Functional group chemistry at the zirconocene backbone: Addition reactions to pendant alkynyl substituents

Article abstract of DOI:10.1002/ejic.200700749

The nickel-catalyzed cross-coupling of 2-bromoindene with propynyl- or (phenylethynyl)magnesium bromide gives the corresponding 2-alkynyl-substituted indenyl ligands. Subsequent deprotonation and transmetallation with the bis-(tetrahydrofuran)zirconium te

Full text of DOI:10.1002/ejic.200700749

FULL PAPER
DOI: 10.1002/ejic.200700749
Functional Group Chemistry at the Zirconocene Backbone: Addition Reactions
to Pendant Alkynyl Substituents
Liyi Chen,[a] Gerald Kehr,[a] Roland Fröhlich,[a][‡] and and Gerhard Erker*[a]
Keywords: Zirconium / Cobalt / Boron / Hydroboration / Heterometallic complexes
The nickel-catalyzed cross-coupling of 2-bromoindene with
propynyl- or (phenylethynyl)magnesium bromide gives the
corresponding 2-alkynyl-substituted indenyl ligands. Sub-
sequent deprotonation and transmetallation with the bis-
(tetrahydrofuran)zirconium tetrachloride adduct yields
the corresponding bis(2-alkynylindenyl)dichloridozirconium
complexes 4a and 4b, which cleanly add a Co2(CO)6 unit to
their pairs of alkynyl substituents to give the dimetallic com-
plexes 5a and 5b. Complex 5b was characterized by an X-
ray crystal structure analysis. Complex 4a adds HB(C6F5)2 to
the alkynyl substituents to yield a mixture of α- and β-(boryl-
alkenyl)metallocenes. Activation of these complexes with
MAO gives active ethene polymerization catalysts, and the
4a,4b,6a/MAO systems are also active in propene polymeri-
zation.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
thesis and characterization of some key compounds and
their typical reactions with a carbonylmetal [Co2(CO)8] or
a hydroboration reagent [HB(C6F5)2].
Introduction
Group 4 metallocenes that bear functional substituents
at their cyclopentadienyl (Cp) or indenyl rings,[1] including
amino acid, peptide- or carbohydrate-derived substitu-
ents,[2–4] have become of considerable interest lately, and
such systems have contributed to the rapid growth of the
emerging field of bio-organometallic chemistry.[5] The at-
tachment of various types of alkenyl substituents has also
been of considerable interest since this has allowed for the
development of organic functional group chemistry at the
framework of the pre-assembled bent metallocene systems.
Prior to this development most Cp or indenyl substituents
had been attached to the π-ligand framework early on at
the ligand stage prior to the transmetallation step to the
sensitive oxophilic early transition metal atom. An increas-
ing number of examples are now known where pre-attached
groups allow functional-group interconversions at the bent
metallocene complex stage. This development includes ad-
dition reactions[6] but has also allowed a variety of impor-
tant and useful carbon–carbon coupling reactions to be
performed at the metallocene backbone such as the forma-
tion of novel ansa-metallocenes by intramolecular olefin
metathesis (RCM),[7,8] photochemical [2+2] cycloaddition
reactions,[9,10] and even by a variant of the Mannich reac-
tion.[11] We have now extended this work to the chemistry
of alkynyl-substituted zirconocenes and report here the syn-
Results and Discussion
Synthesis and Characterization of the Bis(2-alkynylindenyl)-
zirconium Complexes
The alkynyl substituents used for this study were at-
tached at the 2-positions of the indenyl ligands in the con-
ventional way, namely at the organic ligand stage prior to
the introduction of the group 4 transition metal atom, by
coupling 2-bromoindene (1) with propynylmagnesium bro-
mide in a reaction catalyzed by [NiCl2(dppe)]. The cross-
[a] Organisch-Chemisches Institut der Universität Münster,
Corrensstrasse 40, 48149 Münster, Germany
Fax: +49-251-83-36503
E-mail: erker@uni-muenster.de
[‡] X-ray crystal structure analyses
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Scheme 1.
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L. Chen, G. Kehr, R. Fröhlich, G. Erker
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coupling reaction went smoothly, and product 2a was iso- alkynyl CH3 singlet at δ = 1.86 ppm. The alkynyl 13C NMR
lated in 77% yield. The 2-phenylethynyl-substituted indenyl resonances of 3a appear at δ = 80.9 and 82.1 ppm, respec-
system 2b was synthesized analogously (41% yield). Subse- tively.
quent deprotonation was carried out by treatment with n-
Transmetallation of complexes 3a and 3b by treatment
butyllithium to give 3a or 3b, respectively. Both these com- with [ZrCl4(thf)2][12] cleanly gave the corresponding bis(2-
plexes were characterized spectroscopically. Typically, the alkynylindenyl)dichloridozirconium complexes 4a (67%
1
alkynyl-substituted indenyllithium system 3a exhibits a H yield) and 4b[13] (76% yield), respectively (see Scheme 1).
NMR singlet for the indenyl 1-H/3-H protons at δ = Both these complexes were characterized by X-ray crystal
6.45 ppm (2 H), an AAЈBBЈ pattern of signals (δ = 6.84 and structure analyses. Single crystals of complex 4a (R = CH3)
7.54 ppm) for the phenylene hydrogen atoms, and a sharp were obtained from toluene (Figure 1). The X-ray crystal
Figure 1. Two projections of the molecular structure of complex 4a (R = CH3) showing the typical bent metallocene conformation in the
crystal. Selected bond lengths [Å] and angles [°]: Zr1–Cl1 2.442(1), Zr1–Cl2 2.405(1), Zr1–C1A 2.468(2), Zr1–C2A 2.485(2), Zr1–C3A
2.534(2), Zr1–C4A 2.639(2), Zr1–C9A 2.570(2), Zr1–C1B 2.510(2), Zr1–C2B 2.545(2), Zr1–C3B 2.523(2), Zr1–C4B 2.631(2), Zr1–C9B
2.588(2), C1A–C2A 1.420(3), C2A–C3A 1.420(2), C3A–C4A 1.420(2), C4A–C9A 1.439(2), C9A–C1A 1.426(2), C2A–C10A 1.430(2),
C10A–C11A 1.188(3), C11A–C12A 1.466(3), C1B–C2B 1.411(3), C2B–C3B 1.432(2), C3B–C4B 1.428(2), C4B–C9B 1.424(3), C9B–C1B
1.434(3), C2B–C10B 1.440(2), C10B–C11B 1.185(2), C11B–C12B 1.469(3); Cl1–Zr–Cl2 95.45(2), C9A–C1A–C2A 108.2(2), C1A–C2A–
C3A 108.2(2), C1A–C2A–C10A 126.0(2), C10A–C2A–C3A 125.7(2), C2A–C3A–C4A 108.2(2), C3A–C4A–C9A 107.8(2), C4A–C9A–
C1A 107.4(2), C2A–C10A–C11A 178.6(2), C10A–C11A–C12A 178.6(2), C9B–C1B–C2B 107.5(2), C1B–C2B–C3B 108.8(2), C1B–C2B–
C10B 125.1(2), C10B–C2B–C3B 126.0(2), C2B–C3B–C4B 107.0(2), C3B–C4B–C9B 108.1(2), C4B–C9B–C1B 108.0(2), C2B–C10B–C11B
177.7(2), C10B–C11B–C12B 178.2(2).
