New mercury(II) and cadmium(II) complexes with (p-methylbenzoyl)methylene triphenylphosphorane: Synthesis, spectroscopic and structural characterization

Article abstract of DOI:10.1016/j.crci.2013.03.015

Reaction of Ph₃PCHCOC₆H₄Me (L), with HgX₂ and CdCl₂·H₂O in methanol with equimolar ratios give binuclear complexes of the type [MX(μ-X){CH(PPh ₃)C(O)C₆H₄Me}

Full text of DOI:10.1016/j.crci.2013.03.015

C. R. Chimie 16 (2013) 1017–1023
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´
Full paper/Memoire
New mercury(II) and cadmium(II) complexes with
(p-methylbenzoyl)methylene triphenylphosphorane:
Synthesis, spectroscopic and structural characterization
a
a
Seyyed Javad Sabounchei a, , Mohsen Ahmadi , Fateme Akhlaghi Bagherjeri ,
*
Farzaneh Hejazi a, Keyhaneh Sanaie-Noorani a, Hamid Reza Khavasi b, Sepideh Samiee c
a Faculty of Chemistry, Bu-Ali Sina University, 65174 Hamedan, Iran
b Department of Chemistry, Shahid Beheshti University, G.C., Evin, Tehran, Iran
c Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahvaz, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Reaction of Ph3PCHCOC6H4Me (L), with HgX2 and CdCl2ÁH2O in methanol with equimolar
Received 18 January 2013
Accepted after revision 25 March 2013
Available online 9 May 2013
ratios give binuclear complexes of the type [MX(m-X){CH(PPh3)C(O)C6H4Me}]2 (M = Hg;
X = Cl (1), Br (2), I (3), M = Cd; Cl(4)). The bridge-splitting reaction of binuclear complexes
[MX( -X){CH(PPh3)C(O)C6H4Me}]2 by dimethyl sulfoxide (DMSO) yields the mono-
m
nuclear complexes [MX2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (M = Hg; X = Cl (5), Br (6), I (7),
M = Cd; Cl (8)). The characterization of these complexes was carried out by elemental
analysis and FT-IR, 1H, 31P, and 13C NMR spectroscopies. C-coordination of ylide and O-
coordination of DMSO are demonstrated by single-crystal X-ray analysis of mononuclear
complex of [HgBr2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (6). Complex 6 is monomeric with
tetrahedral geometry around the metal ion.
Keywords:
Phosphorus ylide
Coordination mode
Tetrahedral geometry
X-ray crystal structure
´
ß 2013 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
(A1 and A2) (Scheme 1). Although many bonding modes are
possible for keto ylides [6], coordination through carbon is
Phosphorus ylides are important reagents in organic
chemistry, especially in the synthesis of naturally occur-
ring products with biological and pharmacological activ-
ities [1]. The utility of metalated phosphorus ylides in
synthetic chemistry has been well documented [2–4].
Ylides play in coordination chemistry other roles aside
from its coordination to the metal [5]. Juxtaposition of the
keto group and of the carbanion in the phosphorus ylides
allows resonance delocalization of the ylidic electron
density, providing additional stabilization to the ylide
more predominant and observed with soft metal ions, e.g.,
Pd(II) [7], Pt(II) [7h,8], Ag(I) [9], Hg(II) [9d,10], Au(I) [11],
Cd(II) [7i,9d,12], whereas O-coordination dominates when
the metals involved are hard, e.g., Ti(IV), Zr(IV), and Hf(IV)
[13].
Synthesis of complexes derived from phosphorus ylides
and Hg(II) halides was initiated in 1965 by Nesmeyanov
et al. [14] In 1975, Weleski et al. [15] proposed a symmetric
halide-bridged dimeric structure for Hg(II) halide com-
plexes, whereas Kalyanasundari et al. [10a] reported an
asymmetric halide-bridged dimeric structure in 1995. In
1985, Sanehi et al. [16] reported a mononuclear Hg(II)
complex of phosphorus ylides without any structural
characterization. We have recently worked on the synth-
esis of mononuclear [9d,10b], binuclear [17–20] com-
plexes derived from mercury (II) salts and phosphorus
ylides.
