Imino-amido Hf and Zr complexes: Synthesis, isomerization, and olefin polymerization

Article abstract of DOI:10.1021/om1008742

New hafnium and zirconium imino-amido complexes containing trimethylethylidene bridging groups are reported. Investigation into the thermal stability of these complexes revealed that they undergo facile rearrangement of the ligand backbone at 80 °C to produce isomeric imino-amido complexes. Mechanistic experiments and DFT calculations indicate that this isomerization reaction proceeds via a direct 1,2-methyl shift rather than a multistep mechanism involving the metal center. The initial imino-amido complexes (pre isomerization) exhibit high ethylene/1-octene copolymerization activities and generate polymers with very high molecular weights and relatively low comonomer contents. On the other hand, the isomerized complexes display significantly lower polymerization activities and give polymers with lower molecular weights and broad molecular weight distributions, indicative of multisite behavior.

Full text of DOI:10.1021/om1008742

Organometallics 2011, 30, 251–262 251
DOI: 10.1021/om1008742
Imino-Amido Hf and Zr Complexes: Synthesis, Isomerization, and Olefin
Polymerization
Robert D. J. Froese, Brian A. Jazdzewski, Jerzy Klosin,* Roger L. Kuhlman,
Curt N. Theriault, and Dean M. Welsh
Corporate R&D, The Dow Chemical Company, 1776 Building, Midland, Michigan 48674, United States
Khalil A. Abboud
Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
Received September 8, 2010
New hafnium and zirconium imino-amido complexes containing trimethylethylidene bridging groups
are reported. Investigation into the thermal stability of these complexes revealed that they undergo facile
rearrangement of the ligand backbone at 80 °C to produce isomeric imino-amido complexes. Mechanistic
experiments and DFT calculations indicate that this isomerization reaction proceeds via a direct 1,2-methyl
shift rather than a multistep mechanism involving the metal center. The initial imino-amido complexes
(pre isomerization) exhibit high ethylene/1-octene copolymerization activities and generate polymers with
very high molecular weights and relatively low comonomer contents. On the other hand, the isomerized
complexes display significantly lower polymerization activities and give polymers with lower molecular
weights and broad molecular weight distributions, indicative of multisite behavior.
Introduction
polymerization, resulting in the discovery of previously
unknown polymerization behaviors2 and new polymeric mate-
rials.2a,3 Recently, we4 and researchers from Osaka University5
have been interested in group 4 imino-amido complexes,6 a class
of olefin polymerization catalysts that was originally introduced
by Murray and co-workers at Union Carbide.7 These complexes
are of interest due to several factors, including ease of synthesis,
good polymerization characteristics, and dependence of catalyst
reactivity toward R-olefins on the metal and/or ligand substitu-
tions. We recently described the synthesis of these imino-amido
complexes (e.g., 1 and 3) in high yields via the reaction of
hafnium or zirconium alkyls with bis-imines, as shown in
Scheme 1.4a
The use of complexes such as 1 as procatalysts for olefin
polymerization is limited because these complexes are thermally
unstable and can undergo dibenzyl elimination via a radical
pathway to form ene-diamido complexes (2).4a This conversion
is particularly facile for Zr complexes, occurring even at ambient
temperature. In complexes such as 3, additional reaction path-
ways also may be observed.4a,5a For example, not only does
thermal treatment of 3 lead to the formation of an ene-diamido
complex (5), but a related imino-amido complex (4) is also
observed. This species forms following an isomerization of the
imino-amido fragment, presumably via a 1,2-hydrogen shift. A
similar ligand framework rearrangement was proposed in the
synthesis of an imino-amido manganese complex.8 Even though
There has been considerable research in the last 15 years in
the area of non-Cp-based molecular catalysts1 for olefin
*To whom correspondence should be addressed. E-mail: jklosin@
dow.com.
(1) (a) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428–447. (b) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev.
2003, 103, 283–316. (c) Makio, H.; Kashiwa, N.; Fujita, T. Adv. Synth.
Catal. 2002, 344, 477–493. (d) Park, S.; Han, Y.; Kim, S. K.; Lee, J.; Kim,
H. K.; Do, Y. J. Organomet. Chem. 2004, 689, 4263–4276.
(2) (a) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. Rev. 2000,
100, 1169–1203. (b) Tian, J.; Hustad, P. D.; Coates, G. W. J. Am. Chem. Soc.
2001, 123, 5134–5135. (c) Bollmann, A.; Blann, K.; Dixon, J. T.; Hess, F. M.;
Killian, E.; Maumela, H.; McGuinness, D. S.; Morgan, D. H.; Neveling, A.;
Otto, S.; Overett, M.; Slawin, A. M. Z.; Wasserscheid, P.; Kuhlmann, S.
J. Am. Chem. Soc. 2004, 126, 14712–14713. (d) Boussie, T. R.; Diamond,
G. M.; Goh, C.; Hall, K. A.; LaPointe, A. M.; Leclerc, M. K.; Murphy, V.;
Shoemaker, J. A. W.; Turner, H.; Rosen, R. K.; Stevens, J. C.; Alfano, F.;
Busico, V.; Cipullo, R.; Talarico, G. Angew. Chem., Int. Ed. 2006, 45, 3278–
3283.
(3) Arriola, D. J.; Carnahan, E. M.; Hustad, P. D.; Kuhlman, R. L.;
Wenzel, T. T. Science 2006, 312, 714–719.
(4) (a) De Waele, P.; Jazdzewski, B. A.; Klosin, J.; Murray, R. E.;
Petersen, J. L.; Theriault, C. N.; Vosejpka, P. C. Organometallics 2007,
26, 3896–3899. (b) Kuhlman, R. L.; Klosin, J. Macromolecules 2010, 43,
7903–7904.
(5) (a) Mashima, K.; Ohnishi, R.; Yamagata, T.; Tsurugi, H. Chem.
Lett. 2007, 36, 1420–1421. (b) Tsurugi, H.; Ohnishi, R.; Kaneko, H.; Panda,
T. K.; Mashima, K. Organometallics 2009, 28, 680–687.
(6) For main group imino-amido compounds see: (a) Klerks, J. M.;
Stufkens, D. J.; v. Koten, G.; Vrieze, K. J. Organomet. Chem. 1979, 181,
271–283. (b) Jastrzebski, J. T. B. H.; Klerks, J. M.; v. Koten, G.; Vrieze, K.
J. Organomet. Chem. 1981, 210, C49–C53. (c) Kaupp, M.; Stoll, H.; Preuss,
H.; Kaim, W.; Stahl, T.; v. Koten, G.; Wissing, E.; Smeets, W. J. J.; Spek, A. L.
J. Am. Chem. Soc. 1991, 113, 5606–5618. (d) Wissing, E.; Jastrzebski,
J. B. H.; Boersma, J.; v. Koten, G. J. Organomet. Chem. 1993, 459, 11–16.
(e) Wissing, E.; v. Gorp, K.; Boersma, J.; v. Koten, G. Inorg. Chim. Acta
1994, 220, 55–61. (f) Bruce, M.; Gibson, V. C.; Redshaw, C.; Solan, G. A.;
White, A. J. P.; Williams, D. J. Chem. Commun. 1998, 2523–2524.
(7) (a) Murray, R. E. U.S. Patent 6,096,676, 2000. (b) Murray, R. E.;
George, V. M.; Nowlin, D. L.; Schultz, C. C.; Petersen, J. L. Polym. Prepr.
(Am. Chem. Soc., Div. Polym. Chem.) 2002, 43, 294–295. (c) Murray, R. E.
Int. Pat. Appl. 2003051935, 2003.
(8) Riollet, V.; Coperet, C.; Basset, J.-M.; Rousset, L.; Bouchu,
D.; Grosvalet, L.; Perrin, M. Angew. Chem., Int. Ed. 2002, 41, 3025–
3027.
r
2010 American Chemical Society
Published on Web 12/29/2010
pubs.acs.org/Organometallics

252 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
Scheme 1
good polymerization activities are observed for some group 4
imino-amido procatalysts,4a the high polymer polydispersity
(Mw/Mn) values observed suggest that multiple species may be
present during polymerization. We have recently focused our
attention on a subclass of imino-amido complexes containing
the trimethylethylidene bridging group (e.g., 6, 7). We hypothe-
sized that complexes bearing these ligands would be more
thermally stable and lead to polymerization catalysts that
displayed improved olefin polymerization behavior.
Scheme 2. Synthesis of Complexes 10a and 11a
formation reaction9 between keto-amine 87c,10 and ethyl amine
in toluene (Scheme 2).
We have recently demonstrated that such complexes (6, 7)
not only lead to very active olefin polymerization catalysts
but, more importantly, also are capable of undergoing
reversible chain transfer reactions with diethylzinc in the
production of various types of olefin block copolymers.4b
Because of our previous experience with the thermal reactiv-
ity of complexes 1 and 3, investigations of the thermal
behavior of group 4 imino-amido complexes containing
trimethylethylidene bridging groups were warranted.
Reaction of 9a with either hafnium or zirconium tetrabenzyl
in toluene gives complex 10a or 11a, respectively, in good yields.
Both complexes exhibit Cs symmetry in solution, as shown by
NMR spectroscopy. For example, the 1H NMR spectrum of
10a (in toluene-d8, Figure 1) shows only one i-Pr methine signal
at 3.33 ppm and two doublets appearing at 1.33 and 1.21 ppm,
corresponding to the i-Pr methyl groups. This indicates that
both isopropyl groups have the same chemical environment
in solution. The appearance of two separate resonances for
the i-Pr methyl groups is indicative of hindered rotation of the
2,6-diisopropylphenyl fragment (DIP) along the N-C(ipso)
Results and Discussion
Synthesis of Ligands and Complexes. For the purpose of
this study we chose to explore the synthesis, characterization,
and polymerization behavior of complexes related to 6 (vide
supra). Ligands bearing an N-ethyl substituent were favored
over the N-n-octyl found in complex 6, as it was believed that
the group 4 complexes derived from this ligand would possess
lower solubility in nonpolar solvents such as hexane, thus
facilitating purification by crystallization. The desired ligand
9a was synthesized via the titanium tetrachloride-induced imine
(9) (a) Carlson, R.; Nilsson, A. Acta Chem. Scand. 1984, B 38, 49–53.
(b) Armesto, D.; Bosch, P.; Gallego, M. G.; Martin, J. F.; Ortiz, M. J.;
ꢀ
Perez-Ossorio, R.; Ramos, A. Org. Prep. Proc. Int. 1987, 19, 181–186.
(c) De Kimpe, N.; D'hondt, L.; Stanoeva, E. Tetrahedron Lett. 1991, 32,
3879–3882. (d) Carlson, R.; Larsson, U.; Hansson, L. Acta Chem. Scand.
1992, 46, 1211–1214. (e) Klosin, J. U.S. Patent 6,617,407, 2003.
(10) See Supporting Information for single-crystal X-ray analysis of
this compound.

