The influence of substituents at C2 Carbon of thiosemicarbazones on the bonding pattern of bis(diphenylphopshano)alkanes in palladium(II) Complexes

Article abstract of DOI:10.1002/zaac.200801307

Reactions of trans-PdCl₂(PPh₃)₂ with acetone thiosemicarbazone (Hactsc) and benzaldehyde thiosemicarbazone (Hbtsc) in a 1:1 molar ratio in the presence of Et3N yielded the neutral complexes [Pd(η²-N³,

Full text of DOI:10.1002/zaac.200801307

ARTICLE
DOI: 10.1002/zaac.200801307
The Influence of Substituents at C2 Carbon of Thiosemicarbazones on the
Bonding Pattern of Bis(diphenylphopshano)alkanes in Palladium(II) Complexes
Tarlock S. Lobana,*[a] Gagandeep Bawa,[a] Geeta Hundal,[a] Ray J. Butcher,[b] and
Alfonso Castineiras[c]
Keywords: Palladium; Phosphane ligands; Thiosemicarbazones; Dimerizations; Chelates
Abstract. Reactions of trans-PdCl2(PPh3)2 with acetone thiosemi-
with cis-PdCl2(dppm) (dppm ϭ bis(diphenylphosphanyl)methane)-
carbazone (Hactsc) and benzaldehyde thiosemicarbazone (Hbtsc) and cis-PdCl2(dppp) yielded the dinuclear complexes [Pd2(η3-
in a 1:1 molar ratio in the presence of Et3N yielded the neutral
complexes [Pd(η2-N3,S-actsc)(PPh3)Cl] (1) and [Pd(η2-N3,S-
btsc)(PPh3)Cl] (2) respectively. In contrast, reactions of cis-
PdCl2(dppe) (dppe ϭ bis(diphenylphosphanyl)ethane) and cis-
O,N3,S-stsc)2(µ-dppm)] (5) and [Pd2(η3-O,N3,S-stsc)2(µ-dppp)] (6).
Complexes 1Ϫ6 were characterized with spectroscopic techniques
1
[IR, H, 31P{1H} NMR], and single-crystal X-ray crystallography.
The ligands are negative bidentate in complexes 1Ϫ4 and di-
negative tridentate (O, N3, S) in complexes 5 and 6. Diphosphanes
exhibited both chelating (η2; 3, 4) as well as bridging (µ; 5, 6)
modes.
PdCl2(dppp) (dppp
ϭ bis(diphenylphosphanyl)propane) with
Hbtsc gave the ionic complexes [Pd(η2-N2,S-btsc)(η2-dppe)]Cl (3)
and [Pd(η2-N3,S-btsc)(η2-dppp)]Cl (4) because of the chelation
effect. The reaction of salicylaldehyde thiosemicarbazone (H2stsc)
aldehyde thiosemicarbazone (H2stsc), acetophenone thio-
semicarbazone (H2aptsc) and pyrrole-2-carbaldehyde thio-
semicarbazone (H2ptsc) (Scheme 1).
Introduction
Thiosemicarbazones (structure I, Scheme 1) are an im-
portant class of organic ligands, and have been explored for
their analytical applications, variable bonding modes and
biological relevance [1Ϫ3]. Palladium(II) and platinum(II)
complexes with thiosemicarbazones have been particularly
interesting because of their antitumor, antibacterial, anti-
fungal and catalytic activities [4, 5]. In the absence of co-
ligands such as tertiary phosphane or bipyridyl compounds,
mono-, tri- and tetranuclear complexes of PdII with thiose-
micarbazones have been reported [6].
Our research focused on reactions of thiosemicarbazones
with transition metals [7], and a series of mononuclear
palldium(II) complexes, namely (i) trans- [Pd(η2-N3,S-L)2]
(L ϭ ttscϪ, ftscϪ) [8], (ii) [Pd(η3-X,N3,S-L)(PPh3)] (X, L ϭ
C, aptsc2Ϫ; N, ptsc2Ϫ; O, stsc2Ϫ) [9, 10], (iii) [Pd(η2-N3,S-
L)(PPh3)Cl] (L ϭ ttscϪ, ftscϪ) [8], have been reported using
Scheme 1.
