Synthesis of new phosphonium ylides containing thiophene and furan rings and study of their reaction with mercury(II) halides: Spectral and structural characterization

Article abstract of DOI:10.1002/hlca.200900305

Reactions of phosphonium ylides (4-MeC₆H₄) ₃PCHC(=O)(2-C₄H₃S) (tptpy), Ph ₃PCHC(=O)(2-C₄H₃O) (fppy), and (4-MeC ₆H₄)₃PCHC(=O)(4-BrC₆H₄) (bbtppy) with HgX₂ (X=Cl, Br, and I) in equimolar ratios in MeOH as solvent leads to the binuclear products 1-3 (Scheme 1). The bridgesplitting reaction of the binuclear complex [{HgI₂(bbtppy)}₂] (3c) by DMSO yields the mononuclear complex [HgI₂ · (bbtppy) (DMSO)] (3d) (Scheme 2). This bridge-splitting reaction can also be a method for the synthesis of mononuclear products. C-Coordination of the ylide and O-coordination of DMSO are demonstrated by a single-crystal X-ray-analysis of the mononuclear complex 3d. Characterization of the obtained compounds was also performed by means of elemental analysis and IR and ¹H-, ³¹P-, and ¹³C-NMR spectroscopy. A theoretical study of some Hg^II complexes with phosphonium ylides is also reported.

Full text of DOI:10.1002/hlca.200900305

Helvetica Chimica Acta – Vol. 93 (2010)
1105
Synthesis of New Phosphonium Ylides Containing Thiophene and Furan
Rings and Study of Their Reaction with Mercury(II) Halides: Spectral and
Structural Characterization
by Seyyed Javad Sabounchei*a), Vida Jodaianb), Sadegh Salehzadeha), Sepideh Samieea),
Alireza Dadrassa), Mehdi Bayata), and Hamid Reza Khavasic)
a) Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 65174, Iran
(phone: þ 98-811-8282807; fax: þ 98-811-8257407; e-mail: jsabounchei@yahoo.co.uk)
b) Islamic Azad University, Islamshahr Branch 33135/369
c) Department of Chemistry, Shahid Beheshti University, Evin, Tehran, 19839-63113, Iran
Reactions of phosphonium ylides (4-MeC6H4)3PCHC(¼O)(2-C4H3S) (tptpy), Ph3PCHC(¼O)(2-
C4H3O) (fppy), and (4-MeC6H4)3PCHC(¼O)(4-BrC6H4) (bbtppy) with HgX2 (X ¼ Cl, Br, and I) in
equimolar ratios in MeOH as solvent leads to the binuclear products 1 – 3 (Scheme 1). The bridge-
splitting reaction of the binuclear complex [{HgI2(bbtppy)}2] (3c) by DMSO yields the mononuclear
complex [HgI2 · (bbtppy) (DMSO)] (3d) (Scheme 2). This bridge-splitting reaction can also be a method
for the synthesis of mononuclear products. C-Coordination of the ylide and O-coordination of DMSO are
demonstrated by a single-crystal X-ray-analysis of the mononuclear complex 3d. Characterization of the
obtained compounds was also performed by means of elemental analysis and IR and 1H-, 31P-, and
13C-NMR spectroscopy. A theoretical study of some HgII complexes with phosphonium ylides is also
reported.
Introduction.
–
The coordination chemistry of the phosphonium ylides
(¼ phosphoranes) of the type R3PþꢀCH2 , is well known [1 – 4]. Resonance-stabilized
phosphonium ylides, particularly, the keto ylides, are also successfully used as ligands in
organometallic and coordination chemistry owing to their accessibility and stability
towards air and moisture [5][6]. Juxtaposition of the keto group and the carbanion in
the phosphonium ylides allows for the resonance delocalization of the ylide electron
density providing additional stabilization to the ylide species. This so-called a-
stabilization provides ylides with the potential to act as an ambidentate ligand and thus
bond to an HgII center through either the C-atom (see B) or O-atom (see A1 and A2).
ꢀ
Although many bonding modes are possible for keto ylides [7], coordination
through the C-atom is more predominant and observed with soft metal ions, e.g., PdII,
PtII, AgI, HgII, AuI, and AuIII [8][9 – 12], whereas O-coordination dominates when the
metals involved are hard, e.g., TiIV, ZrIV, and HfIV [13].
ꢀ 2010 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Helvetica Chimica Acta – Vol. 93 (2010)
The investigation of the reactivity and coordination chemistry of C¼O-group-
stabilized ylides is the research field of our group. We were interested in the synthesis of
new types of phosphonium ylides containing thienyl or furanyl groups and the study of
their interaction with HgII halides.
Results and Discussion. – Spectroscopy. The ˜nC¼O of the phosphonium ylide ligands,
which is sensitive to complexation to HgII, occurs at higher frequencies in the
complexes 1 – 3 (see Schemes 1 and 2) as compared to the parent ylides, indicating
coordination of the ylides through their C-atom (Table 1). C-Coordination causes an
þꢀCꢀ
~
increase in ˜nC¼O, but for O-coordination, a lowering is expected. The nP
, which is
also diagnostic for the coordination, occurs at lower frequencies for the complexes,
suggesting some lowering of the electron density of the PꢀC bond [14][15] (Table 1).
Scheme 1
Scheme 2
The 1H- and 31P-NMR data for the HgII complexes, along with those of the parent
1
ylides, are listed in Table 2. The expected downfield shifts of the 31P and H signals of

