Palladium(II) complexes of new OPN phosphine ligands and their application in homogeneously catalysed reactions of CO with alkenes or alkynes

Article abstract of DOI:10.1039/b405586c

Palladium complexes of a series of functionalised phosphines bearing the OPN donor set [2-pyCH₂P(Ph)CH₂-(CHOCH₂CH ₂CH₂), 1; 2-py CH₂P(Ph)-CH₂CH ₂(CHOCH₂CH₂O), 2; 2-pyCH₂P(Ph) CH₂CH₂CO₂Me, 3; 2-pyP(Ph)CH ₂(CHOCH₂CH₂-CH₂), 4; 2-py = 2-pyridyl] have been prepared and characterised. Ligands 1-3 form five membered P-N chelates which is confirmed for PdCl₂ complexes of 1 and 3 by X-ray crystallography. O-coordination appears to be generally disfavoured although there is evidence of transient O-coordination for selected Pd complexes of 4. Palladium methyl and acetate complexes of all four ligands have been tested for catalytic activity in ethene/CO copolymerisation as well as alkoxy-carbonylation of propyne. Complexes of 1 and 4 show some activity in the copolymerisation reaction and complexes of 4 are active in the methoxy carbonylation of propyne. Unlike related pyridyl(diaryl)phosphines, 4 produces a much more stable catalyst system that does not require large excesses of ligand to maintain activity.

Full text of DOI:10.1039/b405586c

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F U L L P A P E R
Palladium(II) complexes of new OPN phosphine ligands and their
application in homogeneously catalysed reactions of CO with
alkenes or alkynes†
Melinda J. Green,a Kingsley J. Cavell,*a Peter G. Edwards,*a Robert P. Tooze,‡b
Brian W. Skeltonc and Allan H. Whitec
a
School of Chemistry, Cardiff University, PO Box 912, Cardiff, UK CF10 3TB
Lucite International, Wilton, Middlesbrough, UK TS80 8JE
Department of Chemistry, University of Western Australia, Nedlands, 6907, Australia
b
c
Received 14th April 2004, Accepted 28th July 2004
First published as an Advance Article on the web 31 August 2004
Palladium complexes of a series of functionalised phosphines bearing the OPN donor set [2-pyCH2P(Ph)CH2-
(CHOCH2CH2CH2), 1; 2-py CH2P(Ph)–CH2CH2(CHOCH2CH2O), 2; 2-pyCH2P(Ph)CH2CH2CO2Me, 3; 2-
pyP(Ph)CH2(CHOCH2CH2-CH2), 4; 2-py = 2-pyridyl] have been prepared and characterised. Ligands 1–3 form five
membered P–N chelates which is confirmed for PdCl2 complexes of 1 and 3 by X-ray crystallography. O-coordination
appears to be generally disfavoured although there is evidence of transient O-coordination for selected Pd complexes of
4. Palladium methyl and acetate complexes of all four ligands have been tested for catalytic activity in ethene/CO copoly-
merisation as well as alkoxy-carbonylation of propyne. Complexes of 1 and 4 show some activity in the copolymerisation
reaction and complexes of 4 are active in the methoxy carbonylation of propyne. Unlike related pyridyl(diaryl)phosphines,
4 produces a much more stable catalyst system that does not require large excesses of ligand to maintain activity.
The primary reason for the development of most OPN ligands was
Introduction
for use in homogeneous catalysis3f,g,9b,d,f and therefore they are not
intended to form strong tridentate chelates, as this could suppress the
catalytic activity of the complex. When coordination studies have
been carried out, it is commonly found that PN chelation is the pre-
ferred coordination mode, with a pendant oxygen donor arm.3f,g,9b,c,f
Several Pd(II) complexes of OPN ligands, which have the potential
ability to form a tridentate chelate, have been reported although
bidentate PN coordination was observed in each case.3f,9f Notably,
tridentate coordination of a ligand with an OPN donor set has never
been reported with any metal in a square planar environment.3f,g,9b–d,f
Similarly, square planar Rh(I) complexes of the type [Rh(cod)L]+,
with a potential OPN coordinating ligand, have shown only
bidentate coordination.3g,9b The Rh(I) complex studied by Yang et
al. is interesting since it exhibits both the PO and PN bound isomers
which are in rapid exchange in solution at room temperature and
were identified by low temperature 1H NMR spectroscopy.3g
It could be envisaged that for OPN ligands, the phosphorus may
be strained if all three donor atoms become coordinated in the same
plane, thus distorting the normal pyramidal geometry of phosphorus
(Fig. 1).10 This may account in part for the lack of observed tridentate
coordination of OPN ligands, even though bidentate coordination of
similar ligand fragments is well known (for examples see above and
refs 4b, 11) in contrast, planar tridentate coordination of functional
phosphine ligands which have two 5- or 6-membered chelates and
terminal P or N donors, do not appear particularly strained.3c,10,12 It
is noted however that in coordination studies of phosphines bear-
ing two or more substituents with donor atoms (i.e. with a central P
donor), facial coordination is frequently preferred over meridional
coordination for octahedral complexes.9d,13
Polydentate phosphine ligands bearing oxygen and nitrogen donor
atoms are of interest as ligands suitable for application in homo-
geneous catalysis.1 The new coordination modes which may arise
from the combination of hard and soft donor atoms in the one ligand
are of fundamental interest. We have previously reported coordina-
tion studies of OPO ligands,2a and in this study we focus on OPN
ligands, previously described in a recent paper.2b Pd(II) complexes
with ligands containing phosphine, amine, imine or pyridyl donor
functions have been frequently shown to exhibit catalytic activity in
reactions involving C–C bond formation.1 Increasingly, ligands with
more exotic combinations of these functional groups are sought for
the effects they may produce in catalysis.3 Particular interest has
been directed towards hemilabile ligands for their ability to stabi-
lise catalytic intermediates, and in some cases to affect the product
distribution.1,3m,4 For Pd(II), most hemilabile chelates bear a neutral
O or S donor function in combination with a P or N donor group.5
There are few reports of a Pd(II) catalyst having a tridentate
ligand for any kind of catalysed co-reaction of CO with alkenes
or alkynes,6 although recently, two relevant publications have
appeared. In one study, a complex bearing a ligand with a PON
donor set showed slight activity for the copolymerisation of CO
and ethene.6a In the second, a more rigid chelating POP ligand was
found to form a Pd(II) complex active for the hydroxycarbonylation
of ethene, propene or styrene.6b
It is uncommon to find phosphines which contain both N and O
donor atoms and which have the potential to chelate in a tridentate
fashion in a square planar complex. These phosphines can be clas-
sified into one of three different types: PNO,3a,d,f,h,i,7 PON3b,f,6a,7h,8 or
OPN,3f,g,k depending on the arrangement of the donor atoms. The
ligands were designed to include PN and PO moieties9 which are
known to be successful ligands for Pd(II) catalysed co-reactions of
CO with unsaturated hydrocarbons, such as ethene and propyne.
The scarcity of ligands with an OPN donor set may be due to the
difficulties associated with introducing different functional sub-
stituents to the same phosphorus centre.
A limited number of reports of the application of OPN ligands
in homogeneous catalysis have appeared. These include a range
of different metals and processes, for example, asymmetric cross-
† Electronic supplementary information (ESI) available: Comments and
observations upon the nature of compound 4. See http://www.rsc.org/
suppdata/dt/b4/b405586c/
‡ Present address: Sasol Technology UK (Ltd), St Andrews Laboratory,
North Haugh, St. Andrews, Fife, KY16 9ST
Fig. 1 Strain of pyramidal geometry of P by coordination of two donor
functionalised substituents, D1 and D2.
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0
3 2 5 1

