The synthesis and characterisation of heterosubstituted aminoferrocenes

Article abstract of DOI:10.1016/S0022-328X(97)00528-7

The synthesis of 1-bromo-1′-aminoferrocene is reported using a simple synthetic methodology. This compound serves as a useful precursor to other heterosubstituted aminoferrocenes. For example, (1′-amino)ferrocenecarboxylic acid has been obtained and is conveniently isolated in its C-protected form by lithiation of 1-bromo-1′-aminoferrocene, quenching with solid carbon dioxide and esterification of the resulting carboxylate with methanolic HCl. The new ligand 1-diphenylphosphino-1′-aminoferrocene has also been obtained using a similar methodology.

Full text of DOI:10.1016/S0022-328X(97)00528-7

Ž
.
Journal of Organometallic Chemistry 552 1998 63–68
The synthesis and characterisation of heterosubstituted aminoferrocenes
)
Ian R. Butler , Scott C. Quayle
Department of Chemistry, UniÕersity of Wales, Bangor, Gwynedd, LL57 2UW, UK
Received 5 June 1997
Abstract
X
The synthesis of 1-bromo-1-aminoferrocene is reported using a simple synthetic methodology. This compound serves as a useful
X
Ž
.
precursor to other heterosubstituted aminoferrocenes. For example, 1-amino ferrocenecarboxylic acid has been obtained and is
X
conveniently isolated in its C-protected form by lithiation of 1-bromo-1-aminoferrocene, quenching with solid carbon dioxide and
esterification of the resulting carboxylate with methanolic HCl. The new ligand 1-diphenylphosphino-1-aminoferrocene has also been
X
obtained using a similar methodology. q 1998 Elsevier Science S.A.
Keywords: Aminoferrocene; C-protected; Solid carbon dioxide
1. Introduction
get molecule of particular interest is the simple hetero-
X
Ž
.
substituted aminoferrocene, 1-amino ferrocenecarbo-
xylic acid 2. In addition to being an interesting com-
pound for coordination studies this molecule may be
thought of as the monomer of the ferrocene-based poly-
mer ferrolon,
X
The 1,1-heterodisubstitution of ferrocene has re-
ceived considerable attention recently with new syn-
thetic methodology allowing the preparation of a num-
ber of useful synthetic precursors such as heterosubsti-
w x
w x
w
x
tuted aldehydes 1 , halides 2 , phosphines 3,4 and
w x
stannyl derivatives 5 . In several of these synthetic
X
procedures 1-bromo-1-lithioferrocene has been used as
w
x
a key precursor 2,4,6 . This compound may be gener-
ated in situ from 1,1-dibromoferrocene on treatment
X
with n-butyllithium at y708C, providing a convenient
w
x
route to previously published ligands 7,8 such as those
shown in Scheme 1. Moreover, our group has made
extensive use of this reaction in the preparation of
heterosubstituted phosphine ligands, particularly difer-
Ž
.
rocenes, Scheme 2 .
Our longstanding interest in this area of chemistry is
aimed primarily at the preparation of compounds which
should find use as catalysts or catalyst precursors, viz.
phosphines and amines, and we therefore envisaged that
a route to heterosubstituted aminoferrocenes might use-
X
fully start from 1-bromo-1-aminoferrocene 1. One tar-
and it will undoubtedly be of interest in peptide synthe-
sis as a non-natural amino acid Plate 1 .
Ž
.
Aminoferrocenes have been known for a consider-
able time and a number of synthetic routes are available
w
x
for their synthesis, for example via lithiated 9,10 or
)
w
x
phthalimido 11 intermediates, reduction of nitrofer-
Corresponding author.
0022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

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64
I.R. Butler, S.C. QuaylerJournal of Organometallic Chemistry 552 1998 63–68
reaction of the lithiated amine with n-butyl bromide,
which is formed in the initial exchange reaction. The
X
Ž
.
small quantity of 1,1-bis- amino ferrocene which is also
obtained in the synthesis decomposes during work-up.
