Olefin-aminocarbyne coupling in diiron complexes: Synthesis of new bridging aminoallylidene complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.10.015

The bridging aminocarbyne complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃] (R = Me, 1a; Xyl, 1b; 4-C₆H₄OMe, 1c; Xyl = 2,6-Me₂C₆ H₃) react wit

Full text of DOI:10.1016/j.jorganchem.2007.10.015

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 57–67
www.elsevier.com/locate/jorganchem
Olefin–aminocarbyne coupling in diiron complexes: Synthesis
of new bridging aminoallylidene complexes
*
Luigi Busetto, Mauro Salmi, Stefano Zacchini, Valerio Zanotti
`
Dipartimento di Chimica Fisica e Inorganica, Universita di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
Received 21 September 2007; received in revised form 9 October 2007; accepted 9 October 2007
Available online 13 October 2007
Abstract
The bridging aminocarbyne complexes [Fe2{l-CN(Me)(R)}(l-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b; 4-C6H4OMe, 1c;
Xyl = 2,6-Me2C6 H3) react with acrylonitrile or methyl acrylate, in the presence of Me3NO and NaH, to give the corresponding l-ally-
lidene complexes [Fe2{l-g1:g3- Ca(N(Me)(R))Cb(H)Cc(H)(R0)}(l-CO)(CO)(Cp)2] (R = Me, R0 = CN, 3a; R = Xyl, R0 = CN, 3b; R =
4-C6H4OMe, R0 = CN, 3c; R = Me, R0 = CO2Me, 3d; R = 4-C6H4OMe, R0 = CO2Me, 3e). Likewise, 1a reacts with styrene or diethyl
maleate, under the same reaction conditions, affording the complexes [Fe2{l-g1:g3-Ca(NMe2)Cb(R0)Cc(H)(R00)}(l-CO)(CO)(Cp)2]
(R0 = H, R00 = C6H5, 3f; R0 = R00 = CO2Et, 3g). The corresponding reactions of [Ru2{l-CN(Me)(CH2Ph)}(l-CO)(CO)2(Cp)2][SO3CF3]
(1d) with acrylonitrile or methyl acrylate afford the complexes [Ru2{l-g1:g3-Ca(N(Me)(CH2Ph))Cb(H)Cc(H)(R0)}(l-CO)(CO)(Cp)2]
(R0 = CN, 3h; CO2Me, 3i), respectively.
The coupling reaction of olefin with the carbyne carbon is regio- and stereospecific, leading to the formation of only one isomer. C–C
bond formation occurs selectively between the less substituted alkene carbon and the aminocarbyne, and the Cb–H, Cc–H hydrogen
atoms are mutually trans.
The reactions with acrylonitrile, leading to 3a–c and 3h involve, as intermediate species, the nitrile complexes [M2{l-CN(Me)(R)}
(l-CO)(CO)(NC–CH@CH2)(Cp)2][SO3CF3] (M = Fe, R = Me, 4a; M = Fe, R = Xyl, 4b; M = Fe, R = 4-C6H4OMe, 4c; M = Ru,
R = CH2C6H5, 4d).
Compounds 3a, 3d and 3f undergo methylation (by CH3SO3CF3) and protonation (by HSO3CF3) at the nitrogen atom, leading to the
formation of the cationic complexes [Fe2{l-g1:g3-Ca(N(Me)3)Cb(H)Cc(H)(R)}(l-CO)(CO)(Cp)2][SO3CF3] (R = CN, 5a; R = CO2Me,
5b; R = C6H5, 5c) and [Fe2{l-g1:g3-Ca(N(H)(Me)2)Cb(H)Cc(H)(R)}(l-CO)(CO)(Cp)2][SO3CF3] (R = CN, 6a; R = CO2Me, 6b;
R = C6H5, 6c), respectively.
Complex 3a, adds the fragment [Fe(CO)2(THF)(Cp)]+, through the nitrile functionality of the bridging ligand, leading to the forma-
tion of the complex [Fe2{l-g1:g3-Ca(NMe2)Cb(H)Cc(H)(CNFe(CO)2Cp)}(l-CO)(CO)(Cp)2][SO3CF3] (9).
In an analogous reaction, 3a and [Fe2{l-CN(Me)(R)}(l-CO)(CO)2(Cp)2][SO3CF3], in the presence of Me3NO, are assembled to give
the tetrameric species [Fe2{l-g1:g3-Ca(NMe2)Cb(H)Cc(H)(CN[Fe2{l-CN(Me)(R)}(l-CO)(CO)(Cp)2])}(l-CO)(CO)(Cp)2][SO3CF3]
(R = Me, 10a; R = Xyl, 10b; R = 4-C6H4OMe, 10c).
The molecular structures of 3a and 3b have been determined by X-ray diffraction studies.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Aminocarbyne; Dinuclear complexes; Allylidene; Coupling reactions; C–C bond formation
1. Introduction
cules (typically alkynes and, at a lower extent, alkenes)
provide valuable routes to the C–C bond formation in
dinuclear complexes [1]. These reactions, which take
advantage of distinct reactivity patterns due to the bridging
coordination, lead to synthesis of new multisite-bound
hydrocarbyl ligands otherwise unattainable [2], and also
offer helpful models for investigating the C–C bond
Coupling reactions between bridging alkylidyne or
alkylidene ligands (C1 ligands) with small organic mole-
*
Corresponding author. Tel.: +39 0512093695.
E-mail address: valerio.zanotti@unibo.it (V. Zanotti).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.10.015

58
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
SO3CF3
SO3CF3
2. Results and discussion
R
Me
Fe
R
N
H
C
N
C
R'
OC
The bridging aminocarbyne complexes [Fe2{l-CN(Me)-
(R)}(l-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b; 4-
C6H4OMe, 1c; Xyl = 2,6-Me2C6H3) react with olefins
(methyl acrylate, acrylonitrile, styrene, diethyl maleate),
in THF solution at room temperature, in the presence of
Me3NO/NaH, to give the corresponding l-allylidene com-
plexes 3a–g in 70–80% yields (Scheme 2).
The reaction parallels that of the thiocarbyne complex 2
with olefins: in both cases the carbyne–alkene coupling
requires the displacement of a CO ligand and the presence
of NaH in order to remove a proton from the olefin. How-
ever, significant differences have been evidenced in the ste-
reochemistry of the reaction products, which concern the
mutual orientation of the Cp ligands and will be discussed
later.
CO
C
C
Me
CO
a
Fe
HC CR'
Me3NO
Fe
Fe
C
O
C
O
1
R = Me, Xyl; R' = H, alkyl, aryl
SO3CF3
Me
Me
S
H
S
R
Cβ
C
Cγ
H
R
H
Cα
OC
CO
H
OC
C
C
b
Fe
Fe
Fe
Fe
H
C
O
C
O
NaH /
Me3NO
2
Scheme 1.
Compounds 3a–g were purified by chromatography on
alumina and characterized by IR and NMR spectroscopy,
and elemental analysis. Moreover, the molecular structures
of 3a and 3b have been determined by X-ray diffraction.
The ORTEP diagrams are shown in Figs. 1 and 2, while
the main bond lengths and angles are reported in Table
1. The bonding parameters of the bridging ligand can be
evaluated with respect to other C3-bridging ligands present
in closely related diiron complexes (Table 2). In particular,
3a–b are to be compared with the l-allylidene complexes
[Fe2{l-g1:g3-C(Tol)CH@CHNMe2}(l-CO)(CO)(Cp)2] [9]
(Chart 1, I), and [Fe2{l-g1:g3-C(SMe)C(H)C(H)(CO2Me)}-
(l-CO)(CO)(Cp)2] [7] (Chart 1, II). This analysis points out
a close similarity in the bonding situation of 3a–b, I, and II
indicating that the l-g1:g3-C(N(Me)(R))C(H)C(H)(CN)
[R = Me, 3a; Xyl, 3b] ligand acts mainly as a bridging
allylidene, as inferable also from the fact that both the
formation steps relevant to the hydrocarbon chain growth
in the Fischer Tropsch chemistry [3].
Our work in the field has been focused on the reactions
of bridging amino- and thiocarbyne complexes with
alkynes and alkenes. In particular, we have investigated
the coupling between alkynes and the l-aminocarbyne
ligand in 1, leading to the formation of l-vinyliminium
(azoniabutadienyl) complexes (Scheme 1a) [4]. Consequent
studies revealed that the vinyliminium ligand can be further
modified by the addition of carbon nucleophiles like acety-
lides [5] or cyanide [6], generating bridged fragments of
increased complexity.
More recently we have described the coupling between
the bridging thiocarbyne ligand in complex 2 and activated
olefins, leading to the formation of new bridging thiometh-
ylallylidene complexes (Scheme 1b) [7].
In these coupling reactions alkynes and alkenes behave
differently: the reaction of 1 with alkynes simply consists
of the alkyne insertion in the metal carbyne–carbon bond
(Scheme 1a), whereas the coupling of the thiocarbyne
ligand with olefins requires a deprotonation step (Scheme
1b).
