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Catalysis by Hydrotalcite in Liquid-phase Organic Reactions
363
Catalysis by Hydrotalcite in Liquid-phase Organic Reactions
Y. Ono. E. S u z u k i , and M. Okamoto Department o f Chemical Engineerinng, Meguro-ku, Tokyo 152, Japan
Tokyo I n s t i t u t e o f Technology,
Ookayama,
ABSTRACT The i n t e r l a y e r C1- a n i o n s i n a s y n t h e t i c h y d r o t a l c i t e - l i k e m a t e r i a l , Mg A12(OH)16C1~4H20, were found t o r e a c t w i t h o r g a n i c bromides i n a non-polar so v e n t o f toluene, a l m o s t a l l c h l o r i d e i o n s i n t h e i n t e r l a y e r space appearing i n t h e l i q u i d phase as t h e corresponding o r g a n i c c h l o r i d e s . The h y d r o t a l c i t e l i k e m a t e r i a l was found t o c a t a l y z e o r g a n i c r e a c t i o n s i n w h i c h t h e i n t e r l a y e r C1- anions p l a y t h e r o l e o f c a t a l y s t . Thus, t h e m a t e r i a l c a t a l y z e d t h e h a l i d e exchange r e a c t i o n s between a1 k y l h a l i d e s i n t o l u e n e and t h e d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e t o g i v e s i l a n e and t e t r a m e t h o x y s i l a n e .
P
INTRODUCTION Hydrotalcite,
Mg6A12(oH)16c0~4H20. i s one o f t h e n a t u r a l l y o c c u r r i n g a n i o n i c
c l a y m i n e r a l s and can be s y n t h e s i z e d [1,2]. Mg6A12(OH)16C1~4H$,
A hydrotalcite-like material,
can a l s o be synthesized [2].
Here,
Mg*+ and A13+ c a t i o n s
c o n s t i t u t e p o s i t i v e l y charged h y d r o x i d e l a y e r s between which w a t e r molecules and C1- anions a r e i n t e r c a l a t e d ,
t h e l a t t e r b e i n g anion-exchangeable [3].
The e x c h a n b e a b l e a n i o n s a r e known t o r e a c t w i t h o r g a n i c h a l i d e s i n a nonp o l a r s o l v e n t such as toluene.
Thus,
b y the, a c t i o n o f i n t e r l a y e r I-anions i n
a h y d r o t a l c i t e - l i k e m a t e r i a l , Zn2Cr(OH)6I2-2H20, i n t o b u t y l i o d i d e [4].
b u t y l b r o m i d e was c o n v e r t e d
The f i r s t a i m o f t h i s work i s t o examine t h e r e a c t i o n s
o f i n t e r l a y e r C1- anions i n Mg6A12(OH)16C1~4H20 w i t h benzyl o r b u t y l bromide i n t o l u e n e t o expand t h e knowledge o f t h e r e a c t i v i t y o f t h e i n t e r l a y e r anions w i t h o r g a n i c h a l i d e s i n a non-polar solvent. The second a i m o f t h i s work i s t o demonstrate t h e c a t a l y s i s o f t h e i n t e r l a y e r a n i o n s i n o r g a n i c r e a c t i o n s such as h a l i d e - e x c h a n g e r e a c t i o n s b e t w e e n a l k y l h a l i d e s i n t o l u e n e (eq. 1).
364 Y. Ono, E. Suzuki and M. Okarnoto
Thus,
f o r example,
f o r a system o f benzyl chloride,
hydrotalcite-like material,
b u t y l b r o m i d e , and t h e
we expect t h e f o l l o w i n g r e a c t i o n s t o occur.
Butyl
b r o m i d e w o u l d u n d e r g o a h a l i d e s u b s t i t u t i o n b y t h e i n t e r l a y e r C1- a n i o n s , t h e i n t e r c a l a t e d B r - anions would,
l e a v i n g Br- anions i n t h e i n t e r l a y e r space;
i n t u r n , a t t a c k b e n z y l c h l o r i d e t o y i e l d b e n z y l b r o m i d e l e a v i n g C1- a n i o n s i n t h e i n t e r l a y e r space, t h e i n t e r l a y e r C1- anions b e i n g c y c l e d as f o l l o w s :
Here, H.T.-Cl-
and H.T.-Br-
d e n o t e h y d r o t a l c i t e - 1 i k e m a t e r i a l s c o n t a i n i n g C1-
and Br- i n t e r l a y e r anions,
respectively.
Since t h e h y d r o t a l c i t e - l i k e m a t e r i a l c o n t a i n s exchangeable i n t e r l a y e r anions, i t can be used as a c a t a l y s t f o r r e a c t i o n s f o r which anion-exchange
been used as c a t a l y s t . 4 (CH30)3SiH
__+
r e s i n s have
The d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e (eq. SiH4
2) i s
(2)
3 (CH30)4Si
t
c a t a l y z e d b y an anion-exchange r e s i n such as D i a i o n PA-306 [5].
The c a t a l y t i c
d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e i n t h e p r e s e n c e o f a h y d r o t a l c i t e - 1 ike m a t e r i a l c o n t a i n i n g i n t e r l a y e r C1- o r CH3O- anions w i l l a l s o be demonstrated. EXPERIMENTAL Synthesis
of
hydrotalcite-like materials
The h y d r o t a l c i t e - 1 i k e m a t e r i a l , aqueous s o l u t i o n s o f MgC12.6H20, a t 433 K [ 2 ] .
MggA12(OH)16C12.4H20,
AlCly6H20,
and NaOH (Mg2+/A13+
CH30Na (CH30-/N03-
i n a methanol s o l u t i o n o f
m o l a r r a t i o = 10) a t 338 K f o r 43 h.
and
disproportionation reactions
For t h e halide-exchange condenser,
m o l a r r a t i o = 3)
The m a t e r i a l c o n t a i n i n g CH3O- a n i o n s was o b t a i n e d b y a n i o n -
e x c h a n g i n g NO3- a n i o n s o f Mg6A12(oH)16(N03)2'4H20
Halide-exchange
was synthesized f r o m
reactions,
i n t o a 50-cm3 f l a s k e q u i p p e d w i t h a
30 cm3 o f t o l u e n e o r DMF as a s o l v e n t and 1.0 g p o r t i o n o f t h e
h y d r o t a l c i t e - 1 i k e m a t e r i a l (3.3
mmol o f i n t e r l a y e r C1- anions) were introduced.
