Synthesis and characterization of sterically hindered thiolate Pd(II) complexes of the type [Pd(SR)2(TMEDA)]: Examination of their catalytic properties in phosphane-free Suzuki-Miyaura cross couplings

Article abstract of DOI:10.1016/j.ica.2009.08.013

The sterically hindered thiolate complexes [Pd(SR)₂(TMEDA)] SR = SC₆F₅ (2), SC₆F₄-4-H (3), SC₆H₄-2-SiPh₃ (4) were easily synthesized by metathetical reactions of the corresponding palladium chloro compound [Pd(Cl)₂(TMEDA)] (1) and the lead salt of the corresponding thiol. The identity of the three species being unequivocally determined by single crystal X-ray diffraction techniques. The catalytic activity of the palladium species [Pd(SR)₂(TMEDA)] was explored in the Suzuki-Miyaura cross coupling reactions of different p-substituted bromobenzenes.

Full text of DOI:10.1016/j.ica.2009.08.013

Inorganica Chimica Acta 363 (2010) 1222–1229
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Inorganica Chimica Acta
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Synthesis and characterization of sterically hindered thiolate Pd(II) complexes of the
type [Pd(SR)2(TMEDA)]: Examination of their catalytic properties in phosphane-free
Suzuki-Miyaura cross couplings
Manuel Basauri-Molina, Simón Hernández-Ortega, Rubén A. Toscano, Jesús Valdés-Martínez,
*
David Morales-Morales
Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito exterior, Coyoacán 04510, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 May 2009
Received in revised form 4 August 2009
Accepted 12 August 2009
Available online 19 August 2009
The sterically hindered thiolate complexes [Pd(SR)2(TMEDA)] SR = SC6F5 (2), SC6F4-4-H (3), SC6H4-2-SiPh3
(4) were easily synthesized by metathetical reactions of the corresponding palladium chloro compound
[Pd(Cl)2(TMEDA)] (1) and the lead salt of the corresponding thiol. The identity of the three species being
unequivocally determined by single crystal X-ray diffraction techniques. The catalytic activity of the pal-
ladium species [Pd(SR)2(TMEDA)] was explored in the Suzuki–Miyaura cross coupling reactions of differ-
ent p-substituted bromobenzenes.
This paper is dedicated with great
admiration to the teacher and friend Prof.
Jonathan R. Dilworth on the occasion of his
65th birthday.
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
C–C cross coupling reactions
Suzuki–Miyaura reaction
Palladium complexes
Thiolate compounds
TMEDA
Crystal structures
Catalysis
1. Introduction
for industrially relevant organic transformations [3]. Although in
these cases the probable structure of the resulting species may well
The N,N,N0,N0-tetramethylethylenediamine (TMEDA) has been
widely studied as a N–N quelate ligand with a wide variety of tran-
sition-metals, today being known complexes of most of the transi-
tion-metals with this ligand. The importance of TMEDA in modern
chemistry has arrived with the astonishing advancement that
supramolecular chemistry and crystal engineering have had in the
last decade, being this diamine employed as chelate-blocking ligand
in order to reduce degrees of freedom in the formation of ordered
molecular networks thus allowing the potential prediction of com-
plex solid state arrangements [1]. The application of this species has
not been limited to its direct use as ligand in coordination chemis-
try, but for long time been used as a fundamental ingredient in lith-
iation reactions enhancing the nucleophilicity of lithium derivatives
or stabilizing intermediates relevant in organic synthesis [2]. In fact,
in recent years organic chemists have turned their attention to the
use of TMEDA as ligand for the stabilization of a number of metals
be assumed, no studies have been carried out using well defined
TMEDA complexes in, for instance, cross coupling reactions.
In addition, monomeric platinum group metal complexes con-
taining thiolate ligands on its structure do not occur regularly
[4], due in part to the well known tendency of these complexes
to polymerize [5], affording in most of the cases intractable solids
useless as potential catalysts in homogeneous catalysis. Usually,
compounds containing sulfur on its structure have been neglected
as potential homogeneous catalysts due to the extended belief of
sulfur to be a catalyst poison. Thus, given our continuous interest
in the design and synthesis of active and robust complexes for their
employment as potential catalysts in industrial relevant transfor-
mations [6], and the used of sterically hindered thiolates for the
potential fine tuning of electronic properties [7], we would like
to report here the synthesis and characterization of the complexes
[Pd(SR)2(TMEDA)] SR = SC6F5 (2), SC6F4-4-H (3), SC6H4-2-SiPh3 (4)
and their use as catalysts precursors for the efficient Suzuki–
Miyaura cross coupling reactions of different para-substituted
bromobenzenes.
