Cyclometalated complexes derived from calix[4]arene bisphosphites and their catalytic applications in cross-coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2011.06.027

Palladium and platinum dichloride complexes of a series of symmetrically and unsymmetrically substituted 25,26;27,28-dibridged p-tert-butyl-calix[4]arene bisphosphites in which two proximal phenolic oxygen atoms of p-tert-butyl- or p-H-calix[4]arene are c

Full text of DOI:10.1016/j.jorganchem.2011.06.027

Journal of Organometallic Chemistry 696 (2011) 3169e3179
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Journal of Organometallic Chemistry
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Cyclometalated complexes derived from calix[4]arene bisphosphites and their
catalytic applications in cross-coupling reactions
*
Pathik Maji, Lepakshaiah Mahalakshmi, Setharampattu S. Krishnamurthy , Munirathinam Nethaji
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Palladium and platinum dichloride complexes of a series of symmetrically and unsymmetrically
substituted 25,26;27,28-dibridged p-tert-butyl-calix[4]arene bisphosphites in which two proximal
phenolic oxygen atoms of p-tert-butyl- or p-H-calix[4]arene are connected to a P(OR) (R ¼ substituted
phenyl) moiety have been synthesized. The palladium dichloride complexes of calix[4]arene
bisphosphites bearing sterically bulky aryl substituents undergo cyclometalation by CeC or CeH bond
scission. An example of cycloplatinated complex is also reported. The complexes have been
characterized by NMR spectroscopic and single crystal X-ray diffraction studies. During crystallization of
Received 29 March 2011
Received in revised form
23 June 2011
Accepted 23 June 2011
Keywords:
Calix[4]arene bisphosphites
Palladium and platinum dichloride
complexes
Cyclometalation
Heck and Suzuki coupling reactions
the palladium dichloride complex of
a symmetrically substituted calix[4]arene bisphosphite in
dichloromethane, insertion of oxygen occurs into the PdeP bond to give a P,O-coordinated palladium
dichloride complex. The calix[4]arene framework in these bisphosphites and their metal complexes
adopt distorted cone conformation; the cone conformation is more flattened in the metal complexes
than in the free calix[4]arene bisphosphites. Some of these cyclometalated complexes proved to be active
catalysts for Heck and Suzuki CeC cross-coupling reactions but, on an average, the yields are only
modest.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
[4]arene bisphosphites (L7eL9) [10] (Chart 1). In view of the
current interest in palladacycles as active catalysts for CeC bond-
Calixarenes constitute an important class of synthetic macro-
cycles which display remarkable features such as conformational
flexibility, presence of well-defined cavities, and ability to undergo
modifications at both upper and lower rims. Calixarene chemistry
has grown along several directions in recent years [1,2]. Particu-
larly striking are the developments in the transition metal chem-
istry of phosphorus(III) functionalized calix[4]arenes [3e9] and the
use of these phosphaecalixarene ligands in catalysis
[2a,3b,4d,4j,6b,7,8d]. A previous study in our laboratory has shown
that the palladium dichloride complex of p-tert-butyl-calix[4]
arene bisphosphite L1 readily undergoes cyclometalation by CeC
bond scission to give a palladacycle [5a]. In this paper, we elabo-
rate on this theme by reporting the synthesis of cyclometalated
complexes derived from palladium and platinum dichloride
complexes of a series of symmetrically substituted calix[4]arene
bisphosphites (L2eL6) and the unsymmetrically substituted calix
forming reactions [11,12], we also present here our preliminary
results on the use of the cyclometalated complexes of calix[4]
arene bisphosphites as catalysts for Suzuki- and Heck-type cross-
coupling reactions. The utility of bisphosphites of the type L1eL6 in
rhodium-catalyzed hydroformylation reactions has been reported
by Paciello et al [7].
* Corresponding author. Tel.: þ91 80 2293 2401; fax: þ91 80 2360 0683.
E-mail address: sskrish@ipc.iisc.ernet.in (S.S. Krishnamurthy).
Chart 1.
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.027

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P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
2. Results and discussion
mixture turned black indicating the decomposition of the complex
to palladium metal. The above reactions are shown in Scheme 1 (for
symmetrically substituted bisphosphites) and Schemes 2 and 3 (for
unsymmetrically substituted bisphosphites). The calixarene
bisphosphite L1, its palladium dichloride complex 1 and the cor-
responding cyclopalladated complex 7 previously reported from
our laboratory [5a] are also included in Scheme 1 for comparison.
The cyclometalated complexes 9a, 9b and 14 are formed by CeH
bond activation whereas the formation of the cyclometalated
complexes 8 and 15 must involve the loss of a tert-butyl group prior
to CeH activation as noted previously for complex 7 [5a].
2.1. Palladium and platinum complexes of symmetrically and
unsymmetrically substituted calix[4]arene bisphosphites
The symmetrically substituted calix[4]arene bisphosphites
L2eL5 react with 1 M equivalent of PdCl2(PhCN)2 or PdCl2(COD) in
toluene at 75 ꢀC to give the complexes 2, 3a, 4 and 5 respectively
which are isolated as pale yellow solids. The analogous dichloro
platinum complex 3b is isolated as a colourless solid from the
reaction of PtCl2(COD) with the symmetrically substituted calix[4]
arene bisphosphite L3.The symmetrically substituted calix[4]arene
bisphosphite L6 forms the dichloro palladium complex 6 at room
temperature. Similarly, the dichloro palladium complexes 11e13
are synthesized from the unsymmetrically substituted bisphos-
phites L7eL9. The dichloro palladium complexes 2, 3a, 11 and 12
and the dichloro platinum complex 3b are transformed into the
corresponding cyclometalated complexes 8, 9a, 9b, 14 and 15 when
heated in toluene at 95 ꢀC. These cyclometalated complexes are also
obtained directly from the reaction of PdCl2(PhCN)2 or PtCl2(COD)
with the respective calix[4]arene bisphosphite at 95 ꢀC. The
dichloro palladium complexes 4 and 13 do not undergo cyclo-
metalation reaction when heated at or above 95 ꢀC. The reaction
During crystallization of the palladium dichloride complex 1 in
dichloromethane, insertion of oxygen occurs into the PePd bond to
give the P,O-coordinated palladium dichloride complex 10 (Scheme
4). The structure of complex 10 has been established by X-ray crys-
tallography (see below). Mahalakshmi [13] had noted that the
oxidation of the bisphosphite L1 to the corresponding bisphosphate
by treatment with hydrogenperoxide was difficult but the oxidation
occurred readily with palladium acetate in dichloromethane in the
presence of atmospheric air to give the corresponding bisphosphate.
