Mixed ligand, palladium(II) and platinum(II) complexes of tertiary diphosphineswithS-1H benzo[d] imidazole-2-yl benzothioate

Article abstract of DOI:10.13005/ojc/330205

Palladium(II) and platinum(II) complexes containing the mixed ligands tertiary diphosphinesdppm. dppp and dppf with Thioester ligand S-1H benzo[d] imidazole-2-yl benzothioate (HSBIBT) have been prepared by the reaction of PdCl₂ and PtCl₂

Full text of DOI:10.13005/ojc/330205

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ISSN: 0970-020 X
CODEN: OJCHEG
2017, Vol. 33, No. (2):
Pg. 584-592
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Mixed Ligand, Palladium(II) and Platinum(II) Complexes of
Tertiary DiphosphineswithS-1H Benzo[d] Imidazole-2-yl
Benzothioate
KARWAN OMER ALI1, HIKMAT ALI MOHAMMAD2,
3
3
THOMAS GERBER and ERIC HOSTEN
1 College of Education and Human Sciences, university of Halabja, Halabja, Iraq.
2 Department of Chemistry, college of Education, university of Salahaddin, Erbil.
3Department of Chemistry, Nelson Mandela Metropolitan University,
Port Elizabeth, 6031, South Africa.
*Corresponding author E-mail: Thomas.Gerber@nmmu.ac.az
HTTP://DX.DOI.ORG/10.13005/OJC/330205
(Received: October 24, 2016; Accepted: January 01, 2017)
ABSTRACT
Palladium(II) and platinum(II) complexes containing the mixed ligands tertiary
diphosphinesdppm. dppp and dppf with Thioester ligand S-1H benzo[d] imidazole-2-yl benzothioate
(HSBIBT) have been prepared by the reaction of PdCl2 and PtCl2 with one equiv of tertiary
diphosphines ligands to form [Pd(k2-dppf)Cl2], [Pd(k2-dppp)Cl2] and [Pt(k2-dppmCl)Cl2] complexes
and then add the ligand HSBIBT to these complexes to form mixed ligand complexes.The prepared
complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, magnetic
susceptibility, molar conductance, IR spectral data and UV-Visible. The results suggested that the
ligand HSBIBT bonded to the metal through N atom and square planner geometries were assigned
for the complexes.
Keywords: Palladium,Platinum,Tertiarydiphosphine,Thioester ligand complexes.
INTRODUCTION
derived from benzimidazole with thiol group in the
2-position. It holds extra chemical names such
as, o-phenylenthiourea, benzimidazol-2-thion with
formula of C7H6N2S3,4. In 2-mercaptobenzimidazole
have two N atoms and one S atom and they can
independently contribute to its binding to metal5.
2-mercaptobenzimidazole derivatives, one of
Benzimidazole is the heterocyclic aromatic
organic compound1.This bicyclic ring system consist
of benzene ring joined with 4- and 5- situation of
imidazole ring, imidazole ring having non adjacent
two nitrogen atoms2. 2-Mercaptobenzimidazole

