3-R-Thio- and 3-R-Oxy-substituted metal acetylacetonates

Article abstract of DOI:10.1134/S1070363207110035

New S- and O-substituted metal acetylacetonates were prepared from phenylthio-, butylthio-, benzenesulfonato-, and 3-acetoxyacetylacetone and appropriate metal salts. The spectral characteristics of the compounds were obtained. The effect of the α-substit

Full text of DOI:10.1134/S1070363207110035

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 11, pp. 1859 1863.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
pp. 1799 1804.
I.V. Svistunova, N.P. Shapkin, O.V. Nikolaeva, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 11,
3-R-Thio- and 3-R-Oxy-substituted Metal Acetylacetonates
I. V. Svistunova, N. P. Shapkin, and O. V. Nikolaeva
Far-Eastern State University,
ul. Oktyabr’skaya 27, Vladivostok, 690950 Russia
e-mail: sgm@mail.primorye.ru
Received August 3, 2006
Abstract New S- and O-substituted metal acetylacetonates were prepared from phenylthio-, butylthio-,
benzenesulfonato-, and 3-acetoxyacetylacetone and appropriate metal salts. The spectral characteristics of the
compounds were obtained. The effect of the -substituent on the stability of the chelates under the conditions
of chromatographic separation on silica gel was revealed. The reactivity of the acetate group bonded to the
chelate ring is decreased, which does not allow preparation of new substituted complexes by common trans-
formations of esters.
DOI: 10.1134/S1070363207110035
Numerous acetylacetone derivatives substituted at
the central carbon ( -C) atom have been reported
[1 3]. However, the majority of them were never
tested in syntheses of metal chelates. From these
diketones, it is possible to prepare a wide range of
acetylacetonate complexes (including those previously
inaccessible) substituted at the -C atom. Further-
more, with these compounds the range of metals for
which it is possible to prepare substituted acetylace-
tonates can be substantially extended. The existing
procedures for preparing substituted complexes in-
volve introduction or transformation of functional
groups in ready chelates. The pathways of all these
reactions critically depend on the central metal ion,
so that these reactions can be successfully applied to
only a limited range of metals.
acetate, and benzenesulfonate substituents from the
corresponding acetylacetone derivatives.
The majority of the complexes were prepared by
the standard procedure involving the reaction of metal
chlorides with diketones in aqueous-alcoholic solu-
tion:
O
O
(1)
R
R
M
MCln + nH
n
O
O
I XX
M = Cr, n = 3, R = SPh (I); M = Al, n = 3, R = SPh (II);
M = Fe, n = 3, R = SPh (III); M = Cu, n = 2, R = SPh
(IV); M = Be, n = 2, R = SPh (V); M = Cr, n = 3, R = SBu
(VI); M = Al, n = 3, R = SBu (VII); M = Fe, n = 3, R =
SBu (VIII); M = Cu, n = 2, R = SBu (IX); M = Cr, n = 3,
R = OSO2Ph (X); M = Al, n = 3, R = OSO2Ph (XI); M =
Fe, n = 3, R = OSO2Ph (XII); M = Cu, n = 2, R = OSO2Ph
(XIII); M = Ni, n = 2, R = OSO2Ph (XIV); M = Pd, n = 2,
R = OSO2Ph (XV); M = Cr, n = 3, R = O2CCH3 (XVI);
M = Al, n = 3, R = O2CCH3 (XVII); M = Fe, n = 3, R =
O2CCH3 (XVIII); M = Cu, n = 2, R = O2CCH3 (XIX);
M = Ni, n = 2, R = O2CCH3 (XX).
Among the simplest thio-substituted acetylaceto-
nates, phenylthio-substituted complexes of Cr(III) and
Co(III) [4, 5] and chromium(III) ethylthioacetylaceto-
nate [6] have been reported. Attempts to apply the
protocols from [5] to the synthesis of thioethyl-substi-
tuted complexes failed [7], and it is unlikely that
3-phenylthio-substituted acetylacetonates of other
metals can be prepared by similar procedures.
