Application of a base-induced [1,2]-rearrangement to synthesize thiophosphonate bidentate S(sp2)-N monoanionic ligand: Characterization of its silver and palladium complexes

Article abstract of DOI:10.1016/j.jorganchem.2009.08.035

The O,O-diethyl thiophosphonate functional group has been introduced on position 2 of a pyrrole heterocycle following a two steps sequence that makes use of a [1,2] base-induced rearrangement applied for the first time to a O,O-diethyl thiophosphoramide i

Full text of DOI:10.1016/j.jorganchem.2009.08.035

Journal of Organometallic Chemistry 694 (2009) 4001–4007
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Application of a base-induced [1,2]-rearrangement to synthesize
thiophosphonate bidentate S(sp2)–N monoanionic ligand: Characterization of
its silver and palladium complexes
Sabrina Marie a, Martin Lutz b, Anthony L. Spek b, Robertus J.M. Klein Gebbink c, Gerard van Koten c,
a,
Nelly Kervarec d, François Michaud e, Jean-Yves Salaün a, , Paul-Alain Jaffrès
*
*
a Université Européenne de Bretagne, Université de Brest, CNRS UMR 6521, CEMCA, IFR 148 ScInBios, 6 Avenue Le Gorgeu, 29238 Brest, France
b Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
c Chemical Biology and Organic Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
d Université de Brest, Service commun d’analyse par RMN, 6 Avenue Le Gorgeu, 29238 Brest, France
e Université de Brest, Service commun d’analyse par Diffraction des Rayons X, 6 Avenue Le Gorgeu, 29238 Brest, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 July 2009
Received in revised form 26 August 2009
Accepted 26 August 2009
Available online 31 August 2009
The O,O-diethyl thiophosphonate functional group has been introduced on position 2 of a pyrrole hetero-
cycle following a two steps sequence that makes use of a [1,2] base-induced rearrangement applied for
the first time to a O,O-diethyl thiophosphoramide intermediate. This rearrangement has been studied by
low temperature NMR and the intermediates have been fully characterized. The coordination of this
monoanionic bidentate (N,Ssp2) ligand to silver or palladium is studied The bidentate ligand 2 (O,O-
diethyl pyrrol-2-ylthiophosphonate), associated with a palladium precursor, produces in the presence
of triethylamine the complex trans-[Pd(g2-20)2] 3 (20 is deprotonated ligand 2). Ligand 2 also reacts with
silver oxide in dichloromethane to give an unstable complex 20-Ag that can be stabilized by addition of
triphenylphosphine to produce the coordination complex 4 [Ag((g2-20)(PPh3)2].
Keywords:
Thiophosphonate
Lithiation
Rearrangement
N,S-ligand
Ó 2009 Elsevier B.V. All rights reserved.
Pyrrole
1. Introduction
Concerning the functional groups possessing a P@S double bond,
the majority of the coordination studies report the use of phos-
The synthesis of original ligands possessing a good stability in
the presence of air and moisture constitute a valuable interest
for applications in the field of catalysis [1] after being associated
with a metal or as building blocks to define coordination polymers
[2]. With the aim to synthesize coordination complexes obtained
from air and moisture stable ligands, the use of the phosphorus(V)
functional group to design new ligands has drawn our attention.
Phosphorus(V) functional groups which are usually air and mois-
ture stable have been used in many coordination complexes. It
must be noted that the coordination site in this phosphorus(V)
functional group can be an oxygen, a sulfur or a nitrogen atom,
respectively, present in the following double bonds: P@O (e.g.
phosphonate [3]), P@S (e.g., phosphine thiooxide [4]) or P@N
(e.g., iminophosphorane [5]). The nature of the metallic partner
that can be coordinated to these atoms is greatly dependent of
the hardness/softness of the binding site of these P(V) ligands.
phine thiooxide, probably due to the simplicity of their synthesis
by a simple thiooxidation of phosphine. Nevertheless some coordi-
nation complexes involving thiophosphoramidate [6], or thi-
ophosphonate [7] have been reported. The limitation of their use
in coordination chemistry could arise from synthetic difficulties
since their preparation usually requires the use of very air sensitive
phosphorus(III) intermediates. We have recently reported the syn-
thesis of O,O-diethylthiophosphonate achieved, from phenol deriv-
atives and via stable phosphorus V intermediates [8], by a base-
induced [1,3] phospho-Fries [9] rearrangement. On the basis of
our recent results, we report herein the synthesis of O,O-diet-
hylthiophosphonate-pyrrole NH,S ligand via a [1,2] phospho-Fries
rearrangement. It must be noted that this kind of rearrangement
has been previously used to produce phosphinethiooxides [10].
In the present work an important effort has been done to charac-
terize, by low temperature NMR spectroscopy, the intermediate
species involved in the course of this [1,2] phospho-Fries rear-
rangement. Furthermore, the temperature at which the [1,2]-rear-
rangement occurs has been determined. Finally The coordination
behavior of this new pyrrolic N,S-ligand is illustrated by the char-
acterization of palladium and silver complexes.
* Corresponding authors.
