Solid State Chemistry of Energy Conversion and ... - ACS Publications

17 Chemical Conversion Using Sheet-Silicate Intercalates

Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

JOHN M . THOMAS, JOHN M. ADAMS, SAMUEL H . GRAHAM, and D. TILAK Β. TENNAKOON Edward Davies Chemical Laboratories, University College of Wales, Aberystwyth, SY23 1NE, U.K.

The use of layered silicates as matrices within and upon which novel chemical reactions may be carried out are summarized. The feasibility of controlled variation in the nature and siting of certain transition-metal and other cations, the magnitude of the interlamellar spacing, and ori entation as well as two-dimensional ordering of intercalated organic molecules is demonstrated. Specific examples of structures based on one-dimensional Fourier plots derived from x-ray and neutron diffraction data are cited, and one three-dimensional crystal structure for a rather special inter calate (dickite:formamide) is reported. The selective gener ation of a variety of aromatic products by thermostimulation is summarized, and the particular ability of copper mont morillonite to activate, preferentially, olefinic double bonds (in oligomerizations) is illustrated by reference to the ther mal reactivity of intercalated indene and trans-stilbene.

Because

of the mystery that still surrounds the phenomenon of catalysis,

i t is n o t y e t g e n e r a l l y p o s s i b l e t o d e s i g n , a b i n i t i o , n e w c h e m i c a l agents t h a t c a n serve as catalysts f o r t h e synthesis o f d e s i r e d s t r u c t u r a l l y or stereochemically

specified

products.

Some

progress

along

specific

d i r e c t i o n s has b e e n m a d e , h o w e v e r , a f a c t b o r n e o u t b o t h b y t h e success of Z e i g l e r - N a t t a catalysts a n d t h e existence o f a n e s t a b l i s h e d p r o c e d u r e f o r t h e " s o l i d - s t a t e " syntheses o f p o l y p e p t i d e s .

Catalyst design, however,

is s t i l l i n its i n f a n c y , n o t w i t h s t a n d i n g t h e significant advances t h a t h a v e b e e n m a d e r e c e n t l y u s i n g z e o l i t i c solids a n d t r a n s i t i o n - m e t a l c o m p l e x e s . 298

Goodenough and Whittingham; Solid State Chemistry of Energy Conversion and Storage Advances in Chemistry; American Chemical Society: Washington, DC, 1977.

17.

T H O M A S

E T

Sheet-Silicate

A L .

299

Intercalates

H e t e r o g e n e o u s catalysts cannot as y e t b e d e s i g n e d w i t h the same f a c i l i t y , precision, and variation n o w

a c h i e v a b l e w i t h the syntheses

classes of o r g a n i c m o l e c u l e s — f r o m o r g a n i c

fluorescers

of

many

and photochromic

m a t e r i a l s to s y n t h e t i c s t e r o i d s — o r w i t h the same success i n e n g i n e e r i n g super-ionic inorganic conductors,

s u c h as ^ a l u m i n a , o r

continuously

variable electronic band-gaps i n I I I - V ternary or quaternary semicon ductors. O n e p a r t i c u l a r l y p r o d u c t i v e r o u t e to t h e syntheses of n e w a n d i n t e r e s t i n g m o l e c u l a r catalysts relies o n the use of m e t a l v a p o r s w h i c h are u s u a l l y c o - c o n d e n s e d w i t h a h y d r o c a r b o n reactant. I n essence, t h i s a p Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

p r o a c h , w h o s e l i n e a g e m a y b e t r a c e d to P i m e n t e l ' s m a t r i x i s o l a t i o n t e c h n i q u e , c i r c u m v e n t s the necessity to p r o v i d e t h e r m a l a c t i v a t i o n d u r i n g r e a c t i o n — a s w o u l d b e r e q u i r e d b y processes i n v o l v i n g s o l i d m e t a l s — t h e r e b y r e n d e r i n g f e a s i b l e t h e f o r m a t i o n of a n u m b e r of n o v e l m o l e c u l a r species s u c h as d i b e n z e n e t i t a n i u m o r p o l y b u t a d i e n e , a n d vinylcyclohexenes.

cyclododecatrienes,

T h e m e t a l - v a p o r synthesis, w h i c h has b e e n

ploited by T i m m s ( I ) , Green (2), Skell (3)

ex

a n d others (4, 5 ) , y i e l d s

t h e d e s i r e d p r o d u c t u n d e r solvent-free c o n d i t i o n s . A n o t h e r successful r o u t e , also u t i l i z e d to a d v a n t a g e b y G r e e n , c a p i talizes u p o n the f a c t t h a t w h e n c e n t r a l m e t a l atoms are s i t u a t e d i n l i g a n d e n v i r o n m e n t s w h i c h m a k e the m e t a l atoms h i g h l y e l e c t r o n r i c h the r e s u l t i n g c o m p l e x e s , w h i c h n o w possess o r b i t a l s of s t r o n g m e t a l c h a r a c t e r a n d h i g h energy, are l i k e l y to b e r e a c t i v e t o w a r d r e l a t i v e l y i n e r t species s u c h as N , N 0 , a n d C H o r i n e r t b o n d s s u c h as C - H a n d C - C . 2

2

4

T h e route w h i c h w e ourselves h a v e chosen to i n v e s t i g a t e

(6-15)

entails t h e use of c e r t a i n sheet s i l i c a t e structures w i t h i n w h i c h i o n e x c h a n g e m a y first b e p e r f o r m e d .

T o date, as is d e s c r i b e d b e l o w ,

our

efforts h a v e b e e n c o n c e n t r a t e d p r i n c i p a l l y o n s t r u c t u r a l studies of

the

p a r e n t silicates a n d t h e i r d e l i b e r a t e l y m o d i f i e d d e r i v a t i v e s . I t is to

be

n o t e d t h a t : ( a ) w i d e v a r i a t i o n is p o s s i b l e i n r e g a r d to t h e n a t u r e of t h e p a r t i c u l a r cations t h a t c a n b e i n s e r t e d b e t w e e n t h e infinite, t w o - d i m e n sional anions; ( b )

t h e i n t e r l a y e r s p a c i n g , w h i c h o b v i o u s l y governs

the

ease of d i f f u s i o n of i n t e r c a l a t e d reactants a n d p r o d u c t s , is, to a d e g r e e , a d j u s t a b l e d e p e n d i n g , i n t e r a h a , u p o n factors s u c h as t h e h u m i d i t y a n d t h e n a t u r e of the o r g a n i c m o l e c u l e s present i n t h e s y s t e m ; a n d ( c )

in

c e r t a i n c i r c u m s t a n c e s , h i g h l y specific reactions a m o n g t h e i n t e r c a l a t e d species m a y b e s t i m u l a t e d , a n d the p r o d u c t s released, u n d e r solvent-free conditions.

