The reaction of ortho-halogenated aromatic aldazine ligands with Fe2(CO)9: Symmetrical cleavage of the azine and carbon-halogen activation

Article abstract of DOI:10.1016/j.jorganchem.2004.04.049

Azine ligands derived from hydrazine and benzaldehyde derivatives bearing halogen substituents in ortho-position with respect to the carbonyl function upon treatment with Fe₂(CO)₉ show two typical reaction principles. One is the symmetrical cleavage of the N-N bond of the azine to yield either di- or trinuclear iron carbonyl compounds [Fe₂(CO)₆(μ₂-N - CHR)₂] and [Fe₃(CO)₉(μ₂-N - CHR)(μ₂-η²-N - CHR)] each showing two arylidenimido moieties. In addition, a trinuclear iron carbonyl cluster compound exhibiting a tetrahedral Fe₃N cluster core is isolated. The cluster shows only one half of the former azine ligand. It is a ionic compound of the general formula [Fe₃(CO ₉(μ₃-η²-N - CHR ]Na×H₂O. This trinuclear cluster compound is quantitatively converted into [Fe₃(CO ₉(μ₂-H) (μ₃-η²-N - CHR)] upon treatment with phosphorous acid. Most interestingly, we were also able to isolate two types of compounds in which an activation of one of the carbon halogen bonds in ortho-position with respect to the imine functions of the azine has occured in terms of an ortho-metallation reaction. In [Fe₂(CO ₆(μ₃-η²-C=C(F)-C(H)= C(H)-C(H =C-CH₂-N-N=CHR)] the N-N bond of the azine is still preserved, whereas in [Fe₃(CO ₉(μ₃-η³-N - CHR)] again only one half of the former azine ligand is coordinated in an arylidenimido fashion. In both types of compounds one additional iron carbon bond is present due to the activation of an aromatic carbon halogen bond. The reaction of iron carbonyls with 2,6-difluorobenzonitrile produces [Fe₃(CO )₉(μ₃-η²-N≡CR)] as the sole product. All new iron carbonyl compounds are characterized by means of X-ray crystallography.

Full text of DOI:10.1016/j.jorganchem.2004.04.049

Journal of Organometallic Chemistry 689 (2004) 2707–2719
www.elsevier.com/locate/jorganchem
The reaction of ortho-halogenated aromatic aldazine ligands
with Fe2(CO)9: symmetrical cleavage of the azine and
carbon–halogen activation
*
Daniel Donnecke, Kathi Halbauer, Wolfgang Imhof
¨
Institut fu¨r Anorganische und Analytische Chemie der Friedrich-Schiller-Universita¨t Jena, August-Bebel-Str. 2, 07743 Jena, Germany
Received 4 March 2004; accepted 30 April 2004
Abstract
Azine ligands derived from hydrazine and benzaldehyde derivatives bearing halogen substituents in ortho-position with respect to
the carbonyl function upon treatment with Fe2(CO)9 show two typical reaction principles. One is the symmetrical cleavage of the N–N
bond of the azine to yield either di- or trinuclear iron carbonyl compounds [Fe2(CO)6(l2-N‚CHR)2] and [Fe3(CO)9(l2-N‚CHR)(l2-
g2-N‚CHR)] each showing two arylidenimido moieties. In addition, a trinuclear iron carbonyl cluster compound exhibiting a tetra-
hedral Fe3N cluster core is isolated. The cluster shows only one half of the former azine ligand. It is a ionic compound of the general
formula [Fe3(CO)9(l3-g2-N‚CHR)]Na·H2O. This trinuclear cluster compound is quantitatively converted into [Fe3(CO)9(l2-
H)(l3-g2-N‚CHR)] upon treatment with phosphorous acid. Most interestingly, we were also able to isolate two types of compounds
in which an activation of one of the carbon halogen bonds in ortho-position with respect to the imine functions of the azine has occured
2
in terms of an ortho-metallation reaction. In
the N–N bond of
[Fe2(CO)6(µ3-η -C=C(F)-C(H)=C(H)-C(H)=C-CH2-N-N=CHR)]
the azine is still preserved, whereas in [Fe3(CO)9(l3-g3-N‚CHR)] again only one half of the former azine ligand is coordinated in
an arylidenimido fashion. In both types of compounds one additional iron carbon bond is present due to the activation of an aromatic
carbon halogen bond. The reaction of iron carbonyls with 2,6-difluorobenzonitrile produces [Fe3(CO)9(l3-g2-N„CR)] as the sole
product. All new iron carbonyl compounds are characterized by means of X-ray crystallography.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: C–F activation; C–Cl activation; Iron; Cluster compounds; X-ray analyses
1. Introduction
the properties of fluorinated organic compounds usually
differ compared to those of the corresponding hydrocar-
bon derivatives [2]. Secondly, the transition metal in-
duced activation of carbon halogen bonds might lead
to strategies allowing the efficient degradation of envi-
ronmentally critical halogenated hydrocarbons.
Since transition metal compounds have successfully
been used in stoichiometric and catalytic activations of
C–C (ꢀ350 kJmolꢁ1) and C–H (ꢀ410 kJmolꢁ1) bonds,
the question arose whether transition metal compounds
could also activate C–F bonds. Mechanistical studies on
C–F activation reactions have revealed different activa-
tion mechanisms depending on the electronic structure
The activation of carbon halogen bonds and in this
context especially of carbon fluorine bonds has attracted
the interest of several research groups mainly for two
reasons. First of all perfluorinated organic compounds
may be functionalized that way to produce new fluori-
nated compounds [1]. This is an attractive goal since
*
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 ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.04.049