Helvetica Chimica Acta – Vol. 93 (2010)
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Table 1. Assignment of Characteristic FT-IR Vibrations of Ligands and Their HgII Halide Complexes
˜nC¼O [cmꢀ1
]
[cmꢀ1
]
Ref.
þꢀCꢀ
nP
Ph3PCHC(¼O)(4-MeOC6H4) (mbppy)
1521
1615
1524
1613
1618
1609
1526
1633
1624
1625
1598
1646
1635
1641
1640
1630
1626
1620
1702
1699
884
811
927
808
804
803
874
811
810
811
882
805
804
800
797
825
820
812
805
806
[16]
[17]
(4-MeC6H4)3PCHCO2CH2Ph (btpy)
a
(4-MeC6H4)3PCHC(¼O)(2-C4H3S) (tptpy)
)
)
)
)
)
)
)
)
)
)
)
)
a
1a
1b
1c
a
a
a
Ph3PCHC(¼O)(2-C4H3O) (fppy)
a
2a
2b
2c
a
a
a
(4-MeC6H4)3PCHC(¼O)(4-BrC6H4) (bbtppy)
a
3a
3b
3c
3d
a
a
a
)
[{HgCl2(mbppy)}2]
[{HgBr2(mbppy)}2]
[{HgI2(mbppy)}2]
[{HgCl2(btpy)}2]2
[{HgBr2(btpy)}2]2
[16]
[16]
[16]
[17]
[17]
a) This work.
Table 2. 31P- and 1H-NMR Data of Ligands and Their HgII Halide Complexes. d in ppm.
31P{1H}-NMRa)
CHa)
Ref.
Ph3PCHC(¼O)(4-MeOC6H4) (mbppy)
14.06 (s)
13.90 (s)
12.63 (s)
23.74 (s)
23.63 (s)
22.42 (s)
13.69 (s)
20.00 (s)
22.28 (s)
21.88 (s)
13.28 (s)
23.45 (s)
22.14 (s)
21.72 (s)
21.57 (s)
24.58 (s)
23.58 (s)
23.85 (s)
4.25 (d)
2.88 (d)
4.24 (br.)
5.36 (d)
5.30 (d)
[16]
[17]
(4-MeC6H4)3PCHCO2CH2Ph (btpy)
(4-MeC6H4)3PCH(¼O)(2-C4H3S) (tptpy)b)
)
)
)
)
)
)
)
)
)
)
)
)
c
1ad)
c
1bd)
c
1cd)
5.29 (d)
c
Ph3PCH(¼O)(2-C4H3O) (fppy)b)
4.17 (br.)
5.06 (br.)
5.15 (br.)
5.24 (br.)
4.43 (d)
5.30 (br.)
5.30 (d)
5.53 (br.)
5.43 (br.)
5.43 (d)
c
2ad)
c
2bd)
c
2cd)
c
(4-MeC6H4)3PCHC(¼O)(4-BrC6H4) (bbtppy)b)
c
3ad)
c
3bd)
c
3cd)
c
3dd)
)
c
[{HgCl2(mbppy)}2]
[{HgBr2(mbppy)}2]
[{HgCl2(btpy)}2]
[16]
[16]
[17]
5.45 (d)
4.25 (br.)
a) At T 298 K; chemical shifts in ppm relative to internal Me4Si (¼ 0.00 ppm) and external 85% H3PO4.
b) In CDCl3. c) This work. d) In (D6)DMSO.

