Deprotonation and dehydrogenation of Di(2-pyridylmethyl)amine with M[N(SiMe3)2]2 (M = Mn, Fe, Co, Zn) and Fe(C6H2-2,4,6-Me3)2

Article abstract of DOI:10.1016/j.jorganchem.2010.04.009

The reaction of di(2-pyridylmethyl)amine with FeCl₂ yields [Fe{HN(CH₂Py)₂}₂]Cl₂ (1) with the tridentate amines coordinating in a facial manner at the iron(II) center. Transamination of this amine with [M{N(SiMe₃)₂} ₂] in an equimolar ratio leads to the formation of heteroleptic [(Me₃Si)₂N-M{μ-N(CH₂Py)₂}] ₂ [M = Mn (2a), Fe (2b), and Zn (2c)]. The metallation of di(2-pyridylmethyl)amine with dimesityl iron(II) gives [Mes-Fe{μ-N(CH ₂Py)₂}]₂ (3). At temperatures below -30 °C the transamination reaction of [Fe{N(SiMe₃)₂}₂] with di(2-pyridylmethyl)amine in a molar ratio of 1:2 yields [Fe{N(CH ₂Py)₂}₂] (4). The reaction of [Co{N(SiMe ₃)₂}₂] with HN(CH₂Py)₂ leads to the formation of [Co{N(CHPy)₂}₂] (5b) with 1,3-di(2-pyridyl)-2-azaallyl ligands, regardless of the employed stoichiometry. The compounds 2b, 2c, 3, and 4 have to be handled and manipulated at low temperatures because they degrade already at room temperature whereas the manganese(II) derivative 2a is stable under these conditions. The degradation products [M{N(CHPy)₂}₂] [M = Fe (5a), Zn (5c)] contain the 1,3-di(2-pyridyl)-2-azaallyl ligands and can be considered as the dehydrogenation products of [M{N(CH₂Py)₂}₂]. A metathetical approach via the reaction of lithium di(2-pyridylmethyl)amide with FeCl₂ did not give the desired product 4 but a mixture of 1 and 5a. A ¹H NMR and EPR spectroscopic pursuit of the degradation of [(Me ₃Si)₂N-Zn{μ-N(CH₂Py)₂}] ₂ (2c) in tetrahydrofuran at temperatures between 253 and 328 K showed diminishing amounts of 2c and the appearance of 1,3-di(2-pyridyl)-2- azaallyl anions whereas the EPR experiments clearly verify the presence of di(2-pyridylmethyl)aminyl radicals in solution.

Full text of DOI:10.1016/j.jorganchem.2010.04.009

Journal of Organometallic Chemistry 695 (2010) 1641e1650
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Deprotonation and dehydrogenation of Di(2-pyridylmethyl)amine with
M[N(SiMe3)2]2 (M ¼ Mn, Fe, Co, Zn) and Fe(C6H2-2,4,6-Me3)2
Astrid Malassa, Christine Agthe, Helmar Görls, Manfred Friedrich, Matthias Westerhausen
*
Institut für Anorganische und Analytische Chemie, Friedrich-Schiller-Universität Jena, August-Bebel-Str. 2, D-07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of di(2-pyridylmethyl)amine with FeCl2 yields [Fe{HN(CH2Py)2}2]Cl2 (1) with the tri-
dentate amines coordinating in a facial manner at the iron(II) center. Transamination of this amine
with [M{N(SiMe3)2}2] in an equimolar ratio leads to the formation of heteroleptic [(Me3Si)2N-M{m-N
Received 26 February 2010
Received in revised form
30 March 2010
Accepted 4 April 2010
Available online 21 April 2010
(CH2Py)2}]2 [M ¼ Mn (2a), Fe (2b), and Zn (2c)]. The metallation of di(2-pyridylmethyl)amine with
dimesityl iron(II) gives [Mes-Fe{
m
-N(CH2Py)2}]2 (3). At temperatures below ꢀ30 ꢁC the transamination
reaction of [Fe{N(SiMe3)2}2] with di(2-pyridylmethyl)amine in a molar ratio of 1:2 yields [Fe{N
(CH2Py)2}2] (4). The reaction of [Co{N(SiMe3)2}2] with HN(CH2Py)2 leads to the formation of [Co{N
(CHPy)2}2] (5b) with 1,3-di(2-pyridyl)-2-azaallyl ligands, regardless of the employed stoichiometry.
The compounds 2b, 2c, 3, and 4 have to be handled and manipulated at low temperatures because they
degrade already at room temperature whereas the manganese(II) derivative 2a is stable under these
conditions. The degradation products [M{N(CHPy)2}2] [M ¼ Fe (5a), Zn (5c)] contain the 1,3-di(2-
pyridyl)-2-azaallyl ligands and can be considered as the dehydrogenation products of [M{N
(CH2Py)2}2]. A metathetical approach via the reaction of lithium di(2-pyridylmethyl)amide with FeCl2
did not give the desired product 4 but a mixture of 1 and 5a. A 1H NMR and EPR spectroscopic pursuit
Keywords:
Deprotonation reactions
Azaallyl ligands
Metallation reactions
Transamination reactions
Redox reactions
Dehydrogenation reactions
of the degradation of [(Me3Si)2N-Zn{m-N(CH2Py)2}]2 (2c) in tetrahydrofuran at temperatures between
253 and 328 K showed diminishing amounts of 2c and the appearance of 1,3-di(2-pyridyl)-2-azaallyl
anions whereas the EPR experiments clearly verify the presence of di(2-pyridylmethyl)aminyl radicals
in solution.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
is reversible [3e6] whereas with R ¼ SiR’3 only the CeC coupled
dimer was observed [2,7]. Iron(III) compounds are even able to
2-Pyridylmethylamines (abbreviated in Scheme 1 as H2L) offer
a rich chemistry including deprotonation (amide formation) as
well as redox reactions (imine formation). In Scheme 1 possible
pathways are summarized. Single and double deprotonations of
(H2L) lead to the formation of amides (HL)ꢀ (deprotonation of the
amino group) and bisamides (L)2ꢀ (deprotonation at the methy-
lene fragment and delocalization of the anionic charge into the
pyridyl unit), respectively. Whereas the amides (HL)ꢀ represent
widely used ligands, the doubly metallated amines are only stable
as salts with cations of very electropositive metals such as lithium
[1] and magnesium [2]. Nobler metals such as tin(II) and zinc(II)
initiate a single electron transfer reaction yielding the radical
doubly oxidize the amides leading to the imines (Lox2 0
)
which
form adducts with the iron(II) cations [8]. The imine (Lox2 0
)
(R ¼ H) formed also from the reaction of cobalt(III) with 2-pyr-
idylmethylamine (H2L) (R ¼ H) in anaerobic basic aqueous solu-
tions [9]; the proposed mechanism for the oxidative
dehydrogenation of the amine (H2L) to (Lox2 0
) included unob-
served intermediates which could be considered as (HLox1) and
(HLox2)þ; the latter was finally deprotonated by OHꢀ anions.
However, the aerial oxidation of cobalt(II)-bound 2-pyr-
idylmethylamine (R ¼ H) was explained by oxidation of (H2L)
with air yielding an intermediate of the type (H2Lox1 þ
) which can
be deprotonated. If deprotonation occurs at the methylene unit
a CeC coupling reaction could follow yielding 1,2-diamino-1,2-di
(2-pyridyl)ethane H2(Lox12) [10]. Subsequent reaction sequences
lead to isolated heterocycles. In general, the small substituent
R ¼ H can lead to various side-products [11] whereas trialkylsilyl
groups at the amido functionality allow an easier control of the
reaction behaviour of these amides. The reduction of (Lox2) with
anion (Lox1)ꢀ, which can dimerize to CeC coupled (Lox1 2ꢀ, and
elemental metal. If R represents an alkyl group the dimerization
)
2
* Corresponding author. Tel.: þ49 3641 948110; fax: þ49 3641 948102.
