Co-ordination chemistry of macrocyclic compounds with dangling phosphines. Unusual NMR shifts in metallo-calix[4]arenes

Article abstract of DOI:10.1039/a905814a

The chelating behaviour of three polyphosphines, cone-5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinomethoxy) calix[4]arene L¹, cone-5,11,17,23-tetra-tert-butyl-25,26,27-tris(diphenylphosphinomethoxy)-28- methoxycalix[4]arene L², and cone-5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinomethoxy)-27,28- dihydroxycalix[4]arene L³, has been investigated. When [Mo(CO)₃(C₇H₈)] and tetraphosphine L¹ are heated together under reflux in tetrahydrofuran (THF) complex [Mo(CO)₃L¹] 1 is formed, for which the calixarene behaves as a fac-bonded tridentate ligand with one phosphine remaining free. Similar fac-chelating behaviour is found with [Mo(CO)₃L²] 2, which is obtained from triphosphine L². Formation of this latter complex is accompanied by the calixarene matrix adopting a partially flattened-cone conformation. In contrast, the conventional cone conformation is maintained in the trinuclear complex [(AuCl)₃L²] 3, obtained quantitatively by treating L² with [AuCl(THT)] (THT = tetrahydrothiophene). Reaction of L¹ with [RuCl₂(DMSO)₄] (DMSO = Me₂SO) in CH₂Cl₂ results in selective formation of the deep purple complex [RuCl₂L²] 4 built around a fac-trigonal bipyramidal RuCl₂P₃ structure. Complex 4 reacts reversibly and stepwise with two equivalents of CH₃CN. The calculated stability constants, as determined from a spectrophotometric titration, are log β₁ = 9.1 and log β₂ = 12.4. The proximally substituted calixarene L³ reacts with [PtCl₂(COD)] (COD = cycloocta-1,5-diene) to afford the chelate complex cis-[PtCl₂L³] 5. As revealed by an X-ray diffraction study, the P-Pt vectors point away from the calixarene axis in the solid state. The axial H atom of the C₆H₂CH₂ group located between the two phosphine units of L³ undergoes a significant low-field shift upon complexation (δ 7.32 vs. 4.48 for free L³) presumably due to interaction with the lone pairs of the two neighbouring O-atoms. Complex 5 displays dynamic behaviour in solution, which can be rationalized as follows: (i) a fast flip-flop motion of the hydroxyl groups at low temperature, alternately forming hydrogen bonds with each of two neighbouring phenolic oxygens; (ii) a reversible inversion of the phenol ring through the lower-rim annulus, triggered by breakage of the hydrogen bonds at higher temperature. Reaction of [PtCl₂(COD)] with one equivalent of L¹, followed by in situ oxidation with NH₂CONH₂·H₂O₂, results in formation of a chelate complex, containing two proximal phosphines bonded to platinum as in 5 and two pending CH₂P(O)Ph₂ phosphine oxides. Stepwise reaction of [PtCl₂(COD)] with one equivalent of L¹ and two equivalents of [AuCl(THT)] gives a cis complex in which the platinum atom is again bonded to two proximal phosphines and the two AuCl units to the other two phosphine arms. As in 5, an anomalous low-field shift is observed for the axial C₆H₂CH belonging to the platinocycle of these complexes. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a905814a

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Co-ordination chemistry of macrocyclic compounds with dangling
phosphines. Unusual NMR shifts in metallo-calix[4]arenes†
Cedric B. Dieleman,a Claire Marsol,a Dominique Matt,*a Nathalie Kyritsakas,b
Anthony Harrimanc and Jean-Pierre Kintzingerd
a Groupe de Chimie Inorganique Moléculaire, UMR 7513 CNRS, 1 rue Blaise Pascal,
F-67008 Strasbourg Cedex, France. E-mail: dmatt@chimie.u-strasbg.fr
b Laboratoire de Cristallographie, UMR 7513 CNRS, 4 rue Blaise Pascal,
F-67008 Strasbourg Cedex, France
c Ecole Européenne de Chimie, Polymères et Matériaux, 1 rue Blaise Pascal,
F-67008 Strasbourg Cedex, France
d Laboratoire de RMN et Modélisation Moléculaire, UMR 7510 CNRS, 4 rue Blaise Pascal,
F-67008, Strasbourg, France
Received 19th July 1999, Accepted 7th October 1999
The chelating behaviour of three polyphosphines, cone-5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenyl-
phosphinomethoxy)calix[4]arene L1, cone-5,11,17,23-tetra-tert-butyl-25,26,27-tris(diphenylphosphinomethoxy)-
28-methoxycalix[4]arene L2, and cone-5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinomethoxy)-27,28-
dihydroxycalix[4]arene L3, has been investigated. When [Mo(CO)3(C7H8)] and tetraphosphine L1 are heated
together under reflux in tetrahydrofuran (THF) complex [Mo(CO)3L1] 1 is formed, for which the calixarene
behaves as a fac-bonded tridentate ligand with one phosphine remaining free. Similar fac-chelating behaviour is
found with [Mo(CO)3L2] 2, which is obtained from triphosphine L2. Formation of this latter complex is accompanied
by the calixarene matrix adopting a partially flattened-cone conformation. In contrast, the conventional cone
conformation is maintained in the trinuclear complex [(AuCl)3L2] 3, obtained quantitatively by treating L2 with
[AuCl(THT)] (THT = tetrahydrothiophene). Reaction of L1 with [RuCl2(DMSO)4] (DMSO = Me2SO) in CH2Cl2
results in selective formation of the deep purple complex [RuCl2L2] 4 built around a fac-trigonal bipyramidal RuCl2P3
structure. Complex 4 reacts reversibly and stepwise with two equivalents of CH3CN. The calculated stability
constants, as determined from a spectrophotometric titration, are log β1 = 9.1 and log β2 = 12.4. The proximally
substituted calixarene L3 reacts with [PtCl2(COD)] (COD = cycloocta-1,5-diene) to afford the chelate complex
cis-[PtCl2L3] 5. As revealed by an X-ray diffraction study, the P–Pt vectors point away from the calixarene axis in
the solid state. The axial H atom of the C6H2CH2 group located between the two phosphine units of L3 undergoes a
significant low-field shift upon complexation (δ 7.32 vs. 4.48 for free L3) presumably due to interaction with the lone
pairs of the two neighbouring O-atoms. Complex 5 displays dynamic behaviour in solution, which can be rationalized
as follows: (i) a fast flip-flop motion of the hydroxyl groups at low temperature, alternately forming hydrogen bonds
with each of two neighbouring phenolic oxygens; (ii) a reversible inversion of the phenol ring through the lower-rim
annulus, triggered by breakage of the hydrogen bonds at higher temperature. Reaction of [PtCl2(COD)] with one
equivalent of L1, followed by in situ oxidation with NH2CONH2ؒH2O2, results in formation of a chelate complex,
containing two proximal phosphines bonded to platinum as in 5 and two pending CH2P(O)Ph2 phosphine oxides.
Stepwise reaction of [PtCl2(COD)] with one equivalent of L1 and two equivalents of [AuCl(THT)] gives a cis complex
in which the platinum atom is again bonded to two proximal phosphines and the two AuCl units to the other two
phosphine arms. As in 5, an anomalous low-field shift is observed for the axial C6H2CH belonging to the platinocycle
of these complexes.
Macrocyclic platforms that contain several phosphino groups
attached to their periphery are powerful tools for the construc-
tion and study of multimetal species that contain discrete
metal centres maintained in close proximity.1–5 In particular,
several recent publications have described the properties of the
p-tert-butylcalix[4]arene-derived tetraphosphine L1, a ligand
containing four pendant CH2PPh2 units that can bind up to
four transition metal centres.1,6,7 It has also been reported that,
in certain cases, L1 behaves as a small P4 surface around which
several gold or silver ions can migrate rather easily. These prior
studies have revealed that individual metal centres may be
bonded to L1 by way of either a single pendant phosphorus()
unit or with two adjacent P atoms functioning as cis or trans
chelators. No instance could be found whereby three phos-
phorus atoms co-ordinate to a single metal centre. Such tri-
podal co-ordination, which is described here for the first time,
results in formation of two adjacent 12-membered metallo-
cycles and in the fixation of a metal centre at the apex of the
calixarene cavity. The current study also focuses on the struc-
tural implications associated with co-ordination of a metal
centre to two adjacent CH2PPh2 phosphine units tethered at
the lower rim of the calix[4]arene platform. This complements
earlier work on distal co-ordination of substituted calix[4]-
arenes.8,9
† Dedicated to Professor Reinhard Schmutzler on the occasion of his
65th birthday. With our warmest wishes.
