Structural, theoretical, and spectroscopic study of mercury(ii) complexes of two new unsymmetric phosphorus ylides

Article abstract of DOI:10.1080/10426507.2013.779274

The reaction of Ph₂PCH₂PPh₂ (dppm) with 4-methylphenacyl bromide and 2-(bromoacetyl)naphthalene in chloroform produce the new phosphonium salts [Ph₂PCH₂PPh₂CH ₂C(O)C₆H₄Me]Br (1) and [Ph₂PCH ₂PPh₂CH₂C(O)C₁₀H₇]Br (2). Further, by reaction of the monophosphonium salts of dppm with the strong base Et₃N the corresponding bidentate phosphorus ylides, Ph ₂PCH₂P(Ph)₂ = C(H)C(O)C₆H ₄Me (3) and Ph₂PCH₂P(Ph)₂ = C(H)C(O)C₁₀H₇ (4) were obtained. The reaction of these ligands with mercury(II) halides in dry methanol led to the formation of the mononuclear complexes {HgX ₂[(Ph₂PCH₂PPh ₂C(H)C(O)C₆H₄Me)]} [X = Cl (5), Br (6), and I (7)] and {HgX ₂[(Ph₂PCH₂PPh₂C(H)C(O) C₁₀H₇)]} [X = Cl (8), Br (9), and I (10)]. Characterization of the obtained compounds was performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR spectra. The structure of compounds 3 and 10 are unequivocally determined by single crystal X-ray diffraction techniques. X-ray analysis of 10 reveals the presence of mononuclear complex containing Hg atom in a distorted tetrahedral environment. In all complexes, the title ylides are coordinated through the ylidic carbon and the phosphine phosphorus. Computational studies on ligand 4 and complexes 8, 9, and 10 at DFT (B3LYP) level of theory are also reported. It was shown that the formation of P,C-coordinated 1+1 complex 10 is energetically more favored than corresponding P,P-coordinated 1+2 product.

Full text of DOI:10.1080/10426507.2013.779274

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STRUCTURAL, THEORETICAL AND SPECTROSCOPIC
STUDY OF MERCURY(II) COMPLEXES OF TWO NEW
UNSYMMETRIC PHOSPHORUS YLIDES
Seyyed Javad Sabounchei a , Mohammad Panahimehr a , Sadegh Salehzadeh a , Mehdi Bayat a
, Hamid Reza Khavasi b & David Morales-Morales c
a Faculty of Chemistry , Bu-Ali Sina University , Hamedan , 65174 , Iran
b Department of Chemistry , Shahid Beheshti University, G.C. , Evin , Tehran , 1983963113 ,
Iran
c Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria,
Circuito Exterior , Coyoacán, 04510, México , D.F. , Mexico
Accepted author version posted online: 01 Aug 2013.
To cite this article: Phosphorus, Sulfur, and Silicon and the Related Elements (2013): STRUCTURAL, THEORETICAL AND
SPECTROSCOPIC STUDY OF MERCURY(II) COMPLEXES OF TWO NEW UNSYMMETRIC PHOSPHORUS YLIDES, Phosphorus, Sulfur, and
Silicon and the Related Elements, DOI: 10.1080/10426507.2013.779274
To link to this article: http://dx.doi.org/10.1080/10426507.2013.779274
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STRUCTURAL,
THEORETICAL AND
SPECTROSCOPIC STUDY OF
MERCURY(II) COMPLEXES OF TWO NEW UNSYMMETRIC PHOSPHORUS
YLIDES
Seyyed Javad Sabounchei,1 Mohammad Panahimehr,1 Sadegh Salehzadeh,1 Mehdi
Bayat,1 Hamid Reza Khavasi2 and David Morales-Morales3
1Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran
2Department of Chemistry, Shahid Beheshti University, G.C., Evin, Tehran, 1983963113,
Iran
3Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria,
Circuito Exterior, Coyoacán, 04510, México, D.F., Mexico
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Abstract The reaction of Ph2PCH2PPh2 (dppm) with 4-methylphenacyl bromide and 2-
(bromoacetyl)naphthalene in chloroform produce the new phosphonium salts
[Ph2PCH2PPh2CH2C(O)C6H4Me]Br (1) and [Ph2PCH2PPh2CH2C(O)C10H7]Br (2). Further, by
reaction of the monophosphonium salts of dppm with the strong base Et3N the corresponding
bidentate
phosphorus
ylides,
Ph2PCH2P(Ph)2=C(H)C(O)C6H4Me
(3)
and
Ph2PCH2P(Ph)2=C(H)C(O)C10H7 (4) were obtained. The reaction of these ligands with
mercury(II) halides in dry methanol led to the formation of the mononuclear complexes
{HgX2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]} [X= Cl (5), Br (6),
I
(7)] and
{HgX2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} [X= Cl (8), Br (9), I (10)]. Characterization of the
1
31
13
obtained compounds was performed by elemental analysis, IR, H, P, and C NMR spectra.