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D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
of the transition metal as well as additional ligands be-
ing present in the system. Quite a lot of reactions take
place with titanium or zirconium compounds with hy-
dride ligands present [3]. The reaction then is believed
to take place via a transition state typical for r-bond
metathesis reactions in the case of fluoroaromatics. A
similar transition state might also work in the reaction
of [OsH6(PiPr3)2], compound being able to activate C–
H as well as C–F bonds [4]. Most of the stoichiometric
C–F activation reactions reported in the literature are
realized by treatment of the corresponding fluorinated
organic compounds with transition metal complexes of
late transition metals. Especially nickel [5], rhodium
[6], platinum [7] and rhenium [8] have been commonly
used for this purpose. In the reaction of fluoroaromatic
compounds there is experimental evidence for two com-
peting pathways. On one hand, the formation of tight
ion-pairs by a complete electron transfer due to the high
electron affinity of fluorine is discussed [9]. On the other
hand, concerted mechanisms with an intermediate g2-
coordination of the C–F bond in the transition state
have been made plausible by investigations of the kinet-
ics as well as by the regioselectivity of C–F activation of
heteroaromatic fluorocarbons, although in the latter
case a pre-coordination via the heteroatom cannot be
ruled out completely [1e]. In the case of aromatic hydro-
carbons a g2-coordination of the aromatic system has
been identified in intermediates of C–F activation reac-
tions and the compounds have been structurally charac-
terized [5d,10]. Examples of catalytic reactions
proceeding via C–F activation steps are very rare, the
most prominent one being the synthesis of C6F5H from
C6F6 catalyzed by rhodium compounds [11]. Of course
catalytical activation of carbon halogen bonds plays a
crucial role in dehalogenation reactions in vivo by re-
ductive dehalogenases [12].
as the precatalyst. In order to develop reactions of im-
proved atom economy we looked at the chemistry of
Fe2(CO)9 towards aromatic azines, in which two a,b-un-
saturated imine moieties are directly linked. We found
that this reaction follows two major pathways. One of
them is C–H activation in ortho-position with respect
to the exocyclic imine substituent, the other one is a met-
al induced disproportionation of the azine into a pri-
mary imine and a nitrile. The same reaction principles
are also observed in catalytic C–C coupling reactions
starting from the same substrates [15].
Herein we report the chemistry of aromatic azines de-
rived from benzaldehyde derivatives with halogen sub-
stituents in ortho-position with respect to the carbonyl
function. In analogy to the corresponding hydrocarbons
the reaction with Fe2(CO)9 proceeds via cleavage of the
central N–N bond of the ligand or via the activation of a
carbon halogen bond in terms of an ortho-metallation
reaction. The latter reactivity is somehow related to
the reactions of (perfluorovinyl)diiron complexes with
amines, hydrazines, thiols or alcohols with the activa-
tion of a vinylic carbon fluorine bond as the initial step
of the reaction [16]. The activation of carbon chlorine
bonds has been reported during the reaction of
Fe2(CO)9 with chlorobutadienes [17].
2. Results and discussion
The azines 1a and 1b are easily prepared by reacting
hydrazine hydrate with two equivalents of 2,6-dichloro-
benzaldehyde or 2,6-difluoro-benzaldehyde, respective-
ly. Scheme 1 shows the reaction of 1a with Fe2(CO)9
in heptane as the solvent. Chromatographic workup of
the reaction mixture shows, that it consists mainly of un-
reacted 1a and Fe3(CO)12. In addition, the trinuclear
cluster compound 2a is produced in small yields. The
molecular structure of 2a is presented in Fig. 1 together
with the most important bond lengths and angles. The
cluster is best described as a Fe3N tetrahedron, in which
the nitrogen atom is part of an arylidenimido moiety.
The imine C–N double bond coordinates to Fe1 in a
side-on fashion. In addition, there is a carbon iron bond
(Fe2–C7) showing that the chlorine atom, that was situ-
ated at C7 in the starting compound, has been removed
by an iron mediated activation of the corresponding
The above mentioned details are highly related to the
synthetic problems and mechanistical discussions on
transition metal induced C–H activation reactions. In
the last years we were working on C–H activation reac-
tions of aromatic imines both in stoichiometric [13] and
catalytic reactions [14]. In this context we found that re-
actions of the imines with Fe2(CO)9 lead to iron carbon-
yl compounds that may serve as model compounds for
the initiating reaction steps in catalytic reactions of the
same imines as substrates in the presence of Ru3(CO)12
Scheme 1.

D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
2709
carbon chlorine bond. One of the CO ligands at Fe2
shows a semi-bridging coordination mode towards Fe3
leading to a slightly enhanced iron carbon bond length
Fe2–C13 compared to the corresponding bond lengths
of terminal CO ligands and a bond angle of Fe2–C13–
O6 of 164.0ꢁ. Similar trinuclear iron carbonyl cluster
compounds with a bridging hydride ligand instead of a
formal carbanion have been observed from the reaction
of carbonylferrates with nitriles in the presence of a pro-
ton source and from the iron induced disproportion-
ation reaction of aromatic azines [15,16]. So we think
that the formation of 2a is also due to a disproportion-
ation of 1a into a primary imine and a nitrile and 2a be-
ing the product of the reaction of the nitrile with
Fe2(CO)9. 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 determined [19].
The fluoro compound 1b turns out to be much more
reactive when treated with Fe2(CO)9 compared to 1a.
Unfortunately, the reaction of 1b is very unselective
and we were able to identify and characterize five iron
carbonyl cluster compounds, which are shown in
Schemes 2 and 3. Scheme 2 shows the products 2b and
3 which are produced via the activation of a carbon fluo-
rine bond in 1a. The trinuclear iron carbonyl cluster 2b
Fig. 1. Molecular structure of 2a. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 257.63(8), Fe1–Fe3 253.11 (9), Fe2–Fe3 263.7(1),
Fe1–N1 194.8(3), Fe2–N1 185.5(3), Fe3–N1 182.5(3), Fe1–C1 223.3(4),
Fe2–C7 202.9(4), C1–N1 134.5(4), Fe2–Fe1–Fe3 62.16(2), Fe1–Fe2–
Fe3 58.08(2), Fe2–Fe3–Fe1 59.76(3), Fe2–Fe1–N1 45.86(8), Fe3–Fe1–
N1 45.83(8), Fe1–Fe2–N1 48.91(9), Fe3–Fe2–N1 43.77(9), Fe1–Fe3–
N1 49.98(9), Fe2–Fe3–N1 44.70(9), Fe1–N1–Fe2 85.2(1), Fe1–N1–Fe3
84.2(1), Fe2–N1–Fe3 91.5(1), C1–N1–Fe1 83.2(2), C1–N1–Fe2
119.9(2), C1–N1–Fe3 144.8(3), N1–Fe2–C7 81.2(2), Fe2–C7–C2
111.1(3), C7–C2–C1 113.6(3), C2–C1–N1 111.6(3).
Scheme 2.
Scheme 3.

