Bidentate phosphorus complexes of oxodimethylenemethanepalladium(II)

Article abstract of DOI:10.1016/S0277-5387(02)01287-1

The reactions of the zerovalent palladium complex [Pd₂(dba)₃]·CHCl₃ (dba = dibenzylideneacetone, PhCH=CH-C(O)-CH= CHPh), in the presence of bidentate phosphorus ligand L₂ and dioxygen, with esters of 3-oxopentan

Full text of DOI:10.1016/S0277-5387(02)01287-1

Polyhedron 21 (2002) 2653ꢂ2657
/
www.elsevier.com/locate/poly
Bidentate phosphorus complexes of
oxodimethylenemethanepalladium(II)
Ayfer Mentes a,ꢀ,1, Raymond D.W. Kemmitt b
a Department of Chemistry, Incivez Zonguldak Karaelmas University, Zonguldak 67100, Turkey
b Inorganic Research Laboratories, Department of Chemistry, The University of Leicester, Leicester LE1 7RH, UK
Received 12 March 2002; accepted 10 October 2002
Abstract
The reactions of the zerovalent palladium complex [Pd2(dba)3]×
CHPh), in the presence of bidentate phosphorus ligand L2 and dioxygen, with esters of 3-oxopentanedioic acid (RCH2COCH2R) in
diethylether, afford, in good yield, the palladocyclobutan-3-one compounds [Pd(CHRCOCHR)L2] [RꢁCO2Me, L2ꢁdppe, dppp,
dppb, dppf]. The compounds [Pd(CHRCOCHR)L2] [RꢁCO2Me, L2ꢁdppe, dppp, dppb, dppf; RꢁCO2Et, L2ꢁdppe] are also
formed by treating dichloromethane solution of [Pd(COD)Cl2] (CODꢁcyclo-octa-1,5-diene) with RCH2COCH2R in the presence
of silver(I) oxide and the appropriate bidentate ligand. Ligand exchange reactions of [Pd(h3-CHRCOCHR)(L?)2], (Rꢁ
CO2Me,
L?ꢁPPh3 or AsPh3) complexes with appropriate chelating phosphorus donor ligand in dichloromethane have also afforded new
complexes [Pd(CHRCOCHR)L2] (L?ꢁPPh3, L2ꢁdppe, dppp; L?ꢁAsPh3, L2ꢁdppe, dppp, dppb, dppf). Spectroscopic data (IR,
/
CHCl3 (dbaꢁ
/
dibenzylideneacetone, PhCHÄ
/
CHÃ
/
C(O)Ã
/
CHÄ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
NMR, FAB MS) for the new compounds are reported.
# 2002 Published by Elsevier Science Ltd.
Keywords: Cyclo-addition; Metallacycles, oxo ligands; P ligands; Palladium; Structure elucidation
1. Introduction
some oxodimethylenemethanepalladium complexes of
bidentate phosphorus ligand.
Interest in organometallic derivatives of 1,3-dipoles
trimethylenemethane and oxodimethylenemethane de-
rives their participation as key intermediates in a range
of cyclo-addition reactions [1]. There are several reports
of substituted or unsubstituted oxodimethylenemetha-
nepalladium and platinum complexes with monodentate
2. Results and discussion
Oxodimethylenemethanepalladium complexes were
synthesised by three different methods as shown in
Scheme 1. In method I, the reactions of zerovalent
palladium complex [Pd2(dba)3]×
the presence donor ligands L2 (L2ꢁ
phosphorus and arsenic donor ligands [2ꢂ9]. The
/
corresponding bidentate phosphorus complexes of pla-
tinum have also been reported [10,11].
/
CHCl3 with ketones in
Although oxodimethylenemethanepalladium com-
plexes with monodentate phosphorus have been well
characterised [6,10] there is no information on com-
plexes with bidentate phosphorus ligands. In this paper
we now describe the preparations and properties of
/dppe, dppp, dppb,
dppf) and dioxygen were investigated. In method II,
silver(I) oxide was used for the for the synthesis of
metalꢂ
/
carbon s-bonds starting from readily available
halide complexes. Thus, silver(I) oxide acts con-
metalꢂ
/
veniently as both a halide-abstracting reagent and a
strong base to remove weakly acidic protons. In method
III ligand displacement reactions from [Pd(h3-
ꢀ Corresponding author. Tel.: ꢃ
257-4181
/
90-272-257-7225; fax: ꢃ90-372-
/
CH{CO2Me}COCH{CO2Me})(L?)2], (L?ꢁPPh3 (2a)
/
or AsPh3 (2b)) with appropriate chelating phosphorus
donor ligand in dichloromethane are described.