The structure of compounds 3 and 10 are unequivocally determined by single crystal X-ray
diffraction techniques. X-ray analysis of 10 reveals the presence of mononuclear complex
containing Hg atom in a distorted tetrahedral environment. In all complexes the title ylides are
coordinated through the ylidic carbon and the phosphine phosphorus. Computational studies on
ligand 4 and complexes 8, 9 and 10 at DFT (B3LYP) level of theory are also reported. It was
shown that the formation of P,C-coordinated 1+1 complex 10 is energetically more favored than
corresponding P,P-coordinated 1+2 product.
Keywords Phosphorus ylide; Mercury(II) halides complexes; Multinuclear NMR study; X-
ray crystal structure; Computational studies
2
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[Supplementary materials are available for this article. Go to the publisher’s online
edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following
free supplemental files: Additional figures.]
<AQ> Editorial work on your manuscript has created a file of supplemental materials
that will be available on-line only.</AQ>
We are grateful to the Bu-Ali Sina University for a grant and Mr. Zebarjadian for recording
the NMR spectra. Mehdi Bayat thanks the Marburg University of Germany for their support for
doing the computation during his academic visit.
Address correspondence to Seyyed Javad Sabounchei, Faculty of Chemistry, University of
Bu–Ali Sina, Hamedan, 65174 Iran. E-mail: jsabounchei@yahoo.co.uk
INTRODUCTION
Phosphorus ylides are important reagents in organic chemistry, especially in the synthesis
of naturally occurring products with biological and pharmacological activities.1 They are
synthetic targets of interest, because of their value for a variety of industrial, biological and
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chemical synthetic uses.2-5 The coordination and organometallic chemistry of α-ketostabilized
phosphorus ylides has been investigated and their ambidenticity explained in terms of a delicate
balance between electronic and steric factors.6-11 These ligands are particularly appropriate for
the synthesis of low-valent metal complexes.12-16 Transition metal complexes of these ligands
have attracted much attention due to their versatile coordination chemistry and their application
in
catalysis.17-22
The
α-ketostabilized
ylides
derived
from
bisphosphines,
Ph2PCH2P(Ph)2=C(H)C(O)R, Ph2PCH2CH2PPh2=C(H)C(O)R (R= Me, Ph or OMe)23 and
PhC(O)C(H)=PPh2CH2CH2PPh2=C(H)C(O)Ph24 form an important class of such ligands which
can exist in ylidic and enolate forms.
The remarkable change in reactivity arises from a subtle variation in the molecular
electronic structure of the ylide due to the presence of additional keto stabilization.25 These
compounds have been used as reducing agents in coordination chemistry. The utility of
metalated phosphorus ylides in synthetic chemistry has been well documented.26-31 Much of the
interest in the coordination properties of resonance stabilized phosphorus ylides stemming from
their bond versatility due to the presence of different functional groups in their molecular
structure.32-35 Coordination of ligands towards Hg(II) has assumed importance since, in nature’s
mercury detoxification process, the initial Hg–C bond cleavage involves the increase in the
coordination number around Hg.36 Furthermore, evidence for new classes of metal-binding
motifs in enzymes, transcription factors, and regulatory proteins emphasize the need for
structural insights about local Hg(II) coordination environments.37 Ebrahim et al. have reported
the reactivity of mercury(II) halides with the phosphine-ylide ligand with ethylenic
Ph2P(CH2)2PPh2=C(H)C(O)Ph25 and methylenic PPh2CH2PPh2=C(H)C(O)Ph spacer,38 these
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compounds giving place to different monomeric and polymeric products. Recently, we have
reported bidentate phosphorus ylide and their complexes with Hg(II)32,39,40 and Pd(II).22,41 In this
work, we report the reactivity of the new ligands Ph2PCH2P(Ph)2=C(H)C(O)C6H4Me (3) and
Ph2PCH2P(Ph)2=C(H)C(O)C10H7 (4), towards mercury(II) halides.
RESULTS AND DISCUSSION
Synthesis
The ligands were synthesized by treating bis(diphenylphosphino)methane with 4-
methylphenacyl bromide and 2-(bromoacetyl)naphthalene and removal of the proton from the
phosphonium salts by triethylamine.23 Reaction of HgX2 with the ylides 3 and 4 in a 1:1
stoichiometry afforded the P, C-coordinated complexes with a chelating structure (Scheme 1).
All complexes are insoluble in most common organic solvents, but soluble in dichloromethane
and all were obtained in good yields.
