Activation of C-F and C-H bonds by polyalkylcyclopentadienylrhodium complexes: Crystal structure of [(η5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+·BF4-

Article abstract of DOI:10.1016/S0022-328X(97)00704-3

The reaction between [(η⁵-C₅Me₄Et)RhCl(μ-Cl)]₂ and the diphosphine, (C₆F₅)₂PCH₂CH₂P(C₆F₅)₂ (dfppe), proceeded via the activation of two C-F and two C-H bonds and the formation of two C-C bonds to give a mixture of isomers of a salt with formulation '[(η⁵-C₅Me₄Et)RhCl{(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂}-2HF]⁺·Cl^-' (3a). Treatment of [(η⁵-C₅Me₄Et)RhCl(μ-Cl)]₂ with NH₄BF₄ followed by dfppe yielded [(η⁵-C₅Me₄Et)RhCl{(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂}]⁺·BF₄^- (4b) which, on thermolysis in ethanol underwent C-F and C-H bond activation to yield the tetrafluoroborate salt of 3a (3b). The structure of 4b was determined by a single crystal X-ray diffraction study. The salt 4b crystallizes in the triclinic space group P1 with a=15.743 (4), b=16.429 (2), c=16.970 (3) A, α=79.41 (2), β=84.34 (2), γ=82.01 (2)° and Z=4. Refinement gave final R₁ and wR²[I>2σ(I)] values of 0.0955 and 0.2200 respectively for 7254 observed reflections. When the reaction between [(η⁵-C₅Me₄Et)RhCl(μ-Cl)]₂ and dfppe was carried out in ethanol, a mixture of 3b, 4b and the singly C-F bond activated complex '[(η⁵-C₅Me₄Et)RhCl{(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂}-HF]⁺·BF₄^-' (5b) were obtained after addition of NH₄BF₄. The monophosphines P(C₆F₅)₃ and PPh(C₆F₅)₂ failed to react with [(η⁵-C₅Me₅)RhCl(μ-Cl)]₂ and the reaction between [(η⁵-C₅Me₅)RhCl(μ-Cl)]₂ and PPh₂(C₆F₅) did not lead to C-F bond activation but yielded (η⁵-C₅Me₅)RhCl₂{PPh₂( C₆F₅)} (6).

Full text of DOI:10.1016/S0022-328X(97)00704-3

Journal of Organometallic Chemistry 555 (1998) 67–79
Activation of C–F and C–H bonds by
polyalkylcyclopentadienylrhodium complexes: crystal structure of
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4−
Malcolm J. Atherton a, John Fawcett b, J.H. Holloway b, Eric G. Hope b, Sine´ad M. Martin b,
David R. Russell b, Graham C. Saunders b,*
a F2 Chemicals, Springfields, Salwick, Preston PR4 0XJ, UK
b Department of Chemistry, Uni6ersity of Leicester, Leicester LE1 7RH, UK
Received 16 September 1997
Abstract
The reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2 and the diphosphine, (C6F5)2PCH2CH2P(C6F5)2 (dfppe), proceeded via the
activation of two C–F and two C–H bonds and the formation of two C–C bonds to give a mixture of isomers of a salt with
formulation ‘[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}-2HF]+ ·Cl−’ (3a). Treatment of [(p5-C5Me4Et)RhCl(v-Cl)]2 with
NH4BF4 followed by dfppe yielded [(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4− (4b) which, on thermolysis in
ethanol underwent C–F and C–H bond activation to yield the tetrafluoroborate salt of 3a (3b). The structure of 4b was
(
determined by a single crystal X-ray diffraction study. The salt 4b crystallizes in the triclinic space group P1 with a=15.743 (4),
b=16.429 (2), c=16.970 (3) A, h=79.41 (2), i=84.34 (2), k=82.01 (2)° and Z=4. Refinement gave final R1 and
˚
wR2[I\2|(I)] values of 0.0955 and 0.2200 respectively for 7254 observed reflections. When the reaction between [(p5-
C5Me4Et)RhCl(v-Cl)]2 and dfppe was carried out in ethanol, a mixture of 3b, 4b and the singly C–F bond activated complex
‘[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}–HF]+ ·BF4−’ (5b) were obtained after addition of NH4BF4. The monophosphi-
nes P(C6F5)3 and PPh(C6F5)2 failed to react with [(p5-C5Me5)RhCl(v-Cl)]2 and the reaction between [(p5-C5Me5)RhCl(v-Cl)]2 and
PPh2(C6F5) did not lead to C–F bond activation but yielded (p5-C5Me5)RhCl2{PPh2(C6F5)} (6). © 1998 Elsevier Science S.A. All
rights reserved.
Keywords: C–F bond activation; C–H bond activation; Rhodium; Crystal Structure; 1,2-Bis{bis(pentafluorophenyl)phos-
phino}ethane
metal complexes [1], but reactions proceeding in high
yield under mild conditions are rare [2–9]. Recently,
1. Introduction
we reported that the fluorinated diphosphine,
(C6F5)2PCH2CH2P(C6F5)2 (dfppe), reacts with [(p5-
The activation of C–F bonds, which are amongst the
strongest known, has recently received much attention
because of the important applications of functionalized
fluorocarbons and the destruction of ozone depleting
C5Me5)RhCl(v-Cl)]2 under mild conditions to afford, in
quantitative yield, a cationic complex (1)1, in which two
aryl C–F bonds and two pentamethylcyclopentadienyl
chlorofluorocarbons [1]. There are a small number of
C–H bonds have been cleaved and two C–C bonds
reports of the cleavage of C–F bonds by transition
have been formed (Eq. (1)) [10,11].
* Corresponding author. Present address: School of Chemistry, The
Queen’s University of Belfast, David Keir Building, Belfast, BT9
5AG, UK. E-mail: g.saunders@qub.ac.uk
1 For salts the numbers refer to the cation and the letters indicate
the anion: a=Cl− and b=BF4−
.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00704-3

