Reaction time dependent formation of Pd(ii) and Pt(ii) complexes of bis(methyl)thiasalen podand

Article abstract of DOI:10.1039/c2dt31630g

Thiasalen podand 9 having S2N2 donor set has been synthesized by the condensation of 2-methylthiobenzaldehyde with ethylenediamine. The reaction of the thiasalen podand ligand with Pd(ii) afforded two complexes depending on the reaction time. Shorter reaction time (5 min) afforded thioether complex 10; whereas with increase in reaction time (4 h) thioether-thiolate complex 11 was obtained via cleavage of one of the two S-C(Me) bonds of bis(methyl)thiasalen podand upon complexation. The reaction of 9 with Pt(ii) afforded only thiolate-thioether complex 12 independent of the reaction time. The cleavage of both the S-C(Me) bonds of bis(methyl)thiasalen to afford bisthiolate complexes has never been observed. The structures of thiasalen podands and all three complexes have been determined by single crystal X-ray diffraction analysis. All three complexes possess a square planar geometry around the metal centres. Weak van der Waals interactions through C-H...F interactions are present in all three complexes leading to the formation of supramolecular synthons and the supramolecular structures are stabilized by aromatic π...π interactions, which leads to the formation of 3D pseudo-double helical network packing. Under similar conditions bis(methyl)salen did not form any complexes with Pd(ii) and Pt(ii).

Full text of DOI:10.1039/c2dt31630g

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Reaction time dependent formation of Pd(II) and Pt(II)
complexes of bis(methyl)thiasalen podand†
Cite this: Dalton Trans., 2013, 42, 476
Pradip Kr. Dutta, Snigdha Panda,* G. Rama Krishna, C. Malla Reddy and
Sanjio S. Zade*
Thiasalen podand 9 having S2N2 donor set has been synthesized by the condensation of 2-methylthio-
benzaldehyde with ethylenediamine. The reaction of the thiasalen podand ligand with Pd(II) afforded
two complexes depending on the reaction time. Shorter reaction time (5 min) afforded thioether
complex 10; whereas with increase in reaction time (4 h) thioether–thiolate complex 11 was obtained via
cleavage of one of the two S–C(Me) bonds of bis(methyl)thiasalen podand upon complexation. The reac-
tion of 9 with Pt(II) afforded only thiolate–thioether complex 12 independent of the reaction time. The
cleavage of both the S–C(Me) bonds of bis(methyl)thiasalen to afford bisthiolate complexes has never
been observed. The structures of thiasalen podands and all three complexes have been determined by
single crystal X-ray diffraction analysis. All three complexes possess a square planar geometry around the
metal centres. Weak van der Waals interactions through C–H⋯F interactions are present in all three com-
plexes leading to the formation of supramolecular synthons and the supramolecular structures are stabil-
ized by aromatic π⋯π interactions, which leads to the formation of 3D pseudo-double helical network
packing. Under similar conditions bis(methyl)salen did not form any complexes with Pd(II) and Pt(II).
Received 21st July 2012,
Accepted 18th September 2012
DOI: 10.1039/c2dt31630g
www.rsc.org/dalton
Se–C(alkyl) bonds upon complexation.
Introduction
Transition metal complexes of salen-type (N, O donor) ligands
have been known for many years.1 The importance of salen
ligands in homogeneous catalysis and organic synthesis has
unambiguously been demonstrated over the last two decades.2
The salen metal complexes have also found applications in
electroanalysis and biochemistry3,4 as well as potentiometric
sensors.5 Though reports on thiasalen (N, S donor) ligands
and their transition metal complexes are numerous,6 only a
few thiasalen complexes with alkylated sulphur atoms are
known.7 There are no reports of the thiasalen ligand complexa-
tion with Pd(II) and Pt(II).
