Chelating diamide group IV metal olefin polymerization catalysts

Article abstract of DOI:10.1021/om010101l

The novel group IV metal chelating diamide complexes [(2,6-diisopropylanilido)B(NMe₂)B-(NMe₂) (2,6-diisopropylanilido)]MX₂, 7a (M = Ti, X = Cl), 7b (M = Ti, X = Me), and 8 (M = Zr, X = CH₂Ph), have been prepared and characterized by ¹H and ¹³C{H} NMR spectroscopy and single-crystal X-ray structure analysis (7a). These complexes are active polymerization catalysts upon combining with the appropriate activator. The catalyst efficiencies, however, are considerably lower than those of Cp-based catalysts. The molecular weights of the polymers produced are activator dependent, and the polydispersities were found to be broader than those observed for Cp-based single-site catalytic systems.

Full text of DOI:10.1021/om010101l

Organometallics 2001, 20, 3399-3405
3399
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 Shaoguang G. Feng
The Dow Chemical Company, Chemical Sciences, Midland, Michigan 48674
Khalil A. Abboud
Department of Chemistry, University of Florida, Gainesville, Florida 32611
Received February 9, 2001
The novel group IV metal chelating diamide complexes [(2,6-diisopropylanilido)B(NMe2)B-
(NMe2)(2,6-diisopropylanilido)]MX2, 7a (M ) Ti, X ) Cl), 7b (M ) Ti, X ) Me), and 8 (M )
Zr, X ) CH2Ph), have been prepared and characterized by 1H and 13C{H} NMR spectroscopy
and single-crystal X-ray structure analysis (7a ). These complexes are active polymerization
catalysts upon combining with the appropriate activator. The catalyst efficiencies, however,
are considerably lower than those of Cp-based catalysts. The molecular weights of the
polymers produced are activator dependent, and the polydispersities were found to be broader
than those observed for Cp-based single-site catalytic systems.
In tr od u ction
Numerous studies of homogeneous single-site olefin
polymerization catalysis have led to the rapid develop-
ment of group IV cyclopentadienyl (Cp)-based com-
plexes, which have seen extensive applications to the
stereospecific polymerization of R-olefins.1 Application
of Cp-silylamido ligands to group III and group IV
metals has led to complexes such as [(η5-C5Me4)SiMe2-
(N-t-Bu)]TiMe2 (1) that exhibit high polymerization
activity toward R-olefins and other vinyl monomers
upon activation.2
Recent modifications to the Cp-based ligand frame-
work have included the use of aryl- and amide-
substituted boranes as the ansa bridge as in compounds
2,3 3,4 and 4,5 which upon activation are effective olefin
polymerization catalysts.
The development of non-Cp-based early transition
metal complexes as homogeneous Ziegler-Natta olefin
* Corresponding author. Tel: (517) 636-1978. Fax: (517) 638-9350.
E-mail: jtpatton@dow.com.
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Goddard, R. Chem. Commun. 1999, 12, 1105.
polymerization catalysts remains an active area of
research.6 One strategy that has met with considerable
success involves the use of chelating diamide ligands
resulting in the formation of a variety of four- and five-
coordinate group 4 complexes.7-9 Selected examples of
this class of complexes are represented in Figure 1 (5,9
(4) (a) Ashe, A. J ., III; Fang, X.; Kampf, J . W. Organometallics 1999,
18, 2288. (b) Braunschweig, H.; Dirk, R.; Muller, M.; Nguyen, P.;
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10.1021/om010101l CCC: $20.00 © 2001 American Chemical Society
Publication on Web 07/06/2001

3400 Organometallics, Vol. 20, No. 16, 2001
Patton et al.
F igu r e 1. Molecular structure and partial numbering
scheme for 7a with 40% probability thermal elipsoids.
Hydrogen atoms are omitted for clarity.
610). These complexes have been shown upon activation
to yield catalysts capable of the living polymerization
of 1-hexene and the copolymerization of ethylene and
R-olefins. In general, chelating diamide-based complexes
have produced many active olefin polymerization cata-
lysts but remain inferior to their Cp-based predecessors.
This paper describes our efforts into a new class of
diborane-bridged bis(amide)-based complexes. The re-
search is driven to determine if the inclusion of the
boron-amido linkage for amide-based complexes would
result in improved catalytic properties. We now report
(7) (a) Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B.;
Wainwright, A. P. J . Organomet. Chem. 1995, 501, 333. (b) Tinkler,
S.; Deeth, R. J .; Duncalf, D. J .; McCamley, J . J . Chem. Soc., Chem.
Commun. 1996, 23, 2623. (c) Cloke, F. G. N.; Geldbach, T. J .; Hitchcock,
P. B.; Love, J . B. J . Organomet. Chem. 1996, 506, 343. (d) Male, N. A.
H.; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc., Dalton Trans.
1997, 14, 2487. (e) Aoyagi, K.; Gantzel, P. K.; Kalai, K.; Tilley, T. D.
Organometallics 1996, 15, 923. (f) J eon, Y-. M.; Park, S. J .; Heo, J .;
Kim, K. Organometallics 1998, 17, 3161. (g) J eon, Y.-M.; Heo, J .; Lee,
W. M.; Chang, T.; Kim, K. Organometallics 1999, 18, 4107. (h) Lorber,
C.; Donnadieu, B.; Choukroun, R. Organometallics 2000, 19, 1963. (i)
Gibson, V. C.; Kimberley, B. S.; White, A. J . P.; Williams, D. J .;
Howard, P. Chem Commun. 1998, 313. (j) Warren, T. H.; Schrock, R.
