Carbonylation (hydroformylation and hydrocarbalkoxylation) reactions in the presence of transition metal: P-tert-butyl-calix[4]arene-based phosphine and phosphinite systems

Article abstract of DOI:10.1016/S0022-328X(98)00837-7

In this study, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphinoxy-ethoxy) calix[4]arene (5) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphinoethoxy)- calix[4]arene (6), as well as their platinum and palladium complexes (PtCl₂)₂(5), (PdCl₂)₂(5) were synthesised and characterised. In addition to these transition metal-containing complexes the catalytic systems formed in situ, from catalytic precursors PtCl₂(PhCN)₂, [Rh(nbd)Cl]₂ and PdCl₂(PhCN)₂ and the corresponding calixarene ligand, were tested as catalysts in hydroformylation and hydrocarbalkoxylation, respectively. High chemoselectivity was obtained in hydroformylation in the presence of rhodium-containing catalysts both with the above calixarene-based phosphine and phosphinite ligands. The regioselectivity towards branched aldehyde shows a strong temperature dependence in case of phosphinite derivative. Although the platinum-containing systems show much lower catalytic activity, the regioselectivities are undoubtedly higher than those obtained with PtCl₂(diphosphine)-SnCl₂ systems.

Full text of DOI:10.1016/S0022-328X(98)00837-7

Journal of Organometallic Chemistry 570 (1998) 23–29
Carbonylation (hydroformylation and hydrocarbalkoxylation) reactions
in the presence of transition metal: p-tert-butyl-calix[4]arene-based
phosphine and phosphinite systems
Zsolt Cso´k a,c, Ga´bor Szalontai a, Ga´bor Czira b, La´szlo´ Kolla´r c,d,
*
a Uni6ersity of Veszpre´m, Department of Silicate and Materials Engineering, P.O. Box 158, H-8200 Veszpre´m, Hungary
b Central Research Institute of Chemistry of the Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary
c Uni6ersity of Veszpre´m, Department of Organic Chemistry, P.O. Box 158, H-8200 Veszpre´m, Hungary
d Janus Pannonius Uni6ersity, Department of Inorganic Chemistry, P.O. Box 266, H-7601 Pe´cs, Hungary
Received 27 March 1998
Abstract
In this study, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphinoxy-ethoxy)calix[4]arene (5) and 5,11,17,23-te-
tra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphinoethoxy)-calix[4]arene (6), as well as their platinum and palladium com-
plexes (PtCl2)2(5), (PdCl2)2(5) were synthesised and characterised. In addition to these transition metal-containing complexes the
catalytic systems formed in situ, from catalytic precursors PtCl2(PhCN)2, [Rh(nbd)Cl]2 and PdCl2(PhCN)2 and the corresponding
calixarene ligand, were tested as catalysts in hydroformylation and hydrocarbalkoxylation, respectively. High chemoselectivity was
obtained in hydroformylation in the presence of rhodium-containing catalysts both with the above calixarene-based phosphine
and phosphinite ligands. The regioselectivity towards branched aldehyde shows a strong temperature dependence in case of
phosphinite derivative. Although the platinum-containing systems show much lower catalytic activity, the regioselectivities are
undoubtedly higher than those obtained with PtCl2(diphosphine)–SnCl2 systems. © 1998 Elsevier Science S.A. All rights reserved.
ligands in transition metal complexes, which show hy-
droformylation and hydrocarbalkoxylation activity
[6,7]. Of the various ligands used in catalytic hydro-
formylation, chiral diphosphines of C2 symmetry
proved to be excellent ligands in asymmetric hydro-
formylation [8–14]. Diphosphines with diphenylphos-
phino groups in stereochemically different environment
have been also reported as efficient ligands [15]. How-
ever, recent studies with heterobidentate phosphine–
phosphite ligands show the importance of different
donor atoms in rhodium-catalysed reactions [16,17].