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Helvetica Chimica Acta – Vol. 93 (2010)
the PCH group upon complexation are observed with respect to the free ylides in the
corresponding spectra. The appearance of single signals for the PCH group, in both the
1
31P- and H-NMR spectra at room temperature, indicates the presence of only one
molecule for all complexes, as expected for C-coordination. It must be noted that O-
coordination of the ylide leads to the formation of a cisoid and a transoid isomer giving
rise to two different signals in the 31P- and 1H-NMR spectra [13]. Moreover, there is no
significant difference in the data reported for the binuclear 3c and the related
mononuclear complex 3d.
The 13C-NMR data of the complexes and the title ylides along with possible
assignments are listed in Tables 3 – 5. The 13C-NMR shifts of the C¼O group in the
complexes are around d 170, i.e., at lower field than for the free phosphonium ylides,
indicating a much lower shielding of the C-atom of the C¼O group in the complexes.
Table 3. 13C-NMR Data of (4-MeC6H4)3PCH(¼O)(2-C4H3S) (tptpy) and Its Complexes with HgII
Halides
tptpya)
50.67
[{HgCl2(tptpy)}2] (1a)b) [{HgBr2(tptpy)}2] (1b)b) [{HgI2(tptpy)}2] (1c)b)
CH
(br.)
–
(br.)
–
(br.)
–
1J(P,C) 112.82
C(2,6)c) 132.47
10.27
C(3,5)c) 128.99
133.1
10.49
129.91
12.86
132.22
–
133.04
10.67
129.88
13.02
132.81
–
133.39
10.49
130.39
12.86
133.62
–
2J(P,C)
3J(P,C)
C(4)c)
4J(P,C)
C(1)c)
1J(P,C)
Mec)
12.50
126.27
5.47
123.12
92.41
20.81
119.79
91.68
20.95
119.76
93.55
20.95
119.81
100.88
21.37
C4H3S
123.12, 125.29, 128.06, 143.97,
141.95, 148.35 144.64 (2 : 1 : 1)
128.02, 144.04,
144.05 (2 : 1 : 1)
183.68
128.60, 133.6,
144.67 (2 : 1 : 1)
183.83
C¼O
177.33
183.97
a) In CDCl3. b) In (D6)DMSO. c) C-Atoms of P(4-MeC6H4)3.
No coupling to Hg is observed at room temperature in the 1H-, 13C-, and 31P-NMR
spectra. Failure to observe satellites in the above spectra was previously noted for the
ylide complexes of HgII [14] and AgI [11] which had been explained by fast exchange of
the ylide with the metal.
Crystal-Structure Analysis of 3d. Table 6 provides the crystallographic results and
refinements for complex 3d. The molecular structure is shown in Fig. 1, and selected
bond distances and angles are given in Table 7.
The HgII center of complex 3d is coordinated by one C-, one O-, and two I-atoms in
a distorted tetrahedral geometry. The two different HgꢀI distances of 3d (2.6776(8)
and 2.7130(8) ꢂ) are smaller than those found in the mononuclear complex
[HgI2(PPh3)2] (2.733(1) and 2.763(1) ꢂ) [16] indicating relatively strong HgꢀI bonds
in 3d. The above distances are comparable to the HgꢀI distances of 2.693(2) and
2.727(2) ꢂ found in [HgI2{Ph2P(S)CH2PPh2}] [18] and to the terminal HgꢀI distance
of 2.6999(6) ꢂ reported for the dimeric complex [{HgI2{(4-MeC6H4)3PCHC(¼O)(4-

Helvetica Chimica Acta – Vol. 93 (2010)
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Table 4. 13C-NMR Data of P3PCH(¼O)(2-C4H3O) (fppy) and Its Complexes with HgII Halides
fppya)
[{HgCl2(fppy)}2] (2a)b) [{HgBr2(fppy)}2] (2b)b) [{HgI2(fppy)}2] (2c)b)
CH
50.11
113.58
46.32
72.06
133.21
10.00
129.39
12.32
133.43
–
47.13
70.42
133.27
10.52
129.53
12.39
133.5
(br.)
–
133.2
9.91
129.56
12.32
133.42
–
123.24
89.84
112.49, 117.01,
146.54, 151.61
179.41
1J(P,C)
C(2,6)c) 132.9
2J(P,C)
C(3,5)c) 128.61
3J(P,C)
C(4)c)
4J(P,C)
C(1)c)
1J(P,C)
C4H3O
10.20
12.23
131.92
2.53
126.39
91.35
–
123.39
89.72
123.15
89.81
112.37, 116.33,
146.37, 152.13
179.03
109.08, 110.97, 112.09, 115.81,
141.99, 155.81 145.90, 152.18
174.88
C¼O
178.8
a) In CDCl3. b) In (D6)DMSO. c) C-Atoms of PPh3.
Table 5. 13C-NMR Data of (4-MeC6H4)3PCHC(¼O)(4-BrC6H4) (bbtppy) and Its Complexes with HgII
Halides
bbtppya)
[{HgCl2(bbtppy)}2]
[{HgBr2(bbtppy)}2]
[{HgI2(bbtppy)}2]
(3a)b)
(3b)b)
(3c)b)
CH
1J(P,C)
Mec)
51.46 (d)
107.12
21.52
(br.)
–
20.87
(br.)
–
21.04
(br.)
–
21.72
C(2,6)c)
2J(P,C)
C(3,5)c)
3J(P,C)
C(4)c)
C(1)c)
1J(P,C)
4-BrC6H4
133.13
10.58
129.66
12.84
130.73
126.12
118.27
142.71, 128.75,
121.9, 123.44
183.11
133.02
10.58
129.47
12.61
130.76
127.76
101.82
143.74, 130.05,
122.37, 118.32
188.73
133.17
10.13
129.97
11.93
130.92
128
99.12
143.89, 132.57,
122.47, 118.34
189.17
133.02
9.05
129.47
12.82
130.76
129.17
89.01
144.86, 136.58,
120.72, 119.48
191.48
C¼O
a) In CDCl3. b) In (D6)DMSO. c) C-Atoms of P(4-MeC6H4)3.
ClC6H4)}}2] [19]. The difference between the two distances in these complexes might be
arising from steric effects of the large ylide moieties.
The HgꢀI(1), HgꢀI(2), and HgꢀC bond lengths of 3d (2.6776(8), 2.7130(8), and
2.261(7) ꢂ, resp.) are shorter than those found in the binuclear complex [{HgI2{(4-
MeC6H4)3PCHC(¼O)(4-ClC6H4)}}2 (2.699(6), 2.7902(5), and 2.310(6) ꢂ, resp.) in-
dicating relatively strong bonds in the mononuclear complexes compared to the
binuclear complexes [19].
The C-coordination of the title ylides is in contrast to the O-coordination of the
phosphonium ylide Ph3PC(COMe)(COPh) (abppy) in a different HgII complex [20].

