Synthesis, characterization, and structural studies of mercury(II) complexes of new bidentate phosphorus ylide

Article abstract of DOI:10.1016/j.ica.2010.01.024

The reaction of Ph₂PCH₂CH₂PPh₂ (dppe) with BrCH₂C(O)C₆H₄NO₂ (1:1.05 molar ratio) in acetone produces a mixture of the new monophosphonium salt [Ph₂PCH₂CH₂PPh₂CH ₂C(O)C₆H₄NO₂]Br (1) and the diphosphonium salt [NO₂C₆H₄C(O)CH₂PPh ₂CH₂CH₂PPh₂CH₂C (O)C₆H₄NO₂]Br₂ (2). Compound 2 was insoluble in acetone and thus easily separated from the solution of 1. Further, by reacting both the mono- and diphosphonium salts with the appropriate bases the bidentate phosphorus ylides, [Ph₂PCH₂CH₂PPh₂{double bond, long}CHC(O)C₆H₄NO₂] (3) and [NO₂C₆H₄C(O)CH{double bond, long}PPh₂CH₂CH₂PPh₂{double bond, long}CHC(O)C₆H₄NO₂] (4) were obtained. The reaction of ligand 3 with mercury(II) halides in dry methanol leads to the formation of the P,P-coordinated monomeric complexes {HgX₂(Ph₂PCH₂CH₂PPh ₂CHC(O)C₆H₄NO₂)₂} [X = Cl (5), Br (6), I (7)]. The structure of complex 7 being unequivocally determined by single crystal X-ray diffraction techniques. Characterization of these species was also performed by elemental analysis, IR spectroscopy and ¹H, ³¹P, and ¹³C NMR techniques. These analyses being consistent with a 2:1 stoichiometry ylide/Hg(II) for compounds 5 through 7. Results obtained from theoretical studies are also consistent with a product in which two ylides are coordinated to the Hg(II) center through their phosphine groups, being this product the most stable among all the possible products.

Full text of DOI:10.1016/j.ica.2010.01.024

Inorganica Chimica Acta 363 (2010) 1254–1261
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, characterization, and structural studies of mercury(II) complexes
of new bidentate phosphorus ylide
a
a
a
Seyyed Javad Sabounchei a, , Sepideh Samiee , Sadegh Salehzadeh , Mehdi Bayat ,
*
Zabihollah Bolboli Nojini b, David Morales-Morales c,
*
a Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
b Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahwaz, Iran
c Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito Exterior, Coyoacán, 04510 México, DF, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of Ph2PCH2CH2PPh2 (dppe) with BrCH2C(O)C6H4NO2 (1:1.05 molar ratio) in acetone pro-
duces a mixture of the new monophosphonium salt [Ph2PCH2CH2PPh2CH2C(O)C6H4NO2]Br (1) and the
diphosphonium salt [NO2C6H4C(O)CH2PPh2CH2CH2PPh2CH2C(O)C6H4NO2]Br2 (2). Compound 2 was insol-
uble in acetone and thus easily separated from the solution of 1. Further, by reacting both the mono- and
diphosphonium salts with the appropriate bases the bidentate phosphorus ylides,
[Ph2PCH2CH2PPh2@CHC(O)C6H4NO2] (3) and [NO2C6H4C(O)CH@PPh2CH2CH2PPh2@CHC(O)C6H4NO2] (4)
were obtained. The reaction of ligand 3 with mercury(II) halides in dry methanol leads to the formation
of the P,P-coordinated monomeric complexes {HgX2(Ph2PCH2CH2PPh2CHC(O)C6H4NO2)2} [X = Cl (5), Br
(6), I (7)]. The structure of complex 7 being unequivocally determined by single crystal X-ray diffraction
techniques. Characterization of these species was also performed by elemental analysis, IR spectroscopy
and 1H, 31P, and 13C NMR techniques. These analyses being consistent with a 2:1 stoichiometry ylide/
Hg(II) for compounds 5 through 7. Results obtained from theoretical studies are also consistent with a
product in which two ylides are coordinated to the Hg(II) center through their phosphine groups, being
this product the most stable among all the possible products.
Received 24 December 2009
Accepted 19 January 2010
Available online 25 January 2010
Dedicated to Jonathan R. Dilworth.
Keywords:
Bidentate phosphorus ylide
Mercury(II) complexes
Crystal structure
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
the same ylide shows a combination of bonding modes. For example,
for compound Ph2PCH2CH2PPh2@C(H)C(O)C6H4NO2 different bond-
Phosphorus ylides are important reagents in organic chemistry,
this being especially true in the synthesis of naturally occurring
products with important biological and pharmacological activities
[1]. Moreover, the utility of metalated phosphorus ylides in syn-
thetic chemistry has been well documented [2–6]. Much of the
interest in the coordination properties of resonance stabilized phos-
phorus ylides stemming from their bond versatility due to the pres-
ence of different functional groups in their molecular structure [2].
ing modes have been observed (Chart 1).