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coupling,3f hydrogenation of ketones,9c,d oligomerisation or poly-
merisation reactions of alkenes and alkynes.9b,f
PdCl2(1) 1a. (Found: C, 37.1; H, 3.65; N, 2.46. C17H20Cl2NOPP
d·0.85(CDCl3) requires C, 37.9; H, 3.57; N, 2.48%); H (400 MHz;
CDCl3) 9.65maj, 9.52 (1H, 2d, J = 5.8, 5.8 Hz, 6-py), 7.9 (2H, m,
Ph), 7.76 (1H, m, py), 7.5–7.3 (4H, m, Ph + py), 7.2 (1H, m, py),
4.8, 4.4, 4.0–3.6 (5H, m, PCH2py + CHOCH2), 3.2–1.5 (6H, m,
PCH2thf + CH2CH2CH); C(100 MHz; CDCl3) 161.4maj, 161.2 (2d,
JCP = 4.4, 4.2 Hz, 2-py), 153.5maj, 153.4 (2s, 6-py), 139.6, 139.5maj
(2s, 4-py), 132.6, 131.8maj (2d, JCP = 10.5, 10.5 Hz, orthoPh), 132.3,
132.2maj (2s, paraPh), 129.3maj, 129.2 (2d, JCP = 11.2, 11.3 Hz,
metaPh), 123.6 (s, 5-py), 123.4, 123.3maj (2d, JCP = 13.2, 13.3 Hz,
3-py), 75.5maj, 74.2 (2d, JCP = 2.5, 10.3 Hz, OCH), 68.5, 68.4maj (2s,
OCH2), 41.0, 40.4maj (2d, JCP = 32.1, 29.1 Hz, PCH2py), 33.7maj, 33.0
(2d, JCP = 15.2, 11.5 Hz, OCHCH2), 33.4, 32.8maj (2d, JCP = 34.3,
36.7 Hz, PCH2thf), 25.4, 25.2maj (2s, CH2CH2CH2); P(146 MHz;
CDCl3) 50.0maj, 46.9; m/z (ES) 887 ({2M–Cl}+, 100%), 426 ({M–
Cl}+, 90%). (Note: that species such as {2M − Cl}+ forming with
PdCl complexes does not necessarily imply the complex is dimeric;
(the monomeric nature of 1a was confirmed by single crystal X-ray
diffraction).
The phosphines are also designed to enable comparison of the
coordination properties of OPN donors and 2-pyridyl phosphines
vs. structures that can form chelates. The ligands chosen for this
study include the ability to provide hemi-labile structures or tran-
sient stabilisation of intermediates. As part of this study, we have
recently reported the syntheses of a series of bifunctionalised phos-
phines bearing the OPN donor set.
In this paper, we present the synthesis and characterization
of Pd(II) complexes with OPN phosphine ligands 1–4. NMR
studies investigating the fluxional, and coordination behaviour
are described. Several of the complexes, or in situ preparations
of the OPN ligands with palladium acetate, act as catalysts for the
copolymerisation of CO and ethene to form polyketone, and/or for
the methoxycarbonylation of propyne to give methylmethacrylate.
The results of the coordination studies are discussed with respect
to their relevance to the catalytic behaviour of the palladium
complexes of 1–4.
Experimental
PdCl2(2) 2a. (Found: C, 42.7; H, 4.06; N, 2.91. C17H20Cl2NO2PPd
requires C, 42.7; H, 4.21; N, 2.93%); H(400 MHz; CDCl3) 9.66
(1H, d, J = 6.0 Hz, 6-py), 7.89 (2H, m, Ph), 7.68 (1H, d, J = 7.2 Hz,
py), 7.48 (4H, m, Ph + py), 7.33 (1H, t, J = 6.6 Hz), 4.99 (1H,
m, OCHO), 4.23 (1H, m, PCHaHbpy), 3.89 (5H, m, PCHaHbpy +
OCH2CH2O), 2.67, 2.45, 2.31, 2.05 (4H, 4m, PCH2CH2);
C(100 MHz; CDCl3) 160.6 (d, JCP = 4.5 Hz, 2-py), 153.4 (6-py),
139.9 (py), 132.4 (d, JCP = 3.0 Hz, paraPh), 131.9 (d, JCP = 10.7 Hz,
orthoPh), 129.4 (d, JCP = 11.4 Hz, metaPh), 126.8 (d, JCP = 53.1 Hz,
All reactions were carried out under a dry nitrogen atmosphere.
Solvents were dried using conventional drying agents under a
nitrogen atmosphere and were freshly distilled before use. Carbon
monoxide (99.95%) was purchased from Linde Industrial Gases
UK or BOC gases, propyne was purchased from Linde Industrial
Gases UK, ethene (polymer grade) was purchased from Mathe-
son. PdCl2(benzonitrile)2,14 PdCl2(cod),15 PdClMe(cod)16 and
Pd2(dba)3(CHCl3)17,18 were prepared according to literature proce-
dures. PdCl2, PdCl2(MeCN)2 and Pd(OAc)2 were purchased from
Johnson-Matthey and used as received for the preparation of com-
plexes, for catalytic studies, Pd(OAc)2, was purified by dissolving in
CH2Cl2, filtering through Celite®, and evaporating to dryness under
vacuum.All other reagents were obtained from theAldrich Chemical
Company and used as received unless otherwise stated. The ligands
1–4 were prepared according to our previously described procedure.2
Microanalyses were obtained using either a Carlo Erba EA1108 or
a Perkin Elmer 240C elemental analyser. IR spectra were recorded
on a Bruker IFS-66 FTIR Spectrometer in the range 400–4000 cm−1.
NMR spectra were recorded using the following: a JEOL FX90Q at
36.23 MHz (31P), a Bruker WM360 at 145.784 MHz (31P), a Bruker
AM-300 at 300.13 (1H), 75.48 (13C) and 121.50 MHz (31P), a Bruker
DPX400 at 400.13 (1H) or 100.486 (13C) MHz, a Varian Unity Inova
400 WB at 161.926 or 161.807 (31P), 100.587 or 100.509 (13C),
399.716 (1H) MHz and a Varian Gemini-200 at 50.289 (13C), 199.98
(1H) MHz. Chemical shifts (in ppm) are quoted relative to internal
SiMe4 or residual solvent for 1H and 13C spectra, and to external 85%
H3PO4 for 31P spectra. Electrospray (ES) mass spectra were recorded
on a Platform II Fisons VG machine (ES), and liquid secondary
ion mass spectra (LSIMS) were recorded on a Kratos Concept ISQ
spectrometer using 10 kV cesium ions as the primary beam, 5.3 kV
accelerating voltage in a m-nitrobenzyl alcohol matrix scanning at 2s
decade−1 between m/z 100 to 1200.
ipsoPh) 124.1 (d, JCP = 12.9 Hz, py), 123.9 (py), 102.7 (d, JCP
=
15.2 Hz, OCHO), 65.1 (OCH2), 39.3 (d, JCP = 30.4 Hz, PCH2py),
27.9 (CH2CH), 20.7 (d, JCP = 38.0 Hz, PCH2); P(162 MHz; CDCl3)
47.9; m/z (LSIMS) 442 ({M–HCl}+, 15%), 409 ({M–2Cl}+, 12%),
362 ({M–2Cl–HCO2H}+, 20%), 318 ({2 + OH}+, 100%), 306
({PdPPhCH2py}+, 38%).
PdCl2(3) 3a. (Found: C, 41.3; H, 3.98; N, 3.11. C16H18Cl2NO2PPd
requires C, 41.4; H, 3.90; N, 3.01%); H(400 MHz; d6-acetone)
9.67 (1H, d, J = 6.0 Hz, 6-py), 8.1 (2H, m, Ph), 7.91 (1H, d, J =
8.0 Hz, py), 7.60 (5H, m, Ph + py), 4.59 (1H, dd, JHaHb = 18.0 Hz,
JHaP = 11.2 Hz, PCHaHbpy), 4.30 (1H, dd, JHaHb = 18.0 Hz, JHbP
=
16 Hz, PCHaHbpy), 3.67 (3H, s, OMe), 3.0–2.8 (4H, m, PCH2CH2);
C(100 MHz; d6-acetone) 172.4 (d, JCP = 17.4 Hz, CO), 162.4
(d, JCP = 4.5 Hz, 2-py), 153.4 (d, JCP = 16.7 Hz, 6-py), 140.8 (py),
132.9 (d, JCP = 3.0 Hz, paraPh), 132.7 (d, JCP = 10.6 Hz, orthoPh),
129.8 (d, JCP = 11.4 Hz, metaPh), 128.2 (d, JCP = 52.4 Hz, ipsoPh)
124.8 (d, JCP = 12.9 Hz, py), 124.3 (py), 52.0 (OMe), 39.2 (d, JCP
=
39.2 Hz, PCH2py), 28.9 (signal due to CH2COOMe obscured by d6-
acetone), 22.2 (d, JCP = 38.0 Hz, PCH2); P(162 MHz; d6-acetone)
51.2; m/z (LSIMS) 428 ({M–HCl}+, 30%), 307 (matrix, 100%).
Preparation of complexes 1b–3b. [Pd(MeCN)2(1)](BF4)2.
1b(MeCN) was prepared by addition of a solution of 1a (0.29 g,
0.63 mmol) in CH2Cl2 (25 cm3) to a suspension of AgBF4 (0.250 g,
0.13 mmol) in acetonitrile (4 cm3) and CH2Cl2 (5 cm3) at 0 °C.
Precipitation of AgCl occurred immediately. After 15 min, the
AgCl was removed by filtering through Celite®. The solvent was
reduced to approximately 5 cm3 and the product was precipitated
and washed with toluene, and then dried under vacuum to leave
1b(MeCN). Procedures for the synthesis of 1b(thf), 2b(thf) and
3b(thf) were similar, except MeCN was replaced by THF and the
reaction was performed at −60 °C, −40 °C and −40 °C, respectively.
All complexes were yellow powders. While the yields appeared
quantitative, complete removal of coordinated solvent was not pos-
sible in vacuo, and recrystallisation led to contamination by differ-
ent solvent ligated complexes. For this reason, microanalyses were
unsatisfactory and are not included here.
Syntheses
Preparation of 1a–3a. PdCl2(1) 1a was prepared by the addi-
tion of a solution of 1 (0.49 g, 1.72 mmol) in CH2Cl2 (25 cm3) to a
suspension of PdCl2(benzonitrile)2 (0.66 g, 1.72 mmol) in CH2Cl2
(10 cm3) at room temperature. The mixture formed a clear, yellow
solution and was filtered through Celite®.After reducing the solvent
to approximately 1 cm3, the oily residue was washed with toluene
(10 cm3), redissolved in CH2Cl2 (3 cm3) and triturated with toluene
(40 cm3) for 2 days. The solvents were decanted and the product
washed with toluene (15 cm3) and dried under vacuum. A yellow
powder (0.69 g, 87%) resulted. Complexes 2a and 3a were prepared
similarly using PdCl2(MeCN)2 in CH2Cl2 and PdCl2(cod) in acetone,
respectively. The complexes were obtained as yellow powders (2a:
0.44 g, 96%). The phosphine, 3, which was contaminated with poly-
methylacrylate,2 was used without purification, thus the yield of 3a
was not determined.
[Pd(MeCN)2(1)](BF4)2 1b(MeCN). H(400MHz;CDCl3)8.62maj
,
8.59 (1H, 2d, J = 6.4, 5.6 Hz, 6-py), 8.06 (1H, m, 4-py), 7.94–7.81
(2H, m, Ph), 7.78–7.67 (2H, m, paraPh + 3-py), 7.61–7.55 (3H, m,
3 2 5 2
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0

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Ph + 5-py),4.59, 4.54maj (1H, 2d, JHaP = 16.0, 15.6 Hz, PCHaHbpy),
4.47 maj, 4.02 (1H, 2m, OCH), 4.25 (1H, m, PCHaHbpy), 3.90, 3.66,
3.48 (2H, 3m, OCH2) 3.30, 3.05, 2.90, 2.45 (2H, 4m, PCH2thf),
2.40 (6H, s, 2MeCN), 2.27, 2.16, 2.00–1.70 (4H, 3m, PCH2thf );
C(100 MHz; CDCl3) 161.7maj, 160.7 (2s, 2-py), 152.6, 152.3maj
(2s, 6-py), 142.1, 141.9maj (2s, 4-py), 133.7 (m, paraPh), 131.43,
131.24maj (2d, JCP = 10.7, 10.6 Hz, Ph), 129.9, 129.8maj (2d,
JCP = 12.1, 12.9 Hz, Ph), 125.1, 124.8maj (2s, 5-py), 124.4, 124.31maj
(2d, JCP = 13.6, 14.5 Hz, 3-py), 123.7, 121.8 (2d, JCP = 60.7,
58.4 Hz, 2MeCN), 74.7maj, 73.7 (2d, JCP = 5.3, 9.1 Hz, OCH), 68.4,
68.2maj (2s, OCH2), 40.5maj, 40.0 (2d, JCP = 35.7, 36.5 Hz, PCH2py),
33.0maj, 32.7 (2d, JCP = 13.7, 12.9 Hz, OCHCH2), 31.8, 31.6maj (2d,
JCP = 32.7, 33.4 Hz, PCH2thf), 25.0, 24.8maj (2s, CH2CH2CH2), 2.8
(m, 2MeCN); P(162 MHz; CDCl3) 61.7maj, 60.0; m/z (LSIMS)
391 ({M − 2MeCN}+, 77%), 306 ({PdPPhCH2py}+, 100%), 230
({PdPHCH2py}+ or {PdP(CH3)Ph}+, 61%).
124.7, 124.5maj (2s, 5-py), 121.1(s, MeCN), 76.9maj, 75.6(s + d,
JCP = 5.0 Hz, OCH), 69.0maj, 68.9 (2s, OCH2), 42.8maj, 42.4 (2d,
JCP = 30.9, 32.6 Hz, PCH2py), 34.4maj, 33.6 (2d, JCP = 14.1, 9.8 Hz,
OCHCH2), 32.5, 32.2maj (2d, JCP = 32.3, 34.8 Hz, PCH2thf), 26.2,
26.0maj (2s, CH2CH2CH2), 3.6 (s, MeCN), −6.0, −7.5maj (2s, PdMe);
P(162 MHz; CDCl3) 43.0maj, 36.6; m/z (ES) 406 ({M–MeCN}+,
100%).
[Pd(COMe)(MeCN)(1)](BF4) 1e. Treatment of a CD2Cl2 solu-
tion of 1d at between −40 °C and −25 °C with 40 bar CO for 4.5 h
in a steel autoclave resulted in approximately 30% conversion to
1e. Complete conversion was not achieved due to the instability
of 1e even at low temperatures. Selected NMR data are given.
H(400 MHz; CD2Cl2) (20 °C) 8.59 (1H, br m, 6-py), 2.46maj, 2.38
(3H, 2d, JHP = 1.30, 1.24 Hz, PdCOMe); C(100 MHz; CD2Cl2)
(−20 °C) 39.7 (2d overlapped, PdCOMe); P(162 MHz; CD2Cl2)
(−20 °C) 24.8, 21.0maj
.
[Pd(MeCN)2(1)](BF4)2 1b(thf). H (400 MHz; CD2Cl2) (−20 °C)
8.24 (1H, br s, 6-py); P(162 MHz; d6-acetone) 60.3maj, 58.2;
(CD2Cl2, −80 °C) 61.1, 59.6min, 58.0, 57.4.
Pd(OAc)2(1) 1f. A solution of 1 (0.42 g, 1.47 mmol) in CH2Cl2
(25 cm3) was added to a solution of Pd(OAc)2 (0.33 g, 1.47 mmol) in
CH2Cl2 (10 cm3).After 10 min, the deep red–brown product (0.75 g,
100%) was obtained by evaporation of CH2Cl2 in vacuo (Found: C,
49.4; H, 5.19; N, 2.70. C21H26NO5PPd requires C, 49.5; H, 5.14;
[Pd(thf)2(2)](BF4)2 2b(thf). H(400 MHz; CD2Cl2) (20 °C) 8.20
(1H, br d, J = 5.6 Hz, 6-py); P(162 MHz; CD2Cl2) 63.3 (br); (d6-
acetone, −20 °C) 69.8, 66.0maj (br), 63.6, 62.2, 48.1, −43.3, −44.4.
N, 2.75%);
/cm−1 (CO) 1603vs, 1579vs and (C–O) 1375s,

