Complexes of titanium tetrachloride with benzilmonoxime and benzildioxime

Article abstract of DOI:10.1081/SIM-100001940

Some new titanium(IV) derivatives of benzilmonoxime and benzildioxime have been synthesized by the reactions of titanium tetrachloride and the sodium salt of oximes in different molar ratios. All of the newly synthesized complexes have been characterized

Full text of DOI:10.1081/SIM-100001940

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COMPLEXES OF TITANIUM TETRACHLORIDE WITH
BENZILMONOXIME AND BENZILDIOXIME
M. S. Singh a & Prem Narayan a
a Department of Chemistry , D.D.U. Gorakhpur University , Gorakhpur, 273 009, India
Published online: 20 Aug 2006.
To cite this article: M. S. Singh & Prem Narayan (2001) COMPLEXES OF TITANIUM TETRACHLORIDE WITH BENZILMONOXIME
AND BENZILDIOXIME, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 31:1, 149-156, DOI: 10.1081/
SIM-100001940
To link to this article: http://dx.doi.org/10.1081/SIM-100001940
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(1), 149–156 (2001)
COMPLEXES OF TITANIUM
TETRACHLORIDE WITH
BENZILMONOXIME AND
BENZILDIOXIME
M. S. Singh∗ and Prem Narayan
Department of Chemistry, D.D.U. Gorakhpur University,
Gorakhpur 273 009, India
ABSTRACT
Some new titanium(IV) derivatives of benzilmonoxime and
benzildioxime have been synthesized by the reactions of titanium
tetrachloride and the sodium salt of oximes in different molar ratios.
All of the newly synthesized complexes have been characterized by
elemental analyses, molecular weight determinations, and spectral
(IR, 1H, and 13C NMR) studies.
INTRODUCTION
Titanium tetrachloride (1) and titanium compounds (2,3) have been used
to perform a wide variety of different reactions in organic synthesis. These
include TiCl4-mediated Friedel-Crafts reactions, Ti(OR)4-promoted transesteri-
fications, olefin metathesis (4), and the all important Sharpless epoxidation (5).
It became clear that the transmetallation of classical ‘carbanions’ using titanating
agents produces new reagents which display a high degree of chemo-, regio- and
∗Corresponding author. E-mail: dr m s singh@yahoo.com
149
Copyright ꢀ 2001 by Marcel Dekker, Inc.
www.dekker.com
C

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SINGH AND NARAYAN
stereoselectivity (6). A number of oximates (7–9) of transition metals have been
reported having interesting stereochemistry. Benzilmonoxime and benzildioxime
are important from the biochemical and analytical point of view. In view of this and
our continuing studies on the synthesis of new titanium(IV) complexes (10–12),
we herein describe the synthesis and characterization of some new titanium(IV)
derivatives of oximes.
RESULTS AND DISCUSSION
The reaction of TiCl4 with the sodium salt of benzilmonoxime and benzil-
dioxime (prepared in situ by the reaction of sodium isopropoxide with benzil-
monoxime or benzildioxime in 1:1 molar ratio in a refluxing benzene-isopropanol
mixture) in different stoichiometric ratios in dry benzene leads to the formation of
Ti(IV) complexes. These reactions were found to be quite facile and the sodium
chloride formed during the course of the reaction was filtered off.
ꢀ
ꢁ
ꢀ
ꢁ
benzene
– ==
Ph C O
– == –
Ph C N OH
– ==
Ph C O:
– == –
Ph C N O
TiCl4−n
TiCl4 + n
+ n Na−−−→
✱
i−PrOH
−nNaCl
n
n = 1, Compd. (1); n = 2, Compd. (2;) n = 3, Compd. (3); (n = 4), Compd. (4).


ꢀ
ꢁ
OH
benzene
– == –
Ph C N OH
– == –
Ph C N OH


– ==
TiCl4 + n
+ n Na−−−→ Ph C N
TiCl4−n
i−PrOH
✱
– == –
Ph C N O
−nNaCl
n
n = 1, Compd. (5); n = 2, Compd. (6); n = 3, Compd. (7); n = 4, Compd. (8).
Similarly, the disodium salt of benzildioxime was reacted with TiCl4 in
benzene in 1:1 and 2:1 molar ratios to give titanacyclic complexes.
ꢀ
ꢁ
ꢀ
ꢁ
benzene
– == –
Ph C N OH
– == –
Ph C N OH
– == –
Ph C N O
– == –
Ph C N O✱
❧
TiCl4 + m
+ n Na−−−→
TiCl4−n
i−PrOH
−nNaCl
m
m = 1, n = 2, Compd. (9); m = 2, n = 4, Compd. (10).
Allofthesenewcomplexesarefairlysolubleincommonorganicsolventsand
coordinating solvents like DMSO and DMF. The molecular weight determination
in CHCl3 solution shows the monomeric nature of these complexes at room tem-
perature. These complexes are susceptible to hydrolysis. The compounds with
their physical properties and elemental analyses are listed in Table 1.

