Synthesis and characterization of β-diketiminate zinc complexes

Article abstract of DOI:10.1002/zaac.200801382

Reactions of the monomeric β-diketiminate zinc complex MesNacNacZnMe (MesNacNac = {[2,6-(2,4,6-Me₃-C₆H₂)-N(Me)C)] ₂CH}) with ROH (R = Me, Et, iPr) yielded the corresponding zinc alkoxides [MesNacNacZnOR]₂

Full text of DOI:10.1002/zaac.200801382

ARTICLE
DOI: 10.1002/zaac.200801382
Synthesis and Characterization of β-Diketiminate Zinc Complexes
Stephan Schulz,*[a] Tamara Eisenmann,[a] Dieter Bläser,[a] and Roland Boese[a]
Dedicated to Professor Gerd Meyer on the Occasion of His 60th Birthday
Keywords: Zinc; β-Diketiminate; X-ray diffraction; Coordination chemistry; NMR spectroscopy
Abstract. Reactions of the monomeric β-diketiminate zinc complex
MesNacNacZnMe (MesNacNac {[2,6-(2,4,6-Me3ϪC6H2)-
N(Me)C)]2CH}) with ROH (R ϭ Me, Et, iPr) yielded the corre-
sponding zinc alkoxides [MesNacNacZnOR]2 (R ϭ Me 1, Et 2,
reducing agents such as potassium graphite, potassium, or sodium
gave the ZnII complex [MesNacNac]2Zn 4. Compounds 1Ϫ4
were characterized by elemental analyses, mass and multinuclear
(1H, 13C{1H}) NMR spectroscopy, and by single-crystal X-ray
ϭ
iPr 3). In addition, the reaction of MesNacNacZnCl with various analysis.
reduction reactions of MesNacNacZnX (X ϭ Cl, I) with
reducing agents such as sodium, potassium, and potassium
graphite, respectively.
Introduction
β-Diketiminato-ligands {(RN(RЈ)C]2CH} have been
demonstrated in the past to efficiently stabilize unusual low-
valent [1], multiple-bonded [2], and cationic metal com-
plexes [3]. One of the most striking features is that their
steric demand can be precisely controlled by variation of
the organic substituents R bound to the imine centre. β-
Diketiminate zinc complexes, which are known for a long
time [4], have received growing interest over the last decade.
Amide and alkoxide complexes LZnX (X ϭ NR2, OR; L ϭ
β-diketiminato), in particular those containing the sterically
demanding DippNacNac substituent (DippNacNac ϭ
{[(2,6-iPr2ϪC6H3)N(Me)C)]2CH}[5]), are very efficient liv-
ing single-site catalysts for the ring-opening polymerization
Experimental Section
General Procedure
Manipulations were performed in a glovebox under argon or with
standard Schlenk techniques. Dry solvents were obtained from a
solvent purification system (MBraun) and degassed prior to use.
MesNacNacZnX (X ϭ Me, Cl) [9] was prepared according to lit-
erature methods, alcohols were obtained from Acros and dried
prior to use. A Bruker DMX300 spectrometer was used for NMR
spectroscopy. 1H and 13C{1H} NMR spectra were referenced to
(ROP) of lactide [6] and the copolymerization of epoxides internal C6D5H (1H: δ ϭ 7.154; 13C: δ ϭ 128.0). IR spectra were
recorded with a Bruker Alpha-T FT-IR spectrometer. Melting
points were measured in sealed capillaries and were not corrected.
Elemental analyses were performed at the Elementaranalyse Labor
of the University of Essen.
and carbon dioxide [7]. Moreover, the high potential of β-
diketiminato-ligands to stabilize low-coordinate and low-
valent compounds was demonstrated by the synthesis of the
ZnϪZn bonded complex DippNacNac2Zn2 [8].
We became only recently interested in β-diketiminate zinc
complexes and reported on the synthesis of several com-
plexes of the type MesNacNacZnX (MesNacNac ϭ
{[(2,4,6-Me3ϪC6H2)N(Me)C)]2CH}, X ϭ Cl, I, Me) [9] as
well as the low-valent complex MesNacNac2Zn2 [10].
