From 2- to 3-Substituted Ferrocene Carboxamides or How to Apply Halogen dance to the Ferrocene Series

Article abstract of DOI:10.1021/acs.organomet.7b00659

Two methods were compared to convert ferrocene into N,N-diisopropylferrocenecarboxamide, N,N-diethylferrocenecarboxamide, N,N-dimethylferrocenecarboxamide, and (4-morpholinocarbonyl)ferrocene, namely, deprotometalation followed by trapping using dialkylcarbamoyl chlorides and amide formation from the intermediate carboxylic acid. The four ferrocenecarboxamides were functionalized at C² in the case of the less hindered and more sensitive amides, recourse to a mixed lithium-zinc 2,2,6,6-tetramethylpiperidino-based base allowed us to achieve the reactions. Halogen migration using lithium amides was next optimized. Whereas it appeared impossible to isolate the less hindered 3-iodoferrocenecarboxamides, 3-iodo-N,N-diisopropylferrocenecarboxamide proved stable and was converted to new 1,3-disubstituted ferrocenes by Suzuki coupling or amide reduction. DFT calculations were used to rationalize the results obtained.

Full text of DOI:10.1021/acs.organomet.7b00659

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
From 2- to 3‑Substituted Ferrocene Carboxamides or How to Apply
Halogen “Dance” to the Ferrocene Series
Mehdi Tazi,† William Erb,*,† Yury S. Halauko,*,‡ Oleg A. Ivashkevich,‡ Vadim E. Matulis,§
Thierry Roisnel,¶ Vincent Dorcet,¶ and Florence Mongin†
†Equipe Chimie Organique et Interfaces, Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Universite
Batiment 10A, Case 1003, Campus Scientifique de Beaulieu, 35042 Cedex Rennes, France
‡UNESCO Chair of Belarusian State University, 14 Leningradskaya Str., Minsk 220030, Belarus
§Research Institute for Physico-Chemical Problems of Belarusian State University, 14 Leningradskaya Str., Minsk 220030, Belarus
¶Centre de Diffractomet
rie X, Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Universite de Rennes 1, Batiment 10B,
́
de Rennes 1,
̂
́
́
̂
Campus de Beaulieu, 35042 Cedex Rennes, France
S
* Supporting Information
ABSTRACT: Two methods were compared to convert ferrocene into N,N-
diisopropylferrocenecarboxamide, N,N-diethylferrocenecarboxamide, N,N-
dimethylferrocenecarboxamide, and (4-morpholinocarbonyl)ferrocene, namely,
deprotometalation followed by trapping using dialkylcarbamoyl chlorides and
amide formation from the intermediate carboxylic acid. The four ferrocene-
carboxamides were functionalized at C2; in the case of the less hindered and
more sensitive amides, recourse to a mixed lithium−zinc 2,2,6,6-tetramethylpiperidino-based base allowed us to achieve the
reactions. Halogen migration using lithium amides was next optimized. Whereas it appeared impossible to isolate the less
hindered 3-iodoferrocenecarboxamides, 3-iodo-N,N-diisopropylferrocenecarboxamide proved stable and was converted to new
1,3-disubstituted ferrocenes by Suzuki coupling or amide reduction. DFT calculations were used to rationalize the results
obtained.
successfully used for this purpose, and enantiopure derivatives
could be obtained.12,11e
INTRODUCTION
■
Polysubstituted ferrocenes are much appreciated scaffolds for
various applications including catalysis, fuel additives, material
sciences, and medicinal chemistry.1
Base-catalyzed aromatic halogen “dance” is an elegant way to
convert 2-halogeno substituted benzenes (I > Br) into the
corresponding 3-substituted derivatives.13 Relatively well-
developed in the benzene series, the reaction has been
subjected to very few studies for ferrocenes. In 2010, we
reported the competitive formation of 1-bromo-3-iodoferro-
cene in the course of the deprotometalation−iodolysis of
bromoferrocene using the base in situ prepared from ZnCl2·
TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine)
and LiTMP (TMP = 2,2,6,6-tetramethylpiperidino) in a 1:3
ratio14 and supposed to be a 1:1 mixture of LiTMP and
Zn(TMP)2.15 More recently, Wang, Weissensteiner, and co-
workers showed that the reactions performed on ferrocenyl 1,2-
dihalides (1-chloro-2-iodo-, 1-bromo-2-iodo-, 1,2-dibromo-,
and 1,2-diiodoferrocene) using LiTMP look more like a
“scrambling” than a “dance”, with complex mixtures obtained.16
We thought a way to reduce this complexity was to involve in
such reactions 1,2-disubstituted ferrocenes bearing only one
halogen and a fixed N,N-dialkylcarboxamide directing group.
We thus chose 2-iodoferrocenecarboxamides to attempt base-
catalyzed halogen migration. Herein, we describe our efforts to
efficiently synthesize the required substrates and to convert
Methods to access 1,2-disubstituted ferrocenes have been
largely developed from monosubstituted ferrocenes.2 Among
the methods used, deprotonative lithiations directed at
neighboring sites by coordinating or acidifying groups are of
crucial importance. Ferrocenecarboxylic acid derivatives such as
hindered N,N-dialkylcarboxamides3 and oxazolines2b,4 have
been often employed for this purpose, with stereoselective
reactions being possible by using chiral ligands or chiral
directing groups, respectively.
In sharp contrast, if 1,3-disubstituted ferrocenes appear as
promising for different applications,5 their synthesis is far less
developed. Obtaining such structures by building the ferrocene
core6 is possible but subject to tedious preparation of the
required substrates. Thus, access by functionalization of
ferrocene is an attractive approach. From monosubstituted
ferrocenes, direct electrophilic substitutions are hardly
regioselective.7 Stoichiometric and catalytic CH-functionaliza-
tions can take place at positions remote from substituents, but
these reactions are limited to specific groups8 or bases,9 and can
hardly be made stereoselective. Alternative ways to access 1,3-
disubstituted ferrocenes consist in using retractable directing
groups. Chlorine,10 bromine,11 and sulfoxide12 have been
Received: August 30, 2017
© XXXX American Chemical Society
A
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them into the corresponding 3-iodoferrocenecarboxamides.
The molecular structure of the above-mentioned ferrocenes was
studied by 1H and 13C NMR spectroscopy, and DFT
calculations were used to rationalize the results.
