Nickel(II), copper(II), cobalt(II), and palladium(II) complexes with a Schiff base: Crystal structure, DFT study and copper complex catalyzed aerobic oxidation of alcohol to aldehyde

Article abstract of DOI:10.1080/00958972.2015.1075241

Ni(II), Cu(II), Co(II), and Pd(II) complexes were synthesized with a Schiff base containing thioether with ONS donors chelating to the metal center. The ligand and complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, UV-visible sp

Full text of DOI:10.1080/00958972.2015.1075241

This article was downloaded by: [Emory University]
On: 29 July 2015, At: 22:50
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: 5 Howick
Place, London, SW1P 1WG
Journal of Coordination Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gcoo20
Nickel(II), copper(II), cobalt(II) and palladium(II)
complexes with a Schiff base: Crystal structure,
DFT study and copper complex catalyzed aerobic
oxidation of alcohol to aldehyde
a
a
a
b
a
Kuladip Sarma , Namita Devi , Mukul Kalita , Bipul Sarma & Pranjit Barman
a
Department of Chemistry, National Institute of Technology, Silchar 788010, Assam,
India
b
Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam, India
Accepted author version posted online: 29 Jul 2015.
Click for updates
To cite this article: Kuladip Sarma, Namita Devi, Mukul Kalita, Bipul Sarma & Pranjit Barman (2015): Nickel(II), copper(II),
cobalt(II) and palladium(II) complexes with a Schiff base: Crystal structure, DFT study and copper complex catalyzed
aerobic oxidation of alcohol to aldehyde, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2015.1075241
To link to this article: http://dx.doi.org/10.1080/00958972.2015.1075241
Disclaimer: This is a version of an unedited manuscript that has been accepted for publication. As a service
to authors and researchers we are providing this version of the accepted manuscript (AM). Copyediting,
typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication
of the Version of Record (VoR). During production and pre-press, errors may be discovered which could
affect the content, and all legal disclaimers that apply to the journal relate to this version also.
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of
the Content. Any opinions and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied
upon and should be independently verified with primary sources of information. Taylor and Francis shall
not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other
liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://dx.doi.org/10.1080/00958972.2015.1075241
Nickel(II), copper(II), cobalt(II) and palladium(II) complexes with a Schiff
base: Crystal structure, DFT study and copper complex catalyzed aerobic
oxidation of alcohol to aldehyde
KULADIP SARMA†, NAMITA DEVI†, MUKUL KALITA†, BIPUL SARMA‡ and PRANJIT BARMAN*†
†
‡
Department of Chemistry, National Institute of Technology, Silchar 788010, Assam, India
Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam, India
Ni(II), Cu(II), Co(II) and Pd(II) complexes were synthesized with a Schiff base containing
thioether with ONS-donors chelating to the metal center. The ligand and complexes were
1
characterized by elemental analysis, FT-IR, H-NMR, UV-visible spectroscopy and magnetic
studies. The crystal structures of the ligand and its Ni(II) and Pd(II) complexes were determined
by single-crystal X-ray diffraction analysis. The structure reveals that ligand-chelated Ni(II) and
Pd(II) in slightly distorted octahedral and slightly distorted square planar environment,
respectively. DFT studies of the Pd(II) complex reveal that the calculated structural parameters
are very close with the experimentally observed data. The Cu(II) complex shows very good
catalytic activity towards conversion of alcohol to aldehyde under aerobic oxidation with
ammonium persulfate.
Keywords: Schiff base; Crystal structure; Catalytic activities; DFT Study
1
. Introduction
Schiff bases have influenced coordination chemistry [1] because they have good coordinating
ability to form stable complexes with most transition metal ions. Such behavior of Schiff base
offered opportunities for inducing substrate chirality, tuning metal centered electronic factors,
enhancing stability of either homogeneous or heterogeneous catalyst [2-11]. Schiff base metal
*Corresponding author. barmanpranjit@yahoo.co.in
1

complexes with nitrogen-sulfur donors are important because they mimic biologically significant
metalloenzymes [12]. Also, Schiff bases form charge-transfer complexes with O and N with the
aid of metals like Ni, Cu and Co showing the importance as enzyme models. The rapid
development of these types of ligands have enhanced research activity in coordination chemistry.
Metal complexes with ONS-donors show antitumor, fungicidal, bactericidal, antibacterial,
antifungal, anti-inflammatory and antiviral activities [13-22]. Ni(II) Schiff base complexes
efficiently catalyze C-S cross-coupling of thiols with organic chlorides [23]. Ni(II) complexes of
chelating ligands incorporating thioether and imine donors have relevant properties with various
metalloproteins such as blue copper proteins, hemocyanin, tyrosinase and metalloenzymes as
well as their stability [24-26]. Pd(II) complexes with ONS donor Schiff bases also have wide
catalytic activity in organic transformations such as polymerization of ethylene, epoxidation,
allylic alkylation, Heck reaction, Suzuki–Miyaura coupling reactions, etc. [27-31]. Moreover,
Cu(II) Schiff base complexes are used as versatile catalysts in various oxygenation reactions in
homogeneous as well as heterogeneous conditions [32].
The oxidation of alcohol to aldehyde is an important reaction in organic chemistry.
Numerous reagents and methods are reported for these conversions [33-47], but development of
environmentally benign processes are a challenge. Cu(II) complexes are useful metal mediated
catalysts in these conversions.
Here we synthesize a Schiff base from 2-hydroxynaphthaldehyde and
2
-(benzylthio)aniline and a series of metal complexes with Cu(II), Ni(II), Co(II) and Pd(II) ions.
We have also studied catalytic activity of the Cu(II) complex towards aerobic oxidation of
alcohol to aldehyde in acetonitrile by using ammonium persulfate as oxidant.
2
2
. Experimental
.1. Materials
All chemicals were used without purification. Nickel chloride hexahydrate, copper nitrate
trihydrate and cobalt acetate tetrahydrate were purchased from Merck India and
2
-hydroxynaphthaldehyde and sodium tetrachloropalladate were purchased from Alfa Aesar. All
alcohols were purchased from Aldrich. 2-(Benzylthio)aniline was prepared according to
literature method [48]. Solvents used were extra pure grade purchased from Merck India and
were dried by the reported procedure [49].
2