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Helvetica Chimica Acta – Vol. 93 (2010)
Table 6. Crystallographic Data of Compound 3d
Identification code
119 kh
Empirical formula
Mr
C31H32BrHgI2O2PS
1033.90
Crystal demensions [mm]
Temperature [K]
0.30 ꢁ 0.20 ꢁ 0.20
293(2)
Crystal system
Space group
monoclinic
P2(1)/n
Z
4
Unit cell parameters:
a [ꢂ]
b [ꢂ]
c [ꢂ]
11.644(10)
14.4249(17)
21.2686(17)
104.223(6)
3462.9(6)
b [8]
V [ꢂ3]
Absorption coefficient [mmꢀ1
]
7.513
F(000)
1944
q Range for data collection [8]
Limiting indices
Reflections collected, unique
Completeness to q ¼ 26.80
Absorption correction
1.72 – 26.88
ꢀ 14 ꢂ h ꢂ 14; ꢀ 18 ꢂ k ꢂ 18; ꢀ 26 ꢂ l ꢂ 26
35267, 7355 (R(int) ¼ 0.1113)
98.5%
numerical
Max. and min. transmission
Refinement method
Data, restraints, parameters
Goodness-of-fit on F2
0.985; 0.620
full-matrix least-squares on F2
7355, 0, 354
1.167
Final R indices (I > 2s(I))
R Indices (all data)
Largest diff. peak and hole [e ꢂ3]
R1 ¼ 0.0575, wR2 ¼ 0.1348
R1 ¼ 0.0704, wR2 ¼ 0.1417
1.538; ꢀ 1.396
Table 7. Selected Bond Lengths and Bond Angles of 3da)
Bond lengths [ꢂ]
2.6776(8)
2.7130(8)
2.261(7)
1.791(8)
1.799(7)
1.806(7)
1.797(8)
1.496(7)
Bond angles [8]
Hg(1)ꢀI(1)
Hg(1)ꢀI(2)
Hg(1)ꢀC(1)
P(1)ꢀC(23)
P(1)ꢀC(1)
P(1)ꢀC(9)
P(1)ꢀC(16))
O(2)ꢀS(1)
C(1)ꢀHg(1)ꢀI(1)
C(1)ꢀHg(1)ꢀI(2)
I(1)ꢀHg(1)ꢀI(2)
O(2)ꢀHg(1)ꢀI(1)
O(2)ꢀHg(1)ꢀI(2)
C(1)ꢀHg(1)ꢀO(2)
C(2)ꢀC(1)ꢀP(1)
C(2)ꢀC(1)ꢀHg(1)
P(1)ꢀC(1)ꢀHg(1)
C(23)ꢀP(1)ꢀC(16)
119.33(17)
121.38(17)
117.38(3)
101.94(17)
97.95(17)
84.1(2)
113.5(5)
107.3(5)
110.2(3)
109.6(4)
a) See Fig. 1 for the atom numbering.
The difference in the coordination mode of abppy and of the present ylides to HgII can
be rationalized in terms of the electronic properties, steric requirements, size, and shape
of the ligand in the final bonding mode. This may also be explained by the electronic
nature of the metal (Pd, Pt, Ru, Au, etc.) and even the position of the coordination site

Helvetica Chimica Acta – Vol. 93 (2010)
1111
Fig. 1. ORTEP View of the X-ray crystal structure of [HgI2(bbtppy)(DMSO)] (3d). Arbitrary atom
numbering.
(trans to a C-, N-, or O-atom, etc.). The nucleophilicity of the carbanion in abppy is
smaller than in our ylides; this is due to the additional delocalization of the ylide
electron density in abppy which is facilitated by the second C¼O group. This will
reduce the ability of abppy to form bonds via the ylide C-atom. Facchin and co-workers
have studied the steric influences on the coordination modes of ylide molecules to PtII
systems [21]. These authors concluded that the preferred coordination takes place via
the ylide C-atom, but that steric hindrance around the metal center or the ylide C-atom
will favor O-coordination. Indeed, this trend is reflected here, our ylides are sterically
slightly less demanding than abppy and are C-coordinated to HgII.
Literature data show that the coordination mode of dimethyl sulfoxide
(¼sulfinylbis[methane] ¼ DMSO) to relatively soft metal atoms depends on both
electronic and steric factors originating from the moderate p-acceptor properties of
DMSO and its greater steric demand in the case of S-bonding [22]. In the case of RuII
complexes, coordination through the S-atom of DMSO seems to be preferred over
coordination through the O-atom of DMSO to get stable species, unless ligand
overcrowding occurs [23] or DMSO is trans-oriented to strong p-acceptors like C¼O
[24] and NO [25][26]. A similar overestimate is found for the calculated SꢀO distance
in ꢃfreeꢄ DMSO (1.509 ꢂ), which is 0.018 ꢂ longer than the experimental reference
value of 1.492(1) ꢂ [27]. The significant elongation of the SꢀO distance upon O-
coordination is further confirmed by the recent X-ray structure analysis of a disulfoxide

