Mercury(II) complexes of new bidentate phosphorus ylides: Synthesis, spectra and crystal structures

Article abstract of DOI:10.2478/s11696-013-0487-5

The reaction of dppm (1,1-bis(diphenylphosphino)methane) with 2-bromo-4-phenylacetophenone and benzyl bromoacetate in chloroform produces new phosphonium salts, [Ph₂PCH₂PPh₂CH ₂C(O)C₆H₄Ph]Br (I) and [Ph₂PCH ₂PPh₂CH₂COOCH₂Ph]Br (II). By allowing the phosphonium salts to react with the appropriate base, the bidentate phosphorus ylides, Ph₂PCH₂PPh₂=C(H)C(O)C ₆ H₄Ph (III) and Ph₂PCH₂PPh ₂=C(H)C(O)OCH₂Ph (IV), were obtained. The reaction of these ligands with mercury(II) halides in dry methanol led to the formation of the mononuclear complexes {HgX₂[(Ph₂PCH ₂PPh₂C(H)C(O)C₆H₄Ph)]} (X = Cl (V); X = Br (VI); X = I (VII)) and {HgX₂[(Ph₂PCH ₂PPh₂C(H)COOCH₂Ph)]} (X = Cl (VIII); X = Br (IX); X = I (X)). The FTIR and ¹H, ³¹P and ¹³C NMR spectra were studied. The structure of compound III was unequivocally determined by the single-crystal X-ray diffraction technique. Single-crystal X-ray analysis of the {HgBr₂[(Ph₂PCH₂PPh ₂C(H)C(O)C₆H₄Me)]} complex (XI) revealed the presence of a mononuclear complex containing the Hg atom in a distorted tetrahedral environment. In all complexes, the ylides referred to above were coordinated through the ylidic carbon and the phosphine atom.

Full text of DOI:10.2478/s11696-013-0487-5

Chemical Papers 68 (5) 624–632 (2014)
DOI: 10.2478/s11696-013-0487-5
ORIGINAL PAPER
Mercury(II) complexes of new bidentate phosphorus ylides:
synthesis, spectra and crystal structures
a
b
aSeyyed Javad Sabounchei*, Mohammad Panahimehr, Hamid Reza Khavasi,
aFateme Akhlaghi Bagherjeri, Collete Boscovic
c
aFaculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran
bDepartment of Chemistry, Shahid Beheshti University, Evin, Tehran 1983963113, Iran
cSchool of Chemistry, University of Melbourne, Victoria, 3010, Australia
Received 6 April 2013; Revised 28 July 2013; Accepted 9 August 2013
The reaction of dppm (1,1-bis(diphenylphosphino)methane) with 2-bromo-4-phenylacetophenone
and benzyl bromoacetate in chloroform produces new phosphonium salts, [Ph2PCH2PPh2CH2C(O)
C6H4Ph]Br (I ) and [Ph2PCH2PPh2CH2COOCH2Ph]Br (II ). By allowing the phosphonium salts
—
to react with the appropriate base, the bidentate phosphorus ylides, Ph2PCH2PPh2—C(H)C(O)C6
—
H4Ph (III ) and Ph2PCH2PPh2—C(H)C(O)OCH2Ph (IV ), were obtained. The reaction of these
ligands with mercury(II) halides in dry methanol led to the formation of the mononuclear com-
plexes {HgX2[(Ph2PCH2PPh2C(H)C(O)C6H4Ph)]} (X = Cl (V ); X = Br (VI ); X = I (VII )) and
{HgX2[(Ph2PCH2PPh2C(H)COOCH2Ph)]} (X = Cl (VIII ); X = Br (IX ); X = I (X )). The FTIR
1
and H, 31P and 13C NMR spectra were studied. The structure of compound III was unequivocally
determined by the single-crystal X-ray diffraction technique. Single-crystal X-ray analysis of the
{HgBr2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]} complex (XI ) revealed the presence of a mononu-
clear complex containing the Hg atom in a distorted tetrahedral environment. In all complexes, the
ylides referred to above were coordinated through the ylidic carbon and the phosphine atom.
