Heteroleptic palladium(II) and platinum(II) complexes of 1,1-bis(diphenylphosphino)ferrocene (dppf) and heterocyclic thionates: Crystal structures of [Pt(Phozt)2(κ2-dppf)] (PhoztH = 5-phenyl-1,3,4-oxadiazole-2-thione) and [Pd(bzoxt)2(κ 2-dppf)] (bzoxtH = benz-1,3-oxazoline-2-thione)

Article abstract of DOI:10.1016/j.poly.2012.04.007

Treatment of [MCl₂(κ²-dppf)] (M = Pd or Pt) with two equivalents of potassium heterocyclic thionate salts (KL) affords mixed ligand complexes [ML₂(κ²-dppf)] [L = 5-phenyl-1,3,4-oxadiazole-2-thionate (Phozt), 4,5-diphenyl-1,2,4-triazole-3- thionate (Ph₂tzt), benz-1,3-thiazoline-2-thionate (bztzt) and benz-1,3-oxazoline-2-thionate (bzoxt)]. X-ray structures of two examples, [Pt(Phozt)₂(κ²-dppf)] and [Pd(bzoxt) ₂(κ²-dppf)], show that the ligands are coordinated in a monodentate fashion via the sulfur atom.

Full text of DOI:10.1016/j.poly.2012.04.007

Polyhedron 41 (2012) 20–24
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Heteroleptic palladium(II) and platinum(II) complexes of
1,1-bis(diphenylphosphino)ferrocene (dppf) and heterocyclic thionates: Crystal
structures of [Pt(Phozt)2(
j
2-dppf)] (PhoztH = 5-phenyl-1,3,4-oxadiazole-2-thione)
and [Pd(bzoxt)2(
j
2-dppf)] (bzoxtH = benz-1,3-oxazoline-2-thione)
a
a
b
c
Subhi A. Al-Jibori a, , Thaaer F. Khaleel , Shihab A.O. Ahmed , Lamaan J. Al-Hayaly , Kurt Merzweiler ,
⇑
Christoph Wagner c, Graeme Hogarth d,
⇑
a Department of Chemistry, College of Science, University of Tikrit, Tikrit, Iraq
b Department of Chemistry, College of Pharmacy, Hawler University of Medicine, Erbil, Iraq
c Institut fur Anorganische Chemie, Martin-Luther-Universität, Halle-Wittenberg, Kurt-Mothes-Str. 2, D-06120 Halle, Germany
d Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of [MCl2(
j
2-dppf)] (M = Pd or Pt) with two equivalents of potassium heterocyclic thionate
2-dppf)] [L = 5-phenyl-1,3,4-oxadiazole-2-thionate
Received 31 December 2011
Accepted 11 April 2012
Available online 3 May 2012
salts (KL) affords mixed ligand complexes [ML2(
(Phozt), 4,5-diphenyl-1,2,4-triazole-3-thionate (Ph2tzt), benz-1,3-thiazoline-2-thionate (bztzt) and
benz-1,3-oxazoline-2-thionate (bzoxt)]. X-ray structures of two examples, [Pt(Phozt)2(
2-dppf)] and
2-dppf)], show that the ligands are coordinated in a monodentate fashion via the sulfur
j
j
[Pd(bzoxt)2(
atom.
j
Keywords:
Palladium
Platinum
Ó 2012 Elsevier Ltd. All rights reserved.
1,1-Bis(diphenylphosphino)ferrocene
Complexes
X-ray studies
1. Introduction
related examples of platinum(II) with simple organic thiolates
and dppf have been recently reported [21,22].
