Synthetic studies on extended S-donor ligands as potential molecular conductors

Physica 143B (1986) 321-323 North-Holland, Amsterdam

321

SYNTHETIC STUDIES ON EXTENDED S-DONOR LIGANDS A~ POTENTIAL MOLECUIA%R CONDU~PORS

K. SUKUMAR VARMA

and ALLAN E. UNDERHILL

Department of Chemistry and Instititue of Molecular and Biomolecular Electronics, University College of North Wales, Bangor, Gwynedd LL57 2UW, Great Britain

The syntheses of vinylenedlthlolethlone (VDT-DTT) and its dimerised derivative bis(vinylenedithio)tetrathiafulvalene (BVDT-TTF) is reported as part of our studies on new synthetic pathways to planar extended S-donor ligands. These and other derived ligands have been discussed as materials for the synthesis of new organic conductors and one--dlmensional metals.

i. INTRODUCTION There is presently great interest in new aniso%roplc materials with novel solid state properties including organic metals, organic super-conductors, ID metallic complexes and conducting polymers.

VDT-DTT

BVDT-TTF

In the search for

improved materials we are interested in new

We have synthesized VDT--DTT b y a different

molecular conductors based on structurally

synthetic pathway, involving a 'pseudo-

modified analogues of 4,5-dlmercapto-

nucleophilic' dithiolate attack on a

i, 3-dithiole-2-thione ligand (dmit ) and

I, 2-dihalogenoethylene.

B E D T - ~ F 1,2 .

proceeds through successive addition-

These two well-studied ligand

systems are not completely planar due to the presence of sp 3 carbon atoms in their molecular framework.

We are therefore concentrating on

The reaction probably

elimination sequences. The dithlabenzoyl ester 1 was synthesized b y a reported procedure .6

Subsequent

the synthesis and solid state properties o f

deprotection of 1 b y sodium ethoxlde in

completely planar analogues and derivatives of

tetrahydrofuran generated the

these llgands which might be expected to have

1,3-dlthiole-2-thione-4,5-dithiolate dlanion

improved intra-stack S...S interactions.

which was then reacted with a 2.5 fold molar

As

the first part of our study we have

excess of a cls/trans mixture of

concentrated on finding new synthetic routes

1,2-dlbromoethylene in dry THF affording 2

which will most readily afford these

albeit in low yield, due to difficult work-up

derivatives in higher ylelds.

procedures involving the removal of substantlal

Schumaker et al 3 have reported the syntheses

amounts of the ethyl benzoate formed during the

of his( vinylenedlthio )tet rathiafu Ivalene

reaction.

( BVDT-TTF ) and bis( dlmethylvlnylenedithlo )-

trlethyl phosphite in refluxlng toluene gave

tetrathiafulvalene (BDMVDT-TTF ) without

bls( vlnylene dlthlo )tet rathiafu Ivalene

experimental details.

(BVDT-TTF) in low yield.

0378 - 4 3 6 3 / 8 6 / $ 0 3 . 5 0 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division) and Yamada Science F o u n d a t i o n

The coupling o£ VDT-DTT 2--with

K, S. Varma and A.E. Underhill / Synthetic studies on extended S-donor ligands

322

S

<~

Ii

NaOCH:,CH~

+

±

S ¸

S ¸

ocs 5L- s /

"--"

- S

"

3

ii

01

mix poured into dry ether

Hg(OA ~ /

S Na + - s..b~

ir

S, i;

s

,>=0

" . S .¸¸'~-- S"

Na+ -S ~

5

S

Dithiolate disodium salt

+Na 0~:

2 BrCH----CHBr in CH3CN

S"

...v~ s\

]•s 3

s-

Na+j

6

l t a l i de

MX2;TAA

S'rS\

VDT-DTT

]! /

"

ii

M

AA

il

S "/I""S

S

2

purified by flash column chromatography (CH2CI2/CHCI3) FAA = tetraalkylanmJonium Scheme In f u r t h e r a t t e m p t s obtain

synthesized

VDT-DDT 3by

disodium

salt

2

further

a different

eliminates

VDT-D~'P3was

dithlolate

the b y - p r o d u c t

through

dianion 6 produced

5which

All solvents

the oxo-carbon.