Figure 2. Two projections of the molecular structure of complex 4b. Selected bond lengths [Å] and angles [°]: Zr1–Cl1 2.411(1), Zr1–Cl2
2.388(2), Zr1–C1A 2.525(2), Zr1–C2A 2.518(2), Zr1–C3A 2.465(2), Zr1–C4A 2.544(2), Zr1–C9A 2.595(3), Zr1–C1B 2.473(2), Zr1–C2B
2.485(2), Zr1–C3B 2.541(39, Zr1–C4B 2.632(2), Zr1–C9B 2.580(2), C1A–C2A 1.410(4), C2A–C3A 1.403(4), C3A–C4A 1.426(4), C4A–
C9A 1.422(4), C9A–C1A 1.415(3), C2A–C10A 1.424(4), C10A–C11A 1.195(4), C11A–C12A 1.432(4), C1B–C2B 1.420(4), C2B–C3B
1.409(4), C3B–C4B 1.421(4), C4B–C9B 1.436(4), C9B–C1B 1.403(4), C2B–C10B 1.428(3), C10B–C11B 1.187(3), C11B–C12B 1.431(4);
Cl1–Zr–Cl2 97.17(3), C9A–C1A–C2A 107.9(2), C1A–C2A–C3A 108.4(2), C1A–C2A–C10A 126.5(3), C10A–C2A–C3A 125.1(3), C2A–
C3A–C4A 108.1(2), C3A–C4A–C9A 107.2(2), C4A–C9A–C1A 108.0(2), C2A–C10A–C11A 179.5(3), C10A–C11A–C12A 179.2(3), C9B–
C1B–C2B 108.4(2), C1B–C2B–C3B 108.2(2), C1B–C2B–C10B 125.6(3), C10B–C2B–C3B 126.1(3), C2B–C3B–C4B 108.0(2), C3B–C4B–
C9B 107.5(2), C4B–C9B–C1B 107.8(2), C2B–C10B–C11B 179.5(3), C10B–C11B–C12B 179.3(3).
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Functional Group Chemistry at the Zirconocene Backbone
structure analysis shows that linear propynyl substituents Complexation of the Alkynyl Substituents at the Bent
are attached at the C2 positions of each of the indenyl li- Metallocene Stage
gands [C2A–C10A 1.430(2), C10A–C11A 1.188(3), C11A–
C12A 1.466(3) Å; C2A–C10A–C11A 178.6(2), C10A–
The zirconium complexes 4 were both treated with
C11A–C12A 178.6(2)°; C2B–C10B 1.440(2), C10B–C11B [Co2(CO)8]. As is often observed with purely organic acetyl-
1.185(2), C11B–C12B 1.469(3) Å; C2B–C10B–C11B enes, the “organometallic” alkynyl systems 4a and 4b both
177.7(2), C10B–C11B–C12B 178.2(2)°]. The indenyl–CϵC– react rapidly with the carbonylcobalt reagent to form the
CH3 units of complex 4a are differentiated by an asymmet- respective [(alkyne)Co2(CO)6] complexes.[15–17] The prod-
ric metallocene conformational arrangement[14] where one ucts were isolated by crystallization from the toluene solu-
of the propynyl groups at the bent metallocene wedge [Cl1– tion and obtained in 67% (5a) and 27% (5b) yield, respec-
Zr–Cl2 95.45(2)°; Zr–Cl1 2.442(1), Zr–Cl2 2.405(1) Å] is tively. Complex 5a features a single 13C NMR carbonyl res-
oriented toward the lateral sector, whereas the other is onance at δ = 199.9 ppm.[18] It shows three strong ν(CO)
˜
found in the same sector but oriented markedly further to- IR bands at 2089, 2048, and 2019 cm–1 (plus one or two
ward the narrow bent metallocene back side. Both the in- shoulders).[19] The 13C NMR signals of the coordinated
denyl rings are η5-coordinated to the zirconium atom. The CϵC triple bond appear at δ = 83.7 and 95.4 ppm. Com-
1
Zr–CH bond lengths lie in a narrow range [Zr–C1A plex 5a exhibits a single sharp H NMR CH3 signal at δ =
2.468(2), Zr–C2A 2.485(2), Zr–C3A 2.534(2) Å; Zr–C1B 2.85 ppm (6 H) and a resonance for the indenyl 1-H/3-H
2.510(2), Zr–C2B 2.545(2), Zr–C3B 2.523(2) Å], whereas protons at δ = 5.78 ppm (4 H).
the Zr–C indenyl bonds are slightly longer [Zr–C4A
2.639(2), Zr–C9A 2.570(2) Å; Zr–C4B 2.631(2), Zr–C9B NMR: δ = 5.93 (indenyl 1-H/3-H), 7.41/7.85 (indenyl 5/6-
Complex 5b shows similar spectroscopic features [1H
2.588(2) Å].
H/4/7-H) ppm; 13C NMR: δ = 199.6 (CO), 83.1/92.8 (coor-
Single crystals of complex 4b (R = Ph; Figure 2)[13] were dinated CϵC) ppm], and this complex was also charac-
obtained from dichloromethane/pentane (1:1) solution. The terized by X-ray diffraction. Single crystals were obtained
structure is similar to that of 4a, except that the slightly by diffusion of pentane into a solution of 5b in dichloro-
more bulky phenylethynyl substituents are both oriented methane.
towards the same lateral sector of the bent metallocene
The crystal structure shows isolated molecules of the tri-
wedge. The terminal phenyl substituents are oriented close nuclear metal complex 5b (Figure 3) with each of the acetyl-
to coplanar with their respective indenyl planes [deviations ene substituents coordinated to a Co2(CO)6 moiety. This
from coplanarity: 17.9° (A) and 15.4° (B)].
results in a marked elongation of the C10–C11 bond in
Figure 3. View of the molecular structure of complex 5b (R = Ph). Selected bond lengths [Å] and angles [°]: Zr1–Cl1 2.422(1), Zr1–Cl2
2.415(1), Zr1–C1A 2.504(3), Zr1–C2A 2.588(3), Zr1–C3A 2.522(3), Zr1–C8A 2.553(3), Zr1–C9A 2.586(3), Zr1–C1B 2.561(3), Zr1–C2B
2.586(3), Zr1–C3B 2.463(3), Zr1–C8B 2.599(3), Zr1–C9B 2.531(3), C1A–C2A 1.410(4), C2A–C3A 1.428(4), C3A–C9A 1.432(4), C9A–
C8A 1.434(4), C8A–C1A 1.435(4), C2A–C10A 1.453(4), C10A–C11A 1.342(4), C11A–C12A 1.472(4), C1B–C2B 1.414(4), C2B–C3B
1.421(4), C3B–C9B 1.441(4), C9B–C8B 1.430(4), C8B–C1B 1.426(4), C2B–C10B 1.462(4), C10B–C11B 1.346(4), C11B–C12B 1.465(4),
Co1–Co2 2.461(1), Co1–C10A 2.004(3), Co1–C11A 1.950(3), Co2–C10A 1.955(3), Co2–C11A 1.980(3), Co3–Co4 2.462(1), Co3–C10B
1.962(3), Co3–C11B 1.964(3), Co4–C10B 1.996(3), Co4–C11B 1.979(3); Cl1–Zr–Cl2 95.69(3), C8A–C1A–C2A 108.4(3), C1A–C2A–C3A
107.9(3), C1A–C2A–C10A 126.9(3), C10A–C2A–C3A 124.8(3), C2A–C3A–C9A 108.0(3), C3A–C9A–C8A 107.4(3), C9A–C8A–C1A
107.5(3), C2A–C10A–C11A 142.6(3), C10A–C11A–C12A 141.6(3), C8B–C1B–C2B 108.0(3), C1B–C2B–C3B 108.5(3), C1B–C2B–C10B
123.5(3), C10B–C2B–C3B 127.5(3), C2B–C3B–C9B 107.3(3), C3B–C9B–C8B 107.6(3), C9B–C8B–C1B 107.8(3), C2B–C10B–C11B
139.2(3), C10B–C11B–C12B 142.5(3), Co1–C10A–Co2 76.8(1), Co1–C11A–Co2 77.5(1), Co3–C10B–Co4 76.9(1), C03–C11B–Co4
77.3(1).