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Helvetica Chimica Acta – Vol. 93 (2010)
and related CuII complexes, where the average SꢀO distances are 1.487(4) ꢂ (free) and
1.520(3) ꢂ (O-bonded) [28]. The present work reports the example of a HgII complex
containing DMSO as ligand with an O-coordination mode. It is worth noting that in 3d,
the SꢀO bond distance of 1.496(7) ꢂ is ca. 0.004 ꢂ longer than the experimental
reference value of 1.492(1) ꢂ for the free DMSO ligand [27].
Theoretical Studies. As discussed in the previous section, the mononuclear complex
3d is formed by the reaction of complex 3c with DMSO. Recently, according to a
theoretical gas-phase study with only a LanL2MB basis set, we showed that such a
reaction is ca. 32 – 40 kcal/mol exothermic for a number of HgII complexes [19]. Thus,
we became interested to know whether and to what an extent the formation of
mononuclear complexes in the gas phase in which DMSO acts as ligand is energetically
favored over that of binuclear complexes containing the ylide bbtppy. The structures of
the mononuclear complexes derived from the reaction of compounds 3a – 3c with
DMSO were optimized with the LanL2MB and LanL2DZ basis sets. The LanL2DZ-
optimized structures are shown in Fig. 2. A comparison between the calculated bond
lengths and bond angles of 3d obtained with the LanL2MB and LanL2DZ basis sets
Fig. 2. Calculated molecular structures of a) [HgI2(bbtppy)(DMSO)], b) [HgBr2(bbtppy)(DMSO)],
and c) [HgCl2(bbtppy)(DMSO)]. Arbitrary atom numbering.

Helvetica Chimica Acta – Vol. 93 (2010)
1113
with corresponding experimental values is presented in Table 8. A list of calculated key
bond lengths and bond angles for compounds [HgX2(bbtppy)(DMSO)] (where X ¼ Cl
and Br) are also presented in Table 9.
As can be seen, the data derived from the more expensive basis set LanL2DZ are
much closer to the experimental data of 3d than those derived from the cheaper basis
set LanL2MB. As can be seen, in the case of the LanL2DZ calculations, the calculated
bond lengths are slightly longer than the measured ones, but there are good agreements
between the calculated and measured bond angles. Thus, it seems that for complexes
containing both the ylides and halides coordinated to HgII, the results of calculations
with the LanL2DZ basis set is, as expected, more reliable than those derived from the
LanL2MB calculations. The electronic energies of the mononuclear and corresponding
binuclear complexes are given in Table 10. The results show that the products of the
proposed reaction (Eqn. 1) are more stable than the reactants. These stabilities are ca.
30.5, 34.9, and 41.0 kcal/mol for X ¼ Cl, Br, and I, respectively. Therefore, it is clear that
for all compounds synthesized here, the gas-phase reaction shown in Eqn. 1 is an
exothermic reaction. Thus, it seems that the bridge-splitting reaction in DMSO solution
is potentially possible for all dimeric complexes of bbtppy. The data also show that in
the case of the I complex, the formation of the mononuclear complex is relatively more
favorable than in the case of the corresponding Cl and Br complexes (Table 10).
Table 8. Comparison of the Calculated Bond Lengths ([ꢂ]) and Bond Angles ([8]) of 3d with the
Corresponding Experimental Valuesa)
X-Ray
LanL2MB
LanL2DZ
Bond length [ꢂ]:
Hg(1)ꢀI(1)
2.677
2.713
2.681
2.260
1.791
1.799
1.806
1.797
3.028
3.069
2.309
2.260
1.917
1.965
1.932
1.924
2.843
2.852
2.458
2.423
1.844
1.843
1.806
1.849
Hg(1)ꢀI(2)
Hg(1)ꢀO(2)
Hg(1)ꢀC(1)
P(1)ꢀC(23)
P(1)ꢀC(1)
P(1)ꢀC(9)
P(1)ꢀC(16))
Bond angle [8]:
I(1)ꢀHg(1)ꢀI(2)
I(1)ꢀHg(1)ꢀC(1)
I(1)ꢀHg(1)ꢀC(2)
I(1)ꢀHg(1)ꢀO(2)
O(1)ꢀC(2)ꢀC(1)
O(1)ꢀC(2)ꢀC(3)
C(23)ꢀP(1)ꢀC(1)
C(9)ꢀP(1)ꢀC(23)
C(23)ꢀP(1)ꢀC(16)
C(1)ꢀP(1)ꢀC(9)
C(16)ꢀP(1)ꢀC(1)
C(16)ꢀP(1)ꢀC(9)
117.382
119.316
121.384
97.948
121.780
120.606
113.744
108.004
109.527
111.405
107.340
106.578
111.583
114.141
118.966
102.442
122.709
120.740
110.492
109.634
109.935
111.289
110.188
105.175
116.878
118.314
121.009
99.309
120.385
118.817
113.520
108.920
109.154
111.696
107.882
105.315
a) See Fig. 1 for the atom numbering.

