Platinum(II) and palladium(II) complexes containing 1,3-dimethylcyanurate ligand

Article abstract of DOI:10.1016/j.poly.2011.11.045

New platinum(II) and palladium(II) complexes, cis-[PtCl(DMC)(PPh ₃)₂] (1·CH₂Cl₂) and trans-[PdCl(DMC)(PPh₃)₂] (2·2CHCl₃), where DMC = 1,3-dimethylcyanurate, were synthesized and characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, ³¹P NMR and FAB mass spectroscopy. The structures of complexes are determined by X-ray diffraction and proved to have a distorted square-planar geometry around the metal ions. Both complexes exhibit a high stability in the solid state.

Full text of DOI:10.1016/j.poly.2011.11.045

Polyhedron 33 (2012) 297–301
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Platinum(II) and palladium(II) complexes containing 1,3-dimethylcyanurate ligand
b
b
b
Qutaiba Abu-Salem a, , Norbert Kuhn , Cäcilia Maichle-Mößmer , Manfred Steimann ,
⇑
Wolfgang Voelter c
a Department of Chemistry, Faculty of Science, University of Al al-Bayt, Al-Mafraq 25113, Jordan
b Institute for Inorganic Chemistry, University of Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
c Interfacultary Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, D-72076 Tübingen, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
New platinum(II) and palladium(II) complexes, cis-[PtCl(DMC)(PPh3)2] (1ꢀCH2Cl2) and trans-
[PdCl(DMC)(PPh3)2] (2ꢀ2CHCl3), where DMC = 1,3-dimethylcyanurate, were synthesized and characterized
by elemental analysis, IR, 1H NMR, 13C NMR, 31P NMR and FAB mass spectroscopy. The structures of com-
plexes are determined by X-ray diffraction and proved to have a distorted square-planar geometry around
the metal ions. Both complexes exhibit a high stability in the solid state.
Received 19 September 2011
Accepted 22 November 2011
Available online 9 December 2011
Keywords:
1,3-Dimethylcyanurate
Palladium(II)
Ó 2011 Elsevier Ltd. All rights reserved.
Platinum(II)
Crystal structure
Heterocycles
1. Introduction
been reported by Abu-Salem and Kuhn [31–33], most of them have
concentrated on the first-row divalent transition metals. However,
Cyanuric acid (CYH3) was first synthesized by Wöhler in 1829
[1]. The X-ray structures of its potassium [2–4], calcium [5,6] and
rubidium [2] salts have been studied and suggested that the hard
metals of these main group elements are coordinated to the cyan-
urate ligand at the deprotonated enol oxygen. On the other hand,
transition metal complexes of cyanurates have also been prepared
[7–22], and the donor site of the deprotonated cyanurate anion
a literature survey indicates that group d8 metal complexes of
cyanuric acid are rare. In the course of our studies on cyanurate–
metal ion interactions, we have succeeded in preparing the first
two new platinum(II) and palladium(II) complexes of DMC with
ancillary triphenylphosphine ligand. Herein, we report the
synthesis, characterization and crystal structures of cis-[PtCl(DMC-
)(PPh3)2] (1) and trans-[PdCl(DMC)(PPh3)2] (2).
ꢁ
CYH2 is the deprotonated N atom. Furthermore in the case of
di- and tri-anionic cyanurate ligands were found to be N,O-che-
lated [23–28].
2. Experimental
Among cyanurates, 1,3-dimethylcyanuric acid (DMCH, also
named as 1,3-dimethyl-2,4,6-trioxo-1,3,5-triazine) was known
since 1881 [29]. The presence of several potential donor sites such
as one amine nitrogen atom and three carbonyl oxygen atoms
makes DMCH a very interesting polyfunctional ligand in coordina-
tion chemistry. By comparing with CYH3, DMCH has two methyl
groups which lower the tendency for making intra and intermolec-
ular hydrogen bonding [30]. This has prompted us to investigate its
coordination behavior. Proton loss from the amine N atom to form
amide is necessary for the complexation of the 1,3-dimethylcyan-
urate monoanion (DMCꢁ). The DMC ligand readily forms com-
plexes with many metal ions and earlier work in this field has
2.1. Materials and measurements
Lithium1,3-dimethylcyanurate (LiDMC) was obtained according
to a published procedure [33]. Other chemicals were purchased
and used as received. The elemental analysis for C, H and N were
performed using a Carlo Erba 1106 elemental analyzer. IR spectra
were recorded on a VERTEX 70 FT-IR spectrometer using drift spec-
troscopy method in the range 4000–200 cmꢁ1. The high resolution
NMR spectra were acquired by a Bruker DRX 400 NMR spectrome-
ter (1H 400 MHz; 13C 100 MHz, using TMS as external standard; 31
162 MHz, 85% H3PO4 as external standard). FAB mass spectra were
carried out on a TSQ 70 quadrupole mass spectrometer with xenon
P
⇑
Corresponding author. Tel.: +962 795488048.