Herein, we report on the synthesis of β-diketiminate zinc
alkoxides complexes of the type LZnOR (X ϭ Me 1, Et 2,
iPr 3) and MesNacNac2Zn (4), which was obtained from
General synthesis of {[(2,4,6-Me3؊C6H2)N(Me)C)]2CH}ZnOR
(R ؍ Me 1, Et 2, iPr 3): ROH (R ϭ Me 1, Et 2, iPr 3, 5 mmol)
was added at ambient temperature to MesNacNacZnMe (2.07 g,
5 mmol) dissolved in Et2O (40 mL). After the gas evolution has
stopped, the solution was stirred for additional 12 h. Colorless
solids precipitate, which were isolated by filtration and recrys-
tallized from solutions in toluene at Ϫ30 °C.
1: Yield 1.93 g (90 %), Mp:
> 230 °C. Elemental Analysis
C48H64N4O2Zn2 (859.80 g·molϪ1): found (calcd): H, 7.39 (7.50);
C, 66.67 (67.05); N, 6.23 (6.52) %.
* Prof. Dr. S. Schulz
Fax: ϩ49-201-1833830
1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 1.50 (s, 6 H, β-CCH3), 2.05
(s, 12 H, o-CH3), 2.39 (s, 6 H, p-CH3), 3.5 (s, 3 H, OCH3), 4.76 (s,
1 H, γ-CH), 6.86 (s, 4 H, m-H). 13C NMR (75 MHz, C6D6, 25 °C):
δ ϭ 17.8 (o-CH3), 20.9 (β-CCH3), 22.7 (p-CH3), 64.5 (OCH3), 93.8
(γ-C), 129.1 (m-C), 131.6 (o-C), 132.1 (p-C), 145.2 (ipso-C), 167.5
E-Mail: stephan.schulz@uni-due.de
[a] Institute of Chemistry
University of Duisburg-Essen
Universitätsstr. 5Ϫ7, S07 S03 C30
45117 Essen, Germany
Z. Anorg. Allg. Chem. 2009, 635, 995Ϫ1000
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
995

S. Schulz, T. Eisenmann, D. Bläser, R. Boese
ARTICLE
(β-C). IR: ν1543, 1521, 1454, 1378, 1259, 1202, 1148, 1079,
application to The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: ϩ44-1223-336-033; E-Mail for
inquiry: fileserv@ccdc.cam.ac.uk; E-Mail for deposition:
deposit@ccdc.cam.ac.uk).
1013 cmϪ1
.
2: Yield 1.69 g (77 %), Mp:
> 230 °C. Elemental Analysis
C50H68N4O2Zn2 (887.86 g·molϪ1): found (calcd): H, 7.64 (7.72);
C, 67.42 (67.64); N, 6.30 (6.31) %.
Results and Discussion
1H NMR (300 MHz, [D8]THF, 25 °C):
δ ϭ 0.89 (m, 3 H,
OCH2CH3), 1.39 (s, 6 H, β-CCH3), 1.77 (s, 12 H, o-CH3), 2.37 (s,
6 H, p-CH3), 3.48 (m, 2 H, OCH2CH3), 4.70 (s, 1 H, γ-CH), 6.78
(s, 4 H, m-H) 13C NMR (75 MHz, [D8]THF, 25 °C): δ ϭ 18.6
(o-CH3), 21.1 (OCH2CH3), 21.4 (β-CCH3), 23.1 (p-CH3), 61.7
(OCH2CH3), 94.4 (γ-C), 130.0 (m-C), 132.4 (o-C), 133.0 (p-C),
146.7 (ipso-C), 167.8 (β-C). IR: ν1544, 1523, 1403, 1261, 1202, 1148,
Equimolar amounts of MesNacNacZnMe and ROH
react at ambient temperature with smooth evolution of
methane and subsequent formation of the corresponding
alkoxides MesNacNacZnOR (R ϭ Me 1, Et 2, iPr 3) in
high yield (Scheme 1).
1021, 856 cmϪ1
.
3: Yield 1.8 g (78 %), Mp:
> 230 °C. Elemental Analysis
C52H72N4O2Zn2 (915.91 g·molϪ1): found (calcd): H, 7.86 (7.92);
C, 68.2 (67.67); N, 6.08 (6.12) %.