I n one

sense a n e w

t y p e of

" h o m o g e n e o u s " catalysis is

involved, the phase i n question b e i n g the two-dimensional intercalate. M o r e o v e r , there is e v i d e n c e t h a t w i t h c e r t a i n types of silicates i t m a y b e p o s s i b l e to l a y o u t a n o r d e r e d t w o - d i m e n s i o n a l sheet of one

reactant

i n w h i c h t h e i n t e r m o l e c u l a r s p a c i n g p a r a l l e l to the sheets m a y also b e adjustable.


SOLID S T A T E


300

Q.____0-—o—--o—

OICKITE

CHEMISTRY

-o

KAO UNITE

Figure 1. Projections of the structures of the sheet silicates mentioned in the text: (a) montmorillonite, (b) vermiculite, (c) kaolinite, (d) dickite. ( ) octahedral cations, (®) tetrahedral cations, (O) oxygen, ( ® j hydroxyl, (©) water molecules. 9


17.

THOMAS

E T

Sheet-Silicate

AL.

Resume of Structural

301

Intercalates

Characteristics

of Sheet Silicates

I n p r e v i o u s p u b l i c a t i o n s ( 8 - 1 5 ) f r o m these laboratories the v a r i o u s r e l e v a n t attributes of the p a r t i c u l a r sheet silicates of interest i n the c o n text of i n t e r c a l a t i o n h a v e b e e n s u m m a r i z e d . salient features

W e must recall here

the

of m o n t m o r i l l o n i t e , v e r m i c u l i t e , k a o l i n i t e , a n d d i c k i t e

only (Figure 1).

I n the w e l l k n o w n t e t r a h e d r a l - o c t a h e d r a l - t e t r a h e d r a l

( T O T ) f r a m e w o r k c h a r a c t e r i s t i c of m o n t m o r i l l o n i t e , t h e layers [ i d e a l i z e d f o r m u l a A l 4 S i 0 o ( O H ) ] are n e g a t i v e l y c h a r g e d b e c a u s e of r e p l a c e m e n t 8

of A l

3 +

by A l . Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

3 +

4

2

i n o c t a h e d r a l sites b y F e * or M g 2

a n d of S i

2 +

4 +

i n t e t r a h e d r a l sites

T h e cation-exchange c a p a c i t y (c.e.c.) is g o v e r n e d b y t h e extent

of these r e p l a c e m e n t s , a n d the d i s t r i b u t i o n of c h a r g e i n t u r n d e p e n d s o n t h e l o c a t i o n of the r e p l a c e d ions. C l e a r l y m u c h v a r i a t i o n is p o s s i b l e here, so that i n h o m o g e n e i t i e s

of c h a r g e d i s t r i b u t i o n i n t w o d i m e n s i o n s ,

and

c o n s e q u e n t l y of s t a c k i n g i n three, m a y arise f r o m this a n d other sources. M o n t m o r i l l o n i t e is almost i n v a r i a b l y m i c r o c r y s t a l l i n e a n d possesses s u r face areas g e n e r a l l y w e l l i n excess of several h u n d r e d m g , a n d c.e.c. of 2

_ 1

0. 5-0.7 e p e r f o r m u l a u n i t . V e r m i c u l i t e m a y , for c o n v e n i e n c e , be r e g a r d e d as a sheet s i l i c a t e i n w h i c h w a t e r has b e e n i n t e r c a l a t e d i n a m o r e or less o r d e r e d f a s h i o n . T h e s e s a n d w i c h e d w a t e r molecules m a y b e p r o g r e s s i v e l y d r i v e n out w i t h heat treatment. I n k a o l i n i t e [ i d e a l i z e d f o r m u l a A l S i O i o ( O H ) ] the T O 4

w h i c h extends

8

4

t w o - d i m e n s i o n a l l y is w e a k l y i n t e r c o n n e c t e d

direction v i a A l - O H . . . O - S i hydrogen bonds.

framework in a third

Dickite, a two-layer

m o n o c l i n i c m o d i f i c a t i o n of k a o l i n i t e , is also s h o w n i n p r o j e c t i o n i n F i g u r e 1. W e h a v e f o u n d that this p a r t i c u l a r s i l i c a t e forms a t h r e e - d i m e n s i o n a l l y o r d e r e d i n t e r c a l a t e ( 1 6 ) , w h i c h is discussed b r i e f l y b e l o w .

Formation

and Structural

Aspects of Sheet Silicate

Intercalates

A vast a m o u n t of w o r k ( a d m i r a b l y s u m m a r i z e d b y B r i n d l e y u p to 1970 a n d b y T h e n g (18)

o n the c o n d i t i o n s u n d e r w h i c h a w i d e range of o r g a n i c m o l e c u l e s b e a s s i m i l a t e d b y v a r i o u s sheet silicates. systems

r e l e v a n t to

assessment.

