Synthesis and characterisation of Hg (II) and Ag (I) complexes of 4-fluorobenzoylmethylenetriphenylphosphorane and 4-chlorobenzoyl methylenetriphenylphosphorane, with spectroscopic studies

Article abstract of DOI:10.3184/030823407X275955

4-flourobenzyloxymethylenetriphenylphosphorane ylide [Ph ₃PCHCOC₆H₄F], (FBPPY), and 4- chlorobenzyloxymethylenetriphenylphosphorane ylide [Ph₃PCHCOC ₆H₄Cl](CBPPY), have been synthesised. Th

Full text of DOI:10.3184/030823407X275955

JOURNAL OF CHEMICAL RESEARCH 2007
DECEMBER, 725–727
RESEARCH PAPER 725
Synthesis and characterisation of Hg (II) and Ag (I) complexes of
4-fluorobenzoylmethylenetriphenylphosphorane and 4-chlorobenzoyl
methylenetriphenylphosphorane, with spectroscopic studies
Kazem Karami*
Department of Chemistry Isfahan University of Technology, Isfahan, 84156/83111, Iran
4-flourobenzyloxymethylenetriphenylphosphorane ylide [Ph3PCHCOC6H4F], (FBPPY), and 4-chlorobenzyl-
oxymethylenetriphenylphosphorane ylide [Ph3PCHCOC6H4Cl],(CBPPY), have been synthesised. The reactions of the
title ylides with HgX2 (X =Cl,I) in equimolar ratios using dry acetone as solvent, have yielded [{HgCl2(FBPPY)}2](1),
[{HgI2(FBPPY)}2](2), [{HgCl2(CBPPY)}2](3) and [{HgI2 (CBPPY)}2](4) respectively. The reactions of the title ylides with
AgNO3 in molar ratios (2:1) using dry acetone as solvent have yielded [Ag(FBPPY)2]NO3 (5) and [Ag(CBPPY)2]NO3
(6). The analytical data, IR and 1H and 31P NMR data of the products were obtained.
Keywords: Hg(II), Ag(I), α-ketostabilised phosphorus ylide
points were measured on a SMPI apparatus. Elemental analysis for
C, H and N were performed using a PE 2400 series analyser. IR
spectra were recorded on a FT-IR JASCO 680 spectrophotometer and
the measurements were made by the KBr disk method.
Mercury halides, 4-flouroacetophenone, 4-chloroacetophenone
and triphenyl phosphine were purchased from Merck. The ylides
were synthesised by the reaction of triphenylphosphine with a
chloroform solution of 2-bromo-4-flouroacetophenone or 2-bromo-
4-chloroacetophenone and dehydrogenated by NaOH.16 All solvents
were dried by the reported methods.17
The α-ketostabilised phosphorus ylide Ph3PCH=C(H)COR
(R = Me, Ph, OMe) has been found to be an interesting
ligand in organometallic chemistry and a useful intermediate
for organic synthesis.1-4 In general, carbonyl-stabilised
phosphorus ylides are interesting ligands because they can
behave as C- or O- donors owing to the delocalisation of the
ylidic electron pair.5 This delocalisation also makes these
ylides weak nucleophiles, but this does not reduce their
interest as ligands, and surprisingly, it was their weak donor
ability that allowed other workers to prepare new types of
ylide complexes.5 This ambidentate character facilitates the
preparation of stable metal complexes in which the ylide
could be O- (forms cisoid and transoid, B, Scheme 1)6 or
C-coordinated (A, Scheme 1),7 with both modes rationalised
in terms of the resonance forms a–c together with the isomeric
forms (cisoid and transoid, c).
Synthesis of FBPPY and CBPPY
To chloroform solution (15 ml) of triphenylphosphine (1 mmol)
was added 2-bromo-4-flouroacetophenone or 2-bromo-4-
chloroacetophenone (1 mmol) and the resulting mixture was stirred
for 12 h. The solution was filtered off, and the precipitate washed
with diethyl ether and air-dried. Further treatment with aqueous
NaOH solution (0.5 M) led to elimination of HBr, giving the free
ligand precursors FBPPY or CBPPY.