* Corresponding author. Tel.: +52 55 56224514; fax: +52 55 56162217.
E-mail address: damor@unam.mx (D. Morales-Morales).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.08.013

M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
1223
[Pb(SR)2]; SR = C6F5, C6F4-4-H, C6H4-2-F, C6H4-3-F, C6H4-4-F were
prepared according to published procedures [9].
2. Experimental
2.1. Material and methods
2.2. Synthesis of [PdCl2(TMEDA)] (1)
Unless stated otherwise, all reactions were carried out under an
atmosphere of dinitrogen using conventional Schlenk glassware,
solvents were dried using established procedures and distilled un-
der dinitrogen immediately prior to use. The 1H NMR spectra were
recorded on a JEOL GX300 spectrometer. Chemical shifts are re-
ported in ppm down field of TMS using the solvent (CDCl3,
d = 7.27) as internal standard. 19F{1H} spectra were recorded with
complete proton decoupling and are reported in ppm using C6F6
as external standard. 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 acceler-
ating voltage of 10 kV. Samples were desorbed from a nitrobenzyl
alcohol (NOBA) matrix using 3 keV xenon atoms. Mass measure-
ments in FAB are performed at a resolution of 3000 using magnetic
field scans and the matrix ions as the reference material or, alter-
natively, by electric field scans with the sample peak bracketed
by two (polyethylene glycol or cesium iodide) reference ions. Melt-
ing 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 cap-
illary column coupled to an Agilent 5973 Inert Mass Selective
detector. The PdCl2 was purchased from Pressure Chemical Co.,
and TMEDA, [Pb(CH3COO)2], HSC6F5, HSC6F4-4-H, HSC6H4-2-F,
HSC6H4-3-F, HSC6H4-4-F were commercially obtained from Aldrich
Chemical Co. All compounds were used as received without further
purification. The starting materials HSC6H4-2-SiPh3 [8] and
The title compound was synthesized by a slight modification of
the method reported by Van Koten and co-workers [10]. Thus, to a
suspension of PdCl2 (100 mg, 0.56 mmol) in CH2Cl2 (20 mL), an ex-
cess of TMEDA (0.1 mL, 6.62 mmol) was added dropwise under
stirring, the solution was allowed to proceed under stirring for
2 h. After this time, the formation of a yellow solid was observed
which was filtered off and then washed with hexane (2 ꢀ 10 mL).
Yield 91%.
2.3. Synthesis of [Pd(SC6F5)2(TMEDA)] (2)
To a solution of [Pd(Cl)2(TMEDA)] (1) (50.00 mg, 0.1703 mmol)
in methylene chloride (10 mL),
a solution of [Pb(SC6F5)2]
(103.1 mg, 0.1703 mmol) in acetone (30 mL) was added dropwise
under stirring, the resulting deep red solution was allowed to stir
overnight, after such a time, the solution was filtered through a
short plug of CeliteÒ and the solvent removed under vacuum.
The residue was recrystallized from CH2Cl2–hexane, to afford
[Pd(SC6F5)2(TMEDA)] (2) as a red microcrystalline powder. Yield
76%. M.P.: 190–193 (decomposition). NMR 1H (300 MHz, CDCl3), d
2.79 (s, CH3, 12H), 2.81 (s, CH2, 4H); NMR 19F{1H} (282 MHz, CDCl3),
d ꢁ136.92 (m, o-F), ꢁ165.34 (t, J3F–F = 21.15 Hz, p-F), ꢁ168.45 (m, p-
F). MS-FAB+ [M+] = 620 (30%) m/z, [M+-SC6F5] = 421 (61%) m/z,
[M+ꢁ2 SC6F5] = 221 (42%) m/z. Anal. Calc. for C18H16F10N2PdS2
(Mr = 620.87): C, 34.82; H, 2.60. Found: C, 34.89; H, 2.56%.
