Potential Group IV olefin polymerization catalysts that contain a diamido ligand substituted with hexaisopropylterphenyl groups

Article abstract of DOI:10.1016/j.poly.2005.09.005

The diamine rac-H₂[HIPTN₂] (HIPTN₂ = (N-hexa-iso-propyl-3,5-terphenyl)diaminobinaphthalene) has been prepared through palladium-catalyzed N-aryl coupling of diaminobinaphthalene and 3,5-bis(2,4,6-triisopropylphenyl)bromobenzene. The reaction between H ₂[HIPTN₂] and M(NMe₂)₄ (M = Ti, Zr, and Hf) yields [HIPTN₂] M(NMe₂)₂ complexes. Other complexes of [HIPTN₂]^2- that have been prepared include [HIPTN₂]ZrCl₂, [HIPTN₂]ZrMe ₂, [HIPTN₂]Zr(CH₂CMe₃)₂, [HIPTN₂]HfCl₂, [HIPTN₂]HfMe₂, and [HIPTN₂]Hf(CH₂CHMe₂)₂. Activation of [HIPTN₂]ZrMe₂ with a variety of Lewis acids gives rise to different species depending on the nature of the activator employed. For example, [HIPTN₂]ZrMe₂ reacts with [Ph₃C] [B(C₆F₅)₄] to give a cationic complex that is active toward oligomerization of 1-hexene, while activation with B(C ₆F₅)₃ leads to formation of [HIPTN ₂]Zr(C₆F₅)₂. No polymerization of 1-hexene by activated complexes was observed.

Full text of DOI:10.1016/j.poly.2005.09.005

Polyhedron 25 (2006) 469–476
www.elsevier.com/locate/poly
Potential Group IV olefin polymerization catalysts that contain a
diamido ligand substituted with hexaisopropylterphenyl groups
*
Zachary J. Tonzetich, Richard R. Schrock
Department of Chemistry, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
Received 26 August 2005; accepted 12 September 2005
Available online 27 October 2005
This paper is dedicated to Malcolm H. Chisholm on the occasion of his 60th birthday.
Abstract
The diamine rac-H2[HIPTN2] (HIPTN2 = (N-hexa-iso-propyl-3,5-terphenyl)diaminobinaphthalene) has been prepared through
palladium-catalyzed N-aryl coupling of diaminobinaphthalene and 3,5-bis(2,4,6-triisopropylphenyl)bromobenzene. The reaction
between H2[HIPTN2] and M(NMe2)4 (M = Ti, Zr, and Hf) yields [HIPTN2] M(NMe2)2 complexes. Other complexes of [HIPTN2]2ꢀ that
have been prepared include [HIPTN2]ZrCl2, [HIPTN2]ZrMe2, [HIPTN2]Zr(CH2CMe3)2, [HIPTN2]HfCl2, [HIPTN2]HfMe2, and
[HIPTN2]Hf(CH2CHMe2)2. Activation of [HIPTN2]ZrMe2 with a variety of Lewis acids gives rise to different species depending on
the nature of the activator employed. For example, [HIPTN2]ZrMe2 reacts with [Ph3C][B(C6F5)4] to give a cationic complex that is active
toward oligomerization of 1-hexene, while activation with B(C6F5)3 leads to formation of [HIPTN2]Zr(C6F5)2. No polymerization of
1-hexene by activated complexes was observed.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Olefin; Polymerization; Zirconium; Hafnium
1. Introduction
to prepare catalysts that effect both living and stereospecific
olefin polymerizations [13]. A binaphthyl-based ligand sys-
tem in which pyridine donors are incorporated has demon-
strated that six-coordinate dialkyl complexes of zirconium
and hafnium could be prepared and activated cleanly [14].
However, activated versions of these compounds do not
polymerize 1-hexene, presumably because the pyridine do-
nors prevent coordination of the olefin to the cationic me-
tal center. We felt that a potential remedy for this situation
might involve C2-symmetric amido complexes that lacked a
pendant donor moiety. Cationic complexes that contain
diamido ligands were among the first that were found to
exhibit living characteristics, as long as large aryl groups
(e.g., mesityl or 2,4,6-triisopropylphenyl) were present on
nitrogen [15,16].
The number of non-metallocene-based catalysts for the
polymerization of ordinary olefins has increased markedly
in the last decade [1]. Some of these catalysts offer activity
that is comparable to metallocene catalysts, and also in
some cases display characteristics of a living polymeriza-
tion [2]. Many of the most successful catalysts contain
nitrogen-based ligands, and examples of both early and late
metal catalysts are abundant. Amido ligands have been
found to be especially useful for preparing early transition
metal polymerization catalysts [3].
We have been interested in the synthesis of complexes
that contain new amido-based supporting ligands, particu-
larly those that when activated display characteristics of a
living olefin polymerization [4–12]. However, we have yet
In this paper, we report the preparation and Group IV
chemistry of complexes that contain a diamido ligand de-
rived from diaminobinaphthalene, one that is N-substi-
tuted with the bulky hexa-iso-propyl-3,5-terphenyl, or
HIPT, group. The HIPT group recently has been useful
*
Corresponding author. Tel.: +1 617 253 1596; fax: +1 617 253 7670.
E-mail address: rrs@mit.edu (R.R. Schrock).
0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.09.005

470
Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
as a substituent in triamidoamine ligands bound to molyb-
denum. Such species are catalysts for the catalytic reduc-
tion of dinitrogen to ammonia with protons and electrons
at a single Mo center [17–21]. The HIPT group is believed
to provide a significant degree of steric hindrance ‘‘at a dis-
tance’’ that leads to the success of catalytic dinitrogen
reduction.
of the methine protons of the triisopropylphenyl ring, indi-
cating that rotation about the aryl–aryl bond of the terphe-
nyl groups is not possible, but rotation about the N-aryl
bond is facile. Other features of the H NMR spectrum
are consistent with C2-symmetry and no rotation about
the aryl–aryl bond.
1
The ligand can be attached to Ti, Zr, or Hf readily upon
addition of it to M(NMe2)4 (Scheme 1). In the case of
hafnium and zirconium, the parent diamine reacts with
M(NMe2)4 in pentane at room temperature to yield
[HIPTN2]M(NMe2)2 as yellow microcrystals after 24 h.
