Zirconium complexes of amine-bis(phenolate) ligands as catalysts for 1-hexene polymerization: Peripheral structural parameters strongly affect reactivity

Article abstract of DOI:10.1021/om0101285

Novel amine bis(phenolate) zirconium dibenzyl complexes were synthesized in quantitative yields from a versatile family of chelating amine-bis((2-hydroxyaryl)methyl) ligand precursors, their X-ray structures solved, and their reactivity in the polymerization of 1-hexene in the presence of B(C₆F₅)₃ studied. Several minor peripheral structural modifications were studied and found to have a major influence on the catalyst performance. Thus, a variety of reactivities, ranging from extremely high to negligible, were obtained, demonstrating a unique structure-reactivity relationship. This relationship is partially revealed from the crystal structures of the precatalysts, indicating similar [ONO] ligand cores in all structures solved. A correlation between the solid and the solution structures is obtained from ¹H NMR spectra, which reveal a rigid binding of the ligand to the metal. The solid structures are therefore proposed to serve as reliable references when studying structure-reactivity relationships. The most significant structural parameter was found to be the existence of an extra donor located on a pendant arm. [ONO]-type pentacoordinate complexes lacking such an additional donor are rapidly deactivated and lead only to traces of oligomers. On the other hand, hexacoordinate complexes based on [ONNO]-type ligands, in which strong donation of a side donor to the metal is obtained through formation of a five-membered chelate, lead to extremely reactive polymerization catalysts. The nitrogen hybridization and aromatic ring substituents have a more subtle effect on reactivity. Increasing the chelate size results in either no binding of the side donor, yielding negligible reactivity, or strong binding yet moderate polymerization reactivity. Increasing the steric bulk on the donor results in weakening of the metal-donor bond, leading to a moderate oligomerization catalyst. The sidearm nitrogen is therefore proposed to play a crucial role in determining the propagation process rate, as well as the propagation/termination rate ratio.

Full text of DOI:10.1021/om0101285

Organometallics 2001, 20, 3017-3028
3017
Zir con iu m Com p lexes of Am in e-Bis(p h en ola te) Liga n d s
a s Ca ta lysts for 1-Hexen e P olym er iza tion : P er ip h er a l
Str u ctu r a l P a r a m eter s Str on gly Affect Rea ctivity
Edit Y. Tshuva, Israel Goldberg, and Moshe Kol*
School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences,
Tel Aviv University, Tel Aviv 69978, Israel
Zeev Goldschmidt*
Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
Received February 16, 2001
Novel amine bis(phenolate) zirconium dibenzyl complexes were synthesized in quantitative
yields from a versatile family of chelating amine-bis((2-hydroxyaryl)methyl) ligand precur-
sors, their X-ray structures solved, and their reactivity in the polymerization of 1-hexene in
the presence of B(C6F5)3 studied. Several minor peripheral structural modifications were
studied and found to have a major influence on the catalyst performance. Thus, a variety of
reactivities, ranging from extremely high to negligible, were obtained, demonstrating a unique
structure-reactivity relationship. This relationship is partially revealed from the crystal
structures of the precatalysts, indicating similar [ONO] ligand cores in all structures solved.
1
A correlation between the solid and the solution structures is obtained from H NMR spectra,
which reveal a rigid binding of the ligand to the metal. The solid structures are therefore
proposed to serve as reliable references when studying structure-reactivity relationships.
The most significant structural parameter was found to be the existence of an extra donor
located on a pendant arm. [ONO]-type pentacoordinate complexes lacking such an additional
donor are rapidly deactivated and lead only to traces of oligomers. On the other hand,
hexacoordinate complexes based on [ONNO]-type ligands, in which strong donation of a side
donor to the metal is obtained through formation of a five-membered chelate, lead to
extremely reactive polymerization catalysts. The nitrogen hybridization and aromatic ring
substituents have a more subtle effect on reactivity. Increasing the chelate size results in
either no binding of the side donor, yielding negligible reactivity, or strong binding yet
moderate polymerization reactivity. Increasing the steric bulk on the donor results in
weakening of the metal-donor bond, leading to a moderate oligomerization catalyst. The
sidearm nitrogen is therefore proposed to play a crucial role in determining the propagation
process rate, as well as the propagation/termination rate ratio.
In tr od u ction
The design of new ligands which may lead to highly
reactive olefin polymerization catalysts is not straight-
forward. The structural factors that control the reactiv-
ity of the complex are not understood completely. Even
the influence of basic parameters such as complex
coordination number and ligand connectivity has not
Until recently, most of the research in the field of
catalytic R-olefin polymerization involved group IV
metal complexes of cyclopentadienyl-type ligands. The
search for alternative ligands, which may diversify the
complex type, the catalyst reactivity, and the resulting
polymer properties, gave birth to a wide range of
nonmetallocene complexes.1 The most commonly re-
ported non-Cp type ligands are of the diamido type,
which have been studied extensively in the past decade.2
Several such complexes gave good polymerization re-
sults, in terms of molecular weight and molecular
weight distribution, and the reactivities commonly
obtained with such systems toward high olefins upon
activation with boron-based cocatalysts are considered
moderate.1 In comparison, only a few alkoxo ligands
were introduced, and fewer were found to lead to fairly
reactive polymerization catalysts.3,4
(2) (a) Gade, L. H. Chem. Commun. 2000, 173. (b) Kempe, R. Angew.
Chem., Int. Ed. 2000, 39, 468. (c) Scollard, J . D.; McConville, D. H. J .
Am. Chem. Soc. 1996, 118, 10008. (d) Gue´rin, F.; McConville, D. H.;
Vittal, J . J .; Yap, G. A. P. Organometallics 1998, 17, 5172. (e)
Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am. Chem. Soc. 1997,
119, 3830. (f) Aizenberg, M.; Turculet, L.; Davis, W. M.; Schattenmann,
F.; Schrock, R. R. Organometallics 1998, 17, 4795. (g) Liang, L.-C.;
Schrock, R. R.; Davis, W. M.; McConville, D. H. J . Am. Chem. Soc.
1999, 121, 5797. (h) J eon, Y.-M.; Park, S. J .; Heo, J .; Kim, K.
Organometallics 1998, 17, 3161. (i) Lee, C. H.; La, Y.-H.; Park, S. J .;
Park, J . W. Organometallics 1998, 17, 3648. (j) Tinkler, S.; Deeth, R.
J .; Duncalf, D. J .; McCamley, A. Chem. Commun. 1996, 2623. (k)
Gibson, V. C.; Kimberley, V. S.; White, A. J . P.; Williams, D. J .;
Howard, P. Chem. Commun. 1998, 313. (l) Ziniuk. Z.; Goldberg, I.; Kol,
M. Inorg. Chem. Commun. 1999, 2, 549. (m) Shah, S. A. A.; Dorn, H.;
Voigt, A.; Roesky, H. W.; Parisini, E.; Schmidt, H.-G.; Noltemeyer, M.
