Pallada- and platinacycle complexes of phosphorus ylides; synthesis, X-ray characterization, theoretical and electrochemical studies and application of Pd(II) complexes as catalyst in Suzuki-Miyaura coupling reaction

Article abstract of DOI:10.1002/aoc.3850

The new unsymmetrical phosphonium salts [Ph₂PCH₂PPh₂CH₂C(O)C₆H₄R]Br (R= m-Br (S₁) and p-CN (S₂)) were synthesized in the reaction of 1,1-bis(diphenylphosphino)methane (dppm) and BrCH₂C(O)C₆H₄R (R= m-Br and p-CN) ketones, respectively. Further treatment with NEt₃ gave the α-keto stabilized phosphorus ylides Ph₂PCH₂PPh₂C(H)C(O)C₆H₄R (R= m-Br (Y₁) and p-CN (Y₂)). These ligands were reacted with [MCl₂(cod)] (M= Pd and Pt; cod= 1,5-cyclooctadiene) to give the pallada- and platinacycle complexes [MCl₂(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄R)] (M= Pd, R= m-Br (3); R= p-CN (4) and M= Pt, R= m-Br (5); R= p-CN (6)). Cyclic voltammetry, elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods were used for characterization of the obtained compounds. Further, the structure of complexes 3 and 4 were characterized crystallographically. Palladacycles 3 and 4 were proved to be excellent catalysts for the Suzuki-Miyaura coupling reactions of various aryl chlorides and arylboronic acids in mixed DMF/H₂O media. Also, the bonding situations between two interacted fragments [PtCl₂] and Y₁ and Y₂ ligands in platinacycles 5 and 6 were investigated based on DFT method by using NBO, EDA and ETS-NOCV analysis.

Full text of DOI:10.1002/aoc.3850

Received: 27 December 2016
DOI: 10.1002/aoc.3850
Revised: 16 March 2017
Accepted: 25 March 2017
F U L L PA P E R
Pallada‐ and platinacycle complexes of phosphorus ylides;
synthesis, X‐ray characterization, theoretical and electrochemical
studies and application of Pd(II) complexes as catalyst in Suzuki‐
Miyaura coupling reaction
Seyyed Javad Sabounchei1
| Asieh Sedghi1 | Ali Hashemi1 | Marjan Hosseinzadeh1 |
Mehdi Bayat1 | Robert W. Gable2
1 Faculty of Chemistry, Bu‐Ali Sina
University, Hamedan, 65174, Iran
2 School of Chemistry, University of
Melbourne, Victoria, 3010, Australia
The new unsymmetrical phosphonium salts [Ph2PCH2PPh2CH2C(O)C6H4R]Br
(R= m‐Br (S1) and p‐CN (S2)) were synthesized in the reaction of 1,1‐
bis(diphenylphosphino)methane (dppm) and BrCH2C(O)C6H4R (R= m‐Br and p‐
CN) ketones, respectively. Further treatment with NEt3 gave the α‐keto stabilized
phosphorus ylides Ph2PCH2PPh2C(H)C(O)C6H4R (R= m‐Br (Y1) and p‐CN
(Y2)). These ligands were reacted with [MCl2(cod)] (M= Pd and Pt; cod= 1,5‐
cyclooctadiene) to give the pallada‐ and platinacycle complexes
[MCl2(Ph2PCH2PPh2C(H)C(O)C6H4R)] (M= Pd, R= m‐Br (3); R= p‐CN (4) and
M= Pt, R= m‐Br (5); R= p‐CN (6)). Cyclic voltammetry, elemental analysis, IR
and NMR (1H, 13C and 31P) spectroscopic methods were used for characterization
of the obtained compounds. Further, the structure of complexes 3 and 4 were
characterized crystallographically. Palladacycles 3 and 4 were proved to be excel-
lent catalysts for the Suzuki‐Miyaura coupling reactions of various aryl chlorides
and arylboronic acids in mixed DMF/H2O media. Also, the bonding situations
between two interacted fragments [PtCl2] and Y1 and Y2 ligands in platinacycles
5 and 6 were investigated based on DFT method by using NBO, EDA and ETS‐
NOCV analysis.
Correspondence
Seyyed Javad Sabounchei, Faculty of
Chemistry, Bu‐Ali Sina University,
Hamedan, 65174, Iran.
Email: jsabounchei@yahoo.co.uk
KEYWORDS
DFT method, pallada‐ and platinacycle, phosphorus ylide, Suzuki‐Miyaura reaction, theoretical studies
1 | INTRODUCTION
The coordination behavior of these compounds towards
several metal ions has been studied and it was found that
Stabilized phosphorus ylides are an important class of com-
pounds that have attracted considerable interest because of
their value for a variety of industrial, biological and chemical
synthetic uses.[1–4] Unsymmetrical α‐keto stabilized ylides
derived from diphosphines have shown more useful applica-
tion in organometallic chemistry due to their ambidentate
character as ligands[5–9] Furthermore, they are valuable key
intermediates in metal‐mediated organic synthesis.[10,11]
phosphorus ylides can coordinate to metal ions in three
modes as depicted in Chart 1: monodentate (or unidentate),
bidentate (or chelating) and bridging (or bridging bidentate)
modes.
When a metal ion such as Hg(II) or Ag(I) interacts only
with the free P atom of phosphorus group, the coordination
structure is regarded as monodentate mode.[12,13] If the
coordination of ylide occurs through the Cα atom of ylidic
Appl Organometal Chem. 2017;e3850.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
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SABOUNCHEI ET AL.
to elucidate the physical and chemical nature of interactions.
We have now focused our attention to the synthesis, spectro-
scopic (IR and NMR) and electrochemical study of the new
pallada‐ and platinacycles complexes of phosphorus ylide.
2 | EXPERIMENTAL
2.1 | Materials and methods
The synthesis reaction of phosphorus ylides and their
Pd/Pt(II) complexes was carried out under dry nitrogen using
standard Schlenk techniques. 2,3′‐dibromoacetophenone, 2‐
bromo‐4′‐cyanoacetophenone and dppm were purchased
from commercial sources and used without further purifica-
tion. [MCl2(cod)] (M = Pd and Pt) complexes were prepared
according to the published procedures.[35] Toluene and
chloroform were used as reagent grade and dried over
Na/benzophenone and P2O5, respectively. Elemental analysis
was performed on a Leco, CHNS‐932 apparatus. The NMR
spectra (1H, 13C and 31P) were recorded on BrukerAvance
400 MHz, 250 MHz and Jeol 90 MHz spectrometers in
CDCl3 or DMSO‐d6 as solvents at 25 °C. IR spectra were
recorded on KBr pellets using a Shimadzu 435‐U 04
spectrophotometer in the region of 4000‐400 cm−1. Cyclic
voltammetry was performed using an Autolab model
PGSTAT 20 potentiostat/galvanostat. The working electrode
used in the voltammetry experiments was a glassy carbon
disc (1.8 mm2 area), and a platinum wire was used as the
counter electrode. The working electrode potentials were
measured versus the Ag/AgCl electrode (all electrodes were
purchased from AZAR Electrodes co.).
CHART 1 The possible bonding modes of phosphorus ylides to
metal M
group, it was also categorized in above mentioned coordina-
tion mode.[14] Though the ylides can coordinate to the metal
ions through the O atoms of carbonyl group, there are few
examples of O‐coordinated ylides which are known. Some
of these complexes include a hard and very oxophilic metal
center, such as Sn(IV)[15] or group 4 metal ions with high
oxidation number e.g. Ti(IV), Zr(IV) and Hf(IV).[16]
Bidentate (or chelating) coordination mode occurs when
a metal ion (for example Pd(II) or Cu(I)) interacts with two
P and C atoms of ylidic group to give the P, C‐chelated com-
plexes.[17,18] Although the P, O‐chelated coordination mode
was also possible, but to the best of our knowledge, it was
only observed in the Pd(II) complexes of a mixed
phosphine–β‐ketophosphorus ylide.[19] Finally, the bridging
coordination mode can be seen when a metal ion bound to
one phosphorus ylide through P atom and another metal ion
bound to the Cα or O atom.[20] The investigation of reactivity
and coordination chemistry of carbonyl stabilized ylides is an
important research field of our group.[12–14,17,18] Recently, we
reported the synthesis of palladium(II) complexes containing
such phosphorus ylides.[17,21–23] We aim to expand the scope
of these complexes to the new platinacycle complexes of
bidentate phosphorus ylides.
Pd(II) complexes bearing phosphine groups have been
extensively applied as efficient catalysts in some cross‐cou-
pling reactions.[21–27] Specifically, the Suzuki‐Miyaura reac-
tion which emerged as the most important and reliable
method for construction of functionalized biaryl, have been
catalysed with the P, C‐chelated Pd(II) complexes of such
phosphorus ylides.[28–31] Recently, it was reported a variety
of catalytic systems for the Suzuki‐Miyaura coupling reaction
using mixed aqueous media.[31–34] Application of
palladacycle complexes of phosphorus ylides as efficient cat-
alyst in Suzuki‐Miyaura coupling reactions of aryl chlorides
under relatively mild experimental conditions is one of the
purposes of this work. Although there is no X‐ray structure
available in this report to prove the molecular structures of
platinacycles, however DFT theoretical studies by using
NBO, EDA and ETS‐NOCV analysis have been performed
2.2 | Synthesis of phosphonium salts
General procedure: A chloroform solution (5 ml) of dppm
(0.5 mmol) and ketone (0.55 mmol) was stirred at room tem-
perature for 15 h. The resulting solution was concentrated to
ca. 3 ml under reduced pressure and then treated with diethyl
ether to precipitate phosphonium salt.
2.2.1 | Data for phosphonium salt
[Ph2PCH2PPh2CH2C(O)C6H4‐m‐Br]Br (S1)
Yield: 0.314 g (94%). Anal. Calcd for C33H28Br2OP2 (%): C,
59.84; H, 4.26. Found: C, 59.77; H, 4.22. M.p. 196–198 °C.
Selected IR absorption in KBr (cm−1) ν(CO): 1676. 1H
NMR (89.6 MHz, CDCl3) δH (ppm): 4.31 (d, 2H, PCH2P,
2
2JP–H = 12.23), 5.96 (d, 2H, PCH2CO, JP–H = 12.81),
7.30–7.99 (m, 24H, Ph). 31P NMR (36.26 MHz, CDCl3)
2
δP (ppm): −28.67 (d, PPh2, JP‐P = 62.37 Hz), 21.12 (d,
2
PCH2CO, JP‐P = 63.85 Hz). 13C NMR (62.90 MHz,
2
CDCl3) δC (ppm): 191.40 (d, CO, JP–C
= 5.85),
1
117.15–151.83 (m, Ph), 37.38 (d, CH2, JP–C = 60.38),

