Mechanistical studies on C-H activation reactions of benzaldimines using selectively deuterated ligands: Synthesis and crystal structures of [μ2-η3-(R)N-CH 2-C=C-C(H)=C(H)-C(H)=C(H)]Fe2(CO)6

Article abstract of DOI:10.1016/S0022-328X(99)00082-0

The reaction of Fe₂(CO)₉ with imine ligands derived from benzaldehyde leads to the formation of dinuclear iron cluster compounds of the general formula [μ₂-η³-N-CH ₂-C=C-C(H)=C(H)-C(H)=C(H)]Fe₂(CO)₆ by a C-H activation/1,3-hydrogen shift reaction sequence. Six cluster compounds with alkyl and aryl substituents bound to nitrogen have been synthesised and characterised, five of them also by means of X-ray crystallography. The mechanism of the reaction has been investigated by the use of ligands being selectively deuterated in the 2-position. By several NMR experiments including deuterium spectra it can be demonstrated that the hydrogen/deuterium atom of the activated aromatic C-H bond is transferred to the former imine carbon atom producing a methylene group instead and that this reaction strictly follows an intramolecular pathway.

Full text of DOI:10.1016/S0022-328X(99)00082-0

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 33–43
Mechanistical studies on C–H activation reactions of
benzaldimines using selectively deuterated ligands: synthesis and
crystal structures of
¸¹¹¹¹¹¹¹¹¹¹¹¹¹¹º
[m2-h3-(R)N–CH2–CꢀC–C(H)ꢀC(H)–C(H)ꢀC(H)]Fe2(CO)6
Wolfgang Imhof a,*, Angela Go¨bel a, Dietmar Ohlmann a, Joachim Flemming b,
Hartmut Fritzsche b
a Institut fu¨r Anorganische und Analytische Chemie der Uni6ersita¨t, August-Bebel-Straße 2, D-07743 Jena, Germany
b Institut fu¨r Molekularbiologie der Uni6ersita¨t, Winzerlaer Straße 10, D-07745 Jena, Germany
Received 10 January 1999
Abstract
The reaction of Fe2(CO)9 with imine ligands derived from benzaldehyde leads to the formation of dinuclear iron cluster
¸¹¹¹¹¹¹¹¹¹¹¹¹¹¹º
compounds of the general formula [m2-h3-N–CH2–CꢀC–C(H)ꢀC(H)–C(H)ꢀC(H)]Fe2(CO)6 by a C–H activation/1,3-hydrogen
shift reaction sequence. Six cluster compounds with alkyl and aryl substituents bound to nitrogen have been synthesised and
characterised, five of them also by means of X-ray crystallography. The mechanism of the reaction has been investigated by the
use of ligands being selectively deuterated in the 2-position. By several NMR experiments including deuterium spectra it can be
demonstrated that the hydrogen/deuterium atom of the activated aromatic C–H bond is transferred to the former imine carbon
atom producing a methylene group instead and that this reaction strictly follows an intramolecular pathway. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: C–H activation; Iron; Imines; Deuterium-NMR; X-ray
a,b-unsaturated imines towards metal carbonyls of
Group 8 metals. It is well known that 1-azadiene
ligands react with Fe2(CO)9 to give mononuclear com-
plexes of the type (h4-azadiene)Fe(CO)3 [3]. Their reac-
tivity [4] is distinctively different compared with the
related (1,3-butadiene)Fe(CO)3 [5] and (1,4-diazadi-
ene)Fe(CO)3 [6] complexes. We recently synthesised a
series of (1-azadiene)Fe(CO)3 complexes and character-
ised them by means of single-crystal X-ray diffraction
[7]. In contrast to cinnamaldehyde derivatives, a,b-un-
saturated imines in which the C–C double bond is part
of a heterocyclic or carbocyclic aromatic system react
with Fe2(CO)9 by means of a C–H activation reaction
in b-position to the exocyclic imine group [8]. The
reaction then proceeds via a 1,3-hydrogen shift reaction
to produce a m2-h3-enyl–amido ligand bridging a
Fe2(CO)6 moiety. The first compounds of this type has
first been reported in Ref. [8c,f] where the reactions of
benzylideneaniline derivatives with Fe2(CO)9 have been
1. Introduction
The understanding of C–H activation processes is a
field of research with growing interest especially with
respect to the development of catalytic C–C bond
formation reactions. Due to this fact both inter- and
intramolecular C–H activation reactions have been in-
tensively studied and thoroughly reviewed in the last
years [1]. In recent times C–H activation reactions of
aromatic imines or ketones have been used to develop
catalytic C–C coupling reactions with CO and/or a
wide variety of olefins using Ru3(CO)12 or mononuclear
ruthenium complexes as catalysts [2]. To get a deeper
insight into these catalytic reactions which include C–H
activation steps we are interested in the reactivity of
* Corresponding author. Tel.: +49-3641-948114/488; fax: +49-
3641-948102.
E-mail address: cwi@rz.uni-jena.de (W. Imhof)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00082-0

34
W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
described. The same cluster compound is also available
from the reaction of Fe3(CO)12 with benzalazine [9].
Structural information is only available for the cluster
compounds described in Refs. [8f,9b] as well as for a
substitution product of the complex reported in [9b] in
which one CO ligand has been replaced by
triphenylphosphane [10]. Only very recently the first
corresponding dinuclear iron complex of an imine
derived from cinnamaldehyde has been isolated and
structurally characterised [8g]. Complexes with m2-h3-
enyl–amido moieties bridging dinuclear transition
metal fragments have been observed as byproducts
from the reaction of Ru3(CO)12 with a,b-unsaturated
imines of the cinnamaldehyde type [11] and by reacting
[CpCo(C2H4)2] with N-phenylbenzylideneamine [12].
Related iron compounds of the formula [(R)N–C(H)–
C(H)–Fe(CO)3–C(O)]Fe(CO)3 with a keto group in-
stead of the methylene moiety have been prepared from
the reaction of the carbene cluster (m2-CH2)Fe2(CO)8
with phosphine imides in the presence of CO [13].
Thermally induced rearrangement of those binuclear
cluster compounds yields the isomeric clusters [C(H)–
C(H)–N(R)–Fe(CO)3–C(O)]Fe(CO)3 [13]. Interestingly
the reaction of Ru3(CO)12 with imines derived from
benzaldehyde leads to the formation of mononuclear
complexes of the general formula Ru(imine)2(CO)2 in
which ruthenium is octahedrally coordinated by the
ligands [14] and to a trinuclear ruthenium cluster com-
pound in which the imine is coordinated via the CꢀN
double bond and no C–H activation reaction occurred
[14b].