νmax
1318m (KBr); H400 MHz; CDCl3 8.77maj, 8.73 (1H, 2d, J = 5.2,
5.2 Hz, 6-py), 8.04, 7.96maj (2H, 2dd, J = 8.0, 7.4, J = 12.0, 12.6 Hz,
Ph), 7.78, 7.76maj (1H, 2t, minor triplet obscured, Jmaj = 7.8 Hz, py),
7.5–7.4 (3H, m, Ph), 7.33 (1H, d, J = 7.2, py), 7.26(m, 1H, py),
4.46–4.10 (1H, m, OCH), 4.0–3.4 (4H, m, PCH2py + OCH2),
3.2–2.8, 2.3–1.6 (6H, m, PCH2thf + CH2CH2CH), 2.05 (6H, s,
MeCOO−); C(100 MHz; CDCl3) 176.5 (br m, MeCOO−), 176.4,
176.3maj (2s, MeCOO−), 162.3 (d, JCP = 5.2 Hz, 2-py), 151.6,
151.5maj (2s, 6-py), 139.2, 139.0maj (2s, 4-py), 131.9, 131.3maj (2d,
JCP = 10.9, 11.1 Hz, orthoPh), 131.5, 131.4maj (2d, JCP = 2.9, 2.7 Hz,
paraPh), 128.7(d, JCP = 11.6 Hz, metaPh), 123.1, 123.0maj (2s,
5-py), 122.9, 122.6maj (2d, JCP = 10.8, 11.1 Hz, 3-py), 75.8maj, 75.0
(s + d, JCP = 6.8 Hz, OCH), 68.1, 67.8maj (2s, OCH2), 44.9maj, 44.1
(2d, JCP = 27.9, 30.7 Hz, PCH2py), 34.8maj, 33.4 (2d, JCP = 18.3,
17.1 Hz, PCH2thf), 33.4maj, 31.9 (2d, JCP = 7.4, 4.7 Hz, OCHCH2),
25.3, 25.1maj (2s, CH2CH2CH2), 23.3 (br s, MeCOO−), 21.6, 21.2maj
(2d, JCP = 1.9, 1.9 Hz, MeCOO−); P(146 MHz; CDCl3) 35.7maj, 32.1;
m/z (LSIMS) 450 ({M–MeCOO−}+, 100%), 306 ({PdPPhCH2py}+,
89%), 230 ({PdPHCH2py}+ or {PdP(Me)Ph}+, 78%).
[Pd(thf)2(3)](BF4)2 3b(thf). H(400 MHz; CD2Cl2) (20 °C) 8.37
(1H, br d, J = 5.2 Hz, 6-py); P(162 MHz; CD2Cl2) (20 °C) 69.1 (br),
(−80 °C) 87.5, 80.4, 72.5(br), 67.0, 58.5maj, 57.0 (br); (thf/C6D6,
20 °C) 64.8 (br).
PdClMe(1) 1c. A solution of 1 (1.02 g, 3.58 mmol) in CH2Cl2
(20 cm3) was added to a solution of PdClMe(cod) (0.95 g,
3.58 mmol) in CH2Cl2 (5 cm3) at room temperature, resulting in a
slightly darker yellow solution. The solvent was removed in vacuo
and the product was recrystallised from CH2Cl2/ether to leave a
pale yellow solid (1.01 g, 64%). (Found: C, 48.7; H, 5.24; N, 3.03.
C18H23ClNOPPd requires C, 48.9; H, 5.24; N, 3.17%); H(400 MHz;
CDCl3) 9.36maj, 9.33 (1H, 2dd, J = 1.1,1.1, J = 5.5, 5.5 Hz, 6-py),
7.8–7.7 (2H, m, Ph), 7.7–7.6 (1H, m, 4-py), 7.4–7.2 (5H, m,
Ph + py), 4.4–4.2, 4.1–3.5 (5H, m, PCH2py + CHOCH2), 2.5–1.5
(6H, m, PCH2thf + CH2CH2CH), 0.73, 0.63maj (3H, 2d, JHP = 2.6,
2.2 Hz, PdMe); C(100 MHz; CDCl3) 157.5maj, 157.1 (2d, JCP = 4.3,
4.7 Hz, 2-py), 149.8, 149.7maj (2s, 6-py), 137.1, 136.9maj (2s, 4-py),
131.7, 131.5maj (2d, JCP = 11.8, 12.5 Hz, orthoPh), 130.5maj, 130.3 (2d,
JCP = 2.6, 3.1 Hz, paraPh), 128.0maj, 127.9 (2d, JCP = 11.9, 10.6 Hz,
metaPh), 122.04, 121.97maj (2d, JCP = 9.9, 10.4 Hz, 3-py), 121.8,
121.6maj (2s, 5-py), 75.1maj, 74.2 (2d, JCP = 1.6, 4.0 Hz, OCH), 67.1
Oxidation of 4. Asmall sample of 4 was oxidised to 4-oxide using
excess H2O2 and evaporated to dryness under vacuum. C(100 MHz;
CD3OD) 157.9. 156.6 (2d, JCP = 4.2, 5.1 Hz, 2-py), 151.6, 151.4 (2d,
JCP = 19.2, 19.3 Hz, 6-py), 138.1, 137.9 (2d, JCP = 9.2, 9.1 Hz, 4-py),
133.4, 133.3 (2d, JCP = 2.7, 2.8 Hz, paraPh) (ipso peaks around
132–134 partly obscured by para and meta peaks), 132.0, 131.9
(2d, JCP = 9.2, 9.2 Hz, orthoPh), 129.8, 129.7 (2d, JCP = 4.6, 4.6 Hz,
metaPh), 128.2, 128.0 (2d, JCP = 3.7, 3.6 Hz, 3- or 5-py), 127.2,
126.9 (2d, JCP = 2.7, 3.2 Hz, 3- or 5-py), 74.9, 74.8 (2d, JCP = 1.3,
2.8 Hz, OCH), 68.5, 68.4 (2s, OCH2), 36.2, 35.5 (2d, JCP = 11.0,
10.5 Hz, PCH2thf), 33.7, 33.5 (2d, JCP = 7.7, 6.0 Hz, OCHCH2),
26.4, 26.3 (2s, CH2CH2CH2); P (36 MHz; CD3OD) 31.8, 31.7.
(s, OCH2), 40.9, 40.5maj (2d, JCP = 30.2, 27.8 Hz, PCH2py), 32.8maj
,
31.7 (2d, JCP = 14.0, 8.6 Hz, OCHCH2), 31.2, 30.6maj (2d, JCP = 28.9,
31.8 Hz, PCH2thf), 24.6, 24.2maj (2s, CH2CH2CH2), −8.2, −9.6maj
(2d, JCP = 1.9, 2.5 Hz, PdMe); P(146 MHz; CDCl3) 37.1maj, 30.4; m/z
(ES) 405 ({M − HCl}+, 100%), 320 ({M − HCl − CH2thf}+, 20%).
[PdMe(MeCN)(1)](BF4) 1d. A solution of 1c (0.55 g,
1.24 mmol) in CH2Cl2 (20 cm3) was added to a suspension ofAgBF4
(0.245 g, 1.26 mmol) in CH2Cl2 (20 cm3) and MeCN (2.5 cm3) at
0 °C. Precipitation ofAgCl occurred immediately. After 10 min, the
reaction mixture was filtered through Celite® and collected at 0 °C.
The solvent was reduced to approximately 1 cm3 and the product
precipitated by the addition of ether (20 cm3). Apale yellow powder
was isolated (0.64 g, 97%). A satisfactory microanalysis for this
complex was not obtained due to the ease of replacement of the
MeCN ligands by other solvent molecules. H(400 MHz; CDCl3)
8.55 (1H, br s, 6-py), 7.8–7.7 (2H, m, orthoPh), 7.7–7.4 (6H, m,
Ph + py), 4.5–3.5 (5H, m, PCH2py + CHOCH2), 2.5–1.5 (6H, m,
PCH2thf + CH2CH2CH), 2.38 (3H, s, MeCN), 0.45, 0.28maj (3H, 2s,
PdMe); C(100 MHz; CDCl3) 159.3maj, 158.6 (2d, JCP = 2.8, 2.2 Hz,
2-py), 150.8, 150.6maj (2s, 6-py), 140.3, 140.0maj (2s, 4-py), 133.2,
133.0maj (2d, JCP = 12.0, 12.2 Hz, orthoPh), 132.8maj, 132.7 (2d,
JCP = 2.5, 2.7 Hz, paraPh), 130.0maj, 129.9 (2d, JCP = 11.4, 11.4 Hz,
metaPh), 124.9maj, minor peak obscured (d, JCP = 10.4 Hz, 3-py),
Catalytic studies
For reactions with ethene, solutions of the preformed catalysts
(complexes 1d and 1f) and in situ catalysts were prepared under
N2 in dry and deoxygenated solvents. For in situ catalysts, a solu-
tion of the ligand was added to a solution of Pd(OAc)2, followed
by addition of methanesulfonic acid. Runs 1–5 were performed in
a 350 ml 316 stainless steel autoclave, while a 75 ml 316 stainless
steel autoclave was used for runs 6–9. Results and experimental
conditions for these experiments are summarised in Table 1.
For reactions with propyne, the catalyst solution was prepared
by adding a preweighed amount of Pd(OAc)2 to a Schlenk flask
containing the preweighed phosphine ligand (1 or 4) under N2.
Anhydrous methanol (160 ml) was degassed with a stream of
N2 before being added to the ligand and Pd(OAc)2 with stirring;
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0
3 2 5 3