E-mail addresses: q.abusalem@gmail.com, q.abusalem@aabu.edu.jo (Q. Abu-Salem).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.11.045

298
Q. Abu-Salem et al. / Polyhedron 33 (2012) 297–301
O
O
O
O
N
N
N
N
N
N
HN
NH
N
Pd
Cl
2
N
N
H
N
H
O
O
O
O
O
O
O
O
Ph3P
PPh3
Cl
Pt
PPh3
DMCH
CYH3
PPh3
1
atoms as bombarding particles (kinetic energy ca. 8 keV). Unless
otherwise stated, 3-nitrobenzyl alcohol (3-NBA) was used as ma-
trix material at ion source temperature of ca. 60 °C. In the FAB mass
spectra, M represents the solvent-free molecular masses.
stream of liquid nitrogen. The intensity data of the complexes were
collected using a STOE IPDS 2 diffractometer with graphite-mono-
chromated Mo K
a radiation (k = 0.71073 Å). The structures were
solved by direct methods and refined on F2 with the SHELX-97 and
SHELXL-97 programs [34]. All non-hydrogen atoms were found from
the difference Fourier map and refined anisotropically. All hydro-
gen atoms were included using a riding model. The details of data
collection, refinement and crystallographic data are summarized in
Table 1.
2.2. Synthesis of the platinum(II) and palladium(II) complexes
2.2.1. cis-[PtCl(DMC)(PPh3)2] (1ꢀCH2Cl2)
To a solution of cis-[PtCl2(PPh3)2] (0.250 g, 0.316 mmol) in
methanol (30 mL) was added LiDMC (0.052 g, 0.319 mmol). The
mixture was warmed to 53 °C and stirred for 5 h, whereupon the
LiDMC dissolved giving a clear colorless solution. Then the mixture
was stirred overnight at room temperature to yield a white precip-
itate. The mixture was evaporated to dryness under reduced pres-
sure and the product was extracted with dichloromethane (30 mL)
and filtered. The filtrate was reduced in volume to ca. 5 mL and
light petroleum (25 mL) was added. After 1 day, white crystals at
ꢁ32 °C were obtained.
3. Results and discussion
3.1. Synthesis and characterization
Complexes 1 and 2 were synthesized by the ligand displace-
ment reaction of cis-[MCl2(PPh3)2] with the anhydrous lithium salt
of 1,3-dimethylcyanuric acid, Li(DMC) [35], and isolated as air-
stable solids in moderate yields (over 50%). The complexes can
be isolated in a pure state from the mixture of products by recrys-
tallization from chlorinated solvents-light petroleum, being solu-
ble in most organic solvents at room temperature.
Yield: 0.217 g (69%). Anal. Calc. for C42H38Cl3N3O3P2Pt (M =
996.15 g/mol): C, 50.64; H, 3.84; N, 4.22. Found: C, 50.96; H,
4.28; N, 3.82%. 1H NMR (CDCl3): d 2.96 (s, 6H, NCH3), 7.19–7.84
(m, 30H, Ph), 5.29 (s, 2H, CH2Cl2). 13C NMR (CDCl3): d 28.93
(CH3), 53.5 (CH2Cl2), 127.87–135.21 (m, Ph), 151.75 (C2), 152.94
(C4,6), 31P NMR (CDCl3): AB spin system, d 6.72 (d, PPh3 trans to
N, 2J(PP) 19.29), 14.21 (d, PPh3 trans to Cl, 2J(PP) 19.41). IR(DRIFT):
mCO (cmꢁ1) 1726vs, 1681s, 1636vs. MS [FAB, (3-NBA matrix)]: m/z
(%) = 912.2 [10, M+H], 875.7 [18, MꢁCl], 755.2 [25, MꢁDMC],
718.7 [100, MꢁClꢁDMCꢁ1H].
