Ligand properties of aromatic azines: C-H activation, metal induced disproportionation and catalytic C-C coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2003.11.018

The reaction of aromatic azines with Fe₂(CO)₉ yields dinuclear iron carbonyl cluster compounds as the main products. The formation of these compounds may be rationalized by a C-H activation reaction at the aromatic substituent in ortho position with respect to the exocyclic C-N double bond followed by an intramolecular shift of the corresponding hydrogen atom toward the former imine carbon atom. The second imine function of the ligand does not react. Additional products arise from the metal induced disproportionation of the azine into a primary imine and a nitrile. So also one of the imine C-H bonds may be activated during the reaction. Depending on the aromatic substituent of the azine ligands iron carbonyl complexes of the disproportionation products are isolated and characterized by X-ray crystallography. C-C coupling reactions catalyzed by Ru₃(CO)₁₂ result in the formation of ortho-substituted azines. In addition, ortho-substituted nitriles are identified as side-products showing that the metal induced disproportionation reaction also takes place under catalytic conditions.

Full text of DOI:10.1016/j.jorganchem.2003.11.018

Journal of Organometallic Chemistry 689 (2004) 585–594
www.elsevier.com/locate/jorganchem
Ligand properties of aromatic azines: C–H activation, metal
induced disproportionation and catalytic C–C coupling reactions
*
€
Daniel Donnecke, Joachim Wunderle, Wolfgang Imhof
Institut fu€r Anorganische und Analytische Chemie der Friedrich-Schiller-Universit€at Jena, August-Bebel-Str. 2, 07743 Jena, Germany
Received 18 July 2003; accepted 10 November 2003
Abstract
The reaction of aromatic azines with Fe2(CO)9 yields dinuclear iron carbonyl cluster compounds as the main products. The
formation of these compounds may be rationalized by a C–H activation reaction at the aromatic substituent in ortho position with
respect to the exocyclic C–N double bond followed by an intramolecular shift of the corresponding hydrogen atom toward the
former imine carbon atom. The second imine function of the ligand does not react. Additional products arise from the metal induced
disproportionation of the azine into a primary imine and a nitrile. So also one of the imine C–H bonds may be activated during the
reaction. Depending on the aromatic substituent of the azine ligands iron carbonyl complexes of the disproportionation products
are isolated and characterized by X-ray crystallography. C–C coupling reactions catalyzed by Ru3(CO)12 result in the formation of
ortho-substituted azines. In addition, ortho-substituted nitriles are identified as side-products showing that the metal induced dis-
proportionation reaction also takes place under catalytic conditions.
Ó 2003 Elsevier B.V. All rights reserved.
1. Introduction
potential reaction sites for the catalytic synthesis of
heterocyclic compounds in which the unsaturated imine
moieties are connected by a N–N bond.
It is well accepted that organometallic compounds
may be regarded as model compounds for intermediates
in catalytic processes. During the last years our research
was focussed on the chemistry of aromatic imines both
in terms of iron carbonyl complexes derived from stoi-
chiometric reactions of Fe2(CO)9 with the correspond-
ing imine and ruthenium catalyzed C–C bond formation
reactions starting from the same imines as the sub-
strates. It became evident from these investigations that
the initial step of the catalytic reactions is a metal in-
duced C–H activation reaction which is also observed in
the formation of the dinuclear iron carbonyl compounds
with the same regioselectivity [1]. Some of the imines
may be reacted with CO and ethylene in a three-com-
ponent reaction to yield chiral lactams [2].
The organometallic chemistry of azines has been the
subject of quite a number of publications in the last
decades. Most of the reactions lead to the symmetrical
cleavage of the azine moiety producing two imide units
which undergo subsequent reactions [3]. Very recently,
the rhodium induced cleavage of an azine into a nitrile
and a imine has been reported and the molecular
structure of the corresponding nitrile complex was de-
termined [4]. In context with our research on iron or
ruthenium induced C–H activation reactions the reac-
tivity of aromatic imines towards iron carbonyls was of
considerable interest. It was reported that in analogy to
other transition metals the reaction of ketazines with
iron carbonyls leads to the formation of bis(l-iminato)
complexes by a symmetrical cleavage of the N–N bond
of the corresponding azine [5]. Azines derived from
aromatic aldehydes upon reaction with iron carbonyls
yield dinuclear complexes in which one of the C–H
bonds of the aromatic substituent is activated and the
hydrogen atom is transferred towards the former imine
carbon atom whereas the N–N bond is still preserved [6].
In order to achieve a reaction with an enhanced atom
economy we considered the use of azines as the sub-
strates. Aromatic azines represent diimines with two
* Corresponding author. Tel.: +49-3641-948144; fax: +49-3641-
948102.
E-mail address: cwi@rz.uni-jena.de (W. Imhof).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.11.018

586
D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
The same reaction sequence of C–H activation and hy-
drogen transfer is observed for aromatic imines in gen-
eral and is believed to be closely related to the initial
reactions during the catalytic C–C coupling induced by
ruthenium precatalysts in the same position of the li-
gands [1,2]. In some reactions of azines with Fe3(CO)12
trinuclear compounds are formed in which the third iron
carbonyl moiety is coordinated to the aromatic sub-
stituent in an g6-fashion [7]. Treatment of acetaldazine
with Fe3(CO)12 yields a dinuclear pyrazolidin-diyl li-
gand by an intramolecular ring closure following the
activation of a C–H bond of one of the methyl groups
[8]. In contrast the reaction of iron carbonyls with azine
ligands derived from cinnamaldehyde yields mono- or
dinuclear iron carbonyl complexes, in which 1-azadiene
substructures of the ligand are g4-coordinated to the
metal atoms [9].
nitrile or of the primary imine may be isolated. The
latter are the first examples of imine complexes pro-
duced by the metal mediated cleavage of an azine. We
will also report on catalytic C–C coupling reactions in
the presence of Ru3(CO)12 as the precatalyst.
