Ferrocene-based olefin polymerization catalysts: Activation, structure, and intermediates

Article abstract of DOI:10.1021/om020780f

This paper describes abstraction of a benzyl group from the Zr dibenzyl complex 1,1′-Fc[(NSiMe₃)₂]ZrBn₂ (1) using B(C₆F₅)₃ and [Ph₃C][B(C₆F₅)₄] (TB). In both cases, clean formation of the corresponding cationic monobenzyl species LZrBn⁺ (L = 1,1′-Fc(NSiMe₃)₂^2-) was observed by NMR spectroscopy. In the case of [LZrBn][BnB(C₆F₅)₃] (2), an X-ray crystal structure determination confirmed an η⁶ coordination of the borate benzyl group to the cationic Zr center. Reaction of this complex with 1 equiv of C₂H₂ or RCCR (R = Me, Ph) proceeded with rapid single insertion of the olefin or acetylene into the Zr-carbon σ-bond. With ethylene or 2-butyne further insertions occur more slowly and longer chains were obtained upon addition of more monomer. Activation of 1 with TB leads to an active ethylene polymerization catalyst, producing 102 g of PE mmol^-1 atm^-1 h^-1. Compound 2 reacted with CH₂Cl₂ to form the dimeric [LZrCl₂]₂, which was characterized crystallographically.

Full text of DOI:10.1021/om020780f

Organometallics 2003, 22, 567-575
567
F er r ocen e-Ba sed Olefin P olym er iza tion Ca ta lysts:
Activa tion , Str u ctu r e, a n d In ter m ed ia tes
Alexandr Shafir and J ohn Arnold*
Department of Chemistry, University of California, Berkeley, and the Chemical Sciences
Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460
Received September 18, 2002
This paper describes abstraction of a benzyl group from the Zr dibenzyl complex 1,1′-Fc-
(NSiMe3)2]ZrBn2 (1) using B(C6F5)3 and [Ph3C][B(C6F5)4] (TB). In both cases, clean formation
of the corresponding cationic monobenzyl species LZrBn+ (L ) 1,1′-Fc(NSiMe3)22-) was
observed by NMR spectroscopy. In the case of [LZrBn][BnB(C6F5)3] (2), an X-ray crystal
structure determination confirmed an η6 coordination of the borate benzyl group to the
cationic Zr center. Reaction of this complex with 1 equiv of C2H2 or RCCR (R ) Me, Ph)
proceeded with rapid single insertion of the olefin or acetylene into the Zr-carbon σ-bond.
With ethylene or 2-butyne further insertions occur more slowly and longer chains were
obtained upon addition of more monomer. Activation of 1 with TB leads to an active ethylene
polymerization catalyst, producing 102 g of PE mmol-1 atm-1 h-1. Compound 2 reacted with
CH2Cl2 to form the dimeric [LZrCl2]2, which was characterized crystallographically.
In tr od u ction
dimethyl complex actively polymerized 1-hexene and,
when activated with B(C6F5)3, did so in a “living”
manner.3,4 Closely related systems incorporating ad-
ditional donor atoms have also been investigated.10 The
Schrock group has developed a range of such tridentate
diamido/donor ligands for group IV catalyzed 1-hexene
polymerization.11-14
Ferrocene derivatives have long served as scaffolds
for a variety of ligands used in catalytic transforma-
tions.1 The success of these systems is attributed mainly
to the steric bulk of a ferrocene group and the fairly
constrained directionality of the chelate vectors imposed
by the relative rigidity of the metallocene. Additionally,
many ferrocene-based ligands feature a combination of
planar and central chirality, rendering them useful in
asymmetric catalysis.
The bulk and the rigidity of the ferrocene group made
it an attractive candidate for the design of new types of
olefin polymerization catalysts. We chose diaminofer-
rocene as a ligand precursor on the basis of the fact that
various diamide ligands are well-known to support Ti-
and Zr-based olefin polymerization systems. While some
of the earlier examples of group 4 diamide systems are
based on nonbridged diamide ligands,2 more recently
the research in this area has been focused on more
restricted linked diamide complexes. Several diamines
have served as the basis for these complexes, including
propylenediamine,3,4 phenylenediamine,5,6 biphenylene-
diamine,7 and naphthalenediamine.8,9 Perhaps the most
striking example was discovered by the McConville
group, who reported that a propylenediamine-based Ti
Our group recently reported the synthesis of a series
of Ti and Zr complexes based on the silylated15 and
arylated16 diaminoferrocenes (C5H4NHR)2Fe; closely
related ferrocenediamide complexes have also been
prepared by other groups.17,18 In these compounds the
N-donor atoms are attached directly to the ferrocene
backbone. Several features of this arrangement are
notable. As is often the case with ferrocene-based
ligands, diamidoferrocene provides for a fairly rigid and
highly directing scaffold. Despite the low rotation bar-
rier around the Cp(centroid)-Fe axis, all of our struc-
turally characterized group 4 complexes featured a fully
eclipsed syn-periplanar ferrocene group and an open
N-M-N angle (>130°). In addition, the electron-rich
ferrocene group may stabilize an extremely electron-
poor Ti or Zr center. Indeed, an X-ray crystal structure
(10) Horton, A. D.; De With, J .; van der Linden, A. J .; van de Weg,
H. Organometallics 1996, 15, 2672-2674.
(11) Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am. Chem. Soc.
1997, 119, 3830-3831.
(12) Baumann, R.; Stumpf, R.; Davis, W. M.; Liang, L. C.; Schrock,
R. R. J . Am. Chem. Soc. 1999, 121, 7822-7836.
(13) Liang, L. C.; Schrock, R. R.; Davis, W. M.; McConville, D. H. J .
Am. Chem. Soc. 1999, 121, 5797-5798.
(14) Liang, L. C.; Schrock, R. R.; Davis, W. M. Organometallics 2000,
19, 2526-2531.
(15) Shafir, A.; Power, M. P.; Whitener, G. D.; Arnold, J . Organo-
metallics 2001, 20, 1365-1369.
(16) Shafir, A.; Arnold, J . Inorg. Chim. Acta, in press.
(17) Siemeling, U.; Kuhnert, O.; Neumann, B.; Stammler, A.;
Stammler, H. G.; Bildstein, B.; Malaun, M.; Zanello, P. Eur. J . Inorg.
Chem. 2001, 913-916.
(18) Gibson, V. C.; Long, N. J .; Marshall, E. L.; Oxford, P. J .; White,
A. J . P.; Williams, D. J . J . Chem. Soc., Dalton Trans. 2001, 1162-
1164.
(1) Togni, A.; Hayashi, T., Ferrocenes; VCH: Weinheim, Germany,
1995.
(2) Horton, A. D.; de With, J . Chem. Commun. 1996, 1375-1376.
(3) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996, 118,
10008-10009.
(4) Scollard, J . D.; McConville, D. H.; Vittal, J . J .; Payne, N. C. J .
Mol. Catal. A: Chem. 1998, 128, 201-214.
(5) Aoyagi, K.; Gantzel, P. K.; Kalai, K.; Tilley, T. D. Organometallics
1996, 15, 923.