Scheme 1 here
IR Spectroscopy
The IR data confirm the complete formation of the carbonylic ylides with the
disappearance of the CO band at 1661 and 1666 cm-1 in phosphonium salts 1 and 2 and the
presence of a new strong CO band at 1500 and 1517cm-1 in resulting carbonyl stabilized ylides 3
and 4, respectively.42,43 The coordination of the ylide through carbon causes a significant
increase in the ν(C=O) frequency.44 Thus infrared absorption bands observed at higher
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frequencies (around 1590 cm-1) for carbonyl group of all complexes indicate that coordination of
the ylides through ylidic carbon atom have occurred.40 The carbonyl frequency for all complexes
and parent ylides are reported in Table 1.
NMR Results
The 31P NMR spectrum of 1 exhibits two doublets at 21.0 and -29.3 ppm that indicate the
1
PCH2CO and PPh2 groups, respectively. The H NMR spectrum shows a doublet at 5.81 ppm,
2
with a coupling constant JPH of 12.6 Hz, due to a CH2 group of a 4-methylphenacyl bromide
system bonded to a phosphonium moiety.11 The 31P NMR spectrum of 3 exhibits two doublets at
11.2 ppm and -29.4 ppm that indicate the phosphonium phosphorus and free phosphine
phosphorus atoms, respectively. The phosphonium atom of this compound shows upfield shifts
compared to that of parent phosphonium salt (1), suggesting an increase of electron density in
1
the P–C bond.42 The H NMR spectrum of this compound shows, in addition to the aromatic
resonances, three signals centered at 4.23 (t), 3.66 (d) and 2.34 (s) of relative intensity 1:2:3
attributed to the PCH2P, P=CH and methyl protons, respectively.45 The 31P NMR data for all
complexes appear to be shifted downfield with respect to the parent ylides, also indicate that
31
coordination of the ylides have occurred. The P NMR spectrum for the complexes exhibit the
presence of the PCH group as a doublet around 26 ppm, this chemical shift is at lower field than
that observed for the corresponding free ylides (around 11.3 ppm), indicating that coordination
of the ylides have occurred. The 1H and 31P NMR data of compound 2 and 4 are similar to that
observed for 1 and 3, respectively. The 13C chemical shift values for compounds 1- 4 also
indicating that synthesis of these compounds have occurred. The 31P NMR spectrum of 5
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exhibits a doublet at 26.6 with a coupling constant 2JPP of 43.8 Hz and a broad signal at 6.0 ppm,
1
attributable to PCH and PPh2 groups, respectively. The H NMR spectrum of this complex
shows a doublet at 5.73 ppm, with a 2JPH of 12.60 Hz, related to a CH group bonded to mercury
atom that be shifted downfield with respect to the parent ylide 3.43 The NMR data of complexes
6 and 7 are similar to that of 5 and listed in Table 1. The 31P NMR spectrum of 8 shows a
2
doublet at 25.6 ppm with a coupling constant JPP of 41.0 Hz and a broad signal at 7.30 ppm,
1
which are assigned to the PCH and PPh2 groups, respectively. The H NMR spectrum shows a
2
doublet at 5.93 ppm attributable to the ylidic proton with a coupling constant JPH of 14.4 Hz.39
The expected downfield shifts of 1H and 31P signals for the PCH group upon complexation of 10
were observed. This compound exhibits in the 31P NMR spectrum a doublet at 28.1 ppm with a
coupling constant 43.9 Hz and a broad signal at -9.3 ppm, attributable to the phosphonium
1
31
phosphorus and to the free phosphine phosphorus atoms, respectively. In the H and P NMR
spectra, the signals due to the methynic proton and two phosphorus atom for complex 9 are
13
broad and Similar to that observed for 8 and 10. The C NMR shifts of the CO group in the
complexes are around 192 ppm, relative to around 184 ppm noted for the same carbon in the
parent ylides, indicating much lower shielding of the carbon of the CO group in these
complexes. The selected NMR data for all complexes and parent ylides are reported in Table 1.
Table 1 here
Crystal Structure
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Colorless crystals of 3 were obtained from a chloroform solution by slow evaporation of
the solvent. An ORTEP plot (Figure 1) shows that in this molecule the geometry around the P
atom is nearly tetrahedral, and the O atom is oriented cis to the P(1) atom. The P(1)–C(9)
(1.712(4) Å) and C(9)–C(8) (1.402(6) Å) bond lengths are shorter than the (P+–C (sp3) (1.800 Å)
and (C–C (sp3) (1.511 Å) normal values, respectively. This is due to the ylidic resonance and
intermediate between common values for single (P–C = 1.80 Å) and double (P=C = 1.66 Å)
bonds. The CO bond (1.258(5) Å) also is longer than the normal value (1.210 Å). This bond
distance suggests electron delocalization in this molecule.46 Suitable crystals of complex 10 were
obtained from dimethylsulfoxide solution by the slow evaporation of the solvent after 15 days.