2
.2. Methods
Infrared spectra of the ligand and complexes were recorded with a FT-IR-3000 Hyperion
Microscope (Bruker, Germany). Elemental analyses were performed on a Flash 2000 Thermo
1
Scientific instrument. H-NMR spectra of the ligand and Pd(II) complex were performed on a
VARIAN Mercury plus 300 MHz NMR spectrometer using CDCl as solvent. Electrical
3
conductivities were measured on a CM-180 Conductivity meter (Elico India). Electronic spectra
of the compounds were carried out with a Cary 100 Bio UV-visible spectrometer in DMF.
Magnetic susceptibilities were measured on a conventional Gouy balance using freshly prepared
4
Hg[Co(NCS) ] as calibrant using a Magway MSB MK1 Magnetic susceptibility balance,
Sherwood Scientific, Cambridge, UK. Melting points were recorded on a Veego melting point
apparatus and were uncorrected.
2
.3. Synthesis of ligand HL (1)
2
-(Benzylthio)aniline (0.215 g, 1 mmol) was dissolved in ethanol. To the above solution, an
ethanolic solution of 2-hydroxynaphthaldehyde (0.172 g, 1 mmol) was added dropwise with
continuous stirring. The resulting solution was allowed to stir for 30 min at room temperature.
The color of the solution changed to dark yellow. The solution was kept at 0 °C for 4 h; a yellow
crystalline product formed, was filtered off, washed with 25% ethanol-water and dried in
-2
vacuum (10 torr). The product was recrystallized in ethanol, giving suitable crystals for single
-1
crystal X-ray diffraction analysis. Yield was almost quantitative. M.P: 185 °C. IR (KBr, cm )
1
3
435 (m), 1610 (s), 1457 (s), 1167 (s), 743 (s). H-NMR (CDCl
3
, 300 MHz): δ 15.30 (1H, s,
OH), 9.2 (1H, s, CH=N), 7.1-8.09 (12H, m, Ar-H), 4.1 (2H, s, CH ). UV-Vis [DMF, λmax, nm
2
-1
-1
(ε
max, M cm )]: 267 (15600), 319 (9490), 392 (11250), 466 (4020). Anal. Calc. for C24
H19NOS:
C, 78.02; H, 5.18; N, 3.79; S, 8.68; O, 4.33. Found: C, 77.95; H, 5.31; N, 3.82; S, 8.54; O, 4.90.
3

CH
NH2
N
S
OH
S
Ph
EtOH
OHC
RT,30 min
OH
HL(1)
Scheme 1. Synthesis of HL (1).
2
2
.4. Synthesis of complexes
.4.1. Synthesis of [NiL ] (2). HL (1) (0.738 g, 2 mmol) was dissolved in hot methanol followed
2
by addition of a methanolic solution of NaOH (0.08 g, 2 mmol). A hot methanolic solution of
NiCl ·6H O (0.237 g, 1 mmol) was added drop-by-drop to the above solution with continuous
2
2
stirring. The reaction mixture was stirred for 1 h and color of the solution changed to dark
brown. Concentrating to half volume and storing for 3-4 days at room temperature gave a dark
brown needle-type crystal suitable for single-crystal X-ray diffraction analysis. The crystals were
washed several times with 25% methanol-water to remove impurities and dried under vacuum at
-
2
-1
1
1
4
0 torr (Purity was checked by TLC). Yield 65%; MP: > 300 °C. IR (KBr, cm ): 1604 (s),
-1
-1
455 (s), 1167 (s), 750 (s). UV-Vis [DMF, λmax, nm (εmax, M cm )]: 281 (20450), 331 (18050),
2
-1
96 (15000), 601 (160). Conductivity (λ , S cm mol ): 18.3. Anal. Calc. for C H N O S Ni:
M
48 36
2
2 2
C, 72.46; H, 4.56; N, 3.52; S, 8.06; O, 4.02. Found: C, 71.89; H, 4.10; N, 3.88; S, 7.87; O, 3.95.
2
.4.2. Synthesis of [Cu L (NO ) ] (3). Complex 3 was prepared by the same procedure as 2 with
2 2 3 2
HL (1) (0.369 g, 1 mmol), NaOH (0.04 g, 1 mmol) and Cu(NO ) ·3H O (0.199 g, 1 mmol). The
3
2
2
color of the solution changed to dark-green and was kept for 2 days. A green precipitate was
-2
collected, washed with 25% methanol-water and dried under vacuum at 10 torr (Purity was
-1
checked by TLC). Yield 62%; MP: > 300 °C. IR (KBr, cm ): 1604 (s), 1440 (s), 1297 (s), 1150
-1
-1
(
s), 741 (s). UV-Vis [DMF, λmax, nm (εmax, M cm )]: 275 (19650), 320 (17250), 413 (11300),
2
-1
6
3
52 (120). Conductivity (λ
M 36 4 8 2 2
, Scm mol ): 21.7. Anal. Calc. for C48H N O S Cu : C, 58.35; H,
.67; N, 5.67; S, 6.49; O, 12.95. Found: C, 57.79; H, 4.11; N, 5.43; S, 6.21; O, 12.58.
4