Organometallics 1996, 15, 3176. (n) Stephan, D. W.; Gue´rin, F.; Spence,
R. E. v. H.; Koch, L.; Gao, X.; Brown, S. J .; Swabey, J . W.; Wang, Q.;
Xu, W.; Zoricak, P.; Harrison, D. G. Organometallics 1999, 18, 2046.
(1) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed.. 1999, 38, 428.
10.1021/om0101285 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 06/08/2001

3018 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
been established yet. Structural modifications on the
ligands usually cause major distortion of the complex;4
thus, the source of the reactivity difference is difficult
to evaluate. Among the few factors known to affect
reactivity is the relative proximity of the active posi-
tions, enabling the metallacyclobutane formation in the
polymerization catalytic cycle. In addition, a relatively
spacious catalytic site is probably required for the olefin
coordination. The role of the metal electrophilicity in
determining the catalyst reactivity is, however, obscure.
On one hand, a highly electron deficient complex is
expected to interact more strongly with an incoming
olefin.5 On the other hand, additional donor groups
which lower the electrophilicity may stabilize the com-
plex or, alternatively, lower the insertion energy and
thus improve the catalyst performance.6
tions made are minor and relate to the peripheral area
of the catalyst, they were found to have a major
influence on reactivity.
Resu lts a n d Discu ssion
Liga n d Design . Our approach for deepening the
structure-reactivity dependence studies is based on
modifying several parameters on the ligand and study-
ing their effect on the catalytic reactivity. Since the
[ONNO]-type complex was found to be a much better
catalyst than the [ONO]-type one, we aimed at ligands
having additional donor located on a pendant arm. The
factors investigated include steric effects derived from
the substituents on the aromatic rings, as well as steric
and electronic effects relating to the pendant amine arm,
as shown in Scheme 1.
We have recently introduced the amine-bis(pheno-
late) family of ligands to group IV transition metal
chemistry.7-9 Our initial findings indicated that a
dimethylamino donor group attached to a sidearm in a
amine bis(phenolate) zirconium dibenzyl complex has
a major effect on the 1-hexene polymerization reactivity,
in the presence of tris(pentafluorophenyl)borane as a
cocatalyst.8 We have found that the less electrophilic
[ONNO]-type complex 1a leads to unprecedented reac-
tivity, whereas one lacking the extra donor (2a ) of the
[ONO]-type is rapidly deactivated and leads only to
traces of oligomeric material. This behavior could not
have been predicted, since an extra sidearm donor was
found to have an opposite effect in other cases.10 In the
present study, we describe our investigations aimed at
developing new catalysts of this family and broadening
the reactivity range. We describe here the synthesis of
a variety of amine bis(phenolate) ligand precursors,
their zirconium dibenzyl complexes, and the structure
dependent reactivity of these complexes in the polym-
erization of 1-hexene, a representative of high olefins.
On the basis of our preliminary findings, we focused on
ligands featuring a sidearm donor and studied the
effects of several structural parameters and their influ-
ence on reactivity. Although most structural modifica-
The bulky t-Bu groups in the position ortho to the
oxygen atoms may be responsible for inhibiting termi-
nation processes and stabilizing one major reactive
conformation of the catalyst.11 To evaluate the effect of
the bulky t-Bu groups in 1a on the reactivity observed,
we synthesized the ligand precursors 3 having methyl
groups as substituents rather than t-Bu groups (Scheme
1).
The chelate size effect was investigated by introducing
the ligand precursor 4 having an additional methylene
unit between the central and side nitrogen donors
relative to 1 (Scheme 1). A larger chelate ring may result
in different bond lengths and angles around the metal,
thus affecting reactivity.
Another parameter we addressed is the hybridization
of the sidearm nitrogen, namely sp2 nitrogen as a part
of a pyridine ring, vs the sp3 donor described thus far.
The two electronic configurations have different elec-
tronic and steric manifestations, since a pyridine donor
is expected to be more compact and less basic relative
to a tertiary amine. The ligand precursor 5 has a
sidearm pyridine group (Scheme 1), which is expected
to form a five membered chelate. To evaluate the chelate
size effect in a sp2-type system, the ligand precursor 6
(Scheme 1) was studied as well.
(3) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M. J . Am. Chem. Soc. 2000,
122, 10706. (b) van der Linden, A.; Schaverien, C. J .; Neijboom, N.;
Ganter, C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008. (c) Tjaden,
E. B.; Swenson, D. C.; J ordan, R. F.; Petersen, J . L. Organometallics
1995, 14, 371. (d) Matilainen, L.; Klinga, M.; Leskala, M. J . Chem.
Soc., Dalton Trans. 1996, 219. (e) Bei, X.; Swenson, D. C.; J ordan, R.
F. Organometallics 1997, 16, 3282. (f) Thorn, M. G.; Etheridge, Z. C.;
Fanwick, P. E.; Rothwell, I. P. Organometallics 1998, 17, 3636.
(4) (a) Fokken, S.; Spaniol, T. P.; Okuda, J .; Sernetz, F. G.;
Mu¨lhaupt, R. Organometallics 1997, 16, 4240. (b) Okuda, J .; Fokken,
S.; Kleinhenn, T.; Spaniol, T. P. Eur. J . Inorg. Chem. 2000, 1321. (c)
Nakayama, Y.; Watanabe, K.; Ueyama, N.; Nakamura, A.; Harada,
A.; Okuda, J . Organometallics 2000, 19, 2498.
(5) (a) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics
1998, 17, 308. (b) Ewart, S. W.; Sarsfield, M. J .; Williams, E. F.; Baird,
M. C. J . Organomet. Chem, 1999, 579, 106. (c) Tsukahara, T.; Swenson,
D. C.; J ordan, R. F. Organometallics 1997, 16, 3303.
(6) (a) Porri, L.; Ripa, A.; Colombo, P.; Miano, E.; Capelli, S.; Meille,
S. V. J . Organomet. Chem. 1996, 514, 213. (b) Sernetz, F. G.; Mu¨lhaupt,
R.; Fokken, S.; Okuda, J . Macromolecules 1997, 30, 1562. (c) Froese,
R. D. J .; Musaev, D. G.; Natsubara, T.; Morokuma, K. J . Am. Chem.
Soc. 1997, 119, 7190. (d) Froese, R. D. J .; Musaev, D. G.; Morokuma,
K. Organometallics 1999, 18, 373.
The bulk of the substituents on the nitrogen donor
atom may affect its binding to the zirconium, as well
as the conformation of the [ONO] binding to the metal.
