Synthesis, characterization and nuclear magnetic resonance study of the stoichiometry and stability of several zwitterionic mercury(II) complexes in dimethylsulfoxide

Article abstract of DOI:10.1016/j.molstruc.2013.02.042

The reaction of the non-symmetric phosphonium salts [PPh₂CH ₂PPh₂CH₂C(O)R]Br₂ (R = 4′-biphenyl (L₁); OCH₂Ph (L₂); 4-methylphenyl (L₃); 2-naphtyl (L₄

Full text of DOI:10.1016/j.molstruc.2013.02.042

Journal of Molecular Structure 1040 (2013) 184–191
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization and Nuclear Magnetic Resonance study of the
stoichiometry and stability of several zwitterionic mercury(II) complexes
in dimethylsulfoxide
⇑
Seyyed Javad Sabounchei , Mohammad Panahimehr, Hassan Keypour, Mohammad Hassan Zebarjadian
Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Synthesis and characterization of some Hg(II) complexes of the phosphorus ligands.
IR, 1H- and 13C-NMR data demonstrate P-coordination of the ligands to the metal.
31P chemical shifts were measured as a function of [HgX2]/[ligand] mole ratio.
a r t i c l e i n f o
a b s t r a c t
The reaction of the non-symmetric phosphonium salts [PPh2CH2PPh2CH2C(O)R]Br2 (R = 40-biphenyl (L1);
OCH2Ph (L2); 4-methylphenyl (L3); 2-naphtyl (L4); 3-nitrophenyl (L5) and [PPh2CH2PPh2CH2C(O)R]Cl2
(R = 2,4-dichlorophenyl (L6)), with mercury(II) halides in 1:1 (for chloride and bromide) and 1:2 (for
iodide) mole ratio in methanol under mild conditions afford the monomeric P-coordinated complexes,
[HgCl2(Br)(Ph2PCH2PPh2CH2C(O)R)] (R = 40-biphenyl (1), OCH2Ph (2), 4-methylphenyl (3), 2-naphtyl (4),
3-nitrophenyl (5)) and [HgCl3(Ph2PCH2PPh2CH2C(O)C6H4Cl2)] (6), [HgBr3(Ph2PCH2PPh2CH2C(O)R)]
(R = 40-biphenyl (7), OCH2Ph (8), 4-methylphenyl (9), 2-naphtyl (10), 3-nitrophenyl (11) and [HgBr2-
(Cl)(Ph2PCH2PPh2CH2C(O)C6H4Cl2)] (12)), [HgBr2(I)(Ph2PCH2PPh2CH2C(O)R)] (R = 40-biphenyl (13),
OCH2Ph (14), 4-methylphenyl (15), 2-naphtyl (16), 3-nitrophenyl (17)) and [HgCl2(I)(Ph2PCH2PPh2CH2-
C(O)C6H4Cl2)] (18). These complexes were fully characterized by elemental analysis and IR, 1H, 13C and
31P{1H} NMR spectra. In addition, 31P{1H} NMR spectroscopy was used to investigate the stoichiometry
and stability of all complexes in pure dimethylsulfoxide solvent. The formation constants of the resulting
1:1 complexes were evaluated from computer fitting of the mole ratio data to an equation that relates the
observed chemical shifts to the formation constant. It was found that, in pure dimethylsulfoxide, the sta-
bilities of the resulting 1:1 complexes vary in the order L3 > L4 > L1 > L5 > L6 > L2 and HgCl2 > HgBr2 > HgI2.
Crown Copyright Ó 2013 Published by Elsevier B.V. All rights reserved.
Article history:
Received 20 December 2012
Received in revised form 17 February 2013
Accepted 26 February 2013
Available online 7 March 2013
Keywords:
Phosphonium ligands
Hg(II) complexes
NMR studies
Formation constants
1. Introduction
phine group), or even situations in which the same ylide shows a
combination of bonding modes. Different types of bonding are
Phosphonium salts are useful intermediates in organic
synthesis [1] and an important class of ligands that find wide-
spread use in transition metal chemistry [2]. Different types of
ylide complexes of transition metals such as Hg(II), Pd(II) and
Au(I) were prepared using the corresponding phosphonium salts
as precursors [3–7]. Phosphorus ylides are known to demonstrate
rich coordination chemistry. The coordination chemistry of keto-
stabilized phosphorus ylides, are interested to investigate because
of the different bonding modes upon coordination of ylides to me-
shown as depicted in Chart 1 for Ph2PCH2PPh2C(H)C(O)R.
Due to the resonance delocalisation of the ylide electron den-
sity, some ylides are also capable of chelating to the metals via
two atoms in a bidentate manner [17–26]. Mono keto ylides with
a methylenic spacer, Ph2PCH2PPh2 = C(H)C(O)PhR [R = H, Cl, Br,
NO2, OCH3] affords P, C-coordinated complexes with mercury(II)
halides [27–29]. On the other hand, Ph2PCH2CH2PPh2 = C(H)C(O)Ph
with a ethylenic spacer forms polymeric Hg(II) complexes with
HgCl2 via P, C-bridging mode while HgBr2 and HgI2 react with
the same ylide giving polymeric halogen bridged phosphine com-
plexes with dangling ylide [18]. In this work, we report the forma-
tion of zwitterionic P-coordinated complexes of mercury(II)
halides with phosphine–phosphonium salts. Among a variety of
spectroscopic and electrochemical methods used for the study of
tal [8–16]: C-coordinated (through the C atom), O-bonded
a
(through the carbonyl O), P-bonded (through the P of the phos-
⇑
Corresponding author. Tel.: +98 811828280; fax: +98 8118257408.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
0022-2860/$ - see front matter Crown Copyright Ó 2013 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.02.042

S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
185
Cl
Cl
Ph2P
P
CH2
Ph2
Ph2
P
H2
C
HgX2
Cl
C
O
Cl
C
O
Cl-
Hg
Cl
MeOH, RT
X
(6) X = Cl
(12) X = Br
X
PPh2
Cl
Ph2P
P
CH2
Ph2
Cl
C
Hg
Cl
Cl
O
I
(18)
Chart 1. The possible bonding modes of Ph2PCH2PPh2C(H)C(O)R to metal M.