The hydroformylation of simple substrates is of high
practical importance and the investigation of various
ligands in mono- and biphasic reactions is still the
frontier of homogeneous catalysis [3].
1. Introduction
The importance of carbonylation reactions has given
rise to many studies, aimed at extending the range of
applicability and at elucidating the mechanism [1]. In
particular, a large number of simple and functionalised
olefins have been investigated with the aim of obtaining
compounds of industrial interest [2,3]. Large efforts
have been made for the synthesis of chiral building
blocks and biologically important derivatives in asym-
metric hydroformylation reaction as well [4].
Hundreds of ligands with different steric and elec-
tronic parameters, shapes and functionalities have al-
ready been tested in various homogeneous catalytic
reactions [5], among them carbonylations. A number of
mono- and bidentate phosphines have been used as
Although the ‘lower rim’ functionalization of calix-
arene derivatives has been studied in detail and the
application of these host molecules for various purposes
* Corresponding author. E-mail: kollar@ttk.jpte.hu
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00837-7

24
Z. Cso´k et al. / Journal of Organometallic Chemistry 570 (1998) 23–29
Scheme 1. Schematic pathway for 5 and 6.
has been investigated [18], the number of applications
as novel ligands in transition metal complexes is rather
limited. A novel class of calixarene derivatives with
phosphorus [19–23] and nitrogen donor atoms [24,25]
was reported and their coordination to copper [19] and
platinum [21,26,27] has been investigated. Calix[n]arene
phosphine oxides have been used for the inter- and
intra-group separations of lanthanides and actinides
[22].
However, to the best of our knowledge, only one
attempt has been made to employ these calixarene-
based potential ligands in homogeneous catalytic reac-
tions [28]. Their use as bidentate (and potentially
multidentate) ligands, able to influence both steric and
electronic properties of molecularly defined catalysts,
was encouraged by the importance of obtaining new
information on ligand structure–reactivity and ligand
structure–stereochemical outcome relationships [29].
In the present paper the synthesis and characteriza-
tion of calixarene phosphine and phosphinite ligands is
described. Efforts to improve the chemo- and regiose-
lectivities in carbonylation reactions led to the synthesis
of platinum, palladium and rhodium complexes with
these calixarene ligands, which were used as preformed
or in situ catalysts in the hydroformylation and hydro-
carbalkoxylation of styrene.
alternative route to that described earlier [22]. The
appropriate ethyl carboxylate (2) [30] was reduced to
the corresponding primary alcohol (3) by lithium alu-
minium hydride, followed by tosylation with toluene-
para-sulfonyl chloride resulting in 4 [31], which was
reacted with lithium diphenylphosphide (Scheme 1). In
the 31P-NMR spectrum of 6, the phosphorus atoms
appear as a singlet at −22.99 ppm.
The analogous phosphinite derivative, 5,11,17,23-te-
tra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphi-
noxy-ethoxy)-calix[4]arene (5), was obtained directly
from the alcohol (3) by the reaction with
chlorodiphenylphosphine in THF (Scheme 1). The 31P-
NMR spectrum of 5 shows a single peak at 113.78
ppm.
2.2. In6estigation of the coordination of 5 and 6 to Pt,
Pd and Rh
2.2.1. Complexes with 5
Both the preparation and the in situ reaction bring
about the formation of (PtCl2)2(5) and the analogous
(PdCl2)2(5) complexes where the two neighbouring
phosphinite phosphorus donor coordinate to the metal
in cis position (Scheme 2). The synthesis of both com-
plexes was based on the facile benzonitrile substitution
in the reaction of
5
with PtCl2(PhCN)2 and
PdCl2(PhCN)2 precursors, respectively.
