Calix[4]arene derived phosphites: Their hydrolytic stability and complexes with gold(I), platinum(II,0), palladium(II) and iridium(I)

Article abstract of DOI:10.1039/a908960h

Improved syntheses of the monophosphites L_a and L_b derived from calix[4]arene and p-tert-butylcalix[4]arene respectively are reported. Both L_a and L_b are thermally stable and air stable even in refluxing toluene; moreover they are not hydrolysed by aqueous HC1 or NaOH. The two-coordinate gold(i) complexes [AuCl(L_a)] and [AuCl(L_b)] are readily made from [AuCl(tht)](tht = tetrahydrothiophene). Treatment of K[PtCl₃(C₂H₄)] with L_a gives the mononuclear cis-[PtCl₂(L_a)₂] whereas L_b gives the binuclear trans-[Pt₂Cl₂(μ-Cl)₂(L_b) ₂]. The platinum(O) complexes [Pt(L)-(nor)₂] and [Pt(L)₂(nor)](L = L_a or L_b, nor = norbornene) have been characterised in solution by ³¹P and ¹⁹⁵Pt NMR spectroscopy. Treatment of [PdCl₂(NCPh)₂] with L_a gives a poorly soluble complex assigned the structure [PdCI₂(L_a)₂]. Treatment of [PdCl₂(NCPh)₂] with L_b gives the binuclear [Pd₂Cl₂(μ-Cl)₂(L_b)₂] which reacts with Y to give bridge-cleaved products [PdCl₂(Y)(L_a)](Y = CO, CNBu_t or CNMe). The iridium complexes [IrCl(L_a)(cod)] and [IrCI(L_b)(cod)] are made by the additions of L_a or L_b to [Ir₂(μ-Cl)₂(cod)₂]. The crystal structures of [Pt₂Q₂-(μ-Cl)₂(L_b)₂], [Pd₂Cl₂(μ-Cl)₂(L_b)₂], [PdCl₂(CNBu_t)(L_b)] and [IrCI(L_a)(cod)] have been determined. The calixarene conformation in all cases has arenes in {down, out, up, up} orientations with one aryl blocking an axial site at the square planar metal. The cone angles are 160° for L_x and 176° for L_b. The bulkiness of the ligand is such as to preclude octahedral geometry at the metal. The trans influence of the ligands La and Lb appear to be greater than either chloride or isocyanide. The P-O distances and the O-P-O angles imply that L_a and L_x are less π-acidic than most triarylphosphite ligands. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/a908960h

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Calix[4]arene derived phosphites: their hydrolytic stability and
complexes with gold(I), platinum(II,0), palladium(II) and iridium(I)
Christopher J. Cobley, Dianne D. Ellis, A. Guy Orpen and Paul G. Pringle*
School of Chemistry, University of Bristol, Cantock’s Close, Bristol, UK BS8 1TS
Received 11th November 1999, Accepted 1st February 2000
Improved syntheses of the monophosphites La and Lb derived from calix[4]arene and p-tert-butylcalix[4]arene
respectively are reported. Both La and Lb are thermally stable and air stable even in refluxing toluene; moreover
they are not hydrolysed by aqueous HCl or NaOH. The two-coordinate gold() complexes [AuCl(La)] and [AuCl(Lb)]
are readily made from [AuCl(tht)] (tht = tetrahydrothiophene). Treatment of K[PtCl3(C2H4)] with La gives the mono-
nuclear cis-[PtCl2(La)2] whereas Lb gives the binuclear trans-[Pt2Cl2(µ-Cl)2(Lb)2]. The platinum(0) complexes [Pt(L)-
(nor)2] and [Pt(L)2(nor)] (L = La or Lb, nor = norbornene) have been characterised in solution by 31P and 195Pt
NMR spectroscopy. Treatment of [PdCl2(NCPh)2] with La gives a poorly soluble complex assigned the structure
[PdCl2(La)2]. Treatment of [PdCl2(NCPh)2] with Lb gives the binuclear [Pd2Cl2(µ-Cl)2(Lb)2] which reacts with Y to
give bridge-cleaved products [PdCl2(Y)(Lb)] (Y = CO, CNBut or CNMe). The iridium complexes [IrCl(La)(cod)]
and [IrCl(Lb)(cod)] are made by the additions of La or Lb to [Ir2(µ-Cl)2(cod)2]. The crystal structures of [Pt2Cl2-
(µ-Cl)2(Lb)2], [Pd2Cl2(µ-Cl)2(Lb)2], [PdCl2(CNBut)(Lb)] and [IrCl(La)(cod)] have been determined. The calixarene
conformation in all cases has arenes in {down, out, up, up} orientations with one aryl blocking an axial site at the
square planar metal. The cone angles are 160Њ for La and 176Њ for Lb. The bulkiness of the ligand is such as to
preclude octahedral geometry at the metal. The trans influence of the ligands La and Lb appear to be greater than
either chloride or isocyanide. The P–O distances and the O–P–O angles imply that La and Lb are less π-acidic than
most triarylphosphite ligands.
the slow addition of CF3CO2H to a stirred solution of the six-
coordinate phosphorus() precursor 1b gave Lb along with ca.
Introduction
The susceptibility of phosphites to hydrolysis1 limits their
10% of an impurity identified as a phosphonate from its charac-
application as ligands for homogeneous catalysis.2,3 Cyclic
teristic doublet in the 31P NMR spectrum at δ ϩ2.1 with 1J(PH)
phosphites, particularly those derived from biphenols or
806 Hz and assigned structure 2b; this assignment is further
binaphthols, are kinetically relatively stable to hydrolysis3 and
1
supported by the observation of three AB patterns in the H
are important ligands for hydroformylation,4,5 hydrocyan-
NMR spectrum (δ 3.5–4.5) in the intensity ratio 1:2:1 for the
benzylic CH2 which is consistent with 1,2-isomer 2b. Sub-
sequent purification gave pure Lb in multigram quantities. The
ation,3,6 and other catalyses.7
The fused tricyclic monophosphites La and Lb derived from
calix[4]arenes were reported by Lattman et al.8 and attracted
partial cone conformation of the calixarene phosphites is
our attention because they should be highly kinetically stabil-
deduced from 1H and 13C NMR in solution11 and X-ray crystal-
ised to hydrolysis and therefore potentially useful for catalysis.
lography (see below).
