From bis(Imidazol-2-yl)methanes to asymmetrically substituted bis(heterocyclo)methanides in metal coordination

Article abstract of DOI:10.1002/ejic.201601470

As an extension to the known symmetric bis(heterocyclmethanes containing two identical heterocycles, new asymmetric ligand systems, based on benzoxazole, benzothiazole and 1-methylbenzimidazole, are presented. Furthermore, the syntheses and reactions of two new symmetrically substituted methane derivatives, containing either 1-methylimidazole or 1-methylbenzimidazole, are discussed. In this context, firstly, (1-MeNCNC₂H₂)₂CH₂ and (1-MeNCNC₆H₄)₂CH₂, and secondly, (NCSC₆H₄)CH₂(NCOC₆H₄) and (NCSC₆H₄)CH₂(1-MeNCNC₆H₄), are used as parent compounds. They can be easily deprotonated at the central methylene bridge to generate a monoanionic structure akin to NacNac, so that the following complexes can be obtained: [Me₂Al{(1-MeNCNC₂H₂)₂CH}], [Me₂Al{(1-MeNCNC₆H₄)₂-CH}], [Me₂Al{(NCSC₆H₄)CH(NCOC₆H₄)}], [Me₂Ga{(NCSC₆H₄)CH-(NCOC₆H₄)}], [Me₂Al{(NCSC₆H₄)CH(1-MeNCNC₆H₄)}],[(THF)₂Li{(1-MeNCNC₆H₄)₂CH}] and [(diox)₂Li{(NCSC₆H₄)CH(1-MeNCNC₆H₄)}]. These compounds have been fully characterised by single-crystal X-ray diffraction (in the solid statand NMR spectroscopy (in solution).

Full text of DOI:10.1002/ejic.201601470

DOI: 10.1002/ejic.201601470
Full Paper
Bis(heterocyclo)methane Ligands
From Bis(imidazol-2-yl)methanes to Asymmetrically Substituted
Bis(heterocyclo)methanides in Metal Coordination
[a]
[a]
[a]
[a]
David-R. Dauer, Ingo Koehne, Regine Herbst-Irmer, and Dietmar Stalke*
Dedicated to Professor Dr. Evamarie Hey-Hawkins on the occasion of her 60th birthday
Abstract: As an extension to the known symmetric bis(hetero- the central methylene bridge to generate a monoanionic struc-
cyclo)methanes containing two identical heterocycles, new ture akin to NacNac, so that the following complexes can be
asymmetric ligand systems, based on benzoxazole, benzothi- obtained: [Me Al{(1-MeNCNC H ) CH}], [Me Al{(1-MeNCNC H ) -
2
2
2 2
2
6 4 2
azole and 1-methylbenzimidazole, are presented. Furthermore, CH}], [Me Al{(NCSC H )CH(NCOC H )}], [Me Ga{(NCSC H )CH-
2
6
4
6
4
2
6 4
the syntheses and reactions of two new symmetrically substi- (NCOC H )}], [Me Al{(NCSC H )CH(1-MeNCNC H )}], [(THF) Li{(1-
6
4
2
6
4
6
4
2
tuted methane derivatives, containing either 1-methylimidazole MeNCNC H ) CH}] and [(diox) Li{(NCSC H )CH(1-MeNCNC H )}].
6
4 2
2
6
4
6 4
or 1-methylbenzimidazole, are discussed. In this context, firstly, These compounds have been fully characterised by single-crystal
(
1-MeNCNC H ) CH and (1-MeNCNC H ) CH , and secondly, X-ray diffraction (in the solid state) and NMR spectroscopy (in
2 2 2 2 6 4 2 2
(
NCSC H )CH (NCOC H ) and (NCSC H )CH (1-MeNCNC H ), are solution).
6
4
2
6
4
6
4
2
6 4
used as parent compounds. They can be easily deprotonated at
Introduction
The first transition-metal complexes of the ꢀ-diketiminate (Nac-
[
1]
Nac, A; Scheme 1) ligand were mentioned in 1968, and in the
past two decades, many ꢀ-diketiminate structures containing
main-group metals have been synthesised and fully character-
[
2]
ised. These complexes embrace aluminium(III), gallium(III) and
indium(III) compounds. For aluminium, these range from alkyl-
to hydrido- to halido-substituted metal centres. Remarkably, the
dialkylaluminium ꢀ-diketiminates show catalytic activities simi-
[
3]
lar to those of transition-metal catalysts.
This has sparked interest, and the rising research activity in
the broad field of NacNac metal complexes has fuelled the fo-
cus on other promising ligand platforms, which are closely re-
lated to the ubiquitous ꢀ-diketiminato ligand. Most of them
mimic its chelating coordination behaviour, so that upon metal-
lation, six-membered metalloheterocycles with six delocalised
π-electrons are formed, in which two imine nitrogen atoms are
operating as Lewis donors to the metal centre. In this paper,
the two RC=NR′ moieties of the archetypical NacNac ligand are
replaced by fused heterocycles, which also possess an endo-
cyclic C=N imine moiety each, to retain the same coordination
abilities (B and C; Scheme 1).
Scheme 1. N,N-Chelating monoanionic ligands.
tioned oxazolines (D; Scheme 1). With a methylene bridge, the
[
5]
resulting dipyridylmethane and the corresponding methan-
ides were already investigated in the 1990s. As communicated
in previous publications, our group synthesised a series of lith-
ium and Group 13 metal complexes of bis(pyrid-2-yl)methanide,
and an associated structure–reactivity study was performed on
[
4]
[
6]
the basis of the results of X-ray diffraction experiments. Repre-
senting the Group 1 complexes, [(12-crown-4) Li][Li{(2-NC H ) -
2
5 4 2
Another ligand class is launched when two 2-pyridyl moie-
ties are introduced as side arms, instead of the above-men-
CH} ] can be highlighted as a solvent-separated ion-pair lithium
2
lithiate, or [(THF) Li{(2-NC H ) CH}] as the related contact ion
2
5 4 2
[
6a,6c]
pair, both solely yielding Li–N contacts.
These two lithiated
[
a] Institut für Anorganische Chemie, Georg-August-Universität Göttingen,
Tammannstraße 4, 37077 Göttingen, Germany
compounds were easily accessible through deprotonation reac-
tions of the parent dipyridylmethane with equimolar amounts
of nBuLi in either hexane or THF as the solvent. As an intermedi-
ate of that deprotonation, it was possible to isolate the complex
[{(2-NC H ) CH }Li{(2-NC H ) CH}] at –80 °C. In this complex,
E-mail: dstalke@chemie.uni-goettingen.de
www.uni-goettingen.de/de/53448.html
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201601470.
5
4 2
2
5 4 2
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Full Paper
only one half of the starting material is deprotonated, whereas trophile. The intermediate ketone derivative 1a is formed after
the other 0.5 equiv. remains unreacted to give a lithium com- cleavage of lithium ethanolate and an aqueous workup. To ob-
plex containing one monoanionic and one neutral ligand at the tain the methylene-bridged ligand 1, the intermediate 1a un-
[
6b]
same time.
dergoes a classical Wolff–Kishner reduction by reaction with
Additionally, various Group 13 metal complexes, like KOH and hydrazine hydrate at elevated temperatures (see
[
(
Me Al{(2-NC H ) CH}] and [Me Ga{(2-NC H ) CH}], where the Scheme 2). Compound 1 is isolated in a moderate, but suitable,
2
5
4 2
2
5 4 2
THF) Li unit is formally replaced by an Me Al or Me Ga moiety, overall yield of 43 %.
2
2
2
were prepared by adding AlMe Cl or GaMe Cl, respectively, to
2
2
[
6b,7]
the lithiated compound.
During the past three decades, the bis(heterocyclo)methane
ligand systems received little attention in coordination chemis-
[
8]
try and were almost forgotten. Although the synthesis of
bis(benzothiazol-2-yl)methane has been known for many
[
9]
years, only a few studies have been conducted concerning
this interesting ligand. Most of them have presented NMR spec-
Scheme 2. Synthesis of bis(1-methylimidazol-2-yl)methane 1.
[
10]
troscopic investigations.
the tautomerism of different alkyl-substituted bis(benzothiazol-
-yl)methane derivatives. Others have examined the benzox-
They have frequently emphasised
The related benzannulated species 2 was prepared by an-
other synthetic approach, as shown in Scheme 3: different from
2
1, in this case, the five-membered imidazole heterocycles have
azole- and benzimidazole-containing ligands and the derived
deprotonated species to estimate the specific charge demands
to be generated in the same step, as the coupling is accom-
plished through the methylene bridge. As appropriate starting
materials, N-methylphenylenediamine (2 equiv.) and diethyl
malonate (2 equiv.) were used. The malonic acid derivative
[
11]
of the heteroaryl substituents.
This classification has been
largely accomplished by validating 13C and N NMR spectro-
scopic shift/charge ratios, which have been determined for sev-
eral heteroaromatic and primary organic substituents in related
methylene-bridged species. Furthermore, it has been shown
that the bis(heterocyclo)methanes are appropriate ligands in
transition-metal complexation, because they can act either as
15
serves as a C building block, which enables the cyclocondensa-
3
tion reaction to give the imidazole moieties and to introduce
[
12]
the required CH bridge. The reaction is performed in half-con-
2
centrated aqueous hydrochloric acid (boiling) to facilitate the
ongoing cyclisation reaction, and so, the crude ligand 2 is iso-
lated by the addition of ammonia to initiate precipitation. Rig-
orous purification by column chromatography gives a yield of
–
[11a]
neutral ligands LH or as monoanionic ligands L .