E-mail address: ayfermentes@yahoo.com (A. Mentes).
1
E-mail: mentes@karaelmas.edu.tr
0277-5387/02/$ - see front matter # 2002 Published by Elsevier Science Ltd.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 2 8 7 - 1

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A. Mentes, R.D.W. Kemmitt / Polyhedron 21 (2002) 2653ꢂ2657
/
static structure, with two signals for the methyl protons
of the CO2Me groups on the oxodimethylenemethane,
and two signals for the CH protons. The two signals for
the CH protons can be assigned on the basis of previous
work [6]. The equatorial hydrogen, the lower frequency
signal, couples to both the cis-phosphorus and trans-
phosphorus, and appears as a broad signal. The higher
frequency signal is assigned to the axial hydrogen,
showing no discernible coupling to its cis-phosphorus
ligand and appears as a doublet (3J(PH)ꢁ
8.53 Hz) due
/
to trans-phosphorus coupling only. In addition to these
signals there is a methyl resonance at d 2.84 ppm and a
doublet at d 3.20 ppm due to the CH protons of a small
amount of the equatorialꢂ/equatorial isomer, which is
also present.
Previous studies on oxodimethylenemethane metal
complexes have shown that the complexes undergo
ring inversion in solution at room temperature and
1
that the complexes exhibited temperature dependent H
NMR spectra. Activation energies for ring inversion
1
have been determined. Examination of the H NMR
spectra of 3a showed that the CH protons of the
palladium complex appeared as a doublet (d 4.34) at
room temperature which split into a doublet at d 4.68
and a broad singlet at d 3.97 ppm. These signals are
assigned to the axial and equatorial protons of 3a,
respectively, by analogy with related systems [6]. The
coalescence temperature for the complex 3a, was found
to be ꢄ
/
48 8C and application of the GutowskyꢂHolm
/
equations [12] gave a value for barrier to ring inversion
of 43.1 kJ molꢄ1. This value is very similar to those
observed for the reported palladacyclobutan-3-ones [6].
A coalescence temperature for the methyl resonances in
3a could not be observed.
Scheme 1. Complex A: [Pd(h3-CH{CO2Me}COCH{CO2Me})(L?)2]
(L?ꢁPPh3 or AsPh3).
/
The room temperature 1H NMR spectra of com-
plexes, [Pd(h3-CH{CO2Me}COCH{CO2Me})L2] (3),
showed the expected features, with a singlet resonance
at low frequency for methyl protons of the CO2Me
groups and one doublet for the CH protons of the
The CH protons of the palladium complex 3d
appeared as a doublet (d 4.34) at room temperature
which collapsed to a broad signal at ꢄ34 8C. At lower
/
temperature the complex began to crystallise from the
solution.
The IR spectra of the oxodimethylenemethane metal
1
oxodimethylenemethane ligand. The H NMR spectra
complex
of
the
palladium
[Pd(h3-
complexes normally exhibit five maxima in the 1705ꢂ
/
CH{CO2Et}COCH{CO2Et})(dppe)] (4a), exhibited a
triplet resonance at low frequency for the methyl
protons, a quartet for the methylene protons of the
CO2Et groups, and one doublet for the CH protons of
the oxodimethylenemethane ligand.
The room temperature 31P{1H} NMR spectra for all
the bidentate phosphorus complexes of oxodimethyle-
nemethane consist of two sets of resonances, in a 5:1 or
4:1 ratio. This is thought to be due to the presence of
1550 cmꢄ1 region. For the complexes with methyl ester
groups, two bands are observed in the region 1705ꢂ1660
/
cmꢄ1 and are assigned to n(CO) of the ester carbonyls.
