Zn(ii) Robson macrocycles as templates for chelating diphosphines

Article abstract of DOI:10.1039/c1dt10905g

Chelating diphosphines were constructed using dinuclear Zn(ii) complexes of Robson macrocycles (Zn-RMCs) as templates. The assembly process is driven by the interaction between the metal centers (Lewis acids) with anionic and neutral Lewis base-functionalized monophosphines. The stability of the final structure depends on the geometry and the affinity of the functional groups of the ditopic phosphines and on the structure of the RMC. In the free ligand the ditopic phosphines coordinate at opposite faces of the pseudo-planar macrocycle as is shown in the molecular structure of several of the assemblies, according to X-ray diffraction. Pre-organization of the system by coordinating the phosphorus atoms to a transition metal center enforced coordination of the functional groups at the same face of the RMC. For several templated diphosphines cis-PtCl₂ complexes were identified by NMR. The in situ assembled diphosphines showed a chelating effect in the rhodium catalyzed hydroformylation of 1-octene. Combination of Zn-RMC 3 and phosphine A gave the highest l/b ratio (13) in acetonitrile.

Full text of DOI:10.1039/c1dt10905g

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PAPER
Zn(II) Robson macrocycles as templates for chelating diphosphines†
Sergio Ponsico,a Henrik Gulyas,b Marta Mart´ınez-Belmonte,a Eduardo C. Escudero-Ada´n,a Zoraida Freixa*c
and Piet W. N. M. van Leeuwen*a
Received 13th May 2011, Accepted 22nd July 2011
DOI: 10.1039/c1dt10905g
Chelating diphosphines were constructed using dinuclear Zn(II) complexes of Robson macrocycles
(Zn-RMCs) as templates. The assembly process is driven by the interaction between the metal centers
(Lewis acids) with anionic and neutral Lewis base-functionalized monophosphines. The stability of the
final structure depends on the geometry and the affinity of the functional groups of the ditopic
phosphines and on the structure of the RMC. In the free ligand the ditopic phosphines coordinate at
opposite faces of the pseudo-planar macrocycle as is shown in the molecular structure of several of the
assemblies, according to X-ray diffraction. Pre-organization of the system by coordinating the
phosphorus atoms to a transition metal center enforced coordination of the functional groups at the
same face of the RMC. For several templated diphosphines cis-PtCl2 complexes were identified by
NMR. The in situ assembled diphosphines showed a chelating effect in the rhodium catalyzed
hydroformylation of 1-octene. Combination of Zn-RMC 3 and phosphine A gave the highest l/b ratio
(13) in acetonitrile.
metals in its structure, which interact with two ditopic ligands.11,12
Introduction
The work presented here falls under the last approach. Salen-like
Organometallic homogeneous catalytic processes can be opti-
ligands, containing N2O2 pockets capable of hosting two metals,
mized by tuning the ligand properties. The bite angle of bidentate
are well known and have been extensively studied in the last
ligands exerts a dramatic influence on the outcome of several
decades.13–16 Jacobsen reported the catalytic application of M–
catalyzed reactions.1,2 In recent years new strategies have been
salen compounds in enantioselective epoxidation processes.17 The
introduced to generate new and large libraries of bidentate ligands
modular construction of salen ligands enabled the development
for the fine tuning of the catalytic results. Some of them are
of sophisticated structures, such as chiral derivatives, the modifi-
based on the construction of bidentate ligands using conventional
cation of their properties and the development of new generations
organic reactions3 to generate covalent bonds (strong interaction),
of ligands.18 In the early seventies Robson reported19 a new family
while others are based on supramolecular (weak) interactions4
of ligands that give binuclear complexes. Robson macrocycles
between two monodentate ligands,5,6 such as hydrogen bonding,1
(RMCs) are Schiff-base macrocyclic structures containing a N4O2
ionic interactions,7 or dynamic metal–ligand interactions. For
bis-anionic core based on two phenolate and four imine func-
the latter, several strategies have been applied: (a) the use of an
tionalities. They can coordinate to two dications (such as Zn(II))
“assembly” metal (without catalytic activity) to hold together
generating a bis-cationic metallamacrocycle. These binuclear com-
two monodentate, ditopic ligands,8,9 (b) incorporation of an
pounds have been studied in recent years because of their singular
“assembly” metal in the structure of one of the monodentate
structural properties13–16 and have been applied as platforms for
ligands, which interacts with a complementary ditopic ligand,10
the formation of ladder polymers20 and other supramolecular
and (c) the application of an external template, containing two
structures (e.g. porous coordination materials21). Like Jacobsen’s
ligands, RMCs are modular frameworks and their properties
can be modified easily by changing their building blocks. For
aInstitute of Chemical Research of Catalonia (ICIQ), Av. Pa¨ısos Catalans
16, 43007, Tarrgaona, Spain. E-mail: pvanleeuwen@iciq.es; Fax: +34 977
example, with the use of chiral diamines, chiral macrocycles can
be obtained.22–24 This modular nature together with their pseudo-
planar geometry makes them interesting candidates for templating
agents to generate libraries of bidentate ligands by interaction
between their metal centers and different ditopic monophosphines.
A similar approach has been previously reported for salphen
derivatives.12,25
920221; Tel: +34 977 920227
bDepartment de Qu´ımica F´ısica i Inorga`nica, Universitat Rovira i Virgili,
43007, Tarragona, Spain
cFacultad de Qu´ımica de San Sebastia´n. Universidad del Pa´ıs Vasco, 20080,
San Sebastia´n, Spain, IKERBASQUE, Basque Fundation for Science,
48011, Bilbao, Spain. E-mail: zoraida_freixa@ehu.es
† Electronic supplementary information (ESI) available: NMR and
MALDI-MS spectra and X-ray crystallographic data for 7C, 9E¢,
8E¢, and 9D¢. CCDC reference numbers 825586–825589. For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/c1dt10905g
The interaction of Zn(II) metallated tetradentate macrocycles,
such as porphyrins26,27 or salen-like28 structures with different
10686 | Dalton Trans., 2011, 40, 10686–10697
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The Royal Society of Chemistry 2011
©

Scheme 1 General synthesis of Zn-Robson macrocycles (Zn-RMCs) 1–6.
neutral functional groups, is well documented. The coordination
The length of the diamine backbone plays a crucial role
in the geometry of the final metallamacrocycle. The metallic
centers embedded in the RMC can adopt different geometries
depending on the N–N linker. For example, when a five-membered
ring is formed (n = 1) a square pyramidal geometry around
the Zn(II) metal centre is generally observed,34,37,38 and a few
exceptions with octahedral or square planar geometry have been
reported for Ni(II)37 and Cu(I),39 respectively. Instead, when 1,3-
propylenediamine is used (n = 2) a six-membered ring is formed
and, although some examples of octahedral geometry of the
metal centre can be found,20,40–42 the formation of a square
pyramidal geometry is most common.20,34,40–48 For larger spacers,
forming seven or eight-membered rings, formation of a trigonal
bipyramidal geometry around the metal centers can be observed in
the solid state.34,41,49,50 In these structures, the RMC does not retain
its planarity. As we were interested in pseudoplanar templates, we
decided to study the formation of the RMC using diamines with
only two and three carbon atoms as spacers. By changing the N–
N linker, not only the geometry around the metal centre can be
modified, but also the fluxionality of the final RMC changes.