The coordination chemistry of heterocyclic thiones and thio-
nates is rich and varied with some examples having important
chemical and biological properties [1–6]. Thionates can exist in
two tautomeric forms which enables them to behave in an ambid-
entate fashion binding through either the sulfur (thiolate) or
nitrogen (thione) atom, while in some cases they can act as chelate
or bridging ligands upon binding of both of these atoms. These tau-
tomers are shown (Chart 1) for the specific ligands used in this
study which is part of our systematic investigation of the coordina-
tion chemistry of thioamide ligands [7–13]. Thus, we have
2. Experimental
2.1. General
1H and 13C NMR spectra were recorded on Varian Unity 500 and
Gemini 2000 spectrometers, respectively, with CDCl3 as solvent
and internal reference. 31P NMR spectra were recorded on a Gemini
2000 spectrometer with CDCl3 as solvent and H3PO4 (85%) as exter-
nal reference. The NMR spectra were measured at the Institut fur
Anorganische Chemie, Martin-Luther-Universität, Halle-Witten-
berg, Germany. IR spectra were recorded on a Shimadzu FT-IR
8400 spectrophotometer in the 200–4000 cmÀ1 range using CsI
discs. Elemental analyses were carried out on a CHN analyzer type
1106 (Carlo-Erba). Melting points were measured on electrother-
mal 9100 melting point apparatus and were uncorrected. K2[PtCl4],
1,1-bis(diphenylphosphino)ferrocene (dppf) benz-1,3-oxazoline-2-
thione, benz-1,3-thiazoline-2-thione were commercial products
and were used as supplied. The compounds 4,5-diphenyl-1,2,4-tri-
azole-3-thione [23], 5-phenyl-1,3,4-oxadiazole-2-thione [24],
previously shown that complexes of the type [ML2(j
2-Ph2P(CH2)n
PPh2)] with mercapto-1,3-azole ligands, benz-1,3-thiazoline-2-
thionate (X = S, bztzt) and benz-1,3-oxazoline-2-thionate (X = O,
bzozt) exist as a mixture of isomers resulting from either the
N- or S-coordination of the ligands [13]. Herein we report the
synthesis and characterization of palladium(II) and platinum(II)
complexes of heterocyclic thionates containing the flexible diphos-
phine, 1,1-bis(diphenylphosphino)ferrocene (dppf) [14–20]. Some
⇑
Corresponding authors.
E-mail address: g.hogarth@ucl.ac.uk (G. Hogarth).
trans-[PdCl2(DMSO)2], cis-[PdCl2(DMSO)2] [25], [PdCl2(j
2-dppf)]
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.04.007

S.A. Al-Jibori et al. / Polyhedron 41 (2012) 20–24
21
Table 1
E = O, Phozt; E = NPh, Ph2tzt
Crystallographic and data collection parameters for complexes 2 and 6.
Complex
2.EtOH
6
N
N
N
N
Empirical formula
Formula weight
Crystal system
T (K)
Space group
Z
a (Å)
b (Å)
c (Å)
C
52H44FeN4O3P2PtS2 C48H36FeN2O2P2PdS2
S
Ph
1149.91
triclinic
223(2)
961.10
orthorhombic
223(2)
Pna21
4
23.5022(14)
18.4617(16)
9.8761(6)
90
90
90
S
Ph
E
E
ꢀ
P1
thiolate
N
thione
2
9.4541(9)
15.223(2)
18.236(1)
76.71(1)
78.13(1)
72.49(1)
2409.3(4)
1.585
N
X
S
S
a
(°)
b (°)
(°)
V (Å3)
X
c
4285.1(5)
1.490
0.966
X = S, bztzt; X = O, bzozt
q
l
(g cmÀ3
)
(Mo K
a
) (mmÀ1
)
3.401
1148
Chart 1.
F(000)
1952
Scan range (°)
Reciprocal lattice segments h,
k, l
1.99 < 25.84
À11 ? 11
À18 ? 18
À22 ? 22
18742
8655
0.0428
8655/0/587
0.972
2.05 < h < 25.88
À28 ? 28
À22 ? 22
À12 ? 11
33063
8155
0.0502
8155/1/523
0.985
and [PtCl2(j
2-dppf)] [20] were prepared by literature methods. The
potassium salts of all ligands used in this work were prepared by
mixing equimolar quantities of KOH and the ligand in EtOH. The
mixture was stirred at room temperature for 1 h. Solvent was then
evaporated on steam bath, and the resulting solid was dried under
vacuum.
