Chloroaluminate(III) ionic liquid mediated synthesis of transition metal-cyclophane; Complexes: Their role as solvent and Lewis acid catalyst1

Article abstract of DOI:10.1016/S0022-328X(98)00734-7

The preparation of transition metal-cyclophane complexes using the ionic liquid system [bmim]Cl-AlCl₃ ([bmim]⁺=1-butyl-3-methylimidazolium cation) as both the solvent and Lewis acid catalyst is described. Both known and novel complex

Full text of DOI:10.1016/S0022-328X(98)00734-7

Journal of Organometallic Chemistry 573 (1999) 292–298
Chloroaluminate(III) ionic liquid mediated synthesis of transition
metal–cyclophane; complexes: their role as solvent and Lewis acid
catalyst1
David Crofts, Paul J. Dyson 2, Katharine M. Sanderson, Narmatha Srinivasan,
Thomas Welton *
Department of Chemistry, Imperial College of Science, Technology and Medicine, London, SW7 2AY, UK
Received 11 May 1998
Abstract
The preparation of transition metal–cyclophane complexes using the ionic liquid system [bmim]Cl–AlCl3 ([bmim]+ =1-butyl-
3-methylimidazolium cation) as both the solvent and Lewis acid catalyst is described. Both known and novel complexes are
prepared. Simple arene complexes of manganese have also been prepared in order to demonstrate the chemistry and these
reactions are compared with the literature preparations conducted in conventional organic solvents. © 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Ionic liquid; Aluminium chloride; Cyclophane; Metal–arene complexes
minium halide mediated synthesis is a widely used type
of reaction in organometallic chemistry, in particular,
in the preparation of metal–arene complexes and the
synthesis of these complexes is covered in several
prominent review articles [7–13]. Two main types of
reaction are generally used; firstly, when aluminium(III)
chloride, functioning as a dehalogenating agent, is re-
acted with a suitable metal halide precursor in the
presence of an arene, and secondly, when aluminium
metal is also added, acting as a reducing agent, afford-
ing metal–arene compounds in lower oxidation states.
With their high concentrations of chloroalumi-
nate(III) species, room-temperature chloroalumi-
nate(III) ionic liquids offer a potential environment for
these reactions. The composition of a particular
chloroaluminate(III) ionic liquid, and hence its chem-
istry, is determined by the ratio in which the aluminiu-
m(III) chloride and the organic chloride salt are mixed.
This is best described by the apparent mole fraction of
AlCl3 present {X(AlCl3)}. When aluminium(III) chlo-
ride is in excess {X(AlCl3)\0.5} the melt is described
1. Introduction
Room-temperature ionic liquids are a novel class of
solvents with highly unusual properties which may pro-
mote a different reactivity to that seen in conventional
molecular solvents [1,2]. Still the most widely investi-
gated of these solvents are the chloroaluminates(III),
which may be exemplified by [bmim]Cl–AlCl3 (where
[bmim]+ =1-butyl-3-methylimidazolium cation) [1].
Thus far, the synthetic chemistry reported in these ionic
liquids has mostly focused on organic reactions [3,4],
and very little synthetic organometallic chemistry has
been reported to date. In fact, the acylation of fer-
rocene [5] and arene exchange reactions of ferrocene [6]
represent the only examples, with only the latter involv-
ing metal–carbon bond formation. However, alu-
* Corresponding author. Fax: +44 171 5945804; e-mail:
t.welton@ic.ac.uk; URL, http://www.ch.ic.ac.uk/welton
1 Dedicated to Professor Brian Johnson on the occasion of his 60th
birthday.