Article
Organometallics, Vol. 30, No. 2, 2011 253
Figure 1. 1H and NOESY 1D NMR spectra of 10a (toluene-d8).
bond.11 This leads to different chemical environments of the
methyl groups, pointing either toward or away from the
trimethylethylidene bridge. Signals corresponding to the three
methyl groups of the ligand’s bridge resonate as singlets at 1.21
ppm (3H) and 0.66 ppm (6H), further confirming the Cs molec-
ular symmetry of the complex in solution. Methylene protons
of the three benzyl groups appear as a sharp singlet at 2.14 ppm
(6H), indicating fast exchange of the benzyl groups on the NMR
time scale. To further confirm the structure in solution, a series
of NOE experiments was conducted (Figure 1). Irradiation of the
quartet at 2.84 ppm (corresponding to the methylene protons of
the N-ethyl substitutent) results in the observation of strong
NOEs with the triplet at 0.75 ppm (corresponding to the methyl
protons of the N-ethyl substituent), the singlet at 2.14 ppm
(benzyl methylene protons, as described above), and the singlet
at 1.21 ppm (corresponding to one methyl group attached to
the imine carbon of the ligand backbone). As expected, no
NOE enhancement is observed between this quartet and the
singlet observed for the two equivalent methyl groups attached
to the ligand backbone appearing at 0.66 ppm. Similar NMR
spectroscopic characteristics also are observed for complex 11a
in solution. Gratifyingly, both complexes 10a and 11a were
found to be highly crystalline relative to 6 and are readily
crystallized from the toluene/hexane solvent mixtures, facilitat-
ing the further characterization of complex 10a via single-
crystal X-ray analysis (vide infra).
Scheme 3. Isomerization of 10a and 11a
with one significant difference: unlike in the case of 10a, there
is no trace of NOE enhancement of the methyl group attached
to the imine carbon (singlet at 1.35 ppm, 3H). Instead, a strong
NOE enhancement of the singlet corresponding to two equiva-
lent methyl groups attached to the ligand’s bridge (0.91 ppm,
6H) is observed. These data clearly indicate that the ethyl group
is in close proximity to the gem-dimethyl fragment, indicative of
an isomerized complex resulting from the migration of the
methyl group. The identity of 10b was corroborated by a
single-crystal X-ray analysis and full characterization of the
independently synthesized complex 10b. Ligand 9b (the ex-
pected ligand of 10b) was prepared in two steps starting from
3-bromo-3-methylbutan-2-one (12) as shown in Scheme 4.
Reaction of 9b with hafnium tetrabenzyl in toluene solution
gives 10b in close to quantitative yield.
To investigate the thermal stability of the newly prepared
complexes, 10a was dissolved in toluene-d8 and heated for 16 h
The thermal rearrangements of 10a and 11a in solution were
studied extensively utilizing NMR spectroscopy. These reactions
are found to follow first-order kinetics with kobs values of 5.1 ꢀ
10-5 s-1 (t1/2 = 228 min) and 9.6 ꢀ 10-5 s-1 (t1/2 = 120 min) at
80.4 °C, respectively. Full kinetic analysis of 10a gives ΔH‡ and
1
at 90 °C. The H NMR spectrum of the reaction mixture
shows complete disappearance of 10a and clean formation
of a new complex, which displays the same number of reso-
nances and coupling patterns as 10a, but different chemical
shifts. The identity of the product, 10b, was determined to be
a constitutional isomer of 10a (Scheme 3), initially estab-
lished by NOE experiments. The most revealing NOE data
are observed upon irradiation of the quartet resonating at
3.13 ppm, corresponding to the methylene of the N-ethyl
group (Figure 2). NOEs similar to those of 10a are observed
ΔS‡ of 29.1(7) kcal/mol and 4(2) cal/mol K, respectively.
3
Mechanism of Isomerization of 10a and 11a. We considered
two plausible isomerization mechanisms for the conversion of
10a to 10b and 11a to 11b. One mechanism involves a direct
1,2-methyl shift (Scheme 5), whereas the other mechanism
involves participation of the metal center (Scheme 6). The latter
mechanism was proposed by Copert and co-workers to account
for the observed product from the reaction of an aryl bis-imine
and a neopentyl manganese complex.8 These two pathways can
be distinguished by following the isomerization reaction of the
Hf(CD3)3 derivative. A direct 1,2-shift should occur without
scrambling between CH3 and CD3 groups, whereas the metal
(11) Hindered rotation of the 2,6-diisopropylphenyl fragmentis observed
commonly in bis-imine complexes. For examples see: (a) Schleis, T.; Spaniol,
€
T. P.; Okuda, J.; Heinemann, J.; Mulhaupt, R. J. Organomet. Chem. 1998,
569, 159–167. (b) Bianchini, C.; Giambastiani, G.; Rios, I. G.; Mantovani, G.;
Meli, A.; Segarra, A. M. Coord. Chem. Rev. 2006, 250, 1391–1418.

254 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
Figure 2. 1H and NOESY 1D NMR spectra of 10b (toluene-d8).
Scheme 4. Synthesis of 9b
Scheme 5. Reaction Diagram for the Direct 1,2-Methyl Shifta
Scheme 6. Possible Hf-Assisted Isomerization Pathwaysa
a DFT enthalpies (in kcal/mol) relative to 14a (0.0) on the potential
energy surface are provided in parentheses.
participation mechanism (Scheme 6) would lead to replacement
of some CD3 groups with CH3, an event that could be easily
detected by 1H NMR spectroscopy. To investigate the mecha-
nism operating in the isomerization of 10a, the perdeuteromethyl
metal-alkyl analogue 14a was prepared as shown in Scheme 7.
Complex 10a was reacted with three equivalents of iodine in
methylene chloride at ambient temperature to produce the
triiodo derivative 15. This reaction is very fast at ambient tem-
perature, as evidenced by the rapid disappearance of the purple
color of added iodine. Reaction between 15 and three equivalents
of CD3MgI gives the desired 14a. Complex 14a was fully charac-
terized both by NMR spectroscopy and single-crystal X-ray
analysis.10 The 1H NMR spectrum of the isolated 14a in
toluene-d8 is shown in Figure 3 (top spectrum). The 2H NMR
spectrum of 14a shows a singlet at 0.31 ppm corresponding to
three equivalent metal-bound CD3 ligands. An NMR tube
containing 14a was heated at 80 °C for 24 h, revealing that
complex 14a isomerizes with the first-order rate constant, kobs, of
2.3 ꢀ 10-5 s-1 (t1/2 = 492 min). This reaction rate is approxi-
a DFT enthalpies (kcal/mol) relative to 14a (0.0) of various minima
and transition states on the potential energy surface are provided in
parentheses.
the 1H NMR spectrum is very similar to the equivalent deuterons
in 2H NMR, the expected chemical shift for the Hf-CH3
resonances was close to 0.30 ppm. Additionally, an analogue of
14a with CH3 instead of CD3 groups attached to hafnium was
prepared (14a-CH3) by the salt metathesis route and subse-
quently thermolyzed to give 14b-CH3. The chemical shifts of
the Hf methyl groups in 14a-CH3 and 14b-CH3 were found to
resonate in toluene-d8 at 0.30 and 0.25 ppm, respectively. The
absence of any CH3 resonances in this region during thermolysis
1
mately 50% lower than the conversion of 10a to 10b. The H
NMR spectrum shows about 90% conversion of 14a to 14b
(Figure 3, bottom spectrum), but no Hf-CH3 resonances are
observed around 0.3 ppm. Since the chemical shift of protons in

Article
Organometallics, Vol. 30, No. 2, 2011 255
Figure 3. 1H NMR spectra (toluene-d8) of 14a (top spectrum) and reaction mixture after 90% conversion of 14a to 14b (bottom
spectrum). The resonance at 4.00 ppm belongs to ferrocene used as an internal standard.
Scheme 7. Synthesis of 14a
of 14a rules out the metal-assisted mechanism and therefore
favors the 1,2-methyl shift.
The computed enthalpy of activation for the tribenzyl deriva-
tive 10a is slightly lower (24.7 kcal/mol), consistent with the
faster reaction rate observed experimentally for this complex com-
pared to its trimethyl analogue, 14a. Two possible Hf-assisted
Computational Study.12 A series of calculations was per-
formed to estimate activation parameters for the different
isomerization pathways. The relative enthalpies of the direct
1,2-methyl shift and the Hf-assisted isomerization pathways
for 14a are presented in Schemes 5 and 6, respectively.
The direct 1,2-methyl shift from 14a to 14b proceeds across
transition state TS1 with a ΔH‡ of 26.3 kcal/mol (Scheme 5).
(12) Three-dimensional structures of all calculated compounds are
included (in sd file format) in the Supporting Information. SD files can
be read by the free Mercury program available at http://www.ccdc.cam.
ac.uk/products/mercury/.