Lattman et al.9 also reported the iron(0) complex [Fe(CO)4Lb].
In this paper we describe our studies on the hydrolytic stabil-
ity of La and Lb and their coordination chemistry with gold,
platinum, palladium and iridium. We and others have found
that the rhodium complexes of La, Lb and related phosphites
are hydroformylation catalysts as discussed in the following
papers.10
Results and discussion
The phosphites La and Lb were made in multigram quantities
by a scale-up of Lattman’s method (eqn. 1).8 For example,
The stability of La and Lb is remarkable: no decomposition
was observed by 31P NMR after solid samples of La and Lb
had been heated in air at 300 ЊC for 1 h nor when toluene solu-
tions of La and Lb were refluxed in air for 24 h. When triphenyl-
phosphite is refluxed in aqueous acetone it decomposes fully
within 3 h but under similar conditions (see Experimental
section) both La and Lb showed no decomposition after 24 h.
Solutions of La and Lb in CDCl3 were shaken with 1 M aqueous
HCl or 1 M aqueous NaOH and after 30 min, no decom-
position was detected by 31P NMR spectroscopy.
DOI: 10.1039/a908960h
J. Chem. Soc., Dalton Trans., 2000, 1101–1107
This journal is © The Royal Society of Chemistry 2000
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Table 1 Selected interatomic bond lengths (Å) and bond angles (Њ) for
5bؒ4CH2Cl2ؒC6H6
Gold(I) chemistry
Complexes 3a and 3b were prepared by the addition of
[AuCl(tht)] (tht = tetrahydrothiophene) to one equivalent of the
appropriate phosphite La or Lb in CH2Cl2. The p-tert-butyl-
calix[4]arene phosphite complex 3b was soluble in common
organic solvents while the unsubstituted analogue 3a was
insoluble in CH2Cl2 and only sparingly soluble in dmso. The
complex [AuCl{P(OPh)3}] has been reported12 but not its 31P
chemical shift and so we determined it to be δ 110 which means
it has a coordination chemical shift ∆δ (Ϫ18) similar to the new
complexes 3a (Ϫ12) and 3b (Ϫ14).
Pt(1)–P(1)
Pt(1)–Cl(2)
Pt(1)–Cl(1)
Pt(1)–Cl(2A)
P(1)–O(2)
P(1)–O(3)
P(1)–O(4)
2.169(2)
2.326(2)
2.275(2)
2.396(2)
1.593(4)
1.584(4)
1.569(4)
P(1)–Pt(1)–Cl(1)
Cl(1)–Pt(1)–Cl(2A)
P(1)–Pt(1)–Cl(2)
Cl(2)–Pt(1)–Cl(2A)
O(2)–P(1)–O(3)
O(4)–P(1)–O(3)
O(2)–P(1)–O(4)
93.98(6)
89.00(6)
92.92(6)
83.99(6)
104.0(2)
106.6(2)
104.5(2)
Symmetry operation for suffix A: Ϫx, Ϫy, Ϫz.
Platinum(II) chemistry
Addition of the unsubstituted calix[4]arene phosphite La to
K[PtCl3(C2H4)] produced a white solid that was insoluble in
most common solvents and was sparingly soluble only in dmso;
this made purification difficult and we were unable to obtain
satisfactory elemental analyses. The product was assigned the
mononuclear structure 4a on the basis of the triplet 195Pt NMR
signal and absorptions at 307 and 325 cmϪ1 in the IR spectrum
typical of ν(PtCl) bands for a cis-PtCl2 group. The value of
1J(PtP) in 4a of 6629 Hz is significantly larger than the value of
5793 Hz reported13 for cis-[PtCl2{P(OPh)3}2].
Fig. 1 Molecular structure of binuclear platinum() complex 5b.
Selected atoms are labelled and all hydrogens are omitted for clarity.
Platinum(0) chemistry
Addition of [Pt(nor)3] (nor = η-norbornene) to a CH2Cl2 solu-
tion containing either phosphite La or Lb gave mixtures of com-
plexes which were unambiguously characterised in solution as
PtL and PtL2 (L = La or Lb) species from the doublet and trip-
let 195Pt NMR signals respectively. The products are assigned
the structures 6a,b and 7a,b on the basis of the 31P NMR data
which are similar to those for [Pt{P(OPh)3}(nor)2] and
[Pt{P(OPh)3}2(nor)].13 Mixtures were obtained regardless of
the quantity of ligand added showing that the equilibria in
eqn. (2) are established in solution. Attempts to isolate single
Treatment of K[PtCl3(η2-C2H4)] with Lb did not give the
corresponding mononuclear 4b even in the presence of an
excess of Lb. Instead the binuclear platinum() complex 5b is
formed which has been fully characterised (see Experimental
section). The binuclear structure of 5b is supported by the
doublet resonance in the 195Pt NMR spectrum, the very large
1J(PtP) of 7348) consistent with the phosphite being trans to a
bridging chloro ligand, and absorptions at 350 and 270 cmϪ1 in
the IR spectrum as expected for terminal and bridging ν(PtCl)
bands.
Single crystals of 5b as a solvate were grown from CH2Cl2/
hexane. The crystal structure (see Fig. 1) shows molecules of 5b
lying at sites of crystallographic inversion symmetry and con-
taining a typical planar Pt2(µ-Cl)2Cl2P2 core based on square
planar coordination geometry (mean deviation from plane
0.047 Å) at the Pt() centres. The Pt–P and Pt–Cl distances (see
Table 1) are of normal dimensions (and similar to the Pd–L
distances in 8b, see below) although the Pt–(µ-Cl) distance trans
to the phosphite is substantially longer than that trans to the
terminal chloride ligand (by ca. 0.12 Å) indicating that the
phosphite Lb has a much stronger trans influence than the chlor-
ide ligand. Both of the P–Pt–Cl angles are greater than the ideal
90Њ (P(1)–Pt(1)–Cl(1) 93.98(6)Њ, P(1)–Pt(1)–Cl(2A) 92.92(6)Њ).18b
The observation that Lb forms the binuclear 5b rather than 4b
while La forms the mononuclear 4a rather than 5a is consistent
with the greater bulk of Lb.
species were unsuccessful since the components had very
similar solubilities. There was no evidence for the formation
of [PtL3] or [PtL4] species when a large excess of calix[4]arene
phosphites La or Lb was added which is consistent with the large
bulk of these ligands.