E-mail addresses: m.we@uni-jena.de, m.we@uni-jena.de (M. Westerhausen).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.04.009

1642
A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
- H+
- H+
_
H
H
N
N
+ H+
+ H+
N
N
_
NR
NR
_
NR
NHR
_
_
(L)2-
(H L)
(HL)-
2
+ e - e
x 2
N
N
H
.
_
N
RN
NR
_
NR
_
(Lox1
-
)
2-
(Lox1
)
2
+ e - e
H
N
(Lox2
NR
0
)
Scheme 1. Reaction portfolio starting from 2-pyridylmethylamine. Proton transfer reactions (acidebase reactions) are shown within rows, electron transfer reactions (redox
reactions) are shown within columns.
sodium gives the anions (Lox1 ꢀ
which can be coordinated to
metal(II) atoms such as Cr, Mn, Fe, Co, Ni, and Zn [12]. These
transition metal complexes show no tendency to dimerize via
a CeC coupling reaction.
)
H
H
CH3
O
H
O
N
N
N
N
N
N
Whereas in Scheme 1 the amino-bound group R remained an
innocent substituent, this is not the case if R is another 2-pyr-
idylmethyl group. Iron(II) complexes with coordinated di(2-pyr-
idylmethyl)amine molecules are well-known for several decades.
These ligands are stable toward oxidation even in the coordina-
tion sphere of iron(III) and under aerobic conditions [13]. Several
of these iron(II) complexes with different counter anions have
been characterized by X-ray structure determinations and show
an octahedrally surrounded iron(II) center with a facial arrange-
ment of the tridentate ligands, counter ions being e.g. chlorides
[13] or bromides [14]. The formation of dialkylamides is far less
common for the late 3d transition metals from Mn to Cu. Dia-
[Fe]
[Fe]
(1)
+
+
COOH
H3C
NH2
NH2
Lithiation of Py-CH2-N ¼ CH-Py and reaction with metal(II) salts
such as (thf)2FeBr2, CoCl2, and (dme)NiCl2 yielded the bis[1,3-di(2-
pyridyl)-2-azaallyl] derivatives of iron, cobalt, and nickel. In addition
a direct metallation of Py-CH2-N ¼ CH-Py with (thf)Fe[N(SiMe3)2]2
also gave this iron(II) derivative [26]. Thermal degradation of meth-
ylzinc di(2-pyridylmethyl)amide led to the formation of bis[1,3-di(2-
pyridyl)-2-azaallyl] zinc [27]. However, heteroleptic 1,3-di(2-pyr-
idyl)-2-azaallyl iron(II) bis(trimethylsilyl)amide shows an equilib-
rium with the CeC coupled dimer as shown in equation (2) [26]. A
similar C-C-coupled bridging hexadentate azabase was already
detected as a zinc complex from the reaction of 2-pyridylmethyl-
amine with excess of dimethylzinc [11].
First experiments showed that a dimethylzinc-mediated inter-
molecular deprotonation of methylzinc di(2-pyridylmethyl)amide
allowed the isolation of a trinuclear zinc complex as shown in
equation (3) [28]. We investigated the metallation of di(2-pyr-
idylmethyl)amine with the bis(trimethylsilyl)amides of manganese
(II), iron(II), cobalt(II), and zinc(II) (transamination reactions) as well
as with dimesityl iron(II). The transamination of N-substituted 2-
pyridylmethylamines with M[N(SiMe3)2]2 was already successfully
employed to prepare homoleptic bis(2-pyridylmethyl)amides of Mg,
Mn, Fe, Co, and Zn [29]. A heteroleptic complex was isolated after the
reaction of lithium 2-pyridylmethylamide with an equimolar amount
of (thf)2FeCl2.
lkylamides act as two-electron
position to act as two-electron
s
donors but they are also in the
p
donors, and therefore they favor
complex formation with early transition metals which have
vacant d orbitals and act as acceptor metals [15,16]. However,
p
an increasing interest in these compounds led to vast develop-
ment of the amide chemistry also of the late transition metals,
employing electronic and steric protection [17]. In contrast to the
finding that dialkylamides of manganese(II), iron(II), and cobalt
(II) are difficult to prepare and handle, the homoleptic bis(tri-
methylsilyl)amides of these late 3d metals Mn [18e20], Fe
[20e22], and Co [19,20,22] are stable and therefore they often
serve as starting materials in metallation and transamination
reactions.
Dehydrogenation of di(2-pyridylmethyl)amine yields Py-CH2-
N¼CH-Py(which, of course, couldbeunderstoodas asequenceof two
deprotonation and two oxidation steps) but this imine can easily be
prepared from 2-pyridylcarbaldehyde and 2-pyridylmethylamine, too
[23]. This ligand was also synthesized in the coordination sphere of
iron(II) according to equation (1) where [Fe] represents a complex
fragment of iron(II) [24]. Spectroscopic investigations of [Fe(Py-CH2-
N ¼ CH-Py)2]2þ with perchlorate counter ions showed a strong
s-
bonding ligand [25].

A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
1643
(2)
(5)
(3)
2. Results and discussion
2.1. Synthesis
Di(2-pyridylmethyl)amine acts as a tridentate ligand at iron(II).
The reaction of this amine with iron(II) chloride in dichloro-
methane led to the formation of [Fe{HN(CH2Py)2}2]Cl2. (equation
(4)).
The synthesis of homoleptic iron bis[di(2-pyridylmethyl)amide]
(4) was performed via transamination of Fe[N(SiMe3)2]2 with HN-
(CH2Py)2 at temperatures below ꢀ30 ꢁC according to equation (6)
(see also supplementary information of ref. [26]). This compound
precipitated immediately from the reaction solution, thus pre-
venting subsequent degradation reactions. In addition, the iron(II)
center is electronically saturated according to the 18-electron rule
and sterically shielded thus stabilizing this diamido iron(II)
complex.
(4)
(6)
The transamination reaction of the metal bis[bis(trimethylsilyl)-
amides] of manganese, iron, and zinc [30] with di(2-pyr-
idylmethyl)-amine in an equimolar ratio yielded the corresponding
heteroleptic dimeric complexes [(Me3Si)2N-M-N(CH2Py)2]2
[M ¼ Mn (2a), Fe (2b), Zn (2c)] (equation (5)) which precipitated
from the reaction mixtures. A similar deprotonation reaction
occurred between dimesityl iron [31] and di(2-pyridylmethyl)
amine leading to the formation of [Mes-Fe-N(CH2Py)2]2 (3). A dis-
mutatation into the homoleptic compounds MR2 and M[N
(CH2Py)2]2 was not observed. A heteroleptic amido complex [Me-
The compounds 2 and 3 proved to be very reactive and already
degraded below room temperature. C-H activation and formation
of 1,3-di(2-pyridyl)-2-azaallyl ligands led to the formation of
homoleptic M[N(CHPy)2]2 [M ¼ Fe (5a), Zn (5c)] (equation (7)). The
tridentate ligands show a meridional coordination behaviour. In
order to follow this reaction by NMR spectroscopy, the zinc
complex 2c was dissolved in tetrahydrofuran and spectra were
recorded during heating of the sample from 253 K to 328 K (Fig. 1).
