Fluorosulfur containing pincer potential ligands, 1,3-(CH2SRf)2C6H4 and 1,2,4,5-(CH2SRf)4C6H2. X-ray structure of 1,3-(CH2SC6</su

Article abstract of DOI:10.1055/s-2003-40514

The fluorosulfur containing pincer ligands 1,3-(CH₂SR_f)₂C₆H₄ [R_f = C₆F₅ (1) and 4-HC₆F₄ (2)] and 1,2,4,5(CH₂SR_f)₄

Full text of DOI:10.1055/s-2003-40514

PAPER
1565
Fluorosulfur Containing Pincer Potential Ligands, 1,3-(CH2SRf)2C6H4 and
1,2,4,5-(CH2SRf)4C6H2. X-Ray Structure of 1,3-(CH2SC6F5)2C6H4
Fluorosulfur
C
ontainin
a
gPince
r
Li
r
gands ibel Arroyo,*a Ruy Cervantes,b Valente Gómez-Benítez,c Paola López,a David Morales-Morales,c Hugo Torrens,b
Rubén A. Toscanoc
a
Centro de Química del Instituto de Ciencias, BUAP, Apdo. Postal J-42, San Manuel, C. P. 72571, Puebla, Pue., México
Fax +52(222)2295551; E-mail: slarroyo@siu.buap.mx
b
División de Estudios de Posgrado, Facultad de Química, UNAM, Cd. Universitaria, D. F. 04510 México
c
Instituto de Química, UNAM, Cd. Universitaria, D. F. 04510 México
Received 3 March 2003
cer like fashion,16 we turned our efforts towards the syn-
thesis of fluorine based thioether pincer ligands.
Abstract: The fluorosulfur containing pincer ligands 1,3-
(CH2SRf)2C6H4 [Rf = C6F5 (1) and 4-HC6F4 (2)] and 1,2,4,5-
(CH2SRf)4C6H2 [Rf = C6F5 (3) and 4-HC6F4 (4)] have been prepared
by treatment of 1,3-(CH2Br)2C6H4 or 1,2,4,5-(CH2Br)4C6H2 with
the corresponding lead thiolate Pb(SRf)2.
In this paper we describe the synthesis and characteriza-
tion of pincer dithioether and tetrathioether ligands with
fluorinated substituents 1,3-(CH2SRf)2C6H4 [Rf = C6F5 (1)
and 4-HC6F4 (2)] and 1,2,4,5-(CH2SRf)4C6H2 [Rf = C6F5
(3) and 4-HC6F4 (4)]. The structure of 1 was corroborated
with a single crystal X-ray analysis.
Key words: fluorine, sulfur, fluorinated pincer ligands
There is a growing interest in new materials bearing fluo-
rosulfur moieties since they are expected to display inter-
esting and useful properties relevant to several fields.
Thus, the presence of fluorine in biologically active com-
pounds can impart a profound influence on their biologi-
cal activity. This influence has led to the development of
several potent agricultural and therapeutic agents1 as ex-
emplified in pheromone chemistry, fluorinated retinoids,
pyrethroids and enzyme inhibitors.2–6
The reactions between metal thiolates and hydrocarbon
halides have been used frequently to provide the corre-
sponding thioether compounds.17 We have used lead poly-
fluoroaryl thiolates for the introduction of the polyfluoro-
arylthiolate moiety through their metathesis reactions
with the appropriate bromide species.
Thus lead polyfluoroarylthiolates, Pb(SRf)2, react with
1,3- (CH2Br)2C6H4 to give the dithioether compounds 1,3-
(CH2SRf)2C6H4 [Rf = C6F5 (1) and 4-HC6F4 (2)]
(Equation 1) or with 1,2,4,5-(CH2Br)4C6H2 to give the
On the other hand, an increasing number of academic and
industrial groups are working on the design of ligands and
homogeneous catalysts containing perfluoroalkyl or -aryl
groups and their application in fluorous biphase systems
(FBS) catalysis.7 As a consequence, organofluorine chem-
istry has seen a flurry of research activity recently and a
growing emphasis has been placed on the development
and evaluation of new fluorinating reagents,8 enantiose-
lective synthesis of fluorocarbonyl compounds,8,9 and the
synthesis of fluorinated transition metal complexes.10
tetrathioether
compounds
1,2,4,5-(CH2SRf)4C6H2
[Rf = C6F5 (3) and 4-HC6F4 (4)] (Equation 2).
Pincer ligands of several types have been a continuous
topic of research in organometallic chemistry and cataly-
sis in recent years.11 The exploration of metal complexes
with these ligands has shown them suitable for novel ap-
plications in the activation of small molecules and bonds
otherwise difficult to activate (e.g. C–H, C–Cl, C–F).12
These ligands have also rendered iridium species active
for selective dehydrogenation of n-alkanes to -olefins13
and helped palladium complexes in opening a potential
new field in the research of the C–C coupling reactions.14
Thus, following our current interest in transition metal
complexes with fluorinated thiolates and sulfides,15 and
the synthesis of new compounds able to complex in a pin-
Equation 1
Equation 2
Synthesis 2003, No. 10, Print: 21 07 2003.
Art Id.1437-210X,E;2003,0,10,1565,1568,ftx,en;M00503SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
In all reactions, stoichiometric quantities of the corre-
sponding bromomethyl-substituted benzene and lead
polyfluoroarylthiolate were suspended in toluene and the

