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The preparation and base hydrolysis kinetics of macrocyclic trans-diammine([14]diene)cobalt(III) complexes
INORG.
NUCL.
C H E M . LET'rERS
Vol.
12,
pp.
85-88,
1976.
Pergamon
Press.
Printed
in
Great
Britain.
THE PREPARATION AND BASE HYDROLYSIS KINETICS OF MACROCYCLIC trans-DIAMMINE([14]DIENE)COBALT(III) COMPLEXES Geoffrey A. Lawrlnce Department of Inorganic Chemistry, University of Melbourne, Parkville
3052, Australia
~ece~ed 20 Sep~mber 1975)
Recently, preparation
a great deal of interest has been shown in the
(1) and hydrolysis kinetics (2) of c o b a l t ( I I I )
complexes of macrocyclic Me6114]-4,11-diene* Mez[14]-4,11-diene
amines. The Curtis macrocycle
( I ) and the s t r u c t u r a l l y similar macrocycle
( I I ) can be readily prepared (3,4) and have
been shown to have the trans-diene structure from c r y s t a l lographic evidence (5,6).
Geminal methyl groups present in the
Me6114]-4,11-diene ligand are absent in the Me2114]-4,11-diene ligand.
Fourteen-membered tetraamine macrocycles with a
cis-diene structure, such as Mez[14]-1,3-diene been reported
(III)
have also
(7).
During the course of recent investigations of the preparation and kinetics of macrocyclic
c o b a l t ( I I I ) complexes, a simple
preparation of the trans-diammine
c o b a l t ( I I I ) complexes of the
macrocycles Me6114]-4,11-diene and Me2114]-4,11-diene was developed. observations
This reaction is reported here, together with some on the base hydrolysis kinetics of the prepared
complexes.
* The abbreviations Me6114]-4,11-diene = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, Me2114]-4,11-diene = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene,and Me2114]-1,3-diene = 2,3-dimethyl-1,4,8,11tetraazacyclotetradeca-l,3-diene w i l l be used throughout. 85
86
Base Hydrolysis Kinetics
Vol. 12, No. I
C (R = CH3)
(±)
(~)
The preparation
(±is)
of the complexes was performed in the
trans-[Co(Me2114]-4,11-diene)C12](ClO~) and trans-[Co(Me6114]-4,11-diene)C12](ClO,) were prepared as previously reported (4,8). The trans-dichloro camplex (1 g) was following manner:
s t i r r e d at approximately 55° in hot methanol (50 cm3), and concentrated aqueous ammonia (2 cm~) was added. The solution went rapidly brown, and then concentrated hydrochloric acid was added dropwise u n t i l
the solution was j u s t acid to litmus.
Finally, more concentrated aqueous ammonia (3 cm3) was added, and the yellow suspension which formed immediately cooled in an ice-bath for approximately 30 minutes, then separated by f i l t r a t ion (yield approx. 0.8 g).
The complexes can be recrystallized
from hot d i l u t e perchloric acid as the r e l a t i v e l y insoluble perchlorate s a l t , or rapidly from hot water as the mixed chloride perchlorate s a l t .
(Analysis for [Co(Me6114]-4,11-diene)(NH3)2]
(CIO,)3.½H20 requires 28.2%C, 5.7%H and 12.3%N; Found : 28.2%C, 5.5%H and 12.3%N. Analysis for [Co(Me2114]-4,11-diene)(NH3)2] Cl2(ClO,)
requires 29.6%C, 6.2%H and 17.2%N; Found : 29.8%C,
5.9%H and 17.0%N.) Visible absorption, infrared and proton magnetic resonance spectra are consistent with the assignment of a trans configuration to the complexes.
This preparation
is more readily
performed than that previously reported for the Me6114]-4,11diene complex using ligand ammonia (9), with the complexes prepared by both methods being spectroscopically identical.
Vol. 12, No. 1
Base Hydrolysis Kinetics
87
K i n e t i c s of the base h y d r o l y s i s of the f i r s t
ammine l i g a n d
in the two complexes prepared were f o l l o w e d s p e c t r o p h o t o m e t r i c a l l y at 290nm using a Cary 17 spectrophotometer f i t t e d statted cell-holder.
w i t h a thermo-
B u f f e r s of 2 , 6 - 1 u t i d i n e - p e r c h l o r i c acid
(pH range 6.0 to 6.8) or sodium carbonate-sodium b i c a r b o n a t e (pH range 9.8 to 10.6) at an i o n i c s t r e n g t h of 0.1 mol dm-3 adjusted w i t h sodium p e r c h l o r a t e were used.
