Synthesis and structural characterization of monomeric three-coordinated β-diketoiminate organozinc derivatives

Article abstract of DOI:10.1021/om010301x

The monomeric zinc compounds with three-coordinated zinc (dipp)NacNacZnCl (1), (dipp)NacNacZnMe (2), (dipp)NacNacZntBu (3), and (dipp)NacNacZnPh (4) were prepared under mild conditions in strong coordinating donor solvents. Compounds 2-4 have been structu

Full text of DOI:10.1021/om010301x

Organometallics 2001, 20, 3825-3828
3825
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of Mon om er ic
Th r ee-Coor d in a ted â-Dik etoim in a te Or ga n ozin c
Der iva tives†
J o¨rg Prust, Andreas Stasch, Wenjun Zheng, Herbert W. Roesky,*
Eftichia Alexopoulos, Isabel Uso´n, Dieter Bo¨hler, and Thomas Schuchardt
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received April 11, 2001
Summary: The monomeric zinc compounds with three-
coordinated zinc (dipp)NacNacZnCl (1), (dipp)NacNac-
ZnMe (2), (dipp)NacNacZntBu (3), and (dipp)NacNac-
ZnPh (4) were prepared under mild conditions in strong
coordinating donor solvents. Compounds 2-4 have been
structurally characterized. The â-diketoiminate ligand
(2-((2,6-diisopropylphenyl)amino)-4-((2,6-diisopropyl-
phenyl)imino)pent-2-ene) ((dipp)NacNac) acts as a chelat-
ing ligand through its two N atoms, forming a six-
membered ring with the zinc atom.
However, all the known monomeric three-coordinated
zinc compounds were synthesized using weakly coordi-
nating solvents such as pentane or toluene. Therefore,
application of these compounds will be limited to weakly
coordinating solvents; otherwise solvents such as Et2O
or THF will occupy the vacant site at the zinc and
decrease the reactivity.
Herein we report the facile synthesis of monomeric
compounds with three-coordinated zinc in Et2O and
THF using a bulky â-diketoiminate ligand, 2-((2,6-diiso-
propylphenyl)amino)-4-((2,6-diisopropylphenyl)imino)pent-
2-ene ((dipp)NacNac).9 The other substituents on the
zinc atom are chlorine, alkyl, and phenyl groups,
respectively. To the best of our knowledge these com-
pounds represent the first monomeric three-coordinated
zinc derivatives forming no stable adducts in strong
coordinating solvents.
In tr od u ction
Organozinc complexes are extensively used in both
organic and organometallic syntheses.1,2 In particular,
organozinc reagents offer valuable alternatives to the
corresponding magnesium and lithium reagents in
terms of both their reactivity and selectivity. However,
in contrast to dialkylmagnesium reagents, in which the
magnesium centers are typically four-coordinated and
tetrahedral, dialkylzinc complexes exist as monomeric
two-coordinated molecules.3
Although the chemistry of four-coordinated orga-
nozinc complexes is well developed, monomeric three-
coordinated zinc compounds are still quite rare. Only
few examples including [{(Me3Si)2N(Ph)P(µ-NSiMe3)2-
ZnPh],4 [N{P(NMe2)2NSiMe3}2ZnN(SiMe3)2],5 [Et2ZnC-
{N(1-Ad)CH}2],6 [{(Me3Si)2N}2ZnCH2P(NMe2)3],7 and
[BpBut]ZntBu8 have been reported in the literature.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were performed
using standard Schlenk techniques under a dry nitrogen
atmosphere due to the extreme sensitivity of the reactants and
products toward air and moisture. A Braun Labmaster 130
drybox was used to store the compounds and to prepare the
samples for spectroscopic characterizations. All solvents were
dried over sodium/benzophenone, freshly distilled and de-
gassed prior to use. (dipp)NacNacH was prepared as described
in the literature.9 NMR spectra were recorded on Bruker AM
200 and Bruker AM 250 instruments. Chemical shifts are
reported in ppm with reference to tetramethylsilane as
external standard. EI mass spectra were obtained on Finnigan
MAT 8230 or Varian MAT CH 5 instruments, and FT-IR
spectra were measured on a Bio-Rad FTS-7 as Nujol mulls
between KBr plates in the range 4000-400 cm-1. Elemental
analyses were performed by the Analytisches Labor des
Instituts fu¨r Anorganische Chemie der Universita¨t Go¨ttingen.
