Regioselective functionalization of iminophosphoranes through Pd-mediated C-H bond activation: C-C and C-X bond formation

Article abstract of DOI:10.1039/c003241g

The orthopalladation of iminophosphoranes [R₃PN-C ₁₀H₇-1] (R₃ = Ph₃1, p-Tol ₃2, PhMe₂3, Ph₂Me 4, N-C₁₀H ₇-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C ₆H₄-(PPh₂N-1-C₁₀H ₇)-2)-κ-C,N]₂ (5) or endo-[Pd(μ-Cl)(C ₆H₃-(P(p-Tol)₂N-C₁₀H ₇-1)-2-Me-5)-κ-C,N]₂ (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C₁₀H ₆-(NPPhMe₂)-8)-κ-C,N]₂ (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C₁₀H₆-(NPPh₂Me)-8)-κ-C,N] ₂ (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C₆H₄-(PPhMeN-C₁₀H ₇-1)-2)-κ-C,N]₂ (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C ₁₀H₆-(NPPh₂Me)-8)-κ-C,N]₂ (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C₆H₄-(PPhMeN-C₁₀H ₇-1)-2)-κ-C,N]₂ (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C₁₀H₆- (NPPhMe₂)-8)-κ-C,N]₂ (7), [Pd(μ-Cl)(C ₆H₄-(PPh₂NPh)-2)]₂ (17) and [Pd(μ-Cl)(C₆H₃-(C(O)NPPh₃)-2-OMe-4)] ₂ (18) with I₂ or with CO results in the synthesis of the ortho-halogenated compounds [PhMe₂PN-C₁₀H₆-I-8] (19), [I-C₆H₄-(PPh₂NPh)-2] (21) and [Ph ₃PNC(O)C₆H₃-I-2-OMe-5] (23) or the heterocycles [C₁₀H₆-(NPPhMe₂)-1-(C(O))-8]Cl (20), [C ₆H₅-(NPPh₂-C₆H₄-C(O)-2] ClO₄ (22) and [C₆H₃-(C(O)-1,2-N-PPh ₃)-OMe-4]Cl (24).

Full text of DOI:10.1039/c003241g

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Dalton Discussion 12: Catalytic C-H and C-X Bond
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PAPER
www.rsc.org/dalton | Dalton Transactions
Regioselective functionalization of iminophosphoranes through Pd-mediated
C–H bond activation: C–C and C–X bond formation†‡
David Aguilar,a Rafael Navarro,a Tatiana Solerb and Esteban P. Urriolabeitia*a
Received 16th February 2010, Accepted 6th May 2010
DOI: 10.1039/c003241g
=
The orthopalladation of iminophosphoranes [R3P N–C10H7-1] (R3 = Ph3 1, p-Tol3 2, PhMe2 3, Ph2Me
4, N–C10H7-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P
=
atom in 1 and 2, giving endo-[Pd(m-Cl)(C6H4-(PPh2 N-1-C10H7)-2)-k-C,N]2 (5) or endo-[Pd(m-Cl)-
=
(C6H3-(P(p-Tol)2 N–C10H7-1)-2-Me-5)-k-C,N]2 (6), while in 3 the 1-naphthyl group is metallated
=
instead, giving exo-[Pd(m-Cl)(C10H6-(N PPhMe2)-8)-k-C,N]2 (7). In the case of 4, orthopalladation at
room temperature affords the kinetic exo isomer [Pd(m-Cl)(C10H6-(N PPh2Me)-8)-k-C,N]2 (11exo),
while a mixture of 11exo and the thermodynamic endo isomer [Pd(m-Cl)(C6H4-(PPhMe N–C10H7-1)-
2)-k-C,N]2 (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer
=
=
=
[Pd(m-OAc)(C10H6-(N PPh2Me)-8)-k-C,N]2 (13exo) promotes the facile transformation of the exo
=
isomer into the endo isomer [Pd(m-OAc)(C6H4-(PPhMe N–C10H7-1)-2)-k-C,N]2 (13endo), confirming
that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have
led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes
=
=
[Pd(m-Cl)(C10H6-(N PPhMe2)-8)-k-C,N]2 (7), [Pd(m-Cl)(C6H4-(PPh2 NPh)-2)]2 (17) and
=
[Pd(m-Cl)(C6H3-(C(O)N PPh3)-2-OMe-4)]2 (18) with I2 or with CO results in the synthesis of the
=
=
ortho-halogenated compounds [PhMe2P N–C10H6–I-8] (19), [I–C6H4-(PPh2 NPh)-2] (21) and
[Ph3P NC(O)C6H3–I-2-OMe-5] (23) or the heterocycles [C10H6-(N PPhMe2)-1-(C(O))-8]Cl (20),
[C6H5-(N PPh2-C6H4–C(O)-2]ClO4 (22) and [C6H3-(C(O)-1,2-N–PPh3)-OMe-4]Cl (24).
=
=
=
The use of transition metals (TM) provides a brilliant solution
Introduction
to the lack of reactivity, since TM are able to activate and finally
cleave the C–H bond replacing it for a more reactive C–M bond.2
This new bond is, in most cases, highly reactive towards a large
variety of substrates. In addition, several strategies have been
developed to achieve selective C–H bond activations. Among
them, one of the most successful is based on the introduction
of ancillary groups, bonded to the target substrate, containing
donor atoms able to bond to the metal.4 This group is usually
called a “directing group” (DG). After the DG bonds to the metal,
only the C–H bonds in the vicinity of the metal will be activated.
The metallic systems that result from the bonding of a donor
atom and subsequent intramolecular C–H bond activation, with
concomitant C–M bond formation, are called cyclometallated
(Fig. 1).5
The transformation of the C–H bond, ubiquitous in organic
entities, in other types of C–X bonds (X = C, O, N, S, P and so on)
is a versatile strategy to build new structures or to introduce new
functional groups.1 This methodology is very convenient since
it avoids the use of pre-functionalized substrates, decreases the
number of reaction steps, and reduces waste disposals. However,
this useful and apparently easy reaction has two main drawbacks.
The first one is the inherent inertia of the robust and slightly
polar C–H bond,2 since the cleavage of most types of C–H bonds
involve energies of dissociation of around or higher than 100 kcal
mol-1.3 The second one is the ubiquity of the C–H bond since,
in the absence of a given source of discrimination, many C–H
bonds in the same molecule can be simultaneously functionalized,
resulting in the formation of isomers. For instance, an aryl ring
can be functionalized in ortho, meta or para with respect to a given
position. Therefore, there is not an efficient synthetic pathway for
a particular isomer.
aDepartamento de Compuestos Organometa´licos, Instituto de Ciencia de
Materiales de Arago´n, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12,
50009, Zaragoza, Spain. E-mail: esteban@unizar.es; Fax: +34976761187
Fig. 1 General strategy CH bond activation-functionalization.
bServicios Te´cnicos de Investigacio´n, Facultad de Ciencias Fase II, 03690,
San Vicente de Raspeig, Alicante, Spain
Cyclometallated compounds derived from Pd, or palladacycles,6
are by far the most widely used in synthesis, although cyclomet-
allated complexes of other metals, mainly Ru, Rh and Cu, have
also interesting applications.7 During the last few years the use
of palladacycles as synthetic tools has increased dramatically, as
evidenced by the number of papers appearing in the literature.8
† Based on the presentation given at Dalton Discussion No. 12, 13–15th
September 2010, Durham University, UK.
