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Dependence of RF values ofcobalt(III) complexes on the size of diamine chelate ligands on silica gel thin layers
JOWL of Chmwogruph~. Elsevier Science Publishers CHROM.
354 ( 1988) 362 366 B.V.. Amsterdam ~ Printed
in The Netherlands
20 808
Note
Dependence of R, values chelate ligands on silica
of cobalt( III) complexes gel thin layers
on the size of diamine
In a previous paper’ wc reported the dependence of the RF values of cobalt(I11) complexes. obtained by thin-layer chromatography (TLC) on silica gel, on the size of the five- and six-membered aminocarboxylato and diamine ligands. It was found that in the TLC separations &ith monocomponent solvent systems the RF values of the complexes with aminocarboyylato ligands decrease with increasing chelate ring size. In contrast, the complexes which in addition to aminocarboxylato ligands contained oxalato ligands instead of nitro groups exhibited the reverse order. Finally. in TLC separations of complexes containing diamine ligands the RF values of the complexes increased with increasing chelate ring size. except when elution was carried out with water. when the reverse order occurred. However, when TLC separations were carried out with multicomponent solvent systems no regularity was observed for any of the aforementioned series. In all instances a linear dependence was found between the number of five-membered rings substituted by six-membered rings and the Rw values of the complexes. Continuing these investigations, in this study we examined complexes containing seven-membered diamine ligands and possible separation mechanisms. EXPERIMENTAL
The complexes investigated were prepared according to procedures reported in the literature (Table I). TLC separations on silica gel 60 G (Merck, Darmstadt, F.R.G.) were carried out as described in an earlier paper’ and the solubility of the complexes was determined as described in a subsequent paper’. RESULTS
AND
DISCUSSION
Twenty-one cationic and neutral cobalt(II1) complexes were chromatographed on silica gel thin layers. In addition to the five-, six- or seven-membered diamine ligands, the investigated complexes also contained, except in one instance, glycinato, (R)-alaninato or nitro ligands (Table I). The chromatographic separations were performed with the use of ten monocomponent solvent systems (Table II). As can be seen from Table I, with the application of nine non-aqueous solvent systems the RF values 002 I -9673/88/$03.50
#T
I988 Elsevier Science Publishers
B.V.
I
2
3
4
19 20 21
* glyH = glycine: R-alaH = (R)-alanine: en = 1,2-diaminoethanc; tn = 1,3-diaminopropanc: ** The compositions of the solvent systems I-I 0 are given in Table II.
17 ~
5
tram-(NOJ-
16 17 18
_ ~ _
56 _ 23 ~ ,O _ tmd = 1,4-diaminobutanr.
9 9 IO
~ ~
~ 45 24 39 34 33 40
_ _ _
-
-
-~ -
4926 -
7 x
cir-(NO,)
13 14 15
~ -
88 53 40 20 79 60 53 29 67 6s 63 43
6 6 5
7 8 5
5
6
7
80 27
.--
~ -
~ --
9
-
7(,,2 78 17 -
~ -
-.~
x
~
~ -
~ -
~ -
10
~ _ ~
~ _ ~
~ _ ~
_ _ ~ _
25 79 18 5 57 30 82 26 I I 62 32 87 30 26 72
-
~
87 -90 ~ 93
._ ~ ._. _ _ _
~ -
-
-
~ ~
x7 63 59 21 0 84 74 6X 67 33 7 89 61 71 75 42 10 92 ~
I
CD-(NOJ-
BY TLC
10 I1 12
OBTAINED
6 6 5
COMPLEXES
cis-(NO,)-
rrun,-(NO,)-
OF THE INVESTIGATED
7 R 9
4 5 6
R,.VALUES
TABLE
364
NOTES
TABLE
II
SOLVENTS NO.
USED
Sohen
FOR TLC Time of de relopmen
t
t
(min]
Distilled water Methanol Ethanol Acetone Acetylacetonc 1,3-Propandiol N,N-Dimethylformamide Ethylene glycol monomethyl Dimethyl sulphoxide Glycerine
1 2 3 4 5 6 I 8 9 IO
15 15 40 10 60 540 10 55 45 1080
ether
of the complexes increased with increase in the chelate ring size. In contrast, with the use of water the reverse order was obtained. In all instances a linear dependence was found between the chelate ring size and the RM values of the complexes; with non-aqueous solvents this dependence was negative and with water it was positive (Figs. 1 and 2). We attempted to correlate the results obtained with the solubility of the complexes in the solvent systetns used. For this purpose we determined the solubility of three complexes in. three solvent systems. As can be seen from Table III, in nonaqueous solvent systems an increase in solubility was followed by an increase in the RF value, whereas in water this was not so.