In the first
2
+
case, a salt complex [M(LH) ] is obtained by adding divalent
2
II
transition-metal halides M X to the neutral ligand. In contrast,
addition of the corresponding metal acetates M (OAc) gives
2
2
6 %.
II
2
the deprotonation of the ligand, which yields disubstituted
metal complexes [ML2].
Results and Discussion
Scheme 3. Synthesis of bis(1-methylbenzimidazol-2-yl)-methane 2.
Synthesis of the Ligands
Apart from the symmetrically or homodisubstituted bis(hetero-
The crystal structures of 1 and its benzo-annulated derivative
cyclo)methane derivatives 1 and 2, the related ligand systems 2 were determined and are depicted in Figures 1 and 2, respec-
and 4, containing two different methylene-bridged heteroaro- tively, and structural data are given in Table 1. The N-methyl
3
matic side arms, are also part of the investigations within this groups and the corresponding imine nitrogen atoms on the
work. In those ligands, the intrinsic properties of two different other side of the specific heterocycle in both compounds are
benzannulated heteroaryls are combined. Presumably, these hy- quite differently orientated. While in 1 the methyl groups are
brid species exhibit new synergistic features in contrast to the pointing almost in opposite directions, this twisting is not as
comparable symmetrically substituted ligands, which might re- pronounced in 2. The main reason for this difference is the
sult in, for example, different metal coordination. In the follow- absence of the aromatic C perimeter. In 1, two hydrogen atoms
6
ing paragraphs, the syntheses of 1–4, as well as their derived next to the imine nitrogen atoms are available for hydrogen
Group 1 and Group 13 metal complexes 5–11, are described in bonding, but are missing in 2. They are prone to building up
a comparative approach. In principal, the structural characteri- three-dimensional networks of hydrogen bonds to neighbour-
sation was accomplished by applying single-crystal X-ray dif- ing imine nitrogen atoms due to the distinct polarisation of the
fraction experiments and in-depth NMR spectroscopic investi- C–H bonds adjacent to the endocyclic heteroatoms. Therefore,
gations in solution.
two different hydrogen bonds are present in the solid state of
On the basis of 1-methylimidazole, the chelating ligand sys- 1: one is rather strong and refers to the N2···H3 distance of
tem 1 was synthesised in a two-step procedure. The starting 2.468 Å and the corresponding N2···H3–C3 angle of 151.5°. The
material (2 equiv.) was lithiated with nBuLi and reacted in a second one seems to be less stable, due to the increased
one-pot synthesis with diethyl carbonate (1 equiv.) as an elec- N2···H4 distance of 2.649 Å, even though the corresponding
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N2···H4–C4 angle (156.0°) is slightly closer to favourable linear- with ortho-aminothio-phenol (1 equiv.) to give the mono-
[
13]
ity.
(benzothiazol)-substituted methane derivative (analogous to
the procedure depicted in Scheme 2) that provides one nitrile
group for the introduction of a second heterocycle. In the sec-
ond step, the corresponding ortho-substituted aniline derivative
(ortho-aminophenol or N-methylphenylenediamine) is added,
which undergoes a cyclocondensation reaction with 2-(benzo-
thiazol-2-yl)acetonitrile to give the second heterocycle. This re-
action takes place at elevated temperatures of 180 °C in the
presence of polyphosphoric acid (PPA) as the solvent under vig-
orous stirring for several hours. After aqueous workup and puri-
fication, the two different ligand systems 3 and 4, which differ
by only the benzoxazole or benzimidazole unit, can be ob-
tained in yields of 89 % and 48 %, respectively.
2 2 2 2
Figure 1. Molecular structure of (1-MeNCNC H ) CH (1). Anisotropic displace-
ment parameters are depicted at the 50 % probability level. C–H hydrogen
atoms are omitted for clarity, except those on the bridging carbon atom.
Structural data are given in Table 1.
As a side product in the synthesis of 3, the amide 2-(benzo-
thiazol-2-yl)-N-(2-hydroxyphenyl)acetamide 3a could also be
isolated by column chromatography. It is characterised by NMR
spectroscopy and single-crystal X-ray determination. Com-
pound 3a can be envisaged as an intermediate species that
occurs while generating the benzoxazole moiety in 3. After the
first nucleophilic attack of the amine nitrogen atom on the posi-
tive-polarised nitrile carbon atom, a primary imine is formed
temporarily, which is then attacked by the hydroxy group to
give a five-membered heterocycle. Because of insufficient reac-
tion time, the cyclisation reaction was not fully completed, so
that some amount of the primary imine remained, which was
hydrolysed by the aqueous workup to give 3a (Figure 3 and
Table 2).
6 4 2 2
Figure 2. Molecular structure of (1-MeNCNC H ) CH (2). Anisotropic displace-
ment parameters are depicted at the 50 % probability level. C–H hydrogen
atoms are omitted for clarity, except those on the bridging carbon atom.
Structural data are given in Table 1.
Table 1. Selected bond lengths [Å] and angles [°] for the ligands 1 and 2.
The asymmetrically substituted methane derivative 3 crystal-
lises in the triclinic space group P 1¯ , and the asymmetric unit
contains one complete molecule. Due to the very slight differ-
ences of the benzoxazole and benzothiazole moiety, there is no
preferred orientation of those residues in the solid state. How-
ever, this positional disorder could be deconvoluted, and the
1
2
C1–C1′, C8–C1′
C1–N2, C8–N4
C1–C1′–C1A/C8
1.5018(14)
1.3254(15)
111.97(13)
1.4984(15), 1.4911(14)
1.3154(14), 1.3166(15)
113.54(9)
The syntheses of the parent ligand systems 3 and 4 are de- structure was refined satisfactorily. This problem of the disor-
picted in Scheme 4. A two-step procedure was employed to dered heterocyclic substituents is omnipresent in the other de-
connect two different benzo-annulated heterocycles to a bridg- termined structures containing asymmetric ligands, but can be
ing methylene moiety. First, malonic dinitrile (1 equiv.) is treated tackled successfully (vide infra).
Scheme 4. Synthesis route to the asymmetric bis(heterocyclo)methanes 3 and 4.
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neighbouring parent ligands through the endocyclic imine
nitrogen atoms. Each oxygen atom acts as a double hydrogen
donor (O–H···O and O–H···N) and as a single hydrogen acceptor
from the previous water molecule (O···H–O) (see Figure 5).
6 4 2 6 4
Figure 3. Molecular structure of (NCSC H )CH (NCOC H ) (3). Anisotropic dis-
placement parameters are depicted at the 50 % probability level. Positional
disorder and C–H hydrogen atoms are omitted for clarity, except those on
the bridging carbon atom. Structural data are given in Table 2.
Table 2. Selected bond lengths [Å] and angles [°] for the ligand species 3 and
4. Due to the presence of two molecules in the asymmetric unit of 4, two
values are given.
3
4
C1–C1′
C1–N1
C1–C1′–C8
H1′···N3
H3′···N3A
H2′···O2
H4′B···O1
O1–H1′···N3
O2–H3′···N3A
O1–H2′···O2
O2B–H4′B···O1
1.5034(18)
1.2929(17)
112.87(11)
1.503(4); 1.516(4)
1.304(3); 1.296(3)
111.0(2); 110.2(2)
2.03(2)
2.06(2)
1.90(2)
1.92(3)
168(3)
173(4)
178(3)
Figure 5. Hydrogen-bonding pattern of (NCSC
Structural data are given in Table 2.
6 4 2 6 4
H )CH (1-Me-NCNC H ) (4).
–
–
–
–
–
–
–
–
Synthesis of the Metallated Species
The next synthetic step covers the various metallation reactions
that were applied to the discussed ligand systems. As depicted
in Scheme 5, the synthesis of the metallated species was ac-
complished by adding the neat organometallic reagent (AlMe3
163(5)
The same is valid for the imidazole and thiazole moiety in
the crystal structure of the related ligand 4, which carries a N-
methylbenzimidazole unit instead of the benzoxazole substitu-
ent in 3. Compound 4 crystallises in the chiral monoclinic space
or GaMe , 1.1 equiv.) or an organic solution of nBuLi to 1, 2, 3
3
and 4, which were either dissolved in toluene as a nonpolar
solvent or 1,4-dioxane as a polar donor solvent. After complete
addition, the reaction mixture was stirred for several hours over-
night to complete full conversion. The reaction of 1 and AlMe3
yields the methanide derivative 5. By using recrystallisation
from toluene, suitably diffracting crystals could be obtained,
which afforded the corresponding molecular structure shown
in Figure 6. A NacNac-like coordination motif is observed, in
which both imine nitrogen atoms act as electron donors to
chelate the implemented metal fragment after deprotonation.