1
The H NMR spectra are characteristic, showing one
X
Ž . Y
Ž .
Scheme 1. Reagents: i BuLi ii CIPR2.
ferrocenyl proton resonance, that of the protons alpha
to the amino group, downfield of the other three. The
relatively high yields of compound 1
w
x
w
x
w x
rocenes 12–14 diazines 15 and ferrocenylazides 11
w
x
or deprotection of acetylated amines 11 .
2. Results and discussion
The methodology we chose to use was a modified
X
version of the monolithiation of 1,1-dibromoferrocene,
w x
recently published by Lai and Dong 2 and outlined
above. The monolithiated intermediate was reacted with
0.4 equivalents of O-benzylhydroxylamine to yield 1-
X
bromo-1-aminoferrocene 1, in yields of 45–55% based
in comparison to the similar literature preparation of
aminoferrocene is the result of the slow addition of a
limited amount of the quenching reagent. The main
byproduct bromoferrocene, which was removed in a
neutral fraction and isolated by column chromatogra-
phy, serves as a useful synthon in its own right.
on the quenching reagent, as a pale yellow crystalline
solid which may be stored at low temperature under an
inert atmosphere. In common with other aminofer-
rocenes the compound decomposes to a black oil under
ambient aerobic conditions over several hours. How-
ever, if nodules of sufficient size are obtained on crys-
tallisation we have found that a protective coat is formed
and we have had samples of this type exposed to air for
several months without apparent decomposition. A small
quantity ;14% of the n-butyl-substituted amine
byproduct, 4, was also identified by H NMR and mass
spectrometry in the supernatant solution together with
smaller quantities of the dibutyl-substituted amine prod-
X
Lithiation of 1-bromo-1-aminoferrocene was carried
out using 2.5 equivalents of n-butyllithium. The use of
dry solid carbon dioxide as a quenching reagent resulted
in the immediate precipitation of amino acid 2 in the
form of a water-soluble salt which was removed by
filtration and washed with diethyl ether. The identity of
the crude product was confirmed by NMR, however the
salt was contaminated somewhat with butylated byprod-
ucts. Further evidence for the presence of the Zwitteri-
onic salt was demonstrated by its inability to be ex-
tracted from aqueous solution under either acidic or
basic conditions. Attempts at dissolution in water fol-
lowed by organic solvent washing, evaporation and
Ž
.
1
Ž
.
Ž
. Ž
.
uct 5, 6% Plate 2 .
These may be separated by conventional column
chromatography from compound 1 which is slower to
elute than the alkyl-substituted byproducts. The byprod-
ucts are presumably formed as a consequence of the
X
Ž . Y
Ž .
Ž .
Scheme 2. Reagents: i BuLi ii CIPR2 iii Cl2 PR .

(
)
I.R. Butler, S.C. QuaylerJournal of Organometallic Chemistry 552 1998 63–68
65
Ž . Y
Scheme 3. Reagents: i BuLi ii BnONH2 iii CO2 iv AcClrMeOH v NaOH.
Ž .
Ž
.
Ž
.
Ž .
extraction into dry methanol met with limited success.
Finally a procedure was developed, using conventional
organic synthetic techniques, which allowed for the
isolation of the methyl ester by treatment of the crude
solid initially obtained with methanolic hydrogen chlo-
ride. Rapid exothermic dissolution occurred and the
mixture was stirred overnight before being treated with
a dilute aqueous sodium hydroxide solution and ex-
tracted with diethyl ether. Three major products were
then isolated by column chromatography, compounds 6,
7 and 81
The major product 8 was obtained as deep orange
crystals which were found to be considerably more
stable than either of compounds 6
and 7.
Ž
. Ž
.
in the ratio 62:9:24, Plate 3 Scheme 3 .