256 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
Scheme 8. Calculated Energies (kcal/mol) for Imino-Amido
Complexes and Associated Transition States
Table 1. Relative Energies (ΔH in kcal/mol) of the Nine Impor-
tant Structures on the Potential Energy Surface for the Neutral
(LMMe3) and the Cationic (LMMe2þ) Speciesa
neutral
HfMe3 (14)
cationic
HfMe2 (16)
neutral
ZrMe3 (17)
cationic
ZrMe2 (18)
a
b
c
d
TS1
TS2
TS3
TS4
TS5
0.0
-2.9
22.4
-2.9
26.3
37.2
46.4
38.7
43.3
0.0
-4.8
4.3
19.1
25.6
38.6
46.5
37.6
43.5
0.0
-4.5
21.5
-3.3
25.1
36.9
43.8
37.7
40.3
0.0
-4.5
5.3
15.6
26.8
37.6
45.5
37.3
42.8
a The labeling scheme is consistent with Schemes 5 and 6.
pathways are shown in Scheme 6. The first pathway, involving
the formation of bis-amido complex 14d by methyl transfer
from Hf to the ligand, requires traversing TS2 with a ΔH‡ of
37.2 kcal/mol. Coincidently, intermediate 14d has the same
ground-state energy as 14b. The second pathway involves the
formation of a bis-imine-Hf complex 14c, which is a highly endo-
thermic process (ΔH° = 22.4 kcal/mol). This observation helps
explain why the reverse reaction, addition of bis-imines to
hafnium tetrabenzyl, leads to benzyl-inserted complex. The for-
mation of bis-imine complex 14c from 14a has a barrier (TS3)
of 46.4 kcal/mol, whereas the reverse reaction (14c to 14a)
occurs with a barrier of 24.0 kcal/mol. These computational
data clearly indicate that the lowest barrier for isomerization of
14a to 14b occurs for the direct 1,2-methyl transfer, which is
lower by 10.9 and 20.1 kcal/mol compared to the processes pro-
ceeding via bis-amido and bis-imine intermediates, respectively.
The conclusions from this computational study are in full agree-
ment with the experimental data, which indicate that Hf-assisted
isomerization does not occur during interconversion of 14a to 14b.
The computed activation parameters of ΔH‡ = 26.3 kcal/mol
representative for the active catalyst to determine if the isomer-
ization barriers change significantly. Even though the cationic
active catalyst species may live only for a few minutes under
polymerization conditions, the active catalyst may experience
very high polymerization temperatures (120-160 °C), which
might lead to the isomerization of the catalyst before its
deactivation and thus influence its performance. The relative
energies of the neutral and cationic hafnium and zirconium
species for the different structures are collected in Table 1.
A number of trends can be observed from these data. The
isomerization from 14a to 14b is an exothermic process for both
the cationic and neutral systems. For the cationic species, the
direct 1,2-methyl shift (via TS1) also is favored over the bis-
imine or bis-amide pathways. The barrier for this isomerization
process is comparable to those found for the neutral systems.
Thus if the experimentally measured kinetic parameters are used
and a similar isomerization rate for the cationic system is
assumed, the half-life for catalyst conversion at 120 °C would
be ∼3 min, which is in the range of the lifetime of the catalyst
under polymerization conditions.
It is interesting to note that, relative to 14a, the neutral bis-
amide (14d) is significantly more stable than the cationic bis-
amide (16d). The electrophilic cationic transition metal com-
plexes prefer to have a saturated metal center (four-coordinate
16a is favored over three-coordinate 16d), while the neutral
systems prefer less ligation of the metal (four-coordinate 14d is
favored over five-coordinate 14a). The barrier for bis-imine
formation is high for both neutral and cationic complexes.
However, the reaction from the imino-amido to the bis-imine
complex is more likely to occur in the cationic system, where the
electrophilic nature of the metal can better support the extra
ligation. The reaction to form the bis-imine (16c) from the
imino-amido (16a) for the cationic system is still endothermic
(4.3 kcal/mol), but it is substantially less than that computed for
the neutral species (22.4 kcal/mol). Similar trends are calculated
for the analogous neutral (17) and cationic (18) zirconium
complexes.
and ΔS‡ = 3.5 cal/mol K for the direct 1,2-methyl shift agree well
3
with those determined experimentally (ΔH‡ = 29.1(7) kcal/mol
and ΔS‡ = 4(2) cal/mol K). It is possible that the same direct
1,2-methyl shift might be taking place in the case of isomeriza-
3
tion of the manganese imino-amido complex.8,13
The driving force for the isomerization of 14a to 14b is the
increased stability of isomer 14b, which was calculated to be 2.9
kcal/mol (ΔH°) lower in energy than 14a.14 To examine the
reasons for this thermodynamic preference, the energies of two
additional sets of complexes were computed (Scheme 8). The
first set contains N-Ph instead of N-DIP substituents, and the
second group contains three hydrogen atoms instead of three
methyl groups in the backbone of the ligand. In both cases,
the ground-state energies are reversed; that is, complexes with
amide-aryl substituents are more stable than their amide-alkyl
counterparts. The opposite trend observed for 14a and 14b is
most likely due to unfavorable steric interactions between the
gem-dimethyl and the isopropyl groups of DIP in 14a, which
lead to destabilization of 14a relative to 14b. For the ligand
itself, DIP prefers to reside adjacent to the imine, as this species
(9b) was calculated to be more stable than the DIP-amide (9a)
by 5.0 kcal/mol.
Single Crystal X-ray Structures of 10a and 10b. Molecular
structures of complexes 10a (Figure 4) and 10b (Figure 5) each
show a five-coordinate hafnium atom bound to two nitrogen
donors and three benzyl groups. Metallacycles composed of Hf,
two carbon (C1, C2) atoms, and two nitrogen (N1, N2) atoms
are almost coplanar with mean deviation from the plane of
While isomerization of the neutral species is important for
stability of the catalyst precursor, we were also interested in
examining the stability of the dimethyl cationic species as a
˚
0.026 and 0.066 A for 10a and 10b, respectively. A comparison
of bond lengths within metallacycles in 1, 10a, and 10b is shown
in Figure 6. The X-ray crystal structure of 10a reveals a
(13) A detailed computational study is currently underway in our
laboratory to gain insight into the isomerization mechanism of these
manganese complexes.
(14) Calculated enthalpy of reaction from 10a to 10b is -4.5 kcal/
mol.
˚
considerably longer Hf-N(imino) bond (2.301(3) A) as com-
˚
pared to the Hf-N(amido) bond (2.074(3) A). Noticeably
greater bonding asymmetry was observed in complex 10b, with

Article
Organometallics, Vol. 30, No. 2, 2011 257
Figure 4. Molecular structure of 10a. The hydrogen atoms have
been omitted for clarity. Thermal ellipsoids are shown at the 40%
probability level. Selected bonds (A) and angles (deg): Hf-N1 =
2.074(3), Hf-N2 = 2.301(3), C1-N1 = 1.497(4), C2-N2 =
1.270(5), C1-C2 = 1.508(5), N2-Hf-N1 = 72.6(1).
˚
Figure 6. Comparison of important bond lengths (A) in 1, 10a,
and 10b.
˚
Table 2. Polymerization Data for Complexes 10a, 10b, 11a, 11b,
and CGCa
octene
content
catalyst
(μmol)
polymer catalyst
run #
yield (g) activity Mw ꢀ 10-3 Mw/Mn Tm (mol %)
1
2
3
4
5
10a (0.25)
10b (1.00)
11a (0.25)
11b (1.00)
35.2 140 800
633
520
782
294
108
3.1 102
5.2 112
2.8 112
3.8
3.3
6.7
22.9
5.5
6700
91 600
5500
1.7
2.9
60
2.6
120
60
CGC (0.20) 113.8 569 000
14.9
a Polymerization conditions: 120 °C; 533 mL of Isopar-E; 250 g of
octene; ethylene pressure: 460 psi; procatalyst:activator:MMAO =
1:1.2:10; activator: [HNMe(C18H37)2][B(C6F5)4]; reaction time 15 min.
Activity: g of polymer/mmol cat. CGC = {(η5-C5Me4)(SiMe2-N-
t-Bu)}TiMe2.
are in the range of 110.1° and 121.7°, indicating a η1-bonding
mode for all benzyl groups.
Polymerization Study. Complexes 10a, 10b, 11a, and 11b
were evaluated as catalysts for ethylene/1-octene copolymeriza-
tion in a 2 L batch reactor at 120 °C containing 460 psi ethylene
pressure and 250 g of 1-octene. (η5-C5Me4)(SiMe2-N-t-Bu)-
TiMe2 (CGC) also was included in the study for comparison.
Procatalysts were activated with 1.2 equivalents (relative to
procatalyst) of [HNMe(C18H37)2][B(C6F5)4] activator. All po-
lymerization reactions were carried out for 15 min and stopped
by venting the ethylene pressure.
Figure 5. Molecular structure of 10b. The hydrogen atoms have
been omitted for clarity. Thermal ellipsoids are shown at the 40%
˚
probability level. Selected bonds (A) and angles (deg): Hf-N1 =
2.380(4), Hf-N2 = 2.030(4), C1-N1 = 1.291(6), C2-N2 =
1.454(6), C1-C2 = 1.515(6), N2-Hf-N1 = 68.9(1).
The data presented in Table 2 show that the imino-amido
complexes 10a and 11a (runs 1 and 3) result in active catalysts
upon activation, with complex 10a possessing higher activ-
ity. While the hafnium complex 10a was found to be 50%
more active than zirconium analogue 11a, it is less active by a
factor of 4 than the titanium-based CGC. Complexes 10a
and 11a give very high molecular weight copolymers albeit
with low 1-octene incorporation, with zirconium-based cata-
lyst 11a giving the highest (783 K) weight average molecular
weight. This molecular weight is much higher than that
produced by CGC (Mw of 107 K), although caution needs
to be applied when comparing molecular weight capabilities
of catalysts having very different reactivity toward R-olefins.
Since CGC is a much better 1-octene incorporator than 10a
and 11a (Table 2) and it is known15 that 1-octene leads to
Hf-N(imino) and Hf-N(amido) bond lengths of 2.380(4) and
2.030(3) A, respectively. The differences in bonding in both
˚
complexes can be better visualized by comparing the Hf-
˚
N(imido) and Hf-N(amido) bond differences of 0.227 A for
˚
10a and 0.350 A for 10b. A very long Hf-N(imino) bond of
˚
2.423(3) A also was observed in complexes 1 with aryl (DIP)
substituents attached to both imino and amido nitrogen atoms.4
The significant elongation of the Hf-N(imido) bond in 10b and
1 is likely due to the presence of the aryl (DIP) substituent,
which presumably competes for nitrogen electron density, thus
weakening Hf-N(imido) bonding. A similar description per-
tains to the case of Hf-N(amido) bond lengths in 10a and 10b,
but the effect is less pronounced. The Hf-N(amido) bond
in 10a is identical within experimental error to that in 1
˚
(2.070(3) A). The Hf-C-Cipso bond angles in both complexes

