Reactions of Coordinated Ligands and Homogeneous Catalysis

13 Cobalt-Catalyzed Cleavage of N-Hydroxyethylethylenediamine to Ethylenediamine in the Presence of Oxygen DALE HUGGINS and W. C. DRINKARD

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University of California, Los Angeles,

Calif.

Oxidation of cobalt(II) to cobalt(III) by

oxygen

in the presence of N-hydroxyethylethylenediamine and carbon produces large amounts of ethylenediamine.

Other

products

formic acid, and ammonia.

are

formaldehyde,

The sum of the moles

of ethylenediamine and ammonia produced is equal to the total number of moles of cobalt(II) oxidized.

A steady-state concentration of Co(II)-

Co(III) is established in which the ratio Co(III)/ Co(II) =

1.207.

Thus cobalt ion behaves as a

true catalyst for cleavage of the N-hydroxyethylethylenediamine.

The total amount of cobalt(II)

oxidized per unit time, X, was calculated from the derived

equation:

X

=

3.8

,where k2 = 0.65

3.8e-2.2k2t

+

7.0

hr.-1

-

kT 2

The observed

rate of formation of ethylenediamine plus ammonia also follows this equation.

It is proposed

that the cobalt ion serves as a center where a superoxide ion [derived from oxidation of cobalt(II) by oxygen] and the ligand are brought together for reaction.

Ane

of the most w i d e l y u s e d m e t h o d s for the f o r m a t i o n of cobalt (III)

involves the oxidation of a cobalt (II) Generally, activated

c a r b o n is a d d e d as a c a t a l y s t .

was

useful for the

reported

amine workers

to

be

c o b a l t (III)

chloride

s t u d y it w a s

noted

that the

those of t r i s e t h y l e n e d i a m i n e (6)

that ethylenediamine

amine

cobalt (III)

preparation

(15).

to o b t a i n t h i s c o m p l e x

The

same

possessed

cobalt (III)

procedure

may

be

properties

chloride.

is f o r m e d d u r i n g t h e

chloride

This experimental

isolated.

was

relationship

used

Subsequently,

reaction The

a n d that

purpose

of

between

the

amount

of

cobalt (II)

by

other In

(16).

remarkably

v e s t i g a t i o n w a s to e l u c i d a t e t h e n a t u r e o f t h i s c l e a v a g e r e a c t i o n quantitative

procedure

of t r i s - N - h y d r o x y e t h y l e t h y l e n e d i -

for a s t u d y of p h y s i c a l properties

complex

complexes

salt b y o x y g e n i n t h e p r e s e n c e o f a l i g a n d .

the

similar

it w a s

to

shown

trisethylenedi-

the

present

in-

a n d to o b t a i n

oxidized

a m o u n t of e t h y l e n e d i a m i n e f o r m e d .

181 Busch; Reactions of Coordinated Ligands Advances in Chemistry; American Chemical Society: Washington, DC, 1962.

and

a

the

ADVANCES IN CHEMISTRY SERIES

182 Products

of the reaction

have

b e e n i d e n t i f i e d as e t h y l e n e d i a m i n e ,

hyde, formic acid, a n d ammonia.

formalde-

A kinetic e v a l u a t i o n of rate experiments

indi-

c a t e s t h a t f o r e a c h c o b a l t ( II ) i o n o x i d i z e d e i t h e r o n e m o l e c u l e o f e t h y l e n e d i a m i n e or o n e m o l e c u l e of a m m o n i a

appears.

Experimental Materials. Eastman

N-Hydroxyethylethylenediamine

( b . p . 8 8 ° C . at 1 m m . H g ) . Commercial Apparatus. three-necked fitted

solution

Experiments

flask,

fitted

hydride

O n l y the m i d d l e fraction was retained.

o i l - p u m p e d nitrogen

through a chromium(II)

tube

(2,2-aminoethylaminoethanol),

W h i t e L a b e l , was purified b y v a c u u m distillation f r o m c a l c i u m was freed

of oxygen

b y passing

the gas

(27).

were

carried

out in a

250-ml.

round-bottomed,

w i t h a g a s i n l e t t u b e , a s a m p l e d i p t u b e , a n d a g a s exit

w i t h a reflux c o n d e n s e r .

E x i t gas w a s p a s s e d t h r o u g h traps of stand-

a r d s u l f u r i c a c i d to r e m o v e a n y b a s i c gases. A

Beckman

Model

D U spectrophotometer

was used

for the

spectrophoto-

m e t r i c d e t e r m i n a t i o n o f c o b a l t ( II ). Reaction Conditions. grams

(0.020 mole)

Unless otherwise

of C o C l . 6 H 0 , 2

stated, a l l r é a c t i o n s

52.05

2

grams

(0.500

contained

mole)

4.76

of A -hydroxy7

e t h y l e t h y l e n e d i a m i n e , 1.0 m l . o f 1 2 N h y d r o c h l o r i c a c i d , 1 0 0 m l . o f w a t e r , a n d 2.5 grams of activated

carbon.