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D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
impurity by monosubstituted compounds and were able
to exclude this possibility. So the additional hydrogen
atom at C7 in 3 presumably is also due to the dispropor-
tionation of the azine into an imine and a nitrile, be-
cause in this reaction one of the imine carbon
hydrogen bonds has to be broken.
Scheme 3 shows all iron carbonyl compounds from
the reaction of 1b with Fe2(CO)9, which are formed
via the cleavage of the central N–N bond of the ligand.
The molecular structure of 4 is shown in Fig. 4 together
with the most important bond lengths and angles. 4 is a
dinuclear iron carbonyl compound, which is best de-
scribed as a bis-(l-iminato)-complex. Compounds of
this type are quite commonly obtained from the reaction
of aldazines or ketazines with iron carbonyls [20]. The
typical features for these complexes are the short C–N
bond lengths of 123.9(9) and 125.2(9) pm, respectively,
clearly indicating double bonds as well as the butter-
fly-structure of the Fe2N2 moiety with an angle of
79.4ꢁ between the two Fe2N planes. In principle com-
pounds like 4 may be obtained as syn- or anti-isomers
due to the different substituents at the iminato carbon
Fig. 2. Molecular structure of 2b. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 258.01(5), Fe1–Fe3 252.22(4), Fe2–Fe3 261.92(4),
Fe1–N1 194.9(2), Fe2–N1 186.0(2), Fe3–N1 183.2(2), Fe1–C1 223.6(2),
Fe2–C7 202.6(2), C1–N1 133.9(3), Fe2–Fe1–Fe3 61.76(1), Fe1–Fe2–
Fe3 58.03(1), Fe2–Fe3–Fe1 60.21(1), Fe2–Fe1–N1 45.91(5), Fe3–Fe1–
N1 46.19(6), Fe1–Fe2–N1 48.85(5), Fe3–Fe2–N1 44.37(6), Fe1–Fe3–
N1 50.18(6), Fe2–Fe3–N1 45.23(6), Fe1–N1–Fe2 85.25(7), Fe1–N1–
Fe3 83.62(8), Fe2–N1–Fe3 90.40(9), C1–N1–Fe1 83.5(1), C1–N1–Fe2
119.7(2), C1–N1–Fe3 145.9(2), N1–Fe2–C7 81.66(9), Fe2–C7–C2
111.0(2), C7–C2–C1 113.5(2), C2–C1–N1 112.1(2).
1
atoms. H NMR spectroscopy shows the syn- and the
anti-isomer in 40:60 ratio. Crystals suitable for X-ray
diffraction experiments could be obtained for the anti-
isomer only (Fig. 4).
Since crystals of compound 5 were of unsufficient
quality, we were only able to obtain a structural motif
of 5, which is shown in Fig. 5. Bond lengths and angles
will not be discussed. Compound 5 is a trinuclear iron
carbonyl cluster being closely related to 4, from which
it is most probably produced by the reaction with an ad-
ditional Fe(CO)3 fragment. The molecule consists of a
nearly planar Fe2N2 ring with two iminato units bridg-
ing the iron atoms. In contrast to 4 there is no iron–iron
bond between the iron atoms of the Fe2N2 ring in 5. One
of the carbon nitrogen double bonds of the iminato moi-
eties is coordinated to the third Fe(CO)3 group in a side-
on fashion. This iron atom (Fe1) is bound to both iron
atoms of the Fe2N2 ring. So in summary the cluster core
consists of an open triangle of iron atoms, one l3-nitro-
gen atom (N1) and one nitrogen atom (N2) bridging on-
ly two iron centers. It is obvious, that 5 is of much lower
symmetry when compared to 4 leading to two sets of res-
onances for the iminato groups and their aromatic sub-
stituents in the NMR spectra. In addition, two isomers
of 5 are observed according to the syn- and anti-isomers
of 4 from which 5 most probably is produced (cf. Sec-
tion 3).
is an isomer of 2a with a fluoro substituent instead of a
chloro group. The molecular structure is shown in Fig. 2
together with selected bond lengths and angles. 2b shows
the same bonding modes of the ligands at the trinuclear
cluster core as they have been discussed for 2a and the
bond lengths and angles are nearly identical. As it can
be seen from Table 1, in which all crystal and intensity
data of the structural analyses are summarized, 2a and
2b are almost isostructural. Compound 3 is a dinuclear
iron complex in which the central N–N bond of the
azine ligand is still preserved. The molecular structure
of 3 is depicted in Fig. 3, the most important bond
lengths and angles may be found in the Figure Caption.
One of the ortho-fluorinated aromatic moieties also
shows a C–F activation reaction and a new carbon iron
bond instead (Fe1–C1). To our surprise there is an
additional hydrogen atom at C7 thus building up a
methylene group at this position. The resulting aza-
ferra-cyclopentadiene system is apically coordinated by
the second Fe(CO)3 moiety. This coordination mode
has quite frequently been observed in the reaction of ar-
omatic imines or azines, respectively [13,15]. In this
cases, the formation of the dinuclear product clusters
has been rationalized by the reaction sequence of a
C–H activation in ortho-position with respect to the
exocyclic imine function followed by an intramolecular
hydrogen transfer towards the former imine nitrogen at-
om [13]. So we very carefully looked at the substrates
2,6-difluoro-benzaldehyde and 1b, if there was any
Fig. 6 shows the molecular structure of the cluster an-
ion in 6 together with selected bond lengths and angles.
6 was obtained as it is sodium salt together with two
equivalents of water per ion pair. During the chromato-
graphic workup of the product mixture of the reaction
of 1b with Fe2(CO)9 we recognized, that there was a
compound which could neither be eluted with pure

Table 1
Crystal and intensity data for 2a, 2b, 3, 4, 6–8
2a
2b
3
4
6
7
8
Formula
C16H4NO9CIFe3
C16H4NO9FFe3
C16H9N2O6F3Fe2
C16H8N2O6F4Fe2
[C16H4NO9F2Fe3]Na·H2O
C16H5NO9F2Fe3
C16H3NO9F2Fe3
Molecular weight (gmolꢁ1
Radiation
)
557.20
Mo Ka
Graphite
183
540.75
Mo Ka
Graphite
183
541.99
559.98
600.07
Mo Ka
Graphite
183
560.76
Mo Ka
Graphite
183
558.74
Mo Ka
Graphite
183
Mo Ka
Graphite
183
Mo Ka
Graphite
183
Monochromator
Temperature (K)
Crystal color
Red
Orange
0.1·0.04·0.03
12.6823(4)
13.0148(6)
11.3316(6)
90
Red
Orange
0.1·0.1·0.06
7.3162(4)
12.216(1)
12.812(1)
82.19(4)
77.21(4)
73.60(4)
1068.0(2)
2
Red
Red
Red
Crystal size
˚
0.3·0.3·0.02
12.9019(6)
1 3.059(1)
11.632(1)
90
0.2·0.2·0.01
8.626(3)
9.407(3)
13.408(4)
73.30(2)
80.05(2)
79.87(1)
1017.2(5)
2
0.4·0.2·0.2
15.9274(4)
13.3940(5)
20.4140(6)
90
0.3·0.1·0.01
15.225(2)
7.065(2) 4
18.183(3)
90
0.03·0.03·0.02
14.3458(2)
16.0535(3)
16.4510(4)
90
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.25(5)
90
103.952(3)
90
108.169(2)
90
101.62(1)
90
90
90
3
˚
Volume (A )
1922.1(3)
4
1096
1815.2(1)
4
1064
4137.8(2)
8
2368
1911.1(6)
4
1104
3788.7(1)
8
2192
Z
F(000)
qcalc (gcmꢁ3
540
1.770
556
1.741
)
1.925
1.979
1.929
1.949
1.959
Orthorhombic
Pbca
Crystal system
Space group
Absorption coefficient (mmꢁ1
Monoclinic
P21/c
2.424
Monoclinic
P21/c
2.428
Triclinic
ꢀ
Triclinic
ꢀ
Monoclinic
P21/n
2.170
Monoclinic
P21/c
2.318
P1
1.495
P1
1.434
)
2.338
h limit (ꢁ)
Scan mode
2.24<h<27.44
x-scan
6403
2.28<h<27.48
x-scan
7281
2.28<h<27.63
x-scan
6493
2.96<h<27.54
x-scan
7795
1.43<h<27.50
x-scan
17154
1.37<h<27.56
x-scan
5592
2.27<h<27.47
x-scan
8116
Reflections measured
Independent reflections
Rint
4311
4151
4210
4767
9212
4220
4322
0.0450
2885
287
0.0307
3221
287
0.0739
2489
309
0.0567
3346
311
0.0551
9206
619
0.0896
1889
284
0.0337
3297
292
Reflections observed ðF 20 > 2rðF 02ÞÞ
No. of parameters
Goodness-of-fit
R1
0.991
1.004
1.049
1.200
1.026
1.011
1.007
0.0439
0.0814
0.421
0.0315
0.0636
0.459
0.0772
0.1717
0.883
0.1179
0.3027
5.365
0.0504
0.0935
0.433
0.0841
0.1676
1.016
0.0333
0.0758
0.340
wR2
Final diffraction map electron
ꢁ3
˚
density peak (eA
)

