Structural, theoretical and multinuclear NMR study of mercury(II) complexes of phosphorus ylides: Mono and binuclear complexes

Article abstract of DOI:10.1016/j.poly.2008.03.009

Reaction of phosphorus ylide Ph₃PCHC(O)C₆H₄Cl (Y₁) with HgX₂ (X = Cl, Br and I) and ylide (p-tolyl)₃PCHC(O)CH₃ (Y₂) with HgI₂ in equimolar ratios using methanol as solvent leads to binuclear products. The bridge-splitting reaction of binuclear complex [(Y₁) · HgCl₂]₂ by DMSO yields a mononuclear complex containing DMSO as ligand. O-coordination of DMSO is revealed by single crystal X-ray analysis in mononuclear complex of [(Y₁) · HgCl₂ · DMSO]. C-coordination of ylides is confirmed by X-ray structure of binuclear complex [(Y₂) · HgI₂]₂. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. Theoretical studies on mercury(II) complexes of Y₁ show that formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is more favorable than that of binuclear complexes.

Full text of DOI:10.1016/j.poly.2008.03.009

Polyhedron 27 (2008) 2015–2021
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural, theoretical and multinuclear NMR study of mercury(II) complexes
of phosphorus ylides: Mono and binuclear complexes
a
a
a
a
Seyyed Javad Sabounchei a, , Hassan Nemattalab , Sadegh Salehzadeh , Sima Khani , Mehdi Bayat ,
*
Hamid Reza Khavasi b
a Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
b Department of Chemistry, Shahid Beheshti University, Evin, Tehran 19839-63113, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of phosphorus ylide Ph3PCHC(O)C6H4Cl (Y1) with HgX2 (X = Cl, Br and I) and ylide (p-tolyl)3PCH-
C(O)CH3 (Y2) with HgI2 in equimolar ratios using methanol as solvent leads to binuclear products. The
bridge-splitting reaction of binuclear complex [(Y1) ꢀ HgCl2]2 by DMSO yields a mononuclear complex
containing DMSO as ligand. O-coordination of DMSO is revealed by single crystal X-ray analysis in mono-
nuclear complex of [(Y1) ꢀ HgCl2 ꢀ DMSO]. C-coordination of ylides is confirmed by X-ray structure of
binuclear complex [(Y2) ꢀ HgI2]2. Characterization of the obtained compounds was also performed by ele-
mental analysis, IR, 1H, 31P, and 13C NMR. Theoretical studies on mercury(II) complexes of Y1 show that
formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is
more favorable than that of binuclear complexes.
Received 10 February 2008
Accepted 4 March 2008
Available online 21 April 2008
Keywords:
Mercury(II) halide
Phosphorus ylide
DMSO
Triphenylphosphine
Triparatolylphosphine
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
[5,12–15], whereas, O-coordination dominates when the metals in-
volved are hard, e.g., Ti(IV), Zr(IV), and Hf(IV) [16]. Only W(0) com-
The utility of metalated phosphorus ylides in synthetic chemis-
try has been well documented [1,2]. Synthesis of complexes de-
rived from phosphorus ylides and Hg(II) halides was started in
1965 by Nesmeyanov et al. [3]. In 1975, Weleski et al. [4] proposed
a symmetric halide-bridged dimeric structure for Hg(II) halide
complexes whereas Kalyanasundari et al. [5] reported an asym-
metric halide-bridged dimeric structure in 1995. In 1985, Sanehi
et al. [6] reported a mononuclear Hg(II) complex of phosphorus
ylides without any structural characterization. We have recently
focused on the synthesis of binuclear and polynuclear complexes
derived from mercury(II) salts and phosphorus ylides [7–9]. The
a-keto-stabilized phosphorus ylides R3P@C(R0)COR00 show interest-
ing properties such as their high stability and their ambidentate
character as ligands (C- versus O-coordination) [10]. This ambiden-
tate character can be rationalized in terms of the resonance forms
A–C, together with the isomeric form D (Chart 1).
plexes of the type W(CO)5L (L = ylide) [17] and Pd(II) complexes of
stoichiometry [Pd(C6F5)(L2)(APPY)](ClO4) [12] [APPY = Ph3PCH-
COMe; L = PPh3 and PBu3; L2 = bipy] contain stable ylides O-linked
to a soft metal centre.
2. Experimental
2.1. Materials
All reactions were performed in air. Starting materials were
purchased from commercial sources and used without further
purification. The ligands were synthesized by the reaction of re-
lated phosphine with 2-bromo-40-chloroacetophenone or chloro-
acetone and concomitant elimination of HBr by NaOH [18].