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Table 1 Experimental conditions and results of CO–ethene co-polymerisations
Results:
Productc
Runa
Complex/Ligand
Molar Pd/ligand/acidbratio (mmol Pd)
Solvent (vol ml−1)
Pd(0)d
Some
Substantial
Substantial
Some
Complete
None
None
1
2e
3
4
5
6
7
8
9
1d
1d
1d
1f
4f
1:1:0 (0.099)
1:1:0 (0.198)
1:1:0 (0.196)
1:1:0 (0.208)
1:1:0 (0.202)
1:2.5:3 (0.111)
1:5:5 (0.111)
1:2:2.5 (0.199)
1:2:2.5 (0.244)
CH2Cl2 (60)
CH2Cl2 (80)
MeOH (80)
CH2Cl2 (80)
MeOH (80)
MeOH (20)
MeOH (20)
CH2Cl2 (20)
CH2Cl2 (20)
10 mg
300 mg
—
—
—
30 mg
—
—
4f
4f
2
3
Complete
Complete
—
Notes: a Reaction conditions: 20 bar CO, 20 bar ethene, 20 °C, 24 h. b Methanesulfonic acid. c CO–ethene polymer isolated. d Qualitative estimation of palladium
black deposited. eAt 40 °C. f In situ catalysts prepared from Pd(OAc)2, ligand 4 and acid.
Table 2 Experimental conditions and results of propyne methoxycarbonylations
Methylmethacrylate yield/g
Runa
Ligandb
Molar Pd/ligand/acidcratio (mmol Pd)
1 h
2 h
3 h
24 h
TOFd
10
11
12
13
14
15
16
17
1
1
1
1
4
4
4
4
1:9:11 (0.071)
1:19:22 (0.071)
1:37:43 (0.071)
1:1.2:1.4 (0.143)
1:2.5:2.7 (0.143)
1:10:11 (0.071)
1:20:22 (0.071)
1:39:43 (0.071)
0
0
0
2.28
8.86
2.21
1.71
1.14
0
0
0
0
0
0
—
—
—
10.12
30.37
—
—
—
0
0
0
159
620
309
239
160
2.53
3.42
12.02
2.66
2.02
1.39
15.19
3.04
2.47
1.77
Notes: a Reaction conditions: MeOH (160 ml), propyne (15 g), CO (10 bar), 50 °C. bAll catalysts were prepared in-situ from Pd(OAc)2, ligand 1 or 4 and acid.
c Methanesulfonic acid. d Turn over frequency in mol(product)/mol(Pd) h−1 calculated after 1 h.
Table 3 Selected bond lengths and angles for compounds 1a and 3a
methanesulfonic acid was then added via syringe. The catalyst solu-
tion was weighed before being transferred, with the exclusion of air,
to an evacuated 1 litre Zipperclave autoclave (Hastelloy™, fitted
with a Magnadrive mechanical stirrer operating at 1000 rpm, with
computerised temperature and pressure control). The catalyst solu-
tion was heated to 50 °C under static vacuum. At this temperature,
propyne (15 g) was added from a sample bomb, and the autoclave
filled with 10 bar CO. The CO pressure was maintained at 10 bar
throughout the course of the catalytic test. After all the reactants
had been added and the temperature returned to 50 °C, the time was
recorded as zero hours. Samples for GC analysis were collected at
1, 2 and 3 and in some cases 24 h from the beginning of the test
via a flushed sampling line. Experimental details of the reactions
performed (runs 10–17) are summarised in Table 2.
Atoms
1a
3a
Distances/Å
Pd–P(1)
Pd–N(1)
Pd–Cl(1)
2.1985(6)
2.076(3)
2.3900(7)
2.194(1)
2.074(3)
2.371(1)
Angles/°
Pd–Cl(2)
2.295(1)
82.80(6)
171.46(3)
90.63(3)
95.47(6)
173.27(6)
91.23(3)
119.8(2)
117.1(2)
108.7(2)
101.11(9)
120.65(8)
107.6(1)
108.55(8)
109.3(1)
109.1(1)
2.291(1)
P(1)–Pd–N(1)
P(1)–Pd–Cl(1)
P(1)–Pd–Cl(2)
N(1)–Pd–Cl(1)
N(1)–Pd–Cl(2)
Cl(1)–Pd–Cl(2)
Pd–N(1)–C(15)
N(1)–C(15)–C(16)
C(15)–C(16)–P(1)
C(16)–P(1)–Pd
Pd–P(1)–C(25)
C(1)–P(1)–C(25)
Pd–P(1)–C(1)
83.3(1)
177.91(5)
89.84(5)
94.6(1)
Structure determinations. Full spheres of CCD area-detector
diffractometer data were measured at room-temperature (Bruker
AXS instrument, T ca. 300 K; -scans, 2max = 58°; monochromatic
Mo K radiation,  = 0.71073 Å) yielding Nt(otal) reflections, these
merging to N unique (Rint cited) after ‘empirical’/multiscan absorp-
tion correction (proprietary software) No with F > 4(F) considered
‘observed’ and used in the full matrix least squares refining of
anisotropic displacement parameter forms for the hydrogen atoms,
(x,y,z,Uiso)H also constrained at estimates. In the latter, C(24) of
the furan ring was modelled as disordered over the two possible
inversion image sites, separated by 0.98(1) Å, occupancies were set
at equivalent after trial refinement. Conventional residuals R, Rw
(weights: (2(F) + 0.0004 F2)−1) are cited at convergence. Neutral
atom complex scattering factors were employed within the Xtal 3.5
program system.19 Pertinent results are given in Table 3; views of
the structures are presented in Figs. 2 and 3, showing non-hydrogen
atoms with 20% probability amplitude displacement ellipsoids
(hydrogen atoms having arbitrary radii of 0.1 Å).
172.49(10)
92.21(5)
119.8(3)
116.2(3)
109.5(3)
101.1(1)
120.5(2)
106.3(2)
112.3(2)
107.2(2)
108.8(2)
C(16)–P(1)–C(25)
C(1)–P(1)–C(16)
Torsion angles/°
P(1)–Pd–N(1)–C(15)
Pd–N(1)–C(15)–C(16)
N(1)–C(15)–C(16)–P(1)
C(15)–C(16)–P(1)–Pd
C(16)–P(1)–Pd–N(1)
Pd–P(1)–C(1)–C(6)
Cl(2)–Pd–P(1)–C(25)
Cl(2)–Pd–P(1)–C(1)
14.7(2)
4.8(3)
11.9(3)
7.7(5)
−26.5(3)
33.2(2)
−23.9(1)
43.0(3)
34.0(1)
−90.7(1)
−28.0(5)
32.8(3)
−22.4(2)
74.1(4)
42.8(2)
−83.7(2)
Crystal/refinement data. 1a. C18H21Cl5NOPPd, M = 582.0. Tri-
clinic, space group P1 (Cli, No. 2), a = 9.1509(5), b = 10.7309(6),
3 2 5 4
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0

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Scheme 1 Pd(II) complexes of 1–3 and ligand 4 (i) PdCl2(cod) or
PdCl2(PhCN)2 or PdCl2(MeCN)2, CH2Cl2, 20 °C; (ii) 2AgBF4, solv = thf
or MeCN, 1b(MeCN) (0 °C) 1b(thf) (−60 °C) 2b(thf) (−40 °C) 3b(thf)
(−40 °C), –2AgCl.
The chloride ligands in 1a–3a may be abstracted in the presence
of a weakly coordinating solvent at low temperature to give the
significantly less stable solvated dicationic complexes, 1b(MeCN)
and 1b(thf)–3b(thf) (Scheme 1). All these solvated cationic com-
plexes are air sensitive, yellow solids, which are thermally unstable
especially in solution. Residual coordinated solvent could not be
completely removed under vacuum, and recrystallisation from
alternative solvents resulted in partial substitution of the solvent
ligands. This was evident from the emergence of new peaks in the
31P NMR spectrum, which varied only slightly in chemical shift.
Thus, reliable microanalyses were not obtained for these complexes.
The structures of complexes 1b(MeCN), 1b(thf)–3b(thf) shown in
Scheme 1, are based on NMR data. Some fluxionality of oxygen
coordination is thought to occur in solutions of 1b(thf)–3b(thf).
The reaction sequence shown in Scheme 2, gave methylpalladium
complexes of ligand 1. Both the chloro and acetonitrile complexes
are air sensitive pale yellow solids, with the cationic complex,
1d, being significantly more thermally unstable, than the chloro
complex 1c. Two geometrical isomers are possible for both 1c and
1d, although only one isomer, presumed to be the isomer with phos-
phine cis to methyl ligands, is observed in each case.
Fig. 2 Molecular projection of 1a.
Fig. 3 Molecular projection of 3a showing the approach of the chloroform
solvent molecule.
c = 12.7937(7) Å,  = 107.815(1),  = 90.329(1),  = 105.775(1)°,
V = 1145.6 Å3. Dc (Z = 2) = 1.687 g cm−3. Mo = 14.7 mm−1; speci-
men: 0.4 × 0.3 × 0.2 mm; ‘T’min/max = 0.79. Nt = 13221, N = 5571
(Rint = 0.015), No = 5212; R = 0.033, Rw = 0.055. |max| =
0.85(1) e Å−3.
3a. C16H18Cl2NO2PPd, M = 464.6. Monoclinic, space group
P21/c (C52h, No. 14), a = 8.435(2), b = 10.810(3), c = 20.243(7) Å,
 = 99.115(5)°, V = 1823.0 Å3. Dc (Z = 4) = 1.693
g
cm−3.
Scheme 2 Methylpalladium(II) complexes of 1.