1566
M. Arroyo et al.
PAPER
stirred mixture set to reflux for 24 hours. After this time, shows an additional triplet of triplets in the aromatic re-
PbBr2 was separated by filtration, the solvent was evapo- gion that corresponds to the para hydrogen of the 4-HC6F4
rated under vacuum and the residue purified by chroma- rings. The 19F NMR spectra of compounds 1 and 3 exhibit
tography to afford microcrystalline white powders.
three different resonances for the ortho, para and meta
fluorine atoms,18 while compounds 2 and 4 show two res-
onances corresponding to the ortho and meta fluorine at-
oms. The 1H and 19F chemical shifts of compounds 1 to 4
and relevant coupling constants are collected in Table 2.
In the FAB-mass spectra all compounds show the signals
corresponding to the molecular ion [M]+ and the ion due
to the loss of a proton [M – H]+, which are of significant
intensities for the dithioether compounds 1 and 2 and of
low intensities for the tetrathioether compounds 3 and 4. Compound 1 was recrystallized by slow evaporation from
Compounds 1 and 2 show peaks that correspond to the a mixture hexane–CH2Cl2 (4:1), which afforded single
loss of one SRf group, [C6H4(CH2SRf)(CH2)]+ (high inten- crystals which were analyzed by X-ray diffraction crystal-
sities), and to the loss of two SRf groups [C6H4(CH2)2]+ lography.19 The corresponding structure is shown in
(intensities higher than 15%). Compounds 3 and 4 exhibit Figures 1 and 2. Selected bond lengths and angles are col-
identifiable peaks with fragments corresponding to suc- lected in Table 3. The solid-state structure corresponds to
1
cessive loss of one, two, and three SRf groups, the results found from H and 19F NMR spectroscopy in
[C6H2(CH2SRf)3(CH2)]+, [C6H2(CH2SRf)2(CH2)2]+ and solution.
[C6H2(CH2SRf)(CH2)3]+ (several intensities) (Table 1).
In summary, we have synthesized four new fluorosulfur
compounds. These molecules can be used as potentially
tridentate and hexadentate pincer ligands with transition
metals.
Table 1 Molecular and Fragmentation Peaks for Compounds 1,3-
(CH2SRf)2C6H4 and 1,2,4,5-(CH2SRf)4C6H2
Product
FAB-MS, m/z (%)
1,3-(CH2SC6F5)2C6H4 (1)
502 (33), 501 (34), 303 (100), 104
(35)
1,3-[CH2S(4-HC6F4)]2C6H4 (2) 466 (25), 465 (18), 285 (92), 104
(16)
1,2,4,5-[(CH2SC6F5)]4C6H2 (3) 926 (2), 925 (4), 727 (32), 528 (6),
329 (15)
1,2,4,5-[CH2S(4-HC6F4)]4C6H2 854 (4), 853 (5), 673 (25), 492 (2),
(4)
311 (9)
The IR spectra of these compounds exhibit the character-
Figure 1 ORTEP diagram of 1,3-(CH2SC6F5)2C6H4 (1)
1
istic absorptions of SRf groups. The H and 19F NMR
spectra are more illustrative. 1H NMR spectra of 1 and 2
show a multiplet at low field corresponding to the aromat-
ic protons of the C6H4 skeleton and a single signal for the
CH2 groups. In addition, the 1H NMR spectrum of 2 pre-
sents a triplet of triplets in the aromatic region attributed
1
to the para hydrogen of the 4-HC6F4 moieties. The H
NMR spectra of the tetrathioether compounds 3 or 4 ex-
hibit two signals (singlets), which reveal the presence of
the aromatic protons in the C6H2 skeleton and the aliphatic
CH2 protons. The 1H NMR spectrum of the compound 4
Figure 2 ORTEP diagram of 1. View along the planes of the aryl
rings
Table 2 1H and 19F NMR Chemical Shifts , of 1,3-(CH2SRf)2C6H4 and 1,2,4,5-(CH2SRf)4C6H2
Product
1H NMR
19F NMR
1,3-(CH2SC6F5)2C6H4 (1)
7.12 (m, 4 H, C6H4), 4.00 (s, 4 H, 2 CH2)
–132.86 (m, 4 Fo, 2 C6F5), –152.62 (t, 2 Fp, 2
C6F5, 3JFF = 20.7 Hz), –161.56 (m, 4 Fm, 2 C6F5)
1,3-[CH2S(4-HC6F4)]2C6H4 (2)
1,2,4,5-(CH2SC6F5)4C6H2 (3)
7.14 (m, 4 H, C6H4), 7.00 (tt, 2 H, 2 C6F4H,
–134.04 (m, 4 Fo, 2 C6F4H), –138.78 (m, 4 Fm, 2
3JHF = 9.6 Hz, 4JHF = 7.2 Hz), 4.06 (s, 4 H, 2 CH2) C6F4H)
6.86 (s, 2 H, C6H2), 4.20 (s, 8 H, 4 CH2)
–133.26 (m, 8 Fo, 4 C6F5), –151.80 (t, 4 Fp, 4
C6F5, 3JFF = 20.7 Hz), –161.25 (m, 8 Fm, 4 C6F5)
1,2,4,5-[CH2S(4-HC6F4)]4C6H2 (4) 7.06 (tt, 4 H , 4 C6F4H, 3JHF = 9.6 Hz, 4JHF = 7.2
–133.91 (m, 8 Fo, 4 C6F4H), –138.22 (m, 8 Fm, 4
C6F4H)
Hz), 6.88 (s, 2 H, C6H2), 4.22 (s, 8 H, 4 CH2)
Synthesis 2003, No. 10, 1565–1568 © Thieme Stuttgart · New York

