Original palladium pincer complexes deriving from 1,3-bis(thiophosphinoyl) indene proligands: Csp3-H versus Csp2-H bond activation

Article abstract of DOI:10.1039/c1dt10118h

A series of original 2-indenylidene palladium pincer complexes {PdL[Ind(Ph₂PS)₂]} (L = HNCy₂, PPh₃, Cl^-) have been prepared by double C-H activation of a 1,3-bis(thiophosphinoyl)indene proligand. Crys

Full text of DOI:10.1039/c1dt10118h

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Pincers and other hemilabile ligands
Guest Editors Dr Bert Klein Gebbink and Gerard van Koten
Published in issue 35, 2011 of Dalton Transactions
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PERSPECTIVE:
Cleavage of unreactive bonds with pincer metal complexes
Martin Albrecht and Monika M. Lindner
Dalton Trans., 2011, DOI: 10.1039/C1DT10339C
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Pincer Ru and Os complexes as efficient catalysts for racemization and deuteration of alcohols
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Mechanistic analysis of trans C–N reductive elimination from a square-planar macrocyclic aryl-
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Lauren M. Huffman and Shannon S. Stahl
Dalton Trans., 2011, DOI: 10.1039/C1DT10463B
CSC-pincer versus pseudo-pincer complexes of palladium(II): a comparative study on
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Dalton Trans., 2011, DOI: 10.1039/C1DT10269A
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PAPER
Original palladium pincer complexes deriving from
3
2
1,3-bis(thiophosphinoyl)indene proligands: Csp –H versus Csp –H bond
activation†
Noel Nebra,a Je´roˆme Lisena,a Nathalie Saffon,b Laurent Maron,*c Blanca Martin-Vaca*a and
Didier Bourissou*a
Received 20th January 2011, Accepted 7th March 2011
DOI: 10.1039/c1dt10118h
A series of original 2-indenylidene palladium pincer complexes {PdL[Ind(Ph2P S)2]} (L = HNCy2,
PPh3, Cl-) have been prepared by double C–H activation of a 1,3-bis(thiophosphinoyl)indene
proligand. Crystallographic analyses and DFT calculations indicate that the bonding situation of the
{Pd[Ind(Ph2P S)2]} fragment is essentially governed by the conjugated and rigid nature of the
dianionic pincer ligand, the nature of the coligand having little influence. The formation of the
2-indenylidene complexes involves either a 2-indenyl pincer or a four-membered cyclometalated
2
3
complex as an intermediate, suggesting that Csp –H or Csp –H bond activation takes place. However,
3
deuterium labelling experiences show that in all cases, Csp –H bond activation occurs followed
2
eventually by a Pd/H exchange. Nevertheless, evidence for direct Csp –H bond activation under mild
3
conditions is obtained when a methyl group is introduced at the indene proligand to prevent Csp –H
bond activation. The ensuing dissymmetrical 2-indenyl palladium pincer complex has been fully
characterized.
Introduction
Cyclometalated pincer complexes were first reported in the middle
1970’s by Moulton and Shaw.1 After a period of latency, they
have attracted a surge of interest over the last two decades.2
In these complexes, the central M–C bond is enforced by the
coordination of the peripheral donor groups, and the chelating
rigid nature of the ZCZ pincer ligand bestow a unique balance
of stability versus reactivity. This has led to spectacular catalytic
developments especially towards alkane deshydrogenation3 and
alkane metathesis.4 In addition, the peculiar properties of ZCZ
pincer complexes have allowed for the isolation of a variety of
highly reactive species relevant to key catalytic transformations.5–10
The structure of the ZCZ pincer ligand has been extensively
modified in order to finely tune the stereoelectronic properties
and thus the reactivity of the ensuing complexes.11–15 Some rep-
resentative systems are depicted in Chart 1. Most commonly, the
aUniversity of Toulouse, UPS, LHFA, 118 route de Narbonne, F-31062
Toulouse, (France)CNRS, LHFA UMR 5069, F-31062 Toulouse, (France).
E-mail: bmv@chimie.ups-tlse.fr, dbouriss@chimie.ups-tlse.fr; Fax: (+33)5
6155-8204
Chart 1 Representative cyclometalated pincer complexes: symmetrical
aryl-based complexes I–III, symmetrical alkyl-based complexes IV–V and
dissymmetrical complexes VI–VII.
bInstitut de Chimie de Toulouse, Universite´ Paul Sabatier, FR2599, 118
Route de Narbonne, 31062 Toulouse Cedex 09, (France)
cUniversity of Toulouse, INSA, UPS, LPCNO, 135 avenue de Rangueil, F-
31077 Toulouse, (France)CNRS, LPCNO UMR 5215, F-31077 Toulouse,
(France). E-mail: laurent.maron@irsamc.ups-tlse.fr
† Electronic supplementary information (ESI) available. CCDC reference
numbers 800695–800701. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt10118h
peripheral donor groups are chosen among phosphines, amines,
thioethers, thioamides . . . The central moiety is typically an aryl
or an alkyl fragment, so that the great majority of pincer ligands
developed thus far are formally monoanionic. A few neutral and
8912 | Dalton Trans., 2011, 40, 8912–8921
This journal is
The Royal Society of Chemistry 2011
©

dianionic ZCZ ligands based on N-heterocyclic and methanediide
skeletons have also been reported.16 Because of synthetic issues,
most of the cyclometalated pincer complexes are symmetrical,
but dissymmetrical systems are attracting increasing interest,
particularly those displaying hemilabile character.7,15
2 is complete in less than two hours at room temperature in
CH2Cl2, compared to 10 days using [Pd(cod)Cl2]. Crystals of
2 were obtained from a CH2Cl2–Et2O solution at 20 ◦C and
its structure was definitively confirmed by single-crystal X-ray
diffraction study (Fig. 1a). The Pd atom is bonded to the two
sulfur atoms, the chlorine atom and C2, which are organized in
a quasi-ideal square planar arrangement. The most noticeable
geometric difference between 2 and the 2-indenylidene complex
3 is the tetrahedral versus planar environment around C1, as the
result of the presence, or not, of a residual proton of the proligand.
In complex 2, the C1P1 bond deviates from the mean indenyl
plane by 52◦, but rotation around this C1P1 bond allows the
sulfur atom to be positioned adequately to complete the square
planar arrangement around Pd. The dissymmetrical nature of the
indenyl in 2 is also apparent from the difference in the C1C2 and
Recently, we have shown that the introduction of coordinating
side arms on indene may induce unusual coordination modes.17
In particular, the presence of two donor buttresses on positions 1
and 3 was found to support the novel 2-indenylidene coordination
mode.17c Original pincer complexes of Zr and Pd were obtained by
double C–H activation of 1,3-bis(thiophosphinoyl)indene and 1,3-
bis(phosphazene)indene proligands. Formally, these complexes
feature dianionic ZCZ (Z = S, N) pincer ligands. Their bonding
situation was analyzed on the basis of crystallographic data and
computational studies.17c Hereafter, we report a comprehensive
study on a series of 2-indenylidene Pd complexes. The coligand
in trans position to the indenylidene moiety was varied from
NHCy2 to Cl- and PPh3. A detailed mechanistic study was carried
out to gain more insight into the formation of such complexes,
˚
C2C3 bond lengths [1.510(5) and 1.353(5) A, respectively], which
are typical for single and double CC bonds, respectively. The Pd–
˚
C2 bond length [1.962(4) A] of 2 is similar to that observed in
17c
˚
3 [1.984(5) A] and falls in the low range of those reported for
palladium SCsp S pincer complexes (1.952–2.006 A).
12c,18
˚
3
2
2
and particularly into the underlying Csp –H versus Csp –H bond
activation of the 1,3-bis(thiophosphinoyl)indene proligand. A new
type of dissymmetrical pincer complex has also been synthesized
from a 1-methylated proligand.