The 31P-NMR spectra of the in situ reactions of 5
with PtCl2(PhCN)2, at molar ratio ligand (5)/
PtCl2(PhCN)2=1/2, even at molar ratio 1/1, show only
one signal at 85.8 ppm (J(3lP, l95Pt)=4173 Hz) upfield
to the free ligand (113.78 ppm). The isolated platinum
complex also gave the above signal exclusively. The
structure proposed above is also proved by the two
2. Results and discussion
2.1. Synthesis of p-tBu-calix[4]arenephosphinite (5) and
phosphine (6)
The lower rim functionalised calixarene, 5,11,17,23-
tetra-tert-butyl-25,26,27,28-tetrakis(2-diphenylphosphi-
noethoxy)-calix[4]arene (6) was synthesised in an
1
pairs of benzylic methylene doublets in H-NMR (for

Z. Cso´k et al. / Journal of Organometallic Chemistry 570 (1998) 23–29
25
analytical data see Section 3). The formation of any
oligomeric species can be ruled out by the presence of
the above simple NMR pattern showing equivalent
phosphorus donor atoms. Although the (PtCl2)4(5)2
symmetric dimeric species (each of the four phosphorus
donor atoms of the ligand is bound to different plat-
inum trans to the chloro ligand) may possess the same
simple 31P-NMR spectrum, a single pair of doublets is
expected as a consequence of the four equivalent ben-
The in situ reaction of [Rh(nbd)Cl]2 and 5 was also
followed by 31P-NMR at r.t. A broad signal at 122 ppm
(Dw1/2=ca. 600 Hz) reflects fast exchange between co-
ordinated and noncoordinated phosphorus donor
atoms (molar ratio ligand (5)/[Rh(nbd)Cl]2=2/1, P/
Rh=4/1). RhClP3-type complex(es) and the free fourth
phosphorus of the calixarene-based ligand are supposed
to be involved in this exchange process. The variable
temperature measurement up to 100°C in toluene-d8 did
not bring about substantial changes neither in the
chemical shift nor the half-width of the above signal.
The stepwise addition of two further equivalents of
the Rh precursor (P/Rh=2/1 and P/Rh=l/l) results in
1
zylic methylene groups in H-NMR.
The analogous reaction for palladium furnished a
(PdCl2)2(5) dinuclear complex as major component,
which shows a predominating signal at 112.7 ppm (at
molar ratio ligand (5)/PdCl2(PhCN)2=1/2). The struc-
ture of the complex analogous to platinum shows a
similar pattern for the benzylic methylene protons. The
cis arrangement of both pairs of phosphorus atoms of 5
has also been shown by Raman spectroscopy. The
bands with wavenumbers of 300.4 and 323.1 cm−1 have
been assigned to w(Pd–Cl) of the cis(PdCl2)2(5) species
as described for analogous platinum-containing systems
[23].
In addition to the above cis-complex ca. 5% trans-
Pd-P2 moieties have also been observed in 31P-NMR
and Raman spectra (363.5 cm−1). Since their amount
increases upon standing, they could be considered as
parts of oligomeric decomposition products. The pres-
ence of the suggested multinuclear species is in agree-
ment with osmometric molecular weight determination.
The molecular weight (2260950) higher than expected
for cis-(PdCl2)2(5) (MW=1916.5) can also be consid-
ered as an indication for the presence of oligomeric
species.
1
three sets of doublets showing J(3lP, 103Rh)=200 Hz
coupling only. These results reflect highly symmetric di-
and tetranuclear complexes containing RhP2 and
Rh(nbd)P moieties, respectively.
2.2.2. Complexes with 6
At a molar ratio ligand (6)/PtCl2(PhCN)2=1/2, two
major components at −1.75 ppm, J(31P, 195Pt)=3558
Hz and 10.02 ppm, J(31P, 195Pt)=3538 Hz (their ratio
is ca. 3/1) were observed. The lack of J(31P, 31P)
coupling is an indication for equivalent phosphorus
donor atoms. The J(31P, 195Pt) coupling constant of
about 3500 Hz is an indication of their cis-
arrangement.