Table 1
Crystal data and structure parameters for [Pd(SC6F5)2(TMEDA)] (2), [Pd(SC6F4-4-H)2(TMEDA)] (3) and [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4).
Identification code
(2)
(3)
(4)
Empirical formula
Formula weight
C18H16F10N2PdS2
620.85
C18H18F8N2PdS2
290.86
C54H54N2PdS2Si2ꢂCH2Cl2
1042.62
Temperature (K)
298(2)
0.71073
298(2)
0.71073
298(2)
0.71073
0
Wavelength (AÅ)
Crystal system
Space group
monoclinic
C2/c
monoclinic
I2/a
monoclinic
P2/n
Unit cell dimensions
0
9.0015(8)
13.1230(10)
10.8040(10)
15.352(2)
20.7892(11)
11.1242(6)
22.4803(12)
a (AÅ)
0
19.9065(18)
12.2688(11)
b (AÅ)
0
c (AÅ)
a
(°)
90
90
90
b (°)
99.7990(10)
99.7880(10)
94.5510(10)
c
(°)
90
2166.4(2)
90
2144.9(4)
90
5182.5(5)
Volume (Å3)
Z
4
4
4
Density (calc.) (Mg/m3)
Absorption coefficient (mmꢁ1
F(0 0 0)
1.904
1.144
1224
1.811
1.136
1160
1.336
0.626
2160
)
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.26 ꢀ 0.10 ꢀ 0.06
2.05–24.98
ꢁ10 ꢃ h ꢃ 10, ꢁ23 ꢃ k ꢃ 23,
ꢁ14 ꢃ l ꢃ 14
8633
0.298 ꢀ 0.116 ꢀ 0.088
2.32–25.38
ꢁ15 ꢃ h ꢃ 15, ꢁ13 ꢃ k ꢃ 13,
ꢁ18 ꢃ l ꢃ 18
8660
0.30 ꢀ 0.25 ꢀ 0.18
1.82–25.35
ꢁ25 ꢃ h ꢃ 25, ꢁ13 ꢃ k ꢃ 13,
ꢁ27 ꢃ l ꢃ 27
6152
Reflections collected
Independent reflections [Rint
Absorption correction
Maximum and minimum
transmission
]
1910 [0.0405]
Analytical
0.9443 and 0.7925
1969 [0.0337]
Analytical
0.9158 and 0.7861
9505 [0.0648]
None
Refinement method
Full-matrix least-squares on F2
1910/0/152
0.949
Full-matrix least-squares on F2
1969/0/143
1.001
Full-matrix least-squares on F2
9505/37/601
0.848
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0306, wR2 = 0.0603
R1 = 0.0363,wR2 = 0.0618
0.590 and ꢁ0.387
R1 = 0.0224, wR2 = 0.0499
R1 = 0.0252, wR2 = 0.0509
0.354 and ꢁ0.197
R1 = 0.0425, wR2 = 0.0740
R1 = 0.0723, wR2 = 0.0809
0.581 and ꢁ0.401
Largest difference peak and hole
(eÅꢁ3
)
R1 = |FoꢁFc|/|Fo|, wR2 = [w((Fo)2ꢁ(Fc)2ꢁw(Fo)2]1/2
.

1224
M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
Table 2
Bond distances (Å), and angles (°) for compounds 2–4.