A 33 mmol o f benzyl c h l o r i d e was added t o t h e m i x t u r e and t h e t e m p e r a t u r e was k e p t a t 343 o r 373 K w i t h s t i r r i n g ,
f o l l o w e d b y t h e a d d i t i o n o f a g i v e n amount
o f an a l k y l bromide ( o r i o d i d e ) (33-195 mmol). a n i t r o g e n atmosphere.
Reactions were conducted under
The l i q u i d p h a s e was w i t h d r a w n p e r i o d i c a l l y a n d
a n a l y z e d b y a gas c h r o m a t o g r a p h e q u i p p e d w i t h a 2-m l o n g SE-30 c o l u m n and a
Catalysis by Hydrotalcite for Organic Reactions 365
f l a m e i o n i z a t i o n detector. F o r t h e d i s p r o p o r t i o n a t i o n r e a c t i o n s , t h e h y d r o t a l c i t e - l i k e m a t e r i a l s were evacuated a t 453 K f o r 2 h b e f o r e use t o d r i v e o u t i n t e r l a y e r w a t e r molecules. A 41 mmol o f t r i m e t h o x y s i l a n e was added i n t o t h e f l a s k c o n t a i n i n g 0.62 g o f t h e m a t e r i a l (2.0 mmol o f i n t e r l a y e r a n i o n s ) u n d e r a n i t r o g e n a t m o s p h e r e . r e a c t i o n m i x t u r e was
analyzed f o r
chromatograph d e s c r i b e d above,
(CH30)3SiH
and (CH30)4Si
The
b y t h e gas
u s i n g heptane as a standard.
RESULTS AND DISCUSSION Reaction
of
i n t e r l a y e r anions w i t h o r g a n i c h a l i d e s
To know t h e r e a c t i v i t y o f i n t e r l a y e r C1- anions towards o r g a n i c h a l i d e s i n a non-polar solvent, o f H.T.-Cl-
t h e f o l l o w i n g e x p e r i m e n t s were c a r r i e d out.
A 1.0 g p o r t i o n
(C1-= 3.3 mmol) was added t o a t o l u e n e s o l u t i o n o f b u t y l o r b e n z y l
bromide (33 mmol) a t 373 K:
t h e f o r m a t i o n o f t h e corresponding a l k y l c h l o r i d e s ,
g e n e r a t e d by t h e h a l i d e exchange b e t w e e n H.T.-Clf o l l o w e d w i t h time.
and t h e a l k y l b r o m i d e s , was
As shown i n Fig. 1, t h e y i e l d o f b u t y l c h l o r i d e i n c r e a s e d
w i t h t i m e and a t t a i n e d a c e i l i n g value.
The exchange was a l m o s t complete i n 1
h, a b o u t 90% o f t h e c h l o r i d e i o n s i n t h e i n t e r l a y e r s a p p e a r i n g i n t h e l i q u i d phase as b u t y l c h l o r i d e .
- 3 0
E E
80
60
%01 C
a
-c
h)
ul
40
$ 1
t
.oc a
20
&
)r
rd
0
0
20
40 60 t I min
80
Fig. 1. Change i n b u t y l ( o r b e n t y l ) c h l o r i d e y i e l d w i t h r e a c t i o n t i m e i n a h a l i d e exchange between b u t y l ( o r b e n z y l ) bromide and t h e h y d r o t a l c i t e - l i k e m a t e r i a l c o n t a i n i n g i n t e r l a y e r C1- anions. Reaction c o n d i t i o n s : CqHgBr ( o r C H CH2Br)= 33 mmol, s o l v e n t ( t o l u e n e ) = 30 cm3, h y d r o t a l c i t e - l i k e m a t e r i a l (H.T.-C(i-?= 1.0 g ( i n t e r l a y e r C1- anions= 3.3 m o l ) , and r e a c t i o n temperature= 373 K.
366 Y. Ono. E. Suzuki and M. Okamoto
Compared t o t h e h a l i d e exchange b e t w e e n H.T.-Clh a l i d e exchange b e t w e e n H.T.-Cl-
and b u t y l b r o m i d e , t h e
and b e n z y l b r o m i d e p r o c e e d e d much f a s t e r .
Thus, as shown a l s o i n Fig. 1, t h e h a l i d e exchange was a l m o s t complete w i t h i n 10 min. Because o f t h e s i z e o f t h e a l k y l h a l i d e s , t h e h a l i d e exchange p r o b a b l y o c c u r s a t t h e e x t e r n a l edge s u r f a c e s o f t h e h y d r o t a l c i t e - l i k e m a t e r i a l , n o t i n t h e i n t e r l a y e r space,
T h i s i s supported b y t h e f a c t t h a t no expansion o f t h e
i n t e r l a y e r space was observed a f t e r t h e m a t e r i a l was used i n t h e halide-exchange reaction.
The d i f f u s i o n o f t h e h a l i d e i o n s i n t h e i n t e r l a y e r space i s n o t t h e
r a t e - d e t e r m i n i n g step, s i n c e t h e r a t e o f t h e r e a c t i o n g r e a t l y depends on t h e k i n d o f a l k y l bromide. H a l i d e exchanqe between a l k y l h a l i d e s i n t o l u e n e C a t a l y s i s o f t h e i n t e r l a y e r a n i o n s i n t h e h a l i d e exchange b e t w e e n a l k y l h a l i d e s (eq.
A r e a c t i o n between benzyl c h l o r i d e (33 mmol) and
1) was examined.
b u t y l b r o m i d e ( 3 3 mmol) i n t o l u e n e a t 373 K was c a r r i e d o u t u s i n g a 1.0 g The r e a c t i o n p r o c e e d e d and, a s l i s t e d i n T a b l e 1, t h e
p o r t i o n o f H.T.-Cl-.
y i e l d o f b e n z y l b r o m i d e was 31% a t 4 h, i n c r e a s i n g t o 37% a f t e r 20 h.