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D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
Fig. 3. Molecular structure of 3. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 244.2(1), Fe1–N1 196.4(6), Fe1–C1 200.4(6), Fe2–
N1 195.4(5), Fe2–C1 218.8(6), Fe2–C6 231.6(6), C1–C6 142.1(9), C6–
C7 149.5(9), N1–C7 149.5(8), N1–N2 139.4(8), N2–C8 129.7(9), C8–
C9 145.0(1), N1–Fe1-C1 78.9(2), Fe1–C1–C6 111.9(5), C1–C6–C7
117.1(5), C6–C7–N1 99.3(5), C7–N1–Fe1 113.7(4), Fe1–Fe2–N1
51.6(2), N1–Fe1–Fe2 51.3(2), Fe1–N1–Fe2 77.1(2), Fe1–Fe2–C1
50.9(2), Fe2–Fe1–C1 58.0(2), Fe1–C1–Fe2 71.1(2), Fe1–Fe2–C6
73.8(1), N1–F2–C1 74.8(2), N1–Fe2–C6 63.9(2), C1–Fe2–C6 36.7(2),
Fe2–C1–C6 76.6(4), Fe2–C6–C1 66.8(3), Fe1–N1–N2 116.5(4), Fe2–
N1–N2 124.7(4), C7–N1–N2 118.1(5), N1–N2–C8 117.6(5), N2–C8–
C9 123.0(6).
Fig. 5. Structural motif of 5.
Fig. 4. Molecular structure of 4. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 241.2(2), Fe1–N1 193.5(6), Fe1–N2 191.8(6), Fe2–
N1 192.8(6), Fe2–N2 194.1(6), N1–C1 123.9(9), N2–C8 125.2(9), Fe1–
Fe2–N1 51.5(2), Fe1–Fe2–N2 50.9(2), N1–Fe1–Fe2 51.2(2), N1–Fe1–
N2 73.7(2), Fe1–N1–Fe2 77.3(2), Fe1–N2–Fe2 77.4(2), Fe1–N1–C1
140.9(5), Fe2–N1–C1 140.0(5), Fe1–N2–C9140.7(6), Fe2–N2–C9
138.9(6), N1–C1–C2 122.4(7), N2–C8–C9 122.7(7).
Fig. 6. Molecular structure of the cluster anion of 6. Selected bond
lengths (pm) and angles (ꢁ): Fe1–Fe2 255.2(1), Fe1–Fe3 254.51(9),
Fe2–Fe3 251.22(9), Fe1–N1 195.4(4), Fe2–N1 185.4(4), Fe3–N1
185.7(3), Fe1–C1 218.4(4), C1–N1 133.6(5), C1–C2 149.4(6), Fe2–
Fe1–Fe3 59.06(2), Fe1–Fe2–Fe3 60.34(3), Fe2–Fe3–Fe1 60.60(3), Fe2–
Fe1–N1 46.3(1), Fe3–Fe1–N1 46.5(1), Fe1–Fe2–N1 49.6(1), Fe3–Fe2–
N1 47.5(1), Fe1–Fe3–N1 49.8(1), Fe2–Fe3–N1 47.3(1), Fe1–N1–Fe2
84.1(1), Fe1–N1–Fe3 83.8(1), Fe2–N1–Fe3 85.2(1), C1–N1–Fe1
80.8(3), C1–N1–Fe2 137.1(3), C1–N1–Fe3 132.0(3), C1–Fe1–N1
37.2(2), C1–Fe1–Fe2 77.4(1), C1–Fe1–Fe3 76.0(1), Fe1–C1–N1
62.0(2), Fe1–C1–C2 119.7(3), N1–C1–C2 123.7(5). The bond lengths
and angles of the second anion being present in the asymmetric unit of
the crystal structure are identical within experimental errors.
CH2Cl2 nor with ether, which was pre-dried over
NaOH, as the solvent. But using ethanol 6 was obtained
from the chromatography. So most probably ether is the
source of the sodium cations as well as of the water pres-
ent in the crystal structure. Cluster anions as in 6 were
identified on the basis of spectroscopic evidence by
Kaesz and coworkers as the intermediates in the reac-
tion of carbonyl ferrates with moist nitriles [16a]. To
the best of our knowledge this is the first time that these
cluster anions are structurally characterized and thus
may be compared to their derivatives of types 2 and 7
(vide infra).
The anion of 6 shows a trinuclear cluster core con-
sisting of a Fe3N tetrahedron with one of the FeN edg-
es of the tetrahedron being bridged by the former

D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
2713
imine carbon atom. So the anion may also be described
as a formally six electron donating arylidenimido li-
gand coordinated to a triangular Fe3(CO)9 cluster
fragment. The carbon nitrogen bond length of course
is elongated due to the coordination towards the
transition metal centers and is very similar to those
observed for the closely related compounds 2a and
2b, respectively.
The crystal structure of 6 is shown in Fig. 7. The crys-
tal packing is realized by the coordination of the two
water molecules to sodium cations building up a four
membered ring. Both sodium cations show a distorted
octahedral coordination sphere being completed by in-
teractions with carbon monoxide ligands of neighboring
cluster anions. In addition, the water molecules each
show two hydrogen bonding interactions with CO
groups of cluster anions. On the right side of Fig. 7
the coordination mode of the sodium cations together
with the hydrogen bridges is depicted.
It is has been pointed out before, that ionic com-
pounds of type 6 have been postulated to be the inter-
mediates in the reaction of carbonyl ferrates with
nitriles in the presence of a proton source leading to
the formation of tetrahedral cluster compounds of
the composition [Fe3(CO)9(l2-H)(l3-g2-N‚CHR)]
[18]. Scheme 4 shows the reaction of 6 with phospho-
ric acid leading to the quantitative formation of 7. In
analogy to derivatives of 7 the molecular structure is
closely related to 6 with the exception, that the iron
iron bond between Fe2 and Fe3, which are not coor-
dinated to arylidenamido ligand, now are bridged by a
hydride ligand [15,16]. Fig. 8 shows the molecular
structure of 7 together with the most interesting bond
lengths and angles. The position of the hydride ligand
Fig. 7. Crystal structure of [Fe3(CO)9(l3-g2-N‚CHR)]Na·H2O, 6, showing the coordination sphere of the sodium cations built up by water
molecules and CO ligands from neighboring cluster anions. Selected bond lengths (pm) and angles (ꢁ): Na1–O19 243.7(4), Na1–O20 241.5(5), Na2–
O19 240.3(5), Na2–O20 244.4(4), Na1–O6 235.6(4), Na1–O12 242.4(4), Na1–O13 273.4(4), Na1–O17 241.2(3), Na2–O2 304.2(5), Na2–O3 244.4(4),
Na2–O8 243.9(3), Na2–O15 235.4(4), O11–H19a 221(1), O5–H19b 224(1), O14–H20a 220(1), O1–H20b 218 (1), O19–Na1–O20 80.9(1), Na1–O20–
Na2 98.8(2), O20–Na2–O19 81.0(1), Na2–O19–Na1 99.3(2).
Scheme 4.

