Synthesis and characterization of rac-[ethylene-1,2-bis(η5-4,5,6,7-tetrahydro-1-indenyl)]zirconium bisamides (EBTHI)Zr(NHR)2

Article abstract of DOI:10.1016/S0022-328X(98)00835-3

C₂-symmetric rac-ethylene-1,2-bis(η⁵-4,5,6,7-tetrahydro-1-indenyl)-zirconium dichloride (EBTHI)ZrCl₂ (rac-1) reacts with the lithium amides of 2,6-dimethylaniline, aniline and 2,3,4,5,6-pentafluoroaniline to yield the corr

Full text of DOI:10.1016/S0022-328X(98)00835-3

Journal of Organometallic Chemistry 566 (1998) 287–291
Synthesis and characterization of
rac-[ethylene-1,2-bis(p5-4,5,6,7-tetrahydro-1-indenyl)]zirconium
bisamides (EBTHI)Zr(NHR)2
Rudolf Wartchow a, Sven Doye b,*
a Institut fu¨r Anorganische Chemie der Uni6ersita¨t Hanno6er, Callinstr. 9, D-30167 Hanno6er, Germany
b Institut fu¨r Organische Chemie der Uni6ersita¨t Hanno6er, Schneiderberg 1B, D-30167 Hanno6er, Germany
Received 15 June 1998
Abstract
C2-symmetric rac-ethylene-1,2-bis(p5-4,5,6,7-tetrahydro-1-indenyl)-zirconium dichloride (EBTHI)ZrCl2 (rac-1) reacts with the
lithium amides of 2,6-dimethylaniline, aniline and 2,3,4,5,6-pentafluoroaniline to yield the corresponding rac-ethylene-1,2-bis(p5-
4,5,6,7-tetrahydro-1-indenyl)-zirconium bis(monoarylamido) complexes (EBTHI)Zr(NHR)2 (rac-3a-c). These new bisamides repre-
sent potential chiral versions of the known Cp2Zr(NHR)2 derivatives which are active hydroamination catalysts. © 1998 Elsevier
Science S.A. All rights reserved.
Keywords: Zirconium; Zirconocene; ansa-Metallocene; bis(Tetrahydroindenyl); Crystal structure; Metal amide
1. Introduction
house group in 1992. The reactive intermediate is a
titanium imidoderivative [8]. In addition, Bergman et
al. showed that [2+2]-cycloadditions between zir-
conocene imidoderivatives and alkenes (norbornene,
ethylene), giving access to azametallacyclobutanes, are
also possible [4,9]. A similar cycloaddition between the
titanium imidocomplex (t-Bu3SiO)2TiꢀNSit-Bu3 and
ethylene was reported by Wolczanski et al. [9]. Unfor-
tunately, the Bergman group did not succeed in devel-
oping an analogous and much more interesting
hydroamination protocol for olefins (except in the case
of the more reactive allene) using Cp2Zr(NHR)2 as
catalysts [2,10]. However, to the best of our knowledge
no zirconium complexes with other ligands than Cp has
been used for these investigations. Furthermore, no
effort has been made to increase the scope of the alkyne
hydroamination (e.g. regarding turnover numbers and
frequencies) or to extend it to alkene substrates by
varying the ligands in compounds like L2M(NHR)2
(M=Ti, Zr, Hf).
