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On the α-dioximine complexes of transition metals—XLI.
J. inorg, aud. Chem., 1974, Vol. 36, pp. 2199 2202. Pergamon Press. Printed in Great Britain.
ON THE 0~-DIOXIMINE COMPLEXES OF TRANSITION
METALS -XLI.
THE AZIDO-HALOGENO-BIS-DIMETHYLGLYOXI MATO-COBALTIAT A C I D S A N D THE AQUATION KINETICS OF T H E [Co(DH)2(N3)X]
- IONS
Z. FINTA and Cs. VARHELYI Faculty of Chemistry, "Babes-Bolyai" University, Cluj, Rumania (Receired 13 Noremher 1973) The synthesis of the complex acids H[Co(DH)2(N3JX ], iDH 2 = dimethylglyoxime, X - ('1. Br or I), their chemical properties, i.r. spectra and the synthesis of 15 of its salts are reported. In aqueous solutions of these complex anions halide ions are liberated due to an aquation process. The aquation rate is practically independent on pH between 1 and 5. The rate constants of the aquation decrease, while the corresponding activation enthalpy values increase in the order CI < Br < I. This order is similar to that of the increasing values of the nucleophilic constants of the halide ions.
Abstract
THE FORMATION of complex metal-azides in aqueous solutions and in n o n a q u e o u s solvents has been investigated by means of spectroscopic, potentiometric and electric conductance measurements, and the existence of some metal-azide specia (IMe(H2OI s(N3)] "+, [Me(H20),dN3)2] "+, etc.) was demonstrated
The azide ion enters easily in the inner coordination sphere of mixed cobaltllll)-complexes and due to the r~-donor properties of this ligand, the overlapping of its occupied n-orbitals with the d-orbitals of the transition metal ion also occurs. We have observed that the mixed azido-halogcnobis-dimethyl-glyoximato-cobalt{lll) ions [ ( ' o I D t l ) : ( N 3 ) X ] are formed easily by treating the ct)rrcsponding dihalogeno-acids with a stoichiometrlc a m o u n t of N a N 3 :
[l 5]. Homogeneous [Me(N3h]" and [Me(N3)6]"- type azido-complexes were obtained with chromium[6], cobalt(II)[7], copper[8], iron(Ill)t9], etc. The slightly explosible alkaline salts of the [Sn(N3)6] 2 , [Rh(N3)613 , [Pt(N3)6] 2-, [Mn(N3)4] 2-, [Au(N3)4] and [Hg(N3)4] 2- were stabilized by their transformation in tetraphenylarsonium- and t e t r a p h e n y l p h o s p h o n i u m salts[10, 11]. " M i x e d " classical azido-complexes and chelate c o m p o u n d s are also known in a considerable n u m b e r (e.g. ICo(NH3)5(N3)]2+, [Cr(en)2(N3)2]+ [12], ICo(en)2(NO2)(N3)] +,[Co(en)2(N3)2] + [ 13],[Fe(o_phen)2(N3)2] + [14], [Rh(NH3)5(N3)] 2+ [15]). In the class of the mixed bis-c~-dioximine-chelates of cobalt(III), the first azido-derivative: [Co(DH)2(NO2)(N3)]- has been isolated and described in a previous paper I 16].