2
3
4(a)
4(b)
Pd1–S1
Pd1–N1
2.2870(9)
2.128(3)
176.04(7)
92.02(3)
91.78(7)
84.45(10)
105.41(19)
106.44(10)
121.3(2)
123.9(2)
ꢁ135.0(2)
47.0(3)
Pd1–S1
Pd1–N1
2.2900(6)
2.1223(18)
174.07(5)
90.59(2)F4
92.65(5)
Pd1–S1
Pd1–N1
2.2696(9)
2.152(4)
93.66(10)
90.05(3)
173.29(11)
83.21(14)
110.98(11)
105.0(3)
118.1(2)
122.8(3)
179.3(2)
ꢁ1.4(3)
Pd2–S2
Pd2–N2
S2–Pd2–N2
2.2833(10)
2.145(3)
92.52(7)
91.50(3)
172.89(8)
84.10(10)
110.05(11)
104.9(2)
119.1(2)
122.0(3)
179.3(2)
ꢁ0.5(3)
S1–Pd1–N1
S1–Pd1–S1_a
S1–Pd1–N1_a
N1–Pd1–N1_a
Pd1–N1–C7
Pd1–S1–C1
S1–C1–C2
S1–C1–C6
Pd1–S1–C1–C2
Pd1–S1–C1–C6
N1–C7–C7a–N1a
N1–Pd1–S1–C1
S1–Pd1–N1
S1–Pd1–S1_a
S1–Pd1–N1_a
N1–Pd1–N1_a
Pd1–N1–C7
Pd1–S1–C1
S1–C1–C2
S1–C1–C6
Pd1–S1–C1–C2
Pd1–S1–C1–C6
N1–C7–C7a–N1a
N1–Pd1–S1–C1
S1–Pd1–N1
S1–Pd1–S1_a
S1–Pd1–N1_a
N1–Pd1–N1_a
Pd1–S1–C1
Pd1–N1–C25
S1–C1–C2
S1–C1–C6
S2–Pd2–S2_b
S2–Pd2–N2_b
N2–Pd2–N2_b
Pd2–S2–C28
Pd2–N2–C52
S2–C28–C29
S2–C28–C33
Pd2–S2–C28–C29
Pd2–S2–C28–C33
N2–C52–C52b–N2b
84.57(7)
105.10(13)
105.36(8)
124.70(17)
120.82(17)
46.7(2)
Pd1–S1–C1–C2
Pd1–S1–C1–C6
N1–C25–C25a-N1a
ꢁ138.27(17)
56.4(4)
115(1)
57.9(2)
ꢁ40.8(9)
58.1(4)
67.4(5)
Fig. 1. Representation of molecules 2–4, showing the atom labeling scheme of the asymmetric unit atoms (thermal ellipsoids plotted at 30% probability). H atoms and
symmetry generated atoms are shown as circles of arbitrary radius. The structure of the two independent molecules in 4 are shown as 4(a) and 4(b), solvent molecules in 4
not shown for clarity.
2.4. Synthesis of [Pd(SC6F4-4-H)2(TMEDA)] (3)
Me Me
N
Me Me
N
Cl
Cl
SR
SR
+
Pd
[Pb(SR)2]
Pd
+
PbCl2
The title complex was synthesized in similar manner as that of
complex (2) from: [Pd(Cl)2(TMEDA)] (1) (50.0 mg, 0.1703 mmol) in
N
N
Me Me
Me Me
methylene chloride (10 mL),
a solution of [Pb(SC6F4-4-H)2]
(1)
(97.0 mg, 0.1703 mmol) in acetone (30 mL). Yield 77%. M.P: 264–
267 (decomposition). NMR 1H (300 MHz, CDCl3), d 2.79 (s, CH3,
12H), 2.83–2.94 (s, CH2, 4H), 6.68 (m, SC6F4-4-H, 2H). NMR
SR = SC6F5 (2), SC6F4-4-H (3), SC6H4-2-SiPh3 (4)
Scheme 1. General route of synthesis of the complexes [Pd(SR)2(TMEDA)].

M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
1225
19F{1H} (282 MHz, CDCl3), d ꢁ133.04 (m, o-F), ꢁ141.25 (m, m-F).
3. Results and discussion
MS-FAB+ [M+] = 584 (12%) m/z, [M+-SC6F4-4-H] = 403 (16%) m/z,
[M+-2 SC6F4-4-H] = 221 (8%) m/z. Anal. Calc. for C18H18F8N2PdS2
(Mr = 584.89): C, 36.96; H, 3.10. Found: C, 36.93; H, 3.15%.
The stoichiometric reactions of [Pd(Cl)2(TMEDA)] (1) with the
corresponding thiolate-lead salts [Pb(SR)2] (ꢁSR = ꢁSC6F5, ꢁSC6F4-
4-H, ꢁSC6H4-2-SiPh3) afford complexes [Pd(SR)2(TMEDA)]
ꢁSR = ꢁSC6F5 (2), ꢁSC6F4-4-H (3), ꢁSC6H4-2-SiPh3 (4) in good yields
(Scheme 1).