M a n y of

(17)

u p to 1974) has a l r e a d y b e e n p u b l i s h e d may

H e r e w e refer to o n l y those

the u l t i m a t e q u e s t i o n the o r g a n i c molecules

of

r e a c t i v i t y or s t r u c t u r a l or exchangeable

cations

chosen b y us for i n i t i a l s t u d y w e r e so selected b e c a u s e i t was felt that t h e y w o u l d f a c i l i t a t e the i n t e r p r e t a t i o n of x-ray a n d n e u t r o n d i f f r a c t i o n studies. T h u s w e see f r o m F i g u r e 2, w h i c h i n t u r n has b e e n d e r i v e d f r o m n e u t r o n d i f f r a c t i o n studies, p r e c i s e l y w h e r e a l o n g the z-axis lar to t h e b a s a l p l a n e ) the N i

2 +

(perpendicu

i o n resides i n a v e r m i c u l i t e , the cations of

w h i c h h a d b e e n e x c h a n g e d for N i . 2 +

L i k e w i s e , F i g u r e 3 shows h o w r e

p l a c i n g N a w i t h S r , w h i c h has a p p r o x i m a t e l y t w i c e its c h a r g e d e n s i t y , +

2 +


302

S O L I D

S T A T E

C H E M I S T R Y

as t h e i n t e r l a m e l l a r c a t i o n s i g n i f i c a n t l y modifies t h e o r i e n t a t i o n of t e t r a h y d r o p y r a n . T h e o x y g e n - r i n g a t o m lies closest to the s i l i c a t e l a y e r w h e n t h e c a t i o n is N a , a n d a c a r b o n - r i n g a t o m lies closest w h e n the c a t i o n +

is

ST *. 2

I t is e v i d e n t that w i t h t h e m o n t m o r i l l o n i t e s b o t h n e u t r a l a n d c h a r g e d o r g a n i c species m a y b e a s s i m i l a t e d i n t o the i n t e r l a m e l l a r spaces.

Neutral

species m a y b e i n t r o d u c e d e i t h e r f r o m s o l u t i o n o r f r o m t h e v a p o r , the l a t t e r a p p r o a c h b e i n g advantageous

i f traces of i n t e r c a l a t e d solvent,

n o t a b l y w a t e r , are to b e a v o i d e d . T h o u g h t h e r e is a p a u c i t y of t h e r e l e v a n t t h e r m o d y n a m i c i n f o r m a t i o n , i t is c l e a r that t h e b i n d i n g energies of Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

these i n t e r c a l a t e d species m a y v a r y w i d e l y . I t seems p o s s i b l e f o r o r g a n i c m o l e c u l e s to b e a t t a c h e d b o t h d i r e c t l y to a n associated c a t i o n — v i a σ- o r

14 -

Mg-

12 -

0 H Si

11 -

0

13 -

10 3 Ζ M

M

»

ϋ

i

OH 8 7 -

Ni

6 β 4 3 -

01

2 -

M

O

1 0 -

NUCLEAR SCATTERING DENSITY (ARB* SCALD Figure 2.

One-dimensional

Fourier map of nuclear scattering Ni *-vermiculite

density for

2



17.

THOMAS

Sheet-Silicate

ET AL.

Να*

Figure 3.

Electron

303

Intercalates

exchanged

clay

Sr2* exchanged

clay

density projections of Ν a*- and nite-tetrahydropyran intercalates

S^-montmoriUo-

π-bonding, the r e l a t i v e p r o p o r t i o n of w h i c h is e x p e c t e d , o n t h e basis of t h e p r i n c i p l e s of g e n e r a l o r g a n o m e t a l l i c c h e m i s t r y , to v a r y as a f u n c t i o n of t e m p e r a t u r e a n d c h e m i c a l e n v i r o n m e n t — o r loosely as i n a s e c o n d a r y " s o l v a t i o n ' shell or physically adsorbed

state.

Some

organic

entities

( s u c h as a m i n e s ) w h i c h are c a p a b l e of f o r m i n g cations m a y d i s p l a c e t h e i n t e r l a m e l l a r cations o r i g i n a l l y present i n t h e sheet s i l i c a t e . O t h e r s s h o w a greater p r o p e n s i t y to b e a d s o r b e d at t h e e x t e r n a l r a t h e r t h a n t h e i n t e r l a m e l l a r surfaces of t h e sorbent.

Another relevant phenomenon

is the

s e q u e n t i a l s e l f - c o n v e r s i o n t h a t c e r t a i n o r g a n i c intercalates of m o n t m o r i l lonite undergo.

T h e p y r i d i n e i n t e r c a l a t e of N a - e x c h a n g e d m o n t m o r i l l o +

n i t e is g r a d u a l l y c o n v e r t e d at r o o m t e m p e r a t u r e f r o m a l a r g e r to a s m a l l e r i n t e r l a m e l l a r s p a c i n g (23.3 A to 14.8 A ) : -py M(py)

4

• 2H 0

> M(py)

2

2

•4H 0 2

+H 0 2

where

M =

2[(Al3.5Mgo.5)Si 0 o(OH) Nao.5]; 8

2

4

and

the

y-butyrolac-


304

SOLID S T A T E

CHEMISTRY

t o n e / S r - e x c h a n g e d montmorillonite shows a double conversion i n w h i c h 2+

t h e i n t e r l a m e l l a r s p a c i n g changes f r o m 23.1 A w h e n t h e i n t e r c a l a t e is first f o r m e d to 18.3A a n d t h e n to the stable 13.2-A i n t e r c a l a t e . T h e 1 D F o u r i e r m a p s ( F i g u r e 4 ) of these three f o r m s of the

butyrolactone-Sr * 2

c o m p l e x e s , i m p l y t h a t t h e s e q u e n t i a l changes i n v o l v e a c o n v e r s i o n of t h e parent

i n t e r c a l a t e , w h i c h appears

organic

to i n c o r p o r a t e

species b e t w e e n c o n t i g u o u s

two-layer form and,

finally,

t h r e e layers of

m o n t m o r i l l o n i t e sheets,

the

first

to

a

to the m o r e stable, s i n g l e - l a y e r i n t e r c a l a t e .

( F o r f u r t h e r details o n these systems see R e f .

16).

M o r e w o r k m u s t b e d o n e o n the s t r u c t u r a l aspects of these v a r i o u s


types of intercalates of m o n t m o r i l l o n i t e , b u t progress is severely

ham

p e r e d b o t h b y t h e u n a v a i l a b i l i t y of this m i n e r a l i n other t h a n m i c r o c r y s t a l l i n e forms a n d b y t h e fact that the intercalates of m o n t m o r i l l o n i t e d o not seem to t a k e u p t h r e e - d i m e n s i o n a l l y o r d e r e d structures, a s i t u a t i o n w h i c h p e r h a p s is n o t u n e x p e c t e d charge

i n v i e w of the i r r e g u l a r i t i e s of

d i s t r i b u t i o n a n d s t a c k i n g sequences i n t h e c*

parent mineral (20).

the

d i r e c t i o n of

the

X - r a y d i f f r a c t i o n is n o t l i k e l y to r e v e a l t h e neces

sary, d e s i r e d i n f o r m a t i o n . H o w e v e r , c o m b i n a t i o n w i t h n e u t r o n - d i f f r a c t i o n d a t a o n w e l l o r i e n t e d samples of the intercalates leads to a greater u n d e r s t a n d i n g of the d e l i c a t e v a r i a t i o n s i n s t r u c t u r e t h a t are d i s p l a y e d b y , f o r example,

the

transition-metal exchanged

montmorillonites.