Melting points were measured in sealed glass tubes and are
uncorrected.
† Dedicated to Professor Rudolf Taube on the occasion of his 70th
birthday.
(1) (a) Boersma, J . In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G., Abel, E. W., Eds.; Pergamon Press: Oxford,
U.K., 1982; Vol. 2, pp 823-862. (b) Coates, G. E.; Green, M. L. H.;
Wade, K. Organometallic Compounds. Volume I: The Main Group
Elements, 3rd ed.; Methuen: London 1967. (c) Elschenbroich, C.;
Salzer, A. Organometallics: A Concise Introduction, 2nd ed.; VCH:
New York, 1992.
(2) (a) Miginiac, L. In The Chemistry of the Metal-Carbon Bond;
Hartley, F. R., Patai, S., Eds.; Wiley: New York, 1985; Vol. 3, Chapter
2. (b) Furukawa, J .; Kawabata, N. Adv. Organomet. Chem. 1974, 12,
83-134.
P r ep a r a tion of (d ip p )Na cNa cZn Cl (1). To a suspension
of ZnCl2 (420 mg, 1.55 mmol) in Et2O (20 mL) was slowly added
a solution of (dipp)NacNacLi‚OEt210 (3.11 g, 1.55 mmol) in Et2O
(20 mL) at -78 °C. The mixture was allowed to warm to room
(3) Bickelhaupt, F. J . Organomet. Chem. 1994, 475, 1-14.
(4) Chernega, A. N.; Antipin, M. Yu.; Struchkov, M. Y.; Romanenko,
V. D. Koord. Chim. 1989, 15, 894-901.
(5) Pandey, S. K.; Steiner, A.; Roesky, H. W.; Stalke, D. Inorg. Chem.
1993, 32, 5444-5446.
(9) [(dipp)NacNacH] has been proved to be a good ligand suitable
for main group metals and has led to several interesting results. (a)
First monomeric three-coordinated â-diketoiminate magnesium com-
pound was synthesized: Gibson, V. C.; Segal, J . A.; White, A. J . P.;
Williams, D. J . J . Am. Chem. Soc. 2000, 122, 7120-7121. (b) First
monomeric aluminum(I) compound with â-diketoiminate ligand was
synthesized: Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.;
Hao, H.; Cimpoesu, F. Angew. Chem. 2000, 112, 4444-4446; Angew.
Chem., Int. Ed. 2000, 39, 4274-4276.
(6) Arduengo, A. J ., III; Dias, H. V. R.; Davidson, F.; Harlow, R. L.
J . Oganomet. Chem. 1993, 462, 13-18.
(7) Steiner, M.; Gru¨tzmacher, H.; Pritzkow, H.; Zsolnai, L. Chem.
Commun. 1998, 285.
(8) (a) Looney, A.; Han, R.; Gorrell, I. B.; Cornebise, M.; Yoon, K.;
Parkin, G.; Rheingold, A. L. Organometallics 1995, 14, 274-288. (b)
Gorrell, I. B.; Looney, A.; Parkin, G.; Rheingold, A. L. J . Am. Chem.
Soc. 1990, 112, 4068-4069.
10.1021/om010301x CCC: $20.00 © 2001 American Chemical Society
Publication on Web 07/13/2001

3826 Organometallics, Vol. 20, No. 17, 2001
Notes
temperature and then stirred for additional 3 h and filtered.
The solution was concentrated to 10 mL. 1 was recrystallized
at -24 °C to yield a colorless crystalline solid after 2 days (yield
1.48 g, 92%). Mp: 275 °C. 1H NMR (CDCl3): δ 1.15 (d, J ) 6.8
Hz, 12 H, CH(CH3)2), 1.18 (d, J ) 6.8 Hz, 12 H, CH(CH3)2,
1.70 (s, 6 H, CH3), 3.02 (sept, J ) 6.8 Hz, 4 H, CH(CH3)2),
4.87 (s, 1 H, CH), 7.12 (m, 6 H, ArH). 13C NMR (C6D6): δ 22.8,
23.3, 25.4, 28.3, 28.8, 94.2, 123.8, 125.2, 141.2, 142.3, 165.4.
MS (EI; m/z(%)): 481 ((M - Cl)+, 41), 516 (M+, 100). IR (Nujol
mull, cm-1): 1660, 1599, 1261, 1225, 1021, 873, 795, 443. Anal.