2 Also corresponding author. E-mail: p.dyson@ic.ac.uk
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00734-7

D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
293
as acidic and the formation of the Lewis acid [Al2Cl7]−
is strongly favoured. When the concentration of alu-
minium(III) chloride is B0.5 the melt is described as
basic. The reactions described in this paper all use
acidic [bmim]Cl–AlCl3 ionic liquids.
sis of [Fe(p-C5H5)]+ complexes of [2.2]paracyclophane
[Fe(p-C5H5)(p-C16H16)][PF6] 1 and [{Fe(p-C5H5)}2(p-
C16H16)][PF6]2 2 and of the novel compounds [Fe(p-
C5H5)(p-C24H24)][PF6] 3 and [{Fe(p-C5H5)}2(p-C24H24)]
[PF6]2
4 and [{Fe(p-C5H5)}3(p-C24H24)] [PF6]3 5
In a previous paper we showed that the same ionic
liquid can be used as the solvent for arene-exchange
reactions of ferrocene [6]. In this paper this work is
extended to the preparation of both known and novel,
iron–cyclophane complexes. We also report that, using
(Scheme 1).
The positive ion FAB mass spectrum of 3 contains a
parent peak at 433 Th together with fragment ions
which correspond to loss of either the [2.2.2]
paracyclophane or cyclopentadienyl ligands. The mass
spectra of 4 and 5 are somewhat more complicated
given that they are multiply charged. Compound 4
shows a strong peak at 699 Th which corresponds to
the sum of the dictation and one anion, namely
{[{Fe(p-C5H5)}2(p-C24H24)][PF6]}+, together with a
number of fragments of this ion. Similarly, the highest
mass peak of 5 occurs at 965 Th and corresponds to the
ion {[{Fe(p-C5H5)}3(p-C24H24)][PF6]2}+.
similar reaction conditions,
a
number of man-
ganese(arene)tricarbonyl complexes can be prepared.
2. Results and discussion
The reactions described in this paper are illustrated in
Schemes 1–3 and full details are given in the experi-
mental section.
1
The H-NMR spectra of 3–5 were recorded in ace-
tone-d6. The 1H-NMR spectrum of 3 contains four
peaks centred at 6.77, 5.93, 5.01 and 3.1 ppm. The peak
at 6.77 ppm is a multiplet and corresponds to the
protons of uncoordinated rings. The peaks at 5.93 and
5.01 are both singlet resonances and correspond to the
protons of the coordinated cyclophane and cyclopenta-
dienyl rings, respectively. The peak centred at approxi-
mately 3.1 ppm is a complicated multiplet resonance,
2.1. Iron complexes
In our previous paper [6] we showed that it was
possible to prepare iron(arene)cyclopentadienyl com-
plexes (for a range of simple arene ligands and
biphenyls) in the [bmim]Cl–AlCl3 {X(AlCl3)=0.65}
ionic liquid. This has now been extended to the synthe-
Scheme 1. The synthesis of 1–5 from ferrocene.

294
D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
Scheme 2.
partially obscured by impurities in the solvent and is
attributed to the CH2 protons in the [2.2.2]paracyclo-
phane ligand. Compound 4 gives rise to four signals at
The room-temperature ionic liquid [bmim]Cl–AlCl3
is ideally suited to these reactions as it can easily be
prepared proton-free [17]. Indeed, because of its aprotic
nature, the addition of [bmim][HCl2] as a proton source
is required to complete the arene exchange reactions of
ferrocene [6]. This is because one of the cyclopentadi-
enyl rings must first be protonated before it can be
replaced by the arene. In order to minimise the risk of
isomerisation of the cyclophanes, the [bmim][HCl2] was
only added after all of the other starting materials were
well mixed. This strategy proved successful and at no
time did we see evidence for the isomerisation of either
of the cyclophanes used.
The original preparation of compounds 1 and 2 [14],
led to the formation of a mixture of the products which
could only be separated by preparative scale TLC. An
important synthetic advantage of our reaction condi-
tions is that it allows us to prepare pure products
without the need for chromatography. We found that
the pure products could be prepared by careful stoi-
chiometric addition of the starting materials, combined
with control of the reaction times.
1
6.78, 6.05, 5.00 and 3.1 ppm in the H-NMR spectrum.
The peaks at 6.78, 6.05 and 5.00 are singlet resonances
corresponding to the free cyclophane ring, coordinated
cyclophane rings and cyclopentadienyl rings, respec-
tively. The multiplet resonance centred at approxi-
mately 3.1 ppm corresponds to the cyclophane CH2
1
protons. The H-NMR spectrum of 5 is very simple.