species. This so-called a-stabilization provides ylides with
the potential to act as an ambidentate ligand and thus bond
to a metal centre through the either carbon (B) or oxygen
* Corresponding author.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
1631-0748/$ – see front matter ß 2013 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.crci.2013.03.015

1018
S.J. Sabounchei et al. / C. R. Chimie 16 (2013) 1017–1023
˚
P+R3
C
R''
C
K
a
radiation (
l
= 0.71073 A). The data collection was
-scan technique and using the STOE
C
C
R''
performed using the
v
R3P
O
[M]
O
X-AREA software package [21]. The crystal structure was
solved by direct methods and refined by full-matrix least-
squares on F2 by SHELX [22] and using the X-STEP32
crystallographic software package [23]. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
inserted at calculated positions using a riding mode with
fixed thermal parameters.
[M]
R'
R'
A1
A2
O-co-ordination, cisoid
O-co-ordination, transoid
R''
C
[M]
C(O)R'
P+R3
2.3. Synthesis and characterization of compounds
2.3.1. Ph3PCHCOC6H4Me (L)
/cmÀ1), 1582 (
n
C5O) and 895
B
Selected IR data (KBr,
n
(
n
P+–CÀ). 1H NMR (CDCl3, ppm):
d
= 2.38 (s, 3H, CH3), 4.32
C-co-ordination
2
(d, 1H, JPH = 23.29 Hz, CH), 7.1–8.1 (m, 19H, arom). 31P
Scheme 1. The possible bonding modes of an
a
-keto stabilized ylide to
NMR (CDCl3, ppm):
d
= 12.98. 13C NMR (CDCl3, ppm):
1
the metal center.
d
= 21.48 (s, CH3), 45.63 (d, JPC = 70.42 Hz, CH), 115.4 (d,
1JPC = 91.43 Hz, PPh3 (i)), 131.7 (d, JPC = 12.36 Hz, PPh3
(m)), 133.2 (d, 2JPC = 8.07 Hz, PPh3 (o)), 142.31 (s, PPh3 (p)),
145.50 (s, COPh (i)), 126.19 (s, COPh (m)), 132.03 (s, COPh
(o)), 128.7 (s, COPh (p)), 191.34 (s, CO).
3
Based on the above backgrounds, we have focused on
the synthesis, structure, and properties of coordination
mononuclear Hg (II) and Cd (II) complexes with ambi-
dentate phosphorus ylide as a ligand, and DMSO has been
successfully utilized for the preparation of a series of
complexes. In this study, we describe the preparation,
structural and spectroscopic characterization of Hg(II) and
Cd(II) complexes with the title ylide. Herein the structure
of a new mononuclear mercury complex was reported and
the single-crystal X-ray diffraction of 6 demonstrates the
C-coordination of the ylide and O-coordination of the
DMSO to the metal center.
2.3.2. [HgCl(
General procedure: To HgCl2 (0.172 g, 0.63 mmol)
dissolved in 5 mL of dried methanol was added
m-Cl){CH(PPh3)C(O)C6H4Me}]2 (1)
L
(0.250 g, 0.63 mmol) at room temperature. The mixture
was stirred for 4 h. The white solid product was filtered,
washed with diethyl ether and dried under reduced
pressure. Yield: (84%); mp 208–210 8C; Selected IR data
(KBr,
(DMSO-d6, ppm):
2JPH = 3.85 Hz, CH), 6.94–8.12 (m, 19H, arom). 31P NMR
(DMSO-d6, ppm):
= 24.60. 13C NMR (DMSO-d6, ppm):
n
/cmÀ1), 1632 (
nC5O) and 817 (n
P+–CÀ). 1H NMR
d
= 2.35 (s, 3H, CH3), 5.42 (d, 1H,
2. Experimental
d
d
= 20.89 (s, CH3), 46.11 (d, 1JPC = 70.42 Hz, CH), 122.91 (d,
3
2.1. Materials and measurements
1JPC = 89.99 Hz, PPh3 (i)), 129.21 (d, JPC = 12.36 Hz, PPh3
2
(m)), .17 (d, JPC = 9.77 Hz, PPh3 (o)), 134.33 (d,
Methanol and dichloromethane were distilled over
magnesium powder and diethyl ether (Et2O) over a
mixture of sodium and benzophenone just before use.