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FULL PAPER
both these units [C10A–C11A 1.342(4), C10B–C11B NMR singlet for the alkenyl CH3 (δ = 2.12 ppm) and =CH
1.346(4) Å] with respect to the starting material 4b (see (δ = 7.02 ppm) groups (see Figure 4) and the alkenyl 13C
above). The C10,C11,Co2 unit forms a distorted tetrahedral NMR resonances appear at δ = 146.8 (=C[B]) and 149.8
substructure [unit B: Co3–Co4 2.462(1), C10B–Co3 (=CH) ppm. Due to a rapid conformational equilibrium,
1.962(3), C10B–Co4 1.996(3), C11B–Co3 1.964(3), C11B– the indenyl 1-H/3-H protons appear as a singlet at δ = 6.31
Co4 1.979(3) Å]. Both ligands are again slightly different (4 H) ppm and the corresponding phenylene hydrogen
due to the specific conformational arrangement of the sys- atoms of the indenyl ligand core as an AAЈBBЈ pattern at
tem, and both the very bulky C2(Ph)Co2(CO)6 substituents δ = 7.65 and 7.30 (8 H) ppm.
are found oriented toward different lateral sectors of the
However, hydroboration of 4a with HB(C6F5)2 (Piers’
bent metallocene wedge. The overall geometry deviates borane) turned out to be remarkably nonregioselective. This
markedly from C2 symmetry, with one of the substituents became evident when we treated a sample of 4a with
turned somewhat toward the front and the other toward the [HB(C6F5)2] in CD2Cl2 under slightly different experimen-
narrow metallocene backside. The indenyl ligands are quite tal conditions and monitored the reaction directly by NMR
uniformly η5-coordinated to the zirconium atom [ring B: spectroscopy without workup. This procedure revealed the
Zr–C3B 2.463(3), Zr–C2B 2.586(3), Zr–C1B 2.561(3), Zr– formation of all three regioisomeric hydroboration products
C8B 2.599(3), Zr–C9B 2.531(3) Å]. The coordinated acetyl- 6a, 6b, and 6c in a 45:43:12 ratio. The symmetrical β,β-
ene groups in the pentanuclear complex are rotated only bis(hydroboration) product 6a, which we had isolated ear-
slightly out of the planes of their respective indenyl ligands lier (see above), was one of the main products with the un-
[dihedral angles: C1A–C2A–C10A–C11A 170.6(4), C3B– symmetrical α,β-bis(hydroboration) isomer 6b being formed
C2B–C10B–C11B –171.5(4)°].
in almost equal amounts. This isomer was readily identified
from the mixture by its typical 1H NMR features. Thus, the
3
signals for ligand I (α-B) occur at δ = 1.63 (d, J = 7.2 Hz,
Hydroboration of the Alkynyl Substituents
3
3 H), 5.71 (q, J = 7.2 Hz, 1 H, =CHCH3), 5.95 (s, 2 H,
Complex 4a was employed as a substrate for a hydrobor- indenyl 1-H/3-H), and 7.39/7.82 (phenylene 4-H to 7-H)
ation reaction.[20] Thus, treatment of 4a with the strongly ppm, whereas the 1H NMR resonances (β-B) of the
[21]
electrophilic hydroboration reagent HB(C6F5)2 in an ap- “mixed” isomer (ligand II) appear at δ = 2.09 (s, 3 H), 6.01
proximate 1:2 molar ratio resulted in a clean addition to (s, 2 H, indenyl 1-H/3-H), 7.01 (br. s, 1 H, CH=C[B]CH3),
the CϵC triple bonds of both alkynyl substituents. The bis- and 7.26/7.59 (4-H to 7-H) ppm, as shown in Figure 4.
(hydroboration) product 6a (see Scheme 2) was isolated in
The third (and minor) isomer was assigned the structure
27% yield from the reaction mixture. The characteristic of 6c. This is the sterically most encumbered of the three
NMR features of 6a allowed us to assign its structure as products, which determines some of its properties. The sym-
that of the symmetrical regioselective β-borylalkenyl cis hy- metrical product 6c was identified by observation of the
3
droboration product. It shows a slightly broadened 1H typical NMR signals for ligand I [δ = 1.57 (d, J = 7.2 Hz,
Scheme 2.
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Functional Group Chemistry at the Zirconocene Backbone
1
Figure 4. H NMR spectra of 6a (top) and the 6a/6b/6c mixture (600 MHz, CD2Cl2, 298 K).
1
Figure 5. Temperature-dependent H NMR spectra of the 6a/6b/6c mixture of isomers (C6D5CD3, 600 MHz).
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L. Chen, G. Kehr, R. Fröhlich, G. Erker
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3
6 H), 5.73 (q, J = 7.2 Hz, 2 H, =CHCH3), 7.44/7.82 (in- Table 1. Ethene polymerization with the homogeneous 4a, 4b, 5a,
5b, and 6a/MAO metallocene Ziegler–Natta catalyst systems.[a]
1
denyl 4-H to 7-H) ppm]. The indenyl 1-H/3-H H NMR
Cat. Zr cat. Yield PE Activity[b] M.p. [°C]
resonance appears at δ = 5.49 ppm as a broad singlet at
298 K (600 MHz). However, hindered rotation around the
indenyl C2 olefin Cα bond in this isomer (6c),[22] which is
probably due to the increased steric bulk of the α-boryl-
substituted alkenyl side-chain, means that decoalescence of
Polymer
[mg]
[g]
PE1
PE2
PE3
PE4
PE5
PE6
PE7
4a
4b
5a
5a
5b
5b
6a
11.7
14.8
26.0
26.0
29.1
29.1
29.0
30.7
38.2
2.95
1.79
0.47
0.39
14.2
1228
1528
118
71
19
16
125
127
124
126
126
126
124
1
the indenyl 1-H/3-H H NMR resonance of complex 6c is
observed upon lowering the temperature (see Figure 5).