H[Co{DH)2X2] + N 3- = H[Co(DH)e(N~IX] ! Y . If an excess of N a N 3 is used, the second halide ion is also exchanged and the diazido- ion : (Co(DH),i N 3 !~ is formed. The [Co(DH)2(N3)X ] ions may be obtained also by the substitution of water with (NO ion in [CoII)tt!~t H 2 0 ) X ] nonelectrolytic complexes, but in this
Table 1. New complex acids of the lype H[ColDH)2(N3~X ] Mol. wt. calcd
Yield ( ",,1
H[Co(DH)2(N3}Cll . 2H20
403.6
75
Green rhomb, plates
H[Co(DH)2(Br)(N ~)]. 2H20
448-05
60
Green-yellow r h o m b plates
H[Co(DH)2(N3)II. 2H20
495.1
80
Brilliant brown irregular plates
Formula
Analysi~
2199
Aspect Co H20 Co H20 N Co N
Calcd
t mind
14.59 8.92 13.14 8.01 21.SS I 1.91 19-81
14.47 8.711 12.711 7.40 21.6ti I 1.92 19.60
Z. FINTA and Cs. VARHELYI
2200
The azido-halogeno-acids obtained are characterized in Table 1. Like the other [Co(~-diox. H)2XY] - type anions, the azido-halogeno- complexes readily form slightly soluble precipitates with monovalent metal ions, as Cu +, Ag +, T1 +, Cs ÷, Hg~ + and with diacido-tetramine type complexes of cobalt(Ill)- and chromium(III) (e.g. [Me(NH3)4X2]+, [Me(en)2X2] +, [Me(pn)2X2] +). One cannot perform double decomposition reactions with hexamine- and monoacido-pentamine type complexes of this metal, as [Me(NH3)6] 3+, [Me(en)3] 3+, [Me(pn)3] 3 +, [Me(en)2X amine] 2 +, etc. The formation of crystalline products of the type [Co(,-diox.H)2(amine)2 ] . [Co(DH)2(N3)X] is characteristic also in this case (,-diox.H2 stands for a molecule of cyclopentane-, cyclohexane-, or cycloheptanedionedioxime, dimethylglyoxime, or diamino-glyoxime, respectively, amine stands for ammonia, aromatic amines, or pyridine bases). Data for 15 new derivatives of the H[Co(DH)z(N3)X] acids are given in Table 2. The i.r. spectra of the H[Co(DH)2(N3)X] complex acids (Fig. 1) show the presence of strong intramolecular O - - H . . . O hydrogen bridges, similar to
100
50
i i
t00 i
50
rl 2400
2000
1600
1200
800
Wovele ngt"h,
600 500 400
cm -I
Fig. 1. Infrared absorption spectra of H[Co(DH)2(N3)CII and H[Co(DH)2(Na)Br ]. those observed in the case of the analogous H[Co(a-diox. H)2X2] derivatives (~O--H : 2300-2350 c m - 1 (weak), 6 0 - - H : 1700-1750 c m - 1 (weak)). These hydrogen bridges stabilize the coplanar Co(DH)2 ring system,
Table 2. Cobalt(Ill)- and chromium(IIl)-amine derivatives of the H[Co(DH)z(N3)XI- acids
No.
Formula
Mol. wt. calcd
Analyis Yield ("~,)
1. trans-[Co(en)2C12]. [Co(DH)/(N3)CI ]
616.4
60
2. trans-[Co(en)2Cl2] . [Co(DH)E(N3)Br]
660.9
50
3. trans-[Co(en)2Cl2]. [Co(DH)2(N3)I ]
707.9
70
4. trans-[Cr(en)z(NCS)2]. [Co(DH)2(N3)CI]
655-8
80
Aspect Green-yellow rhomb, prisms Green-yellow short prisms Brilliant, brown rhomb, plates Brilliant, yellow
Calcd Co N Co
1 9 . 1 2 19.90 24.98 24.70 17.83 17.70
Co N
16.27 21.76
700.25 80
6. trans-[Cr(en)z(NCS)z]. [Co(DH)z(N3)I]
747-25
85
7. [Co(DH)2(pyridine)2 ]. [Co(DH)2(N3)CI]
813.9
70
8. [Co(DH)2(pyridine)2]. [Co(DH)2(Na)Br] 9. [Co(DH)2(pyridine)2]. (Co(DH)2(N3)I]
858.4 905.4
76 80
942.1
85
986.6
80
1033-6
85
10. [Co(DH)2(p-naphtyl-amine)2] [Co(DH)2(N 3)C1] 11.
[Co(DH)2(fl-naphtyl-amine)2][Co(DH)2(N3)Br]
12. [Co(DH)2(fl-naphtyl-amine)2][Co(DH)2(N3)I] 13. [Co(DH)z(p-toluidine)2 ] . [Co(DH)z(N3)CI]
870
60
14. [Co(DH)2(p-toluidine)2 ]. [Co(DH)z(N3)Br ] 15. [Co(DH)z(p-toluidine)z ]. [Co(DH)z(N3)I ]
914.4 961.4
65 75
16.10 21.48
1 C0304 q_ i C r 2 0 3
23.82 27.77
N 5. trans-[Cr(en)z(NCS)2] . [Co(DH)2(N3)Br]
Found
23.50 27.89
dendrites Brown dendrites
I C03O 4 11 1 Cr203
Dark brown hexagonal plates
C0304 ~- 2tCr203
Sparkling, brown plates Brown plates Dark brown plates Light brown microcryst. Brown microcryst. Dark brown microcryst Brown-yellow irregular plates Brown dendrites Dark brown prisms
22.31 26.00
N
22.14 26.30
N Co
20.91 24.37 14.48
20.60 24.31 14-25
Co Co N Co
13.73 13-02 20-11 12.51
13-45 12-86 19.70 12-37
Co N Co
11.95 11-70 18.44 18.63 1 1 . 4 0 11.18
Co N Co Co N
13.50 20.93 12-89 12.26 18.94
13.30 21.25 12.77 12-35 18.73
On the c~-dioximine complexes of transition metals
2201
XLI
Table 4. pH values of the half neutralized H[Co{ D H L, N 3 iX i acids
0"4
II
Complex acid
O3
pH
HICo(DH)2(N3)CI H'~Co(DH)z(N3)Br ~ H ~Co(DHJ2(N3)I OI
2.99 3.00 3.02
Concentration of lhe complexes: 2.10 :~M, t (" = 25' u = 0-t M; neutralization with KOtt tip to 50" ,. : I0
20
40
30 t
?
