Zwitterionic diiron vinyliminium complexes: Alkylation, metalation and oxidative coupling at the S and Se functionalities

Article abstract of DOI:10.1016/j.jorganchem.2008.04.010

The zwitterionic vinyliminium complex [Fe₂{μ-η¹:η³-C(R′){double bond, long}C(S)C{double bond, long}N(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (2a) (R′ = p-Me-C₆H₄ (Tol), Xyl = 2,6-Me₂C₆

Full text of DOI:10.1016/j.jorganchem.2008.04.010

Journal of Organometallic Chemistry 693 (2008) 2383–2391
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Zwitterionic diiron vinyliminium complexes: Alkylation, metalation and
oxidative coupling at the S and Se functionalities
Luigi Busetto a, Marco Dionisio a, Fabio Marchetti b,1, Rita Mazzoni a, Mauro Salmi a, Stefano Zacchini a,
Valerio Zanotti a,
*
a Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
b Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy
a r t i c l e i n f o
a b s t r a c t
The zwitterionic vinyliminium complex [Fe2{l-g1:g3-C(R0)@C(S)C@N(Me)(Xyl)}(l-CO)(CO)(Cp)2] (2a)
(R0 = p-Me-C6H4 (Tol), Xyl = 2,6-Me2C6H3) undergoes electrophilic addition at the S atom by HSO3CF3,
MeSO3CF3, SiMe3Cl, BrCH2Ph, ICH2CH@CH2 affording the complexes [Fe2{l-g1:g3-C(Tol)@C(SX)C@N
(Me)(Xyl)}(l-CO)(CO)(Cp)2][Y] (X = H, Y = SO3CF3, 4a; X = Me, Y = SO3CF3, 4b; X = SiMe3, Y = Cl, 4c;
X = CH2Ph, Y = Br, 4d; X = CH2CH@CH2, Y = I, 4e).
Article history:
Received 18 March 2008
Received in revised form 4 April 2008
Accepted 4 April 2008
Available online 11 April 2008
Compound 2a and the corresponding vinyliminium complexes 2b and 2c (R0 = CH2OH, 2b; R0 = Me, 2c)
react also with etherated BF3 leading to the formation of the corresponding S-adducts [Fe2{l-g1:g3-
C(R0)@C(SBF3)C@N(Me)(Xyl)}(l-CO)(CO)(Cp)2] (R0 = Tol, 5a; R0 = CH2OH, 5b; R0 = Me, 5c).
In analogous reactions, the zwitterionic vinyliminium complexes undergo S-metalation upon treatment
with in situ generated [Fp]+[SO3CF3]ꢀ [Fp = Fe(CO)2(Cp)], leading to the formation of [Fe2{l-g1:g3-
C(R0)@C(S–Fp)C@N(Me)(Xyl)}(l-CO)(CO)(Cp)2][SO3CF3](R0 = CH2OH, 6a; R0 = Me, 6b; R0 = Bun, 6c).
Similarly, zwitterionic vinyliminium containing Se in the place of S also undergo Se-electrophilic addi-
tion. Thus, the complexes [Fe2{l-g1:g3-C(R0)@C(SeX)C@N(Me)(R)}(l-CO)(CO)(Cp)2][SO3CF3] (R = X = Me,
R0 = Tol, 7a; R = Xyl, R0 = Me, X = Fp+, 7b) are obtained upon treatment of the neutral zwitterionic precur-
sors with MeSO3CF3 and [Fp][SO3CF3], respectively.
Keywords:
Vinyliminium
Zwitterionic complexes
Oxidative coupling
Alkylation
Disufides
Diselenides
Alkylation at the S or Se atom of the bridging ligand is also accomplished by CH2Cl2, used as solvent,
although the reaction is slower compared to more efficient alkylating reagents. The complexes formed
by this route are [Fe2{l-g1:g3-C(R0)@C(E-CH2Cl)C@N(Me)(R)}(l-CO)(CO)(Cp)2][X] [E = S, R = Xyl, R0 = Tol,
X = Cl, 8a; E = S, R = Xyl, R0 = Me, X = Cl, 8b; E = Se, R = R0 = Me, X = BPh4, 8c].
Finally, treatment of the zwitterionic vinyliminium complexes with I2 results in the oxidative coupling with
formation of S–S (disulfide) or Se–Se (diselenide) bond. The reactions, performed in the presence of NaBPh4
afford the tetranuclear complexes [Fe2{l-g1:g3-C(R0)@C(E)C@N(Me)(R)}(l-CO)(CO)(Cp)2]2[BPh4]2 [R = Xyl,
R0 = CH2OH, E = S, 9a; R = Xyl, R0 = Me, E = S, 9b; R = Xyl, R0 = Bun, E = S, 9c; R = Xyl, R0 = Me, E = Se, 9d; R = Me,
R0 = Bun, E = Se, 9e].
The molecular structures of 4a, 8c and 9e have been determined by X-ray diffraction studies.
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
ligand susceptible to nucleophilic addition by a variety of reagents.
However, as a consequence of the bridging coordination, these
Multisite bound organic fragments display unique reaction pat-
terns, which allow transformations not observed in uncoordinated
species or in complexes containing a single metal centre [1]. This
is also the case of the bridging vinyliminium ligand, in diiron com-
plexes of the type 1 (Scheme 1) which we have investigated in recent
years [2]. The presence of an iminium functionality and the overall
positive charge of the complex 1 make the bridging vinyliminium
nucleophilic attacks exhibit unconventional routes: instead of the
usual 1,4 conjugated addition (Michael type nucleophilic addition),
attacks involve iminium carbon or the adjacent Cb position [3].
Further transformations of the vinyliminium ligand have been
obtained exploiting the iminium–enamine activation and the con-
sequent acidic character of the Cb–H hydrogen [4]. The latter has
been replaced by different functionalities [5], including group 16
heteroatoms, leading to the transformation of 1 into the thio-
and seleno-complexes 2 and 3, shown in Scheme 1 [6].
* Corresponding author. Tel.: +39 0512093695.
E-mail address: valerio.zanotti@unibo.it (V. Zanotti).
Compounds 2 and 3 evidence a zwitterionic character, with the
positive charge localized on the N atom and the negative charge
1
Fabio Marchetti, born in 1974 in Bologna, Italy.
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.010

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L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
tance; its presence is in agreement with the cationic charge of
the complex as inferred from the presence of the CF3SO3 anion
_
R
H
−
ꢀ
Me
R
E
SO3CF3
+
+
R'
N
Cβ
R'
N
Cβ
in the unit cell. There is also a H2O molecule but only the oxygen
atom has been located. A hydrogen bond exists between the –SH
group and the water molecule [S(1)ꢁ ꢁ ꢁO(4) 2.884(16) Å]. The struc-
ture of the cationic complex 4a resembles those previously re-
ported for other diiron vinyliminium complexes [2]. The Cp
ligands in the [Fe2(l-CO)(CO)(Cp)2] core display a relative cis
arrangement and, as usually found in Cb-substituted vinyliminium
complexes, the Me and Xyl groups with respect to the Ca@N double
bond possess a Z geometry [2b]. The bonding parameters of the
bridging {l-g1:g3-Cc(Tol)@Cb(SH)Ca@N(Me)(Xyl)} ligand of 4a are
compared in Table 2 with those of the parent zwitterionic com-
pound 2a and a typical Cb-substituted vinyliminium complex, i.e.
cis-[Fe2{l-g1:g3-Cc(Me)@Cb(Me)Ca@N(Me)(Xyl)}(l-CO)(CO)(Cp)2]+
(I) [2b]. A comparison between the bond lengths in 4a and I clearly
indicates that the bridging ligand is better described as a vinyli-
minium (form A, Scheme 3). S-Protonation of 2a to give 4a results
in the elongation of the C(14)–S(1) interaction [1.736(4) Å in 2a vs.
1.788(10) Å in 4a] and shortening of Fe(2)–C(14) [2.151(4) Å in 2a
vs. 2.072(14) Å in 4a], which can be interpreted as an increase of
the p-allyl ligand character with respect to the Fe(2), and is better
described by the resonance form A. On the other hand, since the
Fe(2)–C(15) bond is even shortened with respect to 2a, a contribu-
tion of the resonance form B (Scheme 3), is also to be considered.
The spectroscopic properties of 4a–e are in agreement with
those of analogous cationic vinyliminium complexes [2]. The IR
spectra (in CH2Cl2 solution) exhibit the typical m-CO band pattern
consisting of two adsorptions due to terminal and bridging carbon-
yls (e.g. for 2a at 1990 and 1830 cmꢀ1). These are 30–40 cmꢀ1
shifted to higher frequencies compared to the parent neutral zwit-
terionic complexes, due to the cationic character of the complexes.
