A novel linkage-isomeric pair of dinuclear Pd(ii) complexes bearing a bis-bidentate tetraphos ligand

Article abstract of DOI:10.1039/b815392b

The tetraphosphane all trans tetrakis-(di(2-methoxyphenyl)phosphanyl) cyclobutane) (o-MeO-dppcb) has been employed to coordinate metal dichlorides (metal = Ni^II, Pd^II and Pt^II), stereoselectively yielding the dinuclear com

Full text of DOI:10.1039/b815392b

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PAPER
www.rsc.org/dalton | Dalton Transactions
A novel linkage-isomeric pair of dinuclear Pd(II) complexes bearing
a bis-bidentate tetraphos ligand†
a
a
a
a
a
b
Markus Fessler, Georg Czermak, Sylvia Eller, Barbara Trettenbrein, Peter Br u¨ ggeller,* Lorenzo Bettucci,
b
b
b
b
Claudio Bianchini, Andrea Meli, Andrea Ienco and Werner Oberhauser*
Received 3rd September 2008, Accepted 21st November 2008
First published as an Advance Article on the web 27th January 2009
DOI: 10.1039/b815392b
The tetraphosphane all trans tetrakis-(di(2-methoxyphenyl)phosphanyl)cyclobutane) (o-MeO-dppcb)
II
II
II
has been employed to coordinate metal dichlorides (metal = Ni , Pd and Pt ), stereoselectively
yielding the dinuclear complexes [Ni Cl (m-(kP :kP :kP :kP -o-MeO-dppcb))] (3a ) and
(m-(kP ,kP :kP ,kP -o-MeO-dppcb))] (2a ), characterized by two six and two five-membered
metallacycles, respectively. Conversely, the reaction with PdCl led, under comparable synthetic
conditions, to the formation of the linkage-isomeric pair [Pd Cl
) in a ca. 4 : 1 ratio. The compounds
obtained have been characterized in solution by multinuclear NMR spectroscopy and in the solid state
by CP-MAS NMR spectroscopy, XRPD and single crystal X-ray diffraction. Compounds 1a and 1a
1
2
3
4
2
4
6
1
2
3
4
[
Pt
2
Cl
4
5
2
1
2
3
4
2
4
(m-(kP ,kP :kP ,kP -o-MeO-dppcb))]
1
2
3
4
(
1a
5
) and [Pd
2
Cl
4
(m-(kP :kP :kP :kP -o-MeO-dppcb))] (1a
6
5
6
have been tested as catalyst precursors for the CO–ethene–propene co-and terpolymerization in
water–acetic acid mixtures. Their catalytic performance has been compared to that of
[
[
PdCl
PdCl
2
(o-MeO-dppe)] (1b) (o-MeO-dppe = 1,2-(bis(di(2-methoxyphenyl)phosphanyl))ethane) and of
2
(o-MeO-dppp)] (1c) (o-MeO-dppp = 1,3-bis(di(2-methoxyphenyl)phosphanyl)propane). The
5
most striking result that emerged from the CO–ethene copolymerization study was that 1a was
three times more productive than 1a
6
, outperforming, under identical catalytic conditions, even 1b and
1c, that are classified amongst the most active catalysts for the CO–ethene copolymerization reaction.
II
Introduction
the Pd centre has been suggested to occur in the course of
copolymerization reactions, influencing the kinetics of the overall
The architecture of conformationally rigid polyphosphine ligands
for coordination to transition metals is of much current interest
in organometallic chemistry and homogeneous catalysis as the
overall conformational properties of the corresponding metal–
phosphane complexes can significantly influence the catalytic
4
catalytic process.
The reaction conditions for CO–olefin copolymerization
can significantly influence the performance of Pd –diphosphane
precursors, as shown by a comparison of the catalytic productivity
II
-1
-1
II
2+
(
kg(polyketone)
g
(Pd)
h ) achieved in MeOH with [Pd (P-P)]
1
outcome in terms of both activity and selectivity.
compounds, bearing 1,3-bis(di(2-methoxyphenyl)phosphanyl)-
propane (o-MeO-dppp), rac-2,4-bis(di(2-methoxyphenyl)pho-
sphanyl)pentane (rac-o-MeO-bdpp) and 6,7-di(di-2-methoxy-
phenyl)phosphanyl-2,2,4,4-tetra(di-2-methoxyphenyl)-2l ,4l -
diphosphoniumbicyclo-[3.1.1]heptane-bis(PF (o-MeO-PCP)-
in the presence of different amounts of Brønsted acid
In the case of CO–ethene copolymerization reactions, a strict re-
lation between ligand rigidity and catalytic performance, especially
productivity and average molecular weight of the copolymers, has
been observed. In addition to the ligand skeletal rigidity, also the
nature of the phosphane substituents has been found to affect the
catalytic activity and selectivity.
of 2-methoxyphenyl substituents on the phosphorus donor atoms
of the ligand has been found to significantly enhance the catalytic
4
4
2
6
)
(
(
PF
6
)
2
2m,n
For example, the introduction
2b,3f
HOTs = p-toluenesulfonic acid) (Scheme 1).
II
productivity of the corresponding Pd precursors as compared
to precursors bearing analogous phenyl-modified diphosphanes,
3
due to a favourable combination of electronic and steric effects.
A direct interaction between the o-methoxy oxygen atoms and
a
Institut f u¨ r Allgemeine, Anorganische und Theoretische Chemie der Uni-
versit a¨ t Innsbruck, Innrain 52a, 6020, Innsbruck, Austria. E-mail: Peter.
Brueggeller@uibk.ac.at; Fax: +43-512-5072934
b
Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area di
Ricerca CNR di Firenze, via Madonna del Piano 10, 50019, Sesto Fiorentino,
Italy. E-mail: werner.oberhauser@iccom.cnr.it; Fax: +39-055-5225203
Scheme 1 Reaction conditions: (a) MeOH, HOTs (2 equiv.); (b) MeOH,
HOTs (20 equiv.).
†
Electronic supplementary information (ESI) available: Cartesian coordi-
nates and XRPD spectra. CCDC reference numbers 694966 and 694967.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b815392b
Although MeOH is the solvent of choice for CO–olefine
copolymerization reactions, water–acetic acid (AcOH) mixtures
This journal is © The Royal Society of Chemistry 2009
Dalton Trans., 2009, 1859–1869 | 1859

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have been proved to be highly suitable as reaction media for
these latter catalytic reactions. This experimental finding may be
accounted for by the stabilizing effect of water–AcOH mixtures
on Pd–hydride species that are key intermediates in the initiation
process of the copolymerization.
Herein, we report the synthesis and characterization
(COD = 1,5-cyclooctadiene) in dichloromethane in a 1 : 1 molar
ratio. The obtained Pt intermediate was then irradiated in DMF
with a high pressure Hg-vapour UV lamp. Upon reaction of the
obtained Pt complex, which was only slightly soluble in DMF,
with an excess of NaCN, the free ligand ( i.e. o-MeO-dppcb)
was obtained as white powder in 76.4% yield. The latter ligand is
5
3
1
1
of o-MeO-dppcb, of
dium complexes of the formula [Pd
o-MeO-dppcb))] (1a ) and [Pd Cl (m-(kP :kP :kP :kP -o-MeO-
dppcb))] (1a
) (o-MeO-dppcb = all trans tetrakis-(di(2-methoxy-
phenyl)phosphanyl)cyclobutane), of their analogous Pd–acetate
a
linkage-isomeric pair of palla-
characterized in CD
2
Cl
2
at room temperature by a P{ H} NMR
1
2
3
4
◦
2
Cl
4
1
(m-(kP ,kP :kP ,kP -
singlet at -25.8 ppm, while at low temperature (i.e. -95 C) in the
same solvent two broad singlets centred at -20.4 and -37.2 ppm
have been observed, that have been attributed to the axial and
2
3
4
5
2
4
6
equatorial phosphanyl groups of the tetraphosphine.
1
2
3
4
4
complexes [Pd
and [Pd (OAc)
the related Pt and Ni complexes [Pt
o-MeO-dppcb))] (2a ) and [Ni Cl (m-(kP :kP :kP :kP -o-MeO-
dppcb))] (3a ) (Scheme 2).