The
r e a c t i o n d i d n o t proceed i n t h e absence o f t h e H.T.-Cl-. The H.T.-Cl-
can a l s o be a c a t a l y s t f o r a l k y l i o d i d e p r o d u c t i o n i n t o l u e n e .
Thus, b e n z y l i o d i d e c o u l d be o b t a i n e d b y t h e r e a c t i o n o f b e n z y l c h l o r i d e ( 3 3
mmol) w i t h b u t y l i o d i d e (33 mmol) a t 373 K (Table 1).
T a b l e 1. H a l i d e exchange b e t w e e n b e n z y l c h l o r i d e and b u t y l bromide ( o r iodide1.a ~~
Alkyl halideb
CqHgBr CqHgBr C4H9I C4H9I
~
Weight o f H.T.-ClC 4
Benzyl bromide ( o r iodide) y i e l d
/
Reaction t i m e 4
20
1.0
31
31
1.0
26
-
0 0
0
0
/
/ % h
0
0
aSolvent (toluene)= 30 cm3 and r e a c t i o n temp e r a t u r e 373 K. bBenzyl c h l o r i d e = b u t y l c h l o r i d e ( o r i o d i d e ) = 33 mmol. Cone g r a m o f H.T.-Clc o n t a i n s 3.3 mmol o f i n t e r l a y e r C1- anions.
Catalysis by Hydrotalcite for Organic Keactions 367
H a l i d e exchange u s i n g v a r i o u s bromoalkanes The h a l i d e exchange i n DMF b e t w e e n b e n z y l c h l o r i d e a n d b u t y l b r o m i d e g a v e F i g u r e 2 shows t h e t i m e
h i g h e r y i e l d o f benzyl bromide t h a n t h a t i n toluene.
course o f benzyl bromide y i e l d i n a r e a c t i o n between benzyl c h l o r i d e (33 mmol) and b u t y l b r o m i d e (33 mmol) i n DMF a t 343 K u s i n g a 1.0 g p o r t i o n o f H.T.-Cl-. The y i e l d i n c r e a s e d w i t h t i m e a n d was 51% a t 4 h. I n t h e h a l i d e exchange i n DMF,
t h e y i e l d was 53%
i n t h e a b s e n c e o f H.T.-Cl-,
I n a p r o l o n g e d r u n o f 20 h, t h e r e a c t i o n proceeded even
t h e y i e l d b e i n g 27% a t 4 h.
A l k y l b r o m i d e s can be o b t a i n e d f r o m t h e c o r r e s p o n d i n g c h l o r i d e s i n t h e presence o f NaBr o r t r i - n - b u t y l a m i n e ,
u s i n g bromoalkanes such as e t h y l bromide,
p r o p y l bromide,
as w e l l as b u t y l bromide as a b r o m i n a t i o n
a g e n t [6,7].
and 1,4-dibromobutane
These b r o m o a l kanes w e r e t e s t e d a s b r o m i n a t i o n a g e n t s t o w a r d s As l i s t e d i n T a b l e 2 ( e n t r i e s 1
b e n z y l c h l o r i d e i n t h e p r e s e n c e o f H.T.-Cl-. and 3-5),
t h e bromoalkanes gave benzyl bromide y i e l d s a t 4 h o f 51-652 under t h e
same r e a c t i o n c o n d i t i o n s as those i n Fig. 2.
Benzyl bromide y i e l d a t 20 h and
a t e q u i l i b r i u m a r e a l s o l i s t e d i n T a b l e 2.
It i s c l e a r t h a t t h e r e a c t i o n s
p r o c e e d c l o s e t o e q u i l i b r i u m e v e n a t t h e r e a c t i o n t i m e o f 4 h. T a b l e 2,
1,4-dibromobutane
i s t h e m o s t e f f i c i e n t b r o m i n a t i o n agent.
halide-exchange r e a c t i o n s proceed c l o s e t o e q u i l i b r i u m u s i n g H.T.-Cl-
60
I
As seen i n
50 -
as a s o l i d
I
I
I
The
o/o0 o 4 .
40
/
30
/*-
20
*/.-*-
10 0
I
0
1 2 3 Reaction time I h
I
4
Fig. 2. Change i n benzyl bromide y i e l d w i t h r e a c t i o n t i m e i n a h a l i d e exchange between benzyl c h l o r i d e and b u t y l bromide. Reaction conditions: CgH CH C1= CqHgBr= 33 mmol, s o l v e n t (DMF)= 30 cm3, hydrot a l c i t e - l i k e m a t e r i a l (H.?.-il-)= 1.0 g ( i n t e r l a y e r C1- anions= 3.3 mmol), and r e a c t i o n t e m p e r a t u r e = 3 4 3 K. I n t h e p r e s e n c e ( 0 ) o r absence ( 0 ) o f t h e h y d r o t a l c i t e - 1 ike m a t e r i a l .
368 Y. Ono. E. Suzuki and M. Okamoto
T a b l e 2. H a l i d e exchange between benzyl c h l o r i d e and v a r i o u s bromoal kanes.a Bromoalkaneb
Entry
1
Benzyl bromide y i e l d Reaction t i m e
CqHgBr C4HgBrC C3H7Br C HgBr Br(ZH2)qBr
2 3 4 5
4
20
51
53 90 58 63 66
-
53 60 65
/
h
/ %
Equ 1ib r iurn 54 90 60 64 66
~-
~
~
a S o l v e n t (DMF)= 30 cm3, H.T.-Cl-= 1.0 g, a n d r e a c t i o n temperature= 343 K. bBenzyl c h l o r i d e = bromoal kane= 33 mmol. CReaction c o n d i t i o n s as above e x e p t f o r CqHgBr= 195 mmol.
c a t a l y s t i n p l a c e o f a homogenenous c a t a l y s t of t r i - n - b u t y l a m i n e
o r NaBr [6,7].