R.; Davis, W. M. Organometallics 1996, 15, 562. (k) Warren, T. H.;
Schrock, R. R.; Davis, W. M. Organometallics 1998, 17, 308. (l) Tsuie,
B.; Swenson, D. C.; J ordon, R. J .; Petersen, J . L. Organometallics 1997,
16, 1392.
the synthesis, spectroscopy characterization, X-ray crys-
tallographic analysis, and polymerization activity of
novel electrophilic diborane-bridged diamide titanium
and zirconium complexes 7 and 8.
(8) (a) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478. (b) Gue´rin, F.; McConville, D. H.; Payne, N. C.
Organometallics 1996, 15, 5085. (c) Gue´rin, F.; McConville, D. H.;
Vittal, J . J . Organometallics 1996, 15, 5586. (d) Scollard, J . D.;
McConville, D. H.; Payne, N. C.; Vittal, J . J . Macromolecules 1996,
29, 5241. (e) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996,
118, 10008. (f) Scollard, J . D.; McConville, D. H.; Vittal, J . J .
Organometallics 1997, 16, 4415. (g) Scollard, J . D.; McConville, D. H.;
Vittal, J . J .; Payne, N. C. J . Mol. Catal. A: Chem. 1998, 128, 201.
(9) (a) Horton, A. D.; de With, J .; van der Linden, A. J .; van de Weg,
H. Organometallics 1996, 15, 2672. (b) Guerin, F.; McConville, D. H.;
Vittal, J . J . Organometallics 1997 16, 1491. (c) Baumann, R., Davis,
W. M.; Schrock, R. R. J . Am. Chem. Soc. 1997, 119, 3830. (d) Guerin,
F.; McConville, D. H.; Vittal, J . J .; Yap, G. A. P. Organometallics 1998,
17, 5172. (e) Baumann, R.; Schrock, R. R. J . Organomet. Chem. 1998,
557, 69. (f) Schrock, R. R.; Schattenmann, F.; Aizenberg, M.; Davis,
W. M. Chem. Commun. 1998, 2, 199. (g) Schattenmann, F. J .; Schrock,
R. R.; Davis, W. M. Organometallics 1998, 17, 989. (h) Baumann, R.;
Stumpf, R.; Davis, W. M.; Liang, L.-C.; Schrock, R. R. J . Am. Chem.
Soc. 1999, 121, 7822. (i) Liang, L.-C.; Schrock, R. R.; Davis, W. M.;
McConville, D. H. J . Am. Chem. Soc. 1999, 121, 5797. (j) Schrock, R.
R.; Baumann, R.; Reid, S. M.; Goodman, J . T.; Stumpf, R.; Davis, W.
M. Organometallics 1999, 18, 3649. (k) Flores, M. A.; Manzoni, M. R.;
Baumann, R.; Davis, W. M.; Schrock, R. R. Organometallics 1999, 18,
3220. (l) Morton, C.; Munslow, I. J .; Sanders, C. J .; Alcock, N. W.; Scott,
P. Organometallics 1999, 18, 4608. (m) Liang, L.-C.; Schrock, R. R.;
Davis, W. M. Organometallics 2000, 19, 2526.
Resu lts a n d Discu ssion
Liga n d Syn th esis. The preparation of the ligand is
represented in Scheme 1. The initial approach to the
synthesis of 9 was taken using a slight modification of
a synthetic route described in the literature.10 Solid
dimethyl sulfide adduct of borontrichloride was used in
the initial disproportionation reaction due to the ease
of handling over the volatile boron trichloride.11 The
reaction proceeds cleanly and quantitatively at room
temperature with the loss of dimethyl sulfide. Reduction
of chlorobis(dimethylamido)borane with Na/K resulted
in the isolation of the desired product 9 in low yield
(35%) after distillation.12 During the course of this
(11) Chavant, P. Y.; Vaultier, M. J . Organomet. Chem. 1993, 455,
37.
(12) (a) Brotherton, R. J .; McCloskey, A. L.; Petterson, L. L.;
Steinberg, H. J . Am. Chem. Soc. 1960, 82, 6242. (b) No¨th, H.; Meister,
W. Z. Naturforsch., Teil B 1962, 17, 714. (c) No¨th, H.; Meister, W.
Chem. Ber. 1961, 94, 509. (d) Loderer, D.; No¨th, H.; Pommerening,
H.; Rattay, W.; Schick, H. Chem. Ber. 1994, 127, 1605.
(10) No¨th, H.; Schick, H.; Meister, W. J . Organomet. Chem. 1964,
1, 401.

Group IV Metal Olefin Polymerization Catalysts
Organometallics, Vol. 20, No. 16, 2001 3401
Sch em e 1
investigation a more efficient synthetic route to com-
pound 9 was discovered from the reaction of bis-
(catecholato)diboron and 4 equiv of lithium dimethyl-
amide. This reaction proceeds cleanly in a single step
in 66% yield after distillation. Compound 9 was con-
verted to 10 via reaction with 4 equiv of HCl.13b
Compound 10 was transformed to the final ligand 11
in high yield upon mixing with 2 equiv of the respective
lithium anilinide. Compounds 11a and 11b are then
converted to the corresponding dilithium salts 12a ,b
using 2 equiv of n-BuLi. The reaction of 11c with 2 equiv
of n-BuLi gives a mixture of unidentified products.
