Indium-bridged chelating diamide group IV metal olefin polymerization catalysts

Article abstract of DOI:10.1021/om020021x

The group IV metal chelating diamide complex 2 has been prepared and characterized by ¹H and ¹³C{¹H} NMR spectroscopy and single-crystal X-ray structure analysis. This complex is an active catalyst upon combining with the

Full text of DOI:10.1021/om020021x

Organometallics 2002, 21, 2145-2148
2145
Notes
In d iu m -Br id ged Ch ela tin g Dia m id e Gr ou p IV Meta l
Olefin P olym er iza tion Ca ta lysts
J asson T. Patton* and Marilyn M. Bokota
Chemical Sciences, The Dow Chemical Company, Midland, Michigan 48674
Khalil A. Abboud
Department of Chemistry, University of Florida, Gainesville, Florida 32611
Received J anuary 9, 2002
Summary: The group IV metal chelating diamide com-
1
plex 2 has been prepared and characterized by H and
13C{1H} NMR spectroscopy and single-crystal X-ray
structure analysis. This complex is an active catalyst
upon combining with the appropriate activator. The
catalyst efficiencies, however, are considerably lower
than those of Cp-based catalysts. The polydispersities of
the polymers produced were found to be broader than
those observed for Cp-based single-site catalytic systems.
In tr od u ction
The development of non-Cp-based early-transition-
metal complexes that provide suitable precursors for the
generation of homogeneous Ziegler-Natta olefin polym-
erization catalysts remains an active area of industrial
and academic research.1 One strategy which has met
with considerable success involves the replacement of
both cyclopentadienyl (Cp) ligands with an amido
functionality. Of particular note are the recent reports
of the preparation of a variety of four-, five-, and six-
coordinate group 4 metal complexes that contain a
chelating diamido ligand.2 These compounds have been
subsequently shown, upon activation, to afford catalysts
capable of the living polymerization of 1-hexene and the
copolymerization of ethylene and R-olefins. A recent
extension of this work involved the incorporation of a
bis(dimethylamido) diboron bridge into the ligand struc-
ture, resulting in complex 1.3 This class of complexes
proved to be olefin polymerization catalysts upon acti-
vation, albeit demonstrating low activities and stability.
to include an indium bridge.4 The research is driven to
determine if the inclusion of the indium linkage for
amide-based complexes results in improved catalytic
properties relative to the previously described diboron
analogues. We now report the synthesis, spectroscopic
characterization, X-ray crystallographic analysis, and
polymerization activity of the electrophilic indium-
bridged titanium complex 2.
Resu lts a n d Discu ssion
Syn th esis. The preparation of complex 2 is repre-
sented in Scheme 1. Initial attempts to synthesize the
analogous complex starting with the simple Et2N-InCl2
reagent5 as the potential bridging synthon were unsuc-
cessful, due to the formation of multiple unidentified
reaction products upon addition of 2 equiv of 2,6-
diisopropylaniline lithium salt. An observed product in
this reaction is metallic indium, characteristic of these
reactions.6 The tert-butyl-N,N′-diisopropylamidinate
group was turned to as a stabilizing group to impart
greater electronic as well as steric stabilization of the
reactive indium center. This strategy resulted in the
successful synthesis of 4 in good yield following recrys-
tallization from toluene. Attempts to deprotonate 4 with
This paper describes our efforts into extending the
class of Lewis acid bridged bis(amide) based complexes
* To whom correspondence should be addressed. Tel: (989) 636-
1978. Fax: (989) 638-9350. E-mail: jtpatton@dow.com.
(1) Britovsek, G. J . P.; Gibson, V. C.; Duncan, F. W. Angew. Chem.,
Int. Ed. 1999, 38, 428.
(2) (a) Scollard, J . D.; McConville, H. H.; Vittal, J . J .; Payne, N. C.
J . Mol. Catal. 1998, 128, 201. (b) Schrock, R. R.; Bonitatebus, P. J .,
J r.; Schrodi, Y. Organometallics 2001, 20, 1056. (c) Schrodi, Y.; Schrock,
R. R.; Bonitatebus, P. J ., J r. Organometallics 2001, 20, 3560. (d)
O’Connor, P. E.; Morrison, D. J .; Steeves, S.; Burrage, K.; Berg, D. J .