Reflections collected
Reflections independent
Rint
Data/restraints/parameters
Goodness-of-fit on F2
R1, wR2 [I > 2
R1, wR2 (all data)
r
(I)]
0.0305, 0.0645
0.0496, 0.0778
1.28 and À1.39
0.0276, 0.0595
0.0356, 0.0617
1.052 and À0.250
2.2. Preparation of complexes
Largest difference in peak and
hole (e ÅÀ3
)
All the complexes were prepared and isolated by the following
general method. A solution of the appropriate potassium salt of the
ligand in a minimum amount of EtOH was added to a solution of
Absolute structure factor
CCDC No.
À0.015(14)
767746
767747
[MCl2(j
2-dppf)] (M = Pd or Pt) in a minimum a mount of CHCl3
in a mole ratio ligand to metal 2:1. The resulting solution was
boiled on steam bath for ca. 10 min. Solvent was then left to evap-
orate at room temperature. The resulting solid washed with water,
cold EtOH and dried under vacuum. Crystals of 2.EtOH and 6 suit-
able for single-crystal diffraction analysis were grown at 25 °C by
slow evaporation of chloroform–ethanol solutions.
Complex 5: Yellow solid, 73%. Anal. Calc. for C46H36FeN2P2PtS4: C,
53.2; H, 3.4; N, 2.6. Found: C, 53.5; H, 3.2; N, 2.7%. IR (KBr): 3057m,
2925w, 1585m, 1240m, 1097m, 1031m, 752s, 437m, 380w cmÀ1
.
1H NMR (CDCl3): d 7.85–6.95 (m, 28H, Ph), 4.30 (m, 8H, Cp).
13C{1H} NMR (CDCl3): 134.6, 134.0, 131.3, 130.7, 127.6, 124.3,
121.8, 119.6, 75.8, 73.2 ppm. 31P{1H} NMR (CDCl3): d 16.5 (JPt–P
3264 Hz). Melting point: 240–243 °C.
Complex 1: Orange solid, 86%. Anal. Calc. for
C50H38Fe-
N4O2P2PdS2: C, 58.9; H, 4.2; N, 5.3. Found: C, 59.0; H, 4.2; N,
5.5%. IR (KBr): 3470m, 3056m, 2925w, 1554m, 1305w, 1070m,
Complex 6: Red-brown solid, 91%. Anal.
46H36FeN2P2PdS2O2: C, 60.0; H, 3.8; N, 2.9. Found: C, 60.1; H,
3.9; N, 2.0%. IR (KBr): 3055m, 2925w, 1604m, 1244m, 1081m,
Calc. for
995m, 748s, 438m, 400w cmÀ1 1H NMR (CDCl3): d 7.90–7.30 (m,
.
C
30H, Ph), 4.39 (m, 4H, Cp), 4.38 (m, 4H, Cp). 13C{1H} NMR (CDCl3):
171.4, 163.6, 134.8, 131.7, 131.5, 127.9, 124.8, 76.3, 74.0, 73.4 ppm.
31P{1H} NMR (CDCl3): d 31.7. Melting point: 210–213 °C.
1037m, 748s, 433m, 380w cmÀ1 1H NMR (CDCl3): d 7.98–7.10
.
(m, 28H, Ph), 4.44 (m, 4H, Cp), 4.37 (m, 4H, Cp). 13C{1H} NMR
(CDCl3): 151.6, 134.7, 131.3, 130.8, 122.5, 121.3, 115.6, 113.9,
108.4, 76.0, 73.2 ppm. 31P{1H} NMR (CDCl3): d 28.5. Melting point:
186–188 °C.