energy for this fluxional process is about 17 kcal/mol
for all three compounds. Compound 11a also exhibits
fluxionality around 1 ppm, corresponding to the reso-
nances of the isopropyl methyl groups that appear as a
broad resonance at room temperature, which become a
sharp doublet upon warming. In addition to the broad-
ening of the isopropyl methyl resonances the isopropyl
methine resonance is not observed at room temperature
and grows in at 3.3 ppm at higher temperature. The
fluxional nature of the isopropyl resonances in 11a is
consistent with a restricted rotation about the methine
carbon of the isopropyl group and the Cipso bond due to
the steric hindrance of the isopropyl groups. The reso-
nances of the 2,6-methyl groups in 11b and the 2-tert-
butyl groups in 11c appear as sharp singlets at room
temperature. The amine protons for 11a ,b appear as a
single resonance in the region of 3.6-3.7 ppm and at
5.4 ppm for 11c. The aromatic resonances of 11a ,b
appear as an unresolved broad resonance in the region
of 6.8-7.0 ppm. The resonances of the unsymmetrically
substituted phenyl ring in 11c appear as discrete
multiplets in the range of 6.7-7.5 ppm.
1
The H NMR spectra of compounds 11a -c exhibit a
pair of singlets in the region of 2-3 ppm corresponding
to the resonances of the dimethylamido groups. The
inequivalency of the methyl resonances presumably
arises from the restricted rotation about the B-N bond
due to double-bond character of the B-N linkage. The
coalesence temperature of these resonances is 97.5 °C
for 11a ,b and 65.0 °C for 11c. The corresponding free
(13) Finch, W. F.; Anslyn, E. V.; Grubbs, R. H. J . Am. Chem. Soc.
1988, 110, 2406.

3402 Organometallics, Vol. 20, No. 16, 2001
Patton et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p lex 7a
Deprotonation of 11a ,b gave the dilithium salts
12a ,b. The NMR spectra are consistent with the desired
structures with the dimethylamido resonances appear-
ing as a singlet at 2.4 ppm and the resolved aromatic
resonances appearing as a doublet in the region of 6.2-
6.3 ppm and a triplet at 6.7 ppm.
chemical formula
space group
C28H46B2Cl2N4Ti
P21/n
a
b
c
12.3735(6) Å
15.2227(7) Å
18.1093(9) Å
90°
R
â
107.584(1)°
90°
Com p lex Syn th esis. Complexation of these ligands
described above to group IV metals proved to be
problematic. Treating 11a -c with reagents such as
M(NMe2)4 or M(CH2Ph)4 to form the Ti and Zr com-
plexes was unsuccessful. The complexation to titanium
was successfully accomplished by reacting 12a with
TiCl3(THF)3 followed by oxidation with PbCl2 to form
12a . Multiple reaction products were observed in the
crude reaction mixture, with the desired product being
isolated via recrystallization from hexane. Complex 7a
can be cleanly converted to the corresponding TiMe2
complex 7b using 2 equiv of MeMgBr. Attempts to
generate the Zr analogue by reacting 12a with zirco-
nium halide were unsuccessful. Application of Cl2Zr-
γ
V
3251.7(3) Å3
579.11
fw
Fcalc
Z
µ
T
1.183 mg/mm3
4
0.450 mm-1
-100 °C
λ
0.71073 Å
0.0320
0.0815 [5769]
R1a
wR2b
R1 ) ∑(||Fo| - |Fc||)/∑|Fo|. b wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2
a
[I > 2σ(I)].
Ta ble 2. Selected Bon d Len gth s [Å] a n d An gles
[d eg] for 7a
8k
Ti-N4
Ti-N1
Ti-Cl2
Ti-Cl1
Ti-B1
1.867(1)
1.885(1)
2.2307(5)
2.2602(5)
2.404(2)
2.456(2)
1.431(2)
1.460(2)
1.397(2)
1.462(2)
1.462(2)
1.407(2)
1.461(2)
1.467(2)
1.431(2)
1.447(2)
1.800(2)
N4-Ti-N1
N4-Ti-Cl2
N1-Ti-Cl2
N4-Ti-Cl1
N1-Ti-Cl1
Cl2-Ti-Cl1
C11-N1-B1
C11-N1-Ti
B1-N1-Ti
B1-N2-C2
B1-N2-C1
C2-N2-C1
C5-N4-B2
C5-N4-Ti
B2-N4-Ti
N2-B1-N1
N2-B1-B2
N1-B1-B2
N3-B2-N4
N3-B2-B1
N4-B2-B1
110.59(5)
108.63(4)
108.94(4)
107.27(4)
111.10(4)
110.28(2)
132.1(1)
137.0(1)
90.96(9)
124.8(1)
124.1(1)
110.9(1)
133.6(1)
129.44(9)
94.82(9)
124.4(1)
122.6(1)
113.0(1)
123.6(1)
120.2(1)
115.9(11)
(CH2TMS)2 in the reaction with 12a also resulted in
an unidentified mixture of products. Ultimately the
desired product 8 was successfully synthesized by
reacting Cl2Zr(CH2Ph)2(OEt2)x, generated in situ, with
12a . This reaction sequence resulted in the formation
of a significant amount of unidentified byproduct, which
could be removed by successive precipitations as a white
solid from cold hexane. The desired product 8 was
isolated as a yellow oil.