Compound 8 may be considered as a useful latent
source of the polymer 3. Preliminary attempts at struc-
tural characterisation of compound 8 using X-ray crys-
tallography have been unsuccessful due to twinning
however it has been established that the compound
crystallises as a hydrogen-bonded dimer. An alternative
isolation procedure which involved chromatography of
1 Compound 7 identified by spectral comparison with an authentic
sample arises from the use of solid carbon dioxide which condensed
traces of water during transfer.

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66
I.R. Butler, S.C. QuaylerJournal of Organometallic Chemistry 552 1998 63–68
an aqueous solution of the amino acid fraction using
Sephadex resulted in the isolation of compound 2 as a
buff coloured powder however it was found to be
contaminated with small quantities of pentanoic acid
which was formed as a byproduct from the reaction of
residual butyllithium with carbon dioxide. Nevertheless
it was possible to characterise compound 2 using NMR
and mass spectrometry. The difficulty experienced in
the isolation of the amino acid may in part be due to the
formation of intermediate complexes in which the N-
pounds including the new ligand 1-diphenylphosphino-
X
X
Ž
1-aminoferrocene and substituted derivatives of 1-
.
amino ferrocenecarboxylic acid.
4. Experimental
4.1. General
All experiments were run under a dry nitrogen atmo-
sphere using standard Schlenk glassware. 1H NMR
spectra were recorded on a Bruker AC250 instrument
lithio function has also been trapped with carbon diox-
X
w
x
ide 15 . The reaction of 1-diphenylphosphino-1-lithio-
X
Ž
ferrocene prepared in situ from 1-bromo-1- diphenyl-
phosphino ferrocene with O-benzylhydroxylamine us-
1
operating at 250 MHz for H. d values are given in
.
ppm and are relative to TMS as internal standard. J
values are given in Hz. Mass spectra were recorded
using a variety of techniques including electron impact,
chemical ionization, FAB and electrospray at the EP-
SRC National Laboratory Service at the University of
Wales, Swansea. Column chromatography was routinely
performed using a neutral alumina support, Brockman
Grade 1. All solvents were predried using conventional
ing a similar work-up procedure to that used in the
preparation of compound 2 resulted in the formation of
X
1-diphenylphosphino-1-aminoferrocene, 9 which may
be considered as the ferrocene equivalent of the well-
Ž
.
known organic ligand 2- diphenylphosphino aniline.
This compound was observed to darken on prolonged
standing in air and thus may not be such a useful ligand
for want of ease of handling. The 31 P NMR spectrum
consists of a singlet at y17.57 ppm which is only
X
methods and were distilled prior to use. 1,1-Dibromo-
ferrocene was made by a modification of the literature
procedure typically on a 50 g scale.
Ž
slightly shifted downfield from that of diphenylphos-
.
Ž
.
phino ferrocene y17.2 ppm . A preliminary investiga-
tion into the coordination behaviour of this ligand with
X
4.2. Preparation of 1-bromo-1-aminoferrocene, 1
Ž .
palladium II resulted in the formation of the bidentate
complex although the reaction was not clean, possibly
due to the rapid coordination of the phosphorus and the
slower coordination of the nitrogen which would give
intermediate diligand complexes. Further coordination
studies on this ligand will be reported in a subsequent
communication Plate 4 .
Clearly the use of other quenching reagents will lead
to the preparation of a wide range of aminoferrocenes,
X
Ž
A solution of 1,1-dibromoferrocene 3.44 g, 10
.
Ž
.
mmol in THF 25 ml was cooled to y708C in an
external acetonerdry ice bath. To this solution was
Ž
.
added n-butyllithium 4 ml of a 2.5 M sol. in hexane .
Ž
.
The mixture was allowed to stir for 10 min. A solution
of O-benzylhydroxylamine 0.49 g, 4 mmol in THF
10 ml was then added and the mixture was allowed to
warm to ambient temperature with stirring over 1 h. The
product was quenched with water 10 ml before being
extracted into 20 ml of dilute HCl. The aqueous layer
Ž
.
Ž
.
for example quenching with DMF gives rise to the
X
Ž
.
Ž
.
anticipated 1-amino ferrocenecarbaldehyde and substi-
2
tuted derivatives which are readily separable by col-
w
x
Ž
.