2
.4.3. Synthesis of [CoL ] (4). Complex 4 was prepared by the same procedure as 2 with
2
Co(CH COO) ·4H O (0.249 g, 1 mmol). The color of the solution changed to red and was kept
3
2
2
-2
for 2 days. A black precipitate was collected, washed with 25% methanol-water and dried at 10
-1
torr (Purity was checked by TLC). Yield 70%; MP: >300 °C. IR (KBr, cm ): 1603 (s), 1455 (s),
-1
-1
1
170 (s), 749 (s). UV-Vis [DMF, λmax, nm (εmax, M cm )]: 281 (13400), 322 (5625), 485
2
-1
(
2410), 624 (500). Conductivity (λ
M 36 2 2 2
, Scm mol ): 26. Anal. Calc. for C48H N O S Co: C, 72.44;
H, 4.56; N, 3.52; S, 8.06; O, 4.02. Found: C, 72.80; H, 4.98; N, 2.77; S, 7.12; O, 4.55.
2
.4.4. Synthesis of [PdLCl]·0.5(CH
2
Cl
2
) (5). An ethanolic solution of Na
2 4
PdCl (0.147 g,
0
.5 mmol) was added dropwise to an ethanolic solution of HL (1) (0.185 g, 0.5 mmol). The
resulting solution was stirred under reflux for 1 h. The orange precipitate formed was filtered off
and washed with 25% ethanol-water solution several times to remove impurities and dried under
-2
vacuum (10 torr) (Purity was checked by TLC). Orange red, needle-like crystals suitable for
single crystal X-ray diffraction analysis were obtained by recrystallization from DCM-hexane
(10:1) followed by slow evaporation of the solvent (2 days). Yield 68%; MP: > 300 °C. IR (KBr,
-1
1
cm ): 1604 (s), 1459 (s), 1170 (s), 746 (s). H-NMR (CDCl , 300 MHz): δ 8.95 (1H, s, CH=N),
3
7
.10-7.75 (13 H, m, Ar-H), 4.53 and 4.34 (2H, dd, CH
2
). UV-Vis [DMF, λmax, nm (εmax
,
-1
-1
M cm )]: 268 (7965), 347 (3000), 356 (3100), 444 (2575), 472 (2500). Conductivity (λ ,
M
2
-1
Scm mol ): 24.1. Anal. Calc. for [C24
2 2
H18NOSPdCl]·0.5(CH Cl ): C, 53.23; H, 3.46; N, 2.53; S,
5
.80; O, 2.89. Found: C, 53.39; H, 3.40; N, 2.45; S, 5.64; O, 2.74.
2
.5. General procedure for Cu(II) complex catalyzed aerobic oxidation of alcohol to aldehyde
Here we have reported aerobic oxidation of alcohol to aldehyde using 3. In this method, substrate
(4 mmol), 5 mol % Cu(II) complex and ammonium persulfate (5 mmol) were added to 20 mL
acetonitrile. The reaction mixture was stirred at room temperature. The conversion takes place
within 2 min and the progress of the reaction was monitored by TLC. The product was extracted
with EtOAc and purified by column chromatography. The reaction scheme is shown in
scheme 2.
5

O
Cu(II) complex
R
OH
R
H
CH CN, (NH ) S O
4 2 2 8
3
Scheme 2. Oxidation of alcohol to aldehyde.
2
.6. Crystallography
All data were collected on a Bruker APEX-II CCD diffractometer with graphite monochromated
Cu Kα radiation by the ω-scan technique at 298 K (HL (1)), 100 K (2) and 296 K (5). Structures
were determined using SHELXS-97 [50, 51]. Cell measurement and data reduction were done by
Bruker SAINT [52]. Multi-scan method (SADABS) was used for absorption corrections [52].
2
Full matrix least-squares on F were performed using the SHELXS-97 program. All non-H atoms
were refined in anisotropic approximation using reflections with I>2σ (I). Crystal data and
structure refinements of 1, 2 and 5 are given in table 1.
2
.7. DFT calculation
Full geometry optimization of Pd(II) complex was performed using Gaussian 09W [53].
Structural calculation was carried out using B3LYP method and mixed basis sets of LanL2DZ
for Pd and 6-31+G(d) for all other atoms, i.e. Cl, S, N, O, C and H.
3
3
. Results and discussion
.1. Synthesis
The reactions of ONS-donor Schiff base ligand with corresponding metal salts are shown in
scheme 3. HL (1) binds with nickel and cobalt ions with a 2:1 molar ratio forming octahedral
geometry around the metal. However, physicochemical analyses reveal the Cu(II) complex has
five-coordinate binuclear square pyramidal geometry around Cu(II). A new FT-IR band around
-1
1
297 cm was observed for coordinated nitrate in 3. The Pd(II) complex shows distorted square
planar geometry. Molar conductivity studies reveal that the metal complexes are non-
electrolytes. The reaction scheme is shown in scheme 3.
6