As observed in the reported molecular structures, metal centers
of Zn-RMC (2, 3) are slightly out of the plane of the RMC,
in opposite directions, generating a C2 symmetry axis that passes
through the phenolate oxygen atoms. This distortion entails a local
differentiation of both sides of the plane of the RMC reflected in
the inequivalence of the CH2 protons (Scheme 2). In the case
of 2, two different groups of signals (4.6 ppm, 3.6 ppm) were
observed at room temperature for the CH2 protons in the 1H-NMR
spectrum (supporting information†), belonging to the two faces
of the plane. In contrast, for 3 two proton signals were observed
for the 1,3-propanediyl spacer, one at 4.07 ppm for the a protons,
and the other at 2.20 ppm for the b protons with a 2 : 1 intensity
(supporting information†). The equivalence of the protons at
both faces in this case indicates rapid interconversion between the
conformers of 3 in solution at room temperature. The formation
of a six-membered ring facilitates the chair-boat conformational
isomerization, which renders these protons equivalent, and also
enables a movement of the metals from one side to the other
of neutral, nitrogen-containing ligands (pyridine, DABCO, quin-
uclidine) to Zn(II) porphyrins was extensively studied as it became
a popular binding motif in supramolecular chemistry.26,27 The
strength of the interaction is well known and association constants
were determined for many compounds.26 The group of Reek van
Leeuwen used this binding motif to construct “supramolecular”
catalytic entities based on the selective assembly of nitrogen
containing phosphines with Zn(II) metallomacrocycles.29,30 For
their use as catalysts at 1 mM concentration the interaction in
some instances was just strong enough. We considered that the
use of bis-cationic Zn-RMCs as templates would lead to stronger
interactions not only with neutral nitrogen donors, but especially
with anionic functional groups.31 These ionic metal–ligand in-
teractions combine the strongest non-covalent interaction (ionic)
and the directionality32 of the dynamic metal–ligand interactions
increasing the stability of the final assembled structure. Here we
report on the use of metallated RMCs as templates for ditopic
ligands, their complexes with Pt, and their use as ligands in Rh
catalyzed hydroformylation.
Results and discussion
Robson macrocycle formation
For the synthesis of Zn-RMCs (1–6),33–35 two different isophtha-
laldehydes were applied in order to introduce different alkyl groups
into the macrocyclic structures (Scheme 1). The number of carbon
atoms of their substituents influences the solubility of the final
ionic compound, the t-butyl groups enhancing the solubility in
solvents of low polarity. Both isophthalaldehydes were obtained
in good yields (76–85%) from a modified Lindoy synthesis.36
The synthesis of Zn-RMCs was carried out in the presence of
different Zn(II) salts (Scheme 1) in order to study the effect of the
counteranion on the macrocycle formation and the self assembly
process. Excellent yields (>90%) were obtained when ZnCl2 was
used as the metal source. Moderate to good yields (60–80%) were
obtained with acetate or perchlorate as the counterion.
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Construction of the Robson-templated diphosphines
We studied the possibility of using these Zn-RMCs as templates
for pyridine, aniline, benzylamine, phenol/phenolate, and benzoic
acid/benzoate functionalized phosphines (Scheme 3), for the
construction of bidentate ligands. Neutral ligands A–F form
dicationic assemblies (Scheme 4). It should be noticed that the
functional groups of D, E, and F have an acidic proton that can
be abstracted with a base in order to generate the anionic D¢, E¢,
and F¢ ligands that will render the assembled structures neutral
(Scheme 5).
Most of the ditopic phosphines, see Scheme 3, were synthesized
according to reported methods. 3-Pyridyl phosphine A, which
is usually synthesized by the reaction of 3-pyridyllithium and
chlorodiphenylphosphine,51 was obtained in high yield by the
Steltzer method,52 i.e. Pd-catalyzed P–C coupling of diphenylphos-
phine and 3-iodopyridine.
Scheme 2 Diastereotopic protons of 2 and 3.
of the plane of the macrocycle. These chair and boat confor-
mations could be deduced from the solid state of 9E¢ by Single
Crystal X-Ray Diffraction (SCXRD) analysis, as will be discussed
below.
The nature of the counterion of the RMC plays a dominant
role in the outcome of the formation of the self-assemblies. As
Scheme 3 Functionalized monophosphines employed to build the assemblies.
Scheme 4 Ionic self-assembled bidentate ligands.
Scheme 5 Neutral self-assembled bidentate ligands.
10688 | Dalton Trans., 2011, 40, 10686–10697
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©

Fig. 1 ORTEP representation of 7C (some hydrogen atoms and solvent molecules have been omitted for clarity. Thermal ellipsoids are drawn at 50%
probability level. “A” denotes symmetry operation: -x + 1, -y + 1, -z + 1).
mentioned before, the use of the ZnCl2 as metal precursor for the
formation of macrocycles was beneficial, both in terms of yield and
purity. However, none of the attempts to substitute the chlorine
ion in 6 by any of the monophosphines (A–F) was successful, not
even when deprotonated D¢–F¢ were employed. Instead, the use of
the weakly coordinating perchlorate anion permitted the complete
formation of the desired assembled products. According to these
findings, in spite of the lower yields, Zn(II) salts containing weakly
coordinating ions should be used in the synthesis of the RMCs to
facilitate their displacement by the ditopic ligand.
To study the formation of the assembly between the RMC
and the functionalized phosphines an alcoholic solution of
the corresponding phosphine (A–F) was added to an alcoholic
solution of the RMC. The nitrogen functionalized phosphine C
produced instantaneously the precipitation of the self-assembled
product (Scheme 4) confirming the high affinity of the neutral
nitrogen donor towards the cationic Zn(II) metal centers. In the
case of the phosphines containing oxygen donor atoms (D, E, F),
deprotonation of the functional group with a hard base, such as
aqueous NaOH (to generate the corresponding anionic D¢, E¢,
F¢), was required to initiate precipitation of the assembled product
(Scheme 5). For the weakly coordinating functional groups (D,
E, F) no interaction with the cationic Zn(II) metal centre was
observed, but upon deprotonation of the protic functional groups
the Coulombic contribution strengthens the Lewis acid–base in-
teraction permitting the formation of the assembled diphosphine.
The products obtained were fully characterized by MALDI-
TOF-MS and NMR spectroscopy. Molecular structures of com-
pounds 7C, 8E¢, 9D¢ and 9E¢ were obtained by X-ray diffraction
of crystalline samples. Visual inspection of 7C and 9E¢ (Fig. 1 and
Fig. 2) confirms that the RMC templates are nearly planar, and in
both structures the two metal centers deviate symmetrically (0.519
in the solid state, due to the fixed orientation of phosphines,
the symmetry is reduced to Ci. Additionally, as the assembly
is dicationic, the perchlorate counterion is present in the final
structure of 7C; it is located close to the cationic metal centre,
but on the opposite side of the N2O2 plane with respect to the
functional group of C. Instead, compound 9E¢ (Fig. 2) forms a
neutral assembly, as ligand E¢ is anionic. The ionic interaction
with the metal center is stronger than the neutral Lewis acid–
base M–N interaction; this can be noticed in the shorter distance
of the functional group to Zn, the longer distance between Zn
and the imine nitrogens, and the larger distance of the metal
to the N2O2 pocket observed in this structure when compared
with the distances in 7C. The carboxylate group of E¢ enforces
a perpendicular disposition of the benzoate aromatic ring, unlike
the structure of 7C, perhaps due to a repulsion between the oxygen
atoms (O3,O1) or crystal packing forces. This is reflected in the lack
˚
of coplanarity of the RMC. A distance of 0.536 A can be measured
between the two parallel planes containing phenol carbons from
C1 to C6 (nearly coplanar in the case of 7C).