Selected FT-IR spectroscopic data for 1 and 2 are listed in Table
2. The relatively medium and weak bands in the 2835–3002 cmꢁ1
range are characteristic of both aromatic and aliphatic
m(C–H)
vibrations. The metal complexes of DMC are well characterized
by the presence of sharp IR bands due to the absorption of the
Table 1
Crystallographic data and structure refinement for 1ꢀCH2Cl2 and 2ꢀ2CHCl3.
Complex
1ꢀCH2Cl2
C42H38Cl3N3O3P2Pt
996.13
2ꢀ2CHCl3
C43H38Cl7N3O3P2Pd
1061.25
173(2)
0.71073
orthorhombic
P212121
11.8784(6)
13.8627(7)
28.0916(19)
90
90
90
4625.8(5)
4
1.524
2.2.2. trans-[PdCl(DMC)(PPh3)2] (2ꢀ2CHCl3)
A suspension solution of cis-[PdCl2(PPh3)2] (0.291 g, 0.415
mmol) in 21 mL dichloromethane was added to a stirred solution
of LiDMC (0.068 g, 0.415 mmol) in methanol (20 mL) and the mix-
ture was refluxed for 7 h. The resulting red solution was evapo-
rated to dryness under reduced pressure and the product was
extracted with chloroform (50 mL). The filtrated solution was re-
duced in volume to ca. 10 mL and light petroleum (25 mL) was
added. After 1 day, yellow crystals at ꢁ32 °C were obtained.
Formula
M
T (K)
173(2)
k (Å)
0.71073
monoclinic
P21/c
11.9923(8)
19.5050(10)
19.7441(11)
90
104.920(5)
90
4462.6(5)
4
1.483
3.434
1976
5.68–24.71
ꢁ14 6 h 6 14,
ꢁ22 6 k 6 22,
ꢁ23 6 l 6 23
44004
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a
(°)
Yield: 0.273 g (62%). Anal. Calc. for
C43H38Cl7N3O3P2Pd
b (°)
(M = 1061.318 g/mol): C, 48.66; H, 3.61; N, 3.96. Found: C, 48.06;
H, 3.24; N, 4.02%. 1H NMR (CDCl3): d 2.64 (s, 6H, NCH3), 7.28–
7.75 (m, 30H, Ph), 7.18 (s, 2H, CHCl3). 13C NMR (CDCl3): d 28.93
(CH3), 77.20 (CHCl3), 128.09–134.70 (m, Ph), 151.29 (C2), 152.39
(C4,6), 31P NMR (CDCl3): d 21.39 (s). IR(DRIFT): mCO (cmꢁ1) 1721vs,
1649s, 1621vs. MS [FAB, (3-NBA matrix)]: m/z (%) = 823.3 [15,
M+H], 786.8 [35, MꢁCl], 666.3 [25, MꢁDMC], 629.8 [70,
MꢁClꢁDMCꢁ1H].
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
l
(mmꢁ1
)
0.917
2144
F(000)
h range (°)
Index range (h, k, l)
3.03–26.37
ꢁ14 6 h 6 14,
ꢁ17 6 k 6 17,
ꢁ35 6 l 6 35
59893
Reflections collected
Data/parameters
7489/528
1.253
9441/685
1.056
2.3. X-ray crystallography
Goodness-of-fit (GOF) on F2
R1 [I > 2
wR2
r]
0.0634
0.0979
0.0450
0.0833
The crystals of 1ꢀCH2Cl2 and 2ꢀ2CHCl3 were mounted on a glass
fiber with epoxy cement at room temperature, and cooled in a cold

Q. Abu-Salem et al. / Polyhedron 33 (2012) 297–301
299
Table 2
and palladium(II) diphosphine complexes MCl2(Ph2P(CH2)5PPh2)
based on the gas-phase methodologies has been reported [41,42].
Selected FTIR spectral dataa for 1ꢀCH2Cl2 and 2ꢀ2CHCl3.
Assignment
1
2
m(CH)
3057m, 3026w, 2989w,
2949w
3020m, 2974w, 2931w,
2890w
(PPh3)M
Ph2P
3
m
m
m
m
m
(CO)
(CC)
(CH)
(CN)
1726vs, 1681s, 1636vs
1572w, 1527w
1482s
1257s
336m
1721vs, 1649s, 1621vs
1550w, 1526w
1460s
1260s
330m
(MꢁCl)
550
5
547vs
535sh
m = medium; w = weak; vs = very strong; s = strong; sh = shoulder.
a
Frequencies in cmꢁ1
.
