The μ-sulfonium-methylidene diiron complexes [Fe2(μ-C(X)SMe2)(μ-CO)(CO)2(Cp) 2]SO3CF3 (X=CN, H) as precursors of μ-alkylidene complexes

Article abstract of DOI:10.1016/s0020-1693(99)00105-x

The reactions of [Fe₂(μ-C(X)SMe₂)(μ-CO)(CO)₂(Cp) ₂]SO₃CF₃ (X=CN 2a, H 2b; Cp=η-C₅H₅) with Li₂Cu(CN)R₂ (R=Me, Buⁿ, Ph, CCC₆H₄Me-4, C₄H₃S) give the neutral μ-alkylidene complexes [Fe₂(μ-C(X)R)(μ-CO)(CO)₂(Cp)₂] (3) arising from nucleophilic attack at the bridging carbon and SMe₂ displacement. Likewise, 2a,b react with the sodium salt of dimethylmalonate, diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane and benzylcyanide, resulting in the formation of the corresponding functionalized μ-alkylidene complexes [Fe₂(μ-C(X)R)(μ-CO)(CO)₂(Cp)₂] (5-7) (X=CN, H; R=CH(COOMe)₂, CH(COOEt)₂, CH(COOMe)(COMe), CH(COMe)₂, CH(COPh)₂, CH(Ph)CN). The dichetone adducts [Fe₂(μ-C(X)CH(COR)₂)(μ-CO)(CO)₂(Cp) ₂] (X=CN, H; R=Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the complexes [Fe₂(μ-C(X)CH₂C(O)R)(μ-CO)(CO)₂(Cp) ₂]. Reactions of 2a,b with LiBu or PhLi result in the formation the metallacycles [Fe₂(μ-C(X)S(Me)CH₂)(μ-CO)(CO)(CO)(Cp)₂] (X=CN, 4a; H 4b) which arise from the deprotonation of an SMe group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a,b with that of the μ-carbyne diiron complexes [Fe₂(μ-CX)(μ-CO)(CO)₂(Cp)₂]SO ₃CF₃ (X=H, SMe, NMe₂) is presented.

Full text of DOI:10.1016/s0020-1693(99)00105-x

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 291 (1999) 333–340
The m-sulfonium–methylidene diiron complexes
[Fe2{m-C(X)SMe2}(m-CO)(CO)2(Cp)2]SO3CF3 (X=CN, H) as
precursors of m-alkylidene complexes
S. Bordoni, L. Busetto 1, M.C. Cassani, A. Palazzi, V. Zanotti *
Dipartimento di Chimica Fisica ed Inorganica, 6iale Risorgimento 4, I-40136 Bologna, Italy
Received 29 December 1998
Abstract
The reactions of [Fe2{m-C(X)SMe2}(m-CO)(CO)2(Cp)2]SO3CF3 (X=CN 2a, H 2b; Cp=h-C5H5) with Li2Cu(CN)R2 (R=Me,
Bun, Ph, CCC6H4Me-4, C4H3S) give the neutral m-alkylidene complexes [Fe2{m-C(X)R}(m-CO)(CO)2(Cp)2] (3) arising from
nucleophilic attack at the bridging carbon and SMe2 displacement. Likewise, 2a,b react with the sodium salt of dimethylmalonate,
diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane and benzylcyanide, resulting in the formation of the
corresponding functionalized m-alkylidene complexes [Fe2{m-C(X)R}(m-CO)(CO)2(Cp)2] (5–7) (X=CN, H; R=CH(COOMe)2,
CH(COOEt)2, CH(COOMe)(COMe), CH(COMe)2, CH(COPh)2, CH(Ph)CN). The dichetone adducts [Fe2{m-C(X)CH(COR)2}(m-
CO)(CO)2(Cp)2] (X=CN, H; R=Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the
complexes [Fe2{m-C(X)CH2C(O)¸R¹}(¹m¹-C¹O¹)¹(CºO)2(Cp)2]. Reactions of 2a,b with LiBu or PhLi result in the formation the
metallacycles [Fe2{m-C(X)S(Me)CH2}(m-CO)(CO)(CO)(Cp)2] (X=CN, 4a; H 4b) which arise from the deprotonation of an SMe
group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a,b with
that of the m-carbyne diiron complexes [Fe2(m-CX)(m-CO)(CO)2(Cp)2]SO3CF3 (X=H, SMe, NMe2) is presented. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Iron complexes; Alkylidene complexes; Dinuclear complexes
potential as models for related processes occurring on
metal surfaces. Dirhodium [3], diruthenium [4], and
diiron [5] complexes with bridging carbene ligands,
have offered valuable model systems for investigating
the Fisher–Tropsch polymerization reaction [6]. There-
fore, we decided to extend our investigations on C–C
bond formation to the diiron thiocarbene complexes
[Fe2{m-C(X)SMe2}(m-CO)(CO)2(Cp)2]SO3CF3 (X=CN,
2a; H, 2b) which, like 1a,b, exhibit a considerable
electrophilic character. Indeed, both 2a [7] and 2b [8]
have been shown to undergo SMe2 displacement easily
by a variety of nucleophiles forming heteroatom substi-
tuted bridging alkylidene complexes. In particular, the
reactions of 2a with amines [9], alcohols [10], and
phosphines [11], have been described in detail. In con-
trast, only a few reactions of 2a,b with carbon nucleo-
philes, including NBu4n CN, have been investigated
[7c,8]. Herein, we report on the reactivity of 2a,b to-
wards stabilized carbanions, and organolithium, Grig-
1. Introduction
We have recently reported [1] on the carbon–carbon
bond formation at the cationic diiron m-carbyne com-
plexes [Fe2(m-CX)(m-CO)(CO)2(Cp)2]SO3CF3 (X=
NMe2, 1a; SMe, 1b) via addition of carbon
nucleophiles, like organo-copper, -magnesium and
-lithium reagents. Interestingly, these addition reactions
have been shown to occur selectively at the different
ligands: the bridging carbyne, the carbonyl and the
C5H5 ring, depending on the nature of the nucleophiles
and of the heteroatom adjacent to the bridging carbyne
carbon [2].