Scheme 1.
selectively deuterated ligands and their corresponding
cluster compounds have been synthesised. Their 1H-
and H-NMR spectra indeed show the hydrogen shift
2
reaction to proceed strictly intramolecularly.
2. Results and discussion
The aromatic imine ligands 1–6 are easily prepared
by condensation of benzaldehyde with the correspond-
ing amine. Reaction of these imine ligands with
Fe2(CO)9 in n-heptane at 60°C leads to the formation
of the dinuclear iron cluster compounds [m2-h3-N–
¸¹¹¹¹¹¹¹¹¹¹¹¹¹¹º
CH2–CꢀC–C(H)ꢀC(H)–C(H)ꢀC(H)]Fe2(CO)6 (7–12)
in moderate yields. Compared to the reaction of hetero-
cyclic imine ligands the yields are distinctively lower
[8a,b] (Scheme 1).
In the first report on a dinuclear iron carbonyl
complex with a m2-h3-enyl-amido ligand, the compound
was described as an aza-ferra-cyclopentadiene being
coordinated to a second Fe(CO)3 moiety in an apical
position with two identical iron carbon bond lengths
from the aromatic carbon atoms towards the apical
iron atom [8f]. The complexes in Refs. [9b,10] show two
significantly different iron carbon bond lengths al-
though the only difference is a phenyl group attached
to nitrogen instead of a p-toyl substituent in [8f]. In the
X-ray structures of thecorresponding complexes derived
from heterocyclic imines we also observed this very
unsymmetrical coordination of the apical iron atom by
the aromatic carbon atoms [8a,b]. So we synthesised six
dinuclear iron cluster compounds of the general for-
mula [m2-h3-(R)N–CH2–CꢀC–C(H)ꢀC(H)–C(H)ꢀC-
(H)]Fe2(CO)6 (Scheme 1) by changing the substituent at
nitrogen to see whether the variation of electronic
properties also causes changes in the structural proper-
ties of these compounds. 2D-NMR experiments of the
derivative with R=C6H11 are described in order to
explain the NMR properties of the compounds. Since
we were particularly interested in the question whether
the hydrogen transfer reaction is strictly intramolecular
or if there are also intermolecular reaction pathways,
2.1. Structural determination
The cluster compounds 7–11 may be recrystallised
from mixtures of light petroleum (b.p. 40–60°C) and
CH2Cl2 at −20°C to give crystals suitable for X-ray
diffraction. The molecular structure of 7 is shown in
Fig. 1; the numbering scheme concerning the cluster
Fig. 1. Molecular structure of [m2-h3-C6H11–N–CH2–CꢀC–
C(H)ꢀC(H)–C(H)ꢀC(H)]Fe2(CO)6 (7).

W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
35
Table 1
Selected bond lengths (pm) and angles (°) of 7–11
7
8
9
10
11
Fe1–Fe2
Fe2–C1
C1–C6
C6–C7
N1–C7
Fe2–N1
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
Fe1–C1
Fe1–C6
Fe1–N1
N1–C8
244.1(1)
198.0(4)
141.3(6)
151.0(6)
147.0(5)
198.8(3)
144.0(6)
136.9(7)
140.5(7)
136.4(7)
141.6(6)
218.1(4)
233.6(4)
197.2(3)
149.2(5)
246.08(5)
198.7(2)
141.8(3)
150.5(3)
148.4(3)
198.2(2)
142.7(3)
136.9(3)
140.4(4)
137.2(3)
141.2(3)
217.3(2)
231.0(2)
197.0(2)
143.9(3)
244.54(8)
200.4(2)
141.4(3)
149.3(4)
147.9(3)
198.3(2)
141.3(3)
137.4(4)
139.6(5)
135.8(5)
141.4(3)
216.9(2)
236.9(2)
197.7(2)
143.8(3)
243.5(1)
198.7(5)
141.5(7)
150.5(7)
149.1(6)
199.4(4)
142.6(7)
138.2(9)
140(1)
136.5(9)
142.0(8)
217.8(5)
234.7(5)
197.9(4)
143.6(6)
244.59(8)
200.6(4)
140.4(5)
149.1(5)
147.8(5)
198.4(3)
141.9(5)
136.9(6)
139.7(7)
136.2(6)
141.2(5)
216.7(4)
237.0(4)
197.5(3)
144.3(4)
N1–Fe2–C1
Fe2–C1–C6
C1–C6–C7
C6–C7–N1
C7–N1–Fe2
C1–C2–C3
C2–C3–C4
C3–C4–C5
C4–C5–C6
C5–C6–C1
C6–C1–C2
C7–N1–C8
Fe2–N1–C8
Fe1–N1–C8
Fe2–Fe1–C1
Fe2–Fe1–C6
Fe2–Fe1–N1
C1–Fe1–C6
C1–Fe1–N1
C6–Fe1–N1
78.8(2)
114.2(3)
113.8(4)
101.7(3)
111.6(3)
121.6(4)
120.7(4)
120.3(4)
119.6(4)
122.0(4)
115.7(4)
115.1(3)
122.0(3)
125.4(3)
50.4(1)
78.80(8)
113.7(1)
114.2(2)
101.0(2)
111.4(2)
121.3(2)
120.8(2)
120.2(2)
119.7(2)
121.3(2)
116.7(2)
115.4(2)
119.0(1)
128.7(1)
50.31(5)
73.82(5)
51.70(5)
36.72(8)
74.70(7)
64.63(7)
78.76(9)
112.5(2)
115.2(2)
102.0(2)
110.8(1)
121.3(3)
120.8(3)
119.9(3)
120.3(3)
120.8(2)
116.9(2)
113.1(2)
122.5(2)
127.8(1)
51.05(6)
72.91(5)
51.97(5)
35.97(8)
75.04(8)
63.46(8)
79.3(2)
113.6(4)
114.7(5)
101.8(4)
110.7(3)
120.5(6)
121.5(6)
120.6(6)
118.4(6)
122.9(5)
116.1(5)
113.5(4)
122.0(3)
129.4(3)
50.7(1)
78.3(1)
113.1(3)
114.8(3)
102.0(3)
110.7(2)
121.1(4)
121.0(4)
119.9(4)
119.8(4)
121.5(4)
116.8(3)
112.7(3)
122.4(2)
128.4(2)
51.12(9)
72.97(8)
52.02(8)
35.7(1)
73.7(1)
52.2(1)
36.2(2)
74.5(2)
73.5(1)
52.5(1)
36.2(2)
75.2(2)
74.8(1)
63.4(1)
64.3(2)
64.3(2)
bonds; the bonds inside the metallated phenyl group
now are of alternating values, indicating a loss of
delocalisation caused by the coordination to the iron
atoms. So the bonds C1–C2, C3–C4 and C5–C6 are
significantly shorter than the bonds C2–C3 and C4–
C5. The bond between C1 and C6 is elongated com-
pared with the distances between C2–C3 and C4–C5
due to a p-coordination to the apical Fe(CO)3 group.
