Effect of the ligand L on the transesterification processes of bismethoxycarbonyl iron complexes: Cis Fe(CO2Me)2(CO)3L, L=CO, PMe3, PPh3, P(OEt)3

Article abstract of DOI:10.1016/S0022-328X(98)00545-2

The synthesis of the new mer or fac Fe(CO₂Me)₂(CO)₃ (L) (L=PMe₃: 2a; L=PPh₃: 2b; L=P(Cy)₃: 2c; L=P(OEt)₃: 2d) complexes of various electron densities has been realized in order to study the transesterification reactions between these methoxycarbonyl complexes and alcohols. The easy formation of [Fe(CO₂Me)(CO)₄(L)] [BF₄] by removing a methoxy group from these complexes clearly indicates that their methoxy group and particularly the one trans to the phosphane ligand are mobile. However whereas the unsubstituted complex Fe(CO₂Me)₂(CO)₄ (1) presents fast exchange reactions with ethanol, 2a and 2b are found unreactive towards the same reagent and 2d (L=P(OEt)₃) only undergoes slow transesterification reactions at 28°C. It is proposed an associative mechanism for this transesterification process probably induced by a preliminary nucleophilic addition of an alcohol molecule at a terminal carbonyl ligand prior to the elimination of the methoxy group of a methoxycarbonyl.

Full text of DOI:10.1016/S0022-328X(98)00545-2

Journal of Organometallic Chemistry 562 (1998) 183–189
Effect of the ligand L on the transesterification processes of
bismethoxycarbonyl iron complexes: cis Fe(CO2Me)2(CO)3L, L=CO,
PMe3, PPh3, P(OEt)3
Murielle Sellin, Denis Luart, Jean-Yves Salau¨n *, Pascale Laurent, Herve´ des Abbayes
Laboratoire de Chimie, Electrochimie Mole´culaires et Chimie Analytique, UMR CNRS 6521, Uni6ersite´ de Bretagne Occidentale,
UFR Sciences et Techniques, 6 A6enue le Gorgeu, BP 809, 29285 Brest Cedex, France
Received 17 November 1997
Abstract
The synthesis of the new mer or fac Fe(CO2Me)2(CO)3 (L) (L=PMe3: 2a; L=PPh3: 2b; L=P(Cy)3: 2c; L=P(OEt)3: 2d)
complexes of various electron densities has been realized in order to study the transesterification reactions between these
methoxycarbonyl complexes and alcohols. The easy formation of [Fe(CO2Me)(CO)4(L)] [BF4] by removing a methoxy group from
these complexes clearly indicates that their methoxy group and particularly the one trans to the phosphane ligand are mobile.
However whereas the unsubstituted complex Fe(CO2Me)2(CO)4 (1) presents fast exchange reactions with ethanol, 2a and 2b are
found unreactive towards the same reagent and 2d (L=P(OEt)3) only undergoes slow transesterification reactions at 28°C. It is
proposed an associative mechanism for this transesterification process probably induced by a preliminary nucleophilic addition of
an alcohol molecule at a terminal carbonyl ligand prior to the elimination of the methoxy group of a methoxycarbonyl. © 1998
Elsevier Science S.A. All rights reserved.
Keywords: Iron; Alkoxycarbonyl; Transesterification; Phosphane
1. Introduction
their great ability to give rapid exchanges of their alkoxy
group by reaction with alcohols [3]. These facile exchange
reactions strongly contrast with the transesterifications
of organic esters wich require acid or base catalysis.
This process has been observed for a wide range of
alkoxycarbonyl complexes: Pt [4], Re [5], Ir [6], Mn [7],
Ru [8], and Fe [7,9–11]. However the mechanism of the
reaction seems to depend on the nature of the metal
centre of the complex, on the electronic effects of the
ancillary ligands and to proceed according to two differ-
ent pathways.
Carbonylation reactions via nucleophilic activation of
carbon monoxyde mediated by transition metals have
been the subject of considerable attention. Alkoxycar-
bonyl or related carbamoyl complexes have often been
put forward as possible intermediates in such catalytic or
stoichiometric carbonylation processes and, for this
reason, have been studied for many years [1,2]. An
important feature of the alkoxycarbonyl complexes is
Thus a dissociative mechanism (Eq. 1) has been
postulated for the exchange processes observed on rhe-
nium: (ReCp(NO)(CO2Me)(CO); ReCp(NO)(CO2Me)-
* Corresponding author. Tel.: +33 2 98016286; fax: +33 2
98016594; e-mail: jean-yves.salaun@univ-brest.fr
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00545-2

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M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
(PPh3)) [5] or on iron complexes: (FeCp(CO2Men-
thyl)(CO)(PPh3)) [7] whose homologues: FeCp(COR)
(CO)(PPh3) (R=OMe, OPh, SMe, SPh) exhibit spon-
taneous ionizations in polar solvents [9,10].