Organometallics 2001, 20, 1153 and references therein.
(3) Patton, J . T.; Feng, S. G.; Abboud, K. A. Organometallics 2001,
20, 3399.
(4) Campbell, R. E., J r.; Devore, D. D.; Feng, S.; Frazier, K. A.;
Green, P. D.; Patton, J . T. Gallium or Indium Bridged Group IV Metal
Complexes for Catalysts for Polymerization of Olefins, WO 01/46201.
(5) Prust, J .; Mu¨ller, P.; Rennekamp, C.; Roesky, H. W.; Uso´n, I. J .
Chem. Soc., Dalton Trans. 2000, 2265.
(6) Bradley, D. C.; Frigo, D. M.; Hursthouse, M. B.; Hussain, B.
Organometallics 1988, 7, 1112.
10.1021/om020021x CCC: $22.00 © 2002 American Chemical Society
Publication on Web 04/09/2002

2146 Organometallics, Vol. 21, No. 10, 2002
Notes
Sch em e 1
reagents such as alkyllithiums were unsuccessful, lead-
ing to unidentified byproducts likely due to the high
reactivity of the indium center. Successful metalation
occurred when the ligand 4 was heated in a benzene
solution of Ti(NMe2)4, resulting in the clean isolation
of 2 following recrystallization. Attempts to exchange
the dimethylamido groups from 2 with either chloride
substituents using reagents such as TMS-Cl, BCl3, and
HCl-NEt3 or direct conversion to the methyl substit-
uents using AlMe3 all met with failure: again, likely
1
due to the reactive indium center. The H NMR spec-
trum for compound 2 exhibits a sharp doublet and
singlet for the isopropyl methyls and the tert-butyl group
of the amidinate group, respectively. The isopropyl
groups of the aniline substituents appear as a broad
resonance at 1.36 ppm, indicating a hindered rotation
about the isopropyl-aryl bond linkage. This broad
resonance sharpens to a single doublet upon heating to
40 °C. The remainder of the room-temperature spectrum
shows septets for the isopropyl methine groups of the
amidinate and the aniline substituents at 3.80 and 3.93,
respectively. The aromatic resonances exhibit the ex-
pected sharp triplet at 6.95 ppm and doublet at 7.17
ppm.
X-r a y Cr ysta l Str u ctu r e An a lysis. The molecular
structures of 27 and 48 were confirmed by single-crystal
X-ray structure analysis. The thermal ellipsoid drawings
are shown in Figures 1 and 2. Selected bond distances
and angles are included in Tables 1 and 2.9 The X-ray
single-crystal analyses reveal that compounds 2 and 4
exhibit symmetrically bound amidinate ligands to the
indium moiety through the two nitrogen atoms, forming
the expected planar four-membered rings. In the free
ligand 4 the In-N1 and In-N4 bond lengths are
virtually identical. The corresponding bond angles for
4, In-N1-C11 and In-N4-C5 at 125.34(14) and 117.23-
(13)°, respectively, differ significantly, likely due to the
F igu r e 1. Molecular structure and numbering scheme for
bis(2,6-diisopropylaniline)indium-tert-butyl-N,N′-diisopro-
pylamidinate (4) with 40% probability thermal ellipsoids.
distortion of these bonds, allowing for steric relief from
the large isopropyl substituents. These same angles for
2 continue to exhibit asymmetry, but to a lesser degree
at 117.89(16) and 120.17(16)° respectively. Again, this
is likely attributed to the sterics of having six isopropyl
groups on a single ligand fragment. This asymmetry in
2 can also be observed in the In-N1 and In-N4 bond
lengths of 2.118(2) and 2.134(2) Å, respectively. One
might speculate that, as the ligand is reorganized to
accommodate the titanium chelation, one of the In-
N(aniline) bonds is lengthened to decrease the isopropyl
(aniline) and isopropyl (amidinate) steric congestion. In
compound 2, the N4-In-N1 bond angle is 85.14(8)°,
relative to 107.61(7)° for 4, due to the chelation of N1
and N4 to the titanium metal center again forming a
planar four-membered metallacycle spirally linked to
the other metallacycle through the indium center.
