Complexation of nickel(II) with dioximes in Ni2[Fe(CN) 6] gelatin-immobilized matrix implants

Article abstract of DOI:10.1023/A:1015573301672

The complexation of Ni(II) with α-dioximes, which occurs due to the contact of Ni₂[Fe(CN)₆] gelatin-immobilized matrix implants with water-alkaline (pH 12.0 ± 0.1) solutions of dimethylglyoxime, α-benzyldioxime, and nioxime (H_2<

Full text of DOI:10.1023/A:1015573301672

Russian Journal of Coordination Chemistry, Vol. 28, No. 5, 2002, pp. 352–357. Translated from Koordinatsionnaya Khimiya, Vol. 28, No. 5, 2002, pp. 377–382.
Original Russian Text Copyright © 2002 by Mikhailov.
Complexation of Nickel(II) with Dioximes
in Ni2[Fe(CN)6] Gelatin-Immobilized Matrix Implants
O. V. Mikhailov
Kazan State Technical University, ul. Karla Marksa 68, Kazan, 420015 Tatarstan, Russia
Received December 18, 2000
Abstract—The complexation of Ni(II) with α-dioximes, which occurs due to the contact of Ni2[Fe(CN)6] gel-
atin-immobilized matrix implants with water-alkaline (pH 12.0 ± 0.1) solutions of dimethylglyoxime, α-ben-
zyldioxime, and nioxime (H2L) used as ligands, was studied. It was shown that in each system, the [Ni(HL)2],
[Ni(H2L)2]2+, and [Ni(H2L)]2+ coordination compounds were formed, while in the Ni(II)–dimethylglyoxime
system at pH > 13, the [NiL(OH2)2] complex was additionally formed.
INTRODUCTION
are presented, for example, in monograph [2]. These
studies established that in an alkaline medium, dimeth-
ylglyoxime (I), α-benzyldioxime (II), and nioxime
(III) form bischelate coordination compounds with
The complexation of Ni(II) with dimethylglyoxime
and its analogs has long ago and repeatedly been stud-
ied by numerous researchers beginning with
L.A. Chugaev [1]. Generalizing data on these studies Ni(II).
H3C C C CH3 C6H5CH2 C C CH2C6H5
HON NOH
HON NOH
HON
NOH
(I)
(II)
(III)
Complexation in systems containing Ni(II) and These conclusions were further confirmed in paper
some of the α-dioxime in the metal-containing gelatin- [10], which was devoted to studying processes in the
immobilized matrix systems, in general, and in the Ni2[Fe(CN)6]–GIM systems containing Ni(II) and 8-
nickel(II) hexacyanoferrate(II) systems, in particular, mercaptoquinoline, as well as its various 5-substituted
has not been discussed in the literature to date. Previ- derivatives.
ously [3–9], we studied complexation in the
Ni2[Fe(CN)6] gelatin-immobilized matrices (GIM) in
the Ni(II)–dithiooxamide [3–5], Ni(II)–N,N'-diphe-
nylthiooxamide [6, 7], Ni(II)–N,N'-diphenyldithioox-
amide [5], and Ni(II)–quinoxaline-2,3-dithiol systems
[7–9], which contain N,S-donating ligands capable of
forming two deprotonated forms (HL– and L2–).
In this connection, it seems interesting to reveal the
regularities of complexation in the Ni2[Fe(CN)6] gela-
tin-immobilized implants in the binary systems con-
taining Ni(II) and N,O-donating ligands capable of
forming two deprotonated forms (HL– and L2–) in an
aqueous solution. The α-dioximes can serve as exam-
ples of such compounds.