Three broad singlet resonances are observed at 5.0, 4.1
and 3.2 ppm which correspond to the [2.2]paracyclo-
phane ring, cyclopentadienyl and [2.2]paracyclophane
aliphatic protons, respectively.
Compounds 1 and 2 have been prepared previously,
using two different routes [14,15]. The first involves the
exchange of a cyclopentadienyl ring in ferrocene for the
[2.2]paracyclophane ligand using the Fischer-Hafner
method [14]. However, it has been found that
[2.2]paracyclophane can isomerise in the presence of
traces of HAlCl4 [16], which is ubiquitously present in
all but the purest aluminium(III) chloride. The arene
rings are easily protonated and the resulting carboca-
tion can then rearrange to [2.2]metaparacyclophane.
Although we did not investigate this, we assumed that
[2.2]paracyclophane will undergo similar isomerisation
reactions. To avoid this problem the other route to 1
and 2 involves the arene exchange reaction with the
p-xylene complex [Fe(p-C5H5)(p-C6H4Me2-1,4)]+ [15].
The xylene-complex is still prepared from ferrocene
using Al/AlCl3 and is subsequently replaced by the
2.2. Manganese carbonyl complexes
In order to investigate the possibility of forming
manganese(arene)tricarbonyl complexes in the chloroa-
luminate ionic liquids, we first attempted the reaction
with a number of simple arenes. Initially, reaction of
Mn(CO)5Br with these arenes in the acidic ionic liquid,
followed by extraction into a number of common coun-
ter anions, afforded yellow oils which could not be fully
characterised, although their IR spectra in dichloro-
methane were characteristic of complexes with the for-
[2.2]paracyclophane in
a
photochemical process,
thereby preventing isomerisation of the [2.2]paracyclo-
phane ring. These reactions are illustrated in Scheme 2.

D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
295
mula [Mn(CO)3(p-arene)]+ [18]. However, when
Mn(CO)5Br was reacted with arenes in a stoichiomet-
ric amount of acidic [bmim]Cl–AlCl3 ionic liquid, i.e.
1:1 ratio of Mn(CO)5Br:[Al2Cl7]−, the tricarbonyl
cationic compounds of formula [Mn(CO)3(p-arene)]+
(arene=C6H6 6, C6H5Me 7, C6H4Me2-1,3 8,
C6H3Me3-1,3,5 9, C6H4Ph 10, C16H16 11, C24H24 12)
are obtained as yellow solids (Scheme 3). A similar
phenomenon has been noted previously when
excess AlCl3 is used in a conventional Fischer-Hafner
reaction in the preparation of palladium complexes
[19].
Unlike the reactions of ferrocene, it is unnecessary
to add aluminium metal to the reaction mixture. This
is because the manganese is less susceptible to oxida-
tion under the reaction conditions and consequently
no reducing agent is required to return it to the origi-
nal oxidation state. Similarly, there is no need for a
proton source, which serves to make the cyclopentadi-
enyl ligand into the better leaving group cyclopentadi-
ene in the arene exchange reactions of ferrocene, as
the two carbonyl ligands which need to be lost from
the [Mn(CO)5]+ fragment are thermally labile.
assigned to the CH2 group protons, the former signal
being due to those further from the [Mn(CO)3]+ frag-
ment and the latter signal being due to those nearest
1
to the [Mn(CO)3]+ fragment. The H-NMR spectrum
of 12 contains three peaks at 7.24, 6.62 and 3.04 ppm
with relative intensities of 1:2:3, respectively. The
peaks at 7.24 and 6.62 ppm are singlet resonances and
correspond to the coordinated and two uncoordinated
rings whereas the peak centred at 3.04 is a multiplet
which can be assigned to the CH2 protons in the
aliphatic bridges.