2. Results and discussion
2.1. Stoichiometric reactions with Fe2(CO)9
The azines 1–4 are easily obtained by the reaction of
hydrazine hydrate with the corresponding aldehyde in
ethanol. Scheme 1 shows the reaction of the azine li-
gands with Fe2(CO)9 to produce the iron carbonyl
cluster compounds 5–7 and 9–13, respectively. In all
reactions we performed the dinuclear iron carbonyl
compounds 5, 6, 9 or 12 were the main products, the
reaction of the bis(b-naphthyl)-azine yields only the di-
nuclear complex 5. The formation of these complexes
proceeds via a C–H activation reaction at the aromatic
substituent in ortho position with respect to the exocy-
clic imine moiety. The corresponding hydrogen atom is
We report herein the reaction of a series of aromatic
aldazines with Fe2(CO)9 yielding the expected dinuclear
iron complexes as the main products. We were also
able to isolate additional products generated by a non-
symmetrical cleavage of the azines. Depending on the
aromatic substituent iron carbonyl complexes of the
(CO)3
Fe
(CO)3
Fe
H
Fe2(CO)9
N
N
N
N
50˚C, 30 min
H
H
H
H
1
5
(CO)3
Fe
(CO)3
Fe
CN
(CO)3
Fe
(CO)3
Fe
H
Fe2(CO)9
N
N
N
N
H
+
+
N
50˚C, 30 min
H
H
H
H
H
H
2
6
7
8
(CO)2
Fe
MeO
(CO)2
Fe
MeO
(CO)3
Fe
(CO)3
(CO)3
MeO
(CO)3
Fe
(CO)
Fe
(CO)
Fe
Fe
Fe
3
3
MeO
H
Fe2(CO)9
N
N
N
N
N
H
N
+
+
N
OMe
50˚C, 30 min
OMe
H
H
H
H
H
H
H
H
H
OMe
3
9
11
10
Cl
N
(CO)3
Fe
H
(CO)3
Fe
Cl
H/Cl
Fe2(CO)9
Cl
N
H
N
N
+
N
Cl
50˚C, 30 min
H
H
(CO)3Fe
Fe(CO)3
H
Cl/H
Fe
(CO)3
H
4
12
13
Scheme 1.

D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
587
transferred towards the former imine carbon atom
producing a methylene group. So the observation of a
singlet at about 4 ppm in the 1H NMR as well as a signal
at about 70 ppm in the 13C NMR clearly indicates the
formation of 5, 6, 9 or 12. It is remarkable that we never
observed the formation of a compound in which both
imine functions of the azine ligands reacted in that
manner. So obviously the coordination of a Fe2(CO)6
moiety to the ligand system decreases the ability of the
second imine moiety to interact with additional transi-
tion metal centers.
Fig. 1 shows the molecular structure of 6, the most
important bond lengths and angles are depicted in the
figure caption. In accordance with the molecular struc-
tures of other iron carbonyl complexes of aromatic
imines [1], one of the imine functions of the azine 2 is
transformed into a formally 6e-donating enyl-amido
ligand coordinating a Fe2(CO)6 moiety. Another de-
scription would be that of an aza-metalla-cyclopent-
adiene ligand with another apical Fe(CO)3 group
attached to it. The second imine moiety is not coordi-
nated to iron carbonyl fragments and the naphthyl
substituent is turned out of the plane of the aza-ferra-
cyclopentadiene by 56.9°. The bond between N1 and N2
clearly represents a N–N single bond and is only slightly
elongated compared to corresponding bonds in unco-
ordinated azines.
nation mode of the iron carbonyl fragments is nearly
identical. The only difference is the bond between the
apical Fe(CO)3 group and C2, which is about 20 pm
longer in 12 when compared with 6. Since in the azine 4
the aromatic substituent exhibits a chlorine atom in
meta position with respect to the imine function, in
principle two different pathways of the C–H activation/
hydrogen transfer reaction sequence are possible. In one
of them the C–H bond ortho to both substituents at the
aromatic system would be activated leading to the iso-
mer of 12 as it is shown in Fig. 2. The other reaction
pathway then would proceed via the activation of the C–
H bond in trans position to the chlorine atom. Indeed
both reaction pathways are observed by NMR spec-
troscopy in a 70:30 ratio preferring the formation of the
isomer shown in Fig. 2. Interestingly, in the crystal
structure of 12 both isomers are statistically disordered
in the same ratio. Fig. 2 shows the isomer with the
higher occupation factors.
The reaction of the azine derived from hydrazine and
p-methoxybenzaldehyde produces the trinuclear com-
pound 10 in small yields. The cluster is closely related to
9, since the same C–H activation and hydrogen transfer
reaction sequence has been performed ending up in the
formation of an enyl-amido ligand. But in contrast to 9
three iron carbonyl moieties are coordinating the ligand.