In 1988, Bergman et al. reported the synthesis of
several zirconocene bisamides Cp2Zr(NHR)2 (Cp=p5-
C5H5,
R=t-Bu,
C6H4-t-Bu,
2,6-Me2C6H3,
CH(SiMe3)2) [1–7]. Upon heating to temperatures of
]85°C these complexes lose 1 equiv of amine RNH2
resulting in the formation of very reactive zirconocene
imidoderivatives Cp2ZrꢀNR. These compounds show
an extensive reaction chemistry including [2+2]-cy-
cloadditions with alkynes leading to azametallacy-
clobutenes which can be protonated by additional
amine leading to enamines and regenerating the
bisamides. Combining these facts mentioned above,
Bergman et al. developed an intermolecular hydroami-
nation procedure for alkynes based on zirconocene
bisamides Cp2Zr(NHR)2 as catalysts [2,3]. A related
CpTiCl3-catalyzed intramolecular hydroamination pro-
cedure for amino alkynes was developed in the Living-
Regarding these facts, it seems to be a challenging
and promising goal to develop a hydroamination pro-
* Corresponding author. Fax: +49 511 7623011; e-mail:
sven.doye@oci.uni-hannover.de
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00835-3

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cess for olefins based on related in situ prepared group
IV transition metal imidocomplexes. Therefore the syn-
thesis of a wide variety of group IV metallocene
bisamides as potential catalyst precursors is of great
interest to us. Being aware of the big differences be-
tween group IV ansa-metallocenes and simple metal-
locenes in their performance as catalysts for
Ziegler-Natta-olefin-polymerisations [11], we were first
interested in the synthesis of ansa-zirconocene
bisamides which may possess some advantages in their
catalytic behavior for hydroamination processes com-
pared with Cp2Zr(NHR)2. Keeping in mind that the
hydroamination of olefins can be an enantioselective
process, we focused on chiral ansa-zirconocene com-
plexes, in particular on compounds bearing the exten-
h and resulted in the formation of the desired products
rac-3a–c in good to modest yields (Scheme 1). How-
ever, due to their greater solubility in most solvents, the
benzylamido-, n-butylamido- and cylohexylamido com-
pounds could not be isolated yet.
The sensitivity of the title compounds rac-3a–c to
moisture increases with less steric demanding amido
ligands. Therefore compound rac-3a with the bulky
2,6-dimethylphenylamido-ligand shows only modest
sensitivity to moisture and can be exposed briefly to air,
in particular in a crystalline form. rac-3b and rac-3c are
much more sensitive against moisture and should be
handled only under an inert atmosphere [15].
2.2. Characterization of rac-(EBTHI)Zr(NHR)2
sively
and
successfully
used
C2-symmetric
ethylene-1,2-bis(p5-4,5,6,7-tetrahydro-1-indenyl) ligand
(EBTHI), introduced by Brintzinger et al. [12]. Whereas
ansa-bis(indenyl) dialkylamido complexes are well
known [13], to the best of our knowledge, related
monoalkyl or monoarylamido complexes have never
been reported.
1
The new compounds were characterized by H- and
13C-NMR and MS spectra as well as elemental analysis
in the case of rac-3a [15]. All 1H- and 13C-NMR spectra
of rac-3a–c showed the presence of small amounts of
the corresponding free anilines. These were presumably
produced by hydrolysis of rac-3a–c due to traces of
water on the glassware. An analogous decomposition
has also been reported for Cp2Zr(NHR)2 derivatives [2]
and could not be prevented. Nevertheless, the NMR
spectra show that in solution all (EBTHI)Zr(NHR)2
derivatives possess the desired C2 symmetry and there-
fore represent potential chiral hydroamination catalyst
precursors. Furthermore, it can be seen from the NMR
spectra that the two ortho hydrogen atoms (rac-3b) or
methyl carbon atoms (rac-3a) and the two meta hydro-
gen atoms (rac-3a, rac-3b) in the arylamido ligands are
equivalent. Only one signal for each pair of atoms is
observed. This indicates that the rotation around the
aryl-nitrogen-bond is not hindered by steric interactions
and therefore fast at the NMR time scale, even for the
bulky 2,6-dimethylphenylamido ligand in rac-3a. How-
ever, a very interesting and surprising fact is that at
room temperature the 1H-NMR of rac-3a shows no
typical CH3 singlet signal for the aromatic methyl
Herein we want to report the synthesis and character-
ization of C2-symmetric and potential chiral ansa-zir-
conocene
bisamides
rac-(EBTHI)Zr(NHR)2
(R=2,6-Me2C6H3, Ph, C6F5) [14].