Mo = 14.1 mm−1; specimen: 0.30 × 0.24 × 0.13 mm; ‘T’min/max
=
0.80. |max| = 0.85(1) e Å−3.
Treatment of 1c with CO at room temperature and atmospheric
pressure did not produce an acyl complex, although small amounts
of the acyl complex, 1e, were formed by adding CO to a solution
of 1d under the same conditions. The carbonylation reaction was
slow, and the complex 1e was thermally unstable to the extent that
we were unable to isolate a pure product. Lowering the tempera-
ture of the reaction did improve the stability of 1e somewhat, but
it also slowed the migratory insertion of CO quite markedly. Ap-
proximately 30% conversion was the maximum obtained without
substantial decomposition. This was adequate to identify the char-
acteristic acyl peaks by NMR spectroscopy.
CCDC reference numbers 236147 and 236148.
See http://www.rsc.org/suppdata/dt/b4/b405586c/ for crystallo-
graphic data in CIF or other electronic format.
Results and discussion
Pd(II) complexes with phosphines 1–3
Mixing a CH2Cl2 solution of any of the phosphine ligands
1–3 with a suitable source of PdCl2, such as PdCl2(benzonitrile)2,
PdCl2(MeCN)2 or PdCl2(cod), resulted in the immediate formation
of the PN chelated dichloropalladium complexes 1a, 2a and 3a,
respectively (Scheme 1). All complexes 1a–3a are air stable yellow
solids and were readily characterised by microanalysis, NMR
spectroscopy and mass spectrometry.
As the OPN ligands 1 and 4 were used for in situ catalytic experi-
ments with palladium acetate, the coordination chemistry of the
ligands was investigated. A mixture of solutions of 1 and Pd(OAc)2
in equal stoichiometry (Scheme 3) provided a deep red–brown solid,
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0
3 2 5 5

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1f, in quantitative yield and good purity. This complex must be
stored under nitrogen, but is reasonably air-stable in the short term.
Complex 1f is assigned a monomeric structure with monodentate
acetate ligands and PN chelation of 1 as shown in Scheme 3.
of 1d does not occur in solution at ambient temperatures. During
the carbonylation of 1d, CO coordination and migratory insertion
might have provided a coordination site adjacent to phosphine en-
abling the oxygen donor to coordinate. However, it appears that the
preferred isomer of 1e which has cis phosphine and acyl ligands, is
the only product of the reaction and hence oxygen coordination is
again prevented.
Crystals of 1a and 3a suitable for diffraction studies were ob-
tained from chloroform solution. The results are consistent in terms
of stoichiometry and connectivity with the formulations presented
above. Each have one formula unit, devoid of crystallographic sym-
metry, comprising the asymmetric unit of the structure in each case
(that of 1a is accompanied by a chloroform of solvation) (Fig. 2).
Both compounds crystallize in centrosymmetric, i.e. racemic, space
groups. The PN chelation mode of the ligand is confirmed in each
case; in 1a, disorder about the chiral methine carbon of the tetra-
hydrofurfuryl substituent indicates both R and S forms to be present
in equal amounts. In neither complex do the pendant oxygens of
the ligands approach within bonding range of the palladium atoms,
either intra- or intermolecularly. By virtue of their proximity to
crystallographic inversion centres, parallel coordination planes in
1a are disposed so that the PdPd distance is 3.7165(3) Å.
The coordination environments in both 1a (Fig. 2) and 3a
(Fig. 3) are essentially similar; palladium has a slightly distorted
square planar geometry in both complexes and the PN chelate
bite angle is approximately 83°. The Pd–Cl distances in each dif-
fer consistently and substantially, presumably in consequence of
trans effects of their different donors. Substantial and significant
differences are found in Cl(1)–Pd–P(1) and Pd–P(1)–C(1) and in
the torsion Pd–P(1)–C(1)–C(6) describing the orientation of the
pendant phenyl. While the extent to which these are concerted
may be debatable, it seems very likely that the differences in
Cl(1)–Pd–P(1) at least may be consequent upon the approach of the
Scheme 3 Reaction of 1 with palladium acetate.
Due to the complex coupling patterns and the presence of diaste-
reomers, the 1H and 13C NMR spectra are complicated and in some
cases, HETCOR (heteronuclear chemical shift correlation) NMR
spectroscopy was used to correctly assign the peaks. Several distinct
changes in the NMR spectra of the ligands 1–3 are observed when
they become coordinated to Pd(II). The most characteristic of these
are the increases in chemical shift of the 31P NMR and 6-pyridyl 1H
NMR resonances. Typically, the 31P NMR chemical shift increases
from  −30 or −20 ppm (for the free ligand) to around  50 ppm
for the dichloropalladium complexes, 1a–3a, and to around  60–
70 ppm for the dicationic complexes, 1b(MeCN), 1b(thf)–3b(thf).
Deshielding of the 6-pyridyl hydrogen ( ~8.4 ppm to  ~9.6 ppm)
is also observed on complexation of the OPN ligand to palladium.
This chemical shift increase can be used as an indicator for the
coordination of the pyridyl nitrogen to a metal.3e,8,9c The deshield-
ing is not as pronounced in complexes with solvent ligands [i.e.
1b(MeCN), 1b(thf)–3b(thf), 1d, 1e], and in some instances a de-
crease is observed. These observations are consistent with other re-
ported dicationic, PN ligated complexes with weakly coordinating
ligands.3b,20 Nevertheless, it is likely that the pyridyl nitrogen has
coordinated to Pd in 1b(thf) and 2b(thf) also, since displacement
of the N donor by a weak donor solvent is improbable. Furthermore,
the expected ratio of solvent to palladium, shown in Schemes 1 and
2 is in agreement with NMR data.
x
chloroform hydrogen to Cl(1):H(30)Cl(1) (1 − ,1 − y , 1 − z )
2.69 Å (est.); C–HCl(1) 149° (est); the phenyl orientation may
be a consequence of its disposition close to an inversion image in
the lattice. In other respects, bond lengths and angles of 1a and 3a
(Table 3) are similar to related complexes.3f,7b,22g,24
As discussed above, the OPN ligand in complexes 1b(MeCN),
1b(thf)–3b(thf) forms a PN chelate, and little evidence for the
coordination of the oxygen donor could be found, as has been pre-
viously observed for related complexes.25 For every complex, the
stoichiometry of solvent molecules to palladium was determined to
be two or greater using NMR spectroscopy or microanalysis. This
suggests that weakly bonded solvent molecules occupy coordina-
tion sites in place of the oxygen donor of the OPN ligand, which
remains pendant.
For complexes 1b(thf)–3b(thf), the broad NMR signals evident
at room temperature sharpened at lower temperature and new peaks
emerged indicating that fluxional processes are operating. The room
temperature 31P NMR spectrum of 1b(thf) shows a very broad, flat
peak at around  60 ppm and two broad singlets at  ~56 ppm.
These transform into four sharper singlets as the solution is cooled
to 193 K. A similar series of changes were observed for 2b(thf)
and 3b(thf). However, for 2b(thf), the spectrum shows that two
new sharp singlets emerge at around  −44 ppm on lowering the
temperature to 253 K. It is difficult to ascertain the exact nature of
the dynamic processes which may be occurring.
One possibility is that complexes in which oxygen is coordinated
(such as b and c, Scheme 4) may form in equilibrium with mono-
dentate P bound or bidentate PN complexes (a and d, Scheme 4).
Several studies have been carried out by Lindner et al.11a,b and
others25a,c dealing with Pd(II) complexes with PO chelating ligands
which are chemically similar to the PO moiety in phosphines 1 and
2. However, complexes of other metals may provide a more useful
comparison since previous reports have shown that a switch of coor-
dination between PN and PO chelated forms produces similar NMR
behaviour to that observed here.3g,26 Thus, it is tentatively proposed
that a similar type of equilibrium involving species a, c and possibly
d (Scheme 4) may be occurring in solutions of 1b(thf)–3b(thf).
Although a bridging configuration of acetate groups is possible
in complex 1f leading to binuclear or dimeric structures, mass
spectrometry indicates a monomeric complex. An IR spectrum of
complex 1f shows that the acetate stretching frequencies ((CO) and

(C–O)) are in the expected regions, and are similar to these in other
reported monodentate acetate complexes.7c,21
1
New resonances appeared in both the H and 13C NMR spectra
when 1d was treated with moderately high pressures of CO (40 bar)
in CD2Cl2. These appeared as two doublets at  2.46 and 2.38 ppm in
the 1H NMR spectrum with a corresponding decrease in the signals
due to the PdMe resonance of complex 1d (below  0.5 ppm).
The 13C NMR spectrum shows two emerging doublets at around
 39.7 ppm. These signals are weak and so a confident assignment
of the JPC coupling constants, or of the major and minor peaks due
to the diastereomeric complexes cannot be made. Furthermore, a
decrease in the 31P NMR chemical shift is observed on conversion
of 1d to 1e. This spectroscopic data is consistent with other reported
acyl palladium complexes which have PN ligands, thus indicating
the probable formation of the acyl complex, 1e.22
For complexes 1c–e there is the possibility of geometrical
isomers (P cis or trans to the methyl/acyl ligand), however all
complexes isolated exist as only one isomer. This is clear from the
presence of only two peaks in their 31P NMR spectra, which are due
to the two pairs of ligand diastereomers. Spectroscopic data do not
allow a definitive assignment of the preferred geometric isomer,
although it has invariably been found from single crystal X-ray
diffraction on similar complexes that the P cis to the methyl/acyl
isomer is preferred.9f,22a,c,e,g,23 Thus a phosphine cis to the methyl/
acyl configuration is also predicted for complexes 1c–1e.24 The 1H
and 13C NMR spectra indicate the presence of one MeCN ligand
in complex 1d, and so coordination of the oxygen donor in 1d is
unlikely as all coordination sites are occupied. No broadening of
the NMR signals was observed for 1d, indicating that isomerization
3 2 5 6
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0