In continuation of our interest in the chemistry of PdII-
thiosemicarbazones, we used ditertiary phosphanes, which
offer a variety of bonding possibilities (see Scheme 1), as
co-ligands. In this paper, palladium(II) complexes with a
series of thiosemicarbazones (Scheme 2) in presence of
mono- and ditertiary phosphanes are reported.
thiophene-2-carbaldehyde
thiosemicarbazone
(Httsc),
furan-2-carbaldehyde thiosemicarbazone (Hftsc), salicyl-
* Prof. Dr. T. S. Lobana
E-Mail: tarlokslobana@yahoo.co.in
[a] Department of Chemistry
Guru Nanak Dev University
Amritsar Ϫ 143 005, India
[b] Department of Chemistry
Howard University
Experimental Section
Materials and Methods
Washington DC 20059, USA
[c] Departmento de Quimica Inorganica
Facultad de Farmacia
Benzaldehyde, acetone, salicylaldehyde, thiosemicarbazide, Ph3P,
bis(diphenylphosphanyl)methane (dppm), bis(diphenylphosphanyl-
)propane (dppp) and PdCl2 were purchased from Aldrich Sigma
Ltd. The thiosemicarbazone ligands were prepared by the reported
Universidad de Santiago
15782-Santiago, Spain
Z. Anorg. Allg. Chem. 2009, 635, 1447Ϫ1453
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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T. S. Lobana, G. Bawa, G. Hundal, R. J. Butcher, A. Castineiras
ARTICLE
Scheme 2.
methods [11]. The ligand bis(diphenylphosphanyl)ethane (dppe)
0.089 mmol), followed by the addition of Et3N (0.726 g,
7.175 mmol). Afterwards, the mixture was stirred for 3 h. A clear
orange solution formed. The solution was allowed to evaporate and
after a few days, additionally formed Et3NHϩClϪ was separated
was prepared by
a reported method [12]. The complexes
PdCl2(PPh3)2 and PdCl2L (L ϭ dppm, dppe, dppp) were prepared
by the reaction of a PdCl2 solution in CH3CN with PPh3 or diter-
tiaryphosphane [13]. C, H and N analyses were carried out with a by filtration. After further evaporation, the filtrate gave a yellow
thermoelectron FLASHEA1112 analyzer. The melting points were solid, which was recrystallized from an acetonitrile-ethanol mix-
determined with a Gallenkamp electrically heated apparatus. IR ture. Yield: 0.037 g, 60 %, m.p. 180 °C. C34H32ClN3P2PdS: C, 56.8;
spectra were recorded as KBr pellets with a PyeϪUnicam SP3Ϫ300
spectrophotometer. H NMR spectra were recorded with a JEOL
AL300 FT spectrometer at 300 MHz in CDCl3 with TMS as in-
ternal reference. The 31P{1H} NMR spectra were recorded at
121.5 MHz with 85 % phosphoric acid as external reference.
H, 4.5; N, 5.8 %. Found: C, 57.1; H, 4.7; N, 6.1 %. IR (KBr):
ν(NϪH) 3426 b, 3348 sh, ν(CϭN), δ(NϪH) and ν(CϭC) 1608 s,
1
1528 b, ν(PϪCPh) 1095 s, ν(CϪS) 842 s cmϪ1 1H NMR (CDCl3):
.
δ ϭ 8.51 (d, C2H, 1 H), 8.14Ϫ8.18 (m, C4H, 8 H, 2 H) 7.30Ϫ7.82
(m, o, m & p-H ϩ C5Ϫ7H, 23 H), 4.88 (s, NH2, 2 H), 2.85 {m,
(CH2)2, 4H}.
[Pd(η2-N3,S-actsc)(PPh3)Cl] (1)
[Pd(η2-N3,S-btsc)(η2-P,P-dppp)]Cl·C2H5OH (4)
To trans-PdCl2(PPh3)2 (0.05 g, 0.07 mmol) suspended in toluene
(15 mL) was added solid Hactsc (0.009 g, 0.09 mmol), followed by
Compound 4 was prepared by the same method used for complex
the addition of Et3N (0.726 g, 7.175 mmol). The mixture was 3 with PdCl2(dppp) (0.05 g, 0.084 mmol) and solid Hbtsc (0.015 g,
stirred for 3 h. clear light orange solution formed and 0.084 mmol). Yield: 0.034 g, 52 %, m.p. 205 °C.
Et3NHϩClϪ precipitated at the bottom of the flask. The solution
C37H40ClN3OP2PdS: C, 57.0; H, 5.1; N, 5.4 %. Found: C, 56.8; H,
was filtered to remove Et3NHϩClϪ and allowed to evaporate at 4.4; N, 5.2 %. 1H NMR (CDCl3): δ ϭ 8.52 (d, C2H, 1 H), 7.71Ϫ7.78
A
room temperature. After evaporation, a red crystalline product was
(m, o, p & m-H ϩ C5Ϫ7H, 23 H), 4.98 (s, NH2, 2 H), 3.20 {m,
formed. Yield: 0.021 g, 56 %, m.p. 248 °C. C22H23ClN3PPdS: C, (CH2)3, 6H}. 31P{1H} NMR (CDCl3): δ ϭ 8.3, 4.1.
49.4; H, 4.3; N, 7.9 %. Found: C, 48.9; H, 4.3; N, 7.1 %. IR (KBr):
ν(NϪH) 3526 b, 3338 sh, 3334 w, ν(CϭN), δ(NϪH) and ν(CϭC)
[Pd2(η3-O,N3,S-stsc)2(µ-dppm)] (5)
1598 s, 1568 b, ν(PϪCPh) 1090 s, ν(CϪS) 842 s cmϪ1 1H NMR
.
