The synthesis and X-ray crystal structure of[(4-ferrocenylphenyl-imido)]trichlorobis(triphenylphosphine)rhenium(V) and related ferrocenyl-rhenium(V) compounds

Article abstract of DOI:10.1039/b102372c

The reaction of 4-ferrocenylaniline with trans-[ReOCl₃(PPh₃)₂] gave [(4-ferrocenylphenylimido)]trichlorobis-(triphenylphosphine)rhenium(V) (1). The molecular structure of 1 has been determined by X-ray diffraction. The X-ray crystal structure of [(4-ferrocenylphenylimido)]tribromobis(triphenylphosphine)rhenium(V) (2) has also been determined and its molecular structure is compared with that of 1. The complexes 1 and 2 have also been investigated by cyclic voltammetry and UV-visible spectroscopy. The results of the cyclic voltammetry suggest that there is insignificant electron delocalization from the ferrocenyl group towards rhenium in 1 and 2. However, both 1 and 2 show a long wavelength absorption in their electronic spectra which is characteristic of conjugated ferrocenyl derivatives. The synthesis and characterization of two further similar imido-complexes but in which the ferrocenyl-phenyl group is part of a more extended unit is described (complexes 5 and 6). The synthesis of a rhenium oxo-complex,fac-oxotrichloro[1,1′-bis(diphenylphosphine) ferrocene]rhenium(V) (3) has also been achieved and 3 has been further derivatized with two different ferrocenylamines to provide rhenium complexes containing two ferrocenyl groups (4 and 7).

Full text of DOI:10.1039/b102372c

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The synthesis and X-ray crystal structure of [(4-ferrocenylphenyl-
imido)]trichlorobis(triphenylphosphine)rhenium(V) and related
ferrocenyl–rhenium(V) compounds†
Christopher Imrie,*‡a Jonathan R. Dilworth,b Yifan Zheng,b Abubak’r Abrahams,c
Thomas I. A. Gerbera and Vincent O. Nyamoria
a Department of Chemistry, University of Port Elizabeth, PO Box 1600, Port Elizabeth 6000,
South Africa. E-mail: chacci@upe.ac.za
b Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford,
UK OX1 3QR
c Department of Chemistry, Vista University Port Elizabeth, Private Bag X613,
Port Elizabeth 6000, South Africa
Received 13th March 2001, Accepted 19th June 2001
First published as an Advance Article on the web 30th August 2001
The reaction of 4-ferrocenylaniline with trans-[ReOCl3(PPh3)2] gave [(4-ferrocenylphenylimido)]trichlorobis-
(triphenylphosphine)rhenium() (1). The molecular structure of 1 has been determined by X-ray diffraction.
The X-ray crystal structure of [(4-ferrocenylphenylimido)]tribromobis(triphenylphosphine)rhenium() (2) has
also been determined and its molecular structure is compared with that of 1. The complexes 1 and 2 have also
been investigated by cyclic voltammetry and UV-visible spectroscopy. The results of the cyclic voltammetry
suggest that there is insignificant electron delocalization from the ferrocenyl group towards rhenium in 1 and 2.
However, both 1 and 2 show a long wavelength absorption in their electronic spectra which is characteristic of
conjugated ferrocenyl derivatives. The synthesis and characterization of two further similar imido-complexes
but in which the ferrocenyl-phenyl group is part of a more extended unit is described (complexes 5 and 6). The
synthesis of a rhenium oxo-complex, fac-oxotrichloro[1,1Ј-bis(diphenylphosphine)ferrocene]rhenium() (3) has
also been achieved and 3 has been further derivatized with two different ferrocenylamines to provide rhenium
complexes containing two ferrocenyl groups (4 and 7).
Introduction
The current interest in organometallic compounds in the field
of new materials for applications in 21st century technology is
significant and developments in ferrocene and metallocene
chemistry are leading the way in this respect.1 We are interested
in the design of ferrocenomesogens with new interesting shapes
and structures, especially ones in which the ferrocenyl group is
at the terminal position in a molecule.2 The molecules in the
first series of ferrocenomesogens reported by us incorporated a
terminal ferrocenyl group onto a rod-like organic core and the
compounds are represented by the general structure shown in
Fig. 1.2 Recently we have become interested in the effect of
introducing a second metal into such a molecule, in which the
second metal is in conjugation with the ferrocenyl group. Here,
we report on the synthesis and X-ray crystal structure deter-
mination of [(4-ferrocenylphenylimido)]trichlorobis(triphenyl-
phosphine)rhenium() (1) which is one of the first examples
of an imido-rhenium() complex with an appended organo-
metallic group. We also report on the X-ray crystal structure of
[(4-ferrocenylphenylimido)]tribromobis(triphenylphosphine)-
rhenium() (2) and on the synthesis and structure of a
ferrocenyl–rhenium oxo-compound, fac-oxotrichloro(1,1Ј-bis-
(diphenylphosphine)ferrocene)]rhenium() (3). Furthermore,
Fig. 1 General structure representing the first series of ferroceno-
mesogens prepared by Imrie and Loubser.
we report on the reaction of two different ferrocenylamines
with 3 to provide ferrocenyl–rhenium complexes containing
two ferrocenyl groups (compounds 4 and 7). Finally, the syn-
theses of a further two compounds similar to 1 but in which
the ferrocenyl ligand is part of a more extended structure are
reported (compounds 5 and 6).
A number of reports have been published on the synthesis
and structure of arylimido-complexes of rhenium().3 The
majority of these studies are concerned with the chemistry
of [(phenylimido)]trichlorobis(triphenylphosphine)rhenium(),
and the others with compounds containing simple substituents
at the para position in the phenyl group. Interest in these com-
pounds stems from their potential use either as metathesis
catalysts or therapeutic radiopharmaceuticals. There are a
number of examples of rhenium complexes with ferrocenyl
ligands in the literature4 but most involve low oxidation state
Re() carbonyl compounds with ferrocenylphosphine ligands.
For example, the structures of the compounds [Fe(C5H4PPh2)2-
Re(CO)3Cl] (8) and fac-[(FeC5H4PPh2)2Re(CO)3Cl] (9) have
† Electronic supplementary information (ESI) available: spectroscopic
details for starting materials; Re᎐O bond distances in compounds
᎐
of the type ReOCl3(PR3)2. See http://www.rsc.org/suppdata/dt/b1/
b102372c/
‡ Part of this work was carried out by Dr Imrie during his visit to the
ICL, Oxford.