The NMR spectra, in CDCl3 or CD3CN solution, evidence the pres-
ence of a single isomer, which maintain a cis configuration (cis–
trans is referred to the mutual position of the Cp ligands) and a Z
configuration (referred to the orientation of the Me and Xyl groups
with respect to the Ca@N double bond), as deduced by NOE inves-
tigations carried on 4a–e.
Cα
Cγ
Me
CO
Cα
Cγ
E
CO
Fe
Fe
Fe
Fe
NaH
C
C
O
O
1
E = S, 2; Se, 3
R = Me, Xyl; R' = alkyl, aryl
Scheme 1.
on the S/Se atoms. It has been shown that bridging coordination lar-
gely contributes to the stabilization of the dipolar iminium thiolate/
selenoate ligands in these complexes [6]. Zwitterionic organometal-
lic complexes, although relatively uncommon, represent a topic of
great interest, in that they might provide new interesting properties
[7]. For example, formally charge separated species might exhibit
enhanced catalytic activity due to the absence of counterion effects
[8]. Furthermore, charge separation should be exploited for the con-
struction of three-dimensional (3D) porous metal-organic frame-
works [9], and for possible application as carriers for membranes
[10].
Herein we report on the reactions of the zwitterionic complexes
of the type 2 and 3 with electrophiles, Lewis acids and coordin-
atively unsaturated metal frames. More specifically, the purpose
was to determine whether or not the S or Se atoms, formally bear-
ing a negative charge, might be exploited to add electrophilic frag-
ments, providing routes to the construction of bridging frames of
increased size and complexity.
2. Results and discussion
2.1. Alkylation, protonation and metalation reactions
Complex 2a, in CH2Cl2 solution, rapidly reacts with strong elec-
trophiles, such as HSO3CF3 and MeSO3CF3, to give the correspond-
ing Cb-substituted vinyliminium complexes 4a–b in about 90%
yield (Scheme 2).
Analogous results have been obtained upon treatment of [Fe2{l-
g1:g3-Cc(Tol)@Cb(S)Ca@N(Me)(Xyl)}(l-CO)(CO)(Cp)2] (2a, Tol = p-
Me-C6H4, Xyl = 2,6-Me2-C6H3) with Me3SiCl, benzylbromide
(BrCH2Ph), and allyliodide (ICH2CH@CH2), affording the complexes
4c–e, respectively (Scheme 2).
Complexes 4a–e have been spectroscopically characterized. In
addition, the molecular structure of 4a has been determined by
X-ray diffraction studies. The ORTEP molecular diagram is reported
in Fig. 1 whereas relevant bond lengths and angles are reported in
Table 1. The S-attached hydrogen atom has been located unambig-
uously in the Fourier map and refined with restrained S–H dis-
Major feature in the 13C NMR spectra is given by the resonances
of the bridging C3 carbon skeleton: the resonances due to Ca and Cc
are in the typical regions for an aminocarbene (e.g. for 4b at
227.8 ppm), and bridging alkylidene (e.g. for 4b at 208.5), respec-
tively. The Cb carbon resonance (at 64–70 ppm) is high field shifted
compared to the parent compound 2a (at 112.8 ppm). These data
suggest some contribution of the resonance form B (Scheme 3).
Then, the reactions of the zwitterionic complexes with Lewis
acids were studied. Beside 2a, other vinyliminium complexes were
considered, in order to evidence possible effects due to different
nature of the substituents on the bridging frame. Indeed, the com-
plexes
[Fe2{l-g1:g3-CcR0@Cb(S)Ca@N(Me)(Xyl)}(l-CO)(CO)(Cp)2]
(R0 = CH2OH, 2b; R0 = Me, 2c; R0 = Bun, 2d) differ from 2a, in that
they, respectively, contain CH2OH, CH3 and Bun in the place of
the Tol group on the Cc position. In spite of these differences,
2a–c react in the same manner with BF3, in ethereated solution,
leading to the addition of the Lewis acid at the S atom (Scheme 4).
Likewise, the addition of the Fp+ fragment (Fp+ = [Fe(CO)2Cp]+)
takes place at the sulphur atom and generates the trinuclear com-
plexes 6a–c (Scheme 4). The cationic Fp+, generated in situ upon
treatment of [Fe(CO)2(Cp)]2 with AgSO3CF3 [11], has been selected
among other possible electrophilic metal complexes for the reason
that it is similar to the other metal fragments already present in 2,
and because it is known to coordinate sulphur containing ligands
[12].
−
Y
X
−
S
Me
S
Me
+
+
N
Tol
N
Cβ
Tol
Cβ
Cα
Xyl
Cγ
Cα
Xyl
Cγ
CO
CO
X-Y
Fe
Fe
Fe
Fe
C
C
O
O
X
H
CH3
SiMe3
CH2Ph
Y
2a
SO3CF3
SO3CF3
4a
4b
4c
4d
4e
Cl
Br
I
The spectroscopic properties of 5a–c and 6a–c resemble those
of the complexes 4 above discussed. The addition of BF3 to the
bridging ligand produces a shift in the m-CO frequencies of the
CH2CHCH2
Scheme 2.

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
2385
Fig. 1. Molecular structure of 4a, with key atoms labelled. Displacement ellipsoids are at 30% probability level. All H-atoms (except H(1s)) have been omitted for clarity.
Table 1
BF3
Selected bond lengths (Å) and angles (°) for [Fe2{l-g1:g3-Cc(Tol)@Cb(SH)Ca@N(Me)
(Xyl)}(l-CO)(CO)(Cp)2][SO3CF3] (4a)
S
Me
+
N
R'
Cβ
Cα
Cγ
Xyl
Fe(1)–Fe(2)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(2)–C(12)
Fe(1)–C(13)
Fe(2)–C(13)
Fe(2)–C(14)
2.571(2)
1.765(13)
1.873(11)
1.997(10)
1.977(10)
2.043(9)
2.072(9)
Fe(2)–C(15)
C(13)–C(14)
C(14)–C(15)
C(15)–N(1)
C(14)–S(1)
1.846(9)
CO
1.421(13)
1.433(12)
1.287(11)
1.788(10)
1.131(12)
1.156(11)
Fe
Fe
C
O
BF3
CO
_
5a-c
C(11)–O(11)
C(12)–O(12)
S
Me
+
R'
N
Cβ
Fe(1)–C(13)–C(14)
C(13)–C(14)–C(15)
C(14)–C(15)–N(1)
120.2(7)
116.3(8)
131.4(9)
C(15)–N(1)–C(17)
C(16)–N(1)–C(17)
C(15)–N(1)–C(16)
120.6(8)
116.9(8)
122.3(8)
Cα
_
Cγ
Xyl
SO3CF3
Fe
Fe
C
OC
Fe
O
Me
S
CO
R'
+
N
2a-c
Cβ
Table 2
Cα
Cγ
Xyl
Comparison between the bonding parameters (Å) of the bridging ligands in 2a, 4a and
CO
cis-[Fe2{l-g1:g3-Cc(Me)@Cb(Me)Ca@N(Me)(Xyl)}(l-CO)(CO)(Cp)2]+ (I)
Fe
Fe
[Fp][SO3CF3]
C
2a
4a
I
O
Fe(1)–C(13)
Fe(2)–C(13)
Fe(2)–C(14)
Fe(2)–C(15)
C(13)–C(14)
C(14)–C(15)
C(15)–N(1)
C(14)–S(1)
1.988(4)
2.040(4)
2.151(4)
1.860(4)
1.430(6)
1.440(6)
1.307(5)
1.736(4)
1.977(10)
2.043(9)
2.072(9)
1.846(9)
1.421(13)
1.433(12)
1.287(11)
1.788(10)
1.955(7)
2.035(7)
2.080(7)
1.839(7)
1.39(1)
1.43(1)
1.314(8)
–
6a-c
R’
Tol
CH2OH
Me
2a
2b
2c
2b
2c
2d
5a
5b
5c
6a
6b
6c
CH2OH
Me
Bun
Scheme 4.
X
X
S
S
Me
Me
+
+
of a resonance, in the 19F NMR spectra, at about ꢀ152 ppm. Con-
versely, the addition of Fp+ gives rise to a more complex m-CO band
pattern, derived from the absorptions attributable to the Fp moi-
ety in addition to those of the dinuclear frame. Nevertheless, a
20–25 cmꢀ1 shift to higher frequencies for the bridging CO well
evidences the presence of the electrophilic Fp+ fragment.