Results and discussion
Pincer 2-indenylidene Pd complexes derived from the
1,3-bis(thiophosphinoyl)indene proligand (1-H)
As preliminarily reported,17c the [IndH2(Ph2P S)2] proligand 1-
H reacts slowly with [Pd(cod)Cl2] (cod = cycloocta-1,5-diene) at
room temperature in THF. According to NMR spectroscopy this
leads to the pincer complex 2, in which the Pd atom is bonded
to C2 (Scheme 1). The addition of two equivalents of Cy2NH
3
promotes rapid deprotonation of the Csp –H bond to afford
the novel 2-indenylidene complex 3, which was characterized by
NMR spectroscopy and single-crystal X-ray crystallography. The
low solubility of the Pd precursor in typical organic solvents
(THF, CH2Cl2) probably explains its very slow reaction with 1-
H. With [Pd(PhCN)2Cl2], which is much more soluble in organic
solvents and whose benzonitrile ligands are more labile than cod,
the reaction proceeds much more rapidly and the formation of
Fig. 1 Ellipsoid drawings (50% probability) of the molecular structures
of 2 (a), 4 (b), 5 (c) and 6 (d). For clarity, lattice solvent molecules, hydrogen
atoms and the ammonium counter-cation of 4 are omitted and the phenyl
groups at phosphorus are simplified.
The preparation of the 2-indenylidene complex featuring a
chloride instead of the dicyclohexylamine coligand at Pd was then
attempted. Disappointingly, treatment of 2 with one equivalent of
Cy2NH led to an intractable mixture of complexes including 3. To
avoid coordination of the amine to the metal centre, we then turned
to diisopropylethylamine (DIEA) instead of Cy2NH. Monitoring
of the reaction between 2 and DIEA by 31P NMR showed
the rapid and clean formation of a new symmetrical complex
characterized by a singlet signal at d 43.6 ppm. The signal
corresponding to H1 disappeared in the 1H NMR spectrum,
while the 13C NMR spectrum displayed a Cq multiplet signal
at d 163.3 ppm attributed to C2 and an AXX¢ system signal at
104.2 ppm attributed to C1 and C3. The similarity between these
spectroscopic data and those of 3 strongly argues in favour of
the desired 2-indenylidene chloro-palladate complex 4. Orange
crystals suitable for single-crystal X-ray diffraction analysis were
obtained from a THF solution at -70 ◦C, and the structure of
Scheme
1
Preparation of the pincer complexes 2–4 from the
1,3-bis(thiophosphinoyl)indene proligand 1-H and [Pd(PhCN)2Cl2].
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8912–8921 | 8913
©

complex 4 was unambiguously confirmed (Fig. 1b). The chloro-
palladate and ammonium fragments interact via a N–H ◊ ◊ ◊ Cl
thiophosphinoyl moieties and C1. The overall geometry only
slightly deviates from square planar despite the presence of a
SPC1Pd four-membered ring [SPC1 bond angle: 81.95(13)◦]. The
chlorine atom is located in cis position to C1,22 a favourable
disposition for further dehydrochlorination and pincer formation
(vide infra). The cyclometalated carbon atom C1 adopts a distorted
tetrahedral environment with the C1–P1 bond deviating from the
˚
hydrogen bond [H ◊ ◊ ◊ Cl distance: 2.35(2) A and N–H ◊ ◊ ◊ Cl bond
angle: 167.2(7)◦].19 The Pd centre is surrounded by the two sulfur
atoms, C2 and the chlorine atom, organized altogether in a square
˚
planar arrangement. The Pd–C2 bond length [1.962(7) A] is very
close to those of complexes 2 and 3. The planar environments
around the carbon atoms C1, C2 and C3, combined with the
short and almost equal C1C2/C2C3 bond lengths [1.410(9) and
◦
˚
mean indenyl plane by 41.4 . The Pd–C1 bond length [2.183(5) A]
is significantly longer than those observed in 2 and in 4 [1.962(4)
˚
˚
1.435(8) A] indicate delocalization of the p system, similar to
and 1.962(7) A, respectively] and falls in the typical range of Pd–
3
that found in 3 but in contrast to that observed in 2. Finally,
Csp bond lengths.
˚
the Pd–Cl bond length [2.4362(18) A] is substantially longer
Treatment of 5 with one equivalent of Cy2NH or polystyrene
supported DIEA (PS-DIEA) in refluxing dichloromethane af-
forded the corresponding 2-indenylidene complex 6 within 12 h.
The A2X system observed in the 31P NMR spectrum (a doublet
at d 47.0 ppm and a triplet at d 17.6 ppm, JPP = 50.5 Hz)
indicated the coordination of the second thiophosphinoyl side
˚
than that of 2 [2.3807(10) A] and exceeds those reported for
12c,18
˚
2
neutral palladium SCsp S pincer complexes (2.381–2.407 A).
This feature most likely results from the hydrogen bond with the
(iPr2EtNH)+ counter-cation. Complex 4 is a rare example of an
anionic palladium pincer complex stable enough to be structurally
characterized.20,21
1
arm and the symmetrisation of the overall structure. H NMR
Aiming at further varying the nature of the coligand in the trans
position to C2, the proligand 1-H was reacted with a different
Pd precursor, namely [Pd(PPh3)Cl2]2 (Scheme 2). In this case, no
reaction occurred at room temperature in the absence of a base. But
when the reaction was carried out in the presence of one equivalent
of Cy2NH, 1-H was readily converted into a new compound (5).
The progress of the reaction was easily monitored by 31P NMR
spectroscopy: within 1.5 h, the two doublet signals associated with
1-H (d 45.5 and 31.3 ppm, JPP = 18.2 Hz) disappeared, while an
AMX system appeared. The doublet of doublets at d 28.3 ppm
(JPP = 18.6 and 5.8 Hz) is associated with the PPh3 coligand, while
spectroscopy confirmed the removal of H2 and the 13C NMR
signal corresponding to C2 appeared as a Cq doublet of triplet at
d 177.8 ppm (JPC = 128.3 and 34.5 Hz). The C1 and C3 atoms
are magnetically equivalent and give rise to an AXX¢ system at
105.6 ppm, akin to that observed for the 2-indenylidene complexes
3 and 4. These data are consistent with the coordination of the
second thiophosphinoyle group, the shift of the metal centre from
C1 to C2, and the concomitant abstraction of a hydrogen atom
(see the following section for mechanistic considerations). Fig. 1d
shows the solid state structure of 6 as determined by single-crystal
X-ray diffraction. It closely resembles those of 3 and 4, with
a square planar arrangement of C2, the two sulfur atoms and
the two doublet signals at d 50.4 (JPP = 18.6 Hz) and 33.1 (JPP
=
˚
5.8 Hz) ppm are attributed to non-equivalent thiophosphinoyl
groups. The latter chemical shifts clearly indicated that only the
thiophosphinoyl side arm is coordinated to the Pd atom, in
PPh3 around Pd. The Pd–C2 bond length [1.997(9) A] is similar
˚
to those of 3 and 4 [1.984(5) and 1.962(7) A, respectively]. The
carbon atoms C1, C2 and C3 are in planar environments, and
1
contrast to that observed in complex 2. The H NMR spectrum
p delocalization is apparent from the C1–C2 and C2–C3 bond
˚
of 5 contains no signal attributable to H1 (observed at d 4.97 ppm
for 1-H and at 5.46 ppm for 2) but a dd signal at d 6.49 ppm
lengths [1.426(11) and 1.417(11) A, respectively], which are in
between the lengths typically associated with single and double
bonds.
(JHP = 9.9 and 3.1 Hz) is associated with H2. Consistently, the 13
NMR spectrum displays a Cq ddd signal at d 30.6 ppm (JCP
C
=
The spectroscopic and crystallographic data collected for the
three 2-indenylidene complexes complexes 3, 4 and 6 are very
similar, suggesting that the coligand in the trans position to C2 has
little influence on their structures. To corroborate this observation,
DFT calculations were performed on the actual complexes 4 and
6 at the same level of theory as that used previously for complex
3 [B3PW91/SDD(Pd,P),6-31G**(other atoms)].17c The optimized
structures match nicely those determined experimentally (Table 1),
confirming the ability of this computational method to describe
such complexes. The bonding situation and especially the nature
of the C2–Pd bond was analysed by NBO. As for 3, a highly
covalent s bond was found between C2 and Pd (65% C2/35%
Pd for 4 and 51% C2/49% Pd for 6 compared to 53% C2/47%
Pd for 3) but no p interaction was identified.17c The presence of
essentially single bonds between C2 and Pd was further confirmed
by the corresponding Wiberg indexes (0.73 for 4 and 0.68 for 6,
compared to 0.66 for 3) (Table 2). In line with the metric data, bond
orders significantly higher than 1.0 were found between C1–C2 and
C2–C3 (~1.35), consistent with some multiple bond character as
the result of p delocalization. The nature of the coligand in trans
position to C2 influence slightly the atomic charges at Pd and at
the elements directly bound to it, but the overall bonding situation
71.5, 62.6, 14.1 Hz) for C1 and a broad unresolved CH signal at
d 148.8 ppm for C2. All these spectroscopic data are consistent
with a four-membered metallacyclic structure for complex 5.