˚
and 0.526 A, respectively) from this plane in opposite directions.
The geometry around the Zn(II) metal center corresponds in both
cases to a slightly distorted square pyramid (Table 1,2), as expected
for this type of RMC. The Zn(II) central atoms are out of the
plane of the N2O2 pocket, which constitutes the base of the square
pyramidal coordination, and the apical position is occupied by
the functional groups of the monophosphine. In solution, both
compounds (7C and 9E¢) are C2h symmetric, as indicated by the
Fig. 2 ORTEP representation of 9E¢ (hydrogen atoms and solvent
molecules have been omitted for clarity. Thermal ellipsoids are drawn
at 50% probability level. “A” denotes symmetry operation: -x + 1, -y + 1,
-z + 2).
1
high symmetry of the H-NMR spectra (see experimental), but
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Table 1 Selected bond lengths, angles, and geometrical parameters for
7C
Zn1–N3
Zn1–N1
Zn1–N2
Zn1–O1
Zn1–O1A
2.077(6)
2.052(7)
2.056(6)
2.110(5)
2.008(5)
N1–Zn1–O1A
N2–Zn1–O1
N1–Zn1–O1
O1–Zn1–O1A
O1A–Zn1–N2
N2–Zn1–N1
N3–Zn1–N1
N3–Zn1–N2
N3–Zn1–O1
N3–Zn1–O1A
144.9(2)
153.1(2)
85.8(2)
75.3(2)
90.0(2)
94.4(3)
107.1(3)
114.2(3)
91.3(2)
102.6(2)
19.36
Zn1 ◊ ◊ ◊ O2S
Zn1 ◊ ◊ ◊ a
d ◊ ◊ ◊ d¢
3.643
0.519
0.003
16.186
Fig. 3 Fragmented representation (PPh2Ar, solvent, and some hydrogens
omitted for clarity) of the two configurations observed by SCXRD analysis
of 9E¢: chair 78% occupancy (left) and boat 22% occupancy (right).
P1 ◊ ◊ ◊ P1A
b Ÿ
N3–Zn1 ◊ ◊ ◊ O2S
g
169.51
Complexation studies of the assembled diphosphines
Symmetry code: A -x + 1, -y + 1, -z + 1 a: plane formed by N1, N2, O1,
O1A; b: plane formed by N1, N1A, N2, N2A; g: plane formed by Zn1,
O1, Zn1A, O1A; d: plane formed by C from C1 to C6; d¢: plane formed by
C from C1A to C7A.
Several attempts to coordinate the assembled diphosphines (7C,
8E¢, 9D¢, 9E¢) to transition metals, such as Pt(II) and Rh(I), resulted
in the formation of insoluble solids, most probably due to the
formation of polymeric structures. The key problem when using
these bimetallic flat templates is how to direct the orientation of the
phosphines, originally located on different faces of the template,
toward the same one. Previously reported observations on salen
templates25 indicated that the ditopic ligands moved to the same
face of the macrocycle when a transition metal was added, which
enabled the formation of the desired bidentate ligand. These bis-
salen molecules are less distorted than the ones presented here,
their metal–ligand bonds are weaker, and also the zinc atoms are
farther apart and can act independently. Apparently this is not the
case when preformed Zn-RMC templated diphosphines are used,
and the assembled ligands probably remain in their “transoid”
non-chelating arrangement even in the presence of a transition
metal.
To circumvent this problem, we assayed the construction of the
supramolecular complexes by coordinating the two functionalized
phosphines to a transition metal centre prior to the addition
of the macrocycle. We believe that this pre-organization might
facilitate the “cis-side” interaction between the functional groups
of the monophosphines and the metallic centers of the Zn-RMC
(Scheme 6 and Scheme 7).
Table 2 Selected bond lengths, angles, and geometrical parameters for
9E¢
Zn1–O2
Zn1–N1
Zn1–N2A
Zn1–O1
Zn1–O1A
1.974(2)
2.075(3)
2.108(3)
2.0656(17)
2.028(2)
N1–Zn1–O1A
N2A–Zn1–O1
N1–Zn1–O1
O1–Zn1–O1A
O1A–Zn1–N2A
N2A–Zn1–N1
O2–Zn1–N1
145.93(12)
152.81(11)
87.74(10)
76.92(9)
88.12(9)
92.51(10)
114.73(12)
98.18(10)
106.39(10)
98.83(11)
19.87
N1 ◊ ◊ ◊ O3
Zn1 ◊ ◊ ◊ a
d ◊ ◊ ◊ d¢
3.138
0.526
0.537
18.276
O2–Zn1–N2A
O2–Zn1–O1
P1 ◊ ◊ ◊ P1
O2–Zn1–O1A
b Ÿ
g
Symmetry code: A -x + 1, -y + 1, -z + 2 a: plane formed by N1, N2, O1,
O1A; b: plane formed by N1, N1A, N2, N2A; g: plane formed by Zn1,
O1, Zn1A, O1A; d: plane formed by C from C1 to C6; d¢: plane formed by
C from C1A to C7A.
In both compounds the interaction between the functional
groups of the monophosphines and the two metal centers of
the Zn-RMC occurs on opposite faces of the pseudoplane of
the macrocycle. This is assigned to steric repulsion, as observed
previously for other templates.25 This arrangement is not the
most appropriate one for the use of these assemblies as chelating
diphosphines, and it may well constitute a drawback.
The analysis by X-ray diffraction of the molecular structure
of 9E¢ shows some disorder due to the above mentioned chair-
boat structural fluxionality (Fig. 3). Although this disorder affects
the whole molecule, the most important difference between the
two dispositions is the conformation of the six-membered ring
of the metallated RMC. In the most abundant configuration,
with 78% occupancy, the six-membered ring adopts a chair
like conformation; in the other one, having 22% occupancy, the
six-membered ring shows a boat like conformation. From this
experimental observation it can be concluded that the two chair-
boat conformations, postulated before (vide supra) for the RMCs
containing a 1,3-propanediamine linker, are indeed observed in
the solid state at low temperature (100 K). It is expected that as
a result of this high flexibility of the RMCs derived from 3, these
will be able to interact with two donor groups at the same face
of the macrocycle, enabling that way the formation of chelating
bidentate ligands.
In order to test this hypothesis, reactions of triarylphosphines
(A, B and D–F) with Pt(COD)Cl2 were studied in deuterated
1
dichloromethane by 31P{ H}-NMR spectroscopy (Table 3), in
a 2 : 1 ratio. In all cases, the corresponding cis square planar
complexes were obtained (10A, 10B and 10D–10F) as the major
products (see experimental). In some cases minor impurities
were also formed, i.e. a species with three phosphorus atoms
coordinating to the Pt metal centre was observed in the case of
D (26.73 ppm (2P, d, JP–P = 18 Hz, JPt–P = 2489 Hz), 16.16 ppm
(1P, t, JP–P = 18 Hz)). The values of JPt–P observed for 10A, 10B
and 10D–10F, of approximately 3600 Hz, clearly indicate that
the chloride ligands are trans to the phosphorus atoms.7,53 The cis
coordination mode of the phosphorus atoms in these Pt complexes
should pre-organize the system favoring the interaction with the
Zn-RMC. Indeed, when one equivalent of the Zn-RMC was
1
added to the complexes 10, a well-defined change in the 31P{ H}-
NMR spectrum of the major product could be observed (Table 3).