The nature of the heteroatom (S or N) on the l-carbyne
ligand also exerts some influence on the reactivity. In
general, bridging thio- and aminocarbyne ligands display
similar properties, in that both contain a p donor hetero-
atom which provides stabilization to the adjacent carbyne
carbon. However, the extent of p-interaction is different in
the two ligands and this leads, in some cases, to different
reaction profiles [8]. As an example, the alkyne insertion
in 1 shown in Scheme 1a, does not take place on the thi-
ocarbyne complex 2, neither on its acetonitrile derivative.
Thereby, predictions of the reactivity of 1 based upon
the reactions observed for 2, or vice versa, are often
unreliable.
˚
C–C bonds within the ligand [Ca–Cb 1.434(4) A, Cb–Cc
˚
˚
˚
1.432(4) A in 3a; Ca–Cb 1.416(3) A, Cb–Cc 1.435(3) A in
3b] and the Fe–C interactions between the ligand and the
diiron frame [Fe(2)–C(13) 2.094(3), Fe(2)–C(14) 2.012(3),
Fe(2)–C(15) 2.051(3) in 3a; Fe(2)–C(13) 2.179(2), Fe(2)–
C(14) 2.023(2), Fe(2)–C(15) 2.058(2) in 3b] are very similar.
It is noteworthy that in 3a–b the two hydrogen atoms
SO3CF3
R
Me
Fe
R
R'
R'
H
R''
H
N
C
R''
H
1.
C C
N
Cβ
Me
Cα
Cγ
CO
OC
2.
3.
NaH
Fe
Fe
Fe
Me3NO
THF
C
O
C
OC
O
R
R'
R''
1a
1b
1c
1a
1c
1a
1a
Me
Xyl
4-C6H4OMe
Me
4-C6H4OMe
Me
H
H
H
H
H
H
CN
CN
CN
CO2Me
CO2Me
C6H5
3a
3b
3c
3d
3e
3f
Herein we report on the successful attempt to extend the
coupling reaction with olefins to the aminocarbyne com-
plexes 1 and on further modifications of the bridging ligand
consequently formed.
Me
CO2Et
CO2Et
3g
Scheme 2.

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
59
Table 1
Selected bond lengths (A) and angles (ꢁ) for 3a and 3b
˚
3a
3b
Fe(1)–Fe(2)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(2)–C(12)
Fe(2)–C(13)
Fe(1)–C(13)
Fe(2)–C(14)
Fe(2)–C(15)
C(11)–O(11)
C(12)–O(12)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–N(2)
C(13)–N(1)
2.5602(5)
1.731(3)
1.959(3)
1.884(3)
2.094(3)
1.971(3)
2.012(3)
2.051(3)
1.156(3)
1.170(3)
1.434(4)
1.432(4)
1.435(4)
1.149(4)
1.368(3)
2.5812(5)
1.733(3)
1.991(2)
1.867(2)
2.179(2)
1.967(2)
2.023(2)
2.058(2)
1.155(3)
1.173(3)
1.416(3)
1.435(3)
1.440(3)
1.137(3)
1.375(3)
Fe(1)–C(12)–Fe(2)
Fe(1)–C(13)–Fe(2)
Fe(1)–C(13)–C(14)
C(13)–C(14)–C(15)
C(14)–C(15)–C(16)
C(15)–C(16)–N(2)
C(13)–N(1)–C(17)
C(13)–N(1)–C(18)
C(17)–N(1)–C(18)
83.54(11)
78.01(9)
118.09(19)
120.7(3)
117.8(3)
178.2(4)
122.7(3)
121.2(3)
115.1(3)
83.93(10)
76.82(8)
118.53(16)
121.5(2)
117.6(2)
178.6(3)
123.17(19)
121.34(19)
115.39(19)
Fig. 1. Molecular structure of 3a, with key atoms labelled. Displacement
ellipsoids are at 30% probability level.
Table 2
˚
Comparison between the bonding parameters (A) of C3 units in different
diiron complexes (numbering I and II refers to Chart 1)a
3a
3b
I
II
Fea–Cbbridge
Feb–Ca
Feb–Cb
Feb–Cc
Ca–Cb
Cb–Cc
Ca–Xc
a
1.971(3)
2.094(3)
2.012(3)
2.051(3)
1.434(4)
1.432(4)
1.368(3)
1.967(2)
2.179(2)
2.023(2)
2.058(2)
1.416(3)
1.435(3)
1.375(3)
1.977(6)
2.299(6)
2.070(6)
1.979(6)
1.408(9)
1.441(8)
1.375(8)
1.955(3)
2.049(3)
2.026(3)
2.068(3)
1.415(4)
1.422(4)
1.758(3)
I = [Fe2 {l-g1:g3- C(Tol)CH=CHNMe2}(l-CO)(CO)(Cp)2] [9]; II =
[Fe2{l-g1:g3- C(SMe)C(H)C(H)(CO2Me)}(l-CO)(CO)(Cp)2] [7].
b
Cbridge = Ca in 3a-b and II; Cbridge = Cc in I.
c
Fig. 2. Molecular structure of 3b, with key atoms labelled. Displacement
ellipsoids are at 30% probability level.
X = N in 3a–b and I; X = S in II.
within the ligand, i.e. H(14) and H(15), are in mutual trans
position.
Me
H
Me
S
H
Tol
N
COOMe
H
Cβ
Cβ
One of the most striking features of the complexes 3a–b
is that the Cp ligand are mutually trans, whereas most of
analogous dinuclear complexes (including the l-allylidene
complexes I and II) are cis, with few exceptions [10].
Steric arguments offer a possible explanation for the
observed differences. In complexes 3a–b the Ca carbon dis-
plays a significant bridging alkylidene character (as empha-
sized in Chart 2), which forces the steric demanding
N(Me)(R) substituent to reside closer to the metal centres
than in the species I. In these latter, the Cc assumes a
l-alkylidene character, leaving the N(Me)(R) moiety far
apart. Thereby, when the steric demanding N(Me)(R) is
closer to the dimetal centre (like in 3a–b) a trans configura-
tion for the Cp ligands is favoured.
Cγ
Me
Cα
Cγ
Cα
CO
OC
H
Fe
Fe
Fe
Fe
C
O
C
O
I
II
Chart 1.
Analogous considerations can be drawn comparing 3a–
b with the bridging thiomethylallylidene complexes (Chart
2, II). The coordination mode of the bridging ligand is the
same, but the nature of the Ca substituents is different in
the two cases [N(Me)(R) or SMe]. Presumably, the steric

60
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
R
Interestingly, both cis-3b and cis-3f are quantitatively
H
R
N
H
Me
N
converted into the corresponding trans isomers upon heat-
ing for ca. 4 h in refluxing toluene. On the other hand, solu-
tions containing only the trans forms are stable upon
heating in refluxing toluene. This behavior,which is oppo-
site to previously observed trans to cis isomerizations
[10], indicates that the trans isomer is, in this case, thermo-
dynamically more stable, and that the cis isomer is a kinetic
product rather that being in equilibrium with the trans.
Concerning the stereochemistry of this reaction it has to
be emphasized that beside cis and trans no other isomeric
form was observed in solution. This leads to the important
conclusion that the aminocarbyne–olefin coupling reac-
tions are regio- and stereospecific. Indeed, the incorpora-
tion of asymmetric olefins should generate, in theory, two
regioisomers. Conversely, the 1H NMR spectra of 3a–g evi-
dence that the C–C bond formation occurs selectively
between the less substituted alkene carbon and the amin-
ocarbyne ligand. Likewise, the CbH and CcH protons of
the bridging ligand in 3a–f result placed exclusively on
opposite sides of the Cb–Cc double bond interaction (E iso-
R'
Cβ
R'
Cγ
Cβ
Cα
Me
Cγ
Cα
Cp
Fe
H
Fe
H
Cp
H
Fe
Fe
Cp
Cp
3a-b
I
R
H
H
R'
Me
S
R'
Cγ
Cβ
N
Cβ
Cγ
Cα
Me
Cα
Fe
Fe
Fe
Fe
H
Cp
Cp
Cp
Cp
III
II
Chart 2. CO ligands are omitted for seek of clarity.
demand of the thiomethyl is not so relevant to force the Cp
ligands to assume a trans configuration.
It should also be noted that the species 3a–b and I exhi-
bit the same hydrocarbyl chain: (Me)(R)N–Ca–Cb(H)–
Cc(R0) plus an hydrogen atom, which is bonded to Cc or
Ca, respectively. A third possibility, in which the H atom
is bonded to the Cb carbon, corresponds to the previously
reported bis-alkylidene complexes [Fe2{l-g1:g2-C(R)CH2-
CN(Me)(Xyl)}(l-CO)(CO)(Cp)2] (Chart 2 III) [9]. These
species are not true isomers, since R and R0 are different,
however they evidence that the dinuclear Fe2(CO)2Cp2
frame is very effective and flexible in accommodating C3
bridging organic molecules of different nature. One of the
reasons for this adaptability is the simplicity in which ancil-
lary ligands can rearrange their coordination geometry
around the dimetal centre to respond to different steric
demands of the bridging organic frame.
Finally, it should be outlined that the different, but
strictly related C3 bridged frames (in 3a–b, I and III) do
not interconvert, and are exclusively obtained by distinct
reaction routes: 3a–b derive from l-aminocarbyne–alkene
coupling plus proton abstraction (Scheme 2), whereas I
and II result from aminocarbyne–alkyne coupling (Scheme
1a), followed by hydride addition, which can be selectively
directed to the Ca or Cb carbon, respectively [9].