Presumably, the oxidation proceeds via the complex 10.
The 31P NMR data for the symmetrically substituted calix[4]
arene bisphosphites (L1eL6) and their palladium and platinum
R1
R1
R1
R1
L1- L6
O
O
O
O
(i)
R2
R2
P
P
M
O
O
Cl
Cl
R3
R4
R3
R4
(iii)
1-6
1
(M=Pd, R1 = But, R2, R3 = But, R4 = Me)
(M =Pd, R1 = H, R2, R3 = But, R4 = Me)
(ii)
2
3a (M= Pd, R1 = But, R2, R4 = But, R3 = H)
3b (M= Pt, R1 = But, R2, R4 = But, R3 = H)
R1
R1
O
R1
(M= Pd, R1 =But, R2, R3 = Pri, R4 = H)
(M= Pd, R1 = But, R2, R3 =Me, R4 = H)
(M= Pd, R1 =H, R2, R3 =Me, R4 = H)
R1
4
5
6
O
O
O
R2
P
P
O
M
O
R2
Cl
R4
R3
R4
7-9
7
(M=Pd, R1 = But, R2, R3 = But, R4 = Me)
(M=Pd, R1 = H, R2, R3 = But, R4 = Me)
8
9a (M =Pd, R1 = But, R2, R4 = But, R3 =H)
9b (M =Pt, R1 = But, R2, R4 = But, R3 = H)
Scheme 1. (i) PdCl2 (COD) or PtCl2 (COD) (ii) toluene, 95 ꢀC, 24 h, (iii) PdCl2 (PhCN)2 or PtCl2 (COD), toluene, 95 ꢀC, 24 h.

P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
3171
R1
R1
R1
R1
O
O
O
O
(i)
L7, L8
R2
P
R5
P
O
Pd
O
Cl
Cl
R7
R3
R4
R6
11, 12
(iii)
(ii)
11 (R1 =But, R2, R4, R5, R6 =But, R7=Me, R3=H)
12 (R1 =But, R2, R3 =But, R4 =Me, R5, R6 =Pri, R7=H)
R1
R1
R1
R1
O
O
O
O
R5
P
P
O
Pd
Cl
O
R2
R7
R6
R4
14, 15
14 (R1 = But, R2, R4, R5, R6 = But, R7 = Me)
15 (R1 = But, R2 = But, R4 = Me, R5, R6 = Pri, R7 = H)
Scheme 2. (i) PdCl2 (COD), toluene, 75 ꢀC, 24 h, (ii) toluene, 95 ꢀC, 24 h, (iii) PdCl2 (PhCN)2, toluene, 95 ꢀC, 24 h.
complexes are listed in Table 1. The data for the unsymmetrically
substituted calix[4]arene bisphosphites (L7eL9) and their palla-
dium complexes are given in Table 2. The 31P chemical shifts for
the symmetrically substituted bisphosphite palladium dichloride
complexes 1, 2, 3a, 4e6 and the platinum dichloride complex 3b lie
very much upfield to those of the free ligands (see Table 1). The cis
stereochemistry around the metal (Pd, Pt) centre is inferred from
the far IR spectrum which shows two
n
(M ꢁ Cl) bands in the range
312e328 cmꢁ1 for each of the complexes. The 1H NMR spectra of
these palladium and platinum dichloride complexes display four
doublets for the methylene protons of the calix[4]arene frame-
work as observed for the corresponding bisphosphites (see
Supplementary material).
The 31P NMR spectra of palladium dichloride complexes (11e13)
of unsymmetrically substituted calix[4]arene bisphosphites show
an AB pattern. The spectrum of 13 is illustrated in Fig. S1 (see
Supplementary material). For all the complexes, the downfield
resonance (PA) is assigned tentatively to P(OeC6H2etBu2eMe-
2,4,6) group and the upfield resonance (PB) to P(OeC6H3etBu2-
2,4),P(OeC6Hi3Pr2-2,6) or P(O-menthyl) group. These assignments
are based on the 31P chemical shifts for calix[4]arene bisphosphites
and monophosphites containing various substituted phenyl groups
[5a,e,10]. The 1H NMR spectrum of each these palladium dichloride
complexes (11e13) is similar to that of the respective calix[4]arene
bisphosphite L7, L8 or L9.
But
But
But
But
O
O
O
O
(i)
L9
But
P
Pr i
Me
P
Pd
O
O
Cl
Cl
But
Me
13
The 31P NMR spectra of the cyclometalated complexes 7e9, 14
and 15 show an AX pattern. The 31P NMR spectra of complexes 9a
and 9b are shown in Fig. 1. The phosphorus chemical shifts for the
Scheme 3. (i) PdCl2 (COD), toluene, 75 ꢀC, 24 h.

3172
P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
But
But
But
But
But
But
But
But
crystallization from
CH2Cl2 solution
O
O
O
O
O
O
O
O
O
But
But
PB
PA
"O2" (air)
P
But
But
P
O
O
Pd
O
Pd
O
Cl
But
Cl
Cl
Cl
But
But
Me
Me
1
But
Me
Me
O
10
Scheme 4.
cyclometalated complexes 7e9 lie considerably downfield to those
of the palladium and platinum dichloride complexes of symmetri-
cally substituted bisphosphites (see Table 1). For the cyclopalladated
complexes 8 and 9a, the doublet in the downfield region is assigned
to the phosphorus nucleus (Px) which is trans to the coordinated aryl
carbon atom; the doublet in the upfield region is assigned to the
phosphorus nucleus (PA) cis with respect to the coordinated aryl
carbon atom. For cycloplatinated complex 9b, the doublet (satellites
and 10 and the cyclopalladated complexes 9a and 14 have been
determined by single crystal X-ray diffraction analysis. Details
pertinent to data collection, structure solution and refinement are
summarized in Table 3.