258 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
molecular weight reduction during ethylene/1-octene copo-
lymerization reactions with CGC,16 the effect of R-olefin on
Mw needs to be considered. The main objective, however, was
to determine whether isomerized complexes 10b and 11b are
competent as catalysts in olefin polymerization reactions and,
if so, what type of polymer microstructure is produced. It was
found that complexes 10b and 11b do, indeed, lead to polymer
production, but exhibit activities about 20 times lower than
their isomeric counterparts and produce polymers with lower
molecular weights (e.g., compare entry 1 to entry 3 in Table 2).
GPC traces of polymers clearly show at least bimodal
distribution for 10b and at least trimodal distribution in the case
of 11b. The multimodality exhibited by polymers produced by
10b and 11b implies that these complexes undergo further
transformation(s) during activation and/or polymerization.
Perhaps the enhanced bonding asymmetry observed in the
X-ray structure of 10b leads to higher reactivity of such com-
plexes, which contributes to their higher susceptibility to under-
go conversion into other, active species.
q=quartet, p=pentet, hept = heptet, and m=multiplet), integra-
tion,couplingconstantinHz,and assignment). Chemicalshiftsfor
1H NMR data are reported in ppm downfield from internal
tetramethylsilane (TMS, δ scale) using residual protons in the
deuterated solvent (C6D6, 7.15 ppm; toluene-d8, 2.09 ppm;
C2D2Cl4, 5.99 ppm) as references. 13C NMR data were deter-
mined with 1H decoupling, and the chemical shifts are reported in
ppm versus tetramethylsilane (C6D6, 128 ppm; toluene-d8, 20.4
ppm; C2D2Cl4, 73.8 ppm). All metal complexes were synthesized
and stored in a Vacuum Atmospheres inert atmosphere glovebox
under a dry nitrogen atmosphere or by using standard Schlenk
and vacuum line techniques unless otherwise noted. Elemental
analyses were performed at the Midwest Microlab, LLC.
Preparation of 3-[[2,6-Bis(1-methylethyl)phenyl]amino]-3-
methyl-2-butanone (8). This compound has been reported pre-
viously.7c A modified procedure is described below. A solution of
N,N0-(1,2-dimethyl-1,2-ethanediylidene)bis[2,6-bis(1-methylethyl)-
benzenamine] (17.0 g, 40.0 mmol) in MeOH (500 mL) was treated
with H2O (250 mL), causing the formation of a colorless pre-
cipitate. A 1.0 M (aq) solution of H2SO4 (160 mL) was then added
dropwise over 1 h. The reaction mixture was refluxed for 1 h,
resulting in the formation of a light yellow solution. This solution
was cooled to ambient temperature and cautiously treated with
KOH (slow addition of solid pellets) until pH = 14. The resulting
mixture was extracted with Et2O (3 ꢀ 75 mL), and the combined
organic fractions were dried over anhydrous MgSO4. The solvent
and liberated 2,6-diisopropylaniline were removed under reduced
pressure at 40 °C, resulting in the isolation of an off-white solid.
Addition of a minimum amount of warm hexamethyldisiloxane
(HMDSO) (∼10 mL) and storage at 0 °C resulted in the precipita-
tion of a colorless solid. Multiple crops of the colorless solid were
collected, combined, and washed with cool (∼-70 °C) HMDSO
(5 ꢀ 1 mL). The resulting colorless solid was dried under reduced
Conclusions
Imino-amido complexes can be very active for olefin
polymerization and can give very high molecular weight poly-
mers. This behavior, coupled with their ability to chain shuttle
with metal alkyl reagents, makes them an interesting family of
olefin polymerization catalysts. Previously, we had shown that
group 4 complexes bearing imino-amido ligands possessing
benzyl substituents at the ligand backbone are unstable, leading
to the formation of ene-diamido complexes. In an attempt to
address instability of such complexes, we shifted our attention to
imino-amido complexes containing a trimethylethylidene back-
bone. Imino-amido complexes containing different substituents
on the imino and amino nitrogen atoms (e.g., 6, 10a, and 11a)
are more thermally robust, but do undergo related isomeriza-
tion reactions at higher temperatures. In these cases, we propose
that the mechanism involves a direct 1,2-methyl shift of one of
the methyl groups at the ligand backbone to form structurally
analogous complexes. However, we found that these new
complexes exhibit significantly reduced catalytic activity upon
activation and produce less uniform polymer compositions.
While procatalysts such as 6, 10a, and 11a exhibit very good
polymerization characteristics, their propensity to undergo
isomerization is not a desirable feature. A more attractive option
would be the development of group 4 imino-amido complexes
that are resistant to thermal rearrangement but maintain ex-
cellent olefin polymerization catalytic properties (e.g., high
activity, high polymer molecular weight, and chain shuttling
capability). The discovery of such catalysts is an active research
area in our laboratory.
1
pressure to yield the desired compound, 4.3 g (41%). H NMR
(300 MHz, CDCl3): δ 7.07 (br s, 3H), 3.70 (br s, 1H), 3.11 (hept,
J = 6.6 Hz, 2H), 2.37 (s, 3H), 1.22 (s, 6H), 1.17 (d, J = 6.6 Hz,
12H) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ 212.8, 145.4,
139.5, 124.7, 123.1, 63.6, 28.2, 25.3, 24.0, 23.9 ppm. HREIMS:
calcd for C17H27NO m/z = 284.199, found m/z = 284.195.
Preparation of N-[1,1-Dimethyl-2-(ethylimino)propyl]-2,6-bis-
(1-methylethyl)benzenamine (9a). In a glovebox, a Schlenk flask
was charged with 3-[[2,6-bis(1-methylethyl)phenyl]amino]-3-
methyl-2-butanone (2.78 g, 10.68 mmol) dissolved in toluene
(75 mL). Addition of 1.0 M TiCl4 in toluene (8.00 mL, 8.01
mmol) resulted in the formation of a bright orange solution and
the deposition of an orange solid. The reaction mixture was
transferred from the glovebox to a Schlenk line, and anhydrous
ethylamine was bubbled through the solution. Within 5 min the
color of the reaction mixture had bleached and a colorless pre-
cipitate had formed. Bubbling of ethylamine was continued for 2 h
at ambient temperature. The reaction mixture was then poured into
a solution of saturated Na2CO3 (aq; 150 mL), resulting in a slight
exotherm and the deposition of additional colorless precipitate. The
suspension was filtered and the filtrate was extracted with Et2O (3 ꢀ
20 mL). The combined organic fractions were dried over anhydrous
MgSO4 and evaporated under reduced pressure to yield the desired
product as a pale yellow liquid, 2.71 g (88%). 1H NMR (300 MHz,
C6D6):δ7.12 (br s, 3H), 5.24 (br s, 1H), 3.64 (hept, J=6.9 Hz, 2H),
3.08 (q, J = 7.5 Hz, 2H), 1.46 (s, 3H), 1.23-1.18 (m, 15H), 1.13 (s,
6H) ppm. 13C{1H} NMR (75 MHz, C6D6): δ 172.2, 148.8, 142.2,
124.8, 123.4, 64.1, 45.3, 28.2, 26.8, 24.4, 16.2, 12.7 ppm. HREIMS:
calcd for C19H32N2 m/z = 311.246, found m/z = 311.241.
Experimental Section
General Considerations. All solvents and reagents were obtained
from commercial sources and used as received unless otherwise
noted. Toluene, hexanes, CH2Cl2, and C6D6 were dried and
degassed according to published procedures. NMR spectra were
recorded on Varian Mercury-Vx-300 and VNMRS-500 spectrom-
eters. 1H NMR data are reported as follows: chemical shift
(multiplicity (br = broad, s = singlet, d = doublet, t = triplet,
Synthesis of [N-[1,1-Dimethyl-2-(ethylimino-KN)propyl]-2,6-
bis(1-methylethyl)benzenaminato-KN]tris(phenylmethyl)hafnium
(10a). To a vial containing N-[1,1-dimethyl-2-(ethylimino)pro-
pyl]-2,6-bis(1-methylethyl)benzenamine (0.9835 g, 3.41 mmol)
dissolved in 20 mL of toluene was added HfBn4 (1.8513 g, 3.41
mmol) followed by addition of 10 mL of toluene. The reaction
mixture was stirred overnight. The solution was concentrated to
a volume of 10 mL. During solvent removal a white solid appeared.
(15) Wang, W.-J.; Kolodka, E.; Zhu, S.; Hamielec, A. E. J. Polym.
Sci., Part A: Polym. Chem. 1999, 37, 2949–2957.
(16) Noticeable chain termination is observed after 1,2- and 2,1-octene
insertion during ethylene/1-octene copolymerization with CGC, as
evidenced by the appearance of vinylidene and vinylene chain ends.15