Supplementary data available: rotatable 3-D crystal structure diagram
in CHIME format. See http://www.rsc.org/suppdata/dt/1999/4139/.
Also available: general experimental details. For direct electronic
access see http://www.rsc.org/suppdata/dt/1999/4139/, otherwise avail-
able from BLDSC (No. SUP 57667, 3 pp.) or the RSC Library. See
Instructions for Authors, 1999, Issue 1 (http://www.rsc.org/dalton).
J. Chem. Soc., Dalton Trans., 1999, 4139–4148
This journal is © The Royal Society of Chemistry 1999
4139

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1P) assignable to an unco-ordinated PIII atom. The carbonyl
region of the IR spectrum shows two strong absorption bands
indicating the presence of a Mo(CO)3 unit with local C3v sym-
metry.10 The 1H and 13C NMR spectral data reveal the presence
of two distinct C6H2CH2 fragments but the relevant 13C chem-
ical shifts (δ 32.06 and 31.30) are fully consistent with a cone
conformation. Similarly, the AB patterns observed for each set
of C6H2CH2 groups correspond to a splitting of the A and B
parts (δA Ϫ δB = 1.47 and 1.05) that is further confirmation for
a cone conformation:14 syn-oriented aryl rings usually give AB
separations > ca. 0.7 ppm, while the AB separation is smaller
for anti-oriented aryl rings.
Results and discussion
Tripodal behaviour of calix[4]arene polyphosphines
Should we expect tridentate co-ordination to a single transition
metal centre by a calix[4]arene substituted at the lower rim
by three or four CH2PPh2 groups? At first sight such ligation
seems unlikely since it requires formation of two 12-membered
metallo-macrocycles. To reach a more definitive answer, how-
ever, we have examined the co-ordinative properties of two
suitably functionalized ligands, namely tetraphosphine L1 and
triphosphine L2, towards two metal fragments, “Mo(CO)3” and
“RuCl2”, known to form tris(phosphine) complexes.10,11 Ligand
L2, which is reported for the first time, was prepared in high
yield by reduction of the corresponding tris(phosphine oxide)6
L2 with phenylsilane (Scheme 1) using a known general pro-
ox
For triphosphine L2, reaction with [Mo(CO)3(C7H8)] in
refluxing THF led to complex 2 (58%), which also contains a
fac-MoP3 unit. There was no indication for oligomer formation
in this reaction. The FAB mass spectrum of the complex dis-
plays peaks at m/z 1438 and 1410, with the profile exactly
matching that expected for the Mϩ and [M Ϫ CO]ϩ cations,
respectively. The 13C NMR spectrum displays two distinct
C6H2CH2 signals at δ 30.22 and 35.46. The former value is
typical of a CH2 group bordered by syn-arranged aryl rings
whereas the latter value lies between those reported for syn and
anti C6H2CH2C6H2 arrangements. It seems likely, therefore, that
the calix matrix adopts a partially flattened conformation with
the methoxy group being oriented towards the calix axis and
entrapped between two facing aryl units. Indeed, the strong
upfield shift experienced by the methoxy protons (δ 0.38,
∆δ = Ϫ3 ppm) reflects their encapsulation between aromatic
rings. Finally, we note that one set of C6H2CH2 groups appears
as an AB pattern with an AB separation of only 0.50 ppm. No
significant structural change was apparent from NMR spectra
recorded over the temperature range Ϫ80 to ϩ25 ЊC. It is dif-
ficult to explain the different calix conformations adopted by 1
and 2, especially when allowing for the observation that L2
reacts with 3 equivalents of [AuCl(THT)] (THT = tetrahydro-
thiophene) to form the trinuclear species 3 which persists in the
cone conformation. The major difference between 2 and 3 is
that the P atoms are assembled in one complex via a central
atom whereas they move as three independent arms in the
other. Clearly, a structure with fac co-ordinated phosphines
results in a more strained calix matrix favouring a partially flat-
tened conformation. The latter was not observed in 1 obviously
Scheme 1
cedure. Signals for the phosphine units appear at δ Ϫ17.3 (2P)
and Ϫ18.6 (1P) in the 31P NMR spectrum whilst the calixarene
fragment adopts a cone conformation as deduced from the 13
C
NMR spectrum. This latter assignment is based on the follow-
ing reasoning: CH2 groups that bridge two aryl rings in a
relative syn arrangement exhibit chemical shifts in the range
δ 29–3312 whereas the C6H2CH2 signal for anti-oriented aryl
rings in partial-cone conformers appears at higher values (in
general δ > ca. 37). We are aware that these guidelines, being
most helpful for establishing the conformation of calix[4]-
arenes, must be applied with care in those cases where the
phenolic units of the calixarene are not possessed of bulky
substituents.13 This is because phenolic rings bearing small sub-
stituents can undergo fast transannular rotation around the
bridging methylene groups or, in certain cases, adopt an orien-
tation that positions the substituent inside the calix cavity. For
both situations the chemical shift of the bridging C6H2CH2
groups lies between δ 33 and 37. Even so, it seems reasonable to
assign a cone conformation to ligand L2. Relevant spectro-
scopic data for L2 are given in the Experimental section.
Reaction of L1 with [Mo(CO)3(C7H8)] in refluxing tetra-
hydrofuran (THF) afforded the colourless complex 1 in high
yield. The fact that no oligomers are formed, regardless of reac-
tion conditions, is a good indication for the high degree of pre-
organization of the three podands. The tridentate behaviour of
L1 was inferred from the 31P NMR spectrum which shows two
signals of relative intensity 2:1 corresponding to metal-bound
phosphines (2J(PP) = 13 Hz) and a singlet at δ Ϫ18.7 (intensity
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difficult. Interestingly, the mono-adduct does not absorb in the
region 450–650 nm but the bis-adduct absorbs over this range,
suggesting different geometries.
Chelating behaviour of two proximally positioned CH2PPh2
groups
Tripodal ligation of the type expressed in complexes 1 and 4
forces the metallic centre to reside beneath the lower rim of the
calix cavity. Related complexes are known for which the metal
centre is chelated by two distally tethered CH2PPh2 podands16
and a logical extension of this work is to design suitable 1,2-
disubstituted calixarenes equipped with two proximal CH2PPh2
groups. The simplest such representative is the diphosphine L3,
which was obtained in quantitative yield by reduction of the
corresponding di(phosphine oxide)6 L3 with PhSiH3. Clear
ox
evidence for the cone conformation was obtained from 1H and
13C NMR spectra. In particular, the 1H NMR spectrum shows
three AB systems for the C6H2CH2 groups, with AB separations
of 1.39, 1.21 and 0.83 ppm (relative intensity 2 H:4 H:2 H). The
signal for the two residual OH groups appears at δ 8.91 (cf.
δ 5.50 for p-tert-butylphenol and 10.34 for p-tert-butyl-
calix[4]arene), suggesting their involvement in hydrogen bond-
ing with neighbouring phenolic oxygen atoms.
Fig. 1 Spectrophotometric titration of complex 4 by CH3CN. Condi-
tions: [4]initial = 5 × 10Ϫ4 M. Solvent: CH2Cl2.
because the CH2PPh2 group is sterically much larger than a Me
group. Thus, a subtle balance between the bulk of the non-
metallated phenoxy substituent and the strain within the calix
backbone explains the different structures adopted by com-
plexes 1–3.
Reaction of L1 with [RuCl2(DMSO)4] (DMSO = Me2SO) in
CH2Cl2 (25 ЊC) is very slow but leads to selective formation of
the deep purple complex 4. After 15 d the yield reached 60%.
The FAB mass spectrum of 4 shows a peak at m/z 1577 corre-
sponding to the [M Ϫ Cl]ϩ cation. That only a monomeric
species is formed was apparent from vapour phase osmometry.
In the 31P NMR spectrum the unco-ordinated phosphine
appears at δ Ϫ20.0 while the three bound phosphorus atoms
give rise to an A2B pattern with δA = 35.4 and δB = 60.3. The
purple colour of the complex is a good indication for a
fac-trigonal bipyramidal RuCl2P3 structure.11,15 Further proof
for the mutual cis arrangement of the three phosphorus atoms
includes: (i) the 2J(PAPAЈ) value, ca. 25 Hz, calculated from the
13C NMR signal (a quintet) of the two distal PCH2 groups and
(ii) the 2J(PAPB) value of 41 Hz as obtained from the 31P NMR
spectrum. Note that the overall structure of 4 is reminiscent of
that of 1. There is no indication for fluxional behaviour or
isomerization of 4 in solution. In contrast, reaction of triphos-
phine L2 with [RuCl2(DMSO)4] afforded a mixture of products,
presumed to be oligomers, that could not be resolved. The
NMR spectra do not change when running them at different
concentrations. Thus monomer–oligomer equilibria can be
ruled out.
