Metallated Container Molecules: A Capsular Nickel Catalyst for Enhanced Butadiene Polymerisation

Article abstract of DOI:10.1002/ejic.201901074

A unique, covalently constructed capsular catalyst obtained by reaction of [Ni(η⁵-C₅H₅)(1,5-cyclooctadiene)] BF₄ with the double-calixarene-derived diphosphine 1,3-bis(5-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]aren-17-yl)benzene (1) has been shown to polymerise butadiene at a rate considerably superior to that of previously known catalysts. The reported results indicate that the container structure of the covalent complex is retained during catalysis.

Full text of DOI:10.1002/ejic.201901074

DOI: 10.1002/ejic.201901074
Full Paper
Molecular Containers
Metallated Container Molecules: A Capsular Nickel Catalyst for
Enhanced Butadiene Polymerisation
Fethi Elaieb,[a] Soheila Sameni,[a] Mouhamad Awada,[a] Catherine Jeunesse,[a]
Dominique Matt,*[a] Loic Toupet,[b] Jack Harrowfield,[c] Daisuke Takeuchi,[d] and
Shigenaga Takano[e]
Abstract: A unique, covalently constructed capsular catalyst benzene (1) has been shown to polymerise butadiene at a rate
obtained by reaction of [Ni(η5-C5H5)(1,5-cyclooctadiene)] BF4 considerably superior to that of previously known catalysts. The
with the double-calixarene-derived diphosphine 1,3-bis(5-di- reported results indicate that the container structure of the
phenylphosphino-25,26,27,28-tetrapropoxycalix[4]aren-17-yl)- covalent complex is retained during catalysis.
Introduction
capsular systems immobilising catalytic nickel and palladium
centres inside their cavity. The targeted metallo-capsules were
obtained from double calixarene 1 and were designed so as to
possess portals sufficiently large to formally allow entry of small
substrates and subsequent escape of products formed inside
the cavity. A concrete example of the catalytic potential of such
complexes is provided by the use of a nickel capsule in buta-
diene polymerisation.
The design and synthesis of new molecular catalysts constitutes
a continuing, central theme of chemical research.[1] The con-
duct of metal-catalysed reactions in a confined environment, in
particular, is an important example of a relatively new concept
in homogeneous catalysis. Impressive contributions to this field
have already been made by Nolte,[2] Rebek,[3] Raymond,[4]
Fujita,[5] van Leeuwen,[6] Reek,[7] Tieffenbacher[8] and others,[9]
who have highlighted the properties of deeply embedded cata-
lytic systems, notably in terms of selectivity and efficiency, as
well as their possible use in aqueous media.[10] To date research
in this field has been dominated by a supramolecular approach
relying on the utilisation of functional synthons, some of them
metalated, which readily self-assemble and incidentally create a
microenvironment able to incorporate an active site.[11] A major
drawback of these systems lies in their rather labile nature, ren-
dering them unfit for use in industrial applications. Confined
covalent catalysts offering the advantage of structural robust-
ness, a key property in catalysis, are relatively rare. This arises
in part from the difficulty in synthesising container molecules
with convergent donor atoms able to position a metal inside
the cavity.[12] Here, we describe the development of covalent
Results and Discussion
Our strategy for creating metallo-capsules relied on the use of
the long diphosphine 1, a potential chelator incorporating two
conical calix[4]arene subunits linked by a phenylene spacer. We
anticipated that upon chelation of a metal centre with two free,
cis-positioned binding sites, the diphosphine would not only
adopt a rigid, capsular form, but also confine the coordinated
metal centre inside the resulting container. Thus, capsular com-
plex 2 was obtained quantitatively by reaction of [Ni(η5-C5H5)-
(cod)]BF4 (cod = 1,5-cyclooctadiene) with 1 (Scheme 1, top).