The titanium complex is somewhat more difficult to pre-
pare, requiring elevated temperatures and significantly
longer reaction time to go to completion. Heating
H2[HIPTN2] and Ti(NMe2)4 in toluene at 110 °C for 6 days
2. Results and discussion
2.1. Synthesis of the ligand and Group IV complexes that
contain it
The parent diamine, rac-H2[HIPTN2], was prepared
through a palladium-catalyzed N-aryl coupling between
rac-diaminobinaphthalene and 3,5-bis(2,4,6-triisopropyl-
phenyl)bromobenzene (HIPTBr). Using the XPHOS [22] li-
gand, the reaction is complete in less than 4 h, and can be
scaled up to 15 g with yields of >80% after purification by
flash chromatography (Eq. (1)).
1
affords [HIPTN2]Ti(NMe2)2 as an orange solid. The H
NMR spectra of the dimethylamido complexes are similar,
and all show the expected C2-symmetry. A large singlet of
area 12 near 2.7 ppm is assigned to the NMe2 protons.
The sharp resonances suggest that rotation about the
Pd2(dba)3
XPHOS
NaO-t-Bu
H2N
+
rac-H2[HIPTN2]
rac
2
ð1Þ
toluene, 90ºC 4 hrs.
NH2
Br
White, crystalline H2[HIPTN2] is readily soluble in all or-
ganic solvents including pentane and diethyl ether. The
NMR spectrum contains three septets of area 4 for each
metal–nitrogen bond is fast on the NMR time scale at
room temperature, as is typically observed for early transi-
tion metal dimethylamido complexes.
N
NMe2
M
M(NMe2)4
H2[HIPTN2]
NMe2
pentane or
toluene
N
M = Ti, orange
= Zr, yellow
= Hf, yellow
Scheme 1.

Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
471
Treatment of [HIPTN2]M(NMe2)2 (M = Zr, Hf) with
two equivalents of Me3SiCl in benzene at 60 °C affords
[HIPTN2]MCl2. Proton NMR spectra of the yellow haf-
nium species show the expected sharp features of the ligand
in a C2-symmetric environment. However, proton spectra
of the zirconium species reveal relatively broad resonances.
The zirconium dichloride complex is deep red, but its solu-
tions in diethyl ether are orange-yellow. Proton NMR
spectra of samples recrystallized from diethyl ether show
a broad peak for two equivalents of diethyl ether near
3.70 ppm. Combustion analyses of the Zr compound were
also consistent with the presence of two molecules of
diethyl ether. We suggest that a dynamic mixture of mono-
mer and dimer exists in the zirconium case at room temper-
ature, which gives rise to a broadened spectrum. Dimers of
this type have been structurally characterized in the zirco-
nium chemistry of diamidodonor ligands [9].
according to NMR spectra. These results are similar to
those found in the titanium chemistry of a related diamid-
odonor ligand [23].
Alkylation of ‘‘[HIPTN2]MCl2’’ (M = Zr, Hf) yielded
[HIPTN2]MR2 complexes (R = Me, CH2CMe3, CH2CHMe2;
Scheme 2). The dialkyl species are all yellow solids which
are readily soluble in common organic solvents, including
pentane. Proton NMR spectra are consistent with mono-
meric C2-symmetric species with resonances for the alkyl li-
gands appearing in a range typically encountered for d0
alkyl complexes of hafnium and zirconium (Table 1). At-
tempts to grow X-ray quality crystals of dialkyl complexes
were unsuccessful, leading in each case to small needle-like
crystals or amorphous solids.
2.2. Activation of dialkyl species
Attempts to prepare [HIPTN2]TiCl2 were unsuccessful.
Heating solutions of [HIPTN2]Ti(NMe2)2 with excess
Me3SiCl for several days resulted only in formation of
[HIPTN2]Ti(NMe2)Cl, according to H NMR spectra. A
reaction between [HIPTN2]Ti(NMe2)2 and TMSOSO2CF3
also resulted in formation of only [HIPTN2]Ti(NMe2)(OTf),
Activation of [HIPTN2]ZrMe2 was attempted with
B(C6F5)3, [Ph3C][B(C6F5)4], and [HNMe2Ph][B(C6F5)4]
with the aim of preparing a cationic monomethyl species.
Reaction of [HIPTN2]ZrMe2 with B(C6F5)3 in C6D6
yielded a deep red solution, a proton NMR spectrum of
which showed it to contain a C2-symmetric species,
1
N
RMgX
[HIPTN2]MCl2
Et2O
R
M
R
M = Zr; R = Me, CH2CMe3
= Hf; R = Me, CH2CHMe2
N
Scheme 2.
Table 1
Selected NMR data for the alkyl ligands of complexes of [HIPTN2]2ꢀ
Compound
1H NMR
13C NMR
[HIPTN2]ZrMe2
0.60a
53.17c
51.95b
{[HIPTN2]Zr(Me)(NMe2Ph)}+
{[HIPTN2]Zr(Me)}+
0.73b
0.42b (major); 0.64 (minor)
47.51b (major); 49.76 (minor)
[HIPTN2]Zr(C6F5)2
N/A
148.52c (o); 146.11 (ipso); 142.71 (p); 136.48 (m)
99.91c (CH2); 37.24 (CMe3); 34.76 (Me)
63.16c
[HIPTN2]Zr(CH2CMe3)2
[HIPTN2]HfMe2
{[HIPTN2]Hf(Me)(NMe2Ph)}+
{[HIPTN2]Hf(Me)}+
1.60a, 1.11 (CH2); 0.91 (Me)
0.46a
0.49b
0.66b
[HIPTN2]Hf(CH2CHMe2)2
2.25a (CH); 0.97, 0.85 (CH2); 0.81, 0.63 (Me)
98.11c (CH2)
c
Measured in aC6D6, bC6D5Br, CD2Cl2.