P olym er iza tion Resu lts. The complex 2 was an
active polymerization catalyst upon combination with
appropriate activators. Presumably, the activator pack-
age includes an alkylaluminum species to first exchange
out the dimethylamido substituents on the titanium
metal center followed by alkyl abstraction.10 This method
(7) Crystallographic data for 2: formula C39H69InN6Ti, fw ) 784.72,
monoclinic, space group P21/n (No. 14), a ) 11.147(1) Å, b ) 20.878(2)
Å, c ) 18.418(2) Å, â ) 102.158(2)°, V ) 4190.2(7) Å3, Z ) 4, dcalcd
)
1.244 g cm-3, T ) 173(2) K, ω-2θ scan, 6° < 2θ < 55°, λ(Mo KR) )
0.710 73 Å, R (Rw) ) 0.0359 (0.0728) for 444 parameters against 7143
reflections with I > 2σ(I) out of 9621 unique reflections (Rint ) 0.0563)
by full-matrix least-squares methods, GOF ) 0.937.
(8) Crystallographic data for 4: formula C35H59InN4, fw ) 650.68,
triclinic, space group P1h (No. 2), a ) 9.4828(6) Å, b ) 11.4576(7) Å, c
) 17.958(1) Å, â ) 99.087(1)°, V ) 1780.2(2) Å3, Z ) 2, dcalcd ) 1.214
g cm-3, T ) 173(2) K, ω-2θ scan, 6° < 2θ < 55°, λ(Mo KR) ) 0.710 73
Å, R (Rw) ) 0.0296 (0.0752) for 384 parameters against 7252 reflections
with I > 2σ(I) out of 7941 unique reflections (Rint ) 0.0379) by full-
matrix least-squares methods, GOF ) 1.029.
(9) See the Supporting Information for full crystallographic data
and tables.
(10) Gibson, V. C.; Kimberley, B. S.; White, A. J . P.; Williams, D.
J .; Howard, P. Chem. Commun. 1998, 331.

Notes
Organometallics, Vol. 21, No. 10, 2002 2147
reactor in runs 2-4. In each case activation occurs in
the presence of the olefin monomers. The polymeriza-
tions were conducted with ethylene on demand. The
results for the ethylene/octene copolymerizations are
summarized in Table 3. These results indicate that
these catalysts exhibit low activity toward the polym-
erization of olefin monomers and, like the diborone
bridged analogues, suffer from the formation of multiple
catalyst sites.
Con clu sion s
A group IV metal complex comprised of an indium-
bridged amido ligand has been synthesized. Complex 2
was prepared by reacting the neutral ligand with Ti-
(NMe2)4 via the elimination of HNMe2. This complex has
been shown to be an active olefin polymerization
catalyst upon combination with the appropriate activa-
tor. Efforts to examine the structure-activity relation-
ships of In-bridged amide-based complexes are currently
underway.
Exp er im en ta l Section
The 1H (300 MHz) and 13C{1H} NMR (75 MHz) spectra were
recorded on Varian Mercury Vx and Inova 300 spectrometers.
The 1H and 13C NMR spectra are referenced to the residual
solvent peaks and are reported in ppm relative to tetrameth-
ylsilane. All J values are given in Hz. Tetrahydrofuran (THF),
diethyl ether, toluene, and hexane were used following passage
through double columns charged with activated alumina and
Q-5 catalyst. The compounds Ti(NMe2)4, 1,3-diisopropylcar-
bodiimide, tert-butyllithium, and 2,6-diisopropylaniline were
all used as purchased from Aldrich. All syntheses were
performed under dry nitrogen atmospheres using a combina-
tion of glovebox and high-vacuum techniques. High-resolution
mass spectroscopy (HRMS) was performed by the University
of Florida. Elemental analyses were performed by Oneida
Research Services, Inc., Whitesboro, NY, and University of
Michigan Thermal Analysis Group, Ann Arbor, MI.
F igu r e 2. Molecular structure and numbering scheme for
bis(dimethylamido)bis(2,6-diisopropylaniline)indium-(tert-
butyl-N,N′-diisopropylamidinate)titanium (2) with 40%
probability thermal ellipsoids.