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Table
2
Selected bond lengths (Å) and bond angles (Њ) for
8bؒ6.67CHCl3
Table 3 Selected bond lengths (Å) and bond angles (Њ) for 10ؒC6H6-
C5H12
Pd(1)–P(1)
Pd(1)–Cl(2)
Pd(1)–Cl(1)
Pd(1)–Cl(1A)
P(1)–O(2)
P(1)–O(3)
P(1)–O(4)
2.1874(14)
2.261(2)
2.307(2)
2.392(2)
1.574(3)
1.583(3)
1.573(3)
Pd(1)–P(1)
Pd(1)–Cl(2)
Pd(1)–Cl(1)
Pd(1)–C(50)
P(1)–O(2)
P(1)–O(3)
P(1)–O(4)
2.214(2)
2.291(2)
2.353(2)
1.927(6)
1.562(4)
1.573(4)
1.595(4)
P(1)–Pd(1)–Cl(1)
Cl(2)–Pd(1)–P(1)
Cl(1A)–Pd(1)–Cl(2)
Cl(1)–Pd(1)–Cl(1A)
O(2)–P(1)–O(3)
O(4)–P(1)–O(3)
O(2)–P(1)–O(4)
94.54(5)
88.73(6)
90.54(6)
86.03(5)
104.8(2)
107.5(2)
104.9(2)
P(1)–Pd(1)–C(50)
Cl(1)–Pd(1)–P(1)
Cl(2)–Pd(1)–C(50)
Cl(1)–Pd(1)–Cl(2)
O(2)–P(1)–O(3)
O(4)–P(1)–O(3)
O(2)–P(1)–O(4)
90.9(2)
88.33(6)
89.5(2)
90.94(7)
105.7(2)
105.8(2)
104.3(2)
Symmetry operation for suffix A: Ϫx, Ϫy, Ϫz.
Fig. 2 Molecular structure of binuclear palladium() complex 8b.
Selected atoms are labelled and all hydrogens are omitted for clarity.
Fig. 3 Molecular structure of mononuclear palladium() complex 10.
Selected atoms are labelled and all hydrogens are omitted for clarity.
Palladium(II) chemistry
Treatment of [PdCl2(NCPh)2] with Lb gave the binuclear
palladium() species 8b as the only phosphorus-containing
product, even when an excess of ligand was used. The complex
was fully characterised (see Experimental section) and the
binuclear structure confirmed by X-ray crystallography. Single
crystals of solvated 8b were grown from CDCl3. The molecular
structure of 8b in the crystal (Fig. 2, Table 2) is very similar to
that of the analogous platinum() species 5b reported above,
and again shows exact inversion symmetry with a planar Pd2-
(µ-Cl)2Cl2P2 core and planar coordination geometry (rms devi-
ation 0.045 Å) at palladium. The dimensions of the molecule
are all very close to those in the platinum case and in respect of
the Pd(µ-Cl)2Cl2P2 core they are similar to those of [Pd2(µ-Cl)2-
Cl2{P(OPh)3}2].14
Scheme 1
These results are again consistent with the phosphite ligand Lb
being very bulky.
Single crystals of 10 were grown from C6H6/pentane and its
structure as a solvate was confirmed by X-ray crystallography
(Fig. 3, Table 3). The conformation of ligand Lb is essentially
the same as for 5b and 8b as are its internal dimensions. The
complex shows square planar coordination geometry (rms
deviation 0.025 Å) at palladium as expected with only small
deviation of cis coordination angles from 90Њ. The two better
π-acceptor ligands, the phosphite and the isocyanide, are
mutually cis; similar behaviour in cis-bis-phosphite complexes
of Pt() has been noted by us previously.15 The Pd–Cl distance
trans to Lb is ca. 0.05 Å longer than that trans to C(50), imply-
ing that Lb exerts a stronger trans influence than tert-butyl
isocyanide. The isocyanide ligand is nearly eclipsed with the
P(1)–O(4) bond (torsion angle C(50)–Pd(1)–P(1)–O(4) =
Ϫ20.4Њ), which allows the tert-butyl group and the aryl group
on O(4) to be far apart. In contrast the oxygen with the gauche
conformation, O(2), whose aryl substituent would not be com-
patible with a cis ligand carrying such a bulky substituent, lies
close to Cl(1) (torsion angle Cl(1)–Pd(1)–P(1)–O(2) = 41.0Њ).
A series of reactions was carried out between 8b and CO,
MeNC, ButNC, pyridine, and P(OPh)3, the progress of which
was monitored by 31P{1H} NMR spectroscopy (Scheme 1).
Simple bridge-cleavage occurred only with the smallest ligands.
For example when CO was bubbled slowly through a solution
of 8b, the mononuclear species 9 was formed with ν(CO) 2141
cmϪ1. However if the CO was added too rapidly or an excess of
CO was present, displaced calix[4]arene phosphite Lb was
detected by 31P NMR spectroscopy. Mononuclear complexes 10
and 11 were formed with the rod-like ligands ButNC and
MeNC but when 8b was treated with the larger ligands, LЈ =
pyridine and P(OPh)3, the calix[4]arene phosphite Lb was com-
pletely displaced and presumably [PdCl2LЈ2] were produced.
J. Chem. Soc., Dalton Trans., 2000, 1101–1107
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a
Table 4 Selected bond lengths (Å) and angles (Њ) for 13aؒ0.5C6H6
Ir(1)–P(1)
Ir(1)–Cl(1)
Ir(1)–X1A
Ir(1)–X1B
P(1)–O(2)
P(1)–O(3)
P(1)–O(4)
2.2644(11)
2.3605(11)
2.115(4)
2.000(4)
1.608(3)
1.604(3)
1.596(3)
the case of complexes of Lb. It is apparent from the coordin-
ation chemistry described above that the phosphites La and Lb
are both very bulky. The cone angles16 are calculated from the
crystal structures to be 160Њ for La and average 176Њ for Lb.