A 90% y i e l d o f benzyl bromide was a t t a i n e d ( e n t r y 2 i n Table 2) when 195 mmol o f b u t y l bromide was used (C4HgBr/C6HtjCH2Cl m o l a r r a t i o = 6) and t h e r e a c t i o n was conducted f o r 20 h. Disproportionation
of t r i m e t h o x y s i l a n e
F i g u r e 3 shows t h e change i n t r i m e t h o x y s i l a n e c o n v e r s i o n w i t h r e a c t i o n t i m e f o r t h e r e a c t i o n s i n t h e presence o f t h e h y d r o t a l c i t e - l i k e i n t e r l a y e r C1- anions, unreacted (CH30)3SiH. a t 6 h.
Here,
material containing
t h e c o n v e r s i o n was c a l c u l a t e d f r o m t h e amount o f
The conversion i n c r e a s e d w i t h r e a c t i o n t i m e and was 70%
The s e l e c t i v i t y o f t h e r e a c t i o n i s d e f i n e d as f o l l o w s :
Se 1e c t i v i ty=
[amount of (CH30)4Si produced] [amount o f (CH30)3SiH consumed] x (3/4)
ioa
(3)
The s e l e c t i v i t y was loo%, i n d i c a t i n g t h a t o n l y t h e d i s p r o p o r t i o n a t i o n r e a c t i o n (eq. 2 ) proceeds. T a b l e 3 l i s t s t h e t r i m e t h o x y s i l a n e c o n v e r s i o n a t 6 and 9 h u s i n g hydrotalcite-like
m a t e r i a l s c o n t a i n i n g i n t e r l a y e r c1- and CH3O- anions.
and 2 i n Table 3, 79% a t 9 h.
Entries 1
show t h a t t h e c o n v e r s i o n i n c r e a s e d w i t h r e a c t i o n t i m e and was
The s e l e c t i v i t y , however, decreased,
o t h e r t h a n eq. 2 occur.
indicating that reactions
The u s e o f t w i c e t h e w e i g h t o f t h e m a t e r i a l ( e n t r y 3
i n Table 3) i n c r e a s e d t r i m e t h o x y s i l a n e c o n v e r s i o n t o 92%. w h i l e t h e s e l e c t i v i t y was 95%
D e v i a t i o n o f t h e s e l e c t i v i t y from 100% would be due to,
f o r example,
Catalysis by Hydrotalcite for Organic Reactions 369 I
0
1
I
I
I
I
I
1
I
I
I
I
2
3
4
5
6
Reaction time I h Fig. 3. Change i n trimethoxysilane conversion with reaction time. Reaction conditions: (CH30)3SiH= 41 mmol, hydrotalcite-like material (H.T.C1-)= 0.62 g (interlayer C1- anion= 2.0 mmol), and reaction temperature= 323 K.
Table 3.
Disproportionation o f trimethoxysilane.a
-
Entry
H'T'-X
Weight o f H.T.-X- / g
Reaction time / h
trimethoxysilane conversion / %
Selectivity o f reactionb / %
-~
1 2
3 4 5
H.T.-ClH.T.-ClH.T.-Cl-
H.T.-CH30H.T.-CH30-
0.62 0.62
1.2
0.62 0.62
6 9 6 6 9
70 79
92 a3 95
100
92 95
100 95
~
a(CH30)3SiH= 41 mmol and reaction temperature= 323 K. bOef ined by eq. 3.
polymerization o f (CH30)qSi into si loxanes by the action o f undetectable amount o f water. The hydrotalcite-l ike material containing interlayer CH3O- anions catalyzed the reaction (entries 4 and 5 in Table 3). the trimethoxysilane conversion being 8 3 and 95x with 100 and 95% selectivity, respectively. CONCLUSION The interlayer Cl- anions i n a synthetic hydrotalcite-1 ike material, Mg6A12(OH)16C1~4H20, react with butyl bromide or benzyl bromide in a non-polar solvent o f toluene. Almost all the chloride ions in the interlayer space
370 Y. Ono. E. Suzuki and
M.Okamoto
appear i n t h e l i q u i d phase as t h e corresponding o r g a n i c c h l o r i d e s . t h e r e a c t i o n g r e a t l y depends o n t h e k i n d o f o r g a n i c b r o m i d e .
The r a t e o f I n t e r l a y e r C1-
anions m i g r a t e t o t h e e x t e r n a l edge s u r f a c e s where t h e r e a c t i o n s proceed. The h y d r o t a l c i t e - l i k e m a t e r i a l c a t a l y z e s o r g a n i c r e a c t i o n s i n w h i c h t h e i n t e r l a y e r C1- a n i o n s p l a y t h e r o l e o f c a t a l y s t , halide-exchange
The m a t e r i a l c a t a l y z e d t h e
r e a c t i o n s between benzyl c h l o r i d e w i t h b u t y l bromide o r b u t y l
i o d i d e i n toluene.
The h y d r o t a l c i t e - l i k e
material also catalyzes a
d i s p r o p o r t i o n a t i o n o f t r i methoxys i1ane t o g i v e s i 1ane and t e t r a m e t h o x y s i1ane. The h y d r o t a l c i t e - l i k e m a t e r i a l was f o u n d t o be a p o t e n t i a l c a t a l y s t f o r o r g a n ic r e a c t i o n s .
