Dynamic topochemical reaction control-A principle and its application in ansa-metallocene synthesis

Article abstract of DOI:10.1021/om100467y

The Cp-alkenyl and Cp-dienyl ligand systems 5 and 8 were prepared by fulvene routes. Subsequent transmetalation gave the respective (Cp-propenyl)₂-, (Cp-butenyl)₂-, (Cp-pentadienyl) ₂-, and Cphexadienyl)₂ZrCl₂ and-HfCl ₂ complexes 6, 9, and 10. In the crystal these complexes favor metallocene conformations that feature the alkenyl and dienyl substituents far separated from each other at the open front side of the bent metallocene wedge. Photolysis in the solid state consequently did not result in an intramolecular C-C coupling reaction but led to E/Z isomerization of the alkenyl units. In solution rapid conformational metallocene equilibration takes place. Photolysis of the (Cp-alkenyl)₂ZrCl₂ complexes 6 in solution very efficiently resulted in the formation of the cyclobutylene-bridged ansa-zirconocene isomers 11 by rapid intramolecular [2 + 2] cycloaddition reaction by means of a dynamic topochemical reaction control. Photolysis of the (Cp-dienyl)₂ZrCl₂ and-HfCl₂ complexes (9, 10) in solution proceeded analogously to efficiently yield the cyclooctadienylene bridged ansa-metallocenes (12, 13) by formal dynamic topochemical [4 + 4] cycloaddition reaction control.

Full text of DOI:10.1021/om100467y

3210 Organometallics 2010, 29, 3210–3221
DOI: 10.1021/om100467y
Dynamic Topochemical Reaction Control-A Principle and Its
Application in ansa-Metallocene Synthesis†
‡
Ingo Greger, Gerald Kehr, Roland Frohlich, and Gerhard Erker*
€
€
€
Organisch-Chemisches Institut der Universitat Munster, Corrensstrasse 40, 48149 Munster, Germany.
€
‡X-ray crystal structure analyses.
Received May 14, 2010
The Cp-alkenyl and Cp-dienyl ligand systems 5 and 8 were prepared by fulvene routes. Subsequent
transmetalation gave the respective (Cp-propenyl)2-, (Cp-butenyl)2-, (Cp-pentadienyl)2-, and (Cp-
hexadienyl)2ZrCl2 and -HfCl2 complexes 6, 9, and 10. In the crystal these complexes favor
metallocene conformations that feature the alkenyl and dienyl substituents far separated from each
other at the open front side of the bent metallocene wedge. Photolysis in the solid state consequently
did not result in an intramolecular C-C coupling reaction but led to E/Z isomerization of the alkenyl
units. In solution rapid conformational metallocene equilibration takes place. Photolysis of the
(Cp-alkenyl)2ZrCl2 complexes 6 in solution very efficiently resulted in the formation of the
cyclobutylene-bridged ansa-zirconocene isomers 11 by rapid intramolecular [2 þ 2] cycloaddition
reaction by means of a dynamic topochemical reaction control. Photolysis of the (Cp-dienyl)2ZrCl2
and -HfCl2 complexes (9, 10) in solution proceeded analogously to efficiently yield the cycloocta-
dienylene bridged ansa-metallocenes (12, 13) by formal dynamic topochemical [4 þ 4] cycloaddition
reaction control.
Introduction
proceed with a minimum of movement around their fixed
positions.1 This topochemical principle has led to the dis-
covery of a sizable number of remarkable topochemic-
ally controlled reactions of mostly organic molecules in
single crystals or in the solid state in general.2,3 Some most
noteworthy examples come from the pioneering work by
Schmidt et al.4,5 A typical frequently cited example is the
photochemical [2 þ 2] cycloaddition reaction of pairs of
trans-cinnamic acid. This takes place from the crystalline
R-phase to form the head-to-tail dimer R-truxillic acid, and
upon photolysis of the crystalline β-phase it forms the head-
to-head cyclobutane derivative (β-truxillic acid). In both of
these crystalline phases the cinnamic acid CdC double bonds
Chemical reactions in the solid state are determined by the
position of the atoms and molecules in the crystal lattice
more than anything else because they necessarily have to
† Dedicated to Professor Wolfgang Kirmse on the occasion of his 80th
birthday.
*To whom correspondence should be addressed. E-mail: erker@
uni-muenster.de.
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pubs.acs.org/Organometallics
Published on Web 06/24/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 14, 2010 3211
orientation to allow the photochemical formation of the
cycloadducts to take place. Notable examples were described
by Hopf et al., making use of p-cyclophane-derived systems.6
Even ladderane formation could be achieved in this way.
It occurred to us that bent-metallocene frameworks could
offer a unique new possibility to set the scene for a different
type of topochemical reaction control, namely by bringing
the reacting CdC double bonds into a suitable orientation by
means of their characteristic conformational features. The
bent metallocenes usually undergo rapid rotation around
their Cp-metal vectors.7 Because of the typical bent Cp-
M-Cp situation this may bring conjugated alkenyl subs-
tituents in a manifold of relative orientations to each other.
The global conformational minimum will feature these
substituents oriented toward the open front side of the bent
metallocene wedge, where their large spatial separation
would preclude any coupling reaction to occur. However,
there may be cases where local minimum conformations
become populated in an equilibrium situation that bring
the alkenyl substituent CdC bonds close to each other in a
favorable arrangement for a photochemical cycloaddition to
take place. Indeed, we8 and others9 had shown that ansa-
metallocene formation is possible by intramolecular photo-
chemical [2 þ 2] cycloaddition of suitably bis-alkenyl-sub-
stituted bent-metallocene systems in solution. However, it
remained to be shown that these reactions really proceeded
by a unique “dynamic topochemical reaction control”. Such
a control would have become indicated by the observation of
a formal reversal of the results of the photolysis of a bis-
(alkenyl-Cp) bent metallocene in the solid state and in
solution relative to the conventional topochemically con-
trolled reaction: in the crystal the unfavorable fixed metallo-
cene conformation would in most cases preclude the
intramolecular [2 þ 2] cycloaddition from taking place,
whereas in solution this would in a variety of cases become
possible because of a release of this conformational fixture (see
Scheme1).
Scheme 1
Scheme 2
Scheme 3
Results and Discussion
Synthesis of the Alkenyl- and Dienyl-Substituted Group 4
Bent-Metallocene Complexes. As we shall see, it was crucial
for our analysis to have suitably substituted (alkenyl-Cp)2-
and (dienyl-Cp)2MCl2 complexes available. These were pre-
pared by means of fulvene routes. We prepared the fulvenes
3a,b by means of treatment of the respective 1-acetoxy-1-
chloroalkane (2a,b) with sodium cyclopentadienide, fol-
lowed by triethylamine as described by Neuenschwander et
al.10 The somewhat sensitive fulvenes (3a,b) were obtained as
yellow oils. The fulvene 3c was prepared by the “Stone/Little
procedure”11 from cyclopentadiene, the aldehyde rac-4, and
pyrrolidine (Scheme 2).12
We here wish to report about a series of examples from
(alkenyl-Cp)2- and (butadienyl-Cp)2MCl2 chemistry (M =
Zr, Hf) where the use of suitably substituted examples has
allowed us to detect just these characteristic differences in
photochemical behavior in the solid state and in solution, as
would be expected for such a dynamic topochemical reaction
control.
Deprotonation of these fulvenes was effected by treatment
with lithium diisopropylamide (LDA) in tetrahydrofuran.
The products (5a-c) were isolated (ca. 70-90% yields) and
spectroscopically characterized (Scheme 3).
Deprotonation of 3a gave a ca. 86:14 mixture of E-5a and
Z-5a. The isomers were identified by their typical vicinal
6-H/7-H coupling constants of 15.4 Hz (E) and 11.2 Hz (Z),
respectively, and their 13C NMR methyl substituent reso-
nances at δ 18.6 (E) and δ 15.5 (Z). Deprotonation of 3b gave
mainly a single (1-butenyl-Cp)Li isomer that was identified
as the E-5b product (1H NMR J(6-H/7-H) = 15.4 Hz). Simi-
larly, we have obtained a single isomer of 5c, which we have
assigned as E-5c.
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Chem. 1995, 107, 742-744; Angew. Chem., Int. Ed. 1995, 34, 685-687.
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Bouas-Laurent, H. Eur. J. Org. Chem. 2005, 567–581. See also: Yamada,
S.; Uematsu, N.; Yamashita, K. J. Am. Chem. Soc. 2007, 129, 12100–12101.
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Chem. Soc. 1996, 118, 9623–9630. Dreier, T.; Bergander, K.; Wegelius, E.;
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Frohlich, R.; Erker, G. Organometallics 2001, 20, 5067–5075. Jodicke, T.;
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Menges, F.; Kehr, G.; Erker, G.; Howeler, U.; Frohlich, R. Eur. J. Inorg.
Chem. 2001, 2097–2106.
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(8) Erker, G.; Wilker, S.; Kruger, C.; Nolte, M. Organometallics
1993, 12, 2140–2151. Erker, G.; Nolte, M.; Aul, R.; Wilker, S.; Kr€uger, C.;
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Noe, R. J. Am. Chem. Soc. 1991, 113, 7594–7602. Paradies, J.; Frohlich, R;
Kehr, G.; Erker, G. Organometallics 2006, 25, 3920–3925. Nie, W. L.; Erker,
We then reacted the 86:14 mixture of the reagent E-5a and
Z-5a with ZrCl4(THF)2 in tetrahydrofuran. Workup gave a
€
G.; Kehr, G.; Frohlich, R. Angew. Chem. 2004, 116, 313-317; Angew.
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Chem., Int. Ed. 2004, 43, 310-313. Paradies, J.; Erker, G.; Frohlich, R.;
Bergander, K. Angew. Chem. 2006, 19, 3150-3153; Angew. Chem., Int.
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Ed. 2006, 45, 3079-3082. Tumay, T. A.; Kehr, G.; Frohlich, R.; Erker, G.
Organometallics 2009, 28, 4513–4518.
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(10) Kyburz, R.; Schaltegger, H.; Neuenschwander, M. Helv. Chim.
Acta 1971, 54, 1037–1046.
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(12) Erker, G.; Aul, R. Chem. Ber. 1991, 124, 1301–1310.

3212 Organometallics, Vol. 29, No. 14, 2010
Greger et al.
Figure 1. 13C NMR spectrum of the E,E-, E,Z-, Z,Z-6a mixture (C6 signals are shown) at 298 K and 125.7 MHz in CD2Cl2.
Scheme 4
Scheme 5
mixture of the three products E,E-6a, E,Z-6a, and Z,Z-6a in
a ratio of 18:7:1, which was isolated in a combined yield of
53% (Scheme 4). The major component of the mixture was
separated and eventually characterized by X-ray diffraction
were both isolated in ca. 30% yield. Their NMR analysis
revealed the presence of only trans-C7-C8 CdC double
bonds in these products (for details see the Supporting
Information).
1
(see below). The H/13C NMR signals of the components
overlap heavily. The mixture is best characterized by the
well-separated C6 13C NMR signals (see Figure 1). Complex
E,E-6a features the C6 resonance of the pair of symmetry-
equivalent Cp-(E)-CHdCHCH3 ligands at δ 124.11 (in
CD2Cl2 at room temperature), whereas the E,Z-6a isomer
shows a 1:1 intensity pair of the corresponding C6 carbon
atoms at δ 124.06 (E) and δ 123.41 (Z). There remains a
single signal at δ 123.37, which we tentatively assign to the
pair of Cp-(Z)-CHdCHCH3 ligands of the minor Z,Z-6a
isomer.