Ta ble 1. Selected Bon d Len gth s (Å) for 2 a n d 4
2
4
In-N1
In-N2
In-N3
In-N4
In-Ti
Ti-N1
Ti-N4
Ti-N5
Ti-N6
2.118(2)
2.162(2)
2.163(2)
2.134(2)
2.8160(5)
1.910(2)
1.905(2)
1.901(2)
1.932(2)
2.072(2)
2.167(2)
2.160(2)
2.071(2)
Sin gle-Cr ysta l X-r a y An a lysis of Bis(2,6-d iisop r op yl-
an ilide)in diu m -ter t-Bu tyl-N,N′-diisopr opylam idin ate (4)
a n d Bis(d im eth yla m id o)bis(2,6-d iisop r op yla n ilid e)in d i-
u m -(ter t-Bu tyl-N,N′-d iisop r op yla m id in a te)tita n iu m (2).
Data were collected at 173 K on a Siemens SMART PLAT-
FORM equipped with a CCD area detector and a graphite
monochromator utilizing Mo KR radiation (λ ) 0.710 73 Å).
Cell parameters were refined using 8192 reflections. A hemi-
sphere of data (1381 frames) was collected using the ω-scan
method (0.3° frame width). The first 50 frames were remea-
sured at the end of data collection to monitor instrument and
crystal stability (maximum correction on I was <1%). Absorp-
tion corrections by integration were applied on the basis of
measured indexed crystal faces.
The structures were solved by direct methods in SHELXTL5
and refined using full-matrix least squares.12 The non-H atoms
were refined with anisotropic thermal parameters, and all of
the H atoms were calculated in idealized positions and refined
riding on their parent atoms. In the final cycle of refinement
of 2, 7143 observed reflections with I > 2σ(I) were used to
refine 444 parameters and the resulting R1 and wR2 values
were 3.59% and 7.28%, respectively. In the final cycle of
refinement of 4, 7252 observed reflections with I > 2σ(I) were
used to refine 384 parameters and the resulting R1 and wR2
values were 2.96% and 7.52%, respectively. Refinement was
done using F2.
Ta ble 2. Selected An gles (d eg) for 2 a n d 4
2
4
N4-In-N1
N4-In-N3
N1-In-N3
N4-In-N2
N1-In-N2
N3-In-N2
N3-C3-N2
In-N1-C11
In-N4-C5
N4-Ti-N1
N5-Ti-N6
N5-Ti-In
C11-N1-Ti
Ti-N1-In
C5-N4-Ti
Ti-N4-In
85.14(8)
117.94(8)
138.37(8)
141.13(8)
122.41(8)
61.15(8)
110.3(2)
117.9(2)
120.2(2)
97.91(9)
101.4(1)
133.53(7)
153.4(2)
88.56(8)
150.9(2)
88.24(8)
107.61(7)
113.88(7)
125.83(8)
120.83(7)
121.82(7)
60.91(7)
110.2(2)
125.3(1)
117.2(1)
of activation has proven successful in related bis-
(cyclopentadienyl)-based systems.11 The complex was
activated in runs 1, 5, and 6 by injecting complex 4,
TIBA (triisobutylaluminum), and [CPh3][B(C6F5)4] or
MAO solutions independently into the reactor. Alter-
natively, 4 was activated by premixing the complex with
TIBA and then injecting this mixture and [CPh3]-
[B(C6F5)4] or MAO solutions independently into the
Eth ylen e/Octen e Cop olym er iza tion s. All feeds were
passed though columns of activated alumina and Q-5 catalyst
(11) Kim, I.; J ordan, R. F. Macromolecules 1996, 29, 489.
(12) Sheldrick, G. M. SHELXTL5; Bruker-AXS, Madison, WI, 1998.