2. Results and discussion
2.1. Synthesis of rac-(EBTHI)Zr(NHR)2
According to the work of Bergman et al. [1–7], there
are two promising approaches to the synthesis of com-
plexes (EBTHI)Zr(NHR)2: (a) the reaction of lithium
amides LiNHR with (EBTHI)ZrCl2 resulting in the
elimination of 2 equiv of LiCl, and (b) the reaction of
amines RNH2 with (EBTHI)ZrMe2 at elevated temper-
atures which proceeds under loss of methane. For our
initial studies we have chosen path (a) because
(EBTHI)ZrCl2 is commercially available and less sensi-
tive than (EBTHI)ZrMe2, which must be prepared first
from the mentioned dichloride. Reactions using this
approach can also be run in usual Schlenk-glassware
and do not require the use of glass bombs, which have
to be used for the high temperature reaction of amines
with (EBTHI)ZrMe2.
Due to the steric, more demanding (EBTHI)-ligand,
compared with Cp used by Bergman et al., we were
prepared to apply longer reaction times or elevated
temperatures for the substitution reactions, in particu-
lar for bulky amides such as LiNH-2,6-Me2C6H3. Sur-
prisingly, the reaction of in situ prepared lithium
amides LiNHR (R=2,6-Me2C6H3, Ph, C6F6) with
(EBTHI)ZrCl2 proceeds smoothly at room temperature
in THF. All reactions went to completion in less than 6
Scheme 1.

R. Wartchow, S. Doye / Journal of Organometallic Chemistry 566 (1998) 287–291
289
The X-ray crystal structure analysis further shows
that the exchange of the chloro ligands in
(EBTHI)ZrCl2 by the much bulkier NH-2,6-Me2C6H3
ligands leads to significant changes in the geometry of
the complex [16]. In (EBTHI)ZrCl2, the Cl–Zr–Cl%
bond angle is 98.6° and the Cg–Zr–C% angle is 125.0°
g
(Cg defines the centers of gravity of the five-membered
rings of the corresponding tetrahydroindenyl systems)
[17]. In rac-3a the corresponding angles are RHN–Zr–
N%H%R%=105.9°, and Cg–Zr–C% =123.7°. Further-
g
more, rac-3a can be compared with the related
compound (EBTHI)Zr(CH2–Ph)2 which lacks the 2,6-
dimethyl substitution and shows a C–Zr–C% angle of
only 94.7°, and a Cg–Zr–C% angle of 124.4° [18]. In
g
particular, the fact that the RHN–Zr–N‘H‘R bond
angle in rac-3a is more than 7° bigger than in the
related chloro or benzyl compound shows that rac-3a
suffers from large steric strain. Due to this high steric
strain it is likely to predict an easy loss of amine from
rac-3a and its enantiomerically pure counterpart which
should possess analogous properties. This should give
access to a reactive and potential chiral imidocomplex
under relatively mild conditions.
Fig. 1. PLATON-drawing of rac-3a. Hydrogen atoms (except NH)
are omitted for clarity. Thermal ellipsoids are drawn at 30% probabil-
ity level. Selected bond lengths (pm) and angles (°): Zr(1)–C(1)
253.2(4), Zr(1)–C(2) 246.0(5), Zr(1)–C(3) 252.4(3), Zr(1)–C(3a)
264.0(4), Zr(1)–C(7a) 262.8(4), Zr(1)–N(1) 213.7(3), C(1)–C(8)
150.7(5), C(8)–C(8‘) 153.0(6), N(1)–C(9) 141.9(5), C(9)–C(10)
140.2(6), C(9)–C(14) 141.2(5), C(10)–C(15) 151.3(6), C(14)–C(16)
150.4(6), N(1)–Zr(1)–N(1) 105.9(1), Zr(1)–N(1)–C(9) 138.9(2),
N(1)–C(9)–C(10) 121.1(3), N(1)–C(9)–C(14) 121.5(4), C(9)–C(10)–
C(15) 122.7(4), C(9)–C(14)–C(16) 119.9(4), Cg–Zr(1)–C%g 123.7, (Cg
defines the centers of gravity of the five-membered rings of the
corresponding tetrahydroindenyl systems).
