Reactivity of fluorinated thioether ligands of the type [C6H4Br-2-(CH2SRF)] towards transition metal complexes of the group 10

Article abstract of DOI:10.1016/j.ica.2007.05.056

The fluorinated thioether compounds [C₆H₄Br-2-(CH₂SR_F)] (SR_F = SC₆F₅ (1), SC₆F₄-4-H (2), SC₆H₄-2-F (3), SC₆H₄-3-

Full text of DOI:10.1016/j.ica.2007.05.056

Available online at www.sciencedirect.com
Inorganica Chimica Acta 360 (2007) 4133–4141
www.elsevier.com/locate/ica
Reactivity of fluorinated thioether ligands of the type
[C6H4Br-2-(CH2SRF)] towards transition metal complexes
of the group 10
a
a
a
´
´
´
´
Alma Itzel Olivos-Suarez , Gustavo Rıos-Moreno , Simon Hernandez-Ortega ,
a
b
a,
*
´
´
Ruben A. Toscano , Juventino J. Garcıa , David Morales-Morales
a
Instituto de Quı´mica, Universidad Nacional Auto´noma de Me´xico, Cd. Universitaria, Circuito Exterior, Coyoaca´n 04510 Me´xico D.F., Mexico
b
Facultad de Quı´mica, Universidad Nacional Auto´noma de Me´xico, Cd. Universitaria, Circuito Interior, 04510, Me´xico D.F., Mexico
Received 20 March 2007; received in revised form 25 May 2007; accepted 28 May 2007
Available online 7 June 2007
Abstract
The fluorinated thioether compounds [C6H4Br-2-(CH2SRF)] (SRF = SC6F5 (1), SC6F4-4-H (2), SC6H4-2-F (3), SC6H4-3-F (4),
SC6H4-4-F (5)) were synthesized and the reactivity of (1) was explored with transition metal complexes of the group 10. The results
obtained indicate that the reactivity of these ligands is strongly dependent on the oxidation state of the metal center on the complex.
Thus, products of the coordination of Pd(II) and Pt(II) to the sulfur moiety were obtained and unequivocally characterized by sin-
gle crystal X-ray diffraction analyses. While spectroscopic evidence indicates that reaction of the Pt(0) compound [Pt(PEt3)3] leads to
the formation of C–Br activation products, it is worth noting that similar reactions with Ni(0) and Pd(0) compounds only afford
complex mixtures that in most of the cases indicate desulfurization of the ligands and decomposition of the metallic starting
materials.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Platinum complexes; Fluorinated thiolates; Fluorinated thioether; Palladium complexes; Crystal structures; Catalysis
1. Introduction
case of the Heck coupling, the most accepted reaction
mechanism involves Pd(0)/Pd(II) species [7], thus the ini-
tial step would in most of the cases start with a Pd(0)
species, either generated by reduction of a Pd(II) metal
source or placed from the beginning in the zero oxida-
tion state, which after oxidative addition of a haloben-
zene would initiate the C–C coupling process. However,
even today there is still some discussion regarding the
possibility for the participation of Pd(IV) species [8],
although many authors agree on the fact that there are
no real Pd(IV) intermediates but Pd-nanoparticule mate-
rials are generated as a decomposition product of many
Pd complexes [9]. This is generally accepted for the case
of palladacycles and particularly true at temperatures
higher than 120 ꢁC [10]. Thus, following our continuous
interest [11] in the design and development of potentially
chelating ligands and their complexes containing thiolate
The oxidative addition reaction is probably one of the
most important and studied processes in organometallic
chemistry and catalysis [1]. The importance that this
reaction has acquired is due to the fact that, in many
cases, it represents the initial or rate determining step
in different industrial relevant organic transformations
catalyzed by transition metal complexes [2]. This is par-
ticularly true in the case of the Heck reaction [3], this
being extended to other cross coupling reactions includ-
ing the Suzuki–Miyaura [4], thiolation [5] and amination
(Hartwig–Buchwald) [6] reactions, etc. For the particular
*
Corresponding author. Tel.: +52 55 56224514; fax: +52 55 56162217.
E-mail address: damor@servidor.unam.mx (D. Morales-Morales).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.05.056

4134
A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
moieties as tuning fragments for the electronics and ster-
ics on their structures, and further use as catalyst precur-
sors for industrial relevant organic transformations, we
have synthesized compounds of the type [C6H4Br-2-
(CH2SRF)] (SRF = SC6F5 (1), SC6F4-4-H (2), SC6H4-2-
F (3), SC6H4-3-F (4), SC6H4-4-F (5)) and examined their
reactivity against transition metal complexes of group 10
in different oxidation states. Moreover, the presence of a
bromide in the ortho position would offer the possibility
of ortho-metallation affording metallacycles as final prod-
ucts. The results of our investigations concerning these
studies and preliminary catalytic studies of the palladium
derivatives in the Heck coupling reaction of bromoben-
zene and styrene will be described herein.
phosphinoethane) [18], were prepared according to pub-
lished procedures.
