α,β-Unsaturated diimines as substrates in catalytic C-H activation reactions and as ligands in iron carbonyl complexes

Article abstract of DOI:10.1016/j.jorganchem.2004.10.054

The reaction of 3-[4-(3-oxo-propenyl)-phenyl]-propenal with two equivalents cyclohexylamine as well as the treatment of cyclohexane-1,4-diamine or bis-(4-aminocyclohexyl)-methane with two equivalents of cinnamaldehyde leads to the formation of the corresponding diimines. Mono- or dinuclear iron carbonyl complexes are produced if the diimines are reacted with iron carbonyls. Two of these complexes have been characterized by X-ray crystallography showing that one or two of the α,β-unsaturated imine side chains are coordinated by an iron tricarbonyl moiety in a η⁴-fashion. The packing is realized by intermolecular C-H?O contacts. The same diimines are used as the substrates in ruthenium catalyzed C-H activation reactions together with carbon monoxide and ethylene to produce bis-dihydropyrrolone derivatives in almost quantitative yields.

Full text of DOI:10.1016/j.jorganchem.2004.10.054

Journal of Organometallic Chemistry 690 (2005) 1092–1099
www.elsevier.com/locate/jorganchem
a,b-Unsaturated diimines as substrates in catalytic C–H
activation reactions and as ligands in iron carbonyl complexes
*
Wolfgang Imhof , Angela Go¨bel
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University, August-Bebel-Str. 2, 07743 Jena, Germany
Received 26 August 2004; accepted 12 October 2004
Abstract
The reaction of 3-[4-(3-oxo-propenyl)-phenyl]-propenal with two equivalents cyclohexylamine as well as the treatment of cyclo-
hexane-1,4-diamine or bis-(4-aminocyclohexyl)-methane with two equivalents of cinnamaldehyde leads to the formation of the cor-
responding diimines. Mono- or dinuclear iron carbonyl complexes are produced if the diimines are reacted with iron carbonyls. Two
of these complexes have been characterized by X-ray crystallography showing that one or two of the a,b-unsaturated imine side
chains are coordinated by an iron tricarbonyl moiety in a g4-fashion. The packing is realized by intermolecular C–Hꢀ ꢀ ꢀO contacts.
The same diimines are used as the substrates in ruthenium catalyzed C–H activation reactions together with carbon monoxide and
ethylene to produce bis-dihydropyrrolone derivatives in almost quantitative yields.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Iron carbonyls; Catatlysis; C–H activation; Pyrrolones; Structure determination
1. Introduction
the corresponding substrates. In addition, we wanted
to investigate, whether the catalytic formation of hetero-
cyclic compounds proceeds via the same reaction path-
way as it was observed for monofunctional imines.
Another interesting question was, whether the catalytic
formation of heterocyclic substructures was possible
on both sides of the bifunctional substrates.
The reaction of acyclic a,b-unsaturated imines with
Fe2(CO)9 yields mononuclear iron tricarbonyl com-
plexes [1–7]. On the other hand, the same imine sub-
strates are converted into c-lactams in the reaction
with carbon monoxide and a-olefins catalyzed by
Ru3(CO)12 [8–13]. As a side product of this catalytic
three component reactions 2,3-disubstituted pyrrole
derivatives are observed [11]. Interestingly, one of the
very few procedures to synthesize 2,3-disubstituted pyr-
roles starts from (g4-azadiene)Fe(CO)3 complexes and
EtLi with subsequent quenching of the reaction mixture
with BuBr [14,15]. During our investigations on the
reactivity of bis-imines we synthesized the diimines 1, 4
and 6 (Scheme 1) as model compounds to study the
interaction of a group 8 metal carbonyl fragment with
2. Results and discussion
The diimines 1, 4 and 6 are easily produced from the
condensation of 3-[4-(3-oxo-propenyl)-phenyl]-propenal
with two equivalents cyclohexylamine (to produce 1) as
well as of cyclohexane-1,4-diamine or bis-(4-amin-
ocyclohexyl)-methane with two equivalents of cinnamal-
dehyde to yield 4 and 6, respectively. Scheme 1 shows
the synthesis of the iron carbonyl compounds 2, 3, 5
and 7 from the corresponding diimine ligands. After
chromatographic workup and recrystallization from
*
Corresponding author. Tel.: +49 3641 94 8129; fax: +49 3641 94
8102.