2.2. Physical measurements
Form B can be considered as leading to coordination by the car-
bon atom to give a complex of form E, whereas isomers C and D
would both lead to coordination by the oxygen atom, affording
structures F (transoid) and form G (cisoid), respectively. Although
many coordination modes are possible for keto ylides [11], coordi-
nation through carbon is more predominant and observed with
soft metal ions, e.g., Pd(II), Pt(II), Ag(I), Hg(II), Au(I) and Au(III)
Melting points were measured on a SMPI apparatus. Elemental
analysis for C and H atoms were performed using a Perkin–Elmer
2400 series analyzer. IR spectra were recorded on a Shimadzu
435-U-04 FT spectrophotometer from KBr pellets. 1H, 13C, and 31P
NMR spectra were recorded on a 300 MHz Bruker spectrometer
in DMSO-d6 or CDCl3 as solvent at 25 °C. Chemical shifts (ppm)
are reported according to internal TMS and external 85% phospho-
ric acid. Coupling constants are given in Hz. The single crystal
X-ray diffraction analyses were performed on a STOE IPDS-II two
* Corresponding author.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.03.009

2016
S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
H
A
H
H
H
+
C-
+
+
Ar3P
Ar3 P
C
C
Ar3 P
Ar3 P
C
O-
R
C
R
R
-O
O
O
R
B
C
D
H
H
H
+
M
+
C
Ar3 P
C
Ar3 P
O-
C(O)R
R
M
P+Ar3
O-
R
M
E
F
G
Chart 1.
circle diffractometer at 293(2) K, using graphite monochromated
Mo Ka X-ray radiation (k = 0.7107 nm). The data collection were
performed at room temperature using the x-scan technique and
using the STOE X-AREA software package [19]. The crystal struc-
tures were solved by direct methods and refined by full-matrix
least-squares on F2 by SHELX [20] and using the X-STEP32 crystallo-
graphic software package [21]. All non-hydrogen atoms were re-
fined anisotropically using reflections I > 2r(I). Hydrogen atoms
were located in ideal positions.
50 ml) led to elimination of HBr, giving the free ligand Y1. IR
(KBr, cmꢁ1): m 1579 (C@O), 1522, 1480, 1435, 1404, 1383, 1175,
1104, 1085, 1009, 882 (P–C), 848. 1H NMR (CDCl3) dH: 4.38 (d,
2JPH = 23.75 Hz, 1H, CH); 7.25–7.94 (m, 19H, Ph). 31P NMR (CDCl3)
1
dP: 14.19 (s). 13C NMR (CDCl3) dC: 50.65 (d, JPC = 110.3 Hz, CH);
1
126.0 (d, JPC = 91.40 Hz, PPh3 (i)); 127.31 (COPh (m)); 128.03
3
(PPh3 (p)); 128.48 (d, JPC = 12.41 Hz, PPh3 (m)); 131.80 (d,
2
4JPC = 2.73 Hz, COPh (o)); 132.60 (d, JPC = 10.25 Hz, PPh3 (o));
2
134.71 (COPh (p)); 139.15 (d, JPC = 14.69 Hz, COPh (i)); 182.84
2
(d, JPC = 3.1 Hz, CO).
2.3. Theoretical studies
2.5. (p-tolyl)3PCHCOCH3 (Y2)
The geometries of compounds were fully optimized at the Har-
tree–Fock (HF) level of theory using the GAUSSIAN98 program [22] on
a Pentium-PC computer with 3600 MHz processor. The standard
LanL2mb basis set was used for all complexes [23]. This basis set
includes effective core potentials (ECP) for both the mercury and
phosphorus as well as halide (Cl, Br and I) ions. Vibrational fre-
quency analyses, calculated at the same level of theory, indicate
that optimized structures are at the stationary points correspond-
ing to local minima, without any imaginary frequency. Atomic
coordinates for ab initio calculations were obtained from the data
of the X-ray crystal structure analyses.
Anal. Calc. for C24H25OP: C, 80.00; H, 7.00. Found: C, 79.51; H,
7.01%. Yield 0.364 g (92%). m.p., 100–102 °C. IR (KBr disk): m
(cmꢁ1) 1711, 1599 (C@O), 1502, 1448, 1425, 1402, 1363, 1313,
1193, 1156, 1111, 1038, 1002, 848 (P–C), 808 and 777. 1H NMR
(CDCl3): d (ppm) 2.04 (3H, s, COCH3), 2.36 (9H, s, 3CH3), 3.65 (1H,
2
d, JPH = 24.8 Hz, CH); 7.24–7.52 (12H, m, Ph). 31P NMR (CDCl3)
dp: 10.59 (s). 13C NMR (CDCl3) dc: 21.49 (s, 3CH3); 28.43 (d,
1
3JPC = 15.1 Hz, COCH3); 52.53 (d, JPC = 107.7 Hz, CH); 124.29 (d,
2
1JPC = 92.7 Hz, p-tolyl, (i)); 133.05 (d, JPC = 10.5 Hz, p-tolyl, (o));
3
129.51 (d, JPC = 12.3 Hz, p-tolyl, (m)); 142.32 (p-tolyl, (p));
190.38 (CO).
2.4. Preparation of Ph3PCHCOC6H4Cl (Y1), general procedure for ylides
[24]
2.6. Synthesis of the complexes
A solution of triphenylphosphine (0.131 g, 0.5 mmol) and 2-
bromo-40-chloroacetophenone (0.117 g, 0.5 mmol) in acetone
(15 ml) was stirred at room temperature for 4 h. The resulting
white precipitate was filtered off, washed with diethylether and
dried. Further treatment with aqueous solution of NaOH (0.5 M,
The binuclear complexes 1–4 were prepared based on a general
procedure as follows (Scheme 1). According to various papers
[5,7,8,25], the binuclear structures are suggested for above com-
pounds, as shown in Scheme 1. X-ray quality crystals of the com-
plexes
4
and
5
(Schemes
1
and 2) were grown from a
P+Ar3
CH
X
Hg
O
X
CH3OH
Ar3PCHC(O)R+ HgX2
r t, 1h
R
Hg
R
X
O
X
CH
(1): R = C6H4Cl, Ar = Ph, X = Cl
(2): R = C6H4Cl, Ar = Ph, X = Br
(3): R = C6H4Cl, Ar = Ph, X = I
(4): R = CH3, Ar = p-tolyl, X = I
P+Ar3
Scheme 1.