We therefore synthesized the ligand precursor 7, featur-
ing ethyl substituents bound to the nitrogen donor. To
investigate possible steric interactions between the
donor substituents and the substituents on the aromatic
rings, we synthesized the ligand precursor 8, featuring
ethyl substituents on the donor and methyl substituents
in the positions ortho to the hydroxyl groups (Scheme
1).
Liga n d Syn t h esis. This versatile ligand family is
easily synthesized from readily available starting ma-
terials, namely primary amines, formaldehyde, and
substituted phenols, in single-step Mannich condensa-
tions (Scheme 2). Both [ONO]-type and [ONNO]-type
ligands are synthesized by following this procedure.
(7) Tshuva, E. Y.; Versano, M.; Goldberg, I.; Kol, M.; Weitman, H.;
Goldschmidt, Z. Inorg. Chem. Commun. 1999, 2, 371.
(8) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Weitman, H.; Goldschmidt,
Z. Chem. Commun. 2000, 379.
(9) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Inorg. Chem.
Commun. 2000, 3, 610.
(10) Schattenmann, F. J .; Schrock, R. R.; Davis, W. M. Organome-
tallics 1998, 17, 989.
(11) (a) Scollard, J . D.; McConville, D. H.; Payne, N. C.; Vittal, J . J .
Macromolecules 1996, 29, 5241. (b) Lee, C. H.; La, Y.-H.; Park, J . W.
Organometallics 2000, 19, 344. (c) Thorn, M. G.; Etheridge, Z. C.;
Fanwick, P. E.; Rothwell, I. P. J . Organomet. Chem. 1999, 591, 148.
(d) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai, A. Organome-
tallics 1998, 17, 2152.

Zr Complexes of Amine Bis(phenolate) Ligands
Organometallics, Vol. 20, No. 14, 2001 3019
Sch em e 1
Sch em e 2
Sch em e 3
F igu r e 1.
Str u ctu r e a n d Rea ctivity. As previously reported,8
the [ONNO]ZrBn2 complex 1a was obtained quantita-
tively as a single isomer. Two possible geometries of the
phenolate rings in an octahedral complex are cis and
trans configurations (Figure 1), leading to C1 symmetry
and Cs symmetry, respectively. Nevertheless, this ligand
forces a cis configuration between the two active posi-
tions, which may facilitate the metallacyclobutane
formation in the polymerization process.
The 1H NMR spectrum of 1a consists of an AX system
for the Ar-CH2-N methylene units, two symmetry-
related phenolate rings, and two different benzyl groups.
This indicates the formation of a rigid Cs-symmetrical
complex, in which the phenolate rings are in a trans
configuration (Figure 1).13 In this symmetrical isomer,
the pendant donor is relatively remote from the area of
the active benzyl groups.
Com p lex F or m a tion . An entry to zirconium dialkyl
complexes is the single-step metathesis reaction be-
tween zirconium tetrabenzyl and the ligand precursors.
Attempting this reaction at room temperature did not
lead to the desired complexes even after 7 days. How-
ever, raising the temperature to 65 °C enabled success-
ful synthesis of the dibenzyl complexes 1a -8a (Scheme
3). All the [ONO]- and [ONNO]-type ligands featuring
the bulky t-Bu groups as ring substituents, namely 1,
2, and 4-7 (Scheme 1), undergo very clean reactions,
leading to the dibenzyl complexes quantitatively. The
ligands featuring methyl groups ortho to the phenol
groups (Scheme 1), namely 3 and 8, give lower reaction
yields, probably due to the higher tendency to form
homoleptic complexes.7,12 For that reason, further ligands
derived from 2,4-dimethylphenol were not studied.
Additional structural information was obtained from
the X-ray structure of 1a (Figure 2, Table 1), revealing
(13) Hefele, H.; Ludwig, E.; Bansse, W.; Uhlemann, E.; Lu¨gger, Th.;
Hahn, E.; Mehner, H. Z. Anorg. Allg. Chem. 1995, 621, 671.
(12) Tshuva, E. Y.; Kol, M. Unpublished results.

3020 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
F igu r e 3.
conditions, namely neat 1-hexene and the mild B(C6F5)3
cocatalyst. It is surprising that a relatively crowded
octahedral complex featuring bulky t-Bu substituents
exhibits such a reactivity toward sterically demanding
high olefins. Under these conditions, the polymer ob-
tained has a relatively low molecular weight and broad
molecular weight distribution, due to the high reaction
temperature (Table 7). Taming the polymerization by
diluting the monomer in an inert solvent allowed the
production of poly(1-hexene) having higher molecular
weight (Mw ) 170 000) and narrow molecular weight
distribution (Mw/Mn ) 2.0) (Table 7).
2a was also obtained as a single isomer of the formally
pentacoordinate dialkyl [ONO]ZrBn2 complex.7 In anal-
ogy to 1a , the spectral data of 2a also indicated the
formation of a rigid complex, as evident from the AB
system obtained for the Ar-CH2-N methylene hydro-
gens. This complex also reveals symmetry-related phe-
nolate rings and two different benzyl groups, indicating
a Cs symmetry, in analogy to the [ONNO]-type complex
1a . Assuming a similar [ONO] ligand core, the isomer
obtained should have the approximate geometry shown
in Figure 3. The X-ray structure of 2a supported this
notion (Figure 4, Table 2).
F igu r e 2. ORTEP drawing of the molecular structure of
1a (50% probability ellipsoids). H atoms, the solvent of
crystallization, and disorder were omitted, and the methyl
groups on the sidearm nitrogen are shown in reduced size
for clarity. Key atoms are labeled.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 1a
Zr-O2
Zr-O3
Zr-N6
1.995(5)
1.994(5)
2.446(6)
Zr-N9
Zr-C13
Zr-C20
2.594(6)
2.305(7)
2.250(6)
The structure of 2a presents a pseudo-trigonal-
bipyramidal complex, with axial O atoms and equatorial
N,C,C atoms (Figure 3). The angle of 117.4° between
the two benzyl groups in 2a is much wider than in 1a .
An acute Zr-(CH2)-C(Ar) angle of 89.4° as well as a
short Zr-C(Ar) distance of 2.71 Å for one of the benzyl
groups indicate a nonclassical η2 binding of this group
to the Zr atom (Figure 9),16 which may result from the
lower crowding around the metal, as well as from the
electron deficiency of the metal. It is noteworthy that
the cores of the amine bis(phenolate) ligands, namely
the [ONO] units, are bound very similarly in 1a and
2a . This is expressed, for example, in similar O-Zr-O
bond angles and in ca. 30° bending of the phenolate ring
planes away from the equatorial benzyl groups. In both
1a and 2a , this back-bending leaves a relatively open
cleft for the active positions.