T h e temperature of the solution was maintained

at

9 6 - 8 ° C , a n d a i r w a s p a s s e d t h r o u g h t h e s o l u t i o n at a r a t e o f 1 0 0 m l . p e r m i n u t e . Identification

of Reaction

Products.

Carbon dioxide-free

through the previously described reaction

mixture.

carbon was removed b y

filtrate

v o l u m e of ethanol

from a n ethanol-water ANALYSES. 20.7;

filtration,

( 9 5 % ).

a n d the

T h e precipitate

s o l u t i o n a n d finally

C a l c d . for C o C H 6

9

4

p o u r e d s l o w l y i n t o six t i m e s its

w h i c h f o r m e d was recrystallized

from a m i n i m u m amount

N Cl : 6

air was b u b b l e d

A t the e n d of 6 hours, the

C , 20.8; H , 7.0; C I , 30.7.

3

first

of water. Found:

C,

H , 7.0; C I , 31.3. Ethylenediamine

was

salicylaldehyde method

determined

quantitatively

T h e product

(14).

enediamine c o m p a r e d w i t h a theoretical

on

the

product

w a s f o u n d to contain

composition of 52.3% for

by

the

50.1% ethyl[Co(en) ]Cl . 3

3

E x p e r i m e n t s to determine the other reaction p r o d u c t s w e r e p e r f o r m e d i n t w o ways:

(1)

reaction

Q u a l i t a t i v e tests w e r e m a d e o n t h e r e a c t i o n s o l u t i o n a f t e r t h e

period

[Co(en) JCl 3

3

a n d after

b y ethanol;

removal a n d (2)

of c a r b o n

b u t before

after cobalt

6-hour

precipitation

was removed

from the

of the reaction

solution b y precipitation w i t h h y d r o g e n sulfide a n d the solution b o i l e d to h y d r o g e n sufide.

c a r b o n d i o x i d e , a n d c a r b o n m o n o x i d e w i t h n e g a t i v e results. the

reaction

negative

was checked

for carbon

monoxide

acid,

T h e effluent gas f r o m

and carbon

dioxide, again

with

glycol was p e r f o r m e d b y oxidation of the sample

with

results.

T h e test f o r e t h y l e n e periodic acid a n d detection acid reagent Two

remove

Tests were m a d e for ethylene glycol, glycolic acid, oxalic

of the resulting f o r m a l d e h y d e w i t h f u c h s i n - s u l f u r o u s

(9).

tests w e r e u s e d f o r t h e d e t e c t i o n

of glycolic a c i d :

the

chromatropic

a c i d test a n d t h e m e t h o d w h e r e b y t h e g l y c o l i c a c i d is t r e a t e d w i t h s u l f u r i c a c i d a n d the resulting carbon monoxide detected b y p h o s p h o m o l y b d i c a c i d - p a l l a d i u m c h l o r i d e r e a g e n t (10,

12).

T h e a n i l i n e b l u e test w a s u s e d f o r t h e d e t e c t i o n o f oxalic a c i d

(13).

T h e p h o s p h o m o l y b d i c a c i d - p a l l a d i u m c h l o r i d e test w a s u s e d f o r t h e d e t e c t i o n of c a r b o n m o n o x i d e

(25).

C a r b o n dioxide was determined gravimetrically with Ascarite. The

r e l i a b i l i t y o f t h e tests

for ethylene

glycol,

monoxide were verified b y a d d i n g k n o w n amounts

acid,

a n d carbon

of these materials

glycolic

to the reac-

tion solution. A portion of the reaction solution was acidified with sulfuric acid a n d steamdistilled

into

sodium

hydroxide

formaldehyde a n d formic acid. with dimedone

(31).

solution.

T h e distillate

was found

to

contain

T h e formaldehyde was identified b y precipitation

T h e precipitate

h a d a m e l t i n g point of 1 8 6 . 0 - 8 6 . 5 °

Busch; Reactions of Coordinated Ligands Advances in Chemistry; American Chemical Society: Washington, DC, 1962.

C . as

HUGGINS AND DRINKARD compared

w i t h a literature

Cobalt-Catalyzed

183

Cleavage

v a l u e o f 1 8 7 ° C . (17).

T h e formic acid i n the dis

t i l l a t e w a s i d e n t i f i e d b y first r e m o v i n g t h e f o r m a l d e h y d e w i t h d i m e d o n e a n d reducing theformic acid to formaldehyde with magnesium

The

(11).

then

dimedone

p r e c i p i t a t e o f this f o r m a l d e h y d e h a d a m e l t i n g p o i n t o f 1 8 5 . 3 - 6 . 5 ° C . T h e effluent gas f r o m t h e reaction

w a s p a s s e d t h r o u g h a 0.1N

acid solution; the solution was evaporated

to dryness,

hydrochloric

a n d t h e r e s u l t i n g salt w a s

s h o w n b y analysis to b e a m m o n i u m chloride.

Experiment 1. Effect of Carbon Catalyst on Oxidation of Cobalt(II) to Cobalt (III) and Formation of Ethylenediamine and Effect of Cobalt on Forma tion

of Ethylenediamine.

reaction

mixture.