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M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
1/2[(p5-C5Me5)RhCl(v-Cl)]2
(1) and Eq. (2), or whether these are two examples of a
more general type of reaction which might prove of
great synthetic potential. The [CpMX] system offers
scope for investigating and developing this reactivity.
The cyclopentadienyl ligand, the metal, the halide and
the diphosphine ligand can all be varied to aid in
determining the scope of the reaction and elucidating
the mechanism. Here, we describe the results obtained
on variation of the C–H and C–F bond-containing
ligands.
The pentamethylcyclopentadienyl ligand possesses
only one type of C–H bond which may be activated.
The p5-C5Me4Et ligand contains three types of C–H
bond; 12 cyclopentadienyl methyl C–H bonds, two
methylene C–H bonds and three alkyl methyl C–H
bonds. We decided, therefore, to examine whether there
is any selectivity in the C–H bond activation by study-
ing the reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2
and dfppe. We have also attempted to activate the C–F
+(C6F5)2PCH2CH2P(C6F5)2
“[{p5-C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}RhCl]+ ·X−
+2HF(X− =Cl−1a, X− =BF4−1b)
(1)
The reaction exhibits complete regiospecificity: only
one ortho C–F bond of each P(C6F5)2 moiety and
C–H bonds of methyl groups exclusively in a 1,3
disposition are activated. Presumably, this is due solely
to geometric constraints. It is significant that there
are no anomalous bond distances or angles in the
structure of salt 1b [10]. The arrangement of ligands
is such that, when viewed along the C5(centroid)–Rh
axis, the methyl group in the 2 position lies between the
two phosphorus atoms and the chloride lies between
the 4 and 5 methyl groups (Fig. 1). That geometric
constraints determine the geometry of the cation is
corroborated by the hydroalkylation of the bisphos-
phine complex [(p5-C5Me5)RhCl(PPh2CH=CH2)2]+
·Cl−, which yields [{p5-C5Me3(CH2CH2CH2PPh2)2-
1,3}RhCl]+ ·Cl−, which possesses a similar arrange-
ment of ligands to that in 1, as well as the 1,2 isomer
[12,13]. The geometry of the dfppe ligand precludes the
formation of the 1,2 isomer of 1. Although intermedi-
ates were not observed when reaction (1) was carried
out in benzene, when it was performed in ethanol for a
shorter time [(p5-C5Me5)RhCl{(C6F5)2PCH2CH2P(C6-
F5)2}]+ (2) and the singly C–F bond-activated cation
[{p5-C5Me4CH2C6F4P(C6F5)CH2CH2P(C6F5)2}RhCl]+,
as well as the final product (1), were identified in the
reaction mixture by mass spectrometry and multinu-
clear NMR spectroscopies. The complex [(p5-
C5Me5)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4− (2b)
was prepared independently and C–F bond activation
was induced by thermolysis in refluxing ethanol to give
1b (Eq. (2)) [11].
bonds
of
monophosphines
containing
pen-
tafluorophenyl groups by reaction with [(p5-
C5Me5)RhCl(v-Cl)]2.
2. Results and discussion
2.1. Reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2 and
dfppe in benzene
Treatment of dfppe with [(p5-C5Me4Et)RhCl(v-Cl)]2
in refluxing benzene for 10.5 h yielded a yellow solution
from which was isolated a yellow solid, 3a. The positive
ion FAB mass spectrum shows ions, with associated
envelopes at 1005 and 969, consistent with loss of two
molecules
of
HF
from
the
cation
[(p5-
C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ and [M–
Cl]+. The 31P{1H}-NMR spectrum, recorded in CDCl3,
shows a number of resonances between 72 and 80 ppm
which can be assigned as doublets of multiplets with
[(p5-C5Me5)RhCl(C6F5)2PCH2CH2P(C6F5)2]+ ·BF4−
“[{p5-C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}RhCl]+
1
rhodium–phosphorus couplings, JRh–P, of magnitude
ca. 140 Hz (Fig. 2). These data are comparable with the
31P{1H}-NMR data for the cation 1 [10]. Thus, the
mass spectral and 31P-NMR data indicate that C–F
and C–H bond activation and C–C bond formation
has occurred and a mixture of cations similar to 1 have
been formed. Further evidence for this reaction is pro-
vided by the 19F-NMR spectrum of 3a which shows
two resonances at d −153.73 and −153.78 assigned to
the tetrafluoroborate anion, and a singlet at l −139.77
with 28Si satellites assigned to the hexafluorosilicate
dianion. Both are formed by the reaction of evolved
HF with the borosilicate glass reaction vessel. Identical
resonances have been observed in the products of reac-
tion (1). Furthermore, the negative ion FAB mass
spectrum of the crude product shows ions at 86 and 87,
assigned to tetrafluoroborate.
·BF4− +2HF
(2)
We are interested in determining the mechanisms of
these reactions and whether they are restricted to Eq.
Fig. 1. Diagrammatic representation of the cation [{p5-
C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}RhCl]+ (1) viewed along the
C5(centroid)–Rh axis.

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
69
at l 2.05 dominates the lower frequency region and
accounts for over half of the integration of the four
doublets between 1.8 and 2.2 ppm. The assignments
1
were made with the aid of the H{31P}-NMR spectrum
and by analogy with the spectrum of 1a. It is noted that
the resonances of the 4- and 5-methyl group hydrogen
atoms are doublets, with coupling to only one phospho-
rus atom. These are consistent with the spectrum of
1a which exhibits a doublet at l 2.05 with JP–H 7.3
Hz [10]. These data are, however, different from the
1H spectrum of [{p5-C5Me3(CH2CH2CH2PPh2)2-
1,3}RhCl]+ ·PF6−, which exhibits a triplet at l 1.86
with a coupling of 6.5 Hz assigned to both the 4- and
5-methyl groups [13]. It is also noted that the hydrogen
resonances of the methyl groups in the 2-positions of 1a
and 3a show little or no coupling to phosphorus.
The 19F-NMR spectrum, recorded at 298 K and at a
spectrometer frequency of 282.41 MHz, exhibits several
resonances, consistent with the presence of a mixture of
isomers, as well as those assigned to tetrafluoroborate
and hexafluorosilicate anions. However, all the isomers
possess similar fluorine atom resonances in six regions,
all of which can be related to the resonances of 1a; the
ortho, meta and para fluorines of the equivalent C6F5
rings and four non-equivalent fluorines of the equiva-
lent C6F4 rings. There are six multiplets in the region
−115 to −121 ppm, which are assigned to one of the
fluorine atoms of each C6F4 group. There are broad
resonances in the range −126 to −133 ppm, assigned
to the ortho fluorine atoms of the C6F5 rings. The broad
nature of these resonances is indicative of hindered
rotation about the P–C6F5 bonds, consistent with that
found for 1a. From −134 to −137 ppm there are four
resonances which are assigned to one fluorine atom of
each C6F4 ring. There are seven resonances between
−142 and −146 ppm, which are assigned either to two
fluorine atoms of each C6F4 group or to one C6F4
fluorine atom and the para fluorine atoms of the C6F5
groups. There are four resonances between −150 and
−154 ppm, excluding those assigned to tetrafluorobo-
rate, which are assigned to either the para fluorine
atoms of the C6F5 groups or one fluorine atom of the
C6F4 groups and between −157 and −161 ppm there
are three resonances which are assigned to the meta
fluorine atoms of the C6F5 groups. At higher tempera-
ture the spectrum shows little change, except that the
ortho-C6F5 fluorine resonances are considerably
sharper. At 218 K there are at least ten resonances
assigned to the ortho-C6F5 fluorine atoms. Integration
at higher or lower temperature is consistent with the
assignments made by comparison of the spectrum with
that of 1a.
Fig.
2.
31P{1H}
NMR
spectrum
of
‘[(p5-
C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}-2HF]+ ·Cl−’ (3a).
The H- and 19F-NMR spectra of 3a are consistent
with a mixture of isomers of formulation ‘[(p5-
C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}-2HF]+’.
1
1
The H-NMR spectrum exhibits several resonances in
the region 3–5 ppm, which are assigned to PCH2 and
C6F4CH2 methylene hydrogen atoms by analogy with
the spectrum of 1a, and the region 0.9–2.6 ppm, which
are assigned to pentaalkylcyclopentadienyl hydrogen
atoms. There are a number of distinctive resonances
which are presented in Table 1. In particular, a doublet
Table 1
Selected 1H NMR data for ‘[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2-
P(C6F5)2}-2HF]+ ·X−’ (X−=Cl− 3a, X−=BF−4 3b)
3aa
3bb
Assignment
1.03 (t, 3JH–H=7.7
1.22 (t, 3JH–H=7.4 Hz) CH2CH3
1.38 (t, 3JH–H=7.6 Hz) CH2CH3
Hz)
1.19 (t, 3JH–H=7.45
Hz)
1.66 (d, 3JH–H=7.3 Hz) CHCH3
1.79 (d, 3JH–H=7.4 Hz) CHCH3
1.83 (t, 4JP–H=2.3 Hz) 2-CH3
1.87 (d, 4JP–H=8.7 Hz) 4- or 5-CH3
4
1.85 (d, JP–H:7.5
Hz)
2.01 (d, JP–H:9 Hz) 2.02 (d, 4JP–H=7.5 Hz) 4- or 5-CH3
4
2.05 (d, JP–H:7 Hz) 2.07 (d, 4JP–H=7.3 Hz) 4- or 5-CH3
4
2.13 (d, JP–H:5 Hz) 2.14 (d, 4JP–H=7.8 Hz) 4- or 5-CH3
4
2.28 (m)
2.36 (m)
2.32 (m)
2.46 (m)
CH2CH3
CH2CH3
The salt 3a could not be obtained analytically pure,
due to contamination by tetrafluoroborate and hex-
afluorosilicate anions. However, the tetrafluoroborate
salt, 3b, prepared by anion metathesis with NH4BF4 in
a Recorded in CDCl3 at 300.14 MHz.
b Recorded in CDCl3 at 400.13 MHz.