3
This would result from the activation of the Csp –H bond,
similarly to what had been observed for the reaction of 1-H and
the analogous bisphosphazene derivative [IndH2(Ph2P NMes)2]
with Zr(NMe2)4.17c
Scheme
2
Preparation of complexes
5
and
6
from the
1,3-bis(thiophosphinoyl)indene proligand 1-H and [Pd(PPh3)Cl2]2.
Crystals of complex 5 were obtained from a CH2Cl2–Et2O
solution at room temperature, and its molecular structure was
assessed by single-crystal X-ray diffraction (Fig. 1c). The co-
ordination sphere of Pd is composed of Cl, PPh3, one of the
8914 | Dalton Trans., 2011, 40, 8912–8921
This journal is
The Royal Society of Chemistry 2011
©

Table 1 Selected geometric data (bond lengths in A, bond angles in ◦) for complexes 3, 4, 6 and 8 determined experimentally and computed at the
˚
B3PW91/SDD(Pd,P),6-31G**(other atoms) level of theory
S–Pd
C2–Pd
1.984(5)
1.97
S–P
P–C
S–P–C
RC1a
359
360
360
360
359
360
323
323
RC3a
360
360
360
360
359
360
360
360
RC2a
360
360
360
360
360
360
359
360
C1–C2
1.418(7)
1.42
C2–C3
1.425(7)
1.42
3
4
6
8
X-Ray
DFT
2.3398(17)
2.3360(17)
2.36
2.0297(19)
2.030(2)
2.07
1.719(6)
1.714(5)
1.75
105.13(19)
106.39(19)
106
2.36
2.07
1.75
106
X-Ray
DFTa
X-Ray
DFT
2.3438(19))
2.3341(19
2.36
1.962(7)
1.97
2.021(3)
2.018(3)
2.06
1.742(7)
1.719(7)
1.75
106.7(3)
106.9(2)
107
1.435(8)
1.42
1.410(9)
1.42
2.36
2.06
1.75
2.346(2)
2.319(3)
2.35
1.997(9)
2.01
2.033(4)
2.038(4)
2.07
1.740(8)
1.722(9)
1.75
105.8(3)
105.3(3)
106
1.417(11)
1.42
1.426(11)
1.42
2.36
2.07
1.75
106
X-Ray
DFT
2.3503(16)
2.3285(16)
2.37
1.961(5)
1.96
2.015(2)
2.025(2)
2.04
1.842(5)
1.772(6)
1.88
104.01(17)
105.37(18)
104
1.520(7)
1.53
1.362(7)
1.37
2.35
2.06
1.80
105
a The ammonium counter-cation was not included in the calculations.
Table 2 NBO atomic charges and Wiberg indexes for complexes 3, 4, 6 and 8
NBO Atomic Charges
Wiberg indexes
C1/C3
Pd
C2
S
P
Pd–C2
0.66
C2–C1/C3
3
4
6
8
0.44
0.01
0.33
-0.002
-0.09
-0.05
-0.14
-0.05
-0.55
-0.36
-0.40
-0.31
1.64
1.60
1.64
1.58
-0.66
-0.65
-0.64
1.35
1.35
1.33
1.33
1.34
1.35
0.98
1.63
0.73
0.68
-0.46
-0.54
0.73
Table 3 Crystallographic Data for Compounds 2, 4–8 and 1-Me
2
4
5
6
7
1-Me
8
Empirical formula C34H27Cl3P2PdS2 C45H52ClNOP2PdS2 C52H42Cl3P3PdS2 C52H41Cl2P3PdS2 C52H42Cl2P3PdS2,BF4 C34H28P2S2 C35H29Cl3P2PdS2
Formula weight
Crystal system
Space group
774.37
Monoclinic
P21/n
890.79
Monoclinic
P21/c
11.5761(5)
24.9932(10)
14.8809(6)
90
94.803(3)
90
4290.3(3)
4
1036.64
Triclinic
P1
1000.18
Monoclinic
P21/c
8.9679(12)
20.433(3)
24.908(5)
90
94.220(12)
90
4551.7(13)
4
1088.02
Triclinic
P1
562.64
Monoclinic Monoclinic
P21/c
9.3107(2)
15.8384(3) 33.9812(9)
20.4529(4) 10.6863(3)
90
106.571(1) 101.622(2)
90 90
2890.85(10) 3371.46(17)
788.39
¯
¯
P21/n
9.4787(3)
˚
a/A
10.4520(2)
14.1161(3)
21.7006(5)
90
92.020(2)
90
3199.75(12)
4
11.4556(3)
12.5154(3)
18.2257(6)
102.868(2)
96.921(2)
108.763(2)
2359.21(11)
2
12.1914(3)
14.4571(3)
14.9919(3)
110.963(1)
97.985(1)
93.245(2)
2427.34(9)
2
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
90
3
˚
V/A
Z
4
4
Densitycalcd, Mg
1.607
1.379
1.459
1.460
1.489
1.293
1.553
m-3
m/mm-1
Reflections
collected
1.086
34 209
0.701
41 879
0.789
19 928
0.759
25 044
0.729
36 403
0.317
33 762
1.032
35 458
Independent
reflections
R1 (I > 2s(I))
6487
7258
7970
7635
8875
6721
6823
0.0407
0.0699
0.479 and
-0.544
173(2)
0.0525
0.0986
0.595 and
-0.850
173(2)
0.0517
0.1146
0.628 and
-0.854
173(2)
0.0702
0.0790
0.651 and
-0.534
173(2)
0.0428
0.0857
1.096 and
-0.809
193(2)
0.0419
0.0804
0.427 and
-0.314
193(2)
0.0513
0.0901
0.643 and
-0.774
193(2)
wR2
-3
˚
(D/r)max/e A
T
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8912–8921 | 8915
©

remains nearly unchanged. Thus, the geometric and electronic
properties of the 2-indenylidene complexes 3, 4 and 6 appear to
be governed essentially by the conjugated and rigid nature of the
pincer ligand.
introduced in this position. The labelled proligand 1-D was then
reacted with [Pd(PhCN)2Cl2] and [Pd(PPh3)Cl2]2 under the same
conditions as those used with 1-H. The ensuing complexes 2 and 5
were characterized by 1H NMR spectroscopy, and both reactions
were found to proceed with complete removal of the D-labelling.
This result is consistent with the mechanism proposed to account
Mechanistic investigations of the formation of the pincer
3
2
3
complexes: Csp –H versus Csp –H bond activation
for the formation of 5 (activation of the Csp –D bond of 1-D), but
2
rules out the Csp –H bond activation envisioned for 2. Apparently,
the reaction of 1-H/D with [Pd(PhCN)2Cl2] also proceeds via
From a mechanistic viewpoint, the formation of complexes 2
2
and 5 from the same proligand 1-H suggests that either Csp –H
3
activation of the Csp –H/D bond. The initially formed four-
3
or Csp –H bond activation might take place depending on the
membered metallacycle B would then rearrange by coordination
of the second thiophosphinoyl group and concomitant shifts of
Pd (from C1 to C2) and H (from C2 to C1).
nature of the metal precursor, [Pd(PhCN)2Cl2] or [Pd(PPh3)Cl2]2.
In the first case, the presence of two labile nitrile ligands might
enable coordination of the two thiophosphinoyl groups of 1-H,
To provide evidence of such a rearrangement from a four-
membered metallacycle of type B to a 2-indenyl pincer complex of
type C, complex 5 was used as a model compound. As mentioned
above, the addition of an amine readily converts 5 into the
corresponding 2-indenylidene complex 6. But no intermediate
(related to C) could be detected by NMR even at low temperature.
The thermal activation of 5 in the absence of an amine was
also found to afford 6, but this required temperatures as high as
120 ◦C and no intermediate could be detected either under these
conditions. We thus decided to induce the rearrangement of 5 by
creating a vacant site on Pd by chloride abstraction (Scheme 5).
The addition of one equivalent of AgBF4 to a CH2Cl2 solution of 5
led to a dark red solution. In addition to the signal associated with
2
and thereby, the Csp –H bond would be ideally positioned to be
activated. Since the displacement of PPh3 is much less favourable
than that of PhCN, the reaction of 1-H with [Pd(PPh3)Cl2]2 would
rather proceed by coordination of one thiophosphinoyl side arm
and activation of the Csp –H bond corresponding to the most
acidic proton. These two pathways are summarized in Scheme 3.