The ORTEP plots of the molecular structures of symmetrically
substituted bisphosphites L1, L2 and L6 are shown in Figs. 2e4
respectively. Selected bond lengths and angles are given in
Table 4. The conformation of calix[4]arene backbone in these
phosphites can be described in terms of relevant dihedral angles or
torsion angles. The torsion angles involving the bridging methylene
carbon atoms and aryl ring carbon atoms are listed in Supple-
mentary material (Tables S1eS3). The torsion angles show the
1
195Pt, JPteP ¼ 3390 Hz) in the downfield region is assigned to the
phosphorus atom (Px) which is trans with respect to the coordinated
aryl carbon atom. The other doublet (satellites 195Pt,
1JPteP ¼ 6496 Hz) in the upfield region is assigned to the phosphorus
atom (PA) cis with respect to the coordinated aryl carbon atom. These
assignments are based on the phosphorus chemical shift values for
the methyl palladium chloro complexes of calix[4]arene bisphos-
phites [5e]. The 1H NMR spectra of cyclometalated complexes show
six doublets (three doublets in the downfield and other three
doublets in the upfield region) with coupling constants typical of
germinal protons. The formation of a 10-membered metallacycle in
addition to the two eight membered rings containing phosphorus, is
responsible for the nonequivalence of the methylene protons of the
calix[4]arene framework [5a] (see Supplementary material for
illustrative spectra).
sequence of signs for
expected for cone conformation. However, the values of the torsion
angles indicate that there is an appreciable deviation from the ideal
f
and
c
to be ꢂ, ꢂ, ꢂ, ꢂ for all bisphosphites as
cone conformation [
f
¼ 90ꢀ and
c
¼ ꢁ90ꢀ] [14]. The distortion from
the cone conformation is also reflected in the dihedral angles of the
calix[4]arene aryl rings {A, B, C and D (for L1; A ¼ A0, B ¼ B0)} with
the plane X of the four methylene carbon atoms {C1, C2, C10 and C20
for L1 and C1, C8, C14 and C20 for L2 and L6}, which are listed in
Table 5. The distortion from ideal cone conformation in these
bisphosphites is similar to that observed for calix[4]arene
bisphosphites and monophosphites [5c,10].
The 31P NMR spectrum of the palladium dichloride complex 10
shows two singlets at 74.4 (PA) and ꢁ6.8 (PB) ppm as the two
phosphorus are in two different oxidation states (III and V)
respectively. Because of the unsymmetrical nature, all the eight
methylene protons of the calix[4]arene framework are nonequiv-
alent (see Fig. S5 in Supplementary material).
The ORTEP plots of the molecular structures of palladium
dichloride complexes (4 and 10) are shown in Figs. 5 and 6
respectively. Selected bond lengths and bond angles are given
Table 6. The dihedral angles of the calix[4]arene aryl rings (A, B, C
and D) with the plane X of the methylene carbon atoms (C2, C8, C14
and C20) are listed in Table 7. The torsion angles are listed in
Supplementary material (Tables S4 and S5). The sequence of signs
for the two torsion angles
f and c confirms the cone conformation
2.2. X-ray crystallographic studies
of calix[4]arene framework. In these two palladium dichloride
complexes, the two aryl rings with larger torsion angles are parallel
to each other; the other two aryl rings with smaller torsion angles
The solid state structures of the symmetrically substituted
bisphosphites L1, L2 and L6, the palladium dichloride complexes 4
Table 1
The 31P{1H} NMR data for symmetrical bisphosphites (L1eL6) and transition metal complexes 1e9.a
Symmetrical bisphosphites
d
Dichloride complexes
d
Dd
Cyclometallated complexes
d
2JPeP (Hz)
L1
123.8
1
72.4
51.4
7
120.7(d)
78.1
103.6(d)
121.3(d)
101.6(d)
119.8(d)
L2
L3
123.1
115.6
2
69.2
72.9
52.6
53.9
46.9
63.0
8
78.9
81.3
42.1
3a
3b
9a
9b
106.9(d)
114.2(d) (1JPteP ¼ 3390 Hz),
94.8 (d) (1JPteP ¼ 6496 Hz)
bL4
bL5
L6
119.8
118.8
117.9
4
5
6
71.5
70.7
70.1
48.3
48.1
47.8
a
Recorded in CDCl3 at 25 ꢀC and at 161.9 MHz,
Data from Ref. [10].
d
in ppm, Dd ¼ (dligand
ꢁ
dcomplex) in ppm.
b

P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
3173
Table 2
The 31P{1H} NMR data for unsymmetrical bisphosphites (L7eL9) and transition metal complexes 11e15.a
Unsymmetrical
Bisphosphitesb
d
8JPeP (Hz)
Dichloride
complexes
d
2JPeP (Hz)
Cyclometallated
complexes
d
2JPeP (Hz)
PA
PB
PA
PB
PA
PB
L7
L8
L9
123.2(d),
123.6(d),
126.6(d),
116.1(d)
119.3(d)
124.8(d)
243.1
236.7
223.8
11
12
13
73.0(d),
73.1(d),
81.3(bs),
70.8(d)
70.7(d)
70.3(d)
71.3
72.9
66.4
14
15
121.4(d),
120.9(d),
103.6(d)
106.3(d)
78.9
74.5
a
Recorded in CDCl3 at 25 ꢀC and at 161.9 MHz,
Data from Ref [10].
d in ppm.
b
are tilted from the mean plane X of the methylene carbon atoms.
This type of conformation is known as “flattened cone conforma-
tion” [14]. The OePeO bond angles around phosphorus of the
phosphate group in palladium dichloride complex 10 are larger
than the OePeO bond angles around the phosphorus of the
phosphite group in the same complex 10 or complex 4. The PeO
bond distance (1.478 Å) of the phosphate group in which the
oxygen is coordinated to palladium is longer than that observed for
the corresponding p-tert-butyl-calix[4]arene bisphosphate ligand
(1.448 Å) [13] whereas the other PeO bond distances are shorter.
The ORTEP plot of the molecular structure of the cyclopalladated
complexes 9a and 14 are shown in Figs. 7 and 8 respectively. Selected
bondlengthsandbondanglesforcomplexes9aand14 andtherelated
cyclopalladated complex 7, previously reported [5a] are listed in
Table 8. The metrical data for the three cyclopalladated complexes 9a,
14 and 7 are comparable. The calix[4]arene framework in the cyclo-
palladated complexes 9a, 14 and 7 adopts a distorted cone confor-
mation similar to that observed in the palladium dichloride
complexes 4 and 10. The distortion from cone conformation for
complex 9a is more than that observed for complexes 14 and 7 as can
be inferred from the relevant dihedral angles (listed in Table 9) and
torsion angles (see Supplementary material Tables S6 and S7 for
complexes 9a and 14 respectively). This is also reflected in the larger
separation of the two opposite para-carbon atoms [C(11)eC(23)] in
complexes 9a and 14 (distance 10.09 Å and 9.67 Å respectively)
compared to the analogous separation (9.44 Å) in complex 7 [5a].
