Synthesis and characterization of tridentate schiff base derivative of indenyl lanthanoid chloride tetrahydrofuranate complexes for catalytic applications

Article abstract of DOI:10.14233/ajchem.2013.13435

Four kinds of novel lanthanocene complexes were synthesized in reasonable yield by the reaction of equimolar quantity of sodium salt of tridentate Schiff base [N-(2-methoxyphenyl)salicylideneimine] with indenyl lanthanoid dichloride tetrahydrofuranate in tetrahydrofuran. All the complexes after purification were characterized by MS and EA, respectively. These complexes isomerized successfully the 1,5- hexadiene into a mixture of products such as 1,4-hexadiene, 2,4-hexadiene,1,3-hexadiene, methylenecyclopentane and methylcyclopentene. Similarly they also proved effective for the polymerization of methylmethacrylate (MMA), 56.45 % yield and high molecular weight (355 × 10³).

Full text of DOI:10.14233/ajchem.2013.13435

Asian Journal of Chemistry; Vol. 25, No. 1 (2013), 518-520
http://dx.doi.org/10.14233/ajchem.2013.13435
Synthesis and Characterization of Tridentate Schiff Base Derivative of Indenyl
Lanthanoid Chloride Tetrahydrofuranate Complexes for Catalytic Applications
1
1*
2
1
MUHAMMAD YOUSAF , AMEER FAWAD ZAHOOR , ANBREEN ANJUM , TANVEER HUSSAIN BOKHARI ,
1
1
1
1
3
KULSOOM GHULAM ALI , BUSHRA PURVEEN , SHAZIA NAHEED , ABDUL JABBAR and HAFIZ BADARUDDIN AHMAD
1Department of Chemistry, Government College University, Allama Iqbal Road, Faisalabad, Pakistan
2Department of Applied Chemistry, Government College University, Allama Iqbal Road, Faisalabad, Pakistan
3Department of Chemistry, Bahauddin Zikeria University, Multan, Pakistan
*Corresponding author: E-mail: fawad.zahoor@gmail.com
(Received: 12 January 2012;
Accepted: 2 August 2012)
AJC-11915
Four kinds of novel lanthanocene complexes were synthesized in reasonable yield by the reaction of equimolar quantity of sodium salt of
tridentate Schiff base [N-(2-methoxyphenyl)salicylideneimine] with indenyl lanthanoid dichloride tetrahydrofuranate in tetrahydrofuran.
All the complexes after purification were characterized by MS and EA, respectively. These complexes isomerized successfully the 1,5-
hexadiene into a mixture of products such as 1,4-hexadiene, 2,4-hexadiene,1,3-hexadiene, methylenecyclopentane and methylcyclopentene.
Similarly they also proved effective for the polymerization of methylmethacrylate (MMA), 56.45 % yield and high molecular weight
(355 × 103).
Key Words: Indene, Tridentate Shiff base, Lanthanoid complexes.
of amino group5. Catalytic synthesis of polymethylmethacrylate6,
isomerization of I, 5-hexadiene into various products7 and so
on. Similarly a series of Schiff base derivative of lanthanoid
INTRODUCTION
The literature survey explains that metal complexes of
Schiff bases occupy a central role in coordination chemistry
for analytical, physical and biological properties1.
complexes with β-diketone hydrazone derivatives were synthe-
sized which exhibited the antibacterial and antifungal potential
activity8. A large number of lanthanoid complexes with
A contemporary theme in modern lanthanoid chemistry
is the design of new ligand environments of lanthanoid comp-
cyclopentadiene/its substituted products and different types
lexes which are capable of saturating the coordination sphere
of the Schiff bases such as monodentate, bidentate, tridentate,
tetradentate, etc. have exhibited their importance in industrial
of lanthanoid (Ln3+) ions and exhibiting high reactivity.
Accordingly Schiff bases have the advantages of ease of
as well as biological fields. Schiff bases derivative of lanthanoid
synthesis, low cost, a hard donor atom framework and tunable
complexes with indenyl are not so much reported. In this work,
steric and electronic effects.
The recent growth in organolanthanoid chemistry has
new series of tridentate Schiff base derivative of lanthanoid
complexes with indenyl ligand have been reported. After
primarily focused on complexes stabilized by tridentate Schiff
characterization, their catalytic potential have been studied for
base ligand system.Further interest in exploring the metal ion
the polymerization of methylmethacrylae and isomerization
complexes with Schiff base ligands has continueously increased,
of 1,5-hexadiene.
since it has been recognized that many of Schiff base derivative
EXPERIMENTAL
of lanthanocene complexes may serve as biologically important,
naturally occurring ionophores. Literature verifies that
lanthanocene hydride complexes are fundamental components
in a wide range of stoichiometric and catalytic organometallic
reactions2.A large number of Schiff bases and their complexes
with lanthanoids have been studied for their interesting and
important properties, such as, their ability to reversibly bind
oxygen3, catalytic activity in hydrogenation of olefins4, transfer
Standard schlenk techniques, a vacuum atmospheres
and N2 filled glovebox were used through the isolation and
handling of metal complexes.All the analytical grade solvents
were dried over sodium metal, refluxed and distilled over blue
sodium benzophenone under argon immediately before use.
Anhydrous LnCl3 and indenyl lanthanoid dichloride
tetrahydrofuranate complexes were prepared according to the