REFERENCES
C. Frondel, Am. Miner., 26 (1941) 295: R. Allmann, Chimia, 24 (1970) 99. S. M i y a t a and T. Kumura, Chem. Lett., (1973) 843; S. M i y a t a , C l a y s C l a y Miner., 23 (1975) 369; S. Miyata, ibid., 28 (1980) 50. 305. 3 S. Miyata, Clays C l a y Miner., 31 4 K. J. M a r t i n and T. J. Pinnavaia, J. Am. Chem. SOC., 108 (1986) 541. 5 Eur. P a t e n t Appl., (1986) 201919. 6 W. E. W i l l y , D. R. McKean, a n d B. A. G a r c i a , B u l l . Chem. SOC. Jpn., 49 (1976) 1989. 7 Y. Sasson and M. Y.- Weiss, J. Mol. Catal., 10 (1981) 357. 1 2
(1985J
Catalysis by Hydrotalcite in Liquid-phase Organic Reactions
Y. Ono. E. S u z u k i , and M. Okamoto Department o f Chemical Engineerinng, Meguro-ku, Tokyo 152, Japan
Tokyo I n s t i t u t e o f Technology,
Ookayama,
ABSTRACT The i n t e r l a y e r C1- a n i o n s i n a s y n t h e t i c h y d r o t a l c i t e - l i k e m a t e r i a l , Mg A12(OH)16C1~4H20, were found t o r e a c t w i t h o r g a n i c bromides i n a non-polar so v e n t o f toluene, a l m o s t a l l c h l o r i d e i o n s i n t h e i n t e r l a y e r space appearing i n t h e l i q u i d phase as t h e corresponding o r g a n i c c h l o r i d e s . The h y d r o t a l c i t e l i k e m a t e r i a l was found t o c a t a l y z e o r g a n i c r e a c t i o n s i n w h i c h t h e i n t e r l a y e r C1- anions p l a y t h e r o l e o f c a t a l y s t . Thus, t h e m a t e r i a l c a t a l y z e d t h e h a l i d e exchange r e a c t i o n s between a1 k y l h a l i d e s i n t o l u e n e and t h e d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e t o g i v e s i l a n e and t e t r a m e t h o x y s i l a n e .
P
INTRODUCTION Hydrotalcite,
Mg6A12(oH)16c0~4H20. i s one o f t h e n a t u r a l l y o c c u r r i n g a n i o n i c
c l a y m i n e r a l s and can be s y n t h e s i z e d [1,2]. Mg6A12(OH)16C1~4H$,
A hydrotalcite-like material,
can a l s o be synthesized [2].
Here,
Mg*+ and A13+ c a t i o n s
c o n s t i t u t e p o s i t i v e l y charged h y d r o x i d e l a y e r s between which w a t e r molecules and C1- anions a r e i n t e r c a l a t e d ,
t h e l a t t e r b e i n g anion-exchangeable [3].
The e x c h a n b e a b l e a n i o n s a r e known t o r e a c t w i t h o r g a n i c h a l i d e s i n a nonp o l a r s o l v e n t such as toluene.
Thus,
b y the, a c t i o n o f i n t e r l a y e r I-anions i n
a h y d r o t a l c i t e - l i k e m a t e r i a l , Zn2Cr(OH)6I2-2H20, i n t o b u t y l i o d i d e [4].
b u t y l b r o m i d e was c o n v e r t e d
The f i r s t a i m o f t h i s work i s t o examine t h e r e a c t i o n s
o f i n t e r l a y e r C1- anions i n Mg6A12(OH)16C1~4H20 w i t h benzyl o r b u t y l bromide i n t o l u e n e t o expand t h e knowledge o f t h e r e a c t i v i t y o f t h e i n t e r l a y e r anions w i t h o r g a n i c h a l i d e s i n a non-polar solvent. The second a i m o f t h i s work i s t o demonstrate t h e c a t a l y s i s o f t h e i n t e r l a y e r a n i o n s i n o r g a n i c r e a c t i o n s such as h a l i d e - e x c h a n g e r e a c t i o n s b e t w e e n a l k y l h a l i d e s i n t o l u e n e (eq. 1).
364 Y. Ono, E. Suzuki and M. Okarnoto
Thus,
f o r example,
f o r a system o f benzyl chloride,
hydrotalcite-like material,
b u t y l b r o m i d e , and t h e
we expect t h e f o l l o w i n g r e a c t i o n s t o occur.
Butyl
b r o m i d e w o u l d u n d e r g o a h a l i d e s u b s t i t u t i o n b y t h e i n t e r l a y e r C1- a n i o n s , t h e i n t e r c a l a t e d B r - anions would,
l e a v i n g Br- anions i n t h e i n t e r l a y e r space;
i n t u r n , a t t a c k b e n z y l c h l o r i d e t o y i e l d b e n z y l b r o m i d e l e a v i n g C1- a n i o n s i n t h e i n t e r l a y e r space, t h e i n t e r l a y e r C1- anions b e i n g c y c l e d as f o l l o w s :
Here, H.T.-Cl-
and H.T.-Br-
d e n o t e h y d r o t a l c i t e - 1 i k e m a t e r i a l s c o n t a i n i n g C1-
and Br- i n t e r l a y e r anions,
respectively.
Since t h e h y d r o t a l c i t e - l i k e m a t e r i a l c o n t a i n s exchangeable i n t e r l a y e r anions, i t can be used as a c a t a l y s t f o r r e a c t i o n s f o r which anion-exchange
been used as c a t a l y s t . 4 (CH30)3SiH
__+
r e s i n s have
The d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e (eq. SiH4
2) i s
(2)
3 (CH30)4Si
t
c a t a l y z e d b y an anion-exchange r e s i n such as D i a i o n PA-306 [5].
The c a t a l y t i c
d i s p r o p o r t i o n a t i o n o f t r i m e t h o x y s i l a n e i n t h e p r e s e n c e o f a h y d r o t a l c i t e - 1 ike m a t e r i a l c o n t a i n i n g i n t e r l a y e r C1- o r CH3O- anions w i l l a l s o be demonstrated. EXPERIMENTAL Synthesis
of
hydrotalcite-like materials
The h y d r o t a l c i t e - 1 i k e m a t e r i a l , aqueous s o l u t i o n s o f MgC12.6H20, a t 433 K [ 2 ] .
MggA12(OH)16C12.4H20,
AlCly6H20,
and NaOH (Mg2+/A13+
CH30Na (CH30-/N03-
i n a methanol s o l u t i o n o f
m o l a r r a t i o = 10) a t 338 K f o r 43 h.
and
disproportionation reactions
For t h e halide-exchange condenser,
m o l a r r a t i o = 3)
The m a t e r i a l c o n t a i n i n g CH3O- a n i o n s was o b t a i n e d b y a n i o n -
e x c h a n g i n g NO3- a n i o n s o f Mg6A12(oH)16(N03)2'4H20
Halide-exchange
was synthesized f r o m
reactions,
i n t o a 50-cm3 f l a s k e q u i p p e d w i t h a
30 cm3 o f t o l u e n e o r DMF as a s o l v e n t and 1.0 g p o r t i o n o f t h e
h y d r o t a l c i t e - 1 i k e m a t e r i a l (3.3
mmol o f i n t e r l a y e r C1- anions) were introduced.
