New trisubstituted cyclopentadienyl ligands: Synthesis, characterisation and catalytic properties of mono and dinuclear cobalt, rhodium, iron and ruthenium complexes

Article abstract of DOI:10.1016/S0022-328X(00)00652-5

The synthesis of a set of dialkyl 4-alkoxycarbonylcyclopenta-1,3-diene-1,2-diacetates (1a-e) is described. Their coordinating abilities as anions have been investigated in relation to the formation of new sandwich, half-sandwich and dinuclear complexes and their structural features. We report here the preparation and characterisation of some complexes such as a mononuclear half-sandwich cobalt(1,5-COD) complex which has shown to be a very efficient catalyst for the cyclocotrimerisation reaction of alkynes and nitriles to pyridines. Half-sandwich rhodiumdicarbonyl complexes containing trisubstituted cyclopentadienyl ligands with ester chains of different length have been employed successfully as catalysts for hydroformylation of styrene. Finally ligands 1a-e have been used for the synthesis of ferrocenes and dinuclear carbonyl complexes of iron and ruthenium. The structures of the complexes 1,5-cycloctadiene[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene) cyclopentadienyl]cobalt [Co(MDMCp)COD] (9), dicarbonyl[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene)cyclopentadienyl] rhodium [Rh(MDMCp)(CO)₂] (2a) and of a new ferrocene complex [Fe(MDMCp)₂] (15a) have been determined by X-ray diffraction methods.

Full text of DOI:10.1016/S0022-328X(00)00652-5

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Journal of Organometallic Chemistry 619 (2001) 179–193
New trisubstituted cyclopentadienyl ligands: synthesis,
characterisation and catalytic properties of mono and dinuclear
cobalt, rhodium, iron and ruthenium complexes
Mirco Costa a,*, Enrico Dalcanale a, Francisco Santos Dias b, Claudia Graiff c,
Antonio Tiripicchio c, Lorenzo Bigliardi a
a Dipartimento di Chimica Organica e Industriale, Uni6ersita` degli Studi di Parma, Parco Area delle Scienze 17A, 43100 Parma, Italy
b Departamento de Qu´ımica Orgaˆnica e Inorgaˆnica, Uni6ersidade Federal do Ceara`, C.P. 12200, CEP 60455-760, Fortaleza, CE, Brazil
c Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Centro di Studio per la Strutturistica Diffrattometrica del C.N.R., Parco Area delle Scienze 17A, 43100 Parma, Italy
Received 3 August 2000; accepted 18 August 2000
Abstract
The synthesis of a set of dialkyl 4-alkoxycarbonylcyclopenta-1,3-diene-1,2-diacetates (1a–e) is described. Their coordinating
abilities as anions have been investigated in relation to the formation of new sandwich, half-sandwich and dinuclear complexes
and their structural features. We report here the preparation and characterisation of some complexes such as a mononuclear
half-sandwich cobalt(1,5-COD) complex which has shown to be a very efficient catalyst for the cyclocotrimerisation reaction of
alkynes and nitriles to pyridines. Half-sandwich rhodiumdicarbonyl complexes containing trisubstituted cyclopentadienyl ligands
with ester chains of different length have been employed successfully as catalysts for hydroformylation of styrene. Finally ligands
1a–e have been used for the synthesis of ferrocenes and dinuclear carbonyl complexes of iron and ruthenium. The structures of
the complexes 1,5-cycloctadiene[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene)cyclopentadienyl]cobalt [Co(MDMCp)-
COD] (9), dicarbonyl[1-methoxycarbonyl-3,4-di(methoxycarbonylmethylene)cyclopentadienyl]rhodium [Rh(MDMCp)(CO)2] (2a)
and of a new ferrocene complex [Fe(MDMCp)2] (15a) have been determined by X-ray diffraction methods. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Substituted cyclopentadiene; Cyclopentadienyl complexes: cobalt, rhodium, iron, ruthenium; Alkyne cyclisation; Hydroformylation
1. Introduction
clopentadienyl ligands and their sandwich and half-
sandwich metal complexes [2–4].
Derivatives of cyclopentadiene form one of the most
important and versatile classes of ligands in the metal-
lorganic chemistry. In their substituted or unsubstituted
form they are able to stabilise metals in both high or
low oxidation states through h1–h5 bonding modes [1].
The functionalisation of the cyclopentadienyl ring can
alter significantly the steric and electronic properties of
the corresponding complexes [2].
Several synthetic strategies are available for the syn-
thesis of substituted mono- and di-h5-cyclopentadienyl
metal complexes. Two main experimental approaches
can be distinguished: the former is based on the direct
use of suitable substituted cyclopentadienyl rings which
are caused to react with transition metal complexes
according to the procedure for the synthesis of sand-
wich and half-sandwich complexes [5]; the latter is
based on the introduction of substituents in the ring
after preparation of a cyclopentadienyl metal complex.
This includes metallation reactions and electrophilic
aromatic substitution reactions [6].
In the last few years, significant efforts have been
devoted to work out smooth synthetic procedures for
the preparation of new multiple functionalised cy-
Recently we developed a new multistep procedure to
prepare a cyclopentadiene derivative substituted by one
* Corresponding author. Fax: +39-0521-905472.
E-mail address: costa@unipr.it (M. Costa).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00652-5

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M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
methoxycarbonyl and two methoxycarbonylmethylene
functions (1a, HMDMCp) [7].
appropriately adapted in order to obtain trisubstituted
cyclopentadiene derivatives containing suitable ester
groups. For this purpose we prepared alkyl benzyl
2,2-diprop-2-ynylmalonate (3a–d) which underwent
palladium-catalysed oxidative carbonylation to cyclic
ester derivatives.
Our procedure consists of a palladium-catalysed ring-
forming oxidative carbonylation of benzyl methyl 2,2-
diprop-2-ynylmalonate, followed by the elimination of
the benzyloxycarbonyl group and double bond isomeri-
sation. The cyclopentadienyl anion (1a) was caused to
react with rhodium complexes [{RhCl(L)2}2], [L=CO,
C2H4, 1,5-cyclooctadiene (COD)], yielding the corre-
sponding h5-cyclopentadienyl complexes (2a–a%%).
The presence of a smoothly hydrolisable ester benzyl
group favoured decarboxylation followed by double
bond isomerisation to a trisubstituted cyclopentadiene
derivative. Product 3a was obtained as reported [7]
starting from the commercially available methyl benzyl
malonate. Substrates 3b–d could be prepared through
two alternative ways (Scheme 1) both starting from
2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum acid).
Procedure (a) allows the synthesis of a variety of
malonic benzyl-alkyl diesters. Alternatively procedure
(b), if the alkyl chloroformate is not commercially
available, diester 5 can be prepared from the acid
chloride of 4(b).
The overall yields of isolated malonic diesters 5b–d
(R=Et, C8H17, C12H25) based on the starting Meldrum
acid were ca. 35–40%. The propynylation of benzyl
alkyl malonates (5a–d) was carried out according to the
procedure reported previously [7] with yields of 3a–d
ranging from 83 to 72%.
Complexes 2a% and 2a are efficient catalysts for the
alkyne-nitrile cyclocotrimerisation to pyridines and for
the hydroformylation of styrene and 1-hexene, respec-
tively, showing a higher activity compared with the
corresponding unsubstituted cyclopentadienylrhodium
complexes [7].
Herein we report the results concerning the synthesis
and characterisation of a mononuclear half-sandwich
cobalt complex containing ligand 1a. Its catalytic activ-
ity was tested in cyclocotrimerisation reactions of alky-
nes and nitriles to pyridines. Moreover our synthetic
procedure gave easy access to a set of trisubstituted
cyclopentadienyl ligands with C1 to C12 ester chains and
their corresponding h5-cyclopentadienylrhodiumdicar-
bonyl complexes, which were tested as catalysts for the
hydroformylation of styrene. Trisubstituted cyclopenta-
dienyl ligands of the type 1a–e were also used in the
synthesis of ferrocenes and dinuclear carbonyl com-
plexes of iron and ruthenium.
The subsequent oxidative carbonylation was based
on our procedure described previously [7]. Reactions
and yields are shown in Scheme 2.
The crystal structures of the complexes 1,5-cyclocta-
diene[1 - methoxycarbonyl - 3,4 - di(methoxycarbonyl-
methylene)cyclopentadienyl]cobalt
[Co(MDMCp)-
COD], (9), dicarbonyl[1methoxycarbonyl-3,4-di-
Scheme 1.
(methoxycarbonylmethylene)cyclopentadienyl]rhodium
[Rh(MDMCp)(CO)2] (2a), and of a new ferrocene com-
plex [Fe(MDMCp)2] (15a) are also reported.
2. Results and discussion
2.1. Ligand synthesis
The synthetic procedure yielding dimethyl 4-
methoxycarbonylcyclopenta-1,3-diene-1,2-diacetate was
Scheme 2.