Ž
umn chromatography 16 and are obtained as orange air
and light sensitive solids after purification. The initial
derivatisation of compound 1 will allow for the synthe-
sis of a wide range of heterosubstituted aminoferrocene
derivatives such as azoferrocenes and ferrocenylisoni-
triles. The work is now focused on the preparation of
polyferrocene derivatives from these precursors.
was washed with diethyl ether 20 ml . Fresh ether 20
ml was added and the mixture was slowly made basic
.
with dil. sodium hydroxide. The yellow product trans-
ferred to the ether layer which was separated and a
further extraction was performed with the same volume
of ether. The combined organic fractions were dried
over anhydrous magnesium sulfate and the solvent was
removed in vacuo. Purification was achieved either by
crystallisation of the product 1 from a minimum volume
of hexane overnight at y108C, yield 0.8 g, 71% or by
column chromatography on a basic alumina support,
which also afforded the faster eluting n-butyl-sub-
Ž
.
3. Summary
A convenient and rapid synthesis of heterosubstituted
aminoferrocenes has been developed which allows for
the preparation of simple yet important precursor com-
Ž
.
stituted aminoferrocene, 4 14% and small quantities of
the dibutylated derivative 5 6% . 1: C10 H10 BrFeN: H
1
Ž
.
Ž
.
Ž
.
Ž
.
NMR CDCl3 ds2.71 bs, 2H , 3.94 t, 2H, Js1.6 ,
Ž
.
Ž
.
Ž
3.95 t, 2H, Js1.6 , 4.05 t, 2H, Js1.8 , 4.32 t, 2H,
1
.
Ä13
4 Ž . Ž .
C NMR CDCl3 ds60.4 2=CH ,
Js1.8 .
H
2 N-substitution is also observed.
Ž
.
Ž
.
Ž
.
63.7 2=CH , 67.3 2=CH , 70.7 2=CH , 79.3

(
)
I.R. Butler, S.C. QuaylerJournal of Organometallic Chemistry 552 1998 63–68
67
Ž
.
Ž
.
Ž
.
)C- , 106.4 )C- . Mass spectrum mrz rel.
careful addition of acetyl chloride to methanol . After
stirring overnight the reaction mixture was brought to
pH8 by the dropwise addition of dil. sodium hydroxide.
The product mixture was extracted into diethyl ether
.
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
int. : 281 45 , 279 47 , 257 100 , 201 81 , 108 26 .
1
Ž
.
Ž
4: C14 H18 BrFeN: H NMR CDCl3 ds0.95 t, 3H,
.
Ž
.
Ž
Js7.0 , 1.41 pseudo sxt, 2H, Js7.0 , 1.55 pseudo
.
Ž
.
Ž
.
Ž
.
sxt, 2H, Js7.0 , 2.24 bs, 1H , 2.92 t, 2H, Js7.0 ,
3=20 ml and dried over magnesium sulfate and the
solvent was removed in vacuo. Column chromatography
on neutral alumina afforded compounds 6 24% , 7
9% and the major product compound 8 1.6 g, 62%
as a deep orange-red solid from the third orange band.
Ž
.
Ž
.
Ž
3.83 t, 2H, Js1.8 , 3.90 t, 2H, Js1.8 , 4.00 t, 2H,
1
.
Ž
.
Ä13
4
Ž
.
Ž
.
Js1.9 , 4.32 t, 2H, Js1.9 . H C NMR CDCl3
Ž
.
Ž
Ž
.
Ž
.
Ž
.
.
Ž
.
Ž
.
ds14.1 CH3 , 20.5 CH2 , 32.1 CH2 , 46.7 CH2 ,
Ž
.
.
Ž
57.5 2=CH , 65.3 2=CH , 66.8 2=CH , 70.1
1
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
2=CH , 78.9 )C- , 112.5 )C- . Mass spec-
8: C10 H13FeNO2: H NMR CDCl3 ds1.59 bs, 2H ,
q
Ž
.