(6) Daniele, S.; Hitchcock, P. B.; Lappert, M. F.; Merle, P. G. J .
Chem. Soc., Dalton Trans. 2001, 13-19.
(7) Cloke, F. G. N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J .
Organomet. Chem. 1996, 506, 343-345.
(8) Lee, C. H.; La, Y.-H.; Park, S. J .; Park, J . W. Organometallics
1998, 17, 7, 3648.
(9) Lee, C. H.; La, Y.-H.; Park, J . W. Organometallics 2000, 19, 344.
10.1021/om020780f CCC: $25.00 © 2003 American Chemical Society
Publication on Web 01/09/2003

568 Organometallics, Vol. 22, No. 3, 2003
Shafir and Arnold
Sch em e 1
F igu r e 1. Partial ORTEP diagram of [Fc(NSiMe3)2Zr(CH2-
Ph)][PhCH2B(C6F5)3] (2) drawn with 50% thermal el-
lipsoids. For clarity, methyl groups and all hydrogen atoms
are omitted. Selected bond distances (Å): Fe1-Zr1 (non-
bonding) ) 3.1981(7), Zr1-Phcentroid ) 2.385(4), Zr1-N1 )
2.086(4), Zr1-N2 ) 2.068(4), Zr1-C11 ) 2.283(5), Zr1-
C25 ) 2.853(4), Zr1-C26 ) 2.735(4), Zr1-C27 ) 2.727(4),
Zr1-C28 ) 2.733(4), Zr1-C29 ) 2.754(4), Zr1-C30 )
2.805(4). Selected bond angles (deg): N1-Zr1-N2 ) 136.9-
(1), N1-Zr1-C11 ) 96.0(2), N2-Zr1-C11 ) 95.3(2), C11-
Zr1-Phcentroid ) 104.7(1), Zr1-C11-C12 ) 105.7(3).
2+
of [Fc(NSiMe3)2TiCl]2 revealed a highly unusual ge-
ometry with a very short Fe-Ti distance.19 The nature
of this interaction is currently being investigated.
Preliminary study of the catalytic activity of LTiMe2
(L ) 1,1′-Fc(NSiMe3)2) indicated that stable cationic
species could be obtained through the abstraction of a
methide group with strong Lewis acids and that these
cations were active catalysts for oligomerization of
1-hexene.19 In this paper we extend this study to LZrBn2
(1) and report the synthesis of stable cationic species of
the type [LZrBn+][A-] (A- ) PhCH2B(C6F5)-, B(C6F5)4-).
Solid- and solution-state structures of these species are
reported. Additionally, reactivity of these species toward
unsaturated substrates is reported, including polymer-
ization of ethylene.
is found 0.28 Å out of the Fe1-N1-N2 plane, and the
Zr-Ph(centroid) distance is 2.34 Å.
The coordination of a benzyl borate anion to a cationic
group IV metal center in an η6 fashion was first
established by Pellecchia et al., who demonstrated
this mode of binding in the solid-state structures of
[Bn3Zr][η6-PhCH2B(C6F5)3]20 and [CpZrBn2][η6-PhCH2B-
(C6F5)3].21 Following their work, several related species
have been characterized in solution and in the solid
state.2,10,22-24 The Zr-Ph(centroid) distance in 2 is
similar to the distances observed in related compounds,
e.g. [Ar′O)2ZrBn][η6-BnB(C6F5)3] (Ar′O ) 2,6-disubsti-
tuted phenoxide).22 While this mode of binding generally
renders the cationic Ti or Zr species less active for olefin
polymerization (as compared to their B(C6F5)4-contain-
ing counterparts), the increased stability of these species
generally facilitates the investigation of their structure
and reactivity.
NMR studies of 2 in C6D6 suggest that close ion
pairing is maintained in solution. The presence of the
borate anion was supported by a single sharp resonance
at -12.7 ppm in the 11B NMR spectrum, a significant
change from a very broad resonance at +59.2 ppm
observed for the three-coordinate parent B(C6F5)3. In the
1H NMR spectrum, two new benzylic resonances at 3.05
ppm (broad) and 2.30 ppm (sharp singlet) were assigned
to the boron-bound and zirconium-bound methylene
groups, respectively. The ferrocene group gives rise to
four resonances in the 1H NMR spectrum. This is in
contrast to the spectrum of LZrBn2 (1), in which the C2v
symmetry of the ferrocene group leads to just two
resonances, each an AA′BB′ virtual triplet (Figure 2a).
Resu lts a n d Discu ssion
Gen er a tion of [LZr Bn ]+ a n d Its Rea ctivity w ith
Eth ylen e a n d Acetylen es. Reaction of LZrBn2 (1; L
) 1,1′-Fc(NSiMe3)22-) with B(C6F5)3 in toluene or ben-
zene produced the cationic [LZrBn][BnB(C6F5)3] (2)
(Scheme 1). With toluene as a solvent, the product
precipitated after 24 h as a red crystalline solid incor-
porating 1 equiv of toluene. Upon isolation, the material
is only sparingly soluble in benzene and toluene;
therefore, 2 was generated in situ for reactivity studies
(see below).
Crystals of 2 suitable for X-ray diffraction were grown
from a C6D6 solution. In the solid state, the compound
exists as a close-contact ion pair with the benzylborate
[BnB(C6F5)3]- anion bound to zirconium in an η6 fashion
(Figure 1). The distorted-tetrahedral environment of
zirconium is comprised of two nitrogen donors of the
diamide ligand, a phenyl centroid, and the methylene
carbon atom of the remaining σ-bound benzyl group.
Alternatively, the structure may be viewed as being six-
coordinate, with the phenyl ring occupying three (fac)
coordination sites. The interatomic distance of 3.20 Å
between Zr and Fe precludes any significant metal-
metal interaction. In addition, the rather wide Zr-C11-
C12 angle of 105.7° argues against an η2-bound benzyl
ligand. The ferrocene group is in a fully eclipsed (syn-
periplanar) 1,1′-conformation, but the two mean Cp
planes are at a 10.85° angle to each other. The Zr atom
(20) Pellecchia, C.; Grassi, A.; Immirzi, A. J . Am. Chem. Soc. 1993,
115, 1160-1162.
(21) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organome-
tallics 1993, 12, 4473-4478.
(22) Thorn, M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P.
J . Organomet. Chem. 1999, 591, 148-162.
(23) Gauvin, R. M.; Osborn, J . A.; Kress, J . Organometallics 2000,
19, 2944-2946.
(24) Horton, A. D.; de With, J . Organometallics 1997, 16, 5424-
5436.
(19) Shafir, A.; Arnold, J . J . Am. Chem. Soc. 2001, 123, 9212-9213.

Ferrocene-Based Polymerization Catalysts
Organometallics, Vol. 22, No. 3, 2003 569
1
F igu r e 2. Partial H NMR spectra of 1 (a) and 2 (b). The ORTEP diagrams below the spectra illustrate the solid-state
geometry of the two molecules as determined by X-ray diffraction.