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AlI et al., Orient. J. Chem., Vol. 33(2), 584-592 (2017)
the most important derivatives of benzimidazole susceptibility values of the prepared complexes
exhibited a wide range of importance biological were carried out at room temperature using Bruker
activities such as antimicrobial6, antihistamine7, Magnet BM6. Conductivity measurements were
neutropic8 and analgesic9, antiprotozoal, antiviral, made on a conductivity meter type Senz µSiemen
and anticancer activities10. Metal derivatives of tester 4200 (093 cell constant) (UK.). Melting points
heterocyclic-2-thiones have shown a variety of were measured on Melting Point-MPD-100 Pixel
biochemical application: as antidandruff, antifungal, Technology CO., limited apparatus.
antibacterial, antibiotic and in shampoos, hair
creams, plant diseases and hepatitis11.
Synthesis of[Pd(k2-dppf)Cl2].CH2Cl2 (1)
The solution of dppf (1.6632g, 3mmol)
Thioesters are important class of in 15ml CH2Cl2 was added to a solution of PdCl2
organosulfur compounds that play a major role (0.5320g, 3mmol) that dissolved in 2 cm3 ethanol
in the construction of pharmaceutical, biological, and 2 cm3 concentrate HCl. The mixture was reflux
industrial and natural products. In this respect, for 3 hrs.And then the solvent was evaporate at room
thioesters synthesis is one of the most important temperature to give red precipitate.A small portion of
tasks in organosulfur chemistry. The esterification this complex was dissolve in CH2Cl2 and set to slow
of thiols is the best and most common strategy for evaporation at room temperature after a few days, the
the synthesis of Thioesters12. Diphosphines are a red colored needle crystals were formed suitable for
class of chelating ligands that contain two phosphine single-crystal diffraction analysis15.The melting point
groups connected by a bridge (also referred to as a is 253°C, yield is 2.086gm (95%), formula: [Pd(k2-
backbone).The bridge, for instance, might consist of dppf)Cl2] and M.wt.is 816.58 gm/mole, as shown in
one or more methylene groups or multiple aromatic Figure 1.
rings with heteroatoms attached13. The structure of
the backbone and the substituents attached to the Synthesis of [Pd(k2-dppf)(HSBIBT)Cl]Cl(2)
phosphorus atoms influence the chemical reactivity
A solution of ligand (0.0509 g, 0.2 mmol)
of the diphosphine ligand in metal complexes through in CH2Cl2 (15 cm3) was added to a solution of
steric and electroniceffects13.Phosphorus ligands [Pd(k2-dppf)Cl2] (0.1463 g, 0.2 mmol) in CH2Cl2
typically bind to the metal centers via the lone pair (15cm3), and the mixture was heated under reflux
of electrons on the phosphorus14.
for 4 hrs and then the Solvent was evaporated at
room temperature to give a red solid. Yield= 91 %,
m.p= 139-141°C. as shown in Figure 1.
ExPERIMENTAL
Materials and Instrumentation
Synthesis of [Pd(k2-dppp)Cl2] (3)
The compounds PtCl2, PdCl2, dppm, dppp,
The solution of dppp (1.2373g, 3mmol)
dppf and S-1H benzo[d] imidazole-2-yl benzothioate in 15ml CH2Cl2 was added to a solution of PdCl2
(HSBIBT) were commerciallyavailable and obtained (0.5320g, 3mmol) that dissolved in 2 cm3 ethanol
fromYacoo chem.China.The complexes [Pd(k2-dppf) and 2cm3 concentrate HCl. The mixture was reflux
(HSBIBT)Cl]Cl, [Pd(k2-dppp) (HSBIBT)Cl]Cl, [Pt(k2- for 3 hrs.And then the solvent was evaporate at room
dppm) (HSBIBT)Cl]Cl were prepared according to temperature to give pale yellow precipitate. A small
the literature.
portion of this complex was dissolve in CH2Cl2 and set
to slow evaporation at room temperature after a one
Elemental CHNS analysis were carried out week, the yellow colored needle crystals were formed
on a EuroEA 3000 instrument. The FT-IR spectra in suitable for single-crystal diffraction analysis15. The
range (4000-200 cm-1) were recorded as CsI disc on Melting point is 277°C, yield is 1.664gm (94%),
ShimadzuIRAffinity-1SFTIRSpectrophotometer, and formula: [Pd(k2-dppp)Cl2] and M.wt.is 589.72
FT-IR spectra in range (4000-400 cm-1) were recorded gm/mole.as shown in Figure 1.
as KBr disc on Shimadzu, FT-IR spectroscopy Mod IR
Affinity-1CE spectrophotometer. UV-Visible spectra Synthesis of [Pd(k2-dppp)(HSBIBT)Cl]Cl(4)
were measured using AE-UV1609 (UK) CO., lTD
A solution of ligand (0.0509 g, 0.2 mmol) in
Shimadzu, in the range (200-800) nm.The magnetic CH2Cl2 (15 cm3) was added to a solution of [Pd(k2-