‡ Electronic supplementary information (ESI) available: Experimental
details for the synthesis of compounds 2–4, 8–10, 12exo, 14 and 15,
and complete crystallographic tables of 13exo. CCDC reference number
766306. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c003241g
10422 | Dalton Trans., 2010, 39, 10422–10431
This journal is
The Royal Society of Chemistry 2010
©

Orthopalladation provides an easy incorporation of functional
groups on target molecules. The introduction of methyl,9 acetate,10
methoxy,10 arylsulfonyl,11 ethoxycarbonyl,12 halogen,13 amide,14
amine,15 alkynyl,16 alkenyl,17 acyl18 or aryl19 functional groups,
as well as cyclization processes20 and mechanistic studies21 have
been reported. We have used this strategy very recently for the
successful functionalization of a-amino acids.22
those derived from C are unknown. We have found that species
A can be functionalized regioselectively at the ortho position
of the benzamide ring, and that species B are functionalized
only at the phenyl ring bonded to the P atom. In the case
of C we have found that the orthopalladation can be directed,
regioselectively, to either the N-naphthyl ring or the P-aryl ring
(kinetic vs. thermodynamic control), as a function of the reaction
conditions and the nature of the phosphine substituents. From
the kinetic isomer, functionalization at the 1-naphthyl ring has
been easily achieved. Therefore, at least three different modified
species have been obtained, providing selective reaction paths to
high-added value modified materials that are not easily prepared
by conventional methods.
Our aim here is to use the sequence orthopalladation-
functionalization for modification of iminophosphoranes (Fig. 2),
=
species of stoichiometry R3P NR¢ (R = alkyl, aryl; R¢ =
alkyl, aryl, cyano, keto, etc.) which are versatile and valuable
precursors in organic synthesis.23,24 Therefore to provide new
synthetic methods, alternative to the already established methods
of Staudinger,25 Kirsanov26 or Pomerantz,27 is highly desirable.
The proposed method seems feasible since orthopalladation of
iminophosphoranes through C–H bond activation is a well known
process.28,29 We have also shown that in these species it is possible
to direct the activation to a particular C–H bond in the cases
where two palladations are available.29b,d,f,h,i When the substrates
are carbonyl-stabilized iminophosphoranes (Fig. 3a) the pallada-
tion is selectively directed to this ring, giving exo compounds.
In contrast, non-stabilized benzyl iminophosphoranes (Fig. 3b)
undergo palladation either at the benzyl ring or at the aromatic
rings bonded to the phosphine group, depending on the phosphine
substituents and the reaction conditions. This fact is advantageous,
since it allows the functionalization of the same substrate at two
different positions only by changing the reaction conditions.
Results and discussion
Study of orthopalladation of naphthyl-iminophosphoranes
=
The iminophosphorane Ph3P N-1-C10H7 (1) has been prepared
following reported methods.30a The substrates 2–4, also containing
the 1-naphthyl group, have been prepared following the same
experimental procedure, by reaction of 1-naphthyl azide30b with
the corresponding phosphines. The IR spectra of 1–4 show
intense absorptions in the 1335–1350 cm-1 region, assigned to the
nP= stretch. These values are similar to those found in related
N
1
species.28i,29a The 31P{ H} NMR spectra of 1–4 show a single peak
on each case, with chemical shifts around 4–8 ppm, similar to
previous values found for related systems.28i,29a
The reactivity of 1–4 towards Pd has been carried out using the
usual palladating systems, and the best results were obtained with
Pd(OAc)2 (OAc = acetate). Thus, the reaction of Pd(OAc)2 with
1 (1 : 1 molar ratio) in CH2Cl2 at 25 ◦C, and further treatment of
the plausible acetate intermediate (see below) with LiCl in MeOH
Fig. 2 Functionalizable positions on iminophosphoranes.
=
gives the orthopalladated [Pd(m-Cl)(C6H4-(PPh2 N–C10H7-1)-2)-
k-C,N]2 (5) (Scheme 1). Other conditions were tested, from
refluxing CH2Cl2 to refluxing toluene, but 5 was obtained in
all studied cases. The incorporation of the Pd atom takes place
regioselectively at the ortho position of one phenyl ring bonded
to the P atom, giving endo derivatives.29 5 is insoluble in common
organic solvents, and a full characterization has been carried out
on the more soluble acac complex 8 (acac = acetylacetonate),
obtained by reaction of 5 with Tlacac (1 : 2 molar ratio) (Scheme 1).
Fig. 3 Different orientations in orthopalladated iminophosphoranes.
Driven by this hypothesis, we have attempted the func-
tionalization of three types of iminophosphoranes, shown in
Fig. 4: stabilized systems containing the benzamide ring (A), semi-
stabilized systems containing the N-phenyl ring (B) and semi-
stabilized systems containing the N-1-naphthyl group (C). While
orthopalladated complexes of A and B have been reported,28j,29b,i
Fig. 4 Iminophosphoranes of interest.
Scheme 1 (i) Pd(OAc)2, CH2Cl2; (ii) LiCl, MeOH; (iii) Tl(acac), CH2Cl2.
Dalton Trans., 2010, 39, 10422–10431 | 10423
This journal is
The Royal Society of Chemistry 2010
©

1
The endo palladation is evident from the observation in the H
and another one zwitterionic in which the N atom supports a
formal negative charge while the P atom supports a formal positive
charge P(+)–N(-). In complexes 5 and 6 the palladation reaction
occurs at the aryl rings bonded to the phosphonium P atom, which
are the most electron-deficient rings of the molecule compared
with the naphthyl rings. This observation is incompatible with
an electrophilic substitution on an aromatic ring (SEAr), where
palladation is favoured at the most electron-rich aryl group, and
strongly suggests a concerted metalation–deprotonation (CMD)
mechanism.31 In iminophosphorane 3, two phenyl groups have
been replaced by two methyl groups, decreasing notably the formal
positive charge at the P atom. In 3, the Ph ring bonded to the
P atom is less electron-deficient than in previous cases, but the
comparison should also be done with the competing naphthyl
group. This decrease, according to the experimental data, seems
to be large enough to promote the change in the orientation of the
palladation, which is directed to the naphthyl ring in 7.
NMR spectrum of 8 of seven signals due to the naphthyl ring. The
permanence of the peak at 9.10 ppm, assigned to the proton at
8-position of the naphthyl ring, is especially relevant since this
position should be the most prone to undergo activation and
further metalation. Moreover, four well separated signals in the 1H
NMR spectrum of 8 can be assigned to the presence of a PdC6H4
ring. The formation of the endo palladacycle is also inferred from
the deshielding of the 31P resonance, which moves from 3.50 ppm in
1 to 47.80 ppm in 8. This large downfield shift has been observed in
related endo systems.29 In the case of 5, two signals were observed
1
in the 31P{ H} NMR spectrum, in the same region, due to the
presence of the cis and trans isomers.
Since the variation of the reaction conditions and/or the palla-
dating reagent did not change the orientation of the palladation,
we modified the phosphine. We had found previously that the
=
palladation of Ph3P NCH2Ph occurs at the PPh3 fragment, and
that more basic phosphines promoted changes in selectivity.29d
Thus, iminophosphoranes 2–4, derived from P(p-tol)3, PPhMe2
and PPh2Me, respectively, were reacted with Pd(OAc)2 (Schemes 1
and 2). We indeed found the expected change of reactivity.
The change from the regioselective endo palladation in
=
Aryl3P N–Np systems (1 or 2; Np = naphthyl) to the regios-
=
elective exo palladation in Me2PhP N–Np (3) in mild reaction
conditions suggests that the modulation of the electronic prop-
erties of the iminophosphorane by phosphine modification is
relevant. Therefore, intermediate behaviour should be expected
for a phosphine with intermediate electronic and steric properties
with respect to those known for PAryl3 and PPhMe2.
=
Indeed, the reaction of [MePh2P N–C10H7-1] (4) with
Pd(OAc)2 (1 : 1 molar ratio) in CH2Cl2 at 25 ◦C and further
treatment of the acetate intermediate with excess LiCl in MeOH
=
gives the exo complex [Pd(m-Cl)(C10H6-(N PPh2Me)-8)-k-C,N]2
(11exo). Complex 11exo reacts with Tlacac (1 : 2 molar ratio)
=
to give [Pd(acac-O,O¢)(C10H6-(N PPh2Me)-8)-k-C,N] (12exo).