The only exception was Co(III) whose chelates
were prepared starting from the complex carbonate:
Among complexes containing an O-bonded sub-
stituent at the central carbon atom, the complexes
Cu(acacOMe)2 and Cu(acacOOCCH3)2 prepared by
chelation have been reported [8]. Kasuga et al. [9]
also mention copper and aluminum acetylacetonates
containing a phenoxy group.
O
O
Na3[Co(CO3)3] + 3H
R
(2)
R
Co
3
O
O
XXI XXIV
The goal of this study was synthesis of acetylace-
tonate complexes containing phenylthio, butylthio,
R = SPh (XXI); R = SBu (XXII); R = OSO2Ph (XXIII);
R = OOCCH3 (XXIV).
1859

1860
SVISTUNOVA et al.
Irrespective of the substituent in acetylacetone, the
a formate substituent. However, the reactions of for-
myloxyacetylacetone with copper, chromium, and iron
salts yielded the chelates neither in aqueous-alcoholic
solution nor in DMF. Analysis of the reaction mixture
showed that the ligand fully disappeared. Apparently,
under the reaction conditions formyloxyacetylacetone
decomposes so rapidly that it has no time to react with
metal ions.
copper and iron complexes were prepared in the high-
est yields, and the reaction could be performed with-
out heating. The chromium and aluminum complexes
were prepared in considerably lower yields, and syn-
thesis of Al(acacSBu)3 in aqueous-alcoholic solution
failed. In addition, we attempted to synthesize in
aqueous-alcoholic solution, following scheme (1),
phenylthio- and butylthio-substituted Rh(III) acetyl-
acetonates, but none of the rhodium complexes was
prepared.
The properties of complexes I and XXI agree with
the published data. The structures of the other com-
pounds were proved by elemental analysis, IR spec-
Apparently, differences in the readiness of forma-
tion and in the yields of the complexes are due to
different kinetic stability of the aqua ions. The most
labile aqua ions of copper and iron form the com-
plexes rapidly and in a high yield. With more stable
aqua ions of aluminum and chromium, the reaction is
slower and requires heating, which leads to partial hy-
drolysis of the ligands, competing formation of non-
chelate complexes, and decreased yields of the target
products. In the case of the kinetically inert rhodium
ion, the side processes prevail over the complexation.
1
troscopy, mass spectrometry, and H NMR.
The IR spectra of the compounds prepared are typi-
cal of substituted acetylacetonates: In the range 1600
1
1500 cm , there is a single strong absorption band
traditionally assigned to vibrations of chelated C=O
groups in substituted acetylacetonates. In addition,
there are bands characteristic of the introduced sub-
stituents. In I V and XXI, this is the band of the
1
phenylthio group at 1480 cm . In the spectra of
CH3COO-substituted chelates XVI XX and XXIV,
To increase the yield of chromium and aluminum
complexes, we performed reaction (1) in a nonaque-
ous solvent (DMF). By so doing, we succeeded in the
synthesis of butylthio-substituted aluminum acetyl-
acetonate VII which is not formed in aqueous-alco-
holic solution. Furthermore, in DMF chromium com-
plexes I, X, and XVI were prepared in higher yields
than in aqueous-alcoholic solution. Nevertheless, the
procedure in aqueous-alcoholic solution can be recom-
mended for use, because it is simple and the reactants
are readily accessible.
there are bands of the free carbonyl group (1750
1
1755 cm ) and two bands of the ester bond C O C
1
(1215, 1147 cm ). The PhSO2O group in the spectra
of X XV and XXIII gives four strong bands at 1190,
1
1131, 1090, and 820 cm . In the spectra of all the
oxygen-substituted acetylacetonates X XX, XXIII,
1
and XXIV, there is a strong band at 1485 1470 cm ,
apparently caused by O C (chelate ring) vibrations.
