Synthesis and characterization of some new monophenylantimony(III) derivatives of bifunctional tetradentate ligands

Article abstract of DOI:10.1081/SIM-100002228

Monophenylantimony(III) derivatives of bifunctional tetradentate ligands having the general formula PhSb[RC(NC₆H₄S)CH₂ (NC₆H₄S) CR¹] where R=CH₃, R′=CH₃,C₆H

Full text of DOI:10.1081/SIM-100002228

Synthesis and Reactivity in Inorganic and Metal-Organic
Chemistry
ISSN: 0094-5714 (Print) 1532-2440 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt19
SYNTHESIS AND CHARACTERIZATION OF SOME
NEW MONOPHENYLANTIMONY(III) DERIVATIVES OF
BIFUNCTIONAL TETRADENTATE LIGANDS
Rajendra K. Sharma , Yashpal Singh & Audhesh K. Rai
To cite this article: Rajendra K. Sharma , Yashpal Singh & Audhesh K. Rai (2001) SYNTHESIS
AND CHARACTERIZATION OF SOME NEW MONOPHENYLANTIMONY(III) DERIVATIVES OF
BIFUNCTIONAL TETRADENTATE LIGANDS, Synthesis and Reactivity in Inorganic and Metal-
Organic Chemistry, 31:3, 405-415, DOI: 10.1081/SIM-100002228
To link to this article: http://dx.doi.org/10.1081/SIM-100002228
Published online: 15 Feb 2007.
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Date: 18 December 2016, At: 05:45

SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(3), 405–415 (2001)
SYNTHESIS AND CHARACTERIZATION
OF SOME NEW
MONOPHENYLANTIMONY(III)
DERIVATIVES OF BIFUNCTIONAL
TETRADENTATE LIGANDS
Rajendra K. Sharma, Yashpal Singh,∗
and Audhesh K. Rai
Department of Chemistry, University of Rajasthan,
Jaipur-302004, India
ABSTRACT
Monophenylantimony(III) derivatives of bifunctional tetra-
dentateligandshavingthegeneralformulaPhSb[RC(NC6H4S)CH2
1
ꢀ
=
=
(NC6H4S) CR ] where R CH3, R CH3,C6H5 and 4-CH3C6H4;
1
–
–
=
=
=
=
R CF3, R CF3 and C CH CH CHS have been prepared by
the reactions of triphenylantimony(III) and the corresponding lig-
ands. These compounds have been characterised by elemental anal-
yses, molecular weight determinations, IR,1H, 13C and 19F NMR
spectral studies.
INTRODUCTION
During the last one and a half decades, the chemistry of organoantimony(III)
derivatives with N and S donor ligands has been extensively perused in view of the
∗Corresponding author. E-mail: vijaya29@id.eth.net
405
Copyright ꢁ 2001 by Marcel Dekker, Inc.
www.dekker.com
C

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SHARMA, SINGH, AND RAI
HS
SH
N
C
N
C
R
R’
R = CH3, R1 = CH3(1), C6H5 (2) and 4-CH3C6H4 (3);
R = CF3, R1 = CF3 (4) and
CH CH CHS (5)
CH2
C
Figure 1. Structure of the bifunctional tetradentate ligands.
potential fungicidal (1), bactericidal (2) and chemotherapeutic (3) applications as
well as stereochemical aspects (4–6) of such compounds.
A perusal of the literature (7) reveals that most of the work on organoanti-
mony(III) complexes is confined to monofunctional bidentate ligands and almost
no work has been reported with bifunctional tetradentate ligands. In view of this,
it has been considered worthwhile to synthesise and characterise some organoan-
timony(III) complexes using bifunctional tetradentate ligands containing S and N
donor atoms (Fig. 1).
RESULTS AND DISCUSSION
Reactions of triphenylantimony(III) with the ligands [RC(NC6H4SH)–CH2
(NC6H4SH)CR1] in 1:1molar ratio proceed with the cleavage of the antimony
carbon bond of Ph3Sb and yield the monosubstituted derivatives as given below:
C6H6
Ph3Sb + [RC(NC6H4SH)CH2(NC6H4SH)CR1]
S
S
Sb
+2PhH
N
C
N
C
R
R’
CH2
R = CH3, R’ = CH3,C6H5 and 4-CH3C6H4; R = CF3, R1= CF3 and
C
CH CH CHS

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BIFUNCTIONAL TETRADENTATE LIGANDS
407
After removing the solvent under reduced pressure, light yellow coloured
semi-solid compounds were obtained which were found to be sparingly soluble in
CH2Cl2, CHCl3 and CCl4 but highly soluble in benzene. Osmometric molecular
weight measurements reveal their monomeric nature in benzene solution. These
compounds could not be distilled even under reduced pressure as they are thermally
unstable and decomposed on heating above 130◦C.
IR Spectra
The disappearance of the ν(SH) absorption band in the spectra of these
monophenylantimony(III) complexes, which has been observed at 2499–
2603 cm−1 in the spectra of the ligands, indicates the deprotonation of the SH
group of the ligand and the formation of a Sb-S bond. The formation of the Sb-
S bond has been further confirmed by the appearance of a new band at 372–
395 cm−1 which has been assigned to ν(Sb-S) (8). Another new band appearing at
430–435 cm−1 in the spectra of complexes has been assigned to ν(Sb-N) (9). The
=
formations of a Sb←N bond is further supported by the lowering of the ν(C N)
frequency by 12–18 cm−1 on complexation (complexes: 1607–1614 cm−1; lig-
ands: 1619–1632 cm−1). The ν(Sb-C) (8–10) band has been observed at 434–
453 cm−1 in these derivatives.
1H NMR Spectra
A comparative study of the 1H NMR spectra of these derivatives (Table I)
with those of the corresponding free ligands shows the disappearance of the SH
signal which was observed as a broad signal in the range of δ 2.44–4.40 ppm in
the spectra of the free ligands. The methylene protons are observed as a singlet in
the range of δ 2.82–4.49 ppm and a small shift is observed in the complexes as
compared to their position in the free ligands. The protons of the various R and R1
groups have been observed in the range δ 2.59–2.78 ppm. Phenyl and thiophene
protons of the ligand moieties are found to be merged with the signals of the phenyl
protons attached to the antimony atom and observed as multiplet in the range δ
6.46–8.37 ppm.
13C NMR Spectra
A comparison of the 13C NMR spectra of the monophenylantimony(III)
complexes with those of the ligands provides very useful information about the
mode of bonding. The spectra of the ligand show one set of signals for the car-
bons of R and R1 groups as well as CH2 carbons. However, two sets of signals