Results obtained at
25 ° are reported i n Table 1. TABLE 1. Base H y d r o l y s i s K i n e t i c s f o r the F i r s t Ammine Ligand o f t r a n e - [ C o ( L ) ( N H 3 ) 2 ] 3+ at 25° and I : [OH-]
pH
( m o l dm-3)
kob s (s - I )
0.1 mol dm-3 koH (mol-ldm3s - I )
(L = Me6114]-4,11-diene) 5.98
1.25 x 10 -8
0.96 x 10 -3
7.68 x 104
6.20
2.07 x 10 -8
1.60 x 10-3
7.75 x 10 ~
6.40
3.28 x 10 -8
2.56 x 10-3
7.80 x 104
6.52
4.32 x 10 -8
3.23 x 10 -3
7.50 x 104
6.82
8.63 x 10-8
6.43 x 10 -3
7.45 x 10~
(L = Me2114]-4,11-diene) 9.80
8.24 x I0 -s
2.62 x 10-4
3.17
9.98
1.25 x 10-4
3.84 x 10 -~
3.08
10.19
2.02 x 10-4
6.27 x 10-4
3.10
10.37
3.06 x 10 -4
10.00 x 10 -~
3.27
10.58
4.97 x 10 -~
16.05 x 10 -~
3.23
A large lysis
(2 x 10 ~ ) r a t e enhancement i s observed f o r the hydro-
o f the ammine l i g a n d i n the Me6114]-4,11-diene complex
(kOH = 7.6 x 104 mol-ldm3s - I ) Me2114]-4,11-diene complex
r e l a t i v e to t h a t observed f o r the
(kOH = 3.2 m o l - l d m 3 s - 1 ) .
This i s
l a r g e r than a r a t e enhancement of 8 x 102 reported f o r the base h y d r o l y s i s o f the f i r s t relative
to t h a t
ammine i n the M e B [ 1 4 ] - 4 , 1 1 - d i e n e complex
i n the Me2114]-1,3-diene complex
enhancement observed i n t h i s
(10).
The r a t e
study o f the trans-diammine complexes
c o n t r a s t s w i t h the reported 3 x 102 decrease i n the r a t e of h y d r o l y s i s o f the f i r s t Cl2] + r e l a t i v e
c h l o r i n e in t r a n s - [ C o ( M e 6 1 1 4 ] - 4 , 1 1 - d i e n e )
to t h a t recorded f o r the t~ans-[Co(Me2114]-4,11-
88
Base Hydrolysis Kinetics
Vol. 12, No. 1
diene)Cl2] + complex (11). Base hydrolysis of amine complexes of c o b a l t ( I l l ) is thought to follow an SNICB mechanism, involving deprotonation ligand followed base (12).
of an amine
by a dissociative reaction of the amido conjugate
When dissociation of the amido complex is the rate-
determining step steric acceleration would be expected, but ratedetermining proton extraction may lead to steric retardation (11). A change in the rate determining step may therefore account for the d i f f e r e n t behaviour in the trans-diammine and trans-dichloro complexes, though detailed speculation
is not warranted u n t i l
mechanistic details for the reactions become available. REFERENCES 1.
L.F. LINDOY and D.H. BUSCH, Prep. Inorg. React.,
2.
C . K . POON, Coord. Chem. Rev., 1973, 10, 1.
3.
R.W. HAY, G.A. LAWRANCE and N.F. CURTIS, J.C.S.(Perkin I ) ,
1971, 6, 1.
1975, 591. 4.
R.W. HAY and G.A. LAWRANCE, J.C.S.(Dalton), in press.
5.
M.F. BAILEY and I.E. MAXWELL, J.C.S.(Dalton), 1972, 938.
6.
R.J. RESTIVO, J. HORLEY and G. FERGUSON, J.C.S.(Dalton), in press.
7.
S . C . JACKELS, K, FARMERY, E.K. BAREFIELD, N.J. ROSE and D.H. BUSCH, Inorg. Chem., 1972, 11, 2893.
8.
N . F . SADISIVAN, J.A.
KERNOHAN and J.F. ENDICOTT, Inorg. Chem.,
1967, 6, 770. 9. 10.
D . P . RILLEMA and J.F. ENDICOTT, Inorg. Chem., 1972, 11, 2361. D . P . RILLE~A, J.F. ENDICOTT and J.R. BARBER, J. Amer. Chem. Soc., 1975, 95, 6987.
11.
R.W. HAY and G.A. LAWRANCE, J.C.S.(Dalton), in press.
12.