Tol
Cβ
N
Cβ
Tol
N
Cα
Cα
Xyl
Cγ
Xyl
Cγ
CO
CO
Fe
Fe
Fe
Fe
C
C
O
O
B
A
Additional studies were aimed to evidence possible effects due to
the presence of selenium in the place of sulphur in the bridging
ligand. Therefore, the reaction of the complex [Fe2{l-g1:g3-Cc
(Tol)] = Cb(Se)Ca@N(Me)2}(l-CO)(CO)(Cp)2] (3a) with MeSO3CF3
was investigated. Methylation occurred at the Se atom yielding 7a
(Scheme 5) in a reaction which parallels those of the corresponding
S-functionalized vinyliminium complexes 2a–c. Likewise, the
Scheme 3.
diiron moiety, of about 30 cmꢀ1, and the 13C NMR spectra of 5a–c
exhibit the usual pattern for the Ca, Cb and Cc resonances. The pres-
ence of the BF3 unit in 5a–c is also documented by the occurrence

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L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
_
SO3CF3
OC
Fe
Se
_
Me
SO3CF3
Se
Cβ
CO
Me
Me
+
N
+
N
Tol
Me
Cβ
Cα
Cα
Fe
Me
Cγ
Xyl
Cγ
Fe
CO
CO
Fe
Fe
C
C
O
O
7a
7b
Scheme 5.
reaction of [Fe2{l-g1:g3-Cc(Me) = Cb(Se)Ca@N(Me)(Xyl)}(l-CO)-
(CO)(Cp)2] (3b) with Fp+ leads to the formation of the trinuclear
complex 7b (Scheme 5), analogous to 6a–c.
Compounds 7a–b display spectroscopic properties similar to
those of the corresponding species of type 4 and 6, respectively
(see 4).
The formation of the trinuclear complexes 6a–c and 7b evi-
dences that the S or Se atom, which formally bears the negative
charge in the parent zwitterionic complexes, can be exploited to
coordinate unsaturated metal fragments and, consequently in-
crease the nuclearity and the complexity of the bridging frame.
In the reactions with Fp+ and, at a lesser extent, in the alkylation
reactions reported in Scheme 2, we noticed the formation of minor
amounts (less then 5–8%) of a secondary product. Further investi-
gations suggested that these products might derive from the reac-
tions of 2 and 3 with the solvent, which was CH2Cl2 in all of cases.
Indeed, we found that complexes 2a, 2c and 3a, upon standing in
CH2Cl2 solution, slowly react with the solvent leading to the alkyl-
ation of the S (Se) atom (Scheme 6).
Fig. 2. Molecular structure of 8c, with key atoms labelled. Displacement ellipsoids
are at 30% probability level. All H-atoms have been omitted for clarity. Only the
main image of the disordered Cp bound to Fe(1) is drawn.
Table 3
Selected bond lengths (Å) and angles (°) for [Fe2{l-g1:g3-Cc(Me)@Cb(SeCH2Cl)-
Ca@N(Me)2}(l-CO)(CO)(Cp)2][BPh4] (8c)
Fe(1)–Fe(2)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(2)–C(12)
Fe(1)–C(13)
Fe(2)–C(13)
Fe(2)–C(14)
Fe(2)–C(15)
2.5460(8)
1.755(5)
1.908(5)
1.942(5)
1.957(4)
2.020(4)
2.046(4)
1.841(4)
C(13)–C(14)
C(14)–C(15)
C(15)–N(1)
C(14)–Se(1)
Se(1)–C(19)
C(19)–Cl(2)
C(11)–O(11)
C(12)–O(12)
1.409(6)
1.416(5)
1.284(5)
1.949(4)
1.931(5)
1.767(5)
1.138(5)
1.163(5)
Formation of the complexes 8a–b occurs in about 80% yield
ꢀ
after 12 h at room temperature. Complex 8c was isolated as BPh4
salts, after anion exchange in order to obtain crystals suitable for
X-ray diffraction. In addition to X-ray structural determination,
complexes 8a–c were characterized by spectroscopy and elemental
analysis.
Fe(1)–C(13)–C(14)
C(13)–C(14)–C(15)
C(14)–C(15)–N(1)
C(15)–N(1)–C(16)
119.0(3)
116.5(3)
132.5(4)
123.3(4)
C(15)–N(1)–C(17)
C(16)–N(1)–C(17)
C(14)–Se(1)–C(19)
Se(1)–C(19)–Cl(2)
121.1(4)
115.6(4)
99.2(2)
The molecular structure of 8c is displayed in Fig. 2 whereas the
most relevant bond distances and angles are reported in Table 3.
Moreover, the bonding parameters of the bridging ligands in 8c,
the closely related zwitterionic complex 3b (which differs from
the parent 3a only for having a Xyl instead of a Me-group on the
nitrogen) [6], the tetranuclear diselenide 9e (which will be de-
scribed in the next section) and a typical vinyliminium complex
(I) are compared in Table 4. The cationic complex 8c can be per-
fectly described as a bridging vinyliminium, as indicated by its
bonding parameters. As reported above for S-protonation of 2a,
also Se-alkylation results in elongation of C(14)–Se(1) [1.899(3) Å
in 3b vs. 1.949(4) Å in 8c] which becomes an almost pure single
116.1(3)
Table 4
Comparison between the bonding parameters (Å) of the bridging ligands in 3b, 8c, 9e
and cis-[Fe2{l-g1:g3-Cc(Me)@Cb(Me)Ca@N(Me)(Xyl)}(l-CO)(CO)(Cp)2]+ (I)
3b
8c
9e
I
Fe(1)–C(13)
Fe(2)–C(13)
Fe(2)–C(14)
Fe(2)–C(15)
C(13)–C(14)
C(14)–C(15)
C(15)–N(1)
C(14)–Se(1)
1.966(4)
2.034(4)
2.158(3)
1.864(3)
1.435(5)
1.431(5)
1.307(4)
1.899(3)
1.957(4)
2.020(4)
2.046(4)
1.841(4)
1.409(6)
1.416(5)
1.284(5)
1.949(4)
1.967(6)
2.033(6)
2.044(6)
1.855(6)
1.427(8)
1.439(8)
1.275(8)
1.952(6)
1.955(7)
2.035(7)
2.080(7)
1.839(7)
1.39(1)
1.43(1)
1.314(8)
–
−
CH2Cl
−
X
E
Me
E
Me
R
+
+
R'
N
Cβ
bond, and strengthening of the Fe(2)–C(14) interaction
[2.158(3) Å in 3b vs. 2.046(4) Å in 8c].
R'
N
Cβ
Cα
R
Cγ
Cα
Cγ
CO
R
CO
CH2Cl2
Fe
Fe
Fe
Fe
Spectroscopic characterization of 8a–c (see 4) was straightfor-
ward, in that their IR and NMR data exhibit close similarities with
those of the related compounds 4b–e and 7a. Moreover, the addi-
tion of the CH2Cl unit is consistent with the occurrence of two dou-
blets (e.g. at 4.44 and 4.25 ppm for 8a), attributable to the CH2
protons. The chemical shift and coupling constants are similar to
those observed in 4d, which also contains diastereotopic geminal
hydrogen atoms. Finally, in the cases of 8a–b, NOE studies have
C
C
O
O
R’
E
X
2a
2c
3a
Xyl Tol
Xyl Me
S
S
Se
Cl
Cl
BPh4
8a
8b
8c
Me
Me
Scheme 6.

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
2387
evidenced significant interaction between the resonance of one Cp
and that of the N–Me group, indicating that the complexes main-
tain the Z configuration exhibited by their parent compounds 2a
and 2c.
It should be remarked that CH2Cl2 is usually unreactive with
neutral metal complexes, with relevant exceptions that mostly in-
volve oxidative addition [13]. In general, CH2Cl2 is not an efficient
alkylating reagent, at least compared to those reported in Scheme
2, and nucleophilic attacks on dichloromethane are uncommon
[14]. In particular, chloride displacement by thiolates is rare [15],
although this type of reaction might have a relevant role in the bac-
terial dichloromethane dehalogenase [16]. In view of these consid-
erations, the formation of 8a–c clearly remarks the strong
nucleophilic character of the chalcogenide functionality in the zwit-
terionic ligand in 2 and 3, and represent an unusual and interesting
example of nucleophilic addition involving dichloromethane.