The conjugated fulvenes 7a,b were deprotonated by treat-
ment with potassium hexamethyldisilylamide (KHMDS)
in diethyl ether. We isolated a 55:45 mixture of E,E-8a and
E,Z-8a in a combined yield of 95%. The NMR analysis (see
the Experimental Section and the Supporting Information)
revealed the presence of a trans-C6-C7 CdC double bond
for each of the isomers and a trans-C8-C9 linkage (3J(H8,
H9)=14.2 Hz) for E,E-8a and a cis-C8-C9 linkage (3J(H8,
H9) =10.5Hz) for theE,Z-8a isomer. TheKHMDS deproto-
nation reaction of the fulvene 7b gave a similar result. We
obtained a 71:29 mixture of the substituted cyclopentadienide
products E,E-8b and E,Z-8b isolated in a combined yield of
86% (see Scheme 5).
Transmetalation of the 55:45 mixture of E,E-8a and
E,Z-8a with ZrCl4(THF)2 gave a 4:4:1 mixture of the respec-
tive substituted zirconocene dichlorides E,E;E,E-9a, E,E;E,
Z-9a, and E,Z;E,Z-9a (combined yield, isolated, 71%). The
NMR analysis showed that in each case the C6-C7 CdC
double bonds of the conjugated dienyl side chains were in an
E configuration, whereas the terminal C8-C9 CdC double
bonds were responsible for the formation of the isomeric
mixture. The overall C8-C9 E:Z ratio was found to be 67:33
for 9a, which slightly deviated from the original E:Z ratio
found in the respective reagent 8a. The reaction of the E-/Z-8a
mixture with HfCl4(THF)2 in THF gave a similar result
(4:4:1 ratio of the three isomers of 10a; see Scheme 6).
Treatment of the 71:29 mixture of the E,E-8b/E,Z-8b
reagents with ZrCl4(THF)2 gave the product 9b as a 6:4:1
mixture of the three respective isomers (see Scheme 6). This
corresponds to an overall C8-C9 E:Z ratio of 73:27, which
in this case is close to that of the starting material. The
mixture was isolated in a combined yield of 70%. We also
The observed E,E-6a:E,Z-6a:Z,Z-6a ratio corresponds to
an overall alkenyl E:Z ratio of 83:17, which is very close to
the E:Z ratio of the alkenyl side chain in the original reagent
E-/Z-5a. The reaction of the ethyl-substituted reagent E-5b
with ZrCl4(THF)2 was carried out analogously. It gave only
a single product, namely E,E-6b, which was isolated in 55%
yield. In solution the compound shows a pair of symmetry-
equivalent Cp-(E)-CHdCHEt ligands; they feature a pair of
1
6-H (δ 6.22) and 7-H (δ 6.14) H NMR resonances with a
characteristic vicinal coupling constant of 3JHH = 15.8 Hz.
The analogous reaction of the reagent E-5c with ZrCl4-
(THF)2 furnished the metallocene E,E-6c (73% isolated) as
a single isomer (1H NMR: δ 6.63 (6-H)).
The Cp-dienyl systems were also prepared by means of
fulvene routes. We prepared the new fulvenes 7a (R = CH3)
and 7b (R = ethyl) in analogy to a procedure developed by
Neuenschwander et al.,13 which used sodium ethoxide as the
base to deprotonate cyclopentadiene and react the resulting
sodium cyclopentadienide with the corresponding R,β-un-
saturated aldehydes in ethanol at -20 °C. The fulvenes 7a,b
(13) Neuenschwander, M.; Meuche, D.; Schaltegger, H. Helv. Chim.
Acta 1964, 47, 1022–1032.

Article
Organometallics, Vol. 29, No. 14, 2010 3213
Scheme 6
Figure 2. View of the molecular geometry of the metallocene com-
˚
plex E,E-6a. Selected bond lengths (A) and angles (deg) (major
component): Zr-Cl1 = 2.4376(4), Zr-CCp = 2.464(2)-2.549(2),
C1-C6 = 1.489(3), C6-C7 = 1.313(6), C7-C8 = 1.555(15);
Cl1-Zr-Cl1* = 96.31(2), C1-C6-C7 = 122.3(3), C6-C7-
C8 = 124.2(6), C1-C6-C7-C8 = 178.3(7). Throughout this
paper thermal ellipsoids are depicted at the 50% probability
level.
prepared the corresponding hafnium compounds (72%
yield, 8:5:1 ratio of the E,E;E,E-, E,E;E,Z-, and E,Z;E,Z-10b
isomers, overall C8-C9 E:Z ratio 75:25).
Characterization by X-ray Diffraction. Three typical ex-
amples of the alkenyl- and dienyl-substituted group 4 bent
metallocenes were characterized by X-ray crystal structure
analyses. Single crystals of the pure (Cp-(E)-CHdCH-
CH3)2ZrCl2 isomer E,E-6a were obtained from the mixture
of isomers by crystallization from a toluene solution at -30 °C.
The structure of complex E,E-6a (see Figure 2) shows a typical
bent-metallocene core with a Cl1-Zr-Cl1* angle of 96.31(2)°
and a Cp(centroid)-Zr-Cp*(centroid) angle of 129.9°. The
metallocene features a C2-symmetric conformation that has
both of the (E)-CHdCHCH3 substituents oriented toward the
open front side of the bent-metallocene wedge. This results in a
large vertical separation of the pair of olefinic π-systems
open front side of the metallocene. The C1(Cp)-C6(dienyl)
vector is almost perfectly oriented in the bisecting plane of
the Cl1-Hf-Cl2 σ unit. Both attached chains then are offset
to the Hf-Cl1 side which has both the C6-C7 and the
C26-C27 vectors oriented similarly in the projection (see
Figure 3). This overall orientation leads to a large vertical
separation of the two substituent π systems from each other
across the separating metallocene σ-ligand plane.
Photolysis of the (Cp-CHdCHR)2ZrCl2 Systems. We per-
formed the photolysis of the 18:7:1 mixture of the E,E-, E,Z-
and Z,Z-6a isomers in the solid state. For this purpose we
precipitated a thin film of 6a on the glass wall of a Schlenk
flask and irradiated it with Pyrex-filtered UV light for ca. 3 h
at room temperature. During this time an almost complete
cis-trans isomerization took place and we obtained almost
pure E,E-6a (see Figure 4). On redissolution in CD2Cl2 the
compound features a pair of symmetry-equivalent Cp-(E)-
CHdCHCH3 ligands (1H NMR δ 6.25 (dq, 3JH,H = 15.8 Hz,
˚
˚
(distances C6 C6* = 6.551 A, C7 C7* = 8.080 A). In
3 3 3
3 3 3
addition the alkenyl CdC double bonds are found slightly
offset in their projection onto the metallocene σ plane (dihedral
angle C7-C6 C6*-C7* = 125.7°). The closely related
3 3 3
complex E,E-6b was also characterized by X-ray diffraction.
It shows a very similar structure. Both (E)-CHdCHC2H5
substituents are found oriented toward the open front side of
the metallocene in an overall C2-symmetric geometry (dihedral
4JH,H = 1.6 Hz, 6-H), δ 6.10 (dq, 3JH,H = 15.8 Hz, 3JH,H
=
angle C7-C6 C6*-C7* = -97.0°; for further details and a
6.7 Hz, 7-H)) The corresponding 13C NMR signals were
found at δ 124.1 (C6), δ 129.2 (C7) and δ 18.6 (C7-CH3).
Photolysis (HPK 125, Pyrex filter) of the 18:7:1 mixture of
E,E-, E,Z-,and Z,Z-6a isomers in dichloromethane for 2.5 h
at room temperature resulted in a complete conversion to the
ansa-metallocene isomers Me2-cis-11a and Me2-trans-11a in
a ratio of 1.7:1. The mixture was isolated on a preparative
scale in a combined yield of 72% (see Scheme 7). The same
mixture of [2 þ 2] photocycloaddition products was obtained
by photolyzing the pure E,E-6a isomer, which was obtained
from the solid-state photolysis of the 6a isomer mixture, on
redissolution in CD2Cl2. The major Me2-cis-11a isomer was
characterized by an X-ray crystal structure analysis (see
below). This structure and the NMR analysis revealed that
the metallocene fragment is 1,2-cis-connected to the newly
formed cyclobutane rings in both of the products 11a. In
Me2-cis-11a the spectra feature an averaged Cs-symme-
tric compound with the Cp rings and methyl substituents
3 3 3
figure of the structure of complex E,E-6b in the crystal, see the
Supporting Information).
Single crystals of the (Cp-dienyl)2HfCl2 complex E,E;E,
E-10b (R = ethyl) were obtained from a toluene/pentane
solvent mixture. To the best of our knowledge, it represents
the first crystal structure analysis of a bent-metallocene
complex with a butadienyl-derived conjugated Cp side chain.
In the crystal the molecule attains a close to Cs-symmetric
molecular geometry (see Figure 3). The conjugated side
chains exhibit the expected alternation of carbon-carbon
single and double bonds. The dienyl chains are in a coplanar
orientation with their Cp rings, which allows for optimal
overlap of their π-electron systems. The pairs of CdC double
bonds in both the dienyl side chains are found in the E
configuration. It is seen in the respective projection that the
system shows a metallocene conformation that has both of
the -CHdCHCHdCHC2H5 chains oriented toward the

3214 Organometallics, Vol. 29, No. 14, 2010
Greger et al.
˚
Figure 3. Two projections of the molecular geometry of the hafnium complex E,E;E,E-10b. Selected bond lengths (A) and angles (deg)
(major components): Hf-Cl1=2.411(2), Hf-Cl2=2.420(2), Hf-CCp=2.447(10)-2.565(19), C1-C6=1.47(3), C21-C26=1.49(2), C6-C7=
1.35(2), C26-C27=1.34(2), C7-C8=1.45(2), C27-C28=1.44(2), C8-C9=1.33(3), C28-C29=1.36(2), C9-C10=1.58(2), C29-C30=
1.58(2), C10-C11=1.46(2), C30-C31=1.46(2); Cl1-Hf-Cl2=96.60(9), C1-C6-C7=125(1), C21-C26-C27=124(1), C6-C7-C8=
125(1), C26-C27-C28 = 123(1), C7-C8-C9 = 124(2), C27-C28-C29 = 122(1), C8-C9-C10 = 139(2), C28-C29-C30 = 114(2),
C9-C10-C11=96(3), C29-C30-C31=106(2).
Figure 4. 1H NMR spectrum of the 6a isomers before (bottom) and after (top) photolysis in the solid state (599.6 MHz, CD2Cl2,
298 K).
oriented trans to each other. In the minor Me2-trans-11a
isomer one Me substituent is oriented trans to Cp and the
other cis. The observed 1.7:1 ratio of Me2-cis-11a to Me2-
trans-11a would correspond to an overall 81:19 ratio of

Article
Organometallics, Vol. 29, No. 14, 2010 3215
Scheme 7
Figure 5. View of the molecular structure of the cis-dimethyl-
cyclobutylene-bridged ansa-zirconocene complex Me2-cis-11a.
˚
Selected bond lengths (A) and angles (deg): Zr-Cl1=2.437(1),
Zr-Cl2 = 2.435(1), Zr-CCp = 2.477(4)-2.521(3), C1-C6 =
1.498(5), C11-C16=1.502(5), C6-C7=1.568(5), C16-C17=
1.545(5), C7-C8 = 1.501(5), C17-C18 = 1.519(5), C6-C16 =
1.571(5), C7-C17 = 1.551(7); Cl1-Zr-Cl2 = 97.77(4), C1-
C6-C7 = 116.5(3), C11-C16-C17 = 119.4(3), C6-C7-C8 =
113.0(3), C16-C17-C18 = 116.7(3), C1-C6-C16 = 113.7(3),
C11-C16-C6 =115.5(3), C6-C7-C17 =89.7(3), C16-C17-
C7=89.1(3), C6-C16-C17=89.7(3), C16-C6-C7=87.6(3).