SABOUNCHEI ET AL.
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1
21.95 (dd, CH2, JP–C = 51.96, 34.47).2.2.2 Data for phos-
phonium salt [Ph2PCH2PPh2CH2C(O)C6H4‐p‐CN]Br (S2).
Yield: 0.301 g (98%). Anal. Calcd for C34H28BrNOP2
(%): C, 67.12; H, 4.64; N, 2.30. Found: C, 67.01; H, 4.51;
N, 2.41. M.p. 191–194 °C. Selected IR absorption in KBr
2.4 | Synthesis of the Pd/Pt(II) complexes
General procedure: To a dichloromethane solution of
[MCl2(cod)] (M = Pd or Pt) (0.5 mmol, 5 ml), a solution of
ylide (0.5 mmol) (5 ml, CH2Cl2) was added. The resulting
solution was stirred for 2 h at room temperature and then con-
centrated to a ca. 2 ml under reduced pressure and treated
with n‐hexane (15 ml) to afford the Pd(II) or Pt(II) complexes
of phosphorus ylide.
(cm−1) ν(CO): 1682. H NMR (250.13 MHz, CDCl3) δH
1
2
(ppm): 4.25 (d, 2H, PCH2P, JP–H = 14.75), 6.08 (d, 2H,
PCH2CO, JP–H = 12.75), 7.24–7.89 (m, 24H, Ph). 31P
2
NMR (202.45 MHz, CDCl3) δP (ppm): −25.83 (d, PPh2,
2JP‐P = 64.17 Hz), 24.41 (d, PCH2CO, JP‐P = 63.57 Hz).
2
13C NMR (62.90 MHz, CDCl3) δC (ppm): 191.66 (s, CO),
1
2.4.1 | Data for Pd(II) complex
[PdCl2(Ph2PCH2PPh2C(H)C(O)C6H4‐m‐Br)] (3)
117.13–137.95 (m, Ph), 36.90 (d, CH, JP–C = 62.40),
21.93 (dd, CH2, 1JP–C = 70.86, 35.29).
Yield: 0.303 g (80%). Anal. Calc. for C33H27BrCl2OP2Pd
(%): C, 52.24; H, 3.59. Found: C, 52.18; H, 3.62. M.p.
198–201 °C (dec). Selected IR absorption in KBr (cm−1
)
2.3 | Synthesis of phosphorus ylides
ν(CO): 1619. 1H NMR (89.60 MHz, DMSO‐d6) δH
(ppm): 4.65 (br, PCH2P, 2H), 5.98 (s, 1H, PCH),
7.25–8.31 (m, 24H, Ph). 31P NMR (36.26 MHz, DMSO‐d6)
General procedure: The resulted phosphonium salt was fur-
ther treated with triethyl amine (0.5 ml) in dry toluene. The
triethyl amine hydrobromide was filtered off. Concentration
of the toluene solution to ca. 3 ml and subsequent addition
of petroleum ether (20 ml) resulted in the precipitation of
phosphorus ylide.
2
δP (ppm): 26.73 (d, PPh2, JP‐P = 49.07 Hz), 38.04 (d,
PCH, 2JP‐P = 47.29 Hz). 13C NMR (62.90 MHz, DMSO‐d6)
δC (ppm): 195.80 (s, CO), 121.32–140.04 (m, Ph), 32.62 (d,
1
PCH, JP–C = 56.48 Hz).
2.3.1 | Data for phosphorus ylide
Ph2PCH2PPh2C(H)C(O)C6H4‐m‐Br (Y1)
2.4.2 | Data for Pd(II) complex
[PdCl2(Ph2PCH2PPh2C(H)C(O)C6H4‐p‐CN)] (4)
Yield: 0.234 g (80%). Anal. Calc. for C33H27BrOP2 (%): C,
68.17; H, 4.68 Found: C, 68.11; H, 4.59. M.p.
157–160 °C. Selected IR absorption in KBr (cm−1) ν(CO):
Yield: 0.248 g (90%). Anal. Calc. for C34H27NCl2OP2Pd (%):
C, 57.94; H, 3.86; N, 1.99. Found: C, 57.83; H, 3.82; N, 2.08.
M.p. 190–192 °C (dec). Selected IR absorption in KBr (cm
1
1
−1) ν(CO): 1620. H NMR (250.13 MHz, DMSO‐d6) δH
1572. H NMR (89.60 MHz, CDCl3) δH (ppm): 3.64 (d,
2
2H, PCH2P, JP–H = 14.06 Hz), 4.31 (br, 1H, PCH),
(ppm): 4.86 (t, PCH2P, 2H), 6.03 (s, 1H, PCH), 7.20–8.12
6.70–7.91 (m, 24H, Ph). 31P NMR (36.26 MHz, CDCl3)
(m, 24H, Ph). 31P NMR (101.24 MHz, DMSO‐d6) δP
2
2
δP (ppm): −26.82 (d, PPh2, JP‐P = 66.71 Hz), 14.53 (d,
(ppm): 27.51 (b, PPh2), 37.66 (d, PCH, JP‐P = 42.21 Hz).
2
PCH, JP‐P = 65.99 Hz. 13C NMR (62.90 MHz, CDCl3) δC
13C NMR (62.90 MHz, DMSO‐d6) δC (ppm): 196.12 (s,
CO), 115.03–141.73 (m, Ph), 33.43 (d, PCH,
1JP–C = 54.97 Hz).
(ppm): 183.07 (s, CO), 121.99–143.22 (m, Ph), 50.62 (d,
CH, 1JP–C = 111.39), 24.42 (dd, CH2, 1JP–C = 57.86, 32.07).
2.3.2 | Data for phosphorus ylide
Ph2PCH2PPh2C(H)C(O)C6H4‐p‐CN (Y2)
2.4.3 | Data for Pt(II) complex
[PtCl2(Ph2PCH2PPh2C(H)C(O)C6H4‐m‐Br)] (5)
Yield: 0.194 g (73%). Anal. Calc. for C34H27NOP2 (%): C,
77.41; H, 5.16; N, 2.66. Found: C, 77.38; H, 5.12; N, 2.72.
Yield: 0.305 g (72%). Anal. Calc. for C33H27BrCl2OP2Pt (%):
C, 46.77; H, 3.21. Found: C, 46.90; H, 3.34. M.p. 231–233 °C
(dec). Selected IR absorption in KBr (cm−1) ν(CO): 1634. 1H
NMR (250.13 MHz, CDCl3) δH (ppm): 4.77 (br, PCH2P, 2H),
5.56 (s, 1H, PCH, 3JPt‐H = 65.07 Hz), 7.05–8.29 (m, 24H, Ph).
31P NMR (101.24 MHz, CDCl3) δP (ppm): 3.91 (d, PPh2,
M.p. 149–153 °C. Selected IR absorption in KBr (cm−1
)
1
ν(CO): 1572. H NMR (500.13 MHz, CDCl3) δH (ppm):
2
3.68 (d, 2H, PCH2P, JP–H = 14.00 Hz), 4.33 (t, 1H, PCH),
7.27–7.90 (m, 24H, Ph). 31P NMR (202.45 MHz, CDCl3)
2
2
δP (ppm): −26.48 (d, PPh2, JP‐P = 64.18 Hz), 15.35 (d,
1JPt‐P = 3947.73 Hz, JP‐P = 36.85 Hz), 41.14 (d, PCH,
2
PCH, JP‐P = 63.98 Hz. 13C NMR (62.90 MHz, CDCl3) δC
2JP‐P = 36.97 Hz). 13C NMR (62.90 MHz, CDCl3) δC
(ppm): 194.47 (s, CO), 119.95–141.72 (m, Ph), 27.73 (d,
(ppm): 183.18 (s, CO), 127.40–144.76 (m, Ph), 45.62 (s,
CH), 25.35 (dd, CH2, 1JP–C = 59.03, 32.20).
PCH, JP‐C = 56.37 Hz).
1

