1-Indenyldialkylphosphines and cyclopentadienyldialkylphosphines as ligands for high-activity palladium-catalyzed cross-coupling reactions with aryl chlorides

Article abstract of DOI:10.1021/om070094m

The reactions of three deprotonated indenes (1,2,3-trimethyl, 1,2,3,4,7-pentamethyl, and 1,2,3-trimethyl-4,7-dimethoxy) and the lithium salt of pentamethylcyclopentadiene (Cp*) with C1PR₂ (R = iPr, Cy) resulted in the formation of six indenylph

Full text of DOI:10.1021/om070094m

2758
Organometallics 2007, 26, 2758-2767
1-Indenyldialkylphosphines and Cyclopentadienyldialkylphosphines
as Ligands for High-Activity Palladium-Catalyzed Cross-Coupling
Reactions with Aryl Chlorides
Christoph A. Fleckenstein and Herbert Plenio*
Anorganische Chemie im Zintl-Institut, Petersenstr. 18, 64287 Darmstadt, Germany
ReceiVed January 31, 2007
The reactions of three deprotonated indenes (1,2,3-trimethyl, 1,2,3,4,7-pentamethyl, and 1,2,3-trimethyl-
4,7-dimethoxy) and the lithium salt of pentamethylcyclopentadiene (Cp*) with ClPR2 (R ) iPr, Cy)
resulted in the formation of six indenylphosphines and two cyclopentadienylphosphines, isolated as the
respective phosphonium salts. The Pd-phosphine complexes, formed in the presence of Na2PdCl4, base,
and coupling partners, were shown to be highly active Pd complexes for various aryl chloride cross-
coupling reactions. Quantitative yields in the Suzuki coupling are possible with 0.05-0.1 mol % of
catalyst. Aryl chlorides can be coupled in quantitative yields in the Sonogashira reaction using 1 mol %
of catalyst complex, while the Buchwald-Hartwig reaction typically requires 0.5 mol % of catalyst. In
addition to the standard substrates, ferrocenylamine was subjected to Buchwald-Hartwig aminations,
resulting in ferrocenylarylamines in near-quantitative yield.
tion,36 Negishi,37 Stille,38-40 Hiyama,41 Kumada,42 R-aryla-
Introduction
tion,43,44 and carbonylation types.45 In particular, tBu3P has been
Trialkylphosphines with bulky substituents are highly useful
ligands for catalytically active palladium complexes in various
cross-coupling reactions of the Suzuki,1-11 Sonogashira,12-22
Heck,23-28 Buchwald-Hartwig amination29-35 and ether forma-
used for a wide range of different coupling reactions, due to
the high catalytic activity of its Pd complexes and its commercial
availability.46 tBu3P combines the two features which are
said to be essential for trialkylphosphines for cross-coupling
* To whom correspondence should be addressed. E-mail: plenio@
tu-darmstadt.de.
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10.1021/om070094m CCC: $37.00 © 2007 American Chemical Society
Publication on Web 04/11/2007

Pd-Catalyzed Cross-Coupling Reactions
Organometallics, Vol. 26, No. 10, 2007 2759
Chart 1. Relationship of Fluorenyl-, Indenyl-, and
Cyclopentadienyldialkylphosphines
Scheme 1. Synthesis of Indenylphosphonium Saltsa
a Reagents and conditions: (a) AlCl3; (b) CH3Li or CH3MgI, H+;
(c) nBuLi, R2PCl, Et2O, -60 °C, HBF4‚Et2O.
Results and Discussion
Synthesis of 1-Indenyldialkylphosphonium and Cyclopen-
tadienyldialkylphosphonium Salts. Only a few cyclopentadienyl-
reactions: electron richness and steric bulk. We have recently
reported a new class of 9-fluorenylphosphines47 which combine
the high catalytic activity of tBu3P with the wide variability
needed for the fine-tuning of the catalysts48,49 or the introduction
of phase tags20,50-55 enabling biphasic catalysis56 as well as
catalyst recycling.57,58
59-63
and indenyl-based trialkylphosphines64-67 have been
described in the literature, and none of them have been utilized
in cross-coupling catalysis. In order to increase the steric bulk
and to diversify the electronic nature of the such ligands, 1,2,3-
trimethylindene (4), 1,2,3,4,7-pentamethylindene (7), and 4,7-
dimethoxy-1,2,3-trimethylindene (9) were synthesized as back-
bones for phosphines. In general, the indenes were prepared
via Friedel-Crafts acylation of the arene with tigloyl chloride
(2) and subsequent ring closure, methylation, and acidic
dehydration (Scheme 1). This synthetic strategy enables the easy
modification of the 4,7-positions of indenes using the respective
para-substituted arenes.
2,3-Dimethylindanone (3) was prepared according to the
method of Rausch et al.68 by reacting benzene (1) with AlCl3
and tigloyl chloride (2) in benzene as a solvent in near-
quantitative yield. When the same reaction protocol was utilized
for the synthesis of 2,3,4,7-tetramethylindanone (6) with p-
xylene (5) as reactant (and solvent), large amounts of iso-
merization products (32%) were formed due to a methyl shift
of the aromatic methyl groups.69,70 The separation of the
two isomers was impractical on a multigram scale using
rectification or column chromatography. It is noteworthy that
even the improved synthesis of O’Hare et al.,71,72 replacing the
Encouraged by the high catalytic activity and the facile
synthesis of the fluorenyldialkylphosphines (isolated as the
respective phosphonium salts), we wished to broaden this class
of phosphines by variation of the fluorene lead structure. As
visualized in Chart 1, the cyclopentadienyl ring embodies the
core of the fluorenyl system. Replacement of the aromatic rings
of fluorene by alkyl groups first leads to alkylated indenes and
then to pentamethylcyclopentadiene (HCp*). All of these
compounds are characterized by enhanced CH acidity of the
central cyclopentadienyl ring, facilitating the selective formation
of the respective carbanions. In this manner efficient C-C and
C-P bond-forming reactions are possible. The respective
phosphines stand a good chance to form a class of ligands with
excellent properties in various Pd-mediated cross-coupling
reactions.
Consequently, we wish to report here on the synthesis and
characterization of various 1-indenyldialkylphosphonium and
cyclopentadienyldialkylphosphonium salts and the application
of the Pd complexes of the respective phosphines in Sonogash-
ira, Suzuki, and Buchwald-Hartwig coupling reactions.
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2760 Organometallics, Vol. 26, No. 10, 2007
Fleckenstein and Plenio
Scheme 2. Synthesis of Cyclopentadienylphosphonium
Saltsa
(entry 8) and electron-rich substrates (entry 2) require 0.1 mol
% of catalyst to reach full conversion.
Pd Complexes of 1-Indenyl- and Cyclopentadienylphos-
phines in the Buchwald-Hartwig Reaction. In the present
work we also examined the conversion of aryl chlorides as cheap
and readily available starting materials with various aromatic
and aliphatic amines. When the conditions recently reported by
Beller et al. were applied without further optimization,74 the
screening of several indenyldialkylphosphines and cyclopenta-
dienyldialkylphosphines in the reactions of 4-chlorotoluene with
3,5-dimethylaniline and 2,4-dimethylaniline revealed 1,2,3,4,7-
pentamethylindenyldicyclohexylphosphine (13) to be the most
active ligand for palladium (Table 2, entries 1 and 2). Typical
catalyst loadings of 0.5 mol % Pd were applied at 120 °C using
NaOtBu as the base in toluene to give quantitative conversion.
Some deactivated substrates required 1 mol % Pd to reach full
conversion.
a Reagents and conditions: (a) nBuLi, R2PCl, THF/Et2O, -60 °C;
(b) HBF4‚Et2O.
undesirable CS2 by dry CH2Cl2, could not completely suppress
the isomerization (26% of the undesired isomer) in our hands.