Figure

w h i c h shows F o u r i e r maps d e r i v e d f r o m neutron-diffraction data c l e a r l y i n d i c a t e s that w h e r e a s the N i calate

of

Ni -exchanged 2 +

2 +

i o n i n the t e t r a h y d r o f u r a n i n t e r

montmorillonite,

( Al . Mgo.5)Si 0 o(OH) 3

N i o . 2 5 ( C H 0 ) 2 . 3 , is s i t u a t e d c e n t r o - s y m m e t r i c a l l y 4

5,

(21),

8

5

8

2

4

i n the interlamellar

r e g i o n , the C o - i o n i n a closely s i m i l a r i n t e r c a l a t e , ( A l . 5 M g . 5 ) S i 0 o 2 +

3

8

0

2

( O H ) C o o . 2 5 ( C H 0 ) 2 . 2 , is off-center . 4

4

8

K a o l i n i t e a n d d i c k i t e also f o r m intercalates w h i c h , i n g e n e r a l ,

do

n o t a p p e a r to b e t h r e e - d i m e n s i o n a l l y o r d e r e d ( 2 2 ) .

H o w e v e r , one such

ordered

(16):

complex

intercalate of

dickite

has and

been

discovered

formamide,

recently

4

4

0

p r o j e c t i o n of its s t r u c t u r e is s h o w n i n F i g u r e 6.

8

a

1:1

dimensionally and three-dimensionally ordered

2

Rather remarkably no

t w o - d i m e n s i o n a l s u p e r l a t t i c e exists i n this structure. (23)

i t is

Al Si Oi (OH) (HCONH )2. A Contrast the

intercalates of

a n d the t r a n s i t i o n - m e t a l c h a l c o g e n i d e s (24,25,26).

two-

graphite

T h i s f a c t arises

p r o b a b l y b e c a u s e f o r m a m i d e , b e i n g s u c h a s m a l l m o l e c u l e , m a y fit s n u g l y w i t h i n t h e u n i t m e s h p a r a l l e l to (001)

of t h e d i c k i t e s t r u c t u r e . O f great

interest h e r e is t h e o c c u r r e n c e of r e l a t i v e l y

rigidly

clamped intercalated

species. I t is k n o w n f r o m W e i s s ' w o r k ( 2 2 ) that the rates of i n t e r c a l a t i o n of k a o l i n i t e s are r e l a t i v e l y s l u g g i s h a n d that at r o o m t e m p e r a t u r e

both

f o r m a m i d e a n d u r e a , after a n i n d u c t i o n p e r i o d of s o m e one or t w o days, are e a c h g r a d u a l l y i n c o r p o r a t e d i n t o the h o s t m a t r i x , t h e final p a r t of t h e f o r m a t i o n c u r v e b e i n g r e a c h e d a s y m p t o t i c a l l y after a n i n t e r v e n i n g



Figure 4.

Electron

density projections for the three distinct "phases" of the S^-montmoriUonite-y-butyrolactone (1.6, 3.2, and 4.8 y-butyrolactone/formula unit)


intercalate

g ox


Figure

5.

Projections

2

of nuclear scattering density for (a) Ni +-montmoriUonite-tetrahydrofuran (b) Co?*-montmoriUonite-tetrahydrofuran (2.2 THF/formula unit)


(2.3 THF/formula

unit)

and

Sheet-Silicate

THOMAS E T A L .

307

Intercalates


17.

Figure

6a.

Projection

of the

structure of the along the a axis

dickite-formamide

intercalate

l i n e a r rate of u p t a k e . C l e a r l y i t w o u l d b e of interest, i n the context of catalysis, to i n t r o d u c e a s e c o n d reactant i n t o the system w h e n t h e first t w o - d i m e n s i o n a l l y o r d e r e d reactant ( i n this case f o r m a m i d e ) t i a l l y completes

t h e sites a v a i l a b l e f o r its o c c u p a t i o n .

only par

Co-adsorption

studies h a v e b e e n w e l l c h a r a c t e r i z e d w i t h m o n t m o r i l l o n i t e , a n d L a i l a c h a n d B r i n d l e y (27)

f o u n d t h a t t h y m i n e , w h i c h is n o t o n its o w n i n c o r p o

r a t e d i n t o m o n t m o r i l l o n i t e f r o m aqueous s o l u t i o n , is r e a d i l y t a k e n u p i n t h e presence of a d e n i n e or h y p o x a n t h i n e , e a c h of w h i c h is also a d s o r b e d



308

S O L I D

S T A T E

C H E M I S T R Y

y — Figure 6b. Projection of the A10 octahedra of the dickite-formamide intercalate onto the ab plane. The hydrogen bonding of the formamide molecules is also shown. 6

i n i s o l a t i o n . I t is b e l i e v e d ( 1 7 ) t h a t a d e n i n e a n d t h y m i n e f o r m t h e w e l l k n o w n p u r i n e - p y r i m i d i n e base-pairs i n t h e i n t e r l a m e l l a r r e g i o n . E x t e n s i v e c o m p i l a t i o n s of s i m p l e c r y s t a l l o g r a p h i c i n f o r m a t i o n r e l a t i n g to t h e n u m e r o u s types of o r g a n i c m o l e c u l e s that m a y b e i n t e r c a l a t e d b y sheet silicate m i n e r a l s a r e g i v e n i n t h e r e c e n t m o n o g r a p h b y T h e n g (18),

w h o also r e v i e w s t h e w o r k of m a n y of t h e e a r l i e r

(MacEwan,

W a l k e r , H o f m a n n , Bodenheimer, Brindley, a n d W e i s s ) a n d more recent investigators

