Effect of a (hetero)aromatic spacer on the direction of cyclopalladation in ditopic pincer ligands with thione sulfur donors

Article abstract of DOI:10.1016/j.jorganchem.2019.02.014

3-Diphenylthiophosphorylaniline and isophthalic or 2,6-pyridinedicarboxylic acids were used as key precursors for the synthesis of ditopic pincer ligands bearing thioamide and thiophosphoryl donor groups. Depending on the nature of a (hetero)aromatic spac

Full text of DOI:10.1016/j.jorganchem.2019.02.014

Accepted Manuscript
Effect of a (hetero)aromatic spacer on the direction of cyclopalladation in ditopic
pincer ligands with thione sulfur donors
Diana V. Aleksanyan, Svetlana G. Churusova, Zinaida S. Klemenkova, Yulia V.
Nelyubina, Alexander S. Peregudov, Vladimir A. Kozlov
PII:
S0022-328X(19)30058-0
DOI:
https://doi.org/10.1016/j.jorganchem.2019.02.014
JOM 20716
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 11 December 2018
Revised Date: 11 February 2019
Accepted Date: 13 February 2019
Please cite this article as: D.V. Aleksanyan, S.G. Churusova, Z.S. Klemenkova, Y.V. Nelyubina, A.S.
Peregudov, V.A. Kozlov, Effect of a (hetero)aromatic spacer on the direction of cyclopalladation in
ditopic pincer ligands with thione sulfur donors, Journal of Organometallic Chemistry (2019), doi: https://
doi.org/10.1016/j.jorganchem.2019.02.014.
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ACCEPTED MANUSCRIPT
Effect of a (hetero)aromatic spacer on the direction of cyclopalladation in
ditopic pincer ligands with thione sulfur donors
Diana V. Aleksanyan,a Svetlana G. Churusova,a Zinaida S. Klemenkova,a Yulia V. Nelyubina,a,b
Alexander S. Peregudov,a and Vladimir A. Kozlova
aNesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
bKurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 117901 Russia
*corresponding author: aleksanyan.diana@ineos.ac.ru
Abstract
3-Diphenylthiophosphorylaniline and isophthalic or 2,6-pyridinedicarboxylic acids were
used as key precursors for the synthesis of ditopic pincer ligands bearing thioamide and
thiophosphoryl donor groups. Depending on the nature of a (hetero)aromatic spacer (meta-
functionalized phenylene or pyridine rings), the ligands derived underwent coordination either at
the lateral or central pincer units, selectively affording binuclear (in the case of phenylene-based
ligand) or mononuclear (in the case of pyridine-based derivative) Pd(II) pincer complexes. The
mononuclear pyridine-based palladacycle is prone to deprotonation of the secondary thioamide
groups, resulting in sulfide clusters. A structure of the tetramer obtained was elucidated by
single-crystal XRD.
Key words: pincer complex, ditopic ligand, palladium, cyclometalation.
1. Introduction
Among the rich variety of organometallic compounds, pincer complexes comprise one of
the most thoroughly studied classes that attract continuous research interest [1, 2]. High stability
and tunability provided by specific tridentate ligands promote wide application scope of these
complexes—from organic synthesis and catalysis to materials science and medicinal chemistry.
Whereas the overwhelming majority of the reported examples represent mononuclear species,
there are a limited number of Pd(II), Pt(II), Ru(III), and Re(I) binuclear and trinuclear complexes
combining several pincer motifs in their structures (see, for example, Fig. 1) [3]. Besides
interesting reactivity patterns and supramolecular structures [3c–f,h–j,m,n], these complexes
exhibited remarkable redox properties [3a,g], catalytic activity [3k,l], and photophysical
characteristics [3b], sometimes exceeding in the performance their mononuclear prototypes.

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2OTf
H
H
N
N
N
Pt
N
N
Pt
N
O
PiPr2
S
S
Pd
S
S
Cl
N
Pd
Cl
Cl
Cl
S
S
N
N
iPr2P
O
Pd
N
Pd
Ir
N
N
H
H
(CO)3
N
N
Ph2P
PPh2
Re
N
PPh3
Cl
Ph3P
Cl
N
N
N
N
Ru
Ru
N
Re
N
N
Ph2P
PPh2
(CO)3
Fig. 1. Examples of ditopic pincer complexes.
Most of the known ditopic pincer complexes are appended with nitrogen donors, while
their sulfur- and phosphorus-containing analogs remain essentially underexplored. At the same
time, mononuclear S,C,S-pincer complexes, in particular, those bearing thione sulfur donors
were shown to possess intriguing chemical behavior, valuable luminescence properties, and high
catalytic activity in different reactions (Fig. 2) [4]. Therefore, it seemed interesting to develop
related ditopic pincer systems. In this communication, we report on the synthesis of potentially
dinucleating ligands having thiophosphoryl and thiocarbamoyl coordination arms, where two
pincer moieties are bridged by (hetero)aromatic spacers. The peculiarities of their complexation
with Pd(II) ions are considered.
+
X
EtO
EtO
iPr2P
S
PiPr2
S
OEt
OEt
P
S
P
S
N
Ph2P
S
O
P
Ph2P
S
PPh2
S
-
R1
R2
Rh
Me
BF4
Ph2P
S
PPh2
S
Pd
Pd
Cl
M
S
Me
O
Pd
Cl
Cl
Cl
R1 = R2 = NMe2, NEt2, Ph
R1 = Me, R2 = OBu
Me
M = Pd, Pt
X = CMe, N
Fig. 2. Mononuclear pincer complexes with thione sulfur donors.
2. Results and discussion
A convenient key precursor for the synthesis of novel ligands appeared to be 3-
diphenylthiophosphorylaniline 1 (Scheme 1). It should be noted that its phosphorylated analog
has been used successfully for the creation of hybrid S,C,S'-pincer ligands that led to
mononuclear Pd(II) complexes [5]. The synthesis of the P(S)-functionalized aniline was
accomplished by analogy with its P(O)-counterpart starting from triphenylphosphine oxide. An
additional thionation step was introduced to facilitate the construction of a multidentate ligand