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AlI et al., Orient. J. Chem., Vol. 33(2), 584-592 (2017)
586
dppp)Cl2] (0.1179 g, 0.2 mmol) in CH2Cl2 (15cm3),
and the mixture was heated under reflux for 4 hrs
and then the Solvent was evaporated at room
temperature to give a yellow solid.Yield= 93 %,
m.p= 142-144°C. as shown in Figure 1.
solved by direct methods applying SHElXl-201317,
with SHElXlE18 as a graphical interface.
Red crystals of 1, yellow crystals of 3 and
yellow crystals of 5 suitable for X-ray crystallographic
measurements were obtained by slow evaporation of
dichloromethane solutions of the respective complex.
Table 4 gives the crystallographic data and collection
parameters. All Non-hydrogen atoms were refined
with anisotropic displacement parameters.Hydrogen
atoms were included in the models by calculating the
positions (riding model) and refined with calculated
isotropic displacement parameters.
Synthesis of [Pt(k2-dppmCl)Cl2](5)
The solution of dppm (1.1532g, 3mmol)
in 15ml CH2Cl2 was added to a solution of PtCl2
(0.7979g, 3mmol) that dissolved in 2 cm3 ethanol
and 2cm3 concentrate HCl. The mixture was reflux
for 3 hrs. And then the solvent was evaporate at
room temperature to give yellow precipitate. A small
portion of this complex was dissolve in CH2Cl2 and
set to slow evaporation at room temperature after
a one week, the yellow colored needle crystals
were formed suitable for single-crystal diffraction
analysis15. The melting point is ˃ 300°C, yield is
1.756gm (90%), formula: [Pt(k2-dppmCl)Cl2] and
M.wt.is 667.43 gm/mole.as shown in Figure 1.
RESULTS and DISCUSSIONS
The mixed ligand complexes were
synthesized by two steps. The first step include
the preparation of metal complexes with tertiary
diphosphines ligands [MCl2(k2-PPh2(CH2)nPPh2)]
where n= 1,3 with [MCl2(k2-dppf)], and M= Pd and
Pt. The second step include the synthesis of mixed
ligand complexes by addition of S-1H-benzo[d]
imidazole-2-yl benzothioate (HSBIBT) ligand
to tertiary diphosphines metal complexes. The
physical data of complexes are given in Table (1),
the suggested molecular formula are supported by
IR spectra, UV-Visible sepectra, elemental analysis,
magnetic moment and conductivity measurement.
Synthesis of [Pt(k2-dppmCl)(HSBIBT)Cl]Cl(6)
A solution of ligand (0.0509 g, 0.2 mmol)
in CH2Cl2 (15 cm3) was added to a solution of
[Pt(k2-dppmCl)Cl2] (0.1300 g, 0.2 mmol) in CH2Cl2
(15cm3), and the mixture was heated under reflux
for 4 hrs and then the Solvent was evaporated at
room temperature to give a yellow solid.Yield= 90 %,
m.p= 117-119°C. as shown in Figure 1.
x-ray crystallography
IR spectral studies
Single crystal X-ray crystallography studies
were performed at 200 k using a Bruker Kappa
Apex II diffractometer with graphite monochromated
Mo Ka radiation (l = 0.71073 °A).For data collection,
Apex-II was used while for cell refinement and data
reduction, SAINT was used16. The structures were
The infraredspectrumoffree (HSBIBT)
ligand ischaracterized by intense absorption bandat
1712 cm-1.This band is assigned to ν(C=O) group19,4
.
The stretching frequency of ν(C=N) bandwhich
appeared at 1618 cm-1 forfree (HSBIBT) ligand.
This band was shifted to lower frequency during
Table 1: physical characteristics and analytical data for metal complexes
Complex
Color
Yield %
M.P °C
Elemental analysis, calc. (found) %
C
H
N
S
[Pd(k2-dppf)(HSBIBT)
Cl]Cl
Red
91
93
90
142-144
139-141
117-119
58.47
-58.47
58.45
-58.35
51.46
-51.78
3.84
-3.75
4.18
-4.15
3.6
2.75
-2.84
3.26
-3.32
2.93
-3.09
3.15
-3.24
3.46
-3.79
3.44
-3.54
[Pd(k2-dppp)(HSBIBT)
Cl]Cl
Yellow
Yellow
[Pt(k2-dppmCl)
(HSBIBT)Cl]Cl
-3.43