Nine

Carbon

dioxide-free

determinations

each

tilized, the ethylenediamine concentration, m a d e over a p e r i o d o f 18 h o u r s .

0

2

4

air was b u b b l e d

of the amounts

through the

of ammonia

vola

and the cobalt (II) concentration

were

T h e r e s u l t s a r e s h o w n i n F i g u r e 1.

6

8

10

12

14

16

18

T I M E (hours)

X A • Ο •

Figure 1. Charge of concentration in air at 95° C. Ethylenediamine, carbon present Ethylenediamine, no carbon present Cobalt(II), carbon present Cobalt(II), no carbon present Ethylenediamine, carbon but no cobalt ion present

The

amount

of ammonia

volatilized was determined

standard sulfuric a c i d c o n s u m e d i n the traps. the salicylaldehyde m e t h o d made

slightly

acidic

with

sample f r o m the reaction T h ecarbon

(18). was

determined

complex, The

acid

wasremoved

2

experiment

4

the amount of

immediately

determination was

upon

removal

of the

i n order to prevent further oxidation of the cobalt by

filtration,

spectrophotometrically

(NH ) Co(NCS) 4

T h e sample forcobalt(II)

(14).

hydrochloric

flask,

from

E t h y l e n e d i a m i n e was determined b y

as

a n d the cobalt(II)

concentration

the cobalt-ammonium

thiocyanate

(28).

was repeated

with n o carbon

e x p e r i m e n t a r e a l s o s h o w n i n F i g u r e 1. cobalt or hydrochloric acid present

present.

T h e results

T h e reaction was repeated

o f this

again with n o

( F i g u r e 1 ).

Experiment 2 . Step Involving Ligand Cleavage and A t t e m p t to Detect Reaction Intermediate.

Oxygen-free nitrogen wasb u b b l e d through t h e reaction

mixture.

were

T w o samples

ethylenediamine

analysis

taken

to make

at 20-minute

certain

that

intervals

n o reaction

for cobalt (II) a n d w a s occurring.

Im

m e d i a t e l y a f t e r t h e s e c o n d s a m p l e w a s t a k e n , t h e flow o f a i r t h r o u g h t h e s a m p l e solution w a sb e g u n a n d maintained f o r 2 0 minutes. placed

b y the nitrogen

flow.

A sample

Then

for cobalt (II)

t h e a i r flow w a s r e a n d ethylenediamine

a n a l y s i s w a s t a k e n i m m e d i a t e l y a t t h e e n d o f t h e a i r flow, f o l l o w e d b y t w o m o r e



184

s a m p l e s at 2 0 - m i n u t e i n t e r v a l s w h i l e t h e n i t r o g e n flow w a s c o n t i n u i n g . air was i n t r o d u c e d for 20

minutes, a n d the

same procedure

was

O n c e again

repeated.

The

d a t a f r o m t h i s e x p e r i m e n t a r e p l o t t e d i n F i g u r e 2.

T I M E (hours)

Figure 2. Effect of air on formation of ethylenediamine and cobalt(III) con centration Ο Ethylenediamine φ Cohalt(III) Experiment Rate

of

through mined

3.

Rates of F o r m a t i o n

Disappearance the

of

solution.

measured calculated

are was

a

collected actually

Carbon

total

reaction

in Table

the

I

and

time

of

plotted

and Ammonia

dioxide-free and

5

was

cobalt (II)

hours.

in

air

The

Figure

a m m o n i a volatilized d u r i n g the

3.

were The

vs.

bubbled

results

reaction,

as m o l e s p e r l i t e r o f s o l u t i o n i n o r d e r to b e c o n s i s t e n t

e n e d i a m i n e a n d c o b a l t (II)

Table I.

of E t h y l e n e d i a m i n e

A m m o n i a , ethylenediamine,

periodically over

experiment

C o b a l t (II).

deter of

this

ammonia

but

w i t h the

it

was

ethyl

results.

Formation of Ethylenediamine and Ammonia and Disappearance of Cobalt(ll) ( F r o m E x p e r i m e n t 3)

Reaction Time, Hours 0.00 0.08 0.58 0.95 1 .32 1 .82 2.48 3.13 3.58 4.03 4.48 5.00

Ethylenediamine, Moles/Liter X 10* 0.0 \'.S 3.6 4.7 6.7 9.5 11.5 12.9 14.4 15.8 17.6

Ammonia, Moles/Liter X 10* 0.0 0.85 1.72 2.50 3.57 5.12 6.09 7.01 7.73 8.44 9.38

Cobalt(II) Moles/Liter X 12.8 11.6 9.1 7.4 7.7 5.6 5.8 5.8 5.8 5.8


HUGGINS AND DRINKARD

Cobalt-Catalyzed

chloride (6)

185

Rates of Formation of Ethylenediamine and Ammonia vs.

Experiment 4 .