The X-ray analysis confirms unequivocally the P–C chelate coordination of the ylide 4 to the Hg
atom in complex 10. Relevant parameters concerning data collection and refinement of
compounds 3 and 10 are given in Table 2 and selected bond distances and angles in Table 3.
Table 2 here
Table 3 here
The Hg(II) center in this complex is four-coordinate with sp3 hybridization. The mercury
atom is surrounded by one P atom of the PPh2 unit, one ylidic C atom and two I atoms. The
angles subtended by the ligand at the Hg(II) center in 10 vary from 87.5(2) to 115.56(5) Å
indicating a distorted tetrahedral environment. The stabilized resonance structures for the parent
ylide are destroyed by the complex formation, thus the C(11)–C(12) bond length 1.475(12) Å is
longer than the corresponding distances found in the similar uncomplexed phosphoranes
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[Ph2PCH2PPh2C(H)C(O)Ph] (1.404(3) Å)38 and 3 (1.402(6) Å). On the other hand, the bond
length of P–C(H) in the similar ylides [Ph2PCH2PPh2C(H)C(O)Ph] 1.705(2) Å38 and 3 (1.712(4)
Å) show that the corresponding bonds are considerably elongated to 1.747(9) Å.40 The Hg–P
bond length in 10 (2.594(2) Å) is comparable to analogous distance in Hg(II)–phosphine
complexes
such
as
{HgI2[(Ph2PCH2PPh2C(H)C(O)C6H4NO2)]}
2.519(19
Å),39
{HgI2[(PPh2CH2PPh2C(H)C(O)Ph)]} 2.568(19) Å38 and {HgBr2[(PPh3)2]} 2.550(4) Å.47 The
terminal Hg–I distances in 10 (2.7301(8) and 2.7469(7) Å) are comparable to analogous
distances in {HgI2[(PPh3)2]} (2.733(1) and 2.763(1) Å)48 and {HgI2[(Ph2PCH2PPh2C(H)-
C(O)C6H4Cl)]} (2.7270(14) and 2.7483(3) Å).40 For compound 10 the largest peak in the final
difference Fourier map (3.035 Å3) is located near to Hg1 haevy atom (0.89 Å from Hg1). The
molecular structure of 10 is shown in Figure 2.
Figure 1 here
Figure 2 here
Computational Studies
Both ligands 3 and 4 have three donor atoms in their structures, one phosphine phosphorus,
one O atom and one C(ylidic). In these ligands there is only one methylene group between the
phosphorus atoms. Thus a five-membered chelate ring will be formed upon the coordination of
phosphine phosphorus atom along with the ylidic carbon to the metal ion. Recently we reported
the DFT optimized strucure of the mercury(II) complexes of a similar bidentate phosphorus
ylide derived from dppe (Ph2PCH2CH2PPh2).32 In the latter ligand there are two methylene
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groups between the phosphorus atoms. Thus a six-membered chelate ring will be formed upon
the P,C-coordination of ligand to the metal ion. For the reaction between the mercury halides
(HgX2) and this type of ligands (L) we can consider two possible products, 1+1 (HgLX2) or 1+2
(HgL2X2), where X= Cl, Br and I. The result of our previous work32 showed that among the six
studied products/isomers, the 1+2 product in which two ligands are coordinated to HgI2 from
their phosphine phosphorus atom is the most stable product. Herein we report a comparison
between the calculated and relative energies (G, H, E0) for two possible products of reaction
between ligand 4 and HgI2 (See Table 4). The result of above calculation showed that the 1+1
product in which one ligand is coordinated to HgI2 from its ylidic carbon and also phosphine
phosphorus is thermodynamically the least stable product (See Table 4). However, in contrast,
the present calculations on reaction between HgI2 and the ylidic ligand (4) synthesized here
shows that the formation of latter 1+1 product is more favored than the corresponding 1+2
product (see Scheme 2 and Table 4).
Scheme 2 here
Table 4 here
We note that the nature of the donor atoms in the ligands synthesized here with those in our
previous work are the same. Thus it seems that for this type of ligands the P,C-coordination will
occur when it forms a six-membered chelate ring. On the other hand, the P,C-coordination is
energetically more favored when it forms a five-membered chelate ring. We note that the latter
mode of coordination is the observed one for compound 10 in the solid state. Thus the
10
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computational study is in agreement with results of X-ray structure analysis of compound 10,
indicating that the complex 10 has adopted the most stable structure (Figure 3, product II) in the
solid state. According to result of above computational studies and due to same spectroscopic
data between the complexes 8 and 9, we can assume that the structures of these complexes
would be the same with that exhibited by compound 10. The geometry of complexes 8, and 9
were also fully optimized at density functional (B3LYP) level of theory (see Supplemental
Materials, Figure S1).