All other solvents were reagent grade and used without
further purifications. The ligand L was prepared and
characterized according to the published procedure [17].
Melting points were measured on a SMPI apparatus.
Elemental analyses for C, H and N were performed using
a PerkinElmer 2400 series analyzer. Fourier transform IR
spectra were recorded on a Shimadzu 435-U-04 spectro-
photometer and samples were prepared as KBr pellets.
4JPC = 9.84 Hz, PPh3 (p)), 142.46 (s, COPh (i)), 128.19 (s,
COPh (m)), 133.38 (s, COPh (o)), 128.54 (s, COPh (p)),
190.87 (s, CO). Anal. calcd. (%) for C54H46Cl4Hg2O2P2
(1332): C, 48.69; H, 3.48. Found (%): C, 48.45, H, 3.54.
2.3.3. [HgBr(
Yield: (85%); mp 197–199 8C. Selected IR data (KBr,
cmÀ1), 1630 ( P+-CÀ). 1H NMR (DMSO-d6,
C5O) and 814 (
ppm): = 2.39 (s, 3H, CH3), 5.52 (br, 1H, CH), 7.04–8.24 (m,
19H, arom). 31P NMR (DMSO-d6, ppm): = 23.46. 13C NMR
(DMSO-d6, ppm): = 21.06 (s, CH3), 47.13 (d,
m-Br){CH(PPh3)C(O)C6H4Me}]2 (2)
n
/
n
n
d
d
d
1
1H, 13C and 31P NMR spectra were recorded on
a
1JPC = 73.95 Hz, CH), 123.01 (d, JPC = 89.52 Hz, PPh3 (i)),
129.27 (d, 3JPC = 12.43 Hz, PPh3 (m)), 133.23 (d,
2JPC = 9.41 Hz, PPh3 (o)), 133.44 (s, PPh3 (p)), 142.41 (s,
COPh (i)), 126.57 (s, COPh (m)), 131.97 (s, COPh (o)), 128.64
(s, COPh (p)), 190.75 (s, CO). Anal. calcd. (%) for
300 MHz Bruker and 90 MHz Jeol spectrometer in
DMSO-d6 or CDCl3 as a solvent at 25 8C. Chemical shifts
(ppm) are reported according to internal TMS and
external 85% phosphoric acid. Coupling constants are
given in Hz.
C
54H46Br4Hg2O2P2 (1510): C, 42.96; H, 3.07. Found (%):
C, 43.21, H, 3.11.
2.2. Crystallographic data collection and structure
determination
2.3.4. [HgI(
Yield: (81%); mp 186–189 8C. Selected IR data (KBr,
cmÀ1), 1621 ( P+–CÀ). 1H NMR (DMSO-d6,
C5O) and 797 (
ppm):
= 2.34 (s, 3H, CH3), 5.25 (d, 1H, 2JPH = 8.44 Hz, CH),
7.07–8.12 (m, 19H, arom). 31P NMR (DMSO-d6, ppm):
m-I){CH(PPh3)C(O)C6H4Me}]2 (3)
n
/
The single-crystal X-ray diffraction analyses of suitable
crystal of 6 was performed on a STOE IPDS-II diffract-
ometer at 298 K, using the graphite monochromated Mo
n
n
d

S.J. Sabounchei et al. / C. R. Chimie 16 (2013) 1017–1023
1019
d
= 21.51. 13C NMR (DMSO-d6, ppm):
d
= 20.83 (s, CH3),
ppm):
19H, arom). 31P NMR (DMSO-d6, ppm):
(DMSO-d6, ppm):
= 21.0 (s, CH3), 48.58 (d, 1JPC = 72.85 Hz,
d
= 2.39 (s, 3H, CH3), 5.19 (br, 1H, CH), 7.35–8.23 (m,
1
1
44.23 (d, JPC = 72.49 Hz, CH), 123.61 (d, JPC = 87.65 Hz,
PPh3 (i)), 128.93 (d, JPC = 12.57 Hz, PPh3 (m)), 132.86 (d,
2JPC = 9.19 Hz, PPh3 (o)), 135.07 (s, PPh3 (p)), 141.34 (s,
COPh (i)), 127.58 (s, COPh (m)), 132.86 (d, JPC = 9.19 Hz,
COPh (o)), 128.25 (s, COPh (p)), 189.40 (d, JPC = 15.97 Hz,
CO). Anal. calcd. (%) for C54H46I4Hg2O2P2 (1698): C, 38.20;
H, 2.73. Found (%): C, 38.37, H, 2.67.