2.2. General procedure for the synthesis of the ligands
[C6H4Br-2-(CH2SRF)] SRF = SC6F5 (1), SC6F4-4-H (2),
SC6H4-2-F (3), SC6H4-3-F (4), SC6H4-4-F (5)
The ligands (1)–(5) were synthesized by using the same
experimental procedure. Thus, as a representative example,
the synthesis of [C6H4Br-2-(CH2SC6F5)] (1) is described.
2.2.1. Synthesis of [C6H4Br-2-(CH2SC6F5)] (1)
A
suspension consisting of [Pb(SC6F5)2] (364 mg,
0.6 mmol) and [C6H4Br-2-(CH2Br)] in toluene (20 mL)
was set to reflux for 24 h. After the prescribed reaction
time, the resulting solution was filtered through a short
plug of Celiteꢂ and the volume reduced in vacuum to
obtain a yellowish oily residue that crystallizes with time.
2. Experimental
2.1. Material and methods
1
Yield 97%. M.P. 42–43 ꢁC. H NMR (300 MHz, CDCl3),
Unless stated otherwise, all reactions were carried out
under an atmosphere of argon using conventional Schlenk
glassware. Solvents were dried using established proce-
dures and distilled under dinitrogen immediately prior to
use. The IR spectra were recorded on a Nicolet-Magna
750 FT-IR spectrometer as Nujol mulls. The 1H NMR
spectra were recorded on a JEOL GX300 spectrometer.
Chemical shifts are reported in ppm down field of TMS
using the solvent (CDCl3, d 7.27) as internal standard.
31P{1H} NMR and 19F NMR spectra were recorded with
complete proton decoupling and are reported in ppm using
85% H3PO4 and C6F6, respectively, as external standards.
Elemental analyses were determined on a Perkin–Elmer
240. Positive-ion FAB mass spectra were recorded on a
JEOL JMS-SX102A mass spectrometer operated at an
accelerating voltage of 10 kV. Samples were desorbed from
a nitrobenzyl alcohol (NOBA) matrix using 3 keV xenon
atoms. Mass measurements in FAB are performed at a res-
olution of 3000 using magnetic field scans and the matrix
ions as the reference material or, alternatively, by electric
field scans with the sample peak bracketed by two (poly-
ethylene glycol or cesium iodide) reference ions. Melting
points were determined in a MEL-TEMP capillary melting
point apparatus and are reported without correction. GC–
MS analyses were performed on a Agilent 6890N GC with
a 30.0 m DB-1MS capillary column coupled to an Agilent
5973 Inert Mass Selective detector. PdCl2 and PtCl2 were
purchased from Pressure Chemical Co. and 2-bro-
mobenzylbromide, HSC6F5, HSC6F4-4-H, HSC6H4-2-F,
HSC6H4-3-F, HSC6H4-4-F were commercially obtained
from Aldrich Chemical Co. and the phosphine PEt3 was
purchased from STREM Chemicals, Inc. All compounds
were used as received without further purification. The
starting materials Pb(SRF)2 (SRF = SC6F5, SC6F4-4-H,
SC6H4-2-F, SC6H4-3-F, SC6H4-4-F) [12], cis-[(MeCN)2-
PtCl2] [13], [(COD)PdCl2] [14], Ni(PEt3)3] [15], [Pd(PEt3)3]
[15], [Pd(dba)2] (dba = dibenzylidene acetone) [16],
[Pt(PEt3)3] [17], and [(dippe)NiH]2 (dippe = diisopropyl-
d 7.56–7.10 (m, Ph, 4H), 4.17 (s, CH2, 2H); 19F{1H}
3
NMR (282 MHz, CDCl3), d ꢀ130.87 (dd, JFo–Fm
=
4
3
22.56 Hz, JFo–Fp = 5.64 Hz, o-F), ꢀ150.93 (t, JFm–Fp
3
4
= 22.56 Hz, p-F), ꢀ160.27 (m, JFm–Fp = 22.56, JFo–Fp
= 5.64 Hz, m-F). Elem. Anal. Calc. for C13H6BrF5S: C,
42.30; H, 1.64. Found: C, 42.26; H, 1.66%. MS-EI
[M+1] = 370 m/z.
2.2.2. Synthesis of [C6H4Br-2-(CH2SC6F4-4-H)] (2)
[C6H4Br-2-(CH2Br)]
(300 mg,
1.20 mmol)
and
[Pb(SC6F4-4-H)2] (341 mg, 0.60 mmol) in toluene
(20 mL). Microcrystalline white solid. Yield 93.5%. M.P.
1
39–41 ꢁC. H NMR (300 MHz, CDCl3), d 7.71–7.26 (m,
Ph, 4H), 7.18–7.04 (m, SC6F4-4-H, 1H), 4.23 (s, CH2,
2H); 19F{1H} NMR (282 MHz, CDCl3), d ꢀ132.01 (m,
4
3JFo–Fm = 22.56 Hz, JFo–Fp = 5.64 Hz, o-F), ꢀ131.70 (m,
4
3JFm–Fp = 22.56, JFo–Fp = 5.64 Hz, m-F). Elem. Anal.