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these differences in coordination behaviour are due to the oxygen
functionality.
NMR data suggests that 4 forms a 4-membered chelate in
PdCl2(4)2 in contrast to the proposed tridentate OPN coordination
of 2 in complex 2b(thf) at lower temperatures (see ESI†).35
When the reaction was performed in methanol the redox reac-
tion proceeded more rapidly (see below) and with higher yields
of 4-oxide. The oxidation of phosphines by Pd(OAc)2 has often
been noted previously and occurs with concomitant reduction
of Pd(OAc)2.36 We have previously shown that 2 equivalents of
diphenyl-(2-pyridyl)-phosphine reacted with Pd(OAc)2 to yield
[Pd2(Ph2Ppy)2(OAc)2], a PN bridged Pd(I) dimer.36g It was proposed
that a Pd(II) species, of the type “Pd(OAc)2(phosphine)2”, initially
forms and is subsequently reduced to a Pd(0) phosphine species
(with concomitant reductive elimination of two acetate ligands)
which then reacts with the Pd(II) intermediate to give the observed
Pd(I) complex.36g Since 4 has important similarities to Ph2Ppy, it
may be expected that a similar reaction may occur resulting in the
formation of Pd(I) dimers. The oxide of 4 and other species formed
could not be separated after extensive attempts at purification via
reprecipitation, crystallisation or column chromatography.
Since 4 did not form a stable complex with Pd(OAc)2 when one
equivalent of ligand was used, the reaction was carried out with
two equivalents of 4. The brown colour of the Pd(OAc)2 solution
in CH2Cl2 lightened to orange–brown immediately after the addi-
tion of 4. After 10 min, the solvent was reduced and the product
was then precipitated and washed with diethylether. The 31P NMR
spectrum of the resulting product in CDCl3 is quite similar to that
obtained from the 1:1 product mixture, except that in addition to
the peaks due to 4-oxide, and unidentified species at  0 to −3 ppm,
a large broad peak initially appears at  22 ppm and disappears
after ~1–2 days in solution. Based upon previous observations,36f
the position and broadness of the peak indicates the presence of the
expected, but unstable, “Pd(OAc)2(4)2”.
Scheme 4 Possible coordination modes of OPN ligands 1–3 with
2+
Pd(solv)2
.
This appears to be rapid enough at room temperature to produce a
broad time averaged 31P NMR signal, but the sharp peaks of the dif-
ferently chelated species can be seen at low temperatures.
The 31PNMR spectrum of 2b(thf) at −20 °C (253 K) shows peaks
at  −44 ppm. The appearance of a set of peaks at higher field than
observed for the free ligand is unusual; 31P NMR chemical shifts
are more commonly observed to increase upon coordination to a
metal,27 although the dependence of 31P NMR chemical shifts on
the chemical and structural environment of the phosphorus atom
is complex.28 Previous studies of phosphine ligands and phosphine
complexes have identified various trends in the 31P NMR chemical
shift data and for tridentate chelates in square planar complexes,
these do not follow a simple pattern.10,29 Coordinated phosphines
have been observed to undergo large positive and negative chemical
shift changes; this variation being ascribed to variations in chelate
strain.28a Thus, that 2b(thf) exhibits an unusually low 31P NMR
chemical shift indicating that the chelate strain in this complex is
different to that in the other complexes described above and that 2 is
adopting an entirely different coordination mode to the possibilities
discussed above. A tridentate OPN coordination mode (structure b,
Scheme 4) is consistent with the spectroscopic data since it is ex-
pected that angles around phosphorus would be under some degree
of strain compared to mono- and bidentate coordination modes.
Palladium complexes of phosphine 3, which is also capable of
forming a less strained 6-membered PO chelate and a 5-membered
PN chelate, do not show any high field peaks at low temperatures
in CD2Cl2 although the NMR data for complexes of ligands 1–3 do
point to a weak interaction of the oxygen donor with the metal.31
In the light of previous work which shows the ease of reduction of
Pd(OAc)2 by both monodentate36a,d–g and bidentate phosphines,36b it
may seem surprising that the reaction of 1 and Pd(OAc)2 produces a
stable Pd(II) complex with no sign of 1-oxide. The successful prepa-
ration of relatively stable Pd(II) phosphine complexes with acetate
ligands, is probably due to the lower susceptibility of some phos-
phines to oxidation by Pd(OAc)2, and/or an appropriate choice of
solvent.7g,21a,b,d,30,36b,37 It appears that 1f, which is a monomeric com-
plex with a 5-membered PN chelate, is stable enough to be isolated
from CH2Cl2 solutions. However, methanol or ethanol solutions of
1f begin to decompose in less than an hour at room temperature with
deposition of Pd(0).
Palladium complexes of phosphine 4
Attempted preparation of Pd(0) and Pd(I) complexes of 4
Following the procedure that was successfully used to prepare 1a,
attempts to prepare a 1:1 complex of phosphine 4 and dichloro-
palladium resulted in a multitude of complexes. The analogous
reaction with 2-pyridyl(diphenyl)phosphine (Ph2Ppy) appears to
produce a monomeric palladium complex with a PN chelate.30 How-
ever, due to the strained nature of the resulting 4-membered PN che-
late, the most frequently reported complexes with PdCl2, have two
monodentate P bound phosphine or bridging PN configurations.32
The 2:1 reaction of 4 with PdCl2(benzonitrile)2 was attempted
using standard procedures.31a,c,32a–c,e,33,34 The 31P NMR spectra of
the product in CDCl3 showed a complex series of changes over the
temperature range 40 °C to −55 °C, which is entirely reproducible
if the NMR sample is successively warmed or cooled. At 40 °C,
the spectrum appears as a sharp pseudotriplet at approximately 
16 ppm which is expected to arise from combinations of the dia-
stereomeric ligand pairs (present in approximately equal amounts)
of the complex PdCl2(4)2. A dramatic change is observed on cool-
ing to −30 °C with a new sets of broad peaks appearing at  46, 30
and −45 ppm which sharpen around −55 °C. Clearly, the coordina-
tion behaviour of 4 with PdCl2 is considerably more complicated
than that observed for similar bis(phosphine) complexes having
potential 4-membered PN chelates.32a–c,33a,34 It is most likely that
Routes to Pd(0) or Pd(I) complexes of 4 were sought for positive
identification of the Pd(0) or Pd(I) complexes that appear to be pres-
ent in reactions of Pd(OAc)2 with 4. Preparative methods for Pd(0)
or Pd(I) complexes commonly start from dichloropalladium(II)
phosphine complexes or other Pd(II) phosphine complexes.38
Unfortunately, since no pure complexes of 4 and PdCl2 could be
prepared, neither of these types of complexes was available in this
study. Pd(I) complexes are also often formed by co-proportionation
of Pd(0) and Pd(II) complexes.38c Therefore, attempts were made to
prepare these complexes using Pd(0) and Pd(I) starting materials
with weakly bound ligands.
Reaction of Pd2(dba)3(CHCl3) (dba = dibenzylideneacetone) with
two equivalents of phosphine 4 gave a product with a very similar
31P NMR spectrum to that seen in the reaction of 4 with Pd(OAc)2.
An attempt to form a Pd(0) complex via the addition of a large ex-
cess of 4 to Pd(OAc)2, using the excess phosphine to reduce Pd(II)
to Pd(0),36g was unsuccessful. Apart from the presence of 4-oxide,
the 31P NMR spectrum in CD3OD showed no species corresponding
to those formed when fewer equivalents of ligand were added. The
Pd(I) dimer, [PdCl(t-butylisocyanide)2]2, was reacted with 4 in a
1:1 phosphine/Pd molar ratio.18 After washing the resulting orange
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0
3 2 5 7

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complex with diethylether, the 31P NMR spectrum in CDCl3 showed
peaks at  −6 to −8 ppm and  4 to 0 ppm which are similar in ap-
pearance to those around  0 to −3 ppm found in reactions of 4 with
Pd(OAc)2. In order to prepare a Pd(I) complex with acetate ligands,
a slight deficiency of silver acetate was added (a small excess gave
immediate decomposition to Pd(0)). The 31PNMR spectrum again
showed a distinctive set of peaks between  4 and −1 ppm.
Thus it appears that the complexes observed in 1:1 and 2:1
reactions of 4 and Pd(OAc)2 which give 31P NMR resonances
around  0 to −3 ppm are similar to both the complexes prepared
for comparison (“Pd(I)(OAc)(4)” and “Pd(0)(dba)(4)2”). However,
the reactions still give rise to complicated mixtures and no clear
conclusion can be drawn from these results, other than it is likely
that both Pd(0) or Pd(I) complexes of 4 are formed when Pd(OAc)2
is reduced by 4.
Catalytic experiments
Experiments were carried out to determine if palladium complexes
of the OPN phosphine ligands, or in situ mixtures of the ligands
with Pd salts, are catalytically active for reactions of CO with ethene
or propyne. The results of the reactions studied are collected in
Table 1. Complex 1d produced approximately 10 mg of polyketone
at room temperature when a CH2Cl2 solution was treated with 20 bar
CO and 20 bar ethene for 24 h. The catalytic activity improved at
higher temperatures, with 30 mg of polyketone obtained at 40 °C
under comparable conditions, but with significant deposition of
Pd(0). Polyketone was also produced using an in situ catalyst
preparation of 4 (1:2.5:3 molar ratio of Pd(OAc)2, 4 and methane-
sulfonic acid) in MeOH at 20 °C under 20 bar CO and 20 bar ethene.
In this case approximately 30 mg of polyketone was obtained and
no Pd(0) metal was detected.
Phosphines 1 and 4 were tested to determine if they had any
potential in the methoxycarbonylation of propyne; the results of
these reactions are summarised in Table 2. In situ catalyst prepa-
rations containing the phosphine, Pd(OAc)2 and methanesulfonic
acid were employed. Phosphine 4, when combined with Pd(OAc)2,
was found to give rise to an active catalyst system for the produc-
tion of methylmethacrylate (MMA). However, no catalytic activity
was observed when using phosphine 1. This latter observation was
not unexpected since ligands known to give active catalysts for the
formation of MMA are usually phosphines with either a 2-pyridyl
group bound directly to phosphorus, or they have no nitrogen donor
substituents at all.
A catalyst system prepared from Pd(OAc)2, phosphine 4
and methanesulfonic acid in a 1:2.5:2.7 molar ratio, gave the
most notable catalytic performance, producing 15.2 g of methyl-
methacrylate in 3 h, at 50 °C with 10 bar CO, 160 cm3 MeOH and
15 g propyne. This particular ratio of catalyst components was also
the most successful for the CO/ethene copolymerisation reaction
and this catalyst system appears very stable as no Pd(0) deposition
is observed at any stage for either reaction. Higher or lower ligand
ratios produced less active catalysts and of particular significance
is the very low optimal ligand/Pd ratio of 2.5:1; the dependance
of MMA production on Pd:ligand ratios is summarised in Fig. 4.
Typically, around 20–40 equivalents of phosphine are required to
produce the best results in most reported 2-pyridylphosphine based
catalyst systems.39 Such a dramatic reduction in ligand requirement
is of significant interest since the use of large excesses of ligands
in commercial processes is undesirable due to the considerable
expense, waste and problems of product contamination which
commonly result. Furthermore, the reaction with 4 appears to be
highly selective for the production of methylmethacrylate as only
negligible amounts of any other products (e.g. methylcrotonate)
were detected by GC analysis.
Fig. 4 Rate of Pd catalysed formation of MMAas a function of Pd:ligand
ratio.
(Pd/ligand/acid ratio of 1:20:22, the most active system for this re-
action reported to date) consumes, over 3 h, approximately 2.5 times
the amount of propyne (TON of 890 mol/mol h−1) consumed by the
catalyst system using phosphine 4 (after 3 h, the TOF for run 14,
Table 2, is 354 mol/mol h−1). The exact reason for the lower activity
of the catalyst system based on 4 is not clear, although several fac-
tors in combination may be responsible. Interestingly, the use of the
phosphine, n-butyl(4-methoxyphenyl)(2-pyridyl)phosphine instead
of Ph2Ppy, results in little difference in catalytic activity for MMA
production.39a,b Therefore, it seems that the presence of n-butyl and
4-methoxyphenyl substituents in place of the two phenyl groups of
Ph2Ppy has little affect on catalyst performance. It is likely that the
improved stability, but lower activity, of the catalyst formed from
phosphine 4 when compared to that formed from related phosphines
is most probably caused by interaction of the tetrahydofurfuryl
oxygen of 4 with Pd in the active catalytic species.Although coordi-
nation of the oxygen donor of phosphine 4 with Pd was not detected
in the coordination studies, transient interaction is possible and it
seems highly probable that interaction does occur in complexes of
phosphine 1, which has the same O donor substituent.
Conclusion
OPN phosphine ligands 1–3 were found to form a range of
palladium and methylpalladium complexes 1a–f, 2a–b, 3a–b. The
tetrahydrofuran complexes 1b(thf), 2b(thf) and 3b(thf) showed
interesting low temperature NMR behaviour that suggests unusual
coordination of the phosphine ligands. This may include tridentate
OPN coordination, which has not been observed before in square
planar complexes. All complexes exhibit 5-membered PN chelation
of the OPN phosphine ligand, which is confirmed by single crystal
X-ray diffraction studies of 1a and 3a.
The coordination behaviour of phosphine 4 with equimolar
amounts of simple palladium(II) starting materials such as
PdCl2(cod) and Pd(OAc)2 gave complex product mixtures. Variable
temperature NMR studies showed dramatic changes over the
temperature range 40° to −55 °C indicating 4-membered PN chela-
tion and some interaction of the oxygen of the tetrahydrofurfuryl
moiety of 4 with Pd. Whatever ratio of 4 to Pd(OAc)2 was used in
these studies, the reaction resulted in oxidation of 4 and reduction
of palladium. It appears likely that Pd(0) and/or Pd(I) complexes
are present in the reaction mixture. However, attempts to identify
these by independent preparation of Pd(0) and Pd(I) complexes of 4
proved inconclusive. More straightforward coordination chemistry
Quantitative comparisons with other systems are tenuous since
most reported catalysts have been tested under different conditions
than those studied here. Nonetheless, catalyst systems based on 4
seem to have an activity that corresponds favourably with other
Pd(II) catalysts for the co-reaction of CO and alkynes.32e,39,40 Under
the same reaction conditions, a catalyst system containing Ph2Ppy
3 2 5 8
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0