Scheme 8
Structural Characterization of the Substituted Cyclobuty-
lene-bridged ansa-Zirconocene Complexes. Single crystals of
the Me2-cis-11a ansa-metallocene (see Figure 5) were grown
by slow cooling of a toluene solution of the Me2-cis-/Me2-
trans-11a mixture of isomers. The compound shows an ansa-
metallocene framework characterized by a Cp(centroid)-Zr-
Cp(centroid) angle of 126.2° and a Cl1-Zr-Cl2 σ-ligand angle
of 97.77(4)° (see Figure 5). The Zr-C(Cp) distances are in the
Scheme 9
˚
range 2.477(4)-2.521(3) A. The four-membered carbocycle
that was formed by [2 þ 2] photocycloaddition of the former
alkenyl substituents at the Cp rings is oriented toward the
narrow back side of the bent-metallocene wedge. The Cp rings
are connected cis to each other at the bridging atoms C6 and
C16. The methyl substituents at the distal cyclobutane
C7-C17 bond are found to be oriented cis to each other.
The four-membered carbocycle in Me2-cis-11a is slightly puck-
ered (dihedral angle C7-C6-C16-C17 = 14.8(2)°).14
Upon cooling of the 1:1.1 mixture of the Et2-cis-11b/Et2-
trans-11b isomers in toluene/pentane we obtained single
crystals that contained these two complexes in a 2:1 ratio
(see Figure 6). The quality of the data set and the structure
solution was not sufficient to allow for a detailed discussion
of the specific structural data of this pair of complexes. It
served, however, to support the general structural assign-
ments of these compounds as the Et2-cis- and Et2-trans-11b
isomers.
Photolysis of the (Cp-dienyl)2MCl2 Complexes. Photolysis
of the 4:4:1 mixture of the (Cp-pentadienyl)2ZrCl2 isomers E,
E;E,E-9a, E,E;E,Z-9a, and E,Z;E,Z-9a was carried out in
solution and in the solid state (see Scheme 10). Irradiation of
the mixture as a polycrystalline film resulted in an effective
cis/trans isomerization of the distal CdC double bond of the
conjugated dienyl system to eventually yield the pure E,E;E,
E-9a metallocene isomer. Its 1H NMR spectrum features the
7-H resonance at δ 6.34 and the corresponding 6-H signal
trans- to cis-CHdCHCH3 units having been connected. This
is close to the trans-/cis-alkenyl ratio of the original 18:7:1
mixture of the 6a precursor isomers, but it should be
remembered that the 1.7:1 11a isomer mixture is also ob-
tained by photolysis of the pure E,E-6a precursor.
The photolysis reaction of the ethyl-substituted (Cp-alke-
nyl)2ZrCl2 complex 6b leads to a similar result. UV irradi-
ation of a solution of the pure E,E-6b isomer in CH2Cl2 (1.5 h,
room temperature, Pyrex filter) gives the isomeric [2 þ 2]
cycloaddition products Et2-cis-11b and Et2-trans-11b in a
1:1.1 ratio (isolated in 83% yield; see Scheme 8). This
corresponds to a hypothetical CpCHdCHEt trans to cis
ratio of 74:26. The products were characterized spectro-
scopically (for details see the Experimental Section and the
Supporting Information), and both were characterized by
X-ray diffraction (see below).
Photolysis of the highly substituted complex E,E-6c
marked the limits of [2 þ 2] cyclobutylene-bridged ansa-
metallocene formation. As expected, the UV irradiation of
complex E,E-6c in the solid state only resulted in E/Z
isomerization of the trisubstituted double bonds, resulting
in the rapid formation of a mixture of the nonbridged E,E-6c,
E,Z-6c, and Z,Z-6c metallocene isomers in a 1:4:5 ratio (see
Scheme 9). Photolysis of the pure E,E-6c isomer in CD2Cl2
solution in this case did not result in any measurable for-
mation of intramolecular [2 þ 2] cycloaddition products.
Instead, we observed a rapid E/Z double-bond isomeriza-
tion to take place to yield the same 1:4:5 mixture of the
(Cp-alkenyl)2ZrCl2 isomers of 6c.
(14) Eliel, E. L.; Wilen, S. H.; Doyle, M. P. Basic Organic Stereo-
chemistry; Wiley-Interscience: New York, 2001.

3216 Organometallics, Vol. 29, No. 14, 2010
Greger et al.
Figure 6. Projections of the molecular structures of the Et2-cis-11b (left) and Et2-trans-11b (right) isomers.
Scheme 10
Figure 7. View of the molecular structure of the cyclooctadieny-
lene-bridged ansa-zirconocene complex Me2-trans-12a. Selected
˚
bond lengths (A) and angles (deg): Zr-Cl1=2.442(1), Zr-Cl2=
at δ 6.03 (3J(6-H, 7-H) = 15.8 Hz). The 8-H and 9-H
hydrogen resonances are found at δ 5.93/δ 5.55 (3J(8-H,
9-H) = 15.2 Hz) and the 9-CH3 signal at δ 1.56. The hafnium
system 10a shows analogous solid-state photochemical be-
havior. Irradiation of the corresponding 4:4:1 mixture of the
geometrical isomers eventually led to a sample highly en-
riched in E,E;E,E-10a with only traces of the other two
residual isomers detectable.
Photolysis of the 4:4:1 mixture of the three (Cp-pentadie-
nyl)2ZrCl2 9a isomers in dichloromethane (HPK 125, Pyrex
filter) for 2 h at room temperature resulted in the formation
of a 1:3.3 mixture of the pair of isomeric formal [4 þ 4]
cycloaddition products Me2-cis-12a and Me2-trans-12a (see
Scheme 10). The NMR spectra of both systems show a cis-
1,2-substitution pattern of the Cp rings at the newly formed
nonplanar doubly unsaturated eight-membered carbocycle.
In Me2-cis-12a the methyl substituents are attached cis to
each other and (according to the detailed NMR analysis; see
the Supporting Information for details) cis to the Cp sub-
stituents. Consequently, the methyl groups in Me2-trans-12a
are attached trans to each other at the cyclooctadienylene
ansa bridge. The structual assignment of the Me2-trans-12a
was supported by the X-ray crystal structure analysis of the
compound (see below).
2.439(1), Zr-CCp=2.470(2)-2.527(2), C1-C6=1.515(3), C11-
C16=1.515(3), C6-C7=1.505(3), C16-C17=1.516(3), C7-C8=
1.323(3), C17-C18=1.322(3), C8-C9=1.505(4), C18-C19=
1.502(3), C9-C10=1.521(4), C19-C20=1.535(3), C6-C16=
1.567(3), C9-C19=1.549(3); Cl1-Zr-Cl2=97.87(3), C1-C6-
C7=113.4(2), C11-C16-C17=110.2(2), C6-C7-C8=127.3(2),
C16-C17-C18=128.1(2), C1-C6-C16=108.3(2), C11-C16-
C6=110.3(2), C6-C16-C17=115.2(2), C16-C6-C7=113.2(2),
C7-C8-C9 = 130.0(2), C17-C18-C19 = 127.5(2), C8-C9-
C10 = 109.2(2), C18-C19-C20 = 110.8(2), C8-C9-C19 =
115.8(2), C18-C19-C9 = 109.6(2), C9-C19-C20 = 111.1(2),
C19-C9-C10=112.7(2).
(1:3.3). The (Cp-pentadienyl)2HfCl2 system reacted analo-
gously upon photolysis. Irradiation of the 4:4:1 mixture of
the three 10a isomers gave a 1:4 mixture of the dimethyl-
substituted cyclooctadienylene-bridged ansa-hafnocene com-
plexes Me2-cis-13a and Me2-trans-13a (see Scheme 10). The
latter compound was also characterized by X-ray diffraction.
Again, photolysis of the pure E,E;E,E-10a isomer led to the
same product mixture. The photolysis reaction of the haf-
nium system is slightly complicated by the formation of
increasing amounts of as yet not positively identified fol-
low-up products upon prolonged photolysis of the samples.
The observed Me2-cis-:Me2-trans ratios theoretically corre-
late with an overall dienyl E:Z ratios of 62:38 (Zr) and 60:40
(Hf), respectively.
Photolysis of the pure E,E;E,E-9a isomer under similar
conditions in d8-toluene gave the [4 þ 4] cycloaddition
products Me2-cis-12a and Me2-trans-12a in the same ratio

Article
Organometallics, Vol. 29, No. 14, 2010 3217
Scheme 11
The photolysis reaction of the (Cp-hexadienyl)2MCl2
prevented as long as this conformationally fixed situation
persists. Consequently, we see other reactions than cycload-
dition to occur upon photolysis in the solid state.
zirconium and hafnium complexes (9b, 10b) proceeded ana-
logously. Irradiation of the mixtures of the three isomers
in the solid state in both cases resulted in a rapid cis/trans
isomerization to take place, which eventually made the
pure E,E;E,E-9b (Zr) and E,E;E,E-10b (Hf) isomers avail-
able.
Photolysis of the 6:4:1 (Zr) or 8:5:1 (Hf) mixture of the
three respective (Cp-hexadienyl)2MCl2 isomers in solution
(CH2Cl2) resulted in the formation of 1:5 (Zr) or 1:6 (Hf)
mixtures of the respective [4 þ 4] photocycloaddition pro-
ducts Et2-cis-/Et2-trans-12b (Zr) and Et2-cis-/Et2-trans-13b
(Hf). Their structures were derived by a close comparison of
their typical spectroscopic data with those of the systems
12a/13a (see above and Scheme 10).
The situation changes upon bringing these systems into
solution. Now a very effective and rapid conformational
equilibration of the bent-metallocene rotamers takes place
which may bring the intramolecular pairs of CdC double
bonds attached at the bent-metallocene framework into close
proximity and a favorable relative orientation for the photo-
chemical cycloaddition reaction can occur. During this
process the stereochemical information present at the pendant
CdC double bond side chains is in most cases not carried
through to the product. This may indicate the possibility of
rotational scrambling at some intermediate stage of the reac-
tion, as is formally sketched in Scheme 11. From previous
detailed mechanistic studies we know that the formal [4 þ 4]
cycloaddition reaction of the (Cp-butadienyl)2ZrCl2 system
proceeds stepwise with initial [2 þ 2] cycloaddition at the distal
CdC double bonds followed by conformational equilibration
and a final thermally induced Cope rearrangement.16 There-
fore, a tentative formal description of the stereochemical
scrambling taking place at a respective intermediate stage
(15) might be followed from that study, although the mechan-
istic details of the photochemical steps of the cycloaddition
sequences need to be clarified.17
The remarkable features of the dynamic topochemical
reaction control have here been used to add an attractive
and useful tool to synthetic metallocene chemistry. It has
made new types of ansa-metallocene precursors for homo-
geneous Ziegler-Natta olefin polymerization catalysts18
easily available. It is quite conceivable that similar properties
may lead to the development of related systems at confor-
matively flexible organic frameworks that will lead to new
applications of the principle of dynamic topochemical reac-
tion control in organic synthesis as well.