(CDCl3): δ ϭ 7.71Ϫ7.84 (m, o-H, 6 H), 7.38Ϫ7.51 (m, m & p-H,
9 H), 4.45 (s, NH2, 2 H), 2.70 (s, CH3, 3 H), 2.12 (s, CH3, 3 H).
31P{1H} NMR (CDCl3): δ ϭ 28,3, ∆δ (δcomplexϪδPPh3) ϭ 33.0.
To PdCl2(dppm) (0.05, 0.09 mmol) suspended in toluene (15 mL)
was added H2stsc (0.017 g, 0.09 mmol). Afterwards, Et3N (1.452 g,
14.350 mmol) was added and the mixture was stirred for 4 h. Solid
Et3NHϩClϪ settled at the bottom of the flask was separated. Slow
evaporation of the yellow solution at room temperature yielded yel-
low crystals of the product. Yield: 0.067 g, 65 %, m.p. 277 °C.
C41H36N6O2P2Pd2S2: C, 50.1; H, 3.6; N, 8.5 %. Found: C, 49.9; H,
3.8; N, 8.5 %. IR (KBr): ν(NϪH) 3548 b, 3365 sh, 3280 w, ν(CϭN),
[Pd(η2-N3,S-btsc)(PPh3)Cl] (2)
Compound 2 was prepared similarly using trans-PdCl2(PPh3)2
(0.05 g, 0.07 mmol) and solid Hbtsc (0.013 g, 0.07 mmol). Yield:
0.023 g, 56 %, m.p. 265 °C. C26H23ClN3PPdS: C, 53.4; H, 4.0; N, δ(NϪH) and ν(CϭC) 1600 s, 1587 b, ν(PϪCPh) 1097 s, ν(CϪS)
1
7.2 %. Found: C, 53.5; H, 4.3; N, 7.1 %. IR (KBr): ν(NϪH) 3467 s, 795 s cmϪ1. H NMR (CDCl3): δ ϭ 8.06 (d, C2H, 2 H), 7.75 (m,
3461 sh, 3377 s, ν(CϭN), δ(NϪH) and ν(CϭC) 1596 s, 1508 b, o-H, 8 H), 7.16Ϫ7.37 (m, C5H ϩ m & p-H, 14 H), 6.59 (m, C6Ϫ8H,
1
ν(PϪCPh) 1095 s, ν(CϪS) 840 s cmϪ1. H NMR (CDCl3): δ ϭ 8.58 6 H), 4.78 (s, NH2, 4H), 4.39 (t, CH2, 2H). 31P{1H} NMR (CDCl3):
(d, C2H, 1 H), 8.14 (m, C4,8H, 2 H), 7.72Ϫ7.79 (m, o & p-PhH,
9 H) 7.38Ϫ7.75 (m, m-H ϩ C5Ϫ7H, 6 H), 4.38 (s, NH2, 2 H).
31P{1H} NMR (CDCl3): δ ϭ 18.0, ∆δ (δcomplexϪδPPh3) ϭ 22.7.
δ ϭ 21.2, ∆δ (δcomplexϪδdppm) ϭ 42.8.
[Pd2(η3-O,N3,S-stsc)2(µ-dppp)] (6)
Compound 6 was prepared by the same method used for com-
pound 5 with PdCl2(dppp) (0.05 g, 0.084 mmol) and solid H2stsc
(0.017 g, 0.084 mmol). Yield: 0.048 g, 56 %, m.p. 245 °C.
C43H40N6O2P2Pd2S2: C, 51.0; H, 4.00; N, 8.3 %. Found: C, 50.7;
[Pd(η2-N2,S-btsc)(η2-P,P-dppe)]Cl (3)
To PdCl2(dppe) (0.05 g, 0.087 mmol) suspended in a 15 mL tolu-
ene-acetonitrile mixture (3:1 v/v) was added solid Hbtsc (0.016 g,
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Substituent Effects in Palladium(II) Complexes
H, 4.3; N, 8.5 %. IR (KBr): ν(NϪH) 3548 b, 3365 sh, 3280 w, ν(Cϭ
N), δ(NϪH) and ν(CϭC) 1600 s, 1587 b; ν(PϪCPh) 1097 s, ν(CϪS)
1
810 s cmϪ1. H NMR (CDCl3): δ ϭ 8.20 (m, C2H, 2 H), 7.2Ϫ7.75
(m, o-H, 8 H), 7.16Ϫ7.37 (m, C5H ϩ m & p-H, 14 H), 6.59 (m,
C6Ϫ8H, 6 H), 4.70 (s, NH2, 4H), 1.96Ϫ2.25 {m, (CH2)3, 6H}.