3
ACCEPTED MANUSCRIPT
framework, since the conversion of tertiary phosphine oxides to the corresponding sulfides
requires harsh reaction conditions and is more complicated than the thionation of amides [6].
Interestingly, this modification did not affect the overall yield of the target product. In contrast,
optimization of the reaction conditions and isolation procedures led even to the more facile and
efficient multigram synthesis of the key phosphorus precursor.
P(O)Ph2
P(S)Ph2
P(S)Ph2
SnCl2.2H2O, EtOH,
reflux, 9.5 h
KNO3, H2SO4 (conc.)
50-60oC, 3 h
RL, PhCl,
reflux, 3 h
Ph3P=O
NO2
NH2
NO2
1
S
S
RL
=
MeO
P
P
S
OMe
S
Scheme 1. Synthesis of key thiophosphorylated aniline 1.
The reactions of aniline 1 with isophthalic and 2,6-pyridinedicarboxylic acid chlorides
under mild conditions smoothly afforded bis(amides) 2 and 3 in high yields (Scheme 2). The
latter were transformed to the corresponding bis(thioamides) (compounds 4 and 5, Scheme 2)
upon refluxing with an excess of the Lawesson reagent in chlorobenzene. The structures of the
ligands derived were unambiguously confirmed by the multinuclear NMR and IR spectroscopic
data. In particular, 2D NMR spectra (COSY, HMQC, and HMBC) allowed for the full
assignment of the signals of hydrogen and carbon nuclei (see, for example, Figs. S1–S8 in
Supplementary Data (SD)). In the case of bis(thioamide) 4, most of the signals in the NMR
spectra registered at room temperature appeared to be broadened; however, a temperature
decrease to 258 K afforded the resolved signals (see Experimental section).
The choice of the mentioned meta-functionalized carbonyl derivatives ensured the
formation of two lateral pincer motifs. At the same time, the central (hetero)aromatic moiety
with two thiocarbamoyl pendant arms can also adopt a tridentate coordination mode, either
monoanionic (in the case of phenylene-containing ligand 4) or neutral (in the case of pyridine-
substituted ligand 5). The realization of the second complexation scenario would afford
mononuclear complexes with two equivalent five-membered fused palladacycles, whereas the
expected ditopic coordination involving the P=S and C=S donor groups would lead to 5,6-
membered unsymmetrical binuclear derivatives. Therefore, it seemed interesting to estimate the
possibility of selective cyclopalladation in these systems.