Earlier we8 reported the complexation behaviour of bis-
(alkyl)selenasalen podands 1–3 towards Pd(II) and Pt(II). The
reaction of podands 1–3 with Pd(II) and Pt(II) afforded seleno-
ether–selenolate complexes 4–7 via cleavage of one of the two
In the present study, our aim was to explore the complexation
behaviour of S-alkylated thiasalen and O-alkylated salen
podands towards Pd(II) and Pt(II). Here we report the interest-
ing results of Pd and Pt complexation with the bis(methyl)thia-
salen ligand (Scheme 1). The complexation with Pd(II) afforded
two complexes depending on the reaction time. Shorter reac-
tion time (5 min) afforded thioether complex 10; whereas with
increase in reaction time (4 h) thioether–thiolate complex 11
was obtained via cleavage of one of the two S–C(Me) bonds of
bis(methyl)thiasalen podand upon complexation. The reaction
of 9 with Pt(II) afforded only thiolate–thioether complex 12
independent of the reaction time. Under similar conditions
bis(methyl)salen did not form any complexes with Pd(II) and
Pt(II).
Department of Chemical Sciences, Indian Institute of Science Education and
Research, Kolkata, PO: BCKV campus main office, Mohanpur 741252, Nadia,
West Bengal, India. E-mail: snigdha@iiserkol.ac.in, sanjiozade@iiserkol.ac.in;
Fax: +91-33-25873020
†Electronic supplementary information (ESI) available: Calculated absolute ener-
gies and coordinates of the optimized geometries, reaction coordinates of the
demethylation reactions for DFT calculation. CCDC 882776, 882778, 882777 and
882779. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c2dt31630g
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Scheme 1 Synthesis of podand ligands 9 and complexes 10–12.
relatively soft Pd(II) and Pt(II) metal ions. Previously, we
reported the coordination properties of the analogous selena-
salen ligand with Pd(II) and Pt(II).8
Results and discussion
Synthesis of ligands
Bis(methyl)thiasalen 9 was obtained by the condensation of
When thiasalen ligand 9 was refluxed with Pd(C6H5CN)2Cl2
ethylenediamine with two equivalents of 2-(methylthio)benz- in dry methanol for 3 h, the complex 11 was isolated as the
aldehyde. Podand 9 was obtained as a pure light yellow solid. predominant product with a small amount of complex 10.
The vibrational frequency for the CvN bond (ν(CvN)) of the Therefore, the reaction of 9 with Pd(C6H5CN)2Cl2 was repeated
compound 9 was observed at 1635 cm−1 in the FT-IR spec- and the formation of products with respect to the reaction
trum. The podand 9 showed a singlet at δ ∼ 8.73 ppm for azo- time was monitored. When the reaction mixture was allowed
methine protons in the 1H NMR spectrum. In the 13C NMR to reflux only for 5 min, bisthioether complex 10 was obtained
spectrum of 9, azomethine carbon was observed at δ ∼ as a sole product where both the methyl groups were intact.
160.9 ppm. Ligand
9 showed the molecular ion peak However, the reaction of 9 with Pd(C6H5CN)2Cl2 was continued
[(C18H20N2S2 + H)]+ at 329.1 in the ESI-MS spectra. 2-Meth- for 4 h at reflux, interestingly, only the complex 11 was
oxybenzaldehyde 13 was prepared by methylation of salicyl- obtained with the cleavage of one of the methyl groups of the
aldehyde with methyl iodide.9 Bis(methyl)salen 14 (Scheme 2) ligand. Upon increasing the reaction time up to 24 h, the clea-
was obtained by the condensation of ethylenediamine with vage of both the methyl groups has never been observed.
two equivalents of 13.10
Under similar reaction conditions, the reaction of podand 9
with PtCl2 afforded the complex 12, irrespective of the reaction
time. All the complexes were soluble in CH3CN, DMSO and
acetone, however, insoluble in chlorinated solvents.