In our earlier papers, benzo-annulated methanide and amide
derivatives could be obtained and structurally characterised,
though those complexes consist of a ligand backbone substi-
tuted twice with the same benzo-annulated heterocycle. For
the benzo-annulated 6, unfortunately no suitable crystals could
be grown due to the needle-like shape, which is responsible
for weak X-ray scattering. Nevertheless, this dimethylaluminium
species 6 was appropriately characterised in solution by using
group P2 , and two target molecules (together with two water
1
molecules) can be found in the asymmetric unit. These water
molecules originate from the aqueous ethanol solution used in
the recrystallisation process of the ligand and are incorporated
in an interesting hydrogen-bonding network (Figure 4 and
Table 2).
1
13
H and C NMR spectroscopy.
The aluminium compound 7, derived from the neutral ligand
system 3, crystallises in the monoclinic space group P2 /c, and
1
Figure 4. Molecular structure of one molecule of (NCSC
6 4 2
H )CH (1-Me-
NCNC ) (4). Anisotropic displacement parameters are depicted at the 50 %
6
H
4
the asymmetric unit contains one target molecule (Figure 7). As
in the parent ligand system 3, positional disorder also occurs in
probability level. Positional disorder and C–H hydrogen atoms are omitted
for clarity, except those on the bridging carbon atom. Structural data are
given in Table 2.
7, because in the solid state, no favoured orientation (neither
of the benzoxazole nor of the benzothiazole moiety) is attained.
The water molecules form a hydrogen-bonded chain in the Again, this disorder leads to a slight unreliability of the deter-
solid state, with every second molecule further linked to two mined bond lengths and angles within this structure, because
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Scheme 5. Metallation reactions of the bis(heterocyclo)methanes 1–4 (n.a.: not annulated).
of the two differently oriented molecules, which are rotated
by about 180° with respect to each other. Hence, no detailed
discussion concerning the bond lengths and angles within the
heterocycles will be given. Only the unambiguous values for
the bite angle, the N–M distances and the displacement of the
metal atom from the chelating C N plane are discussed for all
3
2
metallated species (see Table 3).
The distorted tetrahedral coordination geometry of Al1 in 7
results in averaged Al–N distances of 1.924 Å, a bite angle of
3
+
9
3.43° and a slight dislocation of the Al cation from the che-
lating C N plane of about 0.053 Å. In comparison with previous
3
2
work on related bis(heterocyclo)methanide ligand systems like
–
–
[
(NCSC H ) CH] or [(NCOC H ) CH] , which contain two identi-
6 4 2 6 4 2
cal benzoxazole or benzothiazole substituents, respectively, the
obtained values for the dimethylaluminium species range be-
2 2 2 2
Figure 6. Molecular structure of [Me Al{(1-MeNCNC H ) CH}] (5). Anisotropic
displacement parameters are depicted at the 50 % probability level. C–H
hydrogen atoms are omitted for clarity, except for that on the bridging
carbon atom.
[
4a]
tween those of the complexes [Me
Al{(NCOC H )
2 6 4
CH}] [Al–N
2
[
4a]
1
.91(20) Å; N–Al–N 91.76(9)°] and [Me Al{(NCSC H ) CH}] [Al–
2 6 4 2
N 1.92(14) Å; N–Al–N 94.78(6)°], but notably, 7 is closer to the
bis(benzothiazol-2-yl)methanide derivative.
The crystal structure of the second dimethylaluminium-con-
taining complex 9, could be refined successfully, despite the
positional disorder. Again, the metal cation is coordinated ex-
clusively by the ring-imine nitrogen donor atoms and the two
methyl groups in a distorted tetrahedral fashion. The disloca-
3
+
tion of the Al cation from the chelating C N plane, compared
3
2
with 7, is five times larger. The parent ligand system 4 is a
hybrid between the bis(benzothiazol-2-yl)methane and the
bis(1-methylbenzimidazol-2-yl)methane ligand 2. Unfortunately,
the solid-state structure of the corresponding dimethylalumin-
ium complex [Me Al{(1-MeNCNC H ) CH}] (6) could not be ob-
2
6 4 2
2 6 4 6 4
Figure 7. Molecular structure of [Me Al{(NCSC H )CH(NCO C H )}] (7). Aniso-
tained, due to hampered crystallisation. However, the values of
tropic displacement parameters are depicted at the 50 % probability level.
Positional disorder and C–H hydrogen atoms are omitted for clarity except
for that on the bridging carbon atom. Structural data are given in Table 3.
[
4a]
[Me Al{(NCSC H ) CH}] [Al–N 1.9233(14) Å; N–Al–N 94.79(6)°]
2
6 4 2
compare with those expected for 9.
Table 3. Selected bond lengths and angles for the metallated species 7–9 and 11.
7
8
9
11
M–N (mean) [Å]
1.924
1.993
1.911
1.954
N–M–N [°]
Deviation of M from the C N plane [Å]
3 2
93.43(11)
0.053(3)
91.3(3)
0.289(7)
94.3(3)
0.240(5)
97.0(2)
0.018(12)
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In addition to the aluminium complexes, the higher homo- whereas that angle is much wider in the homodisubstituted
logue, containing the GaMe moiety in 8, and the lithium com- imidazole compound 10 (mean 111.5°). The observed de-
2
plexes 10 and 11 could be investigated by X-ray diffraction creased O1–Li1–O2 angle and Li···ligand plane distance in 11
experiments (Figures 8 and 9).
are presumably caused by the higher steric demand of the diox-
ane molecules and the resulting coordination polymer in 11,
which reduces that angle and forces the lithium cation more
into the plane of the metalloheterocycle.
The comparison with the literature-known lithiated bis(pyrid-
[
6a]
2
-yl)methanide species [(THF) Li{(2-NC H ) CH}] also quarries
2 5 4 2
some similarities. The average Li–N distance is 1.97 Å and the
bite angle is 96.4°, while the O1–Li1–O2 angle involving the
[6a,6c,14]
donating THF molecules is 98.9°.
Furthermore, the lithium
cation is almost ideally placed within the plane of the metallo-
heterocycle, also seen for the asymmetrically substituted meth-
anide compound 11.
NMR Spectroscopic Investigations
1
The H NMR spectrum of the dimethylaluminium complex 7 is
shown in Figure 10. Besides the two singlets at δ = –0.45 and
2 6 4 2
Figure 8. Molecular structure of [(THF) Li{(1-MeNCNC H ) CH}] (10). Aniso-
5
.76 ppm for the methyl groups on the aluminium atom and
tropic displacement parameters are depicted at the 50 % probability level.
Positional disorder and C–H hydrogen atoms are omitted for clarity except
for that on the bridging carbon atom.
the remaining proton on the bridging carbon atom, respec-
tively, the multiplets in the aromatic region of the spectrum
show a distinct coupling pattern. Due to the fact that both side
arms only differ by the chalcogen ring atom (oxazole or thiaz-
ole), the hydrogen atoms on the annulated benzene perimeters
exhibit slightly different chemical shifts. The reasonable resolu-
tion of the recorded spectrum allows the determination of the
underlying coupling constants, which can be derived from the
observed multiplets. Each aromatic proton couples to three
other protons of the corresponding heterocycle, resulting in a
ddd coupling pattern. With the terminal hydrogen atoms H3,
3
H6 or H10, H13, the relatively large J coupling constant to-
4
wards the ortho-protons, as well as the smaller J coupling con-
5
stants for the meta-protons and J coupling constants for the
para-protons, could be identified. The other protons H4, H5 or
3
H11, H12 show two large J couplings to both neighbouring
4
protons in the ortho-position and a smaller J coupling towards
the remaining proton in the meta-position. By the application
of these values, and with the assistance of other 2D NMR spec-
1
13
troscopic experiments like H, C HSQC and HMBC, it was pos-
sible to properly assign the observed signals in the aromatic
region. The exact assignment of these sometimes partially or
completely superimposed signals is magnified in the upper part
of Figure 10. Notably, the resonance signal of the terminal
2 6 4 6 4
Figure 9. Molecular structure of [(diox) Li{(NCSC H )CH(1-MeNCNC H )}] (11).
Anisotropic displacement parameters are depicted at the 50 % probability
level. Positional disorder and C–H hydrogen atoms are omitted for clarity.
Structural data are given in Table 3.
Compound 8 almost perfectly matches the values found in hydrogen atom H3 is the most downfield-shifted (δ =
[
4a]
[
Me Ga{(NCOC H ) CH}] [Ga–N 1.996(20) Å; N–Ga–N 89.2(2)°] 7.69 ppm), whereas that of the neighbouring H4 is the most
2 6 4 2
[
4a]
and [Me Ga{(NCSC H ) CH}]
[Ga–N 1.994(13) Å; N–Ga–N upfield-shifted (δ = 7.19 ppm) with respect to the considered
2.99(8)°] for either side of the substituents. The lithiated spe- aromatic area. This fact can also be observed in the recorded
2
6 4 2
9
1
cies 11, also derived from the asymmetrically substituted ligand
, compares nicely with compound 10, a similarly bis(hetero-
H NMR spectra of the metallated species 6, 8 and 9 (vide infra).
