Functionalized ferrocenes from [3 + 2] cycloadditions in bridging vinylalkylidene diiron complexes

Article abstract of DOI:10.1021/om9002472

Reactions of the vinylalkylidene complexes [Fe₂{μ- η¹:η³-CRCHCH(NMe₂)}(μ-CO)(CO)(Cp) ₂](R) SiMe₃, 1a; Tol, 1b; CO₂Me, 1c, Tol) 4-MeC₆H₄) with HC t CR′ (R′)

Full text of DOI:10.1021/om9002472

Organometallics 2009, 28, 3465–3472
3465
Functionalized Ferrocenes from [3+2] Cycloadditions in Bridging
Vinylalkylidene Diiron Complexes
Luigi Busetto,† Fabio Marchetti,‡,§ Rita Mazzoni,† Mauro Salmi,† Stefano Zacchini,† and
Valerio Zanotti*,†
Dipartimento di Chimica Fisica e Inorganica, UniVersita` di Bologna, Viale Risorgimento 4, 40136
Bologna, Italy, and Dipartimento di Chimica e Chimica Industriale, UniVersita` di Pisa,
Via Risorgimento 35, I-56126 Pisa, Italy
ReceiVed March 31, 2009
Reactions of the vinylalkylidene complexes [Fe2{µ-η1:η3-CRCHCH(NMe2)}(µ-CO)(CO)(Cp)2] (R )
SiMe3, 1a; Tol, 1b; CO2Me, 1c, Tol ) 4-MeC6H4) with HCt CR′ (R′ ) CPh2OH, CO2Me, Ph) lead to
the formation of a mixture of 1,3-disubstituted ferrocenes [1-R-3-R′-Fc] (5, 7, 9, 11) and 1,2,4-trisubstituted
ferrocenes [1-NMe2-2-R′-4-R-Fc] (4, 6, 8, 10) (R ) SiMe3, R′ ) CPh2OH, 4 and 5; R ) SiMe3, R′ )
CO2Me, 6 and 7; R ) SiMe3, R′ ) Ph, 8 and 9; R ) Tol, R′ ) CPh2OH, 10 and 11). The polysubstituted
Cp ring of the ferrocenyl products results from the cycloaddition of the alkyne with the bridging
vinylalkylidene ligand and involves the cleavage of one of the two substituents (H or NMe2) on the vinyl
moiety, as well as of the Fe-Fe bond. The cycloaddition reaction has been extended to a variety of
bridging vinylalkylidene diiron complexes with different substituents and functionalities on the C3 bridging
ligand, and to different alkynes. Thus, the vinylalkylidene complex 1b reacts with HCt CPh, yielding a
mixture of four different ferrocenes, due to the absence of regioselectivity in the alkyne cycloaddition:
[1-NMe2-2-Ph-4-Tol-Fc] (12), [1-Tol-3-Ph-Fc] (13), [1-NMe2-3-Ph-4-Tol-Fc] (14), and [1-Tol-2-Ph-Fc]
(15). Conversely, the reactions with symmetric alkynes do not produce regioisomers: treatment of 1b
and 1c with R′Ct CR′ (R′ ) Et, Ph) affords a mixture of 1,2,3-trisubstituted ferrocenes [1-R-2-R′-3-R′-
Fc] (17, 19, 21, 23) and tetrasubstituted ferrocenes [1-NMe2-2-R′-3-R′-4-R-Fc] (16, 18, 20, 22) (R )
SiMe3, R′ ) Et, 16 and 17; R ) Tol, R′ ) Et, 18 and 19; R ) Tol, R′ ) Ph, 20 and 21; R ) CO2Me,
R′ ) Ph, 22 and 23).
Likewise, the vinylalkylidene complexes [Fe2{µ-η1:η3-C(X)CHCH(R)}(µ-CO)(CO)(Cp)2] (R ) CO2Me,
X ) NMe2, 2a; R ) CN, X ) NMe2, 2b; R ) CO2Me, X ) SMe, 3a; R ) CN, X ) SMe, 3b) react
with alkynes HCt CR′ (R′ ) Tol, Ph), yielding a mixture of trisubstituted ferrocenes [1-X-2-R′-4-R-Fc]
(24, 26, 28) and [1-X-3-R′-4-R-Fc] (25, 27, 29) (X ) NMe2, R ) CO2Me, R′ )Tol, 24 and 25; X )
NMe2, R ) CN, R′ )Tol, 26 and 27; X ) SMe, R ) CO2Me, R′ ) Ph, 28 and 29). Finally, the reactions
of 2a and 3b with PhCt CPh afford the tetrasubstituted ferrocenes 22 and [1-SMe-2-Ph-3-Ph-4-CN-Fc]
(30), respectively. The crystal structures of 4 and 11 have been determined by X-ray diffraction studies.
laborious and in some cases ineffective. In particular, the
syntheses of ferrocenes in which only one of the two Cp rings
contains different substituents3 or the introduction of some
specific functionalities (e.g., amino groups) remains difficult,
in spite of some improvements.4
Introduction
Ferrocene-containing compounds continue to attract consider-
able interest, largely due to applications in catalysis and material
science.1 The design of new and more efficient unsymmetrical
ferrocenyl ligands or of novel ferrocene-based molecular
architectures requires access to ferrocene complexes with
appropriate substituent groups on the cyclopentadienyl ring.2
This might represent a challenge, in that common synthetic
methods based upon lithiation of the Cp ring followed by
substitutions, functionalizations, and modifications are rather
Alternative synthetic methods remain largely unexplored
despite the fact that a number of metal-mediated [3+2]
cycloadditions are well known5 which should, in theory, provide
more direct routes to the formation of substituted cyclopenta-
(3) (a) Stoll, A. H.; Mayer, P.; Knochel, P. Organometallics 2007, 26,
6694–6697. (b) Wang, Y.; Weissensteiner, W.; Spindler, F.; Arion, V. B.;
Mereiter, K. Organometallics 2007, 26, 3530–3540. (c) Christophe, P.;
Odell, B.; Brown, J. M. Chem. Commun. 2004, 598–599. (d) Steurer, M.;
Tiedl, K.; Wang, Y.; Weissensteiner, W. Chem. Commun. 2005, 4929–
4931.
(4) (a) Butler, D. C. D.; Richards, C. J. Organometallics 2002, 21, 5433–
5436. (b) van Leusen, D.; Hessen, B. Organometallics 2001, 20, 224–226.
(c) Metallinos, C.; Zaifman, J.; Dodge, L. Org. Lett. 2008, 10, 3527–3530.
(5) For reviews of transition-metal-mediated [3+2] cycloaddition see:
(a) Li, C. L.; Liu, R. S. Chem. ReV. 2000, 100, 3127–3161. (b) Welker,
M. E. Chem. ReV. 1992, 92, 97–112. (c) Wojcicki, A.; Shuchart, C. E.
Coord. Chem. ReV. 1990, 105, 35–60. (d) Rosenblum, M. J. Organomet.
Chem. 1986, 300, 191–218. (e) Fruehauf, H. W. Chem. ReV. 1997, 97, 523–
596.
* To whom correspondence should be addressed. E-mail:
valerio.zanotti@unibo.it.
† Universita` di Bologna.
‡ Universita` di Pisa.
§ Fabio Marchetti, born in 1974 in Bologna, Italy.
(1) For a comprehensive overview of ferrocene and other metallocenes
see: (a) Ferrocenes: Homogeneous Catalysis-Organic Synthesis-Materials
Science; Togni, A.; Hayashi, T., Eds.; Wiley-VCH: Weinheim, 1995. (b)
Metallocenes; Togni, A.; Halterman, R. L., Eds.; Wiley-VCH: Weinheim,
ˇ
1998. (c) Ferrocenes-Ligands Materials and Biomolecules; St`ıpnicˇka, P.,
Ed.; John Wiley & Sons: West Sussex, 2008.