(Mortland, Matsunaga, Blumstein, Fripiat, Farmer, a n d

o t h e r s ) . T a b l e I s u m m a r i z e s a f e w facts r e l a t i n g to some of t h e s i m p l e s t r u c t u r a l characteristics of t h e intercalates d i s c u s s e d i n this section a n d studied b y us. Some Specific Chemical

Conversions

I d e a l l y o n e w o u l d w i s h to h a v e a v a i l a b l e i n f o r m a t i o n w h i c h relates the r e a c t i v i t y a n d associated stereo- o r regio-specificity o f t h e r m a l l y i n d u c e d reactions of v a r i o u s o r g a n i c intercalates of t h e sheet silicates o n t h e o n e h a n d w i t h t h e s t o i c h i o m e t r y a n d d e t a i l e d s t r u c t u r a l properties of t h e s t a r t i n g m a t e r i a l o n t h e other. U n f o r t u n a t e l y , s u c h i n f o r m a t i o n i s , at present, almost t o t a l l y u n a v a i l a b l e . W h e r e t h e r e a c t i o n is efficient, interesting, or well-identified, the accompanying structural information


17.

THOMAS

E T

AL.

Sheet-Silicate

Intercalates

309

has t u r n e d out to b e s i m p l y inaccessible b e c a u s e of the l a c k of c r y s t a l l i n e order, w h i c h i n t u r n y i e l d s t h e necessary w e l l - d e f i n e d x - r a y d a t a f r o m w h i c h the o n e - d i m e n s i o n a l F o u r i e r plots are extracted. those intercalates w h e r e i t has b e e n p o s s i b l e n e u t r o n - d i f f r a c t i o n d a t a to y i e l d more-or-less

Conversely,

for

to process t h e x - r a y

or

accurate s t r u c t u r a l i n f o r

m a t i o n , the degree of r e a c t i v i t y or n o v e l t y of t h e r e a c t i o n is itself l o w . O n e p a r t i c u l a r l y efficient r e a c t i o n is t h e t h e r m a l l y i n d u c e d c o n v e r s i o n to a n i l i n e of the i n t e r c a l a t e ( 1 4 . 5 À s p a c i n g ) c o n s i s t i n g of

diproto-

n a t e d , 4,4'-diamino-frans-stilbene a n d m o n t m o r i l l o n i t e ( a p p r o x i m a t e s t o i chiometry :

(Ala.sMgo.s) S i O ( O H ) ( H N C H C H = C H C N 4 N H 3 )0.25. 8

2 0

4

3

6

4

e


T h i s r e a c t i o n , w h i c h p r o c e e d s r a p i d l y at ca. 2 7 0 ° C , y i e l d s a n i l i n e ( c l o s e to 4 5 %

of t h e p a r e n t d i a m i n e )

as the sole gaseous p r o d u c t .

Another

efficient r e a c t i o n that o c c u r s o n the surfaces of m o n t m o r i l l o n i t e is the almost q u a n t i t a t i v e c o n v e r s i o n i n the t e m p e r a t u r e range 4 0 ° - 1 5 0 ° C of t r i p h e n y l a m i n e to

N,N,N',jV'-tetraphenylbenzidine, when

the

complex

f o r m e d b y the exposure of N a - m o n t m o r i l l o n i t e to a l c o h o l i c solutions of +

t r i p h e n y l a m i n e is h e a t e d . It seems v e r y l i k e l y that r a d i c a l cations ( w h i c h c e r t a i n l y f o r m w i t h ease at L e w i s a c i d sites i n t h e silicate w h e n b e n z i d i n e a n d other s i m i l a r m o l e c u l e s are e x p o s e d to m o n t m o r i l l o n i t e

the

(see

M o s s b a u e r a n d s p e c t r o s c o p i c studies of T r i c k e r et a l . (8, 13, 2 8 ) ) first f o r m e d a n d that these p r o c e e d a l o n g either of t w o p o s s i b l e ways:

(a)

dimerization followed

by deprotonation

a n d the

are path

benzidine

rearrangement

2 ( P h N ) -> ( P h N N P h ) 3

or ( b )

+

3

3

2 +

a d i r e c t c o u p l i n g b e t w e e n p a r a positions of the b e n z e n e rings of

t h e t w o t r i p h e n y l a m i n e r a d i c a l cations, a g a i n f o l l o w e d b y t h e e l i m i n a t i o n of t w o protons.

I t m u s t be n o t e d that t h e i n t e r a c t i o n of m o n t m o r i l l o n i t e

a n d t r i p h e n y l a m i n e m a y b e r e s t r i c t e d solely to the exterior surface of the c l a y m i n e r a l : the i n t e r l a y e r s p a c i n g ( a d m i t t e d l y a c r u d e c r i t e r i o n f o r t h e o c c u r r e n c e of i n t e r c a l a t i o n ) r e m a i n s essentially u n c h a n g e d p r i o r to a n d f o l l o w i n g u p t a k e of the t e r t i a r y a m i n e . W h e n d i p h e n y l e t h y l e n e is h e a t e d to reflux for 30 m i n i n c o n t a c t w i t h Cu(II)-exchanged

m o n t m o r i l l o n i t e , t h e i n d a n d i m e r ( s p e c i f i c a l l y 1-meth-

y l - l , 3 , 3 - t r i p h e n y l - i n d a n ) is r e a d i l y o b t a i n e d i n g o o d ( 3 0 % ) y i e l d .

The

p r o d u c t crystallizes out as s m a l l p r i s m s , m.p. 1 4 2 ° C ( h t . 1 4 2 - 1 4 3 ) f r o m acetic a c i d ( 1 2 ) .

T h i s n e w p r o c e d u r e seems to p r o v i d e t h e m o s t c o n

v e n i e n t p r e p a r a t i o n of this d i m e r .


310

S O L I D

Table I.

S T A T E

A Summary of the Crystallographic

C H E M I S T R Y

Information


System* 1. 2. 3. 4. 5. 6. 7. 8.