E-mail addresses: Jean-Yves.Salaun@univ-brest.fr (J.-Y. Salaün), pjaffres@
univ-brest.fr (P.-A. Jaffrès).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.08.035

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S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
O,O-dialkylthiophosphonate. This rearrangement is very selective:
2. Results and discussion
the nucleophilic addition of n-butyllithium on the phosphorus
atom was never observed. This selectivity can be explained by
the poor polarization of the P@S bond that produces a phosphorus
atom with a weak electrophilic character. This result is to compare
with that obtained by Buono and coworkers [14], who observed
that a base-induced [1,3]-rearrangement involving a phosphoram-
idate (P@O bond) was not efficient when n-BuLi was used as a base
due to the addition of n-BuLi on the electrophilic phosphorus. This
comparison illustrates the weaker reactivity of the thiophosph-
oramidate versus phosphoramidate towards nucleophilic reagents.
In order to get further information about the intermediates in-
volved in this [1,2] base-induced rearrangement, a 31P NMR mon-
itoring of the reaction was performed at low temperature. Below
ꢀ40 °C, only the signal of the starting compound 1 (d31P: 63.6
ppm) was observed. Between ꢀ35 and ꢀ40 °C the metallation of
2.1. Synthesis of the of thiophosphonate and low temperature NMR
study of [1,2] phospho-Fries rearrangement
O,O-diethylpyrrol-2-ylthiophosphonate 2 has been synthesized
following a two step process which comprises the generation of
the N-lithium salt of pyrrole by deprotonation with n-butyllithium
followed by addition of O,O-diethylchlorothiophosphate (a depro-
tonation by sodium hydride is also successful). According to this
procedure the thiophosphoramidate 1, which results from a N-
thiophosphonylation, is isolated in 91% yield (Scheme 1, Step i).
The synthesis of thiophosphonate 2 from 1 is then achieved by
orthometallation of 1 with n-butyllithium at ꢀ80 °C. After warm-
ing to room temperature and hydrolysis 2 is obtained by a [1,2]-
rearrangement leading to the formation of a C–P bond (Scheme
1, step ii). Compound 2 is characterized by a 31P NMR signal at
74.2 ppm and the observation, by 13C NMR, of the signal of a ter-
tiary carbon as a doublet at 122.27 ppm (1JCP = 187.1 Hz) which is
consistent with the presence of a C–P bond. In spite of the poorly
ortho-directing effect of the sulfur atom, the yield of this rearrange-
ment is high (95%). It is worth noting that this [1,2]-rearrangement
occurs more easily than the analogous [1,3]-rearrangement in the
phenolic series [8]. Indeed in the latter case, when the metallation
is achieved by abstraction of a hydrogen atom with BuLi, a low
yield of transposed complex is obtained (15%) [8]. The efficiency
of this [1,2]-rearrangement probably results from a selective lithi-
the pyrrole in a-position from the nitrogen atom gives rise to inter-
mediate Ia (d31P: 73.0 ppm). At nearly the same temperature this
intermediate is converted into a second product Ib (Scheme 2
and Fig. 1).
Fig. 1 illustrates the evolution of the reaction performed at
ꢀ38 °C. In order to characterize intermediates Ia and Ib, the reac-
tion, after 10 h at ꢀ38 °C was cooled down to ꢀ80 °C. The resulting
reaction mixture was then found to be composed of 1 (28%), Ia
(48%) and Ib (24%). From this mixture at ꢀ80 °C, compounds Ia
and Ib were unambiguously characterized by several NMR experi-
ments (1H, 31P, 13C, COSY 1H–1H, HMBC 1H–13C, HMBC 1H–31P,
HMBC 1H–15N and HMQC 1H–13C). Moreover, in an independent
reaction, compound Ib was obtained quantitatively by reaction of
2 with n-BuLi. The NMR data of compounds 1, Ia, Ib and 2 are sum-
marized in Table 1. The lithiation of 1 produced intermediate Ia
characterized by a deshielded 31P NMR resonance and by the
observation of three aromatic signals in 1H NMR. 13C NMR dis-
placements of this intermediate were indirectly determined by
HMQC 1H–13C sequences. 15N NMR chemical shifts, (determined
by 1H–15N HMBC sequences), strongly depend on the electron den-
sity around the nitrogen atom. Noticeably, for the lithiated species
Ia (ꢀ196.6 ppm) and even more for Ib (ꢀ133.5 ppm), the 15N NMR
values are shifted toward the lower fields. Even if in earlier reports
intermediates of type Ia and Ib were suggested to be formed in
base-induced rearrangements (formation of arylphosphonate [12]
or phosphonodiamidate [14]), to the best of our knowledge this re-
port represents the first full characterization of these intermedi-
ates by multinuclear NMR experiments.