Consequently, for the synthesis of 6 we prefer CS2, since the
use of this solvent prevented the shift of methyl groups. 1H NMR
spectroscopy revealed that all indanones (3, 6, 8) were isolated
as mixtures of the two cis/trans isomers in an approximate ratio
of 3:1 for 3 and 6 and 4:1 for 8. This poses no problem, since
the cis/trans isomers react to give identical indenes. In order,
to obtain the indenes 4, 7, and 9, the respective indanones 3, 6,
and 8 were reacted with MeLi or MeMgI to give the indanols,
which were converted in situ into the desired indenes by acid-
catalyzed elimination of water. As noted by O’Hare et al.,72
the use of MeMgI as methylation agent gave better results than
MeLi.
Deprotonation of the indenes 4, 7, and 9 with nBuLi and
quenching with Cy2PCl or iPr2PCl gave the respective 1-inde-
nylphosphines in good yields, which were isolated as the
respective phosphonium salts. The Cp*-based phosphines were
prepared in good yields (Scheme 2) by reactions of LiCp* with
various chlorophosphines (iPr2PCl, Cy2PCl) and converted in
situ into the respective phosphonium salts for easier storage and
handling.21,73 The free phosphines can be liberated from the
phosphonium salts in quantitative yields by treatment with Et3N
(see the Experimental Section). The Cp* group provides steric
bulk as well as an electron-rich environment.
Pd Complexes of 1-Indenyldialkylphosphines and Cyclo-
pentadienyldialkylphosphines in the Suzuki Reaction. We
first tested Pd complexes of the 1-indenyldialkylphosphines 10-
15 and the Cp*-derived dialkylphosphines Cp*PiPr2 (17) and
Cp*PCy2 (18) for their reactivity in the Suzuki coupling (Table
1). As a reference phosphine, the recently reported highly active
EtFluPCy247 (21) was incorporated in the screening experiments.
The reaction of p-chloroacetophenone with p-tolylboronic acid
using 0.125 mol % Na2PdCl4 and 0.25 mol % phosphonium
salt with Cs2CO3 in dioxane at 80 °C was initially used to probe
the performance of the various phosphines. In general, com-
plexes formed with phosphines bearing two Cy groups showed
significantly better results than those with two iPr groups. The
top performers among the phosphines examined, Cp*PCy2 (17),
1,2,3,4,7-Me5IndPCy2 (13), and 1,2,3-Me3-4,7-(MeO)2IndPCy2
(15), showed nearly twice the high activity of EtFluPCy2 (21),
the best phosphine of the recently reported fluorenylphosphine
family. In addition, 4,7-disubstituted 1-indenylphosphines and
the cyclopentadienylphosphines show a better performance than
phosphines based on the unsubstituted indene. Because of its
high activity and its easy synthetic access, Cp*PCy2 (17) was
used as the ligand for further investigations.
Activated and deactivated aryl chlorides were reacted with
the respective amines (aniline, morpholine, R-methylbenzy-
lamine, dibutylamine) under the same conditions in quantitative
yields, whereas full conversion of deactivated aryl chlorides was
only possible with difficulties applying the previously reported
fluorenyldialkylphosphines.47
In addition to anilines, we also tested the coupling reactions
of organometallic amines such as ferrocenylamine in Pd-
catalyzed amination reactions for the first timesto the best of
our knowledge. The resulting N-arylated aminoferrocenes have
been rarely reported75-78 and were said to be elusive.79 Simple
N-arylated aminoferrocenes such as ferrocenylphenylamine have
been prepared by the reaction of ferrocenyl bromide with the
sodium salt of an amide in the presence of copper(I) bromide/
pyridine.75 A recent synthetic strategy developed by Knochel
et al.79 requires a toxic tin reagent (FcSnBu3), which is converted
to FcMgBr and reacted with an arylazotosylate to obtain the
aminated ferrocenyl derivative in 58% yield in the last reaction
step. Utilizing Pd-catalyzed C-N coupling, ferrocenylary-
lamines can be synthesized in 85% yield in a single reaction
step by employing the respective aryl chloride and ferroceny-
lamine, which is readily available using the improved synthesis
of van Leusen and Hessen.80 The amination of 3-chlorobenzyl
trifluoride or 4-chloroanisole as a deactivated aryl chloride with
ferrocenylamine using 0.5 mol % Pd and phosphine 13 gave
the respective N-arylated aminoferrocenes (Table 2, entries 11
and 12). The redox potentials of the two ferrocenes (Table 2,
entries 11 and 12) were determined by cyclic voltammetry
and found to vary significantly depending on the nature of the
para substituent (R ) OMe, E1/2 ) 0.142 V; R ) CF3, E1/2
0.268 V).
)
Pd Complexes of 1-Indenyl- and Cyclopentadienylphos-
phines in the Sonogashira Reaction. We initially tested the
complexes of Pd with the various 1-indenyl- and Cp*-dialky-
lphosphines for their activity in the Sonogashira cross-coupling
of phenylacetylene and 4-chloroanisole, applying the conditions
described previously by us47 (Table 3, entry 1). The top six of
the eight phosphines screened show similar catalytic activities;
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As found by screening a wide range of different activated
and deactivated aryl chlorides, 0.05 mol % of catalyst is
sufficient to reach full conversion over 20 h; sterically hindered
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Pd-Catalyzed Cross-Coupling Reactions
Organometallics, Vol. 26, No. 10, 2007 2761
Table 1. Suzuki Reactions with Aryl Chloridesa
a Conditions: 1 mmol of aryl chloride, 1.5 mmol of boronic acid, 2.0 mmol of Cs2CO3, 5 mL of dioxane, 100 °C. The reaction conditions and the amount
of catalyst have not been optimized. b Catalyst Na2PdCl4/ligand (1:2). c Average of two runs, determined by GC using hexadecane as internal standard.
d Reaction was performed at 80 °C.
only 12 and 13, which have methyl groups at the 4,7-positions
of the indenyl ring, are less efficient. Interestingly, the same
two phosphines did not behave conspicuously in Suzuki and
amination reactions. A similar decrease in activity was also
observed when Pd complexes of the related and recently reported
fluorenyldialkylphosphines, bearing methyl moieties at the 1,8-
positions, were used for Sonogashira reactions with aryl
bromides.47 With this in mind, it is quite surprising that
phosphine ligands 14 and 15, bearing a methoxy group instead
of a methyl group at the 4,7-positions, show the highest catalytic
activities within the range of the examined ligands. Steric effects
within the phosphine ligand play a minor role in the Sonogashira
reaction: phosphines bearing PiPr2 moieties at the phosphorus
atom show activities comparable to those with a PCy2 moiety.
Because of its high activity, (4,7-dimethoxy-1,2,3-trimethylin-
denyl)dicyclohexylphosphine (15) was studied in more detail.
Sonogashira coupling of phenylacetylene with several aryl
chlorides was tested (Table 2, entries 2-5). Excellent conver-
sions of the reactants were observed for all substrates at 100-
120 °C at 1 mol % of catalyst. More difficult acetylene substrates
such as 1-hexyne were converted with activated as well as with
deactivated aryl chlorides, giving conversions as high as 94%.
Indenylphosphine- and cyclopentadienylphosphine-based pal-
ladium catalysts compare favorably with other catalytic systems
described by us and by others for the conversion of aryl
chlorides.14,19,47,81-86
There are several ligands of comparable (high) activity not
different from those reported for other highly active phosphine
ligands such as tBu3P and Ad2PBn.14 This indicates that the
nature of the applied ligand is not limiting the catalytic activity
of a Pd phosphine complex in the Sonogashira reaction with
aryl chlorides. Further improvement of catalytic activity in
Sonogashira reactions with aryl chlorides must go along with
optimization of other factors such as reaction conditions and
additives.