M . L . TOBE, Aoc. Chem. Res., 1970, 3, 337.
NUCL.
C H E M . LET'rERS
Vol.
12,
pp.
85-88,
1976.
Pergamon
Press.
Printed
in
Great
Britain.
THE PREPARATION AND BASE HYDROLYSIS KINETICS OF MACROCYCLIC trans-DIAMMINE([14]DIENE)COBALT(III) COMPLEXES Geoffrey A. Lawrlnce Department of Inorganic Chemistry, University of Melbourne, Parkville
3052, Australia
~ece~ed 20 Sep~mber 1975)
Recently, preparation
a great deal of interest has been shown in the
(1) and hydrolysis kinetics (2) of c o b a l t ( I I I )
complexes of macrocyclic Me6114]-4,11-diene* Mez[14]-4,11-diene
amines. The Curtis macrocycle
( I ) and the s t r u c t u r a l l y similar macrocycle
( I I ) can be readily prepared (3,4) and have
been shown to have the trans-diene structure from c r y s t a l lographic evidence (5,6).
Geminal methyl groups present in the
Me6114]-4,11-diene ligand are absent in the Me2114]-4,11-diene ligand.
Fourteen-membered tetraamine macrocycles with a
cis-diene structure, such as Mez[14]-1,3-diene been reported
(III)
have also
(7).
During the course of recent investigations of the preparation and kinetics of macrocyclic
c o b a l t ( I I I ) complexes, a simple
preparation of the trans-diammine
c o b a l t ( I I I ) complexes of the
macrocycles Me6114]-4,11-diene and Me2114]-4,11-diene was developed. observations
This reaction is reported here, together with some on the base hydrolysis kinetics of the prepared
complexes.
* The abbreviations Me6114]-4,11-diene = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, Me2114]-4,11-diene = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene,and Me2114]-1,3-diene = 2,3-dimethyl-1,4,8,11tetraazacyclotetradeca-l,3-diene w i l l be used throughout. 85
86
Base Hydrolysis Kinetics
Vol. 12, No. I
C (R = CH3)
(±)
(~)
The preparation
(±is)
of the complexes was performed in the
trans-[Co(Me2114]-4,11-diene)C12](ClO~) and trans-[Co(Me6114]-4,11-diene)C12](ClO,) were prepared as previously reported (4,8). The trans-dichloro camplex (1 g) was following manner:
s t i r r e d at approximately 55° in hot methanol (50 cm3), and concentrated aqueous ammonia (2 cm~) was added. The solution went rapidly brown, and then concentrated hydrochloric acid was added dropwise u n t i l
the solution was j u s t acid to litmus.
Finally, more concentrated aqueous ammonia (3 cm3) was added, and the yellow suspension which formed immediately cooled in an ice-bath for approximately 30 minutes, then separated by f i l t r a t ion (yield approx. 0.8 g).
The complexes can be recrystallized
from hot d i l u t e perchloric acid as the r e l a t i v e l y insoluble perchlorate s a l t , or rapidly from hot water as the mixed chloride perchlorate s a l t .
(Analysis for [Co(Me6114]-4,11-diene)(NH3)2]
(CIO,)3.½H20 requires 28.2%C, 5.7%H and 12.3%N; Found : 28.2%C, 5.5%H and 12.3%N. Analysis for [Co(Me2114]-4,11-diene)(NH3)2] Cl2(ClO,)
requires 29.6%C, 6.2%H and 17.2%N; Found : 29.8%C,
5.9%H and 17.0%N.) Visible absorption, infrared and proton magnetic resonance spectra are consistent with the assignment of a trans configuration to the complexes.
This preparation
is more readily
performed than that previously reported for the Me6114]-4,11diene complex using ligand ammonia (9), with the complexes prepared by both methods being spectroscopically identical.
Vol. 12, No. 1
Base Hydrolysis Kinetics
87
K i n e t i c s of the base h y d r o l y s i s of the f i r s t
ammine l i g a n d
in the two complexes prepared were f o l l o w e d s p e c t r o p h o t o m e t r i c a l l y at 290nm using a Cary 17 spectrophotometer f i t t e d statted cell-holder.
w i t h a thermo-
B u f f e r s of 2 , 6 - 1 u t i d i n e - p e r c h l o r i c acid
(pH range 6.0 to 6.8) or sodium carbonate-sodium b i c a r b o n a t e (pH range 9.8 to 10.6) at an i o n i c s t r e n g t h of 0.1 mol dm-3 adjusted w i t h sodium p e r c h l o r a t e were used.
