Phosphine ligands in the Palladium-catalysed methoxycarbonylation of ethene: Insights into the catalytic cycle through an HP NMR spectroscopic Study

Article abstract of DOI:10.1002/chem.200903158

Novel cis-1,2-bis(di-tertbutyl-phosphinomethyl) carbocyclic ligands 6-9 have been prepared and the corresponding palladium complexes [Pd(O ₃SCH₃)(L-L)][O₃SCH₃] (L-L = diphosphine) 32-35 synthesised and characterised by NMR spectroscopy and Xray diffraction. These diphosphine ligands give very active catalysts for the palladium-catalysed methoxycarbonylation of ethene. The activity varies with the size of the carbocyclic backbone, ligands 7 and 9, containing four- and six-membered ring backbones giving more active systems. The acid used as co-catalyst has a strong influence on the activity, with excess trifluoroacetic acid affording the highest conversion, whereas excess methyl sulfonic acid inhibits the catalytic system. An in oper-ando NMR spectroscopic mechanistic study has established the catalytic cycle and resting state of the catalyst under operating reaction conditions. Although the catalysis follows the hydride pathway, the resting state is shown to be the hydride precursor complex [Pd(O₃SCH₃)(L-L)][O₃SCH₃], which demonstrates that an isolable/detectable hydride complex is not a prerequisite for this mechanism.

Full text of DOI:10.1002/chem.200903158

FULL PAPER
DOI: 10.1002/chem.200903158
Phosphine Ligands in the Palladium-Catalysed Methoxycarbonylation of
Ethene: Insights into the Catalytic Cycle through an HP NMR Spectroscopic
Study
Verꢀnica de la Fuente,[a] Mark Waugh,[b] Graham R. Eastham,*[b] Jonathan A. Iggo,*[c]
Sergio Castillꢀn,[d] and Carmen Claver*[a]
Abstract:
Novel
cis-1,2-bis(di-tert-
membered ring backbones giving more
active systems. The acid used as co-cat-
alyst has a strong influence on the ac-
tivity, with excess trifluoroacetic acid
affording the highest conversion,
whereas excess methyl sulfonic acid in-
hibits the catalytic system. An in oper-
ando NMR spectroscopic mechanistic
study has established the catalytic cycle
and resting state of the catalyst under
operating reaction conditions. Al-
though the catalysis follows the hydride
pathway, the resting state is shown to
be the hydride precursor complex [Pd-
butyl-phosphinomethyl) carbocyclic li-
gands 6–9 have been prepared and the
corresponding palladium complexes
[PdACHTUNGTRENNUNG(O3SCH3)ACHTUNGTRENNUNG(L-L)]ACHTUNGTRENNUNG[O3SCH3] (L-L=di-
phosphine) 32–35 synthesised and char-
acterised by NMR spectroscopy and X-
ray diffraction. These diphosphine li-
gands give very active catalysts for the
palladium-catalysed methoxycarbonyla-
tion of ethene. The activity varies with
the size of the carbocyclic backbone, li-
gands 7 and 9, containing four- and six-
AHCUTNERTGGU(NNN O3SCH3)ACHTUNRGTENGUN(N L-L)]ACTHUNGRTEN[NUGN O3SCH3], which dem-
onstrates that an isolable/detectable
hydride complex is not a prerequisite
for this mechanism.
Keywords: hydroesterification
methoxycarbonylation
·
·
NMR
spectroscopy
·
palladium
·
X-ray diffraction
Introduction
transformed into compounds of industrial interest by using a
palladium catalyst. Phosphine ligands and the presence of
acid are required to stabilize the palladium intermediates in
the reaction.[13]
Alkoxycarbonylation reactions are one of the most impor-
tant industrial processes using homogeneous transition-
metal catalysts.[1–16] In these reactions, a low-cost substrate is
In the case of ethene, polyketones and/or low boiling liq-
uids, such as methyl propanoate (n=1) can be obtained
(Scheme 1),[9,17] the selectivity of the reaction showing a
marked dependence on the nature of the phosphine ligand
employed. There have been many experimental[11–12,18–49] and
theoretical studies of the reaction.[50–52] Initially, it was con-
cluded that monodentate phosphines favour hydroesterifica-
tion of ethene to give methyl propanoate, whereas bidentate
phosphines lead to polyketones.[9] Subsequently, van Leeu-
wen showed that the chemoselectivity of the reaction can be
[a] Dipl.-Chem. V. de la Fuente, Prof. Dr. C. Claver
Departament de Quꢀmica Fꢀsica i Inorgꢁnica
Universitat Rovira i Virgili, C/Marcel·lꢀ Domingo s/n
43007 Tarragona (Spain)
Fax : (+34)97-755-9563
E-mail: carmen.claver@urv.cat
[b] Dr. M. Waugh, Dr. G. R. Eastham
Lucite International, Technology Centre
PO Box 90, Wilton, Middlesborough
Cleveland, TS68 JE (UK)
[c] Dr. J. A. Iggo
Department of Chemistry, University of Liverpool
Oxford Street, Liverpool, L69 7ZD (UK)
[d] Prof. Dr. S. Castillꢂn
Departament de Quꢀmica Analꢀtica i Orgꢁnica
Universitat Rovira i Virgili, C/Marcel·lꢀ Domingo s/n
43007 Tarragona (Spain)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200903158.
Scheme 1. Methoxycarbonylation versus copolymerisation of ethene.
Chem. Eur. J. 2010, 16, 6919 – 6932
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6919

controlled by the appropriate
choice of the diphosphine
ligand, methoxycarbonylation
being favoured by sterically
hindered
diphosphines.[50]
Recent computational studies
also concluded that sterically
bulky
diphosphine
ligands
strongly favour ester formation
over polymerisation.[51] Exten-
sive screening of monodentate
and bidentate ligands has
shown[17,53] that trialkyl phos-
phine ligands, such as PACTHNUTRGENUNG(nBu3),
are more effective than aryl
monodentate phosphines, for
example, PPh3, in the methoxy-
carbonylation of olefins with
Scheme 2. Proposed mechanisms for the methoxycarbonylation of ethene: A=hydride cycle, B=methoxycar-
bonyl cycle (& indicates different groups coordinated to palladium along the catalytic cycle.).
À
[Pd
(OAc)2L2/L] catalysts. Similarly, alkyl diphosphine li-
lowed by insertion into the Pd H bond then affords a Pd–
alkyl complex, which is transformed into an acyl complex by
the migratory insertion of CO.[45] Inter- or intramolecular
nucleophilic attack of methanol on the acyl carbonyl leads
to the formation of methyl propanoate and reformation of
the palladium hydride species, completing the catalytic
cycle.[11,41,47] The methoxycarbonyl mechanism (B) starts
with a Pd–OMe complex[1,40] Then, the insertion of CO into
gands containing bulky end groups (1–4) are preferred, af-
fording methyl propanoate with 98% selectivity.[53]
À
the Pd OMe bond leads to the formation of a methoxycar-
bonyl complex. Coordination and insertion of ethene fol-
lowed by methanolysis then occurs to give the product and
regenerate the catalyst.[40]
There is a lot of evidence and general agreement that sys-
tems affording ester product operate exclusively by the hy-
dride catalytic cycle,[45] and that both cycles operate in co-
polymerisation catalysis.[40]
In the light of the known influence of ligand structure on
the catalysis, and particularly the influence of alkyl substitu-
ents, we have prepared the novel diphosphine ligands 6–9
In the 1990s, ICI developed a highly active and selective
catalyst for the formation of methyl propanoate by the pal-
ladium-catalysed methoxycarbonylation of ethene.[2] This
process similarly uses sterically bulky diphosphine ligands in
the methoxycarbonylation of ethene giving methyl propa-
noate with>99.9% selectivity with a turnover frequency of
50000 mol product per mol of palladium per hour, under
that are related to 5, but have saturated cycloalkyl back-
bones, which confers flexibility on the ligand backbone. We
have also prepared and characterized by X-ray diffraction,
the corresponding palladium(II) phosphine complexes and
compared the structural features of the complexes. The per-
formance of these ligands/complexes in the Pd-catalysed
methoxycarbonylation of ethene has been determined and
an in operando mechanistic study performed.
À
very mild conditions (353 K and 10 atm. pressure of CO
C2H4).[3,13] This technology has been commercialised as the
Lucite ALPHA process.[4] The catalyst is generated in situ
from [Pd2ACHTUNGTRENNUNG(dba)3] (dba=dibenzylideneacetone), 1,2-bis(di-
tert-butylphosphinomethyl)benzene (5, ALPHA), and meth-
anesulfonic acid.
The mechanism of palladium-catalysed methoxycarbony-
lation of ethene has been studied by using NMR and IR
spectroscopic techniques, and it has been shown that the re-
action can occur through two different pathways
(Scheme 2).[43,45,54–55]
Results and Discussion
The hydride mechanism (A) starts with the formation of a
Synthesis of the phosphine ligands: The bidentate phosphine
ligands 6–9 with a saturated alkyl ring backbone containing
palladium hydride complex.[43] Coordination of ethene, fol-
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Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
three, four, five and six carbon atoms, respectively, were syn-
thesised from the diols 10–13 in a three-step synthesis
(Scheme 3).
constant (Table 1). The variation in JACTHNGUTERNNUG
(31P–77Se) between 5–9
is small compared with the range of values for 31P–77Se cou-
plings reported previously for other phosphine sele-
nides,[63,64] thus we conclude that all the diphosphines used
in this study should have comparable electronic properties.
However, a titrimetric study of the protonation of diphos-
phines 5–9 indicated that the basicity of the cycloalkyl di-
phosphines is significantly greater than that of ligand 5
(Table 2, see also the Supporting Information). Thus,
Table 2 reveals that diprotonation of the cycloalkyl ligands
The diol cis-1,2-cyclohexanedimethanol (13) is commer-
cially available, whereas the diols 10[56,57] and 11[56,57] were
prepared by reduction of dimethyl cis-cyclopropane-1,2-di-
carboxylate (18) and cis-cyclobutane-1,2-dicarboxylic acid
(19), respectively, with lithium aluminium hydride (Sche-
me 4a). cis-Cyclopentane-1,2-dimethanol (12)[57,58] was pre-
pared in three steps from ethyl 2-oxocyclohexanecarboxy-
late (20) by bromination to give compound 21, followed by
treatment in a basic medium to induce a Favorskii[59] rear-
rangement affording the diacid 22 and finally reduction with
lithium aluminium hydride (Scheme 4b).