Up to a temperature of 283 K the spectrum remained nearly
unchanged and degradation was very slow. Above this temperature
the formation of the 1,3-di(2-pyridyl)-2-azaallyl ligand was
observed. During heating of the sample the degradation of
[(Me3Si)2NeZneN(CH2Py)2]2 (2c) became faster and the intensity
Zn{m-N(CH2Py)2}]2 contains a four-membered Zn2N2 ring with
tetra-coordinate zinc atoms [27] because only one pyridyl unit of
each ligand was bound to the metal atoms.

1644
A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
Fig. 1. Temperature-dependent 1H NMR experiment of the degradation of [(Me3Si)2N-
Zn{ -N(CH2Py)2}]2 (2c) in [D8]THF. Only the region between 5.7 and 8.9 ppm of
aromatic fragments is displayed. From the bottom to the top, the spectra of [(Me3Si)2N-
Zn{ -N(CH2Py)2}]2 (2c) were recorded at 283 K, 300 K, 313 K, and 328 K. The formation
m
m
of the 1,3-(2-pyridyl)-2-azaallyl anion can best be seen at the appearance of the
resonances between 5.7 and 6.7 ppm and at the diminishing resonances of 2c between
6.8 and 7.0 ppm.
Fig. 2. EPR spectrum taken during the degradation of [(Me3Si)2N-Zn{m-N(CH2Py)2}]2
(2c) leading to the formation of [Zn{N(CHPy)2}2] (5c) at r.t. ([D8]THF solution, bottom
spectrum). This organic radical was simulated with the following values: g ¼ 2.00718, a
(Namide) ¼ 2.19 G, a(Npy) ¼ 3.97 G, and a(H) values of 3.66 G, 1.10 G, 0.70 G, 0.33 G, and
0.12 G (simulated spectrum at the top).
of the resonances between
d
¼ 5.8 and 6.7 of the 1,3-di(2-pyridyl)-
2-azaallyl anions increased. In Table 1 the 1H NMR parameters of
the involved compounds are listed. The dehydrogenation leads to
a strong low field shift of the hydrogen atoms in a-position to the
amido functionality. The first reaction steps involve deprotonation
at the methylene units before the azaallyl moieties formed. This fact
is in agreement with earlier investigations, shown in equation (3).
Other species appear as intermediates in the reaction solution
which disappear again at higher temperatures. A repetition of this
reaction in an EPR spectrometer showed that also organic radicals
play an important role as intermediates (Fig. 2). A simulation of the
EPR spectrum reveals that hydrogen abstraction (deprotonation
N
N
N
N
N
N
N
N
N
N
.
N
.
N
_
and single electron transfer) leads to the radical Py-CH-N¼CH-Py
.
which is stabilized by a far-reaching delocalization of the electron.
This delocalization gives rise to intense coupling of the electron
with all nitrogen atoms. However, the coupling a(N) to the pyridyl-
nitrogen bases is approximately twice as large as the coupling to
the azaallyl N base. This fact is a consequence of the delocalization
shown in Scheme 2. A similar observation was made for the a(H)
coupling constants. The largest value can be addressed to the allylic
CH moieties. For the pyridyl groups two larger and two smaller
.
Scheme 2. Mesomeric forms of the 1,3-di(2-pyridyl)-2-azaallyl radical showing the
delocalization of the radical electron. Similar drawings which are also possible for the
other 2-pyridylmethyl group are not represented.
couplings are found which is in agreement with the valence bond
formula given in Scheme 2.
The analysis of the space above the solution showed that small
amounts of hydrogen gas were liberated from this reaction mixture.
The reaction of cobalt bis[bis(trimethylsilyl)amide] with di(2-
pyridylmethyl)amine gave directly cobalt bis[1,3-di(2-pyridyl)-2-
azapropenide] (5b) and we were unable to isolate intermediate
Table 1
Comparison of the 1H NMR parameters of HN(CH2Py)2, [(Me3Si)NeZneN(CH2Py)2]2
(2c), and M[N(CHPy)2]2 (5c) ([D8]thf solution, 25 ꢁC, chemical shifts
coupling constants J [Hz]). Numbering scheme:
d [ppm],
[(Me3Si)NeCoeN(CH2Py)2]2.
manganese bis[bis(trimethylsilyl)amide] does not lead to the
formation of 1,3-di(2-pyridyl)-2-azaallyl ligand but to the
A similar reaction protocol with
a
formation of heteroleptic 2a.
.
HN(CH2Py)2
[(Me3Si)NeZneN
(CH2Py)2]2 (2c)
M[N(CHPy)2]2 (5c)
d
(H1)
3J(H,H)
(H2)
3J(H,H)
(C3)
3J(H,H)
(C4)
3J(H,H)
8.47
4.8
7.11
5.2
7.62
7.6
7.42
8.0
8.40
5.0
6.95
6.3
7.43
7.6
6.86
7.8
7.51
5.2
6.18
6.4
7.11
7.8
6.59
8.4
N
N
N
N
N
d
(7)
2 M{N(SiMe3)2}2 + 4
H
N
N
N
Fe
N
2
d
- 4 HN(SiMe3)2
- 4 H2
d
d
(H6)
(NH)
3.89
2.65
4.45
e
7.01
e
M = Fe (5a), Co (5b), Zn (5c)
d

A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
1645
The addition of lithium di(2-pyridylmethyl)amide to a solution
of FeCl2 yielded a mixture of [Fe{HN(CH2Py)2}2]Cl2 (1) and Fe[N-
(CHPy)2]2 (5a) according to equation (8). However, the expected
metathesis product [Fe{N(CH2Py)2}2]2 (4) was not found in the
reaction mixture. Nevertheless, this complex 4 might form in the
first reaction step. Subsequent reactions with still present lithium
amide gave the product mixture via deprotonation (lithiation) and
redox active intermediates. In this reaction sequence the di(2-
pyridylmethyl)amide ligand acted as a hydrogen donor (leading to
the formation of the azaallyl complex 5a) and at the same time as
a proton acceptor which gives the neutral di(2-pyridylmethyl)-
amine ligand in the coordination sphere of iron(II). From this
cations as well as the electronic influence of different valence
electron counts on structural parameters.
Selected structural parameters of the iron(II) derivatives 1, 4,
and 5a are listed in Table 2. The major differences can be expected
at the amino/amido functionality. In all complexes the iron atom is
in a distorted octahedral environment. In 1 the tridentate ligands
bind in a facial fashion whereas in 4 and 5 the ligands show
a meridional arrangement. In 1 (Fig. 3) the amino nitrogen atom N2
is in a distorted tetrahedral environment leading to a rather large
average N2-C distance of 149.9 pm and a long Fe-N2 bond of 203.1
pm. Deprotonation of the amino group (leading to the amido ligand
of 4, see Fig. 4) also gives a shorter Fe-N2 distance of 200.6 pm due
to an additional electrostatic attraction between the Fe cation and
the amido anion. A much larger effect is observed for the N2-C
bonds (142.3 pm) due to an enhancement of the s-orbital contri-
bution (in 1 the N2 atom is sp3 hybridized, in 4 a sp2 hybridization
reaction
mixture
crystalline
[Fe{HN(CH2Py)2}2]Cl2$CH2Cl2
(1$CH2Cl2) was isolated after recrystallization from dichloro-
methane.
