Synthesis and reactions of the rhenium fulvene complexes [Re(η6-C5Me4CH2)(CO) 2(C6F4R)] (R = F or CF3): Products derived from initial C-F activation

Article abstract of DOI:10.1039/a802899k

The UV irradiation of [Re(η⁵-C₅Me₅)(CO)₃] in the presence of C₆F₆ effected intermolecular C-F and intramolecular C-H activation generating [Re(η⁶-C₅Me₄CH₂)(CO) ₂(C₆F₅)] 1a in two isomeric forms. In the major isomer the CH₂ group lies trans to the C₆F₅ group both in solution and in the crystal. In the minor isomer the CH₂ lies cis to the C₆F₅ group. A similar reaction with C₆F₅CF₃ generates [Re(η⁶-C₅Me₄CH₂)(CO) ₂(C₆F₄CF₃)] 1b in four isomeric forms. In the major form the CF₃ group is in the 4 position and the CH₂ group lies trans to the C₆F₄CF₃ group. The other three isomers are formed by rotation of the η⁶-C₅Me₄CH₂ ligand as above, by placing the CF₃ at the 3 position, and by a combination of the two. Complex 1a reacted with PMe₃ to form the zwitterionic complex [Re(η⁵-C₅Me₄CH₂PMe ₃)(CO)₂(C₆F₅)] and with MeO^- to form the anion [Re(η⁵-C₅Me₄CH₂OMe)(CO) ₂(C₆F₅)]^-, isolable as the NEt₄⁺ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η⁵-C₅Me₅)(CO)₂(C ₆F₅)X] initially. More prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a with HBF₄ in Et₂O in the presence of MeCN led to formation of the salt [Re(η⁵-C₅Me₅)(CO)₂(C ₆F₅)(NCMe)]⁺[BF₄]^-. The halogens Cl₂, Br₂ and I₂ reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η⁵-C₅Me₄CH₂X)(CO) ₂(C₆F₅)X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.

Full text of DOI:10.1039/a802899k

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Synthesis and reactions of the rhenium fulvene complexes
[Re(ç6-C5Me4CH2)(CO)2(C6F4R)] (R ؍ F or CF3): products
derived from initial C᎐F activation
A. Hugo Klahn,*a Beatriz Oelckers,a Fernando Godoy,a Maria T. Garland,b Andres Vega,b
Robin N. Perutz*c and Catherine L. Higgittc
a Instituto de Química, Universidad Católica de Valparaiso, Casilla 4059, Valparaiso, Chile
b Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 653, Santiago,
Chile
c Department of Chemistry, University of York, York, UK YO1 5DD
Received 17th April 1998, Accepted 8th July 1998
The UV irradiation of [Re(η5-C5Me5)(CO)3] in the presence of C6F6 effected intermolecular C᎐F and intramolecular
C–H activation generating [Re(η6-C5Me4CH2)(CO)2(C6F5)] 1a in two isomeric forms. In the major isomer the CH2
group lies trans to the C6F5 group both in solution and in the crystal. In the minor isomer the CH2 lies cis to the
C6F5 group. A similar reaction with C6F5CF3 generates [Re(η6-C5Me4CH2)(CO)2(C6F4CF3)] 1b in four isomeric
forms. In the major form the CF3 group is in the 4 position and the CH2 group lies trans to the C6F4CF3 group.
The other three isomers are formed by rotation of the η6-C5Me4CH2 ligand as above, by placing the CF3 at the 3
position, and by a combination of the two. Complex 1a reacted with PMe3 to form the zwitterionic complex [Re(η5-
C5Me4CH2PMe3)(CO)2(C6F5)] and with MeOϪ to form the anion [Re(η5-C5Me4CH2OMe)(CO)2(C6F5)]Ϫ, isolable as
the NEt4ϩ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η5-C5Me5)(CO)2(C6F5)X] initially. More
prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a
with HBF4 in Et2O in the presence of MeCN led to formation of the salt [Re(η5-C5Me5)(CO)2(C6F5)(NCMe)]ϩ[BF4]Ϫ.
The halogens Cl2, Br2 and I2 reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η5-
C5Me4CH2X)(CO)2(C6F5)X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.
The C᎐H bond activation of methyl groups in metal-bound
pentamethylcyclopentadienyl complexes, leading to the form-
ation of a tetramethylfulvene ligand, has been the source of
much recent interest. This transformation has been shown to
occur thermally, photochemically or under the influence of
strong bases with complexes of Ru,1,2 Rh,3,4 Ir,4,5 Os,6 Ti7 and
Zr.8
1a and its reactions with PMe3 and HCl to give the zwitterionic
complex [Re(η5-C5Me4CH2PMe3)(CO)2(C6F5)] 2 and cis-[Re(η5-
C5Me5)(CO)2(C6F5)Cl] 4a respectively.11 Here full details
are given of the synthesis of 1a and its CF3-aryl substituted
analogue [Re(η6-C5Me4CH2)(CO)2(C6F4CF3)] 1b via C᎐F bond
activation of C6F6 and C6F5CF3 respectively. Also included in
this work are the reactions of 1a with methoxide to form the
anion [Re(η5-C5Me4CH2OMe)(CO)2(C6F5)]Ϫ 3, with HX to give
[Re(η5-C5Me5)(CO)2(C6F5)X] (X = Cl 4a or Br 4b), as well as
the reactions of 1a with X2, leading to the complexes trans-
[Re(η5-C5Me4CH2X)(CO)2(C6F5)X] (X = Cl 5a, Br 5b or I 5c).
The proposed structure of 5b is supported by X-ray crystal-
lography. The protonation reaction of 1a with HBF4 to produce
the cationic complex [Re(η5-C5Me5)(CO)2(C6F5)(NCMe)]ϩ 6 is
also described. These reactions are summarized in Scheme 1.
In recent years there has also been considerable interest in
using co-ordinated or unco-ordinated fulvene molecules in the
preparation of organometallic complexes bearing substituted
cyclopentadienyl ligands, C5H4R or C5Me4R, where R is a pen-
dant arm which may or may not contain a functional group.
For instance, Behrens and co-workers9 reported the reaction of
the complex [Cr(η6-fulvene)(CO)3] (fulvene = 6,6-dimethyl- or
1,2,3,4-tetraphenylfulvene) with tertiary phosphines to produce
the zwitterionic addition products [Cr(η5-C5R4CRЈ2PRЉ3)-
(CO)3] (R = H or Ph; RЈ = H or Me; RЉ = Me, Et or Ph), in a
demonstration of the electrophilic nature of the exocyclic
methylene carbon. By contrast, the reaction of [Zr(η6-
C5Me4CH2)(η5-C5Me5)(Ph)] with iodine to produce the ring-
substituted cyclopentadienyl phenyl iodide complex, [Zr(η5-
C5Me4CH2I)(η5-C5Me5)(Ph)], has also been reported.8 Maitlis
and co-workers1 reported that the complex [Ru(η5-
C5H4CH2Cl)(CO)2Cl] can be produced in high yield by treating
the dimeric fulvene complex [{Ru(η6-C5H4CH2)Cl2}2] with
carbon monoxide. More recently, Koelle and co-workers10
reported the reactions of several cationic tetramethylfulvene
Results
1. Tetramethylfulvene complexes [Re(ç6-C5Me4CH2)(CO)2-
(C6F4R)], R ؍ F 1a or CF3 1b
Photolysis of [Re(η5-C5Me5)(CO)3] (λ = 300 nm) in a quartz
tube in neat C6F6 or C6F5CF3 at room temperature gave, in both
cases, one major dicarbonyl product. These compounds,
isolated as air stable orange crystals in good yield, were identi-
fied as the tetramethylfulvene complexes, [Re(η6-C5Me4CH2)-
(CO)2(C6F4CF3R)] (R = F or CF3). In each case, however, the
product was present in more than one form (see below). The
crystal structure of 1a, described in a previous communic-
ation,11 shows that the C6F5 group occupies a position ‘trans’ to
the CH2 group of the fulvene. The C᎐C bond to the CH2 group
is relatively long [1.43(2) Å] and is bent out of the C5Me4 plane
by 39.6Њ.
ruthenium complexes [Ru(η6-C5Me4CH2)Cppc]ϩ (Cppc
=
prochiral cyclopentadienyl ligand) with optically active phenyl-
ethylamine to produce diastereomeric ruthenocene complexes.