Table 5. Kinetic parameters of the aquation of ~Co(DH)2(N3)X 1- type complexes
50
rain
Fig. 2. First order kinetic curves of the aquation of [Co{DH)2(N3)X 3- ions at 40°C and pH = 1.0: I. [Co(DH)z(NdCI] : II. [Co(DHJ2(N3)Br ]- ;IIl. [Co(DH)z(N3)I]-. i.e. the trans geometric configuration of the azidohalogeno-complexes and therefore ligand exchange reactions occur with retention of configuration. Valence vibrations of the coordinated N3-grou p and the N3 deformation vibrations appear at v N 3 : 2 0 3 5 - 2 0 4 0 (strong), 1330, 1280 (medium), ON3: 6 2 0 - 6 3 0 c m 1 (strong). The "~Co-N 3 are observed at 400-410 c m - t . The values ~'N3 and 6N 3, as compared to those of N a N 3 C N 3 : 2 1 2 0 - 2 1 4 0 (strong) a n d 6 N 3 : 6 4 3 cm 1 (strong) show a strong covalent character of the Coazide bond. The ; ' C ~ N , ~'N--O frequencies of the coordinated dimethyl-glyoxime appear at 1560-1570 (medium), 1235 1240 (strong), 1085--1090 c m - X ( s t r o n g - - not influenced by coordination effect. In aqueous solutions of the azido-halogeno-complex acids a ligand exchange reaction occurs leading to the liberation of halide ions : [Co(DH)2(N3)X ] - + H 2 0 = ICo(DH)2(N3)(H20)] + X - .
(2)
Kinetics of these reactions were studied in acidic solutions at a constant ionic strength of ,u = 0.1 M. In order to test the influence of acidity on the aquation rate, kinetic measurements were carried out at differing hydrogen ion concentrations, in a pH range between
'(
AH ;= (kcal/mole)
AS s (e.u.)
/,,,
(?1 Fir l
25.5 _+ 0-3 26.3 + 0-3 27-2 _+ 0.4
9.3 10.5 6-3
1.24 1.51 2.06
1 and 5, taking in account the possibility of the following protolytic equilibrium H +
[Co(DH)2(N3)X ] - ~ [ C o ( D H ) ( D H 2 i i N 3 j X ] [3! The reactions were followed by measuring the variation of the concentration of free halide ions, by means of the method described in the experinaental part. The plot of log Co/C o - c values vs. time give a good linearity, as seen in Fig. 2. The first order rate constant values calculated froln these straight lines and given in Table 3 show thai aquation rate is practically independent on pH, and this result enables us to conclude that in our experimental conditions the equilibrium (3) is shifted to the conjugated base, i.e. the corresponding protonaled forms are rather strong acids. This conclusion is also supported by the resuhs ot the pH-measurements presented in Table 4. F r o m the linear relationship between log k. T and 1 / T , activation parameters of the studied reactions wcrc derived, by means of the least square method. These values are given in Table 5. The data presented in Tables 3 and 5 show that the rate constants of the studies reactions decrease, while
Table 3. First order rate constants for the aquation of ICo(DH)2(N3)X]- complexes 10Sk, sec X CI Br I
pH 1.0 2.0 5.0 1-0 2.0 5.0 I-0 2-0 5.0
20°
25°
30°.
35°
40 °
45 °
50°
55°
6.65 6.58 6.72 3.06 3-12 2-99 -
14.3 --
28.8
60.1
-13-8
28.8
116 114 120 60.0 60.7 59.4 1.60
3.11
6.14
11.9
6.65 -----
0-728 0-729 0.734
12-0 12.4
2202
Z. FINTA and Cs. V,~RHELY1
the c o r r e s p o n d i n g activation e n t h a l p y values increase in the o r d e r C1, Br, I. This o r d e r is similar to that of the increasing values o f the nucleophilic c o n s t a n t s of halide ions k,[17], which are also included in Table 5, and indicate a "soft a c i d " b e h a v i o u r of the Co(III) ion in these complexes.