The reaction of 9 with Pd(C6H5CN)2Cl2 in refluxing meth-
anol for 5 min led to the formation of a light yellow colour
solution and complex 10 was precipitated by the addition of
NH4PF6. The NMR spectroscopic characterization and elemen-
tal analysis of the complex 10 showed the formation of a sym-
metrical complex where both S–Me bonds remained intact. It
was further confirmed by single crystal X-ray structure determi-
nation. The integration in the 1H NMR spectrum of 10
Complexation of thiasalen with Pd(II) and Pt(II)
The thiasalen podand 9 was studied for its coordination prop-
erties towards Pd(II) and Pt(II) with varying reaction time. Reac-
tions of podand 9 with Pd(C6H5CN)2Cl2 and PtCl2, in refluxing
methanol, afforded the complexes 10, 11 and 12. Bis(methyl)-
salen podand 14 was obtained to compare the C-chalcogen
(O/S/Se) bond cleavage upon complexation with Pd(II) and Pt(II).
However, under similar reaction conditions the podand 14 did
not react with the Pd(II) and Pt(II). It may be due to the hard
nature of N, O donor atoms which are non-coordinating to
Scheme 2 Synthesis of bis(methyl)salen podand 14.
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indicated the presence of two S–Me groups. The 1H NMR spec- out DFT calculation (see theoretical methods). In our previous
trum of the complex 10 showed only one singlet peak at δ study,8 we have shown that SN2 substitution at the methyl
9.03 ppm for azomethine protons. The peak at δ 2.96 ppm cor- group by the halide ion where the selenolate complex acts as a
responds to S–Me in 10 (δ 2.36 ppm for the precursor ligand 9, leaving group to eliminate the alkyl halide is the most likely
methyl protons). Complex 10 showed 9 signals in the 13C NMR reaction pathway for the dealkylation of selenoether upon
spectrum for 9 different types of carbons indicating the sym- complexation with Pd(II) and Pt(II). Experimentally we have
metrical structure of the ligand in the complex. The FT-IR observed the formation of alkyl halides in the complexation
−
spectrum of 10 indicates the presence of a PF6 counter ion reaction of 2 and 3 with Pd(II) and Pt(II), respectively.8 Pre-
{836 [ν(P–F)], 558 [δ(F–P–F)] cm−1}. In addition the FT-IR spec- viously, we have assumed the formation of a bis-selenoether
trum of 10 displayed the characteristic ν(CvN) stretching fre- complex analogous to 10·Cl2, as a reactant for the dealkylation
quency around 1650 cm−1, which was shifted to higher energy via SN2 reaction. Indeed, we have isolated now the analogous
values compared with the ν(CvN) stretching frequencies of bisthioether complex 10·Cl2. Calculated activation energies for
1635 cm−1 for the free ligand 9.
the demethylation in Pd and Pt complexes 11·Cl2 and 12·Cl2
The reaction of 9 with Pd(C6H5CN)2Cl2 in refluxing metha- are 10.9 and 8.7 kcal mol−1. Activation energies for SN2 tran-
nol for 4 h led to the formation of a light brown colour sol- sition states in the thiasalen complexes are 0.6 and 1.8 kcal
ution and complex 11 was precipitated by the addition of mol−1 less than those of the corresponding selenasalen com-
NH4PF6. The NMR spectroscopic studies show the formation plexes. DFT calculations indicated two important points: deal-
of thiolate–thioether complex 11 via cleavage of one of the kylation in the case of the Pt-complex (thia or selenasalen)
S–Me groups. The FT-IR spectrum of 11 indicates the presence requires slightly less energy than the corresponding Pd-com-
of a PF6 counter ion {838 [ν(P–F)], 557 [δ(F–P–F)] cm−1}. In plexes. Demethylation of bis(methyl)thiasalen complexes is
−
addition the spectrum displays the characteristic ν(CvN) more facile than selenasalen complexes. Our calculations
stretching frequencies at 1647 cm−1 and 1629 cm−1, which are suggested that second dealkylation requires significantly less
shifted to higher and lower energy values, respectively, com- activation energy (4.4 kcal mol−1, in the case of demethylation
1
pared with that of the free podand 9. The H NMR spectrum of the thioether–thiolate complex) than first demethylation.