This metallation has been attempted at different temperatures.
Interestingly, we have found that an increase of the temperature
promotes the formation of the endo complex [Pd(m-Cl)(C6H4-
=
(PPhMe N–C10H7-1)-2)-k-C,N]2 (11endo). Therefore, when 4 was
reacted with Pd(OAc)2 in refluxing CH2Cl2, followed by the usual
workup, we obtained a mixture of 11exo/11endo in molar ratio
1/0.2. Further increase of the temperature (toluene 80 C) gives
Scheme 2 (i) Pd(OAc)2, CH2Cl2; (ii) LiCl, MeOH; (iii) Pd(OAc)2, tol, D;
(iv) Tl(acac), CH2Cl2; (v) AgOAc, CH2Cl2.
◦
a 11exo/11endo molar ratio of 0.5/1 and when the reaction is
performed in refluxing toluene the 11exo/11endo molar ratio is
0.4/1. The reaction of 4 with Pd(OAc)2 in toluene at 25 ◦C gives
11exo as the only reaction product, showing that the reaction
temperature, and not the nature of the solvent, is the critical
parameter in the final distribution of the products. Complex
11endo could no be isolated in pure form, and could not be fully
characterized.
The results mentioned above suggest that 11exo is the kinetic
isomer of the reaction and that 11endo is the thermodynamic
isomer. However, it could also be possible that the formation of
11exo from 4 and Pd(OAc)2 was irreversible and that the isomer
exo does not transform in the isomer endo. Aiming to clarify
this point we have attempted the transformation of 11exo into
11endo by heating 11exo in toluene and monitoring the reaction
by 31P NMR. However, we did not observe any transformation
under these reaction conditions. Our group reported that this
type of transformation occurs only under the assistance of acetate
ligands.29d We prepared then the acetate bridge 13exo (Scheme 3)
by reaction of 11exo with AgOAc (1 : 2 molar ratio). Subsequent
heating of 13exo in toluene-d8 promotes the slow disappearance of
=
The reaction of [(p-tol)3P N-1-C10H7] (2) with Pd(OAc)2 under
the same reaction conditions as those employed in the palladation
of 1 (CH2Cl2, 25 ◦C) afforded the endo complex [Pd(m-Cl)(C6H3-
(P(p-tol)2 N–C10H7-1)-2-Me-5)-k-C,N]2 (6). Other reaction con-
ditions (reflux, CH2Cl2 or toluene) also afforded 6 with only small
changes in the reaction yield. In clear contrast with these results,
=
=
the treatment of [PhMe2P N–C10H7-1] (3) with Pd(OAc)2 (1 : 1
molar ratio) in CH2Cl2 at r.t., and further reaction with LiCl in
=
MeOH, yields the exo complex [Pd(m-Cl)(C10H6-(N PPhMe2)-
8)-k-C,N]2 (7). A moderate or strong increase of the temperature
(refluxing CH2Cl2, CHCl3 or toluene) does not promote a different
palladation pathway, since 7 is obtained under all the studied
conditions. It is noteworthy that 7 is obtained as a single isomer,
since only one peak is observed in the 31P{ H} NMR spectrum.
1
The trans configuration is probably adopted to minimize the
interaction between the two phosphine groups.
The change of orientation in the orthopalladation seems to
shed light on its mechanism. The starting substrates 1 and 2,
and in general the iminophosphoranes, can be represented in two
canonical forms,29 one neutral with a formal double bond P N
=
10424 | Dalton Trans., 2010, 39, 10422–10431
This journal is
The Royal Society of Chemistry 2010
©

Scheme 3 (i) Ag(OAc), CH2Cl2, rt; (ii) Toluene, 80 ◦C.
the peak at 35.13 ppm (due to 13exo) and the appearance of new
signals at 48.50 ppm, assigned to the acetate dimer 13endo (see
Scheme 3). The molar ratio after heating at 40 ◦C for 30 min
(13exo/13endo = 1/0.1) is very similar to that found for the
mixture 11exo/11endo obtained in refluxing CH2Cl2. Further
heating at 80 ◦C and at reflux temperature produced mixtures
of composition 0.5/1 and 0.4/1, respectively, reproducing the
ratios 11exo/11endo obtained from isolated products. In a separate
experiment, 13exo was heated at 80 ◦C since the beginning of
the reaction. The observed 13exo/13endo molar ratios were 1/0.2
(after 10 min) 1/0.8 (after 1 h) and 0.4/1 (after 2 h). It seems
clear that the metallation of 13exo is reversible and that 13exo and
13endo are the kinetic and thermodynamic isomers, respectively,
of the orthopalladation of 4 with Pd(OAc)2. It is remarkable that
the transformation of the isomers occurs in toluene, an aprotic
and apolar solvent. While similar isomerizations reported the use
of acidic medium as acetic acid,32 very few have been reported
in aprotic media.33 The transformation of 13exo into 13endo in
non protic solvents seems to suggest an intramolecular transfer
of the proton, assisted by the basic acetate ligand, although the
participation of the solvent in the proton transfer (mainly in the
case of toluene) could not be discarded.34
Fig. 5 Molecular structure of 13exo with ellipsoids drawn at the 50%
probability level.
phosphine groups is high, as can be deduced by the fact that the
two molecular planes are not eclipsed, but slightly staggered.
Each Pd atom is located on a slightly distorted square-planar
environment, surrounded by the iminic nitrogen, the two oxygens
of the acetate groups and the carbon atom at the peri positions of
the naphthalene ring, confirming the exo palladation. The Pd(1)–
˚
N(1) and Pd(1)–N(2) bond distances [2.086(2) and 2.079(2) A,
respectively] are larger than those found in related acetate bridged
complexes,35 which are in the range 2.006(2)–2.037(2) A. The Pd–
˚
˚
C bond distances [Pd(1)–C(101) 1.954(3) A and Pd(2)–C(201) =
˚
1.956(3) A] fall in the usual range of distances found for this type
The X-ray determination of the molecular structure of complex
13exo confirms the structure proposed here. Crystals of 13exo
adequate for X-ray diffraction were obtained by slow diffusion of
vapour of Et2O into a CH2Cl2 solution of the crude complex at
of complex,35 as well as the Pd–O bond distances. Other internal
parameters are as expected and do not merit further comment.
Aiming to expand the scope of functionalizable substrates, we
have also tested the orthopalladation of iminophosphorane 14,
which contains an additional phosphine group and is expected to
behave as a tridentate ligand. Compound 14 has been obtained
by reaction of Ph2PCH2PPh2 with 1-naphthylazide (1 : 1 molar
ratio). The reaction was performed maintaining an excess of
phosphine, by adding dropwise the azide to a solution of the bis-
◦
5 C. A drawing of the molecular structure of 13exo is shown in
˚
Fig. 5 and selected bond distances (A) and angles (deg) are sum-
marized in Table 1. The most relevant crystallographic parameters
are collected in Table S1 (ESI). Complex 13exo shows the typical
open-book structure, very usual in complexes with acetate bridges.
The relative arrangement of the two cyclopalladated units is trans,
probably in order to minimize intramolecular interactions. Even
with this conformation the steric hindrance between the two bulky
=
phosphine; otherwise, the bis-iminophosphorane H2C(PPh2 N-
1-C10H7)2 was obtained. As expected, 14 reacts with Pd(OAc)2
(1 : 1 molar ratio) in refluxing CH2Cl2, followed by treatment with
LiCl in MeOH, to give 15 as depicted in Scheme 4.