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H
N
H
N
H
N
H
N
RL, PhCl,
reflux, 5 h
O
O
S
S
Cl
Cl
X
Ph2P
PPh2
Ph2P
PPh2
O
O
S
S
S
S
2 Et3N, CH2Cl2, rt, 1 day
X = CH, N
92% (2)
69% (4)
1
H
N
H
N
H
N
H
N
RL, PhCl,
reflux, 9 h
N
N
O
O
S
S
Ph2P
PPh2
Ph2P
PPh2
S
S
S
S
84% (3)
87% (5)
Scheme 2. Synthesis of ditopic pincer ligands with (hetero)aromatic spacers 4 and 5.
Reaction of ligand 4 with two equivalents of PdCl2(NCPh)2 in CH2Cl2 at room temperature
smoothly afforded the desired binuclear complex 6 with two pincer fragments in a high yield
(Scheme 3). Interestingly, the 31P NMR spectrum of the reaction mixture at room temperature in
5 days displayed broadened signals in the range of 46.5–48.6 ppm, which were partially resolved
upon cooling to 258 K (Fig. S9 in SD). Presumably, the steric congestion of a ditopic pincer
system with the bulky Ph2P(S) pendant arms resulted in restricted rotation and formation of
conformational isomers, which slowly interconverted in chlorinated hydrocarbons (vide infra).
Thus, for example, addition of DMF led to conversion of these signals to a sole singlet at 48.4
ppm (Fig. S10 in SD). A significant downfield shift of the phosphorus resonances compared to
that of the free ligand unambiguously indicated coordination of the P=S donor groups (∆δP up to
~5.5 ppm). Note that a relatively long reaction time (cf. 5 days instead of 1 day in the case of a
mononuclear analog [5]) was stipulated by the slow conversion of an intermediate complex (or a
mixture of complexes) formed immediately after mixing of the reagents, which, in turn, was
connected with its (or their) low solubility in CH2Cl2. The addition of more polar solvents, such
as DMF, although accelerated the reaction, but essentially complicated the product isolation.
31
The P NMR monitoring of the analogous reaction of ligand 5, having a pyridine spacer,
with PdCl2(NCPh)2 in CH2Cl2 did not reveal coordination of the thiophosphoryl groups.
Independent from a relative amount of the metal precursor (1–3 equivalents), the 31P NMR
spectra showed signals in a narrow range of 42–43 ppm—a region typical for the non-
coordinated phosphine sulfides. Furthermore, a sole singlet signal (at 42.3 ppm) was detected
only in the case of 1:1 metal/ligand ratio. This suggests that the coordination of ligand 5 occurred
selectively at the central pincer unit involving the pyridine ring and the thiocarbamoyl donor
groups. Optimization of the reaction conditions allowed for the isolation of mononuclear
complex 7 in a good yield (Scheme 3).

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ACCEPTED MANUSCRIPT
2 PdCl2(NCPh)2
CH2Cl2, rt, 5 days
PdCl2(NCPh)2
CH2Cl2, rt, 5 days
4 or 5
H
N
H
N
H
N
H
N
N
Pd
Cl
Cl
S
S
Pd
Cl
S
S
Pd
Cl
Ph2P
PPh2
Ph2P
PPh2
S
S
S
S
76% (6)
73% (7)
Scheme 3. Complexation of ditopic pincer ligands 4 and 5 with Pd(II) ions.
The compositions of complexes 6 and 7 were confirmed by the elemental analyses. Their
structures were supported by the IR spectroscopic data. Thus, the lower-frequency shift of the
P=S bond stretching vibrations was detected only in the case of complex 6. This is a
characteristic feature of pincer complexes involving P=S ancillary donor groups [5, 6]. In the
case of complex 7, the mentioned absorption band was observed in the region typical for free
phosphine sulfides (cf. 640 cm–1 for complex 7 and 637 cm–1 for the corresponding ligand 5).
Furthermore, the IR spectra of the complexes obtained showed N–H stretching vibrations in the
range of 3150–3220 cm–1 instead of 3234–3258 cm–1 for the free ligands, which confirms the
coordination of thioamide groups in both compounds.
Unfortunately, after isolation and drying, complex 6 appeared to be poorly soluble in
31
chlorinated hydrocarbons. Furthermore, as well as in the case of the reaction mixture, the P
NMR spectrum of a solution of this palladacycle in CDCl3 at room temperature showed
broadened signals in the region characteristic for the coordinated Ph2P(S) groups, which
converted to a number of singlet signals in the range of 45.5–48.6 ppm upon cooling to 258 K
(Fig. S11 in SD). The existence of several conformers was further supported by the presence of a
1
range of well resolved signals at 11.33–12.51 ppm in the H NMR spectrum registered at the
reduced temperature, which were attributed to the NHC(S) protons (Figs. S12 and S13 in SD).
31
1
Although complex 6 rapidly decomposes in coordinating solvents, the P and H NMR spectra
registered in 5 min after its dissolution in (CD3)2SO eventually confirmed the suggested structure
of this complex (Figs. S14 and S15 in SD). Note that the content of undefined decomposition
products reached 12% even over such a short period of time. However, a strongly downfield-
shifted phosphorus resonance of the main component was indicative of coordination of lateral
1
pincer units (δP = 49.09 ppm). Furthermore, the H NMR spectrum displayed the characteristic
singlet of H(C1) proton of the non-metallated central phenylene ring along with the other
aromatic and NHC(S) proton signals.
Dissolution of palladacycle 7 even in non-coordinating solvents led to spontaneous
deprotonation of the secondary thioamide groups accompanied by oligomerization. This made

6
ACCEPTED MANUSCRIPT
1
impossible its characterization by single-crystal XRD and NMR spectroscopy. Thus, the H
NMR spectra registered directly after dissolution of this complex in CDCl3 did not reveal the
expected signals of the NH protons and contained only broadened patterns in the range of
aromatic proton signals. Slow diffusion of Et2O into NMP–CHCl3 solution of complex 7
afforded red prisms suitable for XRD analysis. The latter appeared to be tetramer 8, resulting
from deprotonation of the coordinated NHC(S) moieties (Scheme 4, Fig. 3). This confirmed that
coordination of ligand 5 involved the central pincer unit. All the thioamide groups in chloride-
free complex 8 converted into iminothiolate ones; and one of the iminothiolate group from each
dianionic pincer fragment serves as a bridging ligand.
S
S
- 2 HCl
Ph2P
N
N
PPh2
7
N
S
Pd
S
4
8
Scheme 4. Clusterization of complex 7.
Fig. 3. General view of complex 8. For clarity, Ph2P(S) groups are shown as thermal ellipsoids of the
phosphorous atoms given at 50% probability level. Solvate NMP and CHCl3 molecules are omitted.
Deprotonation of secondary thioamide groups in S,N,S-pincer systems with central
pyridine units has already been described in the literature [7]. Thus, the spontaneous loss of
protons in one or both of the NHC(S)Ph coordination arms in symmetrical ligands afforded