O2-Zr-O3
N6-Zr-N9
C13-Zr-C20
160.3(2)
69.7(2)
93.7(2)
Zr-C13-C14
Zr-C20-C21
104.9(5)
115.8(5)
a slightly distorted octahedral complex. As expected, a
relatively long N(9)-Zr distance of 2.59 Å indicates a
weak bond between the sidearm nitrogen and the metal
(Figure 9). In comparison, the bond between the central
nitrogen and the metal is relatively short (N(6)-Zr )
2.45 Å). The two benzyl groups are indeed forced into a
cis geometry (C(13)-Zr-C(20) angle of 93.7°).
Although the X-ray structures described herein are
of precatalysts, and not of the actual reactive species
in the catalytic cycle, they may nonetheless reveal basic
structural features of the reactive intermediates. Espe-
cially, since the NMR studies indicate that the [ONO]
core of the complex is rigid, we expect that this portion
of the complex will not distort substantially during the
polymerization cycle.
Upon activation with the tris(pentafluorophenyl)-
borane cocatalyst, 1a was found to be remarkably
reactive in the polymerization of 1-hexene.14 The best
reactivities obtained thus far in polymerization of
1-hexene induced by 1a were measured using the
following procedure: approximately 1 equiv of B(C6F5)3
was added to 13 µmol of 1a in 100 mL of neat 1-hexene
at room temperature. A fast polymerization reaction was
initiated and was accompanied by considerable heat
release, causing boiling of the monomer; this yielded
22.3 g of poly(1-hexene) after 5 min, corresponding to a
reactivity of 21 000 g mmol cat-1 h-1. To the best of our
knowledge, this is the highest reactivity ever observed
in the polymerization of 1-hexene under such mild
(14) Addition of B(C6F5)3 to 1a in d5-chlorobenzene gave a relatively
stable compound in >90% yield according to 1H NMR. The 19F NMR
spectrum of this compound is consistent with formation of a [(C6F5)3B-
CH2Ph]- anion, whose benzyl arene ring is not coordinated to the
zirconium.15 This may result from the relative crowding around the
metal in this [ONNO]-type complex. 1H NMR (C6D5Cl): δ 7.63 (m, 4H),
7.29-7.01 (m, 8H), 6.89 (t, J ) 6.2 Hz, 2H), 3.85 (d, J ) 13.8 Hz, 2H),
3.47 (br s, 2H), 3.27 (d, J ) 13.8 Hz, 2H), 3.03 (s, 2H), 2.62 (br, 2H),
1.98 (s, 6H), 1.64 (s, 18H), 1.44 (s, 18H), 1.63-1.44 (m, 2H). 19F NMR
(C6D5Cl): δ -130.64 (o), -164.36 (p), -167.02 (m). In comparison, the
1H NMR spectrum of 2a /B(C6F5)3 in d5-chlorobenzene is more complex
and features somewhat broadened peaks. The 19F NMR spectrum could
not rule out a coordination of the B-benzyl group or fluorine atoms to
the zirconium. 19F NMR (C6D5Cl): δ -130.82 (o), -162.94 (br, p),
-166.30 (m).
(15) (a) Horton, A. D.; de With, J . Chem. Commun. 1996, 1375. (b)
Horton, A. D.; de With, J .; van der Linden, A. J .; van de Weg, H.
Organometallics 1996, 15, 2672. (c) Horton, A. D.; de With, J .
Organometallics 1997, 16, 5424.
(16) Cloke, F. G. N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J .
Organomet. Chem. 1996, 506, 343.

Zr Complexes of Amine Bis(phenolate) Ligands
Organometallics, Vol. 20, No. 14, 2001 3021
F igu r e 4. ORTEP drawing of the molecular structure of
2a (50% probability ellipsoids). H atoms, the solvent of
crystallization, and disorder were omitted for clarity. Key
atoms are labeled.
F igu r e 5. ORTEP drawing of the molecular structure of
4a (50% probability ellipsoids). H atoms were omitted for
clarity. Key atoms are labeled.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 4a
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 2a
Zr-O2
Zr-O18
Zr-N10
2.010(5)
2.004(5)
2.325(6)
Zr-C41
Zr-C48
Zr-C49
2.273(8)
2.289(7)
2.768(8)
Zr-O2
Zr-O18
Zr-N
2.002(2)
2.000(2)
2.378(2)
Zr-C38
Zr-C45
Zr-C46
2.272(2)
2.292(2)
2.714(2)
O2-Zr-O18
C41-Zr-C48
157.8(2)
118.2(3)
Zr-C48-C49
Zr-C41-C42
92.0(5)
105.0(6)
O2-Zr-O18
C45-Zr-C38
157.33(6)
117.39(9)
Zr-C38-C39
Zr-C45-C46
108.8(2)
89.4(1)
The convenient synthesis of complexes having t-Bu
substituents, as mentioned, prompted us to continue
working with such ligands, derived from 2,4-di-tert-
butylphenol.
Effect of th e Sid e-Ch a in Len gth . 4a , having a
three-carbon bridge between the two nitrogen donors,
was also obtained quantitatively as a single isomer. The
spectral data of 4a are similar to those obtained for 1a
and 2a , reflecting a Cs-symmetrical complex having a
rigid core.
The small structural difference between 1a and 4a ,
namely the addition of a single methylene unit, was not
expected to lead to a substantial difference in reactivity.
Surprisingly, upon activation with approximately 1
equiv of B(C6F5)3, 4a was found to be almost unreactive
in the polymerization of neat 1-hexene (Table 7). Traces
of oligomeric material were obtained after 2 min, in
analogy to the results obtained with 2a . The origin of
this behavior was found by solving the X-ray structure
of 4a , shown in Figure 5 (Table 3).
The structure features a complex having a pseudo-
trigonal-bipyramidal geometry, with axial O atoms and
equatorial N,C,C atoms, and the [ONO] core resembles
those of the previous complexes. Most importantly, the
sidearm nitrogen is not coordinated to the metal, as
evidenced by the long distance of 5.4 Å between it and
the metal (Figure 9).
2a was found to be a poor catalyst for the polymeri-
zation of neat 1-hexene (Table 7). Adding approximately
1 equiv of B(C6F5)3 to 12 µmol of 2a yielded only traces
of oligomeric material after 2 min.14 Chain-end analysis
1
by H NMR indicated an average of less than 10 units
of monomer per chain. Terminal (4.75 ppm) as well as
internal (5.35 ppm) olefinic end groups were observed,
suggesting several possible termination processes, in-
cluding those following a 2,1-misinsertion. The weight
of the oligomeric product did not increase with time,
indicating that the catalyst is rapidly deactivated. The
substantial difference in reactivities between 1a and 2a
supports the correlation between binding of the sidearm
nitrogen to the metal in 1a observed in the solid-state
structure (Figure 2) and its binding in the catalytic
cycle.