Scheme 3.
X-ray Crystallography
Single crystal of compounds 1Ϫ6 were mounted on Bruker AXS
SMART APEX CCD (1, 2), Bruker Smart CCD-1000 (3), Siemens
P4 (4), Oxford Diffraction Gemini (5) and Bruker X8 Kappa Apex
II (6) diffractometers each equipped with a graphite monochroma-
˚
tor and Mo-Kα radiaton (λ ϭ 0.71073 A). The unit cell dimensions
and intensity data were measured at 298(2) (1), 100(2) (2, 6), 293(2)
(3), 295(2) (4) and 200(2) (5) K respectively. The data for complexes
1 and 2 were processed with SAINT and corrected for absorption
using SADABS or multiscan. The structure was solved by direct
methods and refined by full-matrix least-squares techniques using
the program SHELXS-97 (3, 5, 6) and SHELXTL 6.14 (1, 2) [14].
Positional and anisotropic atomic displacement parameters were
refined for all non-hydrogen atoms. The data for 4 was collected
using the θϪ2θ technique. Cell parameters were refined in the θ
range, 10Ϫ12.5° using XSCANS [15] The data were corrected for
Lorentz and polarization factors. An empirical psi absorption cor-
rection was applied. The structure was solved by the direct methods
and refined by full-matrix least-squares methods based on F2. All
hydrogen atoms were refined isotropically, fixed geometrically, and
were not refined. Scattering factors from the International Tables
for X-ray crystallography were used [16]. Data reduction, structure
solution, refinement and molecular graphics were performed using
SHELXTL-PC [17] and WinGX. [18]. Supplementary data is avail-
able from CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax:
ϩ44-12336033; E-Mail: deposit@ccdc.cam.ac.uk) on request quot-
ing the deposition number CCDC-691196, 691197, 691198, 666764,
691199, and 691200 for 1Ϫ6 respectively.
Scheme 4.
dinuclear
complexes
[Pd2(stsc)2(dppm)]
(5)
and
[Pd2(stsc)2(dppp)] (6) respectively with bridging dppm and
dppp ligands (Scheme 5). The deprotonation of N2H group
occurs in all the complexes and in 6, additionally OH group
also deprotonates. The thio-ligands are N3, S-chelating in
1, 2 and 4; N2,S-chelating in 3 and coordination is through
O, N3, S donor atoms in 5 and 6.
Crystal Structures
Complexes 1, 2, 3 and 6 crystallize in the monoclinic
space group whereas complexes 4 and 5 crystallize in the
triclinic space group. The crystallographic data for
complexes 1Ϫ6 are given in Table 1 and selected bond
parameters are presented in Table 2.
Results and Discussion
In [Pd(η2-N3,S-actsc)(PPh3)Cl] (1) (Figure 1), acetone
thiosemicarbazonate (btscϪ) binds through nitrogen (N2
Synthesis
Reaction of PdCl2(PPh3)2 with acetone thiosemicarba- for 1, N1 for 2) and sulfur donor atoms to the PdII atom.
zone (Hactsc) in 1:1 molar ratio yielded orange complex The other two sites are occupied by the chlorido and PPh3
[Pd(actsc)(PPh3)Cl] (1); similar reaction with benzaldehyde ligands. The PdϪS, PdϪN and PdϪP bond lengths
˚
thiosemicarbazone (Hbtsc) gave [Pd(btsc)(PPh3)Cl] (2) [2.2552(5), 2.118(2) and 2.2565(5) A] of complex 1 are com-
(Scheme 3). Reactions of PdCl2(dppe) and PdCl2(dppp) parable with those of similar complexes reported in litera-
with Hbtsc in 1:1 molar ratio yielded crystals of ionic com- ture [8]. The SϪPdϪCl and NϪPdϪP bond angles of com-
plexes [Pd(btsc)(dppe)]Cl (3) and [Pd(btsc)(dppp)]Cl (4) plex 1 [170.32(2), 172.81(5)°] are close to linearity. The
respectively (Scheme 4). The behavior of salicylaldehyde structure of [Pd(η2-N3, S-btsc)(PPh3)Cl] (2) (Figure 2) is
thiosemicarbazone (H2stsc) is different and on reaction similar to 1, its bond angles are somewhat closer to linearity
with PdCl2(dppm) and PdCl2(dppp), it has formed [NϪPdϪP, 175.34(10); SϪPdϪCl, 174.02(4)°]. Addition-
Scheme 5.
Z. Anorg. Allg. Chem. 2009, 1447Ϫ1453
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T. S. Lobana, G. Bawa, G. Hundal, R. J. Butcher, A. Castineiras
ARTICLE
Table 1. Crystallographic data for Complexes 1Ϫ6.