O O
M
N
O
)
N
H
6
&
.
l
iC
O
N
H
.
4
O
S
O
C
S
H
C
(
o
C
Ni(II) and Co(II) complex
OH
O NO
2
O
S
N
N
Cu(NO ) .3H O
3
2
2
Cu
Cu
S
N
S
O
ONO2
Cu(II) complex
O
N
Pd
S
Cl
Pd(II) complex
Scheme 3. Synthesis of metal complexes.
1
3
.2. H-NMR spectra of HL (1) and [PdLCl]·0.5(CH Cl ) (5)
2
2
1
The H-NMR (300 MHz) spectra of HL and 5 were recorded in CDCl . A singlet for phenolic
3
OH is at 15.317 ppm for HL, shifted downfield due to the presence of phenol-amine hydrogen
bonding. A singlet for benzilidemine proton is at 9.22 ppm. The aromatic (Ar-H) and benzylic
(
CH
2
) protons are a multiplet and singlet at 7.1-8.09 ppm and 4.1 ppm, respectively.
In the spectrum of Pd(II) complex, the OH proton disappears, signifying the
deprotonation upon complexation. Peaks at 8.95 ppm, 7.12-7.88 ppm and 4.45 ppm appeared for
CH=N, aromatic protons and CH protons, respectively. The methylene proton appeared as two
2
separate doublets having germinal-coupling.
3
.3. Magnetic measurements
8
The magnetic moment (μ ) for Ni(II) complex is 2.80 BM, near to the expected value of d
eff
octahedral symmetry. The binuclear Cu(II) complex possesses magnetic moment value of
1
4
.62 BM, smaller than spin-only value [54]; the Co(II) complex shows magnetic moment of
.81 BM for high-spin octahedral symmetry and the Pd(II) complex is diamagnetic.
7

3
.4. Electronic spectra
-4
-4
Electronic spectra of the ligand at 10 M and complexes at 2×10 M in DMF are shown in
figure 1. Electronic spectra of the ligand and its complexes are also taken in higher
-3
concentrations (10 M) for the region 500-800 nm, shown as insets in figure 1. The electronic
spectrum of ligand shows peaks at 267, 319, 392 and 466 nm which may be assigned to π-π*
transitions for the phenyl ring and n-π* transitions of the imine moiety [55]. Electronic
transitions of complexes are grouped in different spectral zones: 268-281 nm due to π-π*
transition of the phenyl ring, 320-356 nm of complexes due to n-π* transition and 413-496 nm
may be assigned to MLCT. Complexes show a relatively weak absorption from 601-652 nm due
to ligand field transitions, except the Pd(II) complex. All electronic spectral data of 1-5 are given
in table 2.
3
.5. X-ray crystallography
The crystal of HL (1) was obtained by recrystallization from extra pure ethanol and 5 was
obtained through slow diffusion of hexane into DCM solution. Prospective view of molecular
structure of 1, 2 and 5 are given in figures 2-4.
Compound 1 crystallizes in the tetragonal space group P4(1). The C=N bond length
provides evidence of formation of azomethine group (1.295(6) Å as N(1)-C(7)) in the range of
normal C=N bond lengths of imines. The angles N(1)-C(7-C(8) and C(6)-N(1)-C(7) are
1
22.2(4)° and 122.7(4)° and suggest that the 2-hydroxynaphthyl moiety and N-methyl
benzamine are trans to each other and reside in the same plane. The benzylsulfanyl unit forms
trans-geometry about the imine double bond to form ONS donor chelate. All important bond
lengths and angles of 1 are given in table 3.
Compound 2 crystallizes in the triclinic space group P-1 containing one molecule in the
asymmetric unit. The crystal shows lower R, wR and bond length e.s.d values compare to the
reported one [55], indicating better crystallographic data [56]. Two deprotonated ligand units
coordinate through N S O -donors forming octahedral Ni(II) complex. The C—N, C—S and
2
2
2
C—O bond lengths in Ni(II) complex are shifted compared to the free ligand. The imine bond
N(3)—C(27) increases to 1.308(3) Å from 1.295(6) Å and S(2)—C(21) increases to 1.839(2) Å
from 1.821(5) Å due to donation of electron cloud of N and S to nickel. However, the O(1)—
C(11) bond decreases to 1.287(3) Å from 1.343(6) Å due to the delocalization of negative charge
8

of deprotonated oxygen to the ligand, acquiring partial double bond character. The two
deprotonated oxygens of two ligands bonded to Ni(II) are cis to each other and two sulfurs also
cis. These four donors are the basal plane and two nitrogens are axial at an angle N(3)—Ni(1)—
N(2), 173.43(7)°. The bite angles O(1)—Ni(1)—O(4), O(4)—Ni(1)—S(2), O(1)—Ni(1)—S(3)
and S(2)—Ni(1)—S(3) are 93.03(6)°, 92.54(4)°, 84.66(4)° and 90.910(19)°, respectively. All the
bite angles deviate from 90°, indicating that the Ni(II) complex has distorted octahedral
geometry. All the important bond lengths and angles of 2 are given in table 4.
Complex 5 crystallizes in the monoclinic space group P2(1)/c containing two molecules
in the asymmetric unit. One DCM molecule is also observed in the asymmetric unit of the crystal
lattice. Important bond lengths and angles of 5 are given in table 5. The Pd—S and Pd—O bond
lengths show regular Pd—S and Pd—O bond lengths [57]. Pd(II) coordinates with O, N and S of
-
the ligand and one Cl to fulfill the square planar geometry. The bite angles O(1)—Pd(1)—Cl(1),
S(1)—Pd(1)—Cl(1), O(2)—Pd(2)—N(2) and N(2)—Pd(2)—S(2) are 89.1(2)°, 90.60(10)°,
9
1
3.0(4)° and 87.0(3)°, respectively; angles N(1)—Pd(1)—Cl(1) and O(2)—Pd(2)—S(2) at
75.8(3)° and 179.5(3)° confirm slightly distorted square planar geometry.
3
.6. Cu(II) complex catalyzed aerobic oxidation of alcohol to aldehyde
The reaction conditions were optimized by performing a series of experiments with different
solvents, oxidants, catalysts and reaction time. The optimized reaction conditions for benzyl
alcohol and results are shown in table 6; 5 mol% Cu(II) complex as catalyst and 5 mmol
ammonium persulfate as oxidant were optimum concentrations for conversion of 4 mmol benzyl
alcohol to benzyldehyde in 20 mL acetonitrile. The oxidation reaction was performed for
different alcohols as shown in table 7. 3 exhibits very good catalytic activity with high yield at
room temperature.
We proposed the mechanism of binuclear Cu(II) complex catalyzed oxidation of primary
alcohol to aldehyde. Cu(II)Cu(II) binuclear complex undergoes reduction to intermediate
Cu(I)Cu(I) form without breaking the oxobridge [58] in CH
3
CN and oxidizes alcohol to
aldehyde. Here, (NH ) S O enhances the formation of molecular oxygen in the system and helps
4
2
2
8
the conversion of Cu(I)Cu(I) to Cu(II)Cu(II) by releasing water as byproduct to complete the
catalytic cycle [59-63]. The reaction takes place by two electron transfer from alcohol to
9