Complex 2: Yellow solid, 79%. Anal. Calc. for
C50H38Fe-
N4O2P2PtS2: C, 54.4; H, 3.5; N, 5.1. Found: C, 54.2; H, 3.4; N, 5.0%.
IR (KBr): 3057m, 2925w, 1554m, 1307m, 1070m, 995m, 755s,
441m, 400w cmÀ1 1H NMR (CDCl3): d 7.87–7.30 (m, 30H, Ph),
.
4.36 (m, 8H, Cp). 13C{1H} NMR (CDCl3): 171.4, 163.6, 134.9,
131.0, 130.7, 127.8, 124.8, 76.1, 73.3 ppm. 31P{1H} NMR (CDCl3):
d 18.4 (JPt–P 3298 Hz). Melting point: 247–250 °C.
2.3. X-ray crystallography
Complex 3: Orange solid, 76%. Anal. Calc. for C50H38FeN6P2PdS2:
C, 63.9; H, 4.2; N, 7.2. Found: C, 64.1; H, 4.4; N, 7.5%. IR (KBr):
3058m, 2925w, 1596m, 1255w, 1065m, 1033m, 767s, 439m,
Yellow crystals of 2 and red-brown crystals of 6 suitable for X-
ray crystallographic measurements were obtained by slow evapo-
ration of chloroform/ethanol (ca. 50:50) solutions of the respective
complex. Table 1 gives the crystallographic data and collection
parameters. Intensity data were collected on a STOE-IPDS diffrac-
400w cmÀ1 1H NMR (CDCl3): d 7.97–6.80 (m, 40H, Ph), 4.43 (m,
.
4H, Cp), 4.31 (m, 4H, Cp). 13C{1H} NMR (CDCl3): 152.3, 135.1,
132.3, 130.5, 127.8, 76.0, 72.9 ppm. 31P{1H} NMR (CDCl3): d 29.6.
Melting point: 203–205 °C.
tometer with Mo K
a radiation (k = 0.7103 Å, graphite monochro-
mator). Absorption corrections were made using the IPDS
software package [26]. All structures were solved by direct meth-
ods with SHELX-97 [27] and refined using full-matrix least-square
routines against F2 with SHELXL-97 [28]. 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. Illustrations were generated using DIAMOND 3.0 soft-
ware [29].
Complex 4: Red-brown solid, 88%. Anal. Calc. for C46H36FeN2P2
PdS4: C, 58.0; H, 3.7; N, 2.8. Found: C, 58.1; H, 3.8; N, 2.6%. IR
(KBr): 3057m, 2925w, 1587m, 1238m, 1097m, 1030m, 750s,
438m, 380w cmÀ1 1H NMR (CDCl3): d 7.97–7.00 (m, 28H, Ph),
.
4.42 (m, 4H, Cp), 4.35 (m, 4H, Cp). 13C{1H} NMR (CDCl3): 176.5,
153.8, 137.3, 134.7, 132.1, 130.7, 127.7, 124.5, 121.9, 119.8,
119.0, 76.0, 74.8, 73.2 ppm. 31P{1H} NMR (CDCl3): d 27.5. Melting
point: 177–180 °C.

22
S.A. Al-Jibori et al. / Polyhedron 41 (2012) 20–24
Ph
N
N
E
N
N
Ph2
P
Ph2
P
KS
Ph
2
Cl
Cl
S
E
Fe
M
Fe
M
EtOH/CHCl3
S
P
P
Ph2
Ph2
N
E = O, Phozt
E
E = NPh, Ph2tzt
N
1 M = Pd, E = O
2 M = Pt, E = O
3 M = Pd, E = NPh
Ph
Scheme 1.
