Zinc Chloride Complexes with Aliphatic and Aromatic Guanidine Hybrid Ligands and Their Activity in the Ring-Opening Polymerisation of d,l-Lactide

Article abstract of DOI:10.1002/ejic.201600870

The synthesis of the new hybrid guanidine ligands DMEGdmap, DMEGdeae, TMGdmab, DMEGdmab, TMGdeab and DMEGdeab is reported. These ligands were combined with zinc chloride, and the six obtained new complexes were structurally characterised by X-ray crystall

Full text of DOI:10.1002/ejic.201600870

A Journal of
Accepted Article
Title: Zinc chloride complexes with aliphatic and aromatic guanidine hybrid ligands
and their activity in the ring-opening polymerisation of D,L-lactide
Authors: Sonja Herres-Pawlis; Angela Metz; Ramona Plothe; Britta Glowacki;
Andreas Koszalkowski; Michael Scheckenbach; Andreas Beringer; Thomas
¨
¨
Rosener; Janna Michaelis De Vasconcellos; Ulrich Florke; Alexander Hoffmann
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201600870
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European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
Zinc chloride complexes with aliphatic and aromatic guanidine
hybrid ligands and their activity in the ring-opening
polymerisation of D,L-lactide
Angela Metz,[a] Ramona Plothe,[b][#1] Britta Glowacki,[b] Andreas Koszalkowski,[c] Michael
Scheckenbach,[c] Andreas Beringer,[c] Thomas Rösener,[a] Janna Michaelis de Vasconcellos,[d][#2] Ulrich
Flörke,[d] Alexander Hoffmann,[a] and Sonja Herres-Pawlis*[a]
Abstract: The synthesis of the new hybrid guanidine ligands
TMGdmab, DMEGdmab, TMGdeab and DMEGdeab is reported.
These ligands were combined with zinc chloride and the four new
obtained complexes were structurally characterized by X-ray
crystallography and NMR spectroscopy. Furthermore, eight new zinc
chloride complexes were obtained by reaction of the hybrid
guanidine ligands TMGdmae, DMEGdmae, TMGdeae, DMEGdeae,
TMGdmap, DMEGdmap, TMGdeap and TEGdeap. All twelve
complexes possess a tetrahedral coordination geometry. The donor
situation between guanidine and amine donors was evaluated using
density functional theory. These complexes show robust activity in
the melt polymerization of technical unsublimed lactide. For selected
complexes kinetic polymerization experiments have been performed
which show first-order behavior. The end-group was proven by NMR
spectroscopy.
Polylactide is synthesised from lactic acid which is the starting
material for the following dimerisation and ring-opening
polymerisation (ROP) initiated by well-defined metal-based
initiator systems.[7,15] After use, PLA can be either combusted,
recycled or composted.[6,16,17] The aim is to generate PLA with
controllable molecular weights and polydispersity (PD) values
smaller than 1.5.[4,7] Besides, the tacticity plays an important role
for the mechanical properties of the polymer.[8,18-21] A great
diversity of metals and ligands has been tested as
initiators/catalysts for the ROP of cyclic esters. However, the
toxic tin(II) octanoate is still commercially used as initiator.[8,22]
Due to the multitude of application fields a catalyst is urgently
required which fulfills following properties: non-toxic, biologically
tolerant, highly Lewis acidic and cost-efficient.[23,24] These
requirements are met by Mg (II), Zn(II), Ca(II) and Ti(IV)
complexes.[24] For the stabilisation of these metal, anionic N
donor ligands such as aminophenolates,[25] β-ketiminates,[26-32]
phenolate Schiff bases[33] and trispyrazolylborates[34,35] have
found considerable attention as stabilising ligands for lactide
ROP initiators. Furthermore, Jones et al. published Zr(IV), Ti(IV),
Hf(IV) and Al(III) complexes based on bipyrrolidine salan
proligands being active in the ROP of rac-lactide.[36-38] Williams
et al. obtained excellent rates and high degrees of
polymerisation with yttrium, lanthanum and lutetium
phosphasalen complexes.[39-41] Moreover, they synthesised
dizinc(II)-complexes bearing a Schiff base ligand and isopropyl
alcohol. These complexes show initiating properties for racemic
lactide with moderately high activity at room temperature in
solvent.[42] The working group of Okuda investigated catalysts
using the same metal centres as Jones et al. for the ROP of
lactide.[43,44] Here, a tetradentate dianionic thio-imine diphenolate
ligand featuring an ortho-phenylene core was discovered.[43]
Using zinc, further metal complexes have been tested for the
ROP of lactide: Di lulio et al. synthesised Zn(II) silsesquioxane
and Kwon et al. investigated the influence of Zn(II) complexes
bearing camphor-based iminopyridines as pre-catalysts for the
ROP of lactide.[18,45] These anionic systems exhibit sensitivity
towards moisture and air which demonstrate a problem for
industrial use. In addition to the ligands mentioned so far neutral
Introduction
Polylactide (PLA) is a biodegradable plastic and the production
starts from renewable raw materials such as sugar beets, starch
or agricultural waste.[1-9] So it consists of 100% bio-based
contents.[2] Owing to the similar mechanical properties to
poly(ethylene terephthalate) (PET) and poly(propylene) (PP),
PLA is a viable alternative to petrochemical based materials.[10-
14] Nowadays PLA materials are used in many applications such
as packaging, in biomedical fields, consumer electronics and as
fibres.[11,12] Producing biodegradable polymers from renewable
raw materials will reduce the use of fossil resources.
____________
[a]
Angela Metz, Thomas Rösener, Dr. Alexander Hoffmann,
Prof. Dr. Sonja Herres-Pawlis
Institut für Anorganische Chemie
RWTH Aachen University
Landoltweg 1, 52074 Aachen, Germany
E-Mail: sonja.herres-pawlis@ac.rwth-aachen.de
Ramona Plothe, Britta Glowacki
[b]
[c]
Technische Universität Dortmund
Fakultät Chemie und Chemische Biologie
Otto-Hahn-Str. 6, 44227 Dortmund, Germany
Andreas Koszalkowski, Michael Scheckenbach, Andreas
Beringer
Ludwig-Maximilians-Universität München
Department of Chemistry,
and robust
trispyrazolylmethanes,[46] carbenes,[47,48] phenoxy imines,[49]
amidates,[50] heteroscorpionates,[51]
phosphine-modified
N ,
donor ligands such as iminopyridines[18]
Butenandtstr. 5–13, 81377 München, Germany
Dr. Janna Michaelis de Vasconcellos , Dr. Ulrich Flörke
Universität Paderborn
[d]
Anorganische Chemie, Department Chemie
Warburger Str. 100, 33098 Paderborn, Germany
[#1] Née Tillmann.
piperidinyl-benzyl-anilines[52] and guanidines[15,53-59] are used
successfully for the polymerisation. As an example,
[#2] Née Börner.
Supporting information for this article is available on the WWW under
http://www.eurjic.org/ or from the author.

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
Results and Discussion
Mehrkhodavandi et al. investigated the influence of neutral
secondary vs. tertiary amine donor ligands for dinuclear indium
catalysts and their activity in the ROP of lactide.[60]
Table 1. Overview of zinc chloride complexes C1-C12.
Guanidine ligands represent an import group of neutral N donor
ligands, since they possess excellent donor properties, high
basicity and as good coordination properties for several
transition metals.[15,61-63] The guanidine ligands can differ in their
bridging unit, in their guanidine moiety and in their N-donor
function (Figure 1). Guanidines have been studied in various
fields in chemistry: General coordination chemistry topics are
investigated by the group of Himmel and Tamm.[62,64-70] For
example, Tamm et al. investigated the impact of transition metal
complexes (Ti, U, Ru, …) by basic imidazolin-2-imine N-donor
ligands on the activity in polymerisation of ε-caprolactone.[68,71,72]
Guanidine ligands in combination with Zn, Mg or cationic Al
attract much interest as alkyl transfer reagents and (co-)catalyst
in the group of Himmel.[62,64-66] Besides general coordination
chemistry, guanidines are common in bioinorganic chemistry, so
for tyrosinase model systems[73-80] or as model complexes for the
entatic state.[81,82] Furthermore, zinc guanidine complexes are
robust and highly active initiators in the ROP of lactide[53,59] and
they are also active in the ATRP (atom transfer radical
polymerisation) of styrene.[83-89]
Ligand
TMGdmae[74]
DMEGdmae[74]
TMGdeae[74]
DMEGdeae
Complex
Ligand
C1
TMGdmap[73]
C5
C2
DMEGdmap
C6
C3
TMGdeap[73]
C7
C4
TEGdeap[73]
C8
Complex
Ligand
TMGdmab
DMEGdmab
TMGdeab
DMEGdeab
Complex
C9
C10
C11
C12
The guanidine hybrid ligands TMGdmae[74], DMEGdmae[74]
TMGdmap[73] TMGdeae[74]
DMEGdmap, DMEGdeae,
TEGdeap[73] and TMGdeap[73] were prepared by the reaction of
,
,
,
the
corresponding
Vilsmeier
salt
N,N’-
N,N,N’,N’-
N,N,N’,N’-
dimethylethylenchloroformamidiniumchloride,
tetramethylchloroformamidiniumchloride
or
tetraethylchloroformamidiniumchloride with the appropriate
primary amine. For the synthesis of TMGdmab, DMEGdmab,
TMGdeab and DMEGdeab 1-fluoro-nitrobenzene was used as
starting material. The first step is a nucleophilic attack of
dimethylamine (dmab) or diethylamine (deab) at the carbon
atom next to the flourine atom. Afterwards the nitro group is
reduced in a hydrogen atmosphere with a palladium-catalyst
(Scheme 1).[90] In the next step, the synthesis of the guanidine
ligand follows the protocol of Herres-Pawlis et al. based on the
protocol of Kantlehner.[76,91] To obtain the corresponding zinc
complexes C1-C12, the ligands were combined with zinc
chloride in an aprotic, dry solvent (MeCN or THF) (Table 1).
Single crystals could be obtained by gas phase diffusion of
diethylether or by slowly removing the solvent. Furthermore, all
these complexes were identified by means of NMR and IR
spectroscopy, mass spectrometry measurements as well as
elemental analysis and single crystal X-ray diffraction.
Herein we report the synthesis of six hybrid guanidine ligands
(DMEGdeae, DMEGdmap, TMGdmab, DMEGdmab, TMGdeab,
DMEGdeab) and twelve new zinc chloride guanidine-hybrid
complexes (Table 1). Eight complexes contain aliphatic ligands
whereas four complexes have an aromatic backbone which
allows the investigation of sterical and electronic influences.
Selected complexes were tested in the polymerisation of
technical, unsublimed D,L-lactide at 150 °C with no further
purification of the lactide. Furthermore, DFT and NBO
calculations were carried out to receive more information on the
donor-acceptor properties and on the influence of the guanidine
substituents.
Scheme 1. Synthesis of dmab and deab ligands.[90]
Figure 1. Overview of aliphatic hybrid guanidine ligands.
Molecular structures