3
the PPh3 coligand (dd, d 18.9 ppm, JPP = 47.6 and 30.4 Hz), the 31
P
NMR spectrum of the ensuing complex 7 displayed two dd at d
54.2 (JPP = 30.4 and 5.3 Hz) and 53.3 ppm (JPP = 47.6 and 5.3 Hz),
indicating the coordination of the two thiophosphinoyl side arms
in a dissymmetrical manner. In addition, the shift of the proton
from C2 to C1 was clearly apparent by 1H NMR spectroscopy. The
corresponding signal resonates at 6.38 ppm in 5 and 5.74 ppm in 7.
These data are consistent with a cationic 2-indenyl pincer structure
for 7. This hypothesis was further corroborated by the formation
of the 2-indenylidene complex 6 upon treatment of 7 with Cy2NH,
and definitely confirmed by single-crystal X-ray crystallography
(crystals of 7 were obtained by slow diffusion of pentane into a
CH2Cl2 solution at room temperature). The molecular structure of
7 (Fig. 2) is similar to that of 2. The most noticeable difference is the
Scheme 3 Plausible pathways for the first C–H bond activation of the
indene proligand 1-H with dichloro palladium precursors.
In order to shed light into the different outcomes ob-
served from the two palladium precursors, the deuter-
ated 1,3-bis(diphenylthiophosphinoyl)indene 1-D was prepared
(Scheme 4). Compound 1-H was readily deprotonated with
nBuLi in THF. The ensuing anion [IndH(Ph2P S)2]- is highly
stabilized by conjugation, to the extent that it did not react with
D2O. Deuteration was thus achieved with CF3CO2D. The absence
˚
˚
slightly longer Pd–C2 bond [2.009(4) A compared to 1.962(4) A in
2], which is probably due to the presence of the triphenylphosphine
coligand in the trans position to C2.
1
of the signal characteristic of H1 in the H NMR spectrum of
1-D unambiguously indicated that the deuterium atom had been
Scheme 5 Pincer formation and Pd/H exchange at C1/C2 upon reaction
of complex 5 with a silver salt.
From these mechanistic studies, it can be concluded that the
3
2
activation of the Csp –H bond of 1 is favoured over that of the Csp
–
2
H bond whatever the palladium precursor. The apparent Csp –H
bond activation leading to 2 results in fact from the activation
3
of the Csp –H bond and subsequent rearrangement. The ability
Scheme 4 Preparation of 1-D and its reactions with [Pd(PhCN)2Cl2] and
[Pd(PPh3)Cl2]2.
of 1,3-bis(thiophosphinoyl)indene proligands to undergo direct
8916 | Dalton Trans., 2011, 40, 8912–8921
This journal is
The Royal Society of Chemistry 2011
©

neously. 31P NMR spectroscopy indicated the complete consump-
tion of 1-Me and the formation of a new complex 8 with the
two thiophosphinoyl side arms coordinated to Pd (two singlet
signals are observed at d 59.7 and 51.6 ppm). The absence of any
1H NMR signal attributable to H2 suggested that Csp –H bond
2
activation had occurred. Consistently, a Cq signal at d 191.7 ppm
was found for C2 in the 13C NMR spectrum. Crystals of 8 were
obtained from a CH2Cl2–Et2O solution at room temperature,
and its 2-indenyl pincer structure was confirmed by single-crystal
X-ray diffraction (Fig. 3b). The Pd centre is surrounded by
a chlorine atom, the two thiophosphinoyl side arms and C2
organized in a square-planar arrangement. The metric data of
8 are very close to those of 2, including the Pd–C2 bond length
Fig. 2 Ellipsoid drawing (50% probability) of the molecular structure
of 7. For clarity, lattice solvent molecules, hydrogen atoms and the
tetrafluoroborate counter-anion are omitted and the phenyl groups at
phosphorus are simplified.
˚
[1.961(5) A], the tetrahedral environment around C1 (the C1–P1
bond deviates by 57.7◦ from the mean indenyl plane) and the
2
Csp –H bond activation (Pathway (a) in Scheme 3) thus remains
pronounced difference in the C1–C2 and C2–C3 bond lengths
an open question. To address this point, a methyl group was in-
˚
[1.520(7) and 1.362(7) A, respectively]. The formation of complex 8
3
troduced at C1 to obviate the competitive Csp –H bond activation,
demonstrates that thiophosphinoyl side arms can indeed promote
and the preparation of a 2-indenyl pincer complex was envisaged
starting from 1-methylindene.
2
direct Csp –H bond activation of indene under mild conditions.
This gives access to a new type of pincer complex supported by a
dissymmetrical monoanionic ligand.
Pincer 2-indenyl Pd complex derived from the
Finally, DFT calculations were performed to compare the
bonding situation in the 2-indenyl complex 8 with that of the
2-indenylidene complexes 3, 4 and 6. The geometry determined
crystallographically was again nicely reproduced computationally
(Table 1). The computed Wiberg indexes are consistent with a
single bond character for Pd–C2 and C1–C2 and a double bond
character for C2–C3 (Table 2). In addition, NBO analyses revealed
noticeable negative atomic charges on C1 and C3 (-0.46 and -0.54,
respectively) albeit lower that those found for complexes 3, 4
and 6.
1,3-bis(thiophosphinoyl)-1-methylindene proligand (1-Me)
The 1,3-bis(thiophosphinoyl)-1-methylindene proligand 1-Me
(Scheme 6) was prepared from 1-methylindene, applying a
procedure similar to that used for 1-H. Two consecutive se-
quences of deprotonation with nBuLi followed by addition
of chlorodiphenylphosphine, and subsequent oxidation with S8
1
afforded 1-Me in 55% overall yield. Most diagnostic are the H
NMR signals associated with the methyl group (d, d 1.75 ppm,
JPH = 17.5 Hz) and H2 (dd, d 6.60 ppm, JPH = 10.1 and 3.1 Hz), as
well as the 13C NMR signal corresponding to C1 (dd, d 58.7 ppm,
JPC = 42.7 and 12.3 Hz). The molecular structure of 1-Me, as
assessed by single-crystal X-ray diffraction, is shown in Fig. 3a.
Conclusion
From the 1,3-bis(thiophosphinoyl)indene proligand 1-H, a series
of 2-indenylidene palladium pincer complexes have been prepared
and characterized by experimental (NMR spectroscopy and
single-crystal X-ray diffraction) and theoretical methods. The
nature of the coligand in the trans position to C2 (NHCy2, Cl-
or PPh3) was found to have only little influence on the geometric
and electronic properties of the complexes that are essentially
governed by the conjugated and rigid nature of the pincer ligand.
Depending on the palladium precursor used, the 2-indenylidene
complex was formed via either a 2-indenyl pincer or a four-
membered cyclometalated intermediate complex. This suggested
Fig. 3 Ellipsoid drawings (50% probability) of the molecular structures of
1-Me (a), and 8 (b). For clarity, lattice solvent molecules, hydrogen atoms
are omitted and the phenyl groups at phosphorus are simplified.
2
3
that either Csp –H or Csp –H bond activation took place on 1-H.
However, the deuterium labelling experiences substantiated that in
3
all cases, the coordination of 1-H involved Csp –H bond activation
that was eventually followed by concomitant and opposite shifts
3
of Pd and H between C1 and C2. When no competitive Csp –H
bond activation was possible, the two thiophosphinoyl side arms
2
efficiently promoted direct Csp –H bond activation, as evidenced
with the 1-methylated indene 1-Me as proligand. An original
dissymmetrical 2-indenyl palladium pincer complex was obtained
thereby.
Scheme
6
Preparation of the 2-indenyl pincer complex 8 from
the 1,3-bis(thiophosphinoyl)-1-methylindene proligand 1-Me and
[Pd(PhCN)2Cl2].
Ongoing studies aim at modulating further the ligand backbone.
The reactivity of 2-indenylidene and 2-indenyl pincer complexes
is also currently being explored.
Upon addition to 1-Me to a THF solution of [Pd(PhCN)2Cl2]
at room temperature, a light brown solid precipitated instanta-
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8912–8921 | 8917
©

of pentane (40 mL) to the red solution resulted in the precipitation
of an orange–red solid. The solvent was filtered off and the
orange solid was dried under vacuum to yield 5 (140 mg, 75%
yield). Single crystals were grown from a CH2Cl2–Et2O solution at
Experimental
General comments
All reactions were performed using standard Schlenk tech-
niques under an Argon atmosphere. Solvents were dried and
distilled prior to use (Et2O, THF and toluene over sodium
and pentane and dichloromethane over CaH2). All organic
reagents were obtained from commercial sources and used
as received. [Pd(PhCN)2Cl2] was purchased from STREM.