This interaction shows a very unsymmetrical bonding
mode with the bond between Fe1–C6 always being
about 20 pm longer than the Fe1–C1 bond distance.
The other bond lengths and angles are of expected
values.
core has been adopted for the structure analyses of
8–11. Selected bond lengths and angles are depicted in
Table 1. The molecular structure of 8 has been reported
in the literature [9b] but has been determined again in
order to localise the hydrogen atoms by difference
Fourier analysis to prove the formation of a methylene
group at C7 which is the former imine carbon atom of
the free ligand. In the structure analyses of 7–11 all
hydrogen atoms have been localised by difference
Fourier analyses and have been refined isotropically
without constraints.
As shown in Fig. 1, the structure consists of a
Fe2(CO)6 moiety adopting a nearly ecliptic conforma-
tion and a formal six-electron donating enyl–amido
ligand. The bond lengths and angles in Table 1 indicate
that mainly the bond distance between N1 and the ipso
atom C8 is affected by the variation of the organic
group at the former imine nitrogen atom whereas the
other bond lengths and angles show no significant
differences. The bond lengths at C7 are clearly single
2.2. NMR spectroscopy
1
The most characteristic features in the H- and 13C-
NMR spectra of 7–12 are the signals of the methylene
group which was formed during the C–H activation/
1
1,3-hydrogen shift reaction sequence. In the H-NMR

36
W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
spectra a singlet at l=3.92 is observed for 7 with R
being a cyclohexyl group, whereas the signals in 8–12
with aromatic substituents bound to nitrogen are found
at nearly identical chemical shifts at about l=4.35.
The corresponding 13C resonance is observed at about
l=75 for the compounds with aromatic substituents
bound to nitrogen and at l=64.8 for 7.
nance at l=125.5 whereas the signal at l=145.6 is
representing C1. The 13C signals of the metallated
phenyl group in 8–12 with aromatic substituents being
bound to nitrogen show almost identical chemical
shifts, whereas the corresponding resonances of 7 with
a alkyl group instead are observed at slightly different
values (see Section 3).
In order to achieve an unequivocal assignment of the
1H and especially of the 13C resonances of the metal-
lated phenyl group, several 2D-NMR spectra of 7 have
been recorded. Compound 7 was chosen as the model
2.3. Deuterated ligands and complexes
Scheme 2 shows the synthesis of deuterated ligands
and the corresponding dinuclear iron cluster com-
pounds. The 2H-NMR spectrum of 1a proves the ligand
to be selectively deuterated since there is only one signal
present at l=7.78. If the ligands 1a and 2a are reacted
with Fe2(CO)9 the deuterated homologues of 7 and 8
are produced (7a and 8a).
1
compound since in the H-NMR spectrum the remain-
ing four aromatic hydrogen atoms at C2–C5 show four
clearly separated signals and in the 13C-NMR spectrum
of course only the six resonances for the metallated
phenyl group are observed in the downfield region of
the spectrum. With the help of a NOESY spectrum of
7 it can be shown that there is a NOE between the
resonance of the methylene group and the signal at
l=7.50 which thus has to be assigned to the proton at
C5. The resonance of H5 shows a second NOE
crosspeak with the signal at l=7.32 which therefore is
representing H4. Again there is a second NOE of H4
with the signal at l=7.07 which therefore has to be the
resonance of H3 and which also shows a second NOE
with the doublet at l=8.12 which then is the signal of
H2. Using this information, the assignment of the 13C
spectrum is easily interpreted by means of a HMQC
spectrum. This spectrum clearly shows that the 13C
resonance at l=125.6 represents C3, the one at l=
128.1 C5, at l=130.5 C4 and at l=151.0 C2. The two
quaternary carbon signals at l=125.5 and l=145.6,
respectively, are assigned by comparing the spectra with
those of related m2-vinyl complexes in which the reso-
nance of the carbon atom which interacts with both
metal centres is observed downfield compared to the
signal of the carbon atom which is only part of the
p-coordination of the double bond towards one of the
metal atoms [15]. So C6 gives rise to a carbon reso-
If there was no isotopic effect the two ortho positions
in 1a and 2a should both be activated to the same
extend during the reaction with Fe2(CO)9 and so the
product compound should be a 1:1 mixture of two
different cluster compounds. In one of them the ortho
C–H bond would have been activated and thus by
1,3-hydrogen shift a methylene group would have been
produced at the former imine carbon atom, whereas the
deuterium atom would still adopt its position at the
metallated phenyl ring at C5. The other isomer would
be produced by activation of the ortho C–D bond in 1a
or 2a, so the product would show a CHD group at the
former imine carbon atom and a hydrogen at C5
1
(Scheme 2). The H-NMR spectrum of 7a shows the
signal of H5 at l=7.46 with approximately half the
intensity compared to the resonances of H4, H3 and
H2. In addition the signal representing the methylene
group at l=3.91 shows an integral representing about
1.5 hydrogen atoms. So the product indeed consists of
a 50:50 mixture as it is depicted in Scheme 2. The
deuterium-NMR spectrum of 7a thus shows two signals
at l=3.89 and l=7.49 representing the two possible
Scheme 2.

W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
37
Scheme 3.
1
positions of deuterium in the molecule. From these H-
and H-NMR spectra of 7a a scrambling of deuterium
3. Experimental
2
towards other positions in the molecule such as the
ones shown in Scheme 2 can clearly be excluded. There-
fore, it is reasonable that the hydrogen/deuterium atom
to be transferred towards the former imine carbon
atom is exactly the one that has been connected to the
now metallated carbon atom of the phenyl ring before
the reaction.
In order to prove whether the hydrogen transfer
reaction being responsible for the formation of the
methylene group in the dinuclear product clusters 7–12
proceeds via an intramolecular pathway we looked at
the reaction of Fe2(CO)9 with 1a and a heterocyclic
imine ligand namely 2-thiophenemethylenecyclohexyl-
amine 13 (Scheme 3). Recently, we reported the reactiv-
ity of 13 towards Fe2(CO)9 leading to derivatives of
7–12 [8a].
3.1. General
All procedures were carried out under an argon
atmosphere in anhydrous, freshly distilled solvents.