1H NMR (300 MHz, [D8]THF, 25 °C):
δ ϭ 0.86 (d, 6 H,
CH(CH3)2), 1.41 (s, 6 H, β-CCH3), 1.83 (s, 12 H, o-CH3), 2.36 (s,
6 H, p-CH3), 3.48 (m, 1 H, (CH)O), 4.77 (s, 1 H, γ-CH), 6.86 (s,
4 H, m-H). 13C NMR (75 MHz, [D8]THF, 25 °C): δ ϭ 19.3 (o-
CH3), 21.1 (β-CCH3), 23.5 (p-CH3), 28.2 (CH(CH3)2), 65.8
(OCH(CH3)2), 95.1 (γ-C), 130.0 (m-C), 132.7 (o-C), 133.2 (p-C),
146.9 (ipso-C), 168.1 (β-C). IR: ν1460, 1376, 1260, 1093, 1019,
Scheme 1. Synthesis of β-diketiminate zinc alkoxides by methane
elimination reaction.
799 cmϪ1
.
Compounds 1Ϫ3 were obtained as colorless crystalline
{[(2,4,6-Me3؊C6H2)N(Me)C)]2CH}2Zn (4): A solution of sodium
naphtalenide (5 mmol) in THF was added dropwise to
MesNacNacZnCl (2.16 g, 5 mmol) dissolved in THF (20 mL). The
suspension was stirred at ambient temperature for 12 h and then
filtered. The extract was reduced in volume and stored for 48 h at
Ϫ30 °C. Compound 4 was obtained in form of colorless crystals.
solids after recrystallization from solutions in toluene at
1
Ϫ30 °C. H and 13C NMR spectra of 1Ϫ3 show the ex-
pected resonances due to the MesNacNac ligand and the
OR groups in the expected 1:1 intensities, whereas the
resonances of the ZnϪMe group has disappeared.
Single crystals of 1Ϫ3 suitable for X-ray structure deter-
minations were obtained from solutions in THF (1, 2) and
benzene (3), respectively, at Ϫ30 °C. The molecular struc-
tures of 2 and 3 are shown in Figure 1 and Figure 2.
4: Yield 1.8 g (78 %), Mp:
> 230 °C. Elemental Analysis
C46H58N4Zn (732.36 g·molϪ1): found (calcd): H, 7.92 (7.98); C,
75.14 (75.44); N, 7.48 (7.65) %.
1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 1.52 (s, 6 H, β-CCH3), 1.96
(s, 12 H, o-CH3), 2.22 (s, 6 H, p-CH3), 4.80 (s, 1 H, γ-CH), 6.70 (s,
4 H, m-H). 13C NMR (75 MHz, C6D6, 25 °C): δ ϭ 18.2 (o-CH3),
20.6 (β-CCH3), 23.4 (p-CH3), 94.1 (γ-C), 128.6 (m-C), 131.7 (o-C),
132.7 (p-C), 141.5 (ipso-C), 160.8 (β-C). IR: ν1552, 1515, 1453,
1398, 1258, 1148, 1007, 854, 779.
¯
1 and 2 crystallize in the triclinic space group P1 with
two molecules in the unit cell, whereas 3 crystallizes in the
monoclinic space group P21/c with four molecules in the
unit cell. 1Ϫ3 adopt dimeric structures in the solid state
with bridging OR groups, forming centrosymmetric
four-membered Zn2O2 rings. As a consequence, the zinc
atoms in 1Ϫ3 adopt distorted tetrahedral coordination
spheres as was observed previously for complexes of the
type {[(2,6-iPr2ϪC6H3)N(Me)C)]2CH}ZnOR. Only {[(2,6-
iPr2ϪC6H3)N(Me)C)]2CH}ZnOt-Bu containing the steri-
cally slightly more hindered tert-butoxy substituent is
X-ray Structure Solution and Refinement of 1؊4
Crystallographic data of 1Ϫ4 are given in Table 2. Figure 1, Figure
2 and Figure 4 show ORTEP diagrams of the solid-state structures
of 2Ϫ4, Figure 3 the reduced structure of 1 and Figure 5 the re-
duced structure of 4. Single crystals of 1Ϫ4 were obtained from monomeric in the solid state [6a]. The β-diketiminato cores
solutions in THF (1, 2, 4) and benzene (3) at Ϫ30 °C. Data were
collected on a Bruker-AXS SMART APEX CCD. The structures
were solved by Direct Methods (SHELXS-97) [11] and refined by
full-matrix least-squares on F2 (SHELXL-97) [12]. All non-
hydrogen atoms were refined anisotropically and hydrogen atoms
by a riding model. Multi-scan absorption corrections were applied.