Calc. for C13H7BrF4S: C, 44.46; H, 2.01. Found: C,
44.42; H, 1.99%. MS-EI [M+1] = 352 m/z.
2.2.3. Synthesis of [C6H4Br-2-(CH2SC6H4-2-F)] (3)
[C6H4Br-2-(CH2Br)]
(300 mg,
1.20 mmol)
and
[Pb(SC6H4-2-F)2] (278 mg, 0.60 mmol) in toluene
(20 mL). Yellowish oil. Yield 92.8%. 1H NMR
(300 MHz, CDCl3), d 7.06–6.89 (m, Ph and SC6H4-2-F,
8H), 4.09 (s, CH2, 2H); 19F NMR (282 MHz, CDCl3), d
ꢀ107.45 (m, o-F). Elem. Anal. Calc. for C13H10BrFS: C,
52.54; H, 3.39. Found: C, 52.52; H, 3.39%. MS-EI
[M+1] = 298 m/z.
2.2.4. Synthesis of [C6H4Br-2-(CH2SC6H4-3-F)] (4)
[C6H4Br-2-(CH2Br)] (300 mg, 1.20 mmol) and [Pb(SC6-
H4-3-F)2] (278 mg, 0.60 mmol) in toluene (20 mL). Yellow-
1
ish oil. Yield 98.0%. H NMR (300 MHz, CDCl3), d 7.16–
6.82 (m, Ph and SC6H4-3-F, 8H), 4.18 (s, CH2, 2H); 19F
NMR (282 MHz, CDCl3), d ꢀ111.16 (m, m-F). Elem. Anal.
Calc. for C13H10BrFS: C, 52.54; H, 3.39. Found: C, 52.01;
H, 3.36%. MS-EI [M+1] = 298 m/z.

A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
4135
2.2.5. Synthesis of [C6H4Br-2-(CH2SC6H4-4-F)] (5)
[C6H4Br-2-(CH2Br)] (300 mg, 1.20 mmol) and [Pb(SC6-
H4-4-F)2] (278 mg, 0.60 mmol) in toluene (20 mL). Yellow-
2.7. Data collection and refinement for [C6H4Br-2-
(CH2SC6F5)] (1), [C6H4Br-2-(CH2SC6F4-4-H)] (2),
trans-[PdCl2{C6H4Br-2-(CH2SC6F5)}] (6), trans-
[PtCl2{C6H4Br-2-(CH2SC6F5)}] (7)
1
ish oil. Yield 91.0%. H NMR (300 MHz, CDCl3), d 7.27–
6.84 (m, Ph and SC6H4-4-F, 8H), 4.07 (s, CH2, 2H); 19F
NMR (282 MHz, CDCl3), d ꢀ112.99 (m, p-F). Elem. Anal.
Calc. for C13H10BrFS: C, 52.54; H, 3.39. Found: C, 52.28;
H, 3.37%. MS-EI [M+1] = 298 m/z.
Colorless prisms of 1 and 2 were obtained from the cor-
responding oily products that slowly crystallized, whilst
for complexes 6 and 7, orange prisms were grown indepen-
dently from a double layer solvent system of CH2Cl2/pen-
tane solvents system. All crystals were mounted on glass
fibers. In all cases, the X-ray intensity data were measured
at 293 or 291 K on an Bruker SMART APEX CCD-based
X-ray diffractometer system equipped with a Mo-target X-
2.3. Reactions of [C6H4Br-2-(CH2SC6F5)] (1) with
[CODPdCl2]
A mixture consisting of [C6H4Br-2-(CH2SC6F5)] (1)
(100 mg, 0.26 mmol) and [CODPdCl2] (39 mg, 0.13 mmol)
in toluene (30 mL) was set to reflux, under nitrogen for
24 h. After the prescribed reaction time, the resulting
mixture was dried under vacuum to afford a yellow-
˚
ray tube (k = 0.71073 A). The detector was placed at a dis-
tance of 4.837 cm from the crystals in all cases. A total of
1800 frames were collected with a scan width of 0.3 in x
and an exposure time of 10 s/frame. The frames were inte-
grated with the Bruker SAINT software package [19] using a
narrow-frame integration algorithm. The integration of
the data was done using an orthorhombic unit cell for 1,
monoclinic for 2 and 6 and triclinic for 7, to yield a total
of 7279, 5703, 41498 and 59248 reflections for 1, 2, 6 and
green residue which after recrystallization from
a
CH2Cl2/n-hexane affords complex trans-[PdCl2{C6H4Br-
2-(CH2SC6F5)}] (6) as a microcrystalline yellow-orange
powder.