of the complex 11 showed two closely spaced singlet peaks at δ However, experimentally we never observed the formation of
8.94 and 9.07 ppm for two types of azomethine protons. The bisthiolate or bisselenolate complexes. It can be ascribed to
peak at δ 2.93 ppm corresponds to the S–Me fragment.
the depletion of concentration of chloride ions on first
The reaction of 9 with PtCl2 in refluxing methanol led to dealkylation.
the formation of a light brown colour solution and complex 12
was precipitated by the addition of NH4PF6. The NMR spectro-
scopic studies show the formation of thiolate–thioether com-
plexes via cleavage of one of the methyl groups. Lindoy et al.
reported sp3 C–S bond cleavage of 8-methylthioquinoline upon
complexation with Pd and Pt.11 Reid et al. reported a similar
type of S–C bond cleavage upon complexation with the metal
ion.12 The C(sp2)–S bond activation by Pt(0) leading to break-
age of the terminal C–S bond has been reported,13 which
occurred via an oxidative addition pathway. The FT-IR spec-
Crystal structure
Bis(methyl)thiasalen podand 9. Podand 9 crystallizes in the
ˉ
triclinic P1 space group with one molecule in the asymmentric
unit (Z = 8, Z′ = 1). The ORTEP digram of the ligand is shown
in Fig. 1. The inversion related molecule present in the asym-
metric unit does not have any conventional functional groups
to form conventional hydrogen bonds. The molecule forms the
1D tapes by C–H⋯π (C9⋯H7, 2.93 Å) intermolecular inter-
actions along the c-axis as shown in Fig. 2. The interactions
present in the molecule lead to the formation of 2D zigzag
packing along the bc-plane as shown in Fig. 3.
−
trum of 12 indicates the presence of the PF6 counter ion {837
[ν(P–F)], 557 [δ(F–P–F)] cm−1}. Similar to the complex 11, the
FT-IR spectrum of 12 displayed the characteristic ν(CvN)
stretching frequencies at 1638 cm−1 and 1621 cm−1. The
1HNMR spectrum of the complex 12 showed two closely
spaced singlet peaks at δ 8.92 and 8.96 ppm for two types of
azomethine protons. The peak at δ 2.82 ppm corresponds to
the S–Me fragment in 12. For all three complexes 10–12,
ESI-MS spectra showed the expected molecular ion peaks. The
base peaks for 10 and 12 were observed at m/z = 434.96
[C18H20N2PdS2] and 508.95 [C17H17N2PtS2] which can be
assigned to [(M + H) − PF6] and the base peak for 11 was
observed at m/z = 418.72 [C17H17N2PdS2] which can be
assigned to [M − PF6].
Palladium complex 10. Complex 10 crystallizes in the mono-
clinic space group P21/n with one molecule and two counter
ions in the asymmetric unit (Z = 4, Z′ = 1) with a square planar
DFT calculation
To shed more light on our observation about the cleavage of
Fig. 1 ORTEP representation of podand 9; thermal ellipsoids are drawn at
one and/or both S-methyl groups sequentially, we have carried 50% probability levels.
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Fig. 2 Formation of 1D tapes via C–H⋯π interactions along the c-axis in the
crystal structure of 9.
Fig. 5 The 3D pseudo-double helical type network packing via C–H⋯F inter-
actions in the crystal of complex 10.