Figure 3 here
Table 5 here
A comparison between the calculated bond lengths (Å) and bond angles (º) for compounds
8-10 with corresponding experimental values for compound 10 is presented in Table 3. The
calculated structure for complex 10 in the gas phase agrees well with the structure determined by
X-ray crystallography. As can be seen in Table 5, the calculated Hg–C bond lengths in
compounds 8, 9, and 10 are, 2.42, 2.45, and 2.48 (Å), respectively, which are slightly longer than
corresponding X-ray value for compound 10. On the other hand, the Hg–P bond lengths in
compounds 8, 9, and 10 are 2.91, 2.93, and 2.96 (Å), respectively, which are about 0.3 Å longer
than related X-ray value for compound 10. Obviously, one of the reasons for this large difference
is the size of the basis set used. However, in respect to the size of the complexes the considerably
larger basis sets are too expensive. The similarity of the metal-ligand bond lengths in compounds
8-10 suggests that the coordinated halide has a slight effect on the Hg–P and Hg-C bond lengths.
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As it can be seen in the Table 5, there is good agreements between the calculated bond angles for
compound 10 with those derived from X-ray crystal structure.
The
HOMO
and
LUMO
for
all
three
mononuclear
complexes,
{HgX2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} where X= Cl, Br and I, are illustrated in Figure 4. It is
interesting that the contribution of the coordinated halide in the HOMO increases from Cl to I,
whereas the LUMO does not significantly change in the series of these complexes.
Figure 4 here
CONCLUSION
The present study describes the synthesis and characterization of a series of chelate
mercury(II) complexes derived from mercury halides and new unsymmetric phosphorus ylides
Ph2PCH2P(Ph)2=C(H)C(O)C6H4Me and Ph2PCH2P(Ph)2=C(H)C(O)C10H7. On the basis of the
physicochemical and spectroscopic data we propose that ligands herein exhibit a chelate P–C
coordination behavior to the metal center affording a five-membered chelate rings, which is
further confirmed by the X-ray crystal structure of the complex 10. The result of computational
study showed that the formation of P,C-coordinated 1+1 complex is energetically more favored
than corresponding P,P-coordinated 1+2 product. Thus both the experimental and computational
results of this work showed that the P,C-coordination of ylide will be occurred when it forms a
five-membered chelate ring.
EXPERIMENTAL PART
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Materials and Physical Measurements
All reactions were carried out under an atmosphere of dry nitrogen. Methanol was 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.
Melting points were measured on a SMP3 apparatus. IR spectra were recorded on a Shimadzu
1
13
31
435-U-04 spectrophotometer from KBr pellets. H, C and P NMR spectra were recorded on
300 MHz Bruker and 90 MHz Jeol spectrometer in DMSO-d6 or CDCl3 as solvent at 25°C.
Chemical shifts (ppm) are reported according to internal TMS and external 85% phosphoric acid.
Coupling constants are given in Hz. Elemental analysis for C, H and N atoms were performed
using a Perkin–Elmer 2400 series analyzer.
X-Ray Diffraction
The single crystal X-ray diffraction data of suitable crystals of 3 and 10 were collected on a
STOE IPDS-II diffractometer at 298 K, using graphite monochromated Mo Ka radiation λ=
0.71073 Å). The data collection was performed using the ω-scan technique using the Stoe X-
AREA software package,49 while data reduction was carried out using the program X-RED.49
The crystal structures were solved by direct methods and refined by full-matrix least-squares on
F2 using the programs SHELXS and SHELXL, respectively,50 and using the X-STEP32
crystallographic software package.51 The H atoms were included in calculated positions and
treated as riding atoms using SHELXL50 default parameters. Numerical absorption corrections
were applied for both structures. Crystallographic data for the structures 3 and 10 have been
deposited in the Cambridge Crystallographic Data Center as the supplementary publication
numbers 837047 and 856741, respectively. These data can be obtained free of charge via
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http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data
Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Computational Methods
In this work among the known DFT methods we used the B3LYP52,53 to calculate the
molecular structure and thermodynamic properties of free ligand as well as ‘‘1 + 1’’ and ‘‘1 + 2’’
complexes of Hg(II) metal ion. B3LYP has been used with good success in a number of studies
involving similar Hg(II) species,54-56 and we have found good agreement with experimental
results for a number of metal-containing systems from using B3LYP.32,40,57-60 The CEP-31G
basis set was used for free ligand and all studied complexes. The latter basis set includes
effective core potentials (ECP) for both the mercury and phosphorus atoms as well as halide (Br−
and I−) ions. The program Gaussian 03 was employed in all calculations.61 The molecular
structures of these molecules in the ground state were fully optimized. In all cases vibrational
frequency analysis, calculated at the same level of theory, indicate that optimized structures are
at the stationary points corresponding to local minima without any imaginary frequency. Atomic
coordinates for DFT calculations were obtained from the data of the X-ray crystal structure
analysis of compound 10.