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2.4.4 | Data for Pt(II) complex
[PtCl2(Ph2PCH2PPh2C(H)C(O)C6H4‐p‐CN)] (6)
2.7 | Typical procedure for the Suzuki‐
Miyaura coupling reaction
Yield: 0.311 g (79%). Anal. Calc. for C34H27NCl2OP2Pt (%):
C, 51.46; H, 3.43; N, 1.77. Found: C, 51.59; H, 3.57; N, 1.90.
General procedure: A mixture of aryl chloride (0.5 mmol),
arylboronic acid (0.75 mmol), palladacycle complex
(0.005 mmol) and K2CO3 (1 mmol) was heated at 110 °C
in DMF/H2O (2 ml, 1:1) for 6 h in the presence of air. The
reactions were monitored by thin‐layer chromatography
(TLC). The reaction mixture was then cooled to room tem-
perature. After completion of reaction, the mixture was
diluted with n‐hexane (15 ml) and water (15 ml). The organic
layer was washed with brine (15 ml) and dried over CaCl2.
The solvent was evaporated under reduced pressure and a
M.p. 218–220 °C (dec). Selected IR absorption in KBr (cm−1
)
ν(CO): 1601. 1H NMR (250.13 MHz, CDCl3) δH (ppm): 4.85
3
(dd, PCH2P, 2H), 5.58 (s, 1H, PCH, JPt‐H = 70.04 Hz),
6.98–8.04 (m, 24H, Ph). 31P NMR (101.24 MHz, CDCl3) δP
(ppm): 2.00 (d, PPh2, 1JPt‐P = 3921.02 Hz, 2JP‐P = 38.47 Hz),
2
39.62 (d, PCH, JP‐P = 39.48 Hz). 13C NMR (62.90 MHz,
CDCl3) δC (ppm): 197.17 (s, CO), 120.60–136.32 (m, Ph),
119.17 (s, CN), 31.92 (d, PCH, 1JP‐C = 53.46 Hz).
1
crude product was obtained, which was analyzed by H and
13C NMR.
2.5 | Crystallography
2.7.1 | Data for Ph‐Ph (7a)
Data collection for complex 3 was performed on an Oxford
Diffraction SuperNova diffractometer using mirror
monochromated Mo Kα radiation (λ = 0.71073 Å) at
130 K. Using Olex2,[36] the structure was solved with the
ShelXT[37] structure solution program using Direct Methods
and refined with the ShelXL[38] refinement package using
Least Squares minimization on F2. Gaussian absorption cor-
rections were applied to the data. All non‐hydrogen atoms
were refined with anisotropic displacement parameters, using
all data.
Also, Crystallographic data for complex 4 were collected
on an MAR345 dtb diffractometer equipped with image plate
detector using Mo Kα X‐ray radiation. The structure was
solved by direct methods using SHELXS‐97, and refined
using full‐matrix least‐squares method on F2, SHELXL‐97.
All non‐hydrogen atoms were refined anisotropically. Hydro-
gen atoms were added at ideal positions and refined using a
riding model.
1
M.p. 67–69 °C. H NMR (400.61 MHz, CDCl3) δH (ppm):
7.40–7.64 (m, 10H, phenyl). 13C NMR (100.62 MHz,
CDCl3) δC (ppm): 141.29, 128.79, 127.29, 127.21.
2.7.2 | Data for p‐CHO‐Ph‐Ph (7b)
1
M.p. 89–91 °C. H NMR (400.61 MHz, CDCl3) δH (ppm):
7.40–7.86 (m, 9H, phenyl), 9.98 (s, 1H, CHO). 13C NMR
(100.62 MHz, CDCl3) δC (ppm): 191.94 (s, CO), 147.23,
139.74, 135.22, 130.29, 129.03, 128.49, 127.71, 127.39.
2.7.3 | Data for p‐CH3O‐Ph‐Ph (7c)
1
M.p. 90–92 °C. H NMR (400.61 MHz, CDCl3) δH (ppm):
3.78 (s, 3H, OCH3), 6.89–7.49 (m, 9H, phenyl). 13C NMR
(100.62 MHz, CDCl3) δC (ppm): 159.15, 140.84, 133.79,
128.73, 128.17, 127.75, 126.75, 126.67, 114.30, 114.20,
55.36 (s, OCH3).
2.7.4 | Data for p‐CH3OC‐Ph‐Ph‐et (7d)
2.6 | Computational studies
M.p. 105–108 °C. 1H NMR (400.61 MHz, CDCl3) δH (ppm):
1.24 (t, 3H, CH3), 2.51 (s, 3H, CH3), 2.59 (q, 2H, CH2),
7.25–8.01 (m, 8H, phenyl). 13C NMR (100.62 MHz, CDCl3)
δC (ppm): 197.76 (s, CO), 154.74, 144.57, 137.18, 135.58,
129.3, 128.89, 128.49, 127.18, 126.90, 28.55 (s, CH2),
26.64 (s, CH3), 15.52 (s, CH3).
The geometries of the aforementioned Pt(II) complexes were
fully optimized at BP86[39,40]/def2‐SVP[41] level of theory. It
has been shown that BP86 is a suitable level for calculation
of bonding situation between the M ← L in such as these
complexes.[42–50] All calculations were performed using the
Gaussian 09 set of programs.[51] NBO analyses[52] were also
carried out with the internal model GAUSSIAN 09. For
bonding analyses between two fragment (Ylide and PtCl2),
the terms of energy decomposition analysis (EDA) were car-
ried out at BP86/TZ2P (ZORA)//BP86/def2‐TZVPP with C1
symmetry. The basis sets for all elements have triple‐ζ
quality augmented by one set of polarization functions
(ADF basis set TZ2P (ZORA)) with the program package
ADF2009.01.
2.7.5 | Data for p‐CH3‐Ph‐Ph (7e)
M. p. 51–53 °C. 1H NMR (89.61 MHz, CDCl3) δH
(ppm): 2.61 (S, 3H, CH3), 7.46–8.09 (m, 9H, phenyl).
13C NMR (100.62 MHz, CDCl3) δC (ppm): 137.60,
137.46, 134.67, 129.73, 129.09, 128.76, 127.85, 126.85,
126.77, 21.27 (s, CH3).

