Synthesis, reactivity, and some photochemistry of ortho-N, Ndimethylaminomethyl substituted aryl and ferrocenyl pentamethylcyclopentadienyl dicarbonyl iron complexes

Article abstract of DOI:10.1016/j.jorganchem.2013.05.031

Ortho-lithiated N,N-dimethylaminomethyl ferrocene and benzyldimethylamine react with Cp*Fe(CO)₂I to give the new complexes ((Cp*Fe(CO)₂)-2-(CH₂NMe₂)C5H ₃)Fe(Cp) and Cp*Fe(CO)2-C₆H₄(o- CH2NMe₂). Access to a wide variety of alkoxy-substituted complexes ((Cp*Fe(CO)₂)-2-(CH2OR)C₅H₃)Fe(Cp) can be easily achieved by tandem quaternization/alcoholysis of ((Cp*Fe(CO) ₂)-2-(CH₂NMe₂)C₅H ₃)Fe(Cp). Preliminary results show that chelated complexes can be obtained by displacement of one of the carbonyl ligands by photolysis. Crystal structures of ((Cp*Fe(CO)₂)-2-(CH₂NMe ₂)C₅H₃)Fe(Cp), ((Cp*Fe(CO) ₂)-2-(CH₂OR)C₅H₃)Fe(Cp) (R = Ph, Bz, CHPh2 and d-menthyl) and [Cp*Fe(CO)2-C₆H₄(o-CH ₂NMe₂)][I] are reported.

Full text of DOI:10.1016/j.jorganchem.2013.05.031

Accepted Manuscript
Synthesis, Reactivity, and Some Photochemistry of Ortho-N,N-dimethylaminomethyl
Substituted Aryl and Ferrocenyl Pentamethylcyclopentadienyl Dicarbonyl Iron
Complexes
Grelaud Guillaume, Thierry Roisnel, Vincent Dorcet, Mark G. Humphrey, Fré dé ric
Paul, Gilles Argouarch
PII:
S0022-328X(13)00418-X
10.1016/j.jorganchem.2013.05.031
JOM 18053
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 25 March 2013
Revised Date: 15 May 2013
Accepted Date: 23 May 2013
Please cite this article as: G. Guillaume, T. Roisnel, V. Dorcet, M.G. Humphrey, F. Paul, G. Argouarch,
Synthesis, Reactivity, and Some Photochemistry of Ortho-N,N-dimethylaminomethyl Substituted Aryl
and Ferrocenyl Pentamethylcyclopentadienyl Dicarbonyl Iron Complexes, Journal of Organometallic
Chemistry (2013), doi: 10.1016/j.jorganchem.2013.05.031.
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ACCEPTED MANUSCRIPT
Graphical Abstract

ACCEPTED MANUSCRIPT
Highlights
•
•
•
New pentamethylcyclopentadienyl dicarbonyl iron complexes are synthesized
The parent alkoxy-substituted complexes are obtained by quaternization/alcoholysis
Photolytic displacement of carbonyl ligands is achieved to form chelated complexes

ACCEPTED MANUSCRIPT
Synthesis, Reactivity, and Some Photochemistry of
Ortho-N,N-dimethylaminomethyl Substituted Aryl
and Ferrocenyl Pentamethylcyclopentadienyl
Dicarbonyl Iron Complexes
Grelaud Guillaume,†,‡ Thierry Roisnel,§ Vincent Dorcet,§ Mark G. Humphrey,‡ Frédéric Paul,†
and Gilles Argouarch†,*
† Institut des Sciences Chimiques de Rennes, Organométalliques: Matériaux et Catalyse, UMR
CNRS 6226, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France.
‡ Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
§ Institut des Sciences Chimiques de Rennes, Centre de Diffractométrie X, UMR CNRS 6226,
Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France.
E-mail: gilles.argouarch@univ-rennes1.fr
Keywords: Iron complexes, Piano-stool structures, Ferrocenes, Alcoholysis.
1

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Abstract:
Ortho-lithiated N,N-dimethylaminomethyl ferrocene and benzyldimethylamine react with
Cp*Fe(CO)2I to give the new complexes ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp) and
Cp*Fe(CO)2-C6H4(o-CH2NMe2). Access to a wide variety of alkoxy-substituted complexes
((Cp*Fe(CO)2)-2-(CH2OR)C5H3)Fe(Cp)
can
be
easily
achieved
by
tandem
quaternization/alcoholysis of ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp). Preliminary results
show that chelated complexes can be obtained by displacement of one of the carbonyl ligands by
photolysis. Crystal structures of ((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp), ((Cp*Fe(CO)2)-2-
(CH2OR)C5H3)Fe(Cp) (R = Ph, Bz, CHPh2 and d-menthyl) and [Cp*Fe(CO)2-C6H4(o-
CH2NMe2)][I] are reported.
2

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Graphical Abstract
3

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Highlights
•
•
•
((Cp*Fe(CO)2)-2-(CH2NMe2)C5H3)Fe(Cp) and Cp*Fe(CO)2-C6H4(o-CH2NMe2) are
synthesized from Cp*Fe(CO)2I and ortho-lithiated N,N-dimethylaminomethyl ferrocene
or benzyldimethylamine
alkoxy-substituted complexes ((Cp*Fe(CO)2)-2-(CH2OR)C5H3)Fe(Cp) can be easily
obtained
by
tandem
quaternization/alcoholysis
of
((Cp*Fe(CO)2)-2-
(CH2NMe2)C5H3)Fe(Cp).
Photolytic displacement of one of the carbonyl ligands of Cp*Fe(CO)2-C6H4(o-
CH2NMe2) yield the corresponding chelated complex.
4