Summary and Conclusions
We were able to synthesize eight new 1-indenyldialkylphos-
phonium and cyclopentadienyldialkylphosphonium salts (alkyl
) iPr, Cy). The respective Pd complexes with the liberated
phosphines are highly active for various cross-coupling reactions
with aryl chlorides. Quantitative yields in Suzuki coupling
screening for a wide range of different substrates were achieved
with 0.05-0.1 mol % of catalyst. Aryl chlorides could be
coupled in quantitative yields in the Sonogashira reaction using
1 mol % of catalyst and in the Buchwald-Hartwig reaction
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(81) Gelman, D.; Buchwald, S. L. Angew. Chem., Int. Ed. 2003, 42, 5993.
(82) Thathagar, M. B.; Rothenberg, G. Org. Biomol. Chem. 2006, 4, 111.

2762 Organometallics, Vol. 26, No. 10, 2007
Table 2. Buchwald-Hartwig Aminationa of Aryl Chlorides
Fleckenstein and Plenio
a Conditions: 5 mL of toluene, 5 mmol of aryl chloride, 6 mmol of amine, 6 mmol of NaOtBu, Pd(OAc)2-ligand (phosphonium salt) (1:2), 120 °C. The
reaction conditions have not been optimized. b Average of two runs, determined by GC using hexadecane as internal standard. c Isolated yield.
benzophenone under an argon atmosphere. Dioxane was dried over
CaH2
using 0.5 mol % of catalyst. Worthy of note is the successful
implementation of ferrocenylamine in the Buchwald-Hartwig
amination, resulting in ferrocenylarylamines in a single step in
near-quantitative yield. In Sonogashira reactions the majority
of the applied ligands showed activities comparable to reported
activities of other highly active phosphine ligands such as tBu3P
and Ad2PBn.14 Further improvement of catalytic activity in
Sonogashira reactions with aryl chlorides must go along with
optimization of other factors such as reaction conditions and
additives. Cp*PCy2 (17) and 1,2,3,4,7-Me5IndPCy2 (13) are
favorable ligands for amination reactions; Cp*PCy2 (17) is
favorable for Suzuki reactions involving aryl chlorides. Worthy
of note is the facile synthesis of Cp*PCy2 in a single step from
commercially available precursors and the remarkable catalytic
activity of the respective Pd complexes.
. Proton (1H NMR), carbon (13C NMR), and phosphorus (31P
NMR) nuclear magnetic resonance spectra were recorded on a
Bruker DRX 500 spectrometer at 500, 125.75 and 202.46 MHz,
respectively, or on a Bruker DRX 300 spectrometer at 300 and
75.07 MHz at 293 K. The chemical shifts are given in parts per
million (ppm) on the delta scale (δ) and are referenced to
tetramethylsilane (δ 0 ppm) for 1H NMR and 65% aqueous H3PO4
(δ 0 ppm) for 31P NMR. Abbreviations for NMR data: s ) singlet;
d ) doublet; t ) triplet; q ) quartet; qi ) quintet; dd ) doublet of
doublets; dt ) doublet of triplets; dq ) doublet of quartets; tt )
triplet of triplets; m ) multiplet. Mass spectra were recorded on a
Finnigan MAT 95 magnetic sector spectrometer. Thin-layer chro-
matography (TLC) was performed using Fluka silica gel 60 F 254
(0.2 mm) on aluminum plates. Silica gel columns for chromatog-
raphy were prepared with E. Merck silica gel 60 (0.063-0.20 mesh
ASTM).
Experimental Section
Cyclic voltammetry was carried out with an EG&G 263A-2
potentiostat. Cyclic voltammograms were recorded in dry CH2Cl2
under an argon atmosphere at ambient temperature. A three-
electrode configuration was employed. The working electrode was
a Pt disk (diameter 1 mm) sealed in soft glass with a Pt wire as
counter electrode. The pseudo reference electrode was an Ag wire.
Potentials were calibrated internally against the formal potential
All chemicals were purchased as reagent grade from commercial
suppliers and used without furher purification, unless otherwise
noted. Methyllithium (3.0 M in dimethoxyethane) was purchased
from Sigma-Aldrich. THF was distilled over potassium and
benzophenone under an argon atmosphere, diethyl ether was
distilled over sodium/potassium alloy and benzophenone under an
argon atmosphere, and toluene was distilled over sodium and

Pd-Catalyzed Cross-Coupling Reactions
Organometallics, Vol. 26, No. 10, 2007 2763
Table 3. Sonogashira Reactions with Aryl Chloridesa
a Conditions: 1.5 mmol of aryl chloride, 2.1 mmol of acetylene, 3 mmol of Na2CO3, 5 mL of DMSO, catalyst 1 mol % (Na2PdCl4-ligand-CuI (4:8:3)).
b Average of two runs.
of ferrocene (460 mV (CH2Cl2) vs Ag/AgCl).87 NBu4PF6 (0.1 mol/
L) was used as the supporting electrolyte.
3:1). The 1H NMR spectrum was identical with that in the
literature.71,72,90
1,2,3,4,7-Pentamethylindene (7). In a 1 L three-necked round-
bottomed flask fitted with a magnetic stirrer and a reflux condenser,
2,3,4,7-tetramethyl-1-indanone (6; 19.52 g, 0.1 mol) was dissolved
in dry diethyl ether (300 mL) under an argon atmosphere. The
mixture was cooled with an ice bath; methyllithium (45 mL, 3.0
M solution in dimethoxyethane, 0.135 mol) was added dropwise
via a syringe. The mixture was refluxed for 3 h. The yellow reaction
mixture was cooled to ambient temperature, and a mixture of
concentrated HCl (20 mL) and H2O (60 mL) was added via an
addition funnel. The resulting mixture was transferred to a
separation funnel and extracted with diethyl ether (3 × 200 mL).
The combined organic layers were stirred overnight with 15 mL
of concentrated HCl. After this time the reaction mixture was
carefully adjusted to pH 7 with a saturated aqueous solution of
Na2CO3. The reaction mixture was transferred into a separation
funnel. The organic layer was washed with H2O (3 × 100 mL),
dried over MgSO4, and filtered, and the volatiles were removed
under reduced pressure to give a yellow liquid. This residue was
purified via column chromatography (SiO2, 25 × 9 cm; eluent
cyclohexane) to afford 1,2,3,4,7-pentamethylindene (7; 8.35 g, 44%)
as a yellow liquid followed by 6 (starting material; 9.60 g, 49%)
(eluent cyclohexane-ethyl acetate (10:1)) as a yellow liquid. The
NMR spectra were identical with those reported in the literature.72
4,7-Dimethoxy-2,3-dimethyl-1-indanone (8). AlCl3 (64 g, 0.48
mol) and CH2Cl2 (250 mL) (dried over MgSO4) were placed under
an argon atmosphere in a 500 mL three-necked round-bottomed
flask fitted with a magnetic stirrer, addition funnel, inner thermom-
eter, and reflux condenser. A mixture of tigloyl chloride (2; 42 g,
0.35 mol) and 1,4-dimethoxybenzene (22; 48.4 g, 0.35 mol,
dissolved in 75 mL of CH2Cl2) was added over a period of 1 h
at -10 °C with vigorous stirring. After 2 h of stirring at -2 to
-5 °C, the mixture was warmed to ambient temperature and was
GC experiments were run on a Clarus 500 GC instrument with
autosampler and FID detector: column, Varian CP-Sil 8 CB (l )
15 m, di ) 0.25 mm, dF ) 1.0 µm); N2 flow (17 cm/s (split 1:50));
injector temperature, 270 °C; detector temperature, 350 °C;
temperature program, isotherm 150 °C for 5 min, heating to 300 °C
at a rate of 25 °C/min, isotherm for 15 min. HCp* was synthesized
according to the Kohl and Jutzi procedure.88 2,3-Dimethyl-1-
indanone (3) and 1,2,3-trimethylindene (4) were prepared according
to the method of Rausch et al.68 The 1H NMR spectra were identical
with those in the literature for 389 and for 4.68
2,3,4,7-Tetramethyl-1-indanone (6).72 Under an argon atmo-
sphere AlCl3 (64 g, 0.48 mol) and CS2 (250 mL) were placed
in a 1 L three-necked round-bottomed flask fitted with a magnetic
stirrer, addition funnel, thermometer, and reflux condenser. A
mixture of tigloyl chloride (2; 42 g, 0.35 mol) and p-xylene (5;
42.8 mL, 0.35 mol) was added over a period of 1 h at -10 °C
with vigorous stirring. The reaction mixture was stirred for 2 h at
that temperature and then warmed to ambient temperature and
stirred overnight. The brown reaction mixture was then refluxed
for 3 h, cooled to ambient temperature, and poured carefully
onto a mixture of concentrated HCl (300 mL) and ice (500 g).