The square planar coordination environment of the palladium
atom in the complexes 4, 10, 7, 9a and 14 shows a pronounced
tetrahedral distortion. This distortion is the largest for complex 4
(the P1Pd1P2/Cl1Pd1Cl2 dihedral angle 15.50ꢀ) and is the least for
the complex 10 (O4Pd1P2/Cl2Pd1Cl2 6.20ꢀ); the cyclopalladated
complexes 9a, 14 and 7 display intermediate level of distortion
(P1Pd1P2/Cl1Pd1C34 8.37ꢀ, P1Pd1P2/Cl1Pd1C34 9.33ꢀ and P1Pd1P2/
Cl1Pd1C36 8.80ꢀ respectively). The tetrahedral distortion in complex
4 is higher than that (8.4e14.80ꢀ) observed in many palladacycles
derived from sterically congested phosphites [15]. These data
suggest that the relief of steric strain is the driving force for
cyclometalation observed for the complexes 1e3, 11 and 12.
2.3. Palladium catalyzed Heck coupling reaction
The palladium catalyzed Heck coupling reaction between
styrene and aryl halides (X ¼ Br, I) was investigated using
cyclopalladated complexes 7, 8, 9a (derived from symmetrically
substituted bisphosphites), 14 and 15 (derived from unsymmet-
rically substituted bisphosphites) as catalysts (see Scheme 5). In
all the Heck reactions, only a single product (trans-stilbene) was
obtained. The cis isomer or any other by-product was not formed
as shown by thin layer chromatography and the 1H NMR spec-
trum of the isolated product. The yields (%) of the product with
different aryl halides and the turn-over-numbers (TONs) are
shown in Table 10. The cyclopalladated complex 7, which is
derived from a sterically bulky p-tert-butyl bisphosphite L1, is the
most effective catalyst among the cyclopalladated calix[4]arene
bisphosphite complexes reported in this study. However, these
cyclopalladated calix[4]arene bisphosphite complexes are less
effective catalysts compared to other reported cyclopalladated
complexes [16].
2.4. Palladium and platinum catalyzed Suzuki coupling reaction
Preliminary studies on Suzuki coupling reaction between phenyl
boronic acid and aryl halides or substituted aryl halides (X ¼ H, Me,
OMe; Y ¼ I, Br, Cl) in the presence of cyclopalladated complexes 7, 8,
Fig. 1. The 31P NMR spectra of cyclopalladated complex 9a and cycloplatinated complex 9b respectively.

Table 3
Crystal data for symmetrically substituted bisphosphites (L1, L2, L6), palladium dichloride complexes 4, 10 and cyclopalladated complexes 9a, 14.
Empirical formula
Formula weight
Temperature
C78H120O13P2 (L1)
1327.72
293(2) K
C59H68Cl2O6P2 (L2)
1005.97
293(2) K
C44H38O6P2 (L6)
724.68
293(2) K
C68H86Cl2O6P2 Pd1 (4)
1238.61
293(2) K
C74H102Cl2O9P2Pd1 (10)
1374.80
293(2) K
C72H93Cl1O6P2Pd1 (9a)
1258.25
293(2) K
C80H107Cl1O8P2Pd1 (14)
1400.45
293(2) K
Wavelength
0.71070 Å
0.71073 Å
0.71073 Å
0.71073 Å
0.71073 Å
0.71073 Å
0.71073 Å
Crystal system
Space group
Unit cell dimensions
Monoclinic
C2/c
Triclinic
P ꢁ 1
Monoclinic
P2/n
Monoclinic
C2/c
Monoclinic
C2/c
Trigonal
R-3
Monoclinic
P2/c
A ¼ 23.551(5) Å
b ¼ 17.508(7) Å
c ¼ 19.299(5) Å
a ¼ 12.411(5) Å
b ¼ 13.624(6) Å
c ¼ 18.195(8) Å
a ¼ 13.374(2) Å
b ¼ 18.593(3) Å
c ¼ 14.827(2) Å
a ¼ 52.034(5) Å
b ¼ 19.831(2) Å
c ¼ 15.137(1) Å
a ¼ 24.406(7) Å
b ¼ 17.723(5) Å
c ¼ 39.158(1) Å
a ¼ 37.92(2) Å
b ¼ 37.92(2) Å
c ¼ 29.84(3) Å
a ¼ 17.335(5) Å
b ¼ 18.386(5) Å
c ¼ 28.672(5) Å
a
b
¼
g
¼ 90.00(2)ꢀ,
a
b
g
¼ 102.174(7)ꢀ,
¼ 91.731(8)ꢀ,
¼ 111.907(7)ꢀ
a
b
¼
g
¼ 90ꢀ,
a
b
¼
g
¼ 90.00ꢀ,
a
b
¼
g
¼ 90.00ꢀ,
a
b
¼
g
¼ 90.00ꢀ,
a
b
¼
g
¼ 90.00ꢀ,
¼ 102.35(2)ꢀ
¼ 102.304(6)ꢀ
¼ 105.655(2)ꢀ