Coordination of the functional groups, pyridyl (A), amino (B) and
hydroxyl (D), to the Zn atoms of the RMC resulted in a 4–5 ppm
upfield shift of the phosphorus signals of the Pt-complexes, and a
considerable, 350–400 Hz, decrease in the JPt–P coupling constants
(Table 3, Entries 1–3 and 8–10, Fig. 4).
10690 | Dalton Trans., 2011, 40, 10686–10697
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©

Scheme 6 Neutral Pt templated assemblies.
Scheme 7 Ionic Pt templated assemblies.
1
Table 3 Main products observed by 31P{ H}-NMR in CD2Cl2
It should be emphasized that coupling constants around
3300 Hz still correspond to cis complexes, but the electronic and
steric properties of the assembled diphosphines 11 are evidently
different from those of the non-assembled monophosphines 10.
Although the interaction between the donor groups in PPh2Y and
the macrocycle may decrease slightly the electron density on the
phosphorus atom, we rather attribute the spectroscopic changes
observed to a change in the geometry of the phosphine. The 31P
chemical shift and the coupling constants in complexes strongly
depend on the geometry, as reported.54,55 Although this effect
could be clearly observed, other products were also present in the
Pt(PPh2Y)2Cl2
Entry
Compound
d (ppm)
JP–Pt (Hz)
1
2
3
4
5
6
7
10A
10B
10D
10E
10E¢
10F
10F¢
13.33
17.30
17.01
17.26
16.95
17.36a
16.80a
16.80b
3660
3692
3696
3669
3699
3659a
3673a
3685b
1
31P{ H}-NMR spectra (supporting information†); for example in
the case ofD a new signal appears at 23.29 ppm with a JPt–Pcoupling
of 3094 Hz that could correspond to other geometries around the
Pt(II) metal centre.
Pt(PPh2Y)2Cl2 + RMC
Entry
Compound
d (ppm)
JP–Pt (Hz)
Interesting phenomena were observed when platinum com-
plexes of the carboxylated monophosphines (E, F) were combined
with the Zn-RMC. When one equivalent of 3 was added to
platinum complex 10E in order to form 11E, unlike in previous
8
9
10
11
12
13
14
11A
7.92
3287
3310
3304
3674
3230
3672a
3266a
3282b
11B
11.79
11.67
17.04
12.08
17.06a
11.75a
11.54b
11D
10E + 3
12E¢
1
examples, only minor changes were observed in the 31P{ H}-
10F + 3
12F¢
NMR, that is a slight upfield shift in the main signal (Table 3, Entry
11) and the appearance of a tiny signal at 11.24 ppm (supporting
information†). When two equivalents of triethylamine were added
[Pt] = 20 mM.a Method 1. b Method 2.
1
to this mixture, new products appeared in the 31P{ H}-NMR
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©

1
Fig. 4 31P{ H}-NMR of 10B (blue, bottom) and 11B (red, top).
spectrum. The chemical shift of the major signal is 5 ppm upfield
and the JPt–P coupling constant about 440 Hz smaller than that
of the original platinum complex of the monophosphine (Table 3,
Entry 12). This NMR pattern is very similar to those observed for
A, B, and D derivatives, and thus we conclude that the addition of
base initiates the formation of the fully assembled structure 12E¢
(Scheme 7), suggesting that, upon deprotonation, the carboxylate
groups have stronger affinity for the RMC. In the same NMR
spectrum other signals could be observed; on the one hand, a signal
similar to the original platinum complex 10E, but with slightly
different chemical shift and JPt–P coupling constant that could
correspond to the Pt(II) complex with the deprotonated ligand
10E¢, and on the other hand a set of 2 doublets (see experimental)
that corresponds to a desymmetrization of the two phosphorus
atoms around the transition metal centre, but still coordinated to
it as indicated by the chemical shift and the coupling constants
(see experimental). The existence of these compounds indicates
that even after deprotonation most of the carboxylates remain
uncoordinated to the Zn-RMC.
1
Fig. 5 31P{ H}-NMR of 10F (blue, bottom), 10F + base (red, middle),
and 12F¢ (10F + base + 3) (green, top).
product also depends on the geometry of the ditopic ligand. In
the MALDI-TOF-MS analysis (Fig. 6) of the reaction mixture
the molecular mass of the assembled complex 12E¢ was detected
showing the appropriate isotopic distribution pattern compared to
the calculated one, providing additional evidence for the formation
of the desired product.
A similar behavior was observed for ligand F when the same
procedure (Method 1) was applied. When one equivalent of 3 was
added to platinum complex 10F in order to form 11F, no major
1
change in the 31P{ H}-NMR was observed (Table 3, Entry 13,
Fig. 5), but when two equivalents of triethylamine were added
1
to this mixture, new products appeared in the 31P{ H}-NMR
spectrum: a major signal (12F¢) 4 ppm upfield and JPt–P coupling
constant about 400 Hz smaller than that of 10F, a signal (10F¢)
similar to 10F, and a set of 2 doublets (see experimental).
Using the same procedure (Method 1) platinum complex 10E¢,
containing the meta-carboxylated monophosphine (E¢), forms the
fully assembled product 12E¢ to a lower extent (40% by NMR
integration) and the signal is broader than that of 12F¢ having
para-substituted monophosphines (58% by NMR integration).
This finding demonstrates that the stability of the assembled
Fig.
6 Isotopic distribution pattern of 12E¢: experimental by
MALDI-TOF-MS (top), and calculated (bottom).
10692 | Dalton Trans., 2011, 40, 10686–10697
This journal is
The Royal Society of Chemistry 2011
©

Table 4 Rhodium catalyzed hydroformylation of 1-octene
Entry
Ligand
RMC
Solvent
T/◦C
Time (h)
Conversion (%)
Isomerization (%)
TOFa,c
l/bb
1
2
3
4
5
6
7
8
Me–xantphos
—
—
—
5
Toluene
Toluene
Toluene
Toluene
Toluene
THF
Acetonitrile
Toluene
THF
Ethyl acetate
2-Butanone
Dichloroethane
Acetonitrile
Acetonitrile
Acetonitrile
Acetonitrile
Dichloroethane
Acetonitrile
Dichloroethane
Acetonitrile
Acetonitrile
Dichloroethane
60
60
60
60
60
50
60
60
50
60
60
60
60
60
60
60
60
60
60
60
60
60
5.13
3.16
2.34
5.21
4.08
4.88
7.84
4.68
4.92
2.6
7.23
4.98
5.16
7.18
8.00
4.44
3.27
2.44
8.75
8.04
7.8
15.4
97.5
98.3
8.7
1.6
1.8
56.5
4.6
1.5
0.7
1.5
1.5
0
20 (15)
345 (42)
332 (59)
11 (9)
48.9
2.9
2.6
2.8
2.9
2.8
2.9
2.9
2.8
2.9
7.4
9.7
13.0
4.1
2.4
2.5
2.5
2.2
2.6
2.8
1.7
2.7
PPh3
—
—
A
—
—
—
3
97.6
55.8
94.8
96.7
23.9
22.4
50.1
48.2
39.2
35.8
60.0
95.3
98.8
48.3
97.9
88.2
<1
348 (27)
86 (27)
160 (35)
271 (25)
33 (24)
58 (22)
65 (24)
72 (20)
67 (22)
36 (22)
73 (20)
253 (20)
298 (30)
132 (20)
89 (47)
155 (22)
<1
A
A
A
9
A
3
10
11
12
13
14
15
16
17
18
19
20
21
22
A
3
0
A
3
4.0
4.1
5.7
1.4
0
1.2
1.3
2.6
0.4
0.4
0.3
0
A
3
A
3
A
2
B
3
C
3
C
3
D
D
E
3
3
3
F
F
3
3
5.71
82.7
78 (26)
Incubation: CO : H2 (1 : 1); 20 bar; 80 ◦C; 90 min. Reaction: CO : H2 (1 : 1); 20 bar; P : Rh (10 : 1); 1-octene : Rh (670 : 1); RMC : ligand (1 : 2); [Rh] =
1 mM.a Turnover frequency in (mol aldehyde) (mol Rh)-1 h-1. b Linear to branched aldehyde ratio. c In parentheses the conversion at which the TOF was
calculated.