1
2
3
Empirical formula
M
C22H23ClN3PPdS
534.31
monoclinic
P21/n
9.4915(5)
25.0846(13)
9.6424(5)
C26H23ClN3PPdS
582.35
C34H32ClN3P2PdS
718.48
monoclinic
P21/n (No. 14)
15.103(6)
15.964(6)
16.437(6)
Crystal system
Space group
monoclinic
P21/n
10.3584(7)
14.4039(10)
17.0380(12)
101.8400(10)
2488.0(3)
˚
a /A
˚
b /A
˚
c /A
β /°
99.6990(10)
2262.9(2)
117.201(6)
3525(2)
3
˚
V /A
Z
4
4
4
Unique reflections/ Rint
GOF
5613, 0.0230
6108, 0.0249
6454, 0.0377
1.047a)
1.032b)
1.028c)
R indices (all data)
R1 ϭ 0.0309, wR2 ϭ 0.0737
R1 ϭ 0.0593, wR2 ϭ 0.1309
R1 ϭ 0.0662, wR2 ϭ 0.0937
4
5
6
Empirical formula
M
C37H40ClN3OP2PdS
778.57
C49H48N10O2P2Pd2S2
1147.83
C43H40N6O2P2Pd2S2
1011.67
monoclinic
P21/c (No. 14)
10.740(3)
45.015(10)
8.772(3)
Ϫ
Crystal system
Space group
triclinic
triclinic
¯
¯
P1
P1
˚
a /A
9.832(1)
9.872(1)
18.491(2)
79.40(1)
80.70(1)
78.03(1)
1711.5(3)
16.3294(4)
18.4736(5)
20.0836(5)
76.701(2)
67.081(2)
73.554(2)
˚
b /A
˚
c /A
Ͱ /°
β /°
γ /°
105.647(5)
Ϫ
4084(2)
3
˚
V /A
5302.5(2)
Z
2
4
4
Unique reflections/ Rint
GOF
6348, 0.0377
34450, 0.0429
8654, 0.0369
1.028d)
0.671e)
1.302f)
R indices (all data)
R1 ϭ 0.0625, wR2 ϭ 0.1308
R1 ϭ 0.1634, wR2 ϭ 0.0954
R1 ϭ 0.0493 and wR2 ϭ 0.1137
a) w ϭ 1[S2(Fo )ϩ(0.0382P)2ϩ0.9240P]; b) w ϭ 1/[S2 (Fo )ϩ(0.0495P)2ϩ12.6758P]; c) w ϭ 1/[S2 (Fo )ϩ(0.0438P)2]; d) w ϭ 1/[S2
2
2
2
2
2
2
2
2
(Fo )ϩ(0.0727P)2]; e) w ϭ 1/[S2 (Fo )ϩ(0.0411P)2]; f) w ϭ 1/[S2 (Fo )ϩ27.7956P] where P ϭ (Fo ϩ2Fc )/3 in each case.
removal of both halogens bonded to the palladium(II) ion
and the formation of complexes with the stoichiometry
[Pd(η3-X,N3,S-L)(PPh3)] (X, L ϭ C, aptsc2Ϫ; N4, ptsc2Ϫ
;
O, stsc2Ϫ) [9, 10].
Figure 1. ORTEP diagram of the complex [Pd(η2-N3,S-
actsc)(PPh3)Cl] (1) with atomic numbering scheme. Hydrogens have
been removed for clarity.
Figure 2. ORTEP diagram of the complex [Pd(η2-N3,S-
btsc)(PPh3)Cl] (2) with numbering scheme. Hydrogens have been
removed for clarity.
ally, the PdϪS, PdϪN and PdϪP bond lengths [2.236(2),
2.1024(4) and 2.254(1) A] are similar to those of complex
˚
1. Hactsc and Hbtsc are negative chelating bidentate li-
gands and thus one halogen ion retained in each complex.
In the mononuclear complexes [Pd(η2-N2,S-btsc)-
Recently, we reported that acetophenone thiosemicarba- (dppe)]Cl (3) (Figure 3), and [Pd(η2-N3,S-btsc)(dppp)]Cl (4)
zone (H2aptsc), pyrrole-2-carbaldehyde thiosemicarbazone (Figure 4), the diphosphane ligands dppe and dppp are co-
(H2ptsc) and salicylaldehyde thiosemicarbazone (H2stsc) ordinated in a chelating manner to PdII and form five and
behave as tridentate ligands, their coordination causes the six membered rings, respectively. Their PdϪP distances
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Substituent Effects in Palladium(II) Complexes
Table 2. Bond Parameters for Complexes 1Ϫ6.