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5 of 15
Thus, the obtained IR data indicates that the chelation of
ylide to Pd(II) and Pt(II) occurs through the ylidic carbon
atom and PPh2 group (see supplementary data).[17,20]
The 31P NMR spectra of phosphonium salts S1 and S2
show two doublets around 21, −28 and 24, −25 ppm, which
3 | RESULTS AND DISCUSSION
3.1 | Synthesis
Reaction of diphosphine Ph2PCH2PPh2 with 1 equiv. of 2,3′‐
dibromoacetophenone or 2‐bromo‐4′‐cyanoacetophenone
gave the new phosphonium salts S1 and S2. Further treatment
of these salts with triethyl amine led to elimination of HBr
and formation of new unsymmetrical phosphorus ylides Y1
and Y2. Reaction of these ligands with [MCl2(cod)]
(M = Pd and Pt) in equimolar ratio yielded the new P, C‐
chelated pallada‐ and platinacycle complexes 3–6 (Scheme 1).
are assigned to the PCH and PPh2 groups, respectively. In 31
P
NMR spectra of ylides Y1 and Y2, the phosphonium group of
these compounds shows upfield shifts compared to that of
parent phosphonium salts. These peaks were shifted to
around 14, −26 and 15, −26 ppm, respectively, consistent
with some increase of electron density in the P = C bonds.
The 31P chemical shift values for complexes 3–6 appear to
be shifted to downfield with respect to phosphorus ylides
Y1 and Y2, indicating that coordination of the ylide has been
occurred. The 31P NMR spectra of palladacycles 3 and 4
exhibit two doublets around 26, 38 and 27, 37 ppm, which
are assigned to the PPh2 and PCH groups, respectively.
Whereas, the 31P NMR spectra of platinacycles 5 and 6 show
these peaks around 41, 4 and 40, 2 ppm along with two
satellite peaks due to 195Pt‐31P coupling (see supplementary
data).
3.2 | Spectroscopy
The structure of products was characterized successfully by
1H, 13C and 31P NMR spectroscopic methods and other con-
ventional techniques such as IR and elemental analysis.
Table 1 shows the brief summary of these data.
Also, the exact structure of complexes 3 and 4 with
atomic resolution were being unequivocally determined by
single crystal X‐ray diffraction technique. The CHN elemen-
tal analysis of pallada‐ and platinacycle complexes indicates a
1:1 stoichiometry between the MCl2 (M = Pd and Pt) and
phosphorus ylide.
The ν(CO) band in the IR spectra of phosphorus ylides
Y1 and Y2 were observed at lower frequencies compared to
the related phosphonium salts S1 and S2, indicating formation
of P = C double bond and decrease of C = O bond order.
Coordination of ylide through the carbon atom (chelating
mode) causes an increase in the ν(CO) frequency, while for
O‐coordination a lowering shift for this frequency is
expected.[53] The ν (CO) in IR spectra of complexes 3–6
occurs around 1600–1630 cm−1 and shows significantly shift
to higher frequency than those of related phosphorus ylides.
Also, the 1H NMR spectra show all the expected
1
resonances of compounds S1, S2, Y1, Y2 and 3–6. The H
NMR spectra of ylides Y1 and Y2 show an upfield shift for
the CH signals compared to the those of phosphonium salts
S1 and S2 indicating that synthesis of the ylides has occurred.
The 1H chemical shift values for complexes 3–6 appear to be
shifted to downfield with respect to the parent ylide, as a
consequence of P, C‐coordination character of the ylide.
Similar behavior was observed earlier in the case of ylide
complexes of copper(I) chlorides.[18]
In the 13C NMR spectra of ylides Y1 and Y2, a downfield
shift of the signals due to the ylidic carbon is also observed
and it was attributed to the change in hybridization of the
ylidic carbon atom. Further, the signals due to the carbonyl
group in 13C NMR spectra of ylides Y1 and Y2 shifted to
higher field compared to the parent phosphonium salts. The
most important aspect of 13C NMR spectra of these
complexes is the downfield shift of signals due to the
carbonyl group. The 13C NMR spectra of complexes 3–6
show the characteristic peaks of carbonyl group around
196 ppm, compare to 183 ppm for the same carbon in the
parent free ylides, indicating a much lower shielding of the
carbon of the CO group in these complexes (see supplemen-
tary data). Thus, the spectral data indicate the bidentate coor-
dination of the ylides through both the phosphine group and
the ylidic carbon atom.
3.3 | Crystallography
Suitable single crystals of complexes 3 and 4 were grown by
vapor diffusion of methanol into DMSO solution. The molec-
ular structures of 3 and 4 were shown in Figure 1 and
SCHEME 1 Synthesis of compounds S1, S2, Y1, Y2 and 36‐