The authors of these works noted that, when the sys-
The interest in studying complexation in such sys-
tem contains an N,S-donating ligand capable of pro- tems is dictated by the following circumstances. On the
ducing the L2– form (dithiooxamide, N,N'-diphenyl- one hand, the coordination compounds of Ni(II) with
thiooxamide, quinoxaline-2,3-dithiol) in an aqueous dimethylglyoxime, according to data in [11], are prom-
solution, the character of complexation and the amount ising supports for nonsilver photographic images,
and stoichiometric composition of the coordination which are mainly formed at the stage of “toning.” The
compounds that are formed in the Ni2[Fe(CN)6] GIM chemistry of this stage consists in the complexation
differ substantially from those for complexation in the between Ni(II) and an organic compound. On the other
same systems in solutions or in the solid phase. When hand, dimethylglyoxime, α-benzyldioxime, and
the ligand exhibits no tendency to give the L2– form in nioxime can play the role of a ligand and also of one of
solution (N,N'-diphenyldithiooxamide), the indicated the so-called ligand synthons during template synthe-
distinctions in complexation in a solution, solid phase, sis, resulting in supramolecular metal-capsulated coor-
and gelatin-immobilized matrix are not observed. dination compounds [12].
1070-3284/02/2805-0352$27.00 © 2002 åÄIä “Nauka /Interperiodica”

COMPLEXATION OF NICKEL(II) WITH DIOXIMES
353
Mathematical analysis of the D᭢ = f(cFe, cH L , τ)
EXPERIMENTAL
2
kinetic curves was performed on a Pentium-166MMX
PC. Absorbances were measured on a Macbeth TD 504
photometer in the 0.1–5.0 interval with an accuracy of
±2% (rel. units). Electronic absorption spectra were
recorded on Specord UV-VIS (Carl Zeiss) and PU-
8710 (Philips) spectrophotometers in the 400- to
800-nm range.
Ni2[Fe(CN)6] GIM were synthesized according to a
described procedure [3–6]. The obtained implants were
brought in contact with water-alkaline solutions of the
ligands with concentrations from 5.0 × 10–3 to 5 ×
10−1 mol/l and with unchanged pH, 12.0 ± 0.1. The
duration of the implant–ligand solution contact was
varied from 1 to 10 min at constant temperature (20.0 ±
0.1)°C. After the complexation was completed, the
polymeric layers were washed with running water for
15 min and dried for 2–3 h at room temperature.
RESULTS AND DISCUSSION
The contact of Ni2[Fe(CN)6] GIM with alkaline
solutions of dimethylglyoxime, α-benzyldioxime, and
nioxime at pH 9–13 accompanied by the complexation
process in the gelatin bulk results in the accumulation
of substances, which color is pink-purple in the case of
I and impart various shades of red-brown in the case of
II and III.
For the obtained metallocomplex gelatin-immobi-
lized implants, we measured the absorbances (D᭢) cor-
responding to the starting concentration of
Ni2[Fe(CN)6] in the matrix (cFe, mol/dm3), the concen-
tration of the ligand in a solution (cH L , mol/l), and the
2
Figures 1 and 2 present typical D᭢ = f(cFe, cH L , τ)
curves describing the kinetics of the process in the
Ni(II)–dimethylglyoxime and Ni(II)–nioxime systems,
time the implant was in contact with the solution (in
fact, the time of complexation between Ni(II) and the
corresponding ligand) (τ, min). Then, the D᭢ = f(cFe,
2
cH L , τ) functions were plotted in the two-dimensional respectively. These curves have simple shape and are
2
characterized by a monotonic increase in D᭢ with cFe,
cH L , and τ; they do not contain any pronounced bents
coordinate cut-away views [cFe = const, varied cH L
,
2
2
variables τ] and [cH L = const, varied τ, variables cFe].
2
or inflections. The electronic absorption spectra of the
gelatin layers obtained at the indicated pH values and
Further, according to a procedure described in [13], the
stoichiometric coefficients of elementary steps of com-
plexation in the studied binary systems were deter-
mined.
any combination of cFe, cH L , and τ are identical and
2
coincide with the spectra of aqueous suspensions of
nickel(II) bisdioximates. Both these facts indicate that
NiCl2 · 6H2O, K3[Fe(CN)6], trisubstituted sodium the formation of one Ni(II) coordination compound
with the corresponding ligand prevails in each system.