Sample Preparation
Synthesis of [Ph2PCH2PPh2CH2C(O)C6H4Me]Br (1)
Bis(diphenylphosphino)methane (dppm) (0.50 g, 1.30 mmol) was dissolved in 8 ml of
chloroform and then a solution of 4-methylphenacyl bromide (0.28 g, 1.30 mmol) in the same
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solvent (5 ml) was added dropwise to the above solution. The resulting solution was stirred for
10 h at room temperature and then was concentrated under reduced pressure to about 2 ml.
Diethyl ether (20 ml) was added and the white solid formed was filtered off, and dried under
˚
reduced pressure. Yield: 0.63 g (81%); m.p. 173–175 C. Anal. Calcd. for C34H31BrOP2 (%): C,
68.35; H, 5.23. Found: C, 68.61; H, 5.18. Selected IR absorption in KBr (cm-1): 1661 (νC=O). 1H
NMR (CDCl3) δH: 4.24 (d, 2H, PCH2P, 2JPH = 15.31); 5.81 (d, 2H, PCH2CO, 2JPH = 12.60); 2.29
31
2
(s, 3H, CH3); 7.20–8.20 (m, 24H, Ph). P NMR (CDCl3) δP: -29.3 (d, PPh2, JPP = 62.12); 21.0
2
13
1
(d, PCH2CO, JPP = 62.37). C NMR (CDCl3) δC: 21.3 (dd, PCH2P, JPC = 50.5, 51.3); 34.8 (d,
PCH2, 1JPC = 60.0); 20.7 (s, CH3); 119.3–137.5 (Ph); 190.7 (d, CO, 2JPC = 5.80).
Synthesis of [Ph2PCH2PPh2CH2C(O)C10H7]Br (2)
A solution of dppm (0.50 g, 1.30 mmol) and 2-(bromoacetyl)naphthalene (0.32 g, 1.30
mmol) in chloroform was stirred at room temperature for 10 h. The white solid formed was
˚
filtered off, and dried under reduced pressure. Yield: 0.70 g (85%); m.p. 168–170 C. Anal.
Calcd. for C37H31BrOP2(%): C, 70.15; H, 4.93. Found: C, 69.97; H, 4.88. Selected IR absorption
1
2
in KBr (cm-1): 1666 (νC=O). H NMR (CDCl3) δH: 4.23 (d, 2H, PCH2P, JPH = 14.40); 5.89 (d,
2H, PCH2CO, 2JPH = 13.50); 6.88–8.05 (m, 27H, Ph and 2-naphthyl). 31P NMR (CDCl3) δP: -29.4
2
2
13
(d, PPh2, JPP = 65.3); 21.3 (d, PCH2CO, JPP = 64.7). C NMR (CDCl3) δC: 20.8 (dd, PCH2P,
1
1JPC = 50.88, 51.60); 34.8 (d, PCH2, JPC = 60.24); 115.9–135.0 (Ph and 2-naphthyl); 191.1 (d,
CO, 2JPC = 5.06).
Synthesis of Ph2PCH2P(Ph)2=C(H)C(O)C6H4Me (3)
The monophosphonium salt (1) (0.30 g,0.50 mmol) was treated with triethylamine (0.50
mL) in toluene (15 mL). The triethylamine hydrobromide thus obtained was filtered off.
15
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Concentration of the toluene layer to about 2 mL and subsequent addition of diethyl ether (20
mL) resulted in the precipitation of the desired ligand as white solid. Yield: 0.22 g (87%); m.p.
˚
148–150 C. Anal. Calcd. for C34H30OP2(%): C, 79.06; H, 5.85. Found: C, 78.81; H, 5.76.
1
Selected IR absorption in KBr (cm-1): 1500 (νC=O). H NMR (CDCl3) δH: 3.66 (d, 2H, CH2, 2JPH
= 14.40); 4.23 (br, 1H, CH); 2.34 (s, 3H, CH3); 7.20–7.80 (m, 24H, Ph). 31P NMR (CDCl3) δP: -
2
2
13
29.4 (d, PPh2, JPP = 63.1); 11.2 (d, PCH, JPP = 62.4). C NMR (CDCl3) δC: 21.5 (dd, PCH2P,
1JPC = 50.4, 51.3); 48.6 (d, CH, 1JPC = 108.3); 20.7 (s, CH3); 124.6–138.5 (Ph); 184.6 (s, CO).