Effect of th e Ar om a tic Rin g Su bstitu en ts. To
estimate the role of the bulky t-Bu groups, located ortho
to the binding oxygen atoms, in the high reactivity of
1a and the formation of high-molecular-weight poly-
mers, 3a was also tested as a polymerization precata-
lyst. Upon reaction of 3 (Scheme 1) with zirconium
tetrabenzyl, a mixture of products was obtained, whose
complete purification could not be achieved. The product
mixture, containing the dibenzyl complex 3a , was tested
nonetheless in the polymerization of neat 1-hexene and
exhibited very high reactivity, which resulted in the
boiling of the monomer, in analogy to the results
obtained with 1a . The polymer obtained had a molecular
weight of Mw ) 100 000 and a PDI of 1.9 (Table 7). The
large substituents are therefore not prerequisites for the
high polymerization reactivity and for the high-molec-
ular-weight polymers obtained from 1a 11 and do not play
a considerable role in inhibiting termination processes.
The wide angle between the two benzyl groups and
the apparent η2 binding of one of them to the zirconium,
as evidenced by the corresponding bond lengths and
angles,16 indicate that 4a is isostructural with 2a . It
would therefore appear that although 4a is formally an
[ONNO]-type complex, it is in fact an [ONO]-type
complex. The correlation between binding of the donor

3022 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
F igu r e 6. ORTEP drawing of the molecular structure of
5a (50% probability ellipsoids). H atoms and the solvent
of crystallization were omitted for clarity. Key atoms are
labeled.
F igu r e 7. ORTEP drawing of the molecular structure of
6a (50% probability ellipsoids). H atoms were omitted for
clarity. Key atoms are labeled.
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 6a
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 5a
Zr-O2
Zr-O18
Zr-N10
1.922(1)
2.000(1)
2.466(2)
Zr-N30
Zr-C50
Zr-C43
2.496(2)
2.309(2)
2.333(2)
Zr-O2
2.000(4)
2.008(4)
2.418(4)
2.519(4)
Zr-C42
Zr-C43
Zr-C49
2.306(5)
2.771(5)
2.320(5)
Zr-O18
Zr-N10
Zr-N29
O2-Zr-O18
N10-Zr-N30
C43-Zr-C50
158.70(5)
77.34(5)
88.47(7)
Zr-C43-C44
Zr-C50-C51
122.0(1)
105.0(1)
O2-Zr-O18
N10-Zr-N29
C42-Zr-C49
159.2(1)
68.4(1)
112.2(2)
Zr-C42-C43
Zr-C49-C50
92.2(3)
126.5(4)
mately 1 equiv of B(C6F5)3 to 13 µmol of 5a in 5 mL of
neat 1-hexene at room temperature initiated a fast
polymerization reaction accompanied by heat release,
causing immediate boiling of the monomer. The highest
reactivity obtained using this precatalyst was 5700 g
mmol cat-1 h-1. This reactivity is in good correlation
with the structure of 5a , featuring strong binding of the
sidearm nitrogen to the metal, and is consistent with
the results obtained so far. The lower reactivity of 5a
compared to that of 1a may result from electronic
effects, derived from the sp2 nature of the donor.
Diluting the monomer in an inert solvent had an effect
similar to that observed using 1a (Table 7).
To evaluate the possible formation of a six-membered
chelate via a pyridine side donor, the ligand precursor
6 (Scheme 1) was synthesized and reacted with zirco-
nium tetrabenzyl, yielding a single isomer of the diben-
zyl complex 6a , quantitatively.
The NMR spectra of 6a are analogous to those
obtained for all previous complexes. The crystal struc-
ture of 6a is shown in Figure 7 (Table 5).
As expected from the structures analyzed before, the
[ONO] core of 6a closely resembles those of complexes
discussed thus far. Somewhat less expectedly, the
pyridine nitrogen is bound to the metal and thus forms
a six-membered chelate ring. The Zr-N(30) bond length
of 2.50 Å is even shorter than the equivalent bond in
5a . As may be expected of a six-membered ring, the
pyridine nitrogen in 6a is located higher, as evidenced
by the N(10)-Zr-N(30) angle of 77.3°, relative to the
corresponding angle of 68.4° in 5a (Figure 9). This may
cause steric interactions of the pyridine ring with the
top benzyl unit. Indeed, the binding of the benzyl units
in 6a differs from that in 5a in two ways: the two units
are not pointing in the same direction and are both
arm in the precatalyst expressed in the crystal structure
and the polymerization reactivity of the reactive species
in solution supports the notion that the sidearm donor
remains attached to the metal during the polymeriza-
tion process induced by 1a .8
sp 2-Typ e Sid ea r m Nitr ogen Don or s. The spectral
features of 5a , having a side pyridine donor, are similar
to those obtained for 1a , 2a , and 4a , namely a Cs-
symmetrical complex containing a rigid [ONO] core and
two different benzyl groups. Single crystals of 5a
suitable for X-ray analysis were grown from pentane
at -35 °C, and the structure of 5a is shown in Figure 6
(Table 4).
The structure reveals a complex having a slightly
distorted octahedral geometry. The [ONO] core of 5a is
similar to those of 1a , 2a , and 4a , and the sidearm
pyridine nitrogen is coordinated to the metal, as evi-
denced by the Zr-N(29) distance of 2.52 Å (Figure 9).
A relatively wide angle between the benzyl groups
(C(Ar)-Zr-C(Ar) ) 112.2°) is probably a consequence
of the η2 binding of one benzyl group to the metal,
evidenced by the Zr-CH2-C(Ar) angle of 92° as well
as a short Zr-C(Ar) distance of 2.77 Å, as was found in
2a and 4a .16 This is our first example of an [ONNO]-
type amine bis(phenolate) zirconium dibenzyl complex,
in which one of the benzyl groups is bound to the metal
in a nonclassical fashion. The short bond between the
sidearm nitrogen and the metal in 5a imply a very
strong coordination. We therefore assume that the η2
binding of one of the benzyl groups in this case is due
to a lesser degree of crowding, and not to the electron
deficiency of the zirconium center.
5a was found to be almost as reactive as 1a in the
polymerization of 1-hexene (Table 7). Adding approxi-

Zr Complexes of Amine Bis(phenolate) Ligands
Organometallics, Vol. 20, No. 14, 2001 3023
bound to the metal in an η1 fashion (Figure 9). The
resulting increase in the electrophilicity of the metal
center may explain the shortening of the metal-
nitrogen bond in 6a .