Table 2. Formation of the N,N-Dialkyl 2-
Iodoferrocenecarboxamides 5−8
RESULTS AND DISCUSSION
■
Compared Methods to Access N,N-Dialkyl Ferrocene-
carboxamides. N,N-dialkyl ferrocenecarboxamides are im-
portant substrates for subsequent elaboration. Therefore, we
planned the synthesis of four ferrocenecarboxamides, namely,
the N,N-diisopropyl, N,N-diethyl, N,N-dimethyl, and morpho-
lino. Direct reaction of ferrocene with dialkylcarbamoyl
chlorides was reported to give the corresponding carboxamides
in moderate yields.17 In our hands, reacting ferrocene with
diethylcarbamoyl chloride in the presence of AlCl3 (1.1 equiv)
at dichloromethane reflux provided N,N-diethylferrocene-
carboxamide in 33% yield (5% yield by using 2 equiv of
AlCl3; no product and 66% recovered ferrocene by employing
1.1 equiv of SnCl4). This disappointing yield led us to consider
alternative syntheses.
a
entry
product
base
Li
yield (%)
1
2
3
4
5
5
5
6
7
8
88
84
88
78
84
Li−Zn
Li−Zn
Li−Zn
Li−Zn
a
Yields after purification by column chromatography over silica gel.
We considered and evaluated two routes toward these
substrates: ferrocene deprotometalation followed by trapping
using dialkylcarbamoyl chlorides (route A)18 and amide
formation from ferrocenecarboxylic acid19 (route B).20 As
shown in Table 1, the two routes work in similar yields
tolithiated by butyllithium in Et2O at −80 °C.3a,b From 1, using
the chelate BuLi·TMEDA followed by iodolysis led to the
expected iodide 521 in 88% yield. Alternatively, employing at
room temperature the base in situ prepared from ZnCl2·
TMEDA (0.5 equiv) and LiTMP (1.5 equiv)14 (supposed to be
a 1:1 mixture of LiTMP and Zn(TMP)2)15 furnished 5 in 84%
yield. From 2, we preferred the latter method, and we isolated
the 2-iodo derivative 6 in 88% yield.
Table 1. Formation of the N,N-Dialkyl
Ferrocenecarboxamides 1−4 Using Route A and Route B
When compared to 1 and 2, N,N-dimethylferrocene-
carboxamide (3) and morpholinoferrocenecarboxamide (4)
are more sensitive to nucleophilic attacks. Consequently,
ketones are concomitantly formed upon their treatment by
organolithiums, and lower yields of 2-substituted derivatives are
noticed after subsequent quenching. Recourse to LiTMP with
in situ trapping (e.g., ClSiMe3) makes functionalization of such
substrates possible.22 Although iodine cannot be used as in situ
trap, the zinc species formed next to the directing group by
deprotolithiation−“trans-metal trapping”23 using the combina-
tion of LiTMP (0.5 equiv) and Zn(TMP)2 (0.5 equiv) can be
converted to the corresponding iodides 7 and 8, which were
isolated in 78% and 84% yield, respectively. The main
spectroscopic and X-ray diffraction data are given in Supporting
Information or Figure 1.
Halogen Dance to Afford N,N-Dialkyl 3-Iodo-
ferrocenecarboxamides. Deprotonation-triggered heavy hal-
ogen migration13 appeared to be a suitable approach for the
conversion of 1-substituted 2-iodoferrocenes into their 1-
substituted 3-iodo isomers.14,16 A N,N-dialkylcarboxamide
being capable of coordinating lithium when located at a
neighboring position on a ring, it can contribute to the
stabilization of a lithio compound and thus direct halogen
migration. To the best of our knowledge, such a group has only
been used to direct halogen migration in the case of 3-iodo-
N,N-diisopropyl-2-pyridinecarboxamide (Chart 1, left).24 Ac-
cording to the generally accepted mechanism,13 the reaction
promoted by a lithium amide (LiDA = lithium diisopropyla-
mide) proceeds through deprotonation at the 4 position and
repetitive halogen/metal exchanges.
a
entry
product
route
yield (%)
1
2
3
4
5
6
7
8
1
1
2
2
3
3
4
4
A
B
A
B
A
B
A
B
71
94 (80)
86.5
95 (81)
77
82 (70)
76
83 (71)
a
The yields (after purification by column chromatography over silica
gel) for Routes A and B were calculated from ferrocene and
ferrocenecarboxylic acid, respectively. The yields in parentheses are
calculated from ferrocene.
although route A provides the ferrocenecarboxamides 1−4 in
only one step from cheap ferrocene. All the products obtained
were fully characterized, and their main spectroscopic and X-ray
diffraction data are furnished in Supporting Information.
Deprotometalation to Afford N,N-Dialkyl 2-Iodo-
ferrocenecarboxamides (Table 2). N,N-Diisopropyl- and
N,N-diethylferrocenecarboxamide (1 and 2) can be depro-
Besides different electronic and geometrical features (e.g.,
angles), the position next to the carboxamide is locked by the
pyridine nitrogen in the reported example, whereas it can be
B
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Figure 1. ORTEP diagrams (30% probability level) of the ferrocene-
carboxamides 5 (C9−C10−C11−O12 torsion angle 94.36°), 7 (C9−
C10−C11−O12 121.02°), 8 (C9−C10−C11−O12 −70.86°), and 9 (C9−
C10−C11−O1 27.01°).
Figure 2. Energy profiles (kJ/mol) of 1 (top) and 5 (bottom) upon
torsion angle (deg) C2−C1−CO change.
Chart 1. Substrate on Which a Carboxamide Has Been Used
to Direct Halogen Migration (left) and Planned Substrates
to Attempt Ferrocene Halogen “Dance” (right)
Scheme 1. Proposed Mechanism for Halogen Dance on 2-
Iodoferrocenecarboxamides
attacked by a base in the case of the ferrocenecarboxamides 5−
8 (Chart 1). Although silyl protection is possible, we did not
consider this strategy as studies showed that hindered ferrocene
carboxamides22 bearing such silanes at C2 can hardly be
deprotonated at C5, but rather on the unsubstituted Cp ring.
Carboxamide orientation seems to impact the metalation
efficiency, the reaction being favored when the CO group
is in the plane of the substituted Cp ring.25
Different aspects of the molecular structure of ferrocenes and
their derived properties were studied by quantum chemical
calculations.26 It is established that ferrocenes can exist as
eclipsed and staggered conformations with a low internal
rotation barrier.27 In our case (see Supporting Information),
the investigated ferrocenes are predominantly in an eclipsed
form with hydrogens slightly bent inward. We considered the
carboxamide conformation space next.
ferrocenecarboxamides the bulkier the substituent is, the greater
the value of the angle between the Cp and amide planes is.