Article
Organometallics, Vol. 30, No. 2, 2011 259
To this suspension was added 30 mL of hexane, causing further
precipitation of product. The solid was collected on the frit, washed
with hexane (2 ꢀ 5 mL), and dried under reduced pressure to give
1.45 g of product. The filtrate was put into a freezer for 3 days, re-
sulting in formation of large crystals. The solvent was decanted, and
the crystals were washed with 2 mL of cold hexane and dried under
reduced pressure to give 0.290 g of product. Combined yield: 69%.
1H NMR (C6D6, 300 MHz, 23 °C): δ 7.15 (m, 9H), 6.84 (m, 9H),
(101 MHz, toluene-d8): δ 200.68 (CdN), 147.86 (quat), 145.08
(quat), 139.07 (quat), 128.23 (CH), 127.66 (CH), 127.49 (CH),
124.58 (CH), 121.53 (CH), 83.08 (CH2Ph), 72.54 (s), 36.06
(CH2CH3), 28.89 (s), 26.57 (s), 24.29 (s), 23.79 (s), 19.62 (s),
19.03 (s). Peak assignments were facilitated by HSQC, COSY,
and APT spectra. Anal. Calcd for C40H52HfN2: C, 64.98; H, 7.09;
N, 3.79. Found: C, 64.66; H, 6.96; N, 3.74.
Preparation of [N-[1,1-Dimethyl-2-(ethylimino-KN)propyl]-2,
6-bis(1-methylethyl)benzenaminato-KN]tris(phenylmethyl)zirco-
nium (11a). A colorless solution of N-[1,1-dimethyl-2-(ethyl-
imino)propyl]-2,6-bis(1-methylethyl)benzenamine (0.250 g,
0.870 mmol) in toluene (10 mL) was added to a solution of
ZrBn4 (0.396 g, 0.870 mmol) in toluene (10 mL). The resulting
orange solution was stirred at ambient temperature for 3 h, and
the solvent was removed under reduced pressure to yield a sticky
orange residue. This residue was dissolved in toluene (15 mL),
and hexanes (30 mL) were added. The resulting solution was
filtered and stored at -30 °C overnight, resulting in the deposi-
tion of yellow crystals. The mother liquor was decanted, and the
crystals were dried under reduced pressure to yield a yellow
solid, 0.280 g (49%). 1H NMR (400 MHz, C6D6): δ 7.16 (s, 3H,
DIP), 7.12 (tm, J= 7.7 Hz, 6H, meta-Ph), 6.88 (tm, J= 7.3 Hz, 3H,
para-Ph), 6.83 (dm, J = 7.1 Hz, 6H, ortho-Ph), 3.41 (hept, J = 6.6
Hz, 2H, CH(CH3)2), 2.85 (q, J = 7.2 Hz, 2H, CH2CH3), 2.38 (s,
6H, CH2Ph), 1.33 (d, J = 6.7 Hz, 6H, CH(CH3)2), 1.26 (s, 3H,
CH3), 1.19 (d, J = 6.6 Hz, 6H, CH(CH3)2), 0.74 (s, 6H, CH3), 0.72
(t, J = 7.3 Hz, 3H, CH2CH3). 13C NMR (101 MHz, C6D6): δ
190.56 (NdC), 148.20 (quat), 147.37 (quat), 143.75 (quat), 128.97
(meta-CH2Ph), 126.49 (ortho-CH2Ph), 126.43 (DIP), 125.22 (DIP),
121.59 (para-CH2Ph), 75.37 (quat), 75.14 (CH2Ph), 44.60 (CH2-
CH3), 28.53 (CH(CH3)2), 27.44 (2ꢀCH3), 27.23 (CH(CH3)2), 25.57
(CH(CH3)2), 15.58 (CH3), 13.91 (CH2CH3). Peak assignments
were facilitated by HSQC, COSY, and APT spectra. Anal. Calcd
for C40H52N2Zr: C, 73.68; H, 8.04; N, 4.30. Found: C, 74.05; H,
7.97; N, 4.22.
3.34 (sept, 2H, 3JH-H=6.6 Hz, CH(CH3)2), 2.81 (q, 2H, 3JH-H
=
=
3
7.2 Hz, CH2CH3), 2.21 (s, 6H, CH2Ph), 1.34 (d, 6H, JH-H
6.6 Hz, CH(CH3)2), 1.21(d, 6H, 3JH-H = 6.6 Hz, CH(CH3)2), 1.17
(s, 3H, CH3), 0.68 (t, 3H, 3JH-H=7.2 Hz, CH2CH3), 0.65 (s, 6H,
CH3). 1H NMR (400 MHz, toluene-d8): δ 7.16-7.13 (m, 3H, DIP),
7.11 (t, J = 7.7 Hz, 6H, meta-Ph), 6.84 - 6.76 (m, 9H, ortho,para-
Ph), 3.33 (hept, J = 6.6 Hz, 2H, CH(CH3)2), 2.84 (q, J=7.2 Hz,
2H, CH2CH3), 2.14 (s, 6H, CH2Ph), 1.33 (d, J = 6.7 Hz, 6H,
CH(CH3)2), 1.28 (s, 3H, CH3), 1.21 (d, J = 6.6 Hz, 6H, CH-
(CH3)2), 0.75 (t, J = 7.2 Hz, 3H, CH2CH3), 0.66 (s, 6H, CH3).
13C{1H} NMR (C6D6, 75 MHz, 23 °C): δ 191.63 (NdC), 148.68
(quat), 147.69 (quat), 142.81 (quat), 128.51 (CH), 126.92 (CH),
126.36 (CH), 125.28 (CH), 121.66 (CH), 83.89 (CH2Ph, 1JCH
=
116.7 Hz), 76.53 (quat), 44.32 (CH2CH3), 28.43 (CH(CH3)2), 27.47
(CH(CH3)2), 27.06 (2CH3), 25.38 (CH(CH3)2), 15.80 (CH3), 13.78
(CH2CH3). 13C NMR (101 MHz, toluene-d8): δ 191.63 (NdC),
148.67 (quat), 147.64 (quat), 142.86 (quat), 128.44 (CH), 126.93
(CH), 126.38 (CH), 125.24 (CH), 121.62 (CH), 83.88 (CH2Ph),
76.55 (quat), 44.35 (CH2CH3), 28.46 (s), 27.48, 27.10, 25.38, 15.79
(CH3), 13.84 (CH2CH3). Peak assignments were facilitated by
HSQC, COSY, and APT spectra. Anal. Calcd for C40H52HfN2:
C, 64.98; H, 7.09; N, 3.79. Found: C, 64.90; H, 7.03; N, 3.63.
Preparation of (N-(1,2-Dimethyl-2-(ethylamino-KΝ)propyl-
idene)-2,6-bis(1-methylethyl)benzenaminato-KΝ)tris(phenylmethyl)-
hafnium (10b). Method 1. An NMR tube was charged with 138 mg
of 10a, which was dissolved in 0.7 mL of toluene-d8. Thesamplewas
heated overnight at 85 °C. Upon cooling to ambient temperature,
hexane (3 mL) was added. After standing overnight, the solvent
was decanted, and the formed crystals were washed with hexane
(2 ꢀ 2 mL) and dried under reduced pressure to give 97 mg of
product. Yield: 70.0%. Method 2. A solution of N-(3-(ethylamino)-
3-methylbutan-2-ylidene)-2,6-diisopropylbenzenamine (9b) (0.206 g,
0.714 mmol) in toluene (1 mL) was treated with a solution of
HfBn4 (0.388 g, 0.714 mmol) in toluene (5 mL) to form a yellow
solution. The reaction mixture was stirred at ambient temperature
for 30 min, and the solvent was removed under reduced pressure.
The resulting tan solid was redissolved in CH2Cl2 (1 mL), hexanes
were added (3 mL), and the solution was filtered. Storage at
ambient temperature overnight led to the deposition of off-white
crystals. The mother liquor was decanted, and the crystals were
dried under reduced pressure. A second crop of material was
isolated upon storage of the mother liquor at -40 °C overnight.
The solids were combined to yield the final product, 0.230 g (44%).
1H NMR (400 MHz, C6D6): δ 7.22-7.16 (m, 6H, meta-CH2Ph),
7.07-6.99 (m, 3H, DIP), 6.98 (d, J = 7.1 Hz, 6H, ortho-CH2Ph),
6.86 (tt, J = 7.6, 1.2 Hz, 3H, para-CH2Ph), 3.15 (q, J = 6.8 Hz, 2H,
CH2CH3), 2.51 (hept, J = 6.6 Hz, 2H, CH(CH3)2), 2.05 (s, 6H,
CH2Ph), 1.30 (s, 3H, CH3), 1.25 (d, J = 6.8 Hz, 6H, CH(CH3)2),
1.02 (t, J = 6.8 Hz, 3H, CH2CH3), 0.91 (d, J = 6.8 Hz, 6H,
Preparation of (N-(1,2-Dimethyl-2-(ethylamino-KΝ)propyl-
idene)-2,6-bis(1-methylethyl)benzenaminato-KΝ)tris(phenylmethyl)-
zirconium (11b). A solution of N-(3-(ethylamino)-3-methylbutan-
2-ylidene)-2,6-diisopropylbenzenamine (9b) (0.200 g, 0.693 mmol)
in toluene (1 mL) was added to a solution of ZrBn4 (0.316 g,
0.693 mmol) in toluene (9 mL) to form an orange solution. The
reaction mixture was stirred at ambient temperature for 3 h, and the
solution was concentrated (to ∼7 mL) at reduced pressure. The
reaction mixture was then filtered and stored at -40 °Cfor 2.5days,
resulting in the formation of a yellow microcrystalline solid. The
mother liquor was decanted, and the yellow solid was dried under
reduced pressure. Additional crops of product were isolated upon
crystallization either from a minimum amount of toluene or a 3:5
toluene/hexanes mixture at -40 °C. The crops were combined to
1
afford the desired product as a yellow solid, 0.260 g (58%). H
NMR (500 MHz, C6D6): δ 7.15 (t, J = 7.7 Hz, 6H, meta-Ph),
7.10-7.01 (m, 3H, DIP), 6.94 (d, J = 7.3 Hz, 6H, ortho-Ph), 6.88 (t,
J = 7.3 Hz, 3H, para-Ph), 3.07 (q, J = 6.7 Hz, 2H, CH2CH3), 2.57
(hept, J = 6.7 Hz, 2H, CH(CH3)2), 2.27 (s, 6H, CH2Ph), 1.36 (s,
3H, CH3), 1.27 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.04 (t, J = 6.7 Hz,
3H, CH2CH3), 0.94 (d, J = 6.8 Hz, 6H, CH(CH3)2), 0.86 (s, 6H,
CH3). 13C NMR (126 MHz, C6D6):δ198.46 (CdN), 147.46 (quat),
145.21 (quat), 138.96 (quat), 128.64 (meta-CH2Ph), 127.35 (ortho-
CH2Ph), 127.26 (DIP), 124.64 (DIP), 121.43 (para-CH2Ph), 72.46
(quat), 72.08 (CH2Ph), 36.81 (CH2CH3), 28.77 (CH(CH3)2), 25.99
(2ꢀCH3), 24.32 (CH(CH3)2), 23.85 (CH(CH3)2), 19.43 (CH3),
19.30 (CH2CH3). Peak assignments were facilitated by HSQC,
COSY, and APT spectra. Anal. Calcd for C40H52N2Zr: C, 73.68;
H, 8.04; N, 4.30. Found: C, 74.05; H, 7.97; N, 4.22.
Preparation 3-Bromo-3-methyl-2-butanone (13). In a 500 mL,
three-neck, round-bottom flask equipped with a Teflon-coated
thermocouple, an addition funnel, and a reflux condenser con-
nected to a NaOH trap, 3-methylbutan-2-one (46.4 g, 0.5 mol) and
acetic acid (75 mL) were combined. Bromine (78.3 g, 0.5 mol) and
acetic acid (25 mL) were combined and placed in the addition
1
CH(CH3)2), 0.88 (s, 6H, CH3). H NMR (400 MHz, toluene): δ
7.14 (tm, J = 7.7 Hz, 6H, meta-CH2Ph), 7.06-6.97 (m, 3H, DIP),
6.91 (d, J = 7.2 Hz, 6H, ortho-CH2Ph), 6.82 (t, J = 7.3 Hz, 3H,
para-CH2Ph), 3.13 (q, J = 6.8 Hz, 2H, CH2CH3), 2.50 (hept, J =
6.8 Hz, 2H, CH(CH3)2), 1.97 (s, 6H, CH2Ph), 1.35 (s, 3H, CH3),
1.26 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.04 (t, J = 6.8 Hz, 3H,
CH2CH3), 0.93 (d, J = 6.8 Hz, 6H, CH(CH3)2), 0.91 (s, 6H, CH3).
13C NMR (75 MHz, C6D6) δ 200.69 (CdN), 147.92 (quat),
144.98 (quat), 139.03 (quat), 128.29 (meta-CH2Ph), 127.63
(ortho-CH2Ph), 127.43 (para-DIP), 124.59 (meta-DIP), 121.57
(para-CH2Ph), 83.09 (CH2Ph), 72.46 (quat), 35.98 (CH2CH3),
28.84 (CH(CH3)2), 26.55 (2ꢀCH3), 24.28 (CH(CH3)2), 23.78
(CH(CH3)2), 19.61 (CH3), 19.00 (CH2CH3). 13C{1H} NMR