c
ꢀ 2013 Institute of Chemistry, Slovak Academy of Sciences
Keywords: unsymmetrical phosphorus ylides, Hg(II) complexes, X-ray crystal structure
Introduction
dari et al., 2010). Transition metal complexes of these
ligands have attracted much attention due to their
versatile coordination chemistry and their applica-
tion in catalysis (Abu-Gnim & Amer, 1996; Grushin,
2004; Wegman et al., 1987). Much of the interest
in the coordination properties of resonance-stabilised
phosphorus ylides stems from their ligating versatil-
ity due to the presence of different functional groups
in their molecular skeleton (Ebrahim et al., 2009;
Urriolabeitia, 2008; Falvello et al., 2001; Vicente et
al., 2002; Viau et al., 2001). Hence, it is clear that
these ligands can engage in different kinds of bonding
with different metal ions (Falvello et al., 2000, 2003;
Sbovata et al., 2008; Sabounchei et al., 2010a; Oo-
sawa et al., 1976; Lin et al., 1990; Ebrahim et al.,
Multi-functional ligands are organic entities that
possess more than one functional group; these ligands
have attracted interest due to the wide field of ap-
plications based on their multi-functionality (Navarro
& Urriolabeitia, 1999). Phosphorus ylides are remark-
able and important ligands that have attracted much
attention in the synthetic, catalytic and theoretical
fields of transition metal chemistry (Johnson, 1993;
Sabounchei et al., 2013a). These compounds are very
interesting ligands in organometallic chemistry, as
well as being useful intermediates in organic synthe-
sis (Kokotos & Aggarwal, 2007; Heinicke et al., 2005;
Janardanan & Sunoj, 2007; Kolodiazhnyi, 1997; Hey-
*Corresponding author, e-mail: jsabounchei@yahoo.co.uk

S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
625
2007; Spannenberg et al., 2000; Saravanabharathi et
al., 2003; Usón et al., 1987; Takahashi et al., 1976).
The asymmetrical bidentate P,C-coordination of the
type Ph2P(CH2)nPPh2CHC(O)R (n = 1 or 2; R =
Me, Ph or OMe) containing both phosphine and keto-
stabilised phosphorus ylide moieties was recently ob-
served and their transition metal complexes are mostly
confined to mercury halides (Ebrahim et al., 2007,
2009; Sabounchei et al., 2010b, 2010c). The transi-
tion metal complexes of keto-stabilised ylides have
been well studied and are of interest due to the sta-
bility of the ylides as ligands and the ease of detec-
tion of the coordination of the ylide carbon to the
metal by means of infrared spectroscopy (Koezuka
et al., 1974, 1976; Nishiyama et al., 1975; Weleski et
al., 1975). It is apparent that the presence of differ-
ent donor atoms in the same ligand induces different
geometries and structures in the Hg(II) complexes.
Furthermore, the coordination of ligands to Hg(II)
has assumed importance since, in the natural mercury
detoxification process, the initial Hg—C bond cleav-
age involves the increase in the coordination numbers
around Hg (Barbaro et al., 1994). Within this context,
attention is focused here on studying the coordina-
tion mode adopted by the resonance-stabilised ylides
when ligated to Hg(II). The results of these studies
including the full characterisation of the complexes
obtained (performed by elemental analysis, IR, mult-
inuclear NMR techniques and electrochemical data)
are presented and discussed in this paper.
II diffractometer (Stoe & Cie, Germany) at 298 K,
using graphite monochromic Mo Kα radiation (λ =
˚
0.71073 A). The data collection was performed using
the ω-scan technique using the Stoe X-AREA soft-
ware package (Stoe & Cie, 2005a), while data reduc-
tion was carried out using the X-RED program (Stoe
& Cie, 2005a). The crystal structure was solved by di-
rect methods and refined by full-matrix least-squares
on F2 using the SHELXS and SHELXL programs, re-
spectively (Sheldrick, 2008) and using the X-STEP32
crystallographic software package (Stoe & Cie, 2005b).
The H atoms were included in calculated positions
and treated as riding atoms using SHELXL (Sheldrick,
2008) default parameters. Numerical absorption cor-
rections were applied to III. Data collection from suit-
able crystals of XI (Sabounchei et al., 2013b) was per-
formed on an Oxford Diffraction single-crystal X-ray
diffractometer (Oxford Diffraction, UK) using mirror
˚
monochromatic Mo Kα radiation (λ = 0.71073 A)
at 130 K. Gaussian absorption corrections were car-
ried out using a multi-faceted crystal model, using
CrysAlisPro software (Agilent Technologies, 2011).
The structure was solved by direct methods and
refined by the full-matrix least-squares method on
F2 using the SHELXTL-97 crystallographic package
(Sheldrick, 2008; Dolomanov et al., 2009). All non-
hydrogen atoms were refined anisotropically. Hydro-
gen atoms were inserted at calculated positions using
a riding model, with isotropic displacement parame-
ters.