ation in the a-position of the nitrogen atom (Ia, Scheme 2) as a re-
sult of the proximity of both nitrogen and oxygen atoms of the
thiophosphonamidate group. The driving force of this reaction
could be the formation of a lithium amidure (after the [1,2]-rear-
rangement) (Ib, Scheme 2) which would be more stable (less basic)
than the carbanion initially formed (Ia, Scheme 2). Base-assisted
[1,2]- or [1,3]-rearrangements, which are well documented, have
been previously used to synthesize 2-hydroxyphenylphosphonate
[11], 2-mercaptoarylphosphonate [12] or phosphonodiamidate
[13] compounds. In the pyrrolic series, a [1, 2]-rearrangement
has been reported to produce a phosphine oxide or a phosphine
thiooxide [10]. However, to the best of our knowledge, this report
represents the first example of a [1,2]-rearrangement producing an
S
OEt
H
P
H
OEt
N
N
N
2.2. Coordination
S
i
ii
P
OEt
OEt
The coordination properties of the bidentate ligand 2 were stud-
ied as reported in Schemes 3 and 4. A palladium complex has been
readily obtained by reaction, at room temperature, of two equiva-
lents of 2 with [PdCl2(MeCN)2] and triethylamine. The obtained
palladium complex 3 is air stable and has been purified by silica
gel chromatography. Its 31P NMR spectrum displays only one signal
1
2
Scheme 1. (i) n-BuLi, ꢀ80 °C, THF, then O,O-diethylchlorothiophosphate, ꢀ80 °C to
RT. (ii) n-BuLi, THF, ꢀ80° to RT then hydrolysis.
S
S
OEt
OEt
P
OEt
OEt
Li
H
2
P
N
N
N
N
S
S
1
1
5
4
1
1
5
4
BuLi
5
4
H2O
5
4
2
2
Li
2
P
P
OEt
OEt
OE
t
3
3
3
3
OEt
1
Ia
31P : 73.0 ppm
Ib
2
31P : 63.6 ppm
31P : 88.8 ppm
31P : 74.2 ppm
Scheme 2. Intermediates observed in the course of the base-induced [1,2]-rearrangement of 1 into 2.

S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
4003
Fig. 1. 31P NMR spectrum (from 60 to 90 ppm; THF + 8D-THF ꢀ38 °C) showing the chemical species observed after the addition of n-BuLi on a THF solution of 1 at ꢀ80 °C. The
first spectrum was recorded after 15 min at ꢀ38 °C. The different spectra were drawn every hour.
Table 1
NMR data of the aromatic part of compounds 1, 2, Ib and of intermediate Ia.
1 (CDCl3)
Ia (8D-THF)
Ib (8D-THF)
2 (CDCl3)
31P
63.6
73.0
88.8
74.2
15N
ꢀ210.0
ꢀ196.6
5.89 (H3)
5.92 (H4)
7.20 (H5)
110.8
ꢀ133.5
ꢀ226.2
1H (Ar)
6.17 (H3; H4)
7.04 (H2; H5)
6.02 (H4)
6.30 (H4)
6.48
6.80
6.72 (H3)
6.98 (H5)
110.5 (C4, JCP = 13.4 Hz)
116.5 (C3, JCP = 15.9 Hz)
122.3 (C2, JCP = 187.1 Hz)
123.4 (C5, JCP = 11.6 Hz)
13C (Ar)
112.65 (C3, C4, JCP = 10.1 Hz)
123.5(C2, C5, JCP = 6.7 Hz)
109.9 (C4, JCP = 12 Hz)
114.8 (JCP = 29 Hz)
127.3 (C2, JCP = 124 Hz)
133.9 (JCP = 26 Hz)
123.3
124.0 (C5)
C2a
a
Not determined.
at 89.8 ppm which corresponds to a deshielding of 15.6 ppm com-
pared to the resonance of the free ligand 2 (74.2 ppm). This desh-
ielding suggests a possible coordination of the P@S group to
palladium via its sulfur atom. Indeed, similar deshielding effects
OEt
OEt
S
N
N
H
i
P
Pd
(Dd from 9.2 to 13.9 ppm) are observed when phosphine thiooxide
P
groups are coordinated to a palladium atom [4h,4d]. The structure
of 3, which adopts a trans-square planar configuration has been
established by X-ray diffraction study (Fig. 2). The angles S1–
Pd1–N1 and S10–Pd1–N1 (respectively 90.92(4)° and 89.08(4))
are in agreement with a square planar complex. The P@S bond in
3 (1.9972(6) Å) is lengthened when compared to the values of
P@S bond length of free thiophosphonate or phosphine thiooxide
P
N
EtO
S
EtO
EtO
S
EtO
2
3
31P NMR : 74.2 ppm
31P NMR : 89.8 ppm
Scheme 3. Synthesis of complex 3. (i) PdCl2(MeCN)2, NEt3, THF, 20°.
(from 1.921(2) to 1.966(2) Å) [15,16]. In
3 the Pd–S bond
(2.3382(5) Å) is longer than those reported for triarylphosphine
thiooxide Pd complexes (2.317(2) to 2.321(2) Å) [4i,17]. Probably
due to the presence of two trans N pyrrolic atoms, the Pd–N bonds
(2.0264(13) Å) are slightly shorter than those observed in a
bis(oxazolinyl)pyrrole) palladium complex (Pd–N = 2.039(8)–
2.052(8) Å) [18]. Several attempts to prepare a silver complex by
reaction of ligand 2 with silver oxide in dichloromethane at room
temperature suggest the formation of a new compound whose
spectroscopic data (see Section 4) are indicative of the complexa-
tion of ligand 2 to the metal via the S atom of the thiophosphonate
group (deshielding of ꢁ7.5 ppm of the phosphorus NMR signal of
N
S
PPh3
N
H
i
ii
Complex
2'-Ag
Ag
P
P
EtO
EtO
EtO
EtO
S
PPh3
2
4
31P NMR : 74.2 ppm
31P NMR : 81.6 ppm
31P NMR : 89.8 and 4.0 ppm
Scheme 4. Synthesis of complex 4. (i) Ag2O, CH2Cl2 (ii) PPh3.