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1. Introduction
In the last decade the importance of iron in catalysis has grown due to its sustainability,
environmentally benign impact, and low-cost. Iron-catalyzed transformations now compete and
sometime outperform expensive transition-metal catalyzed processes,[1-11] making iron a viable
alternative to rhodium, ruthenium and palladium, for example. In this regard, special attention is
given to well-defined complexes possessing a cyclopentadienyl mono- or dicarbonyl iron
moiety.[12-29] Among such catalysts, the importance of the neutral complex CpFe(CO)2Me (1,
Cp: cyclopentadienyl = η5-C5H5)[14-20] and the cationic complex [CpFe(CO)2(THF)][BF4]
(2)[21-24] are particularly noteworthy (Figure 1). Indeed, the readily accessible complex 1 has
been used as a precursor to more elaborate iron catalysts for various catalytic transformations,
and more recently its catalytic activity for the dehydrogenative coupling reaction between thiols
andh hydrosilanes to form thiosilanes was reported.[15] The commercially available THF adduct
2 of the 16-electron complex [CpFe(CO)2]+ has been employed extensively as a mild Lewis acid
catalyst in many homogeneous reactions such as cyclopropanation of alkenes, epoxidation of
aromatic aldehydes, or aziridination of aryl imines. More recently, efficient visible light-
promoted reduction of aldehydes, ketones, esters, imines and amides has been described by
Darcel et al. using NHC and phosphine complexes 3 and 4 as well as some of their
derivatives.[25-30].
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Figure 1. Selected catalysts incorporating the [CpFe(CO)2] fragment.
In addition to the increasing number of [CpFe(CO)n]-based complexes that are active in
catalytic processes, half-sandwich iron carbonyl molecules with modified Cp rings or
incorporating the bulky and electron-rich Cp* ligand (Cp*: pentamethylcyclopentadienyl = η5
-
C5Me5) have been recently designed for applications in catalysis.[17, 31, 32] For example, Royo
et al. synthesized the iodo carbonyl complexes 5 which display good catalytic activity for the
transfer hydrogenation of ketones and reduction of sulfoxides,[33, 34] despite the presence of the
sterically demanding N-heterocyclic carbene-functionalized cyclopentadienyl ligand, while
Sawamoto et al. have prepared and used complex 6 in the living radical polymerization of methyl
methacrylate,[35] showing that superior control of the polymerization reaction is exhibited by a
complex bearing a Cp* ligand over that shown by a complex ligated by a Cp ligand (Figure 2).
Figure 2: Selected Cp-modified or Cp* iron carbonyl catalysts. R = H, Me; X = H, Me, OMe.
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In a previous communication,[36] we have reported the synthesis of a series of piano-
stool iron(II) σ–aryl complexes of general formula Cp*Fe(CO)2Ar (7-X, X = H, Me, OMe),
together with the ferrocenyl analogue 8. This family of molecules was found to display good
catalytic activity for the photo-catalyzed reductive etherification of aldehydes;[37] the 16-
electron catalytically-active species were unambiguously shown to originate from photochemical
decarbonylation of these complexes. In an attempt to develop this class of catalysts, our attention
was drawn to the introduction of new functionalities on the ancillary phenyl or ferrocenyl
moieties σ-bonded to the [Cp*Fe(CO)2] fragment, as a preamble to the exchange of the reactive
carbonyl ligands connected to the iron metal center. Hence, we describe herein the synthesis of
new pentamethylcyclopentadienyl dicarbonyl iron complexes featuring 2-dimethylaminomethyl-
substituted ferrocenyl and phenyl ligands. Their reactivities toward alcohols following
quaternization of their amine function are also presented, as an efficient pathway to new
ferrocene-based ethers. Electrochemical (from cyclic voltammetry) and structural properties
(from single-crystal X-ray structural studies) are reported. Finally, initial results of the UV-
promoted intramolecular ligand exchange at these compounds are described.
2. Results and discussion
The
synthesis
of
the
2-(N,N-dimethylamino)methyl-substituted
ferrocenyl
pentamethylcyclopentadienyl dicarbonyl iron complex 10 was achieved by reaction between the
iodo precursor Cp*Fe(CO)2I 9 [38] and ortho-lithiated N,N-dimethylaminomethyl ferrocene [39]
in diethyl ether (Scheme 1). Nucleophilic substitution of the iodide in 9 by lithium reagent readily
takes place, 10 being isolated in moderate yield as an air-stable orange solid. Since deprotonation
at the 2-position of N,N-dimethylaminomethyl ferrocene with n-BuLi occurs without any
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diastereoselectivity [40], 10 was obtained as its racemic mixture. The phenyl analogue 11 was
obtained by the same method, using (o-(N,N-dimethylaminomethyl)phenyl)lithium [41, 42] as the
lithium reagent, but in somewhat higher yield, as a yellow solid with a marked light sensitivity in
solution.
Scheme 1: Synthesis of complexes 10 and 11.
The complexes were readily identified by microanalysis, spectroscopy and, in the case of
10, single-crystal X-ray diffraction (vide infra). The ESI spectra contain molecular ions at m/z
489.1 (10, [M]+) and 382.1 (11, [M+H]+) with, in the case of 10, a fragmentation peak
corresponding to the loss of the dimethylamino substituent (m/z = 445.06, 46%). The presence of
the [Cp*Fe(CO)2] moiety in these complexes is evidenced by two strong νC≡O bands at ca. 1990
and 1930 cm-1 in the IR spectra. The Cp* ligand gives typical NMR resonances at δH ca. 1.70
ppm and δC ca. 96 and 10 ppm. The carbonyl ligands are also visible by 13C NMR spectroscopy,