A 33 mmol o f benzyl c h l o r i d e was added t o t h e m i x t u r e and t h e t e m p e r a t u r e was k e p t a t 343 o r 373 K w i t h s t i r r i n g ,
f o l l o w e d b y t h e a d d i t i o n o f a g i v e n amount
o f an a l k y l bromide ( o r i o d i d e ) (33-195 mmol). a n i t r o g e n atmosphere.
Reactions were conducted under
The l i q u i d p h a s e was w i t h d r a w n p e r i o d i c a l l y a n d
a n a l y z e d b y a gas c h r o m a t o g r a p h e q u i p p e d w i t h a 2-m l o n g SE-30 c o l u m n and a
Catalysis by Hydrotalcite for Organic Reactions 365
f l a m e i o n i z a t i o n detector. F o r t h e d i s p r o p o r t i o n a t i o n r e a c t i o n s , t h e h y d r o t a l c i t e - l i k e m a t e r i a l s were evacuated a t 453 K f o r 2 h b e f o r e use t o d r i v e o u t i n t e r l a y e r w a t e r molecules. A 41 mmol o f t r i m e t h o x y s i l a n e was added i n t o t h e f l a s k c o n t a i n i n g 0.62 g o f t h e m a t e r i a l (2.0 mmol o f i n t e r l a y e r a n i o n s ) u n d e r a n i t r o g e n a t m o s p h e r e . r e a c t i o n m i x t u r e was
analyzed f o r
chromatograph d e s c r i b e d above,
(CH30)3SiH
and (CH30)4Si
The
b y t h e gas
u s i n g heptane as a standard.
RESULTS AND DISCUSSION Reaction
of
i n t e r l a y e r anions w i t h o r g a n i c h a l i d e s
To know t h e r e a c t i v i t y o f i n t e r l a y e r C1- anions towards o r g a n i c h a l i d e s i n a non-polar solvent, o f H.T.-Cl-
t h e f o l l o w i n g e x p e r i m e n t s were c a r r i e d out.
A 1.0 g p o r t i o n
(C1-= 3.3 mmol) was added t o a t o l u e n e s o l u t i o n o f b u t y l o r b e n z y l
bromide (33 mmol) a t 373 K:
t h e f o r m a t i o n o f t h e corresponding a l k y l c h l o r i d e s ,
g e n e r a t e d by t h e h a l i d e exchange b e t w e e n H.T.-Clf o l l o w e d w i t h time.
and t h e a l k y l b r o m i d e s , was
As shown i n Fig. 1, t h e y i e l d o f b u t y l c h l o r i d e i n c r e a s e d
w i t h t i m e and a t t a i n e d a c e i l i n g value.
The exchange was a l m o s t complete i n 1
h, a b o u t 90% o f t h e c h l o r i d e i o n s i n t h e i n t e r l a y e r s a p p e a r i n g i n t h e l i q u i d phase as b u t y l c h l o r i d e .
- 3 0
E E
80
60
%01 C
a
-c
h)
ul
40
$ 1
t
.oc a
20
&
)r
rd
0
0
20
40 60 t I min
80
Fig. 1. Change i n b u t y l ( o r b e n t y l ) c h l o r i d e y i e l d w i t h r e a c t i o n t i m e i n a h a l i d e exchange between b u t y l ( o r b e n z y l ) bromide and t h e h y d r o t a l c i t e - l i k e m a t e r i a l c o n t a i n i n g i n t e r l a y e r C1- anions. Reaction c o n d i t i o n s : CqHgBr ( o r C H CH2Br)= 33 mmol, s o l v e n t ( t o l u e n e ) = 30 cm3, h y d r o t a l c i t e - l i k e m a t e r i a l (H.T.-C(i-?= 1.0 g ( i n t e r l a y e r C1- anions= 3.3 m o l ) , and r e a c t i o n temperature= 373 K.
366 Y. Ono. E. Suzuki and M. Okamoto
Compared t o t h e h a l i d e exchange b e t w e e n H.T.-Clh a l i d e exchange b e t w e e n H.T.-Cl-
and b u t y l b r o m i d e , t h e
and b e n z y l b r o m i d e p r o c e e d e d much f a s t e r .
Thus, as shown a l s o i n Fig. 1, t h e h a l i d e exchange was a l m o s t complete w i t h i n 10 min. Because o f t h e s i z e o f t h e a l k y l h a l i d e s , t h e h a l i d e exchange p r o b a b l y o c c u r s a t t h e e x t e r n a l edge s u r f a c e s o f t h e h y d r o t a l c i t e - l i k e m a t e r i a l , n o t i n t h e i n t e r l a y e r space,
T h i s i s supported b y t h e f a c t t h a t no expansion o f t h e
i n t e r l a y e r space was observed a f t e r t h e m a t e r i a l was used i n t h e halide-exchange reaction.
The d i f f u s i o n o f t h e h a l i d e i o n s i n t h e i n t e r l a y e r space i s n o t t h e
r a t e - d e t e r m i n i n g step, s i n c e t h e r a t e o f t h e r e a c t i o n g r e a t l y depends on t h e k i n d o f a l k y l bromide. H a l i d e exchanqe between a l k y l h a l i d e s i n t o l u e n e C a t a l y s i s o f t h e i n t e r l a y e r a n i o n s i n t h e h a l i d e exchange b e t w e e n a l k y l h a l i d e s (eq.
A r e a c t i o n between benzyl c h l o r i d e (33 mmol) and
1) was examined.
b u t y l b r o m i d e ( 3 3 mmol) i n t o l u e n e a t 373 K was c a r r i e d o u t u s i n g a 1.0 g The r e a c t i o n p r o c e e d e d and, a s l i s t e d i n T a b l e 1, t h e
p o r t i o n o f H.T.-Cl-.
y i e l d o f b e n z y l b r o m i d e was 31% a t 4 h, i n c r e a s i n g t o 37% a f t e r 20 h.