˚
2.4. Reaction of [C6H4Br-2-(CH2SC6F5)] (1) with cis-
[(MeCN)2PtCl2]
7, respectively, to a maximum 2h angle of 50.00 (0.93 A
resolution), of which 2346 (1), 3695 (2), 41498 (6) and
59248 (7) were independent. Analysis of the data showed
in all cases negligible decays during data collections. The
structures were solved by Patterson method using
SHELXS-97 [20] program. The remaining atoms were
located via a few cycles of least squares refinements and
difference Fourier maps, using the space group P212121
Under similar reaction conditions as those described
above for complex (6),
a mixture of [C6H4Br-2-
(CH2SC6F5)] (1) (100 mg, 0.28 mmol) and cis-
[(MeCN)2PtCl2] (64 mg, 0.14 mmol) in toluene (30 mL)
was set to reflux under nitrogen for 24 h. The yellow prod-
uct of trans-[PtCl2{C6H4Br-2-(CH2SC6F5)}] (7), was
obtained analytically pure after recrystallization from a
CH2Cl2/n-hexane.
ꢀ
with Z = 4, P21 with Z = 2, C2/c with Z = 4 and P1 with
Z = 4 for 1, 2, 6 and 7, respectively. Hydrogen atoms were
input at calculated positions, and allowed to ride on the
atoms to which they are attached. Thermal parameters
were refined for hydrogen atoms on the phenyl groups
2.5. Reaction of [C6H4Br-2-(CH2SC6F4-4-H)] (1) with
[Pt(PEt3)3]
˚
using Ueq = 1.2 A to precedent atom in all cases. For all
complexes, the final cycle of refinement was carried out
on all non-zero data using SHELXL-97 and anisotropic ther-
mal parameters for all non-hydrogen atoms. The details of
structure determinations are given in Table 1. Numbering
of atoms is shown in Figs. 1–4, respectively (ORTEP)
[21].
To a THF (15 mL) solution of [C6H4Br-2-(CH2SC6F4-4-
H)] (1) (100 mg, 0.28 mmol), a solution of [Pt(PEt3)3]
(64 mg, 0.14 mmol) in THF (15 mL) was added and the
resulting solution was set to reflux under argon for 2 h.
After this time, the reaction mixture was dried under vac-
uum to afford an off-yellow residue of trans-
[PtBr(PEt3)2{C6H4(CH2SC6F4-4-H)}] (8).
3. Results and discussion
2.6. General procedure for the catalytic reactions
The fluorinated thioether compounds [C6H4Br-2-
(CH2SRF)] (SRF = SC6F5 (1), SC6F4-4-H (2), SC6H4-2-F
(3), SC6H4-3-F (4), SC6H4-4-F (5)) were synthesized in a
very easy manner, attaining quantitative yields in all cases.
A typical procedure involves the methathetical reaction of
2 equiv. of 2-bromobenzylbromide with one equivalent of
the corresponding thiolate lead salt [Pb(SRF)2] under reflux
conditions in toluene as solvent (Scheme 1). As in many
other cases involving the use of lead–thiolate [Pb(SRF)2]
compounds as thiolate transfer agents, the reaction is dri-
ven by the formation of insoluble lead salts [PbX2] [22].
Thus, the purification of the corresponding products is
A DMF solution (5 mL) of 2.5 mmol of bromobenzene,
3.2 mmol of styrene, and the prescribed amount of catalyst
(4.33 · 10ꢀ3 mmol) were introduced into a Schlenk tube in
open air. The tube was charged with a magnetic stir bar
and an excess of Na2CO3 (3.77 mmol) as base, sealed,
and fully immersed in a 120 ꢁC silicon oil bath. After the
prescribed reaction time (5 h), the mixture was cooled to
room temperature and the organic phase was analyzed by
gas chromatography (GC–MS) coupled to a selective mass
detector.

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A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
Table 1
Summary of crystal structure data for [C6H4Br-2-(CH2SC6F5)] (1), [C6H4Br-2-(CH2SC6F4-4-H)] (2), trans-[PdCl2{C6H4Br-2-(CH2SC6F5)}2] (6), trans-
[PtCl2{C6H4Br-2-(CH2SC6F5)}2] (7)
Compound
[C6H4Br-2-
(CH2SC6F5)] (1)
[C6H4Br-2-(CH2SC6F4-4-
H)] (2)
trans-[PdCl2{C6H4Br-2-
(CH2SC6F5)}2] (6)
trans-[PtCl2{C6H4Br-2-
(CH2SC6F5)}2] (7)
Empirical formula
Formula weight
Temperature (K)
Crystal system
C
369.15
291(2)
orthorhombic
P212121
13H6BrF5S
C13H7BrF4S
351.16
293(2)
monoclinic
P21
C52H24Br4Cl4F20Pd2S4
1831.19
293(2)
monoclinic
C2/c
C26H12Br2Cl2F10PdS2
1004.29
293(2)
triclinic
ꢀ
Space group
P1
Crystal size (mm)
Unit cell dimensions
