Ethylene carbonylation in methanol and in aqueous media by palladium(II) catalysts modified with 1,1′-bis(dialkylphosphino)ferrocenes

Article abstract of DOI:10.1021/om049109w

Palladium(II) complexes with the formula [Pd(H₂O)(OTs)(P-P)]OTs, where P-P is 1,1′-bis-(dimethylphosphino)ferrocene (dmpf), 1,1′-bis(diethylphosphino)ferrocene (depf), or 1.1′-bis- (diisopropylphosphino)ferrocene (dippf), have been synthesized

Full text of DOI:10.1021/om049109w

1018
Organometallics 2005, 24, 1018-1030
Ethylene Carbonylation in Methanol and in Aqueous
Media by Palladium(II) Catalysts Modified with
1,1′-Bis(dialkylphosphino)ferrocenes
Claudio Bianchini,* Andrea Meli, Werner Oberhauser, and Sebastien Parisel
Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area di Ricerca CNR di
Firenze, via Madonna del Piano snc, 50019 Sesto Fiorentino, Italy
Elisa Passaglia and Francesco Ciardelli
ICCOM-CNR, Sezione di Pisa, Dipartimento di Chimica e Chimica Industriale,
via Risorgimento 35, 56126 Pisa, Italy
Oleg V. Gusev, Alexander M. Kal’sin, and Nikolai V. Vologdin
N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences,
Vavilov St. 28, 119991 Moscow, Russian Federation
Received November 18, 2004
Palladium(II) complexes with the formula [Pd(H2O)(OTs)(P-P)]OTs, where P-P is 1,1′-bis-
(dimethylphosphino)ferrocene (dmpf), 1,1′-bis(diethylphosphino)ferrocene (depf), or 1,1′-bis-
(diisopropylphosphino)ferrocene (dippf), have been synthesized and used to catalyze the
carbonylation of ethylene in MeOH, water, or a 1/1 water/1,4-dioxane mixture. In MeOH,
the reactions catalyzed by the dmpf and depf complexes gave alternating polyketone (alt-
E-CO), while methyl propanoate and 3-pentanone were selectively produced with the dippf
catalyst. The last catalyst was inactive in aqueous solvent. In contrast, the dmpf and depf
catalysts were active in either water or water/1,4-dioxane for the copolymerization of CO
with ethylene. These two catalysts were efficient also for the terpolymerization of CO with
ethylene and propene in MeOH or water/1,4-dioxane. Operando high-pressure NMR
experiments and in situ reactions with model compounds have provided useful information
to rationalize the activity and selectivity of the catalytic systems investigated.
Introduction
amination,7 hydroamination of alkenes,8 glioxylate-ene
reaction with chiral controllers,9 cooligomerization of
1,3-butadiene with CO2,10 alternating copolymerization
of CO and ethylene,11,12 and methoxycarbonylation of
styrene or ethylene.3,11,13
The success of 1,1′-bis(diorganylphosphino)metallo-
cene ligands in homogeneous catalysis is largely ascrib-
able to their excellent structural and electronic flexibil-
ity. Indeed, the coordination behavior of these ligands
can be effectively tuned by an appropriate choice of the
central metal (Fe, Ru, or Os) and of the substituents on
either the Cp rings or the phosphorus atoms. The three
Metal complexes containing 1,1′-bis(diorganylphos-
phino)metallocenes are active catalysts for a variety of
important catalytic reactions.1-13 Representative ex-
amples include cross-coupling reactions,4 the Heck
reaction,5 carbonylation of chloroarenes,6 aryl halide
(1) (a) Colacot, T. J. Platinum Met. Rev. 2001, 45, 22. (b) Gan, K.-
S.; Hor, T. S. A. In Ferrocenes: Homogeneous Catalysis, Organic
Synthesis, Materials Science; Togni, A., Hayashi, T., Eds.; VCH-
Wiley: Weinheim, Germany, 1995; Chapter 1.
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J. M.; Guiry, P. J. Inorg. Chim. Acta 1994, 220, 249.
(3) Gusev, O. V.; Kal’sin, A. M.; Petrovskii, P. V.; Lyssenko, K. A.;
Oprunenko, Y. F.; Bianchini, C.; Meli, A.; Oberhauser, W. Organome-
tallics 2003, 22, 913.
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2000, 19, 1567. (b) Bosch, B. E.; Bru¨mmer, I.; Kunz, K.; Erker, G.;
Fro¨lich, R.; Kotila, S. Organometallics 2000, 19, 1255. (c) Xie, Y.: Tan,
G. K.; Yan, Y. K.; Vittal, J. J.; Ng, S. C.; Hor, T. S. A. J. Chem. Soc.,
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W. N. M.; Zuideveld, M. A.; Freixa, Z.; Kamer, P. C. J.; Spek, A. L.;
Gusev, O. V.; Kal’sin, A. M. Organometallics 2003, 22, 2409. (b) Gusev,
O. V.; Kal’sin, A. M.; Peterleitner, M. G.; Petrovskii, P. V.; Lyssenko,
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10.1021/om049109w CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/02/2005