◦
˚
Table 1 Selected bond distances (A) and angles ( ) for 13exo
Pd1–C1O1
Pd1–O2
Pd1–O4
Pd1–N1
P1–N1
N1–C109
O3–C124
O4–C124
C101–Pd1–O2
C101–Pd1–N1
O2–Pd1–O4
N1–Pd1–O4
C101–Pd1–Pd2
O2–Pd1–Pd2
N1–Pd1–Pd2
1.954(3)
2.0524(19)
2.153(2)
2.086(2)
1.621(2)
1.419(3)
1.270(3)
1.247(3)
90.48(11)
81.81(10)
84.19(8)
102.74(8)
119.09(8)
80.44(5)
105.73(6)
Pd2–C2O1
Pd2–O3
Pd2–O1
Pd2–N2
P2–N2
N2–C209
O1–C224
O2–C224
C201–Pd2–O3
C201–Pd2–N2
O3–Pd2–O1
N2–Pd2–O1
C201–Pd2–Pd1
O3–Pd2–Pd1
N2–Pd2–Pd1
1.956(3)
2.0466(18)
2.1658(18)
2.079(2)
1.622(2)
1.421(3)
1.242(3)
1.265(3)
91.40(10)
81.91(10)
82.91(7)
102.75(8)
119.32(7)
80.32(5)
106.39(6)
Scheme 4 (i) Pd(OAc)2, CH2Cl2; (ii) LiCl, MeOH.
3
The characterization of the k -C,N,P bonding mode of the
iminophosphorane in 15 is unambiguous. Moreover, the structure
of 15 is relevant, since it contains a naphthyl group and a
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 10422–10431 | 10425
©

phosphine fragment arranged in trans. This type of disposition is
usually very unstable due to the antisymbiotic effect.36 This effect,
referred to the pair of groups aryl/phosphine, has been renamed as
transphobia.37 Probably the release of energy during the formation
of two chelating rings is responsible for the stabilization. In
summary, we have demonstrated the possibility to palladate
several iminophosphoranes at selected positions. In most cases
the palladation is selective regardless of the reaction conditions,
while in others it is also possible to direct it as a function of
the temperature. The next step will be the functionalization of
iminophosphoranes by using these new orthopalladated com-
plexes as synthetic tools.
with phenantroline giving PdCl2(phen) and releasing the free
iminophosphorane.
Therefore, we have been able to synthesize three different
types of modified iminophosphoranes, using orthopalladated
complexes, by regioselective introduction of an iodine atom at
specific positions. Compound 19 contains the 8-I-C10H6-1-N
skeleton, which could be used in the preparation of other useful
derivatives, for instance 8-iodo-1-aminonaphthalene. Although
the synthesis reported here involves a four step process (azide,
iminophosphorane, orthopalladation, iodination) from the 1-
aminonaphthalene to the final product, it can be considered an
alternative to traditional methods.39 Not only do our obtained
yields range from moderate to high, but also in most reported
synthesis the starting material is an halogenated and/or aminated
derivative or a doubly aminated substrate. Besides, compound 21 is
also very interesting, since it contains the fragment o-IC6H4PPh2,
and it is a precursor for (2-iodophenyl)-diphenylphosphine, a very
versatile reagent.40a Two main methods have been reported for the
synthesis of this phosphine. The method of Tunney and Stille40b
involves the use of Ph2PSiMe3 under Pd-catalysis but gives low
yields (20%), while the method of Schlosser40c uses the borane-
adduct Ph3P·BH3 as starting material and strong deprotonating
reagents (BuLi and KOtBu). The method reported here is the
simplest of all methods currently available. However, for iodinated
benzamide 30, this method is not competitive with standard
procedures from lithiated complexes. More work to determine
the tolerance towards different functional groups present on the
benzamide ring has to be done in order to assess the competitivity
of this method for similar iodinated benzamides.
Stoichiometric functionalization of iminophosphoranes
The formation of new C–I and C–C bonds in iminophospho-
ranes has been achieved by the reaction of the corresponding
orthopalladated complexes with stoichiometric amounts of I2 or
CO, respectively. Reactions on selected compounds (of types C,
B and A in Fig. 4) are depicted in Schemes 5 (I2) and 6 (CO).
3 belongs to C-type compounds and has been functionalized
=
through orthopalladated 7. Ph3P NPh and 16 belong to the B-
and A-type compounds, respectively, and react through 17 and 18.
It has been demonstrated that almost all the different functional
=
groups—the naphthyl in 3, the phosphine in Ph3P NPh and the
benzamide ring in 16—have been successfully modified.
A different approximation to the functionalization of orthopal-
ladated substrates is the carbonylation process. The treatment
of palladacycles with CO is an excellent method for the for-
mation of new C–C bonds, resulting in the synthesis of carbo-
or heterocycles.6,41 We have used this methodology recently to
synthesize isoindolones from phenylglycine.22 Therefore, if we
react the orthopalladated derivatives from iminophosphoranes A,
B and C we can expect the incorporation of the CO molecule
at a naphthyl ring, at a P-phenyl ring and at a benzamide ring,
respectively. A solution of the chloride bridge dimers 7 and 18, or
a freshly prepared solution of the solvate obtained by reaction of
17 with AgClO4 (1 : 2 molar ratio) in THF, were stirred under
a CO atmosphere for 15 h (Scheme 6). During this time the
starting organometallic complexes decomposed to black Pd0. The
corresponding heterocycles 20, 22 and 24 (Scheme 6) can be
isolated after elimination of the Pd0 and removal of the solvent.
The new heterocycles are interesting since they contain frag-
ments that are potentially biologically active. For instance, het-
erocycle 20 can be considered as a N-phosphonium derivative
of the benzo[cd]indol-2(1H)-one.42 These types of derivative have
been tested as enzyme inhibitors or hypotensive agents.42 On the
other hand, compounds 22 and 24 can also be considered as
P-derivatives of the isoindolone skeleton: in the case of 22 the
PPh2 group replaces the CH2 unit, while 24 is a N-phosphonium
substituted isoindoldione. The isoindolone skeleton is also present
on a wide variety of molecules with high biological activity.
All these organic structures can be built up very easily from
iminophosphoranes, under controlled conditions and in a few
reaction steps (4). The tolerance of these reactions towards the
presence of different functional groups on the aryl rings to
Scheme 5 (i) I2, phen, CH2Cl2, r.t.
The treatment of 7, 17 or 18 with elemental iodine (1 : 2 molar
ratio) in CH2Cl2 for 15 h at room temperature gives a black sus-
pension, from which a solid characterized as PdI2 was separated.
Subsequent workup of the respective solutions following reported
procedures22,38 gives the corresponding iodinated derivatives 19,
21 or 23 (Scheme 5). The proposed reaction mechanism is very
similar to that reported previously,22,38 via the oxidative addition
of the I2 to the cyclopalladated complex, followed by the formation
of the C–I bond by reductive elimination. A symmetrization
process is responsible for the formation of the insoluble PdI2
(eliminated from the reaction medium) and one intermediate
(not isolated) of plausible stoichiometry PdCl2L2 (L = modified
N-bonded iminophosphorane). This intermediate was reacted
10426 | Dalton Trans., 2010, 39, 10422–10431
This journal is
The Royal Society of Chemistry 2010
©

in CDCl3, CD2Cl2 and DMSO-d6 solutions at 25 ◦C on Bruker
AV300, AV400 or AV500 spectrometers (d in ppm, J in Hz) at 1H
operating frequency of 300.13, 400.13 or 500.13 MHz respectively.
1H and 13C spectra were referenced using the solvent signal as
internal standard, while 31P spectra were externally referenced
to H3PO4 (85%). ESI (ESI+) mass spectra were recorded using
an Esquire 3000 ion-trap mass spectrometer (Bruker Daltonic
GmbH) equipped with a standard ESI/APCI source. Samples
were introduced by direct infusion with a syringe pump. Nitrogen
served both as the nebulizer gas and the dry gas. The mass
spectra (MALDI+) were recorded from CHCl3 solutions on
a MALDI-TOF Microflex (Bruker) spectrometer (DCTB as
=
matrix). Ph3P NPh is commercial (Aldrich) and was used as sup-
30a
=
=
plied. Compounds Ph3P N-1-C10H7 (1), Ph3P NC(O)C6H4-
3-OMe (16)27,29i and complexes [Pd(m-Cl)(C6H4-(PPh2 NPh)-2)-
=
k-C,N]2 (17)28i,j and [Pd(m-Cl)(C6H3-(C(O)N PPh3)-2-OMe-4)-k-
=
C,N]2 (18)29b,i were preparared by reported methods.