2148 Organometallics, Vol. 21, No. 10, 2002
Ta ble 3. Eth ylen e/Octen e Cop olym er iza tion Resu lts
Notes
run
monomer
activator
Tp (°C)
exotherm (°C)
activity ((g of P)/(g of Ti))
Mw (PDI)
1
2
3
4
5
E/O
E/O
E/O
E/O
E/O
50 TIBA/1000 MAO
50 TIBA/1000 MAO
50 TIBA/[CPh3][B(C6F5)4]
50 TIBA/[CPh3][B(C6F5)4]
50 TIBA/1000 MAO
70
70
70
140
140
0.0
2.0
4.0
1.0
1.3
25 991
27 151
34 113
6 683
167 000 (9.54)
562 000 (9.95)
598 000 (13.56)
132 000 (17.4)
144 000 (12.8)
4 595
prior to introduction to the reactor. A stirred 2 L Parr reactor
was charged with about 740 g of Isopar-E solvent and 118 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 25 psi (2070 kPa). The reactor
contents were then heated to the polymerization temperature
of 140 °C and saturated with ethylene at 500 psig (3.4 Mpa).
The metal complex and activators were mixed as dilute toluene
solutions, transferred to a catalyst addition tank, and injected
into the reactor through a stainless steel transfer line. The
polymerization conditions were maintained for 15 min with
ethylene added on demand. Heat was continually removed
from the reaction with an internal cooling coil. The resulting
solution was removed from the reactor, quenched with isopro-
pyl alcohol, and stabilized by the addition of 10 mL of a toluene
solution containing approximately 67 mg of a hindered phenol
antioxidant (Irganox 1010 from Ciba Geigy Corp.) and ap-
proximately 133 mg of a phosphorus stabilizer (Irgafos 168
from Ciba Geigy Corp.). Between polymerization runs a wash
cycle was conducted in which 850 g of mixed alkanes were
added to the reactor, which was then heated to 150 °C and
then emptied of the heated solvent immediately prior to a new
polymerization run.
Polymers were recovered by drying for about 20 h in a
vacuum oven set at 140 °C. High-temperature gel permeation
chromatography (GPC) analysis of polymer samples were
carried out in 1,2,4-trichlorobenzene at 135 °C on a Waters
150C high-temperature instrument. A polystyrene/polyethyl-
ene universal calibration was carried out using narrow mo-
lecular weight distribution polystyrene standards from Poly-
mer Laboratories with lonol as the flow meter.
P r ep a r a tion of ter t-Bu tyl-N,N′-d iisop r op yla m id in a te
Lith iu m Sa lt. 1,3-Diisopropylcarbodiimide (7.000 g, 55.47
mmol) was stirred in hexane (50 mL) at 0 °C as t-BuLi (1.7 M
solution in pentane) was added dropwise. This mixture was
stirred overnight at room temperature, during which time a
white precipitate formed. This mixture was then filtered and
the white solid washed with hexane, dried under vacuum, and
used without further purification or analysis (9.629 g, 91.2%
yield).
stirred for 3 h, during which time a white precipitate formed.
After the reaction period the mixture was filtered and the
white salt washed with hexane, dried under vacuum, and used
without further purification or analysis (9.988 g, 96.7% yield).
P r ep a r a t ion of Bis(2,6-d iisop r op yla n ilin e)in d iu m -
ter t-Bu tyl-N,N′-d iisop r op yla m id in a te (4). 2,6-Diisopropy-
laniline lithium salt (2.880 g, 15.72 mmol) in diethyl ether (10
mL) was added dropwise to a slurry of dichloroindium-tert-
butyl-N,N′-diisopropylamidinate (2.900 g, 7.86 mmol) in di-
ethyl ether (50 mL) at 0 °C. This mixture was then stirred
overnight at room temperature. After the reaction period the
volatiles were removed under vacuum and the residue ex-
tracted and filtered using hexane. Concentration of the filtrate
and cooling to -10 °C overnight resulted in the isolation of
the desired product as a pale yellow crystalline solid (2.982 g,
58.3% yield). 1H NMR (C6D6): δ 0.86 (d, 3J HH ) 6.0 Hz, 12 H),
3
3
1.06 (s, 9 H), 1.28 (d, J HH ) 6.9 Hz, 24 H), 3.24 (sept, J HH
)
6.6 Hz, 4 H), 3.48 (s, 2 H), 3.93 (sept, 3J HH ) 6.3 Hz, 2 H), 6.90
3
3
(t, J HH ) 7.5 Hz, 2 H), 7.13 (d, J HH ) 2.4 Hz, 4 H). 13C{1H}
NMR (C6D6): δ 23.45, 26.59, 28.98, 29.80, 46.38, 118.83,
123.02, 137.46, 148.52. HRMS (EI): calcd for C35H59N4In m/z
650.3780, found 650.3752. Anal. Calcd for C34H59N4In: C,
63.94; H, 9.31; N, 8.77. Found: C, 63.83; H, 9.81; N, 8.64.