β

mont =

N a - m o n t (dried) N a - m o n t (hydrated) C u - m o n t (hydrated) A g - m o n t (hydrated) S r - m o n t (hydrated) N i - m o n t (hydrated) C o - m o n t (hydrated) Sr^-mont-y-butyrolactone +

+

2 +

+

2 +

2 +

2 +

9. 10. 11. 12. 13.

Na Sr Ni Co Na

14. 15. 16. 17. 18.

Ag -moni>-azobenzene Cu -mont>-azobenzene Ni -vermiculite Co -vermiculite Dickite-formamide

+

-montr-tetrahydropyran -mont-tetrahydropyran -mont-tetrahydrof uran -monk-tetrahydrofuran -mont>-py r idine

2 +

2 +

2 + +

+

2+

2 +

2 +

montmorillonite.

I t has r e c e n t l y b e e n e s t a b l i s h e d t h a t t r a n s i t i o n - m e t a l - e x c h a n g e d s a m ples of m o n t m o r i l l o n i t e r e a d i l y f o r m complexes

w i t h a w i d e range

of

a r o m a t i c h y d r o c a r b o n s a n d t h e i r s i m p l e d e r i v a t i v e s s u c h as c h l o r o b e n zene, anisole, a n d azobenzene.

I t seems t h a t m e t a l - a r e n e complexes

b e s t a b i l i z e d i n s i d e , or at the surfaces of, m o n t m o r i l l o n i t e .

may

T h e r e is

c l e a r l y a vast t e r r i t o r y of s y n t h e t i c o r g a n i c c h e m i s t r y h e r e w h i c h a w a i t s exploration.

A f e w investigations h a v e a l r e a d y b e e n i n i t i a t e d i n these

l a b o r a t o r i e s , a n d w e n o w present a b r i e f a c c o u n t of t h e b e h a v i o r dehydrated

C u - m o n t m o r i l l o n i t e (hereafter 2 +

designated

Cu-M)

of

com

plexes f o l l o w i n g exposure to a n u m b e r of selected a r o m a t i c h y d r o c a r b o n s . Spectroscopic

a n d o t h e r studies (28-^33) i n d i c a t e t h a t C u - M m a y

b i n d a r o m a t i c m o l e c u l e s , s u c h as b e n z e n e , toluene, x y l e n e , etc., i n three d i s t i n c t f o r m s : t h e s i m p l e , loosely b o u n d

(physically adsorbed)

state;

t h e m o r e s t r o n g l y a t t a c h e d state i n w h i c h t h e b o n d - s t r e n g t h s w i t h i n the a r e n e l i g a n d are s l i g h t l y p e r t u r b e d ( t h e s o - c a l l e d t y p e I complexes t h e classification of P i r m a v a i a a n d M o r t l a n d (31));

in

a n d the t y p e - I I c o m

plexes w h i c h are u s u a l l y c o l o r e d differently f r o m t h e t y p e I

complexes,

w h e r e the a r o m a t i c i t y a n d p o i n t s y m m e t r y of t h e arene is d e s t r o y e d .


It

17.

THOMAS

Sheet-Silicate

E T A L .

Relating to the Intercalates


Approx.

6

Discussed i n the T e x t

Formula*

Na .5

M M M M M M M

Na · 3.5H 0 Cu · 3.5H 0 Ago Β · 3 . 5 H 0 Sro 25 · 7 . 0 H O Ni · 7.0H O Coo 25 · 7 . 0 H O Sro. 5 · ( C H e O ) i . e

M M Μ

Sro.25 · ( C H 0 ) 3 . 2 Sro.25 · ( C H e 0 ) 4 . 8 Ν8Ο. (ΟΒΗΙ 0)Ι.,

M M M M M M M V V Al

Sr .2e(C H 0)i.o Ni . (C H O) . C0 .25(C H 0) .2 Na .5(C5H N) .o(H 0) .o Na .5(C H5N) .o(H 0)2.o Ago. (Ci H N )o.9 Cu . 5(Ci H N )o. Nio.75 COo.75 Si O (OH) · (HCONH )

2

0 2 5

2

2

2

0

2

5

2

2

2

4

a

4

e

2

4

2

β

0

0

e

0

2 5

1 0

4

0

8

4

0

5

4

2

5

0

2

1 0

3

2

5

0

4

2

8

2

1

2

1 0

2

1

2

2

1 0

2

8

8

2

3 6 6 6 5 5 5 13 14 18 13 13 12 12 16 13 6 11 12 12 22

9.6 12.4 12.5 12.5 15.2 15.1 15.2 13.2 18.3 23.1 14.99 14.81 14.50 14.58 23.3 14.8 22.3 20.5 14.4 14.4 20.19

0

5

No. of Orders of Diffraction Observed

Basal Spacing (A)

M

0

311

Intercalates

2

M = (Al .5Mgo.5)Si802o(OH) ; V = Mg (Ali. Sie. )02o(OH)4. 3

4

is t h o u g h t t h a t i n t y p e I c o m p l e x e s

e

5

5

t h e a r e n e is edge-rr-bonded t o t h e

c o p p e r , r a t h e r s i m i l a r to t h e b o n d i n g t h a t exists i n C H C u A l C l 4 e

T u r n e r a n d A m m a (34)). (12,28)

M o r t l a n d (32),

R u p e r t (33),

(see

e

and Tennakoon

h a v e s h o w n t h a t o n l y t h e s y m m e t r i c a l arenes s u c h as b e n z e n e ,

b i p h e n y l , naphthalene, a n d anthracene

form

type-II

C u - M ; a n i s o l e is a p p a r e n t l y a n e x c e p t i o n (32). f o r m e d b y b e n z e n e a n d a l l t h e a l k y l benzenes

complexes

a n d s y m m e t r i c a l arenes

s t u d i e d to date, a n d d e h y d r a t i o n of t h e C u - M complexes m e t r i c a l arenes

with

T y p e - I complexes are

u s u a l l y results i n t h e ( r e v e r s i b l e )

of the s y m

conversion

of the

t y p e - I t o t h e t y p e - I I state. L i g a n d s i n t y p e - I complexes a p p e a r to r e t a i n their aromaticity; a n d spectroscopic

e v i d e n c e also suggests t h a t i n b o t h

t y p e - I a n d t y p e - I I c o m p l e x e s t h e o r g a n i c moieties f o r m r a d i c a l cations. T y p e - I I species c a n also b e f o r m e d w i t h F e

3 +

and V 0

2 +

ions, a n d i t h a s

b e e n suggested that these species a r e p a i r s o f associated r a d i c a l cations r a t h e r t h a n i n t e r c a l a t e d o r g a n o m e t a l l i c species

(35).

