Russian Journal of General Chemistry, Vol. 75, No. 5, 2005, pp. 734 738. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005,
pp. 778 782.
Original Russian Text Copyright
2005 by Zazybin, Khusnutdinova, Osipova, Solomonov.
Addition of Tetrachloromethane to Alkenes,
Catalyzed by Pt(II) Complexes
A. G. Zazybin, Yu. R. Khusnutdinova, O. L. Osipova, and B. N. Solomonov
Kazan State University, Kazan, Tatarstan, Russia
Received December 26, 2003
Abstract Platinum(II) complexes [dichlorobis(triphenylphosphine)platinum(II), dichlorobis(tri-m-tolyl-
phosphine)platinum(II), dichloro(2,9-dimethyl-1,10-N, N -phenanthroline)platinum(II), etc.] showed catalytic
activity in addition of tetrachloromethane across the double bond in 1-hexene, 1-heptene, 1-octene, 1-decene,
and cyclohexene. The stability of the platinum catalysts was evaluated by GLC, gas chromatography mass
3
1
spectrometry, and P NMR and IR spectroscopy; the kinetic relationships of the addition reactions were
determined. A reaction mechanism involving formation of trichloromethyl radical was suggested. A correla-
tion was revealed for the first time between the catalytic activity of platinum, palladium, and rhodium com-
plexes and the capability of these complexes to generate hexachloroethane.
The addition of tetrachloromethane to alkenes can
As a model substrate we chose hexene. Although
be effected by free-radical initiatiors [1] or by transi- the Pt(II) complexes catalyze the addition of CCl to
4
tion metal salts and complexes [2 4]. As a rule, the
reaction products in this case are not only 1 : 1 ad-
ducts but also telomeric homologs [1, 5]. With organ-
ic peroxides used as initiators of tetrachloromethane
addition, the necessary condition for obtaining the
1-hexene in a wide temperature range (67 140 C),
we chose the temperature of 120 C for consistency.
We found that cis-PtCl (PPh ) (I), PtI (PPh )
3 2
2
3 2
2
(
II), PtI (COD) (III) (COD = 1,4-cyclooctadiene),
2
PtCl [P(m-Tol) ] (IV), PtMe (PPh ) (V), and PtCl
2
3 2
2
3 2
2
1
: 1 adduct is a 7 10-fold excess of tetrachlorometh-
(
1
1
2,9-Me phen) (VI) (2,9-Me phen = 2,9-dimethyl-
,10-N, N -phenanthroline) catalyze the addition, with
,1,1,3-tetrachloroheptane VII being the major prod-
2 2
ane relative to alkene [1]. In the case of using coordi-
nation catalysts, tetrachloromethane is also taken in
excess (usually fivefold) to increase the yield of the
target product [3, 6].
uct. PtCl (COD) shows no appreciable catalytic activ-
2
ity in this reaction. Data on the catalytic activity of
the Pt(II) complexes used are given in Table 1.
We have found previously [7] that Pt(II) complexes
show high activity in addition of tetrachloromethane
to alkenes. In particular, the reaction performed in the
presence of PtCl (PPh ) gives the 1 : 1 adduct as the
The highest yields of the adducts were attained
with complexes II and V. However, these complexes
are unstable under the reaction conditions: at 120 C
within 2 h they virtually fully transform into PtCl2
2
3 2
major product in a high yield. As compared to the
known catalytic systems for Kharasch addition, the
system that we developed has certain advantages. In
particular, with Co(II) [3] and Cu(I) [2] as catalysts,
(
PPh ) .
3 2
In contrast to iodides II and III, platinum(II) chlo-
CCl was taken in a large excess relative to the alkene
4
ride triarylphosphine complexes I and IV preserve
their activity even at high olefin conversions. We
examined the solid residues isolated after heating I
at 120 C for 10.5 h in the mixtures CCl CH CN
[(5 10) : 1]. In the presence of Pt(II) phosphine com-
plexes, the addition is very selective at 1.3 : 1 molar
ratio of CCl to the alkene. The catalytic system based
4
4
3
on PtCl (PAr ) preserves the activity for several tens
2
3 2
1-hexene (sample 1), CCl CH CN (sample 2), and
4 3
of hours. In contrast to the known catalysts, e.g., to
those based on transition metal carbonyls [8], the
Pt(II) complexes are stable under the reaction condi-
tions for a long time. Also, the addition is effected at
a catalyst concentration as low as 0.06 0.50 mol %,
which is more than an order of magnitude lower than
the necessary concentrations of the catalysts contain-
1
-hexene CH CN C H (sample 3). The IR spectra
3 6 6
of all these samples contain two bands at 320 and
1
2
94 cm , corresponding to the starting cis-PtCl
2
(
PPh ) [9].
3 2
In the 31P NMR spectra of samples 1 3, the signals
of the starting cis-dichlorobis(triphenylphosphine)-
ing Re(III) (2 mol % [4]) and Co(II) (16 mol % [3]). platinum at 14.8 14.9 ppm, with two platinum satel-
1
070-3632/05/7505-0734 2005 Pleiades Publishing, Inc.