Calcd for C29H41ClN2Zn (518.49): C, 67.18; H, 7.97; N, 5.40.
Found: C, 67.0; H, 7.6; N, 5.3. Molecular weight (cryoscopic
in THF; g/mol): calcd 518.49; found 505.
P r ep a r a tion of (d ip p )Na cNa cZn Me (2). (a) ZnMe2 (2.15
mL of a 2 M solution in toluene, 4.30 mmol) was added to a
solution of (dipp)NacNacH (1.80 g, 4.30 mmol) in toluene (20
mL) at 0 °C. The mixture was allowed to warm to room
temperature and refluxed for 3 days. The pale yellow solution
was concentrated (5 mL) and stored overnight at -24 °C to
afford pale yellow crystals of 2 suitable for X-ray single-crystal
structural analysis (yield 1.78 g, 83%).
1.14 (d, J ) 6.8 Hz, 12 H, CH(CH3)2), 1.21 (d, J ) 6.8 Hz, 12
H, CH(CH3)2), 1.74 (s, 6 H, CH3), 3.21 (sept., J ) 6.8 Hz, 4 H,
CH(CH3)2), 5.04 (s, 1 H, CH), 6.83-7.15 (m, 11 H, ArH). 13C
NMR (C6D6) δ 1.3, 22.6, 23.2, 23.6, 23.7, 28.5, 33.3, 95.1, 123.5,
124.2, 127.8, 127.9, 139.7, 141.7, 145.1, 148.6, 168.0. MS (EI
m/z(%)): 417 ((dipp)NacNac, 100), 481 ((M - Ph)+, 25), 558
(M+, 36). IR (Nujol mull, cm-1): 3061, 1623, 1552, 1529, 1262,
1239, 1102, 1024, 935, 884, 757, 721, 701. Anal. Calcd for
C35H46N2Zn (560.14): C, 75.05; H, 8.28; N 5.00. Found: C, 75.3;
H, 8.7; N, 5.3.
Cr ysta l Str u ctu r e Solu tion a n d Refin em en t for 2-4.
Crystals were mounted on a glass fiber in a rapidly cooled
perfluoropolyether.11 Diffraction data of 2 and 4 were collected
on a Stoe-Siemens-Huber four-circle-diffractometer coupled to
a Siemens CCD area-detector at 133(2) K, with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). Diffraction
data of 3(THF) were collected on a Stoe IPDS-II at 133(2) K,
with graphite-monochromated Mo KR radiation (λ ) 0.71073
Å). The structures were solved by direct methods (SHELXS-
97)12 and refined against F2 on all data by full-matrix least-
squares using SHELXL-97.13 All hydrogen atoms were refined
anisotropically. The hydrogen atoms were included in the
model at geometrically calculated positions and refined using
a riding model if not otherwise stated. The hydrogen atoms
on the methyl group at the central â-diketoiminate-backbone-
Zn ring in compound 3(THF) were refined as disordered
idealized methyl groups with two half-occupied positions
related to each other by rotation of 60°. These hydrogen atoms
are allowed to ride on the carbon atoms and rotate about the
C(1)-C(3) and C(1A)-C(3A) bond, respectively. Included in
the crystal lattice in compound 3 are THF molecules, which
do not fulfill the crystallographic symmetry. Their disorder
was modeled with the help of similarity restraints for 1,2- and
1,3-distances and rigid bond and similarity restraints on the
displacement parameters. The structure parameters and
refinement procedures are summarized in Table 1.
(b) A solution of MeLi (1.52 mL of a 1.6 M solution in Et2O,
2.44 mmol) was slowly added to a solution of 1 (1.26 g, 2.44
mmol) in Et2O (20 mL) at -78 °C. The mixture was allowed
to warm to room temperature and stirred for 3 h. The mixture
was filtered, concentrated (ca. 5 mL), and stored overnight at
-24 °C to afford pale yellow crystals of 2 suitable for X-ray
single-crystal structural analysis (yield 1.15 g, 95%). Mp: 127
1
°C. H NMR (C6D6): δ -1.24 (s, 3 H, ZnCH3), 1.16 (d, J ) 6.8
Hz, 12 H, CH(CH3)2), 1.20 (d, J ) 6.8 Hz, 12 H, CH(CH3)2),
1.70 (s, 6 H, CH3), 3.02 (sept, J ) 6.8 Hz, 4 H, CH(CH3)2),
4.89 (s, 1 H, CH), 7.12 (m, 6 H, ArH). 13C NMR (C6D6): δ 23.0,
23.2, 24.1, 28.3, 29.1, 95.2, 123.5, 125.7, 141.3, 142.5, 167.3.