The use of a cationic nickel reactant allowed for a fast binding
process, thereby favouring chelate formation over that of oligo-
meric complexes, which often form with long diphosphines.[13]
Complex formation was inferred from the mass spectrum,
which shows a strong peak at m/z 1750.75 having exactly the
isotopic profile expected for [M – BF4]+. Complex 2 has Cs sym-
metry, consistent with chelation of the metal, as deduced from
analysis of both the 31P NMR and 1H NMR spectra, which display
respectively a single peak at 35.3 ppm and four distinct AB
patterns for the bridging methylene groups (see SI). The C5H5
ring protons of 2 appear at relatively high field (δ = 2.76 ppm)
in the 1H NMR spectrum as a result of aromatic ring-current
effects of the capsule. In contrast, the spectrum of the related
bis-phosphine complex 4 (Figure 1) shows a much lower-field
Cp signal (δ = 4.48 ppm).
[a] Laboratoire de Chimie Inorganique Moléculaire et Catalyse, UMR 7177
CNRS, Université de Strasbourg,
4, rue Blaise Pascal, 67008 Strasbourg Cedex, France
E-mail: dmatt@unistra.fr
http://lcimc.u-strasbg.fr
[b] Université de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
[c] ISIS, UMR 7606 CNRS, Université de Strasbourg,
8, rue Gaspard Monge, 67083 Strasbourg Cedex, France
[d] Department of Frontier Materials Chemistry, Graduate School of Science
and Technology, Hirosaki University,
3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
[e] Laboratory for Chemistry and Life Science, Tokyo Institute of Technology,
4259 Nagatsuda, Yokohama 226-8503, Japan
The ultimate proof of the strong metal confinement in 2
came from a single-crystal X-ray diffraction study (Figure 2). In
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201901074.
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Scheme 1. Formation of capsular complexes with embedded metal centres.
Figure 2. Molecular structure of the cationic complex 2 showing the encapsu-
lated Ni(η5-C5H5) moiety; left: view perpendicular to the NiP2 plane; right:
view along the axis of one of the calixarene ends. Only one of the two iso-
mers (A) present in the unit cell is shown. The uncoordinated [BF4]– anion
has been omitted for clarity.
Figure 1. Formula of complex 4 containing two upper-rim phosphinated
calix[4]arenes (5).
the unit cell, two inequivalent but only slightly different mole-
cules (A and B) are present, both having their cyclopentadienyl
unit embedded in the capsule formed by complexation. Each
molecule has its Ni–(η5-C5H5) axis distinctly inclined towards
one of the calixarene units, this enabling weak π–π interactions
to occur between the C5H5 ring and two (distal) phenol rings
of the calixarene unit (shortest inter-ring C···C separations:
3.28 Å and 3.17 Å in isomer A; 3.3 Å and 3.5 Å in isomer B) as
well as with the central phenylene ring. As the two calixarene
units are equivalent on the NMR time scale, the Ni–C5H5 axis
of 2 must alternate in orientation towards the two calixarene
moieties. However, this motion could not be frozen out (varia-
ble temperature study carried out in CD2Cl2 in the range –60 °C
Figure 3. Molecular structure of the cationic palladium complex 3 ([BF4]– an-
ion not shown).
Significantly, the allyl group displays a specific orientation
– 25 °C, see SI).[14] The ligand bite angle of 2 (105.0° in A; 104.4° within its host, its central carbon atom pointing towards the
in B) is just a little larger than that observed for the PMP angle most open part of the capsule′s entry, thereby obviously mini-
in [Ni(η5-C5H5)(PPh3)2]+ (102.9°; see DOSNAB[15] in CCDC).[16] For mising its steric interactions with the phenylene linker. The C···C
comparison we also determined the solid-state structure of the separations between the terminal allylic carbon atoms and the
related capsular complex [Pd(η3-C3H5)(1)]BF4 (3) (Figure 3), closest carbon atoms of the phenylene moiety are 3.41 and
which was formed quantitatively by reacting 1 with [Pd- 3.38 Å, respectively. Overall, the reactions leading to 2 and 3
(η3-C3H5)(THF)2]BF4.[17] While for 3 the ligand bite angle value constitute an illustration of the remarkable structuring proper-
(104.6°) is very close to that of 2, the organometallic part of the ties of diphosphine 1, which enables creation of a capsule upon
complex, i.e. the Pd–allyl moiety, is nearly symmetrically located chelation of a metal centre and, in the case of 3, controlled
within the capsule.
orientation of the metal-bound allylic ligand.
