On the oximine complexes of transitionmetals : PPart CXIX. Thermal and spectral studies on Ni(Diox.H)2 type chelate compounds

Article abstract of DOI:10.1007/s10973-005-6825-2

Fourteen chelates of the type [Ni(II)(Diox.H)₂], ((Diox.H) ₂: various α-dioximes) have been studied by means of FTIR, NMR, MS data and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic parameters of the ther

Full text of DOI:10.1007/s10973-005-6825-2

Journal of Thermal Analysis and Calorimetry, Vol. 83 (2006) 3, 701–707
ON THE OXIMINE COMPLEXES OF TRANSITION METALS
Part CXIX. Thermal and spectral studies on Ni(Diox.H)2 type chelate compounds
Cs. Várhelyi Jr.1*, G. Pokol2, Á. Gömöry3, A. G²nescu4, P. Sohár5, G. Liptay2 and Cs. Várhelyi1
1Babeê-Bolyai University, 400 028 Cluj, Romania
2Budapest University of Technology and Economics,1521 Budapest, Hungary
3Hungarian Academy of Science, Chemical Research Centre, 1525 Budapest, Hungary
4University of Craiova, Craiova, Romania
5Eötvös Loránd University of Science, Budapest, Hungary
Fourteen chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2: various α-dioximes) have been studied by means of FTIR, NMR, MS
data and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic parameters of the thermal decomposition
of the complexes were also calculated using Zsakó’s ‘nomogram method’. The mechanism of the decomposition processes was
characterised on the basis of mass spectra.
Keywords: chelate compounds, oximine complexes, Schiff bases, spectral data, thermal stability, transition metal complexes
Introduction
mixed aliphatic-, aromatic-, alicyc1ic- and heterocyclic
α-dioximes) for investigations. Various properties (solu-
bility, thermal stability, spectral data, etc.) of these chelat-
ing agents can be influenced by the nature of the groups
linked to the –C(=NOH)–C(=NOH)– moiety [13, 14].
Thermal behavior of the transition metal derivatives
with azomethines (Schiff bases, hydrazones, oximes)
stand also in the present, in the attention of the re-
searcher in various branches of theoretical and techni-
cal chemistry [1–4].
Nickel(II) chelates of monodeprotonated di-
oximes: R–C(=NOH)–C(=NOH)–Rx, R=Rx and R≠Rx,
R, Rx=H, alkyl, aryl-alicyclic, heterocyclic groups
find extensive use in analytical chemistry, especially
in the gravimetric and spectrophotometric determina-
tion of this metal in various alloys, minerals, rocks,
industrial products, waste waters, etc.
Experimental
Chelating agents
The symmmetric α-dioximes were obtained from the
corresponding α-dicarbonyl compounds (glyoxal,
alicyclic-diketones with NH2–OH⋅HCl neutralized with
NaOH, or pyridine in alcoholic solution by refluxing.
The asymmetric dioximes are formed by iso-
nitrozation of the R–CO–CH2–Rx monoketones with
gaseous ethyl nitrite at 0...+5°C, followed by oxima-
tion of the keto-oximes with NH2–OH. The crude
products were recrystallized from alcohol.
Some physico-chemical properties of these com-
pounds have been studied also from the analytical
point of view [5–7].
The complexes with alkyl- or aryl-substituted
glyoximes have been prepared by the reaction of
nickel(II) salts with the appropriate ligand in aqueous
or ethanolic solution or in aqueous alcoholic mix-
tures. In most cases the reaction is promoted by addi-
tion of ammonia or base and/or refluxing at a suitable
temperature [8–10].
Ni(Diox.H)2
10 mmoles NiCl2 (or NiSO4) in 200 mL water were
treated with 20–30 mmoles of NH3 or CH3–COONa.