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ACCEPTED MANUSCRIPT
stable mononuclear Pd(II) and Pt(II) complexes with either mono- or dianionic ligands [7e]. In
the case of the related Ru(II) complex, the stepwise deprotonation of the thioamide protons led
firstly to a mononuclear derivative, which then converted to a dimer with two dianionic S,N,S-
ligands [7a]. A propensity of a Pt(II) bis(thioamide) pincer complex for reversible
deprotonation/protonation enabled its use as a molecular switch for half sulfur mustard [7b].
Finally, treatment of Pd(II) counterparts with organozinc or Grignard reagents afforded
bis(thioimide) pincer clusters which efficiently catalyze the Negishi cross-coupling [7c,d]. Thus,
the coordination behavior of ligand 5 with a pyridine central ring is in good agreement with the
literature data, and the presence of the thiophosphoryl pendant arms does not affect the
selectivity upon complexation with Pd(II) ions, although facilitates deprotonation of the
thioamide groups. As for the related monotopic pincer systems with phenylene central moieties,
a literature survey has revealed only several mononuclear complexes with iminothiolate donor
groups (M = Pt, Ru, Ni) which were formed upon addition of strong bases [8]. Spontaneous
deprotonation in phenylene-based bis(thioamide) pincer systems was observed only once and
afforded a Pt(II) chalcogenide cluster in 4% yield [9]. Therefore, the stability of complex 6 is in
line with the previously published data. What is important to note about this system is the
selective activation of unsymmetrical lateral pincer units instead of a symmetrical central pocket.
Furthermore, the conjugation of two S,C,S-pincer units through a meta-phenylene spacer resulted
in a sterically congested system with complicated interconversion of conformational isomers.
3. Conclusions
In this work, new ditopic pincer ligands bearing P=S and C=S donor groups were shown to
undergo site-selective cyclopalladation/coordination depending on the nature of (hetero)aromatic
spacers. Further studies will shed more light on the reactivity and properties of the related
dinucleating systems with thione sulfur donors.
4. Experimental
4.1. General remarks
Unless otherwise mentioned, all manipulations were carried out without taking precautions
to exclude air and moisture. Dichloromethane was distilled over P2O5. Isophthaloyl [10] and 2,6-
pyridinedicarbonyl [11] dichlorides were obtained by treatment of the corresponding acids with
an excess of SOCl2 according to the published procedures. All other chemicals and solvents were
used as purchased.
The NMR spectra were recorded on Bruker Avance 400 and Avance 500 spectrometers,
and the chemical shifts (δ) were referenced internally by the residual solvent signals relative to

8
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13
13
tetramethylsilane (1H, C) or externally to H3PO4 (31P). In most cases, C{1H} NMR spectra
were registered using the JMODECHO mode; the signals for the C nuclei bearing odd and even
numbers of protons have opposite polarities. The assignment of the NMR spectra of ligands 4
and 5 was carried out based on the 1H–1H-COSY, HMQC, and HMBC experiments. The results
obtained were used for interpretation of the NMR spectra of the other compounds from this
study.
The IR spectra were recorded on a Nicolet Magna-IR750 FT-spectrometer, resolution 2
cm–1, 128 scans. The assignment of absorption bands in the IR spectra was made according to
ref. [12]. Column chromatography was carried out using Macherey-Nagel silica gel 60 (MN
Kieselgel 60, 70–230 mesh). Melting points were determined with an MPA 120 EZ-Melt
automated melting point apparatus (Stanford Research Systems).
4.2. Syntheses
3-Diphenylthiophosphorylaniline, 1.
A mixture of triphenylphosphine oxide (10.40 g, 0.037 mol) and conc. H2SO4 (50 mL) was
stirred at room temperature until complete dissolution of Ph3P(O). Then KNO3 (4.25 g, 0.042
mol) was added portionwise, and the mixture was heated at 50–60 °C for 3 h. After cooling to
room temperature, it was poured onto ice, and the resulting solution and resin-like precipitate
were extracted with chloroform. The organic layer was separated, sequentially washed with
saturated aq. NaHCO3 and water, dried over anhydrous Na2SO4, and evaporated to dryness. A
stirred mixture of the resulting residue, the Lawesson reagent (8.08 g, 0.020 mol), and
chlorobenzene (60 mL) was refluxed for 3 h. The solution obtained was diluted with chloroform,
washed with saturated aq. NaHCO3 and water, dried over anhydrous Na2SO4, and evaporated to
dryness. The resulting residue was purified by column chromatography on silica gel (eluent:
CHCl3) to give
a
viscous brown oil bearing
a
mixture of isomeric
(nitrophenyl)diphenylphosphine sulfides. A stirred mixture of this residue, SnCl2·2H2O (50.7 g,
0.225 mol), and ethanol (150 mL) was refluxed for 9.5 h. After cooling to room temperature, it
was poured onto ice. Then NaOH was added portionwise to pH ~10, and the resulting solution
was extracted with chloroform. The aqueous phase was separated, filtered (using filter paper),
and additionally extracted with chloroform. The combined organic layer was dried over
anhydrous Na2SO4 and evaporated to dryness. The residue obtained was purified by column
chromatography (eluent: CHCl3). The crude product was additionally purified by column
chromatography using EtOAc–hexane (1:1) mixture to give 5.11 g of meta-thiophosphorylated
31
aniline as a white crystalline solid. Yield: 44%. P{1H} NMR (161.98 MHz, CDCl3): 43.73
ppm. Mp: 182–184 °C (compare with 182–183 °C in ref. [13]).