Structural Characterization of the [4 þ 4] Photocycloaddition
Products. Crystals of the complex Me2-trans-12a suitable for
the X-ray crystal structure analysis were obtained from a
toluene solution of the mixture of [4 þ 4] cycloaddition
products upon cooling (see Figure 7). The structure shows
that a bridging cyclooctadienylene system had been formed
in the photolysis reaction. The zirconocene is characterized
by a Cp(centroid)-Zr-Cp(centroid) angle of 124.1°. The
Zr-C(Cp) bond lengths are found within a small range of
˚
2.470(2)-2.527(2) A. The newly formed cyclooctadiene ring
features a slightly twisted boat conformation.15 The metal-
locene Cp rings were found 1,2-cis attached at the cyclo-
octadiene C6-C16 single bond. The methyl substituents are
arranged trans to each other at C9 and C19. The latter is
found cis to the Cp rings.
The hafnium complex Me2-trans-13a is almost isostruc-
tural with Me2-trans-12a. Its structure is depicted in the
Supporting Information.
Conclusions
Experimental Section
The systems described in this account show the typical
features that one would expect for dynamic topochemical
reactions, including their characteristic inverted behavior
relative to conventional topochemical reactions. The latter
typically show photochemical cycloaddition reactions con-
trolled by their molecular orientation in the crystal lattice, a
behavior which necessarily breaks down in solution. In
contrast to this, our systems feature fixed conformational
arrangements in the solid state that have the pairs of double
bonds within these molecules efficiently separated so far
from each other at the open front side of the bent metallocene
wedge that any photochemical cycloaddition is effectively
General Procedures. Reactions with air- and water-sensitive
compounds were carried out under argon using Schlenk-type
glassware or in a glovebox. Solid compounds were collected
on sintered-glass frits and washed with appropriate solvents
before being dried under vacuum. Solvents were dried and
(16) Paradies, J.; Greger, I.; Kehr, G.; Erker, G.; Bergander, K.;
€
Frohlich, R. Angew. Chem. 2006, 118, 7792-7795; Angew. Chem., Int.
Ed. 2006, 45, 7630-7633.
(17) See for comparison: Bartlett, P. D.; Montgomery, L. K.; Seidel,
B. J. Am. Chem. Soc. 1964, 86, 622–628. Bartlett, P. D.; Montgomery, L. K.
J. Am. Chem. Soc. 1964, 86, 628–631.
€
(18) Greger, I.; Kehr, G.; Frohlich, R.; Erker, G. Organometallics
€
(15) Rocha, W. R.; De Almeida, W. B. J. Comput. Chem. 1997, 18,
254–259.
2010, 29, 860–866. Paradies, J.; Kehr, G.; Frohlich, R.; Erker, G. Proc. Natl.
Acad. Sci. U.S.A. 2006, 103, 15333–15337.

3218 Organometallics, Vol. 29, No. 14, 2010
Greger et al.
distilled under argon prior to use. 6-Ethylfulvene, 6-propylful-
vene (3a,b), 6-(phenylethyl)fulvene (3c), and (((E)-2-phenyl-
1-propenyl)cyclopentadienyl)lithium (5c) were prepared as des-
cribed in the literature.8,10 The fulvenes 7a and 7b were prepared
in analogy to a literature procedure13 (for details see the Supporting
Information). The following instruments were used for physical
characterization of the compounds. Elemental analyses: Foss-
Heraeus CHNO-Rapid. NMR: Varian UNITY plus NMR
spectrometer (1H, 599.7 MHz; 13C, 150.8 MHz), Varian 500 MHz
INOVA (1H, 499.8 MHz; 13C, 125.7 MHz). Assignments of the
resonances were supported by 2D experiments. X-ray diffrac-
tion: data sets were collected with a Nonius KappaCCD dif-
fractometer, equipped with a rotating anode generator. Programs
used: data collection COLLECT (Nonius BV, 1998), data reduction
Denzo-SMN,19 absorption correction SORTAV20 and Denzo,21
structure solution SHELXS-97,22 structure refinement SHELXL-
97,23 and graphics XP (BrukerAXS, 2000). Thermal ellipsoids in
all figures are drawn at the 50% probability level. R1 values are
given for observed reflections and wR2 values for all reflections.
Preparation of ((1-Propenyl)cyclopentadienyl)lithium (E-/Z-5a).
LDA(1.71g, 16mmol) was dissolvedintetrahydrofuran(100mL)
and cooled to -78 °C. A solution of 6-ethylfulvene (3a; 1.7 g,
16 mmol) in tetrahydrofuran (10 mL) was added, and the reaction
mixture was warmed to room temperature within 5 h. The solvent
was removed in vacuo, and the remaining solid was treated with
diethyl ether (30 mL) and precipitated with pentane (30 mL). The
white product was filtered, washed with pentane, and dried under
vacuum. The product was formed as a mixture of ((E)-(1-propenyl)-
cyclopentadienyl)- and ((Z)-(1-propenyl)cyclopentadienyl)lithium
129.4 (C6), 119.2 (C1), 118.3 (C7), 104.3 (C3, C4), 102.8 (C2, C5),
27.2 (C8), 15.5 (C9) ppm.
Preparation of ((1,3-Pentadienyl)cyclopentadienyl)potassium
(E,E/E,Z-8a). KHMDS (2.0 g, 10.1 mmol) was dissolved in
diethyl ether (80 mL). A solution of 6-(trans-1-butenyl)fulvene
(7a; 1.33 g, 10.1 mmol) in diethyl ether (10 mL) was added slowly
at 0 °C, and the reaction mixture was stirred for another 2 h at
room temperature. The solvent was removed, and the remaining
solid was suspended in pentane (50 mL). The yellow product was
filtered, washed several times with pentane, and dried under
vacuum. This way a mixture of E,E- and E,Z-8a (1.64 g, 9.6 mmol,
95%) with a ratio of 55:45 was obtained. E,E-8a: 1H NMR (600
3
MHz, d8-THF, 298 K) δ 6.28 (d, JH,H = 14.9 Hz, 1H, 6-H),
6.04 (ddm, 3JH,H = 14.2 Hz, 3JH,H = 10.4 Hz, 1H, 8-H), 5.98 (dd,
3JH,H = 14.9 Hz, 3JH,H = 10.4 Hz, 1H, 7-H), 5.72 (m, 2H, 2-H,
5-H), 5.58 (m, 2H, 3-H, 4-H), 5.19 (dq, 3JH,H = 14.2 Hz, 3JH,H
=
6.8 Hz, 1H, 9-H), 1.70 (dd, 3JH,H = 6.8Hz, 5JH,H = 1.2 Hz, 3H, 10-
H) ppm; 13C{1H} NMR (151 MHz, d8-THF, 298 K) δ 136.1 (C8),
132.4 (C6), 120.2 (C1), 116.9 (C9), 115.5 (C7), 107.8 (C3, C4), 105.8
(C2, C5), 18.4 (C10) ppm. E,Z-8a: 1H NMR (600 MHz, d8-THF,
298 K) δ 6.36 (d, 3JH,H = 15.0 Hz, 1H, 6-H), 6.25 (dd, 3JH,H = 15.0
Hz, 3JH,H = 10.9 Hz, 1H, 7-H), 5.98 (m, 1H, 8-H), 5.78 (m, 2H,
3
2-H, 5-H), 5.61 (m, 2H, 3-H, 4-H), 4.86 (dq, JH,H = 10.5 Hz,
3JH,H = 7.0 Hz, 1H, 9-H), 1.72 (dd, 3JH,H = 7.0 Hz, 5JH,H = 1.5
Hz, 3H, 10-H) ppm; 13C{1H} NMR (151 MHz, d8-THF, 298 K) δ
134.4 (C6), 134.0 (C8), 120.4 (C1), 114.0 (C9), 110.7 (C7), 108.2
(C3, C4), 106.3 (C2, C5), 13.4 (C10) ppm.
Preparation of ((1,3-Hexadienyl)cyclopentadienyl)potassium
(E,E/E,Z-8b). KHMDS (1.39 g, 7.0 mmol) was dissolved in
diethyl ether (50 mL). A solution of 6-(trans-1-pentenyl)fulvene
(7b; 1.39 g, 7.0 mmol) in diethyl ether (10 mL) was added slowly
at 0 °C, and the reaction mixture was stirred for another 2 h at
room temperature. The solvent was removed, and the remaining
solid was suspended in pentane (40 mL). The yellow product was
filtered, washed several times with pentane, and dried under
vacuum. In this way a mixture of E,E- and E,Z-8b (1.1 g, 6.0 mmol,
86%) with a ratio of 71:29 was obtained. E,E-8b: 1H NMR (600
MHz, d8-THF, 298 K) δ 6.29 (d, 3JH,H = 14.7 Hz, 1H, 6-H), 6.03
1
(1.62 g, 14.5 mmol, 90%) in a ratio of about 86:14. E-5a: H
NMR (600 MHz, d8-THF, 298 K) δ 6.25 (dq, 3JH,H = 15.4 Hz,
4JH,H = 1.7 Hz, 1H, 6-H), 5.75 (m, 2H, 2-H, 5-H), 5.60 (m, 2H,
3-H, 4-H), 5.41 (dq, 3JH,H = 15.4 Hz, 3JH,H = 6.5 Hz, 1H, 7-H),
1.70 (dd, 3JH,H = 6.5 Hz, 4JH,H = 1.7 Hz, 3H, 8-H) ppm; 13C{1H}
NMR (151 MHz, d8-THF, 298 K) δ 131.5 (C6), 119.3 (C1), 110.3
1
(C7), 104.2 (C3, C4), 102.6 (C2, C5), 18.6 (C8) ppm. Z-5a: H
NMR (600 MHz, d8-THF, 298 K) δ 6.28 (dq, 3JH,H = 11.2 Hz,
4JH,H = 1.6 Hz, 1H, 6-H), 5.84, 5.69 (each m, each 2H, C5H4), 4.84
(dq, 3JH,H = 11.2 Hz, 3JH,H = 6.9 Hz, 1H, 7-H), 1.84 (dd, 3JH,H
=
3
3
(ddm, JH,H = 14.4 Hz, JH,H = 10.6 Hz, 1H, 8-H), 5.97 (dd,
3JH,H = 14.7 Hz, 3JH,H = 10.6 Hz, 1H, 7-H), 5.72 (m, 2H, 2-H,
5-H), 5.58 (m, 2H, 3-H, 4-H), 5.24 (dt, 3JH,H = 14.4 Hz, 3JH,H =6.7
6.9 Hz, 4JH,H = 1.6 Hz, 3H, 8-H) ppm. 13C{1H} NMR (151 MHz,
d8-THF, 298 K) δ 130.3 (C6), 110.5 (C7), 106.3, 104.6 (C5H4), 15.5
(C8), n.o. (C1) ppm.
3
Hz, 1H, 9-H), 2.06 (m, 2H, 10-H), 0.98 (t, JH,H = 7.5 Hz, 3H,
11-H) ppm; 13C{1H} NMR (151 MHz, d8-THF, 298 K) δ 134.0
(C8), 132.7 (C6), 124.8 (C9), 120.2 (C1), 115.5 (C7), 107.9 (C3, C4),
105.8 (C2, C5), 26.8 (C10), 15.1 (C11) ppm. E,Z-8b: 1H NMR (600
MHz, d8-THF, 298 K) δ 6.36 (d, 3JH,H = 14.9 Hz, 1H, 6-H), 6.23
Preparation of (((E)-1-Butenyl)cyclopentadienyl)lithium (E/Z-5b).