The spectroscopic data of 3a–f are consistent with the
structures observed in the solid. In particular, the NMR
data of 3a, 3c–e and 3g reveal the presence, in solution,
of a single isomeric form, in which the Cp ligands are
mutually trans. Conversely, both cis and trans isomers of
3b and 3f are observed, with prevalence of the trans iso-
mers. The presence of an isomeric mixture in the case of
3b and 3f was clearly indicated, in the NMR spectra, by
the presence of two sets of resonances, and in the IR spec-
tra (in CH2Cl2 solution) by the observation of two absorp-
tions due to the terminally bonded CO ligand (e.g. at 1958
and 1932 cmꢀ1 for cis-3b and trans-3b, respectively). The
cis and trans isomeric forms were identified by NMR,
since NOE effect is detected between the Cp resonances
for the cis isomers, but not for the trans (e.g. for cis-3b
NOE effect was revealed between the Cp signals at d
4.71 and 4.41 ppm).
1
mer). This is evidenced, in the H NMR spectra, by the
occurrence of two doublets, attributable to the CbH and
CcH protons, respectively, with a coupling constant that
corresponds to trans olefin hydrogen atoms (e.g. 8.0 Hz
for 3a). Moreover, CcH proton resonance is shifted to
low frequencies (e.g. ꢀ0.92 ppm for 3a), accordingly to
the proximity and the shielding effect exerted by the metal
centre. Thus, the structure of the complexes in solution is
the same of that observed in the solid (X-ray structure of
3a–b). Moreover, the regio- and stereoselective character
of the olefin–aminocarbyne coupling is almost identical
to that found in the corresponding reaction with thi-
ocarbyne (Scheme 1b) [7].
The 13C NMR spectra show the resonances due to the
Ca, Cb and Cc of the bridging allylidene (e.g. for 3a, at
203.9, 59.8 and 21.5 ppm, respectively).
Finally, for complexes 3a, d, f and g the N-methyls give
rise to a single resonance in both 1H and 13C NMR spectra
(e.g. for 3a, at 3.62 ppm and 46.5 ppm, respectively). The
equivalence of the N-methyls is consistent with the loss of
double bond character in the Ca–N interaction consequent
to the aminocarbyne–alkene coupling.
The aminocarbyne–olefin coupling has not a general
character. The reaction is limited to olefins activated by
electron withdrawing groups, which favour the deprotona-
tion step. The conformation of the olefin is also important,
in that 1a react with diethyl maleate but not with diethyl
fumarate.
The nature of the N(Me)R substituents in the l-amin-
ocarbyne ligand also exhibits some influence on the
reaction rate. We observed that 1a (R = Me) and 1c (R =
4-C6H4OMe) display comparable reactivity, whereas 1b
(R = Xyl) is significantly less reactive and only with acrylo-
nitrile it gives appreciable yields.
Finally, the reactions involving the diruthenium com-
plex 1d, analogue to 1a–c, do not evidence any effect due

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
61
SO3CF3
SO3CF3
SO3CF3
R
CH2Ph
Me
M
Me
M
R
Ph CH2
Me
Ru
H
Cβ
H
H
R
H
H
H
H
N
C
N
C
N
C
H
H
CN
H
R
H
1.
C C
N
C C
Me
1.
C C
OC
Cα
CO
Cγ
OC
NC
OC
Ru
CO
M
2. NaH
3.
M
2. Me3NO
Ru
Ru
C
O
Me3NO
THF
C
O
C
O
THF
C
O
OC
M
R
1a
Fe
Fe
Fe
Ru
Me
Xyl
4-C6H4OMe
CH2C6H5
4a
4b
4c
4d
R
CN
CO2Me
1b
1c
1d
1d
1d
3h
3i
Scheme 3.
Scheme 4.
to the nature of the metal atoms. The presence of ruthe-
nium in the place of iron does not produce any relevant
change in the reaction path. Thus, reactions with acryloni-
trile or methyl acrylate afford the corresponding bridging
allylidene complexes 3h and 3i, respectively (Scheme 3).
Under the same reaction conditions, 1d is less reactive
than the diiron compounds 1a and 1c and the reactions
yields are consequently lower. Moreover, the reaction
products consist of a mixture of the cis and trans isomers,
with predominance of the trans. Also in this case, the cis
isomer is converted into the trans upon heating at reflux
in THF.
(l-CO)(CO)(NC–CH@CH2)(Cp)2][SO3CF3] (M = Fe,
R = Me, 4a; M = Fe, R = Xyl, 4b; M = Fe, R =
4-C6H4OMe, 4c; M = Ru, R = CH2C6H5, 4d) (Scheme
4). Coordination of acrylonitrile through the nitrile, rather
than with the olefin functionality, is in a good agreement
with the demonstrated reactivity of type 1 complexes
towards nitriles [12]. Obviously, the nitrile complexes 4a–
d can be obtained in better yields upon treatment of 1a–d
with acrylonitrile and Me3NO without NaH. The observa-
tion that the nitrile complexes 4a–d are transformed into
3a–c and 3h, respectively, upon treatment with NaH, indi-
cate that they are effective reaction intermediates.
As expected, the spectroscopic data of the diruthenium
complexes 3h and 3i closely resemble those of the analo-
gous diiron species described above, and do not deserve
further comments.
Compounds 4a–d have been characterized by IR and
NMR spectroscopy, and elemental analysis (see Section
4). Their spectroscopic data closely resemble those of anal-
ogous diiron and diruthenium nitrile complexes [M2{l-
CN(Me)(R)}(l-CO)(CO)(NCR0)(Cp)2][SO3CF3] reported
in the literature [12,13]. In particular these compounds
are characterized, in the 13C NMR spectra, by the typical
low field resonance of the bridging aminocarbyne carbon,
in the 330–340 ppm range (e.g. at 331.0 ppm for 4a). Also
consistent is the observation that 4a, in which the substitu-
ents at the N atom are both methyls, displays a single iso-
meric form, whereas complexes 4b–d are a mixture of two
isomers. These are due to the different orientations that
Me and R (R = Xyl, 4-C6H4OMe, CH2C6H5) can assume
with respect to the non-equivalent metal atoms, and are
consequence of the double bond character of the l-C@N
interaction (E and Z isomerism).
The reaction described in Schemes 1–3 are among the
few examples of coupling between bridging carbyne ligands
and olefins [11]. Among these, the most remarkable reactiv-
ity was exhibited by the l-methylidyne complex [Fe2(l-CH)-
(l-CO)(CO)2(Cp)2]+, in which the methylidyne–olefin
coupling was described as ‘hydrocarbation reaction’,
because of the analogies with the hydroboration reaction
[11c,11d,11e,11f,11g]. Less reactive bridging carbyne
ligands, like the l-ethylidyne complex [Ru2(l-CMe)(l-
CO)(CO)2(Cp)2]+ [11a] and the thiocarbyne complex 2,
mentioned in the introduction, undergo coupling with ole-
fins but require the presence of a base in order to remove a
proton from the olefin.
Concerning the reaction mechanism, the conclusions we
can draw are very similar to those reported for the olefin–
carbyne coupling reactions involving the l-ethylidyne com-
plex [Ru2(l-CMe)(l-CO)(CO)2(Cp)2]+ [11a] or the thi-
ocarbyne complex 2 [7]. The reaction sequence should
include, as preliminary step, the g2-olefin coordination at
the site made available by CO removal. This is accom-
plished, in our case, by the use of Me3NO. Without this
reagent the reaction does not take place. Subsequent steps
include intramolecular coupling, which might entail a
metallacyclobutane ring, and deprotonation. Unfortu-
nately, none of the supposed intermediates have detected.
Even the initial g2-olefin intermediate appears very elusive.
Only in one case, namely in the reactions with acrylonitrile,
it was possible to isolate intermediate species which were
identified as the nitrile complexes [M2{l-CN(Me)(R)}-
The reactivity of complexes of type 3 was then investi-
gated. In particular, we have found that compounds 3a, d
and f undergo methylation (by CH3SO3CF3) and proton-
ation (by HSO3CF3) at the NMe2 group, affording, in
nearly quantitative yields, the cationic species [Fe2{l-g1:
g3-Ca(N(Me)3)Cb(H)Cc(H)(R)}(l-CO)(CO)(Cp)2][SO3CF3]
(R = CN, 5a; R = CO2Me, 5b; R = C6H5, 5c) and [Fe2-
{l-g1:g3-Ca(N(H)(Me)2)Cb(H)Cc(H)(R)}(l-CO)(CO)(Cp)2]-
[SO3CF3] (R = CN, 6a; R = CO2Me, 6b; R = C6H5, 6c),
respectively (Scheme 5). The reactions were carried out in
CH2Cl2 solution at room temperature.
Compounds 5 and 6 have been purified by filtration on
celite and characterized by IR and NMR spectroscopy, and
elemental analysis.
