ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 1, pp. 85 88. Pleiades Publishing, Inc., 2006.
Original Russian Text V.S. Tkach, D.S. Suslov, M. Gomboogiin, G.V. Ratovskii, F.K. Shmidt, 2006, published in Zhurnal Prikladnoi Khimii, 2006,
Vol. 79, No. 1, pp. 88 91.
CATALYSIS
Isomerization of Alkenes in the Presence of Pd(acac)2 BF3OEt2
Catalytic System
V. S. Tkach, D. S. Suslov, M. Gomboogiin, G. V. Ratovskii, and F. K. Shmidt
Irkutsk State University, Irkutsk, Russia
Mongolian State University, Ulan-Bator, Mongolian Republic
Received October 20, 2005
Abstract Positional isomerization of alkenes was studied in the presence of Pd(acac)2 + 20BF3OEt2 cata-
lytic system. The reactivity of alkenes decreases in the following order: 1-hexene > 1-heptene > 2-methyl-
1-pentene > 4-methyl-2-pentene (cis + trans).
DOI: 10.1134/S1070427206010186
Systems containing bis(acetylacetonato)palladium
EXPERIMENTAL
Pd(acac) and trifluoroboron etherate are efficient
2
catalysts of dimerization of vinylaromatic hydrocar-
bons, e.g., selective dimerization of styrene [1, 2],
telomerization of diene hydrocarbons with secondary
amines [3, 4], and di- and oligomerization of ethylene
and propylene [5 7]. These systems exhibit relatively
high catalytic activity in positional isomerization of
1-hexene [8]. Isomerization of alkenes in the presence
of Pd(II) complexes as catalysts has been extensively
studied. Different isomerization mechanisms were
proposed. The following processes are believed to be
key steps of isomerization: (a) oxidative addition of
alkene to Pd(II) to form allylpalladium(IV) hydride
[9], (b) formation of carbenium ion by reaction of
Pd(II) with alkene coordinated to the transition metal
[10], (c) reversible addition of olefin to Pd(II) hy-
drides without a change in the Pd oxidation state [11].
Akenes like 1-hexene play a critical role in formation
of Pd H bonds in reactive complexes (RC) formed in
the presence of Pd(acac) BF OEt catalytic system.
Isomerization of alkenes was performed under
argon in a glass reactor equipped with a magnetic
stirrer. A solution of appropriate alkene and Pd(acac)
2
was allowed to stand at 10 C for 15 min. The iso-
merization was initiated by addition of BF OEt . An
3
2
aliquot (1 ml) of the reaction mixture was taken at
regular intervals and placed into a test tube containing
3% aqueous hydrochloric acid to decompose the cata-
lyst. The organic layer was separated and dried over
calcium chloride. The isomerization products in the
sample were analyzed by gas liquid chromatography
(GLC) on Tsvet-100M and Chrom-42M chromato-
graphs equipped with a flame-ionization detector and
a 100-m copper column with an internal diameter
of 0.5 mm. We used vacuum oil as the stationary
phase. The inlet pressure of the carrier gas was 0.6
5
10 Pa. The column temperature was 45 C.
Synthesis of Pd(acac) . To a solution of KOH
2
3
2
3
2
(0.7310 g, 13.028 10 mol) in 15 ml of H O
2
Probably, the composition of these square-planar
in a beaker was added acacH (1.2423 g, 12.408
10
complexes is HPd(L,L )BF , where L is unsaturated
3
4
mol). The mixture was heated at 45 5 C.
hydrocarbon and L = L or PR [12].
3
A transparent solution of acacK was obtained.
Here we experimentally studied isomerization of
alkenes in the presence of Pd(acac) BF OEt cata-
To an aqueous solution (50 ml) of KCl (0.8830 g,
3
2
3
2
11.844 10
mol) in another beaker was added
lytic system, as influenced by various factors includ-
ing the composition of the catalyst, preparation condi-
tions of RC, and the solvent. With the positional iso-
merization of alkenes as an example, we intended to
gain insight into the mechanism of transformation
of unsaturated hydrocarbons including alkenes and
vinylaromatic and diene hydrocarbons in the presence
of bis(acetylacetonato)palladium boron trifluoride
etherate catalytic system.
3
PdCl (1.0000 g, 5.64 10 mol). The mixture was
2
heated at 45 5 C with stirring until the brown pre-
cipitate completely dissolved to form a brown solu-
tion. The solution was filtered while hot.
The solutions were mixed at 45 5 C. The yellow
precipitate was filtered off on a Buchner funnel,
washed 5 7 times with 100-ml portions of H O, and
2
dried at 50 C. Pd(acac) was recrystallized from ace-
2
85