S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
2017
Cl
Hg
Cl
C6H4Cl
O
r t
O
[(Ph3PCHC(O)C6H4Cl).HgCl2]2 + 2 DMSO
2
CH
P+Ph3
S
H3C
CH3
Scheme 2.
1
dimethylsulfoxide solution of compounds 4 and 1, respectively.
This was carried out by the slow evaporation of the solvent over
several days.
1JPC = 63.8 Hz, CH); 119.97 (d, JPC = 92.6 Hz, p-tolyl (i)); 129.84
3
2
(d, JPC = 12.6 Hz, p-tolyl (m)); 133.09 (d, JPC = 10.2 Hz, p-tolyl
(o)); 143.81 ((p-tolyl) (p)); 197.91 (CO).
2.6.1. Synthesis of [(Y1) ꢀ HgCl2]2 (1), general procedure for dimeric
structures
2.6.5. [(Y1) ꢀ HgCl2 ꢀ DMSO] (5)
0.137 g (0.1 mmol) of binuclear complex 1 was dissolved in
DMSO (2 ml). The pale yellow crystals formed by the slow evapo-
ration of the solvent over several days. Yield 0.147 g (96%). Decom-
position at 180 °C. IR (KBr, cmꢁ1): m 1635 (C@O), 1586, 1567, 1483,
1437, 1398, 1312, 1284, 1184, 1108, 1091, 1005, 823 (P–C). 1H
To a methanolic solution (15 ml) of HgCl2 (0.082 g, 0.3 mmol)
was added a methanolic solution (10 ml) of Y1 (0.124 g, 0.3 mmol).
The mixture was stirred for 1 h. The separated solid was filtered
and washed with diethyl ether. Anal. Calc. for C26H20Cl3HgOP: C,
45.50; H, 2.94. Found: C, 44.41; H, 2.81%. Yield 0.115 g (56%).
m.p. 215–217 °C. IR (KBr, cmꢁ1): m 1635 (C@O), 1586, 1567, 1483,
1437, 1398, 1312, 1284, 1184, 1108, 1091, 1005, 823 (P–C). 1H
2
NMR (DMSO-d6) dH: 5.46 (d, JPH = 6.36 Hz, 1H, CH); 7.46–8.10
(m, 19H, Ph). 31P NMR (DMSO-d6) dp: 22.16 (s). 13C NMR (DMSO-
1
1
d6) dc: 46.77 (d, JPC = 75.58 Hz, CH); 123.33 (d, JPC = 89.46 Hz,
2
3
NMR (DMSO-d6) dH: 5.46 (d, JPH = 6.36 Hz, 1H, CH); 7.46–8.10
PPh3 (i)); 127.81 (COPh (m)); 129.16 (d, JPC = 12.35 Hz, PPh3
(m)); 129.16 (COPh (p)); 129.74 (PPh3 (p)); 133.10 (d, JPC
9.46 Hz, PPh3 (o)); 136.22 (COPh (o)); 136.63 (COPh (i)); 188.82
(s, CO).
(m, 19H, Ph). 31P NMR (DMSO-d6) dp: 22.16 (s). 13C NMR (DMSO-
=
2
1
1
d6) dc: 46.77 (d, JPC = 75.58 Hz, CH); 123.33 (d, JPC = 89.46 Hz,
3
PPh3 (i)); 127.81 (COPh (m)); 129.16 (d, JPC = 12.35 Hz, PPh3
(m)); 129.16 (COPh (p)); 129.74 (PPh3 (p)); 133.10 (d,
2JPC = 9.46 Hz, PPh3 (o)); 136.22 (COPh (o)); 136.63 (COPh (i));
188.82 (s, CO).
3. Results and discussion
3.1. Spectroscopy
2.6.2. [(Y1) ꢀ HgBr2]2 (2)
Anal. Calc. for C26H20Br2ClHgOP: C, 40.28; H, 2.60. Found: C,
40.13; H, 2.57%. Yield 0.193 g (83%). m.p. 195–197 °C. IR (KBr,
cmꢁ1): m 1625 (C@O), 1586, 1566, 1482, 1435, 1398, 1317, 1292,
1195, 1108, 1030, 1010, 997, 885, 819 (P–C) and 805. 1H NMR
The m (CO) band, which is sensitive to complexation, is observed
for complexes at higher frequencies compared to the parent ylides,
indicating coordination of the ylide thorough carbon atom in each
case [26]. The m (P+–Cꢁ) band, (823, 819 and 820 cmꢁ1 for com-
plexes 1–3, respectively) which is also diagnostic of the coordina-
tion modes, occurs at lower frequencies (882 cmꢁ1) in comparison
to the parent ylide (Y1), consistent with some removal of electron
density in the P–C bonds [7–9]. C-coordination causes an increase
in m (CO) and decrease in m (P+–Cꢁ) while for O-coordination a low-
ering for both frequencies is expected [15]. It should be noted that
there is not any significant difference in the IR absorption bands for
binuclear complex 1 and related mononuclear complex 5.