(8)
2.2. Molecular structures
gives the nearly planar coordination sphere). The strong electro-
static attraction between the amido group and the iron atom leads
to a significant elongation of the Fe-N1/N3 bonds to the pyridyl
units (1: av. Fe-NPy 198.7 pm, 4: 221.4 pm). The negative charge of
the azaallyl ligand is delocalized not only within the allyl fragment
but short C5-C6 and C7-C8 bonds (av. value 141.2 pm) also suggest
a delocalization into the pyridyl units whereas values around 150
pm are characteristic for 1 and 4. The negative charge leads to short
Fe-N bonds to the azaallyl fragment as well as to the pyridyl
moieties Table 3.
The chemistry offers two interesting series which are worth to
be discussed in detail. On the one hand the series of the iron(II)
derivatives 1, 4, and 5a with the ligands HN(CH2Py)2 (amino
complex), N(CH2Py)2 (amido complex), and N(CHPy)2 (azaallyl
derivative), respectively. In all these compounds iron(II) (3d6
transition metal cation) is located in a distorted octahedral envi-
ronment. On the other hand, the heteroleptic complexes of
manganese(II) (2a), iron(II) (2b), and zinc(II) (2c) as well as complex
3 offer the possibility to discuss the influence of the size of the
Table 2
Selected structural parameters of the iron(II) derivatives 1, 4, and 5a with the ligands
HN(CH2Py)2 (amino complex), N(CH2Py)2 (amido complex), and N(CHPy)2 (azaallyl
derivative) (bond lengths [pm] and angles [ꢁ]).
1
4
5a
N1-C1
N1-C5
C1-C2
C2-C3
C3-C4
C4-C5
C5-C6
C6-N2
N2-C7
C7-C8
C8-C9
C9-C10
C10-C11
C11-C12
C12-N3
C8-N3
134,6(5)
135,1(5)
137,8(5)
137,0(6)
138,4(6)
138,7(5)
150,1(5)
148,8(5)
150,9(5)
147,6(5)
140,0(6)
137,2(6)
138,5(6)
139,4(6)
135,6(5)
133,4(5)
198,7(3)
203,1(3)
198,7(3)
83,6(1)
134,2(4)
133,2(4)
136,4(5)
140,6(5)
137,7(6)
138,7(5)
152,0(4)
142,7(4)
141,9(4)
149,8(4)
139,6(4)
137,2(4)
140,2(4)
137,5(4)
135,0(4)
134,8(3)
220,6(2)
200,6(2)
222,2(2)
75,81(9)
75,36(9)
151,17(8)
133,9(4)
137,2(4)
138,0(4)
138,8(5)
137,3(5)
141,1(4)
141,2(4)
133,7(4)
134,0(4)
141,1(4)
139,3(4)
137,0(4)
139,6(4)
138,2(4)
133,9(4)
138,4(3)
196,9(2)
190,5(2)
196,9(2)
82,1(0)
Fe-N1
Fe-N2
Fe-N3
N1-Fe-N2
N2-Fe-N3
N1-Fe-N3
Fig. 3. Molecular structure and numbering scheme of the cation [Fe{HN(CH2Py)2}2]2þ
of 1. The ellipsoids represent a probability of 40%, for clarity reasons only the amine H
atoms are drawn.
83,2(1)
86,7(1)
82,4(1)
164,4(1)

1646
A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
Fig. 4. Molecular structure and numbering scheme of [Fe{N(CH2Py)2}2]2 (4). The
ellipsoids represent a probability of 40%, H atoms are neglected for the sake of clarity.
Fig. 5. Molecular structure and numbering scheme of [(Me3Si)N-Fe{m-N(CH2Py)2}]2
(2b). The ellipsoids represent a probability of 40%, the hydrogen atoms are neglected
for clarity reasons. The Mn (2a) and Zn derivatives (2c) show very similar molecular
structures.
Molecular structures and numbering schemes of the iron
derivatives 2b and 3 are shown in the Figs. 5 and 6. The molecular
structures of 2a and 2c are very similar to 2b. The M-N2 bonds (av.
values for 2a: 220.8, 2b: 214.9, 2c: 212.2, and 3: 211.5 pm) strongly
reflect the radii of the metal cations M2þ (radius of high spin/low
spin Mn2þ 0.97/0.81 and Fe2þ 0.92/0.75, as well as of Zn2þ 0.88 pm).
Due to the bridging position of the amido group the M-N2 bond
lengths are larger as observed in the mononuclear derivatives
discussed before. The Fe-NPy distances resemble similar trends but
are larger than the other M-N2 bond lengths. The rather large Zn-
N1/3 distances could also be discussed on the basis of an N1-Zn-N3
4-electron 3-center bond with the amido bases binding into the
pz(Zn) ortibal. Manganese often favors high spin states and shows
peculiar properties resembling similarities with the magnesium
compounds [32].
deprotonation steps starting from the amide (H2L)ꢀ leads to a 1,3-di
(2-pyridyl)-2-azaallyl ligand (Lox2 ꢀ
which resembles the dehy-
)
drogenated 1,3-di(2-pyridylmethyl)amide anion. Iron(II), cobalt(II)
and zinc(II) bis[bis(trimethylsilyl)amides] are able to follow this
reaction sequence whereas the reaction of Mn[N(SiMe3)2]2 with HN
(CH2Py)2 only gives the heteroleptic dinuclear complex [(Me3Si)2N-
Mn{m-N(CH2Py)2}]2 and the formation of an azaallyl ligand does not
occur under these reaction conditions. This finding is in agreement
with the observations that manganese(II) with a high spin state is
rather similar to magnesium(II) in many aspects (ionic compounds,
weak redox activity) but that iron(II), cobalt(II) and zinc(II) are
highly redox active and able to activate C-H bonds.
The reaction behaviour of [M{N(SiMe3)2}2]2 toward di(2-pyr-
idylmethyl)amine in dependency of the 3d-metal (and hence the
valence electron count) can be summarized as follows:
3. Summary and conclusion
Di(2-pyridylmethyl)amine enriches the possible reaction spec-
trum in comparison to the 2-pyridylmethylamines. In Scheme 3 the
reactivity of this amine is shown. The combination of redox and
- The iron(II) derivatives are the most stable compounds allow-
ing the isolation of complexes of the types [Fe{HN
(CH2Py)2}2]2þ (1 with amino ligands), [(Me3Si)2N-Fe{
m-N
Table 3
(CH2Py)2}]2 (2b), [Mes-Fe-N(CH2Py)2]2 (3), and [Fe{N
(CH2Py)2}2] (4, containing amido ligands), as well as [Fe{N
(CHPy)2}2] (5a with 2-azaallyl ligands). Similar derivatives are
also known for zinc(II). The amido ligands undergo a trans-
formation to the 2-azaallylic systems already at room
temperature (dehydrogenation).
- The transamination of HN(CH2Py)2 with [Mn{N(SiMe3)2}2]2
leads to the formation of [(Me3Si)2N-Mn{m-N(CH2Py)2}]2 (2a).
This complex is stable at room temperature.
- The reaction of [Co{N(SiMe3)2}2]2 with HN(CH2Py)2 yields [Co
{N(CHPy)2}2] (5b) with 2-azaallyl ligands regardless of the
applied stoichiometry. Di(2-pyridylmethyl)amido ligands seem
to be unstable in the vicinity of cobalt(II).
- The degradation of di(2-pyridylmethyl)amides and formation
of 1,3-di(2-pyridyl)-2-azaallyl anions proceeds via the inter-
mediate radical [(2-Py-CH)2N$].