Table 1 Selected bond lengths (Å) and angles (°) for 10
S. No
Bond lengths
Bond angles
1
2
3
4
5
6
7
8
Pd1–S1 2.2755(14)
Pd1–S2 2.2785(15)
Pd1–N1 2.023(5)
Pd1–N2 2.014(5)
S1–C1 1.811(7)
S1–C2 1.775(5)
S2–C17 1.785(5)
S2–C18 1.778(7)
S1–Pd1–S2 94.98(5)
S1–Pd1–N1 93.27(13)
S1–Pd1–N2 175.35(14)
S2–Pd1–N1 168.22(13)
S2–Pd1–N2 88.20(14)
N1–Pd1–N2 84.10(18)
Fig. 3 Formation of 2D zigzag packing in the crystal structure of 9 via C–H⋯π
interactions along the bc-plane.
Fig. 6 ORTEP representation of palladium complex 11; thermal ellipsoids are
Fig. 4 ORTEP representation of palladium complex 10; thermal ellipsoids are
drawn at 50% probability levels.
drawn at 50% probability levels.
synthon and the supramolecular structure is stabilized by aro-
matic π⋯π interactions, which leads to the formation of 3D
pseudo-double helical network packing (Fig. 5). Selected bond
lengths and bond angles are shown in Table 1 respectively.
Palladium complex 11. Palladium complex 11 crystallizes in
the monoclinic space group P21/n with one molecule and one
counter ion in the asymmetric unit (Z = 4, Z′ = 1) with a square
planar geometry around the Pd (II) centre (Fig. 6). The crystal
structure showed the cleavage of one of the S–Me bonds
leading to the formation of a thioether–thiolate complex. The
distances between the two Pd–S bonds (thiolate (Pd1–S2),
geometry around the Pd(II) centre (Fig. 4). One of the thioether
bonds has equatorial orientation (S1–C1) whereas the other
(S2–C18) bond has an axial orientation, which results in loss
in planarity of the molecule in the solid state. The distances
between the two Pd–S (thioether) bonds [(Pd1–S1), 2.2755(14)
Å and (Pd2–S2), 2.2785(15) Å] are nearly the same and the two
Pd–N bond distances are 2.023(5) and 2.014(5) Å (sum of the
covalent radii 2.05 Å, van der Waals radii 2.84 Å). Weak van der
Waals interactions through C–H⋯F interactions are present in
the complex leading to the formation of a supramolecular
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Fig. 7 The 3D single helical network packing via C–H⋯F interactions in the
crystal structure of complex 11.
Table 2 Selected bond lengths (Å) and angles (°) for 11
Fig. 8 ORTEP representation of platinum complex 12; thermal ellipsoids are
S. No
Bond lengths
Bond angles
drawn at 50% probability levels.
1
2
3
4
5
6
7
Pd1–S1 2.2744(7)
Pd1–S2 2.2504(7)
Pd1–N1 2.036(2)
Pd1–N2 2.0100(19)
S1–C1 1.813(3)
S1–C2 1.785(3)
S2–C17 1.745(3)
S1–Pd1–S2 87.05(3)
S1–Pd1–N1 94.84(6)
S1–Pd1–N2 178.32(6)
S2–Pd1–N1 177.75(6)
S2–Pd1–N2 94.48(6)
N1–Pd1–N2 83.64(8)
2.2504(7) Å and thioether (Pd1–S1), 2.2744(7) Å) are nearly the
same and the two Pd–N bond distances are 2.036(2) and
2.0100(19) Å (sum of the covalent radii 2.05 Å, van der Waals
radii 2.84 Å). There are weak van der Waals interactions
through C–H⋯F leading to the formation of supramolecular
synthons and formation of 3D single helical type network
packing is observed (Fig. 7), which are stabilized by aromatic
π⋯π interactions. Selected bond lengths and bond angles are
shown in Table 2 respectively.
Fig. 9 Showing the 3D single helical network packing via C–H⋯F interactions
in the crystal structure of 12.