2
(DMSO-d6) dH: 5.38 (d, JPH = 7.62 Hz, 1H, CH); 7.45–8.08 (m,
19H, Ph). 31P NMR (DMSO-d6) dp: 22.72 (s). 13C NMR (DMSO-d6)
1
1
dc: 48.04 (d, JPC = 79.40 Hz, CH); 124.13 (d, JPC = 89.97 Hz, PPh3
3
(i)); 128.52 (COPh (m)); 129.92 (d, JPC = 11.40 Hz, PPh3 (m));
130.54 (PPH3 (p)); 133.87 (d, 2JPC = 9.28 Hz, PPh3 (o)); 133.93 (COPh
(p)); 136.96 (COPh (o)); 137.22 (COPh (i)); 189.41 (s, CO).
2.6.3. [(Y1) ꢀ HgI2]2 (3)
Anal. Calc. for C26H20ClHgI2OP: C, 35.92; H, 2.32. Found: C,
35.86; H, 2.17%. Yield 0.170 g (82%). m.p. 192–194 °C. IR (KBr,
cmꢁ1): m 1620 (C@O), 1586, 1565, 1482, 1434, 1398, 1316, 1291,
1266, 1193, 1108, 1092, 1030, 1009, 998, 878, 820 (P–C) and
In the 1H NMR spectra, the signals due to the methinic protons
for complexes are doublet or broad. Similar behavior was observed
earlier in the case of ylide complexes of platinum(II) chloride [27].
The expected downfield shifts of 31P and 1H signals for the PCH
group upon complexation in the case of C-coordination were ob-
served in their corresponding spectra. The proton decoupled 31P
NMR spectra show only one sharp singlet between 20.63 and
22.72 ppm in the complexes. The appearance of a single signal
for the PCH group in each of the 31P and 1H NMR spectra indicates
that all ligands are in the same environment in these complexes, as
expected for C-coordination. It must be noted that O-coordination
of the ylide generally leads to the formation of a mixture of cisoid
and transoid isomers, giving rise to two different signals in 31P and
1H NMR spectra (Chart 1) [12]. The 31P chemical shift values for the
complexes appear to be shifted downfield by about 6.5–10 ppm
with respect to the parent ylides also indicating that coordination
of the ylide has occurred [5,7–9,25]. Satellites due to coupling to
199Hg for ylidic complexes of Hg(II) are only observed at low tem-
perature [7,25] or by solid-state 31P NMR [25] and also in the case
of Hg(NO3)2 ꢀ H2O as metal source [9]. Failure to observe satellites
802. 1H NMR (DMSO-d6) dH: 5.12 (d, JPH = 12.46 Hz, 1H, CH);
2
7.42–8.05 (m, 19H, Ph). 31P NMR (DMSO-d6) dp: 20.64 (s).
13C NMR (DMSO-d6) dc: 48.90 (d, JPC = 83.25 Hz, CH); 124.71
1
1
(d, JPC = 89.74 Hz, PPh3 (i)); 128.45 (COPh (m)); 129.85 (d,
3JPC = 12.15 Hz, PPh3 (m)); 130.24 (PPh3 (p)); 133.75 (d,
2JPC = 9.13 Hz, PPh3 (o)); 133.81 (COPh (p)); 136.66 (COPh (o));
3
137.67 (d, JPC = 10.64 Hz, COPh (i)); 187.81 (s, CO).
2.6.4. [(Y2) ꢀ HgI2]2 (4)
Anal. Calc. for C24H25HgI2OP: C, 35.38; H, 3.09. Found: C, 35.24;
H, 3.54%. Yield 0.218 g, 89%. m.p. 206–208 °C. IR (KBr, cmꢁ1): m
1655 (C@O), 1596, 1497, 1399, 1350, 1289, 1192, 1149, 1106,
964, 902, 852 and 805. 1H NMR (DMSO-d6): d (ppm) 2.14 (3H, s,
COCH3); 2.39 (9H, s, 3CH3); 4.59 (1H, br, CH); 7.44–7.66 (12H, m,
Ph). 31P NMR (DMSO-d6) dp: 20.63 (s). 13C NMR (DMSO-d6)
3
dc: 21.03 (3CH3); 30.54 (d, JPC = 11.2 Hz, COCH3); 50.39 (d,

2018
S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
in above spectra was previously noted in the complexes of Hg(II)
[28] and Ag(I) [15] and was assigned to fast exchange of the ylide
with the metal at higher temperatures.
and 2.7036(8) Å) are comparable to analogous distances in
[(Ph3PCHCOPh) ꢀ HgI2]2 (2.312(13) and 2.705(1) Å, respectively)
[5].
The most interesting aspect of the 13C NMR spectra of the com-
plexes is the upfield shift of the signals due to the ylidic carbon
atoms. Such an upfield shift was observed in [PdCl(g3-2-XC3H4)
(C6H5)3PCHCOR] (X = H, CH3; R = CH3, C6H5), and is due to the
change in hybridization of the ylidic carbon atom on coordination
[29]. Similar up field shifts of 2–3 ppm with reference to the parent
ylide were also observed in the case of [(C6H5)3PC5H4HgI2]2 [28].