This eventually leads to the observation of separate signals
for the indenyl 1-H (δ = 4.27 ppm) and 3-H (δ = 6.41 ppm)
protons (in C6D5CD3, 600 MHz). A Gibbs activation en-
ergy barrier of ∆G϶(293 K) = 12.5Ϯ0.9 kcalmol–1 was de-
termined for this rotational process at the coalescence tem-
perature. A close inspection of the NMR spectra shown in
Figure 5 also shows that the corresponding ligand I indenyl
568
[a] Reaction conditions: 200 mL of toluene, 20 mL of 1.6  MAO
solution in toluene, 2 bar of ethene, 30 min, 20 °C, 600 rpm of stir-
ring, 2.5ϫ10–5 mol of Zr catalyst (Al/Zr = 1280). [b] kgPE/
[(molZr)hbar(ethene)].
The 5/MAO catalysts turned out to be inactive in pro-
pene polymerization under our applied reaction conditions.
However, the 4a,4b/MAO systems were quite active homo-
geneous metallocene Ziegler–Natta catalysts for propene
polymerization. As can be seen from Table 2, both the mo-
nonuclear metallocene complexes 4a and 4b give very active
propene polymerization catalysts when activated with
MAO. A marked temperature dependence of the catalyst
activity is observed in both cases, with a maximum at
1
1-H/3-H H NMR resonance of the unsymmetrical isomer
6b also broadens with decreasing temperature, although the
limiting low-temperature NMR spectrum under static con-
ditions could not be reached in this case.
Olefin Polymerization Reactions
Ethene polymerization reactions were carried out with around 0 °C, which drops off upon either decreasing or in-
the mononuclear zirconium complexes 4a and 4b, the di- creasing the reaction temperature. The molecular weight of
metallic systems 5a and 5b, and the Zr/B system 6a. In each the polypropylene formed with the 4a/MAO catalyst system
case, the bent metallocene catalyst precursor was activated is high at –20 °C (Mw Ͼ 200000) but drops off rapidly to a
in toluene by treatment with a large excess (Al/Zr = 1280) mere 30000 at +40 °C. A similar trend is observed for the
of methylalumoxane (MAO).[23] As can be seen from polypropylene obtained from the 4b/MAO catalyst system,
Table 1, the metallocene catalysts derived from systems 4 which starts at an even higher molecular weight at –20 °C
are both very active, although the activity drops drastically (see Table 2). The boryl-functionalized 6a/MAO catalyst is
upon going to the dimetallic systems 5/MAO, which may also active in propene polymerization, albeit slightly less
be due to the enormous steric bulk of the alkynyl/Co2- than the former pair of metallocene catalyst systems.
(CO)6 substituents. It is nevertheless remarkable that the
The polypropylenes obtained are atactic, although in a
presence of the highly functionalized carbonylmetal units certain temperature range (approx. 0 to +20 °C) a measur-
does not interfere with olefin polymerization activity, except able positive deviation of the mmmm pentad content was
perhaps sterically. The system 6a/MAO is again quite active noted. This is potentially due to some stereoblock polymer
in ethene polymerization, and it seems that here the at- formation. Consequently, some of the polymer samples fea-
tached CH=CMeB(C6F5)2 groups primarily serve as inert ture elastomeric properties, although of a clearly inferior
substituents at the indenyl ligands.
quality to PP samples obtained from related 2-arylindene-
Table 2. Results of selected propene polymerization reactions employing 4/6a/MAO catalyst systems.[a]
Activity[c]
[b]
[b]
Polymer
Cat.
T [°C]
mmmm [%]
Mn
Mw
PDI
PP yield [g]
PP1
PP2
PP3
PP4
PP5
PP6
PP7
PP8
PP9
PP10
PP11
4a
4a
4a
4a
4a
4b
4b
4b
4b
6a
6a
–20[d]
–20[d],[e]
0
+20
+40
–20[d]
0
+20
+40
0
9.0
9.5
13.3
9.83
5.79
2.30
0.92
18.4
6.83
3.56
1.17
7.45
4.00
23.8
18.9
13.7
6.24
2.98
35.6
19.8
9.59
3.67
15.2
7.28
1.78
1.92
2.37
2.71
3.26
1.94
2.90
2.70
3.14
2.06
1.82
5.30
8.40
41.4
25.9
10.9
7.32
41.3
32.0
18.4
11.7
2.55
424
336
1656
1036
436
12.6
13.8
11.8
10.3
16.0
16.7
13.4
10.5
11.6
586
1652
1280
736
468
102
+20
[a] Reaction conditions: 200 mL of toluene, 2.5ϫ10–5 mol of Zr catalyst, 20 mL of 1.6  MAO solution in toluene (Al/Zr = 1280), 2 bar
of propene, 600 rpm of stirring, 30 min reaction time. [b] ϫ104 gmol–1. [c] kgPP/[(molZr)hbar(propene)]. [d] 25 mL of liquid propene
was used. [e] 60 min reaction time.
78
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 73–83

Functional Group Chemistry at the Zirconocene Backbone
Figure 6. Stress vs. strain curve of an elastomeric polypropylene sample obtained at –20 °C with the 4b/MAO catalyst system.
or -hetareneindene-derived catalyst systems.[22,24,25] A typi-
formed with a Foss-Heraeus CHN-O Rapid instrument. The IR
spectra were recorded with a Varian 3100 Excalibur FT-IR spec-
trometer. NMR spectra were recorded with a Bruker AC200 P, a
Varian 500 MHz INOVA or a Varian Unity Plus 600 NMR spec-
cal stress/strain behaviour of a polypropylene sample
(PP23) obtained with the 4b/MAO catalyst at –20 °C
(60 min reaction time; see the Supporting Information for
details) is shown in Figure 6.
trometer. Most NMR assignments were based on a series of NOE,
1
Tocsy, and 2D NMR experiments. Variable-temperature H NMR
experiments were conducted with a Varian Unity Plus 600 NMR
spectrometer. The 1H and 13C NMR chemical shifts were refer-
enced to solvent signals. Analysis of the elasticity of the polypropyl-
Conclusions
enes was carried out with a Zwicki 1120 from Zwick company. 2-
This study has shown that alkynyl-substituted bent
[27]
Bromoindene (1),[26] [ZrCl4(thf)2][12], and HB(C6F5)2
were pre-
metallocenes can readily be synthesized by a route em-
ploying the respective preassembled ligand systems. The
pendant alkynyl functionalities at the bent metallocene
framework have been shown to cleanly undergo some typi-
cal reactions which are tolerated at the rather sensitive bent
metallocene core. We have thus been able to add carbon-
ylcobalt groups to the pair of substituted alkynyl groups to
yield the heterodimetallic complexes 5 and have been able
to utilize the alkynyl groups as building blocks in chemose-
lective (but not regioselective) hydroboration reactions. In
all cases, the newly introduced functional groups tolerate
the special conditions employed in the generation of active
metallocene olefin polymerization catalysts. The results of
our study add to the increasing evidence that a functional
group chemistry can be developed at the bent metallocene
stage if the specific features of the sensitive group 4 bent
metallocene systems are adequately taken into account.
pared according to literature procedures. [NiCl2(dppe)], propyn-
ylmagnesium bromide thf solution (0.5 ), phenylacetylene, and
Co2(CO)8 were commercially available.