3.2. Description of crystal structures
carbonyl groups. The DMC ligand exists in triketo form, three types
of strong absorption bands were observed in the frequency range
1621–1726 cmꢁ1 characterize vibrations of the carbonyl groups.
The weak bands in the frequency range 1526–1572 cmꢁ1 can be as-
signed to the C@C vibrations of the phenyl groups. The bands with
The molecular structure of complex 1ꢀCH2Cl2 with the atom
labeling is shown in Fig. 1. Selected bond distances and angles
are listed in Table 3. Complex 1ꢀCH2Cl2 crystallizes in the mono-
clinic space group P21/c. The crystal lattice of complex 1 consists
of one dichloromethane molecule of solvation; there are no close
contacts between them. The platinum(II) ion has a distorted
square-planar coordination arrangement with two cis triphenyl-
phosphine ligands, a chloride ligand and a monodentate N-bonded
1,3-dimethylcyanurate ligand. The maximum deviation of any
atom from the least-squares plane defined by Pt, P1, P2, N40, and
Cl3 is only 0.002 Å. The plane of 1,3-dimethylcyanurate ligand is
approximately orthogonal to the platinum coordination plane,
with a twist angle of 96(1)° between the two planes. This is also
illustrated by the torsions angles Cl3–Pt–N40–C45 and Cl3–Pt–
N40–C41 which are ꢁ85(1)° and 94(1)°, respectively. Presumably,
the DMC ligand seems to be out of correct perpendicularity occurs
as a result of a steric interaction with a phenyl ring on P1. The Pt–
P1 and the Pt–P2 bond distances are different (2.250(2) and
2.265(2) Å), consistent with the amide, trans to P2, having slightly
larger trans influence. The DMC ligand in 1, appears to have a lower
trans influence than the corresponding barbiturate analog in
cis-[PtCl(debarb)(PPh3)2] (4) (debarb: 5,5-diethylbarbiturate), as
evidenced by the slightly longer Pt–P1 2.274(2) Å [43] when com-
pared with that of 1. The Pt–N40 distance, 2.064(6) Å, is slightly
shorter than that in the related complex 4 (2.077(4) Å). The Pt–Cl
distance of 1, 2.357(2) Å, is similar to the Pt–Cl distance in 4
medium intensity 1460 and 1482 cmꢁ1 correspond to the
m
(C–H)
deformation vibrations and the strong band centered around
1260 cmꢁ1 is attributed to the
(C–N) stretching vibrations [36].
m
The appearance of a very strong absorption band at 547 cmꢁ1 in
complex 1 is important because this band seems to correspond
to the absorption which is characteristic for cis-PtXY(PPh3)2 and
appears at 550 5 cmꢁ1; the intensity of this band in complex 2
is weak and appears at 535 cmꢁ1 as shoulder [37]. The medium
intensity bands at 336 and 330 cmꢁ1 can be assigned to MꢁCl
stretching mode for complexes 1 and 2, respectively. This assign-
ment appears reasonable, because in the case of MꢁCl interactions
such vibrations are often found in this spectral region [38,39].
The 1H NMR spectra of complexes 1 and 2 are consistent with
their proposed structures. In CDCl3 the signals at 2.96 and
2.64 ppm for complexes 1 and 2, respectively, were assigned to
the methyl groups of the DMC ligand. The phenyl ring protons dis-
play two multiplets in the range 7.19–7.84 ppm.
The 13C NMR spectra of complexes 1 and 2 displayed, in addi-
tion to the expected resonances for the PPh3 ligands, three signals
one for the methyl groups at 28.93 ppm and two for the carbonyl
groups in an approximate 2:1 intensity ratio. The more intense res-
onance for the two carbonyl groups near the N atom which is the
deprotonation site was observed downfield at 152.94 and
152.39 ppm from the smaller signal assigned to the carbonyl group
near both the N-methyl groups at 151.74 and 151.29 ppm for com-
plexes 1 and 2, respectively.
(2.353(2) Å), such Pt–Cl bonds trans to
a phosphine ligands
The 31P NMR spectrum of the phosphine complex 2 displayed a
single resonance at 21.39 ppm consistent with a square-planar
geometry with two equivalent trans phosphine ligands, while in
complex 1 the 31P NMR spectrum show the expected AB patterns
for two cis-phosphines trans to ligands having differing trans influ-
ences. Thus for complex 1 the two values of 6.72 (2J(PP) 19.29 Hz)
and 14.21 (2J(PP) 19.41 Hz) ppm were assigned to the phosphines
trans to 1,3-dimethylcyanurate and chloride ligands, respectively.