Thus, it is clear that these ligands can engage in different kinds
of bonding with different metal ions [7–18]. Recently, Ebrahim
et al. [16] have reported the reactivity of mercury(II) halides
with the phosphine-ylide ligand with an ethylenic spacer
Ph2P(CH2)2PPh2@C(H)C(O)Ph, this compound giving place to two
different polymeric products. However, in this work we have found
quite different patterns of reactivity of similar ligands toward mer-
cury(II) halides. Hence, the goals of this report are (i) the tandem
synthesis of mono- and diphosphonium salts and (ii) the synthesis
and characterization of new bidentate phosphorous ylides and
their corresponding mononuclear Hg(II) complexes. The results of
theoretical studies on various potential types of coordination of li-
gand (3) towards Hg(II) metal ions are also discussed in this paper.
For instance, the
a-keto stabilized ylides derived from bisphos-
phines, viz., Ph2PCH2PPh2@C(H)C(O)R, Ph2P(CH2)2PPh2@C(H)C(O)R
(R = Me, Ph or OMe) [7] and PhC(O)C(H)@PPh2CH2CH2PPh2@C(H)-
C(O)Ph [8] form an important class of hybrid ligands containing both
phosphine and ylide functionalities, and can exist in ylidic and
enolate forms. This versatility has allowed the characterization of
coordinated ylides in different bonding modes: C-coordinated
(through the C
a atom), O-bonded (through the carbonyl O), P-
2. Experimental
bonded (through the phosphine group), or even situations in which
2.1. Materials
* Corresponding authors. Tel.: +98 8118272072; fax: +98 8118273231.
E-mail addresses: jsabounchei@yahoo.co.uk (S.J. Sabounchei), damor@servidor.
unam.mx (D. Morales-Morales).
All reactions were carried out under nitrogen using standard
Schlenk techniques. Solvents were reagent grade and used without
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.01.024

S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
1255
O
CH
C
Ph2P
Ph2P
NO2
O
O
O
M
H
Ph2
P
Ph2
P
Ph2
P
Ph2P
Ph2P
C6H4NO2
Ph2P
C6H4NO2
C6H4NO2
M
M
(a) P-bonding
(b) O-bonding
PPh2
(c) C-bonding
O
H
Ph2P
PPh2
Ph2
P
H
Ph2P
M
PPh2
C6H4NO2
M
M
O
COC6H4NO2
M
C6H4NO2
(f) P, C-bonding, bridging
(d) P, O-bonding, chelate
(e) P, C-bonding, chelate
O
M
O
X
X
P
P
CH2
CH
CH
CH2
CH2
C
C
Ph2
P
Hg
NO2
O2N
CH2
Ph2P
C6H4NO2
P
P
M
(g) P, O-bonding, bridging
(h) P, P-bonding
X
O
X
P
P
X
O
P
X
P
CH2
H2C
CH2
P
H2C
CH2
CH2
H2C
Hg
H2C
Hg
CH
C
P
CH
P
P
O
CH
C
C
CH
C
O
NO2
NO2
NO2
NO2
(i) O, O-bonding
(j) C, C-bonding
Chart 1. The possible bonding modes of Ph2PCH2CH2PPh2@CHC(O)C6H4NO2 to metal M.
further purifications. Reactants and reagents were obtained from
Merck Chemical Company and used without further purification.
The solvents were dried and distilled using standard methods [19].
IR spectra were recorded on a Shimadzu 435-U-04 FT spectropho-
tometer from KBr pellets. 1H, 13C{1H}, and 31P{1H} NMR spectra
were recorded either on a 300 MHz Bruker and a 90 MHz Jeol spec-
trometer in DMSO-d6 or CDCl3 as solvents at 25 °C. Chemical shifts
(ppm) were reported according to internal TMS (1H, 13C) and exter-
nal 85% phosphoric acid (31P). Coupling constants were given in Hz.
Suitable crystals were obtained from dimethylsulfoxide solu-
tion by slow evaporation of the solvent and mounted in random
2.2. Physical measurements
Melting points were measured on a SMPI apparatus. Elemental
analysis was performed using a Perkin–Elmer 2400 series analyzer.

1256
S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
Table 1
Table 2
Crystallographic
data
summary
for
complex
{HgI2(Ph2PCH2CH2PPh2CH-
Selected bond lengths (Å) and bond angles (°) for 7.
C(O)C6H4NO2)2} (7).