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
The molecular structures of C1 ([Zn(TMGdmae)Cl2]), C2
methyl groups next to the amine instead of the inflexibly
ethylene bridge of the DMEG moiety. As an example the
guanidine twist in the TMG complex C1 is 33.7° and the
comparable DMEG complex C2 shows an angle of 14.4°.
([Zn(DMEGdmae)Cl2]),
([Zn(DMEGdeae)Cl2]),
([Zn(DMEGdmap)Cl2]),
([Zn(TEGdeap)Cl2]),
C3
C5
C7
([Zn(TMGdeae)Cl2]),
([Zn(TMGdmap)Cl2]),
([Zn(TMGdeap)Cl2]),
([Zn(TMGdmab)Cl2]),
C4
C6
C8
C9
C10
In the complexes C1-C4 and C9-C12
a five-membered
([Zn(DMEGdmab)Cl2]), C11 ([Zn(TMGdeab)Cl2]) and C12
([Zn(DMEGdeab)Cl2]), were determined by single crystal X-ray
diffraction. In all these zinc chloride complexes the zinc atom is
fourfold coordinated by the N donor atoms of the guanidine and
amine and by two chloride atoms (Fig. 2). The coordination
geometry of the zinc atom possesses a distorted tetrahedral
coordination environment. In all complexes the Zn-Ngua bond
length of the guanidine unit lies between 1.99 – 2.04 Å and is
thus much shorter in comparison to the Zn-Namine bond lengths
(2.03 –2.16 Å). The bond length of the zinc-chloride bonds is
between 2.21 – 2.27 Å. The angle between the N atoms and the
zinc atom depends on the backbones of the guanidine ligands.
With ethylene backbone (C1-C4) the angle is between 85.6(1)° –
86.5(1)° whereas a propylene bridge (C5-C8) leads to an angle
of 97.4(1)° – 98.4(1)° and an aromatic backbone (C9-C12) to an
angle of 80.5(1)° – 82.5(1)° (Tab. 2). Hence, all bite angles are
diminished in comparison to the ideal angle in a tetrahedral
geometry of 109.5°. The angle between the coordination planes
(∡ (ZnCl2, ZnN2)) of the complexes is with 83.9° – 90°
(depending on the complexes) in accordance with the value
expected for an ideal tetrahedral geometry of 90°. The 4 factor
reflects the coordination geometry of the complex: In an ideal
tetrahedral coordination environment the 4 value is 1 whereas in
an square-planar coordination environment the 4 value is 0.[92]
The zinc complexes exhibit 4 values in the range of 0.88 to 0.94,
indicating also a tetrahedral coordination geometry. Regarding
the details, the Zn-Ngua bond lengths of the TMG complexes
(2.004(3) in C1, 2.012(1) in C3) are shorter than those of the
comparable DMEG complexes (2.037(1) in C2, 2.034(1) in C4).
This leads to the assumption that the TMG guanidine moiety is a
stronger donor than the DMEG unit.[84,89] As reported before in
all complexes, the Zn-Ngua bond lengths (e. g. 2.004(3) in C1,
2.037(1) in C2, 2.034(1) in C4, 2.013(1) in C9) are shorter than
the comparable Zn-Namine bonds (2.106(3) in C1, 2.089(1) in C2,
2.100(1) in C4, 2.116(1) in C9) (Tab. 2).[84] The reason is the
stronger -donor character of the guanidine function.[89]
heterocycle is formed. The five-membered ring is in the
energetically favoured envelope conformation (Fig. 3).[94] C1
contains a plane with four atoms (Zn-Ngua-C-Namine) with one
carbon atom pointing out of this plane (0.57 Å). The
conformation with C9 displays the zinc atom 0.85 Å out of the
plane (Ngua-Namine-C-C). In C1 we have a carbon atom in the
endo position and in C9 a zinc atom. The different arrangement
is caused by the inflexible, aromatic backbone of the C9
complex.
Figure 3. Different envelope conformations of the molecular
structures of C1 (left) and C9 (right).
To quantify the delocalisation in the guanidine group the
structural parameter  was introduced.[93] The parameter  can
be obtained by using the ratio of the Cgua=Ngua bond length to the
sum of the bond lengths of the Cgua - Namine bonds. It describes
how good the double bond in the guanidine moiety is delocalised.
The complexes with an aromatic backbone C9-C12 show by
trend a larger  value than the aliphatic ones C1-C8. Thus the
guanidine unit is slightly better delocalised in the aromatic
ligands than in the aliphatic ones.[54] As next parameter, the
guanidine twist is determined by the dihedral angles between
the plane of three nitrogen atoms (Namine- Ngua -Namine) and
(Camine- Cgua -Camine) of the guanidine unit. TMG complexes
demonstrate a much higher twisting than comparable DMEG
complexes.[54-56,58,74,89] This is due to the free rotation of the

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
Figure 2. Molecular structures in the solid state of C1-C12.
Table 2. Selected bond lengths [Å] and angles [°] of C1-C12.
C1
C2
C3
C4
C5
C6
Zn-Ngua
Zn-Namine
Zn-Cl
2.004(3)
2.106(3)
2.234(1)
2.226(1)
86.5(1)
85.2(1)
34.1(2)
0.96
2.037(1)
2.089(1)
2.229(1)
2.245(1)
86.3(1)
84.3
2.012(1)
2.033(1)
2.223(1)
2.250(1)
85.7(1)
83.9(1)
24.9(1)
0.97
2.034(1)
2.100(1)
2.231(1)
2.242(1)
85.6(1)
86.1(1)
11.6(1)
0.96
1.993(2)
2.095(2)
2.227(1)
2.261(1)
98.4(1)
87.5(1)
30.4(1)
0.97
1.997(3)
2.088(3)
2.242(1)
2.255(1)
97.5(1)
86.4(1)
30.7(1)
0.97
N-Zn-N
∡ (ZnCl2, ZnN2)
∡ (ZnNguaNamine, CN3)
[a]
14.0
0.96
[b]
τ4
0.89
0.88
0.90
0.91
0.94
0.93
Guanidine twist[c]
33.7
14.4
34.2
15.0
32.9
12.9
C7
C8
C9
C10
C11
C12
Zn-Ngua
Zn-Namine
Zn-Cl
1.992(1)
2.111(1)
2.251(1)
2.243(1)
98.4(1)
87.1(1)
32.2(1)
0.97
2.002(3)
2.119(3)
2.265(1)
2.231(1)
97.4(1)
87.9(1)
17.8(1)
0.97
2.013(1)
2.116(1)
2.232(1)
2.208(1)
82.4 (1)
87.2 (1)
27.3(1)
0.97
2.022(1)
2.102(1)
2.208(1)
2.232(1)
82.5(1)
89.3(1)
32.9(1)
0.99
2.026 (2)
2.158 (2)
2.214 (1)
2.219 (1)
80.5 (1)
89.7 (1)
32.7 (2)
0.97
2.030 (2)
2.139 (2)
2.215 (1)
2.227 (1)
81.2(1)
90.0 (1)
27.2 (2)
0.98
N-Zn-N
∡ (ZnCl2, ZnN2)
∡ (ZnNguaNamine, CN3)
[a]
[b]
τ4
0.92
0.90
0.90
0.88
0.92
0.88
Guanidine twist[c]
34.9
37.1
32.6
9.2
32.2
7.3
[a]
( )
.
[92] [c] The dihedral angles between the planes represented by Ngua, Namine, Namine
with a = d(Cgua- Ngua) and b and c = d(Cgua- Namine).[93] [b]
(
)
and Cgua, CAlk, CAlk Two twist angles for each guanidine moiety. Average value of all dihedral angles.