Preparation of 2-(Prop-1-ynyl)indene (2a): thf (20 mL) was added to
a mixture of 2-bromoindene (1; 3.90 g, 20 mmol) and [NiCl2(dppe)]
(200 mg, 0.22 mmol, approx. 10 mol-%) in a Schlenk tube. The red
suspension was stirred at 0 °C, and propynylmagnesium bromide
(0.5  solution in thf; 44 mL, 22 mmol) was added to the mixture
dropwise. The mixture turned yellow. The water/ice bath was re-
moved and the reaction mixture was refluxed for 3 h to afford a
deep red mixture. Water (20 mL) was added to quench the reaction,
and the product was extracted with diethyl ether (3ϫ40 mL). The
combined organic phases were washed successively with a saturated
NaHCO3 solution (2ϫ30 mL) and brine (2ϫ30 mL) and dried
with anhydrous MgSO4. The solvent was then removed in vacuo,
and the remaining yellow mixture was purified by column
chromatography with pentane to give 2.38 g of colorless product
1
(Rf = 0.14). Yield: 77%. M.p. 64 °C (DSC). H NMR (600 MHz,
CD2Cl2, 298 K): δ = 2.07 (s, 3 H, CH3), 3.48 (m, 2 H, 3-H), 6.95
(m, 1 H, 1-H), 7.20 [td, JH,H = 7.5, 1.2 Hz, 1 H, 5-H), 7.26 (tm,
JH,H = 7.5 Hz, 1 H, 6-H), 7.34 (dm, JH,H = 7.5 Hz, 1 H, 7-H), 7.40
(dm, JH,H = 7.5 Hz, 1 H, 4-H) ppm. 13C{1H} NMR (151 MHz,
CD2Cl2, 298 K): δ = 4.7 (CH3), 43.2 (C-3), 77.0 (ϵC–), 91.3 (ϵC–
Me), 121.3 (C-7), 123.8 (C-4), 125.7 (C-5), 126.9 (C-6), 128.8 (C-
2), 135.9 (C-1), 143.0 (C-3a), 144.6 (C-7a) ppm. MS (EI): m/z (%)
Experimental Section
General Considerations: All manipulations were carried out under
argon using Schlenk-type glassware or in a glove box, unless other-
wise noted. Solvents, including deuterated solvents used for NMR
spectroscopy, were dried and distilled prior to use according to
standard procedures. Melting points were determined with a TA
Instruments DSC 2010. Mass spectra were recorded with a Finni-
gan MAT 8200 mass spectrometer. Elemental analyses were per-
= 154.0 (100) [M+]. IR (KBr): ν = 3067 (m), 2952 (w), 2895 (w),
˜
2846 (w), 2760 (w), 2327 (w), 2219 (w), 1457 (s), 1386 (s), 1230 (m),
1201 (m), 847 (s), 744 (s), 714 (s), 599 (m) cm–1. C12H10 (154.2):
calcd. C 93.46, H 6.54; found C 93.07, H 6.46.
Eur. J. Inorg. Chem. 2008, 73–83
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
79

L. Chen, G. Kehr, R. Fröhlich, G. Erker
FULL PAPER
Preparation of 2-(Phenylethynyl)indene (2b): 2-Bromoindene (1;
3.90 g, 20 mmol) and [NiCl2(dppe)] (200 mg, 0.22 mmol, 10 mol-
%) were mixed, and thf (20 mL) was added. The red suspension A
was stirred at 0 °C. Magnesium turnings (608 mg, 25 mmol) and
thf (10 mL) were added to a three-necked, round-bottomed flask,
and bromoethane (2.72 g, 25 mmol) in thf (20 mL) was added drop-
wise. The reaction was initiated by brief heating with a heat gun.
The suspension was kept refluxing by the controlled addition of
the C2H5Br solution. When the addition was finished, the mixture
was stirred for another 1 h. The Grignard reagent solution was co-
oled to –78 °C, and phenylacetylene (2.55 g, 25 mmol) was added
dropwise. The mixture was stirred at –78 °C for 1 h and then slowly
warmed to room temperature. The resulting (phenylethynyl)magne-
sium bromide Grignard reagent B was added to suspension A at
0 °C. The mixture turned brown. The water/ice bath was then re-
moved, and the reaction mixture refluxed for 3 h to give a brown
mixture. Water (20 mL) was added to quench the reaction, and the
product was extracted with Et2O (3ϫ40 mL). The combined or-
ganic phases were washed with a saturated NaHCO3 solution
(2ϫ30 mL), then with brine (2ϫ30 mL) and dried with anhydrous
MgSO4. The solvent was removed in vacuo, and the remaining yel-
low mixture was purified by column chromatography with pentane
to give 1.79 g of the colorless product (Rf = 0.09). Yield: 41%. M.p.
6), 120.4 (C-4, C-7), 126.4 (p-Ph), 126.8 (i-Ph), 128.5 (m-Ph), 128.7
(C-3a, C-7a), 131.1 (o-Ph) ppm.
Preparation of Bis[2-(prop-1-ynyl)indenyl]zirconium Dichloride (4a):
2-(Prop-1-ynyl)indenyllithium (3a; 0.96 g, 6.0 mmol) and ZrCl4·
2thf (1.13 g, 3.0 mmol) were added to a Schlenk tube, and the mix-
ture was cooled to –78 °C. Cold toluene (30 mL, –78 °C) was added
to the mixture, then the suspension was stirred at –78 °C for 2 h
and slowly warmed to room temperature and stirred overnight. The
resulting yellow suspension was filtered to give a yellow solution.
CH2Cl2 (50 mL) was used to extract additional product from the
remaining solid. The yellow solution was concentrated in vacuo.
Crystallization at about –30 °C gave 0.95 g of the yellow product.
Yield: 67%. Crystals suitable for X-ray crystallography were ob-
tained from toluene at about –30 °C. M.p. 223 °C (DSC). 1H NMR
(600 MHz, CD2Cl2, 298 K): δ = 2.21 (s, 3 H, CH3), 6.55 (s, 2 H, 1-
H, 3-H), 7.20 (m, 2 H, 5-H, 6-H), 7.43 (m, 2 H, 4-H, 7-H) ppm.
13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ = 4.8 (CH3), 74.1
(ϵC–), 93.4 (ϵC–CH3), 109.6 (C-1, C-3), 115.3 (C-2), 124.9 (C-4,
C-7), 126.8 (C-3a, C-7a), 127.4 (C-5, C-6) ppm. IR (KBr): ν = 3110
˜
(w), 2912 (w), 2843 (w), 2240 (m, CϵC), 1614 (w), 1436 (m), 1209
(m), 838 (s), 749 (s), 642 (m), 588 (w) cm–1. C24H18Cl2Zr (468.53):
calcd. C 61.52, H 3.87; found C 61.42, H 3.63.