0.39 · 0.13 · 0.12
0.622 · 0.094 · 0.038
0.168 · 0.64 · 0.064
0.202 · 0.174 · 0.064
˚
a (A)
5.3598(8)
8.7186(13)
28.420(4)
90
90
90
1328.1(3)
4
1.846
8.861(1)
5.2560(6)
14.039(2)
90
102.776
90
637.7(1)
2
1.829
21.206(2)
16.006(1)
21.711(2)
90
111.243(2)
90
6869(1)
4
1.771
12.981(2)
13.248(2)
18.355(3)
89.467(3)
78.970(3)
75.116(3)
2991.6(8)
4
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Density (g/cm3)
h Range for data
collection
2.230
1.59 a 32.70ꢁ
2.44 a 25ꢁ
1.49 a 31.55ꢁ
1.64 a 30.60ꢁ
Reflections collected
7279
5703
41498
59248
Independent reflections 2346(0.0429)
3695(0.0560)
10441(0.1331)
21378(0.0705)
(Rint
)
F(000)
720
344
3520
1888
Absorption correction
Goodness-of-fit on F2
R indices (all data)
analytical
0.838
analytical:face indexed
0.957
analytical:face indexed
0.995
analytical:face indexed
0.971
R1 = 0.0655,
wR2 = 0.0558
R1 = 0.0350,
wR2 = 0.0526
2346/0/181
R1 = 0.1046,
wR2 = 0.0592
R1 = 0.0361,
wR2 = 0.0532
3695/1/172
R1 = 0.2569,
wR2 = 0.2790
R1 = 0.0863,
wR2 = 0.2540
10441/0/350
R1 = 0.1598,
wR2 = 0.0615
R1 = 0.0498,
wR2 = 0.0524
21378/0/790
Final R indices
[I > 2r(I)]
Data/restrains/
parameters
Index ranges
ꢀ6 6 k 6 6,
ꢀ10 6 h 6 10,
ꢀ33 6 l 6 27
ꢀ12 6 k 6 10,
ꢀ7 6 h 6 7,
ꢀ30 6 k 6 30,
ꢀ21 6 h 6 22,
ꢀ30 6 l 6 30
ꢀ19 6 k 6 19,
ꢀ19 6 h 6 20,
ꢀ27 6 l 6 23
ꢀ16 6 l 6 19
Fig. 2. An ORTEP representation of the structure of [C6H4Br-2-
Fig. 1. An ORTEP representation of the structure of [C6H4Br-2-
(CH2SC6F4-4-H)] (2). Displacement ellipsoids are drawn at 50% proba-
bility level showing the atom labeling scheme. Bond lengths (A): Br(1)–
(CH2SC6F5)] (1). Displacement ellipsoids are drawn at 50% probability
level showing the atom labeling scheme. Bond lengths (A): Br(1)–C(9)
˚
˚
C(8) 1.904(3), S(1)–C(1) 1.749(4) S(1)–C(13) 1.831(4). Bond angles (ꢁ):
C(1)–S(1)–C(13) 99.63(16).
1.882(4), S(1)–C(1) 1.761(4), S(1)–C(7) 1.824(4). Bond angles (ꢁ): C(1)–
S(1)–C(7) 99.69(18).
yellowish or colorless oils. For the particular cases of com-
pounds 1 and 2, these oily products slowly crystallize with
time.
attained in a very facile manner by simple filtration of the
resulting solution through a short plug of Celiteꢂ. Further
evaporation under vacuum of the filtrates afford in all cases

A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
4137
3.2318 Å
3.277 Å
Fig. 3. An ORTEP representation of the structure of trans-
[PdCl2{C6H4Br-2-(CH2SC6F5)}2] (6). Displacement ellipsoids are drawn
Fig. 4. An ORTEP representation of the structure of trans-
[PtCl2{C6H4Br-2-(CH2SC6F5)}2] (7). Displacement ellipsoids are drawn
at 50% probability level showing the atom labeling scheme. Hydrogen
at 50% probability level showing the atom labeling scheme. Hydrogen
˚
atoms have been omitted for clarity. Bond lengths (A): Pd(1)–Cl(1)
2.307(2), Pd(1)–Cl(1)#1 2.307(2), Pd(1)–S(1) 2.314(3), Pd(1)–S(1)#1
2.314(3), Pd(1)–Pd(2) 3.2318(17), Pd(2)–S(2) 2.313(3), Pd(2)–S(2)#1
2.313(3), Pd(2)–Cl(2)#1 2.316(3), Pd(2)–Cl(2) 2.316(3). Bond angles (ꢁ):
Cl(1)–Pd(1)–Cl(1)#1 179.02(15), Cl(1)–Pd(1)–S(1) 95.23(10), Cl(1)#1–
Pd(1)–S(1) 84.78(10), Cl(1)–Pd(1)–S(1)#1 84.78(10), Cl(1)#1–Pd(1)–
S(1)#1 95.23(10), S(1)–Pd(1)–S(1)#1 178.94(16), Cl(1)–Pd(1)–Pd(2)
90.49(7), Cl(1)#1–Pd(1)–Pd(2) 90.49(7), S(1)–Pd(1)–Pd(2) 89.47(8),
S(1)#1–Pd(1)–Pd(2) 89.47(8), S(2)–Pd(2)–S(2)#1 179.47(16), S(2)–Pd(2)–
Cl(2)#1 95.36(11), S(2)#1–Pd(2)–Cl(2)#1 84.63(11), S(2)–Pd(2)–Cl(2)
˚
atoms have been omitted for clarity. Bond lengths (A): Pt(1)–S(2)
2.2807(15), Pt(1)–S(1) 2.2859(14), Pt(1)–Cl(2) 2.2891(14), Pt(1)–Cl(1)
2.2905(14), Pt(2)–S(3) 2.2814(13), Pt(2)–Cl(3) 2.2866(15), Pt(2)–Cl(4)
2.2878(16), Pt(2)–S(4) 2.2930(13). Bond angles (ꢁ): S(2)–Pt(1)–S(1)
174.56(5), S(2)–Pt(1)–Cl(2) 84.10(5), S(1)–Pt(1)–Cl(2) 95.03(5), S(2)–
Pt(1)–Cl(1) 95.73(5), S(1)–Pt(1)–Cl(1) 85.47(5), Cl(2)–Pt(1)–Cl(1)
176.37(6), S(3)–Pt(2)–Cl(3) 95.12(5), S(3)–Pt(2)–Cl(4) 84.70(5), Cl(3)–
Pt(2)–Cl(4) 175.70(6), S(3)–Pt(2)–S(4) 169.46(5), Cl(3)–Pt(2)–S(4)
85.73(5), Cl(4)–Pt(2)–S(4) 95.24(5).