Synthesis of Ph2PCH2P(Ph)2=C(H)C(O)C10H7 (4)
This phosphorus ylide was obtained using the same procedure as adopted for the
preparation of 3 using monophosphonium salt (2) (0.32 g, 0.50 mmol). Yield: 0.21 g (76%); m.p.
˚
153–155 C. Anal. Calcd. for C37H30OP2(%): C, 80.42; H, 5.47. Found: C, 80.35; H, 5.51.
1
Selected IR absorption in KBr (cm-1): 1517 (νC=O). H NMR (CDCl3) δH: 3.72 (d, 2H, CH2, 2JPH
= 14.40); 4.47 (br, 1H, CH); 7.20–7.90 (m, 27H, Ph and 2-naphthyl). 31P NMR (CDCl3) δP: -29.4
2
2
13
1
(d, PPh2, JPP = 62.7); 11.4 (d, PCH, JPP = 64.54). C NMR (CDCl3) δC: 24.6 (dd, CH2, JPC
=
56.2, 57.6); 50.5 (d, CH, 1JPC = 112.4); 123.6–140.1 (Ph and 2-naphthyl); 183.6 (s, CO).
Data for {HgCl2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]}(5): General procedure for
Hg(II) halide complexes
To a solution of HgX2 (0.40 mmol) in methanol (8 mL), a solution of 3 or 4 (0.40 mmol)
°
in the same solvent (8 mL) was added dropwise at 0 C and the reaction allowed to proceed
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 Celite. Addition of excess
methanol to the concentrated filtrate caused the precipitation of the products as solids.
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°
Yield: 0.19 g, 61%. M.p. 200-202 C. Anal. Calc. for C34H30Cl2HgOP2: C, 51.82; H, 3.84.
Found: C, 52.12; H, 3.76%. IR (KBr, cm-1): 2886, 1602 (C=O), 1437, 1327, 1183, 1107, 773,
1
2
2
749, 691. H NMR (DMSO-d6): δH = 4.87 (t, 2H, CH2, JPH = 13.40); 5.73 (d, 1H, CH, JPH
=
31
12.60); 2.39 (s, 3H, CH3); 7.20–7.95 (m, 24H, Ph). P NMR (DMSO-d6): δp = 6.0 (br, PPh2);
2
13
26.6 (d, PCH, JPP= 43.8). C NMR (DMSO-d6): δc = 21.1 (s, CH3); 25.6 (br, CH2); 30.8 (br,
CH); 128.7-132.6 (Ph); 191.4 (s, CO).
Data for {HgBr2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]} (6)
Yield: 0.20 g, 58%. M.p. 197-199 °C. Anal. Calc. for C34H30Br2HgOP2: C, 46.57; H, 3.45.
Found: C, 46.76; H, 3.37%. IR (KBr, cm-1): 2888, 1602 (C=O), 1437, 1326, 1182, 1106, 772,
748, 691. 1H NMR (DMSO-d6): δH = 4.84 (br, 2H, CH2,); 5.70 (br, 1H, CH,); 2.38 (s, 3H, CH3);
31
2
7.20–7.95 (m, 24H, Ph). P NMR (DMSO-d6): δp = 10.8 (br, PPh2); 25.0 (d, PCH, JPP= 60.5).
13C NMR (DMSO-d6): δc = 21.4 (s, CH3); 25.2 (br, CH2); 33.3 (br, CH); 128.3-141.9 (Ph); 192.3
(s, CO).
Data for {HgI2[(Ph2PCH2PPh2C(H)C(O)C6H4Me)]} (7)
°
Yield: 0.20 g, 53%. M.p. 194-196 C. Anal. Calc. for C34H30I2HgOP2: C, 42.06; H, 3.11.
Found: C, 41.86; H, 3.18%. IR (KBr, cm-1): 2891, 1601 (C=O), 1437, 1323, 1180, 1104, 772,
747, 690. 1H NMR (DMSO-d6): δH = 4.83 (br, 2H, CH2,); 5.71 (br, 1H, CH,); 2.38 (s, 3H, CH3);
7.20–7.90 (m, 24H, Ph). 31P NMR (DMSO-d6): δp = -13.0 (br, PPh2); 26.4 (d, PCH, 2JPP= 55.1).
13C NMR (DMSO-d6): δc = 21.5 (s, CH3); 25.6 (br, CH2); 34.1 (br, CH); 128.2-133.6 (Ph); 190.4
(s, CO).
Data for {HgCl2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} (8)
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°
Yield: 0.19 g, 60%. M.p. 203-205 C.