Two of them show the same coordination mode as it is
observed for the dinuclear derivatives 5, 6, 9 and 12. In
addition, a third Fe(CO)2 group is g6-coordinated to the
aromatic ring. Although we did not achieve crystals of
The molecular structure of 12, which is presented in
Fig. 2 together with the most important bond lengths
and angles, is closely related to that of 6. The coordi-
Fig. 1. Molecular structure of 6; selected bond lengths (pm) and angles (°): Fe1–Fe2 243.68(4), Fe1–N1 197.3(2), N1–C1 147.1(2), C1–C2 150.8(3),
C2–C3 140.9(3), Fe1–C3 198.0(2), Fe2–N1 196.4(2), Fe2–C2 227.4(2), Fe2–C3 217.2(2), N1–N2 140.7(2), N2–C12 128.5(2); N1–Fe1–C3 77.94(7),
Fe1–C3–C2 114.6(1), C3–C2–C1 114.2(2), C2–C1–N1 99.5(1), C1–N1–Fe1 114.1(1), Fe1–N1–N2 120.6(1), C1–N1–N2 119.2(1), N1–N2–C12
118.0(2), N2–C12–C13 120.9(2).

588
D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
Fig. 2. Molecular structure of 12; selected bond lengths (pm) and angles (°): Fe1–Fe2 243.43(6), Fe1–N1 196.5(2), N1–C1 147.5(4), C1–C2 150.1(5),
C2–C3 141.3(5), Fe1–C3 200.2(3), Fe2–N1 195.4(2), Fe2–C2 247.4(3), Fe2–C3 218.4(3), N1–N2 141.5(3), N2–C8 127.4(4); N1–Fe1–C3 77.4(1), Fe1–
C3–C2 112.8(2), C3–C2–C1 115.5(3), C2–C1–N1 100.9(3), C1–N1–Fe1 112.8(2), Fe1–N1–N2 115.9(2), C1–N1–N2 118.8(2), N1–N2–C8 118.4(2),
N2–C8–C9 121.1(3).
sufficient quality to perform a X-ray structure determi-
nation, the structure of 10 is unequivocally demon-
strated by its spectroscopic data [7].
under the same reaction conditions produces 7, although
the yields are as low as in the reaction of Fe2(CO)9 with
the free azine 2.
The most interesting feature of the reaction of aro-
matic azines with Fe2(CO)9 is the observation of prod-
ucts that arise from the unsymmetrical formal
disproportionation of the azine into an imine and a ni-
trile. To the best of our knowledge a reaction like this
has not been reported from the treatment of azines with
iron carbonyls. Very recently a closely related reaction
was described starting from a rhodium pincer complex
exhibiting the very labile dinitrogen ligand [4].
The molecular structure of 7 is shown in Fig. 3 to-
gether with the most important bond lengths and angles
in the figure caption. Formally 7 is a Fe2(CO)6 complex
of a primary imine that also showed the reaction se-
quence of ortho-metallation and subsequent hydrogen
transfer towards the imine carbon atom. The fact that in
the related cleavage of an azine by a rhodium complex
Depending on the aromatic substituent we were able
to isolate either complexes formally derived from the
primary imine (7 and 11) or from the nitrile (13). In one
case the nitrile itself was detected by means of IR
spectroscopy (8). The disproportionation of the azine
ligands can only proceed via the activation of the imine
C–H bond of the second imine moiety followed by the
transfer of this hydrogen atom towards the former imine
nitrogen atom together with a cleavage of the N–N bond
of the azines. The question then arises whether the for-
mation of 7, 8, 11 and 13 is just the result of a thermal
decomposition of the dinuclear complexes 6, 9 and 12.
Then the C–H activation of the imine hydrogen atom
would be due to the electron deficiency of the a,b-un-
saturated diimine system induced by the coordination of
the Fe2(CO)6 moiety. Another possibility would be the
coordination of additional iron carbonyl fragments to 6,
9 and 12 leading to the observed unsymmetrical cleavage
of the azines. To us the latter possibility seems to be
more reasonable, since stirring a solution of 6 in heptane
at 50 °C does not lead to the formation of 7. On the
other hand, the reaction of 6 with additional Fe2(CO)9
Fig. 3. Molecular structure of 7; selected bond lengths (pm) and angles
(°): Fe1–Fe2 245.75(3), Fe1–N1 194.4(1), N1–C1 146.5(2), C1–C2
150.9(2), C2–C3 141.6(2), Fe1–C3 198.9(2), Fe2–N1 194.8(2), Fe2–C2
228.9(2), Fe2–C3 217.4(2); N1–Fe1–C3 77.76(6), Fe1–C3–C2 114.2(1),
C3–C2–C1 113.4(1), C2–C1–N1 99.6(1), C1–N1–Fe1 114.3(1).

D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
589
no imine and no complex of the imine was detectable [4]
to our opinion is an additional hint that in the reaction
described herein the cleavage of the N–N bond of the
azine follows the reaction of the first imine moiety of the
ligand. The hydrogen atom at the former imine nitrogen
atom gives rise to characteristic signals in the IR- and
NMR-spectra of 7 (cf. Section 3). The coordination of
the enyl-amido ligand in 7 is very similar as in 6 with the
exception that the nitrogen atom is more basic in 7
because of the loss of the second imine moiety and thus
the nitrogen iron bond lengths are decreased to some
extend.
If the azine from p-methoxybenzaldehyde (3) is used
in the reaction a very similar iron carbonyl complex of a
primary imine may be isolated. The molecular structure
of the trinuclear cluster 11 is depicted in Fig. 4. 11 also
shows a hydrogen atom at the former imine nitrogen as
well as a methylene group at the former imine carbon
atom (C1). The C–H bond in ortho position with respect
to the former imine substituent has been activated.