An associative route is also conceivable for this
transesterification reaction; it has been proposed for
MnCp(NO)(CO2Menthyl)(PPh3) [7] or Ru(CO2Me)2
(CO)2(dppe)1 [8]. However it is still unclear wether the
nucleophilic attack of the alcohol occurs on a terminal
CO or on the alkoxycarbonyl itself (Eq. 2).
Since an increase of the electron density of the metal
centre is expected to favour a dissociative pathway (or
to disfavour an associative process) of the transesterifi-
cation reactions of alkoxycarbonyl complexes, we have
realized the preparation of alkoxycarbonyl complexes
of higher electron density than 1 by substituting one
CO ligand of this compound by different phosphanes.
In the present paper we describe the synthesis of
bis(alkoxycarbonyl)Iron complexes: Fe(CO2Me)2CO)3L
It is well known that nucleophilic additions of R−,
OR− or R2N− on terminal carbonyls give rise to the
formation of acyl, aryl, alkoxycarbonyl or carbamoyl
complexes [12–17]. However, it has also been described
that the addition of MeLi [18] or RONa [7] to alkoxy-
carbonyl complexes bearing no carbonyl occurs on the
alkoxycarbonyl itself inducing the formation of new
acyl or alkoxycarbonyl ligands. When acetyl and car-
bonyl ligands are present on the same complex, addi-
tion of nucleophiles such as organolithium reagents
occurs on a terminal CO rather than at the acyl [15].
However as alkoxycarbonyl are more electrophilic than
acyl ligands, a nucleophilic addition on their carbonyl
cannot be dismissed. To our knowledge only one exam-
ple of nucleophilic attack of alcoholate on a polyfonc-
tional organometallic complex bearing both CO and
CO2R ligands has been described. Indeed complex
Co(CO2Me)(CO)4 by reaction with MeO− affords
the anion [Co(CO2Me)2(CO)3]− formally formed by
addition of MeO− on a terminal CO [17]. However,
due to the same nature of the alcoholate and the alkoxy
group of the complex, a rapid exchange alkoxy-alcohol
resulting from an attack of the alcoholate on the car-
bonyl of the alkoxycarbonyl ligand cannot be pre-
cluded.
(L=PMe3, PPh3, PCy3 P(OEt)3) and the influence of
2
the ligand L on the transesterification reactions of these
compounds.
2. Results
2.1. Preparation of Fe(CO2Me)2(CO)3(PR3) (R=Me,
Ph, Cy, OEt)
When heated for 24 h at 28°C in CH2Cl2, cis
Fe(CO2Me)2(CO)4: 1 and 1.1 equivalent of phosphane
give rise to the formation of the new complexes
Fe(CO2Me)2(CO)3(PR3): (2) R=Me: 2a; Ph: 2b; Cy:
2c; OEt: 2d obtained in ca 40% yield after recrystalliza-
tion. The coordination of a phosphorous ligand on
these complexes induces in IR spectroscopy a shift of
their w CO stretching bands towards low frequencies
(see Table 1). This shift is consistent with an increase in
the y back-bonding to the carbonyl ligands induced by
a higher electron density of the metal centre [19]. An
analogous effect is observed in 13C-NMR where the
presence of the phosphane on the complex, indicated by
a coupling between the phosphorus and the CO linked
to the metal, induces a deshielding of the carbonyl
resonances of the remaining CO ligands [20].
We recently showed that cis Fe(CO2R)2(CO)4 com-
plexes (1) undergo rapid exchanges of their alkoxy
group with alcohols, oxalates or other bis(alkoxycar-
bonyl)iron compounds [11].
The substitution of one terminal carbonyl of 1 by a
phosphorous ligand may form three possible isomers of
2 (Eq. 3).
1 dppe=1,2-bis diphenylphosphinoethane.