d
= 21.15. 13C NMR
3
d
1
CH), 123.29 (d, JPC = 90.68 Hz, PPh3 (i)), 129.84 (d,
4
2
3JPC = 14.01 Hz, PPh3 (m)), 134.28 (d, JPC = 11.51 Hz, PPh3
2
(o)), 134.72 (s, PPh3 (p)), 142.39 (s, COPh (i)), 127.18 (s,
COPh (m)), 132.65 (s, COPh (o)), 129.46 (s, COPh (p)),
192.11 (s, CO). Anal. calcd. (%) for C29H29HgI2O2PS (927): C,
35.57; H, 3.15. Found (%): C, 35.12; H, 3.11.
2.3.5. [CdCl(m-Cl){CH(PPh3)C(O)C6H4Me}]2 (4)
To CdCl2. H2O (0.150 g, 0.38 mmol) dissolved in 5 mL of
dried methanol was added L (0.077 g, 0.38 mmol) at room
temperature. The mixture was stirred for 12 h. The white
solid product was filtered, washed with dietyl ether and
dried under reduced pressure. Yield: (64%); mp 197–
2.3.9. [CdCl2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (8)
Yield: (65%); Decomp. 183–185 8C. Selected IR data
(KBr,
n
/cmÀ1), 1635 (
n
C5O) and 828 (
n
P+-CÀ). 1H NMR
(DMSO-d6, ppm):
d
= 2.12 (s, 3H, CH3), 5.0 (br, 1H, CH),
7.33–8.12 (m, 19H, arom). 31P NMR (DMSO-d6, ppm):
200 8C. Selected IR data (KBr,
n
/cmÀ1), 1653 (
= 2.30 (s, 3H, CH3),
n
C5O) and 739
d
= 23.12. 13C NMR (DMSO-d6, ppm):
d
= 19.68 (s, CH3),
1
1
(
n
P+–CÀ). 1H NMR (DMSO-d6, ppm):
d
49.32 (d, JPC = 75.61 Hz, CH), 124.21 (d, JPC = 92.59 Hz,
4.40 (d, 1H, 2JPH = 27.68 Hz, CH), 6.85–7.78 (m, 19H, arom).
PPh3 (i)), 130.24 (d, JPC = 15.14 Hz, PPh3 (m)), 134.18 (d,
3
31P NMR (DMSO-d6, ppm):
d
= 16.35. 13C NMR (DMSO-d6,
2JPC = 13.84 Hz, PPh3 (o)), 135.62 (s, PPh3 (p)), 143.08 (s,
COPh (i)), 127.84 (s, COPh (m)), 133.12 (s, COPh (o)), 129.82
(s, COPh (p)), 187.13 (s, CO). Anal. calcd. (%) for
1
ppm):
d
= 20.77 (s, CH3), 44.56 (d, JPC = 72.56 Hz, CH),
121.30 (d, 1JPC = 90.31 Hz, PPh3 (i)), 128.83 (d,
2
3JPC = 12.07 Hz, PPh3 (m)), .66 (d, JPC = 10.36 Hz, PPh3
C29H29CdCl2O2PS (656): C, 53.10; H, 4.46. Found (%): C,
(o)), 132134.08 (s, PPh3 (p)), 153.23 (s, COPh (i)), 121.94 (s,
COPh (m)), 126.60 (s, COPh (o)), 128.57 (s, COPh (p)),
183.66 (d, JPC = 2.43 Hz, CO). Anal. calcd. (%) for
52.41; H, 4.44.
2
3. Results and discussion
3.1. Chemistry
C54H46Cd2Cl4O2P2 (1156): C, 56.13; H, 4.01. Found (%):
C, 56.22; H, 4.03.