1
4
The resulting H NMR spectrum of 8, in which the aluminium
cyclo)methanide-substituted complex. The main difference be- cation is replaced by its higher congener gallium, is displayed
tween those structures is the donating solvent (THF in 10 and in Figure 11; it shows certain similarities to the spectrum of the
dioxane in 11). The determined N1–Li1–N3 bite angle of 97.0° above-mentioned 7. There is also a singlet at δ = –0.03 ppm
and the C1–C1′–C8 backbone angle of 124.6° in 11 are quite for the dimethylgallium moiety and another one for the depro-
similar to the related values in [(THF) Li{(1-MeNCNC H ) CH}] tonated methylene bridge at δ = 5.58 ppm. The region of the
2
6 4 2
(
10; 96.9° and 124.3°). The O1–Li1–O2 angle is 99.6° in 11, aromatic protons covers a range similar to that for 6 (δ = 7.65–
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Figure 10. 1H NMR spectrum of 7 (500 MHz, [D
]THF, room temperature; solvent signals are highlighted with *).
8
Figure 11. 1H NMR spectrum of 8 (400 MHz, [D
]THF, room temperature; solvent signals are highlighted with *).
8
7.13 ppm), which again is determined by the chemical shifts of pronounced in the gallium species 8 than in the aluminium
the protons H3 and H4. In analogy to the assignment in 7, the complex 7. With respect to the parent CH bridge or the CH
2
observed signals could be matched to their correct positions linker, respectively, upon deprotonation of that position, the
(
see magnification in Figure 11), because – in this case – the corresponding resonance signal in both cases is significantly
1
13
resolution and separation of the signals is even more advanta- shifted downfield in the H and C NMR spectroscopic experi-
geous for gaining reliable coupling constants. ments. Compound 3 resonates at δ = 4.85 ppm/34.38 ppm for
For a better comparison of the chemical shifts regarding the H1′ and the connected C1′, while metallation results in chemi-
parent ligand 3 and the two Group 13 metal complexes 7 and cal shifts of δ = 5.76 ppm/71.35 ppm in 7 and 5.58 ppm/
1
8
, Figure 12 shows the H NMR spectra (focussed on the signals 70.09 ppm in 8.
in the aromatic region). Deprotonation and subsequent metalla-
To emphasise the differences in the spectra of the aluminium
tion of 3 shifts the resonance signals of the aromatic protons compound 7 and the gallium compound 8, the signals of the
significantly towards higher field, because the generated lone four terminal protons H3, H6 and H10, H13 have to be high-
pair and negative charge of the whole ligand backbone causes lighted. The protons H6 and H13 seem to be most sensitive to
a higher electronic shielding of the protons. This effect is more the change of the coordinated metal cation, because they are
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1
Figure 12. H NMR spectra of the parent ligand system 3 (in green), the aluminium complex 7 (in blue) and the gallium complex 8 (in red). For clarity reasons,
only the aromatic region is displayed.
pointing directly towards the chelated metal centre, whereas H13. Due to the larger ionic radius and more closed electron
3
+
3+
H3 and H10 are pointing to the opposite direction and are shells of the Ga cation, in contrast to the Al cation, these
therefore less affected by the metal atom. In the parent ligand two protons experience a higher electronic shielding in the case
3
, the protons H3 and H6 show quite a similar chemical shift, of 8 than that of 7, causing the corresponding resonances to
but after metal coordination, the signals of those protons are be shifted more upfield.
influenced in a different manner. In 7 and 8, the change in
Similar observations can be found in the second ligand sys-
the chemical shifts referring to the protonated ligand is more tem 4, in which the benzoxazole moiety of 3 is formally re-
pronounced for the inwardly pointing protons H6 (7: Δδ = placed by an N-methylbenzimidazole residue. With this ligand,
0.37 ppm; 8: Δδ = 0.56 ppm) and H13 (7: Δδ = 0.27 ppm; 8: two metallated species could also be synthesised, but in con-
Δδ = 0.40 ppm) than for the outwardly arranged ones H3 (7: trast to the afore-mentioned ligand system, here, a dimethyl-
Δδ = 0.26 ppm; 8: Δδ = 0.30 ppm) and H10 (7: Δδ = 0.13 ppm; aluminium-containing complex 9 and a lithiated compound 11
8
: Δδ = 0.17 ppm). On the basis of these differences, it can be donated by the Lewis base 1,4-dioxane are compared. The re-
1
assumed that the size of the coordinated metal ion has quite a corded H NMR spectra of those three compounds are dis-
significant impact on the chemical shifts of the protons H6 and played in Figure 13. The differences of the resonance signals of
Figure 13. 1H NMR spectra of the parent ligand system 4 and the metallated species 9 and 11; for clarity reasons, only the aromatic region is displayed.
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H6 (9: Δδ = 0.49 ppm; 11: Δδ = 0.83 ppm) and H13 (9: Δδ = Ligand Syntheses
.13 ppm; 11: Δδ = 0.48 ppm) are significantly larger than those
of H3 (9: Δδ = 0.36 ppm; 11: Δδ = 0.58 ppm) and H10 (9: Δδ = 46.5 mL, 100 mmol, 2.0 equiv.) was added to a solution of 1-meth-
.05 ppm; 11: Δδ = 0.39 ppm). These results correlate with the ylimidazole (8.21 g, 7.00 mL, 100 mmol, 2.0 equiv.) in THF (75 mL)
0
(
1-MeNCNC H ) CO (1a): A solution of nBuLi (2.15
M in hexane,
2
2 2
0
observations made before that the protons on the side of the at –60 °C over a period of 30 min. After an additional 30 min of
coordinated metal ion interact more with the coordinated frag-
ment. Furthermore, it is evident that the changes of the ob-
served chemical shifts are higher in the case of the lithiated
species 11. This observation was expected due to the increas-
ing ionic radii of the involved metal cations (0.39 Å for Al ,
0
nation.
stirring at this temperature, diethyl carbonate (5.91 g, 6.1 mL,
50 mmol, 1.0 equiv.) was added dropwise to the reaction mixture.
Afterwards, the suspension was warmed to room temperature,
stirred overnight, and then demineralised water (150 mL) was
added to quench the reaction. The resulting suspension was ex-
tracted with dichloromethane (6 × 50 mL), the combined organic
3
+
3
+
+
.47 Å for Ga and 0.59 Å for Li ), with each in fourfold coordi-
layers were dried with MgSO , and the remaining solvent was re-
4
[
14]
+
As in 7, the cationic radius of Li is larger than that
moved under reduced pressure. Colourless block-shaped crystals
3
+
of Al , and therefore, the signals of the inner protons H6 and were obtained in 47 % yield (4.44 g, 23.3 mmol) upon recrystallisa-
H13 are shifted more upfield in lithium complex 11 than in 9. tion from acetone. C H N O (190.2): calcd. C 56.83, H 5.30, N 29.46;
9
10 4
1
In contrast to 7 and 8, the observed coupling pattern of 9 is found C 56.55, H 5.20, N 29.70. H NMR (300 MHz, [D
]DMSO): δ =
6
3
3
7
.52 (d, J = 0.8 Hz, 2 H, H2), 7.12 (d, J = 0.9 Hz, 2 H, H3), 3.89
partially more complex. The protons on the benzimidazole moi-
ety do not show distinct ddd structures, but rather signals of
higher orders, so that the coupling constants are not so easily
accessible. However, the spectrum at the bottom of Figure 13
again shows a first-order splitting pattern for both moieties
H,H
H,H
13
1
(
s, 6 H, H4) ppm. C{ H} NMR (75 MHz, [D ]DMSO): δ = 174.25 (s, 1
C, C1′), 142.97 (s, 2 C, C1), 129.05 (s, 2 C, C3), 127.25 (s, 2 C, C2),
5.16 (s, 2 C, C4) ppm. EI-MS: m/z (%) = 190 (100) [M] , 175 (8) [M
Me] , 161 (80) [M – 2 Me] , 109 (97) [M – 1-MeNCNC H ] .
6
+
3
–
+
+
+
2
2
(
1-MeNCNC H ) CH (1): Hydrazine hydrate (35 % aqueous solu-
2 2 2 2
(
benzothiazole and benzimidazole) due to the chemical-shift
tion, 48.3 mL, 540 mmol, 34.0 equiv.) was added to a mixture of 1a
3.00 g, 15.8 mmol, 1.0 equiv.) and KOH (3.00 g, 53.5 mmol,
.4 equiv.), and the reaction solution was stirred at 150 °C for 3 h.
difference between the coupled protons being much larger
than the coupling constant.
