Monodentate S-vs. bidentate 1,5-O,S-coordination of N-phosphoryl-N′-(R)-thioureas with Pd(II)

Article abstract of DOI:10.1016/j.poly.2008.03.012

Reaction of N-phosphorylated thioureas of common formula RNHC(S)NHP(O)(OiPr)₂ (R = tBu, HL^I; R = Ph, HL^II; R = 4′-benzo-15-crown-5, HL^III) with Pd(PhCN)₂Cl₂ in acetonitrile leads to complexes of the structure Pd(HL^I-S)₂Cl₂ (1), Pd(HL^II-S)₂Cl₂ (2) and Pd(HL^III-S)₂Cl₂ (3). Reaction of N-phosphorylated thioureas of common formula RC(S)NHP(O)(OiPr)₂ (R = Et₂N, HL^IV; R = morpholine-N-yl, HL^V) in the same conditions leads to complexes Pd(L^IV-O,S)₂ (4) and Pd(L^V-O,S)₂ (5), where the palladium(II) atoms are coordinated in a square-planar fashion by the C{double bond, long}S sulfur atoms and the P{double bond, long}O oxygen atoms of two anionic ligands. The crystal structure of complex 1 has been investigated by X-ray crystallography. It was established that the thiourea ligands are in a trans-configuration and the palladium(II) cation is coordinated by the sulfur atoms of the C{double bond, long}S groups and the chlorine atoms. Complex 1 is the first example of palladium(II) complex in which the potentially chelating N-phosphorylated thiourea ligand is bound through the sulfur atom only.

Full text of DOI:10.1016/j.poly.2008.03.012

Polyhedron 27 (2008) 1995–1998
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Monodentate S-vs. bidentate 1,5-O,S-coordination of
N-phosphoryl-N0-(R)-thioureas with Pd(II)
a
b
a
a
Damir A. Safin a, , Felix D. Sokolov , Łukasz Szyrwiel , Sergey V. Baranov , Maria G. Babashkina ,
*
Timur R. Gimadiev a, Henryk Kozlowski b
a A.M. Butlerov Chemistry Institute, Kazan State University, Kremlevskaya Street 18, 420008 Kazan, Russian Federation
b Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie Str. 14, 50383 Wroclaw, Poland
a r t i c l e i n f o
a b s t r a c t
Reaction of N-phosphorylated thioureas of common formula RNHC(S)NHP(O)(OiPr)2 (R = tBu, HLI; R = Ph,
HLII; R = 40-benzo-15-crown-5, HLIII) with Pd(PhCN)2Cl2 in acetonitrile leads to complexes of the struc-
ture Pd(HLI-S)2Cl2 (1), Pd(HLII-S)2Cl2 (2) and Pd(HLIII-S)2Cl2 (3). Reaction of N-phosphorylated thioureas
of common formula RC(S)NHP(O)(OiPr)2 (R = Et2N, HLIV; R = morpholine-N-yl, HLV) in the same condi-
tions leads to complexes Pd(LIV-O,S)2 (4) and Pd(LV-O,S)2 (5), where the palladium(II) atoms are coordi-
nated in a square-planar fashion by the C@S sulfur atoms and the P@O oxygen atoms of two anionic
ligands. The crystal structure of complex 1 has been investigated by X-ray crystallography. It was estab-
lished that the thiourea ligands are in a trans-configuration and the palladium(II) cation is coordinated by
the sulfur atoms of the C@S groups and the chlorine atoms. Complex 1 is the first example of palla-
dium(II) complex in which the potentially chelating N-phosphorylated thiourea ligand is bound through
the sulfur atom only.