Anal. Calc. for C37H30Cl2HgOP2: C, 53.92; H,
3.67. Found: C, 54.03; H, 3.69%. IR (KBr, cm-1): 1587 (C=O), 1437, 1354, 1180, 1105, 779,
1
743, 689. H NMR (DMSO-d6): δH = 4.70 (br, 2H, CH2,); 5.93 (d, 1H, CH, 2JPH = 14.40); 7.20–
8.00 (m, 27H, Ph and 2-naphthyl). 31P NMR (DMSO-d6): δp = 7.3 (br, PPh2); 25.6 (d, PCH, 2JPP
13
= 41.0). C NMR (DMSO-d6): δc = 22.6 (br, CH2); 125.1-134.8 (Ph and 2-naphthyl); 192.1 (s,
CO); (CH, was not observed).
Data for {HgBr2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} (9)
Yield: 0.22 g, 57%. M.p. 196-198 °C. Anal. Calc. for C37H30Br2HgOP2: C, 48.67; H, 3.31.
Found: C, 48.58; H, 3.35%. IR (KBr, cm-1): 1591 (C=O), 1435, 1356, 1178, 1107, 780, 745, 687.
1H NMR (DMSO-d6): δH = 4.68 (br, 2H, CH2,); 5.47 (br, 1H, CH,); 7.20–8.00 (m, 27H, Ph and 2-
2
naphthyl). 31P NMR (DMSO-d6): δp = 1.8 (br, PPh2); 26.9 (d, PCH, JPP = 41.9). 13C NMR
(DMSO-d6): δc = 23.7 (br, CH2); 125.1-135.0 (Ph and 2-naphthyl); 191.2 (s, CO); (CH, was not
observed).
Data for {HgI2[(Ph2PCH2PPh2C(H)C(O)C10H7)]} (10)
°
Yield: 0.21 g, 55%. M.p. 199-201 C. Anal. Calc. for C37H30I2HgOP2: C, 44.13; H, 3.00.
Found: C, 44.26; H, 2.97%. IR (KBr, cm-1): 1596 (C=O), 1436, 1356, 1174, 1107, 777, 740, 689.
1H NMR (DMSO-d6): δH = 4.60 (br, 2H, CH2,); 5.40 (br, 1H, CH,); 7.20–8.00 (m, 27H, Ph and 2-
2
naphthyl). 31P NMR (DMSO-d6): δp = -9.3 (br, PPh2); 28.1 (d, PCH, JPP = 43.9). 13C NMR
(DMSO-d6): δc = 25.0 (br, CH2); 124.4-136.0 (Ph and 2-naphthyl); 192.4 (s, CO); (CH, was not
observed).
Supplemental Materials
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Supplemental Materials contain some selected spectra of products. CIF files for the two X-
ray structures are available.
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CAPTIONS:
Scheme 1 Synthetic route for the preparation of compounds 1-10.
PPh2
PPh2
Ph2 P
Ph2 P
C
O
R
CH2
H2
C
Chloroform
RT, 24h
C
O
R
Br
Br
+
(1): R = 4-methylphenyl
(2): R = 2-naphtyl
PPh2
Et3N
CH
C
O
Ph2P
R
Hg
Ph2 P
Ph2 P
C
O
R
CH
x
x
CH3OH
under N2, 2h
HgX2
(5): R = 4-methylphenyl, X = Cl
(6): R = 4-methylphenyl, X = Br
(7): R = 4-methylphenyl, X = I
(8): R = 2-naphtyl, X = Cl
(9): R = 2-naphtyl, X = Br
(10): R = 2-naphtyl, X = I
+
(3): R = 4-methylphenyl
(4): R = 2-naphtyl
Scheme 2 Two different products resulting from 1+2 and 1+1 reaction between ylidic ligand 4
and HgI2. The product II corresponds to compound 10 which was observed in this work.
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I
I
Hg
I
1+2
PPh2CH2PPh2CHC(O)C10H7
C10H7(O)CHCPh2PCH2Ph2P
Ph2PCH2PPh2=CHC(O)C10H7
+
HgI2
I
I
Hg
II
Ph2P
CH C(O)C10H7
PPh2
1+1
Figure 1 Molecular structure of 3 with ellipsoids at the 50% probability level.
25
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Figure 2 Molecular structure of 10 with ellipsoids at the 50% probability level. Hydrogen atoms
and methanol molecule are omitted for clarity.
26
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Figure 3 Calculated molecular structures for ligand 4 and two different products (I and II) of
reaction between it and HgI2 at CEP-31G level of theory.
(I)
27
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(II)
(4)
Figure 4 Calculated HOMOs (a, c, e) and LUMOs (b, d, f) for {HgX2[(Ph2PCH2PPh2C(H)C(O)
C10H7)]}complexes, where X=Cl (a, b), Br (c, d), and I (e, f), respectively.
28
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(a)
(b)
(c)
(d)
(e)
(f)
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