complexes [30–32] it has been found that nuclear magnetic reso-
nance spectrometry offers a very sensitive technique for studies
of changes in the immediate chemical environment of phos-
phine–phosphonium salts in solution. In recent years, we have
used proton and alkali metal NMR techniques to study the thermo-
dynamics [33,34] and kinetics [35,36] of metal ion complexation
with some macroacyclic ligands in nonaqueous and mixed sol-
vents. In this study, our interest in the physicochemical properties
of the phosphorus ligands, encouraged us to determine the forma-
tion constants of mercury(II) complexes of phosphorus ligands and
to gain some useful information about the properties of complex
formation in the solvent.
10 mL methanol and 10 mL diethylether and dried under reduced
pressure.
2.3.1.1. Data for [HgCl2(Br)(Ph2PCH2PPh2CH2C(O)C6H4Ph)] (1). Yield:
0.22 g, 81%. M.p. 155–157 °C. Anal. Calc. for C39H33BrCl2HgOP2: C,
50.32; H, 3.57. Found: C, 50.79; H, 3.52. IR (KBr, cmꢁ1): 1670
2
(t
C@O). 1H NMR (DMSO-d6): d 4.24 (t, 2H, PCH2P, JPH = 13.50);
5.65 (d, 2H, PCH2CO, JPH = 11.07); 7.30–8.00 (m, 29H, Ph). 31P
NMR (DMSO-d6): d ꢁ26.24 (d, PPh2, 2JPP = 68.71); 23.88 (d, PCH2CO,
2JPP = 66.72). 13C NMR (DMSO-d6): d 19.45 (br, PCH2P); 34.24 (d,
PCH2); 119.17–145.53 (Ph); 192.41 (s, CO).
2
2.3.1.2. Data for [HgCl2(Br)(Ph2PCH2PPh2CH2CO2CH2Ph)] (2). Yield:
0.19 g, 72. M.p. 143–145 °C. Anal. Calc. for C34H31BrCl2HgO2P2: C,
2. Experimental
46.15; H, 3.53. Found: C, 45.84; H, 3.47. IR (KBr, cmꢁ1): 1718
C@O). 1H NMR (DMSO-d6): d 4.53 (d, PCH2P, CH2, JPH = 15.93);
2
(
t
2.1. Materials
2
5.11 (d, 2H, PCH2CO, JPH = 13.76); 4.97 (s, 2H, CH2O); 7.13–8.05
(m, 25H, Ph). 31P NMR (DMSO-d6):
d
ꢁ14.73 (d, PPh2,
All reactions were carried out under an atmosphere of dry nitro-
gen using standard Schlenk techniques. Reactants and reagents
were obtained from Merck Chemical Company and used without
further purification. The solvents were dried and distilled using
standard methods [37].
2
2JPP = 49.32); 22.66 (d, PCH2CO, JPP = 48.84). 13C NMR (DMSO-
d6): d 19.65 (br, PCH2P); 29.82 (br, PCH2); 68.20 (s, CH2O);
117.22–135.39 (Ph); 164.58 (s, CO).
2.3.1.3. Data for [HgCl2(Br)(Ph2PCH2PPh2CH2C(O)C6H4Me)] (3). Yield:
0.22 g, 85%. M.p. 147–149 °C. Anal. Calc. for C34H31BrCl2HgOP2: C,
2.2. Physical measurements
46.99; H, 3.59. Found: C, 47.17; H, 3.64. IR (KBr, cmꢁ1): 1669
(
t
C@O). 1H NMR (DMSO-d6): d 4.52 (d, 2H, PCH2P, JPH = 12.78);
2
Melting points were measured on a Stuart SMP3 apparatus.
Elemental analysis for C, H and N were performed using a Per-
kin–Elmer 2400 series analyzer. The IR spectra in the interval of
4000–400 cmꢁ1 were recorded on a Shimadzu 435-U-04 spectro-
photometer and samples were prepared as KBr pellets. 1H and
31P{1H} NMR spectra were recorded on 90 MHz Jeol and 13C NMR
spectra on 300 MHz Bruker spectrometers in DMSO-d6 as solvent
at 25 °C. Chemical shifts (ppm) are reported according to internal
TMS and external 85% H3PO4.
2
5.74 (d, 2H, PCH2CO, JPH = 12.60); 2.38 (s, 3H, CH3); 7.33–8.05
(m, 24H, Ph). 31P NMR (DMSO-d6):
d
ꢁ17.11 (d, PPh2,
2
2JPP = 54.53); 23.35 (d, PCH2CO, JPP = 54.03). 13C NMR (DMSO-
d6): d 22.64 (br, PCH2P); 34.33 (br, PCH2); 21.90 (s, CH3); 118.65–
145.17 (Ph); 191.71 (s, CO).