( S e e S c h e m e B). reported

to use;

Hatfield

ligands derived

Vinylene

in t h e s y n t h e s i s

atmosphere

prior

were carried

unless

out

otherwise

dlthio-tetrathlafulvalene

et of

is b e i n g

of the dicyano

3=

Method A

4.06 g (0.01 m o l ) o f 1 , 3 - d i t h i o l e - 2 - t h l o n e ester 1 was suspended

cm 3 tetrahydrofuran.

in 75

To t h i s s t i r r e d

was added a solution

(0.021 tool) s o d i u m m e t a l

o f 0.48 g

in I0 c m 3 m e t h a n o l

over 5 mins and the mixture kept stirring further

20 mins.

dithiolate strategy

elsewhere.

and d e g a s s e d

and all p r o c e d u r e s

suspension

at

the preparation

f r o m ~'I~EO. similar

(BDCVDT-q'PF)

were dried

4, 5 - d i t h i a b e n z o y l

dithiolate

ion a t t a c k

al 6 h a v e r e c e n t l y

employed

to

m a y be

to n e w o n e - d i m e n s i o n a l

with analogous

and t h i s w i l l be r e p o r t e d

stated.

by Hg(OAc)25

the ring-opened by alkoxide

and t e t r a c y a n o

unaer nitrogen

oxo derivative

u s e d as the p r e c u r s o r

Essentially

ester

in a c e t o n i t r i l e .

also oxidized

(DCVDT--D~P) derivatives

procedure

reaction with the

the c o r r e s p o n d i n g

Ni c o m p l e x e s

and

we have

B

2. E X P E R I M E N T A L

o f the c r l m s o n - r e d

dihalogenoethylene

(1D) m e t a l s

product,

(See S c h e m e A).

The isolation

before

to improve the yield

an e a s i l y p u r i f i a b l e

o u t l i n e d below.

~cheme

A

s o l u t i o n w a s added d r o p w i s e

m i n s to a s t i r r e d

for a

This dark-coloured

solution

tool) I, 2 - 4 i b r o m o - e t h y l e n e

o v e r iO

o f 4.65 g (0.025 (cis/trans)

in 50 cm 3

K.S. Varma and A.E. Underhill / Synthetic studies on extended S-donor ligands

tetrahydrofuran.

The reaction mixture was

323

r e f l u x e d for 2 hours, c o o l e d a n d filtered t o

s t i r r e d at room t e m p e r a t u r e for 24 h o u r s and

remove small a m o u n t s o f p r e c i p i t a t e d sulphur.

the m i x t u r e w a s then p o u r e d s l o w l y i n t o 800 a m 3

The filtrate w a s t h e n e v a p o r a t e d to d r y n e s s l__nn

i c e - c o l d w a t e r w i t h stirring.

vacuo.

After standing

The r e d d l s h - b r o w n p a r t l a l l y o i l y

for a few h o u r s the s o l u t i o n w a s filtered, the

residue w a s t h e n r e d l s s o l v e d in a s m a l l v o l u m e

s o l i d b r o w n r e s i d u e d r i e d in air and r e p e a t e d l y

o f CHC13 and flash c h r o m a t o g r a p h e d u s l n g C H C l 3

r e c r y s t a l l l z e d from C H C 1 3 z C S 2 (281) to give a

and C H C 1 3 / C H 3 0 H (2tl).

y e l l o w compound, y i e l d 10-15%;

eluted gave 50 m g o f 4.

(decomp.);

m.p. 139-142 ° C

V i n y l e n e d i t h l o d i t h i o l e - o n e 5t

M.W. c a l c d 222, found (mass

s p e c t r o s c o p y ) 222;

8 - 7.45

(0.0045 mol5 H g ( I I ) a c e t a t e and 50 c m 3 g l a c i a l acetic a c l d w e r e

88 (i~), 70 (12), 70 (i0)I

I H - N M R (DMSO-d6)t

1 g (0.0045

mol) o f V D T - D T T 3, 80 c m 3 C H 2 C I 2, 1.43 g

M S [m/e (% r e l a t i v e

a b u n d a n c e ) ] - 222 (i00), 146 (385, 76 (155, 76 (14), 88 (13),

The s e c o n d f r a c t i o n

r e f l u x e d for 6 hours.