The IR spectra (in CH2Cl2 solution) of 5a–c exhibit
absorptions due to the terminal and bridging carbonyls

62
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
Me
+
SO3CF3
Me
+
R
H
H
Me
E
Me
H
Me
OC
H
R
N
S
R
Me
Me
Cβ
Cβ
R
H
N
N
Me
R
H
Cβ
Cβ
Cγ
Cγ
Cα
Cα
Cα
Cα
Cγ
CO
Cγ
H
H
Fe
Fe
Fe
Fe
ESO3CF3
CH2Cl2
C
O
Fe
Fe
C
O
Fe
Fe
C
C
O
OC
OC
7
8
O
R
CN
CO2Me
C6H5
CN
E
Chart 3.
+
3a
3d
3f
3a
3d
3f
CH3+
CH3+
CH3
H+
5a
5b
5c
6a
6b
6c
Beside the protonation and methylation reactions, the
presence of nitrogen functional groups (NMe2 and CN),
potential able to act as ligands, could be exploited to coor-
dinate further metal complexes. Thereby, we have investi-
gated the reaction of 3a with [Fe(CO)2(THF)(Cp)]+,
generated by treatment of [Fe2(CO)4(Cp)2] with AgSO3-
CF3. The reaction, carried out in THF, leads to the
formation of the trinuclear complex 9 in good yields
(Scheme 6).
Likewise, the reaction of 3a with [Fe2{l-CN(Me)(R)}-
(l-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b;
4-C6H4OMe, 1c) affords the corresponding tetranuclear
adducts 10a–c, respectively, in about 70% yield (Scheme
6). The reaction requires the presence of Me3NO in order
to generate a vacant coordination site on the aminocarbyne
complexes and promote the nitrile coordination.
By contrast with the methylation and protonation,
which occur at the NMe2 group of 3a, the addition of the
iron frame takes place selectively through the nitrile
coordination. The preference for the nitrile coordination
is consistent with previous observations which evidenced
that nitriles, better than amines, displace the CO ligand
in the aminocarbyne complexes 1a–c [12].
Compounds 9 and 10a–c have been isolated by chroma-
tography on alumina and characterized by IR and NMR
spectroscopy and elemental analysis.
CO2Me
C6H5
H+
H+
Scheme 5.
(e.g. at 1986 and 1815 cmꢀ1 for 5a). Additional bands are
observed for 5a, due to the CN group (at 2205 cmꢀ1),
and for 5b, attributable to the CO2Me (at 1710 cmꢀ1). As
expected, the CO bands are shifted to higher frequencies
(ca. 30 cmꢀ1) compared to the parent complexes, as effect
of the positive charge in 5a–c.
Analogous considerations concern the protonation reac-
tion. In addition, the IR spectra of 6a–c (in KBr pellets)
show the typical NH absorption around 3200 cmꢀ1 (e.g.
at 3215 cmꢀ1 for 6a).
The 1H NMR spectra (in CD3CN solution) of com-
pounds 5 and 6 indicate the presence of a single isomer,
since only one set of resonances is observed. In particular,
the N-methyls give rise to one singlet signal in both 1H and
13C NMR spectra (e.g. for 5a at 3.12 and 58.8 ppm, respec-
tively), indicating free rotation around the Ca–NMe3 bond.
Moreover, NOE investigations revealed that 5–6 retain the
trans configuration of the Cp ligands, shown by their par-
ent species 3.
The electrophilic addition at the aminic nitrogen atom
does not modify significantly the 13C NMR resonance
pattern for the C3 bridging ligand: Ca gives rise to a low
frequency resonance (180 ppm for 5a), whereas Cb and
Cc signals occur in 80–20 ppm range.
The protonation reactions, which lead to 6a–c are
reversible and the parent complexes are restored upon
treatment with bases (e.g. NaH), whereas methylation reac-
tions are not.
The IR spectra of 10a–c (in CH2Cl2 solution) show two
absorptions for the terminal carbonyls (e.g. at 1981 cmꢀ1
and 1940 cmꢀ1 for 10a) and two for the bridging ones
SO3CF3
Cp
CO
Fe
Me
N
SO3CF3
H
Cp
Fe
CN
H
CO
Cβ
Me
Cp
Cα
Cγ
OC
THF
The complexes 5a–c present several similarities with the
ammonium and the sulphonium complexes 7 [14] and 8 [7]
(Chart 3), previously published.
Fe
OC
Fe
Cp
OC
C
O
9
SO3CF3
Also 7 and 8 were obtained by methylation (with
MeSO3CF3) of the heteroatom in their corresponding neu-
tral precursors. The main difference between the ammo-
nium complexes 5 and 7 with respect to the sulphonium 8
is that the SMe2 group can be displaced by nucleophiles
like hydride (NaBH4) and cyanide (NBu4CN) [7], whereas,
under similar reaction conditions, neither 7 nor 5 release
the NMe3 group. Thereby, the ammonium allylidene ligand
in 5 fails to become the precursor of other bridging C3
frames via NMe3 displacement.
O
C
SO3CF3
Cp
Cp
R
Me
Fe
3a
Fe
R
Fe
N
C
Me
H
CO
C
N
CN
N
Cβ
OC
Cp
CO
Cp
Me
Cp
Cα
Cγ
Fe
Me
H
C
O
Fe
Fe
Cp
C
OC
O
Me3NO
R = Me, 10a; Xyl, 10b; 4-C6H4OMe 10c
Scheme 6.

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
63
(e.g. at 1812 cmꢀ1 and 1785 cmꢀ1 for 10a). Moreover, the
l-CN band is observed (e.g. at 1586 cmꢀ1 for 10a).
The corresponding NMR spectra (in CDCl3) exhibit res-
onances consistent with those of the parent compounds 3a
and 1a–c. In particular, the 1H NMR spectra show the CcH
proton resonance, shifted to low frequencies (e.g. ꢀ1.35
ppm for 10a), accordingly to the shielding effect exerted
by the metal centre. On the other hand, the 13C NMR spec-
tra exhibit the signals due to the Ca, Cb and Cc of the bridg-
ing allylidene (e.g. for 10a, at 203.1, 53.1 and 19.6 ppm,
respectively) and the typical downfield resonance of the
bridging aminocarbyne carbon, (e.g. at 331.2 ppm for
10a). Interestingly, each of the compounds 10a–c exists as
in a single isomeric form. In particular, NOE investigations
pointed out that the Cp rings of the aminocarbyne frag-
ment are mutually cis, whereas those of the allylidene moi-
ety are trans, as in their parent species 1a–c and 3a,
respectively.
at 298 K on Mercury Plus 400 instrument. The chemical
1
shifts for H and 13C were referenced to internal TMS.
The spectra were fully assigned via DEPT experiments
1
and H,13C correlation through gs-HSQC and gs-HMBC
experiments [15]. NOE measurements were recorded using
the DPFGSE-NOE sequence [16]. NMR signals due to a
second isomeric form (where it has been possible to detect
and/or resolve them) are italicized. All the reagents were
commercial products (Aldrich) of the highest purity
available and used as received. [Fe2(CO)4(Cp)2] was pur-
chased from Strem and used as received. Compounds
1a,b [17], 1c [18] and 1d [19] were prepared by published
methods.
4.2. Synthesis of [M2{l-g1:g3-Ca(N(Me)(R))Cb(R0)-
Cc(H)(R00)} (l-CO)(CO)(Cp)2] (M = Fe, R = Me,
R0 = H, R00 = CN, 3a; M = Fe, R = Xyl, R0 = H, R00 = CN,
3b; M = Fe, R = 4-C6H4OMe, R0 = H, R00 = CN, 3c;
M = Fe, R = Me, R0 = H, R00 = CO2Me, 3d; M = Fe, R =
4-C6H4OMe, R0 = H, R00 = CO2Me, 3e; M = Fe, R = Me,
R0 = H, R00 = C6H5, 3f; M = Fe, R = Me, R0 = CO2Et,
R00 = CO2Et, 3g; M = Ru, R = CH2C6H5, R0 = H, R00 =
CN, 3h; M = Ru, R = CH2C6H5, R0 = H, R00 = CO2Me, 3i)
3. Conclusions
The bridging aminocarbyne complexes 1a–d reacts with
olefins generating bridging allylidene ligands. This result,
together with those previously reported on related thi-
ocarbyne complexes, show that the coupling between acti-
vated olefin and heteroatom substituted l-carbynes has a
general character, and that the reactions proceed as well
with diiron and diruthenium complexes characterized by
the M2(CO)2(Cp)2 frame. This latter effectively supports
the bridging allylidene ligand, in that it can easily arrange
the coordination geometry of the ancillary CO and Cp
(e.g. cis trans isomers) to better respond to the steric
requirements of the bridging ligand.
Olefin incorporation into the aminocarbyne ligand is
regio- and stereospecific. It represents a valuable example
of bridging hydrocarbyl transformation (specifically: C1–
C3 chain growth). Further modifications of the bridging
frame are feasible due to the presence nitrogen functional
groups. These reactions include electrophilic additions at
the NR2 functional group, or assembling with unsaturated
organometallic iron complexes through the nitrile
functionality.
To a solution of 1a (531 mg, 1.0 mmol) in THF (20 mL)
were successively added: acrylonitrile (0.4 mL, 10 mmol),
NaH (120 mg, 5.0 mmol), and Me3NO (110 mg, 1.5 mmol).