E-mail address: wolfgang.imhof@uni-jena.de (W. Imhof).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.10.054

W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
1093
Scheme 1.
mixtures of light petroleum and dichloromethane at ꢁ20
ꢁC 2 and 3 were obtained as crystalline compounds suit-
able for X-ray structure determination.
The most important bond lengths and angles of 2 and
3 are depicted in Table 1. The molecular structure of one
of the three molecules per asymmetric unit observed for
2 is presented in Fig. 1. In 2 only one of the imine func-
tions is coordinated by an iron tricarbonyl fragment.
Corresponding to other (1-azadiene)Fe(CO)3 complexes
the ligand shows a s-cis conformation whereas the non-
coordinated imine subunit exhibits the expected s-trans
conformation. The iron carbon bond lengths in 2 are
not identical. As it has been pointed out before [6,7],
the bond of Fe1 with C3 is about 7–10 pm longer than
Fe1–C2, which again is about 2–3 pm shorter compared
to Fe1–C1. There are three molecules in the asymmetric
unit of the unit cell, which are linked by C–Hꢀ ꢀ ꢀO inter-
actions (Fig. 2, Table 2). These trimers again are
Table 1
˚
Selected bond lengths [A] and angles [ꢁ] of 2 and 3
2, Molecule 1
Fe1–N1
Fe1–C3
C10–C11
2.084(4)
2.119(5)
1.319(8)
Fe1–C1
N1–C13
C11–C12
2.082(5)
1.480(6)
1.441(8)
Fe1–C2
C3–C4
2.051(6)
1.486(7)
1.280(7)
C12–N2
C1–C2–C3
C10–C11–C12
C13–N1–C1
C2–C3–C4
C11–C12–N2
115.9(4)
122.5(5)
123.1(6)
N1–C1–C2
C7–C10–C11
C12–N2–C19
115.8(5)
128.6(6)
118.4(5)
117.1(6)
125.7(6)
2, Molecule 2
Fe2–N3
Fe2–C30
2.072(4)
2.151(6)
1.303(8)
Fe2–C28
N3–C40
C38–C39
2.077(6)
1.475(6)
1.462(8)
Fe2–C29
C30–C31
2.052(6)
1.456(7)
1.262(8)
C37–C38
C39–N4
C28–C29–C30
C37–C38–C39
C40–N3–C28
C29–C30–C31
C38–C39–N4
114.5(4)
123.4(6)
123.0(7)
N3–C28–C29
C34–C37–C38
C39–N4–C46
116.2(5)
128.1(6)
119.0(6)
118.5(6)
124.4(7)
2, Molecule 3
Fe3–N5
Fe3–C57
2.081(4)
2.112(5)
1.314(8)
Fe3–C55
N5–C67
C65–C66
2.075(6)
1.468(6)
1.456(8)
Fe3–C56
C57–C58
2.045(6)
1.473(7)
1.264(7)
C64–C65
C66–N6
C55–C56–C57
C64–C65–C66
C67–N5–C55
C56–C57–C58
C65–C66–N6
115.0(5)
124.6(5)
123.3(7)
N5–C55–C56
C61–C64–C65
C66–N6–C73
116.4(6)
129.4(6)
116.1(6)
117.0(6)
121.7(7)
3
Fe1–N1
Fe1–C3
C7–N1–C1
C2–C3–C4
2.076(4)
2.141(5)
115.7(4)
124.4(5)
Fe1–C1
N1–C7
N1–C1–C2
2.068(5)
1.466(6)
115.6(5)
Fe1–C2
C3–C4
C1–C2–C3
2.059(5)
1.481(7)
116.5(5)

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W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
Fig. 1. Molecular structure of 2. Displacement ellipsoids drawn at the 50% probability level.
connected by another intermolecular C–Hꢀ ꢀ ꢀO contact
to produce infinite chains of trimers (Fig. 2).
Table 2
˚
Shortest intermolecular contacts [A] and angles [ꢁ] in the crystal
structures of 2 and 3
The molecular structure of 3 is shown in Fig. 3. The
center of the aromatic ring system is a crystallographic
center of inversion. So the imine substituents show a
trans-configuration with respect to the central phenyl
ring and the iron tricarbonyl moieties are situated above
and below the plane of the ligand. Both imine function-
alities are coordinated by Fe(CO)3 fragments and thus
show a s-cis conformation. Again Fe–C3 is about 7–8
pm longer compared to the other iron carbon bond
lengths. The molecules are connected to infinite chains
by intermolecular C–Hꢀ ꢀ ꢀO contacts (Fig. 4, Table 2)
between one of the terminal carbon monoxide ligands
and the hydrogen atom at C2.