The downfield shifts of the carbonyl C atom in the complexes com-
pared to the same carbon atom in the parent ylides, indicate a
much lower shielding of the CO group in these complexes.
The angles subtended by the ligands at the Hg(II) centre in 4
vary from 95.53(3) to 121.7(2) indicating a much distorted tetrahe-
dral environment. The widening of the IHgC angle from the tetra-
hedral angle must be due to the higher s character of the sp3
hybrid mercury orbitals involved in the above bonds and the for-
mation of a strong halide-bridge between Hg atoms which requires
the internal IHgI angle (95.53(3)) to be considerably smaller. The
two mercury atoms and two bridging halides are perfectly copla-
nar. The internuclear distance between mercury atoms in complex
4 were found to be 3.926 Å, which is much longer than the sum of
Van der Waals radii (3 Å) of the two mercury atoms [30], indicating
the absence of significant bonding interactions between the mer-
cury atoms in the molecular structures.
3.2. X-ray crystallography
Table 1 provides the crystallographic results and refinement
information for complexes 4 and 5. The molecular structures are
shown in Figs. 1 and 2. Pertinent bond distances and angles for 4
and 5 are given in Tables 2 and 3, respectively. Packing diagrams,
fractional atomic coordinates and equivalent isotropic displace-
ment coefficients (Ueq) for the non-hydrogen atoms of complexes
are shown in Supplementary materials.
The Hg(II) centre in complex 5 is coordinated by one carbon,
one oxygen and two chloro atoms in a distorted tetrahedral geom-
etry. The two different Hg–Cl distances in 5 (2.3986(13) and
2.5106(12) Å) are less than those of found in mononuclear complex
of [HgCl2(PPh3)2] [31] (2.559(2) and 2.545(3) Å), indicating rela-
tively strong Hg–Cl bonds in 5. Difference between two distances
in these complexes might be arising from steric effects of the large
ylidic groups. The angles around mercury in complex 5 vary from
87.39(13) to 139.45(11), indicating a much distorted tetrahedral
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 needing the C–Hg–Cl angle to
be larger.
The Hg(II) centre in complex 4 forms four-coordinate with sp3
hybridization. This environment is contained of one short terminal
Hg–I bond, one Hg–C bond and two asymmetric bridging Hg–I
bonds. The Hg–C and terminal Hg–I bond lengths in 4 (2.279(8)
Table 1
The stabilized resonance structure for the parent ylides are de-
stroyed by the complex formation, thus, the C(H)–C bond lengths,
1.473(12) Å (4) and 1.491(5) Å (5) are significantly longer than the
corresponding distances found in the uncomplexed similar phos-
phoranes (1.407(8) Å [32] and 1.401(2) Å [33]). On the other hand,
the bond length of P–C(H) in the similar ylide is 1.7194(17) Å [33]
which shows that the corresponding bonds are considerably elon-
gated to 1.786(8) Å (4) and 1.787(4) Å (5).
Crystallographic data summary for complexes 4 and 5
Compound
4
5
Empirical formula
C
48H50Hg2I4O2P2
C28H26Cl3HgO2PS
764.47
293(2)
0.71073
orthorhombic
Pbca
11.1014(11)
18.7168(14)
28.292(3)
90
90
90
5878.5(9)
8
1.727
Fw
1629.6
293(2)
0.71073
triclinic
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a (°)
b (°)
ꢀ
P1
11.697(2)
11.968(3)
11.933(2)
105.371(16)
106.160(16)
115.223(15)
1302.4(5)
1
The C-coordination of the title ylides is in contrast to the O-
coordination of the phosphorus ylide Ph3PC(COMe)(COPh) (ABPPY)
in a different Hg(II) complex [34]. The difference in coordination
mode between ABPPY and present ylides to Hg(II) can be rational-
ized in terms of the electronic properties, steric requirements and
size and shape of the ligand in the final bonding mode. This may
also explain by the electronic nature of the metal (Pd, Pt, Ru, Au,
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). The nucle-
ophilicity 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. Bel-
luco et al. have studied steric influences on the coordination modes
of ylide molecules to Pt(II) systems [35]. These authors concluded
that the preferred coordination 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).
c (°)
Volume (Å3)
Z
DCalcd (Mg/m3)
Absorption coefficient
2.078
8.353
5.658
(mmꢁ1
F(000)
)
752
2976
Crystal size (mm)
Theta range for data
collection (°)
0.35 ꢂ 0.22 ꢂ 0.12
0.50 ꢂ 0.30 ꢂ 0.04
1.98–26.76
2.25–26.82
Limiting indices
ꢁ14 6 h 6 14,
ꢁ15 6 k 6 15,
ꢁ15 6 l 6 15
ꢁ13 6 h 6 14,
ꢁ23 6 k 6 20,
ꢁ31 6 l 6 35
Reflections collected/
unique [R(int)]
7728/5006 [0.0304]
22647/6214 [0.0359]
Completeness to theta
(%)
Absorption correction
26.76, 90.5
numerical
26.82, 98.8
numerical
0.800 and 0.145
Maximum and minimum 0.370 and 0.131
transmission
Refinement method
full-matrix least-squares
full-matrix least-squares
on F2
on F2
3.3. DMSO as ligand
Data/restraints/
parameters
5006/0/262
6214/0/327
Literature data show that the coordination mode of dimethyl-
sulfoxide (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 [36]. In the case of ruthenium(II) complexes, coor-
dination through sulfur (DMSO–S) seems to be preferred over
Goodness-of-fit on F2
Final R indices
1.113
1.161
R1 = 0.0375, wR2 = 0.1240
R1 = 0.0372, wR2 = 0.0619
[I > 2sigma(I)]
R indices (all data)
Largest difference peak
R1 = 0.0456, wR2 = 0.1362
0.891 and ꢁ1.003
R1 = 0.0524, wR2 = 0.0658
0.870 and ꢁ0.597
and hole (e Åꢁ3
)

S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
2019
Fig. 1. ORTEP view of X-ray crystal structure of [(Y2) ꢀ HgI2]2 (4).