1114
Helvetica Chimica Acta – Vol. 93 (2010)
Table 9. Selected Calculated Bond Lengths ([ꢂ]) and Bond Angles ([8]) of [HgX2(bbtppy) (DMSO)]
(X ¼ Cl, Br)a)
X ¼ Cl
LanL2MB
X ¼ Br
LanL2MB
LanL2DZ
LanL2DZ
Bond length [ꢂ]:
Hg(16)ꢀX(19)
2.660
2.702
2.306
2.271
1.916
1.930
1.967
1.927
2.566
2.572
2.394
2.380
1.843
1.849
1.849
1.851
2.828
2.863
2.309
2.277
1.917
1.931
1.966
1.924
2.697
2.695
2.695
2.401
1.843
1.850
1.846
1.850
Hg(16)ꢀX(24)
Hg(16)ꢀO(62)
Hg(16)ꢀC(11)
P(8)ꢀC(9)
P(8)ꢀC(10)
P(8)ꢀC(11)
P(8)ꢀC(7)
Bond angle [8]:
X(19)ꢀHg(16)ꢀX(24)
C(11)ꢀHg(16)ꢀX(24)
C(11)ꢀHg(16)ꢀXl(19)
X(19)ꢀHg(16)ꢀO(62)
O(23)ꢀC(17)ꢀC(25)
O(23)ꢀC(17)ꢀC(11)
C(7)ꢀP(8)ꢀC(9)
C(7)ꢀP(8)ꢀC(10)
C(7)ꢀP(8)ꢀC(11)
C(9)ꢀP(8)ꢀC(10)
C(9)ꢀP(8)ꢀC(11)
C(10)ꢀP(8)ꢀC(11)
110.658
107.507
122.103
98.093
120.792
122.557
109.716
107.649
108.114
109.279
110.435
111.587
113.590
119.583
121.062
97.534
119.042
120.393
108.489
106.523
107.840
109.146
113.281
111.294
114.142
110.617
118.262
100.137
120.736
122.747
109.691
105.515
110.151
109.707
110.110
111.565
115.606
118.901
120.799
98.231
118.940
120.379
108.911
105.793
107.966
109.118
113.150
111.602
a) See Fig. 1 for the atom numbering.
Table 10. Calculated Electronic Energies for Binuclear Complexes, DMSO, and Mononuclear Complexes
X
[{HgX2(bbtppy)}2]
DMSO
[HgX2(bbtppy)(DMSO)]
DE [kcal molꢀ1]a)
Cl
Br
I
ꢀ 2527.4032043
ꢀ 2520.317148
ꢀ 2513.2343402
ꢀ 161.8305649
ꢀ 161.8305649
ꢀ 161.8305649
ꢀ 1425.5564682
ꢀ 1422.0169333
ꢀ 1418.4804131
30.50
34.88
41.01
a) Released energy in the gas-phase reaction of Eqn. 1.
gas phase
½fHgX ðbbtppyÞg ꢃ þ 2 DMSO
2 ½HgX ðbbtppyÞðDMSOÞꢃ
(1)
ƒƒƒƒ!
2
2
2
The calculated energies for HOMO and LUMO of [HgX2(bbtppy)(DMSO)] (X ¼
Cl and Br) are given in Table 11. The hardness h of a molecule is defined by Eqn. 2,
where I and A are the ionization potential and the electron affinity of the system,
respectively. Obviously, the energy gap between the HOMO and LUMO is equal to
(I ꢀ A). Thus, we can easily calculate the hardness of the present molecules by Eqn. 3
[29].