The mixture was stirred at room temperature for 2 h and
then filtered on an alumina pad. Removal of the solvent
and chromatography of the residue on an alumina column,
with CH2Cl2 as eluent, afforded a green solid, correspond-
ing to 3a. Yield: 78%. Anal. Calc. for C18H18Fe2N2O2: C,
53.20; H, 4.47; N, 6.90. Found: C, 53.09; H, 4.44; N,
6.96%. IR (CH2Cl2) m(CN) 2204 (w); m(CO) 1933 (vs),
1777 (s) cmꢀ1 1H NMR (CDCl3) d 4.60 (d, 1H, CbH,
.
3JHH = 8.0 Hz); 4.49 (s, 5H, Cp); 4.32 (s, 5H, Cp); 3.62
3
(s, 6H, NMe2); ꢀ0.92 (d, 1H, CcH, JHH = 8.0 Hz).
13C{1H} NMR (CDCl3) d 269.3 (l-CO); 213.0 (CO);
203.9 (Ca); 126.3 (C„N); 89.4 (Cp); 86.5 (Cp); 59.8 (Cb);
46.5 (NMe2); 21.5 (Cc).
Compounds 3b–i were prepared with the same proce-
dure described for 3a, by reacting 1a–d with NaH, Me3NO
and the appropriate olefin.
4. Experimental details
Compound 3b (yield: 38%). Anal. Calc. for C25H24-
Fe2N2O2: C, 60.48; H, 4.88; N, 5.65. Found: C, 60.40;
H, 4.92; N, 5.67%. IR (CH2Cl2) m(CN) 2204 (w), m(CO)
4.1. General
1958 (vs), 1932 (vs), 1791 (s) cmꢀ1 1H NMR (CDCl3)
.
All reactions were routinely carried out under a nitrogen
atmosphere, using standard Schlenk techniques. Solvents
were distilled immediately before use under nitrogen from
appropriate drying agents. Chromatography separations
were carried out on columns of deactivated alumina (4%
w/w water). Glassware was oven-dried before use. Infrared
spectra were recorded at 298 K on a Perkin–Elmer Spec-
trum 2000 FT-IR spectrophotometer and elemental analy-
ses were performed on a ThermoQuest Flash 1112 Series
EA Instrument. All NMR measurements were performed
d 7.34–6.86 (m, 3H, C6H3Me2); 4.71, 4.65 (s, 5H, Cp);
4.67, 4.17 (d, 1H, CbH, JHH = 8.0 Hz); 4.44, 4.41 (s,
3
5H, Cp); 3.83, 3.55 (s, 3H, NMe); 2.63, 2.61 (s, 3H,
C6H3Me); 2.23, 2.19 (s, 3H, C6H3Me); ꢀ0.80, ꢀ0.92 (d,
3
1H, CcH, JHH = 8.0 Hz). trans/cis Ratio 2:1. 13C{1H}
NMR (CDCl3) d 265.4, 265.0 (l-CO); 213.1, 213.0
(CO); 205.9, 203.8 (Ca); 148.4, 148.3 (Cipso Xyl); 129.0,
126.5 (C„N); 134.0–128.6 (Carom); 88.2, 87.7, 85.2,
84.9 (Cp); 59.0, 58.3 (Cb); 48.3, 46.1 (NMe); 20.2, 19.3
(Cc); 18.4, 17.9 (Me2C6H3); 17.5, 17.2 (Me2C6H3).

64
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
3
Compound 3c (yield: 75%). Anal. Calc. for
C24H22Fe2N2O3: C, 57.83; H, 4.45; N, 5.62. Found: C,
1H, CbH, JHH = 8.0 Hz); 4.98, 4.89 (s, 5H, Cp); 4.75,
4.66 (s, 5H, Cp); 3.73–3.55 (m, 2H, CH2C6H5); 3.75, 3.69
3
57.75; H, 4.52; N, 5.67%. IR (CH2Cl2) m(CN) 2203 (w),
(s, 3H, NMe); 1.32, 1.19 (d, 1H, CcH, JHH = 8.0 Hz).
m(CO) 1935 (vs), 1779 (s) cmꢀ1
.
1H NMR (CDCl3) d
trans/cis Ratio 1.2:1. 13C{1H} NMR (CDCl3) d 246.0,
245.8 (l-CO); 206.1, 205.5 (CO); 170.1, 168.9 (Ca); 140.5–
127.0 (Carom + C„N); 96.0, 94.7 (Cc); 88.8, 88.2 85.6,
84.1 (Cp); 68.1, 67.5 (Cb); 61.2, 61.0 (CH2C6H5); 48.3,
47.1 (NMe).
7.36–6.78 (m, 4H, C6H4OMe); 4.68 (d, 1H, CbH,
3JHH = 8.0 Hz); 4.49 (s, 5H, Cp); 4.43 (s, 5H, Cp); 3.85
(s, 3H, NMe); 3.75 (s, 3H, C6H4OMe); -0.92 (d, 1H,
3
CcH, JHH = 8.0 Hz). 13C{1H} NMR (CDCl3) d 265.0 (l-
CO); 213.0 (CO); 205.0 (Ca); 150.0, 128.5, 128.0, 115.0,
114.1 (Carom); 126.0 (C„N); 88.0, 85.8 (Cp); 59.6 (Cb);
56.1 (C6H4OMe); 46.6 (NMe); 21.5 (Cc).
Compound 3i (yield: 36%). Anal. Calc. for
C25H25NO4Ru2: C, 49.42; H, 4.15; N, 2.31. Found: C,
49.51; H, 4.66; N, 2.33%. IR (CH2Cl2) m(CO) 1932 (vs),
Compound 3d (yield: 80%). Anal. Calc. for
C19H21Fe2NO4: C, 51.93; H, 4.82; N, 3.19. Found: C,
51.87; H, 4.75; N, 3.28%. IR (CH2Cl2) m(CO) 1933 (vs),
1765 (s), 1695 (m) cmꢀ1 1H NMR (CDCl3) d (ppm):
.
7.55–7.11 (m, 5H, CH2C6H5); 5.23, 5.02 (d, 1H, CbH,
3JHH = 8.0 Hz); 4.91, 4.82 (s, 5H, Cp); 4.65, 4.59 (s, 5H,
Cp); 3.99–3.49 (m, 2H, CH2C6H5); 3.77, 3.72 (s, 3H,
NMe); 3.67, 3.59 (s, 3H, CO2Me); 1.74, 1.39 (d, 1H,
1777 (s), 1693 (m) cmꢀ1
.
1H NMR (CDCl3) d 4.97 (d,
3
1H, CbH, JHH = 8.0 Hz); 4.34 (br s, 10H, Cp); 3.64 (s,
9H, NMe2 + CO2Me); ꢀ0.29 (d, 1H, CcH, 3JHH = 8.0 Hz).
13C{1H} NMR (CDCl3) d 261.5 (l-CO); 213.7 (CO); 204.6
(Ca); 175.9 (CO2Me); 87.6, 84.2 (Cp); 60.2 (Cb); 51.3
(CO2Me); 46.7 (NMe2); 43.1 (Cc).
3
CcH, JHH = 8.0 Hz). trans/cis Ratio 1.3:1. 13C{1H}
NMR (CDCl3) d 246.2, 245.8 (l-CO); 206.6, 205.8 (CO);
177.5, 175.9 (CO2Me); 170.9, 169.5 (Ca); 140.5–127.0
(Carom); 88.6, 88.0, 84.9, 84.1 (Cp); 68.8, 67.3 (Cb); 61.4,
60.9 (CH2C6H5); 47.6, 46.5 (NMe).
Compound 3e (yield: 78%). Anal. Calc. for
C25H25Fe2NO5: C, 56.49; H, 4.74; N, 2.64. Found: C,
56.59; H, 4.75; N, 2.56%. IR (CH2Cl2) m(CO) 1930 (vs),
4.3. Synthesis of [M2{l-CN(Me)(R)}(l-CO)(CO)(NC–
CH@CH2)(Cp)2][SO3CF3] (M = Fe, R = Me, 4a;
M = Fe, R = Xyl, 4b; M = Fe, R = 4-C6 H4 OMe, 4c;
M = Ru, R = CH2 C6 H5, 4d)
1
1773 (s), 1694 (m) cmꢀ1. H NMR (CDCl3) d 7.41–6.82
3
(m, 4H, C6H4OMe); 5.02 (d, 1H, CbH, JHH = 8.0 Hz);
4.46 (s, 5H, Cp); 4.37 (s, 5H, Cp); 3.88 (s, 6H, NMe +
C6H4OMe); 3.57 (s, 3H, CO2Me); ꢀ0.32 (d, 1H, CcH,
3JHH = 8.0 Hz). 13C{1H} NMR (CDCl3) d 265.1 (l-CO);
212.9 (CO); 204.1 (Ca); 176.0 (CO2Me); 150.0, 128.5,
128.0, 115.0, 114.1 (Carom); 89.1 (Cp); 87.7, 68.5 (Cb);
56.1 (C6H4OMe); 51.4 (CO2Me); 46.5 (NMe); 43.3 (Cc).