Reaction of L3 with [PtCl2(COD)] (COD = cycloocta-1,5-
diene) in dichloromethane afforded complex 5 in 72% yield
after chromatography (Scheme 2). To prevent formation of
Scheme 2
oligomers, reaction was carried out at modest concentration. In
this complex the platinum centre forms part of a 12-membered
metallo-macrocycle. The NMR spectral data collected indicate
a plane of symmetry. For example, the 1H NMR spectrum
shows three sets of AB patterns for the C6H2CH2 groups and
two But signals. The cis stereochemistry around platinum was
inferred from the J(PPt) coupling constant of 3672 Hz. Interest-
ingly, the C6H2CH2 group lying between the two phosphines
gives rise to an AB system with an exceptionally large splitting
of the A and B parts: ca. 3.6 ppm (!). The corresponding axial
H atom was found at ca. δ 7.34. The assignment of this particu-
lar AB signal was made on the basis of a two-dimensional
ROESY (rotating frame Overhauser enhancement spectro-
scopy) experiment (at 218 K). We note also that the 13C NMR
signal (δ 36.98) for the C6H2CH2 group within the metallocycle
(as identified by an HETCOR (heteronuclear correlation)
experiment) lies considerably outside the range expected for
methylene groups bordered by syn oriented aryl rings.
Addition of a few drops of CH3CN to a solution of complex
4 in CH2Cl2 caused an instantaneous change to pale yellow.
Evaporation of the solvent fully regenerated 4. Attempts to
isolate a complex formed with CH3CN were unsuccessful but
spectrophotometric titrations (Fig. 1) established that 4 reacts
stepwise with two molecules of CH3CN. The calculated stabil-
ity constants are log β1 = 9.1 0.2 and log β2 = 12.4 0.5,
indicating that addition of the first solvent molecule is
exceptionally favourable, corresponding to a binding energy of
50 kJ molϪ1. Addition of a second acetonitrile molecule is more
Note that Floriani and co-workers17 have recently reported
that the axial C6H2CH hydrogen of the 10-membered metallo-
cycles present in complex 6 undergoes also an anomalous
downfield shift (δA 5.86) with respect to the “free” ligand. This
phenomenon which was attributed to ring current effects gener-
ated by the metallomacrocycles is however less important than
that observed in 5. In order to identify other effects that could
account for the rather unusual downfield shift observed for 5
and also to clarify the mutual positioning of the metal centre
and the cavity (A or B form), an X-ray diffraction study was
J. Chem. Soc., Dalton Trans., 1999, 4139–4148
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Table 1 Selected bond lengths (Å) and angles (Њ) for complex 5
Pt–Cl(1)
Pt–Cl(2)
Pt–P(1)
Pt–P(2)
O(1) ؒ ؒ ؒ O(3)
O(2) ؒ ؒ ؒ O(4)
2.342(2)
2.372(2)
2.241(2)
2.253(2)
4.192(8)
4.069(8)
O(1) ؒ ؒ ؒ O(2)
O(2) ؒ ؒ ؒ O(3)
O(3) ؒ ؒ ؒ O(4)
O(1) ؒ ؒ ؒ O(4)
C(24) ؒ ؒ ؒ Pt
3.379(7)
2.780(8)
2.668(9)
2.897(8)
3.546(8)
Cl(1)–Pt–Cl(2)
Cl(1)–Pt–P(1)
Cl(1)–Pt–P(2)
Cl(2)–Pt–P(1)
P(1)–Pt–P(2)
C(11)–P(1)–C(12)
C(11)–P(1)–C(18)
87.06(8)
171.61(8)
83.32(8)
85.79(9)
103.43(8)
106.8(4)
102.2(4)
C(12)–P(1)–C(18)
C(35)–P(2)–C(36)
C(35)–P(2)–C(42)
C(36)–P(2)–C(42)
C(30)–O(2)–C(35)
C(6)–O(1)–C(11)
101.6(4)
103.5(4)
102.9(4)
103.8(4)
110.0(6)
109.9(6)
Angles between facing phenolic rings: 66.5(2) and 56.0(2)Њ.
Table 2 Selected bond lengths (Å) and angles (Њ) for L3
ox
O(1) ؒ ؒ ؒ O(3)
O(5) ؒ ؒ ؒ O(3)
O(2) ؒ ؒ ؒ O(3)
2.971(6)
2.824(6)
2.710(4)
O(3) ؒ ؒ ؒ O(4)
O(5) ؒ ؒ ؒ O(4)
O(1) ؒ ؒ ؒ O(5)
5.339(6)
3.404(6)
3.149(5)
O(4)–C(57)–P(2)
107.2(4)
O(1)–C(11)–P(1)
112.1(4)
Angles between facing phenolic rings: 1.8(2) and 110.8(2)Њ.
Fig. 2 Molecular structure (PLATON18) of complex 5.
Fig. 3 Molecular structure (PLATON18) of L3ox. The four But groups
have been omitted for clarity.
could then explain the observed low-field shift. The rather
short O(1) ؒ ؒ ؒ O(4), O(3) ؒ ؒ ؒ O(4) and O(2) ؒ ؒ ؒ O(3) distances
(respectively 2.90, 2.67 and 2.78 Å, Table 1) are indicative of
hydrogen bonding between the hydroxy functions and the
adjacent phenolic O atoms. The calixarene matrix is close to
that found in an ideal cone. This is in marked contrast to the
structure of the non-metallated oxidized form of L3 (Fig. 3,
Table 2) which displays the conventional flattened cone shape
found in the solid state for most calix[4]arenes. The idealized
cone conformation seen for the matrix in 5 probably arises from
a combination of effects caused by the presence of the strained
metallocycle and the O ؒ ؒ ؒ HO bridges.
carried out for 5. The result of this investigation is shown in
Fig. 2.18
The X-ray analysis confirmed the chelating behaviour of L3
and established the cone conformation. This complex crystal-
lizes with one molecule of water and six molecules of dichloro-
methane, one of which lies inside the cavity. The two PPt
vectors are directed away from the centre of the cavity, so that
the two bound chlorides lie well away from the lower rim (B
form), with the result that the Pt atom lies 2.67 Å beneath the
axial C6H2CH proton. Note, this distance might be too long for
agostic interaction, although in solution shorter separations
will abound. It is notable that the axial C6H2CH atom, which
is located between the two P atoms, resides only 2.42 Å from
the two neighbouring phenolic O atoms. Although on the
upper limit for hydrogen bonding, we cannot rule out the
possibility of weak interactions between these atoms. These
A variable temperature NMR study (CD2Cl2, 500 MHz, Fig.
4) carried out between 198 and 308 K revealed that complex 5
undergoes a structural modification in solution on varying the
1
temperature. The low temperature H NMR spectra are fully
consistent with a cone conformation (e.g. large separations for
the C6H2CH2 groups at 198 K). On raising the temperature the
two sets of AB signals corresponding to the C6H2CH2 groups
centred on C59 and C(48)/C(70) (for labelling see Fig. 2; for
simplification these atoms are respectively labelled # and * in
Fig. 4) begin to broaden, reaching a maximum of broadening
around 238 K, and eventually reappearing as two new sets of
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Fig. 4 Variable temperature NMR study (1H NMR, 500 MHz, CD2Cl2) for complex 5 (partial view). The spectra show the AB systems correspond-
ing to the PCH2 and C6H2CH2C6H2 protons. The symbols *, # and ∆ have been used for indexing the bridging C6H2CH2C6H2 protons. The signal of
the axial C6H2CH atom belonging to the platinomacrocycle is out of this view (δ 7.34, 308 K).
Scheme 3 Proposed dynamics for complex 5.