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SHARMA, SINGH, AND RAI

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BIFUNCTIONAL TETRADENTATE LIGANDS
409
=
have been observed for the carbons of >C N and the substituted phenyl rings.
The appearance of the two sets of signals may be due to the presence of two
magnetically non-equivalent phenyl rings. This may be explained by considering
two -NC6H4SH rings in two different planes due to the steric hindrance of
the -NC6H4SH groups.
In the spectra of the complexes, the signals for R and R1 carbons show
=
a small shift but the signal for the >C N carbon shows a down field shift of
2–3 ppm in comparison to their positions in the parent ligands. This indicates
the involvement of the nitrogen atom of the ligand moiety in the bonding. A
new set of four signals for phenyl carbons attached to antimony appears in the
spectra of the complexes in the range δ 126–154.9 ppm. The corrected chemi-
cal shift values δ1 defined (11–12) as δ1 δ C(p)-δ C(m) (where δ C(p) and δ
=
C(m) are the chemical shift values of para and meta carbon atoms of the phenyl
group) are found in the range −2.77 to −0.86 in these complexes. This neg-
ative value of δ1 indicates the release of electrons from antimony atom to the
phenyl ring through dπ-pπ conjugation. σR◦ values (13) (calculated by the re-
lation σR◦ = δ1/22.06) of these complexes are also found to have negative val-
ues. A small value of σR◦ indicates the poor donor capability of the antimony
atom.
19F NMR Spectra
The 19F NMR spectrum of the complex PhSb[CF3C(NC6H4S)CH2
(NC6H4S) CCF3] exhibits only one signal at −82.47 ppm for both CF3 groups.
This indicates that both CF3 groups are in same environment. This observation is
in close agreement with the 13C NMR data of the complex.
In view of the monomeric nature of these derivatives and the tetradentate
behaviour of the ligands in the complexes as well as the IR and NMR spectral
data observed, the following structure (Fig. 2) in which the central antimony atom
acquires an octahedral geometry with phenyl group and lone pair occupying trans
positions appear to be highly plausible.
EXPERIMENTAL
Moisture was carefully excluded throughout the experiments. The chemi-
cals used were of reagent grade. Triphenylantimony (Aldrich) was used as such
without further purification. The ligands have been synthesised by the condensa-
tion reaction of β-diketones and 2-aminothiophenol (Merck) in 1:2 molar ratio.
Antimony was determined iodometrically. Nitrogen and sulfur were determined
by Kjeldhal’s and Messenger’s methods, respectively (14). Molecular weights

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SHARMA, SINGH, AND RAI

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BIFUNCTIONAL TETRADENTATE LIGANDS
411

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SHARMA, SINGH, AND RAI
S
S
Sb
N
C
N
C
R
R'
CH2
R= CH3, R1 = CH3 (1), C6H5 (2) and 4-CH3C6H4 (3);
R= CF3, R1 = CF3 (4) and
CH CH CHS (5)
C
Figure 2. Proposed structure of the monophenylantimony(lll) complexes of bifunctional
tetradentate ligands.
were measured on a Knauer vapour pressure osmometer in benzene solution. IR
spectra have been recorded in a Csl cell on a Nicolet DXFT IR spectrophotome-
ter. 1H and 13C NMR spectra were recorded on a Jeol-FX-90Q (90 MHz) NMR
spectrometer in CDCl3 and C6H6 solutions, respectively, using TMS as internal
reference. 19F NMR spectra were recorded in CDCl3 solution using trifluoroacetic
acid as external reference.
Since all of the complexes have been synthesised by the same method, for
the sake of brevity, the synthesis of one representative compound is being given
in detail.
Synthesis of PhSb[CH3C(NC6N4S)CH2(NC6H4S)CCH3]
About 25 mL of a benzene solution of Ph3Sb (1.529 g, 4.33 mmol) was
added to a benzene suspension (−15 mL) of the ligand [CH3C(NC6H4SH)CH2
(NC6H4SH)CCH3] (1.362 g, 4.33 mmol) and the solution was refluxed for
5–6 hours. After the completion of the reaction, the excess solvent was removed
under reduced pressure. For purification, this compound was dissolved in a small
amount of benzene (∼15 mL) and then petroleum ether(bp. 40–60◦C) was added
slowly till a viscous compound began to seperate. The solution was kept overnight
at about −10◦C. The viscous compound left after decanting off the solvent, was
dried under reduced pressure. Yield, 1.75 g (86%).

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413

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SHARMA, SINGH, AND RAI
ACKNOWLEDGMENT
One of the authors (R. K. Sharma) is thankful to the University Grants
Commission, New Delhi, for financial assistance.
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Received January 27, 2000
Accepted January 3, 2001
Referee I: L. K. Krannich
Referee II: K. Moedritzer

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