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1019
Chart 1
Scheme 1
major coordination modes in isolated complexes are cis-
κ2-P,P,2,3,5,10-18 κ3-P,P,M,3,11,13,17,18 and µ2-κ1-P,18b,19,20
while the plain unidentate (κ1) bonding is often invoked
for transient species (Chart 1).
Chart 2
In the vast majority of 1,1′-bis(diorganylphosphino)-
metallocene ligands employed in catalysis the phospho-
rus atoms contain aryl groups, generally phenyls.
Recently, however, much interest has been focused on
ligands bearing P(alkyl)2 groups.5b,8a,10,15,16,18 Besides
increasing the basicity of the phosphorus donors,21 alkyl
substituents have proved more amenable than aryl
substituents to control the steric hindrance at the
P-M′-P grouping, which, in turn, is a key factor to
switch the coordination mode from cis-κ2-P,P to κ3-P,P,M
with remarkable effects on the chemical reactiv-
ity.3,11,13,18 Another peculiar aspect of 1,1′-bis(dialky-
lphosphino)metallocenes is their capability to form
water-soluble metal complexes with no need of polar
groups incorporated into the ligand skeleton, as is
required for classical chelating diphosphines such as
dppp and dppe.22 However, the use of bis(dialkylphos-
phino)metallocene metal complexes in aqueous catalysis
seems to have no precedent in the relevant literature.
The aim of this paper is to provide unprecedented
information on the catalytic behavior of palladium(II)
precursors modified with 1,1′-bis(dialkylphosphino)-
ferrocene ligands, with particular attention to processes
performed in aqueous media. The reaction investigated
is the carbonylation of either ethylene or ethylene-
propene mixtures in the typical MeOH solvent as well
as in aqueous solvents such as water and water/1,4-
dioxane. Indeed, over the last 5 years, palladium(II)
complexes with 1,1′-bis(diarylphosphino)metallocene
ligands have been extensively used both as effective
catalysts for the carbonylation of ethylene and as model
compounds to study this relevant reaction.3,11,12,18c The
catalytic performance of such complexes is strictly
controlled by the nature of both the metallocene metal
(Fe, Ru, Os) and the substituents on the Cp rings, to
the extent that a variation of either parameter may
result in the selective formation of a variety of products
spanning from alternating polyketones (alt-E-CO) to
low-molecular-weight esters, diesters, and ketones
(Scheme 1).3,11,12
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Zuideveld, M. A.; Swennenhuis, B. H. G.; Boele, M. D. K.; Guari, Y.;
van Strijdonck, G. P. F.; Reek, J. N. H.; Kamer, P. C. J.; Goubitz, K.;
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2002, 2308. (c) van Leeuwen, P. W. N. M.; Zuideveld, M. A.; Swen-
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The ligands and the palladium complexes employed
as catalyst precursors in this study are illustrated in
Chart 2.
Experimental Section
General Procedures. All reactions and manipulations
were carried out under an atmosphere of nitrogen using
Schlenk-type techniques. All reagents and solvents were used
as purchased from commercial suppliers. The compounds 1,1′-
bis(dimethylphosphino)ferrocene (dmpf),23 bis(diethylphos-
phino)ferrocene (depf),24 bis(diisopropylphosphino)ferrocene
(dippf),10 PdCl(Me)(COD) (COD ) cycloocta-1,5-diene),25 PdCl2-
(dippf)10 (3), PdCl(Me)(depf)18b (9), and PdCl(Me)(dippf)15 (10)
were synthesized according to published procedures. Carbo-
nylation reactions were performed with a 325 mL stainless
steel autoclave, constructed at the ICCOM-CNR (Firenze,
Italy), equipped with a magnetic drive stirrer and a Parr 4842
temperature and pressure controller. The autoclave was
connected to a gas reservoir to maintain a constant pressure
over all the catalytic reactions. Deuterated solvents for NMR
(20) (a) Unruh, J. D.; Christenson, J. R. J. Mol. Catal. 1982, 14, 19.
(b) Casellato, U.; Corain, B.; Graziani, R.; Longato, B.; Pilloni, G. Inorg.
Chem. 1990, 29, 1193. (c) Viotte, M.; Gautheron, B.; Kubicki, M. M.;
Mugnier, Y.; Parish, R. V. Inorg. Chem. 1995, 34, 3465.
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W.; Merrill, R. E.; Smart, J. C. J. Organomet. Chem. 1971, 27, 241. (b)
Kumada, M.; Kiso, Y.; Umeno, M. Chem. Commun. 1970, 611.
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Org. Chem. 1985, 15, 109.
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R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; van Leeuwen, P. W.
N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769.
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1030-1033.
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1020 Organometallics, Vol. 24, No. 5, 2005
Bianchini et al.
measurements were dried over molecular sieves. 1H, 13C{1H},
and 31P{1H} NMR spectra were routinely obtained on a Bruker
ACP 200 spectrometer (200.13, 50.32, and 81.01 MHz, respec-
tively). 1H and 13C{1H} NMR spectra of both polymer materials
and selected complexes were recorded on a Bruker AMX 400
spectrometer (400.13 and 100.61 MHz, respectively). Chemical
shifts are reported in ppm (δ) with reference to either TMS as
an internal standard (1H and 13C{1H} NMR spectra) or 85%
H3PO4 as an external standard (31P{1H} NMR spectra). The
10 mm sapphire NMR tube was purchased from Saphikon,
Milford, NH, while the titanium high-pressure charging head
was constructed at the ICCOM-CNR (Firenze, Italy).26 Cau-
tion! Since high gas pressures are involved, safety precautions
must be taken at all stages of studies involving high-pressure
NMR tubes. Infrared spectra were recorded on a Perkin-Elmer
Spectrum BX FT-IR spectrophotometer; a cell with KBr
windows and 0.2 mm spacer between the KBr plates was
employed for solution measurements. Elemental analyses were
performed using a Carlo Erba Model 106 elemental analyzer.
Conductivities were measured with an ORION Model 990101
conductance cell connected to a Model 101 conductivity meter.
The conductivity data27 were obtained at sample concentra-
tions of ca. 10-3 M in nitroethane solutions. Melting points
were recorded on a Electrothermal IA 9000 Series digital
melting point apparatus. DSC analyses were performed at 5
and 20 °C min-1 on a Perkin-Elmer Series 7 instrument
calibrated with In and Zn standards. TGA analyses were
obtained under nitrogen (60 mL min-1) with a TGA Mettler
Toledo instrument at 10 °C min-1. GC analyses were per-
formed on a Shimadzu GC-14 A gas chromatograph equipped
with a flame ionization detector and a 30 m (0.25 mm i.d., 0.25
µm film thickness) SPB-1 Supelco fused silica capillary column.
The product composition of the catalytic reactions was deter-
mined by using 1,2-dimethoxyethane as the internal standard.
GC/MS analyses were performed on a Shimadzu QP 5000
apparatus equipped with a column identical with that used
for GC analysis.
Catalytic Carbonylation of Ethylene and Ethylene/
Propene in Methanol, Water, and 1/1 (v/v) Water/1,4-
Dioxane. Typically, a solution of the precatalyst (0.01 mmol)
in 100 mL of the appropriate solvent was introduced by suction
into a 325 mL autoclave, previously evacuated by a vacuum
pump, containing, if required, solid samples of benzoquinone
(BQ) and/or p-toluenesulfonic acid monohydrate (TsOH). The
desired amount of propene was charged by cooling the auto-
clave with an ice/acetone bath. The autoclave was then charged
with 1/1 CO/ethylene (30 bar) at room temperature and heated
to 85 °C. As soon as the temperature was reached, stirring
was applied (1400 rpm) and the autoclave was connected to a
CO/ethylene reservoir to maintain a constant pressure of 40
bar during the experiment. After the desired reaction time
(1-3 h), the autoclave was disconnected from the gas reservoir
and cooled to 10 °C by means of an ice/acetone cooling bath.
Afterward, the pressure was released from the autoclave and
the polymer, if any, was filtered off, washed with methanol,
and dried to a constant weight at 50 °C under vacuum.
Alternatively, the solution was analyzed by GC.
2. Anal. Calcd for C18H28Cl2FeP2Pd: C, 40.07; H, 5.23.
Found: C, 39.99; H, 5.22. 1H NMR (CDCl3): δ 1.33 (br s, 12H,
CH2CH3), 2.19 (br s, 4H, CHHCH3), 2.50 (br s, 4H, CHHCH3),
4.49 (br s, 4H, â-H Cp), 4.52 (br s, 4H, R-H Cp). 31P{1H} NMR
(CDCl3): δ 42.8 (s).
Synthesis of [Pd(OTs)(H2O)(dmpf)]OTs (4), [Pd(OTs)-
(H2O)(depf)]OTs (5), and [Pd(OTs)(H2O)(dippf)]OTs (6).
Solid silver tosylate (1.17 mmol) was added to the orange
solution of PdCl2(P-P) (0.56 mmol) in CH2Cl2 (50 mL) at room
temperature under nitrogen. The resulting suspension was
stirred for 2 h at room temperature and then filtered through
a column of Celite. The deep red filtrate was concentrated to
ca. 5 mL, and then deaerated diethyl ether was added to
precipitate the red product, which was filtered off, washed with
diethyl ether, and dried under a stream of nitrogen. The yields
ranged from 70 to 85%.
4. Crystals suitable for X-ray analysis were obtained by
recrystallization from CH2Cl2 and toluene. Anal. Calcd for
C28H36FeO7P2PdS2: C, 43.51; H, 4.69. Found: C, 43.45; H, 4.64.
ΛM (nitroethane) ) 16 Ω-1 cm2 mol-1. 1H NMR (CDCl3): δ 1.99
(d, J(HP) ) 12.7 Hz, 12H, Me), 2.32 (s, 6H, Me OTs), 4.10 (br
s, 2H, H2O), 4.49 (br s, 4H, â-H Cp), 5.02 (br s, 4H, R-H Cp),
7.07 (br s, 4H, H OTs), 7.76 (br s, 4H, H OTs). 13C{1H} NMR
(CD2Cl2): δ 17.30 (s, Me), 21.73 (s, Me OTs), 74.10 (t, J(CP) )
3.9 Hz, â-C Cp), 75.06 (t, J(CP) ) 6.2 Hz, R-C Cp), 77.70 (m,
1
2
| J(CP) + J(CP)| ) 68.3 Hz, ipso-C Cp), 126.90 (s, CH OTs),
129.48 (s, CH OTs), 141.40 (s, C OTs), 142.10 (s, C OTs). 31P-
{1H} NMR (CDCl3): δ 30.4 (s).
5. Anal. Calcd for C32H44FeO7P2PdS2: C, 46.36; H, 5.35.
Found: C, 46.24; H, 5.29. ΛM (nitroethane) ) 17 Ω-1 cm2 mol-1
.
1H NMR (CD2Cl2, 400.13 MHz): δ 1.26 (dt, J(HP) ) 19.1 Hz,
J(HH) ) 7.6 Hz, 12H, CH2CH3), 2.34 (m, 4H, CHHCH3), 2.38
(m, 4H, CHHCH3), 2.38 (s, 6H, Me OTs), 4.57 (m, 4H, â-H Cp),
5.10 (m, 4H, R-H Cp), 5.72 (br s, 2H, H2O), 7.12 (d, J(HH) )
7.8 Hz, 4H, H OTs), 7.72 (d, J(HH) ) 7.8 Hz, 4H, H OTs).
13C{1H} NMR (CD2Cl2, 100.61 MHz): δ 7.81 (s, CH2CH3), 19.16
(d, J(CP) ) 33.4 Hz, CH2CH3), 20.87 (s, Me OTs), 72.43 (t,
J(CP) ) 3.9 Hz, â-C Cp), 74.05 (t, J(CP) ) 4.9 Hz, R-C Cp),
1
2
74.07 (m, | J(CP) + J(CP)| ) 64.5 Hz, ipso-C Cp), 124.97 (s,
CH OTs), 127.41 (s, CH OTs), 139.12 (s, C OTs), 140.06 (s, C
OTs). 31P{1H} NMR (CDCl3): δ 53.4 (s).
6. Anal. Calcd for C36H52FeO7P2PdS2: C, 48.85; H, 5.92.
Found: C, 48.74; H, 5.89. ΛM (nitroethane) ) 15 Ω-1 cm2 mol-1
.
1H NMR (CDCl3): δ 1.34 (dd, J(HP) ) 17.7 Hz, J(HH) ) 7.2
Hz, 12H, CHMeMe), 1.67 (dd, J(HP) ) 17.7 Hz, J(HH) ) 7.2
Hz, 12H, CHMeMe), 2.31 (s, 6H, Me OTs), 2.66 (m, 4H,
CHMeMe), 4.25 (br s, 2H, H2O), 4.58 (br s, 4H, â-H Cp), 4.97
(br s, 4H, R-H Cp), 7.06 (d, J(HH) ) 7.8 Hz, 4H, H OTs), 7.69
(d, J(HH) ) 7.8 Hz, 4H, H OTs). 13C{1H} NMR (CDCl3): δ
19.77 (s, CHMeMe), 20.72 (s, CHMeMe), 21.68 (s, Me OTs),
1
2
28.32 (m, CHMeMe), 72.92 (m, | J(CP) + J(CP)| ) 56.6 Hz,
ipso-C Cp), 73.76 (t, J(CP) ) 3.5 Hz, â-C Cp), 75.54 (t, J(CP)
) 5.5 Hz, R-C Cp), 126.49 (s, CH OTs), 129.09 (s, CH OTs),
140.51 (s, C OTs), 141.75 (s, C OTs). 31P{1H} NMR (CDCl3): δ
82.9 (s).
Compounds 4-6 are soluble in polar organic solvents as well
as in water, where concentrations of 48, 21, and 11 mg/mL
can be obtained, respectively.
Synthesis of PdCl2(dmpf) (1) and PdCl2(depf) (2). These
orange complexes were synthesized in 80-90% yield by
reaction of the appropriate diphosphine ligand with PdCl2(COD)
in CH2Cl2. Crystals of 1 suitable for a single-crystal diffraction
analysis were obtained by concentrating a CH2Cl2 solution of
1 at room temperature.
Synthesis of [PdCl(Me)(dmpf)]2 (7). A solution of PdCl-
(Me)(COD) (106 mg, 0.40 mmol) and dmpf (128 mg, 0.42 mmol)
in benzene (10 mL) was stirred for 2 h at room temperature
under nitrogen. Portionwise addition of diethyl ether (10 mL)
led to the precipitation of the product, which was filtered off
and dried under a stream of nitrogen; yield 85%. Anal. Calcd
for C30H46Cl2Fe2P4Pd2: C, 38.91; H, 5.01. Found: C, 38.85; H,
1. Anal. Calcd for C14H20Cl2FeP2Pd: C, 34.78; H, 4.17.
1
Found: C, 34.71; H, 4.12. H NMR (CDCl3): δ 2.06 (d, J(HP)
) 10.3 Hz, 12H, Me), 4.50 (s, 8H, H Cp). 31P{1H} NMR (CDCl3)
δ 15.4 (s).16
1
4.99. H NMR (CD2Cl2): δ 0.56 (t, J(HP) ) 6.5 Hz, 6H, Pd-
Me), 1.49 (br s, 12H, Me), 1.74 (br s, 12H, Me), 4.53 (br s, 8H,
â-H Cp), 5.17 (br s, 8H, R-H Cp). 31P{1H} NMR (CD2Cl2): δ
-10.0 (s).
(26) Bianchini, C.; Meli, A.; Traversi, A. Ital. Patent FI A000025,
1997.
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Sacconi, L. J. Chem. Soc. A 1971, 492.
Synthesis of PdCl(Me)(dmpf) (8). A solution of 7 (40 mg,
0.04 mmol) in CH2Cl2 (20 mL) was refluxed under nitrogen