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S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
Fig. 2. Displacement ellipsoid plot (50% probability level) of 3 in the solid state.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg.):
Pd1–S1 2.3382(5), Pd1–N1 2.0264(13), P1@S1 1.9972(6), P1–C4 1.7388(17), P1–O1
1.5800(12), P1–O2 1.5644(12); S1–Pd1–N1 90.92(4), S10–Pd1–N1 89.08(4), S1–P1–
C4 108.96(6), P1–C4–N1 118.27(13), P1–S1–Pd1 98.78(2). Symmetry operation i:
1ꢀx, 1ꢀy, 1ꢀz.
Fig. 3. Low temperature 31P NMR spectra of complex 4. (3a) Thermal evolution
from 25 to ꢀ95 °C of the 31P NMR signals of the PPh3 ligands of 4. (3b) Evolution of
the same signal in the presence of an excess of PPh3.
this function at 81.6 ppm) and via the pyrrolic nitrogen (disappear-
ance of the N–H resonance at 9.0 ppm). This complex was found to
be unstable and we were unable to isolate it. However, addition of
two equivalents of triphenylphosphine allowed us to obtain a new
complex (4) which was stable even in the presence of air and light
(Scheme 4). The structure of this complex 4 (see below) suggests
that its unstable precursor involves a complexation of the N and
S atoms of ligand 2 on a single metal: this entity ‘‘20-Ag” could
be weakly stabilized by molecules of solvent or by water (ligand
20 corresponds to the ligand 2 deprotonated on the nitrogen atom
of the pyrrole heterocycle). The 1H NMR spectrum of 4 confirms the
presence of two PPh3 ligands together with L20; its 31P NMR spec-
trum displays at room temperature two signals at 90.0 and
5.7 ppm that are attributed to the thiophosphonate group and to
the triphenylphosphine ligands, respectively. Compared to the
starting ligand 2, the complexation of the sulfur atom of the thi-
ophosphonate group on the silver atom induces a deshielding of
the phosphorus resonance (15.6 ppm). The absence of J1 P–Ag cou-
pling constants between the phosphorus atoms of PPh3 and the
metal suggests that the two phosphines undergo rapid exchanges
on the NMR time scale at room temperature. The reality of this dy-
namic system has been established by a low temperature 31P NMR
study (Fig. 3). The thin signal observed for the phosphines at
5.7 ppm at 25 °C broadens as the temperature decreases and coa-
lesces at ꢀ62 °C to evolve at lower temperature into a double dou-
stoichiometry of the reaction of formation of 4 is not affected by
reducing the amount of the added phosphine to one equivalent.
Crystals of 4 suitable for an X-ray diffraction study were obtained
from a hexane–CH2Cl2 (90/10) mixture at ꢀ40 °C. Fig. 4 displays
the ORTEP drawing of the molecule and some selected bonds and
angles. The molecular structure study of 4 shows that the silver
atom of this complex is linked to ligand 20 and to two PPh3.
The coordination angles around Ag1 are in agreement with a pseu-
do tetrahedral coordination around the metal center. This is illus-
trated by the angles S1–Ag1–N1 (84.25(7)), N1–Ag1–P2
(104.76(8)) and P2–Ag1–P3 (119.88(3)). Furthermore the distances
of P2 and P3 atoms from the plane defined by the atoms Ag1, N1
and S1 are respectively 2.140(1) and 2.216(1) Å, respectively. In
complex 4, the ligand 20 is N,S-chelated to the metal giving rise
to a five-membered metallacycle with a reduce bite angle (N1–
Ag1–S1 = 84.25(7)°). This angle is smaller than that observed for
complex 3 displaying the same ligand on a square planar palladium
(90.92(4)°). It is, however larger than S–Ag–S angles observed for
dithiocarbamate or dithiophosphinate ligands forming four-mem-
bered metallacycles on tetrahedral Ag metal centers (68.00(2)° and
74.71(3)°, respectively) [20]. The P@S bond of 4 is shorter than its
homologue of the same ligand on 3 (1.9603(12) Å vs 1.9972(6) Å).