1
X-ray Crystal Structure Analysis of Complex 4a: Formula
C24H18Cl2Zr, M = 468.50, yellow crystal 0.30ϫ0.20ϫ0.15 mm, a
= 27.904(1), b = 7.676(1), c = 19.846(1) Å, β = 109.61(1)°, V =
4004.3(6) Å3, ρ = 1.554 gcm–3, µ = 8.22 cm–1, empirical absorption
correction (0.791 Յ T Յ 0.887), Z = 8, monoclinic, space group
C2/c (no. 15), λ = 0.71073 Å, T = 198(2) K, ω and φ scans, 13229
reflections collected (Ϯh, Ϯk, Ϯl), [(sin θ)/λ] 0.67 Å–1, 4881 inde-
pendent (Rint = 0.041) and 4284 observed reflections [I Ն 2σ(I)],
246 refined parameters, R = 0.026, wR2 = 0.064, max. residual elec-
tron density 0.28 (–0.75) eÅ–3.
100 °C (DSC). H NMR (600 MHz, CD2Cl2, 298 K): δ = 3.64 (m,
2 H, 3-H), 7.17 (td, JH,H = 1.8, 0.8 Hz, 1 H, 1-H), 7.24 (td, JH,H
=
7.4, 1.2 Hz, 1 H, 5-H), 7.30 (tdt, JH,H = 7.4, 1.2, 0.8 Hz, 1 H, 6-
H), 7.36, 7.37 (m, 3 H, p,m-Ph), 7.41 (dm, JH,H = 7.4 Hz, 1 H, 7-
H), 7.45 (dm, JH,H = 7.4 Hz, 1 H, 4-H), 7.52 (m, 2 H, o-Ph) ppm.
13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ = 43.1 (C-3), 86.9
(ϵC–), 94.3 (ϵC–Ph), 121.7 (C-7), 123.7 (i-Ph), 123.9 (C-4), 126.1
(C-5), 127.1 (C-6), 127.7 (C-2), 128.7 (p-Ph), 128.8 (m-Ph), 131.8
(o-Ph), 137.6 (C-1), 143.5 (C-3a), 144.5 (C-7a) ppm. MS (EI): m/z
(%) = 216.1 (100) [M+]. IR (KBr): ν = 3069 (w), 2959 (w), 2921
˜
(w), 2351 (w), 2192 (w), 1597 (m), 1487 (m), 1458 (m), 1382 (m),
1207 (w), 862 (m), 755 (s), 714 (m), 687 (m) cm–1. C17H12 (216.3):
calcd. C 94.41, H 5.59; found C 94.33, H 5.37.
Preparation of Bis[2-(phenylethynyl)indenyl]zirconium Dichloride
(4b): 2-(Phenylethynyl)indenyllithium (3b; 1.33 g, 6.0 mmol) and
ZrCl4·2thf (1.13 g, 3.0 mmol) were mixed in a Schlenk tube and the
mixture cooled to –78 °C. Cold toluene (40 mL, –78 °C) was added
to the mixture, then the suspension was stirred at –78 °C for 2 h
and then slowly warmed to room temperature and stirred over-
night. The resulting yellow suspension was filtered to give a yellow
solution. CH2Cl2 (50 mL) was used to extract additional product
from the remaining solid. The yellow solution was concentrated in
vacuo. Crystallization at about –30 °C gave 1.36 g of the yellow
product. Yield: 76%. Crystals suitable for X-ray crystallography
were obtained from a mixture of dichloromethane and pentane at
about +4 °C. M.p. 207 °C (DSC). 1H NMR (600 MHz, CD2Cl2,
298 K): δ = 6.75 (s, 2 H, 1-H, 3-H), 7.23 (m, 2 H, 5-H, 6-H), 7.39
(m, 2 H, m-Ph), 7.41 (m, 1 H, p-Ph), 7.49 (m, 2 H, 4-H, 7-H), 7.59
(m, 2 H, o-Ph) ppm. 13C{1H} NMR (150.8 MHz, CD2Cl2, 298 K):
δ = 83.8 (ϵC–), 95.8 (ϵC–Ph), 109.5 (C-1, C-3), 114.2 (C-2), 122.6
(i-Ph), 125.0 (C-4, C-7), 127.3 (C-3a, C-7a), 127.8 (C-5, C-6), 129.0
Preparation of 2-(Prop-1-ynyl)indenyllithium (3a): A solution of
nBuLi in hexane (1.6 ; 12.7 mL, 20 mmol) was added dropwise to
a solution of 2-(prop-1-ynyl)indene (2a; 3.13 g, 20 mmol) in diethyl
ether (40 mL) at 0 °C, and the mixture was slowly warmed to room
temperature and stirred overnight. The solvent was removed in
vacuo from the yellow suspension to give an orange solid, which
was washed with pentane (60 mL). Filtration gave a yellow solid,
which was dried in vacuo to yield 3.13 g of the product. Yield:
1
98%. H NMR (600 MHz, C6D5CD3 with two drops of [D8]THF,
298 K): δ = 1.86 (s, 3 H, CH3), 6.45 (s, 2 H, 1-H, 3-H), 6.84 (m, 2 H,
5-H, 6-H), 7.54 (m, 2 H, 4-H, 7-H) ppm. 13C{1H} NMR (151 MHz,
C6D5CD3 with two drops of [D8]THF, 298 K): δ = 4.6 (CH3), 80.9
(ϵC–Me), 82.1 (ϵC–), 96.7 (C-1, C-3), 110.4 (C-2), 116.6 (C-5, C-
6), 120.2 (C-4, C-7), 128.0 (C-3a, C-7a) ppm.
Preparation of 2-(Phenylethynyl)indenyllithium (3b): A solution of
nBuLi in hexane (1.6 ; 8.0 mL, 12.8 mmol) was added dropwise
to a solution of 2-(phenylethynyl)indene (2b; 2.77 g, 12.8 mmol) in
diethyl ether (40 mL) at 0 °C, and the mixture was kept at 0 °C for
2 h. The solvent was then removed in vacuo to give a sticky yellow
solid, which was solidified by treatment with pentane (40 mL). Fil-
tration gave a yellow solid, which was dried in vacuo to yield 2.52 g
of the product. Yield: 88%. 1H NMR (600 MHz, C6D5CD3 with
two drops of [D8]THF, 298 K): δ = 6.59 (s, 2 H, 1-H, 3-H), 6.86
(m, 2 H, 5-H, 6-H), 6.92 (m, 1 H, p-Ph), 7.02 (m, 2 H, m-Ph),
(m-Ph), 129.5 (p-Ph), 132.1 (o-Ph) ppm. IR (KBr): ν = 3107 (w),
˜
3057 (w), 2216 (m, CϵC), 1635 (m, br.), 1535 (m), 1498 (m), 1440
(m), 1367 (w), 1205 (w), 834 (s), 758 (s), 692 (m), 644 (w), 530 (w)
cm–1. C34H22Cl2Zr (592.67): calcd. C 68.90, H 3.74; found C 68.87,
H 3.45.