Rate of Appearance of Cobalt (II). (III)

Cleavage

(0.020 mole)

Tris-N-hydroxyethylethylenediamine

cobalt-

w a s p l a c e d i n t h e r e a c t i o n flask w i t h 1 0 0 m l . o f

water, 45.80 grams of N - h y d r o x y e t h y l e t h y l e n e d i a m i n e , a n d 2.5 grams of activated c a r b o n , a n d t h e r e a c t i o n w a s c a r r i e d o u t as i n E x p e r i m e n t

3.

T h e experimental

results are s h o w n i n F i g u r e 4.

1

1

1

1

Γ

TIME (hours )

Figure 3. Rates of formation of ethylenediamine and ammonia and rate of disappearance of cobalt(II) X Ethylenediamine Ο Ammonia Φ Cobalt(II) Experiment 5 . Solubility of Ammonia in Reaction Solution. A m m o n i a was determined complete

o n the stream

of air l e a v i n g the reaction

r e m o v a l of a m m o n i a f r o m the reaction

determine

the amount

gravimetric

analysis

volatilization

of a m m o n i a

with

sodium

solution.

seemed

remaining i n the reaction c o b a l tin irrite

or distillation techniques,

and sodium

etc., w i t h o u t

Immediate

doubtful.

and

Attempts

to

solution i n c l u d e d tetraphenyl

success.

boron,

T h e amount

of

a m m o n i a " h o l d u p " i n the solution was estimated b y sweeping a n initially a m m o n i a free reaction

solution identical w i t h the starting

solution i n E x p e r i m e n t

nitrogen containing a k n o w n a m o u n t of a m m o n i a . from

the solution for ammonia,

it w a s d e t e r m i n e d

3

with

B y a n a l y z i n g t h e gas c o m i n g that after

about

3

/

c o n s t a n t a m o u n t o f a m m o n i a ( 0 . 8 m e q . ) is h e l d b y t h e r e a c t i o n s o l u t i o n .

4

hour

a

Correc

t i o n s f o r t h i s h o l d u p w e r e m a d e i n t h e final d a t a .

Discussion The must

formation

occur

of e t h y l e n e d i a m i n e

through rupture

f r o m the N-hydroxyethylethylenediamine

of the carbon-nitrogen

b o n d between

the hydroxy-

e t h y l g r o u p a n d t h e s e c o n d a r y n i t r o g e n as f o l l o w s : H H H ( H H N — C ^ C — W C ^ C — O H H H H H [ H H The

formaldehyde

a n d formic

—

H H H H N — C — C — N + H H H H

acid

detected

other products

i n the reaction

solution

were

d e r i v e d f r o m t h e h y d r o x y e t h y l g r o u p w h i c h is s p l i t o f f i n t h e f o r m a t i o n o f e t h y l enediamine.

T h e fact that n o t w o - c a r b o n

derivatives

of the h y d r o x y e t h y l


group

186


(ethylene age

g l y c o l , g l y c o l i c a c i d , etc.)

of the

hydroxyethyl

group

were detected indicates that oxidative

occurs

simultaneously

w i t h the

cleav-

cleavage

of

the

carbon-nitrogen b o n d b e t w e e n the h y d r o x y e t h y l group a n d the secondary

nitrogen.

All

mixtures.

two-carbon

The

fragments

w e r e s h o w n to s u r v i v e i n s y n t h e t i c

p r e s e n c e of f o r m i c a c i d i n the

reaction

t h a t f o r m i c a c i d is a p r o d u c t

of the

hydroxyethyl group.

both carbon

form

Rather,

formaldehyde

alcohols

in a manner

by periodic acid

c l e a v a g e of the

and

does

reaction

not

necessarily

carbon-carbon

mean

b o n d of

atoms of the h y d r o x y e t h y l g r o u p

s i m i l a r to

(19),

mixture

the

then

glyco-type

b e c a u s e of the

cheavage

of

oxidizing

the may

2-amino

state of

the

e n v i r o n m e n t , p a r t o f t h e f o r m a l d e h y d e m a y b e o x i d i z e d to f o r m i c a c i d . T h e formation of a m m o n i a f r o m the the

reaction

suggests that some

consideration product

is

product

is f o r m e d .

of the m e c h a n i s m p r o p o s e d , one w o u l d postulate

ethanolamine.

Efforts

b e c a u s e of the large c o n c e n t r a t i o n Figure

N-hydroxyethylethylenediamine

additional reaction

1

shows

the

effect

to

detect

this

compound

that this were

unsuccessful

of N - h y d r o x y e t h y l e t h y l e n e d i a m i n e . of

cobalt

and

activated

carbon

on

the

W h e n b o t h c o b a l t a n d c a r b o n are present

rate

when

cobalt

is p r e s e n t

but

carbon

is a b s e n t ,

and

of

aeration

in the

t i o n s o l u t i o n , t h e r a t e o f f o r m a t i o n o f e t h y l e n e d i a m i n e is a p p r o x i m a t e l y greater than

a

reaction

formation of e t h y l e n e d i a m i n e f r o m N - h y d r o x y e t h y l e t h y l e n e d i a m i n e u p o n of a hot aqueous solution.