In a preliminary communication we have described the syn-
thesis of the fulvene complex [Re(η6-C5Me4CH2)(CO)2(C6F5)]
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Scheme 1 Reactions of the fulvene complex 1a.
Two extreme canonical forms can be envisaged for the bond-
ing of a η6-conjugated triene ligand, η6-tetramethylfulvene A or
η5-tetramethylcyclopentadienyl-σ-alkyl (“tucked-in”) B. The
crystal structure is close to expectations for a “tucked-in”
complex.11,12
observation of two isomers is more easily understood if there is
an appreciable contribution from the tucked-in canonical form,
B, generating a barrier to internal rotation. The equivalence of
the CH2 protons and the presence of two resonances for the
C5Me4 protons show that the major isomer in solution is
the same as that revealed by the crystal structure. In addition to
the resonances of the major species, the 1H and 19F NMR spec-
tra of 1a showed a set of weak resonances which are assigned to
a minor isomer with the η6-C5Me4CH2 ligand rotated relative to
the C6F5 group (Scheme 2). The proportion of the minor isomer
is 14% in chloroform at 293 K. For the minor isomer, as
expected, all methyl groups and the CH2 protons are inequiv-
CH2
CH2
Re
Re
F5C6
C
F5C6
C
O
O
C
O
C
O
alent in the 1H NMR spectrum, as are the CO groups in the 13
C
B
NMR spectrum. The EXSY experiments for 1a revealed
A
no evidence for interconversion of the two isomers on the
1
An assessment of the bonding can also be obtained from
the NMR spectra. For the major isomer of each complex
(Scheme 2) both H chemical shifts of the methylene group
(δ 4.10 1a and 4.17 1b) and the C᎐H coupling constants meas-
ured in the 13C-gated spectrum for each CH2 triplet (JCH 162 1a
and 163 Hz 1b) suggest that the C5Me4CH2 ligand is bound to
the rhenium in a η6-triolefinic fashion, form A.13 The separate
NMR timescale at 300 K. Complex H and 13C NMR spectra
resulting from the presence of several isomers have also
been reported for the dimeric tetramethylfulvene complex
[{Ru(η6-C5Me4CH2)Cl2}2].14
1
In contrast to complex 1a, the 1H NMR spectrum of 1b
shows the presence of four species. The major isomer (isomer 1,
66%) has a “trans” orientation of the methylene group with a
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CH2
CH2
Re
Re
F5C6
C
C
C
O
O
O
C
O
C6F5
1a major
1a minor
CH2
CH2
F
F
Re
Re
C
F
C
C
O
O
C
O
F
F
F3C
O
F
F
F
CF3
1b isomer 1
1b isomer 2
Scheme 3 Possible mechanisms for formation of complex 1a.
CH2
CH2
produce the zwitterionic complex [Re(η5-C5Me4CH2PMe3)-
(CO)2(C6F5)] 2 and the anion [Re(η5-C5Me4CH2OMe)(CO)2-
(C6F5)]Ϫ 3, respectively. Both complexes were isolated as white
F
F
Re
Re
C
F3C
F
C
C
O
O
O
F
C
F
O
ϩ
F
microcrystalline solids, the latter as the NEt4 salt. They are
F3C
F
insoluble in non-polar organic solvents, but 3 dissolves in
CH2Cl2 and CHCl3, while 2 only dissolves in MeCN. The
anionic nature of these complexes at rhenium was easily recog-
nized from the large frequency shift of the ν(CO) bands when
compared with the uncharged precursor 1a [∆ν = 122 (MeCN)
and 142 cmϪ1 (CH2Cl2), for 2 and 3, respectively]. The formal
negative charge at the metal centre shifted δ(CO) by about 10
ppm to lower field in the 13C NMR spectrum, when compared
to 1a. Both the ν(CO) bands and 13C chemical shifts of the
carbonyls of 2 and 3 are in the same region as those observed
for the three legged anion [Re(η5-C5Me5)(CO)2Br]Ϫ [ν(CO)
F
1b isomer 3
1b isomer 4
Scheme 2 Isomers of complexes 1a and 1b.
4-C6F4CF3 ligand. Consequently, two singlets are observed for
the methyl protons and one singlet for the CH2 protons. The
second isomer (isomer 2, 24.4%) possesses a “cis” conformation
of the CH2 and 4-C6F4CF3, similar to that found for the minor
isomer of 1a. Isomer 3 (12.2%) contains the CH2 group “trans”
to a 3-C6F4CF3 ligand and shows a similar 1H NMR pattern to
those previously described. However, the 19F NMR spectrum of
this isomer shows, as expected, three different resonances for
the fluorine atoms bound to the aryl ring. The assignment of
these resonances was made by using selective 19F᎐19F NMR
decoupling techniques. The “cis” arrangement of the CH2 and
3-C6F4CF3 groups for isomer 4 was assigned on the basis of the
inequivalent resonances for the methyl and CH2 protons in the
1H NMR spectrum. The 19F NMR spectrum shows resonances
which support the presence of the meta substituted aromatic
ligand. The low abundance of this isomer (2.4%) precludes us
from observing the 13C NMR spectrum.
The formation of complex 1a (Scheme 3) should involve an
unsaturated 16-electron fragment [Re(η5-C5Me5)(CO)2] C, by
photodissociation of CO from [Re(η5-C5Me5)(CO)3], which
reacts with the fluorinated arene to give the intermediate [Re(η5-
C5Me5)(CO)2(η2-C6F6)] D, and/or the C᎐F oxidative addition
intermediate [Re(η5-C5Me5)(CO)2(C6F5)F] E. However, we
could not detect any intermediates in these reactions by IR
spectroscopy. The postulated η2 co-ordination of the perfluoro-
arene in an intermediate stage D is supported by the isolation
and characterization of the analogous [Re(η5-C5H4R)(CO)2(η2-
C6F6)], R = H or Me.15 The final stage of the reaction involves
release of HF. Rather than attacking the product in an analo-
gous way to HCl (see below), the HF attacks the glassware.
(CH2Cl2): 1860s and 1718s cmϪ1 13C-{1H} NMR (CD2Cl2)
;
δ 213.1].16
The presence of the PMe3 and methoxy groups bound to the
CH2 was deduced from 1H and 13C NMR spectra. For instance,
the CH2 groups were observed in the proton spectra as a doub-
let (JPH 12 Hz) at δ 3.42 for 2 and a singlet at δ 4.11 for 3. A
similar pattern was observed in the 13C NMR spectra: a doublet
at δ 22.73 (JCP 47 Hz) for 2 and a singlet at δ 67.09 for 3.
3. Reaction of complex 1a with hydrogen halides
The reaction of the fulvene complex 1a with aqueous HX
(X = Cl, or Br) in diethyl ether or thf occurs in a similar manner
to that previously reported for HCl gas, in the same solvent.11 In
both cases only a single product, formulated as cis-[Re(η5-
C5Me5)(CO)2(C6F5)X], cis-4a and cis-4b, is formed in good
yield. Under similar conditions aqueous HF does not react with
1a.
