New Routes to η1- and (η3?η 5)-Indenylpalladium Complexes: Synthesis, Characterization, and Reactivities

Article abstract of DOI:10.1021/om034253n

The dimer {(η⁸-Ind)Pd(μ-Cl)}₂ (6) reacts with t-BuNC to give the dimeric species {(η ¹-Ind)-(t-BuNC)Pd(μ-Cl)}2 (10), whereas reaction with PR ₃ gives the complexes (η-Ind)Pd(PR₃)Cl (R = Ph (4), Cy (7), Me (8), OMe (9)). Complexes 4 and (1-Me-Ind)Pd(PPh₃)Cl (5) can also be prepared by reacting (PhCN)₂PdCl₂ with Lilnd and PPh₃. The structural characterization of complexes 4-7, 9, and 10 by ¹H and ¹³C NMR spectroscopy and single-crystal X-ray diffraction studies has allowed an analysis of the indenyl ligand's mode of coordination, both in the solid-state and in solution. Compounds 4, 6, and 7 react with PhSiH₃ in the absence of cocatalysts, whereas reaction with ethylene requires the presence of excess MAO to give polyethylene.

Full text of DOI:10.1021/om034253n

1236
Organometallics 2004, 23, 1236-1246
New Rou tes to η1- a n d (η3Tη5)-In d en ylp a lla d iu m
Com p lexes: Syn th esis, Ch a r a cter iza tion , a n d Rea ctivities
Christine Sui-Seng,† Gary D. Enright,‡ and Davit Zargarian*,†
De´partement de chimie, Universite´ de Montre´al, Que´bec, Canada H3C 3J 7, and
Steacie Institute for Molecular Sciences, National Research Council,
Ottawa, Ontario, Canada K1A 0R6
Received October 22, 2003
The dimer {(η3-Ind)Pd(µ-Cl)}2 (6) reacts with t-BuNC to give the dimeric species {(η1-Ind)-
(t-BuNC)Pd(µ-Cl)}2 (10), whereas reaction with PR3 gives the complexes (η-Ind)Pd(PR3)Cl
(R ) Ph (4), Cy (7), Me (8), OMe (9)). Complexes 4 and (1-Me-Ind)Pd(PPh3)Cl (5) can also be
prepared by reacting (PhCN)2PdCl2 with LiInd and PPh3. The structural characterization
1
of complexes 4-7, 9, and 10 by H and 13C NMR spectroscopy and single-crystal X-ray
diffraction studies has allowed an analysis of the indenyl ligand’s mode of coordination, both
in the solid-state and in solution. Compounds 4, 6, and 7 react with PhSiH3 in the absence
of cocatalysts, whereas reaction with ethylene requires the presence of excess MAO to give
polyethylene.
In tr od u ction
chemistry of these compounds. Relatively little is known
about the reactivities of IndPd complexes, but the
preparation and characterization of the following com-
pounds have been reported: {(η3-Ind)Pd(µ-Cl)}2,10 {(µ-
η3-Ind)Pd(CNR)}2 (R ) t-Bu, 2,6-(CH3)2C6H3, 2,4,6-
(CH3)3C6H2, 2,4,6-(t-Bu)3C6H2),11 (η3-Ind)Pd(PMe3)-
(CH(SiMe3)2),12 and [(η3-Ind)Pd(LL)]+ 13 (LL ) bipy,
tmeda). In addition, a preliminary communication has
appeared on the preparation of a series of Ind derivates
from the reaction of cyclopropene and (PhCN)2PdCl2.14
In comparison to their Cp analogues, some indenyl
complexes of transition metals possess enhanced reac-
tivities in catalysis and in various stoichiometric reac-
tions, notably ligand substitution. This characteristic
has been attributed to the relative ease with which
metals can slip reversibly across the indenyl ligand’s
five-membered ring, thus forming a reactive η3-indenyl
tautomer that has both benzenoid resonance stabiliza-
tion and an accessible coordination site on the metal.
Various manifestations of this so-called “indenyl effect”,1
including superior catalytic activities,2 have been ob-
served for many indenyl complexes, in particular those
of group 6-9 metals.3 In contrast, the chemistry of
group 10 metal indenyl complexes is at an early phase
of its development.4
(5) (a) Huber, T. A.; Be´langer-Garie´py, F.; Zargarian, D. Organo-
metallics 1995, 14, 4997. (b) Bayrakdarian, M.; Davis, M. J .; Dion, S.;
Dubuc, I.; Be´langer-Garie´py, F.; Zargarian, D. Can. J . Chem. 1996,
74, 2115. (c) Huber, T. A.; Bayrakdarian, M.; Dion, S.; Dubuc, I.;
Be´langer-Garie´py, F.; Zargarian, D. Organometallics 1997, 16, 5811.
(d) Groux, L. F.; Be´langer-Garie´py, F.; Zargarian, D.; Vollmerhaus, R.
Organometallics 2000, 19, 1507. (e) Fontaine, F.-G.; Dubois, M.-A.;
Zargarian, D. Organometallics 2001, 20, 5156.
(6) (a) Vollmerhaus, R.; Be´langer-Garie´py, F.; Zargarian, D. Orga-
nometallics 1997, 16, 4762. (b) Dubois, M.-A.; Wang, R.; Zargarian,
D.; Tian, J .; Vollmerhaus, R.; Li, Z.; Collins, S. Organometallics 2001,
20, 663. (c) Groux, L. F.; Zargarian, D. Organometallics 2001, 20, 3811.
(d) Groux, L. F.; Zargarian, D.; Simon, L. C.; Soares, J . B. P. J . Mol.
Catal. A 2003, 193(1-2), 51. (e) Groux, L. F.; Zargarian, D. Organo-
metallics 2003, 22, 3124. (f) Groux, L. F.; Zargarian, D. Organometallics
2003, 22, ASAP.
(7) (a) Wang, R.; Be´langer-Garie´py, F.; Zargarian, D. Organometal-
lics 1999, 18, 5548. (b) Wang, R.; Groux, L. F.; Zargarian, D.
Organometallics 2002, 21, 5531. (c) Wang, R.; Groux, L. F.; Zargarian,
D. J . Organomet. Chem 2002, 660(1), 98. (d) Rivera, E.; Wang, R.; Zhu,
X. X.; Zargarian, D.; Giasson, R. J . Mol. Catal. A 2003, 204-205, 325.
(8) (a) Fontaine, F.-G.; Kadkhodazadeh, T.; Zargarian, D. J . Chem.
Soc., Chem. Commun. 1998, 1253-1254. (b) Fontaine, F.-G.; Zargarian,
D. Organometallics 2002, 21, 401.
(9) Fontaine, F.-G.; Nguyen, R.-V.; Zargarian, D. Can. J . Chem.
2003, 81, 1299.
(10) (a) Nakasuji, K.; Yamaguchi, M.; Murata, I.; Tatsumi, K.;
Natamura, A. Organometallics 1984, 3, 1257. (b) Samuel, E.; Bigorgne,
M. J . Organomet. Chem. 1969, 19, 9.
(11) Tanase, T.; Nomura, T.; Fukushina, T.; Yamamoto, Y.; Koba-
yashi, K. Inorg. Chem. 1993, 32, 4578.
(12) (a) Alias, F. M.; Belderrain, T. R.; Paneque, M.; Poveda, M. L.;
Carmona, E. Organometallics 1998, 17, 5620. (b) Alias, F. M.; Belder-
rain, T. R.; Carmona, E.; Graiff, C.; Paneque, M.; Poveda, M. L. J .
Organomet. Chem. 1999, 577, 316.
Our group has studied the chemistry of the complexes
IndNi(L)(X) (Ind ) indenyl and its substituted deri-
vates),5 some of which can act as precatalysts in the
oligo- and polymerization of alkenes,6 alkynes,7 and
8
PhSiH3 and in the hydrosilylation of alkenes and
ketones.9 Our interest in the structures and catalytic
activities of the IndNi complexes prompted us to explore
the chemistry of analogous Pd compounds in order to
elucidate the influence of the metal center on the
† Universite´ de Montre´al.
‡ National Research Council.
(1) (a) Rerek, M. E.; J i, L.-N.; Basolo, F. J . Chem. Soc., Chem.
Commun. 1983, 1208. (b) J i, L.-N.; Rerek, M. E.; Basolo, F. Organo-
metallics 1984, 3, 740. (c) Casey, C. P.; O’Connor, J . M. Organometallics
1985, 4, 384. (d) O’Connor, J . M.; Casey, C. P. Chem. Rev. 1987, 87,
307.
(2) (a) Frankom, T. M.; Green, J . C.; Nagy, A.; Kakkar, A. K.;
Marder, T. B. Organometallics 1993, 12, 3688. (b) Gamasa, M. P.;
Gimeno, J .; Gonzalez-Bernado, C.; Martin-Vaca, B. M.; Monti, D.;
Basseti, M. Organometallics 1995, 15, 302.