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
to the Namine atom. Now we can compare the donor acceptor
interactions of the TMG complexes with an ethylene (C1),
propylene (C5) and benzene (C9) bridge. C1 has a Zn-Ngua
interaction energy of 45.5 and C5 of 47.7 kcal/mol. The
propylene bridge of C5 leads to a slightly stronger donation of
the guanidine moiety than C1. The interaction energy of the
Namine lone pair to zinc is almost the same in both cases, in C1
30.0 and in C5 30.6 kcal/mol. In comparison to C1 and C5, C9
has the lowest interaction energy for both, LP(Ngua)-LV(Zn) (42.4
kcal/mol) and LP(Namine)-LV(Zn) (26.9 kcal/mol). In summary, the
donor-acceptor interactions, the charge on the N atoms and the
bond lengths highlight the stronger bonding ability of the Ngua
atom in comparison to the Namine atom. Furthermore, the
aliphatic complexes (especially C1 and C5) have by trend
stronger donor properties of the nitrogen atoms to the zinc than
comparable aromatic complexes (C9-C12). The reason could be
the delocalised π-electron system of the aromatic system which
weakens the donor properties of both nitrogen groups.
Density Functional Theory Calculations
In order to gain insights into the donor properties of the ligands
in their complexes, quantum chemical calculations have been
performed at DFT level. At first the appropriate basis set and
functional have to be found. The functional TPSSh and the basis
set def2-TZVP in the solvent acetonitrile with empirical
dispersion correction with Becke Johnson damping turned out to
be the best combination for these systems (see Table S1 in the
Supporting Information). This methodology was then utilised for
all complexes. In Table
3 the results of the geometry
optimisations are summarised. The calculated structures are in
good accordance with the molecular structures in the solid state.
In the calculated structures, the Zn-Ngua, Zn-Namine and Zn-Cl
bond lengths are longer than the comparable solid-state
structure bond lengths. But the trends are reflected well. As
discussed before, the Zn-Ngua bond length in C1 (2.025 Å) is
shorter than that in C2 (2.057 Å). In C3 (2.042 Å) and C4 (2.063
Å) the same trend is obtained. Additionally in the calculations,
the Zn-Ngua bond length of the TMG unit is shorter than the
comparable bond length of the DMEG unit. The calculation
shows that the angles between the plane of ZnN2 and CguaN3 are
bigger in the aliphatic TMG complexes than in the comparable
DMEG complexes. C1 has an angle between the planes ZnN2
and CguaN3 of 29.1° and C2 of 18.7°. In case of aromatic
complexes C9-C12 there is no difference between TMG and
DMEG systems. All the angles between the ZnN2 and CguaN3
planes are nearly similar. As discussed before, the -value of the
complexes with aromatic systems is higher than that of aliphatic
systems. C9-C12 have a calculated -value from 0.98-0.99 and
C1-C8 the value is between 0.95 and 0.97. For a more detailed
analysis of the donor situation in all complexes, we performed a
natural population analysis (NBO)[95-97] using the geometries
obtained with the TPSSh/def2-TZVP combination. So we
obtained the NBO charges and the charge transfer energies (by
second order perturbation theory) for the donation from the N
donor units to the zinc ion. NBO charges do not represent
absolute charges but the trends give an impression of the
electronic effects. The calculated charges on the zinc atoms
range from 1.5 to 1.6 (Table 4). The charge on the donating N
atom of the guanidine unit is in all complexes much more
negative (-0.8) than that of the N atom of the amine function (-
0.5). Thus, the Ngua atom appears more basic than the Namine
atom.
To elucidate the coordination properties, the donor acceptor
interaction was investigated by second order perturbation theory.
In C2, C3, C6, C7 and C8 the bond of the Ngua and Namine atoms
to the zinc atoms was treated as covalent bond by the NBO
code and hence could not be seen as a coordinative bond and
no donor-acceptor energies could be obtained. In summary, n
the NBO calculations a larger donor ability of the Ngua lone pair
of the guanidine to the zinc metal centre was obtained. This
reveals stronger donor properties of the Ngua atom in comparison

European Journal of Inorganic Chemistry
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Table 3. Calculated bond lengths [Å] and angles [°] of C1-C12 [Gaussian09, TPSSh, def2-TZVP, GD3BJ, SMD:MeCN].
C1
C2
C3
C4
C5
C6
Zn-Ngua
Zn-Namine
Zn-Cl
2.025
2.153
2.285
2.289
85.8
2.057
2.126
2.27
2.29
85.6
85.4
18.7
0.95
0.93
2.042
2.139
2.278
2.295
84.1
2.063
2.129
2.283
2.295
85.1
2.010
2.124
2.3
2.013
2.122
2.284
2.315
98.7
2.286
96.4
87.1
36.4
0.97
0.88
N-Zn-N
∡ (ZnCl2, ZnN2)
87.6
84.7
85.5
88.6
∡ (ZnNguaNamine, CN3)
29.1
27.5
20.0
33.3

0.97
0.97
0.96
0.96
τ4
0.88
0.89
0.89
0.90
C7
C8
C9
C10
C11
C12
Zn-Ngua
Zn-Namine
Zn-Cl
2.022
2.197
2.304
2.301
97.8
2.015
2.131
2.284
2.321
98.1
2.044
2.169
2.256
2.283
80.4
2.053
2.164
2.274
2.261
79.8
2.047
2.168
2.270
2.297
80.8
2.049
2.169
2.267
2.296
80.3
N-Zn-N
∡ (ZnCl2, ZnN2)
85.6
88.3
88.2
89.1
86.6
87.9
∡ (ZnNguaNamine, CN3)
35.8
69.9
30.5
31.1
28.5
31.1

0.97
0.97
0.98
0.98
0.99
0.99
τ4
0.93
0.87
0.87
0.87
0.88
0.88
Table 4. Natural charge on zinc, Ngua, Namine and Cl atoms, energies [kcal/mol] for donor-acceptor interactions for C1-C12 [Gaussian09, TPSSh/def2-TZVP and
NBO 6.0].
C1
C2
C3
C4
C5
C6
Zn
1.55
-0.77
-0.53
-0.84
-0.85
45.5
30.0
1.55
-0.76
-0.53
-0.84
-0.84
cov
1.56
-0.78
-0.54
-0.84
-0.84
cov
1.56
-0.77
-0.54
-0.84
-0.84
42.2
29.8
1.57
-0.78
-0.54
-0.84
-0.85
47.7
30.6
1.56
-0.80
-0.54
-0.84
-0.85
cov
Ngua
Namine
Cl
LP(Ngua)-LV(Zn)
LP(Namine)-LV(Zn)
cov
cov
cov
C7
C8
C9
C10
C11
C12
Zn
1.57
-0.79
-0.54
-0.84
-0.85
cov
1.57
-0.80
-0.54
-0.83
-0.85
cov
1.56
-0.76
-0.53
-0.83
-0.84
42.4
26.9
1.56
-0.77
-0.53
-0.83
-0.83
42.1
27.7
1.55
-0.77
-0.54
-0.84
-0.83
41.2
26.5
1.56
-0.78
-0.54
-0.84
-0.83
41.9
26.7
Ngua
Namine
Cl
LP(Ngua)-LV(Zn)
LP(Namine)-LV(Zn)
cov
cov
monomer:catalyst ratio was chosen to be 500:1 (Scheme 2).
The conversion was determined by NMR spectroscopy, and by
GPC (gel permeation chromatography) the number-averaged
molecular weights as well as polydispersity were analysed.
Kinetic measurements
The polymerisation of technical rac-lactide with the complexes
C1, C2, C5, C6, C9 and C10 was realised in the lactide melt
without any coinitiator at 150 °C and variable times. Technical,
unsublimed lactide with no further purification was used with
regard to the industrial applicability. These complexes were
tested for the kinetic measurements, because only the influence
of the bridging unit was investigated and compared. The other
complexes (C3, C4, C7, C8, C11 and C12) have the same
bridging unit and differ only by their amine function. The
Scheme 2. ROP of lactide.

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
the aliphatic complexes (C1, C2, C5, C6) than of the aromatic
ones (C9, C10). This could be the reason for the varying results.
Table 5. Polymerisation of lactide.[a]
kapp [s-1][b]
t
conversion
[%][c]
Mn,exp.
Mn,calcd
PD
[min]
[g/mol][d] [g/mol]
C1
C1
C2
C2
C5
C5
C6
C6
C9
C9
C10
C10
1.5 10-5
1.5 10-5
1.7 10-5
1.7 10-5
2.2 10-5
2.2 10-5
3.3 10-5
3.3 10-5
5.0 10-6
5.0 10-6
5.0 10-6
5.0 10-6
830
64
76
59
75
70
86
94
76
27
38
21
41
19400
18000
18200
16100
15600
16600
13000
13000
-*
46000
54700
42500
54000
50400
61900
67700
54700
1.52
1.63
1.21
1.60
1.55
1.60
1.77
1.58
-
1430
830
1430
830
1430
830
Figure 4. First-order plot of ln([LA]0/[LA]t) versus time [min] of C1, C2, C5, C6,
C9, C10 at 150°C.
1430
830
Kinetic measurements were carried out to determine the order of
1430
830
-*
-
the chain propagation and the rate constant kapp
. The
-*
-
semilogarithmic relationship of the lactide concentration against
the time is depicted in Figure 4. A first-order polymerisation is
observed, which is in good accordance with a controlled
polymerisation.[7,15,53,58,84,85,98] The zinc chloride complexes with
an aromatic backbone (C9 and C10) show slow activity in the
polymerisation. The rate constant for C9 and C10 is 5.0 10-6
s-1. The conversion after 24h is about 40% for C9 and C10.
Complexes with ethylene bridge polymerise faster than those
with aromatic backbone. Here the rate constant kapp is for C1 1.5
10-5 s-1 and for C2 1.7 10-5 s-1. With a propylene bridge in
C6 we obtained the fastest polymerisation with a kapp of 3.3
10-5 s-1. Besides, a conversion of up to 80% after 14h could be
reached. However, a decrease of conversion after 24h could be
observed and the molecular weights decrease. The reason
might be a depolymerisation after 14h. The variation of the
guanidine unit (TMG or DMEG) has no significant influence on
the polymerisation activity. In case of dmae and dmap the
complex with DMEG is faster than with TMG unit. This trend is
not obtained for dmab-complexes. In summary the dmap-
complexes (C5, C6) are by trend faster in the polymerisation
than dmae-complexes (C1, C2). Dmab-complexes (C9, C10)
show the lowest activity for polymerisation. A large difference
between these three different bridging units is the angle between
zinc and the two coordinating N atoms. The angles in the
complexes with a propylene bridge (C5 and C6) are around 98 °,
with an ethylene bridge (C1 and C2) are about 86 ° and
complexes with a benzene bridge (C9 and C10) are 82 °. In
addition, the results indicate that the bond length of the bridging
group between the guanidine and amine moiety has an influence
on the rate. The shorter the bridging unit the lower the
polymerisation activity. C5 and C6 with the longest bridge
(propylene) show the best conversion and C9 and C10 with the
shortest bond (aromatic C-C-bond) lead to slow polymerisation
activity. Furthermore, the donor-acceptor interaction energies,
which are discussed before in the NBO analysis, are stronger for
1430
-*
-
* chains are too short for measuring with GPC.
[a] Polymerisation conditions: bulk, 150°C, M/I = 500/1. [b] Determined from
the slope of the plots of ln([LA]0/LA]t) versus time. [c] Determined by integration
of the methine region of the 1H NMR spectrum. [d] Determined by gel
permeation chromatography (GPC) in THF.
The number-averaged molecular weights are between 13000-
19400 g/mol. These values differ from the theoretically
calculated values which should amount to 42500-67700 g/mol. A
possible reason are intramolecular and intermolecular
transesterification reactions.[5] The polydispersity index is in all
cases around 1.5. We relate this behaviour to water acting as
coinitiator leading to more short chains.
To study the ring opening mechanism of lactide in more detail,
we added to the lactide monomer and catalyst benzyl alcohol as
initiator. Polymerisations were carried out in bulk at 150°C for 14
h with a ratio M/I/C (benzyl alcohol) = 500/1/1. As catalyst C1,
C5 and C6 was utilised. The conversion is with the addition of
benzyl alcohol by trend higher than without. The molecular
weights are around half the size of the molecular weights without
a coinitiator (Table 6). C5 has a Mn with a coinitiator of
8400 g/mol and without benzyl alcohol 15600 g/mol. This leads
to the assumption that the lactide monomer can be opened by
the coinitiator.
1
To underline this statement an end group analysis via H NMR
of the polylactide was performed. The reaction time was
shortened in order to obtain a smaller conversion and thus a
better resolution in NMR spectroscopy. The lactide monomer
was capped with a benzyloxy group (d) on one side and a
hydroxyl group on the other side (b) (Figure 5). This points
toward an insertion of the benzyloxy group into the lactide.[99]
Besides the synthesis of polylactide, cyclic oligomers are
obtained by intramolecular transesterification (x).