binuclear Cu(II)Cu(II) complex. Intermediate Cu(I)Cu(I) is stabilized by CH CN, hence the
3
reaction is efficient. The probable mechanism for oxidation of alcohol is given in scheme 4.
2
HOCH R
2 OCHR
2
Cu(II)Cu(II)
Cu(I)Cu(I)
2
H
H O
2
1/2 O2
Scheme 4. Probable mechanism for oxidation of alcohol to aldehyde.
3
.7. DFT calculation
The optimized geometry of 5 was performed by DFT/B3LYP method. The calculated bond
distances and angles are included in table 8. The calculated structural parameters are in
agreement with the experimentally observed data. The Pd-S bond of the complex shows
maximum deviation of 0.072 Å compared with other metal-atom bonds. The contour plots of
HOMO-1, HOMO, LUMO and LUMO + 1 of the complex are shown in figure 5.
4
. Conclusion
We have synthesized a tridentate ONS-donor and four complexes and characterized by spectral
and single-crystal X-ray diffraction analysis. Complexes 2 and 4 have the 2:1 ratio of tridentate
ligand:metal ion and 3 and 5 have the 1:1 ratio of tridentate ligand:metal ion. The geometry of
the Ni(II) complex is slightly distorted octahedral and Pd(II) complex is slightly distorted square
planar. We have developed a catalytic system using the Cu(II) complex and (NH ) S O for
4
2
2
8
selective oxidation of alcohol to aldehyde in acetonitrile. The system is attractive due to simple
procedure, environmentally benign, high yield within shorter reaction at room temperature. The
DFT study of the Pd(II) complex 5 using B3LYP method show quite good agreement with the
data obtained from single-crystal X-ray diffraction studies.
10

Appendix A. Supplementary data
CCDC 997116, 997117 and 997118 contains the supplementary crystallographic data for the
ligand, the Ni(II) complex and the Pd(II) complex, respectively. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (+44) 1223-336-
0
33; or E-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
The authors gratefully acknowledge Indian Association for the Cultivation of Science, Kolkata
for the Gaussian 09 program package, Tezpur University, Tezpur and IIT Bombay, Mumbai for
spectral and analytical data. Also thanks to Director of NIT, Silchar for financial assistance (K.S,
N.D and M.K).
References
[
1]
2]
Z.L. You, H.L. Zhu. Z. Anorg. Allg. Chem., 630, 2754 (2004).
K.P. Balasubramanian, K. Parameswari, V. Chinnusamy, R. Prabhakaran, K. Natarajan.
Spectrochim. Acta, Part A, 65, 678 (2006).
[
[3]
[4]
[5]
[6]
[7]
[8]
[9]
K.S. Murray, A.M. van den Bergen, B.O. West. Aust. J. Chem., 31, 203 (1978).
H. Doine, F.F. Stephens, R.D. Cannon. Bull. Chem. Soc. Jpn., 58, 1327 (1985).
K. Nakajima, Y. Ando, H. Mano, M. Kojima. Inorg. Chim. Acta, 274, 184 (1998).
B.D. Clercq, F. Verpoort. Macromolecules, 35, 8943 (2002).
T. Opstal, F. Verpoort. Synlett, 6, 0935 (2002).
T. Opstal, F. Verpoort. Angew. Chem. Int. Ed., 42, 2876 (2003).
S.N. Pal, S. Pal. Inorg. Chem., 40, 4807 (2001).
[
[
[
10] B.D. Clercq, F. Verpoort. Adv. Synth. Catal., 344, 639 (2002).
11] B.D. Clercq, F. Lefebvre, F. Verpoort. Appl. Catal. A, 247, 345 (2003).
12] A. Patra, S. Sarkar, M.G.B. Drew, E. Zangrando, P. Chattopadhyay. Polyhedron, 28,
1
261 (2009).
13] S.A. Patil, V.H. Naik, A.D. Kulkarni, P.S. Badami. Spectrochim. Acta, Part A, 75, 347
2010).
[
(
11