Chromatography was done using silica gel 60 and
silanised silica gel 60, 70–230 mesh ASTM (Merck),
which were dried at 10−2 bar (103 Pa) for 2 days before
use. Fe2(CO)9 was prepared from Fe(CO)5 (Lancaster)
by irradiation in acetic acid [16]. Infrared spectra were
recorded on a Perkin–Elmer FT-IR System 2000 using
0.2 mm KBr cuvettes. NMR spectra were recorded on
a Bruker AC 200 spectrometer (1H: 200 MHz with
SiMe4 as internal standard; 13C: 50.32 MHz with
1
CDCl3 as internal standard), H, HMQC and NOESY
spectra of 7 on a Bruker DRX 400 spectrometer (1H:
400 MHz; 13C: 100.62 MHz with CDCl3 as internal
We chose 13 because in the resulting dinuclear cluster
compound 14 the 1H-NMR resonances of the two
remaining aromatic protons have the same chemical
shift and the signal of the methylene group in the
product is well separated from the corresponding reso-
2
standard), H-NMR spectra of 1a, 7a and the mixture
of 7a and 14 on a Varian Inova 500 spectrometer (2H:
76.75 MHz). Mass spectra were recorded on a Finnigan
MAT SSQ 710 instrument. Elemental analyses were
carried out at the laboratory of the Institute of Organic
Chemistry and Macromolecular Chemistry of the
Friedrich-Schiller-University, Jena.
1
nance of 7a. In the H-NMR spectrum of the product
mixture (Fig. 2) the signal of the aromatic hydrogen
atoms of 14 is observed at about the same chemical
shift as H4 in 7a, but the resonances of H2, H3 and H5
still are clearly separated. Since the yield of 7a and 14
may be different we can only compare the intensity of
the signals belonging to the same compound. As ex-
pected, the intensity of H5 in 7a is half the intensity of
H2 and H3 and the signal of the corresponding
methylene group is 1.5 times the intensity of H2 and H3
as it was already shown for pure 7a. If on the other
hand, the intensity of the methylene resonance of 14
represents two protons in 14, the multiplet at about
l=7.3 representing the aromatic protons in 14 and H4
in 7a is exactly the sum of two protons in 14 and one in
3.2. X-ray crystallographic studies
Structural determination was carried out on a
Siemens P4 diffractometer using graphite monochro-
mated Mo–Ka radiation. The crystals were mounted in
a stream of cold nitrogen. Data were corrected for
Lorentz and polarisation effects but not for absorption.
The structures were solved by direct methods and
refined by full-matrix least-squares techniques against
F2 using the programs SHELXS-86 and SHELXL-93 [17].
Computations of the structures were done with the
program XPMA [18] and the molecular illustrations were
drawn using the program XP [19]. The crystal and
intensity data are given in Table 2. Additional material
on the structure analyses is available from the Fachin-
formationszentrum Chemie, Physik, Mathematik
GmbH, 76344 Eggenstein-Leopoldshafen 2, Germany
by mentioning the deposition numbers CSD-410169 (7),
-410170 (8), -410171 (9), -410172 (10), -410173 (11), the
author and the journal citation.
2
7a. In addition, the H-NMR spectrum of the mixture
of 7a and 14 only shows the signals of 7a but no
resonances that would arise from deuterium incorpora-
tion in 14 during the formation of the cluster com-
pounds. This result proves that the C–H
activation/1,3-hydrogen shift reaction sequence strictly
follows an intramolecular pathway since there is also
no deuterium scrambling from the deuterated ligand 1a
towards the reaction product of Fe(CO)9 with the thio-
phene ligand 13.

38
W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
3.3. Preparation of 1–6
77 (C6H5+, 26), 63 (C5H3+, 7), 51 (C4H3+, 13), 39
1
(C3H3+, 13); H-NMR (in CDCl3, 298 K) (ppm): 7.18–
The imines are prepared by stirring 5 g (47.2 mmol)
of benzaldehyde with an equimolar amount of the
corresponding amine (1: R=C6H11, 4.67 g; 2: R=
C6H5, 4.39 g; 3: R=4-CH3–C6H4, 5.05 g; 4: R=4-Br–
C6H4, 8.11 g; 5: R=4-CF3–C6H4, 7.59 g; 6:
R=3,5-(CF3)2–C6H3, 10.80 g) at 50°C. The proceeding
of the reaction is monitored by GC. After the reaction
is finished the resulting yellow to orange coloured oil is
distilled in vacuo to yield yellow oils, which crystallise
upon standing at room temperature (r.t.). Yields: 1:
R=C6H11, 7.28 g, 85.3%; 2: R=C6H5, 8.15 g, 92.4%;
3: R=4-CH3–C6H4, 9.12 g, 99.2%; 4: R=4-Br–C6H4,
7.99 g, 65.2%; 5: R=4-CF3–C6H4, 11.64 g, 99.1%; 6:
R=3,5-(CF3)2–C6H3, 11.90 g, 79.6%. The identity and
purity of 1–4 is confirmed by comparison of the boiling
points and the NMR spectra with the data reported in
the literature [20].
7.22 (m, 2 H, ꢀCH), 7.39–7.55 (m, 3 H, ꢀCH), 7.57–
7.61 (m, 2 H, ꢀCH), 7.84–7.89 (m, 2 H, ꢀCH), 8.36 (s,
1 H, NꢀCH); 13C-NMR (in CDCl3, 298 K) (ppm):
1
121.0 (ꢀCH), 124.4 (CF3, JCF=272 Hz), 126.4 (ꢀCH,
2
3JCF=4 Hz), 127.8 (ꢀC, JCF=33 Hz), 128.8 (ꢀCH),
129.1 (ꢀCH), 132.4 (ꢀCH), 135.8 (ꢀC), 155.2 (ꢀC), 161.9
(NꢀCH).