with two signals at δC 219.2 and 218.3 ppm for 10 (due to rotational constraints that are also
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related to the planar chirality) and one for 11 at 218.1 ppm. Resonances at δH 2.20 – 2.30 ppm
and δC ca. 46 ppm are related to the dimethylamino moieties whereas the ferrocenyl (10) and aryl
(11) signals are found within the expected ranges. The presence of the substituted redox-active
ferrocene in 10 is also confirmed by the observation of a fully reversible wave by cyclic
voltammetry in CH2Cl2 at 0.16 V (vs. SCE in CH2Cl2), a feature absent in the voltammogram of
11. The assignment of the reversible process in the cyclic voltammogram of 10 to the ferrocenic
moiety is definitely supported by the observation of a similar chemically reversible wave in the
voltammogram of 8,[43] its Cp analogue CpFe(CO)2Fc,[44-47] and for their ruthenium
counterparts CpRu(CO)2Fc and Cp*Ru(CO)2Fc.[48] Moreover, in the voltammograms of both 10
and 11 two irreversible waves at higher potential can be seen, likely to be related to the oxidation
of the [Cp*Fe(CO)2] and dimethylamino moieties.
Displacement of trimethylammonium groups by nucleophiles such as cyanide or hydroxyl
anion is a known reaction at α-dimethylaminomethyl ferrocene methiodide substrates [49-51].
Thus, in order to introduce other functional groups at 10, its quaternization with methyl iodide
was attempted. However, these reactions were unsuccessful in most polar solvents, giving only
decomposition products, while the reactivity of 10 towards methyl iodide was sluggish in apolar
media. However, when methanol was used as the solvent, an orange complex could be isolated in
pure form by column chromatography. This complex exhibits typical signatures for the carbonyl
ligands (νC≡O bands at 1990 and 1934 cm-1, 13C NMR resonances at δC 219.0 and 218.1 ppm) and
Cp* ligands (δC: 96.4 and 9.6 ppm, δH: 1.71 ppm) of a [Cp*Fe(CO)2] moiety along with those of
a 1,2-substituted ferrocene. The reversible wave observed by cyclic voltammetry at 0.13 V (vs.
SCE in CH2Cl2), at a very similar potential to that in 10, was also indicative of the presence of the
redox-active ferrocenic moiety. Finally, the presence of singlets at δH 3.33 ppm and δC 58.1 ppm
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in the NMR spectra and the appearance of bands at 2815 and 1031 cm-1 in the IR spectra are
consistent with assignment of the compound as the methoxy-substituted complex 13-Me,
resulting from solvolysis of the elusive methiodide 12 (Scheme 2). By optimizing the reaction
conditions, 13-Me was obtained in up to 71 % yield and changing the solvent to ethanol or
isopropanol led to the isolation of two other alkoxy derivatives 13-Et and 13-iPr in 57 and 68 %
yield, respectively.
Scheme 2: Solvolysis of 10 in the presence of iodomethane.
The reactivity of 10 towards alcohols in the presence of methyl iodide contrasts to that
observed with the aryl complex 11, which only gave the corresponding ammonium salt 14 in 92
% yield under similar conditions (Scheme 3). The formulation of 14 as the methiodide of 11 and
not the methoxy-substituted complex 15 was clearly established by X-ray analysis on a single
crystal (see below), and is in line with the spectroscopic data. The new complex 15 was prepared
by an alternative procedure, namely reaction between 9 and 2-(methoxymethyl)phenyl lithium,
isolated in 53 % yield, and fully characterized.
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Scheme 3: Synthesis of 14 and 15.
To assess if the reactivity of 10 results from the presence of the ferrocenyl substituent,
N,N-dimethylaminomethylferrocene (16) was subjected to the same reaction conditions as were
successfully utilized for the formation of 13-Me. In accordance with literature reports for these
type of substrates [40, 52, 53], N,N-dimethylaminomethylferrocene methiodide (17) was formed
in high yield (84 %), but together with a small amount of methoxymethylferrocene (18, 14 %
isolated yield). This proves that methanolysis of the ammonium salt 17 occurs under these
reaction conditions but is a slow process. Indeed, 17 had to be refluxed for 24 h in methanol in
order to obtain a similar yield than that observed for the formation of 13-Me from 10 (Scheme 4)
[54], the latter readily taking place at room temperature in a significantly shorter period of time.
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S
cheme 4: Syntheses of 17 and 18.
It can be concluded that the stabilization of the carbocation formed by the loss of the
trimethylamino group, via coordination of the cyclopentadienyl-methylidene ligand (in a η6-
fulvenic fashion) by the iron atom [55], is favored by the presence of the electron-rich
[Cp*Fe(CO)2] synthon in 10, which increases the electron density at the iron center of the
ferrocene. This is supported by the lower value of the oxidation potential of the ferrocenyl in 10
compared to that of N,N-dimethylaminomethylferrocene (16) (0.16 and 0.66 V vs. SCE in
CH2Cl2, respectively) [56]. The release of the trimethylammonium group in 12 may occur
spontaneously at room temperature in polar solvents, preventing its isolation and giving only
decomposition products in the absence of nucleophiles.. Although the electron-rich
[Cp*Fe(CO)2] synthon is also present on 14, the lower stabilization of the “benzylic” carbocation
probably makes the displacement of the ammonium more difficult at 14. As a result, 14 retains
the same inertness toward methanolysis as benzyltrimethylammonium iodide [57].
Using acetonitrile as the solvent enabled to extend the scope of the dimethylamino/alkoxy
substitution reaction at 10 (via the elusive methiodide 12) to other (non-solvent) alcohols. A
12