Carbon–carbon bond forming reactions in dinuclear
complexes are of considerable interest because of their
* Corresponding author. Tel.: +39-051-644 3700; fax: +39-051-
644 3690.
1 Also corresponding author.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00105-X

334
S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
Scheme 1.
nard and organocopper reagents, aimed at developing
synthetic entries into disubstituted m-CR2 complexes via
formation of a C–C bond.
2.2. Reactions with organolithium and Grignard
reagents
In contrast with the above described reactions, treat-
ment of 2a,b with alkyl- or aryl-lithium led to the
metallacycles 4a,b, presumably via deprotonation of an
SMe, followed by addition at the terminally coordi-
nated CO ligand (Scheme 2). Compounds 4a,b have
been obtained as dark green crystalline solids in about
41–34% yield, from 2a and 2b, respectively, together
with minor amounts of by-products. For example, in
the case of 2a, [Fe2(m-CO)2(CO)2(Cp)2] (12%) and
[Fe2{m-C(H)CN}(m-CO)(CO)2(Cp)2] (7%) were also
obtained.
2. Results
2.1. Reactions with of organocopper reagents
The reactions of 2a,b with Li2Cu(CN)R2, in thf at
−40°C, afforded the alkylidene complexes [Fe2{m-
C(X)R}(m-CO)(CO)2(Cp)2] (3a–g) (Scheme 1).
These complexes, which are moderately air-stable
solid red crystals, have been isolated after column
chromatography in 30–50% yield. Their IR spectra, in
CH2Cl2, exhibit the expected three band pattern for the
two terminal and one bridging w(CO) bands (with
relative intensities strong-weak-medium) that typify the
m-alkylidene compounds [Fe2{m-C(X)R}(m-CO)(CO)2-
(Cp)2] [7,9–11], adopting a cis conformation (Cp cis to
each other). Moreover, a weak band attributable to the
w(CN) is observed in the cyanoalkylidene complexes
3a–e (e.g. at 2148 cm−1 for 3a). Both 1H and 13C
NMR spectra of 3a–c and 3f,g show one singlet for the
Cp ligands according to the presence of only one of the
two possible cis-isomers (e.g. for 3a at 4.99 and 91.5
ppm, respectively); presumably that with the smaller
(CN or H) substituent on the carbene carbon on the
more hindered Cp side of the molecule, as found in the
structurally characterized m-cyanoalkylidene complexes
[7a,10,11a,12]. However, as in the case of the complex
[Fe2{m-C(H)CN}(m-CO)(CO)2(Cp)2] [7c], compounds
3d,e present a small amount of the trans isomer, beside
the more abundant cis. For example, the 1H NMR
spectrum of 3d shows, in addition to the usual Cp
resonances at 4.92, two minor signals of equal intensity
at 4.95 and 4.82 ppm which account for the presence of
the trans isomer. Finally, the 13C NMR spectra of 3a–e
show resonances for the bridging carbene carbon at
about 130–165 ppm, within the range typical for bridg-
ing alkylidene carbons. Complexes 3f,g have been iden-
tified by comparison of their spectroscopic properties
with those previously reported in the literature [13].
The IR spectra of 4a,b show three w(CO) absorptions
(at 1946s, 1788m, 1634m cm−1 for 4a) attributable to
the terminally bonded, bridging and acyl CO groups,
respectively. Moreover, a weak w(CN) band is observed
at 2168 cm−1 in the spectrum of 4a. The non equiva-
lence of the Cp ligands in 4 originates two equally
intense resonances in the NMR spectra (e.g. for 4a at
1
4.83, 4.66 ppm and at 90.5, 88.2 ppm in the H and 13C
NMR, respectively). The diastereotopic methylene pro-
tons in the metallacycle give rise to two doublets (JAB
17 Hz).
Reactions of 2a,b with RMgCl (R=Me, CH2Ph)
unexpectedly failed to produce any identifiable product.
Previously reported electrochemical investigations [14]
have shown that the diiron cyanoalkylidene complexes
can undergo one electron reduction to unstable 19-elec-
tron species. This suggests that other processes, based
upon electron-transfer, may effectively take place.
Scheme 2.

S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
335
Scheme 3.
2.3. Reactions with stabilized carbanions
Unlike 5a–d, that possess a plane of symmetry,
compounds 6a,b are chiral molecules and two
diastereotopic Cp groups are observed in their NMR
Like the reactions of Scheme 1, the SMe2 molecule
in 2a,b is readily displaced by the sodium salt of
dimethylmalonate, diethylmalonate and ethylacetoac-
etate to afford the corresponding alkylidene com-
plexes 5a–d and 6a,b in high yield (80–90%) (Scheme
3).
The IR spectra of 5a–d and 6a,b in CH2Cl2 solu-
tion, show, in addition to the usual w(CO) band pat-
tern due to the terminal and bridging carbonyls, the
absorptions attributable to the COOR and COMe
groups (e.g. for 5b at 1747 and 1725 cm−1). More-
over, the cyanoalkylidene complexes 5a,b and 6a ex-
hibit a weak w(CN) absorption (for 5b at 2160
cm−1). Only one singlet signal is observed in the
NMR spectra of 5a–d for the Cp ligands, indicating
their equivalence and the presence, in solution, of one
single cis-isomer. The two Me groups in 5a also ap-
1
spectra (e.g. for 6a at 4.92 and 4.88 ppm in the H
NMR). Compounds 5c,d and 6b show the characteris-
tic downfield resonance at about 12 ppm assigned to
the proton on the bridging carbon which appears as a
doublet due to the coupling to the tertiary b-hydro-
gen.
Complexes 5d and 6b have been previously ob-
tained from [Fe2(m-CH)(m-CO)(CO)2(Cp)2]+ by treat-
ment with the CH2(COOMe)2 and CH2(COOEt)2,
respectively, in the presence of a tertiary amine [13a].
The bridging carbene carbon resonance of type 5
and 6 complexes occurs, as expected, in the 160–116
ppm range. It is worth noting that cyanocarbene–car-
bon resonances (5a,b, 6a) are about 30–40 ppm up-
field shifted with respect to the methylidene analogues
(5c,d, 6b).