Ti-B2
N1-C11
N1-B1
N2-B1
N2-C2
N2-C1
N3-B2
N3-C3
N3-C4
N4-C5
N4-B2
B1-B2
The 1H NMR spectra of compounds 7a ,b exhibit a pair
of singlets in the region of 2.1-2.7 ppm corresponding
to the resonances of the dimethylamido groups. As in
the case of the free ligands, these complexes also exhibit
fluxional behavior at room temperature. The tempera-
ture of coalecense for the methyl groups of the dimethyl-
amido fragments was found to be 100 and 80 °C for 7a
and 8, respectively. The free energy of rotation about
the B-NMe2 bond in both cases was about 17 kcal/mol,
which is the same as that observed for the free ligands,
suggesting that ligand chelation has little effect on the
double-bond character of the B-NMe2 linkage. As
expected, complexes 7a ,b exhibit similar spectral fea-
tures of the ligands in their 1H and 13C NMR spectra.
The Ti-Me resonance appears as a singlet at 1.05 ppm
rotate to provide steric relief. The isopropyl methyl
resonances appear as a sharp doublet at 1.1 ppm and a
broad resonance at 1.2 ppm at room temperature. These
resonances sharpened to a pair of resolved doublets at
higher temperature. The ortho aromatic protons of the
benzyl groups appear as a sharp doublet at 6.59 ppm,
which remains unchanged at -50 °C. The upfield
chemical shift of these protons suggests that the phenyl
π systems of the benzyl groups may be interacting with
the zirconium center.14 In the closely related compound,
5b, the ortho protons of the benzyl groups appear as a
doublet at 6.65 ppm, and an η2 benzyl-zirconium
interaction was proposed.8a
X-r a y Cr ysta l Str u ctu r e An a lysis. The molecular
structure of 7a was confirmed by a single-crystal X-ray
structure analysis. The thermal ellipsoid drawing is
shown in Figure 1. Crystal data are presented in Table
1, while selected bond distances and angles are included
in Table 2. The B-B bond distance of 1.800(2) Å is
slightly longer than that of reported series of compounds
of the type (Cp)(NMe2)B-B(NMe2)(Cp) (1.72-1.76 Å).15
This lengthening of the B-B bond reflects a more
1
in the H NMR and 57.4 ppm (J CH ) 119.5 Hz) in the
13C NMR spectrum. It has been reported that the J CH
value of a Ti-Me resonance can be correlated with the
electrophilicity of the Ti center as dictated by its ligand
environment.13 On the basis of this report the lower J CH
value (J CH ) 118.4 Hz) observed for Ti-Me resonance
in 5a suggests that the B-B bridged ligand imparts
more electrophilicity on the Ti center in 7b.
Compound 8 exhibits fluxionality due to restricted
rotation about the B-NMe2 bond. The isopropyl
methine protons appear as two multiplets at 3.1 and
3.4 ppm, which coalesce at 50 °C. The benzylic protons
appear as a pair of doublets at 1.7 and 1.8 ppm, which
coalesce at 45 °C. The rotational barriers for these
processes were about 17 kcal/mol, which is the same as
determined for the barrier for the B-NMe2 bond rota-
tion. It seems that the observed fluxional processes are
dependent on the ability of the dimethylamide to rotate
about the B-N bond to a conformation that in turn
allows the isopropyl groups and the benzyl groups to
(14) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I.
P.; Huffman, J . C. Oganometallics 1985, 4, 902.
(15) (a) Littger, R.; Metzler, N.; No¨th, H.; Wagner, M. Chem. Ber.
1994, 127, 1902. (b) Knizek, J .; Krossing, I.; No¨th, H.; Ponikwar, W.
Eur. J . Inorg. Chem. 1998, 505.

Group IV Metal Olefin Polymerization Catalysts
Organometallics, Vol. 20, No. 16, 2001 3403
tor solutions immediately prior to injection to the
reactor. The polymerizations were conducted for 15 min
with ethylene on demand. The polymerization results
for ethylene/octene are summarized in Table 3 and show
that the catalysts generated from 7 and 8 exhibit
significantly lower activities compared to those derived
from 1 and 5a . The polydispersities of the polymers
produced from 7 and 8 were broader than those pro-
duced from 1 and 5a , presumably as a result of the
formation of multiple catalyst sites.
Con clu sion s
Novel group IV metal complexes comprising diborane-
bridged amido ligands have been synthesized. Complex
7b was prepared by reacting the dilithium ligand salt
with TiCl3(THF)3 followed by oxidation with PbCl2. This
TiCl2 complex was then converted to the corresponding
TiMe2 complex via reaction with MeMgBr. Complex 8
was synthesized by the reaction of the dilithium ligand
salt with the disproportionation product of Zr(CH2Ph)4
and ZrCl4. These complexes have been shown to be
active catalysts upon combination with the appropriate
activator. Additionally, efforts to examine the structure-
activity relationships of B-bridged amide-based com-
plexes are currently underway.
Exp er im en ta l Section
F igu r e 2. Schematic comparison of bond angles and
distances for 7a and 5a .
The H (300 MHz) and 13C{H} NMR (75 MHz) spectra were
1
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 tetramethyl-
silane. 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 BCl3-SMe2, B(NMe2)3, n-BuLi,
2,6-dimethylaniline, 2-tert-butylaniline, bis(catecholato)di-
boron, LiNMe2, and 2,6-diisopropylaniline were used as pur-
chased from Aldrich. The compound B(C6F5)3 was used as
purchased from Boulder Scientific. The compounds TiCl3-
(THF)3 and Zr(CH2Ph)4 were prepared as described in the
literature. All syntheses were performed under dry nitrogen
or argon atmosphere using a combination of glovebox and high-
vacuum techniques. High-resolution mass spectroscopy (HRMS)
was performed by the University of Florida. Elemental analy-
ses were performed by Oneida Research Services, Inc., Whites-
boro, NY, and the University of Michigan, Ann Arbor, MI.