Crystallographic data of the structures (excluding structure
factors) have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication no. CCDC-711909 (1),
CCDC-711910 (2), CCDC-711911 (3), and CCDC-711912 (4).
in 1Ϫ3 are almost planar with the sum of bond angles at
N1, N2, C1 and C3 ranging from 359.9 to 360°. Moreover,
the NϪC and CϪC bonds lengths of 1 and 2 within the
six-membered ring are almost equal. They are in between
typical values observed for single and double bonds, indi-
cating a delocalized π-electron system. In contrast, the
CϪC bond lengths within the backbone of the β-diketimin-
˚
ato core of 3 [C1ϪC2 1.422(13), C2ϪC3 1.383(12) A] differ
significantly, indicating a disturbed π-electron system,
Copies of the data can be obtained free of charge on which most likely results from the larger repulsive interac-
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Synthesis and Characterization of β-Diketiminate Zinc Complexes
Figure 2. Molecular structure and atom numbering scheme of 3;
thermal ellipsoids are drawn at the 30 % probability level. Hydro-
gen atoms and disordered benzene molecule have been omitted
for clarity.
Figure 1. Molecular structure and atom numbering scheme of 2;
thermal ellipsoids are drawn at the 30 % probability level. The THF
molecule and the hydrogen atoms have been omitted for clarity.
˚
Table 1. Selected bond lengths /A and angles /° of 1Ϫ4.
tions between the sterically encumbered MesNacNac sub-
stituent and the iPr group.
1
2
3
4
The repulsive interactions between the MesNacNac sub-
stituent and the OR groups steadily increase with increasing Zn1ϪN2
Zn1ϪN1
1.977(3)
1.969(3)
1.951(3)
1.983(3)
1.325(5)
1.433(5)
1.340(5)
1.439(5)
1.394(5)
1.406(5)
98.3(2)
1.981(3)
1.978(3)
1.987(3)
1.949(3)
1.326(5)
1.435(5)
1.321(5)
1.439(5)
1.393(7)
1.403(6)
97.5(2)
1.990(7)
1.995(7)
1.952(5)
2.005(5)
1.339(10)
1.451(11)
1.347(11)
1.437(12)
1.422(13)
1.383(12)
96.1(3)
2.039(2)
2.017(2)
Zn1ϪO1
steric demand of the alkoxy group as was expected. This
Zn1ϪO1A
can clearly be seen when comparing the deviation of the
N1ϪC1
1.332(2)
1.441(2)
1.330(2)
1.439(2)
1.403(3)
1.403(3)
95.0(1)
six-membered ZnN2C3 metallacycle from planarity. The
N1ϪC6
N2ϪC3
N2ϪC15
C1ϪC2
C2ϪC3
N1ϪZn1ϪN2
N1ϪZn1ϪO1
tetracoordinate zinc atom in 1 has moved out of the plane
˚
by 0.419(3) A, resulting in a boat-type conformation (see
Figure 3). This value significantly increases up to
˚
˚
0.524(3) A (2) and 0.592(3) A (3), respectively. Comparable
findings have been previously observed for DippNac-
NacZntBu(THF) and DippNacNacZnPh complexes [5d]. N2ϪZn1ϪO1
In addition, the increasing steric demand of the alkoxy sub-
stituent is reflected by a steady increase of the ZnϪN bond
˚
lengths [average values 1.973 (1), 1.980 (2), 1.993 A (3)].