Other related reactions are currently in progress as
the acidic [bmim]Cl–AlCl3 ionic liquids are well suited
to Fischer-Hafner synthesis. We are also investigating
the potential use of these systems for the generation of
in situ catalysts for organic transformations, as a num-
ber of transition metal–arene complexes have been
found to be active catalysts.
3. Experimental
3.1. General comments
Compounds 6–10 have been prepared previously in
conventional molecular solvents using AlCl3 as a
halide abstractor [20,21]. Alternative routes to these
compounds, as well as other arene derivatives, include
the use of silver(I) salts as the dehalogenating agent
for Mn(CO)5Br [22], oxidation of Mn2(CO)10 with
trifluoroacetic anhydride [23], and arene exchange
methods [24].
Compounds 11 and 12 are new and of particularly
interest as potential precursors to mixed valence
bimetallic complexes with transannular communication
between the metal sites. The mass spectra of 11 and 12
exhibit peaks at 347 and 451 Th, respectively, which
correspond to the intact parent ions [Mn(CO)3(p-
C16H16)]+ and [Mn(Co)3(p-C24H24)]+. The 1H-NMR
spectrum of 11 contains four peaks at 7.07, 6.21, 3.46
and 3.32 ppm with equal relative intensities. The peaks
at 7.07 and 6.21 ppm are both singlet resonances and
may be assigned to the C–H protons of the uncoordi-
nated and coordinated rings, respectively. The peaks
at 3.46 and 3.32 ppm are both multiplets and may be
Room temperature ionic liquids are formed by the
direct combination of substituted imidazolium chloride
salts and aluminium(III) chloride. There are a number
of ways in which the precise composition of the ionic
liquid can be described and in this paper we use an
ionic liquid with an apparent mole fraction of AlCl3
{X(AlCl3)}=0.65 and refer to this as the acidic ionic
liquid. In fact, the ionic liquids contain no free AlCl3
but have significant concentrations of the [Al2Cl7]−
ion, which is the active Lewis acid species. All reagents
were used as received expect for the following; AlCl3
was repeatedly sublimed, [bmim]Cl and [bmim][HCl2]
were made using the literature procedures [6]. The
preparation of the ionic liquids, by addition of AlCl3
to 1-butyl-3-methylimidazolium chloride, followed pre-
viously described methods in a dry nitrogen atmo-
sphere glove box [25]. Reactions were conducted under
an atmosphere of nitrogen gas using a combination of
glove box and Schlenk techniques. IR spectra were
recorded using a Matson Research Series FTIR instru-
ment, mass spectra were recorded in positive mode
using fast atom bombardment on a VG AutoSpec Q
instrument using 3-nitrobenzyl alcohol as the matrix
1
and H-NMR spectra were recorded on an Jeol JNM-
EX270 FT instrument.
3.2. Synthesis of [Fe(p-C5H5)(p-C16H16)][PF6] 1
In an inert atmosphere glove box, ferrocene (0.89 g,
4.81 mmol) and [2.2]paracyclophane (1.00 g, 4.81
mmol) were dissolved in [bmim]Cl–AlCl3 {X(AlCl3)=
0.65} ionic liquid (8 g) in a Schlenk flask. Aluminium
Scheme 3. The synthesis of 6–12 from Mn(CO)5Br {arene=benzene
(6), toluene (7) mxylene (8), mesitylene (9) biphenyl (10),
[2.2]paracyclophane (11) or [2.2.2]paracyclophane (12)}.

296
D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
powder (0.13 g) was added, the flask was sealed and
transferred to a Schlenk line. Finally, under an atmo-
sphere of N2, [bmim][HCl2] (0.1 cm3) was added to the
reaction mixture. The reaction mixture was heated at
80°C for 40 h. The reaction mixture was cooled to r.t.