Helvetica Chimica Acta – Vol. 93 (2010)
1115
Table 11. Calculated Energies of HOMO and LUMO Molecular Orbitals, Hardness, and Energy Gap
between the HOMO and LUMO of [HgX2(bbtppy)(DMSO)] Complexes
X
HOMO [hartree]
LUMO [hartree]
h [eV]
Gap [eV]
Cl
Br
I
ꢀ 0.33545
ꢀ 0.32141
ꢀ 0.29403
0.06302
0.06256
0.06122
5.42
5.22
4.83
10.84
10.44
9.66
ðI ꢀ AÞ
h ¼
(2)
(3)
2
ðELUMO ꢀ EHOMO
Þ
h ¼
2
We note that hard molecules have a large HOMO – LUMO gap, and soft molecules
have a small one [30]. The results of the LanL2DZ calculation demonstrate that the
HOMO and LUMO show up with a negative and positive charge, respectively (see
Table 11). Furthermore, the calculated energy gap between these orbitals for
complexes containing I is smaller than that for the other complexes. Thus, complexes
including I as a ligand are softer than the other complexes described here. This is
completely consistent with the fact that a hard group makes a molecule hard, and a soft
group makes it soft. The HOMO and LUMO for all three mononuclear
[HgX2(bbtppy)(DMSO)] (X ¼ Cl, Br, and I) complexes are illustrated in Fig. 3. 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.
Conclusions. – The present study describes the synthesis and characterization of
mononuclear and binuclear HgII complexes of phosphonium ylides. On the basis of the
physicochemical and spectroscopic data, we propose that the herein described
phosphonium ylide ligands exhibit monodentate C-coordination to the metal center.
This study also presents a method for the synthesis of mononuclear HgII complexes of
phosphonium ylides via a bridge-splitting reaction involving DMSO as ligand.
Theoretical studies on the gas-phase structure of the complexes confirm that the
bridge-splitting reaction in DMSO solution is potentially possible for all dimeric
complexes in which DMSO can act as a ligand.
Experimental Part
General. All reactions were performed in air. Starting materials were purchased from commercial
sources and used without further purification. All solvents were dried by reported methods [31]. M.p.:
SMPI apparatus; uncorrected. FT-IR Spectra: Shimadzu-435 spectrophotometer; KBr pellets; ˜n in cmꢀ1
.
1H-, 13C- and 31P-NMR Spectra: Bruker-200 and Jeol-90 spectrometer; d in ppm rel. to Me4Si as internal
standard, J in Hz. Elemental analysis: Perkin-Elmer 2400 analyzer for C, H, and N.
[(2-Thienylcarbonyl)methylene]tri(p-tolyl)phosphorane (¼1-(2-Thienyl)-2-[tris(4-methylphenyl)-
phosphoranylidene]ethanone; tptpy). To a soln. of 2-(bromoacetyl)thiophene (0.102 g, 0.5 mmol) in

1116
Helvetica Chimica Acta – Vol. 93 (2010)
Fig. 3. a) c) e) Calculated HOMOs and b) d) f) LUMOs for compounds [HgX2(bbtppy)(DMSO)],
where X ¼ Cl (a, b), Br (c, d), and I (e, f), respectively
acetone (10 ml) was added a soln. of tri(p-tolyl)phosphine (0.152 g, 0.5 mmol) in the same solvent (5 ml).
The brown soln. was stirred at r.t. for 12 h. The suspension was concentrated to 3 ml. After addition of
Et2O, the precipitate was filtered off, washed with Et2O (2 ꢁ 10 ml), and dried under reduced pressure.