These values lie between those for P(OC6H4Me-2)3 (θ = 141Њ)
and P(OC6H3Me2-2,6)3 (θ = 190Њ). The greater bulk of Lb and
La is manifest from the fact that at no time are two cis Lb ligands
on platinum() or palladium() observed. The calixarene con-
formation in all cases reported here is of type e,10b with arenes
in sequence douu {down, out, up, up} for oxygens O(1, 2, 3 and
4) respectively. This leads to a very asymmetric ligand profile in
which one aryl (that at O(1)) occupies a position near a
vacant axial site of the square planar metal and lies nearly
parallel to the coordination plane. This arrangement implies
rotation about the M–P bond will be a high energy process.
In each case the most bulky substituent at phosphorus, the
“down” aryl at O(1), is eclipsed with the least bulky aspect of
the square planar centre, its empty axial site. This implies that
the O(3) site at phosphorus is also cis to an axial site (that trans
to the site blocked by the aryl at O(1)) while O(2) and O(4) are
both close to the (filled) equatorial sites cis to the phosphite.
The bulkiness of the ligand is such as to preclude octahedral
geometry at the metal (and also TBPY geometry probably), at
least in this conformation.
Cl(1)–Ir(1)–P(1)
Cl(1)–Ir(1)–X1A
X1B–Ir(1)–X1A
P(1)–Ir(1)–X1B
O(2)–P(1)–O(3)
O(4)–P(1)–O(3)
O(2)–P(1)–O(4)
94.51(14)
88.6(1)
86.2(1)
91.1(1)
101.9(1)
103.9(2)
103.0(1)
a X1A, X1B are the centroids of the C᎐C bonds in the cod ligand.
᎐
The ligand symmetry is clearly C1, but dynamic interconver-
sion of conformations douu and duuo10b would interconvert the
environments of O(2) and O(4) and hence give time-averaged Cs
symmetry to the NMR spectra and the chemistry of La and Lb.
This is not however compatible with the asymmetry of the cis
ligands in species such as 10. Therefore complexes such as 10
are chiral and seem likely to retain chirality in the absence of
ligand dissociation.
Fig. 4 Molecular structure of mononuclear iridium() complex 13a.
Selected atoms are labelled and all hydrogens are omitted for clarity.
Addition of [PdCl2(NCPh)2] to two equivalents of La gave
an orange precipitate which was insoluble in most common
solvents but sparingly soluble in warm dmso. The 31P NMR
spectrum showed a mixture of products present. Three singlets
in the intensity ratio of ca. 1:2:1 were tentatively associated
with the components of the equilibrium shown in eqn. (3). One
The observed calixarene conformation is associated with a
conformation at phosphorus17 in which the M–P–O–C torsion
at O(2) is gauche (M–P–O–C torsion angle ca. Ϫ40Њ) and anti at
O(3), O(4) (Pt–P–O–C torsion angles ca. 160 and 180Њ). This is
unusual compared with most P(OR)3 species18 and is doubtless
required by the constraints of the calixarene. The distortions
that are associated in the M–P–O angles and P–O–C angles
presumably arise from the same source. Thus the M–P–O(2)
angle is close to 120Њ while the other Pt–P–O angles are ca. 109Њ
and conversely the P–O–C angle at O(3) is relatively small, ca.
120Њ, while those at O(2) and O(4) are larger (ca. 130 and 140Њ
respectively). The P–O distances and the O–P–O angles show
less variation and are somewhat shorter and somewhat larger
respectively than is the norm for triarylphosphite species (aver-
age values ca. 1.58 Å and 105Њ).15 This may therefore imply that
Lb and La will be less π-acidic than most triarylphosphite
ligands without such constrained bond angles. The trans influ-
ence of the ligands La and Lb appear to be greater than either
chloride or isocyanide (at least as measured by trans M–Cl or
M–alkene bond lengths).
of the singlets at δ 116 was free phosphite, a second δ 47.6 was
assigned to the binuclear species 8a, the analogue of 8b, on the
basis of the similarity of their δ(P) values; the third singlet at
δ 64.1 is tentatively assigned to the mononuclear complex 12a,
the analogue of the platinum() species 4a.
Iridium(I) chemistry
Addition of [Ir2Cl2(cod)2] to a CH2Cl2 solution containing two
equivalents of La or Lb gave the mononuclear complexes 13a
and 13b, which have been fully characterised (see Experimental
section). Single crystals of 13a as a benzene solvate were grown
from CH2Cl2/benzene and the structure determined by X-ray
crystallography (see Fig. 4, Table 4). The complex has square-
planar geometry at Ir distorted such that the Ir–Cl bond lies out
The kinetic inertness and large bulk of La and Lb make them
of interest as ligands for hydroformylation catalysis.10
of the plane formed by Ir(1), P(1) and the centroids of the C᎐C
᎐
Experimental
double bonds (rms deviation from that plane = 0.019 Å, Cl(1)
deviation 0.46 Å). The Ir–C distances show the phosphite
ligand to be exerting a stronger trans influence than the
chloride ligand (Ir–C trans to P being longer by ca. 0.11 Å).
In all the structures reported here, as is often the case with
calixarenes, the crystals are solvated, particularly heavily so in
Unless otherwise stated, all reactions were carried out under a
dry nitrogen atmosphere using standard Schlenk line tech-
niques. With the exception of the Pt(0) species, all the metal
complexes were air stable in the solid state, so once prepared
were stored in air. Solvents were dried and nitrogen-saturated
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by refluxing them under a nitrogen atmosphere over appropri-
ate drying agents: calcium hydride (for dichloromethane,
chloroform and acetonitrile), sodium/benzophenone (for
diethyl ether and tetrahydrofuran), sodium (for pentane, tolu-
ene, benzene and hexane) and anhydrous magnesium sulfate
(for acetone). Commercial reagents were used as supplied
unless otherwise stated and other starting materials prepared by
literature methods: K[PtCl3(η2-C2H4)],19 [Pt(nor)3],20 [PdCl2-
(cod)],21 [PdCl2(NCPh)2],22 [AuCl(tht)]23 and [Ir2Cl2(cod)2].24
Unsubstituted H-calix[4]arene was prepared by the reverse
Friedel–Crafts method of Gutsche.25 Infrared spectra were
recorded on either a Nicolet 5ZDX or a Perkin-Elmer 1600.
phite La was synthesised and purified using the above procedure
(69%). Elemental analysis, found (calc.); C, 73.7 (74.3); H, 4.8
1
(4.7); P, 6.1 (6.9)%. 31P NMR (CDCl3): δ 112.9. H NMR
(CDCl3): δ 3.57 [d, 2H, Ar-CHH-Ar, 2J(HH) 15.1], 3.67 [d, 2H,
2
2
Ar-CHH-Ar, J(HH) 16.8], 4.28 [d, 2H, Ar-CHH-Ar, J(HH)
2
16.8], 4.54 [d, 2H, Ar-CHH-Ar, J(HH) 15.1], 4.66 (br s, 1H,
OH), 6.66–7.21 (m, 12H, Ph). 13C NMR (CDCl3): δ 33.1 (s,
CH2), 36.3 (s, CH2), 122.2–135.3 (m, Ph), 146.2–152.1 (m, Ph).