It is also shorter than the P@S distances observed for thiophos-
phine [19d] or dithiophosphinate [20b] Ag complexes (from
1.990(3) Å to 2.004(1) Å). However, similar short P@S bonds have
been observed for a thiophosphinate Ag complex [21] (from
1.957(2) Å to 1.971(2) Å). These distances are longer than those ob-
served for the P@S bonds of free thiophosphonate or phosphine
thiooxide ligands (from 1.921(2) Å to 1.966(2) Å [15,16]. Compared
to similar bond lengths (average of 2.35 Å) described in the litera-
ture [19c,22], the Ag–N distance observed for 4 is rather short
(2.273(3) Å). On the other hand, the Ag–P distances are rather
long: 2.4492(9) and 2.4761(9) Å compared to similar Ag–PPh3
bonds previously described (from 2.3465(6) to 2.4736(10) Å)
[19c,20a,22a–c,23]. The value of the angle P2–Ag1–P3 measured
between the two PPh3 ligands (119.88(3)° is small when compared
to their homologues on several Ag complexes (from 122.02(4)° to
135.158(9)°) [19c,22a,c,d] The structure of 4 then confirms that
for a given phosphane, the Ag–P bond length is expected to in-
crease as the Ag–P–Ag angle decreases. A correlation has already
107
109
blet centered at 4.3 ppm (J31
Ag = 346.26 Hz; J31
=
Ag
P–
P–
399.08 Hz). These coupling constants are typical of a (phos-
phine)2Ag system [19]. The equivalence of the two phosphines at
low temperature suggests a tetrahedral coordination around the
metal. In the observed range of temperature the thiophosphonate
signal remains unchanged (singlet at 90.0 ppm). The lability of
the phosphines is again shown by reaction of 4 with an excess of
triphenylphosphine. When one equivalent of PPh3 is added to 4,
the 31P NMR spectrum of the solution performed at room temper-
ature displays a single signal in the phosphine resonance area (at
1 ppm) showing a rapid exchange on an NMR scale between the
two phosphines linked to the metal and the free phosphine in solu-
tion. By cooling dawn this solution, the signal becomes broad and
coalesces at ꢀ50 °C. It then evolves at lower temperature and gives
rise to the double doublet previously observed and to the signal of
the free PPh3 at ꢀ6.85 ppm. Even in the presence of an excess of
PPh3 (Fig. 3b) there is no sign of hemilability of ligand 2 with an
eventual insertion of PPh3 into the Ag–S bond; the signal of the thi-
ophosphonate group remains unchanged. It is noteworthy that the

S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
4005
Fig. 4. Displacement ellipsoid plot (50% probability level) of 4 in the solid state. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg.): Ag1–S1
2.7169(9), Ag1–N1 2.273(3), Ag1–P2 2.4761(9), Ag1–P3 2.4492(9), P1@S1 1.9603(12), S1–Ag1–N1 84.25(7), N1–Ag1–P2 104.76(8), S1–Ag1–P3 111.61(3), S1–Ag1–P2
112.96(3), P2–Ag1–P3 119.88(3), N1–Ag1–P3 117.93(8). P1–S1–Ag1 95.67(4) Dihedral angles: N1–S1–Ag1–P3 117.80(1), S1–N1–Ag1–P2 112.27(1).
1
been observed between P–Ag–P angles and JAg–P measured in
observed but addition of triphenylphosphine produces an air and
light stable silver complex L0Ag(PPh3)2. It can be conclude that
N,S pyrrol-thiophosphonate ligand is readily obtained in high yield
following a base-induced [1,2]-rearrangement. This ligand can be
coordinated to palladium or silver under mild condition producing
air and light stable complexes.
solution for some Ag complexes [22d,24], for example, an average
value of JAg–P = 387 Hz has been observed for a P–Ag–P angle of
122.51°; 411 Hz for 127.75°and 455 Hz for 135.15°. The value
found for 4 (372.34 Hz for 119.88°) is in good accordance with
these previous results.
1
3. Conclusion
4. Experimental
A new (S,NH)-bidentate ligand displaying a pyrrole core and
one thiophosphonate functional group in position 2 of pyrrole het-
erocycle have been prepared. This ligand is air and moisture stable.
Its synthesis has been performed by a base-induced [1,2]-rear-
rangement which has been applied, for the first time, to the syn-
thesis of thiophosphonates. Its synthesis uses the nitrogen atom
4.1. General
All manipulations involving air and moisture sensitive organo-
metallic compounds were performed using standard Schlenk tech-
niques under nitrogen. Pentane and toluene were dried over Na
sand, THF and diethyl ether over Na/benzophenone, and CH2Cl2
was dried over CaH2. All solvents were freshly distilled under
nitrogen prior to use. NMR spectra (1H (300.1 MHz), 13C
(75.5 MHz), and 31P (121.4 MHz)) experiments were recorded on
a Varian Inova 300 MHz spectrometer. Low temperature NMR
experiments were recorded on a Bruker DRX500 equipped with
an indirect 5 mm probhead TBI 1H/{BB}/13C. Chemical shift values
are reported in ppm (d) and referenced internally to residual sol-
vent signals (1H, 13C) or externally (31P, H3PO4 85%; 15N, neat
CH3NO2). All reagents were purchased from Acros Chemicals and
used as received. Elemental analyses were performed by Kolbe,
Mikroanalytisches Laboratorium, Mülheim an der Ruhr, Germany
and by the ‘‘Centre de Mesures Physiques de l’Ouest” Rennes,
France.