The 31P-NMR of the reaction of
PdCl2(PhCN)2 (at molar ratio ligand (6)/
6
with
a
PdCl2(PhCN)2=1/2) shows an even more complicated
reaction mixture: a sharp singlet at 16.61 ppm, four
singlets of lower intensity between 10.04 and 11.17 ppm
showing the presence of both mono and bidentate
coordination resulting in a mixture of cis and trans-
PdP2-type complexes.
The in situ reaction of the tetraphosphine (6) with
[Rh(nbd)Cl]2 (ligand (6)/[Rh(nbd)Cl]2=2/1, P/Rh=4/
1) resulted in a doublet at 15.67 ppm and a broad
doublet at 15.05 ppm (Dw1/2=ca. 65 Hz), with the
coupling constants being nearly the same (J(31P,
103Rh)=134 Hz) reflecting a similar geometry.
The in situ reaction with PdCl2(PhCN)2 results in a
species showing a signal at 110 ppm (Dw1/2=ca. 600
Hz). The line broadening can be explained both by the
exchange between benzonitrile and phosphinite ligands,
and the intramolecular exchange of the phosphinite
donor moieties of 5.
Upon further addition of [Rh(nbd)Cl]2 precursor (P/
Rh=2/1) the two doublets have been sharpened, their
ratio is ca. 3/1, and in the same time a broad doublet at
20.58 ppm appeared (J(31P, 103Rh)=ca. 170 Hz).
2.3. Homogeneous carbonylations using 5 and 6 as
ligands in transition metal catalysed reactions
2.3.1. Platinum-catalysed hydroformylation reactions
Styrene (7) as model compound was reacted with
CO/H2 (1/1) at 50–105°C, under a pressure of 80 bar,
in the presence of platinum-containing in situ catalysts
prepared from (PtCl2)2(5) and tin(II)chloride, as well as
PtCl2(PhCN)2, 6 and tin(II)chloride (Table 1).
Scheme 2. Schematic representation of (MCl2)2(5) (M=Pt, Pd).

26
Z. Cso´k et al. / Journal of Organometallic Chemistry 570 (1998) 23–29
Table 1
Hydroformylation of styrene in the presence of platinum–5 and platinum–6 systemsa
Catalyst
R. temp. (°C)
R. time (h)
Convb (%)
Rcc (%)
Rdbr (%)
(PtCl2)2(5)
(PtCl2)2(5)
(PtCl2)2(5)
(PtCl2)2(5)+2PPh3
(PtCl2)2(5)
PtCl2(PhCN)2+6
PtCl2(PhCN)2+6
PtCl2(PhCN)2+6
PtCl2(PhCN)2+6
PtCl2(PhCN)2+6+2PPh3
50
75
95
95
105
55
75
95
105
105
135
41
21
21
17
290
100
28
28
28
57
64
60
37
54
57
60
62
85
71
93.3
91.6
87.3
86.9
87.7
91.6
87.5
82.2
80.1
80 5
46.7
46.3
42.8
40.6
39.8
48.3
48.2
47.3
46.3
43.6
a Reaction conditions: Pt/P/SnCl2/styrene=1/2/1/2000; 0.05 mol styrene; partial pressure of CO=partial pressure of H2=40 bar, solvent:
toluene.
b (Mol of 8+mol of 9+mol of 10)/(initial mol of 7)×100.
c (Mol of 8+mol of 9)/(mol of 8+mol of 9+mol of 10)×100 (chemoselectivity towards aldehydes).
d Mol of 8/(mol of 8+mol of 9)×100 (regioselectivity towards branched aldehyde).
CO/H
PhCHꢀCH2 “ 2PhCH(CH3)CHO+Ph(CH2)2CHO
catalysts (Table 2). At 55°C both rhodium-containing
systems resulted in practically same regioselectivities.