3. Conclusion
groups. This can only be explained by a strong hin-
drance of the rotation of the methyl groups around the
corresponding C–C bonds which results in the presence
of three non-equivalent hydrogen atoms in each methyl
group. The reason for this rotational barrier must be a
steric or electronic interaction between the methyl
groups and the (EBTHI) ligand, because an analogous
behavior has not been observed for the Cp2Zr(NH-2,6-
Me2C6H3)2 derivative [4]. In order to investigate this
different behavior, and to prove the proposed structure
for the (EBTHI)Zr(NHR)2 derivatives, the molecular
structure of rac-3a has been determined by X-ray crys-
tal structure analysis. A PLATON-drawing of rac-3a is
shown in Fig. 1. Table 1 gives the atomic coordinates
and equivalent isotropic thermal parameters of rac-3a.
Crystallographic data (excluding structure factors) for
the structure of rac-3a have been deposited with the
Cambridge Crystallographic Data Centre as supple-
mentary publication no. CCDC-101562.
Novel C2-symmetric and potential chiral [14] ansa-
zirconocene bisamides bearing the ethylene-1,2-bis(p5-
4,5,6,7-tetrahydro-1-indenyl)-ligand (EBTHI)Zr(NHR)2
rac-3a–c (R=Ph, 2,6-Me2C6H3, C6F5) are accessible
for the first time from rac-1,2-bis(p5-4,5,6,7-tetrahydro-
Table 1
Atomic coordinates and equivalent isotropic thermal parameters of
rac-3a
2
˚
Atom
x
y
z
Ueq (A )
Zr(1)
N(1)
C(1)
C(2)
C(3)
C(3a)
C(4)
C(5)
C(6)
C(7)
C(7a)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
0.5000
0.25337(4)
0.1659(2)
0.3963(2)
0.3537(3)
0.2733(3)
0.2650(3)
0.1994(3)
0.2178(4)
0.3084(3)
0.3634(3)
0.3408(3)
0.4841(2)
0.1194(3)
0.0477(3)
0.0017(3)
0.0217(4)
0.0927(3)
0.1416(3)
0.0165(3)
0.2208(3)
0.2500
0.0408(1)
0.0462(10)
0.0567(14)
0.0700(19)
0.0703(18)
0.0617(16)
0.091(2)
0.6398(2)
0.4547(3)
0.5508(4)
0.5139(5)
0.3963(4)
0.3135(5)
0.1921(5)
0.1648(4)
0.2366(3)
0.3600(3)
0.4532(3)
0.6877(3)
0.6301(3)
0.6801(5)
0.7845(5)
0.8432(4)
0.7962(3)
0.5139(4)
0.8598(3)
0.22486(17)
0.1728(3)
0.1390(3)
0.1018(2)
0.1119(2)
0.0746(3)
0.0975(4)
0.1083(4)
0.1663(2)
0.1561(2)
0.2187(3)
0.1593(2)
0.1223(3)
0.0597(3)
0.0323(3)
0.0670(3)
0.1301(3)
0.1483(3)
0.1646(3)
0.122(3)
0.106(3)
Fig. 1 shows that the structure of rac-3a obtained by
X-ray analysis is in agreement with the spectroscopic
data. However, an obvious reason for the lack of
0.0683(16)
0.0530(14)
0.0743(19)
0.0470(12)
0.0607(16)
0.086(2)
0.099(3)
0.084(2)
0.0613(16)
0.0890(19)
0.092(2)
1
methyl signals in the H-NMR of rac-3a could not be
found. In the solid state all distances between other
atoms and the methyl carbon atoms are longer than 2.7
˚
A. Therefore a restricted rotation of the methyl groups
caused by steric interactions between the methyl groups
and parts of the (EBTHI) ligand is unlikely. Further
investigations to clarify this behavior of rac-3a in the
1H-NMR are underway in our laboratories.