[Pd(PPh3)Cl2]2,23 1,3-bis(diphenylphosphino)indene24 and 1,3-
bis(diphenylthiophosphinoyl)indene 1-H25 were prepared accord-
ing to literature procedures. 31P, 1H and 13C NMR spectra
were recorded on Bruker Avance 300 or 400 and AMX500
◦
1
20 C. 31P{ H}-NMR (121.4 MHz, CDCl3): dppm 50.4 (d, 3J(P,P) =
5
3
18.6 Hz, P1), 33.1 (d, J(P,P) = 5.8 Hz, P2), 28.3 (dd, J(P,P) =
18.6 Hz, 5J(P,P) = 5.8 Hz, PPh3). 1H-NMR (500.3 MHz, CDCl3):
dppm 8.38–8.32 (m, 2H, HorthoPhP), 7.99–7.93 (m, 5H, PPh and
H5 or 8), 7.75–7.23 (m, 30H, PPh and H5 or 8), 7.05 (m, 2H, H6,7), 6.49
3
3
1
(dd, 1H, J(H,P) = 9.1 Hz, J(H,P) = 3.3 Hz, 1H, H2). 13C{ H}-
NMR (100.6 MHz, CDCl3): dppm 147.1 (m, C2), 144.5 (m, C9),
141.6 (ddd, J(C,P) = 12.9 Hz, J(C,P) = 9.9 Hz and J(C,P) =
0.8 Hz, C4), 135.1–127.9 (Ph2P and Ph3P), 127.1 (dd, J(C,P) =
12.0 Hz and J(C,P) = 6.2 Hz, C3), 123.8 (s, CInd), 123.5 (s, CInd),
123.1 (s, CInd), 30.6 (ddd, J(CP) = 71.5 Hz, J(C,P) = 62.6 Hz
and 3J(C,P) = 14.1 Hz, C1). Elemental analysis calcd (%) for
C51H40ClP3PdS2: C 64.36, H 4.24; found C 64.16, H 4.29. M. p.
192–193 ◦C.
2
3
4
1
3
spectrometers. 31P, H and 13C chemical shifts are expressed with
1
1
2
a positive sign, in parts per million, relative to external 85%
H3PO4 and Me4Si. Unless otherwise stated, NMR was recorded at
293 K. The 1H and 13C resonance signals were attributed thanks to
2D HMQC and HMBC experiments. The same atom numbering26
has been used for the indenyl skeleton of all compounds. The N
Synthesis of {Pd(PPh3)[Ind(Ph2P S)2]} 6. Compound 5
(210 mg, 0.230 mmol) and polystyrene supported diisopropylethy-
lamine (PS-DI◦EA, 0.330 mg, 4 equiv.) were heated in CH2Cl2
(20 mL) at 35 C during 12 h. Total consumption of compound
5 was confirmed by 31P NMR spectroscopy. The deep-orange
solution was then filtered to remove the PS-DIEA ammonium
salts. The solution was concentrated under vacuum and an orange
solid was precipitated by addition of pentane (40 mL). Filtration
and vacuum drying yielded an orange solid (175 mg, 83% yield).
Single crystals of 6 were grown from a CH2Cl2–Et2O solution
values corresponding to 1 (JAX + JAX¢) are provided when second
2
order AXX¢ systems are observed in the 13C NMR spectra.27
Preparations
Synthesis of {PdCl[IndH(Ph2P S)2]} 2. A colourless solution
of 1-H (1.097 g, 2 mmol) in CH2Cl2 (20 mL), was added at room
temperature to an orange solution of [Pd(PhCN)2Cl2] (768 mg,
2 mmol) in CH2Cl2 (20 mL) After stirring for two hours, the
solution slightly decoloured and a yellow precipitate appeared.
The yellow precipitate was recovered by filtration, washed with
CH2Cl2 (10 mL) and finally with pentane (2 ¥ 20 mL). After
drying under vacuum, 2 was obtained as a pale yellow powder
(1.30 g, 95%). NMR data were in agreement with those previously
reported.17c Single crystals of 2 were grown from a CH2Cl2–Et2O
solution at 20 ◦C.
at 20 ◦C. 31P{ H}-NMR (121.4 MHz, CDCl3): dppm 47.0 (d,
1
3
1
3J(P,P) = 50.5 Hz, P S), 17.6 (t, J(P,P) = 50.5 Hz, PPh3). H-
NMR (500.3 MHz, C6D6): dppm 7.84 (m, 8H, HmetaPh2P), 7.67 (m,
6H, HmetaPPh3), 7.50–7.30 (m, 15H, Hortho,para Ph2P and PPh3), 7.18
(m, 2H, H6,7), 6.83 (m, 2H, H5,8). 13C{ H}-NMR (125.8 MHz,
1
C6D6): dppm 177.8 (dt, 2J(C,P) = 128.3 and 34.5 Hz, C2), 137.9 (m,
C4,9), 134.6 (d, 3J(C,P) = 12.6 Hz, CorthoPh3P), 132.8 (d, 1J(C,P) =
82.1 Hz, CipsoPhP), 132.2 (d, 2J(C,P) = 11.7 Hz, CorthoPhP), 131.3
(m, CparaPhP), 130.0 (m, CparaPhP), 129.08 (m, CmetaPhP), 128.17
(m, CparaPhP), 117.60 (s, C5,8), 116.9 (s, C6,7), 105.6 (AXX¢, N =
76.1 Hz, C1,3). Elemental analysis calcd (%) for C51H39P3PdS2: C
66.92, H 4.29; found: C 66.62, H 4.10. M.p. 234–236 ◦C (dec.).
Synthesis of {PdCl[Ind(Ph2P S)2]}(iPr2EtNH) 4. iPr2EtN
(28 mL, 0.156 mmol) was added to a solution of 2 (107 mg,
0.156 mmol) in THF (30 mL) at -78 ◦C. After 2 h at this
temperature, pentane (40 mL) was added. The resulting precipitate
was recovered by filtration and dried under vacuum. Complex
4 was obtained as a yellow solid in good yield (80 mg, 63%).
Orange crystals suitable for single-crystal X-ray crystallography
Synthesis of [IndHD(Ph2P S)2]. nBuli (230 mL, 1,6 M in
hexane) was added to a degassed solution of [IndH2(P S)2]
(201 mg, 0,366 mmol) in THF (20 mL) at -80 ◦C. The mixture
was stirred for 30 min and then the reaction mixture was warmed
slowly to room temperature under stirring. CF3COOD was then
added (30 mL) at -80 ◦C. After warming up to room temperature,
the THF was partially eliminated under vacuum, and a white
precipitate appeared. The deuterated ligand was then recovered
by filtration and dried under vacuum. The product is moisture
sensitive (lost of D-labelling), and was stored in glove box. Yield
were grown from a THF solution at -70 ◦C. 31P{ H}-NMR
1
1
(203 K, 121.4 MHz, CD2Cl2): dppm 43.6 (s). H-NMR (203 K,
400 MHz, CD2Cl2): dppm 7.90 (m, 8H, HorthoPPh2), 7.55–7.40 (m,
12H, Hmeta,paraPPh2) 6.99 (m, 2H, H5,8), 6.68 (m, 2H, H6,7), 3.54 (m,
2H, NCH2), 2.95 (m, 2H, NCH), 1.40 (br, 6H, CH3), 1.29 (br, 3H,
1
CH3). 13C{ H}-NMR (203 K, 75.5 MHz, CD2Cl2): dppm 163.3 (m,
C2), 136.4 (m, C4,9), 133.4 (d, 1J(C,P) = 81.8 Hz, CipsoPhP), 131.8
(m, CmetaPhP), 128.3 (m, Cpara,orthoPhP), 117.0 (s, C6,7), 115.3 (s, C5,8),
104.2 (AXX¢, N = 73.7 Hz, C1,3), 53.6 (s, CH2), 42.0 (s, CH), 17.8
(s, CH3), 16.4 (s, CH3). M. p. 165 ◦C (dec.).