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1021
for 30 min. Afterward, the solution was concentrated to half
of the original volume and 20 mL of n-pentane was added to
complete the precipitation of the orange product, which was
filtered off and dried under a stream of nitrogen. Yield: 85%.
Anal. Calcd for C15H23ClFeP2Pd: C, 38.91; H, 5.01. Found: C,
38.78; H, 4.95. 1H NMR (CD2Cl2): δ 0.66 (dd, J(HP) ) 4.5 Hz,
J(HP) ) 8.1 Hz, 3H, Pd-Me), 1.63 (d, J(HP) ) 7.9 Hz, 6H,
Me), 1.64 (d, J(HP) ) 10.0 Hz, 6H, Me), 4.34-4.41 (m, 8H,
Cp). 31P{1H} NMR (CD2Cl2): δ 3.2 (d, J(PP) ) 29.8 Hz), -12.8
(d).
Synthesis of [Pd(Me)(MeCN)(P-P)]B(Ar′)4 (P-P ) dmpf
(11), depf (12), dippf (13)). MeCN (300 µL) and NaB(Ar′)4
(Ar′ ) 3,5-bis(trifluoromethyl)phenyl, 55 mg, 0.06 mmol) were
added in sequence to a solution of the appropriate chloro
methyl derivate 8-10 (0.06 mmol) in CH2Cl2 (10 mL) at room
temperature under nitrogen. The suspension was stirred for
10 min and then filtered through a column of Celite to remove
the formed NaCl. The filtrate was concentrated to dryness,
and the orange residue was washed with diethyl ether and
collected by filtration; yield 80-90%.
11. Anal. Calcd for C49H38BF24FeNP2Pd: C, 44.19; H, 2.87.
Found: C, 44.15; H, 2.85. 1H NMR (CD2Cl2): δ 0.67 (dd, J(HP)
) 7.4 Hz, J(HP) ) 3.3 Hz, 3H, Pd-Me), 1.57 (d, J(HP) ) 7.6
Hz, 6H, Me), 1.66 (d, J(HP) ) 10.6 Hz, 6H, Me), 2.08 (s, 3H,
MeCN), 4.48 (br s, 8H, Cp), 7.59 (br s, 4H, p-aryl), 7.75 (br s,
8H, o-aryl). 31P{1H} NMR (CD2Cl2): δ 6.1 (d, J(PP) ) 33.0 Hz),
-13.7 (d).
12. Anal. Calcd for C53H46BF24FeNP2Pd: C, 45.88; H, 3.31.
Found: C, 45.45; H, 3.10. 1H NMR (CD2Cl2): δ 0.67 (dd, J(HP)
) 7.2 Hz, J(HP) ) 3.2 Hz, 3H, Pd-Me), 1.11 (t, J(HH) ) 8.0
Hz, 6H, CH2CH3), 1.20 (t, J(HH) ) 8.6 Hz, 6H, CH2CH3), 1.92
(m, 8H, CH2CH3), 2.12 (s, 3H, MeCN), 4.39-4.49 (m, 8H, Cp),
7.58 (br s, 4H, p-aryl), 7.74 (br s, 8H, o-aryl). 31P{1H} NMR
(CD2Cl2): δ 32.6 (d, J(PP) ) 29.1 Hz), 9.3.
13. Anal. Calcd for C57H54BF24FeNP2Pd: C, 47.43; H, 3.74.
Found: C, 47.30; H, 3.50. 1H NMR (CD2Cl2): δ 0.77 (dd, J(HP)
) 6.5, 2.2 Hz, 3H, Pd-Me), 1.15 (m, 12H, CHMeMe), 1.30 (m,
12H, CHMeMe), 2.10 (s, 3H, MeCN), 2.30 (m, 2H, CHMe2),
2.51 (m, 2H, CHMe2), 4.38 (s, 2H, Cp), 4.45 (s, 2H, Cp), 4.50
(s, 4H, Cp), 7.58 (br s, 4H, p-aryl), 7.74 (br s, 8H, o-aryl). 31P-
{1H} NMR (CD2Cl2): δ 55.1 (d, J(PP) ) 21.0 Hz), 33.1.
Carbonylation of the Methyl Acetonitrile Complexes
11-13. In Situ NMR Synthesis of the Acetyl Complexes
[Pd(MeCN)(C(O)Me)(P-P)]B(Ar′)4 (P-P ) dmpf (14), depf
(15)) and [Pd(C(O)Me)(dippf)]B(Ar′)4 (16). CO was bubbled
through the orange solution of the appropriate methyl aceto-
nitrile complex 11-13 (0.03 mmol) in CD2Cl2 (1.5 mL) at -20
°C for 5 min. Afterward, the solution was purged with a stream
of nitrogen for 1 min and transferred into a 5 mm NMR tube
at -20 °C. 31P{1H} and 1H NMR spectra recorded at room
temperature showed the quantitative conversion of 11-13 into
14-16. Better resolution of the 1H NMR spectra was obtained
by acquiring the spectra at lower temperatures (-40 °C for
14 and -10 °C for 15).
8H, o-aryl). 31P{1H} NMR (CD2Cl2, 20 °C): δ 15.4 (s). IR (CH2-
Cl2): ν(CO) 1698 cm-1
.
Reaction of the Acetyl Complexes 14-16 with Ethyl-
ene. In Situ NMR Synthesis of the â-Chelate Derivatives
[Pd(CH2CH2C(O)Me)(P-P)]B(Ar′)4 (P-P ) dmpf (17), depf
(18), dippf (19)). Typically, a solution of an acetyl complex
(0.03 mmol) in CD2Cl2 (1.5 mL), prepared in situ as reported
above under nitrogen at -20 °C, was saturated with ethylene.
1
31P{1H} and H NMR spectra recorded at -20 °C showed the
quantitative formation of the â-chelate. Parallel experiments
were carried out in CH2Cl2, and the final solutions were
analyzed by IR spectroscopy. Given the selectivity of the
reactions, no attempt was made to isolate the â-chelates, and
their solutions were straightforwardly employed for further
reactivity studies.
1
17. H NMR (CD2Cl2, -20 °C): δ 1.63 (d, J(HP) ) 8.2 Hz,
6H, Me), 1.64 (d, J(HP) ) 11.2 Hz, 6H, Me), 1.81 (m, 2H, Pd-
CH2), 2.39 (s, 3H, C(O)Me), 3.21 (dt, J(HP) ) 15.0 Hz, J(HH)
) 6.3 Hz, 2H, CH2C(O)Me), 4.50 (br s, 8H, Cp), 7.59 (br s, 4H,
p-aryl), 7.75 (br s, 8H, o-aryl). 31P{1H} NMR (CD2Cl2, -20
°C): δ 7.4 (d, J(PP) ) 35.7 Hz), -9.8 (d). IR (CH2Cl2): ν(CO)
1632 cm-1
.
1
18. H NMR (CD2Cl2, -20 °C): δ 1.10 (m, 12H, CH2CH3),
1.70 (dt, J(HP) ) 6.0 Hz, J(HH) ) 2.3 Hz, 2H, Pd-CH2), 1.90
(m, 8H, CH2CH3), 2.40 (s, 3H, C(O)Me), 3.12 (dt, J ) 9.1 Hz,
J ) 6.2 Hz, 2H, CH2CO), 4.45 (br s, 8H, Cp), 7.56 (br s, 4H,
p-aryl), 7.75 (br s, 8H, o-aryl). 31P{1H} NMR (CD2Cl2, -20
°C): δ 31.8 (d, J(PP) ) 33.6 Hz), 12.1 (d). IR (CH2Cl2): ν(CO)
1633 cm-1
.
19. Better resolution of the 1H NMR spectrum was obtained
at 0 °C. 1H NMR (CD2Cl2, 0 °C): δ 1.25 (m, 24H, CHMe2), 1.89
(dt, J(HP) ) 6.0 Hz, J(HH) ) 2.3 Hz, 2H, Pd-CH2), 2.31 (m,
4H, CHMe2), 2.44 (s, 3H, C(O)Me), 3.12 (dt, J(HP) ) 9.1 Hz,
J(HH) ) 6.2 Hz, 2H, CH2C(O)Me), 4.48 (br s, 8H, Cp), 7.58
(br s, 4H, p-aryl), 7.75 (br s, 8H, o-aryl). 31P{1H} NMR (CD2-
Cl2, -20 °C): δ 57.9 (d, J(PP) ) 23.6 Hz), 34.9 (d). IR (CH2-
Cl2): ν(CO) 1634 cm-1
.
Reaction of the â-Chelate Complexes 17-19 with
Water. In Situ NMR and IR Experiments. A solution of
the appropriate â-chelate (0.03 mmol) in CD2Cl2 (1.5 mL) was
prepared in situ as reported above at -20 °C under ethylene
and then transferred into a 5 mm NMR tube equipped with a
rubber cap at room temperature under nitrogen. A 75 µL
sample of H2O was injected by syringe into the tube. The tube
was shaken and immediately transferred into the NMR probe.
1
The reaction was followed by 31P{1H} and H NMR spectros-
copy at room temperature. All the starting â-chelates were
converted into the binuclear compounds [Pd(µ-OH)(P-P)]2-
(B(Ar′)4)2 (P-P ) dmpf (20), depf (21), dippf (22)) and free
2-butanone with rates that increased in the order 17 (t1/2
)
20 min) < 18 (t1/2 ) 7 min) < 19 (t1/2 ) 4 min). Some
unidentified compounds (ca. 20%) were also observed in the
final 31P{1H} NMR spectra. In parallel experiments, a 200 µL
portion of the initial â-chelate solution was transferred by a
syringe into an IR cell for liquids under nitrogen, and the
reaction was followed by IR spectroscopy at room temperature
(spectral range from 1500 to 1900 cm-1). With time, the
characteristic â-chelate band at ca. 1634 cm-1 decreased with
formation of a new band at 1712 cm-1 due to 2-butanone, at a
rate comparable to that observed in the NMR experiments (see
Figure 4 for the dippf â-chelate 19).
Parallel experiments were carried out in CH2Cl2, and the
final solutions were analyzed by IR spectroscopy.
1
14. H NMR (CD2Cl2, -40 °C): δ 1.46 (d, J(HP) ) 6.0 Hz,
6H, Me), 1.50 (d, 6H, J(HP) ) 8.8 Hz, Me), 2.06 (s, 3H, MeCN),
2.50 (br s, 3H, C(O)Me), 4.40 (br s, 4H, H Cp), 4.45 (br s, 4H,
H Cp), 7.58 (br s, 4H, p-aryl), 7.74 (br s, 8H, o-aryl). 31P{1H}
NMR (CD2Cl2, -40 °C): δ -2.2 (d, J(PP) ) 59.0 Hz), -17.5
1
20. H NMR (CD2Cl2): δ -1.45 (br s, µ-OH). 31P{1H} NMR
(d). IR (CH2Cl2): ν(CO) 1694 cm-1
.
1
(CD2Cl2): δ 22.1 (s).
15. H NMR (CD2Cl2, -10 °C): δ 1.03 (t, J(HH) ) 7.8 Hz,
6H, CH2CH3), 1.11 (t, J(HH) ) 7.8 Hz, 6H, CH2CH3), 1.81 (m,
8H, CH2CH3), 2.09 (s, 3H, MeCN), 2.52 (s, 3H, C(O)Me), 4.40-
4.51 (m, 8H, Cp), 7.58 (br s, 4H, p-aryl), 7.73 (br s, 8H, o-aryl).
31P{1H} NMR (CD2Cl2, -10 °C): δ 19.9 (d, J(PP) ) 57.0 Hz),
1
21. H NMR (CD2Cl2): δ -1.56 (br s, µ-OH). 31P{1H} NMR
(CD2Cl2): δ 45.7 (s).
22. 1H NMR (CD2Cl2): -2.34 (br s, µ-OH). 31P{1H} (CD2-
Cl2): δ 73.2 (s).
5.1 (d). IR (CH2Cl2): ν(CO) 1694 cm-1
16. H NMR (CD2Cl2, 20 °C): δ 1.29 (m, 24H, CHMeMe),
2.39 (m, 4H, CHMeMe), 2.81 (s, 3H, C(O)Me), 4.22 (br s, 4H,
H Cp), 4.89 (br s, 4H, H Cp), 7.58 (br s, 4H, p-aryl), 7.73 (br s,
.
Copolymerization of CO and Ethylene. HPNMR Ex-
periments with 4 as Catalyst Precursor. (A) MeOH-d4.
A 10 mm sapphire HPNMR tube was charged with a solution
of 4 (10 mg, 0.013 mmol) in MeOH-d4 (2 mL) under nitrogen
1