We decided to invert the addition order for the formation of
12F¢, adding first the base and then the RMC (Method 2) to
10F. When two equivalents of triethylamine were added to 10F,
complexes of structurally similar monodentate ligands. This
difference between the activities can be rationalized by the fact
that monodentate ligands are more prone to dissociation than
the bidentate ones facilitating the coordination of the reactants
to the rhodium central atom. Another characteristic effect of
diphosphines, if they have the appropriate bite angle, is that they
can dramatically increase the regioselectivity of the hydroformy-
lation reaction. It has been observed that ligands with natural
bite angles56–58 around 110◦ prefer a diequatorial coordination
mode to equatorial–apical chelation in the catalytically active
trigonal bipyramidal (bidentate P-ligand)Rh(CO)2H complexes,
which ultimately leads to a higher linear : branched ratio.
1
in the absence of any RMC, 10F¢ appeared in the 31P{ H}-NMR
spectrum as a slightly upfield shift and the JPt–P coupling constant
slightly decreased (Table 3, Entry 7) and the set of 2 doublets
(21.19 ppm, JP–Pt = 3945 Hz; 4.66 ppm, JP–Pt = 3589; Hz JP–P
=
18 Hz) similar to the one described for phosphine E¢ was also
observed (Fig. 5). Although we are not certain about the nature
of the species responsible of these two signals, it could well be that
a deprotonated carboxylate coordinates to the Pt(II) metal center
differentiating the two phosphorus atoms; these species may be
cyclic oligomers. After addition of RMC 3 to that mixture the main
signal corresponds to a species containing equivalent phosphorus
nuclei (Fig. 5). The singlet character, the chemical shift, and
the JPt–P coupling constant of this signal correspond to the fully
assembled product 12F¢ (Table 3, Entry 14) previously observed.
The assembled ligands presented here were tested in the Rh-
catalyzed hydroformylation of 1-octene in order to probe the
robustness of the assemblies and their coordinating properties
under catalytic conditions.
The assembled bidentate ligands were formed in situ by mixing a
solution containing the ditopic phosphine and the corresponding
Rh(I) precursor with the solution/suspension of the Zn-RMC, in
the autoclave. The P : Rh : Zn-RMC ratio was 2 : 1 : 1 in all cases.
1
It should be noted that using this Method 2 the 31P{ H}-NMR
spectrum is much cleaner than the one obtained by Method 1, as
eventually the set of doublets almost disappears. This observation
indicates that the addition order of the base and the RMC to 10F
has an important influence in the formation of the fully assembled
complex 12F.
◦
The hydroformylation reactions were carried out at 50–60 C,
20 bar of synthesis gas (CO : H2 1 : 1), and in a range of non-protic
solvents (Table 4). As reference for monodentate and bidentate
ligands triphenylphosphine and Me–xantphos were tested under
the same reaction conditions (Entries 1 and 2). As is well known,
in the absence of ligand the substrate is rapidly consumed but the
main products are the isomerization products (Entry 3).
When one of the Zn-RMC (5) was tested under the same
conditions in absence of phosphine ligand (Entry 4) the activity is
dramatically reduced; this lack of activity could be due to Zn/Rh
Catalytic application of the assembled diphosphines
Monophosphines and chelating diphosphines show different per-
formance as ligands in rhodium catalyzed hydroformylation of
1-alkenes.2,56 One of the effects of chelating bidentate ligands is
a decrease in activity compared to the activity of the rhodium
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10686–10697 | 10693
©

transmetalation or formation of aggregates thus trapping rhodium
in an inactive form, as isomerization was not observed either.
For comparison, the ditopic ligand A was first tested under
the same reaction conditions in the absence of the templating
agentZn-RMC(Entries 5–7). As expected, theditopicligandalone
behaves as PPh3 (Entries 2 and 5), showing high activities but low
linearity in the product. Although there is some influence of the
solvent on the activity (TOF) no major changes in the selectivity
(l/b ratio) were observed.
The addition of Zn-RMC 3 led to slower catalytic systems
(Entries 5 and 8, 6 and 9, 7 and 13), most likely due to a bidentate
effect resulting from the formation of the supramolecular chelate.
From the NMR studies on platinum chloride it was known that
formation of phosphine complexes prior to the addition of the
RMC favoured the formation of bidentate ligand systems, but
in view of the incubation at high temperature and the reaction
temperature this was not necessary for the catalytic studies.
Only in acetonitrile the drop in activity is accompanied by
a spectacular improvement of the selectivity (from 2.9 to 13.0)
whilst in other solvents it remains basically unaltered after
addition of template 3. For toluene, THF, and ethyl acetate as the
solvent (Entries 8–10) low selectivities were obtained, but when
2-butanone, dichloroethane, and acetonitrile (Entries 11–13) were
used, the selectivity to the linear aldehyde went up to a l/b ratio of
13. The solvent may influence the rate of formation of the bidentate
assembly ligands and/or the equilibrium. As mentioned above,
this may be a disadvantage of the supramolecular approach, in
that the formation of the desired species is not always sufficiently
fast. Acetonitrile may facilitate rearrangements of the complexes
to the desired bidentate ligands, but for dichloroethane this is not
obvious.
The best two solvents for A, dichloroethane and acetonitrile,
were used to test ditopic ligands B–F, but much lower selectivities
were obtained than those encountered for ligand A. The low l/b
ratios and relatively high activities found for C, D, and E are typical
of monophosphines (entries 2 and 7), which indicates that these
ligands do not give the desired assembly to a large extent. Ditopic
ligands B and C containing N-donors did form the corresponding
Pt-assemblies as was observed by NMR spectroscopy, albeit at
higher concentrations, and perhaps the rhodium ligated species
are not formed for steric reasons or because of the stoichiometry
used. The weak O–Zn interaction, already observed at the
concentrations used in the NMR experiments, may account for the
weakness of the assembly in the case of ligands D–F. Furthermore,
the carboxylic acid function of F may hamper the formation of
rhodium hydride, as excess of carboxylic acids will do so.59
When templating agent 3 in complexes of ligand A was changed
for the more rigid one 2 (Entry 14), the selectivity is lower than
that obtained for 3, but it is still higher than that of the free ligand.
of templates studied, Zn-RMCs containing propylenediamine
linkers constitute much more flexible platforms than the ones
containing ethylenediamine spacers. When the former platforms
are used, addition of a transition metal forces the functional
groups of the phosphine to coordinate to the Zn-RMC on the same
face. The in situ assembled diphosphines showed a chelating effect
in the rhodium catalyzed hydroformylation of 1-octene probing
the presence of a supramolecular interaction under catalytic
conditions and the robustness of the system. In a few systems
containing the propylenedianine RMC an increased preference
for linear aldehyde formation was found (l/b = 13 : 1), indicative
of a wide bite angle. The ethylenediamine RMC with the same
pyridylphosphine ditopic ligand gave only a modest increase in the
l/b ratio. The nature of the solvent plays a crucial role, which is not
understood. The results evidence that many factors influence the
stability of the supramolecular assembly; structure and electronic
nature of the ditopic ligand, rigidity of the template and solvent
must be carefully selected to guarantee the robustness of the
system under catalytic conditions. The intermediate strength of the
pyridyl group to Zn gave the best results in catalysis. The desired
stronger bonding of the anionic groups retard the formation
of the assemblies that can function as bidentates and they give
inactive rhodium complexes. Thus, although a wide variety of new
bidentate phosphines can be readily obtained, their applicability
in catalysis is limited.