The diols 10–13 were then converted in high yield to the
dibromo compounds 14–17 by reaction with in situ prepared
PPh3Br2.[60] The dibromides are easily separated from the tri-
phenylphosphine oxide by-product by extraction into pen-
tane (Scheme 3).
Reaction of the dibromides 14–17 with the lithium salt of
the boron-protected secondary phosphine tBu2PH.BH3 (27)
gave the boron-protected bidentate phosphine ligands 23–
26.[61,62] Deboronation of the phosphines 23–26 was achieved
by the addition of an excess of tetrafluoroboric acid to give
an in situ prepared phosphonium salt that was then reduced
to the desired phosphine by the addition of potassium hy-
droxide.[61] 31P{1H} NMR spectroscopic data for the four
novel diphosphine ligands 6, 7, 8 and 9 are given in Table 1.
We have also prepared the phosphine diselenides of li-
gands 5–9 to establish any differences in the electronic prop-
erties and basicity of the ligands by the 31P–77Se coupling
Table 1. 31P{1H} NMR spectroscopic data for 5–9 and for the correspond-
ing diselenides.
Entry Ligand Ligand back-
bone
d
(31P)
Diselenide
(31P)
dAHCTUNGTERNNNUG JPÀ
[ppm]
Se
[ppm]
[Hz]
1
2
3
4
5
5
6
7
8
9
xylene
25.3
30.0
20.9
24.3
24.7
77.4
77.5
74.7
80.3
81.3
695
691
687
688
689
cyclopropane
cyclobutane
cyclopentane
cyclohexane
Table 2. Equilibrium constants for protonation of the ligands 5–9.
pK
Equilibrium constant
Entry
Ligand
pk1
pk2
K1
K2
1
2
3
4
5
5
6
7
8
9
1.12
–
–
1.51
0.98
0.56
1.01
1.21
1.12
0.77
0.075
–
–
0.031
0.105
0.275
0.098
0.062
0.075
0.170
6–9 occurs at a higher pH than
for ligand 5, and that diprotona-
tion of ligands 6 and 7 is strong-
ly favoured compared to dipro-
tonation of ligand 5.
We show below that the bite
angle of the cycloalkyl ligands
6–9 and ligand 5 are practically
identical (see Table 3), differen-
ces in catalytic activity between
5 and 6–9 should, therefore, re-
flect the differences in basicity
of the ligands and, possibly, the
flexibility of the ligand back-
bone.
Scheme 3. Synthesis of phosphines 6–9 from diols 10–13.
Synthesis and characterization
of cationic palladium complexes
(L-L)]+
[PdACHTUNRTGENNUG(O3SCH3)ACHUTNGTRENNGUN
Synthesis of cationic complexes:
The palladium complexes 32–35
containing ligands 6–9 have
been prepared and the X-ray
Scheme 4. Synthesis of diols 10–12.
Chem. Eur. J. 2010, 16, 6919 – 6932
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C. Claver, J. A. Iggo, G. R. Eastham et al.
Table 3. Selected X-ray data of complexes 32–36.
Complex [Pd
(O3SCH3)(6)]+
A
[Pd
A
[Pd
A
[Pd
A
[PdACTHUNGETRNNUG
(O3SCH3)(5)]+
(32)
(33)
(34)
(35)
(36)
ACHTUNGTRENNUNG(L-L)
ligand bite angle
bond lengths
101.2
100.6
99.4
100.9
100.6
a
b
c
d
a–b
a–c
a–d
b–c
b–d
c–d
2.272(4)
2.276(4)
2.182(11)
2.197(11)
100.55(16)
160.57(3)
95.61(3)
98.48(3)
163.84(3)
65.38(4)
2.262(10)
2.266(11)
2.194(3)
2.194(2)
99.09(4)
162.93(7)
97.83(7)
97.96(7)
163.05(7)
65.11(9)
2.285(9)
2.283(10)
2.184(2)
2.187(2)
100.94(3)
161.97(6)
96.97(6)
97.08(6)
162.09(6)
65.01(8)
2.267(8)
2.285(9)
2.283(10)
2.184(2)
2.187(2)
100.94(3)
161.97(6)
96.97(6)
97.08(6)
162.09(6)
65.01(8)
2.273(8)
2.268(8)
2.174(2)
2.199(3)
101.23(3)
162.79(7)
97.29(7)
95.86(7)
161.21(7)
65.53(9)
2.273(66)
2.172(80)
2.188(38)
100.58(7)
160.99(13)
95.82(13)
98.19(13)
163.21(14)
65.68(17)
bond angles
crystal structures of the complexes determined to compare
the structural features of these complexes with those of the
palladium complex of the reference ligand 5, with the aim
of establishing structure–catalytic performance correlations.
The asymmetric unit of the structure contains one cation
(with a single bidentate sulfonate ligand), one sulfonate
anion and one sulfonic acid molecule (Figure 1). The palla-
dium atom is coordinated in a square-planar geometry.
There is disorder in the coordinated sulfonate and in what is
presumed to be the sulfonic acid molecule for which the
acid H atom was not located and the assignment of oxygen
and methyl was based on interatomic distances.
Direct reaction of diphosphines 6–9 with [Pd
2ACHTUNGTERN(NUNG dba)3] af-
fords the [Pd(dba)(diphosphine)] complexes 28–31. These
ACHTUNGTRENNUNG
complexes can then be oxidized (without prior isolation) in
the presence of traces of O2 to give the palladium(II) com-
plexes[43] 32–35 by the addition of two equivalents of meth-
[PdACTHNUTRGENNGU(O3SCH3)(7)]ACHUTNTGERN[NUGN O3SCH3] (33) crystallizes in a triclinic
A
space group with a=11.2245(12), b=13.0794(14), c=
16.0019(17) ꢄ and V=2113.4(4) ꢄ3. The structure was
¯
X-ray crystal structures of cationic palladium complexes 32–
35: Single crystals suitable for X-ray crystal structure deter-
minations were obtained by slow diffusion of diethyl ether
(32, 33 and 35) or tert-butyl methyl ether (34) into tetrahy-
drofuran solutions of the complexes.
In the X-ray structure of the complexes 32–35, two sulfo-
nate ions (one coordinated and the other as the counterion)
and one molecule of sulfonic acid are present. During the
formation of the single crystals, some palladium black pre-
cipitated, probably as a result of decoordination of sulfo-
nate, which provides the additional sulfonic acid molecule
that was observed in the crystal structure.
solved in space group P1. The R1 value is 0.0233. The asym-
metric unit of the structure contains one cation (with a
single bidentate sulfonate ligand), one sulfonate anion, one
sulfonic acid molecule (hydrogen bonded to the sulfonate
anion, with an essentially symmetrical hydrogen bond) and
two molecules of THF (Figure 1). The palladium atom is co-
ordinated in a square-planar geometry. There is no disorder
in the structure. Hydrogen atoms are omitted in this figure,
except for the one involved in the hydrogen bond.
Compound [PdACHTNUGTRNE(UNG O3SCH3)(8)]O3SCH3 (34) crystallizes in a
triclinic space group with a=10.8149(13), b=11.278(2), c=
31.700(5) ꢄ and V=3376.7(9) ꢄ3. The structure was solved
¯
in space group P1. The R1 value is 0.0396. The asymmetric
ic space group with unit cell parameters a=9.8572(14), b=
12.8636(18), c=26.605(4) ꢄ and V=3326.6(8) ꢄ3. The struc-
ture was solved in space group P21/c. The R1 value is 0.0449.
unit contains two cations, two uncoordinated anions (one of
which is disordered, the second component is not shown in
the figure), a sulfonic acid molecule and a water molecule
(these form hydrogen bonds).
The palladium atom is coordi-
nated in a square-planar geom-
etry. The five-membered ring
has an envelope conformation
(Figure 1).
Compound [Pd
ACHTUGNTRNEN(UGN O3SCH3)(9)]-
AHCTUNTGREG[NUNN O3SCH3] (35) crystallizes in a
monoclinic space group with
a=20.680(4), b=11.156(2), c=
32.862(7) ꢄ and V=7397(3) ꢄ3.
The structure was solved in
Scheme 5. Synthesis of PdII complexes 32–35.
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Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
Figure 1. X-ray crystal structure of complexes 32–35.
Table 4. Palladium-catalysed methoxycarbonylation of ethene by using
space group C2/c. The R1 value is 0.0353. The palladium
atom is coordinated in a square-planar geometry. The six-
membered ring has two disordered conformations in the
structure, which represent the chair and boat conformations
of the ligand (Figure 1). Only C and H atoms are affected,
and the metal coordination remains the same. The uncoordi-
nated anion and acid molecule are hydrogen bonded togeth-
er. Table 3 compares the bond lengths, and interbond angles
in 32–35 with those of the [1,2-bis(di-tert-butylphosphinome-
thyl)benzene] palladium(II) complex (36).[55] Bond lengths
and angles are broadly comparable across the five com-
plexes. The (P-Pd-P) bite angles of the ligand in 32, 33 and
35 are 101.23, 100.55 and 100.948, respectively, and in 34, in
which two cations are present, the bite angles are 99.09 and
99.428. The palladium(II) complex of the cyclopentane-
based phosphine (8) has the smallest bite angle of the four
cycloalkyl phosphines at (av. 99.258), whereas the palladiu-
m(II) complex of the cyclopropane-based phosphine (6) has
the largest bite angle at (101.28). The bite angle of the cyclo-
butane-based phosphine (7) in 33 is similar to that of 1,2-
bis(di-tert-butylphosphinomethyl)benzene in 36. We con-
clude that all these palladium complexes might be expected
to show a similar catalytic performance (vide infra) if this is
determined by ligand bite angle.[65]
diphosphines 5–9.[a]
Entry
Ligand
X [g][b]
TON[c]
Average rate[d]
1
2
3
4
5
5
6
7
8
9
21.1
21.6
33.4
8.2
630
646
997
245
758
315
323
499
123
379
25.4
[a] Pd/L/MeSO3H 1:3:2.5; substrate/Pd 1079; Pd
ACHTUNGTRENNUNG
MeSO3H (1.50ꢅ10À3 mol), ethene (0.65 mol);
P
=
45 bar; methyl propanoate (180 mL), MeOH (120 mL); T=1008C.