3.3.2. MS and spectroscopical data for 6
MS (EI): m/z (%) 317 (M+, 69), 316 (M+ −H, 100),
248 (C14H9NF3+, 7), 240 (C9H4NF6+, 8), 229
(C14H9NF2+, 11), 213 (C8H3F6+, 35), 182 (C7H3F5+, 3),
163 (C7H3F4+, 8), 122 (C7H5NF+, 11), 104 (C7H6N+,
15), 89 (C7H5+, 8) 77 (C6H5+, 39), 63 (C5H3+, 5), 51
(C4H3+, 11), 39 (C3H3+, 4); 1H-NMR (in CDCl3, 298 K)
(ppm): 7.31–7.47 (m, 3 H, ꢀCH), 7.53 (s, br, 2 H,
ꢀCH), 7.67 (s, br, 1 H, ꢀCH), 7.79–7.87 (m, 2 H, ꢀCH),
8.32 (s, 1 H, NꢀCH); 13C-NMR (in CDCl3, 298 K)
3.3.1. MS and spectroscopical data for 5
MS (EI): m/z (%) 249 (M+, 90), 248 (M+ −H, 100),
230 (M+ −F, 10), 180 (M+ −CF3, 7), 172
(C8H5NF3+, 13), 152 (C12H8+, 8), 145 (C7H4F3+, 63),
125 (C7H3F2+, 11), 105 (C7H2F+, 11), 95 (C7H5+, 17),
(ppm): 119.1 (ꢀCH, JCF=4 Hz), 121.1 (ꢀCH, JCF=3
3
4
1
Hz), 128.1 (CF3, JCF=206 Hz), 128.9 (ꢀCH), 129.5
2
(ꢀCH), 132.4 (ꢀCH), 133.3 (ꢀC, JCF=33 Hz), 135.4
(ꢀC), 153.5 (ꢀC), 163.1 (NꢀCH).
Fig. 2. 1H-NMR spectrum of a mixture of 7a (*) and 14 (c); cyclohexyl signals are not shown.

W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
39
Table 2
Crystal and intensity data for compounds 7–11
7
8
9
10
11
Formula
C19H17NO6Fe2
C19H11NO6Fe2 C20H13NO6Fe2 C19H10BrNO6Fe2 C20H10F3NO6Fe
2
Molecular weight (g mol−1
Radiation
Monochromator
Temperature (K)
Crystal colour
)
467.04
Mo–Ka
Graphite
213
460.99
475.01
Mo–Ka
Graphite
213
539.89
Mo–Ka
Graphite
213
528.99
Mo–Ka
Graphite
213
Mo–Ka
Graphite
213
Red
Red
Red
Red
Red
Crystal size (mm)
0.4×0.4×0.3
26.182(6)
8.337(2)
17.802(5)
90
97.91(2)
90
3849(2)
8
0.4×0.4×0.4
7.568(1)
8.363(1)
15.435(2)
77.702(8)
78.331(9)
80.16(1)
926.4(2)
2
0.6×0.4×0.2
12.684(4)
11.824(3)
13.582(4)
90
104.08(2)
90
1975(1)
4
0.5×0.3×0.05
12.675(4)
11.746(2)
13.400(3)
90
94.26(2)
90
1989.5(8)
4
0.3×0.3×0.2
13.227(2)
11.535(2)
13.831(5)
90
104.90(2)
90
2039.3(9)
4
,
a (A)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
Volume (A )
Z
3
,
F(000)
1904
1.612
464
1.653
960
1.597
1064
1.802
1056
1.723
Dcalc (g cm−3
)
Crystal system
Space group
Monoclinic
C2/c
1.789
1.57–26.02
q–2q
3–60
Triclinic
Monoclinic
P21/n
1.509
1.97–27.49
q–2q
Monoclinic
P21/c
3.506
2.13–27.50
q–2q
3–60
Monoclinic
P21/c
1.492
1.90–24.99
q–2q
3–60
(
P1
Absorption coefficient (mm−1
q Limit
)
1.606
1.37–25.00
q–2q
Scan mode
Scan speed (° min−1
)
3–60
3–60
No. reflections measured
Independent reflections
Rint
4631
3782
0.0359
2760
4028
3227
0.0129
2938
4513
4513
0.0000
3857
5652
4550
0.0300
3123
4535
3596
0.0318
2840
No. observed reflections F2o=2|(Fo2)
No. of parameters
321
297
304
302
329
GOF
R1
wR2
1.026
0.981
0.0256
0.0651
0.233
1.036
1.035
1.097
0.0500
0.1189
0.894
0.0367
0.0949
0.521
0.0626
0.1491
1.355
0.0409
0.0950
0.675
−3
,
Final difference map electron density (e A
)
yield of 10 improves to 32%. Compounds 7–12 are
recrystallised from a mixture of light petroleum/CH2Cl2
at −20°C.
3.4. Preparation of 7–12
A 500 mg (1.4 mmol) sample of Fe2(CO)9 was stirred
together with 1.2 equivalents of the corresponding
imine (7: R=C6H11, 308 mg; 8: R=C6H5, 298 mg; 9:
R=4-CH3–C6H4, 321 mg; 10: R=4-Br–C6H4, 429
mg; 11: R=4-CF3–C6H4, 410 mg; 12: R=3,5-(CF3)2–
C6H3, 523 mg) in 30 ml n-heptane at 50°C. During the
reaction the colour of the solution changes from orange
to deep red and the undissolved Fe2(CO)9 slowly disap-
pears. After 1 h all of the starting material is dissolved
and the solvent is evaporated in vacuo. The resulting
oily residue is dissolved in 10 ml CH2Cl2 and 1 g
silanised silica gel is added. Chromatography in all
cases first yields a green fraction of Fe3(CO)12 using a
mixture of light petroleum (b.p. 40–60°C)/CH2Cl2 10:1
and a second red coloured band of 7–12 using a
mixture of light petroleum/CH2Cl2 4:1 (yields: 222 mg
7, 34%; 181 mg 8, 28%; 140 mg 9, 21%; 136 mg 10,
18%; 178 mg 11, 24%; 184 mg 12, 22%). If the reaction
mixture producing 10 is stirred at r.t. instead of being
heated the formation of Fe3(CO)12 is reduced and the
7: m.p. 109°C; C19H17NO6Fe2; Anal. Found (Calc.)
C: 48.79 (48.86), H: 3.71 (3.67), N: 3.00 (3.00)%.
8: m.p. 89°C; C19H11NO6Fe2; Anal. Found (Calc.) C:
49.44 (49.50), H: 2.45 (2.41), N: 3.04 (3.04)%.
9: m.p. 102°C; C20H13NO6Fe2; Anal. Found (Calc.)
C: 50.82 (50.57), H: 2.99 (2.76), N: 2.94 (2.95)%.
10: m.p. 140°C; C19H10BrNO6Fe2; Anal. Found
(Calc.) C: 42.50 (42.27), H: 1.85 (1.87), N: 2.64 (2.59)%.
11: m.p. 107°C; C20H10F3NO6Fe2; Anal. Found
(Calc.) C: 45.33 (45.41), H: 2.02 (1.91), N: 2.60 (2.65)%.
12: m.p. 93°C; C21H9F6NO6Fe2; Anal. Found (Calc.)
C: 41.97 (42.25), H: 1.58 (1.52), N: 2.31 (2.35)%.