9
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General procedure for the synthesis of bis(amides) 2 and 3.
A solution of the corresponding acid dichloride (0.65 mmol) in CH2Cl2 (10 mL) was added
to a stirred solution of aniline 1 (402 mg, 1.30 mmol) and Et3N (135 mg, 1.33 mmol) in CH2Cl2
(10 mL). The reaction mixture was stirred at room temperature for 2 h and left under ambient
conditions for 1 day. The solvent was removed under vacuum. The resulting residue was purified
by column chromatography (eluent: hexane–acetone (2:1) (2) or CH2Cl2–EtOH (100:1) (3)) to
give the target compounds as white crystalline solids. Note that bis(amide) 3 was additionally
rinsed with Et2O to remove traces of the unreacted aniline.
N,N'-bis[3-(diphenylthiophosphoryl)phenyl]benzene-1,3-dicarboxamide, 2.
4
3
5
H
H
12
12'
N
N
2
6
11
10
11'
10'
7
8
7'
8'
1
O
O
9
9'
Ph2P
PPh2
S
S
31
Yield: 448 mg (92%). Mp: 149–151 °C. P{1H} NMR (161.98 MHz, CDCl3): δ 43.19
1
ppm. H NMR (400.13 MHz, CDCl3): δ 7.26–7.38 (m, 12H, HAr), 7.42–7.46 (m, 5H, HAr), 7.65
3
3
(dd, 8H, o-H in P(S)Ph2, JHP = 13.4 Hz, JHH = 7.2 Hz), 7.90–7.97 (m, 4H, HAr), 7.99 (d, 2H,
13
H(C8) + H(C8'), 3JHP = 14.8 Hz), 8.28 (s, 1H, H(C1)), 8.88 (br s, 2H, NH) ppm. C{1H} NMR
(100.61 MHz, CDCl3): δ 123.97 (s, C12 + C12'), 124.08 (d, C8 + C8', 2JCP = 13.2 Hz), 125.52 (s,
C4), 127.94 (d, C10 + C10', 2JCP = 10.3 Hz), 128.57 (d, m-C in P(S)Ph2, 3JCP = 12.6 Hz), 129.08
(d, C11 + C11', 3JCP = 13.6 Hz), 129.22 (s, C1), 131.39 (s, C3 + C5), 131.72 (s, p-C in P(S)Ph2),
132.13 (s, ipso-C in P(S)Ph2, 1JCP = 82.6 Hz), 132.14 (d, o-C in P(S)Ph2, 2JCP = 10.8 Hz), 133.31
(d, C9 + C9', 1JCP = 85.0 Hz), 134.49 (s, C2 + C6), 138.34 (d, C7 + C7', 3JCP = 15.4 Hz), 165.51
(s, C=O) ppm. IR (KBr, ν/cm–1): 513(m), 581(vw), 615(w), 640(m) (νP=S), 691(m), 716(s),
747(w), 791(vw), 997(vw), 1027(vw), 1102(m), 1182(vw), 1244(m), 1306(m), 1395(sh, w),
1412(m), 1436(m), 1480(m), 1529(m) (C(O)NH), 1587(m), 1659(sh, m) and 1677(m) (both
νC=O), 3053 (vw), 3309 (br, w) (νNH). Anal. Calcd for C44H34N2O2P2S2: С, 70.57; Н, 4.58; N,
3.74. Found: C, 70.31; H, 4.83; N, 3.80%.
N,N'-bis[3-(diphenylthiophosphoryl)phenyl]pyridine-2,6-dicarboxamide, 3.
4
3
5
H
H
12
12'
N
N
2
6
11
10
11'
10'
N
7
8
7'
8'
O
O
9
9'
Ph2P
PPh2
S
S
31
Yield: 410 mg (84%). Mp: 270–272 °C (dec.). P{1H} NMR (161.98 MHz, CDCl3): δ
1
43.06 ppm. H NMR (400.13 MHz, CDCl3): δ 7.38–7.50 (m, 16H, HAr), 7.71 (ddd, 8H, o-H in
3
3
4
P(S)Ph2, JHP = 13.4 Hz, JHH = 7.8 Hz, JHH = 1.5 Hz), 7.97–8.00 (m, 2H, HAr), 8.04–8.10 (m,