[b] Grams of methyl propionate produced during the reaction. [c] Turn-
over number. [d] Average rate during the catalytic reaction [sÀ1].
catalysed methoxycarbonylation of ethene to methyl propa-
noate (Scheme 1). The catalytic systems were prepared in
situ by adding the diphosphine ligand (5–9) to a solution of
PdACTHNUTRGEN(UGN OAc)2 in MeOH/methyl propanoate to form the com-
plexes 37–41 followed by the addition of methanesulfonic
acid to give the catalyst precursors 32–36. The catalytic solu-
tions were introduced into the autoclave under vacuum,
which was then charged with 20 bar of ethene and 45 bar of
carbon monoxide. The overall ratio Pd/L/MeSO3H was
1:3:2.5.
Ligands 6–9 vary both in the size of the cyclic backbone,
and consequently the conformational freedom of the ligand,
and in relative basicity (vide supra). The catalytic systems
Methoxycarbonylation of ethene: Table 4 reports the cata-
lyst performance for the diphosphines 6–9 in the palladium-
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C. Claver, J. A. Iggo, G. R. Eastham et al.
incorporating ligands 6, 7 and 9, with three-, four- and six-
membered rings in the ligand backbone, were all more
active than the catalytic system with ligand 5 albeit with
ligand 6 only marginally more active (compare Table 4, en-
tries 2, 3 and 5 with 1). The catalytic systems incorporating
ligands 6, 7 and 9 are all significantly more active than that
with ligand 8 containing a five-membered ring (entry 4).
There is, thus, no clear correlation between flexibility in the
chelate ring and catalyst performance. However, in contrast
to the commercialized system incorporating ligand 5, for
which higher turnover numbers are obtained on increasing
no excess of acid over ligand is present, protonated phos-
phines can be deprotonated by the acetate ion, leading to
complexes 32–35.
Consistent with this hypothesis, good catalytic results
were obtained upon using a large excess of the weaker acid,
trifluroacetic acid (pKa =0.5). Under these conditions, the
catalytic activity of the system PdACHTNUTRGNEUNG(OAc)2/5/TFA is similar to
that obtained in the presence of MeSO3H (cf. Tables 4
and 5, entry 1). The systems with cycloalkyl ligands 7 and 9
Table 5. Palladium-catalysed methoxycarbonylation of ethene by using
the amount of acid present,[56–57] we find that the Pd
ACTHNUTRGNEN(UG OAc)2/
diphosphines 5–9 and trifluoroacetic acid.[a]
6–9 systems are deactivated by an excess of methanesulfonic
acid. Thus, on changing the acid to palladium ratio from
2.5:1 to 12.5:1, low yields of methyl propanoate, and large
amounts of palladium black are observed. We attribute this
to the protonation of the more basic cycloalkyl ligands
(Table 2). Thus, in NMR spectroscopic experiments in which
12.5 equivalents of methanesulfonic acid were added to sol-
utions containing 37–40 in methanol, immediate formation
of the protonated phosphines (42–45) and Pd metal was ob-
served (Scheme 6c). However, when the protonated diphos-
phines 42–45, obtained by adding 3.3 equivalents of metha-
nesulfonic acid to ligands 6–9, were allowed to react with
Entry
Ligand
X [g][b]
TON[c]
Average rate[d]
1
2
3
4
5
5
6
7
8
9
20.2
13.1
28.1
27.9
28.8
603
392
839
834
860
302
196
420
417
430
[a] Pd/L/CF3CO2H 1:3:125; Pd
(8.5 mol); ethene =20 bar, CO =45 bar; methyl propionate (180 mL),
MeOH (120 mL); T=1008C. [b] Grams of methyl propionate produced
during the reaction. [c] Turnover number. [d] Average rate during the
catalytic reaction [sÀ1].
(OAc)2 (5.98ꢅ10À4 mol), CF3CO2H
ACHTUNGTRENNUNG
P
P
Pd
(OAc)2, the catalyst precursors 32–35 were formed
are again slightly more active than the system with ligand 5
(Tables 4 and 5, entries 3 and 5 vs. 1). However, ligand 8 af-
fords significantly higher (Tables 4 and 5, entry 4) and
ligand 6 significantly lower (Tables 4 and 5, entry 2) activity.
These results illustrate the complexity of homogeneous cat-
alysis and the dependence of each catalyst system on several
factors.
As was mentioned before, catalyst systems based on the
more basic ligands (6–9) are inactive when run in the pres-
ence of excess methanesulfonic acid (as the typically used
commercial operation). For
(Scheme 6d). This is consistent with the redistribution of the
various equilibria involving protonated phosphine, free acid
and palladium coordinated phosphine, the differing basici-
ties of 5 versus 6–9 resulting in differing concentration ef-
fects on the position of the equilibrium. When excess metha-
nesulfonic acid is present, the more basic ligands 6–9 remain
protonated, and thus unable to complex Pd, whereas the
less basic ligand 5 is deprotonated in the presence of palladi-
um acetate leading to complex formation. However, when
these ligands, good activity in
the presence of excess acid is
only possible when an acid of
lower pKa is employed. Drent
and Pugh have previously noted
the complex influence of ligand
basicity and acid strength on
catalyst selectivity in palladi-
um–diphosphine carbonylation
catalysis.[7] Further studies are
required to fully understand the
relationship between acid pKa,
ligand basicity and catalyst ac-
tivity (Scheme 6).
High-pressure NMR spectro-
scopic study: As noted above,
Pd-catalysed alkoxycarbonyla-
tion reactions normally show an
acceleration of reaction rate on
increasing the amount of strong
acid present, which is attributed
Scheme 6. Influence of acid on the formation of the catalyst precursors.
6924
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Chem. Eur. J. 2010, 16, 6919 – 6932

Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
À
to the formation of the catalytically active Pd H species
methanol solution to 353 K in a sapphire NMR tube. How-
ever, we find that starting from either the isolated com-
being favoured.[66,67] In contrast, we observe the opposite
trend for catalyst systems based on ligands 6–9, which are
deactivated by an excess of strong acid. We have, therefore,
performed a mechanistic study by NMR and HP NMR spec-
troscopy to establish if the hydride mechanism is indeed op-
erating in this catalytic system.
(L-L)]+ (L-L=6–9) (46–49) or from
plexes [PdACTHNUTRGENNUG(O2CCF3)ACHUTNGTRENNGUN
(46–49) prepared in situ, the trifluoroacetate complexes (46–
49) are recovered unchanged following heating in methanol
to 353 K, in the presence of a stoichiometric amount or with
an excess of acid (see Figures 18–21 in the Supporting Infor-
mation; a slight decomposition of the ligand is observed),
with no evidence for the formation of the hydride com-
Attempted preparation of palladium–carbomethoxy or palla-
dium–hydride initiators from [Pd
No reaction was observed on heating a methanolic solution
of Pd(OAc)2/9/TFA with CO in a sapphire NMR tube
A
(6–9)]+
N
plexes [Pd(H)
dride mechanism (Scheme 2a).
(6–9)]+ (55–58) required for a hy-
ACHUTGTNRNEUG(N MeOH)ACHTUTGNRENNUGN
ACHTUNGTRENNUNG
(353 K, 20 bar CO), which indicated that the catalysis does
not proceed by a carbomethoxy complex (Scheme 2b).
Consistent with the report of Heaton and co-workers,[43]
Reaction of [Pd
(10 bar): We next studied the direct reaction of the trifluor-
oacetate complexes [Pd(O2CCF3)
(6–9)]+ (46–49) with
ACHTUGNTRENU(GNN O2CCF3)ACHTUNRTGEUNNNG ACHTGUNTREN(NNGU 46–49) with ethene
(6–9)]+
A
ACHTUNGTRENNUNG
who found that [Pd
catalytic conditions to the hydride complex [Pd(H)-
(MeOH)(5)]+ (53) at 353 K (Scheme 7),[55] we find that [Pd-
(O2CCF3)(5)]+ (50) is transformed into 53 on heating in a
(O3SCH3)(5)]+ (36), is converted under
ethene in methanol and successfully generated the Pd–ethyl
complexes required by the hydride pathway. Thus, on heat-
ing methanolic solutions of 46–48 in a sapphire NMR tube
in the presence of an excess of trifluoroacetic acid and
ethene (10 bar) at 353 K for 20 min, followed by cooling to
193 K, the 31P{1H} NMR spectra showed the presence of two
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
new doublets that can be assigned (vide infra) to [Pd
ACHTUNGTRENNUNG(6–8)-
AHCTUNGTRENNUNG
Table 6. Selected 31P{1H} NMR spectroscopic data for 61–64.
Entry
Complex
d P1/P2 [ppm]
JPP [Hz]
1
2
3
61
62
63
67.9/50.3
63.4/41.2
77.3/47.0
major: 87.8/38.6
minor: 64.3/58.4
24.3
23.1
23.0
22.4
22.4
4
64
ment was repeated with complex 49, two sets of doublets
were observed corresponding to two conformers of the ethyl
complex 64 (vide infra).
Attempts to isolate 62–64 were unsuccessful, thus on re-
moval of methanol at a reduced pressure and redissolution
of the resulting residue in deuterated dichloromethane, the
31P{1H} NMR spectra revealed only the presence of the pre-
cursors 47–49. However, for complex 61, the 31P{1H} NMR
spectrum showed, in addition to 46, the presence of a new
complex containing two broad resonances at d=70.4 and
37.9 ppm that can be assigned as the hydride–solvento com-
plex 55 (Scheme 7, Figure 2b).