3. Results and discussion
We have developed a three step synthesis of group 10 diphos-
phine–thionate complexes [ML2(
2-diphosphine)] complexes
j
[8–13]. This involves treatment of thiones LH (LH = Phozt and
Ph2tzt) with palladium(II) or platinum(II) precursors including
Na2PdCl4, trans-[PdCl2(DMSO)2], K2PtCl4 or cis-[PtCl2(DMSO)2] to
give complexes of the type [MCl2(LH)2] (M = Pd or Pt). These can
then be converted to [ML2] by treatment with base, which in turn
react with diphosphines Ph2P(CH2)nPPh2 (n = 1–4) to give [ML2(j2
-
diphosphine)] in which the thionate anion binds to the metal
center in either the thiolate or thione form (Chart 1). Attempts to
prepare [ML2(j
2-dppf)] complexes via this method were only par-
tially successful leading to mixtures of products. While the desired
complexes 1–3 were generated (as confirmed by 1H NMR spectros-
copy) we were unable to isolate pure products. The nature of the
secondary species is not clear but they possibly result from the
dppf ligand acting in a bridging rather than a chelating capacity
since it is well-known that dppf is a highly flexible diphosphine
[19]. We consequently sought another synthetic route to the de-
sired products and in contrast to the first route, treatment of
[MCl2(
salt of 5-phenyl-1,3,4-oxadiazole-2-thionate (KPhozt) [24] in a
CHCl3/EtOH mixture cleanly afforded [M(Phozt)2(
2-dppf)] (1–2)
j
2-dppf)] (M = Pd, Pt) with two equivalents of the potassium
Fig. 1. Molecular structure of [Pt(Phozt)2(j
2-dppf)] (2): hydrogen atoms are
omitted and only the labels of the ipso C atoms of the phenyl and cyclopentadienyl
rings are represented for clarity, selected bond lengths (Å) and angles (°); Pt–P(1)
2.305(1), Pt–P(2) 2.317(1), Pt–S(1) 2.406(1), Pt–S(2) 2.370(1), C(2)–N(2) 1.308(7),
C(10)–N(4) 1.335(7), N(1)–N(2) 1.420(6), N(3)–N(4) 1.396(7), S(1)–Pt–S(2)
85.25(4), P(1)–Pt–P(2) 98.08(5), Pt–S(1)–C(2) 99.8(2), Pt–S(2)–C(10) 99.9(2).
j
after work-up as orange (M = Pd) and yellow (M = Pt) solids in
86% and 79% yield, respectively. A similar reaction between potas-
sium 4,5-diphenyl-1,2,4-triazole-3-thionate (KPh2tzt) [30] and
[PdCl2(
in 76% yield (Scheme 1).
j j
2-dppf)] gave [Pd(Ph2tzt)2( 2-dppf)] (3) as an orange solid
Characterization was relatively straight-forward on the basis of
spectroscopic and analytical data. 1H NMR spectra were as ex-
pected, each displaying multiplets between d 6.80–7.98 assigned
to the aromatic protons and either one or two broad signals be-
tween d 4.31–4.44 due to the protons of the cyclopentadienyl
ligands. The broadness of these later signals is attributed to the
well-known fluxionality of the dppf ligand [19,31]. In the 31P{1H}
NMR spectrum each shows a single phosphorus resonance indicat-
ing that both of the chlorides had been replaced and all exist in a
single isomeric form. The relatively small phosphorus–platinum
considered further. Compound 2 consists of the expected PtS2P2
square-planar array as is seen in related complexes [21,32,33].