of the pyrrole ring to introduce the functional group on the a-posi-
tion possessing a sp2-hybridized sulfur atom as a binding site. This
reaction proceeds in two steps: firstly, an ortho-lithiation and sec-
ondly a [1,2]-migration of the thiophosphono group from the nitro-
gen to the a-carbon atom. The lithiated intermediate has been fully
characterized by low temperature, multinuclear NMR experiments
(1H, 13C, 31P, 15N). The lithiation step occurs between ꢀ35 and
ꢀ40 °C and the rearrangement proceeds almost at the same tem-
perature. After deprotonation of 2 performed by an additional
amine or by the metallic precursor itself (Ag2O), the monoanionic
N,S-bidentate ligand 20 has been coordinated to palladium and sil-
ver. In the first case an air stable Pd[20]2 complex is isolated. In the
second case, the formation of an unstable silver complex has been

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S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
4.2. C4H4N–P(S)(OEt)2. O,O-diethyl-N-pyrrolylthiophosphoramidate
(1)
3JHH = 7.0 Hz, 12 H, CH3–CH2–O), 4.12 and 4.28 (2m, 8H, CH3–
CH2–O), 6.26 (m, 2H, C–H), 6.62 (m, 2H, C–H), 7.08 (m, 2H, C–H).
3
31P (CDCl3): d 89.8. 13C (CDCl3): d 16.14 (d, JCP = 8.2 Hz, CH3),
2
Butyllithium (1.6 M in hexane; 40 mL, 65 mmol) is added
dropwised to a solution of Pyrrole (4.0 g; 59.7 mmol) in THF
(60 mL) at ꢀ80 °C. After 30 min at ꢀ80 °C, a solution of O,O-dieth-
ylchlorothiophosphate (11.26 g; 59.7 mmol) in THF (10 mL) is
added at ꢀ80 °C. The temperature of the solution is raised to
20 °C in 5 h time. Then the mixture is stirred at 20 °C overnight.
The resulting solution is poured into water (150 mL) and the solu-
tion is extracted twice with diethylether (2 ꢂ 80 mL). The organic
phase is washed with brine (60 mL) and dried over MgSO4. Filtra-
tion and evaporation of the solvents produce a pale yellow oil
which is purified by Kugelrohr distillation (4 ꢂ 10ꢀ2 Torr; 80 °C).
Compound 1 is obtained as a colorless oil (11.94 g) in 91% yield.
1H NMR (CDCl3): d 1.28 (m, 6H, CH3–CH2–O), 4.05 and 4.18 (2m,
4H, CH3–CH2–O), 6,30 (m, 2H, C3–H et C4–H); 7,12 (m, 2H, C2–H
64.98 (d, JCP = 4.3 Hz, CH3–CH2O), 111.01 (d, J = 12.8 Hz, CH),
1
117.91 (d, J = 24.4 Hz, CH), 125.59 (d, JCP = 199.3 Hz, C–P),
137.71(d, J = 21.1 Hz, CH). IR (ATR, cmꢀ1): 729, 776, 794, 958,
973, 1007, 1098, 1190, 1248, 1389. Anal. Calc. for
C16H26N2O4P2S2Pd: C, 35.40; H, 4.83; N, 5.16; S, 11.81. Found: C,
35.51; H, 4.73; N, 5.12; S, 11.88%.
4.6. Complexation of 2-(NC4H3)–P(S)(OEt2) by (Ag)2O
A solution of silver oxide (143 mg; 0.62 mmol) and O,O-diethyl
pyrrol-2-ylthiophosphonate 2 (270 mg; 1.23 mmol) in dichloro-
methane (10 mL) is stirred in the dark for 16 h. The dark suspen-
sion is then filtered on celite and the pad is rinsed with
dichloromethane (20 mL). The colorless filtrate is concentrated in
vacuo to produce a viscous colorless oil (380 mg; 95% yield). This
intermediate complex is unstable and a chloroform solution of this
complex turns black after few hours. Before degradation its NMR
spectroscopic characterization was as follow: 1H NMR (CDCl3): d
3
et C5–H). 31P (CDCl3): d 63.6. 13C (CDCl3): d 15.92 (d, JCP = 7.9 Hz,
2
3
CH3), 62.68 (d, JCP = 4.6 Hz, CH3–CH2O), 112.65 (d, JCP = 10.1 Hz,
2
C3 and C4), 123.06 (d, JCP = 6.7 Hz, C2 and C5).
4.3. (2-(NHC4H3)–P(S)(OEt)2. O,O-diethyl pyrrol-2ylthiophosphonate
(2)
3
1.30 and 1.31 (2t, JHH = 7.0 Hz, 6 H, CH3–CH2–O), 4.10 (m, 4H,
CH3–CH2–O), 6.35 (m, 1H, C–H), 6.85 (m, 1H, C–H), 6.94 (m, 1H,
C–H). 31P (CDCl3): d 81.6 (s).