X-ray Crystal Structure Analysis of Complex 4b: Formula
C34H22Cl2Zr, M = 592.64, yellow crystal 0.20ϫ0.20ϫ0.20 mm, a
= 11.801(1), b = 13.040(1), c = 17.255(1) Å, V = 2655.3(3) Å3, ρ =
1.428 gcm–3, µ = 6.37 cm–1, empirical absorption correction (0.883
7.44 (m, 2 H, o-Ph), 7.57 (m, 2 H, 4-H, 7-H) ppm. 13C{1H} NMR Յ T Յ 0.883), Z = 4, orthorhombic, space group P212121 (no. 19),
(151 MHz, C6D5CD3 with two drops of [D8]THF, 298 K): δ = 87.4
λ = 0.71073 Å, T = 198(2) K, ω and φ scans, 20825 reflections
(ϵC–Ph), 93.8 (ϵC–), 97.5 (C-1, C-3), 108.7 (C-2), 117.0 (C-5, C- collected (Ϯh, Ϯk, Ϯl), [(sin θ)/λ] 0.67 Å–1, 6439 independent (Rint
80
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Eur. J. Inorg. Chem. 2008, 73–83

Functional Group Chemistry at the Zirconocene Backbone
= 0.058) and 5423 observed reflections [I Ն 2σ(I)], 334 refined pa-
rameters, R = 0.038, wR2 = 0.060, Flack parameter –0.05(3), max.
residual electron density 0.58 (–0.50) eÅ–3.
moved in vacuo to give an orange residue. Pentane (20 mL) was
added to the mixture, and the suspension was stirred for about
30 min to give an orange precipitate. The orange solid was collected
by filtration and dried in vacuo to afford 133 mg of the product.
Yield: 27%. M.p. 151 °C (DSC). 1H NMR (600 MHz, CD2Cl2,
298 K): δ = 2.12 (d, JH,H = 1.3 Hz, 6 H, CH3), 6.31 (s, 4 H, 1-H,
3-H), 7.02 (q, JH,H = 1.3 Hz, 2 H, =CH), 7.30 (m, 4 H, 5-H, 6-H),
7.65 (m, 4 H, 4-H, 7-H) ppm. 11B NMR (64 MHz, CD2Cl2, 300 K):
δ = 66 (ν1/2 = 3300 Hz) ppm. 13C{1H} NMR (151 MHz, CD2Cl2,
298 K): δ = 18.4 (CH3), 108.4 (C-1, C-3), 114.4 (i-C6F5), 125.7 (C-
4, C-7), 127.6 (C-5, C-6), 127.6 (C-3a, C-7a), 131.6 (C-2), 137.9
(dm, J = 252 Hz, C6F5), 143.3 (dm, J = 256 Hz, p-C6F5), 146.8
(=C–B), 146.9 (dm, J = 246 Hz, C6F5), 149.8 (1JC,H = 159 Hz,
=CH) ppm. 19F NMR (546 MHz, CD2Cl2, 298 K): δ = –129.7 (2
Preparation of the Dimetallic Zr/Co Complex 5a: Complex 4a
(200 mg, 0.43 mmol) and Co2(CO)8 (301 mg, 0.88 mmol) were
added to a Schlenk tube, which was cooled to –78 °C. Cold toluene
(15 mL, –78 °C) was then added to the mixture, and the suspension
was slowly warmed to room temperature with stirring. Filtration
gave a brown solution from which the solvent was partly removed
in vacuo. The concentrated solution was kept at about –30 °C for
crystallization, and a brown solid was collected by filtration and
dried in vacuo to yield 305 mg of the product. Yield: 67%. 1H
NMR (500 MHz, 298 K, CD2Cl2): δ = 2.85 (s, 3 H, CH3), 5.78 (s,
2 H, 1-H, 3-H), 7.39 (m, 2 H, 5-H, 6-H), 7.83 (m, 2 H, 4-H, 7-H)
ppm. 13C{1H} NMR (126 MHz, 298 K, CD2Cl2): δ = 22.6 (CH3),
83.7, 95.4 (CϵC), 106.0 (C-1, C-3), 126.1 (C-5, C-6), 126.4 (C-3a,
C-7a),126.6 (C-4, C-7), 142.3 (C-2), 199.9 (br., CO) ppm. M.p.
F, o), –150.0 (1 F, p), –162.0 (2 F, m) ppm. IR (KBr): ν = 2964 (w),
˜
2920 (w), 1647 (s), 1576 (m), 1519 (s), 1471 (s), 1389 (m), 1311 (m),
1287 (m), 1232 (m), 1100 (s), 974 (s), 902 (s), 837 (w), 805 (w), 747
(m), 688 (m), 634 (w), 578 (w) cm–1. C48H20B2Cl2F20Zr (1160.4):
calcd. C 49.68, H 1.74; found C 49.19, H 1.92.
193 °C (DSC). IR (KBr): ν = 2964 (w), 2929 (w), 2904 (w), 2858
˜
(w), 2089 (s), 2048 (s), 2019 (s), 1634 (m), 1427 (w), 1384 (w), 1258
(w), 1203 (w), 1146 (w), 1051 (m), 1011 (m), 820 (m), 750 (m), 637
(w), 516 (s), 469 (m), 415 (w) cm–1. C36H18Cl2Co4O12Zr (1040.38):
calcd. C 41.56, H 1.74; found C 41.55, H 1.60.
Preparation of Complexes 6a, 6b, and 6c in CD2Cl2 in an NMR
Tube: Complex 4a (20 mg, 0.043 mmol) and HB(C6F5)2 (59 mg,
0.17 mmol) were mixed, and CD2Cl2 (0.8 mL) was added at room
temperature. The yellow solution was transferred to an NMR tube
[a small amount of HB(C6F5)2 remained undissolved], which was
sealed for the NMR measurements. The resulting ratio of com-
plexes 6a/6b/6c was 45:43:12. Complex 6a: 1H NMR (600 MHz,
CD2Cl2, 298 K): δ = 2.12 (br. s, 6 H, CH3), 6.31 (s, 4 H, 1-H, 3-
H), 7.04 (br., 2 H, =CH), 7.30 (m, 4 H, 5-H, 6-H), 7.65 (m, 4 H,
4-H, 7-H) ppm. Complex 6b: 1H NMR (600 MHz, CD2Cl2, 298 K):
Preparation of the Dimetallic Zr/Co Complex 5b: Complex 4b
(302 mg, 0.51 mmol) and Co2(CO)8 (349 mg, 1.02 mmol) were
added to a Schlenk tube, which was cooled to –78 °C. Cold toluene
(15 mL, –78 °C) was then added to the mixture and the suspension
was stirred and slowly warmed to room temperature. Filtration
gave a brown solution from which the solvent was removed in
vacuo. The brown residue was dissolved in a mixture of pentane
(10 mL) and CH2Cl2 (5 mL). The solution was filtered and kept
at about –30 °C for crystallization. The resultant brown solid was
collected and dried in vacuo to yield 159 mg of the product. Yield:
27%. M.p. 209 °C (DSC). Crystals suitable for X-ray crystallogra-
phy were obtained by diffusion of pentane into a CH2Cl2 solution
3
δ = 1.63 [d, J = 7.2 Hz, 3 H, CH3 (6b-I)], 2.09 [s, 3 H, CH3 (6b-
3
II)], 5.71 [q, J = 7.2 Hz, 1 H, =CH (6b-I)], 5.95 [s, 2 H, 1-H, 3-H
(6b-I)], 6.01 [s, 2 H, 1-H, 3-H (6b-II)], 7.01 [br, 1 H, =CH (6b-II)],
7.26 [m, 2 H, 5-H, 6-H (6b-II)], 7.39 [m, 2 H, 5-H, 6-H (6b-I)], 7.59
[m, 2 H, 4-H, 7-H (6b-II)], 7.82 [m, 2 H, 4-H, 7-H (6b-I)] ppm.