Sin gle-Cr ysta l X-r a y An a lysis of Dich lor o[1,2-bis(2,6-
d iisop r op yla n ilid e)-1,2-b is(d im et h yla m id o)d ib or a n e]-
tita n iu m (7a ). Data were collected at 173 K on a Siemens
SMART PLATFORM equipped with A CCD area detector and
a graphite monochromator utilizing Mo KR radiation (λ )
0.71073 Å). Cell parameters were refined using 8192 reflec-
tions. A hemisphere of data (1381 frames) was collected using
the ω-scan method (0.3° frame width). The first 50 frames were
remeasured at the end of data collection to monitor instrument
and crystal stability (maximum correction on I was <1%).
Absorption corrections by integration were applied on the basis
of measured indexed crystal faces.
electron-rich amido substituent weakening the B-B
bond. The B-NMe2 bond distances of 1.397(2) and
1.407(2) Å suggest some degree of double-bond character
and are similar to those observed in the (Cp)(NMe2)B-
B(NMe2)(Cp) compounds (1.386-1.429 Å). The sum of
the angles about the N atoms of these fragments equals
359.85° and 359.81°, indicating sp2 hybridization of
these N atoms. The distances of 1.447(2) and 1.460(2)
Å observed for the B-N(aniline) bonds are in the range
for B-N single-bond linkage. Figure 2 depicts selected
structural comparisons between complexes 5a as the
dichloride and 7a . The Ti-N(aniline) bond distances of
1.867(1) and 1.885(1) Å are slightly longer than those
observed for 5a (1.839 and 1.856 Å), suggesting a
weaker Ti-N interaction, which is consistent with the
electron-deficient nature of the B-B bond linkage
relative to the propyl linkage for 5a .11d The N1-Ti-N4
and Cl-Ti-Cl bond angles of 110.59(5)° and 110.28-
(2)°, respectively, for 7a compared to the analogous
values of 99.2° and 107.77° for 5a suggest that 7a
possesses a more symmetrically substituted tetrahedral
Ti metal center than 5a . The Ti-Cl bond distances for
7a and 5a are essentially the same. Another notable
feature of 7a is the observed envelope conformation of
the five-member metallacycle. The plane consisting of
atoms Ti-N1-B1 lies 34.08(9)° out of the Ti-N4-B2-
B1 plane, resulting in the puckering of one of the ring
anilido groups of the metallacycle. The aryl rings are
positioned from the metalloheterocycle plane with di-
hedral angles of 89.75(5)° and 60.80(4)°.
16
17
The structure was solved by the direct methods in SHELX-
TL5 and refined using full-matrix least squares.18 The non-H
atoms were refined with anisotropic thermal parameters, and
all of the H atoms were calculated in idealized positions and
P olym er iza tion Resu lts. Complexes 7a ,b and 8
provide active polymerization catalysts upon combina-
tion with appropriate activators. In the cases of B(C6F5)3
(1 equiv) and MAO (1000 equiv) each complex was
activated by mixing the appropriate catalyst and activa-
(16) Manzer, L. E. Inorg. Synth. 1982, 21, 135.
(17) Zucchini, U.; Albizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357.
(18) Sheldrick, G. M. SHELXTL5; Bruker-AXS: Madison, WI, 1998.

3404 Organometallics, Vol. 20, No. 16, 2001
Ta ble 3. Eth ylen e/Octen e Cop olym er iza tion Resu lts
Patton et al.
complex
activator
T (°C)
efficiency (g P/g M)
exotherm (°C)
Mw/Mn (PDI)
1
1
MAO
B(C6F5)3
MAO
B(C6F5)3
MAO
MAO
B(C6F5)3
MAO
B(C6F5)3
70
140
70
140
70
70
140
70
1 561 195
1 070 000
163 504
36 000
23 571
9548
2.7
2.8
2.2
0.6
1.1
0.9
0.3
1.0
0.9
220 000/102 000 (2.16)
65 500/24 300 (2.69)
120 000/28 600 (4.20)
76 300/11 300 (6.77)
22 600/5500 (4.13)
58 800/1600 (37.9)
31 000/4300 (7.25)
101 000/2600 (38.9)
5a
5a
7a
7b
7b
8
20 000
15 973
1000
8
140
refined riding on their parent atoms. In the final cycle of
refinement, 5769 observed reflections with I > 2σ(I) were used
to refine 335 parameters, and the resulting R1 and wR2 were
3.20% and 8.15%, respectively. Refinement was done using F2.
Eth ylen e/Octen e Cop olym er iza tion s. All feeds were
passed though columns of activated alumina and Q-5 catalyst
prior to introduction to the reactor. A stirred 2 L Parr reactor
was charged with 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. The reactor contents were
then heated to the polymerization temperature of 140 °C and
saturated with ethylene at 500 psig. The metal complexes 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 isopropyl alcohol,
and stabilized by the addition of 10 mL of a toluene solution
containing approximately 67 mg of a hindered phenol anti-
oxidant (Irganox 1010 from Ciba Geigy Corp.) and approxi-
mately 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 was added to
the reactor, which was then heated to 150 °C and then emptied
of the heated solvent immediately prior to a new polymeriza-
tion run.
P r ep a r a t ion of Ch lor ob is(d im et h yla m id o)b or a n e.