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Scheme 2. Palladium-catalysed alkylation of 3-phenylallyl acetate.
A question arises concerning the ability to achieve a catalytic to retain a capsular structure during catalysis, both P atoms
reaction at such highly confined metal centres. Thus, we first need to remain bonded to the nickel atom. Interestingly, on the
assessed the palladium complex 3 in the alkylation of 3-phenyl- basis of a theoretical study published in 1998,[19] the mecha-
allyl acetate 6 with dimethyl malonate, a reaction for which two nism of butadiene polymerisation with [Ni(η3-allyl)(PH3)2]+ (see
products were expected, 7a and 7b (Scheme 2). In CH2Cl2 at SI) has been proposed to pass through η3-allylic nickel interme-
room temperature, metallocapsule 3 showed activities similar diates containing a single phosphine ligand, the other phos-
to those obtained with classical Pd/phosphine systems. Further- phine having undergone dissociation. These theoretical find-
more, the “linear” alkylation compound 7a (which in its coordi- ings are thus in contradiction with our deduction that both
nated form fits better inside the cavity than the corresponding P atoms of 2 remain coordinated during catalysis. What we now
branched isomer) was formed with 96 % selectivity, a value propose is that the particular steric crowding imposed by a
which corresponds to a slightly higher proportion than that capsular structure favours the formation of η1-allylic intermedi-
obtained with [Pd(η3-C3H5)(Ph2PCH2 CH2PPh2)](BF4) (91 %) un- ates that precede the insertion step {notably complexes of
der similar conditions. These findings suggest that the substrate the type [Ni(η1-CH2-CH=CH·P) (chelating-1)(butadiene)]BF4, in
used has good access to the embedded metal centre, although which ·P represents a polymeric fragment}. This then enhances
we have no formal proof that during catalysis the capsular the rate of butadiene insertion. It is noteworthy that the ability
shape is retained (vide infra).
of chelated metal units to form easily η1-allyl complexes was
[20]
recently demonstrated by Braunstein et al.
It should further
We then turned our attention to metallocapsule 2, which
was found suitable for polymerisation reactions. Thus, once acti-
vated with methylaluminoxane (MAO/Ni = 1000:1) complex 2
becomes an efficient butadiene polymerisation catalyst, leading
to a mixture of cis-1,4-, trans-1,4-, and 1,2-polybutadiene show-
ing a classical distribution (89.4:6.5:4.1) (Table 1). Remarkably,
when carrying out the polymerisation at room temperature,
and by applying a butadiene pressure of 1 atm (4 μmol Ni,
20 mL of toluene), the catalytic system displayed an activity
be mentioned that the capsule which embeds the metal centre
may itself behave as a butadiene receptor, thereby leading to
an increased local substrate concentration of butadiene, which
necessarily would impact on the reaction rate.
Conclusions
which was ca. 30–40 (!) times higher than that of the non- We have shown that diphosphine 1 readily forms metallo-cap-
confined complexes [Ni(η5-C5H5)(dppe)](BF4) and [Ni(η5-C5H5)- sules when opposed to metal ions with two free, cis-configured
(PPh3)2](BF4) (with the latter two complexes leading to compa- binding sites. The superior activity of its capsular Ni(II)-π-allyl
rable selectivities, see Table 1). The reason for the high activity complex 2 as a catalyst for butadiene polymerisation compared
of 2 compared with that of its bis-PPh3 analogue is a matter of to non-capsular but otherwise similar complexes implies that
speculation. It is tempting to consider that the activity of 2 is the capsular form and thus the binding of both phosphine cen-
related to its container structure. This notion is reinforced by tres in maintained during catalysis. It is particularly significant
the observation that the calixarene-based complex 4, which that encapsulation of the catalytic centre apparently does not
contains two monodentate P(III)-ligands, provides, like the sim- result in any inhibition of access and we suggest that any steric
ple complex of PPh3, a lower degree of activity[18] with respect restraints imposed by encapsulation may in fact accelerate reac-
to that of 2 (with unchanged selectivity, see Table 1). Of course, tion by favouring the involvement of η1-allylic intermediates.