2.3.1.4. Data for [HgCl2(Br)(Ph2PCH2PPh2CH2C(O)C10H7)] (4). Yield:
0.21 g, 78%. M.p. 148–150 °C. Anal. Calcd. for C37H31BrCl2HgOP2:
C, 49.11; H, 3.45. Found: C, 48.97; H, 3.48. Selected IR absorption
in KBr (cmꢁ1): 1667 (
m
C@O). 1H NMR (DMSO-d6): d 4.60 (d, 2H,
2
2
2.3. Sample preparation
PCH2P, JPH = 13.95); 5.89 (d, 2H, PCH2CO, JPH = 12.15); 7.32–8.89
(m, 27H, Ph and 2-naphtyl). 31P NMR (DMSO-d6): d-13.20 (d,
The ligands [PPh2CH2PPh2CH2C(O)R]Br2 [R = 40-biphenyl (L1);
OCH2Ph (L2); 4-methylphenyl (L3); 2-naphtyl (L4); 3-nitrophenyl
(L5) and [PPh2CH2PPh2CH2C(O)C6H3Cl2]Cl2 (L6)] were prepared by
our group previously [38].
2
2
PPh2, JPP = 40.83); 22.97 (d, PCH2CO, JPP = 28.53). 13C NMR
(DMSO-d6): d 19.80 (br, PCH2P); 37.75 (br, PCH2); 124.20–138.50
(Ph and 2-naphtyl); 196.42 (s, CO).
2.3.1.5.
Data
for
[HgCl2(Br)(Ph2PCH2PPh2CH2C(O)C6H4NO2)]
2.3.1. Synthesis of Hg(II) halide complexes
(5). Yield: 0.23 g, 85%. M.p. 142–144 °C. Anal. Calcd. for C33H28-
General procedure: To a solution of HgX2 , X = Cl and Br
(0.30 mmol) or HgI2 (0.15 mmol) in methanol (10 mL), a solution
of L (L = L1–L6) (0.30 mmol) in the same solvent (5 mL) was added
dropwise at 25 °C and the reaction allowed to proceed under stir-
ring for 5 h. The resulting solid was isolated, washed twice with
BrCl2HgNO3P2: C, 44.04; H, 3.13; N, 1.55. Found: C, 43.82; H,
3.06; N, 1.64. Selected IR absorption in KBr (cmꢁ1): 1685 (
m
C@O).
2
1H NMR (DMSO-d6): d 4.31 (d, 2H, PCH2P, JPH = 15.57); 5.77 (t,
2H, PCH2CO, JPH = 13.23); 7.26–8.73 (m, 24H, Ph). 31P NMR
2
2
(DMSO-d6) dP: ꢁ26.75 (d, PPh2, JPP = 65.65); 23.70 (d, PCH2CO,

186
S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
2JPP = 73.28). 13C NMR (DMSO-d6): d 21.71 (br, PCH2P); 34.84 (br,
PCH2); 118.71–151.15 (Ph); 191.64 (s, CO).
2JPH = 12.59); 7.35–8.02 (m, 23H, Ph). 31P NMR (DMSO-d6): d
2
2
ꢁ24.08 (d, PPh2, JPP = 61.79); 23.48 (d, PCH2CO, JPP = 61.72). 13C
1
NMR (DMSO-d6): d 22.57 (d, PCH2P, JPC = 61.54); 38.73 (d, PCH2,
2
2.3.1.6. Data for [HgCl3(Ph2PCH2PPh2CH2C(O)C6H3Cl2)] (6). Yield:
0.19 g, 75%. M.p. 169–171 °C. Anal. Calcd. for C33H27Cl5HgOP2: C,
45.1; H, 3.09. Found: C, 45.17; H, 3.14. Selected IR absorption in
1JPC = 58.14); 114.85–139.64 (Ph); 190.73 (d, CO, JPC = 4.57).
2.3.1.13.
Data
for
[HgBr2(I)(Ph2PCH2PPh2CH2C(O)C6H4Ph)]
KBr (cmꢁ1): 1689 ( C@O). 1H NMR (DMSO-d6): d 4.56 (bd, 2H, PCH2-
m
(13). Yield: 0.091 g, 57%. M.p. 109–111 °C. Anal. Calc. for C39H33-
P, 2JPH = 13.5); 5.79 (d, 2H, PCH2CO, 2JPH = 12.6); 7.37–8.15 (m, 23H,
Ph). 31P NMR (DMSO-d6): d ꢁ14.05 (d, PPh2, 2JPP = 48.30); 22.93 (d,
Br2HgIOP2: C, 43.90; H, 3.12. Found: C, 43.97; H, 3.08. IR (KBr,
cmꢁ1): 1672 (
t
C@O). 1H NMR (DMSO-d6): d 4.27 (d, PCH2P, CH2,
2
PCH2CO, JPP = 51.11). 13C NMR (DMSO-d6): d 22.35 (br, PCH2P);
2
2JPH = 15.66); 5.62 (d, 2H, PCH2CO, JPH = 12.42); 7.29–8.11 (m,
2
38.21 (br, PCH2); 115.27–139.97 (Ph); 191.14 (d, CO, JPC = 4.01).
29H, Ph). 31P NMR (DMSO-d6): d ꢁ28.24 (d, PPh2, JPP = 67.73);
2
23.68 (d, PCH2CO, JPP = 67.99). 13C NMR (DMSO-d6): d 20.17 (br,
2
2.3.1.7. Data for [HgBr3(Ph2PCH2PPh2CH2C(O)C6H4Ph)] (7). Yield:
0.27 g, 88%. M.p. 130–132 °C. Anal. Calc. for C39H33Br3HgOP2: C,
PCH2P); 34.87 (br, CH2); 119.42–146.52 (Ph); 192.17 (s, CO).