1
Pd1ϪN2
Pd1ϪP1
N(2)ϪPd(1)ϪS(1)
N(2)ϪPd(1)ϪP(1)
S(1)ϪPd(1)ϪCl(2)
2.118(2)
2.2565(5) Pd1ϪS1
80.84(4)
172.81(5) N2ϪPd1ϪCl2
170.32(2) P1ϪPd1ϪCl2
Pd1ϪCl2
2.3576(6)
2.2552(5)
94.52(2)
99.26(4)
86.24(2)
S1ϪPd1ϪP1
2
Pd(1)ϪN(1)
Pd(1)ϪP(1)
N(1)ϪPd(1)ϪS(1)
N(1)ϪPd(1)ϪP(1)
S(1)ϪPd(1)ϪP(1)
2.102(4)
2.254(1)
84.5(1)
175.3(1)
92.83(4)
Pd(1)ϪCl(1)
Pd(1)ϪS(1)
N(1)ϪPd(1)ϪCl(1)
S(1)ϪPd(1)ϪCl(1)
P(1)ϪPd(1)ϪCl(1)
2.345(1)
2.236(2)
94.1(1)
174.02(4)
88.97(4)
3
Figure 3. ORTEP diagram of the complex [Pd(η2-N2,S-btsc)(η2-
P,P-dppe)]Cl (3) with partial atomic numbering scheme. Hydrogens
have been removed for clarity.
Pd1ϪN2
Pd1ϪP2
N2ϪPd1ϪP2
N2ϪPd1ϪP1
P2ϪPd1ϪP1
2.093(3)
2.254(2)
171.51(8) N2ϪPd1ϪS1
103.94(8) P2ϪPd1ϪS1
Pd1ϪS1
Pd1ϪP1
2.367(2)
2.263(2)
69.48(8)
102.15(4)
171.61(4)
84.52(4)
P1ϪPd1ϪS1
4
PdϪN1
PdϪS
N1ϪPdϪP1
N1ϪPdϪS1
P1ϪPdϪS1
2.127(4)
2.294(2)
170.4(2)
82.5(2)
PdϪP2
PdϪP1
N1ϪPdϪP2
P1ϪPdϪP2
S1ϪPdϪP2
2.308(2)
2.267(2)
99.3(2)
88.07(5)
175.89(5)
90.57(5)
5
Pd1AϪN11A
Pd1AϪO1A
Pd1AϪS1A
Pd1AϪP1A
Pd2AϪN21A
Pd2AϪO2A
Pd2AϪS2A
Pd2AϪP2A
2.013(2)
2.018(1)
2.2487(5) Pd1BϪS1B
2.2540(4) Pd1BϪP1B
Pd1BϪN11B
Pd1BϪO1B
2.028(2)
2.034(2)
2.2494(5)
2.2527(4)
2.029(2)
2.029(1)
2.2508(4)
2.2541(4)
2.017(1)
Pd2BϪN21B
2.0235(9) Pd2BϪO2B
2.2474(4) Pd2BϪS2B
2.2527(4) Pd2BϪP2B
N11AϪPd1AϪO1A 92.41(5)
N11AϪPd1AϪS1A 85.05(4)
O1AϪPd1AϪS1A
N11BϪPd1AϪO1B 93.47(5)
N11BϪPd1BϪS1B 84.01(4)
175.47(3) O1BϪPd1BϪS1B
175.00(3)
Figure 4. ORTEP diagram of the complex [Pd(η2-N3,S-btsc)(η2-
P,P-dppp)]Cl·C2H5OH (4) with partial atomic numbering scheme.
Hydrogens have been removed for clarity.
N11AϪPd1AϪP1A 174.47(3) N11BϪPd1BϪP1B 174.63(3)
O1AϪPd1AϪP1A
S1AϪPd1AϪP1A
88.42(3)
93.75(2)
O1BϪPd1BϪP1B
S1BϪPd1BϪP1B
88.18(3)
93.95(2)
N21AϪPd2AϪO2A 93.01(4)
N21BϪPd2BϪO2B 92.67(5)
N21BϪPd2BϪS2B 84.89(4)
175.20(4) O2BϪPd2BϪS2B 174.88(4)
N21AϪPd2AϪS2A 84.12(3)
O2AϪPd2AϪS2A
S2AϪPd2AϪP2A
nation in 4 happens through nitrogen (N1) and sulfur do-
93.83(2)
S2BϪPd2BϪP2B
93.95(2)
˚
nor atoms. The PdϪN distance in complex 3 [2.093(3) A] is
N21AϪPd2AϪP2A 174.87(4) N21BϪPd2BϪP2B 173.97(4)
˚
shorter than in complex 4 [2.127(4) A], whereas the PdϪS
O2AϪPd2AϪP2A
88.71(3)
O2BϪPd2BϪP2B
88.02(3)
˚
distance is longer [2.367(2) in 3, 2.294(2) A in 4]. The bite
6
angle is quite different in both complexes because of the
binding mode. The difference in bonding may be attributed
to the greater flexibility offered by dppp in comparison to
dppe, which allows the formation of a five membered che-
late ring by the thiosemicarbazone (N3,S) rather than a four
membered chelate ring (N2,S). The NϪPdϪP bond angle is
comparable in both complexes [171.61(4)° for 3; 170.4(2)°
for 4], whereas the other bond angle SϪPdϪP in complex
4 [175.89(5)°] is closer to linearity than in complex 3
[171.51(8)°]. The chloride ions are outside the coordination
sphere in both complexes to maintain charge neutrality and
Pd1ϪO11
Pd1ϪN12
Pd1ϪS1
Pd1ϪP1
O11ϪPd1ϪN12
O11ϪPd1ϪS1
N12ϪPd1ϪS1
O11ϪPd1ϪP1
N12ϪPd1ϪP1
S1ϪPd1ϪP1