Since a similar situation is also observed for the Ni(II)–
α-benzyldioxime system, we shall further discuss the
details of complexation for one of the three studied sys-
tems, namely, Ni(II)–dimethylglyoxime.
It is known that α-dioximes, depending on pH of the
medium, can exist in four forms:
citrate Na3C6H5O7, and Na2S2O3 · 5H2O (analytical
grade) were used for the preparation of solutions. In
order to prepare alkaline solutions of I, II, and III, the
corresponding α-dioximes (analytical grade) were
used. Coordination compounds formed in the metal-
lochelate GIM were isolated following a described pro-
cedure [4].
+
R1 C NH OH
R1 C N OH
R1 C N O–
R1 C N O–
Kb
Ka1
Ka2
R2 C N OH
R2 C N OH
R2 C N O–
R2 C N OH
(1)
(H3L+)
(HL–)
(L2–)
(H2L)
(R1, R2 = H, alkyl, aryl, aralkyl, and others)
Since the pKb, pKa1, and pKa2 values [2] for α- sponding to the Ni(II) complex with dimethylglyoxime
dioximes lie in the 0.1–2.5, 9.5–10.8, and 11.2–12.3 Ni(HL)2. In the case of the two other studied systems,
intervals, respectively, we can expect that, during the coordination compounds similar in composition were
contact of Ni2[Fe(CN)6] GIM with alkaline solutions of isolated from the gelatin bulks (table).
dimethylglyoxime, Ni(II) complexes with HL– or L2–
A computer-simulation analysis of the D᭢ = f(cFe,
cH L , τ) kinetic plots for all systems studied showed
will be accumulated in the polymer bulk.
When the gelatin-immobilized implats obtained as a
2
result of this contact are decomposed with proteolytic that, although complexes with the molar ratio Ni(II) :
enzymes, the dark pink substance can be isolated from ligand = 1 : 2 are formed during complexation, the lim-
the GIM. According to chemical analysis data, this sub- iting stage of the process is the formation of the 1 : 1
stance has the molecular formula C8H14N4O4Ni corre- complexes. However, all our attempts to isolate com-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 5 2002

354
MIKHAILOV
D▼
5
D▼
5
(a)
(a)
4
3
2
1
4
3
2
1
3'
2'
1'
3'
2'
1'
3
3
2
2
1
1
0
2
4
6
8
10
0
2
4
6
8
10
τ, min
τ, min
5
4
3
2
1
5
4
3
2
1
(b)
(b)
5'
4'
5'
4'
3'
5
4
3'
2'
5
2'
1'
4
3
2
1
1'
3
2
1
0
0.5 1.0 1.5
2.0
0
0.5 1.0 1.5 2.0
cFe, mol/dm3
cFe, mol/dm3
Fig. 1. Kinetic curves for the Ni(II)–dimethylglyoxime sys-
᭢
Fig. 2. Kinetic curves for the Ni(II)–nioxime system: a, plot
tem: a, plot of D vs. τ at c = (1–3) 0.55 and (1'–3')
Fe
᭢
3
3
–2
of D vs. τ at c = (1–3) 0.55 and (1'–3') 1.50 mol/dm and
Fe
1.50 mol/dm and (1, 1') cH L = 2.5 × 10 , (2, 2') 5.0 ×
2
–2
–2
cH L = (1, 1') 2.5 × 10 , (2, 2') 5.0 × 10 , and (3, 3') 2.0 ×
−2
–1
᭢
2
10 , and (3, 3') 2.0 × 10 mol/l; b, plot of D vs. c at
Fe
–1
᭢
–2
–2
–1
10 mol/l; b, plot of D vs. c at c
= (1–3) 2.5 × 10
Fe
cH L = (1–3) 2.5 × 10 and (1'–3') 2.0 × 10 mol/l, τ = (1,
H2L
2
–1
and (1'–3') 2.0 × 10 mol/l and τ = (1, 1') 1, (2, 2') 2, (3, 3')
1') 1, (2, 2') 2, (3, 3') 4, and (4, 4') 6, and (5, 5') 10 min
max
4, (4, 4') 6, and (5, 5') 10 min (λ
= 540 nm).
