NMR and X-ray crystallographic studies of unsymmetrical 25,26;27,28-dibridged para-tert-butyl calix[4]arene bisphosphites with a large "through-space" P-P coupling

Article abstract of DOI:10.1039/b903771c

Three 25,26-bridged para-tert-butyl-calix[4]arene phosphites, 1-3, have been synthesized by linking two proximal phenolic oxygen atoms of para-tert-butyl-calix[4]arene to a P(OR) [R = 2,6-Bu^t ₂-4-Me-C₆H₂ (1), 2,

Full text of DOI:10.1039/b903771c

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
NMR and X-ray crystallographic studies of unsymmetrical
25,26;27,28-dibridged para-tert-butyl calix[4]arene bisphosphites
with a large ‘‘through-space’’ P–P couplingw
Pathik Maji, Setharampattu S. Krishnamurthy* and Munirathinam Nethaji
Received (in Gainesville, FL, USA) 24th February 2009, Accepted 7th May 2010
First published as an Advance Article on the web 4th June 2010
DOI: 10.1039/b903771c
Three 25,26-bridged para-tert-butyl-calix[4]arene phosphites, 1–3, have been synthesized by
linking two proximal phenolic oxygen atoms of para-tert-butyl-calix[4]arene to a P(OR)
[R = 2,6-But2–4-Me-C6H2 (1), 2,6-Pri2-C6H3 (2) or 2,4-But2-C6H3 (3)] moiety. NMR
spectroscopic data and X-ray crystallographic studies (1 and 2 only) show that the calixarene
framework in 1 adopts a cone conformation, whereas in 2 and 3 it assumes a partial cone
conformation. Unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites
5–7 have been synthesized by the reaction of 25,26-bridged para-tert-butyl-calix[4]arene phosphite
1 with (R0O)PCl2 [R0 = 2,4-But2-C6H3 (5), 2,6-Pri2-C6H3 (6) or (1R,2S,5R)-(ꢀ)menthyl (7)].
NMR investigations (homonuclear 31P COSY) revealed an unprecedented ‘‘through-space’’
phosphorus–phosphorus coupling of 223–244 Hz for these unsymmetrical 25,26;27,28-dibridged
para-tert-butyl-calix[4]arene bisphosphites. The molecular structure of unsymmetrical
25,26;27,28-bridged bisphosphite 5 was determined by X-ray crystallography; the two phosphorus
atoms are in close proximity and the Pꢁ ꢁ ꢁP distance (3.543(2) A) is less than the sum of their
van der Walls radii.
calix[4]arene phosphites of type B-1. A 25,26,27-bridged calix-
1. Introduction
[4]arene phosphite of type C, in which phosphorus(III) is
connected to three phenolic oxygen atoms at the lower rim,
was first reported by Lattman and co-workers.7 Subsequently,
several derivatives of this phosphite and their metal complexes
have been reported.8 The chemistry of calix[4]arene phos-
phates of types A, B and C has been reviewed by Gloede.9
Functionalization of calix[4]arenes by incorporating soft donor
phosphorus atom(s) and the transition metal chemistry of such
‘‘phospha-calixarenes’’ have been the subject of numerous
investigations during the last twenty years.1 Calix[4]arene
phosphites can be divided into three main categories (A, B
and C in Fig. 1), depending on whether one, two or three
phenolic oxygen atoms at the lower rim are connected to a
single phosphorus atom. Among these, by far the most widely
investigated are those belonging to type A.2–4 25,26;27,28-
Dibridged calix[4]arene bisphosphites of type B-2, in which
each of the adjacent pairs of phenolic oxygen atoms at the
lower rim are bonded to a phosphorus atom, were first
reported by Paciello et al.5 and Mahalakshmi et al.6 Paciello
et al. have shown that bisphosphites of type B-2 are good
catalysts for rhodium-catalyzed hydroformylation reactions.5
Mahalakshmi’s work involved the synthesis of a calix[4]arene
bisphosphite, in which two P(OC6H2-2,6-But2-4-Me) groups
were anchored at the lower rim, and its PdCl2 complex, which
underwent cyclometallation upon heating with the loss of a
tert-butyl group.6 There are no reports of 25,26-bridged
Department of Inorganic and Physical Chemistry,
Indian Institute of Science, Bangalore-560012Karnataka, India.
E-mail: sskrish@ipc.iisc.ernet.in; Fax: +91 80 2360 0683;
Tel: +91 80 2293 2401
w Electronic supplementary information (ESI) available: Further experi-
mental details and data. CCDC 695456, 695457 and 695459 contain the
supplementary crystallographic data for 25,26-bridged phosphites 1, 2
and unsymmetrical 25,26;27,28-dibridged bisphosphite 5, respectively.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b903771c
Fig. 1 Different types of calix[4]arene phosphites. For each type,
various conformations are possible; here only the cone conformations
are shown.
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
1478 | New J. Chem., 2010, 34, 1478–1486

View Article Online
As a part of our research program on calix[4]arene phosphites
and their transition metal chemistry,6,10,11 we report here
the synthesis and characterization of three 25,26-bridged
para-tert-butyl-calix[4]arene phosphites by linking two proximal
oxygen atoms of a calix[4]arene framework to a P(OR) moiety.
We also report the synthesis of unsymmetrical 25,26;27,28-
dibridged para-tert-butyl-calix[4]arene bisphosphites. The struc-
tures of these calix[4]arene mono- and bisphosphites have been
elucidated by NMR and X-ray crystallographic studies.
The 31P NMR chemical shifts for 25,26-bridged and
25,26,27-bridged para-tert-butyl calix[4]arene phosphites 1–4
are shown in Table 1. The 31P NMR chemical shift of 25,26-
bridged para-tert-butyl calix[4]arene phosphite 1 lies upfield to
that of the corresponding 25,26;27,28-dibridged para-tert-
butyl-calix[4]arene bisphosphite,6 but the chemical shifts for
the 25,26-bridged para-tert-butyl calix[4]arene phosphites 2
and 3 lie downfield to those of the corresponding 25,26;27,28-
dibridged bisphosphites.5,11
The 1H NMR spectra of 25,26-bridged para-tert-butyl
calix[4]arene phosphites 1–3 show two different peaks in the
tert-butyl region with a relative intensity of 1 : 1. The 1H NMR
spectrum of 1 shows one AX and two AB patterns of relative
intensity 2H : 4H : 2H for the methylene protons of the calixarene
framework. From the range of chemical shifts spanned by the
CH2 resonances (d 3.35–4.99) and our previous results,6,10c we
tentatively assign a cone conformation for 1 in solution. The
cone conformation in the solid state is revealed by X-ray
crystallography (see below). The 1H NMR spectrum of
25,26-bridged para-tert-butyl calix[4]arene phosphites 2 and
3 shows three distinct AB quartets of relative intensity
2H : 4H : 2H for the methylene protons of the calixarene
framework. The range of chemical shifts (d 3.39–4.79) is less
than that observed for 1. Also, the difference in chemical shift
of the pair of nuclei of one of the AB quartets is very small
(d 0.1–0.3), indicating that both 2 and 3 adopt a different
conformation compared to that of 1 in solution. An X-ray
crystallographic study of 2 revealed a partial cone conforma-
tion in the solid state (see below). If this conformation were to
be retained in solution, the 1H NMR spectrum of 2 and 3
should show four AB quartets. The observation of only three
AB quartets implies that the ArOH groups undergo fast
flipping through the cone conformation.