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J. Chem. Soc., Dalton Trans., 2001, 2624–2633
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b102372c

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Results and discussion
Preparation of [(4-ferrocenylphenylimido)]trichlorobis(triphenyl-
phosphine)rhenium(V)
[(4-Ferrocenylphenylimido)]trichlorobis(triphenylphosphine)-
rhenium() 1 was synthesized by reacting 1.5 equivalents of
4-ferrocenylaniline
with
trans-oxotrichlorobis(triphenyl-
phosphine)rhenium() in benzene (Scheme 1). Compound 1 was
Scheme 1 Preparation of complex 1.
readily purified by passing it through a column of silica gel. The
compound eluted with diethyl ether as a red band but on
removing the solvent, a blue-green solid was obtained. The
blue-green solid exhibited a low solubility in diethyl ether but
was readily soluble in dichloromethane. The blue-red colour
interchange was observed when running 1 on a tlc plate. On
elution of the initial dark-blue/green spot with diethyl ether,
it rapidly turned red and returned to green again after evap-
oration of the diethyl ether. Compound 1 was characterized
1
by H, 13C and 31P NMR spectroscopy as well as by IR and
FAB mass spectrometry. The NMR data for 1 are consistent
with its structure and are discussed more fully below. The IR
spectrum contains a band at 1092 cmϪ1 which falls in the range
for a Re᎐N bond.
᎐
X-Ray crystal structure of trans-[(4-ferrocenylphenylimido)]-
trichlorobis(triphenylphosphine)rhenium(V) (1)
Suitable crystals of 1ؒCH2Cl2 were grown by slow evaporation
of a solution in dichloromethane–hexane. The ZORTEP struc-
ture of 1 is shown in Fig. 2 and the packing diagram is shown
in Fig. 3. A selection of bond lengths and angles are provided
in Table 1. The coordination geometry around the rhenium
atom is distorted octahedral. The chloride ligands are in a
meridional-configuration and the triphenylphosphine ligands
are trans. The ligand arrangement around the rhenium is
consistent with the spectroscopic data for 1 in solution. The
Re–N bond length in 1 is 1.724(18) Å. It is interesting to
compare this value with the Re–N bond lengths for similar
compounds in which the ferrocenyl unit is replaced by other
substituents (Table 2). The range of substituents at the para
position is rather limited but they cover the spectrum from
electron-releasing groups through to an electron-withdrawing
group. The variation in Re–N bond length with substituent
shows little clear evidence for any imido substituent effect.
Chatt et al.7 investigated the dipole moments of a series of
arylimido-complexes of rhenium and developed an argument
that an electron-releasing group para to the nitrogen in this
type of system can be expected to cause a drift of electrons
towards the nitrogen, and this in turn should lead to an
enhanced interaction of the nitrogen lone pair electrons with
the d-orbitals of the rhenium atom. This should however be
reflected in the Re–N bond length with an expectation that as
the substituent becomes a more efficient electron-donor, the
rhenium–nitrogen bond should take on a greater triple bond
character and so should become considerably shorter.
been determined by X-ray crystallography.4a An exception is the
Re(v) complex [ReO(L)(PPh3)][PF6] (H2L = 1,6-diferrocenyl-
N,NЈ-bis(2-hydroxypropyl)-2,5-diazahexane.4e
Recently, Knoesen et al.5 have published work on ferrocenyl
ligands in mixed valence high-oxidation state rhenium com-
plexes. As part of their paper, the synthesis and X-ray crystal
structure determination of compound 3 is also described. The
crystal structure of the phenylimido derivative of compound 3
has been described recently by Lee and Choi.6
The extent to which electron density is removed from
the ferrocenyl group manifests itself as a distinct trend in the
J. Chem. Soc., Dalton Trans., 2001, 2624–2633
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Table 1 Selected bond lengths (Å) and bond angles (Њ) for compounds
1 and 2
Compound 1
Compound 2
Re–N
1.724(18)
2.413(5)
2.434(5)
2.397(6)
2.497(6)
2.483(7)
1.350(3)
1.820(2)
1.420(3)
1.340(3)
1.390(3)
1.450(3)
Re–N
1.721(4)
2.5561(5)
2.5884(5)
2.5649(5)
2.4963(13)
2.4925(13)
1.351(3)
1.839(5)
1.386(7)
1.376(7)
1.383(8)
1.459(7)
Re–Cl1
Re–Cl2
Re–Cl3
Re–P1
Re–Br1
Re–Br2
Re–Br3
Re–P1
Re–P2
Re–P2
N–C71
P1–C31
C71–C72
C72–C73
C73–C74
CO–C74
N–C71
P1–C31
C71–C72
C72–C73
C73–C74
CO–C74
N–Re–Cl3
N–Re–Cl1
Cl3–Re–Cl2
Cl1–Re–Cl2
N–Re–P (2)
175.1(5)
93.5(5)
84.7(2)
176.0(2)
95.5(6)
N–Re–Br3
N–Re–Br1
Br3–Re–Br2
Br1–Re–Br2
N–Re–P2
173.95(13)
93.50(13)
85.059(18)
177.601(18)
95.16(13)
Fig. 2 Molecular structure of 1 with numbering scheme.
Table 2 Re–N bond distances (Å) in compounds of the type [ReCl3-
(NC6H4X)(PR3)2]
R
X
Re–N
Ref.
Ph
Et2Ph
Ph
CH3
Ph
Et2Ph
OCH3
Ferrocenyl
OCH3
H
H
CH2CH2CH2CO2CH2CH3
COCH3
H
1.724(18)
1.709(4)
1.726(6)
1.711(6)
1.713(4)
1.690(5)
1.710(8)
This work
3a
3b
3c
3d
3a
3c
Fig. 3 Packing diagram for compound 1.
1H chemical shifts of the C5H4 protons. Selected values of
the chemical shifts obtained from some ferrocenylphenyl-
derivatives prepared by us (10) in other work2c are given in
Fig. 4 together with ferrocenylphenyl-derivatives prepared by
other workers (11 and 12) and help to illustrate this point,
and make an interesting comparison with compound 1. Com-
pounds having the general structures 10, 11 and 12 have a
number of common features. Firstly, each contains a ferro-
cenylphenyl group to which is attached an electron-withdrawing
group. Secondly, the chemical shift values of the Cp protons for
these molecules are remarkably similar (α-Hs all in the range
4.69–4.77). Compounds 11 and 12 exhibit significant non-linear
optical activity arising from the asymmetric charge distribution
along the molecular framework, electrons flowing from
the ferrocenyl group towards the 4-nitrophenyl group.8 If the
electron-withdrawing substituents on compounds 11 and 12 are
replaced with groups such as amino and methoxy which donate
electrons into the aromatic ring, the chemical shifts for the α-Hs
on the Cp ring fall to 4.54 ppm and 4.58 ppm respectively. In
comparison, the chemical shift value of the α-Hs in 1 (4.61
ppm) is similar to the situation where we have an electron-
Fig. 4 Selected 1H chemical shift values for some ferrocenylphenyl
derivatives.
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J. Chem. Soc., Dalton Trans., 2001, 2624–2633

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donating group attached to the ferrocenylphenyl unit. The
NMR results provide no evidence therefore for significant
electron flow from the ferrocenyl unit towards the rhenium
metal. If delocalization in the sense Fe
Re was significant
this should also be reflected in the X-ray crystal structure in that
the phenyl ring next to the ferrocenyl group would tend towards
a cyclohexadienyl structure which should lead to a reasonable
reduction in bond length between C73–C72 and C75–C76.
There are however no significant bond length differences in the
linking phenyl group.