LDA (1.16 g, 10.8 mmol) was dissolved in tetrahydrofuran
(100 mL) and cooled to -78 °C. A solution of 6-propylfulvene
(3b; 1.16 g, 9.8 mmol) in tetrahydrofuran (10 mL) was added, and
the reaction mixture was warmed to room temperature within 2 h.
The solvent was removed and the remaining solid was suspended
in pentane (40 mL). The white product (0.91 g, 7.2 mmol, 74%)
was filtered, washed with pentane, and dried under vacuum.
The product was formed as nearly pure ((E)-(1-butenyl)cyclo-
pentadienyl)lithium with only traces of the Z isomer (E:Z = 95:5).
Z-5b: 1H NMR (600 MHz, d8-THF, 298 K) δ 6.22 (d,
3JH,H = 11.2 Hz, 1H, 6-H), 5.82 (m, 2H, 2-H, 5-H), 5.68 (m,
2H, 3-H, 4-H), 4.72 (dt, 3JH,H = 11.2 Hz, 3JH,H = 6.6 Hz, 1H,
7-H), 2.37 (dq, 3JH,H = 7.5 Hz, 3JH,H = 6.6 Hz, 2H, 8-H), 1.03 (t,
3JH,H = 7.5 Hz, 3H, 9-H) ppm; 13C{1H} NMR (151 MHz, d8-THF,
298 K) δ 128.6 (C6), n.o. (C1), 119.5 (C7), 106.3, 104.6 (C5H4), 23.4
(C8), 15.2 (C9) ppm. E-5b: 1H NMR (600 MHz, d8-THF, 298 K) δ
6.24 (d, 3JH,H = 15.4 Hz, 1H, 6-H), 5.77 (m, 2H, 2-H, 5-H), 5.61 (m,
2H, 3-H, 4-H), 5.47 (dt, 3JH,H = 15.4Hz, 3JH,H = 6.7 Hz, 1H, 7-H),
(dd, 3JH,H = 14.9 Hz, 3JH,H = 10.9 Hz, 1H, 7-H), 5.93 (tm, 3JH,H
=
10.9 Hz, 1H, 8-H), 5.76 (m, 2H, 2-H, 5-H), 5.61 (m, 2H, 3-H, 4-H),
4.82 (dt, 3JH,H = 10.9 Hz, 3JH,H = 7.3 Hz, 1H, 9-H), 2.19 (m, 2H,
10-H), 0.99 (t, 3JH,H = 7.5 Hz, 3H, 11-H) ppm; 13C{1H} NMR (151
MHz, d8-THF, 298 K) δ 134.6 (C6), 132.5 (C8), 122.5 (C9), 120.4
(C1), 110.8 (C7), 108.2 (C3, C4), 106.3 (C2, C5), 21.8 (C10), 15.2
(C11) ppm.
Metallocene Complexes. Procedure. Throughout the proce-
dure the compounds have to be kept in the dark to avoid a
photochemical reaction. The alkali-metal salt of the ligand and
MCl4(THF)2 (M = Zr, Hf) were put together in a Schlenk flask
in a 2:1 ratio and cooled to -78 °C. Precooled THF was added
slowly, and the stirred mixture was warmed to room temperature
overnight. The THF was removed in vacuo, and the same amount
of dichloromethane or toluene was added. The resulting suspension
was filtered through Celite to remove the alkali-metal chloride.
The solid was washed with several portions of dichloro-
methane or toluene until the portion remained colorless. The
filtrate was evaporated to dryness, and the resulting crude product
was suspended in pentane, filtered, and dried under vacuum.
Preparation of Bis[(1-propenyl)cyclopentadienyl]zirconium
Dichloride (E,E-/E,Z-/Z,Z-6a). From the reaction of the isomeric
mixture of 5a (1.0 g, 8.9 mmol) and bis(tetrahydrofuran)zirconium
tetrachloride (1.7 g, 4.5 mmol) in THF (70 mL) and workup using
2.07 (dq, 3JH,H =7.5Hz, 3JH,H = 6.7 Hz, 2H, 8-H), 0.99 (t, 3JH,H
=
7.5 Hz, 3H, 9-H) ppm; 13C{1H} NMR (151 MHz, d8-THF, 298 K) δ
(19) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307–326.
(20) Blessing, R. H. Acta Crystallogr. 1995, A51, 33–37. Blessing,
R. H. J. Appl. Crystallogr. 1997, 30, 421–426.
(21) Otwinowski, Z.; Borek, D.; Majewski, W.; Minor, W. Acta
Crystallogr. 2003, A59, 228–234.
(22) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467–473.
(23) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.

Article
Organometallics, Vol. 29, No. 14, 2010 3219
toluene a light yellow solid (890 mg, 2.4 mmol, 53%) was isolated.
The ratio of E,E- to E,Z- to Z,Z-complex was 18:7:1. Crystals of
E,E-6a suitable for X-ray diffraction were obtained from a toluene
solution of the isomeric mixture upon cooling. Anal. Calcd for
C16H18Cl2Zr (372.4 g/mol): C, 51.60; H, 4.87. Found: C, 51.46; H,
4.58. Characteristic data are as follows. E,E-6a: 1H NMR
(500 MHz, CD2Cl2, 298 K) δ 6.37, 6.29 (each m, C5H4), 6.10 (dq,
3JH,H = 15.8 Hz, 3JH,H = 6.6 Hz, 7-H), 1.89 (dd, 3JH,H = 6.6 Hz,
5JH,H = 1.7 Hz, 8-H);13C{1H} NMR (126 MHz, CD2Cl2, 298 K) δ
129.2 (C7), 128.9 (C1), 124.11 (C6), 115.0, 114.87 (C5H4),18.6(C8).
E,Z-6a:1H NMR (500 MHz, CD2Cl2, 298K) δ6.44/6.34, 6.37/6.30
(each m, C5H4), 6.11 (dq, 3JH,H = 15.8 Hz, 3JH,H = 6.6 Hz), 5.84
129.8 (C8), 132.01, 126.8 (C7), 131.0, 127.8 (C9), 122.8, 124.83 (C6),
18.306, 13.58 (C10) ppm.
Preparation of Bis[(1,3-pentadienyl)cyclopentadienyl]hafnium
Dichloride (E,E;E,E-/E,E;E,Z-/E,Z;E,Z-10a). From the reac-
tion of the isomeric mixture of 8a (500 mg, 2.9 mmol) and bis-
(tetrahydrofuran)hafnium tetrachloride (680 mg, 1.45 mmol) in
THF (40 mL) and workup using dichloromethane a white solid
(460 mg, 0.90 mmol, 62%) was isolated. The ratio of E,E;E,E-10a
toE,E;E,Z-10a toE,Z;E,Z-10a was 4:4:1. Anal. Calcd for C20H22-
Cl2Hf (511.8 g/mol): C, 46.94, H, 4.33. Found: C, 46.16; H, 4.33.
1
Characteristic data are as follows. E,E/E,E-10a: H NMR (600
3
3
MHz, d8-toluene, 298 K) δ 6.31 (dd, JH,H = 15.7 Hz, JH,H
=
10.5 Hz, 2H, 7-H), 6.05 (d, 3JH,H = 15.7 Hz, 2H, 6-H), 5.95 (ddm,
3JH,H = 15.0 Hz, 10.5 Hz, 2H, 8-H), 5.89, 5.73 (each m, C5H4), 5.54
(dqm, 3JH,H =15.0Hz, 3JH,H = 6.8 Hz, 9-H), 1.58 (dm, 3JH,H =6.8
Hz, 10-H) ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K) δ
132.1 (C8), 131.8 (C7), 130.7 (C9), 122.9 (C6), 113.58, 113.32
(C5H4),18.283 (C10) ppm. E,E/E,Z-10a: 1H NMR (600 MHz,
d8-toluene, 298 K) δ 6.72 (dd, 3JH,H = 15.4 Hz, 3JH,H = 11.3 Hz),
(dq, 3JH,H = 11.4 Hz, 3JH,H = 7.2 Hz) (7-H), 1.927 (dd, 3JH,H
=
7.2 Hz, 5JH,H = 1.8 Hz), 1.89 (dd, 3JH,H = 6.6 Hz, 5JH,H = 1.7 Hz)
(8-H); 13C{1H} NMR (126 MHz, CD2Cl2, 298 K) δ 129.4, 128.6
(C7), 128.7, 127.7 (C1), 124.06, 123.41 (C6), 117.7, 115.0, 114.85,
114.8 (C5H4), 18.6, 15.3 (C8). Z,Z-6a: 1H NMR (500 MHz,
CD2Cl2, 298 K) δ 6.46, n.o. (m, C5H4), 5.85 (dq, 3JH,H = 11.4 Hz,
3JH,H = 7.2 Hz, 7-H), 1.932 (dd, 3JH,H = 7.2 Hz, 5JH,H = 1.8 Hz,
8-H); 13C{1H} NMR (126 MHz, CD2Cl2, 298 K) δ 123.37 (C6).
X-ray Crystal Structure Analysis of E,E-6a: Mr = 372.42 g/mol,
6.31 (dd, 3JH,H = 15.5 Hz, 3JH,H = 10.5 Hz) (7-H), 6.14 (d, 3JH,H
=
15.4 Hz), 6.04 (d, 3JH,H = 15.5 Hz) (6-H), 5.91, 5.88, 5.720, 5.715
(each m, C5H4), 5.54 (dqm, 3JH,H = 15.0 Hz, 3JH,H = 6.8 Hz), 5.38
˚
yellow crystal 0.30 ꢀ 0.20 ꢀ 0.10 mm, a = 14.2011(5) A, b =
(dqm, 3JH,H = 10.6 Hz, 3JH,H = 7.0 Hz) (9-H), 1.63 (dm, 3JH,H
=
3
˚
˚
˚
6.6487(2) A, c = 16.7868(6) A, β = 97.411(2)°, V = 1571.75(9) A ,
Fcalcd = 1.574 g cm-3, μ = 1.023 mm-1, empirical absorption
correction (0.749 e T e 0.896), Z = 4, monoclinic, space group
7.0 Hz), 1.57 (dm, 3JH,H = 6.8 Hz, 10-H) ppm; 13C{1H} NMR (151
MHz, d8-toluene, 298 K) δ 132.0, 129.73 (C8), 131.9, 126.7 (C7),
130.7, 127.6 (C9), 122.8, 124.84 (C6), 113.88, 113.57, 113.32, 113.30
(C5H4), 18.275, 13.5 (C10) ppm. E,Z/E,Z-10a: 1H NMR (600 MHz,
d8-toluene, 298 K) δ 6.71 (dd, 3JH,H = 15.6 Hz, 3JH,H = 11.3 Hz,
7-H), 6.13 (d, 3JH,H = 15.4 Hz, 6-H), 5.38 (m, 9-H) ppm; 13C{1H}
NMR (151 MHz, d8-toluene, 298 K) δ129.67 (C8), 126.8 (C7), 127.7
(C9), 124.80 (C6), 113.87, 113.34 (C5H4), 13.6 (C10) ppm.
˚
C2/c (No. 15), λ = 0.710 73 A, T = 223(2) K, ω and j scans,
-1
˚
12 961 reflections collected ((h, (k, (l), (sin θ)/λ = 0.67 A
1953 independent (Rint = 0.023) and 1852 observed reflections
,
(I g 2σ(I)), 117 refined parameters, R1 = 0.020, wR2 = 0.056,
-3
˚
maximum (minimum) residual electron density 0.34 (-0.22) e A
,
hydrogen atoms calculated and refined as riding atoms; group
C6-C7-C8 refined with split positions.