[14] A.K. Nandi, S. Chaudhuri, S.K. Mazumdar, S. Ghosh. J. Chem. Soc., Perkin Trans. 2, 11,
1
729 (1984).
[
[
[
[
[
15] M.A. Ali, D.A. Chowdhury-I, M. N. Uddin. Polyhedron, 3, 595 (1984).
16] J.P. Scovill, D.L. Klayman, C.F. Franchino. J. Med. Chem., 25, 1261 (1982).
17] N.K. Singh, S.B. Singh. Ind. J. Chem., Sect. A, 40A, 1070 (2001).
18] R.K. Agarwal, L. Singh, D.K. Sharma. Bioinorg. Chem. Appl., 2006, 1 (2006).
19] M.E. Hossain, M.N. Alam, J. Begum, M.A. Ali, M. Nazimuddin, F.E. Smith, R.C.
Hynes. Inorg. Chim. Acta, 249, 207 (1996).
[20] P. Bindu, M.R.P. Kurup, T.R. Satyakeerty. Polyhedron, 18, 321 (1998).
[21] A.K. Pramanik, M.S. Jana, T.K. Mondal. J. Coord. Chem., 66, 4067 (2013).
[22] M. Kalita, P. Gogoi, P. Barman, B. Sarma. J. Coord. Chem., 67, 2445 (2014).
[23] P. Gogoi, S. Hazarika, M.J. Sarma, K. Sarma, P. Barman. Tetrahedron, 70, 7484 (2014).
[24] D. Banerjee, U. Ray, S. Jasimuddin, J.C. Liou, T.H. Lu, C. Sinha. Polyhedron, 25, 1299
(2006).
[
[
[
[
25] R. Balamurugan, M. Palaniandavar, M.A. Halcrow. Polyhedron, 27, 1077 (2006).
26] B. Turner, S. Swavey. Inorg. Chem. Commun., 10, 209 (2007).
27] M.M. Tamizh, R. Karvembu. Inorg. Chem. Commun., 25, 30 (2012).
28] J. Hurtado, M. Portaluppi, R. Quijada, R. Rojas, M. Valderrama. J. Coord. Chem., 62,
2
772 (2009).
29] D.Y. Ma, L.X. Zhang, X.Y Rao, T.L. Wu, D.H. Li, X.Q. Xie. J. Coord. Chem., 66, 1486
2013).
[
(
[
[
[
30] K. Karami. J. Coord. Chem., 63, 3688 (2010).
31] K.C. Gupta, A.K. Sutar. Coord. Chem. Rev., 252, 1420 (2008).
32] S. Ray, S. Jana, A. Jana, S. Konar, K. Das, S. Chatterjee, R.J. Butcher, S.K. Kar.
Polyhedron, 46, 74 (2012).
[
[
[
[
[
[
33] I.E. Marko, A. Gautier, R. Dumeunier. Angew. Chem. Int. Ed., 43, 1588 (2004).
34] P. Gamez, I.W.C.E. Arends, J. Reedijk, R.A. Sheldon. Chem. Commun., 19, 2414 (2003).
35] P. Belanzoni, C. Michel, E.J. Baerends. Inorg. Chem., 50, 11896 (2011).
36] Y. Zhu, B. Zhao, Y. Shi. Org. Lett., 15, 992 (2013).
37] J.M. Hoover, S.S. Stahl. J. Am. Chem. Soc., 133, 16901 (2011).
38] N. Tyagi, R. Kumar, K. Mahiya, P. Mathur. J. Coord. Chem., 66, 3335 (2013).
12

[39] Z. Nadealian, V. Mirkhani, B. Yadollahi, M. Moghadam, S. Tangestaninejad, I.M.
Baltork. J. Coord. Chem., 66, 1264 (2013).
[
[
[
40] X.F. Yin, H. Lin, A.Q. Jia, Q. Chen, Q.F. Zhang. J. Coord. Chem., 66, 3229 (2013).
41] C.K. Modi, P.M. Trivedi. J. Coord. Chem., 67, 3678 (2014).
42] R. Benramdane, F. Benghanem, A. Ourari, S. Keraghel, G. Bouet. J. Coord. Chem., 68,
5
60 (2015).
[
[
[
[
[
[
[
43] S. Velusamy, A. Srinivasan, T. Punniyamurthy. Tetrahedron Lett., 47, 923 (2006).
44] P. Gamez, I.W.C.E. Arends, J. Reedijk, R.A. Sheldon. Chem. Commun., 1414 (2003).
45] P. Belanzoni, C. Michel, E.J. Baerends. Inorg. Chem., 50, 11896 (2011).
46] A. Pui. Synth. React. Inorg. Met.-Org. Nano-Met. Chem., 36, 523 (2006).
47] D.A. Rockcliffe, A.E. Martell. J. Mol. Catal. A: Chem., 106, 211 (1996).
48] Q.X. Shi, R.W. Lu, Z.X. Zhang, D.F. Zhao. Chin. Chem. Lett., 17, 1045 (2006).
rd
49] D.D. Perrin, W.L.F. Armarego, Purification of laboratory Chemicals, 3 Edn., Pergamon,
New York (1988).
[50] G.M. Sheldrick. Acta Crystallogr. A, 64, 112 (2008).
[
51] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Fortran Programs for Crystal Structure
Solution and Refinement, University of Gottingen, Gottingen, Germany (1997).
52] SMART, SAINT and SADABS, Bruker AXS Inc., Madison, Wisconsin, USA (2007).
53] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, G.
Scalmani, V. Barone, B. Mennucci, G.A. Petersson, Gaussian 09, Revision C.01,
Gaussian, Inc., Wallingford, CT (2010).
[
[
[
54] P. Kamatchi, S. Selvaraj, M. Kandaswamy. Polyhedron, 24, 900 (2005).
55] P. Pattanayak, J.L. Pratihar, D. Patra, P. Brandao, V. Felix. Inorg. Chim. Acta, 418, 171
[
(2014).
[56] P.G. Jones. Chem. Soc. Rev., 13, 157 (1984).
[57] S. Acharya, A. Kejriwal, A.N. Biswas, P. Das, D.N. Neogi, P. Bandyopadhyay.
Polyhedron, 38, 50 (2012).
[
58] L.R. Martins, E.T. Souza, T.L. Fernandez, B. de Souza, S. Rachinski, C.B. Pinheiro, R.B.
Faria, A. Casellato, S.P. Machado, A.S. Mangrich, M. Scarpellini. Braz. Chem. Soc., 21,
1
218 (2010).
[59] E.A. Lewis, W.B. Tolman. Chem. Rev., 104, 1047 (2004).
13