-1 6
I
en
\
9,
a)
b)
C) L
tT’
tmd
Trik
t&i
,
en
tn
tmd
llgand
Fig. 1. Dependence of K,%,value\ on the chelate ring size of the following complexes (see Table I): (a) 1-~3: (b) 4 6: (c) 7-9: (d} 10-11. 7he numbers on the lines refer to the solvent systems used (see Table II).
Cl
-1.6 L
en
tn
tmd
en
in tmd llgand
en
tn
tmd
Fig. 2. Dcpcndencc of R,w \alucs on 111~chclatc ring sire of the follo\\mg complexes (see l’ahlc I): (a) 13-15: (b) 16 IR; (c) 19-21. The numbers on the lines rcfcr to the solvent systems used (see Table II).
It is known that when monocomponent solvent systems are used the RF value of a complex depends on two factors: the strength of the adsorption of the dissolved substance to the adsorbent and the solubility of the substance in the solvent system used. The more strongly the complex is adsorbed the smaller its RF value should be, whereas with increasing solubility of a complex its RF value should increase. As can be seen from Table III. in the chromatographic separations with water the solubility is not of major importance for the separation of the complexes, but rather the strength of their adsorption. The complex with 1,2-diaminobutane displays the lowest RF value. as it forms the strongest hydrogen bonds. This is in agreement with the fact that in this series 1.4-diaminobutane is the strongest base (Table III). In contrast, when TLC was carried out with non-aqueous solvent systems the other tactor had the major influence, so that the complexes with ligands having larger chelate ring sizes displayed higher RF values, on account of their higher solubility in the solvent system used.
TABLE
III
SOLUBILITIES,
Compk I-’
R,: AND
pK VALI!ES
OF SOME
:Mrthunn/ R, x l(i(l
.\-**
R, x 100
5**
0.067 0.417 0.149
35 -39 3.3
0.003 14 O.OU7 34 0.017 10
-Abbreviations as in Tahlc I. ** s = solubility at 20°C‘ (mol~dm $1 I** Taken from ref. I I. l
COMPLEXES
.so/wtil Uirrcv
nans-[Co(NO&n]rruns-[Co(NOz)ztn]rrans-[Co(NOz),tmd]+
OF THE INVESTIGATED
pK,***
pK,***
7.00 8.64 9.35
10.09 IO.61 IO.80
,~!,N-Dirn~~~hl;!~~r?rrr?iiJr \**
R,
0.007 0.033 0.193
79 82 87
x 100
_
366
NOTES
CONCLUSION
The regularities earlier established for cobalt(II1) complexes containing fiveandior six-membered chelate rings appear to be valid also for complexes with sevenmembered diamine rings. Hence a new possibility is offered for the determination of the composition of the corresponding complexes. ACKNOWLEDGEMEhTS
The authors are grateful to the Serbian Republic Research Fund for financial support and to Dr. Ru2ica Tasovac and Mrs. Zorica Lukanic for elemental microanalyses. REFERENCES I M. B. &lap, Gordana VuPkovli, M. J. Malinar, T. J. Janji? and P. N. RadivojSa. J. Chrwwfogr., 196 (1980) 59. 2 G. VuekoviC. N. JuraniC and M. B. celap. J. Chromatogr.. 361 (1986) 217. 3 N. Matsuoka, J. Hidaka and Y. Shimura, &t/i. Chem. Sock. Jpn., 39 (1966) 1257. 4 M. B. &lap. M. J. Malinar and T. J. Janjii. Rev. Chinr. Miner., 13 (1976) 269. 5 M. J. Malinar and R. Herak. in preparation. 6 M. J. Malinar, R. Herak. M. B. (Ielap, N. PavloviC. S. Milik and D. Stojanov. G/as. Hem. Dru.?. Bwgrcrrl, 46 ( 198 1) 303. 7 Y. Shimura. J. Am. Chcm. SW.. 73 (1951)5079. 8 M. B. celap. M. J. Malinar and P. N. RadirojSa, Inorg. C’Iwm., 14 (1975) 2965. 9 F. Woldbye, Proc. R. SK. L_ondon. Ser. ‘4.. 297 (1967) 79. IO J. Fujita and H. O&o. Ciwrr~. Lrli , (1974) 57. 11 C. R. Bertsch. W. C. Ferneiius and B. P. Blade, J. Phtx. C%cm.. 62 (195X) 444.