260 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
funnel. The flask was placed in a cold water bath (15 °C), and the
bromine solution was added dropwise. The rate of addition was
controlled so the bromine color disappeared before the next drop
was added. After the bromine addition was complete, the reaction
mixture was stirred at ambient temperature overnight. Water (100
mL) was added to the reaction mixture. The solution was trans-
ferred to a separatory funnel, more water was added (100 mL),
and the water layer was extracted with Et2O (3ꢀ150 mL). The
combined Et2O layers were washed with cold, saturated NaHCO3
solution (3 ꢀ 200 mL). The Et2O layer was dried with anhydrous
MgSO4, and the solvent was removed in vacuo to yield the crude
product as a yellow oil (95% pure by GC). The product was
further purified by vacuum distillation (33 °C, ∼25 mmHg) to
yield a colorless oil, 59.0 g (74%). 1H NMR (300 MHz, CDCl3): δ
2.44 (s, 3H), 1.86 (s, 6H) ppm. 13C{1H} NMR (75 MHz, CDCl3):δ
203.4, 63.8, 29.6, 24.2 ppm. GC purity: 98%.
(s, 3H, CH3), 1.28 (d, 6H, 3JH-H = 6.9 Hz, CH(CH3)2), 0.93 (s,
6H, CH3), 0.86 (t, 3H, 3JH-H = 6.3 Hz, CH2CH3). 1H NMR (500
MHz, toluene-d8, 30 °C): δ 7.19-7.10 (m, 3H), 3.61 (hept, J = 6.8
Hz, 2H, CH(CH3)2), 3.30 (q, J = 7.3 Hz, 2H, CH2CH3), 1.39 (s,
3H, CH3), 1.34 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.27 (d, J = 6.7
Hz, 6H, CH(CH3)2), 0.95 (s, 6H, CH3), 0.90 (t, J = 7.3 Hz, 3H,
2
CH2CH3). H NMR (toluene-d8, 76.8 MHz, 30 °C): δ 0.31 (s,
CD3). 13C{1H} NMR (C6D6, 75 MHz, 23 °C): δ 189.12 (NdC),
149.19 (quat), 140.33 (quat), 126.30 (CH), 124.70 (CH), 76.40
(quat), 44.67 (CH2CH3), 28.59 (CH(CH3)2), 27.57 (2CH3), 26.95
(CH(CH3)2), 24.78 (CH(CH3)2), 15.38 (CH3), 13.67 (CH2CH3).
13C NMR (126 MHz, toluene-d8, 30 °C): δ 189.17, 149.18, 140.41,
126.30, 124.63, 76.27, 44.56, 28.41, 27.45, 26.74, 24.60, 15.11, 13.47.
Peak assignments were facilitated by HSQC, COSY, and APT
spectra. Anal. Calcd for C22H31D9HfN2: C, 50.80; H, 7.75; N, 5.39.
Found: C, 50.26; H, 7.78; N, 5.26.
Preparation of 3-(Ethylamino)-3-methyl-2-butanone (12). In a
500 mL, three-neck, round-bottom flask equipped with a nitro-
gen inlet, 3-bromo-3-methyl-2-butanone (19.8 g, 120.0 mmol),
DMF (50 mL), and MgO (8.4 g, 210.0 mmol) were combined. A
solution of ethyl amine in THF (2 M, 90 mL, 180 mmol) was
added via syringe, and the mixture was stirred at ambient tem-
perature overnight. The temperature was increased to 60 °C and
the mixture was stirred for 18 h. After cooling, the mixture was
filtered and the filtrate was concentrated under reduced pressure.
The residue was dissolved in Et2O(100mL) andwashedwithwater
(3 ꢀ 100 mL). The Et2O layer was dried with anhydrous MgSO4,
and the solvent was removed under reduced pressure to yield an
orange oil. The oil was dissolved in Et2O (40 mL), and a 2.0 M
solution of HCl in Et2O was added to form the yellow HCl salt. The
salt was recrystallized from ethanol/ethyl acetate to yield white
crystals. The free base was obtained by treating the salt with NaOH
to yield the product as a colorless oil, 3 g (19%). GC purity >99%.
1H NMR (toluene-d8, 300 MHz): δ 4.74 (s, 1H), 2.21 (q, J = 7.2
Hz, 2H), 1.86 (s, 3H), 0.99 (s, 6H), 0.90 (t, J = 7.2 Hz, 3H) ppm.
13C{1H} NMR (d8-toluene, 75 MHz): δ 211.7, 137.5, 62.9, 38.3,
24.3, 23.8, 16.1 ppm.
NMR Spectra for (N-(1,2-Dimethyl-2-(ethylamino-KΝ)pro-
pylidene)-2,6-bis(1-methylethyl)benzenaminato-KΝ)tri(methyl-d3)-
hafnium, 14b. 1H NMR (500 MHz, C6D6, 30 °C): δ 7.07-7.00 (m,
3H), 3.56 (q, J = 6.9 Hz, 2H, CH2CH3), 2.50 (hept, J = 6.8 Hz,
2H, CH(CH3)2), 1.40 (s, 3H, CH3), 1.32 (t, J = 6.8 Hz, 3H,
CH2CH3), 1.20 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.12 (s, 6H, CH3),
0.93 (d, J=6.9 Hz, 6H, CH(CH3)2). 1H NMR (500 MHz, toluene-
d8, 30 °C): δ 7.02-7.00 (m, 3H), 3.55 (q, J=6.9Hz, 2H, CH2CH3),
2.50 (hept, J=6.8 Hz, 2H, CH(CH3)2), 1.45 (s, 3H, CH3), 1.31 (t,
J = 6.8 Hz, 3H, CH2CH3), 1.19 (d, J = 6.8 Hz, 6H, CH(CH3)2),
1.15 (s, 6H, CH3), 0.95 (d, J = 6.9 Hz, 6H, CH(CH3)2). 2H NMR
(toluene-d8, 76.7 MHz, 30 °C): δ 0.27 (s, CD3). 13C{1H} NMR
(126 MHz, C6D6, 30 °C): δ 199.09 (CdN), 145.73 (s), 138.69 (s),
126.73 (s), 124.04 (s), 72.43 (s), 35.58 (s), 28.69 (s), 27.66 (s), 24.12
(s), 23.49 (s), 20.11 (s), 18.85 (s).
Preparation of [N-[1,1-Dimethyl-2-(ethylimino-KN)propyl]-2,6-
bis(1-methylethyl)benzenaminato-KN]triiodohafnium (15). Iodine
(0.9109 g, 3.59 mmol) was dissolved in CH2Cl2 (10 mL) and added
to a solution of 10a (0.87 g, 1.18 mmol) in CH2Cl2 (10 mL) within
10 min. Rapid discoloration occurred during I2 addition until the
final addition of the iodine solution. After the addition was com-
plete, the reaction mixture was stirred for 2 h. Solvent was removed
under reduced pressure, leaving a yellow solid. This solid was
crystallized from a methylene chloride/hexane mixture (8 mL/
20 mL) at -40 °C to give 0.70 g of product as a light yellow solid.
Yield: 70.3%. 1H NMR (C2D2Cl4, 300 MHz, 23 °C): δ 7.37 (dd,
1H, 3JH-H=8.4 Hz, 3JH-H=7.2 Hz), 7.23 (d, 2H, 3JH-H=7.8 Hz),
Preparation of N-(3-(Ethylamino)-3-methylbutan-2-ylidene)-
2,6-diisopropylbenzenamine (9b). In a 100 mL, three-neck, round-
bottom flask equipped with a nitrogen inlet, 3-(ethylamino)-
3-methyl-2-butanone (1.6 g, 12.0 mmol), 2,6-diisopropylaniline
(6.8 mL, 36.0 mmol), and toluene (25 mL) were combined. A solu-
tion of TiCl4 in toluene (1 M, 6.0 mL, 6.0 mmol) was added via
syringe, and the mixture was stirred at ambient temperature for 18 h.
The mixture was filtered, and the filtrate was transferred to a sepa-
ratory funnel with water (150 mL). The water layer was washed with
toluene (2 ꢀ 100 mL). The water layer was treated with aqueous
NaOH solution (5 N) until it became basic and then extracted with
Et2O (3 ꢀ 100 mL). The combined Et2O layers were dried with
anhydrous MgSO4, and the solvent was removed under reduced
pressure to yield a pale brown oil, 1.4 g (40%). 1H NMR (C6D6,
300 MHz): δ 7.14-7.17 (m, 2H), 7.05-7.11 (m, 1H), 2.83 (hept,
J=6.9 Hz, 2H), 2.53 (q, J= 7.2 Hz, 2H), 1.54 (s, 3H), 1.30 (s, 6H),
1.17 (d, J = 6.9 Hz, 6H), 1.16 (d, J = 6.9 Hz, 6H), 1.02 (t, J = 7.2
Hz, 3H) ppm. 13C{1H} NMR (C6D6, 75 MHz): δ 176.2, 147.2,
135.8, 123.5, 123.2, 60.4, 38.3, 28.4, 26.4, 23.3, 23.0, 16.3, 15.6 ppm.
Preparation of [N-[1,1-Dimethyl-2-(ethylimino-KN)propyl]-
2,6-bis(1-methylethyl)benzenaminato-KN]tri(methyl-d3)hafnium
(14a). To 458 mg (0.54 mmol) of 15 dissolved in 20 mL of THF
was added 1.89 g of CD3MgI as a 1 M solution in ether. During the
CD3MgI addition, a white precipitate appeared. After stirring for
2 h, the solution was filtered and the solvent was removed under
reduced pressure. The residue was dissolved in 6 mL of hexane, and
the solution was filtered. The filtrate was put into the freezer
overnight (-40 °C). The solvent was decanted, and the white
crystals that formed were washed with cold hexane (2 ꢀ 2 mL) and
then dried under reduced pressure to give 125 mg of product. Yield:
44.4%. 1H NMR (300 MHz, C6D6, 23 °C): δ 7.20 (m, 3H), 3.65
(hept, 2H, 3JH-H = 6.9 Hz, CH(CH3)2), 3.27 (q, 2H, 3JH-H = 6.3
3.89 (q, 2H, 3JH-H=7.2 Hz, CH2CH3), 3.46 (hept, 2H, 3JH-H
=
6.6 Hz, CH(CH3)2), 2.21 (s, 3H, CH3), 1.55 (t, 3H, 3JH-H=7.2 Hz,
CH2CH3), 1.43 (d, 6H, 3JH-H=6.6 Hz, CH(CH3)2), 1.32 (s, 6H,
CH3), 1.26 (d, 6H, 3JH-H = 6.6 Hz, CH(CH3)2). 13C{1H} NMR
(C2D2Cl4, 75 MHz, 23 °C): δ 192.90 (NdC), 147.81 (quat), 136.70
(quat), 128.13 (CH), 125.52 (CH), 79.05 (quat), 47.48 (CH2CH3),
28.35 (CH3), 27.08 (CH3), 26.89 (CH3), 25.16 (CH3), 15.38 (CH3),
13.67 (CH3). Peak assignments were facilitated by COSY and APT
spectra. Anal. Calcd for C19H31HfI3N2: C, 26.95; H, 3.69; N, 3.31.
Found: C, 26.76; H, 3.95; N, 3.16.
Preparation of the Lithium Salt of N-[1,1-Dimethyl-2-(ethyl-
imino)propyl]-2,6-bis(1-methylethyl)benzenamine. A light yellow
solution of N-[1,1-dimethyl-2-(ethylimino)propyl]-2,6-bis(1-
methylethyl)benzenamine (0.784 g, 2.723 mmol) in hexanes
(5 mL) was treated with 2.5 M n-butyllithium in hexanes
(1.2 mL, 3.0 mmol), resulting in the formation of a yellow solution.
The reaction mixture was stirred at ambient temperature for 5 min,
resulting in the formation of a colorless precipitate. This suspen-
sion was stored at -40 °C overnight, the solid material was
removed via filtration, and the filter cake was washed with cold
(∼-40 °C) hexanes (3 ꢀ 2 mL) and dried under reduced pressure
to yield a colorless solid, 0.5 g (62%). Material of higher purity
may be obtained upon recrystallization from hexanes at -40 °C.
1H NMR (300 MHz, C6D6, ambient temperature): δ 7.18-
7.07 (m, 3H), 3.87 (br s, 2H), 3.04 (br d, 2H), 1.44 (s, 3H),
1.29 (br d, 6H), 1.20-1.07 (br m, 12H), 0.97 (t, J = 7.2 Hz, 3H)
ppm. 1H NMR (300 MHz, d8-THF, ambient temperature): δ 6.67
3
Hz, CH2CH3), 1.39 (d, 6H, JH-H = 6.9 Hz, CH(CH3)2), 1.29