(λ
= 540 nm).
max
pounds in which Ni(II) : HL– = 1 : 1 failed. This is caused,
most likely, by the fact that in the Ni(HL)2 complexes,
where H2L = I–III, in addition to two five-membered N-
containing metallocycles typical of α-dioximates, two
six-membered N,O-containing metallocycles also appear
due to the formation of intramolecular hydrogen bonds,
which substantially increases the stability of the Ni(HL)2
(R1 = R2 = methyl, benzyl, 1,2-cyclohexylene)
When acting with aqueous solutions of strong min-
eral acids with pH < 4 (without pronounced oxidative
properties, in particular, diluted H2SO4 or HCl) on the
GIM containing nickel(II) bis(dimethyl dioximate), the
polymer bulk immediately changes its color from pur-
ple-pink to bluish green. This is accompanied by a con-
siderable decrease in D᭢. When the HCl-treated gelatin
layer is decomposed by proteolytic enzymes, it yields a
gray-green product, whose chemical composition sug-
gests that it contains two coordination compounds,
[Ni(H2L)2]Cl2 and [Ni(H2L)Cl2], in a molar ratio close
to 1 : 3. Both these compounds have long been known
[14]. A similar situation is also observed in the systems
with II and III.
complexes. The [NiHL]+ complexes do not and cannot
contain such additional six-membered cycles.
Taking into account the above said, we can suggest
that, in the studied systems, the following complexation
process is realized in the Ni2[Fe(CN)6] GIM:
R1 C N OH
R2 C N OH
Ni2[Fe(CN)6] + 4
+ 4 OH–
.
H
.
.
O
O
(2)
R1 C N
N C R1
Taking into account the composition established
above for the compounds formed in the GIM,
namely, Ni(HL)2, the processes that occur under the
action of acids on these GIM can be described as fol-
lows:
+ [Fe(CN)6]4– + 4H2O
2
Ni
R2 C N
O
N C R2
O
.
.
.
H
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 5 2002

COMPLEXATION OF NICKEL(II) WITH DIOXIMES
355
Elemental analysis of coordination compounds formed in the Ni(II)–α-dioxime systems in Ni2[Fe(CN)6] gelatin-immobilized
matrix implants
Content (found/calculated), %
Compound
Molecular formula
C
H
N
Ni
Ni(II)–dimethylglyoxime
[Ni(HL)2]
C8H14N4O4Ni
C4H10N2O2Ni
C8H16N4O4Cl2Ni
C4H8N2O2Cl2Ni
x = 0.27
33.1/33.22
4.9/4.84
5.0/4.78
4.7/4.42
3.6/3.25
3.6/3.57
19.2/19.38
13.2/13.40
15.2/15.47
11.1/11.38
12.4/12.48
20.3/20.41
28.1/28.23
16.6/16.30
24.2/23.98
21.7/21.91
[NiL(OH2)2]
22.7/22.97
26.4/26.52
19.3/19.51
21.5/21.40
[Ni(H2L)2]Cl2
[Ni(H2L)Cl2]
x[Ni(H2L)2]Cl2 +
y[Ni(H2L)Cl2]
y = 0.73
Ni(II)–α-benzyldioxime
[Ni(HL)2]
C32H30N4O4Ni
C32H32N4O4Cl2Ni
C16H16N2O2Cl2Ni
x = 0.24
65.0/64.81
57.2/57.71
47.9/48.32
50.7/50.57
5.1/5.06
5.0/4.81
3.8/4.02
4.2/4.21
9.6/9.44
8.4/8.41
7.0/7.04
7.3/7.37
10.1/9.90
8.4/8.81
[Ni(H2L)2]Cl2
[Ni(H2L)Cl2]
x[Ni(H2L)2]Cl2 +
y[Ni(H2L)Cl2]
15.0/14.76
13.4/13.33
y = 0.76
Ni(II)–nioxime
[Ni(HL)2]
C12H18N4O4Ni
C12H20N4O4Cl2Ni
C6H10N2O2Cl2Ni
x = 0.26
42.0/42.28
35.0/34.82
26.9/26.51
28.5/28.67
5.4/5.28
4.9/4.48
3.4/3.68
4.0/3.98
16.6/16.43
13.2/13.54
10.1/10.31
11.3/11.15
17.0/17.23
14.4/14.19
22.0/21.61
19.8/19.68
[Ni(H2L)2]Cl2
[Ni(H2L)Cl2]
x[Ni(H2L)2]Cl2 +
y[Ni(H2L)Cl2]
y = 0.74
.