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variety of them were thus reacted with 10 in the presence of methyl iodide to give the new
alkoxy-substituted complexes 13-R in moderate yields (Table 1).
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Entry
Alcohol
Complex
Yield
1
57 %
13-Ph
2
3
58 %
53 %
13-Bz
13-CHMePh
13-CHPh2
4
5
29 %
40 %
13-Menthyl
OH
Table 1: Alcoholysis of 10 in acetonitrile.
No difference in reactivity between the previous aliphatic alcohols and phenol (Entry 1)
or benzyl alcohol (Entry 2) was observed. The only limitation of this reaction can be ascribed to
14

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steric considerations: with benzhydrol (Entry 4) the yield dropped significantly when compared
to 1-phenylethanol (Entry 3), and with the spatially demanding triphenylmethanol no reaction
took place at all. Finally the introduction of a menthyl group was also achieved using d-menthol
(Entry 5). All these complexes were fully characterized and the solid-state structures of four of
them (R = Ph, Bz, CHPh2, Menthyl) were obtained (Figure 6).
The excess of methyl iodide required in this procedure precluded extending the scope to
embrace N-, S- and P-nucleophiles. Indeed, these are likely to be quaternized and thereby
becoming unreactive toward 12. Nevertheless, this method could also be applied to the
trimethylammonium derivative 17. As exemplified in Scheme 5, refluxing an acetonitrile solution
of 17 in the presence of excess benzhydrol gave benzhydriloxymethyl ferrocene 19 in 16 % yield
(not optimized).
Scheme 5: Alcoholysis of 17 with benzhydrol.
Next, introduction of simple structural changes within the iron carbonyl coordination
sphere of the present complexes was attempted by means of intramolecular ligand exchange
reactions. Taking advantage of the easy photodecarbonylation of iron carbonyl piano-stool
complexes, clean formation of the chelate 20 was achieved when a toluene solution of 11 was
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irradiated under UV-light for 16 h (Scheme 6). Compound 20 was isolated in 71 % yield after
purification by precipitation from n-pentane at -90 °C. It is noteworthy that 20 has an asymmetric
iron atom and is obtained as a racemic mixture. Unfortunately, such clean and selective
photodecarbonylation was not observed when the same procedure was applied to complexes 10
and 15 in various solvents, since some dimeric [Cp*Fe(CO)2]2 species (resulting from Fe-C bond
cleavage) was generated along with unstable side-products and/or incomplete chelate formation.
Scheme 6: Formation of 20 by photolysis.
In the case of 11, the completeness of the monodecarbonylation/chelation reaction can be
assessed in a convenient fashion by IR spectroscopy: the two original νC≡O bands in 11 at 1989
and 1932 cm-1 are replaced by a single band at 1886 cm-1. A molecular ion peak in the ESI
spectrum at m/z 353.1 in addition to fragments corresponding to the loss of the remaining
carbonyl ligand (m/z: 325.2; 62 %) and to [Cp*FePh] (m/z: 268.2; 10 %) were also consistent
with the formulation of 20 as depicted above. The most visible changes following formation of
1
this metallacycle can still be seen by H NMR. Around the asymmetric iron center there is
constrained rotation, and the signals of the dimethylamino moiety and of the benzylic protons are
2
both split, into two individual singlets and into two doublets (with JH,H = 9 Hz), respectively.
The signals found at higher field can be assigned to the protons closest to the Cp* ligand, the ring
current deshielding the signals (Figure 3).
16

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Figure 3: Comparison of the 1H NMR spectra of 11 (in CDCl3) and 20 (in C6D6).
Coordination of the dimethylamino moiety to the iron centre also induces changes in the
redox behavior of the complex: while the CV trace of 11 only shows two irreversible waves at
around 0.9 – 1.20 V for both the amino and iron centers (vide supra), an additional perfectly
reversible process is observed for 20 at ca. 0.0 V vs. SCE (Figure 4). The chemical reversibility
of this redox event is very likely to be related to the Fe(II)/Fe(III) couple,indicating a better
stabilization of the Fe(III) species on the measurement timescale when the σ-donor nitrogen
ligand is coordinated to the iron atom, as already observed with mono-phosphine complexes[58,
59].
17