(3) Reactivity differences have also been noted between the Cp/Ind
complexes of early transition metals, but since these complexes are
generally electronically unsaturated, their reactivity differences are
less likely to be related to the hapticity of the ligands and more likely
influenced by steric and symmetry factors.
(4) For a recent review on the chemistry of group 10 metal indenyl
complexes see: Zargarian, D. Coord. Chem. Rev. 2002, 233-234, 157.
(13) (a) Vicente, J .; Abad, J .-A.; Bergs, R.; J ones, P. G.; De Arellano,
M. C. R. Organometallics 1996, 15, 1422. (b) Vicente, J .; Abad, J .-A.;
Bergs, R.; De Arellano, M. C. R.; Martinez-Vivente, E.; J ones, P. G.
Organometallics 2000, 19, 5597.
10.1021/om034253n CCC: $27.50 © 2004 American Chemical Society
Publication on Web 02/10/2004

New Routes to Indenylpalladium Complexes
Organometallics, Vol. 23, No. 6, 2004 1237
Sch em e 1
Sch em e 3
give (η1-Ind)2M(PR3)2, which produces 1,1′-biindene and
M0(PR3)n, presumably by reductive elimination.16
In an attempt to circumvent the above-discussed
homocoupling side reaction, we studied the use of alkyl-
substituted Ind precursors Li(1-R-Ind) (R ) Me, i-Pr,
SiMe3), a strategy that was successful in suppressing
the coupling side reaction in the case of Ni precursors.5c
Interestingly, however, this approach had no effect on
the course of the Pd reactions, implying that the Pd
precursors are more effective for the coupling reaction.17
We surmised that the use of Pd precursors bearing
more labile auxiliary ligands would accelerate ligand
dissociation from the putative intermediate (η1-Ind)PdL2-
Cl (Scheme 2), thereby favoring the formation of the
target complexes. Indeed, reacting (PhCN)2PdCl2 (1)
with Li(1-R-Ind) (R ) H, Me) appeared to give the target
complexes IndPd(NCPh)Cl, as indicated by a color
change from yellow to dark brown; the isolation of the
new products was hampered, however, by a gradual
decomposition that occurred even at -78 °C to give an
insoluble black solid. To circumvent this decomposition,
we added ca. 0.6 equiv of PPh3 to the reaction mixture
following the addition of Li(1-R-Ind) in order to convert
the presumably thermally unstable IndPd(NCPh)Cl to
the phosphine adduct (Scheme 3). This approach led to
the isolation of (1-R-Ind)Pd(PPh3)Cl (R ) H (4), Me (5))
as brown-red powders in moderate yields (36% on the
basis of (PhCN)2PdCl2, 60% on the basis of PPh3). It is
noteworthy that reacting 1 with a mixture of LiInd and
PPh3 at -78 °C, or adding LiInd to a mixture of 1 and
PPh3 at low temperature, produced 1,1′-biindene and
only a small amount of the target complexes 4 and 5,
giving mainly (PPh3)2PdCl2 and Pd(0).
Sch em e 2
Herein we report two different synthetic routes to the
complexes (η-Ind)Pd(PR3)Cl (R) Ph, Cy, Me, OMe) and
compare their structures and reactivities to those of
their analogous Ni complexes. The preparation of the
dimeric complex {(η1-Ind)(t-BuNC))Pd(µ-Cl)}2 from the
precursor {(η3-Ind)Pd(µ-Cl)}2 and the solid-state struc-
tures of these dimeric species will also be described.
The low yields obtained from the metathetic reactions
outlined above prompted us to explore alternative routes
not involving anionic sources of Ind in order to minimize
the homocoupling side reaction. Indeed, Boudjouk and
Lin have reported that 1-SiMe3-Ind can be an effective
source for the preparation of the polymeric species {(η3-
Ind)Pd(µ-Cl)}n (Scheme 4).18 The latter seemed like a
promising precursor to the complexes (η-Ind)Pd(L)Cl.
This approach was attempted and proved successful, as
described below.
Resu lts a n d Discu ssion
Syn t h esis. The main synthetic pathway to known
IndPd compounds involves the metathetic reactions of
MInd (M ) Li, Na) with various LnPdClm precursors
(Scheme 1).10-12 However, when we applied this meth-
odology for the synthesis of the complexes IndPd(PR3)-
Cl from the precursors (PR3)2PdCl2 (R ) Ph, Me), we
obtained the homocoupling products 1,1′-biindene and
Pd(PR3)n (Scheme 2). A similar observation has been
made during the syntheses of the analogous IndNi(PR3)-
Cl complexes.5a These side reactions may be attributed
to the sequence of steps depicted in Scheme 2: reaction
of Ind- with the precursors gives the initial intermediate
(η1-Ind)M(PR3)2Cl; conversion of the latter to the desired
(η-Ind)M(PR3)Cl is hampered by the slow dissociation
of one of the phosphine ligands;15 this brings about the
competitive addition of a second equivalent of Ind- to
(16) Different metal-containing side products are generated in this
side reaction depending on the metallic precursors used. For example,
(PPh3)2NiIICl2 generates (PPh3)3NiICl, which is thought to arise from
the conproportionation of the NiII precursor and the (PPh3)nNi0 species
generated in the coupling reaction. On the other hand, reaction of the
analogous (PMe3)2NiCl2 gives only Ni(PMe3)4, which can be detected
by its characteristic 31P signal at - 22 ppm (Tolman, C. A. J . Am.
Chem. Soc. 1970, 92, 2956). For the palladium precursor (PPh3)2PdCl2,
only the species Pd(PPh3)n (n ) 3, 4) has been detected by 31P{1H}
NMR (singlet at +24 ppm).
(17) We have noted that the independently prepared (η-Ind)Pd(PR3)-
Cl species react much more readily than their Ni counterparts with
IndLi to give 1,1′-biindene; this might explain why the metathetic
routes involving Ind anions are particularly ineffective for the synthesis
of indenyl-Pd complexes.
(14) Fiato, R. A.; Mushak, P.; Battiste, M. A. J . Chem. Soc., Chem.
Commun. 1975, 869.
(15) Consistent with this proposal, this side reaction is most
prevalent with the Ni precursors containing the weakly labile ligand
PMe3.
(18) Lin, S.; Boudjouk, P. J . Chin. Chem. Soc. 1989, 36, 35.

1238 Organometallics, Vol. 23, No. 6, 2004
Sui-Seng et al.
Sch em e 4
Sch em e 6
Sch em e 5
Sch em e 7
Reacting 8.3 mmol of 1-SiMe3-Ind with 7.2 mmol of
Na2[PdCl4] in ethanol gave a brown mixture from which
a brown solid precipitated gradually. Filtration and
successive washing of the collected solid with distilled
water, Et2O, and ethanol gave a material whose physical
appearance matched that of the compound {(η3-Ind)Pd-
(µ-Cl)}n, reported by Boudjouk and Lin.18 Interestingly,
however, the NMR data for this product were different
from those reported by Boudjouk and Lin but exactly
similar to the data reported by Murata’s group for the
dimer {(η3-Ind)Pd(µ-Cl)}2 (6).10a To establish the identity
of this compound unequivocally, we undertook an X-ray
diffraction study that confirmed the dimeric structure
of the product of our synthesis (vide infra). The factors
responsible for the preferred formation in our syntheses
of the dimer, as opposed to the polymeric species
proposed by Boudjouk and Lin, are not known. Never-
theless, in our hands Boudjouk’s procedure gives access
to 80-90% yields of complex 6, which has served as a
versatile precursor for the preparation of other IndPd
complexes, as outlined below.
The monomeric phosphine adducts (η-Ind)Pd(PR3)Cl
(R ) Ph (4), Cy (7), Me (8), OMe (9)) were obtained by
reacting the dimeric product 6 with PR3 (Scheme 5);
these complexes have been isolated as orange-red solids
in ca. 70-90% yields. On the other hand, a different
reactivity was observed when 6 was reacted with CO
and t-BuNC. Thus, reaction with CO resulted in a color
change from brown to red, but this change was main-
tained only as long as the solution was saturated with
CO. The 1H NMR spectrum of the mixture (with CO
present in the head gas) showed that the signals due to
6 had been replaced by a series of broad peaks, while
the 13C{1H} NMR spectrum displayed no signals at all,
implying an exchange process. Curiously, the IR spec-
trum did not show any absorption in the ν(CO) region.
All attempts at isolating the new species were unsuc-
cessful, as evaporation of the solvent or addition of
hexane to precipitate the product resulted in the regen-
eration of the starting material. We conclude, therefore,
that the putative CO adduct is in equilibrium with 6.
In contrast, t-BuNC converted 6 to the dimeric
derivative {(η1-Ind)(t-BuNC)Pd(µ-Cl)}2 (10; Scheme 6),
which could be isolated in 57% yield. Complex 10 is the
first example of an isolated and fully characterized PdII
complex featuring an η1-Ind moiety, but Poveda and co-
workers have reported the in situ generation and
spectroscopic characterization of a monomeric (η1-Ind)-
PdII complex (Scheme 7).12a The conversion of 6 to the
complexes 4 and 7-10 is analogous to a ligand displace-
ment reaction and likely proceeds by the initial coordi-
nation of the incoming ligand (associative mechanism);
it is interesting to note, however, that phosphine ligands
displace the bridging Cl, whereas t-BuNC causes a
change in the hapticity of Ind.