Vol. 25, No. 1 (2013)
Synthesis and Characterization of Tridentate Schiff Base Derivative of Indenyl Lanthanoid Chloride 519
literature method9. Tridentate Schiff base, N-(2-methoxy-
phenyl)salicylideneimine was prepared by the condensation
of equimolar quantities of purified salicylaldehyde and
anisidine in toluene at room temperature. The resulting Schiff
base was purified by recrystallization in petroleum ether, dried
and was used to prepare its salt with sodium metal in tetra-
hydrofuran (THF).
2.9) Anal. C31H35NO4ClEu. Calcd: C, 54.11; H, 5.09; N, 2.04
Found: C, 54.14; H, 5.12; N, 2.07.
RESULTS AND DISCUSSION
The synthetic route of all the complexes (1-4) is explained
in the Scheme-I.
Synthesis of (Ind)Sm(C14H13NO2)Cl·2THF(1):Toa stirring
40 mL of THF solution of indnyl (Ind) samarium dichloride
tetrahydrofuranate (8 mmol) was syringed an equimolar solution
of sodium salt of N-(2-methoxyphenyl)-salicylideneimine in
THF. After stirring for 16 h at room temperature, the orange
yellow solution was concentrated under reduced pressure in
order to get saturated THF solution which was set aside at
room temperature for several days. The orange yellow micro-
crystalline solid was deposited in the bottom which was sepa-
rated from the solution and after drying yield was calculated
to be 48 %. m/z (%): 372.5 (M+-Indenyl-THF-Cl 100), 483.5
(M+-Schiff base-THF-Cl 56.5), 115 (indenyl 2.7), 226 (Schiff
base 1.5), 72 (THF 2.5) Anal. C31H35NO4ClSm. Calcd: C,
55.48; H, 5.22; N, 2.08. Found: C, 55.52; H, 5.02; N, 2.06.
Synthesis of (Ind)Eu(C14H13NO2)Cl·2THF (2): This
compound was prepared analogously to complex 1 from the
reaction of equimolar indenyl europium dichloride
tetrahydrofuranate (7.5mmol) and sodium salt of N-(2-
methoxyphenyl)salicylideneimie in THF. The yellow micro
crystalline solid was obtained in 52 % yield. m/z (%): 374.5
(M+-indenyl-THF-Cl 100), 485.5 (M+-Schiff base-THF-Cl
55.7), 115 (indenyl 2.5), 226 (Schiff base 1.9) 72 (THF 2.1)
Anal. C31H35NO4ClEu. Calcd: C, 55.32; H, 5.20; N, 2.08
Found: C, 55.29; H, 5.21; N, 2.09.
THF
+ LnCl3
+ NaCl
Cl
THF
THF
Na
Ln
Cl
ONa
OCH3
+ NaCl
C
H
N
+
Cl
THF
THF
Ln
Cl
THF
.2THF
Cl
H3
C
Ln
O
O
+ NaCl
N
C
H
Synthesis of (Ind)Gd(C14H13NO2)Cl·2THF (3): The
complex 3 was also synthesized analogously to complex 1 by
reacting equimolar indenyl-gadoliniumdichloride tetrahydro-
furanate (8.8 mmol) with sodium salt of N-(2-methoxyphenyl)
salicylideneimine in THF. The deep yellow microcrystalline
solid in 49 % yield was obtained. m/z (%): 379.5 (M+-indenyl-
THF-Cl 100), 490.5 (M+-Schiff base-THF-Cl 56.7), 115
(indenyl 2.3), 226 (Schiff base 2.0) 72 (THF 2.5) Anal.
C31H35NO4ClEu. Calcd: C, 54.71; H, 5.17; N, 2.07 Found: C,
54.76; H, 5.20; N, 2.09.
Ln = Sm, Eu, Gd, Er
Scheme-I:Synthesis of tridentate Schiff base derivative of indenyl lanthanoid
complexes
These complexes along with NaH successfully isomerized
the 1,5-hexadiene (Scheme-II) into various products such as
1,4-headiene, 2,4-hexadiene, methylcyclopentene and
methylenecyclopentane Table-1.
Synthesis of (Ind)Er(C14H13NO2)Cl·2THF (4): Similarly
this complex was prepared analogously to complex 1 from
the reaction of equimolar amount of indenylerbiumdichloride
tetrahydrofuranate (6.5 mmol) with sodium salt of N-(2-
methoxyphenyl) salicylideneimine in THF. The Orange yellow
microcrystalline solid in 51 % yield was obtained. m/z (%):
389.5 (M+-indenyl-THF-Cl 100), 500.5 (M+-Schiff base-THF-
Cl 55.9), 115 (indenyl 2.5), 226 (Schiff base 2.4) 72 (THF
Cat, NaH
THF, 60 ºC
Scheme-II: Isomerization of 1,5-hexadiene in presence of lanthanide
complexes
TABLE-1
EFFECT OF CATALYST ON THE ISOMRIZATION OF 1,5-HEXADIENE
Conversion
(%)
1,4-Hexadiene
(%)
2,4-Hexadiene
(%)
Methylene
cyclopentane (%)
Methyl
cyclopentene (%)
S. No.
Catalyst
Linear/Cyclic
1
2
3
4
5
C31H35NO4ClSm
C31H35NO4ClEu
C31H35NO4ClGd
C31H35NO4ClEr
ErCl3
29.2
25.7
24.9
21.4
0.6
83.5
80.7
74.9
56.5
40.0
2.5
2.9
12.8
12.1
4.9
4.3
86.0/17.7
83.6/16.4
81.6/19.7
64.0/33.1
–
6.7
14.7
5.0
7.5
24.6
8.5
20.0
Traces
Traces
Reaction conditions: Catalyst/Hexadiene (1:20), Catalyst/NaH (1:50), time (20 h), temperature (60 ºC), solvent (THF).