EXPERIMENTAL Synthesis of H[Co(DH)2(N3)X] acids 0.1mole H[Co(DH)2CI2], H[Co(DH)2Br2] or H[Co(DH)212], respectively, were treated in 200-300ml water with 00.8-00.9 mole NaN 3 in 25 ml aqueous solution. The dihalogeno-acids dissolve after 5-10 min. by a continuous stirring and reddish-violet solutions are formed. The mixture was ice cooled and filtered after 20-25 min and the free acids were precipitated with a large excess of 30-35 per cent sulfuric acid. The crystalline precipitates are filtered after 1 i hr, washed with a small amount of ice cold water and with a 10:1 mixture of ether and alcohol and dried in air.
Kinetic measurements The concentration of the liberated halide ions has been determined by Selbin and Bailar's method[18], measuring the EMF of the following concentrations cell : Ag/AgX, studied solution/0.1 M NaNO3/10 -3 M K X solution, AgX/Ag. Both the studied solution and the standard one have contained the same amounts of HCIO 4 or acetic acid sodium acetate buffer solution and NaNO3, in order to ensure the acidity desired and a constant ionic strength of ,u = 0.1 M. Samples were dissolved in the preheated solution and the system was thermostated at the working temperature, with an accuracy of +0.01°C. Electrodes were prepared according to the indications of Selbin and Bailar, but a less current density was used, in order to improve their quality. Silvering of the platinum electrodes was made 10 hr long, with a current density of 1 mA/cm 2. The formation of AgX layer lasted 1 hr, in the same conditions. Electrodes were calibrated before and after each kinetic run, measuring the EMF of the used KX solutions in dilutions by ratios of 1 : 1, 1 : 10 and 1 : 100.
Synthesis of [Me(amine)4X2]. [Co(DH)2(N3)X 1 and [Co(DH)2 (amine)2]. [Co(DH)2(N3)X] 5 mmole of the corresponding diacidotetramine salt (C0(en)2CI23. C1, [Cr(en)2(NCS)2]. C10 4, [Co(DH)2(amine)23acetate) in 80-100ml water, or in 50 per cent alcohol, respectively, are treated with 5 mmole of H[Co(DH)2(Na)X] in 30-40 ml dil, alcohol (1:1). The crystalline precipitate is filtered after 4--2 1 1 hr, washed with a small amount of water and dried in air. Analysis Cobalt was determined complexometrically, by using murexide as indicator. Organic ligands were destroyed by heating with concentrated sulfuric acid and several crystals of K N O 3. After diluting with water to a volume of 60-80 ml, the solution was neutralized with sodium acetate and ammonia. In the chromium derivatives the sum of the oxides was determined, weighing Co30 4 + Cr20 3 after an hour of heating at 900°C. Nitrogen has been determined by the micro-Dumas method. Spectral investigations The i.r. spectra of HCo(DI-I)2(N3JX have been recorded in KBr pellets, by means of a UR 20 Carl Zeiss-Jena spectrophotometer from 40(~4000 c m - ~. pH-measurements pH-measurements were carried out at 25°C with an LPU-01 (U.S.S.R.) pH-meter having a glass-electrode as indicator and a saturated calomel as standard electrode. Samples were dissolved in thermostated 1-10-3 M KOH solutions containing 0-1 M KNO3, in order to obtain 2.10-3 M solutions of the complex acids neutralized up to 50 per cent and an ionic strength of # = 0.1 M. Measurements were performed immediately, excluding the possibility of the aquation.