and ice water (200 cm3) was added slowly. The aqueous
solution was filtered and washed with petroleum ether
(5×20 cm3). The aqueous layer was collected and
filtered directly into an aqueous solution of [NH4][PF6]
(2 g in 10 cm3). An orange precipitate formed immedi-
ately. After standing for 1 h, the product was filtered
and dried in vacuo for 24 h and characterised as 1
(orange, 1.8 g, 79%). Analytical data, C, 53.04; H, 4.30;
C21H22F6FeP requires C, 53.16; H, 4.43%. 1H-NMR
((CD3)2CO, 270 MHz): l (ppm) 6.71 (s, uncomplexed
ring), 5.78 (s, complexed ring), 4.84 (s, cyclopentadienyl
ring) and 3.07 (s, CH2); FAB-MS; m/z 329
[C21H21Fe]+.
solution formed was filtered to remove solid impurities,
washed with light petroleum (60–80°C, 5×20 cm3) and
then filtered into a concentrated aqueous solution of
ammonium hexafluorophosphate (1.00 g in 5 cm3) upon
which, precipitation of a yellow solid occurred. The
product was collected by filtration and recrystallized
from an acetone/water mixture. The resulting yellow
crystalline salt was dried over phosphorus pentoxide
and then dried in vacuo for 24 h, and was characterized
as 3 (orange, 0.02 g, 23%). Analytical data, C, 59.47; H,
4.57; C29H29F6FeP requires C, 60.23; H, 5.05%. 1H-
NMR ((CD3)2CO, 270 MHz): l (ppm) 6.77 (m, uncom-
plexed rings), 5.93 (s, complexed ring), 5.01 (s,
cyclopentadienyl ring) 3.1 (m, CH2); FAB-MS; 433
[C29H29Fe]+, 368 [C24H24Fe]+, 121 [C5H5Fe]+.
3.5. Synthesis of [{Fe(p-C5H5)}2(p-C24H24)][PF6]2 4
In an inert atmosphere glove box, ferrocene (0.058 g,
0.315 mmol), aluminium powder (0.05 g) and
[2.2.2]paracyclophane (0.05 g, 0.160 mmol) were dis-
solved in [bmim]Cl–AlCl3 {X(AlCl3)=0.65} ionic liq-
3.3. Synthesis of [{Fe(p-C5H5)}2(p-C16H16)][PF6]2 2
In an inert atmosphere glove box, ferrocene (0.89 g,
4.81 mmol) and [2.2]paracyclophane (0.50 g, 2.42
mmol) were dissolved in [bmim]Cl–AlCl3 {X(AlCl3)=
0.65} ionic liquid (8 g) in a Schlenk flask. Aluminium
powder (0.13 g) was added, the flask was sealed and
transferred to a Schlenk line. Finally, under an atmo-
sphere of N2, [bmim][HCl2] (0.1 cm3) was added to the
reaction mixture. The reaction mixture was heated at
80°C for 65 h. After cooling to r.t., ice water (200 cm3)
was added slowly to the mixture. The aqueous solution
was filtered and washed with petroleum ether (5×20
cm3). The aqueous layer was collected and filtered
directly into an aqueous solution of [NH4][PF6] (2 g in
10 cm3). An orange precipitate formed immediately.
After standing for an hour, the product was filtered and
dried in vacuo for 24 h, and characterised by spec-
troscopy as 2 (orange, 1.6 g, 72%). Analytical data, C,
58.19; H, 5.94; C26H26F6FeP requires C, 57.91; H,
uid (10 g) in
a Schlenk tube. Under dry N2
[bmim][HCl2] (2 drops) was added and the reaction
mixture was heated at 80°C for 65 h with rapid stirring.
After this time, the reaction mixture was allowed to
cool to r.t. ice water (100 cm3) was added. The mixture
was filtered to remove solid impurities, washed with
light petroleum (60–80°C, 5×10 cm3) and then filtered
into a concentrated aqueous solution of ammonium
hexafluorophosphate (1.00 g in 5 cm3) upon which,
precipitation of a yellow solid occurred. The product
was collected by filtration and washed with ether. The
resulting yellow salt was dried over phosphorus pentox-
ide and then dried in vacuo for 24 h, and characterized
as 4 (orange, 0.053 g, 20%). Analytical data, C, 48.28;
H, 4.19; C34H34F6FeP requires C, 48.37; H, 4.06%.