Scheme 6 (i) CO, -Pd(0); (ii) AgClO4, CO, -Pd(0).
=
[Pd(l-Cl)(C6H4-(PPh2 N–C10H7-1)-2)-j-C,N]2 (5)
be functionalized is currently under study in our laboratories.
This will determine the prospect of applicability of the synthetic
methods described here.
To a solution of 1 (0.40 g, 1.00 mmol) in CH2Cl2 (20 mL), Pd(OAc)2
(0.223 g, 1.00 mmol) was added. The resulting orange solution
was stirred at 25 ◦C for 4 h. After the reaction time, partial
decomposition was evident since black palladium was observed.
This suspension was filtered through a Celite pad, and the resulting
orange solution was evaporated to dryness. The orange residue
was dissolved in methanol (20 mL) and anhydrous LiCl (0.168 g,
4.0 mmol) was added. The subsequent stirring (2 h at 25 ◦C) results
in the precipitation of 5 as an orange solid, which was filtered,
washed with MeOH (5 mL) and Et2O (25 mL) and dried in vacuo.
Obtained: 0.36 g (67% yield). Anal. Calc. for [C56H42Cl2N2P2Pd2]
(1088.6): C, 61.78; H, 3.89; N, 2.57. Found: C, 61.50; H, 3.52; N,
2.28. IR: 1274 (nP=N) cm-1. MS (MALDI+): 509 (40%) [M/2-Cl]+.
Conclusions
The orthopalladation of naphthyl-substituted semistabilized
iminophosphoranes can be oriented regioselectively towards the
naphthyl ring or towards the phosphine aryl rings, as a function
of the substituents at the P atom and the reaction temperature,
giving exo or endo complexes, respectively. The exo compound is
the kinetic isomer while the endo is the thermodynamic isomer. The
=
functionalization of different iminophosphoranes, as PhMe2P N-
=
=
1-Np (Np = naphthyl), Ph3P N–Ph and Ph3P NC(O)C6H3R,
31P{ H} NMR (CDCl3): d = 44.52, 45.53. 1H NMR (CDCl3): d =
1
has been achieved through their orthopalladated complexes. The
=
exo derivative of PhMe2P N-1-Np allows for the introduction
6.72–8.28 (m, 20 H, C10H7+H3+H4+H5, C6H4, cis + trans), 8.98,
9.44 (2d, 2H6, C6H4, cis + trans, 3JHH = 7.5).
of an iodine atom or a CO group at the 8 position of the
naphthyl fragment, giving derivatives of 8-iodo-naphthaleneamine
=
or of benzo[cd]indolone, while the orthopalladation of Ph3P N–
Ph results in the synthesis of derivatives like Ph2PC6H4-2-
I or phosphaisoindolones. The stabilized iminophosphorane
=
[Pd(l-Cl)(C6H3-(P(p-tol)2 N–C10H7-1)-2-Me-5)-j-C,N]2 (6)
Complex 6 was obtained following a synthetic method similar to
that described for 5. Therefore, Pd(OAc)2 (0.126 g, 0.56 mmol)
reacted with 2 (0.250 g, 0.56 mmol) in dry CH2Cl2 (20 mL) and
with anhydrous LiCl (0.095 g, 2.24 mmol) in MeOH (20 mL) to
give 6 as a yellow solid. Obtained: 0.208 g (64% yield). Anal. Calc.
for [C62H54Cl2N2P2Pd2] (1172.78 g mol-1): C, 63.49; H, 4.64; N,
2.39. Found: C, 62.95; H, 4.30; N, 2.19. IR: 1269 (nP=N) cm-1. MS
=
Ph3P NC(O)C6H3R undergoes stoichiometric introduction of
iodine or CO gives iodobenzamido-iminophosphoranes or N-
substituted phthalimides with a phosphonium group.
Experimental section
(MALDI+): 544 (45%) [M/2-Cl]+. 31P{ H} NMR (CDCl3): d =
1
Safety note
1
42.78, 44.71. H NMR (CDCl3): d = 2.04, 2.05, 2.14, 2.18, 2.31,
Caution! Perchlorate salts of metal complexes with organic ligands
are potentially explosive. Only small amounts of these materials
should be prepared and they should be handled with great caution.
See J. Chem. Educ. 1973, 50, A335–A337.
2.35 (6 s, Me, cis and trans), 6.28–8.21 (m, 28 H, C10H7 + H3 + H4,
C6H3, cis and trans), 9.06, 9.88 (d, 2H, H6, C6H3, cis and trans,
3JHH = 7.5).
=
[Pd(l-Cl)(C10H6-(N PPhMe2)-8)-j-C,N]2 (7)
General methods
Complex 7 was obtained following a synthetic method similar to
that described for 5. Therefore, Pd(OAc)2 (0.241 g, 1.07 mmol)
reacted with 3 (0.300 g, 1.07 mmol) in dry CH2Cl2 (30 mL) and
with anhydrous LiCl (0.180 g, 4.2 mmol) in MeOH (20 mL) to
give 7 as a yellow solid. Obtained: 0.20 g (45% yield). Anal. Calc.
for [C36H34Cl2N2P2Pd] (840.36): C, 51.45; H, 4.08; N, 3.33. Found:
Solvents were dried and distilled using standard procedures
before use. Elemental analyses (CHNS) were carried out on a
Perkin-Elmer 2400-B microanalyser. IR spectra (4000–380 cm-1)
were recorded on Perkin-Elmer Spectrum One or Spectrum 100
spectrophotometers. 1H, 13C and 31P NMR spectra were recorded
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 10422–10431 | 10427
©

C, 50.93; H, 3.80; N, 2.91. IR: 1288 (nP=N) cm-1. MS (FAB +): 385
stirred under exclusion of light for 30 min. After the reaction time,
the suspension obtained was filtered through a Celite pad, and the
resulting solution was evaporated to dryness. The orange residue
was stirred with Et2O (25 mL), giving 13exo as a yellow solid.
Obtained: 0.170 g (71% yield). Anal. Calc. for [C50H44N2O4P2Pd2]
(1011.68): C, 59.36; H, 4.38; N, 2.77. Found: C, 58.95; H, 4.19; N,
2.56. IR: 1581 (nCO, acac), 1548 (nCO, acac), 1256 (nP=N) cm-1. MS
1
1
(40%) [M/2-Cl]+. 31P{ H} NMR (CDCl3): d = 33.81. H NMR
(CDCl3): d = 2.24 (d, 6H, Me, PMe2, 2JHP = 12.8), 5.95 (d, 1H, H7,
C10H6, 3JHH = 7.5), 6.80 (t, 1H, H6, C10H6, 3JHH = 7.8), 6.92–6.94
(m, 2H, H4 + H3, C10H6), 7.01 (d, 1H, H5, C10H6, 3JHH = 7.0), 7.24
(d, 1H, H2, C10H6, 3JHH = 7.9), 7.44–7.53 (m, 3H, Hm + Hp, PPh),
1
7.77 (m, 2H, Ho, PPh). 13C{ H} NMR (CDCl3): d = 16.52 (d,
Me, PMe2, 1JPC = 70.7), 111.10 (d, C7, C10H6, 3JPC = 7.6), 118.45,
122.61, 124.78, 125.03, 128.61 (s, C2, C3, C4, C5, C6, C10H6), 129.46
(d, Cm, PPh, 3JPC = 12.0), 130.67 (d, Co, PPh, 2JPC = 10.1), 132.78
(s, Cp, PPh), 141.94 (d, C8, C10H6, 2JPC = 4.1), 144.33 (d, C1, C10H6,
3JPC = 1.9). Peaks assigned to the C4 and C8 carbons of the C10H7
ring, and Ci carbon of the Ph ring were not observed.