The carbonyl of the oxodimethylenemethane ligand
gives a band in the region of 1595ꢂ
1580 cmꢄ1. The
observed frequencies for the ring carbonyl are lower
than that found for the analogous platinum complexes
/
which occurs in the region of 1625ꢂ
The lower values for the ring carbonyls of palladium
complexes suggest that the metalꢂCO interactions in
/
1635 cmꢄ1 [2,11].
both the equatorialꢂ/equatorial and more favourable
/
axialꢂequatorial isomers. In order to identify the
/
palladium complexes are stronger than those in plati-
num complexes.
The FAB MS spectra indicate the presence of parent
ions and fragmentation patterns due to loss of the
dialkyl ester and the donor ligand.
1
presence of both isomers, various low temperature H
NMR experiments were performed. The 1H NMR
spectrum of 3a measured at ꢄ
/
86 8C at 300 MHz,
showed the expected features for the axialꢂ
/equatorial

A. Mentes, R.D.W. Kemmitt / Polyhedron 21 (2002) 2653ꢂ
/
2657
2655
3. Experimental
diethyl ether gave a pale yellow solid, 3a (0.250 g,
38%). Found: C, 59.0; H, 5.0; P, 8.9. C33H32O5P2Pd
Microanalytical results, melting points (m.p.), IR,
mass spectral and NMR data are presented for the new
complexes. Microanalysis were carried out by Butter-
worth Laboratories Ltd., 54-56 Waldegrave Rd., Ted-
dington, Middlessex, TW11 8LG. M.p. were measured
on a Gallenkamp apparatus and are uncorrected. The
FAB MS spectrum of the solid complexes were obtained
on a Kratos Concept Double Focusing Sector Mass
requires C, 58.6; H, 4.7; P, 9.2%. M.p. 180ꢂ
/
182 8C
(dec.); IR: 1705, 1668, 1595 n(CO) cmꢄ1. 1H NMR (250
MHz, [2H1]chloroform), dꢁ
/
7.85ꢂ
/
7.32 (20H, m, Ph),
4.34 [2H, d, CH, j J(PH)transꢃ3
/
J(PH)cisj 8.53], 2.94
3
1
(6H, s, CH3), 2.50ꢂ2.20 (4H, m, CH2); H NMR (300
/
MHz, [2H1] dichloromethane, ꢄ
/
86 8C), dꢁ
/
7.80ꢂ
(20H, m, Ph), 4.68 [1H, d, CH, J(PH) 10.8], 3.97 (1H,
bs, CH), 2.68 (3H, s, CH3), 2.65 (3H, s, CH3), 2.13ꢂ2.0
(4H, m, CH2CH2) ppm. 31P{1H} NMR (24 MHz,
/7.18
3
/
1
Spectrometer. The H NMR spectra were recorded at
room temperature in [2H1]chloroform on a Bruker
AM300 spectrometer operating at 300.13 MHz or on a
Bruker ARX 250 spectrometer at 250.13 MHz with
SiMe4 (0.0 ppm) as internal reference. Coupling con-
stants J are in Hz. The 31P{1H} NMR spectra were
recorded at room temperature in dichloromethane on a
JEOL JNM-FX90 spectrometer operating at 36.2 MHz,
with [P(OH)4]ꢃ in [2H2]water (0.0 ppm) as external
CD2Cl2), dꢁ49.8 ppm (s), 48.3 ppm (s) (5:1 ratio).
/
Mass spectrum (FAB), [MH]ꢃ 677.
3.1.2. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppp)] (3b)
A mixture of [Pd2(dba)3]×/CHCl3, dppp (1 g, 2.4
mmol) and 3-oxopentanedioic acid dimethyl ester was
stirred for 72 h. Recrystallisation from dichloro-
reference. The IR spectra were recorded on a Perkinꢂ
Elmer 580B spectrophotometer in Nujol mulls between
NaCl plates in the range 2000ꢂ
1400 cmꢄ1
/
methaneꢂdiethyl ether gave a pale yellow solid, 3b (0.5
/
g, 75%). Found: C, 59.3; H, 5.2; P, 8.3. C34H34O5P2Pd
requires C, 59.1; H, 5.0; P, 9.0%. IR: 1705, 1665, 1592
/
.