during From

reac-

five

times

19

times

about

g r e a t e r t h a n w h e n c o b a l t is a b s e n t a n d c a r b o n is p r e s e n t . E x p e r i m e n t 1 reveals an i m p o r t a n t difference i n the b e h a v i o r of the cobalt concentration

i n the presence a n d absence of c a r b o n .

c a r b o n the cobalt (II) 4

hours.

the

w a s c o m p l e t e l y o x i d i z e d to c o b a l t ( I I I )

H o w e v e r , w h e n activated

c o b a l t (II)

concentration

f o u r t h of the initial c o b a l t (II) T h e possibility was

carbon

reached

was

present

easily

detected.

intermediate.

considered that a reaction

Accordingly, Experiment

As can

be

b y the air stream

in the

a steady-state value

(II)

activated

reaction

in

solution,

of approximately

one

concentration.

d u r i n g the reaction, w i t h a lifetime sufficiently l o n g be

In the absence of

seen

from Figure

2

2,

intermediate

may

be

formed

(about 5 minutes or more) was

performed

ethylenediamine

to

detect

forms

to this

while

the

s o l u t i o n is a e r a t e d , b u t u p o n s w i t c h i n g f r o m a s t r e a m o f a i r t o a s t r e a m o f o x y g e n free nitrogen, indicates

the

ethylenediamine

formation

stops i m m e d i a t e l y .

that a relatively l o n g - l i v e d intermediate

does not occur

This

behavior

in the

reaction,

a n d t h a t n o e t h y l e n e d i a m i n e is p r o d u c e d b y r e d u c t i o n o f c o b a l t ( I I I ) . A n o t h e r interesting result was the d e m o n s t r a t i o n that the cobalt (III) d u r i n g t h e a e r a t i o n is r e d u c e d a g a i n to c o b a l t ( I I ) t i o n is h a l t e d . activated value.

T h i s is c o n s i s t e n t

carbon

is p r e s e n t ,

W h e n no carbon

the

w i t h the

finding

c o b a l t (II)

is p r e s e n t ,

the

in Experiment

concentration

c o b a l t (II)

formed

d u r i n g the time that the attains

is e s s e n t i a l l y

1, a

that

aerawhen

steady-state

all o x i d i z e d

to

cobalt (III). F i g u r e 4 s h o w s the results mine

if the

action

of E x p e r i m e n t

cobalt(II)-cobalt(III)

were performed

w i t h the

steady

cobalt

4, w h i c h w a s p e r f o r m e d to

state w o u l d

all present

be

established

deter-

if t h e

i n i t i a l l y as c o b a l t ( I I I ) .

reThe

s t e a d y state w a s e s t a b l i s h e d . E x p e r i m e n t 5 to d e t e r m i n e the reliability of the a m m o n i a analyses that after solution.

3

/

4

hour a constant amount

Since the a m m o n i a analyses

the reaction

of a m m o n i a

(0.8

meq.)

were p e r f o r m e d on the

s o l u t i o n , this i n d i c a t e s that the

a m m o n i a analyses

was

indicated

held by

air s t r e a m

the

leaving

would be low

a n a m o u n t i n c r e a s i n g f r o m t h e start o f t h e r e a c t i o n to a m a x i m u m v a l u e o f 0 . 8 in V 4 hour.


by

meq.


187

Cobalt-Catalyzed Cleavage

TIME ( hours)

Figure 4. Rate of formation of ethyl enediamine and rate of appearance of cohalt(II) • Ethylenediamine Ο Cobalt(II) Ethylenediamine corrected for initial ethylenediamine concentration

Experimental balt (III)

and

diamine

occur

assumed

in other

observations

the

formation

simultaneously. instances

indicate

of

that

This

o x i d a t i o n of cysteine

d i t h i o g l y c o l i c a c i d (5,

23 ),

is

to

quite

and unsaturated

c o b a l t (II)

to

the

opposite

to

what

of o r g a n i c

is

usually

reactions—for

i n the o x i d a t i o n of o x a l i c a c i d

cystine

co

from N-hydroxyethylethylene-

(7,

8),

a n d of t h i o g l y c o l i c a c i d

(22)

to

of c o p p e r i n the o x i d a t i o n of p y r o c a t e c h o l to q u i n o n e

a n d i n the o x i d a t i o n of ascorbic a c i d aldehydes

o x i d a t i o n of

of transition m e t a l catalysis

e x a m p l e , the c a t a l y t i c effect of m a n g a n e s e of iron i n the

the

ethylenediamine

(29,

a n d of cobalt i n the o x i d a t i o n of

30),

hydrocarbons

In all these reactions

(4).

the

oxida

tion of the organic m o l e c u l e occurs b y the abstraction of an electron b y the o x i d i z e d f o r m of the m e t a l i o n . To

e x p l a i n the simultaneous o x i d a t i o n of cobalt (II)

e t h y l e n e d i a m i n e , it is p r o p o s e d t h a t t h e c o b a l t ( I I ) hydroxyethylethylenediamine

and

oxygen

appearance

of

functions b y b r i n g i n g the

N-

molecules

S e v e r a l investigators h a v e suggested that cobalt (II)

a n d the

within

reaction

proximity.

may form an addition product

w i t h m o l e c u l a r o x y g e n or the s u p e r o x i d e i o n a n d that this a d d i t i o n p r o d u c t be

an intermediate

in cobalt-catalyzed

oxidations

have p r o p o s e d that such a c o m p l e x occurs

(21)

in the presence

(3,

i n the

an

intermediate

The

chemistry

addition product of

the

of

oxygen

oxygen-carrying

c y a n i n , a n d the c o b a l t ( I I )

and

Calvin

p o l a r o g r a p h y of

oxygen

of cobalt (II).