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D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
In 2a and 2b also the Fe1–Fe2 bonds are elongated com-
pared to 6 due to the coordination of the aromatic sub-
stituent to Fe2 after the activation of the corresponding
carbon–halogen bonds (Figs. 1 and 2). The coordination
of the nitrogen atoms of the arylideneamido ligand is
nearly identical in all compounds. In 6 the iron nitrogen
bond Fe1–N1 is app. 10 pm longer compared to Fe2–N1
and Fe3–N1. The reason for this is obviously the side-on
coordination of the carbon nitrogen double bond to
Fe1. The C1–N1 bond length measures to 133.6(5)
pm. Significantly different are the C1–Fe1 bond lengths
which are about 5 pm longer in 2a and 2b compared to 6
(218.4(4) pm) and 7.
Kaesz and coworkers [18] showed that the synthesis
of compounds of type 7 may be achieved by reacting
the corresponding nitriles with carbonylferrates. The
yield of 6, from which we were able to produce 7
(Schemes 3 and 4), was very low. So we decided to react
2,6-difluorobenzonitrile with Fe2(CO)9 to produce larg-
er quantities of 7. The trinuclear iron carbonyl cluster
compound 8 is however the sole product, that might
be isolated from the reaction mixture after chromato-
graphic workup (Scheme 5). Fig. 9 shows the molecular
structure of 8 together with the most important bond
lengths and angles. Compounds of type 8 have also been
obtained and structurally characterized earlier from the
reaction of [HFe3(CO)11]ꢁ with most nitriles in the pres-
ence of a proton source leading to [Fe3(CO)9(l2-H)(l3-
g2-N‚CHR)] as an intermediate, which produces
[Fe3(CO)9(l3-g2-N„CR)] by air oxidation [18]. In an-
other reference a derivative of 8 was directly synthesized
from Fe3(CO)12 and benzonitrile in the presence of a
proton source [21]. The structural properties of 8 are es-
sentially identical to the compounds reported in the lit-
erature. 8 is a trinuclear iron carbonyl cluster which is
best described as a Fe3N tetrahedron with one of the
Fe2N faces of the tetrahedron being capped by a carbon
atom. So the nitrile ligand shows a l3-g2-coordination
to the iron triangle. The iron nitrogen bond length
Fe1–N1 measures to 178.7(2) pm and is therefore signif-
icantly shorter as the other iron nitrogen bonds (195.9(2)
and 196.2(2) pm). The bond lengths of C1 towards Fe2
and Fe3 are nearly identical and the carbon nitrogen
bond of the nitrile ligand is slightly elongated to
Fig. 8. Molecular structure of of 7. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 254.3(2), Fe1–Fe3 256.1(2), Fe2–Fe3 258.9(2),
Fe1–N1 194.8(8), Fe2–N1 188.3(7), Fe3–N1 185.1(8), Fe1–C1 218.6(9),
C1–N1 134.8(9), C1–C2 149(1), Fe2–Fe1–Fe3 60.95(5), Fe1–Fe2–Fe3
59.87(5), Fe2–Fe3–Fe1 59.18(5), Fe2–Fe1–N1 47.3(2), Fe3–Fe1–N1
46.0(2), Fe1–Fe2–N1 49.5(2), Fe3–Fe2–N1 45.6(2), Fe1–Fe3–N1
49.2(2), Fe2–Fe3–N1 46.6(2), Fe1–N1–Fe2 83.2(3), Fe1–N1–Fe3
84.7(3), Fe2–N1–Fe3 87.8(3), C1–N1–Fe1 80.9(5), C1–N1–Fe2
128.9(6), C1–N1–Fe3 138.0(7), C1–Fe1–N1 37.5(3), C1–Fe1–Fe2
76.0(2), C1–Fe1–Fe3 77.7(2), Fe1–C1–N1 61.6(5), Fe1–C1–C2
117.6(7), N1–C1–C2 122.8(8).
was determined from the Difference Fourier map and
was refined without any constraints.
The most significant differences in the bond lengths of
2a, 2b, 6 and 7 correspond to the iron iron bonds. In 6
Fe1–Fe2 and Fe1–Fe3 are nearly identical whereas the
Fe2–Fe3 bond is about 3 pm shorter (251.22(9) pm).
In contrast to this observation the corresponding Fe2–
Fe3 bonds are longer in 7 (258.9(2) pm), in which this
bond is bridged by a hydride ligand and 2a and 2b with
a semi-bridging CO ligand (263.7(1) and 261.92(4) pm).
Scheme 5.

D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
2715
sponding halide. The minor pathway is represented by
compound 3, in which the azine ligand is still preserved.
During the formation of 3 also one of the carbon fluo-
rine bonds has been activated.
3. Experimental
3.1. General
All procedures were carried out under an argon at-
mosphere in anhydrous, freshly distilled solvents ex-
cept the synthesis of 6, in which neat diethylether
has been used. 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.
High resolution mass spectra (HRMS) were carried
out using a Finnigan MAT 95 XL spectrometer using
FAB techniques.
Fig. 9. Molecular structure of 8. Selected bond lengths (pm) and
angles (ꢁ): Fe1–Fe2 263.82(5), Fe1–Fe3 261.56(5), Fe2–Fe3 246.90(5),
Fe1–N1 178.7(2), Fe2–N1 195.9(2), Fe3–N1 196.2(2), Fe2–C1 204.0(4),
Fe3–C1 206.0(2), C1–N1 128.4(3), C1–C2 145.0(3), Fe2–Fe1–Fe3
56.06(1), Fe1–Fe2–Fe3 61.51(1), Fe2–Fe3–Fe1 62.43(1), Fe2–Fe1–N1
47.95(6), Fe3–Fe1–N1 48.58(6), Fe1–Fe2–N1 42.62(6), Fe3–Fe2–N1
51.03(6), Fe1–Fe3–N1 43.06(6), Fe2–Fe3–N1 50.92(6), Fe1–N1–Fe2
89.43(9), Fe1–N1–Fe3 88.36(9), Fe2–N1–Fe3 78.05(7), C1–N1–Fe1
159.33(2), C1–N1–Fe2 74.7(2), C1–N1–Fe3 75.6(1), C1–Fe2–N1
37.39(9), C1–Fe2–Fe3 53.35(7), C1–Fe2–Fe1 79.36(7), C1–Fe3–Fe1
79.57(7), C1–Fe3–Fe2 52.61(7), C1–Fe3–N1 37.14(9), Fe2–C1–Fe3
74.04(9), Fe2–C1–N1 67.9(1), Fe3–C1–N1 67.3(1), Fe2–C1–C2
144.6(2), Fe3–C1–C2 136.5(2), N1–C1–C2 133.1(2).
3.2. X-ray crystallographic studies
The structure determinations of 2a, 2b, 3–8 were
carried out on an Enraf Nonius Kappa CCD diffrac-
tometer, crystal detector distance 25 mm, using graph-
ite monochromated Mo Ka radiation. The crystal was
mounted in a stream of cold nitrogen. Data were cor-
rected for Lorentz and polarization effects but not for
absorption. The structure was solved by direct methods
and refined by full-matrix least squares techniques
against F2 using the programs SHELXS-86 and SHEL-
XL-97 [22]. Computation of the structure was acom-
plished with the program XPMA [23] and the
molecular illustration was drawn using the program
XP [24]. The crystal and intensity data are given in
Table 1.
Additional material on the structure analyses is
available from the Cambridge Crystallographic Data
Centre by mentioning the deposition number CCDC-
228279 (2a), CCDC-228280 (2b), CCDC-228281 (3),
CCDC-228282 (4), CCDC-228283 (8), CCDC-228284
(6), CCDC-228285 (7). The quality of the crystals of
5 was only sufficient to obtain a structural motif of
the compound. The crystal and intensity data are there-
fore not given and were also not deposited at the
CCDC.
128.4(3) pm due to the triply bridging coordination
mode. The iron iron bond that is bridged by the nitrile
ligand (Fe2–Fe3) is circa 18 pm longer compared to
the other two iron iron bonds.
In conclusion we were able to show that the reaction
of aromatic aldazines with halogen substituents in the 2-
and 6-positions with Fe2(CO)9 proceeds via two main
pathways. The major pathway is the symmetrical cleav-
age of the central nitrogen nitrogen bond leading to the
bis-(l-iminato) compounds 4. Addition of another
Fe(CO)3 moiety produces clusters of type 5. The elimi-
nation of one of the iminato moieties leads to trinuclear
ionic compounds of type 6. In addition, we were able to
isolate compounds in which one of the carbon halogen
bonds in ortho-position with respect to the imine func-
tion is activated creating a new iron carbon bond. Ac-
cording to the nearly identical cluster cores in 6 and
2a or 2b, respectively, it might be suggested, that the lat-
ter are produced from 6 by the elimination of the corre-
3.3. Synthesis of 1a, 1b
A 1 ml portion of hydrazine hydrate (20 mmol) was
stirred together with an equimolar amount of the corre-
sponding aldehyde (2.84 g, 2.16 ml difluorobenzaldehyde;