Experimental
[Ph PCH PPh2CH C(O)C H Ph]Br (I)
Materials and methods
A
solution of 2-bromo-4-phenylacetophenone
(0.36 g, 1.30 mmol) in chloroform (4 mL) was added
dropwise to the solution of dppm (0.50 g, 1.30 mmol)
in chloroform (8 mL) and the mixture was stirred at
ambient temperature for 15 h. The mixture was then
concentrated under reduced pressure to approximately
2 mL. Diethyl ether (25 mL) was added and the solid
thus formed was filtered and dried under reduced pres-
sure.
All reactions were carried out under an atmosphere
of dry nitrogen. Prior to use, methanol and diethyl
ether were dried with magnesium powder and a mix-
ture of sodium and benzophenone, respectively. All
other solvents were of reagent grade and used with-
out further purification. Melting points were measured
on a Stuart SMP3 apparatus (Stuart, USA). IR spec-
tra (in KBr pellets) were recorded on a Shimadzu
1
435-U-04 spectrophotometer (Shimadzu, Japan). H,
[Ph PCH PPh CH CO CH Ph]Br (II)
13C and 31P NMR spectra were recorded on a 300
MHz (Bruker, Germany) and a 90 MHz (Jeol, Japan)
spectrometers in DMSO-d6 or CDCl3 as solvent at
25◦C. Chemical shifts (δ) were referenced against the
tetramethylsilane (TMS) as the internal standard and
85 % phosphoric acid as the external standard. Ele-
mental analyses were performed using a Perkin–Elmer
2400 Series II CHNS/O elemental analyser (Perkin–
Elmer, USA).
A solution of dppm (0.50 g, 1.30 mmol) and benzyl
bromoacetate (0.30 g, 1.30 mmol) in chloroform was
stirred at ambient temperature for 10 h. The white
solid thus formed was filtered and dried under reduced
pressure.
—
Ph PCH PPh2 C(H)C(O)C H Ph (III)
—
The monophosphonium salt (I ) (0.33 g, 0.50 mmol)
was treated with triethylamine (0.50 mL) in toluene
(15 mL) and the triethylamine hydrobromide thus
obtained was removed by filtration. Evaporation of
toluene to approximately 1 mL and the subsequent
X-ray crystal structure determination
The single-crystal X-ray diffraction data of suit-
able crystals of III were collected on a STOE IPDS

626
S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
Table 1. Characterisation data of compounds I–X
wi(calc.)/mass %
wi(found)/mass %
Yield
M.p.
Compound
Formula
Mr
C
H
%
85
82
71
62
67
68
56
54
58
49
◦C
180
166
145
138
209
214
217
205
210
218
I
II
C39H33BrOP2
C34H31BrO2P2
C39H32OP2
659.53
613.46
578.62
532.55
850.11
939.02
1033.02
804.04
892.95
986.95
71.02
70.91
66.56
66.64
80.95
80.86
76.68
76.94
55.10
54.95
49.88
49.76
45.34
45.21
50.79
50.95
45.73
45.58
41.38
41.54
5.04
5.09
5.09
5.11
5.57
5.56
5.68
5.77
3.79
3.72
3.43
3.49
3.12
3.07
3.76
3.69
3.38
3.43
3.06
3.01
III
IV
V
C34H30O2P2
C39H32Cl2HgOP2
C39H32Br2HgOP2
C39H32I2HgOP2
C34H30Cl2HgO2P2
C34H30Br2HgO2P2
C34H30I2HgO2P2
VI
VII
VIII
IX
X
Fig. 1. Reaction scheme for synthesis of phosphine–phosphonium ylides. Reaction conditions: i) chloroform, ambient temperature,
24 h; ii) triethylamine, toluene; Ph = phenyl.
addition of diethyl ether (25 mL) resulted in precipita-
tion of the desired ligand (bidentate phosphorus ylide)
as a white solid.
ucts as solids. Characterisation data of compounds I–
X are given in Table 1.
Results and discussion
—
Ph PCH PPh2 CHCO CH Ph (IV)
—
Synthesis and spectral determination
This phosphorus ylide was obtained using the pro-
cedure adopted for the preparation of III starting from
monophosphonium salt (II ) (0.31 g, 0.50 mmol).
The ligands were synthesised by allowing bis(di-
phenylphosphino)methane to react with 2-bromo-4-
phenylacetophenone and benzyl bromoacetate and re-
moval of the proton from the phosphonium salts by
triethylamine (Fig. 1) (Oosawa et al., 1976).