3.4.1. MS and spectroscopical data for 7
MS (EI): m/z (%) 467 (M+, 5), 439 (M+ −CO, 3),
411 (M+ −2CO, 16), 383 (M+ −3CO, 13), 355
(M+ −4CO, 19), 327 (M+ −5CO, 85), 299 (M+
−
6CO, 100), 237 (C8H11NFe2+, 41), 215 (C11H13NFe+,
24), 203 (C10H13NFe+, 6), 190 (C9H12NFe+, 9), 178

40
W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
(C8H12NFe+, 24), 164 (C7H10NFe+, 28), 148
(C6H6NFe+, 46), 135 (C5H5NFe+, 35), 112 (Fe2+, 70),
91 (C7H7+, 26), 84 (C6H1+2 , 8), 56 (Fe+, 53); IR (in
CH2Cl2, 298 K) (cm−1): 2060 (m), 2023 (vs), 1979 (br);
1H-NMR (in CDCl3, 298 K) (ppm): 1.04–1.87 (m, 10
H, CH2), 2.30–2.32 (m, 1 H, CH), 3.95 (s, 2 H, CH2),
(in CH2Cl2, 298 K) (cm−1): 2067 (m), 2029 (vs), 1989
(br); H-NMR (in CDCl3, 298 K) (ppm): 4.31 (s, 2 H,
1
CH2), 6.88–6.93 (m, 2 H, ꢀCH), 7.05–7.12 (m, 1 H,
ꢀCH), 7.27–7.35 (m, 3 H, ꢀCH), 7.56–7.60 (m, 1 H,
ꢀCH), 8.00–8.03 (m, 1 H, ꢀCH); 13C-NMR (in CDCl3,
298 K) (ppm): 75.0 (CH2), 118.3 (ꢀC), 120.6 (ꢀC), 124.4
(ꢀCH), 126.2 (ꢀCH), 129.4 (ꢀCH), 130.0 (ꢀCH), 132.0
(ꢀCH), 149.1 (ꢀC), 150.2 (ꢀCH), 158.0 (ꢀC), 210.2
(CO).
3
3
7.07 (ddd, 1 H, ꢀCH, JHH=8.1 Hz, JHH=6.9 Hz,
3
4JHH=1.3 Hz), 7.32 (ddd, 1 H, ꢀCH, JHH=8.1 Hz,
3JHH=6.9 Hz, 4JHH=1.1 Hz), 7.50 (dd, 1 H, ꢀCH,
3JHH=8.1 Hz, 4JHH=1.3 Hz), 8.12 (dd, 1 H, ꢀCH,
4
3JHH=8.1 Hz, JHH=1.1 Hz); 13C-NMR (in CDCl3,
3.4.5. MS and spectroscopical data for 11
298 K) (ppm): 26.1 (CH2), 26.2 (CH2), 35.4 (CH2), 64.8
(CH2), 74.2 (CH), 125.5 (ꢀC), 125.6 (ꢀCH), 128.1
(ꢀCH), 130.5 (ꢀCH), 145.6 (ꢀC), 151.0 (ꢀCH), 210.6
(CO).
MS (EI): m/z (%) 529 (M+, 3), 501 (M+ −CO, 1),
473 (M+ −2CO, 12), 445 (M+ −3CO, 7), 417 (M+
−
4CO, 12), 389 (M+ −5CO, 17), 361 (M+ −6CO, 68),
286 (C8H7NF3Fe2+, 6), 267 (C8H7NF2Fe2+, 7), 247
(C5H4NF3Fe2+, 11), 240 (C9H5NF3Fe+, 12), 230
(C8H7NF3Fe+, 13), 192 (C5H5NF3Fe+, 100), 165
(C4H4F3Fe+, 76), 91 (C7H7+, 10), 89 (C7H5+, 17), 56
(Fe+, 24); IR (in CH2Cl2, 298 K) (cm−1): 2068 (m),
2030 (vs), 1990 (br); 1H-NMR (in CDCl3, 298 K)
(ppm): 4.35 (s, 2 H, CH2), 7.07–7.13 (m, 3 H, ꢀCH),
7.29–7.36 (m, 1 H, ꢀCH), 7.47–7.51 (m, 2 H, ꢀCH),
7.59–7.63 (m, 1 H, ꢀCH), 8.00–8.04 (m, 1 H, ꢀCH);
13C-NMR (in CDCl3, 298 K) (ppm): 74.4 (CH2), 120.2
3.4.2. MS and spectroscopical data for 8
MS (EI): m/z (%) 461 (M+, 7), 433 (M+ −CO, 3),
405 (M+ −2CO, 18), 377 (M+ −3CO, 13), 349
(M+ −4CO, 24), 321 (M+ −5CO, 52), 293 (M+
−
6CO, 100), 237 (C13H11NFe+, 60), 159 (C7H5NFe+,
24), 147 (C6H5NFe+, 70), 133 (C5H3NFe+, 23), 112
(Fe2+, 21), 77 (C6H5+, 9), 56 (Fe+, 50); IR (in CH2Cl2,
298 K) (cm−1): 2066 (m), 2028 (vs), 1987 (br); 1H-
NMR (in CDCl3, 298 K) (ppm): 4.36 (s, 2 H, CH2),
7.03–7.34 (m, 7 H, ꢀCH), 7.56–7.60 (m, 1 H, ꢀCH),
8.01–8.05 (m, 1 H, ꢀCH); 13C-NMR (in CDCl3, 298 K)
(ppm): 75.3 (CH2), 120.7 (ꢀC), 122.8 (ꢀCH), 125.4
(ꢀCH), 126.0 (ꢀCH), 128.9 (ꢀCH), 129.3 (ꢀCH), 129.9
(ꢀCH), 149.3 (ꢀC), 150.1 (ꢀCH), 158.8 (ꢀC), 210.4
(CO).
1
(ꢀC), 122.8 (ꢀCH), 123.8 (CF3, JCF=265 Hz), 126.3
3
2
(ꢀCH, JCF=3 Hz), 126.4 (ꢀCH), 126.8 (ꢀCH, JCF
=
23 Hz), 129.6 (ꢀCH), 130.1 (ꢀCH), 149.2 (ꢀC), 150.1
(ꢀCH), 161.8 (ꢀC), 210.1 (CO).