2716
D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
3.5 g dichlorobenzaldehyde) in 50 ml ethanol. After pre-
cipitation of the product it was washed twice with cold
ethanol to yield 5.09 g (74%) 1a or 4.59 g (82%) 1b, respec-
tively, as analytically pure yellow crystalline material. 1a
was identified by its melting point, which was identical to
the one reported in the literature [25].
bonyl compounds 3–6. The bis-(l-iminato) complexes 4
and 5 are obtained with a light petroleum CH2Cl2 ratio
of 40:1. Increasing the amount of CH2Cl2 to 10:1 leads
to the elution of a red band containing 3. Using
CH2Cl2/ether 1:1 as the solvent leads to the elution of un-
converted 1b. The ionic compound 6 may be eluted with
ethanol as the solvent only if the column was washed with
ether (pre-dried over NaOH) in advance. Yields (based
on the portion of the converted azines): 2 mg 2a
(0.003 mmol, 1%), 6 mg 2b (0.01 mmol, 3%), 2 mg 3
(0.004 mmol, 1%), 12 mg 4, (0.02 mmol, 7%), 10 mg 5
(0.01 mmol, 5%), 7 mg 6 (0.01 mmol, 4%). Due to the very
3.4. MS and spectroscopical data for 1a
HRMS calcd. for C14H8N2NaCl4 (MNa+) 366.9341.
Found 366.9339, D=0.19 mmu. MS (El): m/z (%) 344
(M+, 7), 309 (M+ ꢁCl, 100), 276 (M+ ꢁ2CI, 69), 239
(M+ ꢁ3Cl, 5), 172 (C7H4NCl2+, 5), 145 (C6H3Cl2+, 4),
136 (C7H3NCl+, 8), 123 (C7H4Cl+, 7), 109 (C6H2Cl+,
5), 100 (C7H2N+, 5), 75 (C6H3+, 4). IR (KBr, cmꢁ1):
1625 s, 1581 s, 1557 s, 1428 s, 1331 s, 1267 m, 1215 m,
1190 s, 1151 m, 1093 m, 969 w, 948 m, 897 w, 873 s,
low yields of 2a, 2b and 3 and the poor solubility of 6 13
C
NMR spectra could not be obtained for these com-
pounds and HRMS could not be determined for 3 and
6. Nevertheless, the molecular structure of these com-
plexes was unequivocally demonstrated by X-ray analy-
ses. Recrystallization of the complexes was performed
from mixtures of light petroleum (b.p. 40–60 ꢁC) and
CH2Cl2 at ꢁ20 ꢁC for 2a, 2b, 3–5. 6 was recrystallized
from an ethanolic solution carefully underlayered with
CH2Cl2 at room temperature. Only one single crystal of
2a was obtained after the chromatographic work up
procedure which proved sufficient to carry out a crystal-
lographic analysis but prevented a thorough spectroscop-
ic characterization of the cluster. Since crystalline 6 is not
soluble in common solvents it was not possible to obtain
NMR spectra.
1
777 vs, 728 s, 679 s, 533 w, 514 w, 456 s, 402 s. H
NMR (200 MHz, CDCl3, 298 K): 7.17–7.36 (m, 3H,
3JHH =8.7 Hz), 8.76 (s, 1H). 13C NMR (50.3 MHz,
CDCl3, 298 K): 128.94, 130.21, 130.99, 135.51, 157.61.
3.5. MS and spectroscopical data for 1b
HRMS calcd. for C14H9N2F4 (MH+) 281.0704.
Found 281.0702, D=0.17 mmu. MS (EI): m/z (%) 280
(M+, 100), 261 (M+ ꢁF, 36), 153 (C8H5NF2+, 23), 140
(C7H4NF2+, 48), 126 (C7H4F2+, 20), 120 (C7H3NF+,
43), 113 (C6H3F2+, 14), 100 (C7H2N+, 11), 63 (C5H3
,
+
18). IR (KBr, cmꢁ1): 3092 w, 1625 s, 1584 s, 1579 s,
1562 s, 1477 s, 1458 s, 1336 s, 1298 m, 1273 m, 1244 s,
1212 s, 1157 m, 1015 s, 971 m, 956 m, 879 w, 851 s,
3.7. MS and spectroscopical data for 2b
The compound is too volatile to obtain a HRMS
spectrum. C16H4NFO9Fe3 MS (El): m/z (%) 541 (M+,
6), 513 (M+ ꢁCO, 53), 485 (M+ ꢁ2CO, 100), 457
(M+ ꢁ3CO, 22), 429 (M+ ꢁ4CO, 39), 401 (M+ ꢁ5CO,
72), 373 (M+ ꢁ6CO, 65), 345 (M+ ꢁ7CO, 42), 317
1
785 s, 717 s, 610 s, 533 s, 517, w, 506 m, 424 w. H
NMR (400 MHz, CDCl3, 298 K): 6.98 (dd, 2H,
3
4
3JHH =8.4 Hz, JHF =8.7 Hz), 7.39 (tt, 1H, JHF =6.2
3
Hz, JHH =8.4 Hz), 8.87 (s, 1H). 13C NMR (100.6
2
MHz, CDCl3, 298 K): 111.7 (t, JCF =13 Hz), 112.12
(M+ ꢁ8CO,
42),
289
(M+ ꢁ9CO,
35),
233
2
(d, JCF =25 Hz), 132.54 (t, JCF =11 Hz), 153.69 (s),
3
+
(C7H4NFFe2+, 16), 196 (C7H4NF2Fe+, 16), 168 (Fe3
,
161.86 (dd, JCF =259 Hz, JCF =6 Hz).
3.6. Synthesis of 2a, 2b, 3–6
15), 112 (Fe2+, 24), 84 (FeCO+,13), 56 (Fe+, 15). IR
(KBr, cmꢁ1): 2085 s, 2051 s, 2044 s, 2032 s, 2021 s,
2008 s, 2001 s, 1995 s, 1977 s, 1966 m, 1949 s, 1631 m,
1591 w, 1464 w, 1262 m, 1230 w, 1106 m, 1021 m, 856
w, 802 m, 776 m, 742 w, 620 w, 594 w, 553 m, 535 w.
1H {19F} NMR (200 MHz, CD2Cl2, 298 K): 6.71 (d,
1
3
A 360 mg portion Fe2(CO)9 (1 mmol) together with an
equimolar amount of the corresponding azine (280 mg
1a, 310 mg 1b) and 20 ml n-heptane are stirred together
at 50 ꢁC for 45 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 petro-
leum (b.p. 40–60 ꢁC) as the eluent first yields a green band
containing Fe3(CO)12 followed by a dark brown band of
2a or 2b, respectively. Adding small portions of CH2Cl2
to the light petroleum allows the elution of the iron car-
3
3
1H, JHH =8.3 Hz), 6 93 (dd, 1H, JHH =8.3 Hz,
3
3JHH =7.5 Hz), 7.42 (d, 1H, JHH =7.5 Hz), 8.02 (s,
1
1H). H NMR (200 MHz, CD2Cl2, 298 K): 6.71 (dd,
1H,3JHH =8.3 Hz, JHF =9.8 Hz), 6.93 (ddd, 1H,
3
3JHH =8.3 Hz, JHH =7.5 Hz, JHF =5.4 Hz), 7.42 (d,
3
4
3
1H, JHH =7.5 Hz), 8.02 (s, 1H).
3.8. MS and spectroscopical data for 3
HRMS calcd. for C20H9N2F3O6Fe2 541.9121. Found
541.9130, D=0.99 mmu. MS (El): m/z (%) 542 (M+, 10),
514 (M+ ꢁCO, 18), 486 (M+ ꢁ2CO, 60), 458