1
n(CO), cmꢄ1. H NMR (250 MHz, [2H1]chloroform),
All reactions were performed under a dry, oxygen-
free, nitrogen atmosphere unless otherwise stated, using
solvents which were dried and distilled under nitrogen
just prior to use. The following drying agents were used:
dichloromethane (calcium hydride) and diethyl ether
dꢁ
/
7.70ꢂ
/
7.22 (20H, m, Ph), 3.6 (2H, m, CH), 2.78 (6H,
1.92(6H, m, CH2CH2) ppm. 31P{1H}
s, CH3), 2.35ꢂ
/
NMR (24 MHz, CH2Cl2), dꢁ6.7 ppm (s), 5.5 ppm (5:1
/
ratio). Mass spectrum (FAB), [MH]ꢃ 691.
(sodiumꢂ
fraction that boils in the 40ꢂ
/
benzophenone). Light petroleum refers to the
60 8C range. The com-
/
3.1.3. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppb)] (3c)
pounds triphenylphosphine (Lancaster), silver(I) oxide,
1,3-dimethylacetonedicarboxylate, triphenylarsine, 1,3-
diethylacetone-dicarboxylate 1,2-bis(diphenylphosphi-
no)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-
A mixture of [Pd2(dba)3]×
/
CHCl3, dppb (0.93 g, 2
mmol) and 3-oxopentanedioic acid dimethyl ester was
stirred for 96 h. Recrystallisation from dichloro-
bis(diphenylphosphino)butane,
sphino)-ferrocene (Aldrich) were used as supplied by
commercial sources. The complexes [Pd2(dba)3]×CHCl3
[13], [PdCl2(COD)] [14], and [Pd{h3-CH(CO2Me)CO-
CH(CO2Me)}(L?)2] (L?ꢁPPh3 or AsPh3) [6] were all
1,1?-bis(diphenylpho-
methaneꢂ
g, 90%). Found: C, 59.2; H, 5.6; P, 8.5. C35H36O5P2Pd
requires C, 59.6; H, 5.1; P, 8.8%. M.p. 220ꢂ222 8C
(dec.). IR: 1705, 1670, 1556 n(CO), cmꢄ1. H NMR
(250 MHz, [2H1]chloroform), dꢁ
7.8ꢂ7.24 (20H, m,
Ph), 4.2 (2H, br, CH), 3.0 (3H, s, CH3), 2.9 (3H, s,
CH3), 2.50ꢂ
2.20 (8H, m, CH2CH2) ppm. 31P{1H} NMR
(24 MHz, CDCl3), dꢁ19.5 ppm (s). Mass spectrum
(FAB), [MH]ꢃ 705.
/diethyl ether gave a pale yellow solid, 3c (0.7
/
/
1
/
/
/
prepared as described in the literature. Precious metal
salts were obtained on loan from Johnson Matthey plc.
/
/
3.1. Method I
An excess of the appropriate diphosphine was added
CHCl3 (0.5 g, 0.48
to a stirred suspension of [Pd2(dba)3]×
/
3.1.4. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppf)] (3d)
mmol) in diethyl ether (50 cm3) containing the required
3-oxopentanedioic acid dialkyl ester (1 cm3) under
A mixture of [Pd2(dba)3]×/CHCl3 (0.3 g, 0.3 mmol),
oxygen for 24ꢂ/96 h. The resulting pale yellow solid
dppf (0.28 g, 0.5 mmol) and 3-oxopentanedioic acid
dimethyl ester was stirred for 48 h. Recrystallisation
was collected, recrystallised from dichloromethaneꢂ
/
diethyl ether and dried in vacuo.
from dichloromethaneꢂ
(0.420 g, 84%). Found: C, 59.5; H, 4.2; P, 7.9. C41H36-
FeO5P2Pd requires C, 59.1; H, 4.4; P, 7.4%. M.p. 178ꢂ
/
diethyl ether gave a solid, 3d
3.1.1. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppe)] (3a)
/
180 8C (dec.). IR: 1690, 1660, 1590 n(CO), cmꢄ1. H
1
A mixture of [Pd2(dba)3]×
and 3-oxopentanedioic acid dimethyl ester was stirred
for 24 h. Recrystallisation from dichloromethaneꢂ
/CHCl3, dppe (0.4 g, 1 mmol)
NMR (300 MHz, [2H1]chloroform), dꢁ
/
7.74ꢂ
/
7.08
j
3
(20H, m, Ph), 4.34 [2H, d, CH, j J(PH)transꢃ3
/
J(PH)cis
3.83 (8H, m, Cp), 2.98 (6H, s, CH3) ppm.