Fast-atom bombardment (FAB) mass spectrometry of 1 and 2 by
dissolving in 3-nitrobenzylalcohol matrix show a relatively weak
parent (protonated) molecular ions [M+H]+ at m/z 912.2 (10%)
and 823.3 (15%), respectively. There are also two additional peaks
in common, at m/z 875.7 (18%) and 786.8 (35%). These are assigned
to the complexes [MꢁCl]+. The formation of cations by loss of an
anionic halide ligand is a common ionization pathway for neutral
transition metal halide complexes [40]. The two fragments of weak
intensity at m/z 755.2 and 666.3 (25%) were assigned to
[MꢁDMC]+. The FAB mass spectra are dominated by peaks at m/z
718.7 (100%) and 629.8 (70%). These are assigned to complex
containing an orthometallated triphenylphosphine ligand
[M(C6H4PPh2-o)(PPh3)]+ (3). The cyclometallation of platinum(II)
Fig. 1. Molecular structure of the complex cis-[PtCl(DMC)(PPh3)2]ꢀCH2Cl2 (1),
showing the atom numbering scheme. The dichloromethane molecule of crystal-
lization is not shown.

300
Q. Abu-Salem et al. / Polyhedron 33 (2012) 297–301
Table 3
Table 4
Selected bond lengths (Å) and angles (°) for 1ꢀCH2Cl2.
Selected bond lengths [Å] and angles [°] for 2ꢀ2CHCl3.
Pt–N40
Pt–P2
2.064(6)
2.265(2)
1.366(10)
1.327(10)
1.401(10)
1.425(10)
1.383(12)
1.367(11)
1.822(8)
1.826(8)
1.822(8)
Pt–P1
Pt–Cl3
2.250(2)
2.357(2)
1.460(11)
1.471(11)
1.231(10)
1.211(10)
1.224(9)
1.814(7)
1.835(8)
1.826(7)
Pd–N1
2.023(3)
2.319(2)
2.321(2
N5–C10
C2–O7
C6–O11
C4–O9
C2–N3
N3–C4
1.455(6)
1.207(5)
1.229(5)
1.213(6)
1.401(5)
1.357(6)
1.468(6)
1.821(4)
1.813(5)
1.820(4)
Pd–P20
Pd–P10
Pd–Cl1
N1–C2
N1–C6
C4–N5
N40–C45
C41–N40
N44–C45
C41–N42
C43–N44
N42–C43
P1–C7
N44–C49
N42–C47
C45–O50
C43–O48
C41–O46
P1–C1
2.294 (2)
1.372(5)
1.355(5)
1.389(6)
1.389(6)
1.816(5)
1.815(5)
1.824(4)
N3–C8
N5–C6
P10–C30
P10–C50
P10–C70
P1–C13
P2–C26
P20–C60
P20–C40
P20–C20
P2–C32
P2–C20
C41–N40–Pt
C45–N40–Pt
C41–N40–C45
C43–N44–C45
N42–C43–N44
N40–C41–N42
C45–N44–C49
C43–N44–C49
O50–C45–N40
N40–Pt–P1
N40–Pt–P2
P1–Pt–P2
C1–P1–C7
C7–P1–C13
C20–P2–C26
C1–P1–Pt
C7–P1–Pt
C13–P1–Pt
119.9(5)
116.2(5)
123.9(7)
123.5(7)
115.2(7)
117.0(7)
117.0(7)
119.5(7)
123.4(7)
89.08(18)
171.31(18)
99.16(7)
110.0(4)
100.7(4)
103.3(3)
110.3(3)
116.6(3)
113.7(2)
C43–N42–C47
C41–N42–C47
C43–N42–C41
N40–C45–N44
O46–C41–N40
O46–C41–N42
O48–C43–N42
O48–C43–N44
O50–C45–N44
N40–Pt–Cl3
P1–Pt–Cl3
P2–Pt–Cl3
C13–P1–C1
C20–P2–C32
C32–P2–C26
C26–P2–Pt
119.2(7)
117.4(7)
123.4(7)
116.9(7)
124.1(7)
118.9(7)
122.3(9)
122.5(8)
119.7(7)
85.33(18)
173.59(7)
86.59(7)
104.6(3)
105.1(4)
103.3(4)
122.4(3)
110.3(3)
110.9(3)
C2–N1–Pd
C6–N1–Pd
N1–C2–N3
N1–C6–N5
C2–N3–C4
C2–N3–C8
N3–C4–N5
C8–N3–C4
118.2(3)
118.9(3)
116.5(3)
117.6(4)
124.0(4)
117.4(4)
115.7(4)
118.6(4)
123.0(4)
178.36(10)
90.27(9)
92.28(9)
109.3(2)
105.8(2)
114.47(14)
110.33(16)
112.73(16)
103.8(2)
N1–C6–O11
N1–C2–O7
N3–C4–O9
121.8(4)
122.5(3)
122.6(5)
121.7(5)
120.6(4)
117.6(4)
121.0(4)
118.3(4)
118.6(4)
172.52(4)