Bond lengths (Å)
Bond angle (°)
Compound
{HgI2(Ph2PCH2CH2PPh2CHC(O)C6H4NO2)2}
(7)
Hg–P(2)
Hg–P(3)
Hg–I(1)
Hg–I(2)
O(1)–C(1)
O(4)–C(49)
C(1)–C(2)
C(49)–C(50)
P(1)–C(2)
P(4)–C(50)
P(3)–Hg–P(2)
P(3)–Hg–I(1)
P(3)–Hg–I(2)
P(2)–Hg-I(1)
P(2)–Hg–I(2)
I(1)–Hg–I(2)
C(23)–P(2)–Hg
C(43)–P(3)–Hg
C(1)–C(2)–P(1)
C(49)–C(50)–P(4)
2.5285(13)
2.5050(14)
2.7921(4)
2.7970(5)
1.252(6)
1.277(6)
1.379(7)
1.358(7)
1.711(5)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C68H58I2HgN2O6P4
1577.43
298(2)
0.71073
monoclinic
P21/n
14.5919(10)
25.1082(18))
17.2604(12)
90
91.5740(10)
90
b (Å)
c (Å)
1.744(5)
117.21(4)
103.21(3)
112.53(3)
112.95(3)
103.19(3)
107.65(15)
120.92(17)
116.80(2)
121.00(4)
120.9(4)
a
(°).
b (°)
c
(°)
Z
4
Absorption coefficient (mmÀ1
Index ranges
)
3.566
À17 6 h 6 17
À30 6 k 6 30
À20 6 l 6 20
51 865
11 567 [R(int) = 0.0811]
0.4140 and 0.2859
Reflections collected
Independent reflections
Maximum and minimum
transmission
Goodness-of-fit on F2
0.905
(k = 0.71073 Å) radiation. The detector was placed at a distance
of 4.837 cm from the crystals in all cases. A total of 1800 frames
were collected with a scan width of 0.3° in
of 10 s/frame. The frames were integrated with the Bruker SAINT
software package [20a] using a narrow-frame integration algo-
rithm. The integration of the data was done using a monoclinic unit
cell to yield a total of 51 865 reflections to a maximum 2h angle of
50.00° (0.93 Å resolution), of which 11 567 were independent.
Analysis of the data showed in all cases negligible decays during
Final R indices [I > 2
R indices (all data)
r(I)]
R1 = 0.0391, wR2 = 0.0834
R1 = 0.0581, wR2 = 0.0876
3.481 and À0.607
x and an exposure time
Largest difference in peak and
hole (e ÅÀ3
)
orientation on glass fibers. The X-ray intensity data were measured
at 298 K on a Bruker SMART APEX CCD-based three-circle X-ray
diffractometer system using graphite mono-chromated Mo K
a
Fig. 1. ORTEP view of X-ray crystal structure of 7. The hydrogen atoms have been omitted for clarity.

S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
1257
data collections. The structures were solved by Patterson method
using SHELXS-97 [20b] program. The remaining atoms were located
via a few cycles of least squares refinements and difference Fourier
maps using P21/n space group with Z = 4. Hydrogen atoms were in-
put at calculated positions, and allowed to ride on the atoms to
which they are attached. Thermal parameters were refined for
hydrogen atoms on the phenyl groups with Uiso(H) = 1.2 Ueq of
the parent atom in all cases. The final cycle of refinement was car-
ried out on all non-zero data using SHELXL-97 [20c] and anisotropic
thermal parameters for all non-hydrogen atoms. The details of the
structure determination are given in Table 1 and selected bond dis-
tances and angles in Table 2. The numbering of the atoms is shown
in Fig. 1 (ORTEP) [20d].
2.3. Computational method
The geometry of the metal complex 7 as determined by X-ray
crystal structure analysis (see Fig. 1) was fully optimized at DFT
(B3LYP) [21,22] level of theory using the GAUSSIAN 03 [23] set of pro-
grams. The standard CEP-31G basis set was used in all calculations.
Fig. 2. Illustrations of possible isomers for complex 7.

1258
S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
This basis set includes effective core potentials (ECP) for both the
mercury and phosphorus atoms as well as halide (Cl, Br, and I) ions.
The observed geometry of compound 7 was used as a basis of DFT
calculations for compounds 5 and 6. The geometries of other pos-
sible isomers for compound 7 (Fig. 2, isomers (I and II)) and/or pos-
sible isomer for 1+1 product of reaction between HgI2 and 3 (Fig. 2,
isomers (III–VI)) were also optimized at same level of theory. A
starting molecular-mechanics for isomers (II–VI) for the ab initio
calculations was obtained using the HYPERCHEM 5.02 program [24].
Calculations were performed on a Pentium-PC computer with a
4400 MHz processor.
dH = 3.56 (m, 2H, CH2); 4.29 (br, 1H, CH); 7.56–8.15 (m, 14H, Ph).
31P{1H} NMR (CDCl3): dP = 15.24 (s, PPh2); 13C{1H} NMR (CDCl3):
dC = 18.47 (br, CH2); 51.22 (d, CH, JPC = 107.4); 123.30–148.32
1
(Ph); 182.54 (s, CO).
2.4.3. Synthesis of Hg(II) halide complexes
General procedure: To a solution of HgX2 (0.36 mmol) in metha-
nol (8 mL), a solution of 3 (0.202 g, 0.36 mmol) in the same solvent
(8 mL) was added dropwise at 0 °C and the reaction allowed to pro-
ceed under stirring for 2 h. The resulting solid, admixed with gray
material was treated with dichloromethane (25 mL) and filtered
through a short plug of CeliteÒ. Addition of excess methanol to
the concentrated filtrate caused the precipitation of the products
as yellow solids.