2
(OAc)
4
(m-(kP ,kP :kP ,kP -o-MeO-dppcb))] (5a
5
)
The reaction between o-MeO-dppcb and [PdCl
a 1 : 2 stoichiometric ratio in CH Cl
the two dinuclear linkage-isomeric Pd(II) complexes 1a
in a ca. 4 : 1 isomeric ratio (Scheme 4). Analogous reactions
2
(h -COD)] in
1
2
3
4
2
4
II
(m-(kP :kP :kP :kP -o-MeO-dppcb))] (5a
6
) and of
(m-(kP ,kP :kP ,kP -
2
2
at room temperature gave
II
1
2
3
4
2
Cl
4
1
5
and 1a
6
2
3
4
5
2
4
4
6
with [PtCl
2
(h -COD)] and NiCl
2
2
·6H
2
3
O stereoselectively yielded
1
4
the complexes [Pt
2
Cl
4
(m-(kP ,kP :kP ,kP -o-MeO-dppcb))] (2a
5
)
1
2
3
4
and [Ni
2
Cl
4
6
(m-(kP :kP :kP :kP -o-MeO-dppcb))] (3a ), respec-
tively (Scheme 4) as a result of the possible coordination modes
of the ligand to a metal centre (i.e. 1,2 and 1,3 phosphorus
coordination to the same metal centre).
Scheme 2
6
were tested as catalyst precursors for
Compounds1a
5
and 1a
the alternating CO–ethene–propene co- and terpolymerization
reactions in water–AcOH mixtures. The results were compared to
Scheme 4
those obtained with the mononuclear counterparts [PdCl (P-P)]
2
(
P-P = 1,2-bis(di(2-methoxyphenyl)phosphanyl)ethane) (o-MeO-
4
The reaction between o-MeO-dppcb and [PdCl
2
(h -COD)] was
dppe) (1b) and o-MeO-dppp (1c) under comparable experimental
conditions.
carried out in different solvents (i.e. CH CN and DMF) with no
3
effect on the isomeric ratio.
Selected bond distances, angles and relative energies of
geometry-optimized model complexes (i.e. 2-methoxyphenyl
groups have been replaced by hydrogen atoms) of the isomeric
Results and discussion
Synthesis and characterization of o-MeO-dppcb and its complexes
II
dinuclear metal chloride compounds and their mononuclear Pd ,
II
II
Pt and Ni counterparts (Fig. 1) are reported in Table 1. A perusal
of Table 1 reveals that the dinuclear complexes that contain two six-
membered metallarings (i.e. 1a6¢, 2a6¢ and 3a6¢) are lower in energy
than the corresponding isomer (i.e. 1a5¢, 2a5¢ and 3a5¢), showing a
The ligand o-MeO-dppcb has been obtained following a synthetic
protocol that resembles very much that employed for the synthesis
of cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphanyl)cyclobutane.
Scheme 3 shows the basic synthetic steps for the synthesis of
6
comparable energy gap (DE(M
5
- M )) within the pairs of isomers
6
1
o-MeO-dppcb.
-
(between -23.7 and -25.9 kcal mol ).
A comparison of the geometrical parameters reported in Table 1
(Cartesian coordinates have been reported as ESI†) showed that
the M–P bond distances in the dinuclear metal complexes (i.e.
˚
1a5¢, 2a5¢ and 3a5¢) is around 0.03 A longer as compared to
the corresponding isomer, while an analogous comparison with
the mononuclear counterparts gave no significant differences
(Table 1), indicating that 1a5¢, 2a5¢ and 3a5¢ are characterized by
weaker M–P bonds compared to their isomers due to the geometric
constraints of the ligand imposed by the cyclobutane ring. On
the other hand, the ligand bite angles of the five-membered
Scheme 3
7
The reaction of the Li-salt of bis(2-methoxyphenyl)phosphane
with trans-1,2-dichloroethylene gave trans-1,2-(bis(2-methoxy-
phenyl)phosphanyl)ethylene (o-MeO-trans-dppen) in low yield
14%). The latter phosphine was reacted with [PtCl
◦
dinuclear metal complexes are around 4 narrower than in their
isomers, while an analogous analysis concerning the mononuclear
4
(
2
(h -COD)]
1
860 | Dalton Trans., 2009, 1859–1869
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Table 1 Selected bond distances, angles and relative energies for the
optimized metal chloride complexes
DE(M
5
6
- M )/
◦
◦
-1
M–Cl/A˚
M–P/ A˚ Cl–M–Cl/
P–M–P/
kcal mol
1
1
1
1
2
2
2
2
3
3
3
3
a
a
5¢
6¢
2.35
2.36
2.30
2.27
2.27
2.27
2.28
2.25
2.25
2.26
2.21
2.18
2.17
2.18
97.0
98.0
97.7
97.0
94.0
95.0
94.4
93.3
99.0
99.0
100.2
97.7
91.0
96.0
87.5
97.1
92.0
96.0
87.8
97.4
92.0
96.0
88.3
96.8
-23.7
b¢ 2.35
c¢
a
a
2.36
2.37
2.38
5¢
Scheme 5
6¢
-24.3
-25.9
b¢ 2.38
1
2
3
4
c¢
a
a
2.38
2.20
2.20
[Pd
2
(OAc)
4
(m-(kP :kP :kP :kP -o-MeO-dppcb))] (5a
6
) as yellow
5¢
powders in 51 and 25% yield, respectively (Scheme 2). The
direct reaction of Pd(OAc) with o-MeO-dppcb gave 5a and
in an approximately 4 : 1 isomeric ratio as observed for the
6¢
2
5
b¢ 2.20
c¢ 2.21
5a
6
4
analogous reaction with [PdCl (h -COD)] (Scheme 4), along with
2
the formation of still unidentified side products.
The isolated dinuclear metal chloride complexes, possessing two
six-membered metallarings (i.e. 1a
6
, 3a
6
6
and 4a ) are soluble in
organic solvents such as CH Cl and have been straightforwardly
2
2
characterized by multinuclear NMR spectroscopy and ESI-MS
measurements in solution and by elemental analysis in the solid
3
1
6
state. Complex 1a was also authenticated by CP-MAS P NMR
spectroscopy and a single crystal X-ray structure analysis. The
3
1
1
P{ H} NMR spectrum of 1a
6
acquired in CD
2
Cl
2
showed two
broad singlets at 17.80 and 36.16 ppm, while 3a
6
exhibited in the
2
same solvent two doublets at 7.37 and 25.55 ppm with J(PP) of
4.0 Hz indicating two chemically inequivalent phosphorus atoms
9
3
1
coordinated to the same metal centre. The CP-MAS P NMR
spectrum of 1a
(Fig. 2) (d = 17.94 (br s), 38.00 (br s)) along
with the single crystal X-ray structure analysis of 1a
·2.8DCE
6
6
(
DCE = 1,2-dichloroethane) unambiguously showed inequivalent
phosphorus atoms in the solid state, due to Pd–o-MeO-oxygen
interactions (vide infra), persisting also in solution.
Fig. 1 Geometry-optimized model complexes.
complexes (Table 1) showed a difference in the bite angles between
◦
the five- and six-membered metallacycles of around 8–10 .
Intrigued by the fact that o-MeO-dppcb formed linkage isomers
II
with Pd , we searched for a synthetic procedure aimed at
increasing the yield of 1a (i.e. minor product) (Scheme 4). To this
6
III
purpose, we exploited (i) the selective coordination of Cr to o-
MeO-dppcb (leading to the exclusive formation of six-membered
II
metallarings as occurs with other 3d metals such as Ni (vide
II
8
III
supra) and Co ) and (ii) the easy displacement of Cr from the
II
coordination sphere by Pd , due to the weaker binding affinity of
31
III
9
5 5 6
Fig. 2 CP-MAS P NMR spectra of 1a , 2a and 1a . Spinning sidebands
Cr to phosphorus donor atoms.
The reaction of [CrCl (THF)
yielded selectively the pink complex [Cr
kP :kP :kP :kP -o-MeO-dppcb))] (4a
complex was isolated and was further reacted with [PdCl
are denoted by asterisks.