REFERENCES 1. R. (3, Clem and E. H. Huffman, J. inorg, nucl. Chem. 27, 365 (1965). 2. R. G. Clem and E. H. Huffman, Anal. Chem. 37, 86, 1155 (1965). 3. F. G. Sherif and K. F. Michail, J. inorg, nucl. Chem. 25, 999 (1963). 4. F. G. Sherif and A. M. Awad, J. inorg, nucl. Chem. 24, 179 (1962). 5. V. Gutmann and O. Leitmann, Mh. Chem. 97, 926 (1966). 6. E. Oliveri-Mandala and G. Gomella, Gazz. chim. ital. 52, 112 (1922). 7. P. Senise, J. Am. chem. Sac. 81, 4196 (1959). 8. M. Straumanis and A. Cirulis, Z. anorg, allg. Chem. 252, 9, 121 (1944). 9. F. Kr6hnke and B. Sander, Z. anorg, allg. Chem. 334, 66 (1964). 10. W. Beck, E, Schuierer, K. Feldl, P. P611mann and W. P. Fehlhammer, Angew. Chem. 77, 458 (1965); 78, 267 (1966). 11. W. Beck, W. P. Fehlhammer, P. P611mann, E. Sehuierer and K. Feldl, Chem. Bet. 100, 2335 (1967). 12. M. Linhard, H. Flygare and M. Weigel, Z. anorg. allg. Chem. 262, 328 (1950); 263, 233, 245 (1950). 13. P. J, Staples and M. L. Tobe, J. chem. Sac. 4812 (1960) 3226 (1963). 14. K. Madeja, W. Wilke and S. Smidt, Z. anorg, allg. Chem. 346, 306 (1966). 15. C. S. Davis and G. C. Lalor, J. chem. Sac. (A), 445 (1970). 16. Cs. Vfirhelyi, F. Mfinok and S. Kiss, Studia Unit,. BabesBolyai, Chem. 18, (2) 105 (1973). 17. F. Basolo and R. G. Pearson, Mechanism Of Inorganic Reactions, 2nd Edn., pp. 183, 188. John Wiley, New York (1967). 18. J. Selbin and J. C. Bailar, J. Am. chem. Sac. 79, 4285 (1957).
ON THE 0~-DIOXIMINE COMPLEXES OF TRANSITION
METALS -XLI.
THE AZIDO-HALOGENO-BIS-DIMETHYLGLYOXI MATO-COBALTIAT A C I D S A N D THE AQUATION KINETICS OF T H E [Co(DH)2(N3)X]
- IONS
Z. FINTA and Cs. VARHELYI Faculty of Chemistry, "Babes-Bolyai" University, Cluj, Rumania (Receired 13 Noremher 1973) The synthesis of the complex acids H[Co(DH)2(N3JX ], iDH 2 = dimethylglyoxime, X - ('1. Br or I), their chemical properties, i.r. spectra and the synthesis of 15 of its salts are reported. In aqueous solutions of these complex anions halide ions are liberated due to an aquation process. The aquation rate is practically independent on pH between 1 and 5. The rate constants of the aquation decrease, while the corresponding activation enthalpy values increase in the order CI < Br < I. This order is similar to that of the increasing values of the nucleophilic constants of the halide ions.
Abstract
THE FORMATION of complex metal-azides in aqueous solutions and in n o n a q u e o u s solvents has been investigated by means of spectroscopic, potentiometric and electric conductance measurements, and the existence of some metal-azide specia (IMe(H2OI s(N3)] "+, [Me(H20),dN3)2] "+, etc.) was demonstrated
The azide ion enters easily in the inner coordination sphere of mixed cobaltllll)-complexes and due to the r~-donor properties of this ligand, the overlapping of its occupied n-orbitals with the d-orbitals of the transition metal ion also occurs. We have observed that the mixed azido-halogcnobis-dimethyl-glyoximato-cobalt{lll) ions [ ( ' o I D t l ) : ( N 3 ) X ] are formed easily by treating the ct)rrcsponding dihalogeno-acids with a stoichiometrlc a m o u n t of N a N 3 :
[l 5]. Homogeneous [Me(N3h]" and [Me(N3)6]"- type azido-complexes were obtained with chromium[6], cobalt(II)[7], copper[8], iron(Ill)t9], etc. The slightly explosible alkaline salts of the [Sn(N3)6] 2 , [Rh(N3)613 , [Pt(N3)6] 2-, [Mn(N3)4] 2-, [Au(N3)4] and [Hg(N3)4] 2- were stabilized by their transformation in tetraphenylarsonium- and t e t r a p h e n y l p h o s p h o n i u m salts[10, 11]. " M i x e d " classical azido-complexes and chelate c o m p o u n d s are also known in a considerable n u m b e r (e.g. ICo(NH3)5(N3)]2+, [Cr(en)2(N3)2]+ [12], ICo(en)2(NO2)(N3)] +,[Co(en)2(N3)2] + [ 13],[Fe(o_phen)2(N3)2] + [14], [Rh(NH3)5(N3)] 2+ [15]). In the class of the mixed bis-c~-dioximine-chelates of cobalt(III), the first azido-derivative: [Co(DH)2(NO2)(N3)]- has been isolated and described in a previous paper I 16].