2.4. Sample preparation
2.4.1. Synthesis of mono- and diphosphonium salts
General procedure: A solution of bis(diphenylphosphino)ethane
(dppe) (0.398 g, 1 mmol) and 4-nitrophenacyl bromide (0.256 g,
1.05 mmol) in acetone (30 mL) was stirred at room temperature
overnight. The resulting yellow suspension, consisting of a mixture
of both the mono- and diphosphonium salts was filtered to remove
the diphosphonium salt (2) from the solution as yellow solid. The
resulting solid was washed with diethyl ether (10 mL), and dried
under vacuum. The residual solution was concentrated under re-
duced pressure to 5 mL, and crashed with diethyl ether (20 mL).
The resulting orange solid was filtered off, washed with petroleum
diethyl ether, and dried under vacuum to afford the monophospho-
nium salt (1).
2.4.3.1. Data for 5. Yield: 0.236 g, 47%. M.p. >135 °C (decomposes).
Anal. Calc. for C68H58Cl2HgN2O6P4: C, 58.56; H, 4.19; N, 2.01.
Found: C, 58.92; H, 3.98; N, 2.18%. IR (KBr, cmÀ1): 1532 (C@O),
1H NMR (DMSO-d6): dH = 3.06 (m, CH2, 4H merged with residual
2
H2O); 4.61 (d, 1H, CH, JPH = 23.31); 7.57–8.17 (m, 24H, Ph).
3
31P{1H} NMR (DMSO-d6): dP = 17.85 (d, PCH, JPP = 59.57); 26.38
(br, PPh2). 13C{1H} NMR (DMSO-d6): dC = 18.92 (br, CH2); 48.84
1
(d, CH, JPC = 108.45); 123.55–148.28 (Ph); 181.35 (s, CO).
2.4.3.2. Data for 6. Yield: 0.269 g, 51%. M.p. >152 °C (decomposes).
Anal. Calc. for C68H58Br2HgN2O6P4: C, 58.05; H, 3.94; N, 1.89.
Found: C, 58.25; H, 3.78; N, 1.77%. IR (KBr, cmÀ1): 1530 (C@O),
1H NMR (DMSO-d6): dH = 3.11 (m, CH2, 4H merged with residual
2.4.1.1. Data for 1. Yield: 0.546 g, 85%. M.p. 169–171 °C. Anal. Calc.
for C34H30BrNO3P2: C, 63.56; H, 4.71; N, 2.18. Found: C, 64.09; H,
4.42; N, 2.55%. IR (KBr, cmÀ1): 1683 (C@O), 1H NMR (CDCl3):
dH = 2.24 (m, 2H, CH2); 3.24 (m, 2H, CH2); 6.26 (d, 2H, PCH2CO,
2JPH = 12.27); 7.27–8.42 (m, 24H, Ph). 31P{1H} NMR (CDCl3):
2
H2O); 4.56 (d, 1H, CH, JPH = 23.03); 7.49–7.88 (m, 24H, Ph).
3
31P{1H} NMR (DMSO-d6): dP = 17.89 (d, PCH, JPP = 57.32); 24.68
(br, PPh2). 13C{1H} NMR (DMSO-d6): dC = 19.76 (br, CH2); 48.71
1
(d, CH, JPC = 105.65); 123.56–148.30 (Ph); 181.38 (s, CO).
3
dP = À15.05 (br, PPh2); 20.93 (d, PCH2CO, JPP = 43.18). 13C{1H}
2.4.3.3. Data for 7. Yield: 0.339 g, 60%. M.p. >168 °C (decomposes).
Anal. Calc. for C68H58I2HgN2O6P4: C, 51.77; H, 3.71; N, 1.78. Found:
C, 51.64; H, 3.63; N, 1.61%. IR (KBr, cmÀ1): 1529 (C@O), 1H NMR
(DMSO-d6): dH = 3.21 (m, CH2, 4H merged with residual H2O);
NMR (CDCl3): dC = 19.20 (br, CH2); 36.43 (d, PCH2CO,
2
1JPC = 58.48); 116.80–150.78 (Ph); 191.52 (d, CO, JPC = 6.04).
2.4.1.2. Data for 2. Yield: 0.079 g, 9%. M.p. 250–252 °C. Anal. Calc.
for C42H36Br2N2O6P2: C, 56.90; H, 4.09; N, 3.16. Found: C, 57.32;
H, 3.92; N, 2.87%. IR (KBr, cmÀ1): 1682 (C@O), 1H NMR (DMSO-
d6): dH = 3.85 (m, CH2, 2H merged with residual H2O); 6.24 (br,
2H, PCH2CO); 7.74–8.31 (m, 14H, Ph). 31P{1H} NMR (DMSO-d6):
dP = 26.66 (s, PPh2); 13C{1H} NMR (DMSO-d6): dC = 20.67 (br,
CH2); 49.69 (br, CH); 123.24–148.33 (Ph); 182.37 (s, CO).