Whereas the computed conformations of lowest energy are
very close to the structures obtained by X-ray diffraction, a local
maximum (+24 kJ/mol) is noticed for the conformation of 1
with the CO group in the plane of the Cp (Figure 2, top),
and two maxima (local at +30 and global at +50 kJ/mol) were
recorded for the two “in-plane” conformers of 5 (Figure 2,
bottom; respectively, 0° in the case of the CO group on the
iodine side (syn) and 180° for the CO group on the opposite
side (anti)).28 This large value led us to suppose that the CO
group can hardly stabilize a 2-iodo-5-lithioferrocene-
carboxamide by lithium coordination, and we were confident
that halogen migration will take place without a protective
group.
Due to the presence of the heavy halogen at C2 in 5, as in the
case of silyl-protected carboxamide, the favored conformation
seems to have the carboxamide CO out of the Cp plane
(even nearly perpendicular, see Figure 1) and thus is not
suitable to induce metalation at C.5 We thus tried to assess, for
1 and 5, the energy difference between the most stable
conformation and the conformation with coplanar CO and
Cp ring. Because we could not get this information by using
dynamic NMR studies (see Supporting Information), we
calculated their energy profiles upon rotation around their
C1−CO bond (Figure 2). It was found earlier28 that for
C
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We decided to optimize the reaction on 2-iodo-N,N-
diisopropylferrocenecarboxamide (5) and to next apply the
best conditions to the other N,N-dialkyl-2-iodoferrocene-
carboxamides 6, 7 and 8. On the basis of the mechanism
proposed in Scheme 1, we considered LiTMP as a better
lithium amide than LiDA.29 Indeed, 2,2,6,6-tetramethylpiper-
idine (H-TMP; pKa = 37.3)30 is less prone to protonate 2-
lithio-N,N-diisopropylferrocenecarboxamide than diisopropyl-
amine (pKa = 35.7).30
Thus, we treated the 2-iodoferrocenecarboxamide 5 by
LiTMP (1.1 equiv) in THF (THF = tetrahydrofuran) for 2 h at
different reaction temperatures (from −30 to −80 °C) before
subsequent hydrolysis. In all these experiments, we observed
(gas chromatography (GC) mass spectrometry) the formation
of 3-iodo-N,N-diisopropylferrocenecarboxamide (9) as well as
the deiodinated compound 1 in addition to the recovered
starting material 5. Whereas −30 °C favored deiodination (1
formed in ∼40% estimated yield), starting material 5 was
importantly recovered at −80 °C (∼55% estimated yield).
Regarding the expected isomerized iodide 9, its formation was
favored at −50 °C. Other mono- and diiodides were formed,
but in general as minority products.
To understand why deiodination competes, we treated the
ferrocenecarboxamide 1 with LiTMP (1.1 equiv) in THF at
−50 °C for 6 h. After subsequent iodolysis, we isolated the 2-
iodo derivative 5 in a low 7% yield. Similarly, iodolysis of the
halogen dance reaction mixture after 6 h at −50 °C produces
much more 1 (∼ 60% yield) than 2-lithioferrocenecarboxamide
(∼ 10%). That the latter easily reacts with H-TMP could
explain why 1 first and easily accumulates in the reaction
mixture before disappearing. In order to reduce such a
protonation, we tried to use 2 equiv of LiTMP. Unfortunately,
the formation of 9 is not favored under these conditions. By
decreasing the amount of lithium amide to 0.5 equiv, the
halogen dance is considerably prevented with 5 remaining
present in ∼30% yield and deiodination similarly taking place
(see Supporting Information).
Last but not least, as N,N-diisopropyl-2-lithioferrocene-
carboxamide, 3-iodo-N,N-diisopropyl-2-lithioferrocenecarbox-
amide is prone to in situ protonation by H-TMP. Indeed,
trapping the halogen dance reaction mixture with electrophiles
(PhCHO, PhSSPh, ClPPh2) led to complex mixtures, while
using DCl−D2O only allowed 2-deuterio-3-iodo-N,N-
diisopropylferrocenecarboxamide to be isolated as a 1:1 mixture
(∼30% yield) with 9.
Consequently, we kept −50 °C and checked different
reaction times (5 min, 15 min, 30 min, 6 h, 14 h and 20 h;
see Supporting Information). The results show that the 2-
lithioferrocenecarboxamide is rapidly formed (giving 1 by
hydrolysis), but the conversion to the 3-iodo-2-lithio derivative
(affording 9 by hydrolysis) takes more time. Once the starting 5
exhausted (∼14 h), there is no benefit to use longer reaction
times.
In most cases, the deiodination is accompanied by formation
of unwanted unstable mono- and diiodides. Because we could
not isolate any of the side products, we tried to get information
from the NMR spectra of fractions containing them. First, we
completely assigned the 1H and 13C NMR signals of 1, 5, and 9
and deduced the NMR increments of both the CONiPr2 and
iodo substituents (see Supporting Information).
In several experiments (notably by using an excess of base to
attempt the reaction), we observed the formation (<10% yield
estimated by GC mass spectrometry) of an isomer of 5 and 9.
This compound was identified as being 1′-iodo-N,N-
diisopropylferrocenecarboxamide by NMR and GC comparison
with the product resulting from silyl deprotection of 1′-iodo-
N,N-diisopropyl-2-(trimethylsilyl)ferrocenecarboxamide.
Concerning the diiodides, we could get information from the
13C NMR spectra of fractions containing them. In particular,
the chemical shift of the C1 carbon (connected to CO)
largely depends on the presence of iodine atoms at C2 and C5.
Indeed, at 81.3 ppm in the absence of neighboring iodine
(compound 1), this signal moves to 92.6 ppm in the presence
of iodine at C2 (compound 5), but is not modified significantly
with iodine at C3 (82.8 ppm, compound 9). Thus, with a C1 at
97.2 ppm, we are inclined to think that the diiodide most often
formed in our halogen dance−hydrolysis sequences is the 2,5-
diiodocarboxamide. After halogen dance−iodolysis, a new
diiodide is formed (longer retention time on GC mass
spectrometry); we supposed it is the 2,3-diiodocarboxamide
shown in Scheme 1, formed by iodolysis of the 3-iodo-2-lithio-
ferrocenecarboxamide. Nevertheless, this second diiodide is
rarely observed in our halogen dance-hydrolysis reactions;
instead, in addition to the 2,5-diiodocarboxamide, a third
diiodide is often noticed. We have no clue to identify it, but the
2,4-diiodo derivative could be a possible candidate. This NMR
study at least seems to show that deprotometalation of 5 lacks
regioselectivity (next to iodine vs carboxamide).