2.5. Synthesis of [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4)
The simplicity on the synthesis of these compounds is compara-
ble to the facility in the analysis of their corresponding 1H NMR
spectra, exhibiting singlets for complex (2) for the methyls and
methylene groups of TMEDA moiety at d 2.71 and 2.81 ppm,
respectively. However, analysis by 19F{1H} NMR were more infor-
mative showing three different multiplets at d ꢁ136.92 (Fo),
ꢁ165.34 (t, J3F–F = 21.15 Hz, Fp) and ꢁ168.45 (Fm) ppm, exhibiting
the presence of the ꢁSC6F5 fragment in the molecule. Further anal-
ysis by FAB+-MS showed the molecular ion at [M+] = 620 (29%) m/z
and two more intense peaks at [M+-SC6F5] = 421 (61%) m/z and
[M+-2SC6F5] = 221 (42%) m/z corresponding to the consecutive loss
of the two thiolate ligands, all these results are in agreement with
the proposed formulation for complex (2).
The title complex was synthesized in similar manner as that of
complex (2) from: [Pd(Cl)2(TMEDA)] (1) (50.0 mg, 0.1703 mmol) in
methylene chloride (10 mL), a solution of [Pb(SC6H4-2-SiPh3)2]
(161 mg, 0.1703 mmol) in acetone (30 mL). Yield 64%. M.P.:
226–229 (decomposition). NMR 1H (300 MHz, CDCl3), d 2.68
(s, CH3, 12H), 2.81 (s, CH2, 4H), 6.71–7.73 (m, Ar, 38H). MS-FAB+
[M+] = 956 (6%) m/z, [M+-SC6H4-2-SiPh3] = 589 (16%) m/z. Anal.
Calc. for C54H54N2PdS2Si2 (Mr = 956.23): C, 67.72; H, 5.68. Found:
C, 67.63; H, 5.72%.
2.6. General method for the Suzuki–Miyaura couplings
A similar 1H NMR spectrum was obtained for compound
[Pd(SC6F4-4-H)2(TMEDA)] (3) presenting signals for the methyl
and methylene fragments at d 2.77 and 2.84 ppm respectively.
Additionally a nice multiplet centered in d 6.69 ppm can be ob-
served this signal being due to the aromatic proton in the SC6F4-
4-H ligands in the molecule. As is the case for compound (2),
the spectrum obtained from the analysis by 19F{1H} NMR was
A DMF solution (5 ml) of 4.0 mmol of halobenzene, 4.0 mmol of
phenyl boronic acid, and the prescribed amount of catalyst (0.1%
mol) was introduced into a Schlenk tube in the open air. The tube
was charged with a magnetic stir bar and an equimolar amount of
base (K2CO3, 4 mmol), and sealed, then fully immersed in a 110 °C
silicon oil bath. After the prescribed reaction time (12 h), the mix-
ture was cooled to room temperature and the organic phase ana-
lyzed by gas chromatography (GC–MS) by duplicate.
more informative, showing two multiplets at
d 133.04 and
ꢁ141.25 ppm due to the fluorine atoms at the ortho and meta posi-
tions in the SC6F4-4-H fragment respectively. In the FAB+-MS spec-
trum of this compound it is possible to observe the molecular ion
at [M+] = 584 (12%) m/z and a similar fragmentation pattern as that
observed for complex [Pd(SC6F5)2(TMEDA)] (3) with peaks at [M+-
SC6F4-4-H] = 403 (16%) m/z and [M+-2SC6F4-4-H] = 221 (8%) m/z.
In the case of complex [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4), analy-
sis by 1H NMR, shows the expected signals for the methyl and
methylene groups at d 2.68 and 2.81 ppm respectively, besides
these signals, a broad multiplet from d 6.7–7.7 ppm can be as-
signed to the protons in the aromatic rings of the ligands SC6H4-
2-SiPh3 in the molecule. Analysis by FAB+-MS exhibit the molecular
ion at [M+] = 956 (6%) m/z. This complex also presents a similar
fragmentation pattern as that observed for species containing the
fluorinated thiolates (2) and (3) with an additional peak in the
spectrum at [M+-SC6H4-2-SiPh3] = 589 (16%) m/z due to the loss
of one of the thiolate ligands. In all cases elemental analysis results
were in agreement with the proposed formulations.