1
pear as one single resonance (at 3.87 ppm in the H
Treatment of 2a,b with NaCH(COR)2 (R=Me, Ph)
provided the expected alkylidene derivatives [Fe2{m-
C(X)CH(COR)2}(m-CO)(CO)2(Cp)2] (7a–d) in good
yields (Scheme 4). As previously described by Casey
[13a], 7c was deacetylated to form 8c upon chrom-
NMR) whereas, in 5b the methylene protons of the
ethyl group are diastereotopic because of their pro-
chiral relationship, and originate two distinct multi-
plets (at 4.29 and 4.28 ppm).
Scheme 4.

336
S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
dene complexes, contributing to the emerging field of
CN-based organometallic complexes [16].
matography on alumina. Similarly, compounds 7a,b, 7d
have been converted into 8a,b, 8c, respectively, upon
analogous treatment (Scheme 4). As reported [13a], the
deacylation reaction does not occur by using silica gel
in place of alumina.
The characterization of 7 and 8 has been straightfor-
ward since their spectroscopic properties are similar to
those of compounds 3 and 5 discussed above.
Compared to the related m-carbyne complexes [Fe2(m-
CX)(m-CO)(CO)2(Cp)2]SO3CF3 (X=NMe2, 1a; SMe,
1b), which have been shown to be susceptible of nucleo-
philic addition at the m-carbyne as well as at the CO
and Cp ligand [1,2], in compounds 2a,b the m-
C(X)SMe2 (X=CN, H) moiety appears as the unique
target of nucleophiles, thus favoring the C–C bond
formation at the bridging carbene carbon atom with
organocuprates and stabilized carbanions. However, in
the reactions with organo-lithium reagents, 4a,b deriva-
tives are formed as a consequence of a intramolecular
cyclization. Thus, the goal of forming a C–C bond is
achieved via nucleophilic addition of deprotonated SMe
at the terminally bonded carbonyl group. Although
there are examples of intramolecular cyclization involv-
ing the m-carbene ligand in the complexes [Fe2{m-
C(CN)X)(m-CO)(CO)2(Cp)2] (X=SMe, OCH2CHꢀ
CH2) [10,12a] this represents the first case in which
cyclization includes the CO instead of producing its
displacement. The cyclization appears possible because
the SMe2 and the CO groups are placed on the same
side of the Fe–Fe bond [12c]. The formation of 4a,b
was rather unexpected in view of the fact that SMe
deprotonation has never been observed so far, in spite
of the large variety of nucleophiles and bases with
which 2a,b have been treated.
It should finally be noted that only Li2Cu(CN)R2,
and, not LiR or RMgCl, appears to be able to form
C–C bonds at the m-carbene carbon of 2a,b.
Organocopper reagents have been shown to be the most
efficient at forming C–C bonds at the m-carbyne of
[Fe2(m-CR)(m-CO)(CO)2(Cp)2]+ (R=H, Ph) including
the m-ethylinyl complex (R=Me), in which deprotona-
tion of the acidic hydrogens of the m-CMe unit might
compete with the nucleophilic addition [13a,17]. Like-
wise, Li2Cu(CN)R2 complexes have been shown to
attack selectively the m-carbyne carbon of [Fe2(m-
CSMe)(m-CO)(CO)2(Cp)2]SO3CF3 (1b) [2a].
Reactions with carbanions stabilized by the presence
of CN groups have also been investigated. Upon treat-
ment with NaCH(CN)Ph, compounds 2a,b afforded the
expected m-carbene complexes [Fe2{m-C(X)CH(CN)Ph}-
(m-CO)(CO)2(Cp)2] (X=CN 9a; H, 9b) in 88 and 51%
yields, respectively. These complexes, like 6a,b, are chi-
ral molecules and two diastereotopic Cp groups are
observed in their NMR spectra (e.g. for 9a at 4.92 and
4.88 ppm).
Rather surprisingly, the analogous reaction of 2b
with NaCH(CN)2 instead of forming the expected m-
alkylidene [Fe2{m-C(CN)CH(CN)2}(m-CO)(CO)2(Cp)2],
gave a mixture of products which included the vinyli-
dene complex [FpC(CN)ꢀC(CN)2] (Fp=Fe(CO)2Cp)
and the trinuclear cyanocarbyne [Fe3(m3-CCN)(m-
CO)3(Cp)3] in 12 and 31% yields, respectively. Their
formation must be interpreted in terms of Fe–Fe bond
cleavage in 2b and rearrangements of the metal frag-
ments, generating both mononuclear and trinuclear spe-
cies. The latter has been identified by comparison of its
spectroscopic properties with those of the same com-
pound previously obtained by a different route [15].
3. Discussion
The reactions presented confirm our previous find-
ings which suggested that the sulfonium–methylidene
complexes 2a,b provide excellent entries into disubsti-
tuted m-methylidene diiron complexes via SMe2 replace-
ment by a variety of nucleophiles [7–11]. Here the
method has been used to synthesize m-CRR% (R%=CN,
H) derivatives by reactions with carbon nucleophiles
such as organocopper reagents Li2Cu(CN)R2 (R=Me,
Bu, Ph, CꢁCC6H5Me, C4H3S) and carbanions derived
from methyl or ethyl malonate, ethyl acetoacetate, 2,4-
pentanedione, dibenzoylmethane and benzylnitrile,
yielding the functionalized alkylidene complexes 5–7.
Note, the compounds 3f,g, 5d, 6b and 7c have been
previously obtained by nucleophilic addition at the
m-methylidyne complex [Fe2(m-CH)(m-CO)(CO)2(Cp)2]-
SO3CF3 [13]. However, since the latter is considerably
more reactive and difficult to handle, compound 2b can
be viewed as an advantageous alternative to [Fe2(m-
CH)(m-CO)(CO)2(Cp)2]SO3CF3, at least for the reaction
with the above mentioned carbon nucleophiles. On the
other hand, 2a is a remarkable source of cyanoalkyli-
4. Experimental
4.1. General
All reactions were carried out routinely under nitro-
gen using standard Schlenk techniques. Solvents were
distilled immediately before use under nitrogen from
appropriate drying agents. Glassware was oven-dried
before use. IR spectra were recorded on a Perkin–
Elmer 983-G spectrophotometer, 1H and 13C NMR
spectra on a Varian Gemini 300. The shiftless relax-
ation reagent [Cr(acac)3] (acac=acetylacetonate) was
added to solution studied by 13C NMR spectroscopy.