The CS2 layer was separated in a separation funnel, and the
aqueous layer was extracted with diethyl ether (3 × 100 mL). The
combined organic layers were dried over magnesium sulfate
and filtered, and the volatiles were removed in a rotary evaporator
to give a red-brown liquid. This residue was rectified using a
35 cm Vigreux column to afford 2,3,4,7-tetramethyl-1-indanone
(6; 34 g, 52%, 95-100 °C, 1.5-1.2 mbar) as a pale yellow liquid.
6 was found to be a mixture of the two isomers of 2,3,4,7-
tetramethyl-1-indanone (the ratio of 6a to 6b was approximately
(87) Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877.
(88) Kohl, F. X.; Jutzi, P. Organomet. Synth. 1986, 3, 489.
(89) Sarrazin, J.; Tallec, A. Tetrahedron Lett. 1977, 18, 1579.
(90) Kaminsky, W.; Rabe, O.; Schauwienold, A.-M.; Schupfner, G. U.;
Hanss, J.; Kopf, J. J. Organomet. Chem. 1995, 497, 181.

2764 Organometallics, Vol. 26, No. 10, 2007
Fleckenstein and Plenio
stirred overnight. The dark red mixture was then refluxed for 2 h;
after it was cooled to ambient temperature, the reaction mixture
was poured carefully onto a mixture of concentrated HCl (300 mL)
and ice (500 g). Then the resulting yellow mixture was transferred
to a separation funnel, the lower (CH2Cl2) layer was isolated, and
the aqueous layer was extracted with diethyl ether (3 × 100 mL).
The combined organic layers were dried over magnesium sulfate
and filtered, and the volatiles were removed under reduced pressure
to give a dark brown liquid. This residue was distilled using a 15
cm Vigreux column to give an orange-yellow light viscous liquid
(110-115 °C, 0.8 mbar). The liquid was purified via column
chromatography (SiO2, 25 × 9 cm; eluent cyclohexane-ethyl
acetate (1:1)) to afford 2,3-dimethyl-4,7-dimethoxy-1-indanone (8;
9.53 g, 12%), Rf ) 0.35 (cyclohexane-ethyl acetate (5:1)) as a
yellow solid. 8 was found to be a mixture of the two isomers of
4,7-dimethoxy-2,3-dimethyl-1-indanone (the ratio of 8a to 8b was
Chart 2. Indenyl- and Cyclopentadienyldialkylphosphonium
Salts
1
Diagrams of the indenyl- and Cp*-dialkylphosphonium salts
are given in Chart 2.
approximately 4:1). H NMR (500 MHz, CDCl3): 8a, δ 7.01 (d,
3J ) 8.0 Hz, 1H, arom), 6.74 (d, 3J ) 8.5 Hz, 1H, arom), 3.89 (s,
3
3
(1,2,3-Tetramethylindenyl)diisopropylphosphonium Tetraflu-
oroborate (10‚HBF4). In a 250 mL Schlenk flask 1,2,3-trimeth-
ylindene (4; 5.14 g, 32.5 mmol) was dissolved in Et2O (100 mL)
under an argon atmosphere. The mixture was cooled to -60 °C
(N2/isopropyl alcohol), and nBuLi (12.38 mL, 2.5 M solution in
hexane, 31 mmol) was added. The solution was stirred for 10 min
at -60 °C and then for 3 h at ambient temperature. A white
precipitate was formed. Then the mixture was cooled to -60 °C
and iPr2PCl (4.1 mL, 25.8 mmol) was added. The mixture was
warmed to room temperature and stirred for an additional 2 h, and
the LiCl that formed was removed by filtration over a pad of
Celite under Schlenk conditions. The resulting slightly yellowish
filtrate was treated dropwise with HBF4‚Et2O (4.42 mL, 32 mmol)
to give a white precipitate, which was separated via filtration
and dissolved in 10 mL of acetonitrile. After filtration the clear
filtrate was dropped into Et2O (900 mL, vigorously stirred). The
white precipitate that formed was separated via suction filtration.
Removal of the volatiles in vacuo afforded 10‚HBF4 as a white
solid (8.53 g, 91%). 1H NMR (500 MHz, CDCl3): δ 7.68 (d, 3J )
8.0 Hz, 1H, arom), 7.49-7.46 (m, 1H, arom), 7.39-7.35 (m, 2H,
3H, O-CH3), 3.84 (s, 3H, O-CH3), 2.97 (qd, J ) 7.0 Hz, J )
3
3
3.0 Hz, 1H, CH position 2), 2.22 (qd, J ) 7.5 Hz, J ) 3.0 Hz,
1H, CH position 3), 1.40 (d, 3J ) 7.0 Hz, 3H, CHCH3), 1.26 (d, 3J
3
) 7.5 Hz, 3H, CHCH3); 8b, δ 6.99 (d, J ) 9.0 Hz, 1H, arom),
6.72 (d, J ) 7.5 Hz, 1H, arom), 3.89 (s, 3H, O-CH3), 3.86 (s,
3
3H, O-CH3), 3.53 (qi, 3J ) 7.5 Hz, 1H, CH position 2), 2.74 (qi,
3J ) 7.5 Hz, 1H, CH position 3), 1.20 (d, 3J ) 7.0 Hz, 3H, CHCH3
position 2) 1.16 (d, 3J ) 7.0 Hz, 3H, CHCH3 position 3). 13C{1H}
NMR (125.77 MHz, CDCl3): 8a, δ 207.2, 151.8, 150.9, 148.2,
124.8, 117.5, 109.8, 56.0, 55.8, 51.6, 39.8, 19.5, 16.2; 8b, δ 206.5,
151.5, 150.3, 149.3, 124.8, 116.9, 109.7, 56.0, 55.8, 47.1, 34.5,
16.1, 14.2. HRMS (m/z): calcd for C13H16O3, 220.1099; found,
220.10909.