As expected when similar metathetical reactions were carried
out between [Pd(Cl)2(TMEDA)] (1) and lead salts containing less
electron-withdrawing/less sterically hindered groups such as
[Pb(SR)2] SR = C6H4-2-F, C6H4-3-F, C6H4-4-F, the reactions only
afforded insoluble polymers, these compounds were not studied
further.
Additionally, crystals suitable for single crystal X-ray diffraction
analysis of [Pd(SC6F5)2(TMEDA)] (2), [Pd(SC6F4-4-H)2(TMEDA)] (3)
and [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4) were grown by slow evapo-
ration of CH2Cl2/MeOH solvent systems, thus the identity of these
species was unequivocally identified. Given the structural similar-
ity of compounds 2 and 3 they also share a number of molecular
and crystal common structural features and, as expected, 4 has
some important differences. For instance, the asymmetric unit of
compounds 2 and 3 consist in one half of the [Pd(SRF)2(TMEDA)2]
complex, with the Pd atom in special position lying on a twofold
rotational axis. While the crystal structure of complex 4 presents
two half molecules, from now on referred as Pd1 and Pd2, in the
asymmetric unit, with the Pd atoms lying on a twofold rotational
2.7. Data collection and refinement for [Pd(SC6F5)2(TMEDA)] (2),
[Pd(SC6F4-4-H)2(TMEDA)] (3) and [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4)
Crystalline red prisms for [Pd(SC6F5)2(TMEDA)] (2) and
[Pd(SC6F4-4-H)2(TMEDA)] (3) and red-brownish for [Pd(SC6H4-2-
SiPh3)2(TMEDA)] (4) were grown by slow evaporation of CH2Cl2/
MeOH solvent systems, and mounted in random orientation on
glass fibers. In all cases, the X-ray intensity data were measured
at 298 K on a Bruker SMART APEX CCD-based three-circle X-ray
diffractometer system using graphite mono-chromated Mo-K
a
(k = 0.71073 Å) radiation. The detector was placed at a distance
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 integrated with the Bruker SAINT
software package [11] using a narrow-frame integration algorithm.
The integration of the data was done using a monoclinic unit cell in
all cases to yield a total of 8633, 8660 and 6152 reflections for 2, 3,
and 4, respectively to a maximum 2h angle of 50.00° (0.93 Å reso-
lution), of which 1910 (2), 1969 (3) and 9505 (4) were indepen-
dent. Analysis of the data showed in all cases negligible decays
during data collections. The structures were solved by Patterson
method using SHELXS-97 [12] program. The remaining atoms were
located via a few cycles of least-squares refinements and difference
Fourier maps, using C2/c, I2/a and P2/n space groups for complexes
2, 3 and 4 respectively, with Z = 4 for all compounds. 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 with Uiso(H) =
1.2 Ueq of the parent atom in all cases. For all complexes, the final
cycle of refinement was carried out on all non-zero data using
SHELXL-97 [13] and anisotropic thermal parameters for all non-
hydrogen atoms. The details of the structure determinations are
given in Table 1 and selected bond lengths (Å) and angles (°) are
given in Table 2. Geometric calculations were done using PLATON
[14], molecular graphics were done with X-Seeds [15] (Fig. 1).

1226
M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
Fig. 2. (a) p–p interactions, (b) C–Hꢂ ꢂ ꢂF–C H-bonds and (c) molecular packing in 3.
axis, and a CH2Cl2 molecule. The Cl atoms of the solvent molecules
are disordered over two positions with partial occupancies of 0.63
and 0.37. There are no significant differences in geometry between
the two molecules (Table 2). The molecular structures of three
compounds can be described as distorted square planar, with the
TMEDA ligand coordinated in a bidentate manner and two thiol-
ates in a cis conformation completing the coordination sphere
(Fig. 1). Bond distances and angles are within the expected values
(Table 2). The aromatic rings of the thiolates in 2 and 3 are copla-
Table 3
Intermolecular interactions for 2–4.