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6 (a) G. J. P. Britovsek, K. J. Cavell, M. J. Green, F. Gerhards, B. W.
Skelton and A. H. White, J. Organomet. Chem., 1997, 533, 201;
(b) M. S. Goedheijt, J. N. H. Reek, P. C. J. Kamer and P. W. N. M.
van Leeuwen, J. Chem. Soc., Chem. Commun., 1998, 2431.
7 (a) L. Sacconi, G. P. Speroni and R. Morassi, Inorg. Chem., 1968, 7,
1521; H. J. Banbery, W. Hussain, T. A. Hamor, C. J. Jones and J. A.
McCleverty, J. Chem. Soc., Dalton Trans., 1990, 657; (b) A. Bacchi,
M. Carcelli, M. Costa, P. Pelagatti, C. Pelizzi and G. Pelizzi, Gazz.
Chim. Ital., 1994, 124, 429; J. R. Dilworth, S. D. Howe, A. J. Hutson,
J. R. Miller, J. Silver, R. M. Thompson, M. Harman and M. B.
Hursthouse, J. Chem. Soc., Dalton Trans., 1994, 3553; S. D. Perera
and B. L. Shaw, J. Chem. Soc., Dalton Trans., 1995, 641; A. Bacchi,
M. Carcelli, M. Costa, A. Leporati, E. Leporati, P. Pelagatti, C. Pelizzi
and G. Pelizzi, J. Organomet. Chem., 1997, 535, 107; U. Casellato,
P. Guerriero, S. Tamburini and P. A. Vigato, Inorg. Chim. Acta, 1997,
260, 1; (c) U. Nagel and H. G. Nedden, Chem. Ber./Recueil, 1997,
130, 385; I. D. Kostas and C. G. Screttas, J. Organomet. Chem., 1999,
585, 1.
is exhibited by other 4-membered PN chelating phosphines with
Pd(II), and therefore it is suspected that interaction of the oxygen
donor substituent of 4 with Pd is responsible for the observed
differences.
In situ catalyst mixtures of 1 and 4 showed low activity for the
co-polymerization of CO and ethene, whereas the latter gave a
moderately active catalyst system for the methoxycarbonylation of
propyne, which had excellent stability and required surprisingly low
ligand/palladium ratios. The aim of this ligand design study was to
obtain a ligand which could act to stabilise catalytic intermediates
and thus reduce the need for large excesses of ligand, as well as fa-
cilitate the next step of the catalytic cycle by “trapping” more highly
reactive intermediates. Improved catalyst stability in the presence
of much lower amounts of ligand has been achieved, but at the
cost of a somewhat reduced activity. Nevertheless, good activity
and selectivity is observed with the catalyst system formed from 4
and this represents the first pyridylphosphine based system for the
carbonylation of alkynes, which does not require a large excess of
phosphine ligand to maintain catalyst stability.
8 M. Yabuta, S. Nakamura, T. Yamagata and K. Tani, Chem. Lett., 1993,
323.
9 (a) G. U. Spiegel and O. Stelzer, Chem. Ber., 1990, 123, 989;
(b) H.-J. Haupt and U. Ortmann, Z. Anorg. Allg. Chem., 1993, 619, 1209;
(c) H. Yang, N. Lugan and R. Mathieu, Anal. Quím., Int. Ed., 1997,
93, 28; (d) H. Yang, M. Alvarez-Gressier, N. Lugan and R. Mathieu,
Organometallics, 1997, 16, 1401; (e) G. Zhu, M. Terry and X. Zhang,
J. Organomet. Chem., 1997, 547, 97; (f ) E. K. van den Beuken,
W. J. J. Smeets, A. L. Spek and B. L. Feringa, J. Chem. Soc., Chem.
Commun., 1998, 223.
Acknowledgements
Financial support from the Australian Research Council and Lucite
International (UK), and the generous loan of Pd salts by Johnson-
Matthey are all gratefully acknowledged. We also thank staff from
Cardiff University and the Central Science Laboratory, University
of Tasmania, for their expertise and assistance with the collection of
spectroscopic and analytical data.
10 S. A. Wander, A. Miedaner, B. C. Noll, R. M. Barkley and D. L.
DuBois, Organometallics, 1996, 15, 3360.
11 (a) E. Lindner, J. Dettinger, H. A. Mayer, H. Kühnbauch, R. Fawzi and
M. Steimann, Chem. Ber., 1993, 126, 1317; (b) E. Lindner, R. Schreiber,
M. Kemmler, H. A. Mayer, R. Fawzi and M. Steimann, Z. Anorg. Allg.
Chem., 1993, 619, 202; (c) J.-S. Sun, C. E. Uzelmeier, D. L. Ward and
K. R. Dunbar, Polyhedron, 1998, 17, 2049; (d) P. Braunstein, M. D.
Fryzuk, F. Naud and S. J. Rettig, J. Chem. Soc., Dalton Trans., 1999,
589.
12 (a) P. R. Bernatis, A. Miedaner, R. C. Haltiwanger and D. L. DuBois,
Organometallics, 1994, 13, 4835; (b) A. Miedaner, B. C. Noll and
D. L. DuBois, Organometallics, 1997, 16, 5779; (c) C. J. Smith,
V. S. Reddy and K. V. Katti, J. Chem. Soc., Dalton Trans., 1998, 1365.
13 (a) E. Lindner, H. Rauleder and W. Hiller, Z. Naturforsch., 1983, 38b,
417; (b) J. Bank, O. Gevert, W. Wolfsberger and H. Werner, Organo-
metallics, 1995, 14, 4972; (c) J. R. Dilworth, A. J. Hutson, J. S. Lewis,
J. R. Miller, Y. Zheng, Q. Chen and J. Zubieta, J. Chem. Soc., Dalton
Trans., 1996, 1093.
14 M. S. Kharasch, R. C. Seyler and F. R. Mayo, J. Am. Chem. Soc., 1938,
60, 882.
15 D. Drew and J. R. Doyle, Inorg. Synth., 1990, 28, 348.
16 R. E. Rülke, J. M. Ernsting, A. L. Spek, C. J. Elsevier, P. W. N. M.
van Leeuwen and K. Vrieze, Inorg. Chem., 1993, 32, 5769.
17 T. Ukai, H. Kawazura, Y. Ishii, J. J. Bonnet and J. A. Ibers,
J. Organomet. Chem., 1974, 65, 253.
18 M. F. Rettig and P. M. Maitlis, Inorg. Synth., 1977, 17, 134.
19 The Xtal 3.5. System, ed. S. R. Hall, D. J. du Boulay and R. Olthof-
Hazekamp, University of Western Australia, 1999.
References
1 W. A. Herrmann and B. Cornils, Applied Homogeneous Catalysis with
Organometallic Compounds, 1st edn., VCH, Weinheim, Germany,
1996, vol. 1; W. A. Herrmann and B. Cornils, Applied Homogeneous
Catalysis with Organometallic Compounds, 1st edn., VCH, Weinheim,
Germany, 1996, vol. 2.
2 (a) S. J. Chadwell, S. J. Coles, P. G. Edwards, M. B. Hursthouse and
A. Imran, Polyhedron, 1995, 14, 1057; S. J. Chadwell, S. J. Coles,
P. G. Edwards and M. B. Hursthouse, J. Chem. Soc., Dalton
Trans., 1995, 3551; S. J. Chadwell, S. J. Coles, P. G. Edwards and
M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1996, 1105;
(b) M. J. Green, K. J. Cavell and P. G. Edwards, J. Chem. Soc., Dalton
Trans., 2000, 853.
3 (a) K. K. Hii, S. D. Perera and B. L. Shaw, J. Chem. Soc., Dalton
Trans., 1994, 3589; (b) K. Tani, M. Yabuta, S. Nakamura and
T. Yamagata, J. Chem. Soc., Dalton Trans., 1993, 2781; (c) A. Heßler,
J. Fischer, S. Kucken and O. Stelzer, Chem. Ber., 1994, 127, 481;
(d) D. B. Grotjahn and C. Joubran, Organometallics, 1995, 14, 5171;
(e) J. A. Casares, P. Espinet, K. Soulantica, I. Pascual and A. G. Orpen,
Inorg. Chem., 1997, 36, 5251; (f ) U. Nagel and H. G. Nedden, Chem.
Ber./Recueil, 1997, 130, 989; (g) H. Yang, N. Lugan and R. Mathieu,
Organometallics, 1997, 16, 2089; (h) J. Andrieu, B. R. Steele,
C. G. Screttas, C. J. Cardin and J. Fornies, Organometallics, 1998, 17,
839; (i) P. Bhattacharyya, J. Parr and A. M. Z. Slawin, J. Chem. Soc.,
Dalton Trans., 1998, 3609; (j) A. Jacobi, G. Huttner and U. Winterhalter,
J. Organomet. Chem., 1998, 571, 231; (k) V. D. Romanenko, J.-F.
Colom Toro, F. Rivière, J.-G. Wolf and M. Sanchez, J. Chem. Soc.,
Chem. Commun., 1998, 2183; (l) E. K. van den Beuken, N. Veldman,
W. J. J. Smeets, A. L. Spek and B. L. Feringa, Organometallics, 1998,
17, 636; (m) P. Espinet and K. Soulantica, Coord. Chem. Rev., 1999,
193–195, 499.
20 K. Tani, S. Nakamura, T. Yamagata and Y. Kataoka, Inorg. Chem.,
1993, 32, 5398.
21 (a) T. A. Stephenson, S. M. Morehouse, A. R. Powell, J. P. Heffer
and G. Wilkinson, J. Chem. Soc., 1965, 3632; (b) J. A. Goodfellow,
T. A. Stephenson and M. C. Cornock, J. Chem. Soc., Dalton Trans.,
1978, 1195; (c) K. Nakamoto, Infrared and Raman Spectroscopy of
Inorganic and Coordination Compounds, 4th edn., John Wiley & Sons,
New York, 1986; (d) S. J. Coles, P. G. Edwards, M. B. Hursthouse,
K. M. A. Malik, J. L. Thick and R. P. Tooze, J. Chem. Soc., Dalton
Trans., 1997, 1821.
22 (a) G. P. C. M. Dekker, A. Buijs, C. J. Elsevier, K. Vrieze, P. W. N. M.
van Leeuwen, W. J. J. Smeets, A. L. Spek, Y. F. Wang and C. H. Stam,
Organometallics, 1992, 11, 1937; (b) P. Wehman, R. E. Rülke, V. E.
Kaasjager, P. C. J. Kamer, H. Kooijman, A. L. Spek, C. J. Elsevier,
K. Vrieze and P. W. N. M. van Leeuwen, J. Chem. Soc., Chem.
Commun., 1995, 331; (c) H. A. Ankersmit, B. H. Løken, H. Kooijman,
A. L. Spek, K. Vrieze and G. van Koten, Inorg. Chim. Acta, 1996,
252, 141; (d) H. A. Ankersmit, N. Veldman, A. L. Spek, K. Vrieze
and G. van Koten, Inorg. Chim. Acta, 1996, 252, 339; (e) R. E. Rülke,
V. E. Kaasjager, P. Wehman, C. J. Elsevier, P. W. N. M. van Leeuwen,
K. Vrieze, J. Fraanje, K. Goubitz and A. L. Spek, Organometallics,
1996, 15, 3022; (f ) A. Aeby, F. Bangerter and G. Consiglio, Helv. Chim.
Acta, 1998, 81, 764; (g) A. G. J. Ligtenbarg, E. K. van den Beuken,
A. Meetsma, N. Veldman, W. J. J. Smeets,A. L. Spek and B. L. Feringa,
J. Chem. Soc., Dalton Trans., 1998, 263; (h) P. H. P. Brinkmann and
G. A. Luinstra, J. Organomet. Chem., 1999, 572, 193.
4 (a) J. C. Jeffrey and T. B. Rauchfuss, Inorg. Chem., 1979, 18, 2658;
(b) A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108, 27;
(c) C. S. Slone, D. A. Weinberger and C. A. Mirkin, Prog. Inorg. Chem.,
1999, 48, 233.
5 (a) C. Pisano, G. Consiglio, A. Sironi and M. Moret, J. Chem. Soc.,
Chem. Commun., 1991, 421; (b) E. Lindner, J. Dettinger, R. Fawzi
and M. Steimann, Chem. Ber., 1993, 126, 1347; (c) W. Keim, H. Maas
and S. Mecking, Z. Naturforsch., 1995, 50b, 430; (d) Y. Kataoka,
Y. Tsuji, O. Matsumoto, M. Ohashi, T. Yamagata and K. Tani, J. Chem.
Soc., Chem. Commun., 1995, 2099; (e) H. A. Ankersmit, N. Veldman,
A. L. Spek, K. Eriksen, K. Goubitz, K. Vrieze and G. van Koten,
Inorg. Chim. Acta, 1996, 252, 203; (f ) S. Mecking and W. Keim,
Organometallics, 1996, 15, 2650; (g) M. J. Green, G. J. P. Britovsek,
K. J. Cavell, F. Gerhards, B. F. Yates, K. Frankcombe, B. W. Skelton
andA. H. White, J. Chem. Soc., Dalton Trans., 1998, 1137; (h) D. Kruis,
N. Ruiz, M. D. Janssen, J. Boersma, C. Claver and G. van Koten, Inorg.
Chem. Commun., 1998, 1, 295.
D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0
3 2 5 9