(2) (a) Debroy, P.; Roy, S. Coord. Chem. ReV. 2007, 251, 203–221. (b)
Osakada, K.; Sakano, T.; Horie, M.; Suzaki, Y. Coord. Chem. ReV. 2006,
250, 1012–1022.
10.1021/om9002472 CCC: $40.75
2009 American Chemical Society
Publication on Web 05/13/2009

3466 Organometallics, Vol. 28, No. 12, 2009
Busetto et al.
Scheme 1
Scheme 2
dienyl ligands. Few examples are reported in which [3+2]6 or
[1+2+2]7 cycloadditions of coordinated ligands result in the
direct assembling of cyclopentadienyls bearing substituents and
functional groups. Even less investigated is the possibility that
functionalized cyclopentadienyl complexes might be directly
generated by assembling of bridging organic frames (C2 or C3
ligands), taking advantage of the activation effects due to
multisite coordination.8
We have been exploring the chemistry of bridging vinyla-
lkylidene (allylidene) diiron complexes and have described
synthetic methods for obtaining a variety of bridging C3 ligands
containing various functional groups distributed on the alky-
lidene carbon or on the vinyl end. Examples include the
complexes 1,9 2,10 and 311 (Scheme 1).
We were intrigued by the possibility that our functionalized
vinylalkylidene ligands might be involved in cycloaddition
reactions with alkynes, affording cyclopentadienes or cyclo-
pentadienyl ligands, incorporating the same functionalities.
Herein we report on these investigations that involved a range
of vinylalkylidene complexes with different substituents, as well
as a number of different alkynes, in order to elucidate possible
factors influencing the reaction course.
staggered conformation [mean relative rotations 24° and 23°
for 4 and 11, respectively].
The Fe-C interactions with the substituted C5 ring [average
2.048(6) and 2.041(7) Å for 4 and 11, respectively] are sensibly
longer than those with the unsubstituted Cp rings [average
2.038(7) and 2.034(7) Å for 4 and 11, respectively] and also
the C-C distances are elongated in the substituted rings [average
1.429(7) and 1.423(7) Å for 4 and 11, respectively] compared
to the nonsubstituted cyclopentadienyl rings [average 1.380(10)
and 1.391(10) Å for 4 and 11, respectively].
The N(1) atom in 4 is essentially sp3 hybridized, displaying
a strong pyramidalization [sum angles 335.1(3)°], and the
C(8)-N(1) interaction [1.439(3) Å] is essentially a single bond.
In fact, this bonding distance is very similar to the N-Me
interactions within the same molecule [N(1)-C(11) 1.461(3)
Å; N(1)-C(12) 1.461(3) Å]. The lone pair on N(1) is, therefore,
Results and Discussion
Cycloaddition Reactions of Bridging Enaminoalkylidene
Complexes. The bridging enaminoalkylidene complexes 1a and
1b react with primary alkynes HCt CR′ (R′ ) CPh2OH,
CO2Me, Ph) in toluene at reflux temperature, leading to the
formation of a mixture of substituted ferrocenes, as shown in
Scheme 2.
Separation of the ferrocene products was easily accomplished
by column chromatography, and all of the ferrocenyl complexes
4-11 were characterized by spectroscopy and elemental analy-
sis. Moreover, the molecular structures of 4 and 11 have been
determined by X-ray diffraction. The structures of 4 (Figure 1
and Table 1) and 11 (Figure 2 and Table 2) are those of typical
ferrocenes 1,2,4-trisubstituted and 1,3-disubstituted on one Cp
ring, respectively. The two Cp rings are almost parallel [angles
between the least-squares mean planes of the five-membered
rings are 3.5° and 3.3° for 4 and 11, respectively] and adopt a
Figure 1. ORTEP diagram of 4. All the hydrogens have been
omitted except H(50). Thermal ellipsoids are drawn at the 30%
probability level.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 4
Fe(1)-C5H2R3(av)
C(6)-C(7)
2.048(6)
1.423(3)
1.428(3)
1.423(3)
1.430(3)
1.440(3)
1.380(10)
1.529(3)
1.429(2)
109.87(17)
107.00(16)
108.06(17)
109.49(17)
105.57(16)
128.36(17)
124.52(17)
123.36(18)
Fe(1)-C5H5(av)
O(1)-H(50)
H(50) · · · N(1)
O(1) · · · N(1)
C(8)-N(1)
C(11)-N(1)
C(12)-N(1)
C(10)-Si(1)
2.038(7)
0.821(10)
2.027(15)
2.793(2)
1.439(3)
1.461(3)
1.461(3)
1.855(2)
(6) Lutsenko, Z. L.; Aleksandrov, G. G.; Petrovskii, P. V.; Shubina,
E. S.; Andrianov, V. G.; Struchkov, Yu. T.; Rubezhov, A. Z. J. Organomet.
Chem. 1985, 281, 349–364.
(7) (a) Carriedo, G. A.; Howard, J. A. K.; Lewis, D. B.; Lewis, G. E.;
Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1985, 905–912. (b) Van der
Heijden, H.; Gal, A. W.; Pasman, P.; Orpen, A. G. Organometallics 1985,
4, 1847–1853. (c) Morrow, J. R.; Templeton, J. L.; Bandy, J. A.; Bannister,
C.; Prout, C. K. Inorg. Chem. 1986, 25, 1923–1925.
(8) Blenkiron, P.; Breckenridge, S. M.; Taylor, N. J. A.; Carty, J.;
Pellinghelli, M. A.; Tiripicchio, A.; Sappa, E. J. Organomet. Chem. 1996,
506, 229–240.
(9) Albano, V. G.; Busetto, L.; Marchetti, F.; Monari, M.; Zacchini, S.;
Zanotti, V. Organometallics 2004, 23, 3348–3354.
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
C(10)-C(6)
C-C(av) in C5H5
C(7)-C(13)
C(13)-O(1)
C(7)-C(6)-C(10)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
C(8)-C(9)-C(10)
C(9)-C(10)-C(6)
C(6)-C(7)-C(13)
C(8)-C(7)-C(13)
C(7)-C(8)-N(1)
N(1)-C(8)-C(9)
C(6)-C(10)-Si(1)
C(9)-C(10)-Si(1)
C(8)-N(1)-C(11)
C(8)-N(1)-C(12)
C(11)-N(1)-C(12)
C(7)-C(13)-O(1)
O(1)-H(50) · · · N(1)
128.52(18)
128.62(15)
125.77(15)
111.41(18)
113.87(18)
109.8(2)
(10) Busetto, L.; Salmi, M.; Zacchini, S.; Zanotti, V. J. Organomet.
Chem. 2008, 693, 57–67.
(11) Busetto, L.; Marchetti, F.; Salmi, M.; Zacchini, S.; Zanotti, V. J.
Organomet. Chem. 2007, 692, 2245–2252.
109.38(15)
155(3)

Functionalized Ferrocenes from [3+2] Cycloadditions
Organometallics, Vol. 28, No. 12, 2009 3467
Scheme 3
The results reported in Scheme 2 went beyond the expected
release of the bridging vinylalkylidene ligand in the form of
five-membered cycloadducts. This latter possibility was sug-
gested by the fact that R,ꢀ-unsaturated alkylidene ligands are
known to undergo cyclization with alkynes, which, beside the
classical Do¨tz reaction, can afford cyclopentadienes as well as
other cycloadducts.12 In our case the [3+2] cyclization does
not lead to the release of the organic fragment, but rather it
produces its transformation into a cyclopentadienyl ring, which
remains coordinated to one Fe atom.