The loss of a mirror plane on going from 1 to 2 reduces
the molecular symmetry to Cs with the four Cp-bound
hydrogens residing in distinct chemical environments
(note that the two Cp rings are still related by a mirror
plane) (Figure 2b). The four ferrocene resonances are
comprised of a pair of six-line resonances (apparent
triplets of doublets) for the 3,4-hydrogens and a pair of
five-line resonances (apparent overlapping doublets of
triplets) for the 2,5-hydrogens. Of note is the unusual
chemical shift of one of the 2,5-ferrocene resonances at
2.23 ppm, significantly upfield from the normal chemical
shift of approximately 3.5-4.5. We attribute this phe-
nomenon in part to the ring-current effect of the
zirconium-bound benzyl group, which in the solid state
is bent toward one of the ortho protons of the ferrocene
ring. Interestingly, this phenomenon is paralleled in the
1H NMR spectrum of the parent LZrBn2, where the two
(equivalent) 2,5-ferrocene hydrogens appear at 2.57
ppm. The 13C NMR spectrum of 2 is also consistent with
a Cs-symmetric structure, showing distinct resonances
for each of the five Cp carbon atoms. The Zr-bound
methylene carbon appeared at 69.4 ppm; the shift for
the boron-bound CH2 group was inferred from a 1H-
13C HMQC experiment to be at approximately 36 ppm
(the resonance was not observed in the 13C{1H} spec-
trum due to quadrupole broadening caused by the
neighboring boron nucleus).
Sch em e 2
spectrum of 2, complex 3 features two broad ferrocene
resonances at room temperature, suggesting a fluxional
behavior in solution. The process is likely to involve the
flipping of the benzyl group between two equivalent
coordination sites. While in 2 the freed coordination site
of the cation was occupied by a fairly tightly bound
arene group of the borate anion, making the molecule
static on the NMR time scale, in 3 this coordination site
is most likely occupied by a weakly bound solvent
molecule. The benzyl group site exchange is therefore
more facile in 3 (Figure 3). Nevertheless, cooling the
solution to -30 °C slows this process to a point where
four ferrocene resonances are seen, consistent with a
static Cs-symmetric conformation; at +70 °C the site
exchange process is accelerated to the point where the
The difference between the 19F NMR shifts of meta
and para resonances, ∆δF(m-p), has been reported to
be a useful tool for distinguishing between coordinated
and noncoordinated BnB(C6F5)3- anions.2,10 Values >3
ppm are taken as an indication of coordination; those
<3 ppm imply a free anion. For 2, the value of
∆δF(m-p) is 4.34 ppm, consistent with a coordinated
BnB(C6F5)3-. A similar value was observed for a closely
related cationic Zr system reported by Horton and de
With.24
Reaction of 1 with [Ph3C][B(C6F5)4] in C6D5Cl resulted
in the clean formation of [LZrBn][B(C6F5)4] (3) and 1
equiv of PhCH2CPh3 (Scheme 2). (We note that reactions
in C6D6 resulted in an oily precipitate.) In contrast to
the four sharp ferrocene resonances in the 1H NMR
1
two sides of the molecule become equivalent on the H
NMR time scale, thus imposing a time-averaged C2v
symmetry on the cation and collapsing the ferrocene
pattern to the usual pair of AA′BB′ virtual triplets.
Exposing a solution of 2 in C6D6 to 1 atm of ethylene
led, after 2 min, to the consumption of 1 equiv of
ethylene and formation of the monoinsertion product 4
(Scheme 3). This new species is Cs symmetric, as
1
evidenced by four ferrocene resonances in the H NMR
spectrum (4.01, 3.85, 3.04, and 2.66 ppm). The singlet

570 Organometallics, Vol. 22, No. 3, 2003
Shafir and Arnold
F igu r e 4. GC-MS trace of the hydrolysis products of the
reaction between 2 and approximately 2 equiv of ethylene.
The peaks correspond to the series PhCH2(CH2CH2)nH.
F igu r e 3. Fluxionality of the LMBn+ species leading to a
time-averaged C2v-symmetric structure. The possible mol-
ecule of coordinated solvent is omitted from this illustra-
tion.
GC-MS analysis of the hydrolysis products revealed, in
addition to propyl-, pentyl-, and heptylbenzene, small
amounts of higher molecular weight alkylbenzenes, all
conforming to the general formula Bn(CH2CH2)nH
(Figure 4). No other types of hydrocarbons were ob-
served by GC-MS, suggesting that the rate of â-H
elimination is negligible in this system.25
Sch em e 3
Two different structures can be envisioned for 4. The
benzylborate anion could bind zirconium in an η6
fashion, leaving a dangling γ-phenylpropyl ligand (4A).
corresponding to the zirconium-bound benzyl methylene
group in 2 was replaced by three methylene multiplets
at 2.30, 1.00, and 0.98 ppm for the newly formed
propylphenyl ligand. To confirm the stoichiometry of
this reaction, the mixture was hydrolyzed with 1 M HCl
and the organic products were analyzed using GC-MS.
The only products observed were propylbenzene and
toluene; the presence of the latter was attributed to
hydrolysis of the benzylborate anion.
Alternatively, the increased flexibility of the three-
methylene chain could allow the cation to be stabilized
through an η6 binding of the pendant γ-phenyl group
to zirconium. Such binding would result in a separated
ion pair (4B). Both types of structures are known in
the literature, and the result often depends on the
exact nature of the inserted molecule (e.g. ethylene
vs propylene) and the counterion (BnB(C6F5)3 vs
B(C6F5)4).22-24,26 To probe the role of the anion, we
attempted the preparation of the B(C6F5)4-containing
analogue of 4. By using an anion incapable of binding
to zirconium in an η6 fashion, we expected to produce a
type B structure; nonetheless, we were unable to obtain
Even though subsequent insertions of ethylene were
slower, the formation of longer chains was observed
when ethylene was present in excess. With approxi-
mately 2 equiv of ethylene, di- and triinsertion products
1
were detected by H NMR spectroscopy after 20 min.
(25) Burger, B. J .; Thompson, M. E.; Cotter, W. D.; Bercaw, J . E. J .
Am. Chem. Soc. 1990, 112, 1566-1577.
(26) Pellecchia, C.; Immirzi, A.; Zambelli, A. J . Organomet. Chem.
1994, 479, C9-C11.
Each of the new species exhibited a set of four ferrocene
resonances. The aliphatic protons of the growing poly-
mer chain appeared as a multiplet at 0.8-1.3 ppm. The

Ferrocene-Based Polymerization Catalysts
Organometallics, Vol. 22, No. 3, 2003 571
Zr cation can be stabilized either by an η6 binding of
the benzylborate anion (A) or by an η6 binding of the
Sch em e 4
an ethylene monoinsertion product with compound 3.