3
3
]
with o-MeO-dppcb in
Cl (THF) (m-
) (Scheme 5). The latter
CH
(
2
1
Cl
2
2
6
2
2
3
4
6
Crystals of 1a
structure analysis have been obtained by a slow evaporation of
a DCE solution of 1a at room temperature. An ORTEP diagram
of 1a
and angles as well as crystallographic data are reported in Tables 2
and 4, respectively.
6
·2.8DCE suitable for a single crystal X-ray
4
2
(h -
COD)] at room temperature to give 1a and 1a in a ca. 1 :
5
6
6
3
isomeric ratio, which is opposite to the product distribution
6
·2.8DCE is shown in Fig. 3, while selected bond distances
4
obtained by the direct reaction of [PdCl
dppcb (Scheme 4).
2
(h -COD)] with o-MeO-
The further reaction of either 1a
AgOAc) in CH CN or THF yielded the CH
plexes [Pd (OAc)
5
or 1a
6
with silver acetate
Cl -soluble com-
(m-(kP ,kP :kP ,kP -o-MeO-dppcb))] (5a ) and
The asymmetric unit of the crystal structure of 1a
tains the metal complex and 2.8 molecules of 1,2-dichloroethane.
Two were disordered.
6
·2.8DCE con-
(
3
2
2
1
2
3
4
2
4
5
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◦
◦
2b
Table 2 Selected bond lengths ( A˚ ) and angles ( ) for 1a
·2.8DCE and 2a
PCP)](PF
The deviations of the palladium atoms in 1a
coordination planes, defined by P(1), P(2), Cl(1) and Cl(2) or P(3),
)
exhibits a comparable dihedral angle of 86.43(10) .
6
5
6
2
6
·2.8DCE from the
1
a
6
·2.8(DCE)
2a
5
˚
P(4), Cl(3) and Cl(4), are 0.031(1) (Pd(1)) and 0.017(1) A (Pd(2)),
respectively. The cyclobutane carbon ring shows a folding angle of
152.4 . Both ligand bite angles P(1)–Pd(1)–P(2) and P(3)–Pd(2)–
P(4) of 94.52(11) and 94.35(10) , respectively, are significantly
larger than that found for the more flexible mononuclear counter-
Pt(1)–P(1)
2.2360(15)
2.3443(16)
Pt(1)–Cl(1)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–Cl(1)
Pd(1)–Cl(2)
Pd(2)–P(3)
Pd(2)–P(4)
Pd(2)–Cl(3)
◦
2.258(3)
2.255(3)
2.379(3)
2.347(3)
2.254(3)
2.266(3)
2.347(3)
2.360(3)
◦
◦
◦
part 1c of 90.09(4) , while the Pd–P bond lengths are comparable
in either complex: 2.259(3), 2.254(3), 2.254(3) and 2.265(3) A˚
3f
˚
(
1a
6
·2.8DCE) vs. 2.250(1)A (1c). A short intramolecular distance
Pd(2)–Cl(4)
between the metal centre and one o-methoxy oxygen atom of
each Pd coordination sphere (i.e. Pd(1) ◊ ◊ ◊ O(1) and Pd(2) ◊ ◊ ◊ O(8)
P(1)–Pt(1)–P(1A)
P(1)–Pt(1)–Cl(1)
Cl(1)–Pt(1)–Cl(1A)
P(1)–Pt(1)–Cl(1A)
P(1)–Pd(1)–P(2)
P(1)–Pd(1)–Cl(1)
Cl(1)–Pd(1)–Cl(2)
P(2)–Pd(1)–Cl(2)
P(1)–Pd(1)–Cl(2)
P(2)–Pd(1)–Cl(1)
P(3)–Pd(2)–P(4)
P(3)–Pd(2)–Cl(3)
Cl(3)–Pd(2)–Cl(4)
P(4)–Pd(2)–Cl(4)
P(3)–Pd(2)–Cl(4)
P(4)–Pd(2)–Cl(3)
Intramolecular distances ( A˚ )
90.91(8)
89.04(5)
91.28(8)
176.03(5)
˚
˚
of 2.805(8) A and 2.825(7) A, respectively), accounts for the
slight asymmetry observed in each coordination sphere of 1a
Analogous interactions have also been found to occur in 3a
6
.
94.47(11)
86.82(11)
91.94(11)
86.80(11)
178.64(12)
176.27(11)
94.36(10)
86.12(10)
90.86(11)
88.69(11)
176.19(11)
179.24(11)
6
(a complete X-ray structure analysis will be reported elsewhere)
˚
showing Ni ◊ ◊ ◊ O distances of 2.620(5) and 2.604(6) A.
The higher trans influence of the acetate ligand as compared to
chloride increases the palladium–phosphorus bond length. As a
consequence, the palladium–o-MeO-oxygen interactions that are
responsible for the inequivalence of the phosphorus donor atoms
(vide infra) are significantly weakened and hence the Pd
acetate complex (5a ) showed a symmetric coordination sphere at
palladium, at least on the NMR time scale, indicated by a P{ H}
9
in 1a
6
6
31
1
Pt(1) ◊ ◊ ◊ O(1)
Pt(2) ◊ ◊ ◊ O(2)
Pd(1) ◊ ◊ ◊ O(1)
Pd(2) ◊ ◊ ◊ O(8)
3.539(5)
5.151(4)
NMR singlet at 29.76 ppm.
Due to the insolubility in organic solvents of the dinuclear metal
chloride complexes containing two five-membered metallarings
2.811(8)
2.825(7)
(
i.e. 1a
5
5
and 2a ) both complexes were characterized in the solid
Symmetry transformation used to generate equivalent atoms: A = y, x, -z.
3
1
state by CP-MAS P NMR spectroscopy (Fig. 2), X-ray powder
diffraction (XRPD spectra have been reported as ESI†) and
5
elemental analysis, while 2a was additionally characterized by
a single crystal X-ray structure analysis (vide infra).
3
1
The CP-MAS P NMR spectra of 1a
5
5
and 2a (Fig. 2)
showed for each complex one singlet centred at 44.60 and
1
2
0.29 ppm ( J(PtP) = 3717 Hz), respectively. The chem-
ical shift of the latter compound resembles very much
that obtained for the related mononuclear Pt complex
II
[
PtCl
2
(P-P)] (P-P = all trans-1,2-(bis(diphenylphosphanyl))-3,4-
1
0
1
diphenylcyclobutane) (d 26.80 ppm, J(PtP) = 3727 Hz), that
is also characterized by a strained five-membered metallaring.
3
1
1
A comparison of the P{ H} NMR chemical shift of 5a
5.99 ppm) with that of the flexible mononuclear complex
Pd(OAc) (o-MeO-dppe)] (d 61.94 ppm) clearly indicates that
5
(d
3
[
2
3
1
the five-membered ring contribution to the P chemical shift is
low in strained five-membered metallarings. This may be due to
hampered electron delocalization via pp–pp conjugation within
the five-membered metallaring as previously suggested to explain,
in conjunction with conformational and steric effects, the strong
Fig. 3 ORTEP diagram of 1a
6
·2.8DCE with 30% probability ellipsoids.
Hydrogen atoms, solvent molecules and all 2-methoxyphenyl units show-
ing no interaction with the metal centre have been omitted, instead their
ipso carbon atoms are presented.
3
1
low-field P NMR chemical shifts observed in transition metal–
11
phosphorus chelate complexes.
5
The XRPD patterns of 1a and 2a confirm that these complexes
5
Both palladium atoms of the binuclear complex show a square-
planar coordination environment, built up by two cis coordinating
chloride atoms and two phosphorus donor atoms attached to the
are isostructural and exhibit a comparable stereochemistry at the
metal centre.