2. Results and discussion
2.1 The synthesis of 25,26-bridged and 25,26,27-bridged
calix[4]arene monophosphites and their NMR spectra
25,26-Bridged para-tert-butyl calix[4]arene phosphites 1–3
were synthesized in moderate yields by the 1 : 1 stoichiometric
reaction of the sodium salt of para-tert-butyl-calix[4]arene
with phosphorodichloridites (ROPCl2;
R =
2,6-But2-4-
Me-C6H2, 2,4-But2-C6H3 or 2,6-Pri2-C6H3), as shown in
Scheme 1. When the temperature of the reaction mixture
was raised to 95 1C, the major product was the 25,26,27-bridged
para-tert-butyl-calix[4]arene phosphite 4 in all the reactions.
Phosphite 4 is formed by cleavage of the P–OR bond with the
concomitant loss of phenol. Compound 4 was previously
synthesized by Lattman’s7 and Pringle’s research groups8a by
a different method. The yields of the isolated products are low
because of irreversible adsorption or decomposition during the
chromatographic separation process. These monophosphite
ligands are quite stable under an inert atmosphere for several
months. They are moisture sensitive and easily oxidized by
exposure to air and are moderately stable in dry methanol for
a few days.
Scheme 1 Synthesis of 25,26-bridged and 25,26,27-bridged para-tert-butyl calix[4]arene phosphites 1–4: (i) NaH, toluene, 85 1C, 3 h; (ii) ROPCl2,
70 1C, 2 h; (iii) ROPCl2, 70 1C, 1.5 h; (iv) ROPCl2, 95 1C, 4 h.
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 1478–1486 | 1479

View Article Online
Table 1 The 31P 1{H}NMRa data for 25,26-bridged calix[4]arene phosphites 1–3, 25,26,27-bridged phosphite 4 and unsymmetrical 25,26;27,28-
dibridged bisphosphites 5–7a
d
db
Unsymmetrical bisphosphite
nJP–P/Hz
PA
PB
Monophosphite
d
1
2
3
4
118.2
119.8
120.5
113.2
123.8
115.6
119.8
—
5
6
7
—
123.2 (d)
123.6 (d)
126.6 (d)
—
116.1 (d)
119.3 (d)
124.8 (d)
—
243.1
236.7
223.8
—
a
b
Recorded in CDCl3 at 25 1C and at 161.9 MHz; d in ppm. Chemical shift for symmetrical bisphosphites of respective 25,26-bridged phosphites.
The 1H and 31P NMR data for the 25,26,27-bridged
para-tert-butyl-calix[4]arene phosphite 4 agree well with those
reported previously.7 The 31P NMR chemical shift of phosphite
4 lies upfield compared to the chemical shifts of 25,26-bridged
phosphites 1–3 (see Table 1). The IR spectra of 25,26-bridged
and 25,26,27-bridged para-tert-butyl-calix[4]arene phosphites
phosphorus renders all the methylene protons non-equivalent.
Actually, four doublets are observed in the downfield region
(4.52–5.15 ppm) that arise from the equatorial protons
oriented away from the calix[4]arene cavity, whereas one
doublet and three overlapping doublets (3.24–3.85 ppm) are
observed for the axial methylene protons oriented towards the
calix[4]arene cavity.
1–4 display strong absorption bands at 3510–3520 cmꢀ1
,
typical of the presence of hydroxyl groups.
A remarkable feature of the 31P NMR spectra of unsymmetrical
25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites
5–7 is the observation of a very large (223–244 Hz) phosphorus–
phosphorus coupling (see Table 1). The existence of a large
coupling between the two magnetically non-equivalent
phosphorus nuclei could be established by 2D-homonuclear
31P COSY measurements. The homonuclear 31P COSY NMR
spectrum of 5 is shown in the ESI (Fig. S2).w The magnitude of
the observed large phosphorus–phosphorus coupling for the
unsymmetrical bisphosphites varies in the order 5 4 6 4 7
(see Table 1). Only limited data are available for long range
2.2 The synthesis of unsymmetrical 25,26;27,28-dibridged
calix[4]arene bisphosphites and their NMR spectra
Achiral and chiral unsymmetrical 25,26;27,28-dibridged
para-tert-butyl-calix[4]arene bisphosphites 5–7 were synthesized
by the reaction of achiral 25,26-bridged para-tert-butyl-calix[4]-
arene phosphite 1 with 2,4-di-tert-butyl-phenyl, 2,6-diiso-propyl-
phenyl or (1S,2R,5S)-(ꢀ)-menthyl phosphorodichloridites,
respectively, as shown in Scheme 2. Achiral 25,26-bridged
para-tert-butyl-calix[4]arene phosphite 1 was used as the starting
material for the synthesis of unsymmetrical 25,26;27,28-di-
bridged para-tert-butyl-calix[4]arene bisphosphites 5–7 because
the other two proximal hydroxyl groups are on the same side of
the calixarene core. Bisphosphites of the type 5–7 could not
be synthesized by starting from 25,26-bridged phosphites 2 or
3 because the two remaining hydroxyl groups are in a trans
orientation.
phosphorus–phosphorus coupling constants. A 7JP–P of 4.8 Hz
0
was observed for ZZ-Ph2PCH2C(t-Bu)QN–NQC(t-Bu)-
12
7
0
JP–P of 22.0 Hz has been reported for
CH2PPh2.