The ferrocenylphenyl imido group has a linear Re–N–C
system indicative of formal donation of four electrons from the
imido group. The angles N–Re–Cl3 (175.1Њ) and Cl1–Re–Cl2
(176.0Њ) deviate only marginally from the ideal linear arrange-
ment. The Re–Cl bond distances in positions trans and cis
to the imido ligand do not show significant differences. The
Re–Cl bond (mean 2.415 Å) and the Re–P bond distances in
1 (mean 2.490 Å) are also closely similar to those of related
compounds.3
The packing diagram of 1 (Fig. 3) clearly shows the presence
of dichloromethane in the crystal lattice and the NMR results
confirm its presence. The closest atomic distance between
the carbon atom of the solvent (C14) and 1 is to C66, but
this is 3.73 Å. The solvent resides in cavities in the crystal
lattice.
Fig. 5 Molecular structure of 2 with numbering scheme.
found wide application in organic synthesis (in cross-coupling
reactions for example), coordination chemistry and catalysis.1
Preparation of trans-[(4-ferrocenylphenylimido)]tribromo-
bis(triphenylphosphine)rhenium(V) (2)
Preparation of fac-oxotrichloro[1,1Ј-bis(diphenylphosphine)-
ferrocene]rhenium(V)
Compound 2 was synthesized in a similar fashion to 1,
replacing trans-oxotrichlorobis(triphenylphosphine)rhenium()
by the bromo-equivalent. The reaction between 4-ferrocenyl-
aniline and trans-[ReOBr3(PPh3)2] was appreciably slower than
that for compound 1 indicating that the less electronegative
and more bulky bromine atoms exert a retarding effect on the
reaction. As with compound 1, 2 was purified by passing it
through a column of silica gel. It was eluted with diethyl ether
as a red band and this again yielded a blue-green solid after
evaporation of the solvent. The solubility characteristics of 2
were similar to those of 1. It was very soluble in cold dichloro-
methane but relatively insoluble in cold diethyl ether. This solu-
bility trend was however reversed on the silica gel column; elution
of 2 occurred readily with diethyl ether and hardly at all with
dichloromethane. It is interesting to compare the 1H NMR
spectrum of 2 with that of 1. The chemical shift values of the
cyclopentadienyl protons for both complexes are very similar
indicating that the resonances of the cyclopentadienyl protons
are not very sensitive to alterations in the electronic environ-
ment around the rhenium. This can be contrasted with the
effects of the ligand exchange on the resonances of the aromatic
phenyl moiety in the ferrocenylphenyl group [6.83 and 6.78 ppm
(2 × d) for 1 versus a singlet at 6.70 ppm for 2].
The reaction of 1,1Ј-bis(diphenylphosphine)ferrocene with
ammonium perrhenate in the presence of HCl provided fac-
oxotrichloro[1,1Ј-bis(diphenylphosphine)ferrocene]rhenium()
3 in good yield as dark green crystals. Alternatively, 3 was
also obtained by the reaction of 1,1Ј-bis(diphenylphosphine)-
ferrocene with [ReOCl3(PPh3)2]. This method is similar to the
one recently described by Knoesen et al.5 except that in our
method, heating the reaction is avoided. This reaction has been
repeated several times and yields have been consistently high (in
the range 80–90%) compared to the low yield reported by
Knoesen et al. (36%). It is also interesting to compare the NMR
data obtained for 3 by us with that obtained by Knoesen et al.
In our case, the 31P chemical shift in CDCl3 is at Ϫ25.32 ppm
whereas Knoesen et al. report a 31P chemical shift at 20.7 ppm
in acetone-d6. The IR spectrum for 3 shows a strong band at
960 cmϪ1 which is indicative of the Re᎐O bond (Re᎐O bond
᎐
᎐
distances in compounds of the type ReOCl3(PR3)2 available in
ESI†).
The reaction of 3 with 4-ferrocenylaniline provided the
imido-compound 4 containing two ferrocenyl groups. This
compound was again easily purified by passing it through a
column of silica gel. Attempts to grow crystals of this material
suitable for X-ray analysis have so far failed. The infrared spec-
trum of the compound shows a band at 1087 cmϪ1 indicative of
X-Ray crystal structure of trans-[(4-ferrocenylphenylimido)]-
tribromobis(triphenylphosphine)rhenium(V) (2)
the Re᎐N bond. The NMR spectra of the compound (1H, 31P)
᎐
Suitable crystals of 2ؒCH2Cl2 were again grown using the
solvent combination dichloromethane–hexane. The ZORTEP
structure of 2 is shown in Fig. 5. A selection of bond lengths
and angles are provided in Table 1. A comparison of the bond
lengths and angles for 2 with those of 1 indicates that
exchanging the chloro substituents for bromo substituents
has little effect on the overall geometry of the molecule.
Compounds 1 and 2 were prepared from the respective
trans-oxotrihalobis(triphenylphosphine)rhenium() derivatives.
[ReOCl3(PPh3)2] has been used extensively in the preparation of
rhenium() compounds and in the preparation of rhenium
compounds in other oxidation states.9 In view of our interest
in ferrocenyl–rhenium compounds, it was decided to replace
the two triphenylphosphine ligands in [ReOCl3(PPh3)2] by 1,1Ј-
bis(diphenylphosphine)ferrocene (dppf ), a compound that has
are consistent with its structure.
Preparation of complexes 5 and 6
With a view to synthesizing ferrocenomesogens containing the
terminal rhenium moiety, complexes 5 and 6 were synthesized,
in which the section of the complex containing the ferrocenyl-
phenyl unit was extended. For complex 5, 4-ferrocenylbenzoic
acid was coupled with 4-nitrophenol using dicyclohexylcarbo-
diimide (DCC) and the resulting nitro derivative was reduced to
the amine using catalytic hydrogenation. The amine was reacted
with trans-oxotrichlorobis(triphenylphosphine)rhenium() in
benzene in a similar fashion as for the synthesis of 1. The
product was again purified by column chromatography on silica
gel and in this case, the colour of the product was noticeably
J. Chem. Soc., Dalton Trans., 2001, 2624–2633
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Scheme 2 Preparation of complex 6.
different to that of 1 and 2, being a yellow-brown colour as
compared to a blue-green colour. Complex 5 was characterized
1
by H, 13C and 31P NMR spectroscopy and by IR and FAB
mass spectrometry and the data are consistent with its struc-
ture. The melting behaviour of 5 was normal and no liquid
crystal phases were observed during the heating or cooling of
the molecule.
We considered that it could be of interest to invert the ester
functional group in complex 5 since this should give rise to a
different electron flow along the molecule. To this end, 4-ferro-
cenylphenol was coupled with 4-nitrobenzoic acid again using
DCC and the resulting nitro derivative was reduced to the amine
using catalytic hydrogenation. Attempted reaction of the amine
with
trans-oxotrichlorobis(triphenylphosphine)rhenium()
failed and only the starting materials were recovered after
several hours of heating the mixture under reflux in benzene.