Under the optimized reaction conditions, LiTMP proved
superior to LiDA, often employed as halogen dance mediator.13
With LiDA, extending the reaction time favored the
deiodinated product 1 to the detriment of the expected 3-
iodoferrocenecarboxamide 9 (see Supporting Information).
These results, which could be due to the higher propensity of
diisopropylamine to protonate the 2-lithioferrocene-
carboxamide when compared with LiTMP, led us to abandon
LiDA.
These optimized conditions (1.1 equiv of LiTMP, THF, −50
°C, 14 h) in hand, we studied the behavior of the less hindered
2-iodoferrocenecarboxamides 6−8 in the reaction. For more
sensitive 2-iodo-N,N-dimethylferrocenecarboxamide (7), the
estimated yield of the 3-iodo product 11 was improved at a
lower temperature. From N,N-diethyl-2-iodoferrocene-
carboxamide (6) and 1-iodo-2-(4-morpholinocarbonyl)ferro-
cene (8), conducting the reaction at a larger scale (4.0 mmol
instead of 1.0) provided the respective 3-iodo derivatives 10
and 12 more efficiently (see Supporting Information).
One main issue of the approach is to isolate the isomerized
products 9−12. Unlike the N,N-diisopropylferrocene-
carboxamide 9, separable from the deiodinated compound 1
and the other iodides by column chromatography over silica gel
(36% yield at a 1.0 mmol scale; 53% yield at a 4.0 mmol scale),
the less hindered N,N-dialkyl ferrocenecarboxamides 10−12
proved much less stable. The N,N-diethylcarboxamide 10 could
be purified by column chromatography over silica gel (32%
yield at a 1.0 mmol scale), but in a nonreproducible way. Even
worse, the N,N-dimethylcarboxamide 11 and the morpholino-
based carboxamide 12 were never isolated. As a consequence,
crystals suitable for X-ray diffraction were only obtained for the
3-iodo derivative 9 (Figure 1).
To get more information on these diiodides, we attempted
the use of the base in situ prepared from ZnCl2·TMEDA (0.5
equiv) and LiTMP (1.5 equiv)14 to prepare diiodides from the
iodocarboxamide 5. Under the conditions used in Table 2, the
preponderant formation of 2,5-diiodinated ferrocene-
D
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carboxamides was suspected on the basis of the 13C NMR data
of the mixture obtained (peaks at 97.2 and 98.1 ppm for the
main polyiodides formed). This evidenced a favored kinetic
deprotometalation of 5 next to the carboxamide function.
All these observations led us to consider the results in the
light of the pKa values of key ferrocene derivatives. In 1973,
Denisovich and Gubin described ferrocene as being more acidic
than benzene, with a pKa value of 39 3 on the MSAD scale
(polarography).31 To our knowledge, this represents the only
ferrocene pKa determination. Thus, we calculated the CH
acidity (pKa values) in THF solution of Fc-H, Fc-I, 1, 5, and 9
within the DFT framework by using the approach elaborated
earlier32 (Chart 2). Whereas iodine exerts its known short- and
The reason why reaction times exceeding 14 h are not
suitable to reach high yields could be due to LiTMP
destruction,33 favoring 2-lithioferrocenecarboxamide reproto-
nation. Competitive iodine/lithium exchange by LiTMP34
could also be advanced to rationalize the iodine loss observed
all along the reaction.
In order to obtain new kinds of ferrocenes, we made
derivatives from the 3-iodoferrocenecarboxamide 9 (Scheme
2). Using 4-methoxyphenyl- and 4-(trifluoromethyl)phenyl-
Scheme 2. Conversion of 9 by Suzuki Coupling and
Carboxamide Reduction
Chart 2. Selected Calculated pKa Values in THF Solution for
a
Fc−H, Fc−I, 1, 5, and 9
a
Top and middle, most stable conformation; bottom, Cp and CO
boronic acid in the presence of cesium fluoride,35 and catalytic
amounts of Pd(dba)2 (dba = dibenzylideneacetone) and
triphenylphosphine, at the reflux temperature of toluene,36
afforded the Suzuki coupling products 13 and 14, respectively,
in moderate yields. The N,N-diisopropylaminomethylferrocene
15 was in turn prepared by reduction of the carboxamide
function using BH3·THF, as documented previously.3a
We have thus shown that it is possible to access 1,3-
disubstituted ferrocenes, which are promising substrates for
different applications,5 with recourse to halogen dance.
coplanar 92 and 95 with the CO group, respectively, pointing toward
C2 and C5.
long-range acidifying effects, the carboxamide function as such
acidifies more moderately. When coordinated to lithium
(calculations performed by using LiF), the carboxamide
becomes a stronger directing group, as shown in Chart 3.
Chart 3. Selected Calculated pKa Values in THF Solution for
5·LiF (Most Stable Conformation of 5) and 9·LiF (Cp and
CO Coplanar)
CONCLUSION
■
We studied the halogen dance reaction from different N,N-
dialkyl 2-iodoferrocenecarboxamides. In spite of the low
stability of the less hindered 3-iodoferrocenecarboxamides, we
could optimize the reaction giving 3-iodo-N,N-diisopropyl-
ferrocenecarboxamide (9) and identify possible reasons for the
origin of the side product formation.
One limit encountered in this halogen dance is the formation
of undesirable diiodides, notably due to the relatively high
acidity found at C5 on 2-iodo-N,N-diisopropylferrocene-
carboxamide (5). By using deuterium to protect this position
toward deprotonation,4b one could favor the formation of the
expected 3-iodo-2-lithioferrocenecarboxamide.
Competitive deiodination and lithioferrocene reprotonation
proved to be main issues of the reaction. We will devote efforts
in order to identify ferrocene substituents capable of making
the generated ferrocenyllithiums more stable toward H-TMP.
Upon carboxamide coordination to lithium, the 1′ position of
ferrocene 5 is greatly acidified and amenable to deprotonation;
this might explain why 1′-iodo-N,N-diisopropylferrocene-
carboxamide is observed in experiments. Besides, when
compared to the site next to iodine, the position adjacent to
the carboxamide is somewhat more activated; this could explain
why deprotonation competitively takes place at C5, as
demonstrated by 2,5-diiodocarboxamide formation.
Once coordinated to the metal, the C2 position of the 3-
iodoferrocenecarboxamide 9 is highly activated; this allows us
to explain why the equilibria between the different
lithioferrocenes are shifted toward the expected 3-iodo-2-
lithioferrocenecarboxamide.