A
a 1,100-biferrocene derivative bearing –CHMe(PPh2) and
–CHMe{P(C6H4Me-4)2}groups.13 Pastor et al. have observed
7
8
0
0
JP–P and JP–P values of 30.3 and 30.6 Hz, respectively,
for sterically-congested biaryl bisoxazaphospholidines and
8
0
JP–P values of 27.5 and 72.8 Hz for sterically-congested
bisphosphites.14–16 A nine bond P–P coupling of 10.2 Hz
has been observed for a bis(diphenylphosphino)-b-cyclodextrin
derivative.17 More recently, Matt and co-workers have
reported a phosphorus–phosphorus coupling of 8.0 Hz
for a pendent calix[4]arene diphosphine with a ten bond
The 31P NMR spectra of the unsymmetrical 25,26;27,28-
dibridged para-tert-butyl-calix[4]arene bisphosphites 5–7 display
two doublets (AB pattern) (see the ESI, Fig. S1w). The
31P NMR chemical shifts are shown in Table 1. The chemical
shifts of the two phosphorus nuclei (PA and PB) are tentatively
assigned by comparing them to the 31P NMR chemical shifts
of the corresponding symmetrical 25,26;27,28-dibridged
para-tert-butyl-calix[4]arene bisphosphites5,6,10c,11 and 25,26-
bridged para-tert-butyl-calix[4]arene phosphites 1–3. A high
temperature 31P NMR experiment (toluene-d8, 90 1C) indicated
no change in the spectral pattern, and we conclude that
25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites
5–7 are conformationally rigid. The cone conformation of 5
in the solid state was confirmed by X-ray crystallography
Pꢁ ꢁ ꢁP separation.18 Large P–P coupling constants have been
19a,b
0
reported for 1,8-di(phosphinyl)naphthalene (JP–P = 221.6 Hz),
l,8-bis(diphenylphosphino)naphthalene (199 Hz)19c,d and
1-bis(dimethylamino)phosphinyl-8-[(dimethylamino)(methoxy)-
phosphinyl]naphthalene (246 Hz).20 To date, there has been no
report of large phosphorus–phosphorus coupling constants for
25,26;27,28-dibridged para-tert-butyl-calix[4]arene bisphosphites
such as the ones observed in this study.
Regarding the origin of the large P–P coupling observed for
25,26;27,28-dibridged para-tert-butyl calix[4]arene bisphosphites
5–7, the contribution from a ‘‘through-space’’ interaction would
be predominant as the contribution from the ‘‘through-bond’’
interaction should be small or negligible, as even for a con-
jugated system, such as the one in 2,6-bis(diethoxylphosphinoyl-
1
(see below). The H NMR spectra of achiral unsymmetrical
bisphosphites 5 and 6 show six doublets in the intensity ratio
1 : 1 : 2 : 1 : 1 : 2 (three doublets in the upfield region overlap
for bisphosphite 5) for the methylene protons of the calixarene
framework, as would be expected for a cone conformation.5,6,10c
Chiral unsymmetrical bisphosphite 7 would be expected
to show eight doublets (intensity ratio 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1)
because the chirality of the substituent attached to the
methyl)naphthalene, a 9JP–P of only 4.0 Hz has been reported.21
0
The large coupling arises because of through-space spin–spin
interactions mediated by the lone pairs of electrons residing on
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
1480 | New J. Chem., 2010, 34, 1478–1486

View Article Online
Scheme 2 Synthesis of unsymmetrical achiral and chiral 25,26;27,28-dibridged calix[4]arene bisphosphites 5–7: (i) 2,4-di-tert-butyl-phenyl-
phosphorodichloridite, THF, Et3N, 25 1C, 14 h; (ii) 2,6-diiso-propyl-phenyl-phosphorodichloridite, THF, Et3N, 25 1C, 12 h; (iii) (1R,2S,5R)-(ꢀ)
menthyl-phosphorodichloridites, THF, Et3N, 25 1C, 6 h.
the two phosphorus atoms. This lone pair overlap theory was
originally developed by Mallory et al. for through-space 19F–19F
couplings in organic compounds.22 Recently, this model has
been extended to through-space 31P–31P couplings in a ferro-
cenyl tetraphosphine ligand and its metal complexes.23 Evidently,
the two phosphorus atoms of unsymmetrical 25,26;27,28-
dibridged calix[4]arene bisphosphites 5–7 are brought into
close proximity because of the cone conformation (see section 3
below, dealing with the crystallographic studies).
The difference in conformation assumed by the calix[4]arene
core in phosphites 1 and 2 arises from the different steric bulk
of the alkyl groups at the ortho positions of the phenyl
substituent. The NMR data indicate that the conformation
observed in the solid state of calix[4]arene phosphites 1 and 2
are retained in solution.
We attempted to determine the structure of 25,26,27-
bridged para-tert-butyl-calix[4]arene phosphite 4 by X-ray
crystallography. The poor quality of the crystals resulted in
high R-factors and the structure is not of a publishable quality.
Nevertheless, from the gross connectivities, we can infer that
the calix[4]arene backbone adopts an ‘‘up–out–down–out’’
conformation,11 which is in between the conformation of the
corresponding para-H-calix[4]arene phosphate (up–up–out–down)
reported by Khasnis et al.8e and the para-tert-butyl-calix[4]-
arene phosphite derivative, in which the free hydroxyl group
was substituted by a –OCH2C6H5 group (up–up–out–up),
reported by Parlevliet et al.8c
3. X-Ray crystallographic studies
The solid-state structures of 25,26-bridged para-tert-butyl-
calix[4]arene phosphites 1 and 2 and unsymmetrical 25,26;27,28-
dibridged para-tert-butyl-calix[4]arene bisphosphite 5 were
determined by single crystal X-ray diffraction analysis. The
ORTEP plots of the molecular structures of 25,26-bridged
para-tert-butyl-calix[4]arene phosphites 1 and 2 are shown in
Fig. 2 and Fig. 3, respectively. Selected bond lengths and
angles are given in Table 2. The calix[4]arene framework in
phosphite 1 adopts a cone conformation (up–up–up–up),
whereas phosphite 2 shows a partial cone conformation
(up–up–up–down) for the calixarene core. Phosphite 1 has
crystallographically imposed mirror symmetry and the molecule
is inherently chiral.24,25 The unit cell contains four molecules
and there is an inversion centre. The molecular assembly thus
consists of a pair of enantiomers and the crystal is racemic.
The conformation of the calix[4]arene backbone of phosphites
1 and 2 can be defined in terms of torsion angles or dihedral
angles. The torsion angles are listed in Table 3 and Table 4 for
phosphites 1 and 2, respectively. An examination of the
torsion angles show the sequence of signs for f and w to be
+ ꢀ,+ ꢀ,+ ꢀ,+ ꢀ for phosphite 1 and + ꢀ,+ ꢀ,+ +,ꢀ ꢀ
for phosphite 2, as expected for cone and partial cone con-
formations, respectively. For phosphite 1, the torsion angles
differ significantly from the ideal cone conformation.26
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 1478–1486 | 1481

View Article Online
Table 2 Selected structural parameters for calix[4]arene phosphites 1
and 2, and unsymmetrical bisphosphite 5 (distances in A, angles in 1)
1a
2
5b
Bond distance
P(1)–O(1)
P(1)–O(2)
P(1)–O(3)
P(2)–O(4)
P(2)–O(5)
P(2)–O(6)
Bond angle
1.622(3)
1.655(3)
1.652(4)
1.607(4)
1.640(4)
1.637(4)
1.619(4)
1.649(4)
1.634(4)
1.621(4)
1.641(4)
O(1)–P(1)–O(2)
O(1)–P(1)–O(3)
O(2)–P(1)–O(3)
O(4)–P(2)–O(5)
O(4)–P(2)–O(6)
O(5)–P(2)–O(6)
101.2(1)
104.9(2)
102.0(2)
98.5(2)
100.6(2)
98.7(2)
100.7(2)
103.6(2)
100.2(2)
103.5(2)
97.5(2)
a
b
O(1)–P(1)–O(3) = O(1)–P(1)–O(1)0. P(1)ꢁ ꢁ ꢁP(2) = 3.543(2) A.