The
r e a c t i o n d i d n o t proceed i n t h e absence o f t h e H.T.-Cl-. The H.T.-Cl-
can a l s o be a c a t a l y s t f o r a l k y l i o d i d e p r o d u c t i o n i n t o l u e n e .
Thus, b e n z y l i o d i d e c o u l d be o b t a i n e d b y t h e r e a c t i o n o f b e n z y l c h l o r i d e ( 3 3
mmol) w i t h b u t y l i o d i d e (33 mmol) a t 373 K (Table 1).
T a b l e 1. H a l i d e exchange b e t w e e n b e n z y l c h l o r i d e and b u t y l bromide ( o r iodide1.a ~~
Alkyl halideb
CqHgBr CqHgBr C4H9I C4H9I
~
Weight o f H.T.-ClC 4
Benzyl bromide ( o r iodide) y i e l d
/
Reaction t i m e 4
20
1.0
31
31
1.0
26
-
0 0
0
0
/
/ % h
0
0
aSolvent (toluene)= 30 cm3 and r e a c t i o n temp e r a t u r e 373 K. bBenzyl c h l o r i d e = b u t y l c h l o r i d e ( o r i o d i d e ) = 33 mmol. Cone g r a m o f H.T.-Clc o n t a i n s 3.3 mmol o f i n t e r l a y e r C1- anions.
Catalysis by Hydrotalcite for Organic Keactions 367
H a l i d e exchange u s i n g v a r i o u s bromoalkanes The h a l i d e exchange i n DMF b e t w e e n b e n z y l c h l o r i d e a n d b u t y l b r o m i d e g a v e F i g u r e 2 shows t h e t i m e
h i g h e r y i e l d o f benzyl bromide t h a n t h a t i n toluene.
course o f benzyl bromide y i e l d i n a r e a c t i o n between benzyl c h l o r i d e (33 mmol) and b u t y l b r o m i d e (33 mmol) i n DMF a t 343 K u s i n g a 1.0 g p o r t i o n o f H.T.-Cl-. The y i e l d i n c r e a s e d w i t h t i m e a n d was 51% a t 4 h. I n t h e h a l i d e exchange i n DMF,
t h e y i e l d was 53%
i n t h e a b s e n c e o f H.T.-Cl-,
I n a p r o l o n g e d r u n o f 20 h, t h e r e a c t i o n proceeded even
t h e y i e l d b e i n g 27% a t 4 h.
A l k y l b r o m i d e s can be o b t a i n e d f r o m t h e c o r r e s p o n d i n g c h l o r i d e s i n t h e presence o f NaBr o r t r i - n - b u t y l a m i n e ,
u s i n g bromoalkanes such as e t h y l bromide,
p r o p y l bromide,
as w e l l as b u t y l bromide as a b r o m i n a t i o n
a g e n t [6,7].
and 1,4-dibromobutane
These b r o m o a l kanes w e r e t e s t e d a s b r o m i n a t i o n a g e n t s t o w a r d s As l i s t e d i n T a b l e 2 ( e n t r i e s 1
b e n z y l c h l o r i d e i n t h e p r e s e n c e o f H.T.-Cl-. and 3-5),
t h e bromoalkanes gave benzyl bromide y i e l d s a t 4 h o f 51-652 under t h e
same r e a c t i o n c o n d i t i o n s as those i n Fig. 2.
Benzyl bromide y i e l d a t 20 h and
a t e q u i l i b r i u m a r e a l s o l i s t e d i n T a b l e 2.
It i s c l e a r t h a t t h e r e a c t i o n s
p r o c e e d c l o s e t o e q u i l i b r i u m e v e n a t t h e r e a c t i o n t i m e o f 4 h. T a b l e 2,
1,4-dibromobutane
i s t h e m o s t e f f i c i e n t b r o m i n a t i o n agent.
halide-exchange r e a c t i o n s proceed c l o s e t o e q u i l i b r i u m u s i n g H.T.-Cl-
60
I
As seen i n
50 -
as a s o l i d
I
I
I
The
o/o0 o 4 .
40
/
30
/*-
20
*/.-*-
10 0
I
0
1 2 3 Reaction time I h
I
4
Fig. 2. Change i n benzyl bromide y i e l d w i t h r e a c t i o n t i m e i n a h a l i d e exchange between benzyl c h l o r i d e and b u t y l bromide. Reaction conditions: CgH CH C1= CqHgBr= 33 mmol, s o l v e n t (DMF)= 30 cm3, hydrot a l c i t e - l i k e m a t e r i a l (H.?.-il-)= 1.0 g ( i n t e r l a y e r C1- anions= 3.3 mmol), and r e a c t i o n t e m p e r a t u r e = 3 4 3 K. I n t h e p r e s e n c e ( 0 ) o r absence ( 0 ) o f t h e h y d r o t a l c i t e - 1 ike m a t e r i a l .
368 Y. Ono. E. Suzuki and M. Okamoto
T a b l e 2. H a l i d e exchange between benzyl c h l o r i d e and v a r i o u s bromoal kanes.a Bromoalkaneb
Entry
1
Benzyl bromide y i e l d Reaction t i m e
CqHgBr C4HgBrC C3H7Br C HgBr Br(ZH2)qBr
2 3 4 5
4
20
51
53 90 58 63 66
-
53 60 65
/
h
/ %
Equ 1ib r iurn 54 90 60 64 66
~-
~
~
a S o l v e n t (DMF)= 30 cm3, H.T.-Cl-= 1.0 g, a n d r e a c t i o n temperature= 343 K. bBenzyl c h l o r i d e = bromoal kane= 33 mmol. CReaction c o n d i t i o n s as above e x e p t f o r CqHgBr= 195 mmol.
c a t a l y s t i n p l a c e o f a homogenenous c a t a l y s t of t r i - n - b u t y l a m i n e
o r NaBr [6,7].