2 Cy=cyclohexcyl.

M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
185
Table 1
Spectroscopic data for complexes 1, 2 and 3
Complex
IR hexane (cm−1
)
NMR (CD2Cl2 −20°C) l (ppm)
13C
1H
31P
wCꢁO
wCꢀO
CꢁO
JCꢂP (Hz)
CO2Me
192.2:2
JC–P (Hz)
Me
OMe
3.69(s)
1
2138(s)
2080(sh)
2052(vs)
2075(vs)
2080(w)
2030(s)
2100(w)
2035(s)
2010(s)
2090(w)
2020(s)
2010(sh)
2095(w)
2050(s)
2030(s)
2155(m)
2115(sh)
2090(s)
2075(sh)
2160(w)
2120(w)
2100(s)
2080(sh)
2160(w)
2120(sh)
2100(s)
2085(sh)
1665(m,br)
199.7:2
199.3:2
53.5
2aa
2b
1640(w,br)
205.1:2(d)
205.7:1(d)
205.8:2(d)
205.6:1(d)
18.9
37.0
16.0
9.5
201.6:2(d)
29.7
51.9(s)
3.47(s)
15.0
45.1
1645(w,br)
1630(w,br)
201.8:1(d)
197.0:1(d)
19.0
30.5
52.2(s)
51.2(s)
3.66(s)
3.26(s)
2c
2d
3a
1625(w,br)
1595(w,br)
209.3:2(d)
207.3:1(d)
14.5
10.6
203.2:1(d)
198.5:1(d)
18.7
25.3
52.5(s)
51.3(s)
3.61(s)
3.49(s)
50.6
150.0
37.3
1670(w,br)
1645(w,br)
204.3:2(d)
203.8:1(d)
27.4
15.9
199.9:1(d)
198.5:1(d)
30.4
56.4
51.5(s)
51.0(s)
3.51(s)
3.47(s)
1670(m)
1685(m)
1685(m)
198.7:2(d)
197.2:1(d)
196.0:1(d)
27.5
24.2
12.7
189.9:1(d)
188.4:1(d)
186.1:1(d)
23.0
23.0
32.1
55.9(s)
55.9(s)
56.2(s)
3.34(s)
3.34(s)
3.17(s)
3b
3d
197.8:2(d)
195.9:1(d)
195.3:1(d)
25.6
26.4
12.9
37.3
195.8:2(d)
193.7:1(d)
192.4:1(d)
42.8
43.8
22.3
107.8
a As the mer isomer 2a% has never been isolated, some of its characteristics are missing. NMR 13C: CꢁO: 205.7(d) (18.7 Hz); CO2Me 207.7:1(d)
(22.3 Hz); 199.1(d) (27.4 Hz); Me 51.4(s). 1H: OMe: 3.59(s) 3.49(s). 31P: 7.5.
The IR spectra of complexes 2b, 2c and 2d clearly
a cis JC–P (from 18 to 30 Hz) coupling constants for the
indicate that these compounds display the same geometry.
signals of the CO of the methoxycarbonyl ligands. The
The presence of two  CꢀO bands in the 1625–1670 cm−1
resonances of the terminal CO present only cis couplings
area of their IR spectra suggests that the two methoxy-
(from 9 to 27 Hz) with the phosphorus. The weakness
carbonyl ligands of these complexes are not equivalent.
of the coupling constants between the phosphorus and
This result is confirmed by their 13C-NMR spectra which
the CO trans to the alkoxycarbonyl ligand is noteworthy,
exhibit two doublets between 203 and 209 ppm for the
it probably results from a reduced back bonding toward
resonances of the CO of the alkoxycarbonyl ligands and
this CO trans to an electron-withdrawing ligand.
two singlets about 52 ppm for their methoxy groups and
As generally observed the magnitude of 2JC–P couplings
1
by the H-NMR which shows two singlets for the same
is significantly larger for the complex 2d bearing the
methoxygroups. Thenonequivalenceofthetwomethoxy-
phosphite ligand (from 15.9 to 56.4 Hz).
carbonyl ligands is consistent with the mer geometry B
The spectroscopic data obtained for 2a formed by
(Eq. 3) of the complexes 2b, 2c and 2d.
reaction of 1 with PMe3 are quite different from those
observed for 2b, 2c and 2d. The IR spectrum of this
compound exhibits only one CꢀO stretching band at
1640 cm−1 for the CO of the two methoxycarbonyl
The other 13C-NMR signals observed for these com-
plexesareingoodaccordancewiththeproposedstructure.