Thermal and hydrolytic stability tests for calixarene phosphites
La and Lb
NMR spectra were recorded on a JEOL GX400 at ca. 23 ЊC: 31
P
(a) In air, Lb (150 mg, 0.22 mmol) was placed in a round-bottom
flask and heated in an oven at 300 ЊC for 1 h and then allowed
to cool to ambient temperature. Then the 31P NMR spectrum
was measured and no decomposition was detected. In a separ-
ate experiment La was subjected to the same conditions again
with no decomposition detected. (b) In air, a toluene (5 cm3)
solution of Lb (150 mg, 0.22 mmol) was refluxed for 24 h. After
this time the 31P NMR spectrum was measured and no decom-
position was detected. In a separate experiment La was sub-
jected to the same conditions again with no decomposition
detected. (c) To a solution of Lb (1.0 g, 1.48 mmol) in CH2Cl2
(10 cm3) and acetone (10 cm3), distilled water (1.67 cm3, 93.1
mmol) was added and the solution appeared homogeneous.
(162 MHz, δ to high frequency of 85% H3PO4), 13C (100 MHz,
δ to high frequency of SiMe4), 195Pt (81 MHz, δ to high
frequency Ξ(Pt) of 21.4 MHz) and H (400 MHz, δ to high
1
frequency of SiMe4), J in Hz.
Preparation of precursor 1b
To a stirred suspension of p-tert-butylcalix[4]arene (20.0 g, 30.9
mmol) in benzene (350 cm3), P(NMe2)3 (6.16 cm3, 34.0 mmol)
was added dropwise over 30 min. After stirring the mixture for
24 h at room temperature, the resulting white precipitate was
filtered off, washed with benzene (50 cm3) and dried in vacuo for
24 h to yield the white solid 1b (19.13 g, 86%). Elemental anal-
ysis, found (calc): C, 76.7 (76.5); H, 8.4 (8.4); N, 1.9 (1.9); P, 4.3
This mixture was heated under reflux, with stirring, and the 31
P
NMR spectrum of a sample was recorded after 30 min, 1 h, 3 h
and 24 h and showed no decomposition had taken place. In a
separate experiment La was subjected to the same conditions
again with no decomposition detected. (d) To a solution of Lb
(30 mg) in CDCl3 (0.6 cm3) in an NMR tube was added 1 M
aqueous HCl (0.4 cm3) and the biphasic system shaken for 30
min. The 31P NMR spectrum was then recorded which showed
no decomposition had taken place. In a separate experiment La
was subjected to the same conditions again with no decom-
position detected. (e) To a solution of Lb (30 mg) in CDCl3 (0.6
cm3) in an NMR tube was added 1 M aqueous NaOH (0.4 cm3)
and the biphasic system shaken for 30 min and then the 31P
NMR spectrum was recorded which showed no decomposition
had taken place. In a separate experiment La was subjected to
the same conditions again with no decomposition detected.
1
(4.3)%. 31P NMR (CDCl3): δ Ϫ117.5 [1J(PH) 729]. H NMR
(CDCl3): δ 1.21 [s, 36H, C(CH3)3], 3.13 [dd, 4H, Ar-CHH-Ar,
5
3
2J(HH) 11.2, J(PH) 1.8], 3.51 [dd, 6H, N(CH3)2, J(PH) 9.7,
3J(PH) 5.6], 4.63 [d, 1H, PH, 1J(PH) 729], 4.67 [dd, 4H,
2
5
Ar-CHH-Ar, J(HH) 11.2, J(PH) 6.7], 6.25 (br s, 1H, NH),
7.25 (s, 8H, Ph). 13C{1H} NMR (CDCl3): δ 31.7 [s, C(CH3)3],
2
34.4 [s, C(CH3)3], 36.1 (s, CH2), 44.8 [d, N(CH3)2, J(PC) 4],
124.8 (s,CH), 137.7 [d, C(CH2), 3J(PC) 9], 145.8 [d, CC(CH3)3,
5J(PC) 5], 148.0 [d, CO, 2J(PC) 7]. Using a similar procedure the
analogue 1a was synthesised from H-calix[4]arene. Elemental
analysis, found (calc): C, 71.9 (72.3); H, 5.7 (5.7); N, 2.4 (2.4); P,
5.6 (6.2)%. 31P NMR (CDCl3): δ Ϫ119.5 [1J(PH) 729]. 1H NMR
(CDCl3): δ 3.20 [dd, 4H, Ar-CHH-Ar, 2J(HH) 11.7, 5J(PH) 2.1],
3
3
3.54 [dd, 6H, N(CH3)2, J(HH) 9.4, J(PH) 5.9], 4.69 [d, 1H,
PH, 1J(PH) 729], 4.70 [dd, 4H, Ar-CHH-Ar, 2J(HH) 11.7,
5J(PH) 6.7], 6.30 (br s, 1H, NH), 6.73 [dt, 4H, Ph, 3J(HH) 7.4,
Preparation of [AuCl(Lb)] 3b
5J(PH) 2.8], 7.02 [d, 8H, Ph, J(HH) 7.3]. 13C NMR (CDCl3):
3
To a CH2Cl2 (10 cm3) solution of [AuCl(tht)] (71.1 mg, 0.22
mmol), Lb (150 mg, 0.22 mmol) was added. The solution was
stirred for 2 h at room temperature. All volatiles were then
removed in vacuo to yield white solid 3b (183 mg, 91%). Elem-
ental analysis found (calc.): C, 58.9 (58.1); H, 6.1 (5.8); P, 3.4
(3.4)%. 31P NMR (CDCl3): δ 99.1.1H NMR (CDCl3): δ 1.22 [s,
9H, C(CH3)3], 1.29 [s, 18H, C(CH3)3], 1.33 [s, 9H, C(CH3)3],
3.48 [d, 2H, Ar-CHH-Ar, 2J(HH) 14.7], 3.76 [d, 2H, Ar-CHH-
Ar, 2J(HH) 16.5], 4.22 [d, 2H, Ar-CHH-Ar, 2J(HH) 16.5], 4.30
δ 35.0 (s, CH2), 44.5 [d, N(CH3)2, 2J(PC) 4], 123.3 (s, CH), 127.6
3
5
[d, C(CH2), J(PC) 9], 138.2 [d, CH, J(PC) 6], 150.0 [d, CO,
2J(PC) 7].