View Article Online
23 W. de Graaf, S. Harder, J. Boersma, G. van Koten and J. A. Kanters, J.
Organomet. Chem., 1988, 358, 545.
34 T. Suzuki, A. Morikawa and K. Kashiwabara, Bull. Chem. Soc. Jpn.,
1996, 69, 2539.
24 A. Yamamoto, Organotransition Metal Chemistry: Fundamental Con-
cepts and Applications, Wiley-Interscience, New York, 1986.
25 (a) A. R. Siedle, R. A. Newmark and L. H. Pignolet, J. Am. Chem. Soc.,
1982, 104, 6584; (b) S. Okeya, T. Miyamoto, S. Ooi, Y. Nakamura
and S. Kawaguchi, Bull. Chem. Soc. Jpn., 1984, 57, 395; (c) U. Nagel
and T. Krink, Chem. Ber., 1993, 126, 1091; (d) K. R. Dunbar and
J.-S. Sun, J. Chem. Soc., Chem. Commun., 1994, 2387; (e) M. J. Green,
G. J. P. Britovsek, K. J. Cavell, B. W. Skelton andA. H. White, J. Chem.
Soc., Chem. Commun., 1996, 1563.
26 A. Ecke, W. Keim, M. C. Bonnet, I. Tkatchenko and F. Dahan, Organo-
metallics, 1995, 14, 5302.
27 B. E. Mann, B. L. Shaw and R. M. Slade, J. Chem. Soc. A, 1971, 2976.
28 (a) P. E. Garrou, Chem. Rev., 1981, 81, 229; (b) J. A. Davies, in The
Chemistry of the Metal-Carbon Bond, ed. F. R. Hartley and S. Patai,
John Wiley & Sons, Chichester, 1982, vol. 1, p 813.
29 (a) D. L. DuBois, A. Miedaner and R. C. Haltiwanger, J. Am. Chem.
Soc., 1991, 113(87), 8753; (b) G. Dyer and J. Roscoe, Inorg. Chem.,
1996, 35, 4098.
30 C. G. Arena, E. Rotondo, F. Faraone, M. Lanfranchi and A. Tiripicchio,
Organometallics, 1991, 10, 3877.
31 (a) E. Lindner, R. Speidel, R. Fawzi and W. Hiller, Chem. Ber.,
1990, 123, 2255; (b) R. J. Coyle, Y. L. Slovokhotov, M. Y. Antipin
and V. V. Grushin, Polyhedron, 1998, 17, 3059; (c) E. Lindner and
J. Dettinger, Z. Naturforsch., 1991, 46b, 432.
32 (a) A. Maisonnet, J. P. Farr, M. M. Olmstead, C. T. Hunt and
A. L. Balch, Inorg. Chem., 1982, 21, 3961; (b) T. Suzuki, M. Kita,
K. Kashiwabara and J. Fujita, Bull. Chem. Soc. Jpn., 1990, 63, 3434;
(c) Y. Xie, C.-L. Lee, Y. Yang, S. J. Rettig and B. R. James, Can.
J. Chem., 1992, 70, 751; (d) S.-L. Li, Z.-Z. Zhang, B.-M. Wu and
T. C. W. Mak, Inorg. Chim. Acta, 1997, 255, 239; (e) M. T. Reetz,
R. Demuth and R. Goddard, Tetrahedron Lett., 1998, 39, 7089.
33 (a) J. P. Farr, M. M. Olmstead and A. L. Balch, Inorg. Chem., 1983, 22,
1229; (b) J. P. Farr, F. E. Wood andA. L. Balch, Inorg. Chem., 1983, 22,
3387; (c) J. P. Farr, M. M. Olmstead, F. E. Wood andA. L. Balch, J. Am.
Chem. Soc., 1983, 105, 792; (d) V. K. Jain, V. S. Jakkal and R. Bohra, J.
Organomet. Chem., 1990, 389, 417.
35 Z.-Z. Zhang and H. Cheng, Coord. Chem. Rev., 1996, 147, 1.
36 (a) C. Amatore, A. Jutand and M. A. M’Barki, Organometallics,
1992, 11, 3009; (b) F. Ozawa, A. Kubo and T. Hayashi, Chem. Lett.,
1992, 2177; (c) T. Mandai, T. Matsumoto, J. Tsuji and S. Saito, Tetra-
hedron Lett., 1993, 34, 2513; (d ) C. Amatore, E. Carré, A. Jutand,
M. A. M’Barki and G. Meyer, Organometallics, 1995, 14, 5605;
(e) C. Amatore, E. Carré, A. Jutand and M. A. M’Barki, Organo-
metallics, 1995, 14, 1818; (f ) C. Amatore, E. Blart, J. P. Genêt,
A. Jutand, S. Lemaire-Audoire and M. Savignac, J. Org. Chem.,
1995, 60, 6829; (g) A. Dervisi, P. G. Edwards, P. D. Newman,
R. P. Tooze, S. J. Coles and M. B. Hursthouse, J. Chem. Soc., Dalton
Trans., 1998, 3771.
37 (a) A. S. Berenblyum, A. G. Knizhnik, S. L. Mund and I. I. Moiseev,
J. Organomet. Chem., 1982, 234, 219; (b) C. Pisano and G. Consiglio,
Gazz. Chim. Ital., 1994, 124, 393; (c) F. Benvenuti, C. Carlini,
M. Marchionna, R. Patrini, A. M. R. Galletti and G. Sbrana, J. Inorg.
Organomet. Polym., 1997, 7, 183; (d) F. Benvenuti, C. Carlini,
A. M. R. Galletti, G. Sbrana, M. Marchionna and R. Patrini, J. Mol.
Catal. A, 1999, 137, 49.
38 (a) L. Malatesta and M. Angoletta, J. Chem. Soc. A, 1957, 1186;
(b) L. Malatesta and S. Cenini, Zerovalent Compounds of Metals,
Academic Press, London, 1974; (c) C. F. J. Barnard and M. J. H.
Russell in Comprehensive Coordination Chemistry, 1st edn., ed.
R. D. Gillard and J. A. McCleverty, Pergamon Press, Oxford, 1987,
vol. 5, p. 1099; (d) D. R. Coulson, Inorg. Synth., 1990, 28, 107;
(e) V. V. Grushin, C. Bensimon and H. Alper, Inorg. Chem., 1994, 33,
4804.
39 (a) E. Drent and P. H. M. Budzelaar, Eur. Pat Appl. EP-A-386 834,
1990; (b) E. Drent, P. Arnoldy and P. H. M. Budzelaar, J. Organomet.
Chem., 1993, 455, 247; (c) J. Keijsper, P. Arnoldy, M. J. Doyle and
E. Drent, Recl. Trav. Chim. Pays-Bas, 1996, 115, 248.
40 (a) K.-T. Huh, A. Orita and H. Alper, J. Org. Chem., 1993, 58, 6956;
(b) A. Scrivanti and U. Matteoli, Tetrahedron Lett., 1995, 36, 9015;
(c) A. L. Monteiro, V. R. Lando and V. Gasparini, Synth. Commun.,
1997, 27, 3605; (d) K. Tezuka, Y. Ishizaki and Y. Inoue, J. Mol. Catal.
A: Chem., 1998, 129, 199.
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D a l t o n T r a n s . , 2 0 0 4 , 3 2 5 1 – 3 2 6 0