(
3
After cooling to room temperature, the resulting solution was ex-
tracted with dichloromethane (3 × 40 mL), and the combined or-
ganic layers were washed with demineralised water (2 × 15 mL) to
Conclusion
Compounds 1–4 were successfully introduced as new non-an- remove the remaining hydrazine. The organic layers were dried with
MgSO , and the residual solvent was removed under reduced pres-
nulated and benzo-annulated bis(heterocyclo)methane ligands,
respectively. In contrast to species 1 and 2, which are examples
of homodisubstituted methanes, the ligand systems 3 and 4
exhibit two different benzo-annulated heterocycles connected
to the bridging methylene moiety. All ligand systems were suc-
cessfully used to synthesise new Group 13 (Al, Ga) (5–9) and/or
Group 1 (Li) (10 and 11) metal complexes through concerted
deprotonation metallation reactions. All presented compounds (23) [M
were fully characterised and extensively studied by single-crys- MeNCNC
tal X-ray structure determination and solution NMR spectro-
4
sure. A pale-brown powder was obtained in 98 % yield (2.72 g,
1
5.4 mmol). C H N (176.2): calcd. C 61.34, H 6.86, N 31.79; found
9 12 4
1
C 60.35, H 6.60, N 31.45. H NMR (300 MHz, [D ]THF): δ = 6.79 (d,
8
3
3
JH,H = 1.1 Hz, 2 H, H2), 6.71 (d, J = 1.2 Hz, 2 H, H3), 4.12 (s, 6
H,H
1
13
H, H1′), 3.65 (s, 6 H, H4) ppm. C{ H} NMR (75 MHz, [D ]THF): δ =
8
1
44.85 (s, 1 C, C1), 127.70 (s, 2 C, C3), 121.74 (s, 2 C, C2), 33.01 (s, 2
+
C, C4), 27.06 (s, 1 C, C1′) ppm. EI-MS: m/z (%) = 176 (100) [M] , 161
+
+
–
H
Me] , 95 (52) [M – 1-MeNCNC H ] , 81(10) [1-
] .
2 2
+
2
2
(
1-MeNCNC H ) CH (2): A solution of N-methyl-ortho-phenylene-
6 4 2 2
scopic techniques.
diamine (13.4 g, 12.5 mL, 110 mmol, 2.0 equiv.) and diethyl malon-
ate (8.81 g, 8.3 mL, 55 mmol, 1.0 equiv.) in aqueous HCl (6
50 mL) was heated to 120 °C and stirred for 2 d. Afterwards, the
volume of the reaction mixture was reduced to half of its volume,
and the pH value was adjusted to 10 by stepwise addition of aque-
ous ammonia solution (25 %). The resulting precipitate was filtered
off and purified by column chromatography [acetone/Et O (1:1) +
HNEt2 (5 %)] and by recrystallisation from acetone. Compound 2
was isolated as pale-pink crystals (2.22 g, 8.0 mmol, 26 %). C17H N
M,
1
Experimental Section
Procedures: All manipulations were carried out under N or Ar by
2
using Schlenk techniques.[
15]
All solvents used within the metalla-
2
tion reactions were distilled from Na or K before use. The starting
materials were purchased commercially and were used as received.
1
7
13
15
27
16 4
H, Li, C, N and Al NMR spectroscopic data were recorded
(
2
276.3): calcd. C 73.89, H 5.84, N 20.27; found C 73.00, H 5.73, N
0.48. H NMR (300 MHz, [D ]THF): δ = 7.58–7.53 (m, 2 H, H3), 7.35–
with a Bruker Avance 500 MHz, a Bruker Avance 400 MHz or a
Bruker Avance 300 MHz spectrometer, and they were referenced to
the deuterated solvent ([D ]THF or [D ]DMSO).
ses (C, H, N and S) were carried out with a Vario EL3 at the Mikro-
analytisches Labor, Institut für Anorganische Chemie, University of
Göttingen. Several compounds contain lattice solvent, as confirmed
by X-ray diffraction data, because the crystals were grown in the
mother liquor. As a result of drying these samples, the whole
amount of incorporated lattice solvent could not be removed, so
1
8
[16]
7.30 (m, 2 H, H6), 7.18–7.07 (m, 4 H, H4 + H5), 4.63 (s, 2 H, H1′),
Elemental analy-
8
6
.92 (s, 6 H, H8) ppm. 13C{ H} NMR (75 MHz, [D ]THF): δ = 150.90
1
3
8
(s, 1 C, C1), 144.03 (s, 2 C, C7), 137.45 (s, 2 C, C2), 122.71 (s, 2 C, C4),
122.11 (s, 2 C, C5), 120.04 (s, 2 C, C6), 110.02 (s, 2 C, C3), 30.43 (s, 2
+
C, C8), 28.32 (s, 1 C, C1′) ppm. EI-MS: m/z (%) = 276 (100) [M] ,
+
+
261 (12) [M – Me] , 145 (36) [M – 1-MeNCNC H ] , 131(14) [1-
6 4
+
MeNCNC H ] .
6
4
that no solvent-free compounds were obtained. The remaining sol- (NCSC H )CH (NCOC H ) (3): 2-(Benzothiazol-2-yl)acetonitrile
6
4
2
6 4
vent led to slightly enhanced values in the elemental analyses for
C and H. All EI mass spectra (70 eV) were recorded with a Finnigan
MAT95.
(12.86 g, 74.0 mmol, 1.00 equiv.), 2-aminophenol (8.08 g, 74.0 mmol,
1.00 equiv.) and polyphosphoric acid (80 %, ca. 250 mL) were
heated to 185 °C while being vigorously stirred with a sealed preci-
Eur. J. Inorg. Chem. 2017, 1966–1978
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1974
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+
sion glass (KPG) stirrer under an inert gas for an additional 7 h
to complete the cyclisation reaction. Afterwards, it was cooled to
approximately 80 °C, then poured onto ice and stirred overnight.
The resulting brown solid was filtered, washed several times with
demineralised water (6 × 100 mL) and saturated aqueous NaHCO3
solution (3 × 30 mL) until pH neutrality was achieved. The desired
product 3 was obtained as a brown powder (17.5 g, 65.7 mmol,
(s, Al1) ppm. EI-MS: m/z (%) = 176 (100) [M – AlMe ] , 95 (77) [M –
2
+
+
AlMe – 1-MeNCNC H ] , 81 (18) [1-MeNCNC H ] .
2
2
2
2 2
[
Me Al{(1-MeNCNC H ) CH}] (6): Pure AlMe (0.23 mL, 165 mg,
.40 mmol, 1.2 equiv.) was slowly added to a solution of 2 (352 mg,
.00 mmol, 1.0 equiv.) in toluene (40 mL) at room temperature, and
the clear reaction mixture was stirred overnight. Afterwards, the
volume of the solution was reduced to a few mL, and the resulting
concentrated solution was stored at –32 °C in a freezer. The crystals
thus formed were filtered, washed twice with precooled toluene
and finally dried in vacuo. Colourless, needle-shaped crystals were
obtained in 44 % yield (72 mg, 0.22 mmol). 1H NMR (300 MHz,
2 6 4 2 3
2
2
8
9 %). C H N OS (266.32): calcd. C 67.65, H 3.78, N 10.52, S 12.04;
15 10 2
1
found C 67.42, H 3.78, N 10.39, S 12.29. H NMR (300 MHz, [D ]THF):
8
δ = 7.99–7.90 (m, 2 H, H3 + H6), 7.73–7.65 (m, 1 H, H13), 7.59–7.51
(
+
m, 1 H, H10), 7.49–7.41 (m, 1 H, H5), 7.40–7.28 (m, 3 H, H4 + H11
1
3
1
H12), 4.85 (s, 2 H, H1′) ppm. C{ H} NMR (75 MHz, [D ]THF): δ =
8
[
D ]THF): δ = 7.35–7.28 (m, 2 H, H6), 7.18–7.11 (m, 2 H, H3), 7.10–
8
1
1
1
64.62 (s, 1 C, C1), 163.00 (s, 1 C, C8), 154.37 (s, 1 C, C7), 152.27 (s,
C, C9), 142.69 (s, 1 C, C14), 137.06 (s, 1 C, C2), 126.82 (s, 1 C, C5),
26.00 (s, 1 C, C4), 125.86 (s, 1 C, C11), 125.15 (s, 1 C, C12), 123.93
7
6
.02 (m, 4 H, H3 + H4), 4.72 (s, 1 H, H1′), 3.57 (s, 6 H, H15), –0.57 (s,
H, H1M) ppm. 13C{ H} NMR (75 MHz, [D ]THF): δ = 156.98 (s, 2 C,
1
8
C1), 139.32 (s, 2 C, C7), 135.98 (s, 2 C, C2), 122.33 (s, 2 C, C5), 121.47
s, 2 C, C4), 112.58 (s, 2 C, C6), 108.07 (s, 2 C, C3), 55.41 (s, 1 C, C1′),
9.09 (s, 2 C, C15), –9.85 (s, 2 C, C1M) ppm.
(
s, 1 C, C6), 122.47 (s, 1 C, C3), 120.83 (s, 1 C, C13), 111.29 (s, 1 C,
(
2
1
5
1
C10), 34.38 (s, 1 C, C1′) ppm. N{ H} NMR (30 MHz, [D ]THF): δ =
–
1
8
+
64.40 (s, N1), –132.37 (s, N2) ppm. EI-MS: m/z (%) = 266 (100) [M] ,
+
48 (15) [M – NCOC H ] .
[Me Al{(NCSC H )CH(NCOC H )}] (7): A slight excess of pure Al-
2 6 4 6 4
6
4
Me (0.22 mL, 158 mg, 2.20 mmol, 1.1 equiv.) was slowly added to
3
(
NCSC H )CH (1-MeNCNC H ) (4): 2-(Benzothiazol-2-yl)acetonitrile
6 4 2 6 4
a solution of 3 (0.533 g, 2.00 mmol, 1.0 equiv.) in toluene (40 mL)
at 0 °C. The reaction mixture was stirred overnight and warmed to
room temperature. The reaction mixture afforded a clear solution.