¼ 98.888(5)ꢀ
¼ 120ꢀ
¼ 106.84ꢀ
Volume
Z
Density (calculated)
Absorption coefficient
F (000)
7774(4) Å3
4
2770(2) Å3
2
3602.2(10) Å3
4
15040(2) Å3
8
16735(8) Å3
8
37147(6) Å3
18
8746(4) Å3
4
1.102 Mg/m3
0.112 mmꢁ1
2768
1.206 Mg/m3
0.223 mmꢁ1
1068
1.336 Mg/m3
0.172 mmꢁ1
1520
1.094 Mg/m3
0.402 mmꢁ1
5216
1.091 Mg/m3
0.370 mmꢁ1
5824
1.102 Mg/m3
0.336 mmꢁ1
11988
1.064 Mg/m3
0.325 mmꢁ1
2976
Crystal size (mm)
Theta range for
data collection
Index ranges
0.14 ꢃ 0.08 ꢃ 0.12
0.38 ꢃ 0.32 ꢃ 0.28
0.46 ꢃ 0.38 ꢃ 0.32
0.48 ꢃ 0.38 ꢃ 0.03
0.56 ꢃ 0.42 ꢃ 0.36
0.42 ꢃ 0.36 ꢃ 0.28
0.64 ꢃ 0.32 ꢃ 0.24
1.70e24.97ꢀ
1.66e26.50ꢀ
2.50e26.50ꢀ
1.59e24.71ꢀ
1.43e25ꢀ
2.50e27.50ꢀ
2.50e27ꢀ
0 ꢄ h ꢄ 27
ꢁ16 ꢄ h ꢄ 16
ꢁ17 ꢄ h ꢄ 17
ꢁ23 ꢄ h ꢄ 22
29546
ꢁ17 ꢄ h ꢄ 15
ꢁ23 ꢄ h ꢄ 23
ꢁ17 ꢄ h ꢄ 19
28286
ꢁ61 ꢄ h ꢄ 58
ꢁ23 ꢄ h ꢄ 22
ꢁ17 ꢄ h ꢄ 17
53094
ꢁ26 ꢄ h ꢄ 28
ꢁ21 ꢄ h ꢄ 21
ꢁ44 ꢄ h ꢄ 46
59210
ꢁ43 ꢄ ꢄ h ꢄ 45
ꢁ45 ꢄ h ꢄ 45
ꢁ35 ꢄ h ꢄ 32
78747
ꢁ20 ꢄ h ꢄ ꢄ 13
ꢁ21 ꢄ h ꢄ 21
ꢁ34 ꢄ h ꢄ 34
80035
0 ꢄ h ꢄ 20
ꢁ22 ꢄ h ꢄ 22
Reflections collected
6761
Independent reflections
6538 [R(int) ¼ 0.0707]
97.3%
11672 [R(int) ¼ 0.0660]
7562[R(int) ¼ 0.0829]
12829 [R(int) ¼ 0.0915]
14728[R(int) ¼ 0.2445]
14792 [R(int) ¼ 0.0994]
15411 [R(int) ¼ 0.1133]
Completeness to
q
90.9%
92.1%
100.0%
100.0%
97.9%
100%
Absorption correction
Max. and
Empirical
0.9714 and 0.9549
Empirical
0.9401 and 0.9200
Empirical
0.9472 and 0.9253
Empirical
0.9980 and 0.8303
Empirical
0.8783 and 0.8195
Empirical
0.9117 and 0.8186
Empirical
0.9261 and 0.8190
min. transmission
Refinement method
Full-matrix-least-squares Full-matrix-least-squares Full-matrix-least-squares Full-matrix-least-squares Full-matrix-least-squares Full-matrix-least-squares Full-matrix-least-squares
on F2
on F2
on F2
on F2
on F2
on F2
on F2
Data/restraints/parameters 6538/0/403
11672/0/636
0.764
7562/7/473
1.035
12829/0/732
1.050
14728/7/813
0.976
14792/2/763
0.846
15411/3/829
1.152
Goodness-of-fit
Final R indices
[I > 2sigma(I)]
R indices (all data)
0.832
R1 ¼ 0.0968,
wR2 ¼ 0.2360
R1 ¼ 0.2239,
wR2 ¼ 0.3547
0.584 and ꢁ0.471 e Åꢁ3
R1 ¼ 0.0678,
wR2 ¼ 0.1897
R1 ¼ 0.1303,
wR2 ¼ 0.2440
0.475 and ꢁ0.445 e Åꢁ3
R1 ¼ 0.1317,
wR2 ¼ 0.2714
R1 ¼ 0.2095,
wR2 ¼ 0.3154
0.503 and ꢁ0.309 e Åꢁ3
R1 ¼ 0.0955,
wR2 ¼ 0.2604
R1 ¼ 0.1357,
wR2 ¼ 0.2885
2.523 and ꢁ1.013 e Åꢁ3
R1 ¼ 0.1078,
wR2 ¼ 0.2719
R1 ¼ 0.2766,
wR2 ¼ 0.3249
1.224 and ꢁ0.443 e Åꢁ3
R1 ¼ 0.0560,
wR2 ¼ 0.1649
R1 ¼ 0.1117,
wR2 ¼ 0.1883
0.873 and ꢁ0.470 e Åꢁ3
R1 ¼ 0.1053,
wR2 ¼ 0.3067
R1 ¼ 0.1841,
wR2 ¼ 0.3506
2.409 and ꢁ0.649 e Åꢁ3
Largest diff. peak
and hole

P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
3175
Fig. 4. ORTEP plot of p-H-calix[4]arene bisphosphite L6. Thermal ellipsoids are drawn
at the 50% probability level. Hydrogen atoms are omitted for clarity.
Fig. 2. ORTEP plot of p-tert-butyl-calix[4]arene bisphosphite L1. Thermal ellipsoids are
drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.
Table 4
Selected structural parameters for symmetrically substituted bisphosphites L1, L2
6
and L (distances in Å, angles in ꢀ).
9a (derived from symmetrically substituted calix[4]arene
bisphosphites), 14 and 15 (derived from unsymmetrically
substituted calix[4]arene bisphosphites) and cycloplatinated
complex 9b (derived from symmetrically substituted calix[4]arene
bisphosphite) as catalysts have been carried out (see Scheme 6).
The results are summarized in Table 11. The highest activity was
observed when the concentration of the catalysts was 3 mol%.