Table 3 Torsion angles to define the calixarene conformation in
phosphite 1
Torsion angle
f (1)
Torsion angle
w (1)
C6–C8–C9–C10
C3–C2–C1–C20
C50–C60–C80–C90
C12–C13–C15–C130
80.5(4)
92.2(5)
83.1(5)
87.6(5)
C5–C6–C8–C9
ꢀ83.1(4)
ꢀ92.2(5)
ꢀ80.5(4)
ꢀ87.6(5)
C30–C20–C1–C2
C60–C80–C90–C100
C120–C130–C15–C13
Fig. 2 An ORTEP plot of para-tert-butyl-calix[4]arene phosphite 1.
Thermal ellipsoids are drawn at the 50% probability level. The lattice-
held water molecule and hydrogen atoms are omitted for clarity.
Table 4 Torsion angles to define the calixarene conformation in
phosphite 2
Torsion angle
f (1)
Torsion angle
w (1)
C5–C6–C7–C80
C11–C12–C14–C15
C22–C21–C17–C18
C25–C26–C28–C2
84.4(6)
C6–C7–C8–C9
ꢀ120.8(5)
ꢀ55.0(6)
120.8(6)
ꢀ126.1(6)
112.3(5)
113.8(6)
ꢀ121.8(6)
C20–C15–C14–C12
C17–C21–C22–C23
C3–C2–C28–C26
atoms (X) and the plane of the aryl ring (D) (which contains
the hydroxyl group) for phosphite 2 indicates an inverted
orientation of this phenyl ring compared with the other three
phenyl rings (A, B and C), thus confirming the partial cone
conformation.
A perspective view of the molecular structure of unsymmetrical
25,26;27,28-dibridged bisphosphite 5 is shown in Fig. 4. The
calixarene framework adopts a cone conformation. The dihedral
angles and torsion angles are listed in Table 5 and Table 6,
respectively. These values indicate that the cone conformation
in 5 is more flattened than in phosphite 1. The important
finding from the crystallographic studies is that the non-
bonded Pꢁ ꢁ ꢁP distance is 3.543(2), which is less than the sum
of the van der Waals radii of the two phosphorus atoms
(3.67 A). Apparently, this rigid structure is retained in solu-
tion, providing a through-space pathway for the large Pꢁ ꢁ ꢁP
coupling.
Fig. 3 An ORTEP plot of para-tert-butyl-calix[4]arene phosphite 2.
Thermal ellipsoids are drawn at the 50% probability level. The
hydrogen atoms are omitted for clarity.
4. Conclusions
The dihedral angles of the calix[4]arene aryl rings (A, B, C
and D) with plane X of the four methylene carbon atoms of
phosphites 1 and 2 are listed in Table 5. The observed dihedral
angle (88.51) between the plane of the methylene carbon
The present study describes the synthesis of the first 25,26-
bridged calix[4]arene monophosphites, in which two neighbouring
phenoxy rings are linked by a P(OR) unit. These mono-
phosphites can adopt different conformations, depending on
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
1482 | New J. Chem., 2010, 34, 1478–1486

View Article Online
our previous publications.10 (1R,2S,5R)-(ꢀ)-Menthyl phospho-
rodichloridite was synthesized by a literature procedure.27
The syntheses of the other phosphorodichloridites (ROPCl2;
R = 2,6-But2-4-Me-C6H2, 2,4-But2-C6H3 and 2,6-Pri2-C6H3)
are given in the ESI.w
Synthesis of achiral 25,26-bridged para-tert-butyl-calix[4]arene
phosphite 1
Sodium hydride (60% dispersion in oil) (0.320 g, 8.0 ꢃ 10ꢀ3 mol)
was added to a stirred suspension of para-tert-butyl-calix[4]-
arene (2.46 g, 3.8 ꢃ 10ꢀ3 mol) in toluene (80 cm3) and the
mixture heated under reflux for 3 h at 85 1C. The suspension
was cooled to 0 1C and 2,6-di-tert-butyl-4-methyl-phenyl
phosphorodichloridite (1.24 g, 3.8 ꢃ 10ꢀ3 mol) added dropwise
in toluene (10 cm3). The reaction mixture was heated under
reflux at 70 1C for 2 h. During this time, the thick insoluble
suspension gradually dissolved to give a pale yellow solution
and a white precipitate. The precipitate was filtered off, the
solvent evaporated from the filtrate and the residue subjected
to column chromatographic separation over silica gel using
petroleum ether and EtOAc (200 : 4 v/v) to afford 25,26-bridged
para-tert-butyl-calix[4]arene 2,6-di-tert-butyl-4-methyl-phenyl
phosphite 1. Phosphite 1 was crystallized from dichloro-
methane : methanol (1 : 2) to obtain colorless crystals. Yield:
0.82 g (24%); m.p. = 282–289 1C. Anal. calc. for C59H77O5Pꢁ
H2O (mol. wt.: 915.19): C, 77.4; H, 8.7. Found: C, 77.8; H,
Fig. 4 An ORTEP plot of unsymmetrical para-tert-butyl-calix[4]-
arene bisphosphite 5. Thermal ellipsoids are drawn at the 50%
probability level. The hydrogen atoms are omitted for clarity.
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 phosphites 1 and 2, and unsymmetrical
bisphosphite 5
1
8.4%. H NMR (400 MHz, CDCl3) d = 1.08 (s, 18H, But),
Plane–plane
1
2
5
1.25 (s, 18H, But), 1.35 (s, 18H, But), 2.29 (s, 3H, Me), 3.35
(d, H, Hb1, J = 14.0 Hz), 3.44 (d, 2H, Hb2, J = 14.0 Hz), 3.73
(d, H, Hb3, J = 14.4 Hz), 3.92 (d, H, Ha3, J = 14.8 Hz), 4.29
(d, 2H, Ha2, J = 14.0 Hz), 4.99 (d, H, Ha1, J = 14.0 Hz), 5.15
(s, 2H, OH), 6.88 (s), 6.97 (s) (4H, calixarene aromatic protons),
7.03 (s, H, Ar), 7.05 (s, H, Ar), 7.10 (s), 7.15 (s) (4H, calixarene
aromatic protons).