4,7-Dimethoxy-1,2,3-trimethylindene (9). Diethyl ether (100
mL) and Mg turnings (0.96 g, 39 mmol) were placed in a 250 mL
three-necked round-bottomed flask fitted with a magnetic stirrer
and reflux condenser. Under an argon atmosphere a solution of
CH3I (2.66 mL, 43 mmol) in degassed and dried diethyl ether (50
mL) was added via an addition funnel. The resulting gray solution
was stirred for 45 min before addition of dry light petroleum (bp
80-110 °C; 20 mL). The ether was then removed under reduced
pressure to yield a gray suspension which was cooled with ice. A
solution of 2,3-dimethyl-4,7-dimethoxy-1-indanone (8; 7 g, 32
mmol) in pentane (50 mL) was added dropwise over a period of
40 min; then the mixture was refluxed for 3 h. At this point the
yellow reaction mixture was cooled to 0 °C and a mixture of HCl
(10 mL) and H2O (40 mL) was added via an addition funnel. The
resulting solution was transferred into a separation funnel and
extracted with diethyl ether (3 × 50 mL). The combined organic
layers were washed with 0.25 M aqueous sodium thiosulfate (3 ×
30 mL) and filtered into a round-bottomed flask. Concentrated HCl
(15 mL) was added, and the mixture was stirred at ambient
temperature overnight. Then pH 7 was adjusted by addition of a
saturated aqueous solution of Na2CO3. The organic layer was
washed with water (3 × 100 mL), dried over MgSO4, and filtered,
and the volatiles were removed in vacuo. The residual liquid was
purified via column chromatography (SiO2, 35 × 9 cm; initial eluent
cyclohexane-ethyl acetate (50:1)) to afford two fractions: 1,2,3-
trimethyl-4,7-dimethoxyindene (9; 4.63 g, 66%) as a yellow liquid
with Rf ) 0.42 (eluent cyclohexane-ethyl acetate (2:1)) and 4,7-
dimethoxy-2,3-dimethyl-1-indanone (8; starting material) with Rf
) 0.35 (cyclohexane-ethyl acetate (5:1)) as a pale yellow liquid.
1
3
arom), 6.44 (dt, J(P) ) 473 Hz, J ) 4.0 Hz, 1H, P-H), 2.74-
2.65 (m, 1H, CH), 2.45-2.36 (m, 1H, CH), 2.16 (s, 3H, CH3
3
position 3), 2.15 (d, J ) 3.5 Hz, 3H, CH3 position 2), 1.81 (d,
3
3J(P) ) 17 Hz, 3H, CH3 position 1), 1.44 (ddd, J(P) ) 96.0 Hz,
3J ) 18.5 Hz, 3J ) 7.5 Hz, 6H, CH3), 1.13 (ddd, 3J(P) ) 91.0 Hz,
3J ) 18.0 Hz, J ) 7.0 Hz, 6H, CH3). 13C{1H} NMR (125.77 MHz,
CDCl3): δ 145.1 (d, J ) 3.8 Hz), 141.6, 138.9 (d, J ) 8.0 Hz),
137.7 (d, J ) 3.8 Hz), 129.8, 126.7, 123.5 (d, J ) 3.5 Hz), 120.2,
51.5 (d, J ) 32.6 Hz), 21.1 (d, J ) 6.7 Hz), 20.8 (d, J ) 5.6 Hz),
20.0 (d, J ) 2.6 Hz), 19.9, 19.1 (d, J ) 2.1 Hz), 18.2 (d, J ) 2.3
Hz), 17.7 (d, J ) 2.3 Hz), 11.1, 10.8. 31P{1H} NMR (202.46 MHz,
CDCl3): δ 36.6. 31P NMR (202.46 MHz, CDCl3): δ 36.6 (d, J )
472.9 Hz).
(1,2,3-Trimethylindenyl)dicyclohexylphosphonium Tetrafluo-
roborate (11‚HBF4). In a 100 mL Schlenk 1,2,3-trimethylindene
(4; 2.44 g, 15.4 mmol) was dissolved in Et2O (50 mL) under an
argon atmosphere. The mixture was cooled to -60 °C (N2/isopropyl
alcohol), and nBuLi (5.9 mL, 2.5 M solution in hexane, 14.7 mmol)
was added. The solution was stirred for 10 min at -60 °C and
then for 3 h at ambient temperature. A white precipitate was formed.
Then the mixture was cooled to -60 °C and Cy2PCl (2.7 mL, 12
mmol) was added. The mixture was warmed to room temperature
and stirred for additional 2 h, and the LiCl that formed was removed
by filtration over a pad of Celite under Schlenk conditions. The
resulting slightly yellowish filtrate was treated dropwise with HBF4‚
Et2O (2 mL, 14.9 mmol) to give a white precipitate, which was
separated via filtration and dissolved in 10 mL of acetonitrile. After
filtration the clear filtrate was dropped into Et2O (900 mL,
vigorously stirred). The white precipitate that formed was separated
via suction filtration. Removal of the volatiles in vacuo afforded
3
1H NMR (500 MHz, CDCl3): δ 6.70 (d, J ) 8.5 Hz, 1H, arom),
6.56 (d, 3J ) 9 Hz, 1H, arom), 3.81 (s, 3H, O-CH3), 3.78 (s, 3H,
O-CH3), 3.23 (q, 3J ) 7.5 Hz, 1H, CH), 2.17 (m, 3H, CH3), 1.90
3
(m, 3H, CH3), 1.28 (d, J ) 7.0 Hz, 3H, CHCH3). 13C{1H} NMR
(125.77 MHz, CDCl3): δ 150.6, 149.1, 142.9, 137.2, 135.7, 131.1,
111.1, 107.5, 56.7, 56.0, 46.4, 14.7, 13.4, 12.0. HRMS (m/z): calcd
for C14H18O2, 218.1306; found, 218.13110.

Pd-Catalyzed Cross-Coupling Reactions
Organometallics, Vol. 26, No. 10, 2007 2765
1
11‚HBF4 as a white solid (2.82 g, 53%). H NMR (500 MHz,
1H, arom), 6.30 (dq, 1J(P) ) 470 Hz, J ) 3.5 Hz, 1H, P-H), 2.58
(s, 3H, CH3 benzylic), 2.58 (s, 3H, CH3 benzylic), 2.46-2.39 (m,
3
3
CDCl3): δ 7.64 (d, J ) 7.5 Hz, 1H, arom), 7.48 (t, J ) 7.5 Hz,
1
4
1H, arom), 7.40-7.35 (m, 2H, arom), 6.36 (dt, J(P) ) 475 Hz,
1H, CH), 2.31 (d, J(P) ) 4.5 Hz, 3H, CH3 position 2), 2.11 (s,
4J ) 3.5 Hz, 1H, P-H), 2.34-2.26 (m, 1H, CH), 2.16 (d, 4J(P) )
4.0 Hz, 3H, CH3 position 2), 2.14 (s, 3H, CH3 position 3), 2.09-
3H, CH3 position 3), 1.89 (d, J(P) ) 16.5 Hz, 3H, CH3 position
3
1), 1.86-0.93 (m, 21H, CH2 and CH). 13C{1H} NMR (125.77 MHz,
CDCl3): δ 143.0, 140.9 (d, J ) 9.3), 140.3, 136.0 (d, J ) 4.9 Hz),
133.1, 131.9 (d, J ) 4.0), 129.7, 129.6, 52.8 (d, J ) 29.2 Hz),
31.5 (d, J ) 7.2 Hz), 31.2, 29.6 (d, J ) 3.5 Hz), 29.1 (d, J ) 3.3
Hz), 28.2 (d, J ) 3.5 Hz), 27.9 (d, J ) 3.8 Hz), 27.0 (d, J ) 11.9
Hz), 26.8, 26.7, 26.6 (d, J ) 13.1), 25.0, 24.8, 20.2, 19.8, 18.1,
14.8, 11.9. 31P NMR (202.46 MHz, CDCl3): δ 25.5 (d, J ) 472.3
Hz).
3
1.14 (m, 21H, CH2 and CH), 1.81 (d, J(P) ) 17.5 Hz, 3H, CH3
position 1). 13C{1H} NMR (125.77 MHz, CDCl3): δ 145.2 (d,
J ) 3.1 Hz), 141.8, 138.8 (d, J ) 7.8 Hz), 137.8 (d, J ) 2.9 Hz),
129.8, 126.7, 123.4, 120.0, 51.6 (d, J ) 32.2 Hz), 31.0, 30.7 (d,
J ) 10.8 Hz), 30.5, 29.8 (d, J ) 3.0 Hz), 29.0 (d, J ) 3.5 Hz),
28.2 (d, J ) 3.3 Hz), 28.1 (d, J ) 3.1 Hz), 26.9 (d, J ) 6.0 Hz),
26.8 (d, J ) 5.8 Hz), 26.6, 26.5, 24.9 (d, J ) 3.8 Hz), 19.6, 11.2,
10.7. 31P{1H} NMR (202.46 MHz, CDCl3): δ 29.2. 31P NMR
(202.46 MHz, CDCl3): δ 29.2 (d, J ) 473.7 Hz).