Butyllithium (1.6 M in hexane; 31.7 mL, 50.7 mmol) is added
dropwised to a solution of O,O-diethyl-N-pyrrolylthiophosph-
oramidate 1 (10.10 g; 46.0 mmol) in THF (50 mL) at ꢀ80 °C. The
solution is slowly left to reach 20 °C (5 h) and then stirred at
20 °C overnight. The obtained mixture is poured into a saturated
aqueous ammonium chloride solution (100 mL) and extracted
twice with diethylether (2 ꢂ 90 mL). The organic phase is treated
as above to produce after distillation (4.10–2 Torr; 115 °C) com-
pound 2 as a colorless oil (9.64 g) in 95.4% yield. 1H NMR (CDCl3):
4.7. [Ag{(j j
2-(N, S) 2-(NC4H3)-P(S)(OEt2)}{ 1-(P) P(C6H5)3}2] (4)
To the dark suspension obtained above, two equivalents of PPh3
(2.46 mmol, 645 mg) in solution in dichloromethane were added at
room temperature and the resulting mixture stirred for 3 h. After
filtration on celite and evaporation of the solvent, a colorless oil
is obtained. When washed with hexane at ꢀ20 °C this oil crystal-
lizes to give a white powder (785 mg, 75% yield). Crystallisation
of this powder in a hexane/CH2Cl2 mixture (90/10) affords crystals
suitable for a X-ray diffraction study. 1H NMR (CD2Cl2): d 1.18 (t,
3JHH = 6.75 Hz, 6H, CH3–CH2–O), 3.78 and 3.85 (2m, 4H, CH3–
3
d 1.28 and 1.29 (2t, JHH = 7.0 Hz, 6 H, CH3–CH2–O), 4.06 (m, 4H,
CH3–CH2–O), 6.30 (m, 1H, C3–H), 6.72 (m, 1H, C2–H), 6.98 (m,
1H, C4–H), 9.00 (s broad, 1H, N–H). 31P (CDCl3): d 74.2. 13C (CDCl3):
3
2
d 15.93 (d, JCP = 7.9 Hz, CH3), 62.68 (d, JCP = 5.2 Hz, CH3–CH2O),
3
3
3
2
CH2–O), 6.32 (d, JHH = 1.5 Hz, 1H, C–H), 6.75 (d, JHH = 2.0 Hz, 1H,
110.47 (d, JCP = 13.4 Hz, C3–H), 116.51 (d, JCP = 15.9 Hz, C2–H),
3
1
4
C–H), 6.96 (d, JHH = 3.5 Hz, 1H, C–H) 7.39ꢀ7.26 m, 30H, P(Ph)3).
122.27 (d, JCP = 187.1 Hz, C1), 123.38 (d, JCP = 11.6 Hz, C4–H). IR
(ATR, cmꢀ1): 740, 773, 949, 1013, 1081, 1161, 1217, 1388, 2981,
3381.
31P (CD2Cl2): d 89.8 (P@S), 4.0 P(Ph)3. 13C (CD2Cl2): d 16.05 (d,
3JCP = 8.3 Hz, CH3), 62.46 (s, CH3–CH2O), 111.06 (s, CH), 115.0 (d,
1
JCP = 26.0 Hz, CH), 125.50 (d, JCP = 199.1 Hz, C–P), 135.05 (d,
JCP = 27.0 Hz, CH), 128.80 (d, JCP = 8.5 Hz, aromatic CH), 129.80 (s,
aromatic CH), 134.00 (d, JCP = 17.0 Hz, aromatic CH), 134.25 (d,
JCP = 15.0 Hz, aromatic CP) Anal. Calc. for C44H43NO2P3SAg: C,
62.12; H, 5.10; N, 1.65; S, 3.77. Found: C, 61.91; H, 5.18; N, 1.66;
S, 3.51%.
4.4. Monitoring of the base-induced rearrangement
Three hundred milligrams (1.37 ꢂ 10ꢀ3 mole) of 2 in a small
schlenk tube are dissolved in 5 mL of THF. The solution is cooled
to ꢀ80 °C and 0.92 mL of cold BuLi in solution 1.5 N in hexanes is
then added. The mixture is stirred for 5 min then quickly trans-
fered into an NMR tube itself transfered into the probe of the
NMR machine at ꢀ80 °C. The obtained spectra are mentioned in
Table 1 and Fig. 1. See supporting informations for the different
NMR sequences.
4.8. Crystal structure determinations
X-ray intensities were measured, for 3, at a temperature of
150 K on a Nonius KappaCCD diffractometer with rotating anode
(graphite monochromator, k = 0.71073 Å) up to a resolution of
(sinhk)max = 0.65 Åꢀ1 and, for 4, at 100 K on an Oxford Diffraction
X-Calibur 2 CCD diffractometer with ordinary sealed X-ray tube
(graphite monochromator, k = 0.71073 Å) up to (sinhk)max =
0.62 Åꢀ1. The structures were solved with automated Patterson
methods (DIRDIF-99 [25]) for 3 or direct methods (SHELXS-97 [26])
for 4 and refined with SHELXL-97 [26] against F2 of all reflections.