(MALDI +): 447 (60%) [M/2-OAc]+. 31P{ H} NMR (CDCl3): d =
1
35.09. 1H NMR (CDCl3): d = 1.87 (s, 3H, Me, OAc), 2.20 (d, 3H,
3
Me, PMe,2JHP = 12.9), 5.93 (d, 1H, H7, C10H6, JHH = 7.4), 6.72
3
3
(t, 1H, H6, C10H6, JHH = 7.0), 6.80 (d, 1H, C10H6, JHH = 7.0),
3
3
6.88 (d, 1H, H5, C10H6, JHH = 7.6), 6.99 (t, 1H, C10H6, JHH
=
6.7), 7.18–7.21 (m, 1H, C10H6), 7.44–7.70 (m, 10H, Hm + Hp + Ho,
PPh2). 13C{ H} NMR (CDCl3): d = 18.13 (d, Me, PMe, JPC
=
1
1
=
79.5), 24.87 (s, Me, OAc), 112.32 (s broad, C7, C10H7), 117.62 (s
broad, C5, C10H7), 122.33 (s broad, C10H7), 124.28 (s broad, C10H7),
124.82 (s broad, C6, C10H7), 127.19 (s broad, C10H7), 128.87 (s
broad, Cm, PPh2), 131.87 (s broad, Cp, PPh2), 132.47 (s broad, Co,
PPh2), 141.84 (s broad, C1, C10H7), 153.78 (s broad, C8, C10H7).
The peaks assigned to the Ci, (PPh2), C4a, C8a (C10H6) and CO
(OAc) carbon atoms were not observed.
[Pd(l-Cl)(C10H6-(N PPh2Me)-8)-j-C,N]2 (11exo)
Complex 11exo was obtained following a synthetic method similar
to that described for 5. Therefore, Pd(OAc)2 (0.131 g, 0.58 mmol)
reacted with 4 (0.200 g, 0.58 mmol) in dry CH2Cl2 (30 mL) at 25 ◦C
and with anhydrous LiCl (0.100 g, 2.36 mmol) in MeOH (20 mL)
to give 11exo as a yellow solid. Obtained: 0.110 g (40% yield).
Anal. Calc. for [C46H38Cl2N2P2Pd2] (964.57): C, 57.28; H, 3.97;
N, 2.90. Found: C, 56.53; H, 3.41; N, 2.69. IR: 1288 (nP=N) cm-1.
=
[Pd(l-OAc)(C10H6-(N PPh2Me)-8)-j-C,N]2 (13exo) and
1
MS (FAB +): 446 (40%) [M/2-Cl]+. 31P{ H} NMR (CDCl3): d =
=
[Pd(l-OAc)(C6H4-(PPhMe N–C10H7-1)-2)-j-C,N]2 (13endo)
31.62. 1H NMR (CDCl3): d = 2.70 (d, 3H, Me, PMe), 5.72 (d, 1H,
H7, C10H6, 3JHH = 7.4), 6.64 (t, 1H, H6, C10H6, 3JHH = 7.7), 6.74 (d,
1H, C10H6, 3JHH = 7.1), 6.78–6.83 (m, 2H, H5 + H3, C10H6), 6.92
The mixture 13exo/13endo was prepared following the same syn-
thetic method as that reported for 13exo. Therefore, 11exo/11endo
(0.18 g, 0.19 mmol) reacted with AgClO4 (0.069 g, 0.41 mmol) in
CH2Cl2 (20 mL) to give 13exo/13endo as a deep orange solid.
Obtained: 0.11 g (58% yield). This solid was characterized as the
mixture 13endo/13exo (1/0.4) by integration of the corresponding
(m, 1H, C10H6), 7.48–7.59 (m, 6H, Hm+ Hp, PPh2), 7.75 (m, 4H,
1
Ho, PPh2). 13C{ H} NMR (CDCl3): d = 18.90 (d, Me, PMe, 1JPC
=
77.4), 110.73 (d, C7, C10H6, 3JPC = 7.7), 117.41 (s, C5, C10H6), 121.37
(s, C10H6), 123.92 (s, C3, C10H6), 124.02 (s, C6, C10H6), 126.90 (d,
1
Ci, PPh2, JPC = 93.6), 127.91 (s, C10H6), 128.49 (d, Cm, PPh2,
1
resonances in the 31P{ H} NMR spectrum: a broad peak at
3JPC = 12.4), 131.61 (d, Co, PPh2, 2JPC = 9.9), 132.15 (s, Cp, PPh2),
133.48 (s, C4a, C10H6), 141.12 (d, C8a, C10H6, 3JPC = 16.6), 141.83
(s, C1, C10H6), 152.39 (d, C8, C10H6, 2JPC = 2.6).
35.1 ppm is assigned to 13exo, while a very broad signal about
48–49 ppm is assigned to the different isomers of 13endo. IR: 1579
(nCO,acac), 1545 (nCO, acac), 1265 (nP=N) cm-1. MS (MALDI +):
447 (55%) [M/2-OAc]+.
=
[Pd(l-Cl)(C10H6-(N PPh2Me)-8)-j-C,N]2 (11exo) and
=
[Pd(l-Cl)(C6H4-(PPhMe N–C10H7-1)-2)-j-C,N]2 (11endo)
=
[PhMe2P N–C10H6–I-8] (19)
To a solution of 4 (0.35 g, 1.02 mmol) in toluene (20 mL), Pd(OAc)2
(0.230 g, 1.02 mmol) was added. The resulting brown solution was
refluxed for 2 h. Decomposition of the Pd salt was evident since
black Pd was observed. The suspension was filtered through a
Celite pad, the resulting orange solution was evaporated to dryness
and the residue was dissolved in methanol (20 mL). The addition
of anhydrous LiCl (0.174 g, 4.1 mmol) resulted in the precipitation
of an orange solid, which was filtered, washed with MeOH (10 mL)
and Et2O (25 mL) and dried in vacuo. Obtained: 0.21 g (42% yield).
This solid was characterized as the mixture 11endo/11exo (1/0.4)
To a solution of 7 (0.237 g, 0.28 mmol) in 20 mL of CH2Cl2,
I2 (0.143 g, 0.56 mmol) was added. The black suspension was
stirred for 15 h at 25 ◦C, then the precipitated PdI2 was
eliminated by filtration through a Celite pad. The resulting red
solution was evaporated to half volume, and 1,10-phenanthroline
(0.055 g, 0.28 mmol) was added. The immediate precipitation of
PdCl2(phen) was evident. This suspension was stirred at 25 ◦C for
4 h, then the solid PdCl2(phen) was eliminated by filtration, and
the solution was evaporated to a small volume (about 1–2 mL). By
addition of a mixture of Et2O–n-hexane (20 mL 1 : 3) and stirring,
19 was obtained as an orange solid, which was filtered, washed with
n-hexane and dried in vacuo. Obtained: 0.143 g (63% yield). Anal.
Calc. for [C18H17INP] (405.2): C, 53.35; H, 4.23; N, 3.46. Found: C,
52.85; H, 4.21; N, 3.32. IR: 1335 (nP=N) cm-1. MS (MALDI +): 405
1
by integration of the corresponding resonances in the 31P{ H}
NMR spectrum: a sharp peak at 31.6 ppm matches with that found
for 11exo, while a very broad resonance centered at 47.95 ppm is
assigned to the different isomers of 11endo since it falls in the same
region as that found in 5 and 6. IR: 1290 (nP=N) cm-1. MS (FAB +):
446 (30%) [M/2-Cl]+.