General procedure for preparation of com-
plexes V–X
Reactions of HgX2 with ylides III and IV in a 1 : 1
stoichiometry afforded the P,C-bonding complexes V–
X with a chelating structure (Fig. 2). All complexes
were soluble in dichloromethane and were obtained
with fair yields (49–68 %). The spectral data of com-
pounds I–X are given in Table 2.
A solution of III or IV (0.35 mmol) in methanol
(4 mL) was added dropwise at 0◦C to a solution of
HgX2 (0.35 mmol) in methanol (8 mL) and the mix-
ture was stirred for 2 h. The resulting solid, admixed
with grey material, was treated with dichloromethane
(25 mL) and filtered through a short plug of Celite.
The addition of an excess volume of methanol to the
concentrated filtrate caused precipitation of the prod-
1
The H NMR spectrum of I exhibited, in addition
to the aromatic resonances, two doublets at δ = 5.91
(2JP,H = 12.15 Hz) and δ = 4.27 (2JP,H = 14.85 Hz)

S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
627
Fig. 2. Reaction of ylides III and IV with Hg(II) halides. Reaction conditions: i) MeOH, N2 atmosphere, 0◦C, 2 h.
Table 2. Spectral data of compounds I–X
Compound
Spectral dataa
I
IR, ν˜/cm−1: 1669 (C O)
—
—
2
1H NMR (CDCl3), δ: 4.27 (d, 2H, PCH2P, 2JP,H = 14.85 Hz), 5.91 (d, 2H, PCH2CO, JP,H = 12.15 Hz), 7.20–8.25
(m, 29H, Harom
)
1
1
1
13C NMR (CDCl3), δ: 22.00 (dd, PCH2P, JP,C = 51.01 Hz, JP,C = 34.33), 36.34 (dd, PCH2, JP,C = 60.50 Hz,
3
—
JP,C = 5.02 Hz), 117.93–147.05 (Carom), 191.70 (s, C O)
—
31P NMR (CDCl3), δ: –29.25 (d, PPh2, JP,P = 63.42 Hz), 21.09 (d, PCH2CO, JP,P = 63.58 Hz)
2
2
II
IR, ν˜/cm−1: 1729 (C O)
—
—
2
2
1H NMR (CDCl3), δ: 4.28 (d, 2H, PCH2P, JP,H = 15.21 Hz), 4.99 (d, 2H, PCH2CO, JP,H = 13.50 Hz), 4.78 (s,
2H, CH2O), 6.85–7.92 (m, 25H, Harom
)
13C NMR (CDCl3), δ: 21.13 (dd, PCH2P, 1JP,C = 51.03 Hz, 1JP,C = 36.00 Hz), 32.35 (dd, PCH2, 1JP,C = 57.00 Hz,
3
—
JP,C = 2.02 Hz), 68.11 (s, CH2O), 116.71–134.70 (Carom), 164.27 (s, C O)
—
31P NMR (CDCl3), δ: –29.55 (d, PPh2, JP,P = 65.78 Hz), 20.17 (d, PCH2CO, JP,P = 65.05 Hz)
2
2
III
IV
IR, ν˜/cm−1: 1565 (C O)
—
—
2
1H NMR (CDCl3), δ: 3.70 (d, 2H, CH2, JP,H = 14.22 Hz), 4.36 (brs, 1H, CH), 7.27–8.02 (m, 29H, Harom
)
13C NMR (CDCl3), δ: 24.52 (dd, PCH2P, JP,C = 57.64 Hz, JP,C = 32.28 Hz), 49.94 (d, CH, JP,C = 114.46 Hz),
124.89–141.84 (Carom), 184.60 (s, C O)
31P NMR (CDCl3), δ: –29.78 (d, PPh2, JP,P = 63.67 Hz), 11.32 (d, PCH, JP,P = 63.24 Hz)
1
1
1
—
—
2
2
IR, ν˜/cm−1: 1583 (C O)
—
—
1H NMR (CDCl3), δ: 3.39 (d, 2H, CH2, JP,H = 13.77 Hz), 3.00 (brs, 1H, CH), 4.86 (s, 2H, CH2O), 7.02–7.85 (m,
25H, Harom
13C NMR (CDCl3), δ: 21.13 (dd, PCH2P, JP,C = 55.08 Hz, JP,C = 40.12 Hz), 53.31 (d, CH, JP,C = 107.28 Hz),