MS (EI; m/z (%)): 202 (DippNCCH3, 100), 481 ((M - Me)+,
41), 496 (M+, 36). IR (Nujol mull, cm-1): 1658, 1268, 1021,
884, 759, 600, 435. Anal. Calcd for C30H44N2Zn (498.05): C,
72.34; H, 8.90; N, 5.62. Found: C, 73.51; H, 9.12; N, 5.80.
P r ep a r a tion of (d ip p )Na cNa cZn tBu (3). A solution of
tBuLi (1.17 mL of a 2 M solution in hexane, 2.35 mmol) was
slowly added to a solution of 1 (1.21 g, 2.35 mmol) in Et2O (20
mL) at -78 °C. The mixture was allowed to warm to room
temperature and stirred for 3 h. The mixture was filtered,
concentrated to 5 mL, and stored for 7 days at -24 °C to yield
a pale yellow solid of 3 (yield 1.16 g, 92%). A solution of 3 in
THF affords crystals of 3(THF) suitable for X-ray single-crystal
Resu lts a n d Discu ssion
Syn th esis of (d ip p )Na cNa cZn Cl (1). Treatment of
(dipp)NacNacLi‚OEt210 with ZnCl2 in Et2O gave solvent-
free (dipp)NacNacZnCl (1) in good yield (eq 1). The EI
mass spectrum shows a molecular ion M+ (m/z 516),
which is consistent with monomeric 1. The formation
of 1 is also confirmed by the 1H NMR spectrum, in which
one single resonance for the γ-CH and two doublets for
CHMe2 are observed. No resonances of any Et2O hy-
drogen are found (eq 1).
1
structural analysis. Mp: 186 °C. H NMR (C6D6): δ 0.94 (s, 9
H, C(CH3)3), 1.14 (d, J ) 6.8 Hz, 12 H, CH(CH3)2), 1.22 (d, J
) 6.8 Hz, 12 H, CH(CH3)2), 1.75 (s, 6 H, CH3), 3.24 (sept, J )
6.8 Hz, 4 H, CH(CH3)2), 5.02 (s, 1 H, CH), 7.14 (m, 6 H, ArH).
13C NMR (C6D6): δ 22.6, 23.2, 23.6, 23.7, 28.5, 33.3, 95.1, 123.6,
125.7, 141.1, 145.6, 167.3. MS (EI; m/z(%)): 481 ((M - tBu)+,
100), 538 (M+, 6). IR (Nujol mull, cm-1): 1655, 1590, 1554,
1529, 1262, 1239, 1020, 935, 884, 759, 701, 444. Anal. Calcd
for C33H50N2Zn (540.15): C, 73.38; H, 9.32; N, 5.18. Found:
C, 73.6; H, 9.3; N, 5.3.
P r ep a r a tion of (d ip p )Na cNa cZn P h (4). (a) A solution of
PhLi (1.14 mL of a 2 M solution in cyclohexane/Et2O, 2.28
mmol) was slowly added to a solution of 1 (1.18 g, 2.28 mmol)
in Et2O (20 mL) at -78 °C. The mixture was allowed to warm
to room temperature and stirred for 8 h. The mixture was
filtered and concentrated to 5 mL and stored for 3 days at -24
°C to afford pale yellow crystals of 4 suitable for X-ray single-
crystal structural analysis (yield 1.08 g, 85%).
(b) A solution of Na[BPh4] (995 mg, 2.90 mmol) in toluene
(20 mL) was slowly added to a suspension of 1 (1.50 g, 2.90
mmol) in toluene (20 mL) at -78 °C. The mixture was allowed
to warm to room temperature and then stirred for an ad-
ditional 24 h. The mixture was filtered and concentrated to
10 mL. 4 was recrystallized at -24 °C to yield pale yellow
crystals of 4 suitable for X-ray single-crystal structural
(10) Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H.-G.; Noltemeyer,
M. Angew. Chem. 2000, 112, 1885-1887; Angew. Chem., Int. Ed. 2000,
39, 1815-1817.