Reversal of the ester grouping would clearly make the amine
funtionality less nucleophilic and hence less reactive but the
total lack of reactivity was a surprise. The synthesis of complex
6 is outlined in Scheme 2. 4-Ferrocenylbenzoic acid was coupled
with 4-hydroxy-4Ј-nitrobiphenyl using typical DCC conditions.
The nitro compound was obtained in very good yield and was
then reduced to the amine using catalytic hydrogenation. The
nitro derivative decomposed before melting at temperatures
above 260 ЊC. The amine melted at 235 ЊC and did not show any
abnormal melting characteristics on the heating cycle. On the
cooling cycle however, it appeared to exhibit a very short liquid
crystal phase just at the point of crystallization. Reaction of
the amine with trans-oxotrichlorobis(triphenylphosphine)-
rhenium() in benzene provided complex 6 in a low yield. The
complex was characterized by 1H, 13C, 31P NMR spectroscopy,
IR and FAB mass spectrometry. Again the complex exhibited
normal melting behaviour. Future studies will investigate the
effect of introducing extended alkyl chains into the tertiary
phosphine groups around rhenium.
Fig. 6 UV-Visible spectra for ferrocenyl derivatives.
Electronic spectral studies
Electronic spectra were recorded in dichloromethane solu-
tion for complexes 1, 2 and 5 and data are presented in Table 3
along with data for simple monoferrocenes. The spectra are
represented graphically in Fig. 6. There is a marked batho-
chromic shift of the longer wavelength absorption on increasing
the resonance interaction or electron flow from the ferrocenyl
moiety. This is highlighted by comparing the results for
4-ferrocenylaniline and 4-nitrophenylferrocene. The longer
wavelength absorptions are 449 nm (356 molϪ1 dm3 cmϪ1) and
510 nm (2073 molϪ1 dm3 cmϪ1) respectively. This type of reson-
ance interaction of ferrocene with substrates has been observed
before with for example ferrocenylazobenzenes.10 Complexes
1 and 2 show a long wavelength absorption at 577 nm and
589 nm respectively clearly suggesting a strong resonance
effect from the ferrocenyl group towards rhenium. It is interest-
ing to compare the spectra of 1 and 2 with that of 5. In 5, the
conjugation from the ferrocenyl group towards rhenium
is disrupted by the introduction of the ester group and this is
Fig. 7 Cyclic voltammograms of (i) FcC6H4NH2-4, Fc = ferrocenyl,
(ii) 1 and (iii) [ReCl3(NC6H4CO2Me)(PPh3)2].
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Table 3 Electronic spectra of compounds 1, 2 and 5 compared with those of simple ferrocenes
Compound
Structure of compound
λmax/nm (εmax/molϪ1 dm3 cmϪ1
)
328 (47), 444 (72)
450 (182)
406 (1918), 510 (2073)
449 (356)
1
2
5
388 (22 483), 577 (5695)
394 (14 201), 589 (4593)
462 (192)
Table 4 Cyclic voltammetry dataa
Re centred process
Complex
Fe centred process/V
Oxidationb/V
Reductionb/V
[(C5H5)2Fe]
[(C5H5)Fe(C5H4C6H4NH2-4)]
[(C5H5)Fe(C5H4C6H4NO2–4)]
[ReCl3(NPh)(PPh3)2]
[ReCl3(NC6H4COOMe-4)(PPh3)2]
[ReCl3(NC6H4Fc)(PPh3)2] 1
[ReBr3(NC6H4Fc)(PPh3)2] 2
ϩ0.44r
ϩ0.33r
ϩ0.58r
—
—
ϩ0.40r
ϩ0.40r
—
—
—
—
—
—
Ϫ1.23i
Ϫ0.91i
Ϫ1.27i
Ϫ1.24i
ϩ0.86qr
Not observed
ϩ0.89qr
ϩ0.87qr
a Recorded in dichloromethane with a vitreous carbon working electrode, 0.2 M tetrabutylammonium tetrafluoroborate as supporting electrolyte,
scan rate 0.4 V sϪ1
processes.
.
b Potentials quoted relative to SCE, r = reversible, qr = quasi reversible, i = irreversible. E0 quoted for reversible, EP for irreversible
reflected in the hypsochromic shift of the long wavelength
absorbance.
The results for the ferrocenyl derivatives clearly show
the effect of the introduction of the electron-withdrawing
C6H4NO2-4 group in increasing the oxidation potential from
the value for ferrocene. Conversely, the introduction of the
electron-donating NH2 group lowers the reduction potential
significantly. The cyclic voltammograms of the complexes
[ReCl3(NC6H4R-4)(PPh3)2] (R = H, CO2Me) show a quasi
reversible reduction step at ca. Ϫ1 V due to the formation of the
Re() imide species. This becomes more reversible at faster
scan rates, consistent with an electrochemical–chemical (EC)
mechanism. It is probable that the chemical step following
reduction involves loss of chloride. The presence of the
electron-withdrawing CO2Me group as expected causes the
reduction to shift to less negative potentials. The oxidation for
the unsubstituted imide occurs at ϩ0.86 V and is reversible at
all scan rates investigated, as assessed by ipa/ipc ratios close to
unity and a linear plot for peak current versus scan rate1/2. The
oxidation process for the CO2Me derivative was not observed,
Electrochemical studies
The electrochemical properties of complexes 1 and 2 and
related rhenium imido-complexes and ferrocene derivatives
were investigated in dichloromethane solution by cyclic
voltammetry and the results are given in Table 4. A vitreous
carbon working and Pt wire auxiliary electrode and a silver wire
pseudo reference electrode were used with 0.2 M [Bun Nϩ]-
4
[BF4Ϫ] as supporting electrolyte over a range of scan rates. The
results are summarized in Table 4. Potentials are corrected to
the SCE by use of the ferrocene–ferrocenium couple as internal
standard (taken as ϩ0.44 V). Typical cyclic voltammograms
for the oxidation of complex 1 and for the reduction of
[ReCl3(NC6H4CO2Me)(PPh3)2] are shown in Fig. 7. The voltage
scale in the figure is relative to the silver pseudo electrode.
J. Chem. Soc., Dalton Trans., 2001, 2624–2633
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perhaps because it has been shifted outside the accessible
potential window.
using a mixture of diethyl ether–dichloromethane (1 : 1) as the
eluant. The solvent was removed from the collected fractions
and a red solid was obtained which was recrystallized from
methanol–dichloromethane (0.71 g, 63%), mp 198–200 ЊC; νmax
(KBr) 3108, 1721, 1604, 1596, 1524, 1422, 1349, 1270, 1218,
1185, 1086, 1066, 1034, 1015, 882, 813, 770, 750, 698, 527, 489
cmϪ1; δH (CDCl3) 8.34 (2H, d, J 9.1, ArH), 8.10 (2H, d, J 8.5,
ArH), 7.60 (2H, d, J 8.5, ArH), 7.43 (2H, d, J 8.5, ArH), 4.76
(2H, t, J 1.8, C5H4), 4.44 (2H, t, J 1.8 Hz, C5H4), 4.06 (5H, s,
C5H5); δC (CDCl3) 156.3, 147.5, 145.7, 130.9, 126.3, 125.8,
125.6, 123.0, 96.5, 83.1, 70.3, 67.4; m/z (εI) 428 (28), 427 (Mϩ,
100), 277 (45), 249 (13), 121 (44) (Found: Mϩ, 427.0511;
C23H17FeNO4 requires Mϩ, 427.05034).