Compounds 4-10 are thermally stable and can be
handled in air for a few hours (both in the solid and in
solution) without appreciable decomposition. The identi-
ties of these complexes were deduced from their NMR
spectra and confirmed by the results of elemental
analyses and single-crystal X-ray diffraction studies.
These studies have provided valuable information on
the structural features of this family of complexes, as
described in the following section.
Sp ectr oscop ic Ch a r a cter iza tion . A singlet reso-
nance is observed in the 31P{1H} NMR spectra of the
complexes 4, 5, and 7-9, similar to those of the
analogous Ni compounds; in the case of 4, 5, and 8, the
31P chemical shifts are close to the corresponding signals
1
of their Ni homologues (Table 1). The H NMR and 13C-
{1H} NMR spectra of these compounds were also quite
similar to those of the corresponding Ni compounds.
Reliable peak assignments were made by means of
inverse-gated decoupling, COSY, and HMQC experi-
ments; the results of these detailed studies have proven
particularly informative for the coordination mode of the
Ind ligand in these compounds. For instance, the 13C
NMR spectra of Ind complexes can help identify the type
of M-Ind interactions present in solution following an
empirical protocol described by Baker19 and Marder.20
According to this protocol, the magnitude of the param-
eter ∆δav(13C) ) δav(C3a/C7a of Μ-Ind) - δav(C3a/C7a
of Na+Ind-) (ca. 130.7 ppm) reflects the solution hap-
ticity of the Ind ligand in a given complex; thus, the
solution hapticity is thought to be closer to η5 when
∆δav(C) , 0 (e.g., ∆δav(C) for Ind2Fe is ca. - 42 ppm),20
closer to η3 when ∆δav(C) . 0 (e.g., ∆δav(C) for (Ind)Ir-
(19) Baker, R. T.; Tulip, T. H. Organometallics 1986, 5, 839.
(20) Westcott, S. A.; Kakkar. A. K.; Stringer, G.; Taylor, N. J .;
Marder, T. B. J . Organomet. Chem. 1990, 394, 777.

New Routes to Indenylpalladium Complexes
Organometallics, Vol. 23, No. 6, 2004 1239
Ta ble 1. Electr och em ica l a n d NMR Da ta for Com p lexes 4-9 a n d An a logou s Nick el Com p lexesa
compd
31P{1H} (δ, ppm)
H1/H3 (δ, ppm) H3
C1/C3 (δ, ppm)
∆δav (ppm)
Ered1e (V)
Ered2e (V)
-1.41
(Ind)Pd(PPh3)Cl (4)
27.98
28.20
30.03
31.10
49.04
6.51/4.57
5.91/3.33b
-/4.28
97.2/79.9
6.7
-2
8.5
-2.0
8.5
-0.94
-0.64
-1.03
-0.75
-1.07
(Ind)Ni(PPh3)Cl (11)
(1-Me-Ind)Pd(PPh3)Cl (5)
(1-Me-Ind)Ni(PPh3)Cl (12)
(Ind)Pd(PCy3)Cl (7)
(1-Me-Ind)Ni(PCy3)Cl
(Ind)Pd(PMe3)Cl (8)
90.2/69.71b
113.3/76.5
103.4/67.2c
94.3/ 70.9
97.10/55.42
97.0/ 70.2
101.29/59.53
99.4/ 73.2d
-1.48
-1.05
-1.64
-/3.37
6.21/5.11
-/4.11
37.17
-1.0
6.6
-7.56
-10.61
131.21d
6.42/5.26
-/3.58
-1.24
-1.24
(1-Me-Ind)Ni(PMe3)Cl
(Ind)Pd(P(OMe)3Cl (9)
-2.0
6.49/5.69d
6.3d
Unless otherwise indicated, all spectroscopic data were collected at room temperature in C6D6. At 233 K, in toluene-d8. c In acetone-
a
b
d6. In CDCl3. e In CH3CN.
d
Ch a r t 1
mate an average energy barrier for the rotation of
indenyl rings using the Holmes-Gutowski equation.24
The ∆Gq value of ca. 16.5 kcal/mol obtained for the
complexes 4, 7, and 9 is similar to the values of ca. 16
kcal/mol measured for the analogous Ni-Cl complexes,
whereas energy barriers of ca. 10 kcal/mol have been
measured for the corresponding Ni-Me complexes.
The NMR data obtained for complex 10 were very
similar to those found for other transition-metal η1-
indenyl complexes that have been reported in the
literature.12a,25 In the 1H NMR spectrum of 10, the
proton on the carbon bonded directly to palladium
appeared as a broad signal at 5.85 ppm, whereas the
six remaining, nonequivalent Ind protons gave rise to
three doublets at 6.77 ppm (H2), 7.32 ppm (H7), 7.89
ppm (H4) and one multiplet between 7.02 and 7.12 ppm
for H3, H5, and H6. In the 13C NMR spectrum, the
chemical shift of the signal for C1 (44.1 ppm) differs
substantially from that of the η-Ind complexes 4, 5, and
7-9.
Solid -Sta te Str u ctu r a l Stu d ies. X-ray crystallo-
graphic analyses of the IndPd complexes prepared
during the course of this work were undertaken to study
the type of Ind-Pd interaction present in each com-
pound (e.g., η3 versus η1 in 6 and 10) and the influence
on Ind hapticity of the auxiliary ligands (e.g., µ-Cl in 6
versus PR3 and Cl in 4, 5, 7, and 9), phosphine
substituents (4 versus 7 and 9),26 and Ind substituent
(4 versus 5). The ORTEP views for these complexes are
shown in Figures 1-3, while crystal data and details of
the diffraction experiments are listed in Table 2 (for 4,
5, 7 and 9) and Table 3 (for 6 and 10). A selection of
bond distances and angles is given in Table 4 (for 4, 5,
7, and 9)27 and Table 5 (for 628 and 10); the correspond-
ing data for the compounds IndNi(PPh3)Cl (11)5a and
(1-Me-Ind)Ni(PPh3)Cl (12)5c are also included in Table
(PMe3)3 is ca. +28 ppm),21 and intermediate when
∆δav(C) ≈ 0 (e.g., ∆δav(C) for (Ind)2Ni22 is ca. +5 ppm).20
The ∆δav(C) values for our complexes are ca. +6.5 ppm
for 4, 6, 8, and 9 and ca. +8.5 ppm for 5 and 7 (Table
1); in comparison, ∆δav(C) values for the analogous
IndNi complexes are ca. -2 ppm, indicating that the η5
f η3 distortions in the Ind hapticity are much greater
in the Pd complexes.
The chemical shifts of the symmetry-related carbons
C1 and C3 (labeling shown in Chart 1 and on ORTEP
diagrams) and their respective protons H1 and H3 also
help shed light on the character of the Pd-Ind inter-
action. Inspection of the data in Table 1 shows that H3
resonates upfield of H1 by more than 1 ppm, while C3
resonates upfield of C1 by more than 20 ppm in all
compounds. This phenomenon, which has also been
observed for the analogous Ni complexes,4 can be
attributed to the relatively large difference in the trans
influences of PR3 and Cl ligands;23 the nonsymmetrical
Pd-C interactions resulting from this difference distort
the Ind-Pd bonding toward a localized mode (η1:η2;
Chart 1), which is manifested in different hybridizations
at C1 (closer to sp2) and C3 (closer to sp3).
Another consequence of nonsymmetrical Pd-Ind in-
teractions in solution is a high energy barrier for the
rotation of the Ind ligand about the Pd-Ind axis. This
was measured experimentally by studying the variable-
1
temperature H NMR spectra for complexes 4, 7, and
(24) Abraham. R. J .; Loftus, P. Proton and Carbon-13 NMR Spec-
troscopy; Wiley: New York, 1985; Chapter 7, pp 165-168, eq 7.11: (RTc
) 22.96 + ln(Tc/δν).
(25) (a) Casey, C. P.; O’Connor, J . M. Organometallics 1985, 4, 384.
(b) Hermmann, W. A.; Kuhn, F. E.; Romao, C. C. J . Organomet. Chem.
1995, 489, C56. (c) O’Hare, D. Organometallics 1987, 6, 1766.
(26) We have also studied the solid-state structure of the PMe3
analogue, complex 8, but the low quality of the crystal results have
precluded their inclusion here.
9. The coalescence temperature (Tc) and the frequency
differences (δν) measured for each pair of exchanging
resonances (Η1/Η3, Η4/Η7, Η5/Η6) allowed us to esti-
(21) Merda, J . S.; Kacmarcik, R. T.; Engen, D. V. J . Am. Chem. Soc.
1986, 108, 329.
(22) Kohler, F. H. Chem. Ber. 1974, 107, 570.