Compound 3f (yield: 56%). Anal. Calc. for
C23H23Fe2NO2: C, 60.39; H, 5.07; N, 3.06. Found: C,
60.46; H, 5.00; N, 3.05%. IR (CH2Cl2) m(CO) 1958 (vs),
To a solution of 1a (531 mg, 1.0 mmol) in THF (20 mL)
were successively added acrylonitrile (0.4 mL, 10 mmol)
and Me3NO (110 mg, 1.5 mmol). The mixture was stirred
at room temperature for 15 min, and then filtered on an
alumina pad. Removal of the solvent and chromatography
of the residue on an alumina column, with methanol as elu-
ent, afforded a brown solid, corresponding to 4a. Yield:
94%. Anal. Calc. for C19H19F3Fe2N2O5S: C, 41.01; H,
3.44; N, 5.04. Found: C, 40.96; H, 3.47; N, 5.05%. IR
(CH2Cl2) m(CO) 1983 (vs), 1814 (s), m(CN) 1585 (m)
1
1938 (vs), 1767 (s) cmꢀ1. H NMR (CDCl3) d 7.43–6.95
3
(m, 5H, C6H5); 4.85, 4.45 (d, 1H, CbH, JHH = 8.0 Hz);
4.74, 4.70 (s, 5H, Cp); 4.66, 4.64 (s, 5H, Cp); 3.95, 3.65
(s, 6H, NMe2); ꢀ0.87, ꢀ1.13 (d, 1H, CcH, 3JHH = 8.0 Hz).
trans/cis Ratio 1.5:1. 13C{1H} NMR (CDCl3) d 265.0,
264.1 (l-CO); 213.0, 212.2 (CO); 206.0, 204.0 (Ca); 131.5–
125.2 (Carom); 90.1, 89.6, 87.0, 86.6 (Cp); 60.1, 58.3 (Cb);
52.6, 51.4 (NMe2); 21.7, 21.0 (Cc).
1
3
cmꢀ1. H NMR (CDCl3) d 5.78 (d, 1H, JHH = 12.0 Hz,
3
NCCH@CH2); 5.68 (d, 1H, JHH = 16.0 Hz, NCCH@
CH2); 5.42 (dd, 1H, NCCH@CH2); 4.90 (s, 5H, Cp); 4.78
(s, 5H, Cp); 4.46 (s, 3H, NMe); 4.16 (s, 3H, NMe).
13C{1H} NMR (CDCl3) d 331.0 (l-CN); 265.8 (l-CO);
211.0 (CO); 140.1 (NCCH@CH2); 129.3 (NCCH@CH2);
106.5 (NCCH@CH2); 88.7, 87.3 (Cp); 54.0, 53.3 (NMe).
Compounds 4b–d were prepared with the same proce-
dure described for 4a, by reacting 1b–d with acrylonitrile
and Me3NO.
Compound 3g (yield: 74%). Anal. Calc. for
C23H27Fe2NO6: C, 52.57; H, 5.18; N, 2.67. Found: C,
52.49; H, 5.24; N, 2.65%. IR (CH2Cl2) m(CO) 1939 (vs),
1
1780 (s), 1716 (m) cmꢀ1. H NMR (CDCl3) d 4.90 (s, 5H,
Cp); 4.83 (s, 5H, Cp); 4.30–3.60 (m, 4H, CO2CH2CH3);
3.70 (s, 6H, NMe2); 1.50–1.08 (m, 6H, CO2CH2CH3);
ꢀ0.56 (s, 1H, CcH). 13C{1H} NMR (CDCl3) d 265.0 (l-
CO); 213.0 (CO); 199.3 (Ca); 170.4 (CO2CH2CH3); 90.1,
88.0 (Cp); 68.5 (Cb); 59.9, 58.0 (CO2CH2CH3); 46.4
(NMe2); 33.8 (Cc); 14.5, 14.1 (CO2CH2CH3).
Compound 4b (yield: 95%). Anal. Calc. for
C26H25F3Fe2N2O5S: C, 48.30; H, 3.90; N, 4.34. Found:
C, 48.26; H, 3.91; N, 4.35%. IR (CH2Cl2) m(CO) 1985
1
(vs), 1815 (s), m(CN) 1521 (m) cmꢀ1. H NMR (CDCl3) d
7.37–7.23 (m, 3H, C6H3Me2); 5.97–5.86 (m, 2H, NCCH@
CH2); 5.78-5.69 (m, 1H, NCCH@CH2); 5.10, 5.03 (s, 5H,
Cp); 4.85, 4.80 (s, 3H, NMe); 4.50, 4.43 (s, 5H, Cp); 2.69,
2.65 (s, 3H, C6H3Me); 2.14, 2.08 (s, 3H, C6H3Me). E:Z
ratio 1.3:1. 13C{1H} NMR (CDCl3) d 338.8, 338.6 (l-
CN); 264.5, 263.8 (l-CO); 211.6, 211.4 (CO); 148.4, 148.3
Compound 3h (yield: 41%). Anal. Calc. for
C24H22N2O2Ru2: C, 50.18; H, 3.86; N, 4.88. Found: C,
50.08; H, 3.91; N, 4.83%. IR (CH2Cl2) m(CN) 2202 (w),
m(CO) 1960, (vs), 1931 (vs), 1762 (s) cmꢀ1 1H NMR
.
(CDCl3) d 7.49–7.18 (m, 5H, CH2C6H5); 5.23, 5.11 (d,

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
65
(Cipso Xyl); 140.3, 140.1 (NCCH@CH2); 134.3-128.5
(Carom); 129.4, 129.3 (NCCH@CH2); 107.3, 107.1
(NCCH@CH2); 88.6, 88.5 (Cp); 88.4, 88.3 (Cp); 54.6,
54.4 (NMe); 18.5, 18.2, 17.6, 17.3 (Me2C6H3).
Cp); 3.62 (s, 3H, CO2Me); 3.12 (s, 9H, NMe3); ꢀ0.56 (d,
3
1H, CcH, JHH = 7.8 Hz). 13C{1H} NMR (CD3CN) d
266.7 (l-CO); 213.3 (CO); 181.2 (Ca); 174.4 (CO2Me);
89.1, 87.1 (Cp); 71.4 (Cb); 55.4 (NMe3); 52.4 (CO2Me);
39.1 (Cc).
Compound 4c (yield: 92%). Anal. Calc. for
C25H23F3Fe2N2O6S: C, 46.30; H, 3.58; N, 4.32. Found:
C, 46.33; H, 3.64; N, 4.35%. IR (CH2Cl2) m(CO) 1985
Compound 5c (yield: 87%). Anal. Calc. for
C25H26F3Fe2NO5S: C, 48.31; H, 4.22; N, 2.25. Found:
C, 48.40; H, 4.18; N, 2.24%. IR (CH2Cl2) m(CO) 1986
1
(vs), 1817 (s), m(CN) 1527 (m) cmꢀ1. H NMR (CDCl3) d
1
7.61–7.16 (m, 4H, C6H4OMe); 5.94–5.80 (m, 2H,
NCCH@CH2); 5.60 (m, 1H, NCCH@CH2); 5.08, 4.99
(s, 5H, Cp); 4.46, 4.35 (s, 5H, Cp); 4.87, 4.79 (s, 3H,
NMe); 3.90, 3.86 (s, 3H, OMe). E:Z ratio 1.2:1. 13C{1H}
NMR (CDCl3) d 336.4, 336.2 (l-CN); 265.1, 264.8 (l-
CO); 211.7, 211.0 (CO); 159.7, 159.3, 144.2, 143.6, 126.5,
125.9, 115.0, 114.6 (Carom); 140.5, 140.2 (NCCH@CH2);
129.2, 129.1 (NCCH@CH2); 107.0, 106.7 (NCCH@CH2);
88.6, 88.3 (Cp); 87.9, 87.5 (Cp); 56.5, 56.0 (NMe); 55.6,
55.4 (OMe).
(vs), 1817 (s) cmꢀ1. H NMR (CD3CN) d 7.41–7.01 (m,
3
5H, C6H5); 5.99 (d, 1H, CbH, JHH = 8.2 Hz); 5.48 (s,
5H, Cp); 5.33 (s, 5H, Cp); 3.10 (s, 9H, NMe3); -0.74
3
(d, 1H, CcH, JHH = 8.2 Hz). 13C{1H} NMR (CD3CN)
d 266.5 (l-CO); 213.0 (CO); 179.7 (Ca); 132.0-125.0
(Carom); 89.9 (Cp); 86.0 (Cp); 73.4 (Cb); 56.7 (NMe3);
35.4 (Cc).
4.5. Synthesis of [Fe2{l-g1:g3-Ca(N(H)(Me)2)Cb(H)-
Cc(H)(R)}(l-CO)(CO)(Cp)2][SO3CF3] (R = CN, 6a;
R = CO2 Me, 6b; R = C6 H5, 6c)
Compound 4d (yield: 90%). Anal. Calc. for
C25H23F3N2O5Ru2S: C, 41.44; H, 3.20; N, 3.87. Found:
C, 41.50; H, 3.20; N, 3.83%. IR (CH2Cl2) m(CO) 1980
A solution of 3a (406 mg, 1.0 mmol) in CH2Cl2 (20 mL)
was treated with HSO3CF3(0.10 mL, 1.1 mmol). The
resulting solution was stirred at room temperature for
1 h. Removal of the volatile material under reduced pres-
sure and filtration of the residue on a celite pad afforded
a dark brown solid, corresponding to 6a. Yield: 90%. Anal.