The cis-[Re(η5-C5Me5)(CO)2(C6F5)X] (X = Cl or Br) com-
plexes, isolated as red microcrystalline solids, exhibit mass spec-
1
tra which show Mϩ, [MϪCO]ϩ and [MϪ2CO]ϩ peaks. The H
and 19F NMR spectra just exhibit resonances expected for a
single isomer. In addition to the resonances of the η5-C5Me5
carbons, the 13C NMR spectra in the carbonyl region clearly
show two resonances due to the non-equivalent CO ligands in a
cis or lateral arrangement. Similarly, the IR spectra (CH2Cl2
solution) in each case consist of only two ν(CO) absorptions in
the region 1953–2052 cmϪ1, of which the higher wavenumber
one is much more intense. A similar pattern of intensities is
observed for other cis-dicarbonyl complexes of this type for
which the structure is known by X-ray crystallography.17
2. Reactions of [Re(ç6-C5Me4CH2)(CO)2(C6F5)] 1a with
nucleophiles
Complex 1a underwent facile reactions with PMe3 and OMeϪ at
the methylene CH2 group of the tetramethylfulvene ligand, to
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From the reaction of the fulvene complex 1a with aqueous
HI in thf, under similar conditions to those used for the prepar-
ation of cis-4a and cis-4b, only trans-[Re(η5-C5Me5)(CO)2-
(C6F5)I], trans-4c, could be isolated in good yield. At an early
stage of the reaction the IR spectrum of the mixture showed, in
addition to the absorptions of the final product at 2034 and
1968 cmϪ1 (CH2Cl2 solution), the presence of two weak bands
at 2028 and 1953 cmϪ1 which are probably due to the cis isomer.
These bands quickly disappear at room temperature, producing
an increase in intensity of the bands of the isolated product.
When the reaction was carried out at 0 ЊC the cis:trans ratio
was estimated to be 2:1, but all attempts to separate the mix-
ture by column chromatography were unsuccessful due to rapid
cis → trans isomerization on the silica gel. The chloro and
bromo complexes cis-4a and cis-4b also proved unstable with
respect to the thermal isomerization in solution. Both com-
pounds can be converted into the corresponding trans isomers
trans-4a and trans-4b in thf solution at room temperature. The
conversion of the chloro derivative (18 h) is slower than that of
the bromo derivative (5 h). This trend can be explained on the
basis of steric arguments: the two bulkiest ligands in the iodo
derivative (C6F5 and I) will adopt the trans or diagonal position
more easily than in the smaller chloro and bromo analogues.
Thermal cis → trans isomerization in solution of organic
solvents is a well known process in four-legged piano stool
complexes of rhenium.18,19
The trans-4a–4c isomers, obtained as orange-red solids after
column purification, show considerably greater solubility than
the cis isomers, especially in hydrocarbon solvents. These com-
pounds are recognizable by their two IR ν(CO) absorptions in
which the higher wavenumber one [ν(CO)sym] is now the less
intense of the pair. Both bands are also shifted to higher
wavenumber by comparison with the corresponding cis isomer
by amounts which increase in the order I < Br < Cl. Almost
exactly the same trend was observed previously for cis- and
trans-[Re(η5-C5Me5)(CO)2X2] (X = Cl, Br or I) and explained in
terms of the increased competition for rhenium d electrons
between the carbonyl groups when they are mutually trans.17
All of these complexes exhibit a single 13CO resonance for
equivalent CO groups in the 13C NMR spectrum. Accordingly,
we are confident that all adopt the trans geometry, that is
the geometry which places the bulky C6F5 and halogen ligands
in a less hindered position. Furthermore, very recently we
reported the synthesis and characterization of the closely
related complex trans-[Re(η5-C5Me5)(CO)2(Ph)I] which was
shown to have a trans orientation of the CO ligands by X-ray
crystallography.20
cyclopentadienyl halide complexes trans-[Re(η5-C5Me4CH2X)-
(CO)2(C6F5)X] 5a–5c as orange-yellow or red crystalline solids.
The bromo and iodo derivatives were obtained in almost quan-
titative yield. The lower yield of the chloro analogue is associ-
ated with the formation of a green-brown material that is
devoid of carbonyl ligands and that has resisted purification via
chromatography as it is irreversibly adsorbed onto neutral
alumina.
The presence of the (halogenomethyl)tetramethylcyclopenta-
dienyl ligand in these complexes was easily detected by 1H and
13C NMR spectroscopy. Two distinct methyl groups and a lower
field resonance for the methylene group are observed for the
chloro and bromo derivatives 5a and 5b by both techniques. In
contrast, the 13C NMR spectrum for the iodo complex 5c shows
the methylene group resonance at high field (δ Ϫ3.06 in CDCl3),
as a consequence of the “heavy atom effect”. Similar patterns to
those described here have been reported for the related com-
pounds [Ru(η5-C5Me4CH2Cl)(CO)2Cl],1 [Rh(η5-C5Me4CH2X)-
(η5-C5H5)]ϩ (X = Cl or I),3 [Zr(η5-C5Me4CH2I)(η5-C5Me5)-
(Ph)I],8 [Re(η5-C5Me4CH2PMe3)(CO)2(C6F5)],11 and [Fe(η6-
C6Me5CH2X)(η5-C5H5)]ϩ (X = Cl, Br or I).21
The presence of the C6F5 ligand in complexes 5a–5c was
clearly established by the three multiplets observed in the 19F
NMR spectrum (see Experimental section). The 13C NMR
spectra show a single resonance for the CO group for each of
these compounds. The IR spectrum (CH2Cl2 solution) in each
case consists of only two ν(CO) absorptions in the 2060–1970
cmϪ1 region, of which the higher wavenumber band is much less
intense, implying a trans or diagonal orientation of the CO
ligands.
5. Crystal structure of trans-[Re(ç5-C5Me4CH2Br)(CO)2(C6F5)-
Br] 5b
The structure of trans-[Re(η5-C5Me4CH2Br)(CO)2(C6F5)Br] 5b
confirms the presence of the (bromomethyl)tetramethyl-
cyclopentadienyl ligand (Fig. 1; Tables 1, 2). The complex exists
as discrete molecules in the unit cell, with no unusually short
intermolecular contacts. The rhenium atom is formally in the 
oxidation state and is seven-co-ordinated if the η5-C5Me4CH2Br
group is considered as three-co-ordinate. The Re᎐C (CO) bond
lengths are in the range 1.89–2.03 Å reported for trans-[Re-
(η5-C5Me5)(CO)2Br2],17trans-[Re(η5-C5Me5)(CO)2(Ph)I],20trans-
[Re(η5-C5Me5)(CO)2Et2],22
trans-[Re(η5-C5Me5)(CO)2H2],23
trans-[Re(η5-C5H5)(CO)2(COMe)Me]24 and trans-[Re(η5-C5H5)-
(CO)2(SnPh3)2].25 The interbond angle relating the carbonyl
groups C(17)᎐Re᎐C(18) of 100.5(5)Њ is in the range for the
complexes mentioned above, for which the trans orientation of
the CO ligands has been confirmed by X-ray crystallography.
The Re᎐C (C6F5) bond length of 2.203(10) Å is almost identi-
cal, in terms of the achieved precision, to that reported for the
parent fulvene complex 1a.11 The angle relating the C6F5 group
and Br(1) C(11)᎐Re᎐Br(1) of 142.6(3)Њ is greater than that
reported for trans-[Re(η5-C5Me5)(CO)2(Ph)I] [140.8(2)Њ].20
Other bond lengths and angles are unexceptional.