(23) The difference in the chemical shifts of the H1/H3 signals is
much larger in 4 (ca. 2 ppm) than in 7-9 (ca. 1 ppm). This is partially
caused by the anisotropic current effects of the PPh3 phenyl rings. This
same phenomenon is clearly evident in the Ni complex 11, for which
the chemical shift difference between H1 and H3 signals is greater
than 2.5 ppm (Table 1). We believe that the reason for the smaller
anisotropic shift in the Pd complexes is the longer Pd-PPh3 and Pd-
Ind bond distances, which place H3 farther from the Ph rings of PPh3
(by ca. 0.2 Å).
(27) The unit cells of complexes 4, 7, and 9 contain two independent
molecules differing from each other by the orientation of the phosphine
ligand in each case. In the case of 7 and 9, the distances and angles
are quite similar and have been averaged; in the case of complex 4,
however, the distances and angles of the two molecules are too
dissimilar to allow averaging.
(28) The unit cell of complex 6 contains four independent half-
molecules; the distances and angles are similar and have been
averaged.

1240 Organometallics, Vol. 23, No. 6, 2004
Sui-Seng et al.
F igu r e 1. ORTEP views of complexes 4, 5, 7, and 9. Thermal ellipsoids are shown at 30% probability, and hydrogen
atoms are omitted for clarity.
F igu r e 3. ORTEP view of complex 10. Thermal ellipsoids
are shown at 30% probability, and hydrogen atoms are
omitted for clarity.
largest structural distortion in the latter compounds
arises from the small C(1)-Pd-C(3) angle of ca. 61°,
F igu r e 2. ORTEP view of complex 6. Thermal ellipsoids
are shown at 30% probability, and hydrogen atoms are
omitted for clarity.
which is fairly similar to the corresponding value of ca.
66° in the analogous Ni complexes. It is instructive to
begin the structural discussion of Ind hapticity with the
structures of the η-Ind complexes; the main structural
features of complex 10 will be discussed last.
4 to facilitate structural comparisons between the Pd
and Ni complexes.
The overall geometry around Pd in 10 is very nearly
square planar (less than 5° deviation in all angles) but
much more irregular in the remaining compounds. The
The metal center in all of the η-Ind complexes is
within reasonable bonding distance from the P, Cl, C(1),
C(2), and C(3) atoms but considerably farther away from

New Routes to Indenylpalladium Complexes
Organometallics, Vol. 23, No. 6, 2004 1241
Ta ble 2. Cr ysta l Da ta a n d Da ta Collection a n d Str u ctu r e Refin em en t P a r a m eter s of 4, 5, 7, a n d 9
4
5
7
9
formula
mol wt
C
27H22ClPPd
C28H24ClPPd.CH2Cl2
618.218
C27H40ClPPd
537.41
C12H16O3ClPPd
381.07
519.27
cryst color, habit
cryst dimens, mm
symmetry
space group
a, Å
red, block
0.08 × 0.25 × 0.33
triclinic
red, block
0.30 × 0.34 × 0.47
monoclinic
P21/c
14.3388(1)
11.0454(1)
17.7748(1)
90
orange, plate
0.02 × 0.11 × 0.65
monoclinic
P21
11.6214(3)
19.4114(5)
11.8247(3)
90
red, block
0.11 × 0.12 × 0.18
monoclinic
P21/c
14.8857(4)
17.2545(4)
11.1260(4)
90
P1h
9.99970(10)
14.5450(2)
17.2588(2)
65.630(1)
83.151(1)
89.093(1)
4
b, Å
c, Å
R, deg
â, deg
108.156(1)
90
4
102.441(2)
90
4
91.905(2)
90
8
γ, deg
Z
D(calcd), g cm-3
diffractometer
temp, K
1.520
1.535
1.370
1.661
Bruker AXS SMART 2K
223(2)
λ(Cu KR), Å
µ, mm-1
scan type
F(000)
1.541 78
8.421
9.035
7.336
13.255
ω scan
1048
1248
1120
1520
θmax (deg)
72.90
72.90
72.93
73.03
h,k,l ranges
-12 e h e 12
-17 e k e 17
-21 e l e 21
7969
-17 e h e 17
-13 e k e 13
-22 e l e 21
4825
-23 e h e 23
-14 e k e 14
-23 e l e 23
8753
-18 e h e 18
-21 e k e 21
-10 e l e 12
4016
no. of rflns used (I > 2σ(I))
abs
cor
multiscan
SADABS
T(min, max)
R(F2 > 2σ(F2)), Rw(F2)
GOF
0.1200, 0.5100
0.0322, 0.0885
1.027
0.0630, 0.0670
0.0521, 0.1385
1.029
0.4370, 0.8640
0.0426, 0.0994
1.012
0.1850, 0.2330
0.0883, 0.2194
1.030
Flack param
0.022(7)
Ta ble 3. Cr ysta l Da ta a n d Da ta Collection a n d
Str u ctu r e Refin em en t P a r a m eter s of 6 a n d 10
Interestingly, the ∆(M-C), HA, and FA values observed
for complex 6 (Table 5) are larger than those of all
known monomeric Pd complexes (Table 4), implying a
larger degree of η5 f η3 distortion in this complex. Since
6 is the only neutral PdIIInd compound not bearing a
phosphine ligand, it is tempting to speculate on the
importance of Pdfphosphine π-back-bonding in these
complexes; however, the closeness of the structural
parameters for complexes 4, 7, and 9, bearing phos-
phines of different π acidities, seems to discount this
possibility.
Let us turn now to comparing the structural features
of the monomeric Ni and Pd complexes. The data listed
in Table 4 show that the Pd complexes exhibit signifi-
cantly larger values of ∆(M-C) (ca.. 0.32-0.39 Å versus
0.25 Å) and HA/FA (ca. 13.3-15.5° versus 10.9-11.8°),
implying that η5 f η3 slip-fold distortions are more
pronounced in IndPd complexes relative to their analo-
gous Ni counterparts. The same trend is observed in the
reported structural data for previously studied IndPd
complexes.4 For example, the ∆(M-C) values for IndPd-
(PMe3)(CH2SiMe3)12b and its close analogue (1-Me-Ind)-
Ni(PMe3)(CH3)8b are 0.39 and 0.27 Å, respectively. The
generally weaker Pd-Ind interaction presumably re-
flects the more electron rich nature of Pd versus Ni; this
assertion is borne out by the results of our electrochemi-
cal studies (vide infra).
6
10
formula
mol wt
C
18H14Cl2Pd2
C14H16ClNPd
340.13
513.99
cryst color, habit
cryst dimens, mm
symmetry
space group
a, Å
orange, needle
orange, block
0.15 × 0.25 × 0.50 0.08 × 0.10 × 0.39
triclinic
P1h
monoclinic
P21/c
6.37760(10)
13.9174(3)
16.0809(3)
90
90.26(10)
90
1427.32(5)
4
10.2103(6)
12.5513(7)
12.7249(7)
87.970(1)
78.209(1)
89.497(1)
1592.32(16)
4
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
D(calcd), g cm-3
diffractometer
2.141
1.583
Bruker AXS
SMART 1K
173(2)
0.7107
2.580
ω scan
992
Bruker AXS
SMART 2K
223(2)
1.541 78
12.018
ω scan
680
temp, K
λ, Å
µ, mm-1
scan type
F(000)
θmax deg
h,k,l range
29.62
72.88
-14 e h e 14
-17 e k e 17
-17 e l e 17
-7 e h e 6
-17 e k e 16
-19 e l e 19
2498
no. of rflns used (I > 2σ(I)) 11 089
abs
cor
multiscan
SADABS
0.27, 0.38
T(min, max)
R(F2 > 2σ(F2)), Rw(F2)
GOF
0.53, 0.86
0.0596, 0.1451
0.894
0.0263, 0.0680
1.018
As expected on the basis of the unequal trans influ-
ences of PR3 and Cl ligands, the Pd-Ind interactions
in 4, 5, 7, and 9 are also quite nonsymmetrical: Pd-
C(3) < Pd-C(1) by about 15-40 times the esd values.
The net result of this distortion is a partial localization
of bonding in the allyl moiety of the Ind ligand (i.e., η1:
BASF, %
17.6
C3a and C7a. The extent of M-Ind interaction can be
most conveniently estimated by the relative values of
the “slip” parameter ∆(M-C), which corresponds to the
difference between the average M-C distances from the
two allylic carbons (C1, C3) and the two quaternary
carbons (C3a, C7a); the hinge and fold angles (HA, FA,
as defined in Table 4) are also useful for this purpose.29
(29) The ∆(M-C), HA, and FA values for a range of Ind complexes
are given in refs 19 and 20. The corresponding data for group 10
complexes are given in ref 4.

1242 Organometallics, Vol. 23, No. 6, 2004
Sui-Seng et al.