EXPERIMENTAL SECTION
General Details. All the reactions were performed under an argon
atmosphere using standard Schlenk techniques. THF was distilled over
■
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sodium/benzophenone. Column chromatography separations were
achieved on silica gel (40−63 μm). Melting points were measured on a
Kofler apparatus. IR spectra were taken on a PerkinElmer Spectrum
298 K) δ 0.95 (br s, 3H, CH3), 1.04 (br s, 3H, CH3), 1.41 (br s, 6H,
2CH3), 3.44 (br s, 1H, CHMe2), 3.50 (br s, 1H, CHMe2), 4.27 (t, 1H,
J = 2.4 Hz), 4.28 (s, 5H, Cp-H), 4.41 (dd, 1H, J = 2.5 and 1.3 Hz),
1
1
100 spectrometer. H and 13C NMR spectra were recorded either (i)
4.50 (dd, 1H, J = 2.4 and 1.3 Hz); H NMR (500 MHz, (CD3)2SO,
on a Bruker Avance III spectrometer at 300 and 75 MHz, respectively,
or (ii) on a Bruker Avance III HD at 500 and 126 MHz, respectively.
1H chemical shifts (δ) are given in ppm relative to the solvent residual
peak, and 13C chemical shifts are relative to the central peak of the
solvent signal.37 Ferrocenecarboxylic acid is commercially available but
can be easily prepared according to a previously reported procedure.19
For 2−4, 6−9, and 13, the X-ray diffraction data were collected
using D8 VENTURE Bruker AXS diffractometer at the temperature
given in the crystal data. The samples were studied with
monochromatized Mo Kα radiation (λ = 0.71073 Å). The structure
was solved by dual-space algorithm using the SHELXT program38 and
then refined with full-matrix least-squares methods based on F2
(SHELXL).39 All non-hydrogen atoms were refined with anisotropic
atomic displacement parameters. H atoms were finally included in
their calculated positions. The molecular diagrams were generated by
ORTEP-3 (version 2.02).40
383 K) δ 1.21 (d, 6H, J = 6.7 Hz, CH3), 1.26 (d, 6H, J = 6.5 Hz, CH3),
3.56 (sept, 2H, J = 6.7 Hz, 2CHMe2), 4.27 (t, 1H, J = 2.5 Hz), 4.29 (s,
5H, Cp), 4.38 (br s, 1H, Cp-H), 4.48 (br s, 1H, Cp-H); 13C NMR (75
MHz, CDCl3, 291 K) δ 21.0 (4CH3), 40.6 (C−I), 46.0 (CHMe2), 50.9
(CHMe2), 66.9 (CH), 67.7 (CH), 72.9 (5CH, Cp), 73.7 (CH), 92.8
(C−CO), 166.4 (CO); 13C NMR (126 MHz, CDCl3, 298 K) δ
20.7 (CH3), 20.8 (CH3), 21.0 (CH3), 21.0 (CH3), 40.5 (C−I), 45.9
(CHMe2), 50.8 (CHMe2), 66.8 (CH, C5), 67.7 (CH, C4), 72.7 (5CH,
Cp), 73.6 (CH, C3), 92.6 (C−CO), 166.3 (CO). These data are
similar to those reported previously.3a The obtained crystal structure
was found to be similar to that described (CCDC 170421;
NEMLAS).21
General Procedure 3. To a stirred, cooled (0 °C) solution of H-
TMP (0.85 mL, 5.0 mmol) in THF (4 mL) were successively added
BuLi (∼1.6 M in hexanes, 4.5 mmol) and, 5 min later, ZnCl2·
TMEDA42 (0.38 g, 1.5 mmol). The mixture was stirred for 10 min at 0
°C before introduction of the required ferrocene (3.0 mmol) at 0−10
°C. After 2 h at room temperature, a solution of I2 (0.75 g, 3.0 mmol)
in THF (4 mL) was added. The mixture was stirred overnight before
addition of an aqueous saturated solution of Na2S2O3 (10 mL) and
extraction with AcOEt (3 × 20 mL). The combined organic layers
were dried over MgSO4 and concentrated under reduced pressure.
The crude product was purified by chromatography over silica gel (the
eluent is given in the product description; see Supporting Information
for experimental data on the compound 6).
General Procedure 1 (Route A). The protocol was adapted from
a previously reported procedure.41 To a stirred mixture of ferrocene
(0.93 g, 5.0 mmol) and tBuOK (56 mg, 0.5 mmol) in THF (45 mL) at
t
−80 °C was added dropwise BuLi (∼1.9 M in pentane, 10 mmol).
After 1.5 h at this temperature, the mixture was rapidly transferred
dropwise through a cannula to a solution of the required dialkyl
carbamoyl chloride (the amount is given in the product description) in
THF (15 mL) at −80 °C, and the resulting mixture was allowed to
warm to −40 °C before quenching by an aqueous saturated solution of
NH4Cl (50 mL). Extraction with AcOEt (3 × 20 mL), washing with
brine (20 mL), drying over MgSO4, removal of the solvents, and
purification by chromatography on silica gel (the eluent is given in the
product description) led to the expected compound (see Supporting
Information for experimental data on the compounds 2−4).
2-Iodo-N,N-dimethylferrocenecarboxamide (7, Racemic Mixture).
The general procedure 3 using N,N-dimethylferrocenecarboxamide (3,
0.77 g) gave 7 (eluent, heptane−AcOEt 70:30; Rf = 0.28) in 78% yield
as an orange powder: mp 58 °C; IR (ATR) 689, 816, 872, 961, 999,
1008, 1106, 1117, 1224, 1262, 1360, 1379, 1418, 1453, 1496, 1631,
1
2926 cm−1; H NMR (500 MHz, CDCl3, 298 K) δ 2.71 (br s, 3H,
General Procedure 2 (Route B).20 To a stirred mixture of
ferrocenecarboxylic acid (4.6 g, 20 mmol) in CH2Cl2 (50 mL)
containing DMF (5 drops) was added dropwise oxalyl chloride (3.5
mL, 40 mmol). After 2 h at room temperature, the solvent and excess
oxalyl chloride were removed under vacuum. The crude ferrocenoyl
chloride was next dissolved in CH2Cl2 (65 mL) before dropwise
addition of the required amine (60 mmol) at 0 °C. After stirring for 3
h, 1 M aqueous HCl (30 mL) was added. Extraction with Et2O (20
mL) and AcOEt (2 × 20 mL), washing with brine (20 mL), drying
over MgSO4, removal of the solvents, and purification by
chromatography on silica gel (the eluent is given in the product
description) led to the expected compound (see Supporting
Information for experimental data on the compound 1).