Cg–Cga
ab
CgI – Perpc
Slippaged
p–p interactions (Å, °)
[Pd(SC6F4-4-H)2
(TMEDA)] (3)
Cg(1)–Cg(1)f
3.574(2)
3.851(2)
0
0
3.393(1)
3.482(1)
1.123
1.645
[Pd(SC6F5)2
(TMEDA)] (2)
Cg(1)–Cg(1)e
-
nar, The SRF rings point one up and one down with respect to the
a
b
c
d
e
f
plane formed by the metal centers and the coordinated atoms, but
deviate from the normal to this plane as indicated by the corre-
sponding N1–Pd1–S1–C1 torsion angles (expected value 90°)
(Table 2). In 4 the angle between the mean planes of the thiolate
rings are 84.0(2)° and 84.8(2)° for Pd1 and Pd2, respectively.
In [Pd(SC6F4-4-H)2(TMEDA)] (3) the molecules are organized in
Distance between ring Centroids (Å).
Dihedral Angle between Planes I and J (o).
Perpendicular distance of Cg(I) on ring J (Å).
Distance between Cg(I) and Perpendicular Projection of Cg(J) on Ring I (Å).
3/2ꢁx, 1/2ꢁy, 1ꢁz.
1/2ꢁx, ꢁ1/2ꢁy, 3/2ꢁz.
the crystal through
actions (Fig. 2b) see Table 3. Chains along the c-axis are formed
through the
hydrogen bonds these chains pack in such a way that when moving
parallel to the crystallographic ac plane, ꢁSRF rings alternate with
TMEDA chelate rings as shown in Fig. 2b.
p
–
p
interactions (Fig. 2a) and C–Hꢂ ꢂ ꢂF–C inter-
interactions. A C10–H10ꢂ ꢂ ꢂ
p(C34–C39) interaction organize Pd1
and Pd2 molecules in chains running along the crystallographic
p–p
interactions. Due to the presence of C–Hꢂ ꢂ ꢂF–C
c-axis (Fig. 4a). These chains are interconnected into a 2D structure
through centrosymmetric C15–H15ꢂ ꢂ ꢂ
p (C7–C12) interactions, as
shown in Fig. 4b and c.
Complexes [Pd(SC6F5)2(TMEDA)] (2), [Pd(SC6F4-4-H)2(TMEDA)]
(3) and [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4) were also tested as cata-
lysts precursors for the C–C Suzuki–Miyaura couplings. Thus, ini-
tial screening of the three species reacting bromobenzene and
phenylboronic acid for the production of biphenyl were performed
(Scheme 2). The reactions were carried out in DMF as solvent and
K2CO3 as the selected base. A typical experiment was set to 110 °C
under continuous stirring, immersed in a silicon bath for 12 h.
After the prescribed reaction time, the resulting reaction mixtures
were allowed to cool down to room temperature and the organic
phase analyzed by gas chromatography (GC/MS). Yields were
determined on the base of the residual bromobenzene and were
the average of two runs.
In [Pd(SC6F5)2(TMEDA)] (2) the molecules are organized by p–p
interactions into chains (Fig. 3a) in such a way that when moving
on the ac plane only -SRF rings (or TMEDA chelate rings) are found,
as shown in Fig. 3b. It is interesting to note how the presence of a
weak C–Hꢂ ꢂ ꢂF–C H-bonds produces such a difference in the packing
of the molecules in the crystal. This results are in agreement to the
importance of C–Hꢂ ꢂ ꢂF–C hydrogen bonds reported by Janiak and
co-workers [16], but is not observed in the structure of the
[Pt(bpy)(SRF)2] (bpy = 2,20-bipyridyl and ꢁSRF = SC6F5, SC6F4-4-H)
compounds previously reported by us [17].
On the other hand, the packing of the molecules in [Pd(SC6H4-2-
SiPh3)2(TMEDA)] (4) is mainly due to the presence of C–Hꢂ ꢂ ꢂ
p

M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
1227
Fig. 3. (a) p–p interactions and (b) molecular packing in [Pd(SC6F5)2(TMEDA)] (2).