Article history:
Received 26 February 2008
Accepted 14 March 2008
Available online 2 May 2008
Keywords:
Complex
Crown-ether
Monodentate coordination
Palladium(II)
Thiourea
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
rylthioureas, containing secondary (Scheme 1) and tertiary
(Scheme 2) nitrogen at the N-thioacylamidophosphate moiety
The coordination chemistry of polyfunctional ligands, capable
to realize different coordination modes with metal cations [1] is
of interest for synthesis of new selective complexing agents and
analytical reagents. Koch and others have shown that the coordina-
tion of N,N-dialkyl-N0-aroylthioureas leads to bidentate-O,S-coordi-
nation to Pd(II) [2,3]. It was also shown that the coordination mode
of N-alkyl-N0-aroylthioureas depends on an intramolecular hydro-
gen bond between the donor oxygen atom of the carbonyl group
and the hydrogen atom of the NH group [2].
C(S)NHP(O)(OiPr)2. The crystal structure of trans-Pd(HLI-S)2Cl2,
the first example of N-phosphorylthiourea coordinated to Pd(II)
only through the S atom in the monodentate fashion, is also
reported.
2. Experimental
2.1. Synthesis of HLI–HLV
We have become interested in the coordination chemistry of N-
phosphorylated thioureas RR0NC(S)NHP(O)(OiPr)2 (R = R0 = alkyl;
R = H, R0 = alkyl, aryl) towards various transition metal cations [4]
in view of their application in metals separation [5]. Recently, we
reported, that in the square-planar complexes of N-phospho-
rylthioureas M[RNHC(S)NP(O)(OiPr)2]2, where (M = Ni(II), R = Ph
[6], p-MeOC6H4, p-BrC6H4, tBu, iPr, c-Hex [7]; M = Pd(II), R = Ph
[6], iPr [7]; M = Cu(II), R = Ph, c-Hex [6]), 1,3-N,S-coordination of
the anionic ligand is realized.
N-Diisopropoxyphosphorylthioureas were prepared according
to the previously described methods [9].
2.2. Synthesis of 1–5
A portion of Pd(PhCN)2Cl2 (0.192 g, 0.5 mmol) dissolved in
30 mL of acetonitrile was added dropwise to 30 mL of a well stirred
solution containing HLI–V (0.296, 0.316, 0.506, 0.295 or 0.310 g;
1 mmol) in the same solvent. The mixture was stirred at room tem-
perature for a further 10 h. The solvent was then removed in vacuo.
A precipitate was isolated from dichloromethane by n-hexane.
Recently, we reported some synthetic results presented here as
a preliminary communication [8]. Herein, we report the compara-
tive study on the complexes of the Pd(II) ions with N-phospho-
2.2.1. Pd(HLI–S)2Cl2 (1)
Yield: 0.331 g (86%). M.p. 128–129 °C. 1H NMR (CDCl3): d 1.38–
1.43 (m, 12H, CH3), 1.49–1.53 (m, 9H, CH3, tBu), 4.58–4.73 (m, 2H,
* Corresponding author. Fax: +7843 254 37 34.
E-mail address: damir.safin@ksu.ru (D.A. Safin).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.03.012

1996
D.A. Safin et al. / Polyhedron 27 (2008) 1995–1998
9.4. IR: m 1003 (POC), 1142 (P@O), 1529 (SCN) cmꢀ1. Anal. Calc. for
22H48N4O6P2PdS2 (696.15): C, 37.90; H, 6.94; N, 8.04. Found: C,
37.84; H, 6.99; N, 8.11%.
O
S
H
N
P(OiPr)2
C
N
H
R
2.2.5. Pd(LV–O,S)2 (5)
HLI-III
Yield: 0.199 g (55%). M.p. 157–158 °C. 1H NMR (CDCl3): d 1.33
3
3
(d, JH,H = 6.1 Hz, 12H, CH3), 1.34 (d, JH,H = 6.1 Hz, 12H, CH3),
Pd(PhCN)2Cl2
3
3
3.62–3.97 (m, 16H, CH2), 4.68 (d sept, JP,H = 7.6 Hz, JH,H = 6.1 Hz,
4H, OCH). 31P{1H} NMR (CDCl3): d 9.9. IR: m 1005 (POC), 1144
O
O
(COC), 1154 (P@O), 1547 (SCN) cmꢀ1
.