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for 4, 5, 7, a n d 9 a n d th e An a logou s Nick el
Com p lexes 11 a n d 12
427
11
727
927
5
12
M-P
2.2785(6)
2.3474(6)
2.244(2)
2.186(2)
2.192(2)
2.607(2)
2.610(2)
1.404(4)
1.410(4)
1.474(4)
1.415(4)
1.464(4)
96.23(2)
158.71(7)
104.91(7)
97.29(7)
164.25(7)
61.4(1)
2.2673(6)
2.3560(7)
2.282(3)
2.209(3)
2.165(3)
2.544(3)
2.580(2)
1.393(4)
1.413(4)
1.468(4)
1.422(4)
1.465(4)
97.04(2)
160.78(8)
101.75(8)
99.48(8)
161.72(8)
61.3(1)
2.1835(7)
2.1822(7)
2.094(2)
2.061(2)
2.042(2)
2.318(2)
2.344(2)
1.399(4)
1.417(4)
1.449(3)
1.422(3)
1.459(3)
98.82(4)
161.51(8)
99.33(8)
95.48(8)
165.6(7)
66.5(1)
2.2702(14)
2.3521(13)
2.290(7)
2.193(6)
2.179(6)
2.595(5)
2.647(6)
1.401(12)
1.430(10)
1.454(9)
1.422(8)
1.434(10)
95.89(6)
161.1(2)
102.5(2)
100.5(2)
163.4(2)
61.3(3)
2.216(3)
2.355(2)
2.339(10)
2.198(10)
2.120(9)
2.570(10)
2.671(10)
1.397(16)
1.436(15)
1.440(15)
1.413(14)
1.463(15)
99.7(9)
163.6(3)
96.4(3)
103.1(3)
156.9(3)
61.1(4)
0.39
15.54
15.57
2.2649(8)
2.3585(8)
2.314(4)
2.228(4)
2.144(4)
2.520(3)
2.586(3)
1.392(6)
1.419(6)
1.479(6)
1.417(4)
1.475(5)
97.56(3)
159.4(1)
102.9(1)
98.1(1)
2.1782(11)
2.1865(10)
2.137(2)
2.072(2)
2.026(3)
2.308(2)
2.351(2)
1.403(4)
1.421(4)
1.451(4)
1.417(4)
1.457(4)
97.43(2)
161.52(7)
100.69(7)
95.83(8)
166.34(8)
66.3(1)
M-Cl
M-C1
M-C2
M-C3
M-C3a
M-C7a
C1-C2
C2-C3
C3-C3a
C3a-C7a
C7a-C1
P-M-Cl
C3-M-Cl
C3-M-P
C1-M-Cl
C1-M-P
C1-M-C3
∆M-Ca(Å)
HAb (deg)
FAc (deg)
132.1(1)
61.3(1)
0.32
14.72
13.32
0.39
15.49
14.84
0.39
14.58
14.40
0.26
10.9
11.7
0.39
15.49
14.03
0.25
11.00
11.80
a
b
∆(M-C) ) 0.5{(M-C3a + M-C7a)} - 0.5{(M-C1 + M-C3)}. HA is the angle formed between the planes formed by the atoms C1,
C2, C3 and C1, C3, C3a, C7a. c FA is the angle formed between the planes formed by the atoms C1, C2, C3 and C3a, C4, C5, C6, C7 and
C7a.
Pd-Cl bond distances trans to η1-Ind are longer (by ca.
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 6 a n d 10
10 esd values) than those trans to t-BuNC, indicating
that η1-Ind exerts a larger trans influence than t-BuNC.
The remaining structural parameters for this complex
are similar to those found in structurally characterized
η1-Ind complexes.30 For example, the metal-bound car-
bon atom is sp3 hybridized, as reflected in the C1-C7a
(ca. 1.50 Å) and C1-C2 (ca. 1.48 Å) distances that are
in the normal range for single C-C bonds, whereas the
C2-C3 distance (ca. 1.35 Å) is in the expected range
for a C(sp2)-C(sp2) double bond.
The structural parameters for the isocyanide ligand
(C8-N ≈ 1.14 Å, C8-N-C9 ≈ 171°) and the ν(CN)
absorption band in 10 (2204 cm-1), which is at higher
energy than for the free ligand (2136 cm-1), are consis-
tent with little π-back-bonding. Similar ν(CN) values,
Pd-C and C-N distances, and C-N-C angles have
been reported for other Pd(II)-isocyanide complexes.31
The IR data in particular indicate an increased C-N
bond order, probably caused by a strong σ donation from
the isocyanide ligand’s lone pair to Pd with little or no
π-back-donation.
Electr och em ica l Stu d ies. Table 1 lists the reduc-
tion potentials obtained from the cyclic voltammetry
(CV) studies carried out on complexes 4, 5, 7, 8, 11, and
12. The CV measurements of these complexes showed
that they undergo two successive and irreversible one-
electron reductions (presumably MII f MI and MI f M0)
at potentials ranging from -0.64 to -1.24 V for the first
wave and from -1.05 to -1.64 V for the second. (In the
case of complexes 8 and 12, second reductions were too
628
10
Pd-C1
2.204(6)
2.137(7)
2.165(7)
2.640(7)
2.656(6)
1.424(10)
1.404(10)
1.491(9)
1.419(9)
1.479(9)
62.4(3)
165.88(18)
87.06(6)
165.34(18)
92.94(6)
0.463
Pd-C1
2.063(3)
1.929(3)
2.3634(7)
2.4580(7)
1.138(4)
1.463(3)
1.477(5)
1.495(4)
1.349(5)
1.435(4)
1.408(4)
87.66(12)
177.77(8)
90.37(9)
95.22(8)
176.25(8)
86.79(2)
93.21(2)
171.3(3)
179.3(3)
Pd-C2
Pd-C8
Pd-C3
Pd-Cl
Pd-Cl#1
C8-N
Pd-C3a
Pd-C7a
C1-C2
C9-N
C1-C2
C1-C7a
C2-C3
C3-C3a
C3a-C7a
C1-Pd-C8
C8-Pd-Cl
C1-Pd-Cl
C2-C3
C3-C3a
C3a-C7a
C7a-C1
C1-Pd-C3
C1-Pd-Cl
Cl-Pd-Cl#1
Cl#1-Pd-C3
Pd-Cl-Pd#1
∆(M-C)
HA
C8-Pd-Cl#1
C1-Pd-Cl#1
Cl-Pd-Cl#1
Pd-Cl-Pd#1
C8-N-C9
17.30
16.39
FA
N-C8-Pd
η2 distortion; Chart 1), which is also reflected in the
nominally shorter C(1)-C(2) versus C(2)-C(3) dis-
tances. Moreover, the localization of bonding inside the
Ind moiety is also reflected in the 1H and 13C{1H} NMR
chemical shifts of these complexes (vide supra); there-
fore, the solid-state hapticity of the Ind ligand in these
Pd complexes is maintained in solution, as observed for
the previously studied Ni complexes. Consistent with
this correspondence between the solid-state and solution
structures, we have noted a correlation between ∆(M-
C) and ∆δ(13C) parameters of Ni and Pd complexes
(Figure 4); a similar correlation has also been demon-
stated previously for a wide range of Ind complexes.19
In contrast to the η-Ind complexes discussed above,
the Ind ligand in complex 10 adopts a η1 coordination
mode. This compound crystallizes in the centrosymmet-
ric space group P21/c and lies on an inversion center.
The Pd center is surrounded by η1-Ind, t-BuNC, and two
µ-Cl ligands. As expected, the Pd-C8 distance (ca. 1.93
Å) is shorter than the Pd-C1 distance (ca. 2.06 Å). The
(30) (a) Gue´rin, F.; Beddie, C. L.; Stephan, D. W.; Spence, E. v. H.;
Wurz, R. Organometallics 2001, 20, 3466. (b) Deck, P. A.; Fronczek,
F. R. Organometallics 2000, 19, 327. (c) Blenkiron, P.; Enright, G. D.;
Taylor, N. J .; Carty, A. J . Organometallics 1996, 15, 2855. (d) Thorn,
M. G.; Fanwick, P. E.; Chesnut, R. W.; Rothwell, I. P. Chem. Commun.
1999, 2543. (e) Radius, U.; Sundermeyer, J .; Peters, K.; von Schering,
H. G. Z. Anorg. Allg. Chem. 2002, 628, 1226.
(31) (a) Otsuka, S.; Nakamura, A.; Yoshida, T. J . Am. Chem. Soc.
1969, 91, 7196. (b) Crociani, B.; Boschi, T.; Belluco, U. Inorg. Chem.
1970, 9, 2021. (c) Cherwinski, W. J .; Clark, H. C.; Manzer, L. E. Inorg.
Chem. 1972, 11, 1511. (d) De Munno, G.; Bruno, G.; Grazia Arena, C.;
Drommi, D.; Faraone, F. J . Organomet. Chem. 1993, 450, 263.