All the reagents were commercial products (Aldrich) of

S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
337
the highest purity available and used as received.
[Fe2(CO)4(Cp)2] was from Strem and used as received.
Compounds [Fe2{m-C(X)SMe2}(m-CO)(CO)2(Cp)2]SO3-
CF3 (X=CN, 2a; H, 2b) were prepared as described in
the literature [8,12c]. Li2Cu(CN)R2 species were pre-
pared from CuCN and the appropriate organolithium
reagent according to the literature [18].
tributable to the trans isomer are italicized) lH (CDCl3):
7.28–7.00 (4 H, m, C6H4), 4.92, 4.95 4.82 (10 H, s, Cp),
2.32 and 2.27 (3 H, s, CH3) ppm (cis/trans ratio=4.1).
lC(CDCl3): 265.6 (m-CO), 209.3 (CO), 137.9 (m-C),
130.9, 129.9, 129,5, 122.1 (C6H4Me), 107.4, 96.3 (CꢁC),
90.8, 92.9, 92.3 (Cp), and 22.0 (Me) ppm.
3e: (31%). Anal. Found: C, 51.07; H, 3.01%.
C19H13Fe2NO3S requires: C, 51.05; H, 2.93%. IR
(CH2Cl2) wmax(cm−1) 2157w (CN), 2001s, 1963m and
1803m (CO). NMR: (resonances attributable to the
trans isomer are italicized) lH (CDCl3): 7.12, 6.90, 6.77,
7.41, 7.27, 6.88 (3 H, m, C4H3S), 4.95, 4.92, and 4.70
(10 H, s, Cp) ppm. lC(CDCl3): 265.6 (m-CO), 210.4,
209.7 (CO), 164.3 (m-C), 134.6 (CN), 128.4, 127.3,
125.7, 125.3, 124.8, 124.3, 116.1 (C4H3S), 91.6, 90.8,
92.9, 92.0 (Cp), and 22.0 (Me) ppm.
4.2. Synthesis of [Fe2{v-C(CN)Ph}(v-CO)(CO)2(Cp)2]
(3a)
Compound 2a (99 mg, 0.171 mmol) in thf (10 ml) at
−30°C was treated with Li2Cu(CN)Ph2 prepared from
dry CuCN (0.018 g, 0.2 mmol) and LiPh (0.4 mmol) in
thf (4 ml) at −60°C. The mixture was then warmed to
0°C, stirred for an additional hour and filtered on an
alumina pad. Removal of the solvent and chromatogra-
phy on an alumina column with CH2Cl2 as eluent gave
a first red fraction containing [Fe2(m-CO)2(CO)2(Cp)2]
followed by a second red fraction which was collected.
Evaporation of the solvent and crystallization from
CH2Cl2 and n-pentane at −20°C afforded yellow crys-
tals of 3a (30 mg, 39%). Anal. Found: C, 57.16; H,
3.43%. C21H15Fe2NO3 requires: C, 57.19; H, 3.43%. IR
(CH2Cl2) wmax(cm−1) 2148w (CN), 2001s, 1964m and
1801m (CO). NMR: lH (CDCl3): 7.52–7.21 (5 H, m,
Ph) and 4.99 (10 H, s, Cp) ppm. lC(CDCl3): 266.3
(m-CO), 209.8 (CO), 157.4 (m-C), 135.8 (CN); 131.2,
130.4, 128.0, 126.8 (Ph) and 91.5 (Cp) ppm.
4.4. Syntheses of [Fe2{v-C(H)R}(v-CO)(CO)2(Cp)2]
(R=Ph, 3f; R=Me, 3g)
Compound 2b (182 mg, 0.33 mmol) in thf (10 ml) at
−30°C was treated with Li2Cu(CN)Ph2 prepared from
dry CuCN (0.075 g, 0.84 mmol) and LiPh (1.69 mmol)
in thf (4 ml) at −60°C. The mixture was then warmed
to room temperature (r.t.) and stirred for an additional
2 h. Filtration on an alumina pad and removal of the
solvent gave a red residue which was chromatographed
on an alumina column with CH2Cl2 as eluent. A first
red fraction afforded [Fe2{m-C(H)Ph}(m-CO)(CO)2-
(Cp)2] (45 mg, 33%) which was identified by compari-
son of its spectroscopic properties with those reported
in the literature [13a]. A second red fraction obtained in
about 6% yield was identified as [Fe2{m-C(CN)H}(m-
CO)(CO)2(Cp)2] [7a].
Complex 3g, identified by comparing spectroscopic
data with those reported [13b], was obtained as de-
scribed for the synthesis of 3f, by reacting 2b (186 mg,
0.34 mmol) in thf (10 ml) at −10°C, with a slight
excess of Li2Cu(CN)Bun2 (0.35 mmol). Yield: 42 mg
(34%).
4.3. Syntheses of [Fe2 {v-C(CN)R}(v-CO)(CO)2(Cp)2]
(R=Me, 3b; Bun, 3c; CꢁCC6H4Me-4 3d; C4H3S, 3e)
Complexes 3b–e were obtained following the same
procedure described for the synthesis of 3a by reacting
2b with Li2Cu(CN)Me2, Li2Cu(CN)Bun2 , Li2Cu(Cꢁ
CC6H4Me-4)2, Li2Cu(C4H3S)2, respectively.
3b: (42%). Anal. Found: C, 50.55; H, 3.49%.
C16H13Fe2NO3 requires: C, 50.71; H, 3.46%. IR
(CH2Cl2) wmax(cm−1) 2150w (CN), 1993s, 1960w and
1799m (CO). NMR: lH (CDCl3): 4.81 (10 H, s, Cp) and
2.71 (3 H, s, Me) ppm. lC(CDCl3): 267.9 (m-CO), 211.2
(CO), 127.3 (m-C), 91.1 (Cp) and 45.5 (Me) ppm.