520 Yousaf et al.
Asian J. Chem.
The complex 1 expressed better activity than all other
ACKNOWLEDGEMENTS
attempted ones, which may be due to greater ionic radius of
samarium metal than any other metal used (Gd, Eu and Er). It
means that greater the ionic radius greater will be the coordi-
nation sphere of the metal. Hence, the easier the monomeric
unit will make attachment with metal during isomerization.
Similarly these catalysts along withAl(i-bu)3 yielded high
molecular weight (355 × 103) polymethylmethacrylate with
narrow polydispersity (1.70) (Table-2).Among all the catalysts
the complex 1 exhibited better efficiency than others which
again is due to the greater ionic radius of the samarium metal
than other used during the formation of complexes (1-4).
Financial Support from the University Research Fund
(URF) of Government College University, Faisalabad, Pakistan
is highly acklowledged.
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(1984).
TABLE-2
EFFECT OF CATALYSTS ON THE POLYMERIZATION
OF METHYLMETHACRYLATE (MMA)
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S.
No.
Conversion Mv × Mw/
Catalyst
103
355
310
280
195
13
Mv
1.70
1.80
1.75
1.83
-
7. M. Yousaf, G.A. Kulsoom, B. Bushra, A. Jabbar, H.B. Ahmad and H.
Ma, Asian J. Chem., 22, 5254 (2010).
(%)
56.45
53.70
51.45
40.50
9.5
1
2
3
4
5
6
IndenylSmCl(C34H33NO2)·2THF
IndenylEuCl(C34H33NO2)·2THF
IndenylGdCl(C34H33NO2)·2THF
IndenylErCl(C34H33NO2)·2THF
SmCl3*
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(2011).
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740 (2000).
Al(i-Bu)3*
15.5
15
-
Reaction conditions: Time = 20 h, cat/MMA = 1:1000, cat/Al = 1:20,
Temp. = 70 ºC, blank = *