H[Co{DH)2X2] + N 3- = H[Co(DH)e(N~IX] ! Y . If an excess of N a N 3 is used, the second halide ion is also exchanged and the diazido- ion : (Co(DH),i N 3 !~ is formed. The [Co(DH)2(N3)X ] ions may be obtained also by the substitution of water with (NO ion in [CoII)tt!~t H 2 0 ) X ] nonelectrolytic complexes, but in this
Table 1. New complex acids of the lype H[ColDH)2(N3~X ] Mol. wt. calcd
Yield ( ",,1
H[Co(DH)2(N3}Cll . 2H20
403.6
75
Green rhomb, plates
H[Co(DH)2(Br)(N ~)]. 2H20
448-05
60
Green-yellow r h o m b plates
H[Co(DH)2(N3)II. 2H20
495.1
80
Brilliant brown irregular plates
Formula
Analysi~
2199
Aspect Co H20 Co H20 N Co N
Calcd
t mind
14.59 8.92 13.14 8.01 21.SS I 1.91 19-81
14.47 8.711 12.711 7.40 21.6ti I 1.92 19.60
Z. FINTA and Cs. VARHELYI
2200
The azido-halogeno-acids obtained are characterized in Table 1. Like the other [Co(~-diox. H)2XY] - type anions, the azido-halogeno- complexes readily form slightly soluble precipitates with monovalent metal ions, as Cu +, Ag +, T1 +, Cs ÷, Hg~ + and with diacido-tetramine type complexes of cobalt(Ill)- and chromium(III) (e.g. [Me(NH3)4X2]+, [Me(en)2X2] +, [Me(pn)2X2] +). One cannot perform double decomposition reactions with hexamine- and monoacido-pentamine type complexes of this metal, as [Me(NH3)6] 3+, [Me(en)3] 3+, [Me(pn)3] 3 +, [Me(en)2X amine] 2 +, etc. The formation of crystalline products of the type [Co(,-diox.H)2(amine)2 ] . [Co(DH)2(N3)X] is characteristic also in this case (,-diox.H2 stands for a molecule of cyclopentane-, cyclohexane-, or cycloheptanedionedioxime, dimethylglyoxime, or diamino-glyoxime, respectively, amine stands for ammonia, aromatic amines, or pyridine bases). Data for 15 new derivatives of the H[Co(DH)z(N3)X] acids are given in Table 2. The i.r. spectra of the H[Co(DH)2(N3)X] complex acids (Fig. 1) show the presence of strong intramolecular O - - H . . . O hydrogen bridges, similar to
100
50
i i
t00 i
50
rl 2400
2000
1600
1200
800
Wovele ngt"h,
600 500 400
cm -I
Fig. 1. Infrared absorption spectra of H[Co(DH)2(N3)CII and H[Co(DH)2(Na)Br ]. those observed in the case of the analogous H[Co(a-diox. H)2X2] derivatives (~O--H : 2300-2350 c m - 1 (weak), 6 0 - - H : 1700-1750 c m - 1 (weak)). These hydrogen bridges stabilize the coplanar Co(DH)2 ring system,
Table 2. Cobalt(Ill)- and chromium(IIl)-amine derivatives of the H[Co(DH)z(N3)XI- acids
No.
Formula
Mol. wt. calcd
Analyis Yield ("~,)
1. trans-[Co(en)2C12]. [Co(DH)/(N3)CI ]
616.4
60
2. trans-[Co(en)2Cl2] . [Co(DH)E(N3)Br]
660.9
50
3. trans-[Co(en)2Cl2]. [Co(DH)2(N3)I ]
707.9
70
4. trans-[Cr(en)z(NCS)2]. [Co(DH)2(N3)CI]
655-8
80
Aspect Green-yellow rhomb, prisms Green-yellow short prisms Brilliant, brown rhomb, plates Brilliant, yellow
Calcd Co N Co
1 9 . 1 2 19.90 24.98 24.70 17.83 17.70
Co N
16.27 21.76
700.25 80
6. trans-[Cr(en)z(NCS)z]. [Co(DH)z(N3)I]
747-25
85
7. [Co(DH)2(pyridine)2 ]. [Co(DH)2(N3)CI]
813.9
70
8. [Co(DH)2(pyridine)2]. [Co(DH)2(Na)Br] 9. [Co(DH)2(pyridine)2]. (Co(DH)2(N3)I]
858.4 905.4
76 80
942.1
85
986.6
80
1033-6
85
10. [Co(DH)2(p-naphtyl-amine)2] [Co(DH)2(N 3)C1] 11.