45.93; H, 3.26. Found: C, 45.97; H, 3.20. IR (KBr, cmꢁ1): 1669
2
(t
C@O). 1H NMR (DMSO-d6): d 4.40 (d, PCH2P, CH2, JPH = 6.12);
2.3.1.14. Data for [HgBr2(I)(Ph2PCH2PPh2CH2CO2CH2Ph)] (14). Yield:
0.078 g, 51%. M.p. 117–119 °C. Anal. Calc. for C34H31Br2HgIO2P2:
5.72 (d, 2H, PCH2CO, JPH = 5.00); 7.31–8.03 (m, 29H, Ph). 31P
NMR (DMSO-d6): d ꢁ22.80 (d, PPh2, 2JPP = 60.16); 23.40 (d, PCH2CO,
2JPP = 58.38). 13C NMR (DMSO-d6): d 19.69 (br, PCH2P); 33.36 (br,
PCH2); 119.21–145.50 (Ph); 192.12 (s, CO).
2
C, 40.00; H, 3.06. Found: C, 39.85; H, 3.02. IR (KBr, cmꢁ1): 1718
(
t
C@O). 1H NMR (DMSO-d6): d 4.31 (d, PCH2P, CH2, JPH = 15.82);
2
2
4.74 (d, 2H, PCH2CO, JPH = 14.06); 5.05 (s, 2H, CH2O); 7.06–8.11
(m, 25H, Ph). 31P NMR (DMSO-d6):
d
ꢁ27.64 (d, PPh2,
2
2.3.1.8. Data for [HgBr3(Ph2PCH2PPh2CH2CO2CH2Ph)] (8). Yield:
0.24 g, 83%. M.p. 134–136 °C. Anal. Calc. for C34H31Br3HgO2P2: C,
2JPP = 64.29); 23.48 (d, PCH2CO, JPP = 65.82). 13C NMR (DMSO-
1
d6): d 19.92 (br, PCH2P); 29.31 (d, PCH2, JPC = 55.05); 68.12 (s,
41.97; H, 3.21. Found: C, 41.86; H, 3.14. IR (KBr, cmꢁ1): 1718
CH2O); 117.75–135.28 (Ph); 164.74 (s, CO).
(
t
C@O). 1H NMR (DMSO-d6): d 4.34 (d, PCH2P, CH2, JPH = 14.85);
2
2
4.84 (d, 2H, PCH2CO, JPH = 13.56); 4.98 (s, 2H, CH2O); 7.12–7.94
2.3.1.15.
Data
for
[HgBr2(I)(Ph2PCH2PPh2CH2C(O)C6H4Me)]
(m, 25H, Ph). 31P NMR (DMSO-d6):
d
ꢁ23.00 (d, PPh2,
(15). Yield: 0.088 g, 59%. M.p. 111–113 °C. Anal. Calc. for C34H31-
2
2JPP = 58.46); 23.15 (d, PCH2CO, JPP = 58.60). 13C NMR (DMSO-
Br2HgIOP2: C, 40.64; H, 3.11. Found: C, 41.02; H, 3.06. IR (KBr,
1
1
d6): d 19.95 (d, PCH2P, JPC = 53.55); 29.40 (d, PCH2, JPC = 38.4);
cmꢁ1): 1667 (
t
C@O). 1H NMR (DMSO-d6): d 4.23 (d, 2H, PCH2P,
68.16 (s, CH2O); 117.48–135.34 (Ph); 164.65 (s, CO).
2
2JPH = 14.85); 5.52(d, 2H, PCH2CO, JPH = 13.23); 2.41 (s, 3H, CH3);
7.29–7.90 (m, 24H, Ph). 31P NMR (DMSO-d6): d ꢁ27.80 (d, PPh2,
2.3.1.9. Data for [HgBr3(Ph2PCH2PPh2CH2C(O)C6H4Me)] (9). Yield:
0.25 g, 89%. M.p. 139–141 °C. Anal. Calc. for C34H31Br3HgOP2: C,
2JPP = 66.32); 23.68 (d, PCH2CO, JPP = 67.44). 13C NMR (DMSO-
2
d6): d 22.05 (br, PCH2P); 33.88 (br, PCH2); 21.12 (s, CH3); 119.24–
146.28 (Ph); 191.57 (s, CO).
42.68; H, 3.26. Found: C, 42.72; H, 3.31. IR (KBr, cmꢁ1): 1669
(
t
C@O). 1H NMR (DMSO-d6): d 4.38 (d, 2H, PCH2P, JPH = 16.20);
2
2
5.62(d, 2H, PCH2CO, JPH = 11.61); 2.38 (s, 3H, CH3); 7.30–7.96
(m, 24H, Ph). 31P NMR (DMSO-d6):
d
ꢁ15.00 (d, PPh2,
2.3.1.16. Data for [HgBr2(I)(Ph2PCH2PPh2CH2C(O)C10H7)] (16). Yield:
0.081 g, 52%. M.p. 105–107 °C. Anal. Calcd. for C37H31Br2HgIOP2:
C, 42.69; H, 3.00. Found: C, 42.58; H, 2.95. Selected IR absorption
2
2JPP = 61.93); 19.10 (d, PCH2CO, JPP = 57.72). 13C NMR (DMSO-
d6): d 22.86 (br, PCH2P); 34.02 (br, PCH2); 21.82 (s, CH3); 119.16–
146.16 (Ph); 191.95 (s, CO).
in KBr (cmꢁ1): 1668 (
m
C@O). 1H NMR (DMSO-d6): d 3.43 (br, 2H,
2
PCH2P); 5.65 (bd, 2H, PCH2CO, JPH = 20.16); 7.06–7.95 (m, 27H,
2.3.1.10. Data for [HgBr3(Ph2PCH2PPh2CH2C(O)C10H7)] (10). Yield:
0.26 g, 89%. M.p. 141–143 °C. Anal. Calcd. for C37H31Br3HgOP2: C,
44.76; H, 3.14. Found: C, 44.87; H, 3.11. Selected IR absorption in
Ph and 2-naphtyl). 31P NMR (DMSO-d6): d ꢁ28.20 (d, PPh2,
2JPP = 51.12); 23.89 (d, PCH2CO, JPP = 45.32). 13C NMR (DMSO-
2
d6): d 19.67 (br, PCH2P); 36.89 (br, PCH2); 123.66–138.74 (Ph and
2-naphtyl); 195.32 (s, CO).