Platinum complex 12. Platinum complex 12 crystallizes in
the monoclinic space group P21/n with one molecule and one
counter ion in the asymmetric unit (Z = 4, Z′ = 1) with a square
planar geometry around the Pt(II) centre (Fig. 8). The crystal
structure showed the cleavage of one of the S–Me bonds
leading to the formation of a thioether–thiolate complex. The
distances between the two Pd–S bonds (thiolate (Pt1–S2),
2.2539(7) Å and thioether (Pt1–S1), 2.2614(7) Å) are nearly the
same and the two Pd–N bond distances are 2.028(2) and 2.004(2)
Å. Similar to complexes 10 and 11, the complex 12 shows
the 3D supramolecular structure (Fig. 9) by aromatic π⋯π
interactions and short contacts with the counter ion. Selected
Table 3 Selected bond lengths (Å) and angles (°) for 12
S. No
Bond lengths
Bond angles
1
2
3
4
5
6
7
Pt1–S1 2.2614(7)
Pt1–S2 2.2539(7)
Pt1–N1 2.028(2)
Pt1–N2 2.004(2)
S1–C1 1.811(3)
S1–C2 1.777(3)
S2–C17 1.743(3)
S1–Pt1–S2 86.56(3)
S1–Pt1–N1 95.15(7)
S1–Pt1–N2 178.24(7)
S2–Pt1–N1 178.12(7)
S2–Pt1–N2 95.00(7)
N1–Pt1–N2 83.31(9)
JEOL-FT NMR-AL 400 MHz spectrophotometer using CDCl3/
CD3CN/DMSO-d6 as a solvent and tetramethylsilane (SiMe4) as
an internal standard. Data are reported as follows: chemical
shifts in ppm (δ). UV-vis studies were performed in dry aceto-
nitrile. IR spectra of the compounds have been recorded on a
Perkin-Elmer FT-IR spectrometer as KBr pellets. The mass
spectra were recorded on a WATERS micromass Q-Tof microTM
instrument. Melting points were measured using a digital
melting point apparatus, SECOR INDIA.
bond lengths and bond angles are shown in Table
respectively.
3
Experimental section
All reagents were purchased from Aldrich/Merck and used
without further purification. Acetonitrile was distilled from
P2O5 and kept over molecular sieves. UV-vis spectra were
recorded on a Hitachi U4100 spectrophotometer, with a quartz
Synthesis of ligands
cuvette (path length, 1 cm). 1H and 13C NMR spectra were The compounds 139 and 1410 were synthesized according to
recorded on a Bruker 500 MHz and 77Se NMR spectra on a the reported procedures.
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N,N-Bis[(2-methylthio)-phenylmethylene]-1,2-ethanediamine
(9)
unscaled zero-point vibrational energies (ZPVEs). Gas phase
values were corrected by using single-point calculations on gas
phase optimized geometries for methanol as a solvent with
the Polarized Continuum Model (PCM) at the same level of
theory.18 All complexes were calculated as neutral species by
placing appropriate numbers of counter ions (chloride) in
close proximity of S/Se of the thio-/selenoether moiety in the
complexes. Basis set superposition errors (BSSE) were evalu-
ated for each of the complexes by the counterpoise corrections
method,19 and the resulting corrected energy values were also
included in addition to ZPVE and solvent corrections.
A solution of ethylenediamine (0.118 g, 1.968 mmol) in aceto-
nitrile (10 mL) was added to a stirred solution of compound 8
(0.5 g, 3.28 mmol). The reaction mixture was stirred overnight
and the precipitated white powder was filtered off, washed
with acetonitrile and dried under vacuum. Yield: 0.525 g
(97%). mp 94 °C. 1H NMR (CDCl3): δ 2.36 (6H), 4.0 (4H),
7.1–7.8 (m, 8H), 8.7 (s, 2H). 13C NMR (CDCl3): δ 17.0, 61.9,
125.5, 127.4, 128.5, 130.7, 134.4, 139.3, 160.9. ESI-MS: 329.1
{(C18H20N2S2 + H)+}.