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AlI et al., Orient. J. Chem., Vol. 33(2), 584-592 (2017)
complexationdue to the coordination of nitrogen atom these bands are reasonable to square planner
to the metals20(Table 2).
geometry26. The UV-visible spectrum of Pd(II)
complex(4), gave three spins allowed transitions
The infrared spectra of complexes showed at 24038 cm-1, 29411 cm-1, and 32679 cm-1which
medium intensity bands in the range 513 to are assigned to the A1g→1A2g , A1g→1Eg and
570 cm-1,these bands are attributed to ν(M-N)21.Also charge transfer transition respectively. The UV-
showed a bands in the range 370 to 391cm-1, these visible spectrum of Pt(II) complex(6), shows three
bands are related toν(M-Cl)22.Further support for the absorption bands at 23923 cm-1, 27777 cm-1, and
coordinated phosphines ligands has been provided 32573 cm-1which are assigned to the 1A1g→1A2g ,
by the appearance of new bands in the range 285 to 1A1g→1Eg and charge transfer transition respectively,
1
1
291cm-1, these bands are assigned toí(M-P)23.
These transitions value are indicated to square
planner geometry27.
Magnetic moments
The magnetic moments of complexes Conductivity measurement
[Pd(k2-dppf)(HSBIBT)Cl]Cl (2), [Pd(k2-dppp)(HSBIBT)
The molar conductivity of complexes [Pd(k2-
Cl]Cl(4) and [Pt(k2-dppmCl)(HSBIBT)Cl]Cl (6) dppf)(HSBIBT)Cl]Cl (2), [Pd(k2-dppp)(HSBIBT)
are 0.54, 0.6 and 0.44 B.M. respectively (Table 3), Cl]Cl(4) and [Pt(k2-dppmCl)(HSBIBT)Cl]Cl (6)
suggesting a square planer arrangement around the in dimethyl sulfoxide (DMSO) are 34.2, 41.4 and
metal and complexes are diamagnetic24,25
.
36 (cm2.ohm-1. mol-1)(Table 3)suggesting that they
are electrolytescomplexes28,29
.
Electronic spectral studies
The UV-Vis spectrum in 10-3 M chloroform x-ray Crystal structures
(Table 3)shows three absorption bands of Pd(II)
The [Pd(k2-dppf)Cl2].CH2Cl2 complex was
complex (2), at 20661 cm-1, 28571 cm-1, and crystallized in a dichorometahne (CH2Cl2) at room
1
33783 cm-1which are assigned to the 1A1g→ A2g , temperature.After one week, the red colored needle
1A1g→ 1Eg and charge transfer transition respectively, type crystals had grown from the CH2Cl2 solvent
Table 2: IR frequencies (cm-1) of the compounds
Complex ν(N-H) ν(C=O) ν(C=N) ν(P-Ph) ν(P-C)
ν(M-N)
ν(M-P) ν(M-Cl)
HSBIBT
3151
3165
3159
3153
1712
1712
1712
1712
1618
1608
1612
1608
-
-
-
-
-
-
2
4
6
1435
1435
1436
513
540
559
285
288
291
370
383
391
513
509
Table 3: Electronic spectra, magnetic moments and
molar conductivity of complexes
complex
λmax(nm)/
assignments
µeff (BM)a
ɅM(Ω-1cm2 mol-1)/
Chloroform
DMSO
2
4
6
484
350
296
416
340
306
418
360
307
1A1g→ 1A2g
1A1g→1Eg
C.T
1A1g→1B1g
1A1g→1Eg
C.T
1A1g→1A2g
1A1g→1Eg
C.T
0.54
34.2
41.4
36
0.6
0.44