CH3), 2.92 (br s, 3H, CH3), 4.13 (t, 1H, J = 2.5 Hz, Cp-H), 4.21 (s,
5H, Cp), 4.26 (dd, 1H, J = 2.6 and 1.3 Hz, Cp-H), 4.37 (dd, 1H, J =
2.4 and 1.3 Hz, Cp-H); 13C NMR (126 MHz, CDCl3, 298 K) δ 35.3
(CH3), 38.8 (CH3), 40.3 (C−I), 68.3 (CH), 68.4 (CH), 72.7 (5CH,
Cp), 74.4 (CH), 87.7 (C−CO), 167.8 (CO). Anal. Calcd for
C13H14FeINO: C, 40.77; H, 3.68; N, 3.66. Found: C, 40.84; H, 3.71;
N, 3.69. Crystal data for 7. C13H14FeINO, M = 383.00, T = 150(2) K,
orthorhombic, P212121, a = 7.3581(8), b = 9.0317(11), c = 19.773(3)
Å, V = 1314.0(3) Å3, Z = 4, d = 1.936 g cm−3, μ = 3.480 mm−1. A final
refinement on F2 with 2939 unique intensities and 157 parameters
converged at ωR(F2) = 0.0398 (R(F) = 0.0162) for 2914 observed
reflections with I > 2σ(I). CCDC 1565040.
1-Iodo-2-(4-morpholinocarbonyl)ferrocene (8, Racemic Mixture).
The general procedure 3 using (4-morpholinocarbonyl)-ferrocene (4,
0.90 g) gave 8 (eluent, heptane−AcOEt 80:20; Rf = 0.18) in 84% yield
as a yellowish powder: mp 135−136 °C; IR (ATR) 687, 810, 866, 959,
1001, 1021, 1062, 1111, 1186, 1250, 1273, 1404, 1437, 1466, 2363,
2-Iodo-N,N-diisopropylferrocenecarboxamide (5, Racemic
Mixture). To Et2O (15 mL) containing TMEDA (1.6 g, 2.1 mL, 13
mmol), BuLi (∼1.6 M in hexanes, 13 mmol) was added dropwise at
−80 °C, under stirring. After 15 min at this temperature, a solution of
N,N-diisopropylferrocenecarboxamide (1, 3.6 g, 11.5 mmol) in Et2O
(20 mL) was added, and the mixture was stirred for 1 h before
addition of a solution of I2 (5.8 g, 23 mmol) in Et2O (15 mL) and
THF (8 mL). After 30 min stirring, the cooling bath was removed, and
the mixture was allowed to reach room temperature. Addition of an
aqueous saturated solution of Na2S2O3 (75 mL), extraction with Et2O
(3 × 20 mL), drying over MgSO4, removal of the solvents, and
purification by chromatography on silica gel (eluent, heptane−AcOEt
95:5; Rf = 0.65) gave 5 in 88% yield as an orange powder: mp 138 °C;
IR (ATR) 686, 811, 1002, 1024, 1036, 1315, 1368, 1455, 1620, 2970,
1
2856, 2971, 3081 cm−1; H NMR (300 MHz, CDCl3, 291 K) δ 3.45
(br s, 3H, CH2), 3.66 (br s, 5H, CH2), 4.25 (br s, 1H, Cp-H), 4.34 (s,
5H, Cp), 4.36 (br s, 1H, Cp-H), 4.49 (br s, 1H, Cp-H); 13C NMR (75
MHz, CDCl3, 291 K) δ 40.2 (C−I), 43.1 (2CH2), 47.8 (2CH2), 67.0
(CH), 68.8 (CH), 73.1 (5CH, Cp), 74.8 (CH), 87.6 (C−CO),
167.1 (CO). Anal. Calcd for C15H16FeINO: C, 42.39; H, 3.79; N,
3.30. Found: C, 42.45; H, 3.86; N, 3.33. Crystal data for 8.
C15H16FeINO2, M = 425.04, T = 150(2) K, monoclinic, P21/c, a =
10.3514(15), b = 7.2576(10), c = 20.081(3) Å, β = 101.480(4)°, V =
1478.5(3) Å3, Z = 4, d = 1.910 g cm−3, μ = 3.108 mm−1. A final
refinement on F2 with 3368 unique intensities and 148 parameters
converged at ωR(F2) = 0.0859 (R(F) = 0.0351) for 3211 observed
reflections with I > 2σ(I). CCDC 1565041.
General Procedure 4. To a stirred, cooled (0 °C) solution of H-
TMP (0.19 mL, 1.1 mmol) in THF (2 mL) was added BuLi (∼1.6 M
in hexane, 1.1 mmol). The mixture was stirred for 5 min at 0 °C before
introduction of the required iodoferrocene (1.0 mmol) at −50 °C.
After 14 h at −50 °C, MeOH (2.0 mL) and aqueous 1 M HCl (10
1
3094 cm−1; H NMR (300 MHz, CDCl3, 291 K) δ 0.99 (br s, 3H,
CH3), 1.11 (br s, 3H, CH3), 1.51 (br s, 6H, 2CH3), 3.41 (br s, 1H,
CHMe2), 3.62 (br s, 1H, CHMe2), 4.17 (s, 1H, Cp-H), 4.28 (s, 1H,
Cp-H), 4.34 (s, 5H, Cp-H), 4.42 (s, 1H, Cp-H); 1H NMR (500 MHz,
CDCl3, 298 K) δ 0.94 (d, 3H, J = 6.7 Hz, CH3), 1.05 (d, 3H, J = 6.8
Hz, CH3), 1.47 (t, 6H, J = 6.2 Hz, CH3), 3.36 (t, 1H, J = 7.1 Hz,
CHMe2), 3.57 (t, 1H, J = 7.1 Hz, CHMe2), 4.13 (t, 1H, J = 2.4 Hz,
H4), 4.24 (dd, 1H, J = 2.6 and 1.3 Hz, H5), 4.30 (s, 5H, Cp-H), 4.38
1
(dd, 1H, J = 2.4 and 1.3 Hz, H3); H NMR (500 MHz, (CD3)2SO,
F
DOI: 10.1021/acs.organomet.7b00659
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
mL) were successively added. Extraction with AcOEt (3 × 15 mL),
drying over MgSO4, concentration under reduced pressure, and
purification by azeotropic reflux chromatography43 over silica gel
(eluent, cyclohexane−AcOiPr 78:22) led to the expected product.