Zn1ϪN1ϪC6
118.1(2)
125.6(2)
81.3(2)
117.4(2)
118.3(2)
82.4(2)
124.1(3)
122.2(3)
81.1(2)
O1ϪZn1ϪO1A
Zn1ϪO1ϪZn1A
Zn1ϪN1ϪC1
98.7(2)
97.6(2)
98.9(2)
119.8(2)
121.2(2)
118.9(2)
123.7(2)
118.9(3)
117.3(3)
124.2(3)
124.9(3)
129.4(4)
116.1(4)
116.1(3)
118.5(3)
122.8(3)
119.1(3)
122.2(3)
118.7(4)
118.6(3)
124.6(4)
123.9(4)
129.5(4)
116.2(4)
116.9(3)
119.6(6)
124.8(5)
118.4(7)
123.5(6)
115.6(7)
118.1(8)
123.6(9)
124.9(9)
129.0(8)
116.4(8)
116.6(8)
117.0(2)
127.5(2)
119.1(2)
123.6(2)
115.3(2)
117.3(2)
124.8(2)
124.1(2)
128.7(2)
115.3(2)
115.9(2)
Only {[(2,6-iPr2ϪC6H3)N(Me)C)]2CH}ZnOi-Pr, which
contains the sterically most demanding Dipp substituent
[6f], shows significantly longer ZnϪN bond lengths
Zn1ϪN2ϪC3
Zn1ϪN2ϪC15
C1ϪN1ϪC6
C3ϪN2ϪC15
N1ϪC1ϪC2
N2ϪC3ϪC2
˚
[2.074(4), 2.054(4) A]. In contrast, the ZnϪO and ZnϪN
bond lengths, the endocyclic NϪZnϪN, OϪZnϪO and
ZnϪOϪZn bond angles as well as the bonding parameters C1ϪC2ϪC3
of the MesNacNac ligand of 1Ϫ3 are very similar (see
Table 1) and do not show any remarkable structural
C2ϪC1ϪC4
C2ϪC3ϪC5
Z. Anorg. Allg. Chem. 2009, 995Ϫ1000
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997

S. Schulz, T. Eisenmann, D. Bläser, R. Boese
ARTICLE
differences relative to other β-diketiminate zinc alkoxide
complexes containing {[(2,6-Me2ϪC6H3)N(Me)C)]2CH}
[7b], {[(2,6-Et2ϪC6H3)N(Me)C)]2CH} [7c, 13], and {[(2,6-
Pr2ϪC6H3)N(Me)C)]2CH} [13] substituents, respectively.
Figure 3. Reduced molecular structure and atom numbering
scheme of 1 showing the boat-type conformation of the β-diketimi-
nato groups; thermal ellipsoids are drawn at the 30 % probability
level. Hydrogen atoms, Dipp groups and tBu groups except for the
α carbon atoms have been omitted for clarity.
Due to our long term interest in low-valent metal com-
plexes, we became also interested in complexes of the type
R2Zn2, containing a central ZnϪZn bond with the zinc
atoms in the formal oxidation state ϩ1. Complexes of this
type are known since the epoch-making synthesis of deca- Figure 4. Molecular structure and atom numbering scheme of 4;
thermal ellipsoids are drawn at the 30 % probability level. Hydro-
gen atoms and disordered thf molecule have been omitted for
methyldizincocene Cp*2Zn2 by Carmona et al. in 2004 [14].
Since then, some other low-valent organozinc complexes
clarity.
have been structurally characterized [8, 15]. They were typi-
cally prepared by Wurtz-analogous coupling reactions of
the corresponding halide-substituted compounds RMX
space group C2/c with four molecules in the unit cell
(X ϭ Cl, Br, I) containing sterically encumbered organic
(Figure 4).
substituents. Therefore, we investigated reactions of
The central zinc atom in 4 adopts a distorted tetrahedral
MesNacNacZnX (X ϭ Cl, I) with several reducing agents
coordination sphere with the endocyclic N1ϪZnϪN2 bond
such as sodium, potassium, sodium naphthalenide and
angle [94.98(6)°] being significantly smaller than the exo-
potassium graphite. However, only the ZnII complex
cyclic NϪZnϪN bond angles [N1ϪZn1ϪN1a 113.26(9),
MesNacNac2Zn 4 could be isolated from these reactions.
N1ϪZn1ϪN2a / N2ϪZn1ϪN1a 116.27(6), N2ϪZn1ϪN2a
The formation of 4 can be rationalized by a dispro-
(122.45(8)°]. The β-diketiminato core significantly deviates
portionation reaction of MesNacNac2Zn2, which is most
from planarity as can clearly be seen in Figure 5.
likely formed in situ as a reaction intermediate during the
reduction reaction. However, the low-valent organozinc
complex is not stable under these specific reaction con-
ditions and consequently undergoes disproportionation
reaction with subsequent formation of elemental zinc and
4 (Scheme 2) [16].
Scheme 2. Synthesis of the bis-β-diketiminate zinc complex 4 by
Figure 5. Reduced molecular structure and atom numbering
scheme of 4 showing the boat-type conformation of the β-diketimi-
nato groups; thermal ellipsoids are drawn at the 30 % probability
level. Hydrogen atoms and Dipp groups except for the α carbon
reduction reaction.