Table 1. Butadiene polymerisation using [NiCp(phosphine)2]+/MAO catalysts.[a]
Entry
complex
Polymer
Yield [g]
Activity
[g/mol(Ni) h]
Mn
Mw/Mn
(monomodal)
1,4-cis
[%]
1,4-trans
[%]
1,2
[%]
1
2
3
4
[Ni(η5-C5H5)(1)]BF4 (2)
[Ni(η5-C5H5)(dppe)]BF4
[Ni(η5-C5H5)(PPh3)2]BF4
[Ni(η5-C5H5)(5)2]BF4 (4)
2.841
0.075
0.096
0.199
178000
4670
6010
37300
31800
33900
59200
2.21
1.63
1.77
1.66
89.4
89.1
88.0
88.5
6.5
6.5
7.0
6.3
4.1
4.4
5.0
5.2
12500
[a] Conditions: [Ni] (4 × 10–3 mmol), MAO (4 mmol), butadiene (1 atm), toluene (20 mL), 25 °C, 4 h. Complex 4 is shown in Figure 1.
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10.79, 10.72, 10.03 and 9.89 (4s, CH3). MS (ESI-TOF): m/z (%) 1750.79
(100) [M – BF4]+, expected isotopic profile. Elemental analysis:
Found: C, 75.32; H, 6.84. Calc. for C115H121BF4NiO8P2 (Mr = 1838.63)
C, 75.12; H, 6.63 %. Single crystals of the product were grown as
plates by slow diffusion of pentane into a dichloromethane solution
of the complex at room temperature.
Theoretical investigations may be helpful to confirm these hy-
potheses.
Experimental Section
P,P-(η5-Cyclopentadienyl)-bis-{5-(diphenylphosphino)-
25,26,27,28-tetra-propoxycalix[4]arene}nickel (II) Tetrafluoro-
borate (4): A solution of 5-diphenylphosphino-25,26,27,28-tetra-
propoxy-calix[4]arene (5) (0.152 g, 0.195 mmol) in CH2Cl2 (10 mL)
was added to a solution of [(η5-C5H5)Ni(cod)]BF4 (0.032 g,
0.098 mmol) in CH2Cl2 (10 mL). After stirring for 1 h, the solution
was concentrated to ca. 2 mL and hexane (10 mL) was added. An
olive green precipitate formed, which was separated by filtration
through silica, then dried under vacuum (0.167 g, yield 97 %). 1H
NMR (400 MHz, CDCl3): δ = 7.38–6.39 (36 H, PPh2 and p- and m-H
of OArcalix), 6.39 (m, 4H, m-H of OArcalix in distal position to phos-
phinated Ar), 5.98 (t, 2H, p-H of OArcalix in distal position to phos-
General Methods: All reactions were performed under nitrogen in
Schlenk tubes. Solvents were dried by conventional methods and
distilled immediately prior to use. CDCl3 was passed down a 5 cm-
thick alumina column and stored under nitrogen over molecular
1
sieves (4 Å). Routine H, 13C{1H} and 31P{1H} NMR spectra were re-
corded on FT Bruker AVANCE 300 and AVANCE 400 instruments.
1H NMR spectroscopic data were referenced to residual protiated
solvents [7.26 ppm for CDCl3, 7.16 ppm for C6D6 and 5.32 for
CD2Cl2], 13C chemical shifts are reported relative to deuterated sol-
vents [77.0 ppm for CDCl3, 128.06 ppm for C6D6 and for 54.00
CD2Cl2] and the 31P NMR data are given relative to external H3PO4.
Mass spectra were recorded either on a Maldi TOF spectrometer
(MALDI-TOF) using α-cyano-4-hydroxycinnamic acid as matrix, or on
a Bruker MicroTOF spectrometer (ESI-TOF) using CH2Cl2, MeCN or
MeOH as the solvent. Elemental analyses were performed by the
Service de Microanalyse, Institut de Chimie (UMR 7177 CNRS), Stras-
bourg. Melting points were determined with a Büchi 535 capillary
melting-point apparatus. Ligand 1,[17] palladium complex 3,[17] [(η5-
C5H5)Ni(cod)BF4],[21] [Ni(η5-C5H5)(dppe)]BF4,[22] [Ni(η5-C5H5)(PPh3)2]-
BF4,[23] were prepared according to previously reported procedures.