2
)
1
1
1
—
67.24 (s, CH2O), 117.18–132.87 (Carom), 156.17 (s, C O)
—
2
2
31P NMR (CDCl3), δ: –30.63 (d, PPh2, JP,P = 64.62 Hz), 12.69 (d, PCH, JP,P = 64.84 Hz)
IR, ν˜/cm−1: 1594 (C O)
—
V
—
1H NMR (DMSO-d6), δ: 4.69 (brs, 2H, CH2), 5.31 (brs, 1H, CH), 7.44–8.15 (m, 29H, Harom
)
13C NMR (DMSO-d6), δ: 24.27 (brs, CH2), 33.64 (brs, CH), 126.63–135.66 (Carom), 191.87 (s, C O)
31P NMR (DMSO-d6), δ: 8.25 (brs, PPh2), 26.58 (d, PCH, JP,P = 41.12 Hz)
—
—
2
IR, ν˜/cm−1: 1594 (C O)
—
VI
—
1H NMR (DMSO-d6), δ: 4.64 (brs, 2H, CH2), 5.34 (brs, 1H, CH), 7.43–8.01 (m, 29H, Harom
)
13C NMR (DMSO-d6), δ: 23.97 (brs, CH2), 33.89 (brs, CH), 125.96–135.78 (Carom), 190.94 (s, C O)
31P NMR (DMSO-d6), δ: 0.20 (brs, PPh2), 26.96 (d, PCH, JP,P = 45.29 Hz)
—
—
2
IR, ν˜/cm−1: 1593 (C O)
—
VII
VIII
—
1H NMR (DMSO-d6), δ: 4.48 (brs, 2H, CH2), 5.23 (brs, 1H, CH), 7.40–8.13 (m, 29H, Harom
)
13C NMR (DMSO-d6), δ: 24.11 (brs, CH2), 31.17 (brs, CH), 124.88–136.14 (Carom), 189.73 (s, C O)
31P NMR (DMSO-d6), δ: –13.36 (brs, PPh2), 26.53 (d, PCH, JP,P = 53.70 Hz)
—
—
2
IR, ν˜/cm−1: 1673 (C O)
—
—
1H NMR (DMSO-d6), δ: 4.34 (brs, 2H, CH2), 5.11 (brs, 1H, CH), 4.81 (s, 2H, CH2O), 7.08–8.09 (m, 25H, Harom
)
13C NMR (DMSO-d6), δ: 22.18 (brs, CH2), 35.87 (brs, CH), 64.38 (s, CH2O), 118.56–131.67 (Carom), 162.25 (s,
—
C
O)
—
2
31P NMR (DMSO-d6), δ: 6.20 (brs, PPh2), 25.71 (d, PCH, JP,P = 42.64 Hz)
—
IX
X
IR, ν˜/cm−1: 1667 (C O)
—
1H NMR (DMSO-d6), δ: 4.29 (brs, 2H, CH2,), 4.99 (brs, 1H, CH,), 4.85 (s, 2H, CH2O), 7.01–8.14 (m, 25H, Harom
)
13C NMR (DMSO-d6), δ: 22.95 (brs, CH2), 34.11 (brs, CH), 65.12 (s, CH2O), 118.37–132.18 (Carom), 160.27 (s,
—
C
O)
—
31P NMR (DMSO-d6), δ: 1.76 (brs, PPh2), 25.48 (d, PCH, JP,P = 43.92 Hz)
2
IR, ν˜/cm−1: 1659 (C O)
—
—
1H NMR (DMSO-d6), δ: 4.36 (brs, 2H, CH2,), 4.87 (brs, 1H, CH), 4.92 (s, 2H, CH2O), 7.12–8.23 (m, 25H, Harom
)
13C NMR (DMSO-d6), δ: 23.17 (brs, CH2), 31.27 (brs, CH), 62.17 (s, CH2O), 119.18–132.29 (Carom), 157.74 (s,
—
C
O)
—
2
31P NMR (DMSO-d6), δ: –10.27 (brs, PPh2), 26.04 (d, PCH, JP,P = 49.83 Hz).
a) Harom and Carom mean aromatic protons and carbons of phenyl moieties, respectively; brs means broad signal.

628
S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
due to the PCH2CO and PCH2P groups, respectively
(Navarro & Urriolabeitia, 1999). The 31P NMR spec-
trum exhibited two doublets at δ = 21.09 and δ =
–29.25, indicating the PCH2CO and PPh2 groups, re-
spectively. In the 13C NMR spectrum, two doublet of
The CH group bonded to the mercury atom resulted
in a downfield shift relative to the parent ylide IV. A
singlet at δ = 4.81 was attributed to the CH2O group.