Crystals, suitable for a single crystal X-ray structure anal-
1
,3 positions of the cyclobutane carbon ring, thus forming two
ysis of 2a
solutions of [PtCl
other at room temperature. A selected ORTEP diagram of 2a
5
were obtained by controlled diffusion of CH
2
Cl
2
4
six-membered metallarings almost perpendicular to each other
with a dihedral angle of 86.34(11) . Accordingly, the related
2
(h -COD)] and of o-MeO-dppcb into each
◦
5
mononuclear bis-phosphonium modified complex [PdCl
2
(o-MeO-
is shown in Fig. 4, while selected bond lengths and angles as
1
862 | Dalton Trans., 2009, 1859–1869
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◦
(
i.e. folding angle of 138.7 ) cyclobutane carbon ring. The
metal centre exhibits a square-planar coordination geometry,
deviating from the coordination plane, defined by the atoms
P(1), Cl(1) and their symmetry-equivalent counterparts P(1A)
˚
and Cl(1A), by 0.063(1) A. The ligand bite angle P(1)–Pt(1)–
◦
P(1A) of 90.91(8) is comparable to that observed for the related
mononuclear Pt complex [PtCl
bis(diphenylphosphanyl))-3,4-diphenylcyclobutane), 90.15(3) ,
II
2
(P-P)] (P-P = all trans-1,2-
◦
10
(
but significantly larger than that in complexes bearing the dppe
◦
12
ligand (1,2-bis(diphenylphosphanyl)ethane) (i.e. ca. 85 ). The
rigid twist conformation of the five-membered metallarings in
2
5
a is clearly evidenced by the symmetry-related deviation of the
˚
cyclobutane carbon atoms of 0.447 A from the least-squares plane
defined by Pt(1), P(1), P(1A), Cl(1) and Cl(1A). Unlike 1a
shows no metal–o-methoxy-oxygen interactions (Table 2).
6
, 2a
5
5
Fig. 4 ORTEP diagram of 2a with 30% probability ellipsoids. Hydrogen
atoms as well as all symmetry equivalent 2-methoxyphenyl units are
omitted for clarity, instead only their ipso carbon atoms are presented.
Symmetry transformations used to generate equivalent atoms: y, x, -z;
Catalytic co-and terpolymerization of CO, ethene and propene
Complexes 1a and 1a were employed to catalyse the
1
- x, 1 - y, z; 1 - y, 1 - x, -z. The given labelling pertains to the atoms
without symmetry transformation (i.e. x, y, z).
5
6
CO–ethene and CO–propene copolymerization as well as the
CO–ethene–propene terpolymerization reaction in water–AcOH
3
f ,13
well as the crystallographic data are reported in Tables 2 and 4,
respectively.
The crystal structure of 2a exhibits in the asymmetric unit
5
solvent mixtures.
For comparative purposes some catalytic re-
actions were carried out with 1b and 1c as catalyst precursors under
identical experimental conditions. The results of the catalytic study
are presented in Table 3.
The results obtained with each catalyst precursor are reported
for the maximum of productivity observed (Table 3) which was
only a quarter of the entire molecule (i.e. labelled part of
II
Fig. 4), indicating the equivalence of both Pt coordination
spheres, which comprise two cis-coordinating chloride ions
and two vicinal phosphorus donor atoms of o-MeO-dppcb,
thus forming two five-membered metallarings sharing a folded
actually achieved with 1a
mixture with 1b and 1c in a 75 mol% water–HOAc mixture. It
5
6
and 1a in a 65 mol% water–HOAc
5 6
Table 3 Co- and terpolymerization reactions in water–AcOH, employing the neutral palladium chloride precursors 1a , 1a , 1b and 1c
Entry
CO–ethene copolymerization
Precatalyst
th
Water/mol%
Productivity/kg(polyketone)
g
(Pd) h-1
-
1
M
n
/kg mol-1 [mp/ C]
◦
Propene (%)
h-t Regioselectivity (%)
a
b
1
2
3
4
5
6
7
8
9
0
1a
1a
1b
1b
1b
1a
1a
1c
1c
1c
5
1
2
1
1
2
1
2
1
1
2
65
65
65
75
75
65
65
65
75
12.20
11.28
7.47
8.90
5.50
4.49
3.47
8.39
9.10
6.00
15.3 [251]
5
c
c
5.1 [247]
6
6
18.0 [251]
c
c
>40.0 [256]
1
75
d
CO–propene copolymerization
1
1
1
1
1
2
3
4
1a
1b
1a
1c
5
2
2
2
2
65
75
65
1.77
0.64
0.99
0.73
0.33
0.37
0.30
0.55
62
53
61
55
6
75
d,e
CO–ethene–propene terpolymerization
1
1
1
1
1
2
2
2
5
6
7
8
9
0
1
2
1a
1a
1b
1b
1a
1a
1c
1c
5
1
3
1
3
1
3
1
3
65
65
75
75
65
65
75
75
5.34
3.99
5.51
4.37
2.93
1.19
6.45
3.57
5
10.1 [186]
6.6 [150]
9.5 [186]
13.1 [180]
16.6
26.6
13.2
24.1
6
6
a
13
1
b
(
Head to tail, h-t) regioselectivity given in %, based on C{ H} NMR integration. Catalytic conditions: amount of palladium, 0.0048 mmol; AcOH–
◦
c 3f d
2 4
water, 100 mL; p(CO)/p(C
0
8
H
), 20/20 bar; temperature, 85 C; stirring rate, 1200 rpm. Catalytic precursor, 0.0048 mmol.
.0048 mmol; propene, 33 g and constant CO pressure, 56 bar at 85 C. Propene, 20 g; p(C
Amount of palladium,
◦
e
◦
2
H
4
), 7 bar at 20 C and constant CO pressure, 70 bar at
◦
5 C.
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is generally agreed that the water proportion in the water–AcOH
mixture controls both the solvolysis of the neutral Pd hydrido
chloride species (B, Scheme 6), which generates cationic Pd –H
copolymers with only poly(1-oxo-2-methyltrimethylene) units in
1
13
1
the polymer chain were obtained. The H and C{ H} NMR
II
characterization of the CO–propene copolymers in CDCl showed
3
initiators (C, Scheme 6) and the solubility of the monomers (i.e.
the simultaneous presence of ketone (K) and vinyl (V) end groups
(Scheme 7).
13,14
CO and olefins) in the reaction medium.
A perusal of the CO–ethene copolymerization results (Table 3)
shows that precatalyt 1a is about three times more active than
(Table 3, entry 1 vs. 6), outperforming 1b and 1c (entry 1 vs 3,
and 8, 9, respectively) which are known to be highly active for
5
1a
6
4
3f
this type of reaction. The same productivity trend was observed
for catalytic reactions lasting 2 h, featured by a productivity drop
in the second hour by ca. 7% (1a
5
6
), 38% (1b), 23% (1a ) and 34%
(
1c). One may therefore conclude that 1a
5
is the most active and
also the most stable copolymerization catalyst under the present
experimental conditions. All precatalysts investigated produced
strictly-alternating polyketones containing exclusively ketone end-
Scheme 7
1
1
groups ( H NMR evidence) due to protonolysis of the palladium
On the basis of integration of the corresponding H NMR
alkyl species (F, Scheme 6) by water, leading to the formation of
signals, 1a , 1a , 1b and 1c were assigned vinyl (V) to ketone (K)
ratios of 7 : 33, 6 : 33, 3 : 33 and 1 : 33, respectively. As for
the productivity of the CO–ethene copolymerization reactions,
5
6
II
cationic Pd–OH species (I) that can regenerate a Pd –H initiator
15
by the water gas shift reaction (WGS). Since 1a
5
6
and 1a gave
CO–ethene copolymers of similar average molecular weight, one
may conclude that the chain transfer reaction (i.e. protonolysis)
occurs at a comparable rate. In turn, this suggests that the metal
centre in both catalysts exhibits comparable electrophilicity, hence
similar propensity to promote Pd–b-hydride elimination of the Pd
alkyl species (F, Scheme 6), which is the rate determining step of the
1a showed again the highest performance within the series of
precatalysts studied (entry 11 vs. 12–14) (Table 3).
The regioselectivity of the propene insertion (i.e. 1,2 or 2,1
5
insertion) into the growing polymer chain was determined by
1
3
1
13
1
C{ H} NMR spectroscopy integrating the C{ H} CO signals,
stemming from tail to tail (t-t), head to tail (h-t) and head to head
(h-h) regioisomers (Scheme 8).