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
observed, which is in good accordance with a coordination-
insertion mechanism. It has to be noted that the complexes with
an ethylene or propylene bridge are more active in the
polymerisation than those with an aromatic backbone. The NBO
analysis led to the results that the aliphatic backbones have
higher interaction energies of the N atoms to the zinc atoms than
complexes with aromatic backbones. For the end group analysis
via 1H NMR spectroscopy, polymerisation experiments with
benzyl alcohol as coinitiator were perfomed proving the benzyl
alcohol as end group. Thus, the coinitiator opened the lactide
ring following a coordination-insertion mechanism.
Table 6. Polymerisation of rac-lactide with the addition of the coinitiator benzyl
alcohol.
[a]
conversion
[%][b]
Mn,exp.
Mn,calcd
[g/mol]
PD[c]
[g/mol][c]
C1
C5
C6
75
86
81
8300
8400
10900
27000
31000
29000
1.55
1.64
1.57
These studies open up new design pathways to more robust
zinc catalysts in lactide ROP using additional coinitiators.
[a] Polymerisation conditions: bulk, 150°C, M/I/C = 500/1/1, t = 14 h. [b]
Determined by integration of the methine region of the 1H NMR spectrum. [c]
Determined by gel permeation chromatography (GPC) in THF.
Experimental Section
General: All steps were performed under nitrogen (99.996%) dried with
P4O10 granulate using Schlenk techniques. Solvents were purified
according to literature procedures and also kept under nitrogen.[100] All
chemicals were purchased from Sigma-Aldrich GmbH, TCI GmbH and
ABCR GmbH and were used as received without further purification. D,L-
lactide (Corbion Purac) was dried for three days at 40°C under vacuo.
The precursor of the ligands TMGdmab, DMEGdmab, TMGdeab and
DMEGdeab was synthesised out of 1-fluronitrobenzene.[90] N,N’-
dimethylethylenechloroformamidinium
chloride
(DMEG-VS)
and
N,N,N’,N’-tetramethylchloroformamidinium chloride (TMG-VS) were
synthesised as described in the literature.[76,91]
Physical Methods: Fast-atom bombardment (FAB) mass spectra were
obtained with a Thermo Finnigan MAT 95 mass spectrometer for
complexes C9-C12. Ionisation was achieved with accelerated xenon
atoms (8kV) in glycerine or 2-nitrobenzyl alcohol matrix on a copper
target. ESI spectra were recorded with a Thermo Finnigan LTQ FT
Ultrafourier transform spectrometer (all ligands, C1, C3-C5, C7, C8). As
solvent acetonitrile and water was used. Resolution was adjusted to
100000 at m/z 400. Depending on the method, areas between 50 und
2000 u were measured. EI spectra were obtained with a Finnigan MAT
40 mass spectrometer (C2).
Figure 5. 1H NMR spectrum of PLA initiated by C1 [Zn(TMGdmae)Cl2]/benzyl
alcohol. Conditions: Lactide/Complex/BnOH = 500/1/1, 150 °C, 1h, conversion
= 27%.
Conclusions
ATR-IR spectra were measured with a Thermo Finnigan LTQ FT Ultra
fourier transform spectrometer (ligands, C1, C3-C12) or with the FT-IR-
spectrometer P510 of Nicolet as a KBr pellets (C2). Elemental analyses
were performed with a Vario MICRO CHNS Analyser. NMR spectra were
recorded on the following spectrometers: TMGdmab = Jeol EX270;
DMEGdmab, TMGdeab, DMEGdeab, C1, C3-C12 = Jeol EX400; C2 =
Bruker Avance 500. The NMR signals were calibrated to the residual
signals of the deuterated solvents (δH(CDCl3) = 7.26 ppm and δH(CD3CN)
= 1.94 ppm).
Herein, we presented twelve zinc chloride hybrid guanidine
complexes. The ligands were generated by the reaction of two
different chloroformamidinium chlorides with the corresponding
primary amines. Afterwards a coordination of the ligands to the
zinc chloride resulted in distorted tetrahedrally coordinated
complexes. The structural trends are compared with the results
of DFT calculations. The calculated and experimental structures
are in good accordance when using TPSSh/def2-TZVP together
with a SMD model and empirical dispersion with Becke-Johnson
damping. All results indicate a stronger coordination of the
guanidine N atom than the amine N atom to the zinc atom. The
Ngua-Zn bond lengths are slightly shorter in TMG compounds
than in corresponding DMEG complexes indicating that the TMG
unit is the stronger donor. The guanidine twist in TMG
complexes is higher because of free rotation of the methyl
groups. Besides, the guanidine moiety of complexes containing
an aromatic backbone are slightly better delocalised than
aliphatic complexes. The aliphatic complexes show good
polymerisation activity in the ring-opening polymerisation of
technical unsublimed lactide proving again the superior
robustness of guanidine zinc complexes. In the kinetic
X-ray Analyses: The crystal data for C1 – C12 are presented in Table 7.
The data for C1, C8 and C11 were collected with an Xcalibur
diffractometer from Oxford Diffraction, for C2 with a Bruker AXS SMART
APEX CCD and for C3 – C7, C9, C10 and C12 with a Bruker D8 Venture
APEX2 CCD using MoKα radiation (λ = 0.71073 Å) and a graphite
monochromator. Data reduction and absorption correction was
performed with CRYSALIS (Oxford, 2008) and CRYSALIS RED (Oxford,
2008) for C1, C8 and C11, with SAINT and SADABS for C2[101] and
SAINT and SADABS for C3 – C7, C9, C10 and C12[102]. The structure
was solved by direct methods and successive difference Fourier methods
and all non-hydrogen atoms refined anisotropically with full-matrix least-
squares based on F² (XPREP[103], SHELXTL[101] for C2 or SHELXS-97[104]
and ShelXle[105] for all other complexes). Hydrogen atoms were derived
from difference Fourier maps and placed at idealised positions, riding on
their parent C atoms, with isotropic displacement parameters Uiso(H) =
1.2Ueq(C) and 1.5Ueq(C methyl). All methyl groups were allowed to rotate
but not to tip. Full crystallographic data (excluding structure factors) for
polymerisation measurements
a
first-order behaviour is