1022 Organometallics, Vol. 24, No. 5, 2005
Bianchini et al.
and then placed into a NMR probe at 22 °C (31P{1H} NMR
singlet at δ 34.2). Pressurizing with a 1:1 mixture of CO and
C2H4 to 20 bar at room temperature caused no change in both
the 1H and 31P{1H} NMR spectra. When the temperature was
increased to 80 °C, the copolymerization reaction occurred.
Compound 4 slowly disappeared with time, and formed in its
place were several unidentified species. After 1 h, the tube
was removed from the probe head. Similar NMR pictures were
observed when an excess of BQ and/or TsOH was added to
the reaction mixtures; the only difference was that the polymer
appeared as a more brilliant off-white solid.
Table 1. Crystal Data and Structure Refinement
Details for 1 and 4
1
4
empirical formula
C
29H42Cl6Fe2P4Pd2
C
28H36FeO7P2PdS2
fw
1051.71
772.88
cryst color, shape
cryst size, mm
collection temp, K
cryst syst
space group
a, Å
orange-red, block deep red, prism
0.80 × 0.25 × 0.15 0.70 × 0.50 × 0.20
293(2)
monoclinic
P21
293(2)
monoclinic
P21/n
17.658(9)
9.783(3)
19.863(12)
112.78(3)
3164(3)
4
1.623
1576
Mo KR/0.710 73
1.303
12.618(4)
10.741(15)
14.354(8)
103.25
1894(3)
2
b, Å
(B) D2O. A 10 mm sapphire HPNMR tube was charged with
a D2O (2 mL) solution containing 4 (10 mg, 0.013 mmol) and
a 10-fold excess of TsOH under nitrogen and then placed into
a NMR probe at 22 °C (31P{1H} NMR singlet at δ 32.2).
Pressurizing with an 1:1 mixture of CO and C2H4 to 20 bar at
c, Å
â, deg
V, Å3
Z
calcd density, g/cm3
F(000)
1.845
1044
1
room temperature caused no change in both the H and 31P-
{1H} NMR spectra. Complex 4 was the only phosphorus-
containing species visible by NMR also during the copolym-
erization reaction (1 h at 80 °C), although the intensity of its
31P{1H} NMR signal slowly decreased with time. The tube was
then cooled to room temperature. A comparison between the
31P{1H} NMR spectrum of this sample and the spectrum
acquired at room temperature before the catalytic reaction
showed the concentration of 4 to decrease by ca. 35%.
radiation/wavelength, Å Mo KR/0.710 73
abs coeff, mm-1
no. of rflns collected
no. of unique rflns
no. of data/restraints/
params
2.299
3491
4335
4335
4335/0/378
3491
3491/1/389
goodness of fit on F2
R1, wR2 (I > 2σ(I))
R1, wR2 (all data)
largest diff peak and
hole, e/Å3
1.049
1.049
0.0197, 0.0500
0.0213, 0.0509
0.529, -0.345
0.0327, 0.0782
0.0532, 0.0857
0.677, -0.546
Methoxycarbonylation of Ethylene. HPNMR Experi-
ments with 6 as Catalyst Precursor in MeOH-d4. The
reaction was followed by variable-temperature 31P{1H} and 1H
NMR spectroscopy. A sequence of selected 31P{1H} NMR
spectra is reported in Figure 3. A 10 mm sapphire HPNMR
tube was charged under nitrogen with a solution of 6 (12 mg,
0.013 mmol) in MeOH-d4 (2 mL) and then placed into the NMR
probe at room temperature (δ 91.9, trace a). Pressurizing with
a 1:1 mixture of CO/C2H4 to 40 bar at room temperature (trace
b) led to the formation of two low-intensity doublets at δ 58.5
and 35.9 with a J(PP) value of 24 Hz, attributed to the
â-chelate complexes [Pd(CH2CH2C(O)R)(dippf)]OTs (23) on the
basis of the spectrum of the authentic â-chelate 19. The R
group in 23 may be either C2H4D(H) or OCD3, depending on
whether the reaction starts with Pd-D/H or Pd-OCD3,
respectively. Another minor species, marked by a broad 31P-
{1H} NMR signal at δ 34.5 (trace b), was assigned to the
µ-hydrido µ-carbonyl complex [Pd2(µ-H/D)(µ-CO)(dippf)2]OTs
(24H/D; see the analogue 25H below). The 1H NMR spectrum
contained a very weak signal at ca. δ -7 due to the µ-H
hydrogen in 24H/D, which suggests the involvement of the
water molecules contained both in 6 and in the solvent in the
formation of Pd-H moieties. Alternatively, the proton may
come from H/D scrambling with ethylene via â-hydride elimi-
nation of palladium alkyl intermediates. Increasing the tem-
perature, first to 50 °C and then to 80 °C (trace c), led to the
quantitative conversion of 6 into 24H/D, while the â-chelates
23 disappeared; some minor signals due to unknown species
were also present. After 1 h at 80 °C, the probe head was cooled
to room temperature. The â-chelate 23 reappeared in the 31P-
{1H} NMR spectrum (trace d). The tube was removed from
the probe head; no solid material, except for traces of black
palladium, was observed. The analysis of the solution by GC/
MS showed the formation of deuterated samples of methyl
propanoate and 3-pentanone.
solution of the starting acetyl complex, the deuterated ana-
logue [Pd2(dippf)2(µ-D)(µ-CO)]OTs (25D) was formed; three
signals were observed in the 31P{1H} NMR spectrum in an
intensity ratio of 1:1:1 due to the phosphorus-deuterium
coupling (2J(PD) ) 5.9 Hz). 31P{1H} NMR (CH2Cl2): δ 33.6 (s).
2
1H NMR (CH2Cl2): δ -7.14 (quintet, J(HP) ) 40.4 Hz, 1H,
Pd-H), 1.3-1.6 (m, 24H, CHMe2), 2.59 (m, 4H, CHMe2), 4.42
(br s, 4H, â-H Cp), 4.52 (br s, 4H, â-H Cp), 4.68 (br s, 4H, R-H
Cp), 4.82(d, 4H, R-H Cp).
X-ray Data Collection and Structure Determination
of 1 and 4. Diffraction data for both crystals were collected
at room temperature on an Enraf-Nonius CAD4 automatic
diffractometer with Mo KR radiation (graphite monochroma-
tor). Unit cell parameters of both structures were determined
from a least-squares refinement of the setting angles of 25
carefully centered reflections. Crystal data and data collection
details are given in Table 1.
The intensities were rescaled and assigned a standard
deviation σ(I), calculated using the value of 0.03 for the
instability factor k.28 Lorentz-polarization and absorption
corrections were applied.29 Atomic scattering factors were
taken from ref 30, and an anomalous dispersion correction,
with real and imaginary parts, was applied.31 The structures
were solved by direct methods and refined by full-matrix F2
refinement. All the calculations were performed on a PC using
the WINGX package32 with SIR-97,33 SHELX-97,34 and ORTEP-
335 programs.
(28) Corfield, P. W. R.; Doedens, R. J.; Ibers, J. A. Inorg. Chem. 1967,
6, 197.
(29) Parkin, S.; Moezzi, B.; Hope, H. J. Appl. Crystallogr. 1995, 28,
53.
In Situ Synthesis of [Pd2(µ-H)(µ-CO)(dippf)2](B(Ar′)4)2
(25H). A 5 mm NMR tube was charged with a CD2Cl2 solution
of [Pd(C(O)Me)(dippf)]B(Ar′)4 (16), prepared in situ by follow-
ing a procedure analogous to those reported above. MeOH (10
equiv) was syringed into the solution in the presence of CO at
room temperature. After ca. 1 h, 1H and 31P{1H} NMR spectra
showed the quantitative conversion of the starting acetyl
complex (31P{1H} NMR δ 15.4) into the binuclear species 25H
and methyl acetate.11a The solution was evaporated to dryness,
and the residue was analyzed by IR spectroscopy (KBr, Nujol
mull: ν(CO) 1825 cm-1). When MeOH-d4 was added to the
(30) Wilson, A. J. C. International Tables for X-ray Crystallography;
Kluwer: Dordrecht, The Netherlands, 1992; p 500.
(31) Wilson, A. J. C. International Tables for X-ray Crystallography;
Kluwer: Dordrecht, The Netherlands, 1992; p 219.
(32) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(33) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(34) Sheldrick, G. M. SHELX97 Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(35) Burnett M. N.; Johnson, C. K. Report ORNL-6895; Oak Ridge
National Laboratory, Oak Ridge, TN, 1996.