(11) Kottke, T.; Stalke, D. J . Appl. Crystallogr. 1993, 26, 615-619.
(12) Sheldrick, G. M. SHELXS-90/96, program for structure solution.
Acta Crystallogr. Sect. A 1990, 46, 467-473.
(13) Sheldrick, G. M. SHELXL-93/ 96, program for structure refine-
ment; Universita¨t Go¨ttingen, 1993.
1
analysis. (yield 1.02 g, 63%). Mp: 155 °C. H NMR (C6D6): δ

Notes
Organometallics, Vol. 20, No. 17, 2001 3827
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 2, 3(THF ), a n d 4
3(THF)
C37H58N2OZn
2
4
empirical formula
fw
C
30H44N2Zn
C35H46N2Zn
560.11
498.04
612.22
temper [K]
133(2)
133(2)
133(2)
wavelength [Å]
cryst syst
space group
unit cell dimens [Å]
0.71073
monoclinic
P2(1)/n
a ) 12.482(3)
b ) 17.053(3)
c ) 13.961(3)
R ) 90°
â ) 104.96(3)°
γ ) 90°
2870.9(10)
2
0.71073
orthorhombic
Pnma
a ) 10.475(2)
b ) 18.108(4)
c ) 18.389(4)
R ) 90°
â ) 90°
γ ) 90°
3488.2(12)
4
1.166
0.733
0.71073
orthorhombic
Pnma
a ) 16.850(3)
b ) 20.727(4)
c ) 8.9146(18)
R ) 90°
â ) 90°
γ ) 90°
3113.3(11)
4
1.195
0.813
volume [Å3]
Z
density (calcd) [Mg/m3]
1.152
0.874
abs coeff [mm-1
]
F(000)
1072
1328
1200
cryst size [mm3]
0.70 × 0.40 × 0.10
2.07 to 27.60°
50 433
6633 [Rint ) 0.0634]
full-matrix least squares on F2
6633/0/309
1.242
R1 ) 0.0534
wR2 ) 0.1012
R1 ) 0.0645
wR2 ) 0.1047
0.360 and -0.759
0.50 × 0.40 × 0.35
1.58 to 24.70°
54 534
3071 [Rint ) 0.0911]
full-matrix least squares on F2
3071/54/221
1.043
R1 ) 0.0356
wR2 ) 0.0973
R1 ) 0.0382
wR2 ) 0.0991
0.442 and -0.332
0.20 × 0.20 × 0.10
2.42 to 24.71°
57 604
2735 [Rint ) 0.0656]
full-matrix least squares on F2
2735/0/183
1.090
R1 ) 0.0396
wR2 ) 0.1023
R1 ) 0.0462
wR2 ) 0.1069
0.625 and -0.959
θ range for data collection
no. of reflns collected
no. of ind reflns
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
R indices (all data)
largest diff peak and hole
[e‚Å-3
]
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (d ip p )Na cNa cZn Me (2)
tively, 2 can be prepared from the reaction of (dipp)-
NacNacH with ZnMe2 in toluene in high yield. The EI
mass spectra of 2 and 3 show the molecular ion M+ (m/z
Zn(1)-C(6)
Zn(1)-N(1)
Zn(1)-N(2)
N(1)-C(1)
N(2)-C(3)
C(1)-C(2)
C(2)-C(3)
1.941(3)
1.9480(18)
1.9429(18)
1.329(3)
1.334(3)
1.401(3)
1.399(3)
C(6)-Zn(1)-N(1)
C(6)-Zn(1)-N(2)
N(2)-Zn(1)-N(1)
C(1)-N(1)-Zn(1)
C(3)-N(2)-Zn(1)
N(1)-C(1)-C(2)
N(2)-C(3)-C(2)
130.21(11)
132.78(11)
97.00(8)
123.64(15)
122.73(15)
123.1(2)
1
496 for 2, 538 for 3). The H NMR as well as 13C NMR
spectra are consistent with the formulas given for 2 and
3 (eq 2).