88.67(4)
88.93(4)
104.3(2)
105.7(2)
107.3(2)
114.31(15)
118.77(16)
105.70(15)
N5–C4–O9
N5–C6–O11
O11–C6–N1
N3–C2–O7
C4–N5–C10
C10–N5–C6
P20–Pd–P10
P20–Pd–Cl1
P10–Pd–Cl1
C30–P10–C50
C50–P10–C70
C70–P10–C30
C30–P10–Pd
C50–P10–Pd
C70–P10–Pd
C4–N5–C6
N1–Pd–Cl1
N1–Pd–P20
N1–Pd–P10
C60–P20–C40
C40–P20–C20
C20–P20–Pd
C40–P20–Pd
C60–P20–Pd
C20–P20–C60
C32–P2–Pt
C20–P2–Pt
space group P212121. The complex is composed of two chloroform
molecules of solvation; there are no close contacts between them.
The palladium(II) ion is coordinated by a monodentate N-bonded
1,3-dimethylcyanurate ligand, a chloride ligand and two trans tri-
phenylphosphine ligands forming a distorted square-planar coordi-
nation arrangement. The deviation of palladium(II) ion from the
mean coordination plane is 0.06 Å over the plane. The DMC ligand
is twisted away from the coordination plane 80(1)° in order to min-
imize steric repulsions with the bulky triphenylphosphine ligands.
The torsions angles Cl1–Pd–N1–C6 and Cl1–Pd–N1–C2 which are
34(1)° and ꢁ143(1)°, respectively. The Pd–P10 and Pd–P20 dis-
tances are similar in length (2.321(2) and 2.319(2) Å)) to those
found in trans-[PdCl{EtO2CNC(O)CH2CN}(PPh3)2] (5) (Pd–P1 and
Pd–P2 (2.311(2) and 2.324(2) Å)), which also has the amide trans
to a chloride ligand [45]. The two Pd–N1 and Pd–Cl1 bond distances
(2.023(3) and 2.294(2) Å) in complex 2 are close to the Pd–N1 and
Pd–Cl1 bond distances in N-cyanoacetylurethane complex
(2.039(5)
5
and 2.306(2) Å) [45]. All the bond lengths and angles in the DMC li-
gand are in the normal range, and match the reported value [32,33].
The triazine ring, the two methyl groups and the three carbonyl
groups in both complexes are near planar from the mean plane of
their attached triazine ring.
Fig. 2. Molecular structure of the complex trans-[PdCl(DMC)(PPh3)2]ꢀ2CHCl3 (2),
showing the atom numbering scheme. The chloroform molecules of crystallization
are not shown.
typically lie within this range [41,42]. The C–N bond distances at
the deprotonation site C41–N40 1.327(10), N40–C45 1.366(10) Å
are as expected for sp2 C–N bonds [44] and clearly indicate that
the double bond is localized between C41 and N40. The remaining
structural features are unexceptional. DMCH acid has strong
tendency to associate through hydrogen bonding [32,33]. How-
ever, examination of the packing diagram for 1 did not reveal
any apparent three-dimensional superstructure. This is possibly
as a result of the steric bulk imposed by the two triphenylphos-
phine ligands.
O
Ph3P
N
PPh3
Cl
OEt
CH2CN
Pt
HN
N
Pd
Cl
O
O
Ph3P
PPh3
O
O
Et
Et
The molecular structure of complex 2ꢀ2CHCl3 with the atom
labeling is shown in Fig. 2. Selected bond distances and angles are
listed in Table 4. Complex 2ꢀ2CHCl3 crystallizes in the orthorhombic
5
4

Q. Abu-Salem et al. / Polyhedron 33 (2012) 297–301
301
[7] M.Z. Branzburg, T.F. Sysoeva, N.F. Shugal, N.M. Dyatlova, V.M. Agre, M.Z.