The coordination of an iron tricarbonyl fragment to
the 1-azadiene units can be considered to model the first
interaction of a ruthenium carbonyl moiety in a catalytic
reaction. The next step in the catalytic cycle would then
be the C–H activation reaction in terms of an cyclometa-
lation (Scheme 2). There is one reaction reported in the
literature, in which an imine derived from p-anisidine
Interaction
C–X
C–Hꢀ ꢀ ꢀX
Angle
2
3
C49–H49B–O1
C51–H51B–O7
C74–H74A–O5
C2–H2A–O1
3.593
3.443
3.488
3.414
2.619
2.531
2.577
2.554
167.7
153.1
153.0
150.6
and cinnamaldehyde reacts with Fe2(CO)9 to yield a
dinuclear iron carbonyl compound, in which the C–H
bond in b-position relative to the C–N double bond is
activated and the corresponding hydrogen atom is trans
ferred to the former imine carbon atom [16,17]. The
same reaction sequence on the other hand is typical
for aromatic imines [18–24], although in one case a
mononuclear iron tricarbonyl compound has been iso-
lated from the reaction of Fe2(CO)9 with naphthalen-
2-ylmethylene-phenyl-amine [21].
Scheme 3 shows the three component reactions of 1, 4
and 6 with carbon monoxide and ethylene in the pres-
ence of catalytic amounts of Ru3(CO)12. It has been
Fig. 2. Packing diagram of 2.

W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
1095
Fig. 3. Molecular structure of 3. Displacement ellipsoids drawn at the 30% probability level.
Fig. 4. Packing diagram of 3.
13C NMR spectrum are observed at app. d = 113 and
127. In addition, the methylene protons of the ethyl sub-
stituents are diastereotopic because of the new stereo-
genic center at C3 of the heterocycle and thus give rise
to multipletts in the hydrogen NMR spectra.
Scheme 2.
pointed out before, that the formation of pyrrolone
derivatives works best if the substituents at the imine
nitrogen atoms are aliphatic moieties [11]. Correspond-
ing to this observation, the bis-dihydropyrrolone deriv-
atives 8–10 are produced in yields of 90% (9) or >98%
(8, 10). Only in the reaction of 4 to produce 9 traces
of a product in which the formation of the heterocycle
took place only with one of the imine subunits are ob-
served in the GC-MS investigations of the product mix-
ture. 8–10 are easily identified by some NMR shifts
being characteristic for this class of compounds. First
of all, the C–H functions at C4 and C5 of the heterocy-
3. Experimental
General. All procedures were carried out in anhy-
drous, freshly distilled solvents. The syntheses of the
iron carbonyl complexes 2, 3, 5 and 7 were performed
under an argon atmosphere.
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, 13C: 50.32 MHz, CDCl3 as internal stan-
dard). Mass spectra were recorded on a Finnigan MAT
SSQ 710 instrument. High resolution mass spectra
(HRMS) were carried out using a Finnigan MAT 95
XL spectrometer using FAB techniques. Elemental
1
cles lead to dubletts at app. d = 5.5 and 6.6 in the H
NMR spectrum. The corresponding resonances in the

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W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
Scheme 3.
Table 3
Crystal and intensity data for 2 and 3
analyses were carried out at the laboratory of the Insti-
tute of Organic Chemistry and Macromolecular Chem-
istry, Friedrich-Schiller-University, Jena.
2
3
X-ray Crystallographic Studies. The structure deter-
mination of 2 was carried out on a Enraf–Nonius Kappa
CCD diffractometer, the crystal being mounted in a
stream of cold nitrogen, crystal detector distance 29
mm. The structure determination of 3 was done using
a Enraf–Nonius CAD4 diffractometer, the crystal was
fixed in a glass capillary. In both cases graphite mono-
chromated Mo Ka radiation was used. Data were cor-
rected for Lorentz and polarization effects but not for
absorption. The structures were solved by direct meth-
ods and refined by full-matrix least squares techniques
against F2 using the programs SHELXS86 and SHELXL97
[25,26]. All hydrogen atoms of 3 were constrained in ide-
alized positions during the refinement. The isotropic
replacement parameters of all hydrogen atoms were
fixed. Treatment of hydrogen atoms of 2 was identical
except hydrogen atoms at C1, C2 and C3, which were
identified from difference Fourier map and refined with-
out any constraints. The molecular illustrations were
drawn using the program XP [27]. The crystal and inten-
sity data are given in Table 3. Additional material on the
structure analyses is available from the Cambridge Crys-
tallographic Data Centre by mentioning the deposition
number CCDC-247572 (2) or CCDC-247573 (3).