(4,7-Dimethoxy-1,2,3-trimethylindenyl)diisopropylphos-
phonium Tetrafluoroborate (14‚HBF4). In a 100 mL Schlenk
flask 4,7-dimethoxy-1,2,3-trimethylindene (9; 1.7 g, 7.79 mmol)
was dissolved in Et2O (50 mL) under an argon atmosphere. The
mixture was cooled to -60 °C (N2/isopropyl alcohol), and nBuLi
(3.0 mL, 2.5 M solution in hexane, 7.43 mmol) was added. The
solution was stirred for 10 min at -60 °C and then for 3 h at
ambient temperature. A white precipitate was formed. Then the
mixture was cooled to -60 °C and iPr2PCl (1.0 mL, 6.24 mmol)
was added. The mixture was warmed to room temperature and
stirred for an additional 2 h at ambient temperature, and the LiCl
that formed was removed by filtration over a pad of Celite under
Schlenk conditions. The resulting slightly yellowish filtrate was
treated dropwise with HBF4‚Et2O (1 mL, 7.72 mmol) to give a
white precipitate, which was separated via filtration and dissolved
in 10 mL of chloroform. After filtration the clear filtrate was
dropped into Et2O (700 mL, vigorously stirred). The white
precipitate that formed was separated via suction filtration. Removal
of the volatiles in vacuo afforded 14‚HBF4 as a white solid (1.73
(1,2,3,4,7-Pentamethylindenyl)diisopropylphosphonium Tet-
rafluoroborate (12‚HBF4). In a 100 mL Schlenk flask 1,2,3,4,7
pentamethylindene (7; 3.0 g, 16 mmol) was dissolved in Et2O
(50 mL) under an argon atmosphere. The mixture was cooled to
-60 °C (N2/isopropyl alcohol), and nBuLi (16.1 mL, 2.5 M solution
in hexane, 15 mmol) was added. The solution was stirred for 10
min at -60 °C and then for 3 h at ambient temperature. A white
precipitate was formed. The mixture was cooled to -60 °C, and
iPr2PCl (2.0 mL, 12.8 mmol) was added. The mixture was warmed
to room temperature and stirred for additional 2 h, and the LiCl
that formed was removed by filtration over a pad of Celite under
Schlenk conditions. The resulting slightly yellowish filtrate was
treated dropwise with HBF4‚Et2O (2.2 mL, 16 mmol) to give a
white precipitate that was separated via filtration and dissolved in
10 mL of chloroform. After filtration the clear filtrate was dropped
into Et2O (900 mL, vigorously stirred). The white precipitate that
formed was separated via suction filtration. Removal of the volatiles
in vacuo afforded 12‚HBF4 as a white solid (4.23 g, 84%). 1H NMR
(500 MHz, CDCl3): δ 7.09 (d, 3J ) 8.0 Hz, 1H, arom), 6.97 (d, 3J
) 8.0 Hz, 1H, arom), 6.41 (dq, 1J(P) ) 468 Hz, 3J ) 5.3 Hz, 1H,
P-H), 2.84-2.75 (m, 1H, CH), 2.59 (s, 3H, CH3 benzylic), 2.58
1
3
g, 66%). H NMR (500 MHz, CD3CN): δ 7.13 (dd, J ) 9.0 Hz,
J ) 1.5 Hz, 1H, arom), 6.99 (d, 3J ) 9.0 Hz, 1H, arom), 6.39 (dq,
1J(P) ) 465.5 Hz, 3J ) 3.0 Hz, 1H, P-H), 3.99 (s, 3H, O-CH3),
3.87 (s, 3H, O-CH3), 3.10-3.00 (m, 1H, CH), 2.62-2.51 (m, 1H,
4
4
(s, 3H, CH3 benzylic), 2.31 (d, J ) 4.5 Hz, 3H, CH3 position 2),
CH), 2.30 (dd, J(P) ) 5.0 Hz, J ) 1.0 Hz, 3H, CH3 position 2),
3
2.23-2.14 (m, 1H, CH), 2.13 (s, 3H, CH3 position 3), 1.89 (d,
3J(P) ) 17 Hz, 3H, CH3 position 1), 1.50 (ddd, 3J(P) ) 107 Hz, 3J
) 18.5 Hz, J ) 7.0 Hz, 6H, CH3), 1.12 (ddd, 3J(P) ) 96.5 Hz, 3J
) 18.5 Hz, J ) 7.0 Hz, 6H, CH3). 13C{1H} NMR (125.77 MHz,
CDCl3): δ 143.3, 141.4 (d, J ) 9.2 Hz), 140.6, 136.2 (d, J ) 6.3
Hz), 133.6, 132.2 (d, J ) 2.1 Hz), 130.2, 130.0, 52.9 (d, J ) 29.2
Hz), 22.1 (d, J ) 3.6 Hz), 21.8, 20.7, 20.4 (d, J ) 2.3 Hz), 20.2,
19.1 (d, J ) 1.8 Hz), 18.9 (d, J ) 1.9 Hz), 18.7 (d, J ) 1.8 Hz),
18.1 (d, J ) 3.1 Hz), 15.2, 12.3. 31P{1H} NMR (202.46 MHz,
CDCl3): δ 34.0. 31P NMR (202.46 MHz, CDCl3): δ 34.0 (d, J )
463 Hz).
2.13 (s, 3H, CH3 position 3), 1.86 (d, J(P) )16.5 Hz, 3H, CH3
3
3
3
position 1), 1.45 (ddd, J(P) ) 100 Hz, J ) 19 Hz, J ) 7.0 Hz,
3
3
3
6H, CH3), 1.18 (ddd, J(P) ) 72.5 Hz, J ) 17.5 Hz, J ) 7 Hz,
6H, CH3). 13C{1H} NMR (125.77 MHz, CD3CN): δ 150.8 (d, J )
2.1 Hz), 150.4, 139.7 (d, J ) 9.0 Hz), 137.6 (d, J ) 3.4 Hz), 134.7
(d, J ) 3.5 Hz), 130.5, 115.0, 110.5, 56.6, 56.1, 52.4 (d, J ) 31.8
Hz), 23.4 (d, J ) 35.8 Hz), 21.3 (d, J ) 39.5 Hz), 19.9 (d, J )
2.64 Hz), 19.5 (d, J ) 1.9 Hz), 19.0 (d, J ) 2.9 Hz), 18.3 (d, J )
2.0 Hz), 17.7 (d, J ) 2.3 Hz), 13.8, 10.8. 31P NMR (202.46 MHz,
CD3CN): δ 33.1 (d, J ) 464.8).