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Figure 4: Left: superimposed CV traces of 11 (top) and 20 (bottom) in CH2Cl2/0.10 M [n-
Bu4N][PF6] with a -1.0 – 1.6 V scan range. Right: close-up view of the reversible process of 20.
The crystal structures of complexes 10, 13-R (R = Ph, Bz, CHPh2, menthyl) and 14 were
determined by single-crystal X-ray diffraction. ORTEP representations of complexes 10 and 14
are displayed in Figure 5, while compounds 13-R are represented in Figure 6. Crystallographic
data are combined in Tables 2 and 3. Examination of the packing of racemic ferrocenyl
complexes 10 and 13-R (R = Ph, Bz, CHPh2) shows that both enantiomers are present in the unit
cell whereas for complex 13-Menthyl the crystal studied is constituted only from the RFc-d-
menthyl diastereomer. In all complexes, the iron atom of the [Cp*Fe(CO)2] moiety is in a
pseudo-octahedral environment, with three coordination positions occupied by the Cp* ligand
and the three others by the two carbonyls and ferrocenyl (10, 13-R) or aryl (14) ligands. Bond
lengths and angles are similar to those found in the parent complexes 7-H and 8 [36], the only
significant differences compared with those two unsubstituted complexes being the unequal OC-
Fe-Cispo angles, with the OC-Fe-Cispo angle on the same side of the CH2X substituent being
18

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substantially wider (91.31 – 99.91°) than those on the other side (88.36 – 89.93°). This feature
allows to accommodate the steric bulk of the CH2X substituent. As a consequence, the
geometries around the iron centre are deformed in 10, 13-R and 14 compared than in their
unsubstituted parents 7-H and 8, which are almost perfectly symmetrical. This effect is even
more marked for 14, as the aryl ring brings the substituent closer to the iron center than is the
case with a 1,2-substituted ferrocene. In complexes 10 and 13-R the cyclopentadienyl ligands of
the ferrocenic fragment are in an eclipsed conformation, with a barely discernible tilt angle as
revealed by the Cpsubst-Fe-Cp angles ranging from 177.0 to 179.9°. In most cases the value of the
tilt angle is higher than is the case for 8, the increased steric hindrance of the substituted Cp ring
displacing the entire ferrocenyl unit towards the iron center in a disfavored conformation, the tilt
angle being increased as a consequence. Overall, the ferrocenyl moieties in 10 and 13-R are very
similar (in term of bond lengths) to ferrocene itself [60]. In 14 the iodine atom is closer to the
nitrogen (4.344 Å) than the iron atom (7.112 Å) [61], confirming the presence of the positive
charge on the former. These electrostatic attractions result in an arrangement of the nitrogen and
iodide of two anion/cation pairs in an almost square fashion (side length: 4.344 and 5.055 Å,
angles: 88.83 and 91.97°). Lastly, an explanation of the unsuccessful reaction of 10 (via 12) with
triphenylmethanol due to steric limitations can be deduced from the molecular structure of 13-
CHPh2. The hydrogen atom of the benzhydril substituent is located within a pocket formed by
the Cp*Fe(CO2) and one phenyl of the benzhydril, the C-H bond being on an axis parallel to that
one of the Fe-Cipso bond and pointing toward the bulky Cp* substituent. In the case of a
hypothetical 13-CPh3, it then become apparent that the additional phenyl ring could not be
accommodated in that available space, explaining thereby the absence of reaction between 12 and
triphenylmethanol. With steric repulsion preventing the approach of triphenylmethanol to 12, no
substitution reaction could take place, and only decomposition of 12 occurred.
19

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Figure 5: ORTEP representations of complexes 10 (left, racemic twins) and 14 (right) with 50%
thermal ellipsoids. Hydrogen atoms and CH2Cl2 solvate (14) have been omitted for clarity.
20

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A
B
C
D
Figure 6: ORTEP representation of the RFc enantiomer of complexes 13-Ph (A), 13-Bz (B), 13-
CHPh2 (C) and 13-Menthyl (D) with 50% thermal ellipsoids. Hydrogen atoms have been
omitted for clarity.
21