2.2. Oxidative coupling of S- and Se-functionalized vinyliminium
ligands
Beside nucleophilic addition, the presence of a chalcogenide (S or
Se) on the bridging ligand should be exploited to promote oxidation
reactions. In particular, we have examined the reactions of zwitter-
ionic sulfide complexes 2b–d with iodine, in CH3OH solution, which
resulted in the formation of the bis-cationic tetranuclear complexes
9a–c (Scheme 7). Likewise, the selenium containing complexes 3b
and [Fe2{l-g1:g3-Cc(Bun)@Cb(Se)Ca@NMe2}(l-CO)(CO)(Cp)2] (3c)
react with I2 under similar conditions affording 9d and 9e, respec-
tively (Scheme 7). All these complexes have been obtained in
80–90% yield and isolated as BPh4ꢀ salts, after anion exchange.
Complexes 9a–e have been characterized by IR and NMR spec-
troscopy, and elemental analysis. Furthermore, the structure of 9e
has been established by X-ray studies: the ORTEP molecular dia-
gram is shown in Fig. 3, whereas relevant bond lengths and angles
are reported in Table 5. The molecule is composed by two [Fe2{l-
g1:g3-C(Bun)@C(Se)C@N(Me)2}(l-CO)(CO)(Cp)2]+ moieties joined
by a Se–Se bond. The former has all the characteristics of cationic
vinyliminium complexes and the bonding parameters parallel very
well the ones previously reported for other [Fe2{l-g1:g3-
C(R0)@C(R00)C@N(Me)(R)}(l-CO)(CO)(Cp)2]+ species [2], as well as
those described in this paper for 8c (Table 4). This is not surprising,
since also the parent zwitterionic compound 3c presented a ligand
with a partial vinyliminium character. Therefore, the reaction is a
selective mono-electronic oxidation of the heteroatom, which loses
its negative charge and forms a homonuclear bridge, whereas the
Fig. 3. Molecular structure of 9e, with key atoms labelled. Displacement ellipsoids
are at 30% probability level. All H-atoms have been omitted for clarity. Only the
main images of the disordered groups are reported.
Table 5
Selected bond lengths (Å) and angles (°) for [Fe2{l-g1:g3-C(Bun)@C(Se)C@N(Me)2}(l-
CO)(CO)(Cp)2]2[BPh4]2 (9e)
Fe(1)–Fe(2)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(2)–C(12)
Fe(1)–C(13)
Fe(2)–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)–N(1)
C(14)–Se(1)
Se(1)–Se(2)
2.5467(14)
1.750(8)
1.892(7)
1.949(7)
1.967(6)
2.033(6)
2.044(6)
1.855(6)
1.165(8)
1.185(8)
1.427(8)
1.439(8)
1.275(8)
1.952(6)
2.3136(11)
Fe(3)–Fe(4)
Fe(3)–C(41)
Fe(3)–C(42)
Fe(4)–C(42)
Fe(3)–C(43)
Fe(4)–C(43)
Fe(4)–C(44)
Fe(4)–C(45)
C(41)–O(41)
C(42)–O(42)
C(43)–C(44)
C(44)–C(45)
C(45)–N(2)
C(44)–Se(2)
2.542(3)
1.713(10)
1.866(10)
1.941(11)
1.984(8)
2.065(8)
2.059(7)
1.889(9)
1.169(10)
1.188(11)
1.402(10)
1.481(11)
1.249(10)
1.980(8)
_
O
2 [BPh4]
C
Fe
Fe
R
OC
Cα
Fe(1)–C(13)–C(14)
C(13)–C(14)–C(15)
C(14)–C(15)–Fe(2)
C(14)–C(15)–N(1)
C(14)–Se(1)–Se(2)
118.8(4)
116.0(5)
75.7(4)
136.4(6)
106.85(18)
Fe(3)–C(43)–C(44)
C(43)–C(44)–C(45)
C(44)–C(45)–Fe(4)
C(44)–C(45)–N(2)
C(44)–Se(2)–Se(1)
118.7(6)
117.2(7)
74.2(5)
132.8(7)
110.0(2)
Cγ
N
+
Cβ
E
R'
Me
−
E
Me
R
+
N
E
R'
Cβ
I2
Me
Cα
+
Cγ
R'
Cβ
CO
N
Cγ
NaBPh4
Cα
Fe
Fe
CO
R
C
Fe
Fe
O
C
O
positive charge remains on the vinyliminium without any major
rearrangement. The Cb–Se interactions [C(14)–Se(1) 1.952(6) Å;
C(44)–Se(2) 1.980(8) Å] are almost pure single bonds as in the
dinuclear Se-alkylated vinyliminium 8c [1.949(4) Å]. The Se(1)–
Se(2) interaction [2.3136(11) Å] is in keeping with other organic
and organometallic diselenides as well as the C(11)–Se(1)–Se(2)–
C(44) torsion angle [ꢀ87.1(3)°], which indicates a skew conforma-
tion [17].
R
R’
E
S
S
S
Se
Se
2b
Xyl CH2OH
9a
2c
2d
3b
3c
Xyl Me
9b
9c
9d
9e
Xyl Bun
Xyl Me
Me
Bun
Scheme 7.

2388
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
The IR and NMR data of 9a–e are in good agreement with the pres-
3. Conclusions
ence of 2 equiv. dinuclear moieties, each containing a vinyliminium
ligand. NOE studies carried on 9a–e indicate that the N-substituents
(Me and Xyl) adopt the Z configuration.
The diiron complexes 2 and 3, investigated in this work, contain
zwitterionic bridging vinyliminium ligands, with a negative charge
formally localized on the S/Se heteroatoms. These chalcogenide
functionalities might, in theory, undergo three different type of
reactions: (i) S (or Se) alkylation, (ii) S (or Se) metalation by unsat-
urated metal fragments, (iii) oxidative coupling to generate S–S
(Se–Se) bonds. Each of these reactions has been successfully
accomplished under very selective conditions, involving the S or
Se atoms without affecting the remaining part of the complexes.
The investigated reactions, and in particular the alkylation with
CH2Cl2, reveal the remarkable nucleophilic character of the chalco-
genide functionality.
It should be remarked that, since the complexes 2 are chiral, the
formation of the dimeric complexes 9 from 2, might result in the
formation of the meso and the dl forms. The XRD structure of 9e
corresponds to the meso isomer (with an achiral space group
shown in Table 6). Moreover, different crystals have been analysed,
all showing the same structure and the 1H NMR spectra indicate
the presence of a single isomeric form in solution. These data sug-
gest that 9 consist exclusively of meso form.
The reaction described in Scheme 7 represents an interesting
example of disulfide (diselenide) bond formation by oxidative cou-
pling, which falls within a field of high interest for its biological
and synthetic applications [18]. Indeed, oxidative coupling of thiols
to disulfides is an area of active research, due to the need of provid-
ing selective reaction conditions and avoid thiols over-oxidation
[19]. Disulfide bond formation in coordination and organometallic
compounds mostly involve the syntheses of l-S2 dinuclear com-
plexes by oxidative coupling of SH (or H2S) ligands [20]. Examples
include the formation of tetranuclear species by the oxidative cou-
pling of the bridging hydrogen sulfido ligand in the complexes
[Cp*MCl(l-SH)2MClCp*] (M = Rh, Ir, Cp* = g5C5Me5) [21]. Our find-
ings provide an unusual example in which the S–S, and in particu-
The addition of the coordinatively unsaturated Fp+ metal frag-
ment demonstrate that it is possible to increase the nuclearity of
the complexes by coordination to S or Se, and that the zwitterionic
complexes 2–3, as a whole, might act as ‘organometallic ligands’.
4. Experimental
4.1. General
All reactions were routinely carried out under a nitrogen atmo-
sphere, 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–El-
mer Spectrum 2000 FT-IR spectrophotometer and elemental anal-
yses were performed on a ThermoQuest Flash 1112 Series EA
Instrument. All NMR measurements were performed at 298 K on
Mercury Plus 400 instrument. The chemical shifts were referenced
to internal TMS for 1H and 13C, and to external CCl3F for 19F. The
spectra were fully assigned via DEPT experiments and 1H,13C corre-
lation through gs-HSQC and gs-HMBC experiments [23]. NOE mea-
surements were recorded using the DPFGSE-NOE sequence [24].
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 2a–d and
3a–c were prepared by published methods [6].
lar Se–Se, bond formation involves
a more complex ligand,
resulting in an oxidative dimerization [22]. Finally, it should be re-
marked that the oxidative coupling is reversible, in that treatment
of 9a–c with freshly prepared solution of sodium naphthalenide in
THF, at room temperature, leads to the formation of the parent
complexes 2b–d in about 70% yield.
