712 RESEARCH PAPER
DECEMBER, 712–714
JOURNAL OF CHEMICAL RESEARCH 2011
Preparation of methylphenyldichlorosilane through a catalytic cracking
reaction of 1,2-dimethyl-1,1,2,2-tetrachlorodisilane with halobenzene
Yong-Rui Pia,b, Jun Tanb*, Hui Liub, Jie Chenb, Zhu-You Qunc, Yan-Bo Zengb and Lei Lia,b
aCollege of Petroleum and Chemical Engineering, Changzhou University, Changzhou, 213164, Jiangsu, P. R. China
bCollege of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, 314001, Zhejiang, P. R. China
cCollege of Chemical Engineering and Materials, Zhejiang University ofTechnology, Hangzhou, 310014, Zhejiang, P. R. China
Catalytic cracking reaction of 1,2-dimethyl-1,1,2,2-tetrachlorodisilane with a halobenzene (PhCl, PhBr) to prepare
methylphenyldichlorosilane has been investigated. Pd(PPh3)4 exhibited the best catalytic activity among the catalysts
used. The activity of chlorobenzene was significantly lower than that of bromobenzene. With the latter and toluene
as solvent, in the presence of 0.3 mol % Pd(PPh3)4, the conversion of disilane was 100% with a selectivity to MePhSiCl2
of 97.1%.
Keywords: 1,2-dimethyl-1,1,2,2-tetrachlorodisilane, halobenzene; catalytic cracking reaction, methylphenyldichlorosilane
Methylphenyldichlorosilane (MePhSiCl2) is an important
organic monomer in the synthesis of special silicones and the
synthesis and modification of polymethylphenylsiloxane mate-
rials. In particular, it plays a critical role in improving the heat
resistance, chemical stability and radiation resistance of the
organic polysiloxanes.1–3 At present, the main methods reported
in the literatures for the preparation of MePhSiCl2 are the
thermal condensation method,4 the Grignard method,5 the
disproportionation method6 and the decomposition method.7
1,2-dimethyl-1,1,2,2-tetrachlorodisilane (MeCl2SiSiCl2Me)
is one of the methylchlorodisilanes (MCDS) which are
by-products of high-boiling residues produced from the “direct
process”8 for the preparation of methylchlorosilanes.9,10 The
main methods of converting the MCDS into commercially
valuable products reported in the literature are the catalytic
cracking reactions of MCDS with RX (R is H, Me, Ph, PhCH2,
etc., X is Cl, Br)11–18 to form functional chlorosilicon mono-
mers. Eaborn et al.11 reported that p-O2NC6H4CH2SiMe3 or
p-NCC6H4CH2SiMe3 were prepared by Me3SiSiMe3 reacting
with benzyl halides catalysed by Pd(PAr3)4 (Ar=Ph,
p-MeOC6H4 and p-Me3SiCH2C6H4, etc.). However, the
benzyltrimethylsilanes were only formed in low yield in the
process of silylanisation of benzyl halides, because a strong
electron-withdrawing group could not be formed. Matsumoto
and coworkers12–14 reported that several MCDS such as
MeCl2SiSiCl2Me, Me2ClSiSiClMe2 and MeCl2SiSiClMe2
could be effectively alkylated with benzyl chlorides in the
presence of Pd(PPh3)4, PPh3, Bu4NCl or Bu4NF. Fan described
a method of preparation of MePhSiCl2 using chlorobenzene
with high boiling methylchlorodisilanes mixtures,19 but there
are no detailed reports about the reaction of MeCl2SiSiCl2Me
with halobenzenes. In our work, the research centered on an
approach for preparation of MePhSiCl2 through a catalytic
cracking reaction of 1,2-dimethyl-1,1,2,2-tetrachlorodisilane
with a halobenzene (Scheme 1). In particular, some critical
factors including catalysts, catalyst concentration and solvent
were investigated.
Experimental
PhCl, PhBr, benzene, toluene and mesitylene were purchased
from Aladdin Chemicals. MeCl2SiSiCl2Me was obtained from J&K
Scientific Ltd. RuCl3, PdCl2, Pd/C, RhCl3 and PPh3 were purchased
from Alfa Aesar. Pd(PPh3)2Cl2, Ru(PPh3)3Cl2, RhCl(PPh3)3 and
Pd(PPh3)4 were prepared according to literature procedures.19–23
The reactions were conducted under a nitrogen atmosphere. A
typical reaction procedure was as follows: Cl2MeSiSiMeCl2 (1 mL),
halobenzene (1 mL), with solvent (1 mL) if used, and the catalyst
(0.05–0.5 mol% based on the Cl2MeSiSiMeCl2 charged) were sealed
in 50 mL Schlenk glass instrument and heated by oil bath.
Reaction products were analysed by an Agilent 7890A-5975C
GC-MS using an HP-1 MS columns (30 m × 0.32 mm × 0.25 um),
which was packed with dimethylpolysiloxane, split:100:1, gas flow:
0.8 mL min-1, inlet temperature 220 °C, column temperature 50 °C
(hold 2 min) then 15 °C min-1 up to 220 °C (hold 3 min). The conver-
sion of Cl2MeSiSiMeCl2 and selectivity of MePhSiCl2 were calculated
as follows:
Scheme 1 The cracking reaction of 1,2-dimethyl-1,1,2,2-tetrachlorodisilane with halobenzene.
* Correspondent. E-mail: tanjunzjxu@126.com