Basolo

complexes

histidine complexes

complexes

the

(1,

may

and

of b i s s a l i c y l a l d e t h y l e n e d i i m i n e c o m p l e x e s

a n d Pearson h a v e p o i n t e d out that b i n u c l e a r peroxo

Martell

24).

are

cobalt(II)

such

as

suggestive complex

hemoglobin,

hemo-

lends further support

20)

of (2). to

the existence of s u c h a n o x y g e n - c o b a l t i n t e r m e d i a t e . Although enediamine

no direct evidence was

reaction

that

an

found

oxygen-cobalt

in the cobalt-2V-hydroxyethylethyladdition

complex

was

formed,

s e e m s r e a s o n a b l e to p o s t u l a t e t h a t s u c h a n i n t e r m e d i a t e is p r e s e n t i n t h e

it

reaction.

A n o x y g e n - c o b a l t c o m p l e x i n t e r m e d i a t e a p p e a r s to a f f o r d t h e m o s t l o g i c a l m e t h o d of e x p l a i n i n g the e v i d e n c e that the o x i d a t i o n of c o b a l t (II) in

conjunction

with

the

oxidative

cleavage

of

the

to c o b a l t ( I I I )

carbon-carbon

bond

h y d r o x y e t h y l g r o u p a n d the f o r m a t i o n of e t h y l e n e d i a m i n e .


occurs of

the


188 Based sequence

upon

ethylenediamine results. ucts.

the

existence

of

this

oxygen-cobalt

intermediate,

a

reaction

is p r o p o s e d f o r t h e c o b a l t ( I I ) - c a t a l y z e d c o n v e r s i o n o f J V - h y d r o x y e t h y l to

ethylenediamine,

w h i c h is c o n s i s t e n t

T h e m e c h a n i s m is a s p e c u l a t i o n b a s e d o n t h e

w i t h the

nature

experimental

of the

end

prod

T h e s t o i c h i o m e t r y o f t h e p r o p o s e d r e a c t i o n is : H N. 2

H NCH CH NHCH2CH OH 2

2

2

+

2

C o (II)

Co

HCH

(II)

-Bsg.

H

H, -C H

H

H N 2

/

HCH

H Ο

H Ο

H N

H N 2

2

HCH

\

Co

-(CH,0)

(III)

HCH

(III)

Co

H

-NH

H

2

H A m m o n i a is f o r m e d i n t h e r e a c t i o n .

Since the

ammonia and ethylenediamine

cannot b o t h b e f o r m e d f r o m the same m o l e c u l e of J V - h y d r o x y e t h y l e t h y l e n e d i a m i n e , t h e b e s t e x p l a n a t i o n is t h a t t h e a m m o n i a is f o r m e d b y a r e a c t i o n s e q u e n c e s i m i l a r to the

mechanism

the c a r b o n adjacent coordinated formation

of

proposed

above,

except that the

oxygen

entirely

now

attacks

to t h e p r i m a r y n i t r o g e n o f t h e e t h y l e n e d i a m i n e g r o u p o f

N-hydroxyethylethylenediamine. ethanolamine.

The

presence

Such or

a

absence

process of

would

the

result

ethanolamine

in

in

the

r e a c t i o n m i x t u r e c o u l d n o t b e a s c e r t a i n e d , b e c a u s e n o m e t h o d w a s f o u n d to detect t h e p r e d i c t e d a m o u n t o f e t h a n o l a m i n e i n t h e p r e s e n c e o f a m u c h l a r g e r a m o u n t of N - h y droxyethylethylenediamine. A n i m p o r t a n t f e a t u r e o f t h e m e c h a n i s m p r o p o s e d a b o v e is t h a t o n e c o b a l t a t o m is o x i d i z e d t o c o b a l t ( I I I ) formed.

for e a c h m o l e c u l e of e t h y l e n e d i a m i n e or

S i n c e the cobalt (III)

s t a t e is e s t a b l i s h e d b e t w e e n the a m o u n t of c o b a l t (III)

f o r m e d is r e d u c e d

cobalt (II)

and

a g a i n to c o b a l t ( I I ) ,

cobalt (III)

concentrations,

(II)

ammonia a

steady so

that

p r e s e n t w i l l n o t b e e q u a l to t h e s u m of the a m o u n t s


of



ethylenediamine

formed.

and

ammonia

Instead,

the

189

sum

of

the

amounts

of

e t h y l e n e d i a m i n e a n d a m m o n i a f o r m e d s h o u l d b e e q u a l to t h e t o t a l a m o u n t o f c o balt (II)

oxidized

to

cobalt (III).