Selected structural parameters for the compounds [R-M{m-N(CH2Py)2}]2 of manga-
nese (2a), iron (2b and 3), and zinc (2c). The radii are given for hexa-coordinate
metal ions, the first value refers to low spin state, the second to high spin state metal
ions (bond lengths [pm] and angles [ꢁ]).
Position
M
2a
2b
2c
3
Mn
Fe
Zn
Fe
r(M2þ)
R
M-N1
M-N2
0.81/0.97
N(SiMe3)2
229,3(2)
223,0(2)
226,3(2)
211,3(2)
218,5(2)
147,0(3)
145,9(3)
169,4(2)
170,0(2)
304,26(7)
91,71(7)
122,66(7)
145,49(8)
141,45(7)
87,14(7)
0.69/0.785
N(SiMe3)2
222,5(2)
213,5(2)
219,1(2)
205,0(2)
216,2(2)
145,9(3)
146,0(3)
170,4(2)
170,3(2)
297,02(6)
91,44(7)
117,95(7)
150,49(7)
147,58(7)
87,47(7)
0.88
0.69/0.785
C6H2-2,4,6-Me3
221,2(3)
212,2(3)
219,2(3)
212,6(4)
210,7(3)
146,1(5)
146,0(5)
e
N(SiMe3)2
227,3(2)
215,3(2)
221,6(2)
201,8(2)
209,1(2)
146,1(2)
146,0(2)
170,3(2)
170,0(2)
297,17(4)
90,24(6)
122,40(6)
147,30(6)
144,33(6)
88,87(6)
M-N3
M-N4/C13
M-N2A
N2-C7
N2-C6
Si1-N4
Si2-N2
e
MeM(A)
N2-M-N2A
N4-M-N2A
N4-M-N2
N3-M-N1
M-N2-MA
283,4(1)
95,9(1)
125,4(1)
e
The di(2-pyridylmethyl)amido complex of iron(II) is not
obtainable via a metathetical approach (reaction of LiN(CH2Py)2
with FeCl2) because lithium di(2-pyridylmethyl)amide, a rather
strong deprotonation reagent, immediately lithiates the methylene
147,2(1)
84,1(1)

A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
1647
Fig. 6. Molecular structure and numbering scheme of [Mes-Fe{m-N(CH2Py)2}]2 (3). The ellipsoids represent a probability of 40%, hydrogen atoms are not shown for clarity reasons.
fragments. In contrast to this finding, the compound [Fe{N
(CHPy)2}2] with 1,3-di(2-pyridyl)-2-azaallyl ligands can be isolated
from such procedure.
Activation of C-H bonds was investigated by using 3d transition
metal complexes of manganese, iron, cobalt and iron. Depending on
the metal dehydrogenation can be achieved converting di(2-pyr-
idylmethyl)amides into di(2-pyridyl)-2-azaallyl anions. These
results extend the spectrum of 3d metals in C-H bond activation
which can be used for CeC bond formation [33].
sensitive. Prior to use, all solvents were thoroughly dried and
distilled in an argon atmosphere. Starting [M{N(SiMe3)2}2]2 of
manganese [18], iron [19], cobalt [22], and zinc [30] as well as
dimesityl iron [31] were prepared according to literature proce-
dures. Azaallyl complexes of the type M[N(CHPy)2]2 for Fe (5a) and
Co (5b) were also prepared previously by another route via
deprotonation of PyCH2-N ¼ CHPy with [M{N(SiMe3)2}2]2 or
metathetical by addition of LiN(CHPy)2 to (thf)2FeBr2 or CoCl2 [26].
The synthesis of Zn[N(CHPy)2]2 (5c) was already reported earlier
[27], but a reinvestigation was performed in order to shed light on
the reaction mechanism. IR spectra were recorded at Nujol solu-
tions between KBr windows. The magnetic properties were deter-
4. Experimental details
mined by
a Gouy magnetic balance at 290 K and SQUID
4.1. General procedure
measurements. These compounds are sensitive towards moisture
and air. In addition, weighing and handling of these substances for
C,H,N analytical data proved to be challenging.
All manipulations were carried out in an argon atmosphere
under anaerobic conditions. The compounds are moisture and air
Scheme 3. Schematic representation of the reaction spectrum of di(2-pyridylmethyl)amine.

1648
A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
4.1.1. Synthesis of [Fe{HN(CH2Py)2}2]Cl2$CH2Cl2 (1)
4.1.5. Synthesis of [Mes-Fe-N(CH2Py)2]2 (3)
Di(2-pyridylmethyl)amine (0.37 g, 1.89 mmol) was dissolved in
10 mL of THF at ꢀ78 ꢁC. Then 1.2 mL of a 1.6 M solution of n-BuLi in
hexane (1.92 mmol) was dropped into this solution. Afterwards this
solution was added at ꢀ78 ꢁC to a suspension of 0.24 g of FeCl2
(1.89 mmol) in 10 mL of THF. Thereafter the reaction mixture was
warmed to r.t. and a red solid precipitated from this blue solution.
This red solid was collected and dried in vacuo. Recrystallization
At ꢀ20 ꢁC a solution of 0.28 g of dimesityl iron (0.94 mmol) in
10 mL of toluene was layered with a solution of 0.19 g of di(2-pyr-
idylmethyl)amine (0.94 mmol) in 13 mL of toluene and kept at
ꢀ20 ꢁC for several days. Black crystals formed within 3 days which
were collected, washed with a small amount of cold toluene and
dried in vacuo. Yield: 0.24 g (0.30 mmol, 69%). M.p.: 288 ꢁC. IR
(cmꢀ1): v ¼ 2789 m, 2725 w, 1597 m, 1567 m, 1478 s, 1456 vs, 1435
~
from CH2Cl2 afforded 0.45 g of crystalline 1 (Yield: 0.86 mmol, 93%).
vs, 1337 m, 1274 m, 1210 w, 1151 m, 1127 m, 1097 m, 1067 m,
1046 m, 1029 m, 1009 m, 981 w, 909 w, 848 m, 763 m, 751 s, 726 m,
648 w, 642 w, 636 w, 629 w, 536 w, 485 w. MS (DEI): m/z ¼ 448 ([Fe
(N(CH2-Pyr)2)2]þ, 5%), 200 ([HN(CH2-Pyr)2 þ H]þ, 82%), 120
([Mes þ H]þ, 93%), 105 ([Mes e Me]þ, 93%), 93 ([Pyr-CH3]þ 100%).
Elemental analysis (C42H46Fe2N6, 764.55): calc.: C 67.57, H 6.21, N
ꢀ1
M.p.: 223 ꢁC. IR (cm ): v ¼ 3400 w br, 3109 m, 3084 m, 2724 w,
~
1607 m, 1570 w, 1513 w, 1484 s, 1312 m, 1283 m, 1153 w, 1133 m,
1109 w, 1076 w, 1064 w, 1021 w, 973 w, 945 w, 912 m, 892 w, 820 w,
773 s, 724 vs, 691 m, 649 w, 524 w. MS (DEI,): m/z ¼ 291 ([FeClHN
(CH2-Pyr)2]þ, <3%), 200 ([HN(CH2-Pyr)2 þ H]þ, 66%),107 ([Pyr-CH2-
NH]þ, 95%), 93 ([Pyr-CH3]þ, 100%). Elemental analysis (C25H28Cl4Fe-
N6, 610.19): calc.: C49.06, H 4.61, N 13.73; found: C 46.42, H 4.34, N
12.37.