New Routes to Indenylpalladium Complexes
Organometallics, Vol. 23, No. 6, 2004 1243
F igu r e 4. Correlation between ∆δav (ppm) and ∆(M-C) (Å).
weak to be observed.) The relative reduction potentials
of these complexes indicate that the Ind-Ni complexes
are more easily reduced than the Ind-Pd compounds;
this is consistent with the solid-state data, which
implied more electron rich Pd centers. Inspection of the
electrochemical data also shows that the Ered values for
the species 8 (Ered1 ) -1.24 V) and 4 (Ered1 ) -0.94 V,
Ered2 ) -1.41 V) follow the donor ability of the phos-
phine (PMe3 > PPh3); the reduction potential of the
PCy3 analogue 7 is less negative (Ered1 ) -1.07 V, Ered2
) -1.64 V) than that of the PMe3 analogue, presumably
due to a less effective electron donation caused by the
greater steric volume of PCy3.
200 equiv of PhSiH3 in a C6D6 solution indicated the
disappearance of the substrate Si-H and Ph-Si signals
1
(ca. 20% over 20 min); curiously, however, no new H
signal was detected for the anticipated products of the
reaction (i.e., (PhSiH)n). Monitoring the 31P{1H} NMR
spectra during the course of the reaction showed only a
broad signal at ca. -1.2 ppm (assigned to exchanging
PPh3); the spectrum at the end of the reaction signaled
the presence of free PPh3 (ca. -5 ppm) and OdPPh3 (ca.
+25 ppm).
Additional information was obtained from monitoring
the reaction of the Pd complexes with stoicheometric
1
quantities of PhSiH3. Thus, the H NMR spectrum of
Ca ta lytic Rea ctivities of In d P d Com p lexes. Re-
cent work in our group has shown that the complexes
(Ind)Ni(PR3)Cl are inert toward hydrosilanes and ole-
fins, but they catalyze the dehydrogenative polymeri-
zation of PhSiH3,8a hydrosilylation of olefins and ke-
tones,9 and polymerization of olefins6 in the presence
of excess MAO. We have briefly probed the reactivities
of some of the IndPd species reported here as a
preliminary comparison of their reactivities relative to
those of their Ni analogues. Thus, the reactions of
complexes 4-7 with excess PhSiH3 led to an instanta-
neous darkening of the reaction mixture and the evolu-
tion of a gas, indicating that the Pd complexes react with
this substrate in the absence of cocatalysts. Careful
NMR monitoring of mixtures of the complexes 4-6 and
the reaction of 4 with PhSiH3 (ca. 1:1) showed free IndH,
(PhSiH2)2 (singlet at ca. 4.46 ppm assigned to Si-H of
the dimer),8b and Ph2SiH2 (singlet at ca. 5.1 ppm) in
addition to other, unassigned peaks; the 31P{1H} NMR
spectrum of the final mixture showed only Pd(PPh3)n
(ca. +24 ppm). On the other hand, the analogous
reaction with 6 led to the complete consumption of
PhSiH3 and formation of indene and indane (hydroge-
nated indene), in addition to a number of minor signals;
significantly, no trace of the anticipated Si-containing
products (e.g., dimer, oligomer, and Ph2SiH2) was
observed.
Evidently, these reactions follow a complicated and
as yet not well-understood course. The available data
allow us, however, to offer the following speculation: (a)

1244 Organometallics, Vol. 23, No. 6, 2004
Sui-Seng et al.
13C{1H} (100.56 and 75.42 MHz), and 31P{1H} NMR spectra
(161.92 MHz) at ambient temperature. The NMR spectra are
referenced to (a) the residual solvent resonances for the 1H
and 13C{1H} spectra, and (b) 85% H3PO4 (0 ppm) for the 31P-
{1H} spectra. The ethylene polymerization experiments have
been realized as described in a recent paper.6d
initial reaction of PhSiH3 with the Pd precursors results
in the elimination of IndH and the formation of Pd0; (b)
in the presence of PPh3 ligands (reaction with 4), the
resulting Pd(PPh3)n can react with PhSiH3 to promote
both dehydrogenative Si-Si bond formation and redis-
tribution, whereas these reactions do not seem to occur
in the absence of phosphine (reaction with 6). It is
noteworthy that, unlike the case of the Ni complexes,
the presence of MAO did not change the course of the
reactions involving IndPd complexes. Finally, no hy-
drosilylation of styrene was observed in the presence
of PhSiH3 and the complexes 4-6, with or without
MAO.
We have also studied the catalytic activities of our
Pd complexes in the polymerization of ethylene. Thus,
we found that complexes 4 and 6 produced polyethylene
(PE) with modest activities (204 and 124 kg of PE/((mol
of Pd) h), respectively; polymerization conditions 600
equiv of MAO, ethylene-saturated toluene with Pethylene
≈ 16 atm, 60 °C, 30 min). It appears, therefore, that
these Pd complexes are more active in this reaction
relative to their Ni counterparts; for instance, the
complex (1-Me-Ind)Ni(PPh3)Cl showed an activity of
about 50 kg of PE/((mol of Ni) h) under similar condi-
tions (except for Pethylene ≈ 5 atm).
Cr ysta l Str u ctu r e Deter m in a tion s. The crystal data for
complexes 4-7, 9, and 10 were collected on Bruker AXS Smart
2K and 1K (for 6) diffractometers using SMART.34 Graphite-
monochromated Cu KR radiation was used at 223(2) K for all
crystals except that of 6, for which the radiation used was Mo
KR at 173(2) K. Cell refinement and data reduction were done
using SAINT.35 All structures were solved by direct methods
using SHELXS9736 and difmap synthesis using SHELXL97;37
the refinements were done on F2 by full-matrix least squares.
All non-hydrogen atoms were refined anisotropically, while the
hydrogens (isotropic) were constrained to the parent atom
using a riding model. The crystal structure of 6 presented two
twin components which have been described by a matrix
obtained with the Gemini program.38 In the case of complex
9, the Cu radiation employed resulted in relatively high
absorption and gave less satisfactory data; using SADABS39
improved the results, but the R factor for this structure
remained fairly high (ca. 8.8%). The crystal data and experi-
mental details are listed in Tables 2 and 3, while selected bond
distances and angles are listed in Tables 4 and 5.
Syn th esis of {(η3-In d )P d (µ-Cl)}2 (6). The original syn-
thesis of this compound was reported previously;10 we have
used the following procedure, which has been reported by Lin
and Boudjouk.18 Into a Schlenk flask, under nitrogen, Na2-
PdCl4 (6.5 g, 21.9 mmol) and 200 mL of ethanol were heated
to reflux until a clear brown solution was obtained. After the
solution was cooled to room temperature, 1-SiMe3-Ind (4.7 g,
25 mmol) was added to produce a brown solid, which precipi-
tated gradually. After it was stirred for 20 min, the mixture
was filtered and the collected solid washed successively with
distilled water, Et2O, and ethanol to give the compound {(η3-
Ind)Pd(µ-Cl)}2 (6; 4.9 g, 87%) as a brown powder. Recrystal-
lization of a small portion of this solid from a cold CH2Cl2/
Et2O solution yielded crystals suitable for X-ray diffraction
studies. 1H NMR (CDCl3, 300 MHz): δ 6.88-6.83 (m, H4-7),
5.84 (br, H1-3). 13C{1H} NMR (Me2SO-d6, 75.40 MHz): δ 136.9
(s, C3a-7a), 127.4 (s, C4-7), 118.8 (s, C5,6), 114.0 (s, C2), 85.4 (s,
Con clu sion
Two routes have been developed for the preparation
of indenylpalladium complexes. The first route, involv-
ing the reaction of (PhCN)2PdCl2 with LiInd and PPh3,
gives modest yields, while the second route, the addition
of PR3 to the dimeric compound {(η3-Ind)Pd(µ-Cl)}2 (6),
gives good yields of (η-Ind)Pd(PR3)Cl. The dimeric
derivate {(η1-Ind)(t-BuNC)Pd(µ-Cl)}2 (10), which is the
first example of an isolated (η1-Ind)Pd complex, was
obtained from the reaction of t-BuNC with 6. The
structural studies have revealed significant differences
in the hapticity of the Ind ligand (both in solution and
in the solid state) between the Pd and Ni complexes,
with the IndPd complexes displaying greater η5 f η3
slippage. Electrochemical measurements have con-
firmed that the Pd centers are more electron rich than
their Ni analogues. Preliminary reactivity studies have
shown that the Pd complexes are also somewhat more
reactive, but systematic studies are needed to delineate
the exact differences in the chemistry of these com-
plexes. Studies are underway to probe and expand the
scope of the reactions catalyzed by the IndPd com-
pounds.
C
1-3).
Syn th esis of (In d )P d (P P h 3)Cl (4). Meth od A. An Et2O
solution (60 mL) of IndLi (320 mg, 2.61 mmol) was added
dropwise to a stirred suspension of (PhCN)2PdCl2 (1 g, 2.61
mmol) in Et2O (80 mL) at - 78 °C. The mixture was warmed
to room temperature and stirred for 30 min. After PPh3 was
added (410 mg, 1.56 mmol), the resultant dark red mixture
was stirred for approximately 30 min, filtered through a small
pad of Celite, and concentrated. A red-brown powder precipi-
tated and was isolated by filtration (501 mg, 60%).