Article
Organometallics, Vol. 30, No. 2, 2011 261
(d, J = 7.5 Hz, 2H), 6.22 (t, J = 7.5 Hz, 1H), 3.67 (hept, J = 6.9
Hz, 2H), 3.28 (q, J = 7.5 Hz, 2H), 1.93 (s, 3H), 1.24 (t, J = 7.5 Hz,
3H), 1.22 (s, 6H), 0.99 (br s, 12H) ppm. Anal. Calcd for
C38H62Li2N4: C, 77.51; H, 10.61; N, 9.52. Found: C, 77.82; H,
10.74; N, 9.19.
Parr reactor was used in the polymerizations. All feeds were passed
through columns of alumina and Q-5 catalyst prior to introduction
into the reactor. Procatalyst and cocatalyst (activator) solutions
were handled in the glovebox. A stirred 2 L reactor was charged
with about 533 g of mixed alkanes solvent and 250 g of 1-octene
comonomer. Hydrogen was added as a molecular weight control
agent by differential pressure expansion from a 75 mL addition
tank at 300 psi (2070 kPa). The reactor contents were heated to the
polymerization temperature of 120 °C and saturated with ethylene
at 460 psig (3.4 MPa). Catalysts and cocatalysts, as dilute solutions
in toluene, were mixed and transferred to a catalyst addition tank
and injected into the reactor. The polymerization conditions were
maintained for 15 min with ethylene added on demand. Heat was
continuously removed from the reaction reactor through an inter-
nal cooling coil. The resulting solution was drained from the
reactor, quenched with isopropyl alcohol, and stabilized by addi-
tion of 10 mL of a toluene solution containing approximately 67 mg
of a hindered phenol antioxidant (Irganox 1010 from Ciba Geigy
Corporation) and 133 mg of a phosphorus stabilizer (Irgafos 168
from Ciba Geigy Corporation).
Synthesis of ([N-[1,1-Dimethyl-2-(ethylimino-KN)propyl]-2,6-
bis(1-methylethyl)benzenaminato-KN]trimethylhafnium (14a-CH3).
A pale yellow solution of the lithium salt of N-[1,1-dimethyl-
2-(ethylimino)propyl]-2,6-bis(1-methylethyl)benzenamine (0.312 g,
0.532 mmol) in toluene (5 mL) was treated with HfCl4 (0.341 g,
1.063 mmol) as a solid. The resulting suspension was stirred at
ambient temperature overnight, forming a brown suspension. This
suspension was treated with 3.0 M MeMgBr in Et2O (1.20 mL,
3.60 mmol) and stirred at ambient temperature for 2 h, forming a
dark brown-black suspension. The reaction mixture was dried
under reduced pressure, and the solid residue was extracted with
hexanes (3 ꢀ 15 mL). The combined hexanes fractions were dried
under reduced pressure to yield a yellow solid. This solid was
dissolved in the minimum amount of hexanes and stored at -40 °C
for 2.5 days, resulting in the formation of colorless crystals. Multiple
crops of the crystals were isolated for a total yield of 0.21 g of
colorless solid (40%). 1H NMR (500 MHz, C6D6): δ 7.22-7.16 (m,
3H), 3.64 (hept, J = 7.0 Hz, 2H), 3.27 (q, J = 7.5, 2H), 1.38 (d, J =
7.0 Hz, 6H), 1.29 (s, 3H), 1.27 (d, J = 7.0 Hz, 6H), 0.93 (s, 6H), 0.86
(t, J = 7.5 Hz, 3H), 0.39 (s, 9H) ppm. 1H NMR (400 MHz, toluene-
d8, 30 °C): 7.19-7.10 (m, 3H), 3.61 (hept, J = 6.8 Hz, 2H,
CH(CH3)2), 3.31 (q, J = 7.3 Hz, 2H, CH2CH3), 1.39 (s, 3H,
CH3), 1.34 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.27 (d, J = 6.7 Hz,
6H, CH(CH3)2), 0.95 (s, 6H, CH3), 0.90 (t, J = 7.3 Hz, 3H,
CH2CH3), 0.30 (s, 9H, HfCH3). 13C{1H} NMR (125 MHz,
C6D6): δ 189.3 (CdN), 149.2, 140.5, 126.3, 124.7, 76.2, 56.8, 44.6,
28.4, 27.4, 26.8, 24.6, 15.2, 13.5 ppm. Anal. Calcd for C40H40N2Hf:
C, 51.70; H, 7.89; N, 5.48. Found: C, 51.59; H, 7.58; N, 5.58.
NMR Spectra for (N-(1,2-Dimethyl-2-(ethylamino-KΝ)propyl-
idene)-2,6-bis(1-methylethyl)benzenaminato-KΝ)trimethylhafnium
(14b-CH3). 1H NMR (400 MHz, toluene-d8, 30 °C): δ 7.03-6.99
(m, 3H), 3.55 (q, J = 6.9 Hz, 2H, CH2CH3), 2.50 (hept, J = 6.9
Hz, 2H, CH(CH3)2), 1.45 (s, 3H, CH3), 1.31 (t, J = 6.8 Hz, 3H,
CH2CH3), 1.20 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.15 (s, 6H,
CH3), 0.95 (d, J = 6.8 Hz, 7H, CH(CH3)2), 0.25 (s, 9H, HfCH3).
13C{1H} NMR (100 MHz, toluene-d8, 30 °C): δ 199.02 (CdN),
145.76, 138.69, 126.79, 124.02, 72.48, 56.60 (HfCH3), 35.70,
28.73, 27.66, 24.14, 23.48, 20.14, 18.82.
Decomposition Kinetics of 10a. A stock solution was prepared
by dissolving 180 mg of 10a in 4.0 mL of toluene-d8. Spectra were
collected at 60.4, 70.6, 80.4, and 90.4 °C using the following param-
eters: number of transients = 32 and acquisition time = 6 s.
Rate constants (k) were obtained by least-squares analysis of
a nonlinear form of a first-order equation.17 In this procedure
concentrations at the given time interval are calculated using a
nonlinear form of a first-order equation [A = Ao ꢀ e-kt], and the
rate constant (k) and initial concentration (Ao) are optimized by
least-squares using Microsoft Excel solver. Thermodynamic param-
eters (ΔH‡ and ΔS‡) were obtained by least-squares analysis of a
nonlinear form of the Eyring equation. In this procedure rate
constants are calculated using a nonlinear form of the Eyring
equation and the ΔH‡ and ΔS‡ are adjusted until the sum of the
error squared between the observed and calculated rate constants
reaches a minimum. Microsoft Excel solver was used to perform
this least-squares analysis. This analysis gave ΔH‡ and ΔS‡ of
Between polymerization runs, a wash cycle was conducted in
which 850 g of mixed alkanes was added to the reactor and the
reactor was heated to 150 °C. The reactor was then emptied of
the heated solvent immediately before beginning a new poly-
merization run.
Polymers were recovered by drying for about 12 h in a
temperature-ramped vacuum oven with a final set point of 140 °C.
Melting and crystallization temperatures of polymers were
measured by differential scanning calorimetry (DSC 2910, TA
Instruments, Inc.). Samples were first heated from room tem-
perature to 180 °C at 10 °C/min. After being held at this tempera-
ture for 2-4 min, the samples were cooled to -40 at 10 °C/min,
held for 2-4 min, and then heated to 160 °C. Molecular weight
distribution (Mw, Mn) information was determined by analysis
on a custom Dow-built robotic-assisted dilution high-tempera-
ture gel permeation chromatographer (RAD-GPC). Polymer
samples were dissolved for 90 min at 160 °C at a concentration
of 30 mg/mL in 1,2,4-trichlorobenzene (TCB) stabilized by
300 ppm BHT, while capped and with stirring. They were then
diluted to 1 mg/mL immediately before a 400 μL aliquot of the
sample was injected. The GPC utilized two Polymer Lab-
oratories PLgel 10 μm Mixed-B columns (300 ꢀ 10 mm) at a
flow rate of 2.0 mL/min at 150 °C. Sample detection was
performed using a PolyChar IR4 detector in concentration
mode. A conventional calibration of narrow polystyrene (PS)
standards was utilized, with apparent units adjusted to homo-
polyethylene (PE) using known Mark-Houwink coefficients
for PS and PE in TCB at this temperature. Absolute Mw
information was calculated using a PDI static low-angle light
scatter detector. To determine octene incorporation, 140 μL of
each polymer solution was deposited onto an IR transparent
silicon wafer, heated at 140 °C until the trichlorobenzene had
evaporated, and analyzed using a Nicolet Nexus 670 FTIR with
7.1 version software equipped with an AutoPro auto sampler.
Structure Determination of 10a and 10b. X-ray intensity data
were collected on a Bruker SMART diffractometer using Mo
˚
KR radiation (λ = 0.71073 A) and an APEXII CCD area
detector. Raw data frames were read by the program SAINT19
and integrated using 3D profiling algorithms. The resulting data
were reduced to produce hkl reflections and their intensities and
estimated standard deviations. The data were corrected for
Lorentz and polarization effects, and numerical absorption
corrections were applied on the basis of indexed and measured
faces. The structure was solved and refined in SHELXTL6.1,
using full-matrix least-squares refinement. The non-H atoms
were refined with anisotropic thermal parameters, and all of
the H atoms were calculated in idealized positions and refined
29.1(7) kcal/mol and 3.8(2.2) cal/mol K, respectively. Errors were
3
obtained by nonlinear error analysis using SolvStat macro.18
Ethylene-1-octene Polymerization Procedures and Polymer
Characterizations. Ethylene-1-octene Copolymerization. A 2 L
(17) Espenson, J. H. Chemical Kinetics and Reaction Mechanisms, 2nd
ed.; McGraw-Hill: New York, 1995.
(18) This was accomplished using SolvStat macro included in the
book: Billo, E. J. Excel for Chemists, 2nd ed.; Wiley-VCH: Weinheim,
2001; Chapter 12.
(19) Sheldrick, G. M. SHELXTL6.1, Crystallographic Software Pack-
age; Bruker AXS, Inc.: Madison, WI, USA, 2008.