1
122 mg (60%). 31P{ H} NMR (121.4 MHz, CDCl3): dppm 45.5 (d,
4
1
4J(P,P) = 3.7 Hz, P1), 30.4 (d, J(P,P) = 4.2 Hz, P2). H NMR
(300 MHz, CDCl3): dppm 7.73–6.77 (m, 24H, H5–8 and PPh2), 6.36
(ddd, 3J(P,H) = 10.1 Hz, 3J(P,H) = 3.9 Hz, 3J(H,H) = 0.9 Hz, 1H,
H2), 4.90 (d br, 2J(P,H) = 22.0 Hz, 1H, H1).
Synthesis of {Pd(PPh3)Cl[IndH(Ph2P S)2]} 5. Cy2NH (40 ml,
0.190 mmol) was added to a suspension of [Pd(PPh3)Cl2]2 (86 mg;
0.190 mmol) and 1-H (104 mg, 0.190 mmol) in THF (30 mL) at
-78 ◦C. After 10 min at this temperature, the reaction was warmed
to room temperature and stirred for 1.5 h. The red solution was
then filtered to remove the precipitated ammonium salts. Addition
Synthesis of {Pd(PPh3)[IndH(Ph2P S)2]}[BF4] 7. To a solu-
tion of 5 (50.5 mg, 0.053 mmol) in CH2Cl2 (3 mL) at -80 ◦C was
8918 | Dalton Trans., 2011, 40, 8912–8921
This journal is
The Royal Society of Chemistry 2011
©

added a suspension of AgBF4 in CH2Cl2 (1 mL). The solution was
stirred at -80 ◦C for 1 h. and then warmed to room temperature.
The deep-orange solution was then filtered to remove the silver
salts. The solution was concentrated under vacuum and pentane
(4 mL) was added. Filtration and vacuum drying yielded an orange
solid. Crystals suitable for single-crystal X-ray crystallography
were obtained by slow diffusion of pentane into CH2Cl2 at room
11.2 Hz, CorthoPhP), 131.7 (d, 4J(P,C) = 3.0 Hz, CparaPhP), 131.6 (d,
1J(P,C) = 86.8 Hz, CipsoPhP), 131.6 (d, 2J(P,C) = 11.6 Hz, CorthoPhP),
130.8 (d, 1J(P,C) = 86.5 Hz, CipsoPhP), 130.7 (d, 1J(P,C) = 78.8 Hz,
C
ipsoPhP), 128.7 (d, 3J(P,C) = 2.4 Hz, CmetaPhP), 128.6 (d, 3J(P,C) =
2.4 Hz, CmetaPhP), 128.3 (d, 1J(P,C) = 77.4 Hz, CipsoPhP), 128.3 (d,
3J(P,C) = 2.3 Hz, CmetaPhP), 128.2 (d, 3J(P,C) = 1.9 Hz, CmetaPhP
and C6), 126.4 (d, 3J(P,C) = 1.3 Hz, C8), 124.7 (d, 3J(P,C) = 1.9 Hz,
C5), 123.9 (s, C7), 58.7 (dd, 1J(P,C) = 42.7 Hz, 3J(P,C) = 12.3 Hz,
C1), 19.2 (s, C10). M.p. 185 ◦C (dec.). Elemental analysis calcd (%)
for C34H28P2S2: C 72.58, H 5.02; found: C 72.80, H 4.86. HRMS
(TOF, CI+): calculated for C34H29P2S2: 563.1186, found: 563.1172.
1
temperature. Yield 21 mg (40%). 31P{ H} NMR (121.4 MHz,
CDCl3): dppm 54.2 (dd, 3J(P,P) = 30.4 Hz, 4J(P,P) = 5.3 Hz, P1), 53.3
3
4
3
(dd, J(P,P) = 47.6 Hz, J(P,P) = 5.3 Hz, P2), 18.9 (dd, J(P,P) =
47.7 Hz, 3J(P,P) = 30.4 Hz, PPh3). 1H NMR (500 MHz, CDCl3):
dppm 7.84–7.75 (m, 4H, PhP), 7.71–7.67 (m, 2H, PhP), 7.64–7.59
(m, 8H, PhP), 7.55 (m, 5H, PhP), 7.52 (m, 2H, Ph), 7.46 (m,
6H, Ph), 7.42–7.38 (m, 2H, Ph), 7.33 (m, 1H, H6), 7.27–7.20 (m,
2H, H5,7), 7.13–7.08 (m, 3H, Ph), 7.01–6.98 (m, 4H, Ph), 6.73 (d,
3J(H,H) = 7.5 Hz, 1H, H8), 5.74 (dd, 2J(H,P) = 24.8 Hz, 4J(H,P) =
2.7 Hz, 1H, H1). 13C NMR (125 MHz, CDCl3): dppm 190.6 (ddd,
Synthesis of {PdCl[Ind(Me)(Ph2P S)2]} 8. A solution of 1-
Me (250 mg, 0.444 mmol) in THF (10 mL) was added to a stirred
solution of [Pd(PhCN)2Cl2] (170 mg, 0.444 mmol) in THF (5 mL)
at room temperature. A brown precipitate appeared immediately.
The mixture was stirred for 2 h. to ensure complete reaction.
The precipitate was recovered by filtration and washed with THF
(5 mL). After extraction with CH2Cl2 and drying under vacuum,
complex 8 was obtained as a brown precipitate (196 mg, 63% yield).
Crystals suitable for single-crystal X-ray analysis were obtained by
slow diffusion of Et2O into a CH2Cl2 solution at room temperature.
2
2
2J(P,C) = 7.1 Hz, J(P,C) = 32.2 Hz, J(P,C) = 135.9 Hz, C2),
147.5 (dd, 1J(P,C) = 104.7 Hz, 3J(P,C) = 10.0 Hz, C3), 145.1 (ddd,
4J(P,C) = 3.1 Hz, 3J(P,C) = 6.5 Hz, 2J(P,C) = 19.8 Hz, C4), 140.2 (m,
C9), 134.8–119.7 (m, Ph2P), 133.9 (d, 2J(P,C) = 12.2 Hz, CorthoPPh3),
131.3 (m, CparaPPh3), 130.1 (d, 1J(P,C) = 49.1 Hz, CipsoPh3P), 129.6
(s, C5), 129.0 (d, 3J(P,C) = 10.2 Hz, CmetaPPh3), 125.9 (s, C7), 126.4
1
31P{ H} NMR (121.4 MHz, CDCl3): dppm 59.7 (s, P1), 51.6 (s, P2).
1H NMR (300 MHz, CDCl3): dppm 8.02–7.95 (m, 2H, HorthoPhP),
7.75–7.67 (m, 3H, PhP), 7.65–7.51 (m, 4H, PhP), 7.50–7.40 (m,
5H, PhP and H5), 7.32–7.27 (m, 4H, PhP and H6,7), 7.21–7.08
(d, 1J(P,C) = 80.2 Hz, CipsoPhP), 126.3 (d, 1J(P,C) = 84.7 Hz,
1
C
ipsoPhP), 125.0 (d, J(P,C) = 76.3 Hz, CipsoPhP), 123.8 (s, C6),
1
119.8 (s, C8), 119.7 (d, J(P,C) = 82.4 Hz, CipsoPhP), 71.1 (ddd,
1J(P,C) = 51.9 Hz, 3J(P,C) = 20.2 Hz, 3J(P,C) = 3.1 Hz, C1). M. p.
186–188 ◦C.
3
(m, 5H, PhP), 6.73 (m, 1H, H8), 1.93 (d, J(P,H) = 18.4 Hz, 3H,
H10). 13C NMR (125 MHz, CDCl3): dppm 191.7 (m, C2), 146.5 (d,
2
3
2J(P,C) = 9.1 Hz, C9), 144.2 (dd, J(P,C) = 18.4 Hz, J(P,C) =
1
3
3.7 Hz, C4), 143.2 (dd, J(P,C) = 107.1 Hz, J(P,C) = 9.3 Hz,
C3), 133.6 (d, 4J(P,C) = 2.3 Hz, CparaPhP), 133.3 (d, J(P,C) =
9.7 Hz, Cortho/metaPhP), 133.1 (d, 4J(P,C) = 3.4 Hz, CparaPhP),
133.1 (d, J(P,C) = 9.3 Hz, Cortho/metaPhP), 132.7 (d, 4J(P,C) =
2.7 Hz, CparaPhP), 136.5 (d, J(P,C) = 11.2 Hz, Cortho/metaPhP),
132.4 (d, 4J(P,C) = 4.7 Hz, CparaPhP), 131.8 (d, J(P,C) = 11.5 Hz,
Synthesis of [IndH(Me)(Ph2P S)2] 1-Me. To a solution of 1-
methylindene (3.36 g, 25.8 mmol) in diethyl ether (50 mL) was
added dropwise nBuLi (16.13 mL of a 1.6 M hexane solution,
25.8 mmol) at -80 ◦C. The mixture was stirred at -80 ◦C for 1 h
and then warmed slowly to room temperature. The solution was
◦
cooled again to -80 C and diphenylchlorophosphine (4.77 mL,
C
ortho/metaPhP), 129.2 (d, J(P,C) = 13.5 Hz, Cortho/metaPhP), 129.1 (d,
25.8 mmol) was added. The reaction medium was stirred at -80 ◦C
for 30 min and then warmed to room temperature within 1 h.