A–X
B–X
C–X
D–X
61.5(1)
59.1(1)
61.5(1)
59.1(1)
27.4(2)
74.4(2)
81.4(1)
88.5(2)
33.8(1)
85.0(1)
37.4(1)
82.6(1)
a
A, B, C and D are the planes of the aromatic rings defined by
C9–C14, C2–C8, C9–C14 and C2–C8 for phosphite 1, C8–C13,
C1–C6, C22–C27 and C15–C20 for phosphite
C15–C19), (C27, C9–C13), (C26, C3–C7) and (C1, C21–C25) for
2 and (C28,
unsymmetrical bisphosphite 5, respectively.
Synthesis of 25,26-bridged para-tert-butyl-calix[4]arene
phosphites 2 and 3
25,26-Bridged para-tert-butyl-calix[4]arene phosphite 2 was
synthesized as described above for monophosphite 1 by the
reaction of para-tert-butyl-calix[4]arene (4.00 g, 6.2 ꢃ 10ꢀ3 mol)
in toluene (120 cm3) and NaH (60% dispersion in oil) (0.520 g,
13.0 ꢃ 10ꢀ3 mol) with (2,6-diiso-propyl-phenyl phosphoro-
dichloridite (1.73 gm, 6.2 ꢃ 10ꢀ3 mol). Phosphite 2 was
crystallized from dichloromethane : methanol (1 : 2) to obtain
colorless crystals. Yield: 1.48 g (28%); m.p. = 272–279 1C.
Anal. calc. for C56H71O5P (mol. wt.: 855.10): C, 78.6; H, 8.4.
Table 6 Torsion angles to define the calixarene conformation in
unsymmetrical bisphosphite 5
Torsion angle
f (1)
Torsion angle
w (1)
C24–C1–C2–C3
C6–C7–C8–C9
C12–C13–C14–C15
C18–C19–C20–C21
88.7(5)
94.3(5)
85.4(5)
100.0(5)
C1–C2–C3–C4
ꢀ121.6(5)
ꢀ49.9(5)
ꢀ124.8(5)
ꢀ53.6(5)
C7–C8–C9–C10
C13–C14–C15–C16
C19–C20–C21–C22
the steric bulk of the OR group. The isolation of these mono-
phosphites has enabled us to develop a strategy to synthesize
unsymmetrical 25,26;27,28-dibridged para-tert-butyl-calix[4]arene
bisphosphites. Unusually large through-space P–P coupling con-
stants (223–244 Hz) were observed for the unsymmetrical bis-
phosphites because of the close proximity of the two phosphorus
atoms, held together in a rigid calixarene framework.
1
Found: C, 78.7; H, 8.3%. H NMR (400 MHz, CDCl3) d =
1.05 (s, 18H, But), 1.06 (s, 6H, methyl of isopropyl), 1.23
(s, 6H, methyl of isopropyl), 1.27 (s, 18H, But), 3.23 (m, 2H,
methyne proton of isopropyl), 3.39 (d, H, Hb1, J = 12.8 Hz),
3.54 (d, 2H, Hb2, J = 12.6 Hz), [3.86 (AB quartet, H, Hb3, J =
14.4 Hz), 3.87 (AB quartet H, Ha3, J = 14.4 Hz], 4.25 (d, 2H,
Ha2, J = 14.0 Hz), 4.79 (d, H, Ha1, J = 14.0 Hz), 4.72 (s, 2H,
OH), 6.89 (s), 7.01 (s) (4H, calixarene aromatic protons), 7.05
(3H, m, Ar), 7.08 (s), 7.19 (s) (4H, calixarene aromatic protons).
para-tert-Butyl-calix[4]arene phosphite 3 was synthesized as
described above for phosphite 2 by the reaction of para-tert-
butyl-calix[4]arene (4 gm, 6.2 ꢃ 10ꢀ3 mol) in toluene (80 cm3)
5. Experimental section
The general experimental procedures, and details of the spectro-
scopic and other physical measurements, are as described in
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 1478–1486 | 1483

View Article Online
and NaH (60% dispersion in oil) (0.520 g, 13.0 ꢃ 10ꢀ3 mol)
with 2,4-di-tert-butyl-phenyl phosphorodichloridite (1.72 g,
6.2 ꢃ 10ꢀ3 mol). Yield: 1.36 g (25%); m.p. = 276–281 1C.
Anal. calc. for C58H75O5P (mol. wt.: 883.33): C, 78.8; H, 8.6.
solid. The mixture was then subjected to chromatographic
separation using petroleum ether : EtOAc (200 : 1 v/v) to afford
unsymmetrical and achiral 25,26;27,28-dibridged para-tert-
butyl-calix[4]arene bisphosphite (5). Bisphosphite 5 was crystal-
lized from dichloromethane : methanol (1 : 2) to obtain color-
less crystals. Yield: 1.13 g (20%); m.p. = 182–186 1C. Anal.
calc. for C73H96O6P2 (mol. wt.: 1131.44): C, 77.4; H, 8.5.
Found: C, 77.5; H, 8.0%. 1H NMR d = 1.10 (s, 9H, But),
1.13 (s, 18H, But), 1.17 (s, 18H, But), 1.27 (s, 9H, But), 1.32
(s, 18H, But), 2.26 (s, 3H, Me), 3.35 (d, 3H, Hb3 and Hb2, J =
14.0 Hz), 3.40 (d, H, Hb1, J = 13.6 Hz), 4.64 (d, H, Ha2,
J = 13.8 Hz), 4.75 (d, 2H, Ha3, J = 14.8 Hz), 5.14 (d, H, Ha1,
J = 14.2 Hz), 6.79 (s), 6.83 (s), 6.92 (s), 6.96 (s), 7.10 (s), 7.12
(s), 7.30 (s) (13H, aromatic protons and calixarene protons).
Unsymmetrical achiral para-tert-butyl-calix[4] arene bis-
phosphite 6 was synthesized as described above for bisphosphite
5. Bisphosphite 6 was crystallized from dichloromethane : methanol
1
Found: C, 79.1; H, 8.4%. H NMR (400 MHz, CDCl3) d =
1.10 (s, 18H, But), 1.14 (s, 9H, But), 1.23 (s, 9H, But), 1.27
(s, 18H, But), 3.32 (d, H, Hb1, J = 14.4 Hz), 3.57 (d, 2H, Hb2
,
J = 14.4 Hz), [3.82 (AB quartet, H, Hb3, J = 15.2 Hz), 3.86
(AB quartet, H, Ha3, J = 14.8 Hz)], 4.28 (d, 2H, Ha2, J =
14.6 Hz), 4.52 (d, H, Ha1, J = 14.6 Hz), (the OH peaks were not
resolved), 6.95 (s), 7.00 (s) (4H, calixarene aromatic protons),
7.05 (s), 7.09 (s, 3H, Ar), 7.16 (s), 7.24 (s) (4H, calixarene
aromatic protons).