Afterwards, the volume of the solution was reduced to a few mL,
and the resulting concentrated solution was stored at –32 °C in
a freezer. Crystals suitable for X-ray diffraction experiments were
obtained overnight. The crystals thus formed were filtered, washed
twice with precooled toluene and finally dried in vacuo. Compound
(
(
(
2.82 g, 17.6 mmol, 1.00 equiv.), N-methyl-ortho-phenylenediamine
2.16 g, 2.0 mL, 17.6 mmol, 1.00 equiv.) and polyphosphoric acid
80 %, ca. 40 mL) were heated to 185 °C while being vigorously
stirred with a sealed precision glass (KPG) stirrer for 7 h. Afterwards,
it was cooled to approximately 80 °C, then poured onto ice and
stirred for an additional hour1 h. The resulting green solid was fil-
tered, washed twice with demineralised water (2 × 50 mL) and satu-
rated aqueous NaHCO solution (3 × 50 mL) until pH neutrality was
achieved. Compound 3 was obtained as a green powder (2.35 g,
3
6
was isolated in the form of orange crystals (455 mg, 1.41 mmol,
7
1 %). C H AlN OS (322.36): calcd. C 63.34, H 4.69, N 8.69, S 9.95;
17
15
2
8
.4 mmol, 48 %), and crystals suitable for X-ray diffraction experi-
1
found C 63.26, H 4.78, N 8.54, S 9.77. H NMR (500 MHz, [D ]THF):
8
ments were grown from ethanol. C H N S (279.36): calcd. C 68.79,
H 4.69, N 15.04, S 11.48; found C 67.23, H 4.76, N 14.72, S 11.71. H
NMR (300 MHz, [D ]THF): δ = 7.92 (d, J = 8.1 Hz, 2 H, H6), 7.88
1
6 13 3
δ = 7.69 (ddd, JH,H = 7.9, 1.3, 0.6 Hz, 1 H, H3), 7.58 (ddd, JH,H = 8.2,
1
1
(
1
.0, 0.6 Hz, 1 H, H6), 7.42 (ddd, JH,H = 8.0, 1.1, 0.6 Hz, 1 H, H10), 7.42
ddd, JH,H = 7.9, 1.2, 0.6 Hz, 1 H, H13), 7.39 (ddd, JH,H = 8.2, 7.3,
.3 Hz, 1 H, H5), 7.29 (td, JH,H = 7.7, 1.1 Hz, 1 H, H12), 7.20 (ddd,
3
8
H,H
3
(d, J = 7.9 Hz, 2 H, H3), 7.64–7.56 (m, 1 H, H13), 7.45–7.29 (m, 3
H,H
H, H4 + H5 + H10), 7.22–7.11 (m, 2 H, H11 + H12), 4.80 (s, 2 H, H1′
JH,H = 7.9, 7.6, 1.2 Hz, 1 H, H11), 7.19 (ddd, JH,H = 7.9, 7.4, 1.0 Hz, 1
1
3
1
), 3.83 (s, 3 H, H15) ppm. C{ H} NMR (75 MHz, [D ]THF): δ = 167.44
8
H, H4), 5.76 (s, 1 H, H1′), –0.45 (s, 6 H, H1M) ppm. 13C{ H} NMR
1
(s, 1 C, C1), 154.39 (s, 1 C, C7), 151.16 (s, 1 C, C8), 144.17 (s, 1 C,
(
(
75 MHz, [D ]THF): δ = 170.57 (s, 1 C, C8), 166.62 (s, 1 C, C1), 149.08
s, 1 C, C9), 149.05 (s, 1 C, C7), 137.74 (s, 1 C, C14), 129.55 (s, 1 C,
8
C14), 137.41 (s, 1 C, C9), 137.07 (s, 1 C, C2), 126.64 (s, 1 C, C5), 125.80
s, 1 C, C4), 123.69 (s, 1 C, C6), 122.88 (s, 1 C, C3), 122.45 (s, 1 C,
C11), 122.25 (s, 1 C, C12), 120.33 (s, 1 C, C13), 110.10 (s, 1 C, C10),
(
C2), 127.55 (s, 1 C, C5), 125.79 (s, 1 C, C12), 124.07 (s, 1 C, C4/C11),
23.87 (s, 1 C, C4/C11), 122.52 (s, 1 C, C3), 115.93 (s, 1 C, C6), 113.70
s, 1 C, C13), 110.74 (s, 1 C, C10), 71.35 (s, 1 C, C1′), –9.78 (s, 2 C,
1
1
5
1
3
3.76 (s, 1 C, C1′), 30.33 (s, 1 C, C15) ppm. N{ H} NMR (30 MHz,
(
[D ]THF): δ = –67.71 (s, N1), –132.50 (s, N2), –240.63 (s, N3) ppm.
8
15
1
C1M) ppm. N{ H} NMR (50 MHz, [D ]THF): δ = –202.16 (s, N1),
–
Al1) ppm. EI-MS: m/z (%) = 266 (100) [M – AlMe ] , 148 (24) [M –
AlMe – NCOC H ] .
+
+
8
EI-MS: m/z (%) = 279 (100) [M] , 149 (11) [M – 1-MeNCNC H ] , 131
6
4
228.74 (s, N2) ppm. 27Al{ H} NMR (78 MHz, [D ]THF): δ = 151 (s,
1
+
8
(36) [1-MeNCNC H ] .
6 4
+
2
+
Metallation Reactions
2
6 4
[
Me Al{(1-MeNCNC H ) CH}] (5): Pure AlMe (0.23 mL, 165 mg,
[Me Ga{(NCSC H )CH(NCOC H )}] (8): Pure GaMe3 (0.11 mL,
2 6 4 6 4
2
2
2 2
3
2
2
.40 mmol, 1.2 equiv.) was slowly added to a solution of 1 (352 mg,
.00 mmol, 1.0 equiv.) in toluene (40 mL) at room temperature, and (0.266 g, 1.00 mmol, 1.0 equiv.) in toluene (20 mL) at 0 °C. The
reaction mixture was stirred overnight and warmed to room tem-
volume of the solution was reduced to a few mL, and the resulting perature. Afterwards, the volume of the solution was reduced to a
concentrated solution was stored at –32 °C in a freezer. Crystals few mL, and the resulting concentrated solution was stored at
suitable for X-ray diffraction experiments were obtained overnight. –32 °C in a freezer. Crystals suitable for X-ray diffraction experiments
126 mg,1.10 mmol, 1.1 equiv.) was slowly added to a solution of 3
the clear reaction mixture was stirred overnight. Afterwards, the
The crystals thus formed were filtered, washed twice with precooled
toluene and finally dried in vacuo. Colourless, block-shaped crystals
were obtained in 20 % yield (92 mg, 0.40 mmol). C H AlN
were obtained overnight. The crystals thus formed were filtered,
washed twice with precooled toluene and finally dried in vacuo.
Compound 7 was isolated in the form of dark-orange crystals
(184 mg, 0.50 mmol, 50 %). C H GaN OS (365.10): calcd. C 55.92,
1
1
17
4
(
232.27): calcd. C 56.88, H 7.38, N 24.12; found C 56.52, H 7.76, N
17
15
2
1
1
2
4.36. H NMR (400 MHz, [D ]THF): δ = 6.54 (m, 2 H, H2), 6.52 (m, 2
H 4.14, N 7.67, S 8.78; found C 55.35, H 4.27, N 7.49, S 8.61. H NMR
8
H, H3), 4.06 (s, 1 H, H1′), 3.28 (s, 6 H, H7), –0.85 (s, 6 H, H1M) ppm. (400 MHz, [D ]THF): δ = 7.65 (ddd, J = 7.9, 1.2, 0.6 Hz, 1 H, H3),
8
H,H
1
3
1
C{ H} NMR (75 MHz, [D ]THF): δ = 153.92 (s, 2 C, C1), 118.32 (s, 2
7.39 (ddd, JH,H = 8.2, 1.4, 0.6 Hz, 1 H, H6), 7.38 (ddd, JH,H = 8.0, 1.1,
0.6 Hz, 1 H, H10), 7.34 (ddd, JH,H = 8.2, 7.1, 1.2 Hz, 1 H, H5), 7.29
(ddd, JH,H = 7.8, 1.4, 0.6 Hz, 1 H, H13), 7.24 (ddd, JH,H = 7.8, 7.4,
8
C, C3), 117.45 (s, 2 C, C2), 50.46 (s, 1 C, C1′), 32.07 (s, 2 C, C7), –9.59
s, 2 C, C1M) ppm. 15N{ H} NMR (50 MHz, [D ]THF): δ = –222.08 (s,
1
(
8
2
7
1
N2), –255.73 (s, N1) ppm. Al{ H} NMR (78 MHz, [D ]THF): δ = 149 1.1 Hz, 1 H, H12), 7.15 (ddd, JH,H = 8.0, 7.4, 1.4 Hz, 1 H, H11), 7.13
8
Eur. J. Inorg. Chem. 2017, 1966–1978
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1975
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
(
ddd, JH,H = 7.9, 7.1, 1.4 Hz, 1 H, H4), 5.58 (s, 1 H, H1′), –0.03 (s, 6 H,
reduced to a few mL, and the resulting concentrated solution was
13
1
H1M) ppm. C{ H} NMR (75 MHz, [D ]THF): δ = 169.13 (s, 1 C, C8), stored at –32 °C in a freezer. Crystals suitable for X-ray diffraction
8
1
1
1
1
1
65.71 (s, 1 C, C1), 149.62 (s, 1 C, C7), 148.93 (s, 1 C, C9), 138.46 (s,
C, C14), 129.64 (s, 1 C, C2), 127.37 (s, 1 C, C5), 125.51 (s, 1 C, C12),
23.44 (s, 1 C, C4/C11), 123.30 (s, 1 C, C4/C11), 122.35 (s, 1 C, C3),
15.41 (s, 1 C, C6), 112.99 (s, 1 C, C13), 110.48 (s, 1 C, C10), 70.09 (s,
experiments were obtained overnight. The crystals thus formed
were filtered, washed twice with precooled toluene and finally dried
in vacuo. Compound 8 was isolated in the form of greenish crystals
(49 mg, 0.15 mmol, 30 %, not optimised). C H AlN S (335.40):
18
18
3
1
5
1
C, C1′), –6.97 (s, 2 C, C1M) ppm. N{ H} NMR (40 MHz, [D ]THF): calcd. C 64.46, H 5.41, N 12.53, S 9.56; found C 62.68, H 5.41, N
8
1
δ = –200.07 (s, N1), –228.48 (s, N2) ppm. EI-MS: m/z (%) = 364.0 (13)
11.92, S 9.07. H NMR (400 MHz, [D ]THF): δ = 7.52 (ddd, J = 7.8,
8
H,H
+
+
+
[M] , 349 (100) [M – Me] , 334 (27) [M – 2 Me] , 265 (9) [M –
1.3, 0.6 Hz, 1 H, H3), 7.49–7.44 (m, 1 H, H13), 7.43 (ddd, JH,H = 8.1,
1.1, 0.6 Hz, 1 H, H6), 7.33–7.30 (m, 1 H, H10), 7.27 (ddd, JH,H = 8.1,
+
+
GaMe ] , 69 (58) Ga .