Fig. 2. ORTEP view of X-ray crystal structure of [(Y1) ꢀ HgCl2 ꢀ DMSO] (5).
coordination through oxygen (DMSO–O) to get stable species, un-
less ligand overcrowding occurs [37] or DMSO is trans to strong
p-acceptors like CO [38] and NO [39,40]. A similar overestimate is
found for the calculated S–O distance in ‘free’ DMSO (1.509 Å),
which results 0.018 Å longer than the experimental reference value
of 1.492(1) Å [41]. The significant elongation of the S–O distance
upon O-coordination is further confirmed by the recent X-ray struc-
ture determination of a disulfoxide and related copper(II) com-
plexes, where the average S–O distances are of 1.487(4) Å (free)
and 1.520(3) Å (O-bonded) [42]. This work reports the example of

2020
S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
Table 2
Selected bond lengths (Å) and angles (°) for 4
Bond lengths
C(3)–C(2)
C(3)–P(1)
C(3)–Hg(1)
C(2)–O(1)
I(1)–Hg(1)
I(2)–Hg(1)
I(2)–Hg(1)#1
4
1.473(12)
1.786(8)
2.279(8)
1.214(12)
2.7036(8)
2.7795(9)
3.0544(12)
Bond angles
C(2)–C(3)–Hg(1)
P(1)–C(3)–Hg(1)
Hg(1)–I(2)–Hg(1)#1
C(2)–Hg(1)–I(1)
C(2)–Hg(1)–I(2)
I(1)–Hg(1)–I(2)
C(3)–Hg(1)–I(2)#1
I(1)–Hg(1)–I(2)#1
I(2)–Hg(1)–I(2)#1
101.3(6)
111.2(4)
84.47(3)
119.1(2)
121.7(2)
111.08(3)
98.4(2)
104.96(3)
95.53(3)
Table 3
Selected bond lengths (Å) and angles (°) for 5
Bond lengths
Hg(1)–C(8)
Hg(1)–Cl(1)
Hg(1)–Cl(2)
Hg(1)–O(2)
P(1)–C(8)
O(1)–C(7)
C(8)–C(7)
O(2)–S(1)
5
Fig. 3. The optimized structure of compound 5.
2.208(4)
2.3986(13)
2.5106(12)
2.548(3)
1.787(4)
1.220(5)
1.491(5)
1.507(3)
Table 4
A comparison between the calculated bond lengths (Å) and bond angles (°) for
compound 5 with corresponding experimental values
[(Y1) ꢀ HgCl2 ꢀ DMSO] (5)
X-ray
HF/Lanl2mb
Bond lengths
Hg(1)–Cl(2)
Hg(1)–Cl(1)
Hg(1)–O(2)
C(8)–Hg(1)
P(1)–C(8)
Bond angles
2.511(12)
2.399(13)
2.548(3)
2.207(4)
1.788(4)
1.491(5)
1.220(5)
2.676
2.688
2.301
2.272
1.919
1.538
1.222
Cl(2)–Hg(1)–Cl(1)
C(8)–Hg(1)–Cl(2)
C(8)–Hg(1)–Cl(1)
C(8)–Hg(1)–O(2)
O(2)–Hg(1)–Cl(2)
O(2)–Hg(1)–Cl(1)
C(7)–C(8)–P(1)
C(7)–C(8)–Hg(1)
P(1)–C(8)–Hg(1)
105.46(6)
112.91(11)
139.45(11)
87.39(13)
104.32(9)
95.67(8)
114.4(3)
108.5(3)
109.29(19)
C(8)–C(7)
C(7)–O(1)
Bond angles
C(8)–Hg(1)–Cl(1)
C(8)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–O(2)
Cl(2)–Hg(1)–O(2)
C(8)–C(7)–O(1)
Hg(1)–O(2)–S(1)
139.451
112.912
105.452
95.677
104.327
121.186
139.574
121.872
106.614
120.035
95.351
99.840
122.329
117.325
a mercury(II) complex containing DMSO as ligand with an O-coordi-
nation mode. It is worth noting that in 5, the S–O bond distance of
1.507(3) Å, is about 0.015 Å longer than the experimental reference
value of 1.492(1) Å for free DMSO ligand [41].
posed reaction (Eq. (1)) are more stable than reactants. These sta-
bilities are about 32, 34 and 40 kcal/mol where X is Cl, Br and I,
respectively.