Gurevich, Koord. Khim. 12 (1986) 1658.
4. Conclusions
[8] L.R. Falvello, I. Pascual, M. Tomas, E.P. Urriolabeitia, J. Am. Chem. Soc. 119
(1997) 11894.
[9] L.R. Falvello, I. Pascual, M. Tomas, Inorg. Chim. Acta 229 (1995) 135.
[10] T. Palade, M. Nutiu, Rev. Chim. 37 (1986) 80.
[11] S. Shao, C. Chen, X. Huang, D. Gao, Z. Lin, D. Li, Jiegou Huaxue 15 (1996) 246.
[12] T.F. Sysoeva, Z.A. Starikova, M.Z. Gurevich, M.Z. Branzburg, Koord. Khim. 17
(1991) 971.
[13] R.D. Hart, B.W. Skelton, A.H. White, Aust. J. Chem. 45 (1992) 1927.
[14] C.-Z. Chen, S.-B. Shao, X.-Y. Huang, D.-S. Gao, Z.-B. Lin, Jiegou Huaxue 14 (1995)
356.
[15] J. Server-Carrio, E. Escriva, J.-V. Folgado, Polyhedron 17 (1998) 1495.
[16] A.-Q. Wu, G.-H. Guo, F.K. Zheng, X. Liu, G.-C. Guo, J.-S. Huang, Inorg. Chem.
Commun. 8 (2005) 182.
[17] E. Yang, R.Q. Zhuang, Y.E. Chen, Acta Crystallogr., Sect. E 62 (2006) m2901.
[18] Q. Yue, J. Yang, H.-M. Yuan, J.-S. Chen, Chin. J. Chem. 24 (2006) 1045.
[19] L. Zhang, J. Zhang, P.-X. Yin, J.-K. Cheng, Z.-J. Li, Y.-G. Yao, Z. Anorg. Allg. Chem.
632 (2006) 1902.
[20] J.M. Du, D.J. Kang, Chem. Lett. 36 (2007) 168.
[21] K. Sivashankar, A. Ranganathan, V.R. Pediretti, Proc. Ind. Acad. Sci.: Chem. Sci.
112 (2000) 147.
[22] H. Brunner, A. Hollmann, B. Nuber, M. Zabel, J. Organomet. Chem. 633 (2001) 1.
[23] C.-Z. Chen, Z.-B. Lin, J.-Q. Shi, X.-Y. Huan, D.-S. Gao, D. Li, H.-Y. Liang, Jiegou
Huaxue 13 (1994) 468.
[24] U. Müller, Z. Anorg. Allg. Chem. 422 (1976) 141.
[25] C. Elschenbroich, F. Lu, M. Nowotny, O. Burghaus, C. Pietzonka, K. Harms,
Organometallics 26 (2007) 4025.
[26] Y. Perez, S. Morante-Zarcero, I. Sierra, P. Gomez-Sal, M. Fajardo, A. Otero, I. del
Hierro, Inorg. Chim. Acta 360 (2007) 607.
[27] A. Antinolo, S. Garcia-Yuste, A. Otero, J.C. Perez-Flores, I. Lopez-Solera, A.M.
Rodriguez, J. Organomet. Chem. 692 (2007) 3328.
Commonly, kinetics and thermodynamics of square-planar d8
metal complexes are best understood in terms of trans-effect and
trans-influence [46]. As expected, the platinum complex (1) is
formed by substitution of chloride from cis-[PtCl2(PPh3)2] as the
kinetically stable product while, starting from the palladium pre-
cursor cis-[PdCl2(PPh3)2], the cis-isomer could not be detected even
as an intermediate apparently owing to its highly labile nature.
Comparable ligand properties of DMCꢁ1 and pyridine in their pen-
tacarbonylmetal complexes have been reported by us formerly
[31]. Assuming similar atomic radii of palladium and platinum
and following the arguments discussed for the trans-influence,
additional arguments for the ligand properties may be found here.