Anal. Calc. for
H
N
P(OiPr)2
H
N
P(OiPr)2
C22H44N4O8P2PdS2 (724.11): C, 36.44; H, 6.12; N, 7.73. Found: C,
N
H
N
H
36.49; H, 6.07; N, 7.68%.
R
R
R
S
S
S
Cl
Cl
Pd
2.3. Physical measurements
Pd
S
Cl
Cl
Infrared spectra (Nujol) were recorded with a Specord M-80
spectrometer in the range 400–3600 cmꢀ1. NMR spectra were ob-
tained on a Varian Unity-300 NMR spectrometer at 25 °C. 1H and
31P{1H} spectra were recorded at 299.948 and 75.429 MHz, respec-
tively. Chemical shifts are reported with reference to SiMe4 (1H)
and H3PO4 (31P{1H}). Elemental analyses were performed on a Per-
kin–Elmer 2400 CHN microanalyser.
H
R
N
H
N
N
N
H
(iPrO)2P
H
P(OiPr)2
O
O
trans-isomer
cis-isomer
1-3
Scheme 1. Preparation of complexes 1–3 (R = tBu, HLI (1); Ph, HLII (2); 40-benzo-15-
crown-5, HLIII (3)).
2.4. Crystal structure determination and refinement
The X-ray data for 1 were collected at ꢀ173 °C using a KM4CCD
diffractometer and graphite-monochromated Mo Ka radiation gen-
erated from Diffraction X-ray tube operated at 50 kV and 35 mA.
The images were indexed, integrated and scaled using the KUMA
data reduction package [10]. The structure was solved by direct
method using SHELXS97 and refined by the full-matrix least-squares
method on all F2 data [11]. Non-hydrogen atoms were included in
the refinement, with anisotropic displacement parameters. The
hydrogen atoms were positioned geometrically and refined iso-
tropically. The hydrogen atoms of NH groups were included from
Dq maps and fixed at a distance 0.92 and refined isotropically. Cal-
culations were preformed using WINGX program [12].
R
N
Pd
N
P(OiPr)2
S
O
Pd(PhCN)2Cl2
S
S
O
P(OiPr)2
R
N
H
O
P(OiPr)2
R
HLIV,V
cis-isomer
4, 5
Scheme 2. Preparation of complexes 4 and 5 (R = Et2N, HLIV (4); morpholine-N-yl,
HLV (5)).
OCH), 9.61, 10.02 (2d, 2JPNH = 5.5 Hz, 1H, P(O)NH), 10.37, 10.49 (2s,
1 H, ArNH). 31P{1H} NMR (CDCl3): d ꢀ6.5, ꢀ6.8. IR: m 1002 (POC),
1246 (P@O), 1534 (S@C–N), 3082, 3203 (NH) cmꢀ1. Anal. Calc.
C22H50Cl2N4O6P2PdS2 (770.06): C, 34.31; H, 6.54; N, 7.28. Found:
C, 34.49; H, 6.62; N, 7.37%.
trans-[Pd(HLI2–S)2Cl2] (1). C22H50Cl2N4O6P2PdS2, Mr = 770.02 g
molꢀ1
,
yellow prisms, monoclinic, space group P21/c, a =
10.517(4), b = 17.316(5), c = 9.774(4) Å, b = 99.22(4)°, V =
1757.0(11) Å3, Z = 2, Dc = 1.456 g cmꢀ3, l(Mo Ka) = 0.929 mmꢀ1
,
reflections: 12196 collected, 4171 unique, Rint = 0.032, R1(all) =
0.0285, wR2(all) = 0.0605.
2.2.2. Pd(HLII–S)2Cl2 (2)
Yield: 0.299 g (74%). M.p. 147–148 °C. 1H NMR (CDCl3): d 1.41–
1.48 (m, 12H, CH3), 4.71–4.90 (m, 2H, OCH), 7.23–7.68 (m, 5H,
3. Results and discussion
2
C6H5), 9.80, 10.13 (2d, JPNH = 5.6 Hz, 1H, P(O)NH), 10.67, 10.79
(2s, 1H, PhNH). 31P{1H} NMR (CDCl3): d ꢀ5.6, ꢀ5.9. IR: m 998
(POC), 1258 (P@O), 1521 (S@C–N), 3091, 3217 (NH) cmꢀ1. Anal.