20 mmoles of α-dioxime in 100–150 mL ethanol were
added and warmed on a water bath (70–80°C)
30–40 min. The coloured slightly soluble products were
filtered off, washed with warm water and dried in air
(24–48 h). Note: Ni(n-decan-2,3-dione-diox.H)2 was ob-
tained from 96% ethanol [14, 15]. Analysis: Ni% was de-
termined complexometrically after the digestion of
50–60 mg samples with conc. H2SO4+some cryst. KNO3.
The complexes are always square with general
formulas [Ni(Diox.H)2] (Diox.H: monodeprotonated
α-dioxime). In the crystal structure the Ni(Diox.H)2
molecules generally stack one over the other to give
rise of polydimensional structure which renders the
complexes highly insoluble, especially in aqueous so-
lutions [11, 12].
Preparative organic chemistry produces yearly a
number of these 1igands (symmetric and asymmetric
*
Author for correspondence: vcaba@chem.ubbcluj.ro
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2006 Akadémiai Kiadó, Budapest

VÁRHELYI Jr. et al.
Results and discussion
Methods
Infrared spectra
In the present study, 14 nickel(II) oximine derivatives
were obtained. The compounds are characterized in
Table 1, Ni2(TrioxH2)3 is also included in this table.
The symmetric derivatives (R=Rx) are generally
insoluble in water and methanol or ethanol. They are
soluble in apolar solvents CCl4, CHCl3, benzene, etc.
The asymmetric ones with longer carbon chains in Rx
(-butyl, -hexyl, etc.) are soluble in alcohol, too.
The far IR spectra were recorded with a Bio-Rad-Ninn
spectrophotometer in polyethylene pellets, while the
middle FTIR ones with a PerkinElmer 2000 apparatus
in KBr pellets.
Thermal analysis
The thermal measurements were carried out on a
DuPont Instruments thermal analysis system in argon
and nitrogen atmospheres. Sample mass 5–10 mg;
heating rate: 10 K min–1.
Infrared spectra
In the FTIR spectra of the free oximes and the men-
tioned coordination compounds the most important
absorption bands belong to the various vibration fre-
quencies of the oxime groups (Table 2).
Mass spectra
νO–H: 3400–3100 cm–1 (2–3 strong, broad
bands); νC=N: 1680–1650 cm–1 (by the non-conjugated
systems), 1650–1610 cm–1 (by the conjugated ones);
νN–O: 950–980 cm–1 (a single band ).
The mass spectra were recorded with a VG ZAB-2
SEQ apparatus by direct introduction of the samples.
Ionization: EI.
Table 1 Ni(Diox.H)2 type complexes
Analyis
No.
Formula
Molecular mass calcd.
Aspect
calcd./%
found/%
red
Ni
23.3
7.2
23.1
6.8
[Ni(Glyox.H)2]⋅H2O
[Ni(DMG.H)2]
I
250.8
288.9
316.9
345.0
456.7
microcryst.
H2O
red-violet
II
Ni
Ni
Ni
Ni
20.3
18.5
17.0
12.85
20.2
18.7
17.2
12.75
microcryst.
red-brown
microcryst.
[Ni(Me-Et-Diox.H)2]
[Ni(Propox.H)2]
III
IV
V
orange-brown
microcryst.
orange red
[Ni(n-Decan-2,3-dion diox.H)2]
irreg. prisms
orange-brown
microcryst.
[Ni(Diamino-glyox.H)2]
[Ni(Cpdox.H)2]
VI
292.9
312.9
340.9
Ni
Ni
Ni
20.0
18.75
17.2
20.15
18.5
VII
VIII
tile red cryst.
red-violet
[Ni(Niox.H)2]
17.35
gelatinous mass
orange-brown
microcryst.
[Ni(Heptox.H)2]
[Ni(Octox.H)2]
IX
X
369.0
397.0
255.2
385.0
Ni
Ni
Ni
Ni
15.9
14.8
18.7
15.24
16.1
14.7
18.5
15.4
orange-brown
microcryst.
red-violet
[Ni(Triox.H)2]1.5
[Ni(Phenil-glyox.H)2]
XI
XII
gelatinous mass
red-brown
microcryst.
orange-brown
microcryst.