Preparation of Bis[(1,3-hexadienyl)cyclopentadienyl]zirconium
Dichloride (E,E;E,E-/E,E;E,Z-/E,Z;E,Z-9b). From the reaction
of the isomeric mixture of 8b (480 mg, 2.6 mmol) and bis(tetra-
hydrofuran)zirconium tetrachloride (491 mg, 1.3 mmol) in THF
(50 mL) and workup using toluene a yellow solid (412 mg,
0.91 mmol, 70%) was isolated. The ratio of E,E;E,E-9b to E,E;
E,Z-9b to E,Z;E,Z-9b was 6:4:1. Anal. Calcd for C22H26Cl2Zr
(452.6 g/mol): C, 58.39; H, 5.79. Found: C, 57.96; H, 5.40.
Preparation of Bis[(E-1-butenyl)cyclopentadienyl]zirconium
Dichloride (E,E-6b). From the reaction of E-5b (440 mg, 3.49 mmol)
and bis(tetrahydrofuran)zirconium tetrachloride (658 mg,
1.75 mmol) in THF (40 mL) and workup using toluene a yellow
solid (380 mg,0.95 mmol, 55%) was isolated. Crystals suitable for
X-ray diffraction were obtained from a toluene solution upon
cooling. Anal. Calcd for C18H22Cl2Zr (400.5 g/mol): C, 53.98; H,
1
Characteristic data are as follows. E,E/E,E-9b: H NMR (600
MHz, CD2Cl2, 298 K) δ 6.58 (dd, 3JH,H = 15.6 Hz, 3JH,H = 10.5
Hz, 7-H), 6.42, 6.32 (each m, C5H4), 6.28 (d, JH,H = 15.6 Hz,
1
5.54. Found: C, 53.82; H, 5.60. H NMR (600 MHz, CD2Cl2,
298 K): δ 6.36 (m, 4H, 2-H, 5-H), 6.29 (m, 4H, 3-H, 4-H), 6.22 (dt,
3
3JH,H = 15.8 Hz, 4JH,H = 1.4 Hz, 2H, 6-H), 6.14 (dt, 3JH,H = 15.8
6-H), 6.18 (ddm, 3JH,H = 15.2 Hz, 3JH,H = 10.5 Hz, 8-H), 5.93
(dtm, 3JH,H = 15.2 Hz, 3JH,H = 6.7 Hz, 9-H), 2.18 (m, 10-H), 1.05
Hz, 3JH,H = 6.3 Hz, 2H, 7-H), 2.24 (qdd, 3JH,H = 7.5 Hz, 3JH,H
=
6.3 Hz, 3JH,H = 1.4 Hz, 4H, 8-H), 1.08 (t, 3JH,H = 7.5 Hz, 6H, 9-H)
ppm. 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ 136.1 (C7),
128.8 (C1), 122.0 (C6), 115.2 (C3, C4), 114.8 (C2, C5), 26.3 (C8),
13.8 (C9) ppm.
3
(t, JH,H = 7.6 Hz, 11-H) ppm. 13C{1H} NMR (151 MHz,
CD2Cl2, 298 K) δ 139.29 (C9), 132.6 (C7), 129.3 (C8), 128.5
1
(C1), 122.6 (C6), 26.2 (C10), 13.5 (C11) ppm. E,E/E,Z-9b: H
NMR (600 MHz, CD2Cl2, 298 K) δ 6.88 (ddm, 3JH,H = 15.9 Hz,
3JH,H = 11.2 Hz), 6.58 (dd, 3JH,H = 15.5 Hz, 3JH,H = 10.5 Hz)
(7-H), 6.35 (d, 3JH,H = 15.9 Hz), 6.28 (d, 3JH,H = 15.5 Hz) (6-H),
Preparation of Bis[(1,3-pentadienyl)cyclopentadienyl]zirconium
Dichloride (E,E;E,E-/E,E;E,Z-/E,Z;E,Z-9a). From the reaction
of the isomeric mixture of 8a (520 mg, 3.05 mmol) and bis-
(tetrahydrofuran)zirconium tetrachloride (576 mg, 1.53 mmol)
in THF (40 mL) and workup using toluene a yellow solid (460 mg,
1.1 mmol, 71%) was isolated. The ratio of E,E;E,E-9a to E,E;E,
Z-9a to E,Z;E,Z-9a was 4:4:1. Anal. Calcd for C20H22Cl2Zr (424.5
g/mol): C, 56.59; H, 5.22. Found: C, 56.98; H, 5.07. Characteristic
data are as follows. E,E/E,E-9a: 1H NMR (600 MHz, d8-toluene,
298 K) δ 6.34 (dd, 3JH,H = 15.8 Hz, 3JH,H = 10.7 Hz, 7-H), 6.03 (d,
3JH,H = 15.8 Hz, 6-H), 5.98 (m, 2-H, 5-H), 5.93 (ddm, 3JH,H = 15.2
6.18 (ddm, 3JH,H = 15.2 Hz, 3JH,H = 10.5 Hz), 6.09 (tm, 3JH,H
=
10.9 Hz) (8-H), 5.93 (dtm, 3JH,H = 15.2 Hz, 3JH,H = 6.7 Hz), 5.59
(dtm, 3JH,H = 10.9 Hz, 3JH,H = 7.3 Hz) (9-H), 2.30, 2.18 (each m,
3
10-H), 1.044, 1.043 (each tm, each JH,H = 7.4 Hz, 11-H) ppm.
13C{1H} NMR (151 MHz, CD2Cl2, 298 K) δ 139.34, 136.59 (C9),
132.7, 127.48 (C7), 129.2, 127.81 (C8), 124.49, 122.5 (C6), 26.2, 21.7
(C10), 14.41, 13.5 (C11) ppm. E,Z/E,Z-9b: 1H NMR (600 MHz,
CD2Cl2, 298 K) δ 6.35 (d, 3JH,H = 15.8 Hz, 6-H), 6.88 (m, 7-H),
5.38 (m, 9-H) ppm. 13C{1H} NMR (151 MHz, CD2Cl2, 298 K) δ
136.6 (C9), 127.55 (C7), 127.77 (C8), 124.47 (C6), 21.7 (C10), 14.40
(C11) ppm.
Hz, 3JH,H = 10.7 Hz, 8-H), 5.81 (m, 3-H, 4-H), 5.55 (dqm, 3JH,H
=
15.2 Hz, 3JH,H = 6.9 Hz, 9-H), 1.56 (dm, 3JH,H = 6.9 Hz, 10-H)
ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K) δ 132.1 (C8),
131.9 (C7), 130.9 (C9), 122.9 (C6), 18.314 (C10) ppm. E,E/E,Z-9a:
1H NMR (600 MHz, d8-toluene, 298 K) δ 6.75 (dd, 3JH,H = 15.5
Hz, 3JH,H = 11.1 Hz), 6.34 (dd, 3JH,H = 15.7 Hz, 3JH,H = 10.5 Hz)
(7-H), 6.11 (d, 3JH,H = 15.5 Hz), 6.01 (d, 3JH,H = 15.7 Hz) (6-H),
6.00, 5.97, 5.804, 5.799 (each m, C5H4), 5.55 (dqm, 3JH,H = 15.1
Preparation of Bis[(1,3-hexadienyl)cyclopentadienyl]hafnium
Dichloride (E,E;E,E-/E,E;E,Z-/E,Z;E,Z-10b). From the reac-
tion of the isomeric mixture of 8b (170 mg, 0.92 mmol) and
bis(tetrahydrofuran)hafnium tetrachloride (214 mg, 0.46 mmol)
in THF (20 mL) and workup using toluene a white solid (180 mg,
0.33 mmol, 72%) was isolated. The ratio of E,E;E,E-10b to E,E;
E,Z-10b to E,Z;E,Z-10b was 8:5:1. Crystals of E,E;E,E-10b
suitable for X-ray diffraction were obtained from a toluene/
pentane solution of the isomeric mixture upon cooling. Anal.
Hz, 3JH,H = 6.8 Hz), 5.38 (dqm) (9-H, 3JH,H = 10.7 Hz, 3JH,H
=
6.8 Hz), 1.62 (dm, 3JH,H = 6.8 Hz), 1.55 (dm, 3JH,H = 6.8 Hz) (10-
H) ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K) δ 132.04,

3220 Organometallics, Vol. 29, No. 14, 2010
Greger et al.
3
Calcd for C22H26Cl2Hf (539.8 g/mol): C, 48.95; H, 4.85. Found:
C, 49.04; H, 4.80. Characteristic data are as follows. E,E/E,E-
4H, 10-H), 1.05 (t, JH,H = 7.6 Hz, 6H, 11-H) ppm; 13C{1H}
NMR (151 MHz, CD2Cl2, 298 K) δ 139.3 (C9), 132.6 (C7), 129.3
(C8), 128.5 (C1), 122.6 (C6), 115.17, 115.16 (C5H4), 26.2 (C10),
13.5 (C11) ppm.
10b: 1H NMR (600 MHz, d8-toluene, 298 K) δ 6.34 (dd, 3JH,H
=
15.7 Hz, 3JH,H = 10.5 Hz, 7-H), 6.09 (d, 3JH,H = 15.7 Hz, 6-H),
5.99 (m, 8-H), 5.91 (m, 2-H, 5-H), 5.74 (m, 3-H, 4-H), 5.62 (dt,
3JH,H = 15.2 Hz, 3JH,H = 6.6 Hz, 9-H), 1.95 (m, 10-H), 0.87 (t,
3JH,H = 7.4 Hz, 11-H) ppm; 13C{1H} NMR (151 MHz, d8-
toluene, 298 K) δ 137.8 (C9), 132.0 (C7), 129.74 (C8), 125.9 (C1),
123.1 (C6), 113.6 (C2, C5), 113.3 (C3, C4), 26.2 (C10), 13.60 (C11)
ppm. E,E/E,Z-10b: 1H NMR (600 MHz, d8-toluene, 298 K) δ 6.73
(ddm,3JH,H = 15.6 Hz, 3JH,H = 11.2 Hz), 6.34 (dd, 3JH,H = 15.7 Hz,
1
E,E;E,E-10b: H NMR (600 MHz, d8-toluene, 298 K) δ 6.34
(dd, 3JH,H = 15.7 Hz, 3JH,H = 10.5 Hz, 2H, 7-H), 6.08 (d, 3JH,H
=
15.7 Hz, 2H, 6-H), 5.99 (ddm, 3JH,H = 15.2 Hz, 3JH,H = 10.5 Hz,
2H, 8-H), 5.91 (m, 4H, 2-H, 5-H), 5.74 (m, 4H, 3-H, 4-H), 5.62 (dt,
3JH,H = 15.2 Hz, 3JH,H = 6.6 Hz, 2H, 9-H), 1.95 (psquint, 4H,
10-H), 0.87 (t, 3JH,H = 7.4 Hz, 6H, 11-H) ppm; 13C{1H} NMR
(151 MHz, d8-toluene, 298 K) δ 137.8 (C9), 132.0 (C7), 129.7 (C8),
125.9 (C1), 123.1 (C6), 113.6 (C2, C5), 113.3 (C3, C4), 26.2 (C10),
13.6 (C11) ppm.