Ž
.
Ž
.
Ž
.
Ž
Ž
.
Ž
.
Ž
.
trum mrz rel. int. : 337 88 , 335 93 , M , 257 100 .
3.81 s, 3H , 3.88 t, 2H, Js1.8 , 3.98 t, 2H, Js1.8 ,
1
1
.
Ž
.
Ä13
4
H C
Ž
.
Ž
5: C18 H26 BrFeN: H NMR CDCl3 ds0.94 t, 6H,
4.35 t, 2H, Js1.9 , 4.77 t, 2H, Js1.9 .
.
Ž
.
.
Ž
Ž
.
Ž
.
Ž
.
Js7.0 , 1.34 pseudo sxt, 4H, Js7.0 , 1.56 pseudo
NMR CDCl3 ds59.3 CH3 , 65.1 2=CH , 65.8
.
Ž
Ž
Ž
.
Ž
.
Ž
.
Ž
.
.
Ž .
sxt, 4H, Js7.0 , 2.92 t, 4H, Js7.0 , 3.67 t, 2H,
2=CH , 70.9 2=CH , 71.7 2=CH , 72.3 )C- ,
.
Ž
.
Ž
.
.
Ž
.
Ž
.
Ž
Js1.8 , 3.94 t, 2H, Js1.8 , 4.03 t, 2H, Js1.9 ,
106.9 )C- , 156.3 )C- . Mass spectrum E.I.
Ž
.
Ž
Ž
.
Ž .
Ž
.
Ž .
4.32 t, 2H, Js1.9 . Mass spectrum mrz: 393 98 ,
mrz: 259 100 , 228 4 , 167 12 , 143 3 , 137 8 .
qØ
Ž
.
391 100 , M .
Accurate mass: 259.02731, D s 10 ppm. 6:
C14 H21FeNO2: 1H NMR CDCl3 ds0.94 t, 3H,
Ž
.
Ž
X
(
)
.
Ž
.
Ž
.
Ž
.
4.3. Preparation of 1-amino ferrocenecarboxylic acid,
2
Js7.0 , 1.21 m, 2H , 1.52 m, 2H , 1.61 bs, 1H ,
Ž
.
Ž
.
Ž
.
2.94 t, 2H, Js7.0 , 3.74 s, 3H , 3.83 t, 2H, Js1.8 ,
Ž
.
Ž
.
Ž
3.86 t, 2H, Js1.8 , 4.32 t, 2H, Js1.9 , 4.72 t, 2H,
X
1
.
Ä13
4
Ž
.
.
Ž
.
Ž
.
1-Bromo-1-aminoferrocene 1 2.8 g, 10 mmol in
Js1.9 . H C NMR CDCl3 ds13.9 CH3 , 20.4
Ž
.
Ž
Ž
.
Ž
.
Ž
Ž
.
diethyl ether 30 ml was treated with 2.5 equivalents of
CH2 , 29.7 CH2 , 32.0 CH2 , 56.4 2=CH , 64.7
Ž
.
.
Ž
.
Ž
.
Ž
.
.
n-butyllithium 10 ml of a 2.5 M sol. in hexane at
y708C. The mixture was allowed to warm to y508C
over 10 min, darkening considerably, and was treated
with excess dry carbon dioxide before being allowed to
warm to ambient temperature. The resultant bright yel-
low-orange suspension was filtered and the residue was
2=CH , 65.8 2=CH , 70.2 2=CH , 71.2 )C- ,
Ž
.
Ž
.
Ž
156.6 )C- . Mass spectrum E.I. mrz: 315 100 ,
Ž . Ž . Ž .
Ž
.
Ž
.
284 3 , 259 6 , 240 7 , 223 19 , 189 22 . 7:
1
Ž
.
Ž
.
C10 H11FeN: H NMR CDCl3 ds2.54 bs, 2H , 3.89
Ž
.
Ž
.