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
C1 to C12 have been deposited with the Cambridge Crystallographic
Data Centre as supplementary no. CCDC – 1435628 for C1, CCDC –
1407092 for C2, CCDC – 1435629 for C3, CCDC – 1435630 for C4,
CCDC – 1435631 for C5, CCDC – 1435632 for C6, CCDC – 1435633 for
C7, CCDC –1435634 for C8, CCDC –1435635 for C9, CCDC –1435636
for C10, CCDC – 1435637 for C11 and CCDC – 1435638 for C12.
Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (+44)1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk).
2-(2-(dimethylamino)benzene)-1,1,3,3-tetramethylguanidine
(TMGdmab)
Green oil, yield: 4.45 g (19.2 mmol, 64%). 1H NMR (270 MHz, CDCl3,
25 °C): δ = 6.76-6.90 (m, 3H, CHarom), 6.49 (d, J = 7.3 Hz, 1H, CHarom),
2.74 (s, 6H, CH3), 2.66 (s, 12H, CH3) ppm. 13C{1H} NMR (68 MHz, CDCl3,
25°C): δ = 158.1 (Cgua), 144.8 (Carom), 122.1 (Carom), 121.9 (Carom), 120.0
(Carom), 117.1 (Carom), 42.9 (CH3), 39.1 (CH3) ppm. IR (ATR): ̃ = 3051
[vw (ν(C-Harom.))], 2998 [w (ν(C-Harom.))], 2930 [w (ν(C-Haliph))], 2850 [w
(ν(C-Haliph))], 2817 [w (ν(C-Haliph))], 2769 [w (ν(C-Haliph))], 1600 [s
(ν(C=Ngua))], 1572 [vs (ν(C=Ngua))], 1586 [vs (ν(C=Ngua))], 1444 (s), 1423
(m), 1369 (vs), 1315 (m), 1290 (m), 1263 (w), 1231 (m), 1202 (m), 1134
(vs), 1100 (m), 1046 (m), 1014 (s), 944 (s), 914 (m), 848 (w), 779 (m),
750 (s), 732 (s), 693 (m) cm−1. HR-MS ESI(+): m/z (%): calcd.: 235.1923
[C13H23N4]+, 190.1344 [C11H16N3]+, found: 235.1920 (60) [C13H23N4]+,
190.1340 (100) [C11H16N3]+.
Computational details:
Density functional theory (DFT) calculations were performed with the
program suite Gaussian 09.[106] The starting geometries for all complexes
were generated from the molecular structures from the X-ray
crystallography data. The Gaussian 09 calculations are performed with
the nonlocal hybrid meta GGA TPSSh functional[107] and with the Ahlrichs
type basis set def2-TZVP.[108] As solvent model, we used the SMD Model
(SMD, acetonitrile)[109] as implemented in Gaussian 09. As empirical
dispersion correction, we used the D3 dispersion with Becke-Johnson
damping as implemented in Gaussian, Revision D.01.[110,111] For TPSSh,
the values of the original paper have been substituted by the corrected
values kindly provided by S. Grimme as private communication.[112] NBO
calculations were accomplished using the program suite NBO 6.0.[97,95,96]
Some of these calculations have been performed within the MoSGrid
environment.[113-115]
2-(2-(dimethylamino)benzene)-1,1,3,3-dimethylethylenguanidine
(DMEGdmab)
Dark purple oil, yield: 4.39 g (18.9 mmol, 63%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 6.75-6.85 (m, 4H, CHarom), 3.25 (s,
4H, CH2), 2.79 (s, 6H, CH3), 2.64 (s, 6H, CH3) ppm. 13C{1H} NMR (100
MHz, CDCl3, 25°C): δ = 153.7 (Cgua), 145.6 (Carom), 143.1 (Carom), 123.2
(Carom), 121.5 (Carom), 120.7 (Carom), 117.1 (Carom), 48.4 (CH2), 42.8 (CH3),
34.8 (CH3) ppm. IR (ATR): ̃ = 3047 [w (ν(C-Harom.))], 3017 [vw (ν(C-
Harom.))], 2984 [w (ν(C-Harom.))], 2936 [m (ν(C-Harom.))], 2852 [m (ν(C-
Haliph))], 2819 [m (ν(C-Haliph))], 2772 [m (ν(C-Haliph))], 1649 [vs (ν(C=Ngua))],
1583 (m), 1567 (m), 1483 (s), 1477 (s), 1446 (s), 1435 (s), 1410 (m),
1392 (s), 1377 (m), 1356 (m), 1314 (m), 1278 (s), 1267 (m), 1240 (m),
1227 (m), 1191 (m), 1159 (m), 1120 (m), 1097 (m), 1073 (m), 1051 (m),
1032 (s), 992 (m), 967 (m), 944 (s), 918 (m), 866 (w), 857 (m), 847 (m),
772 (m), 752 (vs), 740 (s), 707 (m), 694 (m) cm−1. HR-MS ESI(+): m/z
(%): calcd.: 233.1766 [C13H21N4]+, found: 233.1762 (100) [C13H21N4]+.
Gel Permeation Chromatography (GPC):
The average molecular weights and the weight distributions of the
obtained polylactide samples were determined by gel permeation
chromatography (GPC) in THF as mobile phase at a flow rate of 1
mL/min. The utilised GPCmax VE-2001 from Viscotek is a combination of
an HPLC pump, two Malvern Viscotek T columns (porous styrene
divinylbenzene copolymer) with a maximum pore size of 500 and 5000 Å
and a refractive index detector (VE-3580) and a viscometer (Viscotek
270 Dual Detector). Universal calibration was applied to evaluate the
chromatographic results.
2-(2-(diethylamino)phenyl)-1,1,3,3-tetramethylguanidine (TMGdeab)
Dark purple oil, yield: 6.12 g (26.7 mmol, 87%).
Polymerisation
1H NMR (400 MHz, CDCl3, 25 °C): δ = 6.89-6.75 (m, 3H, CHarom), 6.50
(dt, 3J = 7.5 Hz, 1H, CHarom), 3.18 (q, 3J = 8.7 Hz, 7.9 Hz, 4H, CH2), 2.65
(s, 12H, CH3), 0.97 (t, 3J = 7.1 Hz, 6H, CH3) ppm. 13C{1H} NMR (100 MHz,
CDCl3, 25°C): δ = 158.6 (Cgua), 147.0 (Carom), 142.1 (Carom), 123.4 (Carom),
122.9 (Carom), 121.6 (Carom), 120.4 (Carom), 45.7 (CH2), 40.1 (CH3), 12.4
(CH3) ppm. IR (ATR): ̃ = 3054 [vw (ν(C-Harom.))], 2968 [w (ν(C-Harom.))],
2927 [m (ν(C-Haliph))], 2870 [m (ν(C-Haliph))], 2807 [w (ν(C-Haliph))], 1602
[vs (ν(C=Ngua))], 1577 [vs (ν(C=Ngua))], 1566 [vs (ν(C=Ngua))], 1484 (vs),
1440 (s), 1425 (m), 1403 (w), 1360 (vs), 1328 (m), 1263 (m), 1233 (s),
1201 (m), 1176 (m), 1134 (vs), 1101 (m), 1064 (m), 1049 (m), 1013 (s),
916 (w), 893 (w), 841 (w), 780 (m), 749 (s), 736 (s), 723 (m), 690 (m)
cm−1. HR-MS ESI(+): m/z (%): calcd.: 263.2236 [C15H28N4]+, found:
263.2228 (100) [C15H28N4]+, 218.1651 [C13H20N3], 147.0915 [C9H11N2].
At the beginning the exact mass of the catalyst (0.039 mmol) was
weighed in air. Furthermore, the lactide was dried for three days at 40°C
under reduced pressure (5 x 10-2 mbar). Afterwards in a nitrogen filled
box the catalyst and the D,L-lactide (3,6-dimethyl-1,4-dioxane-2,5-dione,
2.80 g, 19.40 mmol) were weighed into a morter and the catalyst and
lactide were completely homogenised. Into each of the 14 reaction
vessels about 200 mg are portioned. The reaction vessels were heated
at 150 °C in an oven. The starting point is when the lactide is melted.
After the reaction time the vessels were allowed to cool to room
temperature and dichloromethane is given to the polymer. After complete
dissolving an aliquot was taken for determine the conversion via 1H NMR.
The PLA was precipitated in ethanol (20 mL) and dried at 50°C.
N1-(1,3-dimethylimidazolidin-2-yliden)-N2,N2-diethylbenzene-1,2-
diamin (DMEGdeab)
General Synthesis of guanidine-amine hybrid ligands with
chloroformamidinium chlorides
To the corresponding amine (30 mmol) with trimethylamine (30 mmol)
dissolved in acetonitrile (40 mL) was added dropwise the Vilsmeier salt
(30 mmol) dissolved in acetonitrile (40 mL) at 0°C. Afterwards the
reaction mixture was stirred to reflux overnight. After adding NaOH
(30 mmol) the solvent and NEt3 were evaporated under vacuum. For a
complete deprotonation of the guanidine unit, KOH (15 mL 50 wt.-%) was
added and the guanidine ligand was extracted with acetonitrile (3x30 mL).
The combined organic layer was dried with Na2SO4 and the solvent was
evaporated under reduced pressure.[76]
Dark purple oil, yield: 6.06 g (26.1 mmol, 87%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 6.95-6.74 (m, 4H, CHarom), 3.22 (s,
3
3
4H, CH2), 3.16 (q, J = 7.0 Hz, 4H, CH2), 2.60 (s, 6H, CH3), 0.97 (t, J =
7.0 Hz, 6H, CH3) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25°C): δ = 153.9
(Cgua), 145.4 (Carom), 143.0 (Carom), 124.3 (Carom), 122.5 (Carom), 121.4
(Carom), 121.0 (Carom), 49.1 (CH2), 45.2 (CH2), 35.3 (CH3), 12.8 (CH3) ppm.
IR (ATR): ̃ = 3048 [vw (ν(C-Harom.))], 2967 [w (ν(C-Harom.))], 2928 [w (ν(C-
Haliph))], 2839 [w (ν(C-Haliph))], 1704 (w), 1649 [vs (ν(C=Ngua))], 1601 (m),
1582 (s), 1483 (s), 1437 (s), 1412 (m), 1390 (s), 1328 (w), 1276 (s), 1236
(s), 1196 (m), 1175 (m), 1142 (w), 1099 (m), 1072 (m), 1029 (s), 967 (m),