3JH,H=10.5 Hz) (7-H), 6.14 (d, 3JH,H=15.6 Hz), 6.08 (d, 3JH,H
=
15.7 Hz) (6-H), 5.99, 5.98 (each m, 8-H), 5.92, 5.90, 5.72, 5.72
(each m, C5H4), 5.62 (dt, 3JH,H=15.2 Hz, 3JH,H = 6.6 Hz), 5.35
(dt, 3JH,H=10.6 Hz, 3JH,H=7.7 Hz) (9-H), 2.13, 1.95 (each m,
10-H) ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K) δ
137.9, 135.25 (C9), 132.1, 126.9 (C7), 129.69, 128.3 (C8), 124.9,
123.0 (C6), 114.0, 113.55, 113.29, 113.26 (C5H4), 26.2, 21.6
Photochemical Reactions in Solution. Preparation of [(3,4-
Dimethylcyclobutylene)bis(cyclopentadienyl)]zirconium Dichloride
(Me2-cis-/Me2-trans-11a). The isomeric mixture of 6a (420 mg,
1.13 mmol) was dissolved in dichloromethane (40 mL) and
irradiated for 2.5 h (Pyrex filter). Solvent was removed, and the
remaining solid was suspended in pentane (15 mL). Filtration and
drying of the obtained solid in vacuo gave a Me2-cis- to Me2-trans
mixture of 1.7:1 as a white powder (300 mg, 0.81 mmol, 72%). The
same isomeric mixture was obtained by irradiation of a small
sample of E,E-6a in d8-toluene. Crystals of the Me2-cis isomer
suitable for X-ray diffraction were obtained from a toluene solu-
tion of the isomeric mixture upon cooling. Anal. Calcd for
C16H18Cl2Zr (372.4 g/mol): C, 51.60; H, 4.87. Found: C, 51.47;
H, 4.95. Me2-cis-11a: 1H NMR (600 MHz, d8-toluene, 298 K) δ
6.50 (m, 2H, 3-H), 6.31 (m, 2H, 4-H), 5.79 (m, 2H, 5-H), 5.56 (m,
2H, 2-H), 2.79 (m, 2H, 6-H), 2.30 (m, 2H, 7-H), 0.71 (m, 6H, 8-H)
ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K) δ 138.4 (C1),
125.2 (C3), 120.9 (C4), 109.5 (C5), 109.3 (C2), 48.0 (C6), 34.9 (C7),
1
(C10), 14.44, 13.59 (C11) ppm. E,Z/E,Z-10b: H NMR (600
MHz, d8-toluene, 298 K) δ 6.72 (ddm, 3JH,H = 15.5 Hz, 3JH,H
=
11.1 Hz, 7-H), 6.13 (d, 3JH,H=15.5 Hz, 6-H) ppm; 13C{1H} NMR
(151 MHz, d8-toluene, 298 K) δ 135.32 (C9), 127.0 (C7), 128.2
(C8), 113.9, 113.29 (C5H4), 14.42 (C11) ppm.
X-ray Crystal Structure Analysis of E,E;E,E-10b: Mr =
539.82 g/mol, light yellow crystal, 0.20 ꢀ 0.10 ꢀ 0.02 mm, a =
˚
˚
˚
27.6120(7) A, b = 6.6102(2) A, c = 12.0125(3) A, β = 103.162(2)°,
V = 2134.93(10) A , Fcalcd = 1.679 g cm-3, μ = 5.138 mm-1, empi-
3
˚
rical absorption correction (0.426 e T e 0.904), Z = 4, monoclinic,
˚
space group Cc (No. 9), λ = 0.710 73 A, T = 223(2) K, ω and j
scans, 7802 reflections collected ((h, (k, (l), (sin θ)/λ = 0.66
A
-1, 3572 independent (Rint = 0.043) and 3477 observed
˚
1
14.8 (C8) ppm. Me2-trans-11a: H NMR (600 MHz, d8-toluene,
reflections (I g 2σ(I)), 245 refined parameters, R1 = 0.034,
wR2 = 0.083, maximum (minimum) residual electron density
298 K) δ 6.57 (m, 1H, 40-H), 6.44 (m, 1H, 3-H), 6.38 (m, 1H, 4-H),
6.21 (m, 1H, 30-H), 5.81 (m, 1H, 50-H), 5.69 (m, 1H, 20-H), 5.65 (m,
1H, 5-H), 5.58 (m, 1H, 2-H), 3.26 (m, 1H, 60-H), 2.64 (m, 1H, 6-H),
2.17 (m, 1H, 7-H), 1.63 (m, 1H, 70-H), 0.77 (d, 3JH,H = 6.5 Hz, 3H,
8-H), 0.68 (d, 3JH,H = 7.0 Hz, 3H, 80-H) ppm; 13C{1H} NMR (151
MHz, d8-toluene, 298 K) δ 137.8 (C1), 136.0 (C10), 125.9 (C40),
124.3 (C3), 122.7 (C4), 119.6 (C30), 115.6 (C20), 108.9 (C2), 108.7
(C5), 107.3 (C50), 48.4 (C6), 46.9 (C60), 40.5 (C7), 38.7 (C70), 19.0
(C8), 13.6 (C80) ppm.
1.25 (-0.97) e A-3, hydrogen atoms calculated and refined as
˚
riding atoms, terminal ethyl groups are disordered.
Solid-State Photolysis. General Procedure. A small sample of
the isomeric mixture of the complex was put in a small Schlenk
flask and suspended in pentane (3 mL). The pentane was removed
in vacuo so that a thin film of solid was formed on the glass wall of
the flask. The solid was irradiated for 2 h from two opposite sides
with UV light. This way the nearly pure all-E isomers could be
obtained with only traces of the other isomers.
X-ray Crystal Structure Analysis of Me2-cis-11a: Mr = 372.42
˚
E,E-6a: 1H NMR (600 MHz, CD2Cl2, 298 K) δ 6.36 (m, 4H,
2-H, 5-H), 6.29 (m, 4H, 3-H, 4-H), 6.25 (dq, 3JH,H = 15.8 Hz,
g/mol, colorless crystal, 0.30 ꢀ 0.15 ꢀ 0.05 mm, a= 8.2449(2) A,b=
3
˚
˚
˚
15.6556(4) A, c= 11.8931(3) A, β= 90.727(1)°,V= 1535.02(7) A ,
Fcalcd = 1.612 g cm-3, μ = 1.048 mm-1, empirical absorption
correction (0.744 e T e 0.950), Z = 4, monoclinic, space group
4JH,H = 1.6 Hz, 2H, 6-H), 6.10 (dq, 3JH,H = 15.8 Hz, 3JH,H
=
6.7 Hz, 2H, 7-H), 1.89 (dd, 3JH,H = 6.7 Hz, 4JH,H = 1.6 Hz, 6H,
8-H) ppm; 13C{1H} NMR (151 MHz, CD2Cl2, 298 K) δ 129.2
(C7), 128.8 (C1), 124.1 (C6), 115.0 (C3, C4), 114.9 (C2, C5), 18.6
(C8) ppm.
˚
P21/n (No. 14), λ = 0.710 73 A, T = 223(2) K, ω and j scans, 9188
reflections collected ((h, (k, (l), (sin θ)/λ = 0.66 A-1, 3626
˚
independent (Rint = 0.042) and 3350 observed reflections (I g
2σ(I)), 174 refined parameters, R1 = 0.044, wR2 = 0.103, maxi-
E,E;E,E-9a: 1H NMR (600 MHz, d8-toluene, 298 K) δ 6.34 (dd,
-3
3
3
3JH,H = 15.8 Hz, JH,H = 10.7 Hz, 2H, 7-H), 6.03 (d, JH,H
=
=
˚
mum (minimum) residual electron density 0.67 (-0.68) e A
hydrogen atoms calculated and refined as riding atoms.
,
15.8 Hz, 2H, 6-H), 5.98 (m, 4H, 2-H, 5-H), 5.93 (ddm, 3JH,H
Preparation of [(3,4-Diethylcyclobutylene)bis(cyclopentadienyl)]-
zirconium Dichloride (Et2-cis-/Et2-trans-11b). E,E-6b (150 mg,
0.37 mmol) was dissolved in dichloromethane (20 mL) and
irradiated for 1.5 h (Pyrex filter). The formed precipitate was
filtered off through Celite before the solvent was removed, and the
remaining solid was suspended in pentane (15 mL). Filtration and
drying of the obtained solid in vacuo gave an Et2-cis- to Et2-trans-
11b ratio of 1:1.1 as a white powder (120 mg, 0.31 mmol, 83%).
Crystals suitable for X-ray diffraction were obtained from a
toluene/pentane solution of the isomeric mixture upon cooling.
Anal. Calcd for C18H22Cl2Zr (400.5 g/mol): C, 53.98; H, 5.54.
Found: C, 53.87; H, 5.50. Et2-cis-11b: 1H NMR (600 MHz,
CD2Cl2, 298 K) δ 6.72 (m, 2H, 3-H), 6.56 (m, 2H, 4-H), 6.40
(m, 2H, 5-H), 6.25 (m, 2H, 2-H), 3.64 (m, 2H, 6-H), 2.75 (m, 2H,
7-H), 1.70 (m, 2H, 8-Ha), 1.46 (m, 2H, 8-Hb), 0.88 (t, 3JH,H = 7.4
Hz, 6H, 9-H) ppm; 13C{1H} NMR (151 MHz, CD2Cl2, 298 K) δ
140.5 (C1), 125.5 (C3), 121.4 (C4), 110.3 (C5), 110.1 (C2), 47.2
(C6), 42.7 (C7), 23.5 (C8), 12.2 (C9) ppm. Et2-trans-11b: 1H NMR
15.2 Hz, 10.7 Hz, 2H, 8-H), 5.81 (m, 4H, 3-H, 4-H), 5.55 (dqm,
3JH,H = 15.2 Hz, 3JH,H = 6.9 Hz, 2H, 9-H), 1.56 (dm, 3JH,H = 6.9
Hz, 6H, 10-H) ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K)
δ132.1 (C8), 131.9 (C7), 130.9 (C9), 127.5 (C1), 122.9 (C6), 114.79,
114.77 (C5H4), 18.3 (C10) ppm.
1
E,E;E,E-10a: H NMR (600 MHz, d8-toluene, 298 K) δ 6.31
(dd, 3JH,H = 15.7 Hz, 3JH,H = 10.5 Hz, 2H, 7-H), 6.05 (d, 3JH,H
=
15.7 Hz, 2H, 6-H), 5.95 (ddm, 3JH,H = 15.0 Hz, 10.5 Hz, 2H, 8-H),
5.89 (m, 4H, 2-H, 5-H), 5.73 (m, 4H, 3-H, 4-H), 5.54 (dqm,
3JH,H = 15.0Hz, 3JH,H = 6.8 Hz, 2H, 9-H), 1.58 (dm, 3JH,H = 6.8
Hz, 6H, 10-H) ppm; 13C{1H} NMR (151 MHz, d8-toluene, 298 K)
δ 132.1 (C8), 131.8 (C7), 130.7 (C9), 125.8 (C1), 122.9 (C6), 113.6
(C2, C5), 113.3 (C3, C4), 18.3 (C10) ppm.