P r ep a r a tion of Bis(d im eth yla m id o)bis(2,6-d iisop r o-
p yla n ilid e)in d iu m -(ter t-Bu tyl-N,N′-d iisop r op yla m id in a -
te)tita n iu m (2). Bis(2,6-diisopropylanilide)indium-tert-butyl-
N,N′-diisopropylamidinate (1.000 g, 1.54 mmol) and Ti(NMe2)4
were heated together in benzene (20 mL) at 60 °C for 8 h under
a nitrogen bubbler. During this time the flask was occaission-
ally evacuated and then back-flushed with fresh nitrogen. The
reaction mixture was then placed under full vacuum to remove
all volatiles. The mixture was then extracted and filtered using
toluene. The toluene solution was then concentrated and
placed in a freezer (-10 °C) overnight, during which time the
desired product precipitated as a yellow crystalline solid (0.394
1
3
g, 32.6% yield). H NMR (C6D6): δ 0.67 (d, J HH ) 6.0 Hz, 12
H), 0.90 (s, 9 H), 1.38 (br m, 24 H), 3.24 (s, 12 H), 3.82 (sept,
3J HH ) 6.2 Hz, 2 H), 3.94 (sept, J HH ) 6.9 Hz, 4 H), 6.96 (t,
3
3J HH ) 7.6 Hz, 2 H), 7.18 (d, 3J HH ) 7.8 Hz, 4 H). 13C{1H} NMR
(C6D6): δ 24.6 (br), 25.74, 28.38, 29.46, 31.92, 39.48, 46.56,
46.93, 120.09, 123.22, 138.59, 154.38, 174.86. HRMS (EI):
calcd for C39H69N6InTi m/z 784.4103, found 784.4127. Attempts
to obtain elemental analysis using highly purified crystals
consistently gave low nitrogen analysis.
P r ep a r a t ion of Dich lor oin d iu m -ter t-Bu t yl-N,N′-d i-
isop r op yla m id in a te (3). tert-Butyl-N,N′-diisopropylamidi-
nate lithium salt (9.629 g, 50.61 mmol) and indium trichloride
(11.194 g, 50.61 mmol) were mixed together in diethyl ether
(50 mL) at 0 °C and then stirred overnight at room temper-
ature. After the reaction period the volatiles were removed and
the residue extracted and filtered using hot toluene. The
product was highly insoluble. Following extraction and filtra-
tion the residue was recrystallized from boiling toluene,
resulting in the isolation of the desired product as a slightly
pale yellow crystalline solid (8.990 g, 48.1% yield). 1H NMR
Ack n ow led gm en t. We are grateful to the polypro-
pylene research group of The Dow Chemical Co. for
general discussions. We also thank J udy Gunderson for
the size exclusion chromatography analysis of the
polymers.
3
(CD2Cl2): δ 1.18 (d, J HH ) 6.0 Hz, 12 H), 1.46 (s, 9 H), 4.38
Su p p or tin g In for m a tion Ava ila ble: An ORTEP diagram
and tables of crystal data, data collection, and refinement
parameters, atomic coordinates, bond distances and angles,
and isotropic displacement parameters for complexes 2 and
4. This material is available free of charge via the Internet at
http://pubs.acs.org.
3
(sept., J HH ) 5.9 Hz, 2 H). 13C{1H} NMR (CD2Cl2): δ 26.69,
29.79, 47.75. HRMS (EI): calcd for C11H23N2InCl2 m/z 368.0279,
found 368.0280.
P r ep a r a tion of 2,6-Diisop r op yla n ilin e Lith iu m Sa lt.
n-BuLi (56.40 mmol, 35.25 mL of a 1.6 M solution in hexane)
was added dropwise to a solution of 2,6-diisopropylaniline
(10.00 g, 56.40 mmol) in hexane (100 mL). This mixture was
OM020021X