Formula
Molecular weight (g molꢁ1
Radiation
C27H32N2O3Fe
488.40
C30H32N2O6Fe2
628.28
)
Mo Ka
Graphite
183
Mo Ka
Graphite
183
Monochromator
Temperature (K)
Crystal color
Orange
0.3 · 0.1 · 0.03
14.456(1)
17.051(2)
17.451(2)
102.497(4)
109.566(6)
101.748(7)
3774.5(7)
6
Orange
0.3 · 0.2 · 0.02
6.900(1)
8.740(1)
12.153(2)
87.48(1)
87.69(1)
75.61(1)
709.0(2)
1
Crystal size
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
F(000)
1548
1.289
326
1.472
qcalc (g cmꢁ3
)
Crystal system
Space group
Absorption coefficient (mmꢁ1
Triclinic
ꢀ
Triclinic
ꢀ
P1
0.629
P1
1.072
)
h Limit (ꢁ)
Scan mode
3.11 < h < 23.29 2.41 < h < 29.98
x-Scan
10159
10159
0.0000
5940
x-2h-Scan
4169
3870
Reflections measured
Independent reflections
Rint
0.1265
2918
Reflections observed
ðF 2o > 2rðF 2oÞÞ
No. of parameters
Goodness-of-fit
R1
975
186
0.842
0.0626
0.1634
0.619
1.182
0.0747
0.2088
1.238
wR2
3.1. Synthesis of 1, 4 and 6
Final diffraction map
electron density peak (e A
ꢁ3
˚
)
1 was prepared by the reaction of 1 g (5.38 mmol) 3-
[4-(3-oxo-propenyl)-phenyl]-propenal with 1.06 g (10.75
mmol) cyclohexylamine in 50 ml anhydrous ethanol.
After stirring the solution at room temperature for 10
h, 841 mg 1 (44.9%) precipitated as a pale yellow solid.
MS and spectroscopical data of 1: MS (EI) [m/z (frag-
ment, rel. intensity in %)]: 348 (M+, 100), 265
ðC18H21Nþ2 ; 61Þ, 240 ðC16H20Nþ2 ; 6Þ, 225 ðC15H7Nþ2 ; 30Þ,

W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
1097
183 ðC12H10Nþ; 12Þ, 143 (C10H9N+, 8), 115 ðC9Hþ; 4Þ,
3.2. Synthesis of 2 and 3
2
7
83 ðC6Hþ11; 6Þ, 55 ðC4H9þ; 19Þ, 41 ðC3Hþ5 ; 12Þ; IR (nujol,
1
298 K) [cmꢁ1]: 1630 (m), 1610 (m) (CH@N); H NMR
(CDCl3, 298 K) [ppm]: 1.10–1.80 (m, 20H, CH2), 2.91–
348 mg 1 (1 mmol) are stirred together with 364 mg
Fe2(CO)9 in 20 ml n-heptane at 50 ꢁC for 2 h, the solu-
tion turns orange as the ligand and Fe2(CO)9 dissolve.
After evaporation of all volatile material the crude prod-
uct is chromatographed on silica gel. Use of light petro-
leum (b.p. 40–60 ꢁC) as the eluent yields 3 as a orange
solution (175 mg, 28%). If a mixture of light petroleum
(b.p. 40–60 ꢁC) and CH2Cl2 (5:1) is used as the eluent,
176 mg 2 (36%) are obtained. Crystals of 2 and 3 are
produced from a concentrated solution in light petro-
leum (b.p. 40–60 ꢁC) at ꢁ20 ꢁC.