2.025(3)
2.026(4)
2.243(2)
2.260(2)
93.5(2)
177.4(1)
84.3(1)
89.7(1)
171.3(2)
92.73(5)
Pd2ϪN22
Pd2ϪO21
Pd2ϪS2
Pd2ϪP2
N22ϪPd2ϪO21
N22ϪPd2ϪS2
O21ϪPd2ϪS2
N22ϪPd2ϪP2
O21ϪPd2ϪP2
S2ϪPd2ϪP2
2.020(4)
2.023(4)
2.242(2)
2.270(2)
92.5(2)
84.3(2)
174.5(1)
171.9(2)
87.40(1)
96.43(5)
˚
˚
[2.254(2) and 2.263(2) A for 3; 2.267(2) and 2.308(2) A for are stabilized by hydrogen bonding with amino protons
˚
4] are slightly different. The thiosemicarbazone ligand, in [H···Cl ϭ 3.089(3) and 3.465(3) A for 3]. The lattice is com-
its deprotonated form btscϪ, coordinates through nitrogen pleted by ethanol, its ϪOH group is hydrogen bonded to
(N2) and sulfur donor atoms in complex 3 whereas coordi- Cl and amino groups. Complex 3 represents the first
Z. Anorg. Allg. Chem. 2009, 1447Ϫ1453
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1451

T. S. Lobana, G. Bawa, G. Hundal, R. J. Butcher, A. Castineiras
ARTICLE
PdIIϪthiosemicarbazone in which N2,S-chelation takes trans bond angles OϪPdϪS [177.42(11), 174.45(11)°] are
place. N2,S chelation has been reported earlier for RuII, TlIII quite close to linearity, the other trans angles NϪPdϪP de-
and PbIV complexes [19, 20]. Interestingly, depending on the viate significantly from linearity [171.28(12), 171.87(12)°].
nature of the thiosemicarbazone, dppe has shown bridging
behavior in the dinucelar complex, [{Pd[1-(COMe)-3-
{C(H)ϭN3ϪNϭC(-S)-NHR}C8H4N-κ3C5N3S]}2(µ-Ph2P-
(CH2)2ϪPPh2)] (R ϭ H, Me) [21]. The thio-ligand is nega-
tive tridentate in this complex binding through ring carbon
(C5), nitrogen (N3) and sulfur donor atoms.
In the dimeric complexes [Pd2(η3-O,N3,S-stsc)2(µ-dppm)]
(5) (Figure 5) and [Pd2(η3-O,N3,S-stsc)2(µ-dppp)] (6) (Fig-
ure 6), each PdII atom is coordinated by stsc2Ϫ through oxy-
gen, nitrogen (N3) and sulfur donors. Two of these units are
bridged through dppm and dppp ligands, respectively. The
unit cell of complex 5 is made up by two independent mol-
ecules with slightly different bond parameters (Table 2).
This may be attributed to the different inter- and intramol-
ecular hydrogen bondings. The crystal lattice is completed
by acetonitrile, which is hydrogen bonded to pendant amino
hydrogen atoms. In [Pd2(stsc)2dppm] (5) (only one molecule
˚
will be discussed), the PdϪO [2.0180(11), 2.0235(9) A],
Figure 6. ORTEP diagram of complex [Pd2(η3-O,N3,S-stsc)2(µ-
dppp)] (6) with partial atomic numbering scheme. Hydrogens have
been removed for clarity.
˚
PdϪN [2.0134(13), 2.01739(11) A], PdϪS [2.2487(5),
˚
˚
2.2474(4) A] and PdϪP [2.2527(4), 2.2540(4) A] bond
lengths of the two PdII atoms differ only slightly from one
another as the bonding is similar. These parameters are
comparable to those of the monomeric complex [Pd(η3-
O,N3,S-stsc)(PPh3)] [10] reported earlier. The OϪPdϪN
bite angle is ഠ 92.5° and the NϪPdϪS bite angle is ഠ
85.0°. The trans OϪPdϪS bond angles [175.47(3),
175.20(4)°] and NϪPdϪP [174.47(3), 174.87(4)°] are quite
close to linearity.