16
17
protonolysis reaction. The different overall conformation of the
o-MeO-dppcb ligand in the stereochemically rigid complexes 1a
and 1a , combined with possible Pd–o-MeO-oxygen interactions,
5
6
may account for the slower propagation rate of the reaction
catalyzed by the latter complex.
The same precursors have been employed to catalyse the CO–
propene copolymerization reaction in the presence of a fixed
amount of propene (33 g) and a constant CO feed during the cat-
alytic process, using the same water–AcOH mixture composition
of the analogous CO–ethene copolymerization reactions (Table 3,
entries 11–14). Irrespective of the catalyst precursor, highly viscous
Scheme 8
Thestereochemicallyrigidbinuclear palladiumcatalysts showed
a significantly enhanced regioselectivity for the h-t regioisomer
Scheme 6
1
864 | Dalton Trans., 2009, 1859–1869
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as compared to the mononuclear complexes (Table 3, entries 11
and 13 vs. 12 and 14). However, we do not have any clear-cut
explanation for this result which other authors have previously
observed and attributed to a complex web of steric and electronic
Experimental
Materials and physical measurements
All reactions and manipulations were carried out under a
nitrogen atmosphere by using Schlenk-type techniques. The
solvents were generally distilled over dehydrating reagents and
were deoxygenated before use. The reagents were used as
purchased from Aldrich, Fluka or Strem Chemicals. Bis(2-
18
factors.
The present palladium precursors were also used to catalyse
the terpolymerization reaction of CO–ethene and propene in
the water–AcOH mixtures employed in the CO–ethene copoly-
merization reactions. The catalytic reactions were carried out in
7
4
19
methoxyphenyl)phosphane [PdCl
2
(h -COD)] , [PdCl (P-P)] (P-
2
the presence of a fixed amount of propene (20 g) and ethene
3f
P = o-MeO-dppe, o-MeO-dppp) were prepared according to
literature methods. The irradiation experiment has been carried
out with an high pressure Hg-vapour UV-lamp. Co- and ter-
polymerization reactions were performed with a 320 ml stainless
steel autoclave, constructed at the ICCOM-CNR (Florence,
Italy), equipped with a magnetic drive stirrer and a Parr 4842
temperature and pressure controller. The autoclave was connected
to a gas reservoir to maintain a constant pressure while performing
the catalytic reactions. GC-MS analyses of the solutions were
performed on a Shimadzu QP 5000 apparatus equipped with a
SPB-1 Supelco fused silica capillary column (30 m, 0.25 mm i.d.,
◦
(
7 bar) at 20 C. The results of the catalytic study are reported in
Table 3 (entries 15–22). Low-melting terpolymers were obtained
with all precursors. The precursors 1a and 1a gave terpolymers
5
6
characterized by a significantly lower propene incorporation as
compared to 1b and 1c. In particular, 1b gave the terpolymer
◦
with the lowest melting point (150 C), consistent with the lowest
average molecular weight of the terpolymer and the highest
content of propyl units (Table 3). The end-group analysis of
the terpolymers showed the occurrence of the same type of end-
groups observed for the CO–propene copolymers, confirming that
the Pd–b-hydride elimination in Pd alkyl compounds containing
an isopropylene unit attached to palladium is favoured over
0.25 mm film thickness). Deuterated solvents for routine NMR
1 13 1
measurements were dried over molecular sieves. H, C{ H},
17a
that in compounds containing an ethylene unit. Complexes 1c
and 1a showed the highest and lowest terpolymer productivity,
respectively, while 1a and 1b exhibited a comparable productivity
Table 3).
3
1
1
P{ H} NMR spectra were obtained on a Bruker Avance DPX
6
3
00 spectrometer, measuring at 300.13, 75.48 and 121.50 MHz,
5
respectively. Chemical shifts are reported in ppm (d) with reference
to either TMS as an internal standard ( H and C NMR) or 85%
(
1
13
3
1
31
H
3
PO as an external standard ( P NMR). CP-MAS P NMR
4
spectra were recorded at room temperature on a Bruker Avance
DRX-400 spectrometer equipped with a 4 mm BB CP-MAS probe
at a working frequency of 161.98 MHz. The spectra were recorded
using a cross polarization pulse sequence under magic angle
spinning at a spinning rate of 8.0 kHz. Elemental analyses were
performed using a Perkin Elmer Model 2400 C,H,N elemental
analyser. XRPD spectra were acquired at room temperature with
a Bruker D8-Advance diffractometer, employing Cu Ka radiation
Conclusions
The reaction of the tetraphosphane o-MeO-dppcb with metal
II
dichloride precursors of the Ni triad gives stereoselectively Pt
II
and Ni binuclear complexes characterized by 5-4-5- and a 6-4-
II
6
-membered tricyclic ring systems, respectively. Conversely, Pd
forms, under comparable experimental conditions, the linkage-
isomeric compounds 1a (i.e. 5-4-5-membered ring system) and 1a
i.e. 6-4-6-membered ring system) in a ca. 4 : 1 isomeric ratio. This
5
6
◦
˚
(
l = 1.5418 A) and a scanning range between 2.5 and 80.0 with
(
◦
an acquisition step of 0.030 per second. Infrared spectra were
recorded on a Nicolet 5700 ATR FTIR spectrometer. ESI-MS
spectra were obtained on a Finnigan MAT-95 spectrometer, using
III
ratio was almost reversed by exploiting the template effect of Cr
for the 6-4-6-membered ring system and the smooth substitution
III
II
of Cr by Pd .
3-nitrobenzylalcohol (NOBA) as matrix. Structural optimizations
Compounds 1a
5
6
and 1a have been employed to catalyse the CO–
were carried out applying the hybrid density functional theory
ethene and CO–propene copolymerization and the CO–ethene–
propene terpolymerization in water–AcOH solvent mixtures with
a prevalent water content (65–75 mol%). An analogous study was
20a
(
DFT) using the Gaussian 03 suite of programs. The method
used was the Becke’s three-parameter hybrid exchange–correlation
20b
functional containing the non-local gradient correction of Lee,
II
carried out with the mononuclear Pd complexes 1b and 1c.
20c
Yang and Parr (B3LYP). Calculations of the frequencies were
performed to validate the nature of the optimized stationary
points. The Stuttgart/Dresden effective core potential was used
The results obtained have shown that 1a
active than 1a , outperforming the mononuclear precursors 1b and
c which are known to generate the most active catalysts for CO–
5
is significantly more
6
1
20d
for metals. The basis set used for the remaining atomic species
3
alkene copolymerization and terpolymerization reactions. The
different catalytic activity of 1a and 1a , along with the formation
20e
was the 6-31G(d, p).
5
6
of polyketones with comparable average molecular weight, may
be rationalized by the different overall conformation of the
o-MeO-dppcb ligand in these complexes, which would influence
the propagation step of the copolymerization. Finally, it is worth
Preparations
Synthesis of o-MeO-trans-dppen. A solution of n-BuLi
(56.0 ml, 140.000 mmol) was added drop wise to a clear
THF solution (1 l) of bis(2-methoxyphenyl)phosphane (24.6 g,
7
mentioning that while 1a
5
and 1a
6
favour, more than 1b and
1
c, the head to tail regioselectivity of propene insertion into the
99.959 mmol) at room temperature, during which time interval
the reaction solution turned orange followed by the precipitation
of the yellow Li salt of the phosphane. The obtained suspension
growing polymer chain, they insert less propene in the growing
terpolymer chain, mainly due to the higher steric demand of
propene compared to ethene.
◦
was allowed to stir for 1 h at 42 C. Then 1,2-trans-dichlorethylene
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(
3.87 ml, 50.000 mmol) was slowly added at the latter temperature.
after an additional reaction time of 24 h maintaining the same
Once the addition was complete an orange solution was obtained
which was heated at 62 C for 1 h to complete the reaction. Then
the reaction solution was cooled to room temperature, quenched
with water (3.5 ml) and evaporated to dryness. The slightly yellow
reaction temperature. Then the white CH
1a was removed by filtration and washed with CH
10 mL). Yield (1a ): 81% (76.4 mg, 0.055 mmol). C60
(1387.64): calc. C 51.93, H 4.32; found C 51.85, H 4.45%. CP-MAS
2
Cl
2
-insoluble product
Cl (2 ¥
Pd
◦
5
2
2
5
H
60Cl
4
O
8
P
4
2
3
1
residue was subjected to an extraction with CH
2
Cl
2
–H
2
O. The
P NMR (161.98 MHz, ppm): d 44.60.