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
181
1
IR, H- and 13C-NMR data of complex 9 shows a
close analogy to those of the corresponding rhodium
complex described previously [7] and an X-ray analysis
confirms the proposed structure.
Scheme 3.
A view of the structure is shown in Fig. 1 together
with the atomic labelling system; selected bond dis-
tances and angles are given in Table 1. The cobalt atom
interacts in a h5-fashion with the substituted cyclopen-
tadienyl ring of ligand 1a and completes its coordina-
tion through two h2-interactions with the double bonds
of the COD ligand. The distance of cobalt from the
The results show that the carbonylation reaction is
efficient and general for linear alcohols with chains
from C1 to C12. Elimination of the benzyl group fol-
lowed by decarboxylation and isomerization reactions
to products 1a–e were carried out according to a
reported procedure [8] (Scheme 3).
This multistep process enabled the synthesis of new
trisubstituted cyclopentadiene derivatives functionalized
with aliphatic ester chains of variable length and steric
hindrance.
Alternatively a more direct synthetic way to prepare
cyclopentadienes 1 was worked out, based on a two
stage process consisting of the introduction of two
propynyl groups into Meldrum acid, followed by oxida-
tive carbonylation in methanol in the presence of 10%
PdꢀC and KI. A mixture of two isomers 8a (78:22
molar ratio, GC) was obtained in 38% isolated yield
(Scheme 4).
,
centroid M(1) of the Cp is 1.714(2) A and those from
the midpoints M(2) and M(3) of the two double bonds
,
are 1.905(3) and 1.900(2) A, respectively. The cobalt
atom is practically coplanar with M(1), M(2) and M(3).
The mean planes through the Cp ring and through the
C(14)C(15)C(18)C(19) atoms are almost parallel, the
dihedral angle being 1.9(1)°. The methoxycarbonyl sub-
stituent is practically coplanar with the Cp ring,
whereas the two methoxycarbonylmethylene sub-
stituents point on the same side almost perpendicularly
to the ring and approaching to one another with a
,
short O(4)···O(5) contact of 3.252(2) A.
The C(1)ꢀC(6) bond involving the methoxycarbonyl
substituent on the Cp ring is approximately parallel to
both double bonds of complexed COD.
Isomerization of 8a led to product 1a (70% isolated
yield). Such a procedure, however, works in reasonable
yield only for methyl esters.
Catalytic activities and selectivities of various cobalt
and rhodium complexes containing unsubstituted and
substituted cyclopentadienyl ligands were compared
utilising test reaction 2. The homogeneous cyclo-
cotrimerization of 1-hexyne and propionitrile to pyridi-
nes (Eq. (2)) was carried out catalytically in the
presence of complex 9 under the reaction conditions
used for complex [(MDMCp)Rh(C2H4)2] [7] and for
other analogous experiments reported in the literature
[9].
2.2. Synthesis of the metal complexes
Cyclopentadiene derivatives 1a–e were used as pre-
cursors of ligands for metallorganic complexes.
2.2.1. Mononuclear cobalt complex
Cyclopentadiene derivative 1a was converted into
cyclopentadienyl anion (MDMCp) and caused to react
with CoCl(PPh3)3 in the presence of 1,5-cyclooctadiene.
Complex 9 (39% yield) was obtained as an air stable red
orange solid according to Eq. (1).
LiMDMCp+CoCl(PPh3)3+1,5-COD
(2)
“Co(MDMCp)(COD)+LiCl+3PPh3
(1)
9
Scheme 4.

182
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
Fig. 1. ORTEP view of the structure of the complex 9 together with the atomic numbering scheme. The ellipsoids for the atoms are drawn at 30%
probability level.
present: the catalytic properties of the trisubstituted
(cyclopentadienyl)cobalt confirm that a relationship be-
tween electron distribution at the cobalt and the activ-
ity of the complex in the synthesis of pyridine
derivatives is present. It can be observed that complex
9 containing electron-withdrawing substituents gave the
highest yield. The corresponding rhodium complex did
not give an appreciable yield under the same condi-
tions. To achieve a similar activity, the rhodium com-
plex needs a different neutral ligand (C2H4 instead of
COD) and higher temperature (130°C). Actually the
chelating COD ligand behaves as a ‘blocking’ system
for the (cyclopentadienyl)rhodium complex in the pyri-
dine synthesis, while a weaker stabilising neutral ligand
such as C2H4 is able to provide the propagating cata-
lytic species. The selectivities obtained with the cobalt
complexes are higher than those obtained with the
rhodium complex, cyclization to pyridines (10 and 11)
being mainly preferred to the trimerization of the
alkyne (12) [9,11].
In Table 2 the activity and selectivity data are sum-
marised along with those obtained using the reported
rhodium
complex,
unsubstituted
(cyclopentadi-
enyl)cobalt complex [CpCo(COD)] and (cyclopentadi-
enyl)rhodium complex [CpRh(COD)] as catalysts,
respectively.
Differences in product distribution and yields are due
to the influence of the substituents in the cyclopentadi-
enyl ring and the neutral ligands. In the context of
pyridine syntheses from alkynes and nitrile catalysed
homogeneously by (cyclopentadienyl)cobalt complexes,
it was found that electron-withdrawing groups on the
cyclopentadienyl ring significantly increase the activity.
A good linear correlation between the 59Co chemical
shift and the catalytic properties was found [10] for all
the monosubstituted cyclopentadienyl ligands investi-
gated. Compounds of this type having electron-with-
drawing substituents are more active in catalysis than
the parent compounds [11]. Exceptions are multisubsti-
tuted cyclopentadienyl ligands such as 1,2(Me3Si)2C5H3
and Ph4C5H which gave both high regioselectivity and
activity [11]. This is probably due to steric effects on the
catalytically active species. Sterically demanding sub-
stituents force a parallel orientation of substituents and
COD double bonds. In our case these features are
2.2.2. Mononuclear rhodium complexes
Mono h5-cyclopentadienylrhodiumdicarbonyl was
prepared according to the reported procedure [7] using
ligand 1a (R=R%=Me). Crystals of complex 2a

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
183
Table 2
[Rh(MDMCp)(CO)2] suitable for a X-ray analysis were
grown in n-hexane at low temperature.
Reaction of 1-hexyne with propionitrile at 100°C for 6 h a
Catalytic
complex
Yield (%) b
Selectivity (%) b
10+11
12 10/(10+11)
(10+11)/
(10+11+12)
CpCo(COD) c
(MDMCp)-
Co(COD) 9
CpRh(C2H4)2
(MDMCp)-
65 (55) d 22 59
75
92
88 (77) d
8
52
The structure, in agreement with the proposed one, is
shown in Fig. 2 together with the atomic labelling
system; selected bond distances and angles are given in
Table 3. The rhodium atom interacts in a h5-fashion
with the substituted cyclopentadienyl ring of the ligand
1a and with two terminal carbonyl groups. The distance
of rhodium with the centroid M(1) of the Cp is 1.912(7)
e
67
78
18 56
15 44
79
84
e
Rh(C2H4)2
a 1-Hexyne (1.05 ml, 9.2 mmol), propionitrile (3.62 ml), catalytic
complexes (0.092 mmol), EtCN:n-BuCꢁCH molar ratio=5.5; n-
BuCꢁCH: Co-catalyst=100.
b By GLC, based on starting alkyne.
c Conversion 90%.
,
A. The rhodium atom is coplanar with M(1) and the
C(14) and C(15) atoms of the carbonyls. As in 9 the
methoxycarbonyl substituent is practically coplanar
with the Cp ring, whereas the two methoxycarbonyl-
methylene substituents point on the same side almost
perpendicularly to the ring and approaching to one
d Isolated yields.
e Temperature=130°C.
systems the values of wCO reflect variations in electron
densities on the metal. Complexes 2a [7], 2b and 2d
show identical wCO values (see Section 3) confirming
that the electronic densities on the metal centres are
practically comparable. Such complexes were used as
catalysts for the hydroformylation reaction of styrene
(Eq. (3)) to estimate a possible steric influence of the C8
ester chains on the activity and selectivity of the process
,
another with a short O(3)···O(6) contact of 3.24(1) A.
Complexes 2b (R=Me, R%=C8H17) and 2d (R=
R%=C8H17) were analogously synthesised in 37 and
32% yield, respectively. IR spectral data show two
stretching frequencies (symmetric and antisymmetric) of
the carbonyl groups. It is well-known [12] that for such
Table 1
under practically comparable electronic factors (Table 4).
a
,
Selected bond lengths (A) and angles (°) for 9
2a,b,d
PhCHꢂCH2+CO+H2 “ PhCH(CH3)CHO
13
Bond distances
+PhCH2CH2CHO
(3)
Co1ꢀC1
Co1ꢀC2
Co1ꢀC3
Co1ꢀC4
Co1ꢀC5
Co1ꢀM1
Co1ꢀM2
Co1ꢀM3
C1ꢀC2
C1ꢀC5
C2ꢀC3
C3ꢀC4
C4ꢀC5
2.095(2)
2.106(2)
2.126(2)
2.108(2)
2.054(2)
1.714(2)
1.905(3)
1.899(2)
1.419(2)
1.433(2)
1.421(2)
1.412(2)
1.428(2)
1.461(2)
1.503(2)
C4ꢀC11
C14ꢀC15
C1ꢀC19
C6ꢀO1
C6ꢀO2
C7ꢀO2
C8ꢀC9
C9ꢀO3
C9ꢀO4
C10ꢀO4
C11ꢀC12
C12ꢀO5
C12ꢀO6
C13ꢀO6
1.507(2)
1.398(3)
1.393(3)
1.205(2)
1.340(2)
1.441(3)
1.501(3)
1.189(3)
1.322(3)
1.437(3)
1.510(3)
1.192(3)
1.329(2)
1.444(3)
14
Analogous activities and practically quantitative
yields were obtained for the three complexes under the
adopted conditions. It can be observed that the pres-
ence of the three C8 octyl chains does not substantially
modify the selectivity. From the X-ray structure of 2a it
can be inferred that the ester chains of the two acetyl
groups point perpendicularly to the cyclopentadienyl
ring plane. This steric situation is probably maintained
in solution too. The spatial disposition adopted by the
chains in solution does not present a real steric hin-
drance to olefin coordination on the metal and there-
fore can not influence the regiospecific formation of a
linear or branched alkylrhodium intermediate. A slight
difference in the selectivity was observed when the three
ester groups were not the same, however. Thus a small
change in the substituents of complex 2b with one
methyl and two octyl ester chains probably favoured a
preferential coordination of the olefin to the catalytic
centre with a shift of the selectivity towards the
branched aldehyde. The electronic effects play a more
important role in the transition state, which probably
includes a slippage or haptotropic shift of the cyclopen-
tadienyl ligand to avoid an unfavorable 20-electron
configuration [13,14]. Apparently the three substituents
C1ꢀC6
C3ꢀC8
Bond angles
M1ꢀCo1ꢀM2
M1ꢀCo1ꢀM3
M2ꢀCo1ꢀM3
O1ꢀC6ꢀO2
O1ꢀC6ꢀC1
O2ꢀC6ꢀC1
C9ꢀC8ꢀC3
O3ꢀC9ꢀO4
O3ꢀC9ꢀC8
134.4(1)
134.5(1)
91.1(1)
123.2(2)
124.8(2)
111.9(2)
117.0(2)
123.1(2)
122.9(2)
O4ꢀC9ꢀC8
113.9(2)
112.1(2)
123.8(2)
124.8(2)
111.4(2)
116.5(2)
115.8(2)
117.4(2)
C4ꢀC11ꢀC12
O5ꢀC12ꢀO6
O5ꢀC12ꢀC11
O6ꢀC12ꢀC11
C6ꢀO2ꢀC7
C9ꢀO4ꢀC10
C12ꢀO6ꢀC13
a M1 is the centroid of the Cp ring. M2 is the midpoint of the
C14ꢀC15 double bond of the COD ligand. M3 is the midpoint of the
C18ꢀC19 double bond of the COD ligand.