The regioselectivity towards branched aldehyde de-
creases strongly by the increasing temperature. This
effect is more pronounced when the phosphinite deriva-
tive (5) was used. The addition of a monodentate
phosphine (PPh3) resulted in an increase in branched
regioselectivity from 69.7 to 85.8%. The 86–87%
branched selectivity at 105°C could be an indication for
the presence of Rh–PPh3 species, since much higher
regioselectivities have been obtained with rhodium-cat-
alysts with PPh3 in the hydroformylation of styrene
[32].
7
+PhC2H5
10
8
9
(1)
The use of the two platinum catalysts described
above in the hydroformylation reaction resulted in the
formation of the two aldehyde regioisomers 8 and 9
which is accompanied by the hydrogenation product of
the substrate (10) (Eq. (1)).
The catalytic activity of the systems containing calix-
arene-based ligands is much lower than that of the
Pt(diphosphine)Cl2 systems [6,7]. At low temperature
the difference in the activity of systems containing 5
and 6 is much higher than at higher temperature.
The chemoselectivity of hydroformylation is similar
to that of the widely used PtCl(SnCl3)(PP) systems in
case of 5 and lower when the phosphine (6) has been
used as ligand. The regioselectivity towards branched
aldehyde (8) is close to 50% at 50°C which is by ca.
10% higher than that obtained with PtCl2(PP) catalysts,
and shows some temperature dependence in case of 5,
falling from 46.7 to 39.8%. Surprisingly, an almost
constant regioselectivity has been observed by the vari-
ation of the temperature in case of 6.
The addition of PPh3 to the above phosphinite- and
phosphine-based catalytic systems resulted in a decrease
of the catalytic activity and slightly lower chemo- and
regioselectivities. This observation shows that the selec-
tivities are still determined by the calixarene ligands
bound to platinum. The formation of PtCl2(PPh3)2
complex of low activity could be an explanation for this
phenomenon.
2.3.3. Palladium-catalysed hydroalkoxycarbonylation
reactions
The two palladium containing catalysts, the pre-
formed (PdCl2)2(5) and the in situ system formed from
6 and PdCl2(PhCN)2 (molar ratio=1/2), have been
tested in hydroalkoxycarbonylation of styrene at 130°C,
with a CO pressure of 140 bar (Eq. (2)).
PhCHꢀCH2 “
CO/ROHPhCH(CH3)COOR
11
+Ph(CH2)2COOR
(2)
12
Extremely low conversion (B3%) was obtained with
5 due to the cleavage of the C–O–P bond of the ligand
by the alcohol (Table 3). Reasonable yields were ob-
tained with 6 at 130°C. Neither the high branched
regioselectivity characteristic for monodentate tertiary
phosphines nor the linear selectivity characteristic for
bidentate phosphines were observed under the reaction
conditions used. Formation of branched and linear
esters in a ratio of ca. 1:1 can be explained by the
interplay of reaction mechanisms catalysed by palla-
dium-complexes of monodentate and cis-chelate type
coordination (see Section 2.2). The use of Pd–PPh3 and
Pd–diphosphine systems yields an almost exclusive for-
2.3.2. Rhodium-catalysed hydroformylation reactions
Although the activities of the Rh–5 and Rh–6 sys-
tems are slightly lower than that of the usual rhodium–
phosphine systems (especially in case of 6), the
aldehyde selectivities are similar to the best rhodium-

Z. Cso´k et al. / Journal of Organometallic Chemistry 570 (1998) 23–29
27
Table 2
Hydroformylation of styrene in the presence of rhodium–5 and rhodium–6 systemsa
Catalyst
R. temp. (°C)
R. time (h)
Conv. (%)b
Rcc
Rdbr
[Rh(nbd)Cl]2+5
[Rh(nbd)Cl]2+5
[Rh(nbd)Cl]2+5
[Rh(nbd)Cl]2+5+2PPh3
[Rh(nbd)Cl]2+5
[Rh(nbd)Cl]2+6
[Rh(nbd)Cl]2+6
[Rh(nbd)Cl]2+6
[Rh(nbd)Cl]2+6+2PPh3
[Rh(nbd)Cl]2+6
55
75
105
105
130
55
22
9
5
5
4
32
12
7
7
6
78
99
99
15
100
96
98
94
90
99
99.9
99.5
99.5
98.2
98.0
99.8
99.7
99.6
99.8
96.8
92.3
77.3
69.7
85.8
52.1
92.6
87.0
76.5
87.2
57.0
75
105
105
135
a Reaction conditions: Rh/P/styrene=1/4/4000; 0.05 mol styrene; partial pressure of CO=partial pressure of H2=40 bar, solvent: toluene.