These spectra display a trans JC–P (from 25 to 56 Hz) and

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M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
ligands. The equivalence of these two ligands is confirmed
by the presence of only one doublet at 201.6 ppm
(CO2Me) and one singlet at 51.9 ppm (CH3) in 13C-NMR
are easily transformed into the cationic species [Fe(CO2-
Me)(CO)4(PR3)]+ (3) by reaction with a strong acid
(HBF4) [22] (Eq. 4).
1
and by one singlet at 3.47 ppm in H-NMR.
Both isomers A and C (Eq. 3) present this equivalence.
However, as the starting material 1 bears its two methoxy-
carbonyl ligands in cis position and as, probably due to
a strong trans influence of these ligands, trans bisalkoxy-
carbonyl octahedral complexes have never been observed,
the structure C is highly improbable. The JC–P values
observed in the 13C-NMR spectrum of 2a of geometry
mer (A) indicate that PMe3 is cis to both methoxycarbonyl
The cationic character of the compounds formed by
reaction of the complexes 2a, 2b, and 2d with HBF4 in
THF is indicated in IR by high CꢁO stretching frequen-
cies and in 13C-NMR by a shift of the carbonyl resonances
towards the highest fields (see Table 1). The spectroscopic
data of 3a, 3b and 3d clearly indicate that these cations
formed by reaction of either fac or mer isomers of 2 with
HBF4 present the same geometry. Their 13C-NMR which
display three doublets (intensity 2.1.1) for the resonances
of the terminal CO clearly demonstrate that this geometry
is cis.
Starting from 2b or 2d the observed process indicates
that the phosphane ligand of these mer complexes induces
specifically the dissociation of the methoxycarbonyl trans
to itself. This enhanced mobility probably results from
the reduced y accepting ability of the phosphanes com-
pared with CO which allows the dxy orbital to participate
to a greater extend in back bonding with the alkoxycar-
bonyl trans. These results clearly show that an increase
in the electron density of the described complexes makes
easier the dissociation of the alkoxy groups of their
alkoxycarbonyl ligands and therefore should favour a
transesterification process realized via a dissociative
mechanism.
ligands (JC–P=29.6 Hz) and to two terminal CO (JC–P
=
18.9 Hz). A higher value of the JC–P coupling constant
(37.0 Hz) is observed for the carbonyl trans to the
phosphine.
2a is not the only complex obtained by reaction of PMe3
with 1.The formation of a second compound 2a% which
represents ca. 7% of the reaction products is also ob-
1
served. The similarity of the 13C- and H-NMR spectra
of this complex 2a% (see Table 1) with those observed for
2b, 2c or 2d strongly suggests that 2a% is the mer isomer
B of 2a.
An organic carbonylated ligand is supposed to induce
a dissociative loss of CO from the position cis to itself
[21] therefore the primary product of the reaction of
substitution of one CO of Fe(CO2Me)2(CO)4 by a
phosphane is expected to be the fac compound.
However, careful monitorings realized by 31P-NMR at
the early stages of these reactions of substitution have not
revealed the transitory formation of other isomers of 2b,
2c and 2d and any change in the relative proportions of
complexes 2a and 2%a. These results lead us to assume that,
at the temperature of reaction (28°C), rapid isomeriza-
tions of the fac compounds into their mer isomers could
occur. These processes are possibly realized via alkoxy
hopping from one CO to another as proposed by
Gladfelter and colleagues [8].
2.3. Reactions of transesterification of complexes 2a,
2b and 2d
Contrary to the unsubstituted complex 1 which reacts
with ethanol in dichloromethane to give a fast exchange
(3 h at +10°C) of its methoxy groups, 2a or 2b are found
unreactive even at higher temperatures and after longer
reaction times. Only 2d (L=P(OEt)3) undergoes a slow
transesterification reaction. This process, as shown by
13C-NMR, is achieved after 25 h at 30°C. When the
reaction is realized with a large excess of EtOH it affords
only 2%%%d; on the other hand, when two equivalents of
EtOH are added to 2d the 13C-NMR spectrum of the
reactional mixture shows numerous resonances in the CO
region (190–215 ppm). The assigment of these signals is
consistent with the possible presence of the four com-
plexes described in Scheme 1.