2.3.6. [HgCl2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (5)
In this study, four binuclear complexes and four
mononuclear complexes with the ambidentate phos-
phorus ylide (p-methylbenzoyl)methylene triphenylpho-
sphorane were synthesized and investigated by
physicochemical techniques. Reaction of L with MX2
(M = Hg; X = Cl, Br and I and M = Cd; X = Cl) in methanol
(1:1) yielded the binuclear complexes (Scheme 2) [10a,17].
The bridge-splitting reaction of binuclear complexes
General procedure: 0.150 g (0.1 mmol) of binuclear
complex 1 was dissolved in DMSO (2 ml). The pale yellow
crystals formed by the slow evaporation of the solvent over
several days. Yield: (82%); Decomp. 183 8C. Selected IR data
(KBr,
n
/cmÀ1), 1635 (
nC5O) and 825 (n
P+–CÀ), 1H NMR
(DMSO-d6, ppm):
d
= 2.41 (s, 3H, CH3), 5.36 (br, 1H, CH),
7.24–8.13 (m, 19H, arom). 31P NMR (DMSO-d6, ppm):
d
= 22.03. 13C NMR (DMSO-d6, ppm):
d
= 22.25 (s, CH3),
1
[MX(
mononuclear
m
-X){CH(PPh3)C(O)C6H4Me}]2 by DMSO yields the
complexes [MX2{CH(PPh3)C(O)C6H4-
1
47.89 (d, JPC = 74.14 Hz, CH), 122.21 (d, JPC = 90.09 Hz,
3
PPh3 (i)), 130.14(d, JPC = 11.64 Hz, PPh3 (m)), 133.72 (d,
Me}(OSMe2)] (Scheme 2) [13].
2JPC = 10.0 Hz, PPh3 (o)), 133.93 (s, PPh3 (p)), 143.21 (s,
COPh (i)), 127.64 (s, COPh (m)), 132.0 (s, COPh (o)), 128.19
(s, COPh (p)), 189.58 (s, CO). Anal. calcd. (%) for
3.2. IR studies
C29H29HgCl2O2PS (744): C, 46.81; H, 3.93. Found (%): C,
The n (C5O) band, which is sensitive to complexation,
46.72; H, 3.80.
occurs at 1582, in the parent ylides (L) [17–20,23].
Coordination of ylide through the carbon atom causes
2.3.7. [HgBr2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (6)
an increase in the
coordination a lowering of the n
[10b]. Thus the IR absorption bands for the complexes at
higher frequencies indicate that C-coordination has
occurred. The n(P–C) band frequencies, which are also
diagnostic of the coordination mode, occur at 895 in the
parent ylides (L), and are shifted to lower frequencies for
the complexes, suggesting some removal of the electron
density of the P–C bonds [24]. It should be noted that there
is no significant difference in the IR absorption band
between binuclear and related mononuclear complexes.
n
(C5O) band, whereas for O-
(C5O) band is expected
Yield: (95%); Decomp. 196 8C. Selected IR data (KBr,
n/
cmÀ1), 1628 (
ppm):
n
C5O) and 819 (
n
P+–CÀ). 1H NMR (DMSO-d6,
d
= 2.42 (s, 3H, CH3), 5.65 (br, 1H, CH), 7.42–8.30 (m,
19H, arom). 31P NMR (DMSO-d6, ppm):
d
= 21.65. 13C NMR
(DMSO-d6, ppm):