70
M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
Fig. 3. Diagrammatic representation of the possible isomers of the cation ‘[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}-2HF]+’ (3) viewed
along the C5(centroid)–Rh axes. Isomers II–V exist as enantiomeric pairs.
methanol, was obtained pure, and characterized by
elemental analysis. This confirmed the formulation sug-
gested by the spectroscopic data for 3a. The positive
ion FAB mass spectrum is identical to that of 3a. The
31P{1H}-NMR spectrum of 3b is similar to that of 3a,
exhibiting at least five doublets of multiplets between 70
dependent on the position of the C–H bonds are
activated (Fig. 3). Isomers I and II are those expected if
activation of only the cyclopentadienyl methyl C–H
bonds is occurring, isomer III is that expected if one of
the C–H bonds of the alkyl methyl group is activated
and isomers IV and V are those expected if one of the
methylene C–H bonds is activated. Only isomer I
possesses the same symmetry as cation 1, which gives
rise to chemical equivalence of the two sides of the
cation, and, thus, only one phosphorus resonance, four
C6F4 fluorine atom resonances and one resonance for
both the 4- and 5-methyl hydrogen atoms in the respec-
tive NMR spectra. The phosphorus atoms of isomer I
are chiral, but, as for 1, only the meso stereoisomer can
be formed. Isomers II–V do not possess such symmetry
and all the atoms are unique. Thus, two phosphorus
resonances and eight C6F4 fluorine resonances are ex-
pected for each isomer in the 31P- and 19F-NMR spec-
tra respectively. Isomers II and III contain three chiral
centres, namely, both phosphorus atoms and the
rhodium atom. However, because of the geometry of
the cation, only one pair of enantiomers can exist for
each. Isomers IV and V contain four chiral centres:
1
and 78 ppm with absolute values of JRh–P of 140–150
Hz. The 19F-NMR spectrum of 3b is also similar to that
of 3a, but with more intense resonances assigned to the
tetrafluoroborate anion, no hexafluorosilicate resonance
and more resonances in certain regions. In particular,
there are five resonances between −150 to −154 ppm.
1
The H-NMR spectrum of 3b, however, shows signifi-
cant differences to that of 3a, although some features
are common to both. The prominent features are listed
in Table 1. In addition, there are other unassigned
resonances in the range 0.9–2.0 ppm and many reso-
nances between 2.8 and 5.0 ppm.
It is reasonable to assume that activation of the C–H
bonds occurs at alkyl groups in a 1,3-disposition and
that structures similar to those of cation 1 (Fig. 1) and
[{p5-C5Me3(CH2CH2CH2PPh2)2-1,3}RhCl]+ [12,13] are
formed. Thus, there are five possible isomers which are

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
71
both phosphorus atoms, the rhodium atom and the
C5CHMeC6F4 carbon atom. Isomer V is that formed
by epimerization of IV at this carbon. One pair of
enantiomers exists for both IV and V. The presence of
two sets of resonances assigned to the methylene and
methyl hydrogen atoms of the ethyl group indicates
that both I and II are formed, whilst the presence of
two resonances assigned to the methyl hydrogen atoms
of CHCH3 groups indicates that IV and V are also
formed. The resonances of the C5CHMeC6F4 hydrogen
atoms of these isomers presumably occur in the region
where the resonances for PCH2 and C5CH2C6F4 occur
and cannot be distinguished. The presence of isomers I,
II, IV and V in 3a and 3b should give rise to seven
doublets of multiplets in the 31P{1H}-NMR spectra and
seven resonances in the region −115 to −121 ppm in
the 19F-NMR spectra. Presumably, resonances are coin-
cidental in the observed spectra. As well as the 1H-
NMR resonances already discussed, there should be six
doublets for isomers I, II, IV and V assigned to the 4-
and 5-methyl hydrogen atoms and three singlets, or
triplets with small coupling, assigned to the 2-methyl
Hz, and similar resonances in the range 75–80 ppm.
These can be assigned to a mixture of isomers of a
cation of formulation ‘[(p5-C5Me4Et)RhCl{(C6F5)2-
PCH2CH2P(C6F5)2}-HF]+’ (5) by comparison with
the 31P{1H}-NMR data of [{p5-C5Me4CH2C6F4-
P(C6F5)CH2CH2P(C6F5)2}RhCl]+ ·BF4−
[11].
The
lower frequency resonances are assigned to the P(C6F5)2
phosphorus atoms and those at higher frequency to the
CH2C6F4P(C6F5) phosphorus atoms. There are also less
intense resonances at ca. l 75 which are assigned to the
product cation 3, and two doublets of multiplets at l
1
19.0 and 49.2 with values of JRh–P of 62 and 119 Hz
respectively, which are due to unidentified compounds.
After anion metathesis with NH4BF4 a yellow solid was
obtained, the FAB mass spectrum of which corrobo-
rates the 31P-NMR data. There are peaks with associ-
ated envelopes at 1045 and 1010, which are indicative
of the cation 4 and [4–Cl] respectively, and at 1025 and
989, which correspond to the cation 5 and [5–Cl].
There are also less intense peaks centred at 1005 and
969 which are characteristic of the cation 3. Thus, as
with [(p5-C5Me5)RhCl(v-Cl)]2, intermediate species are
observed in the reaction carried out in ethanol. The
adduct cation 4 is formed initially, and stepwise C–F
and C–H bond activation/C–C bond formation af-
fords 5 and then 3 (Scheme 1).
There are seven possible isomers of the cation 5,
dependent on which C–H bond is activated (Fig. 5).
Each isomer exists as an enantiomeric pair. The pres-
ence of at least three pairs of doublets of multiplets in
the 31P{1H}-NMR spectrum indicates that at least three
of these are formed, but does not preclude the forma-
tion of the other four since resonances may be obscured
and the rate of the reactions may be such that only
small amounts of particular isomers of 5 may be
present. Table 2 details the resulting isomers of the final
product 3 from the isomers of the intermediate 5,
assuming that the Rh–P bonds are not broken during
the reaction. It is not possible to determine from the
31P{1H}-NMR spectrum the selectivity in terms of
1
hydrogen atoms. The H-NMR spectra of both 3a and
3b show four prominent doublets (Table 1) and, al-
though no singlets assigned to the 2-methyl group can
be discerned in the spectrum of 3a, that of 3b does
show a prominent triplet at l 1.83 and a singlet at l
1.29. The other expected resonances may be obscured.
There are no resonances which can be assigned un-
equivocally to isomer III, but this does not necessarily
indicate its absence. Unfortunately, due to the NMR
spectra containing coincidental and obscured reso-
nances, it is not possible to determine the relative
proportions of the isomers of 3a or 3b by integration.
Attempts to separate the isomers by fractional crystal-
lization and grow crystals suitable for single-crystal
X-ray diffraction were unsuccessful.
2.2. Reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2 and
dfppe in ethanol
The reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2
and dfppe was also carried out in ethanol, but, as with
the reaction between [(p5-C5Me5)RhCl(v-Cl)]2 and df-
ppe [11], was halted after 2 h. in order to identify any
intermediates. The 31P{1H}-NMR of the mixture,
recorded in (CD3)2CO, shows a number of doublets of
multiplets (Fig. 4). The resonance at l 28.7 shows a
1
rhodium–phosphorus coupling, JRh–P, of 152 Hz and
is assigned to [(p5-C5Me4Et)RhCl{(C6F5)2PCH2-
CH2P(C6F5)2}]+ (4) by comparison with the 31P{1H}-
NMR spectrum of [(p5-C5Me5)RhCl{(C6F5)2PCH2-
CH2P(C6F5)2}]+ ·BF4− [11] and [(p5-C5Me4Et)RhCl-
{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4− (4b) (see Section
2.3). There are at least three doublets of multiplets in
Fig. 4. 31P{1H} NMR spectrum, in (CD3)2CO, of the mixture of
products obtained in the reaction between [(p5-C5Me4Et)RhCl(v-
Cl)]2 and dfppe in ethanol after 2 h.
1
the range 40–45 ppm with values of JRh–P of ca. 150