2
7.4, 1.3 Hz, 1 H, H5), 7.23–7.16 (m, 2 H, H11 + H12), 7.05 (ddd, JH,H
=
[
(
Me Al{(NCSC H )CH(1-MeNCNC H )}] (9): A solution of AlMe
7.8, 7.4, 1.1 Hz, 1 H, H4), 5.57 (s, 1 H, H1′), 3.63 (s, 3 H, H15), –0.50
2 6 4 6 4 3
0.06 mL, 43 mg, 0.60 mmol, 1.2 equiv.) in toluene (5 mL) was added (s, 6 H, H1M) ppm. 13C{ H} NMR (75 MHz, [D
1
]THF): δ = 166.65 (s, 1
8
dropwise to a solution of 4 (140 mg, 0.50 mmol, 1.0 equiv.) in tolu-
ene (40 mL) at room temperature, and the clear reaction mixture
C, C1), 154.42 (s, 1 C, C8), 149.90 (s, 1 C, C7), 138.64 (s, 1 C, C14),
135.42 (s, 1 C, C9), 128.98 (s, 1 C, C2), 127.00 (s, 1 C, C5), 123.28 (s,
was stirred overnight. Afterwards, the volume of the solution was 1 C, C12), 122.83 (s, 1 C, C11), 122.57 (s, 1 C, C4), 121.90 (s, 1 C, C3),
Table 4. Crystal structure data for 1–5 and 7–11.
1
2
3
3a
4·H
2
O
5
Empirical formula
Formula mass
Wavelength [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C
9
H
12
N
4
C
17
H
16
N
4
C
15
H
10
N
2
OS
C
15
H
12
N
2
O
2
S
C
16
H
11
N
3
S·H
2
O
C
11 4
H17AlN
176.23
0.71073
tetragonal
P4
7.078(2)
7.078(2)
17.810(3)
90
90
90
276.34
266.31
284.33
0.71073
orthorhombic
Pna2
22.104(3)
4.695(2)
12.588(2)
90
90
90
1306.4(6)
4
297.37
0.71073
monoclinic
P2
4.790(2)
28.552(4)
10.749(3)
90
99.92(2)
90
1448.1(8)
4
232.26
0.71073
0.71073
triclinic
P1¯
0.71073
triclinic
P1¯
monoclinic
P2 /c
13.500(3)
17.133(4)
12.370(3)
90
117.14(2)
90
2546.1(11)
8
3
2
1
2
1
1
1
8.292(2)
8.395(2)
5.908(2)
9.841(2)
10.543(3)
68.80(2)
83.69(2)
83.20(2)
677.6(3)
2
10.682(3)
81.96(2)
87.52(3)
81.07(2)
607.4(3)
2
ꢀ
[°]
γ [°]
3
V [Å ]
892.2(3)
4
Z
Reflections measured
Refllections unique
26062
1367
18451
3377
20040
2588
18979
3374
24144
6106
39111
4705
R
int
0.0461
1367/0/65
0.0334
0.0916
not defined relia-
bly
0.0262
3380/0/192
0.0404
0.1112
–
0.0221
0.0339
3374/3/189
0.0277
0.0717
0.03(3)
0.0294
6106/591/426
0.0304
0.0719
0.21(7)
0.0931
4705/393/299
0.0483
0.1410
–
Data/restraints/parameters
R1 [I > 2σ(I)]
wR2 (all reflections)
2588/227/179
0.0297
0.0755
–
[
a]
[
b]
[
24]
Absolute structure parameter
Extinction coefficient
–
–
–
–
–
0.0021(5)
0.395/–0.313
Δρfin [e Å–3
]
0.364/–0.190
0.356/–0.248
0.347/–0.343
0.294/–0.205
0.239/–0.227
7
8
9
10
11·4diox
Empirical formula
Formula mass
Wavelength [Å]
Crystal system
Space group
a [Å]
C
17
H
15AlN
2
OS
C
17
H
15GaN
2
OS
C
18
H
18AlN
3
S
C
25
H
31LiN
4
O
2
16 3 4 8 2
C H12LiN S·4C H O
637.70
0.71073
322.35
0.71073
monoclinic
P2 /c
14.594(3)
7.086(2)
15.288(3)
93.35(2)
1578.3(6)
4
365.09
0.56086
335.39
0.71073
monoclinic
P2 /m
7.230(3)
14.864(4)
8.340(3)
112.67(2)
827.0(5)
2
426.48
0.71073
monoclinic
P2 /c
21.030(2)
9.072(2)
23.894(2)
98.43(2)
4509.3(12)
8
orthorhombic
Pnma
8.262(2)
16.440(4)
11.473(3)
90
monoclinic
P2 /c
1
1
1
1
9.609(2)
12.915(3)
26.515(4)
95.94(3)
3272.8(11)
4
b [Å]
c [Å]
ꢀ
[°]
3
V [Å ]
1558.3(7)
4
Z
Reflections measured
Reflections unique
25152
2916
37294
2464
9160
2210
128019
8298
51453
7527
R
int
0.0543
0.0346
0.0310
0.0704
0.0583
Data/restraints/parameters
2916/287/221
0.0395
0.1037
2464/382/192
0.0490
0.1137
2210/398/201
0.0701
0.2016
8298/826/657
0.0387
0.0948
0.00165(18)
0.199/–0.187
7527/3723/866
0.0718
0.1507
0.0018(3)
0.242/–0.268
[
a]
R1 [I > 2σ(I)]
wR2 (all reflections)
Extinction coefficient
Δρfin [e Å–3
[
b]
–
–
–
]
0.338/–0.281
0.747/–0.883
0.754/–0.947
(Fo2 + 2F )
2
Σ||F | – |F ||
o
c
1
c
[
a] R1 =
. [b]
; w =
; P =
.
(Fo2) + (g P) + g P
2
Σ|Fo|
3
1
2
Eur. J. Inorg. Chem. 2017, 1966–1978
www.eurjic.org
1976
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1
1
14.87 (s, 1 C, C6), 113.67 (s, 1 C, C13), 109.44 (s, 1 C, C10), 70.71 (s,
1521024 (for 9), 1521026 (for 10), 1521027 (for 11·4diox) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre.
C, C1′), 29.35 (s, 1 C, C15), –9.58 (s, 2 C, C1M) ppm. 1 N{ H} NMR
5
1
(50 MHz, [D ]THF): δ = –223.12 (s, N1), –226.41 (s, N3), –257.67 (s,
8
27
1
N2) ppm. Al{ H} NMR (78 MHz, [D ]THF): δ = 150 (s, Al1) ppm. EI-
MS: m/z (%) = 335 (11) [M] , 320 (100) [M – Me] , 305 (19) [M –
2
8
+
+
+
2+
Me] , 160 (12) [M – Me]
.