E,E;E,E-9b: 1H NMR (600 MHz, CD2Cl2, 298 K) δ 6.58 (dd,
3JH,H = 15.6 Hz, 3JH,H = 10.5 Hz, 2H, 7-H), 6.42 (m, 4H, 2-H,
5-H), 6.32 (m, 4H, 3-H, 4-H), 6.28 (d, JH,H = 15.6 Hz, 2H,
3
6-H), 6.18 (ddm, 3JH,H = 15.2 Hz, 3JH,H = 10.5 Hz, 2H, 8-H),
5.93 (dtm, 3JH,H = 15.2 Hz, 3JH,H = 6.7 Hz, 2H, 9-H), 2.18 (m,

Article
Organometallics, Vol. 29, No. 14, 2010 3221
(600 MHz, CD2Cl2, 298 K) δ 6.82 (m, 1H, 40-H), 6.65 (m, 1H,
3-H), 6.62 (m, 1H, 50-H), 6.61 (m, 1H, 4-H), 6.44 (m, 1H, 30-H),
6.36 (m, 1H, 5-H), 6.23 (m, 1H, 20-H), 6.19 (m, 1H, 2-H), 4.11 (m,
1H, 60-H), 3.46 (m, 1H, 6-H), 2.86 (m, 1H, 7-H), 2.14 (m, 1H, 70-
H), 1.72 (m, 1H, 8-Ha), 1.65 (m, 1H, 80-Ha), 1.56 (m, 1H, 80-Hb),
X-ray Crystal Structure Analysis of Me2-trans-12a. Mr =
424.50 g/mol, light yellow crystal, 0.50 ꢀ 0.35 ꢀ 0.30 mm, a =
˚
˚
˚
12.6867(2) A, b = 12.2749(2) A, c = 13.3417(2) A, β = 117.529(1),
3
V = 1842.43(5) A , Fcalcd = 1.530 g cm-3, μ = 0.884 mm-1
,
empirical absorption correction (0.666 e T e 0.778), Z = 4, mono-
˚
3
˚
1.46 (m, 1H, 8-Hb), 0.92 (t, JH,H = 7.4 Hz, 3H, 9-H), 0.66 (t,
clinic, space group P21/c (No. 14), λ= 0.71073 A, T= 223(2) K, ω
3JH,H = 7.4 Hz, 3H, 90-H) ppm; 13C{1H} NMR (151 MHz,
CD2Cl2, 298 K) δ 140.0 (C1), 137.6 (C10), 126.3 (C40), 124.3
(C3), 122.9 (C4), 119.7 (C30), 116.2 (C20), 109.93 (C2), 109.86
(C5), 107.8 (C50), 47.1 (C6, C7), 46.0 (C60), 44.7 (C70), 29.2 (C8),
23.1 (C80), 12.1 (C9), 11.9 (C90) ppm.
and j scans, 16 537 reflections collected ((h, (k, (l), (sin θ)/λ =
0.67 A-1, 4502 independent (Rint = 0.041) and 3858 observed
˚
reflections (I g2σ(I)), 210 refined parameters, R1 = 0.030, wR2 =
0.078, maximum (minimum) residual electron density 0.57 (-0.59)
e A-3, hydrogen atoms calculated and refined as riding atoms.
˚
X-ray Crystal Structure Analysis of Et2-cis-/Et2-trans-11b: Mr =
˚
Preparation of [(5,6-Diethyl-cis,cis-3,7-cyclooctadienylene)-
bis(cyclopentadienyl)]zirconium Dichloride Et2-cis-/Et2-trans-
12b. The isomeric mixture of 9b (150 mg, 0.94 mmol) was
dissolved in dichloromethane (20 mL) and irradiated for 2 h
(Pyrex filter). The resulting precipitate was filtered off through
Celite before the solvent was removed, and the remaining solid
was suspended in pentane (10 mL). Filtration and drying of the
obtained solid in vacuo gave a Et2-cis- to Et2-trans-12b ratio of
1:5 as a yellow solid (131 mg, 0.29 mmol, 88%). The same
isomeric mixture was obtained by irradiation of a small sample
of E,E;E,E-9b in d8-toluene. Anal. Calcd for C22H26Cl2Zr (452.6 g/
mol): C, 58.39; H, 5.79. Found: C, 57.91; H, 5.68. Et2-cis-12b: 1H
NMR (600 MHz, d8-toluene, 298 K) δ 6.47 (m, 2H, 4-H), 6.32
(m, 2H, 3-H), 5.78 (m, 2H, 2-H), 5.36 (m, 2H, 5-H), 5.27 (dm,
3JH,H = 11.7 Hz, 2H, 7-H), 5.19 (dm, 3JH,H = 11.7 Hz, 2H, 8-H),
4.12 (m, 2H, 6-H), 2.35 (br, 2H, 9-H), 1.27 (m, 2H, 10-Ha), 1.13 (m,
400.48, colorless, 0.20 ꢀ 0.10 ꢀ 0.03 mm, a = 12.4775(4) A, b =
˚
˚
14.3156(5) A, c = 16.5925(6) A, R = 76.369(2)°, β = 86.137(2)°,
γ = 66.616(1)°, V = 2642.61(16) A , Fcalcd = 1.510 g cm-3, μ =
3
˚
0.919 mm-1, empirical absorption correction (0.838 e T e 0.973),
˚
Z = 6, triclinic, space group P1 (No. 2), λ = 0.710 73 A, T =
223(2) K, ω and j scans, 46 260 reflections collected ((h, (k, (l),
(sin θ)/λ=0.66 A-1, 13 002 independent (Rint=0.049) and 6743
˚
observed reflections (Ig2σ(I)), 574 refined parameters, R1=0.078,
wR2 = 0.247, maximum (minimum) residual electron density 1.25
(-0.84) e A-3, hydrogen atoms calculated and refined as riding
˚
atoms, quality of the crystals was very poor, the accuracy of the
refinement with thermal restraints for all atoms besides Zr is
limited.
Preparation of [(5,6-Dimethyl-cis,cis-3,7-cyclooctadienylene)-
bis(cyclopentadienyl)]zirconium Dichloride (Me2-cis-/Me2-trans-
12a). The isomeric mixture of 9a (400 mg, 0.94 mmol) was
dissolved in dichloromethane (40 mL) and irradiated for 2 h
(Pyrex filter). Solvent was removed, and the remaining solid was
suspended in pentane (10 mL). Filtration and drying of the
obtained solid in vacuo gave a Me2-cis- to Me2-trans-12a ratio of
1:3.3 as a yellow powder (348 mg, 0.82 mmol, 87%). The same
isomeric mixture was obtained by irradiation of a small sample
of E,E;E,E-9a in d8-toluene. Crystals of the Me2-trans isomer
suitable for X-ray diffraction were obtained from a toluene
solution of the isomeric mixture upon cooling. Anal. Calcd for
C20H22Cl2Zr (424.5 g/mol): C, 56.59; H, 5.22. Found: C, 56.90;
H, 5.11. Me2-cis-12a: 1H NMR (600 MHz, d8-toluene, 298 K) δ
6.46 (m, 2H, 4-H), 6.30 (m, 2H, 3-H), 5.73 (m, 2H, 2-H), 5.38
(m, 2H, 5-H), 5.21 (dm, 3JH,H = 11.6 Hz, 2H, 7-H), 5.10 (dm,
3JH,H = 11.6 Hz, 2H, 8-H), 4.01 (br, 2H, 6-H), 2.52 (m, 2H,
9-H), 0.80 (m, 6H, 10-H) ppm; 13C{1H} NMR (151 MHz,
d8-toluene, 298 K) δ 136.8 (C1), 135.8 (C8), 128.3 (C7), 124.8
(C4), 121.4 (C3), 110.5 (C2), 109.2 (C5), 46.2 (C6), 37.9 (C9),
17.2 (C10) ppm. Me2-trans-12a: 1H NMR (600 MHz, d8-
toluene, 298 K) δ 6.60 (m, 1H, 40-H), 6.45 (m, 1H, 3-H), 6.34
(m, 1H, 4-H), 6.15 (m, 1H, 30-H), 5.85 (m, 1H, 20-H), 5.60 (ddm,
3JH,H = 11.4 Hz, 3JH,H = 7.5 Hz, 1H, 80-H), 5.56 (m, 1H, 2-H),
5.49 (m, 1H, 50-H), 5.43 (m, 1H, 5-H), 5.36 (dd, 3JH,H = 11.4 Hz,
3JH,H = 9.3 Hz, 1H, 70-H), 4.97 (m, 2H, 7-H, 8-H), 4.28 (m, 1H,
60-H), 3.83 (d, 3JH,H = 8.0 Hz, 1H, 6-H), 2.26 (m, 1H, 9-H), 1.59
3
2H, 10-Hb), 0.84 (t, JH,H = 7.2 Hz, 6H, 11-H) ppm; 13C{1H}
NMR (151 MHz, d8-toluene, 298 K) δ 136.90 (C1), 134.5 (C8),
128.9 (C7), 124.8 (C4), 121.4 (C3), 110.6 (C2), 109.2 (C5), 46.4
1
(C6), 44.89 (C9), 24.4 (C10), 13.0 (C11) ppm. Et2-trans-12b: H
NMR (600 MHz, d8-toluene, 298 K) δ 6.58 (m, 1H, 40-H), 6.45 (m,
1H, 3-H), 6.34 (m, 1H, 4-H), 6.14 (m, 1H, 30-H), 5.87 (m, 1H, 20-H),
5.64 (dd, 3JH,H = 11.3 Hz, 3JH,H = 7.8 Hz, 1H, 80-H), 5.59 (m, 1H,
2-H), 5.47 (dd, 3JH,H = 11.3 Hz, 3JH,H = 9.5 Hz, 1H, 70-H), 5.41
(m, 2H, 5-H), 5.40 (m, 2H, 50-H), 5.12 (dm, 3JH,H = 11.2 Hz, 1H,
7-H), 4.98 (dd, 3JH,H = 11.2 Hz, 3JH,H = 9.1 Hz, 1H, 8-H), 4.40 (m,
1H, 60-H), 3.99 (dm, 3JH,H = 7.8 Hz, 1H, 6-H), 2.25 (m, 1H, 9-H),
1.64 (m, 1H, 90-H), 1.51 (m, 1H, 10-Ha), 1.41 (m, 1H, 100-Ha), 1.15
(m, 1H, 100-Hb), 0.85(t, 3JH,H = 7.2 Hz, 3H, 11-H), 0.80 (m, 1H, 10-
Hb), 0.76 (t, 3JH,H = 7.2 Hz, 3H, 110-H) ppm; 13C{1H} NMR (151
MHz, d8-toluene, 298 K) δ139.2 (C1), 136.9 (C80), 134.9 (C8), 134.3
(C10), 133.2 (C7), 127.6 (C40), 125.8 (C3), 125.4 (C70), 122.0 (C4),
117.2 (C30), 113.0 (C20), 111.7 (C5), 108.2 (C2), 106.6 (C50), 47.9
(C6), 47.2 (C90), 44.90 (C60), 44.7 (C9), 27.6 (C10), 25.8 (C100), 12.6
(C11), 11.5 (C110) ppm.
Acknowledgment. Financial support from the Deutsche
Forschungsgemeinschaft is gratefully acknowledged. We
thank the BASF for a gift of solvents.
(m, 1H, 90-H), 0.82(d, 3JH,H =6.2Hz, 3H, 10-H), 0.81(d, 3JH,H
=
Supporting Information Available: Text, figures, and tables
giving further experimental and spectroscopic details for all com-
pounds and CIF files giving crystallographic data for E,E-6a,E,E-6b,
E,E;E,E-10b, Me2-cis-11a, Et2-cis-11b/Et2-trans-11b, Me2-trans-
12a, and Me2-cis-13a. This material is available free of charge via
the Internet at http://pubs.acs.org.
6.9 Hz, 3-H, 100-H) ppm; 13C{1H} NMR (151 MHz, d8-toluene,
298 K) δ 139.1 (C1), 138.5 (C80), 135.7 (C8), 134.3 (C10), 131.5
(C7), 127.5 (C40), 125.8 (C3), 123.9 (C70), 121.9 (C4), 117.3 (C30),
112.9 (C20), 111.6 (C5), 108.1 (C2), 106.7 (C50), 47.8 (C6), 44.3
(C60), 42.8 (C90), 39.2 (C9), 20.2 (C10), 17.7 (C100) ppm.