290
R. Wartchow, S. Doye / Journal of Organometallic Chemistry 566 (1998) 287–291
1-indenyl)-zirconium dichloride and lithium amides. In
connection with our efforts in developing an efficient
catalytic hydroamination process for alkenes based on
transitionmetal imidocomplexes as catalysts, we con-
sider these novel complexes as possible chiral catalyst
precursors. Investigations concerning the reactivity of
the described compounds towards the hydroamination
of alkynes compared with Cp2Zr(NHR)2 and an exten-
sion to alkene substrates are underway in our laborato-
ries and will be published in due course.
(100.6 MHz, DEPT, C6D6): l=155.5 (C), 129.4 (C),
129.4 (C), 119.7 (CH), 119.4 (C), 112.7 (CH), 106.5
(CH), 28.5 (CH2), 24.1 (CH2), 24.0 (CH2), 23.3 (CH2),
22.8 (CH2), 21.5 (CH3) ppm; MS (EI, 150°C): m/z (%):
594 ([M+], 3), 474 ([M+ –NH–2,6-Me2C6H3], 44), 347
(25), 121 ([NH2–2,6-Me2C6H3], 100), 106 (62);
C36H44N2Zr (595.98): Calc. C 72.55, H 7.44, N 4.70;
found C 72.18, H 7.42, N 4.56.
4.1.2. rac-bis(phenylamido)[Ethylene-1,2-bis-
(p5-4,5,6,7-tetrahydro-1-indenyl)]zirconium (rac-3b)
To a solution of aniline (0.24 ml, 2.67 mmol) in THF
(10 ml), 1.6 M n-BuLi in hexane (1.54 ml, 2.46 mmol)
was added dropwise at 25°C. After the solution was
stirred for 30 min, solid rac-(EBTHI)ZrCl2 (0.5 g, 1.17
mmol) was added in one portion. The reaction mixture
turned yellow. The solution was stirred for 6 h at 25°C.
Then the volatile materials were removed under re-
duced pressure. Toluene (20 ml) was added to the
residue and the mixture was stirred for 12 h at 25°C.
The slurry was filtered. The toluene was removed under
reduced pressure. The remaining yellow solid was
washed with Et2O (4×10 ml) and dried under vacuum.
The obtained yellow powder (0.44 g, 0.81 mmol, 69%)
4. Experimental
4.1. General procedures
All reactions were carried out under an inert atmo-
sphere of argon in flame-dried glassware. Toluene,
THF, Et2O and hexane were distiled from sodium
benzophenone ketyl under argon. 2,6-Dimethylaniline
and aniline were distiled from sodium under argon.
2,3,4,5,6-Pentafluoroaniline was purchased from Acros
Organics and used without further purification. rac-
(EBTHI)ZrCl2 was purchased from Witco and used
without further purification. NMR spectra were
recorded on a Bruker Avance 400 MHz spectrometer.
Mass spectra were measured on a Finnigan MAT 312
spectrometer. Elemental analyses were recorded on an
elementar vario EL machine.