Synthesis of 25,26,27-bridged para-tert-butyl-calix[4]arene
phosphite 4
Sodium hydride (60% dispersion in oil) (0.320 g, 8.0 ꢃ 10ꢀ3 mol)
was added to a stirred suspension of para-tert-butyl-calix[4]-
arene (2.5 gm, 3.8 ꢃ 10ꢀ3 mol) in toluene (80 cm3). The reaction
mixture was heated under reflux for 4 h at 85 1C. The suspen-
sion was cooled to 0 1C and 2,6-di-tert-butyl-4-methyl-phenyl
phosphorodichloridite (1.24 gm, 3.8 ꢃ 10ꢀ3 mol) was added
dropwise. The reaction mixture was heated under reflux at
95 1C for 4 h. During this time, the thick insoluble suspension
gradually dissolved to give a pale yellow solution and a white
precipitate. The precipitate was filtered off. The 31P NMR
spectrum of the reaction mixture showed the formation of two
products; two singlets were observed at 113.1 and 118.2 ppm,
corresponding to 25,26,27-bridged phosphite 4 and 25,26-
bridged phosphite 1, respectively. 25,26,27-Bridged phosphite
4 was the major product. The mixture was subjected to column
chromatographic separation over silica gel using EtOAc and
petroleum ether (200 : 4 v/v) to afford the less polar phosphite
4. 4 was also obtained when para-tert-butyl-calix[4]arene was
treated with 2,6-di-isopropyl-phenyl phosphorodichloridite or
2,4-di-tert-butyl-phenyl phosphorodichloridite in boiling toluene.
Phosphite 4 was crystallized from dichloromethane : methanol
(1 : 2) to obtain colorless crystals. Yield: 0.56 g (22%); m.p. =
308–314 1C. Anal. calc. for C44H53O4P (mol. wt.: 673.68): C,
(1 : 2) to obtain colorless crystals. Yield: 1.02
g (18%);
m.p. = 210–214 1C. Anal. calc. for C71H92O6P2 (mol. wt.:
1103.39): C, 77.2; H, 8.4. Found: C, 77.5, H, 8.3%. H NMR
1
d = 1.03 (s, 6H, Pri), 1.05 (s, 6H, Pri), 1.12 (s, 18H, But), 1.13
(s, 18H, But), 1.29 (s, 18H, But), 2.25 (s, 3H, Me), 3.15 (m, 2H,
methyne proton of isopropyl), 3.31 (d, 2H, Hb2, J = 14.6 Hz),
3.39 (d, H, Hb3, J = 14.4 Hz), 3.43 (d, H, Hb1, J = 11.8 Hz),
4.66 (d, 2H, Ha2, J = 13.6 Hz), 4.91 (d, H, Ha3, J = 16.2 Hz),
5.12 (d, H, Ha1, J = 14.2 Hz), 6.82 (s), 6.83 (s), 6.86 (s),
6.93 (s), 7.04 (s), 7.07 (s) (13H, aromatic protons and calixarene
protons).
Synthesis of unsymmetrical and chiral 25,26;27,28-dibridged
para-tert-butyl calix[4]arene bisphosphite 7
Chiral bisphosphite 7 was synthesized as described above
for bisphosphite 5 by the reaction of achiral para-tert-
butyl-calix[4]arene 25,26-bridged phosphite 1 (3.40 gm, 3.8 ꢃ
10ꢀ3 mol) with (1R,2S,5R)-(ꢀ)-menthyl phosphorodichloridite
(0.98 gm, 3.8 ꢃ 10ꢀ3 mol) in 60 cm3 THF in the presence of
triethylamine (1.21 g, 12 ꢃ 10ꢀ3 mol) for 6 h. Yield: 0.99 gm
(24%); m.p. = 173–177 1C; [a] = 90.21 (c 1.0, 25 1C, CHCl3).
Anal. calc. for C69H94O6P2 (mol. wt.: 1081.63): C, 76.6; H, 8.7.
Found: C, 76.1 H, 8.6%. 1H NMR d = 0.55 (d, 3H), 0.57
(d, 3H), 0.82 (d, 3H), 0.87–1.42 (m, 9H, menthyl group +
54H, But), 2.31 (s, 3H, Me), 3.24 (d, Hb3 and Hb4, J = 12.0 Hz),
3.26 (d, Hb2, J = 12.4 Hz), 3.38 (d, Hb1, J = 16.4 Hz), 3.98
(bs, H-methyne protons of the menthyl group), 4.52 (d, Ha4,
J = 10.8 Hz), 4.62 (d, Ha3, J = 12.4 Hz), 4.68 (d, Ha2, J =
14.4 Hz), 5.15 (d, Ha1, J = 16.4 Hz), 6.66 (s), 6.69 (d), 6.82 (s),
6.88 (s), 6.98 (s), 7.16 (s) (10H, aromatic protons and calixarene
protons).
1
78.4; H, 7.9. Found: C, 78.2; H, 7.6%. H NMR (400 MHz,
CDCl3) d = 1.19 (s, 9H, But), 1.30 (s, 9H, But), 1.38 (s, 18H,
But), 3.58 (d, 2H, Hb2, J = 14.8 Hz), 3.69 (d, 2H, Ha2, J =
16.8 Hz), 4.32 (d, 2H, Hb1, J = 16.8 Hz), 4.57 (d, 2H, Ha1, J =
14.8 Hz), (the OH peak was not resolved), 7.10 (s), 7.16 (s),
7.21 (s), 7.23 (s) (Ar, 8H, calixarene aromatic protons).
Synthesis of unsymmetrical and achiral 25,26;27,28-dibridged
para-tert-butyl-calix[4]arene bisphosphites 5 and 6
Triethylamine (1.52 g, 15 ꢃ 10ꢀ3 mol) was added to a stirred
suspension of achiral 25,26-bridged para-tert-butyl-calix[4]-
arene phosphite (1) (4.48 g, 5.0 ꢃ 10ꢀ3 mol) in 80 cm3 THF
and the reaction mixture stirred at room temperature for
15 min. The solution was cooled at 0 1C and 2,4-di-tert-
butyl-phenyl phosphorodichloridite (1.55 g, 5.0 ꢃ 10ꢀ3 mol)
was slowly added through a dropping funnel. The reaction
mixture was stirred at room temperature for 8 h. During this
time, a white precipitate was formed. The precipitate was filtered
off and the filtrate evaporated to obtain a yellowish-white foamy
X-Ray crystallography
X-Ray diffraction data were collected on a Bruker SMART
APEX CCD diffractometer. SMART27 software was used for
cell refinement and data acquisition, and SAINT28 software
was used for data reduction. An absorption correction was
made on the intensity data using the SADABS29 programme.