184
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
Fig. 2. ORTEP view of the structure of the complex 2a together with the atomic numbering scheme. The ellipsoids for the atoms are drawn at 30%
probability level.
on the ring do not produce a particular hindrance on
the metallic centre and on its surroundings.
The synthesis and structural characterisation of sand-
wich and dinuclear iron and ruthenium complexes con-
taining trisubstituted cyclopentadienyl ligands have also
been pursued.
1H-NMR data at room temperature gave evidence
about the steric arrangement of the cyclopentadienyl
ligands of these complexes. Only one signal was ob-
served for the four hydrogen of the two cyclopentadi-
enyl rings. This equivalence points out a complete
rotational freedom of the two rings. Moreover the
hydrogens of the two methylene groups bonded to each
ring are diastereotopic, two doublets with geminal cou-
pling constants of 16.3 Hz being present.
The structure of complex [Fe(MDMCp)2] (15a) deter-
mined by X-ray study, is shown in Fig. 3 together with
the atomic labelling system; selected bond distances and
angles are given in Table 5. The ferrocene type complex
has an imposed crystallographic Ci symmetry with the
inversion center on the Fe atom and can be considered
as a sandwich complex with a staggered conformation.
2.2.3. Ferrocenes
For the synthesis of ferrocenes we started with cy-
clopentadiene 1a which was transformed in its anion
using lithium diisopropylamide. The anion was caused
to react with dry FeCl2 according to the (eq. (4)).
Ferrocene 15a was obtained in 35% isolated yield.
The distance of the centroid of the substituted Cp from
(4)
5
,
the Fe atom is 1.648(2) A and the h interaction is
symmmetrical as the FeꢀC distances range from
,
2.037(2) to 2.050(3) A. As in 9 and 2a, the methoxycar-
bonyl substituent is practically coplanar with the Cp
ring, whereas the two methoxycarbonylmethylene sub-
stituents point on the same side almost perpendicularly
to the ring and approaching to one another with a
Using the same procedure we obtained ferrocenes
15b (R=Me, R%=C8H17) and 15e (R=R%=C12H25) in
28 and 15% isolated yield, respectively. The low yields
obtained have to be attributed to losses in purification.
,
short O(3)···O(6) contact of 3.221(4) A.

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
185
2.2.4. Dinuclear complexes: Fe and Ru complexes
6HMDMPc+2Ru3(CO)12
+3C7H10
+C7H12
“
n-heptane3[(MDMCp)Ru(CO)2]2+12CO
Cyclopentadiene derivative 1a (HMDMCp) was
caused to react with Fe2(CO)9 (Eq. (5)) and Ru3(CO)12
(Eq. (6)) in the presence of norbornene as hydrogen
acceptor according to procedures adapted from the
literature [15]. Complexes [(MDMCp)Fe(CO)2]2 (16)
and [(MDMCp)Ru(CO)2]2 (17) respectively were
obtained.
(reflux)
17, 42% yield
(6)
The infrared spectra restricted to the carbonyl region
(1700–2200 cm−1) of complexes 16 and 17 were
recorded in the solid state (KBr) and in liquid solution
(CH2Cl2). A comparison of these values with the ex-
haustive IR data reported in the literature [16] show a
very strict analogy with the bands of the isomorphous
and isostructural complexes [CpFe(CO)2]2 and
[CpRu(CO)2]2 and other parent complexes of iron and
ruthenium in the cis geometry with two bridging and
two terminal CO groups (molecular symmetry C26)
( Scheme 5, Table 6).
2HMDMPc+Fe2(CO)9
+C7H10
“
n-heptane3[(MDMCp)Fe(CO)2]2+5CO+C7H12
(reflux)
16, 40% yield
(5)
Table 3
a
The two coordinated cyclopentadienyl rings and their
,
Selected bond lengths (A) and angles (°) for 2a
substituents exhibit coincident H- or 13C-NMR single
1
Bond distances
sharp signals in CDCl3 or CD3COCD3 at room temper-
ature for complexes 16 and 17. The NMR equivalence
of the two ligands and the finding that the IR carbonyl
bands in solution are analogous with those in the solid
state, except for slight shifts of the frequencies, confirm
that the cis carbonyl-bridged dimer is present as the
predominant form of 16 and 17 also in solution. Reac-
tions of HCpMDM with Fe2(CO)9 and Ru3(CO)12 like-
wise proceed in selective homogeneous fashion yielding
complexes 16 and 17 in the less common cis geometry.
As the steric bulk of the cyclopentadienyl ligand in-
creases, the stability of the cis bridged isomer decreases
to the point that with [(C5Me5)M(CO)2]2 and
[(C5Me4CF3)M(CO)2]2 (M=Fe, Ru) [17], only the trans
bridged isomer is observed. Some dinuclear carbonyl
metal complexes containing multiply substituted cy-
clopentadienyl ligands exhibit a cis carbonyl-bridged
dinuclear structure either in the solid state or in solu-
tion, however, trans carbonyl-bridged and cis and trans
non bridged dimers being absent [15,18].
In conclusion the syntheses and characterisations of
metal complexes containing a new trisubstituted cy-
clopentadienyl ligand (1a–d) has been described. The
mononuclear complexes of cobalt 9 and rhodium 2a, 2b
and 2d have displayed an interesting catalytic activity.
The ligands used also allow the selective preparation of
dinuclear complexes of iron and ruthenium in their cis
form and sandwich complexes of iron. X-ray analyses
elucidate the structural features of some of these
complexes.
Rh1ꢀC1
Rh1ꢀC2
Rh1ꢀC3
Rh1ꢀC4
Rh1ꢀC5
Rh1ꢀM1
Rh1ꢀC14
Rh1ꢀC15
C1ꢀC2
C1ꢀC5
C2ꢀC3
C3ꢀC4
C4ꢀC5
2.285(6)
2.235(8)
2.289(7)
2.274(7)
2.215(6)
1.912(7)
1.860(8)
1.837(10)
1.419(9)
1.415(9)
1.403(8)
1.412(9)
1.434(8)
1.170(10)
1.325(10)
O2ꢀC7
O3ꢀC9
O4ꢀC9
1.464(10)
1.158(9)
1.322(8)
1.43(2)
1.178(9)
1.29(1)
O4ꢀC10
O5ꢀC12
O6ꢀC12
O6ꢀC13
C1ꢀC6
C3ꢀC8
C4ꢀC11
C8ꢀC9
1.48(2)
1.476(8)
1.509(9)
1.505(9)
1.503(12)
1.488(12)
1.113(10)
1.152(13)
C11ꢀC12
O7ꢀC14
O8ꢀC15
O1ꢀC6
O2ꢀC6
Bond angles
C15ꢀRh1ꢀM1
C14ꢀRh1ꢀM1
C14ꢀRh1ꢀC15
O2ꢀC6ꢀC1
O1ꢀC6ꢀC1
O1ꢀC6ꢀO2
C3ꢀC8ꢀC9
C6ꢀO2ꢀC7
C9ꢀO4ꢀC10
C12ꢀO6ꢀC13
134.9(3)
135.0(3)
90.1(4)
111.1(7)
124.6(7)
124.3(7)
111.7(6)
113.8(7)
116.6(7)
116.8(10)
O4ꢀC9ꢀC8
O3ꢀC9ꢀC8
O3ꢀC9ꢀO4
C4ꢀC11ꢀC12
O6ꢀC12ꢀC11
O5ꢀC12ꢀC11
O5ꢀC12ꢀO6
Rh1ꢀC14ꢀO7
Rh1ꢀC15ꢀO8
110.3(6)
125.5(7)
124.2(7)
111.4(6)
113.2(8)
124.1(7)
122.7(8)
179.4(7)
177.5(8)
a M1 is the centroid of the Cp ring.
Table 4
Reaction of styrene with CO and H2 (1:1 vol/vol, 70 bar) in toluene
(5 ml) at 100°C for 3 h, Rh-catalyst 0.059 mmol, olefin 11.72 mmol
Rh-catalyst
Olefin conversion (%) a
Selectivity
(%) a
13
14 13/14
2a
2b
2d
99
98
98
58
64
59
42 1.38
36 1.78
41 1.44
3. Experimental
Melting points were determined by an Electrothermal
Melting Point apparatus and are uncorrected. Elemen-
a By GLC, based on starting styrene.

