The mechanism of the reaction of Ag(II) with hydrogen peroxide: An Ag2+HO2− complex

tNORG.

NUCL.

CHEM.

LETTERS

vol.

5,

pp.

9-12,

1969.

THE mECHANI5~I OF THE REACTION HYDROGEN by Department

PEROXIDE C.F.

Pergemn~, Presl.

OF Ag(ll)

AN Ag2+H02

:

Wells

and

Printed

Greet

Brlta;n.

WITH

COMPLEX

D. Mays

of Chemistry,

University

of Birmingham,

P.O.

Birmingham

15,

Box 363,

In

Edgbaston,

England.

(Received 2 November 79~)

The rate of oxidation of the same order much

faster

latter

than that

by Co(III)

m n+ second

the presence

except

whether

possibly

with mn(III), order

tified

they

with

first

a very high

mn3+OH - (K ~

mn~

in

the oxidation

order

and

high

[H202]

(5),

(6).

However,

[H202],

:

the

to determine

of FMn(III)],

(1)

is

mn+H02 - is established

the rate determining inner-sphere

electron

the first

step is identransfer

l, with

equilibrium /~

via

2 and 3.

constant

The h i g h value

ions) :

is comparable both arise

H02 aq

for the electronic

1 for

the

for Mn3+H02 - ( K > 5 x lO 16 ~.mole

&.mole -1 ) (7) +

Mn 2+ + HO 2.

\ tendency

are observed,

is independent

the separated

1014

With

and

formation

from

(3).

are observed,

equilibrium

calculated

(1) but

kinetics

for mn3+H02

formation

by mn(III)

kinetics

at very

mn3+H02 ~ constant

Ag(II)

(4) it is not possible

Fe(III)

and acidity

as the first

order

participate

order

rate constant

!Mn(II)!

(2)

by

(2) and Fe(III)

of complexes

spectrophotometrically kinetically

peroxide

as the rate of oxidation

two cations

although

of hydrogen

arrangement

to that for

from the strong

Mn3+HO~

aq

mn3+H02

aq + H20

3 t2g e g

of mn(lll)

to

-1

10

THE REACTION OF Ag(ll)

the t23eg g 2 arrangement

attain

polarizability gen atom

the cation that

this

fication 3+ Feag

for

(g) and complex

the high is also

of the charge

peroxy

these

complexes

confirm

that

and

not H202

which

(8),

as OH-

value

inner

sphere. spectrum

are

inner

sphere.

similar

K is not

related

to the overall

the

t2g3eg2

Evidence

for

this

of Co 3+ aq

with

hydrogen

475 m/~ Plots

independent of acidity

of the in the

oxidation

inner-sphere

order

rate

range

by ~]n(III)

ratio

1.5-3.7 (1)

transfer

values

of K

3 x lOg&.

tendency

3+ " ,

oF the to form

in ~In3+H02

the

HO 2

H20 molecule.

power

Cr aq 3+ and

aq

the

low heat

Fe aq ~+

reaction

(8).

It

of h y d r o g e n

(E ° = 2°Ov)(lO)

(ll). (prepare,l media

stopped-flow

constant

of

Co3+> Mn3+>Fe

potential

of AO(II)

) against

initial

electron

V aq' 3+

in p e r c h l o r a t e

(O.D.-O.D&~

first

with

at 25°C

a Durrum-Gibson

replaced

for F~n~*OH"aq from

has a redox

reaction

peroxide

using

of log

observed

the

rapid

modi-

that

polarizable

extra

to i n v e s t i g a t e

([ ° = 1.gSv)

(2) and

suggestion

polarizing

covalency

found

therefore A gaq 2+ which

with

The

through

is also

the

of m n+ varies

is some

3. compared of Mnaq

is of interest,

~that

there

arrangement

of hydrolysis

peroxide

i.e.

with

suggests

The high

to the

potential

in solution

is c o n t i g u o u s

is the highly

as the redox

cation

the oxy-

¢.mole -I for Mn3+H02 -) at

However,

only

with

~.mo]B -I for Co3+H02-(2),

ligsnd

is very

the higher

compared

of Co 3+ aq

supports

~ 5 x I016

the

and

The c o n s i d e r a b l e

HO 2

(6 x 1013

Vol. 5, No. 1

of K for BIn3+H02

with

mole -I for Fe3+H02-(4), 25°C

atom

transfer

complexes

overlap

oxygen

molecule

(4) on c o m p l e x i n g

these

by sp3-d

of the anionic

in the water

WITH HYDROGEN PEROXIDE

time

has

electrolytically) been

followed

spectrophotometer.

are always

at constant

linear

ionic

and

strength

l A g ( I f ) ] / [ H 2 0 2 ] , or [Ag(1)] ~ HCIO 4.