KBr (cmꢁ1): 1668 (
m
C@O). 1H NMR (DMSO-d6): d 4.47 (d, 2H, PCH2P,
2JPH = 15.39); 5.84 (d, 2H, PCH2CO, 2JPH = 12.06); 7.30–8.88 (m, 27H,
Ph and 2-naphtyl). 31P NMR (DMSO-d6): d ꢁ19.11 (d, PPh2,
2.3.1.17.
Data
for
[HgBr2(I)(Ph2PCH2PPh2CH2C(O)C6H4NO2)]
2JPP = 56.53); 24.48 (d, PCH2CO, JPP = 43.98). 13C NMR (DMSO-
2
(17). Yield: 0.094 g, 61%. M.p. 98–100 °C. Anal. Calcd. for C33H28-
d6): d 19.51 (br, PCH2P); 37.19 (br, PCH2); 123.86–137.92 (Ph and
2-naphtyl); 195.78 (s, CO).
Br2HgINO3P2: C, 38.26; H, 2.72; N, 1.35. Found: C, 37.97; H, 2.66;
N, 1.41. Selected IR absorption in KBr (cmꢁ1): 1684 (
m
C@O). 1H
2
NMR (DMSO-d6): d 4.26 (d, 2H, PCH2P, JPH = 15.93); 5.66 (d, 2H,
2.3.1.11. Data for [HgBr3(Ph2PCH2PPh2CH2C(O)C6H4NO2)] (11). Yield:
0.27 g, 92%. M.p. 128–130 °C. Anal. Calcd. for C33H28Br3HgNO3P2: C,
40.12; H, 2.85; N, 1.42. Found: C, 39.56; H, 2.80; N, 1.45. Selected IR
2
PCH2CO, JPH = 12.87); 7.25–8.74 (m, 24H, Ph). 31P NMR (DMSO-
2
d6):
d
ꢁ27.98 (d, PPh2, JPP = 69.27); 23.70 (d, PCH2CO,
2JPP = 70.89). 13C NMR (DMSO-d6): d 21.51 (br, PCH2P); 33.94 (br,
absorption in KBr (cmꢁ1): 1685 (
m
C@O). 1H NMR (DMSO-d6): d 4.47
PCH2); 124.3–151.16 (Ph); 191.72 (s, CO).
2
2
(d, 2H, PCH2P, JPH = 15.30); 5.83 (d, 2H, PCH2CO, JPH = 11.97);
7.29–8.72 (m, 24H, Ph). 31P NMR (DMSO-d6): d ꢁ22.98 (d, PPh2,
2JPP = 58.99); 22.49 (d, PCH2CO, JPP = 62.84). 13C NMR (DMSO-
2.3.1.18.
Data
for
[HgCl2(I)(Ph2PCH2PPh2CH2C(O)C6H3Cl2)]
2
d6): d 21.13 (br, PCH2P); 34.11 (br, PCH2); 122.7–150.44 (Ph);
(18). Yield: 0.069 g, 48%. M.p. 134–136 °C. Anal. Calcd. for C33H27-
190.52 (s, CO).
Cl4HgIOP2: C, 40.82; H, 2.80. Found: C, 40.92; H, 2.84. Selected IR
absorption in KBr (cmꢁ1): 1684 (
m
C@O). 1H NMR (DMSO-d6): d
2
2.3.1.12.
Data
for
[HgBr2(Cl)(Ph2PCH2PPh2CH2C(O)C6H3Cl2)]
4.23 (d, 2H, PCH2P, JPH = 14.22); 5.52 (d, 2H, PCH2CO,
(12). Yield: 0.23 g, 79%. M.p. 153–155 °C. Anal. Calcd. for C33H27-
2JPH = 12.59); 7.34–7.91 (m, 23H, Ph). 31P NMR (DMSO-d6): d
2
2
Br2Cl3HgOP2: C, 40.99; H, 2.81. Found: C, 41.13; H, 2.82. Selected
ꢁ25.95 (d, PPh2, JPP = 63.85); 23.59 (d, PCH2CO, JPP = 65.45). 13C
NMR (DMSO-d6): d 22.11 (br, PCH2P); 38.41 (d, PCH2); 115.57–
141.28 (Ph); 189.91 (s, CO).
IR absorption in KBr (cmꢁ1): 1685 (
m
C@O). 1H NMR (DMSO-d6): d
2
4.35 (d, 2H, PCH2P, JPH = 15.39); 5.63 (d, 2H, PCH2CO,

S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
187
2½Ph2PCH2PPh2CH2CðOÞRꢂBr þ HgI2
2.4. General experimental procedure for nuclear magnetic resonance
studies
! ½Br2ðIÞHgPh2PCH2PPhCH2CðOÞRꢂ þ ½Ph2PCH2PPh2CH2CðOÞRꢂI
½R ¼ 40-biphenyl; OCH2Ph; 4-methylphenyl; 2-naphtyl;
3-nitophenyl; 2; 4-dichlorophenylꢂ
In a typical experiment, 0.5 mL of the solutions containing
0.06 M of ligand in dimethylsulfoxide (DMSO) was placed in
the NMR tube, thermostated to the desired temperature and
the 31P{1H} NMR spectra of the resulting solutions were recorded
and chemical shift of the NMR signals were measured. Then, a
known amount of a concentrated mercury(II) halide solution
(0.12 M) in the same solvent was added up to the [HgX2]/[li-
gand] mole ratio of 4, in a stepwise manner using a microsy-
ringe. After the mixture was stirred under ultrasonic agitation
for 5 min, 31P NMR spectra of the resulting solutions were re-
corded. According to molar ratio data and KINFIT program,
which acts based on Eq. (1.7), the stoichiometry of complexation
between the ligands and mercury(II) salts was 1:1. Formation
constants of these complexes were derived using 31P{1H} NMR
data.