3c: (52%). Anal. Found: C, 54.18; H, 4.49%.
C19H19Fe2NO3 requires: C, 54.20; H, 4.45%. IR
(CH2Cl2) wmax(cm−1) 2151w (CN), 1986s, 1951w and
1800m (CO). NMR: lH (CDCl3): 4.82 (10 H, s, Cp),
2.60 (2 H, m, CH2CH2CH2CH3), 2.01 (2 H, m,
CH2CH2CH2CH3), 1.42 (2 H, m, CH2CH2CH2CH3),
and 0.96 (3 H, t, CH2CH2CH2CH3) ppm. lC(CDCl3):
267.1 (m-CO), 210.7 (CO), 136.0 (m-C), 134.1 (CN), 90.6
(Cp), 57.5, 37.3, 22.9, and 14.2 (Bun) ppm.
4.5. Reaction of 2a with BuLi
Buthyllithium (0.49 ml, 0.78 mmol, 1.6 M in hexane)
was added to 2a (0.45 g, 0.78 mmol) in thf (25 ml) at
−50°C. The mixture was stirred for 1 h at −50°C and
then allowed to warm to r.t. Filtration on an Celite pad
and removal of the solvent gave a brown residue that
was chromatographed on an alumina column with a
CH2Cl2–hexane mixture (1:1, v/v) as eluent. A first red
fraction, containing [Fe2(m-CO)(CO)2(Cp)2] (12%), was
3d: (47%). Anal. Found: C, 60.21; H, 3.63%.
C24H17Fe2NO3 requires: C, 60.13; H, 3.58%. IR
(CH2Cl2) wmax(cm−1) 2178w (CꢁC), 2164w (CN), 2005s,
1973m and 1805m (CO). NMR: (resonances at-
followed by
C(CN)H}(m-CO)(CO)2(Cp)2] (21 mg, 7%) [7c]. Further
elution with¸¹th¹f¹¹g¹av¹e¹¹¹¹gºreen band of [Fe2{m-
C(CN)S(Me)CH2}(m-CO)(CO)(CO)(Cp)2] (4a) (0.14 g,
a
second red fraction of [Fe2{m-
a

338
S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
41%). Anal. Found: C, 48.15; H, 3.57%.
C17H15Fe2O3NS requires: C, 48.04; H, 3.56%. IR
(CH2Cl2) wmax(cm−1) 2168w (CN), 1946s, 1788ms and
1634m (CO). NMR: lH (CDCl3): 4.83 (5 H, s, Cp), 4.66
(5 H, s, Cp), 2.55 (1 H, d, JAB 17 Hz, CH2SCH3), 2.02
(1 H, d, JAB 17 Hz, CH2SCH3) and 1.45 (3 H, s,
CH2SCH3) ppm. lC(CD2Cl2): 269.4 (m-CO), 218.9
(CH2CO), 209.7 (CO), 117.6 (m-C), 133.1 (CN), 90.5
(Cp), 88.2 (Cp), 40.3 and 21.2 (CH2SCH3) ppm. Reac-
tions of 2a with LiPh or LiCꢁCPh proceeded as above
described, giving the same products.
5b: (91%). Anal. Found: C, 50.45; H, 4.11%.
C22H21Fe2NO7 requires: C, 50.51; H, 4.05%. IR
(CH2Cl2) wmax(cm−1
) 2159w (CN), 1996s, 1961w,
1804m, 1747mw and 1725mw (CO). NMR: lH (CDCl3):
4.87 (10 H, s, Cp), 4.29 (2 H, q, CHHCH3, J=7,1 Hz),
4.28 (2 H, q, CHHCH3, J=7.1 Hz), 3.64 (1 H, s,
m-CCH) and 1.31 (6 H, t, CH2CH3, J=7.1 Hz) ppm.
lC(CDCl3): 264.9 (m-CO), 210.5 (CO), 168.7 (COOEt),
134.3 (CN), 116.9 (m-C), 92.1 (Cp), 73.4 (m-CCH), 62.1
(OCH2CH3) and 14.8 (OCH2CH3) ppm.
6a: (68%). Anal. Found: C, 51.12; H, 3.89%.
C21H19Fe2NO6 requires: C, 51.16; H, 3.88%. IR
(CH2Cl2) wmax(cm−1
) 2157w (CN), 1994s, 1959w,
4.6. Reaction of 2b with BuLi
1804m, 1736mw and 1714mw (CO). NMR: lH (CDCl3):
4.92 (5 H, s, Cp), 4.88 (5 H, s, Cp), 4.35 (2 H, q,
CH2CH3, J=7.0 Hz), 3.77 (1 H, s, m-CCH), 2.38 (3 H,
s, COCH3), and 1.38 (3 H, t, CH2CH3, J=7.0 Hz)
ppm. lC(CDCl3): 265.0 (m-CO), 211.2, 210.6 (CO),
201.8 (COMe), 169.3 (COOEt), 126.2 (m-C), 92.3, 92.1
(Cp), 81.0 (m-CCH), 62.4 (OCH2CH3), 31.0 (COCH3),
and 14.9 (OCH2CH3) ppm.
Compound 2b (0.22 mg, 0.40 mmol) was treated with
LiBun as describe¸d¹f¹o¹r ¹th¹e¹¹syºnthesis of 4a yielding
[Fe2{m-C(H)S(Me)CH2}(m-CO)(CO)(CO)(Cp)2] (4b) (52
mg, 34%). Anal. Found: C, 50.22; H, 4.29%.
C16H16Fe2O3S requires: C, 50.31; H, 4.22%. IR
(CH2Cl2) wmax(cm−1) 1927s, 1771ms and 1667m (CO).