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1023
ligand (Pd(1)-P(1) ) 2.256(2) Å, Pd(1)-P(2) ) 2.280(2)
Å). The tilting of the Cp rings, put in evidence by the
angle between the plane normals of the sandwiching Cp
rings, is in both conformers toward the palladium(II)
center with values of 5.04 and 5.34°, respectively, which
is comparable to the value of 3.70° for 3.10 The confor-
mations of the Cp rings, described by the dihedral
angles C(ipso)-Cpcentroid-Cpcentroid-C(ipso), are stag-
gered (33.8 and 31.5°). Indeed, the values of the distor-
tion angles of the Cp rings of both conformers are very
close to that reported for 3 (32.5°).10 The analysis of the
short contacts within the crystal structure of 1 reveals
the presence of eight short intermolecular distances
between the chloride and hydrogen atoms (2.723-2.940
Å) and one short contact between H(11C) and H(2) of
2.254 Å.
From a perusal of the solid-state structures of the
dichloride complexes 1-3 one may conclude that the
three compounds exhibit similar coordination geom-
etries, the only noticeable difference being the crystal-
lographic bite angle P-Pd-P, which is larger in 3 as a
consequence of the greater bulkiness of the i-Pr groups.
The crystal structure of 4 shows a square-planar
monocationic compound where the metal atom is sur-
rounded by a cis-chelating diphosphine, a tosylate anion,
and a molecule of water. Figure 2 shows an ORTEP
drawing of the complex cation, while selected bond
lengths and angles are listed in Table 2.
The diphosphine forms a P(1)-Pd(1)-P(2) bite angle
of 91.80(6)°, which is significantly smaller than that of
the neutral dichloride precursor 1 (vide supra). The
dihedral angle, defined as C(1)-Cp(1)-Cp(2)-C(6), of
16.20(1.25)° is similarly smaller than that in 1. The
angle between the plane normals related to the Cp rings
is 3.57(0.76)° and is therefore comparable to those of
the analogous dichloride species. Complex 4 exhibits two
practically identical Pd-P bond lengths, as in the
related complex [Pd(H2O)(OTs)(dppp)]OTs (dppp ) 1,3-
bis(diphenylphosphino)propane).37 The coordinated wa-
ter molecule is involved in both intra- and intermolecu-
lar hydrogen bonds, with both coordinated and free
tosylate anions, as evidenced by H‚‚‚O distances of 1.938
and 1.891 Å, respectively.13,37
Catalytic Carbonylation of Ethylene and Ethyl-
ene/Propene. Complexes 4-6 were tested as catalyst
precursors for the carbonylation of ethylene in MeOH
and water or in a 1/1 mixture of water and 1,4-dioxane
(hereafter referred to as DIOX). A preliminary NMR
study showed all the precursors to be stable in these
solvents for at least 2 h at room temperature.
Figure 1. ORTEP drawings of the two conformers of 1
(1a, right; 1b, left). Thermal ellipsoids are drawn at the
30% probability level. Hydrogen atoms have been omitted
for clarity.
Results
Synthesis of the Catalyst Precursors. The PdII
catalyst precursors employed in this study, namely [Pd-
(H2O)(OTs)(dmpf)]OTs (4), [Pd(H2O)(OTs)(depf)]OTs (5),
and [Pd(H2O)(OTs)(dippf)]OTs (6), were synthesized by
reaction of the corresponding dichloride derivatives
PdCl2(P-P) (P-P ) dmpf (1), depf (2), dippf (3)) with
AgOTs in CH2Cl2, followed by precipitation with diethyl
ether. Complexes 4-6 exhibit a fairly good solubility in
water at 20 °C with concentrations as high as 48, 21,
and 11 mg mL-1, respectively. Just for comparison, the
aryl-substituted complex [Pd(H2O)(OTs)(dppf)]OTs (dppf
) 1,1′-bis(diphenylphosphino)ferrocene) shows a much
lower solubility of 0.15 mg mL-1
.
Multinuclear NMR spectroscopy (31P, 1H, 13C) in
either organic solvents (CD2Cl2, CDCl3) or D2O and
conductivity measurements in nitroethane provided a
reliable characterization for all compounds. On the basis
of these studies all compounds were assigned a square-
planar coordination around palladium, comprising a
chelating diphosphine and a mutually cis tosylate anion
and water molecule. A further authentication of the cis-
chelating structures reported in Chart 1 was obtained
by single-crystal X-ray analyses on the dmpf compounds
1 and 4.
The crystal structure of 1 contains two different
conformers (a and b) and one molecule of CH2Cl2 per
asymmetric unit. Figure 1 shows an ORTEP drawing
of the complex, while selected bond lengths and angles
are listed in Table 2. The coordination geometry around
the palladium atom can be described as slightly dis-
torted square planar with cis-coordinating phosphorus
atoms and is very similar to the geometries of PdCl2-
(depf)36 (2) and PdCl2(dippf)5b,10 (3). The values of the
P-Pd-P angles in the conformers 1a and 1b are 99.64-
(9) and 98.95(9)°, respectively. These values are com-
parable to that found in 2 (97.74(3)°)36 but significantly
smaller than that in 3 (103.59(4)°).5b,10 Unlike 3 and
conformer 1b, which show two identical (2.2941(9) Å)
and almost identical Pd-P bond lengths (2.268(2) and
2.266(2) Å), respectively, conformer 1a exhibits an
unsymmetrical coordination of the phosphorus donor
The dmpf and depf complexes 4 and 5 were both
active, yielding selectively alt-E-CO material, irrespec-
tive of the reaction solvent. In contrast, the dippf-
modified precursor 6 gave exclusively low-molecular-
weight oxygenates in MeOH, essentially diketones, keto
esters, and diesters of the general formulas Et(C(O)-
CH2CH2)nH (n ) 1-4), MeO(C(O)CH2CH2)nH (n ) 1-4),
and MeO(C(O)CH2CH2)nC(O)OMe (n ) 1-4). Notably,
the overall selectivity in EtC(O)Et and EtC(O)OMe was
generally higher than 89%.
Initially, the reactions were performed under 40 bar
of a 1/1 ethylene/CO mixture for 1 h at 85 °C with no
(37) Benetollo, F.; Bertani, R.; Bombieri, G.; Toniolo, L. Inorg. Chim.
Acta 1995, 233, 5.
(36) Gusev, O. V.; Beletskaya, I. P. Manuscript in preparation.