354 ( 1988) 362 366 B.V.. Amsterdam ~ Printed
in The Netherlands
20 808
Note
Dependence of R, values chelate ligands on silica
of cobalt( III) complexes gel thin layers
on the size of diamine
In a previous paper’ wc reported the dependence of the RF values of cobalt(I11) complexes. obtained by thin-layer chromatography (TLC) on silica gel, on the size of the five- and six-membered aminocarboxylato and diamine ligands. It was found that in the TLC separations &ith monocomponent solvent systems the RF values of the complexes with aminocarboyylato ligands decrease with increasing chelate ring size. In contrast, the complexes which in addition to aminocarboxylato ligands contained oxalato ligands instead of nitro groups exhibited the reverse order. Finally. in TLC separations of complexes containing diamine ligands the RF values of the complexes increased with increasing chelate ring size. except when elution was carried out with water. when the reverse order occurred. However, when TLC separations were carried out with multicomponent solvent systems no regularity was observed for any of the aforementioned series. In all instances a linear dependence was found between the number of five-membered rings substituted by six-membered rings and the Rw values of the complexes. Continuing these investigations, in this study we examined complexes containing seven-membered diamine ligands and possible separation mechanisms. EXPERIMENTAL
The complexes investigated were prepared according to procedures reported in the literature (Table I). TLC separations on silica gel 60 G (Merck, Darmstadt, F.R.G.) were carried out as described in an earlier paper’ and the solubility of the complexes was determined as described in a subsequent paper’. RESULTS
AND
DISCUSSION
Twenty-one cationic and neutral cobalt(II1) complexes were chromatographed on silica gel thin layers. In addition to the five-, six- or seven-membered diamine ligands, the investigated complexes also contained, except in one instance, glycinato, (R)-alaninato or nitro ligands (Table I). The chromatographic separations were performed with the use of ten monocomponent solvent systems (Table II). As can be seen from Table I, with the application of nine non-aqueous solvent systems the RF values 002 I -9673/88/$03.50
#T
I988 Elsevier Science Publishers
B.V.
I
2
3
4
19 20 21
* glyH = glycine: R-alaH = (R)-alanine: en = 1,2-diaminoethanc; tn = 1,3-diaminopropanc: ** The compositions of the solvent systems I-I 0 are given in Table II.
17 ~
5
tram-(NOJ-
16 17 18
_ ~ _
56 _ 23 ~ ,O _ tmd = 1,4-diaminobutanr.
9 9 IO
~ ~
~ 45 24 39 34 33 40
_ _ _
-
-
-~ -
4926 -
7 x
cir-(NO,)
13 14 15
~ -
88 53 40 20 79 60 53 29 67 6s 63 43
6 6 5
7 8 5
5
6
7
80 27
.--
~ -
~ --
9
-
7(,,2 78 17 -
~ -
-.~
x
~
~ -
~ -
~ -
10
~ _ ~
~ _ ~
~ _ ~
_ _ ~ _
25 79 18 5 57 30 82 26 I I 62 32 87 30 26 72
-
~
87 -90 ~ 93
._ ~ ._. _ _ _
~ -
-
-
~ ~
x7 63 59 21 0 84 74 6X 67 33 7 89 61 71 75 42 10 92 ~
I
CD-(NOJ-
BY TLC
10 I1 12
OBTAINED
6 6 5
COMPLEXES
cis-(NO,)-
rrun,-(NO,)-
OF THE INVESTIGATED
7 R 9
4 5 6
R,.VALUES
TABLE
364
NOTES
TABLE
II
SOLVENTS NO.
USED
Sohen
FOR TLC Time of de relopmen
t
t
(min]
Distilled water Methanol Ethanol Acetone Acetylacetonc 1,3-Propandiol N,N-Dimethylformamide Ethylene glycol monomethyl Dimethyl sulphoxide Glycerine
1 2 3 4 5 6 I 8 9 IO
15 15 40 10 60 540 10 55 45 1080
ether
of the complexes increased with increase in the chelate ring size. In contrast, with the use of water the reverse order was obtained. In all instances a linear dependence was found between the chelate ring size and the RM values of the complexes; with non-aqueous solvents this dependence was negative and with water it was positive (Figs. 1 and 2). We attempted to correlate the results obtained with the solubility of the complexes in the solvent systetns used. For this purpose we determined the solubility of three complexes in. three solvent systems. As can be seen from Table III, in nonaqueous solvent systems an increase in solubility was followed by an increase in the RF value, whereas in water this was not so.