An optimised preparation of 1 is given as supplementary informa-
tion. The catalytic solutions of the allylic alkylations were analysed
by using a Varian 3900 gas chromatograph equipped with a WCOT
fused-silica column (25 m × 0.25 mm). GPC analyses were carried
out with a Waters apparatus. Size Exclusion Chromatography (SEC)
measurements were performed on a Shimadzu Prominence System
equipped with 5 serial mixed B PLgel columns. Detection was per-
formed by a differential refractometer (RID10A, Shimadzu), a UV/
Vis PDA detector (SPD-20A, Shimadzu), a multi-angl-light scattering
(MALS) detector (DAWN TREOS, Wyatt techn.) and a on-line visco-
simeter (Viscostar-II, Wyatt Techn.). The flow rate was 1 mL/min and
high purity THF was used as eluent. The columns were calibrated
with 16 narrow polystyrene standards (Polymer Lab).
3
phinated Ar, JH-H = 8Hz), 4.47 (s, 5H, Cp), 4.44 and 3.16 [AB spin
system, 8H, ArCH2Ar, 2J(AB) = 12 Hz], 4.43 and 3.07 [AB spin system,
2
8H, ArCH2Ar, J(AB) = 12 Hz], 3.94 and 3.73 (2m, 2x8 H, OCH2), 1.94
(2 m, 2 × 8 H, OCH2CH2CH3), 1.07 (t, 6H, CH3), 1.03 (t, 6H, CH3), 0.95
(t, 12H, CH3, 3J = 8 Hz). 31P NMR (162 MHz, CDCl3) δ = 34.4 (s, PPh2).
13C NMR (125.77 MHz, CDCl3) δ = 158.58, 156.90 and 155.85 (3s,
Cq-OCH2), 136.48–120.08 (PPh2 and arom. C's), 97.66 (s, Cp), 77.71
and 76.78 (2s, OCH2), 31.04 and 30.95 (2s, ArCH2Ar), 23.55, 23.48
and 23.14 (3s, CH2CH3), 10.70, 10.66 and 10.16 (3s, CH3). MS (HR-
MS): m/z (%) 1676.7745 (100) [M – BF4]+, expected isotopic profile.
Elemental analysis: calcd. for C109H119O8P2NiBF4 C 74.19, H 6.79
Found: C 73.87, H 6.94.
Single-Crystal X-ray Diffraction
Crystal Data for 2: Crystals suitable for X-ray diffraction were ob-
tained by slow diffusion of pentane into a CH2Cl2 solution of the
complex: C230H242B2F8Ni2O16P4·1.5C5H12, 2M = 3785.36, orthorhom-
bic, space group Pbca, a = 30.5294(7), b = 38.6460(10), c = 38.646(10)
Å, α = ꢀ = γ = 90.00°, V = 44909(2) Å3, Z = 8, μ = 0.260 mm–1
,
F(000) = 16088. Crystals of the compound were mounted on an
Oxford Diffraction CCD Sapphire 3 Xcalibur diffractometer. Data col-
lection with Mo-Kα radiation (λ = 0.71073 Å) was carried out at
100 K. 131039 reflections were collected (2.50 < θ < 23.0°), 28205
being found to be unique (merging R = 0.123). The structure was
solved with SHELXL-2016.[24] Final results: R1 = 0.098, wR2 = 0.312,
goodness of fit = 0.965, 2426 parameters, residual electron density:
min./max. = –0.533/1.752 e Å–3. The level A alerts in the checkcif
arise from disordered atoms in both the four O-alkyl substituents
and the solvent molecules. The main difficulty with this compound
was the very marked decrease of the intensities observed even at
100K with increasing theta values.