Among all the palladium catalysts, cyclopalladated complex 7
proved to be the best palladium precursor (Table 11 entries 1, 6, 12,
17 and 22) and cyclopalladated complex 8 proved to be a poor
L1
L2
L6
Bond distance
P(1)eO(1)
P(1)eO(2)
P(1)eO(3)
P(2)eO(4)
P(2)eO(5)
P(2)eO(6)
1.619 (5)
1.608 (5)
1.645 (5)
1.634 (3)
1.628 (5)
1.625 (4)
1.647 (5)
1.629 (5)
1.623 (5)
1.626 (5)
1.631 (2)
1.652 (2)
1.637 (2)
1.638 (2)
1.649 (2)
P(1)/P(2)
Bond angle
3.323 (2)
3.398 (3)
O(1)eP(1)eO(2)
O(1)eP(1)eO(3)
O(2)eP(1)eO(3)
O(4)eP(2)eO(5)
O(4)eP(2)eO(6)
O(5)eP(2)eO(6)
101.4 (3)
101.3 (2)
103.8 (3)
99.61 (1)
100.59 (1)
104.34 (1)
99.29 (1)
100.89 (1)
103.77 (1)
99.8 (2)
102.2 (2)
100.1 (2)
100.0 (2)
102.0 (2)
99.5 (2)
palladium precursor (Table 11 entries 2, 8, 13, 18 and 23). The fact
that complex 8 shows the lowest activity indicates that the
bisphosphite ligand containing p-H-calix[4]arene backbone is more
p-acidic than the corresponding p-tert-butyl derivative and
presumably the oxidative-addition step in the catalytic cycle is
retarded. Since the palladium centre of cyclopalladated complexes
Table 5
Dihedral angles between the planesa of the aryl rings of the calix[4]arene framework
and the mean plane (X) defined by the methylene carbon atoms in bisphosphites L1,
L2 and L6.
Dihedral angles (ꢀ)
Planeeplane
L1
L2
L6
AeX
BeX
CeX
DeX
51.4 (1)
65.4 (1)
51.4 (1)
65.4 (1)
38.08 (1)
81.09 (1)
36.40 (1)
80.66 (1)
11.67 (2)
76.44 (2)
11.82 (2)
74.07 (2)
a
A, B, C and D are the planes of aromatic rings defined by C1eC6, C8eC13,
C15eC20, C22eC27 for bisphosphite L1; (C28, C15eC19), (C26, C3eC7), (C1,
C21eC25), (C27, C9eC13) respectively for bisphosphites L2 and L6.
Fig. 3. ORTEP plot of p-H-calix[4]arene bisphosphite L2. Thermal ellipsoids are drawn
at the 50% probability level. Hydrogen atoms are omitted for clarity.

3176
P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
Table 6
Selected structural parameters for PdCl2 complexes 4 and 10 (distances in Å, angles
in ꢀ).
Bond distance
4
10
Bond angle
4
10
P(1)ePd(1)
P(2)ePd(1)
Cl(1)ePd(1)
Cl(2)ePd(1)
P(1)eO(1)
P(1)eO(2)
P(1)eO(3)
P(2)eO(4)
P(2)eO(5)
P(2)eO(6)
O(4)ePd(1)
P(1)eO(4)
P(2)eO(7)
2.243 (2)
e
P(2)ePd(1)eP(1)
92.33 (7)
e
2.209 (2) 2.210 (3) P(2)ePd(1)eCl(2) 84.74 (8) 84.14 (1)
2.293 (2) 2.323 (4) P(1)ePd(1)eCl(1) 92.17 (9)
2.334 (2) 2.257 (4) Cl(2)ePd(1)eCl(1) 91.60 (9) 90.72 (2)
1.590 (6) 1.570 (8) O(3)eP(1)eO(1)
1.595 (6) 1.563 (8) O(3)eP(1)eO(2)
1.565 (5) 1.542 (8) O(1)eP(1)eO(2)
e
103.4 (3) 103.3 (4)
103.4 (3) 111.7 (4)
101.8 (3) 105.5 (4)
1.593 (5)
e
O(3)eP(1)ePd(1) 120.1 (2)
e
e
e
1.580 (5) 1.564 (8) O(1)eP(1)ePd(1) 105.0 (2)
1.573 (5) 1.575 (8) O(2)eP(1)ePd(1) 120.4 (2)
e
e
e
2.092 (8) O(6)eP(2)eO(5)
1.478 (8) O(6)eP(2)eO(4)
1.614 (8) O(5)eP(2)eO(4)
101.4 (3) 101.3 (4)
102.7 (3)
103.3 (3)
e
e
O(6)eP(2)ePd(1) 121.2 (2) 108.9 (3)
O(5)eP(2)ePd(1) 112.6 (2) 118.2 (3)
O(4)eP(2)ePd(1) 113.6 (2)
e
O(7)eP(2)ePd(1)
O(4)ePd(1)eP(2)
O(4)ePd(1)eCl(1)
O(4)eP(1)eO(3)
O(4)eP(1)eO(2)
O(4)eP(1)eO(1)
e
e
e
e
e
e
116.6 (3)
94.7 (2)
90.7 (3)
114.0 (4)
111.6 (4)
110.2 (4)
Fig. 5. ORTEP plot of palladium chloride complex 4. Thermal ellipsoids are drawn at
the 50% probability level. Hydrogen atoms are omitted for clarity.
9a, 14 and 15 is more electron rich than that of the cyclopalladated
complex 7, it would be expected that the rate of oxidative-addition
would be higher, but the increased electron density at the palla-
dium does not appear to be beneficial. This result suggests that the
rate-determining step is probably not oxidative addition but
nucleophilic attack of base-activated boronate or reductive elimi-
nation of the biaryl product. Hence cyclopalladated complex 7
seems to have about the right balance of electronic and steric
properties as catalyst for Suzuki coupling reaction. When the
catalyst concentration of 7 was reduced to 1 mol%, the yield of the
product decreased (Table 11, entry 7). The yield of particular biaryl
using phenyl chloride as a starting substrate and cyclopalladated
complexes 7, 8, 9a, 14 and 15 respectively as catalysts (Table 11,
entries 12, 13, 14, 15 and 16), is very poor compared with other aryl
halides. Results of comparative studies of the activity of the
Table 7
Dihedral angles between the planesa of the aryl rings of the calix[4]arene framework
and the mean plane (X) defined by the methylene carbon atoms in palladium
dichloride complexes 4and 10.
Dihedral angles (ꢀ)
Planeeplane
4
10
AeX
BeX
CeX
DeX
83.3 (1)
34.4 (1)
84.8 (2)
29.4 (2)
87.6 (4)
40.7 (3)
79.8 (3)
37.4 (3)
a
A, B, C and D are the planes of aromatic rings defined by the set of carbon atoms
(C28, C15eC19), (C26, C3eC7), (C1, C21eC25), (C27, C9eC13) respectively.
Fig. 6. ORTEP plot of palladium chloride complex 10. Thermal ellipsoids are drawn at
the 50% probability level. Solvent molecules and hydrogen atoms are omitted for
clarity.