p-tert-Butylcalix[4]arene phosphite Lb
To a CH2Cl2 (350 cm3) solution of 1b (20.0 g, 27.7 mmol),
CF3CO2H (2.44 cm3, 30.5 mmol) was added dropwise over 30
min. The clear solution was left stirring for 4 h at room tem-
perature, after which time the solvent was removed in vacuo to
yield a white solid. 31P NMR spectroscopy revealed this solid
product to be a mixture of phosphite Lb and phosphonate 2b.
By passing a CH2Cl2 (100 cm3) solution of this white solid
through a 15 cm3 Al2O3 (grade III) column (ꢀ 3.5 cm) using
further CH2Cl2 (100 cm3) as eluent, pure Lb was obtained as the
only fraction (13.67 g, 73%). Elemental analysis, found (calc.):
C, 77.9 (78.1); H, 8.0 (7.9); P, 4.3 (4.6)%. 31P NMR (CDCl3)
δ 112.9. 1H NMR (CDCl3): δ 1.21 [s, 9H, C(CH3)3], 1.31 [s, 9H,
C(CH3)3], 1.39 [s, 18H, C(CH3)3], 3.62 [d, 2H, Ar-CHH-Ar,
2
[d, 2H, Ar-CHH-Ar, J(HH) 14.7], 7.05–7.20 (m, 8H, Ph). 13C
NMR (CDCl3): δ 29.6–36.6 [m, tert-butyls, ArCH2Ar from
calix[4]arene ligand], 125.5–132.4 (m, CH), 144.2–150.3. The
analogue 3a was made similarly in 73% yield. Elemental anal-
ysis, found (calc. for 3aؒCH2Cl2): C, 44.8 (45.3); H, 3.0 (3.0);
1
P, 3.5 (4.0)%]. 31P NMR (d6-dmso): δ 99.1. H NMR (CDCl3):
δ 3.76 [d, 2H, Ar-CHH-Ar, 2J(HH) 14.7], 3.80 [d, 2H, Ar-CHH-
Ar, 2J(HH) 16.1], 4.24 [d, 2H, Ar-CHH-Ar, 2J(HH) 16.1], 4.30
[d, 2H, Ar-CHH-Ar, 2J(HH) 14.7], 6.67–7.39 (m, 12H, Ph). 13
C
NMR (CDCl3): δ 33.9 (s, ArCH2Ar,), 34.9 (s, ArCH2Ar), 122.3
(s, Ph), 126.1 (m, Ph), 148.5 (s, Ph), 152.8 (s, Ph).
2
2J(HH) 15.4], 3.71 [d, 2H, Ar-CHH-Ar, J(HH) 17.0], 4.29 [d,
2H, Ar-CHH-Ar, 2J(HH) 17.0], 4.49 [d, 2H, Ar-CHH-Ar,
2J(HH) 15.4], 4.74 (br s, 1H, OH), 7.11 (s, 2H, Ph), 7.17 [d, 2H,
Ph, 4J(HH) 2.1], 7.22 (s, 2H, Ph), 7.25 [d, 2H, Ph, 4J(HH) 2.4].
13C NMR (CDCl3): δ 31.5 [m, C(CH3)3], 34.1 [m, C(CH3)3], 37.0
(m, CH2), 125.7 (s, CH), 125.9 (s, CH), 126.4 (s, CH), 126.6 (s,
CH), 129.9 [s, C(CH2)], 131.3 [s, C(CH2)], 133.1 [s, C(CH2)],
134.6 [s, C(CH2)], 144.1–149.7 (m, Ph). H-Calix[4]arene phos-
Preparation of cis-[PtCl2(La)2] 4a
To a pale yellow solution of K[PtCl3(η2-C2H4)] (61.5 mg, 0.17
mmol) in CH2Cl2 (10 cm3) and acetone (10 cm3), La (150 mg,
0.33 mmol) was added. The solution was stirred for 2 h at room
temperature during which time an off-white precipitate was
J. Chem. Soc., Dalton Trans., 2000, 1101–1107
1105

View Article Online
produced. This was filtered off to yield pale yellow solid 4a
(122 mg, 63%). IR (Nujol mull, cmϪ1), 307, 325 (νPt–Cl). 31P NMR
(d6-dmso): δ 37.9 [1J(PtP) 6629]. 195Pt NMR (d6-dmso): δ 458
[t, 1J(PtP) 6629].
(c) With MeNC. To a dark orange solution of 8b (100 mg,
0.06 mmol) in CH2Cl2 (5 cm3), MeNC (ca. 4.8 mg, 0.14 mmol)
was slowly added using a calibrated high vacuum Schlenk line.
The solution was stirred for 5 min during which time the colour
changed to pale yellow. All volatiles were then removed in vacuo
to yield a pale yellow solid whose 31P{1H} NMR spectrum (d6-
dmso), δ 66.6 was very similar to 10 and was therefore assigned
the structure [PdCl2(NCMe)(Lb)] 11. Satisfactory elemental
analyses were not obtained for this product.