Since all of the zirconium complexes described thus
far in which a donor on a sidearm was bound to the
metal exhibited catalytic polymerization reactivity, it
was interesting to see whether 6a , having a six-
membered chelate via the pyridine group, will obey this
rule as well. Indeed, 6a was found to lead to a reactive
1-hexene polymerization catalyst (Table 7). Adding
approximately 1 equiv of B(C6F5)3 to 13 µmol of 6a in 2
mL of neat 1-hexene at room temperature initiated a
relatively slow polymerization reaction, not accompa-
nied by substantial heat release. A total of 280 mg of
poly(1-hexene) was produced after 20 min, correspond-
ing to a reactivity of 65 g mmol cat-1 h-1. A linear
consumption of the 1-hexene for 5 h is consistent with
the catalyst being active for that period of time. 6a also
leads to high-molecular-weight polymers (Mw ) 102 000),
and the PDI values obtained are around 1.7, indicating
a single-site catalyst.
6a is therefore a precursor for a long-lived catalyst
leading to a high-molecular-weight polymer, which is
the first member of its family exhibiting a moderate
reactivity. The additional steric bulk around the metal
in 6a relative to 5a , as revealed from the crystal
structures of the two, may be the cause of the 100-fold
reactivity difference between these complexes. A narrow
angle between the two labile positions is apparently not
required for high reactivity17 (on the basis of the
C-Zr-C angles of 112.2 and 88.5° in 5a and 6a ,
respectively), even though a metallacyclobutane is
proposed to form in the rate-determining step. A ligand
which forces a narrow angle between the two labile
positions by steric interactions (e.g., 6) may also hinder
the approach of an incoming high olefin and thereby
reduce the catalytic reactivity.
F igu r e 8. ORTEP drawing of the molecular structure of
7a (50% probability ellipsoids). H atoms and the solvent
of crystallization were omitted, and the disordered ethyl
groups on the sidearm nitrogen are shown in reduced size
for clarity. Key atoms are labeled.
Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 7a
Zr-O5
Zr-O4
Zr-N2
2.002(2)
2.005(2)
2.412(3)
Zr-N3
Zr-C29
Zr-C22
2.764(3)
2.283(4)
2.314(4)
O5-Zr-O4
N2-Zr-N3
C29-Zr-C22
161.37(1)
69.37(9)
103.3(1)
Zr-C22-C23
Zr-C29-C30
120.9(2)
104.1(2)
high statistic termination processes occurring in a
regular 1,2-insertion reaction. However, since the mo-
lecular weight is determined by the ratio kpropagation
/
k
termination, the low molecular weight may also result from
slower propagation when 7a is involved, relative to
previous highly reactive complexes, rather than from
faster termination processes.
Effect of th e Don or Su bstitu en ts. Another param-
eter we studied concerning the sidearm donor is its
substituents. The NMR spectra of 7a , having two ethyl
groups bound to the side nitrogen, are analogous to
those obtained with the previous complexes.
Interestingly, adding approximately 1 equiv of B(C6F5)3
to 13 µmol of 7a in 2 mL of neat 1-hexene at room
temperature initiated a slow polymerization reaction,
with reactivity similar to that obtained with 6a , namely
60 g mmol cat-1 h-1. The catalyst is active for at least
7 h. However, in contrast to all reactive catalysts
described thus far, only oligomers were obtained (Mw
) 1100, PDI ) 1.6), according to GPC analysis (Table
7). 7a may therefore be considered to be a fair oligo-
merization precatalyst.1
An interesting observation which was found only for
this catalytic system is an additional signal appearing
in the GPC chromatogram, which corresponds to a
molecular weight of around Mw ) 300 000, integration
of which (relative to the oligomer signal) increases with
time. This signal may be attributed to a polymerization
product of the oligomers obtained, which are terminal
high olefins.18 It is yet unclear, and is being currently
investigated, whether the oligomers’ polymerization
results from catalytic reaction induced by 7a or from
cationic polymerization of these disubstituted terminal
olefins induced by the Lewis acid cocatalyst.
The 1H NMR spectrum of the oligomers obtained,
taken after a relatively short time (ca. 1 h), includes
vinyl signals (4.75, 4.69 ppm) corresponding to the
formation of disubstituted terminal olefins, integration
of which is consistent with the Mn value obtained from
the GPC analysis. No evidence for internal olefins was
found. It is therefore plausible that the termination
processes responsible for the low molecular weight do
not follow a 2,1-misinsertion but instead result from
Since the difference in steric effects caused by methyl
and ethyl groups is expected to be small, the polymer-
ization results obtained by 7a were surprising. Single
crystals of 7a suitable for X-ray diffraction were grown
from toluene at -35 °C, and the structure is shown in
Figure 8 (Table 6).
The structure presents a zirconium complex having
a distorted-octahedral geometry. Consistent with all
previous structures, the [ONO] core does not show any
(17) Male, N. A. H.; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc.,
Dalton Trans. 1997, 2487.
(18) Murtuza, S.; Harkins, S. B.; Long, G. S.; Sen, A. J . Am. Chem.
Soc. 2000, 122, 1867.

3024 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
F igu r e 9. Side view of the structures of 1a , 2a , and 4a -7a , in which the t-Bu groups and several aromatic ring atoms
were omitted for clarity.
unusual features. Interestingly, the distance between
the sidearm nitrogen and the zirconium atom was found
to be 2.76 Å, which is exceptionally long (Figure 9). This
larger distance clearly indicates a weaker bond. The
bulkier substituents do not seem to change the [ONO]
ligand core by bending it forward but instead hold the
donor away from the metal. A Zr-CH2-C(Ar) angle of
104° and a Zr-C(Ar) distance of 3.0 Å may indicate a
weak π-interaction between the top benzyl group and
the zirconium atom,16 which may result from an in-
creased electrophilicity of the metal caused by this
weaker binding of the side diethylamine group.
catalyst. This reactivity calls for a relatively high
termination/propagation rate ratio, as well as reinitia-
tion of the reactive species.
One possible source for the steric interactions involv-
ing the diethylamine group is its relative proximity to
the bulky t-Bu ring substituents. To evaluate the role
of these groups in the complex strain and polymerization
results, we turned once again to a ligand having smaller
aromatic ring substituents, derived from 2,4-dimethyl-
phenol.
8a was obtained in 30% yield after recrystallization
of a mixture of products. The spectroscopic data ob-
tained for 8a are analogous to those obtained with the
previous complexes.
Upon activation with B(C6F5)3, 8a led to a catalyst
which is about 1 order of magnitude more reactive than
the catalyst derived from 7a toward 1-hexene (Table 7).
The molecular weight was found to be higher as well
(Mw ) 6700, with a PDI value of 3.3 due to heat release).
It is therefore plausible that reduced steric interactions
in 8a enable a stronger binding of the diethylamine arm
to the metal, resulting in a higher reactivity and
somewhat higher molecular weight.