In the range of absorption of hydroxy groups, each of
complexes XIV and XX gives two broad bands as-
signable to coordinated water.
The cobalt complexes were prepared in lower
yields compared to the complexes of the other metals.
One of the reasons is easy decomposition of substi-
tuted cobalt(III) acetylacetonates. Chelate XXII con-
taining the SBu substituent is the least stable among
the Co(III) complexes we prepared. This compound
decomposes in the course of storage, recrystallization,
and thin-layer chromatography on silica gel. As
judged from the pink color of the products formed, the
decomposition yields cobalt(II) compounds. The other
cobalt complexes (XXI, XXIII, XXIV) are quite stable
after isolation and purification. We believe that easy
decomposition of cobalt(III) complexes is due to the
occurrence of an intramolecular redox reaction. In
XXII, the butylthio substituent exhibiting a positive
inductive effect increases the electron density on the
ligand, thus facilitating the intramolecular redox re-
action.
The information content of the mass spectra of
I XIII, XV, XVI, and XXI XXIII depends on both
the central ion and substituent. The largest number of
heavy ions (including molecular ions) were detected
in the mass spectra of the Be, Al, Cr, Pd, and Cu
complexes. In the spectra of the Fe complexes the
heavy ion peaks are considerably weaker, and in the
spectra of the Co(III) complexes they are lacking at
all. Therefore, electron impact mass spectrometry is
useless when applied to the Co(III) acetylacetonates.
We believe that the decreased intensity of heavy
ion peaks in the mass spectra of the iron complexes
is due to the fact that iron has stable oxidation state
2+, which makes favorable the loss of a ligand from
the molecular ion, with a decrease in the oxidation
state. For cobalt, oxidation state 2+ is still more
stable, and the fragmentation occurs more deeply.
Such behavior of substituted cobalt(III) acetylaceto-
nates was noted in [10].
By analogy with complexes containing acetate
groups, we attempted to prepare complexes containing
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3-R-THIO- AND 3-R-OXY-SUBSTITUTED METAL ACETYLACETONATES
1861
Table 1. Relative intensity of some ions in the mass spectra of thio-substituted chelates, % (L = acacSPh or acacSBu)
+
Comp. no.
Compound
[MLn]+
[MLn 1(acacH)]+
[MLn
]
[MLn 2(acacH)]+
1
I
II
Cr(acacSPh)3
Al(acacSPh)3
Fe(acacSPh)3
Cu(acacSPh)2
Cr(acacSBu)3
Al(acacSBu)3
Fe(acacSBu)3
Cu(acacSBu)2
24
63
29
3
28
100
10
56
45
III
IV
VI
VII
VIII
IX
10
100
41
10
40
6
24
8
100
100
100
35
33
21
22
3
The fragmentation of SPh- and SBu-substituted
acetylacetonates occurs as successive loss of substitu-
ents and whole ligands and is described by scheme (3):
iron acetylacetonates can be chromatographed on
silica gel plates without decomposition. This fact was
unexpected. Our experience, in combination with pub-
lished data [11], suggested that methods of adsorption
chromatography could be applied only to acetylaceto-
nates of Cr(III), Co(III), and Rh(III). Complexes of
other metals are irreversibly sorbed and decompose on
silica gel. Previous studies gave no evidences that an
-substituent could affect the chromatographic stabil-
ity of acetylacetonate complexes.
L
SR
+
[MLn]+
[MLn 1]
[MLn 2(acacH)]+
(3)
SR
[MLn 1(acacH)]+
L = acac S R, R = Ph, Bu, n = 2, 3.
Special experiments showed that compounds XII
and XIII can also be chromatographed on a column
packed with silica gel. The IR spectra of the eluted
products differ from those of the starting substances
insignificantly.
The relative intensities of some ions are given in
Table 1.