Preparation of trans-[Pt2Cl2(ꢀ-Cl)2(Lb)2] 5b
To a pale yellow solution of K[PtCl3(η2-C2H4)] (81.8 mg, 0.22
mmol) in CH2Cl2 (10 cm3) and acetone (10 cm3), Lb (150 mg,
0.22 mmol) was added. The solution was stirred for 2 h at room
temperature during which time an off-white precipitate was
produced. This was filtered off to yield pale yellow solid 5b
(154.7 mg, 74%). Single crystals of 5b were grown by slow
diffusion of hexane into a CH2Cl2 solution layered in an NMR
tube. Elemental analysis, found (calc. for 5bؒ3CH2Cl2): C, 51.5
(51.1); H, 5.6 (5.3)%]. IR (Nujol mull, cmϪ1), 350w (νPt–Cl), 270w
(νPt–µ-Cl). 31P NMR (CDCl3): δ 2.2 [1J(PtP) 7348]. 195Pt NMR
(CDCl3): δ Ϫ650 [d, 1J(PtP) 7348].
(d) With pyridine or P(OPh)3. Treatment of CDCl3 solutions
of 8b with these ligands under similar conditions to those above
were shown by 31P NMR to contain only displaced Lb.
Reaction of [PdCl2(NCPh)2] with La
To a solution of [PdCl2(NCPh)2] (84.7 mg, 0.22 mmol) in
CH2Cl2 (15 cm3), La (200 mg, 0.44 mmol) was added and the
orange solution stirred for 1 h at room temperature. Then the
resulting orange precipitate was filtered off and a 31P NMR
spectrum measured in warm dmso. This showed a mixture of
free La and palladium() complexes to have been produced,
which were assigned structures [Pd2Cl4(La)2] 8a and [PdCl2(La)2]
12, see Results and discussion.
Reaction of [Pt(nor)3] with Lb
To a colourless solution of [Pt(nor)3] (52.8 mg, 0.11 mmol) in
CH2Cl2 (10 cm3), Lb (150 mg, 0.22) was added. The solution was
stirred for 2 h at room temperature and then all volatiles were
removed in vacuo to yield an off-white solid. 31P and 195Pt NMR
spectroscopy showed this to be a mixture of 6b [δ(P) 130.3,
1J(PtP) 6084, δ(Pt) Ϫ1361 (d)] and 7b [δ(P) 137.5, 1J(PtP) 5991,
δ(Pt) Ϫ820 (t)]. Using a similar procedure a mixture of 6a [δ(P)
131.0, 1J(PtP) 6199, δ(Pt) Ϫ1349 (d)] and 7a [δ(P) 137.0, 1J(PtP)
6060, δ(Pt) Ϫ834 (t)] were prepared from La.
Preparation of [IrCl(Lb)(cod)] 13b
To an orange solution of [Ir2Cl2(cod)2] (74.4 mg, 0.11 mmol)
in CH2Cl2 (15 cm3), Lb (150 mg, 0.22 mmol) was added. The
solution was stirred for 2 h at room temperature and then all
volatiles were removed in vacuo to yield pale orange solid 13b
(206 mg, 92%). Elemental analysis, found (calc.): C, 56.4 (56.4);
1
H, 6.4 (6.0); P, 3.0 (2.7)%. 31P NMR (C6D6) δ 77.9. H NMR
Preparation of trans-[Pd2Cl2(ꢀ-Cl)2(Lb)2] 8b
(CDCl3): δ 1.17 [s, 9H, C(CH3)3], 1.20 [s, 9H, C(CH3)3], 1.23 [s,
18H, C(CH3)3], 1.48 [m, 4H, CH2 of cod], 2.28 [m, 4H, CH2 of
cod], 3.38 (m, 2H, CH of cod), 5.02 (m, 2H, CH of cod), 3.50
To an orange solution of [PdCl2(NCPh)2] (170 mg, 0.44 mmol)
in CH2Cl2 (10 cm3), Lb (150 mg, 0.22 mmol) was added. The
solution was stirred for 2 h at room temperature and then all
volatiles were removed in vacuo. The resulting solid was
recrystallised from CH2Cl2 (8 cm3) and pentane (20 cm3) to give
the orange powder 8b (293 mg, 78%). Single crystals of 8b were
grown by slow evaporation of a CDCl3 solution in an NMR
tube. Elemental analysis, found (calc.); C, 61.5 (61.9); H, 6.4
(6.3)%]. 31P NMR (CDCl3) δ 38.1. 1H NMR (CDCl3): δ 1.26 [s,
9H, C(CH3)3], 1.30 [s, 9H, C(CH3)3], 1.66 [s, 18H, C(CH3)3],
3.50 [d, 2H, Ar-CHH-Ar, 2J(HH) 14.3], 3.88 [d, 2H, Ar-CHH-
Ar, 2J(HH) 16.7], 4.26 [d, 2H, Ar-CHH-Ar, 2J(HH) 16.7], 4.53
[d, 2H, Ar-CHH-Ar, 2J(HH) 14.3], 4.37 (br s, 1H, OH), 7.09 (br
s, 2H, Ph), 7.11 (br s, 2H, Ph), 7.18 (s, 2H, Ph), 7.37 (s, 2H, Ph).
13C NMR (CDCl3): δ 31.3 [m, C(CH3)3], 32.4 [m, C(CH3)3],
34.2–35.6 (m, CH2), 124.0–132.8 (m, CH), 143.8–144.5 (m,
CH), 148.8–150.0 (m, CH).
2
[d, 2H, Ar-CHH-Ar, J(HH) 14.2], 3.78 [d, 2H, Ar-CHH-Ar,
2
2J(HH) 16.6], 4.26 [d, 2H, Ar-CHH-Ar, J(HH) 16.6], 4.42 [d,
2
2H, Ar-CHH-Ar, J(HH) 14.2], 4.34 (br s, 1H, OH), 7.08 (s,
2H, Ph), 7.10 (s, 2H, Ph), 7.13 (s, 2H, Ph), 7.15 (s, 2H, Ph). 13
C
NMR (CDCl3): δ 27.3–51.9 (m, cod, tert-butyls, ArCH2Ar from
calix[4]arene ligand), 120.4–134.2 and 147.2–153.0 (m, CH).
The analogue 13a was made by a similar procedure from La in
97% yield. Single crystals of 13a were grown by slow diffusion
of benzene into a CH2Cl2 solution of 13a layered in a NMR
tube. Elemental analysis found (calc. for 13aؒ1.5CH2Cl2): C,
48.8 (49.2); H, 3.8 (4.0); P, 2.7 (3.4)%. 31P NMR (CDCl3) δ 74.8.