3.09 (m, 2H, CH), 6.73–6.93 (m, 4H, =CH), 7.35 (s,
3
4H, CHar), 7.96 (d, 2H, JHH = 6.2 Hz); 13C NMR
(CDCl3, 298 K) [ppm]: 24.6 (CH2), 25.4 (CH2), 34.3
(CH2), 69.5 (CH), 127.4 (CarH), 129.0 (=CH), 136.4
(=CH), 140.0 (=CH), 159.9 (N@CH); m.p. 179 ꢁC. Ele-
mental analysis: Calcd.: C,82.71%; H, 9.25%; N, 8.04%;
found: C, 82.07%; H, 7.32%; N 8.12%.
4 was prepared by the reaction of 2.855 g (0.025 mol)
trans-1,4-diaminocyclohexane which were dissolved in
10 ml anhydrous ethanol and treated with 6.608 g
(0.05 mol) cinnamaldehyde. After stirring at room tem-
perature for 20 h the colorless precipitate is collected
and washed three times with cold anhydrous ethanol
and three times with cold diethylether to yield 6.399 g
(74.7%) 4.
MS and spectroscopical data of 2: MS (EI) [m/z (frag-
ment, rel. intensity in %)]: 488 (M+, 7), 460 (M+–CO,
13), 432 (M+–2CO, 4), 404 (M+–3CO, 44), 348 (M+–
3CO–Fe, 5), 196 (C13H26N+, 24), 168 (C11H22N+, 32),
140 (C9H18N+, 14), 112 (C7H14N+, 26), 84
ðC6Hþ12; 100Þ, 56 ðC4H8þ; 65Þ; IR (CH2Cl2, 298 K)
[cmꢁ1]: 2050 (s), 1988 (very strong), 1967 (m); 1H
NMR (CDCl3, 298 K) [ppm]: 1.13–1.75 (m, 21H, CH2,
MS and spectroscopical data of 4: MS (CI, H2O)
[m/z (fragment, rel. intensity in %)]: 343 (MH+, 100), 211
(C15H17N+, 7), 170 (C12H12N+, 7), 156 (C11H10N+, 5),
132 (C9H10N+/C9H8O+, 4), 115 ðC9Hþ=C6H15Nþ; 4Þ;
3
CH), 2.89 (d, 1H, JHH = 9.2 Hz, =CH), 3.02 (m, 1H,
3
CH), 5.46 (dd, 1H, JHH = 9.2 Hz, JHH = 2.8 Hz,
3
7
2
IR (nujol, 298 K) [cmꢁ1]: 1634 (m) (CH@N); 1H
=CH), 6.56 (d, 1H, JHH = 2.8 Hz, =CH), 6.81–6.85
(m, 2H, =CH), 7.18–7.33 (m, 4H, CHar), 8.00 (dd,
3
NMR (CDCl3, 298 K) [ppm]: 1.42–2.01 (m, 8H,
3/4
4
CH2), 2.93–3.29 (m, 2H, CH), 6.90 (d,
Hz, 2H, CH), 6.92 (s, 2H, CH), 7.19–7.57 (m, 10H,
J
= 1.7
3JHH = 5.9 Hz, JHH = 2.4 Hz); 13C NMR (CDCl3, 298
HH
K) [ppm]: 24.8 (CH2), 25.6 (CH2), 25.7 (CH2), 34.5
(CH2), 36.3 (CH2), 37.8 (CH2), 60.3 (=CH), 67.2 (CH),
70.0 (CH), 71.6 (=CH), 111.4 (N@CH), 126.9 (CarH),
127.5 (CarH), 128.2 (=CH), 134.1 (=CH), 140.6
(=CH), 140.7 (Car), 160.4 (N@CH). Elemental analyis:
Calcd.: C, 66.40%; H, 6.60%; N, 5.74%. Found: C,
66.55%; H, 6.91%; N, 5.63%.
3
4
CHar), 8.08 (dd, JHH = 4.2 Hz, JHH = 4.2 Hz, 2H,
CH@N); 13C NMR (CDCl3, 298 K) [ppm]: 32.6
(CH2), 68.7 (CH), 127.1 (CHar), 128.3 (CHar), 128.7
(CHar), 129.0 (CH), 135.7 (Car), 141.4 (CH), 161.0
(CH@N); m.p. 177 ꢁC. Elemental analysis: Calcd.: C,
84.17%; H, 7.65%; N, 8.18%. Found: C, 84.19%; H,
7.69%; N, 8.11%.