CH), 123.01 (d, JPC = 89.52 Hz, PPh3 (i)), 129.27 (d,
3JPC = 12.43 Hz, PPh3 (m)), 133.23 (d, JPC = 9.41 Hz, PPh3
d
= 21.06 (s, CH3), 47.13 (d, 1JPC = 73.95 Hz,
1
2
(o)), 133.44 (s, PPh3 (p)), 142.41 (s, COPh (i)), 126.57 (s, COPh
(m)), 131.97 (s, COPh (o)), 128.64 (s, COPh (p)), 190.75 (s,
CO). Anal. calcd. (%) for C29H29HgBr2O2PS (833): C, 41.82; H,
3.5. Found (%): C, 42.01; H, 3.4.
3.3. NMR studies
2.3.8. [HgI2{CH(PPh3)C(O)C6H4Me}(OSMe2)] (7)
Yield: (71%); Decomp. 224 8C. Selected IR data (KBr,
n
/
In the 1H NMR spectra, methinic protons exhibit
doublet or broad doublet signals. Similar behavior was
cmÀ1), 1628 ( P+-CÀ). 1H NMR (DMSO-d6,
n
C5O) and 832 (
n

1020
S.J. Sabounchei et al. / C. R. Chimie 16 (2013) 1017–1023
Scheme 2. Synthetic route for the preparation of Hg(II) and Cd(II) complexes. Reagents and conditions: i: in acetone, using dry nitrogen atmosphere, 10 h at
25 8C; ii: in an aqueous solution of NaOH (0.5 mol), 2 h in 40 8C; iii: in methanol, for binuclear Hg complexes, 4 h at 25 8C; for binuclear Cd complexes, 12 h at
25 8C; iv: in dimethyl solfoxide, 3 days at 25 8C.
observed earlier in the case of ylide complexes of
platinum(II) chloride [25]. The expected downfield shifts
of 31P and 1H signals for the PCH group upon complexation
in the case of C-coordination were observed in their
corresponding spectra. It must be noted that O-coordina-
tion of the ylide generally leads to the formation of cisoid
and transoid isomers, giving rise to two different signals in
31P and 1H NMR (Scheme 1) [7h]. The downfield shifts of
the CH proton upon coordination in the 1HNMR spectra
show the coordination of the ylides through methinic
carbon atoms. The proton-decoupled 31P NMR spectra
3.4. X-ray structure analysis
Table provides the crystallographic results and
1
refinement information for complex 6. The molecular
structure is shown in Fig. 1. Pertinent bond distances and
angles for 6 are given in Table 2. The fractional atomic
coordinates and equivalent isotropic displacement coeffi-
cients (Ueq) for the non-hydrogen atoms of the complex are
shown in the supplementary material. The Hg(II) centre in
complex 6 is coordinated by one carbon from ylide, one
oxygen of coordinated DMSO and two bromo atoms in a
distorted tetrahedral geometry. The two different Hg–Br
show only one sharp singlet between
d 16.2–24.6 ppm for
˚
the complexes of Hg(II) halides and CdCl2.H2O. Chemical
shift values for the complexes appear to be downfield by
distances in 6 (2.6166(10) and 2.5204(9) A) are less than
those found in the mononuclear complex of [HgBr2(PPh3)2]
˚
about
d
2–10 ppm with respect to the parent ylide (
d
(2.633(6) and 2.626(8) A) [27], indicating relatively strong
14.10 ppm for L), indicating that coordination of the ylide
has occurred.
Hg–Br bonds in 6. The difference between two distances in
these complexes might be arising from steric effects of the
large ylidic groups. The angles around mercury vary from
88.3(3) to 138.80(17), indicating a much distorted tetra-
hedral environment. This distortion must be due to the
higher s character of the sp3 hybrid mercury orbitals
involved in the above bonds and the steric effects of
phosphine group causing the C–H–Br angle to be larger. In
complex 6, a medium intermolecular interactions, includ-
The most interesting aspect of the 13C NMR spectra of
the complexes is the up-field shift of the signals due to the
ylidic carbon. Similar up-field shifts of 2–3 ppm with
reference to the parent ylide were also observed in the
case of the mercury cyclopentadienyl complex [26] and in
our synthesized Hg(II) complexes [9d,10b]. The 13C shifts
of the CO group in the complexes are lower than noted for
the same carbon in the parent ylide, indicating much
lower shielding of the carbon of the CO group in these
complexes.
˚
ing C–H (25) Phenyl. . ..Br (1) (3.044 A) (symmetry opera-
tions used: 1.5–x, À½+y, ½–z), determine the structural
assembly in this compound (Fig. 2).

S.J. Sabounchei et al. / C. R. Chimie 16 (2013) 1017–1023
1021
Table 1
Table 2
a
˚
Crystal data and refinement details for 6.