Instead, introducing ethylene into an NMR tube con-
taining a solution of 3 in C6D5Cl resulted in the
immediate formation of a polyethylene plug at the top
of the solution. Indeed, compound 3 proved to be a
competent ethylene polymerization catalyst, producing
102 g of PE mmol-1 atm-1 h-1. Presumably, the initially
formed type B monoinsertion product [LZr(CH2)3Ph]-
[B(C6F5)4] (4′) inserted additional molecules of ethylene
very rapidly. The strikingly different behavior of 4 and
4′ suggests that their structures are different, and the
much-reduced reactivity of 4 argues well for the ben-
zylborate-stabilized structure of type 4A. Additionally
for 4, the value ∆δF(m-p) was found to be 4.20 ppm,
confirming coordination of the anion (see above).
allylphenyl ligand -CdCCH2Ph (B). To probe the role
of the anion, a compound was synthesized in which
BnB(C6F5)3- was replaced with B(C6F5)5- by reacting 3
1
with diphenylacetylene in C6D5Cl. The H NMR spec-
trum of the resulting compound [LZrC(Ph)dC(Ph)CH2-
Ph][B(C6F5)4] (5′) was essentially identical with the
spectrum of 5 in C6D5Cl (but obviously lacked the
benzylborate resonances). Neither 5 nor 5′ reacted with
additional equivalents of PhCCPh or with ethylene. The
similarities in the spectroscopic and chemical behavior
of the two compounds are consistent with both belonging
to the same structural type. Since complex 5′ cannot
have a type A structure, both must be of type B with
the pendant C(Ph)dC(Ph)CH2Ph ligand stabilizing the
cation in an η6 fashion. The downfield shifts of the ortho
and meta -CdCCH2Ph phenyl resonances (8.00 and
7.58 ppm) are also consistent with the spectral data for
related compounds.23,26
Considering the slow rate of insertion of ethylene in
2, it was not surprising to find this species to be inert
toward substituted alkenes, such as 1-hexene. Nonethe-
less, we found 2 to be quite reactive toward disubsti-
tuted acetylenes, as shown in Scheme 4. Addition of
diphenylacetylene or di-p-tolylacetylene to a C6D5Cl or
C6D6 solution of 2 resulted in the immediate formation
of a red solution of [LZrC(Ar)dC(Ar)CBn][BnB(C6F5)3]
1
(5, Ar ) Ph; 6, Ar ) p-tol). The H NMR spectrum of 5
in C6D5Cl featured four ferrocene ABCD multiplets
(4.45, 4.16, 2.72, and 2.70 ppm), a broad CH2-B peak
and a sharp Ph-CH2(CdC) methylene singlet. In the
aromatic region one of the phenyl groups appeared
downfield at 7.99 (o), 7.56 (m), and 6.85 (p) ppm, while
another appeared upfield at 6.79 (m), 6.70 (p), and 6.40
ppm. In the spectrum of the p-tol derivative 6 the
downfield resonances appear unchanged while the three
aromatic upfield peaks are replaced by two doublets at
6.67 and 6.35 ppm. This allowed for the assignment of
the downfield resonances to the PhCH2CdC phenyl
group, while the upfield resonances were assigned to
one of the vinylic phenyl ArCdC groups. The signals
for the second vinylic aryl group were obscured by the
solvent and benzylborate aromatic resonances. Further
support for the identity of 5 was obtained from a GC-
MS analysis of the products of hydrolysis of the reaction
mixture with 1 M HCl. The only product observed had
a m/z ratio of 270 corresponding to the expected stilbene
derivative Ph(H)CdC(CH2Ph)Ph.
Solutions of type B self-stabilized salts are expected
to contain “free” BnB(C6F5)3 anion. The 1H NMR
-
spectra of 5 and 6 in C6D5Cl contained a BCH2 meth-
ylene resonance at 3.29 ppm. Addition of approximately
0.5 equiv. of [NEt4][BnB(C6F5)3] to the solutions of these
salts did not change their 1H NMR spectra, with the
exception of the expected increase in the intensity of
the BCH2 peak and the appearance of NEt4-related
resonances. This experiment supports the formulation
of 5 and 6 as separated ion pairs. Finally, the ∆δF(m-
p) value (19F NMR) for 5 was found to be 2.97 ppm,
consistent with a noncoordinated BnB(C6F5)3. The value
is essentially identical to that of the free [NEt4][BnB-
(C6F5)3] (see Experimental Section).
While it is most likely that the cationic portions of 5
and 6 are stabilized through the coordination of pendant
-CdCCH2Ph phenyl groups, the two other phenyl
groups present in the -C(Ph)dC(Ph)CH2Ph fragment
could potentially serve this role. To address this prob-
lem, 2 was reacted with 2-butyne in C6D6, producing
[LZrC(Me)dC(Me)CBn][BnB(C6F5)3] (7) (Scheme 4),
which separated from solution as a red oil. The cationic
As was the case with the ethylene insertion product
4, two possible structures are possible for 5 and 6. The

572 Organometallics, Vol. 22, No. 3, 2003
Shafir and Arnold
Sch em e 5
portion of 7 contains only one phenyl group as a part of
the C(Me)dC(Me)CH2Ph moiety.
The H NMR spectrum of 7 in CD2Cl2 contained four
F igu r e 5. ORTEP diagram of [Fc(NSiMe3)2ZrCl(µ-Cl)]2 (8)
shown with 50% thermal ellipsoids. Hydrogen atoms are
omitted for clarity. Selected bond distances (Å): Zr1-Zr1*
(nonbonding))4.1270(8),Zr1-Fe1 (nonbonding))3.2229(7),
Zr1-Cl1 ) 2.519(1), Zr1-Cl1* ) 2.707(1), Zr1-Cl2 )
2.430(1), Zr1-N1 ) 2.046(4), Zr1-N2 ) 2.046(4). Selected
bond angles (deg): N1-Zr1-N2 ) 136.7(1), Cl1-Zr-Cl1*
) 75.75(4), Cl1-Zr1-Cl2 ) 88.68(4), Cl2-Zr-Cl1* )
164.15(4).
1
ferrocene resonances with the expected ABCD spin
pattern. The two inequivalent methyl groups appeared
at 1.84 and 1.37 ppm, exhibiting mutual long-range
5
coupling with J ) 0.83 Hz. The only product detected
by the GC-MS analysis of the hydrolyzed reaction
mixture was Me(H)CdC(CH2Ph)Me, consistent with the
proposed formulation of 7. In the aromatic region the
1H NMR spectrum contained two sets of benzyl reso-
nances, one assigned to the benzylborate anion and the
other to the C(Me)dC(Me)CH2Ph group. The latter
appeared at 8.16 (o), 7.82 (m), and 7.41 (p) ppm; the
downfield shift of these resonances can be associated
with an η6 mode of binding of this phenyl group to
zirconium. The B-CH2 peak appeared at 2.88 ppm, and
the addition of approximately 1 equiv of [NEt4][BnB-
(C6F5)3] to the sample resulted in the increase in the
integration of this peak from 2H to 4H and the appear-
ance of NEt4-related resonances. As was the case with
5 and 6, such addition of the “free” borate did not lead
to any other changes in the 1H NMR spectrum. This
suggests that in solution compound 7 is structurally
similar to 5 and 6 with a type B self-stabilized cationic
portion and that the pendant CdCCH2Ph is indeed
involved in the η6 binding to zirconium.