[
[
[
60] J.P. Klinman. Chem. Rev., 96, 2541 (1996).
61] R.H. Holm, P. Kennepohl, E.I. Solomon. Chem. Rev., 96, 2239 (1996).
62] K. Asami, K. Tsukidate, S. Iwatsuki, F. Tani, S. Karasawa, L. Chiang, T. Storr, F.
Thomas, Y. Shimazaki. Inorg. Chem., 51, 12450 (2012).
[63] D. Das, Y.M. Lee, K. Ohkubo, W. Nam, K.D. Karlin, S. Fukuzumi. J. Am. Chem. Soc.,
1
35, 2825 (2013).
14

Figure captions
-
4
-4
-4
Figure 1. Electronic spectra of 1 (10 M) (—), 2 (2×10 M) (—), 3 (2×10 M) (—), 4
(
-4
-4
2×10 M) (—) and 5 (2×10 M) (—) in DMF.
Figure 2. Molecular structure of HL (1) with 50% probability ellipsoids.
Figure 3. Molecular structure of 2 with 50% probability ellipsoids.
Figure 4. Molecular structure of 5 with 50% probability ellipsoids.
Figure 5. Contour plots of HOMOs and LUMOs of 5.
15

1
6

1
7

18

19

20

Table 1. Crystal structure and structure refinement details for 1, 2 and 5.
Compound
1
2
5
CCDC entry no.
997116
997117
997118
Empirical formula
C H NOS
C H N NiO S
C H Cl N O Pd S
2 2
2
4
19
48 36
2
2
2
49 38
4
2
2
Formula weight
T (K)
369.46
795.62
1105.53
298(2)
100(2)
296(2)
λ (Å)
0.71073
Tetragonal
P4(1)
0.71073
0.71073
Crystal system
Space group
Unit cell dimensions
a (Å)
Triclinic
P-1
Monoclinic
P2(1)/c
18.2731(8)
18.2731(8)
5.3436(3)
90.00
11.1974(5)
13.4777(5)
14.4106(6)
96.868(3)
110.113(4)
110.134(4)
1846.20(12)
2
11.2548(7)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
20.4902(14)
19.2916(11)
90.00
90.00
93.710(5)
90.00
90.00
3
V (Å )
1784.25(15)
4
4439.6(5)
4
Z
3
D
calc (Mg/m )
1.375
1.431
1.654
-1
μ (mm )
1.708
2.166
9.972
F (0 0 0)
776
828
2216
3
Crystal size (mm )
0.35 × 0.17 × 0.12
3.42-66.53
-21 ≤ h ≤ 19
0.27 × 0.21 × 0.11
3.63-66.60
0.21 × 0.14 × 0.08
3.94- 66.60
θ (°)
Index ranges
-13 ≤ h ≤ 11
-12 ≤ k ≤ 16
-16 ≤ l ≤ 17
10570
-12 ≤ h ≤ 13
-24 ≤ k ≤ 16
-22 ≤ l ≤ 16
13789
-
-
21 ≤ k ≤ 17
6 ≤ l ≤ 4
Reflections collected
Independent reflections (Rint)
Completeness (%)
4072
2153(0.0547)
1.22/0.68
6445(0.0297)
99.00
7305(0.0957)
93.20
Absorption correction
Max and min transmission
Refinement method
Multi-scan (SADABS)
0.8213 and 0.5863
Full matrix
Multi-scan (SADABS) Multi-scan (SADABS)
0.7966 and 0.5924
Full matrix
0.5026 and 0.2286
Full matrix
2
2
2
least-squares on F
least-squares on F
6445 / 0 / 640
1.066
least-squares on F
7305 / 0 / 550
1.035
Data/restraints/parameters
2153 / 1 / 249
1.007
2
Goodness-of-fit on F
Final R indices [I>2σ(I)]
R1=0.0488,
wR2=0.1055
R1=0.0352,
wR2=0.1031
R1=0.0975,
wR2=0.2280
-3
Largest diff. in peak / hole (eÅ )
0.241 / -0.254
0.375 / -0.394
2.102 / -0.972
21

Table 2. Electronic spectral data of 1-5.
-1
-1
Compound
λ (nm)
εmax (M cm )
Ligand, 1
267
15600
9490
11250
4020
20450
18050
15000
160
3
3
4
19
92
66
Ni(II) complex, 2
Cu(II) complex, 3
Co(II) complex, 4
Pd(II) complex, 5
281
3
4
6
31
96
01
275
19650
17250
11300
120
3
4
6
20
13
52
281
13400
5625
2410
500
3
4
6
22
85
24
268
7965
3000
3100
2575
2500
3
3
4
4
47
56
44
72
22

Table 3. Selected bond lengths (Å) and angles (°) for 1.
Bond lengths
(Å)
Bond angles
(°)
S(1)—C(1)
S(1)—C(18)
O(1)—C(9)
O(1)—H(1A)
N(1)—C(7)
N(1)—C(6)
C(7)—C(8)
C(7)—H(7)
1.777(5)
1.821(5)
1.343(6)
1.020(6)
1.295(6)
1.415(6)
1.446(7)
0.930(4)
C(1)—S(1)—C(18)
C(9)—O(1)—H(1A)
C(7)—N(1)—C(6)
N(1)—C(6)—C(1)
N(1)—C(7)—C(8)
O(1)—C(9)—C(8)
C(19)—C(18)—S(1)
102.4(2)
119(3)
122.7(4)
115.8(4)
122.2(4)
122.1(5)
108.0(4)
23