11.26; found: C 64.12, H 6.21, N 11.55. Magnetism: meff ¼ 8.0 mB
,
300 K.
4.1.6. Synthesis of Fe[N(CH2Py)2]2 (4)
4.1.2. Synthesis of [(Me3Si)NeMneN(CH2Py)2]2 (2a)
A solution of 0.21 g of [Fe{N(SiMe3)2}2]2 (0.28 mmol) in 2 mL of
THF was cooled to ꢀ78 ꢁC. At this temperature a solution of 0.22 g
of di(2-pyridylmethyl)amine (1,12 mmol) in 5 mL of diethyl ether
was added dropwise. Then the reaction mixture was filtered at
ꢀ30 ꢁC. The blue mother liquor was kept at or below ꢀ20 ꢁC.
Within a few days, 0.12 g of long needle-like colorless crystals of 4
(0.26 mmol, 40%) precipitated. These crystals contain thf and Et2O.
At r.t. these ethers are liberated abd the remaining compound
dissolves in these ethers. Therefore, no m.p. can be given. IR (cmꢀ1):
A solution of 0.34 g of [Mn{N(SiMe3)2}2]2 (0.45 mmol) in 5 mL of
diethyl ether was cooled to ꢀ78 ꢁC. A second solution of 0.37 g of di
(2-pyridylmethyl)amine (1.80 mmol) in 3 mL of diethyl ether was
layered on top of this solution. This mixture was kept at ꢀ18 ꢁC for 2
days. Yellow crystals of 2a (o,25 g, 0.31 mmol; 67%) formed, were
washed several times with cꢀo1ld diethyl ether and then dried under
vacuum. M.p.: 143 ꢁC. IR (cm ): v ¼ 1602 s, 1571 m, 1479 m, 1435 s,
~
1342 m, 1278 m, 1245 s, 1233 s, 1150 m, 1131 m, 1097 m, 1048 m,
1033 m, 997 vs br, 879 vs, 830 vs br, 773 m, 729 m, 659 m, 638 m,
605 m. MS (DEI): m/z ¼ 447 ([Mn(N(CH2-Pyr)2)2]þ, 1%), 414 ([MnN
(CH2Pyr)2N(SiMe3)2]þ, <1%), 161 ([HN(SiMe3)2]þ, 6%), 146 ([HN
~
v ¼ 1590 s, 1569 m, 1429 s, 1175 w, 1133 m, 1047 m, 994 m, 753 s,
626 w. MS (DEI): m/z ¼ 448 ([Fe(N(CH2-Pyr)2)2]þ, 2%), 200 ([HN
(CH2-Pyr)2 þ H]þ, 82%), 107 ([Pyr-CH2-NH]þ, 55%), 93 ([Pyr-CH3]þ,
100%).
(SiMe3)2
e
Me]þ, 90%), 93 ([Pyr-CH3]þ, 100%). Magnetism:
meff ¼ 6.5 mB, 300 K.
4.1.7. Synthesis of Fe[N(CHPy)2]2 (5a)
4.1.3. Synthesis of [(Me3Si)NeFeeN(CH2Py)2]2 (2b)
A solution of 0.44 g of [Fe{N(SiMe3)2}2]2 (0.59 mmol) in 5 mL of
THF was added dropwise at ꢀ78 ꢁC to a stirred solution of 0.24 g of
di(2-pyridylmethyl)amine (1.19 mmol) in 5 mL of diethyl ether.
Then the reaction mixture was warmed to r.t. and stirred for
additional 30 min. After filtration the volume of the mother liquor
was reduced to half of the original amount. Within several days at r.
t. 0.14 g of colorless platelets of 5a (0.31 mmol, 52%ꢀ) 1precipitated
A solution of 0.29 g of [Fe{N(SiMe3)2}2]2 (0.39 mmol) in 12 mL of
diethyl ether was layered at r.t. with a solution of 0.15 g of di(2-
pyridylmethyl)amine (0.78 mmol) in 5 mL of diethyl ether. Within
1 day 0.15 g of pink needle-shaped crystals of 2b (0.18 mmol, 47%)
precipitated which were dried under reduced pressure. M.p.:
ꢀ1
180 ꢁC. IR (cm ): v ¼ 1600 m, 1570 w, 1435 m, 1339 w, 1276 m,
~
which were dried under vacuum. M.p.: 335 ꢁC. IR (cm ): v ¼ 1585,
~
1247 m, 1236 s, 1150 m, 1134 m, 1098 w, 1048 w, 1032 m, 974 vs,
875 s, 830 s, 778 m, 750 s, 727 m, 658 m, 608 w. MS (DEI): m/
z ¼ 448 ([Fe(N(CH2-Pyr)2)2]þ, 11%), 414 ([Fe-N(CH2Pyr)2N
1542 m br, 1382 vs br, 1320 m, 1285 m, 1261 m, 1176 s, 1132 vs,
1022 m, 1005 s, 844 w, 757 m, 732 m, 684 m, 537 w, 517 w, 479 w.
MS (DEI): m/z ¼ 448 ([M]þ, 63%), 252 ([Fe-N(CH2-Pyr)2]þ, 45%), 107
([Pyr-CH2-NH]þ, 45%), 93 ([Pyr-CH3]þ, 100%). Elemental analysis
(C24H20Fe-N6, 448.30): calc.: C 64.30, H 4.50, N 18.75; found: C
63.40, H 4.62, N 18.54.
(SiMe3)2]þ, 10%), 161 ([HN(SiMe3)2]þ, 7%), 146 ([HN(SiMe3)2
e
Me]þ, 100%). Elemental analysis (C36H60Fe2N8Si4, 828.95): calc.: C
52.16, H 7.30, N 13.52; found: C 51.82, H 6.91, N 13.46. Magnetism:
meff ¼ 7.5 mB, 300 K.
4.1.4. Synthesis of [(Me3Si)NeZneN(CH2Py)2]2 (2c)
4.1.8. Synthesis of Co[N(CHPy)2]2 (5b)
A solution of 0.25 g of di(2-pyridylmethyl)amine (1.34 mmol) in
2 mL of diethyl ether was layered at r.t. on top of a solution of 0.48 g
of Zn[N(SiMe3)2] (1,24 mmol) in 4 mL of diethyl ether. Within 24 h
0.40 g of colorless rod-like crystals of 2c (0.48 mmol, 77%) precip-
itated and were collected and dried under vacuum. 1H-NMR ([D8]
A solution of 0.63 g of di(2-pyridylmethyl)amine (3.16 mmol) in
3 mL of diethyl ether was layered at ꢀ78 ꢁC on top of a solution of
0.60 g of [Co{N(SiMe3)2}2]2 (0.79 mmol) in 5 mL of diethyl ether.
Within 2 days at this temperature 0.34 g of dark violet platelets of
5b (0.76 mmol, 48%) precipitatedꢀa1nd were collected and dried
¼ 8,40 (d br, 3J(H1,H2) ¼ 5,0 Hz, 1 H, H1),
under vacuum. M.p.: 276 ꢁC. IR (cm ): v ¼ 1546 m,1459 m,1395 vs
~
THF, 200 MHz, 253 K):
d
7,43 (dt, 3J(H3,H2/4) ¼ 7,6 Hz, 4J(H3,H1) ¼ 1,6 Hz,1 H, H3), 6,95 (t br,
3J(H2,H1/3) ¼ 6,3 Hz, 1 H, H2), 6,86 (d br, 3J(H4,H3) ¼ 7,8 Hz, 1 H,
br, 1320 m, 1286 m, 1193 s, 1135 vs, 1071 w, 1045 w, 986 s, 788 w,
753 m, 731 m, 670 w, 515 w. MS (DEI): m/z ¼ 451 ([M]þ, 49%), 255
([CoN(CH2-Pyr)2]þ, 28%), 107 ([Pyr-CH2-NH]þ, 58%), 93 ([Pyr-CH3]þ,
100%). Elemental analysis (C24H20CoN6, 451,39): calc.; C 63.86, H
4.43, N 18.63; found: C 63.00, H 4.96, N 17.58. Magnetism:
meff ¼ 3.8 mB, 300 K.