NMR: lH (CDCl3): 10.97 (1 H, s, m-CH), 4.77 (5 H, s,
Cp), 4.53 (5 H, s, Cp), 2.53 (1 H, d, JAB 17 Hz,
CH2SCH3), 2.20 (1 H, d, JAB 17 Hz, CH2SCH3) and
1.38 (3 H, s, CH2SCH3) ppm. lC(CD2Cl2): 276.3 (m-
CO), 220.5 (CH2CO), 216.7 (CO), 152.0 (m-CH), 87.5
(Cp), 85.1 (Cp), 41.0 and 21.3 (CH2SCH3) ppm.
4.9. Syntheses of
[Fe2{v-C(H)CHRR%}(v-CO)(CO)2(Cp)2]
(R=R%=COOMe, 5c; R=R%=COOEt, 5d;
R=COOEt, R%=COMe, 6b)
The complexes 5c,d and 6b were obtained following
the same procedure described for the synthesis of 5a,b
and 6a, by reacting 2b with NaCH(COOMe)2, NaCH-
(COOEt)2 and NaCH(COOEt)(COMe), respectively.
5c: (65%). Anal. Found: C, 48.56; H, 3.89%.
C19H18Fe2O7 requires: C, 48.55; H, 3.86%. IR (CH2Cl2)
wmax(cm−1) 1982s, 1943w, 1785m, 1748mw and 1728mw
(CO). NMR: lH (CDCl3): 11.01 (1 H, d, J=11 Hz,
m-CH), 4.75 (10 H, s, Cp), 3.85 (6 H, s, CH3) and 4.45
(1 H, d, J=11 Hz, m-CCH) ppm. lC(CDCl3): 271.0
(m-CO), 212.1 (CO), 171.0 (COOMe), 157.9 (m-C), 88.3
(Cp), 73.5 (m-CCH), and 53.0 (Me) ppm.
4.7. Synthesis of [Fe2
{v-C(CN)CH(COOMe)2}(v-CO)(CO)2(Cp)2] (5a)
A solution of 2a (0.27 g, 0.47 mmol) in thf (15 ml)
was treated with NaCH(COOMe)2 (0.49 mmol) freshly
obtained from CH2(COOMe)2 and NaH. The mixture
was stirred for 30 min and then evaporated to dryness.
Chromatography of the residue on an alumina column
eluting with CH2Cl2–hexane mixture (1:2; v/v) gave a
red fraction of [Fe2{m-C(CN)CH(COOMe)2}(m-CO)-
(CO)2(Cp)2] (5a) which was crystallized from CH2Cl2
layered with n-pentane at −20°C (0.18 g, 77%). Anal.
Found: C, 48.49; H, 3.59%. C20H17Fe2NO7 requires: C,
48.52; H, 3.46%. IR (CH2Cl2) wmax(cm−1) 2158w (CN),
1996s, 1961w, 1805m, 1752mw and 1732mw (CO).
NMR: lH (CDCl3): 4.91 (10 H, s, Cp), 3.87 (6 H, s,
CH3) and 3.73 (1 H, s, m-CCH) ppm. lC(CDCl3): 264.7
(m-CO), 210.5 (CO), 169.3 (COOMe), 134.4 (CN), 116.5
(m-C), 92.2 (Cp), 73.1 (m-CCH), and 53.3 (Me) ppm.
Compounds 5d (71%) and 6b (78%) were identified
by comparison of their spectroscopic properties with
those reported in the literature [13a].
4.10. Synthesis of [Fe2{v-C(X)CH(COR)2}(v-CO)-
(CO)2(Cp)2] (X=CN, R=Me, 7a; X=CN, R=Ph,
7b; X=H, R=Me, 7c; X=H, R =Ph, 7d)
4.8. Syntheses of [Fe2{v-C(CN)CH(COOEt)2}(v-CO)-
(CO)2(Cp)2] (5b) and [Fe2{v-C(CN)CH(COOEt)-
(COMe)}(v-CO)(CO)2(Cp)2] (6a)
Compound 2a (0.19 g, 0.33 mmol) and NaCH-
(COMe)2 (0.33 mmol), freshly obtained from NaH and
2,4-pentanedione, were stirred in thf (15 ml) for 2 h.
The solvent was then removed and the residue chro-
matographed on silica-gel column with CH2Cl2–hexane
(1:1, v:v) mixture as eluent. A first red fraction of
[Fe2(CO)4(Cp)2] (31 mg, 27%) was discharged. Elution
with CH2Cl2 gave a second red fraction of [Fe2{m-
Complexes 5b and 6a were obtained following the
same procedure described for the synthesis of 5a, by
reacting 2a with equimolar amounts of sodium diethyl-
malonate and sodium ethylacetoacetate, respectively.

S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
339
C(CN)CH(COMe)2}(m-CO)(CO)2(Cp)2] (7a) which was
recrystallized from CH2Cl2 layered with n-pentane at
−20°C. Yield: 69 mg (45%). Anal. Found: C, 3.79; H,
52.02%. C20H17Fe2NO5 requires: C, 51.88; H, 3.70%. IR
ppm. lC(CDCl3): 266.3 (m-CO), 211.6 (CO), 197.9
(COMe), 150.0 (m-C), 137.6–129.3 (Ph), 128.5 (CN),
91.9 (Cp) and 63.7 (m-CCH2), ppm.
8c: (54%) Compound 8c was identified by compari-
son of its spectroscopic data with those reported in the
literature [13a].
(CH2Cl2) wmax(cm−1
) 2153w (CN), 1992s, 1956w,
1805m, 1732mw and 1695mw (CO). NMR: lH (CDCl3):
4.89 (10 H, s, Cp), 4.00 (1 H, s, m-CCH), and 2.41 (3 H,
s, CH3) ppm. lC(CDCl3): 211.0 (CO), 203.0 (COMe),
131.6, 129.5 (CN and m-C), 92.3 (Cp), 90.3 (m-CCH),
and 30.7 (CH3) ppm.