The main difference in this compound compared to the
molecular structures of 6, 7 and 12 is the fact that the
aromatic substituent is coordinated to a third iron car-
bonyl moiety in a g6-fashion. Due to the coordination
of a third iron carbonyl fragment the C2–Fe2 distance in
11 is extremely elongated. The iron–iron bond between
Fe2 and Fe3 also seems to be quite labile. Compounds
closely related to 11 were described earlier from the re-
action of azines with Fe3(CO)12, although in these cases
the N–N bond of the azines was preserved and the
second imine function in analogy to the formation of 6,
9 and 12 did not react [7]. The hydrogen atom at N1
again is clearly identified by IR spectroscopy.
Another trinuclear cluster compound was produced
in the reaction of the azine 4 with Fe2(CO)9. The mo-
lecular structure of 13 is shown in Fig. 5 together with
the most important bond lengths and angles. The cluster
is best described as a Fe3N-tetrahedron with the nitro-
gen atom still being part of an imine function. The
carbon nitrogen bond represents a double bond which is
slightly elongated due to the side-on coordination of this
imine double bond to one of the iron atoms. The iron–
iron bond between the other two iron centers is bridged
by a hydrido ligand. Although there is an imine hy-
drogen atom present in the molecular structure of 13, we
still think that this compound is derived from the nitrile
which is produced by the unsymmetrical cleavage of the
azine 4. The best evidence for this assumption is the fact,
that the only time that compounds of analogous com-
position were synthesized, nitriles and carbonyl ferrates
were reacted in the presence of a proton source [10].
2.2. Catalytic alkylation of the naphthylazines 1 and 2
Aromatic imines may be reacted with CO and/or
alkenes in the presence of catalytic amounts of
Fig. 4. Molecular structure of 11; selected bond lengths (pm) and angles (°): Fe1–Fe2 246.6(1), Fe2–Fe3 283.8(1), Fe1–N1 197.4(5), N1–C1 147.2(7),
C1–C2 148.7(7), C2–C3 143.9(7), Fe1–C3 197.5(5), Fe2–N1 196.9(4), Fe2–C2 294.0(9), Fe2–C3 249.6(5); Fe3–C2 212.3(5), Fe3–C3 221.4(5), Fe3–C4
213.5(5), Fe3–C5 218.3(5), Fe3–C6 213.2(6), Fe3–C7 211.4(5), Fe1–Fe2–Fe3 95.4(4), N1–Fe1–C3 77.1(2), Fe1–C3–C2 113.6(4), C3–C2–C1 113.6(5),
C2–C1–N1 104.2(4), C1–N1–Fe1 112.7(4).

590
D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
Fig. 5. Molecular structure of 13; selected bond lengths (pm) and angles (°): Fe1–Fe2 258.5(1), Fe1–Fe3 254.9(1), Fe2–Fe3 255.7(1), Fe1–N1 186.6(5),
Fe2–N1 185.8(4), Fe3–N1 194.8(4), Fe3–C1 220.4(6), N1–C1 134.7(7), C1–C2 148.2(7); Fe1–Fe2–Fe3 59.44(3), Fe2–Fe3–Fe1 60.81(3), Fe3–Fe1–Fe2
59.75(3), Fe1–N1–Fe2 87.9(2), N1–Fe2–Fe1 46.2(2), Fe2–Fe1–N1 45.9(1), Fe1–N1–Fe3 83.9(2), N1–Fe3–Fe1 46.7(1), Fe3–Fe1–N1 49.4(1), Fe2–N1–
Fe3 84.4(2), N1–Fe3–Fe2 46.3(1), Fe3–Fe2–N1 49.3(1), Fe3–N1–C1 81.8(3), N1–C1–Fe3 61.0(3), C1–Fe3–N1 37.2(2), Fe3–C1–C2 121.9(4), N1–C1–
C2 122.6(5).
Ru3(CO)12 to produce compounds, in which the co-
substrates are formally inserted into the C–H bond in
ortho position with respect to the imine function [11]. So
presumably the imine substituent acts as a donor site for
the catalytically active organometallic species thus con-
trolling the regioselectivity of the C–H activation reac-
tion. This step of the catalytic reaction is then closely
related to the stoichiometric C–H activation reactions
described above. The reaction of a-naphthylimines with
ethylene yielded naphthaline derivatives with an ethyl
group in 2-position. On the other hand, the reaction of
b-naphthylimines with CO and ethylene ended up in the
formation of heterocyclic products [2b].
Scheme 2 shows the products we observed from the
catalytic reaction of 2 with ethylene in the presence
of Ru3(CO)12. GC- and GC-MS measurements showed
that the starting compound has been fully consumed after
16 h and that the main product is the doubly alkylated
species 14. The formation of this compound corresponds
to the C–H activation reactions described above, in which
the central C–C bond of the azine substrate is not cleaved.
Most remarkably, we also observed the formation of 15 in
a 10% yield. The identity of 15 is unequivocally shown by
comparison of its spectra with those reported in the lit-
erature [12]. So the second reactivity pattern in the
stoichiometric reactions – the metal induced dispropor-
CN
H
C2H5
C2H5
4 mol% Ru3(CO)12
N
N
+
N
N
140˚C, 15 h
20 bar C2H4
H
C2H5
14, ~ 85%
15, ~ 10%
Scheme 2.