Non-hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were located in a difference Fourier
map. Hydrogen atoms of the pyrrole rings in 3 were refined freely
with isotropic displacement parameters; all other hydrogen atoms
in 3 and 4 were refined with a riding model. The structure of 3 was
refined as a pseudo-orthorhombic twin with a twofold rotation
4.5. Trans bis(diethyl pyrrol-2-ylthiophosphonate)palladium (II),
trans-[Pd{
j
2-(N, S) 2-(NC4H3)-P(S)(OEt2)}2] (3)
To
a
suspension of palladium dichloride bis(acetonitrile)
(174 mg), in THF (10 mL) is added a solution of O,O-diethyl pyr-
rol-2-ylthiophosphonate 2 (300 mg; 1.37 mmol) and triethylamine
(0.20 g; 1.98 mmol) in THF (3 mL). The reactional mixture is stirred
at 20 °C for 48 h. The solution is then concentrated in vacuo and the
residue is purified by flash chromatography on silicagel (pentane/
ethyl acetate: v/v: 100/10) to produce pure complex 3 as orange-
red solid in 55% yield (200 mg). Recrystallisation in a diethyl-
ether/hexane mixture produces crystals suitable for single X-ray
diffraction analysis. m.p.: 158 °C. 1H NMR (CDCl3): d 1.37 (t,
*
about the c axis as twin operation. The twin fraction refined to

S. Marie et al. / Journal of Organometallic Chemistry 694 (2009) 4001–4007
4007
Table 2
(e) J. Fischer, M. Schürmann, M. Mehring, U. Zachwieja, K. Jurkschat,
Organometallics 25 (2006) 2886–2893;
Summary of crystal data, intensity measurement and structure refinement for
(f) P. Stepnicka, I. Cisarova, R. Gyepes, Eur. J. Inorg. Chem (2006) 926–938.
[4] (a) J.W. Faller, J.C. Wilt, Organometallics 24 (2005) 5076–5083;
(b) V.A. Kozlov, D.V. Aleksanyan, Y.V. Nelyubina, K.A. Lyssenko, E.I. Gutsul, L.N.
Puntus, A.A. Vasil’ev, P.V. Petrovskii, I.L. Odinets, Organometallics 27 (2008)
4062–4070;
compounds 3 at 150 K and 4 at 100 K.
3
4
Formula
Fw
C16H26N2O4P2PdS2
542.85
Orange
0.51 ꢂ 0.36 ꢂ 0.30
Monoclinic
P21/n (No. 14)
8.4244(12)
12.3934(8)
10.4326(10)
–
90.171(8)
–
1089.2(2)
2
1.655
1.214
C45H45AgCl2NO2P3S
935.56
Colourless
(c) B. Djordjevic, O. Schuster, H. Schmidbaur, Inorg. Chem. 44 (2005) 673–676;
(d) T. Kanbara, T. Yamamoto, J. Organomet. Chem. 688 (2003) 15–19;
(e) S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, Eur. J. Inorg. Chem. (2002) 2408–
2418;
(f) T. Cantat, X. Jacques, L. Ricard, X.F. Le Goff, N. Mézailles, P. Le Floch, Angew.
Chem., Int. Ed. 46 (2007) 5947–5950;
(g) M. Doux, L. Ricard, P. Le Floch, N. Mézailles, Dalton Trans. (2004) 2593–
2600;
(h) M. Doux, C. Bouet, N. Mézailles, L. Ricard, P. Le Floch, Organometallics 21
(2002) 2785–2788;
Crystal color
Crystal size [mm]
Crystal system
Space group
a [Å]
0.22 ꢂ 0.15 ꢂ 0.06
Triclinic
ꢀ
P1 (No. 2)
13.0140(7)
13.4931(6)
13.6775(7)
68.726(4)
77.947(4)
85.914(4)
2188.73(19)
2
b [Å]
c [Å]
a
[°]
b [°]
(i) M. Doux, N. Mézailles, M. Melaimi, L. Ricard, P. Le Floch, Chem. Commun.
(2002) 1566–1567.
a
[°]
V [Å3]
[5] (a) A. Buchard, A. Auffrant, C. Klemps, L. Vu-Do, L. Boubekeur, X.F. Le Goff, P. Le
Floch, Chem. Commun. (2007) 1502–1504;
Z
Dx [g/cm3]
1.420
0.777
(b) L. Boubekeur, L. Ricard, N. Mézailles, M. Demange, A. Auffrant, P. Le Floch,
Organometallics 25 (2006) 3091–3094;
l
[mmꢀ1
]
Absorption correction method
Absorption correction range
Reflection (measured/unique)
Parameter/restraints
Multi-scan
0.62–0.70
32604/2498
139/0
0.0149/0.0378
0.0156/0.0382
1.098
Multi-scan
0.951–0.955
18450/8919
498/4
0.0403/0.1175
0.0555/0.1270
1.077
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R1/wR2 [I > 2
r
(I)]
R1/wR2 [all reflection]
S
qmin/max [e/Å3]
ꢀ0.67/0.24
ꢀ1.44/1.20
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0.4890(7). Geometry calculations and checking for higher symme-
try was performed with the PLATON program [27].
Further details of the crystal structure determinations for 3 and
4 are given in Table 2.
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Santini, Dalton Trans. (2007) 4845–4853;
5. Supplementary material
CCDC 736696, 734792 contain the supplementary crystallo-
graphic data for complexes 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.
(d) S.O. Grim, S.A. Sangokoya, A.L. Rheingold, W. McFarlane, I.J. Colquhoun,
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We acknowledge CNRS for funding. This work was partially
supported (ML and ALS) by the Council for Chemical Sciences of
the Netherlands Organization for Scientific Research (NWO/CW).
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