: the rate 4, and

at

This

is analogous

determining

Ag 2 + HO 2

the is and to

step

is the

~nust have

a high

Vol. 5, No. |

THE REACTION OF Ag(ll) WITH HYDROGEN PEROXIDE

formation order

equilibrium

kinetics

to

constant

be

Ag2+H02 Ag suqgests due to

with

Ag(II)]

foltot~fed

by

5

m n+

the

sec

strong

+ HO 2

varying

(8)

3ahn-Teller smooth

out

stabilizations

ligands

with

the

in

H

~3+ ao'

H20.

therefore ionic

M m+ is

+ OH -

increased

are

likely

:

ligand

rL1n+

r~n+

to be

with

same

o×ygen

and

25°C.

the

suggests

(1). d 4 to

two

from

a

Effect

;

half-filled

The

covalency

from

(13).

of

preferential

from

Effect

Crystal , H20

the

field

and

HO 2

(8,13). References

i.

C.F.

W e l l s and D. flays, I n o r q . N u c l . C h e m . L e t t e r s , (lq68) ; ] . C h e m . Soc., A, 665 (lg68).

2.

O.H.

~ a × e n d a l e and C.F. 53, 800 (ig57).

3.

W.G.

Barb, 3°H. B a x e n d a l e , P. G e o r g e and Trans.Faraday 5oc., 47, 591 (lgSl).

Wells,

Trans. Faraday

K.R.

the

+ OH - d i s t a n c e s

Jahn-Teller

OH

and

constancy

Mn+

where

the

d I0 and

Jahn-Teller

for

rapidly

Mn(III)

arising

a dynamic

the

4 is

÷ OH 2 ) d i s t a n c e

distances

Ag(II)

therefore

found

(12). F e3+ aq

of

= 4.0

and

of

Ag2+H02 -

anionic

reaction

complexes

the

, this

stoichiometry

covalency

and

(or

in

d g to a t t a i n

stability

unlikely

mn++

same

as

+ anion

solution

of

strength

P~J zero,

that

rln ~ HO 2

exists

The

first

02

+

polarizability

3+ Craq

for

t 6 2geg3 a r r a n g e m e n t

throuqh

in

+

overlap

temperature,

extra

the

the

+

at

in m n+

suggests

Effect

Ag +

: increased

of

the

)

tendency-for

d sub-shell

in

-i

distance of

HO 2

in

activation

hydrolysis

shortening

may

of

+

the

and

to c h a n g e

influence

of

atom

with

Ag +

sp3-d

for

= 2,

: k = ii

very

filled

of

analogy

~

higher

oxygen

explanations

shorter

are

the

d 5 by c o v a l e n c y

possible

fully

degree

/&[H202]

This

heat

the

energy

attain

k

tendency

insensitive

overall

or

a high

t 26 g e g 4 and

compared

By

HO 2 •

strong

attain

k is

+

that

to the

~[

2+

-1)

(K ~ 5 × l O l 6 ~ . m o l e

observed.

11

~,

43

Soc.,

Hargrave,

as

THE REACTION OF Ag(ll) WITH HYDROGEN PEROXIDE

12

4 .

M.G.

Evans, P. George 230 (194g).

So

C.F.

Wells,

6.

P. Jones, R. Kitching, M.L. Tobe and W.F.K. Trans. Faraday Soc., 55, 79 (1959).

7.

C.F.

l!lells and G. Davies, ~ature, J.Cnem. Soc., A, 1858 (1967).

8o

C.F.

Wells,

9.

C.W.

lO.

A.A.

Noyes, D. DeVault, C.D. Coryell and T.J. O.Amer.Chem.5oc., 59, 1326 (1937)

ii.

D.A.

Johnson

12.

C.5.G. Phillips and R.i.P. Williams, "Inorganic Chemistry", Vol. 2 (Clarendon Press, Oxford, 1966), pp. 169-184.

13.

C.F. ~ells

Discussion

Nature,

and N. Uri,

Vol. 5, No. 1

Faraday

205,

693

lrans. Faraday

5oc., 29,

205,

Sharp,

and G. Oavies,

692

45,

(ig60). Wynne-Oones,

(1965);

(1965).

Davies, J.Chem. Soc., lgSl, 1256; (Butterworths, London, 1962) p.84.

and A.G.

171

Soc.,

"Ion Association"

J.Chem. Soc.,

J.Chem. Soc.,

3490

~858

Oeahl, (1964)

(i967).