D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
591
tionation of the azine ligands – is also a model for the
formation of the side-product of the catalytic reactions.
product mixture from the reaction of the methoxy-
substituted azine 3 yields a fraction containing 9 and 10,
which can be separated repeating the chromatography
using mixtures of light petroleum (b.p. 40–60 °C) and
toluene. In addition, using pure CH2Cl2 or diethylether
as the solvent results in the elution of approximately
0.25 mmol of the corresponding azine. The formation of
8 was confirmed by its IR spectrum. Yields (based on
the portion of the converted azines): 35 mg 5 (0.06
mmol, 24%), 38 mg 6 (0.06 mmol, 26%), 4 mg 7
(0.01 mmol, 4%), 38 mg 9, (0.07 mmol, 28%), 10 mg 10
(0.02 mmol, 6%), 2 mg 11 (0.004 mmol, 2%), 17 mg 12
(0.03 mmol, 12%), 2 mg 13 (0.004 mmol, 1%). Due to the
very low yields of 7, 10, 11, and 13 elemental analyses and
NMR spectra could not be obtained for all compounds.
Nevertheless, the molecular structure of these complexes
was unequivocally demonstrated by X-ray analyses (7, 11
and 13) or by comparison of the spectroscopic properties
with those of closely related compounds reported in the
literature (10) [7]. Recrystallization of the complexes was
performed from mixtures of light petroleum (b.p. 40–60
°C) and CH2Cl2 at )20 °C.
3. Experimental
3.1. General
All procedures were carried out under an argon at-
mosphere in anhydrous, freshly distilled solvents.
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
standard). Mass spectra were recorded on a Finnigan
MAT SSQ 710 instrument. Elemental analyses were
carried out at the Institute of Organic and Macromo-
lecular Chemistry at the Friedrich-Schiller-University
Jena using a LECO-CHNS-932 system.
3.2. X-ray crystallographic studies
The structure determinations of 6, 7, 11, 12 and 13
were carried out on an Enraf Nonius Kappa CCD dif-
fractometer, crystal detector distance 25 mm, using
graphite monochromated Mo Ka radiation. The crystal
was mounted in a stream of cold nitrogen. Data were
corrected for Lorentz and polarization effects but not
for absorption. The structure was solved by direct
methods and refined by full-matrix least-squares tech-
niques against F 2 using the programs SHELXS-86 and
SHELXL-93 [13]. Computation of the structure was ac-
complished with the program XPMA [14] and the mo-
lecular illustration was drawn using the program XP
[15]. The crystal and intensity data are given in Table 1.
3.4. MS and spectroscopical data for 5
Anal. Calc. for C28H16N2O6Fe2: C, 57.18; H, 2.74; N,
4.76. Found: C, 56.58; H, 2.92; N, 4.21%. DEI m=z (%):
588 (Mþ, 4), 560 (Mþ–CO, 18), 532 (Mþ–2CO, 18), 504
(Mþ–3CO, 17), 476 (Mþ–4CO, 19), 448 (Mþ–5CO, 11),
420 (Mþ–6CO, 74), 392 (Mþ–Fe2(CO)3, 2), 364 (Mþ–
Fe2(CO)4, 3), 336 (Mþ–Fe2(CO)5, 2), 308 (Mþ–
Fe2(CO)6, 19), 280 (Fe2(CO)6þ, 9), 252 (Fe2(CO)5þ, 3)
224 (Fe2(CO)4þ, 8), 196 (Fe(CO)5þ, 30), 168 (Fe(CO)4
,
þ
30), 153þ(C11H7Nþ, 61), 140 (Fe(CO)3þ, 17), 112
(Fe(CO)2 , 28), 84 (FeCOþ, 100), 56 (Feþ, 93). IR, KBr,
m (cmꢀ1): 3049 w, 2911 w, 2845 w, 2062 s, 2027 s, 1996 s,
1980 vs, 1967 s, 1958 s, 1621 w, 871 w, 856 w, 824 w, 749
3.3. Synthesis of 5–13
1
m, 627 m, 588 m, 562 m, 548 m, 475 m. H NMR, 400
A 182 mg portion Fe2(CO)9 (0.5 mmol) together with
an equimolar amount of the corresponding azine (154
mg 1, 154 mg 2, 134 mg 3, 138 mg 4) and 20 ml n-
heptane are stirred together at 50 °C for 30 min. In the
course of the reaction the pale yellow suspension slowly
changes to a deep red solution as the ligand and
Fe2(CO)9 dissolve. After the reaction is completed all
volatile materials are removed in vacuo. The residue is
dissolved in CH2Cl2, 1 g silanized silica gel is added and
the solvent is again removed under reduced pressure.
Chromatography on silica gel using light petroleum
(b.p. 40–60 °C) as the eluent first yields a small green
band containing Fe3(CO)12. Adding small portions of
CH2Cl2 to the light petroleum allows the elution of the
iron carbonyl compounds 5–7 and 9–13. In each reac-
tion the complexes resulting from a cleavage of the N–N
bond of the azines (7, 11 and 13) elute prior to the main
products (5, 6, 9 and 12). Chromatography of the
MHz, CD2Cl2, 293 K, d (ppm): 4.87 (s, 2H, CH2), 7.47–
7.59 (m, 3H, CH), 7.60–7.68 (m, 1H, CH), 7.80–7.98 (m,
6H, CH), 8.00–8.07 (m, 2H, CH), 8.28 (s, 1H, CH), 8.78
(s, 1H, CH). 13C NMR, 100.6 MHz, CD2Cl2, 293 K, d
(ppm): 70.43, 121.58, 123.41, 127.02, 127.14, 127.20,
127.51, 127.98, 128.20, 128.26, 128.75, 129.02, 129.10,
129.73, 132.22, 133.64, 134.84, 136.63, 143.98, 148,96,
160.78, 210.69.