Thus, in the proton-coupled 31P NMR spectrum, recorded
at 193 K, the signal at d=70.4 ppm becomes a broadened
doublet (2JPP =19.4 Hz), whereas the signal at d=37.9 ppm
shows an additional coupling due to a trans disposed hy-
2
2
b
dride, (doublet of doublets, JPP =19.4 and JP H =193.8 Hz;
Figure 2a). The resonance of the hydride ligand occurs in
the 1H NMR spectrum, recorded at 193 K, at d=
a
b
À10.69 ppm (dd, 2JP H =13.6, 2JP H =193.8 Hz) (Figure 3).
The resonances of a second, minor hydride complex can be
a
c
seen at d=À10.47 ppm (ddd, 2JP H =22.4, 2JP H =36.0 and
Scheme 7. Formation the palladium–hydride and palladium–ethyl com-
plexes.
b
2JP H =188.4 Hz). The resonances of this new complex are
Chem. Eur. J. 2010, 16, 6919 – 6932
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www.chemeurj.org
6925

C. Claver, J. A. Iggo, G. R. Eastham et al.
ACTHNUTRGNEUNG
Figure 3. Selected region of the 1H NMR spectra of [Pd(H)(MeOH)(6)]+
(55).
Figure 2. a) 31P NMR spectra of
(O2CCF3)(6)]+ (46) and [Pd(H)
b) 31P{1H} NMR spectra of complexes [Pd
[Pd(H)
(MeOH)(6)]+ (55) at 193 K, c) 31P{1H} NMR spectra of complexes
[Pd
(O2CCF3)(6)]+ (46) and [Pd(6)(CH2CH3)]+ (61).
a
ACHTUNGTRENNUNG
mixture of complexes [Pd-
(MeOH)(6)]+ (55) at 193 K,
(O2CCF3)(6)]+ (46) and
G
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
blets are observed in the 31P{1H} NMR spectrum. Those of
G
ACHTUNGTRENNUNG
the major isomer occur at d=87.8 (d, 2JPP =22.4 Hz; P1A
)
2
and 38.6 ppm (d, JPP =22.4; P1B), values similar to those of
not resolved in the 31P{1H} NMR spectrum making assign-
ment of its structure problematic; we tentatively propose
the structure 65 for this complex, consistent with the pres-
ence of an additional P–H coupling (Scheme 7). According
to the law of microscopic reversibility, the forward reaction
[Pd(5)
(CH2CH3)]+
(54) (d=67.7, 36.3 ppm (2JPP
=
31 Hz)).[54–55] The resonances of the minor conformer occur
2
at d=64.3 (d; P2A) and 58.4 ppm (d, JPP =22.4 Hz; P2B). The
two isomers occur in the ratio 2.2:1. These conformers are
in dynamic equilibrium.[16] Figure 4 shows the variable-tem-
perature (VT) 31P{1H} NMR spectra of 64, together with
simulations performed by using gNMR5. The simulations
reveal that concerted intermolecular equivalencing of P1A
with P2A and P1B with P2B occurs, as would be expected for a
chair-to-boat conformational flip. Intramolecular exchange
À
must go by insertion of ethylene into the Pd H bond. On
pressurization of this solution with ethene at room tempera-
ture and cooling to 193 K, the 31P{1H} NMR spectrum
showed the disappearance of the resonances of the hydride
complex and the appearance of the resonances attributed to
the ethyl complex [Pd(6)-
ACHTUNGTRENNUNG
(CH2CH3)]+ (61) (Figure 2c).
We conclude that on heating
methanolic solutions of [Pd-
ACHTUNGTRENNUNG
(O2CCF3)(6)]+ (46) in the pres-
ence of ethene, traces of the hy-
dride complex [Pd(H)-
ACHTUNGTRENNUNG
(MeOH)(6)]+ (55) are formed.
This complex reacts with
ethene to give the ethyl com-
plex [Pd(6)
However, in contrast to [Pd(5)-
ACHTUNGTRENNUNG
(CH2CH3)]+ insertion of ethene
ACHTUNGTRENNUNG
(CH2CH3)]+ (61).
is readily reversible, giving the
hydride complex 55 transiently
on removal of ethene from so-
lution. Complex 55 itself is un-
stable and returns to the pre-
cursor
ACHTUNGTRENNUNG
complex
[Pd-
(O2CCF3)(6)]+ (46) (Scheme 7).
Conformational dynamic pro-
cess in [Pd(9)
(CH2CH3)]+ (64):
ACHTUNGTRENNUNG
We noted above that two con-
formers exist for the ethyl com-
plex [Pd(9)ACHTUNGTRENNUNG
(CH2CH3)]+ (64).
ACTHNUTRGNEUNG
Thus, at 193 K two pairs of dou- Figure 4. 31P{1H} NMR spectra and simulations at VT of the [Pd(9)(CH2CH3)]+ (64).
6926
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Chem. Eur. J. 2010, 16, 6919 – 6932

Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
of P1A with P1B and of P2A with P2B also occurs but at a
slower rate and at different rates for the two isomers. The
uncertainty in the exchange rate constants derived from the
simulations is high, resulting in large uncertainties in the ac-
tivation enthalpies and entropies obtained (see the Support-
ing Information). Both processes appear to have similar ac-
tivation enthalpies of 45 kJmolÀ1 and activation entropies
close to 0 JmolÀ1 KÀ1 as might reasonably be expected for
the proposed exchanges.
Zacchini has previously reported that a rapid insertion–
deinsertion fluxional process occurs in 54 in which the ineq-
uivalent phosphorus donors remain distinct. These donors
are then equivalenced by a much slower fluxional process,
in accord with our results.[54]
The chair and boat conformations of the ethyl complex 64
have been simulated in ArgusLab to determine the energy
of each conformer. We find that the complex in which the
ligand adopts the chair conformation is approximately
38 kJmolÀ1 lower in energy than the boat conformer. Chair
and boat conformers are also observed in the X-ray crystal
structures of the precursor complex 35 (Figure 1).
ACTHNUTRGNEUNG
Figure 5. 31P{1H} NMR spectra. a) Complex [Pd(9)(CH2CH3)]+ (64) and
vinyl acetate in methanol at 193 K. b) Complex [Pd(9)ACTHNUTRGNEUNG
(CH2CH3)]+ (64)
and vinyl-13C2 acetate in methanol at 193 K.
Reaction of complex [Pd(9)ACHTNUGRTNEUNG
(CH2CH3)]+ in methanol in the
presence of vinyl acetate: Due to the difficulty in isolating
the hydride complexes 55–58 and ethyl complexes 61–64 we
turned our attention to the vinyl acetate (VAM) insertion
complex 66 since the b-chelate complex formed is more
easily handled. Thus, the ethyl complex 64 was synthesised,
and a solution of vinyl acetate in methanol was added under
an ethene atmosphere to prevent back reaction to the tri-
fluoroacetate complex 49. Complex 66 was obtained as a
mixture of two conformers (Scheme 8) presumably by an
Scheme 8. Synthesis of [Pd(9)ACHTNUGRTNEUNG
(CH2CH2OC(O)CH3)]+ (66).
alkene exchange reaction that proceeds through b-hydride
elimination, and decoordination of ethene, followed by
Figure 6. Spectrum of [Pd(9)(13CH213CH2OC(O)CH3)]+ (66) obtained by
treating [Pd(9)ACTHNUTRGNEUNG
(CH2CH3)]+ (64) with vinyl-13C2 acetate in methanol at
À
VAM coordination and 2,1-insertion into the Pd H bond.
193 K. a) Spectra b) and c) expanded. b) 13C-{1H} NMR spectra. c)
13C NMR spectra.
Complex 66 was fully characterized by NMR spectrosco-
py. The 31P{1H} NMR spectrum, acquired at 193 K, (Fig-
ure 5a) shows two sets of signals, at d=52.5 and 51.3 ppm
(2JPP =29.7 Hz) and at d=70.2 and 30.5 ppm (2JPP =27.7 Hz)
(relative intensity of 4:1). When 13C-labelled vinyl acetate
was used, additional couplings are seen in the 31P{1H} NMR
onance of Ca shows an additional quartet coupling (JCH
=
127.9 Hz) in the proton-coupled 13C NMR spectrum con-
firming its identity as a CH3 group, whereas the resonance
of Cb becomes a complex multiplet as expected for a me-
thine carbon atom (Figure 6c). The methine resonance of
the minor isomer is seen at d=93.9 ppm (dd, JCC =31.2,
spectrum, the resonances at d=52.5 and 30.5 ppm appearing
2
as doublets of doublets (2JPC =95.6, JPP =30.5 Hz and JPC
=
2
97.7, JPP =30.5 Hz, respectively) (Figure 5b), values of JPC
are consistent with the proposed b-chelate structure.[68]
The resonances of Ca and Cb of the major isomer occur at
J
PC =94.3 Hz) in the 13C{1H} NMR spectrum and a poorly re-
d=23.9 (d, JCC =32.5 Hz) and 96.2 ppm (dd, JCC =32.6, JPC
=
solved doublet around d=27.5 ppm may be assigned to the
methyl carbon atom of the minor isomer (Figure 6b).
94.7 Hz) in the 13C{1H} NMR spectrum (Figure 6b). The res-
Chem. Eur. J. 2010, 16, 6919 – 6932
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6927

C. Claver, J. A. Iggo, G. R. Eastham et al.
Finally, a 31P{1H}–13C{1H} HMQC correlation spectrum
was obtained and shows correlations between the 31P signals
at d=23.9 and 52.5 ppm and 13C signals at d=93.9 and
96.2 ppm, respectively (Figure 7). Thus, we can confidently
ence of the ethyl complexes in the absence of CO; however,
the resting state of the operando catalyst is the trifluoroace-
tate 46–49 (Scheme 8, Figure 2).