186
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
Fig. 3. ORTEP view of the structure of the complex 15a together with the atomic numbering scheme. The ellipsoids for the atoms are drawn at
30% probability level.
3.1. Materials
tal analyses were carried out with a Carlo Erba model
EA 1108 elemental analyzer. GLC analyses were per-
formed on HR 3800 Dani Instrument using a methylsil-
icone (OV101) stationary phase, capillary column (25
m). Products and starting substrates were quantitatively
determined by GLC using the internal standard
method. Merk silica gel 60 (230–400 mesh), Florisil
(100–200 mesh, Floridrin Co., USA) and Fluka 507
neutral alumina (100–125 mesh) were used for prepara-
Solvents were purified by standard methods [19] and
stored on molecular sieves (Type 4A, 1/8 pellets, Union
,
Carbide). 2-Propynylbromide, malonic esters 2,2-
dimethyl-1,3-dioxane-4,6-dione (Meldrum acid), ni-
triles, alkylchloroformates, oxalylchloride, other
acetylenic and olefinic derivatives and Fe2(CO)9 and
Ru3(CO)12 were commercial products. Rhodium com-
plexes [RhCl(CO)2]2 [20], [RhCl(CH2ꢂCH2)2]2 [21],
[CpRh(CH2ꢂCH2)2] [22] and cobalt complexes
CoCl(PPh3)3 [23] and CpCo(COD) [24] were prepared
according to the literature methods.
1
tive column chromatography. H- and 13C-NMR spec-
tra were run on AC 300 Bruker instruments using the
frequence of Me4Si as reference. Mass spectra were
obtained with a Finnigan Mat SSQ 710 at variable
ionizing voltage. GC-MS analyses were made using a
HP-5890 Series II (Hewlett–Packard) gaschro-
matograph, equipped with a HP-5971 Series MSD and
a split-splitless injector. IR spectra were recorded on
Nicolet 5PC FT-IR spectrometer.
3.2. Synthesis of benzyl alkyl 2,2-dipropynylmalonate
3a–d
Preparations of 3a and 1a was previously described
[7]. Substrates 3b–d were prepared as follows.

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
187
Table 5
3.2.1. Preparation of malonic acid mono benzyl ester
4b
a
,
Selected bond lengths (A) and angles (°) for 15a
A solution of 2,2-dimethyl-1,3-dioxane-4,6-dione (25
Bond distances
g, 0.174 mol), benzylic alcohol (36 ml, 0.347 mol) in
toluene (100 ml) was reacted under reflux for 24 h. The
cooled mixture was poured into a Na2CO3 solution (5%
w in water). The aqueous phase was extracted with
Et2O and the combined organic layers were acidified
with 1 N HCl. The organic product was extracted with
EtOAc and dried with Na2SO4. Monoester of malonic
acid was recovered as a white solid (16.98 g, 50% yield)
m.p. 49–50°C. IR (KBr) w cm−1: 3212 (s), 1741 (s),
1704 (s). H-NMR (300 MHz, CDCl3) l: 3.47 (s, 2H,
CH2), 5.20 (s, 2H, CH2), 7.35 (br s, 5H, aromatics),
9.60 (br s, 1H, OH).
Other alkyl monoesters of malonic acid 4a could be
prepared analogously.
Fe1ꢀC1
Fe1ꢀC2
Fe1ꢀC3
Fe1ꢀC4
Fe1ꢀC5
Fe1ꢀM1
C1ꢀC2
C1ꢀC5
C2ꢀC3
C3ꢀC4
C4ꢀC5
O1ꢀC6
O2ꢀC6
2.037(2)
2.042(3)
2.046(3)
2.050(3)
2.049(3)
1.648(2)
1.428(4)
1.429(5)
1.421(4)
1.428(5)
1.411(3)
1.200(5)
1.338(4)
O2ꢀC7
O3ꢀC9
O4ꢀC9
O4ꢀC10
O5ꢀC12
O6ꢀC12
O6ꢀC13
C1ꢀC6
1.442(3)
1.189(3)
1.336(3)
1.438(4)
1.194(3)
1.328(3)
1.440(5)
1.484(4)
1.504(4)
1.507(5)
1.501(4)
1.518(4)
C3ꢀC8
C4ꢀC11
C8ꢀC9
1
C11ꢀC12
Bond angles
O2ꢀC6ꢀC1
O1ꢀC6ꢀC1
O1ꢀC6ꢀO2
C3ꢀC8ꢀC9
C6ꢀO2ꢀC7
C9ꢀO4ꢀC10
C12ꢀO6ꢀC13
111.0(2)
124.8(3)
124.2(3)
114.4(2)
116.5(2)
117.0(2)
115.0(3)
O4ꢀC9ꢀC8
O3ꢀC9ꢀC8
O3ꢀC9ꢀO4
C4ꢀC11ꢀC12
O6ꢀC12ꢀC11
O5ꢀC12ꢀC11
O5ꢀC12ꢀO6
110.0(2)
126.2(3)
123.8(3)
108.9(3)
111.9(3)
124.7(3)
123.4(3)
3.2.2. Preparation of ethyl benzyl and octyl benzyl
malonates
In a dry Schlenk flask (100 ml) 4b (1.94 g, 0.01 mol)
and triethylamine (1.39 ml, 0.01 mol) were dissolved in
THF (30 ml). The cooled mixture (4°C) was added with
alkylchloroformate (R=C2H5, 0.96 ml, 0.01mmol;
R=C8H17 1.96 ml, 0.01 mmol) and stirred for 30 min.
The mixture was filtered and the solution was concen-
trated under vacuum to obtain colourless liquid (R=
C2H5 1.49 g, 67% yield). MS (EI, m/z): 222 (M+, 5),
194 (3), 107 (71), 91 (100). 1H-NMR (300 MHz,
CDCl3) l: 1.22 (t, 3H, J=7.1 Hz, Me), 3.39 (s, 2H,
CH2), 4.14 (q, 2H, J=7.1 Hz, OCH2), 5.17 (s, 2H,
CH2), 7.33 (br s, 5H, aromatics); (R=C8H17 1.99 g,
65% yield). MS (EI, m/z): 306 (M+, 3), 194 (7), 107
a M1 is the centroid of the Cp ring.
1
(100), 91 (90). H-NMR (300 MHz, CDCl3) l: 0.87 (t,
3H, J=7.0 Hz, Me), 1.23–1.29 (m, 10H, 5 CH2),
1.59–1.62 (m, 2H, CH2), 3.41 (s, 2H, CH2), 4.11 (t, 2H,
Scheme 5.
Table 6
Vibrational frequencies of carbonyls (wCO (cm−1)) for [CpM(CO)2]2 complexes
M
Cp
Solvent
Terminal CO
Bridge CO
Ref.
Fe
C5H5
C5H5
C5H5
C5H5
MeC5H4
MeC5H4
[C5H4CH(NMe2)]2
Hexane a
2005
2010
2009
2004
2006
2003
2002
2003
2004
2008
2005
2014
1961
1965
1968
1960
1960
1959
1964
1961
1963
1970
1960
1973
1794.5
1794
1768
1785
1790
1779
1793
1779
1779
1786
1783
1787
[16]
[16]
[16]
[16]
[16]
[16]
[16]
Ru
Ru
Ru
Ru
Ru
Ru
Ru
Fe
Heptane b
b
CHCl3
CS2
a
Heptane b
b
CHCl3
Heptane b
c
b
C9H7
CHCl3
[16]
MDMCp d
MDMCp d
MDMCp d
MDMCp d
KBr b
e
b
e
e
e
Fe
Ru
Ru
CH2Cl2
KBr b
b
CH2Cl2
a At low temperature.
b At room temperature.
c Indenyl.
d 1-Metoxycarbonyl-3,4-di(metoxycarbonylmethylene)cyclopentadienyl.
e This work.