6 of 15
SABOUNCHEI ET AL.
TABLE 1 Spectroscopic data for compounds S1, S2, Y1, Y2 and 3–6
Compound
IR; ν(CO) cm−1
1H NMR; δ(PCH) ppm
13C NMR; δ(CO) ppm
31P NMR; δ(PCH) and (PPh2) ppm
S1
S2
Y1
Y2
3
1676
1682
1572
1572
1619
1620
1634
1601
5.96
6.08
4.31
4.33
6.02
6.03
5.56
5.58
191.40
191.66
183.07
183.18
195.80
196.12
194.47
197.17
21.12, −28.67
24.41, −25.83
14.53, −26.82
15.35, −26.48
38.04, 26.73
37.66, 27.51
41.14, 3.91
4
5
6
39.62, 2.00
FIGURE 1 ORTEP view of X‐ray crystal structure 3
Figure 2, respectively. Relevant parameters concerning data
collection and refinement were given in Table 2. Selected
bond distances and angles for the unit cells of 3 and 4 are
displayed in Table 3.
FIGURE 2 ORTEP view of X‐ray crystal structure 4
Hydrogen atoms of complex 3 were located in ideal posi-
tions. There were two independent molecules in the asymmet-
ric unit. For one of the molecules, the 3‐bromophenylethanone
group and one of the phenyl rings were found to be disordered
and no evidence of disorder was seen in the rest of the mole-
cule. The main difference between them is in the orientation
of the 3‐bromophenylethanone group, with the torsion angle
O1 ‐ C2…C5 ‐ Br1 being −177.51(19)°, for molecule 1 and
the torsion angle O2 ‐ C35…C38 ‐ Br2 being −22.6(18)° for
molecule 2. The dihedral angles of the keto group with the aro-
matic rings are 2.79(15)° and 21.0(5)°, respectively.
For molecule 1 there are three weak intramolecular C‐
H…Cl interactions, between hydrogen atoms on the aromatic
rings and the coordinated chloride. All other C‐H…X inter-
actions are intermolecular interactions that link the molecules
into a 3D network. Refinement was carried out with the
atoms of both groups distributed over 2 positions, the geom-
etry of each component being restrained to be equal. The
final occupancy factors were 0.8057(17) and 0.1943(17),
for the 3‐bromophenylethanone group, and 0.575(19) and
0.425(19).
The coordinates of the two molecules were chosen such
that C1 and C34 had both the S configuration. Both Pd atoms
are in a tetrahedrally distorted square planar environment,
with the P‐Pd‐Cl and the C‐Pd‐Cl angles being significantly
less than 180°. This distortion is more pronounced for mole-
cule 1 than molecule 2. The Pd‐containing five‐membered
rings both adopts a half‐chair conformation, with C1 lying
above (0.507(3) Å) and P1 lying below (−0.368(3) Å) the
plane of the other 3 atoms. For molecule 2, C34 lies below
(−0.269(3) Å) and P1 lies above (0.487(3) Å) the plane.
3.4 | Theoretical studies
In 2014, Samiee and his co‐worker confirmed that the struc-
ture of [R2P(CH2)nPRC(H)C(O)R)MX2] (R = Me, Ph;
M = Ni, Pt and Pd and X = Cl, Br, I; n = 1, 2, 3) complexes
are square planar. In these structures, two halogen atoms are
oriented in cis position.[54] Thus according to this reports, we
considered the square planar structures for [Y1PtCl2] and

SABOUNCHEI ET AL.
7 of 15
TABLE 2 Crystal data and structure refinement for 3 and 4
Compound 3
C33H27Cl2BrOP2Pd
Compound 4
C34H27Cl2NOP2Pd
Empirical formula
Formula weight
T [K]
758.69
704.81
130.00(10)
Triclinic
P‐1
293
Crystal system
Space group
a [Å]
Monoclinic
C2/c
11.2716(3)
16.2651(4)
16.9243(3)
84.1776(16)
83.9247(16)
84.684(2)
3058.92(12)
4
23.033 (5)
15.327 (3)
24.769 (9)
b [Å]
c [Å]
α [°]
Β [°]
134.500 (15)
γ [°]
V [Å3]
6237 (3)
8
Z
Dc [mg m¯3]
μ [mm ¯1]
1.647
1.501
0.90
2.218
F(000)
1512.0
2848
λ (Mo‐Kα)
2θ range [°]
Index ranges
Refl. Collected
Independent reflections
Data/restr./param.
Goodness‐of‐fit on F2
R1/wR2[I > 2σ(I)]
0.71073
5.6–64.5
0.71073
3.2–52.0
−15 ≤ h ≤ 16, −23 ≤ k ≤ 24, −25 ≤ l ≤ 23
−28 ≤ h ≤ 26, −18 ≤ k ≤ 18, −30 ≤ l ≤ 30
45890
19650
19733 [Rint = 0.0226]
19733/35/765
1.022
6108 [Rint = 0.035]
6108/0/379
1.03
0.0290/0.0648
0.030/0.073
[Y2PtCl2] (Y1 = Ph2PCH2PPh2C(H)C(O)C6H4‐m‐Br and
Y2 = Ph2PCH2PPh2C(H)C(O)C6H4‐p‐CN) complexes. A
theoretical study on structure and nature of bond in [Y1PtCl2]
and [Y2PtCl2] complexes with square planar structures have
been reported at the BP86 level using def2‐SVP basis set.
The optimized structures of [Y1PtCl2] and [Y2PtCl2] com-
plexes at the BP86/def2‐SVP level of theory are given in
Figure 3, and important bond lengths and bond angles
extracted from optimized geometry are given in Table 4.
The result show that the optimized bond lengths and bond
angles for [Y1PtCl2] and [Y2PtCl2] are same and these data
are in good agreement with those which recently reported
TABLE 3 Selected bond lengths [Å] and bond angles [°] for 3 and 4
Compound 3
Compound 4
Bond distances
Pd1‐Cl1
2.3756(4)
2.3383(4)
2.2153(5)
2.1075(17)
1.228(2)
Pd1‐Cl1
Pd1‐Cl2
Pd1‐P1
Pd1‐C2
O1‐C3
C2‐C3
P2‐C2
2.3747 (7)
2.3477 (7)
2.2341 (6)
2.095 (2)
1.231 (3)
1.486 (3)
1.787 (2)
1.866 (2)
Pd1‐Cl2
Pd1‐P2
Pd1‐C1
O1‐C2
C1‐C2
1.496(3)
P1‐C1
1.7817(17)
1.8442(17)
with
Samiee
and
his
co‐worker
for
P2‐C21
P1‐C1
[(Ph2P(CH2)2PPh2CHC(O)CH3)PtCl2]
complexes
(see
Table 4).[54]
Bond angles
Cl2‐Pd1‐Cl1
C1‐Pd1‐P2
C1‐Pd1‐Cl1
P2‐Pd1‐Cl1
P2‐Pd1‐Cl2
92.509(16)
89.90(5)
Cl2‐Pd1‐Cl1
C2‐Pd1‐P1
C2‐Pd1‐Cl1
P1‐Pd1‐Cl1
P1‐Pd1‐Cl2
92.71 (3)
88.70 (6)
91.16 (7)
170.97 (2)
88.37 (3)
For studying the nature of metal–ligand bond and/or
possible interactions in [Y1PtCl2] and [Y2PtCl2] complexes,
the NBO analysis was performed.[51] The values of the
Wiberg (WBI) and partial charges on Pt, C and Cl atoms
involved in the bonding interactions between PtCl2 and
Y1 and Y2 fragments in [Y1PtCl2] and [Y2PtCl2]
91.10(5)
170.607(18)
87.343(16)