MS and spectroscopical data of 3: MS (EI) [m/z (frag-
ment, rel. intensity in %)]: 628 (M+, 1), 600 (M+–CO, 4),
572 (M+–2CO, 9), 544 (M+–3CO, 2), 516 (M+–4CO, 8),
488 (M+–5CO, 44), 460 (M+–6CO, 59), 432 (M+–5CO–
Fe, 11), 404 (M+–6CO–Fe, 100), 196 (C13H26N+, 9), 84
6 is synthesized from 5.259 g (0.025 mol) 4,40-diami-
no-dicyclohexylmethane dissolved in 100 ml anhydrous
ethanol and treated with 6.608 g (0.05 mol) cinnamalde-
hyde. After stirring at room temperature for 20 h the
colorless precipitate is collected and washed three times
with cold anhydrous ethanol and three times with cold
diethylether to yield 3.450 g (31.5%) 6. MS and spectro-
scopical data of 6:
ðC6Hþ ; 14Þ; IR (CH2Cl2, 298 K) [cmꢁ1]: 2050 (s), 1987
12
(very strong), 1965 (m); 1H NMR (CDCl3, 298 K)
[ppm]: 1.16–1.68 (m, 22H, CH2, CH), 2.87 (dd, 2H,
4
3JHH = 9.3 Hz, JHH = 1.8 Hz, =CH), 5.41 (dd, 2H,
3
MS (CI, H2O) [m/z (fragment, rel. intensity in %)]:
3JHH = 9.3 Hz, JHH = 2.3 Hz, =CH), 6.52 (d, 2H,
439 (MH+, 100), 325 ðC22H33Nþ; 2Þ, 307 (C22H29N+,
3JHH = 2.3 Hz, =CH), 7.09 (s, 4H, CHar); 13C NMR
(CDCl3, 298 K) [ppm]: 24.8 (CH2), 24.9 (CH2), 25.8
(CH2), 36.3 (CH2), 37.8 (CH2), 61.0 (=CH), 61.1
(=CH), 67.2 (CH), 71.5 (=CH), 71.8 (=CH), 110.9
(N@CH), 111.1 (N@CH), 126.7 (CarH), 137.9 (Car). Ele-
mental analysis: Calcd.: C, 57.35%; H, 5.13%; N, 4.46%.
Found: C, 56.62%; H, 5.16%; N, 4.48%.
2
4), 226 (C16H20N+, 4), 132 (C9H10N+/C9H8O+, 3); IR
(Nujol, 298 K) [cmꢁ1]: 1635 (s) (CH@N); 1H NMR
(CDCl3, 298 K) [ppm]: 0.57–2.17 (m, 20H, CH, CH2),
2.79–3.15 (m, 2H, CH), 6.88 (s, 2H, CH), 6.90 (s, 2H,
3
CH), 7.17–7.57 (m, 10H, CHar), 8.04 (dd, JHH = 4.3
4
Hz, JHH = 4.3 Hz, 2H, CH@N); 13C NMR (CDCl3,
298 K) [ppm]: 31.8 (CH2), 33.6 (CH), 34.2 (CH2), 44.8
(CH2), 70.0 (CH), 127.1 (CHar), 128.5 (CHar), 128.7
(CHar), 128.9 (CH), 135.8 (Car), 141.1 (CH), 160.5
(CH@N); m.p. 151 ꢁC. Elemental analysis: Calcd.: C,
84.88%; H, 8.73%; N, 6.39%. Found: C, 84.31%; H,
8.73%; N 6.37%.
3.3. Synthesis of 5 and 7
In a typical experiment a 0.74 mmol sample of the
coresponding diimine (253 mg 4, 325 mg 6) is irradiated

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W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
together with 0.2 ml (290 mg) Fe(CO)5 in 95 ml
anhydrous THF at 0 ꢁC for 3 h. The yellow suspension
turns to a red solution during the reaction time. After
evaporation of all volatile material the red oily residue
is dissolved in 12 ml CH2Cl2 and 1 g silanized silica is
added. Again the solvent is evaporated under reduced
pressure and the product mixture is chromatographed
on silica. 5 is obtained as a pale brown product using
a mixture of light petroleum (b.p. 40–60 ꢁC) and THF
2:1, yield 75 mg (16.3%). 7 is eluted using a mixture of
light petroleum (b.p. 40–60 ꢁC) and THF 2.5:1, yield
312 mg (58.7%).
all volatile material is evaporated under reduced pres-
sure. The remaining oily residue is used to determine
1
the yield of 8–10 by H NMR spectroscopy and GC-
MS analysis (yields: >98% 8, 90% 9, >98% 10).
