(η5-pentamethylcyclopentadienyl)rhodium complexes of upper-rim monophosphinated calix[4]arene

Article abstract of DOI:10.1021/om000433a

A new and convenient synthesis of the upper-rim monobrominated calix[4]arene Br-calixPR₂ is reported and has been used as the key precursor for the preparation of both the diphenyl- (6a) and diisopropylphosphine ligands (6b). Reactions of these new ligands with [(C₅Me₅)RhCl₂]₂ afford the complexes (calixPR₂)(C₅Me₅)Rh(Cl)₂ (8a,b), which can be converted into their corresponding dihydrides (calixPR₂)(C₅Me₅)Rh(H)₂ (9a,b) using NaBH₄. 6a also reacts with (C₅Me₅)Rh(CO)₂ to form (calixPPh₂)(C₅Me₅)Rh(CO) (10). The X-ray structures for both 8a and 8b confirm the cone geometry of the calix[4]arene bowl and reveal the presence of the phenyl and isopropyl groups over the cavity. With respect to the Rh-P bond, a gauche conformation is depicted in the solid state. Complexes 8a,b and 9a,b appear to be fluxional in solution, as demonstrated from VT ¹H and ³¹P NMR measurements for 8a,b. Molecular modelings confirm the presence of 13 conformers associated with the rotation around the C(calix)-P and P-Rh bonds and the cavity locking groups above it. The minimum energy conformation for the unsaturated (calixPPh₂)(C₅Me₅)Rh complex exhibits the Rh atom well located at the opening of the free cavity.

Full text of DOI:10.1021/om000433a

Organometallics 2001, 20, 273-281
273
(η5-P en ta m eth ylcyclop en ta d ien yl)r h od iu m Com p lexes of
Up p er -Rim Mon op h osp h in a ted Ca lix[4]a r en e
Martin Ve´zina, J onathan Gagnon, Karine Villeneuve, Marc Drouin, and
Pierre D. Harvey*
De´partement de chimie, Universite´ de Sherbrooke, Sherbrooke, Que´bec, Canada J 1K 2R1
Received May 22, 2000
A new and convenient synthesis of the upper-rim monobrominated calix[4]arene Br-
calixPR2 is reported and has been used as the key precursor for the preparation of both the
diphenyl- (6a ) and diisopropylphosphine ligands (6b). Reactions of these new ligands with
[(C5Me5)RhCl2]2 afford the complexes (calixPR2)(C5Me5)Rh(Cl)2 (8a ,b), which can be converted
into their corresponding dihydrides (calixPR2)(C5Me5)Rh(H)2 (9a ,b) using NaBH4. 6a also
reacts with (C5Me5)Rh(CO)2 to form (calixPPh2)(C5Me5)Rh(CO) (10). The X-ray structures
for both 8a and 8b confirm the cone geometry of the calix[4]arene bowl and reveal the
presence of the phenyl and isopropyl groups over the cavity. With respect to the Rh-P bond,
a gauche conformation is depicted in the solid state. Complexes 8a ,b and 9a ,b appear to be
1
fluxional in solution, as demonstrated from VT H and 31P NMR measurements for 8a ,b.
Molecular modelings confirm the presence of 13 conformers associated with the rotation
around the C(calix)-P and P-Rh bonds and the cavity locking groups above it. The minimum
energy conformation for the unsaturated (calixPPh2)(C5Me5)Rh complex exhibits the Rh atom
well located at the opening of the free cavity.
In tr od u ction
Atwood et al. have reported the preparation of the soft
ligand 5,11,17,23-tetrakis(diphenylphosphino)-25,26,
27,28-tetramethoxycalix[4]arene.11 Unfortunately the
spectroscopic data reveal that this molecule must exist
with multiple conformations (cone, 1,2-alternated, 1,3-
alternated, etc.), which in addition can be in equilibrium
with each other. The use of propyl residues at the lower
rim is known to prevent such behavior, and only the
desired cone conformation is obtained.12 So far the
upper-rim functionalization mentioned above appears
in the literature in two ways. These are the tetrasub-
stituted and 5,17-disubstituted calix[4]arenes.5-10 The
dramatic consequence of this chemistry is that the
upper-rim opening giving access to the hosting hydro-
phobic cavity either is blocked if 5,17-chelation with
transition metals occurs10 or is seriously sterically
hindered. Monofunctionalization of the upper rim of the
calix[4]arene molecule appears to be a much more
desirable approach in this case.
The basket-shaped calix[4]arene is a remarkable
molecule, which exhibits a cyclic tetraphenolic structure
giving rise to extremely rich chemistry, as pointed out
by the pioneer works of Gutsche.1 Because of the
presence of ionophoric and hydrophobic cavities and the
generally simple chemistry of the calix[4]arene, many
useful applications in the area of cation binding and
transport are now known, and many elegant highly
selective receptors and novel sensors for polyanionic
species have been designed with this host molecule.2
While attempting to successfully couple the very
convenient host-guest behavior of calix[4]arene with
interesting properties of transition-metal complexes,
numerous researchers have performed the synthesis of
complexes of this platform molecule.3 The literature
shows that functionalization of the lower-rim segment
has been successfully exploited, due primarily to the
relative ease with which the R-OH fragments can be
manipulated chemically.4 On the other hand, few upper-
rim derivatizations has been reported. A list of electron
donor groups that have been successfully anchored at
the upper-rim includes -SO3-,5 -NO2,6 -NH2,7
-NdNR,8 and -PPh2,9 among a few others.10
Recently, Shinkai et al.13 reported a methodology to
prepare the key precursor 5-bromo-25,26,27,28-tetra-
(5) Shinkai, S.; Mori, S.; Koreishi, H.; Tsubaki, T.; Manabe, O. J .
Am. Chem. Soc. 1986, 108, 2409.
(6) No, K.; Noh, Y. Bull. Korean Chem. Soc. 1986, 7, 314.
(7) Mogck, O.; Parzuchowski, P.; Nissinen, M.; Bo¨hmer, V.; Rokicki,
G.; Rissanen, K. Tetrahedron 1998, 54, 10053.
* To whom correspondence should be addressed. Tel: (819) 821-
7092. Fax: (819) 812-8017. E-mail: pharvey@courrier.usherb.ca.
(1) Gutsche, C. D. Calixarenes; Royal Society of Chemistry: Cam-
bridge, U.K., 1989.
(2) Calixarenes: A Versatile class of Macrocyclic Compounds; Vicens,
J ., Bo¨hmer, V., Eds.; Kluwer Academic: Dordrecht, The Netherlands,
1991. Calixarenes 50th Anniversary: Commemorative Issue; Vicens, J .,
Asfari, Z., Harrowfield, J . M., Eds.; Kluwer Academic: Dordrecht, The
Netherlands, 1994.
(3) Wieser, C.; Dieleman, C. B.; Matt, D. Coord. Chem. Rev. 1997,
165, 93.
(4) Iwamoto, K.; Yanagi, A.; Araki, K.; Shinkai, S. Chem. Lett. 1991,
473.
(8) Shinkai, S.; Araki, K.; Shibata, J .; Tsugawa, D.; Manabe, O. J .
Chem. Soc., Perkin Trans. 1 1990, 3333.
(9) J eunesse, C. W.; Matt, D.; De Cian, A. Angew. Chem., Int. Ed.
1998, 37, 2861.
(10) Arduini, A.; Fanni, S.; Menfredi, G.; Pochini, A.; Ungaro, R.;
Sicuri, A. R.; Ugozzoli, F. J . Org. Chem. 1995, 60, 1448.
(11) Hamada, F.; Fukugaki, T.; Murai, K.; Orr, G. W.; Atwood, J .
L. J . Inclusion Phenom. 1991, 10, 57.
(12) (a) Bocchi, V.; Foina, D.; Pochini, A.; Ungaro, R.; Andretti, G.
D. Tetrahedron 1982, 38, 373. (b) Gutsche, C. D.; Dhawan, B.; Levine,
J . A.; No, K. H.; Bauer, L. J . Tetrahedron 1983, 39, 409.
(13) Ikeda, A.; Yoshimura, M.; Lhotak, P.; Shinkai, S. J . Chem. Soc.,
Perkin Trans. 1 1996, 1045.
10.1021/om000433a CCC: $20.00 © 2001 American Chemical Society
Publication on Web 12/16/2000

274 Organometallics, Vol. 20, No. 2, 2001
Ve´zina et al.
Ta ble 1. List of In vestiga ted Com p ou n d s a n d
Com p lexes
compd
R1
R2
R3
1
2
3
H
H
Br
Br
OH
OH
OH
OH
OH
O(CO)Ph
O(CO)Ph
OH
4
5
Br
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
OPr
6a
6b
7
8a
8b
9a
9b
10
P(Ph)2
P(i-Pr)2
OdP(Ph)2
P(Ph)2(C5Me5)Rh(Cl)2
P(i-Pr)2(C5Me5)Rh(Cl)2
P(Ph)2(C5Me5)Rh(H)2
P(i-Pr)2(C5Me5)Rh(H)2
P(Ph)2(C5Me5)Rh(CO)
OPr
propoxycalix[4]arene using the known 25,26,27,28-
tetrapropoxycalix[4]arene and bromine. Although the
desired molecule is formed as a major product, a certain
amount of the dibromo derivatives are also formed.
These products are difficult to separate due to similar
solubilities and polarities. The unfortunate consequence
is found in the poor yield. Alternative routes for the
selective bromination of calix[4]arene in a cleaner
fashion are clearly required.
We have elected to investigate the (C5Me5)Rh com-
plexes of monophosphinated calix[4]arene, because this
metallic fragment is well-known for its ability to cleave
C-H bonds,14 a property that is crucial for the func-
tionalization of saturated hydrocarbons. Branching a
(C5Me5)Rh moiety onto the upper rim of a monophos-
phinated calix[4]arene provides an unprecedented op-
portunity for coupling this very important C-H bond
activation property with the supramolecular behavior
of this bowl-shaped molecule. This way, very elegant
regioselective C-H bond activation can be anticipated
with such complexes, potentially leading toward an
important impact in the field.
We now wish to report a novel and convenient
synthesis of the monobromocalix[4]arene, along with the
diphenyl- and diisopropylphosphine derivatives and a
number of their corresponding (C5Me5)Rh complexes.
The X-ray structure for the diphenylphosphine calix[4]-
arene complex of (C5Me5)RhCl2 is also reported.15 The
complexes are found to be fluxional in solution, and the
1H NMR data are analyzed and complemented with
computer modelings. The list of investigated compounds
and complexes is provided in Table 1.
F igu r e 1. Reaction schemes for the preparation of com-
pounds 6a ,b. Legend: (i) 1-methylimidazole/PhCO2Cl/ACN,
room temperature, 24 h; (ii) Br2/CHCl3, room temperature,
15 min; (iii) NaOH/THF, room temperature, 48 h; (iv) NaH/
1-IPr/DMF, room temperature, 72 h; (v) n-BuLi/ClPPh2
(6a )/ClP(i-Pr)2 (6b)/THF, -78 °C, 24 h.
is the tribenzoylation of 1 to give the known compound
2.16 The literature procedure involves the use of pyridine
as a base and solvent, with a reported chemical yield of
71%. By using 1-methylimidazole in acetonitrile, the
isolated yield is increased to 88%. This compound 2 now
exhibits two types of phenyl residues: an electron-rich
phenolic one and three significantly poorer ones. This
greater difference in electronic density allows a very
good discrimination for the bromination reaction favor-
ing the phenolic ring. As anticipated, the bromination
of 2 affords 3 cleanly, as evidenced by the quasi-
quantitative isolated yield. Both 2 and 3 exhibit 1H
NMR data that are indicative of a partial cone confor-
mation.
The following two steps consist of standard benzoyl
cleavage and propylation reactions in good (90%) and
modest (65%) yields, respectively. In these cases intra-
molecular H bondings in 4 and large n-propyl groups
in 5 favor the cone conformation, as confirmed by the
1H NMR data (Experimental Section). Finally, the
conversion of monobromotetrapropoxycalix[4]arene (5)
into 6a ,b proceeds via lithiation of the bromophenyl
fragment with tert-butyllithium, followed immediately
by the phosphination reaction either with chlorodiphen-
Resu lts a n d Discu ssion
1. Liga n d P r ep a r a tion . The monophosphinated
ligands 6a ,b can be prepared in five steps from the
nonsubstituted calix[4]arene 1 (Figure 1). The key step
(14) J ones, W. D.; Feher, F. J . J . Am. Chem. Soc. 1984, 106, 1650.
(15) A preliminary communication was published in: Vezina, M.;
Gagnon, J .; Villeneuve, K.; Drouin, M.; Harvey, P. D. Chem. Commun.
2000, 1073.
(16) Gutsche, C. D.; Lin, L.-G. Tetrahedron 1986, 42, 1633.

Rhodium Complexes of Calix[4]arene
Organometallics, Vol. 20, No. 2, 2001 275
Ta ble 2. X-r a y Da ta for 8a
chem formula
habit
C62H72Cl2O4PRh
red rectangular cryst
space group
a, Å
P21/c
18.009(7)
b, Å
15.401(2)
c, Å
21.996(5)
â, deg
110.34(2)
5720(3)
V, Å3
Z
F
4
calcd, g/cm3
1.261
radiation
Cu KR, graphite monochromated
1.540 60
λ(KRax), Å
cryst dimens, mm3
T, °C
0.13 × 2.15 × 0.32
293(2)
µ, cm-1
16.35
index range
diffractometer
diff. geom
-21 < h < 19, 0 < k < 18, 0 < 1 < 25
Nonius
CAD-4
θ range, deg
no. of rflns collected
no. of indep rflns
R1a
2.61-64.84
18919
9703 (R(int) + 0.07)
0.0734
0.1897
wR2b
R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑[w(Fo2 - Fc2)2]/∑w(Fo2)2}0.5
.
a
Ta ble 3. Selected Bon d Dista n ces a n d An glesa for
8a
P-Ccalix
P-Rh
1.815(6)
2.335(18)
Rh-Cl1
Rh-Cl2
2.3835(18)
2.405(2)
Rh-CC Me
2.194(29)
110.00(19)
85.71(6)
P-Rh-Cl2
Cl1-Rh-Cl2
93.50(7)
93.54(8)
5
5
Rh-P-Ccalix
P-Rh-Cl1
F igu r e 2. Reaction schemes for the preparation of com-
pounds 9a ,b and 10. Legend: (i) H2O2/THF, room temper-
ature, 24 h; (ii) Cp*Rh(CO)2/C6H6, reflux, 24 h; (iii)
[(C5Me5)RhCl2]2/EtOH/C6H6, reflux, 5 h; (iv) NaBH4/EtOH,
reflux, 1 h.
a
Bond distances in Å and angles in deg.
ylphosphine (6a ) or chlorodiisopropylphosphine (6b).
The overall yields are on the order of 30% and are
explained by the difficult propylation reaction and air
sensitivity of the phosphine compounds. The best results
have been obtained when 1-iodopropane was used
instead of 1-bromopropane for the propylation. While
6a oxidizes slowly in air to give the crystallographically
characterized phosphine oxide 7 (drawing provided in
the Supporting Information), 6b oxidizes readily. The
1H NMR spectrum of 7 also confirms the cone conforma-
tion.17
2. Com p lex Syn th esis. The complexation scheme for
the preparation of the (η5-pentamethylcyclopentadienyl)-
rhodium complexes 9a ,b is presented in Figure 2. The
mononuclear complexes 8a ,b can conveniently be ob-
tained in good yield using the dimeric [(C5Me5)RhCl2]2
complex in the presence of the corresponding aryl- and
alkylphosphine ligands 6a ,b. Both complexes are stable,
and a single crystal suitable for X-ray crystal analysis
(Tables 2 and 3) was obtained for 8a . Figure 3 shows
the ORTEP drawing for 8a and confirms the expected
upper-rim monofunctionalization of the calix[4]arene
host. The coordination environment of the Rh(III) center
is very similar to that reported for [(C5Me5)RhCl2]2 (µ-
dmpe) (dmpe ) bis(dimethylphosphino)ethane).18 In-
F igu r e 3. ORTEP drawing of compound 8a . Ellipsoids are
shown at 10% probability, and the H atoms are not shown
for clarity.
deed, the literature d(Rh-CCp* average, d(Rh-P), and
)
d(Rh-Cl) values of 2.17(4), 2.29(1), and 2.41(1) Å,
respectively, compare favorably to those listed for 8a
in Table 3. The slightly shorter 2.29(1) Å value for
d(Rh-P) in the [(C5Me5)RhCl2]2(µ-dmpe) dinuclear com-
plex is consistent with the better π-back-bonding of this
stronger phosphine base.
(17) Single crystals suitable for X-ray analysis were obtained, but
the residual was too high (Rw ) 16%). Nonetheless, the structure was
indeed as expected in its cone conformation. A picture of the ligand is
provided in the Supporting Information.
(18) Keim, W.; Kraneburg, P.; Dahmen, G.; Deckers, G.; Englert,
U.; Linn, K.; Spaniol, T. P.; Raabe, G.; Kruger, C. Organometallics
1994, 13, 3085.

276 Organometallics, Vol. 20, No. 2, 2001
Ve´zina et al.
8a exhibits P-CCalix and P-Rh single bonds, allowing
many conformers to exist, as discussed below. This
complex in the solid state adopts a geometry where the
two phenyl groups are placed over the cavity, and the
(C5Me5)RhCl2 fragment is in a gauche conformation
with respect to the PPh2(calix) residue. Crystal packing
may be at the origin of this conformation. The bowl-
shaped calix[4]arene moiety does not adopt a sym-
metrical C4v local point group but, rather, a local C2v.
More importantly, two of the phenyl groups are placed
in a quasi face-to-face fashion. The phosphinated phenyl
group and its facing ring slightly point toward each
other with a plane-to-plane angle of 9.01(0.34)°. The
other pair of phenyl rings forms an angle of 85.59(0.31)°
and are open away from each other.
X-ray data for 8b have been obtained and demon-
strate the isostructurality with 8a , but the quality of
the crystal is poor, and the data cannot be formally
reported. A picture of the complex is provided in the
Supporting Information, and the presence of two of the
methyl groups of the isopropyl substituents well above
F igu r e 4. 1H NMR spectra of 8a in toluene-d8 as a
function of temperature. The quartet at 3.85 ppm is due
to residual ethyl acetate impurity.
Ch a r t 1
1
the cavity is obvious. The H NMR spectrum for 8b is
very revealing: four different (CH3)2CH groups are
depicted. Indeed, a pair of doublets are observed at 1.6
ppm as expected, as well as another more shielded one
at 0.8 ppm. The spectral feature can only be explained
by the presence of two CH3 groups locked over the
cavity, in direct contact with the cone of anisotropy of
the benzene ring. The spectral interpretation was
confirmed by the 2D NMR technique HMBC.19
Complexes 8a ,b can easily and predictably be con-
verted into their corresponding dihydride species 9a ,b
via a direct reaction with sodium borohydride in reflux-
ing ethanol. These new complexes turn out to be
relatively unstable with time, particularly in the pres-
ence of light or air. Clearly these complexes must be
limited by the freezing point of the toluene solvent).
Compounds 9a ,b could not be investigated due to their
limited stability in solutions as a function of time.
Interestingly, the full width at half-maximum (fwhm)
is variable vs temperature from one signal to another
within the same sample. This observation indicates that
in fact more than one fluxionality process occurs, as
anticipated for these very flexible molecules (Chart 1).
As a typical example, Figure 4 exhibits the 2.5-5.0 ppm
1
freshly synthesized prior to use. The H NMR spectra
exhibit the expected doublet of doublets centered at
-13.07 and -14.29 ppm for 9a ,b, respectively, with
2
1J (Rh,H) ≈ 28 Hz and J (P,H) ≈ 38 Hz, while the IR-
active ν(Rh-H) bands are located at 2080 and 2008
cm-1, respectively.
1
region of the H NMR spectra of 8a in toluene. The 3.1
6a can also react with the mononuclear complex
and 4.5 ppm signals are the equatorial and axial calix
-CH2- protons, respectively. The slightly more shifted
signals at 4.50 and 3.13 ppm correspond to the calix
-CH2- groups located away from the phosphine resi-
dues, while the pair of shielded doublets found at 4.45
and 3.00-3.13 ppm (depending upon the temperature)
are the calix -CH2- residues placed near the P(C6H5)2
fragment. This assignment is based upon the compari-
son of the data of 25,26,27,28-tetra-n-propoxycalix[4]-
arene (11) and 5,11,17,23-tetrakis(diphenylphosphino)-
25,26,27,28-tetra-n-propoxycalix[4]arene (12).21 With
the lowering of the temperature, the latter undergoes
a coalescence process at a temperature in the neighbor-
hood of 268 K as stated, where the shielded signals are
larger than the deshielded ones. The unsubstituted
propoxyaryl residue facing the phosphine group is less
encumbered and experiences slightly faster molecular
motions. The ∼3.8 ppm signal is attributed to the
O-CH2 protons and exhibits the same phenomena. Two
pairs of triplets are depicted at higher temperature (see
20
(C5Me5)Rh(CO)2 via a simple thermally induced CO
substitution to provide the basket molecule 10. A single
and characteristic ν(CO) absorption is readily observed
at 1960 cm-1 in the solid state. The new complex has
been confidently characterized by standard methods
(chemical analysis, 1H and 31P NMR, IR, and FAB
mass), which confirm its identity and purity. Although
10 is somewhat more stable than 9a and 9b, decomposi-
tion may be depicted when subjected to UV-visible
light.
3. F lu xion a lity. Compounds, 8a and 9a exhibit 1H
NMR signals that are significantly larger than that
found for the other investigated compounds in this work,
at room temperature. A VT study of 8a and 8b (Sup-
porting Information) clearly shows a progressive trans-
formation of the spectra where a coalescence process
appears at ∼268 K for 8a , and ∼205 K for 8b (somewhat
(19) The spectral interpretation was confirmed by the 2D NMR
technique called Heteronuclear Multiple Bond Connectivity (HMBC).
The description of this common technique can be found in the original
paper by: Bax, A.; Summers, M. F. J . Am. Chem. Soc. 1986, 108, 2093.
(20) Drolet, D. P.; Lees, A. J . J . Am. Chem. Soc. 1992, 114, 4186.
(21) Gagnon, J .; Vezina, M.; Drouin, M.; Harvey, P. D. Unpublished
results.

Rhodium Complexes of Calix[4]arene
Organometallics, Vol. 20, No. 2, 2001 277
Ch a r t 2
368 K). When the temperature is lowered (318 K), this
region becomes complex and evolves into a triplet
centered at 3.80 ppm and a broad envelope at 3.74 ppm.
When the temperature is lowered further, the signal
becomes a broad triplet, which progresses toward a
single large signal at ∼3.75 ppm (218 K). In this case,
VT experiments are not reported below this temperature
due to limited solubility below 218 K. However, it
appears that 218 K must be close to the coalescence
temperature based on the shape of this signal. The
greater flexibility of the n-propyl chain can easily
account for the lower coalescence temperature.
Similar observations can be made for the aromatic
region, including signals associated with the (C6H5)-P
groups. A coalescence process is evident at ∼268 K
(Supporting Information). Clearly, the (C6H5)-P group
multiplet at ∼8.0 ppm is also involved in the fluxional
process. The latter broadens upon cooling and separates
spectacularly into two signals at ∼280 K. While the
most deshielded signal becomes a multiplet, the shielded
one at 7.95 ppm sharpens and then broadens further
down at 218 K. Multiple fluxions occur, and molecular
fragments appear to cooperate in various motions, in
agreement with Chart 1.
Ch a r t 3
The VT measurements for 8b again reveal similar
information (spectra provided in the Supporting Infor-
mation). When the temperature is lowered, most of the
signals become significantly broad, but at different
rates. For instance, the signals associated with the
methyl groups in C5Me5 are relatively narrow within
this temperature range, while the very broad signals
in the aromatic region practically vanish. Interestingly,
the shielded P-CH-CH3 signals (at ∼0.75 ppm) broaden
at a higher temperature (256 K), indicating that the
relative steric hindrance is easily felt in the interior of
the cavity. The deshielded P-CH-CH3 resonances
broaden at about 230 K, while the P-CH-(CH3)2
signals (at 3.22 ppm) become broad, somewhat similarly
to that of the former ones. The O-CH2 multiplet
broadens in the 243-230 K range, while the -CH2-
CH3 and -CH2-CH3 fragments of the n-propyl chains
resonating at 2.1 and 1.9 ppm, respectively, undergo
similar processes at lower temperatures. Clearly, the
more flexible the fragments, the lower the broadening
temperature will be (i.e., coalescence temperature). In
contrast to 8a , the calix -CH2- signals broaden only
at temperatures approaching 210 K, indicating that the
bowl structure in 8b is more flexible than that in 8a .
This observation is consistent with the fact that the PR2
groups lie above the cavity, as demonstrated by the
X-ray structure determination, including intramolecular
steric hindrance.
but this doublet becomes broad at lower temperatures.
At 218 K, the fwhm are ∼0.5 and 1.0 ppm for 8a and
8b, respectively, in comparison with ∼0.2 ppm at 293
K. When 8a is cooled further (193 K), a complex
multiplet appears as witness to the presence of more
than one conformer in solution.
4. Con for m a tion a l An a lysis. The VT NMR experi-
ments clearly indicate that more than one conformer
exists at higher temperatures for 8a ,b. The presence of
C(calix)-P and Rh-P single bonds, and a cavity,
controls the number of possible conformers (Chart 1).
The C5Me5 motions are ignored, since no evidence for
coalescence was observed between 210 and 368 K. X-ray
structures reveal that the PR2 residues were found
locked above the cavity, as corroborated by 1H NMR
analysis for R ) i-Pr. Using the program PC-model to
qualitatively address the presence of multiple conform-
ers, computations are performed for both 8a and 8b.
The results are essentially identical for both complexes
and will be discussed simultaneously.
The last comment about compounds 8a ,b concerns the
signals at 7.55 (8a ) and 7.30 ppm (8b) associated with
the ortho hydrogens of the calix phosphinated aromatic
ring. This assignment is also based upon the comparison
1
of the H NMR spectra of 11 and 1221 and their relative
Rotations around the C(calix)-P bond provides four
possible minimum energy conformations where two
groups, either C6H5 or Cl, sit over the cavity as shown
in Chart 2. In addition, rotation around the Rh-P bond
affords three more possibilities (two gauche and one
anti; Chart 3), making a subtotal of 4 × 3 conformations.
Finally, one eclipsed special case also occurs in theory,
where the bulky C5Me5 falls inside the cavity (Chart 3,
intensities. The doublet is due to 3J (P,H). These peaks
broaden at 318 and 256 K for 8a ,b, respectively. This
large difference (∼60 °C) strongly suggests that the
motion of the larger (C5Me5)Rh(Cl)2P(C6H5)2 group must
be slower than that of (C5Me5)Rh(Cl)2P(CH(CH3)2)2. In
addition, the 31P NMR spectra of 8a ,b exhibit a sharp
doublet due to 1J (Rh,P) coupling at room temperature,

278 Organometallics, Vol. 20, No. 2, 2001
Ve´zina et al.
F igu r e 6. Ball and stick model of one of the possible
conformers for the [Ph2P(calix)]Rh(C5Me5) reactive inter-
mediate. The cavity is available for substrate binding.
F igu r e 5. Ball and stick model of one of the 13 possible
conformers of 8a .
bottom structure). Computer modelings predict that in
fact 13 conformers are possible, 4 of which are equiva-
lent because of the gauche geometries.
fragment is expected to be linear.14 Therefore, steric
hindrance is expected to be minimal.
In all cases, CPK models indicate that access of guest
molecules is precluded by the presence of the PR2
groups, which is consistent with the tetrahedral geom-
etry of the coordinated P atom. In addition, the gauche
conformations depicted by the X-ray structures are two
of the most stable conformations based upon the PC-
model relative total energy (i.e., they are in fact the
second most stable). Unexpectedly, the conformation
where the C5Me5 fragment is located inside the cavity
(Figure 5) is the least energetically demanding. One
possible explanation for this interesting result is that
there is a decrease in steric interactions between the
P(C6H5)2 groups with the large calix fragment in that
particular conformation. In the gauche conformation,
such as in Figure 3, the C5H6 groups do not fall inside
the cavity but are just sitting above it, together being
too large to penetrate the cavity. However, this special
“C5Me5 in the cavity” geometry is not accessible, since
the C5Me5 is much too bulky to hop over the calix
aromatic groups, during the rotation aound the
C(calix)-P bond. As anticipated, no evidence for this
conformation is found in the 1H NMR spectra in the
Rh(C5Me5) region. The conformer where the two Cl
ligands lie above the bowl is the most energetic one but
offers the most space near the cavity. This calculated
higher energy conformation results from the fact that
the RhCl2 fragment does not fall into the cavity, forcing
the other substituents, Rh(C5Me5) and P(C6H5)2, to
occupy a more restricted area.
F in a l Rem a r k s
Preliminary results show that 9a ,b and 10 both
thermally and photochemically eliminate H2 and CO,
respectively, to generate the very reactive postulated
species (calixPR2)(C5Me5)RhI; as briefly described above,
C-H bond activation in benzene has been observed.
This important species is expected to activate other
C-H bonds, and regioselectivity due to host-guest
interactions would be an unprecedented asset. Reac-
tivities of this species will be reported in due course.
Exp er im en ta l Section
Ma ter ia ls. 25,26,27,28-Tetrahydroxycalix[4]arene (1) was
prepared according to standard procedures.22 The solvents
were purified according to general procedures.23 Column
chromatography was performed from silica gel 230-400 mesh
(60A) and was used as received. All manipulations were carried
out under N2 or Ar atmospheres, using standard Schlenk
techniques, or in a glovebox. All other reagents were used as
received.
Ap p a r a tu s. The NMR spectra were acquired on a 300 MHz
Bruker instrument (1H, 300.15 MHz; 13C, 75.478 MHz; 31P,
121.497 MHz). The chemical shifts (δ) are reported with
respect to tetramethylsilane, TMS (1H, 13C), which were
determined on the basis of residual proton solvent resonances
and H3PO4 (31P). The coupling constants are reported in ppm.
The FT-IR data were obtained on a Perkin-Elmer spectrom-
eter. Model 1600. The mass spectra (EI) were measured on a
ZAB-1F instrument (VG model). All chemical analyses and
FAB mass spectra were acquired at the Universite´ de Montre´al
(Regional Services).
This observation is crucial. If the Cl ligands were to
be completely removed from the Rh environment, then
the cavity would become more available for host-guest
interactions. Indeed, computer models (see Figure 6 as
an example) illustrate well this behavior well. Again
rotations around the C(calix)-P and P-Rh bonds give
rise to multiple conformers as well. This time, only three
rotamers would be available, since the P-Rh-(C5Me5)
Com p u ter Mod elin g. The calculations were performed
using the commercially available program PC-model from
(22) Tashiro, M.; Fukata, G.; Mataka, S.; Oe, K. Org. Prep. Proced.
Int. 1975, 7, 231.
(23) Perrin, D. D.; Armarego, W. L. F. Purifications of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, U.K., 1988.

Rhodium Complexes of Calix[4]arene
Organometallics, Vol. 20, No. 2, 2001 279
3
3
Serena Software (version 7.0), which uses the MMX empirical
model. The Rh-Cl and Cl-Cl separations were set as crys-
tallographically found and remained fixed during the compu-
tations. For comparison purposes the Rh-C, Rh-Cl, Rh-P,
C(calix)-P and Ph C-P distances are 2.19 vs 2.24 Å, 2.39 vs
2.36 Å, 2.34 vs 2.36 Å, 1.82 vs 1.86 Å, and 1.84 vs 1.90 Å for
the X-ray and calculated data, respectively. The minimum
energy conformations were found by calculating the total
energy as a function of the dihedral angle of the C(calix)-P
and P-Rh bonds. Then, each conformation was minimized
individually around the minimum of the potential to take into
account the presence of substituents (i.e., -C6H5, -CH(CH3)2,
-C5Me5, -calix). These minimizations allowed the extraction
of the relative total energy for each conformer.
2.66, Ph), 6.92 (d, 2H, J H-H ) 7.50, Ph), 6.79 (t, 1H, J H-H )
3
7.36, Ph), 6.76 (t, 1H, J H-H ) 7.44, Ph), 6.65-6.55 (dd + t,
2
4H, Ph), 5.49 (s, 1H, OH), 3.95 (d, 2H, J H-H ) 14.34, CH2-
2
2
Ar), 3.85 (d, 2H, J H-H ) 15.55, CH2-Ar), 3.75 (d, 2H, J H-H
) 15.37, CH2-Ar), 3.53 (d, 2H, J H-H ) 14.23, CH2-Ar). 13C
2
NMR (CDCl3): δ 164.34, 163.76, 152.67, 148.17, 146.60,
133.68, 133.39, 133.10, 132.13, 132.51, 131.19, 130.67, 130.17,
129.78, 129.42, 128.54, 127.95, 126.18, 125.89, 125.01, 119.64,
37.31, 32.30. MS (EI): m/z 736 (M+, relative intensity 20%).
25,26,27-Ben zoyl-5-br om o-28-h yd r oxyca lix[4]a r en e (3).
A 20 g (27 mmol) portion of 2 was dissolved in 400 mL of CHCl3
in the presence of an excess of Br2 (10 mL, 180 mmol), and
the mixture was stirred for 30 min at room temperature. The
reaction was quenched with an aqueous Na2S2O3 solution (4
g/100 mL). The organic layer was extracted once more with
this aqueous Na2S2O3 solution and then twice with a 1 N
aqueous HCl solution and once with water. This organic layer
was then dried over MgSO4 and then filtered and evaporated.
The resulting light yellow powder was then washed overnight
with 1000 mL of methanol. The solution was filtered, and an
off-white solid was obtained. Yield: 21 g, 95%. Mp: dec >250
°C. Anal. Calcd for C49H35O7Br: C, 72.15; H, 4.32. Found: C,
Cr ysta llogr a p h y. Intensity data from a dark red prismatic
crystal were collected at 293(2) K on an Enraf-Nonius CAD-4
automatic diffractometer, with graphite-monochromated Cu
KR radiation (1.541 84 Å). Cell constants and an orientation
matrix for data collection were obtained from a least-squares
refinement using the setting angles of 24 centered reflections
in the range 40° < 2θ < 50°. Space group determination was
based upon systematic absences, packing considerations, a
statistical analysis of intensity distribution, and the successful
solution and refinement of the structure. The NRCCAD
program24 was used for centering, indexing, and data collec-
tion. The NRCVAX programs25 were used for crystal structure
solution by application of direct methods. The SHELX-97
program26 was used for refinement by full-matrix least squares
on F2, with structure factors being taken from ref 27. The
absorption coefficients (µ) are listed in the Supporting Infor-
mation. A Gaussian integration absorption was made. No
significant decay was observed during data collection. Isotropic
extinction coefficients were included in the refinement to
account for secondary extinction effects.28 Three of the four
n-propyl groups are disordered; these were refined using the
SAME and SADI restraints available in SHELXL-97. Hydro-
gens were all geometrically placed, and the respective final
refinements included anisotropic thermal parameters for the
non-hydrogen atoms, except for the disordered atoms, and iso-
tropic thermal parameters for the hydrogen atoms. Individual
displacement parameters were fixed at U(H) ) 1.5[Ueq(C-
methyl)] or U(H) ) 1.2Ueq and were treated as rigid for
refinement. The R(F) and Rw(F2) final discrepancy indices at
1
3
71.95; H, 4.28. H NMR (CDCl3): δ 8,05 (d, 4H, J H-H ) 7.30,
3
Ph), 7.77 (t, 2H, J H-H ) 7.43, Ph), 7.60-7.55 (2t, 1H + 4H,
Ph), 7.35-7.32 (m, 4H, Ph), 7.10 (s, 2H, Ph), 7.07 (dd, 2H,
3J H-H ) 6.56 and 2.74, Ph), 6.87 (d, 2H, J H-H ) 7.50, Ph),
3
6.75-6.60 (3t + dd, 5H, Ph), 5.27 (s, 1H, OH), 3.85-3.65 (3d,
3 × 2H, CH2-Ar), 3.53 (d, 2H, J H-H ) 14.48, CH2-Ar). 13C
2
NMR (CDCl3): δ 164.27, 163.83, 151.99, 148.17, 146.92,
133.76, 133.61, 133.23, 133.11, 131.84, 131.55, 131.26, 130.80,
130.68, 129.70, 129.44, 129.04, 128.78, 128.55, 127.93, 127.80,
125.95, 125.01, 37.22, 32.96. MS (IE): m/z 816 (M+, relative
intensity 10%).
5-Br om o-25,26,27,28-tetr a h yd r oxyca lix[4]a r en e (4). A
20 g (25 mmol) amount of 3 and 1000 mL of THF were treated
with 100 mL of a 70% NaOH aqueous solution for 48 h at room
temperature, during which the mixture turned deep purple.
The THF solvent was then evaporated, and the pink solid was
redissolved in 700 mL of CH2Cl2. The organic phase was then
extracted twice with a 1 N NaOH aqueous solution, twice with
1 N HCl aqueous solution, and twice with water. Finally, the
organic layer was dried over MgSO4, filtered, and evaporated,
resulting in a white product. Yield: 11 g, 90%. Mp: dec >250
°C. Anal. Calcd for C28H23O4Br: C, 66.81; H, 4.61. Found: C,
3
convergence for the Inet 2.0σ(Inet) significant reflections, the
1
number of restraints and variables, and the GOF are listed in
the Supporting Information.
65.22; H, 4.62. H NMR (CDCl3): δ 10.13 (s, 4H, OH), 7.15 (s,
2H, Ph), 7.10-7.03 (m, 6H, Ph), 6.79-6.73 (m, 3H, Ph), 4.25
(br s, 4H, CH2-Ar), 3.50 (br s, 4H, CH2-Ar). 13C NMR
(CDCl3): δ 148.76, 148.53, 148.03, 131.48, 130.36, 129.28,
129.02, 128.31, 128.02, 127.36, 122.37, 113.84, 31.64, 31.49.
MS (IE): m/z 502 (M+, relative intensity 30%).
25,26,27-Tr iben zoyl-28-h yd r oxyca lix[4]a r en e (2). A 30
g (71 mmol) amount of 1 was suspended in 1700 mL of dry
acetonitrile under an N2 atmosphere. To this suspension was
added 15 equiv of 1-methylimidazole (84.5 mL, 1.06 mo), upon
which solubilization of 1 occurred within a few minutes. After
the solution was stirred for 15 min, 2.9 equiv of benzoyl
chloride (24 mL, 200 mmol) was added and the solution was
stirred for another 12 h, during which a white precipitate
appeared. The latter was then filtered and was washed with
20 mL of cold acetonitrile. Yield: 51.7 g, 88%. Mp: 260-262
°C. Anal. Calcd for C49H36O7: C, 79.88; H, 4.92. Found: C,
5-Br om o-25,26,27,28-tetr a -n -p r op oxyca lix[4]a r en e (5).
A 5.0 g (9.9 mmol) amount of 4 was dissolved in 275 mL of
dry DMF under an N2 atmosphere. Then an excess of NaH
(4.77 g, 197 mmol) was slowly added, and gas evolution was
noticed. After the mixture was stirred for 1 h, an excess of
1-iodopropane (24 mL, 247 mmol) was added. The solution was
stirred for an extra 72 h, and the solvent was subsequently
evaporated. The yellow residue was redissolved in 300 mL of
CH2Cl2, and the organic layer was extracted twice with 300
mL of a 1 N HCl aqueous solution and twice with water. The
CH2Cl2 solution was then dried over MgSO4 and was filtered
and evaporated. The white product was purified by column
chromatography (SiO2) using a CH2Cl2/hexanes mixture (20:
80) as solvents. Yield: 4.3 g, 65%. Mp: 144-146 °C. Anal.
Calcd for C40H47O4Br: C, 71.52; H, 7.05. Found: C, 71.74; H,
1
3
79.43; H, 4.89. H NMR (CDCl3): δ 8.12 (d, 4H, J H-H ) 7.35,
3
3
Ph), 7.75 (t, 2H, J H-H ) 7.44, Ph), 7.59 (t, J H-H ) 7.45, 1H,
3
Ph), 7.55 (t, J H-H ) 7.45, 4H, Ph), 7.30-7.20 (m, 4H, Ph),
3
3
7.08 (d, 2H, J H-H ) 7.45, Ph), 7.03 (dd, 2H, J H-H ) 6.67 and
(24) Le Page, Y.; White, P. S.; Gabe, E. J . Proc. Am. Crystallogr.
Hamilton Meet. 1986, Abstract PA23.
(25) Gabe, E. J .; Le Page, Y.; Charland, J .-P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(26) Sheldrick, G. M. SHELX-97; University of Go¨ttingen: Go¨ttin-
gen, Germany, 1997.
(27) International Tables for X-ray Crystallography; Wilson, A. J .
C., Ed.; Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C,
Tables 4.2.6.8 and 6.1.1.4.
1
7.11. H NMR (CDCl3): δ 6.83-6.68 (m, 5H, Ph), 6.60 (t, 2H,
3J H-H ) 7.59, Ph), 6.49 (s, 2H, Ph), 6.41 (d, 2H, J H-H ) 7.47,
3
2
2
Ph), 4.45 (d, 2H, J H-H ) 14.80, CH2-Ar), 4.40 (d, 2H, J H-H
) 13.80, CH2-Ar), 3.92-3.83 (m, 4H, CH2O), 3.81-3.72 (m,
2
4H, CH2O), 3.16 (d, 2H, J H-H ) 13.66, CH2-Ar), 3.09 (d, 2H,
(28) Larson, A. C. Crystallographic Computing; Munksgaard: Copen-
hagen, Denmark, 1970; p 291.
2J H-H ) 13.55, CH2-Ar), 1.95-1.84 (m, 8H, CH2-CH3), 1.06-

280 Organometallics, Vol. 20, No. 2, 2001
Ve´zina et al.
0.97 (m, 6H, CH2-CH3), 0.94 (t, 6H, 3J H-H ) 7.36, CH2-CH3).
13C NMR (CDCl3): δ 157.10, 155.30, 136.88, 137.07, 134.37,
130.77, 130.48, 128.86, 128.41, 128.27, 128.13, 127.84, 122.13,
114.74, 76.79, 76.67, 31.00, 30.88, 23.29, 23.14, 10.54, 10.12.
MS (IE): m/z 670 (M+, relative intensity 20%).
(>95%) as a white-yellow solid. Mp: 117-119 °C. Anal. Calcd
for C52H57O5P: C, 78.76; H, 7.24. Found: C, 77.82; H, 7.11.
IR (cm-1): ν(PdO), 1194 (s). 1H NMR (CDCl3): δ 7.50-7.45
(m, 2H, Ph), 7.40-7.32 (m, 8H, Ph), 6.91-6.87 (m, 2H, Ph),
6.80 (d, 2H, 3J H-H ) 12.38, Ph), 6.68 (d, 2H, 3J H-H ) 7.50, Ph),
3
6.62-6.59 (m, 4H, Ph), 6.44 (t, 1H, J H-H ) 7.48, Ph), 4.50 (d,
5-(Dip h en ylp h osp h in o)-25,26,27,28-t et r a -n -p r op oxy-
ca lix[4]a r en e (6a ). A 3.0 g (4.5 mmol) amount of 5 was placed
in a flame-dried 100 mL flask. Then 20 mL of dry THF was
transferred into the flask under N2. The reaction mixture was
cooled to -78 °C (acetone/dry ice), and 0.29 g (4.5 mmol) of
tert-butyllithium in solution in hexane was added. After 1 h
of reaction, 0.98 mL (5.4 mmol) of ClPPh2 was added to the
solution using a syringe and the solution was stirred for 10 h
at the same temperature. The solution was then warmed to
room temperature and evaporated down until an oily residue
appeared. The crude product was then purified by column
chromatography (SiO2) using a CH2Cl2/hexane (20:80) mixture
as solvents. A white solid was obtained. Yield: 2.0 g, 60%.
Mp: 138-140 °C. Anal. Calcd for C52H57O4P: C, 80.38; H, 7.39.
2H, 2J H-H ) 13.37, CH2-Ar), 4.46 (d, 2H, 2J H-H ) 14.65, CH2-
3
Ar), 4.00-3.90 (m, 4H, CH2O), 3.80 (td, 4H, J H-H ) 7.21 and
2.32, CH2O), 3.22 (d, 2H, 2J H-H ) 13.14, CH2-Ar), 3.11 (d, 2H,
2J H-H ) 13.20, CH2-Ar), 2.06-1.86 (m, 8H, CH2-CH3), 1.09-
1.01 (m, 6H, CH2-CH3), 0.98 (t, 6H, 3J H-H ) 7.46, CH2-CH3).
13C NMR (CDCl3): δ 159.42, 156.07, 135.77, 135.11, 134.96,
134.82, 134.52, 133.34, 132.76, 132.61, 131.94, 131.19, 128.49,
128.26, 128.00, 127.84, 124.89, 123.50, 122.54, 122.10, 77.18,
76.66, 30.92, 30.79, 23.37, 23.14, 10.48, 10.12. 31P NMR
(CDCl3): δ 30.39 (s). MS (IE): m/z 792 (M+, relative intensity
100%).
Dich lor o(η5-p en ta m eth ylcyclop en ta d ien yl)(5-(d ip h en -
ylp h osp h in o)-25,26,27,28-t et r a p r op oxyca lix[4]a r en e)-
r h od iu m (III), (C5Me5)[(C6H5)2P (ca lix)]Rh Cl2 (8a ). In a 100
mL flask, 1.0 g (1.3 mmol) of 6a was placed under N2 in the
presence of 0.4 g (0.65 mmol) of [(C5Me5)RhCl2]2. Then 25 mL
of freshly distilled ethanol was added to the mixture. The
solution was refluxed for 5 h and then cooled to room
temperature. The solvent was then evaporated, and the crude
product was purified by column chromatography using an
ethyl acetate/dichloromethane mixture (30:70) as solvent. Red
crystals suitable for crystallography were obtained from re-
crystallization in ethanol. Yield: 1.19 g, 85%. Mp: dec >280
1
Found: C, 80.17; H, 7.64. H NMR (CDCl3): δ 7.31-7.26 (m,
6H, Ph), 7.19-7.13 (m, 4H, Ph), 6.75 (d, 2H, 3J H-H ) 7.26, Ph),
6.69-6.63 (m, 5H, Ph), 6.58-6.48 (m, 4H, Ph), 4.49 (d, 2H,
2J H-H ) 13.58, CH2-Ar), 4.44 (d, 2H, 2J H-H ) 13.67 CH2-Ar),
2
3.91-3.85 (m, 8H, CH2O), 3.20 (d, 2H, J H-H ) 13.20, CH2-
2
Ar), 3.08 (d, 2H, J H-H ) 13.16, CH2-Ar), 2.01-1.91 (m, 8H,
CH2-CH3), 1.05-0.98 (m, 12H, CH2-CH3). 13C NMR
(CDCl3): δ 157.20, 156.25, 138.10, 135.16, 134.95, 134.59,
133.74, 133.49, 133.26, 128.49, 128.10, 122.09, 121.98, 76.80,
76.62, 30.87, 30.74, 23.17, 10.27. 31P NMR (CDCl3): δ -3.96.