2.2. Preparation of the cationic complexes
[Fe(CO2Me)(CO)4(PR3)] [BF4]: 3
The increase in the electron density of the metal induced
by the phosphorous ligand in complexes 2a,2b, and 2d
should favour their ionization into [Fe(CO2Me)
(CO)4(PR3]+[OMe]− [3,9].
Though complexes 2a,2b, and 2d do not afford spon-
taneous dissociations in polar solvents such as DMF, they
13C-NMR spectra realized at the very first stages of the
reaction have not allowed us to establish whether 2%d is
formed prior to 2%%d and 2%%%d. According to the observed

M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
187
Scheme 1.
carbonyl resonances these spectra suggest that the three
complexes 2%d, 2%%d and 2%%%d are rapidly formed under the
reaction conditions.
resulting from a nucleophilic attack on a terminal car-
bonyl ligand (Eq. 5).
This addition occurs also on complex 2d (L=P(OEt)3)
but, probably because of the reduced electrophilic char-
acter of their CO ligands 2a (L=PPh3) or 2b (L=PMe3)
are found unreactive. It is noteworthy that exchange
reactions are only observed for complexes which undergo
nucleophilic additions of alcoholates on a CO ligand.
These results lead us to suggest the following mecha-
nism for the transesterification reactions observed for 1
(Eq. 6).
This mechanism is of associative type; it includes an
addition of alcohol on a terminal CO prior to the
elimination of the methoxy group of one methoxycar-
bonyl ligand of the original complex. The nucleophilic
addition of alcohol can occur on an axial CO (a) and after
eliminationofmethanolthereactionissupposedtoinduce
the formation of the observed cis bis(alkoxycarbonyl)
complex (path a). According to a similar process, the
3. Discussion
The lack of reaction observed for 2a or 2b and the low
reactivityof2dstronglysuggestthatthetransesterification
processes observed for 1 occur via an associative mech-
anism. These conclusions agree with the results obtained
by Gladfelter and colleagues [8] on bis(alkoxycarbonyl)
ruthenium complexes. However, as shown in Eq. 2, this
associative mechanism involves prior to the exchange a
nucleophilic attack of ethanol either at a carbonyl group
or at the methoxycarbonyl ligand of complex 1.
A study that we realized recently provides an answer
to this question [23]. This work established that EtONa
reacted with complex 1 (L=CO) to induce specifically
the formation of the fac tris(alkoxycarbonyl) anion

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M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
addition of alcohol on an equatorial CO (b) (path b)
should lead to the formation of a trans bis(alkoxycar-
bonyl) complex. This second reactional pathway cannot
be ruled out since equatorial CO trans to electron
withdrawing alkoxycarbonyl ligands are considered
more electrophilic than the axial ones. As careful mon-
itorings of the reaction has never allowed us to estab-
lish the transient formation of the trans
bis(alkoxycarbonyl) complex, path b would involved a
very fast isomerization of this trans compound into its
cis isomer.
The transesterification reactions observed for 2d: mer
(Fe(CO2Me)2(CO)3P(OEt)3) probably occur via similar
processes. However due to the relatively high tempera-
ture required to realize the exchanges, fast isomeriza-
tions may explain the rapid formation of 2%d, 2%%d and
2%%%d.
dichloromethane mixture (5/1). After filtration the solu-
tion was slowly concentrated at −60°C. Complexes 2
which precipitated were obtained after filtration and
drying as pale yellow powders. As separations of 2 and
Fe(CO)3(L)2 by fractionnal crystallizations were rather
tricky, yields of pure 2 were relatively low.
2a: L=PMe3 yield, 30% (500 mg) Anal. Found: C,
36.05; H, 4.47; P, 9.37. C10H15FeO7P Calc.: C, 35.96; H,
4.53; P, 9.21%.
2b: L=PPh3 Yield, 20% (520 mg) Anal. Found: C,
57.71; H, 4.00; P, 5.82. C25H21FeO7P Calc.: C, 57.72; H,
4.07; P, 5.95%.
2c: L=PCy3 Yield, 40% (1.10 g) Anal. Found: C,
55.85; H, 7.48; P, 5.69. C25H39FeO7P Calc.: C, 55.77; H,
7.30; P, 5.75%.
2d:L=P(OEt)3 Yield, 40% (840 mg) Anal. Found: C,
36.61; H, 5.03; P, 7.15. C13H21FeO10P Calc.: C, 36.82;
H, 4.99; P, 7.30%.