The spectra of I IV and VI IX contain no ions
corresponding to the loss of two ligands or destruction
of the chelate ring. However, beryllium complex V
gives ions corresponding to the loss of ketene from
the chelating ligand:
Our further experiments concerned the reactions of
the substituted acetylacetonates with hydrazine. These
reactions were monitored by gas chromatography
mass spectrometry. We examined whether the struc-
tures of the pyrazoles formed in the process corre-
spond to the structures of the starting complexes.
Be(acacH)
L
acacH
SPh
(4)
Be(L)
Be(L)2
Be(L)(acacH)
Phenylthio- and butylthio-substituted complexes,
irrespective of particular metal ion, react with hydra-
zine to form 3-phenylthio(butylthio)-2,4-dimethyl-
pyrazole. The chromatograms always contain a peak
of 2,4-dimethylpyrazole whose intensity is about 5%
of that of the thio-substituted pyrazole peak, i.e., the
metal displacement is accompanied by removal of the
substituent.
CH2CO
CH2CO
(L)Be O
Ph
O
(L)Be
S
L = acac S Ph.
The mass spectra of X XV are poorly informative,
apparently because of high molecular weight of these
complexes, preventing their vaporization. In the mass
spectra of chromium complex X, aluminum complex
XI, and palladium complex XV, there are weak peaks
corresponding to the removal of one sulfonate group
and one ligand. The mass spectra of iron complex XII
and copper complex XIII contain no peaks of metal-
containing ions.
Treatment of the sulfonate-substituted complexes
resulted in the formation of small amounts of 2,4-di-
methylpyrazole and of two to four other volatile prod-
ucts which we failed to identify from the mass spec-
tra. 3-Benzenesulfonato-2,4-dimethylpyrazole was not
detected.
Treatment of the CH3COO-substituted complexes
with hydrazine yielded 2,4-dimethylpyrazole as the
major product. 3-Acetoxy-2,4-dimethylpyrazole was
not detected.
We found that sulfonate-substituted copper and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

1862
SVISTUNOVA et al.
Thus, the reaction with hydrazine is of little use for
EXPERIMENTAL
identification of oxygen-substituted acetylacetonates
by gas chromatography mass spectrometry.
1
The IR spectra in the range 4000 400 cm were
recorded on a Spectrum 100 BX-II device from KBr
pellets. The mass spectra were taken on an LKB-9000
device with direct sample inlet; ionizing voltage
Taking into account the fact that esters are widely
used for preparing other derivatives, we attempted to
involve the CH3COO-substituted acetylacetonates into
some characteristic reactions of esters. Treatment of
XVI with solutions of alkali, aniline, and Grignard
reagent left it unchanged. On the other hand, at-
tempted saponification of XVI at higher alkali concen-
tration or elevated temperature resulted in its decom-
position to inorganic substances. These facts show
that the ester group linked to the acetylacetonate ring
exhibits decreased reactivity. Similar decrease in the
reactivity of functional groups in acetylacetonates was
noted in [5]. Collman [4] believed that the -C atom
in the chelate ring is a particular reaction center,
due to the electronic structure of the chelate ring and
shielding effect of the -methyl groups.
1
70 eV. The H NMR spectra were recorded on a
Bruker WH 250 device with an operating frequency of
250 MHz in CDCl3 relative to TMS. Gas-chromato-
graphic studies were performed on an HP 5890 device
(series II) with a 5972 mass-selective detector (Hew-
lett Packard, the United States). Analysis conditions:
HP-5MS column, 30 m 0.250 mm 0.25 m, carri-
er gas He, constant flow mode, flow rate in the col-
1
umn 0.7 ml min . Temperature schedule: 50 C,
1 min; heating to 280 C, 10 deg min ; 280 C,
1
20 min. Detector: ionizing electron energy 70 eV, full
scanning in the range of m/z 50 410, detection delay
2 min. Thin-layer chromatography was performed
with Sorbfil PTSKh-P-V plates, eluent benzene or
benzene acetone (10 : 1). The analytical characteris-
tics of the products are given in Table 2.