Fig. 7. ORTEP plot of cyclopalladated complex 9a. Thermal ellipsoids are drawn at the
50% probability level. Hydrogen atoms are omitted for clarity.

P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
3177
Table 9
Dihedral angles between the planesc of the aryl rings of the calix[4]arene framework
and the mean plane (X) defined by the methylene carbon atoms cyclopalladated
complexes 9a, 14 and 7.
Dihedral angles (ꢀ)
Planeeplane
9a
14
7
AeX
BeX
CeX
DeX
83.0 (1)
34.0 (1)
81.8 (2)
32.5 (1)
71.2 (2)
36.4 (2)
66.7 (2)
41.5 (2)
71.1 (2)
37.1 (2)
65.7 (2)
45.9 (2)
c
A, B, C and D are the planes of aromatic rings defined (C28, C15eC19), (C26,
C3eC7), (C1, C21eC25), (C27, C9eC13) and C1eC6, C8eC13, C15eC16 (Ref. [5a]) for
cyclopalladated complexes 9a, 14 and 7 respectively.
x
x = Br, I
1,4 Dioxane, K2CO3, NBu4Br
Pd complex Catalysts
H
C
C
+
H
trans stilbene
CH2
CH
Fig. 8. ORTEP plot of cyclopalladated complex 14. Thermal ellipsoids are drawn at the
50% probability level. Solvent molecules and hydrogen atoms are omitted for clarity.
Scheme 5.
cyclopalladated and cycloplatinated complexes 9a and 9b in Suzuki
coupling of aryl halides (X ¼ H, Me, OMe; Y ¼ I, Br, Cl) with phenyl
boronic acid are shown in Table 12. The cycloplatinated complex 9b
proved to be a better catalyst. Overall, the catalytic activities of the
cyclometalated complexes (7, 8, 9a, 9b, 14, 15) in Suzuki coupling
reactions are comparable with those reported for other metal-
lacyclic catalysts [17]. Further studies are required to assess the
specific beneficial role, if any, of the calixarene framework in
catalysis.
modified to prepare the other symmetrically substituted calix[4]
arene bisphosphites (L2-L6) by the reaction p-tert-butyl-calix[4]
arene or p-H-calix[4]arene with substituted phenyl phosphorodi-
chloridites, ROPCl2 (R ¼ 2,6-tBu2e4-MeeC6H2, 2,4-tBu2eC6H3,
2,6-iPr2eC6H3 or 2,6-MeeC6H3). The synthesis of unsymmetrically
substituted calix[4]arene bisphosphites L7eL9 has been described
previously [10]. The palladium and platinum dichloride
complexes and the cyclometalated complexes (2e15) were
prepared by the reaction of the respective bisphosphite with
PdCl2(PhCN)2, PdCl2(COD) or PtCl2(COD). The preparative details
and characterization data can be found in Supplementary material.
3. Experimental
The general experimental procedures and details of spectroscopic
measurements are as described in our previous publications [5,10].
3.2. Catalytic studies
3.1. Synthesis of ligands and complexes
The Heck coupling reactions were carried out in a sealed tube at
110ꢀ C using K2CO3 as the base, 1,4-dioxane as the solvent and
NBu4Br as the co-catalyst under argon atmosphere. Halobenzene
(2 ꢃ 10ꢁ3 mol), styrene (4 ꢃ 10ꢁ3 mol), K2CO3 (3 ꢃ 10ꢁ3 mol),
The synthetic method reported by Mahalakshmi et al. [5a] for
the symmetrically substituted calix[4]arene bisphosphite L1 was
Table 8
Selected structural parameters for cyclopalladated complexes 9a, 14 and 7 (distances in Å, angles in ꢀ).a
Bond distance
9a
14
7
Bond angle
9a
14
7
P(1)ePd(1)
P(2)ePd(1)
Cl(1)ePd(1)
C(34)ePd(1)
P(1)eO(1)
P(1)eO(2)
P(1)eO(3)
P(2)eO(4)
P(2)eO(5)
P(2)eO(6)
P(1)eO(6)
P(2)eO(1)
2.173 (2)
2.317 (3)
2.348 (2)
2.070 (5)
1.592 (3)
1.578 (3)
1.597 (3)
1.615 (3)
1.598 (3)
1.593 (3)
e
2.172 (2)
2.334 (2)
2.315 (3)
2.065 (8)
1.581 (6)
1.586 (5)
1.606 (6)
1.594 (5)
1.600 (5)
1.596 (5)
e
2.165 (2)
2.340 (2)
2.319 (2)
2.064 (8)
e
P(2)ePd(1)eP(1)
P(2)ePd(1)eCl(1)
P(1)ePd(1)eC(34)
C(34)ePd(1)eCl(1)
O(3)eP(1)eO(1)
O(3)eP(1)eO(2)
O(1)eP(1)eO(2)
O(3)eP(1)ePd(1)
O(1)eP(1)ePd(1)
O(2)eP(1)ePd(1)
O(6)eP(2)eO(5)
O(6)eP(2)eO(4)
O(5)eP(2)eO(4)
O(6)eP(2)ePd(1)
O(5)eP(2)ePd(1)
O(4)eP(2)ePd(1)
92.11 (6)
93.32 (7)
79.7 (1)
91.15 (8)
95.92 (9)
81.2 (2)
91.6 (8)
96.4 (8)
79.7 (3)
92.5 (3)
e
94.4 (1)
91.6 (2)
102.9 (2)
108.5 (2)
102.2 (2)
109.1 (1)
122.7 (1)
110.4 (1)
99.2 (2)
106.1 (2)
101.9 (2)
123.3 (1)
112.2 (1)
111.5 (1)
106.0 (3)
103.7 (3)
102.4 (3)
108.5 (2)
115.0 (2)
119.9 (2)
102.9 (3)
106.4 (3)
101.9 (3)
125.6 (2)
109.2 (2)
108.3 (2)
1.590 (6)
1.580 (6)
1.590 (5)
1.592 (6)
e
101.8 (3)
e
110.1 (2)
e
121.6(2)
e
1.592 (6)
1.602 (6)
e
e
e
102.0 (3)
e
126.0 (2)
112.7 (2)
a
C(34) ¼ C(36) for complex 7.