3-Iodo-N,N-diisopropylferrocenecarboxamide (9, Racemic Mix-
ture). The general procedure 4 using 2-iodo-N,N-diisopropyl-
ferrocenecarboxamide (5, 0.44 g) gave 9 (Rf = 0.32) in 36% yield
(53% yield on a 4.0 mmol scale) as an orange powder: mp 112 °C; IR
(ATR) 763, 803, 825, 1007, 1033, 1324, 1368, 1457, 1602, 2959, 3005
2051.40(12) Å3, Z = 4, d = 1.358 g cm−3, μ = 0.754 mm−1. A final
refinement on F2 with 4632 unique intensities and 225 parameters
converged at ωR(F2) = 0.0998 (R(F) = 0.0440) for 4212 observed
reflections with I > 2σ(I). CCDC 1565043.
N,N-Diisopropyl-3-(4-(trifluoromethylphenyl))ferrocene-
carboxamide (14, Racemic Mixture). The general procedure 5 using
4-(trifluoromethyl)phenylboronic acid (0.76 g) gave 14 (eluent,
heptane−AcOEt 85:15; Rf = 0.23) in 26% yield as an orange oil: IR
(ATR) 690, 729, 807, 822, 842, 908, 1040, 1068, 1106, 1121, 1162,
1285, 1321, 1371, 1446, 1468, 1615, 2241, 2933, 2969 cm−1; 1H NMR
(500 MHz, CDCl3, 298 K) δ 1.15−1.35 (br s, 6H, 2CH3), 1.40−1.60
(br s, 6H, 2CH3), 3.47 (br s, 1H, CHMe2), 4.12 (s, 5H, Cp), 4.62 (br
s, 1H, CHMe2), 4.72 (dd, 1H, J = 2.6 and 1.4 Hz, Cp-H, H5), 4.77
(dd, 1H, J = 2.6 and 1.5 Hz, Cp-H, H4), 5.12 (t, 1H, J = 1.8 Hz, Cp-H,
H2), 7.54 (d, 2H, J = 8.6 Hz, H2′), 7.57 (d, 2H, J = 8.5 Hz, H3′); 13C
NMR (126 MHz, CDCl3, 298 K) δ 21.3 (4CH3), 46.5 (CHMe2), 49.9
(CHMe2), 67.3 (CH, C4), 69.1 (CH, C2), 70.9 (CH, C5), 71.7 (5CH,
Cp), 83.4 (C−CO), 84.0 (C, C3), 125.6 (q, 2CH, J = 3.8 Hz, C3′),
126.2 (2CH, C2′), 128.3 (C, J = 32.5 Hz, C4′), 124.5 (q, C, J = 272
Hz, CF3), 142.8 (C1′), 168.7 (CO); 19F NMR (282 MHz, CDCl3,
291 K) δ −62.5. Anal. Calcd for C24H26F3FeNO: C, 63.03; H, 5.73; N,
3.06. Found: C, 63.12; H, 5.75; N, 2.98.
1-(N,N-Diisopropylaminomethyl)-3-iodoferrocene (15, Rac-
emic Mixture). The protocol was adapted from a previously reported
procedure.3a To a stirred solution of 3-iodo-N,N-diisopropylferrocene-
carboxamide (9, 1.0 mmol, 0.44 g) in THF (10 mL) under argon was
added BH3·THF (5.0 mmol, 5.0 mL of a 1.0 M solution). The mixture
was refluxed for 16 h, cooled to room temperature, quenched with
10% aqueous KOH (35 mL) and refluxed for 10 h. The resulting
solution was cooled to room temperature. Brine (50 mL) was added
before extraction with Et2O (3 × 20 mL), drying over MgSO4,
concentration under reduced pressure, and purification by chromatog-
raphy over silica gel (eluent, heptane−AcOEt 60:40 to 0:100). The
compound 15 was isolated in 68% yield: yellow oil; IR (ATR) 748,
818, 871, 933, 1001, 1031, 1106, 1137, 1160, 1202, 1362, 1463, 1673,
2926, 2961, 3096 cm−1; 1H NMR (500 MHz, CDCl3, 298 K) δ 0.98−
1.01 (m, 12H, 4CH3), 3.03 (sept, 2H, J = 6.6 Hz, 2CHMe2), 3.34 (d,
1H, J = 14.4 Hz, CH2N), 3.40 (d, 1H, J = 14.5 Hz, CH2N), 4.13 (s,
5H, Cp), 4.20 (s, 1H, H5), 4.31 (s, 1H, H4), 4.46 (s, 1H, H2); 13C
NMR (126 MHz, CDCl3, 298 K) δ 20.9 (4CH3), 39.8 (C−I), 43.8
(CH2N), 47.6 (2CHMe2), 70.1 (CH, C5), 71.7 (5CH, Cp), 73.7 (CH,
C4), 75.9 (CH, C2), 89.9 (C-CH2). Anal. Calcd for C17H24FeIN: C,
48.03; H, 5.69; N, 3.29. Found: C, 48.11; H, 5.73; N, 3.12.
1
cm−1; H NMR (300 MHz, CDCl3, 291 K) δ 1.25−1.40 (br s, 12H,
4CH3), 3.44 (br s, 1H, CHMe2), 4.25 (s, 5H, Cp), 4.40 (br s, 1H,
CHMe2), 4.50 (dd, 1H, J = 2.5 and 1.2 Hz, Cp-H), 4.57 (dd, 1H, J =
2.5 and 1.4 Hz, Cp-H), 4.73 (t, 1H, J = 1.3 Hz, Cp-H); 1H NMR (500
MHz, CDCl3, 298 K) δ 1.20 (br s, 6H, 2CH3), 1.45 (br s, 6H, 2CH3),
3.42 (br s, 1H, CHMe2), 4.30 (s, 5H, Cp), 4.45 (br s, 1H, CHMe2),
4.51 (s, 1H, H4), 4.58 (s, 1H, H5), 4.73 (s, 1H, H2); 13C NMR (75
MHz, CDCl3, 291 K) δ 21.2 (4CH3), 39.6 (C−I), 46.6 (CHMe2), 49.5
(CHMe2), 71.1 (CH), 73.0 (5CH, Cp), 75.2 (CH), 75.6 (CH), 82.9
(C−CO), 167.8 (CO);13C NMR (126 MHz, CDCl3, 298 K) δ
21.2 (4CH3), 39.6 (C−I), 46.5 (CHMe2), 49.9 (CHMe2), 71.1 (CH,
C5), 73.0 (5CH, Cp), 75.2 (CH, C4), 75.6 (CH, C2), 82.8 (C−C
O), 167.8 (CO). Anal. Calcd for C17H22FeINO: C, 46.50; H, 5.05;
N, 3.19. Found: C, 46.61; H, 5.10; N, 3.29. Crystal data for 9.