D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
2717
3
7.36 (t, 0.6H, JHH =8.4 Hz), 7.44 (t, 0.4H, JHH =8.3
3
(M+ ꢁ3CO, 37), 430 (M+ ꢁ4CO, 25), 402 (M+ ꢁ5CO,
89), 374 (M+ ꢁ6CO, 100), 280 (C10H4NF203Fe+, 47),
261 (C10H4NFO3Fe+, 28), 251 (C7H3NF2Fe2+, 18), 140
(FeC3O3+, 36), 112 (Fe2+, 20). IR (KBr, cmꢁ1): 2074 s,
2031 s, 2005 s, 1983 sh, 1976 s, 1959 s, 1624 m, 1459 w,
1263 m, 1238 m, 1098 s, 1013 s, 805 s, 779 m, 626 w, 596
Hz), 7.46 (t, 0.6H, JHH =8.5 Hz), 8.62 (s, 1H). 13C
3
NMR (50.3 MHz, CDCl3, 298 K, mixture of syn- and
anti-isomers): 107.80 (s), 108.13 (s), 111.81 (m), 117.75
2
(m, JCF =22 Hz), 120.64 (t, JCF =17 Hz), 130.56 (t,
2
3
3JCF =10 Hz), 131.62 (t, JCF =10 Hz), 159.03 (d of d,
1
3
1
w, 569 w, 551 w. H {19F} NMR (200 MHz, CD2Cl2,
1JCF =250 Hz, JCF =7 Hz), 159.09 (d of d, JCF =250
3
298 K): 4.41 (s, 1H), 6.97 (d, 2H, JHH =8.5 Hz), 6.98
3
Hz, JCF =7 Hz), 166.86 (s), 203.56 (s), 204.15 (s),
3
(d, 1H, JHH =8.0 Hz), 7.15 (dd, 1H, JHH =8.0 Hz,
3
204.75 (s), 205.08 (s), 205.34 (s), 208.40 (s), 208.90 (s),
211.09 (s), 211.75 (s), 212.76 (s, broad).
3
3JHH =7.8 Hz), 7.37 (t, 1H, JHH =8.5 Hz) 7.85 (d, 1H,
3JHH =7.8 Hz), 7.97 (s, 1H). 1H NMR (200 MHz, CD2Cl2,
3
298 K): 4.41 (s, 1H), 6.97 (dd, 2H, JHH =8.5 Hz,
3.11. MS and spectroscopical data for 6
3
3
3JHF =8.6 Hz), 6.98 (dd, 1H, JHH =8.0 Hz, JHF =9.1
3
Hz), 7.15 (m, 1H, JHH =8.0 Hz, JHH =7.8 Hz,
3
C16H4NF2O9Fe3Na·H2O; MS (El): m/z (%) 504
3
4
4JHF =6.3 Hz), 7.37 (tt, 1H, JHH =8.5 Hz, JHF =6.3
+
(C16H4NF2O9Fe3+–2CO, 1), 476 (C16H4NF2O9Fe3
–
Hz) 7.85 (d, 1H, 3JHH =7.8 Hz), 8.02 (s, 1H).
3CO, 1), 448 (C16H4NF2O9Fe3+–4CO, 1), 420
+
(C16H4NF2O9Fe3+–5CO, 1), 392 (C16H4NF2O9Fe3
–
3.9. MS and spectroscopical data for 4
6CO, 1), 364 (C16H4NF2O9Fe3+–7CO, 1), 336
+
(C16H4NF2O9Fe3+–8CO, 1), 308 (C16H4NF2O9Fe3
–
,
HRMS calcd. for C20H8N2F4O6Fe2 559.9010. Found
559.9017, D=0.68 mmu. MS (El): m/z (%) 560 (M+, 2),
532 (M+ ꢁCO, 8), 504 (M+ ꢁ2CO, 5), 476 (M+ ꢁ3CO,
27), 448 (M+ ꢁ4CO, 11), 420 (M+ ꢁ5CO, 18), 392
+
9CO, 1), 280 (C8H4NF2OFe2+, 1), 252 (C7H4NF2Fe2
1), 139 (C7H3NF2+, 100). IR (KBr, cmꢁ1): 2924 m,
2074 s, 2035 vs, 1999 sh, 1991 s, 1978 s, 1624 m, 1465
m, 1007 m, 788 m, 580 m.
(M+ ꢁ6CO, 100), 316 (C14H7N2F3Fe+, 17), 271
+
(C7H4NF3Fe+, 71), 251 (C7H3NF2Fe2
, 41), 244
+
(C6H3F3Fe2
,
20), 196 (C7H4NF2Fe+, 52), 177
3.12. Synthesis of 7
(C7H4NFFe+,18), 150 (Fe2F2+, 69), 132 (HF2Fe2+, 92),
112 (Fe2+, 20), 75 (FeF+, 66), 56 (Fe+, 35). IR (KBr,
cmꢁ1): 2924 m, 2076 s, 2037 s, 2004 sh, 1993 vs, 1976
s, 1969 s, 1624 m, 1465 s, 1008 m, 791 m, 762 m, 618
A 10 mg sample of 6 was dissolved in 85% phosphoric
acid. Extraction of the crude reaction mixture with light
petroleum (b.p. 40–60 ꢁC) followed by chromatographic
workup using a mixture of light petroleum and CH2Cl2
5:1 yields 8 mg (85%) of 7. Recrystallization of 7 was
performed from mixtures of light petroleum (b.p. 40–
60 ꢁC) and CH2Cl2 at ꢁ20 ꢁC.
1
m, 573 m. H{19F} NMR (200 MHz, CDCl3, 298 K):
3
6.93 (d, 2H, JHH =8.4 Hz), 7.34 (t, 1H, JHH =8.4
3
Hz), 8.74 (s, 1H). 13C NMR (100.6 MHz, CDCl3, 298
2
K): 111.70 (m, JCF =19 Hz, JCF =5 Hz), 117.58
4
2
(t, JCF =20 Hz), 131.02 (t, JCF =10 Hz), 159.28 (d of
3
1
d, JCF =250 Hz, JCF =7 Hz), 163.66 (s), no CO
3
3.13. MS and spectroscopical data of 7
resonances observed at room temperature.
HRMS calcd. for C16H5NF2O9Fe3 560.7976. Found
560.7971, D=0.48 mmu. MS (El): m/z (%) 561 (M+,
10), 533 (M+ ꢁCO, 6), 505 (M+ ꢁ2CO, 17), 477
(M+ ꢁ3CO, 6), 449 (M+ ꢁ4CO, 8), 421 (M+ ꢁ5CO,
75), 393 (M+ ꢁ6CO, 43), 365 (M+ ꢁ7CO, 43), 337
(M+ ꢁ8CO, 100), 309 (M+ ꢁ9CO, 50), 251
3.10. MS and spectroscopical data for 5
HRMS calcd. for C23H8N2F4O9Fe3 699.8218. Found
699.8222, D=0.40 mmu. MS (FAB): m/z (%) 700 (M+,
3), 672 (M+ ꢁCO, 15), 644 (M+ ꢁ2CO, 11), 616
(M+ ꢁ3CO, 47), 588 (M+ ꢁ4CO, 4), 560 (M+ ꢁ5CO,
6), 532 (M+ ꢁ6CO, 43), 504 (M+ ꢁ7CO, 24), 476
(M+ ꢁ8CO, 100), 448 (M+ ꢁ9CO, 26), 252
+
+
(C7H3NF2Fe2
, 30), 233 (C7H4NFFe2 , 16), 213
(C7H4NFe2+, 33), 196 (C7H4NF2Fe+, 24), 188 (HFFe3
,
+
44), 169 (HFe3+, 30), 168 (Fe3+, 30), 132 (HF2Fe2+, 68),
112 (Fe2+, 77), 75 (FeF+, 18), 56 (Fe+, 55).
+
+
(C7H4NF2Fe2
, 55), 233 (C7H4NFFe2 , 34), 206
+
(C8H3O2FFe+, 24), 188 (C8H4O2Fe+, 14), 150 (Fe2F2
,
14), 132 (HF2Fe2+, 23), 112 (Fe2+, 22), 75 (FeF+, 8),
56 (Fe+, 16). IR (KBr, cmꢁ1): 2923 m, 2080 w, 2049 s,
2025 s, 2000 s, 1990 sh, 1982 sh, 1974 sh, 1963 w, 1646
sh, 1624 m, 1465 m, 1236 w, 1006 m, 784 m, 766 w,
649 m, 616 m, 561 m. 1H{19F} NMR (200 MHz, CDCl3,
298 K, mixture of syn- and anti-isomers): 6.55 (s, 0.4H),
3.14. Synthesis of 8
A 360 mg portion Fe2(CO)9 (1 mmol) together with a
five fold excess of 2,6-difluorobenzonitrile (695 mg, 0.56
ml) was stirred in 20 ml n-heptane at 50 ꢁC for 2 h.
During the reaction time the solution turned deep
green as the iron carbonyl dissolves. After the reaction
is completed all volatile materials are removed in vacuo.
3
7.01 (s, 0.6H), 7.01 (d, 2.4H, JHH =8.4 Hz), 7.03 (d,
3
1.6H, JHH =7.9 Hz), 7.34 (t, 0.4H, JHH =7.6 Hz),
3