The combined CH Cl phases (i.e. mother liquor and washing
phase) were concentrated to dryness and a P{ H} NMR
spectrum thereof acquired in CD Cl revealed 1a as the only
phosphorus containing compound. Yield (1a ): 19% (17.9 mg,
vide infra.
organic phase was concentrated to dryness and the residue was
washed with ethanol (150.0 ml), followed by its filtration with
a DuraporeꢀR membrane filter. The crude product was then re-
2
2
3
1
1
2
2
6
crystallized from CH
2
Cl
2
–MeOH (v/v 1.6 : 1), obtaining a white
6
product which was separated by filtration and dried under vacuum.
Yield: 13.9% (3.59 g, 6.954 mmol). C30 (516.23): calc. C,
9.76; H, 5.85; found: C, 69.63; H, 5.93%. H NMR (CD Cl
), 6.40 (t, JPH = 36 Hz,
H, CH=CH), 6.88 (br s, 8H, Ar-H), 7.00 (br s, 4H, Ar-H), 7.32 (t,
0.0129 mmol). For further characterization of 1a
6
H
30
O
4
P
2
4
1
Alternative synthesis of 1a
6
.
[PdCl
2
(h -COD)] (55.4 mg,
6
3
2
2
,
2
0.194 mmol) was added in one portion to a deaerated suspension
00.13 MHz, ppm): d 3.76 (s, 12H, OCH
3
of compound 4a (144.9 mg, 0.097 mmol) in CH Cl (45 mL) at
6
2
2
2
3
13
1
room temperature. The colour of the reaction mixture changed
immediately to yellow. After an additional reaction time of 20 h,
J
PH = 12 Hz, 4H, o-Ar-H). C{ H} NMR (CD
), 110.50 (s, Ar-C), 121.16 (s, Ar-C), 124.66
d, JPC = 13 Hz, Ar-C), 130.52 (s, Ar-C), 133.83 (s, Ar-C), 139.20
2
Cl
2
, 75.48 MHz,
ppm): d 55.78 (s, OCH
(
3
1
the suspension was filtered and the residue washed with CH
(2 ¥ 10 mL). The combined CH Cl solutions were concentrated
to dryness to give 1a as a light green product which was
suspended in n-hexane (10 mL), removed by filtration and then
dried under vacuum. Yield (1a ): 74% (99.9 mg, 0.072 mmol).
Pd (1387.64): calc. C 51.93, H 4.32; found C 51.80,
H 4.47%. H NMR (CD Cl , 300.13 MHz, ppm): d 2.84 (m, 12H,
OCH ), 3.35 (br s, 12H, OCH ), 3.94 (br s, 4H, CH), 6.23–7.54
m, 30H, Ar-H), 9.06 (br s, 2H, o-Ar-H). P{ H} NMR (CD
2
Cl
2
1
2
2
2
(
t, JPC = 36 Hz, CH=CH), 161.60 (t, JPC = 16 Hz, C-OCH
3
).
3
1
1
6
P{ H} NMR (CD
2
Cl
2
, 121.50 MHz, ppm): d -29.20 (s).
4
Synthesis of o-MeO-dppcb. [PtCl
2
(h -COD)] (3.74 g,
6
9
.998 mmol) was added to a deaerated solution of o-MeO-
C
60
H
60Cl
4
O
8
P
4
2
trans-dppen (5.16 g, 9.995 mmol) in CH
2
2
Cl (200 mL) at room
1
2
2
temperature. The reaction mixture was allowed to stir for 4 h at
room temperature. The white solid that was formed during the
course of the reaction was separated by filtration and washed with
3
3
31
1
(
2
Cl
2
,
1
1
1
21.50 MHz, ppm): d 17.80 (br s), 36.16 (br s). MS (ESI+) m/z:
352.8 (M - Cl + H). CP-MAS P NMR (161.98 MHz, ppm): d
7.94 (s), 38.00 (s).
CH
2
Cl
2
(3 ¥ 50 mL). After the latter solid had been suspended
+
31
in deareated DMF (300 mL) and transferred to a Schlenk tube,
the suspension was irradiated for 21 days. Then the solid which
The CH
2
Cl
2
insoluble product was dried under vacuum and
had formed was separated by filtration, washed with CH
0 mL) and re-suspended in deareated DMF (200 mL). To this
suspension was added NaCN (3.67 g, 75.00 mol) dissolved in H
10 mL), followed by heating the reaction mixture under nitrogen
2
2
Cl (3 ¥
then subjected to elemental analysis and a XRPD measurement,
5
which confirmed the occurrence of 1a
Yield (1a ): 26% (35.0 mg, 0.025 mmol).
5
as the only compound.
2
O
5
(
◦
1
2
3
4
4
[
Pt
2
Cl
4
(l-(jP ,jP :jP ,jP -o-MeO-dppcb))] (2a
5
). [PtCl
2
(h -
and stirring at 115 C for 10 h. Afterwards the solvent mixture
i.e. H O and DMF) was removed completely by means of a
vacuum pump and the residue was washed with H O (130 mL).
The obtained crude product was dissolved in deareated CH Cl
35 mL) and filtered. The clear CH Cl solution was concentrated
COD)] (36.2 mg, 0.096 mmol) was added to a deaerated CH
2
Cl
2
(
2
solution (10 mL) of o-MeO-dppcb (50.0 mg, 0.048 mmol) at
room temperature, causing precipitation of the product as a white
powder. The suspension was allowed to stir for 1 h at room
temperature. The white solid was then removed by filtration,
2
2
2
(
2
2
to a volume of 20 mL and on addition of diethyl ether (150 mL)
the product precipitated as a white micro-crystalline powder, that
was separated by filtration, washed with diethyl ether and dried
washed with CH
The combined organic CH
dryness, yielding no residue, thus indicating that 2a
only compound formed in the course of the reaction. Yield: 98%
73.6 mg, 0.047 mmol). C60 Pt (1565.00): calc. C 46.05,
2
Cl
2
(2 ¥ 5 mL) and dried under vacuum.
Cl phases were concentrated to
was the
2
2
under vacuum. Yield: 76.4% (3.94 g, 3.818 mmol). C60
1033.01): calc. C, 69.76; H, 5.85; found: C, 69.61; H, 5.95%. H
NMR (CD Cl , 300.13 MHz, ppm): d 3.57 (s, 24H, OCH ), 3.43
m, 4H, PCH), 6.57 (m, 8H, Ar-H), 6.64 (m, 8H, Ar-H), 6.99
H
60
O
8
1
P
4
5
(
(
H
60Cl
4
O
8
P
4
2
2
2
3
3
1
H 3.83; found C 45.93, H 3.97%. CP-MAS P NMR (161.98 MHz,
ppm): d 20.29 ( J(PtP) 3717 Hz).
(
(
7
1
1
3
1
m, 8H, Ar-H), 7.08 (m, 8H, Ar-H). C{ H} NMR (CD
2
Cl ,
2
5.48 MHz, ppm): d 38.50 (br s, PCH), 55.63 (s, OCH ), 110.21
3
1
2
3
4
[
H
Ni
2
Cl
4
(l-(jP :jP :jP :jP -o-MeO-dppcb))]
(3a
6
). NiCl
2
·
1
(
(
s, Ar-C), 120.53 (s, Ar-C), 125.76 (d, JPC = 20 Hz, Ar-C), 129.31
6
2
O (57.0 mg, 0.240 mmol), dissolved in a deaerated (5 : 1,
2
s, Ar-C), 134.77 (s, Ar-C), 161.54 (d, JPC = 18 Hz, COCH
3
).
v/v) solvent mixture of ethanol–water (50 mL), was added to
a deaerated solution of o-MeO-dppcb (124.0 mg, 0.120 mmol)
3
1
1
31
1
P{ H} NMR (CD
2
Cl
2
, 121.50 MHz, ppm): d -25.8 (s). P{ H}
◦
NMR (CD
2
Cl
2
, 121.50 MHz, -93 C, ppm): d -20.4 (br s), -37.2
dissolved in CH
2
2
Cl (5 mL). The obtained suspension (i.e.