H4), 0,04 (s, 9 H, Si(CH3)3). IR (cmꢀ1): v ¼ 2732 m, 2672 w, 1602 s,
~
1575 m, 1480 m, 1435 s, 1342 m, 1278 m, 1247 s, 1235 s, 1149 m,
1139 m, 1099 m, 1048 m, 1038 m, 1011 m, 985 vs, 881 s, 830 vs,
780 m, 752 s, 729 m, 659 m, 636 m, 609 m, 496 m. MS (DEI): m/
z ¼ 456 ([Zn(N(CH2-Pyr)2)2]þ, 3%), 161 ([HN(SiMe3)2]þ, 7%), 146
([HN(SiMe3)2 e Me]þ, 45%). Elemental analysis (C36H60N6Si4Zn2,
848.08): calc.: C 50.98, H 7.13, N 13.21; found: C 50.39, H 7.05, N
13.32.
4.1.9. Synthesis of Zn[N(CHPy)2]2 (5c)
M.p.133 ꢁC. 1H-NMR ([D8]THF, 200 MHz, 253 K):
d
¼ 8,40 (d br, 3J
(H1,H2) ¼ 5,0 Hz, 1 H, H1), 7,43 (dt, 3J(H3,H2/4) ¼ 7,6 Hz, 4J(H3,

A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
1649
Table 4
Crystal data and refinement details for the X-ray structure determinations of 1, 2a-2c, 3, and 4.
Compound
formula
1
2a
2a-thf
2a-ether
2b
2c
3
4
[C24H26Fe-N6]2þ
C36H60Mn2
C36H60 Mn2N8Si4, C36H60Mn2N8 C36H60Fe2N8Si4 C36H60N8Si4
0.25(C4H8 O)
C42H46Fe2N6 C24H24Fe-N6,
Zn2 2(C4H10O) 2(C7H8) C4H8O, 0.25(C4H10O)
542.98
2(Clꢀ), 2(CH2Cl2) N8Si4
Si4 2(C4H10O) 2(C4H10O)
fw (g molꢀ1
T/ꢁC
crystal system
space group
a/Å
)
695.11
ꢀ90(2)
monoclinic
P 21/n
9.4237(9)
14.2953(9)
11.4918(6)
90
94.186(5)
90
1543.98(19)
2
827.16
845.19
ꢀ90(2)
975.40
ꢀ90(2)
monoclinic
C 2/c
15.1506(6)
19.5335(5)
18.3900(8)
90
96.497(2)
90
5407.5(3)
4
977.22
ꢀ90(2)
monoclinic
C 2/c
14.9801(4)
19.5413(9)
18.3671(7)
90
96.335(2)
90
5343.8(3)
4
996.26
ꢀ90(2)
monoclinic
C 2/c
930.82
ꢀ90(2)
monoclinic
P 21/c
12.0971(4)
16.2760(7)
14.8301(6)
90
111.581(2)
90
2715.24(18)
2
ꢀ90(2)
ꢀ90(2)
monoclinic
C 2/c
30.2251(9)
8.8782(3)
21.7397(5)
90
104.50(2)
90
5647.8(3)
8
orthorhombic triclinic
ꢀ
P ı
P ca21
16.9586(4)
11.4369(2)
22.8730(5)
90
90
90
4436.30(16)
4
1.238
11.2174(7)
11.7465(4)
17.7512(9)
90.013(3)
98.807(2)
94.995(3)
2302.4(2)
2
14.9743(5)
19.5528(4)
18.3648(6)
90
96.619(1)
90
5341.2(3)
4
1.239
b/Å
c/Å
ꢁ
ꢁ
a
/
b
/
ꢁ
g
/
V/Å3
Z
r
(g∙cmꢀ3
(cmꢀ1
)
1.495
10.35
1.219
6.87
1.198
5.96
1.215
6.74
1.139
5.73
1.277
5.67
m
)
7.11
10.29
measured data
10 594
2325
30 224
7701
16 731
5453
19 209
4053
18 112
4248
18 677
4726
17 679
4549
18 457
4765
data with I > 2
s
(I)
unique data/Rint
3526/0.0627
9316/0.0603
0.0794
0.0366
1.001
0.382/-0.292
770 773
10 469/0.0657
0.1822
0.0660
1.017
0.920/-0.433
763 995
6183/0.0663
0.1111
0.0428
1.015
0.289/-0.397
763 996
6114/0.0596
0.1019
0.0421
1.010
0.314/-0.450
763 997
6110/0.0446
0.0828
0.0330
1.015
0.372/-0.527
763 998
6137/0.0532 6433/0.0397
wR2 (all data, on F2)a 0.1656
0.2334
0.0671
1.103
0.1769
0.0536
1.027
R1 (I > 2
s
(I))a
0.0571
1.028
1.046/-0.562
763 994
sb
Res. dens./e∙Åꢀ3
1.134/-0.552 1.330/-0.451
763 999 763 900
CCDC No.
wR2 ¼ {S[w(Fo2 ꢀ Fc2)2]/S[w(F2o)2]}1/2 with wꢀ1
¼
s
2(F2o) þ (aP)2 þ bP; P ¼ [2Fc2 þ Max(F2O)]/3.
a
Definition of the R indices: R1 ¼ (SjFoj-jFcj)/SêjFoj.
s ¼ {S[w(F2o ꢀ Fc2)2]/(No ꢀ Np)}1/2
.
b
H1) ¼ 1,6 Hz, 1 H, H3), 6,95 (t br, 3J(H2,H1/3) ¼ 6,3 Hz, 1 H, H2), 6,86
References
(d br, 3J(H4,H3) ¼ 7,8 Hz, 1 H, H4), 0,04 (s, 9 H, Si(CH3)3). IR (cmꢀ1):
[1] M. Westerhausen, A.N. Kneifel, N. Makropoulos, Inorg. Chem. Commun. 7
(2004) 990e993.
[2] M. Westerhausen, T. Bollwein, N. Makropoulos, S. Schneiderbauer, M. Suter,
H. Nöth, P. Mayer, H. Piotrowski, K. Polborn, A. Pfitzner, Eur. J. Inorg. Chem.
(2002) 389e404.
[3] J.T.B.H. Jastrzebski, J.M. Klerks, G. van Koten, K. Vrieze, J. Organomet. Chem.
210 (1981) C49eC53.
[4] G. van Koten, J.T.B.H. Jastrzebski, K. Vrieze, J. Organomet. Chem. 250 (1983)
49e61.
~
v
¼ 2732 m, 2672 w, 1602 s, 1575 m, 1480 m, 1435 s, 1342 m,
1278 m, 1247 s, 1235 s, 1149 m, 1139 m, 1099 m, 1048 m, 1038 m,
1011 m, 985 vs, 881 s, 830 vs, 780 m, 752 s, 729 m, 659 m, 636 m,
609 m, 496 m. MS (DEI): m/z ¼ 456 ([Zn(N(CH2-Pyr)2)2]þ, 3%), 161
([HN(SiMe3)2]þ, 7%), 146 ([HN(SiMe3)2 e Me]þ, 45%). Elemental
analysis (C36H60N6Si4Zn2, 848.08): calc.: C 50.98, H 7.13, N 13.21;
found: C 50.39, H 7.05, N 13.32.