2718
D. Do¨nnecke et al. / Journal of Organometallic Chemistry 689 (2004) 2707–2719
(c) P.E. OÕConnor, D.J. Berg, T. Barclay, Organometallics 21
(2002) 3947;
The residue is dissolved in CH2Cl2, 1 g silanized silica
gel is added and the solvent is again removed under re-
duced pressure. Chromatography on silica gel using
light petroleum (b.p. 40–60 ꢁC) as the eluent first yields
a green band containing Fe3(CO)12 followed by a dark
brown band of 8 if a mixture of ight petroleum and
CH2Cl2 20:1 is used as the eluent. Unfortunately, uncon-
verted nitrile elutes together with 8. Recrystallization of
8 from mixtures of light petroleum (b.p. 40–60 ꢁC) and
CH2Cl2 at ꢁ20 ꢁC yields two types of crystals: colourless
plates of 2,6-difluorobenzonitrile and black prisms of 8.
Yield (based on Fe2(CO)9): 15 mg (0.03 mmol, 3%).
(d) B.M. Kraft, R.J. Lachicotte, W.D. Jones, J. Am. Chem. Soc.
123 (2001) 10973;
(e) W.D. Jones, J. Chem. Soc., Dalton Trans. (2003) 3991.
[4] P. Barrio, R. Castarlenas, M.A. Estruelas, A. Lledos, F. Maseras,
E. Onate, J. Tomas, Organometallics 20 (2001) 442.
[5] (a) L. Cronin, C.L. Higgitt, R. Karch, R.N. Perutz, Organomet-
allics 16 (1997) 4920;
(b) T. Braun, S.P. Foxon, R.N. Perutz, P.H. Walton, Angew.
Chem. 111 (1999) 3543;
(c) S.J. Archibald, T. Braun, J.F. Gaunt, J.E. Hobson, R.N.
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(d) T. Braun, L. Cronin, C.L. Higgitt, J.E. McGrady, R.N.
Perutz, M. Reinhold, New J. Chem. 25 (2001) 19;
(e) M.I. Sladek, T. Braun, B. Neumann, H.-G. Stammler, J.
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3.15. MS and spectroscopical data of 8
(f) T. Braun, R.N. Perutz, M.I. Sladek, J. Chem. Soc., Chem.
Commun. (2001) 2254.
HRMS calcd. for C16H3NF2O9Fe3 558.7822. Found
558.7820, D=0.17 mmu. MS (El): m/z (%) 559 (M+,
16), 531 (M+ ꢁCO, 10), 503 (M+ ꢁ2CO, 28), 475
(M+ ꢁ3CO, 4), 447 (M+ ꢁ4CO, 6), 419 (M+ ꢁ5CO,
100), 391 (M+ ꢁ6CO, 28), 363 (M+ ꢁ7CO, 22), 335
(M+ ꢁ8CO, 25), 307 (M+ ꢁ9CO, 31), 251 (M+ ꢁFe–
9CO, 23), 213 (M+ ꢁFeF2–9CO, 13), 195 (M+ ꢁ2Fe–
9CO, 5), 168 (FeC4O4+, 23), 139 (C7H3NF2+, 48), 112
(FeC4O4+, 23), 84 (FeCO+, 8), 75 (FeF+, 11), 56 (Fe+,
37). IR (KBr, cmꢁ1): 2089 s, 2058 s, 2046 sh, 2029 s,
2016 s, 2004 sh, 1985 s, 1970 s, 1965 s, 1621 w, 1596
w, 1583 w, 1470 m, 1263 w, 1243w, 1190 w, 1100 w,
1011 m, 848 w, 789 m, 710 w, 604 m, 577 m, 558m,
[6] (a) D. Noveski, T. Braun, M. Schulte, B. Neumann, H.-G.
Stammler, J. Chem. Soc., Dalton Trans. (2003) 4075;
(b) T. Braun, D. Noveski, B. Neumann, H.-G. Stammler, Angew.
Chem. 114 (2002) 2870;
(c) M. Rausch, D. Steinborn, J. Organomet. Chem. 622 (1–2)
(2001) 172;
(d) R. Bosque, E. Clot, S. Fantacci, F. Maseras, O. Eisenstein,
R.N. Perutz, K.B. Renkema, K.G. Caulton, J. Am. Chem. Soc.
120 (1998) 12634;
(e) R.P. Hughes, D.C. Lindner, A.L. Rheingold, G.P.A. Yap,
Organometallics 15 (1996) 5678;
(f) D. Noveski, T. Braun, M. Schulte, B. Neumann, H.-G.
Stammler, J. Chem. Soc., Dalton Trans. (2003) 4075.
[7] (a) N.A. Jasim, R.N. Perutz, J. Am. Chem. Soc. 122 (2000)
8685;
1
530 w. H NMR (200 MHz, CDCl3, 298 K): 7.13 (d of
(b) M.W. Holtcamp, J.A. Labinger, J.E. Bercaw, J. Am. Chem.
Soc. 119 (1997) 848;
3
d, 2H, JHF =7.5 Hz, JHH =8.5 Hz), 7.51 (t of t, 1H,
3
3
4JHF =6.3 Hz, JHH =8.5 Hz). 13C NMR (100.6 MHz,
(c) M.W. Holtcamp, L.M. Henling, M.W. Day, J.A. Labinger,
J.E. Bercaw, Inorg. Chim. Acta 270 (1998) 467.
[8] (a) F. Godoy, C.L. Higgitt, A.H. Klahn, B. Oelckers, S. Parsons,
R.N. Perutz, J. Chem. Soc., Dalton Trans. (1999) 2039;
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R.N. Perutz, C.L. Higgitt, J. Chem. Soc., Dalton Trans. (1998)
3079.
2
CDCl3, 298 K): 109.56 (t, JCF =16 Hz), 112.45 (d of
2
d, JCF =20 Hz, JCF =4 Hz), 116.44 (s), 132.72 (t,
4
1
3
3JCF =10 Hz), 161.80 (d of d, JCF =257 Hz, JCF =5
Hz) 208.70 (s, broad).
[9] T.T. Tsou, J.K. Kochi, J. Am. Chem. Soc. 101 (1979) 6319.
[10] I. Bach, K.-R. Po¨rschke, R. Goddard, C. Kopiske, C. Kruger, A.
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