1H-NMR ((CD3)2CO, 270 MHz): l (ppm) 6.78 (s,
uncomplexed ring), 6.05 (s, complexed rings), 5.00 (s,
cyclopentadienyl rings) 3.1 (m, CH2); FAB-MS; m/z
699 {[C34H34Fe2][PF6]}+, 554 [C34H34Fe2]+, 433
[C29H29Fe]+, 368 [C24H24Fe]+, 121 [C5H5Fe]+.
1
4.86%. H-NMR ((CD3)2CO, 270 MHz): l (ppm) 5.96
(s, complexed ring), 4.91 (s, cyclopentadienyl ring), and
3.23 (s, CH2); FAB-MS; m/z 595 {[C26H26Fe][PF6]}+,
450
[C26H26Fe]+and
329
[C21H21Fe]+,
242
[(C5H5)Fe2]+, 121 [C5H5Fe]+.
3.6. Synthesis of [{Fe(p-C5H5)}3(p-C24H24)][PF6]3 5
3.4. Synthesis of [Fe(p-C5H5)(p-C24H24)][PF6] 3
In an inert atmosphere glove box, ferrocene (0.087 g,
0.471 mmol), aluminium powder (0.05 g) and
[2.2.2]paracyclophane (0.05 g, 0.160 mmol) were dis-
solved in [bmim]Cl–AlCl3 {X(AlCl3)=0.65} ionic liq-
In an inert atmosphere glove box, ferrocene (0.029 g,
0.160 mmol), aluminium powder (0.5 g) and
[2.2.2]paracyclophane (0.05 g, 0.160 mmol) were dis-
solved in [bmim]Cl–AlCl3 {X(AlCl3)=0.65} ionic liq-
uid (10 g) in
a Schlenk tube. Under dry N2
[bmim][HCl2] (2 drops) was added and the reaction
mixture was heated at 80°C for 85 h with rapid stirring.
After this time, the reaction mixture was allowed to
cool to r.t. and ice water (100 cm3) was added. The
mixture was filtered to remove solid impurities, washed
with light petroleum (60–80°C, 5×10 cm3) and then
uid (10 g) in
a Schlenk tube. Under dry N2
[bmim][HCl2] (2 drops) was added and the reaction
mixture was heated at 80°C for 40 h with rapid stirring.
After this time, the mixture was allowed to cool to
r.t. and ice water (200 cm3) was added. The aqueous

D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
297
filtered into a concentrated aqueous solution of ammo-
nium hexafluorophosphate (1.6 g in 20 cm3) upon
which precipitation of a yellow solid occurred. The
product was collected by filtration and washed with
ether. The resulting yellow crystalline salt was dried
over phosphorus pentoxide and then dried in vacuo for
24 h, and characterized as 5 (orange, 0.078 g 15%)
Analytical data, C, 42.06; H, 3.70; C39H39F6FeP re-
characterized as 7 (yellow, 0.206 g, 30%). Analytical
data, C, 30.52; H, 1.76. C7H8O3MnPF6 requires C,
1
31.94; H, 2.14%. wCO(CH2Cl2, cm−l): 2082, 2024; H-
NMR (CD3COCD3, 270 MHz) l (ppm) 6.92 (s, aro-
matic), 6.66 (s, aromatic), 2.58 (s, CH3); FAB-MS: m/z
231 [C7H8Mn(CO)3]+, 203 [C7H8Mn(CO)2]+, 175
[C7H8Mn(CO)]+.
1
quires C, 42.16; H, 3.51%. H-NMR ((CD3)2CO, 270
3.9. Synthesis of [Mn(CO)3(p-C6H4Me2-1,3)][PF6] 8
MHz): l (ppm) 5.0 (s, complexed rings), 4.1 (s, cy-
clopentadienyl rings) 3.2 (m, CH2); FAB-MS; 965
{[C39H39Fe3][PF6]2}+, 820 {[C39H39Fe3][PF6]}+, 699
{[C34H34Fe2][PF6]}+, 433 [C29H29Fe]+, 368 [C24H24-
Fe]+.