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151

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SINGH AND NARAYAN
R Spectral Data
The broad band present in the region 3450–2900 cm−1 in the infrared
–
spectrum of the ligand is due to ν(N OH) (13). This band is absent in Ti(IV)
derivatives of benzilmpnoxime and in compounds (9) and (10) of benzildioxime,
–
suggesting replacement of the proton from the N OH group. A new band in
the region 580–560 cm−1 appears, which can be attributed to the formation of
–
titanium- oxygen (Ti O) bonds (2,14). This is further supported by the fact that the
ν(N O) mode shifts from 860 cm−1 in the ligand to higher wave numbers (by 20–
–
25 cm−1) in the complexes suggesting strong coordination of the ligand to tita-
nium through oxygen. The band due to the keto carbonyl, which is observed at
1685 cm−1 in benzilmonoxime is shifted to a lower energy (by 30–35 cm−1) in the
compounds (1)–(4) indicating the participation of the carbonyl group in coordina-
tion. A comparison of the IR spectrum of the ligands with those of the complexes
shows that the band at 1615 cm−1 due to ν(C N) in benzilmonoxime is observed
==
==
almost at the same position in compounds (1) to (4) indicating that the C N group
is not taking part in coordination, whereas the band at 1620 cm−1 due to ν(C N)
==
in benzildioxime is observed at lower frequency (by 20–25 cm−1) in the complexes
==
(5)–(8)indicatingtheinvolvementoftheC Ngroupincoordination(15)(Table2),
−1
–
which is further confirmed by the appearance of a Ti N band at ∼540 cm
.
NMR Spectral Data
All titanium(IV) complexes exhibit a multiplet due to the phenyl group in
1
–
the region d 6.75–8.25 ppm in their H NMR spectra. The signal due to the OH
proton at d 10.20 ppm in benzilmonoxime is absent in its complexes (1)–(4) and
compounds (9) and (10), again suggesting deprotonation and the formation of
–
Ti O bonds. In compounds (5)–(8) a signal at d 10.35–10.45 ppm integrates for
the N OH proton. 13C NMR spectroscopy is a good diagnostic tool for determining
–
the mode of bonding. On coordination the resonances of the carbon atoms bonded
to oxygen and nitrogen atoms shift some 12–18 ppm downfield in the complexes
(15). There is no significant shift in the resonances of the carbons of the phenyl
group in all of the complexes as compared to the ligands (Table 2).
Although the actual structure may be elucidated only after an X-ray crystal
diffraction study of at least one of the products, yet on the basis of the above studies
coordination numbers of four (9),(10), five (1),(5), six (2),(6), seven (3),(7) and
eight (4),(8) may be proposed around titanium(IV).
EXPERIMENTAL
All operations were performed under nitrogen atmosphere and with thor-
oughly dried solvents and glassware. Solvents (benzene, isopropanol) were dried

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SINGH AND NARAYAN
by standard methods (16) prior to use. Melting points are uncorrected. The progress
of the reactions was monitored by TLC on silica gel plates. IR spectra were mea-
sured on a Perkin-Elmer model 377 in KBr discs. 1H and 13C NMR spectra were
recorded on a Bruker AC 250 instrument operating at 250 MHz and 62.9 MHz,
respectively in DMSO-d6 solution. All chemical shifts were recorded in ppm rel-
ative to TMS as an internal standard. Molecular weights were measured on a
Knauer Vapour Pressure Osmometer in CHCl3 solution at room temperature. Ti-
tanium was determined gravimetrically as titanium dioxide (16). Elemental anal-
yses for C, H, and N were performed by the Central Drug Research Institute,
Lucknow.
Titanium tetrachloride AR grade was obtained from Rideal-de Haen AG,
Seelze-Hannover, Germany and used as such without further purification. Benzil-
monoxime and benzildioxime were prepared by reported methods (17). Benzil-
monoxime, m.p. 137–38◦C (Lit. (17). 138–39◦C). IR (KBr, cm−1): 3450–
1
–
==
==
2900 ν((N OH); 1615 ν(C N); 1685 ν(C O). H NMR (DMSO-d6, d ppm):
6.80–8.20 (m, 10H, arom.); 10.20 (s, 1H, OH, D2 O exchangeable). Analysis
found: C, 74.48; H,4.94; N, 6.46%. C14 H11 NO2 (225) requires: C, 74.66; H,
4.88; N, 6.22%. Benzildioxime, m.p. 237–39◦C ( Lit. (17) 239–40◦C). IR (KBr,
cm−1): 3435–3085 ν((N OH); 1620 ν(C N). H NMR (DMSO-d6, d ppm): 7.05–
8.16 (m, 10H, arom.); 10.45 (s, 2H, OH, D2 O exchangeable). Analysis found: C,
70.09; H, 5.12; N, 11.50%. C14H12N2O2 (240) requires: C, 70.00; H, 5.00; N,
11.67%.
1
–
==
Reaction Between TiCl4 and Sodium Salt
of Benzilmonoxime in 1:1 Molar Ratio
A quantity of 0.15 g (6.3 m mole) of sodium metal and 25 mL of dry iso-
propanol were placed in a 100 mL three-necked round bottom flask fitted with an
efficient magnetic stirrer, an addition funnel, a nitrogen balloon, and a condenser.
The solution was stirred at reflux for about half an hour till a clear solution of
sodium isopropoxide was obtained. After cooling, 1.42 g (6.3 m mole) of ben-
zilmonoxime was added and the reaction mixture was refluxed again for 2 h.
Subsequently the reaction mixture was allowed to attain room temperature. 1.19 g
(6.3 m mole) of titanium tetrachloride was added dropwise with a dropping funnel
to the reaction vessel. When the addition was completed, the contents were further
stirred at reflux for 2 h to ensure the completion of the reaction. The solution was
then filtered to remove the sodium chloride formed during the course of the reac-
tion. The desired product was isolated by removal of the solvent under reduced
pressure via rotary evaporator. The product was further purified by crystallization
using a benzene-pet.ether (40–60◦) mixture (20 mL each) to yield 1.78 g (75%)
of product.

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155
All other titanium(IV) derivatives of the oximes were synthesized analo-
gously. The pertinent data for this and other compounds are listed in Table 1.
ACKNOWLEDGMENT
The authors are highly grateful to Dr. Ganesh Pandey of the National Chem-
ical Laboratory, Pune, for valuable academic guidance and spectral help.
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Received October 27, 1999
Accepted November 9, 2000
Referee I: K. Moedritzer
Referee II: J. H. Thayer

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