Syn th esis of (d ip p )Na cNa cZn P h (4). The reaction
of 1 with PhLi in Et2O proceeded smoothly in the
formation of 4 in high yield (eq 2). Alternatively, 4 can
be prepared from the reaction of 1 with Na[BPh4] in
toluene. The EI mass spectrum of 4 shows the molecular
124.2(2)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [(d ip p )Na cNa cZn tBu ](THF )
Zn(1)-C(4)
Zn(1)-N(1)
N(1)-C(1)
C(1)-C(2)
2.009(3)
1.9803(16)
1.334(3)
1.400(2)
C(4)-Zn(1)-N(1)
N(1)-Zn(1)-N(1)
C(1)-N(1)-Zn(1)
N(1)-C(1)-C(2)
C(1)-C(2)-C(1)
132.52(10)
94.48(10)
123.97(13)
123.51(19)
128.9(3)
1
ion M+ (m/z 558) and the H NMR as well as 13C NMR
spectra are consistent with the formula given for 4 (eq
3).
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for (d ip p )Na cNa cZn P h (4)
Zn(1)-C(1P)
Zn(1)-N(1)
N(1)-C(1)
C(1)-C(2)
1.939(3)
1.9244(18)
1.325(3)
1.389(3)
C(1P)-Zn(1)-N(1)
N(1)-Zn(1)-N(1)
C(1)-N(1)-Zn(1)
N(1)-C(1)-C(2)
C(1)-C(2)-C(1)
131.76(5)
96.38(11)
123.88(15)
123.5(2)
128.7(3)
Syn th esis of (d ip p )Na cNa cZn Me (2) a n d (d ip p )-
Na cNa cZn tBu (3). The reaction of 1 with MeLi (tBuLi)
in Et2O (THF) leads to the formation of the solvent-free
compounds 2 (3) with three-coordinated zinc. Alterna-
X-ray single-crystal analyses reveal that compounds
2, 3(THF), and 4 exhibit some interesting features.
Selected bond lengths and angles are listed in Tables
2-4. The central core of the three structures is the
(dipp)NacNacZn moiety. The â-diketoiminate ligand
(dipp)NacNac acts as a chelating ligand through its two
N atoms, forming a six-membered ring with the zinc
atom. In compound
C(CH3)-N ring is almost planar, whereas in 3(THF) and
2 the Zn-N-C(CH3)-CH2-

3828 Organometallics, Vol. 20, No. 17, 2001
Notes
N(2) in compound 2 is 0.03 Å, whereas in 3(THF) it is
0.16 Å. The π-electrons of the â-diketoiminate ligand
are delocalized since the C(1)-C(2) and the C(2)-C(3)
as well as the C(1)-N(1) and the C(3)-N(2) bond
lengths in structures 2, 3(THF), and 4 are equal within
experimental error and correspond to C-C and C-N
distances in aromatic systems. Both N-Zn bond lengths
are equal as well. The Zn-N (2, 1.948(2) and 1.943 (2)
Å; 3(THF), 1.980(2) Å; 4, 1.924(2) Å) distances are
shorter than those in comparable Zn-N derivatives.8,14
Compound 2 crystallizes in the monoclinic space group
P2(1)/n with one molecule in the asymmetric unit, while
compounds 3(THF) and 4 crystallize in the orthorhombic
space group Pnma with half a molecule in the asym-
metric unit.
F igu r e 1. Molecular structure of 2 in the crystal (50%
probability). Hydrogen atoms of the â-diketoiminate have
been omitted for clarity.
Ack n ow led gm en t. The financial support of the
Go¨ttinger Akademie der Wissenschaften and the Deut-
sche Forschungsgemeinschaft is highly acknowledged.
4 it displays a boat conformation with the metal at the
prow and the opposite C atom at the stern. The mean
deviation from the plane is 0.01 Å (2), 0.05 Å (3(THF)),
and 0.03 Å (4). The zinc atom in compound 2 is
coordinated by two nitrogen atoms, and one carbon atom
completes the planar triangle arrangement (Figure 1).
The molecule of 3(THF) and 4 is generated by a mirror
plane. The zinc atom acquires a nearly trigonal planar
environment through its coordination to a tBu moiety
(2) or a phenyl ring (3). The distance of the zinc atom
to a plane described by N(1)-C(1)-C(4)-C(3)-C(5)-
Su p p or tin g In for m a tion Ava ila ble: ORTEP plots and
tables of crystal data, refinement details, bond lengths, bond
angles, and thermal parameters for 2, 3(THF), and 4. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM010301X
(14) Westerhausen, M.; Bollwein, T.; Makropoulos, N.; Rotter, T.
M.; Habereder, T.; Suter, M.; No¨th, H. Eur. J . Inorg. Chem. 2001, 851-
857.