Although the two ethyl groups were found to be
disordered in the structure of 7a , the major conforma-
tion is the one shown in Figure 9, which may be
assigned as the most unstable g+g- gauche conformation
of the Et-N-Et unit.19 This is more evidence for the
strong steric interactions involving the ethyl groups,
which are probably responsible for the lengthening of
the Zr-N(3) bond. Although the binding of the sidearm
nitrogen in 7a is weak, we propose that this arm is not
completely detached from the metal during the polym-
erization process; otherwise, an [ONO]-type complex
would result, leading to a fast deactivation process. Two
possible binding modes for the sidearm in the reactive
catalyst are either a constant weak binding or an on-
off binding, which may explain the unique reactivity
pattern of this catalyst: a long-lived oligomerization
Con clu sion s
We have synthesized a series of amine-bis(phenolate)
ligand precursors from readily available starting ma-
terials. Zirconium dibenzyl complexes of these ligands
were obtained in a simple single-step procedure, most
of them in quantitative yields. When the catalytic
(19) Eliel, E. L.; Wilen, S. H. Stereochemistry of Organic Compounds;
Wiley: New York, 1994; p 603.

Zr Complexes of Amine Bis(phenolate) Ligands
Organometallics, Vol. 20, No. 14, 2001 3025
Ta ble 7. P olym er iza tion Da ta a
are unprecedented under the conditions employed. Why
does this ligand system lead to such reactivities in the
polymerization of high olefins? A possible explanation
for this behavior is rigid wrapping of the ligand around
the metal, leaving a relatively open cleft for the olefin
coordination and the polymer growth. The formation of
a well-separated ion pair may also enhance the reactiv-
ity.14 Furthermore, the active positions are trans to
donor atoms and are forced into a cis configuration,
which may lower the activation energy for the metal-
lacyclobutane formation in the rate-determining step of
the polymerization process.17 We are currently studying
additional ligands and complexes of this family as
polymerization catalysts.
precatalyst
solvent
neat
reactivityb
Mw
Mw/Mn
1a
1a
2a
3a
4a
5a
5a
6a
7a
8a
8a
21 000
35 000
170 000
oligomers
100 000
oligomers
15 000
55 000
102 000
1100
3.5
2.0
heptanec 860
neat
neat
neat
neat
negligible
undetermined
negligible
5700
1.9
4.5
1.5
1.7
1.6
3.3
1.6
heptanec 650
neat
neat
neat
65
60
560
6700
8000
heptanec 400
a
The polymerization reactions are performed using 13 µmol of
precatalyst unless otherwise stated, activated with approximately
b
1 equiv of B(C6F5)3. In units of g mmol cat-1 h-1
.
c 3/7 1-hexene/
heptane; 6 µmol of precatalyst is used.
Exp er im en ta l Section
potentials of these complexes were studied, several
manifestations of structure-reactivity relationships
were revealed.
Gen er a l Da ta . Starting materials for the synthesis of
ligand precursors 1-8 were purchased from Aldrich Inc. and
used without further purification. All experiments requiring
a dry atmosphere were performed under a nitrogen atmo-
sphere in a drybox. Toluene was distilled from Na, and pentane
was distilled from Na/benzophenone/tetraglyme. Anhydrous
heptane was purchased from Aldrich Inc. and passed through
alumina prior to use. 1-Hexene was purchased from Aldrich
Inc. and passed through alumina prior to use. All solvents were
stored in the drybox. Zr(Bn)4 was prepared according to a
literature procedure.20 B(C6F5)3 was purchased from Strem
Chemicals Inc. and used as is. Mass spectra were determined
with a Finnigan Model 4021 GC/MS spectrometer. NMR
spectra were recorded using Bruker DMX-600, ARX-500,
AVANCE-400, AMX-360, or AC-200 spectrometers. NMR
solvents were sparged with argon and stored over 4 Å
molecular sieves. The X-ray diffraction measurements were
carried out on a Nonius Kappa CCD diffractometer using Mo
KR (λ ) 0.7107 Å) radiation. The analyzed crystals were
embedded within a drop of viscous oil and freeze-cooled to
ca. 115 K. The structures were solved by a combination of
direct methods and Fourier techniques using SIR-92 and
DIRDIF-96 software21 and were refined by full-matrix least
squares with SHELXL-97.22 Most of the structures contain
partially disordered solvent, which affects to some extent the
precision of the structure determination. Elemental analyses
of the ligand precursors 1-8 were performed in the microana-
lytical laboratory at the Hebrew University of J erusalem. The
zirconium complexes gave consistently low carbon percentage
analyses, due to apparent thermal as well as hydrolytic
instability. All gel permeation chromatography (GPC) experi-
ments were carried out using a TSK-GEL GMHH R-M column
set on a J asco instrument equipped with a refractive index
detector, relative to polystyrene standards and tetrahydro-
furan as the eluting solvent. HPLC grade tetrahytrofuran was
filtered under vacuum prior to use.
The complexes described in this work may be roughly
divided into two categories: pentacoordinate complexes,
derived from [ONO]-type (2a ) or pseudo-[ONO]-type (4a )
ligands, and hexacoordinate complexes, derived from
[ONNO]-type ligands. The two categories of complexes
share very similar binding of the core amine bis-
(phenolate) unit to the metal, as revealed from the X-ray
structures. This similarity is proposed to hold in solution
as well, on the basis of NMR data which imply that this
core is rigidly bound to the metal. The structural
difference between the two categories is the presence
of an additional nitrogen donor on a sidearm. Even
though this donor plays a minor structural role, i.e.,
binding somewhat away from the active site and not
distorting the [ONO] core, it has a major effect on
reactivity. Especially, its presence is a prerequisite for
a long-lived polymerization catalyst. In comparison,
steric effects of the substituents on the aromatic rings
which are much closer to the active site have a much
weaker influence on reactivity.
Structural parameters, including steric crowding,
nitrogen hybridization, chelate ring size, and donor
substituents in [ONNO]-type complexes, were varied
and found to have a major effect on reactivity. Gener-
ally, a strong donation of a sidearm nitrogen led to very
reactive polymerization catalysts. The most reactive
catalysts included five-membered chelates (1a , 3a , and
5a ). In this case, changing the hybridization from sp3
to sp2 or reducing the size of the substituents on the
aromatic rings had minor effects on reactivity. Modify-
ing the sidearm N-Zr bond could be achieved in several
ways and had varying influences on reactivity. Bulky
substituents on the N-donor reduced the reactivity
dramatically and led to oligomers (7a ). This influence
could be somewhat compensated for by reducing the size
of the ring substituents (8a ). A six-membered chelate
featuring a pyridine donor led to a moderate polymer-
ization catalyst (6a ), whereas a six-membered chelate
featuring a dimethylamino group did not form and, thus,
a rapidly deactivated catalyst resulted (4a ).