The data for the Re–Fe complexes 1 and 2 shows that the Fe
and Re centred potentials are relatively little shifted from the
values for the Fe and Re complexes individually. In fact, the
effect of the Re imide group is smaller than that of the NH2 and
NO2 groups discussed above. In view of the substituent effects
observed above, it seems unlikely that there is a significant
electronic communication between the Re and Fe centres. It
may be the case that the electron density is balanced in such
a way that there is no significant shift from one metal to the
other.
Conclusions
4-Aminophenyl-4Ј-ferrocenyl benzoate.
A mixture of 4-
nitrophenyl-4Ј-ferrocenyl benzoate (0.4 g, 1.0 mmol), 10% Pd/C
(0.25 g) and anhydrous THF (400 cm3) was stirred under
hydrogen in a Parr hydrogenation reactor for 48 h. The solution
was then filtered through Celite and concentrated to leave an
orange crystalline material which was recrystallized from
dichloromethane–methanol (0.32 g, 81%), mp 199 ЊC; νmax
(KBr) 3443, 1720, 1617, 1511, 1429, 1275, 1229, 1203, 1021,
864, 826, 776, 707, 650, 525 cmϪ1; δH (CDCl3) 8.09 (2H, d, J 8.5,
ArH), 7.57 (2H, d, J 8.5, ArH), 7.01 (2H, d, J 8.7, ArH), 6.72
(2H, d, J 8.7, ArH), 4.74 (2H, t, J 1.8, C5H4), 4.41 (2H, t, J 1.8
Hz, C5H4), 4.05 (5H, s, C5H5); δC (CDCl3) 165.7, 145.8, 144.1,
143.2, 130.2, 126.9, 125.7, 122.3, 115.7, 96.1, 83.2, 69.9, 66.9;
m/z (εI) 398 (16), 289 (41), 262 (20), 261 (100), 139 (13) (Found:
C, 69.4; H, 4.6; N, 3.5; Mϩ, 397.07699. C23H19NO2Fe requires
C, 69.6; H, 4.8; N, 3.5%; Mϩ, 397.07652).
We have reported on the synthesis of the first examples of
ferrocenyl derivatives in which the ferrocenyl groups are conju-
gated to rhenium through a nitrogen multiple bond. The results
from the X-ray crystal structure determination of the com-
pounds and the NMR chemical shifts provide little evidence for
significant electron flow from the ferrocenyl group towards the
rhenium atom. The results of the UV/vis spectroscopy and cyc-
lic voltammetry are not conclusive on the issue of the extent of
conjugation between the ferrocenyl group and rhenium.
Experimental
Infrared spectra were recorded using a Nicolet Magna 550
1
Fourier Transform spectrometer as KBr discs. H, 13C and 31P
NMR spectra were recorded on either a Varian Unity Plus
(500 MHz) spectrometer (Oxford University) or a Bruker AX
(300 MHz) (University of Port Elizabeth) at room temperature.
The spectra were run in deuteriochloroform using tetramethyl-
4-Nitrobiphenyl-4Ј-ferrocenyl benzoate.
A
solution of
4-ferrocenylbenzoic acid (1.57 g, 5.11 mmol), 4Ј-hydroxy-
4-nitrobiphenyl (1.10 g, 5.11 mmol) and 4-dimethylamino-
pyridine (0.624 g, 5.11 mmol) in anhydrous dichloromethane
(150 cm3) was prepared under an atmosphere of dry nitrogen. A
solution of dicyclohexylcarbodiimide (0.352 g, 1.7 mmol) in
anhydrous dichloromethane (10 cm3) was then added slowly
over 3 min and the solution stirred at room temperature for
72 h. The solution was then filtered and the solvent removed
in vacuo. The crude product was purified by flash chrom-
atography on silica gel using a mixture of diethyl ether–
dichloromethane (1 : 1) as the eluant. The solvent was removed
from the collected fractions and a red solid was obtained which
was recrystallized from methanol–dichloromethane (1.51 g,
59%), mp 264–265 ЊC dec.; νmax (KBr) 3081, 1723, 1603, 1513,
1
silane as internal standard for H and 13C NMR and phos-
phoric acid as an external standard for the 31P NMR. UV-Visible
spectra were run in dichloromethane on a Shimadzu UV
spectrometer. Melting points were recorded using either a
Reichert hot stage apparatus (Oxford University) or an Electro-
thermal IA 900 series digital apparatus (UPE). The melting
characteristics of the new compounds were also determined by
DSC on a Dupont 2000 calorimeter. X-Ray crystallography
determinations were performed at the Inorganic Chemistry
Laboratory, University of Oxford, England. Mass spectra were
determined on either a Micromass Autospec 500 OAT or a
Micromass BIOQ-II Triple Quadrupole ESI mass spectrometer
(University of Oxford) or on a VG-70 SEQ/MSS-MS2 at the
Cape Technikon, South Africa. 4-Nitrophenylferrocene was
prepared by the reaction of 4-nitrobenzenediazonium chloride
and ferrocene.11 trans-Oxotrichlorobis(triphenylphosphine)-
rhenium() was prepared by the method described by Chatt
and Rowe.12 4-Hydroxy-4Ј-nitrobiphenyl was supplied by
Frinton Laboratories, USA and was used without further
purification. 4-Ferrocenylaniline was synthesized by the reduc-
tion of 4-nitrophenylferrocene,13 4-ferrocenylphenol was syn-
thesized by the diazonium method14 as was 4-ferrocenylbenzoic
acid.15 Spectroscopic details for these compounds are provided
as ESI.†
1484, 1342, 1268, 1188, 1068, 1004, 884, 858, 769, 699 cmϪ1
;
δH (CDCl3) 8.32 (2H, d, J 8.8, ArH), 8.13 (2H, d, J 8.4, ArH),
7.76 (2H, d, J 8.8, ArH), 7.69 (2H, d, J 8.6, ArH), 7.60 (2H, d,
J 8.4, ArH), 7.38 (2H, d, J 8.6, ArH), 4.77 (2H, t, J 1.8, C5H4),
4.44 (2H, t, J 1.8 Hz, C5H4), 4.07 (5H, s, C5H5); δC (CDCl3)
165.09, 151.80, 147.17, 146.82, 146.48, 136.42, 130.42, 128.58,
127.80, 126.20, 125.82, 124.20, 122.62, 82.95, 70.08, 69.93,
67.03; m/z (εI) 505 (6), 504 (31), 503 (Mϩ, 91), 502 (2), 501 (6),
487 (5), 290 (5), 289 (24), 262 (20), 261 (100), 260 (6), 259 (7),
205 (9), 203 (4), 144 (14), 139 (15), 121 (4) (Found: C, 69.4; H,
4.3; N, 2.7; Mϩ, 503.08338. C29H21FeNO4 requires C, 69.2; H,
4.2; N, 2.8%; Mϩ, 503.07473).