Calc. for C19H19F3Fe2N2O5S: C, 41.01; H, 3.44; N, 5.04.
Found: C, 40.90; H, 3.50; N, 4.97%. IR (CH2Cl2) m(CN)
1
(vs), 1817 (s), m(CN) 1574 (m) cmꢀ1. H NMR (CDCl3) d
7.49–7.30 (m, 5H, CH2C6H5); 6.01–5.94 (m, 2H,
NCCH@CH2); 5.80–5.53 (m, 3H, CH2C6H5 + NCCH@
CH2); 5.28, 5.25 (s, 5H, Cp); 4.98, 4.90 (s, 5H, Cp); 3.88,
3.83 (s, 3H, NMe). E:Z ratio 1.5:1. 13C{1H} NMR
(CDCl3) d 305.0, 304.7 (l-CN); 238.1, 237.5 (l-CO);
201.1, 200.3 (CO); 140.5–106.9 (Carom + Cacrylonitrile);
89.8, 87.9 (Cp); 51.0, 49.9 (NMe).
2206 (w), m(CO) 1987 (vs), 1814 (s) cmꢀ1
.
1H NMR
3
(CD3CN) d 6.04 (d, 1H, CbH, JHH = 8.0 Hz); 5.22 (s,
5H, Cp); 4.85 (s, 5H, Cp); 3.49 (s, 6H, NMe2); ꢀ1.36 (d,
4.4. Synthesis of [Fe2{l-g1:g3-Ca(N(Me)3)Cb(H)-
Cc(H)(R)}(l-CO)(CO)(Cp)2][SO3CF3] (R = CN, 5a;
R = CO2 Me, 5b; R = C6 H5, 5c)
3
1H, CcH, JHH = 8.0 Hz). NH not observed. 13C{1H}
NMR (CD3CN) d 267.0 (l-CO); 213.5 (CO); 182.4 (Ca);
125.9 (CN); 88.9, 85.9 (Cp); 78.3 (Cb); 52.3 (NMe2); 33.4
(Cc).
Compounds 6b–c were prepared with the same proce-
dure described for 6a, by treating 3d and 3f with HSO3CF3
in CH2Cl2 solution.
CH3SO3CF3 (0.13 mL, 1.1 mmol) was added to a solu-
tion of 3a (406 mg, 1.0 mmol) in CH2Cl2 (20 mL) and the
resulting solution was stirred at room temperature for
4 h. Removal of the volatile material under reduced pres-
sure and chromatography of the residue on an alumina col-
umn, with methanol as eluent, afforded a dark brown solid,
corresponding to 5a. Yield: 87%. Anal. Calc. for
C20H21F3Fe2N2O5S: C, 42.11; H, 3.71; N, 4.91. Found:
C, 42.02; H, 3.66; N, 4.97%. IR (CH2Cl2) m(CN) 2205
Compound 6b (yield: 88%). Anal. Calc. for
C20H22F3Fe2NO7S: C, 40.75; H, 3.76; N, 2.38. Found: C,
40.79; H, 3.86; N, 2.30%. IR (CH2Cl2) m(CO) 1988 (vs),
1
1816 (s), 1712 (m) cmꢀ1. H NMR (CD3CN) d 5.91 (d,
3
1H, CbH, JHH = 8.0 Hz); 5.41 (s, 5H, Cp); 5.05 (s, 5H,
1
(w), m(CO) 1986 (vs), 1815 (s) cmꢀ1. H NMR (CD3CN)
Cp); 3.75 (s, 3H, CO2Me); 3.43 (s, 6H, NMe2); ꢀ0.61 (d,
3
3
d 6.07 (d, 1H, CbH, JHH = 8.2 Hz); 5.15 (s, 5H, Cp);
1H, CcH, JHH = 8.0 Hz). NH not observed. 13C{1H}
4.98 (s, 5H, Cp); 3.12 (s, 9H, NMe3); ꢀ0.77 (d, 1H, CcH,
3JHH = 8.2 Hz). 13C{1H} NMR (CD3CN) d 267.0 (l-
CO); 213.5 (CO); 180.1 (Ca); 126.5 (CN); 87.3, 85.2 (Cp);
75.0 (Cb); 58.8 (NMe3); 38.7 (Cc).
Compounds 5b–c were prepared with the same proce-
dure described for 5a, by treating 3d and 3f with
CH3SO3CF3 in CH2Cl2 solution.
NMR (CD3CN) d 266.5 (l-CO); 213.1 (CO); 183.7 (Ca);
175.0 (CO2Me); 89.2, 85.8 (Cp); 79.0 (Cb); 51.7 (NMe2);
51.2 (CO2Me); 43.5 (Cc).
Compound 6c (yield: 87%). Anal. Calc. for C24H24F3-
Fe2NO5S: C, 47.45; H, 3.98; N, 2.31. Found: C, 47.40;
H, 4.07; N, 2.24%. IR (CH2Cl2) m(CO) 1987 (vs), 1815 (s)
cmꢀ1
.
1H NMR (CD3CN) d 7.37–7.03 (m, 5H, C6H5);
3
Compound 5b (yield: 86%). Anal. Calc. for
C21H24F3Fe2NO7S: C, 41.79; H, 4.01; N, 2.32. Found: C,
41.79; H, 3.96; N, 2.30%. IR (CH2Cl2) m(CO) 1988 (vs),
5.88 (d, 1H, CbH, JHH = 8.2 Hz); 5.51 (s, 5H, Cp); 5.28
(s, 5H, Cp); 3.40 (s, 6H, NMe2); ꢀ0.70 (d, 1H, CcH,
3JHH = 8.2 Hz). 13C{1H} NMR (CD3CN) d 267.1 (l-
CO); 213.5 (CO); 178.9 (Ca); 132.0-125.0 (Carom); 90.1,
87.3 (Cp); 78.4 (Cb); 52.0 (NMe2);35.1 (Cc).
1
1817 (s), 1710 (m) cmꢀ1. H NMR (CD3CN) d 6.01 (d,
3
1H, CbH, JHH = 7.8 Hz); 5.36 (s, 5H, Cp); 5.23 (s, 5H,

66
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
4.6. Synthesis of [Fe2{l-g1:g3-Ca(NMe2)Cb(H)Cc (H)-
(CNFe(CO)2 Cp)}(l-CO)(CO)(Cp)2][SO3 CF3] (9)
13C{1H} NMR (CDCl3) d 338.6 (l-CN); 265.9, 265.0 (l-
CO); 213.0, 212.1 (CO); 203.6 (Ca); 148.0–125.1
(Carom + C„N); 89.2, 88.7, 87.0, 86.5 (Cp); 54.5 (NMe);
52.8 (Cb); 46.5 (NMe2); 20.7–18.5 (Cc + Me2C6H3).
A solution of 3a (406 mg, 1.0 mmol) in THF (20 mL)
was treated with [Fe(CO)2(THF)(Cp)][SO3CF3], freshly
prepared by treatment of [Fe2(CO)4(Cp)2] (213 mg,
0.6 mmol) with AgSO3CF3 (180 mg, 0.7 mmol). The mix-
ture was stirred at room temperature for 1 hour and then
filtered on an alumina pad. Removal of the solvent and
chromatography of the residue on an alumina column,
with methanol as eluent, afforded a green–brown solid, cor-
responding to 9. Yield: 76%. Anal. Calc. for C26H23F3Fe3-
N2O7S: C, 42.63; H, 3.17; N, 3.83. Found: C, 42.71; H,
3.13; N, 3.70%. IR (CH2Cl2) m(CO) 2079 (vs), 2035 (vs),
Compound 10c (yield: 73%). Anal. Calc. for
C40H38F3Fe4N3O8S: C, 47.95; H, 3.83; N, 4.20. Found:
C, 48.03; H, 3.77; N, 4.24%. IR (CH2Cl2) m(CO) 1983
(vs), 1940 (vs), 1819 (s), 1786 (s), m(CN) 1530 (m) cmꢀ1
.
1H NMR (CDCl3) d 7.60–7.10 (m, 4H, C6H4OMe); 5.08
(s, 5H, Cp); 4.86 (s, 5H, Cp); 4.50 (s, 5H, Cp); 4.37 (s,
3
5H, Cp); 4.30 (d, 1H, CbH, JHH = 8.0 Hz); 4.79 (s, 3H,
NMe); 3.90 (s, 3H, C6H4OMe); 3.52 (s, 6H, NMe2);
3
ꢀ1.30 (d, 1H, CcH, JHH = 8.0 Hz). 13C{1H} NMR
(CDCl3) d 336.5 (l-CN); 265.9, 265.0 (l-CO); 213.0,
210.9 (CO); 203.5 (Ca); 159.5–115.0 (Carom + C„N);
89.5, 88.9, 87.4, 87.0 (Cp); 56.5 (NMe); 55.1 (C6H4OMe);
53.0 (Cb); 46.5 (NMe2); 20.1 (Cc).