The dppf ligand subtends a bite-angle of 98.08(5)° and the ferro-
cene backbone is twisted out of the PtS2P2 plane with one cyclo-
pentadienyl ligand lying above and the second below. The key
feature is the binding of the thionate groups through sulfur. The
adoption of the thiolate resonance form is clearly seen from the
metal–sulfur distances (Pt–Sav. 2.388(2) Å) which are similar to
those found in other platinum thiolate and dithiolate complexes
[21,32,33] and the carbon–nitrogen bond lengths within the het-
erocyclic ring (C–Nav 1.31(1) Å) which are indicative of double
bond character. The two thiolate ligands lie relatively close to
one another [S(1)–Pt–S(2) 85.25(4)°] and in order to reduce steric
strain between them, substituents lie on opposite sides of the
PtS2P2 plane (anti-conformation). The bond angles at sulfur of
99.8(2)° and 99.9(2)° are significantly smaller than those seen in
coupling constant for [Pt(Phozt)2(
j
2-dppf)] (2) of 3298 Hz, respec-
tively, as compared to [PtCl2(
j
2-dppf)] (JPt–P 3761.5 Hz) [20]
suggests the ligands bind through the sulfur atom, that is in a thio-
late fashion [32]. For comparison the phosphorus–platinum cou-
pling constant in the closely related complex [Pt(SPh)2(j
2-dppf)]
is 3016 Hz [21]. In order to confirm this, an X-ray crystal structure
was carried out on 2 the results of which are shown in Fig. 1. There
is also a molecule of ethanol in the asymmetric unit but there are
no significant intermolecular interactions and this will not be
[Pt(SPh)2(
j
2-dppf)] [Pt–S–C 107.8(2)° and 109.7(2)°] and [Pt(SPr)2
(j
2-dppf)] [Pt–S–C 105.2(4)° and 107.4(3)°] [21].

S.A. Al-Jibori et al. / Polyhedron 41 (2012) 20–24
23
N
N
X
Ph2
P
Ph2
P
KS
2
Cl
Cl
S
S
X
Fe
M
Fe
M
P
EtOH/CHCl3
P
Ph2
Ph2
N
X
X = S, bztzt
X = O, bzoxt
4 M = Pd, X = S
5 M = Pt, X = S
6 M = Pd, X = O
Scheme 2.
4. Conclusions
We have shown in this work that palladium and platinum dppf
complexes with heterocyclic thionates are easily prepared and
purified with all existing in the sulfur-bound thiolate form (Chart
1). This is in contrast to related complexes with diphosphines with
methylene backbones for which mixtures of sulfur- and nitrogen-
bound linkage isomers are observed. The reasons for this difference
are not immediately obvious but possibly relate to the more flexi-
ble nature of the dppf ligand and its greater steric demands.
Appendix A. Supplementary material
CCDC 767746 and 767747 contain the supplementary crystallo-
graphic data for 2 and 6, respectively. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.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.
References
Fig. 2. Molecular structure of [Pd(bzoxt)2(j
2-dppf)] (6): hydrogen atoms are
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As detailed in Section 1, we have previously found that com-
plexes [ML2{
mixture S- and N-bound isomers [13]. We have now prepared the
related dppf complexes [M(bztzt)2(
2-dppf)] (4–5) and [Pd(bzoxt)2
2-dppf)] (6) as red-brown (M = Pd) or yellow (M = Pt) solids in
73–91% yields upon simple addition of Kbztzt [34] or Kbzoxt [35]
to [MCl2(
2-dppf)] (Scheme 2). Again all showed a single resonance
in the 31P{1H} NMR spectrum and for [Pt(bztzt)2( 2-dppf)] (5) the
j
2-Ph2P(CH2)nPPh2}] (L = bztzt and bzoxt) exist as a
j
(j
j
j
JPt–P coupling constant of 3264 Hz was strongly indicative of the
sulfur-bound coordination of the new ligands [36]. An X-ray crystal
structure of 6 confirmed this, the results of which are summarized
in Fig. 2. The overall geometry is very similar to that found in 2. Pal-
ladium–sulfur distances are within the expected ranges and the
dppf ligand subtends a bite-angle of 96.45(3)°. The two thionate li-
gands are now slightly further apart, the S(1)–Pd–S(2) angle being
89.64(3)°, and again the substituents lie on opposite sides of the
PdS2P2 plane (anti-conformation). Unlike in 2 and related platinum
bis(thiolate) complexes, the angles at sulfur now vary significantly
at 96.15(12)° and 107.21(12)°. The reasons for this are not immedi-
ately clear.

24
S.A. Al-Jibori et al. / Polyhedron 41 (2012) 20–24
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