Two important conclusions follow from these observa-
tions: 1) although the hydride pathway is shown to be domi-
nant in palladium-catalysed hydroesterification of alkenes
when using the ligands described here, the existence or not
of a stable palladium-hydride catalyst precursor is no indica-
tion of the activity of the catalyst system and 2) detection
and characterization of the catalytic intermediates can be
successfully performed in situ, indeed isolation and conven-
tional characterization of such intermediates may not be
possible, particularly if the resting state of the catalyst lies
outside the catalytic cycle, as here.
Figure 7. 31P{1H}–13C{1H} NMR
[Pd(9)(13CH213CH2OC(O)CH3)]+ (66).
correlation
spectra
of
complex
assign 66 as two conformers or two diastereoisomers of the
b-chelate complex resulting from the 2,1-insertion of VAM
À
into the Pd H bond of 57. The two conformers or two dia-
Experimental Section
stereoisomers are proposed to arise from different confor-
mations adopted by the backbone of the ligand, as previous-
ly observed. The Pd–H must originate by b-hydride elimina-
tion of ethene from the alkyl complex 64.
General methods: All experiments were performed under an atmosphere
of nitrogen by using standard Schlenk line, cannula and glovebox tech-
niques. All chemicals were obtained from Aldrich and used as supplied
without further purification: (1R,2S)-cyclopropane-1,2-dicarboxylate, cis-
cyclobutane-1,2-dicarboxylic acid, cis-cyclohexanedimethanol and ethyl
2-oxocyclohexanecarboxylate. NMR spectra were recorded by using a
Varian Mercury Spectrometer (400mHz) or Bruker Avance DPX400.
H NMR spectra were recorded on a Bruker AMX-II 200 spectrometer.
The chemical shifts (d) were reported in ppm and they are referenced to
tetramethylsilane (TMS). Methoxycarbonylation reactions were carried
out in a 1 L stainless steel autoclave.
Conclusion
Four novel bidentate bis(tert-butylphosphine) ligands (6–9)
with saturated cycloalkyl rings of different ring size have
been synthesised in high yield. These ligands have been
used in the synthesis of the palladium complexes 32–35 and
in the palladium-catalysed methoxycarbonylation of ethene.
The synthesis of the palladium(II) phosphine complexes and
their subsequent crystallisation allowed the determination of
the geometries of the molecules and of the bite angles of
the ligands that are very similar for all complexes. Differen-
ces in the catalytic performance of the ligands cannot, there-
fore, be attributed to differences in ligand bite angle or to
differences in the rigidity of the ligand backbone. Thus, cata-
lytic systems containing ligands with high-conformational
mobility (8) or with a rigid backbone (6) afford catalytic sys-
tems of lower performance. The combination of the basicity
of the ligand and the strength of the acid used, however, is
important in determining catalyst performance. Thus, the
Pd/6–9 catalytic systems were activated by weaker acids and
were strongly inhibited by the strong acid required to acti-
vate the Pd/5 catalytic system.
cis-(1,2-Dibromomethyl)cycloalkyl (general procedure): A solution of tri-
phenyldibromophosphorane was prepared by adding bromine
(141 mmol) dropwise to an ice-water-cooled solution of triphenylphos-
phine (141 mmol) in dry acetonitrile (200 mL). A solution of cis-1,2-cy-
cloalkyldimethanol (70 mmol) in dry acetonitrile (100 mL) was added to
the reaction mixture, which was then stirred under nitrogen overnight.
The solvent was evaporated to yield an orange oil. The solid was finely
dispersed in pentane (2ꢅ250 mL) and filtered to remove the triphenyl-
phosphine oxide. The pentane solution was dried under vacuum to give
the desired compound.
cis-1,2-(Dibromomethyl)cyclopropane (10): The synthesis of 10 was car-
ried out in accordance with the general procedure. The product was iso-
lated as
a
colourless oil. Yield: 18.59 g, 80%; 1H NMR (400 MHz,
CDCl3): d=3.47 (m, 4H; CH2), 1.61 (m, 2H; CHcy), 1.13 (m, 1H;
CHcy), 0.39 ppm (m, 1H; CHcy).
cis-1,2-(Dibromomethyl)cyclobutane (11): The synthesis of 11 was com-
pleted according to the general procedure previously described. The
product was isolated as a colourless oil. Yield: 6.68 g, 80%; 1H NMR
(400mHz, CDCl3): d=3.63 (m, 2H; CH2); 3.45 (m, 2H; CH2), 2.88 (m,
2H; CH), 2.15 (m, 2H; CH2); 1.76 ppm (m, 2H; CH2); 13C NMR
(100.6 MHz, CDCl3,): d=39.8 (s, CHcy), 34.0 (s, CH2), 24.1 ppm (s,
CH2cy).
The catalytic cycle when using ligands 6–9 follows a hy-
dride pathway, similar to that proposed by Heaton et al.
However, in contrast to the ALPHA/triflic acid system stud-
ied by Heaton, in which the hydride complex [Pd-
cis-(1,2-Dibromomethyl)cyclopentane (12): By following the general pro-
cedure, compound 12 was obtained as a colourless oil. Yield: 23 g, 80%;
1H NMR (400 MHz, CDCl3): d=3.52- 3.41 (m, 2H; CH2), 3.29 (m, 2H;
CH2), 2.46 (m, 2H; CHcy), 2.09–1.85 (m, 4H; CH2cy), 1.63–1.44 ppm (m,
2H; CH2cy).
ACHTUNGTRENNUNG(ALPHA)HACHTUNGTRENNUNG(MeOH]CAHTNUGTRENN[UGN OTf] could be isolated, in the case of
ligands 6–9, the equilibrium between the trifluoroacetate
(46–49) and hydride (54–57) complexes is strongly shifted in
favour of the trifluoroacetate complexes. In further contrast
to the ALPHA/triflic acid system, the ethyl complexes 61–
64 are only stable in the presence of an overpressure of
ethene. In situ NMR spectroscopic studies confirm the pres-
cis-(1,2-Dibromomethyl)cyclohexane (13): The synthesis of 13 was com-
pleted according to the general procedure previously described. The
product was isolated as a colourless oil. Yield: 11.81 g, 63%; 1H NMR
(400 MHz, CDCl3): d=3.41 (m, 4H; CH2), 2.20 (m, 4H; CH2eq), 1.64 (m,
2H; CH), 1.56 ppm (m, 4H; CH2ax); 13C NMR (100.6 MHz, CDCl3): d=
33.7 (s; CHcy), 32.8 (s; CH2cy), 31.3 (s; C
CH2cy), 17.5 ppm (s; CH2).
ACHTUNGTREN(NNUG CH3)), 29.7 (s; CH3), 26.1 (s;
6928
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Chem. Eur. J. 2010, 16, 6919 – 6932

Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
Di-tert-butylphosphine borane (27): Di-tert-butylphosphine chloride
(34 g, 188.41 mmol) was added to a schlenk flask followed by diethyl
ether (200 mL). The ether solution was cooled in a cold water bath and
LiAlH4 (1m in diethyl ether, 100 mL, 100 mmol) was added slowly. This
gave a yellow suspension that was allowed to stir at room temperature
overnight. The suspension was quenched by the addition of water
(50 mL, degassed with nitrogen for 20 min). This gave a biphasic solution.
The upper (organic layer) was cannula transferred into a clean schlenk
flask and the aqueous residues washed with a further 100 mL of ether.
The ether extracts were combined and dried with sodium sulfate. The
ether extracts were then cannula transferred into a clean schlenk and the
ether removed by distillation. This gave a colourless oil. The colourless
oil was then diluted with THF (200 mL) and cooled to 08C; to this was
added BH3 in THF (1m solution, 250 mL, 250 mmol). The resultant solu-
tion was then stirred at room temperature overnight. The solvent was
then removed under vacuum to give a white crystalline solid that was iso-
lated in the glovebox. Yield: 22.1 g, 73% yield; 1H NMR (400 MHz,
Boron-protected bidentate phosphine (26): By following the general pro-
cedure, the product 26 was obtained as a white solid. Yield: 18.29 g,
97%; 1H NMR (400 MHz, CDCl3): d= 2.95 (s, 3H; BH3), 2.88 (s, 3H;
BH3), 1.81 (m, 4H; CH2), 1.78 (m, 4H; CH2eq); 1.66 (m, 2H; CH); 1.45
ACTHNUTRGNEUNG
(m, 4H; CH2ax); 1.30 (d, 3J(H,P)=24 Hz, 18H; CH3), 1.23 ppm (d, 3J-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
CDCl3): d= 46.71 ppm (m); HRMS (ESI-TOF): m/z: calcd: 429.4122
[M]+; found: 429.4096; elemental analysis calcd (%) for C24H56B2P2: C
67.31, H 13.18, B 5.05, P 14.46; found: C 67.26, H 13.20.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cycloalkyl (general procedure):
The corresponding boron-protected bidentate phosphine (42 mmol) was
suspended in tert-butyl methyl ether (TBME; 300 mL) and to this was
added tetrafluoroboric acid (54% in diethyl ether, 260 mmol). This gave
a rapid gas evolution and the solution was heated to reflux overnight
under nitrogen. The solvent was then removed under vacuum and the
residue quenched with a solution (degassed with N2 for 20 min) of potas-
sium hydroxide in water (21 g, 200 mL, 651 mmol). The potassium hy-
droxide solution was added dropwise to the phosphine residue. This gave
heat evolution and a white suspension. Pentane (2ꢅ250 mL) was added.
The organic layers were removed by cannula to a separate schlenk flask.
The organic extracts were then dried over Na2SO4 and filtered. The solu-
tion was dried under vacuum to give the desired compound in good
yields.
1
3
CDCl3): d=3.9 (dq, J
13.5 Hz, 18H; CH3), 0.4 ppm (brm, 3H; BH3); 13C NMR (100.6 MHz,
ACHTUNGTRENNUNG(H,P)=345, JACHNUTRTGENNUNG ACHTGUNTREN(NUGN H,P)=
(H,H)=6 Hz; 1H), 1.2 (d, 3J
CDCl3): d=38.2 (d, 1J (CH3)), 29.1 ppm (d, 2J
ACHTUNGTRENNUNG(C,P)=29 Hz; CACHNUTRTGENNUNG ACHTGUNTREN(NUGN C,P)=
1.6 Hz; CH3); 31P{1H} NMR (80 MHz, CDCl3): d=49.23 ppm (m);
1
13B NMR (128.4 MHz, CDCl3,): d=À43.7 ppm (d, J=51.1 Hz).