188
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
J=7.0 Hz, OCH2), 5.17 (s, 2H, CH2), 7.33 (br s, 5H,
aromatics).
3.4. Carbonylation reaction: synthesis of benzyl alkyl
3,4-di(alkoxycarbonylmethylene)cyclopentane
3.2.3. Preparation of dodecyl benzyl malonate
3.4.1. Products 6b–e
In a dry flask (100 ml) to 4(a) (R=C12H25, 4.21 g,
21.7 mmol) dissolved in toluene (30 ml) was added
oxalylchloride (5.25 ml, 60 mmol) under argon. After
stirring at 35°C for 24 h the mixture was concentrated
under vacuum. The residue was diluted with THF (15
ml) and added with 1-dodecanol (3.64 g, 19.5 mmol)
and triethylamine (1.72 ml, 19.5 mmol). The mixture
was stirred at room temperature (r.t.) for 24 h. After
the usual work up, product 5 (R=C12H25) was recov-
ered and purified by silica gel flash column chromatog-
raphy (hexane: EtOAc=7:3 as eluent). A pale yellow
oil was obtained (3.23 g, 8.9 mmol, 46% yield).). MS
(EI, m/z): 362 (M+, 3), 194 (10), 107 (92), 91 (100).
1H-NMR (300 MHz, CDCl3) l: 0.89 (t, 3H, J=7.0 Hz,
Me), 1.24–1.30 (m, 18H, 9 CH2), 1.58–1.61 (m, 2H,
CH2), 3.41 (s, 2H, CH2), 4.12 (t, 2H, J=7.0 Hz,
OCH2), 5.17 (s, 2H, CH2), 7.33 (br s, 5H, aromatics).
In a general procedure a 250 ml stainless-steel auto-
clave was loaded with 3b–e (4.60 mmol) dissolved in a
mixture of the selected alcohol and dimethoxyethane
(DME), (50 and 30 ml, respectively) 10%PdꢀC (0.082 g,
0.23 mmol) and KI (0.57 g, 3.40 mmol). The autoclave
was pressurised with air (6 bar) and CO (18 bar) and
heated at 65°C under stirring for 60 h. The brown
mixture was filtered and the solution was distilled under
vacuum for eliminating DME and the alcohol in excess.
In particular the preparation of the single products:
Product 6b (R=Me, R%=C8H17); substrate 3a (1.25
g, 4.60 mmol), 1-octanol (50 ml) and DME (30 ml)
were caused to react with CO and air in the presence of
10% PdꢀC (0.082 g, 0.23 mmol) and KI (0.57 g, 3.40
mmol). Chromatographic purification through silica gel
column (9:1 CH2Cl2–hexane as eluent) gave 6b (1.63 g,
62% yield) as a pale yellow oil. MS (CI, m/z): 599
1
(MH+, 100); H-NMR (300 MHz, CDCl3) l: 0.88 (t,
3.3. Propynylation of malonic esters: synthesis of 3a–e
6H, J=7.1 Hz, 2 Me), 1.22–1.31 (m, 20H, 10 CH2),
1.62–1.67 (m, 4H, 2 CH2), 3.51, 3.58 (2dd, ABX sys-
tem, 4H, J=19.0, J=2.4 Hz, 2 CH2ꢂ), 3.65 (s, 3H,
OMe), 4.12 (t, 4H, J=7.0 Hz, 2 OCH2), 5.16 (s, 2H,
CH2Ph), 6.31 (t, 2H, J=2.4 Hz, CHꢂ), 7.31 (br s, 5H,
aromatics).
Propynylations of benzyl-alkyl malonates were car-
ried out according to the procedure previously reported
[7]. The yields and characterisations of products 3b–e
are the following.
Compound 3b (R=C2H5) yellow oil, yield 80%. MS
(EI, m/z): 298 (M+, 6), 259 (4), 213 (7), 91 (100); IR
(neat), w cm−1: 3300 (w), 2117 (w), 1733 (s), 1300 (m),
Product 6c (R=Et, R%=C8H17); substrate 3b (0.657
g, 2.20 mmol), 1-octanol (25 ml) and DME (15 ml)
were caused to react with CO and air in the presence of
10% PdꢀC (0.04 g, 0.11 mmol) and KI (0.274 g, 1.65
mmol). Chromatographic purification through a silica
gel column (9:1 CH2Cl2–hexane as eluent gave 6c
(0.845 g, 63% yield) as a pale yellow oil. MS (CI, m/z):
1
1212 (m); H NMR (300 MHz, CDCl3) l: 1.16 (t, 3H,
J=7.1 Hz, Me), 2.12 (t, 2H, J=2.7 Hz, 2 HCꢁ), 3.01
(d, 4H, J=2.7 Hz, 2 CH2Cꢁ), 4.16 (q, 2H, J=7.1 Hz,
CH2), 5.20 (s, 2H, OCH2Ph), 7.33 (br s, 5H, aromatics).
Compound 3c (R=C8H17) yellow oil, yield 75%; MS
(CI, m/z): 383 (MH+,29); 1H-NMR (300 MHz, CDCl3)
l: 0.87 (t, 3H, J=7.1 Hz, Me), 1.20–1.26 (m, 10H, 5
CH2), 1.52–1.55 (m, 2H, CH2), 1.99 (t, 2H, J=2.7 Hz,
2 HCꢁ), 3.01 (d, 4H, J=2.7 Hz, 2 CH2Cꢁ), 4.08 (t, 2H,
J=7.0 Hz, OCH2), 5.18 (s, 2H, OCH2Ph), 7.32 (br s,
5H, aromatics).
Compound 3d (R=C12H25) after purification by
flash chromatography silica column (CH2Cl2: hexane=
7:3), yellow oil 72% yield. MS (CI, m/z): 439 (MH+,
33); 1H-NMR (300 MHz, CDCl3) l: 0.88 (t, 3H, J=7.1
Hz, Me), 1.23–1.27 (m, 18H, 9 CH2), 1.52–1.55 (m,
2H, CH2), 2.00 (t, 2H, J=2.6 Hz, 2 HCꢁ), 3.01 (d, 4H,
J=2.6 Hz, 2 CH2Cꢁ), 4.09 (t, 2H, J=7.0 Hz, OCH2),
5.19 (s, 2H, OCH2Ph), 7.32 (br s, 5H, aromatics).
Compound 3e yellow solid m.p. 128–129°C, 88%
yield. MS (EI, m/z): 220 (M+, absent), 205 (6), 162
(18), 89 (67), 43 (100); IR (KBr) w cm−1: 2999 (m),
2124 (w), 1735 (s); 1H-NMR (300 MHz, CDCl3) l:
1.82, 1.83 (2s, 6H, 2 Me), 2.17 (t, 2H, J=2.6 Hz, 2
HCꢁ), 2.86 (d, 4H, J=2.6 Hz, 2 CH2Cꢁ).
1
613 (MH+, 100); H-NMR (300 MHz, CDCl3) l: 0.88
(t, 6H, J=7.1 Hz, 2 Me), 1.13 (t, 3H, J=7.1 Hz, Me),
1.26-1.32 (m, 20H, 10 CH2), 1.65–1.67 (m, 4H, 2 CH2),
3.58, 3.65 (2dd, ABX system, 4H, J=19.0, J=2.4 Hz,
2 CH2ꢂ), 4.08–4.16 (three superimposed q, 6H, 3 CH2),
5.17 (s, 2H, CH2Ph), 6.32 (t, 2H, J=2.4 Hz, 2 CHꢂ),
7.31 (br s, 5H, aromatics).
Product 6d (R=R%=C8H17); substrate 3c (1.025 g,
2.68 mmol), 1-octanol (30 ml) and DME (18 ml) were
caused to react with CO and air in the presence of 10%
PdꢀC (0.048 g, 0.134 mmol), KI (0.334 g, 2.01 mmol).
Chromatographic purification through a silica gel
column (9:1 hexane–EtOAc as eluent) gave 6d (0.967 g,
52% yield) as a yellow oil. MS (CI, m/z): 697 (MH+,
1
100); H-NMR (300 MHz, CDCl3) l: 0.87 (t, 9H, 3
Me), 1.23–1.31 (m, 30H, 15 CH2), 3.51, 3.58 (2dd,
ABX system, 4H, J=19.0, J=2.4 Hz, 2 CH2ꢂ), 4.05 (t,
2H, J=7.0 Hz, CH2), 4.12 (t, 4H, J=7.0 Hz, 2 CH2),
5.16 (s, 2H, CH2Ph), 6.31 (t, 2H, J=2.4 Hz, 2 HCꢂ),
7.29 (br s, 5H, aromatics).