3.4. Theoretical studies
We were interested to determine whether the formation of
mononuclear complexes in the gas phase in which DMSO acts as
ligand, energetically is more favorable than those of binuclear
complexes. The analytical and spectroscopic data for compound 5
can be similar to those of the other complexes synthesized here
containing ylide Y1. Thus the observed geometry of compound 5
was considered for ab initio calculations. The optimized structure
of compounds 5 is shown in Fig. 3. A comparison between the cal-
culated bond lengths (Å) and bond angles (°) for this compound
with corresponding experimental values are presented in Table 4.
A list of calculated key bond lengths and bond angles and the opti-
mized structure of compounds [(Y1) ꢀ HgX2 ꢀ DMSO] (where X = Br
and I) are presented in Supplementary materials.
rt
½ðY1Þ ꢀ HgX2ꢃ2 þ 2DMSO ! 2½ðY1Þ ꢀ HgX2 ꢀ DMSOꢃ
ð1Þ
The similarity of calculated energies for latter reaction of Y1 com-
plexes indicate that the reaction energy mainly depends on the
bridging halide atom. Therefore it is clear that for all compounds
synthesized here, the gas-phase reaction shown in Eq. (1) is an exo-
thermic reaction, thus it seems that the bridge-splitting reaction in
Table 5
Calculated electronic energies for binuclear complexes, DMSO and mononuclear
complexes involved in Eq. (1)
Compounds [(Y) ꢀ HgX2]2
DMSO
(hartree)
[(Y) ꢀ HgX2 ꢀ DMSO] DE
(hartree) )
(kcal.molꢁ1
As can be seen, the calculated bond lengths are slightly longer
than measured ones but the similarity of calculated and measured
bond angles reflects the similar geometrical structures for these
compounds in both the solid state and gas-phase. The results of
calculations (Table 5) show that the products of following pro-
(hartree)
X = Cl
X = Br
X = I
ꢁ2299.4410769 ꢁ161.8305649 ꢁ1311.5770188
ꢁ2292.3597909 ꢁ161.8305649 ꢁ1308.0376782
ꢁ2285.2766229 ꢁ161.8305649 ꢁ1304.5010169
32.524
34.159
40.337

S.J. Sabounchei et al. / Polyhedron 27 (2008) 2015–2021
2021
[10] J. Vicente, M.T. Chicote, J.A. Cayuelas, J. Fernandez-Baeza, P.G. Jones,
G.M. Sheldrick, P. Espinet, J. Chem. Soc., Dalton Trans. (1985) 1163.
[11] J.A. Albanese, A.L. Rheingold, J.L. Burmeister, Inorg. Chim. Acta 150 (1988) 213.
[12] R. Usón, J. Forniés, R. Navarro, P. Espinet, C. Mendívil, J. Organomet. Chem. 290
(1985) 125.
DMSO solution is potentially possible for all dimeric complexes of
Y1 in which DMSO acts as a ligand. The data show that in the case
of iodine complex, the formation of mononuclear complexes is rel-
atively more favorable than corresponding chlorine and bromine
complexes (Table 5).
[13] J. Vicente, M.T. Chicote, I. Saura-Llamas, J. Turpin, J. Fernandez-Baeza,
J. Organomet. Chem. 333 (1987) 129.
[14] J. Vicente, M.T. Chicote, J. Fernandez-Baeza, J. Martin, I. Saura-Llamas, J. Turpin,
P.G. Jones, J. Organomet. Chem. 331 (1987) 409.
[15] H. Koezuka, G. Matsubayashi, T. Tanaka, Inorg. Chem. 25 (1976) 417.
[16] J.A. Albanese, D.L. Staley, A.L. Rheingold, J.L. Burmeister, Inorg. Chem. 29
(1990) 2209.
[17] I. Kawafune, G.E. Matsubayashi, Inorg. Chim. Acta 70 (1983) 1.
[18] F. Ramirez, S. Dershowitz, J. Organomet. Chem. 22 (1957) 41.
[19] Stoe & Cie, X-AREA, version 1.30: Program for the Acquisition and Analysis of
Data, Stoe & Cie GmbH, Darmatadt, Germany, 2005.
[20] G.M. Sheldrick, SHELX97. Program for Crystal Structure Solution and
Refinement, University of Göttingen, Germany, 1997.
4. Conclusions
Present study describes the synthesis and characterization of
mononuclear and binuclear Hg(II) complexes of phosphorus
ylides. On the basis of the physico-chemical and spectroscopic
data we propose that ligands herein exhibit monodentate C-coor-
dination to the metal centre, which is further confirmed by the
X-ray crystal structure of the complexes. This study also presents
a method for synthesis of mononuclear Hg(II) complexes of phos-
phorus ylides via bridge-splitting reaction using DMSO as ligand.
Theoretical studies on the gas-phase structure of the complexes,
confirm that, the bridge-splitting reaction in DMSO solution is
potentially possible for all dimeric complexes in which DMSO acts
as a ligand.
[21] Stoe & Cie, X-STEP32, Version 1.07b: Crystallographic Package, Stoe & Cie GmbH,
Darmatadt, Germany, 2000.