H
.
.
OH HO
O
O
R1C C N
N C R1
R1C C N
N C R1
+ 2H+ + 2Cl–
Cl2
Ni
(3)
(4)
Ni
R2C C N
N C R2
R2C C N
O
N C R2
O
OH HO
.
.
.
H
OH
R1C C N
OH HO
R1C C N N C R1
Cl
Cl
R1C C N OH
R2C C N OH
+
Cl2
Ni
Ni
R2C C N
OH
R2C C N
N C R2
OH HO
However, for the Ni(II)–dimethylglyoxime system, but becomes sufficiently great at pH 12 and higher. A
the chemical analysis data of the compounds isolated similar deviation in the two other systems (with II and
from the metallochelate GIM deviate from the theoret- III) was not observed with changes in pH. However, it
ical values calculated for nickel(II) bis(dimethyl dioxi- is remarkable that the electronic absorption spectra of
mate). This deviation is almost insignificant at pH 9–10 the gelatin-immobilized matrices obtained in the
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 5 2002

356
MIKHAILOV
Ni(II)–dimethylglyoxime system at pH 9 and 12 are as compared to the N,S-donating ligands [3–10]. As a
virtually identical. At the same time, the storage of any result, not only the chelates with HL– but also with L2–
matrix in a solution of NaOH or KOH with pH > 13 for are formed in a solution. This is why complexation in
3–5 min at 20°C is accompanied by an almost insignif- the Ni(II)–α-dioxime systems in the Ni2[Fe(CN)6]–
icant change in the color of the gelatin matrix layer GIM, although providing theoretically more favorable
from purple-pink to carmine red.
conditions for the formation of metallochelates with the
L2– form of the ligands, nevertheless, does not allow
one to synthesize any new coordination compounds
that are not detected during Ni(II) complexation with
α-dioximes in aqueous solutions. In the case of N,S-
donating ligands where the content of the L2– form in
solutions is very high and the proton-donating ability of
the corresponding Ni(II) metallochelates with the HL–
form is poorly pronounced even at very high pH values
(14 and higher), the complexes with the L2– form of the
ligand in the inner coordination sphere are not formed
in a solutions. (However, they are formed during com-
plexation in the Ni2[Fe(CN)6]–GIM when the gelatin
molecules forming the polymer bulk acquire a negative
charge due to the contact with an alkaline solution of
the ligand [17]). As a result, some protons can migrate
from the inner coordination sphere of the Ni(II) che-
lates with the HL– and then can be binded by the gelatin
molecules; as a consequence, Ni(II) metallochelates
with L2– can form.)
The decomposition of the polymeric layer of the
immobilized matrix obtained under these conditions
allows one to isolate a carmine red substance from it,
which, according to chemical analysis data, has a sto-
ichiometric composition C4H10N2O2Ni that coincides
with the molecular formula of the [NiL(OH2)2] com-
pound.
The analysis of the kinetic curves for this case
shows that no additional dimethylglyoxime molecule
was added. All these data suggest that, in the case of the
Ni(II)–dimethylglyoxime system in an alkaline
medium, one more process occurs to a certain extent in
addition to reaction (2):
.
H
.
.
O
O
H3C C N
N C CH3
+ OH– + H2O
Ni
H3C C N
O
N C CH3
O
.
.
.