[Ni(Benzyl-Me-glyox.H)2]
[Ni(Furox.H)2]
XIII
XIV
445.1
497.1
Ni
Ni
13.2
11.8
13.1
11.6
red-violet
I – (Glyox.H)2: HC(NOH)CH(=NOH); II – (DMG.H)2: CH3–C(=NOH)–C(=NOH)–CH3; III – (Me-Et-Diox.H)2:
CH3–C(=NOH)–C(=NOH)–C2H5; IV – (Propox.H)2: CH3–C(=NOH)–C(=NOH)–C3H3; V – (n-Decan-2,3-dion diox.H)2:
CH3–C(=NOH)–C(=NOH)–(CH2)6–CH3; VI – (Diamino-glyox.H)2: H2N–C(=NOH)–C(=NOH)–NH2; VII – (Cpdox.H)2:
C5H6(=NOH)2; VIII – (Nyox.H)2: C6H8(=NOH)2; IX – (Heptox.H)2: C7H10(=NOH)2; X – (Octox.H)2: C8H12(=NOH)2;
XI – (Triox.H)3: C6H6(=NOH)3; XII – (Phenil-glyox.H)2: C6H5–C(=NOH)–C(=NOH)–H; XIII – (Benzyl-Me-glyox.H)2:
C6H5–CH2–C(=NOH)–C(=NOH)–CH3; XIV – (Furox.H)2: C4H3O–C(=NOH)–C(=NOH)– C4H3O
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OXIMINE COMPLEXES OF TRANSITION METALS
Table 2 Some FTIR spectral data of Ni(Diox.H)2 type complexes
ν/cm–1
νO–H
III
IV
VIII
–
IX
X
–
XI
XII
–
XIII
–
–
–
–
3240–3160vs
δO–H..O
1750–1790m
1730–1760m
1720–1800w
1740–1790m
1760–1820m 1700–1800m 1700–1800m 1720–1800m
1610s
νC=N
1564vs
1562vs
1575vs
1570vs
1565vs
1544s
1559vs
1575s
–
νC–C
–
–
–
–
–
1495vs
1260vs
1074s
–
1494vs
1241vs
1063vs
–
(arom)
νN–O
νN–O
1235vs
1110vs
–
1234vs
1077s
–
1240vs
1090vs
–
1235vs
1095vs
–
1245vs
1105vs
–
1235vs
1050vs
985s
530s
–
νN–O
(free)
νNi–N
513vs
202m
520s
205m
518vs
210m
520vs
206m
512s
515s
516vs
205m
δN–Ni–N
205m
207m
vs – very strong, s – strong, m – medium, w – weak; ν – vibration
The above frequencies of the free ligands are
modified by coordination to the transition metals.
In the spectra of the Ni(II) complexes the νO–H
bands disappear, and the azomethine stretching vibra-
tions are shifted to lower frequencies (1550–1570 cm–1).
The N–O band is splitted in two parts and shifted
to higher frequencies (1100–1250 cm–1). The νC=N
and νN–O shifts prove the strong covalent character of
the Ni–N bonds. The weak band at 1700–1800 cm–1
can be assigned to the δO–H...O deformation vibrations
of the very short intramolecular hydrogen bonds,
which stabilize the molecule.
by the neighbouring groups of the molecule. In the
case of the mentioned nickel(II) derivatives this sig-
nal can be observed at 151–154 ppm, generally
splitted [18, 19].
Thermal behaviour of the [Ni(Diox.H)2] complexes
The description of the thermal decomposition of the
oximine complexes of some transition metals is neces-
sary from the analytical chemical point of view. Using
TG measurements, one can determine the temperature
range of the thermal stability, where the above men-
tioned complexes can be dried without decomposition.
Some metal complexes with organic ligands have
been studied by means of TG, DTG and DTA measure-
ments [1–3], especially for gravimetrical purposes.