Experimental
General
Warning: solid perchlorate complexes containing organic ligands
are potentially dangerous and should be handled with care.
5-tert-Butylphenol, para-cresol, hexamethylenetetramine, 1,3-
diaminopropane,
1,2-diaminoethane,
1,2-diaminobenzene,
zinc(II) perchlorate hexahydrate, zinc(II) tetrafloroborate hydrate,
zinc(II) acetate dihydrate, zinc(II) chloride, 3-iodopyridine,
and deuterated solvents were purchased from Sigma-
Aldrich and used as received. Triethylamine, trifluoroacetic
acid 99%, palladium(II) acetate trimer were purchased
from Alfa–Aesar and used as received. Dichloro(1,5-cyclo-
octadiene)platinum(II) was purchased from Across and used
as received. RMC,33,35,60 meta-(diphenylphosphino)benzoic
acid,52 para-(diphenylphosphino)benzoic acid,52 (3-(diphenyl-
phosphino)phenyl)methanamine,61
3-(diphenylphosphino)-
aniline,7 3-(diphenylphosphino)phenol,59 diphenylphosphine,7
and 4,5-(dihexyloxy)-1,2-diaminobenzene62 were synthesized
according to the literature. All manipulation of phosphorous
containing products was carried out under Argon atmosphere
using Schlenk techniques. Methanol and ethanol absolute reagent
grade for RMC synthesis were purchased from Scharlau and
used as received. Solvents were purchased from Sigma–Aldrich as
HPLC grade, dried with an SPS system of ITC-inc. and degassed
using standard methods. NMR spectra unless otherwise stated
were recorded using a Bruker ATM-400 spectrometer operating
at the following frequencies: 400.13 MHz (1H), 161.98 MHz (31P).
31P NMR spectra were recorded using broad band decoupling.
Chemical shifts of 1H NMR spectra are reported in ppm downfield
from TMS, used as internal standard. Chemical shifts of 31P
NMR spectra are referred to H3PO4 as an external standard.
Conclusions
Zn-RMCs were applied as templating agents to generate self-
assembled bidentate ligands. Zn(II) metal centres of RMCs
interact with both neutral and anionic Lewis base functionalized
monophosphines to give supramolecular diphosphines. When
two ditopic ligands coordinate to the Zn-RMC they do so at
opposite faces minimizing steric repulsion. The assembly formed
this way cannot act as a chelating diphosphine. From the two types
10694 | Dalton Trans., 2011, 40, 10686–10697
This journal is
The Royal Society of Chemistry 2011
©

Synthesis of ditopic ligands
temperature in air. SCXRD showed these crystals to be the oxide of
the desired product (supporting information†). Not characterized
by NMR due to its low solubility. MALDI-TOF-MS: 1085.3 (M +
H+), 1101.3 (M + O + H+), 1117.3 (M+2O+H+).
3-(Diphenylphosphino)pyridine (A). Synthesized according to
a modified Steltzer52 procedure: 3-iodopyridine (1 g, 4.9 mmol)
and palladium acetate (2 mg, 0.0034 mmol) were dissolved
in acetonitrile (20 mL) under inert atmosphere. Triethylamine
(4.9 mmol) and diphenylphosphine (0.912 g, 4.9 mmol) were added
to the reaction mixture, and it was stirred at 85 ◦C for 24 h. The
9E¢.
A solution of 50 mg (0.163 mmol) of meta-
(diphenylphosphino)benzoic acid in 5 mL of methanol and 163 ml
of NaOHaq 1 M was added dropwise over a solution containing
61 mg (0.092 mmol) of 4 in 5 mL of methanol. The reaction mixture
was stirred for 2 h and the white precipitate formed was filtered off
from the cold solution and dried in air. 58 mg (62% yield) of a white
powder was obtained. A crystalline sample was obtained by slow
evaporation of methanol at room temperature and characterized
by SCXRD. 1H-NMR (400 MHz, CDCl3): 8.09 ppm (s, 4H, imine),
7.94 ppm (d, 2H, JH–P = 9.8 Hz, HAr(ortho-PPh2)), 7.77 ppm (d,
2H, JH–H = 7.6 Hz, HAr(para-PPh2)), 7.26–7.18 ppm (br m), 7.14–
7.05 ppm (m, 4H), 7.04 ppm (s, 4H), 4.06 ppm (m, 8H), 2.20,
full conversion was confirmed by 31P{ H}-NMR. The solvent was
1
removed in vacuo. The residue was dissolved in dichloromethane
(20 mL), and the organic solution was washed with water (3 ¥
20 mL). The aqueous extract was washed with Et2O (20 mL),
and the combined organic phase was dried over MgSO4. After
filtration and solvent removal, the residue was purified by flash
chromatography (silica, EtOAc). The colorless oily product was
recrystallized from hot hexane (10–15 mL). To complete the
crystallization the Schlenk tube was left in the freezer (-20 ◦C)
for 2 days. The product was filtered in air obtaining 1.01 g (79%
yield) and it was characterized as the reported product.63
1
2.17 ppm (s, 10H). 31P{ H}-NMR (161 MHz, CDCl3): -2.37 ppm
(s). MALDI-TOF-MS: 835.1 (M+), 851.1 (M+ + O).
Characterization of metal templated assembled diphosphines and
intermediate Pt-diphosphine complexes 10
Synthesis of self assembled diphosphines
7C. A solution of 71.3 mg (0.245 mmol) of diphenylphos-
phino(p-benzylamine) in 10 mL of ethanol was added dropwise
over a solution containing 100 mg (0.122 mmol) of 3 in 20 mL of
ethanol. The reaction mixture was stirred for 2 h and the white
precipitate formed was filtered off and dried in air. 114 mg (66%
yield) of a white powder was obtained. A crystalline sample was
obtained by slow evaporation of methanol at room temperature
and characterized by Single Crystal X-Ray Diffraction (SCXRD).