The reaction of complex 1a with HBF4 in the presence of
MeCN, at room temperature, also regenerates the η5-C5Me5
ligand and yields the orange cationic complex [Re(η5-
C5Me5)(CO)2(C6F5)(NCMe)]ϩ which could be isolated as the
BF4Ϫ salt in excellent yield. This solid is air stable and insoluble
in most of the organic solvents but soluble in MeCN. By IR and
NMR spectroscopy, it was identified as a mixture of cis and
trans isomers in a proportion of 2:1. Since attempts to separate
the isomers were unsuccessful, they were characterized in
solution. As expected, a large shift to high energy was observed
for the ν(CO) bands, when compared to those of the other
dicarbonyl complexes, i.e. 5a–5c (see below). These absorption
bands are in the same region as those of cis- and trans-[Re(η5-
C5Me5)(CO)2{P(OMe)3}X]ϩ (X = Cl, Br or I).18 The presence of
the two isomers was clearly shown by 1H, 13C and 19F NMR (see
Experimental section).
Discussion
The photoreactions of [Re(η5-C5Me5)(CO)3] with C6F6 and
C6F5CF3 result in combined C᎐H and C᎐F bond activation
(Schemes 2, 3). This method provides a route to introduce
a fluoroaryl group at rhenium and, simultaneously, activate
one of the ring methyl groups. Since our initial report
of this reaction many more intermolecular C᎐F bond acti-
vation reactions have been discovered.26–28 Another one which
occurs in combination with C᎐H activation is the photoreac-
tion of [Rh(η5-C5H5)(PMe3)(C2H4)] with C6F5OMe which leads
to the metallacycle [Rh(η5-C5H5)(PMe3)(C6F4OCH2)].28 The
thermodynamic driving force for these reactions is provided by
the release of HF. In the present reactions HF is scavenged by
4. (Halogenomethyl)tetramethylcyclopentadienyl complexes
trans-[Re(ç5-C5Me4CH2X)(CO)2(C6F5)X]5a–5c(X ؍ Cl, BrorI)
The fulvene complex [Re(η6-C5Me4CH2)(CO)2(C6F5)] 1a reacts
readily with halogens X2 (X = Cl, Br or I) in hexanes at room
temperature to produce the (halogenomethyl)tetramethyl-
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functionalized cyclopentadienyl complexes. In this paper we
have shown that this method can be used to form η5-C5Me4-
CH2R ligands with R = PMe3, OMe, Cl, Br or I (Scheme 1).
The reactions of the fulvene complex 1a with PMe3 and with
MeOϪ demonstrate the electrophilic character of the methylene
group. In the light of these reactions, it seems unlikely that acids
HX (X = Cl, Br or I) and HBF4 attack directly at the methylene
group. An alternative pathway could involve initial attack of
Hϩ at the metal followed by migration to the CH2 group.
The reactions of the fulvene complex with X2 could proceed
by one of two routes. In the first, primary electrophilic addition
of the halogen to the CH2 group gives the unstable cation
[Re(η5-C5Me4CH2X)(CO)2(C6F5)]ϩ, which then co-ordinates
XϪ. Analogous reactions have been reported for the complexes
[Rh(η4-C5Me4CH2)(η5-C5H5)] and [Fe(η5-C Me ᎐CH )(η5-
᎐
6
5
2
C5H5)] with an excess of iodine, and in both cases the corre-
sponding cations could be isolated.3,21 However, this mechan-
ism conflicts with the electrophilic character of the CH2 group
shown above. Another possible reaction pathway involves direct
attack of the halogen molecule at the metal centre, leading to
the intermediate species [Re(η6-C5Me4CH2)(CO)2(C6F5)X]ϩ,
which then could react at the methylene group with XϪ.
Support for this suggestion is given by the reactions of the
parent carbonyl complex [Re(η5-C5Me5)(CO)3] with halogens,
which yield the cationic complexes [Re(η5-C5Me5)(CO)3X]ϩ.29,30
The mechanism of the reaction and reason for the production
of only one of the two possible isomers remain as unanswered
questions for future study.
Fig. 1 Thermal ellipsoid diagram (50% probability) of trans-[Re(η5-
C5Me4CH2Br)(CO)2(C6F5)Br] 5b.
Table 1 Selected bond lengths (Å) and angles (Њ) with estimated
standard deviations in parentheses for trans-[Re(η5-C5Me4CH2Br)-
(CO)2(C6F5)Br] 5b
Re–C(1)
Re–C(2)
Re–C(3)
Re–C(4)
Re–C(5)
2.332(10)
2.356(12)
2.334(14)
2.246(12)
2.298(11)
Re–C(11)
Re–C(17)
Re–C(18)
Re–Br(1)
Br(2)–C(6)
2.203(10)
1.970(12)
2.032(10)
2.6254(13)
1.965(11)
Experimental
C(17)–Re–C(18)
C(18)–Re–C(11)
C(11)–Re–Br(1)
100.5(5)
80.8(4)
142.6(3)
C(17)–Re–C(11)
C(1)–C(6)–Br(2)
83.9(5)
108.9(8)
All reactions were carried out under nitrogen using standard
Schlenk techniques. All solvents were purified and dried by
conventional methods, and distilled under nitrogen prior to use.
The precursor, [Re(η5-C5Me5)(CO)3], was prepared according to
Gladysz and co-workers.31 Hexafluorobenzene (99%) and
octafluorotoluene (98%) from Aldrich were used as received.
Infrared spectra were recorded in solution (NaCl cell) on a
Perkin-Elmer FT-1605 spectrophotometer, 1H, 19F and 13C
NMR spectra on Bruker AC 200 (complexes 3, 4a–4c and
5a–5c), DRX 400 (19F᎐19F decoupling experiments) and AMX
500 instruments (complexes 1a–1b, 2 and 6). All 1H NMR
chemical shifts were referenced using the chemical shifts of
Table 2 Crystallographic parameters for trans-[Re(η5-C5Me4CH2Br)-
(CO)2(C6F5)Br] 5b
Empirical formula
M
Colour, crystal size/mm
Crystal system, space group
a/Å
b/Å
c/Å
α/Њ
C18H14Br2F5O2Re
703.31
Orange, 0.28 × 0.16 × 0.06
¯
Triclinic, P1
8.372(1)
9.246(1)
14.570(2)
79.56(1)
75.29(1)
63.33(1)
971.9(2)
2
2.40
residual solvent resonances (CDCl3, δ 7.27; CD3CN, δ 2.00), 13
C
NMR chemical shifts to solvent peaks (CDCl3, δ 77.0; CD3CN,
δ 0.3, 117.2) and 19F NMR spectra to external C6F6 at δ
Ϫ162.90. Coupling assignments are indicated, where known.
Mass spectra and elemental analyses were obtained at the
Microanalysis Department of Simon Fraser University,
Canada, and the Centro de Instrumentación of Pontificia
Universidad Católica de Chile, Santiago, Chile.
β/Њ
γ/Њ
U/Å3
Z
Dc/g cmϪ3
µ/mmϪ1
10.42
656
F(000)
θ Range for data collection/Њ
Index ranges
2.47–25.05
Ϫ9 р h р 9, Ϫ10 р k р 10,
0 р l р 17
3627/3343 (Rint = 0.054)
2952 [I > 2σ(I)]
3343/6/253
0.923
Preparations
[Re(ç6-C5Me4CH2)(CO)2(C6F5)] 1a. The complex [Re(η5-
C5Me5)(CO)3] (150 mg, 0.37 mmol) was dissolved in hexafluoro-
benzene (12 cm3) in a quartz tube. The solution was degassed
with three freeze–pump–thaw cycles, and irradiated for 6 h
(λ = 300 nm) at room temperature using a Rayonet RPR-100
photochemical reactor. The solution turned yellowish brown,
and an IR spectrum showed, in addition to the CO bands corre-
sponding to the parent complex, two bands at 2007 and 1940
cmϪ1. Corrosion of the quartz tube was observed. The solvent
was removed under vacuum, and the resulting brown residue
purified by chromatography on a neutral alumina column.