The addition of nBuLi and diphenylchlorophosphine was repeated
under the same conditions. S8 (1.65 g, 51.6 mmol of S) was then
added to the formed solution of 1,3-bis(diphenylphosphino)-1-
methylindene. The mixture was stirred for 10 h, the solvent was
removed by filtration and toluene (80 mL) was added. The whitish
precipitate was recovered by filtration and washed with toluene
and pentane. The Ind(Me)(P S)2 is obtained as a white powder
(7.89 g, 14.02 mmol, 55%). Crystals suitable for single-crystal
X-ray crystallography were obtained from a CH2Cl2 solution at
J(P,C) = 13.1 Hz, Cortho/metaPhP), 128.7 (s, C5), 128.2 (d, J(P,C) =
1
12.4 Hz, Cortho/metaPhP), 128.1 (d, J(P,C) = 84.3 Hz, CipsoPhP),
128.0 (d, 1J(P,C) = 80.6 Hz, CipsoPhP), 124.6 (d, 1J(P,C) = 69.2 Hz,
C
ipsoPhP), 124.5 (s, C7), 122.8 (s, C6), 118.9 (s, C8), 75.3 (dd,
1J(P,C) = 59.0 Hz, 3J(P,C) = 17.7 Hz, C1), 21.3 (d, 3J(P,C) =
18.3 Hz, C10). HRMS (TOF, CI+): calculated for C34H27ClP2PdS2:
703.9752, found: 703.9746. M.p. 280 ◦C (dec.).
Crystal Structure Determination of complexes 2, 4, 5, 6, 7, 1-Me
and 8
1
room temperature. 31P{ H} NMR (121.4 MHz, CDCl3): dppm 53.8
Data were collected using an oil-coated shock-cooled crystal on
(d, 4J(P,P) = 4.4 Hz, P1), 31.2 (d, 4J(P,P) = 4.4 Hz, P2). 1H NMR
(300 MHz, CDCl3): dppm 7.73–7.67 (m, 4H, PhP), 7.63–7.56 (m,
4H, PhP), 7.53–7.46 (m, 4H, PhP), 7.45–7.39 (m, 4H, H5 and PhP),
7.36 (m, 5H, H7 and PhP), 7.32–7.26 (m, 1H, PhP), 7.22–7.19 (m,
2H, H8,6), 6.60 (dd, 3J(P,H) = 10.1 Hz, 3J(P,H) = 3.1 Hz, 1H, H2),
1.75 (d, 3J(P,H) = 17.5 Hz, 3H, H10). 13C NMR (75 MHz, CDCl3):
a Bruker-AXS SMART APEX II diffractometer with Mo-Ka
˚
radiation (l = 0.7103 A). Semi-empirical absorption corrections
were employed.28 The structures were solved by direct methods
(SHELXS-97)29 and refined using the least-squares method on
F2.30 For compounds 2, 4 and 6, restraints were used to refine dis-
orders. The similar-ADP (Anisotrope Displacement Parameter)
and rigid-bond restraints were employed to make the ADP values
of the disordered atoms more reasonable.
2
2
dppm 151.6 (dd, J(P,C) = 8.9 Hz, J(P,C) = 1.4 Hz, C2), 146.5
(dd, 2J(P,C) = 9.5 Hz, 3J(P,C) = 0.4 Hz, C9), 141.6 (dd, 2J(P,C) =
3
1
12.4 Hz, J(P,C) = 3.6 Hz, C4), 138.7 (dd, J(P,C) = 84.8 Hz,
3J(P,C) = 8.5 Hz, C3), 133.3 (d, 2J(P,C) = 9.4 Hz, CorthoPhP),
132.2 (d, 2J(P,C) = 9.5 Hz, CorthoPhP), 132.0 (d, 4J(P,C) = 2.9 Hz,
CCDC 800695 (2), 800696 (4), 800697 (5), 800698 (6), 800699
(7), 800700 (1-Me) and 800701 (8) contain the supplementary
crystallographic data for this paper.† The crystallographic data
for the structures is given in Table 3.
C
paraPhP), 131.9 (d, 4J(P,C) = 3.1 Hz, CparaPhP), 131.9 (d, 2J(P,C) =
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8912–8921 | 8919
©

Computational details
Organometallics, 2007, 26, 4321; (c) J. L. Bolliger, O. Blacque and C. M.
Frech, Chem.–Eur. J., 2008, 14, 7969.
12 (a) K. Okamoto, T. Kanbara, T. Yamamoto and A. Wada,
Organometallics, 2006, 25, 4026; (b) K. Okamoto, T. Yamamoto, M.
Akita, A. Wada and T. Kanbara, Organometallics, 2009, 28, 3307; (c) J.
Kuwabara, G. Munezawa, K. Okamoto and T. Kanbara, Dalton Trans.,
2010, 39, 6255.
13 R. Gerber, O. Blacque and G. M. Frech, ChemCatChem, 2009, 1, 393.
14 (a) C. Azerraf, A. Shpruhman and D. Gelman, Chem. Commun., 2009,
466; (b) C. Azerraf, A. Shpruhman and D. Gelman, Organometallics,
2009, 28, 6578.
15 (a) M. Gagliardo, N. Selander, N. C. Mehendale, G. van Koten, R. J. M.
Gebbink and K. J. Szabo´, Chem.–Eur. J., 2008, 14, 4800; (b) E. M.
Schuster, M. Botoshansky and M. Gandelman, Angew. Chem., Int. Ed.,
2008, 47, 4555; (c) E. M. Schuster, G. Nisnevich, M. Botoshansky and
M. Gandelman, Organometallics, 2009, 28, 5025; (d) E. M. Schuster,
M. Botoshansky and M. Gandelman, Organometallics, 2009, 28, 7001.
16 (a) H. M. Lee, J. Y. Zeng, C.-H. Hu and M.-T. Lee, Inorg. Chem., 2004,
43, 6822; (b) W. Weng, S. Parkin and O. V. Ozerov, Organometallics,
2006, 25, 5345; (c) W. Weng, C.-H. Chen, B. M. Foxman and O. V.
Ozerov, Organometallics, 2007, 26, 3315.
Palladium and Phosphorus were treated with a Stuttgart–Dresden
pseudopotential in combination with their adapted basis set.31,32 In
all cases, the basis set has been augmented by a set of polarization
function (f for Pd and d for P).33 Carbon, sulfur, nitrogen and
hydrogen atoms have been described with a 6-31G(d,p) double-z
basis set.34 Calculations were carried out at the DFT level of theory
using the hybrid functional B3PW91.35,36 Geometry optimisations
were carried out without any symmetry restrictions, the nature
of the extrema (minimum) was verified with analytical frequency
calculations. All these computations have been performed with
the Gaussian 9837 suite of programs. The bonding situation was
analyzed using the NBO technique.38
Acknowledgements
17 (a) C. Freund, N. Barros, H. Gornitzka, B. Martin-Vaca, L. Maron and
D. Bourissou, Organometallics, 2006, 25, 4927; (b) P. Oulie´, C. Freund,
B. Martin-Vaca, L. Maron and D. Bourissou, Organometallics, 2007,
26, 6793; (c) P. Oulie´, N. Nebra, B. Martin-Vaca, L. Maron and D.
Bourissou, J. Am. Chem. Soc., 2009, 131, 3493.
We are grateful to the CNRS, UPS, ANR program (ANR-06-
BLAN-0034) and COST action CM0802 (PhoSciNet) for financial
support of this work. CalMip (CNRS, Toulouse, France) is
acknowledged for calculation facilities. The Institut Universitaire
de France (L. M.), the Spanish MEC and the European Social
Fund (N. N. post-doctoral grant) and French MESR (J. L. PhD
grant) are kindly acknowledged for financial support.
18 (a) S. Takahashi and M. Nonoyama, Transition Met. Chem., 1995, 20,
528; (b) D. E. Bergbreiter, P. L. Osburn and Y.-S. Liu, J. Am. Chem.