1
(40%) [M]+. 31P{ H} NMR (CDCl3): d = 9.85. 1H NMR (CDCl3):
d = 1.45 (d, 3H, Me, PMe2, 2JHP = 13.2), 1.90 (d, 3H, Me, PMe2,
3
2JHP = 12.6), 5.56 (d, 1H, H2, C10H6, JHH = 6.5), 6.71–6.77 (m,
=
[Pd(l-OAc)(C10H6-(N PPh2Me)-8)-j-C,N] (13exo)
2H, H3, C10H6 + Ho, PPh), 7.06 (td, Hm, PPh, 3JHH = 8.0, 4JHP
=
3
5
To a suspension of 11exo (0.227 g, 0.24 mmol)) in 20 mL of CH2Cl2,
AgOAc (0.086 g, 0.52 mmol) was added, and the mixture was
3.2), 7.31 (td, Hp, PPh, JHH = 7.5, JHP = 1.2), 7.54–7.62 (m,
3
2H, H4 + H6, C10H6), 7.73 (d, 1H, H7, C10H6, JHH = 8.0), 7.98
10428 | Dalton Trans., 2010, 39, 10422–10431
This journal is
The Royal Society of Chemistry 2010
©

25 ◦C. During this time the decomposition was evident, since black
Pd was formed. After the reaction time the Pd(0) was filtered off
and the obtained orange solution was evaporated to dryness. The
residue was dissolved in the minimal amount of CHCl3 (about
1–2 mL) and treated with Et2O (25 mL). Further stirring gave 22
as an orange solid. Obtained: 0.100 g (64% yield). Anal. Calc.
for [C25H19NOP]ClO4 (479.85): C, 62.58; H, 3.99; N, 2.92. Found:
C, 62.59; H, 3.85; N, 2.78. IR: 1593 (nC=O). MS (MALDI+): 380
1
(ddd, 1H, H5, C10H6, 3JHH = 7.5, 6JHP = 2.4, 4JHH = 1.3). 13C{ H}
NMR (CDCl3): d = 12.44 (s, Me, PMe2, 1JPC = 81.2), 20.22 (s, Me,
1
5
PMe2, JPC = 59.0), 124.25 (d, C7, C10H6, JPC = 2.6), 124.86 (s,
C3, C10H6), 126.45 (d, C4, C10H6, 5JPC = 2.7), 128.60 (s, C6, C10H6),
3
5
128.03 (d, Cm, PPh, JPC = 11.6), 128.50 (d, C5, C10H6, JPC
=
=
6.4), 129.84 (d, Co, PPh, JPC = 8.4), 129.97 (d, Ci, PPh,1JPC
2
94.4), 131.25 (overlapped C2, C10H6 + Cp, PPh), 133.14 (s, C8,
C10H6), 135.25, 142.84 (2 s, C4a + C8a, C10H6),145.40 (d, C1, C10H6,
2JPC = 5.0).
1
(10%) [M-ClO4]+. 31P{ H} NMR (CD2Cl2): d = 44.97. 1H NMR
3
(CD2Cl2): d = 6.70 (t, Hp, NPh, JHH = 7.3), 6.77–6.99 (m, 7H,
Hm + Ho, NPh + 3H, C6H4), 7.21 (d, 1H, H3, C6H4, 3JHH = 7.6),
=
[C10H6-(N PPhMe2)-1-(C(O))-8]Cl (20)
7.40–7.45 (m, 4H, Hm, PPh2), 7.51–7.54 (m, 2H, Hp, PPh2), 7.70–
A solution of 7 (0.216 g, 0.26 mmol) in 20 mL of CH2Cl2 was
stirred under a CO atmosphere (1 atm) for 15 h. After a few
minutes, a clear decomposition is evident. However, stirring was
maintained during 15 h. After the reaction time the black Pd was
eliminated by filtration, and the orange solution was evaporated to
dryness. By Et2O addition (20 mL) and stirring, 20 was obtained
as an orange solid. Obtained: 0.120 g (68% yield). Anal. Calc. for
[C19H17NOP]Cl (341.8): C, 66.77; H, 5.01; N, 4.10. Found: C, 66.90;
H, 4.70; N, 3.81. IR: 1605 (nC=O). MS (MALDI +): 280 (100%) [M–
1
7.75 (m, 4H, Ho, PPh2). 13C{ H} NMR (CD2Cl2): d = 121.44 (s,
3
Cp, NPh), 124.1 (d, C4, C6H4, JPC = 13.5), 126.42 (d, Co, NPh,
3JPC = 11.1), 127.66 (s, Cm, NPh), 128.05 (d, C3, C6H4, 2JPC = 21.8),
128.98 (d, Cm, PPh2, 3JPC = 11.9), 129.97 (d, C5, C6H4, 4JPC = 2.8),
133.00 (d, Cp, PPh3, 4JPC = 2.4), 133.29 (d, Co, PPh2, 2JPC = 10.1),
135.28 (d, C3, C6H4, 3JPC = 13.9). Peaks due to quaternary C atoms
were not observed.
CO+2H]+. 31P{ H} NMR (CDCl3): d = 44.19. 1H NMR (CDCl3):
1
=
[Ph3P N–C(O)-C6H3–I-2-OMe-5] (23)
d = 1.67, 1.84 (broad, PMe2), 7.00 (d, 1H, H2, C10H6, 3JHH = 6.0),
Compound 23 was prepared following the same experimental
method as that described for 19. Therefore, 18 (0.160 g, 0.14 mmol)
reacted with I2 (0.074 g, 0.29 mmol) and 1,10-phenanthroline
(0.028 g, 0.14 mmol) in CH2Cl2 (20 mL) to give 23 as an
orange solid. Obtained: 0.121 g (39% yield). Compound 23
was recrystallized from CH2Cl2–Et2O (1 : 3). Anal. Calc. for
[C26H21INO2P] (537.33): C, 58.12; H, 3.94; N, 2.61. Found: C,
57.77; H, 3.64; N, 2.39. IR: 1586 (nC=O), 1349 (nP=N) cm-1. MS
7.46–7.63 (m, 5H, 3H, C10H6 + Hm, PPh), 7.75–7.78 (m, 3H, Hp +
Ho, PPh), 8.07–8.11 (m, 2H, C10H6). 13C{ H} NMR (CDCl3): d =
1
17.25, 18.29 (2 s, PMe2), 106.57 (s, C2, C10H6), 119.72 (s, C10H6),
123.87 (s, C10H6), 128.34 (overlapped Cm, PPh + 1 CH, C10H6),
128.72 (d, Co, PPh, 2JPC = 10.6), 129.04 (s, C1, C10H6), 129.59 (d,
Cp, PPh2, 4JPC = 7.2), 130.79 (s, C10H6), 131.98 (s, C10H6), 137.09
(s, C8, C10H6), 169.69 (s, CO).
1
(MALDI+): 537 (20%) [M]+. 31P{ H} NMR (CDCl3): d = 21.11.
=
[I–C6H4-(PPh2 NPh)-2] (21)
1H NMR (CDCl3): d = 3.71 (s, 3H, OMe), 6.73 (dd, 1H, H3, C6H3,
3JHH = 8.7, 4JHH = 3.0), 7.18 (d, 1H, H4, C6H3, 3JHH = 8.5), 7.34
Compound 21 was prepared following the same experimental
method as that described for 19. Therefore, 17 (0.305 g, 0.31 mmol)
reacted with I2 (0.156 g, 0.61 mmol) and 1,10-phenanthroline
(0.061 g, 0.31 mmol) in CH2Cl2 (20 mL) to give 21 as an
orange solid. Obtained: 0.158 g (54% yield). Compound 21
was recrystallized from CH2Cl2–Et2O (1 : 3). Anal. Calc. for
[C24H19INP] (479.3): C, 60.14; H, 4.00; N, 2.92. Found: C, 59.75;
H, 3.81; N, 2.73. IR: 1324 (nP=N) cm-1. MS (MALDI+): 480 (30%)
4
(d, 1H, H6, C6H3, JHH = 3.0), 7.41 (m, 6H, Hm, PPh3), 7.50 (m,
1
3H, Hp, PPh3), 7.77 (m, 6H, Ho, PPh3). 13C{ H} NMR (CDCl3):
d = 55.68 (s, OMe), 115.44 (s, C6H3), 116.25 (s, C6H3), 123.65 (s,
C2, C6H3), 127.73 (d, Ci, PPh3,1JPC = 99.3), 128.75 (d, Cm, PPh3,
4
3JPC = 12.4), 131.04 (s, C6H3), 132.40 (d, Cp, PPh3, JPC = 2.8),
133.28 (d, Co, PPh3, 2JPC = 10.1), 140.31 (d, C1, C6H3, 3JPC = 20.1),
157.84 (s, C5, C6H3), 176.43 (d, CO, 2JPC = 8.2).