T h e t h e r m a l r e a c t i v i t y of these complexes reveals i n t e r e s t i n g t r e n d s . T h u s t h e r o o m - t e m p e r a t u r e stable, t y p e - I I C u - M : b e n z e n e c o m p l e x

(this

c o m p l e x is stable i n a v a c u u m of c a . 1 0 " t o r r a t r o o m t e m p e r a t u r e )

will,

7


312

S O L I D

S T A T E

C H E M I S T R Y

o n h e a t i n g , b r e a k d o w n to y i e l d n u m e r o u s fragments a l l possessing m o l e c u l a r masses less t h a n t h a t of t h e b e n z e n e .

T y p e - I C u - M complexes

w i t h t o l u e n e a n d w i t h t h e v a r i o u s i s o m e r i c xylenes w i l l , u p o n g e n t l e heating, y i e l d volatile products w h i c h show that condensation, h y d r o g e n e l i m i n a t i o n , of t h e arenes has o c c u r r e d . (m/e)

T h u s mass

with peaks

of 272 a n d 182, c o r r e s p o n d i n g to t h r e e t o l u e n e u n i t s m i n u s f o u r

h y d r o g e n atoms a n d t w o toluenes m i n u s t w o h y d r o g e n atoms, respec t i v e l y , are o b s e r v e d .

T h e m a s s - s p e c t r o m e t r i c f r a g m e n t a t i o n patterns of

t h e v o l a t i l e p r o d u c t s are consonant w i t h t h e o c c u r r e n c e of t h e f o u r p r o d u c t s s h o w n i n F i g u r e 7. ( T h e i d e n t i t y of these p r o d u c t s has not, h o w e v e r , Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

b e e n i n d e p e n d e n t l y c o n f i r m e d ) . A l l t h e e v i d e n c e p o i n t s to t h e f a c t t h a t t y p e - I arene c o m p l e x e s of C u - M r e a d i l y y i e l d r a d i c a l s o r r a d i c a l ions w h e n h e a t e d , w h i c h accounts f o r t h e n a t u r e of the r e a c t i o n p r o d u c t s . W h e n t h e a r o m a t i c m o l e c u l e f o r m i n g the c o m p l e x also c o n t a i n s a n e t h y l e n i c l i n k a g e , f u n d a m e n t a l differences t h e n arise i n t h e p a t t e r n o f t h e r m a l r e a c t i v i t y . I n short b o t h frarw-stilbene a n d i n d e n e ( e a c h i n t r o d u c e d separately f r o m t h e v a p o r i n t o t h e d e h y d r a t e d C u - M ) y i e l d o l i g o m e r i c p r o d u c t s i n w h i c h n o loss of h y d r o g e n atoms has o c c u r r e d .

There

appears to b e p r e f e r e n t i a l b o n d i n g to o r a c t i v a t i o n of t h e e t h y l e n i c l i n k ,

(1)

(2)

(3)

(4)

Figure 7. Polymeric material produced upon heating the Cu *-montmorillonitetoluene system 2


17.

THOMAS

ET

Sheet-Silicate

AL.

11


11 A

Φ

y

313

Intercalates

X

ώ τ

Figure 8. Volatile products formed on heating (a) Cu -montmorillonite-tra.ns-stilbene and (b) Cu -montmonllonite-indene 2+

2+

compared

sites.

Reasonable

a m o u n t s of the t r i m e r s a n d d i m e r s of i n d e n e a n d of the

with

the benzene

ring, by

the

copper

cyclobutane

p r o d u c t ( d i m e r of f r a n s - s t i l b e n e ) are o b t a i n e d o n h e a t i n g t h e C u - M : i n d e n e a n d C u - M : f r a n s - s t i l b e n e c o m p l e x e s , r e s p e c t i v e l y , i n v a c u o at 50°— 2 5 0 ° C (see

Figure 8).

T h e r e is, therefore, s t r o n g e v i d e n c e h e r e t h a t a

s o l i d m a t r i x ( t h e m o n t m o r i l l o n i t e ) , w h i c h f u n c t i o n s b o t h as a f r a m e w o r k to w h i c h t h e reactant is a t t a c h e d a n d also as a s u p p o r t o r p r o m o t e r of t h e catalyst ( C u

2 +

ions ), c a n d i s c r i m i n a t e b e t w e e n t w o types of u n s a t u r a t e d

c a r b o n - c a r b o n b o n d s . T h i s p h e n o m e n o n c l e a r l y merits f u r t h e r s t u d y . I n n o case s t u d i e d to d a t e is there e v i d e n c e t h a t c o p p e r atoms are carried away w i t h the volatile products.

H o w e v e r , i t is n o t difficult to

d e s i g n sheet s i l i c a t e systems i n w h i c h o r g a n o m e t a l l i c p r o d u c t s , s u c h as m e t a l l a t e d benzenes, c o u l d b e p r o d u c e d to o r d e r u s i n g o r g a n i c i n t e r calates of sheet silicates. S o m e of these p o s s i b i l i t i e s ^are c u r r e n t l y u n d e r investigation. I n this a r t i c l e w e h a v e r e s t r i c t e d o u r a t t e n t i o n e n t i r e l y to t h e r m a l l y s t i m u l a t e d c h e m i c a l conversions.

It m u s t n o t b e t h o u g h t t h a t r a d i a t i o n -


314

SOLID

STATE

CHEMISTRY

i n d u c e d reactions are either i m p o s s i b l e or h a r d l y w o r t h i n v e s t i g a t i n g . I n d e e d some elegant studies of γ-ray i n d u c e d p o l y m e r i z a t i o n s of i n t e r c a l a t e d m o n o m e r s of a c r y l o n i t r i l e ( A N ) a n d m e t h a c r y l o n i t r i l e ( i n N a +

montmorillonite) have already been reported (36).