Soc., 1999, 121, 9531; (c) D. R. Evans, M. Huang, W. M. Seganish,
J. C. Fettinger and T. L. Williams, Organometallics, 2002, 21, 893;
(d) T. Kanaba and T. Yamamoto, J. Organomet. Chem., 2003, 688, 15;
(e) M. A. Hossain, S. Lucarini, D. Powell and K. Bowman-James, Inorg.
Chem., 2004, 43, 7275; (f) M. Akaiwa, T. Kanbara and T. Yamamoto,
J. Organomet. Chem., 2005, 690, 4192; (g) R. A. Begum, D. Powell and
K. Bowman-James, Inorg. Chem., 2006, 45, 964; (h) H. Meguro, T.-A.
Koizumi, T. Yamamoto and T. Kanbara, J. Organomet. Chem., 2008,
693, 1109; (i) V. A. Kozlov, D. V. Aleksanyan, Y. V. Nelyubina, K. A.
Lyssenko, E. I. Gustul, L. N. Puntus, A. A. Vasil’ev, P. V. Petrovskii
and I. L. Odinets, Organometallics, 2008, 27, 4062; (j) Y. Ogawa, A.
Taketoshi, J. Kuwabara, K. Okamoto, T. Fukuda and T. Kanbara,
Chem. Lett., 2010, 39, 385.
19 Similar ion pair association via N–H ◊ ◊ ◊ Cl hydrogen bonding has
been observed in [Ph3PN(Ph)H][PdCl2(C8H11)]: D. Aguilar, F. Azna´rez,
R. Bielsa, L. R. Falvello, R. Navarro and E. P. Urriolabeitia,
Organometallics, 2007, 26, 6397.
20 For other examples of anionic Pd and Ni pincer complexes charac-
terized by X-ray diffraction studies, see: D. Sellman, F. Geipel and F.
Heinemann, Eur. J. Inorg. Chem., 2000, 271.
Notes and references
1 C. J. Moulton and B. L. Shaw, J. Chem. Soc., Dalton Trans., 1976, 1020.
2 (a) M. E. Van der Boom and D. Milstein, Chem. Rev., 2003, 103,
1759; (b) The Chemistry of Pincer Ligands, D. Morales-Morales and
C. M. Jensen, Ed., Elsevier, Oxford , 2007; (c) D. Benito-Garagorri
and K. Kirchner, Acc. Chem. Res., 2008, 41, 201.
3 (a) M. Gupta, C. Hagen, W. C. Kaska, R. E. Cramer and C. M. Jensen,
J. Am. Chem. Soc., 1997, 119, 840; (b) F. Liu, E. B. Pak, B. Singh, C. M.
Jensen and A. S. Goldman, J. Am. Chem. Soc., 1999, 121, 4086; (c) K.
Krogh-Jespersen, M. Czerw, K. Zhu, B. Singh, M. Kanzelberger, N.
Darji, P. D. Achord, K. B. Renkema and A. S. Goldman, J. Am. Chem.
Soc., 2002, 124, 10797; (d) K. Zhu, P. D. Achord, X. Zhang, K. Krogh-
Jespersen and A. S. Goldman, J. Am. Chem. Soc., 2004, 126, 13044;
(e) I. Go¨ttker-Schnetmann, P. White and M. Brookhart, J. Am. Chem.
Soc., 2004, 126, 1804; (f) I. Go¨ttker-Schnetmann and M. Brookhart,
J. Am. Chem. Soc., 2004, 126, 9330.
4 (a) A. S. Goldman, A. H. Roy, Z. Huang, R. Ahuja, W. Schinski
and M. Brookhart, Science, 2006, 312, 257; (b) R. Ahuja, S. Kundu,
A. S. Goldman, M. Brookhart, B. C. Vicente and S. L. Scott, Chem.
Commun., 2008, 253.
5 M. Albrecht, A. L. Spek and G. van Koten, J. Am. Chem. Soc., 2001,
123, 7233.
21 For examples of anionic Pd pincer complexes too instable to be
characterized structurally, see: (a) J. Liu, H. Wang, H. Zhang, X. Wu,
H. Zhang, Y. Deng, Z. Yang and A. Lei, Chem.–Eur. J., 2009, 15, 4437;
(b) M. Feller, E. Ben-Ari, M. A. Iron, Y. Diskin-Posner, G. Leitus,
L. J. W. Shimon and L. Konstantinovski, Inorg. Chem., 2010, 49, 1615.
22 The NMR spectra showed only one set of signals, denoting that only
one isomer was also present in solution.
6 For an amido hydride complex of iridium, see: J. Zhao, A. S. Goldman
and J. F. Hartwig, Science, 2005, 307, 1080.
23 M. Noskowska, E. Sliwinska and W. Duczmal, Transition Met. Chem.,
2003, 28, 756.
7 For a Pt(IV) oxo complex, see: (a) E. Poverenov, I. Efremenko, A. I.
Frenkel, Y. Ben-David, D. J. W. Shimon, G. Leitus, L. Konstantinovski,
J. M. L. Martin and D. Milstein, Nature, 2008, 455, 1093; (b) C.
Limberg, Angew. Chem. Int. Ed., 2009, 48, 2270.
24 K. A. Falls, G. K. Anderson and N. P. Rath, Organometallics, 1992, 11,
885.
25 M. Stradiotto, C. M. Kozak and M. J. McGlinchey, J. Organomet.
Chem., 1998, 564, 101.
26 Atom numbering for the NMR assignments:.
8 For iridium dioxygen complexes, see: D. B. Williams, W. Kaminsky,
J. M. Mayer and K. I. Goldberg, Chem. Commun., 2008, 4195.
9 For palladium hydrides, see: (a) M. C. Denney, N. A. Smythe, K. L.
Cetto, R. A. Kemp and K. I. Goldberg, J. Am. Chem. Soc., 2006,
128, 2508; (b) G. R. Fulmer, R. P. Muller, R. A. Kemp and K. I.
Goldberg, J. Am. Chem. Soc., 2009, 131, 1346; (c) R. Gerber, T. Fox
and C. M. Frech, Chem.–Eur. J., 2010, 16, 6771; (d) C. Melero, L. M.
´
Mart´ınez-Prieto, P. Palma, D. Del Rio, E. Alvarez and J. Ca´mpora,
Chem. Commun., 2010, 46, 8851.
27 Nuclear Magnetic Resonance Spectroscopy, F. A. Bovey, Ed., Academic
Press, New-York, 1969; R. J. Abraham and H. Berstein, Can. J. Chem.,
1961, 39, 216.
28 SADABS, Program for data correction, Bruker-AXS, 2003, version 2.10.
29 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
10 For a dihydrogen complex of cobalt, see: T. J. Hebden, A. J. St. John,
D. G. Gusev, W. Kaminsky, K. I. Goldberg and D. M. Heinekey, Angew.
Chem., Int. Ed., 2011, 50, 1873.
11 (a) I. Go¨ttker-Schnetmann, P. S. White and M. Brookhart,
Organometallics, 2004, 23, 1766; (b) V. Pandarus and D. Zargarian,
8920 | Dalton Trans., 2011, 40, 8912–8921
This journal is
The Royal Society of Chemistry 2011
©

30 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 1990,
46, 467.
31 D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and H. Preuss, Theor.
Chim. Acta, 1990, 77, 123.
32 A. Bergner, M. Dolg, W. Kuechle, H. Stoll and H. Preuss, Mol. Phys.,
1993, 80, 1431.
33 A. W. Ehlers, M. Bo¨hme, S. Dapprich, A. Gobbi, A. Ho¨llwarth, V.
Jonas, K. F. Ko¨hler, R. Stegmann, A. Veldkamp and G. Frenking,
Chem. Phys. Lett., 1993, 208, 111.
34 P. C. Hariharan and J. A. Pople, Theor. Chim. Acta, 1973, 28, 213.
35 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.
36 K. Burke, J. P. Perdew, W. Yang, Electronic Density Functional Theory:
Recent Progress and New Directions, J. F. Dobson, G. Vignale and
M. P. Das, Ed., Springer, Heildelberg, 1998.
37 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C.
Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci,
M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E.
Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D.
Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.
Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y.
Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. G. Johnson,
W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, GAUSSIAN 03
(Revision D.02), Gaussian, Inc., Wallingford, CT, 2004.
38 A. E. Reed, L. A. Curtiss and F. Weinhold, Chem. Rev., 1988, 88, 899.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8912–8921 | 8921
©