72
M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
Scheme 1. (i) benzene, heat.
which C–H bonds are cleaved first, but it is noted that
isomers VI–IX are formed by the activation of similar
cyclopentadienyl methyl C–H bonds and subsequent
reaction of these can lead to all the isomers of 3.
anion. The values of l are almost identical to those of
2b [11]. One of the ortho resonances is broadened by
hindered rotation about the P–C bonds, as has been
found for 2b.
2.3. Synthesis and characterization of
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+
·BF−4 (4b)
2.4. Crystal structure of
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+
·BF−4 (4b)
Treatment of [(p5-C5Me4Et)RhCl(v-Cl)]2 with
NH4BF4 in methanol, followed by addition of dfppe in
dichloromethane, afforded the air-stable, orange com-
plex [(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+
·BF4− (4b) in moderate yield (Scheme 2). The complex
was characterized by mass spectrometry and NMR
spectroscopies. Elemental analysis indicated that it was
contaminated with small amounts of C–F bond acti-
vated compounds. The mass spectrum exhibited the
parent cation at 1045. The 1H-NMR spectrum,
recorded in (CD3)2CO, exhibits two multiplets at l 3.40
and 1.77 with intensities 4:12 assigned to the PCH2 and
the cyclopentadienyl methyl hydrogen atoms respec-
tively, and a quartet at l 2.33 and a triplet at l 1.31
with intensities 2:3 assigned to the methylene and
methyl hydrogen atoms of the ethyl group respectively.
The 31P{1H}-NMR spectrum of 4b exhibits a doublet of
The structure of complex 4b has been determined by
a single-crystal X-ray diffraction study. The crystallo-
graphic data and atomic coordinates are given in Ta-
bles 3 and 4, respectively and selected interatomic
distances and angles are given in Table 5. The asym-
metric unit consists of two unique ion pairs, which are
similar in structure (Fig. 6). Both cations exhibit a
three-legged piano stool geometry, similar to that
adopted by the cation of 2b [11]. One cation of 4b
possesses P–Rh–Cl angles which are similar, whilst the
angles of the other differ by over 10°. The P–Rh–P
angles of both cations are similar and ca. 1° more acute
than that of 2b [84.05(8)°]. The Rh–Cl distances are the
˚
same as that of 2b [2.380(2) A] within experimental
error. Three of the Rh–P distances are similar to the
˚
shorter Rh–P distance in 2b [2.342(2) A], but one is
˚
longer by ca. 0.04 A. The P–CH2 and CH2–CH2 bond
1
multiplets at l 34.2 with an absolute value of JRh–P of
lengths are identical to those of 2b within experimental
˚
152 Hz. These values are similar to those of l 35.1 and
150.5 Hz for complex 2b [11]. The 19F-NMR spectrum
exhibits six resonances assigned to two pairs of ortho,
meta and para fluorine atoms, consistent with non-
equivalent C6F5 groups on each phosphorus atom, as
well as resonances assigned to the tetrafluoroborate
error, but the P–C6F5 bonds are up to 0.03 A longer
than those of 2b. Each cation of 4b possesses one
smaller and one larger Rh–P–CH2 angle of ca. 105°
and ca. 110°, respectively, consistent with the structure
of 2b. The P–CH2–CH2 angles lie in the range
111.3(9)–112.9(10)°. For each phosphorus atom there is

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
73
Fig. 5. Diagrammatic representation of the possible isomers of the cation ‘[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}-HF]+’ (5) viewed
along the C5(centroid)-Rh axes. All the isomers exist as enantiomeric pairs.
˚
tances of 2.910(19) and 2.997(17) A for C(10)···F(42)
one smaller Rh–P–C6F5 angle of 111.3(5)–117.7(5)°
and one larger angle of 123.1(5)–128.5(5)°.
There are a number of short F···C(methyl) distances
between the ethyltetramethylcyclopentadienyl ring and
the dfppe ligand. In particular, the interatomic dis-
˚
and C(11A)···F(32A), respectively are \0.1 A less than
˚
the sum of the van der Waals’ radii (3.17 A) [14]. These
˚
distances are shorter by ca. 0.1 A than analogous
distances in the structure of salt 2b. This may be due to
the increased steric pressure of the ethyl group com-
pared to that of a methyl group. The ethyl groups
adopt positions such that they are almost eclipsed with
the chlorides, the least bulky ligands, when viewed
along the C5(centroid)–Rh axes, and the ethyl CH3
group is positioned on the other side of the cyclopenta-
dienyl ring to the rhodium atom. There are also a
number of F···H distances which are calculated to be
significantly less than the sum of the van der Waals’
Table 2
Possible isomers of cations 3 and 5 formed in the reaction between
[(p5-C5Me4Et)RhCl(v-Cl)]2 and dfppe
Intermediate 5“
Product 3
VI
I
VII
VIII
IX
III, IV or V
II
II
˚
radii (2.67 A) [14]: F(42)···HC(10) 2.074(18),
F(36)···HC(13) 2.238(20), F(32A)···HC(11A) 2.243(17)
and F(26A)···HC(11A) 2.265(20) A. Each tetrafluorob-
X
XI
IV
V
˚
XII
III
orate anion is situated above the respective cyclopenta-

74
M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
Scheme 2. (i) NH4BF4, methanol; (ii) dfppe, dichloromethane; (iii) ethanol, heat.
1
dienyl ring such that three fluorine atoms of the anion
are almost coplanar with the ring. The plane defined by
F(1), F(3/3%) and F(4/4%) is ca. 15.0° from planarity with
the plane defined by C(3A), C(4A), C(5A), C(6A) and
C(7A) and the plane defined by F(6/6%), F(7/7%) and
F(8/8%) is ca. 7.4° from planarity with the plane defined
by C(3), C(4), C(5), C(6) and C(7). The separation
between the two planes at the centroid of the BF3 base
couplings, JRh–P, of 145, 145 and 140 Hz respectively,
which are assigned to isomers of 3b. Other resonances
may be present but are obscured or coincidental. The
relative intensities of the resonances of 3b formed by
this route are the same as those found in the reactions
between [(p5-C5Me4Et)RhCl(v-Cl)]2 and dfppe. The
31P{1H}-NMR spectrum also exhibits less intense dou-
blets of multiplets at l 41.4, 43.2, 75.2 and 77.1 with
1
˚
for both salts is ca. 3.2 A, which is similar to that found
couplings, JRh–P, of 152, 153, ca. 140 and 148 Hz.
for 2b. The deviations form planarity, however, are
greater than that of 5.1° for 2b, which may be a
consequence of the presence of the ethyl group.
These can be assigned to singly C–F bond activated
species of formulation ‘[(p5-C5Me4Et)RhCl{(C6F5)2-
PCH2CH2P(C6F5)2}-HF]+ ·BF4−’ (5b) by comparison
with the 31P{1H}-NMR spectrum of [{p5-C5Me4-
CH2C6F4P(C6F5)CH2CH2P(C6F5)2}RhCl]+ ·BF4− [11].
The mass spectrum also shows peaks at 1025 and 990
which are consistent with this cation and [M–Cl]+.
2.5. Thermolysis of
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+
·BF−4 (4b)
Thermolysis of 4b in refluxing ethanol for 6 h. af-
forded an orange solid. The FAB mass spectrum shows
ions at 1005 and 969, consistent with cation 3. Thus,
C–F and C–H bond activation and C–C bond forma-
2.6. Reactions between [(p5-C5Me5)RhCl(v-Cl)]2 and
PPhx(C6F5)3−x (x=0–2)
Treatment
of
[(p5-C5Me5)RhCl(v-Cl)]2
with
1
tion has occurred. The H and 19F-NMR spectra of the
PPh2(C6F5) in either refluxing ethanol or benzene
yielded the neutral complex (p5-C5Me5)RhCl2{PPh2-
(C6F5)} (6) (Scheme 3). There is no evidence of C–F
bond activation occurring in either solvent, even on
prolonged reflux. Complex 6 is a red, air-stable solid,
which was characterized by elemental analysis,
product, recorded in CDCl3, are similar to those of 3b,
confirming the conclusion drawn from the mass spectral
data, but also contain some extra resonances of low
intensity. The 31P{1H}-NMR spectrum exhibits promi-
nent doublets of multiplets at l 70.7, 72.4 and 74.0 with