The 31P NMR spectrum of VIII showed a doublet at
δ = 25.71 with a coupling constant of 42.64 Hz and
a broad signal at δ = 6.20, attributable to the co-
ordinated PPh2 and to the uncoordinated phosphine
atoms, respectively. The 13C NMR spectrum of this
complex exhibits, in addition to the aromatic reso-
nances, two broad signals at δ = 22.18 and δ = 35.87
due to the CH2 and CH groups, respectively. The car-
bonyl signal appearing at δ = 162.25 was shifted down-
field relative to the parent ylide. A singlet at δ = 64.38
was attributed to the CH2O group. The NMR data of
complexes IX and X were similar to those of VIII (Ta-
ble 2).
doublet signals were registered at δ = 22.0 (1JP,C
=
=
1
51.01 Hz, JP,C = 34.33 Hz) and δ = 36.34 (1JP,C
3
60.50 Hz, JP,C = 5.02 Hz) due to the PCH2P and
PCH2 groups, respectively. The carbonyl signal ap-
1
peared as a singlet at δ = 191.70. The H NMR spec-
trum of II showed two doublets at δ = 4.28 (2JP,H
= 15.21 Hz) and δ = 4.99 (2JP,H = 13.50 Hz), which
were assigned to the PCH2P and PCH2CO groups,
respectively (Navarro & Urriolabeitia, 1999). A signal
appearing at δ = 4.81 (singlet) was attributed to the
CH2O group. The 31P NMR spectrum exhibited two
doublets at δ = 20.17 and δ = –29.55, indicating the
PCH2CO and PPh2 groups, respectively. In the 13C
The IR data (Table 2) confirmed the formation of
the phosphorus ylides wi−th1 the disappearance of the
—
NMR spectrum, two doublet of doublet signals were
C
O bands at 1669 cm
and 1729 cm−1 in phos-
—
1
observed at δ = 21.13 (1JP,C = 51.03 Hz, JP,C
=
=
phonium salts I and II and the presence of new strong
3
−1
and 1583 cm−1 of sta-
36.00 Hz) and δ = 32.35 (1JP,C = 57.00 Hz, JP,C
C
O bands at 1565 cm
—
—
2.02 Hz) due to the PCH2P and PCH2 groups, respec-
tively. The carbonyl signal appeared as a singlet at δ
= 164.27. A signal appearing at δ = 68.11 as a singlet
was attributed to the CH2O group.
bilised ylides III and IV, respectively (Sbovata et al.,
2008; Vicente et al., 1991). The upward frequency shift
—
of the ν(C O) absorption in complexes, with refer-
—
ence to the free ylides III and IV, strongly indicates
coordination of the ylides through the ylidic carbon
atom (Sabounchei et al., 2010c; Kalyanasundari et al.,
1995).
1
In the H NMR spectra of III and IV, the CH sig-
nals of the ylides are shifted upfield compared with
those of the phosphonium salts due to the electron
density increasing in the P—C bonds and this in-
2
terpretation holds true the increase of JP,H for III
X-ray crystallography
(Falvello et al., 2003). The 31P NMR spectra showed
two doublets around δ = 11 and δ = –30, which were
assigned to the PCH and PPh2 groups, respectively
(Vicente et al., 1991). In the 13C NMR spectra, a
downfield shift for the CH signal was observed for
ylides, suggesting low shielding of carbon atoms (re-
placing the CH2 group with the CH group) but in-
creasing the electron density in the P—C bond. An
The crystallographic results and refinement infor-
mation for compounds III and XI are summarised in
Table 3. Colourless crystals of III were obtained from
a toluene solution by slow evaporation of the solvent.
An ORTEP plot (Fig. 3) shows that the geometry
of molecule III around the P atom is almost tetrahe-
dral, and the O atom is cis-oriented to the P(1) atom.
˚
—
upfield shift of C O signals was also observed for
The P1—C14 (1.722(3) A) and C13—C14 (1.409(4)
—
+
3
˚
A) bond lengths are shorter than the (P —C(sp )
ylides, which is due to the electron density increas-
ing on the carbon atom.
3
˚
˚
(1.800 A) and (C—C(sp ) (1.511 A) normal values,
respectively. This is due to the ylidic resonance and in-
termediate between the common values for the single
P—C bond (1.80 A) and double P C bond (1.66 A).