The

total

amount

of

c o b a l t (II)

oxidized

increases c o n t i n u a l l y d u r i n g the reaction b e c a u s e of the r e d u c t i o n of the r e s u l t i n g cobalt (III) To

to c o b a l t ( I I )

in repeating the cycle.

test t h e v a l i d i t y o f t h e a s s u m p t i o n t h a t o n e c o b a l t ( I I )

cobalt (III)

pression f o r the total a m o u n t of c o b a l t (II) total c o b a l t (II) the

i o n is o x i d i z e d t o

for e a c h a m m o n i a or e t h y l e n e d i a m i n e m o l e c u l e f o r m e d , a kinetic oxidized was derived.

o x i d i z e d as c a l c u l a t e d f r o m t h i s e x p r e s s i o n w e r e

experimentally

determined

sums

of

the

amount

actual

reaction,

of

ex

T h e values compared

ethylenediamine

of

with and

ammonia formed. Because

of the

c o m p l e x i t y of the

four simplifying

assump

tions w e r e m a d e b e f o r e the d e r i v a t i o n was p e r f o r m e d . 1.

T h e a c t i v i t y o f t h e o x y g e n is c o n s t a n t t h r o u g h o u t t h e r e a c t i o n .

2.

T h e a c t i v i t y o f t h e c a r b o n c a t a l y s t is c o n s t a n t t h r o u g h o u t t h e r e a c t i o n .

3.

T h e N - h y d r o x y e t h y l e t h y l e n e d i a m i n e is p r e s e n t i n t h e r e a c t i o n s o l u t i o n i n

s u f f i c i e n t e x c e s s so t h a t its c o n c e n t r a t i o n

m a y b e considered essentially

constant

f o r at l e a s t t h e first 5 h o u r s o f t h e r e a c t i o n . 4.

T h e r e a c t i o n is a s s u m e d t o b e first o r d e r w i t h r e s p e c t t o c o b a l t ( I I )

con

centration. Based

o n these assumptions,

the

reaction

can

be

represented

in

simplified

f o r m as f o l l o w s : *NH CH CH NHCH CH OH 2

2

2

2

aCo

+

2

(II)

bNHoGH CH NH 2

where a > b a n d C o (III)

= NH CH CH NH 2

2

2

C o (III) The

Β = cobalt (III) B

0

0

2

+

2

+ N H

=

3

(a — b) N H b +

{a -

3

+

aCo (III)

(1)

b) = a

(2)

_ ί ϊ > C o (II)

e x p r e s s i o n f o r c o b a l t ( I I ) c o n c e n t r a t i o n at t i m e t w a s d e r i v e d as f o l l o w s :

L e t A = c o b a l t (II)

A

2

concentration concentration

= initial cobalt (II)

concentration

= initial cobalt (III)

at t = 0, A = A

and Β =

0

concentration = 0.

B

0

Then Β = A

— A

= —k\A + k B = k A - (ki + k )A 2

at

0

2

0

(3)

2

U p o n i n t e g r a t i n g a n d e v a l u a t i n g t h e i n t e g r a t i o n c o n s t a n t at t =

0:

*ιΛο*-'*ι + *ι» + *,Λο

(4)

U s i n g this e x p r e s s i o n f o r A , the total a m o u n t of c o b a l t (II) at t i m e t w a s d e r i v e d as f o l l o w s : cobalt (III).

Atf =

0,X

~di

=

=

o x i d i z e d to c o b a l t

total a m o u n t of c o b a l t ( I I )

(III)

o x i d i z e d to

0.

=

k l

I n t e g r a t i n g , a n d e v a l u a t i n g at t = y

Let X

L

(5)

0, g i v e

k^Ap kikoAp (ki + k y ^ (ki + * , ) 2

J

(ΪΓ + Ϊ 3 _

k A + ky 2

x

(*i

Q

{ k i + k i ) t

2


v

}


190 After the c o b a l t ( I I ) - c o b a l t ( I I I )

kB 2

A

f r o m E q u a t i o n 3.

s

and

s

and cobalt (III), respectively. ^ A

s t e a d y s t a t e is a t t a i n e d ,

B

=

0 = kA A

= J = Κ k

Β, = Ao -

A

(7)

a

2

E q u a t i o n 7 c a n b e u s e d to r e d u c e E q u a t i o n s 4 a n d 6 t o t h e f o l l o w i n g H

IA +l)t

X = ?J + k B,t A 0

10

_

2

0

=

12.82 X 1 0 ~

m o l e p e r liter of cobalt (III)

(8)

a

-

2

forms:

+ A

A = B*- « - ' k

F o r e x p e r i m e n t 3, A

?} - ***i** + »* A e

(9)

k

n

2

m o l e p e r liter of c o b a l t ( I I ) , A

H

a n d , therefore,

=

f r o m E q u a t i o n 7, Κ

Inserting these values into E q u a t i o n s 8 a n d 9 gives for A , the cobalt (II) tration, a n d X , the total a m o u n t of cobalt

(II)

o x i d i z e d to cobalt

5.81 X

— 1.207. concen

(III)

A = 7.0 *-2-*i'+ 5.8 X = 3.8 + 7.0ifc / -

squares

value of k

2

(26),

t i n T a b l e I. t calculated

(10)

3.8 *-2-*i«

2

The

+

s

of cobalt (II)

T h i s e x p r e s s i o n r e a r r a n g e s to g i v e :

k

8

dA/dt

are t h e steady-state concentrations

s

(11)

w a s d e t e r m i n e d f r o m E q u a t i o n 10 b y t h e m e t h o d o f least

using the experimental values of A [cobalt(II) T h e result w a s k

2

from Equation

30i

11

=

0.65 h r .