472
Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
although no resonance could be found that could be as-
signed to a methyl group. Examination of the 19F NMR
spectrum of the product showed that the expected
[MeB(C6F5)3]ꢀ anion was not present, although one major
species appeared to be present. Activation of the 13C la-
mer is observed. Not surprisingly, addition of 1-hexene to
{[HIPTN2]Zr(Me)(NMe2Ph)}[B(C6F5)4] yielded no poly-
mer, even at 60 °C, presumably as a consequence of tight
binding of dimethylaniline.
Reaction of [HIPTN2]ZrMe2 with [Ph3C][B(C6F5)4] in
bromobenzene-d5 at ꢀ10 °C over a period of 20–30 min
1
beled derivative gave identical H and 19F NMR spectra
1
to those obtained upon activation of the unlabeled com-
pound. The 13C NMR spectrum was more enlightening,
showing only a very broad resonance at 17 ppm in bromo-
benzene-d5 assignable to the 13CH3 groups. The appear-
ance and chemical shift of these methyl resonances points
to a species with both methyl groups bound to boron.
Decomposition of the [MeB(C6F5)3]ꢀ anion by C6F5 trans-
fer to the metal is a documented reaction pathway for
Group IV methyl cations [24–26]. Such a decomposition
would explain the presence of a C2-symmetric species,
which we believe to be [HIPTN2]Zr(C6F5)2, and one equiv-
alent of Me2B(C6F5) (Eq. (2)). A double exchange of
methyl for pentafluorophenyl is more rare than a single ex-
change and may be due to the highly electron deficient nat-
ure of the metal center and its relatively open
yielded a dark red solution whose H and 13C NMR spec-
tra were consistent with formation of an asymmetric
monomethyl cation. When a full equivalent of trityl was
employed, two similar species were formed in a roughly
1:1 ratio. The two compounds have nearly identical
NMR spectra, which suggests that they may be diastereo-
mers (Table 1). The two species do not grow in at the same
rate; one is formed before all [HIPTN2]ZrMe2 is consumed,
while the other grows in as [HIPTN2]ZrMe2 reacts with the
remaining trityl. The dimethyl species therefore may play a
role in conversion of one diastereomer to the other.
Activation of dimethyl species with trityl has been
shown to produce monocationic dimers through capture
of the monomethyl cation by unreacted dimethyl species
[27,28]. In order to test the likelihood of dimer formation
upon activation of [HIPTN2]ZrMe2, activation was carried
out with 0.5 equivalents of trityl. Proton NMR spectra
from this reaction show a 1:1 ratio of starting material to
one of the diastereomers observed above, indicating that
monocationic dimeric species probably are not present.
½HIPTN2ꢁZrMe2 þ BðC6F5Þ3ꢀ! ½ HIPTN2ꢁZrðC6F5Þ2
þ Me2BðC6F5Þ
ð2Þ
architecture. This reaction can be used on larger scales to
prepare [HIPTN2]Zr(C6F5)2 in good yield. Proton, carbon,
and fluorine NMR spectra, as well as combustion analysis
of the recrystallized material are all consistent with the
product being [HIPTN2]Zr(C6F5)2; NMR spectra are also
all identical to those obtained in NMR scale activation
experiments. Attempts to polymerize 1-hexene by a cationic
species that may be formed transiently upon activation of
[HIPTN2] ZrMe2 with B(C6F5)3 were unsuccessful, even
when the reaction was conducted in neat 1-hexene at
ꢀ30 °C. This result contrasts with that obtained by McCon-
ville for a titanium diamido catalyst where decomposition of
the [MeB(C6F5)3]ꢀ anion could be avoided by conducting
polymerization experiments in neat 1-hexene [25].
1
The JC–H coupling constants of 120 Hz for the methyl
groups in each diastereomer also argue in favor of mono-
meric species. At this stage, we can only suggest that rela-
tively strong ion pairing is the origin of two different
species being observable in NMR spectra.
Solutions of [HIPTN2]ZrMe2 activated with trityl react
instantly and exothermically with several equivalents of
1-hexene at ꢀ30 °C. Examination of these reactions by
13C and 1H NMR revealed that the 1-hexene had been oli-
gomerized, not polymerized. The NMR spectrum, which is
similar to that found with the [(MesN-o-C6H4)2O]2ꢀ ligand
system, suggests that chain termination by b-H elimination
(from either the 1,2 or especially a 2,1 insertion product) is
facile [29–31]. The relatively open environment at the metal
may not allow effective discrimination between 1,2 and 2,1
olefin insertion, thereby leading to an enhanced proclivity
towards b-H elimination [29–31].
The reaction between [HIPTN2]ZrMe2 and [HNMe2Ph]
[B(C6F5)4] in bromobenzene-d5 proceeded as anticipated
with elimination of methane and formation of a dimethy-
laniline adduct of the monomethyl cation, as shown in
Eq. (3). The activation required several hours at
Activation of the [HIPTN2]HfMe2 species with the three
activators discussed above yielded results that are essen-
tially identical to those observed with zirconium (see
Section 4). Interestingly, the [HIPTN2]Hf(C6F5)2 formed
by reaction with B(C6F5)3 we believe to be the first such
compound of hafnium to be formed by aryl transfer from
boron. The [HIPTN2]Hf(CH2CHMe2)2 species showed
similar behavior to the dimethyl species when activated
with [Ph3C][B(C6F5)4] and [HNMe2Ph][B(C6F5)4]. Unlike
the methyl species, however, the isobutyl complex did not
undergo exchange with B(C6F5)3, but rather reacted slowly
to give an asymmetric Hf species and isobutene as judged
½HIPTN2ꢁZrMe2 þ ½HNMe2Phꢁ½BðC6F5Þ4ꢁ
ꢀCH4
ꢀ! f½HIPTN2ꢁZrðMeÞðNMe2PhÞgfBðC6F5Þ4g
ð3Þ
room temperature to go to completion, perhaps as a conse-
quence of the limited solubility of [HNMe2Ph][B(C6F5)4]
in bromobenzene. Proton and carbon NMR spectra are
both consistent with the product being asymmetric and
containing one methyl group. Two singlet resonances are
found for the Me groups of dimethylaniline in the 1H
NMR spectrum, consistent with it being tightly bound.