The C O bond (1.253(3) A) is also longer than the
The 1H NMR spectrum of V exhibited, in addi-
tion to the aromatic resonances, two broad signals at
δ = 5.31 related to a CH group bonded to the mer-
cury atom and shifted downfield relative to the par-
ent ylide III and signal at δ = 4.69 attributed to CH2
group (Sabounchei et al., 2010d). The 31P NMR spec-
trum exhibited a doublet at δ = 26.58 with a coupling
˚
˚
—
—
˚
—
—
˚
normal value (1.210 A). This bond distance suggests
electron delocalisation in this molecule (Sabounchei et
al., 2010d). The relevant bond lengths and angles of
III are given in Table 4.
2
constant JP,P of 41.12 Hz and a broad signal at δ =
8.25, attributable to the PCH2 and PPh2 groups, re-
spectively. The 13C NMR spectrum of V exhibited, in
addition to the aromatic resonances, two broad signals
at δ = 24.27 and δ = 33.64 due to the CH2 and CH
groups, respectively. The carbonyl signal appearing at
δ = 191.87 was shifted downfield relative to the par-
ent ylide. The H NMR spectrum of VIII showed two
broad signals at δ = 4.34 and δ = 5.11, which were
assigned to the PCH2P and CH groups, respectively.
As for the slightly higher R-factors observed for
compound III, it should be noted that some atoms
have a high thermal parameter due to the data be-
ing collected at ambient temperature. An attempt was
made to refine these atoms in two positions with re-
duced occupancy but, while this model converged sat-
isfactorily, there was no decrease in R-value, hence
it was concluded that the original refinement repre-
sented the best that could be achieved and should be
1

S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
Table 3. Crystal data and refinement details for III and XI
629
Compound III
Compound XI
Parameter
Value
Value
Empirical formula
Formula mass
C39H32OP2
578.59
C34H30OP2Br2Hg
876.93
Temperature, T (K)
298(2)
129.98(10)
˚
Wavelength (A)
0.71073
0.71073
Crystal system
Space group
Triclinic
monoclinic
P21/c
P1
˚
˚
b (A)
a (A)
10.4034(18)
11.964(2)
12.9904(3)
16.2273(3)
˚
c (A)
13.943(2)
108.260(13)
98.298(13)
103.846(14)
2
15.6988(3)
90.007(3)
106.953(3)
90.004(3)
α (◦)
β (◦)
γ (◦)
Formula per unit cell, Z
Absorption coefficient, (mm−1
θ range for data collection (◦)
Index ranges
4
)
0.170
3.457
1.58 to 29.22
–14 ≤ h ≤ 14
–15 ≤ k ≤ 16
–19 ≤ l ≤ 19
17402
3.56 to 77.21
–16 ≤ h ≤ 16
–20 ≤ k ≤ 19
–14 ≤ l ≤ 19
32394
Reflections collected
Independent reflections
Refinement method
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
8330 [R(int) = 0.0800]
Full-matrix least-squares on F2
1.036
R1 = 0.1011, wR2 = 0.2111
R1 = 0.1234, wR2 = 0.2146
0.872 and –0.356
6675 [R(int) = 0.0529]
Full-matrix least-squares on F2
1.060
R1 = 0.0328, wR2 = 0.0858
R1 = 0.0382, wR2 = 0.0909
2.07 and –1.18
−3
˚
Largest diff. peak and hole (e · A
)
◦
a
˚
Table 4. Selected bond lengths (A) and bond angles ( ) for III and XI
Compound
Bond
Bond length
Bond
Bond angle
III
C14—P1
C13—C14
C13—O1
C27—P1
–
1.722(3)
1.409(4)
1.253(3)
1.801(3)
–
C14—P1—C27
C14—P1—C15
C27—P1—C15
C14—P1—C21
C27—P1—C21
C15—P1—C21
111.33(13)
107.30(13)
108.92(14)
115.40(14)
107.10(13)
106.56(13)
–
–
XI
C1—Hg1
P2—Hg1
Hg1—Br2
Hg1—Br1
C2—O1
C1—P1
–
2.407(3)
2.504(1)
2.5581(5)
2.6059(4)
1.234(4)
1.759(4)
–
C1—Hg1—P2
C1—Hg1—Br2
P2—Hg1—Br2
C1—Hg1—Br1
P2—Hg1—Br1
Br2—Hg1—Br1
C2—C1—P1
90.69(8)
113.71(8)
115.82(2)
108.44(8)
117.67(2)
109.20(2)
113.1(2)
101.0(1)
112.2(2)
–
–
–
–
C34—P2—Hg1
C1—P1—C34
a) Standard deviations in parentheses.
reported. On the other hand, this compound slowly
decomposed even under perfluoropolyether oil and the
crystal used for data collection incurred some damage.