4.12. Syntheses of [Fe2 {v-C(X)CH(Ph)(CN)}(v-CO)-
(CO)2(Cp)2] (X=CN, 9a; X=H, 9b)
Compound 7b was analogously prepared from 2a
(0.22 g, 0.38 mmol) and NaH(COPh)2 (94 mg, 38
mmol). Yield: 0.13 g (60%). Anal. Found: C, 61.43; H,
3.65%. C30H21Fe2NO5 requires: C, 61.36; H, 3.60%. IR
To a solution of 2a (0.19 g, 0.33 mmol) in thf (15 ml)
was added NaCH(C6H5)(CN) (0.33 mmol) obtained
from benzylcyanide and NaH. The mixture was stirred
for 60 min and then evaporated to dryness. Chromatog-
raphy of the residue on an alumina column with
CH2Cl2 as eluent, gave a purple–red fraction of 9a
which was crystallized from CH2Cl2 layered with n-pen-
tane at −20°C (0.14 g, 88%). Anal. Found: C, 57.44;
H, 3.41%. C23H16Fe2N2O3 requires: C, 57.54; H, 3.36%.
IR (CH2Cl2) wmax(cm−1) 2159w (CN), 1994s, 1958w
and 1810m (CO). NMR: lH (CDCl3): 7.50 (5 H, m,
Ph), 5.02 (5 H, s, Cp), 4.58 (5 H, s, Cp) and 4.07 (1 H,
s, m-CCH) ppm. lC(CDCl3): 262.4 (m-CO), 211.6, 210.6
(CO), 138.1–121.5 (Ph), 133.2 (CN), 126.9 and 121.5
(m-C and CN), 92.7, 91.7 (Cp) and 58.5 (m-CCH) ppm.
Compound 9b was analogously prepared from 2b
(0.27 g, 0.49 mmol) and NaCH(C6H5)(CN) (0.50
mmol). Yield: 0.12 g (51%). Anal. Found: C, 56.22; H,
3.70%. C23H17Fe2N2O3 requires: C, 56.33; H, 3.65%. IR
(CH2Cl2) wmax(cm−1) 2230w (CN), 1980s, 1940w and
1792m (CO). NMR: lH (CDCl3): 10.77 (1 H, d, J=12
Hz, m-CH), 7.68–7.45 (5 H, m, Ph), 4.91 (5 H, s, Cp),
4.46 (1 H, d, J=12 Hz, m-CCH) and 4.31 (5 H, s, Cp)
ppm. lC(CDCl3): 165.6 (m-C), 129.8–121.8 (Ph), 98.1,
88.3 (Cp) and 58.2 (m-CCH) ppm.
(CH2Cl2) wmax(cm−1
) 2157w (CN), 1990s, 1953w,
1804m, 1670mw and 1673mw (CO). NMR: lH (CDCl3):
7.99–7.43 (10 H, m, Ph), 5.77 (1 H, s, m-CCH) and 4.77
(10 H, s, Cp) ppm. lC(CDCl3): 265.0 (m-CO), 211.0
(CO), 196.0 (COPh), 138.2–129.2 (Ph), 92.6 (Cp) and
80.5 (m-CCH) ppm.
Compounds 7c and 7d were obtained as described
above by reacting 2b with equimolar amounts of NaH-
(COMe)2 and NaHC(COPh)2, respectively.
7c: (53%). The spectroscopic properties of 7c were
identical to those reported [13a].
7d: (64%). Anal. Found: C, 61.83; H, 3.99%.
C29H22Fe2O5 requires: C, 61.96; H, 3.94%. IR (CH2Cl2)
wmax(cm−1) 1975s, 1935w, 1784m, 1693mw and 1657mw
(CO). NMR: lH (CDCl3): 11.36 (1 H, d, J=12 Hz,
m-CH), 7.60–7.45 (10 H, m, Ph), 6.78 (1 H, d, J=12
Hz, m-CCH) and 4.66 (10 H, s, Cp) ppm. lC(CDCl3):
272.2 (m-CO), 212.9 (CO), 196.4 (COPh), 164.6
(m-C), 137.9–129.5 (Ph), 88.6 (Cp) and 80.5 (m-CCH)
ppm.
4.11. Syntheses of
[Fe2{v-C(X)CH2(COR)}(v-CO)(CO)2(Cp)2] (X=CN,
R=Me, 8a; X=CN, R=Ph, 8b; X=H, R=Me, 8c)
4.13. Reaction of 2a with NaCH(CN)2
Complex 2a (0.17 g, 0.29 mmol) in thf (15 ml) at
−30°C was treated with NaCH(CN)2 (0.30 mmol)
generated from NaH and malononitrile. The mixture is
then allowed to warm to r.t. and stirred for further 60
min. Evaporation of the solvent and chromatography
of the residue on an alumina column with CH2Cl2–hex-
ane (1:2, v:v) mixture as eluent afforded a first red
fraction of [Fe2(CO)4(Cp)2] (20%) that was discharged.
Elution with CH2Cl2–hexane (1:1, v:v) gave a brown
fraction of [Fe3(m-CO)3(m3-CCN)(Cp)3] (31%) which
was identified by comparison with the reported spectro-
scopic data [15]. Further elution with CH2Cl2 gave a
yellow fraction of [Fe(CO)2{C(CN)ꢀC(CN)2}(Cp)]
(12%). Anal. Found: C, 51.66; H, 1.88%. C12H5FeN3O2
The complexes 8a–c were obtained following the
same procedure described for the synthesis of 7a–c,
using alumina in place of silica gel, for the column
chromatography.
8a: (58%) Anal. Found: C, 3.79; H, 52.02%.
C18H15Fe2NO4 requires: C, 51.35; H, 3.59%. IR
(CH2Cl2) wmax(cm−1
) 2151w (CN), 1990s, 1956w,
1801m and 1719w (CO). NMR: lH (CDCl3): 4.88 (10
H, s, Cp), 3.76 (2 H, s, m-CCH2) and 2.19 (3 H, s, CH3)
ppm. lC(CDCl3): 266.1 (m-CO), 211.5 (CO), 205.9
(COMe), 162.0 (m-C), 129.8 (CN), 91.7 (Cp), 68.3 (m-
CCH2), and 30.6 (CH3) ppm.
8b: (65%) Anal. Found: C, 3.79; H, 52.02%.