PAPER
Fluorosulfur Containing Pincer Ligands
1567
Table 3 Selected Bond Lengths (Å) and Angles (°) for 1,3-
(CH2SC6F5)2C6H4 (1)
time, PbBr2 was filtered off, the solvent was removed under vacuum
and the residue purified by column chromatography (silica gel, hex-
ane–CH2Cl2, 4:1). Compound 1 was obtained as microcrystalline
white powder (1.58 g, 85%); mp 52 °C.
Atoms
Bond Lenghts Atoms
(Å)
Bond An-
gles (°)
IR (KBr): 1522, 1482, 1105, 979, 863 cm–1 (SC6F5).
S(1) C(9)
S(1) C(7)
S(2) C(15)
S(2) C(8)
F(1) C(10)
F(2) C(11)
F(3) C(12)
F(4) C(13)
F(5) C(14)
C(1) C(6)
C(1) C(2)
C(1) C(7)
C(2) C(3)
C(3) C(4)
C(3) C(8)
1.751(3)
1.813(3)
1.748(4)
1.778(3)
1.340(3)
1.356(4)
1.330(4)
1.348(4)
1.339(4)
1.376(4)
1.376(4)
1.497(4)
1.367(4)
1.391(4)
1.502(4)
C(9) S(1) C(7)
100.34(15)
102.37(17)
119.2(4)
120.9(4)
121.4(4)
119.1(4)
120.3(4)
120.6(4)
119.0(4)
122.0(4)
118.6(4)
111.5(2)
108.6(2)
122.0(3)
123.0(3)
122.0(4)
122.5(5)
Anal. Calcd for C20H8F10S2: C, 47.82; H, 1.61. Found: C, 47.54; H,
1.61.
C(15) S(2) C(8)
C(6) C(1) C(7)
C(2) C(1) C(7)
C(3) C(2) C(1)
C(2) C(3) C(4)
C(2) C(3) C(8)
C(4) C(3) C(8)
C(5) C(4) C(3)
C(4) C(5) C(6)
C(5) C(6) C(1)
C(1) C(7) S(1)
C(3) C(8) S(2)
C(14) C(9) S(1)
C(10) C(9) S(1)
C(16) C(15) S(2)
C(20) C(15) S(2)
1,3-[CH2S(4-HC6F4)]2C6H4 (2)
White microcrystalline powder; yield: 83%; mp 75 °C.
IR (KBr): 1488, 1434, 1175, 912 cm–1 (4-HC6F4S).
Anal. Calcd for C20H10F8S2: C, 51.50; H, 2.16. Found: C, 50.44; H,
2.16.
1,2,4,5-(CH2SC6F5)4C6H2 (3)
White microcrystalline powder; yield: 94%; mp 176 °C.
IR (KBr): 1518, 1483, 1096, 977, 859 cm–1 (SC6F5).
Anal. Calcd for C34H10F20S4: C, 44.06; H, 1.09. Found: C, 43.69; H,
1.06.
1,2,4,5-[CH2S(4-HC6F4)]4C6H2 (4)
White microcrystalline powder; yield: 88%; mp 159 °C.
IR (KBr): 1489, 1435, 1173, 917 cm–1 (4-HC6F4S).
Anal. Calcd for C34H14F16S4: C, 47.78; H, 1.65. Found: C, 47.41; H,
1.52.
X-ray Crystal Data for 1
The X-ray diffraction data were collected on a Bruker Smart Apex
CCD diffractometer. Single crystals of 1 were obtained from hex-
ane–CH2Cl2 (4:1) as colorless needles, C20H8F10S2 (502.39); Mon-
oclinic P21/n (No. 14) with a = 19.218(3), b = 4.7630(10),
c = 21.118(3) Å,
= 91.579(4)o, V = 1932.3(6) Å3, Z = 4,
D = 1.727 g/cm3, absorption coefficient 0.376 mm–1 was performed
at 293(2) K using graphite monochromated MoK radiation
( = 0.71073 Å), limiting indices –22
h
22, –5
k 5, –25 l
25, -range for data collection 1.93 to 24.99o, reflections collected
22860, independent reflections 22871 (Rint = 0.1183). Complete-