FBPPY: M.p. 142°C, Anal. Calc for C26H20OPF: C, 78.4; H, 5.1
Anal Found: C, 78.2; H, 5.0%.
CBPPY: M.p. 137–138°C Anal. Calc for C26H20OPCl: C, 75.3; H,
4.9 Anal Found: C, 75.0; H, 4.9%
In the compounds reported to date, the chemical behaviour
of the α-ketostabilised phosphorus ylide has been clearly
dominated by the C-coordinated form,8-11 and very few
examples of O-coordinated ylides are known.6,12-15 In this work,
we report stabilised phosphorus ylides (FBPPY and CBPPY)
and metal complexes with HgX 2 (X = Cl, I) and AgNO3.
Synthesis of the complexes
[{HgCl2 (FBPPY)}2] (1): To a solution (5 ml) of FBPPY (0.198 g,
0.5 mmol) in acetone (5 ml) was added mercury(II) chloride (0.134 g,
0.5 mmol). The mixture was stirred for 4 h. The white solid product
was separated by filtration and washed with diethyl ether. Yield:
92.0%, M.p. 214°C, Anal. Calc for C52H40Cl4F2Hg2O2P2: C, 46.6;
Experimental
Physical measurements and materials
Diethyl ether (Et2O) was distilled over sodium benzophenone ketyl
just before use. All other solvents were reagent grade and used
without further purification. Solution-state 1H and 31P NMR spectra at
300 K were obtained in CDCl3 1using a 400 MHz Bruker spectrometer
operating at 400.13 MHz for H and 161.97 MHz for 31P. Melting
1
H, 3.0 Anal Found: C, 46.45; H, 2.95% H NMR: 5.51(d, 1H, CH,
2JPH = 10.25 Hz), 7.1–8.2 (m, 19H, Ph) ppm and 31P NMR: 21.79 ppm.
[{HgI2(FBPPY)}2] (2): To a solution of FBPPY (0.100 g,
0.25 mmol) in acetone (5 ml) was added mercury (II) iodide (0.114 g,
0.25 mmol). The mixture was stirred for 12 h. On concentration
R1
R1
R1
R1
R3P
C
R3P
R3P
R3P
C
O
C
O
C
O
C
O
C
R2
C
R2
C
R2
R2
b
a
transoid
cisoid
C
R1
R1
R1
R3P
[M]
R3P
[M]
C
C
O
C
COR2
C R2
C
O [M]
R2
PR3
A
transoid
B
cisoid
Scheme 1
* Correspondent. E-mail: karami@cc.iut.ac.ir
PAPER: 07/4897

726 JOURNAL OF CHEMICAL RESEARCH 2007
by removing the solvent by vacuum, a pale yellow precipitate was
obtained. The products were washed with benzene and dried in
vacuo. Yield: 81%, M.p. 214°C, Anal. Calc for C521H40 F2Hg2I4O2P2:
C, 36.6; H, 2.4 Anal Found: C, 36.45; H, 2.3% H NMR: 4.62(d,
CHCl3
+ PPh3
CH2Br
Y
C
O
Y
C
O
CH2PPh3Br
2
1H, CH, JPH = 5.5 Hz), 7.1–8 (m, 19H, Ph) ppm and 31P NMR:
Y
C
O
CH=PPh3
CH-PPh3
20.34 ppm.
[{HgCl2(CBPPY)}2] (3): To a solution (5 ml) of CBPPY (0.207 g,
0.5 mmol) in acetone (5 ml) was added mercury(II) chloride
(0.134 g, 0.5 mmol). The mixture was stirred for 4 h. The white solid
product was separated by filtration and washed with diethyl ether.