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
189
Product 6e (R=R%=C12H25); substrate 3d (1.00 g,
2.30 mmol),1-dodecanol (45 ml) and DME (27 ml) were
caused to react with CO and air in the presence of 10%
PdꢀC (0.041 g, 0.115 mmol) and KI (0.286 g, 1.73
mmol). Chromatographic purification through silica gel
column (9:1 hexane–EtOAc as eluent) gave 6e (0.81 g,
41% yield) as a yellow oil. MS (CI, m/z): 865 (MH+,
column chromatography (85:15 hexane–EtOAc as elu-
ent) 1d (0.387 g, 43% yield) was recovered as a yellow
oil. MS (CI, m/z): 563 (MH+, 100); 1H-NMR (300
MHz, CDCl3) l: 0.87 (t, 9H, 3 Me), 1.25–1.29 (m, 30
H, 15 CH2), 1.59–1.63 (m, 6H, 3 CH2), 3.36 (s, 2H,
CH2), 3.41 (s, 4H, 2 CH2), 4.07, 4.15 (2t, 6H, J=7.0
Hz, 3 OCH2), 7.32 (s, 1H, CHꢂ).
1
Product 1e (R=R%=C12H25) was obtained from 7e
(0.35 g, 0.45 mmol). After purification through silica gel
column chromatography (9:1 hexane–EtOAc as eluent)
1e (0.135 g, 41% yield) was recovered as a yellow oil.
62); H-NMR (300 MHz, CDCl3) l: 0.87 (t, 9H, three
superimposed triplet, 3Me), 1.21–1.29 (m, 54H, 27
CH2), 1.60–1.64 (m, 6H, 3 CH2), 3.51, 3.58 (2dd, ABX
system, 4H, J=19.0, J=2.4 Hz, 2 CH2ꢂ), 4.05 (t, 2H,
J=7.0 Hz, CH2), 4.12 (t, 4H, J=7.0 Hz, 2 CH2), 5.15
(s, 2H, CH2Ph), 6.31 (t, 2H, J=2.4 Hz, 2 HCꢂ), 7.30
(br s, 5H, aromatics).
1
MS (CI, m/z): 731 (MH+, 75); H-NMR (300 MHz,
CDCl3) l: 0.87 (t, 9H, 3 Me), 1.23–1.27 (m, 54H, 27
CH2), 1.59–1.63 (m, 6H, 3 CH2), 3.36 (s, 2H, CH2),
3.41 (s, 4H, 2 CH2), 4.07, 4.15 (2t, 6H, J=7.0 Hz, 3
OCH2), 7.31 (s, 1H, CHꢂ).
Product 8a (R=R%=Me); substrate 3e (1.54 g, 7.0
mmol) in MeOH (80 ml) were caused to react with CO
and air in the presence of 10% PdꢀC (0.37 g, 0.35
mmol) and KI (0.87 g, 5.25 mmol). Chromatographic
purification through a silica gel column (1:1 hexane–
acetone as eluent) gave 8a (0.90 g, 38% yield). MS (CI,
3.6. Synthesis of (p4-1,5-cyclooctadiene) [p5-1-
methoxycarbonyl-3,4-di(methoxycarbonylmethylene)-
cyclopentadienyl]cobalt [Co(MDMCp)(1,5-cod)] (9)
1
m/z): 269 (MH+, 100); H-NMR (300 MHz, CDCl3) l:
The preparation of complex 9 was adapted from the
literature [25]. LiMDMCp was prepared according to
the reported procedure [7] from lithium diisopropy-
lamide and HMDMCp at 0°C in THF: Under argon
atmosphere at r.t. the Li(MDMCp) (1.029 g, 3.84
mmol) in THF (15 ml) was added to a solution of
CoCl(PPh3)3 (3.15 g, 3.57 mmol) and 1,5 COD (0.580 g,
5,36 mmol) in toluene (30 ml) in a Schlenk tube (100
ml). After stirring for 1 h at r.t. the mixture was heated
at 80°C for 1 h. The reaction mixture was filtered
through a short column of alumina (activity grade III).
The filtrate was concentrated to ca. 10 ml and after
addition of hexane (20 ml) the solution was allowed to
stand overnight then was filtered again to eliminate
PPh3 precipitated. The filtered products were separated
through an alumina (activity grade III) chromato-
graphic column (1.5×15 cm). An orange band was
eluted by a 8:2=hexane:EtOAc mixture. The fraction
containing the product was concentrated almost to
dryness. The oily residue was dissolved in hexane–
CH2Cl2 (3/1, vol/vol) and was kept in refrigerator to
separate a red-brown solid (0.60 g, 38% yield). This was
recrystallised from the same solvent, m.p. 78°C. Anal.
Found: C, 58.00; H, 6.21. C21H27O6Co Calc.: C, 58.06;
H, 6.22%. MS (EI, m/z): 434 (50), 327 (87), 326 (100),
296 (54), 59 (56). IR (KBr) w cm−1: 2989 (w), 2934 (m),
2871 (w), 2827 (w), 1734 (s), 1705 (s), 1443 (m), 1229
3.50–3.62 (m, 5H, CH, 2 CH2), 3.67 (s, 3H, OMe), 3.76
(s, 6H, 2 OMe), 6.33 ( t, 2H, J=2.4 Hz, 2CHꢂ).
3.5. Hydrolysis of benzyl esters to 7b–c and
decarboxylation and isomerisation; synthesis of 1b–c
The hydrolisis reactions were carried out in the pres-
ence of AlCl3 following a known procedure [8]. The
monobasic acid was added with dry pyridine (20 ml) in
a Schlenk tube under argon. The mixture was stirred
for 7 h at 80°C and extracted with CH2Cl2. The organic
layer was washed with an aqueous solution of NaHCO3
and dried over Na2SO4.
Product 1b (R=Me, R%=C8H17) was obtained from
7b (0.821 g, 1.62 mmol). After purification through
silica gel column chromatography (8:2 hexane–EtOAc
as eluent) 1b (0.383 g, 51% yield) was recovered as a
1
yellow oil. MS (CI, m/z): 465 (MH+, 70); H-NMR
(300 MHz, CDCl3) l: 0.86 (t, 6H, J=7.1 Hz, 2 Me),
1.24–1.28 (m, 20H, 10 CH2), 1.57–1.60 (m, 4H, 2
CH2), 3.35 (s, 2H, CH2), 3.41 (s, 4H, 2 CH2), 3.74 (s,
3H, OMe), 4.05 (t, 4H, J=7.0 Hz, 2 OCH2), 7.31 (s,
2H, CHꢂ).
Product 1c (R=Et, R%=C8H17) was obtained from
7c (0.57 g, 1.1 mmol). After purification through silica
gel column chromatography (8:2 hexane–EtOAc as
eluent) 1c (0.258 g, 49% yield) was recovered as a
1
(s), 1224 (s), 1141 (m), 1012 (m), 769 (w); H-NMR
1
yellow oil. MS (CI, m/z): 479 (MH+, 72); H-NMR
(300 MHz, CDCl3) l: 1.55–1.67 (m, 4H, 4CH COD),
2.29–2.34 (m, 4H, 4CH COD), 3.28 (br s, 4H, 4CHꢂ
COD), 3.34 (AB system 4H, J=15.7 Hz, 2CH2CO),
3.65 (s, 6H, 2 OMe), 3.88 (s, 3H, OMe), 4.39 (s, 2H, 2
CHꢂ Cp); 13C-NMR (75 MHz, CDCl3) l: 31.55 (4 CH2
cod), 32.27 (2 CH2 Cp), 51.38 (OMe), 70.44 (4 CHꢂ
COD), 84.93 (2 CHꢂ Cp), 85.69 (1qC), 95.92 (2 qC),
167 20 (CO); 170.36 (2 CO).
(300 MHz, CDCl3) l: 0.88 (t, 6H, J=7.1 Hz, 2 Me),
1.26–1.29 (m, 23 H, 10 CH2, Me), 1.59–1.62 (m, 4H, 2
CH2), 3.37 (s, 2H, CH2), 3.43 (s, 4H, 2 CH2), 4.07 (t,
4H, J=7.0 Hz, 2 OCH2), 4.22 (q, 2H, J=6.9 Hz,
OCH2), 7.32 (s, 1H, CHꢂ).
Product 1d (R=R%=C8H17) was obtained from 7d
(0.97 g, 1.6 mmol). After purification through silica gel