Elution with hexanes moved unchanged [Re(η5-C5Me5)(CO)3]
(43 mg, 0.11 mmol) and then the fulvene complex 1a, which was
obtained as a yellow solid after evaporation of the solvent (93
mg, 65%). Recrystallisation of 1a from hexanes yielded orange
crystals. IR [hexanes, ν˜(CO)/cmϪ1]: 2007vs and 1940vs. Mass
spectrum (EI, based on 187Re): m/z 544 (Mϩ), 516 (Mϩ Ϫ CO)
Reflections collected/independent
Observed reflections
Data/restraints/parameters
Goodness of fit on F 2
Final R1, wR2, [I > 2σ(I)]
(all data)
0.038, 0.124
0.048, 0.131
1.70, Ϫ1.82
Largest difference peak, hole/e ÅϪ3
¹
R1 = Σ(|Fo Ϫ Fc|/|Fo|); wR2 = [Σw(Fo2 Ϫ Fc2)2/Σw(Fo )2]²; wϪ1 = σ2(Fo)2 ϩ
2
(aP)2 ϩ bP where P = (Fo2 ϩ 2Fc2)/3, a = 0.08, b = 23.44.
the quartz glassware rather than reacting with the products
or precursors. The formation of 1a and 1b contrasts with the
reactions of [Re(η5-C5H4R)(CO)3] (R = H or Me) with C6F6
which simply give rise to the substitution products [Re(η5-
C5H4R)(CO)2(η2-C6F6)].15
The formation of the tetramethylfulvene group in complex
1a offers considerable opportunities for generating ring-
J. Chem. Soc., Dalton Trans., 1998, 3079–3086
3083

View Article Online
and 488 (Mϩ Ϫ 2CO) (Found: C, 39.70; H, 2.55. Calc. for
C18H14F5O2Re: C, 39.78; H, 2.60%).
1a and new strong bands at 1880 and 1812 cmϪ1. After 15 min
of stirring at 0 ЊC a white precipitate appeared. The volume of
thf was reduced to about one third under vacuum and Et2O
(5 cm3) was added to complete the precipitation. The white
solid was washed twice with Et2O (5 cm3) and then recrystal-
lized from acetonitrile–diethyl ether at 4 ЊC. A colourless
microcrystalline solid was isolated (66 mg, 97% yield), which
decomposed over 90 ЊC. IR [MeCN, ν˜(CO)/cmϪ1]: 1868vs and
Major isomer (trans CH2 and C6F5). 1H NMR (CDCl3): δ 1.72
(s, 6 H, CH3), 2.05 (s, 6 H, CH3) and 4.10 (s, 2 H, CH2). 19F
NMR (CDCl3): δ Ϫ164.37 (m, 2Fmeta), Ϫ160.10 (t, JFF 20 Hz,
Fpara) and Ϫ104.66 (m, 2Fortho). 13C-{1H}NMR (CDCl3): δ 9.62
(s, CH3), 9.75 (s CH3), 47.37 (s, CH2), 96.95 (s, C5Me4), 107.36
(s, C5Me4), 107.43 (s, C5Me4), 109.93 (t, JCF 51, Cipso C6F5),
136.14 (d, JCF 253, C6F5), 138.20 (d, JCF 226, C6F5), 150.39 (d,
JCF 225, C6F5) and 198.27 (t, JCF 5.1 Hz, CO). Gated 13C-
{1H}NMR (CDCl3): δ 9.62 (t, JCH 128, CH3), 9.75 (t, JCH 127,
CH3) and 47.37 (t, JCH 161 Hz, CH2).
1
1795vs. H NMR (CD3CN): δ 1.76 (d, JPH 14 Hz, PMe3), 2.03
(s, CH3), 2.04 (s, CH3) and 3.42 (d, JPH 12 Hz, CH2). 13C-
{1H}NMR (CD3CN): δ 7.69 (d, JCP 53, PMe3), 10.38 (s, CH3),
11.56 (s, CH3), 22.73 (d, JCP 47, CH2), 81.21 (s, C5Me4), 95.59 (s,
C5Me4), 95.81 (d, JCP 1, C5Me4), 121.71 (t, JCF 59, Cipso C6F5),
134.42 (d, JCF 230, C6F5), 135.32 (d, JCF 245, C6F5), 150.53 (d,
JCF 210 Hz, C6F5) and 210.38 (s, CO). 19F NMR (CD3CN):
δ Ϫ161.3 (t, JFF 26 Hz, 2Fmeta), Ϫ160.8 (t, JFF 20 Hz, Fpara),
Ϫ98.5 (d, JFF 26 Hz, 2Fortho). 31P-{1H}NMR (CD3CN): δ 29.1
(s, CH2PMe3). Mass spectrum (FAB, based on 187Re): m/z 620
(Mϩ) (Found: C, 40.33; H, 4.02. Calc. for C21H23F5O2PRe: C,
40.65; H, 3.72%).
Minor isomer, (cis CH2 and C6F5). 1H NMR (CDCl3): δ 1.50
(s, 3 H, CH3), 2.07 (s, 3 H, CH3), 2.33 (s, 3 H, CH3), 2.34 (s, 3 H,
CH3), 4.00 (d, JHH 1.5, 1 H, CH2) and 4.80 (d, JHH 1.5 Hz, 1 H,
CH2). 19F NMR (CDCl3): δ Ϫ165.35 (m, 2Fmeta), Ϫ162.86
(t, JFF 20 Hz, Fpara) and Ϫ105 (broad, 2Fortho). 13C-{1H}NMR
(CDCl3): δ 8.61 (s, CH3), 10.19 (s, CH3), 10.72 (s, CH3), 11.34 (s,
CH3), 64.80 (s, CH2), 94.05 (s, C5Me4), 98.70 (s, C5Me4), 106.91
(s, C5Me4), 109.25 (s, C5Me4), 114.02 (s, C5Me4), 112.3 (m, Cipso
C6F5), 198.01 (s, CO) and 200.75 (s, CO).
[NEt4]؉[Re(ç5-C5Me4CH2OMe)(CO)2(C6F5)]؊ 3. To a solu-
tion of the fulvene complex 1a (60 mg, 0.11 mmol) in CH2Cl2
(15 cm3) was added tetraethylammonium bromide (23 mg, 0.11
mmol) and sodium methoxide (12 mg, 0.22 mmol). After 15
min of stirring at room temperature the solution turned colour-
less, and the IR spectrum only showed CO absorptions at 1855
and 1775 cmϪ1. The mixture was filtered, and the white solid
washed twice with CH2Cl2 (2 cm3). The filtrate was reduced in
volume to ≈5 cm3, and then a layer of diethyl ether was slowly
poured into the flask. After 24 h complex 3 was isolated as a
white crystalline solid (58 mg, 75%). IR [CH2Cl2, ν˜(CO)/cmϪ1]:
[Re(ç6-C5Me4CH2)(CO)2(C6F4CF3)] 1b. This complex was
prepared in a similar manner to that of 1a but using octafluoro-
toluene. Yield 52%. IR [hexane, ν˜(CO)/cmϪ1]: 2006vs and
1942vs. Mass spectrum (EI, based on 187Re): m/z 594 (Mϩ), 566
(Mϩ Ϫ CO) and 538 (Mϩ Ϫ 2CO) (Found: C, 38.39; H, 2.36.
Calc. for C19H14F7O2Re: C, 38.45; H, 2.38%).