Selected bond lengths (A) and angles (8) for 6 .
Identification code
6
Bond lengths
Empirical formula
Formula weight
Temperature
C29H29Br2Hg1O2P1S1
832.95
Hg(1)–C(1)
Hg(1)–Br(1)
Hg(1)–Br(2)
Hg(1)–O(2)
P(1)–C(1)
2.221 (7)
2.6166 (10)
2.5204 (9)
2.540 (7)
1.788 (7)
1.230 (8)
1.498 (10)
1.412 (8)
298(2) K
˚
Wavelength
0.71073 A
Crystal system
Space group
Monoclinic
P2/1n
O(1)–C(2)
C(1)–C(2)
˚
Unit cell dimensions
a = 16.7187(16) A
˚
b = 10.7949(6) A
O(2)–S(1)
˚
c = 18.6553(18) A
= 115.677(7)8
3034.4(4)
Bond angles
b
3
˚
Volume (A )
Br(2)–Hg(1)–Br(1)
C(1)–Hg(1)–Br(2)
C(1)–Hg(1)–Br(1)
C(1)–Hg(1)–O(2)
O(2)–Hg(1)–Br(2)
O(2)–Hg(1)–Br(1)
C(2)–C(1)–P(1)
106.33 (3)
138.80 (17)
113.13 (17)
88.3 (3)
Z, calculated density (mg/m3)
Absorption coefficient (mmÀ1
F(000)
4,1.823
)
7.851
1600
Crystal size (mm)
0.30 Â 0.15 Â 0.10 mm
2.17–29.25
91.3 (2)
u, range for data collection (8)
106.9 (4)
112.8 (5)
109.3 (4)
110.5 (3)
Limiting indices
À18 ꢀ h ꢀ 22
À12 ꢀ k ꢀ 14
C(2)–C(1)–Hg(1)
P(1)–C(1)–Hg(1)
À25 ꢀ l ꢀ 25
Reflections collected/unique
Completeness
21,289/8119 [R(int) = 0.0919]
98.4%
a
See Fig. 1 for the atom numbering.
Absorption correction
Max. and min. transmission
Refinement method
Numerical
0.450 and 0.250
Full-matrix least-squares on F2
8119/0/325
˚
1.7194(17) A [30], which shows that the corresponding
˚
Data/restraints/parameters
Goodness-of-fit on F2
bond is considerably elongated to 1.788(7) A. The C-
0.899
coordination of the title ylide is in contrast to the O-
coordination of the phosphorus ylide Ph3PC(COMe)(COPh)
(ABPPY) in a different Hg(II) complex [30]. The difference
in coordination mode between ABPPY and these ylides to
Hg(II) can be rationalized in terms of the electronic
properties and steric requirements of the ylides. The lower
electronic density at the ylidic C atom in doubly stabilized
ylides compared to simple stabilized ylides has been
calculated by DFT (density functional theory) methods
recently [31]. It was also demonstrated in the same paper
that these factors are not solely responsible for the bonding
Final R indices [I > 2
s
(I)]
R1 = 0.0543, wR2 = 0.1073
R1 = 0.1165, wR2 = 0.1254
1.818 and À0.945
R indices (all data)
˚
Largest diff. peak and hole (eA )
3
The stabilized resonance structure for the parent ylides
is destroyed by the complex formation 6; thus, the C(H)–C
bond length 1.498(10) A is significantly longer than the
corresponding distance found in the similar uncomplexed
phosphorane (1.407(8) A [28] and 1.401(2) A) [29]. On the
other hand, the bond length of P–C(H) in the similar ylide is
˚
˚
˚
Fig. 1. ORTEP view of the asymmetric unit of 6 (30% probability level) showing the numbering scheme.