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
75
1
Table 4
mass spectrometry and NMR spectroscopies. The H-
NMR spectrum, recorded in CDCl3, exhibits two multi-
plets between 7.2 and 8.0 ppm assigned to the aromatic
hydrogen atoms and a doublet at l 1.30 with a phos-
phorus–hydrogen coupling, 4JP–H, of 2.2 Hz assigned
to the pentamethylcyclopentadienyl hydrogen atoms.
The 31P{1H}-NMR spectrum exhibits a doublet of mul-
Atomic coordinates (×104) and equivalent isotropic displacement
2
3
˚
coefficients (A ×10 ) with estimated standard deviations in parenthe-
ses for the non-hydrogen atoms of [(p5-C5Me4Et)RhCl{(C6F5)2PCH2-
CH2P(C6F5)2}]+ ·BF−4 ·{(CH3)2CO}0.25 (4b·{(CH3)2CO}0.25
)
Atom
x
y
z
U(eq)
Rh(1)
Cl(1)
P(1)
P(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
2926(1)
2679(3)
2810(2)
4390(2)
3806(9)
4353(9)
2174(10)
2884(10)
2852(9)
2053(9)
1677(10)
1347(17)
1923(12)
3473(11)
3374(10)
1685(10)
808(10)
2690(9)
3180(10)
3207(12)
2722(12)
2266(10)
2272(10)
3702(6)
3691(7)
2742(8)
1833(7)
1844(6)
1913(9)
2012(10)
1323(15)
505(15)
398(11)
1077(11)
2806(7)
1456(9)
−150(9)
−388(7)
939(5)
5141(9)
5281(10)
5742(11)
6105(12)
6036(12)
5549(10)
4972(6)
5822(8)
6580(9)
6434(8)
5524(7)
5023(10)
4764(10)
5245(11)
6053(12)
6371(11)
5865(9)
3991(6)
4958(7)
6525(8)
2640(1)
2495(2)
1207(2)
2166(2)
619(8)
8897(1)
10321(2)
9119(2)
9143(2)
9491(9)
9807(8)
8796(9)
8217(9)
7685(7)
7905(9)
8604(9)
9086(16)
9425(10)
8094(10)
6898(8)
7390(9)
9010(11)
8311(8)
7589(9)
6964(10)
7045(12)
7760(12)
8383(10)
7494(5)
6295(5)
6452(7)
7855(8)
9090(7)
9877(8)
10672(10)
11236 (10)
11001 (12)
10219 (12)
9649(9)
10969(5)
12025(6)
11543 (8)
9936(8)
8880(5)
8281(8)
7705(9)
6982(9)
6811(12)
7371(12)
8093(9)
7864(5)
6448(6)
6109(7)
7235(8)
8613(6)
9688(8)
9987(9)
10457(9)
10623(10)
10341(10)
9883(8)
9852(5)
10765(6)
11084(7)
34(1)
49(1)
36(1)
34(1)
39(3)
41(3)
44(4)
45(4)
38(3)
43(4)
45(4)
136(11)
63(5)
59(4)
54(4)
54(4)
70(5)
40(3)
46(4)
59(5)
66(5)
60(5)
52(4)
62(2)
80(3)
107(4)
106(4)
76(3)
43(4)
51(4)
85(7)
90(7)
73(5)
53(4)
73(3)
119(5)
162(7)
111(4)
61(2)
40(3)
48(4)
57(4)
70(5)
67(5)
52(4)
62(2)
93(4)
114(4)
105(4)
75(3)
44(4)
45(4)
54(4)
60(5)
56(4)
43(4)
58(2)
78(3)
92(4)
1
tiplets centred at l 18.8 with a value of JRh–P of 149
Hz. These values may be compared with those of l 7.9
and 144 Hz for (p5-C5Me5)RhCl2(PPh3) [15]. No reac-
tion was observed on treatment of [(p5-C5Me5)RhCl(v-
Cl)]2 with either PPh(C6F5)2 or P(C6F5)3 in refluxing
benzene. Presumably, the bulky nature of these ligands
prevents their coordination to the rhodium centre. An
attempt to prepare the bisphosphine cationic complex
[(p5-C5Me5)RhCl{PPh2(C6F5)}2]+ ·BF4− by treatment
of [(p5-C5Me5)RhCl(v-Cl)]2 with NH4BF4 and
PPh2(C6F5) was unsuccessful and yielded only complex
6. Presumably, PPh2(C6F5) is too bulky to permit coor-
dination of two phosphines to the rhodium.
1165(8)
3917(8)
3974(8)
3410(8)
3038(8)
3325(9)
5238(15)
4445(9)
4656(9)
3375(9)
2578(9)
3174(11)
618(8)
C(10)
C(11)
C(12)
C(13)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
F(22)
F(23)
F(24)
F(25)
F(26)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
F(32)
F(33)
F(34)
F(35)
F(36)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
F(42)
F(43)
F(44)
F(45)
F(46)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
F(52)
F(53)
F(54)
Table 3
Crystallographic
CH2P(C6F5)2}]+ ·BF−4 ·{(CH3)2CO}0.25 (4b·{(CH3)2CO}0.25
data
for
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2-
823(9)
)
396(11)
−257(11)
−497(10)
−69(10)
1421(5)
591(6)
−691(8)
−1141 (7)
−364(6)
943(9)
Formula
C37.75H22.50BClF24O0.25P2Rh
Formula weight
Crystal system
Space group
1147.17
Triclinic
(
P1
Unit cell dimension
˚
a (A)
15.743(4)
16.429(2)
16.970(3)
˚
b (A)
˚
c (A)
700(9)
h (°)
i (°)
k (°)
V ( A )
Z
79.41(2)
84.34(2)
82.01(2)
609(14)
727(15)
963(13)
1046(9)
533(6)
3
˚
4260.5(14)
4a
F(000)
2256
1.793
Dc (g cm−3
)
362(9)
620(13)
1084(9)
1270(6)
2001(9)
2690(9)
2660(11)
1924(13)
1195(11)
1259(10)
3447(5)
3354(7)
1857(8)
467(7)
Crystal size (mm)
Radiation (u, A)
0.65×0.09×0.08
Mo-Kh (0.71073)
˚
Monochromator
v (Mo–Kh), cm−1
T (K)
Graphite
6.75
293
Scan method
h, k, l ranges
2q limits (°)
ꢀ
−1–18, −19–19, −20–19
5.0–50.0
Total reflections
Unique reflections
Observed reflections
[Fo\4|(Fo)]
14708
13137 (Rint=0.0536)
7254
Restraints
13
541(6)
Variables
1171
R1, wR2 [I\2|(I)]
R1, wR2 (all data)
Weighting scheme
(D/|)max
0.0955, 0.2200
0.1757, 0.2714
2690(9)
3398(9)
3717(9)
3333(11)
2611(10)
2298(9)
3819(5)
4415(6)
3632(7)
w=1/[|2(Fo)2+0.1279P2+55.10P]b
0.087
0.923, −0.889
1.060
−3
˚
max, min Dz (eA
)
Goodness of fit on F2
a There are two independent ion pairs in the asymmetric unit.
b P=[max(Fo2, 0)+2F2c]/3