AB signals. At the highest temperature these AB separations
are much smaller (∆δ = 0.56 and 0.36 ppm, CD2Cl2, 308 K)
than in the low temperature spectra, thus indicative for the
formation of a structurally different isomer. The smaller AB
splittings could arise from formation of fast interconverting
1,2-alternate conformers or because of fast equilibration
between cone and non-cone species. The third AB system,
which corresponds to H atoms bonded to C24 (only the B
part, labelled ∆, is shown in Fig. 4) remains essentially
unperturbed over this temperature range. To help interpret the
high temperature spectra, two-dimensional ROESY experi-
ments‡ were performed on 5 and its PMe2 analogue 7. This
latter complex is a useful model by which to explain the
*). This observation can be explained only in terms of rapid
various NMR spectral changes because the only aromatic
inversion of the phenol rings.
hydrogens able to correlate with C6H2CH2 protons are those
The spectral modifications observed for complex 5 in the
range 198–308 K are reversible and may be rationalized in
terms of disruption of the hydrogen bonds as the sample is
heated, followed by ring inversion at higher temperatures
belonging to the calix matrix. In fact the NMR spectrum
recorded for 7 shows NOEs between a m-CH of the phenol
rings and both doubly degenerated C6H2CH2 protons (labelled
(Scheme 3). Interestingly, on raising the temperature, one of the
PCH2 hydrogen atoms undergoes a significant change in chem-
‡ No cross peaks due to dynamic exchange were detected.
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ical shift while the other is little affected (Fig. 4). This behaviour
would occur if one CH atom is anti oriented with respect to the
interacting OH atom. The low temperature spectra indicate
a Cs-symmetrical cone structure with hydrogen bonded OH
groups (δ 8.46 at 218 K). Furthermore, two-dimensional
ROESY experiments performed at low temperature show that
the OH atoms correlate with the axial CH atoms of both neigh-
bouring C6H2CH2 groups. These findings are in agreement with
a fast flip-flop motion of the hydroxyl groups, as shown in
Scheme 3 (left side). This movement which could not be frozen
out is reminiscent of the hydroxyl movement observed in native
β-cyclodextrin.19 The free enthalpy of activation for the inter-
conversion between the isomer containing hydrogen bonds and
that obtained after hydrogen bond breaking (T = 238 K) is cal-
culated20 to be 58 kJ molϪ1. Note, hydrogen bond breaking
involving phenolic OH groups in calixarenes is well docu-
mented; for comparison, the energy barrier for cone–cone
interconversion of p-tert-butylcalix[4]arene, a process that
implies the rupture of four hydrogen bonds (followed by inver-
phosphine arms and afforded complex 8 in high yield (Scheme
4a). FAB mass spectrometry revealed peaks due to both Mϩ
and [M Ϫ Cl]ϩ while ROESY, COSY and HETCOR experi-
ments allowing precise assignment of all hydrogen atoms,
except those of the PPh groups (see Experimental section). The
31P NMR spectrum recorded for 8 displays a signal centred at
δ 8.6 (cf. 8.4 for 5), attributable to the metal-bound phos-
phines (J(PPt) = 3631 Hz), and a singlet at δ 24.7, due to the
phosphine oxides. The NMR data point to a plane of sym-
metry. Furthermore, the presence of three distinct types of
methylenic C6H2CH2C6H2 groups is strong indication for prox-
imal chelation, rather than distal co-ordination, such that 1,3
complexation seems not to be favourable in the present case. As
for 5, an important downfield shift is observed for a single
methylenic C6H2CHC6H2 hydrogen (δ 7.43, ∆δ = 3.97 ppm)
whilst the corresponding 13C NMR signal, identified by a
13C–1H HETCOR experiment, appears far outside of the range
expected for a cone conformer (δ 38.88). On the basis of this
spectral correspondence, we tentatively assign the conformation
of the metallocycle in 8 as being similar to that of 5.
sion of the calix matrix), is 70–75 kJ mol .
Ϫ1 21,22 Important con-
formational changes within the metallomacrocycle itself appear
unlikely since the AB separation of the endocyclic C6H2CH2
group remains essentially unchanged during the temperature
variation. However, flipping of the platinum atom under the
calix cavity (with exchange between the A and B forms) cannot
strictly be ruled out. In summary, the modification observed
in the NMR spectra of complex 5 may be interpreted in terms
of hydrogen bond breaking when the temperature is raised.
Thus, we observe the reversible conversion of a species “with
hydrogen bonds” into an isomer “without hydrogen bonds”.
Both isomers undergo fast dynamics involving either hydroxyl
movement (low temperature species) or phenol ring inversion
(high temperature isomer).
An alternative method for preventing oligomerization
involves complexing the phosphines that remain unco-
ordinated after the first step. Thus, addition of two equivalents
of [AuCl(THT)] to the product obtained following reaction of
one equivalent of L1 with [PtCl2(COD)] led to the trinuclear
complex 9 (Scheme 4b). Again a single C6H2CH signal is
strongly deshielded (δ(H) = 7.35; δ(C) = 37.15) and can be
assigned to the C6H2CH2 group of the 12-membered metalla-
cycle. The molecular structure of 9 was confirmed by an X-ray
diffraction study which will be reported elsewhere.23 Surpris-
ingly, reaction of two equivalents of [PtCl2(COD)] with L1 did
not lead to the expected dinuclear complex but gave rise to
polymeric products.
A detailed 31P NMR spectroscopic investigation was made of
the reaction between one equivalent of tetraphosphine L1 and
[PtCl2(COD)]. The resultant platinum complex comprises two
cis-co-ordinated P atoms (δ 8.9, J(PPt) = 3640 Hz) and two free
phosphines (δ Ϫ19.6). Attempts to isolate this compound were
unsuccessful because oligomerization occurred during con-
centration. To overcome this problem, NH2CONH2ؒH2O2 was
added to the reaction mixture after one hour (Scheme 4). This
procedure results in mild oxidation of the unco-ordinated
The triphosphine L2 reacts with [PtCl2(COD)] in a manner
reminescent of the behaviour described for L1; isolation of
chelate complex 10 requiring oxidation of the phosphine
remaining unco-ordinated after the first step. Here, the AB
system of the axial C6H2CH atom assigned to the metallocycle
is characterized by δA = 7.20 and δB = 3.68. The 13C NMR spec-
trum displays four C6H2CH2 signals, three of which lie slightly
under the critical value of δ 37 while the fourth appears at
δ 32.10. It seems reasonable to assign a partial cone conform-
Scheme 4 Construction of chelate complexes involving two proximal phosphines of L1.
4144
J. Chem. Soc., Dalton Trans., 1999, 4139–4148

View Article Online
using the Nonius OpenMoleN32 package and refined by full
matrix least-squares with anisotropic thermal parameters for all
non-hydrogen atoms. Final results: R(F) = 0.085, wR(F) =
0.109, goodness of fit = 1.225, 712 parameters, largest differ-
ence peak = 1.038 e ÅϪ3
.
Crystal data for complex 5. 2C70H156O12P4Ptؒ6CH2Cl2ؒH2O,
M = 3150.30, orthorhombic, space group P212121, colourless
crystals, a = 12.571(1), b = 22.5546(3), c = 26.4894(3) Å, V =
7510.6(8) Å3, Z = 2, Dc = 1.39 g cmϪ3, µ = 2.241 mmϪ1
,
F(000) = 3212. Data were collected as above. 50394 Reflections
(2.5 ≤ θ ≤ 32.39Њ), 9230 data with I > 3σ(I). Absolute structure
determined refining Flack’s x parameter. The structure was
solved and refined as above: R(F) = 0.050, wR(F) = 0.068,
goodness of fit = 1.028, 824 parameters, largest difference
ation to 10. Other important characterizing data are given in
the Experimental section. Note, in view of the absence of any
symmetry element in complex 10, the latter exists as a mixture
of two enantiomers.
peak = 1.416 e ÅϪ3
.
CCDC reference number 186/1684.
See http://www.rsc.org/suppdata/dt/1999/4139/ for crystallo-
graphic files in .cif format.
The present study demonstrates that calixarenes bearing two
proximal CH2PPh2 substituents form readily chelate complexes.
In particular, [PtCl2(COD)] reacts with each phosphine-based
ligand to give a 12-membered metallomacrocycle containing
the PtCl2 unit. A characteristic feature of these platinum
metallomacrocyclic complexes concerns the anomalous chem-
ical shift observed for the axial C6H2CH atom belonging to the
macrocycle, possibly due to interaction with the lone pairs
of the endocyclic oxygen atoms. The metallomacrocycle in
complex 5 appears to weaken pre-existing hydrogen bonds
compared to those found in free L3. Those calixarenes substi-
tuted by three or four dangling CH2PPh2 groups exhibit P3-
chelating behaviour. This unique type of triple co-ordination
leads to formation of fac-oriented complexes with incoming
“Mo(CO)3” and “RuCl2” fragments, wherein the metal centre is
fixed immediately below the calix cavity.