Meth od B. PPh3 (1.14 g, 4.3 mmol) was added to a stirred
Et2O suspension (110 mL) of {(η3-Ind)Pd(µ-Cl)}2 (6; 1.24 g, 2.4
mmol) at room temperature. After it was stirred for 1 h, the
resulting red solution was concentrated to ca. 60 mL. A red-
brown powder precipitated and was isolated by filtration (2.02
g, 89%). Recrystallization of a small portion of this solid from
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations and experiments
were performed under an inert atmosphere using standard
Schlenk techniques and/or a nitrogen-filled glovebox. Dry,
oxygen-free solvents were prepared by distillation from ap-
propriate drying agents and employed throughout. The syn-
theses of (PhCN)2PdCl232 and (PMe3)2PdCl233 were carried out
according to published procedures; all other reagents used in
the experiments were obtained from commercial sources and
used as received. The elemental analyses were performed by
the Laboratoire d’Analyse Ele´mentaire (Universite´ de Mont-
re´al). Bruker ARX400, AV400, AMX300, and AV300 spectrom-
eters were employed for recording 1H (400 and 300 MHz),
(34) SMART, Release 5.059; Bruker Molecular Analysis Research
Tool, Bruker AXS Inc., Madison, WI 53719-1173, 1999.
(35) SAINT, Release 6.06; Integration Software for Single-Crystal
Data; Bruker AXS Inc., Madison, WI 53719-1173, 1999.
(36) Sheldrick, G. M. SHELXS: Program for the Solution of Crystal
Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(37) Sheldrick, G. M. SHELXL: Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.
(38) GEMINI, version 1.02, Twinning Solution Program; Bruker
AXS Inc., Madison, WI 53711-5373, 1999.
(39) Sheldrick, G. M. SADABS, Bruker Area Detector Absorption
Corrections; Bruker AXS Inc., Madison, WI 53719-1173, 1997.
(32) Anderson, G. K.; Lin, M. Inorg. Synth. 1990, 28, 60.
(33) Klein, H.-F.; Zettel, B.; Flo¨rke, U.; Haupt, H.-J . Chem. Ber.
1992, 125, 9.

New Routes to Indenylpalladium Complexes
Organometallics, Vol. 23, No. 6, 2004 1245
a cold CH3CN/hexane solution yielded crystals suitable for
73%). Recrystallization of a small portion of this solid from a
cold toluene/hexane solution yielded crystals suitable for X-ray
diffraction studies and elemental analysis. 1H NMR (CDCl3,
X-ray diffraction studies and elemental analysis. 1H NMR
3
(CDCl3, 300 MHz): δ 7.56-7.39 (m, PPh3), 7.26 (d, J H-H
)
3
3
3
3
7.5 Hz, H7), 7.07 (t, J H-H ) 7.5 Hz, H6), 6.87 (t, J H-H ) 7.4
400 MHz): δ 7.20 (d, J H-H ) 7.6 Hz, H7), 7.04 (t, J H-H ) 7.0
3
3
3
Hz, H5), 6.73 (t, J H-H ) 6.4 Hz, H2), 6.51 (d, J H-H ) 9.9 Hz,
H1), 6.38 (d, 3J H-H ) 7.2 Hz, H4), 4.57 (t, 3J H-H ) 2.01 Hz, H3).
13C{1H} NMR (CDCl3, 100.56 MHz): δ 136.16 (s, C7a), 135.18
Hz, H6), 6.98-6.93 (m, H5 and H4), 6.64 (t, J H-H ) 2.9 Hz,
3
2
H2), 6.42 (d, J H-H ) 9.5 Hz, H1), 5.26 (s, H3), 1.48 (d, J H-P
)
11.4 Hz, PMe3). 13C{1H} NMR (C6D6, 75.40 MHz): δ 136.34
2
1
(s, C3a), 134.30 (d, J C-P ) 12.4 Hz, Cortho), 132.00 (d, J C-P
)
(s, C7a), 134.89 (s, C3a), 126.67 (s, C6), 125.84 (s, C5), 119.55 (s,
3
2
45.57 Hz, Cipso), 130.95 (s, Cpara), 128.96 (d, J C-P ) 10.6 Hz,
meta), 127.45 (s, C6), 126.55 (s, C5), 119.77 (s, C7), 116.91 (s,
C7), 116.23 (s, C4), 111.16 (s, C2), 97.00 (d, J C-P ) 24.6 Hz,
1
C
C1), 70.23 (s, C3), 16.68 (d, J C-P ) 29.4 Hz, PMe3). 31P{1H}
2
2
C4), 111.56 (d, J C-P ) 22.7 Hz, C2), 97.23 (d, J C-P ) 22.7 Hz,
C1), 79.88 (s, C3). 31P{1H} NMR (CDCl3, 121.49 MHz): δ 28.58
(s). 31P{1H} NMR (C6D6, 121.49 MHz): δ 27.98 (s). Anal. Calcd
for C27H22ClPPd: C, 62.45; H, 4.27. Found: C, 61.91; H, 4.56.
Syn th esis of (1-Me-In d )P d (P P h 3)Cl (5). An Et2O solution
(60 mL) of 1-Me-IndLi (355 mg, 2.61 mmol) was added
dropwise to a stirred suspension of (PhCN)2PdCl2 (1 g, 2.61
mmol) in Et2O (80 mL) at -78 °C. The mixture was warmed
to room temperature and then stirred for 30 min. After PPh3
was added (410 mg, 1.56 mmol), the resultant dark red mixture
was stirred approximately 30 min, filtered through a small
pad of Celite, and concentrated. A red-brown precipitate was
isolated by filtration (501 mg, 60%). Recrystallization of a small
portion of this solid from a cold CH2Cl2/hexane solution yielded
crystals suitable for X-ray diffraction studies and elemental
NMR (CDCl3, 161.92 MHz): δ -6.93. Anal. Calcd for C12H16-
ClPPd: C, 43.27; H, 4.84. Found: C, 43.19; H, 4.94.
Syn th esis of In d P d (P (OMe)3)Cl (9). P(OMe)3 (175 µL, 1.6
mmol) was syringed into a stirred Et2O suspension (30 mL) of
{(η3-Ind)Pd(µ-Cl)}2 (6; 400 mg, 0.78 mmol) at room tempera-
ture. After it was stirred for 2 h, the resulting red solution
was filtered and then concentrated to 15 mL. Addition of
hexane (15 mL) resulted in the precipitation of an orange
powder, which was filtered and washed with hexane to give
an orange solid (460 mg, 82%). Recrystallization of a small
portion of this solid from an ether solution at room tempera-
ture yielded crystals suitable for X-ray diffraction studies and
elemental analysis. 1H NMR (CDCl3, 400 MHz): δ 7.24 (d,
3
3J H-H ) 7.5 Hz, H7), 7.10-7.06 (m, H6 and H4), 6.98 (t, J H-H
3
) 7.5 Hz, H5), 6.58-6.56 (m, H2), 6.49 (d, J H-H ) 16.8 Hz,
3
3
1
H1), 5.69 (d, J H-H ) 2.3 Hz, H3), 3.64 (d, J H-P ) 12.9 Hz,
P(OMe)3). 13C{1H} NMR (CDCl3, 100.56 MHz): δ 136.02 (d,
3J C-P ) 7.4 Hz, C7a), 134.56 (d, 3J C-P ) 4.2 Hz, C3a), 127.64 (s,
C6), 126.56 (s, C5), 120.09 (s, C7), 118.25 (s, C4), 111.16 (d, 2J C-P
analysis. H NMR (C6D6, 400 MHz): δ 7.50-7.61 (m, PPh3),
7.03 (d, 3J H-H ) 7.7 Hz, H7), 6.90-6.95 (m, PPh3), 6.94 (t, 3J H-H
) 7.6 Hz, H6), 6.75 (t, 3J H-H ) 7.4 Hz, H5), 6.23 (d, 3J H-H ) 7.5
3
3
Hz, H4), 6.12 (d, J H-H ) 2.7 Hz, H2), 4.28 (d, J H-H ) 2.7 Hz,
2
2
H3), 2.04 (d, J H-P ) 10.4 Hz, Me). 1H NMR (CDCl3, 400
3
) 10.6 Hz, C2), 99.42 (d, J C-P ) 34.95 Hz, C1), 73.15 (d, J C-P
) 7.05 Hz, C3), 53.24 (s, P(OMe)3). 31P{1H} NMR (CDCl3,
161.92 MHz): δ 131.2. Anal. Calcd for C12H16ClO3PPd: C,
37.82; H, 4.23. Found: C, 37.55; H, 4.29.