/
j 10.6], 4.63ꢂ
/

2656
A. Mentes, R.D.W. Kemmitt / Polyhedron 21 (2002) 2653ꢂ2657
/
31P{1H} NMR (24 MHz, CDCl3), dꢁ
/
28.2 (s) and 24.4
ppm (s) (1:4 ratio). Mass spectrum (FAB), [MH]ꢃ 833.
3.2.5. Preparation of [Pd{h3-
CH(CO2Et)COCH(CO2Et)}(dppe)] (4a)
A mixture of [PdCl2(COD)] (0.2 g, 0.7 mmol), dppe
(0.3 g, 0.75 mmol), 1,3-diethylacetone dicarboxylate and
an excess of silver(I) oxide in dichloromethane gave a
pale yellow solid, 4a (0.25 g, 50%). Found: C, 59.5; H,
4.7; P, 9.0. C33H32O5P2Pd requires C, 59.7; H, 5.1; P,
3.2. Method II
An excess of ligand was added to a stirred solution of
[PdCl2(COD)] (0.5 g, 1.75 mmol) in dichloromethane
(25 cm3) containing the required 1,3-dialkylacetone
dicarboxylate (1 cm3) and an excess of silver(I) oxide
(0.7 g) under nitrogen and was refluxed for 5 h.
Filtration to remove silver salts afforded a pale yellow
solution which was evaporated to dryness under reduced
pressure and redissolved in dichloromethane (5 cm3)
followed by the addition of diethyl ether or petroleum
ether to give a pale yellow solid. Removing the solid by
filtration afforded the complex which was dried in
vacuo.
8.8%. M.p. 170ꢂ
1580, n(CO), cmꢄ1. H NMR (250 MHz, [2H1]chloro-
form), dꢁ7.98ꢂ7.54 (20H, m, Ph), 4.74 (2H, d, CH),
/
172 8C (dec.). IR: 1730, 1700, 1668,
1
/
/
3.85 (4H, q, CH2CH3), 2.48 (4H, m, CH2CH2), 1.0 (6H,
t, CH2CH3) ppm. 31P{1H} NMR (24 MHz, CH2Cl2),
dꢁ49.2 ppm (s), 48.8 ppm (s) (5:1 ratio). Mass
/
spectrum (FAB), [MH]ꢃ 705.
3.3. Method III
A
mixture
of
[Pd(h3-
PPh3 (2a)
CH{CO2Me}COCH{CO2Me})(L?)2], (L?ꢁ
/
3.2.1. Preparation of [Pd{h3-
or AsPh3 (2b)) and the appropriate ligand was refluxed
in dichloromethane for several hours. The resulting
CH(CO2Me)COCH(CO2Me)}(dppe)] (3a)
A mixture of [PdCl2(COD)], dppe (0.7 g, 1.75 mmol),
1,3-dimethylacetone dicarboxylate and an excess of
silver(I) oxide in dichloromethane gave a pale yellow
solid which was identified as 3a (0.210 g, 18%) by
comparison of its IR and 1H NMR spectra with an
authentic sample.
mixture was evaporated to 1ꢂ
2 cm3 volume under
/
reduced pressure and addition of diethyl ether afforded
a pale yellow solid which was filtered and washed with
diethyl ether and then dried in vacuo.
3.3.1. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppe)] (3a)
A mixture of 2a (0.085 g, 0.1 mmol) and dppe (0.06 g,
1.5 mmol) in dichloromethane gave a pale yellow solid,
3a (0.070 g, 98%) which was identified by comparison of
3.2.2. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppp)] (3b)
A mixture of [PdCl2(COD)] (0.2 g, 0.7 mmol), dppp
(0.43 g, 1 mmol), 1,3-dimethylacetone dicarboxylate and
an excess of silver(I) oxide in dichloromethane gave an
oily residue of 3b which was identified by comparison of
1
its IR, H and 31P{1H} NMR spectra with that of an
authentic sample.