Calc. for C26H42Cl2N4O6P2PdS2 (810.04): C, 38.55; H, 5.23; N, 6.92.
Found: C, 38.32; H, 5.32; N, 6.78%.
3.1. Synthesis
N-Phosphorylated thioureas were prepared as previously de-
scribed [9] and purified by recrystallization from dichlorometh-
ane–n-hexane mixtures.
Complexes 1–5 were prepared by the following procedure:
Pd(PhCN)2Cl2 was dissolved in acetonitrile and added to a solution
containing the corresponding ligand in the same solvent (Scheme
1). The compounds obtained are crystalline solids that are soluble
in most polar solvents.
The molecular structures of complexes 1–5 were investigated
by IR, 1H, 31P{1H} NMR spectroscopy and elemental analysis. The
crystal structure of 1 was established by single crystal X-ray dif-
fraction analysis.
2.2.3. Pd(HLIII–S)2Cl2 (3)
Yield: 0.483 g (81%). M.p. 139–141 °C. 1H NMR (CDCl3): d 1.43–
1.47 (m, 12H, CH3), 3.65–4.21 (m, 16H, CH2), 4.69–4.89 (m, 2H,
2
OCH), 6.75–6.97 (m, 3H, C6H3), 9.88, 10.16 (2d, JPNH = 5.8 Hz, 1H,
P(O)NH), 10.72, 10.83 (2s, 1H, ArNH). 31P{1H} NMR (CDCl3): d
ꢀ6.0, ꢀ6.4. IR: m 1008 (POC), 1140 (COC), 1241 (P@O), 1515,
1549 (S@C–N), 3094, 3211 (NH) cmꢀ1
.
Anal. Calc. for
C42H72Cl2N4O16P2PdS2 (1192.44): C, 42.30; H, 6.09; N, 4.70. Found:
C, 42.72; H, 5.99; N, 4.59%.
2.2.4. Pd(LIV–O,S)2 (4)
3.2. IR and NMR spectroscopy
Yield: 0.177 g (51%). M.p. 118–119 °C. 1H NMR (CDCl3): d 1.03–
1.26 (m, 12H, CH3, Et2N), 1.29–1.39 (m, 24H, CH3, iPrO), 3.35–3.79
(m, 8H, CH2, Et2N), 4.57–4.74 (m, 4H, OCH). 31P{1H} NMR (CDCl3): d
The IR spectra of complexes 1–3 in Nujol are similar. The
absorption bands of the P@O group of the neutral forms HLI–III

D.A. Safin et al. / Polyhedron 27 (2008) 1995–1998
1997
are shifted by approximately 10–15 cmꢀ1 to high frequencies rela-
tive to the band of the parent ligands. This confirms their nonpar-
ticipation in chelate complex formation. There are two signals for
the NH proton in the IR spectra of complexes in the areas 3082–
3094 and 3203–3217 cmꢀ1 which are the characteristic range for
amide protons participating in hydrogen bonds [4,7]. In the spectra
of 1–3 there is an intense absorption band at 1515–1549 cmꢀ1 cor-
responding to the S@C–N fragment. Besides very strong absorption
bands for the POC group at 1008 cmꢀ1, there is a band of the COC
group at 1140 cmꢀ1 in the IR spectrum of 3, containing crown-
ether fragments. Presence of a wide absorption band of the POC
fragment in the spectra of 1 and 2 in the area 998–1002 cmꢀ1 also
unequivocally confirms the substituted phosphoric fragment.
Application of the same procedure using the thioureas HLIV and
HLV did not result in isolation of products with neutral forms of the
corresponding ligand (Scheme 2). Complexes 4 and 5 obtained con-
tain the central cation coordinated in a square-planar fashion by
the C@S sulfur atoms and the P@O oxygen atoms of two anionic li-
gands. According to the IR, 1H, 31P{1H} NMR spectroscopy, elemen-
tal analyses and melting point data complexes 4 and 5 are found to
be the same as it was synthesized using the potassium salts of the
thioureas HLIV and HLV in the aqueous ethanol medium [7].