A 90% y i e l d o f benzyl bromide was a t t a i n e d ( e n t r y 2 i n Table 2) when 195 mmol o f b u t y l bromide was used (C4HgBr/C6HtjCH2Cl m o l a r r a t i o = 6) and t h e r e a c t i o n was conducted f o r 20 h. Disproportionation
of t r i m e t h o x y s i l a n e
F i g u r e 3 shows t h e change i n t r i m e t h o x y s i l a n e c o n v e r s i o n w i t h r e a c t i o n t i m e f o r t h e r e a c t i o n s i n t h e presence o f t h e h y d r o t a l c i t e - l i k e i n t e r l a y e r C1- anions, unreacted (CH30)3SiH. a t 6 h.
Here,
material containing
t h e c o n v e r s i o n was c a l c u l a t e d f r o m t h e amount o f
The conversion i n c r e a s e d w i t h r e a c t i o n t i m e and was 70%
The s e l e c t i v i t y o f t h e r e a c t i o n i s d e f i n e d as f o l l o w s :
Se 1e c t i v i ty=
[amount of (CH30)4Si produced] [amount o f (CH30)3SiH consumed] x (3/4)
ioa
(3)
The s e l e c t i v i t y was loo%, i n d i c a t i n g t h a t o n l y t h e d i s p r o p o r t i o n a t i o n r e a c t i o n (eq. 2 ) proceeds. T a b l e 3 l i s t s t h e t r i m e t h o x y s i l a n e c o n v e r s i o n a t 6 and 9 h u s i n g hydrotalcite-like
m a t e r i a l s c o n t a i n i n g i n t e r l a y e r c1- and CH3O- anions.
and 2 i n Table 3, 79% a t 9 h.
Entries 1
show t h a t t h e c o n v e r s i o n i n c r e a s e d w i t h r e a c t i o n t i m e and was
The s e l e c t i v i t y , however, decreased,
o t h e r t h a n eq. 2 occur.
indicating that reactions
The u s e o f t w i c e t h e w e i g h t o f t h e m a t e r i a l ( e n t r y 3
i n Table 3) i n c r e a s e d t r i m e t h o x y s i l a n e c o n v e r s i o n t o 92%. w h i l e t h e s e l e c t i v i t y was 95%
D e v i a t i o n o f t h e s e l e c t i v i t y from 100% would be due to,
f o r example,
Catalysis by Hydrotalcite for Organic Reactions 369 I
0
1
I
I
I
I
I
1
I
I
I
I
2
3
4
5
6
Reaction time I h Fig. 3. Change i n trimethoxysilane conversion with reaction time. Reaction conditions: (CH30)3SiH= 41 mmol, hydrotalcite-like material (H.T.C1-)= 0.62 g (interlayer C1- anion= 2.0 mmol), and reaction temperature= 323 K.
Table 3.
Disproportionation o f trimethoxysilane.a
-
Entry
H'T'-X
Weight o f H.T.-X- / g
Reaction time / h
trimethoxysilane conversion / %
Selectivity o f reactionb / %
-~
1 2
3 4 5
H.T.-ClH.T.-ClH.T.-Cl-
H.T.-CH30H.T.-CH30-
0.62 0.62
1.2
0.62 0.62
6 9 6 6 9
70 79
92 a3 95
100
92 95
100 95
~
a(CH30)3SiH= 41 mmol and reaction temperature= 323 K. bOef ined by eq. 3.
polymerization o f (CH30)qSi into si loxanes by the action o f undetectable amount o f water. The hydrotalcite-l ike material containing interlayer CH3O- anions catalyzed the reaction (entries 4 and 5 in Table 3). the trimethoxysilane conversion being 8 3 and 95x with 100 and 95% selectivity, respectively. CONCLUSION The interlayer Cl- anions i n a synthetic hydrotalcite-1 ike material, Mg6A12(OH)16C1~4H20, react with butyl bromide or benzyl bromide in a non-polar solvent o f toluene. Almost all the chloride ions in the interlayer space
370 Y. Ono. E. Suzuki and
M.Okamoto
appear i n t h e l i q u i d phase as t h e corresponding o r g a n i c c h l o r i d e s . t h e r e a c t i o n g r e a t l y depends o n t h e k i n d o f o r g a n i c b r o m i d e .
The r a t e o f I n t e r l a y e r C1-
anions m i g r a t e t o t h e e x t e r n a l edge s u r f a c e s where t h e r e a c t i o n s proceed. The h y d r o t a l c i t e - l i k e m a t e r i a l c a t a l y z e s o r g a n i c r e a c t i o n s i n w h i c h t h e i n t e r l a y e r C1- a n i o n s p l a y t h e r o l e o f c a t a l y s t , halide-exchange
The m a t e r i a l c a t a l y z e d t h e
r e a c t i o n s between benzyl c h l o r i d e w i t h b u t y l bromide o r b u t y l
i o d i d e i n toluene.
The h y d r o t a l c i t e - l i k e
material also catalyzes a
d i s p r o p o r t i o n a t i o n o f t r i methoxys i1ane t o g i v e s i 1ane and t e t r a m e t h o x y s i1ane. The h y d r o t a l c i t e - l i k e m a t e r i a l was f o u n d t o be a p o t e n t i a l c a t a l y s t f o r o r g a n ic r e a c t i o n s .
REFERENCES
C. Frondel, Am. Miner., 26 (1941) 295: R. Allmann, Chimia, 24 (1970) 99. S. M i y a t a and T. Kumura, Chem. Lett., (1973) 843; S. M i y a t a , C l a y s C l a y Miner., 23 (1975) 369; S. Miyata, ibid., 28 (1980) 50. 305. 3 S. Miyata, Clays C l a y Miner., 31 4 K. J. M a r t i n and T. J. Pinnavaia, J. Am. Chem. SOC., 108 (1986) 541. 5 Eur. P a t e n t Appl., (1986) 201919. 6 W. E. W i l l y , D. R. McKean, a n d B. A. G a r c i a , B u l l . Chem. SOC. Jpn., 49 (1976) 1989. 7 Y. Sasson and M. Y.- Weiss, J. Mol. Catal., 10 (1981) 357. 1 2
(1985J