C23H17Fe2NO4 requires: C, 57.19; H, 3.55%. IR
requires: C, 51.65; H, 1.81%. IR (CH2Cl2) wmax(cm−1
2225w (CN), 2057s and 2015s (CO). Mass spectrum:
m/z 279 (M+, 1), 251 (M+ −CO, 2), 223 (M+ −2CO,
4), 147 (CpFeCN+, 100%).
)
(CH2Cl2) wmax(cm−1
)
2155w (CN), 1990s, 1955w,
1801m and 1689w (CO). NMR: lH (CDCl3): 7.96–7.45
(5 H, Ph), 4.95 (10 H, s, Cp) and 4.35 (2 H, s, m-CCH2)

340
S. Bordoni et al. / Inorganica Chimica Acta 291 (1999) 333–340
[6] W.A. Herrman, Angew. Chem., Int. Ed. Engl. 21 (1982) 117.
Acknowledgements
[7] (a) V.G. Albano, S. Bordoni, D. Braga, L. Busetto, A. Palazzi,
V. Zanotti, Angew. Chem., Int. Ed. Engl. 30 (1991) 847. (b) L.
Busetto, V. Zanotti, S. Bordoni, L. Carlucci, A. Palazzi, J.
Cluster Sci. 4 (1993) 9. (c) S. Aime, L. Cordero, R. Gobetto, S.
Bordoni, L. Busetto, V. Zanotti, V.G. Albano, D. Braga, F.
Grepioni, J. Chem. Soc., Dalton Trans. (1992) 2961.
[8] S. Bordoni, F. Mazza, V. Zanotti, Inorg. Chim. Acta 223 (1994)
31.
The authors thank the Ministero dell’Universita’ e
della ricerca Scientifica a Tecnologica (MURST) and
the University of Bologna for financial support.
[9] V. Zanotti, S. Bordoni, L. Busetto, L. Carlucci, A. Palazzi, R.
Serra, V.G. Albano, M. Monari, F. Prestopino, F. Laschi, P.
Zanello, Organometallics 14 (1995) 5232.
[10] L. Busetto, M.C. Cassani, V. Zanotti, V.G. Albano, D. Braga, J.
Organomet. Chem. 415 (1991) 395.
[11] (a) L. Busetto, L. Carlucci, V. Zanotti, V.G. Albano, M.
Monari, Chem. Ber. 125 (1992) 1125. (b) M. Bassi, L. Carlucci,
V. Zanotti, Inorg. Chim. Acta 204 (1993) 171.
[12] (a) L. Busetto, S. Bordoni, V. Zanotti, V.G. Albano, D. Braga,
Gazz. Chim. Ital. 118 (1988) 667. (b) L. Busetto, L. Carlucci, V.
Zanotti, V.G. Albano, D. Braga, J. Chem. Soc., Dalton Trans.
(1990) 243. (c) L. Busetto, V. Zanotti, S. Bordoni, L. Carlucci,
V.G. Albano, D. Braga, J. Chem. Soc., Dalton Trans. (1992)
1105.
References
[1] (a) L. Busetto, V. Zanotti, L. Norfo, A. Palazzi, V.G. Albano,
D. Braga, Organometallics 12 (1993) 190. (b) V.G. Albano, S.
Bordoni, L. Busetto, M. Monari, V. Zanotti, Organometallics 14
(1995) 5455. (c) V.G. Albano, S. Bordoni, L. Busetto, C.
Camiletti, M. Monari, A. Palazzi, F. Prestopino, V. Zanotti, J.
Chem. Soc., Dalton Trans. (1997) 4665.
[2] (a) S. Bordoni, L. Busetto, C. Camiletti, V. Zanotti, V.G.
Albano, M. Monari, F. Prestopino, Organometallics 16 (1997)
1224. (b) V.G. Albano, L. Busetto, C. Camiletti, C. Castellari,
M. Monari, V. Zanotti, J. Chem. Soc., Dalton Trans. (1997)
4671.
[3] (a) M.L. Turner, H.C. Long, A. Shenton, P.K. Byers, P.M.
Maitlis, Chem. Eur. J. 1 (1995) 549. (b) I.M. Saez, N.J. Mean-
well, A. Nutton, K. Isobe, A. Vazquez de Miguel, D.W. Bruce,
S. Okeya, D.G. Andrews, P.R. Ashton, I.R. Johnstone, P.M.
Maitlis, J. Chem. Soc., Dalton Trans. (1986) 1556.
[4] See, for example: (a) S.A.R Knox, J. Cluster Sci. 3 (1992) 385.
(b) S.A.R Knox, J. Organomet. Chem. 400 (1990) 255. (c) M.
Akita, R. Hua, S.A.R. Knox, Y. Moro-oka, S. Nakanishi, M.I.
Yates, Chem. Commun. (1997) 51. (d) M. Akita, R. Hua, T.
Oku, Y. Moro-oka, Organometallics 15 (1996) 2548.
[5] (a) E.L. Hoel, G.B. Ansell, S. Leta, Organometallics 5 (1986)
585. (b) E.L. Hoel, Organometallics 5 (1986) 587 and references
therein.
[13] (a) C.P. Casey, M. Crocker, P.C. Vosejpka, P.J. Fagan, S.R.
Marder, M.A. Gohdes, Organometallics 7 (1988) 760. (b) C.P.
Casey, G.P. Niccolai, Organometallics 13 (1994) 2531.
[14] S. Bordoni, L. Busetto, F. Calderoni, L. Carlucci, F. Laschi, P.
Zanello, V. Zanotti, J. Organomet. Chem. 496 (1995) 27.
[15] L. Busetto, S. Bordoni, V. Zanotti, V.G. Albano, D. Braga, New
J. Chem. 16 (1992) 693.
[16] W.P. Fehlhammer, M. Fritz, Chem. Rev. 93 (1993) 1280.
[17] C.P. Casey, P.C. Vosejpka, M. Crocker, J. Organomet. Chem.
394 (1990) 339.
[18] (a) B.H. Lipshutz, in: M. Scholsser (Ed.), Organometallics in
Synthesis, Wiley, New York, 1994. (b) B.H. Lipshutz, R.S.
Wilhelm, J.A. Kozlowski, Tetrahedron 40 (1984) 5005.
.