1H-NMR (400 MHz, CDCl3): 8.17 ppm (s, 4H, imine), 7.36–
7.31 ppm (m, 16H), 7.30–7.26 ppm (m, 8H), 7.13 ppm (pseudo
t, 7.6 Hz, 4H), 7.02 ppm (d, 7.6 Hz, 4H), 3.88 ppm (br s, 8H),
10A and 11A. 3-(Diphenylphosphino)pyridine (7.03 mg,
0.027 mmol) and dichloro(1,5-cyclooctadiene)platinum(II) (5 mg,
0.0134 mmol) were dissolved in
1 mL of deuterated
dichloromethane under inert atmosphere. After stirring for 30 min
1
at room temperature the mixture was analyzed by 31P{ H}-NMR
(161 MHz, CD2Cl2): 28.15 ppm (s), 19.38 ppm (s), 13.33 ppm (s,
JPt–P = 3660 Hz, 10A). 3 (11 mg, 0.0134 mmol) was dissolved in
the same solution. After stirring for 30 min at room temperature
1
the mixture was analyzed by 31P{ H}-NMR (161 MHz, CD2Cl2):
29.53 ppm (s), 13.56 ppm (s, JPt–P = 3644 Hz, 10A), 7.92 ppm (s,
JPt–P = 3287 Hz, 11A).
1
3.70 ppm (s, 4H), 2.04 ppm (br s, 4H), 1.29 ppm (s, 18H). 31P{ H}-
NMR (161 MHz, CDCl3): -3.01 ppm (s).
10B and 11B. 3-(Diphenylphosphino)aniline (7.4 mg,
0.027 mmol) and dichloro(1,5-cyclooctadiene)platinum(II) (5 mg,
8E¢.
A solution of 171 mg (0.560 mmol) of meta-
0.0134 mmol) were dissolved in
1 mL of deuterated
(diphenylphosphino)benzoic acid in 10 mL of methanol and 560 ml
of NaOHaq 1 M was added dropwise over a solution containing
200 mg (0.280 mmol) of 1 in 10 mL of methanol. The reaction
mixture was stirred for 2 h and the white precipitate formed was
filtered off from the cold solution and dried in air. 184 mg (59%
yield) of a white powder was obtained. A crystalline sample was
obtained by slow evaporation of methanol at room temperature in
air. SCXRD showed these crystals to be the oxide of the desired
product (supporting information†). 1H-NMR (400 MHz, CDCl3):
8.26 ppm (s, 4H, imine), 7.96 ppm (d, 2H, JH–P = 8.8 Hz, HAr(ortho-
PPh2)), 7.81 ppm (d, 2H, JH–H = 6.6 Hz, HAr(para-PPh2)), 7.30–
7.19 ppm (br m), 7.18–7.07 ppm (m, 4H), 7.06 ppm (s, 4H), 4.59–
dichloromethane under inert atmosphere. After stirring for 30 min
1
at room temperature the mixture was analyzed by 31P{ H}-NMR
(161 MHz, CD2Cl2): 17.30 ppm (s, JPt–P = 3692 Hz, 10B). 3 (11 mg,
0.0134 mmol) was dissolved in the same solution. After stirring for
1
30 min at room temperature the mixture was analyzed by 31P{ H}-
NMR (161 MHz, CD2Cl2): 24.00 ppm (s), 11.710 ppm (s, JPt–P
3310 Hz, 11B).
=
10D and 11D. 3-(Diphenylphosphino)phenol (7.4 mg,
0.027 mmol) and dichloro(1,5-cyclooctadiene)platinum(II) (5 mg,
0.0134 mmol) were dissolved in
1 mL of deuterated
dichloromethane under inert atmosphere. After stirring for 30 min
1
at room temperature the mixture was analyzed by 31P{ H}-NMR
1
3.62 ppm (br d, 8H), 2.21 ppm (s, 6H). 31P{ H}-NMR (161 MHz,
(161 MHz, CD2Cl2): 26.73 ppm (d, JP–P = 18 Hz, JPt–P = 2489 Hz),
17.01 ppm (s, JPt–P = 3696 Hz, 10D), 16.16 ppm (t, JP–P = 18 Hz).
3 (11 mg, 0.0134 mmol) was dissolved in the same solution. After
stirring for 30 min at room temperature the mixture was analyzed
CDCl3): -2.46 ppm (s).
9D¢.
A
solution of 150 mg (0.540 mmol) of 3-
(diphenylphosphino)phenol in 5 mL of methanol and 540 ml of
NaOHaq 1 M was added dropwise over a solution containing
200 mg (0.270 mmol) of 4 in 5 mL of methanol. The reaction
mixture was stirred for 2 h and the white precipitate formed
was filtered off from the cold solution and dried in air. 100 mg
(quantitative yield) of a white powder was obtained. A crystalline
sample was obtained by slow evaporation of methanol at room
1
by 31P{ H}-NMR (161 MHz, CD2Cl2): 23.19 ppm (s, JPt–P = 3094
Hz), 17.12 ppm (s, JPt–P = 3701 Hz), 11.67 ppm (s, JPt–P = 3304 Hz,
11D), and other minor impurities. Solvent was then removed in
vacuo and the residue analyzed by MALDI-TOF-MS: 1494.2 ((M
- 2(ClO4) + Cl + H2O)+), 1458.2 ((M - 2(ClO4) + OH)+), 787.2
((Pt + Cl - 2(PR3))+).
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10686–10697 | 10695
©

Table 5 Crystal data and structure refinement
10E and 12E¢. 3-(Diphenylphosphino)benzoic acid (8.3 mg,
0.027 mmol) and dichloro(1,5-cyclooctadiene)platinum(II) (5 mg,
Complex
7C
9E¢
0.0134 mmol) were dissolved in
1 mL of deuterated
dichloromethane under inert atmosphere. After stirring for 30 min
Formula
C70H76Cl8N6O10P2Zn2
1637.65
Monoclinic
P21/c
8.8886(14)
21.225(4)
19.390(3)
90.00
90.878(8)
90.00
3657.7(10)
2
1.487
1.053
100(2)
1688
6814
2641
0.2768
2641/54/482
C66H70N4O10P2Zn2
1271.94
Monoclinic
P21/n
18.8474(12)
7.8500(5)
20.6464(13)
90.00
98.266(3)
90.00
3022.9(3)
2
1.397
0.909
100(2)
1328
12184
9971
0.0454
9971/559/724
1
at room temperature the mixture was analyzed by 31P{ H}-NMR
Mr (g mol-1)
Crystal system
Space group
(161 MHz, CD2Cl2): 17.26 ppm (s, JPt–P = 3669 Hz, 10E). 3 (11 mg,
0.0134 mmol) was dissolved in the same solution. After stirring for
˚
a/A
1
30 min at room temperature the mixture was analyzed by 31P{ H}-
˚
b/A
˚
c/A
NMR (161 MHz, CD2Cl2): 17.04 ppm (s, JPt–P = 3674 Hz, 10E + 3),
11.24 ppm (s). Triethylamine (3.8 ml, 0.027 mmol) was added to the
solution. After stirring for 30 min at room temperature the mixture
a (◦)
b (◦)
g (◦)
1
was analyzed by 31P{ H}-NMR (161 MHz, CD2Cl2): 31.47 ppm
3
˚
V/A
Z
(s), 18.46 ppm (d, JP–P = 18 Hz), 16.95 ppm (s, JPt–P = 3699 Hz,
Dc (g cm-1)
10E¢), 12.08 ppm (s, JPt–P = 3230 Hz, 12E¢), 4.88 ppm (d, JP–P
=
mMo (mm-1)
18 Hz, JPt–P = 3607 Hz). Solvent was then removed in vacuo and the
residue analyzed by MALDI-TOF-MS: 1489.3 (M+), 919.4((M -
Pt - 2Cl - PR3)+).