Figure 2. ORTEP diagram of 11. All the hydrogens have been
omitted except H(50). Thermal ellipsoids are drawn at the 30%
probability level.
Table 2. Selected Bond Distances (Å) and Angles (deg) of 11
Fe(1)-C5H3R2(av)
C(6)-C(7)
2.041(7)
1.422(3)
1.417(3)
1.429(3)
1.422(3)
1.423(3)
Fe(1)-C5H5(av)
C(6)-C(11)
2.034(7)
1.512(3)
1.443(2)
0.8200
C(7)-C(8)
C(11)-O(1)
C(8)-C(9)
O(1)-H(50)
C-C(av) in C5H5
C(9)-C(10)
1.391(10)
C(10)-C(6)
The reaction deserves further comments. First of all, the
observed ferrocene products are clearly the result of the
assembly of alkynes with the bridging vinylalkylidene ligands.
The bridging C3 frame can be easily recognized as a constituent
of the functionalized cyclopentadienyl ring, where it retains its
substituents except for those of the vinyl moiety. Therefore,
the bridging C3 ligands in 1a,b lose one of the two substituents:
H or NMe2, generating the trisubstituted (4, 6, 8, 10) and
disubstituted ferrocenes (5, 7, 9, 11), respectively. Both pos-
sibilities (C-H and C-N cleavage) take place, as indicated by
the composition of the reaction products, with a slight predomi-
nance of the C-N cleavage. Furthermore, the observed cy-
cloaddition reactions are regiospecific, in that the incorporation
of primary alkynes occurs selectively in one of the two possible
modes, affording cyclopentadienyls where the R′ group (R′ )
CPh2OH, CO2Me, Ph) is exclusively placed far from R (R )
SiMe3, Tol). The regioselectivity is presumably originated by
steric reasons and is due to the presence of rather hindered
substituents (R and R′) such as SiMe3 and CPh2OH. Indeed,
the reaction shown in Scheme 3, in which substituents on the
C3 bridging ligand and on the alkyne reagent are less sterically
demanding, does not exhibit the same regioselectivity, leading
to the formation of all four different isomers.
In this case separation of the isomeric mixture by column
chromatography was only partially achieved: 12 and 14 were
isolated from 13 and 15, but separation of the regioisomers was
incomplete.
An obvious strategy to reduce the number of reaction products
is to make use of symmetrically disubstituted alkynes, in order
to avoid the formation of regioisomers. However, this approach
led to the addition of a further substituent on the Cp ring of the
metallocene products and, consequently, might be less favorable
by steric reasons. This point has been investigated through the
reactions reported in Scheme 4.
C(7)-C(6)-C(10)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
C(8)-C(9)-C(10)
106.90(18)
108.65(18)
108.33(19)
106.75(18)
C(7)-C(6)-C(11)
C(10)-C(6)-C(11)
C(6)-C(11)-O(1)
C(9)-C(10)-C(6)
128.23(18)
124.75(18)
109.85(16)
109.36(18)
available for instance for the formation of hydrogen bonds. Thus,
a weak intramolecular hydrogen bond exists in 4 between the
-NMe2 and the -CPh2(OH) substituents [O(1)-H(50) 0.821(10)
Å, H(50) · · · N(1) 2.027(15) Å, O(1) · · · N(1) 2.793(2) Å,
O(1)-H(50)-N(1) 155(3)°].
In the case of 4, all the C(10)-Si(1) [1.855(2) Å], C(7)-C(13)
[1.529(3) Å], and C(13)-O(1) [1.429(2) Å] are essentially single
bonds, as well as C(6)-C(11) [1.512(3) Å] and C(11)-O(1)
[1.443(2) Å] in 11.
The NMR spectroscopic characterization of 4-11, based on
DEPT and NOE experiments and H,13C correlation measured
1
through gs-HSQC and gs-HMBC experiments, is consistent with
the structures found in the solid. The H NMR spectra show
1
the typical pattern of di- and trisubstituted ferrocene derivatives,
whereas the nonsubstituted Cp rings give rise to a singlet in
the range 4.20-3.90 ppm. Noteworthy, in the 1H NMR spectra
of 4, in CDCl3 solution, the two N-methyls give rise to a single
resonance. Their equivalence, on the NMR time scale, is
explained assuming an exchange mechanism that implies free
rotation around the Me2N-CCp bond and inversion at the N
atom. The exchange process takes place in spite of the hydrogen
bond interaction between the OH and NMe2, clearly evidenced
in the solid but also present in solution, as suggested by the
low-field resonance at 8.20 ppm attributable to the OH group.
1
Variable-temperature H NMR experiments suggested a low
activation barrier for this exchange process: complete coales-
cence of the signals due to the NMe2 occurred only at about
-75 °C, whereas two distinct resonances were observed at -90
°C (see Experimental Section).
The ferrocene complexes 4-11 have been also investigated
by electrochemical methods (see Experimental Section). Cyclic
voltammograms show reversible anodic peaks, which, in the
case of the dimethylamino ferrocenes, are at lower potentials
with respect to the ferrocene/ferricinium couple, in agreement
with the electron-donor character of the substituent.
As expected, increasing the number of sterically demanding
substituents makes the cyclization more difficult and reduces
the conversion yield, in particular when R ) SiMe3.
(12) Wu, Y.-T.; Flynn, B.; Schirmer, H.; Funke, F.; Mu¨ller, S.; Labahn,
T.; No¨tzel, M.; de Meijere, A. Eur. J. Org. Chem. 2004, 72, 4–748.

3468 Organometallics, Vol. 28, No. 12, 2009
Busetto et al.
Scheme 4
Scheme 6
leads to the formation of significant amounts of [Fe2(CO)4(Cp)2].
This has been ascertained by carrying out the reaction of 1a
with HCt CPh in a NMR tube, in toluene d8 at 105 °C, and by
monitoring the reaction during a 15 h period of time. Notewor-
thy, in this experiment we did not observe any intermediate
species: the progressive disappearance of the resonances of the
precursor was simply paralleled by the rising of signals due to
the ferrocene products. This evidence supports the hypothesis
that the rate-determining step consists in the creation of a vacant
coordination site by displacement of the vinyl coordination in
the first step of the reaction sequence.
Cycloaddition Reactions of Bridging Vinyl-Aminoalkylidene
and Vinyl-Thioalkylidene Complexes. Further investigations
concerned the complexes 2 and 3. The amino- alkylidene
complexes 2 differ from 1 in that the NMe2 group is placed on
the bridging alkylidene carbon, rather than on the vinyl moiety
of the bridging C3 chain. The structure of 3a is the same as 2a,
except for containing a SMe group in place of NMe2. Beside
these differences concerning the nature and position of the
substituents, all of the bridging ligands in 1, 2, and 3 exhibit
vinylalkylidene character and also react similarly with alkynes,
affording ferrocenyl products. Therefore, complexes 2 and 3
reacted with alkynes affording the ferrocene complexes 24-29
(Scheme 6).
Comparison with the reactions of 1a,b shown in Scheme 2
evidences that in this case the reaction is not regioselective,
and both regioisomers are formed in comparable amounts.
Conversely, the most remarkable aspect of the reactions of 2a,b
and 3a is that cycloaddition is chemoselective, and only the
C-H and not the C-R bond of the bridging ligands undergoes
cleavage. Consequently, the ferrocene products maintain, as
substituents, both functional groups that are present on the
bridging C3 ligand in the precursor complexes: the alkylidene
substituent (NMe2 or SMe) and the CO2Me or CN group. As
initially mentioned, this is a relevant point in consideration of
the fact that the introduction of several different functionalities,
including the NMe2 group, on the same Cp ring is hard to
accomplish by traditional methods, starting from unsubstituted
ferrocene. Indeed, none of the ferrocene complexes reported in
Scheme 6 have been previously synthesized.