2½Ph2PCH2PPh2CH2CðOÞC6H3CI2ꢂCI þ HgI2
! ½CIðIÞHgPh2PCH2PPh2CH2CðOÞC6H3CI2ꢂ
þ½Ph2PCH2PPh2CH2CðOÞC6H3CI2ꢂI
3.2. Spectroscopy
The IR spectra of complexes 1–18 show single sharp and intense
absorption band in the range 1667–1718 cmꢁ1, due to the carbonyl
stretch which is close to the same frequency in free phosphonium
salts (1661–1729 cmꢁ1) indicates the non-involvement of the
PCH2C(O)R group in the reactions [2]. The IR data for all complexes
and free phosphonium salts reported in Table 1. The chemical nat-
ure of the all complexes were checked by means of 31P, 1H and 13
C
All NMR measurements for complex formation constants were
made on a JEOL(FX90Q)-NMR spectrometer with a field strength
of 2.35T equipped with a temperature controller ( 0.1 °C). At this
field, 31P resonates at 36.262 MHz. Typical acquisition parameters
were 20,000 Hz sweep width, 700 scans, 1s relaxation delay, 1s
NMR spectroscopy. The 31P NMR spectra result more informative
which show in all cases the presence of two doublets signals in
ca. 1:1 ratio. These signals indicate the presence of the PCH2CO
and PPh2 groups in the complexes. In contrast to the 31P NMR spec-
trum of Hg(II)-phosphine complexes [39], the coordination of
phosphorous atom to mercury in these complexes did not cause
significant downfield shifts. All complexes show downfield shifts
compared to that of phosphine of the related phosphonium salts.
The chemical shifts show a slight downfield shifts for mercury(II)
iodide complexes (1.01–3.08 ppm) whereas the coordination of
phosphine to mercury(II) bromide and chloride cause significant
downfield shifts (4.95–14.3 and 2.89–14.82 ppm, respectively) to
that of phosphine of the related phosphonium salts. These data
indicate that the presence of a formal negative charge on the metal
may effectively reduce the deshielding experienced by the phos-
acquisition time, 15 ls pulse width (30° pulse) with proton decou-
pling in 90.0 MHz and 64 k = 65,536 words. In 31P{1H} NMR
experiments, the standard was 85% H3PO4. All chemical shift mea-
surements were carried out at a temperature of 25.0 0.1 °C.
3. Results and discussion
3.1. Synthesis
The reaction of mercury(II) halides with non-symmetrical phos-
phonium salts (L1–L6), in 1:1 (for chloride and bromide) and 1:2
(for iodide) mole ratio yield two different types of zwitterionic
mercury(II) complexes (Schemes 1 and 2). The mercury(II) chloride
and bromide produce simple complexation products while the for-
mation of iodide complexes involve a halogen exchange [2]:
1
phorus due to complexation [2]. The H NMR spectra (ratio of sig-
nal intensities for PCH2P and PCH2CO protons) of all compounds
confirm the presence of two sets of signals in agreement with
the other spectroscopic data. Two sets of signals are observed in
the 1H NMR specta of all complexes at around 3.43–4.60 ppm
O
C
Ph2P
Ph2P
CH
R
M
CH
Ph2P
Ph2P
C
O
R
CH
Ph2P
Ph2P
C
H
R
CH
Ph2P
Ph2P
C
O
R
O
M
M
(a) P-bonding
(b) C-bonding
(c) O-bonding
M
CH
Ph2P
C
R
CH
CH
M
Ph2P
Ph2P
Ph2P
Ph2P
C
O
C
R
R
CH
Ph2P
Ph2P
C
O
R
O
M
O
M
Ph2P
M
M
(d) P, C-bonding, chelate
(e) P, O-bonding, chelate
(f) P, C-bonding, bridging (g) P, O-bonding, bridging
Scheme 1. Synthetic route for the preparation of complexes 1–5, 7–11 and 13–17.

188
S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
Ph2P
P
CH2
Ph2
Ph2
P
H2
C
HgX2
C
O
C
O
R
R
Br-
Hg
Br
MeOH, RT
X
X
(1) R = 4'-biphenyl, X= Cl
PPh2
(2) R = OCH2Ph, X= Cl
H
(3) R = 4-methylphenyl, X= Cl
(4) R = 2-naphtyl, X= Cl
g
I
(5) R = 3-nitrophenyl, X= Cl
(7) R = 4'-biphenyl, X= Br
(8) R = OCH2Ph, X= Br
(9) R = 4-methylphenyl, X= Br
(10) R = 2-naphtyl, X= Br
(11) R = 3-nitrophenyl, X= Br
Ph2P
P
CH2
(13) R = 4'-biphenyl
(14) R = OCH2Ph
Ph2
C
R
(15) R = 4-methylphenyl
(16) R = 2-naphtyl
Hg
Br
Br
(17) R = 3-nitrophenyl
O
I
Scheme 2. Synthetic route for the preparation of complexes 6, 12 and 18.
Table 1
3.3. nuclear magnetic resonance study
Relevant 1H, 31P NMR (d, ppm) and IR (cmꢁ1) data for compounds 1–18 and free
phosphorus ligands.