4.2. Preparation of cationic complexes:
[Fe(CO2Me)(CO)4(L)] [BF4]: 3a: L=PMe3, 3b:
L=PPh3, 3d: L=P(OEt)3
4. Experimental section
All operations involving organometallics were carried
out under argon atmosphere. All solvents were distilled
under an inert atmosphere from an appropriate drying
agent [24]. Infrared spectra were recorded in hexane on
A 0.426 ml (3.5 mmol) volume of HBF4,OMe2 were
added dropwise via syringe to a stirred solution of 1.4
mmol of Fe(CO2Me)2(CO)3(L) (2) in THF (15 ml) at
−20°C. A cream coloured precipitate formed rapidly.
The reaction mixture was stirred for 1 h. After filtration
the residue was washed with two portions of cold THF
(5 ml, −40°C) and dried in vacuo to afford complexes
3 as white powders.
3a: L=PMe3 yield, 70% (380mg) Anal. Found: C,
27.68; H, 3.15; B, 2.81; F, 19.56. BC9F4FeH12O6P Calc.:
C, 27.73; H, 3.10; B, 2.77; F, 19.49%.
3b: L=PPh3 Yield, 65% (525 mg) Anal. Found: C,
49.98; H, 3.21; B, 1.92; F, 13.27. BC24F4FeH18O6P
Calc.: C, 50.04; H, 3.15; B, 1.88; F, 13.19%.
1
a Perkin-Elmer 1430 spectrometer. H- (300 MHz) and
13C- (75.47 MHz) NMR spectra were obtained on a
Brucker AC 300 spectrometer with chemical shifts re-
ported in l values relative to residual solvent (1H) or to
the solvent resonance (13C). The 31P (40.32MHz) spec-
tra were recorded on a Jeol FX 100 spectrometer using
87% H3PO4 as an external standard. Elemental analyses
were performed by the Service central d’analyses du
CNRS.
Complex 1: Fe(CO2Me)2(CO)4 was prepared as de-
scribed in Ref. [11]. Other reagents: PPh3, PMe3, PCy3,
P(OEt)3, HBF4 ·OMe2 were obtained from commercial
sources and used without purification.
3d: L=P(OEt)3 Yield, 60% (400 mg) Anal. Found:
C, 30.01; H, 3.84; B, 2.35; F, 15.91. BC12F4FeH18O9P
Calc.: C, 30.03; H, 3.78; B, 2.25; F, 15.84%
4.1. General procedure for the preparation of
phosphorous complexes: Fe(CO2Me)2(CO)3L: (2)
L=PMe3: 2a; L=PPh3: 2b; L=PCy3: 2c;
L=P(OEt)3: 2d
4.3. Reactions of transesterification realized from
2a, 2b and 2c
A 0.4 mmol volume of ethanol (0.022 m) were added
to a solution of Fe(CO2Me)2(CO)3(L) (2) (0.2 mmol) in
0.7 ml of CD2Cl2 in an NMR tube at −20°C. The
solution was warmed to 30°C and 13C-NMR spectra
were recorded periodically.
A 5.5 mmol volume of phosphane were added to a
solution of Fe(CO2Me)2(CO)4 (1) (1.43 g, 5 mmol.) in
30 ml of CH2Cl2 at 28°C. After the reactional mixture
was stirred for 24 h, the IR [13] and the 31P-NMR [25]
spectra of the resulting solution revealed together with
Fe(CO2Me)2(CO)3(L): (2) the presence of small
amounts of Fe(CO)3(L)2 (10%). The solvent was evapo-
rated at r.t.. The oily residue was washed with two
portions of 15 ml of hexane to remove the excess of
phosphane (L=PPh3, PCy3, P(OEt)3). The residue
which crystallizes as a cream coloured powder was
Complexes 2a: (L=PMe3) and 2b (L=PPh3): The
13C-NMR spectra remained unchanged after 20 h at
30°C.
Complex 2d (L=P(OEt)3): The 13C-NMR spectra
realized at t=0.5, 1, 1.5, 2, 3.5, 7.5, 10, 15, and 20 h
revealed the formation of numerous signals in the 190–
215 ppm area. No further evolution of these spectra
was observed after 20 h of reaction.
redissolved into
a
small amount of
a
hexane/
.

M. Sellin et al. / Journal of Organometallic Chemistry 562 (1998) 183–189
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