Syntheses
4-Aminobiphenyl-4Ј-ferrocenyl benzoate. A mixture of 4-
nitrobiphenyl-4Ј-ferrocenyl benzoate (320 mg, 0.636 mmol),
10% Pd/C (250 mg) and anhydrous THF (500 cm3) was stirred
under hydrogen in a Parr hydrogenation reactor for 48 h. The
solution was then filtered through Celite and concentrated to
leave an orange crystalline material which was recrystallized
from dichloromethane–methanol (180 mg, 68%), mp 231–
233 ЊC; νmax (KBr) 3444, 3368, 3076, 3036, 2923, 1725, 1606,
1496, 1420, 1272, 1213, 1182, 1089, 1072, 1002, 878, 856, 806,
770, 700, 643, 507 cmϪ1; δH (CDCl3) 8.13 (2H, d, J 8.4, ArH),
7.59 (2H, d, J 8.5, ArH), 7.58 (2H, d, J 8.7, ArH), 7.25 (2H, d,
4-Nitrophenyl-4Ј-ferrocenyl benzoate. A solution of 4-ferro-
cenylbenzoic acid (1.00 g, 3.0 mmol), 4-nitrophenol (0.42 g,
3.0 mmol) and 4-dimethylaminopyridine (0.35 g, 3.0 mmol)
in anhydrous dichloromethane (200 cm3) was prepared under
an atmosphere of dry nitrogen. A solution of dicyclohexylcarbo-
diimide (0.28 g, 1.0 mmol) in anhydrous dichloromethane (50
cm3) was then added slowly over 3 min and the solution stirred
at room temperature for 72 h. The solution was then filtered
and the solvent removed in vacuo. The crude product was
purified by flash chromatography on aluminium oxide (neutral)
2630
J. Chem. Soc., Dalton Trans., 2001, 2624–2633

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J 8.6, ArH), 6.77 (2H, d, J 8.4, ArH), 4.75 (2H, t, J 1.8, C5H4),
4.42 (2H, t, J 1.8 Hz, C5H4), 4.06 (5H, s, C5H5), 3.76 [2H,
s (broad), NH2]; δC (CDCl3) 165.74, 150.11, 146.45, 146.28,
139.34, 131.25, 130.75, 128.42, 127.79, 127.05, 126.16, 122.28,
115.81, 83.51, 70.35, 70.29, 67.38; m/z (εI) 475 (5), 474 (26),
473 (Mϩ, 76), 290 (7), 289 (36), 262 (19), 261 (100), 260 (6), 259
(7), 205 (8), 185 (5), 184 (6), 139 (11) (Found: C, 73.6; H, 5.1; N,
2.8; Mϩ, 473.10750. C29H23FeNO2 requires C, 73.6; H, 4.9;
N, 2.9%; Mϩ, 473.10782).
(2H, d, J 8.5, ArH), 7.28 (18H, m, ArH), 6.85 (2H, d, J 8.8,
ArH), 6.64 (2H, d, J 8.8, ArH), 4.76 (2H, t, J 1.8, C5H4), 4.44
(2H, t, J 1.8 Hz, C5H4), 4.05 (5H, s, C5H5); δC (CDCl3) 134.9,
134.8, 134.7, 131.6, 131.2, 130.4, 130.1, 127.7, 127.6, 125.8,
126.9, 126.5, 126.3, 70.0, 69.2, 62.3, 66.9; δP (CDCl3) Ϫ19.9
(2P, s, PPh3); m/z (FAB) 1212 (Mϩ), 1176 (Mϩ Ϫ Cl), 949
(Mϩ Ϫ PPh3), 913 (Mϩ Ϫ [PPh3 ϩ Cl]), 878 (Mϩ Ϫ [PPh3 ϩ
2Cl]) (Found: C, 58.8; H, 3.5; N, 1.12. C59H47Cl3FeP2O2ReN
requires C, 58.4; H, 3.9; N, 1.15%).
[(4-Ferrocenylphenylimido)]trichlorobis(triphenylphosphine)-
rhenium(V) (1). 4-Ferrocenylaniline (110 mg, 0.40 mmol) and
trans-oxotrichlorobis(triphenylphosphine)rhenium() (219 mg,
0.26 mmol) were added to anhydrous benzene (40 cm3) and this
solution was heated under reflux for 8 h. The colour of the
solution turned from an orange to a blue very rapidly. After 8 h,
the solvent was removed in vacuo to leave a dark blue oil which
was dissolved in dichloromethane and this solution was passed
through a column of silica gel. A red fraction was removed
from the column using diethyl ether as eluant, which on
removing the solvent left a dark blue solid. Recrystallization
from dichloromethane–hexane afforded dark blue-green
crystals (134 mg, 44%), mp 276 ЊC dec.; νmax (KBr) 3060, 1586,
1483, 1434, 1356, 1172, 1092, 745, 694, 518, 494, 298 cmϪ1; δH
(CDCl3) 7.80 (12H, m, ArH), 7.26 (18H, m, ArH), 6.83 (2H, d,
J 8.5, ArH), 6.78 (2H, d, J 8.5, ArH), 5.30 (2H, s, CH2Cl2), 4.61
(2H, t, J 1.8, C5H4), 4.45 (2H, t, J 1.8 Hz, C5H4), 3.99 (5H, s,
C5H5); δC (CDCl3) 134.96, 131.24, 129.96, 127.61, 125.59,
121.75, 82.88, 70.72, 70.16, 67.90, 66.83; δP (CDCl3) Ϫ19.26 (2P,
s, PPh3); m/z (FAB) 1057 (Mϩ Ϫ Cl), 1056, 1023 (Mϩ Ϫ 2Cl)
(Found: C, 53.4; H, 3.8; N, 1.3. C53H45Cl5FeNP2Re requires C,
54.1; H, 3.8; N, 1.2%).
(4-Ferrocenylbenzoate-1,1-biphenyl-4-imido)trichlorobis-
(triphenylphosphine)rhenium(V)
(6).
4-Aminobiphenyl-4Ј-
ferrocenyl benzoate (130 mg, 0.27 mmol) and trans-
oxotrichlorobis(triphenylphosphine)rhenium() (230 mg, 0.27
mmol) were added to anhydrous benzene (40 cm3) and this
solution was heated under reflux for 12 h. The colour of
the solution changed from orange to brown. The solution
was concentrated and passed through a column of silica gel.