Table 2. Preparation methods, yields, and elemental analyses of I XXIV
Found, %
Calculated, %
Preparation method
and solvent for
recrystallization
Comp.
no.
Yield,
%
mp,
C
Formula
C
H
S
C
H
S
I
I
II
III
IV
V
VI
VII
VIII
IX
A, hexane; alcohol
C, hexane; alcohol
A, hexane; alcohol
A, hexane; alcohol
A, hexane; alcohol
A, hexane; alcohol
A, hexane
C, hexane
B, hexane
B, alcohol
A, alcohol
55
75
45
46
94
83
52
68
85
92
75
48
66
71
74
66
40
78
66
70
73
32
52
107 109a 57.90
14.20 C33H33CrO6S3
C33H33CrO6S3
58.82 4.94 14.28
58.82 4.94 14.28
61.09 5.13 14.83
58.49 4.91 14.19
55.27 4.64 13.41
62.39 5.24 15.14
52.83 7.39 15.67
55.08 7.70 16.34
52.50 7.34 15.57
49.35 6.90 14.64
48.47 4.07 11.76
50.00 4.20 12.13
48.24 4.05 11.71
119 121
144
186
189
60
60.86
58.26
55.09
62.19
54.86
55.34
51.84
48.23
14.70 C33H33AlO6S3
14.18 C33H33FeO6S3
13.04 C22H22CuO4S2
14.93 C22H22BeO4S2
15.64 C27H45CrO6S3
17.21 C27H45AlO6S3
15.75 C27H45FeO6S3
14.61 C18H30CuO4S2
C33H33CrO15S3
52
54
168
162
199
182
228
X
XI
49.04 4.41
49.83 4.14 12.28 C33H33AlO15S3
48.08 4.19 11.56 C33H33FeO15S3
A, alcohol
B, benzene
XII
XIII
XIV
XV
XVI
XVI
B, chloroform alcohol
B, alcohol
B, chloroform alcohol
A, isopropanol
C, hexane
46.29 3.97 11.77 C22H22CuO10S2c 46.03 3.86 11.17
89 (108)b 45.76 3.72
C22H26NiO12S2
41.98 3.46 10.61 C22H22PdO10S2
43.66 4.33 10.59
42.83 3.59 10.39
48.19 5.20
48.19 5.20
50.61 5.46
47.84 5.16
44.50 4.80
41.11 5.42
58.22 4.89 14.13
170
221 223
218 220
220 222
200 203
270 273
48.40 4.72
C21H27CrO12
C21H27CrO12
C21H27AlO12
C21H27FeO12
C14H18CuO8
C14H22NiO10
XVII A, hexane
XVIII B, benzene hexane
XIX
XX
XXI
50.41 4.88
47.87 4.63
44.41 4.35
45.10 4.28
58.50
B, benzene hexane
B, benzene hexane
D, hexane
c
114 115
13.19 C33H33CoO6S3
(decomp.)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

3-R-THIO- AND 3-R-OXY-SUBSTITUTED METAL ACETYLACETONATES
Table 2. (Contd.)
1863
Found, %
H
Calculated, %
Preparation method
and solvent for
recrystallization
Comp.
no.
Yield,
%
mp,
C
Formula
C
S
C
H
S
XXII B, hexane
XXIII D, alcohol
48
13
52.38
47.85 3.58
C27H45CoO6S3
C33H33CoO15S3 48.06 4.03 11.66
52.24 7.31 15.50
126
(decomp.)
138 150
XXIV D, isopropanol
25
47.54 4.50
C21H27CoO12
47.56 5.13
(decomp.)
a
b
c
mp 109 C [4]. Apparently, the second melting point corresponds to the dehydrated complex. With two water molecules.