Our thermoanalytical results are summarised in
Table 3. We observed that the majority of the oximine
complexes do not have a reproducible melting point
and decompose to a dark resinous mass, accompanied
with evolution of gaseous products.
In the far infrared region appear the νNi–N
stretching vibration and various δN–Ni–N deformation
vibrations, as well as skeleton vibrations of the che-
late rings, generally overlapping by other deformation
vibrations δ(CH ) ,δ(C= N) ,δCNO, etc.) [16–17].
3
t
t
1H and 13C NMR spectral data
In the 1H NMR spectra of all Ni(II) chelates the proton
resonance signal of the intramolecular hydrogen bridge
appears at 17.5–18.2 ppm. This chemical shift is very
great, higher than the values observed in the spectra of
the enoles, aldehydes and carboxylates (12–15 ppm).
The value observed proves the high stability of
this hydrogen bridge and the coplanar geometric con-
figuration of the chelate molecules. The splitting of
this signal is due to the cis–trans izomerism of the
complexes with asymmetric α-dioximes.
The TG, DTA measurements show that the thermal
stability of the Ni(Diox.H)2 complexes is higher than
that of the free, non-coordinated α-dioximes, since the
free =C=NOH groups participate in some internal redox
decomposition processes. The electron donor properties
of the =C=N– groups are influenced by the nature of R
and Rx radicals. For this reason the force constants of
Ni–N (oxime) bonds and the temperature ranges of the
decomposition depend on chemical composition.
The following empirical stability order was es-
tablished for the studied complexes:
The 13C NMR resonance signal of the azo-
methine group appears at 145–170 ppm, influenced
J. Therm. Anal. Cal., 83, 2006
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VÁRHELYI Jr. et al.
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OXIMINE COMPLEXES OF TRANSITION METALS
mate kinetic parameters n1, E1 and logA1 obtained in
the first approximation from the nomogram [16] are
shown in the upper part of the table. From the reduced
shape and position parameters (∇x, Δx, τx) obtained
with an iterative procedure, the apparent kinetic pa-
rameters (n, E and logA) were calculated. The results
are shown in the lower part of the table.
Mass spectra
In the mass spectra of the complexes the peak of the
Ni(Diox.H)2 molecule ion (M+) appears with high in-
tensity ratios (60–l00%). The metal containing frag-
ments, Ni(DioxH)NO, Ni(Diox.H) show an intensity
of only 3–40% and 3–30%, respectively (Table 5).
The isotopic effect of 58Ni(67%), 60Ni(26%),
63Ni(3.7%) can be also observed in the case of Ni con-
taining molecule ions.
Fig. 1 Thermoanalytical curves for
[Ni(monophenyl-glyox.H)2] complex
• with aliphatic dioximes: II>III>IV>VI>V
• with oximes of various types:
In the majority of the mass spectra one can ob-
serve the peaks of the free ligands, the 3,4-substituted
furazans (dehydration products of the dioximes):
II>III>XIV>XIII>XII>XI>X>IX>VIII>VII
The symmetric derivatives have higher stability
than the asymmetric ones. The decomposition temper-
ature decreases with increasing –C–C– chain length in
the Rx group. The majority of the Ni(II) complexes of
the mentioned type decompose suddenly (steep steps
on the TG-curves) and in some cases also with explo-
sion (bifurcate steps). On the TG curves in some cases
one or two steps can be observed by stoichiometric ra-
tios: Diox.H/Ni(Diox.H)2=0.85–1.1 corresponding to
the loss of the two Diox.H ligands in subsequent steps.
The reaction probably starts with the dissociation
Ni(Diox.H)2→Ni(Diox)++Diox.H–.
various nitrils, alkyl- and aryl-, and C H+ ions, inter-
n
m
mediary products with –C–C– chains (1–50–70% val-
ues, the latter having very short lifetimes) [22–24].
On the basis of the mass spectra the following
thermal decomposition mechanism can be proposed:
Ni(Diox.H)2→Ni(Diox.H)(Furazan)→
Ni(Diox.H)NO→Ni(Diox.H)
The TG and DTA measurements in inert gas at-
mosphere exclude the participation of air in the de-
composition processes.