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Compound
Formula
10a
13-Pha
13-Bza
C30H32Fe2O3
1104.51
13-CHPh2
C36H36Fe2O3
628.35
13-Menthyl
C33H44Fe2O3
600.38
14
C25H31Fe2NO2
978.42
C29H30Fe2O3
1076.46
C22H30FeINO2
1131.37
Fw, g/mol
Crystal size, mm
Color
0.52 × 0.37 × 0.32
Orange
P b c 21
9.0778(3)
16.9803(7)
29.9753(13)
90
0.6 × 0.34 × 0.28
Orange
0.54 × 0.48 × 0.4
Orange
C c
0.4 × 0.2 × 0.1
Orange
0.6 × 0.1 × 0.08
Red
0.46 × 0.07 × 0.04
Yellow
space group
a, Å
P -1
P -1
P 21 21 21
10.4735(11)
11.9525(12)
24.381(3)
90
C 2/c
13.3551(5)
13.3642(4)
14.4993(5)
98.5850(10)
100.1160(10)
99.4890(10)
2470.05(15)
2
16.7845(4)
14.5218(5)
21.1350(6)
90
10.0067(4)
10.9900(4)
14.3062(6)
89.180(2)
81.398(2)
78.149(2)
1522.23(10)
2
33.5797(8)
7.6772(2)
25.3776(5)
90
b, Å
c, Å
α, deg
90
94.3760(10)
90
90
132.7030(10)
90
β, deg
90
90
γ, deg
V, Å3
4620.5(3)
4
5136.5(3)
4
3052.1(6)
4
4807.79(19)
4
Z
dcalcd, g/cm3
θ range, deg
µ, mm–1
1.407
1.447
1.428
1.371
1.307
1.563
3.15 to 27.41
1.276
3.01 to 27.48
1.203
2.97 to 27.48
1.159
3.04 to 27.48
0.987
3.08 to 27.47
0.981
3.52 to 27.48
2.040
8637
8549
9101
5704
5170
4504
no. of obsd data, I > 2σ (I)
data / restraints / parameters
R1 (all data)b
wR2 (all data)c
(∆ρ)min, e.Å–3
(∆ρ)max, e.Å–3
9925 / 1 / 555
0.0464
11145 / 0 / 623
0.0564
10983 / 20 / 390
0.0488
6903 / 0 / 375
0.0476
6661 / 0 / 343
0.0697
5428 / 0 / 266
0.0447
0.0847
0.0902
0.0864
0.1042
0.0886
0.0687
-0.542
-0.345
-0.435
-0.477
-0.421
-0.72
0.448
0.341
0.457
0.773
0.514
0.723
Table 2.Selected crystallographic data and collection parameters for 10, 13-R and 14. a Two molecules in the asymmetric unit. b R1 = ∑ | |Fo| -
2
2 2
|Fc| | / ∑ |Fo|.c wR2 = {∑ [w(Fo -Fc2)2] / ∑ [w(Fo ) }1/2.
23

ACCEPTED MANUSCRIPT
13-Bz: RFc; SFc
Compound
Bond lengths (Å)
Fe-Cp*
10: RFc; SFc
13-Ph: RFc; R’Fc
13-CHPh2
13-Menthyl
14
1.739; 1.737
2.013(3); 2.019(3)
1.150 (5); 1.764(4)
1.50(4); 1.760(4)
1.150(5); 1.154(5)
1.150(4); 1.159(4)
1.656; 1.655
1.727; 1.721
1.720; 1.735
2.003(8); 2.000(9)
1.751(9); 1.746(9)
1.770(9); 1.745(9)
1.144(10); 1.163(11)
1.124(11); 1.173(11)
1.655; 1.631
1.735
1.733
1.747
2.031(3)
1.755(3)
1.755(3)
1.146(3)
1.151(3)
/
Fe-C
1.997(2); 2.004(2)
1.749(2); 1.755(3)
1.755(3); 1.757(3)
1.155(3); 1.150(3)
1.149(3); 1.147(3)
1.646; 1.646
2.005(2)
1.752(2)
1.754(2)
1.149(3)
1.153(3)
1.644
2.005(3)
1.746(4)
1.757(4)
1.161(4)
1.160(4)
1.651
Fe-CO
C-O
FeFc-Cpsubst
FeFc-Cp
1.661; 1.666
1.651; 1.655
1.653; 1.644
1.648
1.649
/
CCp/Ar-CH2
CH2-N/O
N/O-C
1.517(5); 1.509(5)
1.475(5); 1.466(5)
1.465(5); 1.463(5)
1.463(6); 1.464(6)
1.484(3); 1.492(3)
1.449(2); 1.446(2)
1.372(3); 1.377(3)
1.467(11); 1.512(10)
1.455(9); 1.422(9)
1.407(9); 1.421(8)
1.495(3)
1.443(2)
1.429(3)
1.502(5)
1.442(4)
1.422(4)
1.505(3)
1.538(3)
1.494(3); 1.496(3)
1.500(3)
Angles (°)
Cp*-Fe-CO
122.31; 122.85
124.59; 124.59
121.54; 121.33
88.61(16);88.58(15)
94.19(16); 94.49(15)
96.42(18); 96.57(17)
93.52; 93.2
123.89; 123.45
126.14; 124.48
120.86; 122.10
88.56(10); 88.36(10)
91.31(10); 92.07(10)
96.14(11); 97.04(11)
93.20; 91.43
123.87; 123.91
124.78; 123.73
121.69; 122.49
88.9(4); 89.3(4)
93.4(4); 92.6(4)
95.0(4); 95.7(4)
91.61; 92.63
123.36
126.20
124.22
124.36
123.46
125.31
Cp*-Fe-C
OC-Fe-C
120.33
120.89
118.97
89.96(9)
94.10(9)
93.72(10)
94.48
89.14(15)
94.60(16)
94.74(17)
94.16
89.93(12)
99.91(11)
OC-Fe-CO
91.29(12)
Fe-Cpsubst-FeFc
Cpsubst-FeFc-Cp
Fe-CCp/Ar-CH2
CCp/Ar-CH2-N/O
CH2-N/O-C
/
179.93; 178.7
178.83; 179.58
89.77; 89.00
178.70; 178.12
88.90; 89.51
178.90
177.0
/
89.25; 89.70
89.96
91.20
/
113.70; 113.55
108.6(3); 109.5(3)
108.06(17);
111.3(6); 109.4(6)
111.3(6); 109.5(5)
107.70(18)
113.09(17)
107.7(3)
116.5(3)
115.0(2)
116.96(17);
107.2(2); 110.85(19)
112.8(3); 112.9(3)
113.0(2)
25
Table 3. Selected bond lengths and angles for 10, 13-R and 14.