_

1

using the value

1

1

concentration]

k

2

1

=

1

0.65,

compared

Γ

T I M E (hours)

Figure 5. Total amount of cobalt(II) oxidized to cobalt(III) and sum of ethylenediamine and ammonia formed • Ο

and

F i g u r e 5 shows the c u r v e for X

Calculated total amount of cobalt(II) oxidized to cobalt(III) Sum of experimental amounts of ethylenediamine and ammonia formed


vs.

with the



191

experimentally determined values for the sums of the ethylenediamine and am monia concentrations (assuming that all the ammonia formed remained in solu tion) . The experimental values for the formation of ethylenediamine and ammonia did not enter into the derivation and evaluation of the theoretical curve. Figure 5 shows that the experimental sums of ethylenediamine and ammonia formed fall below the theoretical curve during the early stages of the reaction. This discrepancy may be caused by an error in the method of ammonia determi nation mentioned earlier. The amount of ammonia in the gas stream coming from the reaction solution would be less than the amount of ammonia being formed in the reaction solution during the early stages of the reaction, until the reaction solution becomes saturated with ammonia. Literature Cited (1) Bailar, J. C., "Chemistry of the Coordination Compounds," ACS Monograph 131, pp. 45-7, Reinhold, New York, 1956. (2) Basolo, F., Pearson, R. G., "Mechanisms of Inorganic Reactions," p. 341, Wiley, New York, 1958. (3) Ibid., pp. 340-1. (4) Bawn, C. Ε. H., Discussions Faraday Soc. 14, 181 (1953). (5) Cannan, R. K., Richardson, G. M., Biochem. J. 23, 1242 (1929). (6) Drinkard, W. C., Bauer, H. F., Bailar, J. C., Jr., J. Am. Chem. Soc. 82, 2002 (1960). (7) Duke, F. R., Ibid., 69, 2885 (1947). (8) Ibid., p. 3054. ( 9 ) Feigl, F., "Spot Tests in Organic Analysis," pp. 176-7, Elsevier, New York, 1956. (10) Ibid., p. 329. (11) Ibid., p. 340. (12) Ibid., p. 348. (13) Ibid., p. 355. (14) Huggins, D., Drinkard, W. C., Anal. Chem. 34, 1756 (1962). (15) Keller, R. N., Edwards, L.G.,J.Am. Chem. Soc. 74, 215 (1952). (16) Kida, S., Yoneda, H., Bull. Liberal Arts Coll., Wakayama Univ. (Nat. Sci.) 5, 9 (1955). (17) Klein, G., Linser, H., Mikrochemie (Pregl-Festschrift) 1929, 204. (18) Lewis, W. B., Coryell, C. D., Irvine, J. W., Jr., J. Chem. Soc. Suppl. Issue 2, S386 (1949). (19) Malaprade, M. L., Bull soc. chim. France 43, 683 (1928). (20) Martell, A. E., Calvin, M., "Chemistry of the Metal Chelate Compounds," pp. 33780, Prentice-Hall, New York, 1952. (21) Ibid., pp. 350-52. (22) Michaelis, L.,J.Biol.Chem. 84, 777 (1929). (23) Schubert, M.,J.Am. Chem. Soc. 54, 4077 (1932). (24) Schumb, W. C., Satterfïeld, C. N., Wentworth, R. L., "Hydrogen Peroxide," ACS Monograph 128, pp. 642, 661, Reinhold, New York, 1955. (25) Shepard, M., Ind. Eng. Chem., Anal. Ed. 19, 77 (1947). (26) Sokolnikoff, I. S., Sokolnikoff, E. S., "Higher Mathematics for Engineers and Physicists," pp. 536-44, McGraw-Hill, New York, 1941. (27) Stone, H.,J.Am. Chem. Soc. 58, 2591-5 (1936). (28) Tomula, E. S., Z. anal. Chem. 83, 6 (1931). (29) Weissberger, Α., LuValle, J. E., J. Am. Chem. Soc. 66, 700 (1944). (30) Weissberger, Α., LuValle, J. E., Thomas, D. S., Jr., Ibid., 65, 1934 (1943). (31) Yoe, J. H., Reid, L. C., Ind. Eng. Chem.,Anal.Ed. 19, 77 (1947). RECEIVED August 27, 1962.


Reactions of Coordinated Ligands and Homogeneous Catalysis

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