Ni(Diox.H)→Ni(Furazan)→Ni(nitrile)+various free
and deprotonated dioximes, furazans, and other frag-
ment ions.
The TG curves of the studied compounds only in
a few cases are suitable for the evaluation of decom-
position kinetics. Kinetic parameters of the thermal
decomposition of [Ni(Propox.H)2] (No. IV) and
[Ni(Diamino-glyox.H)2] (No. VI) have been calcu-
lated using Zsakó’s ‘Nomogram method’ [20–22].
The results are summarized in Table 4.
These MS results confirm the assumptions based
on the thermogravimetrical curves, i.e., that the first
step in the sequence of reactions is the dissociation of
the chelate: Ni(Diox.H)2 = Ni(Diox.H)+ + Diox.H–
A similar phenomenon was observed also in the
case of Pd(Diox.H)2 and Pt(Diox.H)2 derivatives (re-
sults to be published in following papers).
The shape and position parameters (τ, Δ, ∇) were
calculated from the T0.1, T0.5, and T0.9. The approxi-
Table 4 Kinetic parameters of the thermal decomposition of [Ni(Propox.H)2] (No. IV) and [Ni(Diamino-glyox.H)2] (No. VI)
x
∇
Complex
T0.1
T0.5
T0.9
Δx
n1
Δx1
E1/kcal mol–1
logA1
[Ni(Propox.H)2]
498
326
523
340
535
350
96
0.309
0.398
0.380
1.120
90.369
33.04
11.07
7.88
[Ni(Diamino-glyoxime)2]
126
105.625
24.810
x
Complex
∇
τx
Δx2
n
E/kcal mol–1
logA
logAx
[Ni(Propox.H)2]
0.309
0.398
1.965
3.013
91.383
0.313
1.068
32.758
28.364
12.312
16.044
11.54
16.44
[Ni(Diamino-glyoxime)2]
107.379
J. Therm. Anal. Cal., 83, 2006
705

VÁRHELYI Jr. et al.
Table 5 Mass spectral data of some [Ni(Diox.H)2] type complexes
Formula
m/z
28 (4%) A, 39 (12%) E, 41 (6%) B, 42 (7.5%) C, 53 (3%) F,
67 (5%) I, 68 (5%) K, 82 (2%)L, 99 (15%) M, 115 (30%) O,
116 (11%) P, 157 (3%) S, 174 (31%) U, 204 (26%) V, 272
(3%) W, 288 (100%) X, 290 (42%) X
[Ni(DMG.H)2]
28 (12%) A, 30 (2%) B, 39 (23%) VI, 41 (37%) D, 55 (9%)
D, 56 (12%) D, 67 (12%) G,
[Ni(Me-Et-Diox.H)2]
81 (4%) G, 99 (19%) M, 130 (24%) N, 169 (67%) S, 187
(17%) U, 299 (4%) Z,
316 (75%) X, 318 (30%) X
28 (5%) A, 30 (25%) B, 41 (42%) D, 55 (6%) G, 68 (18%) F,
70 (19%) D, 81 (3%) G,
[Ni(Propox.H)2]
99 (30%) M, 127 (40%) M, 144 (32%) N, 184 (17%) T, 202
(26%) U, 232 (55%) V,
327 (8%) Z, 344 (100%) X, 346 (40%) X
27 (3%) E, 28 (4%) A, 39 (13%) F, 77 (65%) R, 147 (95%)
M, 164 (55%) R, 220 (3%) U,
[Ni(Phenyl-glyox.H)2]
222 (19%) U, 251 (30%) V, 351 (10%) W, 368 (8%) Z, 384
(55%) X, 386 (25%) X
28 (5%) A, 30 (3%) B, 31 (3%) C, 41 (25%) D, 39 (15%) F,
67 (25%) H, 115 (10%) E,
117 (75%) –, 129 (5%) –, 130 (22%) I, 143 (15%) H, 144
(18%) K, 158 (43%) L,
[Ni(Me-benzyl-Diox.H)2]
174 (22%) M, 190 (2%) N, 192 (77%) P, 232 (12%) S, 249
(35%) U, 279 (35%) V,
407 (8%) W, 424 (8%) Z, 440 (60%) X, 442 (30%) X
3 M. Lalia-Kantouri, J. Therm. Anal. Cal., 82 (2005) 791.
4 T. Premkumar and S. Govindarajan, J. Therm. Anal. Cal.,
79 (2005) 115.