Syntheses
5,11,17,23-Tetra-tert-butyl-25,26,27-tris(diphenylphosphino-
methoxy)-28-methoxycalix[4]arene L2. A suspension of com-
pound L2ox (6.100 g, 4.67 mmol) in phenylsilane (7.00 mL, 97.80
mmol) was heated at 90–100 ЊC for 12 d. After evaporation of
the solvent in vacuo the residue was subjected to flash chrom-
atography using CH2Cl2 as eluent. The fraction corresponding
to Rf = 0.67 (SiO2, CH2Cl2–hexane, 1:1, v/v) was concentrated
to ca. 30 mL. Precipitation with MeOH yielded compound L2
as a colourless powder. Yield: 5.288 g, 90%; mp 152–154 ЊC. 1H
NMR (300 MHz, 293 K, CDCl3): δ 7.50–7.26 (30 H, PPh2), 7.06
and 6.90 (2s, 2 H each, m-H of aryl), 6.42 and 6.38 (AB quartet,
4J ≈ 2, 2 H each, m-H of aryl), 5.48 (broad s, 2 H, PCH2O), 4.66
2
and 4.62 (ABX spin system with X = P, 2J = 12, JAX = 3,
2JBX = 2, 2 H each, PCH2O adjacent to methoxy), 4.51 and 3.01
Experimental
2
(AB quartet, J = 13, 2 H each, C6H2CH2), 4.16 and 3.06 (AB
quartet, 2J = 13 Hz, 2 H each, C6H2CH2), 3.33 (s, 3 H, OCH3),
1.34, 1.32 and 0.83 (3s, 9 H ϩ 9 H ϩ 18 H, tert-butyl). 13C-{1H}
NMR (50 MHz, 293 K, CDCl3): δ 155.68–131.47 (quat. aryl C),
133.81–124.31 (aryl CH), 77.10 (d, JPC ≈ 10, PCH2O), 75.12 (d,
JPC ≈ 20 Hz, PCH2O), 60.26 (s, OCH3), 34.10 and 33.60 (3s,
C(CH3)3), 32.61 (s, C6H2CH2), 31.76 and 31.15 (C(CH3)3) (one
C6H2CH2 signal is probably overlapping with a tert-butyl sig-
nal). 31P-{1H} NMR (121 MHz, 293 K, CDCl3): δ Ϫ17.3 (s, 2P)
and Ϫ18.6 (s, 1P). Found: C, 80.11; H, 7.35. Calc. for C84H91-
O4P3: C, 80.23; H, 7.29%.
General experimental details are given as supplementary data
(see SUP 57667). The global binding constants log βn were
determined by UV-visible spectrophotometric titration in
dichloromethane (spectroscopic grade). For these measure-
ments a quartz cell was filled under N2 atmosphere with a solu-
tion of complex 4 in dichloromethane (5 × 10Ϫ4 M, 3 µL) to
which were added multiples of 10 mL of neat acetonitrile solu-
tion. The “Ru”:MeCN ratio ranged from 0 to 4:1. The spectra
were recorded between 190 and 310 nm using a quartz cell
(1 cm path length) that was thermoregulated at 25 0.5 ЊC.
The absorbance changes monitored were significant enough to
be exploited by multiwavelength numerical treatment based on
a Benesi–Hildebrandt type equation (program SPECFIT© 24),
(Improved preparation of) 5,11,17,23-tetra-tert-butyl-25,26-
bis(diphenylphosphinoylmethoxy)-27,28-dihydroxycalix[4]arene
L3ox. To a suspension of p-tert-butylcalix[4]arene (5.000 g, 7.70
mmol) in DMF (200 mL), cooled at 0 ЊC, was added in portions
NaH (0.647 g, 26.97 mmol). After stirring for 1.5 h, Ph2P(O)-
CH2O-SO2C6H4Me-p (8.920 g, 23.10 mmol) was added and the
solution further stirred for 2 h at 0 ЊC. After 24 h the excess
of NaH was decomposed with MeOH (10 mL), then the solvent
was removed in vacuo. The residue was taken up in CH2Cl2 (250
mL) and washed with 1 M HCl (80 mL), then with water
(2 × 100 mL). The organic layer was dried with MgSO4 and
evaporated to dryness to afford a solid which was purified by
flash column chromatography using ethyl acetate–hexane (1:1,
v/v) as eluent. The fraction eluting first (SiO2, Rf = 0.79, yield
10%), was discarded. Compound L3ox which is the second com-
pound migrating on the column (Rf = 0.55) was obtained as an
analytically pure colourless solid (5.475 g, 66%). Spectroscopic
data have been published previously.6
which yielded the desired global binding constants log βn.
6
Compounds L1,6 L2
,
[AuCl(THT)],25 [RuCl2(DMSO)4],26
ox
[PtCl2(COD)],27 [Mo(CO)3(C7H8)],28 Ph2P(O)CH2O-SO2C6H4-
Me-p,29 and PhSiH3 were prepared according to methods
30
reported in the literature. The di(phosphine oxide) L3 was
ox
synthesized according to an improved procedure (see below).
The P-methylated version of L3 was prepared according to
a procedure similar to that described below for L3, using
Me2P(O)CH2O-SO2C6H4Me-p as alkylating agent and will be
fully described elsewhere (δ 31P: Ϫ53.8 (s)).31
X-Ray crystallography
Crystal data for L3ox. 2C70H78O6P2ؒC2H5OC2H5, M = 2228.82,
¯
triclinic, space group P1, colourless crystals, a = 14.9993(8),
b = 15.351(1), c = 15.4699(9) Å, α = 102.912(9), β = 106.361(9),
γ = 103.676(9)Њ, U = 3156(1) Å3, Z = 1, Dc = 1.17 g cmϪ3
,
µ = 0.116 mmϪ1, F(000) = 1194. Data were collected on a
Nonius KappaCCD diffractometer (graphite Mo-Kα radiation,
0.71073 Å) at Ϫ100 ЊC. 22148 Reflections collected (2.5 ≤ θ ≤
26.38Њ), 5805 data with I > 3σ(I). The structure was solved
5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphino-
methoxy)-27,28-dihydroxycalix[4]arene L3. A suspension of
compound L3 (6.200 g, 5.75 mmol) in toluene (120 mL) was
ox
J. Chem. Soc., Dalton Trans., 1999, 4139–4148
4145

View Article Online
heated at 90–100 ЊC in the presence of phenylsilane (2.1 mL,
28.75 mmol) for 7 days. After evaporation of the solvent in
vacuo the residue was subjected to flash chromatography using
CH2Cl2–hexane (1:1, v/v) as eluent. The fraction obtained with
Rf = 0.23 (SiO2) was concentrated to ca. 40 mL, and addition
of MeOH yielded compound L3 as a colourless powder. Yield:
and 30.22 (2s, C6H2CH2), 34.09 and 33.82 (2s, C(CH3)3), 31.69,
31.33 and 30.97 (3s, C(CH3)3). 31P-{1H} NMR (121 MHz,
293 K, CDCl3): δ 26.6 (broad s) and 18.2 (t) (A2B system,
2J(PA–PB) = 25 Hz). FAB mass spectrum: m/z 1438 (Mϩ, 1) and
1410 ([M Ϫ CO]ϩ, 6). Found: C, 72.83; H, 6.66. Calc. for
C87H91MoO7P3: C, 72.69; H, 6.38%.
5.951 g, 99%; mp 201–203 ЊC. IR (KBr) (νmax
/cmϪ1): 3362 br
˜
(OH). 1H NMR (300 MHz, 293 K, CDCl3): δ 8.91 (s, 2 H, OH),
Trichloro{5,11,17,23-tetra-tert-butyl-25,26,27-tris(diphenyl-
phosphinomethoxy)-28-methoxycalix[4]arene-P,PЈ,PЉ}trigold (I)