3178
P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
Table 10
Table 12
Results of Heck coupling of aryl halides (X ¼ Br, I) with styrene in presence of
Comparison of the results of Suzuki coupling of aryl halides (X ¼ H, Me, OMe; Y ¼ I,
Br, Cl) with phenyl boronic acid in the presence of cyclopalladated complex 9a and
cycloplatinated complex 9b as catalysts.
cyclopalladated complexes 7e9, 14, 15.
Catalyst
Substrate
Base
Time (h)
Yield (%)
TON
Entry Substrate Temp. Time (h) Base
Catalyst (mol) Yield (%) TON
7
8
9a
14
15
7
PhI
PhI
PhI
PhI
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
20
20
20
20
20
24
24
24
24
24
30
24
28
9
27
24
16
18
22
20
3000
2400
2800
2900
2700
2400
1600
1800
2200
2000
1
C6H5I
100 ꢀC 20
K3PO4 9a (0.03)
80
64
58
88
76
67
43
51
9
2672
2
20
9a (0.01)
9a (0.005)
9b (0.03)
9b (0.01)
9b (0.005)
6400
11600
2933
7600
13400
4300
5100
900
3
20
PhI
4
20
PhBr
PhBr
PhBr
PhBr
PhBr
5
6
7
8
20
20
8
9a
14
15
C6H5Br
C6H5Cl
100 ꢀC 20
20
K3PO4 9b (0.01)
9b (0.01)
K3PO4 9a (0.01)
9b (0.01)
K3PO4 9a (0.01)
9b (0.01)
K3PO4 9a (0.01)
9b (0.01)
9
100 ꢀC 24
24
10
11
12
13
14
12
40
53
36
47
1200
4000
5300
3600
4700
4-Mee
C6H4Br
100 ꢀC 20
20
4-MeOe 100 ꢀC 20
C6H4Br
20
Y
X
K3PO4, toluene, 100 0C
Pd or Pt complex
+
X
column chromatography using petroleum ether/chloroform (100:
5 v/v) as eluant. Each reaction was performed at least twice. The
percentage of conversion was calculated on the basis of isolated
yields after column chromatographic purification of the product.
The product was exclusively trans- stilbene as identified by 1H NMR
spectroscopy.
B(OH)2
catalyst
X = H, Me, OMe
X = H, Me, OMe
Y = I, Br, Cl
The Suzuki coupling reactions were carried out using hal-
obenzene or substituted halobenzene, phenyl boronic acid, K3PO4
(ratio 1:1.5:2 respectively) and cyclometalated palladium complex
or platinum complex (3e0.5 mol%) in toluene (4 ml). The reaction
mixture was heated under reflux with stirring at 100 ꢀC for
20e24 h. The reaction mixture was cooled, solvent evaporated and
the residue extracted with diethyl ether to give the crude product,
which was purified by column chromatography using petroleum
ether/chloroform (100: 5 v/v) as eluant. The reactions were per-
formed at least twice and the percentage of conversion was
calculated on the basis of isolated yields, after column chromato-
graphic purification of the product. Suzuki coupling product was
characterized by 1H NMR spectroscopy by comparing its 1H NMR
resonance with that reported for the known compound.
Scheme 6.
cyclometalated palladium complexes (2 mol%) and NBu4Br
(3 ꢃ 10ꢁ3 mol) in 1,4-dioxane (5 ml) were transferred to a tube
(25 ml), fitted with a Teflon cap. The tube was evacuated and
flushed with argon gas. The reaction mixture was heated under
reflux with stirring at 110 ꢀC for 20e24 h. The reaction mixture was
then cooled, solvent evaporated and the residue extracted with
diethyl ether to give the crude product, which was purified by
Table 11
Suzuki coupling of aryl halides (X ¼ H, Me, OMe; Y ¼ I, Br, Cl) with phenyl boronic
acid in the presence of various cyclopalladated complexes 7e9, 14, 15.
3.3. X-ray crystallography
Entry Substrate
Temp.
Time Base
(h)
Catalyst
(mol)
Yield TON
(%)
X-ray diffraction data were collected on a Bruker SMART APEX
CCD diffractometer. The SMART [18] software was used for cell
refinement and data acquisition and the SAINT [19] software used
for data reduction. An absorption correction was made on the
intensity data using SADABS [20] program. The structures were
solved using SHELXS [21] and the WinGX graphical user interface.
Least square refinements were performed by the full-matrix
method with SHELXL [22]. Some of the tert-butyl groups were
disordered and hydrogen atoms of these disordered groups were
neither located nor fixed during the refinement.
1
2
3
4
5
6
7
8
C6H5I
100 ꢀC 20
K3PO4 7 (0.03)
8 (0.03)
89
62
2967
2067
2667
2800
2600
2833
7100
1800
2200
2367
2100
567
20
20
20
20
9a (0.03) 80
14 (0.03) 84
15 (0.03) 78
C6H5Br
100 ꢀC 20
K3PO4 7 (0.03)
85
71
54
20
20
20
20
7 (0.01)
8 (0.03)
9a (0.03) 66
14 (0.03) 71
15 (0.03) 63
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
20
C6H5Cl
100 ꢀC 24
K3PO4 7 (0.03)
8 (0.03)
17
7
24
24
24
24
233
500
533
433
Acknowledgements
9a (0.03) 15
14 (0.03) 16
15 (0.03) 13
We thank the Department of Science and Technology, New
Delhi, India for financial support and also for data collection using
the CCD X-ray facility at IISc, Bangalore set up under IRHPA
program. S.S.K. thanks Indian National Science Academy, New Delhi
for a Senior Scientist position.
4-MeeC6H4Br
100 ꢀC 20
K3PO4 7 (0.03)
8 (0.03)
68
42
2267
1400
1800
1933
1700
2100
1200
1567
1800
1567
20
20
20
20
9a (0.03) 54
14 (0.03) 58
15 (0.03) 51
4-MeOeC6H4Br 100 ꢀC 20
K3PO4 7 (0.03)
8 (0.03)
63
36
20
20
20
20
AppendixA. Supplementary material
9a (0.03) 47
14 (0.03) 54
15 (0.03) 47
CCDC 133304 and 772145-772150 contain the supplementary
crystallographic data for symmetrically substituted bisphosphites

P. Maji et al. / Journal of Organometallic Chemistry 696 (2011) 3169e3179
3179
(L1, L2 and L6), palladium dichloride complexes 4, 10 and cyclo-
palladated complexes 9a, 14. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
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