Again, the use of symmetric alkynes, as shown in Scheme 7,
greatly simplifies the picture, leading to the formation of one
single product, which is a tetrasubstituted ferrocenyl complex.
The synthesis of 22 from 2a, shown in Scheme 7, should
be compared with the corresponding reaction of 1c with
PhCCPh (Scheme 4), which also yields 22, but in mixture
with the trisubstituted ferrocene 23. Noteworthy, complexes
1c and 2a are isomers: in theory, their interconversion should
be achieved by exchanging the position of the NMe2 and
CO2Me substituents. In spite of the similarities, their reactiv-
ity is significantly different, and only 2a exhibits a chemose-
lective character in the cyclization with alkynes. This
observation indicates that a proper choice of the substituents,
Scheme 5
The data so far collected are too limited to provide a realistic
picture of the reaction sequence that leads to the functionalized
ferrocenes. The mechanisms so far proposed for analogous
vinylalkylidene-alkyne-CO cyclization in mononuclear com-
plexes (e.g., the classical Do¨tz benzannulation) provide reason-
able suggestions, although there is only a limited overlap
between the chemistry of bridging and terminally bonded
alkylidenes. In particular, the benzannulation is supposed to
proceed via decarbonylation of the carbene complex precursor,
which is the rate-determining step. This allows alkyne coordina-
tion, immediately followed by insertion in the metal-carbene
bond.13 By analogy, the cyclization involving 1a-c might
proceed through the displacement of the vinyl coordination,
affording an unsaturated µ-η1:η1-vinylalkylidene intermediate,
which allows alkyne coordination and subsequent insertion.
Examples of alkyne insertion and coupling with bridging
vinylalkylidene ligands are known.14 They generally produce
the elongation of the bridging hydrocarbyl chain, which
maintains the bridging alkylidene character (Scheme 5).15
Multiple alkyne insertion (oligomerization) is possible, but the
formation of cyclization products is unusual.16
In the light of these considerations, the observed cyclization
leading to the substituted ferrocenes appears very unique in that,
to the best of our knowledge, it is the first example of cyclization
involving a bridging vinylalkylidene ligand, which affords a
polysubstituted cyclopentadienyl. A further unusual result is the
cleavage of the Fe-Fe bond with fragmentation of the parent
dinuclear species. The dinuclear Fe2CO2Cp2 frame is generally
very robust and remains intact, even supporting quite remarkable
transformations of bridging ligands. Exceptions are rare and
mostly involve the formation of metallacycles.17 The fragmenta-
tion produces a Fe and a C5H5 ring, which give rise to the
observed ferrocenes, whereas the residual part of the molecule,
which formally corresponds to XFe(CO)2Cp (X ) NMe2, H),
(13) Do¨tz, K. H.; Tomuschat, P. Chem. Soc. ReV. 1999, 28, 187–198.
(14) (a) Levisalles, J.; Rose-Munch, F.; Rudler, H.; Daran, J. C.;
Dromzee, Y.; Jeannin, Y.; Ades, D.; Fontanille, M. J. Chem. Soc., Chem.
Commun. 1981, 20, 1055–1057. (b) Green, M.; Orpen, A. G.; Schaverien,
C. J.; Williams, I. D. J. Chem. Soc., Chem. Commun. 1983, 4, 181–183.
(15) Adams, P. Q.; Davies, D. L.; Dyke, A. F.; Knox, S. A. R.; Mead,
K. A.; Woodward, P. J. Chem. Soc., Chem. Commun. 1983, 222–224.
(16) Green, M.; Mercer, R. J.; Orpen, A. G.; Schaverien, C. J.; Williams,
I. D. J. Chem. Soc., Dalton Trans. 1986, 1971–1982.
(17) (a) Busetto, L.; Marchetti, F.; Zacchini, S.; Zanotti, V. Organo-
metallics 2006, 25, 4808–4816. (b) Busetto, L.; Marchetti, F.; Zacchini,
S.; Zanotti, V. Organometallics 2005, 2, 2297–2306.

Functionalized Ferrocenes from [3+2] Cycloadditions
Organometallics, Vol. 28, No. 12, 2009 3469
Scheme 7
Scheme 8
in terms of their nature and position on the bridging
vinylalkylidene ligand, should provide the key to selectively
conduct these cycloaddition reactions.
EA instrument. ESI-MS spectra were recorded on a Waters
Micromass ZQ 4000 with samples dissolved in CH3CN. All
NMR measurements were performed on a Varian Mercury Plus
400 instrument. The chemical shifts for 1H and 13C were
referenced to internal TMS. The spectra were fully assigned via
DEPT experiments and 1H,13C correlation measured through gs-
HSQC and gs-HMBC experiments.19 Unless otherwise stated,
NMR spectra were recorded at 298 K. For the isomers 12-14,
24-25, 26-27, and 28-29, not fully separated by chromatog-
raphy, yields have been determined by integration of the NMR
signals. NOE measurements were recorded using the DPFGSE-
NOE sequence.20 NMR resonances are indicated according to
the numbering scheme shown hereafter (Scheme 8). All the
reagents were commercial products (Aldrich) of the highest
purity available and used as received. [Fe2(CO)4(Cp)2] was
purchased from Strem and used as received. Compounds 1a-c,9
2a,b,10 and 3a,b11 were prepared by published methods.
Conclusions
Our results indicate that the [3+2] cycloaddition of R,ꢀ-
unsaturated carbene ligands with alkynes can be extended to
bridging vinylalkylidenes in diiron complexes. The reaction
leads to the formation of ferrocenes and has a general character,
in that it tolerates different substituents and functional groups
on both bridging vinylalkylidenes and alkyne reagents. In most
of the cases, the nonselective cleavage of one of the two vinyl
substituents on the bridging C3 ligand, occurring along with the
cyclization, gives rise to a mixture of disubstituted and trisub-
stituted ferrocenyl products. Further isomers are generated due
to the lack of regiocontrol in the cycloaddition of primary
alkynes. However, in other cases, where the cycloaddition
reaction is chemoselective and is associated with use of
symmetric alkynes, it leads to the formation of one single
ferrocenyl product.
These results also suggest that a new and more direct
approach to the formation of polyfunctionalized ferrocenes is
possible. The limitations due to the absence of a complete
chemo- and regiocontrol of the reaction and the use of rather
“sophisticated” bridging vinylalkylidene complexes as precur-
sors would be compensated by the direct formation of ferrocenes
characterized by the presence of two or three different substit-
uents in only one of the two cyclopentadienyls. Indeed,
ferrocenes of this type are difficult to obtain, and to the best of
our knowledge, none of the ferrocene complexes herein reported
have been previously synthesized, with the exception of an
isomeric form of complex 7, in which the two ring substituents
are in adjacent position.18
Synthesis of [1-SiMe3-3-CPh2OH-Fc] (5) and [1-NMe2-2-CPh2OH-
4-SiMe3-Fc] (4). To a solution of 1a (400 mg, 0.883 mmol), in
toluene (20 mL), was added HCt CCPh2OH (184 mg, 0.883 mmol).