3. To a stirred solution of compound L2 (0.100 g, 0.08 mmol) in
CH2Cl2 (10 mL) was added a solution of [AuCl(THT)] (0.079 g,
0.25 mmol) in CH2Cl2 (10 mL). After 0.5 h the solution was
filtered over a bed of Celite. Concentration to ca. 5 mL and
addition of pentane precipitated complex 3 as a colourless
powder (SiO2, Rf = 0.20, CH2Cl2–hexane, 4:1, v/v). Yield: 0.139
4
7.49–7.32 (20 H, PPh2), 7.01 and 6.96 (AB system, J = 3, 2 H
each, m-H of aryl), 6.93 and 6.86 (AB system, 4J = 3, 2 H each,
m-H of aryl), 5.19 and 4.93 (ABX system with X = P, 2JAB = 12,
2
2JAX = 2, JBX = 3, 2 H each, PCH2O), 4.59 and 3.20 (AB
quartet, 2J = 13, 1 H each, C6H2CH2), 4.48 and 3.27 (AB quar-
2
tet, J = 13, 2 H each, C6H2CH2), 4.15 and 3.32 (AB quartet,
2J = 14 Hz, 1 H each, C6H2CH2), 1.22 and 1.12 (2s, 18 H each,
tert-butyl). 13C-{1H} NMR (50 MHz, 293 K, CDCl3): δ 152.81–
125.78 (quat. aryl C), 133.58–125.29 (aryl CH), 77.96 (broad s,
PCH2O), 34.06 and 33.94 (2s, C(CH3)3), 33.26, 32.84 and 32.01
(3s, C6H2CH2), 31.63 and 31.33 (2s, C(CH3)3). 31P-{1H} NMR
(121 MHz, 293 K, CDCl3): δ Ϫ20.2 (s). Found: C, 80.20; H,
7.38. Calc. for C70H78O4P2: C, 80.43; H, 7.52%.
1
g, 89%; mp 200 ЊC (decomp.). H NMR (200 MHz, 293 K,
CDCl3): δ 7.72–7.37 (30H, PPh2), 7.03 and 6.93 (2s, 2 H each,
m-H of aryl), 6.44 and 6.23 (AB quartet, 4J = 2, 2 H each, m-H
of aryl), 5.35 (broad s, 2 H, PCH2O), 4.69 and 4.53 (ABX sys-
2
2
2
tem with X = P, JAB = 13, JAX = 0, JBX = 2 Hz, 2 H each,
PCH2O adjacent to methoxy), 4.14 and 2.87 (AB quartet,
2J = 13, 2 H each, C6H2CH2), 4.01 and 3.07 (AB quartet, 2J = 13
Hz, 2 H each, C6H2CH2), 3.93 (s, 3 H, OCH3), 1.34, 1.26 and
0.78 (3s, 9 H ϩ 9 H ϩ 18 H, tert-butyl). 13C-{1H} NMR (50
MHz, 293 K, CDCl3): δ 155.01–125.65 (quat. aryl C), 134.52–
125.04 (aryl CH), 72.14 (d, JPC = 46, PCH2O), 71.87 (d, JPC = 41
Hz, PCH2O), 61.62 (s, OCH3), 34.12 and 33.60 (2s, C(CH3)3),
32.12 (s, C6H2CH2), 31.63, 31.56 and 31.01 (C(CH3)3) (one
C6H2CH2 signal is probably overlapping with a tert-butyl sig-
nal). 31P-{1H} NMR (81 MHz, 293 K, CDCl3): δ 22.7 (s, 2P)
and 20.5 (s, 1P). Found: C, 51.77; H, 4.87. Calc. for C84H91Au3-
Cl3O4P3: C, 51.61; H, 4.69%.
Tricarbonyl{5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-
(diphenylphosphinomethoxy)calix[4]arene-P,PЈ,PЉ}
molyb-
denum(0) 1. A solution of compound L1 (0.100 g, 0.07 mmol)
and [Mo(CO)3(C7H8)] (0.019 g, 0.07 mmol) in THF (80 mL)
was refluxed for 5 min. The orange solution was evaporated to
dryness in vacuo. The residue was subjected to flash chromato-
graphy using CH2Cl2–hexane (1:1, v/v) as eluent. The fraction
with Rf = 0.38 (SiO2) was precipitated from CH2Cl2–hexane
(1:1, v/v) affording the complex 1 as a colourless solid. Yield:
0.072 g, 64%; mp 235 ЊC (decomp.). IR (KBr) (νmax
/cmϪ1): 1946s
˜
1
᎐
and 1854s (C᎐O). H NMR (300 MHz, 293 K, CDCl ): δ 7.90–
᎐
3
6.32 (m, 48 H, PPh2 ϩ m-H of aryl), 5.88 and 5.49 (AB quartet,
2J = 13, 2 H each, PCH2O), 4.98 (br s, 2 H, PCH2O), 4.56 and
3.09 (AB quartet, 2J = 13, 2 H each, C6H2CH2), 4.49 (br s, 2 H,
Dichloro{5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-
(diphenylphosphinomethoxy)calix[4]arene-P,PЈ,PЉ}ruthen-
ium(II) 4. A solution of compound L1 (0.915 g, 0.63 mmol) and
[RuCl2(DMSO)4] (0.323 g, 0.66 mmol) in CH2Cl2 (150 mL) was
stirred for 15 d. The deep purple solution was filtered over a bed
of Celite (5 cm) and concentrated to ca. 5 mL. Addition of
Et2O precipitated complex 4 as a deep purple powder. Yield:
0.610 g, 60%; mp 255 ЊC (decomp.); 1H NMR (500 MHz,
293 K, CD2Cl2): δ 7.97–6.19 (m, 48 H, PPh2 ϩ m-H of aryl),
6.08 and 5.42 (d of filled-in d, AAЈBBЈXXЈ system with X,XЈ =
P, 2JAB = 14, 2 H each, PCH2O), 5.17 (d, 2JPH = 4, 2 H, PCH2O),
2
PCH2O), 3.67 and 2.62 (AB quartet, J = 13 Hz, 2 H each,
C6H2CH2), 1.39, 0.96 and 0.81 (3s, 18 H ϩ 9 H ϩ 9 H, tert-
butyl). 13C-{1H} NMR (50 MHz, 293 K, CDCl3): δ 218.91 (m,
᎐
᎐
᎐
C᎐O), 215.75 (broad d, C᎐O), 153.93 and 151.77 (2 broad s,
᎐
quat. aryl C–O), 150.90 (d, 3JPC = 11, quat. aryl C–O), 145.37–
126.04 (quat. aryl C), 134.10–124.69 (aryl CH), 78.52 (d,
JPC = 8, PCH2O), 75.36 (br s, PCH2O), 72.77 (d, JPC = 13 Hz,
PCH2O), 33.86, 33.73 and 33.53 (3s, C(CH3)3), 32.06 and 31.30
(2s, C6H2CH2), 31.63, 31.17 and 31.04 (3s, C(CH3)3). 31P-{1H}
NMR (121 MHz, 293 K, CDCl3): δ 21.6 (d) and 20.5 (t) (A2B
system, 2J(PA–PB) = 13 Hz), Ϫ18.7 (s). Found: C, 73.02; H,
6.31. Calc. for C99H100MoO7P4: C, 73.32; H, 6.21%.
2
4.64 (d, JPH = 2, 2 H, PCH2O), 4.52 and 3.15 (AB quartet,
2J = 13, 2 H each, C6H2CH2), 3.78 and 2.85 (AB quartet, 2J = 13
Hz, 2 H each, C6H2CH2), 1.32, 0.97 and 0.65 (3s, 18 H ϩ
9 H ϩ 9 H, tert-butyl). 13C-{1H} NMR (125 MHz, 293 K,
CD2Cl2): δ 154.14 and 151.43 (2 broad s, quat. aryl C–O),
150.81 (d, 3JPC = 12, quat. aryl C-O), 146.09–131.43 (quat. aryl
C), 132.10–125.55 (aryl CH), 77.09 (d, JPC = 9 Hz, PCH2O),
77.98 (quintet, JPC = 29, JPЈC ≈ 1, JPPЈ = 25, PCH2O), 70.20 (d,
JPC = 51 Hz, PCH2O free), 34.11, 34.03 and 33.72 (3s, C(CH3)3),
33.44 and 33.15 (2s, C6H2CH2), 31.62, 31.12 and 31.08 (3s,
C(CH3)3). 31P-{1H} NMR (202 MHz, 293 K, CD2Cl2): δ 60.3 (t)
Tricarbonyl{5,11,17,23-tetra-tert-butyl-25,26,27-tris-
(diphenylphosphinomethoxy)-28-methoxycalix[4]arene-P,PЈ,PЉ}-
molybdenum(0) 2. A solution of compound L2 (0.100 g, 0.08
mmol) and [Mo(CO)3(C7H8)] (0.026 g, 0.08 mmol) in THF (100
mL) was refluxed for 10 min. The orange solution was evapor-
ated to dryness in vacuo. The residue was subjected to flash
chromatography using CH2Cl2–hexane (3:2, v/v) as eluent. The
fraction with Rf = 0.42 (SiO2) was precipitated from CH2Cl2–
hexane (1:1, v/v) affording the complex 2 as a colourless solid.