Acknowledgments
[(THF) Li{(1-MeNCNC H ) CH}] (10): At –60 °C, nBuLi (2.15
M in
2
6 4 2
hexane, 0.72 mL, 1.44 mmol, 4.0 equiv.) was added slowly to a solu- Thanks to the Danish National Research Foundation (DNRF93)
tion of 2 (100 mg, 0.36 mmol, 1.0 equiv.) in THF (10 mL), and the funded Center for Materials Crystallography (CMC) for partial
reaction mixture was stirred overnight. Afterwards, the volume of support and the Federal State of Lower Saxony, Germany for
the solution was reduced to a few mL, and the resulting concen-
trated solution was stored at –32 °C in a freezer. Crystals suitable
for X-ray diffraction experiments were obtained overnight. The crys-
providing fellowships in the GAUSS and CaSuS PhD programs.
tals thus formed were filtered, and the remaining solvent was re- Keywords: Organometallic synthesis · Aluminium · Gallium ·
moved under reduced pressure. Yellow, plate-shaped crystals were
Lithium · NacNac
obtained in 92 % yield (142 mg, 0.33 mmol). C H AlN (232.27).
1
1
17
4
1
3
H NMR (400 MHz, [D ]THF): δ = 7.02 (d, J
= 7.6 Hz, 2 H, H6),
.85 (d, J = 7.6 Hz, 2 H, H3), 6.79 (td, JH,H = 7.5, 1.2 Hz, 2 H, H5),
.70 (td, J = 7.5, 1.1 Hz, 2 H, H4), 4.23 (s, 1 H, H1′), 3.46 (s, 6 H,
H8) ppm. C{ H} NMR (100 MHz, [D ]THF): δ = 159.93 (s, 2 C, C1),
8
H,H
3
6
6
[1] a) S. G. McGeachin, Can. J. Chem. 1968, 46, 1903–1912; b) R. Bonnett,
D. C. Bradley, K. J. Fisher, Chem. Commun. (London) 1968, 886–887;
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H,H
H,H
1
3
1
8
[
2] a) M. Stender, B. E. Eichler, N. J. Hardman, P. P. Power, J. Prust, M. Nol-
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1
2
2
46.32 (s, 2 C, C7), 137.23 (s, 2 C, C2), 120.09 (s, 2 C, C5), 117.23 (s,
C, C4), 112.36 (s, 2 C, C6), 105.69 (s, 2 C, C3), 54.10 (s, 1 C, C1′),
7
1
8.91 (s, 2 C, C8) ppm. Li{ H} NMR (155 MHz, [D ]THF): δ = 2.54 (s,
8
Li1) ppm.
[(diox) Li{(NCSC H )CH(1-MeNCNC H )}] (11): At room tempera-
2
6
4
6 4
ture, nBuLi (2.93
M in hexane, 0.17 mL, 0.50 mmol, 1.0 equiv.) was
slowly added to a suspension of 4 (140 mg, 0.50 mmol, 1.0 equiv.)
in 1,4-dioxane (15 mL). The resulting brown suspension was stirred
overnight and filtered to obtain a brown solution. Afterwards, the
volume of the solution was reduced to a few mL, and the resulting
concentrated solution was stored at room temperature. Crystals
suitable for X-ray diffraction experiments were obtained after a
week. The crystals thus formed were filtered and dried in vacuo.
Yellow needles were isolated in 78 % yield (145 mg, 0.39 mmol, not
optimised). C H LiN OS (373.40): calcd. C 64.33, H 5.40, N 11.25, S
2
0, 1190–1194; g) A. Jana, H. W. Roesky, C. Schulzke, A. Döring, T. Beck,
A. Pal, R. Herbst-Irmer, Inorg. Chem. 2009, 48, 193–197; h) Y. Cheng, D. J.
Doyle, P. B. Hitchcock, M. F. Lappert, Dalton Trans. 2006, 4449–4460;
i) N. Kuhn, J. Fahl, S. Fuchs, M. Steimann, G. Henkel, A. H. Maulitz, Z.
Anorg. Allg. Chem. 1999, 625, 2108–2114; j) N. Kuhn, S. Fuchs, M. Stei-
mann, Eur. J. Inorg. Chem. 2001, 359–361; k) N. Kuhn, S. Fuchs, M. Stei-
mann, Z. Anorg. Allg. Chem. 2002, 628, 458–462; l) C. E. Radzewich, I. A.
Guzei, R. F. Jordan, J. Am. Chem. Soc. 1999, 121, 8673–8674.
20
20
3
[
3] a) D. Li, Y. Peng, C. Geng, K. Liu, D. Kong, Dalton Trans. 2013, 42, 11295–
8
.59; found C 60.33, H 6.50, N 7.95, S 6.64 (deviations due to remain-
1
1303; b) Z. Yang, M. Zhong, X. Ma, S. De, C. Anusha, P. Parameswaran,
1
ing lattice solvent). H NMR (400 MHz, [D ]THF): δ = 7.30 (ddd, J
=
8
H,H
H. W. Roesky, Angew. Chem. Int. Ed. 2015, 54, 10225–10229; Angew.
Chem. 2015, 127, 10363–10367; c) Z. Yang, M. Zhong, X. Ma, K. Nijesh,
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2551; d) V. K. Jakhar, M. K. Barman, S. Nembenna, Org. Lett. 2016, 18,
4710–4713; e) A. Bismuto, S. P. Thomas, M. J. Cowley, Angew. Chem. Int.
Ed. 2016, 55, 15356–15359; Angew. Chem. 2016, 128, 15582–15585.
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Dauer, M. Flügge, R. Herbst-Irmer, D. Stalke, Dalton Trans. 2016, 45, 6149–
7
7
.6, 1.3, 0.5 Hz, 1 H, H3), 7.12 (ddd, JH,H = 7.6, 1.3, 0.6 Hz, 1 H, H13),
.09 (ddd, JH,H = 8.0, 1.2, 0.5 Hz, 1 H, H6), 7.01–6.96 (m, 2 H, H5 +
H10), 6.89 (td, JH,H = 7.5, 1.4 Hz, 1 H, H12), 6.83 (td, JH,H = 7.5, 1.3 Hz,
H, H11), 6.68 (ddd, JH,H = 7.6, 7.3, 1.2 Hz, 1 H, H4), 4.95 (s, 1 H,
1
1
3
1
H1′), 3.48 (s, 3 H, H15) ppm. C{ H} NMR (75 MHz, [D ]THF): δ =
8
[
[
1
1
1
67.44 (s, 1 C, C1), 157.78 (s, 1 C, C7/C8), 157.64 (s, 1 C, C7/C8),
45.45 (s, 1 C, C14), 136.62 (s, 1 C, C9), 131.78 (s, 1 C, C2), 125.42 (s,
C, C5), 120.68 (s, 1 C, C12), 120.46 (s, 1 C, C3), 118.74 (s, 1 C, C4/
6
2
158; c) D.-R. Dauer, M. Flügge, R. Herbst-Irmer, D. Stalke, Dalton Trans.
016, 45, 6136–6148.
C11), 118.73 (s, 1 C, C4/C11), 114.75 (s, 1 C, C6), 113.60 (s, 1 C, C13),
07.01 (s, 1 C, C10), 68.46 (s, 1 C, C1′), 28.98 (s, 1 C, C15) ppm.
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Struct. Sci. 1996, 52, 842–853.
1
7
1
15
1
Li{ H} NMR (117 MHz, [D ]THF): δ = 2.37 (s, Li1) ppm. N{ H} NMR
[6] a) H. Gornitzka, D. Stalke, Angew. Chem. Int. Ed. Engl. 1994, 33, 693–695;
Angew. Chem. 1994, 106, 695–698; b) H. Gornitzka, D. Stalke, Organome-
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pp. 85–115.
[8] P. Vasko, V. Kinnunen, J. O. Moilanen, T. L. Roemmele, R. T. Boere, J. Konu,
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[11] a) A. Abbotto, S. Bradamante, A. Facchetti, G. A. Pagani, J. Org. Chem.
2002, 67, 5753–5772; b) A. Abbotto, S. Bradamante, G. A. Pagani, J. Org.
8
(40 MHz, [D ]THF): δ = –168.43 (s, N1), –190.35 (s, N3), –261.53 (s,
8
+
+
N2) ppm. EI-MS: m/z (%) = 293 (13) [M + Li] , 279 (100) [M – Li] ,
1
+
+
49 (18) [M – Li – 1-MeNCNC H ] , 131 (57) [1-MeNCNC H ] .
6 4 6 4
Crystallographic Details: Shock-cooled crystals were selected from
a Schlenk line under argon using the X-TEMP2.
[17]
The data were
[
18]
integrated with SAINT,
and a multiscan absorption correction
SADABS)[
19]
[20]
(
and a 3λ correction were applied.
The structures
[21]
2
were solved by direct methods (SHELXT) and refined on F using
[22]
the full-matrix least-squares methods of SHELXL
within the
SHELXLE GUI.[ Crystal structure data for 1–5 and 7–11 are shown
in Table 4. More details on the crystallographic data and the refine-
ment can be found in the Supporting Information. CCDC 1521021
23]
[
(for 1), 1521022 (for 2), 1521030 (for 3), 1521025 (for 3a), 1521031
(for 4·H O), 1521023 (for 5), 1521028 (for 7), 1521029 (for 8),
2
Eur. J. Inorg. Chem. 2017, 1966–1978
www.eurjic.org
1977
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Chem. 1996, 61, 1761–1769; c) A. Abbotto, S. Bradamante, N. Capri, H.
Rzepa, D. J. Williams, A. White, J. Org. Chem. 1996, 61, 1770–1778.
12] a) S. Bradamante, G. A. Pagani, J. Org. Chem. 1984, 49, 2863–2870; b) A.
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