10
ACCEPTED MANUSCRIPT
3H, HAr), 8.42 (d, 2H, H(C3) + H(C5), 3JHH = 7.8 Hz), 9.82 (br s, 2H, NH) ppm. 13C{1H} NMR
(100.61 MHz, CDCl3): δ 124.70–124.92 (m, overlapping signals of C3, C5, C8, and C8'), 125.85
(br s, C12 + C12'), 128.47–128.60 (m, overlapping signals of m-C in P(S)Ph2, C10, and C10'),
128.99–129.15 (unresolved signal of C11 and C11'), 131.63 (s, p-C in P(S)Ph2), 132.17 (d, o-C
in P(S)Ph2, 2JCP = 10.8 Hz), 132.36 (d, ipso-C in P(S)Ph2, 1JCP = 85.3 Hz), 133.65 (d, C9 + C9',
1JCP = 84.9 Hz), 137.41 (d, C7 + C7', 3JCP = 15.4 Hz), 139.23–139.32 (unresolved signal of C4),
148.76 (s, C2 + C6), 161.95 (s, C=O) ppm. IR (KBr, ν/cm–1): 494(w), 512(m), 615(w), 640(m)
(νP=S), 693(m), 716(s), 748(w), 793(vw), 837(vw), 897(vw), 998(w), 1027(vw), 1072(w),
1102(m), 1243(vw), 1312(w), 1421(m), 1436(m), 1450(w), 1481(m), 1530(br, m) (C(O)NH),
1550(m), 1583(m), 1672(m) and 1685(m) (both νC=O), 2922(w), 3054(w), 3286(br, w) (νNH).
Anal. Calcd for C43H33N3O2P2S2: С, 68.88; Н, 4.44; N, 5.60. Found: C, 68.77; H, 4.58; N,
5.66%.
General procedure for the synthesis of bis(thioamides) 4 and 5.
A mixture of the corresponding bis(amide) (0.35 mmol) and the Lawesson reagent (162
mg, 0.40 mmol) in chlorobenzene (15 mL) was refluxed for 5 h (4) or 9 h (5). After cooling to
room temperature, the reaction mixture was diluted with chloroform and sequentially washed
with saturated aq. NaHCO3 (2×50 mL) and water (50 mL). The organic layer was separated,
dried over anhydrous Na2SO4, and evaporated to dryness. In the case of compound 4, the
resulting residue was purified by column chromatography (eluent: acetone–hexane (1:2)) to give
the target bis(thioamide) as a yellow crystalline solid. In the case of compound 5, the resulting
residue was recrystallized from EtOAc–hexane and then purified by column chromatography
(eluent: CH2Cl2) to give the target bis(thioamide) as an orange crystalline solid.
N,N'-bis[3-(diphenylthiophosphoryl)phenyl]benzene-1,3-dicarbothioamide, 4.
4
3
5
H
H
12
12'
N
N
2
6
11
10
11'
10'
7
8
7'
8'
1
S
S
9
9'
Ph2P
PPh2
S
S
Yield: 188 mg (69%). Mp: >172 °C (dec.). 31P{1H} NMR (202.47 MHz, CDCl3, 258 K): δ
1
43.09 ppm. H NMR (500.13 MHz, CDCl3, 258 K): δ 7.35–7.38 (m, 3H, H(C4) + H(C11) +
H(C11')), 7.40–7.45 (m, 10H, m-H in P(S)Ph2 + H(C10) + H(C10')), 7.49–7.53 (m, 4H, p-H in
3
P(S)Ph2), 7.64–7.68 (m, 8H, o-H in P(S)Ph2), 7.86 (d, 2H, H(C12), JHH = 7.8 Hz), 7.98 (s, 1H,
3
3
H(C1)), 7.99 (d, 2H, H(C3) + H(C5), JHH = 7.3 Hz), 8.05 (d, 2H, H(C8) + H(C8'), JHP = 14.2
13
Hz), 10.14 (br s, 2H, NH) ppm. C{1H} NMR (125.76 MHz, CDCl3, 258 K): δ 123.66 (s, C4),
127.24 (s, C12 + C12'), 127.77 (d, C8 + C8', 2JCP = 12.5 Hz), 128.86 (d, m-C in P(S)Ph2, 3JCP =
3
12.6 Hz), 129.05 (s, C1), 129.38 (d, C11 + C11', JCP = 13.2 Hz), 130.20 (d, C10 + C10', 2JCP =