1
3
Complex 6c: H NMR (600 MHz, CD2Cl2, 298 K): δ = 1.57 (d, J
= 7.2 Hz, 6 H, CH3), 5.49 (br, 4 H, 1-H, 3-H), 5.73 (q, 3J = 7.2 Hz,
2 H, =CH), 7.44 (m, 4 H, 5-H, 6-H), 7.82 (m, 4 H, 4-H, 7-H) ppm.
11B NMR (64 MHz, CD2Cl2, 300 K): δ = 62 ppm (ν1/2 = 2400 Hz).
19F NMR (546 MHz, C6D5CD3, 298 K): 6a: δ = –129.8 (8 F, o),
–148.70 (4 F, p), –161.1 (8 F, m) ppm; 6b: δ = –129.8 (4 F, o),
–148.1, (2 F, p), –160.9 (4 F, m), –127.8 (4 F, o), –152.7 (2 F, p),
–163.4 (4 F, m) ppm; 6c: δ = –127.9 (8 F, o), –151.7 (4 F, p), –162.9
(8 F, m) ppm.
1
of 5b at room temperature. H NMR (600 MHz, CD2Cl2, 298 K):
δ = 5.93 (br., 2 H, 1-H, 3-H), 7.37 (m, 1 H, p-Ph), 7.39 (m, 2 H,
m-Ph), 7.41 (m, 2 H, 5-H, 6-H), 7.60 (m, 2 H, o-Ph), 7.85 (m, 2 H,
4-H, 7-H) ppm. 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ =
83.1 (ϵC–), 92.8 (ϵC–Ph), 105.6 (br., C-1, C-3), 126.3 (C-5, C-6),
126.4 (C-3a, C-7a), 126.6 (C-4, C-7), 128.3 (p-Ph), 128.9 (m-Ph),
130.6 (o-Ph), 138.3 (i-Ph), 142.8 (C-2), 199.6 (br., CO) ppm. IR
(KBr): ν = 3078 (w), 2087 (s), 2052 (s), 2021 (s), 1846 (m), 1635
˜
(m), 824 (m), 750 (m), 693 (m), 648 (m), 508 (m), 512 (m), 459 (m)
cm–1. C46H22Cl2Co4O12Zr (1164.5): calcd. C 47.44, H 1.90; found
C 47.34, H 1.81.
X-ray Crystal-Structure Determination: Data sets were collected
with a Nonius KappaCCD diffractometer equipped with a rotating
anode generator. Programs used: data collection: COLLECT (Non-
ius B.V., 1998); data reduction: Denzo-SMN (Z. Otwinowski, W.
Minor, Methods Enzymol. 1997, 276, 307–326); absorption correc-
tion: SORTAV (R. H. Blessing, Acta Crystallogr. 1995, A51, 33–37;
R. H. Blessing, J. Appl. Cryst. 1997, 30, 421–426); structure solu-
tion: SHELXS-97 (G. M. Sheldrick, Acta Crystallogr. 1990, A46,
467–473); structure refinement: SHELXL-97 (G. M. Sheldrick,
University of Göttingen, 1997); graphics: SCHAKAL (E. Keller,
University of Freiburg, 1997). CCDC-650362 (4a), -650516 (4b)
and -650363 (5b) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
X-ray Crystal Structure Analysis of Complex 5b: For-
mula C46H22Cl2O12Co4Zr,
M
=
1164.48, red crystal
0.40ϫ0.10ϫ0.02 mm, a = 8.364(1), b = 15.278(1), c = 18.277(1) Å,
α = 95.95(1), β = 101.72(1), γ = 92.24(1)°, V = 2270.2(3) Å3, ρ =
1.704 gcm–3, µ = 18.32 cm–1, empirical absorption correction
¯
(0.528 Յ T Յ 0.964), Z = 2, triclinic, space group P1 (no. 2), λ =
0.71073 Å, T = 198(2) K, ω and φ scans, 25819 reflections collected
(Ϯh, Ϯk, Ϯl), [(sin θ)/λ] 0.67 Å–1, 10881 independent (Rint = 0.063)
and 7915 observed reflections [I Ն 2σ(I)], 586 refined parameters,
R = 0.047, wR2 = 0.076, max. residual electron density 0.51
(–0.69) eÅ–3.
Preparation of Complex 6a: Complex 4a (200 mg, 0.43 mmol) and
HB(C6F5)2 (295 mg, 0.85 mmol) were added to a Schlenk tube,
which was cooled to –40 °C. Cold dichloromethane (10 mL,
–78 °C) was then added to the mixture, and the suspension was
stirred and warmed slowly to room temperature (approx. 40 min).
Filtration gave a yellow solution from which the solvent was re-
General Polymerization Procedure (T Ͼ 0 °C): Polymerization reac-
tions were performed in a thermostatted Büchi glass autoclave sys-
tem. The autoclave was evacuated and filled with argon three times
then charged with toluene (200 mL) and methylalumoxane (MAO)/
Eur. J. Inorg. Chem. 2008, 73–83
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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81

L. Chen, G. Kehr, R. Fröhlich, G. Erker
FULL PAPER
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toluene solution (1.6 , 14 mL). The catalyst-addition funnel was
first dried with MAO/toluene solution (2 mL), and then
2.5ϫ10–5 mol of Zr catalyst precursor in MAO/toluene solution
(4 mL) was added to the funnel. The polymerization temperature
was controlled by a cryostat. The autoclave was evacuated for a
short time at the chosen temperature to remove most of the argon
inside, and then it was charged with olefin monomer (2 bar of eth-
ene or propene), the pressure of which was controlled with a
bpc 1202 Büchi pressflow gas controller (with program “bls2”). The
toluene solution in the autoclave was stirred at a speed of 600 rpm
for 30 min to saturate it with monomer and then the catalyst was
added rapidly into the autoclave to start the polymerization reac-
tion. The polymerization was carried out for 30 min, and then the
reaction was quenched by adding a mixture of methanol and a 2 
HCl aqueous solution (1:1, v:v; 20 mL). Excess monomer was
vented, the toluene solution was poured into methanol (1 L), and
the polymer precipitated at the bottom of methanol solution. It
was stirred, filtered and washed with a suitable solvent and then
collected and dried. Details of the low-temperature (–20 °C) pro-
pene polymerization are provided as Supporting Information.
[8]
Elastomer Analysis: Hysteresis curves for the elastomeric polymer
were determined by first establishing a strain on the polymer sam-
ple of 0.5 N. The polymer was then stretched to twice its original
length. Upon reaching the desired elongation, the polymer sample
recovery was measured as the strain was released to 0.5 N. At this
point, this process was continued for 200% elongation, 300%
elongation, etc. until 10 iterations were completed or the polymer
sample broke.
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Financial support from the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie is gratefully acknowledged.
L. C. thanks the NRW International Graduate School of Chemis-
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Received: July 16, 2007
Published Online: November 6, 2007
Eur. J. Inorg. Chem. 2008, 73–83
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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