76
M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
Table 4 (Continued)
Table 4 (Continued)
Atom
x
y
z
U(eq)
Atom
x
y
z
U(eq)
F(55)
F(56)
Rh(2)
Cl(2)
P(3)
P(4)
C(1A)
C(2A)
C(3A)
C(4A)
C(5A)
C(6A)
C(7A)
C(8A)
C(9A)
7151(6)
6206(6)
2772(1)
2665(3)
1307(2)
2248(2)
841(10)
1133(9)
4120(10)
3580(10)
3275(8)
3538(9)
4097(9)
5531(15)
4681(11)
3499(12)
2872(11)
3395(12)
4681(10)
1138(10)
898(9)
2228(6)
1596(5)
2768(1)
2502(2)
2596(2)
4175(2)
3434(8)
4269(9)
2163(9)
1602(9)
1939(9)
2753(9)
2861(9)
1490(16)
1997(11)
746(9)
1466(9)
3271(10)
3513(11)
1616(9)
1484(10)
718(11)
33(12)
10482(7)
9600(5)
83(3)
59(2)
35(1)
50(1)
39(1)
38(1)
50(4)
46(4)
47(4)
44(4)
37(3)
42(4)
41(3)
117(9)
66(5)
62(5)
54(4)
57(4)
62(5)
46(4)
53(4)
59(4)
84(7)
68(5)
49(4)
69(3)
92(4)
114(4)
101(4)
66(3)
45(4)
59(4)
79(6)
77(6)
79(6)
64(5)
80(3)
106(4)
122(5)
104(4)
73(3)
39(3)
49(4)
57(4)
66(5)
56(4)
49(4)
64(3)
73(3)
94(4)
89(3)
63(2)
46(4)
55(4)
67(5)
72(5)
66(5)
52(4)
66(3)
102(4)
113(4)
96(4)
75(3)
B(1)
F(1)
F(2)
F(3)
F(3%)
F(4)
F(4%)
B(2)
F(5)
F(6)
F(6%)
F(7)
F(7%)
F(8)
F(8%)
O(1)
C(14)
C(15)
C(16)
5332(6)
5750(12)
5905(7)
1269(7)
1798(11)
921(7)
1938(6)
2243(11)
1404(6)
60(5)
178(8)
94(4)
82(6)
111(12)
76(6)
13905(1)
15333(2)
14174(2)
13899(2)
14712(9)
14336(9)
13931(9)
13755(8)
12998(7)
12731(8)
13303(8)
14391(13)
14614(10)
14222(10)
12484(9)
11941(8)
13172(10)
14828(8)
15653(9)
16127(10)
15739(15)
14944(13)
14513(10)
16053(5)
16902(6)
16195(8)
14591(8)
13738(6)
13452(9)
12624(11)
12088(11)
12376(14)
13207(14)
13710(12)
12315(6)
11298(7)
11856(9)
13460(8)
14504(7)
14454(8)
14877(9)
15317(9)
15297(10)
14868(10)
14460(9)
14878(6)
15722(6)
15690(7)
14849(7)
14049(6)
12882(9)
12550(9)
11762(11)
11304(11)
11592(11)
12369(9)
12968(5)
11452(6)
10530(6)
11136(6)
12634(6)
5107(13)
5078(22)
4755(11)
4609(10)
8810(10)
9125(9)
9002(26)
8084(16)
8026(13)
8437(16)
9431(17)
9205(15)
2391(18)
1859(28)
1119(42)
1423(41)
790(12)
550(14)
1881(10)
1541(14)
5019(8)
4338(7)
4740(24)
4797(19)
5405(18)
5608(12)
5519(17)
5340(15)
7301(16)
7736(24)
7543(40)
8087(37)
2649(9)
2369(19)
1572(11)
1540(12)
3432(8)
54(6)
89(8)
3953(9)
137(6)
149(13)
157(11)
103(9)
106(7)
120(10)
108(7)
82(7)
2722(15)
3201(19)
3655(18)
3868(13)
3429(20)
2717(11)
12488(16)
12301(24)
12231(41)
12996(34)
C(10A)
C(11A)
C(12A)
C(13A)
C(21A)
C(22A)
C(23A)
C(24A)
C(25A)
C(26A)
F(22A)
F(23A)
F(24A)
F(25A)
F(26A)
C(31A)
C(32A)
C(33A)
C(34A)
C(35A)
C(36A)
F(32A)
F(33A)
F(34A)
F(35A)
F(36A)
C(41A)
C(42A)
C(43A)
C(44A)
C(45A)
C(46A)
F(42A)
F(43A)
F(44A)
F(45A)
F(46A)
C(51A)
C(52A)
C(53A)
C(54A)
C(55A)
C(56A)
F(52A)
F(53A)
F(54A)
F(55A)
F(56A)
74(11)
184(28)
159(24)
722(11)
873(14)
1122(12)
1193(10)
730(7)
3. Conclusion
130(11)
889(9)
2136(6)
662(7)
−711(7)
−551(6)
931(5)
The reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2
and dfppe proceeds similarly to that between [(p5-
C5Me5)RhCl(v-Cl)]2 and dfppe [10,11]. Although the
C–F bond activation is regiospecific, activation of the
C–H bonds of the C5Me4Et ligand is not. Presumably,
cleavage of C–H bonds on alkyl groups in a 1,3-dispo-
sition occurs, but the spectroscopic data indicate that
C–H bonds of all the cyclopentadienyl methyl and
methylene groups can be activated to give a mixture of
isomers. The reactions show little discernible selectivity
in the activation of these bonds. Although there was no
evidence for the activation of the alkyl methyl C–H
bonds this can not be ruled out. The reactions also
showed no stereospecificity as to which methylene C–H
bond was activated, since both isomers IV and V of
cation 3 were identified. The similarity of the relative
intensities of the NMR resonances of the products of
the reactions between [(p5-C5Me4Et)RhCl(v-Cl)]2 and
dfppe carried out in benzene and ethanol, and the
thermolysis of 4b, suggest that the reactions proceed via
the same mechanism, i.e. formation of the cation 4
followed by sequential C–F and C–H bond activation
and C–C bond formation to give 5 then 3.
575(7)
762(9)
1187(8)
1388(6)
495(10)
684(11)
54(17)
−764(15)
−971(12)
−360(12)
1477(7)
280(8)
−1362(9)
−1772(7)
−573(6)
2712(10)
3440(10)
3728(12)
3272(13)
2590(12)
2317(10)
3891(6)
4431(6)
3588(8)
2180(8)
1609(6)
2235(10)
2899(11)
2950(12)
2277(13)
1629(12)
1605(11)
3589(6)
3611(8)
2325(9)
999(7)
2620(9)
2791(10)
2875(11)
2765(12)
2587(12)
2523(10)
2913(7)
3015(8)
2830(8)
2503(8)
2362(6)
4856(8)
4624(9)
5156(10)
5947(12)
6180(10)
5660(9)
3880(5)
4894(6)
6465(7)
6955(6)
5933(5)
4805(9)
5264(10)
5681(11)
5649(11)
5221(11)
4819(9)
5289(6)
6096(8)
6053(8)
5181(8)
4399(6)
4. Experimental details
4.1. General procedures
1H-, 19F- and 31P-NMR spectra were recorded on
Bruker DRX400, AM300 or ARX250 spectrometers.
1H-NMR spectra were referenced using the residual
protio solvent resonance relative to tetramethylsilane
941(6)