8 of 15
SABOUNCHEI ET AL.
The result showed that the calculated partial charge (q) on
both the Pt and C atoms in the Pt − C bonds is negative. Also,
the negative value of q(C) is greater than that for q(Pt) (see
Table 5). On the other hand, the negative values of the total
charge of [PtCl2] fragments show the charge transfer about
0.85 occurred from Y1 and Y2 ligands to [PtCl2] fragments
in the complexes. A second‐order perturbation theory analy-
sis of the Fock matrix was carried out to evaluate the donor–
acceptor interactions on the base of NBO analysis. The
values of donor‐acceptor interactions in [Y1PtCl2] and
[Y2PtCl2] complexes are given in Tables 6.
The results showed that in the aforementioned complexes,
the important donor–acceptor interactions in the case of Pt–C
bond were carried out from the σ(Pt–C) and σ(Pt–P) as donors
to σ*(Pt–P) and σ*(Pt–C) as acceptors (See Table 6).
for better analysis of the nature of the Pt–C bonding
between the Y1 and Y2 and [PtCl2] fragments in [Y1PtCl2]
and [Y2PtCl2] complexes, the quantum chemical calcula-
tions in the terms of energy‐decomposition analysis at the
BP86‐D3/TZ2P(ZORA)//BP86/def2‐SVP with C1 symmetry
by using the program package ADF2009.01 were carried
out. The results of the EDA analyses for aforementioned
complexes are given in Table 7.
As can be seen, the ΔEint between two interacted frag-
ments in both [Y1PtCl2] and [Y2PtCl2] complexes are
156.81 and 153.80 kcal mol−1respectively (See Table 7).
The breakdown of the ΔEint values into the Pauli repulsion
(ΔEPauli) and the three attractive components (ΔEelstat, ΔEor
and ΔEdis) show that roughly 58% of total interaction comes
from the electrostatic attraction (ΔEelstat) while ~37% comes
from the orbital term (ΔEorb) and the remaining (4.7%) con-
cern to ΔEdispersion. Thus the values of ΔEelstat showed that
the nature of Pd–C bonding in both [Y1PtCl2] and [Y2PtCl2]
FIGURE 3 Optimized structures of the [Y1PtCl2] (a) and [Y2PtCl2]
(b) complexes at BP86/SVP level of theory
complexes as well as total charge of Y1 and Y2 fragments
were also evaluated through natural population analysis and
are given in Table 5.
complexes
are
more
electrostatic[Bis − NHC(R) !
Si(Br)2H2]. These data are in good agreement with the
TABLE 4 Selected bond lengths (a°) and bond angles (°) of [Y1PtCl2] and [Y2PtCl2] complexes at the BP86/def2‐SVP level of theory
[(Ph2P(CH2)2PPh2
[Y1PtCl2]
[Y2PtCl2]
CHC(O)CH3)PtCl2]a
Bond lengths
Value
Bond lengths
Pt(63)‐P(1)
Value
Value
Pt(63)‐P(1)
2.241
2.117
2.399
2.385
Value
2.242
2.117
2.399
2.385
Value
2.352
Pt(63)‐C(14)
Pt(63)‐cl(65)
Pt(63)‐cl(64)
Bond angles
Pt(63)‐C(14)
Pt(63)‐cl(65)
Pt(63)‐cl(64)
2.121
2.461
2.454
Bond angles
Value
Cl(65)‐Pt(63)‐P(1)
Cl(64)‐Pt(63)‐C(14)
C (14)‐Pt(63)‐P(1)
Cl(64)‐Pt(63)‐cl(65)
172.23
175.95
90.922
91.614
Cl(65)‐Pt(63)‐P(1)
Cl(64)‐Pt(63)‐C(14)
C (14)‐Pt(63)‐P(1)
Cl(64)‐Pt(63)‐ cl(65)
171.19
176.40
91.32
174.84
170.98
97.67
91.46
91.09
aSee reference.[55]

SABOUNCHEI ET AL.
9 of 15
TABLE 5 Wiberg bond indices(WBI) of Pt − C and Pt‐cl bonds and natural charges of Pt, C and cl atoms as well as total charge of Y1 and Y2
fragments bonds in the complexes studied here at BP86/def2‐SVP level of theory
[Y1PtCl2]
[Y2PtCl2]
WBIs
NPA
Pt‐C
Pt‐cl
0.49
0.71
0.49
0.71
Pt
C
P
Y1
Y2
‐0.015
‐0.88
1.58(1.14)
0.85
‐
‐0.013
‐0.88
1.59(1.14)
‐
0.85
TABLE 6 The most important donor ! acceptor interactions energy concern to Pt─C bonds in the complexes studied here at BP86/def2‐SVP level
of theory
Donor
Acceptor
Pt(63)
Type
E2 (kcal/mol) [Y1PtCl2]
E2 (kcal/mol) [Y2PtCl2]
P(1) − Pt(63)
P(1) − Pt(63)
P(1) − Pt(63)
C(14) − Pt(63)
C(14) − Pt(63)
C(14) − Pt(63)
C(14) − Pt(63)
σ ! Lp*
σ ! σ*
σ ! σ*
σ ! Lp*
σ ! σ*
σ ! σ*
σ ! σ*
4.18
9.78
4.29
9.98
P(1) − Pt(63)
C(14) − Pt(63)
Pt(63)
30.27
10.72
34.53
18.64
10.33
30.40
10.76
34.42
18.83
10.67
P(1) − Pt(63)
P(2) − C(8)
C(14) − C(16)
TABLE 7 EDA analysis (BP86/TZ2P(ZORA)//BP86/def2‐SVP) of [Y1PtCl2] and [Y2PtCl2] complexes with the C1 symmetry
Compound name
ΔE(int)a
ΔE(pauli)
ΔE(elstate)
ΔE(orb)
ΔE(disp)
[Y1PtCl2]
[Y2PtCl2]
−156.81
−153.80
350.87
351.59
−295.40(58.18)
−295.11(58.16)
−188.43(37.14)
−188.39(37.13)
−23.85(4.7)
−23.88(4.7)
aThe value in parenthesis gives the percentage contribution to the total orbital interactions ΔE(orb).
results of NBO analysis which shows charge transfer of
about 0.85 from Y1 and Y2 to [PtCl2] fragment (see
Table 6) and the WBI value of 0.49 for Pt–C bonds in the
complexes.
(Y1 and Y2) in [Y1PtCl2] and [Y2PtCl2] complexes is
negligible.
3.5 | Cyclic voltammetry
The covalent bonding between the [PtCl2] fragment and
Y1 and Y2 Ligands in [Y1PtCl2] and [Y2PtCl2] complexes
becomes visible by the calculated deformation densities Δρ.
Figure 4 shows the important deformation densities Δρ and
the associated energy values which provide about 90% of
the overall orbital interactions for the complex. As it is illus-
trated in Figure 4a and 4b, the dominant terms of ΔEorb for
[Y1PtCl2] and [Y2PtCl2] complexes arise from Δρ1 and
Δρ2, showing σ donation from C(ylide) and P atoms of
Y1 and Y2 fragments to [PtCl2] in [Y1PtCl2] and [Y2PtCl2]
complexes.
Also Figure 4c, d, e, and f display the deformation den-
sity Δρ3, Δρ4, Δρ5 and Δρ6 which show the π‐back dona-
tion from the [PtCl2] fragment to Y1 and Y2 ligand in latter
complexes. In the above theoretical studies, the effect of R
group (R = Br or CN) substituted on aromatic part of ylides
The electrochemical behaviors of the free ylides, Y1 and Y2,
and their related Pd(II) and Pt(II) complexes, 3–6, were
studied by cyclic voltammetry. CV curves of the all com-
pounds at a 50 mVs−1 scan rate in acetonitrile solutions
(1 mM) are given in Figure 5. The reduction of Pd(II)/Pd(0)
was observed for the Pd(II) complexes and the reduction of
Pt(II)/Pt(0) for the Pt(II) complexes.
Figure 5 shows two cathodic peaks for the ylides Y1 and
Y2, C1 and C2, at – 1.00 and – 0.98 V versus Ag/AgCl,
respectively. Under the same conditions, the cyclic voltam-
mogram of a 1 mM solution of the complexes, showed irre-
versible electron transfer. At a scan rate of 50 mVs−1, there
were two cathodic peaks for 3, C3 and CY3, at – 0.91 and
– 0.58 V and one cathodic peak for 5, C5, at – 0.89 V corre-
sponding to the redox pair Pd(II)/Pd(0), the reduction of