2
and 35.4 (d) (A2B system, J(PA–PB) = 41 Hz), Ϫ20.0 (s). FAB
mass spectrum: m/z 1577 ([M Ϫ Cl]ϩ, 32). Found: C, 71.72; H,
6.31. Calc. for C96H100Cl2O4P4Ru: C, 71.45; H, 6.25%.
Yield: 0.072 g, 58%; mp 235 ЊC (decomp.). IR (KBr) (νmax/
˜
1
cmϪ1): 1946s and 1854s (C᎐O). H NMR (300 MHz, 293 K,
cis-(P,P)-Dichloro{5,11,17,23-tetra-tert-butyl-25,26-bis(di-
phenylphosphinomethoxy)-27,28-dihydroxycalix[4]arene-P,PЈ}-
platinum(II) 5. To a solution of L3 (0.100 g, 0.09 mmol)
in CH2Cl2 (400 mL) was added a solution of [PtCl2(COD)]
(0.036 g, 0.09 mmol) in CH2Cl2 (50 mL). After 1 h the solution
was evaporated to dryness in vacuo. The residue was subjected
to flash chromatography using ethyl acetate–hexane (3:7, v/v)
as eluent. The fraction with Rf = 0.48 (SiO2) was recrystallized
from ethyl acetate–hexane (1:1, v/v) yielding the complex 5 as
a colourless solid. Yield: 0.085 g, 72%; mp >250 ЊC (decomp.).
᎐
᎐
CDCl3): δ 7.86–6.84 (m, 38 H, PPh2 ϩ m-H of aryl), 5.25 (br s,
4 H, PCH2O), 5.09 and 5.05 (AB quartet, 2J = 7 Hz, 2 H
2
each, PCH2O), 3.61 and 2.89 (AB quartet, J = 13, 2 H each,
2
C6H2CH2), 3.61 and 3.11 (AB quartet, J = 13 Hz, 2 H each,
C6H2CH2), 1.46, 1.16 and 1.11 (3s, 9 H ϩ 9 H ϩ 18 H, tert-
butyl) and 0.38 (s, 3 H, OMe). 13C-{1H} NMR (50 MHz, 293 K,
᎐
CDCl ): δ 218.7 (m, C᎐O), 155.70 and 154.72 (2 broad s, quat.
᎐
3
aryl C–O), 151.77 (d, 3JPC = 10, quat. aryl C–O), 146.62–132.78
(quat. aryl C), 134.92–125.02 (aryl CH), 74.41 (pseudo t,
PCH2O), 73.52 (d, JPC = 26 Hz, PCH2O), 59.72 (s, OMe), 35.46
IR (KBr) (νmax
/cmϪ1): 3454(br) (OH). 1H NMR (500 MHz,
˜
4146
J. Chem. Soc., Dalton Trans., 1999, 4139–4148

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218 K, CD2Cl2): δ 8.46 (s, OH), 7.45–6.97 (m, 28 H, m-H
of aryl ϩ PPh2), 7.32 and 3.63 (AB quartet, 2J = 13, 1 H
each, C6H2CH2), 5.46 and 5.08 (AB quartet, 2J = 12, 2 H each,
1 H each, C6H2CH2), 6.51 and 5.30 (broad AB quartet,
2JAB = 13, 2 H each, PtPCH2O), 5.14 and 4.68 (ABX system
2
2
2
with X = P, JAB = 13, JAX = 2, JBX = 1, 2 H each, PCH2O),
2
2
PCH2O), 4.25 and 3.51 (AB quartet, J = 13, 2 H each, C6H2-
4.86 and 3.00 (AB quartet, J = 13, 1 H each, C6H2CH2), 4.75
CH2), 4.09 and 3.39 (AB quartet, 2J = 13 Hz, 1 H each,
C6H2CH2), 1.15 and 1.14 (2s, 18 H ϩ 18 H, tert-butyl). 1H
NMR (500 MHz, 308 K, CD2Cl2): δ 7.44–6.98 (m, 28 H, m-H
and 2.86 (AB quartet, J = 13 Hz, 2 H each, C6H2CH2), 1.24
2
and 1.05 (2s, 18 H ϩ 18 H, tert-butyl). 13C-{1H} NMR (50
MHz, 293 K, CD2Cl2): δ 154.46 and 153.91 (2s, quat. aryl C–O),
146.71–132.81 (quat. aryl C), 134.50–125.61 (aryl CH), 73.72
(d, JPC = 78, PCH2O), 73.83 (d, JPC = 48 Hz, PCH2O), 38.88 (s,
C6H2CH2), 34.36 and 34.21 (2s, C(CH3)3), 31.75 (s, 2 ×
C6H2CH2), 31.53 and 31.52 (2s, C(CH3)3). 31P-{1H} NMR
(121 MHz, 293 K, CD2Cl2): δ 24.7 (s), 8.6 (s with Pt satellites,
JP-Pt = 3631 Hz). FAB mass spectrum: m/z 1739 ([M ϩ H]ϩ,
3), 1703 ([M Ϫ Cl]ϩ, 65) and 1667 ([M Ϫ 2Cl]2ϩ, 50%). Found:
C, 66.11; H, 5.82. Calc. for C96H100Cl2O6P4Pt: C, 66.28; H,
5.79%.
2
of aryl ϩ PPh2), 7.34 and 3.76 (AB quartet, J = 13, 1 H each,
C6H2CH2), 5.08 and 5.03 (broad AB quartet, 2J = 12, 2 H
2
each, PCH2O), 4.20 and 3.64 (AB quartet, J = 13, 2 H each,
2
C6H2CH2), 3.97 and 3.61 (AB quartet, J = 13 Hz, 1 H each,
C6H2CH2), 1.26 and 1.20 (2s, 18 H ϩ 18 H, tert-butyl). 1H
NMR (300 MHz, 293 K, CDCl3): δ 7.46–7.03 (m, 20 H, PPh2),
7.20 and 3.85 (AB quartet, 2J = 13, 1 H each, C6H2CH2), 6.75–
2
6.68 (m, 8H, m-H of aryl), 4.96 and 4.70 (AB quartet, J = 10,
2
2 H each, PCH2O), 4.06 and 3.85 (AB quartet, J = 13, 2 H
2
each, C6H2CH2), 3.85 and 3.68 (AB quartet, J = 13 Hz, 1 H
each, C6H2CH2), 1.28 and 1.20 (2s, 18 H ϩ 18 H, tert-butyl).
13C-{1H} NMR (50 MHz, 293 K, CDCl3): δ 153.67–129.90
(quat. aryl C), 133.80–125.31 (aryl CH), 71.85 (d, JPC = 52 Hz,
PCH2O), 36.38 and 35.92 (2s, C6H2CH2), 34.28 and 33.92 (2s,
C(CH3)3), 32.45 (s, C6H2CH2), 31.53 and 31.37 (2s, C(CH3)3).
31P-{1H} NMR (121 MHz, 293 K, CDCl3): δ 8.4 (s with Pt
satellites, JP-Pt = 3672 Hz). Found: C, 64.31; H, 5.99. Calc. for
C70H78Cl2O4P2Pt: C, 64.12; H, 5.99%.