C17H22FeINO, M = 439.10, T = 293(2) K, monoclinic, P21/n, a =
7.5144(6), b = 10.3128(8), c = 22.4379(17) Å, β = 91.475(3)°, V =
1738.2(2) Å3, Z = 4, d = 1.678 g cm−3, μ = 2.642 mm−1. A final
refinement on F2 with 3955 unique intensities and 194 parameters
converged at ωR(F2) = 0.3102 (R(F) = 0.1108) for 3229 observed
reflections with I > 2σ(I). CCDC 1565042.
N,N-Diethyl-3-iodoferrocenecarboxamide (10, Racemic Mixture).
The general procedure 4 using 2-iodo-N,N-diethylferrocene-
carboxamide (6, 0.41 g, 1.0 mmol) gave 10 (Rf = 0.10) in 32% yield
as an orange powder: mp 86−87 °C; IR (ATR) 668, 823, 1001, 1209,
1449, 1474, 1604, 2967 cm−1; 1H NMR (500 MHz, CDCl3, 298 K) δ
1.16 (t, 6H, J = 6.9 Hz, 2CH3), 3.42 (br s, 4H, 2CH2), 4.21 (s, 5H,
Cp), 4.51 (dd, 1H, J = 2.5 and 1.3 Hz, H4), 4.60 (dd, 1H, J = 2.6 and
1.4 Hz, H5), 4.77 (t, 1H, J = 1.4 Hz, H2); 13C NMR (126 MHz,
CDCl3, 298 K) δ 12.9 (CH3), 14.8 (CH3), 39.6 (C−I), 40.9 (CH2),
42.7 (CH2), 71.2 (CH, C5), 72.9 (5CH, Cp), 75.5 (CH, C4), 75.9
(CH, C2), 80.3 (C−CO), 168.1 (CO).
General Procedure 5 (Suzuki Coupling). The protocol was
adapted from a previously reported procedure.36 A solution of CsF
(0.30 g, 2.0 mmol), 3-iodo-N,N-diisopropylferrocenecarboxamide (9,
0.44 g, 1.0 mmol), and boronic acid (4.0 mmol) in toluene (10 mL)
was degassed with Ar before addition of Pd(dba)2 (28 mg, 50 μmol)
and PPh3 (52 mg, 0.20 mmol). The resulting mixture was heated for
14 h under reflux before cooling and dilution with Et2O (60 mL),
washing with H2O, and extraction with CH2Cl2 (3 × 20 mL). After
drying over anhydrous Na2SO4, the solvent was evaporated under
reduced pressure, and the coupled product was isolated by purification
by flash chromatography on silica gel.
Density Functional Theory (DFT) Calculation Details. All the
DFT calculations were performed by using the Gaussian 09 software
package.44 The structures from the X-ray diffraction analysis were used
as starting guess. All the molecular geometries were completely
optimized with no constraints. We used the B3LYP hybrid functional45
together with the LANL2DZ basis set for both Fe and I and the 6-
31G(d) basis set for the other atoms to calculate the optimized
geometries and vibrational frequencies. Relaxed PES scans for 1 and 5
were obtained at the same level of theory. The solvent influence was
treated by using the polarized continuum model (IEF PCM)46 with
the default parameters for THF. The pKa values were calculated from
the Gibbs energy of the homodesmic reaction between the studied and
probe aromatic substrates.47 The single point energies were obtained
at the CAM-B3LYP/LANL2DZ + 6-31+G(d,p) level of theory.48
N,N-Diisopropyl-3-(4-methoxyphenyl)ferrocenecarboxamide (13,
Racemic Mixture). The general procedure 5 using 4-methoxyphe-
nylboronic acid (0.61 g) gave 13 (eluent, heptane−AcOEt 80:20; Rf =
0.43) in 46% yield as an orange powder (slow crystallization): mp
134−136 °C; IR (ATR) 791, 807, 831, 1024, 1036, 1158, 1178, 1246,
1272, 1321, 1342, 1372, 1437, 1452, 1467, 1525, 1609, 2929, 2965,
1
3001 cm−1; H NMR (500 MHz, CDCl3, 298 K) δ 1.15−1.36 (br s,
6H, 2CH3), 1.40−1.58 (br s, 6H, 2CH3), 3.45 (br s, 1H, CHMe2),
3.82 (s, 3H, OCH3), 4.10 (s, 5H, Cp), 4.56 (br s, 1H, CHMe2), 4.64
(dd, 1H, J = 2.5 and 1.4 Hz, Cp-H, H5), 4.67 (dd, 1H, J = 2.4 and 1.5
Hz, Cp-H, H4), 5.01 (t, 1H, J = 1.4 Hz, Cp-H, H2), 6.85−6.89 (m,
2H, H3′), 7.41−7.43 (m, 2H, H2′); 13C NMR (126 MHz, CDCl3, 298
K) δ 21.3 (4CH3), 46.5 (CHMe2), 49.6 (CHMe2), 55.4 (OCH3), 66.9
(CH, C4), 68.3 (CH, C2), 70.1 (CH, C5), 71.4 (5CH, Cp), 81.7 (C−
CO), 86.8 (C, C3), 114.1 (2CH, C3′), 127.3 (2CH, C2′), 130.3 (C,
C1′), 158.5 (C, C4′), 169.5 (CO). Anal. Calcd for C24H29FeNO2:
C, 68.74; H, 6.97; N, 3.34. Found: C, 68.70; H, 6.88; N, 3.31. Crystal
data for 13. C24H29FeNO2, M = 419.33, T = 150(2) K, orthorhombic,
P21cn, a = 6.0222(2), b = 13.0671(5), c = 26.0685(8) Å, V =
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00659.
Optimization of halogen dance reaction, experimental
data for compounds 1−4 and 6, X-ray diffraction data for
compounds 1−4, 6, and 13, and NMR spectra (PDF)
DFT structural data (XYZ)
G
DOI: 10.1021/acs.organomet.7b00659
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
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Accession Codes
CCDC 1565036−1565043 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: william.erb@univ-rennes1.fr.
*E-mail: hys@tut.by.
■
ORCID
William Erb: 0000-0002-2906-2091
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Minister
̀
e de lʼEnseignement
ieur, de la Recherche et de lʼInnovation (grant to M.T.)
de Rennes 1. We also thank the Centre
National de la Recherche Scientifique, the Institut Universitaire
de France and Rennes Metropole. We acknowledge FEDER
super
́
and the Universite
́
́
founds (D8 VENTURE Bruker AXS diffractometer) and
Thermofisher (generous gift of H-TMP).
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