Preparation of metal chelates in aqueous-alco-
Reaction with hydrazine. A mixture of 50 mg of
a complex, 1 ml of hydrazine hydrate, and 5 ml of
alcohol was refluxed until the solution became fully
colorless and a precipitate formed. The cooled solu-
tion was diluted with water and extracted with chloro-
form. The chloroform extract was studied by gas chro-
matography mass spectrometry.
holic solution, method A. A solution of 0.0033 mol
of sodium acetate in 5 ml of water was added drop-
wise with stirring on a magnetic stirrer to combined
solutions of 0.001 mol of metal chloride in 5 ml of
water and of 0.0033 mol of a diketone in 5 ml of al-
cohol. The mixture was heated until its color changed
and an oil precipitated. The mixture was diluted with
water and extracted with chloroform. After removing
the solvent, the residue was recrystallized.
REFERENCES
1. Michalski, J. and Lenard, B., Roczn. Chem., 1956,
In syntheses of the iron complexes, NaHCO3 was
used instead of sodium acetate.
vol. 30, p. 655.
2. Morirty, R.M., Vaid, R.K., Ravikumar, V.T.,
Vaid, B.K., and Hopkins, T.E., Tetrahedron, 1988,
vol. 44, no. 6, p. 1603.
Preparation of metal chelates in aqueous-al-
coholic solution, method B. The reaction was per-
formed similarly to method A without heating. After
stirring for 1 2 h, the precipitate was filtered off and
recrystallized.
3. Yoshida, Z. and Ogoshi, H., Tetrahedron, 1970,
vol. 26, no. 12, p. 2987.
4. Collman, J.P., Marshall, R.L., Young, W.L., and
Sears, C.T., J. Org. Chem., 1963, vol. 28, no. 6,
p. 1449.
Preparation of metal chelates in DMF, method
C. A mixture of 0.001 mol of metal chloride,
0.0033 mol of a diketone, and 0.0033 mol of sodium
acetate trihydrate in 10 ml of DMF was heated at 80
100 C until the spot of the diketone disappeared (TLC
monitoring, after dilution of a sample with water and
extraction with chloroform; development with FeCl3
solution). The reaction mixture was diluted with water
and extracted with chloroform. The residue after re-
moving the solvent was recrystallized.
5. Yoshida, Z., Ogoshi, H., and Shimidzu, Y., Tetra-
hedron Lett., 1969, vol. 27, p. 2255.
6. Shapkin, N.P., Nedel’kin, V.I., Svistunova, I.V., and
Sergeev, V.A., Vysokomol. Soedin., Ser. A, 1990,
vol. 32, no. 9, p. 1910.
7. Reutov, V.A., Svistunov, G.M., and Shapkin, N.P.,
Zh. Obshch. Khim., 1987, vol. 57, no. 9, p. 2060.
8. Fackler, J.P. and Cotton, F.A., Inorg. Chem., 1963,
vol. 2, no. 1, p. 102.
Preparation of cobalt complexes, method D.
A mixture of 3 mmol of Na3[Co(CO3)3], 10 mmol of
a diketone, 10 ml of isopropyl alcohol, and 3 ml of
acetic acid was heated with stirring until it became
homogeneous. After cooling, the mixture was diluted
with water and extracted with chloroform. The extract
was washed with water and a dilute solution of am-
monia to remove traces of the acid. After drying over
CaCl2 and removing the solvent, the residue was re-
crystallized.
9. Kasuga, K., Anami, M., Yamamoto, Y., Bull. Chem.
Soc. Jpn., 1978, vol. 51, no. 2, p. 476.
10. Svistunova, I.V., Shapkin, N.P., and Nikolaeva, O.V.,
Zh. Obshch. Khim., 2005, vol. 75, no. 3, p. 367.
11. Timerbaev, A.R. and Petrukhin, O.M., Zhidkostnaya
adsorbtsionnaya khromatografiya (Liquid Adsorption
Chromatography), Moscow: Nauka, 1989.
12. Svistunova, I.V., Shapkin, N.P., and Nikolaeva, O.V.,
Zh. Obshch. Khim., 2002, vol. 72, no. 6, p. 962.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007