Solution Phase Studies
NMR Spectroscopy
The signals of the ϪNH protons of the free ligands were
absent in all above complexes 1Ϫ6, thus supporting depro-
tonation during complexation. Additional deprotonation of
the ϪOH groups in complexes 5 and 6 was supported by
1
the absence of the corresponding proton signals in their H
NMR spectra. The ϪNH2 protons appear as single signal
in all complexes because of the free rotation of the ϪNH2
group along the C1ϪN1 bond axis. In contrast, of two
broad signals are observed in the free ligands, because of
the restricted rotation of the ϪNH2 group along the C1ϪN1
bond axis at room temperature [11].
The 31P{1H} NMR spectra of complexes 1 and 2 with
the ligand PPh3 show a single signal with a coordination
shift of ഠ 32 ppm. In dppm complex 5, a single signal is
observed, demonstrating the equivalence of the phosphor-
ous atoms of the bridging ligand. The 31P{1H} NMR spec-
trum of mononuclear complex 4 shows two signals owing
to two different chemical environments of the chelating
dppp ligand.
Figure 5. ORTEP diagram of one of the two crystallographically
independent units of the complex [Pd2(η3-O,N3,S-stsc)2(µ-dppm)]
(5) with partial atomic numbering scheme. Hydrogens and solvent
molecules have been removed for clarity.
Conclusions
The co-ligand change from monodentate phosphanes to
The increase in spacer length of the connecting PPh2 bisphosphanes altered the stoichiometry of the complexes,
groups of dppp in 6 vs. dppm in 5 does not affect the PdϪO however, the bonding modes of the thiosemicarbazones re-
[2.025(3), 2.023(4) A] and PdϪS [2.243(2), 2.242(2) A] bond mained the same (N3,S chelation in complexes 1, 2 and 4)
˚
˚
˚
lengths, however, the PdϪN [2.026(4), 2.020(4) A] bond except for complex 3, which showed an N2,S chelation for
lengths, which are trans to PdϪP are longer. Whereas the the first time. The diphosphanes, however, behaved differ-
1452
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 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 1447Ϫ1453

Substituent Effects in Palladium(II) Complexes
ently with a change of the R1 group at C2. For R1 ϭ phenyl,
the coordination mode of the diphosphanes is chelating (3,
4), and for R1 ϭ 2-hydroxyphenyl, the bonding mode is
bridging (5, 6). Thus, the bonding mode of the diphosphane
co-ligand is influenced by the substituents at the C2 carbon
of the thiosemicarbazone molecule in the mixed ligand
complexes.
Lopez-Torres, A. Fernandez, J. J. Fernandez, J. M. Vila, Eur.
J. Inorg. Chem. 2002, 613; c) J. Martinez, L. A. Adiro, J. M.
Antelo, M. Teresa-Pereira, J. J. Fernandez, J. M. Vila, Poly-
hedron 2006, 25, 2848.
[7] a) T. S. Lobana, Rekha, R. J. Butcher, A. Castineiras, E.
Bermejo, P. V. Bharatam, Inorg. Chem. 2006, 45, 1535; b) T. S.
Lobana, P. Kumari, R. J. Butcher, Inorg. Chem. Commun. 2008,
11, 11; c) T. S. Lobana, S. Khanna, Rekha, G. Hundal, R.
Sultana, Manisha, R. J. Butcher, A. Castineiras, Cryst. Growth
Des. 2008, 8, 1203; d) T. S. Lobana, S. Khanna, R. J. Butcher,
A. D. Hunter, M. Zeller, Inorg. Chem. 2007, 46, 5826.
[8] T. S. Lobana, G. Bawa, G. Hundal, A. P. S. Pannu, R. J.
Butcher, B.-J. Liau, C. W. Liu, Polyhedron 2007, 26, 4993.
[9] T. S. Lobana, G. Bawa, G. Hundal, M. Zeller, Z. Anorg. Allg.
Chem. 2008, 634, 931.
[10] T. S. Lobana, G. Bawa, A. Castineiras, R. J. Butcher, Inorg.
Chem. Commun. 2007, 10, 506.
[11] T. S. Lobana, A. Sanchez, J. S. Casas, A. Castineiras, J. Sordo,
M. S. Garcia-Tasenda, E. M. Vazquez-Lopez, J. Chem. Soc.,
Dalton Trans. 1997, 4289.
Acknowledgement
Financial assistance to one of us (Gagandeep) from CSIR New
Delhi (F.No. 9/254(155)-EMR-1) is gratefully acknowledged. The
authors thank Dr. M. Zeller, Department of Chemistry, Youngs-
town University, Youngstown, Ohio, for his help with the X-ray
diffraction studies.
[12] a) A. M. Aguion, J. Org. Chem. 1964, 29, 1660; b) T. S.
Lobana, R. Singh, Polyhedron 1995, 14, 907.
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Received: September 19, 2008
Published Online: March 23, 2009
Z. Anorg. Allg. Chem. 2009, 1447Ϫ1453
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1453