The 31P{1H} NMR spectra of complexes 1–3 contain two singlet
signals at ꢀ6.8 to ꢀ5.6 ppm, and a down-field shift, relative to that
of the free ligands HLI–III, is observed. This confirms the preserva-
tion of neutral forms of ligands [4]. Two different signals corre-
spond to the phosphorus atoms with cis- and trans-configuration
of ligands in the structure of complexes in the solution.
Fig. 1. Molecular structure of complex 1.
Table 1
Selected bond lengths (Å), and bond angles (°) in complex 1
Bond lengths
Pd–Cl
Pd–S
S–C(1)
P–O(2)
2.3152(11)
2.3305(11)
1.708(2)
P–N(1)
N(1)–C(1)
N(2)–C(1)
1.674(2)
1.370(3)
1.328(3)
1.469(2)
Bond angles
Cl–Pd–S
Cl–Pd–Cl(A)
Cl–Pd–S(A)
S–Pd–S(A)
Pd–S–C(1)
85.31(4)
180.00
94.69(4)
180.00
O(2)–P–N(1)
P–N(1)–C(1)
S–C(1)–N(1)
S–C(1)–N(2)
N(1)–C(1)–N(2)
112.07(9)
126.75(14)
120.82(15)
121.71(15)
117.5(2)
113.86(8)
Torsion angles
C(1)–S–Pd–Cl
C(1)–S–Pd–Cl(A)
N(1)–C(1)–S–Pd
N(2)–C(1)–S–Pd
The 1H NMR spectra of 1–3 contain a double set of signals. This
also confirms the presence of cis- and trans-complexes in the solu-
tion. The signals for the methyl protons are observed at 1.38–
1.53 ppm. The signals at 4.58–4.90 ppm correspond to the OCH
protons. The aromatic proton signals in complex 2 are at 7.23–
7.68 ppm and shifted down-field relative to that in complex 3. In
the 1H NMR spectrum of 3 signals for the CH2 protons, correspond-
ing to the crown-ether fragment, are in the area 3.65–4.21 ppm.
There is a double set of signals for the NH protons in the 1H
NMR spectra of complexes 1–3 in the areas 9.61–10.16 and
10.37–10.83 ppm. The high-field shifted signals for the P(O)NH
group are shown as a doublet with a characteristic constant
2JPNH = 5.5–5.8 Hz. The low-field signals correspond to the RNH
protons. Both set of signals are low-field shifted relative to that
in parent ligands [9] because of the intramolecular hydrogen bonds
formation of the RNHꢁ ꢁ ꢁO@P and PNHꢁ ꢁ ꢁCl–Pd types.