10 of 15
SABOUNCHEI ET AL.
FIGURE 4 (Continued)
complexes is expected to take place in separate one‐electron
steps[55,56,60] and this might be achieved via manipulation of
the thermodynamics or electrode kinetics of either step by cor-
rect choice of the experimental conditions. Under our experi-
mental conditions, the Pd(I) complexes are unstable. Thus
peaks C3 and C4 in Figure 5 corresponds to a two‐electron
reduction of the Pd(II) complex which is a consequence of
the thermodynamic instability of the intermediate one‐
electron product under our experimental conditions. A com-
parison of curves a and b with curves c and d in Figure 5
clearly confirms the presence of Pd(II) and Pt(II) centers in
the complexes with different chemical environments.
FIGURE 4 Deformation densities (Δρ) associated with the most
important orbital interactions in [Y1PtCl2] and [Y2PtCl2] complexes.
Note that the color in this figure denotes the charge flow, which is from
the red to the blue region
ylide Y1 and the redox pair Pt(II)/Pt(0), respectively
(Figure 5, curves a and b). This behavior is similar to that
reported previously by Champness et al.,[55] Batchelor
et al[56] and Kvam et al.[57] voltammetric studies of various
types of Pd(II) and Pt(II) complexes in aprotic solvents.
The cyclic voltammogram of 6 shows one irreversible
reduction peak, C6, at – 0.72 V corresponding to the redox pair
Pt(II)/Pt(0) (Figure 5, curve c). Pt(I) and Pt(III) complexes are
noted for instability and any reduction or oxidation processes
centralized on metal orbitals of Pt(II) complexes typically
exhibit irreversible behavior.[57,58] In 4, such as 3, peak C4
(− 0.77 V) is assigned to the two electron reduction of Pd(II)
center in the complex and the second reduction peak, CY2
(− 0.49 V), is related to the reduction of ylide Y2 (Figure 5,
curve d).[17,59] The overall two‐electron reduction of the Pd(II)
3.6 | Suzuki‐Miyaura coupling reaction of aryl
chlorides
The catalytic activity of palladacycles 3 and 4 in Suzuki‐
Miyaura coupling reaction was then examined. Initially, we
carried out a model reaction to optimize the reaction

SABOUNCHEI ET AL.
11 of 15
coupling reaction gave slightly lower yield of product and
the reaction resulted in negligible yield of coupled product
when the catalyst loading decreased to 0.0005 mmol
(Table 8, entries 12 and 13). A control experiment showed
that the reaction fails in blank run (in the absence of Pd‐cat-
alyst) and the coupling reaction did not occur during 6 h
(Table 8, entry 14). Also, excessive amount of catalyst
increased the yield significantly (Table 8, entry 15). How-
ever, with respect to the economic aspect, 0.005 mmol of cat-
alyst was chosen as the best catalyst loading.
Finally, the reactions were carried out at different temper-
atures. Decreasing the temperature of reactions has led to the
fall of the yields and increasing the reaction time to comple-
tion of reactions (Table 8, entries 16 and 17). Thus, the opti-
mum condition obtained for Suzuki‐Miyaura coupling
reaction consisting the DMF/H2O as solvent, K2CO3 as base,
0.005 mmol of palladacycle 3 as catalyst and reaction at
110 °C for 6 h.
Using the optimized reaction conditions, palladacycles 3
and 4 were applied in reaction of various functionalized aryl
chlorides bearing both electron‐donating to electron‐with-
drawing groups with phenylboronic acid. Aryl chlorides were
converted into the corresponding coupled products in high
yields (Table 9). Conversely, increasing electron density on
the aryl chlorides lowered the catalyst activity. That is, excel-
lent yields are achieved when phenylboronic acid reacted
with aryl chlorides bearing electron‐withdrawing substituent
‐CHO and ‐COCH3 (Table 9, entries 1 and 2). Deactivated
aryl chlorides 4‐chlorotoluene and 4‐chloroanisol gave lower
yields indicating that the reaction was sensitive to the electron
density on the aryl chlorides (Table 9, entries 4 and 5). The
reaction of electronically neutral chlorobenzene with
phenylboronic acid also produced good amounts of the prod-
uct (Table 9, entry 3). As can be seen in Table 9, we observed
that in all cross‐coupling reactions catalyst 3 and 4 had
approximately same catalytic activities. It seems that
palladacycles 3 and 4 produce similar catalytically active
species in reactions, since the m‐Br or p‐CN substituents
on the end of the aryl group in phosphorus ylide moiety
could not affect significantly the release of catalitically
active species.
To extend the scope of our work, we next investigated the
coupling reaction of aryl chloride substrates with ethyl
substituted phenylboronic acid. As expected, electron‐donat-
ing substituent on arylboronic acid has decreasing effect on
the yield of reaction (Table 9, entries 6–10). However, cou-
pling reaction of activated aryl chlorides such as 4‐
chloroacetophenone gave the coupled boronic acid deriva-
tives in higher yields (Table 9, entry 10).
To evaluate the homogeneous or heterogeneous nature of
the active species, we carried out the mercury drop test.[61]
Since mercury leads to amalgamation of the surface of a het-
erogeneous catalyst, and in contrast, Hg(0) is not expected to
FIGURE 5 Cyclic voltammograms of 1.0 mM solutions of the
ligands and complexes in acetonitrile, containing 0.1 M tetra‐n‐
butylammonium perchlorate (Bu4NClO4) as supporting electrolyte, at
Pt electrode. Scan rates: 50 mV s‐1; t = 25 ̊C
conditions including base, solvent, temperature and catalyst
loading (Table 8). Reaction of phenylboronic acid with chlo-
robenzene in DMF/H2O (1:1) at 110 °C in the presence of
K3PO4 (1 mmol) and 0.05 mmol of catalyst 3 was chosen
as model reaction. The reaction led to formation of coupled
product in 70% yield (Table 8, entry 1). Then, a series of
experiments was performed to find optimum conditions.
At the first stage of optimization, we study the effect of
base and solvent on the reaction. Since the solubility and
basicity of base strongly depend on the solvent used, these
two parameters are closely connected. This optimization
was done with commonly used bases and solvents, including
organic and inorganic bases and aqueous protic and aprotic
solvents. Coupling reactions carried out in presence of
K2CO3 and K3PO4 give the desired coupling product in mod-
erate to high yields (Table 8, entries 2, 5 and 1, 4). However,
the reactions in presence of NEt3 did not proceed efficiently
even after prolonged stirring at reflux temperature of solvents
(Table 8, entries 6 and 9). Among the tested aqueous sol-
vents, DMF/H2O gave higher yields of coupleld product.
Also, the reactions in water and non‐aqueous DMF led to
lower yields, indicating the important role of solubility of
base in such catalytic systems (Table 8, entries 10 and 11).
Next, we investigate the effect of catalyst loading on the
reaction. As expected, varying the catalyst loading has a sig-
nificant effect on the performance of the catalyst. When the
loading of palladacycle 3 decreased to 0.005 mmol, the