Diethyl ether was used to elute a red fraction and upon concen-
tration, a brown solid was obtained. Recrystallization from
dichloromethane–hexane afforded an orange-brown solid (120
mg, 37%), mp 203 ЊC dec.; νmax (KBr) 3057, 1731, 1604, 1588,
1482, 1434, 1263, 1207, 1177, 1087, 1065, 1002, 810, 745, 693,
521 cmϪ1; δH (CDCl3) 8.05 (2H, m, ArH), 7.80–7.75 (12H, m,
ArH), 7.53 (2H, d, J 8.0, ArH), 7.37–7.24 (18H, m, ArH), 7.16
(2H, d, J 8.6, ArH), 7.09 (2H, d, J 8.4, ArH), 7.02 (2H, d, J 8.4,
ArH), 6.64 (2H, d, J 8.8, ArH), 4.71 (2H, t, J 1.8, C5H4), 4.41
(2H, t, J 1.8 Hz, C5H4), 4.04 (5H, s, C5H5); δP (CDCl3) Ϫ16.50
(2P, s, PPh3); m/z (FAB) 1288 (Mϩ ϩ H), 1287 (Mϩ), 1285
(Mϩ Ϫ 2H), 1252 (Mϩ Ϫ Cl), 1137, 991 (Found: C, 60.5; H, 3.9;
N, 1.0. C65H51Cl3FeP2O2ReN requires C, 60.5; H, 4.0; N, 1.1%).
fac-Oxotrichloro[1,1Ј-bis(diphenylphosphine)ferrocene]-
rhenium(V) (3) from the reaction of ammonium perrhenate, 1,1Ј-
bis(diphenylphosphine)ferrocene and HCl. A suspension of
ammonium perrhenate (105 mg, 0.39 mmol) in concentrated
hydrochloric acid (4 cm3) was added to an orange suspension of
1,1Ј-bis(diphenylphosphine)ferrocene (603 mg, 1.09 mmol) in
glacial acetic acid (10 cm3). The mixture was stirred for 30 min
under nitrogen after which a green solid was isolated from
the mixture. This was washed with diethyl ether (2 × 2 cm3) and
was recrystallized from dichloromethane–hexane to give dark
green crystals identified as fac-oxotrichloro[1,1Ј-bis(diphenyl-
phosphine)ferrocene]rhenium() (224 mg, 67%), mp 244–
246 ЊC; νmax (KBr) 3051, 1486, 1434, 1389, 1309, 1175, 1150,
1091, 1064, 960, 834, 743, 697, 634, 554, 495, 460, 410, 331, 298,
285 cmϪ1; δH (CDCl3) 7.92 (4H, m, ArH), 7.75 (4H, m, ArH),
7.42 (12H, m, ArH), 5.31 (2H, s, C5H4), 4.72 (2H, s, C5H4), 4.47
(2H, s, C5H4), 4.43 (2H, s, C5H4); δC (CDCl3) 135.55, 135.49,
135.45, 135.31, 135.25, 135.19, 133.86, 132.57, 131.75, 131.14,
128.83, 128.77, 128.70, 127.77, 127.70, 127.63, 81.23, 80.46,
76.99, 76.66, 75.63, 75.56, 74.08, 73.54; δP (CDCl3) Ϫ25.32
(2P, s, PPh2); m/z (FAB) 826 (Mϩ Ϫ Cl), 791 (Mϩ Ϫ 2Cl),
756 (Mϩ Ϫ 3Cl), 554 (Mϩ Ϫ ReOCl3) (Found: C, 47.6; H, 3.4.
C34H28Cl3FeOP2Re requires C, 47.3; H, 3.3%).
[(4-Ferrocenylphenylimido)]tribromobis(triphenylphosphine)-
rhenium(V) (2). 4-Ferrocenylaniline (150 mg, 0.50 mmol) and
trans-oxotribromobis(triphenylphosphine)rhenium() (500 mg,
0.50 mmol) were added to anhydrous benzene (40 cm3) and this
solution was heated under reflux for 12 h. The colour of the
solution changed from an orange to a blue-purple during the
reaction. After 12 h, the solvent was removed in vacuo to leave a
dark blue oil which was dissolved in dichloromethane. This
solution was filtered through silica gel and then passed through
a column of silica gel. A red fraction was eluted with diethyl
ether, which on removing the solvent left a dark blue solid.
Recrystallization from dichloromethane–hexane afforded dark
green crystals (312 mg, 48%), mp 190 ЊC; νmax (KBr) 3057, 1601,
1585, 1503, 1487, 1437, 1387, 1357, 1292, 1272, 1198, 1178,
1113, 1038, 1023, 889, 859, 834, 754, 704, 564, 525 cmϪ1
;
δH (CDCl3) 7.92 (12H, m, ArH), 7.22 (18H, m, ArH), 6.70 (4H,
s, ArH), 5.30 (2H, s, CH2Cl2), 4.61 (2H, t, J 1.8, C5H4), 4.47
(2H, t, J 1.8 Hz, C5H4), 4.02 (5H, s, C5H5); δC (CDCl3) 139.59,
128.70, 126.87, 126.54, 126.30, 69.96, 69.25, 66.89, 62.31;
δP (CDCl3) Ϫ26.71 (2P, s, PPh3); m/z (FAB) 1146 (Mϩ Ϫ Br)
(Found: C, 49.4; H, 3.3; N, 1.06. C53H45Br3Cl2FeNP2Re requires
C, 48.6; H, 3.5; N, 1.07%).
(4-Ferrocenylbenzoatephenylimido)trichlorobis(triphenyl-
phosphine)rhenium(V) (5). 4-Aminophenyl-4Ј-ferrocenyl benzo-
ate (0.13 g, 3.0 mmol) and trans-oxotrichlorobis(triphenyl-
phosphine)rhenium() (0.27 g, 3.0 mmol) were added to
anhydrous benzene (40 cm3) and this solution was heated under
reflux for 12 h. The colour of the solution changed from orange
to brown. The solution was concentrated and passed through
a column of silica gel. Diethyl ether was used to elute a red
fraction and upon concentration, a brown solid was obtained.
Recrystallization from dichloromethane–hexane afforded a
yellow-brown needle-like solid (0.21 g, 56%), mp 288 ЊC dec.;
νmax (KBr) 3051, 1735, 1600, 1588, 1484, 1436, 1261, 1200,
fac-Oxotrichloro[1,1Ј-bis(diphenylphosphine)ferrocene]-
rhenium(V) (3) from the reaction of trans-[ReOCl3(PPh3)2] and
1,1Ј-bis(diphenylphosphine)ferrocene. The reaction was carried
out under an atmosphere of high purity nitrogen. trans-
[ReOCl3(PPh3)2] (114 mg, 0.14 mmol) was added to anhydrous
toluene (5 cm3) to which was also added a solution of 1,1Ј-
bis(diphenylphosphine)ferrocene (78 mg, 0.14 mmol) in
anhydrous toluene (5 cm3). The mixture was stirred at room
temperature for 15 h. A green solid was filtered off, washed
with toluene (2 cm3) and diethyl ether (2 cm3) and dried under
vacuum and was finally recrystallized from dichloromethane–
hexane, identified as fac-oxotrichloro[1,1Ј-bis(diphenylphos-
phine)ferrocene]rhenium() (97 mg, 80%), characterization as
above.