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
77
(l=0), 19F- and 31P-NMR spectra externally to CFCl3
and 85% H3PO4 respectively, using the high frequency
positive convention. 19F-NMR spectra of salts contain-
ing BF4−, the fluorine atoms of which have a relatively
high values of T1, were recorded with a relaxation delay
of 10 s. All chemical shifts (l) are quoted in ppm and
coupling constants in Hz. Abbreviations used in multi-
plicities are: s, singlet; d, doublet; t, triplet; q, quartet;
m, multiplet; br denotes a signal broadened due to a
fluxional process. Elemental analyses were performed
by Butterworths. Positive-ion FAB mass spectra were
filtered. Removal of the solvent by rotary evaporation
afforded 0.135 g of a yellow solid comprising 3b, 4b and
5b.
4.3.3. Preparation of
[(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+
·BF−4 (4b)
The salt NH4BF4 (0.10 g, 0.95 mmol) was added to
[(p5-C5Me4Et)RhCl(v-Cl)]2 (0.10 g, 0.15 mmol) in
methanol (50 cm3) and the mixture stirred for 10 min.
Dfppe (0.23 g, 0.30 mmol) in dichloromethane (30 cm3)
was added and the mixture stirred for 2.5 h. The
solvent was removed by rotary evaporation and the
product extracted into dichloromethane (2×50 cm3).
1
obtained on a Kratos Concept H mass spectrometer.
4.2. Reagents
C5Me4EtH, RhCl3 ·xH2O, [(p5-C5Me5)RhCl(v-Cl)]2
(Aldrich) and PPh2(C6F5), PPh(C6F5)2, P(C6F5)3 and
(C6F5)2PCH2CH2P(C6F5)2 (Fluorochem) were used as
supplied. [(p5-C5Me4Et)RhCl(v-Cl)]2 was prepared as
described for [(p5-C5Me5)RhCl(v-Cl)]2 [16].
Table 5
Selected interatomic distances (A) and angles (°) for [(p5-
˚
C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4− ·{(CH3)2CO}0.25
(4b·{(CH3)2CO}0.25
)
Bond lengths
Rh(1)–Cl(1)
Rh(1)–P(1)
Rh(1)–P(2)
Rh(1)–C(3)
Rh(1)–C(4)
Rh(1)–C(5)
Rh(1)–C(6)
Rh(1)–C(7)
P(1)–C(1)
P(1)–C(21)
P(1)–C(31)
P(2)–C(2)
P(2)–C(41)
P(2)–C(51)
C(1)–C(2)
2.383(4)
2.345(4)
2.380(4)
2.247(13) Rh(2)–C(3A)
2.276(13) Rh(2)–C(4A)
2.211(12) Rh(2)–C(5A)
2.224(13) Rh(2)–C(6A)
2.179(14) Rh(2)–C(7A)
1.828(13) P(3)–C(1A)
1.856(14) P(3)–C(21A)
Rh(2)–Cl(2)
Rh(2)–P(3)
Rh(2)–P(4)
2.377(4)
2.353(4)
2.342(4)
2.215(14)
2.188(14)
2.253(12)
2.226(13)
2.241(14)
1.821(13)
1.82(2)
4.3. Preparations
4.3.1. Reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2 and
dfppe in benzene
A slurry of [(p5-C5Me4Et)RhCl(v-Cl)]2 (0.16 g, 0.25
mmol) and dfppe (0.39 g, 0.51 mmol) in benzene (65
cm3) was refluxed under nitrogen for 10.5 h. The result-
ing yellow solution was concentrated to ca. 20 cm3 by
rotary evaporation and light petroleum (b.p. 100–
120°C) added to precipitate 3a as a yellow powder,
which was filtered off, washed with light petroleum
(b.p. 40–60°C) and dried in vacuo. Yield 0.29 g (55%).
FAB MS m/z: 1005 (M+), 969 ([M–Cl–H]+). The
tetrafluoroborate salt, 3b, was prepared by anion
1.86(2)
P(3)–C(31A)
1.85(2)
1.820(13) P(4)–C(2A)
1.824(14) P(4)–C(41A)
1.818(14) P(4)–C(51A)
1.835(14)
1.850(14)
1.84(2)
1.52(2)
C(1A)–C(2A)
1.51(2)
Non-bonded distances
C(10)···F(42)
C(10)···F(52)
C(11)···F(22)
C(11)···F(42)
C(12)···F(36)
C(13)···F(36)
2.910(19) C(9A)···C(42A)
3.181(18) C(11A)···F(26A)
3.170(17) C(11A)···F(32A)
3.186(16) C(12A)···F(32A)
3.241(19) C(13A)···F(42A)
3.153(20) C(13A)···F(52A)
3.263(20)
3.108(20)
2.997(17)
3.137(21)
3.165(18)
3.153(20)
metathesis. Typically,
a
sample of 3a in
dichloromethane (ca. 20 cm3) was added to a large
excess of NH4BF4 in methanol (ca. 150 cm3) and the
mixture stirred for 2 h. The solvent was removed by
rotary evaporation and the product extracted in
dichloromethane (50 cm3) and filtered. The solvent was
removed by rotary evaporation to afford 3b, which was
recrystallized from acetone. FAB MS m/z: 1005 ([M-
BF4]+), 969 ([M–BF4–Cl–H]+). Anal. Found: C,
41.4; H, 2.1; P, 5.5. C37H19BClF22P2Rh·1/2{(CH3)2CO}
Calc: C, 41.2; H, 2.0; P, 5.5%.
Bond angles
Cl(1)–Rh(1)–P(1) 84.27(13) Cl(2)–Rh(2)–P(3)
Cl(1)–Rh(1)P(2)
P(1)–Rh(1)–P(2)
Rh(1)–P(1)–C(1) 109.7(4)
Rh(1)–P(1)–C(21) 123.9(5)
Rh(1)–P(1)–C(31) 111.3(5)
C(1)–P(1)–C(21)
C(1)–P(1)–C(31)
C(21)–P(1)–C(31) 103.9(6)
Rh(1)–P(2)–C(2) 104.2(5)
Rh(1)–P(2)–C(41) 117.7(5)
Rh(1)–P(2)–C(51) 123.1(5)
C(2)–P(2)–C(41)
C(2)–P(2)–C(51)
C(41)–P(2)–C(51) 100.7(7)
P(1)–C(1)–C(2)
P(2)–C(2)–C(1)
79.23(14)
90.65(13)
82.75(13)
105.3(5)
85.59(13) Cl(2)–Rh(2)–P(4)
82.97(13) P(3)–Rh(2)–P(4)
Rh(2)–P(3)–C(1A)
Rh(2)–P(3)–C(21A) 112.7(5)
Rh(2)–P(3)–C(31A) 128.5(5)
C(1A)–P(3)–C(21A) 107.4(7)
C(1A)–P(3)–C(31A) 102.1(7)
C(21A)–P(3)–C(31A) 99.2(7)
98.6(6)
108.1(7)
4.3.2. Reaction between [(p5-C5Me4Et)RhCl(v-Cl)]2 and
dfppe in ethanol
Rh(2)–P(4)–C(2A)
110.1(5)
A slurry of [(p5-C5Me4Et)RhCl(v-Cl)]2 (0.06 g, 0.09
mmol) and dfppe (0.13 g, 0.18 mmol) in ethanol (50
cm3) was refluxed under nitrogen for 2 h. The solvent
was removed by rotary evaporation and NH4BF4 (ca. 1
g) and acetone (70 cm3) was added. After stirring for 2
h. the solvent was removed by rotary evaporation and
the solid extracted with dichloromethane (70 cm3) and
Rh(2)–P(4)–C(41A) 123.7(5)
Rh(2)–P(4)–C(51A) 113.3(5)
C(2A)–P(4)–C(41A) 100.1(7)
C(2A)–P(4)–C(51A) 106.3(7)
C(41A)–P(4)–C(51A) 101.5(6)
107.8(7)
101.5(6)
112.(9)
111.3(9)
P(3)–C(1A)–C(2A)
P(4)–C(2 A)–C(1A) 112.8(9)
112.9(10)