2
4.59 (d, 1H, CH, JPH = 25.26); 7.50–8.17 (m, 24H, Ph). 31P{1H}
3
NMR (DMSO-d6): dP = 18.28 (d, PCH, JPP = 56.08); 11.08 (br,
PPh2). 13C{1H} NMR (DMSO-d6): dC = 19.80 (br, CH2); 48.611 (d,
1
CH, JPC = 108.67); 123.57–148.32 (Ph); 181.51 (s, CO).
3. Results and discussion
2.4.2. Synthesis of bidentate phosphorus ylides
3.1. Synthesis
2.4.2.1. Synthesis of 3. The monophosphonium salt (1) (0.231 g,
0.36 mmol) was treated with triethyl amine (0.36 mL) in toluene
(10 mL). The triethyl amine hydrobromide thus obtained was fil-
tered off. Concentration of the toluene layer to 3 mL and subse-
quent addition of petroleum ether (20 mL) resulted in the
precipitation of the desired ligand as pale orange solid. Yield:
0.138 g, 68%. M.p. 145–147 °C. Anal. Calc. for C34H29NO3P2: C,
72.72; H, 5.21; N, 2.49. Found: C, 72.21; H, 5.36; N, 2.24%. IR
(KBr, cmÀ1): 1530 (C@O), 1H NMR (CDCl3): dH = 2.23 (m, 2H,
CH2); 2.85 (m, 2H, CH2); 4.23 (br, 1H, CH); 7.37–8.14 (m, 24H,
The overnight reaction of dppe with 4-nitrophenacyl bromide in
acetone at room temperature led to the formation of a mixture of
mono- and diphosphonium salts (Scheme 1). Thus, the 31P{1H}
NMR spectra of the above reaction always shows three singlets:
one at 24.38 ppm attributable to the diphosphonium salt, and
two at À14.14 ppm (3JPP = 44.16) and 23.48 ppm (3JPP = 44.16) for
the monophosphonium derivative. However, we found that the
diphosphonium salt will be produced under different experimental
conditions, such as higher temperatures (30–40 °C), shorter reac-
tion times (2–8 h) or using different solvents such as chloroform
and dichloromethane. However, in all cases the product of the
reaction always affords the same three peaks in different ratios.
Further experimentation, lead to find acetone to be the best solvent
for the reaction of dppe with 4-nitrophenacyl bromide due to the
fact that in this solvent the diphosphonium salt is insoluble and
thus can be easily isolated by plain filtration from the monophos-
phonium salt which remains in solution. It should be noted that
the reaction of dppe with 2 equivalents of 4-nitrophenacyl bro-
mide affords exclusively the diphosphonium salt.
3
Ph). 31P{1H} NMR (CDCl3): dP = À15.22 (d, PPh2, JPP = 48.11);
3
14.71 (d, PCH, JPP = 46.81). 13C{1H} NMR (CDCl3): dC = 20.82 (br,
CH2); 49.69 (br, CH); 123.24–148.33 (Ph); 182.37(s, CO).
2.4.2.2. Synthesis of 4. The diphosphonium salt (2) (0.319 g,
0.36 mmol) was treated with an aqueous solution of NaOH
(0.1 M, 10 mL) leading to the elimination of HBr to produce the free
ligand 4. Yield: 0.227 g, 87%. M.p. 211–214 °C. Anal. Calc. for
C42H34N2O6P2: C, 69.61; H, 4.73; N, 3.87. Found: C, 69.83; H,
4.41; N, 4.01%. IR (KBr, cmÀ1): 1527 (C@O), 1H NMR (CDCl3):

S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
1259
soluble
[Ph2PCH2CH2PPh2CH2C(O)C6H4NO2]Br
(1)
acetone
+
BrCH2COC6H4NO2
Ph2PCH2CH2PPh2
insoluble
[NO2C6H4C(O)CH2PPh2CH2CH2PPh2CH2C(O)C6H4NO2]Br2
(2)
Scheme 1. Synthetic route for the preparation of the mono- and diphosphonium salts 1 and 2.
Further, the bidentate phosphorus ylides (3 and 4) can be pre-
pared from the corresponding phosphonium salts by reaction with
the appropriate bases (Scheme 2).
With the aim to investigate the reactivity of the bidentate
phosphorus ylides (3) and (4) towards metallic substrates, we
have reacted these compounds with mercury(II) halides. The
reaction of mercury(II) halides with 3 yielded the formation of
P,P-coordinated monomeric complexes of the type {HgX2(Ph2-
PCH2CH2PPh2CHC(O)C6H4NO2)2} [X = Cl (5), Br (6), I (7)] (Scheme
3). Analogous reactions with ligand 4 failed to proceed.