The low coordination number of (formally) a three-coordi-
nate and sterically accessible metal in the cation apparently
allows tight binding of dimethylaniline. Only one diastereo-
1
by H NMR. This asymmetric species could not be identi-
fied positively as the isobutyl cation, but the fact that it did

Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
473
not react with 1-hexene at room temperature to yield poly-
mer or oligomer argues against it being the isobutyl cation.
The dineopentyl zirconium species was also examined as
an initiator. The complex did not react readily with
B(C6F5)3, and it reacted only very slowly with the other
two activators to give products which could not be identi-
fied by NMR spectroscopy.
ment Facility, and elemental analyses were performed by
H. Kolbe Microanalytics Laboratory, Mulheim de Ruhr,
¨
Germany.
2,20-Diamino-1,10-binaphthalene,
3,5-bis(2,4,6-triiso-
propylphenyl)bromobenzene, Ti(NMe2)4, Zr(NMe2)4, and
Hf(NMe2)4 [32] were prepared according to published pro-
cedures, or slightly modified versions thereof. Me3SiCl,
iso-BuMgBr, and MeMgBr were purchased from Aldrich
Chemical Co. and used as received. Tris(pentafluorophe-
3. Conclusions
nyl)borane,
trimethylsilyl
trifluoromethanesulfonate
Complexes that contain the [HIPTN2]2ꢀ ligand appear
to be similar in some ways to other early transition metal
polymerization catalysts that contain diamido supporting
ligands. Unfortunately, the ‘‘steric hindrance at a dis-
tance’’ that is provided by the HIPT substituents is not
sufficient to stabilize pseudo three-coordinate cations
against various decomposition reactions, and only oligo-
merization of 1-hexene was observed as a consequence
of insufficient steric protection close to the metal. We con-
clude that although three HIPT substituents on amido
nitrogens provides a significant amount of steric protec-
tion in five-coordinate complexes that contain a triamido-
amine ligand [17–21], only two HIPT substituents cannot
counteract the consequences of an inherently open archi-
tecture in a diamido alkyl metal cation.
(TMSOTf), Pd2(dba)3, and XPHOS were purchased from
Strem Chemical Co. and used as received. Trityl tetra-
kis(pentafluorophenyl)borate, {Ph3C}[{B(C6F5)4}], was
obtained as a gift from the Exxon Mobile Corp. and used
as received.
H2[HIPTN2]. A 500 mL Schlenk flask was charged
with 3.97 g (14.0 mmol) of 2,20-diamino-1,10-binaphtha-
lene, 17.15 g (30.5 mmol) of 3,5-bis(2,4,6-triisopropylphe-
nyl)bromobenzene, 4.30 g (44.7 mmol) of NaO-t-Bu, and
300 mL of toluene. To the mixture was added a solution
of 0.130 g (1 mol%) of Pd2(dba)3 and 0.138 g (2 mol%) of
XPHOS dissolved in 5 mL of toluene. The resulting mix-
ture was stirred at 90 °C for 5 h during which time the mix-
ture became brown and a large amount of precipitate had
formed. The mixture was filtered through celite and the
volatiles were removed from the filtrate in vacuo. The
brown residue was dissolved in a minimal amount of pen-
tane and left to stand overnight. The compound precipi-
tated as a white crystalline solid over a period of 18 h.
The remaining mother liquor was purified by flash chroma-
tography on silica gel eluting with 20% toluene in pentane.
The pooled column fractions were evaporated to dryness
in vacuo leaving a white solid; total yield 13.04 g (75%):
1H NMR (CD2Cl2) d 7.87 (d, 2 BINAPH), 7.82 (d, 2
BINAPH), 7.77 (d, 2 BINAPH), 7.26 (t, 2 BINAPH),
7.15 (t, 2 BINAPH), 7.09 (d, 2 BINAPH), 7.00 (app d, 8
m-H), 6.80 (s, 4 o-H), 6.56 (s, 2 p-H), 5.73 (s, 2 NH),
2.89 (sep, 4 p-CHMe2), 2.73 (m, 8 o-CHMe2), 1.26 (d, 24
p-CHMe2), 1.09 (d, 12 o-CHMe2), 1.03 (app q, 36 o-
CHMe2); 13C{1H} NMR (CD2Cl2) d 148.59, 147.06,
142.45, 142.25, 141.54, 137.26, 134.41, 130.18, 129.98,
128.78, 127.47, 126.31, 124.63, 123.99, 120.98, 120.43,
118.45, 116.85, 34.93, 30.96, 24.84, 24.50, 24.48, 24.41;
HRMS Calc. [M + H]+ 1245.8898. Found [M + H]+
1245.8889. Anal. Calc. for C92H112N2: C, 88.69; H, 9.06;
N, 2.25. Found: C, 88.62; H, 8.94; N, 2.17%.
4. Experimental
General comments. All manipulations of air- and mois-
ture-sensitive materials were performed in oven-dried
(200 °C) glassware under an atmosphere of nitrogen on
a dual-manifold Schlenk line or in a Vacuum Atmospheres
glovebox. NMR experiments were carried out in Teflon-
valve sealed J. Young-type NMR tubes. HPLC grade or-
ganic solvents were sparged with nitrogen and dried by
passage through activated alumina (for diethyl ether, tol-
uene, pentane, THF, and methylene chloride) followed
by passage through Q-5 supported copper catalyst (for
˚
benzene) prior to use then stored over 4 A Linde-type
molecular sieves. Benzene-d6, toluene-d8, and THF-d8
were dried over sodium/benzophenone ketyl and vac-
uum-distilled. Methylene chloride-d2 and bromobenzene-
d5 were dried over CaH2, vacuum distilled and stored over
˚
4 A Linde-type molecular sieves. NMR spectra were re-
corded on a Varian 500 or Varian 300 spectrometer.
1
Chemical shifts for H and 13C spectra were referenced
1
to the residual H/13C resonances of the deuterated sol-
[HIPTN2]Ti(NMe2)2. A sealable Schlenk vessel was
charged with 1.145 g (0.919 mmol) of H2[HIPTN2],
0.21 g (0.94 mmol) of Ti(NMe2)4, and 30 mL of toluene.