78
M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
Fig. 6. Molecular structure of one of the independent ion pairs of [(p5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+ ·BF4− (4b). Displacement
ellipsoids are shown a the 30% probability level. All hydrogen atoms are omitted for clarity.
Concentration by rotary evaporation and addition of
light petroleum precipitated 4b as a yellow solid, which
was filtered off, washed with light petroleum (bp 40–
cooling and addition of light petroleum (b.p. 100–
120°C), concentration by rotary evaporation and addi-
tion of more light petroleum precipitated 6 as a red
1
1
60°C) and dried. Yield 0.21 g (62%). H [(CD3)2CO,
solid. Yield 0.055 g (42%). H (CDCl3, 300.14 MHz):
3
4
300.14 MHz]: 3.40 (m, 4H, PCH2), 2.23 (q, JH–H 7.5
7.86 (m, 4H, Ph), 7.41 (m, 6H, Ph), 1.30 (d, JP–H 2.2,
Hz, 2H, CH2CH3), 1.77 (m, 12H, C5CH3), 1.31 (t,
15H, CH3). 19F (CDCl3, 282.41 MHz): −120.43 (dm,
3JFortho–Fmeta 16.8 Hz, 2F, Fortho), −148.29 (m, 1F,
Fpara), −160.11 (m, 2F, Fmeta). 31P{1H} (CDCl3, 121.50
3JH–H 7.5 Hz, 3H, CH2CH3). 19F [(CD3)2CO, 282.41
3
MHz]: −124.29 (br s, 4F, Fortho), −127.43 (d, JF–F
3
1
9.7 Hz, 4F, Fortho), −144.92 (t, JF–F 21.2 Hz, 2F,
MHz): 18.8 (dm, JRh–P 149 Hz). FAB MS m/z: 660
3
Fpara), −146.14 (t, JF–F 20.5 Hz, 2F, Fpara), −150.90
([M–H]+), 625 ([M–Cl–H]+), 590 ([M–2Cl–H]+),
580 ([M–C6H5–H]+). Anal. Found: C, 51.4; H, 3.7; P,
4.7. C28H25Cl2F5PRh Calc.: C, 50.9; H, 3.8; P, 4.7%.
3
and −150.95 (1:4) (4F, BF4−), −158.26 (dd, JFortho–
3
Fmeta ca. JFmeta–Fpara 20.2, 4F, Fmeta), −160.27 (dd,
3JFortho–Fmeta:3JFmeta–Fpara 19.4, 4F, Fmeta). 31P{1H}
1
[(CD3)2CO, 121.50 MHz]: 34.2 (dm, JRh–P 152 Hz).
FAB MS m/z: 1045 ([M–BF4]+), 1010 ([M–BF4–Cl]+
). Anal. Found: C, 40.8; H, 2.2; P, 4.3.
C37H21BClF24P2Rh Calc.: C, 39.2; H, 1.9; P, 5.4%.
(Satisfactory analysis could not be obtained due to
contamination by C–F bond activated species. Charac-
terization was based on the spectroscopic data and by
comparison with complex 2b [11]).
4.4. X-ray crystal structure determination
Crystals of salt 4b suitable for X-ray structure deter-
mination were grown from acetone. The structure was
determined on a Siemens P4 diffractometer. Crystallo-
graphic data are presented in Table 3 and atomic
coordinates and isotropic displacement parameters are
given in Table 4. Accurate unit cell parameters were
determined by least-squares refinement of the optimised
setting angles of 28 reflections in the range 5.55q5
12.5°. Three standard check reflections, monitored ev-
ery 100 reflections, indicated no crystal decay. A
semi-empirical correction, based on the „ scan data,
4.3.4. Preparation of (p5-C5Me5)RhCl2{PPh2(C6F5)}
A slurry of [(p5-C5Me5)RhCl(v-Cl)]2 (0.06 g, 0.10
mmol) and PPh2(C6F5) (0.07 g, 0.20 mmol) in benzene
(160 cm3) was refluxed under nitrogen for 3 h. After

M.J. Atherton et al. / Journal of Organometallic Chemistry 555 (1998) 67–79
79
Acknowledgements
We thank F2 Chemicals (GCS) and the Royal Society
(EGH) for support.
References
[1] (a) J.L. Kiplinger, T.G. Richmond, C.E. Osterberg, Chem. Rev.
94 (1994) 373. (b) G.C. Saunders, Angew. Chem., Int. Ed. Engl.
35 (1996) 2615. (c) J. Burdeniuc, B. Jedlicka, R.H. Crabtree,
Chem. Ber. 130 (1997) 145.
[2] (a) T.G. Richmond, C.E. Osterberg, A.M. Arif, J. Am. Chem.
Soc. 109 (1987) 8091. (b) C.E. Osterberg, M.A. King, A.M. Arif,
T.G. Richmond, Angew. Chem. Int. Ed. Engl. 29 (1990) 888. (c)
B.L. Lucht, M.J. Poss, M.A. King, T.G. Richmond, J. Chem.
Soc. Chem. Commun. (1991) 400.
[3] (a) C.M. Anderson, R.J. Puddephat, G. Ferguson, A.J. Lough,
J. Chem. Soc. Chem. Commun. (1989) 1297. (b) C.M. Anderson,
M. Crespo, G. Ferguson, A.J. Lough, R.J. Puddephat,
Organometallics 11 (1992) 1177. (c) M. Crespo, M. Martinez, J.
Sales, J. Chem. Soc. Chem. Commun. (1992) 822. (d) M. Crespo,
M. Martinez, J. Sales, Organometallics 12 (1993) 4297. (e) M.
Crespo, X. Solans, M. Font-Bard´ıa, Organometallics 14 (1995)
355. (f) M. Crespo, M. Martinez, E. de Pablo, J. Chem. Soc.
Dalton Trans. (1997) 1231.
[4] L.J. Procopio, P.J. Carroll, D.H. Berry, J. Am. Chem. Soc. 116
(1994) 177.
[5] M.L.H. Green, J. Haggitt, C.P. Mehnert, J. Chem. Soc. Chem.
Commun. (1995) 1853.
Scheme 3. (i) benzene, heat.
[6] M. Aizenberg, D. Milstein, J. Am. Chem. Soc. 117 (1995) 8674.
[7] R.M. Ceder, J. Granell, G. Muller, M. Font-Bard´ıa, X. Solans,
Organometallics 14 (1995) 5544.
[8] J.L. Kiplinger, T.G. Richmond, J. Chem. Soc. Chem. Commun.
(1996) 1115.
[9] J. Burdeniuc, R.H. Crabtree, J. Am. Chem. Soc. 118 (1996)
2525.
[10] M.J. Atherton, J. Fawcett, J.H. Holloway, E.G. Hope, A.
Karac¸ar, D.R. Russell, G.C. Saunders, J. Chem. Soc. Chem.
Commun. (1995) 191.
was applied to the data (maximum and minimum trans-
mission factors 0.950 and 0.693, respectively), and the
data were corrected for Lorentz and polarization effects.
The structure was solved by direct methods using the
PATT option of SHELXTL-pc [17] and refined by full
matrix least squares. Hydrogen atoms were included in
˚
calculated positions (C–H 0.95 A) with a single fixed
3
˚
isotropic displacement parameter (Uiso=0.08 A ). The
boron atoms and carbons atoms other than the methyl
and ethyl atoms of the C5Me4Et ligands were refined
with isotropic displacement parameters. All other non-
hydrogen atoms were refined with anisotropic displace-
ment parameters. Due to program constraints of 800
parameters to be refined, the C6F5 rings were refined as
rigid groups with x, y and z of all other atoms riding on
the pivot atom. An analysis of the weighting scheme
over ꢀF0ꢀ and (sin q)/u was satisfactory. The highest
residual electron density peaks were close to the boron
[11] M.J. Atherton, J. Fawcett, J.H. Holloway, E.G. Hope, A.
Karac¸ar, D.R. Russell, G.C. Saunders, J. Chem. Soc. Dalton
Trans. (1996) 3215.
[12] L.P. Barthel-Rosa, V.J. Catalano, J.H. Nelson, J. Chem. Soc.
Chem. Commun. (1995) 1629.
[13] L.P. Barthel-Rosa, V.J. Catalano, K. Maitra, J.H. Nelson,
Organometallics 15 (1996) 3924.
[14] A. Bondi, J. Phys. Chem. 68 (1964) 441.
[15] M.J. Atherton, J. Fawcett, A.P. Hill, J.H. Holloway, E.G. Hope,
D.R. Russell, G.C. Saunders, R.M.J. Stead, J. Chem. Soc.
Dalton Trans. (1997) 1137.
[16] C. White, A. Yates, P.M. Maitlis, Inorg. Synth. 29 (1992) 228.
[17] G.M. Sheldrick, SHELXTL-PC, Release 4.2, Siemens Analytical
X-Ray Instruments, Madison, WI, 1991.
˚
atoms (ca. 1.42 A) consistent with disorder typical of
BF4− anions.