12 of 15
SABOUNCHEI ET AL.
TABLE 8 Optimizations for the Suzuki‐Miyaura coupling reactiona
Entry
Base
Solvent
Catalyst loading (mmol)
Temp. (°C)
Yield (%)b
1
K3PO4
K2CO3
NEt3
DMF/H2O
DMF/H2O
DMF/H2O
Methanol/H2O
Methanol/H2O
Methanol/H2O
Toluene/H2O
Toluene/H2O
Toluene/H2O
H2O
0.05
0.05
110
110
110
70
70
77
58
47
51
45
54
35
40
44
61
70
32
‐
2
3
0.05
4
K3PO4
K2CO3
NEt3
0.05
5
0.05
70
6
0.05
70
7
K3PO4
K2CO3
NEt3
0.05
90
8
0.05
90
9
0.05
90
10
11
12
13
14
15
16
17
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
0.05
100
130
110
110
110
110
65
DMF
0.05
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
0.005
0.0005
None
0.1
92
58
40
0.005
0.005
25
aReaction conditions for Suzuki‐Miyaura coupling reaction: chlorobenzene (0.5 mmol), phenylboronic acid (0.75 mmol), base (1 mmol), solvent (2 mL), catalyst 3, in the air.
bIsolated yield.
have a poisoning effect on homogeneous palladium com-
plexes, the results of desired test help us to determine the
nature of the active species.[62] Addition of a drop of mercury
to the reaction mixture at t = 0 did not affect the conversion
of the reaction, which suggests that amalgamation had not
occurred and the catalysis was homogeneous in nature.
As can be seen in Table 9, by using aryl chlorides good
amounts of functionalized biaryl derivatives are yielded.
TABLE 9 Suzuki‐Miyaura coupling reaction of aryl chlorides catalyzed by palladacycles 3 and 4a
Entry
R
R’
Product
Yield (%)b
1
2
CHO
COCH3
H
H
p‐OHC‐Ph‐Ph
p‐CH3OC‐Ph‐Ph
Ph‐Ph
83, 85
79, 81
70, 68
67, 69
61, 62
78, 80
75, 73
66, 65
61, 64
57, 60
H
3
H
4
Me
H
p‐me‐Ph‐Ph
5
OCH3
CHO
COCH3
H
H
p‐CH3O‐Ph‐Ph
p‐OHC‐Ph‐Ph‐et
p‐CH3OC‐Ph‐Ph‐et
Ph‐Ph‐et
6
Et
Et
Et
Et
Et
7
8
9
Me
p‐me‐Ph‐Ph‐et
p‐CH3O‐Ph‐Ph‐et
10
OCH3
aReaction conditions for Suzuki‐Miyaura coupling reaction: aryl chloride (0.5 mmol), arylboronic acid (0.75 mmol), K2CO3 (1 mmol), DMF/H2O (2 ml), catalyst 3 or 4
(0.005 mmol), in the air.
bIsolated yields for coupling reactions in presence of palladacycles 3 and 4, respectively.

SABOUNCHEI ET AL.
13 of 15
The higher C–Cl bond dissociation energy compared with C–
Br and C–I bonds disfavors oxidative addition step in cata-
lytic coupling reactions.[63] However, the ideal substrates
for coupling reactions are aryl chlorides, since they are
cheaper and more widely available than their bromide or
iodide analogous. Table 10 shows a comparison between
the efficiency of this catalytic system in Suzuki‐Miyaura cou-
pling reaction of aryl chlorides and other catalytic systems.
The results showed that the most active palladacycles, N‐het-
erocyclic carbenes (NHCs) and pyridine‐enhanced
precatalyst preparation stabilization and initiation (PEPPSI)‐
type Pd complexes need to be used in high loadings and
showed lower activity with aryl chloride substrates.[64–72]
From an industrial view point, the low catalyst loading and
short reaction time make this palladacycle as an ideal catalyst
for the Suzuki‐Miyaura coupling reaction.
4 | CONCLUSIONS
In summary, we report the synthesis and characterization of
new phosphinium salts S1 and S2, phosphorus ylides Y1
and Y2, and pallada‐ and platinacycle 3–6. The palladacycles
3 and 4 were characterized fully by spectroscopic methods as
well as X‐ray crystallography method. Results showed that
chelation of ylide through the ylidic carbon atom and phos-
phine group afforded a five‐membered ring. Also, the cata-
lytic activity of palladacycles 3 and 4 towards Suzuki‐
Miyaura coupling reaction was investigated. Results showed
that the coupling reaction of various aryl chlorides with
arylboronic was performed in high yields. The bonding situ-
ations between two interacted fragments [MCl2] and Y1 and
Y2 ligands in platinacycles 5 and 6 were investigated based
on DFT method by using NBO, EDA, and ETS‐NOCV anal-
ysis. The NBO shows the charge transfer about 0.85e from Y1
and Y2 ligands to [PtCl2] fragment in the complexes. The
EDA analysis confirms that the nature of bonds between
two interacted fragments in latter complexes is mostly elec-
trostatic, and its contribution in total interaction energy is
about 58%. The ETS‐NOCV analyses confirm that the mainly
contribution to ΔEorb in [Y1PtCl2] and [Y2PtCl2] complexes
arise from σ‐donation and shortly from πback donation.
ACKNOWLEDGEMENTS
Funding of our research from the Bu‐Ali Sina University is
gratefully acknowledged.
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Hashemi A, Hosseinzadeh M, Bayat M, Gable RW.
Pallada‐ and platinacycle complexes of phosphorus
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