Tetrachloro{5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-
(diphenylphosphinomethoxy)calix[4]arene-1ꢀ2P,PЈ;
2ꢀPЉ,-
3ꢀPٞ}digold(I)platinum(II) 9. To a solution of compound L1
(0.100 g, 0.07 mmol) in THF (5 mL) was added a solution of
[PtCl2(COD)] (0.026 g, 0.07 mmol) in THF (5 mL). After 1 h a
solution of [AuCl(THT)] (0.044 g, 0.14 mmol) in THF (5 mL)
was added. The solution was filtered over a bed of Celite after
10 min, and evaporated to dryness in vacuo. The residue was
subjected to flash chromatography using MeOH–CH2Cl2 (4:96,
v/v) as eluent. The fraction with Rf = 0.42 (SiO2) was recrystal-
lized from ethyl acetate–hexane (1:1, v/v) precipitating complex
9 as a colourless solid. Yield: 0.092 g, 88%; mp 250 ЊC
(decomp.). 1H NMR (400 MHz, 293 K, CDCl3): δ 7.81–6.40 (m,
48 H, m-H of aryl ϩ PPh2), 7.35 and 3.63 (AB quartet,
2JAB = 13, 1 H each, C6H2CH2), 5.83 and 4.85 (AB quartet,
2JAB = 13, 2 H each, PCH2O), 5.12 and 4.90 (ABX system
cis-Dichloro{5,11,17,23-tetra-tert-butyl-25,26-bis(dimethyl-
phosphinomethoxy)-27,28-dihydroxycalix[4]arene-P,PЈ}-
platinum(II) 7. This complex was prepared according to a
method similar to that used for the preparation of 5, but start-
ing from the PMe2 analogue of phosphine L3. Yield: 0.146 g,
55%; mp = 212 ЊC (decomp.). IR (KBr) (νmax
/cmϪ1): 3450(br)
˜
1
(OH). H NMR (500 MHz, 293 K, CD2Cl2): δ 7.26–7.06 (m,
8H, m-H of aryl), 5.62 and 3.65 (AB quartet, 2J = 13, 1 H each,
C6H2CH2), 4.62 (broad s, 4 H, PCH2O), 4.20 and 3.58 (AB
quartet, 2J = 13, 2 H each, C6H2CH2), 4.09 and 3.51 (AB quar-
2
2
2
with X = P, JAB = 13, JAX = 0, JBX = 4, 2 H each, PCH2O),
2
4.98 and 3.07 (AB quartet, J = 13, 1 H each, C6H2CH2), 4.15
2
and 3.35 (AB quartet, J = 13 Hz, 2 H each, C6H2CH2), 1.21
2
tet, J = 13, 1 H each, C6H2CH2), 1.85 (d with Pt satellite not
and 0.94 (2s, 18 H ϩ 18 H, tert-butyl). 13C-{1H} NMR (50
MHz, 293 K, CDCl3): δ 153.23 and 151.77 (2s, quat. aryl
C-O), 146.55–125.09 (quat. aryl C), 134.41–125.76 (aryl CH),
75.02 (d, JPC = 64, PCH2O), 73.73 (d, JPC = 40 Hz, PCH2O),
37.15 (s, C6H2CH2), 34.09 and 33.92 (2s, C(CH3)3), 31.86 (s,
C6H2CH2) and 31.45 (s, C(CH3)3). 31P-{1H} NMR (121 MHz,
resolved, JPH = 13 Hz, 12 H, PMe), 1.25 and 1.21 (2s, 18 H ϩ
18 H, tert-butyl). 13C-{1H} NMR (125 MHz, 293 K, CD2Cl2):
δ 152.69–125.86 (aryl C), 75.85 (m, PCH2O), 34.61 and 34.31
(2s, C(CH3)3), 32.49 and 32.15 (s, C6H2CH2), 31.72 and 31.45
(2s, C(CH3)3), 14.00 (m, PMe2). 31P-{1H} NMR (121 MHz,
293 K, CD2Cl2): δ Ϫ14.1 (s with Pt satellites, JP-Pt = 3535 Hz).
Found: C, 56.22; H, 6.59. Calc. for C50H70Cl2O4P2Pt: C, 56.49;
H, 6.64%.
293 K, CD2Cl2): δ 21.9 (s) and 8.1 (s with Pt satellites, JP-Pt
3634 Hz). Found: C, 53.16; H, 4.56. Calc. for C96H100Au2-
Cl4O4P4Pt: C, 53.07; H, 4.64%.
=
cis-Dichloro{5,11,17,23-tetra-tert-butyl-25,26-bis(diphenyl-
phosphinoylmethoxy)-27,28-bis(diphenylphosphinomethoxy)-
calix[4]arene-P,PЈ}platinum(II) 8. To a solution of compound
L1 (0.100 g, 0.06 mmol) in THF (3 mL) was added a solution of
[PtCl2(COD)] (0.026 g, 0.07 mmol) in THF (2 mL). After 1 h
an excess of H2O2–urea adduct (0.050 g) was added, and the
solution stirred vigorously for 1 h. The solution was filtered
and evaporated to dryness in vacuo. The residue was subjected
to flash chromatography using ethyl acetate–hexane (65:35,
v/v) as eluent. The fraction with Rf = 0.42 (SiO2) was recrystal-
lized from ethyl acetate–hexane (1:1, v/v) yielding the complex
8 as a colourless solid. Yield: 0.092 g, 88%; mp 250 ЊC
cis-Dichloro{5,11,17,23-tetra-tert-butyl-25,26-bis(diphenyl-
phosphinomethoxy)-27-(diphenylphosphinoylmethoxy)-28-
methoxycalix[4]arene-P,PЈ}platinum(II) 10 and its enantiomer.
To a solution of L2 (0.150 g, 0.12 mmol) in CH2Cl2 (3 mL) was
added a solution of [PtCl2(COD)] (0.045 g, 0.12 mmol)
in CH2Cl2 (3 mL). After 1 h an excess of H2O2–urea adduct
(0.050 g) was added, and the solution stirred vigorously for 1 h.
The solution was filtered and evaporated to dryness in vacuo.
The residue was subjected to flash chromatography using ethyl
acetate–hexane (65:35, v/v) as eluent. The fraction with
Rf = 0.58 (SiO2) was recrystallized from ethyl acetate–hexane
(1:1, v/v) affording the complex rac-10 as a colourless solid.
(decomp.). IR (KBr) (νmax
ment). H NMR (400 MHz, 293 K, CD2Cl2): δ 7.85–7.81 and
7.53–7.14 (m, 40 H, PPh2), 7.43 and 3.46 (AB quartet, J = 13,
˜
/cmϪ1): 1192s (P᎐O, tentative assign-
Yield: 0.101 g, 68%; mp >250 ЊC (decomp.). IR (KBr) (ν˜ max/
᎐
1
cmϪ1): 1192s (P᎐O, tentative assignment). 1H NMR (500
᎐
2
MHz, 293 K, CD2Cl2): δ 8.05–7.95 and 7.56–6.56 (m, 38 H,
4
2
1 H each, C6H2CH2), 7.07 and 7.01 (AB quartet, J = 6, 2 H
m-H of aryl ϩ PPh2), 7.20 and 3.68 (AB quartet, J = 13, 1 H
each, m-H of aryl), 6.66 and 6.62 (AB quartet, 4J = 5, 2 H each,
m-H of aryl), 6.06 and 4.91 (ABX system with X = P, 2JAB = 13,
2JAX = 2JBX ≈ 0, 2 H each, PCH2O), 5.12 and 4.79 (AB quartet,
2J = 13, 2 H each, PCH2O), 4.77 and 2.81 (AB quartet, 2J = 13,
each, C6H2CH2), 6.26 and 5.24 (ABX system with X = P,
2
2
2JAB = 11, JAX = 0, JBX = 4, 1 H each, PCH2O), 4.75 and 2.93
(AB quartet, 2J = 13, 1 H each, C6H2CH2), 4.64 and 4.47
(ABX system with X = P, 2JAB = 13, 2JAX = 3, 2JBX = 4, 1 H each,
2
2
1 H each, C6H2CH2), 4.63 and 2.94 (AB quartet, J = 13 Hz,
PCH2O), 4.35 and 3.88 (ABX system with X = P, JAB = 10,
2
2 H each, C6H2CH2), 1.22 and 1.04 (2s, 18 H ϩ 18 H, tert-
2JAX = 3, JBX = 0, 1 H each, PCH2O), 4.32 and 3.62 (AB
1
butyl). H NMR (500 MHz, 293 K, C6D6): δ 8.05–6.57 (m,
quartet, 2J = 13, 1 H each, C6H2CH2), 3.67 and 3.53 (AB
48 H, m-H of aryl ϩ PPh2), 7.36 and 3.59 (AB quartet, 2J = 13,
quartet, J = 13 Hz, 1 H each, C6H2CH2), 1.34, 1.25, 1.11 and
2
J. Chem. Soc., Dalton Trans., 1999, 4139–4148
4147

View Article Online
1.04 (4s, 9 H ϩ 9 H ϩ 9 H ϩ 9 H, tert-butyl). 13C-{1H} NMR
(50 MHz, 293 K, CD2Cl2): δ 158.43, 155.41, 155.16 and 155.05
(4s, quat. aryl C–O), 147.30–130.71 (quat. aryl C), 135.42–
126.14 (aryl CH), 72.30 (d, JPC = 77, PCH2O), 72.37 (d,
JPC = 28, PCH2O), 71.37 (d, JPC = 29 Hz, PCH2O), 59.40 (s,
OMe), 36.92, 36.68 and 36.59 (3s, C6H2CH2), 34.23, 34.20,
34.03 and 33.90 (4s, C(CH3)3), 32.10 (s, C6H2CH2), 31.51, 31.41
and 31.11 (3s, C(CH3)3). 31P-{1H} NMR (121 MHz, 293 K,
CD2Cl2): δ 23.8 (s), 13.5 (br s with Pt satellites, JP-Pt = 3752) and
5.76 (d with Pt satellites, JP-Pt = 3574 Hz). Found: C, 65.69; H,
5.89. Calc. for C84H91Cl2O5P3Pt: C, 65.53; H, 5.96%.
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Acknowledgements
We are indebted to Johnson Matthey for a generous loan of
platinum.
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