MS and spectroscopical data of 8: MS (EI) [m/z (frag-
ment, rel intensity in %)]: 460 (M+, 100), 431 (M+–Et,
56), 402 (M+–2Et, 2), 83 ðC6Hþ ; 3Þ, 55 ðC4Hþ; 6Þ;
11
7
HRMS
(ESI
in
CHCl3/methanol):
483.3002,
C30H40N2O2Na (MNa+), D = ꢁ1.45 mmu; IR (nujol,
298 K) [cmꢁ1]: 1690 (versus) (C@O), 1603 (m), (C–N);
1H NMR (CDCl3, 298 K) [ppm]: 0.76 (t, 6H,
3JHH = 7.2 Hz, CH3), 1.08–1.90 (m, 20H, CH2), 1.91–
2.05 (m, 4H, CH2), 3.87 (m, 2H, CH), 5.52 (d, 2H,
MS and spectroscopical data of 5: MS (FAB in
nitrobenzylalcohol) [m/z (fragment)]: 623 (MH+), 595
(MH+–CO), 566 (M+–2CO), 539 (MH+–3CO), 511
(MH+–4CO), 483 (MH+–5CO), 455 (MH+–6CO), 427
3
3JHH = 5.0 Hz, =CH), 6.59 (d, 2H, JHH = 5.0 Hz,
=CH–N), 7.36 (s, 4H, CHar); 13C NMR (CDCl3, 298
K) [ppm]: 9.1 (CH3), 25.3 (CH2), 25.5 (CH2), 31.0
(CH2), 31.8 (CH2), 32.1 (CH2), 50.3 (CH), 58.5 (C),
113.3 (=CH), 127.0 (CarH), 128.4 (=CH–N), 138.7
(Car), 179.1 (C@O).
(MH+–5CO–Fe), 343 ðC24H27NþÞ; HRMS (FAB in
2
nitrobenzylalcohol):
623.05580,
C30H27N2O6Fe2
(MH+), D = 0.98 mmu; IR (nujol, 298 K) [cmꢁ1]: 2053
(m) (C@O), 2026 (w) (C@O), 2012 (m) (C@O), 1991
(s) (C@O), 1974 (m, br) (C@O); 1H NMR (THF-d8,
298 K) [ppm]: 1.25–2.09 (m, 10H, CH, CH2), 2,95 (d,
MS and spectroscopical data for 9. MS (CI, H2O)
[m/z (fragment, rel. intensity in %)]: 455 (MH+, 71),
427ðC29H35N2Oþ=C28H31N2Oþ; 10Þ, 399 (C27H31-
3JHH = 9.4 Hz, 2H, CH), 5.75 (dd, JHH = 2.6 Hz,
N2O+, 38), 343 ðC24H27Nþ; 5Þ2, 285 (C18H25N2O+, 32),
3
2
3
3JHH = 9.3 Hz, 2H, CH), 6.72 (d, JHH = 2.4 Hz, 2H,
268 (C18H22NO+, 24), 161 (C11H13O+, 36), 133
CH@N), 7.03–7.43 (m, 10H, CHar); 13C NMR (THF-
d8, 298 K) [ppm]: 31.3 (CH2), 62.7 (CH), 68.0 (CH),
72.8 (CH), 112.4 (CH@N), 127.1 (CHar), 127.3 (CHar),
129.2 (CHar), 140.3 (Car), 214.4 (CO).