3.5. MS and spectroscopical data for 6
Anal. Calc. for C28H16N2O6Fe2: C, 57.18; H, 2.74; N,
4.76. Found: C, 56.52; H, 2.97; N, 4.41%. FAB MS m=z
(%): 589 (M + Hþ, 8), 560 (M + Hþ–CO, 5), 532
(M + Hþ–2CO, 7), 504 (M + Hþ–3CO, 26), 476
(M + Hþ–4CO, 20), 448 (M + Hþ–5CO, 6), 420
(M + Hþ–6CO, 20). IR, KBr, m (cmꢀ1): 3047 w, 2957 w,
2922 w, 2892 w, 2837 w, 2064 s, 2028 s, 1990 s, 1972 s,

592
D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
Table 1
Crystal and intensity data for 6, 7, 11, 12 and 13
6
7
11
12
13
Formula
Molecular weight (g molꢀ1
Radiation
C28H16N2O6Fe2
C17H9NO6Fe2
434.95
C16H9NO9Fe3
526.79
C20H10N2O6Cl2Fe2
556.90
C16H6NO9ClFe3
559.22
)
588.13
Mo Ka
graphite
183
Mo Ka
graphite
183
Mo Ka
graphite
183
Mo Ka
graphite
183
Mo Ka
graphite
183
Monochromator
T (K)
Crystal color
red
orange
0.3 ꢁ 0.1 ꢁ 0.02
14.1315(4)
7.2308(2)
16.4641(5)
90
red
red
red
Crystal size
ꢀ
0.5 ꢁ 0.2 ꢁ 0.02
12.3642(3)
13.2762(5)
14.9414(6)
90
0.5 ꢁ 0.3 ꢁ 0.03
7.2734(9)
9.363(1)
14.461(2)
95.833(8)
100.879(9)
108.403(6)
903.8(2)
2
0.4 ꢁ 0.1 ꢁ 0.05
7.6944(4)
9.1139(5)
15.8209(9)
101.653(3)
90.968(3)
96.199(4)
1079.4(1)
2
0.2 ꢁ 0.05 ꢁ 0.05
7.125(1)
11.834(2)
11.845(2)
89.276(9)
83.87(1)
78.83(1)
974.1(3)
2
a (A)
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
97.39(2)
90
98.368(2)
90
3
ꢀ
V (A )
2432.3(2)
4
1192
1664.42(8)
4
872
Z
F ð000Þ
524
1.936
556
1.713
552
1.906
qcalc (g cmꢀ3
Crystal system
)
1.606
1.736
monoclinic
P21=n
1.241
monoclinic
P21=n
1.777
triclinic
ꢁ
triclinic
ꢁ
triclinic
ꢁ
Space group
P1
2.428
P1
1.632
P1
2.391
Absorption coefficient (mmꢀ1
h limit (°)
Scan mode
)
2:02 < h < 27:46
x-scan, /-scan
9574
1:78 < h < 27:45
x-scan, /-scan
6953
2:33 < h < 27:57
x-scan, /-scan
6253
2:30 < h < 27:43
x-scan, /-scan
7715
2:47 < h < 27:46
x-scan, /-scan
5852
Reflections measured
Independent reflections
Rint
5560
3808
0.0154
4078
4880
4133
0.0327
4207
407
0.0551
2343
274
0.0228
3841
299
0.0409
2711
295
Reflections observed ðFo2 > 2rðFo2ÞÞ
3263
271
Number of parameters
Goodness-of-fit
0.996
1.054
0.0275
0.988
1.043
1.036
R1
wR2
0.0348
0.0731
0.320
0.0568
0.1069
0.512
0.0431
0.0954
0.742
0.0578
0.1131
0.579
0.0633
0.264
Final diffracꢀti3on map electron density
ꢀ
peak (e A
)
1947 s, 808 m, 797 m, 772 m, 617 m, 590 m, 573 m, 556
m, 489 w. 1H NMR, 200 MHz, CD2Cl2, 293 K, d (ppm):
4.87 (s, 2H, CH2), 7.42 (d, 1H, JHH ¼ 8 Hz, CH), 7.51–
7.70 (m, 5H, CH), 7.81–7.89 (m, 1H, CH), 7.92–8.02 (m,
4H, CH), 8.03–8.12 (m, 1H, CH), 8.53 (s, 1H, CH),
8.73–8.79 (m, 1H, CH). 13C NMR, 50.3 MHz, CD2Cl2,
293 K, d (ppm): 70.54, 108.02, 124.65, 124.99, 125.83,
126.28, 126.73, 127.78, 127.99, 128.11, 128.91, 129.22
(2C), 129.63, 131.28, 131.86, 133.82, 134.39, 135.08,
143.32, 151,01, 153.85, 210.79.
7.76–7.80 (m, 1H, CH), 7.90–7.95 (m, 1H, CH), 7.89 (d,
1H, JHH ¼ 8.8 Hz, CH). 13C NMR, 100.6 MHz, CD2Cl2,
293 K, d (ppm): 65.44, 113.01, 125.43, 125.96, 127.79,
127.91, 129.28, 133.79, 134.20, 143.51, 153.03, 211.00.