BCl3-SMe2 (62.000 g, 345.78 mmol) and B(NMe2)3 (98.921 g,
691.56 mmol) were stirred together at room temperature
overnight under a nitrogen bubbler. The mixture was then
heated to reflux for 1 h to drive off any residual SMe2. Allowing
the pale yellow liquid to stir to room temperature followed by
filtration resulted in the isolation of the desired product
(139.436 g, 93.3% yield). 1H NMR (C6D6): δ 2.49 (s). 13C{H}
NMR (C6D6): δ 39.86.
P r ep a r a tion of Tetr a k is(d im eth yla m id o)d ibor a n e (9)
via ClB(NMe)2. Chlorobis(dimethylamido)borane (30.000 g,
223.19 mmol) was refluxed in hexane (200 mL) as Na/K alloy
[Na (1.539 g, 66.96 mmol)/K (8.726 g, 223.19 mmol)] was added
dropwise to the solution. After the first several drops the
reaction initiated, as evidenced by a sudden increase in the
reflux. The heat was then turned off and the alloy added slowly
to maintain a reflux. After the addition was complete the
reaction mixture was heated to reflux for an additional hour
and then stirred at room temperature for 3 h. The mixture
was then filtered through a Celite pad, and the volatiles were
removed, resulting in the isolation of a yellow liquid. Fractional
vacuum distillation resulted in the isolation of the desired
compound as a pale yellow liquid (7.756 g, 35.1% yield). 1H
NMR (C6D6): δ 2.73 (s). 13C{H} NMR (C6D6): δ 41.37.
P r ep a r a tion of Tetr a k is(d im eth yla m id o)d ibor a n e (9)
via Bis(ca tech ola to)d ibor on . Lithium dimethylamide (10.70
g, 210.0 mmol) was added slowly as a solid to a solution of
bis(catecholato)diboron (10.00 g, 42.00 mmol) in diethyl ether
(200 mL) at -20 °C. This mixture was then allowed to stir for
an additional 40 h at room temperature. After the reaction
period ether was removed under vacuum and the residue was
extracted and filtered using hexane. Solvent removal and
fractional vacuum distillation resulted in the isolation of the
desired compound as a pale yellow liquid (5.493 g, 66.0% yield).
P r ep a r a tion of Bis(d im eth yla m id o)d ibor on d ich lor id e
(10). Tetrakis(dimethylamido)diborane (7.756 g, 39.19 mmol)
was stirred in diethyl ether (100 mL) at -78 °C as HCl (156.75
mmol, 156.75 mL of 1.0 M solution in diethyl ether) was added
dropwise. This mixture was then allowed to stir for 6 h at room
temperature. After the reaction period the volatiles were
removed and the residue was extracted and filtered using
hexane. The product was obtained as a pale yellow liquid after
solvent removal and vacuum distillation (4.722 g, 66.7% yield).
1H NMR (C6D6): δ 2.40 (s, 6 H), 2.50 (s, 6 H). 13C{H} NMR
(C6D6): δ 37.62, 41.78.
P r ep a r a tion of 2,6-Dim eth yla n ilin e, Lith iu m Sa lt. n-
BuLi (49.54 mmol, 30.94 mL of 1.6 M solution in hexane) was
added dropwise to a solution of 2,6-dimethylaniline (6.000 g,
49.54 mmol) in hexane (100 mL). This mixture was allowed
to stir for 3 h, during which time a white precipitate formed.
After the reaction period the white salt that formed was
filtered and washed with hexane, dried under vacuum, and
used without further purification or analysis (5.954 g, 94.6%
yield).
P r ep a r a tion of 2-ter t-Bu tyla n ilin e, Lith iu m Sa lt. n-
BuLi (24.12 mmol, 15.08 mL of 1.6 M solution in hexane) was
added dropwise to a solution of 2-tert-butylaniline (3.600 g,
24.12 mmol) in hexane (50 mL). This mixture was allowed to
stir overnight, during which time a precipitate formed. After
the reaction period the white salt that formed was filtered and
washed with hexane, dried under vacuum, and used without
further purification or analysis (2.961 g, 79.1% yield).
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 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
allowed to stir for 3 h, during which time a white precipitate
formed. After the reaction period the white salt that formed
was filtered and 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 tion of 1,2-Bis(2,6-d iisop r op yla n ilid e)-1,2-bis-
(d im et h yla m id o)d ib or a n e (11a ). Bis(dimethylamido)di-
borondichloride (2.350 g, 13.00 mmol) in diethyl ether (10 mL)
was added dropwise to a solution of 2,6-diisopropylaniline,
lithium salt (4.765 g, 26.01 mmol) in diethyl ether (50 mL) at
0 °C. This mixture was then allowed to stir overnight at room
temperature. After the reaction period the volatiles were
removed and the residue was extracted and filtered using
hexane. Removal of the hexane resulted in the isolation of the
desired product as a white solid (5.322 g, 88.9% yield). 1H NMR
(C6D6): δ 0.9-1.4 (br m, 24 H), 2.29 (s, 6 H), 2.85 (s, 6 H),
3.71 (s, 2 H), 7.08 (br m, 6 H). 13C{H} NMR (toluene-d8): δ
22.51, 24.03 (br), 28.17, 36.82, 42.67, 123.19, 124.78, 140.71,
145.02 (br). HRMS(EI): calcd for C28H48N4B2 m/z 460.4026,
found 460.4025. Anal. Calcd for C28H48N4B2: C, 72.74; H,
10.46; N, 12.12. Found: C, 72.76; H, 10.34; N, 11.72.