[5] A.L. Spek, J.T.B.H. Jastrzebski, G. van Koten, Acta Cryst. C43 (1987)
2006e2007.
4.1.10. X-ray structure determinations
[6] E. Wissing, S. van der Linden, E. Rijnberg, J. Boersma, W.J.J. Smeets, A.L. Spek,
G. van Koten, Organometallics 13 (1994) 2602e2608.
[7] M. Westerhausen, T. Bollwein, N. Makropoulos, T.M. Rotter, T. Habereder,
M. Suter, H. Nöth, Eur. J. Inorg. Chem. (2001) 851e857.
[8] A. Malassa, N. Herzer, H. Görls, M. Westerhausen, Ph.D. thesis, Jena/Germany,
2010.
[9] N.Y. Murakami Iha, M.A. de Almeida Azzelini, S. Utsuno, Polyhedron 17 (1998)
3379e3390.
[10] K. Ogura, Y. Kurasawa, Y. Yamaguchi, Y. Okamoto, Heterocycles 59 (2003)
283e291.
[11] M. Westerhausen, T. Bollwein, P. Mayer, H. Piotrowski, Z. Anorg. Allg. Chem.
628 (2002) 1425e1432.
[12] C.C. Lu, E. Bill, T. Weyhermüller, E. Bothe, K. Wieghardt, J. Am. Chem. Soc. 130
(2008) 3181e3197.
[13] C.J. Davies, G.A. Solan, J. Fawcett, Polyhedron 23 (2004) 3105e3114.
[14] A. Malassa, H. Görls, A. Buchholz, W. Plass, M. Westerhausen, Z. Anorg. Allg.
Chem. 632 (2006) 2355e2362.
[15] D.C. Bradley, M.H. Chisholm, Acc. Chem. Res. 9 (1976) 273e280.
[16] (a) R. Kempe, Angew. Chem. 112 (2000) 478e504;
(b) Angew. Chem. Int. Ed. 39 (2000) 468e493.
The intensity data for the compounds were collected on a Non-
ius KappaCCD diffractometer using graphite-monochromated Mo-
Ka radiation. Data were corrected for Lorentz and polarization
effects but not for absorption effects [34,35]. Crystal data and
refinement details for the X-ray structure determinations are
summarized in Table 4.
The structures were solved by direct methods (SHELXS) [36]
and refined by full-matrix least squares techniques against Fo2
(SHELXL-97) [37]. All hydrogen atoms were included at calculated
positions with fixed thermal parameters. All non-disordered, non-
hydrogen atoms were refined anisotropically [37]. XP (SIEMENS
Analytical X-ray Instruments, Inc.) was used for structure
representations.
Acknowledgements
[17] (b) M.F. Lappert, P.P. Power, A.R. Sanger, R.C. Srivastava, Metal and Metalloid
Amides. Ellis Horwood, Chichester, 1980;
(b) M. Lappert, P. Power, A. Protchenko, A. Seeber, Metal Amide Chemistry.
Wiley, Chichester, 2009.
[18] H. Bürger, U. Wannagat, Monatsh. Chem. 95 (1964) 1099e1102.
[19] B.D. Murray, P.P. Power, Inorg. Chem. 23 (1984) 4584e4588.
[20] R.A. Andersen, K. Faegri, J.C. Green, A. Haaland, M.F. Lappert, W.-P. Leung,
K. Rypdal, Inorg. Chem. 27 (1988) 1782e1786.
[21] M.M. Olmstead, P.P. Power, S.C. Shoner, Inorg. Chem. 30 (1991) 2547e2551.
[22] H. Bürger, U. Wannagat, Monatsh. Chem. 94 (1963) 1007e1012.
[23] C. Incarvito, M. Lam, B. Rhatigan, A.L. Rheingold, C.J. Qin, A.L. Gavrilova,
B. Bosnich, J. Chem. Soc., Dalton Trans. (2001) 3478e3488.
[24] M.I.D. Holanda, P. Krumholz, H.L. Chum, Inorg. Chem. 15 (1976) 890e893.
[25] E. Baggio-Saitovitch, M.A. de Paoli, Inorg. Chim. Acta 27 (1978) 15e20.
These results were presented on the International Conference
on Coordination Chemistry in July 2008 in Jerusalem, Israel
(ICCC38) and A. Malassa thanks the Deutsche For-
schungsgemeinschaft (DFG, Bonn-Bad Godesberg, Germany) for
a generous stipend to cover the travel expenses. We also appreciate
the financial support of the Deutsche Forschungsgemeinschaft
(DFG, Bonn-Bad Godesberg, Germany). A. Malassa is also grateful to
the Carl-Zeiss-Stiftung (Stuttgart, Germany) for a generous Ph.D.
grant.

1650
A. Malassa et al. / Journal of Organometallic Chemistry 695 (2010) 1641e1650
[26] B.A. Frazier, P.T. Wolczanski, E.B. Lobkovsky, T.R. Cundari, J. Am. Chem. Soc.
131 (2009) 3428e3429.
(e) G. Markgraf, H.-W. Lerner, M. Bolte, M. Wagner, Z. Anorg. Allg. Chem.
630 (2004) 217e218.
[27] M. Westerhausen, A.N. Kneifel, Inorg. Chem. Commun. 7 (2004) 763e766.
[28] M. Westerhausen, A.N. Kneifel, I. Lindner, J. Grcic, H. Nöth, Z. Naturforsch. 59b
[31] (a) B. Machelett, Z. Chem 16 (1976) 116e117;
ꢁ ꢂ
(b) H. Müller, W. Seidel, H. Görls, J. Organomet. Chem. 445 (1993) 133e136.
[32] R.A. Layfield, Chem. Soc. Rev. 37 (2008) 1098e1107.
[33] A.A. Kulkarni, O. Daugulis, Synthesis (2009) 4087e4109.
[34] COLLECT, Data Collection Software; Nonius B.V., Netherlands, 1998.
[35] Z. Otwinowski, W. Minor, Processing of X-ray diffraction data collected in
oscillation mode. in: C.W. . Carter, R.M. Sweet (Eds.), Methods in Enzymology,
Macromolecular Crystallography, Part A, vol. 276. Academic Press, 1997, pp.
307e326.
(2004) 161e166.
[29] C. Koch, A. Malassa, C. Agthe, H. Görls, R. Biedermann, H. Krautscheid,
M. Westerhausen, Z. Anorg. Allg. Chem. 633 (2007) 375e382.
[30] (a) H. Bürger, W. Sawodny, U. Wannagat, J. Organomet. Chem. 3 (1965)
113e120;
(b) A. Haaland, K. Hedberg, P.P. Power, Inorg. Chem. 23 (1984)
1972e1975;
(c) I.E. Gümrükcüoglü, J. Jeffery, M.F. Lappert, J.B. Pedley, A.K. Rai, J.
Organomet. Chem. 341 (1988) 53e62;
(d) M. Bochmann, G. Bwembya, K.J. Webb, Inorg. Synth. 31 (1997) 24;
[36] G.M. Sheldrick, Acta Crystallogr. A46 (1990) 467e473.
[37] G.M. Sheldrick, SHELXL-97 (Release 97-2). University of Göttingen, Germany,
1997.