1939 (vs), 1780 (s) cmꢀ1 1H NMR (CDCl3) d 5.35 (s,
.
5H, Cp); 4.56 (s, 5H, Cp); 4.34 (s, 5H, Cp); 4.18 (d, 1H,
3
CbH, JHH = 8.0 Hz); 3.64 (s, 6H, NMe2); ꢀ1.14 (d, 1H,
3
CcH, JHH = 8.0 Hz). 13C{1H} NMR (CDCl3) d 265.8 (l-
CO); 211.9, 210.5, 209.8 (CO); 204.2 (Ca); 125.0 (C„N);
4.8. X-ray crystallography for 3a and 3b
90.9, 87.9, 85.8 (Cp); 52.0 (Cb); 46.0 (NMe2); 19.1 (Cc).
Crystals of 3a and 3b suitable for X ray analysis were
obtained by a CH2Cl2 solution, layered with petroleum
ether, at ꢀ20 ꢁC.
4.7. Synthesis of [Fe2{l-CN(Me)(R)}(l-CO)(CO)([Fe2-
{l-g1:g3-Ca (N(Me)2)Cb (H)Cc(H)(CN)}(l-CO)(CO)-
(Cp)2 ])(Cp)2][SO3CF3] (R = Me, 10a; R = Xyl, 10b;
R = 4-C6H4OMe, 10c)
Crystal data for 3a and 3b were collected at room tem-
perature on a Bruker APEX II CCD diffractometer using
graphite monochromated Mo Ka radiation. Structures
were solved by direct methods and structures refined by
full-matrix least-squares based on all data using F2 [20].
Crystal data are listed in Table 3. Non-H atoms were
refined anisotropically. H-atoms were placed in calculated
positions, except position of H(14) and H(15) in both 3a
and 3b which were located in the Fourier map. H-atoms
To a solution of 1a (531 mg, 1.0 mmol) in THF (20 mL)
were successively added 3a (406 mg, 1.0 mmol) and
Me3NO (110 mg, 1.5 mmol). The mixture was stirred at
room temperature for 1 h and then filtered on an alumina
pad. Removal of the solvent and chromatography of the
residue on an alumina column, with methanol as eluent,
afforded a brown solid, corresponding to 10a. Yield:
70%. Anal. Calc. for C34H34F3Fe4N3O7S: C, 44.89; H,
3.77; N, 4.62. Found: C, 45.00; H, 3.73; N, 4.60%. IR
(CH2Cl2) m(CO) 1981 (vs), 1940 (vs), 1812 (s), 1785 (s),
Table 3
Crystal data and experimental details for 3a and 3b
Complex
3a
3b
Empirical formula
Formula weight
T (K)
k (A)
Crystal system
C18 H18Fe2N2O2 C25H24 Fe2N2O2
1
m(CN) 1586 (m) cmꢀ1. H NMR (CDCl3) d 5.31 (s, 5H,
406.04
496.16
Cp); 5.02 (s, 5H, Cp); 4.51 (s, 5H, Cp); 4.32 (s, 5H, Cp);
293(2)
295(2)
3
˚
4.25 (d, 1H, CbH, JHH = 8.0 Hz); 4.67 (s, 3H, NMe);
0.71073
Orthorhombic
P212121
7.4182(5)
14.3307(9)
15.8838(10)
90
0.71073
Monoclinic
P21/c
8.0777(5)
15.2350(10)
18.0168(11)
101.5300(10)
2172.5(2)
4
4.32 (s, 3H, NMe); 3.52 (s, 6H, NMe2); ꢀ1.35 (d, 1H,
3
CcH, JHH = 8.0 Hz). 13C{1H} NMR (CDCl3) d 331.2 (l-
Space group
˚
a (A)
CN); 266.4 (l-CO); 265.7 (l-CO); 213.0 (CO); 211.5
(CO); 203.1 (Ca); 125.3 (C„N); 90.1 (Cp); 88.9 (Cp);
87.3 (Cp); 86.1 (Cp); 54.0 (NMe); 53.3 (NMe); 53.1 (Cb);
46.5 (NMe2); 19.6 (Cc).
Compounds 10b–c were prepared with the same proce-
dure described for 10a, by reacting 1b–c with 3a and
Me3NO.
˚
b (A)
˚
c (A)
b (ꢁ)
Cell volume (A )
3
˚
1688.58(19)
4
Z
Dc (g cmꢀ3
)
1.597
1.517
l (mmꢀ1
F(000)
)
1.730
1.360
832
1024
Compound 10b (yield: 66%). Anal. Calc. for
C41H40F3Fe4N3O7S: C, 49.25; H, 4.04; N, 4.21. Found:
C, 49.30; H, 4.13; N, 4.30%. IR (CH2Cl2) m(CO) 1985
Crystal size (mm)
h Limits (ꢁ)
Reflections collected
Independent reflections [Rint
Data/restraints/parameters
Goodness-on-fit on F2
R1 (I > 2r(I))
0.22 · 0.16 · 0.13 0.23 · 0.16 · 0.14
1.91–28.69
1.77–27.00
19654
23749
]
4116 [0.0417]
4116/2/225
1.051
4728 [0.0462]
4728/2/289
1.018
(vs), 1938 (vs), 1819 (s), 1788 (s), m(CN) 1525 (m) cmꢀ1
.
1H NMR (CDCl3) d 7.40–7.03 (m, 3H, Me2C6H3); 5.15
(s, 5H, Cp); 4.89 (s, 5H, Cp); 4.51 (s, 5H, Cp); 4.34 (s,
0.0322
0.0342
3
wR2 (all data)
0.0675
0.0851
5H, Cp); 4.27 (d, 1H, CbH, JHH = 8.0 Hz); 4.80 (s, 3H,
Largest differences in peak and
0.417/ꢀ0.290
0.420/ꢀ0.230
NMe); 3.52 (s, 6H, NMe2); 2.70 (s, 3H, Me2C6H3); 2.20
ꢀ3
˚
hole (e A
)
3
(s, 3H, Me2C6H3); ꢀ1.32 (d, 1H, CcH, JHH = 8.0 Hz).

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 57–67
67
[4] V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini, V.
Zanotti, Organometallics 22 (2003) 1326.
[5] (a) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Eur. J. Inorg.
Chem. (2007) 1799;
were treated isotropically using the 1.2 fold Uiso value of
the parent atom except methyl protons, which were
assigned the 1.5 fold Uiso value of the parent C-atom.
(b) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Eur. J. Inorg.
Chem. (2006) 285.
5. Supplementary material
[6] V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini, V.
Zanotti, J. Organomet. Chem. 691 (2006) 4234.
[7] L. Busetto, F. Marchetti, M. Salmi, S. Zacchini, V. Zanotti, J.
Organomet. Chem. 692 (2007) 2245.
[8] (a) S. Bordoni, L. Busetto, C. Camiletti, V. Zanotti, V.G.
Albano, M. Monari, F. Prestopino, Organometallics 16 (1997)
1224;
CCDC 661224 and 661225 contains the supplementary
crystallographic data for 3a and 3b. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
(b) V.G. Albano, L. Busetto, C. Camiletti, C. Castellari, M.
Monari, V. Zanotti, J. Chem. Soc., Dalton Trans. (1997)
4671.
[9] V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini, V.
Zanotti, Organometallics 23 (2004) 3348.
Acknowledgements
[10] (a) V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini,
V. Zanotti, J. Organomet. Chem. 689 (2004) 528;
(b) V.G. Albano, L. Busetto, F. Marchetti, M. Monari, S. Zacchini,
V. Zanotti, J. Organomet. Chem. 690 (2005) 837;
(c) L. Busetto, F. Marchetti, S. Zacchini, V. Zanotti, Inorg. Chim.
Acta 358 (2005) 1204.
[11] (a) A.F. Dyke, J.E. Guerchais, S.A.R. Knox, J. Roue, R.L. Short,
G.E. Taylor, P. Woodward, J. Chem. Soc., Chem. Commun. (1981)
537;
`
We thank the Ministero dell’Universita e della Ricerca
Scientifica e Tecnologica (MIUR) (Project: ‘New strategies
for the control of reactions: interactions of molecular frag-
ments with metallic sites in unconventional species’) and
the University of Bologna (‘Funds for Selected Research
Topics’) for financial support.
(b) J. Hein, J.C. Jeffery, F. Marken, F.G.A. Stone, Polyhedron 6
(1987) 2067;
(c) C.P. Casey, P.J. Fagan, J. Am. Chem. Soc. 104 (1982) 4950;
(d) C.P. Casey, M.W. Meszaros, S.R. Marder, P.J. Fagan, J. Am.
Chem. Soc. 106 (1984) 3680;
(e) C.P. Casey, M.W. Meszaros, P.J. Fagan, R.K. Bly, S.R. Marder,
E.A. Austin, J. Am. Chem. Soc. 108 (1986) 4043;
(f) C.P. Casey, M.W. Meszaros, P.J. Fagan, R.K. Bly, R.E. Colborn,
J. Am. Chem. Soc. 108 (1986) 4053;
(g) C.P. Casey, M.W. Meszaros, S.R. Marder, R.K. Bly, P.J. Fagan,
Organometallics 5 (1986) 1873.
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