The sealed vessel was heated at 110 °C for 6 days during
which time the solution became bright red-orange. The
toluene was removed in vacuo and the residue was crys-
tallized from a minimal amount of pentane at ꢀ25 °C.
vent (1H: C6D6, d 7.16; C6D5CD3, d 2.15; CD2Cl2,
d 5.32; C6D5Br, d 7.29. 13C: C6D6, d 128.32; C6D5Br, d
121.19) and are reported as parts per million relative to
tetramethylsilane. 19F NMR spectra were referenced exter-
nally to fluorobenzene (d ꢀ113.15 ppm relative to CFCl3).
In the following discussion of NMR shifts, BINAP refers
to protons on the binaphthyl rings, whereas o, m, and p
refer to the aryl positions of the terphenyl substituent.
High-resolution mass spectrometry measurements were
performed at the MIT Department of Chemistry Instru-
1
Yield: 0.733 g (58%). H NMR (C6D6) d 7.73 (app s, 4
BINAPH), 7.47 (d, 2 BINAPH), 7.20 (s, 4 m-H), 7.19
(s, 4 m-H), 7.03 (d, 2 BINAPH), 7.02 (s, 4 o-H), 6.98
(t, 2 BINAPH), 6.56 (s, 2 p-H), 6.54 (t, 2 BINAPH),

474
Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
3.15 (sep, 4 o-CHMe2), 3.07 (sep, 4 o-CHMe2), 2.87 (sep,
4 p-CHMe2), 2.85 (s, 6 N Me2), 1.30 (m, 48 CHMe2),
1.21 (d, 12 CHMe2), 1.08 (d, 12 CHMe2). Anal. Calc.
for C96H122N4Ti: C, 83.56; H, 8.91; N, 4.06. Found: C,
83.37; H, 9.06; N, 3.94%.
125.27, 124.92, 123.90, 121.05, 121.01, 119.29, 53.17
(Me), 34.90 (p-CHMe2), 31.07 (o-CHMe2), 31.01 (o-
CHMe2), 24.87, 24.76, 24.69, 24.61, 24.49, 24.47. Anal.
Calc. for C94H116N2Zr: C, 82.70; H, 8.56; N, 2.05.
Found: C, 82.59; H, 8.50; N, 1.96%.
[HIPTN2]Zr(NMe2)2. A round bottom flask was
charged with 6.269 g (5.03 mmol) of H2[HIPTN2], 1.278 g
(4.78 mmol) of Zr(NMe2)4, and 60 mL of pentane. The
reaction was allowed to stir for 2 days at room temperature
during which time it became bright yellow. The solution
was set aside at ꢀ25 °C from which the compound crystal-
lized as yellow microcrystals. Yield: 5.538 g (82%). 1H
NMR (C6D6) d 7.92 (d, 2 BINAPH), 7.75 (d, 2 BINAPH),
7.41 (d, 2 BINAPH), 7.22 (s, 4 m-H), 7.21 (s, 4 m-H), 7.16
(s, 4 o-H), 7.08 (d, 2 BINAPH), 6.94 (t, 2 BINAPH), 6.60
(t, 2 BINAPH), 6.57 (s, 2 p-H), 3.15 (m, 8 o-CHMe2), 2.65
(s, 12 N Me2), 2.87 (sep, 4 p-CHMe2), 2.64 (s, 12 N Me2),
1.27 (m, 60 CHMe2), 1.18 (d, 12 o-CHMe2). Anal. Calc. for
C96H122N4Zr: C, 78.16; H, 8.40; N, 1.82. Found: C, 77.96;
H, 8.31; N, 1.75%.
[HIPTN2]Zr(13CH3)2 was prepared similarly from
1
13CH3MgI: 13C NMR (C6D6) d 54.50 (q, CH3, JC–H
=
115 Hz).
[HIPTN2]Zr(CH2CMe3)2. This complex was prepared
fashion analogous to that used to prepare
in
a
[HIPTN2]ZrMe2 starting from 0.584 g (0.376 mmol) of
[HIPTN2]ZrCl2(Et2O)2 and 0.54 mL (0.86 mmol) of
Me3CCH2MgCl (1.6 M in Et2O). The pentane extract
was evaporated to dryness to give the complex as a yellow
1
solid. Yield: 0.538 g (88%). H NMR (C6D6) d 7.86 (d, 2
BINAPH), 7.80 (s, 2 BINAPH), 7.44 (s, 4 o-H), 7.36 (d,
2 BINAPH), 7.21 (s, 4 m-H), 7.20 (s, 4 m-H), 6.89 (m, 4 BI-
NAPH), 6.64 (s, 2 p-H), 6.39 (t, 2 BINAPH), 3.16 (sep, 4 o-
CHMe2), 3.08 (sep, 4 o-CHMe2), 2.86 (sep, 4 p-CHMe2),
2
1.60 (d, 2 CH2CMe3, JH–H = 12.5 Hz), 1.34 (d, 12
[HIPTN2]ZrCl2(Et2O)2. A sealable Schlenk vessel was
charged with 5.532 g (3.89 mmol) of [HIPTN2]Zr(NMe2)2,
1.0 mL (8.1 mmol) of Me3SiCl, and 70 mL of benzene. The
reaction was stirred at 70 °C for 18 h during which time it
became deep red. The benzene was removed in vacuo and
the residue crystallized from diethyl ether at ꢀ25 °C. At-
tempts at crystallizing the compound from pentane were
unsuccessful. The 1H NMR spectrum of the orange-yellow
compound was very broad and difficult to interpret with a
peak assignable to ꢂ2 equivalents of coordinated diethyl
CHMe2), 1.27 (m, 36 CHMe2), 1.22 (d, 12 CHMe2), 1.17
(d, 12 CHMe2), 1.11 (d, 2 CH2CMe3), 0.91 (s, 18 CH2C
Me3); 13C{1H} (CD2Cl2) d 151.69, 148.35, 147.19, 147.15,
142.13, 139.29, 137.69, 135.19, 132.36, 131.59, 128.38,
127.68, 127.20, 126.55, 125.78, 125.55, 124.69, 120.90,
120.85, 120.50, 99.91 (CH2CMe3), 37.24 (CMe3), 34.88
(p-CHMe2), 34.76 (C Me3), 30.94 (o-CHMe2), 30.82 (o-
CHMe2), 25.02, 24.91, 24.85, 24.64, 24.47, 24.46 (CHMe2).