Helvetica Chimica Acta – Vol. 93 (2010)
1117
Further treatment with aq. NaOH soln. (0.5m) led to elimination of HBr, giving the free ligand tptpy
(83%). M.p. 179 – 1808. Anal. calc. for C27H25OPS (428.53): C 75.68, H 5.88; found: C 75.70, H 5.84.
[(Furan-2-ylcarbonyl)methylene]triphenylphosphorane (¼1-[(Furan-2-yl)-2-(triphenylphosphora-
nylidene]ethanone; fppy). As described for TPTPY, with 2-bromo-1-(furan-2-yl)ethanone (0.094 g,
0.5 mmol), acetone (10 ml), triphenylphosphine (0.131 g, 0.5 mmol), and acetone (5 ml), at r.t. for 4 h:
fppy (74%). M.p. 219 – 2218. Anal. calc. for C24H19O2P (370.38): C 77.83, H 5.17; found: C 76.31,
H 4.98.
[(4-Bromobenzoyl)methylene]tri(p-tolyl)phosphorane (¼1-(4-Bromophenyl)-2-[tris(4-methylphe-
nyl)phosphoranylidene]ethanone; bbtppy). To a soln. of tri(p-tolyl)phosphine (0.152 g, 0.5 mmol) in
CHCl3 (25 ml) was added 1-(4-bromophenyl)ethanone (0.139 g, 0.5 mmol), and the resulting mixture
was stirred for 12 h. The soln. was filtered off, and the precipitate was washed with Et2O and dried.
Further treatment with aq. NaOH soln. (0.5m) led to elimination of HBr, giving the free ligand bbtppy
(85%). M.p. 177 – 1798. Anal. calc. for C29H26BrOP (501.39): C 69.47, H 5.23; found: C 69.46,
H 5.13.
Complexes 1 – 3: General Procedure. The binuclear complexes were prepared by the following
general procedure and their structures suggested according to [14][15][32]. To tptpy (0.107 g,
0.25 mmol) in MeOH (5 ml) was added HgCl2 (0.067 g, 0.25 mmol). The mixture was stirred at r.t. for
4 h. The formed dimeric complex 1a was separated by filtration and washed with Et2O. The
corresponding bromo and iodo complexes were prepared with HgBr2 (0.09 g, 0.25 mmol) and HgI2
(0.11 g, 0.25 mmol), resp., in the same manner.
Di-m-chlorodichlorobis{2-oxo-2-(2-thienyl)-1-[tris(4-methylphenyl)phosphonio]ethyl}dimercury
([{HgCl2 (tptpy)}2]; 1a): Yield 72.4%. M.p. 179 – 1808. Anal. calc. for C54H50Cl4Hg2O2P2S2 (1400.04): C
46.33, H 3.60; found: C 45.33, H 3.75.
Di-m-bromodibromobis{2-oxo-2-(2-thienyl)-1-[tris(4-methylphenyl)phosphonio]ethyl}dimercury
([{HgBr2 (tptpy)}2]; 1b): Yield 66.2%. M.p. 200 – 2018. Anal. calc. for C54H50Br4Hg2O2P2S2 (1577.85): C
41.11, H 3.19; found: C 42.32, H 3.05.
Di-m-iododiiodobis{2-oxo-2-(2-thienyl)-1-[tris(4-methylphenyl)phosphonio]ethyl}dimercury ([{HgI2
(tptpy)}2]; 1c): Yield 57%. M.p. 193 – 1958. Anal. calc. for C54H50Hg2I4O2P2S2 (1765.85): C 36.73, H 2.85;
found: C 36.69, H 2.83.
Di-m-chlorodichlorobis{2-(furan-2-yl)-2-oxo-1-(triphenylphosphonio)ethyl}dimercury ([{HgCl2
(fppy)}2]; 2a): Yield 64%. M.p. 218 – 2198. Anal. calc. for C48H38Cl4Hg2O4P2 (1283.75): C 44.91, H 2.98;
found: C 45.41, H 2.82.
Di-m-bromodibromobis{2-(furan-2-yl)-2-oxo-1-(triphenylphosphonio)ethyl}dimercury ([{HgBr2
(fppy)}2]; 2b): Yield 56.1%. M.p. 213 – 2158. Anal. calc. for C48H38Br4Hg2O4P2 (1461.56): C 39.45, H
2.62; found: C 39.72, H 2.54.
Di-m-iododiiodobis{2-(furan-2-yl)-2-oxo-1-(triphenylphosphonio)ethyl}dimercury ([{HgI2 (fppy)}2];
2c): Yield 48.1%. M.p. 198 – 1998. Anal. calc. for C48H38Hg2I4O4P2 (1649.56): C 34.95, H 2.32; found: C
35.3, H 2.23.
Di-m-chlorodichlorobis{2-(4-bromophenyl)-2-oxo-1-[tris(4-methylphenyl)phosphonio]ethyl}dimer-
cury ([{HgCl2 (bbtppy)}2]; 3a): Yield 67%. M.p. 182 – 1848. Anal. calc. for C58H52Br2Cl4Hg2P2O2
(1545.78): C 45.07, H 3.39; found: C 45.06, H 3.38.
Di-m-bromodibromobis{2-(4-bromophenyl)-2-oxo-1-[tris(4-methylphenyl)phosphonio]ethyl}dimer-
cury ([{HgBr2 (bbtppy)}2]; 3b): Yield 64%. M.p. 189 – 1918. Anal. calc. for C58H52Br6Hg2P2O2 (1723.58):
C 40.42, H 3.04; found: C 40.82, H 3.00.
Di-m-iododiiodobis{2-(4-bromophenyl)-2-oxo-1-[tris(4-methylphenyl)phosphonio]ethyl}dimercury
([{HgI2 (bbtppy)}2]; 3c): Yield 64%. M.p. 184 – 186 . Anal. calc. for C58H52Br2Hg2I4P2O2 (1911.59): C
36.44, H 2.74; found: C 36.51, H 2.77.
{2-(4-Bromophenyl)-2-oxo-1-[tris(4-methylphenyl)phosphonio]ethyl}{(sulfinyl-kO)bis[methane]}-
mercury ([HgI2 (bbtppy) (DMSO)]; 3d). The binuclear complex 3c (0.191 g, 0.1 mmol) was dissolved in
DMSO (2 ml). Colorless crystals were formed by slow evaporation of the solvent over several days:
0.198 g (96%) of 3d. M.p. 1808 (dec.). Anal. calc. for C31H32BrHgI2O2PS (1033.93): C 36.01, H 3.12;
found: C 35.92, H 3.25.

1118
Helvetica Chimica Acta – Vol. 93 (2010)
X-Ray Crystal-Structure Determination of 3d1). The single-crystal X-ray diffraction analysis of a
suitable crystal of 3d was performed with a Stoe-IPDS-II two-circle diffractometer at 298 K and graphite
monochromated MoKa radiation (l 0.7107 ꢂ). The data collection was performed at r.t. with the w-scan
technique and the X-AREA software package [28]. The crystal structure was solved by direct methods
and refined by full-matrix least-squares on F2 by SHELX [33] and with the X-STEP32 crystallographic
software package [34]. All non-H-atoms were refined anisotropically with reflections I > 2s(I). H-
Atoms were inserted at calculated positions in a riding mode with fixed thermal parameters.
Theoretical Studies. The geometries of the compounds were fully optimized at the Hartree – Fock
(HF) level of theory with the GAUSSIAN98 program [35] on a Pentium personal computer with a
3600 MHz processor. The standard LanL2DZ basis set was used for all complexes [17]. This basis set
includes effective core potentials (ECP) for both the mercury and phosphorus as well as halide (Cl, Br
and I) ions. Vibrational-frequency analyses, 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 ab initio calculations were obtained from the data of the X-ray crystal-structure
analyses.
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