b (Mol of 8+mol of 9+mol of 10)/(initial mol of 7)×100.
c (Mol of 8+mol of 9)/(mol of 8+mol of 9+mol of 10)×100 (chemoselectivity towards aldehydes).
d Mol of 8/(mol of 8+mol of 9)×100 (regioselectivity towards branched aldehyde).
mation of branched and linear esters, respectively [33–
35]. Even if multidentate coordination takes place,
highly flexible chelates of various conformers are ex-
pected, which undergo a facile ‘arm-off’ dissociation of
one of the PPh2 moieties.
1H-, 13C-, and 31P-NMR spectra were obtained on a
Varian UNITY 300 spectrometer using CDCl3 solvent.
1H chemical shifts are reported relative to the residual
nondeuterated solvent of chloroform at 7.24 ppm. The
13C chemical shifts are given relative to CDCl3 at 77.0
ppm. The 31P-NMR data are referenced relative to
external H3PO4. FAB MS spectra were recorded on a
ZAB-2SEQ spectrometer. Elemental analysis were per-
formed on a 1108 Carlo Erba instrument. The product
distribution in catalytic experiment were determined
with a Hewlett Packard 5830A gas chromatograph
fitted with a capillary column coated with OV-1.
3. Experimental
3.1. Reagents
All reactions were performed under an argon atmo-
sphere, and in the preparations of 5 and 6, standard
Schlenk techniques were used. Chlorodiphenylphos-
phine was a Fluka product, and distilled immediately
prior to use. The catalytic precursors PtCl2(PhCN)2,
PdCl2(PhCN)2 and [Rh(nbd)Cl]2 were prepared as de-
scribed previously [36,37]. Solvents were dried by con-
ventional methods, and freshly distilled under argon
before use.
3.2. Synthesis of 5
Compound 3 (420 mg, 0.51 mmol) was dissolved in
dry THF (5 ml) under an inert atmosphere, and
pyridine (412 ml, 5.1 mmol) was added. The solution
was cooled to 0°C, and PPh2Cl (3.87 mmol, 695 ml) was
added dropwise. The reaction mixture was stirred for 1
h, and warmed to r.t. After filtration of the pyri-
dinium–chloride, the solvent was evaporated. The
residue was treated with toluene (6 ml) and addition of
hexane (7 ml) yielded a white precipitate which was
filtered off. The solvents were removed in vacuo to give
a white solid. This compound requires careful handling
since hydrolysis occurs readily.