Ž
.
m, 2H , 3.96 m, 2H , 4.07 s, 5H ; identified by
spectral comparison with an authentic sample prepared
by the direct water quenching of 1-amino-1-lithioferro-
X
Ž
.
washed with ether 3=30 ml . Chromatography of this
solid using Sephadex yielded a yellow-orange powder,
cene.
2, contaminated with pentanoic acid which co-elutes. 2:
C9 H11FeNO2: H NMR D2O ds3.92 bm, 2H , 4.14
1
X
Ž
.
Ž
.
4.4.1. Preparation of 1-diphenylphosphino-1-aminofer-
Ž
Ž
.
Ž
.
Ž
.
bm, 2H , 4.40 bm, 2H , 4.65 bm, 2H . Mass spectrum
rocene, 9
X
q.
.
Ž .
Ž
.
Ž
.
Ž
.
electrospray 245 8 , 244 100 , M –H, 200 22 . Salt
To a solution of 1-bromo-1- diphenylphosphino fer-
1
Ž
.
.
Ž
Ž
.
Ž
.
extract: H NMR D2O, HOD suppressed ds4.38 m,
rocene 4.49 g, 10 mmol in THF 25 ml at y108C
.
Ž
Ž
Ž
.
Ž
.
Ž
2H , 4.21 m, 2H , 4.02 m, 2H , 3.98 m, 2H . Mass
was added 1 equivalent of n-butyllithium 4 ml of a 2.5
Ž
.
.
.
Ž
.
Ž
.
.
spectrum E.I. mrz:378 32 , 334 100 , 290 63 , 275
M sol. in hexane over 10 min., followed by a solution
of O-benzylhydroxylamine 4.9 g, 4 mmol in THF 10
ml . The mixture was allowed to warm to ambient
Ž
.
Ž
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
Ž
31 , 262 46 , 226 27 , 218 41 , 177 81 , 157 28 ,
Ž
.
.
134 67 .
temperature over 1 h. and was then quenched with
X
(
)
Ž
.
4.4. Preparation of methyl 1-amino ferrocenecarboxy-
late, 8
water 20 ml . The product was extracted into dil.
aqueous hydrochloric acid solution which was then
separated from the organic layer. Diethyl ether was
added and the product was liberated from the organic
layer by the slow addition of dil. sodium hydroxide
solution. Following drying over magnesium sulfate, the
solvent was removed from the filtered solution which
was then reduced to an oil under vacuum. The yellow
product was dissolved in the minimum volume of hot
X
Ž
.
.
1-Bromo-1-aminoferrocene 1 2.8 g, 10 mmol in a
mixture of diethyl ether and THF 50:50, 30 ml was
treated with 2.5 equivalents of n-butyllithium 10 ml of
Ž
Ž
.
a 2.5 M sol. in hexane at y708C. The mixture was
allowed to warm to y508C over 10 min and was treated
with excess dry carbon dioxide before being allowed to
warm to ambient temperature. The mixture was then
Ž
hexane and allowed to cool and crystallise. Yield: based
1
Ž
.
Ž
.
quenched with water 20 ml and the aqueous product-
containing fraction was separated and dried under vac-
uum to give a pale yellow powder. This product was
then redissolved in methanol before being treated slowly
on added amine, 0.59 g, 38% 9: C22 H20 FeNP: H
Ž
.
Ž
.
Ž
.
NMR CDCl3 ds2.30 bs, 2H , 3.74 t, 2H, Js1.8
Ž
.
Ž
.
Ž
3.87 t, 2H, Js1.8 , 3.98 t, 2H, Js1.9 , 4.27 t, 2H,
.
Ž
.
Ž
Js1.9 , 7.15–7.45 bm, 10H . Mass spectrum mrz:
1
Ä31
4
.
Ž .
q
Ž
Ž
.
with a solution of methanolic HCl prepared by the
385 100 , M . H P NMR CDCl3 dsy17.57 s .