The 1H NMR spectrum exhibits a doublet at d 6.26 ppm, with a
2JPH of 12.27 Hz, related to a CH2 group of the 4-nitrophenacyl bro-
mide system bonded to a phosphonium moiety [15]. On the other
hand, the 31P{1H} NMR spectrum of 2 shows only one sharp singlet
at d 26.66 ppm. In the 1H NMR spectra of this compound a doublet
at 6.24 ppm can be observed due to the PCH2CO group. The pres-
ence of a single signal for the PCH2CO group in each of the corre-
sponding 31P{1H} and 1H NMR spectra indicates the presence of
only one symmetrical molecule of 2 [26].
The 31P{1H} NMR spectrum for all complexes exhibit the pres-
ence of the PCH group as a doublet around d 17 ppm, this chem-
ical shift being very similar to that observed for the corresponding
free ylide (3) (d 14.71 ppm). The coordination of the PPh2 group is
also evident from the strong downfield shifting of the signal when
compared to that of the free ylide (d À15.22 ppm). Analogously, in
the 1H NMR spectra of all complexes, the doublets due to the
methine proton around d 4.58 ppm, appear in the same region
as observed for the free ligand (d 4.23 ppm). In the 13C{1H}
NMR spectra of all complexes, the signals attributed to the CO
group remain unaffected due to complexation. Hence, these
spectral data are also consistent with the monodentate coordina-
tion of the ligand towards the metal center through the PPh2
group [16].
3.2. Spectroscopy
The IR data confirms the complete formation of the carbonylic
bidentate ylides Hg(II) complexes with the disappearance of the
phosphonium CO bands at
respectively, and the appearance of new strong CO bands relative
to a carbonyl stabilized ylides at
1530 and 1527 cmÀ1 for 3 and
m
1683 and 1682 cmÀ1 for 1 and 2,
m
4, respectively. As we have reported previously [25], the coordina-
tion of the ylide via carbon or oxygen causes a significant increase
or decrease in the m(CO), respectively. Thus, the IR data obtained
indicates that the interaction of the ligands with mercury(II) ha-
lides is only through the PPh2 group [16], as proved by the crystal
structure of 7 (vide supra).
When the reactions were carried at room temperature no coor-
dination to Hg(II) was observed, this observation was confirmed by
1H, 13C{1H} and 31P{1H} NMR techniques, and can be rationalized
due to fast exchange of the ylide with the metal [27].
The 31P{1H} NMR spectrum of 1 results more informative and
exhibits two doublets at d 23.49 and À15.05 ppm that indicate
the presence of the PCH2CO and PPh2 groups in the molecule.
NEt3
[Ph2PCH2CH2PPh2CH2C(O)C6H4NO2]Br
Ph2PCH2CH2PPh2=CHC(O)C6H4NO2
-[HNEt3]Br
(3)
NaOH
[NO2C6H4C(O)CH2PPh2CH2CH2PPh2CH2C(O)C6H4NO2]Br2
NO2C6H4C(O)CH=PPh2CH2CH2PPh2=CHC(O)C6H4NO2
-2 HBr
(4)
Scheme 2. Synthetic route for preparation of the bidentate phosphorus ylides 3 and 4.
Ph2
P
Ph2
P
CH2
X
X
CH
C
CH2
CH2
CH
C
CH3OH
Hg
O
HgX2
Ph2PCH2CH2PPh2=CHC(O)C6H4NO2
+
O
CH2
under N2
P
P
Ph2
Ph2
NO2
NO2
X = Cl (5), Br (6), I (7)
Scheme 3. Reaction of 3 with Hg(II) halides.

1260
S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
3.3. X-ray crystallography
The Hg–P distances of 2.505(14) and 2.528(13) Å in this com-
plex are consistent with the values reported for monomeric
Hg(II)–phosphine complexes [28]. The two terminal Hg–I bond
lengths in 7 (2.792(4) and 2.797(5) Å) are comparable to analo-
gous in [HgI2(PPh3)2] (2.733(1) and 2.763(1) Å) [29],
[HgI2(PPh2CH2PPh2C(H)C(O)Ph)] (2.767(6) and 2.743(7) Å) [14]
and [HgI2(dppeO)]n (2.700(3) and 2.709(3) Å) [30]. As observed
Table 1 provides the crystallographic results and refinement
information for complex {HgI2(Ph2PCH2CH2PPh2CHC(O)C6H4-
NO2)2} (7). The molecular structure is shown in Fig. 1. Pertinent
bond distances and angles for 7 are given in Table 2. Fractional
atomic coordinates and equivalent isotropic displacement coeffi-
cients (Ueq) for the non-hydrogen atoms of the complexes are
shown in Supplementary material.
The X-ray analysis reveals the P,P-coordination mode of the li-
gand 3 to the Hg(II) atom in this complex. The mercury atom is
coordinated to two halogens and two PPh2 groups. The angles sub-
tended by the ligand at the Hg(II) center in 7 vary from 103.19(3)
previously for a-stabilized phosphorus ylides [31], the phosphorus
and oxygen atoms are cis oriented due to significant interaction be-
tween P+ and OÀ centers, as shown by the appropriate length (see
Table 2).