3.7. MS and spectroscopical data for 9
Anal. Calc. for C22H16N2O8Fe2: C, 48.22; H, 2.94; N,
5.11. Found: C, 48.02; H, 2.91; N, 5.04%. DEI MS m=z
(%): 548 (Mþ, 4), 520 (Mþ–CO, 8), 492 (Mþ–2CO, 6),
464 (Mþ–3CO, 23), 436 (Mþ–4CO, 14), 408 (Mþ–5CO,
51), 380 (Mþ–6CO, 100). IR, KBr, m (cmꢀ1): 2940 w,
2838 w, 2066 s, 2024 vs, 1994 vs, 1970 s, 1926 m, 1903 w,
1599 m, 1592 m, 1514 m, 1468 m, 1437 w, 1335 w, 1302
w, 1262 m, 1229 m, 1168 w, 1029 w, 830 w, 790 w, 627
3.6. MS and spectroscopical data for 7
C17H9NO6Fe2, FAB MS m=z (%): 379 (Mþ, 72), 351
(Mþ–CO, 12), 323 (Mþ–2CO, 11), 295 (Mþ–3CO, 10).
IR, KBr, m (cmꢀ1): 3379 m, 3054 w, 3029 w, 3013 w,
2964 w, 2924 w, 2845 m, 2065 s, 2040 s, 2018 m, 1995 s,
1976 s, 1961 s, 1947 s, 809 m, 777 m, 754 m, 748 w, 675
w, 628 m, 595 m, 587 m, 569 m, 546 m, 498 m, 485 w,
1
m, 610 w, 570 m, 553 w, 375 m. H NMR, 200 MHz,
CDCl3, 293 K, d (ppm): 3.78 (s, 3H, OCH3), 3.82 (s, 3H,
OCH3), 4.26 (s, 2H, CH2), 6.87–6.98 (m, 3H, CH), 7.31
(s, 1H, CH), 7.56–7.61 (m, 3H, CH), 7.68 (s, 1H, CH).
13C NMR, 50.3 MHz, CDCl3, 293 K, d (ppm): 55.24,
55.40, 71.55, 110.36, 114.35 (2C), 122.64, 125.79, 126.34,
129.48 (2C), 131.33, 149.49, 152,27, 156.77, 161.75,
210.62.
1
449 w, 426 w. H NMR, 400 MHz, CD2Cl2, 293 K, d
(ppm): 2.02 (s, br, 1H, NH), 4.49 (s, 2H, CH2), 7.33
(d, 1H, JHH ¼ 8.8 Hz, CH), 7.56–7.60 (m, 2H, CH),

D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
593
3.8. MS and spectroscopical data for 10
3.11. MS and spectroscopical data for 13
C24H16N2O10Fe3 DEI MS m=z (%): 660 (Mþ, 15), 604
(Mþ–2CO, 37), 576 (Mþ–3CO, 4), 548 (Mþ–4CO, 7),
520 (Mþ–5CO, 14), 492 (Mþ–6CO, 19), 464 (Mþ–7CO,
30), 436 (Mþ–8CO, 25), 408 (Mþ–2CO–Fe(CO)5, 29),
380 (Mþ–Fe2(CO)6, 67), 149 (C8H9N2Oþ, 84), 133
(C8H7NOþ, 66), 28 (CO, N2, 100). IR, KBr, m (cmꢀ1):
2054 s, 2012 vs, 1987 sh, 1962 s, 1607 w, 1509 m, 1252 s,
C16H5NO9ClFe3, DEI m=z (%): 559 (Mþ, 18), 531
(Mþ–CO, 23), 503 (Mþ–2CO, 11), 475 (Mþ–3CO, 25),
447 (Mþ–4CO, 43), 419 (Mþ–5CO, 100), 391 (Mþ–6CO,
32), 363 (Mþ–7CO, 73), 335 (Mþ–8CO, 100), 307 (Mþ–
9CO, 32). IR, KBr, m (cmꢀ1): 2090 s, 2060 s, 2028 sh,
2013 vs, 2001 vs, 1989 sh, 1983 vs, 1972 sh, 1951 s, 1567
m, 1437 w, 1264 w, 927 m, 792 m, 682 m, 670 m, 622 m,
613 s, 579 m, 556 s.
1
1168 m, 1017 m, 831 w, 563 m, 375 w. H NMR, 400
MHz, CD2Cl2, 293 K, d (ppm): 2.61, 2.64, 3.93, 3.96
(AB, 2H, CH2), 3.76 (s, 3H, OCH3), 3.81 (s, 3H, OCH3),
4.22 (d, 1H, 4JHH ¼ 2.2 Hz, CH), 5.12 (d, 1H, 3JHH ¼ 6.5
3.12. Catalytic ethylene insertion reactions
3
4
Hz, CH), 6.54 (d of d, 1H, JHH ¼ 6.5 Hz, JHH ¼ 2.2
3
A 50 ml autoclave charged with 1 mmol 2 (308 mg),
Ru3(CO)12 (0.03 mmol) and toluene (5 ml) was pres-
surized with ethene (20 bar) and heated at 140 °C
overnight. After the reaction mixture was cooled to
room temperature it was transferred to a Schlenk tube
and all volatile material was removed under reduced
pressure. The remaining oily residue was used to deter-
mine yields of the products 14 and 15 by NMR spec-
troscopy. Column chromatography on silica gel gave 15
as a colorless oil using mixtures of light petroleum (b.p.
40–60 °C) and CH2Cl2 (80/20) as the eluent. The spec-
troscopical data of 15 are identical with those reported
in the literature [12]. Elution with pure CH2Cl2 yielded a
bright yellow fraction from which 14 crystallizes as
yellow needles upon slow removal of the solvent.
Hz, CH), 6.89 (d, 2H, JHH ¼ 8.8 Hz, CH), 7.55 (d, 2H,
3JHH ¼ 8.8 Hz, CH), 7.56 (s, 1H, CH). 13C NMR, 100.6
MHz, CD2Cl2, 293 K, d (ppm): 55.73, 56.53, 68.88,
74.80, 83.32, 87.39, 105.53, 114.59 (2C), 117.01, 127.01,
129.27 (2C), 141.91, 147.12, 161.81, 211.16, 213.66.