Table 3
Hydroalkoxycarbonylation of styrene in the presence of palladiumn˜5
and palladium–6 systemsa
Catalyst
Alcohol R. time (h) Conv. (%)b Rbcr
(PdCl2)2(5)
(PdCl2)2(5)+2NaCl MeOH
(PdCl2)2(5)
MeOH
48
48
48
—
2
3
—
50.0
75.0
1H-NMR (300 MHz, CDCl3, 20°C): 0.99 (s, 36H,
C(CH3)3); 2.86 (d, J=13 Hz, 4H, Heq of ArCH2Ar);
3.99 (brs, 8H, ArOCH2); 4.10 (brs, 8H, CH2OPPh2);
4.25 (d, J=13 Hz, 4H, Hax of ArCH2Ar); 6.63 (s, 8H,
calixAr); 7.05–7.76 (m, 40H, PPh2); 13C-NMR (75
MHz, CDCl3, 20°C): 31.40 (C(CH3)3 overlapped with
ArCH2Ar); 33.66 (C(CH3)3); 69.51 (d, 3JPC=18 Hz;
tBuOH
PdCl2(PhCN)2+6
PdCl2(PhCN)2+6
PdCl2(PhCN)2+6
PdCl2(PhCN)2+6
MeOH
MeOH
tBuOH
tBuOH
48
140
48
39
62.3
54.5
48.6
47.2
68
42
70
140
a Reaction conditions: Pd/P/styrene/alcohol=l/2/2000/4000; 0.05 mol
styrene; pressure of CO=140 bar, R. temp.: 130°C; solvent: toluene.
b (Mol of 11+mol of 12)/(initial mol of 7)×100.
c Mol of 11/(mol of 11+mol of 12)×100 (regioselectivity towards
branched ester).
2
ArOCH2); 75.33 (d, JPC=8 Hz; CH2OPPh2); 124.56–
151.33 (aromatic C); 31P-NMR (121.4 MHz, CDCl3,
20°C): 113.78 (s, OPPh2); FAB MS: 1627 (oxidation
does occur); Analysis calculated for C100H108O8P4

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Z. Cso´k et al. / Journal of Organometallic Chemistry 570 (1998) 23–29
(M=1561.85): C, 76.90; H, 6.97; Found: C, 77.12; H,
6.68; yield: 76%.
was filtered and concentrated to ca. 3 cm3. Addition of
hexane (10 ml) afforded a yellow precipitate which was
filtered off.
3.3. Synthesis of 6
Selected NMR data: 1H-NMR (300 MHz, CDCl3,
20°C): 2.74 (d, J=13 Hz, 2H, Heq of ArCH2Ar); 3.02
(d, J=13 Hz, 2H, Heq of ArCH2Ar); 3.72 (d, J=13
Hz, 2H, Hax of ArCH2Ar); 4.72 (d, J=13 Hz, 2H, Hax
of ArCH2Ar); 13C-NMR (75 MHz, CDCl3, 20°C): 31.30
(C(CH3)3); 33.75 (C(CH3)3); 69.20 (ArOCH2); 73.50
(CH2OPPh2); 31P-NMR (121.4 MHz, CDCl3, 20°C):
A solution of 4 (720.3 mg, 0.5 mmol) in THF (5 ml)
was added dropwise to a stirred solution of LiPPh2 (4
mmol, prepared in situ from PPh2Cl and Li) in THF (5
ml) at 0°C under an inert atmosphere. The reaction
mixture was warmed to r.t., stirred for an additional 1
h, and deoxygenated water (10 ml) was added. The
THF was removed under reduced pressure (40 mmHg)
at 30–40°C, and chloroform (10 ml) was added. The
organic phase was evaporated to give a white foam
which was purified by column chromatography (Al2O3,
toluene).
112.7
(s,
PPh2);
Analysis
calculated
for
C100H108O8P4Pd2Cl4 (M=1916 50): C, 62.67; H, 5.68;
Cl, 7.40; Found: C, 62.88; H, 5.90; Cl, 7.51; yield: 91%.