Boron-protected bidentate phosphine (general procedure): tBu2PH·BH3
(27) (179 mmol) was dissolved in THF (200 mL). The solution was then
cooled. nBuLi (2.5m in hexanes, 179 mmol) was added to this solution.
The resultant solution was stirred at room temperature for 1 h. This mix-
ture was then added dropwise to a solution of the corresponding cis-1,2-
(dibromomethyl)cycloalkyl (82 mmol) in THF (200 mL). The resultant
solution was then stirred overnight at room temperature. The solution
was dried under vacuum and the residue suspended in diethyl ether
(400 mL). Water was added to give a biphasic mixture. The organic layer
was collected by separation and the aqueous layer washed with diethyl
ether (2ꢅ100 mL). The organic layers were then combined and washed
with water (3ꢅ150 mL) and brine solution (3ꢅ100 mL). The organic
layer was dried over Na2SO4 and filtered. The solution was evaporated
under reduced pressure to give the desired compound.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclopropane (6): By following
the general procedure, product 6 was obtained as a colourless oil. Yield=
17.23 g, 84%; 1H NMR (400 MHz, CDCl3): d=1.61 (m, 2H; CH2), 1.50
3
(m, 2H; CH2), 1.14 (d, J
G
0.88 (m, 1H; CHHcy), 0.05 ppm (m, 1H; CHH cy); 13C NMR
(100.6 MHz, CDCl3): d=36.2 (d, J
(C,P)=7.8 Hz; C
A
ACHTUNGTRENNUNG
CH3), 24.8 (m; CH2cy), 11.3 ppm (m; CH2); 31P{1H} NMR (161.97 MHz,
CDCl3): d=30.0 ppm (s); HRMS (ESI-TOF): m/z: calcd: 358.2918 [M]+;
found: 357.2085.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclobutane (7): The synthesis
of 7 was completed according to the general procedure previously de-
scribed. The product was isolated as a colourless oil. Yield=8.5 g, 83%;
1H NMR (400 MHz, CDCl3): d=2.50 (m, 2H; CH2cy), 1.93 (m, 2H;
Boron-protected bidentate phosphine (23): The synthesis of 23 was com-
pleted according to the general procedure previously described. The
product was isolated as a white solid. Yield: 22.17 g, 71%; 1H NMR
(400 MHz, CDCl3): d=1.99 (m, 2H; CH2), 1.56 (s, 6H; BH3), 1.43 (m,
CH2cy), 1.70 (m, 2H; CHcy), 1.42 (m, 2H; CH2), 1.24 (m, 2H; CH2),
2H; CH2), 1.31 (d, 3J
ACHTUNGTRENNUNG(H,P)=17 Hz, 36H; CH3), 1.24 (m, 2H; CHHcy),
3
1.15 ppm (d, J
G
1.08 (m, 1H; CHHcy), 0.08 ppm (m, 1H; CHHcy); 31P{1H} NMR
(161.97 MHz, CDCl3): d=46.6 ppm (m); HRMS (ESI-TOF): m/z: calcd:
387.3652 [M]+; found: 387.3634; elemental analysis calcd (%) for
C21H50B2P2: C 65.31, H 13.05, B 5.60, P 16.04; found: C 65.29, H 13.09.
1
3
2
d=37.6 (dd, J
(C,P)=21.08, J
6.8 Hz; CH3), 29.9 (d, J
G
(161.97 MHz, CDCl3): d=20.9 ppm (s); HRMS (ESI-TOF): m/z: calcd:
373.3153 [M+H]+; found: 373.3137.
Boron-protected bidentate phosphine (24): The synthesis of 24 was com-
pleted according to the general procedure previously described. The
product was isolated as a white solid. Yield: 10.93 g, 98%; 1H NMR
(400 MHz, CDCl3): d=2.85 (m, 6H; BH3); 2.19 (m, 2H; CH2); 1.99 (m,
2H; CH2); 1.79 (m, 2H; CHcy); 1.61 (m, 2H; CH2cy); 1.49 (m, 2H;
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclopentane (8): The synthesis
of 8 was completed according to the general procedure previously de-
scribed. The product was isolated as a yellow oil. Yield: 20.8 g, 80%;
1H NMR (400 MHz, CDCl3): d=1.99 (m, 2H; CH2cy), 1.83 (m, 2H;
CH2cy), 1.64 (m, 2H; CH2cy), 1.60 (m, 2H; CHcy), 1.57–1.54 (m, 4H;
CH2cy); 1.30 (d, 3J
27 Hz, 18H; CH3); 13C NMR (100.6 MHz, CDCl3): d=34.6 (d, 2J
7.64 Hz; CHcy), 27.8 (d, 2J(C,P)=3.82; CH3), 27.4 (d, 2J
(C,P)=3.82 Hz;
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,P)=27 Hz, 18H; CH3); 1.26 ppm (d, 3J
CH2), 1.12 ppm (d, 3J
CDCl3): d=43.9 (dd, 1J
2J(C,P)=22.1 Hz; CH), 31.5 (d, 3J
(C,P)=6.4 Hz; CH3), 30.1 (d, 2J
(C,P)=6.4 Hz; CH3), 22.4 (s; CH2cy);
21.6 ppm (d, 1J(C,P)=21.3 Hz; CH2); 31P{1H} NMR (161.97 MHz,
(H,P)=26 Hz, 36H; CH3); 13C NMR (100.6 MHz,
(C,P)=19.1, 3J
(C,P)=8.3 Hz; C(CH3)3), 32.1 (d,
(C,P)=9.9 Hz; CH2cy), 30.2 (d, 2J-
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
G
E
ACHTUNGTRENNUNG
CH2cy), 18.9 (s), 18.7 ppm (s); 31P{1H} NMR (161.97 MHz, CDCl3): d=
44.3 ppm (m); HRMS (ESI-TOF): m/z: calcd: 401.3809 [M]+; found:
401.3814; elemental analysis calcd (%) for C22H52B2P2: C 66.02, H 13.10,
B 5.40, P 15.48; found: C 66.02, H 13.15.
N
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
CDCl3): d=24.33 ppm (s); HRMS (ESI-TOF): m/z: calcd: 387.3309
[M+H]+; found: 387.3310.
Boron-protected bidentate phosphine (25): The synthesis of boron-pro-
tected bidentate phosphine 25 was completed according to the general
procedure previously described. The product was isolated as a white
solid. Yield: 27.9 g, 75%; 1H NMR (400 MHz, CDCl3): d= 2.30 (m, 2H;
CH2), 2.02 (m, 2H; CH2), 1.97 (m, 2H; CHcy), 1.69–1.59 (m, 4H,
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclohexane (9): According to
the general procedure, product 9 was obtained as a yellow oil. Yield=
1
14.37 g, 82%; H NMR (400 MHz, CDCl3): d=1.77 (m, 4H; CHeq), 1.61
(m, 4H; CH2ax), 1.51 (m, 2H; CH), 1.35 (m, 4H; CH2), 1.14 (d, 3J-
CH2cy), 1.43–1.36 (m, 2H, CH2cy), 1.27 (d, 3J
1.21 ppm (d, 3J(H,P)=23 Hz, 18H; CH3); 31P{1H} NMR (161.97 MHz,
ACHTUNGTREN(NNUG H,P)=26 Hz, 18H; CH3),
ACHUTNGRENNUG CAHTUNGTRENNUNG
(H,P)=18 Hz, 18H; CH3), 1.12 ppm (d, 3J
N
A
ACHTUNGTRENNUNG
CDCl3): d=45.92 ppm (m); HRMS (ESI-TOF): m/z: calcd: 415.3965
[M]+; found: 415.3889; elemental analysis calcd (%) for C23H54B2P2: C
66.69, H 13.14, B 5.22, P 14.95; found: C 66.69, H 13.14.
G
E
ACHTUNGTRENNUNG
U
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Chem. Eur. J. 2010, 16, 6919 – 6932
ꢃ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6929

C. Claver, J. A. Iggo, G. R. Eastham et al.
3
31P{1H} NMR (161.97 MHz, CDCl3): d= 24.7 ppm (s); HRMS (ESI-
TOF): m/z: calcd: 401.3466 [M+H]+; found: 401.3469.
CHcy), 1.91 (m, 4H; CH2cy), 1.58 (d, J
G
(d, 15.2 Hz, 18H; CH3), 1.34 (m, 4H; CH2cy), 1.32 ppm (m, 4H; CH2);
13C NMR (100.6 MHz, CDCl3): d=41.5 (d, 1J
Palladium(II) complexes [Pd
ACHTUNGTRENNUNG
1
40.8 (d, J
G
G
Bidentate phosphine ligand (1.30 mmol) and [Pd CTHUNGTRENNUNG
(d, 2J
(C,P)=1.6 Hz; CH3), 30.6 (d, 2J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
were combined in a schlenk flask. THF (50 mL) was then added and the
resultant solution was stirred overnight at room temperature. Methane-
sulfonic acid was added and the mixture reaction was stirred for 2 h. The
solution was filtered under nitrogen and then dried under vacuum.
CH2cy), 26.3 (d, 4J
(161.97 MHz, CDCl3, 193 K): d=94.4 (d, JPÀP =4.8 Hz), 63.3 (d, JACHTUNGTRENNUNG(P,P)=
4.8 Hz); HRMS (ESI-TOF): m/z: calcd: 507.2501 [MÀCH3SO3+H]+;
found: 507.2527; elemental analysis calcd (%) for C26H56O6P2PdS2: C
44.79, H 8.10, O 13.77, P 8.88, Pd 15.26, S 9.20; found: C 44.67, H 8.21, S
9.23.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclopropane
palladium(II)
complex (32): The synthesis of complex (32) was completed according to
the general procedure previously described (yield: 313 mg, 43%). The
crystals were obtained after purification by the elimination of dba with
diethyl ether (3ꢅ50 mL) and the solid was dissolved in THF (10 mL).