190
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
3.7. Synthesis of bis(carbonyl)p5[1-alkoxycarbonyl-3,4-
di(alkoxycarbonylmethylene) cyclopentadienyl]rhodium
(2b, 2d)
to eliminate FeCl2 unreacted. The complex 15a was
isolated by silica gel column chromatography (1:1 hex-
ane–EtOAc as eluent) (0.060 g, 0.1 mmol 35% yield as
an orange solid recrystallised from pentane, m.p. 183–
184°C. Anal. Found: C, 52.84; H, 5.06; C26H30O12Fe
Calc.: C, 52.88; H, 5.08%. MS (CI, m/z): 591 (MH+,
Complexes 2b and 2d were prepared following the
synthetic procedure already reported for 2a [7].
40), 590 (100), 589 (60), 558 (53); IR (KBr) w cm−1
:
Complex 2b (R Me, R%=C8H17). Under argon atmo-
sphere in a Schlenk tube (50 ml) at 0°C lithium salt of
cyclopentadienyl 1b (0.272 g, 0.59 mmol) in dry THF (5
ml) was added slowly to a degassed solution of
[Rh(CO)2Cl]2 (0.115 g, 0.30 mmol) in dry THF (7 ml).
The brown mixture was stirred at r.t. for 16 h. The
complex was separated by column chromatography on
Florisil (activated at 100°C for 2 h under vacuum)
using pentane:THF=9:1 as eluent. Complex 2b was
isolated as an orange-red wax (0.120 g, 0.19 mmol) 32%
yield. Anal. Found: C, 55.91; H, 6.90; C29H34O8Rh
Calc: C, 55.95; H, 6.91%. MS (CI, m/z): 623 (MH+,
2956 (w), 1739 (s), 1714 (s), 1441 (m), 1226 (m), 1088
1
(w); H-NMR (300 MHz, CDCl3) l: 3.23 (AB system
8H, J=16.3 Hz, 4 CH2), 3.65 (s, 12H, 4 OMe), 3.81 (s,
6H, 2 OMe), 4.79 (s, 4H, CHꢂ Cp); 13C-NMR (75
MHz, CDCl3) l: 31.57 (CH2), 51.71 (Me), 72.36 (qC),
73.54 (CH Cp), 84.2 8qC), 169.55 (CO), 170.19 (CO).
Preparation of complex 15b (R=Me, R%=C8H17).
Following the same procedure adopted for 15a sub-
strate 1b (0.30 g, 0.65 mmol) was transformed in
lithium salt and caused to react with dry FeCl2 (0.041 g,
0.33 mmol). Purification by silica gel column chro-
matography (85:15 hexane–THF as eluent) gave com-
plex 15b (0.041 g, 0.09 mmol, 28% yield) as an
orange–red wax. Anal. Found: C, 65.95; H, 8.75,
C54H86O12Fe Calc: C, 65.99; H, 8.76%. MS (CI, m/z):
983 (MH+, 80); IR (neat) w cm−1: 2954 (w), 1740 (s),
1713 (s), 1441 (m), 1225 (m). 1H-NMR (300 MHz,
CDCl3) l: 0.87 (t, 12H, J=7.0 Hz, 4 Me), 1.24–1.28
(m, 40 H, 20 CH2), 1.56–1.60 (m, 8H, 4 CH2), 3.21 (AB
system 8H, J=16.2 Hz, 4 CH2), 3.80 (s, 6H, 2 OMe),
4.03 (t, 8H, J=6.9 Hz, 4 OCH2), 4.78 (s, 4H, 4CHꢂ
Cp); 13C-NMR (75 MHz, CDCl3) l: 14.12 (Me), 22.61,
25.41, 28.52, 29.27, 29.71, 31.73 (CH2), 51.71 (OMe),
65.25 (OCH2), 72.34 (qC), 73.56 (CH Cp), 84.21 (qC),
168.05 (CO), 170.08 (CO).
10), 596 (25), 595 (100), 567 (40); IR (neat) w cm−1
:
2928 (w), 2856 (w), 2051 (s), 1987 (s), 1739 (s), 1714 (s),
1
1447 (m), 1218 (m); H-NMR (300 MHz, CDCl3) l:
0.88 (t, 6H, J=6.0 Hz, 2 Me), 1.25–1.29 (m, 20H, 10
CH2), 1.59–1.64 (m, 4H, 2 CH2), 3.42 (AB system, 4H,
J=16.1 Hz, 2CH2) 3.76 (s, 3H,OMe), 4.10 (t, 4H,
J=6.8 Hz, 2 OCH2), 5.96 (s, 2H, CHꢂ Cp).
Complex 2d (R=R%=C8H17) Analogously to prepa-
ration of 2b, lithium salt of cyclopentadienyl 1d (0.378
g, 0.67 mmol) was caused to react with [Rh(CO)2Cl]2
(0.130 g, 0.33 mmol) giving after separation through a
Florisil chromatographic column (pentane:THF=95:5
as eluent) 2d (0.152 g, 0.21 mmol) 31% yield as an
orange-red oil. Anal. Found: C, 59.94; H, 7.90;
C36H57O8Rh Calc: C, 60.00; H, 7.92%. MS (CI, m/z).
721 (MH+, 11); IR (neat) w cm−1: 2927 (w), 2857 (w),
Preparation of complex 15e (R=R%=C12H25). Fol-
lowing the same procedure adopted for 15a substrate 1e
(0.506 g, 0.69 mmol) was transformed in lithium cy-
clopentadienyl salt and caused to react with dry FeCl2
(0.044 g, 0.34 mmol). Purification by silica gel column
chromatography (9:1 hexane–THF as eluent) gave
complex 15e (0.081 g, 0.05 mmol, 15% yield) as an
orange–red wax. Anal. Found: C, 72.88; H, 10.69,
C92H162O12Fe Calc: C, 72.92; H, 10.70%. MS (CI, m/z):
1515 (MH+, 100), 1414 (78); IR (neat) w cm−1: 2956
1
2051 (s), 1988 (s), 1740 (s), 1437 (m), 1210 (m); H-
NMR (300 MHz, CDCl3) l: 0.87 (t, 9H, J=7.0 Hz,
3Me), 1.23–1.28 (m, 30H, 15 CH2), 1.57–1.61 (m, 6H,
3 CH2), 3.42 (AB system, 4H, J=16.0 Hz, 2CH2) 3.76
(s, 3H,OMe), 4.09 (t, 4H, J=6.8 Hz, 2 OCH2), 5.96 (s,
2H, CHꢂ Cp); 13C-NMR (75 MHz, CDCl3) l: 14.0
(Me), 22.5, 25.8, 25.9, 28.4, 28.5, 29.1, 30.8, 31.7, 32.4
(CH2), 64.6 (OCH2), 87.6 (CH), 96.2 (qC), 105.7 (qC),
163.1 (CO), 169.8 (CO), 188.7 (d, J=84.6 Hz, RhꢀCO).
1
(w), 1740 (s), 1714 (s), 1441 (m), 1224 (m); H-NMR
(300 MHz, CDCl3) l: 0.89 (t, 18H, J=7.0 Hz, 6 Me),
1.28–1.32 (m, 108H, 54 CH2), 1.62–1.66 (m, 12H, 6
CH2), 3.31 (AB system 8H, J=16.3 Hz, 4 CH2), 4.05
(t, 8H, J=6.8 Hz, 4 OCH2), 4.28 (t, 4H, J=6.9 Hz, 2
OCH2) 4.81 (s, 4H, 4CHꢂ Cp).
3.8. Synthesis of bis-p5[1,1%-di(alkoxycarbonyl)-
3,3%,4,4%-tetra(alkoxycarbonylmethylene)
cyclopentadienyl]iron 15a [(MDMCp)2Fe], (15b, 15e)
3.9. Synthesis of bis[dicarbonyl-p5-methoxycarbonyl-
3,4-di(mehoxycarbonylmethylene) cyclopentadienyliron]
(16) [Fe(MDMCp)(CO)2]2 and bis[dicarbonyl-p5-
methoxycarbonyl-3,4-di(mehoxycarbonylmethylene)-
cyclopentadienylruthenium] (17) [Ru(MDMCp)(CO)2]2
Preparation of complex 15a (R=R%=Me). In a dry
Schlenk tube (50 ml) under argon containing
LiMDMCp (0.162 g, 0.59 mmol) dissolved in dry THF
(10 ml) and cooled at 0°C was added slowly FeCl2
(0.037 g, 0.29 mmol) (dried according the literature
methods [26]) in dry THF (5 ml). The brown mixture
was stirred at r.t. for 24 h then concentrated to dryness.
The residue was added with CH2Cl2 (10 ml) and filtered
Preparation of complex 16. A 250 ml three-necked
flask was equipped with a magnetic stirring bar, reflux