3
MHz): δ 7.39-7.45 (m, PPh3), 7.19 (d, J H-H ) 7.3 Hz, H7),
3
3
7.08 (t, J H-H ) 7.3 Hz, H6), 6.86 (t, J H-H ) 7.6 Hz, H5), 6.49
3
3
(d, J H-H ) 2.8 Hz, H2), 6.24 (d, J H-H ) 7.4 Hz, H4), 4.46 (d,
Syn th esis of [(η1-In d )2(t-Bu NC)2P d (µ-Cl)2] (10). A stirred
benzene solution (10 mL) of t-BuNC (161 µL, 1.44 mmol) was
added to a stirred benzene solution (25 mL) of {(η3-Ind)Pd(µ-
Cl)}2 (6; 400 mg, 0.78 mmol) at room temperature. The
resulting orange solution was stirred for 45 min, filtered, and
evaporated to dryness. The residue was crystallized from Et2O
at 0 °C to give the product as orange crystals (300 mg, 57%).
3J H-H ) 2.8 Hz, H3), 2.05 (d, J H-P ) 10.6 Hz, Me). 13C{1H}
3
3
NMR (C6D6, 100.56 MHz): δ 138.96 (d, J C-P ) 4.1 Hz, C7a),
3
2
136.37 (d, J C-P ) 0.69 Hz, C3a), 135.02 (d, J C-P ) 12.5 Hz,
C
ortho), 133.85 (d, 1J C-P ) 43.7 Hz, Cipso), 131.01 (s, Cpara), 129.13
(d, 3J C-P ) 10.4 Hz, Cmeta), 126.95 (s, C6), 126.84 (s, C5), 118.70
2
(s, C7), 116.48 (s, C4), 113.33 (d, J C-P ) 21.5 Hz, C1), 111.56
2
3
(d, J C-P ) 5.5 Hz, C2), 76.46 (s, C3), 13.09 (d, J C-P ) 5.6 Hz,
3
1H NMR (CDCl3, 300 MHz): δ 7.89 (d, J H-H ) 6.9 Hz, H4),
Me). 31P{1H} NMR (C6D6, 161.92 MHz): δ 30.03 (s). 31P{1H}
7.38 (d,3J H-H ) 7.4 Hz, H7), 7.13-7.02 (m, H3, H5, and H6),
NMR (CDCl3, 161.92 MHz): δ 29.67 (s). Anal. Calcd for C28H24
ClPPd‚2/3LiCl: C, 59.89; H, 4.54. Found: C, 59.32; H, 4.46.
-
3
6.77 (d, J H-H ) 5.01 Hz, H2), 5.85 (br, H1), 0.40 (s, t-BuNC-
(CH3)3). 13C{1H} NMR (C6D6, 75.40 MHz): δ 153.55 (s, C7a),
142.86 (s, C3a), 141.06 (s, C3 or C5 or C6), 125.75 (s, C4), 125.25
(s, C3 or C5 or C6), 125.18 (s, C2), 124.34 (s, C3 or C5 or C6),
121.39 (s, C7), 57.07 (s, CMe3), 44.11 (s, C1), 28.90 (s, CMe3).
The missing resonance for CN is probably obscured under the
residual solvent resonances at ca. 129 ppm. IR (KBr): 2204
cm-1 (s, CN). Anal. Calcd for C28H32Cl2P2Pd2: C, 49.43; H, 4.74;
N, 4.12. Found: C, 50.59; H, 4.90; N, 3.94. All our attempts to
further purify this material were unsuccessful.
Ca lcu la tion of th e En er gy Ba r r ier to th e In d en yl
Rota tion in Com p lexes 4, 7, a n d 9. The Holmes-Gutowski
equation for a two-site exchange process involving molecular
rotation, ∆Gq/RTc ) 22.96 + ln(Tc/δν),24 can be used to calculate
the free energy of activation for the hindered indenyl rotation
process. The two variables in this equation, the coalescence
temperatures (Tc) and frequency differences (δν) for each pair
of exchanging resonances, are listed below along with the
Syn th esis of (In d )P d (P Cy3)Cl (7). A stirred Et2O solution
(30 mL) of PCy3 (436 mg, 1.56 mmol) was added to a stirred
Et2O suspension (110 mL) of {(η3-Ind)Pd(µ-Cl)}2 (6; 1.24 g, 2.4
mmol) at room temperature. After it was stirred for 45 min,
the resulting red solution was filtered and then concentrated
to 60 mL. An orange powder precipitated and was isolated by
filtration (710 mg, 85%). Recrystallization of a small portion
of this solid from a cold CH3CN/hexane solution yielded
crystals suitable for X-ray diffraction studies and elemental
3
analysis. 1H NMR (C6D6, 300 MHz): δ 7.13 (d, J H-H ) 7.6
3
3
Hz, H7), 6.92 (t, J H-H ) 7.2 Hz, H6), 6.88 (d, J H-H ) 6.9 Hz,
H4), 6.81 (t, 3J H-H ) 7.1 Hz, H5), 6.33 (t, 3J H-H ) 3.06 Hz, H2),
6.21 (d, 3J H-H ) 9.4 Hz, H1), 5.11 (s, H3), 1.98-1.08 (m, PCy3).
13C{1H} NMR (C6D6, 75.40 MHz): δ 137.85 (s, C7a), 137.15 (s,
C
3a), 126.34 (s, C6), 124.61 (s, C5), 119.84 (s, C7), 117.83 (s, C4),
2
2
110.87 (d, J C-P ) 5.2 Hz, C2), 94.26 (d, J C-P ) 21.8 Hz, C1),
2
1
70.94 (d, J C-P ) 3.4 Hz, C3), 35.35 (d, J C-P ) 19.8 Hz, Cipso),
2
3
30.2 (d, J C-P ) 11.1 Hz, Cortho), 27.69 (d, J C-P ) 11.7 Hz,
C
meta), 27.61 (d, 3J C-P ) 10.9 Hz, Cmeta), 6.61 (s, Cpara). 31P{1H}
complex exchanging protons
Tc (K) δν (Hz) ∆Gq (kcal/mol)
NMR (C6D6, 161.92 MHz): δ 49.04 (s). 31P{1H} NMR (CDCl3,
161.92 MHz): δ 48.34 (s). Anal. Calcd for C27H40ClPPd: C,
60.34; H, 7.50. Found: C, 59.92; H, 7.66.
4
7
9
H1/H3
H4/H7
H5/H6
H1/H3
H4/H7
H5/H6
H1/H3
H4/H7
H5/H6
368-373
358-368
348-358
358-363
348-358
318-328
358-368
328-338
318-328
824
336
76
409
64
29
344
68
16.2-16.5
16.4-16.8
16.9-17.4
16.2-16.5
17.0-17.5
16.1-16.5
16.4-16.8
16.1-16.5
16.1-16.9
Syn th esis of (In d )P d (P Me3)Cl (8). PMe3 (161 µL, 1.6
mmol) was syringed into a stirred Et2O suspension (50 mL) of
{(η3-Ind)Pd(µ-Cl)}2 (6; 500 mg, 0.97 mmol) at room tempera-
ture. After it was stirred for 45 min, the resulting red solution
was filtered and then concentrated to 60 mL. An orange
powder precipitated and was isolated by filtration (380 mg,
28

1246 Organometallics, Vol. 23, No. 6, 2004
Sui-Seng et al.
corresponding calculated ∆Gq values. It should be noted that
the temperatures at which the spectra were recorded were not
calibrated and that the temperature increments studied were
not sufficiently small to allow the determination of accurate
coalescence temperatures. Nevertheless, these uncertainties
are relatively insignificant and the average ∆Gq values thus
obtained represent a reliable, qualitative estimate of the
energy barrier to the indenyl rotation process.
Cyclic Volta m m etr y. Electrochemical measurements were
performed on an Epsilon electrochemical analyzer using 0.002
M solutions of the palladium(II) complexes in a 0.1 M CH3CN
solution of n-Bu4PF6 (0.1 M). Cyclic voltammograms were
obtained in a standard, one-compartment electrochemical cell
using a graphite disk as the working electrode, a platinum
wire as the counter electrode, and a silver wire as the reference
electrode. The cyclic voltammetry experiments were performed
in the potential range of -2.4 to 1.2 V using a scan rate of
100 mV/s. Under these conditions, the E1/2 value for the Fc+/
Fc couple was 570 mV.
Sciences and Engineering Reserach Council of Canada
(operating grants to D.Z.) and Universite´ de Montre´al
(scholarships to C.S.-S.). We are also indebted to Johnson
Matthey for the generous loan of PdCl2, to Drs. M.
Simard, L. Groux, and F. Be´langer-Garie´py for their
assistance with the X-ray analyses, and to Dr. Yaofeng
Chen for his help in evaluating the catalytic activities
of complexes 4 and 6 in the polymerization of ethylene.
Prof. Boudjouk is thanked for supplying the experimen-
tal details for the reaction of 1-SiMe3-Ind with Na2-
[PdCl4].
Su p p or tin g In for m a tion Ava ila ble: Complete details of
the X-ray analysis of 4-7, 9, and 10, including tables of crystal
data, collection and refinement parameters, bond distances
and angles, anisotropic thermal parameters, and hydrogen
atom coordinates. This material is available free of charge via
the Internet at http://pubs.acs.org.
Ack n ow led gm en t. This work was made possible
thanks to the financial support provided by the Natural
OM034253N