262 Organometallics, Vol. 30, No. 2, 2011
Froese et al.
riding on their parent atoms. The refinement was carried out
using F2 rather than F values. R1 is calculated to provide
a reference to the conventional R value, but its function was
not minimized.
Structure Determination of 9 and 14a. A crystal, mounted on a
Mitegen Micromount, was automatically centered on a Bruker
SMART X2S benchtop crystallographic system. Intensity
measurements were performed using monochromated (doubly
˚
curved silicon crystal) Mo KR radiation (0.71073 A) from
a sealed microfocus tube. Generator settings were 50 kV,
1 mA. Data were acquired using three sets of Omega scans at
different Phi settings. APEX2 software was used for preliminary
determination of the unit cell. Determinations of integrated
intensities and unit cell refinement were performed using
SAINT. Data were corrected for absorption effects with
SADABS using the multiscan technique. The structure was
solved with XS, and subsequent structure refinements were
performed with XL.
(20) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, M. G.; Rega, N.;
Petersson, G. A.; Nakatsuji, H.; Hada, H.; Ehara, M.; Toyota, M. K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross,
J. B.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala,
P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.;
Gonzalez, C.; Pople, J. A. Gaussian 03, Revision C.02; Gaussian, Inc.:
Wallingford, CT, 2004.
(21) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (c) Miehlich, B.; Savin, A.; Stoll,
H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200.
(22) (a) Dunning, T. H., Jr.; Hay, P. J. In Modern Theoretical
Chemistry; Schaefer, H. F., III, Ed.; Plenum: New York, 1976; Vol. 3, p 1.
(b) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (c) Wadt, W. R;
Hay, P. J. J. Chem. Phys. 1985, 82, 284. (d) Hay, P. J.; Wadt, W. R. J. Chem.
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Computational Details. Calculations used the Gaussian0320
program. All optimizations were carried out with the hybrid
density functional theory (DFT) method B3LYP.21 The geometry
optimizations were performed with the LANL2TZ(f)22 basis set on
hafnium/zirconium and 6-31G* (5d)23 on all other atoms (denoted
B3LYP/6-31G*). Frequency calculations confirmed the nature of
the stationary points and provided entropic and thermal correc-
tions. Single-point energies using the B3LYP method and the
LANL2TZ(f) basis set on hafnium/zirconium and the 6-311þG**
basis set on the remaining atoms were also used.
Supporting Information Available: Isomerization kinetics of
10a, additional computational data including SD file containing
coordinates for all the computed structures, NMR spectra, and
X-ray data. This material is available free of charge via the
Internet at http://pubs.acs.org.
(23) (a) Ditchfield, R.; Hehre, W. J.; Pople, J. A. J. Chem. Phys. 1971,
54, 724. (b) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972, 56,
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