The resulting solution was stirred at reflux temperature for 16 h,
then was allowed to cool to room temperature and filtered on a
Celite pad. Solvent removal and chromatography of the residue on
a SiO2 column with petroleum ether (bp 40-60 °C) as eluent gave
first a yellow-orange fraction, corresponding to 5. Yield: 210 mg,
54%. Anal. Calcd for C26H28FeOSi: C, 70.90; H, 6.41. Found: C,
70.79; H, 6.35. 1H NMR (CDCl3) (see numbering scheme):
7.84-7.18 (m, 10H, C6H5), 4.16 (m, 2H, C4H and C5H), 4.12 (s,
4
5H, Cp), 3.99 (t, 1H, JHH ) 1.30 Hz, C2H), 3.40 (s, 1H, OH),
0.22 (s, 9H, SiMe3). 13C NMR (CDCl3): 147.4, 147.3 (Cipso Ph),
137.8-126.9 (Carom), 101.9 (C3), 77.8 (CPh2OH), 73.3 (C1), 73.1,
72.0 (C4 and C5), 72.9 (C2), 68.9 (Cp), 1.24 (SiMe3). ESI-MS (ES+):
441 m/z [M+].
A second orange-red fraction, corresponding to 4, was collected
by using diethyl ether as eluent. Yield: 141 mg, 33%. Anal. Calcd
for C28H33FeNOSi: C, 69.56; H, 6.88; N, 2.90. Found: C, 69.48;
H, 6.80; N, 2.92. 1H NMR (CDCl3): 8.20 (s, 1H, OH), 7.84-7.10
Experimental Section
4
(m, 10H, C6H5), 4.06 (d, 1H, JHH ) 1.30 Hz, C5H), 4.03 (s, 5H,
Cp), 3.82 (d, 1H, 4JHH ) 1.30 Hz, C3H), 2.35 (s, 6H, NMe2), 0.23
(s, 9H, SiMe3). 13C NMR (CDCl3): 146.3 (Cipso Ph), 137.8-126.2
(Carom), 112.5 (C1), 94.4 (C2), 78.4 (CPh2OH), 70.2 (Cp), 70.0 (C3),
67.9 (C4), 62.0 (C5), 46.8 (NMe2), 0.12 (SiMe3). ESI-MS (ES+):
484 m/z [M+]. 1H NMR (CD2Cl2, 183 K): 9.27 (s, 1H, OH),
7.70-7.02 (m, 10H, C6H5), 4.05 (br s, 1H, C5H), 3.85 (s, 5H, Cp),
General Data. 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 SiO2. Glassware was oven-dried
before use. Infrared spectra were recorded at 298 K on a Perkin-
Elmer Spectrum 2000 FT-IR spectrophotometer, and elemental
analyses were performed on a ThermoQuest Flash 1112 Series
(19) Wilker, W.; Leibfritz, D.; Kerssebaum, R.; Beimel, W. Magn.
Reson. Chem. 1993, 31, 287–292.
(18) Metallinos, C.; Szillat, H.; Taylor, N. J.; Snieckus, V. AdV. Synth.
Catal. 2003, 345, 370–382.
(20) Stott, K.; Stonehouse, J.; Keeler, J.; Hwang, T. L.; Shaka, A. J.
J. Am. Chem. Soc. 1995, 117, 4199–4200.

3470 Organometallics, Vol. 28, No. 12, 2009
Busetto et al.
3.72 (br s, 1H, C3H), 2.51 (s, 3H, NMe), 1.59 (s, 3H, NMe), 0.13
(s, 9H, SiMe3). Crystals of 4, suitable for X-ray analysis, were
obtained by slow evaporation of a CH2Cl2 solution.
(CDCl3) 139.1 (Cipso Ph), 135.9 (Cipso Tol), 130.4-126.5 (Carom), 111.2
(C1), 86.4 (C2), 81.8 (C4), 71.6 (C5), 70.4 (Cp), 65.2 (C3), 45.1
(NMe2), 21.5 (C6H4Me).
[1-Tol-3-Ph-Fc] (13). Yield: 32%. Anal. (sample containing a
mixture of the isomers 13 and 15) Calcd for C23H20Fe: C, 78.39;
Complexes 6 and 7 were prepared following the same
proceduredescribedfor4and5, byreacting1awithHCt CCO2Me.
[1-NMe2-2-CO2Me-4-SiMe3-Fc] (6). Yield: 31%. Anal. Calcd for
C17H25FeNO2Si: C, 56.81; H, 7.02; N, 3.90. Found: C, 56.87; H,
1
H, 5.72. Found: C, 78.33; H, 5.70. H NMR (CDCl3): 7.61-7.14
(m, 9H, Ph and C6H4Me), 5.16 (t, 1H, 4JHH ) 1.48 Hz, C2H), 4.81
4
(t, 2H, JHH ) 1.48 Hz, C4H and C5H), 3.96 (s, 5H, Cp), 2.39 (s,
1
4
6.99; N, 3.90. H NMR (CDCl3): 4.48 (d, 1H, JHH ) 1.64 Hz,
3H, C6H4Me). 13C NMR (CDCl3): 139.0 (Cipso Ph), 135.7 (Cipso Tol),
129.1-126.0 (Carom), 86.9 (C3), 86.3 (C1), 71.4 (Cp), 67.3, 67.2
(C4 and C5), 65.2 (C2), 21.4 (C6H4Me).
4
C3H), 4.10 (s, 5H, Cp), 4.02 (d, 1H, JHH ) 1.64 Hz, C5H), 3.72
(s, 3H, CO2Me), 2.62 (s, 6H, NMe2), 0.13 (s, 9H, SiMe3). 13CNMR
(CDCl3): 171.7 (CO2Me), 117.9 (C1), 74.0 (C3), 73.3 (C2), 69.6
(Cp), 69.0 (C4), 64.4 (C5), 51.6 (CO2Me), 45.1 (NMe2), -1.01
(SiMe3).
[1-NMe2-3-Ph-4-Tol-Fc] (14). Yield: 9%. 1H NMR (CDCl3):
7.88-7.08 (m, 9H, Ph and C6H4Me), 4.84 (d, 1H, 4JHH ) 1.30 Hz,
4
C2H); 4.28 (d, 1H, JHH ) 1.30 Hz, C5H), 3.99 (s, 5H, Cp), 2.72
[1-SiMe3-3-CO2Me-Fc] (7). Yield: 47%. Anal. Calcd for
(s, 6H, NMe2), 2.41 (s, 3H, C6H4Me). 13C NMR (CDCl3): 139.4
(Cipso Ph), 136.0 (Cipso Tol), 131.4-126.1 (Carom), 113.3 (C1), 86.9
(C3), 81.4 (C4), 71.5 (Cp), 67.4 (C2), 57.4 (C5), 41.9 (NMe2), 21.4
(C6H4Me).
1
C15H20FeO2Si: C, 56.95; H, 6.38. Found: C, 56.89; H, 6.41. H
3
4
NMR (CDCl3): 4.93 (dd, 1H, JHH ) 2.40 Hz, JHH ) 1.24 Hz,
C4H), 4.74 (t, 1H, JHH ) 1.24 Hz, C2H), 4.31 (dd, 1H, JHH
)
4
3
2.40 Hz, JHH ) 1.24 Hz, C5H), 4.16 (s, 5H, Cp), 3.81 (s, 3H,
CO2Me), 0.24 (s, 9H, SiMe3). 13CNMR (CDCl3): 172.2 (CO2Me),
76.1 (C5), 75.3 (C2), 73.9 (C3), 72.8 (C4), 70.1 (Cp), 68.9 (C1),
51.8 (CO2Me), 0.23 (SiMe3).
4
1
[1-Tol-2-Ph-Fc] (15). Yield: 8%. H NMR (CDCl3): 7.61-7.14
3
(m, 9H, Ph and C6H4Me), 4.57 (t, 2H, JHH ) 2.36 Hz, C3H and
C5H), 4.39 (t, 1H, 3JHH ) 2.36 Hz, C4H),4.13 (s, 5H, Cp), 2.37 (s,
3H, C6H4Me). 13C NMR (CDCl3) 139.5 (Cipso Ph), 135.8 (Cipso Tol),
129.8-125.9 (Carom), 88.7 (C2), 86.3 (C1); 71.2 (Cp); 70.4 (C3 and
C5), 67.6 (C4), 21.1 (C6H4Me).