3.9. MS and spectroscopical data for 11
C16H9NO9Fe3 DEI MS m=z (%): 527 (Mþ, 7), 499
(Mþ–CO, 15), 471 (Mþ–2CO, 6), 443 (Mþ–3CO, 11),
415 (Mþ–4CO, 77), 387 (Mþ–5CO, 43), 359 (Mþ–6CO,
61), 331 (Mþ–7CO, 87), 303 (Mþ–8CO, 58), 301
þ
(C8H7NOFe(CO)4
,
100), 245 (H3COPhCHN[Fe
(CO)2]þ, 61), 189 (H3COPhCHNFeþ, 34), 134 (H3CO
PhCHNþ, 18), 133 (H3COPhCNþ, 13), 112 (Fe(CO)2)þ,
84 (FeCOþ, 9), 56 (Feþ, 24), 28 (CO, N2, 14). IR, KBr, m
(cmꢀ1): 3307 w, 2965 w, 2927 w, 2851 w, 2089 s, 2065 s,
2050 s, 2029 sh, 2005 vs, 1979 s, 1950 s,1941 s, 1931 s,
1603 m, 1510 m, 1465 w, 1335 w, 1301 w, 1263 m, 1107
m, 1032 m, 889 m, 828 w, 801 w, 578 s.
3.13. MS and spectroscopical data for 14
Anal. Calc. for C26H24N2: C, 85.67; H, 6.63; N, 7.68.
Found: C, 85.50; H, 6.27; N, 7.53%. DEI m=z (%): 364
(Mþ, 42), 335 (Mþ–C2H5, 24), 195 (C14H13Nþ, 20), 184
(C13H14Nþ, 43), 183 (C13H13Nþ, 36), 182þ(C13H12Nþ,
96), 181 (C13H11Nþ, 100), 167 (C13H11 , 95), 153
(C11H7Nþ, 41), 139 (C11H7þ, 23), 127 (C10H7þ, 18). IR,
KBr, m (cmꢀ1): 2969 s, 2928 s, 1594 m, 1509 m, 1453 m,
3.10. MS and spectroscopical data for 12
Anal. Calc. for C20H10N2O6Cl2Fe2: C, 43.31; H, 1.81;
N, 5.03. Found: C, 43.46; H, 1.99; N, 4.60%. DEI m=z
(%): 556 (Mþ, 7), 528 (Mþ–CO, 8), 500 (Mþ–2CO, 20),
472 (Mþ–3CO, 27), 444 (Mþ–4CO, 13), 416 (Mþ–5CO,
27), 388 (Mþ–6CO, 100). IR, KBr, m (cmꢀ1): 2894 w,
2831 w, 2066 s, 2034 vs, 1994 vs, 1985 vs, 1972 s, 1963 s,
1596 w, 1576 m, 1560 m, 1469 w, 1429 m, 1360 m, 1264
m, 1232 m, 1076 m, 998 m, 935 w, 871 m, 813 m, 775 m,
748 m, 626 s, 599 m, 573 s, 557 m, 481 m. 1H NMR, 400
MHz, CDCl3, 293 K, d (ppm): 4.34 (s, 2H, CH2), 7.09 (d
1
1377 m, 1216 s, 1058 s, 822 vs, 801 vs, 748 s, 454 m. H
NMR, 200 MHz, CDCl3, 293 K, d (ppm): 1.33 (t, 6H,
3
3JHH ¼ 7.5 Hz), 3.04 (q, 4H, JHH ¼ 7.5 Hz), 7.41 (d,
2H,3JHH ¼ 8.4 Hz, CH), 7.46–7.67 (m, 4H, CH), 7.84 (d,
3
2H,3JHH ¼ 7.9 Hz, CH), 7.86 (d, 2H, JHH ¼ 8.4 Hz,
3
CH), 8.82 (d, 2H, JHH ¼ 7.9 Hz, CH). 13C NMR, 50.3
MHz, CDCl3, 293 K, d (ppm): 16.23, 27.33, 125.50,
125.73, 127.03, 127.18, 127.88, 128.31, 130.86, 131.68,
132.52, 143.84, 162.09.
3
4
of d, 0.3H, JHH ¼ 8.6 Hz, JHH ¼ 2 Hz, CH), 7.22–7.34
(m, 2.4H, CH), 7.37–7.39 (m, 1H, CH), 7.49–7.54 (m,
2H, CH), 7.62–7.63 (m, 1H, CH), 7.69 (s, 1H, CH), 7.99
3
(d, 0.3H, JHH ¼ 8.6 Hz, CH). 13C NMR, 100.6 MHz,
CDCl3, 293 K, d (ppm): 70.98, 71.92, 124.72, 125.89,
125.96, 126.81, 126.97, 127.02 (2C), 127.12, 127.51,
127.58, 130.18 (2C), 130.67, 130.75, 131.09, 134.76,
134.90, 135.01(2C), 137.26, 140.95, 147.21, 148.24,
148.56, 152.52, 156.53, 209.68, 209.77.
4. Supplementary material
Additional material on the structure analyses is
available from the Cambridge Crystallographic
Data Centre by mentioning the deposition number

594
D. D€onnecke et al. / Journal of Organometallic Chemistry 689 (2004) 585–594
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The authors gratefully acknowledge financial support
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Modeled after Nature’’, SFB 436).
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