The trans-influence predicts bond weakening in the trans-L-M-L0 in
case that the ligands compete with the same metal orbitals. In fact,
in the palladium complex (2), the M–P distances are the longest
ones (see Tables 3 and 4) though steric interaction should be min-
imum. The marked difference in the M–N distances of the com-
plexes (1) and (2) may also figure the stronger trans-influence of
the PPh3 ligand compared with Clꢁ1 and DMCꢁ1, for which similar,
i.e. medium
cussed here.
r-donor and weak p-donor properties, may be dis-
Acknowledgments
[28] F.A. Cotton, J.P. Donahue, C.A. Murillo, L.M. Perez, R. Yu, J. Am. Chem. Soc. 125
(2003) 8900.
[29] A.W.v. Hofmann, Ber. Dtsch. Chem. Ges. 14 (1881) 2728.
[30] G.R. Desiraju, Th. Steiner, The Weak Hydrogen Bond, Oxford University Press,
Oxford (UK), 1999.
[31] Q. Abu-Salem, C.M. Mößmer, E. Niquet, N. Kuhn, Z. Anorg. Allg. Chem. 634
(2008) 2463.
Financial support by the Deutsche Forschungsgemeinschaft and
Al al-Bayt University (Funding Short term research scholarship for
Q. Abu-Salem) is gratefully acknowledged (Ref.: VO 141/48-1). Q.
Abu-Salem thanks Prof. Klaus-Peter Zeller for helpful discussions
with mass spectral analyses.
[32] Q. Abu-Salem, N. Kuhn, C.M. Mößmer, M. Steimann, Z. Anorg. Allg. Chem. 634
(2008) 2337.
[33] N. Kuhn, Q. Abu-Salem, C.M. Mößmer, M. Steimann, Z. Anorg. Allg. Chem. 634
(2008) 1276.
[34] G.M. Sheldrick, SHELXS/L-97, Programs for Crystal Structure Determination,
University of Göttingen, Göttingen (Germany), 1997.
[35] Q. Abu-Salem, 1,3-Dimethylcyanuric Acid Derivatives, Ph.D. Thesis, University
of Tübingen, Tübingen, 2009.
[36] L. Levi, C.E. Hubley, Anal. Chem. 28 (1956) 1591.
[37] K. Suzuki, H. Yamamoto, Inorg. Chim. Acta 208 (1993) 225.
[38] M. Mehicic, F.A. Pesa, J.G. Grasselli, J. Phys. Chem. 88 (1984) 581.
[39] A. Romerosa, J.S. Varela, M.A. Hidalgo, J.C.A. Roso´n, E. Colacio, Inorg. Chem. 36
(1997) 3784.
Appendix A. Supplementary data
CCDC 838104 and 838103 contain the supplementary crystallo-
graphic data for (1ꢀCH2Cl2) and (2ꢀ2CHCl3), respectively. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
[40] P. Bergamini, O. Bortolini, O. Curcuruto, M. Hamdan, J. Mass Spectrom. (1995)
S77.
[41] W. Henderson, J. Fawcett, R.D.W. Kemmitt, P. McKenna, D.R. Russell,
Polyhedron 16 (1997) 2455.
References
[42] K.E. Neo, Y.C. Neo, S.W. Chien, G.K. Tan, A.L. Wilkins, W. Henderson, T.S.A. Hor,
Dalton Trans. 15 (2004) 2281.
[43] J. Fawcett, W. Henderson, R.D.W. Kemmitt, D.R. Russell, A. Upreti, J. Chem. Soc.,
Dalton Trans. (1996) 1897.
[44] H.E. Bryndza, W. Tam, Chem. Rev. 88 (1988) 1163.
[45] W. Henderson, B.K. Nicholson, A.G. Oliver, Polyhedron 13 (1994) 3099.
[46] A.T. Hutton, C.P. Morely, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.),
Comprehensive Coordination Chemistry 5, Pergamon Press, Oxford, 1987, p.
1157.
[1] F. Wöhler, Ann. Phys. Chem. 15 (1829) 619.
[2] G.S. Nichol, W. Clegg, M.J. Gutmann, D.M. Tooke, Acta Crystallogr., Sect. B 62
(2006) 798.
[3] T.F. Sysova, M.Z. Branzburg, M.Z. Gurevich, Z.A. Starikova, Zh. Strukt. Khim. 31
(1990) 90.
[4] R.E. Marsh, M. Kapon, S. Hu, F.H. Herbstein, Acta Crystallogr., Sect. B 58 (2002)
62.
[5] Z.-B. Lin, C.-Z. Chen, D.-S. Gao, X.-Y. Huang, D. Li, Jiegou Huaxue 14 (1995) 61.
[6] A.N. Chekhlov, Zh. Neorg. Khim. 51 (2006) 799.