5). Each five-coordinate zirconium atom is bound to two
bridging chlorides, one terminal chloride, and two
2-
nitrogen atoms of the Fc(NSiMe3)2 ligand. The fer-
rocene group is in the fully eclipsed synclinal conforma-
tion, but the two Cp rings are at a 10.72° angle to each
other, with the Cp-Cp wedge opening toward the
zirconium atom. The compound is virtually insoluble in
nonpolar solvents and CH2Cl2 but dissolved well in
1
THF. The H NMR spectrum of 8 in THF-d8 contains
two virtual triplets for the ferrocene group. This pattern
is indicative of a solution C2v symmetry, which is in
contrast to the solid-state structure, where each fer-
rocene group possesses a local Cs symmetry. This
discrepancy can be explained by the coordination of THF
molecules to the Zr center and the formation of mono-
meric LZrCl2(THF)x complexes. In that case a fluxional
process could render each ferrocene group C2v sym-
metric. Interestingly, the 2,5- (but not the 3,4-) ferrocene
resonances in both 1H and 13C{1H} NMR spectra of 8
are slightly broadened, presumably due to this fluxional
process. Previous attempts to prepare this material in
a more direct fashion, using salt metathesis reactions
related to those that are successful in the Ti case, were
in vain.15
Activation of halogenated solvents by cationic Ti and
Zr complexes is not unprecedented,27,28 but the exact
mechanism of this process remains unknown. Hydroly-
sis and subsequent GC-MS analysis of the mixture
revealed the presence of 1,2-diphenylethane (“bibenzyl”,
m/z 182), possibly suggesting a SET mechanism for CH2-
Cl2 activation.
Compound 7 reacted with additional equivalents of
2-butyne. Reaction of 2 with approximately 5 equiv of
2-butyne in C6H6 led, after 24 h, to the formation of a
mixture of products. Hydrolysis of this mixture, and
subsequent analysis by GC-MS, revealed the presence
of the single-insertion product Me(H)CdC(Me)CH2Ph
as well as higher oligoacetylenes. Interestingly, while
the triple- and quadruple-insertion products were found,
GC-MS showed no evidence for the double-insertion
product.
Rea ction of LZr Bn + w ith CH2Cl2. We have previ-
ously reported that the reaction of LTiMe+ with CH2-
Cl2 produced the dimeric dication LTi(µ-Cl)2TiL2+ 19
. The
highly unusual geometry of the species prompted an
attempt to generate the related hitherto unknown Zr
analogue. Leaving a mixture of solutions of LZrBn2 and
B(C6F5)3 in CH2Cl2 undisturbed for 18 h resulted in the
formation of a yellow crystalline solid. X-ray diffraction
Con clu sion s
We have shown that abstraction of a benzyl group
from the ferrocene-containing Zr complex Fc(NSiMe3)2-
analysis showed the solid to be the neutral [LZrCl2]2
2+
(27) Gomez, R.; Green, M. L. H.; Haggitt, J . L. J . Chem. Soc., Dalton
(8) (Scheme 5) rather than the dicationic [LZr(µ-Cl)]2
.
Trans. 1996, 939-946.
In the solid state the compound exists as a dimer
residing on a crystallographic inversion center (Figure
(28) Yue, N. L. S.; Stephan, D. W. Organometallics 2001, 20, 2303-
2308.

Ferrocene-Based Polymerization Catalysts
Organometallics, Vol. 22, No. 3, 2003 573
µmol) in 3.5 mL of toluene. The resulting orange solution was
thoroughly mixed by shaking and then was allowed to stand
for 24 h. At this point the large red crystals which appeared
in the flask were collected by filtration. Drying of the crystals
in vacuo led to a partial loss of solvent and powdering of the
crystals. The crystals were found by 1H NMR to contain 1 equiv
of toluene. Yield (based on the formulation 2‚PhCH3): 418 mg,
76%. 1H NMR (C6D6): δ 7.16 (d, 2H, o-Ph, ZrCH2Ph), 6.85 (m,
2H, m-Ph, ZrCH2Ph), 6.78 (m, 2H, m-Ph, BCH2Ph), 6.59 (m,
2H, two overlapping p-Ph), 6.49 (d, 2H, o-Ph, BCH2Ph), 3.90
(m, 2H, Fc), 3.87 (m, 2H, Fc), 3.09 (m, 2H, Fc), 3.08 (s br, 2H,
B-CH2), 2.30 (s, 2H, Zr-CH2), 2.24 (m, 2H, Fc), 0.08 (s, 18H,
SiMe3) ppm. 13C{1H} NMR (C6D6): δ 156.4, 148.7 (br d, J C-F
) 247 Hz), 142.4, 139.0 (br d, J C-F ) 249 Hz), 137.5 (br d,
J C-F ) 254 Hz), 130.6, 129.8, 129.3, 125.6, 123.3, 88.0 (ipso-
Fc), 75.9 (Fc), 72.4 (Fc), 70.4 (Fc), 69.4 (Zr-CH2), 69.3 (Fc), 36
(B-CH2, not directly observed, value obtained from a 1H-13C
ZrBn2 (LZrBn2, 1) using B(C6F5)3 and [Ph3C][B(C6F5)4]
resulted in formation of the stable cationic species
[LZrBn][A] (2, A ) BnB(C6F5)3; 3, A ) B(C6F5)3).
Compound 2 was found to be a close-contact ion pair
and in the solid state contained an η6-coordinated
benzylborate anion. The compound was found to cleanly
insert ethylene and acetylene, and the rare ethylene
single-insertion product 4 was observed by 1H NMR. In
solution, 4 appears to have an η6-coordinated benzylbo-
rate anion; however, the related acetylene-insertion
products feature noncoordinate benzylborate, as evi-
1
denced by H and 19F NMR spectroscopy. Finally, the
“free” cationic LZrBn+ proved to be an active ethylene
polymerization catalyst.
HMQC experiment), 1.1 (SiMe3) ppm. 11B NMR (C6D6):
δ
Exp er im en ta l Section
-12.7 ppm. 19F NMR (C6D6): δ -132.10 (d, o-F), -161.49 (t,
p-F), -165.81 (m, m-F) ppm. Anal. Calcd for C48H40BF15FeN2-
Si2Zr‚C7H8: C, 53.45; H, 3.91; N, 2.27. Found: C, 53.60; H,
4.04; N, 2.27.
Gen er al Con sider ation s. Standard Schlenk-line and glove-
box techniques were used unless otherwise indicated. Pentane,
toluene, benzene, Et2O, and CH2Cl2 were dried by passing
through a column of activated alumina and degassed with
argon prior to use. PhCl was stirred over CaH2 and distilled.