M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
191
condenser and a Schlenk filter tube that was attached
to another sealed 250 ml three-necked flask fitted with
an argon inlet and serum stoppers. The apparatus was
dried, degassed via successive argon vacuum cycles
and charged in turns under argon with heptane (100
ml) HMDMCp (0.760 g, 2.83 mmol) and norbornene
(1.076 g, 11.43 mmol). Under stirring the solution was
cooled to −78°C and Fe2(CO)9 (1.915 g, 5.26 mmol)
was introduced. The mixture was heated at the reflux
temperature under stirring for 48 h. Then the cooled
solution was concentrated under vacuum at about 1/5
of its initial volume and the precipitate was collected
by filtration. The brown-red solid was chro-
matographed through a Florisil (1.5×20 cm) column
(6:4 hexane–EtOAc as eluent) and the solid was re-
crystallised in CH2Cl2–hexane (1:3, v/v) solution giv-
ing complex 16 (1.59 g, 2.10 mmol) in 40% yield as a
red solid m.p. 127–129°C. Anal. Found: C, 47.47; H,
3.95; C30H30O16Fe2 Calc: C, 47.49; H, 3.96%. MS (CI,
positive ions m/z): (M+, absent), 590 (3), 559 (6), 269
(38), 237 (100), 209 (96); (CI, negative ions m/z):
(M−, absent), 379 (20), 352 (100). MS (EI, positive
ions m/z): (M+, absent), 647 (8), 591 (100); (EI, nega-
tive ions, m/z): (M−, absent), 730 (16), 702 (24), 590
(25), 379 (100), 352 (56); IR (KBr) w cm−1: 2956 (w),
2004 (s), 1963 (m), 1808 (w sh), 1779 (s), 1741 (s),
1718 (s), 1450 (m), 1436 (m), 1350 (m), 1270 (s), 648
(m); (CH2Cl2, 2100–1700 cm−1 region) w cm−1: 2008
(s), 1970 (m), 1818 (w sh), 1786 (s), 1742 (s), 1721
(m); 1H-NMR (300 MHz, CDCl3) l: 3.39, 3.52 (2d,
AB system 8H, J=17.1 Hz, 4 CH2), 3.67 (s, 12H, 4
OMe), 3.95 (s, 6H, 2 OMe), 5.17 (s, 4H, 4 CHꢂ Cp);
13C-NMR (75 MHz, CDCl3) l: 31.75 (CH2), 52.34
(OMe), 52.58 (OMe), 66.75 (CHꢂ), 93.87 (qC), 102.39
(qC), 164.94 (CO), 170.26 (CO).
binations of ruthenium isotopes (CI, m/z): 854 (16),
852 (36), 850 (59), 848 (55), 846 (52), 844 (20), 842
(20), 428 (9), 427 (44), 425 (100), 423 (54), 422 (11),
399 (26), 397 (58), 396 (42), 395 (18); IR (KBr) w
cm−1: 2956 (w), 2005 (s), 1960 (m), 1783 (w sh), 1762
(s), 1739 (s), 1711 (s), 1420 (m), 1414 (m), 1343 (m),
1283 (s), 648 (m); (CH2Cl2 2100–1700 cm−1 region) w
cm−1: 2014 (s), 1973 (m), 1820 (w sh), 1787 (s), 1742
(s), 1721 (m); 1H-NMR (300 MHz, CDCl3) l: 3.33,
3.47 (2d, AB system 8H, J=17.2 Hz, 4 CH2), 3.68 (s,
12H, 4 OMe), 3.85 (s, 6H, 2 OMe), 5.76 (s, 4H, 4
CHꢂ Cp); 13C-NMR (75 MHz, CDCl3) l: 31.98
(CH2), 52.41 (OMe), 52.58 (OMe), 69.57 (CHꢂ), 97.66
(qC), 106.40 (qC), 163.33 (CO), 170.37 (CO).
3.10. Catalytic synthesis of pyridines
A Carius tube (25 ml) fitted with a Rotaflo teflon
tap was charged under argon atmosphere with com-
plex 9 (0.040 g, 0.092 mmol), propionitrile (3.62 ml,
50.6 mmol) and 1-hexyne (1.05 ml, 9.2 mmol). The
reactor was heated in a silicone oil bath (Fischer) at
100°C for 6 h under stirring. Gas chromatographic
yields based on the starting alkynes amounted to 88%
(1.773 g, 8.096 mmol) of two isomeric pyridine
derivatives (10:11=52: 48) and 8% (0.181 g, 0.736
mmol) of alkyne trimers. The same procedure and
amounts of substrates were used with cyclopentadi-
enylcobalt-(1,5-cyclooctadiene (0.021 g, 0.092 mmol)
as catalyst. Yields of 65% (1.309 g, 5.98 mmol) of
two isomeric pyridine derivatives (10:11=59:41) and
22% (0.498 g, 2.024 mmol) of alkyne trimers were
determined by GLC.
Preparation of complex 17. To a suspension of
Ru3(CO)12 (0.637 g, 1.00 mmol) in heptane (100 ml)
under argon was added HMDMCp (0.813 g, 3.00
mmol) and norbornene (0.31 g, 3.3 mmol). The reac-
tion mixture was heated at reflux an vigorously stirred
for 7 h. The solvent was evaporated under vacuum to
1/5 of its initial volume and after cooling a black
solid was filtered and washed with hexane. The solid
was dissolved in CH2Cl2–hexane (1/2 vol/vol) and
precipitated again by concentration under vacuum.
The mixture was cooled to −10°C and a brown solid
was separated. This was purified through a neutral
alumina (water deactivated) column chromatography
(1.5×30 cm) (EtOAc–hexane eluent solution varying
from 2:8 to 4:6 v/v). The 4:6 fraction was concen-
trated under vacuum giving complex 17 (0.534 g, 0.63
mmol) 42% yield as a yellow solid that was recrys-
tallised from a CH2Cl–hexane (1/2 v/v) solution yield-
ing yellow crystals m.p. 122–124°C. Anal. Found: C,
42.42; H, 3.53; C30H30O16Ru2 Calc: C, 42.45; H,
3.54%. MS dinuclear complex 17 shows different com-
3.11. Hydroformylation reactions
The hydroformylation reactions were carried out in
a 50 ml stainless-steel autoclave (Parr) fitted with
magnetic bar and thermostatted (91°C) in a silicone
oil bath (Fischer). In a typical run complex 2a (0.025
g, 0.059 mmol) distilled styrene (1.22 g, 11.76 mmol)
and degassed dry toluene were introduced into the
autoclave under N2. The autoclave cooled at −60°C
was evacuated and then pressurised at r.t. with
H2ꢀCO mixture (1/1) at 70 bar. The reaction mixture
was stirred at 100°C for 3 h. After cooling the
product mixture was recovered by usual work up and
analysed by GLC. A yield of 99% (1.556 g, 11.65
mmol) of aldehydes 13 and 14 (13:14=58:42) was
obtained. The hydroformylation reaction was carried
out analogously with complexes 2b and 2d using the
same molar amounts. The yields were 98% (1.540 g,
11.53 mmol) of aldehydes 13 and 14 (13:14=64:36)
and 98% (1.540 g, 11.53 mmol) of aldehydes 13 and
14 (13:14=59:41), respectively.

192
M. Costa et al. / Journal of Organometallic Chemistry 619 (2001) 179–193
Table 7
Crystal data and structure refinement for 9, 2a, and 15a
9
2a
15a
Formula
C21H27O6Co
434.36
Triclinic
C
15H15O8Rh
C26H30FeO12
590.35
Triclinic
Formula weight
Crystal system
Space group
426.18
Triclinic
P1
9.808(3)
12.304(5)
7.941(3)
95.77(2)
99.73(2)
111.70(3)
863.6(5)
2
1.639
428
(
(
(
P1
P1
,
a (A)
12.288(4)
7.944(3)
,
b (A)
10.201(5)
9.584(3)
84.31(3)
68.08(2)
65.94(3)
1015.7(7)
2
12.383(5)
7.656(3)
103.63(3)
114.64(3)
81.91(2)
664.5(5)
1
1.475
308
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
F(000)
)
1.420
456
Crystal size
0.26×0.27×0.37
8.79
0.21×0.17×0.27
83.58
0.15×0.28×0.31
6.32
v (cm−1
)
Reflections collected
Observed reflections
Final R indices [I\2|(I)]
5940
3258
3885
5030 [I\2|(I)]
3049 [I\2|(I)]
1752 [I\2|(I)]
R1=0.0415 a,
wR2=0.0958 b
R1=0.1099 a,
wR2=0.1279 b
R1=0.0397 a, wR2=0.1153 b
R1=0.0637 a, wR2=0.1771 b
R indices (all data)
R1=0.0473 a, wR2=0.1205 b
R1=0.0659 a, wR2=0.1848 b
a R1=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ.
b wR2=[ꢀ[w(Fo2−Fc2)2]/ꢀ[w(F2o)2]]1/2
.
4. Supplementary material
3.12. Crystal structure determination of complexes 9,
2a and 15a
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC, no. 148800 for compound 2a, no.
148801 for compound 9, no. 148802 for compound 15a.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Rd, Cam-
bridge, CB2 1EZ (fax +44-1223-336033 or e-mail de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
The intensity data of 9, 2a and 15a were collected at
r.t. on a Philips PW 1100 (9 and 15a) and a Siemens
AED (2a) single-crystal diffractometers using a graphite
monochromated Mo–Ka radiation (9 and 15a) and
Cu–Ka radiation (2a) and the q/2q scan technique.
Crystallographic and experimental details for the struc-
tures are summarised in Table 7.
A correction for absorption was made for complex
2a [maximum and minimum value for the transmission
coefficient was 1.000 and 0.704] and for 9 [maximum
and minimum value for the transmission coefficient was
1.000 and 0.743] [27].
The structures were solved by Patterson and Fourier
methods and refined by full-matrix least-squares proce-
dures (based on F2o) (SHELX-97) [28] first with isotropic
thermal parameters and then with anisotropic thermal
parameters in the last cycles of refinement for all the
non-hydrogen atoms.
Acknowledgements
The authors are grateful to Professor Gian Paolo
Chiusoli for his reading and discussing of the
manuscript. This work was carried out within the
framework of Progetto Finalizzato Chimica Fine 2 of
the Italian Centro Nazionale delle Ricerche. CIM of
University of Parma provided the facilities for NMR
and mass spectra.
The hydrogen atoms were introduced into the geo-
metrically calculated positions and refined riding on the
corresponding parent atoms. In the final cycles of
refinement a weighting scheme for 15a was w=
1/[|2F2o+(0.0879 P)2], for 2a was w=1/[|2F2o+
(0.1570 P)2+0.6791 P] and for 9 was w=1/[|2F2o+
(0.0786 P)2+ 0.0983 P] where P=(Fo2 + 2F2c)/3 was
used.
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