All the structures were solved using SHELXS30 and the
WinGX graphical user interface. Least-square refinements
were performed by the full-matrix method with SHELXL.31
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
1484 | New J. Chem., 2010, 34, 1478–1486

View Article Online
Table 7 Crystal data for 25,26-bridged calix[4]arene phosphites 1 and 2, and unsymmetrical 25,26;27,28-dibridged calix[4]arene bisphosphite 5
Empirical formula
C59H79O6P (1ꢁH2O)
C56H71O5P (2)
C73H96O6P2 (5)
Formula weight
Temperature/K
Wavelength/A
Crystal system
Space group
915.19
293(2)
0.71073
Monoclinic
I2/m
855.10
293(2)
0.71073
Monoclinic
P21/n
1131.44
293(2)
0.71073
Triclinic
ꢀ
P1
Unit cell dimensions
a = 14.929(3) A
b = 21.378(3) A
c = 18.173(2) A
a = g = 901
b = 108.9(1)1
a = 10.280(5) A
b = 27.784(5) A
c = 17.984(5) A
a = g = 901
b = 91.060(5)1
a = 13.678(2) A
b = 16.739(2) A
c = 19.432(2) A
a = 71.800(2)1
b = 78.874(2)1
g = 77.135(2)1
4083.7(8)
2
0.920
0.094
1224
Volume/A3
Z
5487.8(2)
4
1.108
0.097
1984
5136.0(3)
4
1.106
0.098
1848
Density (calc.)/Mg mꢀ3
Absorption coefficient/mmꢀ1
F(000)
Crystal size/mm
Theta range for data collection
Index ranges
0.48 ꢃ 0.36 ꢃ 0.30
1.52 to 24.99
ꢀ18 ( h ( 18
ꢀ26 ( h ( 26
ꢀ21 ( h ( 22
21140
5620
Rint = 0.0538
100
0.38 ꢃ 0.32 ꢃ 0.28
1.35 to 251
ꢀ12 ( h ( 12
ꢀ33 ( h ( 33
ꢀ21 ( h ( 21
36813
9034
Rint = 0.1786
99.8
0.48 ꢃ 0.42 ꢃ 0.34
1.78 to 251
ꢀ16 ( h ( 16
ꢀ19 ( h ( 19
ꢀ23 ( h ( 21
29696
Reflections collected
Independent reflections
14290
Rint = 0.0602
99.4
Empirical
Completeness to y (%)
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit
Empirical
0.9714 and 0.9549
Empirical
0.9730 and 0.9636
0.9688 and 0.9564
Full-matrix least-squares on F2 Full-matrix least-squares on F2 Full-matrix least-squares on F2
5620/0/330
1.277
9034/0/583
0.851
14290/6/732
0.763
Final R indices
R1 = 0.1067
wR2 = 0.3228
R1 = 0.1373
wR2 = 0.3451
R1 = 0.1108
wR2 = 0.2505
R1 = 0.2604
wR2 = 0.3289
0.622 and ꢀ0.550
—
R1 = 0.1151
wR2 = 0.3161
R1 = 0.2291
wR2 = 0.3908
0.977 and ꢀ0.387
—
[I 4 2s(I)]
R indices
(all data)
Largest differential peak and hole/e Aꢀ3 1.253 and ꢀ0.478
Absolute structure parameters
—
Details pertinent to the data collection, structure solution and
refinement are summarized in Table 7. The oxygen atom of the
solvent water molecule in compound 1 occupies a special
position; both site occupancy factor and thermal parameters
for this oxygen atom were refined alternately. The hydrogen
atoms attached to this oxygen atom were neither located nor
fixed. Some of the tert-butyl groups of compounds 2 and 5
were disordered and the hydrogen atoms of these disordered
groups were neither located nor fixed. PLATON checks for 5
showed that there is a very large solvent accessible void (1079
A3) centered at (0, 0.5, 0). The PLATON/SQUEEZE routine
was used to remove the contributions of any disordered
solvent molecules. The CIF format output from PLATON
(generated as platon.sqf) is appended to the CIF.
M. Burgard and J. M. C. R. Harrowfield, C. R. Acad. Sci., Ser.
IIc: Chim., 1998, 479–502; (c) I. Neda, T. Kaukorat and
R. Schmutzler, Main Group Chem. News, 1998, 6, 4–29;
(d) C. Jeunesse, D. Armspach and D. Matt, Chem. Commun.,
2005, 5603; (e) D. M. Homden and C. Redshaw, Chem. Rev., 2008,
108(12), 5086.
2 (a) C. Floriani, D. Jacoby, A. Chiesi-Villa and C. Guastini, Angew.
Chem., Int. Ed. Engl., 1989, 28, 1376; (b) J. K. Moran and
D. M. Roundhill, Inorg. Chem., 1992, 31, 4213; (c) D. Jacoby,
C. Floriani, A. Chiesi-Villa and C. Rizzoli, J. Chem. Soc., Dalton
Trans., 1993, 813; (d) W. Xu, R. J. Puddephatt, L. M. Muir,
K. W. Muir and C. S. Frampton, J. Inclusion Phenom. Mol.
Recognit. Chem., 1994, 19, 277; (e) I. Shevchenko, H. Zhang and
M. Lattman, Inorg. Chem., 1995, 34, 5405; (f) M. Stolmar,
C. Floriani, A. Chiesi-Villa and C. Rizzoli, Inorg. Chem., 1997,
36, 1694.
3 (a) C. Loeber, D. Matt, P. Briard and D. Grandjean, J. Chem. Soc.,
Dalton Trans., 1996, 513; (b) P. Faidherbe, C. Wieser-Jeunesis,
D. Matt, A. Harriman, A. D. Cian and J. Fischer, Eur. J. Inorg.
Chem., 1998, 451; (c) C. Jeunesse, C. Dieleman, S. Steyer and
D. Matt, J. Chem. Soc., Dalton Trans., 2001, 881; (d) S. Steyer,
C. Wieser-Jeunesse, J. Harrowfield and D. Matt, Dalton Trans.,
2005, 1301.
4 (a) B. R. Cameron, F. C. J. M. van Veggel and D. N. Reinhoudt,
J. Org. Chem., 1995, 60, 2802; (b) C. Kunze, D. Selent, I. Neda,
M. Freytag, P. G. Jones, R. Schmutzler, W. Baumann and
Acknowledgements
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
the IRHPA program. S. S. K. thanks the Indian National
Science Academy, New Delhi for a Senior Scientist position.