The

r e a c t i o n mixture was cooled, d r i e d w i t h 50 g

(s, 2H).

s o d i u m sulphate,

Method B

CH2CI 2 .

4.06 g (0.01 tool) o f 1 , 3 - d i t h i o l e -

filtered and w a s h e d w i t h

The filtrate w a s s h a k e n w i t h s o d i u m

-2-thione-4,B-dithiabenzoyl ester ~was

carbonate solution to neutrallee any glaclal

s u s p e n d e d in 50 c m 3 methanol.

acetic acid in the o r g a n i c p h a s e (CH2C125 and

To this

suspension was added a solution of sodium

then p a s s e d t h r o u g h a l u n t i n i u m o x l d e (basic).

m e t h o x i d e (0.48 g, 0.021 m o l N a in I0 can3

Solvent was then removed in v a c u o and the solid

m e t h a n o l ) o v e r B m i n s and the m i x t u r e k e p t

r e c r y s t a l l i z e d from C H C 1 3 / p e t r o l e u m e t h e r (4rl).

s t i r r e d for a further 20 mine.

m.p.122-125Oc

The dithiolate

s o l u t l o n was then s l o w l y p o u r e d i n t o a

M.W. c a l c d 206l

w e l l - s t l r r e d 1 lltre s o l u t i o n o f e t h e r at

206;

10Oc.

T h e c r i m s o n - r e d d i t h i o l a t e d i s o d i u m salt

p r e c i p i t a t e d out almost immediately.

After

M.S.

found (by m a s s s p e c t r o s c o p y )

[m/e (% r e l a t i v e abundance)] - 102

(lOO), 88 (805, 206 (485, 178 (425, is9 (365, 146 (275;

I.R. (KBr5 1665 c m -I (C-O).

10 m i n s stirring, the p r e c i p i t a t e was isolated b y s u c t i o n f i l t r a t i o n and r e d i s s o l v e d i m m e d i a t e l y in i00 c m B a c e t o n i t r i l e ( d u r i n g the isolation b y s u c t i o n o f the salt t h e r e is no need for N 2 atmosphere).

I.

M. Bousseau, L. Valade, H.F. B r u n l q u e l and P. Cassoux, N o u v e a u J. Chemle, 8, 1 (19845.

2.

J.M. W i l l i a m s and L. Carneiro, Adv. Chem. Radiochem., 29, 249 (1985).

3.

R.R. Schumaker, V.Y. Lee and E.M. Engler, J. Physique, 44, C 3 - 1 1 3 9 (1983).

4.

G. Stelmecke, H.J. Sleler, R. K i r m s e and E. Hoyer, P h o s p h o r o u s a n d Sulphur, 7, 4 9 (1979).

5.

H. Hartke, T. Kissel, J. Q u a n t e and R. Matusch, Chem. Ber., Ii___~3,1898 (1980).

6.

C.T. Vance, R.D. Bereman, J.,Bordner, W.E. H a t f l e l d and J.H. Helms, Inorg. Chem. 24, 2905 (1985).

T o t h i s d a r k violet

s o l u t i o n was a d d e d 4.65 g (0.025 m o l ) 1 , 2 - d i b r o m o e t h y l e n e ( c i s / t r a n e ) and the m i x t u r e stirred o v e r n i g h t at r o o m temperature.

Inorg.

The

solvent w a s removed in v a c u o and the b r o w n residue was p u r i f i e d b y flash c o l u m n c h r o m a t o g r a p h y (CHCI3) w h e n o n l y the d e s i r e d c o m p o u n d 3 w a s e l u t e d out. Bis-vin¥1enedithlolethione-tetrathlafulvalene (BVDT-TTP) 4z

i g o f V D T - D T T 3 was d i s s o l v e d

in i00 c m 3 t o l u e n e and to this s o l u t i o n w a s added 15 c m 3 f r e s h l y d i s t i l l e d t r l e t h y l phosphite.

The w h o l e m i x t u r e w a s then