1174, 1110, 1068, 1017, 891, 829, 749, 691, 516, 390, 380 cmϪ1
δH (CDCl3) 8.05 (2H, d, J 8.5, ArH), 7.82 (12H, m, ArH), 7.58
;
J. Chem. Soc., Dalton Trans., 2001, 2624–2633
2631

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Table 5 Summary of X-ray structural data for complexes 1 and 2
Trichloro(ferrocenylphenylimido)[1,1Ј-bis(diphenylphosphine)-
ferrocene]rhenium(V) (4). 4-Ferrocenylaniline (51 mg, 0.18
mmol) was dissolved in anhydrous benzene (10 cm3) and this
solution was added to a solution of fac-oxotrichloro[1,1Ј-
bis(diphenylphosphine)ferrocene]rhenium() (103 mg, 0.12
mmol) in anhydrous benzene (10 cm3) and the mixture was
heated under reflux for 24 h. During that time, the solution
changed colour from green to dark red and finally to deep
purple. Evaporation of the solvent left a blue oily residue
which upon addition of dichloromethane followed by hexane
provided a green solid. The latter was washed with hexane
(2 × 2 cm3), dried in vacuo and then passed through a column
of silica gel. Dichloromethane was used to elute a dark red
band which on removing the solvent in vacuo left a dark
solid. This was recrystallized from dichloromethane–hexane
and identified as trichloro(ferrocenylphenylimido)[1,1Ј-bis-
(diphenylphosphine)ferrocene]rhenium() (4) (19 mg, 14%), mp
295 ЊC dec.; νmax (KBr) 1653, 1588, 1483, 1434, 1331, 1165,
1
2
Empirical formula
M
a/Å
b/Å
c/Å
α/Њ
β/Њ
C53H45Cl3FeNP2Re C53H45Br3Cl2FeNP2Re
1177.14
12.206(2)
13.668(2)
15.585(2)
76.617(10)
77.650(10)
80.045(10)
2418.6(6)
Triclinic
P1
1310.52
12.078(1)
13.615(1)
15.518(1)
77.745(3)
77.667(3)
79.351(2)
2410.0(3)
Triclinic
P1
γ/Њ
V/Å3
Crystal system
Space group
Z
2
2
µ(Mo-Kα)/mmϪ1
T /K
3.180
150(2)
5.512
150(2)
Reflections collected
Independent reflections 2941
2941
9060
9060
Reflections observed
R1, wR2
2639
0.0727, 0.1645
7596
0.0397, 0.1008
1087, 1029, 914, 886, 840, 743, 694, 546, 518, 494, 473 cmϪ1
;
δH (CDCl3) 8.00 (4H, m, ArH), 7.85 (4H, m, ArH), 7.32–7.06
(12H, m, ArH), 6.84 (2H, d, J 8.6, ArH), 6.63 (2H, d, J 8.5,
ArH), 5.28 (2H, s, C5H4), 4.67 (2H, s, C5H4), 4.64 (2H, s, C5H4),
4.59 (4H, m, C5H4), 4.43 (2H, t, J 1.7 Hz, C5H4), 4.01 (5H, s,
C5H5); δP (CDCl3) Ϫ16.29; m/z (FAB) 1122 (Mϩ ϩ H), 1121
(Mϩ), 1083 (Mϩ Ϫ Cl), 1052 (Mϩ Ϫ 2Cl) (Found: C, 52.6; H,
3.8; N, 1.2. C50H41Cl3Fe2NP2Re requires C, 53.5; H, 3.7; N,
1.2%).
CCDC reference numbers 167710–167712. This includes
structural data for compound 3.
Acknowledgements
One of us (C.I.) would like to thank the following organizations
and people. Firstly, the Royal Society of Chemistry for their
support through a Grant for Overseas Authors; secondly the
Foundation for Research Development Science Liaison
Department (Pretoria); thirdly the University of Port Elizabeth
Research Committee for the awarding of an Overseas Research
Bursary and Professors Malcolm L. H. Green and Jonathan R.
Dilworth of the Inorganic Chemistry Laboratory, University of
Oxford for their help and useful advice. Finally, last but not
least, Mr John Woollard-Shore (ICL, Oxford) for help with
obtaining the electrochemistry data and some of the mass
spectra data and Dr Pieter Engelbrecht (UPE) for synthesizing
a sample of 4-methoxyphenylferrocene.
Trichloro(4-imidophenyl-4Ј-ferrocenyl
benzoate)[1,1Ј-bis-
(diphenylphosphine)ferrocene]rhenium(V) (7). 4-Aminophenyl-
4Ј-ferrocenyl benzoate (185 mg, 0.47 mmol) was dissolved
in anhydrous benzene (10 cm3) and this solution was added
to a solution of fac-oxotrichloro[1,1Ј-bis(diphenylphosphine)-
ferrocene]rhenium() (403 mg, 0.47 mmol) in anhydrous
benzene (10 cm3) and the mixture was heated under reflux for 72
h. During that time, the solution changed colour from green to
dark red and finally to brown. Evaporation of the solvent left a
dark brown residue. The latter was washed with hexane (2 × 2
cm3), dried in vacuo and then passed through a short silica gel
column. Dichloromethane was used to elute a dark red band
which on removing the solvent in vacuo left a brown solid. This
was recrystallized from dichloromethane–hexane to give a light
brown solid identified as trichloro(4-imidophenyl-4Ј-ferrocenyl
benzoate)[1,1Ј-bis(diphenylphosphine)ferrocene]rhenium()
(221 mg, 39%), mp 265 ЊC dec.; νmax (KBr) 1731, 1605, 1583,
1480, 1434, 1257, 1203, 1171, 1158, 1086, 1051, 1011, 890, 821,
746, 697, 632, 547, 518 cmϪ1; δH (CDCl3) 8.02 (8H, m, ArH),
7.80 (8H, m, ArH), 7.58 (2H, d, J 8.4, ArH), 7.34–7.08 (6H, m,
ArH), 6.69 (2H, d, J 9.1, ArH), 6.65 (2H, d, J 9.1, ArH), 5.26
(2H, s, C5H4), 4.76 (2H, s, C5H4), 4.67 (4H, s, C5H4), 4.60 (2H,
m, C5H4), 4.45 (2H, t, J 1.7 Hz, C5H4), 4.06 (5H, s, C5H5);
δP (CDCl3) Ϫ16.64; m/z (FAB) 1242 (Mϩ ϩ 2H), 1241
(Mϩ ϩ H), 1240 (Mϩ), 1206 (Mϩ Ϫ Cl), 866, 773 (Found: C,
54.3; H, 3.7; N, 1.0. C57H45Cl3Fe2NO2P2Re requires C, 55.2; H,
3.7; N, 1.1%).
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Structure analysis and refinement for compounds 1, 2
Intensity data were collected on an Enraf-Nonius DIP2000
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were included in idealized positions with Uiso free to refine.
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analyses. Sources of scattering factors were as in ref. 17. The
numbering of all the atoms in the structures was produced
with ZORTEP.19 A summary of the X-ray structural data for
complexes 1 and 2 is provided in Table 5.
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J. Chem. Soc., Dalton Trans., 2001, 2624–2633
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