cis-P,P′-(η5-Cyclopentadienyl)-[1,3-bis(5-diphenylphosphino-
25,26,27,28-tetrapropoxy-calix[4]aren-17-yl)benzene]nickel (II)
Tetrafluoroborate (2): A solution of [(η5-C5H5)Ni(cod)]BF4 (0.030 g,
0.092 mmol) in CH2Cl2 (100 mL) and a solution of 1,3-bis(5-diphen-
ylphosphino-25,26,27,28-tetrapropoxy-calix[4]aren-17-yl)benzene
(0.150 g, 0.092 mmol) in CH2Cl2 (100 mL) were simultaneously
added under vigorous stirring over a period of 2 h to a 1000 mL
Schlenk flask containing 500 mL of CH2Cl2. The reaction mixture
was stirred at room temperature for 16 h. The solvent was evapo-
rated to dryness and the resulting olive green solid was washed
with Et2O, then dried under vacuum (0.152 g, 90 %). 1H NMR
Crystal Data for 3: Crystals suitable for X-ray diffraction were ob-
1
(600 MHz, 253K, CDCl3) (owing to a dynamic molecule, all H NMR tained by slow diffusion of pentane into a CH2Cl2 solution of the
signals are somewhat broad at 253K; see also SI): 7.41–6.58 (m, 42H,
PPh2, H of phenylene, para H of OArcalix, meta H of OArcalix), 6.10
(broad s, 2H, para H of OArcalix), 4.53 and 3.28 [AB spin system, 4H,
ArCH2Ar, 2J(AB) = 12 Hz], 4.55 and 3.34 [AB spin system, 8H,
complex: C452H484B4F16O32P8Pd4·CH2Cl2·3C5H12, M = 7750.32,
monoclinic, space group Pn, a = 16.9631(3), b = 35.9731(7), c =
37.8148(7) Å, ꢀ = 91.03°, V = 23071.4(7) Å3, Z = 2, μ = 0.257 mm–1
,
F(000) = 8176. Crystals of the compound were mounted on an Ox-
ford Diffraction CCD Sapphire 3 Xcalibur diffractometer. Data collec-
ArCH2Ar, 2J(AB) = 10.8 Hz], 4.36 and 2.96 [AB spin system, 4H,
2
ArCH2Ar, J(AB) = 12 Hz], 4.25, 4.06, 3.64 and 3.62 (4m, 16H, OCH2), tion with Mo-Kα radiation (λ = 0.71073 Å) was carried out at 110 K.
2.67 (s, 5H, Cp), 2.17, 2.07 and 1.88 (3m, 16H, CH2CH2CH3), 1.04 and
201478 reflections were collected (2.6 < θ < 27.0°), 92585 being
found to be unique (merging R = 0.105). The structure was solved
0.90 (2m, 24H, CH3). 31P{1H} NMR (162 MHz, CDCl3) δ = 35.21 (s,
PPh2). 13C{1H} NMR (150.90 MHz, CDCl3) δ = 157.64, 157.03, 156.92 with SHELXL-2016/4.[24] The elemental cell contains four distinct,
and 155.56 (4s, Cq-OCH2), 137.96- 120.67 (PPh2 and arom. C's), 96.78
but almost identical molecules. The main difficulty in solving this
(s, Cp), 78.15, 78.11, 76.93 and 76,25 (4s, OCH2), 32.07, 31.27, 30.80 structure came from the large thermal motion of some O-propyl
and 30.67 (4s, ArCH2Ar), 23.58, 23.54, 23.23 and 22.869 (4s, CH2CH3), groups and the [BF4]– anions. It was necessary to fix some atoms
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and to apply restraints in order to avoid instability during refine-
ments. The level A alerts in the checkcif are thus mainly due to the
thermal motion of the O-propyl groups and the [BF4]– anions, but
also to the disordered CH2Cl2 molecule. Note that this data collec-
tion was made at 110K. Another data collection was made at 100K:
at this temperature, we observed a phase transition [beta angle
decrease from 91.034(2) to 90.277(1)]. The corresponding space
group was again unambiguously Pn, but seemingly the transition
went to orthorhombic Pnn2. Final results: R1 = 0.067, wR2 = 0.191,
goodness of fit = 0.602, 4518 parameters, residual electron density:
min./max. = –0.821/1.140 e Å–3
.