Complexes 8 and 9 were prepared following the same procedure
described for 4-5, by reacting 1a with HCt CPh.
[1-NMe2-2-Ph-4-SiMe3-Fc] (8). Yield: 28%. Anal. Calcd for
C21H27FeNSi: C, 66.82; H, 7.22; N, 3.71. Found: C, 66.77; H, 7.25;
N, 3.68. 1H NMR (CDCl3): 7.73-7.18 (m, 5H, C6H5), 4.20 (d, 1H,
Complexes 16 and 17 were prepared following the same
procedure described for 4 and 5, by reacting 1a with EtCt CEt.
[1-NMe2-2-Et-3-Et-4-SiMe3-Fc] (16). Yield: 21%. Anal. Calcd
for C19H31FeNSi: C, 63.84; H, 8.75; N, 3.92. Found: C, 63.91; H,
4
4JHH ) 1.28 Hz, C3H), 4.16 (s, 5H, Cp), 4.05 (d, 1H, JHH ) 1.28
Hz, C5H), 2.58 (s, 6H, NMe2), 0.28 (s, 9H, SiMe3). 13CNMR
(CDCl3): 139.4 (Cipso Ph), 128.7, 127.1, 125.1 (Ph), 115.0 (C1), 87.3
(C2), 72.4 (C3), 69.6 (Cp), 65.2 (C4), 62.8 (C5), 44.8 (NMe2), 1.02
(SiMe3).
1
8.69; N, 3.96. H NMR (CDCl3): 3.99 (s, 5H, Cp), 3.68 (s, 1H,
C5H), 2.63 (s, 6H, NMe2), 2.86-1.95 (m, 4H, CH2CH3), 1.26-0.86
(m, 6H, CH2CH3), 0.27 (s, 9H, SiMe3). 13C NMR (CDCl3): 112.9
(C1), 84.9, 84.0 (C2 and C3), 69.8 (Cp), 63.5 (C4), 61.1 (C5), 45.8
(NMe2), 22.3 (CH2CH3), 20.4 (CH2CH3), 17.9 (CH2CH3), 15.9
(CH2CH3), 1.5 (SiMe3).
[1-SiMe3-3-Ph-Fc] (9). Yield: 59%. Anal. Calcd for C19H22FeSi:
1
C, 68.25; H, 6.64. Found: C, 68.19; H, 6.66. H NMR (CDCl3):
3
4
7.57-7.20 (m, 5H, C6H5), 4.84 (dd, 1H, JHH ) 2.36 Hz, JHH
)
1.24 Hz, C4H), 4.61 (t, 1H, JHH ) 1.28 Hz, C2H), 4.28 (dd, 1H,
4
[1-SiMe3-2-Et-3-Et-Fc] (17). Yield: 30%. Anal. Calcd for
C17H26FeSi: C, 64.94; H, 8.34. Found: C, 64.87; H, 8.41. 1H NMR
3JHH ) 2.36 Hz, JHH ) 1.26 Hz, C5H), 4.04 (s, 5H, Cp), 0.32 (s,
4
3
(CDCl3): 4.22 (d, 1H, JHH ) 2.48 Hz, C4H), 4.01 (s, 5H, Cp),
9H, SiMe3). 13CNMR (CDCl3): 139.3 (Cipso Ph), 128.6, 126.4, 126.2
(Ph), 88.5 (C3), 74.0 (C5), 73.6 (C1), 71.5 (C2), 70.1 (Cp), 69.5
(C4), 0.05 (SiMe3).
3
3.90 (d, 1H, JHH ) 2.48 Hz, C5H), 2.81-1.99 (m, 4H, CH2CH3),
1.25-0.92 (m, 6H, CH2CH3), 0.30 (s, 9H, SiMe3). 13C NMR
(CDCl3): 94.1, 92.9 (C2 and C3), 71.6 (C4), 69.9 (C5), 69.6 (Cp),
67.8 (C1), 22.7 (CH2CH3), 21.3 (CH2CH3), 17.4 (CH2CH3), 15.4
(CH2CH3), 1.3 (SiMe3).
Complexes 10 and 11 were prepared following the same
procedure described for 4 and 5, by reacting 1b with HCt CCPh2OH.
[1-NMe2-2-CO2Me-4-Tol-Fc] (10). Yield: 37%. Anal. Calcd for
C32H31FeNO: C, 76.65; H, 6.23; N, 2.79. Found: C, 75.58; H, 6.30;
N, 2.82. 1H NMR (CDCl3): 8.06 (s, 1H, OH), 7.64-7.24 (m, 14H,
Complexes 18 and 19 were prepared following the same
procedure described for 4 and 5, by reacting 1b with EtCt CEt.
[1-NMe2-2-Et-3-Et-4-Tol-Fc] (18). Yield: 35%. Anal. Calcd for
C23H29FeN: C, 73.57; H, 7.79; N, 3.73. Found: C, 73.49; H,
4
C6H5 and C6H4Me), 4.68 (d, 1H, JHH ) 1.60 Hz, C5H), 4.38 (d,
4
1H, JHH ) 1.60 Hz, C3H), 3.89 (s, 5H, Cp), 2.41 (s, 6H, NMe2);
1
2.32 (s, 3H, C6H4Me). 13CNMR (CDCl3): 146.3 (Cipso Ph),
137.8-125.9 (Ph), 110.2 (C1), 93.0 (C2), 81.0 (C4), 78.4 (CPh2OH),
71.9 (Cp), 63.7 (C3), 56.0 (C5), 47.0 (NMe2), 21.4 (C6H4Me). ESI-
MS (ES+): 502 m/z [M+].
7.85; N, 3.68. H NMR (CDCl3): 7.46-7.08 (m, 4H, C6H4Me),
4.14 (s, 1H, C5H), 3.98 (s, 5H, Cp), 2.67 (s, 6H, NMe2), 2.34
(s, 3H, C6H4Me), 2.78-2.22 (m, 4H, CH2CH3), 1.19 (t, 3H, 3JHH
3
) 7.60 Hz, CH2CH3), 1.01 (t, 3H, JHH ) 7.60 Hz, CH2CH3).
13C NMR (CDCl3): 136.7-128.8 (Carom), 111.5 (C1), 84.5, 81.5
(C2 and C3), 81.0 (C4), 71.0 (Cp), 57.4 (C5), 45.7 (NMe2), 21.4
(C6H4Me), 20.3 (CH2CH3), 20.1 (CH2CH3), 16.4 (CH2CH3), 15.6
(CH2CH3).
[1-SiMe3-3-CO2Me-Fc] (11). Yield: 48%. Anal. Calcd for
C30H26FeO: C, 78.61; H, 5.72. Found: C, 78.55; H, 5.70. 1H NMR
(CDCl3): 7.37-7.07 (m, 14H, C6H5 and C6H4Me), 4.74 (dd, 1H,
4
4
3JHH ) 2.56 Hz, JHH ) 1.60 Hz, C5H), 4.53 (t, 1H, JHH ) 1.60
Hz, C2H), 4.16 (dd, 1H, JHH ) 2.56 Hz, JHH ) 1.60 Hz, C4H),
4.01 (s, 5H, Cp), 3.43 (s, 1H, OH), 2.32 (s, 3H, C6H4Me). 13C NMR
(CDCl3): 146.9, 146.8 (Cipso Ph), 134.9-125.9 (Ph), 100.0 (C3), 85.8
(C1), 77.5 (CPh2OH), 70.3 (Cp), 69.2 (C4), 66.8 (C2), 66.0 (C5),
21.1 (C6H4Me). ESI-MS (ES+): 459 m/z [M+].