P r ep a r a t ion of 1,2-Bis(2,6-d im et h yla n ilid e)-1,2-b is-
(d im eth yla m id o)d ibor a n e (11b). Bis(dimethylamido)dibo-

Group IV Metal Olefin Polymerization Catalysts
Organometallics, Vol. 20, No. 16, 2001 3405
ron dichloride (1.000 g, 5.530 mmol) in diethyl ether (10 mL)
was added dropwise to a solution of 2,6-dimethylaniline,
lithium salt (1.407 g, 11.07 mmol) in diethyl ether (50 mL) at
0 °C. This mixture was then allowed to stir overnight at room
temperature. After the reaction period the volatiles were
removed and the residue was extracted and filtered using
hexane. Removal of the hexane resulted in the isolation of the
desired product as a white solid (1.785 g, 92.1% yield). 1H NMR
(toluene-d8): δ 1.87 (s, 12 H), 2.32 (s, 6 H), 2.79 (s, 6 H), 3.58
(s, 2 H), 6.8-6.9 (m, 6 H). 13C{H} NMR (toluene-d8): δ 19.00,
35.91, 42.64, 123.14, 128.21, 133.44, 143.56. HRMS(EI): calcd
for C20H32N4B2 m/z 348.2773, found 348.2777.
overnight, resulting in the formation of orange X-ray quality
crystals (0.156 g, 21.3% yield). 1H NMR (toluene-d8): δ 1.23
3
3
(d, J HH ) 6.6 Hz, 6 H), 1.45 (d, J HH ) 6.6 Hz, 6 H), 2.17 (s,
3
6 H), 2.76 (s, 6 H), 3.53 (septet, J HH ) 6.6 Hz, 4 H), 7.11 (s, 6
H). 13C{H} NMR (toluene-d8): δ 24.94, 24.67, 29.48, 39.33,
42.93, 124.08 (br), 17.23, 150.64. HRMS (EI): calcd for
C
28H46N2B2TiCl2 m/z 578.2781, found 578.2789. Anal. Calcd
for C28H46N2B2TiCl2: C, 58.07; H, 8.01; N, 9.67. Found: C,
58.28; H, 8.20; N, 9.42.
P r ep a r a tion of Dim eth yl[1,2-bis(2,6-d iisop r op yla n il-
id e)-1,2-bis(d im eth yla m id o)d ibor a n e]tita n iu m (7b). Di-
chloro[1,2-bis(2,6-diisopropylanilide)-1,2-bis(dimethylamido)-
diborane]titanium (0.272 g, 0.470 mmol) was stirred in diethyl
ether (40 mL) as MeMgBr (0.940 mmol, 0.313 mL of 3.0 M
solution in diethyl ether) was added dropwise. This mixture
was allowed to stir for 1 h. After the reaction period the
volatiles were removed and the residue was extracted and
filtered using hexane. Removal of the hexane resulted in the
isolation of the desired product as a dark yellow oil (0.209 g,
P r ep a r a tion of 1,2-Bis(2-ter t-bu tyla n ilid e)-1,2-bis(d i-
m eth yla m id o)d ibor a n e (11c). Bis(dimethylamido)diboron-
dichloride (0.833 g, 4.61 mmol) in diethyl ether (10 mL) was
added dropwise to a solution of 2-tert-butylaniline, lithium salt
(1.431 g, 9.22 mmol) in diethyl ether (40 mL) at 0 °C. This
mixture was then allowed to stir at room temperature over-
night. After the reaction period the volatiles were removed and
the residue was extracted and filtered using hexane. Removal
of the hexane resulted in the isolation of the desired product
1
3
82.5% yield). H NMR (C6D6): δ 1.05 (s, 6 H), 1.21 (d, J HH
)
6.9 Hz, 16 H), 1.32 (d, 3J HH ) 6.3 Hz, 16 H), 2.19 (s, 6 H), 2.69
(s, 6 H), 3.58 (br, 2 H), 7.0-7.2 (m, 6 H). 13C{H} NMR (C6D6):
δ 24.06, 24.83, 29.31, 39.58, 42.93, 57.38, 123.97, 125.18, 139.5
(br), 149.45. HRMS (EI): calcd for C30H52N2B2Ti m/z 538.3793,
found 538.3858.
1
as a white solid (1.419 g, 75.7% yield). H NMR (toluene-d8):
δ 1.34 (s, 9 H), 2.61 (s, 6 H), 2.71 (s, 6 H), 5.44 (s, 2 H), 6.80
3
3
(t, J HH ) 7.1 Hz, 2 H), 7.03 (m, 2 H), 7.20 (d, J HH ) 7.7 Hz,
2 H), 7.42 (d, J HH ) 8.0 Hz, 2 H). 13C{H} NMR (toluene-d8):
3
δ 30.37, 34.33, 36.37, 41.99, 120.45, 126.12, 127.00, 136.54,
144.94. HRMS(EI): calcd for C24H40N4B2 m/z 404.3399, found
404.3406. Anal. Calcd for C24H40N4B2: C, 70.96; H, 9.92; N,
13.79. Found: C, 68.96; H, 9.88; N, 13.77.
P r ep a r a tion of 1,2-Bis(2,6-d iisop r op yla n ilid e)-1,2-bis-
(d im eth yla m id o)d ibor a n e, Dilith iu m Sa lt (12a ). 1,2-Bis-
(2,6-diisopropylanilide)-1,2-bis(dimethylamido)diborane (1.820
g, 3.950 mmol) was stirred in hexane (75 mL) as n-BuLi (7.91
mmol, 4.94 mL of 1.6 M solution in hexane) was added
dropwise. This mixture was then allowed to stir overnight.