(4,7-Dimethoxy-1,2,3-trimethylindenyl)dicyclohexylphospho-
nium Tetrafluoroborate (15‚HBF4). In a 100 mL Schlenk flask
4,7-dimethoxy-1,2,3-trimethylindene (9; 1.7 g, 7.79 mmol) was
dissolved in Et2O (50 mL) under an argon atmosphere. The mixture
was cooled to -60 °C (N2/isopropyl alcohol), and nBuLi (3.0 mL,
2.5 M solution in hexane, 7.43 mmol) was added. A white
precipitate was formed. The solution was stirred for 10 min at -60
°C and for 3 h at ambient temperature. Then the mixture was cooled
to -60 °C and Cy2PCl (1.3 mL, 6.19 mmol) was added. The
mixture was warmed to room temperature and then for an additional
2 h at ambient temperature and the LiCl that formed was removed
by filtration over a pad of Celite under Schlenk conditions. The
resulting slightly yellowish filtrate was treated dropwise with HBF4‚
Et2O (1 mL, 7.79 mmol) to give a white precipitate, which was
separated via filtration and dissolved in 10 mL of chloroform. After
filtration the clear filtrate was dropped into Et2O (700 mL,
vigorously stirred). The white precipitate that formed was separated
via suction filtration. Removal of the volatiles in vacuo afforded
(1,2,3,4,7-Pentamethylindenyl)dicyclohexylphosphonium Tet-
rafluoroborate (13‚HBF4). In a 100 mL Schlenk flask 1,2,3,4,7-
pentamethylindene (7; 3.0 g, 16 mmol) was dissolved in Et2O
(50 mL) under an argon atmosphere. The mixture was cooled to
-60 °C (N2/isopropyl alcohol), and nBuLi (6.1 mL, 2.5 M solution
in hexane, 15 mmol) was added. The solution was stirred for 10
min at -60 °C and then for 3 h at ambient temperature. A white
precipitate was formed. Then the mixture was cooled to -60 °C
and Cy2PCl (2.8 mL, 12.7 mmol) was added. The mixture was
warmed to room temperature and stirred for an additional 2 h at
ambient temperature, and the LiCl that formed was removed by
filtration over a pad of Celite under Schlenk conditions. The
resulting slightly yellowish filtrate was treated dropwise with HBF4‚
Et2O (2.2 mL, 16 mmol) to give a white precipitate which was
separated via filtration and dissolved in 10 mL of chloroform. After
filtration the clear filtrate was dropped into Et2O (700 mL,
vigorously stirred). The white precipitate that formed was separated
via suction filtration. Removal of the volatiles in vacuo afforded
1
15‚HBF4 as a white solid (1.72 g, 55%). H NMR (500 MHz,
1
13‚HBF4 as a white solid (4.12 g, 69%). H NMR (500 MHz,
CDCl3): δ 6.93 (dd, 3J ) 9.0 Hz, J ) 1.5 Hz, 1H, arom), 6.77 (d,
1
3
CDCl3): δ 7.10 (d, 3J ) 8.0 Hz, 1H, arom), 6.97 (d, 3J ) 8.0 Hz,
3J ) 9.0 Hz, 1H, arom), 6.24 (ddd, J(P) ) 472.5, J ) 5.5 Hz, J

2766 Organometallics, Vol. 26, No. 10, 2007
Fleckenstein and Plenio
) 2.5 Hz, 1H, P-H), 3.92 (s, 3H, O-CH3), 3.84 (s, 3H, O-CH3),
quantitatively precipitate the Et3NH+ salt. Following the filtration
of the precipitates, the volatiles were evaporated from the filtrate.
The remaining material is pure phosphine, typically formed in
quantitative yields.
4
2.60-2.49 (m, 1H, CH), 2.28 (dd, J(P) ) 4.0 Hz, J ) 1.0 Hz,
3H, CH3 position 2), 2.18-2.11 (m, 1H, CH), 2.06 (s, 3H, CH3
3
position 3), 1.76 (d, J(P) )16.5 Hz, 3H, CH3 position 1), 2.04-
1.01 (m, 20H, CH2). 13C{1H} NMR (125.77 MHz, CDCl3): δ 149.7
(d, J ) 1.9 Hz), 149.5, 138.9 (d, J ) 7.0), 136.9 (d, J ) 3.0 Hz),
134.2 (d, J ) 2.8), 129.7, 113.8, 109.1, 56.3, 55.7, 51.6 (d, J )
32.2 Hz), 32.3, 32.0, 30.6, 30.3, 29.3(d, J ) 3.3 Hz), 29.2 (d, J )
5.3 Hz), 28.2 (d, J ) 3.3 Hz), 27.7 (d, J ) 3.1 Hz), 27.0 (d, J )
13.1 Hz), 26.9 (d, J ) 14.2 Hz), 25.1, 24.9, 17.8, 13.6, 10.7. 31P-
{1H} NMR (202.46 MHz, CDCl3): δ 25.4. 31P NMR (202.46 MHz,
CDCl3): δ 25.4 (d, J ) 471.1 Hz).
General Procedures for the Cross-Coupling Reactions. All
cross-coupling reactions are carried out under an argon atmosphere
in deaerated solvents (freeze and thaw).
Suzuki Reaction of Aryl Chlorides (in Dioxane). (a) Prepara-
tion of the Catalyst Stock Solution. Na2PdCl4 (0.05 mmol),
phosphonium salt (0.1 mmol), and Cs2CO3 (0.2 mmol) were placed
in a Schlenk tube. Dioxane (5.0 mL) was added, and the mixture
was stirred at 45 °C for 2 h until the solution turned off-white.
This stock solution had a concentration of 0.01 M in [Pd].
Cp*PCy2‚HBF4 (17‚HBF4). In a 250 mL Schlenk flask pen-
tamethylcyclopentadiene (HCp* (16);88 2.9 g, 21.3 mmol) was
dissolved in diethyl ether (100 mL) and treated with nBuLi (8.1
mL, 2.5 M in hexane, 20.3 mmol) at -60 °C. The mixture was
stirred for 4 h at ambient temperature, to give a thick white
suspension. THF (absolute, 100 mL) was added, and the suspension
was quenched with Cy2PCl (3.93 g, 16.9 mmol) at -60 °C. The
reaction mixture was stirred at ambient temperature overnight and
filtered over a small pad of Celite. The clear, colorless filtrate was
then quenched with HBF4‚Et2O (2.7 mL, 19.9 mmol), which led
to precipitation of the phosphonium salt as a white solid about 3
min after the addition of the acid. The solid was separated via
suction filtration and washed with Et2O, and the volatiles were
removed in vacuo to afford 17‚HBF4 as a white solid (3.7 g, 52%).
(b) Cross-Coupling Reaction. To the aryl chloride (1 mmol)
were added boronic acid (1.5 mmol), Cs2CO3 (2 mmol), dioxane
(5 mL), and the catalyst stock solution. The reaction mixture was
stirred at 100 °C in an aluminum block. After it was cooled to
room temperature, the reaction mixture was diluted with ether (15
mL) and washed with water (10 mL) and the organic phase was
dried over MgSO4, filtered, and concentrated in vacuo. The product
was isolated by column chromatography (silica, cyclohexane-ethyl
acetate (100:2)). Alternatively, the yield was determined via gas
chromatography with hexadecane or diethylene glycol di-n-butyl
ether as an internal standard.
Sonogashira Reaction of Aryl Chlorides (in dmso). Dry dmso
(5 mL, crown cap), aryl chloride (1.5 mmol), acetylene (2.1 mmol),
and Na2CO3 (3 mmol) were placed in a Schlenk tube. Then the
catalyst was added in the given concentration, Na2PdCl4-ligand
(phosphonium salt)-CuI (4:8:3), under argon. The reaction mixture
was stirred at 100-120 °C in an aluminum block for 12-20 h.
After it was cooled to room temperature, the reaction mixture was
diluted with ether (15 mL) and washed with water (10 mL) and
the organic phase was dried over MgSO4, filtered, and concentrated
in vacuo. The product was isolated by column chromatography
(silica, cyclohexane-ethyl acetate (100:2)). Alternatively, the yield
was determined via gas chromatography with hexadecane or
diethylene glycol di-n-butyl ether as an internal standard.