(C9H11N+/C9H9O
,
100), 93 (C6H7N+, 15), 84
+
(C5H10N+, 17); HRMS (ESI in CHCl3/methanol):
477.25241, C30H34N2O2Na (MNa+), D = ꢁ0.61 mmu;
IR (Nujol, 298 K) [cmꢁ1]: 1681 (s, br) (C@O), 1602
1
MS and spectroscopical data of 7: MS (FAB in
nitrobenzylalcohol) [m/z (fragment)]: 719 (MH+), 691
(MH+–CO), 663 (MH+–2CO), 635 (MH+–3CO), 607
(MH+–4CO), 579 (MH+–5CO), 551 (MH+–6CO), 495
(m, br) (C–N); H NMR (CDCl3, 298 K) [ppm]: 0.79
3
3
(t, JHH = 7.3 Hz, 3H, CH3), 0.79 (t, 3H JHH = 7.3
Hz, CH3), 1.42–1.94 (m, 8H, CH2), 2.01 (m, 4H,
CH2), 3.80–4.16 (m, 2H, CH), 5.61 (d, 2H,
(MH+–6CO–Fe), 439 ðC31H39NþÞ; HRMS (FAB
3JHH = 5.1 Hz, =CH), 6.60 (d, 2H, JHH = 5.1 Hz,
3
2
in nitrobenzylalcohol): 719.15150, C37H39N2O6Fe2
(MH+), D = ꢁ0.81 mmu; IR (nujol, 298 K) [cmꢁ1]:
2044 (very strong) (C@O), 1987 (very strong) (C@O),
1973 (versus) (C@O), 1962 (versus, br) (C@O); 1H
NMR (THF-d8, 298 K) [ppm]: 0.62–1.91 (m, 22H,
=CH–N), 7.11–7.59 (m, 10H, CHar); 13C NMR
(CDCl3, 298 K) [ppm]: 9.0 (CH3), 30.1 (CH2), 30.1
(CH2), 30.4 (CH2), 30.4 (CH2), 31.0 (CH2), 31.0
(CH2), 48.9 (CH), 58.6 (C), 113.7 (=CH), 126.5 (CarH),
126.9 (=CH–N), 127.8 (CarH), 128.3 (CarH), 139.8
(Car), 179.1 (CO).
3
CH, CH2), 2.97 (d, JHH = 9.3 Hz, 2H, CH), 5.71 (dd,
3
3JHH = 2.8 Hz, JHH= 9.2 Hz, 2H, CH), 6.72 (d,
MS and spectroscopical data for 10. MS (CI, H2O)
[m/z (fragment, rel. intensity in %)]: 551 (MH+, 100),
3JHH = 2.4 Hz, 2H, CH@N), 6.95–7.43 (m, 10H, CHar);
13C NMR (THF-d8, 298 K) [ppm]: 32.9 (CH2), 33.0
(CH2), 34.8 (CH), 34.9 (CH), 37.2 (CH2), 38.4 (CH2),
45.1 (CH2), 62.5 (CH), 68.4 (CH), 72.6 (CH), 112.4
(CH@N), 127.1 (CHar), 127.3 (CHar), 129.2 (CHar),
140.4 (Car), 214.5 (CO).
521 ðC36H45N2Oþ=C35H41N2Oþ; 18Þ, 495 (C34H43-
2
N2O+, 3), 381 (C25H37N2O+, 6), 364 (C25H34NO+, 7),
334 (C23H28NO+, 3), 282 (C19H24NO+, 8), 188
(C12H14NO+, 4), 158 (C11H12N+/C10H8NO+, 6); HRMS
(ESI in CHCl3/methanol): 573.34530, C37H46N2O2Na
(MNa+), D = 0.39 mmu; IR (Nujol, 298 K) [cmꢁ1]:
1714–1668 (very strong, several strong bonds) (C@O),
3.4. Synthesis of 8–10
1
1606 (very strong, br), (C–N); H NMR (CDCl3, 298
3
K) [ppm]: 0.83 (t, 6H, JHH = 7.4 Hz, CH3), 1.00–1.93
(m, 20H, CH, CH2), 1.95–2.15 (m, 4H, CH2), 3.82–
1 mmol of the corresponding diimine (348 mg 1, 342
mg 4, 438 mg 6) and 50 mg (0.08 mmol) Ru3(CO)12 and
3 ml toluene are transferred into a 100 ml stainless steel
autoclave. The autoclave is then pressurized with 8 bar
C2H4 and 12 bar CO and heated to 140 ꢁC for 16 h.
After cooling the autoclave to room temperature the
product mixture is transferred to a Schlenk tube and
3
4.04 (m, 2H, CH), 5.60 (d, 2H, JHH = 5,0 Hz, =CH),
3
6.63 (d, 2H, JHH = 5.1 Hz, =CH–N), 7.14–7.37 (m,
6H, CHar), 7.43–7.54 (m, 4H, CHar); 13C NMR (CDCl3,
298 K) [ppm]: 8.9 (CH3), 31.0 (CH2), 31.1 (CH2), 31.4
(CH2), 31.9 (CH2), 33.4 (CH), 43.7 (CH2), 50.2 (CH),

W. Imhof, A. Go¨bel / Journal of Organometallic Chemistry 690 (2005) 1092–1099
1099
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