Fc(NHSiMe3)2,15 Zr(CH2Ph)4,29 Ti(CH2Ph)4,30 B(C6F5)3,31 and
[Ph3C][B(C6F5)4]32 were prepared according to published pro-
cedures. C6D6 and THF-d8 were vacuum-transferred from
sodium/benzophenone. C6D5Cl and CD2Cl2 were vacuum-
Obser va tion of [F c(NSiMe3)2Zr Bn ][B(C6F 5)4)] (3). A
solution of [Ph3C][B(C6F5)] (42 mg, 45 µmol) in 0.8 mL of C6D6
was added to a solution of 1 (28 mg, 44 µmol) in 0.8 mL of
C6D6. The resulting cloudy mixture was allowed to stand
undisturbed for 10 min, resulting in the formation of a layer
of a red oil. The supernatant solution was decanted, and the
oil was dissolved in 0.6 mL of C6D5Cl. In addition to 3 the
solution contained a small amount (approximately 5%) of Ph3-
1
transferred from CaH2. H NMR spectra were recorded on a
Bruker AMX-300 or DRX-500 spectrometer. 13C, 19F, and 11B
NMR data were recorded on a Bruker DRX-500 spectrometer.
1H NMR chemical shifts are given relative to C6D5H (7.16
ppm), CDHCl2 (5.32 ppm), and THF-d7 (1.73 ppm). Due to
overlap with aromatic resonances, the residual solvent protons
in C6D5Cl were difficult to observe. Therefore, all 1H NMR
spectra in this solvent were referenced to an external SiMe4
(0.00 ppm) in C6D5Cl standard. 13C{1H} NMR spectra are
relative to C6D6 (128.3 ppm), CD2Cl2 (58.3 ppm), THF-d8 (25.3
ppm), and C6D5Cl (CCl, 134.2 ppm). 11B NMR spectra are
referenced to external BF3‚Et2O in C6D6 (0.00 ppm). 19F NMR
spectra are relative to C6D5CF3 at -64.0 ppm in C6D6. Peak
assignment was aided by 2D 1H-1H TOCSY and 1H-13C
HMQC experiments. Elemental analyses were determined at
the Microanalytical Laboratory of the College of Chemistry,
University of California, Berkeley. Single-crystal X-ray struc-
ture determinations were performed at CHEXRAY, University
of California, Berkeley.
1
CCH2Ph (CH2 at 3.83 ppm). H NMR of 3 at +70 °C (C6D5Cl):
δ 7.42 (t, 2H, m-Ph), 7.15 (t, 1H, p-Ph), 6.66 (d, 2H, o-Ph), 4.43
(virt t, 4H, Fc), 3.15 (virt t, 4H, Fc), 3.03 (s, 2H, PhCH2), -0.07
1
(s, 18H, SiMe3) ppm. H NMR of 3 at -30 °C (C6D5Cl): δ 7.50
(br s, 2H, m-Ph), 7.20 (t, 1H, p-Ph), 6.66 (d, 2H, o-Ph), 4.60
(br s, 2H, Fc), 4.21 (br s, 2H, Fc), 4.38 (br s, 2H, Fc), 3.10 (s,
2H, PhCH2), 3.02 (br s, 2H, Fc), 0.06 (s, 18H, SiMe3) ppm.
Obser va tion of [F c(NSiMe3)2Zr (CH2CH2CH2P h )][Bn B-
(C6F 5)3] (4). To a solution of 1 (14 mg, 22 µmol) in 0.3 mL of
C6D6 was added a solution of B(C6F5)3 (12 mg, 23 µmol) in 0.3
mL of C6D6. The resulting orange solution was transferred to
an NMR tube capped with a rubber septum. Through the
septum ethylene (approximately 1.2 equiv) was injected using
a syringe. The 1H NMR spectrum was recorded after 2 min.
1H NMR: δ 7.16-7.14 (m, 4H), 4.01 (m, 2H, Fc), 3.85 (m, 2H,
Fc), 3.31 (br d, 2H, B-CH2), 3.04 (m, 2H, Fc), 2.66 (m, 2H, Fc),
2.31 (m, 2H, CH2), 1.00 (m, 4H, CH2), -0.02 (s, 18H, SiMe3)
ppm. 19F NMR (C6D6): δ -131.99 (d, o-F), -161.71 (t, p-F),
-165.92 (m, m-F) ppm.
[NEt4][Bn B(C6F 5)3]. A solution of BnMgCl (1.6 mL, 1.1 M
in Et2O, 1.8 mmol) was added to a solution of B(C6F5)3 (900
mg, 1.75 mmol) in 30 mL of THF cooled to -60 °C. The reaction
mixture was warmed to ambient temperature over a period
of 1 h, at which point the solvent was removed under vacuum,
affording a foamy white solid. The solid was dissolved in CH2-
Cl2, and a solution of NEt4Cl (390 mg, 1.80 mmol) in CH2Cl2
was added. The resulting mixture was filtered, and the solvent
was removed in vacuo, affording 1.06 g (83%) of the product.
1H NMR (CD2Cl2): δ 6.93 (t, 2H, m-Ph), 6.82 (t, 1H, p-Ph),
6.76 (d, 2H, o-Ph), 3.07 (q, 8H, J HH ) 7.2 Hz, NCH2CH3), 2.80
(br s, 2H, BCH2), 1.25 (tt, 12H, J HH ) 7.2 Hz, J HN ) 1.8 Hz)
ppm. 19F NMR (C6D5Cl): δ -131.49 (d, o-F), -164.34 (t, p-F),
-167.37 (m, m-F) ppm.
[F c(NSiMe3)2Zr (C(P h )dC(P h )CH2P h )][Bn B(C6F 5)3] (5).
A Schlenk tube was charged with 1 (250 mg, 0.396 mmol),
diphenylacetylene (72 mg, 0.40 mmol), and 8 mL of benzene.
The resulting solution was added to a solution of B(C6F5)3 (205
mg, 0.400 mmol) in 8 mL of benzene. A red mixture formed
immediately, from which a dark red oil separated after 10 min.
At this point the solvent was removed in vacuo and the red
sticky solid was washed with two 10 mL portions of pentane.
Drying the resulting sticky solid in vacuo at 50 °C for 30 min
resulted in 467 mg of a yellow flaky solid of 5 (350 mmol, 90%).
1H NMR (C6D6): δ 7.74 (d, 2H, 6.9 Hz), 7.34 (t, 2H, 7.6 Hz),
7.28 (d, 2H, 7.3 Hz), 7.07-7.02 (m, 6H), 6.97 (m, 1H), 6.92 (t,
1H, 7.3 Hz), 6.71 (t, 2H, 7.6 Hz), 6.63 (m, 2H), 6.38 (m, 2H),
4.24 (m, 2H, Fc), 4.08 (m, 2H, Fc), 3.95 (s, 2H, Ph-CH2), 3.45
(br s, 2H, B-CH2), 2.63 (m, 2H, Fc), 2.60 (m, 2H, Fc), 0.03 (s,
18H, SiMe3) ppm. 1H NMR (C6D5Cl): δ 7.99 (d, 2H, o-Ph,
PhCH2CdC), 7.56 (t, 2H, m-Ph, PhCH2CdC), 7.2-6.9 (m, 9H),
6.88 (t, 1H, p-Ph, PhCH2CdC), 6.84 (t, 1H, p-Ph), 6.79 (t, 2H,
m-Ph, PhCdC), 6.70 (t, 1H, p-Ph, PhCdC), 6.39 (d, 2H, o-Ph,
PhCdC), 4.45 (m, 2H, Fc), 4.16 (m, 2H, Fc), 4.11 (s, 2H,
PhCH2CdC), 3.29 (s, br, 2H, BCH2), 2.72 (m, 2H, Fc), 2.70 (m,
2H, Fc), 0.06 (s, 18H, SiMe3) ppm. 13C{1H} NMR (C6D6): δ
[Fc(NSiMe3)2Zr Bn )][Bn B(C6F5)3] (2). A solution of B(C6F5)3
(240 mg, 469 µmol) in 3.5 mL of toluene was added to a
Schlenk flask containing a solution of LZrBn2 (1; 280 mg, 443
(29) Felten, J . J .; Anderson, W. P. J . Organomet. Chem. 1972, 36,
87.