T h e insertion poly

mers so f o r m e d w e r e f o u n d to b e extensively c y c l i z e d , a n o c c u r r e n c e w h i c h is interprétable i n terms of the specific o r i e n t a t i o n of the i n t e r c a l a t e d m o n o m e r species.

It is often possible to i n s e r t t w o or e v e n t h r e e

layers of o r g a n i c m o l e c u l e s b e t w e e n the a l u m i n o s i l i c a t e sheets, a n d t h e r e s u l t i n g t w o - d i m e n s i o n a l o r g a n i z a t i o n is t h e n a k i n to that w h i c h p r e v a i l s i n a s m e c t i c mesophase. A g a i n , i t is o b v i o u s that m u c h scope f o r f u r t h e r Downloaded by CORNELL UNIV on October 22, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch017

s t u d y exists w i t h s u c h intercalates. Acknowledgments W e are g r a t e f u l for the n u m e r o u s s t i m u l a t i n g discussions w e h a d w i t h o u r colleagues

have

M . J . Tricker, J . O. W i l l i a m s , Stephen Evans,

a n d J . S. A n d e r s o n . W e are also i n d e b t e d to P . I . R e i d a n d M . J . W a l t e r s for t h e i r h e l p f u l c o n t r i b u t i o n s . J . M . T h o m a s also t h a n k s the P e t r o l e u m R e s e a r c h F u n d of t h e A m e r i c a n C h e m i c a l Society for

financial

assistance

i n a t t e n d i n g the N e w Y o r k M e e t i n g of the Society.

Literature Cited 1. Timms, P. L., J. Chem. Soc., Chem. Comm. (1969) 1033. 2. Benfield, F. W. S., Green, M. L. H., Ogden, J. S., Young, D., J. Chem. Soc., Chem. Comm. (1973) 866. 3. Williams-Smith, D. L., Wolf, L. R., Skell, P. S., J. Am. Chem. Soc. (1972) 94, 4042. 4. Ozin, G. Α., Voet, Α. V., Acc. Chem. Res. (1973) 9, 313. 5. Ogden, J. S., Turner, J. J., Chem. Br. (1971) 7, 186. 6. Tennakoon, D. T. B., Thomas, J. M., Tricker, M. J., Graham, S. H., J. Chem. Soc., Chem. Comm. (1974) 124. 7. Tennakoon, D. T. B., Thomas, J. M., Tricker, M. J., J. Chem. Soc., Dalton Trans. (1974) 2207. 8. Tennakoon, D. T. B., Thomas, J. M., Tricker, M. J., J. Chem. Soc., Dalton Trans. (1974) 2211. 9. Adams, J. M., J. Chem. Soc., Dalton Trans. (1974) 2286. 10. Tricker, M. J., Tennakoon, D. T. B., Thomas, J. M., Heald, J., Clays Clay Miner. (1975) 23, 77. 11. Adams, J. M., Thomas, J. M., Walters, M. J., J. Chem. Soc., Dalton Trans. (1975) 1459. 12. Tricker, M. J., Tennakoon, D. T. B., Thomas, J. M., Graham, S. H., Nature (1975) 253, 110.

13. Tennakoon, D. T. B., Tricker, M. J., J. Chem. Soc., Dalton Trans. (1975) 1802. 14. Adams, J. M., Thomas, J. M., Walters, M. J., J. Chem. Soc., Dalton Trans. (1976) 1975. 15. Adams, J. M., Graham, S. H., Reid, P. I., Thomas, J. M., J. Chem. Soc., Chem. Comm. (1977) 67. 16. Adams, J. M., Jefferson, D. Α., Acta Crystallogr. (1976) B32, 1180.



17.

THOMAS

ET

AL.

Sheet-Silicate Intercalates

315

17. Brindley, G. W., Reun. Hisp.-Belga Miner. Arcilla, An. (1970) 55. 18. Theng, B. K. G., "The Chemistry of Clay-Organic Reactions," Adam Hilger, London, 1974. 19. Adams, J. M., Lukawski, K., Reid, P. I., Thomas, J. M., Walters, M . J., J. Chem. Res. (1977) 301. 20. Weiss, Α., in "Organic Geochemistry," G. Eglington and M. T. J. Murphy, Eds., Springer-Verlag, Berlin, 1969. 21. Adams, J. M., Thomas, J. M., Walters, M. J., J. Chem. Soc., Dalton Trans. (1976) 112. 22. Weiss, Α., Angew. Chem. Int. Ed. Engl. (1963) 2, 697. 23. Evans, E. L., Thomas, J. M., J. Solid State Chem. (1975) 14, 99. 24. Yoffe, A. D., in Festkoerperprobleme, XIII, H . J. Queisser, Ed., p. 1, Pergamon, London, 1973. 25. Parry, G. S., Scruby, C. B., Williams, P. M., Philos. Mag. (1974) 29, 601. 26. Thomas, J. M., Philos. Trans. R. Soc. London (1974) 277, 251. 27. Lailach, G. E., Brindley, G. W., ClaysClay Miner. (1969) 17, 95. 28. Tennakoon, D. T. B., Ph.D. thesis, University College of Wales, Aberyst wyth, 1974. 29. Donor, H. E., Mortland, M. M., Science (1969) 166, 1406. 30. Mortland, M. M., Pinnavaia, T. J., Nature (London) Phys. Sci. (1971) 229, 75. 31. Pinnavaia, T. J., Mortland, M. M., J. Phys. Chem. (1971) 75, 3957. 32. Fenn, D. B., Mortland, M. M., Pinnavaia, T. J., Clays Clay Miner. (1973) 21, 315. 33. Rupert, J. P., J. Phys. Chem. (1973) 77, 784. 34. Turner, R. W., Amma, E. L., J. Am. Chem. Soc. (1966) 88, 1877. 35. Pinnavaia, T. J., Hall, P. L., Cody, S. S., Mortland, M. M., J. Phys. Chem. (1974) 78, 994. 36. Blumstein, R., Blumstein, Α., Parkikh, Κ. K., Appl. Polym. Symp. (1974) 25, 81. RECEIVED July

27, 1976.


Solid State Chemistry of Energy Conversion and ... - ACS Publications

Recommend Documents