[Co(DH)2(fl-naphtyl-amine)2][Co(DH)2(N3)Br]
12. [Co(DH)2(fl-naphtyl-amine)2][Co(DH)2(N3)I] 13. [Co(DH)z(p-toluidine)2 ] . [Co(DH)z(N3)CI]
870
60
14. [Co(DH)2(p-toluidine)2 ]. [Co(DH)z(N3)Br ] 15. [Co(DH)z(p-toluidine)z ]. [Co(DH)z(N3)I ]
914.4 961.4
65 75
16.10 21.48
1 C0304 q_ i C r 2 0 3
23.82 27.77
N 5. trans-[Cr(en)z(NCS)2] . [Co(DH)2(N3)Br]
Found
23.50 27.89
dendrites Brown dendrites
I C03O 4 11 1 Cr203
Dark brown hexagonal plates
C0304 ~- 2tCr203
Sparkling, brown plates Brown plates Dark brown plates Light brown microcryst. Brown microcryst. Dark brown microcryst Brown-yellow irregular plates Brown dendrites Dark brown prisms
22.31 26.00
N
22.14 26.30
N Co
20.91 24.37 14.48
20.60 24.31 14-25
Co Co N Co
13.73 13-02 20-11 12.51
13-45 12-86 19.70 12-37
Co N Co
11.95 11-70 18.44 18.63 1 1 . 4 0 11.18
Co N Co Co N
13.50 20.93 12-89 12.26 18.94
13.30 21.25 12.77 12-35 18.73
On the c~-dioximine complexes of transition metals
2201
XLI
Table 4. pH values of the half neutralized H[Co{ D H L, N 3 iX i acids
0"4
II
Complex acid
O3
pH
HICo(DH)2(N3)CI H'~Co(DH)z(N3)Br ~ H ~Co(DHJ2(N3)I OI
2.99 3.00 3.02
Concentration of lhe complexes: 2.10 :~M, t (" = 25' u = 0-t M; neutralization with KOtt tip to 50" ,. : I0
20
40
30 t
?
Table 5. Kinetic parameters of the aquation of ~Co(DH)2(N3)X 1- type complexes
50
rain
Fig. 2. First order kinetic curves of the aquation of [Co{DH)2(N3)X 3- ions at 40°C and pH = 1.0: I. [Co(DH)z(NdCI] : II. [Co(DHJ2(N3)Br ]- ;IIl. [Co(DH)z(N3)I]-. i.e. the trans geometric configuration of the azidohalogeno-complexes and therefore ligand exchange reactions occur with retention of configuration. Valence vibrations of the coordinated N3-grou p and the N3 deformation vibrations appear at v N 3 : 2 0 3 5 - 2 0 4 0 (strong), 1330, 1280 (medium), ON3: 6 2 0 - 6 3 0 c m 1 (strong). The "~Co-N 3 are observed at 400-410 c m - t . The values ~'N3 and 6N 3, as compared to those of N a N 3 C N 3 : 2 1 2 0 - 2 1 4 0 (strong) a n d 6 N 3 : 6 4 3 cm 1 (strong) show a strong covalent character of the Coazide bond. The ; ' C ~ N , ~'N--O frequencies of the coordinated dimethyl-glyoxime appear at 1560-1570 (medium), 1235 1240 (strong), 1085--1090 c m - X ( s t r o n g - - not influenced by coordination effect. In aqueous solutions of the azido-halogeno-complex acids a ligand exchange reaction occurs leading to the liberation of halide ions : [Co(DH)2(N3)X ] - + H 2 0 = ICo(DH)2(N3)(H20)] + X - .
(2)
Kinetics of these reactions were studied in acidic solutions at a constant ionic strength of ,u = 0.1 M. In order to test the influence of acidity on the aquation rate, kinetic measurements were carried out at differing hydrogen ion concentrations, in a pH range between
'(
AH ;= (kcal/mole)
AS s (e.u.)
/,,,
(?1 Fir l
25.5 _+ 0-3 26.3 + 0-3 27-2 _+ 0.4
9.3 10.5 6-3
1.24 1.51 2.06
1 and 5, taking in account the possibility of the following protolytic equilibrium H +
[Co(DH)2(N3)X ] - ~ [ C o ( D H ) ( D H 2 i i N 3 j X ] [3! The reactions were followed by measuring the variation of the concentration of free halide ions, by means of the method described in the experinaental part. The plot of log Co/C o - c values vs. time give a good linearity, as seen in Fig. 2. The first order rate constant values calculated froln these straight lines and given in Table 3 show thai aquation rate is practically independent on pH, and this result enables us to conclude that in our experimental conditions the equilibrium (3) is shifted to the conjugated base, i.e. the corresponding protonaled forms are rather strong acids. This conclusion is also supported by the resuhs ot the pH-measurements presented in Table 4. F r o m the linear relationship between log k. T and 1 / T , activation parameters of the studied reactions wcrc derived, by means of the least square method. These values are given in Table 5. The data presented in Tables 3 and 5 show that the rate constants of the studies reactions decrease, while
Table 3. First order rate constants for the aquation of ICo(DH)2(N3)X]- complexes 10Sk, sec X CI Br I
pH 1.0 2.0 5.0 1-0 2.0 5.0 I-0 2-0 5.0
20°
25°
30°.