1
1
was pure by H-NMR. H-NMR: (400 MHz, C6D6):
3
l=7.20 (tt, J(H,H)=7.4, 1.9 Hz, 4H, Ar–H), 6.88
(dt, 3J(H,H)=7.5, 1.0 Hz, 4H, Ar–H), 6.80 (tt,
3J(H,H)=7.3, 1.1 Hz, 2H, Ar–H), 6.01 (sbr, 2H, NH),
5.90 (d, 3J(H,H)=3.0 Hz, 2H, Cp–H), 5.13
(3J(H,H)=3.0 Hz, 2H, Cp–H), 2.94–2.85 (m, 2H),
2.67–2.47 (m, 6H), 2.42–2.28 (m, 4H), 1.83–1.70 (m,
4H), 1.60–1.43 (m, 4H) ppm; 13C-NMR (100.6 MHz,
DEPT, C6D6): l=156.5 (C), 129.0 (CH), 128.7 (C),
128.1 (C), 119.5 (C), 118.7 (CH), 117.9 (CH), 110.4
(CH), 103.9 (CH), 27.5 (CH2), 24.3 (CH2), 23.7 (CH2),
23.3 (CH2), 23.3 (CH2) ppm; MS (EI, 130°C): m/z (%):
538 ([M+], 5), 446 ([M–NH–Ph], 52), 147 (29), 134
(100), 117 (28), 93 (NH2–Ph, 80).
4.1.1. rac-bis(2,6-dimethylphenylamido)-
[Ethylene-1,2-bis(p5-4,5,6,7-tetrahydro-1-indenyl)]
zirconium (rac-3a)
To a solution of 2,6-dimethylaniline (0.33 ml, 2.67
mmol) in THF (10 ml), 1.6 M n-BuLi in hexane (1.54
ml, 2.46 mmol) was added dropwise at 25°C. After the
solution was stirred for 30 min, solid rac-
(EBTHI)ZrCl2 (0.5 g, 1.17 mmol) was added in one
portion. The reaction mixture turned yellow. The solu-
tion was stirred for 6 h at 25°C. Then the volatile
materials were removed under reduced pressure.
Toluene (20 ml) was added to the residue and the
mixture was stirred for 12 h at 25°C. The slurry was
filtered. The toluene was removed under reduced pres-
sure. The remaining yellow solid was washed with Et2O
(4×10 ml) and dried under vacuum. The obtained
yellow powder (0.54 g, 0.91 mmol, 77%) was pure by
1H-NMR. Crystals for X-ray analysis were obtained by
layering a THF solution of rac-3a with hexane and
cooling the resulting mixture to −30°C. Yellow crys-
tals formed over several days. 1H-NMR: (400 MHz,
4.1.3. rac-bis(2,3,4,5,6-pentafluorophenylamido)-
[Ethylene-1,2-bis(p5-4,5,6,7-tetrahydro-1-indenyl)]-
zirconium (rac-3c)
To a solution of 2,3,4,5,6-pentafluoroaniline (0.24 g,
1.33 mmol) in THF (5 ml), 1.6 M n-BuLi in hexane
(0.77 ml, 1.23 mmol) was added dropwise at room
temperature. After the solution was stirred for 30 min
at room temperature, solid rac-(EBTHI)ZrCl2 (0.25 g,
0.59 mmol) was added in one portion. The reaction
mixture turned yellow brown. The solution was stirred
for 6 h at 25°C. Then the volatile materials were
removed under reduced pressure. Toluene (20 ml) was
added to the residue and the mixture was stirred for 12
h at 25°C. The slurry was filtered. The toluene was
removed under reduced pressure. The remaining gray-
brown solid was washed with Et2O (1×5 ml), hexane
(1×5 ml) and cold toluene (1×1 ml) and dried under
3
C6D6): l=7.17 (d, J(H,H)=7.4 Hz, 4H, Ar–H), 6.92
3
3
(t, J(H,H)=7.4 Hz, 2H, Ar–H), 5.57 (d, J(H,H)=
3.0 Hz, 2H, Cp–H), 5.40 (sbr, 2H, NH), 5.30 (d,
3J(H,H)=3.0 Hz, 2H, Cp–H), 2.74–2.26 (m, 24H),
1.75–1.52 (m, 4H), 1.40–1.26 (m, 4H) ppm; 13C-NMR

R. Wartchow, S. Doye / Journal of Organometallic Chemistry 566 (1998) 287–291
291
[2] P.J. Walsh, A.M. Baranger, R.G. Bergman, J. Am. Chem.