In an inert atmosphere glove box, Mn(CO)5Br (0.10
g, 0.36 mol) and [bmim]Cl–AlCl3 {X(AlCl3)=0.65}
ionic liquid (0.073 cm3, 0.36 mmol) were placed in a
Schlenk flask. The sealed flask was removed from the
glove box and transferred to a Schlenk line. Under a
nitrogen atmosphere, m-xylene (1 cm3) was added to
the reaction mixture which was then heated at 110°C
for 15 h. The reaction mixture was cooled and ice water
(50 cm3) added slowly. The mixture was filtered and the
yellow solution washed with diethyl ether (5×10 cm3).
The aqueous layer was then filtered into a concentrated
solution of [NH4][PF6] (0.06 g in 5 cm3 of water) which
gave a yellow solid which was removed by filtration and
dried under vacuum and characterised as 8 (yellow,
0.52 g, 37%). Analytical data, C, 33.73; H, 2.55;
C11H10F6MnO3P requires C, 33.87; H, 2.58%.
wCO(Nujol, cm−1) 2075, 2001; 1H-NMR ((CD3)2CO,
270 MHz): l (ppm) 6.7 (s, aromatic), 2.3 (s, CH3);
FAB-MS; m/z 245 [C11H10MnO3]+, 189 [C9H10
MnO]+, 161 [C8H10Mn]+.
3.7. Synthesis of [Mn(CO)3(p-C6H6)][PF6] 6
In an inert atmosphere glove box, Mn(CO)5Br (0.10
g, 0.36 mol) and {X(AlCl3)=0.65} [bmim]Cl–AlCl3
ionic liquid (0.073 cm3, 0.36 mmol) were placed in a
Schlenk flask. The sealed flask was removed from the
glove box and transferred to a Schlenk line. Under a
nitrogen atmosphere benzene (1 cm3) was added to the
reaction mixture which was then heated at 60°C for 15
h with rapid stirring. The reaction mixture was cooled
and ice water (50 cm3) added slowly. The mixture was
filtered and the yellow solution washed with diethyl
ether (5×10 cm3). The aqueous layer was then filtered
into a concentrated solution of [NH4][PF6] (0.06 g in 5
cm3 of water) which gave a yellow solid which was
filtered and dried under vacuum and characterised as 6
(yellow, 0.055 g, 42%). Analytical data, C, 30.08; H,
1.74; C9H6F6MnO3P requires C, 29.86; H, 1.67%.
wCO(Nujol, cm−1) 2082, 2017; 1H-NMR ((CD3)2CO,
270 MHz): l (ppm); 7.03 (s, C6H6); FAB-MS; m/z 217
[C9H6MnO3]+.
3.10. Synthesis of [Mn(CO)3(p-C6H3Me3-1,3,5)][PF6] 9
In an inert atmosphere glove box, Mn(CO)5Br (0.107
g, 0.40 mmol) and [bmim]Cl–AlCl3 {X(AlC3)=0.65}
ionic liquid (0.075 cm3, 0.40 mmol) were placed in a
Schlenk flask. The sealed flask was removed from the
glove box and transferred to a Schlenk line. Under N2,
dry mesitylene (0.5 cm3) was added to the reaction
mixture. Maintaining a N2 atmosphere, the reaction
mixture was heated at 80°C for 15 h. Ice water (50 cm3)
was added to the reaction mixture. The yellow aqueous
solution was filtered to remove solid impurities, and
then washed with diethyl ether (5×10 cm3) in order to
remove any unreacted Mn(CO)5Br. The aqueous layer
was then filtered into a concentrated solution of
[NH4][PF6] (0.3 g in 5 cm3 of water) upon which
precipitation of a yellow solid occurred. The salt was
collected by filtration and dried in vacuo for 24 h and
characterized as 9 (yellow, 0.07 g, 42%) Analytical data,
C, 34.88; H, 2.27; C12H12O3MnPF6 requires C, 35.67;
3.8. Synthesis of [Mn(CO)3(p-C6H5Me)][PF6] 7