Anal. Calc. for C102H132N2Zr: C, 82.92; H, 9.01; N, 1.90.
Found: C, 82.84; H, 8.96; N, 1.86%.
1
ether (see text). Yield: 3.640 g (67%). H NMR (C6D6) all
[HIPTN2]Zr(C6F5)2. A flask was charged with
peaks very broad d 7.62, 7.37, 7.27, 7.16, 6.98, 6.85, 6.60,
6.38, 3.70 (Et2O), 2.97 (CHMe2), 2.87 (CHMe2), 1.36–
1.10 (CHMe2), 1.01, 0.72. Anal. Calc. for C100H130N2-
Cl2O2Zr: C, 77.28; H, 8.43; N, 1.80; Cl, 4.56. Found: C,
76.94; H, 8.12; N, 1.90; Cl, 4.75%.
0.343 g (0.251 mmol) of [HIPTN2]ZrMe2 and dissolved
in 30 mL of pentane. The yellow solution was chilled
to ꢀ25 °C at which point 0.135 g (0.264 mmol) of
B(C6F5)3 was added as a solid. The solution immediately
became bright orange upon addition of borane. The or-
ange solution was stirred at room temperature for
60 min and then evaporated to dryness. The orange res-
idue was crystallized from hot hexane. Yield: 0.318 g
(76%). 1H NMR (C6D6) d 7.65 (d, 2 BINAPH), 7.41
(d, 2 BINAPH), 7.26 (d, 2 BINAPH), 7.16 (s, 4 o-H),
7.12 (s, 4 m-H), 7.11 (s, 4 m-H), 7.00 (t, 2 BINAPH),
6.84 (d, 2 BINAPH), 6.69 (s, 2 p-H), 6.51 (t, 2 BI-
NAPH), 2.92 (m, 8 o-CHMe2), 2.79 (sep, 4 p-CHMe2),
1.22 (d, 24 p-CHMe2), 1.15 (m, 36 o-CHMe2), 1.07 (d,
[HIPTN2]ZrMe2. A flask was charged with 2.005 g
(1.43 mmol) of [HIPTN2]ZrCl2 (Et2O)2 and dissolved in
40 mL of diethyl ether. The solution was chilled to
ꢀ25 °C at which point 0.91 mL (2.9 mmol) of MeMgBr
(3.15 M in Et2O) was added dropwise. The reaction mix-
ture was allowed to stir at room temperature for 60 min
during which time the solution changed from orange to
yellow, and a precipitate formed. The ether was removed
in vacuo and the residue extracted with pentane and fil-
tered through celite. The pentane solution was concen-
trated to ꢂ5 mL and set aside at ꢀ25 °C for several
days. The complex crystallized as a yellow solid in sev-
eral crops. Yield: 1.514 g (78%). 1H NMR (C6D6) d
7.84 (d, 2 BINAPH), 7.59 (d, 2 BINAPH), 7.47 (s, 4
o-H), 7.26 (d, 2 BINAPH), 7.24 (s, 4 m-H), 7.22 (s, 4
m-H), 6.96 (d, 2 BINAPH), 6.90 (t, 2 BINAPH), 6.71
(s, 2 p-H), 6.57 (t, 2 BINAPH), 3.13 (m, 8 o-CHMe2),
2.88 (sep, 4 p-CHMe2), 1.28 (m, 60 CHMe2), 1.17 (d,
12 o-CHMe2), 0.60 (s, 6 CH3); 13C{1H} NMR (CD2Cl2)
d 150.58, 148.53, 147.17, 147.16, 142.57, 138.31, 137.55,
135.05, 133.09, 131.63, 128.61, 128.00, 126.72, 125.98,
12 o-CHMe2); 13C{1H} NMR (CD2Cl2)
d 148.72,
1
148.71, 148.52 (dd, o-CF, JC–F = 228 Hz), 147.07,
146.83, 146.11 (t, Cipso,
2JC–F = 65 Hz), 142.99, 142.71
1
(d, p-CF, JC–F = 257 Hz), 137.52, 136.90, 136.48 (d,
m-CF, JC–F = 261 Hz), 135.03, 133.16, 132.58, 128.53,
1
128.47, 127.78, 127.70, 127.17, 126.71, 125.55, 120.95,
120.84, 119.71, 34.92 (p-CHMe2), 30.97 (o-CHMe2),
30.86 (o-CHMe2), 24.65, 24.47, 24.43, 24.39, 24.28,
24.10; 19F NMR (C6D6) d ꢀ124.12 (d, 4 o-F), ꢀ148.80
(t, 2 p-F), ꢀ159.10 (t, 4 m-F). Anal. Calc. for C104H110
-
N2F10 Zr: C, 74.83; H, 6.64; N, 1.68. Found: C, 74.91;
H, 6.73; N, 1.66%.

Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
475
[HIPTN2]Hf(NMe2)2. This complex was prepared in a
manner strictly analogous to that used to prepare
[HIPTN2]Zr(NMe2)2 starting from 4.092 g (3.28 mmol) of
H2[HIPTN2] and 1.189 g (3.35 mmol) of Hf(NMe2)4. Yield:
2.87 (sep, 4 p-CHMe2), 2.25 (sep, 2 CH2CHMe2), 1.33 (d,
6 CHMe2), 0.97 (dd, 2 CH2CHMe2), 0.85 (dd, 2 CH2CH-
Me2), 0.81 (d, 6 CH2CHMe2), 0.63 (d, 6 CH2CHMe2).