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[10] For reviews about hydroamination of alkenes see: R. Taube
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vacuum. The remaining yellow solid (0.285 g, 0.40 mmol,
68%) was pure by 1H-NMR. 1H-NMR (400 MHz, C6D6):
l=5.71 (m, 2H, Cp–H), 5.13 (d, 3J(HH)=3.1 Hz, 2H,
Cp–H), 5.0 (sbr, 2H, NH), 2.71–2.38 (m, 8H), 2.37–2.22
(m, 4H), 1.80–1.66 (m, 4H), 1.52–1.34 (m, 4H) ppm;
1
13C-NMR (100.6 MHz, C6D6): l=138.9 (d, J(CF)=
233.6 Hz, CF), 138.5 (d, 1J(CF)=245.4 Hz, CF), 131.0,
130.9, 121.9, 111.8, 106.1, 27.6, 23.9, 23.2, 22.8, 22.6 ppm;
The two missing signals for the 2,3,4,5,6-pen-
tafluorophenylamido ligand could not be detected, prob-
ably due to their low intensity.
4.1.4. Crystal structure determination of rac-3a
X-ray structure of rac-3a: formula C36H44N2Zr for-
mula weight, 595.98; crystal system, orthorhombic; space
group, Pbcn (No. 60); a=1181.6(1); b=1471.6(2); c=
1688.2(2) pm; h=90°; i=90°; k=90°; V=2935.5(6)×
106 pm3; Z=4; zcalc=1.349 g cm−1; F000=1256; v=4.0
cm−1; crystal size, 0.37×0.37×0.52 mm; diffractome-
ter type, STOE IPDS; graphite monochromated Mo–Kh,
71.073 pm; measurement at 300 K; range of measure-
ment, 4.4°B2UB48.2°; h,k,l range, −13/13, −16/16,
−19/19; 22439 measured reflections; 2308 unique reflec-
tions; 1159 observed reflections (I0\2.0|(I0)); R1(F0\
4.0|(F0))=0.0304; wR2=0.0654; GOF=0.84; number
[12] F.R.W.P. Wild, J. Zsolnai, G. Huttner, H.H. Brintzinger, J.
Organomet. Chem. 232 (1982) 233.
[13] G.M. Diamond, R.F. Jordan, J.L. Petersen, J. Am. Chem.
Soc. 118 (1996) 8024. G.M. Diamond, S. Rodewald, R.F. Jor-
dan, Organometallics 14 (1995) 5. G.M. Diamond, R.F. Jor-
dan, J.L. Petersen, Organometallics 15 (1996) 4030. A. Vogel,
T. Priermeier, W.A. Herrmann, J. Organomet. Chem. 527
(1997) 297.
[14] For economical reasons we started our project using the less
expensive rac-(EBTHI)ZrCl2 instead of the enantiomeric pure
compound.
−3
˚
of refined parameters, 181; (Dz)min= −0.22 e A
;
(Dz)max=0.22 e A−3; programs used, SHELXS-86,
˚
SHELXL-93, PLATON.
[15] This moisture sensitivity and the lack of equipment for prepar-
ing samples for elemental analysis under an inert atmosphere
in our laboratorium are the reasons why elemental analysis
could not be determined reproducible for the very sensitive
compounds 3b and 3c.
[16] Unfortunately, a comparison with Cp2Zr(NH–2,6-Me2C6H3)2
is not possible because crystallographic data for this com-
pound are not published yet.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft
(DFG) for financial support and Dr M. Dro¨gemu¨ller of
BASF AG for providing rac-(EBTHI)ZrCl2.
[17] F.R.W.P. Wild, M. Wasiucionek, G. Huttner, H.H.
Brintzinger, J. Organomet. Chem. 288 (1985) 63.
[18] R.F. Jordan, R.E. LaPointe, N. Baenziger, G.D. Hinch,
Organometallics 9 (1990) 1539.
References
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