Then, 3 mL of this solution were put in a layer tub and diethyl ether was
added carefully (20 mL) to form a biphasic solution. The solution was
left to stand for 3 days, after which time, the formation of crystals was ob-
served. 1H NMR (400 MHz, CDCl3): d=2.91 (s; CH3), 2.80 (m, 2H;
CHcy), 2.60–1.78 (m, 6H; CH2cy, CH), 1.55–1.17 ppm (m, 38H; CH3,
CH2); 13C NMR (100.6 MHz, CDCl3): d=39.7 (s; CH3), 36.7 (m; C-
Methoxycarbonylation reactions: A 1 L stainless steel autoclave was used
to run these experiments. A standard catalyst solution was comprised of
palladium(II) acetate, the bidentate phosphine ligand and methane sul-
fonic acid in a 1Pd:3ACTHNUTRGNEUNG
(L-L):2.5MeSO3H ratio. 5.98ꢅ10À4 mol of palladium
was used in the catalyst experiment. Palladium acetate and the bidentate
phosphine ligand were weighed into a flask in a glovebox, the flask was
then transferred to a schlenk line. Degassed methyl propionate (180 mL)
and degassed methanol (120 mL) were then added. The reaction mixture
was stirred at room temperature for twenty minutes and then methane-
sulfonic acid was added by syringe to give the palladium(II) complexes
ACHTUNGTRENNUNG AHCTUNGTRNEN(UGN C,P)=
(CH3)3), 28.9 (brs; CH2cy), 26.4 (m; CHcy), 23.7 ppm (d, 1J
8.2 Hz; CH2); 31P{1H} NMR (161.97 MHz, CDCl3): d=77.64 ppm (s);
HRMS (ESI-TOF): calcd: 465.2043 [MÀCH3SO3+H]+; found: 465.2051;
elemental analysis calcd (%) for C23H50O6P2PdS2: C 42.17, H 7.69, O
14.65, P 9.46, Pd 16.24, S 9.79; found: C 42.05, H 7.74, S 9.67.
[PdACHTNUTRGENN(GU O3SCH3)CAHUTNGTREN(NUNG L-L)]O3SCH3. The catalyst solution was then added to the
autoclave by vacuum transfer. The autoclave is pressured with 5 bar of
hydrogen, 20 bar of ethene and 40 bar of carbon monoxide. The auto-
clave was then heated to 1008C. After 3 h at 1008C, the autoclave was
cooled to room temperature and the excess pressure vented. The catalyst
exit solution was then collected, weighted and sampled for GC analysis.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclobutane palladium(II) com-
plex (33): The synthesis of complex (33) was completed according to the
general procedure previously described (yield: 350 mg, 47%). The crys-
tals were obtained after purification by the elimination of dba with dieth-
yl ether (3ꢅ50 mL) and the solid was dissolved in THF (10 mL). Then,
3 mL of this solution was put in a layer tube and diethyl ether was added
carefully (20 mL) to form a biphasic solution. The solution was left to
stand for 3 days, after which time, the formation of crystals was observed.
1H NMR (400 MHz, CDCl3): d=2.90 (s; CH3), 2.80 (m, 2H; CHcy),
2.05–1.59 (m, 4H; CH2cy), 1.55–1.17 ppm (m, 40H; CH3, CH2); 13C NMR
NMR simulations of the VT 31P{1H} NMR spectra of 64: A 0.013m solu-
tion of 64 in methanol was prepared by following the general procedure
below and 31P{1H} NMR spectra recorded at 10 K increments from 193 to
293 K. NMR simulations were performed by using gNMR5. Several ex-
change models were tested including: intramolecular exchange of PA and
PB in each isomer, pairwise intermolecular exchange of PA in isomer 1
with PA in isomer 2 and PB in isomer 1 with PB in isomer 2, pairwise inter-
molecular exchange of PA in isomer 1 with PB in isomer 2 and PB in
isomer 1 with PA in isomer 2, etc. The spectra are best modelled by three
independent exchange processes involving pairwise intermolecular ex-
change of PA in isomer 1 with PA in isomer 2 and PB in isomer 1 with PB
in isomer 2, in combination with intramolecular exchange of PA with PB
in each isomer. The simulations are relatively insensitive to the intramo-
lecular exchange rate for isomer 2. For simplicity, therefore, the exchange
rate constants of the two intramolecular exchanges were set to equal.
(100.6 MHz, CDCl3): d=40.8 (dd, 1J
(C,P)=18.8, 3J
ACHUTGTNRENNUG ACHUTNTGREN(NUGN C,P)=5.2 Hz; C-
ACHTUNGTRENNUNG(CH3)3), 39.7 (s; CH3), 31.7 (brs; CH3), 30.5 (brs; CH3), 29.5 (brs;
CHcy), 26.6 (m; CH2cy), 25.7 ppm (d, 1J
ACHTNUTRGNE(NUG C,P)=10.8 Hz; CH2);
31P{1H} NMR (161.97 MHz, CDCl3): d=73.3 ppm (s); HRMS (ESI-TOF):
m/z: calcd: 479.2188 [MÀCH3SO3+H]+; found: 479.2147; elemental anal-
ysis calcd (%) for C24H52O6P2PdS2: C 43.08, H 7.83, O 14.35, P 9.26, Pd
15.90, S 9.58; found: C 43.02, H 7.86, S 9.53.
cis-(Di-tert-butylphosphinomethyl)cyclopentane palladium(II) complex
(34): By following the general procedure, complex 34 is obtained (yield=
321 mg, 42%). The dba was removed by diethyl ether (3ꢅ50 mL) and
the solid was dissolved in THF (10 mL). Then, 3 mL of this solution were
put in a layer tube and tert-butyl methyl ether was added carefully
(10 mL) to form a biphasic solution. The solution was left to stand for
HP NMR spectroscopic study
General method: All reactions and manipulations were carried out under
a dry oxygen-free nitrogen atmosphere by using Schlenk techniques. All
solvents were carefully purified by appropriate procedures. CD2Cl2 and
CD3OD were subjected to three freeze pump–thaw cycles and stored
over 4 ꢄ molecular sieves under nitrogen. Air sensitive compounds were
stored under nitrogen at 243 K. 13CO was purchased from ISOTEK and
13CH2=13CHOC(O)CH3 from Aldrich. All other chemicals were pur-
chased from Aldrich. Bis(ditertiarybutylphosphinomethyl)benzene
(DTBPMB) was donated by Lucite International. The sapphire tube was
supplied by Saphikon. The recirculating pump by HiT-Hydraulik.[69]
1
3 days, after which time, the formation of crystals was observed. H NMR
(400 MHz, CDCl3): d=2.93 (s; CH3), 2.19 (m, 2H; CHcy), 2.11 (m, 4H;
CH2cy), 1.93 (m, 2H; CHcy), 1.58 (d, 3JHÀP =15.2 Hz, 18H; CH3), 1.52
(d, 3JHÀP =15.2 Hz, 18H; CH3), 1.19 ppm (m, 4H; CH2); 13C NMR
(100.6 MHz, CDCl3): d=40.9 (dd, 1J(C,P)=26.1, 3J
ACTHNUGTRENNUGN ACHTUNGTRENNNUG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
HP NMR spectroscopic measurements: In a typical experiments, the sap-
A
ACHTUNGTRENNUNG
phire NMR tube was charged under N2 with a solution containing the
31P{1H} NMR (161.97 MHz, CDCl3): d=79.5 ppm (s); HRMS (ESI-TOF):
m/z: calcd: 493.2344 [MÀCH3SO3+H]+; found: 493.2347; elemental anal-
ysis calcd (%) for C25H54O6P2PdS2: C 43.95, H 7.97, O 14.05, P 9.07, Pd
15.58, S 9.39; found: C 43.82, H 8.06, S 9.42.
palladium precursor
(0.048 mmol), the
corresponding
ligand
(0.144 mmol) and the corresponding acid CH3SO3H or CF3CO2H (0.12 or
6 mmol, respectively) in methanol. The tube was then pressurised with
ethylene and carbon monoxide to the desired pressure. Most of the com-
pounds reported below have not been isolated due to their instability or
the reversible nature of the reaction involved. However, 1D and
2D NMR spectroscopic measurements and detailed isotopic labelling ex-
periments allow all of these compounds to be assigned unambiguously.
cis-1,2-Bis(di-tert-butylphosphinomethyl)cyclohexane palladium(II) com-
plex (35): The synthesis of complex (35) was completed according to the
general procedure previously described (yield=399 mg, 51%). The crys-
tals were obtained after purification by the elimination of dba with dieth-
yl ether (3ꢅ50 mL and the solid was dissolved in THF (10 mL)). Then,
3 mL of this solution were put in a layer tube and diethyl ether was
added carefully (20 mL) to form a biphasic solution. The solution was
left to stand for 3 days, after which time, the formation of crystals was ob-
served. 1H NMR (400 MHz, CDCl3): d=2.93 (s; CH3), 2.16 (brs, 2H;
[Pd
ACHTUNGNERT(GNUN O2CCF3)ACHTUNRGTEG(NNUN L-L)]O2CCF3 ACTHUNGTRENNUNG
phosphine ligand (0.144 mmol) and Pd
AHCTUNGTRENNUNG
bined in a schlenk flask. MeOH (3 mL) was then added and the resultant
solution was stirred for 2 h at room temperature. Trifluoroacetic acid was
added and the reaction mixture was then stirred for 2 h. The solution was
6930
www.chemeurj.org
ꢃ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 6919 – 6932

Palladium-Catalysed Methoxycarbonylation of Ethene
FULL PAPER
filtered under nitrogen and then concentrated under vacuum. Diethyl
ether (3 mL) was added to precipitate the corresponding complex.
13CHOC(O)CH3 (1.5 equiv, 10 mL) was added. A mixture of 66a and 66b
was formed immediately, as indicated by the 31P{1H} NMR spectrum.