3.4. Theoretical studies
to 117.21(4) indicating
environment.
a
slightly distorted tetrahedral
For the reaction between the HgI2 and ligand (3) we can con-
sider two possible products, 1+1 or 1+2. For both the later products
there are several isomers depending on which atom(s) of the li-
gand are coordinated to the metal ion. We note that each ylide
can be coordinated to the metal ion as a bidentate (P, C- or P, O-
coordinated) or as a monodentate (P-, C- or O-coordinated) ligand.
Thus, if we assume that one ylide will be coordinated to the Hg(II)
metal ion, then for the resulting 1+1 product, five isomers can be
considered. On the other hand, if we assume that two monodentate
ylides are coordinated to the metal ion, then for the resulting 1+2
product, three asymmetrical isomers and three symmetrical iso-
mers can be considered. Obviously, if the first ligand is coordinated
through the P atom then most probably the second one will also be
coordinated through the same atom, and this is the case for C and O
atoms. Thus, the asymmetrical isomers in which one ligand is coor-
dinated through the atom X and the second one is coordinated
Table 3
A
comparison between the calculated energies for the six possible products of
reaction between ligand (3) and HgI2.
Isomer
Type of
Type of
product
E (Hartree)
D )
E (kcal molÀ1
coordination
I
II
III
IV
V
P,P-coordinated
O,O-coordinated
P,O-coordinated
P-coordinated
C-coordinated
P,C-coordinated
1+2
1+2
1+1
1+1
1+1
1+1
À736.305341
À736.293325
À736.281216a
À736.2735417
À736.2710918
À736.2695346
0.0
7.5
15.1
19.9
21.5
22.5
VI
a
The energy of one molecule of free ylide (À279.7504816 (Hartree)) is included
in the electronic energy of 1+1 molecules.
Fig. 3. Calculated molecular structures of complexes: (a) 5 and (b) 6.

S.J. Sabounchei et al. / Inorganica Chimica Acta 363 (2010) 1254–1261
1261
Table 4
with new structures. The theoretical studies show that the ob-
served structure for compound 7 is the most stable structure be-
tween the all studied structures.
A comparison between the selected calculated bond lengths (Å) and bond angles (°)
for compounds 5, 6, and 7 and corresponding experimental values for complex 7.
5
6
7
Acknowledgments
CEP-31G
CEP-31G
CEP-31G
X-ray
Bond lengths
P(2)–Hg
P(3)–Hg
X(1)–Hg
X(2)–Hg
We are grateful to the Bu-Ali Sina University for a grant, Mr.
Zebarjadian for recording the NMR spectra. D.M-M would like to
thank the generous financial support of CONACYT (F58692) and
DGAPA-UNAM (IN227008).
2.610
2.610
2.634
2.634
2.653
2.653
2.719
2.719
2.699
2.702
2.865
2.874
2.529
2.505
2.792
2.797
Bond angles
P(2)–Hg–X(1)
P(3)–Hg–X(1)
P(2)–Hg–X(2)
P(3)–Hg–X(2)
X(1)–Hg–X(2)
P(2)–Hg–P(3)
109.005
97.507
97.511
109.011
105.058
135.940
109.712
102.304
102.295
109.703
109.573
123.004
109.770
104.803
104.270
109.302
112.929
116.012
112.95
103.21
103.20
112.53
107.65
117.21
Appendix A. Supplementary material
CCDC 739884 contains the supplementary crystallographic data
for 7. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via http://www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.ica.2010.01.024.
through atom Y can be ignored. Therefore, herein we have studied
the five possible isomers for 1+1 product and the three symmetri-
cal isomers for 1+2 product. From the all above isomers we could
not optimize O-coordinated isomer for 1+1 product and C,C-coor-
dinated isomer for 1+2 product. While the O-coordinated isomer
was not minimized after one month, the C,C-coordinated isomer
was converted to C-coordinated isomer of 1+1 product and one
molecule of free ligand. Thus it seems that, in the present case,
the formation of a product in which two ligands are coordinated
through the ylidic carbon is not possible (Fig. 2).
As can be seen in Table 3 from the six remaining isomers, the
isomer (I) is the most stable isomer. We note that the latter isomer
is the observed isomer for compound 7 in the solid state. Thus, it
seems that the complex 7 has adopted the most stable structure
in the solid state (see description of X-ray crystal structure for
compound 7). Thus according to result of above theoretical studies
and due to same spectroscopic data between the complexes 5–7,
we can assume that the structures of complexes 5 and 6 would
be the same as that exhibited by compound 7. The geometry of
complexes 5, 6, and 7 were also fully optimized at density func-
tional (B3LYP) level of theory (Fig. 3). A comparison between the
calculated bond lengths (Å) and bond angles (°) for compounds
5–7 with corresponding experimental values for compound 7 is
presented in Table 4. The calculated structure for complex 7 in
the gas phase agrees well with the structure determined by X-
ray crystallography. As can be seen in Table 4, the Hg–P bond
lengths in compound 5, 6, and 7 are 2.610, 2.653, (2.699 and
2.702), respectively. Thus it seems that the coordination halide
has a slightly effect on the Hg–P bond length.