Table 6
Crystal data and experimental details for 4a ꢁ H2O, 8c and 9e ꢁ CH3CN
Complex
4a ꢁ H2O
8c
9e ꢁ CH3CN
Formula
Formula weight
T (K)
C
32H32F3Fe2NO6S2 C43H41BClFe2NO2Se C92H93B2Fe4N3O4Se2
759.41
295(2)
0.71073
Triclinic
P1
8.540(4)
12.444(5)
16.939(7)
109.580(5)
97.292(5)
98.813(5)
840.69
296(2)
1707.63
293(2)
k (Å)
0.71073
Monoclinic
P21/n
0.71073
Triclinic
P1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
ꢀ
ꢀ
12.8773(9)
22.8722(16)
13.3470(10)
90
94.7530(10)
90
12.373(3)
15.537(3)
22.161(4)
81.87(3)
86.19(3)
72.09(3)
4011.8(14)
2
4.2. Synthesis of [Fe2{l-g1:g3-Cc(Tol)@Cb(SX)Ca@N(Me)(Xyl)}(l-CO)
(CO)(Cp)2][SO3CF3] (X = H, 4a; X = Me, 4b)
a (°)
b (°)
c (°)
To a solution of 2a (100 mg, 0.169 mmol) in CH2Cl2 (15 mL), was
added HSO3CF3 (0.02 mL, 0.18 mmol). The solution was stirred for
30 min, then it was filtered on celite. Removal of the solvent gave
4a as brown powder. Yield: 113 mg, 90%. Anal. Calc. for C32H30F3Fe2-
NO5S2: C, 51.84; H, 4.08; N, 1.89. Found: C, 51.89; H, 4.15; N, 1.93%.
IR (CH2Cl2) m(CO) 1990 (vs), 1830 (s), m(CN) 1615 (m) cmꢀ1. IR (KBr)
m(SH) 2548 (m) cmꢀ1. 1H NMR (CDCl3) d 7.67–7.29 (7H, Me2C6H3 and
MeC6H4); 5.01, 4.94 (s, 10H, Cp); 3.57 (s, 3H, NMe); 3.25 (s, 1H, SH);
2.59, 2.03 (s, 6H, Me2C6H3); 2.49 (s, 3H, MeC6H4). 13C{1H} NMR
(CDCl3) d 250.9 (l-CO); 226.8 (Ca); 210.2 (CO); 209.1 (Cc); 149.8
(Cipso Tol); 140.6 (Cipso Xyl); 137.7–125.5 (Carom); 92.6, 89.3 (Cp);
71.8 (Cb); 49.4 (NMe); 21.2 (MeC6H4); 18.0, 17.9 (Me2C6H3).
Complex 4b was obtained by a procedure analogous to that de-
scribed for 4a, by reacting 2a (90 mg, 0.152 mmol), with MeSO3CF3
(0.02 mL, 0.18 mmol). The reaction mixture was dried in vacuo and
the residue was chromatographed on alumina, with MeOH as elu-
ent affording 4b. Yield: 106.3 mg, 93%. Anal. Calc. for C33H32F3Fe2-
NO5S2: C, 52.47; H, 4.27; N, 1.85. Found: C, 52.58; H, 4.31; N, 1.68%.
IR (CH2Cl2) m(CO) 1990 (vs), 1828 (s), m(CN) 1616 (m) cmꢀ1. 1H NMR
(CD3CN) d 7.70–7.30 (m, 7H, MeC6H4 and Me2C6H3); 4.99, 4.97
Cell volume (Å3) 1645.1(12)
3917.6(5)
4
Z
2
Dc (g cmꢀ3
)
1.533
1.070
780
1.425
1.414
l (mmꢀ1
F(000)
)
1.774
1.670
1720
1760
Crystal size
(mm)
0.21 ꢂ 0.15 ꢂ 0.11 0.21 ꢂ 0.16 ꢂ 0.13
0.19 ꢂ 0.14 ꢂ 0.11
h Limits (°)
Reflections
collected
1.30–25.00
10687
1.77–27.00
43585
0.93–25.03
36159
Independent
reflections
5684 [0.0841]
8531 [0.0595]
14177 [0.0827]
[Rint
]
Data/ restraints/ 5684/207/419
parameters
8531/26/459
1.027
14177/506/968
1.017
Goodness-of-fit
0.962
on F2
R1 (I > 2r(I))
wR2 (all data)
Largest
0.0831
0.2796
0.679/ꢀ0.572
0.0497
0.1630
0.468/ꢀ0.680
0.0664
0.1942
0.843/ꢀ0.622
difference in
peak and
hole (e Åꢀ3
)

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
2389
(s, 10H, Cp); 3.54 (s, 3H, NMe); 2.58, 2.04 (s, 6H, Me2C6H3); 2.49 (s,
3H, MeC6H4); 2.13 (s, 3H, SMe). 13C{1H} NMR (CD3CN) d 252.2
(l-CO); 227.8 (Ca); 211.1 (CO); 208.5 (Cc); 150.9 (Cipso Tol); 141.4
(Cipso Xyl); 137.4–122.9 (Carom); 93.7, 88.9 (Cp); 68.2 (Cb); 52.0
(NMe); 21.1 (MeC6H4); 19.8 (SMe); 18.4, 17.9 (Me2C6H3).
m(CO) 1996 (vs), 1827 (s), m(CN) 1609 (w) cmꢀ1
.
1H NMR (CD3CN)
2
d 7.55–7.33 (m, 3H, Me2C6H3); 6.79, 5.74 (dd, 2H, JHH = 13.54 Hz,
3JHH = 2.56 Hz, CH2OH); 5.62, 5.02 (s, 10H, Cp); 3.70 (s, 3H, NMe);
2.69, 1.99 (s, 6H, Me2C6H3). 13C{1H} NMR (CD3CN) d 252.3 (l-CO);
226.8 (Ca); 212.2 (CO); 203.9 (Cc); 142.2 (Cipso Xyl); 135.7–130.9
(Carom); 93.8, 92.9 (Cp); 76.9 (CH2); 56.5 (Cb); 51.2 (NMe); 19.4,
18.9 (Me2C6H3).19F NMR (CD3CN) d ꢀ152.1 (br, BF3).
4.3. Synthesis of [Fe2{l-g1:g3-Cc(Tol)@Cb(SX)Ca@N(Me)(Xyl)}(l-CO)
(CO)(Cp)2][Y] (X = SiMe3, Y = Cl, 4c; X = CH2Ph, Y = Br, 4d;
X = CH2CH@CH2, Y = I, 4e)
5c (yield: 74%). Anal. Calc. for C25H25BF3Fe2NO2S: C, 51.50; H,
4.32; N, 2.40. Found: C, 51.46; H, 4.26; N, 2.45%. IR (CH2Cl2)
m(CO) 1991 (vs), 1825 (s), m(CaN) 1614 (w) cmꢀ1 1H NMR (CDCl3)
.
Complex 4c was obtained by the same procedure described for
4b, by reacting 2a (150 mg, 0.254 mmol) with SiMe3Cl (1.00 mL,
7.85 mmol). Yield: 124 mg, 70%. Anal. Calc. for C34H38ClFe2NO2SSi:
C, 58.36; H, 5.44; N, 2.00. Found: C, 58.42; H, 5.40; N, 2.03%. IR
d 7.45–7.25 (m, 3H, Me2C6H3); 5.32, 4.65 (s, 10H, Cp); 3.96 (s,
3H, CcMe); 3.47 (s, 3H, NMe); 2.53, 2.00 (s, 6H, Me2C6H3). 13C{1H}
NMR (CDCl3) d 252.3 (l-CO); 226.5 (Ca); 209.8 (CO); 204.0 (Cc);
140.5 (Cipso Xyl); 134.0–129.0 (Carom); 91.4, 89.2 (Cp); 68.5 (Cb);
49.1 (NMe); 38.5 (CcMe); 17.8, 17.7 (Me2C6H3).19F NMR (CDCl3) d
ꢀ156.2 (br, BF3).
(CH2Cl2) m(CO) 1993 (vs), 1830 (s), m(CN) 1615 (w) cmꢀ1 1H NMR
.
(CDCl3) d 7.71–6.99 (m, 7H, MeC6H4 and Me2C6H3); 4.67, 4.59 (s,
10H, Cp); 3.48 (s, 3H, NMe); 2.48, 1.95 (s, 6H, Me2C6H3); 2.18 (s,
3H, C6H4Me); 0.09 (SiMe3). 13C{1H} NMR (CDCl3) d 248.8 (l-CO);
226.8 (Ca); 210.2 (CO); 207.7 (Cc); 149.0 (Cipso Tol); 140.0 (Cipso Xyl);
136.9–127.5 (Carom); 95.4, 90.7 (Cp); 64.3 (Cb); 49.7 (NMe); 21.2
(C6H4Me); 18.0 (Me2C6H3); 0.61 (SiMe3).