Suitable crystals of XI were obtained from dime-
thyl sulphoxide solution by slow evaporation of the
solvent for twenty days. The molecular structure of
complex XI is shown in Fig. 4 and the relevant bond
lengths and bond angles are given in Table 4. The
Hg(II) atom is located in a distorted tetrahedral en-
vironment with ‘P’ and ‘C’ atoms. The remaining po-
sitions are occupied by the bromide atoms. The coor-
dination environment around Hg(II) closely resembles
those found in {HgI2[(PPh2CH2PPh2C(H)C(O)Ph)]}
(Ebrahim et al., 2009) and {HgI2[(Ph2PCH2PPh2
C(H)C(O)C6H4Cl)]} (Sabounchei et al., 2010c). The
ligand coordinates to the metal via ‘P’ and ylidic ‘C’
atoms to form a five-membered chelate. The Hg—P
bond length in XI (2.504(1) A) is comparable with
the analogous distance in Hg(II)–phosphine complexes
such as {HgI2[(Ph2PCH2PPh2C(H)C(O)C6H4NO2)]}
˚

630
S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
˚
Table 5. Short contacts distances (A) for XI
Short contacts C12· · ·H24 Br1· · ·H27 Br1· · ·H15 Br1· · ·H34A C5· · ·H34B H5· · ·O1 H5· · ·H34B H9B· · ·O1
˚
Distances/A
2.796
2.822
2.894
2.814
2.839
2.414
2.276
2.652
Fig. 5. Representation of intermolecular contacts of XI.
Dashed lines represent short contacts.
Fig. 3. Molecular structure of III with ellipsoids at 50 % prob-
ability level.
found in similar uncomplexed phosphoranes such as
˚
[Ph2PCH2PPh2C(H)C(O)Ph] (1.404(3) A) (Ebrahim
et al., 2009). Similarly, the C14—P1 bond length in
˚
uncoordinated ylide III is 1.722(3) A, indicating that
the corresponding bond lengths (C1—P1) in XI are
˚
considerably elongated to 1.759(4) A. The structure of
XI has short contacts between the adjacent molecules.
In this case, the interactions between the O atom and
˚
H atoms of the phenyl and methyl groups (2.414 A
˚
and 2.652 A, respectively) assume great importance
to form the packing structure (Fig. 5). The lengths of
all short contacts are reported in Table 5.
Conclusions
The present study describes the synthesis and char-
acterisation of a series of chelate mercury(II) com-
plexes derived from mercuric halides and new mixed
phosphine–phosphonium ylides. The physicochemical
and spectroscopic data indicate that the ligands ex-
hibit bidentate P,C-coordination to the metal centre.
Fig. 4. Molecular structure of XI with ellipsoids at 50 % prob-
ability level. Hydrogen atoms are omitted for clarity.
˚
(2.5199(19) A) (Sabounchei et al., 2010b) and {HgBr2
Acknowledgements. The authors wish to express their grat-
itude to the Bu-Ali Sina University for the provision of a grant
and to Mr. Zebarjadian for recording the NMR spectra.
˚
[(PPh3)2]} (2.550(4) A) (Kubicki et al., 2001). The
˚
terminal Hg—Br distances in XI (2.5581(5) A and
˚
2.6059(4) A) are comparable with analogous distances
˚
˚
in {HgBr2[(PPh3)2]} (2.626(8) A and 2.633(6) A)
Supplementary data
(Bell et al., 1983) and {HgI2[(Ph2PCH2PPh2C(H)
˚
˚
C(O)C6H4Cl)]} (2.7270(14) A and 2.7483(3) A) (Sa-
bounchei et al., 2010c). The resonance-stabilised
structures in the parent ylide are destroyed by the
complex formation, hence the C1—C2 bond length of
Crystallographic data for compounds III and XI
are deposited in the Cambridge Crystallographic Data
Centre, CCDC no. 856742 and CCDC no. 879884,
respectively. Copies of the information may be ob-
tained free of charge from: The Director, CCDC,
˚
1.456(5) A is longer than the corresponding distances

S. J. Sabounchei et al./Chemical Papers 68 (5) 624–632 (2014)
631
12 Union Road, Cambridge, CB21EZ, UK (fax:
+44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk/data request/cif).
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gations on the general reaction profile and diastereoselectiv-
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