
cocatalyst
Et3SiH
cocatalyst
Me4Sn
T
= 27°C
T
= 50°C
T
= 27°C = 50°C
T
T
= 27°C
T
= 50°C
T
= 27°C
T = 50°C
1'
2'
1
63
58
67
62
62
62
52
58
23
36
42
49
49
50
–
–
–
16
32
–
28
12
–
–
–
–
–
–
6.2
1.5
3.3
4.7
6.0
6.5
4.0
3.0
3.9
4.8
3.3
0.5
0.8
1.7
2.7
3.9
2
8.2
–
–
3
13.2
34.0
33.0
–
–
4
–
–
5
–
–
* Hexeneꢀ1 : Mo : cocatalyst = 300 : 1 : 4 for all the cocatalysts at
T = 27°C; hexeneꢀ1 : Mo : Et SiH = 900 : 1 : 4 at T = 50°C.
3
O
CH2
R
R
CH2
IV + CH2=CH–R
SiO2
Mo
CH2 CH2
O
Cl
V
(6)
(7)
O
SiO2
V
+ CH3–CH2–R.
Mo
R
CH
CH2
O
Cl
VI
It is known [9] that 1,1,3,3ꢀtetramethylꢀ1,3ꢀdisilaꢀ molecule adds to form derivative VIII (reaction (9)).
cyclobutane reacts with Ti, Zr, Hf, W, and Mo chloꢀ This derivative degrades, like in other cases, via ꢀН
α
rides with the cleavage of the cyclic Si–C bond to form elimination to give carbene complex IX and [trimethꢀ
derivative VII (reaction (8)), to which a hexeneꢀ1 ylsilyl(chlorodimethylsilyl)]methane X (reaction (10)).
CH2
H3C
H3C
CH3
CH3
O
O
R1
R1
Si
I + 2
SiO2
Si
Mo
Cl
CH2
(8)
VII
CH3
Si
CH3
R =
1
H2C
CH2 Si Cl
CH3
CH3
O
R1
SiO2
VII + CH2=CH–R
Mo
(9)
CH2 CH R1
R
O
Cl
VIII
PETROLEUM CHEMISTRY Vol. 56
No. 2
2016

124
BYKOV et al.
CH3
CH3
CH2 Si Cl
CH3
O
O
VIII
SiO2
Si
+
CH3
Mo
Cl
CH
CH R1
R
(10)
CH3
IX
X
2. V. I. Bykov, T. A. Butenko, E. Sh. Finkelshtein, and
In summary, it has been shown that organosilicon
P. T. Henderson, J. Mol. Catal. 90, 111 (1994).
cocatalysts (1,1,3,3ꢀtetramethylꢀ1,3ꢀdisilacyclobuꢀ
tane and triethylsilane) can be used for the formation
of quite active heterogeneous catalysts for olefin metꢀ
athesis. Unlike tetramethyltin, tetramethylsilane is
not a cocatalyst. Possible routes for the formation of
active centers in the case of organosilicon cocatalysts
have been proposed.
3. V. I. Bykov and E. Sh. Finkelshtein, J. Mol. Catal. 133
,
17 (1998).
4. V. I. Bykov, T. A. Butenko, E. B. Petrova, and
E. Sh. Finkelshtein, Tetrahedron 55, 8249 (1999).
5. V. I. Bykov, E. M. Khmarin, B. A. Belyaev, et al., Pet.
Chem. 46, 110 (2006).
6. V. I. Bykov, E. M. Khmarin, B. A. Belyaev, et al., Kinet.
Catal. 49, 11 (2008).
7. V. I. Bykov, B. A. Belyaev, T. A. Butenko, and
ACKNOWLEDGMENTS
E. Sh. Finkelshtein, Green Metathesis Chemistry: Great
Challenges in Synthesis, Catalysis and Nanotechnology
Ed. by V. Dragutan, A. Demonceau, I. Dragutan, and
E. S. Finkelshtein (Springer, Dordrecht, 2009), p. 115.
,
This work was supported by the Russian Foundaꢀ
tion for Basic Research, project no. 14ꢀ03ꢀ00455.
8. V. I. Bykov, B. A. Belyaev, T. A. Butenko, and
E. Sh. Finkel’shtein, Kinet. Catal. 51, 615 (2010).
9. N. B. Bespalova, Extended Abstract of Doctoral Disꢀ
sertation in Chemistry (Moscow, 2003).
REFERENCES
1. K. J. Ivin and J. C. Mol, Olefin Metathesis and Metatheꢀ
sis Polymerization (Academic, London, 1997).
Translated by E. Boltukhina
PETROLEUM CHEMISTRY Vol. 56
No. 2
2016