T/K
F(000)
No. of reflns collected
No. of ind. reflns
Rint
10F, 10F¢, and 12F¢. Method 1: 4-(diphenylphosphino)benzoic
Data/restraints/
parameters
acid
(8.3
mg,
0.027
mmol)
and
dichloro(1,5-
Goodness of fit on F2
R1 [I > 2s(I)]
wR2 [I > 2s(I)]
R1 (all data)
wR2 (all data)
2qmax
0.933
0.0915
0.1844
0.2536
0.2497
51.28
-9 £ h £ 10
-25 £ k £ 25
-19 £ l £ 23
1.537 and -0.907
1.156
0.0646
0.1687
0.0788
0.1758
67.92
-29 £ h £ 29
-8 £ k £ 12
-32 £ l £ 32
2.782 and -0.777
cyclooctadiene)platinum(II) (5 mg, 0.0134 mmol) were dissolved
in 1 mL of deuterated dichloromethane under inert atmosphere.
After stirring for 30 min at room temperature the mixture was
1
analyzed by 31P{ H}-NMR (161 MHz, CD2Cl2): 17.36 ppm (s,
JPt–P = 3659 Hz, 10F). 3 (11 mg, 0.0134 mmol) was dissolved in
Index ranges
the same solution. After stirring for 30 min at room temperature
1
the mixture was analyzed by 31P{ H}-NMR (161 MHz, CD2Cl2):
17.06 ppm (s, JPt–P = 3672 Hz, 10F + 3). Triethylamine (3.8 ml,
0.027 mmol) was added to the solution. After stirring for
30 min at room temperature the mixture was analyzed by
Largest diff peak and
-3
˚
hole/e A
Crystal size/mm
0.05 ¥ 0.02 ¥ 0.005
0.20 ¥ 0.05 ¥ 0.02
1
31P{ H}-NMR (161 MHz, CD2Cl2): 31.22 ppm (s), 23.44 ppm
(s), 21.21 ppm (d, JP–P = 20 Hz, JPt–P = 3918 Hz), 16.80 ppm
(s, JPt–P = 3673 Hz, 10F¢), 11.75 ppm (s, JPt–P = 3266 Hz,
12F¢), 4.61 ppm (d, JP–P = 20 Hz, JPt–P = 3592 Hz). Method 2:
4-(diphenylphosphino)benzoic acid (8.3 mg, 0.027 mmol) and
dichloro(1,5-cyclooctadiene)platinum(II) (5 mg, 0.0134 mmol)
were dissolved in 1 mL of deuterated dichloromethane under
inert atmosphere, and stirred for 30 min at room temperature.
Triethylamine (3.8 ml, 0.027 mmol) was added to the solution.
After stirring for 30 min at room temperature the mixture was
suspension (26.6 mM of monophosphine or 13.3 mM of diphos-
phine, and 13.3 mM of template, if required). The autoclaves
were then pressurized with 20 bar of syngas and heated to
80 ◦C, stirring at 1000 rpm, for 90 min. After cooling to room
temperature and depressurizing the vessels, 2 mL of a substrate
stock solution (2.7 M of substrate and 15 mM of n-decane) were
added. The autoclaves were then pressurized to 20 bar of syngas
and heated to the reaction temperature, stirring at 1000 rpm, for
8 h approximately. Gas consumption was automatically monitored
and data used to calculate conversions and turnover frequencies.
Aliquots of 0.1 mL were taken automatically at 0.5, 1, 2, 4,
and 8 h approx., quenched with triethyl phosphite, diluted with
dichloromethane, and analyzed by GC-FID to determine final
products and selectivity (supporting information†).
1
analyzed by 31P{ H}-NMR (161 MHz, CD2Cl2): 30.63 ppm (s),
21.26 ppm (d, JP–P = 20 Hz, JPt–P = 3945 Hz), 16.80 ppm (s, JPt–P
=
3685 Hz, 10F¢), 4.54 ppm (d, JP–P = 20 Hz, JPt–P = 3589 Hz). 3
(11 mg, 0.0134 mmol) was dissolved in the same solution. After
stirring for 30 min at room temperature the mixture was analyzed
1
by 31P{ H}-NMR (161 MHz, CD2Cl2): 31.36 ppm (s), 23.46 ppm
(s), 21.19 ppm (d, JP–P = 20 Hz, JPt–P nd), 16.80 ppm (s, JPt–P
=
X-Ray crystallography
3690 Hz, 10F¢), 11.54 ppm (s, JPt–P = 3282 Hz, 12F¢), 4.66 ppm (d,
JP–P = 20 Hz, JPt–P nd).
All crystals were mounted on a magnetic support with 10 micron
nylon fiber cryoloop. Data were collected on a Bruker-Nonius
diffractometer equipped with an APEX II 4 K CCD area detector,
a FR591 rotating anode with Mo-Ka-radiation, MultiLayer
Montel 200 Mirrors and a Kryoflex low temperature device (T =
-173 ◦C). Full sphere data collection was carried out with w
and j scans using Bruker APEX software (versions v1.0-22,
v2009.1-0 and v2009.1-02, 2007, Bruker AXS Inc., Madison,
Wisconsin, USA). Empirical absorption corrections were applied
using SADABS (Version 2008/1 Bruker-Nonius.). Structures were
solved by either Patterson or Direct Methods using SHELXS-97
Rhodium(I) catalyzed hydroformylation of 1-octene
All the catalytic experiments herein presented were carried out
in a parallel mode in a multi autoclave reactor AMTEC-SPR-16
from Advanced Machinery & Technology Chemnitz GmbH. The
general procedure reads as follows: the autoclaves were purged
twice with nitrogen at room temperature, two more times at
100 ◦C, and cooled to room temperature again. To each vessel
were added: 3 mL of a Rh(I) stock solution (2.68 mM of
Rh(acetylacetonate)(CO)2) and 3 mL of a ligand stock solution/
10696 | Dalton Trans., 2011, 40, 10686–10697
This journal is
The Royal Society of Chemistry 2011
©

and refined with SHELXL software (versions V6.12 and 6.14)
(Table 5).
30 V. F. Slagt, P. C. J. Kamer, P. W. N. M. van Leeuwen and J. N. H. Reek,
J. Am. Chem. Soc., 2004, 126, 1526–1536.
31 W. Huang, H. B. Zhu and S. H. Gou, Coord. Chem. Rev., 2006, 250,
414–423.
32 G. Machado, J. D. Scholten, T. de Vargas, S. R. Teixeira, L. H. Ronchi
and J. Dupont, Int. J. Nanotechnol., 2007, 4, 541–563.
33 S. Mohanta, B. Adhikary, S. Baitalik and K. Nag, New J. Chem., 2001,
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34 A. J. Atkins, D. Black, R. L. Finn, A. Marin-Becerra, A. J. Blake, L.
Ruiz-Ramirez, W.-S. Li and M. Schroeder, Dalton Trans., 2003, 1730–
1737.
35 N. H. Pilkington and R. Robson, Aust. J. Chem., 1970, 23, 2225–2236.
36 L. F. Lindoy, G. V. Meehan and N. Svenstrup, Synthesis, 1998, 1029–
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39 B. Liu, H. Zhou, Z. Q. Pan, H. P. Zhang, J. D. Hu, X. L. Hu, H. Zhou
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Acknowledgements
We thank the Ministerio de Cie´ncia e Innovacio´n of Spain for
the financial support (CTQ2005-03416; BES-2006-11627), the
members of the Research Support Unit of the ICIQ, Prof. Pau
Ballester and his co-workers for their collaboration.
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The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10686–10697 | 10697
©