Yield: 92.0%, M.p. 204°C (dec), Anal. Calc for C52H40Cl6Hg2O2P2:
C, 45.5; H, 2.9 Anal Found: C, 45.35; H, 2.8%.
+NaOH (0.5 M)
-NaBr
Y = F (FBPPY)
or
Y
C
O
Y = Cl (CBPPY)
1H NMR: 5.48(s br, 1H, CH), 7.0–8.1 (m, 19H, Ph) ppm and
31P NMR: 21.86 ppm.
[{HgI2(CBPPY)}2](4):ToasolutionofCBPPY(0.104g,0.25mmol)
in acetone (5 ml) was added mercury (II) iodide (0.114 g, 0.25 mmol).
The mixture was stirred for 12 h. On concentration by removing
the solvent by vacuum, a pale yellow precipitate was obtained.
The products were washed with diethyl ether and dried in vacuo.
Yield: 81%, M.p. 219°C (dec), Anal. Calc for C521H40Cl2 Hg2 I4O2P2:
C, 35.9; H, 2.3 Anal Found: C, 36.05; H, 2.4% H NMR: 5.49(s br,
1H, CH), 7.1–8.2 (m, 19H, Ph) ppm and 31P NMR: 21.85 ppm.
[Ag(FBPPY)2]NO3 (5): The ylide FBPPY (0.470 g, 1.18 mmol)
was added to a solution of AgNO3 (0.100 g, 0.59 mmol) in acetone
(10 ml). The solution was stirred, whilst protected from the light,
for 1 h and then filtered through MgSO4. The volume of solvent
was reduced under vaccum to about 2 ml. Diethyl ether (25 ml) was
added to precipitate [Ag{CH(PPh3) C(O) C6H4–F}]NO3 (5) as a
white powder. M.p. 185°C (dec), Anal. Calc for C52H40AgF2NO5P2:
Y
C
CH-PPh3
O
O
PPh3
Hg
CH
X
X
X
Y
Hg
Y
X
HC
Y= F, X =Cl (1)
Y =F, X= I (2)
Y =Cl, X =Cl (3)
Y =Cl, X = I (4)
Ph3P
O
1
C, 64.6; H, 4.2 Anal Found: C, 64.5; H, 4.2% H NMR: 5.06(s br,
Y
1H), 7.1–8.1 (m, 19H, Ph) ppm and 31P NMR: 22.13 ppm.
[Ag(CBPPY)2]NO3 (6) The ylide CBPPY (0.489 g, 1.18 mmol)
was added to a solution of AgNO3 (0.100 g, 0.59 mmol) in acetone
(10 ml). The solution was stirred, whilst protected from the light for
1 h and then filtered through MgSO4. The volume of solvent was
reduced under vaccuum to about 2 ml. Diethyl ether (25 ml) was
added to precipitate [Ag{CH(PPh3)C(O)C6H4-Cl}]NO3 (6) as a white
powder. M.p. 179°C, Anal. Calc for C52H40AgCl2NO5P2: C, 62.5;
Ph3P
NO3
Ag
O
HC
CH
O
Y = F(5) or Cl(6)
1
PPh3
H, 4.0 Anal Found: C, 62.5; H, 3.9% H NMR: 6.06(s br, 1H, CH),
7.2–8.2 (m, 19H, Ph) ppm and 31P NMR: 21.79 ppm.
Results and discussion
Synthesis
Y
Theligandwassynthesisedbytreating2-bromo-4'-flouroacetophenone
or 2-bromo-4'-chloroacetophenone with triphenylphosphine and
removal of the proton from the phosphonium salt.