CCDC 771989 (for 2), and 768418 (for 3) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre.
Allylic Alkylation Experiments: A CH2Cl2 solution (15 mL) of
[Pd(η3-C3H5)(1)]BF4 (0.019 g, 0.01 mmol), cinnamyl acetate (0.176 g,
1.00 mmol), dimethylmalonate (0.396 g, 3.00 mmol), N,O-bis(tri-
methylsilyl)acetamide (BSA) (0.610 g, 3.00 mmol) and a catalytic
amount of KOAc was stirred at room temperature for 2 h. The solu-
tion was then diluted with a saturated aqueous solution of NH4Cl
(10 mL) and CH2Cl2 (10 mL). To determine the conversion and the
product distribution by GC, decane (0.10 mL) was added to the
organic phase. GC analysis gave the following product distribution:
dimethyl [(2E)-3-phenylprop-2-en-1-yl]propanedioate: 96 %; di-
methyl (1-phenylprop-2-en-1-yl)malonate: 4 %.
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Butadiene Polymerisation: To a 25-mL Schlenk flask containing a
nickel complex (4 μmol) was added toluene (18 mL). After the mix-
ture was frozen with liquid nitrogen, the inner gas was evacuated
and the Schlenk flask was backfilled with butadiene by using a
balloon filled with butadiene gas. The mixture was warmed to room
temperature, and a solution of MAO (Al/Ni = 1000) in toluene solu-
tion (2 mL) was added to the mixture. After stirring the mixture at
room temperature (400 rpm) for 4 hours, the reaction was
quenched by adding MeOH (50 μL). The solution was then poured
into a HCl/MeOH solution (HCl/MeOH = 1:4 v/v, 150 mL). The result-
ing precipitate was collected by filtration and dried in vacuo over-
night. The polymer distribution was determined using 13C{1H}
NMR.[25] The molecular weights (Mn) and molecular weight distribu-
tions (Mw/Mn) of the polymer were measured by gel permeation
chromatography (GPC). The Mn and Mw/Mn values were deter-
mined using the polystyrene calibration.
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[14] Slight broadening of the 1H NMR signals (600 MHz, CD2Cl2) was ob-
served in the temperature range 0 °C to +40 °C. This may reflect small
conformational changes involving the phenylene spacer.
[15] T. Yamamoto, C. Shikada, S. Kaita, T. Olivier, Y. Maruyama and Y. Wakat-
suki, CCDC 699721: Experimental Crystal Structure Determination, 2009,
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Acknowledgments
[16] T. Yamamoto, C. Shikada, S. Kaita, T. Olivier, Y. Maruyama, Y. Wakatsuki,
J. Mol. Catal. A 2009, 300, 1–7.
We gratefully acknowledge financial support from the Univer-
sity of Strasbourg Institute for Advanced Study (to D. M.) and
from the Frontier Research in Chemistry Foundation, Strasbourg
(postdoctoral grant to F. E.).
[17] S. Sameni, C. Jeunesse, D. Matt, L. Toupet, Chem. Eur. J. 2009, 15, 10446–
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[18] The higher activity of complex 5 vs. that of [Ni(η5-C5H5)(PPh3)2]BF4 likely
arises from the bulkiness of the two phosphines which promotes the
coupling step.
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Keywords: Nickel · Supramolecular chemistry · Molecular
containers · Calixarenes · Butadiene polymerisation · Allylic
alkylation
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Received: October 4, 2019
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Molecular Containers
A covalently constructed capsular
nickel catalyst was obtained in one
step from a double-calixarene-derived
diphosphine. Its activity in butadiene
polymerisation was found to be 40
times higher than that of related nickel
complexes devoid of a capsular struc-
ture.
F. Elaieb, S. Sameni, M. Awada,
C. Jeunesse, D. Matt,* L. Toupet,
J. Harrowfield, D. Takeuchi,
S. Takano .............................................. 1–6
Metallated Container Molecules: A
Capsular Nickel Catalyst for En-
hanced Butadiene Polymerisation
DOI: 10.1002/ejic.201901074
Eur. J. Inorg. Chem. 0000, 0–0
www.eurjic.org
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim