Synthesis and reactions of Cp-linked phosphine complexes of rhodium

Article abstract of DOI:10.1021/om980263q

The linked Cp ligand [C₅H₄SiMe₂CH₂PPh₂] ^- has been used to synthesize several rhodium derivatives. Reaction with [RhClL₂]₂, where L = C₂H₄, C₈H₁₄, or CO, gives (η⁵:η¹-C₅H₄SiMe₂- CH₂PPh₂)Rh(L) complexes, which have been characterized by single-crystal X-ray diffraction. Reaction of the ethylene complex with CO or PMe₃ gives the carbonyl- and phosphinesubstituted derivatives, respectively. Irradiation of the ethylene complex in the presence of hydrogen gives a new binuclear polyhydride, also structurally characterized, in which the chelating ligand spans the two metal centers. Reaction of the ethylene complex with iodine leads to the formation of the diiodide (η⁵:η¹-C₅H₄SiMe ₂CH₂PPh₂)RhI₂, which in turn can be converted to the dihydride (η⁵:η¹-C₅H₄SiMe ₂CH₂PPh₂)RhH₂ by reaction with NaAl(OCH₂- CH₂OCH₃)₂H₂. The reactivity of the dihydride toward C-H bond activation has been investigated While benzene does not give a stable oxidative addition adduct, pentafluorobenzene yields (η⁵η¹-C₅H₄SiMe ₂CH₂PPh₂)Rh(C₆F₅)H, which was structurally characterized as its chloro derivative. Reaction of the dihydride with C₆F₆ gives the η² complex (η⁵η¹- C₅H₄SiMe₂CH₂PPh ₂)Rh(η²-C₆F₆), also structurally characterized.

Full text of DOI:10.1021/om980263q

Organometallics 1998, 17, 3889-3899
3889
Syn th esis a n d Rea ction s of Cp -Lin k ed P h osp h in e
Com p lexes of Rh od iu m
Laurent Lefort, Todd W. Crane, Michael D. Farwell, David M. Baruch,
J ohn A. Kaeuper, Rene J . Lachicotte, and William D. J ones*
Department of Chemistry, University of Rochester, Rochester, New York 14627
Received April 6, 1998
The linked Cp ligand [C5H4SiMe2CH2PPh2]- has been used to synthesize several rhodium
derivatives. Reaction with [RhClL2]2, where L ) C2H4, C8H14, or CO, gives (η5:η1-C5H4SiMe2-
CH2PPh2)Rh(L) complexes, which have been characterized by single-crystal X-ray diffraction.
Reaction of the ethylene complex with CO or PMe3 gives the carbonyl- and phosphine-
substituted derivatives, respectively. Irradiation of the ethylene complex in the presence of
hydrogen gives a new binuclear polyhydride, also structurally characterized, in which the
chelating ligand spans the two metal centers. Reaction of the ethylene complex with iodine
leads to the formation of the diiodide (η5:η1-C5H4SiMe2CH2PPh2)RhI2, which in turn can be
converted to the dihydride (η5:η1-C5H4SiMe2CH2PPh2)RhH2 by reaction with NaAl(OCH2-
CH2OCH3)2H2. The reactivity of the dihydride toward C-H bond activation has been
investigated. While benzene does not give a stable oxidative addition adduct, pentafluo-
robenzene yields (η5:η1-C5H4SiMe2CH2PPh2)Rh(C6F5)H, which was structurally characterized
as its chloro derivative. Reaction of the dihydride with C6F6 gives the η2 complex (η5:η1-
C5H4SiMe2CH2PPh2)Rh(η2-C6F6), also structurally characterized.
In tr od u ction
operating in concert.6 Nevertheless, true examples of
reactions involving both metallic sites have remained
rare.
Since the discovery of ferrocene in 1951 by T. J . Kealy
and P. L. Pauson,1 a wide range of cyclopentadienyl
analogues have become available as ligands for orga-
nometallic complexes.2 Among them, phosphine-sub-
stituted cyclopentadienyl anions have been prepared by
several methods3 and have been used mainly in the
synthesis of both homo-4 and heterobimetallic5 com-
plexes. Indeed, because of its two different functional-
ities, these ligands have proven to be particularly
efficient at holding two metal centers of a very different
nature (for example, early and late transition metals)
in close proximity to each other, the goal here being to
achieve new and useful reactions with the two metals
If one or several atoms separate the cyclopentadienyl
ring from the phosphine group, the ligand can act as a
chelate, where the two binding sites are connected to
the same metal center. In contrast to the bridging case,
only a few examples of this coordination mode can be
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S0276-7333(98)00263-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 08/05/1998

3890 Organometallics, Vol. 17, No. 18, 1998
Lefort et al.
found in the literature.3d,h,7 Mathey was the first to
observe such a chelate with a carbonyl manganese
complex.3d Irradiation was required in order to release
CO, allowing the formation of a coordination site for the
phosphine. Butenschon used a ligand of this type to
isolate some alkyne adducts of cobalt involved in the
cyclotrimerization reaction of alkynes.7c Wang has
shown that a chelating phosphino-cyclopentadienyl
ligand can prevent the loss of phosphine, usually
observed under thermal or photochemical conditions, in
a carbonyl iron complex.7i Fryzuk7e and Erker7j used
the chelating properties of similar ligands to synthesize
some otherwise unstable Zr compounds. Quite recently,
Bergman reported a chelating phosphino-cyclopenta-
dienyl system in which a tert-butyl group on the Cp ring
results in the formation of chiral complexes.8
Sch em e 1
a new compound, formulated as the mononuclear spe-
cies (η5:η1-C5H4SiMe2CH2PPh2)Rh(C2H4) (1) (eq 1). The
Rhodium complexes bearing both a cyclopentadienyl
ring and a phosphine have been extensively studied by
J ones for the cleavage of C-H,9 C-S,10 C-F,11 and
C-C12 bonds. Nevertheless, one limitation associated
with the use of those complexes is their lack of long-
term thermal stability. The mode of decomposition
usually observed is a loss of phosphine by either the
initial rhodium complex or a product, and the free
phosphine produced then reacts with the initial Cp*Rh-
(PR3) fragment leading to the formation of the unreac-
tive bis-phosphine Cp*Rh(PR3)2.
In this paper, we describe the preparation of a new
class of thermally stable Rh complexes by working with
a tethered phosphine derivative. The ligand employed
has been reported in the literature by Schore,3e and we
have found that it reacts with [RhClL2] (L ) C2H4, CO,
or C8H14) to give mononuclear chelate complexes of the
formula (η5:η1-C5H4SiMe2CH2PPh2)Rh(L). Similar com-
pounds have already been prepared7f with a CH2CH2
link between the Cp and the phosphine ligands, but
little was reported of their reactivity. The chiral ligand
system investigated by Bergman with the fragment [(η5:
η1-3-ButC5H3CH2CH2PMe2)Ir] showed diastereotopic
selectivity for cyclohexane C-H activation. Here, we
report the behavior of these SiMe2CH2-linked complexes
in several chemical reactions including ligand substitu-
tion, reaction with H2, and C-H bond activation.
1H NMR spectrum of this complex displays a high-field
singlet at δ -0.03 for the two SiMe groups, a doublet
at δ 2.17 for the PCH2 group coupled to the phosphorus
(J H-P ) 13.6 Hz), and two multiplets at δ 5.18 and 5.90
for the Cp hydrogens, as well as aromatic multiplets for
the phenyl rings. The ethylene hydrogens appear as
broad singlets at δ 1.26 and 2.84, indicating slow
rotation of the ethylene ligand. The 31P NMR spectrum
shows a doublet at δ 49.1 with J Rh-P ) 206 Hz, typical
of a CpRhI phosphine complex.13
Complex 1 was also characterized by single-crystal
X-ray diffraction (Table 1). 1 crystallizes in triclinic
space group P1h with one molecule within the asym-
metric unit. The structure (Figure 1) confirms coordi-
nation of the cyclopentadienyl ring and the phosphine
to a single metal center. The bonding of the ethylene
ligand is typical of those for other rhodium-ethylene
complexes,7f,14 with dRh-C ) 2.111(3) and 2.102(3) Å and
dC-C ) 1.399(5) Å. Other distances and angles are listed
in Table 2.
The ligand has also been reacted with the cyclooctene
dimer, [RhCl(C8H14)2]2, under the same conditions used
for preparation of 1 (eq 1). In this case, a mixture of
two products was obtained in a ratio of 4:1. The major
Resu lts
1
product exhibits H and 31P NMR spectra almost identi-
cal to those of 1, which allowed us to assign it as the
Liga n d Syn th esis. The ligand Li[C5H4SiMe2CH2-
PPh2] was prepared by a modification of the method
reported by Schore et al. in 1979.5 Reaction of Li-
(TMEDA)CH2PPh2 with neat dimethyldichlorosilane in
THF at -78 °C leads to the formation of Ph2PCH2SiMe2-
Cl only. Further reaction with LiCp followed by depro-
tonation with BuLi gives the desired anionic ligand
(Scheme 1).
cyclooctene analogue of 1, (η5:η1-C5H4SiMe2CH2PPh2)-
1
Rh(C8H14) (2). The H spectrum of the minor product
displays a Cp pattern with four different resonances,
showing that the complex is not symmetrical. Other
1H resonances were difficult to identify, obscured by the
resonances of 2. While it was not possible to isolate the
minor product, slow evaporation of a solution of the
mixture in hexane leads to the formation of crystals of
2. The X-ray structure (Figure 2) shows again that 2
is mononuclear. The bond distances are almost the
Rea ction of th e Liga n d w ith Rh Com p lexes.
Reaction of this ligand with [RhCl(C2H4)2]2 in THF gives
(8) Mobley, T. A.; Bergman, R. G. J . Am. Chem. Soc. 1998, 120, 3253.
Published on the Web: http://pubs.acs.org/journals/jacsat/index.html,
3/19/98.
(9) J ones, W. D.; Feher, F. J . Acc. Chem. Res. 1989, 22, 91-100.
(10) J ones, W. D.; Dong, L.; Myers, A. W. Organometallics 1995,
14, 855-861. Myers, A. W.; J ones, W. D. Organometallics 1996, 15,
2905-2917. Vicic, D. A.; Myers, A. W.; J ones, W. D. Organometallics
1997, 16, 2751-2753.
(11) Edelbach, B. L.; J ones, W. D. J . Am. Chem. Soc. 1997, 119,
7734-7742.
(12) Perthuisot, C.; J ones, W. D. J . Am. Chem. Soc. 1994, 116, 3647-
3648.
same as those for the ethylene adduct, with dRh-C
2.119(4) and 2.101(4) Å and dC-C ) 1.421(5) Å. Other
distances and angles are given in Table 2.
)
(13) Klingert, B.; Werner, H. Chem. Ber. 1983, 116, 1450-1462.
(14) (a) Guggenberger, L. J .; Cramer, R. J . Am. Chem. Soc. 1972,
94, 3779-3786. (b) Porzio, W.; Zocchi, M. J . Am. Chem. Soc. 1978, 100,
2048-2052. (c) Mayer, J . M.; Calabrese, J . C. Organometallics 1984,
3, 1292-1298. (d) Blom, R.; Rankin, D. W. H.; Robertson, H. E.; Perutz,
R. N. J . Chem. Soc., Dalton Trans. 1993, 1983-1986.

Cp-Linked Phosphine Complexes of Rhodium
Organometallics, Vol. 17, No. 18, 1998 3891
F igu r e 1. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(C2H4), 1. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms (except on ethylene) have been
omitted for clarity.
Following an identical procedure, it was also possible
to prepare the CO adduct (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(CO) (3) by reacting [RhCl(CO)2]2 with the bidentate
ligand (eq 1). In this case, a single product was cleanly
1
obtained. 3 has been identified by its H and 31P NMR
spectra, displaying nearly identical features to those of
1
1 and 2. The H NMR spectrum of 3 displays a singlet
at δ -0.08 for the two methyl groups on the silicon, a
doublet at δ 2.12 for the PCH2 group, two broad singlets
at δ 5.62 and 5.72 for the Cp protons, and aromatic
resonances between δ 7 and 8. A doublet is observed
in the 31P spectrum at δ 45.31 with J Rh-P ) 199 Hz.
The IR spectrum of 3 in THF solution exhibits a peak
at 1937 cm-1, as expected for a CO ligand attached to
RhI.
Layering a solution of 3 in THF with hexane allowed
growth of X-ray quality single crystals. The structure
of 3 (Figure 3) shows again that the bidentate ligand
chelates to a single metal center. The bond distance
between the carbonyl group and the rhodium atom
(1.811(4) Å) is identical to that found in the nonchelating
rhodium carbonyl analogues.15
Crystal structures of nonchelating analogues of 1 and
3 have been previously reported.14,15 Consequently, an
interesting comparison can be made of the structural
changes induced by the chelating ligand. In general,
the differences are small and the major effect (as already
noticed by Poilblanc et al.7f) involves a decrease of the
angle Cp-Rh-P due to chelation. In the case of the CO
adduct, this angle is 134.8° in CpRh(PPh3)(CO),15a
compared to 124.4° in 3. For the ethylene adduct, the
values are 133.9° in CpRh(PPh3)(C2H4)14b and 126.6° in
1. The ligand used by Poilblanc et al., where the
phosphine is linked to the cyclopentadienyl ring through
an ethylene moiety, causes a greater change since the
angle Cp-Rh-P in the similar ethylene adduct is equal
to 118.5°. This difference can be attributed to the fact
that the Cp-C-C-P bond distance is smaller than the
Cp-Si-C-P bond distance. In both cases, however, the
chelate ligand leaves the opposite side of the Rh atom
wide open for coordination. From this point of view,
investigating the reactivity of the new complexes ap-
(15) (a) Choi, M.-G.; Brown, T. L. Inorg. Chem. 1993, 32, 5603-
5610. (b) Faraone, F.; Bruno, G.; Lo Schiavo, S.; Tresoldi, G.; Bombieri,
G. J . Chem. Soc., Dalton Trans. 1983, 433-438.

3892 Organometallics, Vol. 17, No. 18, 1998
Lefort et al.
Ta ble 2. Selected Dista n ces (Å) a n d An gles (d eg) for [Rh ]L1L2 ([Rh ] ) (η1:η5-C5H4SiMe2CH2P P h 2)Rh )
compound
L1
L2
dRh-P
dRh-L1
dRh-L2
Cp-Rh-L1
Cp-Rh-L2
Cp-Rh-P
[Rh](C2H4) (1)
[Rh](COE)b (2)
C21
C21
C22
C22
2.195
2.201
2.201
2.236
2.215
2.289
2.255
2.251
2.292
2.264
2.111
2.119
2.116
1.811
1.649c
2.664
2.070
2.270
2.076
2.057
2.102
2.101
2.122
139.0a
141.1a
140.3a
141.3
127.0
126.5
120.8
120.5
121.9
140.8a
126.6
124.3
[Rh](CO) (3)
[Rh]2(µ-H)2 (5)
[Rh]I2 (8)
[Rh](Ph)I (9)
[Rh](Me)I (11)
[Rh](C6F5)Cl (14)
[Rh](C6F6) (15)
C21
H
I1
C21
C21
C21
C21
125.8
124.4
130.1
121.8
123.2
121.6
122.2
H
I2
I1
I1
I1
C26
2.836d
2.677
2.668
2.668
2.398
2.051
129.1
122.1
125.1
127.3
127.9
a
b
c
d
Angle between Cp and olefin centroids. Two molecules per asymmetric unit. dRh-H
.
dRh-Rh
.
Sch em e 2
with the P (J H-P ) 8.8 Hz) and the Rh (J H-Rh ) 1 Hz).
The NMR data are consistent with 4 being the PMe3
adduct (η5:η1-C5H4SiMe2CH2PPh2)Rh(PMe3) (Scheme 2).
If 5 equiv of PMe3 is used, the disappearance of 1 is
about 7 times faster. This effect of the PMe3 concentra-
tion on the rate of reaction suggests that the ligand
substitution occurs by way of an associative mechanism,
as already observed in the case of CpRh(CO)2 by Basolo
et al.16 Moreover, the use of an excess of PMe3 (5 equiv)
leads to the formation of a mixture of 4 and another
product 5 in a ratio of 9:1. The 31P spectrum of 5
exhibits a doublet at δ -2.30 (J ) 214 Hz) in a region
corresponding to PMe3 bound to the metal and a singlet
at δ -20.6, consistent with noncoordinated diphenyl
phosphine. In the 1H NMR spectrum, the protons of
the PMe3 ligands appear as an AX9A′X′9 multiplet17 at
δ 1.135 (J H-P + J H-P′ ) 9.2 Hz). These NMR data
provide strong evidence that 5 is the bis(trimethylphos-
phine) complex (η5-C5H4SiMe2CH2PPh2)Rh(PMe3)2, where
the chelating phosphine has been displaced by PMe3 and
is now dangling away from the metal (Scheme 2).
Addition of more PMe3 to the mixture leads to the
production of more 5, and removal of the excess phos-
phine under vacuum allows the complete reversion of 5
into 4. The facile reversibility of the reaction can be
attributed to the chelating ability of the ligand. That
is, if one side of the chelating ligand is easily displaced,
the diphenylphosphine linked to the cyclopentadienyl
ring stays in proximity to the metal center and can
coordinate back to the metal, regenerating the initial
rhodium complex.
F igu r e 2. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(C8H14), 2. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
F igu r e 3. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(CO), 3. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
peared attractive, in addition to determining any in-
crease in stability brought about by the chelating ligand.
Liga n d Su bstitu tion s. Basic ligand substitution
reactions were first examined to test the reactivity of
the new complexes. 1 reacts with PMe3 upon heating
at 65 °C. If 1 equiv of PMe3 is used, complete conversion
of 1 into a new product (4) occurs after about 1 day. The
31P NMR spectrum of 4 displays two doublets of
doublets, one for each phosphine ligand with both Rh-P
and P-P couplings. The Rh-P coupling constants for
the PPh2 and PMe3 ligands of 225 and 210 Hz, respec-
tively, are consistent with a RhI complex.9 The P-P
Under 1 atm of CO, 1 can be completely converted
into 3 after 2 days at 80 °C in benzene (eq 2). No
intermediate has been observed by NMR spectroscopy
during the course of the reaction.
1
coupling is smaller, 56 Hz. In the H NMR spectrum,
(16) Schuster-Woldan, H. G.; Basolo, F. J . Am. Chem. Soc. 1966,
88, 1657-1663.
(17) Casey, C. P.; O’Connor, J . M.; J ones, W. D.; Haller, K. J .
Organometallics 1983, 2, 535-538.
formation of free ethylene (singlet at δ 5.24) can be
monitored over the course of the reaction. The bound
PMe3 appears as a doublet of doublets due to couplings

Cp-Linked Phosphine Complexes of Rhodium
Organometallics, Vol. 17, No. 18, 1998 3893
The reaction of the CO adduct 3 with PMe3 has also
been examined. In the presence of 2 equiv of PMe3 in
benzene at room temperature, 60% of 3 was converted,
surprisingly not into 4 but into a new compound (6)
displaying the following NMR spectral features. In the
1H NMR spectrum, resonances are observed at δ 0.26
(s, 6 H), 1.04 (dd, J 1 ) 10, 1.6 Hz, 9 H), 1.63 (s, 2 H),
5.05 (br s, 2 H), and 5.28 (br s, 2 H), as well as aromatic
resonances that were difficult to assign due to overlap
F igu r e 4. (1) 1H NMR spectrum of 7 in the hydride region.
(2) Simulated spectrum with the following values for the
coupling constants J 1 ) 22.6 Hz, J 2 ) 15 Hz.
with the resonances of the starting material. In the 31
P
NMR spectrum, a doublet was observed at δ 1.18 (J )
187 Hz) along with a singlet at δ -21.00. These NMR
data provide strong evidence for the formulation of 6
as (η5-C5H4SiMe2CH2PPh2)Rh(PMe3)(CO), where the
phosphine of the chelating ligand has been again
displaced by PMe3 (eq 3). After a few days, small
amounts of 4 start to appear together with another
unidentified compound of the following type (η5:η1-C5H4-
SiMe2CH2PPh2)Rh(X) while 6 is still the major product.
Neither running the reaction at higher temperature nor
under irradiation allowed the clean formation of the
expected product, 4. Upon removal of PMe3 under
vacuum, 6 is almost completely converted into 3,
implicating an equilibrium in this transformation (eq
3), as already seen with 4 and 5.
These first experiments demonstrate that the chelate
effect can be easily overcome since reactions with only
a slight excess of PMe3 under mild conditions led to a
loss of chelation. Nevertheless, if the excess of PMe3
was removed, the chelate complex quantitatively re-
formed, a behavior that would not necessarily be
observed in the case of a nonchelating ligand.
F igu r e 5. ORTEP drawing of [(µ-C5H4SiMe2CH2PPh2)Rh-
(µ-H)]2, 7. Ellipsoids are shown at the 30% probability level.
Hydrogen atoms (except hydrides) have been omitted for
clarity.
reaction, the brown solution gradually turns black, with
the concomitant growth of small amounts of unidentified
species. After 5 days of irradiation, the reaction nears
completion as only 4% of the starting material is still
present in the solution. The major product is the second
hydride complex 7, which accounts for 48% of the
starting material, but small traces of the first hydride
complex can still be observed (eq 4). In benzene solvent,
Rea ction of 1 w ith H2. No reaction was observed
between 1 and H2 (1 atm) upon heating overnight at
100 °C in THF. When the same solution was irradiated
under 1 atm of H2, the appearance of ethane and of a
new hydride resonance can be monitored by NMR
spectroscopy after 1 day. Independent experiments
show that no reaction occurs between 1 and the solvent
(THF or benzene) upon irradiation. The 1H NMR
spectrum of the hydride complex appears as a triplet of
triplets at δ -12.91 with J ) 22.4 and 15.0 Hz, a singlet
at δ -0.07 (SiMe2), a doublet at δ 2.17 with J ) 12.4
Hz (CH2), and two broad singlets at δ 3.61 and 5.46
(C5H4). Further irradiation leads to the decrease of this
hydride complex and to the growth of a new one (7)
exhibiting the same pattern of resonances, a triplet of
triplets at δ -13.00 (J ) 22.6, 15 Hz) (Figure 4),
together with a singlet at δ -0.13, a doublet at δ 1.90
(J ) 14.4 Hz), two broad singlets at δ 4.53 and 4.73,
and two multiplets for the aromatic resonances at δ
7.29-7.37 and 7.67-7.74. Over the course of the
the photochemical reaction leads to the same major
product but was more complicated by the fact that two
other nonhydride-containing products could be observed.
Nevertheless, crystals of the hydride complex 7 formed
from the crude benzene solution upon standing for a few
days.
7 crystallizes in monoclinic space group P21/n. The
structure (Figure 5) shows that 7 is a dimer containing
two bridging hydrides, [(µ-C5H4SiMe2CH2PPh2)Rh(µ-
H)]2. The two metal centers are also connected by the
initially chelating ligands. 7 lies on a crystallographic
center of symmetry, rendering the two phosphines and
the two rhodium centers magnetically equivalent, thereby
giving rise to the triplet of triplets for the hydride

3894 Organometallics, Vol. 17, No. 18, 1998
Lefort et al.
F igu r e 6. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
RhI2, 8. Ellipsoids are shown at the 30% probability level.
Hydrogen atoms have been omitted for clarity.
F igu r e 7. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(Ph)I, 9. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
1
resonances observed in the H NMR spectrum. Assign-
with the complex crystallizing in space group P21/n with
one molecule in the asymmetric unit. Selected distances
and angles are given in Table 2.
ment of the coupling constants was accomplished through
a
1H{31P} NMR spectrum of 7, which shows a triplet
due to residual coupling to two equivalent rhodiums
with J ) 22.6 Hz. In this complex, the formal oxidation
state of the rhodium is +2,18 consistent with the
intermediate value of the coupling constant in the 31P
spectrum, J P-Rh ) 187 Hz. No broadening of the NMR
resonances of 7 is observed, however, due to the pres-
ence of a Rh-Rh bond, with d(Rh-Rh) ) 2.8357(5) Å.
The long-term instability of 7 has precluded its isolation
in sufficient quantities for elemental analysis. On the
basis of the structure obtained for 7, the first hydride
product appearing in the photochemical reaction of 1
with H2 could also be a Rh(II) bridging hydride dimer
in which the ligands Li[C5H4SiMe2CH2PPh2] are still
chelating to a single metal center, rather than bridging
two metal centers. Unfortunately, the extensive de-
composition that accompanies the photochemical reac-
tion does not allow us to conclude definitively whether
this first hydride is an intermediate in the formation of
7.
Because of the difficulties in isolating 7, its reactivity
has only been briefly explored. Under 1 atm of C2H4, a
small fraction of 7 (∼40%) is converted back into the
ethylene complex 1 after 7 days at 80 °C. The reaction
of 7 with CO is much cleaner since complete conversion
of 7 into 3 is obtained after 3 days at 65 °C. Several
intermediates appeared during the course of the reac-
tion, and among them, a new hydride complex was
observed exhibiting a doublet of doublets at δ -13.08
(J 1 ) 36.0 Hz, J 2 ) 27.0 Hz), which does not correspond
to the resonances for the dihydride rhodium complex
(η5:η1-C5H4SiMe2CH2PPh2)RhH2.
Compound 8 appears to be synthetically useful since
reaction with Grignard or lithium reagents allows for
the formation of alkyl or aryl halide compounds of the
general formula (η5:η1-C5H4SiMe2CH2PPh2)Rh(R)I with
R ) an aryl or alkyl group. For example, the phenyl
iodide complex (η5:η1-C5H4SiMe2CH2PPh2)Rh(C6H5)I (9)
has been synthesized by the reaction 8 with C6H5MgBr
(eq 6). Since the rhodium atom is bound to four
different substituents, loss of Cs symmetry occurs, and
1
the H NMR spectrum of 9 now exhibits two singlets at
δ -0.04 and 0.25 for the two Si(Me)2 groups and four
multiplets at δ 5.26, 5.60, 5.63, and 6.34 for the protons
of the Cp ring. No change is observed for the resonances
of the P(CH2) group, which still appears as a doublet.
X-ray quality crystals of 9 have been obtained by
layering a solution in CH2Cl2 with hexane. The X-ray
structure confirms the formulation of 9 as the phenyl
iodide product (Figure 7).
8 also reacts with hydride reagents. An unidentified
paramagnetic compound is formed with Super-Hydride
(LiBEt3H). Reaction of 4 equiv of Red-Al (NaAl(OCH2-
CH2OCH3)2H2) with 8 in THF leads to the formation of
the dihydride compound (η5:η1-C5H4SiMe2CH2PPh2)-
RhH2 (10) (eq 7). The hydride resonance appears as a
Syn th esis of Rh (III) Com p lexes. The reaction of
1 with iodine leads to the formation of (η5:η1-C5H4SiMe2-
CH2PPh2)RhI2, 8 (eq 5). The 31P NMR spectrum of 8
doublet of doublets at δ -13.38 (J H-P ) 26.2 Hz, J H-Rh
1
) 30.8 Hz) in the H NMR spectrum. The 31P spectrum
shows a doublet at δ 55.3 with J P-Rh ) 172 Hz. This
shows a doublet at higher field (δ 23.1, J P-Rh ) 137 Hz),
consistent with the formation of a RhIII compound.9
Compound 8 was characterized structurally (Figure 6),
(18) For a review on Rh(II) complexes, see: Felthouse, T. M. Prog.
Inorg. Chem. 1982, 29, 73-166.

Cp-Linked Phosphine Complexes of Rhodium
Organometallics, Vol. 17, No. 18, 1998 3895
mentioned above, the photolysis of 1 in benzene (380
nm band-pass filter) for 3 days did not result in the
formation of the phenyl hydride complex (η5:η1-C5H4-
SiMe2CH2PPh2)Rh(Ph)H and no change was observed
in the starting material. Nor was there a thermal
reaction of 1 with benzene at temperatures up to 80 °C.
The independent synthesis of the phenyl hydride com-
plex was, therefore, attempted in order to determine the
stability of this complex.
The addition of AgPF6 to a solution of (η5:η1-C5H4-
SiMe2CH2PPh2)Rh(Ph)I (9) in THF led to the formation
of a new compound (12) exhibiting resonances in the
1H NMR spectrum at δ 0.06 (s, 3 H) and 0.33 (s, 3 H)
for the two SiMe groups, δ 2.75 (t, 1 H) and 3.19 (s, 1
H) for the PCH2 group, and δ 4.88, 5.85, 6.26, and 6.49
(br s, 1 H each) for the Cp hydrogens, as well as
aromatic multiplets for the phenyl rings. A doublet at
δ 37.8 (J P-Rh ) 162 Hz) can be observed in the 31P NMR
spectrum. These NMR data are consistent with 12
being formulated as [(η5:η1-C5H4SiMe2CH2PPh2)Rh(Ph)-
(THF)](PF6). Replacement of the THF solvent by ben-
zene led to the decomposition of 12, indicating that the
THF ligand is labile. Since THF is only weakly bound
to the metal, it was thought that 12 might react with
hydride reagents at low temperature to form the aryl
hydride complex.21 Addition of Red-Al to a solution of
12 in THF at -70 °C in an NMR tube led to an
immediate change of color from orange to brown black.
An NMR spectrum of the sample, maintained at -60
°C, did not show a resonance corresponding to a hydride
but did show a singlet at δ 7.23 which can be attributed
to benzene. This experiment indicates that the phenyl
hydride rhodium compound, if it was formed as an
intermediate, is unstable even at -60 °C. Conse-
quently, the absence of a reaction between 1 and C6H6
upon photolysis should be expected, as the phenyl
hydride product is likely to be unstable. Alternatively,
oxidative addition might occur to form the unstable
phenyl hydride compound, but this product immediately
undergoes reductive elimination to regenerate 1. Evi-
dence to this effect was obtained by examination of
arenes containing electron-withdrawing substituents.
The formation of a Rh(III) hydride compound was
observed by NMR spectroscopy upon irradiation of 1 in
neat C6F5H. The reaction was very slow, and the total
consumption of 1 required a week of photolysis and was
accompanied by substantial decomposition. In contrast
to the ethylene adduct, the dihydride compound (10)
loses hydrogen more quickly upon photolysis. The same
reaction performed with 10 instead of 1 went to comple-
tion after 7 h and led to the same hydride species (13).
The 1H NMR spectrum of 13 exhibits a doublet of
doublets at δ -11.04 for the hydride, two singlets for
the inequivalent SiMe2 groups, two doublets of doublets
at δ 2.75 and 3.08 for the CH2 group, four multiplets
for the Cp group, and three multiplets for the PPh2
groups. Addition of CCl4 to 13 led to its complete
conversion to the air-stable chloride derivative (η5:η1-
C5H4SiMe2CH2PPh2)Rh(Cl)(C6F5) (14) (Scheme 3). The
1H NMR spectrum of 14 is similar to that observed for
other alkyl or aryl halide complexes. The 31P spectrum
appears as a doublet of triplets. In contrast to 13, the
F igu r e 8. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(CH3)I, 11. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
dihydride rhodium compound is very air sensitive but
can be stored in THF solution under an inert atmo-
sphere for several days without showing any sign of
decomposition. Purification of 10 by column chroma-
tography can be performed under inert conditions but
was not efficient enough to give a sample suitable for
elemental analysis. An attempted synthesis of 10 by
reaction of the diiodide in THF with Na/Hg in the
presence of H2 was unsuccessful as it leads to an
unidentified paramagnetic compound.
Werner19 has shown that nonchelated analogues of 1
react with CH3I in THF to form the methyl iodide
rhodium compound by oxidative addition in the C-X
bond. By analogy, complete conversion of 1 into the
methyl iodide compound, (η5:η1-C5H4SiMe2CH2PPh2)Rh-
(CH3)I (11), was obtained upon refluxing a solution of
1 in THF in the presence of 6 equiv of CH3I for 7 h (eq
8). Crystals of 11 were obtained by layering a CH2Cl2
solution with hexane, and the structure of 11 was
determined by X-ray crystallography (Figure 8). Similar
reactions run with aryl halides did not lead to a clean
oxidative addition of the C-X bond. Warming a solu-
tion of 1 at 120 °C in THF in the presence of 10 equiv
of C6H5Cl led only to decomposition. With C6F5Br (10
equiv), at 75 °C in THF, 1 was converted into the
dibromide complex after 2 days.
Ar om a tic C-H Bon d Activa tion . Other cyclopen-
tadienylrhodium ethylene complexes20 have been used
as precursors of reactive 16-electron Rh(I) fragments by
photochemical dissociation of ethylene. These frag-
ments can react with C-H bonds of alkanes or arenes
to form an aryl- or alkyl hydride product. 1 absorbs
light over the entire near-UV region to ∼450 nm. As
(19) Werner, H.; Feser, R. J . Organomet. Chem. 1982, 232, 351-
370.
(20) (a) Belt, S. T.; Duckett, S. B.; Helliwell, M.; Perutz, R. N. J .
Chem. Soc., Chem. Commun. 1989, 928-930. (b) Belt, S. T.; Helliwell,
M.; J ones, W. D.; Partridge, M. G.; Perutz, R. N. J . Am. Chem. Soc.
1993, 115, 1429-1440. (c) Selmeczy, A. D.; J ones, W. D.; Partridge,
M. G.; Perutz, R. N. Organometallics 1994, 13, 522-532.
(21) J ones, W. D.; Feher, F. J . J . Am. Chem. Soc. 1984, 106, 1650-
1663.

3896 Organometallics, Vol. 17, No. 18, 1998
Lefort et al.
Sch em e 3
F igu r e 9. ORTEP drawing of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(C6F5)Cl, 14. Ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
phosphorus of 14 is coupled to both fluorine atoms.
Crystals of 14 have been obtained by layering a solution
of 14 in CHCl3 with hexane. A single-crystal X-ray
structure is shown in Figure 9.
It has been shown that formation of an η2 adduct is
the first step in the oxidative addition of arenes to
Cp*Rh(PMe3).9 These labile complexes have been iso-
lated by use of an aromatic compound containing no
C-H bonds, such as perfluorobenzene. Irradiation of
1 in neat C6F6 led to the formation of a new Rh complex
15, formulated as the η2-C6F6 complex (η5:η1-C5H4SiMe2-
CH2PPh2)Rh(η2-C6F6). Here again, the reaction was
very slow and required more than 1 week to go to
completion. 15 was obtained more quickly starting from
the dihydride complex (10) as only a few hours of
irradiation is necessary for complete conversion of the
starting material. The 1H NMR spectrum of 15 displays
a singlet at δ 0.05 for the equivalent SiMe2 groups, a
doublet at δ 2.57 for the methylene group, two broad
singlets for the Cp ring, and aromatic multiplets for the
diphenylphosphine. The 31P spectrum of 15 appears as
a doublet of triplets since the phosphorus is coupled to
the rhodium and to two equivalent fluorines. Three
multiplets can be observed in the 19F NMR spectrum,
each corresponding to the two fluorines in the ortho,
meta, and para positions relative to the metal. A single-
crystal X-ray structure of 15 is shown in Figure 10. The
most noticeable feature of this structure is that the two
fluorines in the proximity of the metal bend strongly
away from the aromatic plane (38°). The angle between
the Rh-C21-C26 plane and the aromatic plane is
109.6°. The ring and the remaining fluorines are
planar. The reactions of arenes with the (η5:η1-C5H4-
SiMe2CH2PPh2)Rh fragment are summarized in Scheme
3.
F igu r e 10. ORTEP drawing of (η5:η1-C5H4SiMe2CH2-
PPh2)Rh(η2-C6F6), 15. Ellipsoids are shown at the 30%
probability level. Hydrogen atoms have been omitted for
clarity.
two metal centers. The unsaturated fragment [(η5:η1-
C5H4SiMe2CH2PPh2)Rh] does not form a stable oxida-
tive addition adduct with benzene, but the electron-
deficient arene C6F5H does produce a stable product.
An η2-arene complex is formed with hexafluorobenzene.
Exp er im en ta l Section
Gen er a l. All reactions, recrystallizations, chromatography,
and routine manipulations, unless otherwise noted, were
carried out at ambient temperature under a nitrogen atmo-
sphere, either on a high-vacuum line using modified Schlenk
techniques or in a Vacuum Atmospheres Corp. Dri-Lab. All
hydrocarbon solvents were distilled under nitrogen or vacuum
from dark purple solutions of sodium benzophenone ketyl.
Chlorinated solvents were distilled under vacuum from cal-
cium hydride suspensions. Silica gel (200-400 mesh, 60 Å)
for column chromatography was purchased from Aldrich
Chemical Co. and dried under vacuum at 200 °C. Silica gel
plates (2 mm) used in preparative thin-layer chromatography
contained a fluorescent indicator and were purchased from
Analtech. [RhCl(C2H4)2]2,22 [RhCl(COD)]2,23 and [RhCl(CO)2]2
22
Con clu sion
were prepared according to literature methods. Organic
chemicals were purchased from Aldrich Chemical Co.
1H (400 MHz) and 31P (160 MHz) NMR spectra were
recorded on a Bruker AMX-400 spectrometer. 19F NMR
spectra were recorded on a Varian 500 NMR spectrometer. All
This paper describes the synthesis and interconver-
sions of a series of cyclopentadienyl complexes with
attached phosphine ligands. The studies show that
despite the intramolecular advantage of phosphine
coordination, external ligands can displace the chelating
PPh2 group reversibly. In one case, a binuclear product
is formed by way of the Cp-phosphine ligand bridging
(22) Cramer, R. Inorg. Synth. 1973, 15, 14.
(23) van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28,
90.

Cp-Linked Phosphine Complexes of Rhodium
Organometallics, Vol. 17, No. 18, 1998 3897
chemical shifts are reported in ppm (δ) relative to tetrameth-
ylsilane and referenced to the chemical shifts of residual
solvent resonances (C6D6, δ 7.15; THF, δ 2.58). 19F NMR
spectra were referenced to external C6H5CF3 (δ 0.00 with
downfield chemical shifts taken to be positive). 31P NMR
spectra were referenced to external 30% H3PO4 (δ 0.0).
Elemental analyses were performed by Desert Analytics.
Infrared spectra were recorded by a Mattson Instruments 6020
Galaxy Series FTIR and processed with First:Aquire v1.52
software. Photolysis experiments were performed using a 200
W Hg(Xe) arc lamp (Oriel). A Siemens SMART CCD area
detector diffractometer equipped with an LT-2 low-tempera-
ture unit or an Enraf-Nonius CAD4 was used for X-ray crystal
structure determination.
tube was heated in an oil bath at 65 °C, and the reaction was
monitored by NMR spectroscopy. After about 6 h, the reaction
had gone to completion, giving a mixture composed of 90% of
4 and 10% of 5. 5, which is not stable in the absence of excess
PMe3, has not been isolated. For 5: 1H NMR(C6D6) δ 0.29 (s,
6 H), 1.13 (m AX9A′X9, J H-P + J H-P′ ) 9.2 Hz, 18 H), 1.70 (s,
2 H), 4.72 (bs, 2 H), 5.54 (bs, 2 H), 7.52-7.58 (m, 4 H), other
aromatic resonances obscured by those of 4; 31P NMR (C6D6)
δ -2.30 (d, J Rh-P ) 214 Hz, 2 P), -20.6 (s, 1 P).
Rea ction of 1 w ith CO. A 10.5 mg (0.023 mmol) amount
of (η5:η1-C5H4SiMe2CH2PPh2)Rh(C2H4) (1) was dissolved in 1
mL of C6D6 in an NMR tube equipped with a Teflon seal. The
solution was freeze-pump-thaw degassed 3 times, and 1 atm
of CO was placed over the solution on a vacuum line. After 2
days of heating at 80 °C, 1 had been quantitatively converted
to (η5:η1-C5H4SiMe2CH2PPh2)Rh(CO) (3), as determined by
NMR spectroscopy. The product was isolated by removal of
solvent under vacuum.
Rea ction of 3 w ith P Me3. A 3.3 µL (0.032 mmol) amount
of PMe3 was added to 6.8 mg (0.015 mmol) of (η5:η1-C5H4SiMe2-
CH2PPh2)Rh(CO) (3) dissolved in 1 mL of C6D6. The reaction
was monitored by 1H and 31P NMR spectroscopy over the next
6 days at room temperature. After 40 min, 60% of the starting
material had been converted into (η5-C5H4SiMe2CH2PPh2)Rh-
(PMe3)(CO) (6). For 6: 1H NMR (C6D6) δ 0.26 (s, 6 H), 1.04
(dd, J H-P ) 10 Hz, J H-Rh ) 1.6 Hz, 9 H), 1.63 (s, 2 H), 5.05 (m,
2 H), 5.28 (m, 2 H), 7.50-7.56 (m, 4 H), other aromatic
resonances obscured by those of 3; 31P NMR (C6D6) δ 1.18 (d,
J P-Rh ) 187 Hz, 1 P), -21.0 (s, 1 P). After 6 days, the
composition of the obtained mixture was 3, 25%; 6, 55%; 4,
5%; unidentified product, 15%.
Rea ction of 1 w ith H2. A 14.6 mg (0.032 mmol) amount
of (η5:η1-C5H4SiMe2CH2PPh2)Rh(C2H4) (1) was dissolved in 1
mL of THF-d8 and placed in an NMR tube equipped with a
Teflon seal. The solution was freeze-pump-thaw degassed
3 times, and the solution was placed under 1 atm of H2. The
solution was then irradiated using a 200 W Xe-Hg lamp, and
the changes were followed by NMR spectroscopy. After 5 days,
48% (determined by NMR) of 1 had been converted into the
bridging hydride dimer [(µ-C5H4SiMe2CH2PPh2)Rh(µ-H)]2 (7).
For 7: 1H NMR (THF-d8) δ -13.00 (tt, J H-P ) 15.0 Hz, J H-Rh
) 22.6 Hz, 2 H), -0.13 (s, 12 H), 1.90 (d, J H-P ) 14.4 Hz, 4 H),
4.53 (bs, 4 H), 4.73 (bs, 4 H), 7.29-7.37 (m, 12 H), 7.67-7.74
(m, 8 H); 31P NMR (THF-d8) δ 44.9 (d, J P-Rh ) 187 Hz). The
instability of 7 combined with its low yield prevented obtaining
satisfactory elemental analysis.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (C2H4), 1.
A 1.653 g amount of LiC5H4SiMe2CH2PPh2 (5.05 mmol) was
dissolved in 10 mL of dry THF. To this solution, a solution of
0.979 g of [RhCl(C2H4)2]2 (2.52 mmol) in 40 mL THF was added
slowly. After the mixture was stirred for 1 h, the solvent was
removed under vacuum. The residue was extracted with
hexane (3 × 25 mL), and the solvent was removed from the
combined extracts under vacuum, leaving 1.334 g (2.951 mmol)
of a brown powder (1). Yield: 59%. For 1: 1H NMR (C6D6) δ
-0.03 (s, 6 H), 1.26 (bs, 2 H), 2.17 (d, J H-P ) 13.6 Hz, 2 H),
2.84 (bs, 2 H), 5.18 (m, 2 H), 5.90 (m, 2 H), 6.99-7.08 (m, 6
H), 7.52-7.59 (m, 4 H); 31P NMR (C6D6) δ 49.08 (d, J Rh-P
)
206 Hz). Anal. Calcd (found) for C22H26PRhSi: 58.41 (58.36)
C, 5.79 (5.75) H.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (C8H14), 2.
A 0.154 g amount of [RhCl(C8H14)2]2 (0.215 mmol) was reacted
with 0.141 g of LiC5H4SiMe2CH2PPh2 (0.431 mmol) using the
same procedure as for 1. A 0.204 g amount of a mixture was
obtained containing 80% of 2 and 20% of an unidentified
product. For 2: 1H NMR (THF-d8) δ 0.01 (s, 6 H), 1.00-1.80
(m, 14 H), 2.38 (dd, J H-P ) 13.6 Hz, J H-Rh ) 1.0 Hz, 2 H), 4.99
(bs, 2 H), 5.64 (bs, 2 H), 7.29-7.34 (m, 6 H), 7.55-7.63 (m, 4
H); 31P NMR (THF-d8) δ 51.28 (d, J Rh-P ) 210 Hz). Anal. Calcd
(found) for C28H36SiPRh: 62.92 (62.96) C, 6.74 (7.33) H. For
the minor product, only some of the resonances could be
observed: 1H NMR (THF-d8) δ - 0.096 (s, 3 H), 0.197 (s, 3 H),
2.45 (d, J H-P ) 12.8 Hz, 1 H), 4.32 (bs, 1 H), 5.12 (bs, 1 H),
5.31 (bs, 1 H), 5.75 (bs, 1 H), 7.03-7.23 (m, 6 H), 7.38-7.50
(m, 4 H). 31P NMR (THF-d8) δ 51.28 (d, J Rh-P ) 210 Hz).
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (CO), 3. A
0.276 g amount of [RhCl(CO)2]2 (0.708 mmol) was reacted with
0.494 g of LiC5H4SiMe2CH2PPh2 (1.507 mmol) using the same
procedure as for 1. A 0.457 g amount of 3 (1.011 mmol) was
obtained. Yield: 71%. 1H NMR (C6D6): δ -0.08 (s, 6 H), 2.12
(d, J H-P ) 13.6 Hz, 2 H), 5.62 (bs, 2 H), 5.72 (m, 2 H), 6.97-
7.07 (m, 6 H), 7.72-7.79 (m, 4 H). 31P NMR (THF-d8): δ 45.31
(d, J Rh-P ) 199 Hz). Anal. Calcd (found) for C21H22OPRhSi:
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh I2, 8. Un-
der inert atmosphere, 76 mg of 1 (0.168 mmol) was dissolved
in 25 mL of dry, olefin-free hexanes. A 43 mg amount of I2
(0.169 mmol) in about 2 mL of dry diethyl ether was slowly
added to the Rh solution at room temperature. A brown
precipitate formed immediately, the solution was filtered in
air, and the solid product was washed with ether and hexanes.
Yield: 133 mg, 79%. For 8: 1H NMR (CDCl3) δ 0.10 (s, 6 H),
2.98 (d, J ) 15.6 Hz, 2 H), 5.67 (s, 2 H), 6.78 (m, 2 H), 7.33-
7.40 (m, 6 H), 7.75-7.82 (m, 4 H); 31P NMR (CDCl3) δ 23.1 (d,
J ) 137 Hz). Anal. Calcd (found) for C20H22I2PRhSi: 35.42
(35.14) C, 3.27 (3.29) H.
55.76 (55.38) C, 4.90 (4.32) H. IR (THF): 1937 cm-1
.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (P Me3), 4.
Under inert atmosphere, 34.7 mg of 1 (0.0768 mmol) was
dissolved in 1 mL of C6D6. The solution was placed in an NMR
tube equipped with a Teflon seal, and 8 µL of PMe3 (0.0773
mmol) was added. The NMR tube was heated at 65 °C, and
1
the reaction was monitored by H and 31P NMR spectroscopy.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (C6H5)I, 9.
A 51 mg amount of (η5:η1-C5H4SiMe2CH2PPh2)RhI2 (8) (0.075
mmol) was dissolved in 20 mL of dry THF and cooled to -40
°C. A 0.04 mL amount of a solution of C6H5MgBr (2 M in THF,
0.08 mmol) was added with stirring over 0.5 h, and the solution
was allowed to warm to room temperature. The brown
solution turned red as the solution warmed. The excess
Grignard reagent was quenched with 0.1 mL of a saturated
solution of NH4Cl, the solution filtered in air, and the solvent
removed. The remaining solid was passed through a short
column of Al2O3 with CH2Cl2 as the eluent. A 39 mg amount
of (η5:η1-C5H4SiMe2CH2PPh2)Rh(C6H5)I, 9, was obtained after
removal of solvent (62% yield). For 9: 1H NMR (CDCl3) δ
Clean and quantitative conversion to 4 was observed after
about 1 day. The product was isolated by removal of the
solvent under vacuum. For 4: 1H NMR (C6D6) δ -0.01 (s, 6
H), 0.87 (dd, J H-P ) 8.8 Hz, J H-Rh ) 1 Hz, 9 H), 2.38 (d, J H-P
) 12.8 Hz, 2 H), 5.47 (bs, 2 H), 6.10 (bs, 2 H), 7.00-7.19 (m,
6 H), 7.84-7.94 (m, 4 H); 31P NMR (C6D6) δ 50.1 (dd, J P-Rh
)
225, J P-P ) 57 Hz), -2.84 (dd, J P-Rh ) 211 Hz, J P-P ) 57 Hz).
Anal. Calcd (found) for C23H31P2RhSi: 55.20 (54.89) C, 6.24
(6.00) H.
P r ep a r a tion of (η5-C5H4SiMe2CH2P P h 2)Rh (P Me3)2, 5.
Under inert atmosphere, 37 mg of 1 (0.0819 mmol) was
dissolved in 1 mL of C6D6 and placed in a resealable NMR
tube together with 42 µL of PMe3 (0.406 mmol). The NMR

3898 Organometallics, Vol. 17, No. 18, 1998
Lefort et al.
-0.04 (s, 3 H), 0.25 (s, 3 H), 2.81 (d, J ) 14.8 Hz, 2 H), 5.26
(bs, 1 H), 5.60 (bs, 1 H), 5.63 (bs, 1 H), 6.34 (bs, 1 H), 6.63-
6.75 (m, 3 H), 7.07-7.22 (m, 3 H), 7.30-7.45 (m, 5 H), 7.55-
7.60 (m, 2 H), 7.73-7.82 (m, 2 H); 31P NMR (CDCl3) δ 34.14
(d, J ) 154 Hz). Anal. Calcd (found) for C26H27IPRhSi: 49.70
(49.52) C, 4.33 (4.43) H.
column chromatography on silica with CH2Cl2 as the eluent
followed by recrystallization from CHCl3 layered with hexanes.
For 14: 1H NMR (THF-d8) -0.047 (s, 3 H), 0.421 (s, 3 H), 2.86
(ddd, J ) 17.6, 13.6, 2.4 Hz, 1 H), 3.06 (dd, J ) 13.6, 13.6 Hz,
1 H), 4.94 (m, 1 H), 5.76 (m, 1 H), 5.97 (m, 1 H), 6.35 (m, 1 H),
7.10-7.38 (m, 6 H), 7.67-7.74 (m, 2 H), 8.03-8.10 (m, 2 H);
31P NMR (THF-d8) δ 34.3 (dt, J P-Rh ) 154 Hz, J P-F ) 9.7 Hz);
19F NMR (C6D6) δ 93.5 (m, 2 Fortho), 36.9 (m, 1 Fpara), 33.6 (bs,
2 Fmeta). Anal. Calcd (found) for C26H22ClF5PRhSi: 49.80
(49.59) C, 3.51 (3.21) H.
P r epar ation of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (C6F6), (15).
In a resealable NMR tube, 41 mg of (η5:η1-C5H4SiMe2CH2-
PPh2)Rh(H)2 (10) (0.0962 mmol) was dissolved in neat C6F6.
The solution was irradiated for 7 h using a 200 W Hg/Xe lamp,
and the solvent was removed under vacuum, leaving a brown
powder. The product was recrystallized from a mixture of
THF/hexane (1:99) at -40 °C. The yield of formation of the
hexafluorobenzene complex (η5:η1-C5H4SiMe2CH2PPh2)Rh(η2-
C6F6) (15) was determined by NMR spectroscopy using hex-
amethylbenzene as an internal reference (93%). For 15: 1H
NMR (THF-d8) δ 0.05 (s, 6 H), 2.57 (d, J ) 13.6 Hz, 2 H), 4.64
(bs, 2 H), 5.88 (bs, 2 H), 7.31-7.39 (m, 6 H), 7.70-7.78 (m, 4
H); 31P NMR (THF-d8) δ 45.4 (dt, J P-Rh ) 200 Hz, J P-F ) 54.4
Hz); 19F NMR (THF-d8) δ 53.3 (m, 2 F), 40.8 (m, 2 F), 26.1 (m,
2 F). Anal. Calcd (found) for C26H22F6PRhSi: 51.15 (51.16)
C, 3.61 (3.61) H.
X-r a y St r u ct u r a l Det er m in a t ion of (η5:η1-C5H 4-
SiMe2CH2P P h 2)Rh (C2H4), 1. Crystals of (η5:η1-C5H4SiMe2-
CH2PPh2)Rh(C2H4) were grown by slow evaporation from
hexane. An orange prism of approximate dimensions 0.37 ×
0.52 × 0.60 mm was mounted on a glass fiber using epoxy and
placed in a cold nitrogen stream at -40 °C on the diffracto-
meter. Lattice constants were obtained from 25 centered
reflections with values of ø between 5° and 70° on an Enraf-
Nonius CAD4 diffractometer. Cell reduction revealed a tri-
clinic crystal system. Data were collected at -40 °C in accord
with the parameters found in Table 1. The intensities of three
representative reflections, which were measured after every
60 min of X-ray exposure time, remained constant throughout
the data collection, indicating crystal and electronic stability.
The Molecular Structure Corp. TEXSAN analysis software
package was used for data reduction, solution, and refinement.
The space group was assigned as P1h on the basis of intensity
statistics. A Patterson map solution of the structure was used
to locate the rhodium atom. The structure was expanded with
the DIRDIF program to reveal all non-hydrogen atoms. An
absorption correction was applied using the program DIFABS
following isotropic refinement. Anisotropic refinement of all
non-hydrogen atoms allowed for the use of a difference Fourier
map for the location of the hydrogen atoms, whose coordinates
and isotropic thermal parameters were subsequently refined.
Full-matrix least-squares refinement of all atoms (on F) was
executed until convergence was achieved, with R1 ) 0.0249
and Rw ) 0.0331.24 Fractional coordinates and thermal
parameters are given in the Supporting Information.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh H2, 10. A
107 mg amount of (η5:η1-C5H4SiMe2CH2PPh2)RhI2 (8) (0.158
mmol) was dissolved in dry THF under inert atmosphere. A
0.2 mL amount of a solution of Red-Al in toluene (65 wt %,
0.621 mmol) was added. The mixture was stirred for 10 min,
and the solvent was removed under vacuum. The remaining
solids were dissolved in 1 mL of a THF/hexane mixture (1:5)
and passed through a SiO2 column using the same solvent
mixture as the eluent. Removal of the solvent under vacuum
gave 51 mg (76% yield) of (η5:η1-C5H4SiMe2CH2PPh2)RhH2 as
a slightly impure oil. For 10: 1H NMR (THF-d8) δ -13.38 (dd,
J H-P ) 26.2 Hz, J H-Rh ) 30.8 Hz, 2 H), 0.09 (s, 6 H), 2.66 (d,
J H-P ) 14.4 Hz, 2 H), 5.40 (m, 2 H), 5.53 (m, 2 H), 7.26-7.31
(m, 6 H), 7.71-7.78 (m, 4 H); 31P NMR (THF) δ 55.3 (d, J P-Rh
) 172 Hz).
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (CH3)I, 11.
In a round-bottom flask, 62 mg of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(C2H4) (1) (0.137 mmol) was dissolved in 10 mL THF.
A
50 µL sample of CH3I (0.803 mmol) was added, and the
mixture was stirred for 7 h under reflux. The solvent was
removed, and the remaining solid was passed through an Al2O3
column using CH2Cl2 as the eluent. A 60 mg amount of (η5:
η1-C5H4SiMe2CH2PPh2)Rh(CH3)I (11) was obtained following
removal of the solvent (yield: 77%). For 11: 1H NMR (THF-
d8) δ -0.21 (s, 3 H), 0.34 (s, 3 H), 1.01 (dd, J ) 6.8, 2.4 Hz, 3
H), 2.63 (t, J ) 13.6 Hz, 1 H), 2.73 (ddd, J ) 20.4, 14.8, 2 Hz,
1 H), 5.14 (bs, 1 H), 5.45 (bs, 1 H), 5.53 (bs, 1 H), 6.18 (bs, 1
H), 7.26-7.43 (m, 6 H), 7.57-7.63 (m, 2 H), 8.05-8.12 (m, 2
H); 31P NMR (THF-d8) δ 40.51 (d, J P-Rh ) 160 Hz). Anal. Calcd
(found) for C21H25IPRhSi: 44.52 (44.50) C, 4.42 (4.60) H.
P r ep a r a tion of [(η5:η1-C5H4SiMe2CH2P P h 2)Rh (C6H5)-
(THF )](P F 6), 12, a n d Rea ction w ith Red -Al. In a reseal-
able NMR tube, 8.6 mg of (η5:η1-C5H4SiMe2CH2PPh2)Rh(C6H5)-
(I) (7) (0.0137 mmol) was dissolved in dry THF-d8. A 3.5 mg
amount of AgPF6 (0.0138 mmol) was added, and the solution
was filtered. For 12: 1H NMR (THF-d8) δ 0.06 (s, 3 H), 0.33
(s, 3 H), 2.75 (t, J ) 16 Hz, 1 H), 3.19 (t, J ) 14.8 Hz, 1 H),
4.88 (bs, 1 H), 5.85 (bs, 1 H), 6.26 (bs, 1 H), 6.49 (bs, 1 H),
6.73-7.62 (m, 15 H); 31P NMR (THF-d8) δ 37.79 (d, J P-Rh
)
162 Hz). The solution was frozen in liquid N2, and 5 µL of
Red-Al (NaH2Al(OCH2CH2OMe)2) was added. The mixture
was warmed to -70 °C and rapidly shaken before being
introduced into the NMR probe, which had previously been
cooled to -60 °C. NMR spectra were recorded as the temper-
ature of the probe was gradually increased to ambient tem-
perature, showing the changes described in the text.
P r ep a r a tion of (η5:η1-C5H4SiMe2CH2P P h 2)Rh (H)(C6F 5)
(13) a n d (η5:η1-C5H4SiMe2CH2P P h 2)Rh (Cl)(C6F 5) (14). In
a resealable NMR tube, 75 mg of (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(H)2 (10) (0.176 mmol) was dissolved in neat C6F5H. The
solution was irradiated with a 200 W Hg/Xe lamp for 7 h. The
solvent was removed under vacuum, leaving a brown powder.
The yield of the pentafluorophenyl hydride complex (η5:η1-
C5H4SiMe2CH2PPh2)Rh(H)(C6F5) (13) was determined by in-
tegration of the NMR resonances relative to an internal
reference (hexamethylbenzene). Yield: 48%. For 13: 1H NMR
(THF) δ -11.04 (dd, J H-P ) 20 Hz, J H-Rh ) 30.8 Hz, 1 H),
-0.181 (s, 3 H), 0.468 (s, 3 H), 2.75 (dd, J ) 13.6, 8.4 Hz, 1 H),
3.08 (dd, J ) 13.6, 13.6 Hz, 1 H), 5.25 (m, 1 H), 5.64 (m, 1 H),
5.75 (m, 1 H), 5.88 (m, 1 H), 6.96-7.06 (m, 4 H), 7.35-7.48
(m, 4 H), 7.91-8.04 (m, 2 H); 31P NMR (THF) δ 54.3 (d, J P-Rh
) 154 Hz). Addition of 50 µL of CCl4 (0.517 mmol) to the
solution of 13 in THF led quantitatively to the immediate
formation of the chloro derivative (η5:η1-C5H4SiMe2CH2PPh2)-
Rh(Cl)(C6F5) (14). Purification of 14 was accomplished by
X-r a y Str u ctu r a l Deter m in a tion s of 2, 3, 7, 8, 9, 11, 14,
a n d 15. Single crystals of each compound were mounted
under Paratone-8277 on glass fibers and immediately placed
in a cold nitrogen stream at -50 to -90 °C on the X-ray
diffractometer. The X-ray intensity data were collected on a
standard Siemens SMART CCD area detector system equipped
with a normal focus molybdenum-target X-ray tube operated
at 1.5 kW (50 kV, 30 mA) for 8 and 2.0 kW (50 kV, 40 mA) for
the remaining crystals. A total of 1321 frames of data (1.3
(24) Using the TEXSAN package, R1 ) (∑||Fo| - |Fc||)/∑|Fo|, Rw
)
2
[∑w(|Fo| - |Fc|)2]1/2/∑w|Fo| , where w ) [σ2(Fo) + (FFo2)2]1/2 for a non-
Poisson contribution weighting scheme. The quantity minimized was
Σw(|Fo| - |Fc|)2. Source of scattering factors fo, f ′, and f ′′: Cromer, D.
T.; Waber, J . T. International Tables for X-ray Crystallography; The
Kynoch Press: Birmingham, England, 1974; Vol. IV, Tables 2.2B and
2.3.1.

Cp-Linked Phosphine Complexes of Rhodium
Organometallics, Vol. 17, No. 18, 1998 3899
hemispheres) were collected using a narrow frame method
with scan widths of 0.3° in ω and exposure times of 30 s/frame
using a detector-to-crystal distance of 5.09 cm (maximum 2θ
angle of 56.54°) for all of the crystals except 3 (5 s/frame), 8
(10 s/frame), and 15 (60 s/frame). The total data collection
time was approximately 6 h for 10 s/frame exposures and 13
h for 30 s/frame exposures. Frames were integrated with the
Siemens SAINT program to 0.75 Å for all of the data sets. The
unit cell parameters for all of the crystals were based upon
the least-squares refinement of three-dimensional centroids
of >5000 reflections.25 Data were corrected for absorption
using the program SADABS.26 Space group assignments were
made on the basis of systematic absences and intensity
statistics by using the XPREP program (Siemens, SHELXTL
5.04). The structures were solved by using direct methods and
refined by full-matrix least-squares on F2.27 For all of the
structures (except as noted below), the non-hydrogen atoms
were refined with anisotropic thermal parameters and hydro-
gens were included in idealized positions, giving data:param-
eter ratios greater than 10:1. The Rh-bound hydride in 7 was
located from the difference Fourier map, and the positional
and isotropic thermal parameters were refined. There was
nothing unusual about the solution or refinement of any of
the structures, with the exceptions of 2, 7, 14, and 15.
Compound 2 crystallized with two independent molecules
within the asymmetric unit. Compound 7 was found to lie on
a center of symmetry, so that only one-half of the dimer was
unique. Complex 14 crystallized along with one molecule of
chloroform, and complex 15 crystallized along with one
molecule of THF. Further experimental details of the X-ray
diffraction studies are provided in Table 1. Positional param-
eters for all atoms, anisotropic thermal parameters, all bond
lengths and angles, as well as fixed hydrogen positional
parameters are given in the Supporting Information for all of
the structures.
Ack n ow led gm en t is made to the U.S. Department
of Energy, Grant No. FG02-86ER13569, for their sup-
port of this work.
(25) It has been noted that the integration program SAINT produces
cell constant errors that are unreasonably small, since systematic error
is not included. More reasonable errors might be estimated at 10 times
the listed value.
Su p p or tin g In for m a tion Ava ila ble: Tables of positional
parameters for all atoms, anisotropic thermal parameters, all
bond lengths and angles, and fixed hydrogen positional
parameters for 1-3, 7-9, 11, 14, and 15 (58 pages). Ordering
information is given on any masthead page.
(26) The SADABS program is based on the method of Blessing,
see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33-38.
(27) Using the SHELX95 package, R1 ) (∑||Fo| - |Fc||)/∑|Fo|, wR2
)
[∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]}1/2, where w ) 1/[σ2(Fo2) + (aP)2 + bP] and
P ) [f 0(Maximum of 0 or Fo2) + (1 - f)Fc2].
OM980263Q