3.4.6. MS and spectroscopical data for 12
MS (EI): m/z (%) 597 (M+, 17), 569 (M+ −CO, 3),
541 (M+ −2CO, 27), 513 (M+ −3CO, 14), 485
3.4.3. MS and spectroscopical data for 9
(M+ −4CO, 14), 457 (M+ −5CO, 7), 429 (M+
−
MS (EI): m/z (%) 475 (M+, 7), 447 (M+ −CO, 1),
419 (M+ −2CO, 15), 391 (M+ −3CO, 16), 363
6CO,
89),
335
(C12H7NF6Fe+,
14),
318
(C11H3NF3Fe2+, 19), 240 (C9H5NF3Fe+, 100), 222
(C9H6NF2Fe+, 35), 214 (C7H3NF3Fe+, 33), 190
(C5H3NF3Fe+, 19), 163 (C4H2F3Fe+, 24), 128
(C9H6N+, 39), 112 (Fe2+, 9), 91 (C7H7+, 27), 76
(C6H4+, 11), 56 (Fe+, 18); IR (in CH2Cl2, 298 K)
(M+ −4CO, 26), 335 (M+ −5CO, 57), 307 (M+
−
6CO, 100), 278 (C13H10Fe2+, 2), 251 (C14H13NFe+, 51),
224 (C12H10NFe+, 11), 194 (C11H6Fe+, 11), 173
(C8H7NFe+, 15), 154 (C2H4NFe2+, 50) 112 (Fe2+, 17),
91 (C7H7+, 11), 56 (Fe+, 32); IR (in CH2Cl2, 298 K)
(cm−1): 2070 (m), 2033 (vs), 1993 (br); H-NMR (in
1
1
(cm−1): 2065 (m), 2027 (vs), 1987 (br); H-NMR (in
CDCl3, 298 K) (ppm): 4.37 (s, 2 H, CH2), 7.09–7.17
(m, 1 H, ꢀCH), 7.32–7.40 (m, 1 H, ꢀCH), 7.42 (s, 2 H,
ꢀCH), 7.58 (s, 1 H, ꢀCH), 7.61–7.65 (m, 1 H, ꢀCH),
8.01–8.04 (m, 1 H, ꢀCH); 13C-NMR (in CDCl3, 298 K)
(ppm): 74.0 (CH2), 118.7 (ꢀCH, 3JCF=4 Hz), 120.4
CDCl3, 298 K) (ppm): 2.29 (s, 3 H, CH3), 4.34 (s, 2 H,
CH2), 6.92–7.12 (m, 5 H, ꢀCH), 7.26–7.34 (m, 1 H,
ꢀCH), 7.56–7.60 (m, 1 H, ꢀCH), 8.01–8.04 (m, 1 H,
ꢀCH); 13C-NMR (in CDCl3, 298 K) (ppm): 20.7 (CH3),
75.5 (CH2), 120.7 (ꢀC), 122.6 (ꢀCH), 126.0 (ꢀCH),
129.3 (ꢀCH), 129.4 (ꢀCH), 129.8 (ꢀCH), 135.1 (ꢀC),
149.3 (ꢀC), 150.1 (ꢀCH), 156.4 (ꢀC), 210.4 (CO).
4
1
(ꢀC), 122.5 (ꢀCH, JCF=3 Hz), 122.8 (CF3, JCF=273
Hz), 126.6 (ꢀCH), 129.6 (ꢀCH), 130.4 (ꢀCH), 132.7
2
(ꢀCH, JCF=34 Hz), 148.6 (ꢀC), 150.3 (ꢀCH), 160.4
(ꢀC), 209.8 (CO).
3.5. 2-Lithiotoluene
3.4.4. MS and spectroscopical data for 10
MS (EI): m/z (%) 539 (M+, 7), 511 (M+ −CO, 3),
483 (M+ −2CO, 15), 455 (M+ −3CO, 11), 427
(M+ −4CO, 18), 399 (M+ −5CO, 16), 371 (M+
−
A total of 73.0 ml (117 mmol) of a 1.6 N solution of
butyllithium in hexane is added to a solution of 20.0 g
(117 mmol) of 2-bromotoluene in 150 ml diethylether at
−60°C. The reaction mixture is allowed to warm to r.t.
6CO, 47), 315 (C13H10NBrFe+, 5), 235 (C13H9NFe+,
100), 209 (C11H7NFe+, 35), 180 (C10H4Fe+, 47), 152
(C3H4Fe2+, 52), 132 (C6H4Fe+, 32), 56 (Fe+, 87); IR

W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
41
and is stirred another 15 min. Then diethylether is
evaporated until only 20 ml are left and 70 ml hexane
are added. After standing overnight at −30°C 2-
lithiotoluene which is free of diethylether has precipi-
tated as a white solid which is filtered and dried in
vacuo. Yield: 16.5 g (81%); m.p. \120°C (dec.).
cyclohexylamine and a catalytic amount of p-toluene-
sulfonic acid. The resulting water is trapped by 1 g
molecular sieve. After stirring overnight at 70°C the
solution is filtered, the solvent is evaporated in vacuo
and the yellow oily residue is distilled using a short
Vigreux column. In an analogous procedure, 1.10 g
(10.3 mmol) of 2-deuterobenzaldehyde was reacted with
0.96 g (10.3 mmol) aniline. The resulting pale yellow
imines 1a and 2a are recrystallised from ethanol/hexane
at −30°C. Yields: 1a: 2.88 g (86%), b.p. 110–130°C/2.5
torr, m.p. 12°C; 2a: 1.39 g (77%), b.p. 120–150°C/2.5
torr, m.p. 44°C.
3.6. 2-Deuterotoluene
To a solution of 16.5 g (168 mmol) of 2-lithiotoluene
in 100 ml diethylether 3.35 g (168 mmol) of D2O are
added dropwise at −30°C. After 1 h of stirring the
reaction mixture is distilled using a Vigreux column.
1
Yield: 13.1 g (84%); b.p. 110°C; H-NMR (in CDCl3,
3.9.1. MS and spectroscopical data for 1a
298 K) (ppm): 2.38 (s, 3 H, CH3), 7.13–7.35 (m, 4 H,
ꢀCH).
MS (EI): m/z (%) 188 (100, M+), 187 (100, M+
−
H), 159 (96, M+ −C2H5), 145 (87, M+ −C3H7), 133
(47, M+ −C4H7), 131 (23, M+ −C4H9), 105 (91,
3.7. 2-Deuterobenzylidenedichloride
M
+ −C6H11), 92 (23, C7H6D+), 91 (22, C7H7+), 78
(19, C6H4D+), 77 (8, C6H5+), 55 (35, C4H7+), 41 (32,
1
A 13.1 g (81 mmol) sample of 2-deuterotoluene is
refluxed together with 22.0 g (162 mmol) SO2Cl2 and 80
mg AIBN. Each hour another 80 mg of AIBN is added.