31P chemical shifts were measured as a function of the mole
ratio of complexant some phosphine–phosphonium ligands to
mercury(II) halides in dimethylsulfoxide solution. The resulting
mole data are shown in Fig. 1. As can be seen in it, in all cases, addi-
tion of HgX2 to the L5 ligand solution causes an almost linear para-
magnetic shift that begins to level off at mole ratio greater than
unity. The slope of the corresponding mole ratio plots changes sig-
nificantly at the point where the cation-to-phosphorus ligand cat-
ion mole ratio is equal to one, showing the formation of a relatively
stable complex. In general, the behavior of the 31P chemical shift as
a function of [HgX2]/[ligand] mole ratio can be approximately di-
vided into two groups:
Compound
d (PCH2C(O)R)b
d (PPh2)b
Da
t(CO)
L1
L2
L3
L4
L5
L6
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
5.83(d)
4.87(d)
5.73(d)
5.78(d)
5.88(d)
5.96(d)
5.65(d)
5.11(d)
5.74(d)
5.89(d)
5.77(d)
5.79(d)
5.72(d)
4.84(d)
5.62(d)
5.84(d)
5.83(d)
5.63(d)
5.62(d)
4.74(d)
5.52(d)
5.65(d)
5.66(d)
5.52(d)
ꢁ30.71(d)
–30.83(d)
–30.68(d)
–30.77(d)
–31.11(d)
–30.54(d)
–26.24(d)
–14.73(d)
–17.11(d)
–13.20(d)
–26.75(d)
–14.05(d)
–22.80(d)
–23.00(d)
–15.00(d)
–19.11(d)
–22.98(d)
–24.08(d)
–28.24(d)
–27.64(d)
–27.80(d)
–28.20(d)
–27.98(d)
–25.95(d)
–
–
–
–
–
–
1669
1729
1661
1666
1682
1683
1670
1718
1669
1667
1685
1689
1669
1718
1669
1668
1685
1685
1672
1718
1667
1668
1684
1684
4.47
16.10
13.57
17.57
4.36
16.49
7.91
7.83
15.68
11.66
8.13
6.46
2.47
3.19
2.88
2.57
3.13
4.59
– 12A gradual paramagnetic shift of the 31P resonance with an
increase in the mercury(II) halide concentration which does
not seem to reach a limiting value even at a mole ratio of 4. Such
behavior, which is observed for HgI2 in all phosphine–phospho-
nium salt cases (Fig. 1), is indicative of the formation of a weak
1:1 complex.
– The paramagnetic chemical shift varies linearly with the
[HgX2]/[ligand] mole ratio until a mole ratio of about 1 is
reached; further increase of the mercury(II) halide does not
change the resonance frequency. Such behavior, observed for
all HgCl2 and HgBr2 complexes except L2 ligand in solvent,
emphasizes the formation of a rather stable 1:1 complex in
solution (Fig. 1).
a
D
= d(coordinated ligands) – d(free ligands). 31P NMR shifts, d, doublet.
Record in DMSO-d6.
b
attributed to PCH2P, and in the region of 4.74–5.89 ppm attributed
to PCH2CO group. The former peaks remain unaffected, while the
latter peaks show a slight upfield shift to that of PCH2CO group
of the related phosphonium salts due to complexation. In the 1H
NMR spectra of complexes 2, 8 and 14 a singlet signal around
5.0 ppm attributed to methinic hydrogens of CH2O group. Signals
appeared around 2.4 ppm in the 1H NMR spectra of complexes 3,
9 and 15 attributed to methyl group. Rest of the chemical shifts
are more or less the same in the ligands and their complexes. These
observations support the assigned structure to the complexes. In
the 13C NMR spectra, signals observed in the complexes due to
the various carbons have either remained unaffected or shifted
slightly with reference to those of the parent ligands. NMR data
for compounds 1–18 and free phosphorus ligands are given in
Table 1.
The formation constant of 1:1 complexes are calculated from
the variation of ligand chemical shift with the [HgX2]/[L] mole ratio
[40]. The observed chemical shift of the ligand (dobs) is a mass aver-
age of the characteristic chemical shifts of L at each site (i.e. L in the
bulk solution and L in the complex). Assuming that a fast exchange
occurs between these two sites with respect to the NMR time scale.
dobs ¼ PLdL þ P
d
ðMLÞ ðMLÞ
where dL and d(ML) are the characteristic chemical shifts for L in
the bulk solution and in the complex, respectively and PL and P(ML)
are the respective mole fractions of these species.
Knowing that PL + P(ML) = 1 and PL = [L]/CL then:
dobs ¼ PLdL þ ð1 ꢁ PLÞd
ð1:1Þ
ðMLÞ

S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
189
L3
L4
L6
L5
L2
L1
L4
L2
L1
L6
L3
L5
a
b
24.5
24
23.5
23
24
23.5
23
22.5
22
22.5
22
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
[M]/[L]
[M]/[L]
24.5
c
L6
L3
L5
L1
L4
L2
24
23.5
23
22.5
22
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
[M]/[L]
Fig. 1. 31P chemical shifts as a function of the (a) [HgCl2]/[L] (b) [HgBr2]/[L] (c) [HgI2]/[L] (L = phosphorus ligand), mole ratio in dimethylsulfoxide solvent at 25.0 0.1 °C.