84.63(11),
S(2)#1–Pd(2)–Cl(2)
95.36(11),
Cl(2)#1–Pd(2)–Cl(2)
177.49(16), S(2)–Pd(2)–Pd(1) 90.26(8), S(2)#1–Pd(2)–Pd(1) 90.27(8),
Cl(2)#1–Pd(2)–Pd(1) 91.26(8), Cl(2)–Pd(2)–Pd(1) 91.26(8).
diffraction analysis were obtained by slow crystallization
of the parent oily product, thus the identity of these species
was unequivocally identified. Both structures show the sul-
fur center in an angular geometry, with angles slightly devi-
ating [C(1)–S(1)–C(7) 99.69(18) (1) and C(1)–S(1)–C(13)
99.63(16) (2)] from the expected ideal tetrahedral geometry
of 109.5ꢁ, this probably being due to both steric hindrance
and electrostatic repulsion effects of the substituents. In
fact, no p–p stacking interaction can be identified in these
species as has been observed in other cases where fluori-
nated C6F5 or C6F4-4-H fragments were present in the mol-
ecules [24]. It is noteworthy, that in both cases the
molecules crystallize in chiral crystal systems, this can be
attributable to the fact that molecules of compounds 1
and 2 are static in the solid state, thus exhibiting a chiral
axis similar to those observed in compounds like BINOL.
To corroborate this, optical rotation measurements were
carried out for both compounds at room temperature in
CH2Cl2 (conc = 1 mg/mL) resulting in 0ꢁ in both cases.
The oxidative addition of C–X bonds has been identified
as a very important process in multiple organic transforma-
tions catalyzed by transition metal compounds, this being
particularly true in the case of the Heck coupling reaction.
For all compounds, analyses by proton NMR spectros-
copy show signals due to the presence of the aromatic pro-
tons around d 6.8–7.7 ppm, and signals due to the
methylene group (CH2) in the range of d 4.07–4.23 ppm.
Analysis by 19F NMR spectroscopy shows signals due to
the presence of the ꢀSC6F5 group which are observed for
compound 1 at d ꢀ130.87, ꢀ150.93 and ꢀ160.27 ppm for
the fluorine atoms in the ortho, para and meta positions,
respectively with the usual splitting pattern [23]. Similar
observations are obtained for compound 2 with signals
assigned to the fluorine atoms in the ortho and meta posi-
tions at d ꢀ132.01 and ꢀ131.70 ppm, respectively. For
the case of compounds 3, 4 and 5, unique signals are
observed for all three compounds at ꢀ107.45 (3),
ꢀ111.16 (4) and ꢀ112.99 (5), respectively. Further analysis
of these compounds by EI-mass spectrometry shows in all
cases the molecular ion plus one unit [M+1]+ at 370 (1),
352 (2) and 298 m/z for 3, 4 and 5, respectively. Elemental
analysis of all five compounds agrees well with the pro-
posed formulations. Additionally, crystals of compounds
1 (Fig. 1) and 2 (Fig. 2), suitable for single crystal X-ray

4138
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Br
SRF
Toluene
reflux
[Pb(SRF)]2
+
+ PbCl2
Br
Br
F
F
F
F
F
F
F
F
F
(1)
(2)
SRF =
F
F
F
(3)
(4)
(5)
Scheme 1. Synthesis of the ligands [C6H4Br-2-(CH2SRF)] SRF = SC6F5 (1), SC6H4-4-H (2), SC6H4-2-F (3), SC6H4-3-F (4), SC6H4-4-F (5).
In fact, advances in the study of this reaction have lead to a
number of research groups to the efficient activation of C–
Cl bonds [25] in less than a decade, thus turning the Heck
reaction into a truly powerful tool in organic synthesis and
an corner stone in the design of highly efficient procedures
that have already been scaled to the industrial level [26].