ness to = 24.99o 100.0%, data/restrains/parameters = 22871/0/
290. The structure was solved by direct methods and refined by full-
matrix least-squares on F2 using SHELXL-97 program system.21
All non-hydrogen atoms were refined anisotropically and the posi-
tion of the hydrogen atoms was calculated as a riding model. The
All reactions were carried out under argon using conventional
Schlenk glassware; solvents were dried using established proce-
dures and distilled under argon immediately prior to use. TLC (Mer-
ck, 5 × 7.5 cm2 Kieselgel 60 F254) was used to monitor the progress
of the reaction under study with hexane–CH2Cl2 (4:1) as eluent. IR
spectra were recorded on a Magna-Nicolet 750 FT-IR spectrometer
as KBr pellets. 1H and 19F NMR spectra were recorded with a Vari-
an Mercury-VX spectrometer operating at 300 MHz and with a
Varian Unity spectrometer operating at 376 MHz respectively.
Chemical shifts are relative to TMS = 0 (1H) and CFCl3 = 0 (19F)
using CDCl3 as solvent. Positive ion FAB mass spectra were record-
ed on a Jeol JMS-SX102A mass spectrometer operated at an accel-
erating 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 resolution of 3000
using magnetic field scans and the matrix ions as the reference ma-
terial or, alternatively, by electric field scans with the sample peak
bracketed by two [poly(ethylene glycol) or CsI] reference ions. El-
emental analyses were determined by Galbraith Laboratories Inc.,
USA. The starting materials, pentafluorothiophenol, 2,3,5,6-tet-
rafluorothiophenol, 1,3-di(bromomethyl)benzene and 1,2,4,5-tet-
rakis(bromomethyl)benzene were obtained from Aldrich Chemical
Co. and used without further purification. Pb(SRf)2 (Rf = C6F5, 4-
HC6F4) were prepared according to published procedures.18,20 In all
reactions stoichiometric quantities of reactants were used.
2
weighting scheme was w = 1/[s2(Fo ) + (0.0001P)2] where P =
2
(Fo + 2Fc2)/3. Goodness-of-fit on F2 0.721; final R indices [I >
2 (I)], R1 = 0.0724, wR2 = 0.0942;
R1 = 0.2415, wR2 = 0.1347.
R
indices (all data)
Acknowledgments
We are grateful to CONACYT (27915E and J41206-Q) and DGA-
PA-UNAM (IN116001). We would like to thank Chem. Eng. Luis
Velasco Ibarra and M. Sc. Francisco Javier Pérez Flores for running
the FAB mass spectra.
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Synthesis 2003, No. 10, 1565–1568 © Thieme Stuttgart · New York

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Synthesis 2003, No. 10, 1565–1568 © Thieme Stuttgart · New York