New complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 3,3-dimethylglutaric acid

Article abstract of DOI:10.1023/A:1014300720524

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3,3-dimethylglutarates were investigated and their quantitative composition, solubility in water at 293 K and magnetic moments were determined. IR spectra and powder diffr

Full text of DOI:10.1023/A:1014300720524

Journal of Thermal Analysis and Calorimetry, Vol. 67 (2002) 623–629
NEW COMPLEXES OF Mn(II), Co(II), Ni(II), Cu(II),
Zn(II) AND Cd(II) WITH 3,3-DIMETHYLGLUTARIC
ACID
W. Brzyska and W. O¿ga
Department of General Chemistry, Faculty of Chemistry, Maria Curie Sk³odowska University,
PL 20031 Lublin, Poland
(Received March 19, 2001; in revised form July 12, 2001)
Abstract
Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3,3-dimethyl-
glutarates were investigated and their quantitative composition, solubility in water at 293 K and
magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes
prepared with general formula MC7H10O4·nH2O (n=0–2) were recorded and their thermal decompo-
sition in air were studied. During heating the hydrated complexes of Mn(II), Co(II), Ni(II) and Cu(II)
are dehydrated in one step and next all the anhydrous complexes decompose to oxides directly (Mn,
Co, Zn) or with intermediate formation free metal (Ni, Cu) or oxocarbonates (Cd). The carboxylate
groups in the complexes studied are bidentate. The magnetic moments for the paramagnetic com-
plexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.62, 5.25, 2.91 and 1.41 M.B., respectively.
Keywords: 3,3-dimethylglutarate, DTA, IR spectra, magnetic moments, synthesis, TG
Introduction
3,3-Dimethylglutaric acid, C5H10(COOH)2, is a crystalline solid soluble in water and
ethanol [1]. It is used in the synthesis of (+) –bicyclohumelone, and important per-
fume component [2]. Compounds of 3,3-dimethyglutaric acid with metal ions are lit-
tle known. The complex of La was prepared as solid sparingly soluble in water [3].
The complexes of Y(III) and lanthanides(III) from La to Lu [4] were prepared as sol-
ids with general formula Ln2C7H10O4·nH2O, sparingly soluble in water. The com-
plexes heated are dehydrated in one or three steps and next the anhydrous compounds
decompose to oxides directly (Ce) or with intermediate formation Ln2O2CO3 (Y, La,
Pr–Lu). The carboxylate groups in the complexes are bidentate.
The aim of our work was to prepare the complexes of Mn(II), Co(II), Ni(II),
Cu(II), Zn(II) and Cd(II) with 3,3-dimethylglutaric acid in solid state and to study
their properties and thermal decomposition.
1418–2874/2002/ $ 5.00
Akadémiai Kiadó, Budapest
© 2002 Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht

624
BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
Experimental
The complexes of Mn(II), Co(II), Ni(II) , Cu(II), Zn(II) and Cd(II) with 3,3-dimethyl-
glutaric acid were prepared by dissolving metal(II) carbonates in hot 0.1 M solution
of 3,3-dimethylglutaric acid and crystallization at room temperature. The precipitates
formed were filtered off, washed with water and dried at 303 K to a constant mass.
The carbon and hydrogen contents in the prepared complexes were determined by el-
emental analysis on a Perkin Elmer CHN 2400 analyser. The contents of metal were
determined by AAS method on an atomic absorption spectrophotometer AAS – 3
(Carl Zeiss Jena). The number of crystallization water molecules was determined
from TG curves and by isothermal heating the hydrated complexes at defined temper-
ature (Table 3). IR spectra of the prepared complexes and spectra of 3,3-dimethyl-
glutaric acid and its sodium salt were recorded as KBr discs on a Specord M-80
spectrophotometer (4000–400 cm–1). The solubility of the prepared complexes in wa-
ter at 293 K was determined by the preparation of saturated solutions (under isother-
mal conditions) and measuring the concentration of metal(II) ions using AAS
method. The powder diffraction patterns of the prepared 3,3-dimethylglutarates are
registered on a Dron-2 diffractometer. The magnetic susceptibility of the prepared
complexes was measured at room temperature by Gouy’s method on a magnetic bal-
ance (Scherwood Scientific MSB MK I) using as standard Co[Hg(SCN)4] (Table 2).
Thermal stability of the prepared 3,3-dimethylglutarates was investigated by TG,
DTG and DTA curves. Measurements were made with Q-1500 D derivatograph by
method described in [4]. The products of decomposition were calculated from TG
curves and verified by registration X-ray diffractograms and IR spectra.
Results and discussion
3,3-Dimethylglutarates of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were pre-
pared as solids with colour characteristic for hydrated metal(II) ions with general for-
mula M(C5H10C2O4)·nH2O, where n=0 for Zn, Cd, n=1 for Ni, n=1.5 for Co, and n=2
for Cu (Table 1). The prepared complexes are crystalline solids of different structures
(Fig. 1). All the prepared complexes, except for Cu(II) complex, are soluble in water
(Table 1). Their solubility is of the order 10–2 mol dm–3, whereas the solubility of
Cu(II) one is 2.4·10–3 mol dm–3. The solubility of the prepared complexes change in
the order:
MnL > NiL > CdL > CoL > ZnL >> CuL
The susceptibility values for paramagnetic Mn(II), Co(II), Ni(II) and Cu(II)
complexes calculated from the results of magnetic measurements at room tempera-
ture were corrected by measuring the diamagnetic susceptibility of ligand. The mag-
netic moments were calculated using formula µeff=2.84(χMT)1/2 (Table 2). The com-
plexes of Zn(II) and Cd(II) were diamagnetic. The magnetic moments determined for
the complexes of Ni(II) (2.91 M.B.) and Mn(II) (5.62 M.B.) are similar to the theoret-
ical values for octahedral complexes with configuration d8 and d5, respectively. The
J. Therm. Anal. Cal., 67, 2002

BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
625
value µeff for Mn(II) complex shows on the high spin configuration (µeff= 5.9–6.2
M.B. [5]) and octahedral structure. For Co(II) complex the measured magnetic mo-
ment (5.25 M.B.) differs to such an extent from the spin-only moment. Its magnetic
moment, instead of spin – only value 3.88 M.B. characteristic for d7 configuration
(three unpaired electrons) attains value 5.25 M.B. Literature data [6] show that mea-
sured magnetic moments for Co(II) complexes with different ligands attain value
5.2–5.5 M.B. The magnetic moment value (1.40 M.B.) for Cu(II) complex shows on
the polymeric structure.
Table 1 Analytical data and solubilities of 3,3-dimethylglutarates of Mn(II), Co(II), Ni(II),
Cu(II), Zn(II) and Cd(II)
M/%
C/%
H/%
Solubility/
Complex
10–2 mol dm–3
calc. found
calc. found calc. found
Mn[C5H10(COO)2]·2H2O
Co[C5H10(COO)2]·1.5H2O
Ni[C5H10(COO)2]·H2O
Cu[C5H10(COO)2]·H2O
Zn[C5H10(COO)2]
22.07 22.00 33.74 33.52 5.60 5.61
24.16 24.10 34.43 33.98 5.32 5.42
24.59 24.60 35.19 35.31 5.03 5.07
26.52 26.50 34.43 34.33 5.00 4.95
29.28 29.25 37.60 37.50 4.47 4.40
41.56 41.55 31.06 31.00 3.69 3.70
3.84
1.63
3.40
0.24
1.03
2.10
Cd[C5H10(COO)2]
All the prepared complexes exhibit similar solid state IR spectra (Table 2).
When the acid is converted to the complex, the stretching vibrations of C=O group,
ν(C=)O in COOH group at 1715 and 1680 cm–1 disappear, whereas the band of asym-
metric vibrations νas(OCO) at 1552–1608 cm–1 and the bands of symmetric vibrations
Fig. 1 Radiogram sheet of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3,3-dimethylglutarates
J. Therm. Anal. Cal., 67, 2002

626
BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
at 1390–1450 cm–1 appear. In the IR spectra of the Mn(II), Co(II), Ni(II) and Cu(II)
3,3-dimethylglutarates there are broad absorption bands of ν(OH) with max. at
3416–3430 cm–1 and narrow bands of δ(H2O) at 1610–1630 cm–1 confirming the pres-
ence of water molecules. The bands of metal–oxygen bond is observed at
500–550 cm–1. The splitting for absorption bands of valency vibrations νas(OCO) and
νs(OCO) (∆ν=νas–νs) have values 156–176 cm–1 (for Cu(II) – 200 cm–1) and are
greater than for the sodium salt (∆ν=126 cm–1). On the basis of ∆ν value and previous
work [7–9] it is possible to suggest that carboxylate groups in the complexes of
Mn(II), Co(II) and Ni(II) act as bidentate chelating, whereas in the complexes of
Cu(II), Zn(II) and Cd(II) as bidentate bridging and water molecules are in inner
Fig. 2 TG, DTG and DTA curves of ZnC7H10O4
Fig. 3 TG, DTG and DTA curves of CdC7H10O4
J. Therm. Anal. Cal., 67, 2002

BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
627
sphere of the complexes. Cu(II) ion has probably CN=5, similarly as in [7, 8] whereas
Co(II), Ni(II) and Mn(II) ions have CN=6, which confirm magnetic measurements,
whereas in the anhydrous complexes of Zn(II) and Cd(II) CN=4. In the Co(II) and
Ni(II) complexes the water molecules act as bidentate ligand.
Table 2 Frequencies of characteristic absorption bands in IR spectra and magnetic moment (M.B.) of
3,3-dimethylglutarates of Mn(II), Co(II), Cu(II), Zn(II), Cd(II) and Ni(II) (cm–1)
Complex
MnL*·2H2O
CoL·1.5H2O
NiL·H2O
CuL·H2O
ZnL
N(OH) νas(OCO) νs(OCO) νas–νs
ν(M–O)
520
µ
eff (M.B.)
n
5
3
2
1
–
–
–
3420
3420
3416
3430
–
1552
1564
1568
1608
1590
1584
1576
1390
1408
1408
1408
1424
1408
1450
162
156
160
200
166
176
126
5.62
5.25
2.91
1.40
–
540
550
525
525
CdL
–
530
–
Na2L·xH2O
3420
500
–
L* – C5H10 (COO)22–; n – number of unpaired electrons
The prepared 3,3-dimethylglutarates are stable at room temperature and can be
stored by for several months without change. During heating they decompose in dif-
ferent ways. Hydrated complexes of Mn(II), Co(II), Ni(II) and Cu(II) heated are sta-
ble up to 318–373 K, whereas anhydrous complexes of Zn(II) and Cd(II) up to 573
and 623 K, respectively. The thermal stability of the prepared complexes increases in
the order:
NiL < CoL < MnL < CuL < Zn < CdL.
Anhydrous complex of Zn(II) heated decomposes to ZnO in the temperature
range 573–793 K (Table 3, Fig. 2), whereas this of Cd(II) (Fig. 3) decomposes to
CdO with intermediate formation oxocarbonate CdO·CdCO3. Dihydrated Mn(II)
3,3-dimethylglutarate heated loses two water molecules (333–433 K) and then anhy-
drous compound decomposes to Mn3O4 (513–763 K). Strong exothermic effect is
connected with combustion of organic ligand. Hydrated Co(II) and Ni(II) complexes
are dehydrated in one step. The anhydrous complex of Co(II) decomposes to free
metal in the temperature range 493–753 K and next oxidizes to Co3O4. Anhydrous
Ni(II) 3,3-dimethylglutarate decomposes directly to NiO in the range 463–743 K.
Monohydrated Cu(II) complex loses water molecule in the range 373–473 K and next
during heating decomposes to free metal, which oxidizes to CuO (633–743 K)
(Fig. 4).The dehydration process is connected with the strong endothermic effect,
whereas the combustion of organic ligand and oxidation of free metal to oxide with
exothermic one.
J. Therm. Anal. Cal., 67, 2002

628
BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
Fig. 4 TG, DTG and DTA curves of CuC7H10O4 . H2O
Table 3 Data for dehydration and decomoposition of 3,3-dimethylglutarates of Mn(II), Co(II),
Ni(II), Cu(II), Zn(II) and Cd(II)
Mass loss/%
Loss of
Mass loss/%
∆T1/K
∆T2/K
Tk/K
Complex
calc. found H2O/mol
calc. found
MnL*·2H2O
CoL·1,5H2O
NiL·H2O
CuL·H2O
ZnL
333–433 14.46 14.50
318–413 11.06 11.05
2
1.5
1
513–783 57.04 57.00
493–773 50.56 50.60
463–743 66.15 66.20
523–743 59.28 59.00
573–793 63.57 63.50
623–853 52.51 52.50
783
775
743
743
793
853
318–393
7.58
7.50
–
7.58
7.55
–
373–473
1
–
–
–
CdL
–
–
–
L* – C5H10 (COO)22–
∆T1 – temperature range of dehydration
∆T2 – temperature range of decomposition
Tk – temperature over which the oxides exist
The results suggest the following schemes of the thermal decomposition of
M(II) 3,3-dimethylglutarates:
MnL·2H2O → MnL → Mn3O4
CoL·1.5H2O → CoL → Co → Co3O4
NiL·H2O → NiL → NiO
CuL·H2O → CuL → Cu → CuO
ZnL → ZnO
CdL → CdO·CdCO3 → CdO
J. Therm. Anal. Cal., 67, 2002

BRZYSKA, O¯GA: 3,3-DIMETHYLGLUTARIC ACID
629
References
1 F. Beilstein, Handbuch der organischen Chemie, Bd 2, Springer Verlag, Berlin 1930, p. 684.
2 A. B. Charette and H. Juteau, Tetrahedron, 53 (1997) 1627.
3 E. C. Amaral and R. A. Guedes de Carvalho, J. Inorg. Chem., 31 (1969) 269.
4 W. Brzyska and W. O¿ga, Polish J. Chem., 75 (2001) 43.
5 S. F. A. Kettle, Physical Inorganic Chemistry, Oxford University Press, 1996.
6 K. Burger, Coordination Chemistry. Experimental Methods. Akadémiai Kiadó, Budapest 1973.
7 W. Brzyska, W. Wo³odkiewicz, Z. Rz¹czyñska and T. G³owiak, Monatsh., 126 (1995) 225.
8 T. Kavata, S. Ochaba, T. Tokii, Y. Muto and M. Koto, Acta Crystal., C, 48 (1992) 1590.
9 W. Clegg, D. R. Harbon, P. A. Hunt, I. N. Little and B. P. Straugham, Acta Crystal., C,
46 (1990) 750.
J. Therm. Anal. Cal., 67, 2002