(30) Zucchini, U.; Albizzat. E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357.
(31) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245-
250.
(32) Lambert, J . B.; Zhang, S. Z.; Ciro, S. M. Organometallics 1994,
13, 3, 2430-2443.

574 Organometallics, Vol. 22, No. 3, 2003
Shafir and Arnold
Ta ble 1. Cr ysta llogr a p h ic Da ta for 2 a n d 8
204.6, 168.6, 154.6, 149.2 (br d, J C-F ) 238 Hz), 149.0, 141.8,
140.1, 138.3 (br d, J C-F ) 238 Hz), 137.3 (br d, J C-F ) 238
Hz), 132.4, 131.6, 128.6, 125.6, 123.9, 123.4, 87.9 (Fcipso), 77.2
(Fc), 71.2 (Fc), 70.7 (Fc), 68.4 (Fc), 47.2 (PhCH2CdC), 33
(BCH2, not directly observed, value obtained from a 1H-13C
2‚C6D6
8‚CH2Cl2
mol formula
C54H46N2BF15
FeSi2Zr
-
C17H28N2Si2-
ZrFeCl4
fw
1221.99
605.4
HMQC experiment), 0.8 (SiMe3) ppm. 11B NMR (C6D6):
δ
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
yellow block
yellow plate
0.32 × 0.24 × 0.12
triclinic
-12.8 ppm. 19F NMR (C6D6): -131.53 (d, o-F), -164.40 (t, p-F),
-167.33 (m, m-F) ppm. Anal. Calcd for C67H62BF15FeN2Si2Zr:
C, 56.32; H, 3.81; N, 2.12. Found: C, 55.89; H, 3.81; N, 2.12.
Obser va tion of [F c(NSiMe3)2Zr (C(P h )dC(P h )CH2P h )]-
[B(C6F 5)4] (5′). A solution of [Ph3C][B(C6F5)] (42 mg, 45 µmol)
in 0.3 mL of C6D6 was added to a vial containing 1 (28 mg, 44
µmol) and diphenylacetylene (8 mg, 45 µmol) dissolved in 0.3
mL of C6D6. A layer of red oil separated from the resulting
solution after 10 min. The supernatant solution was decanted,
0.28 × 0.21 × 0.18
triclinic
P1h
P1h
13.1328(3)
13.7959(3)
16.6316(4)
80.143(1)
79.695(1)
62.849(1)
2624.2(1)
2
10.8988(3)
10.9214(4)
12.2609(4)
112.123(1)
101.207(1)
105.035(1)
1234.16(7)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
1
and the oil was redissolved in C6D5Cl. According to H NMR
spectroscopy the solution contained 5′ as well as residual Ph3-
CCH2Ph (approximately 5%, CH2 at 3.83 ppm). H NMR of 5′
(C6D5Cl): δ 8.01 (d, 2H, o-Ph, PhCH2CdC), 7.57 (t, 2H, m-Ph,
PhCH2CdC), 7.2-6.9 (m, 5 PhCdC protons overlapping with
solvent), 6.89 (t, 1H, p-Ph, PhCH2CdC), 6.81 (t, 2H, m-Ph,
PhCdC), 6.72 (t, 1H, p-Ph, PhCdC), 6.40 (d, 2H, o-Ph, PhCd
C), 4.43 (m, 2H, Fc), 4.11 (m, 2H, Fc), 4.10 (s, 2H, PhCH2Cd
C), 2.70 (m, 2H, Fc), 2.64 (m, 2H, Fc), -0.10 (s, 18H, SiMe3)
ppm.
Z
Dc (g cm-3
)
1.546
1.629
1
temp (°C)
-131
-160
radiation (λ, Å)
µ (cm-1
min/Tmax
Rmerge
Mo KR (0.710 69)
)
6.13
0.786
0.040
15.45
0.720
0.057
T
R, Rw, Rall
GOF
0.040, 0.050, 0.056
1.25
0.034, 0.042, 0.038
1.72
largest shift/error
max, min peak in
0.00
0.66/-1.35
0.00
0.86/-0.96
diff map (e Å-3
)
Obser va tion of [F c(NSiMe3)2Zr (C(p-tol)dC(p-tol)-
CH2P h )][Bn B(C6F 5)3] (6). Addition of a solution of B(C6F5)3
(24 mg, 46 µmol) in 0.3 mL of C6D5Cl to a vial containing 1
(28 mg, 44 µmol) and di-p-tolylacetylene (9.5 mg, 46 µmol)
dissolved in 0.3 mL of C6D5Cl afforded a clear red solution.
1H NMR (C6D5Cl): δ 7.97 (d, 2H, o-Ph), 7.55 (t, 2H, m-Ph),
6.67 (d, 2H, m-tol), 6.35, (d, 2H, o-tol), 4.45 (m, 2H, Fc), 4.16
(m, 2H, Fc), 4.14 (s, 2H, PhCH2CdC), 3.29 (s br, 2H, BCH2),
2.78 (m, 2H, Fc), 2.73 (m, 2H, Fc), 2.04 (s, 3H, Me), 1.93 (s,
3H, Me), 0.07 (s, 18H, SiMe3) ppm. 13C{1H} NMR (C6D5Cl): δ
205.7, 168.5, 154.8, 149.0, 148.8 (br d, J C-F ) 236 Hz), 138.5,
affording an orange powder. 1H NMR of the powder showed
several ferrocene-containing compounds. GC-MS analysis of
a hydrolyzed mixture (1 M HCl) showed peaks consistent with
the single-insertion product Me(H)CdC(Me)CH2Ph (m/z 146),
as well as triple- and quadruple-insertion products (m/z 254
and 308, respectively).
[F c(NSiMe3)2Zr Cl(µ-Cl)]2 (8). A solution of 1 (190 mg, 300
µmol) in 1.7 mL of CH2Cl2 was added to a solution of B(C6F5)3
(156 mg, 305 µmol) in 1.7 mL of CH2Cl2. The resulting yellow
solution was left undisturbed for 18 h, at which point yellow
crystals were collected. The crystals were found to incorporate
1 equiv of CH2Cl2, but this solvent was quickly lost upon drying
under vacuum. Yield: 114 mg, 74%. 1H NMR (THF-d8): δ 4.59
(virt t, 4H, Fc), 3.27 (br, virt t, 4H, Fc), 0.21 (s, 18H, SiMe3)
ppm. 13C{1H} NMR (THF-d8): δ 87.3 (ipso-Fc), 72.0 (Fc), 68.4
(br, Fc), 0.5 (SiMe3) ppm. Anal. Calcd for C32H52N4Cl4Fe2Si4-
Zr2: C, 36.92; H, 5.03; N, 5.38. Found: C, 37.12; H, 5.23; N,
5.18.