[22] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
V.G. Zakrzewski, J.A. Montgomery, R.E. Stratman, J.C. Burant, S. Dapprich,
J.M. Millam, A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi,
V. Barone, M. Cossi, R. Cammi, B. Menucci, C. Pomelli, C. Adamo, S. Clifford,
J. Ochterski, G.A. Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, D.K. Malick,
A.D. Rabuck, K. Raghavachari, J.B. Foresman, J. Ciolowski, J.V. Ortiz,
B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts,
R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara,
C. Gonzales, M. Challacombe, P.M.W. Gill, B.G. Jonhson, W. Chen, M.W. Wong,
J.L. Andres, M. Head-Gordon, E.S. Repogle, J.A. Pople, GAUSSIAN 98, Revision A.6,
Gaussian Inc., Pittsburgh, PA, 1998.
Acknowledgements
We are grateful to the Bu-Ali Sina University for a grant and
Mr. Zebarjadian for recording the NMR spectra.
[23] J.B. Collins, P.V.R. Schleyer, J.S. Binkley, J.A. Pople, J. Chem. Phys. 64 (1976)
5142.
[24] H.J. Bestmann, B. Arnason, Chem. Ber. 95 (1962) 1513.
[25] E.C. Spencer, M.B. Mariyatra, J.A.K. Howard, A.M. Kenwright, K.
Panchanatheswaran, J. Organomet. Chem. 692 (2007) 1081.
[26] J. Vicente, M.T. Chicote, M.C. Lagunas, P.G. Jones, J. Chem. Soc., Dalton Trans.
(1991) 2579.
[27] J.A. Teagle, J.L. Burmeister, Inorg. Chim. Acta 118 (1986) 65.
[28] N.L. Holy, N.C. Baenziger, R.M. Flynn, D.C. Swenson, J. Am. Chem. Soc. 98 (1976)
7823.
[29] G. Facchin, R. Bertani, M. Calligaris, G. Nardin, M. Mari, J. Chem. Soc., Dalton
Trans. (1987) 1381.
[30] J.E. Huheey, Inorganic Chemistry – Principles of Structure and Reactivity, 2nd
ed., Harper Int. Ed., New York, 1978. p. 233.
Appendix A. Supplementary data
CCDC 648212 and 648213 contain the supplementary crystallo-
graphic data for [(Y1) ꢀ HgCl2 ꢀ DMSO] and [(Y2) ꢀ HgI2]2. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033, or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.poly.2008.03.009.
[31] N.A. Bell, T.D. Dee, M. Goldstein, P.J. McKenna, I.W. Novel, Inorg. Chim. Acta 71
(1983) 135.
[32] M. Kalyanasundari, K. Panchanatheswaran, V. Parthasarathi, W.T. Robinson,
H. Wen, Acta Crystallogr. 50 (1994) 1738.
[33] S.J. Sabounchei, A. Dadrass, M. Jafarzadeh, H.R. Khavasi, Acta Crystallogr., Sect.
E 63 (2007) o3160.
[34] P. Laavanya, U. Venkatasubramanian, K. Panchanatheswaran, J.A.K. Bauer,
Chem. Commun. (2001) 1660.
References
[1] H.J. Christau, Chem. Rev. 94 (1994) 1299.
[35] U. Belluco, R.A. Michelin, R. Bertani, G. Facchin, G. Pace, L. Zanotto, M. Mozzon,
M. Furlan, E. Zangrando, Inorg. Chim. Acta 252 (1996) 355.
[36] M. Calligaris, O. Carugo, Coord. Chem. Rev. 153 (1996) 83.
[37] E. Alessio, G. Mestroni, G. Nardin, W.M. Attia, M. Calligaris, G. Sava, S. Zorzet,
Inorg. Chem. 27 (1988) 4099.
[38] E. Alessio, B. Milani, M. Bolle, G. Mestroni, P. Faleschini, F. Todone, S. Geremia,
M. Calligaris, Inorg. Chem. 34 (1995) 4722.
[39] B. Serli, E. Zangrando, E. Iengo, G. Mestroni, L. Yellowlees, E. Alessio, Inorg.
Chem. 41 (2002) 4033.
[2] O.I. Kolodiazhnyi, Tetrahedron 52 (1996) 1855.
[3] N.A. Nesmeyanov, V.M. Novikov, Q.A. Reutov, J. Organomet. Chem. 4 (1965) 202.
[4] E.T. Weleski, J.L. Silver, M.D. Jansson, J.L. Burmeister, J. Organomet. Chem. 102
(1975) 365.
[5] M. Kalyanasundari, K. Panchanatheswaran, W.T. Robinson, H. Wen, J.
Organomet. Chem. 491 (1995) 103.
[6] R. Sanehi, R.K. Bansal, R.C. Mehrotra, Indian J. Chem. 24a (N12) (1985) 1031.
[7] S.J. Sabounchei, A. Dadrass, M. Jafarzadeh, S. Salehzadeh, H.R. Khavasi,
J. Organomet. Chem. 692 (2007) 2500.
[8] S.J. Sabounchei, V. Jodaian, H.R. Khavasi, Polyhedron 26 (2007) 2845.
[9] S.J. Sabounchei, H. Nemattalab, H.R. Khavasi, J. Organomet. Chem. 692 (2007)
5440.
[40] B. Serli, E. Zangrando, E. Iengo, E. Alessio, Inorg. Chim. Acta 339 (2002) 265.
[41] M. Calligaris, N.S. Panina, J. Mol. Struct. 646 (2003) 61.
[42] M. Calligaris, A. Melchior, S. Geremia, Inorg. Chim. Acta 323 (2001) 89.