(
br s).
Reaction of o-MeO-dppcb with [PdCl
the linkage isomers 1a and 1a [PdCl
.136 mmol) dissolved in deaerated CH Cl
o-MeO-dppcb precipitated out of the solvent mixture due to
its low solubility in the latter reaction medium) was allowed
to stir for 4 h, followed by the concentration of the obtained
clear dark-red solution to dryness by means of a vacuum pump.
4
2
(g -COD)]: Synthesis of
4
5
6
.
2
(h -COD)] (38.7 mg,
(30 mL) was added to
0
2
2
o-MeO-dppcb (70.0 mg, 0.068 mmol) and the obtained solution
was allowed to stir for 30 min at room temperature, at the end of
which a white product precipitated. The reaction was completed
The red compound was recrystallized from CH
under vacuum. The NMR spectroscopic study revealed 3a
the only phosphorus containing compound obtained during
2
Cl
2
and dried
as
6
1
866 | Dalton Trans., 2009, 1859–1869
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the course of the reaction. Yield 93% (144.2 mg, 0.112 mmol).
Ni (1292.22): calc. C 55.77, H 4.64; found C 55.83,
H 4.75%. H NMR (CD Cl , 300.13 MHz, ppm): d 1.14 (s, 3H,
OCH ), 1.53 (s, 3H, OCH ), 2.78 (s, 6H, OCH ), 3.02 (br s, 4H,
CH), 3.41 (s, 6H, OCH ), 4.26 (s, 6H, OCH ), 6.19–7.40 (m, 30H,
75.48 MHz, ppm): d 11.18 (s, CO
(s, CO CH ), 21.23 (s, CO CH ), 32.68 (s, CH), 34.93 (s, CH),
37.86 (s, CH), 39.74 (s, CH), 55.48 (s, OCH
2
CH
3
), 14.24 (s, CO
2
CH
3
), 20.82
C
60
H
60Cl
4
2
O
8
P
4
2
3
2
3
1
2
2
3
), 56.53 (s, OCH
), 169.44 (s, CO CH
3
),
),
3
3
3
111.20–162.25 (Ar-C), 167.51 (s, CO
2
CH
3
2
3
3
1
1
3
3
175.94 (s, CO
2
CH
3
). P{ H} NMR (CD
2
Cl
2
+
, 121.50 MHz, ppm):
3
1
1
Ar-H), 9.60 (br s, 1H, o-Ar-H), 10.48 (br s, 1H, o-Ar-H). P{ H}
d 29.76 (s). MS (ESI+) m/z: 1422.90 (M - OAc). IR (KBr,
2
-1
NMR (CD
2
2
Cl
2
, 121.50 MHz, ppm): d 7.37 (d, J(PP) 94.0 Hz),
n(COO)/cm ) 1573(m).
2
+
5.55 (d, J(PP) 94.0 Hz). MS (ESI+) m/z: 1255.0 (M - HCl -
Cl).
Catalytic co-and terpolymerization reactions
1
2
3
4
[
Cr
2
Cl
(THF)
6
(THF)
(58.0 mg, 0.154 mmol) was added to a deaerated
Cl
30 mL) and allowed to stir for 10 h at room temperature
2
(l-(jP :jP :jP :jP -o-MeO-dppcb))]
(4a
6
).
CO–ethene copolymerization reactions in water–AcOH with 1a
5
,
CrCl
3
3
1a
6
, 1b and 1c as catalyst precursors. In a typical experiment, a
solution of o-MeO-dppcb (80.0 mg, 0.077 mmol) in CH
2
2
deaerated solvent mixture of distilled water and AcOH (100 mL)
was introduced by suction into an autoclave (320 mL), previously
evacuated using a vacuum pump, containing the catalyst precursor
(
giving a pink solution. Afterwards, the solvent was removed by
vacuum, giving a pink product, which was used without further
(0.0024 mmol). The autoclave was charged with a 1 : 1 CO–
purification. NMR spectroscopic data of a CD
2
2
Cl solution of
ethene mixture to 21 bar at room temperature and then heated to
the isolated product are in accordance with the formation of
◦
8
5 C, where the gas pressure was adjusted to 40 bar. The reaction
4
C
a
6
as the only product. Yield: 85% (97.8 mg, 0.065 mmol).
Cr (1493.95): calc. C 54.67, H 5.08; found 54.53,
Cl , 300.13 MHz, ppm): d 1.84 (br s, 8H,
THF), 2.86 (br s, 8H, THF), 3.62 (br m, 24H, OCH ), 4.10 (br m,
H, CH), 6.22–7.74 (br m, 32H, Ar-H). P{ H} NMR (CH Cl
21.50 MHz, ppm): d -12.13 (s). MS (ESI+) m/z: 1525.2 (M +
was conducted under stirring (1200 rpm) at constant pressure,
feeding the autoclave with a 1 : 1 CO–ethene gas-mixture from a
gas reservoir. After the desired reaction time, the autoclave was
cooled to room temperature by means of an ice–water bath and
the unreacted gases were released. The insoluble copolymer was
68
H
76Cl
6
2
O
10
P
4
1
H 5.33%. H NMR (CD
2
2
3
3
1
1
4
1
2
2
,
+
◦
filtered off, washed with water, and dried under vacuum at 60 C
MeOH - H).
to constant weight.
1
2
3
4
[
Pd (OAc)
2
4
(l-(jP ,jP :jP ,jP -o-MeO-dppcb))] (5a ). Silver
5
CO–propene copolymerization in water–AcOH with 1a
5
, 1a , 1b
6
acetate (37.0 mg, 0.220 mmol)was addedto adeaeratedsuspension
of 1a (76.9 mg, 0.055 mmol) in acetonitrile (30 mL) at room
and 1c as catalyst precursors. In a typical experiment, a deaerated
mixture of distilled water and AcOH (100 mL) was introduced by
suction into an autoclave (320 mL), previously evacuated using
a vacuum pump, containing the catalyst precursor (0.0048 mmol
5
temperature. The reaction mixture was stirred for 14 h at room
temperature. Afterwards the suspension was filtered and the
residue washed with acetonitrile (2 ¥ 10 mL), followed by the
evaporation of the solvent to dryness by means of a vacuum pump,
obtaining the product as a yellow powder, that was recrystallized
◦
of palladium). The autoclave was cooled to 0 C, followed by
◦
charging it with propene (33 g) and warming it to 20 C. At this
latter temperature the autoclave was charged with CO (7 bar),
from CH
2
Cl
1% (41.6 mg, 0.028 mmol) C68
5.11, H 4.85; found C 55.02, H 4.95%. H NMR (CD
00.13 MHz, ppm): d 1.10 (br s, 12H, CO CH ), 2.79 (s, 12H,
), 4.17 (d, J(HH) 4.0 Hz, 2H, CH),
.19 (d, J(HH) 4.0 Hz, 2H, CH), 6.69–7.67 (m, 30H, Ar-H),
2
–diethyl ether and then dried under vacuum. Yield:
◦
followed by heating it to 85 C. Stirring (1200 rpm) was started as
5
5
3
H
72
O
16
P
4
Pd (1482.02): calc. C
2
1
soon as the latter temperature had been reached and the reaction
was conducted at a constant pressure of CO (56 bar), feeding
the autoclave with CO, derived from a gas reservoir. After a
reaction time of 2 h, the autoclave was cooled to room temperature
by means of an ice–water bath and the unreacted gases were
released. The viscous MeOH solution of the oligomeric material
2
Cl ,
2
2
3
3
OCH
3
), 3.53 (s, 12H, OCH
3
3
4
8
1
3
1
.81 (br s, 2H, Ar-H). C{ H} NMR (CD
CH ), 14.20 (s, CO CH ), 32.25 (s, CH), 55.85
), 56.19 (s, OCH ), 111.98–135.12 (Ar-C), 161.62 (s,
2
Cl
2
, 75.48 MHz, ppm):
d 11.07 (s, CO
s, OCH
CO CH
). P{ H} NMR (CD
2
3
2
3
◦
was evaporated at 50 C by means of a vacuum pump to reach
(
3
3
3
1
1
constant weight of the cooligomers.