13C{1H} NMR (CD2Cl2) d 151.19, 148.42, 147.19, 147.14,
142.31, 138.47, 137.72, 135.22, 132.69, 131.62, 128.45,
127.79, 127.04, 126.06, 125.81, 125.25, 125.12, 120.95,
120.91, 120.27, 98.11 (CH2CHMe2), 34.91 (p-CHMe2),
30.98 (o-CHMe2), 30.90 (o-CHMe2), 29.87, 28.98, 28.20,
24.91, 24.81, 24.74, 24.72, 24.51, 24.48. Anal. Calc. for
1
3.635 g (71%). H NMR (C6D6) d 7.90 (d, 2 BINAPH),
7.75 (d, 2 BINAPH), 7.41 (d, 2 BINAPH), 7.21 (s, 4 m-
H), 7.20 (s, 4 m-H), 7.18 (s, 4 o-H), 7.04 (d, 2 BINAPH),
6.95 (t, 2 BINAPH), 6.56 (m, 2 p-H/2 BINAPH), 3.13 (m
8 o-CHMe2), 2.87 (sep, 4 p-CHMe2), 2.70 (s, 12 N Me2),
1.27 (m, 60 CHMe2), 1.15 (d, 12 CHMe2). Anal. Calc. for
C96H122N4Hf: C, 76.33; H, 8.14; N, 3.71. Found: C,
76.25; H, 8.05; N, 3.57%.
C100H128N2Hf: C, 78.16; H, 8.40; N, 1.82. Found: C,
77.96; H, 8.31; N, 1.75%.
Activation experiments. Activation of [HIPTN2]ZrMe2
and [HIPTN2]Zr(13CH3)2 were conducted as follows. Equi-
molar amounts of the complex and activator were dis-
solved in ꢂ0.4 mL of bromobenzene-d5. The solutions
were cooled to ꢀ30 °C, at which point they were mixed
and quickly transferred to the J-Young tube. The NMR
data of the activated zirconium species are listed below.
[HIPTN2]HfCl2. This complex was prepared in a man-
ner similar to that used to prepare [HIPTN2]ZrCl2 starting
from 3.02 g (2.00 mmol) of [HIPTN2] Hf(NMe2)2 and
0.53 mL (4.2 mmol) of Me3SiCl. The reaction solution re-
mained yellow after heating in contrast to the Zr complex.
All volatiles were removed in vacuo giving a yellow solid.
Yield: 2.90 g (97%). 1H NMR (C6D6) d 7.64 (d, 2 BI-
NAPH), 7.49 (d, 2 BINAPH), 7.34 (s, 4 o-H), 7.16 (m, 2 BI-
NAPH/8 m-H), 6.87 (m, 4 BINAPH), 6.63 (s, 2 p-H), 6.50
(t, 2 BINAPH), 2.98 (m, 8 o-CHMe2), 2.82 (sep, 4 p-
CHMe2), 1.20 (m, 60 CHMe2), 1.11 (d, 12 o-CHMe2).
Anal. Calc. for C92H110N2Cl2Hf: C, 74.00; H, 7.42; N,
1.88; Cl, 4.75. Found: C, 73.85; H, 7.51; N, 1.83; Cl, 4.77%.
[HIPTN2]HfMe2. A flask was charged with 1.138 g
(0.762 mmol) of [HIPTN2]HfCl2 and dissolved in 20 mL
of diethyl ether. The solution was chilled to ꢀ25 °C at
which point 0.47 mL (1.6 mmol) of MeMgBr (3.3 M in
Et2O) was added dropwise. The reaction mixture was al-
lowed to stir at room temperature for 60 min during which
time a precipitate formed. The ether was removed in vacuo
and the residue extracted with pentane and filtered through
celite. The pentane solution was evaporated to dryness
yielding a yellow solid. Yield: 0.978 g (88%). 1H NMR
(C6D6) d 7.83 (d, 2 BINAPH), 7.60 (d, 2 BINAPH), 7.42
(s, 4 o-H), 7.28 (d, 2 BINAPH), 7.23 (s, 4 m-H), 7.21 (s,
4 m-H), 6.96 (d, 2 BINAPH), 6.92 (t, 2 BINAPH), 6.68
(s, 2 p-H), 6.55 (t, 2 BINAPH), 3.12 (m, 8 o-CHMe2),
2.88 (sep, 4 p-CHMe2), 1.30–1.20 (m, 72 CHMe2), 0.46
(s, 6 CH3). 13C{1H} NMR (CD2Cl2) d 150.74, 148.52,
147.19, 147.16, 142.53, 137.82, 137.61, 135.05, 133.10,
131.65, 128.61, 127.98, 126.81, 126.00, 125.40, 125.21,
124.64, 121.05, 121.01, 119.58, 63.16 (Me), 34.92 (p-
CHMe2), 31.05 (o-CHMe2), 31.00 (o-CHMe2), 24.88,
24.77, 24.69, 24.63, 24.51, 24.48. Anal. Calc. for
C94H116N2Hf: C, 77.73; H, 8.05; N, 1.93. Found: C,
77.62; H, 8.15; N, 1.87%.
1
{[HIPTN2]Zr(Me)(NMe2Ph)}{B(C6F5)4}. H NMR
(C6D5Br) d 8.17 (d, 1 ArH), 7.87 (d, 1 ArH), 7.80 (d, 1
ArH), 7.77 (d, 2 ArH), 7.75 (t, 1 ArH), 7.69 (d, 1 ArH),
7.34 (t, 1 ArH), 7.23 (s, 2 ArH), 7.21 (s, 2 ArH), 7.19 (s,
2 ArH), 7.15 (s, 2 ArH), 7.05–6.85 (m, 7 ArH), 6.77 (s, 2
ArH), 6.68 (t, 1 ArH), 6.62 (m, 4 ArH), 6.43 (t, 1 ArH),
3.01–2.79 (m, 12 CHMe2), 2.21 (br s, 3 Me2NPh), 1.47
(br s, 3 Me2NPh), 1.35–1.12 (m, 72 CHMe2), 0.53 (s, 3 Me).
{[HIPTN2]Zr(Me)}{B(C6F5)4} (minor isomer only).