Hence, considering the use of typical starting materials
containing M(II) M = Ni, Pd or Pt, it could be expected
that C–Br activation on ligands 1–5 could proceed thus
leading to the formation of C–S chelated metallocyclic
compounds. Thus, we decide to explore this possibility by
reacting compound 1 with NiCl2, [CODPdCl2] and cis-
[(MeCN)2PtCl2], the reaction conditions were identical in
the three cases, reflux in toluene for 24 h. In the case of
NiCl2, only decomposition products were obtained and
the reaction mixture was not further analyzed. For the case
of [CODPdCl2] and cis-[(MeCN)2PtCl2] (Scheme 2), the
reactions were cleaner and after the prescribed reaction
time, yellow-orange powders were isolated, these products
were filtered and analyzed by proton NMR.
The corresponding spectra exhibit signals in the usual
area for aromatic protons, additionally signals due to the
methylene groups are found at about d 4.6–4.7 ppm for both
complexes. However, the results obtained from the 19F
NMR were more informative, exhibiting unique signals with
typical splitting patterns centered at d ꢀ129.98, ꢀ150.09 and
ꢀ159.44 ppm for the ortho, para and meta fluorine atoms for
the ꢀSC6F5 fragment in the palladium derivative (6). Analo-
gously, the 19F NMR spectrum of the platinum product (7),
shows signals at d ꢀ128.17, ꢀ143.47 and ꢀ155.97 ppm for
the ortho, para and meta fluorine atoms in the fluorinated
fragment. Further analyses of complex (6) by FAB+-mass
spectrometry showed the molecular ion at 748 m/z due to
the loss of a ꢀSC6F5 fragment. Similar analysis for com-
pound (7) shows the molecular ion at 666 m/z due to the loss
ofone [C6H4Br-2-(CH2SC6F5)] ligand. Theseresults indicate
that no C–Br activation happens at all, and a more common
sulfur coordination of the thioether compounds to the metal
centers had occurred. Elemental analysis is also consistent
with formulations having two ligand molecules attached to
each metal center. For both complexes, we were able to
obtain crystals suitable for their single crystal X-ray diffrac-
tion analysis, thus confirming unequivocally the proposed
structures for complexes 6 (Fig. 3) and 7 (Fig. 4).
Both crystal structures are very similar and thus they
share a number of common features. In both structures
the palladium and platinum centers are located in slightly
distorted square planar environments, bearing two mole-
cules of the ligand [C6H4Br-2-(CH2SC6F5)] in a trans
arrangement with two chloride ligands completing the cor-
responding coordination spheres. In both molecules, the
two thioether ligands are oriented in a syn configuration,
thus both ligands are oriented to the same direction leaving
the opposite face practically serving as the base of an open
box. This arrangement apparently favors metal–metal
interactions in the solid state. Hence, the average Pd–Pd
(Fig. 3) and Pt–Pt (Fig. 4) distances are 3.2318 and
˚
3.620 A respectively. In all other respects the bond dis-
tances and angles are within the expected values.
In view of the results reached with the metallic starting
materials employed, we decided to explore further the reac-
tivity of these fluorinated ligands, to see whether it could be
possible at all to carry out C–Br oxidative addition reac-
tions employing these fluorinated thioethers. Thus, we car-
ried out reactions of the ligand [C6H4Br-2-(CH2SC6F5)],
this time with group 10 starting materials in the zero oxida-
tion state, namely, [(dippe)NiH]2, [Ni(PEt3)4], [Pd(PEt3)4],
[Pd(dba)2] and [Pt(PEt3)3]. The reactions with [(dippe)-
NiH]2, [Ni(PEt3)4], [Pd(PEt3)4] and [Pd(dba)2] in THF as
solvent afforded in all cases complex mixtures of products,
that in most of the cases decomposed in the workup pro-
cess (Scheme 2). Apparently, some of the products formed

A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
4139
C6F5
S
Cl
Br
Pd
Br
Cl
S
C6F5
(6)
+ COD
SC6F5
Br
C6F5
S
Cl
Br
Pt
Br
Cl
S
C6F5
(7)
+ PhCN
Scheme 2. Synthesis of the trans-[MCl2{C6H4Br-2-(CH2SRF)}2] M = Pd(II) (6) or Pt(II) (7) complexes.
involved desulfurization of the ligand and C–H activation
processes as is indicative for the formation of hydrides
(detected by H NMR), observed particularly with the Ni
starting materials, thus these products were not further
analyzed (Scheme 3).
Conversely, complex [Pt(PEt3)3] reacts smoothly in THF
with ligand [C6H4Br-2-(CH2SC6F4-4-H)] to afford a single
product (Scheme 4) detectable by 31P NMR spectroscopy,
this spectrum exhibits a unique signal at d 10.095 ppm,
with the corresponding satellites at 21.226 and
d
1
ꢀ1.039 ppm respectively, with a Pt–P coupling constant
of J1Pt–P ¼ 2:7 KHz.