128.09(9)
ꢀ51.91(9)
19.4(2)
S–C(1)–N(1)–P
N(2)–C(1)–N(1)–P
C(1)–N(1)–P–O(2)
ꢀ170.94(11)
10.5(3)
ꢀ38.1(2)
ꢀ162.02(14)
Table 2
Parameters of hydrogen bonds for complex 1 [bond lengths (Å), and bond angles (°)]
N–Hꢁ ꢁ ꢁA
d(N–H)
d(Hꢁ ꢁ ꢁA)
D(Nꢁ ꢁ ꢁA)
\(NHA)
N(1)–H(1)ꢁ ꢁ ꢁCl
0.87(2)
0.90(2)
2.26(2)
2.04(2)
3.113(2)
2.832(3)
167(2)
146(2)
N(2)–H(2)ꢁ ꢁ ꢁO(2)
Inspection of the structure shows the expected square-planar
coordination with two ligands HLI bonded through the sulfur
atoms with Pd–S 2.316(1) Å. The bond lengths Pd–Cl are
2.442(1) Å, while the bond angles S(A)–Pd–Cl 95.54(3)° and S–
Pd–Cl 85.46(3)° deviate significantly from 90°. The distortion being
induced by the two hydrogen bonds between N1(H1)ꢁ ꢁ ꢁCl(A) and
N1A(H1A)ꢁ ꢁ ꢁCl at 3.924 Å. Similar N(H)ꢁ ꢁ ꢁCl and N(H)ꢁ ꢁ ꢁBr hydro-
gen bonds, and the resultant distortion of bond angles from 90°,
have previously been observed for the cis-bis(N-benzoyl-N0-propyl-
thioureato)dichloroplatinum(II) (6) and trans-bis(N-benzoyl-N0-
propylthioureato)dibromopalladium(II) (7) complexes [3]. An
additional hydrogen bond between the N2(H2) and the phosphoryl
oxygen atom O2 of the coordinated ligand at 2.601(4) Å effectively
locks the ring C1–N1–P–O2–H2–N2 into a planar structure. The
structure, bond lengths and angles of the coordinated HLI in
trans-[Pd(HLI-S)2Cl2] complex 1 are similar to that of the unbound
RNHC(S)NHP(O)(OiPr)2 (R = alkyl, aryl) [4], as well as that of the
coordinated ligand corresponding cis-platinum 6 and trans-palla-
dium 7 complexes [3]. This mode of coordination of N-phosphory-
lated thiourea once again highlights the importance and relative
stability of the intramolecular hydrogen bond between the thio-
urea NH group and the phosphoryl oxygen atom of this ligands
in determining the preferred mode of S atom coordination.
The unrecrystallized, pure complexes 1–5 are presumed to be
single isomers, in view of the sharp melting points, respectively.
However, from the 31P{1H} NMR spectra of fresh CDCl3 solutions
of unrecrystallized complexes 1–3, it appears that trans-isomers
predominate. The 31P{1H} NMR spectra of 1–3 remain invariant
for 72 h, suggesting that the isomer distribution rapidly reaches
equilibrium on dissolution of the compound. By contrast to com-
plexes 1–3, the 31P{1H} NMR spectra of 4 and 5 contain the unique
singlet signals in the region characteristic to the deprotonated N-
phosphorylated thioureas and thioamides [4]. The signals observed
correspond to the cis-isomer [7]. Moreover, the 31P{1H} NMR spec-
tra of 4 and 5 remain invariant for 72 h, suggesting that the trans-
isomer is not observed in the solution of CDCl3.
3.3. Crystal structure of 1
Crystals of 1 were obtained by slow evaporation of the solvent
from dichloromethane–n-hexane solution of the complex.
The crystal structure of the trans-[Pd(HLI-S)2Cl2] complex 1 is
shown in Fig. 1, while the geometrical data such as bond distances,
angles, torsion angles and hydrogen bonds are given in Tables 1
and 2.

1998
D.A. Safin et al. / Polyhedron 27 (2008) 1995–1998
4. Conclusions
References
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C(S)NHP(O)(OiPr)2 (Scheme 1), the pure trans-Pd(HLI–III–S)2Cl2
complexes were obtained by reaction with palladium(II). These
complexes undergoes partial isomerization in solution to yield
cis/trans distribution. In contrast the palladium(II) complexes with
thioureas HLIV,V, containing tertiary nitrogen at the N-thioacylam-
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the ligands both in solution and solid state.
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P@Oꢁ ꢁ ꢁHNR is a necessary condition for the monodentate S-isomer
stabilization in a square-planar complexes of Pd(II). When H-bond-
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them and a change of the coordination mode in the Pd(II) com-
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5. Supplementary data
[10] Oxford Diffraction Poland Sp., CCD data collection and reduction GUI, Version
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CCDC 669887 contains the supplementary crystallographic data
for this paper. 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) 1223-336-033; or e-mail:deposit@ccdc.cam.ac.uk.
Acknowledgements
This work was supported by the joint program of CRDF and the
Russian Ministry of Education and Science (BRHE 2008 Y5-C-07-
09); Russian Science Support Foundation.