1024 Organometallics, Vol. 24, No. 5, 2005
Table 2. Selected Geometrical Parameters for 1 and 4
Bianchini et al.
1a
1b
4
Bond Lengths (Å)
Pd(1)-P(1)
Pd(1)-P(2)
Pd(1)-Cl(1)
Pd(1)Cl(2)
Pd(1)-Fe(1)
Fe(1)-Cp(1)a
Fe(1)-Cp(2)a
2.256(2)
2.280(2)
2.368(3)
2.368(2)
4.353(7)
1.632(12)
1.637(12)
Pd(2)-P(3)
Pd(2)-P(4)
Pd(2)-Cl(3)
Pd(2)-Cl(4)
Pd(2)-Fe(2)
2.268(2)
2.266(2)
2.386(3)
2.370(2)
4.390(7)
1.621(12)
1.629(12)
Pd(1)-P(1)
Pd(1)-P(2)
Pd(1)-O(1)
Pd(1)-O(2)
Pd(1)-Fe(1)
Fe(1)-Cp(1)a
Fe(1)-Cp(2)a
2.235(1)
2.234(1)
2.123(4)
2.131(3)
4.118(2)
1.634(13)
1.639(13)
Fe(1)-Cp(3)a
Fe(1)-Cp(4)a
Bond Angles (deg)
P(1)-Pd(1)-P(2)
Cl(1)-Pd(1)-Cl(2)
P(1)-Pd(1)-Cl(2)
99.64(9)
88.89(10
174.53(5)
P(3)-Pd(2)-P(4)
Cl(3)-Pd(2)-Cl(4)
P(3)-Pd(2)-Cl(4)
98.95(9)
88.04(10)
172.77(5)
P(1)-Pd(1)-P(2)
O(1)-Pd(1)-O(2)
O(1)-Pd(1)-P(1)
91.80(6)
86.58(14)
177.35(12)
Dihedral and Pseudotorsion Angles (deg)
C(1)Cp(1)Cp(2)C(6)a
33.81(1.10)
5.04(0.50)
C(15)Cp(3)Cp(4)C(20)a
31.49(1.40)
5.34(0.80)
C(1)Cp(1)Cp(2)C(6)a
16.20(1.25)
3.57(0.76)
RCpb
RCpb
RCpb
Short Intermolecular Distances (Å)
Cl(1)‚‚‚H(11B)
Cl(1)‚‚‚H(28B)
Cl(2)‚‚‚H(25C)
Cl(2)‚‚‚H(9)
2.881
2.893
2.723
2.912
2.254
Cl(2)‚‚‚H(14C)
Cl(3)‚‚‚H(19)
Cl(4)‚‚‚H(29A)
Cl(4)‚‚‚H(13C)
2.662
2.940
2.737
2.781
H(11C)‚‚‚H(2)
Inter- and Intramolecular Hydrogen Lengths (Å) and Angles (deg)
H(1A)-O(5)
1.891
1.938
158.33
176.62
H(1B)-O(4)
O(1)-H(1B)-O(4)
O(1)-H(1A)-O(5)
a Definitions: Cp(1), center of the C(1)-C(5) Cp ligand; Cp(2), center of the C(6)-C(10) Cp ligand; Cp(3), center of the C(15)-C(19) Cp
ligand; Cp(4), center of the C(20)-C(24) Cp ligand. b Dihedral angle between the Cp planes.
it showed a discrete stability (entries 1 and 2). A greater
activity was obtained by adding either BQ (entry 3) or
TsOH (entry 4). When they were added together, these
coreagents improved the productivity up to 10.0 kg of
product ((g of Pd) h)-1 (entry 5). It may be worth noticing
that this productivity is even larger than that obtained
by the traditional PdII catalyst modified with the dppp
ligand under the same reaction conditions (entry 21).38c
A comparable productivity was obtained with the depf
precursor 5, even in the absence of coreagents (entry
8). By simply adding 80 equiv of BQ, the activity of 5
increased to 12.9 kg of product ((g of Pd) h)-1 (entry 9).
Interestingly, unlike 4, no synergistic effect of the
coreagents was observed with 5 (entry 12). The protic
Figure 2. ORTEP drawing of 4. Thermal ellipsoids are
acid lowered the productivity, in fact (entry 8 vs entries
drawn at the 30% probability level. Hydrogen atoms have
10 and 11). Reactions lasting 3 h showed the catalyst
been omitted for clarity.
system generated by 5 to be rather stable both with no
added coreagent (entries 13 and 14) and with BQ alone
(entries 15 and 16).
coreagent. Then, TsOH and BQ were added, separately
or together, to the reaction mixtures using stoichiom-
Unlike the catalysts with the dmpf and depf precur-
sors, the dippf complex 6 promoted the exclusive forma-
tion of low-molecular-weight oxygenates, irrespective of
the experimental conditions (entries 17-20). The overall
selectivity in EtC(O)Et and EtC(O)OMe was remarkably
high, between 89 and 100%, and these products came
out generally in a 1/1 ratio. In contrast, the turnover
frequencies (TOFs) were rather modest, below 300 mol
etries that are typical for alkene carbonylation catalyzed
by diphosphine PdII complexes (20 equiv of TsOH and/
or 80 equiv of BQ).11,38 When appropriate, the catalytic
activity was evaluated for a longer reaction time,
generally 3 h. For the most active catalysts, experiments
were carried out also at a lower pressure (20 bar) in an
attempt to minimize mass transfer phenomena due to
the fast filling up of the reactor by the insoluble
copolymer.
of ethylene incorporated ((mol of Pd) h)-1
.
In either water or DIOX solvents, only the dmpf and
depf catalysts proved active for the carbonylation of
ethylene and the presence of TsOH in the starting
mixture was mandatory for high activity (Table 4).
Indeed, no activity at all was observed without TsOH
(entries 1, 6, and 15), while BQ alone did not signifi-
cantly promote the carbonylation reaction (entries 2, 7,
12, and 16). The combined addition of BQ and TsOH
The results of the reactions performed in MeOH are
reported in Table 3. In the absence of coreagents, the
dmpf precursor 4 was moderately active (entry 1), yet
(38) (a) Bianchini, C.; Meli, A.; Mu¨ller, G.; Oberhauser, W.; Passa-
glia, E. Organometallics 2002, 21, 4965. (b) Bianchini, C.; Lee, H. M.;
Meli, A.; Oberhauser, W.; Peruzzini, M.; Vizza, F. Organometallics
2002, 21, 16. (c) Bianchini, C.; Lee, H. M.; Meli, A.; Moneti, S.; Vizza,
F.; Fontani, M.; Zanello, P. Macromolecules 1999, 32, 4183.

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1025
Table 3. Carbonylation of Ethylene Catalyzed by [Pd(OTs)(H2O)(P-P)]OTs in MeOHa
alt-E-CO
oligomers
amt of amt of CO/C2H4
entry
no.
P-P
BQ
TsOH pressure time amt
Mn
productivityb TOFc (kg mol-1
mp EtC(O)OMe EtC(O)Et
d
ligand (equiv) (equiv)
(bar)
(h)
(g)
)
(°C)
TOFc
TOFc
%
1
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
depf
0
0
80
0
80
80
80
0
80
0
0
80
0
0
80
80
0
80
0
80
80
0
0
40
40
40
40
40
20
20
40
40
40
40
40
20
20
20
20
40
40
40
40
40
1
3
1
1
1
1
3
1
1
1
1
1
1
3
1
3
1
1
1
1
1
2.1
6.2
1.9
1.9
3 750
3 690
10 357
9 286
19 107
7 857
5 952
19 107
24 464
13 214
10 000
23 393
8 036
6 488
10 536
8 631
17.8
247
2
3
0
5.8
5.4
4
20
20
20
20
0
5.2
10.7
4.4
10.0
10.7
13.7
7.4
5.6
13.1
4.5
10.9
5.9
14.5
4.9
5
10.0
4.1
23.9
247
6
7
3.1
8
10.0
12.9
6.9
5.5
3.7
241
240
9
depf
0
10
11
12
13
14
15
16
17
18
19
20
21
depf
20
40
20
0
depf
5.3
depf
12.3
4.2
depf
depf
0
3.4
depf
0
5.5
depf
0
4.5
dippf
dippf
dippf
dippf
dppp
0
35
135
282
165
25
74
277
149
100
94
0
20
20
20
89
93
8.0
7.5
14 276
22.7
248
a Conditions: catalyst (0.01 mmol); MeOH (100 mL); 85 °C; 1400 rpm. b Productivity as kg of product ((g of Pd) h)-1
ethylene incorporated ((mol of Pd) h)-1 d Percentage of EtC(O)OMe + EtC(O)Et with respect to the overall oligomer production:
Et(C(O)CH2CH2)nH, n ) 1-4; MeO(C(O)CH2CH2)nH, n ) 1-4; MeO(C(O)CH2CH2)nC(O)OMe, n ) 1-4.
.
c TOF as mol of
.
Table 4. Carbonylation of Ethylene Catalyzed by [Pd(OTs)(H2O)(P-P)]OTs in Aqueous Solventsa
alt-E-CO
amt of
entry
no.
P-P
ligand
amt of
BQ (equiv)
TsOH
Mn
mp
(°C)
solvent
(equiv)
time (h)
g
productivityb
TOFc
(kg mol-1
)
1
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
dmpf
depf
DIOXd
DIOX
DIOX
DIOX
DIOX
H2O
0
80
0
80
80
0
80
0
80
80
0
80
0
80
0
80
0
80
80
0
0
1
1
1
1
3
1
1
1
1
3
1
1
1
1
1
1
1
1
3
0.0
0.2
3.5
3.8
7.4
0
0.0
0.2
3.3
3.6
2.3
0
2
357
6 250
6 786
4 405
3
20
20
20
0
20.8
242
4
5
6
7
H2O
0
0
8
H2O
20
20
20
0
0.2
0.3
0.6
1.4
1.6
11.3
11.9
0
0.2
0.3
357
536
357
9
H2O
10
11
12
13
14
15
16
17
18
19
H2O
0.2
DIOX
DIOX
DIOX
DIOX
H2O
1.3
2 500
2 857
20 179
21 250
depf
0
1.5
depf
20
20
0
10.6
11.2
5.7
249
depf
depf
depf
H2O
0
0
depf
H2O
20
20
20
0.7
0.8
2.0
0.7
0.7
0.6
1 250
1 429
1 190
depf
H2O
depf
H2O
a Conditions: catalyst (0.01 mmol); solvent (100 mL); CO/C2H4 (40 bar); 85 °C; 1400 rpm. b Productivity as kg of product ((g of Pd) h)-1
c TOF as mol of ethylene incorporated ((mol of Pd) h)-1 d DIOX ) 1/1 (v/v) H2O/1,4-dioxane.
.
.
resulted in an almost negligible increase in productivity
(entries 4, 9, 14, and 18).
productivity obtained with the same catalyst in MeOH
(Table 3, entries 9 and 12) and higher than those
reported for both Na2DPPPDS and DPPPr-S palladium-
(II) catalysts.39,40
Water alone was not a good solvent with either
catalyst; just to make a comparison, the observed
productivities were about 1 order of magnitude lower
than those reported for other PdII catalysts modified
with water-soluble chelating diphosphines such as Na2-
DPPPDS39 ((NaO3S(C6H4)CH2)2C(CH2PPh2)2) and DP-
PPr-S40 (1,3-C3H6(P(C6H4-m-SO3Na)2)2). However, the
activity of the depf catalyst was found to increase
remarkably in DIOX, up to 11.2 kg of product ((g of Pd)
h)-1 (entry 14), which is comparable to the highest
The number-average molecular weight (Mn) (deter-
mined by 1H NMR) of the alt-E-CO materials was found
to depend on the catalyst rather than on the experi-
mental conditions. Mn values between 3 and 6 kg mol-1
were obtained with the depf precursor, while the dmpf
complex gave products with Mn values in the range 17-
24 kg mol-1. The melting points of all materials (240-
250 °C) were comparable to those of copolymers com-
monly produced with chelating diphosphine ligands (see
Table 3, entry 21, for instance). Keto and ester end
groups in a 1/1 ratio were observed by NMR spectros-
copy for the alt-E-CO materials produced in MeOH,
(39) Bianchini, C.; Lee, H. M.; Meli, A.; Moneti, S.; Patinec, V.;
Pretrucci, G.; Vizza, F. Macromolecules 1999, 32, 3859.
(40) (a) Verspui, G.; Schanssema, F.; Sheldon, R. A. Appl. Catal.
2000, 198, 5. (b) Verspui, G.; Schanssema, F.; Sheldon, R. A. Angew.
Chem., Int. Ed. 2000, 39, 804.