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
921 (w), 902 (vw), 878 (vw), 848 (vw), 791 (w), 748 (s), 714 (m), 691 (m)
cm−1. HR-MS ESI(+): m/z (%): calcd.: 261.2079 [C15H26N4]+, found:
261.2072 (100) [C15H26N4]+, 232.1679 [C13H20N4].
ppm. IR (ATR): ̃ = 2922 [s (ν(C-Haliph))], 2853 [m (ν(C-Haliph))], 1736 (m),
1717 (m), 1670 (w), 1616 (m), 1558 [vs (ν(C=Ngua.))], 1531 [s
(ν(C=Ngua.))], 1507 (m), 1469 (vs), 1455 (s), 1392 (vs), 1347 (m), 1309
(m), 1258 (m), 1232 (m), 1216 (m), 1157 (m), 1136 (m), 1081 (s), 1063
(s), 1036 (s), 1005 (m), 942 (w), 919 (m), 889 (m), 820 (m), 781 (s), 736
(s), 669 (m), 611 (m) cm−1. MS ESI(+): m/z (%) = 215.4 (100) [C11H27N4]+
(protonated ligand). C11H26N4Cl2Zn (297.27): calcd: C 37.7, H 7.5, N 16.0,
found C 37.6, H 7.3, N 15.8.
General Synthesis of Zinc Complexes with Guanidine Ligands:
A solution of the ligand (1 mmol), dissolved in dry acetonitrile (C1, C2, C4,
C6, C9, C10, C11, C12) (2 mL) and/or tetrahydrofurane (C1, C3, C4, C5,
C6, C7, C8) (2 mL), was added dropwise to a solution of zinc chloride
(1 mmol, 0.136 g) dissolved in the same solvent as the ligand (2 mL). In
the case of a clear solution, crystals could be obtained by diffusion of
diethyl ether (C1, C5, C6, C7, C11, C12). If the complex precipitate, the
precipitate was filtered off at high temperatures. Single crystals were
obtained by slowly cooling to room temperature (C2, C3, C4, C9, C10) or
controlled evaporisation of the solvent (C8).
N1-(1,3-dimethylimidazolidin-2-ylidene)-N2,N2-diethylethane-1,2-
diamine [Zn(DMEGdeae)Cl2] (C4)
Colourless crystals, yield: 0.19 g (0.55 mmol, 55%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.52 (dd, 3J = 6.3, 4.9 Hz, 2H,
CH2), 3.41 (s, 4H, CH2), 3.22 - 3.12 (m, 2H, CH2), 3.11 (s, 6H, CH3), 2.85
3
2-(2-(dimethylamino)ethyl)-1,1,3,3-tetramethylguanidine-
zinc(II)chloride [Zn(TMGdmae)Cl2] (C1)
- 2.70 (m, 4H, CH2), 1.14 (t, J = 7.18 Hz, 6H, CH3) ppm. 13C{1H} NMR
(100 MHz, CDCl3, 25°C): δ = 163.6 (Cgua), 53.2 (CH2), 50.0 (CH2), 43.9
(CH3), 43.8 (CH2), 37.2 (CH2), 8.2 (CH3) ppm. IR (ATR): ̃ = 2942 [w
(ν(C-Haliph))], 1606 [vs (ν(C=Ngua.))], 1509 (m), 1489 (m), 1458 (m), 1425
(m), 1405 (m), 1384 (m), 1349 (m), 1300 (s), 1246 (m), 1156 (m), 1078
(m), 1039 (m), 1008 (m), 908 (m), 822 (m), 778 (m), 739 (s), 647 (m),
637 (m), 609 (m) cm−1. MS ESI(+): m/z (%) = 213.4 (100) [C11H25N4]+
(protonated ligand). C11H24Cl2N4Zn (348.62): calcd. C 37.9, H 6.9, N 16.1,
found C 37.9, H 6.9, N 16.2.
Colourless crystals: yield: 0.11 g (0.43 mmol, 43%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.21- 3.29 (m, 2H, CH2), 2.95 (s,
6H, CH3), 2.83 (s, 6H, CH3), 2.66 - 2.74 (m, 2H, CH2), 2.56 (s, 6H, CH3)
ppm. 13C{1H} NMR (100 MHz, CDCl3, 25°C): δ = 165.6 (Cgua), 60.5 (CH2),
46.5 (CH3), 44.3 (CH2), 40.0 (CH3) ppm. IR (ATR): ̃ = 3264 [vw (ν(C-
Haliph))], 2892 [w (ν(C-Haliph))], 1623 (w), 1558 [vs (ν(C=Ngua.))], 1541 [s
(ν(C=Ngua.))], 1454 (m), 1427 (m), 1399 (s), 1345 (m), 1329 (m), 1281 (w),
1239 (m), 1154 (m), 1112 (w), 1081 (m), 1060 (m), 1029 (m), 1017 (m),
985 (w), 948 (m), 917 (w), 886 (m), 856 (w), 798 (m), 769 (w), 752 (m),
714 (w), 676 (w), 619 (w), 607 (vw) cm−1. MS ESI(+): m/z (%) = 187.2
(100) [C9H23N4]+ (protonated ligand). C9H22N4Cl2Zn (322.58): calcd: C
33.5, H 6.9, N 17.4, found C 33.5, H 6.7, N 17.4.
2-(3-(dimethylamino)propyl)-1,1,3,3-tetramethylguanidine
[Zn(TMGdmap)Cl2] (C5)
Colourless crystals, yield: 0.30 g (0.83 mmol, 83%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.35 (t, J = 5.22 Hz, 2H, CH2),
2.87 (s, 12H, CH3), 2.52 (s, 8H, CH3/CH2), 1.81 (ddd, 3J = 10.86, 6.32,
4.53 Hz, 2H, CH2) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25°C): δ = 166.4
(Cgua), 61.1 (CH2), 50.5 (CH2), 46.3 (CH2), 39.8 (CH3), 27.4 (CH3) ppm.
IR (ATR): ̃ = 2853 [vw (ν(C-Haliph))], 1564 [vs (ν(C=Ngua.))], 1533 [s
(ν(C=Ngua.))], 1462 (m), 1425 (m), 1393 (s), 1362 (w), 1343 (m), 1303 (w),
1229 (m), 1179 (w), 1154 (m), 1099 (w), 1087 (w), 1056 (m), 1030 (m),
1008 (w), 967 (m), 918 (m), 855 (m), 763 (m), 713 (w), 637 (w), 623 (w)
N1-(1,3-dimethylimidazolidin-2-ylidene)-N2,N2-dimethylethane-1,2-
diamine [Zn(DMEGdmae)Cl2] (C2)
Colourless crystals, yield: 0.20 g (0.74 mmol, 74%).
1H NMR (500 MHz, CD3CN, 25 °C): δ = 3.57 (m, 2H, CH2), 3.42 (s, 4H,
CH2), 3.06 (s, 6H, CH3), 2.68 (m, 2H, CH2), 2.51 (s, 6H, CH3) ppm.
13C{1H} NMR (125 MHz, CD3CN, 25°C): δ = 164.0 (Cgua), 59.7 (CH2),
49.6 (CH2), 45.3 (CH3), 44.2 (CH2), 36.5 (CH3) ppm. IR (KBr): ̃ = 2993
[w (ν(C-Haliph.))], 2972 [w (ν(C-Haliph.))], 2954 [m (ν(C-Haliph.))], 2918 [m
(ν(C-Haliph.))], 2879 [m (ν(C-Haliph.))], 2846 [w (ν(C-Haliph.))], 2804 [w (ν(C-
Haliph.))], 1608 [vs (ν(C=Ngua.))],1508 (m), 1460 (m), 1425 (m), 1404 (m),
1385 (m), 1348 (m), 1302 (m), 1263 (m), 1184 (vw), 1159 (vw), 1105
(vw), 1084 (m), 1041 (w), 1018 (m), 980 (vw), 947 (m), 906 (w), 804 (w),
769 (w), 729 (w), 648 (vw), 611 (w), 561 (vw), 530 (vw) cm−1. MS EI(+):
m/z (%): 324 (2) [C9H20N437Cl266Zn, C9H20N435Cl37Cl68Zn], 323 (1)
[C9H20N435Cl37Cl67Zn, C813CH20N435Cl37Cl66Zn, C813CH20N435Cl268Zn], 322
(3) [C9H20N435Cl37Cl66Zn, C9H20N437Cl264Zn, C9H20N435Cl268Zn], 321 (1)
[C9H20N435Cl267Zn, C813CH20N435Cl266Zn, C813CH20N435Cl37Cl64Zn], 320 (4)
[C9H20N435Cl266Zn, C9H20N435Cl37Cl64Zn], 319 (1) [C813CH20N435Cl264Zn],
318 (3) [C9H20N435Cl264Zn], 285 (33) [C9H20N4ClZn], 283 (37)
[C9H20N4ClZn], 184 (83) [C9H20N4]. C9H20N4Cl2Zn (320.57): calcd: C 33.7,
H 6.3, N 17.5, found C 33.7, H 6.3, N 17.6.
cm−1
.
MS ESI(+): m/z (%)
=
301.2 (20) [C10H24N435Cl66Zn;
C10H24N437Cl64Zn], 299.2 (100) [C10H24N435Cl64Zn]. C10H24Cl2N4Zn
(336.61): calcd. C 35.7, H 7.2, N 16.6, found C 35.6, H 7.1, N 16.6.
N1-(1,3-dimethylimidazolidin-2-ylidene)-N3,N3-dimethylpropane-1,3-
diamine [Zn(DMEGdmap)Cl2] (C6)
Colourless crystals, yield: 0.15 g, (0.46 mmol, 46%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.56 (t, 3J = 5.22 Hz, 2H, CH2),
3.44 (s, 4H, CH2), 2.98 (s, 6H, CH3), 2.85 (d, 3J = 5.43 Hz, 2H, CH2), 2.52
(s, 6H, CH3), 1.80 (q, J = 5.3 Hz, 2H, CH2) ppm. 13C{1H} NMR (100 MHz,
CDCl3, 25°C): δ = 167.4 (Cgua), 61.0 (CH2), 50.0 (CH2), 49.2 (CH2), 46.2
(CH3), 37.4 (CH3), 28.2 (CH2) ppm. IR (ATR): ̃ = 2953 [w (ν(C-Haliph))],
1737 (w), 1603 [vs (ν(C=Ngua.))], 1518 (m), 1464 (m), 1430 (m), 14060
(m), 1363 (m), 1344 (m), 1294 (m), 1229 (m), 1097 (w), 1055 (m), 1035
(m), 1010 (m), 936 (w), 912 (w), 859 (w), 775 (s), 715 (w), 683 (w), 651
(w), 619 (w), 609 (w) cm−1. C10H22N4Cl2Zn (334.59) calcd. C 35.9, H 6.6,
N 16.7, found C 35.8, H 6.4, N 16.6.
2-(2-(diethylamino)ethyl)-1,1,3,3-tetramethylguanidine
[Zn(TMGdeae)Cl2] (C3)
2-(3-(diethylamino)propyl)-1,1,3,3-tetramethylguanidine
[Zn(TMGdeap)Cl2] (C7)
Colourless crystals, yield: 0.21 g (0.61 mmol,61%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.24 (t, 3J = 5.50 Hz, 2H, CH2),
3.15 (dq, 3J=13.9, 7.11 Hz, 2H, CH2), 2.96 (s, 6H, CH3), 2.83 (s, 6H, CH3),
Colourless crystals, yield: 0.25 g (0.68 mmol, 68%).
3
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.31 (br. s., 3H, CH3), 3.24 (dq, 3J
= 14.07, 7.27 Hz, 2H, CH2), 3.08 (br. s., 3H, CH3), 2.95 - 2.90 (m, 2H,
CH2), 2.83 (s, 6H, CH3), 2.76 (dq, J = 14.1, 7.1 Hz, 4H, CH2), 1.78 (dt, 3J
2.79 - 2.83 (m, 2H, CH2), 2.70 - 2.79 (m, 2H, CH2), 1.15 (t, J = 7.1 Hz,
6H, CH3) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25°C): δ = 165.6 (Cgua),
53.8 (CH2), 44.5 (CH2), 43.8 (CH2), 40.1 (CH3), 40.0 (CH3), 8.4 (CH3)