4.5. Synthesis of [Fe2{l-g1:g3-Cc(R0)@Cb{S–Fe(CO)2(Cp)}Ca@N(Me)
(Xyl)}(l-CO)(CO)(Cp)2][SO3CF3] (R0 = CH2OH, 6a; R0 = Me, 6b; R0 = Bun,
6c)
Complexes 4d–e were obtained by the same procedure de-
scribed for 4b, by reacting 2a with BrCH2Ph and ICH2CH@CH2,
respectively.
To a solution of [Fe2(l-CO)2(CO)2(Cp)2] (94 mg, 0.266 mmol) in
CH2Cl2 (10 mL) was added AgSO3CF3 (97 mg, 0.377 mmol). The
mixture was stirred for 3 h in the dark, then filtered on celite
and treated with 2b (100 mg, 0.188 mmol). The resulting solution
was stirred for 1 h. Solvent removal and chromatography of the
residue on alumina, using CH3OH as eluent, gave a brown band
corresponding to 6a. Yield: 121 mg, 75%. Anal. Calc. for
4d (yield: 87%). Anal. Calc. for C38H36BrFe2NO2S: C, 59.87; H,
4.76; N, 1.84. Found: C, 59.92; H, 4.70; N, 1.91%. IR (CH2Cl2)
m(CO) 1992 (vs), 1833 (s), m(CN) 1613 (m) cmꢀ1 1H NMR (CDCl3)
.
d 7.97–6.84 (12H, Me2C6H3, C6H4Me and Ph); 5.13, 5.08 (s, 10H,
2
Cp); 4.52, 4.33 (d, JHH = 11.71 Hz, 2H, CH2Ph); 3.60 (s, 3H, NMe);
C
33H30F3Fe3NO8S2: C, 46.24; H, 3.53; N, 1.63. Found: C, 46.30; H,
3.48; N, 1.56%. IR (CH2Cl2) m(CO) 2034 (s), 1989 (vs), 1973 (sh),
1810 (s), m(CN) 1610 (w) cmꢀ1 1H NMR (CDCl3) d 7.41–7.21 (m,
2.58 (s, 3H, C6H4Me); 2.49, 2.02 (s, 6H, Me2C6H3). 13C{1H} NMR
(CDCl3) d 249.1 (l-CO); 226.8 (Ca); 210.2 (CO); 208.4 (Cc); 149.7
.
(Cipso Tol); 149.1 (Cipso Ph); 140.3 (Cipso Xyl); 137.3–126.0 (Carom
92.2, 89.0 (Cp); 64.6 (Cb); 63.8 (CH2Ph); 51.1 (NMe); 21.1
(C6H4Me); 18.0, 17.7 (Me2C6H3).
)
3H, Me2C6H3); 6.20 (m, 1H, OH); 6.05, 5.80 (m, 2H, CH2OH); 5.41,
5.34, 4.63 (s, 15H, Cp); 3.30 (s, 3H, NMe); 2.59, 2.02 (s, 6H,
Me2C6H3). 13C{1H} NMR (CDCl3) d 256.0 (l-CO); 228.3 (Ca); 217.3,
213.5, 213.4 (CO); 210.8 (Cc); 140.9 (Cipso Xyl); 134.5–128.8 (Carom);
90.7, 89.1, 87.2 (Cp); 79.5 (Cb); 74.3 (CH2OH); 48.6 (NMe); 18.0,
17.8 (Me2C6H3).
4e (yield: 83%). Anal. Calc. for C34H34Fe2INO2S: C, 53.78; H, 4.51;
N, 1.84. Found: C, 53.82; H, 4.60; N, 1.80%. IR (CH2Cl2) m(CO) 1994
(vs), 1832 (s), m(CaN) 1614 (m) cmꢀ1 1H NMR (CDCl3) d 7.68–7.29
.
(7H, Me2C6H3 and C6H4Me); 5.53 (m, 2H, SCH2CHCH2); 5.09, 5.05
(s, 10H, Cp); 3.85 (m, 1H, SCH2CH); 3.61 (s, 3H, NMe); 3.17 (m,
2H, SCH2); 2.59 (s, 3H, C6H4Me); 2.50, 2.04 (s, 6H, Me2C6H3).
13C{1H} NMR (CDCl3) d 249.1 (l-CO); 226.4 (Ca); 209.9 (CO);
208.7 (Cc); 148.9 (Cipso Tol); 140.2 (Cipso Xyl); 137.3–119.5 (Carom
and CH@CH2); 93.1, 88.9 (Cp); 64.5 (Cb); 51.2 (NMe); 39.4
(SCH2); 21.1 (C6H4Me); 17.7, 17.6 (Me2C6H3).
Complexes 6b–c were prepared by the same procedure de-
scribed for synthesis 6a, by reacting in situ generated [Fp][SO3CF3]
with 2c and 2d, respectively.
6b (yield: 85%). Anal. Calc. for C33H30F3Fe3NO7S2: C, 47.11; H,
3.59; N, 1.66. Found: C, 47.04; H, 3.50; N, 1.58%. IR (CH2Cl2)
m(CO) 2037 (s), 1996 (vs), 1981 (sh), 1816 (s), m(CN) 1609 (w)
cmꢀ1 1H NMR (CDCl3) d 7.40–7.20 (m, 3H, Me2C6H3); 5.22, 4.57
.
(s, 15H, Cp); 3.85 (s, 3H, CcMe); 3.31 (s, 3H, NMe); 2.58, 1.99 (s,
6H, Me2C6H3). 13C{1H} NMR (CDCl3) d 255.2 (l-CO); 228.9 (Ca);
213.5, 213.1 (CO); 210.5 (Cc); 140.8 (Cipso Xyl); 134.4–128.7 (Carom);
91.6, 90.0, 86.9 (Cp); 77.9 (Cb); 48.9 (NMe); 40.6 (CcMe); 17.9, 17.8
(Me2C6H3).
4.4. Synthesis of [Fe2{l-g1:g3-Cc(R)@Cb(SBF3)Ca@N(Me)(Xyl)}(l-
CO)(CO)(Cp)2] (R = Tol, 5a; R = CH2OH, 5b; R = Me, 5c)
Complex 2a (125 mg, 0.211 mmol), in CH2Cl2 solution (15 mL),
was treated with BF3, in Et2O solution (0.5 mmol). The solution,
which turned immediately brown, was stirred for an additional
10 min, then was filtered on a celite pad. Removal of the solvent
gave a brown powder corresponding to 5a. Yield: 98 mg, 70%. Anal.
Calc. for C31H29BF3Fe2NO2S: C, 56.49; H, 4.43; N, 2.13. Found: C,
56.52; H, 4.36; N, 2.20%. IR (CH2Cl2) m(CO) 1990 (vs), 1829 (s),
m(CN) 1608 (w) cmꢀ1. 1H NMR (CD3CN) d 7.98–7.20 (m, 7H, MeC6H4
and Me2C6H3); 5.06, 5.04 (s, 10H, Cp); 3.64 (s, 3H, NMe); 2.60, 1.96
(s, 6H, Me2C6H3); 2.52 (s, 3H, MeC6H4). 13C{1H} NMR (CD3CN) d
252.7 (l-CO); 227.7 (Ca); 211.5 (CO); 206.5 (Cc); 143.8 (Cipso Xyl);
135.8–127.7 (Carom); 94.7, 90.2 (Cp); 52.9 (Cb); 50.4 (NMe); 21.7
(MeC6H4); 19.0, 18.6 (Me2C6H3).19F NMR (CD3CN) d ꢀ152.2 (br,
BF3).
6c (yield: 69%). Anal. Calc. for C36H36F3Fe3NO7S2: C, 48.95; H,
4.11; N, 1.59. Found: C, 49.02; H, 4.06; N, 1.55%. IR (CH2Cl2)
m(CO) 2036 (s), 1994 (vs), 1980 (sh), 1815 (s), m(CN) 1609 (w)
cmꢀ1 1H NMR (CDCl3) d 7.40–7.21 (m, 3H, Me2C6H3); 5.20, 5.15,
.
4.64 (s, 15H, Cp); 4.74, 3.98 (m, 2H, CcCH2); 3.41 (s, 3H, NMe);
2.64, 1.99 (s, 6H, Me2C6H3); 1.95, 1.84 (m, 4H, CcCH2CH2CH2);
1.23 (m, 3H, CcCH2CH2CH2CH3). 13C{1H} NMR (CDCl3) d 254.6 (l-
CO); 228.3 (Ca); 213.7, 213.5 (CO); 210.5 (Cc); 140.3 (Cipso Xyl);
134.5–128.8 (Carom); 90.7, 89.8, 86.4 (Cp); 72.5 (Cb); 51.3, 36.7,
23.7, 14.5 (Bun); 49.6 (NMe); 18.1, 17.8 (Me2C6H3).