P r ocedu r e for Eth ylen e P olym er ization by 3. A Schlenk
tube was charged with 46 µmol of complex 1 and 46 µmol of
[Ph3C][B(C6F5)4] (42 mg). In the tube was added 5 mL of C6H5-
Cl,and the mixture was stirred for 2 min. At this point the
flask was evacuated briefly and then refilled with ethylene.
The flask was warmed immediately, and a thick mixture
formed. After 5.0 min the reaction mixture was quenched with
acidified MeOH (30 mL). The resulting white polyethylene was
isolated by filtration, washed with additional portions of
MeOH, and dried for 10 h at 100 °C.
Gen er a l P r oced u r es for X-r a y Cr ysta llogr a p h y. Per-
tinent details for the individual compounds can be found in
Table 1. Crystals of 2 were grown from a C6D6 solution.
Crystals of 8 were formed when a solution of 2 in CH2Cl2 was
allowed to stand undisturbed for 24 h. A crystal of appropriate
size was mounted on a glass capillary using Paratone-N
hydrocarbon oil. The crystal was transferred to a Siemens
SMART diffractometer/CCD area detector,33 centered in the
beam, and cooled by a nitrogen flow low-temperature ap-
paratus that had been previously calibrated by a thermocouple
placed at the same position as the crystal. Preliminary
orientation matrix and cell constants were determined by
collection of 60 10 s frames, followed by spot integration and
138.1, 138.0 (br d, J C-F ) 238 Hz), 137.1, 137.0 (br d, J C-F
)
236 Hz), 135.6, 132.4, 131.7, 131.4, 128.1, 123.8, 123.2, 87.8
(ipso-Fc), 77.0 (Fc), 71.0 (Fc), 70.5 (Fc), 68.6 (Fc), 47.2
(PhCH2CdC), 33 (br, B-CH2, not directly observed, value
1
obtained from a H-13C HMQC experiment), 21.04 (Me), 20.7
(Me), 0.9 (SiMe3) ppm.
[F c(NSiMe3)2Zr (C(Me)dC(Me)CH2P h )][Bn B(C6F 5)3] (7).
Addition of 2-butyne (36 µL, 460 µmol) to a solution of 1 (280
mg, 443 µmol) in 5 mL of C6H6 followed by a solution of
B(C6F5)3 (235 mg, 460 µmol) in 5 mL of C6H6 resulted after 2
min of stirring in the formation of a red cloudy solution. The
mixture was allowed to settle, producing a layer of dark red
oil at the bottom of the flask. The supernatant solution was
decanted, and the oil was washed with two 10 mL portions of
pentane. Upon drying in vacuo at 50 °C for 30 min the product
was isolated as a yellow powder. Yield: 428 mg (358 µmol,
81%). 1H NMR (CD2Cl2): δ 8.15 (m, 2H), 7.82 (m, 2H), 7.41
(m, 1H), 6.94 (m, 2H), 6.86 (m, 1H), 6.82 (m, 2H), 4.99 (m, 2H,
Fc), 4.44 (m, 2H, Fc), 3.95 (s, 2H, Ph-CH2), 3.51 (m, 2H, Fc),
3.05 (m, 2H, Fc), 2.88 (br s, 2H, B-CH2), 1.84 (q, 3H, 5J ) 0.8
5
Hz, CdCMe), 1.38 (q, 3H, J ) 0.8 Hz, MeCdC), 0.12 (s, 18H,
SiMe3) ppm. 13C{1H} NMR (CD2Cl2): δ 206.9, 170.0, 157.4,
148.6 (br d, J C-F ) 246 Hz), 137.9 (br d, J C-F ) 242 Hz), 136.8
(br d, J C-F ) 242 Hz), 133.1, 131.8, 129.1, 127.2, 125.8, 90.0
(ipso-Fc), 77.4 (Fc), 71.5 (Fc), 70.5 (Fc), 69.0 (Fc), 48.7
(PhCH2CdC), 35 (B-CH2, not directly observed, value ob-
1
tained from a H-13C HMQC experiment), 19.2 (CdCMe), 19.1
(MeCdC), 0.9 (SiMe3) ppm. Anal. Calcd for C52H46BF15FeN2-
Si2Zr: C, 52.13; H, 3.87; N, 2.34. Found: C, 52.40; H, 3.80, N,
2.28.
Rea ction of 2 w ith Sever a l Equ iva len ts of 2-Bu tyn e.
The reaction was set up in a manner identical with the
synthesis of 7, but approximately 5 equiv of 2-butyne was
used. The mixture was allowed to react for 24 h, at which point
the volatile fraction was removed under reduced pressure,
(33) SMART: Area-Detector Software Package; Siemens Industrial
Automation, Madison, WI, 1995.

Ferrocene-Based Polymerization Catalysts
Organometallics, Vol. 22, No. 3, 2003 575
least-squares refinement. An arbitrary hemisphere of data was
collected, and the raw data were integrated using SAINT.34
Cell dimensions reported in Table 1 were calculated from all
reflections with I > 10σ. Data were analyzed for agreement
and possible absorption using XPREP.35 An empirical absorp-
tion correction based on comparison of redundant and equiva-
lent reflections was applied using SADABS.36 The data were
corrected for Lorentz and polarization effects, but no correction
for crystal decay was applied. The structures were solved and
refined with the teXsan software package.37 All non-hydrogen
atoms were refined anisotropically, and the hydrogen atoms
were included as fixed contributions. ORTEP diagrams were
created using the ORTEP-3 software package.38
Ack n ow led gm en t. This work was sponsored by the
U.S. Department of Energy (Contract No. DE-AC03-
76SF00098). We thank Dr. Fred Hollander and Dr.
Allen Oliver for help with X-ray crystallography, Dr.
Garth Giesbrecht and Dr. Sarah Mullins for helpful
discussions, and Laura Anderson for invaluable help
with 2-D NOESY experiments. We also wish to thank
the reviewers for making valuable comments and sug-
gestions.
Su p p or tin g In for m a tion Ava ila ble: Text and tables
giving details of the X-ray crystallographic data for 2 and 8;
data are also available as an electronic file in CIF format. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(34) SAINT: SAX Area Detector Integration Program, V4.024;
Siemens Industrial Automation, Madison, WI, 1995.
(35) XPREP: Part of SHELXTL Crystal Structure Determination
Package, V5.03; Siemens Industrial Automation, Madison, WI, 1995.
(36) SADABS: Siemens Area Detector ABSorption Correction Pro-
gram; Siemens Industrial Automation, Madison, WI, 1996.
(37) TeXsan: Crystal Structure Analysis Software Package; Molec-
ular Structure Corp., The Woodlands, TX, 1992.
OM020780F
(38) Farrugia, L. J . J . Appl. Crystallogr. 1997, 30, 565.