[M]+. 31P{ H} NMR (CDCl3): d = 8.50. 1H NMR (CDCl3): d =
1
6.26 (dd, 1H, H3, C6H4, 3JHH = 6.8, 4JHH = 4.0), 6.46 (d, 1H, Ho,
NPh, 3JHH = 8.1), 6.76 (t, 1H, Hp, NPh, 3JHH = 7.4), 6.94 (t, 1H,
[C6H3-((C(O))2-1,2-N–PPh3)-OMe-4]Cl (24)
3
3
Hm, NPh, JHH = 7.8), 7.15 (t, 1H, H4, C6H4, JHH = 7.1), 7.29–
7.36 (m, 2H, H5 + H6, C6H4), 7.46 (m, 1H, Hp, PPh2), 7.54 (m,
2H, Hm, PPh2), 7.63 (m, 2H, Hm, PPh2), 7.70 (m, 2H, Ho, PPh2),
Compound 24 was obtained following the same experimental
procedure as that reported for 20. Therefore, a solution of 18
(0.220 g, 0.20 mmol) in 20 mL of CH2Cl2 was stirred under CO
atmosphere (1 atm) for 15 h at 25 ◦C, giving 24 as a yellow solid.
Obtained: 0.125 g (66% yield). Anal. Calc. for [C27H22NO3P]Cl
(473.9): C, 68.43; H, 4.47; N, 2.96. Found: C, 68.60; H, 4.28; N,
2.80. IR: 1630, 1641 (nC=O). MS (MALDI +): 438 (48%) [M]+.
7.82 (m, 2H, Ho, PPh2). 13C{ H} NMR (CDCl3): d = 120.99 (Co,
1
NPh), 121.09 (Cp, NPh), 128.62 (Cp, PPh2), 129.46 (Cm, NPh),
129.68 (Cm, PPh), 130.21 (Cm, PPh), 132.97 (C3, C6H4), 133.07
(C4, C6H4), 133.28 (overlapped, C5 + C6, C6H4), 133.71 (Co, PPh),
133.92 (Co, PPh).
1
31P{ H} NMR (CD2Cl2): d = 29.34. 1H NMR (CDCl3): d = 3.94
(s, OMe), 7.20 (d, 1H, H5, C6H3, 3JHH = 7.6), 7.33 (d, 1H, H3, C6H3,
4JHH = 1.2), 7.48 (m, 6H, Hm, PPh3), 7.54 (m, 3H, Hp, PPh3), 7.68
=
[C6H5-(N PPh2-C6H4–C(O)-2]ClO4 (22)
1
To a suspension of 17 (0.159 g, 0.16 mmol) in 20 mL of dry
THF AgClO4 (0.073 g, 0.35 mmol) was added, and the resulting
mixture was stirred under exclusion of light for 30 min. After
this time the insoluble AgCl was filtered, and the freshly prepared
solution was stirred under a CO atmosphere (1 atm) for 15 h at
(m, 6H, Ho, PPh3), 7.77 (d, H6, C6H3, 3JHH = 8.0). 13C{ H} NMR
(CD2Cl2): d = 56.24 (s, OMe), 108.07 (s, C3, C6H3), 120.36 (s, C5,
C6H3), 124.58, 135.29 (2 s, C1, C2, C6H3), 125.32 (s, C6, C6H3),
3
128.64 (d, Cm, PPh3, JPC = 12.0), 132.08–132.27 (Cp, Co, PPh3),
164.89 (s, C3, C6H3), 167.78, 167.87 (s, CO).
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 10422–10431 | 10429
©

X-Ray crystallography
Angew. Chem., Int. Ed., 2009, 48, 9412; (o) L. Ackermann, R. Vicente
and A. R. Kapdi, Angew. Chem., Int. Ed., 2009, 48, 9792; (p) A. J.
Canty, Dalton Trans., 2009, 10409; (q) F. Bellina and R. Rossi, Chem.
Rev., 2010, 110, 1082; (r) T. W. Lyons and M. S. Sanford, Chem. Rev.,
2010, 110, 1147.
Crystals of adequate quality for X-ray measurements were grown
by slow diffusion of Et2O into a CH2Cl2 solution of the crude
product at -15 ◦C. A single crystal of 13exo·2OEt2 was mounted
at the end of a quartz fiber in a random orientation, covered
with magic oil and placed under a cold stream of nitrogen.
Data collection was performed at low temperature (150 K) on
an Oxford Diffraction Xcalibur2 diffractometer using graphite-
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12634; (b) R. Giri, N. Maugel, J.-J. Li, D.-H. Wang, S. P. Breazzano,
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2008, 130, 13285; (b) D. C. Powers, M. A. L. Geibel, J. E. M. N. Klein
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12 W. Y. Yu, W. N. Sit, K. M. Lai, Z. Zhou and A. S. C. Chan, J. Am.
Chem. Soc., 2008, 130, 3304.
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7520; (b) S. R. Whitfield and M. S. Sanford, J. Am. Chem. Soc.,
2007, 129, 15142; (c) D. C. Powers and T. Ritter, Nat. Chem., 2009, 1,
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9048; (b) C. E. Houlden, C. D. Bailey, J. G. Ford, M. R. Gagne´, G. C.
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10066.
15 A. R. Dick, M. S. Remy, J. W. Kampf and M. S. Sanford,
Organometallics, 2007, 26, 1365.
16 M. Tobisu, Y. Ano and N. Chatani, Org. Lett., 2009, 11, 3250.
17 W. Rauf, A. L. Thompson and J. M. Brown, Chem. Commun., 2009,
3874.
˚
monochromated Mo-Ka radiation (l = 0.71073 A). An hemi-
sphere of data was collected based on three w-scan or j-scan runs.
The diffraction frames were integrated using the program CrysAlis
RED43 and the integrated intensities were corrected for absorption
with SADABS.44 The structure was solved and developed by
Patterson and Fourier methods.45 All non-hydrogen atoms were
refined with anisotropic displacement parameters. H atoms were
placed at idealized positions and treated as riding atoms. Each H
atom was assigned an isotropic displacement parameter equal to
1.2 times the equivalent isotropic displacement parameter of its
parent atom. The structure was refined to Fo2, and all reflections
were used in the least-squares calculations.46
18 X. Jia, S. Zhang, W. Wang, F. Luo and J. Cheng, Org. Lett., 2009, 11,
Acknowledgements
3120.
19 (a) C. C. Scarborough, R. I. McDonald, C. Hartmann, G. T. Sazama,
A. Bergant and S. S. Stahl, J. Org. Chem., 2009, 74, 2613; (b) H. Zhou,
Y.-H. Xu, W.-J. Chung and T.-P. Loh, Angew. Chem., Int. Ed., 2009, 48,
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2006, 8, 5211.
Funding from Ministerio de Ciencia e Innovacio´n (Project
CTQ2008-01784, Spain) and Gobierno de Arago´n (PI071/09,
Spain) is gratefully acknowledged. D. A. thanks Gobierno de
Arago´n for a PhD grant.
20 (a) K. Mun˜iz, J. Am. Chem. Soc., 2007, 129, 14542; (b) M. Yamashita,
K. Hirano, T. Satoh and M. Miura, Org. Lett., 2009, 11, 2337; (c) L. L.
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