After the reaction period the mixture was filtered and the salt
was washed with hexane and dried under vacuum, resulting
in the isolation of the desired product as a white powder
P r ep a r a tion of Diben zyl[1,2-bis(2,6-d iisop r op yla n il-
id e)-1,2-bis(d im eth yla m id o)d ibor a n e]zir con iu m (8). Zir-
conium tetrachloride (0.100 g, 0.440 mmol) and zirconium
tetrabenzyl (0.192 g, 0.440 mmol) were stirred together in
diethyl ether (30 mL) for 1 h. 1,2-Bis(2,6-diisopropylanilide)-
1,2-bis(dimethylamido)diborane, dilithium salt (0.400 g, 0.842
mmol) in diethyl ether (30 mL) was then added dropwise, and
the mixture was allowed to stir for 3 h. After the reaction
period the volatiles were removed under vacuum and the
residue was extracted and filtered using hexane. The filtrate
was then concentrated and cooled to -10 °C overnight, during
which time a white powder precipitated. The mixture was
again filtered, and the volatiles were removed, resulting in the
isolation of the desired product as a yellow oil (0.123 g, 19.8%
1
3
(1.6878 g, 90.4% yield). H NMR (THF-d8): δ 1.04 (d, J HH
)
3
3
yield). 1H NMR (toluene-d8): δ 1.14 (d, J HH ) 6.6 Hz, 6 H),
6.9 Hz, 6 H), 1.18 (d, J HH ) 6.9 Hz, 6 H), 2.45 (s, 12 H), 3.66
3
3
3
3
(septet, J HH ) 6.9 Hz, 4 H), 6.29 (t, J HH ) 7.5 Hz, 2 H), 6.73
(d, 3J HH ) 7.5 Hz, 4 H). 13C{H} NMR (THF-d8): δ 24.88, 25.34,
28.00, 40.91, 114.40, 121.95, 137.21, 158.76.
1.22 (br, 6 H), 1.70 (d, J HH ) 9.0 Hz, 2 H), 1.83 (d, J HH ) 9.6
Hz, 2 H), 2.10 (s, 6 H) 2.71 (s, 6 H), 3.0-3.2 (br, 2 H), 3.3-3.5
3
3
(br, 2 H), 6.59 (d, J HH ) 7.2 Hz, 4 H), 6.77 (t, J HH ) 7.2 Hz,
2 H), 6.9-7.1 (m, 10 H). 13C{H} NMR (toluene-d8): δ 23.96
(br), 24.22 (br), 24.36 (br), 25.23 (br), 29.47, 39.72, 43.05, 62.23,
122.70, 123.73 (br), 124.08 (br), 124.33, 127.23, 130.82, 139.26
(br), 140.16 (br), 144.90, 144.92, 149.03. HRMS(EI): calcd for
P r ep a r a t ion of 1,2-Bis(2,6-d im et h yla n ilid e)-1,2-b is-
(d im eth yla m id o)d ibor a n e, Dilith iu m Sa lt (12b). 1,2-Bis-
(2,6-dimethylanilide)-1,2-bis(dimethylamido)diborane (1.500 g,
4.280 mmol) was stirred in hexane (75 mL) as n-BuLi (8.57
mmol, 5.36 mL of 1.6 M solution in hexane) was added
dropwise. This mixture was then allowed to stir overnight.
After the reaction period the mixture was filtered and the salt
was washed well with hexane and dried under vacuum,
resulting in the isolation of the desired product as a white
powder (1.413 g, 91.1% yield). 1H NMR (THF-d8): δ 2.09 (s,
12 H), 2.48 (s, 12 H), 6.17 (t, 3J HH ) 7.2 Hz, 2 H), 6.73 (d, 3J HH
) 7.2 Hz, 4 H). 13C{H} NMR (THF-d8): δ 21.22, 40.86, 123.19,
127.53, 128.28, 162.05.
P r ep a r a tion of Dich lor o[1,2-bis(2,6-d iisop r op yla n il-
id e)-1,2-bis(d im eth yla m id o)d ibor a n e]tita n iu m (7a ). 1,2-
Bis(2,6-diisopropylanilide)-1,2-bis(dimethylamido)diborane, di-
lithium salt (0.600 g, 1.27 mmol) in THF (20 mL) was added
dropwise to a slurry of TiCl3(THF)3 (0.471 g, 1.27 mmol) in
THF (50 mL) at 0 °C. This mixture was then allowed to stir
at room temperature for 45 min. PbCl2 (0.177 g, 0.640 mmol)
was then added as a solid and the mixture allowed to stir for
an additional 30 min. After the reaction period the volatiles
were removed and the residue was extracted and filtered using
hexane. The solution was concentrated and cooled to -10 °C
C
42H60N2B2Zr (M+) 732.4037; found {M - [CH2Ph]} m/z
641.3469, {M - [Zr(CH2Ph)2] + H} m/z 461.3976.
Ack n ow led gm en t. The authors are grateful to the
polypropylene research group of The Dow Chemical
Company for general discussions. We also thank M.
Bokota, B. Link, G. Roof, and R. Ruszala for their efforts
in the olefin polymerization screening and J udy Gun-
derson for the size exclusion chromatography analysis
of the polymers.
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagram
and tables of crystal data, data collection, and refinement
parameters, atomic coordinates, bond distances and angles,
1
and isotropic displacement parameters for complex 7a and H
NMR spectra for 7a and 11c. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM010101L