The direct electrochemical synthesis of cationic complexes of metal ions

INORG. NUCL. CHEM. LETTERS VoI.15, pp. 113-116 Pergamon Press Ltd. 1979. Printed in Great Britain

THE DIRECT E L E C T R O C H E M I C A L CATIONIC COMPLEXES

Jacob J. Habeeb, Department

OF

OF METAL IONS

Farouq F. Said and Dennis G. Tuck

of Chemistry,

Windsor,

SYNTHESIS

Ontario,

University Canada

of Windsor

N9B 3P4

(Received 18 December 1978; received for publication 9 January 1979) Abstract.

Transition

be oxidised

and m a i n group metals can

electrochemically

HBF 4 in dimethylsulphoxide;

in cells c o n t a i n i n g the direct products

are the

[M(dmso) 6]n+ salts with BF 4 , but products

such as

[M(bipy)3 ]n+,

can be obtained

[M(en) 3]n+ and

by subsequent

[M(diphos)m ]n+

reaction

(M ~ n = 2,3).

In a recent series of papers ~-~ from this laboratory, we have d e s c r i b e d m e t h o d s inorganic

for the p r e p a r a t i o n

and o r g a n o m e t a l l i c

chemical method

compounds by a direct electro-

in w h i c h the parent metal

anode of a simple cell whose electrolyte aqueous

is the sacrificial phase

is a non-

solution of the ligand or its precursor.

and anionic

complexes were obtained

In an early p u b l i c a t i o n ( @ chemical

of various

oxidation

Both neutral

in such experiments. we noted that the electro-

of indium in the cell

P t ( _ ) / H C l O 4 + CH30H + dmso/In(+) (dmso z dimethylsulphoxide) [In(dmso) 6] (CIO4) 3. approach

gave rise to the known compound

We now report the d e v e l o p m e n t

into a general m e t h o d

complexes.

for the synthesis of cationic

The use of a m i x e d a q u e o u s / o r g a n i c

tetrafluoroboric

acid allows

the complexes

as the stable t e t r a f l u o r o b o r a t e

of this

solution of

to be recovered

salts, which removes 113

the

]14

Electrochemical Sythesis of Organometallic Compounds

h a z a r d s i m p l i c i t b o t h in the use of p e r c h l o r i c acid in o r g a n i c solvents,

and in the h a n d l i n g of p e r c h l o r a t e

salts

of c o m p l e x e s w i t h o r g a n i c ligands. The s o l u t i o n phase is t y p i c a l l y p r e p a r e d by m i x i n g equal v o l u m e s Inorganics)

(40 cm 3) of 48% HBF 4 s o l u t i o n

and p u r i f i e d d i m e t h y l s u l p h o x i d e

a p l a s t i c beaker.

at 0°C.

in

E l e c t r o l y t i c o x i d a t i o n of a n u m b e r of

t r a n s i t i o n and m a i n g r o u p m e t a l s with voltages

(Alfa

(see below)

were a c h i e v e d

in the 0.5 - 3.0 V range, w h i c h gave c u r r e n t s

of i00 - 300 m A in cells v e r y similar to those d e s c r i b e d previously(l,2).

These v o l t a g e s are a p p r e c i a b l y

those found n e c e s s a r y in our p r e v i o u s work,

lower than

and this is no

d o u b t due to the p r e s e n c e of s u b s t a n t i a l amounts of w a t e r originating

in the HBF 4 solution.

h at r o o m temperature,

Over a p e r i o d of 10 - 20

t y p i c a l l y 1 - 2 g of m e t a l dissolved,

g i v i n g ca 5 g q u a n t i t i e s of product. e x a m i n e d thus far,

In the systems

the d i s s o l u t i o n of the m e t a l obeys F a r a d a y ' s

Law, e x c e p t in the case of m a n g a n e s e ,

which undergoes a

s p o n t a n e o u s c h e m i c a l r e a c t i o n w h e n i m m e r s e d in the solution. In some cases,

the p r o d u c t s p r e c i p i t a t e d ,

but w e r e ~ o r e

f r e q u e n t l y o b t a i n e d on r e d u c i n g the v o l u m e of the s o l u t i o n in vacuo. The cations w h i c h we have p r e p a r e d to date by this m e t h o d are the s i x - c o o r d i n a t e dmso c o m p l e x e s of v a n a d i u m ( I I ) , chromium(III), zinc(II),

manganese(II),

cadmium(II)

and indium(III).