35°
40 °
45 °
50°
55°
6.65 6.58 6.72 3.06 3-12 2-99 -
14.3 --
28.8
60.1
-13-8
28.8
116 114 120 60.0 60.7 59.4 1.60
3.11
6.14
11.9
6.65 -----
0-728 0-729 0.734
12-0 12.4
2202
Z. FINTA and Cs. V,~RHELY1
the c o r r e s p o n d i n g activation e n t h a l p y values increase in the o r d e r C1, Br, I. This o r d e r is similar to that of the increasing values o f the nucleophilic c o n s t a n t s of halide ions k,[17], which are also included in Table 5, and indicate a "soft a c i d " b e h a v i o u r of the Co(III) ion in these complexes.
EXPERIMENTAL Synthesis of H[Co(DH)2(N3)X] acids 0.1mole H[Co(DH)2CI2], H[Co(DH)2Br2] or H[Co(DH)212], respectively, were treated in 200-300ml water with 00.8-00.9 mole NaN 3 in 25 ml aqueous solution. The dihalogeno-acids dissolve after 5-10 min. by a continuous stirring and reddish-violet solutions are formed. The mixture was ice cooled and filtered after 20-25 min and the free acids were precipitated with a large excess of 30-35 per cent sulfuric acid. The crystalline precipitates are filtered after 1 i hr, washed with a small amount of ice cold water and with a 10:1 mixture of ether and alcohol and dried in air.
Kinetic measurements The concentration of the liberated halide ions has been determined by Selbin and Bailar's method[18], measuring the EMF of the following concentrations cell : Ag/AgX, studied solution/0.1 M NaNO3/10 -3 M K X solution, AgX/Ag. Both the studied solution and the standard one have contained the same amounts of HCIO 4 or acetic acid sodium acetate buffer solution and NaNO3, in order to ensure the acidity desired and a constant ionic strength of ,u = 0.1 M. Samples were dissolved in the preheated solution and the system was thermostated at the working temperature, with an accuracy of +0.01°C. Electrodes were prepared according to the indications of Selbin and Bailar, but a less current density was used, in order to improve their quality. Silvering of the platinum electrodes was made 10 hr long, with a current density of 1 mA/cm 2. The formation of AgX layer lasted 1 hr, in the same conditions. Electrodes were calibrated before and after each kinetic run, measuring the EMF of the used KX solutions in dilutions by ratios of 1 : 1, 1 : 10 and 1 : 100.
Synthesis of [Me(amine)4X2]. [Co(DH)2(N3)X 1 and [Co(DH)2 (amine)2]. [Co(DH)2(N3)X] 5 mmole of the corresponding diacidotetramine salt (C0(en)2CI23. C1, [Cr(en)2(NCS)2]. C10 4, [Co(DH)2(amine)23acetate) in 80-100ml water, or in 50 per cent alcohol, respectively, are treated with 5 mmole of H[Co(DH)2(Na)X] in 30-40 ml dil, alcohol (1:1). The crystalline precipitate is filtered after 4--2 1 1 hr, washed with a small amount of water and dried in air. Analysis Cobalt was determined complexometrically, by using murexide as indicator. Organic ligands were destroyed by heating with concentrated sulfuric acid and several crystals of K N O 3. After diluting with water to a volume of 60-80 ml, the solution was neutralized with sodium acetate and ammonia. In the chromium derivatives the sum of the oxides was determined, weighing Co30 4 + Cr20 3 after an hour of heating at 900°C. Nitrogen has been determined by the micro-Dumas method. Spectral investigations The i.r. spectra of HCo(DI-I)2(N3JX have been recorded in KBr pellets, by means of a UR 20 Carl Zeiss-Jena spectrophotometer from 40(~4000 c m - ~. pH-measurements pH-measurements were carried out at 25°C with an LPU-01 (U.S.S.R.) pH-meter having a glass-electrode as indicator and a saturated calomel as standard electrode. Samples were dissolved in thermostated 1-10-3 M KOH solutions containing 0-1 M KNO3, in order to obtain 2.10-3 M solutions of the complex acids neutralized up to 50 per cent and an ionic strength of # = 0.1 M. Measurements were performed immediately, excluding the possibility of the aquation.
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