4.6. Synthesis of [Fe2{l-g1:g3-Cc(R0)@Cb(SeX)Ca@N(Me)(R)}(l-CO)
(CO)(Cp)2][SO3CF3] (R = X = Me, R0 = Tol, 7a; R = Xyl, R0 = Me, X = Fp+,
7b)
Complexes 5b–c were obtained by the same procedure de-
scribed for 5a, by reacting BF3 with 2b and 2c, respectively.
5b (yield: 68%). Anal. Calc. for C25H25BF3Fe2NO3S: C, 50.13; H,
4.21; N, 2.34. Found: C, 49.99; H, 4.23; N, 2.36%. IR (CH2Cl2)
Complex 7a was obtained by the same procedure described for
synthesis of 4b, upon treatment of 3a (105 mg, 0.19 mmol) with

2390
L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
MeSO3CF3 (0.022 mL, 0.20 mmol). (Yield: 122 mg, 90%). Anal. Calc.
for C26H26F3Fe2NO5SSe: C, 43.85; H, 3.68; N, 1.97. Found: C, 43.92;
H, 3.76; N, 2.02%. IR (CH2Cl2): m(CO) 1986 (vs), 1802 (s), m(CN) 1651
(m) cmꢀ1. 1H NMR (CDCl3) d 7.58–7.09 (4H, MeC6H4); 5.20, 4.85 (s,
10H, Cp); 3.94, 3.22 (s, 6H, NMe); 2.39 (s, 3H, MeC6H4); 1.89 (s, 3H,
SeMe). 13C{1H} NMR (CDCl3) d 255.4 (l-CO); 220.2 (Ca); 210.0 (CO);
199.6 (Cc); 151.3 (Cipso Tol); 137.3–125.5 (Carom); 92.1, 88.9 (Cp);
66.3 (Cb); 47.8, 45.3 (NMe); 21.5 (MeC6H4); 6.5 (SeMe).
4.8. Synthesis of [Fe2{l-g1:g3-Cc(R0)@Cb(E)Ca@N(Me)(R)}(l-CO)
(CO)(Cp)2]2[BPh4]2 [R = Xyl, R0 = CH2OH, E = S, 9a; R = Xyl, R0 = Me,
E = S, 9b; R = Xyl, R0 = Bun, E = S, 9c; R = Xyl, R0 = Me, E = Se, 9d;
R = Me, R0 = Bun, E = Se, 9e]
Complex 2b (70 mg, 0.132 mmol), was dissolved in MeOH
(10 mL), then NaBPh4 (150 mg, 0.438 mmol) and I2 (17 mg,
0.068 mmol) were added. The mixture, which turned immediately
orange, was stirred for 60 min. Then, the solvent was removed un-
der vacuum and the residue was filtered on a celite pad with
CH2Cl2 (15 mL) as eluent. 9a was obtained as a brown solid upon
removal of the solvent. Yield: 101 mg, 90%. Anal. Calc. for
Complex 7b was obtained by the same procedure described for
synthesis of 6b, upon treatment of 3b (120 mg, 0.21 mmol) with
in situ generated [Fp][SO3CF3] (75 mg, 0.23 mmol). (Yield:
166 mg, 88%). Anal. Calc. for C33H30F3Fe3NO7SSe: C, 44.63; H,
3.40; N, 1.58. Found: C, 44.65; H, 3.30; N, 1.49%. IR (CH2Cl2):
m(CO) 2031 (s), 1993 (vs), 1982 (sh), 1815 (s), m(CN) 1612 (w)
C98H90B2Fe4N2O6S2: C, 69.20; H, 5.33; N, 1.65. Found: C, 69.22; H,
5.25; N, 1.58%. IR (CH2Cl2) m(CO) 2008 (vs), 1829 (s), m(CN) 1619
cmꢀ1
.
1H NMR (CDCl3) d 7.43–7.20 (m, 3H, Me2C6H3); 5.17, 4.57
(w) cmꢀ1
.
1H NMR (CD3CN) d 7.83–6.88 (46H, Me2C6H3 and
2
(s, 15H, Cp); 3.77 (s, 3H, CcMe); 3.24 (s, 3H, NMe); 2.61, 1.98 (s,
6H, Me2C6H3). 13C{1H} NMR (CDCl3) d 256.3 (l-CO); 228.6 (Ca);
213.8, 213.5 (CO); 210.5 (Cc); 140.7 (Cipso Xyl); 134.4–128.9 (Carom);
92.0, 90.2, 86.4 (Cp); 61.6 (Cb); 49.1 (NMe); 37.8 (CcMe); 18.1
(Me2C6H3).
BPh4); 6.05, 6.02 (m, 4H, JHH = 11.1 Hz, CH2OH); 5.63, 4.82 (s,
20H, Cp); 5.55 (m, 2H, OH); 3.88 (s, 6H, NMe); 2.61, 2.15 (s, 12H,
Me2C6H3). 13C{1H} NMR (CD3CN) d 251.2 (l-CO); 227.6 (Ca);
211.5
(CO);
210.9
(Cc);
164.1
(Cipso BPh4); 142.3 (Cipso Xyl); 136.1–131.2 (Me2C6H3); 93.4, 90.3
(Cp); 74.9 (CH2OH); 68.6 (Cb); 55.5 (NMe); 19.5, 19.3 (Me2C6H3).
Complexes 9b–e were obtained by the same procedure described
for 9a, by reacting I2/NaBPh4 with 2b–d and 3b–c, respectively.
Crystals of 9e suitable for X-ray analysis were obtained by an ace-
tone solution, layered with diethyl ether, at room temperature.
9b (yield: 88%). Anal. Calc. for C98H90B2Fe4N2O4S2: C, 70.53; H,
5.44; N, 1.68. Found: C, 70.49; H, 5.55; N, 1.62%. IR (CH2Cl2)
4.7. Synthesis of [Fe2{l-g1:g3-Cc(R0)@Cb(E-CH2Cl)Ca@N(Me)(R)}
(l-CO)(CO)(Cp)2][Y] [E = S, R = Xyl, R0 = Tol, Y = Cl, 8a; E = S, R = Xyl,
R0 = Me, Y = Cl, 8b; E = Se, R = R0 = Me, Y = BPh4, 8c]
Complex 2a (90 mg, 0.152 mmol), was dissolved in CH2Cl2
(10 mL). The solution was stirred overnight, then it was filtered
on a celite pad. Removal of the solvent gave 8a as brown micro-
crystalline solid. Yield: 90 mg, 88%. Anal. Calc. for C32H31Cl2Fe2-
NO2S: C, 56.83; H, 4.62; N, 2.07. Found: C, 56.88; H, 4.55; N,
1.99%. IR (CH2Cl2) m(CO) 1990 (vs), 1830 (s), m(CN) 1615 (m)
m(CO) 1996 (vs), 1833 (s), m(CN) 1619 (w) cmꢀ1 1H NMR (CD3CN)
.
d 7.83–6.88 (46H, Me2C6H3 and BPh4); 5.53, 4.72 (s, 20H, Cp);
4.19 (s, 6H, CcMe); 3.74 (s, 6H, NMe); 2.54, 2.13 (s, 12H, Me2C6H3).
13C{1H} NMR (CD3CN) d 249.7 (l-CO); 225.6 (Ca); 211.8 (CO); 210.6
(Cc); 164.1 (Cipso BPh4); 140.7 (Cipso Xyl); 137.7–117.6 (Carom); 92.6,
89.0 (Cp); 64.5 (Cb); 52.9 (NMe); 39.4 (CcMe); 17.8, 17.5 (Me2C6H3).
9c (yield: 79%). Anal. Calc. for C104H102B2Fe4N2O4S2: C, 71.25; H,
5.86; N, 1.60. Found: C, 71.33; H, 5.94; N, 1.51%. IR (CH2Cl2): m(CO)
1989 (vs), 1835 (s), m(CN) 1611 (w) cmꢀ1. 1H NMR (CD3CN) d 7.84–
6.99 (46H, Me2C6H3 and BPh4); 5.41, 4.83 (s, 20H, Cp); 3.95, 2.97
(m, 4H, CcCH2); 3.34 (s, 6H, NMe); 2.98 (m, 4H, CcCH2CH2); 2.62,
2.07 (s, 12H, Me2C6H3); 2.28 (m, 4H, CcCH2CH2CH2); 1.31 (m, 6H,
CcCH2CH2CH2CH3). 13C{1H} NMR (CD3CN) d 249.6 (l-CO); 225.7
(Ca); 210.8, 210.2 (CO and Cc); 164.4 (Cipso BPh4); 140.4 (CipsoXyl);
135.2–126.8 (Carom); 92.4, 89.4 (Cp); 64.8 (Cb); 50.9 (NMe); 18.2,
17.7 (Me2C6H3); 52.3, 37.8, 23.7, 14.1 (Bun).