ACKNOWLEDGMENTS
H
(5)
This work was supported by the Russian Foundation
for Basic Research (project nos. 96-03-32112 and 99-
03-99212), the Center for Fundamental Natural Sci-
ence of the RF Ministry of Education (grant 97-0-9.2-
13), and the NIOKR Foundation of the Tatarstan Acad-
emy of Sciences (grant no. 07-7.4-07/2001(F)).
O
H3C C N
OH2
H3C C N OH –
H3C C N O
+
Ni
H3C C N
O
OH2
.
REFERENCES
Note that an increase in the concentrations of
ligands I–III in a solution that is in contact with the
matrix even to a very high level (5.0 × 10–1 mol/l and
higher) does not result in a substantial change in the
shape of the kinetic curves in both the Ni(II)–dimeth-
ylglyoxime system and other systems considered. It
can be assumed that no other nickel(II) metallocom-
plexes with the studied α-dioximes are formed, in par-
ticular, those soluble in water, whose existence in aque-
ous solutions at pH > 12 is mentioned in [15, 16].
1. Kukushkin, Yu.N., Khimiya koordinatsionnykh soedine-
nii (Chemistry of Coordination Compounds), Moscow:
Vysshaya Shkola, 1985, p. 7.
2. Peshkova, V.M., Oksimy (Oximes), Moscow: Nauka,
1977.
3. Mikhailov, O.V., Zh. Neorg. Khim., 1990, vol. 35, no. 8,
p. 2050.
4. Mikhailov, O.V., Indian J. Chem. A, 1991, vol. 30, no. 2,
p. 252.
Thus, we can state that, unlike in the previously
studied systems with N,S-donating ligands [3–9], in the
5. Mikhailov, O.V., Transition Met. Chem. (London), 1996,
vol. 21, no. 3, p. 363.
Ni(II)–dimethylglyoxime,
Ni(II)–α-benzyldioxime,
6. Mikhailov, O.V., Zh. Neorg. Khim., 1991, vol. 36, no. 7,
and Ni(II)–nioxime systems during complexation in
the Ni2[Fe(CN)6]–GIM, no other processes occur that
differ from those taking place during complexation in
solutions and the solid phase. This is probably
explained by the fact that the considered N,O-donating
ligands are capable of generating the L2– form into a
solution at rather high pH, although in insignificant
amounts, but still sufficient for complexation with
Ni(II). This occurs due to more strongly pronounced
proton-donating properties of the N,O-donating ligands
p. 1754.
7. Mikhailov, O.V., Zh. Obshch. Khim., 1990, vol. 60,
no. 12, p. 2804.
8. Mikhailov, O.V. and Polonvyak, V.K., Indian J. Chem. A,
1991, vol. 30, no. 9, p. 807.
9. Mikhailov, O.V. and Kazymova, M.A., Transition Met.
Chem. (London), 1998, vol. 23, no. 2, p. 195.
10. Mikhailov, O.V. and Kazymova, M.A., Transition Met.
Chem. (London), 1999, vol. 24, no. 3, p. 350.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 5 2002

COMPLEXATION OF NICKEL(II) WITH DIOXIMES
357
11. Mikhailov, O.V., J. Photogr. Sci., 1993, vol. 41, no. 6,
the title Kurs neorganicheskoi khimii, Moscow: Mir,
1966, vol. II, p. 342.
p. 199.
12. Voloshin, Ya.Z., Ross. Khim. Zh., 1998, vol. 42, nos. 1–2, 15. Okac, A. and Simek, M., Collect. Czech. Chem. Com-
p. 5. mun., 1950, vol. 15, no. 3, p. 978.
13. Mikhailov, O.V., Koord. Khim., 1992, vol. 18, no. 12, 16. Okac, A. and Simek, M., Collect. Czech. Chem. Com-
p. 1173. mun., 1959, vol. 24, no. 8, p. 2709.
14. Remy, Y., Lehrbuch der anorganischen Chemie, 17. Mikhailov, O.V., Rev. Inorg. Chem., 1997, vol. 17, no. 4,
Leipzig: Akademische, 1966, vol. II. Translated under p. 287.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 28 No. 5 2002