Results obtained at
25 ° are reported i n Table 1. TABLE 1. Base H y d r o l y s i s K i n e t i c s f o r the F i r s t Ammine Ligand o f t r a n e - [ C o ( L ) ( N H 3 ) 2 ] 3+ at 25° and I : [OH-]
pH
( m o l dm-3)
kob s (s - I )
0.1 mol dm-3 koH (mol-ldm3s - I )
(L = Me6114]-4,11-diene) 5.98
1.25 x 10 -8
0.96 x 10 -3
7.68 x 104
6.20
2.07 x 10 -8
1.60 x 10-3
7.75 x 10 ~
6.40
3.28 x 10 -8
2.56 x 10-3
7.80 x 104
6.52
4.32 x 10 -8
3.23 x 10 -3
7.50 x 104
6.82
8.63 x 10-8
6.43 x 10 -3
7.45 x 10~
(L = Me2114]-4,11-diene) 9.80
8.24 x I0 -s
2.62 x 10-4
3.17
9.98
1.25 x 10-4
3.84 x 10 -~
3.08
10.19
2.02 x 10-4
6.27 x 10-4
3.10
10.37
3.06 x 10 -4
10.00 x 10 -~
3.27
10.58
4.97 x 10 -~
16.05 x 10 -~
3.23
A large lysis
(2 x 10 ~ ) r a t e enhancement i s observed f o r the hydro-
o f the ammine l i g a n d i n the Me6114]-4,11-diene complex
(kOH = 7.6 x 104 mol-ldm3s - I ) Me2114]-4,11-diene complex
r e l a t i v e to t h a t observed f o r the
(kOH = 3.2 m o l - l d m 3 s - 1 ) .
This i s
l a r g e r than a r a t e enhancement of 8 x 102 reported f o r the base h y d r o l y s i s o f the f i r s t relative
to t h a t
ammine i n the M e B [ 1 4 ] - 4 , 1 1 - d i e n e complex
i n the Me2114]-1,3-diene complex
enhancement observed i n t h i s
(10).
The r a t e
study o f the trans-diammine complexes
c o n t r a s t s w i t h the reported 3 x 102 decrease i n the r a t e of h y d r o l y s i s o f the f i r s t Cl2] + r e l a t i v e
c h l o r i n e in t r a n s - [ C o ( M e 6 1 1 4 ] - 4 , 1 1 - d i e n e )
to t h a t recorded f o r the t~ans-[Co(Me2114]-4,11-
88
Base Hydrolysis Kinetics
Vol. 12, No. 1
diene)Cl2] + complex (11). Base hydrolysis of amine complexes of c o b a l t ( I l l ) is thought to follow an SNICB mechanism, involving deprotonation ligand followed base (12).
of an amine
by a dissociative reaction of the amido conjugate
When dissociation of the amido complex is the rate-
determining step steric acceleration would be expected, but ratedetermining proton extraction may lead to steric retardation (11). A change in the rate determining step may therefore account for the d i f f e r e n t behaviour in the trans-diammine and trans-dichloro complexes, though detailed speculation
is not warranted u n t i l
mechanistic details for the reactions become available. REFERENCES 1.
L.F. LINDOY and D.H. BUSCH, Prep. Inorg. React.,
2.
C . K . POON, Coord. Chem. Rev., 1973, 10, 1.
3.
R.W. HAY, G.A. LAWRANCE and N.F. CURTIS, J.C.S.(Perkin I ) ,
1971, 6, 1.
1975, 591. 4.
R.W. HAY and G.A. LAWRANCE, J.C.S.(Dalton), in press.
5.
M.F. BAILEY and I.E. MAXWELL, J.C.S.(Dalton), 1972, 938.
6.
R.J. RESTIVO, J. HORLEY and G. FERGUSON, J.C.S.(Dalton), in press.
7.
S . C . JACKELS, K, FARMERY, E.K. BAREFIELD, N.J. ROSE and D.H. BUSCH, Inorg. Chem., 1972, 11, 2893.
8.
N . F . SADISIVAN, J.A.
KERNOHAN and J.F. ENDICOTT, Inorg. Chem.,
1967, 6, 770. 9. 10.
D . P . RILLEMA and J.F. ENDICOTT, Inorg. Chem., 1972, 11, 2361. D . P . RILLE~A, J.F. ENDICOTT and J.R. BARBER, J. Amer. Chem. Soc., 1975, 95, 6987.
11.
R.W. HAY and G.A. LAWRANCE, J.C.S.(Dalton), in press.
12.
M . L . TOBE, Aoc. Chem. Res., 1970, 3, 337.