Fig. 4. (a) C–H10ꢂ ꢂ ꢂ
p
interactions, (b) C–H15ꢂ ꢂ ꢂp interactions and (c) molecular packing in [Pd(SC6H4-2-SiPh3)2(TMEDA)] (4)
Me
Me
N
N
SR
SR
[Pd] =
Pd
Me
Me
OH
B
Br
OH
+
0.1 mol % [Pd], K2CO3, DMF
110oC, 12 h
R
R
Scheme 2. The Palladium catalyzed Suzuki-Miyaura coupling reaction using [Pd(SR)2(TMEDA)] as catalyst.

1228
M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
Table 4
Suzuki–Miyaura couplings using Pd(SC6F4-4-H)2(TMEDA)] (3) as catalyst precursor.
Me
Me
N
N
SR
SR
[Pd] =
Pd
OH
B
Me
Me
Br
OH
0.1 mol % [Pd], K2CO3, DMF
110oC, 12 h
+
R
R
Entry
1
p-Bromobenzene
% Conversiona
Br
O2N
O2N
88.01
2
3
Br
NC
NC
88.50
Br
O
O
75.30
59.01
43.20
27.60
4
5
6
Br
Cl
Cl
H
Br
H
Br
Me
Me
a
Yields obtained by GC are based on bromobenzene and are the average of two runs.
Although the three complexes were active for this transforma-
straightforward and affords higher yields, suitable characteristics
for a potential use in other cross coupling reactions. The reaction
conditions were the same as those of the preliminary experiments.
On this opportunity different para-substituted bromobenzenes
were reacted (Table 4).
tion, from the results attained it looks clear that the effect of the
thiolate ligand present in the catalyst is not important, compare
yields of biphenyl 37.7 %, 43.2% and 38.1 % for 2, 3 and 4,
respectively.
Given the afore mentioned results, further experiments were
carried out with complex [Pd(SC6F4-4-H)2(TMEDA)] (3), this spe-
cies was arbitrarily selected on the basis that its synthesis is
The results in Table 4 show that those bromobenzenes contain-
ing the more electron withdrawing substituents (more activated)
afford the higher yields of the series. These results are also

M. Basauri-Molina et al. / Inorganica Chimica Acta 363 (2010) 1222–1229
1229
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20.0
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concurrent when correlated with the Hammet parameter values
[18]. This behavior can be clearly observed on Graphic 1 where a
fairly linear trend is observed.
Under this reaction conditions no decomposition of the catalyst
was observed and the performance of the catalyst in a control
experiment in the presence of Hg° does not change. As it is for
many similar chelating species, it is very likely that the deligation
of the thiols may lead to the formation of Pd(0) species, thus serv-
ing the TMEDA ligand as stabilizing ligand and allowing this spe-
cies to be persistent trough the catalytic cycle to perform the
C–C coupling process efficiently, entering into a typical Pd(0)/Pd(II)
catalytic cycle.
In summary, the results obtained clearly show the simplicity for
the synthesis of complexes of the type [Pd(SR)2(TMEDA)] by met-
athetical reactions, these species were tested as precatalyst for
the Suzuki–Miyaura C–C cross coupling reactions of different
para-substituted bromobenzenes under relatively mild conditions,
attaining competitive yields in the absence of phosphine or any
other additive. The study of the solid state structures of these spe-
cies has also revealed some interesting features, clearly showing
the potential of these complexes as building blocks or tectons of
further utility on crystal engineering. This possibility, as well as
the potential application of these complexes in other cross cou-
pling reactions are still in progress.
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4. Supplementary material
CCDC 730885–730887 contains the supplementary crystallo-
graphic data for complexes 2, 3 and 4. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgements
[10] W. De Graaf, J. Boersma, W.J.J. Smeets, A.L. Spek, G. Van Koten, Organometallics
We would like to thank Chem. Eng. Luis Velasco Ibarra, Dr. Fran-
cisco Javier Pérez Flores, Q. Eréndira García Ríos and M.Sc. Ma. de
las Nieves Zavala for their invaluable help in the running of the
FAB+-Mass, IR and some NMR spectra respectively. The financial
support of this research by CONACYT (F58692) and DGAPA-UNAM
(IN227008) is gratefully acknowledged.
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