c o m p o u n d s of low o x i d a t i o n of the m e t a l

iron(III),

cobalt(III),

nickel(II),

The p r o d u c t i o n of

(V II , Cr III, Mn II) by o x i d a t i o n

is a c h a r a c t e r i s t i c of the e l e c t r o c h e m i c a l

m e t h o d here, as e l s e w h e r e (3. T i t a n i u m d i s s o l v e s in the cell, but we w e r e unable to recover a pure product, p r e s u m a b l y b e c a u s e the Ti III c a t i o n first p r o d u c e d u n d e r g o e s further reaction with dimethylsulphoxide

(c.f. ref.

7).

c o m p o u n d s have beeh c h a r a c t e r i s e d a n a l y t i c a l l y ,

All the and the

Electrochemical presence

Sythesis of Organometallic

of d i m e t h y l s u l p h o x i d e

and the absence

of water,

and tetrafluoroborate

demonstrated

115

Compounds anion,

by infrared

spectroscopy. A further solution other

obtained

cationic

solution

advantage

by electrolysis

complexes.

given rise to the cations [Ni(bipy)3 ]2+ and

[Cu(phen)3]2+

and

[Co(diphos) 2 ] 3 + , anthroline;

oxidation

conc.

between

is produced,

[Mn(phen) 3]

2+

[Fe(en) 3 ]3+

:

and

diphos

Similar 3+

,

= 1,2-bis we have found

yields

the salts

in which a chromium(II) dmso,

where

The species

a chromium(III)

may be due to the oxidation

syntheses

that

in a cell

[Cr(CH3CN) 6] (BF4) 2 respectively.

work on this point,

these electrochemical

,

and

:

of indium or chromium

and that involving

Further

has

2+

(phen = 1,10-phen-

Most recently

this system,

of

of a

salts.

, [Fe(phen) 3]

aq. HBF 4 in acetonitrile

complex was obtained, by dmso.

[Mn(bipy) 3]

all as salts with BF 4 -

[In(CH3CN) 6(BF4)3 contrast

]3+,

all as BF 4

en = ethylenediamine;

electrochemical

the addition

after electrolysis

[Cr(bipy) 3

[Cd(phen) 3 ]2+

(diphenylphosphino)ethane.

containing

(bipy)

[In(bipy)3]3+,

also yielded

is that the

can be used as a source

For example,

of 2,2'-bipyridine

experiments

of the method

Cr II

> Cr III

and on the extension

to other metals,

of

is being

performed. In general,

the methods

summarised

have wide application,

and as in other

simple

direct

and inexpensive

of complex

cations

such work,

syntheses

with a variety

above appear

References i.

J.J. HABEEB, L. NEILSONand D.G. TUCK,

2.

J.J. HABEEB and D.G. TUCK, J. Organometal. Chem.,

Syn. React.

Inorg. Metal-Org. Chem., 6, 105 (1976). 154, 365 (1977). 3.

J.J. HABEEB, F.F. SAID and D.G. TUCK, Can. J. Chem., 55, 3882 (1977).

offer

of an important

of different

to

neutral

series ligands.

I16

Electrochemical Sythesis of Organometallic Compounds

4.

J.J. HABEEB, L. NEILSON and D.G. TUCK, Inorg. Chem., 17, 306 (1978).

5.

J.J. HABEEB, D.G. TUCK and F.H. WALTENS, J. Coord. Chem., 8, 27 (1978).

6.

J.J. HABEEB and D.G. TUCK, J.C.S. Chem. Commtm., 808 (197S).

7.

O. C~ISTOFIS, J.J. HABEEB, R.S. STEEVENSZ and D.G. TUCK, Can. J. Chem., 56, 2269 (1978).