Isomer 1, [Re(η6-C5Me4CH2)(CO)2(4-C6F4CF3)], trans
1
CH2 and 4-CF3C6F4. H NMR (CDCl3): δ 1.75 (s, 6 H, CH3),
2.06 (s, 6 H, CH3) and 4.17 (s, 2 H, CH2). 19F NMR (CDCl3):
δ Ϫ144.58 (m, 2Fmeta), Ϫ104.12 (m, 2Fortho) and Ϫ56.97 (t, JFF
21 Hz, 3F, CF3). 13C-{1H}NMR (CDCl3): δ 9.70 (s, CH3), 9.75
(s, CH3), 48.82 (s, CH2), 97.79 (s, C5Me4), 107.26 (s, C5Me4),
107.39 (s, C5Me4), 121.57 (q, JCF 270, CF3), 126.17 [t, JCF 50,
Cipso C6F4(CF3)], 142.52 [d, JCF 260, C6F4(CF3)], 149.51 [d, JCF
230, C6F4(CF3)], 161.30 [d, JCF 220, C6F4(CF3)] and 197.80
(t, JCF 6 Hz, CO).
1
1855vs and 1775vs. H NMR (CDCl3): δ 1.19 (t, 12 H, CH3
NEt4ϩ), 1.92 (s, 6 H, CH3), 1.95 (s, 6 H, CH3), 2.40 (q, 8 H, CH2
NEt4ϩ), 3.31 (s, 3 H, OCH3) and 4.11 (s, 2 H, CH2). 19F NMR
(CDCl3): δ Ϫ167.50 (m, 2Fmeta), Ϫ166.93 (tt, JFF 20.3, 2.3 Hz,
Fpara) and Ϫ104.42 (m, Fortho). 13C-{1H}NMR (CDCl3): δ 7.32
(s, CH3 NEt4ϩ), 10.59 (s, CH3), 10.79 (s, CH3), 52.45 (s, CH2
NEt4ϩ), 57.74 (s, CH2OCH3), 67.09 (s, CH2OCH3), 89.42 (s,
C5Me4), 95.50 (s, C5Me4), 98.66 (s, C5Me4) and 212.89 (s, CO)
(Found: C, 45.85; H, 5.22. Calc. for C27H37F5NO3Re: C, 46.01;
H, 5.29%).
Isomer 2, [Re(η6-C5Me4CH2)(CO)2(4-C6F4CF3)], cis CH2
1
and 4-CF3C6F4. H NMR (CDCl3): δ 1.52 (s, 3 H, CH3), 2.09
(s, 3 H, CH3), 2.34 (s, 3 H, CH3), 2.36 (s, 3 H, CH3), 4.02 (d, JHH
1.7, 1 H, CH2) and 4.83 (d, JHH 1.7 Hz, 1 H, CH2). 19F NMR
(CDCl3): δ Ϫ145.85 (m, Fmeta), Ϫ105 (broad, Fortho) and Ϫ56.79
(t, JFF 21 Hz, CF3). 13C-{1H}NMR (CDCl3): δ 8.64 (s, CH3),
10.18 (s, CH3), 10.76 (s, CH3), 11.30 (s, CH3), 64.99 (s, CH2),
94.46 (s, C5Me4), 98.98 (s, C5Me4), 106.76 (s, C5Me4), 109.04
(s, C5Me4), 113.95 (s, C5Me4), 129.77 [t, JCF 50 Hz, Cipso
C6F4(CF3)], 197.38 (s, CO), 199.85 (s, CO), and CF aromatic
groups not observed.
cis-[Re(ç5-C5Me5)(CO)2(C6F5)Cl] cis-4a.
A solution of
complex 1a (50 mg, 0.092 mmol) in HCl (1.0 M solution in
diethyl ether, 6 cm3) was stirred at room temperature for 8 h.
The mixture changed from yellow to red, and the IR spectrum
showed no evidence for the starting material. Solvent was
removed under vacuum, and the residual reddish oil was
dissolved in CH2Cl2 (5 cm3) dried over anhydrous Na2SO4, and
filtered. A layer of hexanes was slowly poured into a flask, and
after 2 d at room temperature cis-4a was isolated as red crystals
in 90% yield (48 mg), mp 179 ЊC (decomp.). IR [CH2Cl2, ν˜(CO)/
Isomer 3, [Re(η6-C5Me4CH2)(CO)2(3-C6F4CF3)], trans
CH2 and 3-CF3C6F4. 1H NMR (CDCl3): 1.71 (s, 6 H, CH3), 2.05
(s, 6 H, CH3) and 4.12 (s, 2 H, CH2). 19F NMR (CDCl3):
δ Ϫ166.07 (m, Fmeta), Ϫ140.36 (m, Fpara), Ϫ90.72 (m, Fortho),
Ϫ78.12 (m, Fortho) and Ϫ57.31 (ddd, JFF 25, 21, 1 Hz, CF3). 13C-
{1H}NMR (CDCl3): δ 9.57 (s, CH3), 9.74 (s, CH3), 47.71 (s,
CH2), 97.01 (s, C5Me4), 107.48 (s, C5Me4), 107.35 (s, C5Me4),
198.08 (s, CO), and aromatic carbons not observed.
cmϪ1]: 2033vs and 1959s. 1H NMR (CDCl3): δ 2.06 (s, CH3). 19
F
NMR (CDCl3): δ Ϫ163.94 (m, 2Fmeta), Ϫ160.06 (t, JFF 20.1 Hz,
Fpara) and Ϫ108.82 (m, 2Fortho). 13C-{1H}NMR (CDCl3): δ 10.83
(s, CH3), 108.49 (s, C5Me5), 199.75 (s, CO) and 202.20 (s, CO).
Mass spectrum (EI, based on 187Re and 35Cl): m/z 580 (Mϩ), 552
(Mϩ Ϫ CO) and 524 (Mϩ Ϫ 2CO) (Found: C, 37.64; H, 2.74.
Calc. for C18H15ClF5O2Re: C, 37.28; H, 2.61%).
Isomer 4, [Re(η6-C5Me4CH2)(CO)2(3-C6F4CF3)], cis CH2
and 3-CF3C6F4. 1H NMR (CDCl3): δ 1.50 (s, 3 H, CH3), 2.08 (s,
3 H, CH3), 2.33 (s, 3 H, CH3), 3.95 (d, JHH 1.7, 1 H, CH2), 4.79
(d, JHH 1.7 Hz, 1 H, CH2) and one methyl group not observed.
19F NMR (CDCl3): δ Ϫ167.17 (m, Fmeta), Ϫ143.24 (m, Fpara),
Ϫ57.19 (ddd, JFF 25, 21, 1 Hz, CF3) and the two Fortho not
observed.
trans-[Re(ç5-C5Me5)(CO)2(C6F5)Cl] trans-4a. This complex
was prepared following the same procedure as that used for cis-
4a, but the stirring at room temperature was maintained for 18
h. The yellow-orange solid obtained after evaporation of the
solvent was dissolved in the minimum amount of hexanes, and
crystallized at Ϫ18 ЊC as yellow-orange needles (45 mg, 70%),
mp 175 ЊC (decomp.). IR [CH2Cl2, ν˜(CO)/cmϪ1]: 2054s and
1979vs. 1H NMR (CDCl3): δ 1.83 (s, CH3). 19F NMR (CDCl3):
δ Ϫ162.36 (m, 2Fmeta), Ϫ156.69 (t, JFF 20.3 Hz, Fpara) and
[Re(ç5-C5Me4CH2PMe3)(CO)2(C6F5)] 2. To a solution of
complex 1a (60 mg, 0.11 mmol) in thf (10 cm3) at 0 ЊC was
added an excess of PMe3 (0.05 cm3), with stirring. The solution
immediately changed from yellow to colourless. At this point,
the IR spectrum (in thf) showed the complete disappearance of
3084
J. Chem. Soc., Dalton Trans., 1998, 3079–3086

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Ϫ101.76 (m, 2Fortho). 13C-{1H}NMR (CDCl3): δ 9.80 (s, CH3),
104.78 (s, C5Me5) and 190.58 (s, CO). Mass spectrum (EI, based
on 187Re and 35Cl): m/z 580 (Mϩ), 552 (Mϩ Ϫ CO) and 524
(Mϩ Ϫ 2CO) (Found: C, 37.40; H, 2.71. Calc. for C18H15-
ClF5O2Re: C, 37.28; H, 2.61%).