A. Borner, Z. Anorg. Allg. Chem., 2002, 628, 779.
¨
5 R. Paciello, L. Siggel and M. Roper, Angew. Chem., Int. Ed., 1999,
38, 1920.
6 L. Mahalakshmi, M. Nethaji and S. S. Krishnamurthy, Curr. Sci.,
2002, 83(7), 870.
References
7 D. V. Khasnis, M. Lattman and C. D. Gutsche, J. Am. Chem. Soc.,
1990, 112, 9422.
1 (a) C. Wieser, C. B. Dieleman and D. Matt, Coord. Chem. Rev.,
1997, 165, 93–161; (b) C. Jeunesse, D. Matt, M. R. Yaftian,
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 1478–1486 | 1485

View Article Online
8 (a) C. J. Cobley, D. D. Ellis, A. G. Orpen and P. G. Pringle, J. Chem.
Soc., Dalton Trans., 2000, 1101; (b) C. J. Cobley, D. D. Ellis,
A. G. Orpen and P. G. Pringle, J. Chem. Soc., Dalton Trans., 2000,
1109; (c) F. J. Parlevliet, C. Kiener, J. Fraanje, K. Goubitz,
M. Lutz, A. L. Spek, P. C. J. Kamer and P. W. N. M. van Leeuwen,
J. Chem. Soc., Dalton Trans., 2000, 1113; (d) S. Steyer, C. Jeunesse,
D. Matt, R. Walter and M. Wesolek, J. Chem. Soc., Dalton Trans.,
2002, 4264; (e) D. V. Khasnis, J. M. Burton, J. D. MeNeil,
C. J. Santini, H. Zhang and M. Lattman, Inorg. Chem., 1994, 33,
2657.
19 (a) T. Costa and H. Schmidbaur, Chem. Ber., 1982, 115, 1374;
(b) S. A. Reiter, S. D. Nogali, K. Karaghiosoff and H. Schmidbaur,
J. Am. Chem. Soc., 2004, 126, 15833; (c) A. Karac¸ ar,
H. Thonnessen, P. G. Jones, R. Bartsch and R. Schmutzler, Hetero-
¨
at. Chem., 1997, 8, 539; (d) R. D. Jackson, S. James, A. G. Orpen
and P. G. Pringle, J. Organomet. Chem., 1993, 458, C3.
20 P. Kilian, A. M. Z. Slawin and J. D. Woollins, Phosphorus, Sulfur
Silicon Relat. Elem., 2004, 179, 999.
21 L. Ernst, J. Chem. Soc., Chem. Commun., 1977, 375.
22 (a) F. B. Mallory, J. Am. Chem. Soc., 1973, 95, 7747;
(b) F. B. Mallory, C. W. Mallory, K. E. Butler, M. B. Lewis,
A. Q. Xia, E. D. Luzik, L. E. Fredenburgh, Jr.,
M. M. Ramanjulu, Q. N. Van, D. Francl, A. Freed, C. C. Wray,
C. Hann, M. Nerz-Stormes, P. J. Carroll and L. E. Chirlian, J. Am.
Chem. Soc., 2000, 122, 4108.
23 (a) J.-C. Hierso, A. Fihri, V. V. Ivanov, B. Hanquet, N. Pirio,
B. Donnadieu, B. Rebiere, R. Amardeil and P. Meunier, J. Am.
Chem. Soc., 2004, 126, 11077; (b) J.-C. Hierso, D. Evrard,
D. Lucas, P. Richard, H. Cattey, B. Hanquet and P. Meunier,
J. Organomet. Chem., 2008, 693, 574.
9 J. Gloede, Phosphorus, Sulfur Silicon Relat. Elem., 1997, 127,
97–111.
10 (a) A. Sarkar, M. Nethaji and S. S. Krishnamurthy, Polyhedron,
2007, 26, 3904; (b) A. Sarkar, M. Nethaji and S. S. Krishnamurthy,
J. Organomet. Chem., 2008, 693, 2097; (c) P. Maji,
S. S. Krishnamurthy and M. Nethaji, Polyhedron, 2008, 27(17),
3519; (d) A. Sarkar, S. S. Krishnamurthy and M. Nethaji, Tetra-
hedron, 2009, 65, 374.
11 P. Maji, Phosphite ligands based on the calyx[4]arene scaffold
and their palladium, platinum and rhodium complexes, PhD
Thesis, Indian Institute of Science, Bangalore, India, 2005.
12 S. D. Perera, B. L. Shaw, M. Thornton-Pett and J. D. Vessey,
Inorg. Chim. Acta, 1993, 207, 175.
24 K. Iwamoto, H. Shimizu, K. Araki and S. Shinkai, J. Am. Chem.
Soc., 1993, 115, 3997.
25 A. Ikeda and S. Shinkai, Chem. Rev., 1997, 97, 1713.
26 F. Ugozzoli and G. D. Andretti, J. Inclusion Phenom. Mol.
Recognit. Chem., 1992, 13, 337.
13 M. Sawamura, H. Hamashima, M. Sugawara, R. Kuwano and
Y. Ito, Organometallics, 1995, 14, 4549.
14 S. D. Pastor, J. L. Hyun, P. A. Odorisio and R. K. Rodebaugh,
J. Am. Chem. Soc., 1988, 110, 6547.
15 S. D. Pastor, S. P. Shum, R. K. Rodebaugh, A. D. Debellis and
F. H. Clarke, Helv. Chim. Acta, 1993, 76, 900.
27 J.-M. Brunel and G. Buono, J. Org. Chem., 1993, 58, 7313; Bruker
SMART, v. 6.028, Bruker AXS Inc., Madison, WI, USA, 1998.
28 Bruker SAINT, v. 6.02, Bruker AXS Inc., Madison, WI, USA, 1998.
29 G. M. Sheldrick, SADABS, Program for area detector adsorption
16 S. D. Pastor, S. P. Shum, A. D. DeBellis, L. P. Burke and
R. K. Rodebaugh, Inorg. Chem., 1996, 35, 949.
17 Y. T. Wong, C. Yang, K.-C. Ying and G. Jia, Organometallics,
2002, 21, 1782.
18 P. Kuhn, C. Jeunesse, D. Matt, J. Harrowfield and L. Ricard,
Dalton Trans., 2006, 3454.
correction, Institute for Inorganic Chemistry, University of Go
Germany, 1996.
30 G. M. Sheldrick, SHELXS-97, Program for the solution of crystal
structures, University of Gottingen, Germany, 1997.
¨
31 G. M. Sheldrick, SHELXL-97, Program for the refinement of
¨
ttingen,
crystal structures, University of Gottingen, Germany, 1997.
¨
ꢂc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
1486 | New J. Chem., 2010, 34, 1478–1486