1026 Organometallics, Vol. 24, No. 5, 2005
Bianchini et al.
Table 5. Terpolymerization of Carbon Monoxide with Ethene/Propene Catalyzed by
[Pd(OTs)(H2O)(P-P)]OTsa
alt-E/P-CO
entry
no.
P-P
amt of
amt of
amt of
amt
(g)
Mn
productivityb propene (%)c (kg mol-1
ligand solvent BQ (equiv) TsOH (equiv) propene (g)
)
mp (°C)
1
2
dmpf
dmpf
dmpf
dmpf
dmpf
depf
MeOH
MeOH
MeOH
DIOXd
DIOX
MeOH
MeOH
DIOX
80
80
80
0
20
20
20
20
20
0
3.6
9.4
14.0
3.4
7.0
4.0
11.4
3.4
5.0
6.8
4.7
6.4
7.0
3.2
5.5
11.5
5.6
6.1
5.9
5.3
2.1
5.8
10.8
6.7
6.2
8.2
8.3
4.9
3.9
3.3
3.2
14.1
236
221
220
225
211
231
195
228
199
224
3
7.5
9.9
4
3.4
5.9
4.1
5
0
8.2
6
80
80
0
0
80
12.2
6.0
3.4
7
depf
0
15.6
3.4
8
depf
20
20
20
6.5
9
depf
DIOX
MeOH
6.6
20.0
6.3
11.4
6.0
10
dpppe
17.0
a Conditions: catalyst (0.01 mmol); solvent (100 mL); CO/C2H4 (40 bar); 85 °C; 1 h; 1400 rpm. b Productivity as kg of product ((g of Pd)
h)-1 c Amount of propene incorporated in the polymeric chains as calculated by 1H NMR integration. d DIOX ) 1/1 (v/v) H2O/1,4-dioxane.
e Conditions: catalyst (0.01 mmol); MeOH (100 mL); CO/C2H4 (40 bar); 85 °C; 3 h; 1400 rpm.38b
.
whereas only keto end groups featured the polyketones
obtained in aqueous solvents.39,40
decreases by increasing the incorporation of propene in
the polymer backbone.44 The melting transition of the
terpolymers was characterized by a broad peak consist-
ing of two or three melting points (maximum of peaks);43
the temperature and the enthalpy associated with the
melting decreased by increasing the amount of pro-
pene.45 In both copolymers and terpolymers, lower
melting transition temperatures and enthalpy values
were observed in the second scan after cooling to room
temperature, which has been attributed to extensive
degradation on the basis of DSC measurements per-
formed in different temperature intervals and at slow
cooling rates.43
The dmpf and depf precursors 4 and 5 were able to
generate active catalysts also for the terpolymerization
of CO with ethylene and propene in either MeOH or
DIOX (Table 5). The incorporation of propene into the
polymer chains was high enough with either catalyst
(up to 16% with respect to ethylene) to obtain a
significant modulation of the polymer properties. In-
deed, some terpolymers showed melting points as low
as 199 °C with a decrease of ca. 50 °C as compared to
the copolymers. Surprisingly, the productivity in ter-
polymer obtained with the dmpf catalyst increased with
the initial amount of propene (entries 1-3 in MeOH and
entries 4 and 5 in DIOX).
As was observed for the copolymers, the Mn values of
the terpolymers obtained with the dmpf were higher
than those of the materials produced by the depf
catalyst. The NMR analysis of the terpolymers showed
the presence of keto and ester end groups in a ca. 1/1
ratio for the materials obtained in MeOH and of keto
groups only for the materials obtained in aqueous
solvents. The 13C NMR signals due to the -CH2C(O)-
CH(Me)CH2- and -CH2(CO)CH2CH(Me)- units were
in a ca. 1/1 ratio, thus indicating a comparable prefer-
ence for both 1,2- and 2,1-insertion of propene into the
propagating Pd-C(O)R.
The TGA analysis of the copolymers and terpolymers
showed all the products to degrade around 262-270 °C,
which is likely due to the presence of more than 15 ppm
of residual palladium in the materials.41,43 It is well-
known, in fact, that the residual palladium may promote
intra- and intermolecular dehydration reactions of
polyketones with formation of both cross-links and
heterocyclic compounds.42
The DSC analysis showed the occurrence of at least
two different types of endothermic transitions. The less
intense endotherm was observed at about 70-110 °C
and was attributed to the transition from the R to the â
phase, typical for alt-E-CO materials,43 while the higher
temperature transition (from 160 to 270 °C) was safely
assigned to the melting peaks. From a comparison of
the enthalpy values associated to the R/â transition
(when detectable), one may infer that the R content
The straightforward copolymerization of CO with
propene was attempted several times under different
experimental conditions. In all cases, however, both 4
and 5 produced oligomers in very low yield.
Operando HPNMR Study of the Carbonylation
of Ethylene Catalyzed by 4-6. A 1H and 31P{1H}
HPNMR study38,39 of the reactions catalyzed by the
precursors 4 and 5 in MeOH-d4 and D2O did not provide
any useful information on either intermediates or rest-
ing states. Instead, â-chelate species 23 were unam-
biguously detected along the methoxycarbonylation of
ethylene catalyzed by 6 (Figure 3).
â-Chelates are typical resting states of ethylene
carbonylation by PdII-chelating diphosphine catalysis,
and their presence in the reactions catalyzed by 6
accounts well for the observed formation of EtC(O)Et
and EtC(O)OMe. Authentication of the â-chelates was
provided by the synthesis and characterization of the
model complex [Pd(CH2CH2C(O)Me)(dippf)]B(Ar′)4 (19;
see below).
Besides â-chelates, the HPNMR spectra showed the
formation and persistent presence of the µ-hydrido
µ-carbonyl complex [Pd2(µ-H/D)(µ-CO)(dippf)2]OTs (20H/
D).11 This binuclear complex is a typical end product/
resting state of ethylene carbonylation by PdII-chelating
diphosphine catalysis, especially with ferrocenyldiphos-
phine ligands. Its formation has been proved to involve
the condensation PdII-H species with Pd0(CO) species,
as illustrated in Scheme 2 for a generic ferrocenyl-
diphoshine complex.
(44) Lagaron, J. M.; Vickers, M. E.; Powell, A. K.; Davidson, N. S.
Polymer 2000, 41, 3011.
(45) Lagaron, J. M.; Vickers, M. E.; Powell, A. K.; Bonner, J. G..
Polymer 2002, 43, 1877.
(41) DeVito, S.; Bronco, S. Polym. Degrad. Stab. 1999, 63, 399.
(42) Lommerts, B. J. Polymer 2001, 42, 6283.
(43) Sommazzi, A.; Garbassi, F. Prog. Polym. Sci. 1997, 22, 1547.

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1027
Figure 3. Variable-temperature 31P{1H} NMR study
(sapphire tube, MeOH-d4, 81.01 MHz) of the carbonylation
reaction of ethylene catalyzed by 6: (a) dissolving 6 in
MeOH-d4 under nitrogen at room temperature; (b) after
the tube was pressurized with 40 bar of (1/1) CO/C2H4 at
room temperature; (c) at 80 °C; (d) after the tube was cooled
to room temperature. Asterisks denote unknown species.
Figure 4. IR study of the reaction of 19 with water (CH2-
Cl2, room temperature): (a) addition of water; (b) after 15
min; (c) after 30 min. The asterisk denotes ν(CdO) at 1712
cm-1 of 2-butanone, and the open triangle denotes ν(CdO)
at 1634 cm-1 of 19.
â-chelates as demonstrated by van Leeuwen. Therefore,
an H2O sample (25 µL per 0.01 mmol) was syringed into
an NMR tube containing a CD2Cl2 solution of the
appropriate â-chelate complex. As expected, all com-
pounds were transformed at room temperature into the
binuclear complexes [Pd(µ-OH)(P-P)]2(B(Ar′)4)2 (P-P )
dmpf (20), depf (21), dippf (22)) with formation of free
2-butanone. The transformation rates increased in the
Scheme 2
order 17 (t1/2 ) 20 min) < 18 (t1/2 ) 7 min) < 19 (t1/2
)
4 min). The same order was found when the protonolysis
reactions were monitored by IR spectroscopy in CH2-
Cl2, looking at both the disappearance of the â-chelate
ν(CO) band and the concomitant formation of 2-bu-
tanone (ν(CdO) at 1712 cm-1). Figure 4 shows some
sequential spectra relative to the protonolysis of 19 (ν-
(CO) band at 1634 cm-1).
The faster protonolysis of the â-chelate 18 as com-
pared to 17 is apparently consistent with the lower
molecular weight of the alt-E-CO material obtained with
the depf precursor 5 (Table 3, entries 8 and 9 vs entries
1 and 5).
In Situ HPNMR and IR Studies of the Proto-
nolysis of the â-Chelates [Pd(CH2CH2C(O)Me)(P-
P)]B(Ar′)4. The â-chelates 17-19 were prepared through
a well-known synthetic protocol that involves, as the
final step, the reaction of ethylene with the acetyl
derivatives 14-16 (Scheme 3).
The reaction of PdII â-chelates with water is currently
used to mimic the chain transfer of CO/ethylene copo-
lymerization by protonolysis and, when followed by
NMR spectroscopy, provides a reliable method to esti-
mate the termination rate. In the dashed box of Scheme
3 is illustrated the protonolysis mechanism of the
Discussion
In this work, we have examined the catalytic behavior
of PdII complexes modified with ferrocenyldiphosphine
Scheme 3