MS (IE): m/z 776 (M+, relative intensity 100%).
°C. Anal. Calcd for
C62H72O4PCl2Rh: C, 68.57; H, 6.68.
5-(Diisop r op ylp h osp h in o)-25,26,27,28-tetr a -n -p r op oxy-
ca lix[4]a r en e (6b). A 0.10 g (0.15 mmol) amount of 5 was
placed in a flame-dried 100 mL Schlenk flask. Then 10 mL of
dry benzene was transferred into the flask under N2. The
solution was then stirred for a few minutes, and 11.5 mg (0.180
mmol) of tert-butyllithium in solution in hexane was added
using a syringe. The solution turned orange-brown over a
period of 30 min, and then 0.048 mL (0.30 mmol) of ClP(CH-
(CH3)2)2 was added to the solution using a syringe. The solution
was stirred for 24 h, and a yellow solution was obtained. Then
40 mL of benzene was added and the entire solution was
extracted twice with 50 mL of water inside the glovebox. The
organic phase was dried over MgSO4 and filtered, and the
solvent was removed in vacuo at room temperature. The oily
residue was washed twice with 5 mL of methanol, and a white
powder appeared on the wall of the flask. The product was
1
Found: C, 68.01; H, 6.78. H NMR (CDCl3): δ 7.58 (br t, 4H,
Ph), 7.37-7.00 (m, 8H, Ph), 6.76-6.66 (m, 4H, Ph), 6.55-6.41
(m, 5H, Ph), 4.47 (d, 2H, 2J H-H ) 13.19, CH2-Ar), 4.43 (d, 2H,
2J H-H ) 14.42, CH2-Ar), 3.91-3.78 (m, 8H, CH2O), 3.19 (d,
2H, 2J H-H ) 13.20, CH2-Ar), 3.09 (d, 2H, 2J H-H ) 13.12, CH2-
Ar), 2.00-1.86 (m, 8H, CH2CH3), 1.30 and 1.29 (s + s, 15H,
CH3-Cp), 1.03-0.95 (m, 12H, CH2-CH3). 13C NMR (CD2Cl2):
δ 171.14, 158.87, 156.88, 156.58, 136.01, 134.98, 131.44,
130.10, 128.72, 128.58, 128.41, 127.87, 122.83, 122.24, 99.27,
77.85, 77.48, 77.10, 60.56, 31.21, 24.10, 23.73, 23.50, 10.59,
1
10.35, 8.74. 31P NMR (CDCl3): δ 29.95 (d, J P-Rh ) 137). MS
(FAB+): m/z 1083 (M+, relative intensity 10%).
Dich lor o(η5-p en t a m et h ylcyclop en t a d ien yl)(5-(d iiso-
pr opylph osph in o)-25,26,27,28-tetr apr opoxycalix[4]ar en e)-
r h od iu m (III), (C5Me5)[(CH(CH3)2)2P (ca lix)]Rh Cl2 (8b). In
a 100 mL flask, 0.1 g (0.15 mmol) of 6b was placed under N2
in the presence of 46 mg (0.075 mmol) of [(C5Me5)RhCl2]2. Then
15 mL of benzene and 20 mL of ethanol was added to the
mixture. The solution was refluxed for 5 h and then cooled to
room temperature. The solvent was then evaporated, and the
crude product was purified by column chromatography (SiO2)
using a ethyl acetate/dichloromethane mixture (25:75) as
solvent. A red solid was obtained. Yield: 0.13 g, 85%. Mp: dec
>280 °C. Anal. Calcd for C56H76O4PCl2Rh: C, 66.14; H, 7.48.
Found: C, 65.07; H, 7.81. 1H NMR (CDCl3): δ 7.03 (d, 2H,
1
very air-sensitive and oxidized easily. Yield: 0.08 g, 80%. H
3
NMR (C6D6): δ 7.20 (d, 2H, J H-H ) 6.59, Ph), 6.86-6.63 (m,
2
9H, Ph), 4.54 (d, 2H, J H-H ) 12.98, CH2-Ar), 4.53 (d, 2H,
2J H-H ) 13.02, CH2-Ar), 3.88-3.75 (m, 8H, CH2O), 3.19 (d,
2H, 2J H-H ) 13.16, CH2-Ar), 3.15 (d, 2H, 2J H-H ) 13.17, CH2-
Ar), 2.02-1.85 (m, 10H, CH2-CH3 and P-CH-(CH3)2), 1.19
and 1.09 (d + d, 3H, 3J H-H ) 6.96 and 6.95, P-CH-CH3), 1.09
3
and 1.04 (d + d, 9H, J H-H ) 6.98 and 6.99, P-CH-CH3),
1.00-0.80 (m, 12H, CH2-CH3). 13C NMR (C6D6): δ 156.94,
156.73, 156.22, 137.09, 135.68, 135.40, 135.26, 135.11, 134.89,
134.67, 134.46, 130.84, 128.86, 128.33, 127.69, 127.39, 122.42,
122.17, 76.79, 76.58, 31.09, 23.27, 22.92, 20.05, 19.83, 18.87,
18.72, 10.19, 10.08. 31P NMR (C6D6): δ 10.04 (s). MS (EI): m/z
708 (M+, relative intensity 15%).
3
3J H-H ) 8.55, Ph), 6.77 (d, 4H, J H-H ) 7.47, Ph), 6.66 (t, 2H,
3
3J H-H ) 7.43, Ph), 6.60 (d, 2H, J H-H ) 7.44, Ph), 6.46 (t, 1H,
2
3J H-H ) 7.44, Ph), 4.47 (d, 2H, J H-H ) 12.91, CH2-Ar), 4.45
2
(d, 2H, J H-H ) 12.90, CH2-Ar), 4.00-3.85 (m, 4H, CH2O),
2
3.80-3.73 (m, 4H, CH2O), 3.17 (d, 2H, J H-H ) 13.00, CH2-
5-(Dip h en ylp h op h in e oxid e)-25,26,27,28-tetr a p r op oxy-
ca lix[4]a r en e (7). In a 100 mL Schlenk flask, 0.10 g (0.13
mmo1) of 6a was dissolved in 15 mL of tetrahydrofuran. Then
10 mL of an aqueous solution of hydrogen peroxide (30%) was
added. The solution was stirred for 24 h at room temperature.
Then, the solvent was evaporated and 50 mL of CH2Cl2 was
added. The organic solution was extracted twice with 50 mL
of water. The organic phase was dried over MgSO4, filtered,
and evaporated. The oily residue was then purified by column
chromatography (SiO2) using an acetone/hexane mixture (40:
60) as solvent. Compound 7 was obtained in quantitative yield
2
Ar), 3.16 (d, 2H, J H-H ) 12.99, CH2-Ar), 3.00-2.92 (m, 2H,
P-CH-(CH3)2), 2.10-1.98 (m, 4H, CH2CH3), 1.97-1.83 (m,
3
4H, CH2CH3), 1.39 (d, 3H, J H-H ) 7.26, P-CH-CH3), 1.34
3
(d, 3H, J H-H ) 7.29, P-CH-CH3), 1.22 and 1.21 (s + s, 15H,
3
CH3-Cp), 1.06-0.96 (m, 12H, CH2-CH3), 0.76 (d, 3H, J H-H
) 7.23, P-CH-CH3), 0,72 (d, 3H, 3J H-H ) 7.22, P-CH-CH3),
13C NMR (CD2Cl2): δ 157.61, 156.94, 156.14, 136.06, 135.33,
134.67, 134.47, 132.50, 128.94, 128.57, 128.35, 125.49, 124.97,
122.69, 98.48, 77.98, 77.69, 77.03, 31.22, 31.08, 26.82, 26.60,
23.67, 23.51, 21.11, 20.12, 10.79, 10.64, 10.27, 8.73. 31P NMR

Rhodium Complexes of Calix[4]arene
Organometallics, Vol. 20, No. 2, 2001 281
(CDCl3): δ 34.85 (d, 1J P-Rh ) 137). MS (FAB+): m/z 1016 (M+,
relative intensity 10%).
3.26 (m, 2H, P-CH-(CH3)2), 3.15 (d, 2H, 2J H-H ) 13.15, CH2-
3
Ar), 2.06-1.79 (m, 8H, CH2CH3), 1.09 (d, 3H, J H-H ) 6.75,
Dih ydr ido(η5-pen tam eth ylcyclopen tadien yl)(5-(diph en -
ylp h osp h in o)-25,26,27,28-t et r a p r op oxyca lix[4]a r en e)-
r h od iu m (III), (C5Me5)[(C6H5)2P (ca lix)]Rh H2 (9a ). The com-
plete procedure was performed in the dark and under N2. In
a 100 mL Schlenk flask, 0.050 g (0.046 mmol) of 8a was
dissolved in 15 mL of freshly distilled ethanol. The solution
was refluxed for a few minutes, and then 0.03 g (0.8 mmol) of
NaBH4 was quickly added via a 5 mL suspension in dry
ethanol. The reaction mixture was then stirred for 1 h, and
the volatiles were removed in vacuo at room temperature.
Then the crude product was redissolved in a minimum of
benzene and this solution filtered and reevaporated, also under
vacuum at room temperature. Compound 9a was obtained in
quantitative yield (>98%) as a red solid. Anal. Calcd for
C62H74O4PRh: C, 73.25; H, 7.33. Found: C, 73.14; H, 7.47. IR
(cm-1): ν(Rh-H), 2080. 1H NMR (C6D6): δ 7.71-7.64 (m, 4H,
P-CH-CH3), 1.04 (d, 3H, J H-H ) 6.68, P-CH-CH3), 0.95
3
and 0.93 (s + s, 15H, CH3-Cp), 0.95-0.80 (m, 18H, CH2CH3
1
and P-CH-(CH3)2), -14.29 (dd, 2H, 2J H-P ) 38.81 and J H-Rh
) 28.21, Rh-H). 31P NMR (C6D6): δ 83.08 (d, 1J P-Rh ) 152.88).
MS (FAB+): m/z 947 (M+ - H2, relative intensity 1%, M+ not
observed).
(η5-p en ta m eth ylcyclop en ta d ien yl)ca r bon yl(5-(d ip h en -
ylp h osp h in o)-25,26,27,28-t et r a p r op oxyca lix[4]a r en e)-
r h od iu m (I), (C5Me5)[P h 2P (ca lix)]Rh (CO) (10). An 11.4 mg
(36.6 mmol) amount of (C5Me5)RhCO2 and 30.2 mg (36.6 mmol)
of 6a were dissolved in 10 mL of dry benzene in the dark under
an N2 atmosphere. The solution was then refluxed for 24 h,
and the volatiles were removed in vacuo at room temperature.
The red solid was purified in the dark from column chroma-
tography using silaned silica gel and a 25:75 THF/hexane
mixture. Yield: 0.032 g (80%). Anal. Calcd for C63H72O5PRh:
C, 72.50; H, 6.96. Found: C, 72.41; H, 6.89. IR (cm-1): ν(Rh-
3
Ph), 7.18-7.10 (m, 8H, Ph), 6.90 (d, 2H, J H-H ) 7.46, Ph),
2
1
6.85-6.51 (m, 7H, Ph), 4.55 (d, 2H, J H-H ) 13.12, CH2-Ar),
CO), 1960. H NMR (C6D6): δ 7.75-7.60 (m, 2H, Ph), 7.25 (d,
4.43 (d, 2H, 2J H-H ) 12.66, CH2-Ar), 3.87-3.78 (m, 8H, CH2O),
2H, 3J H-H ) 10.71, Ph), 7.20-7.05 (m, 8H, Ph), 6.85-6.70 (m,
2
2
3
3
3.17 (d, 2H, J H-H ) 12.76, CH2-Ar), 3.01 (d, 2H, J H-H
)
5H, Ph), 6.58 (t, 2H, J H-H ) 7.57, Ph), 6.51 (dd, 2H, J H-H
)
2
13.05, CH2-Ar), 1.95 (s, 15H, CH3-Cp), 1.95-1.74 (m, 8H,
CH2-CH3), 0.94-0.86 (m, 12H, CH2-CH3), -13.07 (dd, 2H,
7.57 and 1.14, Ph), 4.52 (d, 2H, J H-H ) 12.99, CH2-Ar), 4.45
(d, 2H, 2J H-H ) 13.1, CH2-Ar), 3.95-3.75 (m, 8H, CH2O), 3.15
1
2J H-P ) 37.94 and J H-Rh ) 28.70, Rh-H). 31P NMR (C6D6): δ
2
2
(d, 2H, J H-H ) 13.20, CH2-Ar), 3.06 (d, 2H, J H-H ) 13.10,
CH2-Ar), 1.85 and 1.84 (s + s, 15H, CH3-Cp), 2.00-1.70 (m,
8H, CH2-CH3), 0.95-0.80 (m, 12H, CH2-CH3). 31P NMR
1
30.49 (d, J P-Rh ) 145). MS (FAB+): m/z 1015 (M+ - H2,
relative intensity 10%, M+ not observed).
Dih yd r id o(η5-p en ta m eth ylcyclop en ta d ien yl)(5-(d iiso-
pr opylph osph in o)-25,26,27,28-tetr apr opoxycalix[4]ar en e)-
r h od iu m (III), (C5Me5)[(CH(CH3)2)2P (ca lix)]Rh H2 (9b). The
complete procedure was performed in the dark and under N2.
In a 100 mL Schlenk flask, 30 mg (0.030 mmol) of 8b was
dissolved in 15 mL of freshly distilled ethanol. The solution
was refluxed for a few minutes, and then 30 mg (0.8 mmol) of
NaBH4 was quickly added via a 5 mL suspension in dry
ethanol. The reaction mixture was then stirred for 1 h, and
the volatiles were removed in vacuo at room temperature.
Then the crude product was redissolved in a minimum of
benzene and the solution filtered and re-evaporated, also under
vacuum at room temperature. Compound 9b was obtained in
quantitative yield (>98%) as a red solid. Anal. Calcd for
(C6D6): δ 52.81 (d, J P-Rh ) 199). MS (FAB+): m/z 1043 (M+,
1
relative intensity 10%).
Ack n ow led gm en t. This research was supported by
the Natural Science and Engineering Research Council
(NSERC) and the Fonds Concerte´s pour l’Avancement
de la Recherche (RCAR). M.V. acknowledges the Uni-
versite´ de Sherbrooke and the Beaudoin Funds, and J .G.
thanks the NSERC for graduate scholarships.
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tailed crystallographic data, atomic positional parameters,
bond lengths and angles, anisotropic displacement parameters,
hydrogen coordinates and isotropic displacement parameters,
torsion angles, and least-squares planes and deviations and
ORTEP figures for compound 8a and figures giving the
structures of 7 and 8b. This material is available free of charge
via the Internet at http://pubs.acs.org.
C
56H78O4PRh: C, 70.89; H, 8.28. Found: C, 71.12; H, 8.24. IR
1
3
(cm-1): ν(Rh-H), 2008. H NMR (C6D6): δ 7.46 (d, 2H, J H-H
3
3
) 8.82, Ph), 6.95 (d, 2H, J H-H ) 7.29, Ph), 6.84 (t, 1H, J H-H
) 7.27, Ph), 6.65 (d, 2H, 3J H-H ) 7.45, Ph), 6.60-6.51 (m, 4H,
2
2
Ph), 4.63 (d, 2H, J H-H ) 13.13, CH2-Ar), 4.53 (d, 2H, J H-H
) 13.14, CH2-Ar), 4.02-3.92 (m, 4H, CH2O), 3.71 (t, 4H, 3J H-H
) 7.02, CH2O), 3.35 (d, 2H, J H-H ) 13.17, CH2-Ar), 3.34-
2
OM000433A