11
ACCEPTED MANUSCRIPT
1
10.7 Hz), 131.37 (d, ipso-C in P(S)Ph2, JCP = 85.9 Hz), 131.51 (s, C3 + C5), 132.11 (d, p-C in
1
P(S)Ph2, 4JCP = 3.0 Hz), 132.25 (d, o-C in P(S)Ph2, 2JCP = 11.0 Hz), 133.08 (d, C9 + C9', JCP =
3
85.4 Hz), 139.01 (d, C7 + C7', JCP = 15.2 Hz), 141.80 (s, C2 + C6), 197.33 (s, C=S) ppm. IR
(KBr, ν/cm–1): 514(m), 614(w), 639(m) (νP=S), 692(s), 715(s), 749(w), 798(vw), 921(vw),
998(w), 1027(vw), 1103(s), 1185(w), 1308(w), 1344(br, m), 1413(m), 1436(s), 1479(m),
1517(br, m), 1585(m), 2924(w), 3053(w), 3234(br, m) (νNH). Anal. Calcd for C44H34N2P2S4: С,
67.67; Н, 4.39; N, 3.59. Found: C, 67.45; H, 4.77; N, 3.41%.
N,N'-bis[3-(diphenylthiophosphoryl)phenyl]pyridine-2,6-dicarbothioamide, 5.
4
3
5
H
H
12
12'
N
N
2
6
11
10
11'
10'
N
7
8
7'
8'
S
S
9
9'
Ph2P
PPh2
S
S
31
Yield: 238 mg (87%). Mp: 277–280 °C (dec.). P{1H} NMR (161.98 MHz, CDCl3): δ
1
43.04 ppm. H NMR (500.13 MHz, CDCl3): δ 7.44–7.48 (m, 8H, m-H in P(S)Ph2), 7.51–7.54
3
4
(m, 4H, p-H in P(S)Ph2), 7.59 (dt, 2H, H(C11) + H(C11'), JHH = 7.8 Hz, JHP = 3.6 Hz), 7.66
(dd, 2H, H(C10) + HC(10'), 3JHP = 12.5 Hz, 3JHH = 7.8 Hz), 7.77 (dd, 8H, o-H in P(S)Ph2, 3JHP
=
3
3
13.4 Hz, JHH = 7.8 Hz), 8.03 (t, 1H, H(C4), JHH = 7.9 Hz), 8.17–8.19 (m, 2H, H(C12) +
H(C12')), 8.45 (d, 2H, H(C8) + H(C8'), 3JHP = 14.3 Hz), 8.88 (d, 2H, H(C3) + H(C5), 3JHH = 7.9
Hz), 11.29 (br s, 2H, NH) ppm. 13C{1H} NMR (125.76 MHz, CDCl3): δ 126.44 (d, C12 + C12',
2
4JCP = 2.8 Hz), 127.25 (d, C8 + C8', JCP = 12.6 Hz), 127.91 (s, C3 + C5), 128.68 (d, m-C in
P(S)Ph2, 3JCP = 12.6 Hz), 129.52 (d, C11 + C11', 3JCP = 13.3 Hz), 130.48 (d, C10 + C10', 2JCP =
10.1 Hz), 131.80 (d, p-C in P(S)Ph2, 4JCP = 3.1 Hz), 132.30 (d, o-C in P(S)Ph2, 2JCP = 10.7 Hz),
1
1
132.34 (d, ipso-C in P(S)Ph2, JCP = 85.8 Hz), 134.15 (d, C9 + C9', JCP = 84.5 Hz), 138.53 (d,
3
C7 + C7', JCP =15.3 Hz), 138.73 (s, C4), 149.71 (s, C2 + C6), 188.54 (s, C=S) ppm. IR (KBr,
ν/cm–1): 515(s), 561(w), 584(w), 615(m), 637(s) (νP=S), 693(s), 717(s), 733(m), 750(m),
771(vw), 790(w), 823(vw), 873(vw), 904(vw), 998(w), 1028(vw), 1077(m), 1104(s), 1158(vw),
1187(w), 1309(m), 1364(m), 1417(m), 1437(s), 1478(m), 1526(m), 1542(m), 1584(m),
2924(vw), 3053(w), 3074(vw), 3258(m) (νNH). Anal. Calcd for C43H33N3P2S4: С, 66.05; Н,
4.25; N, 5.37. Found: C, 65.91; H, 4.28; N, 5.41%.
Binuclear complex 6 [14].
H
N
H
N
S
S
Pd
Pd
Cl
Cl
Ph2P
PPh2
S
S