1H NMR (CDCl3): δ 1.51 (m, 4H, CH2 of cod), 2.28 (m, 4H,
CH2 of cod), 3.32 (m, 2H, CH of cod), 5.13 (m, 2H, CH of
2
cod), 3.46 [d, 2H, Ar-CHH-Ar, J(HH) 14.0], 3.79 [d, 2H,
2
2
Ar-CHH-Ar, J(HH) 16.5], 4.24 [d, 2H, Ar-CHH-Ar, J(HH)
2
16.5], 4.47 [d, 2H, Ar-CHH-Ar, J(HH) 14.0], 4.36 (br s, 1H,
OH), 6.67 [t, 1H, Ph, 3J(HH) 8.9], 6.95–7.14 (m, 11H, Ph). 13
C
Bridge-cleavage reactions of trans-[Pd2Cl2(ꢀ-Cl)2(Lb)2]
NMR (CDCl3): δ 28.6 [d, ArCH2Ar, 4J(PH) 4.0], 33.6 [d,
(a) With CO. Binuclear complex 8b (150 mg, 0.09 mmol) was
dissolved in CH2Cl2 (10 cm3) and CO was bubbled through the
orange solution at the rate of one bubble per second for 30 min
at room temperature. Then all volatiles were removed in vacuo
to give an orange powder. Satisfactory elemental analyses were
not obtained but the main product was assigned the structure
trans-[PdCl2(CO)(Lb)] 9 on the basis of IR (CH2Cl2, cmϪ1),
2141m (νCO) and 31P NMR (d6-dmso) δ 71.6. Satisfactory elem-
ental analyses were not obtained for this product.
4
ArCH2Ar, J(PH) 4.6], 31.7, 35.5, 35.8, 53.4 (s, cod signals),
121.2–132.7 (m, CH), 148.8, 151.9 (m, CH).
X-Ray crystal structure determinations
Details of the structure determinations of crystals of 5bؒ4CH2-
Cl2ؒC6H6, 10ؒC6H6ؒC5H12, 8bؒ6.67CHCl3 and 13aؒ0.5C6H6 are
given in Table 5. All non-hydrogen atoms were assigned aniso-
tropic displacement parameters and refined without positional
constraints, except for some disordered atoms. All solvent
molecules except for the benzene in 13aؒ0.5C6H6 were dis-
ordered and their Uij and geometries were restrained and con-
strained as necessary. In 8bؒ6.67CHCl3 the tert-butyl group at
C(19) was disordered across two sites with occupancies of
0.848(8) and 0.154(8).
(b) With ButNC. To an orange solution of 8b (100 mg, 0.06
mmol) in CH2Cl2 (5 cm3), ButNC (13.2 µl, 0.12 mmol) was
slowly added over 5 min and the solution stirred for 30 min at
room temperature. All volatiles were then removed in vacuo to
give a pale orange solid. 31P NMR (d6-dmso) δ 63.6. Single
crystals of [PdCl2(NCBut)(Lb)] 10 were grown by slow diffusion
of pentane into a benzene solution of 10 by layering in an
NMR tube.
CCDC reference number 186/1836.
See http://www.rsc.org/suppdata/dt/a9/a908960h/ for crystal-
lographic files in .cif format.
1106
J. Chem. Soc., Dalton Trans., 2000, 1101–1107

View Article Online
Table 5 Selected crystallographic details for the crystal structure determinations of 5bؒ4CH2Cl2ؒC6H6, 8bؒ6.67CHCl3, 10ؒC6H6ؒC5H12 and
13aؒ0.05C6H6
5bؒ4CH2Cl2ؒC6H6
8bؒ6.67CHCl3
10ؒC6H6ؒC5H12
13aؒ0.5C6H6
Empirical formula
Formula weight
C98H120Cl12O8P2Pt2
2303.46
C94H112Cl24O8P2Pd2
2495.38
C60H80Cl2NO4PPd
1087.52
C39H36ClO4PIr
827.30
Crystal system
a/Å
b/Å
c/Å
α/Њ
β/Њ
Triclinic
13.6605(14)
13.821(2)
Triclinic
Monoclinic
22.871(4)
13.852(3)
Triclinic
8.914(2)
10.115(2)
18.556(3)
82.27(2)
13.312(3)
13.923(3)
16.352(3)
106.68(3)
95.68(3)
14.660(2)
18.117(3)
104.270(11)
101.943(12)
104.796(8)
2483.4(5)
93.104(12)
84.47(2)
γ/Њ
107.47(3)
2711.8(9)
173(2)
71.912(14)
1573.3(5)
173(2)
V/Å3
5731(2)
153(2)
Cc (no. 9)
4
0.490
11314
7145
T/K
173(2)
¯
¯
¯
Space group
Z
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
1
1
2
µ/mmϪ1
3.222
15724
10877
0.0576
0.0476
1.004
10006
9545
0.0269
0.0507
4.422
10208
6989
0.0257
0.0288
Total reflns
Independent reflns
Rint
0.0312
0.0447
R1 [I > 2σ(I) data]
7 (a) B. M. Trost and M. C. Matelich, J. Am. Chem. Soc., 1991, 113,
9007; (b) B. M. Trost, J. R. Parquette and A. L. Marquart, J. Am.
Chem. Soc., 1995, 117, 3284; (c) M. T. Reetz and T. Neugebauer,
Angew. Chem., Int. Ed., 1999, 38, 179.
8 (a) D. V. Khasnis and M. Lattman, J. Am. Chem. Soc., 1990, 112,
9422; (b) D. V. Khasnis, J. M. Burton, M. Lattman and H. Zhang,
J. Chem. Soc., Chem. Commun., 1991, 562; (c) D. V. Khasnis, J. M.
Burton, J. D. McNeil, H. Zhang and M. Lattman, Phosphorus
Sulfur Silicon Relat. Elem., 1993, 75, 253.
Acknowledgements
We thank Rhône-Poulenc (Lyon) for a studentship (to C. J. C.),
EPSRC for financial support and Johnson-Matthey for a
generous loan of platinum compounds.
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