Complex 66a (major): 13C NMR (100.6 MHz, CDCl3): d=96.2 (dd,
[Pd
pound 46 was obtained as a yellow powder. Yield: 56 mg, 63%; H NMR
(400 MHz, CDCl3): d=2.67 (m, 4H; CH2), 1.68 (d, 18H, 3J
(H,P)=
14.4 Hz; CH3), 1.46 (d, 18H, 3J
(H,P)=14.4 Hz; CH3), 1.31 (m, 2H;
CH2cy), 1.13 (m, 1H; CHcy), 0.91 ppm (m, 1H; CHcy); 13C NMR
(100.6 MHz, CDCl3): d=162.9 (d, 2J
(C,F)=39.5 Hz; C(CF3)), 117.5 (d,
1J(C,F)=285.2 Hz; CF3), 39.3 (dd, 1J(C,P)=18.4, 3J
(C,P)=9.2 Hz; C-
(CH3)3), 31.3 (brs; CH3), 30.2 (brs; CH3), 29.9 (s; CH2cy), 23.5 (d,
2J CH2); 31P{1H} NMR
(C,P)=20.6 Hz; CHcy), 17.6 ppm (m;
ACHTUNGTRENNUNG(O2CCF3)(6)]O2CCF3 (46): By following the general procedure, com-
1
J
(C,C)=32.5,
J
G
JACTHUNGTERNNU(G C,C)=32.5 Hz);
2
2
31P{1H} NMR (161.97 MHz, CDCl3): d=52. 5 (dd, J
(P,C)=95.6, J
N
AHCTUNGTRENNUNG
30.5 Hz), 51.3 ppm (d, J
AHCTUNGTRENNUNG
Complex 66a (minor): 13C NMR (100.6 MHz, CDCl3): d=93.9 (dd,
(C,C)=31.2,
(C,P)=94.3 Hz), 27.5 ppm; 31P{1H} NMR (161.97 MHz,
CDCl3): d=70.2 (d, 2J(P,P)=29.7 Hz), 30.5 ppm (dd, 2J
(P,C)=97.7,
2J
(P,P)=30.5 Hz).
A
ACHTUNGTRENNUNG
J
N
JACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
(161.97 MHz, CDCl3): d=51.0 ppm (s); HRMS m/z: (ESI-TOF): m/z:
465.2043, calcd: 465.2051 [MÀCF3CO2+H]+; elemental analysis calcd for
C25H44F6O4P2Pd: C 43.46, H 6.42, F 16.50, O 9.26, P 8.97, Pd 15.40;
found: C 43.33, H 6.47.
Acknowledgements
[PdACHTUNGTRENNUNG(O2CCF3)(7)]O2CCF3 (47): Synthesis of 47 was completed according
We thank the Spanish Government, Ministerio de Educaciꢂn y Ciencia
(CTQ2007-62288/BQU, Consolider Ingenio 2010, CSD2006-0003), Gener-
alitat de Catalunya (distinction for Research Promotion 2003 CC, and re-
search PhD grant for V.F. (FI program/2008FI)) and Lucite International
for their financial support. J.A.I. thanks the EPSRC (EP/C005643/1) for
financial support. We also thank William Clegg for elucidating the X-ray
structures.
to the general procedure previously described. 31P{1H} NMR
(161.97 MHz, CDCl3): d=49.0 ppm (s); HRMS (ESI-TOF): m/z: calcd:
479.2188 [MÀCF3CO2+H]+; found: 479.2178; elemental analysis calcd
(%) for C26H46F6O4P2Pd: C 44.29, H 6.58, F 16.17, O 9.08, P 8.79, Pd
15.10; found: C 44.21, H 6.61.
[PdACHTUNGTRENNUNG(O2CCF3)(8)]O2CCF3 (48): The synthesis of 47 was completed accord-
ing to the general procedure previously described. 31P{1H} NMR
(161.97 MHz, CDCl3): d=48.3 (s); HRMS (ESI-TOF): m/z: calcd:
493.2344 [MÀCF3CO2+H]+; found: 493.2341; elemental analysis calcd
(%) for C27H48F6O4P2Pd: C 45.10, H 6.73, F 15.85, O 8.90, P 8.62, Pd
14.80; found: C 45.02, H 6.78.
[1] K. Nozaki in Comprehensive Asymmetric Catalysis (Eds.: I. E. N. Ja-
cobsen, A. Pfaltz, H. Yamamoto), Springer, Heidelberg, 1999,
p. 382.
[PdACHTUNGTRENNUNG(O2CCF3)(9)]O2CCF3 (49): The synthesis of 49 was carried out in ac-
[2] R. P. Tooze, G. R. Eastham, K. Whiston, X. L. Wang, WO/1996/
019434, 1996.
[3] R. Hadden, J. M. Pearson, WO/1998/041495, 1998.
[4] http://www.icis.com/Articles/2009/08/10/9238750/SABIC-Mitsubishi-
Rayon-in-1bn-acrylics-joint-venture.html.
[5] R. I. Pugh, E. Drent in Catalytic Synthesis of Alkene-Carbon Mon-
oxide Copolymers and Cooligomers, Vol. 27 (Ed.: A. Sen), Kluwer,
Dordrecht, 2003.
[6] E. Drent, W. P. Mul, P. H. M. Budzelaar, Comments Inorg. Chem.
2002, 23, 127.
[7] R. I. Pugh, E. Drent, Adv. Synth. Catal. 2002, 344, 837.
[8] E. Drent, Abstr. Pap. Am. Chem. Soc. 1999, 218, 273.
[9] E. Drent, P. H. M. Budzelaar, Chem. Rev. 1996, 96, 663.
[10] E. Drent, J. A. M. van Broekhoven, P. H. M. Budzelaar, Recl. Trav.
Chim. Pays-Bas-J. R. Neth. Chem. Soc. 1996, 115, 263.
[11] C. Bianchini, A. Meli, W. Oberhauser, Dalton Trans. 2003, 2627.
[12] I. del Rio, C. Claver, P. W. M. N. van Leeuwen, Eur. J. Inorg. Chem.
2001, 2719.
[13] W. Clegg, G. R. Eastham, M. R. J. Elsegood, R. P. Tooze, X. L.
Wang, K. Whiston, Chem. Commun. 1999, 1877.
[14] A. Sen in Catalytic Synthesis of Alkene-Carbon Monoxide Copoly-
mers and Cooligomers, Vol. 27 (Ed.: A. Sen), Kluwer, Dordrecht,
2003.
cordance with the general procedure. The product was isolated as a
yellow/green solid. Yield: 148 mg, 77%; 1H NMR (400 MHz, CD2Cl2):
d=1.63 (d, 18H, 3J(H,P)=14 Hz; CH3), 1.54 (d, 3J
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
2
1
(d, J
2J
(C,P)=17.5 Hz; C
(m; CHcy), 31.9 (m; CH2cy), 30.3 (m; CH3), 26.8 (m; CH2cy), 16.9 ppm
(d, 1J(C,P)=19.8; CH2); 31P{1H} NMR (161.97 MHz, CD2Cl2, 193 K): d=
G
E
R
G
N
G
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
76.2 (s), 46.9 ppm (s); HRMS (ESI-TOF): calcd: 507.2501
[MÀCF3CO2+H]+; found: 507.2527; elemental analysis calcd (%) for
C28H50F6O4P2Pd: C 45.88, H 6.87, F 15.55, O 8.73, P 8.45, Pd 14.52;
found: C 45.51, H 6.96.
[Pd
ACHTUNGTRENNUNG(6–9)ACHTUNGTRENNUNG(CH2CH3)]O2CCF3 ACUTHNGTRENNNUG
phosphine ligand (0.144 mmol) and Pd
AHCTUNGTRENNUNG
bined in a schlenk flask. MeOH (3 mL) was then added and the resultant
solution was stirred for 20 min at room temperature. Trifluoroacetic acid
(0.480 mmol) was added and the reaction mixture was then stirred for an-
other 20 min. The solution was then transferred into the sapphire tube
and it was charged with 10 bar of ethene at 353 K for 20 min.
[Pd(6)ACHTUNGTRENNUNG(CH2CH3)]O2CCF3 (61): The synthesis of complex 61 was complet-
ed according to the general procedure previously described.
31P{1H} NMR (161.97 MHz, CDCl3): d=67.9 (d, 2J
N
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3166.
2
50.3 ppm (d, J
N
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[Pd(7)ACHTUNGTRENNUNG(CH2CH3)]O2CCF3 (62): The synthesis of complex 62 was complet-
ed according to the general procedure previously described.
31P{1H} NMR (161.97 MHz, CDCl3): d=63.4 (d, 2J
N
2
41.2 ppm (d, J
N
[Pd(8)ACHTUNGTRENNUNG(CH2CH3)]O2CCF3 (63): The synthesis of complex 63 was complet-
ed according to the general procedure previously described.
31P{1H} NMR (161.97 MHz, CDCl3): d=77.3 (d, 2J
N
2
47.0 ppm (d, J
N
[Pd(9)
ed according to the general procedure previously described.
31P{1H} NMR (161.97 MHz, CDCl3): major isomer: d=87.8 (d, 2J
(P,P)=
22.4 Hz), 38.6 (d, 2J(P,P)=22.4 Hz); minor isomer 64.3 (d, 2J
(P,P)=
ACHTUNGTRENNUNG(CH2CH3)]O2CCF3 (64): The synthesis of complex 64 was complet-
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
2
22.4 Hz), 58.4 ppm (d, J
[Pd(9)(k-2-CH(Me)OAc)]O2CCF3 (66): [Pd(9)
was synthesised as above. Then, CH2=CHOC(O)CH3 or 13CH2=
ACHTUNGTRENNUNG(P-P)=22.4 Hz).
N
ACHTUNGNERT(NGNU CH2CH3)]O2CCF3 (63)
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Received: November 17, 2009
Published online: May 3, 2010
6932
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Chem. Eur. J. 2010, 16, 6919 – 6932