Acknowledgements
5 C. Duval, Inorganic Thermogravimetric Analysis, Elsevier
Pub. Company, Amsterdam, New York, London, 1963.
6 L. Erdey, Gravimetric Analysis, Pergamon Press, Oxford,
New York, London, Vol. I–II, 1963.
The authors wish to thank Ms. E. Tóth for thermoanalytical
measurements. One-month fellowships provided for Csaba
Várhelyi and Csaba Várhelyi Jr. by Foundation ‘Domus
Hungarica’ to Hungary (2001) are gratefully acknowledged.
7 G. Liptay, Atlas of Thermoanalytical Curves, Vol. I–IV,
Akadémiai Kiadó, Budapest – Heyden and Sons,
London 1964–1965.
8 L. A. Chugaev, Ber. Dtsch. Chem. Ges., 38 (1905) 2520;
39 (1906) 3382; 40 (1907) 3498; 41 (1908) 2219.
9 O. Brunk, Angew. Chem., 20 (1907) 834, 1844;
27 (1914) 315.
References
1 Y. Miyazaki, T. Sakakibara, H. Miyasaka, N. Matsumoto
and M. Sorai, J. Therm. Anal. Cal., 81 (2005) 603.
2 H. A. El-Boraey, J. Therm. Anal. Cal., 81 (2005) 339.
10 C. V. Banks and K. Byrd, Anal. Chim. Acta, 10 (1954) 129.
706
J. Therm. Anal. Cal., 83, 2006

OXIMINE COMPLEXES OF TRANSITION METALS
11 L. E. Godycki and R. E. Rundle, Acta Crystallogr.,
19 F. Mánok, Cs.Várhelyi, A. BenkÞ and J. Horák,
Microchim. Acta, 1983 II, 429.
6 (1953) 487.
12 M. Calleri, G. Ferraris and D. Viterbo, Acta Crystallogr.,
22 (1967) 468.
20 J. Zsakó, J. Thermal Anal., 15 (1979) 369.
21 J. Zsakó, J. Thermal Anal., 47 (1996) 1679.
22 C. J. Keattch, An Introduction to Thermogravimetry,
Heyden and Son Ltd. London, Sadtler Research Laborato-
ries Inc., Philadelphia 1969.
13 J. Leidert and J. Weiss, Acta Crystallogr. Ser. B.,
31 (1985) 2877.
14 Houben-Weyl, Methoden der Organischen Chemie,
Bd. X. pp. 7–320, Georg Thieme Verlag, Stuttgart 1968.
15 S. R. Sander and W. Karo, Organic Functional group Prepa-
rations, Vol. III. Chap. 11, Academic Press Inc., Harcourt,
San Diego, New York 1980.
23 J. Watson, Introduction to Mass Spectrometry, Racon Ed.,
New York 1985.
24 O. Kaposi and M. Riedel, Tömegspektrometria II.
Alkalmazások, Tankönyvkiadó, Budapest 1990.
16 K. Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds, J. Wiley and Sons,
Inc. 5th Ed., 1997.
Received: August 28, 2005
Accepted: December 20, 2005
17 J. R. Ferraro, Low Frequency Vibrations of Inorganic and
Coordination Compounds, Plenum Press, New York 1971.
18 P. Sohár, Nuclear Magnetic Resonance Spectroscopy,
CRC Press, Boca Raton, Florida 1983/84.
DOI: 10.1007/s10973-005-6825-2
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