ACCEPTED MANUSCRIPT
3. Conclusion
Syntheses of Cp*Fe(CO)2 ferrocenyl and aryl complexes bearing a dimethylaminomethyl
substituent at their ortho position was achieved by reaction between the iodo precursor 9 and the
corresponding ortho-lithiated N,N-dimethylaminomethylferrocene and benzyldimethylamine. Upon
reaction with methyl iodide in methanol, the expected corresponding ammonium salt was obtained in
the case of the aryl complex 11. In contrast for the ferrocenyl complex 10, etherification of the
elusive ammonium 12 readily takes place by methanolysis and the methoxy-substituted complex 13-
Me is isolated instead. Alcoholysis of 12 also occurs in ethanol, isopropanol and in acetonitrile in the
presence of an excess of alcohol, permitting access to a variety of alkoxy-substituted complexes.
However, the reaction shows a dependence on the steric bulk of the alcohol, with decreased yields (or
no reaction at all) when spatially demanding alcohols are employed. The same reaction occurs with
N,N-dimethylaminomethyl ferrocene methiodide, but at a much slower rate, which demonstrates that
the presence of the electron-rich [Cp*Fe(CO)2] moiety induces an increase in the reactivity of the
ferrocenyl substrate. Finally, photolysis of complexes 10 and 15 leads to the formation of unstable
complexes, decomposition products or incomplete chelate formation. However, in the case of 11
photolysis in toluene proceed cleanly and selectively and allows the isolation of the chelate 20 in
pure form. With the confirmation that this type of complex can be accessed by photolabilization of
one of the carbonyl ligands, further work is now required to obtain chelates of the other complexes
reported herein and to assess their catalytic behavior.
4. Experimental Section
4.1. General comments
Air and/or moisture sensitive reactions were performed under an atmosphere of argon in
distilled and deoxygenated solvents using standard Schlenk techniques. Photolyses were performed
27

ACCEPTED MANUSCRIPT
with a Heraeus UV lamp (TQ150, 150 W, medium pressure) equipped with a water-cooled quartz
jacket. Standard work-up consists of extraction of the reaction mixtures / solid residues with Et2O
(with filtration if necessary), washing of the organic extracts with water and saturated aqueous NaCl,
drying over MgSO4, filtration, and removal of the solvent under reduced pressure. Flash column
chromatography was performed using silica gel (Merck Kieselgel 60, 230 – 400 mesh) in glass
columns of various sizes (indicated as diameter × length). For ferrocenyl and amino-substituted
complexes, 1% Et3N was added in the eluent. Rf values were measured on silica plates.
4.2. Instruments
1H and 13C NMR spectra were recorded on a Bruker Ascend 400 MHz NMR spectrometer,
1
chemical shifts being referenced to the residual chloroform signal (δ 7.26 ppm for H, 77.0 ppm for
13C) [62]. Infrared spectra were obtained as KBr pellets [63], CH2Cl2 solution or liquid film between
NaCl windows, as indicated, on a Bruker IFS28 FT-IR spectrometer (400-4000 cm-1). UV-visible
spectra were measured as CH2Cl2 solutions, using a 1 cm long quartz cell in a Cary 5 spectrometer.
Cyclic voltammograms were recorded using a PAR 263 instrument in dry and degassed CH2Cl2
containing 0.1 M [n-Bu4N][PF6] at 20 °C with 100 mV/s scan rate at a platinum disk (1 mm
diameter), using a SCE reference electrode and ferrocene as internal calibrant (0.46 V vs SCE) [64].
Melting points were measured on a Kofler hot stage calibrated against a reference compound of
similar melting point. High resolution mass spectra and elemental analyses were performed at the
“Centre Regional de Mesures Physiques de l’Ouest” (CRMPO), Université de Rennes 1, France.
4.3. Reagents
Cp*Fe(CO)2I [38], (o-(N,N-dimethylaminomethyl)phenyl)lithium [41, 42], and o-
bromo(methoxymethyl)benzene [65] were prepared according to the literature methods, while other
chemicals were obtained commercially and used without further purification.
28