1H NMR (C6D5Br) d 8.15 (d, 1 ArH), 7.78 (t, 2 ArH),
7.66 (d, 1 ArH), 7.21–6.98 (m, 32 ArH), 6.81 (m, 3 ArH),
6.73 (m, 2 ArH), 2.91 (m, 6 CHMe2), 2.81 (m, CHMe2),
2.03 (s, 3 Ph3CCH3), 1.32–1.12 (m, 72 CHMe2), 0.43 (s, 3
Me); 13C NMR (C6D5Br) d 49.76 (Me, minor isomer,
1
1JC–H = 120 Hz), 47.51 (Me, major isomer, JC–H
=
120 Hz).
[HIPTN2]Hf(C6F5)2. 1H NMR (C6D6) d 7.68 (d, 2 BI-
NAPH), 7.45 (d, 2 BINAPH), 7.31 (d, 2 BINAPH), 7.16 (s,
4 o-H), 7.13 (s, 4 m-H), 7.12 (s, 4m-H), 7.01 (t, 2 BINAPH),
6.85 (d, 2 BINAPH), 6.69 (s, 2 p-H), 6.51 (t, 2 BINAPH),
2.94 (m, 8 o-CHMe2), 2.82 (sep, 4 p-CHMe2), 1.25 (d, 24 p-
CHMe2), 1.18 (m, 36 o-CHMe2), 1.06 (d, 12 o-CHMe2). 19
F
NMR (C6D6) d ꢀ122.85 (br s, 4 o-F), ꢀ148.33 (br s, 2 p-F),
ꢀ159.03 (br s, 4 m-F).
1
{[HIPTN2]Hf(Me)(NMe2Ph)}{B(C6F5)4}. H NMR
(C6D5Br) d 8.18 (d, 1 ArH), 7.82 (d, 1 ArH), 7.77 (d, 1
ArH), 7.72 (d, 1 ArH), 7.36 (d, 1 ArH), 7.22–7.14 (m, 10
ArH), 7.01 (m, 3 ArH), 6.93 (d, 1 ArH), 6.91 (s, 2 ArH),
6.85 (t, 1 ArH), 6.83 (s, 2 ArH), 6.71 (s, 2 ArH), 6.66 (t,
1 ArH), 6.60 (s, 1 ArH), 6.53 (m, 2 ArH), 6.36 (t, 1
ArH), 2.93 (m, 6 CHMe2), 2.79 (m, 6 CHMe2), 2.21 (br
s, 3 Me2NPh), 1.46 (br s, 3 Me2NPh), 1.34–1.10 (m, 72
CHMe2), 0.49 (s, 3 Me).
{[HIPTN2]Hf(Me)}{B(C6F5)4} (major isomer only).
1H NMR (C6D5Br) d 7.97 (br s, 1 ArH), 7.67 (t, 1 ArH),
7.56 (br d, 1 ArH), 7.31 (t, 2 ArH), 7.18–7.05 (m, 30 ArH),
7.01 (s, 1 ArH) 6.80 (br d, 1 ArH), 6.74 (s, 2 ArH), 6.62 (m,
2 ArH), 2.92 (m, 6 CHMe2), 2.78 (m, 6 CHMe2), 2.03 (s, 3
Ph3CCH3), 1.31–1.11 (m, 72 CHMe2), 0.66 (s, 3 Me).
[HIPTN2]Hf(CH2CHMe2)2. This compound was pre-
pared in a manner analogous to that used to prepare
[HIPTN2]HfMe2 starting from 1.076 g (0.721 mmol) of
[HIPTN2]HfCl2 and 0.62 mL (1.5 mmol) of Me2CHCH2-
MgBr (2.4 M in Et2O). Yield: 1.008 g (91%). 1H NMR
(C6D6) d 7.87 (d, 2 BINAPH), 7.76 (d, 2 BINAPH), 7.39
(s, 4 o-H), 7.37 (d, 2 BINAPH), 7.21 (s, 4 m-H), 7.20 (s,
4 m-H), 6.93 (m, 4 BINAPH), 6.64 (s, 2 p-H), 6.43 (t, 2 BI-
NAPH), 3.15 (sep, 4 o-CHMe2), 3.07 (sep, 4 o-CHMe2),

476
Z.J. Tonzetich, R.R. Schrock / Polyhedron 25 (2006) 469–476
[15] J.D. Scollard, D.H. McConville, J.J. Vittal, Organometallics 14
Acknowledgments
(1995) 5478.
[16] J.D. Scollard, D.H. McConville, J. Am. Chem. Soc. 118 (1996)
10008.
[17] D. Yandulov, R.R. Schrock, J. Am. Chem. Soc. 124 (2002)
6252.
[18] D.V. Yandulov, R.R. Schrock, A.L. Rheingold, C. Ceccarelli, W.M.
Davis, Inorg. Chem. 125 (2003) 796.
[19] D.V. Yandulov, R.R. Schrock, Science 301 (2003) 76.
[20] V. Ritleng, D.V. Yandulov, W.W. Weare, R.R. Schrock, A.R. Hock,
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[21] D.V. Yandulov, R.R. Schrock, Inorg. Chem. 44 (2005)
1103.
[22] X. Huang, K.W. Anderson, D. Zim, L. Jiang, A. Klapars, S.L.
Buchwald, J. Am. Chem. Soc. 125 (2003) 6653.
[23] L.-C. Liang, R.R. Schrock, W.M. Davis, Organometallics 19 (2000)
2526.
[24] T. Wondimagegn, Z. Xu, K. Vanka, T. Ziegler, Organometallics 23
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[25] J.D. Scollard, D.H. McConville, S.J. Rettig, Organometallics 16
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[27] P. Mehrkhodavandi, P.J. Bonitatebus Jr., R.R. Schrock, J. Am.
Chem. Soc. 122 (2000) 7841.
[28] R.R. Schrock, A.L. Casado, J.T. Goodman, L.-C. Liang,
P.J. Bonitatebus Jr., W.M. Davis, Organometallics 19 (2000)
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[29] C.R. Landis, K.A. Rosaaen, J. Uddin, J. Am. Chem. Soc. 124 (2002)
12062.
R.R.S. thanks the Department of Energy (DE-FG02-
86ER13564) for research support and Z.J.T. thanks the
National Science Foundation for a predoctoral fellowship.
We thank W.W. Weare for assistance with synthetic
details.
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