12
ACCEPTED MANUSCRIPT
A solution of PdCl2(NCPh)2 (29 mg, 0.076 mmol) in CH2Cl2 (3 mL) was added dropwise
to a solution of ligand 4 (30 mg, 0.038 mmol) in CH2Cl2 (4 mL). The resulting mixture was left
under ambient conditions for 5 days. During this time, a yellow precipitate that was formed
immediately after mixing of the reagents gradually dissolved and regenerated in a small amount
of unidentified brown crystals, which were filtered off. The filtrate was evaporated to dryness.
The resulting residue was rinsed with Et2O, collected by filtration and dried in vacuo to give
complex 6 as a pale-yellow crystalline solid. Yield: 31 mg (76%). Mp: >210 °C (dec.). IR (KBr,
ν/cm–1): 481(w), 517(s), 569(vw), 611(m), 627(m) (νP=S), 690(s), 708(s), 718(m), 747(m),
794(w), 998(w), 1026(vw), 1104(s), 1186(m), 1224(vw), 1280(vw), 1310(vw), 1334(vw),
1382(w), 1406(w), 1437(s), 1481(w), 1527(vw), 1588(br, m), 2928(w), 3053(m), 3148(br, w)
and 3220(br, w) (both νNH). Anal. Calcd for C44H32Cl2N2P2Pd2S4: С, 49.73; Н, 3.04; N, 2.64.
Found: C, 49.49; H, 3.09; N, 2.71%.
Mononuclear complex 7.
H
H
N
N
N
Pd
Cl
Cl
S
S
Ph2P
PPh2
S
S
A solution of PdCl2(NCPh)2 (14 mg, 0.036 mmol) in CH2Cl2 (2 mL) was added dropwise
to a solution of ligand 4 (28 mg, 0.036 mmol) in CH2Cl2 (3 mL). The resulting red solution was
left under ambient conditions for 1 day, partially evaporated to initiate precipitation of the target
product, and left for another 4 days. The precipitate obtained was collected by filtration, rinsed
with Et2O and dried in vacuo to give complex 7 as a dark-red crystalline solid. Yield: 25 mg
(73%). Mp: >200 °C (dec.). IR (KBr, ν/cm–1): 515(m), 597(vw), 614(w), 640(m) (νP=S), 692(s),
716(s), 749(w), 810(vw), 974(vw), 998(w), 1038(w), 1102(s), 1182(vw), 1214(w), 1276(w),
1308(w), 1424(sh, m), 1436(s), 1468(sh, m), 1479(m), 1538(br, s), 2923(vw), 3053(w), 3200(br,
vw) (νNH). Anal. Calcd for C43H33Cl2N3P2PdS4: С, 53.84; Н, 3.47; N, 4.38. Found: C, 53.65; H,
3.62; N, 4.60%.
4.3. X-ray diffraction
Crystals of complex 8 (C172H124N12P8Pd4S16 · 3.25(C5H9NO) · CHCl3, M = 3986.69) are
triclinic, space group P-1: a = 16.2564(16), b = 18.2164(18), c = 34.197(4) Å, α = 80.008(2), β =
83.310(2), γ = 64.148(2)°, V = 8965.6(16) Å3, Z = 2, dcalc = 1.477 gcm–3, µ(MoKα) = 7.57 сm–1,
F(000) = 4067. Intensities of 139667 reflections were measured at 120 K with a Bruker APEX2
DUO CCD diffractometer [λ(MoKα) = 0.71072Å, ω-scans, 2θ<56°], and 43288 independent
reflections [Rint = 0.1457] were used for further refinement. The structure was solved by the

13
ACCEPTED MANUSCRIPT
direct method and refined by the full-matrix least-squares technique against F2 in the anisotropic-
isotropic approximation. The positions of hydrogen atoms were calculated, and they were refined
in the isotropic approximation within the riding model. Note that the obtained crystals of
complex 8 contained solvate N-methyl-2-pyrrolidone molecules most of which had partial
occupancy or were disordered or even both. However, our attempts to model this disorder did
not improve the quality of the structural model. For the best one obtained, the refinement
converged to wR2 = 0.1896 and GOF = 0.997 for all the independent reflections (R1 = 0.0682
was calculated against F for 22835 observed reflections with I>2σ(I)). All calculations were
performed using SHELXTL PLUS 5.0. CCDC 1882961 contains the supplementary
crystallographic information for this paper [15].
Acknowledgements
This work was supported by the Grant of the President of the Russian Federation for young
scientists, project no. MK-238.2017.3, and Russian Foundation for Basic Research, project no.
16-03-00915.
The NMR and X-ray experiments were carried out using the equipment of Center for
Molecular Composition Studies of INEOS RAS.
Appendix A. Supplementary data
NMR spectra of ligand 5;
NMR monitoring of the reaction of ligand 4 with PdCl2(NCPh)2;
NMR spectra of complex 6;
Cif file of complex 8
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ACCEPTED MANUSCRIPT
m-Thiophosphorylaniline is used as a key precursor for new ditopic pincer ligands
Two pincer units in the resulting ligands are bridged by (hetero)aromatic spacers
The ligands obtained undergo site-selective cyclopalladation depending on the spacer
Dinculear S,C,S- and mononuclear S,N,S-complexes are readily obtained in high yields
Pyridine-based S,N,S-complex spontaneously converts to a tetrameric sulfide cluster