-1 6
I
en
\
9,
a)
b)
C) L
tT’
tmd
Trik
t&i
,
en
tn
tmd
llgand
Fig. 1. Dependence of K,%,value\ on the chelate ring size of the following complexes (see Table I): (a) 1-~3: (b) 4 6: (c) 7-9: (d} 10-11. 7he numbers on the lines refer to the solvent systems used (see Table II).
Cl
-1.6 L
en
tn
tmd
en
in tmd llgand
en
tn
tmd
Fig. 2. Dcpcndencc of R,w \alucs on 111~chclatc ring sire of the follo\\mg complexes (see l’ahlc I): (a) 13-15: (b) 16 IR; (c) 19-21. The numbers on the lines rcfcr to the solvent systems used (see Table II).
It is known that when monocomponent solvent systems are used the RF value of a complex depends on two factors: the strength of the adsorption of the dissolved substance to the adsorbent and the solubility of the substance in the solvent system used. The more strongly the complex is adsorbed the smaller its RF value should be, whereas with increasing solubility of a complex its RF value should increase. As can be seen from Table III. in the chromatographic separations with water the solubility is not of major importance for the separation of the complexes, but rather the strength of their adsorption. The complex with 1,2-diaminobutane displays the lowest RF value. as it forms the strongest hydrogen bonds. This is in agreement with the fact that in this series 1.4-diaminobutane is the strongest base (Table III). In contrast, when TLC was carried out with non-aqueous solvent systems the other tactor had the major influence, so that the complexes with ligands having larger chelate ring sizes displayed higher RF values, on account of their higher solubility in the solvent system used.
TABLE
III
SOLUBILITIES,
Compk I-’
R,: AND
pK VALI!ES
OF SOME
:Mrthunn/ R, x l(i(l
.\-**
R, x 100
5**
0.067 0.417 0.149
35 -39 3.3
0.003 14 O.OU7 34 0.017 10
-Abbreviations as in Tahlc I. ** s = solubility at 20°C‘ (mol~dm $1 I** Taken from ref. I I. l
COMPLEXES
.so/wtil Uirrcv
nans-[Co(NO&n]rruns-[Co(NOz)ztn]rrans-[Co(NOz),tmd]+
OF THE INVESTIGATED
pK,***
pK,***
7.00 8.64 9.35
10.09 IO.61 IO.80
,~!,N-Dirn~~~hl;!~~r?rrr?iiJr \**
R,
0.007 0.033 0.193
79 82 87
x 100
_
366
NOTES
CONCLUSION
The regularities earlier established for cobalt(II1) complexes containing fiveandior six-membered chelate rings appear to be valid also for complexes with sevenmembered diamine rings. Hence a new possibility is offered for the determination of the composition of the corresponding complexes. ACKNOWLEDGEMEhTS
The authors are grateful to the Serbian Republic Research Fund for financial support and to Dr. Ru2ica Tasovac and Mrs. Zorica Lukanic for elemental microanalyses. REFERENCES I M. B. &lap, Gordana VuPkovli, M. J. Malinar, T. J. Janji? and P. N. RadivojSa. J. Chrwwfogr., 196 (1980) 59. 2 G. VuekoviC. N. JuraniC and M. B. celap. J. Chromatogr.. 361 (1986) 217. 3 N. Matsuoka, J. Hidaka and Y. Shimura, &t/i. Chem. Sock. Jpn., 39 (1966) 1257. 4 M. B. &lap. M. J. Malinar and T. J. Janjii. Rev. Chinr. Miner., 13 (1976) 269. 5 M. J. Malinar and R. Herak. in preparation. 6 M. J. Malinar, R. Herak. M. B. (Ielap, N. PavloviC. S. Milik and D. Stojanov. G/as. Hem. Dru.?. Bwgrcrrl, 46 ( 198 1) 303. 7 Y. Shimura. J. Am. Chcm. SW.. 73 (1951)5079. 8 M. B. celap. M. J. Malinar and P. N. RadirojSa, Inorg. C’Iwm., 14 (1975) 2965. 9 F. Woldbye, Proc. R. SK. L_ondon. Ser. ‘4.. 297 (1967) 79. IO J. Fujita and H. O&o. Ciwrr~. Lrli , (1974) 57. 11 C. R. Bertsch. W. C. Ferneiius and B. P. Blade, J. Phtx. C%cm.. 62 (195X) 444.