In an inert atmosphere glove box, Mn(CO)5Br
(0.5009 g, 1.84 mmol), and [bmim]Cl–AlCl3
(X(AlCl3)=0.65) ionic liquid (0.36 cm3, 1.84 mmol)
were placed in a Schlenk flask. The sealed flask was
removed from the glove box and transferred to a
Schlenk line. Under N2, dry toluene (0.23 cm3, 1.84
mmol) was added to the reaction mixture. Maintaining
a N2 atmosphere, the reaction mixture was heated at
80°C for 15 h with rapid stirring. Ice water (50 cm3)
was added to the reaction mixture. The yellow aqueous
solution was filtered to remove solid impurities, and
then washed with diethyl ether (5×10 cm3) in order to
remove any unreacted Mn(CO)5Br. The aqueous layer
was then filtered into a concentrated solution of
[NH4][PF6] (0.4 g in 5 cm3 of water) upon which
precipitation of a yellow solid occurred. The salt was
collected by filtration and dried in vacuo for 24 h, and
1
H, 2.99%. nCO(CH2Cl2, cm−1): 2015, 2075; H-NMR
(CD3COCD3, 270 MHz) l (ppm) 6.40 (s, aromatic),
2.59 (s, CH3); FAB-MS; m/z 259 [C9H12Mn(CO)3]+,
203 [C9H12Mn(CO)]+.

298
D. Crofts et al. / Journal of Organometallic Chemistry 573 (1999) 292–298
3.11. Synthesis of [Mn(CO)3(p-C6H5Ph)][PF6] 10
unreacted Mn(CO)5Br. The aqueous layer was then
filtered into a concentrated solution of [NH4][PF6] (0.059
g in 5 cm3 of water) upon which precipitation of a yellow
solid occurred. The salt was collected by filtration and
dried in vacuo for 24 h, and characterized as 12 (yellow,
0.76g, 35%). Analytical data, C, 54.22; H, 4.10;
C27H24F6MnO3P requires C, 54.38; H, 4.06%. IR:
wCO(Nujol, cm−l) 2017, 2076; 1H-NMR ((CD3)2CO, 270
MHz): l (ppm) 7.24 (s, coordinated ring), 6.62 (s,
uncoordinated rings) 3.04 (multiplet, CH2); FAB-MS:
m/z 451 [C27H24MnO3]+, 367 [C24H24Mn]+, 111
[C2MnO2]+, 93 [CMnO]+.
In an inert atmosphere glove box, Mn(CO)5Br (0.10
g, 0.36 mol) and {X(AlCl3)=0.65} [bmim]Cl–AlCl3
ionic liquid (0.073 cm3, 0.36 mmol) were placed in a
Schlenk flask. The sealed flask was removed from the
glove box and transferred to a Schlenk line. Under a
nitrogen atmosphere biphenyl (0.055 g, 0.36 mmol) was
added to the reaction mixture which was then heated at
80°C for 15 h. The reaction mixture was cooled and ice
water (50 cm3) added slowly. The mixture was filtered
and the yellow solution washed with diethyl ether (5×10
cm3). The aqueous layer was then filtered into a concen-
trated solution of [NH4][PF6] (0.06 g in 5 cm3 of water)
which gave a yellow solid which was filtered and dried
under vacuum and characterised as 10 (yellow, 0.047 g,
29%). Analytical data, C, 40.98; H, 2.33; C15H10F6MnO3
P requires C, 41.12; H, 2.30%. wCO(Nujol, cm−1) 2075,
Acknowledgements
We would like to thank the Royal Society for a
University Research Fellowship (P.J. Dyson) and the
EPSRC and Merck for a CASE award (N. Srinivasan).
1
2013; H NMR ((CD3)2CO, 270 MHz): l (ppm) 7.8 (s,
uncoordinated ring), 7.3 (s, coordinated ring); FAB-MS;
m/z 293 [C15H12MnO3]+, 237 [C12H11MnO]+, 209
[C12H10Mn]+.
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