General methodology for the preparation of complexes
Crystal structure determination
A mixture of the podand and Pd(C6H5CN)2Cl2/PtCl2 (in metha-
nol and in equimolar amounts) was stirred for 4 h at reflux
temperature except for complex 10 where the reflux time was
only 5 min. The reaction mixture was filtered off and to the fil-
trate NH4PF6 was added and the product was precipitated, fil-
tered off and dried under vacuum.
Single crystals of the compounds suitable for X-ray diffraction
were grown from an acetonitrile solution by diffusing diethyl
ether vapors in a closed beaker. The crystals were carefully
chosen using a stereomicroscope supported by a rotatable
polarizing stage. The data were collected at 100 (2) K, except
for compound 9 at RT on Bruker’s KAPPA APEX II CCD Duo
with graphite monochromated Mo-Kα radiation (0.71073 Å).
The crystals were glued to a thin glass fibre using FOMBLIN
immersion oil and mounted on the diffractometer. The inten-
sity data were processed using Bruker’s suite of data proces-
sing programs (SAINT), and absorption corrections were
applied using SADABS.20 The crystal structure was solved by
direct methods using SHELXS-97 and the data were refined by
full matrix least-squares refinement on F2 with anisotropic dis-
placement parameters for non-H atoms, using SHELXL-9721
(Table 4). In the case of complex 10, the crystal quality was
poor and ‘q’ peaks near Pd (0.778 Å far) and S (0.86 Å far)
atoms could not be resolved even after the absorption correc-
tion. However, such ‘q’ peaks are typical for structures with
heavy atoms. Figures are drawn from X-seed version 2.0.22
Complex 10
Yield: 0.12 g (53%). mp 248.6 °C (d). Anal. calcd (%) for
C18H20F12N2P2PdS2: C, 29.83, H, 2.78, N, 3.86. Found: C, 29.89,
H, 2.46, N, 4.95. 1H NMR (DMSO-d6): δ 2.96 (s, 6H), 4.11 (s,
4H), 7.90–8.22 (8H, Ar-H), 9.03 (2H). 13C NMR (DMSO-d6): δ
27.1, 62.2, 123.0, 132.5, 133.3, 133.5, 136.1, 138.9, 165.3.
ESI-MS: m/z 434.96 {(C18H20N2PdS2 + H)+}.
Complex 11
Yield: 0.122 g (60%). mp 273.0 °C (d). Anal. calcd (%) for
C17H17F6N2PPtS2: C, 36.15, H, 3.03, N, 4.96. Found: C, 35.93,
H, 2.15, N, 6.68. 1H NMR (DMSO-d6): δ 2.93 (s, 3H), 4.0–4.2 (m,
4H), 7.28–8.14 (8H, Ar-H), 8.95 (1H), 9.07 (1H). 13C NMR
(DMSO-d6): 27.8, 61.8, 62.2, 122.9, 123.3, 129.2, 130.1, 132.0,
133.2, 133.4, 133.5, 135.4, 137.6, 138.1, 140.4, 162.5, 163.7.
ESI-MS: m/z 418.7197 {(C17H17N2PdS2)+}.
Conclusion
Complex 12
Yield: 0.07 g (35%). mp 250.5 °C (d). Anal. calcd (%) for
C17H17F6N2PPtS2: C, 31.24, H, 2.62, N, 4.29. Found: C, 30.98,
H, 2.39, N, 4.84. H NMR (CD3CN): δ 2.82 (s, 3H), 4.0–4.2 (m,
The reaction of bis(methyl)thiasalen podand 9 with Pd(II)
afforded two complexes depending on the reaction time.
Shorter reaction time (5 min) afforded bisthioether complex
10; whereas with increase in reaction time (4 h) thioether–thio-
late complex 11 was obtained via cleavage of one of the two
S–C(Me) bonds of bis(methyl)thiasalen podand upon com-
plexation. The reaction of 9 with Pt(II) afforded only thiolate–
thioether complex 12 independent of the reaction time. The
cleavage of both the S–C(Me) bonds of bis(methyl)thiasalen to
1
4H), 7.2–8.1 (8H, Ar-H), 8.92 (1H), 8.96 (1H). 13C NMR
(CD3CN): 33.6, 63.4, 65.1, 122.0, 124.7, 131.1, 131.6, 133.7,
134.0, 134.8, 135.1, 136.8, 138.2, 138.8, 140.6, 160.8, 161.7.