Table 4. Selected bond lengths (Å) and angles (°) for 2.
Bond lengths
(Å)
Bond angles
(°)
Ni—O(1)
1.9979(15)
2.0074(14)
2.0235(17)
2.0281(17)
2.4390(6)
2.5267(6)
1.287(3)
1.288(3)
1.304(3)
1.423(2)
1.308(3)
1.421(3)
1.778(2)
1.839(2)
1.775(2)
1.833(2)
O(1)—Ni(1)—O(4)
O(1)—Ni(1)—N(3)
O(4)—Ni(1)—N(3)
O(1)—Ni(1)—N(2)
O(4)—Ni(1)—N(2)
N(3)—Ni(1)—N(2)
O(1)—Ni(1)—S(2)
O(4)—Ni(1)—S(2)
N(3)—Ni(1)—S(2)
N(2)—Ni(1)—S(2)
O(1)—Ni(1)—S(3)
O(4)—Ni(1)—S(3)
N(3)—Ni(1)—S(3)
N(2)—Ni(1)—S(3)
S(2)—Ni(1)—S(3)
93.03(6)
90.69(6)
96.32(6)
93.83(7)
88.20(6)
173.43(7)
172.70(5)
92.54(4)
84.00(5)
91.06(5)
84.66(4)
167.32(4)
96.17(5)
79.53(5)
90.910(19)
Ni—O(4)
Ni—N(3)
Ni—N(2)
Ni—S(2)
Ni—S(3)
O(1)—C(11)
O(4)—C(9)
N(2)—C(14)
N(2)—C(15)
N(3)—C(27)
N(3)—C(4)
S(2)—C(5)
S(2)—C(21)
S(3)—C(3)
S(3)—C(16)
24

Table 5. Selected bond lengths (Å) and angles (°) for 5.
Bond lengths
(Å)
Bond angles
(°)
Pd(1)—O(1)
Pd(1)—N(1)
Pd(1)—S(1)
Pd(1)—Cl(1)
Pd(2)—O(2)
Pd(2)—N(2)
Pd(2)—S(2)
Pd(2)—Cl(2)
S(2)—C(41)
S(2)—C(42)
S(1)—C(17)
S(1)—C(18)
Cl(4)—C(49)
Cl(3)—C(49)
O(1)—C(1)
O(2)—C(25)
N(2)—C(35)
N(2)—C(36)
N(1)—C(11)
N(1)—C(12)
2.004(8)
2.010(9)
2.231(3)
2.322(3)
1.978(9)
2.004(8)
2.232(3)
2.330(3)
1.793(11)
1.854(13)
1.779(11)
1.854(12)
1.730(15)
1.788(16)
1.269(15)
1.321(16)
1.303(15)
1.428(15)
1.279(16)
1.436(14)
O(1)—Pd(1)—N(1)
O(1)—Pd(1)—S(1)
N(1)—Pd(1)—S(1)
O(1)—Pd(1)—Cl(1)
N(1)—Pd(1)—Cl(1)
S(1)—Pd(1)—Cl(1)
O(2)—Pd(2)—N(2)
O(2)—Pd(2)—S(2)
N(2)—Pd(2)—S(2)
O(2)—Pd(2)—Cl(2)
N(2)—Pd(2)—Cl(2)
S(2)—Pd(2)—Cl(2)
92.9(3)
176.7(2)
87.6(3)
89.1(2)
175.8(3)
90.60(10)
93.0(4)
179.5(3)
87.0(3)
89.0(3)
176.3(3)
90.92(11)
25

Table 6. Optimized reaction condition for benzyl alcohol to benzyldehyde at room temperature.
Entry
Catalyst
None
Oxidant
Solvent
Time
24 h
4 h
Conversion%
Yield
0
1
2
(NH ) S O
CH CN
0
4
2
2
8
8
3
CuCl2
(NH ) S O
CH CN
56
50
4 2
2
3
3
4
5
6
7
8
Cu(II) Complex
Cu(II) Complex
Cu(II) Complex
Cu(II) Complex
Cu(II) Complex
Cu(II) Complex
(NH
4
)
2
S
2
O
8
CH
CH
3
CN
2 min
2 h
100
80
82
40
42
51
96
71
74
29
32
41
H
2
O
2
3
CN
(NH ) S O
CH Cl
15 min
30 min
30 min
30 min
4
2
2
8
8
8
8
2
2
(NH ) S O
DMF
4
2 2
(NH ) S O
DMSO
THF
4
2
2
(NH
4
)
2
S
2
O
26

Table 7. Oxidation of alcohol to aldehyde catalyzed by Cu(II) complex in CH CN-(NH ) S O system.
3
4 2
2
8
Entry Substrate
1
Product
Time (min)
2
Yield (%)
O
96
OH
H
2
O
3
5
92
OH
H
MeO
MeO
3
O
86
OH
H
Cl
Cl
O
4
4
6
86
92
OH
H
O
O
5
O
OH
H
6
7
O
4
92
OH
H
O
4
3
4
91
89
93
OH
H
8
9
OH
O
H
O
OH
H
27

Table 8. The experimental and calculated bond lengths (Å) and angles (°) for 5.
Bond lengths
Pd(1)—O(1)
Pd(1)—N(1)
Pd(1)—S(1)
Pd(1)—Cl(1)
S(1)—C(17)
S(1)—C(18)
O(1)—C(1)
N(1)—C(11)
N(1)—C(12)
Expt
Calcd
2.028
2.043
2.303
2.358
1.797
1.883
1.283
1.321
1.420
Bond angles
Expt
Calcd
93.69
178.73
86.64
90.20
175.77
2.004(8)
2.010(9)
2.231(3)
2.322(3)
1.779(11)
1.854(12)
1.269(15)
1.279(16)
1.436(14)
O(1)—Pd(1)—N(1)
O(1)—Pd(1)—S(1)
N(1)—Pd(1)—S(1)
O(1)—Pd(1)—Cl(1)
N(1)—Pd(1)—Cl(1)
S(1)—Pd(1)—Cl(1)
92.9(3)
176.7(2)
87.6(3)
89.1(2)
175.8(3)
90.60(10) 89.51
28

29