These data are in agreement with a compound having a
single kind of phosphorus coordinated to the Pt center. The
1H NMR analysis of the same sample shows signals
between d 6.55 and 7.65 ppm due to the presence of the
complex mixture
[(dippe)NiH]2
F
F
F
S
F
F
Br
complex mixture
complex mixture
Scheme 3. Reactivity of the ligand [C6H4Br-2-(CH2SC6F5)] (1) towards [(dippe)NiH]2, [Pd(PEt3)3] and [Ni(PEt3)3].

4140
A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
F
F
F
S
F
F
F
F
S
THF
reflux
+ [Pt(PEt3)3]
F
PEt3
Br
Br
Pt
+ PEt3
Et3P
(8)
Scheme 4. Reactivity of the ligand [C6H4Br-2-(CH2SC6F4-4-H)] (2) with [Pt(PEt3)3].
aromatic protons, and these signals exhibit satellites con-
firming the coordination of the Pt metal center to the aro-
matic ring, most likely via the C–Br activation. This
conclusion is also based on the fact that no hydride signals
F
2
1
3
F
F
1
are observed at a higher field in the H NMR spectrum,
4
7
5
6
thus ruling out a potential metallation via C–H activation
in a different position in the aromatic ring. Additionally,
a multiplet showing the presence of the proton of the
ꢀSC6F4-4-H is clearly observed at d 6.3 ppm. The signals
due to the ethyl groups in the phosphine are observed as
multiplets centered at d 1.59 ppm for the methylenes and
at d 0.89 ppm for the methyl groups. The signals corre-
sponding to the methylene of the benzyl group are very
interesting since two different signals are observed at d
4.72 and 3.85 ppm, respectively, the later exhibiting satel-
lites, this fact can be attributable to an interaction through
the space of one of the protons of the benzylic methylene,
thus justifying the magnetic difference of the two protons in
the CH2 group (Scheme 5).
Results in agreement with the proposed structure for 8
were also obtained from the analysis of the 13C NMR spec-
trum where the eleven different carbons corresponding to
the fluorinated thioether are detected. The quaternary car-
bon bound to the Pt center is observed at d 118 ppm
(Scheme 6).
8
9
S
F
PEt3
Br
11
Pt
10
Et3P
Scheme 6.
a PEt3 ligand [MꢀPEt3]+ and finally a peak at 584 m/z that
represents the parent peak due to the consecutive loss of a
ꢀBr and a PEt3 ligand.
Some preliminary experiments using the palladium com-
plex 6 as catalytic precursor in Heck reaction couplings
using bromobenzene and styrene and Na2CO3 as base in
DMF were carried out. However, probably due to the loss
of the loosely attached fluorinated thioether ligands [28],
complex 6 tends to decompose rapidly under the reaction
conditions, thus affording total yields of only 25% of stilb-
enes (trans/cis = 7:3) after 5 h of reaction time at 120 ꢁC. It
is very likely that the analogous species derived from the
other ligands (2–5) would yield similar results.
Finally, analysis by FAB+-MS of this compound agrees
well with the proposed structure, showing the molecular
ion at 782 m/z with the appropriated isotopic distribution
[27]. Other important peaks are observed at 702 and 664
m/z, corresponding to the loss of a bromide [MꢀBr]+ or
Experiments using chlorobenzene resulted only in traces
of the products probably as a consequence of the quick and
clear decomposition of the complexes in the reaction mix-
ture to palladium black.
In summary, we have reported the markedly different
reactivity exhibited by the fluorinated thioether compounds
of the type [C6H4Br-2-(CH2SRF)] towards group 10 transi-
tion metal starting materials. As expected, the reactivity is
clearly dependant on the oxidation state of the metal cen-
ter, thus plain coordination to sulfur to attain coordination
compounds seems to be the general trend for those com-
pounds bearing M(II), while reactions with complexes hav-
ing M(0) result in complex mixtures of products that
prevent further analysis, except for [Pt(PEt3)3] where the
C–Br oxidative addition product [PtBr(PEt3)2{C6H4(CH2-
SC6F5)}] (8) was identified. Finally, preliminary catalytic
experiments using complex trans-[PdCl2{C6H4Br-2-(CH2-
SC6F5)}] (6) as catalyst show these species to be poor
F
F
F
H
S
F
H
PEt3
Br
Pt
Et3P
(8)
Scheme 5.

A.I. Olivos-Sua´rez et al. / Inorganica Chimica Acta 360 (2007) 4133–4141
4141
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CCDC 639876, 639877, 639878 and 639879 contain the
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These data can be obtained free of charge via http://
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Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
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thank Chem. Eng. Luis Velasco Ibarra, M.Sc. Francisco
´
´
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Javier Perez Flores, Erendira Garcıa Rıos and Ma. de las
Nieves Zavala for their invaluable help in the running of
the FAB+-Mass, IR and 19F{1H} spectra, respectively.
The support of this research by CONACYT (J41206-Q)
and DGAPA-UNAM (IN114605) is gratefully acknow-
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