ESI-MS: m/z 508.95 {(C17H17N2PtS2 + H)+}.
Theoretical methods
All calculations were performed using Gaussian 03 and 0914 afford bisthiolate complexes has never been observed even
with the B3LYP15 hybrid density functional.16 The SDD17 after continuing the reaction for 24 h of reflux. Bis(methyl)
pseudo-potential was used for the palladium center, and the salen 14 did not form any complexes with Pd(II) and Pt(II),
standard 6-31G(d) basis set was used for the other atoms. Tran- which is due to the hard nature of O compared to S and Se.
sition states were located by using the TS routine. At the same Formation of the complexes has been characterised by X-ray
level frequency calculations were performed for all stationary crystallography and the packing diagram of the complexes
points to differentiate them as minima or saddle points. The shows formation of supramolecular structures via aromatic
energies of optimized structures were corrected using the π⋯π interactions and weak van der Waals interactions.
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Table 4 Complete crystallographic information of podand 9 and complex 10, 11 and 12
Formula
C18H20N2S2 (9)
C18H20F12N2P2PdS2 (10)
C17H17F6N2PPdS2 (11)
C17H17F6N2PPtS2 (12)
Crystal System
Triclinic
P1
Monoclinic
P21/c
11.7172(10)
9.4791(8)
22.0704(19)
90
92.691(2)
90
2448.6(4)
4
Monoclinic
P21/c
14.4109(10)
8.1051(5)
17.2294(12)
90
97.665(2)
90
1994.4(2)
4
Monoclinic
P21/c
14.3388(8)
8.1400(4)
17.2968(9)
90
97.5380(10)
90
2001.40(18)
4
ˉ
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
4.9288(14)
7.326(2)
11.922(3)
86.405(6)
86.203(6)
79.513(5)
421.8(2)
8
γ [°]
V [Å3]
Z
λ [Å]
0.71073
1.301
174.0
0.71073
1.966
1432.0
0.71073
1.867
1120.0
0.71073
2.165
1244.0
ρcalcd [gcm−3
F[000]
]
M [mm−1
θ [°]
Index ranges
]
0.314
1.163
1.282
7.361
2.83–27.80
−6 ≤ h ≤ 6
−9 ≤ k ≤ 9
−15 ≤ l ≤ 15
292(2)
2.34–28.31
−14 ≤ h ≤ 14
−12 ≤ k ≤ 12
−28 ≤ l ≤ 28
100(2)
2.39–28.24
−19 ≤ h ≤ 19
−10 ≤ k ≤ 9
−22 ≤ l ≤ 22
100(2)
2.77–28.38
−16 h ≤ 18
−10 ≤ k ≤ 10
−22 ≤ l ≤ 22
100(2)
T [K]
R1
wR2
0.0455
0.1107
0.0554
0.1322
0.0271
0.0559
0.0179
0.0405
Rmerge
Parameters
0.0556
101
0.0688
337
0.0431
264
0.0214
264
GOF
1.105
6056
2052
1609
1.053
24 764
5339
4403
0.953
21 778
4812
3711
1.076
22 789
4373
4004
Reflns total
Unique reflns
Obsd reflns
CCDC
882776
882778
882777
882779
Coord. Chem. Rev., 2005, 249, 1249; (c) E. M. McGarrigle
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Acknowledgements
SP and SSZ are thankful to Department of Science and Tech-
nology (DST), India for funding this work. PD is thankful to
UGC for fellowship. Additional help from Prof. H. B. Singh, IIT
Bombay for CHN analysis is gratefully acknowledged.
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