References
[1] G. Wittig, Angew. Chem. 92 (1980) 671.
[2] E.P. Urriolabeitia, J. Chem. Soc., Dalton Trans. (2008) 5673. and references cited
therein.
[3] G. Wagner, T.B. Pakhomova, N.A. Bokach, J.J.R. Frausto da Silva, J. Vicente, A.J.L.
Pombeiro, V.Y. Kukushkin, Inorg. Chem. 40 (2001) 1683.
[4] N.A. Bokach, V.Y. Kukushkin, M. Haukka, J. da Silva, A.J.L. Pombeiro, Inorg.
Chem. 42 (2003) 3602.
[5] H.J. Christau, Chem. Rev. 94 (1994) 1299.
[6] O.I. Kolodiazhnyi, Tetrahedron 52 (1996) 1855.
[7] Y. Oosawa, H. Urabe, T. Saito, Y. Sasaki, J. Organomet. Chem. 122 (1976) 113.
[8] A. Spannenberg, W. Baumann, U. Rosenthal, Organometallics 19 (2000) 3991.
[9] R. Uson, J. Fornies, R. Navarro, A.M. Ortega, J. Organomet. Chem. 334 (1987)
389.
[10] I.J.B. Lin, H.C. Shy, C.W. Liu, L.-K. Liu, S.-K. Yeh, J. Chem. Soc., Dalton Trans.
(1990) 2509.
[11] D. Saravanabharathi, T.S. Venkatakrishnan, M. Nethaji, S.S. Krishnamurthy,
Proc. Ind. Acad. Sci. (Chem. Sci.). 115 (2003) 741.
[12] L.R. Falvello, S. Fernandez, R. Navarro, E.P. Urriolabeitia, Inorg. Chem. 39 (2000)
2957.
[13] H. Takahashi, Y. Oosawa, A. Kobayashi, T. Saito, Y. Sasaki, Bull. Chem. Soc. Jpn.
50 (1977) 1771.
[14] M.M. Ebrahima, K. Panchanatheswaran, A. Neels, H. Evans, J. Organomet.
Chem. 694 (2009) 643.
[15] S.M. Sbovata, A. Tassan, G. Facchin, Inorg. Chim. Acta 361 (2008) 3177.
[16] M.M. Ebrahim, H. Evans, K. Panchanatheswaran, Polyhedron 26 (2007) 3491.
[17] H. Takahashi, Y. Oosawa, A. Kobayashi, T. Saito, Y. Sasaki, Chem. Lett. (1976)
15.
[18] L.R. Falvello, M.E. Margalejo, R. Navarro, E.P. Urriolabeitia, Inorg. Chim. Acta
347 (2003) 75.
[19] A.J. Gordon, R.A. Ford, The Chemist’s Companion – A Handbook of Practical
Data Techniques and References, Wiley-Interscience, New York, 1972. p. 438.
[20] (a) Bruker AXS, SAINT Software Reference Manual, Madison, WI, 1998.;
(b) G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467;
(c) G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1998.;
(d) L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[21] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
4. Conclusions
[22] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B. 37 (1988) 785.
[23] M.J. Frisch et al., GAUSSIAN 03, Revision B.03, Gaussian, Inc., Pittsburgh, PA, 2003.
[24] HYPERCHEM, Released 5.02, Hypercube, Inc., Gainesville, 1997.
[25] S.J. Sabounchei, H. Nemattalab, S. Salehzadeh, S. Khani, M. Bayat, H. Adams,
M.D. Ward, Inorg. Chim. Acta 362 (2009) 105.
[26] M. Kalyanasundari, K. Panchanatheswaran, W.T. Robinson, H. Wen, J.
Organomet. Chem. 491 (1995) 103.
[27] N.L. Holy, N.C. Baenziger, R.M. Flynn, D.C. Swenson, J. Am. Chem. Soc. 98 (1976)
7823.
[28] M. Kubicki, S.K. Hadjikakou, M.N. Xanthopoulou, Polyhedron 20 (2001) 2179.
[29] L. Fälth, Chem. Sci. 9 (1976) 71.
[30] M.M. Ebrahim, A. Neels, H. Stoeckli-Evans, K. Panchanatheswaran, Polyhedron
26 (2007) 1277.
The present study describes a new method for the synthesis of
the mono- and diphosphonium salts simultaneously. This study
also presents the synthesis and characterization of a new series
of mononuclear Hg(II) complexes of bidentate phosphorus ylide.
On the basis of the physical–chemical and spectroscopic data we
propose that the ligands described herein exhibit monodentate
P,P-coordination to the metal center, coordination that has been
unequivocally confirmed by the X-ray crystal structure of complex
7. The results suggest that the interaction of Hg(II) with different
phosphines remain an active field of research leading to complexes
[31] A. Lledos, J.J. Carbo, E.P. Urriolabeitia, Inorg. Chem. 40 (2001) 4913.