Reactions of HgX2 (X = Cl, I) with the ylide in a 1:1 stoichiometry
afforded the C-coordinated complexes (1–4), with a halo-bridged
dimeric structure, and reaction with AgNO3 in a 2:1 stoichiometry
afforded the C-coordinated complexes (5) and (6).
of the ylide through carbon. The ν(P+–C-), which is also diagnostic
for the coordination, occurs at 897 cm-1 in Ph3P+–C-H2 and at 883
and 881 cm-1 in FBPPY and CBPPY respectively. In the present
study, the ν (P+–C-) values for all complexes were shifted to lower
frequencies (Table 1), suggesting some removal of electron density
in the P–C bond. The 1H NMR data for the mercury (II) complexes,
along with those of the parent ylide, are listed in (Table 2).
The NMR signal due to the methine proton, when recorded in CDCl3,
was broad for complexes 3, 4, 5 and 6. This indicates that probably
the ylide dissociates in solution. Compounds wherein the ylide is
C-coordinated exhibit a 2J(PH) value of 10 Hz or less.11,13
Spectroscopy
The ν(CO) values, which are sensitive to complexation, occur at 1516
and 1521 cm-1 in the parent ylides, as in the case of other resonance
stabilised ylides.11 Coordination of the ylide through carbon causes
an increase in ν(CO), while for O-coordination a lowering of ν(CO)
is expected (Table 1). The IR absorption bands observed for all
complexes show an increase in ν(CO), indicative of coordination
The 31P NMR resonances of the complexes were observed
to occur at a lower field with respect to the free ylide (Table 2).
The expected downfield shifts of 31P and 1H signals for the PCH group
Table 1 n (CO) of selected phosphoranes and their metal complexes
Compound
n (CO)
D(CO)
n (P–C)
Ref.
Ph3PCHCOCH3 (APPY)
1530
1520
1516
1521
–
–
–
–
18
Ph3PCHCOPh (BPPY)
878
883
881
18
Ph3PCHCOC6H4-F( = FBPPY)
Ph3PCHCOC6H4-Cl( = CBPPY)
This work
This work
C-coordination
[{HgCl2(FBPPY)}2] (1)
[{HgI2(FBPPY)}2] (2)
[{HgCl2(CBPPY)}2] (3)
[{HgI2(CBPPY)}2] (4)
[Ag(FBPPY)2]NO3 (5)
[Ag(CBPPY)2]NO3 (6)
1638
1626
1635
1622
1613
1616
+ 122
+ 110
+ 114
+ 101
+ 97
818
808
816
811
880
875
This work
This work
This work
This work
This work
This work
+ 95
O-coordination
[Sn(CH3)3(APPY)]Cl
[Pd{C6F5)(PPh3}2(APPY)]ClO4
1480
1513
–40
–17
12
7d
PAPER: 07/4897

JOURNAL OF CHEMICAL RESEARCH 2007 727
Table 2 1H and 31P NMR data of FBPPY and its complexes with mercury (II), Ag (I) and Pd (II)
Compound
1H chemical shifts (CH) (d ppm)
2J(PH) (Hz)
31P chemical shifts (d ppm)
FBPPY
4.37 (d)
23.99
16.8
CBPPY
4.4(d)
23.87
16.7
[{HgCl2(FBPPY)}2] (1)
[{HgI2(FBPPY)}2] (2)
[{HgCl2(CBPPY)}2] (3)
[{HgI2(CBPPY)}2] (4)
[Ag(FBPPY)2]NO3 (5)
[Ag(CBPPY)2]NO3 (6)
5.51(d)
4.62(d)
5.48 (s br)
5.49 (s br)
5.06 (s br)
6.06 (s br)
10.25
5.48
–
–
–
–
21.79
20.34
21.86
21.85
22.13
21.79
3
4
O.I. Kolodiazhnyi, Russ. Chem. Rev., 1997, 66, 225.
D.E.C. Cobridge, Phosphorus an Outline of Chemistry, Biochemistry and
Uses, 5th edn, Elsevier, Amsterdam, 1995.
J. Vicente, M.T. Chicote, M.C. Lagunas and P.G. Jones, J. Chem. Soc.,
Dalton Trans.,1991, 2579.