1022
S.J. Sabounchei et al. / C. R. Chimie 16 (2013) 1017–1023
of O-bonded species, even in the absence of
p-accepting or
bulky ligands. This suggests that a particular electronic
structure is required in order to favor the metal–sulfur
bond over the metal–oxygen one [33]. Bulkiness of present
ylides and the absence of the above influences in the
structure shown on Fig. 2 lead to preferring O-bonding. An
overestimate is found for the calculated S–O distance in
˚
˚
‘free’ DMSO (1.509 A), which results in a value 0.018 A
˚
longer than the experimental reference one of 1.492(1) A
[37]. The significant elongation of the S–O distance upon
O-coordination is further confirmed by the recent X-ray
structure determination of disulfoxide and related cop-
per(II) complexes, where the average S–O distances are of
˚
˚
1.487(4) A (free) and 1.520(3) A (O-bonded) [38]. It is
˚
worth noting that in 6 the S–O bond distance of 1.412(8) A
˚
is about 0.080 A lower than the experimental reference
˚
value of 1.492(1) A for free DMSO ligand [37]. To get an
idea about the nature of this distance, a Cambridge
Structural Database (CSD) search was carried out with
the help of the Vista program (version 2.1) in the
November 2010 release of the CSD version 5.32 (ref: The
Cambridge Crystallographic Data Center, Cambridge, UK,
2010.). The result of this search on S–O distances for O-
coordinated DMSO to any metal shows that only 18 com-
Fig. 2. A representation of complex 6 packing showing the association of
the adjacent molecules through H (25) Phenyl. . ..Br (1) interactions.
Dotted lines represent the short contacts. For visualization of colors, see
the online version of this article.
properties of doubly stabilized ylides. For ‘‘simple’’stabil-
ized ylides, the C- vs. O-bonding is also a very delicate
balance of steric and electronic properties [32]. In this
balance it is necessary to consider not only the size and
shape of the ligand in the final bonding mode, but also the
electronic nature of the metal (Pd, Pt, Ru, Au, etc.) and the
donor atoms (C, O, N, etc.) and even the position of the
coordination site (trans to a C atom, trans to a N atom, trans
to an O atom, and so on). All these facts must be considered
as a whole in order to account for the final bonding mode of
a given ylide. The nucleophilicity of the carbanion in ABPPY
is less than in our ylides; this is due to the additional
delocalization of the ylide electron density in ABPPY,
which is facilitated by the second carbonyl group. This will
reduce the ability of ABPPY to bind via the ylidic carbon.
Belluco et al. have studied steric influences on the
coordination modes of ylide molecules to Pt(II) systems
[8a]. These authors concluded that the preferred coordina-
tion mode is via the ylidic carbon, but that steric hindrance
around the metal centre or the ylidic carbon will
necessitate O-coordination. Indeed, this trend is reflected
here, these ylides are slightly less sterically demanding
than ABPPY and are C-coordinated to Hg(II).
˚
plexes have shorter distance than 1.413 A.
4. Conclusion
The present study describes the synthesis and char-
acterization of mono- and dinuclear Hg(II) and Cd(II)
complexes of (p-methylbenzoyl)methylene triphenylpho-
sphorane as a ligand. On the basis of the physicochemical
and spectroscopic data, we propose a monodentate C-
coordination to the metals, which is further confirmed by
the X-ray crystal structure of 6.
Acknowledgment
This work was supported by Bu-Ali Sina University
funds. We thank Mr. Zebarjadian for recording NMR
spectra.
Appendix A. Supplementary data
CCDC 805758 contains the supplementary crystallogra-
phic data for complex 6. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online
version, at http://dx.doi.org/10.1016/j.crci.2013.03.015.
Literature data show that the coordination mode of
dimethylsulfoxide (DMSO) to relatively soft metal atoms
depends on both electronic and steric factors deriving from
the DMSO moderate
p-acceptor properties and its greater
steric demand, in the case of S-bonding [33]. In the case of
ruthenium(II) complexes, coordination through sulfur
(DMSO–S) seems to be preferred over coordination
through oxygen (DMSO–O) to get stable species, unless
ligand overcrowding occurs [34] or DMSO is trans to strong
p-acceptors like CO [35] and NO [36]. Although on the basis
of the Hard-Soft-Acid-Base principle, S-bonding is pre-
ferred by ‘soft’ metal ions, but with bulky ligands like
present phosphorus ylides, steric effects can induce O-
bonding. It may also be seen that for ‘soft’ metal ions, such
as Ag(I), Cd(II), and Hg(II), there is evidence of a prevalence
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