Single crystals of 4 were obtained from a solution in THF
at Ϫ30 °C. Compound 4 crystallizes in the monoclinic atoms have been omitted for clarity.
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Synthesis and Characterization of β-Diketiminate Zinc Complexes
Table 2. Crystallographic details of 1Ϫ4.
1
2d)
3e)
4f)
emp. form.
mol. mass
cryst syst.
space group
C48H64N4O2Zn2
429.89
C50H68N4O2Zn2 ·x(thf)
455.94
C52H72N4O2Zn2 ·x(C6H6)
496.99
monoclinic
P21/c
12.6294(9)
11.3811(8)
C50H66N4Zn·x(thf)
876.54
monoclinic
C2/c
16.9305(12)
15.9803(12)
19.9972(15)
triclinic
triclinic
¯
¯
P1
P1
˚
a /A
8.739(3)
10.633(5)
13.575(6)
67.746(10)
80.283(19)
77.155(14)
1133.3(9)
2
11.3832(11)
11.4399(12)
12.4482(13)
96.021(2)
90.778(2)
114.759(2)
1460.9(3)
2
˚
b /A
˚
c /A
21.1965(16)
˚
Ͱ /A
˚
β /A
90.304(6)
98.958(4)
˚
γ /A
3
˚
V /A
Z
3046.7(4)
4
5344.3(7)
4
T /K
193(1)
Mo-Kα (0.71073)
1.099
1.260
48
0.24 ϫ 0.20 ϫ 0.12
23525
296(1)
Mo-Kα (0.71073)
0.857
1. 360
50
0.24 ϫ 0.18 ϫ 0.15
12139
296(1)
Mo-Kα (0.71073)
0.826
1.084
46
0.18 ϫ 0.15 ϫ 0.12
42665
173(1)
Mo-Kα (0.71073)
0.499
1.089
54
0.28 ϫ 0.12 ϫ 0.08
90638
˚
radiation (λ /A)
μ /mmϪ1
Dcalcd. /g·cmϪ3
2θmax /°
cryst dim. /mm
no. reflns
unique
Rmerg
3604
0.0577
4946
0.0574
4298
0.2376
5663
0.0731
param./restraints
254 / 0
0.0412
0.0990
1.053
282 / 0
0.0564
0.1594
0.991
326 / 0
0.0791
0.2617
1.021
277 / 0
0.0420
0.1185
1.043
R1a)
wR2b)
goodness of fitc)
Ϫ3
˚
final max/min. Δρ /e·A
0.311 / Ϫ0.536
0.486 / Ϫ0.261
0.433 / Ϫ0.465
0.339 / Ϫ0.377
2
2 2
2 2
2
2
a) R1 ϭ Σ(ʈFoΗϪΗFcʈ)/ΣΗFoΗ (for I > 2σ (I)). b) wR2 ϭ {Σ [w(Fo ϪFc ) ]/Σ [w(Fo ) ]}1/2. c) Goodness of fit ϭ {Σ [w(ΗFo ΗϪΗFc Η)2]/
(NobservnsϪNparams)}1/2. d) THF molecule refined with reduced SOF 0.5. e) Benzene atoms C(31)ϪC(36) disordered over two sites with
SOF 0.5 together with the riding hydrogen atoms. f) Refinement with corrected reflection data after PLATON/squeeze run based on data
calculated by omitting highly disordered benzene molecule but keeping mostly ordered THF molecule (ref. A. L. Spek, Acta Crystallogr.,
Sect. A 1990, 46, C-34). The alternative original refinement of the untreated reflection data set produces three different Fourier peaks
Ϫ3
˚
with ϳ1.8 e·A caused by a highly disordered benzene molecule positioned around Wyckoff letter ‘c’. The refinement with these three
peaks as carbon atoms with SOF 0.5 results in R1 ϭ 0.0501.
˚
The zinc atom has moved out of the plane by 0.680(3) A,
Acknowledgement
which is an even larger deviation than the value observed
We gratefully acknowledge financial support by the Deutsche
Forschungsgemeinschaft (DFG).
for complex 3. The sum of bond angles at N1, N2, C1 and
C3 is almost 360°. The NϪC [N1ϪC1 1.332(2), N2ϪC3
˚
1.330(2) A] and CϪC bonds lengths [C1ϪC2 1.403(3),
˚
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Received: January 1, 2009
Published Online: April 8, 2009
1000
www.zaac.wiley-vch.de
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 995Ϫ1000