ACCEPTED MANUSCRIPT
4.3.1. General procedure for the syntheses of dicarbonyl(pentamethylcyclopentadienyl)iron
complexes from iododicarbonyl(pentamethylcyclopentadienyl)iron and lithium reagents
A Et2O or THF solution of the appropriate lithium reagent (1.20 – 1.25 eq.) was added
dropwise via a cannula to iododicarbonyl(pentamethylcyclopentadienyl)iron (1.0 eq.) dissolved in the
same solvent at 0°C. After 5 min of stirring at 0°C, the cooling bath was removed, stirring was
maintained for 1 h at room temperature, and the reaction mixture was slowly hydrolyzed with water
(25 mL). The crude oil or solid obtained after standard work-up was adsorbed onto elite and
chromatographed (silica gel). A red band of dicarbonyl(pentamethylcyclopentadienyl)iron dimer was
eluted (preceded by a yellow band of an unidentified volatile carbonyl iron complex) with
hexanes/Et2O 98:2, followed by a yellow or orange band of the desired complex which was eluted
with hexanes/Et2O (95:5 to 4:1). The residue obtained after removal of solvents was recrystallized
from aqueous ethanol, and the crystals obtained after 16 h of standing at -18°C were collected on a
fine porosity glass sintered funnel, washed with 50 % aqueous ethanol (10 mL), and dried in vacuo.
4.3.1.1.
rac-1-(dicarbonyl(pentamethylcyclopentadienyl)iron)-2-(N,N-
dimethylaminomethyl)ferrocene (10)
From
dimethylaminomethylferrocene (0.97 g, 4.0 mmol) and n-BuLi (2.75 mL, 1.60 M in hexanes, 4.40
mmol) in Et2O (25 mL) at room temperature for 16 h) [39] and
rac-2-lithio(dimethylaminomethyl)ferrocene
(prepared
from
N,N-
iododicarbonyl(pentamethylcyclopentadienyl)iron (1.20 g, 3.20 mmol) in Et2O (10 mL), 0.67 g (43
%) of orange needles were obtained. Column size: 5 × 20 cm. Recrystallization: EtOH/water 3:1, 40
mL. Rf (hexanes/ethyl acetate 1:1): 0.39. mp: 128°C. Elemental analysis: calcd for C25H31Fe2NO2: C:
61.38 %, H: 6.39 %, N: 2.86 %; found: C: 61.47 %, H: 6.48 %, N: 2.79 %. HRMS (ESI,
29

ACCEPTED MANUSCRIPT
CH3OH/CH2Cl2 9:1): calc: 489.1054 [M]+, found: 489.1052. IR (CH2Cl2, cm-1): 1989 and 1932 (s,
νC≡O), 813 (s, δC-H Cp Fc). UV-Visible (CH2Cl2): λmax, nm (ε, 103 M-1ꢀcm-1): 366 (1.9); 280 (8.8).
Cyclic voltammetry (CH2Cl2, 0.10 M [n-Bu4N][PF6], V vs. SCE): E1/2: 0.16 (ꢁE1/2 = 0.072 V; ipa/ipc =
1
1.0) 1.26 and 1.47 (irreversible processes). H NMR (400 MHz, CDCl3, ppm): δ 4.27, 4.10 and 3.75
(3 × s, 3 × 1H, Fc), 3.93 (s, 5H, Fc), 3.44 and 3.01 (2 × d, 2JH,H = 13 Hz, CH2), 2.23 (s, 6H, NMe2),
1.70 (s, 15H, Cp*). 13C{1H} NMR (100 MHz, CDCl3, ppm): δ 219.2 and 218.3 (2 × s, C≡O), 96.3 (s,
Cquat Cp*), 93.2 (s, Fe-C), 90.2 (s, Cipso CH2NMe2), 79.0, 71.5 and 68.1 (3 × s, Cp), 71.5 (s, C5H5),
61.8 (s, CH2), 46.0 (s, NMe2), 9.6 (s, CH3 Cp*). X-ray quality crystals were grown by slow cooling
of a saturated EtOH solution to -18°C.
4.3.1.2. dicarbonyl(pentamethylcyclopentadienyl)(o-(N,N-dimethylaminomethyl)phenyl)iron (11)
From (o-(N,N-dimethylaminomethyl)phenyl)lithium (0.85 g, 6.0 mmol) in THF (10 mL) and
iododicarbonyl(pentamethylcyclopentadienyl)iron (1.87 g, 5.0 mmol) in THF (25 mL), 1.10 g (58 %)
of yellow flakes were obtained. Column size: 5 × 15 cm. Recrystallization: EtOH/water 5:3, 80 mL.
Rf (ethyl acetate): 0.11. mp: 114°C. Elemental analysis: calcd for C21H27FeNO2: C: 66.15 %, H: 7.14
%, N: 3.67 %; found: C: 66.53 %, H: 7.19 %, N: 3.52 %. HRMS (ESI, CH3OH/CH2Cl2 9:1): calc:
382.1469 [M+H]+, found: 382.1467. IR (CH2Cl2, cm-1): 1992 and 1935 (vs, νC≡O). UV-Visible
(CH2Cl2): λmax, nm (ε, 103ꢀM-1ꢀcm-1): 360 (1.2), 294 (5.2). Cyclic voltammetry (CH2Cl2, 0.10 M [n-
1
Bu4N][PF6], V vs. SCE): E1/2: 0.97 and 1.24 (irreversible processes). H NMR (400 MHz, CDCl3,
3
3
3
ppm): δ 7.44 (t, 2H, JH,H = 7 Hz, C6H4), 6.96 (t, 1H, JH,H = 7 Hz, C6H4), 6.84 (t, 1H, JH,H = 7 Hz,
C6H4), 3.49 (s, 2H, CH2), 2.34 (s, 6H, NMe2), 1.67 (s, 15H, Cp*). 13C{1H} NMR (100 MHz, CDCl3,
ppm): δ 218.1 (s, C≡O), 156.7 and 148.2 (2 × s, Cquat C6H4), 144.7, 128.5, 124.9, and 122.9 (4 × s,
Caromatics), 96.6 (s, Cquat Cp*), 68.3 (s, CH2), 45.8 (s, NMe2), 9.8 (s, CH3 Cp*).
30