2
3
2
+
Cl
2
, 121.50 MHz, ppm): d 35.99
-1
(
s). MS (ESI+) m/z: 1423.2 (M - OAc). IR (KBr, n(COO)/cm )
CO–ethene–propene terpolymerization in water–AcOH with 1a
5
,
1
584(m).
1
a
6
, 1b and 1c as catalyst precursors. In a typical experiment, a
1
2
3
4
[
Pd (OAc)
2
4
(l-(jP :jP :jP :jP -o-MeO-dppcb))] (5a
6
). Silver
deaerated solvent mixture of distilled water and AcOH (100 mL)
was introduced by suction into an autoclave (320 mL), previously
evacuated using a vacuum pump, containing the catalyst precursor
acetate (64.9 mg, 0.388 mmol)was addedto adeaeratedsuspension
of 1a (133.9 mg, 0.097 mmol) in THF (15 mL) at room
6
◦
temperature. The suspension was allowed to stir for 14 h at the
same temperature, followed by its filtration to remove AgCl. The
obtained solution was concentrated to dryness under vacuum and
(0.0048 mmol of palladium). The autoclave was cooled to 0 C,
followed by charging it with propene (20 g). Then the autoclave
◦
was warmed to 20 C and successively charged with ethene (7 bar)
◦
the greenish-yellow product was recrystallized from CH
hexane, filtered off and dried under vacuum. Yield: 25% (35.6 mg,
.024 mmol). C68 Pd (1482.02): calc. C 55.11, H 4.85;
found C 54.97, H 5.05%. H NMR (CD Cl , 300.13 MHz, ppm):
d 1.89 (s, 6H, CO CH ), 2.19 (s, 6H, CO CH ), 3.08 (br s, 12H,
OCH ), 3.28 (br. s, 12H, OCH ), 4.09 (m, 4H, CH), 6.90–7.67 (m,
0H, Ar-H), 10.18 (br s, 2H, o-Ar-H). C{ H} NMR (CD
2
Cl
2
–n-
and CO (7 bar), followed by heating to 85 C. At this latter
temperature the total gas pressure was adjusted with CO to 70 bar
and the reaction was conducted under stirring (1200 rpm) and
constant CO pressure, feeding the autoclave with CO derived from
a gas reservoir. After the desired reaction time, the autoclave was
cooled to room temperature by means of an ice–water bath and the
unreacted gases were released. The terpolymers were filtered off,
0
H
72
O
16
P
4
1
2
2
2
2
3
2
3
3
3
1
3
1
3
2
2
Cl ,
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Dalton Trans., 2009, 1859–1869 | 1867

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Table 4 Crystallographic data for 1a
6
·2.8DCE and 2a
5
1
a
6
·2.8DCE
2a
5
Empirical formula
Formula weight
T/K
C
65.6
H
71.2Cl9.60
O
8
P
4
Pd
2
60 4 8 4 2
C H60Cl O P Pt
1564.92
243(2)
1657.37
243(2)
0.71073
Monoclinic, P2
12.3220(4)
12.3410(3)
46.7560(10)
90.568(1)
7109.6(3)
4
l/A˚
0.71073
Crystal system, space group
1
/n
Tetragonal, P4
15.2961(2)
15.2961(2)
12.4875(3)
90
2 1
2 2
a/A˚
b/A˚
c/A˚
◦
b/
V/A˚
3
2921.71(11)
2
1.779
5.130
1536
0.10 ¥ 0.09 ¥ 0.04
MULTI-SCAN
26282 (0.0313)
0.99–27.59
Full-matrix least-squares on F
3135/0/180
Z
-3
D
c
/Mg m
m/mm
F(000)
1.548
1.008
3347
-1
Crystal size/mm
Absorption correction
Reflections collected (Rint
H-range for data collection/
Refinement method
Data/restraints/parameter
Goodness-of-fit on F
Final R indices
R indices (all data)
Largest diff. peak, hole/eA˚
0.10 ¥ 0.05 ¥ 0.03
MULTI-SCAN
23218 (0.0290)
0.99–25.40
Full-matrix least-squares on F
12414/2/834
)
◦
2
2
2
0.976
0.995
[I>3s(I)] R1 = 0.0575, wR2 = 0.1317
R1 = 0.0944, wR2 = 0.2078
0.640, -0.510
[I>2s(I)] R1 = 0.0263, wR2 = 0.0575
R1 = 0.0340, wR2 = 0.0665
0.570, -0.330
3
washed with water and then dried at room temperature by means
of a vacuum pump to reach a constant weight of the terpolymers.
a Nonius Kappa CCD diffractometer using j–w-scans. Cell
refinement, data reduction and empirical absorption correction
21a
were carried out with the Denzo and Scalepack programs.
Characterization of the CO–ethene, CO–propene copolymers
All structure determination calculations were performed with
SHELXTL NT V6.1 including SHELXS-97 and SHELXL-
and the CO–ethene–propene terpolymers. The alternating CO–
1
13
1
ethene copolymers have been analysed by H and C{ H} NMR
21b
2
9
7. Final refinements on F were carried out with anisotropic
spectroscopy, carried out in a 1 : 1 (v/v) solvent mixture of
thermal parameters for all non-hydrogen atoms. For 2a , the
5
1
13
1
1
,1,1,3,3,3-hexafluoroisopropanol-d
2
and C
6
D
6
. H and C{ H}
proton attached to the cyclobutane carbon ring was located and
isotropically refined with fixed U. All other hydrogen atoms were
included in the refinement using a riding model with isotropic U
values depending on the Ueq of the adjacent carbon atoms. Two
out of three DCE solvent molecules of the asymmetric unit of
3f ,5
NMR signals were assigned based on literature reports, and the
molecular weight determination was based on integration of the
corresponding H signals.
The alternating CO–propene cooligomers and CO–ethene–
1
3f
1
13
1
propene terpolymers have been analysed by H and C{ H}
structure 1a
6
·2.8DCE are disordered. CCDC reference number
NMR spectroscopy carried out in CDCl as well as by IR
3
for 1a
6
·2.8DCE: 694967 and 2a
5
: 694966.
spectroscopy. The ratio of the regioisomeric propene incorpo-
ration was determined upon integration of the corresponding
1
3
1
C{ H}NMR signals (carbonyl region), deriving from h-h, h-t
Acknowledgements
17
and t-t regioisomers, while the amount of propene incorpo-
rated in the terpolymers was determined by integration of the
corresponding H NMR signals. The most significant IR values
The authors thank Dr P. Barbaro for the assistance in the
3
1
1
acquisition of CP-MAS P NMR spectra. Thanks are also due
to the European Commission for financing the project IDECAT,
NoE contract no. NMP3-CT-2005-011730. Furthermore A. I.
kindly acknowledges CINECA for the computing time provided
in agreement with CNR. This research was financially supported
for the CO–propene cooligomers are: 2966 (w), 2934 (w), 2901
(
(
w), 2879 (w), 1701 (s), 1459 (m), 1388 (m), 1376 (m) and 1023
m) cm . The most significant IR values for the CO–ethene–
-
1
propene terpolymers are: 2967 (w), 2935 (w), 2904 (w), 1701 (s),
by the Fonds zur F
o¨ rderung der wissenschaftlichen Forschung,
-
1
1
458 (w), 1394 (m), 1379 (m), 1360 (m) and 1085 (m) cm . The
Vienna, Austria, the Tiroler Wissenschaftsfonds, Innsbruck, Aus-
tria, and the University of Innsbruck via the action D. Swarovski
& Co.
average molecular weight of the CO–propene copolymers and of
the CO–ethene–propene terpolymers have been determined by
1
integration of the corresponding H NMR signals.
X-Ray crystallographic data collection and refinement of the
structures
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868 | Dalton Trans., 2009, 1859–1869
This journal is © The Royal Society of Chemistry 2009

View Article Online
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