dobs ¼ PLðdL ꢁ dðMLÞÞ þ d
½Lꢂ
ð1:2Þ
ð1:3Þ
ðMLÞ
dobs
¼
ðdM ꢁ dðMLÞÞ þ d
CL
ðMLÞ
CM¼ ½Mꢂ þ ½MLꢂ
CL¼ ½Lꢂ þ ½MLꢂ
ð1:4Þ
ð1:5Þ
½MLꢂ
Kf ¼
ð1:6Þ
½Mꢂ½Lꢂ
By substitution of Eqs. (1.4), (1.5) and (1.6) in Eq. (1.3) one ob-
tains the following equation:
Fig. 2. Computer fit of 31P chemical shift vs. [HgBr2]/[L2] mole ratio in DMSO. (ꢃ)
Experimental point; (o) calculated point; (=) experimental and calculated points are
the same within the resolution of the plot.
n
dobs
¼
½ðKf C
ꢁ Kf CL ꢁ 1Þ þ ðK2C2 þ K2C2
ꢁ 2K2CLC
HgX2
HgX2
f
L
f
HgX2
f
ꢀ
1=2
þ 2Kf CL þ 2Kf CHgX þ 1Þ ꢂðdL ꢁ dHgX ꢁLÞ=2Kf CHgX
2
2
2
þ d
and Kf are varied to obtain the best fit. A non-linear least-squares
program KINFIT [41] was used in the calculations. A sample com-
puter fit of the 31P chemical shift-mole ratio data is shown in
Fig. 2 and the calculated logKf values are given in Table 2. A fair
agreement between the observed and calculated chemical shifts
further supports the formation of a complex with 1:1 stoichiometry
HgX2ꢁL
ð1:7Þ
where Kf is the formation constant for the 1:1 complex, CL and CHgX
are the total concentrations of the phosphine–phosphonium salt
and mercury(II) halide, respectively, dL is the chemical shift of the
uncomplexed ligand and dHgX
2
is the chemical shift of the com-
2ꢁL
between ligand and mercury(II) salts.
plexed ligand. For most complexes dHgX
cannot be obtained di-
The complex stability results from the superposition of several
2ꢁL
rectly. In Eq. (1.7) values of CHgX , CL and dL are known. dHgX
and
factors including the extent of interaction of phosphorus atom of
the ligand with the cation, the consonance between metal ion
and ligand, the extent of ligand conformational changes as a conse-
quence of complex formation, desolvation of the ligand and cation
and solvation of the resulting complex. The two later factors being
2ꢁL
2
Kf are the two unknowns. These parameters are initially estimated
and used to calculate dcal for different values of [HgX2]/[L] mole ra-
tio with the aid of Eq. (1.7). The calculated chemical shifts are iter-
atively fitted to the observed chemical shifts and values of dHgX
2ꢁL

190
S.J. Sabounchei et al. / Journal of Molecular Structure 1040 (2013) 184–191
Table 2
Formation constants for metal ion complexes with L1, L2, L3, L4, L5 and L6 phosphorus ligands in dimethylsolfuxide at 25 °C.
Cation
LogKf
L1
L2
L3
L4
L5
L6
HgCl2
HgBr2
HgI2
2.40 0.04
1.75 0.02
1.62 0.04
1.94 0.07
1.25 0.02
1.15 0.03
2.51 0.04
2.25 0.06
1.82 0.06
2.45 0.05
1.88 0.03
1.73 0.05
2.28 0.05
1.53 0.03
1.47 0.04
2.17 0.07
1.41 0.03
1.31 0.04
strongly dependent on the nature of solvent used [42], so that the
nature of solvent is expected to affect the overall energy balances
involved in the metal ion complexation in solution [30,31,36,43].
It has been well documented that the solvating ability of the sol-
vent, as expressed by the Gutmann donor number [42], plays a
key role in different complexation reactions [44–48]. DMSO is a
solvent of relatively high solvating ability (DN = 29.8) which can
compete with the ligand and counter ion for metal. Thus, it is not
surprising to observe the low stability for the all complexes.
The data given in Table 2 clearly indicate that, the stability of all
complexes decreases in the order HgCl2 > HgBr2 > HgI2, as it shown
in the theoretical studies [49,50]. Thus, there is an important role
on complex stability constant for halides. In DMSO solution, the
stabilities of 1:1 complexes of mercury(II) salts with different
phosphine–phosphonium salts decrease in the order L3 > L4 > L1 > -
L5 > L6 > L2. In all cases, the presence of different groups in ligands
can inductively enhance the electron density of the phosphine–
phosphonium salts and thus increases the basicity of the donate
atom of ligands, while the flexibility of phosphorus moiety is the
same as the others. It has been shown that, the complexation abil-
ity of HgX2 to ligand can be considerably increased by attaching
different endgroups to the ligand backbone. In fact, the stability
of their complexes arises from the two type centers: the phospho-
rus moiety and the aromatic residue which controls the strength of
complexation by donor-electron interactions, steric influences and
supplying two phosphorus atoms [32]. Subsequently, the metal ion
is surrounded by the flexible phosphorus chain, which can easily
adapt to mercury(II) cation sizes, and is better shielded from the
solvent and the counter ions by terminal different aromatic groups
[51,52].
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The present study describes the synthesis and characterization
of a series of mercury(II) complexes derived from mercury halides
and non-symmetric phosphorus ligands. On the basis of the phys-
icochemical and spectroscopic data we propose that ligands herein
exhibit a P-coordination behavior to the metal center affording a
zwitterionic complexes. The complexation reaction between the
Hg(II) ion, with different counter ions, with some posphoruse li-
gands in DMSO solvent was studied by 31PNMR spectroscopy. In
all studied cases, the variation of 31P chemical shift with the [M]/
[L] mole ratio indicated the formation of 1:1 complexes. The data
given in Table 2 shows that, the stability of all complexes decreases
in the order HgCl2 > HgBr2 > HgI2 in DMSO as a solvent of higher
solvating ability can compare with L for the metal as a poor solvat-
ing solvent. These results clearly illustrate the fundamental role of
the various counter ions on complex stability constant. In all cases ,
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