3.6. Hydroformylation experiments
1H-NMR (300 MHz, CDCl3, 20°C): 1.03 (s, 36H,
C(CH3)3); 2.68 (t, J=8.2 Hz, 8H, CH2PPh2); 2.94 (d,
J=12.8 Hz, 4H, Heq of ArCH2Ar); 3.95 (brs, 8H,
OCH2); 4.21 (d, J=12.8 Hz, 4H, Hax of ArCH2Ar);
6.69 (s, 8H, calixAr); 7.10–7.60 (m, 40H, PPh2); 13C-
In a typical experiment a solution of 26.2 mg (0.0125
mmol) of (PtCl2)2(5) and 4.7 mg (0.025 mmol) of SnCl2
(or 5.8 mg (0.0125 mmol) [Rh(nbd)Cl]2 and 39 mg
(0.025 mmol) of 5) in 15 ml toluene containing 5.5 ml
(0.05 mol) of styrene was transferred under argon into
a 150 ml stainless steel autoclave. The reaction vessel
was pressurised to 80 bar total pressure (CO/H2=1/1)
and placed in an oil bath and the mixture stirred with
1
NMR (75 MHz, CDCl3, 20°C): 28.45 (d, JPC=13.2
Hz; CH2PPh2); 31.42 (C(CH3)3 overlapped with
2
ArCH2Ar); 33.81 (C(CH3)3); 71.37 (d, JPC=28.8 Hz;
OCH2); 124.94152.47 (aromatic C); 31P-NMR (121.4
MHz, CDCl3, 20°C): −22.99 (s, PPh2); FAB MS: 1562
(oxidation does occur); Analysis calculated for
a
magnetic stirrer. The pressure was monitored
throughout the reaction. After cooling and venting of
the autoclave, the pale yellow solution was immediately
analysed by GC.
C100H108O4P4 (M=1497.85): C, 80.19; H, 7.27; Found:
C, 80.53; H, 7.75; yield: 62%.
3.7. Hydrocarbalkoxylation experiments
3.4. Synthesis of (PtCl2)2(5)
In a typical experiment 24 mg (0.0125 mmol) of
(PdCl2)2(5) was placed under argon in a 150 ml stainless
steel autoclave first, then 5.5 ml (0.05 mol) styrene, 10
ml toluene, 4 ml (0.1 mol) methanol and a drop of cc.
hydrochloric acid were added. The reaction vessel was
pressurised to 140 bar CO pressure and placed in an oil
bath and the mixture stirred with a magnetic stirrer.
The pressure was monitored throughout the reaction.
After cooling and venting of the autoclave, the yellow
solution was immediately analysed by GC.
A solution of 5 (234 mg, 0.15 mmol) in THF (5 ml)
was slowly added to a solution of PtCl2(PhCN)2 (142
mg, 0.3 mmol) in THF (40 ml). After stirring 0.5 h, the
solution was reduced to ca. 3 cm3 and hexane (10 ml)
was added affording an ivory precipitate which was
filtered off.
Selected NMR data: 1H-NMR (300 MHz, CDCl3,
20°C): 2.75 (d, J=13 Hz, 2H, Heq of ArCH2Ar); 3.04
(d, J=13 Hz, 2H, Heq of ArCH2Ar); 3.75 (d, J=13
Hz, 2H, Hax of ArCH2Ar); 4.69 (d, J=13 Hz, 2H, Hax
of ArCH2Ar); 13C-NMR (75 MHz, CDCl3, 20°C): 31.32
(C(CH3)3); 33.81 (C(CH3)3); 69.27 (ArOCH2); 73.49
(CH2OPPh2); 31P-NMR (121.4 MHz, CDCl3, 20°C):
85.8 (s, PPh2); FAB MS: 1986 (M-3Cl)+; Analysis
calculated for C100H108O8P4Pt2Cl4 (M=2093.82): C,
57.36; H, 5.20; Cl, 6.77; Found: C, 57.08; H, 5.06; Cl,
7.15; m.p.: 250°C; yield: 85%.
Acknowledgements
The authors thank the Hungarian National Science
Foundation for financial support (OTKA T23525 and
T016260) and the Ministry of Education for grant
FKFP 0818.
3.5. Synthesis of (PdCl2)2(5)
References
A solution of 5 (234 mg, 0.15 mmol) in THF (5 ml)
was slowly added to a suspension of PdCl2(PhCN)2
(115 mg, 0.3 mmol) in THF (40 ml). The reaction
mixture turned yellow. After stirring 0.5 h, the solution
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