9d (yield: 85%). Anal. Calc. for C98H90B2Fe4N2O4Se2: C, 66.78; H,
5.15; N, 1.59. Found: C, 66.83; H, 5.19; N, 1.60%. IR (CH2Cl2): m(CO)
1995 (vs), 1833 (s), m(CaN) 1620 (w) cmꢀ1. 1H NMR (CD3CN) d 7.81–
6.86 (46H, Me2C6H3 and BPh4); 5.53, 4.74 (s, 20H, Cp); 4.16 (s, 6H,
CcMe); 3.66 (s, 6H, NMe); 2.55, 2.12 (s, 12H, Me2C6H3). 13C{1H}
NMR (CD3CN) d 250.1 (l-CO); 224.7 (Ca); 210.9, 210.7 (CO and
Cc); 164.3 (Cipso BPh4); 140.6 (Cipso Xyl); 136.0–117.6 (Me2C6H3 and
BPh4); 92.5, 89.0 (Cp); 65.0 (Cb); 51.7 (NMe); 41.2 (CcMe); 17.9,
17.8 (Me2C6H3).
cmꢀ1
.
1H NMR (CDCl3) d 7.63–7.21 (m, 7H, Me2C6H3 and MeC6H4);
2
5.24, 5.05 (s, 10H, Cp); 4.44, 4.25 (d, JHH = 11.3 Hz, 2H, CH2Cl);
3.51 (s, 3H, NMe); 2.49, 1.96 (s, 6H, Me2C6H3); 2.42 (s, 3H, MeC6H4).
13C{1H} NMR (CDCl3) d 249.1 (l-CO); 226.8 (Ca); 210.2 (CO); 208.0
(Cc); 149.1 (Cipso Tol); 140.2 (Cipso Xyl); 137.1–126.8 (Carom); 93.5,
89.2 (Cp); 64.5 (Cb); 50.9 (CH2Cl); 48.4 (NMe); 21.0 (MeC6H4);
17.9, 17.6 (Me2C6H3).
Complexes 8b and 8c were prepared by using a procedure anal-
ogous to what described for 8a, from CH2Cl2 solutions of 2c and 3a,
respectively. Anion exchange for 8c was performed as follows:
complex
[Fe2{l-g1:g3-Cc(Me)Cb(Se–CH2Cl)CaN(Me)2}(l-CO)
(CO)(Cp)2][Cl] (85 mg, 0.153 mmol) was dissolved in CH3CN
(10 mL), and NaBPh4 (157 mg, 0.459 mmol) was added. The mix-
ture was stirred for 2 h, then it was filtered on celite. Removal of
the solvent afforded 8c. Crystals of 8c suitable for X-ray analysis
were obtained by a CH2Cl2 solution layered with diethyl ether, at
ꢀ20 °C.
8b (yield: 86%). Anal. Calc. for C26H27Cl2Fe2NO2S: C, 52.03; H,
4.53; N, 2.33. Found: C, 52.18; H, 4.46; N, 2.31%. IR (CH2Cl2)
m(CO) 1990 (vs), 1825 (s), m(CN) 1616 (m) cmꢀ1 1H NMR (CDCl3)
.
d 7.45–7.25 (3H, Me2C6H3); 5.58, 4.86 (s, 10H, Cp); 5.39, 5.15 (d,
3
2H, JHH = 11.7 Hz, CH2); 4.26 (s, 3H, CcMe); 3.59 (s, 3H, NMe);
9e (yield: 75%). Anal. Calc. for C90H90B2Fe4N2O4Se2: C, 64.86; H,
5.44; N, 1.68. Found: C, 64.93; H, 5.36; N, 1.60. IR (CH2Cl2): m(CO)
2.49, 2.01 (s, 6H, Me2C6H3). 13C{1H} NMR (CDCl3) d 250.5 (l-CO);
226.2 (Ca); 213.6 (CO); 209.7 (Cc); 140.4 (Cipso Xyl); 133.8–128.7
(Carom); 92.0, 89.1 (Cp); 66.7 (Cb); 50.1 (CH2Cl); 49.3 (NMe); 39.8
(CcMe); 17.7, 17.4 (Me2C6H3).
1994 (vs), 1819 (s), m(CaN) 1673 (m) cmꢀ1 1H NMR (CD3CN) d
.
7.30–6.86 (46H, Me2C6H3 and BPh4); 5.36, 5.10 (s, 20H, Cp); 4.21
(m, 4H, CcCH2); 3.83, 3.21 (s, 12H, NMe); 2.18, 1.78 (m, 8H,
CcCH2CH2CH2); 1.20 (m, 6H, CcCH2CH2CH2CH3). 13C{1H} NMR
(CD3CN) d 253.6 (l-CO); 220.8 (Ca); 214.5 (Cc); 210.0 (CO); 164.1
(Cipso BPh4); 136.0–117.6 (BPh4); 91.6, 89.0 (Cp); 68.0 (Cb); 50.6,
45.4 (NMe); 53.8, 37.6, 23.6, 13.8 (Bun).
8c (yield: 84%). Anal. Calc. for C43H41BClFe2NO2Se: C, 61.43; H,
4.92; N, 1.67. Found: C, 61.48; H, 4.84; N, 1.59%. IR (CH2Cl2)
m(CO) 1997 (vs), 1817 (s), m(CN) 1670 (m) cmꢀ1 1H NMR
.
(acetone-d6) d 7.36–6.79 (m, 20H, BPh4); 5.52, 5.15 (s, 10H, Cp);
2
5.30, 5.20 (d, 2H, JHH = 10.25 Hz, CH2Cl); 4.16 (s, 3H, CcMe); 3.92,
3.30 (s, 6H, NMe). 13C{1H} NMR (acetone-d6) d 254.2 (l-CO);
220.9 (Ca) 209.9 (CO); 208.9 (Cc); 164.1 (Cipso Ph); 136.1, 126.0–
117.6 (Carom); 91.5, 88.9 (Cp); 58.3 (Cb); 48.9, 45.4 (NMe); 48.7
(CH2Cl); 40.2 (CcMe).
4.9. X-ray crystallography for 4a ꢁ H2O, 8c and 9e ꢁ CH3CN
Crystal data and collection details for 4a ꢁ H2O, 8c and
9e ꢁ CH3CN are reported in Table 4. The diffraction experiments

L. Busetto et al. / Journal of Organometallic Chemistry 693 (2008) 2383–2391
[4] (a) A. Erkkilä, I. Majander, P.M. Pihko, Chem. Rev. 107 (2007) 5416;
2391
were carried out on a Bruker Apex II diffractometer (for 4a ꢁ H2O,
8c) and on a Bruker SMART 2000 diffractometer (for 9e ꢁ CH3CN)
equipped with a CCD detector using Mo Ka radiation. Data were
corrected for Lorentz polarization and absorption effects (empirical
absorption correction SADABS) [25]. Structures were solved by direct
methods and refined by full-matrix least-squares based on all data
using F2 [26]. Non-H atoms were refined anisotropically, unless
otherwise stated. H-atoms were placed in calculated positions, ex-
cept H(1S) in 4a ꢁ H2O which was located in the Fourier map; con-
versely, it has not been possible to locate the H-atoms for the water
molecule. H-atoms 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. The Cp ligand
bound to Fe(2) in 8c is disordered. Disordered atomic positions
were split and refined using one occupancy parameter per disor-
dered group. The crystal structure of 8e ꢁ CH3CN displays some dis-
order, especially the moiety containing Fe(3) and Fe(4), where also
the two metal atoms are split into two positions. Moreover, also
the nBu group bound to C(13), the two Me-groups bound to N(2)
and the Cp bound to Fe(4) are disordered and have been split into
two positions. For each of these disordered groups an independent
occupancy parameter has been employed during refinement.
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We thank the Ministero dell’Università e della Ricerca Scientif-
ica e Tecnologica (M.U.R.) (project: ‘New strategies for the control
of reactions: interactions of molecular fragments with metallic
sites in unconventional species’) and the University of Bologna
for financial support.
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Appendix A. Supplementary material
CCDC 681321, 681319, and 681320 contain the supplementary
crystallographic data for 4a, 8c, and 9e. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
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