Ϫ155.52 (t, JFF 20.1 Hz, Fpara) and Ϫ101.39 (m, 2Fortho).
13C-{1H}NMR (CDCl3): δ 9.51 (s, CH3), 10.09 (CH3), 37.17 (s,
CH2), 97.56 (s, C5Me4CH2Cl), 105.78 (s, C5Me4CH2Cl),
107.37 (s, C5Me4CH2Cl) and 188.81 (s, CO). Mass spectrum
(EI, based on 187Re and 35Cl): m/z 614 (Mϩ), 586 (Mϩ Ϫ CO)
and 558 (Mϩ Ϫ 2CO) (Found: C, 34.66; H, 2.22. Calc. for
C18H14Cl2F5O2Re: C, 35.19; H, 2.30%).
cis-[Re(ç5-C5Me5)(CO)2(C6F5)Br] cis-4b. The fulvene com-
plex 1a (60 mg, 0.110 mmol) in thf (15 cm3) was stirred at 5 ЊC
with an excess of aqueous HBr (47%, 0.4 cm3, 3.48 mmol). The
reaction was followed by IR spectroscopy until all the fulvene
complex had reacted (ca. 2.5 h). The thf was pumped off and
the reddish oily residue was dissolved in CH2Cl2 (5 cm3) and
treated with a 5% aqueous solution (10 cm3) of Na2CO3. The
organic layer was separated, dried over anhydrous Na2SO4 and
filtered. The solution was reduced to about 3 cm3 under vacuum
and a layer of hexanes poured slowly into the flask. The com-
plex cis-4b (56 mg, 81%) was isolated as red crystals, mp 194 ЊC
(decomp.). IR [CH2Cl2, ν˜(CO)/cmϪ1]: 2032vs and 1958s. 1H
NMR (CDCl3): δ 2.12 (s, CH3). 19F NMR (CDCl3): δ Ϫ163.96
(m, 2Fmeta), Ϫ160.24 (t, JFF 20.1 Hz, Fpara) and Ϫ107.46 (br s,
2Fortho). 13C-{1H}NMR (CDCl3): δ 11.01 (s, CH3), 107.70 (s,
C5Me5), 198.13 (s, CO) and 201.40 (s, CO). Mass spectrum
(EI, based on 187Re and 79Br): m/z 624 (Mϩ), 596 (Mϩ Ϫ CO)
and 568 (Mϩ Ϫ 2CO) (Found: C, 34.82; H, 2.48. Calc. for
C18H15BrF5O2Re: C, 34.62; H, 2.42%).
trans-[Re(ç5-C5Me4CH2Br)(CO)2(C6F5)Br] 5b. To a solution
of the fulvene complex 1a (70 mg, 0.128 mmol) in hexanes (30
cm3) was added a solution (6.6 cm3) prepared by dissolving Br2
(0.1 cm3) in hexanes (10 cm3). After 5 min of stirring at room
temperature an orange precipitate started to form, and an IR
spectrum of the supernatant showed only the presence of the
product. The solution was evaporated to dryness under
vacuum, and the residual orange solid was dissolved in the
minimum amount of CH2Cl2 and crystallized by layer diffusion
of hexanes into this solution. Complex 5b was obtained as a red
crystalline solid (89 mg, 98%), mp 178 ЊC (decomp.). IR
1
[CH2Cl2, ν˜(CO)/cmϪ1]: 2053vs and 1986vs. H NMR (CDCl3):
δ 1.89 (s, 6 H, CH3), 1.93 (s, 6 H, CH3) and 4.07 (s, 2 H, CH2).
19F NMR (CDCl3): δ Ϫ161.60 (m, 2Fmeta), Ϫ155.64 (t, JFF 20.3
Hz, Fpara) and Ϫ101.95 (m, 2Fortho). 13C-{1H}NMR (CDCl3):
δ 10.10 (s, CH3), 10.48 (s, CH3), 24.36 (s, CH2), 97.24
(s, C5Me4CH2Br), 104.86 (s, C5Me4CH2Br), 106.86 (s, C5Me4-
CH2Br) and 187.14 (s, CO). Mass spectrum (EI, based on 187Re
and 79Br): m/z 704 (Mϩ), 676 (Mϩ Ϫ CO) and 648 (Mϩ Ϫ 2CO)
(Found: C, 30.60; H, 1.98. Calc. for C18H14Br2F5O2Re: C, 30.73;
H, 1.99%).
trans-[Re(ç5-C5Me5)(CO)2(C6F5)Br] trans-4b. This complex
was prepared using a similar procedure to that used for cis-4b,
but the reaction mixture was stirred at room temperature for 4.5
h. The complex trans-4b (60 mg, 87%) was isolated as orange-
reddish needles after crystallization from hexanes at Ϫ18 ЊC,
mp 174 ЊC (decomp.). IR [CH2Cl2, ν˜(CO)/cmϪ1]: 2045s and
1974vs. 1H NMR (CDCl3): δ 1.89 (s, CH3). 19F NMR (CDCl3):
δ Ϫ162.42 (m, 2Fmeta), Ϫ156.78 (t, JFF 20.3 Hz, Fpara) and
Ϫ102.29 (m, 2Fortho). 13C-{1H}NMR (CDCl3): δ 10.30 (s, CH3),
104.24 (s, C5Me5) and 189.04 (s, CO). Mass spectrum (EI, based
on 187Re and 79Br): m/z 624 (Mϩ), 596 (Mϩ Ϫ CO) and 568
(Mϩ Ϫ 2CO) (Found: C, 34.83; H, 2.40. Calc. for C18H15-
BrF5O2Re: C, 34.62; H, 2.42%).
trans-[Re(ç5-C5Me4CH2I)(CO)2(C6F5)I] 5c. This complex was
prepared in a similar way to that of 5b, adding I2 (23.3 mg,
0.092 mmol) to a solution of the fulvene complex 1a (50 mg,
0.092 mmol), but the resulting solution was stirred at room
temperature for 2 h. Complex 5c was isolated as dark red crys-
tals in 95% yield, mp 192 ЊC (decomp.). IR [CH2Cl2, ν˜(CO)/
1
cmϪ1]: 2038vs and 1973vs. H NMR (CDCl3): δ 1.98 (s, 6 H,
CH3), 2.02 (s, 6 H, CH3) and 3.99 (s, 2 H, CH2). 19F NMR
(CDCl3): δ Ϫ161.77 (m, 2Fmeta), Ϫ155.94 (tt, JFF 20.4, 2.3
Hz, Fpara) and Ϫ103.14 (m, 2Fortho). 13C-{1H}NMR (CDCl3):
δ Ϫ3.06 (s, CH2), 11.25 (s, CH3), 11.44 (s, CH3), 98.41 (s,
C5Me4CH2I), 102.89 (s, C5Me4CH2I), 105.80 (s, C5Me4CH2I)
and 185.80 (s, CO). Mass spectrum (EI, based on 187Re): m/z
798 (Mϩ), 770 (Mϩ Ϫ CO) and 671 (Mϩ Ϫ I) (Found: C, 27.17;
H, 1.71. Calc. for C18H14F5I2O2Re: C, 27.10; H, 1.76%).