3
4
[1-Tol-2-Et-3-Et-Fc] (19). Yield: 37%. Anal. Calcd for
C21H24Fe: C, 75.88; H, 7.28. Found: C, 75.79; H, 7.30. 1H NMR
(CDCl3): 7.50-7.12 (m, 4H, C6H4Me), 4.27 (d, 1H, 3JHH ) 2.50
3
Hz, C4H), 4.00 (s, 5H, Cp), 3.90 (d, 1H, JHH ) 2.50 Hz, C5H),
2.39 (s, 3H, C6H4Me), 2.80-2.24 (m, 4H, CH2CH3), 1.31-1.00
(m, 6H, CH2CH3). 13C NMR (CDCl3): 136.5-129.0 (Carom), 91.6,
90.4 (C2 and C3), 84.2 (C1), 70.9 (Cp), 70.5 (C4), 66.4 (C5),
21.7 (C6H4Me), 21.4 (CH2CH3), 20.4 (CH2CH3), 16.4 (CH2CH3),
15.3 (CH2CH3).
Complexes 12-15 were prepared following the same procedure
described for 4 and 5, by reacting 1b with HCt CPh.
[1-NMe2-2-Ph-4-Tol-Fc] (12). Yield: 28%. Anal. (sample con-
taining a mixture of the isomers 12 and 14) Calcd for C25H25FeN:
1
C, 75.92; H, 6.38; N, 3.54. Found: C, 75.85; H, 6.43; N, 3.60. H
Complexes 20 and 21 were prepared following the same
procedure described for 4 and 5, by reacting 1b with PhCt CPh.
[1-NMe2-2-Ph-3-Ph-4-Tol-Fc] (20). Yield: 29%. Anal. Calcd for
C31H29FeN: C, 78.95; H, 6.20; N, 2.97. Found: C, 79.02; H, 6.13;
NMR (CDCl3): 7.88-7.08 (m, 9H, Ph and C6H4Me), 5.19 (d, 1H,
4
4JHH ) 1.24 Hz, C3H), 4.23 (s, 5H, Cp); 4.10 (d, 1H, JHH ) 1.24
Hz, C5H), 2.64 (s, 6H, NMe2), 2.39 (s, 3H, C6H4Me). 13C NMR

Functionalized Ferrocenes from [3+2] Cycloadditions
Organometallics, Vol. 28, No. 12, 2009 3471
N, 2.94. 1H NMR (CDCl3): 7.80-7.09 (m, 14H, Ph and C6H4Me),
4.16 (s, 1H, C5H), 4.01 (s, 5H, Cp), 2.66 (s, 6H, NMe2), 2.34 (s,
3H, C6H4Me). 13C NMR (CDCl3): 139.1-126.0 (Carom), 112.5 (C1),
87.0, 86.4 (C2 and C3), 80.9 (C4), 70.6 (Cp), 58.0 (C5), 44.9 (NMe2),
21.7 (C6H4Me).
Table 3. Crystal Data and Experimental Details for 4 and 11
4
11
formula
fw
C28H33FeNOSi
483.49
C30H26FeO
458.36
T, K
293(2)
293(2)
[1-Tol-2-Ph-3-Ph-Fc] (21). Yield: 36%. Anal. Calcd for C29H24Fe:
λ, Å
0.71073
monoclinic
P21/c
12.1178(7)
10.9715(7)
19.5293(12)
90
103.5860(10)
90
2523.8(3)
4
0.71073
triclinic
P1
1
cryst syst
space group
a, Å
C, 81.29; H, 5.65. Found: C, 81.40; H, 5.61. H NMR (CDCl3):
j
3
7.66-7.10 (m, 14H, Ph and C6H4Me), 4.40 (d, 1H, JHH ) 2.36
10.3008(9)
10.6616(9)
11.2231(10)
89.3930(10)
73.7160(10)
73.6680(10)
1132.25(17)
2
3
Hz, C4H), 4.15 (d, 1H, JHH ) 2.36 Hz, C5H), 3.99 (s, 5H, Cp),
b, Å
c, Å
2.36 (s, 3H, C6H4Me). 13C NMR (CDCl3): 138.9-125.7 (Carom),
89.8, 89.5 (C2 and C3), 84.5 (C1), 71.3 (Cp), 69.9 (C4), 66.8 (C5),
21.0 (C6H4Me).
R, deg
ꢀ, deg
γ, deg
Complexes 22 and 23 were prepared following the same
procedure described for 4 and 5, by reacting 1c with PhCt CPh.
[1-NMe2-2-Ph-3-Ph-4-CO2Me-Fc] (22). Yield: 30%. Anal. Calcd
for C26H25FeNO2: C, 71.05; H, 5.74; N, 3.19. Found: C, 71.12; H,
5.68; N, 3.26. 1H NMR (CDCl3): 7.70-7.02 (m, 10H, Ph), 4.84 (s,
1H, C5H), 4.39 (s, 5H, Cp), 3.69 (s, 3H, CO2Me), 2.47 (s, 6H,
NMe2). 13C NMR (CDCl3): 172.8 (CO2Me), 133.5-126.4 (Carom),
113.8 (C1), 91.9, 90.4 (C2 and C3), 71.6 (Cp), 62.4 (C4), 59.6 (C5),
51.2 (CO2Me), 44.1 (NMe2).
cell volume, Å3
Z
Dc, g cm-3
µ, mm-1
F(000)
cryst size, mm
1.272
0.665
1024
1.344
0.686
480
0.22 × 0.15 ×
0.22 × 0.16 ×
0.12
0.14
θ limits, deg
reflns collected
indep reflns
1.73-28.00
28 477
6007
1.90-27.00
12 690
4902
[1-CO2Me-2-Ph-3-Ph-Fc] (23). Yield: 32%. Anal. Calcd for
[Rint ) 0.0367]
6007/1/297
1.023
[Rint ) 0.0266]
4902/198/291
1.034
0.0386
0.0977
C24H20FeO2: C, 72.71; H, 5.09. Found: C, 72.63; H, 5.15. 1H NMR
data/restraints /params
goodness on fit on F2
R1 (I > 2σ(I))
3
(CDCl3): 7.56-7.20 (m, 10H, Ph), 4.89 (d, 1H, JHH ) 2.64 Hz,
3
C4H), 4.77 (d, 1H, JHH ) 2.64 Hz, C5H), 4.31 (s, 5H, Cp), 3.60
0.0368
0.0996
(s, 3H, CO2Me). 13C NMR (CDCl3): 174.3 (CO2Me), 133.6-126.2
(Carom), 90.5, 89.9 (C2 and C3), 73.6 (Cp), 71.8, 71.4 (C4 and C5),
63.0 (C1), 51.0 (CO2Me).
wR2 (all data)
largest diff peak and hole, e Å-3 0.302/-0.179
0.256/-0.208
1
C19H18FeO2S: C, 62.31; H, 4.95. Found: C, 62.15; H, 4.88. H
Complexes 24 and 25 were prepared following the same
procedure described for 4 and 5, by reacting 2a with HCt CTol.