After 20 h the mixture is cooled to r.t., dissolved in 100
ml diethylether, dried with magnesium sulfate and dis-
tilled using a Vigreux column. Yield: 12.5 g (55%); b.p.
C3H5+); IR (298 K) (cm−1): 1643 (vs, CꢀN); H-NMR
(in CDCl3, 298 K): 1.10–1.90 (m, 10 H, CH2), 3.05–
3.28 (m, 1 H, CH), 7.38–7.40 (m, 3 H, ꢀCH), 7.68–7.76
(m, 1 H, ꢀCH), 8.31 (s, 1 H, CHꢀN); 2H-NMR (in
CHCl3, 298 K): 7.73 (s, ꢀCD); 13C-NMR (in CDCl3,
298 K): 23.3 (CH2), 24.9 (CH2), 34.3 (CH2), 69.8 (CH),
127.7 (t, 1JCD=24.2 Hz, ꢀCD), 128.0 (ꢀCH), 128.3
(ꢀCH), 128.4 (ꢀCH), 130.2 (ꢀC), 158.4 (CHꢀN).
1
86°C/1.9 torr; H-NMR (in CDCl3, 298 K) (ppm): 6.70
(s, 1 H, CHCl2), 7.27–7.41 (m, 4 H, ꢀCH).
3.8. 2-Deuterobenzaldehyde
3.9.2. MS and spectroscopical data for 2a
MS (EI): m/z (%) 182 (85, M+), 181 (100, M+ −H),
104 (12, M+ −C6H5), 77 (57, C6H5+), 51 (17, C4H3+);
A total of 12.5 g (77 mmol) of 2-deuterobenzyli-
denedichloride is treated with 100 g of concentrated
sulphuric acid at 0°C in a two-neck vessel with a reflux
condenser and a capillary through which a stream of
nitrogen is bubbled through the reaction mixture. At
the top of the reflux condenser a water-jet vacuum is
applied. The reaction mixture turns reddish brown.
After 2 h the reaction mixture is poured on ice and is
washed three times with diethylether. The combined
diethylether extracts are neutralised with NaHCO3,
dried with MgSO4 and after evaporation of the solvent
distilled in vacuo. The mass spectrum of the product
shows that the degree of deuteration is above 99%.
Yield: 5.0 g (61%); b.p. 64°C/1.7 torr; MS (EI): m/z (%)
107 (M+, 99), 106 (M+ −H, 100), 78 (C6H4D+, 88),
52 (C4H2D+, 11), 51 (C4HD+, 23); 1H-NMR (in
CDCl3, 298 K): 7.46–7.65 (m, 3 H, ꢀCH), 7.86 (d, 1 H,
3JHH=7.8 Hz, ꢀCH), 10.00 (s, 1 H, CHO); 13C-NMR
(in CDCl3, 298 K): 128.8 (ꢀCH), 129.0 (ꢀCH), 129.4 (t,
1JCD=23.9 Hz, CD), 129.7 (ꢀCH), 134.4 (ꢀCH), 136.4
(ꢀC), 192.3 (CHO).
IR (KBr, 298 K) (cm−1): 1703 (vs, CꢀN); H-NMR (in
1
CDCl3, 298 K): 7.20–7.55 (m, 8 H, ꢀCH), 7.85–7.98
(m, 1 H, ꢀCH), 8.47 (s, 1 H, CHꢀN); 13C-NMR (in
CDCl3, 298 K): 120.8 (ꢀCH), 125.9 (ꢀCH), 128.5 (t,
1JCD=24.2 Hz, ꢀCD), 128.6 (ꢀCH), 128.7 (ꢀCH), 129.0
(ꢀCH), 129.7 (ꢀCH), 136.2 (ꢀC), 152.1 (ꢀC), 160.3
(CHꢀN).
3.10. Preparation of 7a and 8a
A total of 500 mg (1.37 mmol) Fe2(CO)9 is suspended
in 30 ml hexane together with an equimolar amount of
the corresponding imine (1a: 260 mg, 2a: 250 mg). After
2 h of stirring at 50°C the solution turns red and the
solvent is evaporated in vacuo. The residue is dissolved
in 5 ml CH2Cl2 and 1 g silanised silica gel is added.
After removing CH2Cl2 the product mixture is chro-
matographed. Compounds 7a and 8a are eluted using a
mixture of light petroleum (b.p. 40–60°C)/CH2Cl2 20:1
as a deep red coloured band. The solutions of 7a and 8a
are evaporated until only a few ml of solvent is left and
crystallised overnight at −30°C. Yields: 7a: 265 mg
(41%), m.p. 108°C, C19H16DFe2NO6 (468.06): Calc. C
48.75, N 2.99; found C 48.76, N 2.90; 8a: 230 mg
(36%), m.p. 91°C, C19H10DFe2NO6 (462.00) Calc.: C,
3.9. Preparation of 1a and 2a
A 1.90 g (17.7 mmol) sample of 2-deuterobenzalde-
hyde in 5 ml ethanol is treated with 1.76 (17.7 mmol)

42
W. Imhof et al. / Journal of Organometallic Chemistry 584 (1999) 33–43
49.39; N, 3.03; Found: C, 49.37; N, 2.96%. Analytical
values for hydrogen are not given since the instrument
used for CHN-analysis cannot determine D2O
quantitatively.
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3
CHD), 7.03 (t, JHH=7.5 Hz, 1 H, ꢀCH), 7.25–7.32
3
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8.09 (d, 3JHH=8.1 Hz, 1 H, ꢀCH); 2H-NMR (in
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1
(CH2), 64.4 (t, JCD=23.2 Hz, CHD), 64.7 (CH2), 74.2
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MS (EI): m/z (%) 462 (M+, 5), 434 (M+ −CO, 1),
406 (M+ −2CO, 20), 378 (M+ −3CO, 17), 350
(M+ −4CO, 29), 322 (M+ −5CO, 58), 294 (M+
−
6CO, 100), 238 (M+ −6CO−Fe, 69), 159
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1
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3
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3
Hz, 0.5 H, ꢀCH), 8.03 (d, JHH=8.2 Hz, 1 H, ꢀCH);
1
13C-NMR (in CDCl3, 298 K): 74.8 (t, JCD=18.2 Hz,
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(ꢀCH), 149.4 (ꢀC), 150.1 (ꢀC), 158.7 (ꢀC), 210.4 (CO),
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We thank the Deutsche Forschungsgemeinschaft
(SFB 436) for financial support and Dr. W. Gu¨nther,
Institute of Organic Chemistry and Macromolecular
Chemistry, Friedrich-Schiller-University, Jena for the
NOESY and HMQC spectra of 7.

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43
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