1
3
1H NMR (500 MHz, CDCl3): δ 6.06 (dt, J(PH) ) 470 Hz, J )
4 Hz, 1 H, PH), 2.15-2.07 (m, 2 H, CH), 2.03-1.99 (m, 2 H,
CH2), 1.98 (s, 6 H, CH3), 1.89 (d, J(PH) ) 3.5 Hz, 6 H, CH3),
4
1.89-1.85 (m, 6 H, CH2), 1.73-1.56 (m, 6 H, CH2), 1.51 (d, 3J(PH)
) 17.5 Hz, 3 H, CH3), 1.32-1.25 (m, 6 H, CH2). 13C{1H} NMR
(125.75 MHz, CDCl3): δ 142.7 (d, J(P-C) ) 6.8 Hz), 134.8, 55.1
(d, J(P-C) ) 28.3 Hz), 30.3, 30.0, 29.6 (d, J(P-C) ) 3.5 Hz),
28.5 (d, J(P-C) ) 3.4 Hz), 26.9 (d, J(P-C) ) 11.9 Hz), 26.7 (d,
J(P-C) ) 13.6 Hz), 25.0, 17.3 (d, J(P-C) ) 3.3 Hz), 11.4 (d,
J(P-C) ) 22.1 Hz). 31P NMR (202.45 MHz, CDCl3): δ 26.7 (d,
J(P-H) ) 471.5 Hz).
Cp*PiPr2‚HBF4 (18‚HBF4). In a 250 mL Schlenk flask pen-
tamethylcyclopentadiene (HCp* (16); 2.79 g, 20.5 mmol) was
dissolved in diethyl ether (absolutely, 175 mL) and treated with
nBuLi (7.8 mL of a 2.5 M solution in hexane, 19.5 mmol) at
-60 °C. The mixture was stirred for 4 h at ambient temperature
(magnetic stirrer), resulting in a thick white suspension. THF
(absolute, 50 mL) was added, followed by iPr2PCl (2.48 g, 16.25
mmol) at -60 °C. The reaction mixture was stirred at ambient
temperature overnight and filtered over a small pad of Celite. The
clear, colorless filtrate was quenched with HBF4‚Et2O (2.76 mL,
20.3 mmol), which led to precipitation of the phosphonium salt as
a white solid. The solid was separated via suction filtration and
washed with Et2O, and the volatiles were removed in vacuo to
afford 18‚HBF4 as a white solid (5.2 g, 94%). 1H NMR (500 MHz,
Buchwald-Hartwig Amination of Aryl Chlorides (in Tolu-
ene). Dry toluene (5 mL), aryl chloride (5 mmol), amine (6 mmol)
and NaOtBu (6 mmol) were placed in a Schlenk tube. Next the
catalyst was added in the given concentration, followed by Na2-
PdCl4/ligand (phosphonium salt) (1:2). The reaction mixture was
stirred at 120 °C in an aluminum block. After it was cooled to
room temperature, the reaction mixture was diluted with ether (15
mL) and washed with water (10 mL) and the organic phase was
dried over MgSO4, filtered, and concentrated in vacuo. The product
was isolated by column chromatography (silica, cyclohexane-ethyl
acetate (90:10)). Alternatively, the yield was determined via GC
with hexadecane or diethylene glycol di-n-butyl ether as an internal
standard.
N-Ferrocenyl-4-methoxyaniline (19). 1H NMR (500 MHz,
1
3
3
3
CDCl3): δ 6.21 (dt, J(PH) ) 468.5 Hz, J ) 4.5 Hz, 1 H, PH),
CDCl3): δ 6.89 (d, J ) 9.0 Hz, 2 H, CH, ar), 6.81 (d, J ) 9.0
Hz, 2 H, CH, ar), 4.61 (s (br), 1 H, NH), 4.16 (s, 7 H, Fc), 3.99 (s,
2 H, Fc), 3.77 (s, 3 H, CH3). 13C{1H} NMR (125.77 MHz,
CDCl3): δ 153.3, 139.5, 117.2, 114.6, 102.8, 68.7, 64.1, 60.4, 55.7.
CV: E1/2 ) 0.142 V; ∆E ) 76 mV. HRMS (m/z): calcd for C17H17-
NOFe, 307.0659, found, 307.06654.
2.52-2.43 (m, 2 H, CH), 2.00 (s, 6 H, CH3), 1.89 (d, 4J(PH) ) 3.0
3
Hz, 6 H, CH3), 1.51 (d, J(PH) ) 17.5 Hz, 3 H, CH3), 1.47 (dd,
3J(PH) ) 18.5 Hz, 3J ) 7.0 Hz, 6 H, CH3), 1.38 (dd, 3J(PH) ) 18
Hz, 3J ) 7.5 Hz, 6 H, CH3). 13C{1H} NMR (125.75 MHz,
CDCl3): δ 143.2 (d, J(P-C) ) 6.7 Hz), 135.0, 55.2 (d, J(P-C) )
29.2 Hz), 20.8 (d, J(P-C) ) 38.4 Hz), 20.1 (d, J(P-C) ) 2.5
Hz), 18.8 (d, J(P-C) ) 3.3 Hz), 18.1 (d, J(P-C) ) 3.4 Hz), 11.8
(d, J(P-C) ) 39.4 Hz). 31P{1H} NMR (202.45 MHz, CDCl3): δ
34.9. 31P NMR (202.45 MHz, CDCl3): δ 34.9 (d, J(P-H) ) 469.3
Hz).
1
N-Ferrocenyl-3-(trifluoromethyl)aniline (20). H NMR (500
3
MHz, CDCl3): δ 7.27-7.24 (m, 2 H, ar), 7.01 (d, J ) 7.5 Hz, 1
H, CH, ar), 6.95 (dd, 3J ) 8.0 Hz, J ) 2.0 Hz, 1 H, CH, ar), 5.10
(s (br), 1 H, NH), 4.23 (t, 3J ) 2.0 Hz, 2 H, Fc), 4.20 (s, 5 H, Fc),
4.07 (t, 3J ) 1.5 Hz, 2 H, Fc). 13C{1H} NMR (125.77 MHz,
CDCl3): δ 146.5, 131.4 (q, 2J ) 31.2 Hz, C-CF3, ar), 129.5, 125.8
General Procedure for the Synthesis of Phosphines from the
Respective Phosphonium Salts. The phosphonium salt was first
dissolved in the minimum amount of CH2Cl2, and then Et3N (10
equiv per phosphonium group) was added. After the mixture was
stirred for 30 min, twice the volume of Et2O was added to
1
3
(q, J ) 273.3 Hz, CF3), 117.4, 114.8 (q, J ) 4.8 Hz), 110.6 (q,
3J ) 4.1 Hz), 98.7, 69.0, 64.9, 62.4. CV: E1/2 ) 0.268 V; ∆E )
72 mV). HRMS (m/z): calcd for C17H14NF3Fe, 345.0427; found,
345.04401.

Pd-Catalyzed Cross-Coupling Reactions
Organometallics, Vol. 26, No. 10, 2007 2767
Acknowledgment. We wish to thank the “Fonds der
Chemischen Industrie” and the “Studienstiftung des Deutschen
Volkes” for a fellowship to C.A.F., Degussa AG and Provadis,
Partner fu¨r Bildung und Beratung GmbH for financial
support, and cand.-chem. Julio Lado-Garrido for experimental
assistance.
Note Added in Proof. After submission of the manuscript a
copper catalyzed amination of ferrocenyl iodide was reported:
O¨ zc¸ubukc¸u, S.; Schmitt, E.; Leifert, A.; Bolm, C. Synth. 2007,
389.
Supporting Information Available: Figures giving NMR
spectra of the new products and cyclic voltammograms of the
ferrocenes. This material is available free of charge via the Internet
at http://pubs.acs.org.
Note Added after ASAP Publication. In the version of this
paper published on the Web on April 11, 2007, the two boldface
paragraph heads in the right-hand column of the third page were
incorrect. The version that now appears is correct.
OM070094M