3.3.2. Preparation of [Pd{h3-
1
its IR, H and 31P{1H} NMR spectra with that of an
CH(CO2Me)COCH(CO2Me)}(dppp)] (3b)
A mixture of 2a (0.1 g, 0.125 mmol) and dppp (0.1 g,
0.24 mmol) in dichloromethane gave a pale yellow solid,
3b (0.04 g, 50%) which was identified by comparison of
authentic sample.
3.2.3. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppb)] (3c)
1
its IR, H and 31P{1H} NMR spectra with that of an
A mixture of [PdCl2(COD)] (0.2 g, 0.7 mmol), dppb
(0.45 g, 1.1 mmol), 1,3-dimethylacetone dicarboxylate
and an excess of silver(I) oxide in dichloromethane gave
a pale yellow solid of 3c (0.325 g, 66%) which was
identified by comparison of its IR, 1H and 31P{1H}
NMR spectra with that of an authentic sample.
authentic sample.
3.3.3. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppe)] (3a)
A mixture of 2b (0.2 g, 0.225 mmol) and dppe (0.1 g,
0.25 mmol) in dichloromethane gave a pale yellow solid,
3a (0.140 g, 92%) which was identified by comparison of
1
its IR, H and 31P{1H} NMR spectra with that of an
3.2.4. Preparation of [Pd{h3-
authentic sample.
CH(CO2Me)COCH(CO2Me)}(dppf)] (3d)
A mixture of [PdCl2(COD)], dppf (0.195 g, 0.35
mmol), 1,3-dimethylacetone dicarboxylate and an excess
of silver(I) oxide in dichloromethane gave a solid of 3d
(0.280 g, 96%) which was identified by comparison of its
IR, 1H and 31P{1H} NMR spectra with that of an
authentic sample.
3.3.4. Preparation of [Pd{h3-
CH(CO2Me)COCH(CO2Me)}(dppp)] (3b)
A mixture of 2b (0.1 g, 0.11 mmol) and dppp (0.7 g,
1.7 mmol) in dichloromethane gave pale yellow solid, 3b
(0.025 g, 33%) which was identified by comparison of its

A. Mentes, R.D.W. Kemmitt / Polyhedron 21 (2002) 2653ꢂ
/
2657
2657
IR, 1H and 31P{1H} NMR spectra with that of an
authentic sample.
References
[1] J. Mann, Tetrahedron 42 (1986) 4611.
3.3.5. Preparation of [Pd{h3-
[2] D.A. Clarke, R.D.W. Kemmitt, M.A. Mazid, D.R. Russell, M.D.
Schilling, J.L.S. Sherry, J. Chem. Soc., Dalton Trans. (1984) 1993.
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Russell, B. Lam, S.K. Kang, T.A. Albright, Organometallics 8
(1989) 1991.
CH(CO2Me)COCH(CO2Me)}(dppb)] (3c)
A mixture of 2b (0.1 g, 0.11 mmol) and dppb (0.1 g,
0.24 mmol) in dichloromethane gave a pale yellow solid
of 3c (0.021 g, 26%) which was identified by comparison
[4] D.A. Clarke, R.D.W. Kemmitt, M.A. Mazid, D.R. Russell, M.D.
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Chem. Soc., Dalton Trans. (1985) 259.
1
of its IR, H and 31P{1H} NMR spectra with that of an
authentic sample.
3.3.6. Preparation of [Pd{h3-
[7] A. Imran, R.D.W. Kemmitt, A.J. Markwick, P. McKenna, D.R.
Russell, L.J.S. Sherry, J. Chem. Soc., Dalton Trans. (1985) 549.
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(1995) 2538.
CH(CO2Me)COCH(CO2Me)}(dppf)] (3d)
A mixture of 2b (0.17 g, 0.18 mmol) and dppf (0.1 g,
0.19 mmol) in dichloromethane gave a pale yellow solid,
3d (0.090 g, 60%) which was identified by comparison of
1
its IR, H and 31P{1H} NMR spectra with that of an
[10] R.D.W. Kemmitt, P. McKenna, D.R. Russell, L.J.S. Prouse, J.
Chem. Soc., Dalton Trans. (1989) 345.
authentic sample.
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Acknowledgements
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The Zonguldak Karaelmas University, Turkey, is
thanked for financial support, the University of Leice-
ster, UK, for laboratory facilities, and Johnson Matthey
plc. for the supply of palladium metal salts.