1028 Organometallics, Vol. 24, No. 5, 2005
Bianchini et al.
Scheme 4
ligands bearing methyl, ethyl, and isopropyl substitu-
ents on the phosphorus atoms. The principal results
obtained may be summarized as follows. (i) Irrespective
of the solvent, the dmpf and depf complexes generate
selective catalysts for the production of alt-E-CO co-
polymers and terpolymers. (ii) The dmpf catalyst is
highly active in MeOH in the presence of both BQ and
TsOH. (iii) The depf catalyst is highly active in MeOH
even in the absence of oxidant or protic acid, whereas,
in aqueous solvents, the presence of TsOH is required
to maintain high activity. (iv) The dippf complex is an
active catalyst only in MeOH, where EtC(O)Et and EtC-
(O)OMe are selectively produced. (iii) The chemical
stability of all catalysts under methoxycarbonylation
conditions is generally high, even in the absence of
added oxidant or protic acid.
For a better comprehension of the results obtained,
especially in an attempt to rationalize structure-
activity relationships, it may be useful to recall the
behavior of the prototypical ligand dppf. In conjunction
with PdII, this ligand forms a poorly selective catalyst
for the carbonylation of ethylene in MeOH, yielding all
the compounds shown in Scheme 1.11 Moreover, its low
chemical stability under methoxycarbonylation condi-
tions does not allow one to extend the reaction time
above 1 h, which apparently limits the overall produc-
tivity. The overall TOFs under experimental conditions
comparable to those adopted in this work (MeOH, 30
bar of 1/1 CO/C2H4, 85 °C) are as follows: 1376 (with
neither BQ nor TsOH), 6143 (with 20 equiv of TsOH),
5464 (with 20 equiv of TsOH and 80 equiv of BQ).11
The dmpf and depf catalysts are much more stable
and productive than the dppf analogue, which can be
ascribed to the greater basicity of the alkyl-substituted
ligands (dppf , dmpf < depf < dippf).21 Cyclic voltam-
metric studies have shown, in fact, that the reduction
potential of PdII ferrocenyldiphosphine complexes be-
comes more negative as the basicity of the phosphorus
donors increases.11,46 Electron-rich phosphorus ligands
would therefore disfavor the degradation of PdII(diphos-
phine) catalysts that is essentially due to the reduction
of PdII to Pd0. For this reason, the CO-ethylene copo-
lymerization reactions generally provide higher produc-
tivities when carried out in the presence of oxidants,
such as BQ, and protic acids.11,38a,b,39,40
literature.22,43,47 It suffices here to say that, with either
Pd-H or Pd-OMe initiators as the starting material,
the alternating addition of ethylene/CO can proceed via
â-chelate (A) or γ-chelate (B) propagating species that
often are rate-limiting steps. The chain transfer can
occur by either methanolysis (M)/hydrolysis (H) of Pd-
acyl or protonolysis (P) of Pd-alkyl. Which of the two
initiation and termination steps prevails depends on
many factors, such as the specific catalyst, solvent, acid,
or oxidant concentration.22,47
The absence of acid end groups (-COOH) in the alt-
E-CO copolymers and terpolymers obtained from the
aqueous reactions (Tables 4 and 5) suggests that the
chain transfer occurs predominantly, if not exclusively,
by protonolysis (Scheme 4, path P). Whether protonoly-
sis is the predominant chain-transfer mechanism also
in MeOH is hard to assess on the basis of the chain-
end analysis, as the polyketones obtained in MeOH
contain ester and ketone end groups in a ca. 1/1 ratio.
Another point that would deserve a further investiga-
tion pertains to the molecular weights Mn of the polyke-
tones, which are higher with the dmpf catalyst (17-24
kg mol-1) than with the depf catalyst (3-6 kg mol-1).
In this case, steric effects should prevail over electronic
effects. In particular, it is possible that the bulkier ethyl
substituents favor the termination by both protonolysis
(destabilizing the propagating â-chelates, see the in situ
IR and HPNMR studies) and methanolysis.11a,18c,48
Surprisingly, the productivity in terpolymer obtained
with the dmpf catalyst has been found to increase with
the initial amount of propene (Table 5, entries 1-3 in
MeOH and entries 4 and 5 in DIOX). This finding is in
contrast with both the present data with depf and
previous reports, as the copresence of propene commonly
shortens the polyketone chains and also reduces the
overall productivity. Indeed, by favoring chain transfer
over chain propagation, the frequency of formation of
unstable Pd-H moieties would increase, thus accelerat-
ing catalyst degradation.
The increased productivity of the terpolymerization
reaction catalyzed by 4 is somehow reminiscent of the
so-called “comonomer effect” that is often encountered
in copolymerization reactions of ethylene with R-olefins
by metallocene or late-transition-metal catalysis.49 The
“comonomer effect” has still not been unraveled mecha-
On the basis of both catalytic and model studies, there
is no reason to exclude the noiton that the present dmpf
and depf catalysts copolymerize CO and ethylene via a
well-established mechanism, whose main steps are
illustrated in Scheme 4. Details of the catalytic cycles
together with kinetic data may be found in the relevant
(47) (a) Sen, A. Acc. Chem. Res. 1993, 26, 303. (b) Drent, E.;
Budzelaar, P. H. M. Chem. Rev. 1996, 96, 663. (c) Robertson, R. A. M.;
Cole-Hamilton, D. J. Coord. Chem. Rev. 2002, 225, 67. (d) Bianchini,
C.; Meli, A.; Oberhauser, W. Dalton 2003, 2627.
(48) Liu, J.; Heaton, B. T.; Iggo, J. A.; Whyman, R. Chem. Commun.
2004, 1326.
(49) (a) Spitz, R.; Duranel, L.; Masson, P.; Darricades-Llauro, M.
F.; Giyot, A. In Transition Metal Catalyzed Polymerizations; Quirk,
R. P., Ed.; Cambridge University Press: Cambridge, U.K., 1988; p 719.
(b) Herfert, N.; Montag, P.; Fink, G. Makromol. Chem. 1993, 194, 3167.
(46) Gusev, O. V.; Peterleitner, M. G.; Vologdin, N. V.; Kal’sin, A.
M. Electrochemistry 2003, 39, 1444.

Pd(II) 1,1′-Bis(dialkylphosphino)ferrocene Catalysts
Organometallics, Vol. 24, No. 5, 2005 1029
Scheme 5
Chart 3
Scheme 6
nistically, and the most common interpretation is that
the addition of the R-olefin wakes “sleeping metal
centers” in ethylene homopolymerization.49 In the present
terpolymerization reaction, it is possible that propene
is more effective than ethylene for the stabilization of
either PdII-H or Pd0 intermediates (Scheme 2). Once
coordinated to palladium, propene can either insert into
Pd-H or be displaced by ethylene. In this picture, the
coordination of propene might be facilitated by the
(diphosphino)ferrocenyl ligand with the smallest sub-
stituents at phosphorus: i.e., dmpf.
If the higher basicity of dmpf and depf as compared
to dppf is the key factor accounting for the higher
productivity exhibited by 4 and 5, the basicity of the
phosphorus donors cannot explain why the dippf-modi-
fied catalyst derived from 6 is much less active and,
most importantly, selective for methyl propanoate and
3-pentanone. Steric effects apparently play a major role
in determining the catalytic activity of 6. As shown in
Chart 3, the phenyl substituents18a as well as the ethyl
ones allow the phosphorus atoms to be mutually cis in
the acetyl complexes [Pd(NCMe)(C(O)Me)(P-P)]+ (P-P
) dppf, depf), whereas the i-Pr groups favor the κ3-P,P,-
Fe bonding mode.18a,c In the case of coligands with no
electron-withdrawing character such as the methyl
group, the bulkier t-Bu groups are required for the trans
disposition of the phosphorus atoms.18b The formation
of the κ3-P,P,Fe bonding mode is actually favored by
electron-withdrawing coligands (-C(O)R and -C(O)OR,
for instance) that make palladium(II) more suitable to
receive the iron-centered e2g electron density.3,11a,13,18
complex (cycle C). The former cycle is probably less
important than cycle C. Indeed, the addition of BQ,
which increases the concentration of Pd-OMe in the
catalytic mixtures,22,47b yields less methyl propanoate
than the reaction performed in the presence of TsOH
alone (Table 3, entry 18 vs entry 19). The stability of
the κ3-P,P,Fe carboalkoxy intermediate to ethylene
insertion may contribute to the sluggishness of cycle
A.11a Indeed, the insertion of ethylene requires a free
coordination site cis to the ester group and cis phos-
phorus atoms. This process is apparently difficult to
accomplish, due to the electron-withdrawing character
of the ester ligand that strengthens the Fe-Pd bond,
favoring a trans disposition of the phosphorus atoms.
3-Pentanone is exclusively produced in cycle B by
protonolysis of the keto â-chelate. Since methyl pro-
panoate and 3-pentanone are obtained with comparable
TOFs (Table 3, entries 17-20), one may conclude that
the reactions of the κ3-P,P,Fe acyl intermediate with
either MeOH (methanolysis) or ethylene (migratory
insertion) occur at a comparable rate. This suggests that
the step limiting both rates is just the hapticity change
of dippf from κ3-P,P,Fe to κ2-P,P, because both the
methanolysis of the propionyl complex and the forma-
tion of the â-chelate require cis-P atoms to occur.18c,48
The overall selectivity of 6 in methyl propanoate and
3-pentanone shows unequivocally that the protonolysis
of the keto â-chelate in cycle B is much faster than the
uptake of CO to give the next γ-chelate (see Scheme 4).
The very fast protonolysis of the first â-chelate (see the
in situ IR and HPNMR studies) can also contribute to
make the dippf precursor 6 inactive in aqueous solvents.
Indeed, the catalytic reaction would immediately stop
by incorporation of active palladium(II) into an inactive
µ-OH binuclear complex (Scheme 6).
Just the formation of a dative Fe-Pd bond, especially
in the acyl and carboalkoxy complexes, may be the factor
that makes the dippf catalyst selective for methyl
propanoate and 3-pentanone. Scheme 5 shows the
possible pathways for the production of the latter
products.
Methyl propanoate can be obtained either by proto-
nolysis of the â-chelate bearing the ester group (cycle
A, dashed box) or by methanolysis of the Pd-propionyl
To the best of our knowledge, 6 is the only bis-
(diorganylphosphino)ferrocenyl PdII complex capable of
producing significant amounts of 3-pentanone in eth-

1030 Organometallics, Vol. 24, No. 5, 2005
Bianchini et al.
ylene methoxycarbonylation reactions. In fact, all the
other known catalysts for low-molecular-weight oxygen-
ates give predominantly methyl propanoate.3,11,47c
and 3-pentanone. The macromolecular properties of the
polyketones can be tuned by an appropriate choice
either of the metallocene ligands or of the reaction
medium.
Conclusions
Acknowledgment. Thanks are due to the European
Commission (Contract HPRN-CT-2002-00196, PAL-
LADIUM project), the Russian Foundation for Basic
Research (Grant 03-03-32471), and the Science Support
Foundation of the Russian Federation for financial
support.
Palladium(II) complexes of the formula [Pd(H2O)-
(OTs){1,1′-bis(dialkylphosphino)ferrocene}]OTs (alkyl )
Me, Et, i-Pr) are active catalysts for the carbonylation
of ethylene in MeOH, water, or a water/1,4-dioxane
mixture. It has been found that the catalytic activity is
affected by both electronic and steric effects induced by
the ferrocenyldiphosphine ligands. Electronic effects
play a major role in controlling the productivity in either
alternating CO-ethylene copolymers or CO-ethylene-
propene terpolymers, while steric effects are crucial in
driving the selectivity toward either alt-E-CO materials
or the single-carbonylation products methyl propanoate
Supporting Information Available: TGA and DSC data
of selected polymers (Table 1S and Figure 1S) and text and
tables giving crystallographic data for compounds 1 and 4. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM049109W