trans-[Re(ç5-C5Me5)(CO)2(C6F5)I] trans-4c. To a solution of
the fulvene complex 1a (60 mg, 0.11 mmol) in thf (15 cm3) was
added an aqueous HI solution (67%, d = 1.97 g cmϪ3; 0.4 cm3,
4.12 mmol). The mixture was stirred at room temperature for 3
h in the dark. Following the same purification procedures to
those described previously, trans-4c (60 mg, 81%) was isolated
as red needles, mp 203 ЊC (decomp.). IR [CH2Cl2, ν˜(CO)/cmϪ1]:
2034s and 1968vs. 1H NMR (CDCl3): δ 2.01 (s, CH3). 19F NMR
(CDCl3): δ Ϫ162.51 (m, 2Fmeta), Ϫ156.97 (tt, JFF 20.2, JFF 2.0
Hz, Fpara) and Ϫ103.24 (m 2Fortho). 13C-{1H}NMR (CDCl3):
δ 11.33 (s, CH3), 103.38 (s, C5Me5) and 187.61 (s CO). Mass
spectrum (EI, based on 187Re): m/z 672 (Mϩ), 644 (Mϩ Ϫ CO)
and 616 (Mϩ Ϫ 2CO) (Found: C, 32.68; H, 2.03. Calc. for
C18H15F5IO2Re: C, 32.20; H, 2.25%).
[Re(ç5-C5Me5)(CO)2(C6F5)(NCMe)]؉[BF4]؊ 6. To a solution
of complex 1a (117 mg, 0.215 mmol) in MeCN (12 cm3), was
added HBF4 (1.7 cm3, 0.215 mmol) in MeCN [prepared by
dilution of 0.25 cm3 of HBF4 in Et2O (54%, d = 1.19 g cmϪ3)].
The mixture was stirred at room temperature for 7 h. After this
time it had changed from yellow to orange and the IR
spectrum, in MeCN, showed only the presence of two strong
absorptions at 2062 and 1982 cmϪ1, a shoulder at about 2075
cmϪ1 and a medium intensity band at 2006 cmϪ1. The solvent
was pumped off and the residual orange solid crystallized from
MeCN–Et2O at Ϫ10 ЊC to give a 2:1 mixture of cis and trans
isomers of 6 as orange needles (82%) (Found: C, 34.15; H,
2.65. Calc. for C20H18BF9NO2Re: C, 34.10; H, 2.58%). Mass
spectrum [FAB(ϩ), based on 187Re]: m/z 586.
trans-[Re(ç5-C5Me4CH2Cl)(CO)2(C6F5)Cl] 5a. To a solution
of the fulvene complex 1a (60 mg, 0.11 mmol) in hexanes (25
cm3) were added 5 drops of a saturated solution of Cl2 in
hexanes and the mixture stirred at room temperature for 5 min.
After this time the IR spectrum showed the complete dis-
appearance of the starting complex. The resulting solution was
evaporated to dryness under vacuum and the yellow greenish
residue was chromatographed on neutral alumina. A yellow
band was eluted with hexane–CH2Cl2 (9:1) from which 5a, an
orange yellowish solid, was obtained after solvent evaporation
(39 mg, 57% yield, mp 171 ЊC (decomp.)). A greenish brown
material remained irreversibly adsorbed on the top of the
column. IR [CH2Cl2, ν˜(CO)/cmϪ1]: 2060vs and 1992vs. 1H
NMR (CDCl3): δ 1.84 (s, 6 H, CH3), 1.88 (s, 6 H, CH3) and 4.18
(s, 2 H, CH2). 19F NMR (CDCl3): δ Ϫ161.51 (m, 2Fmeta),
cis-6. IR [MeCN, ν˜(CO)/cmϪ1]: 2062vs and 1982vs. 1H NMR
(CD3CN): δ 2.23 (s, 15 H, CH3) and 2.67 (s, 3 H, CH3CN). 19
F
NMR (CD3CN): δ Ϫ161.55 (m, 2Fmeta), Ϫ156.54 (tt, JFF 19.5,
1.8 Hz, Fpara), Ϫ149.81, (s, BF4Ϫ) and Ϫ106.50 (m, 2Fortho). 13C-
{1H} NMR (CD3CN): δ 4.48 (s, CH3CN), 10.00 (s, CH3),
105.12 (t, JCF 40, Cipso C6F5), 110.77 (s, C5Me5), 133.72 (s,
CH3CN), 139.80 (d, JCF 250, C6F5), 149.20 (d, JCF 228, C6F5),
151.00 (d, JCF 234, C6F5), 194.64 (s, CO) and 196.61 (t, JCF 3.3
Hz, CO).
trans-6. IR [MeCN, ν˜(CO)/cmϪ1]: 2074m and 2006s. 1H
J. Chem. Soc., Dalton Trans., 1998, 3079–3086
3085

View Article Online
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NMR (CD3CN): δ 2.01 (s, 15 H, CH3) and 3.00 (s, 3 H,
CH3CN). 19F NMR (CD3CN): δ Ϫ160.03 (m, 2Fmeta), Ϫ154.34
(tt, JFF 19.6, 2.9 Hz, Fpara), Ϫ149.81, (s, BF4Ϫ) and Ϫ99.83
(m, 2Fortho). 13C-{1H}NMR (CD3CN): δ 5.35 (s, CH3CN), 9.46
(s, C5Me5), 96.61 (t, JCF 38, Cipso C6F5), 107.98 (s, C5Me5),
137.43 (s, MeCN), 188.83 (t, JCF 6.4 Hz, CO), and CF aromatic
groups not observed.
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Crystallography
Small orange crystals of trans-[Re(η5-C5Me4CH2Br)(CO)2-
(C6F5)Br] 5b suitable for X-ray diffraction were obtained by
recrystallization from hexane at 273 K. A single crystal was
mounted on a glass fiber in epoxy cement. Intensity data were
collected at 293(2) K on a Siemens R3m diffractometer
equipped with
a graphite monochromator and Mo-Kα
(λ = 0.71073 Å) radiation, by the ω–2θ scan technique. The unit
cell parameters were determined by least-squares refinement of
25 centred reflections. Intensities were corrected for Lorentz-
polarization effects, and a semiempirical absorption correction
(ψ scan) was also applied. Two standard reflections were
monitored every 98, and showed no systematic changes.
The structure was solved by direct methods and subsequent
Fourier difference syntheses. It was refined by full-matrix least
squares on F 2, with anisotropic thermal parameters for all
non-hydrogen atoms. The hydrogen atoms were placed in ideal
positions [d(C᎐H) = 0.96 Å] and allowed to ride on their
corresponding carbon atoms. In all cases an isotropic displace-
ment parameter 1.3 times larger than that of the host was used.
The largest peak of 1.7 e ÅϪ3 was located at 1.5 Å from the
rhenium atom, and has no chemical significance.
Computer programs used in this study were SHELXL 97 and
SHELXLTL PC software packages.32,33 Table 2 summarizes the
crystal data and data collection conditions.
CCDC reference number 186/1082.
See http://www.rsc.org/suppdata/dt/1998/3079/ for crystallo-
graphic files in .cif format.
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28 M. Ballhorn, M. G. Partridge, R. N. Perutz and M. K. Whittlesey,
Chem. Commun., 1996, 961.
Acknowledgements
We would like to thank Universidad Catolica de Valparaiso
(DGIP 125782-97) and FONDECYT-Chile for financial
support (grants 1960383 and 7960007). The York group
acknowledges the support of EPSRC. B. O. acknowledges
Fundacion Andes for a Doctoral fellowship.
29 R. B. King and R. H. Reimann, Inorg. Chem., 1976, 15, 179; R. B.
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Paper 8/02899K
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J. Chem. Soc., Dalton Trans., 1998, 3079–3086