J. Buckle and P.G. Harrison, J. Organomet. Chem., 1973, 49, C17.
(a) H. Nishiyama, K. Itoh and Y. Ishii, J. Organomet. Chem., 87, 129
(1975); (b) E.T. Weleski, J.L. Silver, M.D. Jansson and J.L. Burmeister,
J. Organomet. Chem.,1975, 102, 365; (c) P. Bravo, G. Fronza and
T. Ticozzi, J. Organomet. Chem., 1976, 111, 361; (d) H. Koezuka,
G. Matsubayashi and T. Tanaka, Inorg. Chem., 1976, 15, 417;
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J. Chem. Soc., Dalton Trans,1987, 1381.
upon complexation were observed in their corresponding spectra.
The appearance of single signals for the PCH group in both the
31Pand1Hspectraatambienttemperatureindicatesthepresenceofonly
one molecule for all the complexes as expected for C-coordination.
It must be noted that O-coordination of the ylide sometimes leads to
the formation of cis- and trans-isomers giving rise to two different
signals in the 31P and 1H NMR.6b,17 1H and 31P{1H} NMR data
are presented in Table 2. Although two diasteroisomer (RR/SS
and RS) are possible for each complex (because the methane
carbons are chiral) NMR spectroscopy does not distinguish
them at room temperature. The methine resonances are
intermediate between, and 2J(PH) values smaller than, those in
the free ylides and phosphonium salts; this was observed for other
C-coordinated carbonyl-stabilised phosphorus ylide complexes and
is due to the hybridisation change in the ylidic carbon (SP2-SP3)
in the C-coordination mode.7b,15,16 Values of 2J(PH) much larger
(ca 20 Hz) have been observed in complexes where coordination
is through the oxygen atom.12 Neither H–Ag and H–Hg nor
P–Ag and P–Hg coupling was observed at room temperature in
the spectra of our complexes; the same was the case for [Ag(C6F5)
CH(PPh3)CO2Me].18 It is possible that a fast equilibrium between
complexes and free ylides is responsible for the failure observed
either the NMR couplings or presence of two diastereoisomers
5
6
7
8
9
H. Nishiyama, K. Itoh and Y. Ishii, J. Organomet. Chem., 1975, 87, 129.
J. Vicent, M.T. Chicote and J. Fernandez-Baeza, J. Organomet.
Chem.,1989, 364, 407.
10 M. Onishi, Y. Ohama, K. Hiraki and H. Shintani, Polyhedron, 1982, 1, 539.
11 J. Vicent, M.T. Chicote, M.C. Lagunas and P.G. Jones, J. Chem. Soc.,
Dalton Trans., 1991, 2579.
12 J. Buckle, P.G. Harrison, T.J. King and J.A. Richards, J. Chem. Soc.,
Chem. Commun., 1104, 1972.
13 J.A. Albanese, D.A. Staley, A.L. Rheingold and J.L. Burmeister, Inorg.
Chem., 1990, 2209.
14 I. Kawafune and G. Matsubayashi, Inorg. Chim. Acta,1983, 70, 1.
15 R. Uson, J. Fornies, R. Navarro, P. Espinet and C.J. Mendivil, Organomet.
Chem.,1985, 290, 125.
16 J. Vicent, M.T. Chicote, J.A. Cayuelas, J. Fernandez-Baeza, P.G.Jones,
G.M. Sheldrick and P. Espinet, J. Chem. Soc., Dalton Trans., 1985, 1163.
17 J.L. Burmeister, J.L. Silver, E.T. Weleski, E.E. Schweizer and
C.M. Kopay, Synth. Inorg. Met. Org. Chem., 1973, 3, 339.
18J. Vicent, M.T. Chicote, J. Fernandez-Baeza, J. Martin and I. Saura-Llamas,
J. Organomet. Chem., 1987, 331, 409.
Received 17 October 2007; accepted 31 December 2007
Paper 07/4897
doi: 10.3184/030823407X275955
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PAPER: 07/4897