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
= 10.56, 5.40 Hz, 2H, CH2), 1.13 (t, 3J = 7.25 Hz, 6H, CH3) ppm. 13C{1H}
NMR (100 MHz, CDCl3, 25°C): δ = 166.6 (Cgua), 54.4 (CH2), 50.7 (CH2),
44.8 (CH2), 39.8 (CH3), 26.4 (CH2), 7.6 (CH3) ppm. IR (ATR): ̃ = 2905 [w
(ν(C-Haliph))], 1560 [vs (ν(C=Ngua.))], 1540 [vs (ν(C=Ngua.))], 1468 (m),
1448 (m), 1427 (m), 1396 (s), 1362 (w), 1349 (m), 1324 (w), 1283 (w),
1226 (w), 1165 (m), 1150 (m), 1139 (m), 1102 (m), 1062 (w), 1045 (m),
1032 (w), 1011 (w), 962 (w), 942 (w), 907 (w), 884 (w), 822 (w), 783 (w),
Harom.))], 2901 [w (ν(C-Haliph))], 2875 [w (ν(C-Haliph))], 2803 [vw (ν(C-
Haliph))], 1599 (m), 1582 (m), 1564 [s (ν(C=Ngua.))], 1540 [vs (ν(C=Ngua.))],
1484 (s), 1458 (m), 1448 (m), 1421 (s), 1414 (m), 1410 (m), 1387 (m),
1294 (m), 1274 (m), 1235 (w), 1211 (w), 1187 (m), 1166 (m), 1160 (m),
1151 (w), 1102 (m), 1084 (w), 1044 (m), 1022 (m), 981 (m), 945 (w), 923
(s), 865 (m), 822 (m), 774 (vs), 752 (m), 742 (m), 697 (w), 611 (m) cm−1
.
MS FAB(+): m/z (%)
=
335.3 (39) [C13H20N437Cl66Zn], 333.3 (59)
765 (m), 739 (m), 718 (w), 638 (w), 622 (vw), 613 (vw), 606 (vw) cm−1
.
[C13H20N437Cl64Zn, C13H20N4 35Cl 66Zn]+, 331.3 (65) [C13H20N435Cl 64Zn]+,
MS ESI(+): m/z (%) = 229.0 (100) [C12H29N4]+ (protonated ligand).
C12H28N4Cl2Zn (364.66) calcd. C 39.5, H 7.74, N 15.3, found C 39.5, H
7.8, N 15.4.
233.4 (100) [C13H21N4]+. MS FAB(-): m/z (%) = 37.5 (0.6) [37Cl]-, 35.5 (2)
[
35Cl]-. C13H20N4Cl2Zn (368.61) calcd. C 42.4, H 5.5, N 15.2, found C 42.5,
H 5.4, N 15.1.
2-(3-(diethylamino)propyl)-1,1,3,3-tetraethylguanidine
[Zn(TEGdeap)Cl2] (C8)
2-(2-(Diethylamino)phenyl)-1,1,3,3-tetramethylguanidin-zinc(II)-
chloride [Zn(TMGdeab)Cl2] (C11):
Colourless crystals, yield: 0.24 g (0.57 mmol, 57%).
Colourless crystals; yield: 0.26 g (0.65 mmol, 65%).
3
1H NMR (400 MHz, CDCl3, 25 °C): δ = 3.65 (br. s., 2H, CH2), 3.24 (dt, J =
1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.21 (d, J = 8.1 Hz, 1H, CHarom),
3
12.8, 6.7 Hz, 2H, CH2), 3.20 - 3.12 (m, 2H, CH2), 3.08 (d, J = 6.05 Hz,
7.14 (t, 3J = 8.3 Hz, 1H, CHarom), 6.96 (t, 3J = 8.3 Hz, 1H, CHarom), 6.55(d,
3J = 8.3 Hz, 1H, CHarom), 3.22 (s, 4H, CH2), 2.95 (s, 12H, CH3), 1.17 (s,
6H, CH3) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ = 163.8 (Cgua),
142.6 (Carom), 138.7 (Carom), 127.5 (Carom), 124.1 (Carom), 122.1 (Carom),
120.2 (Carom), 47.8 (CH2), 40.8 (CH3), 40.1 (CH3) ppm. IR (ATR): ̃ =
2978 [vw (ν(C-Harom.))], 2937 [vw (ν(C-Haliph.))], 2879 [vw (ν(C-Haliph.))],
2790 [vw (ν(C-Haliph.))], 1631 (vw), 1541 [vs (ν(C=Ngua.))], 1475 (m), 1445
(m), 1420 (m), 1396 (s), 1343 (w), 1287 (vw), 1262 (vw), 1230 (w), 1210
(w), 1152 (m), 1118 (w), 1103 (w), 1061 (w), 1042 (w), 1029 (m), 1011
(w), 922 (vw), 886 (w), 872 (w), 849 (w), 823 (m), 811 (m), 792 (m), 776
4H, CH2), 2.97 - 2.86 (m, 2H, CH2), 2.86 - 2.69 (m, 2H, CH2), 1.75 (dt, 3J
= 10.4, 5.3 Hz, 2H, CH2), 1.35 – 0.89 (m, 18H, CH3) ppm. 13C{1H} NMR
(100 MHz, CDCl3, 25°C): δ = 166.5 (Cgua), 54.37 (CH2), 51.3 (CH2), 43.6
3
(CH2), 42.0 (CH2), 26.3 (CH2), 13.6 (d, J = 18.93 Hz, CH3), 13.1 (CH3),
7.7 (CH3) ppm. IR (ATR): ̃ = 2969 [m (ν(C-Haliph))], 2930 [w (ν(C-Haliph))],
1728 (w), 1536 [vs (ν(C=Ngua))], 1489 (m), 1436 (vs), 1380 (m), 1342 (m),
1284 (s), 1206 (m), 1147 (m), 1103 (m), 1073 (m), 1042 (m), 1016 (m),
1005 (m), 963 (m), 928 (m), 859 (w), 792 (m), 749 (m), 738 (m), 701 (m),
636 (w), 605 (m). MS ESI(+): m/z (%) = 285.3 (100) [C16H37N4]+
(protonated ligand). C16H36N4Cl2Zn (420.77) calcd. C 45.7, H 8.6, N 13.3,
found C 45.7, H 8.9, N 13.3.
(s), 753 (m), 729 (w), 707 (m), 668 (vw), 632 (w), 620 (w), 605 (w) cm−1
.
MS FAB(+): m/z (%)
=
367.1 (3) [C15H2637ClN468Zn]+, 366.1 (3)
[C1413CH2635ClN468Zn]+, 365.1 (10) [C15H2637ClN466Zn; C15H2635ClN468Zn]+,
364.1 (7) [C15H2635ClN467Zn; C1413CH2635ClN466Zn; C1413CH2637ClN464Zn]+,
2-(2-(dimethylamino)phenyl)-1,1,3,3-tetramethylguanidine-
zinc(II)chloride [Zn(TMGdmab)Cl2] (C9)
363.1
(15)
[C15H2635ClN466Zn;
C15H2637ClN464Zn]+,
362.1
(5)
[C1413CH2635ClN464Zn]+, 361.1 (20) [C15H2635ClN464Zn]+, 263.4 (40)
[C15H27N4]+. HR MS FAB(+): m/z (%) = M = C15H26Cl2N4Zn: calcd.
361.1137 [C15H2635ClN464Zn]+; found 361.1128 [C15H2635ClN464Zn]+.
C15H26Cl2N4Zn (396.08): calcd. C 45.2, H 6.6, N 14.1, Cl 17.8, found C
45.0, H 6.5, N 14.0, Cl 17.7.
Colourless crystals, yield: 0.32 mg (0.85 mmol, 85%).
4
1H NMR (400 MHz, CDCl3, 25°C): δ = 7.35 (dd, 3J = 8.1 Hz, J = 1.4 Hz,
1H, CHarom), 7.16 (ddd, J = 8.0, 7.4, 1.4 Hz, 1H, CHarom) 7.02 (ddd, J =
8.1, 7.4, 1.5 Hz, 1H, CHarom), 6.56 (dd, 3J = 8.0 Hz, 4J = 1.4 Hz, 1H,
CHarom), 2.98 (s, 6H, CH3), 2.89 (s, 6H, CH3), 2.72 (s, 6H, CH3) ppm.
13C{1H} NMR (100 MHz, CDCl3, 25°C): δ = 164.0 (Cgua), 142.1 (Carom),
141.9 (Carom), 127.7 (Carom), 122.9 (Carom), 121.0 (Carom), 120.1 (Carom),
48.9 (CH3), 40.6 (CH3), 40.0 (CH3) ppm. IR (ATR): ̃ = 3055 [vw (ν(C-
Harom.))], 3008 [vw (ν(C-Harom.))], 2964 [w (ν(C-Haliph.))], 2867 [w (ν(C-
Haliph.))], 2797 [w (ν(C-Haliph.))], 1608 (vw), 1594 (vw), 1577 (w), 1539 [vs
(ν(C=Ngua.))], 1572 [vs (ν(C=Ngua.))], 1482 (m), 1468 (m), 1453 (m), 1437
(m), 1420 (s), 1407 (m), 1393 (vs), 1343 (m), 1284 (m), 1262 (m), 1239
(m), 1205 (m), 1182 (w), 1156 (s), 1144 (m), 1115 (w), 1102 (m), 1097
(m), 1065 (w), 1041 (m), 1035 (s), 1018 (m), 983 (w), 925 (m), 862 (m),
852 (m), 815 (m), 762 (s), 749 (m), 712 (m) cm−1. MS FAB(+): m/z (%) =
2-((1,3-dimethylimidazolidin-2-ylidene)amino)-N,N-diethylaniline-
zinc(II)chloride [Zn(DMEGdeab)Cl2] (C12)
Green crystals; yield: 0.29 g (0.73 mmol, 73%).
1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.26 (dd, 3J = 8.0, 1.4 Hz, 1H,
3
CHarom), 7.14 (ddd, J = 7.9, 7.4, 1.5 Hz, 1H, CHarom), 6.98-6.89 (m, 2H,
CHarom), 3.63 -3.49 (m, 4H, CH2), 3.28-3.07 (m, 4H, CH2), 2.77 (s, 6H,
CH3), 1.09 (t, 3J = 7.2 Hz, 6H, CH3) ppm. 13C{1H} NMR (100 MHz, CDCl3,
25°C): δ = 161.9 (Cgua), 141.3 (Carom), 137.8 (Carom), 126.1 (Carom), 122.8
(Carom), 120.5 (Carom), 120.2 (Carom), 47.4 (CH2), 45.9 (CH3), 34.2 (CH2),
8.6 (CH3) ppm. IR (ATR): ̃ = 2984 [vw (ν(C-Harom.))], 2936 [vw (ν(C-
Haliph.))], 2887 [vw (ν(C-Haliph.))], 2805 [vw (ν(C-Haliph.))], 1598 (m), 1579
(s), 1563 [vs (ν(C=Ngua.))], 1531 (s), 1482 (s), 1463 (m), 1448 (m), 1417
(s), 1389 (m), 1378 (m), 1293 (s), 1270 (m), 1210 (m), 1154 (m), 1119
(w), 1102 (m), 1081 (w), 1037 (m), 1009 (m), 983 (w), 927 (vw), 888 (w),
858 (w), 818 (w), 797 (w), 767 (vs), 745 (s), 726 (w), 699 (w), 659 (m)
cm−1. MS FAB(+): m/z (%) = 365.1 (10) [C15H2437ClN468Zn]+, 364.1 (10)
[C1413CH2435ClN468Zn]+, 363.1 (30) [C15H2437ClN466Zn; C15H2435ClN468Zn]+,
333.3 (84) [C13H22N435Cl 64Zn]+, 335.3 (76) [C13H22N4 37Cl64Zn,
+
C13H22N435Cl66Zn]
,
337.3 (50) [C13H22N437Cl66Zn], 235.4 (100)
[C13H23N4]+, 190.3 (72) [C11H16N3]+. MS FAB(-): m/z (%) = 35.5 (2) (2)
35Cl-], 37.5 (0.6) [37Cl]- . C13H22N4Cl2Zn (370.63) calcd. C 42.1, H 6.0, N
[
15.1, found C 42.1, H 6.03, N 15.0.
2-((1,3-dimethylimidazolidin-2-ylidene)amino)-N,N-dimethylaniline-
zinc(II)chlorid [Zn(DMEGdmab)Cl2] (C10)
362.1
(10)
[C15H2435ClN467Zn;
C1413CH2435ClN466Zn;
C1413CH2437ClN464Zn]+, 361.1 (45) [C15H2435ClN466Zn; C15H2437ClN464Zn]+,
360.1 (15) [C1413CH2435ClN464Zn]+, 359.1 (50) [C15H2435ClN464Zn]+, 261.4
Yellow crystals, yield: 0.32 g (0.89 mmol, 89%).
(100) [C15H25N4]+ MS FAB(-): m/z (%) = 35.0 (2) [35Cl-]. HR MS FAB(+):
.
1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.30 (dd, 3J = 8.1 Hz, 4J = 1.4 Hz,
CHarom), 7.13 (ddd, J = 8.1, 7.4, 1.5 Hz, 1H, CHarom), 6.97 (ddd, J = 8.0,
m/z (%) = M = C15H24Cl2N4Zn: calcd. 359.0980 [C15H2435ClN464Zn]+,
found: 359.0981 [C15H2435ClN464Zn]+.
4
7.4, 1.5 Hz, 1H, CHarom), 6.85 (dd, 3J = 8.1 Hz, J = 1.4 Hz, 1H, CHarom),
3.65 (d, J = 5.7 Hz, 4H, CH2), 2.90 (s, 6H, CH3), 2.89 (s, 6H, CH3) ppm.
13C{1H} NMR (100 MHz, CDCl3, 25°C) δ = 162.6 (Cgua), 141.9 (Carom),
141.1 (Carom), 127.3 (Carom), 122.3 (Carom), 121.4 (Carom), 120.5 (Carom),
48.5 (CH2), 48.2 (CH3), 35.7 (CH3) ppm. IR (ATR): ̃ = 2961 [w (ν(C-
Acknowledgements