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68
I.R. Butler, S.C. QuaylerJournal of Organometallic Chemistry 552 1998 63–68
4.4.2. Preparation of a palladium complex of compound
M. North and A.L. Boyes for useful discussions. The
mass spectra reported, other than the low resolution
data, were recorded with the aid of the EPSRC central
mass spectrometry service at the University of Wales,
Swansea, to whom we are grateful for such an efficient
service.
Ž
.
A solution of the ligand 9 0.5 g, 1.3 mmol in
References
Ž
.
dichloromethane 7 ml was treated with a solution of
w
Ž
.
x
Ž
.
w x
1 G. Iftime, C. Moreau-Bossuet, E. Manoury, G.G.A. Balavoine,
Pd COD Cl2
0.38 g, 1.3 mmol also in
Ž
.
J. Chem. Soc. Chem. Commun. 1996 527.
L.-L. Lai, T.-Y. Dong, J. Chem. Soc. Chem. Commun. 1994
1078.
Ž
.
dichloromethane 7 ml . The solution changed colour
from yellow to a deep red on addition. The product was
precipitated from solution after 1 h. by the addition of
diethyl ether, as a deep red powder. Attempted recrys-
tallisation from biphasic dichloromethanerether 1:1
w x
2
Ž
.
w x
Ž .
I.R. Butler, W.R. Cullen, Organometallics 3 1984 1846.
3
w x
4
Ž .
I.R. Butler, R.L. Davies, Synthesis 1996 1350.
w x
Ž .
M.E. Wright, Organometallics 9 1990 853.
G.R. Knox, P.L. Pauson, D. Willson, E. Solcaniova, S. Toma,
Organometallics 9 1990 301, and references therein.
5
gave only a powdered product. LPdCl2 : 1H NMR
w x
6
Ž
.
Ž
.
Ž
.
Ž
.
Ž
Ž
.
Ž
.
.
CDCl3 ds3.74 m, 2H , 4.00 m, 2H , 4.21 m, 2H ,
w x
7
A.N. Nesmeyanov, E.G. Perevalova, R.V. Golovnya, L.S.
Shilovtseva, Dokl. Akad. Nauk. SSSR. 102 1955 535.
Ž
.
.
Ž
4.41 m, 2H , 7.14–7.50 m, 6H , 7.50–7.80 m, 4H .
Ž
.
1
Ä31
4
Ž
.
Ž .
Ž
H
P NMR CDCl3 dsq15.77 s . Mass spectrum
w x
Ž .
8
N. Monserrat, A.W. Parkins, A.R. Thomkins, J. Chem. Res. S
q
Ž
.
Ž
.
Ž
.
FAB : cluster centred at mrz 490 100 , M –2 Cl;
1995 336 and references therein.
Ž .
J.F. Helling, H. Shechter, Chem. Ind. 1959 1157.
w x
9
x
x
. Ž
385 60 . N.B. a weak cluster was also observed
w
w
Ž
.
.
10 H. Grubert, K.L. Rinehardt Jr., Tetrahedron Lett. 1959 16.
.
centred at mrz 596 which corresponds to LPd2 .
Ž
11 M. Herberhold, in: T. Hayashi, A. Togni Eds. , Ferrocenes.
Ž
.
VCH press 1995 pp. 225–228.
w
w
x
Ž
.
12 K. Schlogl, H. Mechtler, Monatsh. Chem. 97 1966 150.
x
Acknowledgements
13 A.N. Nesmeyanov, V.D. Drozd, V.A. Sazonova, Dokl. Akad.
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Nauk. SSSR. 150 1963 321.
w
w
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14 M. Herberhold, L. Haumaier, Angew. Chem. Int. Ed. Engl. 23
The work was funded by a University of Wales
research grant which is gratefully acknowledged. The
authors would like to thank Mr. E. Lewis and Mr. D.J.
Williams for their invaluable technical support and Drs.
Ž
.
1984 521.
x
15 A.R. Katritzsky, W.-Q. Fan, K. Akutagawa, Tetrahedron 42
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1986 4026.
x
16 I.R. Butler, S.C. Quayle, A.L. Boyes, to be published.