[1-NMe2-2-Tol-4-CO2Me-Fc] (24). Yield: 30%. Anal. (sample
containing a mixture of the isomers 24 and 25) Calcd for
C21H23FeNO2: C, 66.82; H, 6.15; N, 3.71. Found: C, 66.91; H, 6.24;
N, 3.74. 1H NMR (CDCl3): 7.81-7.10 (m, 4H, C6H4Me), 5.03 (d,
4
NMR (CDCl3): 7.78-7.11 (m, 5H, Ph), 5.05 (d, 1H, JHH
)
4
1.60 Hz, C3H), 4.74 (d, 1H, JHH ) 1.60 Hz, C5H), 4.23 (s, 5H,
Cp), 3.76 (s, 3H, CO2Me), 2.38 (s, 3H, SMe). 13C NMR (CDCl3):
170.8 (CO2Me), 136.1-125.9 (Carom), 90.7 (C4), 85.7 (C1), 85.6
(C2), 76.8 (C5), 73.2 (C3), 73.1 (Cp), 51.5 (CO2Me), 19.5
(SMe).
4
4
1H, JHH ) 1.40 Hz, C5H), 4.83 (d, 1H, JHH ) 1.40 Hz, C3H),
4.32 (s, 5H, Cp), 3.86 (s, 3H, CO2Me), 2.65 (s, 6H, NMe2), 2.48
(br s, 3H, C6H4Me). 13C NMR (CDCl3): 170.3 (CO2Me), 136.2-126.8
(Carom), 114.6 (C1), 76.4 (C2), 70.7 (Cp), 68.9 (C3), 62.8 (C4), 61.3
(C5), 51.5 (CO2Me), 44.3 (NMe2), 21.3 (C6H4Me).
[1-SMe-3-Ph-4-CO2Me-Fc] (29). Yield: 36%. 1H NMR (CDCl3):
4
7.78-7.11 (m, 5H, Ph), 5.18 (d, 1H, JHH ) 1.30 Hz, C2H), 5.07
4
(d, 1H, JHH ) 1.30 Hz, C5H), 4.17 (s, 5H, Cp), 3.83 (s, 3H,
CO2Me), 2.28 (s, 3H, SMe). 13C NMR (CDCl3): 171.4 (CO2Me),
136.1-125.9 (Carom), 90.6 (C4), 86.0 (C1), 85.6 (C3), 73.0 (Cp),
70.8 (C2), 70.1 (C5), 51.7 (CO2Me), 19.1 (SMe).
[1-NMe2-3-Tol-4-CO2Me-Fc] (25). Yield: 37%. 1H NMR
4
(CDCl3): 7.81-7.10 (m, 4H, C6H4Me), 4.61 (d, 1H, JHH ) 1.40
Complex 30 was prepared following the same procedure
described for 4 and 5, by reacting 3b with PhCt CPh.
Hz, C5H), 4.37 (d, 1H, JHH ) 1.40 Hz, C2H), 4.38 (s, 5H, Cp),
4
3.93 (s, 3H, CO2Me), 2.76 (s, 6H, NMe2), 2.48 (br s, 3H, C6H4Me).
13C NMR (CDCl3): 173.1 (CO2Me), 136.2-126.8 (Carom), 116.1
(C1), 85.2 (C3), 70.2 (Cp), 64.1 (C2), 59.4 (C4), 56.4 (C5), 51.2
(CO2Me), 41.8 (NMe2), 21.1 (C6H4Me).
[1-SMe-2-Ph-3-Ph-4-CN-Fc] (30). Yield: 48%. Anal. Calcd for
C24H19FeO: C, 78.61; H, 5.72. Found: C, 78.55; H, 5.89. 1H NMR
(CDCl3): 7.56-7.19 (m, 10H, Ph), 5.05 (s, 1H, C5H), 4.31 (s, 5H,
Cp), 2.16 (s, 3H, SMe). 13C NMR (CDCl3): 135.1-126.5 (Carom
and CN); 91.1, 89.9 (C2 and C3), 86.9 (C1), 73.6 (Cp), 73.2 (C5),
51.1 (C4), 19.1 (SMe).
Electrochemical Measurements. Electrochemical data for 4-11
were obtained form 10-3 M solutions in CH3CN with 0.1 M
[Bu4N][PF6] (E1/2 in mV, referenced to the SCE, at a scan speed υ
) 100 mV s-1): 4, 241; 5, 400; 6, 292; 7, 442, 8, 104; 9, 417; 10,
274; 11, 422 mV.
X-ray Crystallography. Crystal data and collection details for 4
and 11 are reported in Table 3. The diffraction experiments were
carried out on a Bruker APEX II diffractometer equipped with a
CCD detector using Mo KR radiation. Data were corrected for
Lorentz polarization and absorption effects (empirical absorption
correction SADABS).21 Structures were solved by direct methods
and refined by full-matrix least-squares based on all data using F2.22
All hydrogen atoms were fixed at calculated positions and refined
by a riding model, except H(50) in 4, which was located in the
Complexes 26 and 27 were prepared following the same
procedure described for 4 and 5, by reacting 2b with HCt CTol.
[1-NMe2-2-Tol-4-CN-Fc] (26). Yield: 31%. Anal. (sample con-
taining a mixture of the isomers 26 and 27) Calcd for C20H20FeN2:
1
C, 69.75; H, 5.86; N, 8.14. Found: C, 69.80; H, 5.97; N, 8.14. H
NMR (CDCl3): 7.62-6.99 (m, 4H, C6H4Me), 4.40 (d, 1H, 4JHH
)
4
1.40 Hz, C5H), 4.31 (d, 1H, JHH ) 1.40 Hz, C3H), 4.30 (s, 5H,
Cp), 2.51 (s, 6H, NMe2), 2.37 (br s, 3H, C6H4Me). 13C NMR
(CDCl3): 136.9-126.9 (Carom), 120.7 (CN), 116.5 (C1), 85.2 (C2),
71.1 (Cp), 57.3 (C3), 56.6 (C5), 45.3 (C4), 41.7 (NMe2), 21.1
(C6H4Me).
1
[1-NMe2-3-Tol-4-CN-Fc] (27). Yield: 40%. H NMR (CDCl3):
4
7.62-6.99 (m, 4H, C6H4Me), 4.71 (d, 1H, JHH ) 1.40 Hz, C5H),
4
4.53 (d, 1H, JHH ) 1.40 Hz, C2H), 4.36 (s, 5H, Cp), 2.63 (s, 6H,
NMe2), 2.37 (br s, 3H, C6H4Me). 13C NMR (CDCl3): 136.9-126.9
(Carom); 121.4 (CN), 113.8 (C1), 80.0 (C3), 71.5 (Cp), 70.3 (C2),
61.0 (C5), 45.5 (C4), 44.0 (NMe2), 21.2 (C6H4Me).
Complexes 28 and 29 were prepared following the same
procedure described for 4 and 5, by reacting 3a with HCt CPh.
[1-SMe-2-Ph-4-CO2Me-Fc] (28). Yield: 33%. Anal. (sample
containing a mixture of the isomers 28 and 29) Calcd for
(21) Sheldrick, G. M. SADABS, Program for empirical absorption
correction; University of Go¨ttingen: Germany, 1996.
(22) Sheldrick, G. M. SHELX97, Program for crystal structure deter-
mination; University of Go¨ttingen: Germany, 1997.

3472 Organometallics, Vol. 28, No. 12, 2009
Busetto et al.
Fourier map and refined isotropically using the 1.5-fold Uiso value
of the parent O(1) atom; the O(1)-H(50) distance was restrained
to 0.83 Å [s.u. 0.01]. Similar U restraints [s.u. 0.01] were applied
to all C atoms in 11.
metallic sites in unconventional species”) and the University
of Bologna for financial support.
Supporting Information Available: Crystallographic data for
compounds of 4 and 11 in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank the Ministero dell’Universita`
e della Ricerca (MUR) (project: “New strategies for the
control of reactions: interactions of molecular fragments with
OM9002472