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
The authors thank Corbion for the generous donation of rac-
lactide. Calculation time at the Paderborn Cluster for Parallel
Computing (PC2 Paderborn), MoSGrid project and the Leibniz
Rechenzentrum München is gratefully acknowledged. T.R.
thanks the Fonds der Chemischen Industrie for granting a Fonds
fellowship.

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
Table 7: Crystallographic data and parameters of C1-C12

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
C9
C1
C10
C2
C11
C12
C3
C4
Empirical formula
Formula mass [gmol−1
C9H22Cl2N4Zn
C9H20Cl2N4Zn
320.56
C11H26Cl2N4Zn
350.63
C11H24Cl2N4Zn
348.61
]
322.58
Crystal size [mm]
0.33 0.26 0.17
0.37 0.32 0.23
120(0)
0.19 0.11 0.07
200(2)
0.13 0.10 0.10
100(2)
T [K]
100(2)
Crystal system
orthorhombic
Monoclinic
P21/n
monoclinic
P21/n
monoclinic
P21/c
Space group
a [Å]
b [Å]
c [Å]
P212121
7.719(1)
13.201(1)
7.901(1)
13.847(1)
90
7.308(1)
9.869(1)
23.146(1)
90
12.186(1)
8.079(1)
15.643(1)
90
13.662(1)
13.723(1)
α [°]
90
β [°]
90
108.89(1)
90
91.64(1)
90
93.34(1)
90
γ [°]
90
V [Å3]
1447.2(1)
1366.5(2)
4
1668.6(2)
4
1537.5(2)
4
Z
4
ρcalcd. [gcm−3
]
1.481
1.558
1.396
1.506
μ [mm−1
λ [Å]
]
2.049
2.169
1.783
1.935
0.71073
0.71073
664
0.71073
736
0.71073
728
F(000)
672
hkl range
Reflections collected
–4≤h≤10, –16≤k≤17, –5≤l≤17
±17, ±10, ±18
11644
±8, ±11, –26≤l≤28
27371
±14, ±9, ±18
41567
3748
Independent reflections
Rint.
2679
3252
3100
2865
0.0273
151
0.0225
0.0331
0.0374
Number of parameters
R1 [I 2σ(I)]
145
169
167
0.0312
0.0600
0.993
0.0241
0.0213
0.0190
wR2 (all data)
0.0620
0.0591
0.0450
Goodness-of-fit
1.064
1.365
1.077
Largest diff. peak, hole [eÅ−3
]
–0.426, 0.472
–0.350, 0.245
–0.293, 0.288
–0.185, 0.322
C5
C6
C7
C8
Empirical formula
Formula mass [gmol−1
C10H24Cl2N4Zn
336.60
C10H22Cl2N4Zn
334.59
C12H28Cl2N4Zn
364.65
C16H36Cl2N4Zn
420.76
]
Crystal size [mm]
T [K]
0.17 0.09 0.09
100(2)
0.15 0.06 0.04
100(2)
0.19 0.11 0.07
100(2)
0.35 0.15 0.10
100(2)
Crystal system
Space group
a [Å]
monoclinic
P21/c
Orthorhombic
Pca21
monoclinic
P21/n
tetragonal
P
4
10.592(1)
9.821(1)
22.289(1)
11.212(1)
11.687(1)
90
10.673(1)
11.246(1)
14.807(1)
90
17.546(1)
17.546(1)
6.926(1)
90
b [Å]
c [Å]
15.174(1)
90
α [°]
β [°]
γ [°]
V [Å3]
Z
104.63(1)
90
90
106.31(1)
90
90
90
90
1527.3(2)
4
2920.6(2)
8
1705.8(2)
4
2132.2(2)
4
ρcalcd. [gcm−3
]
1.464
1.522
1.420
1.311
μ [mm−1
]
1.944
2.033
1.747
1.407
λ [Å]
0.71073
704
0.71073
1392
0.71073
768
0.71073
F(000)
896
hkl range
Reflections collected
±12, ±11, ±18
33301
2835
±27, ±13, ±14
23458
5900
±12, ±13, ±17
57714
3176
–21≤h≤9, –10≤k≤21, –7≤l≤8
7274
Independent reflections
Rint.
4226
0.0377
160
0.0606
160
0.0493
178
0.0338
216
Number of parameters
R1 [I 2σ(I)]
0.0229
0.0892
1.077
0.0229
0.0892
1.077
0.0204
0.0509
1.101
0.0333
0.0694
1.028
wR2 (all data)
Goodness-of-fit
Largest diff. peak, hole [eÅ−3
]
–0.579, 0.639
–0.579, 0.639
–0.194, 0.331
–0.328, 0.533

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
Empirical formula
Formula mass [gmol−1
C13H22Cl2N4Zn
C13H20Cl2N4Zn
368.60
C15H26Cl2N4Zn
398.67
C15H24Cl2N4Zn
]
370.62
396.65
Crystal size [mm]
0.12 0.08 0.06
123(2)
0.18 0.11 0.10
123(2)
0.30 0.25 0.20
173(2)
0.18 0.10 0.08
T [K]
173(2)
Crystal system
monoclinic
P21/c
Orthorhombic
P212121
9.943(1)
10.311(1)
15.751(1)
90
monoclinic
P21/c
orthorhombic
Space group
a [Å]
b [Å]
c [Å]
Pna21
9.282(1)
15.313(1)
12.340(1)
90
12.245(1)
10.255(1)
15.419(1)
90
16.201(1)
10.387(1)
10.524(1)
α [°]
90
β [°]
107.62(2)
90
90
109.70(1)
90
90
γ [°]
90
90
V [Å3]
1671.6(2)
4
1614.8(2)
4
1822.9(2)
4
1771.1(2)
Z
4
ρcalcd. [gcm−3
]
1.473
1.516
1.453
1.488
μ [mm−1
λ [Å]
]
1.785
1.847
1.642
1.690
0.71073
768
0.71073
760
0.71073
832
0.71073
F(000)
824
hkl range
Reflections collected
±12, ±20, –15≤l≤16
44661
–13≤h≤12, ±13, ±21
43620
±15, ±12, –19≤l≤17
10349
–21≤h≤20, –13≤k≤12, ± 13
55977
Independent reflections
Rint.
4175
4017
3707
4072
0.0379
0.0488
0.0336
0.0477
203
Number of parameters
R1 [I 2σ(I)]
187
185
205
0.0236
0.0223
0.0296
0.0217
0.0649
1.210
wR2 (all data)
0.0566
0.0466
0.0708
Goodness-of-fit
1.058
1.032
1.051
Largest diff. peak, hole [eÅ−3
]
–0.222, 0.437
–0.222, 0.437
–0.323, 0.360
–0.356, 0.404

European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
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European Journal of Inorganic Chemistry
10.1002/ejic.201600870
FULL PAPER
FULL PAPER
lactide polymerization*
Angela Metz, Ramona Plothe,
Britta Glowacki, Andreas Koszalkowski,
Michael Scheckenbach, Andreas Beringer,
Thomas Rösener, Janna Michaelis de
Vasconcellos, Ulrich Flörke, Alexander
Hoffmann, Sonja Herres-Pawlis
Twelve new zinc chloride complexes
with hybrid guanidine ligands are
reported. The structural properties of
these systems were studied
intensively by means of X-ray
crystallography and DFT calculations.
The activity in lactide polymerisation
was correlated with their natural
charges.
Page No. –Page No.
Zinc chloride complexes with aliphatic and
aromatic guanidine hybrid ligands and their
characteristic for the ring opening
polymerization of D,L-lactide