1.23 A solution of 2,4-di-tert-butylphenol (5.0 g, 24.2 mmol),
N,N-dimethylethylenediamine (1.35 mL, 12.3 mmol), and 36%
aqueous formaldehyde (2.5 mL, 33.6 mmol) in methanol (10
(20) Zucchini, U.; Alizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357.
(21) (a) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. SIR-92. J . Appl. Crystal-
logr.1994, 27, 435. (b) Beurskens, P. T.; Beurskens, G.; Bosman, W.
P.; de Gelder, R.; Garcia-Granda, S.; Gould, R. O.; Israel, R.; Smits, J .
M. M. DIRDIF-96; Crystallography Laboratory, University of Nijmegen,
The Netherlands, 1996.
(22) Sheldrick, G. M. SHELXL-97: Program for the Refinement of
Crystal Structures from Diffraction Data; University of Go¨ttingen,
Go¨ttingen, Germany, 1997.
(23) (a) Hirotsu, M.; Kojima, M.; Yoshikawa, Y. Bull. Chem. Soc.
J pn. 1997, 70, 649. (b) Hinshaw, C. J .; Peng, G.; Singh, R.; Spence, J .
T.; Enemark, J . H.; Bruck, M.; Kristovszki, J .; Merbs, S. L.; Ortega,
R. B.; Wexler, P. A. Inorg. Chem. 1989, 28, 4483.
A wide range of reactivities and polymer properties
was therefore obtained by minor structural modifica-
tions in the peripheral area of the catalyst, maintaining
practically identical central [ONO] ligand cores. The
highest 1-hexene polymerization reactivities obtained

3026 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
mL) was stirred at room temperature for 3 days. The mixture
was cooled in the freezer overnight, filtered, and washed
thoroughly with ice-cold methanol, to give the bis-adduct as a
colorless powder (3.7 g, 58% yield), which could be further
purified by recrystallization from methanol. Mp: 133 °C. Anal.
Calcd for C34H56N2O2: C, 77.81; H, 10.75; N, 5.34. Found: C,
(ddd, J ) 7.5, 5.0, 1.5 Hz, 1H), 7.10 (d, J ) 8 Hz, 1H), 7.20 (d,
J ) 2.0 Hz, 2H), 6.92 (d, J ) 2.0 Hz, 2H), 3.84 (m, 6H), 1.40
(s, 18H, C(CH3)3), 1.28 (s, 18H, C(CH3)3). 13C NMR (acetone-
d6): δ 157.6, 148.8, 138.7, 124.4, 125.6, 154.6, 141.1, 136.4,
126.1, 123.9, 122.6, 57.6 (ArCH2), 56.3 (CH2), 35.6 (C(CH3)3),
34.7 (C(CH3)3), 32.0 (C(CH3)3), 30.0 (C(CH3)3).
1
6.23b A solution of 2,4-di-tert-butylphenol (3.45 g, 16.7 mmol),
2-(2-aminoethyl)pyridine (1.0 mL, 8.4 mmol), and 36% aqueous
formaldehyde (1.7 mL, 20.4 mmol) in methanol (8 mL) was
stirred and refluxed for 18 h. The mixture was cooled and
filtered and the solid washed thoroughly with cold methanol
to give 3.7 g (79% yield) of the colorless product. Mp: 175 °C.
Anal. Calcd for C37H54N2O2: C, 79.52; H, 9.74; N, 5.01.
Found: C, 79.60; H, 9.94; N, 5.08. 1H NMR (CDCl3): δ 8.68
(d, J ) 5.0 Hz, 1H), 7.55 (ddd, J ) 7.5, 8.0, 2.0 Hz, 1H), 7.16
(ddd, J ) 7.5, 5.0, 1.5 Hz, 1H), 7.05 (d, J ) 8 Hz, 1H), 7.15 (d,
J ) 2.0 Hz, 2H), 6.88 (d, J ) 2.0 Hz, 2H), 3.75 (s, 4H, CH2),
3.11 (t, J ) 6.0 Hz, 2H, CH2), 2.81 (t, J ) 6.0 Hz, 2H, CH2),
1.29 (s, 18H, C(CH3)3), 1.26 (s, 18H, C(CH3)3). 13C NMR
(CDCl3): δ 158.9, 148.8, 137.4, 123.2, 121.9, 153.0, 140.4, 136.2,
125.2, 123.5, 121.6, 56.9 (ArCH2), 53.9 (CH2), 34.9 (CH2), 34.0
(C(CH3)3), 33.8 (C(CH3)3), 31.7 (C(CH3)3), 29.6 (C(CH3)3).
7. A solution of 2,4-di-tert-butylphenol (5.0 g, 24.2 mmol),
N,N-diethylethylenediamine (1.7 mL, 12.1 mmol), and 36%
aqueous formaldehyde (2.5 mL, 33.6 mmol) in methanol (10
mL) was stirred and refluxed for 24 h. The mixture was cooled
and the mother liquor decanted. The remaining oil was
triturated with hot methanol (15 mL), to give colorless crystals
(5.5 g, 82% yield), which could be further purified by recrys-
tallization from methanol. Mp: 154 °C. Anal. Calcd for
78.08; H, 10.80; N, 5.15. H NMR (CDCl3): δ 7.18 (d, J ) 2.0
Hz, 2H), 6.90 (d, J ) 2.0 Hz, 2H), 3.60 (s, 4H, CH2), 2.59 (m,
4H, CH2), 2.31 (s, 6H N(CH3)2), 1.38 (s, 18H, C(CH3)3), 1.26
(s, 18H, C(CH3)3). 13C NMR (CDCl3): δ 153.3, 140.1, 136.0,
124.8, 123.3, 121.6, 56.6 (ArCH2), 56.9 (CH2), 49.0 (CH2), 44.8
(N(CH3)2), 35.0 (C(CH3)3), 34.0 (C(CH3)3), 31.7 (C(CH3)3), 29.5
(C(CH3)3).
2. A mixture of 2,4-di-tert-butylphenol (5.0 g, 24.2 mmol),
1-aminopropane (1.0 mL, 12.1 mmol), and 36% aqueous
formaldehyde (4.0 mL, 48.0 mmol) in methanol (10 mL) was
stirred and refluxed for 24 h. The mixture was cooled in the
freezer overnight and the supernatant solution decanted. The
residue was triturated with ice-cold methanol, filtered, and
washed thoroughly with cold methanol, to give the bis-adduct
as a colorless powder (2.7 g, 45%), which could be further
purified by recrystallization from ethanol. Mp: 138 °C. Anal.
Calcd for C33H53NO2: C, 79.95; H, 10.77; N, 2.83. Found: C,
80.04; H, 11.01; N, 3.03. 1H NMR (CDCl3): δ 7.23 (s, 2H), 6.92
(s, 2H), 3.68 (s, 4H, CH2), 2.51 (m, 2H, CH2), 1.40 (s, 18H,
C(CH3)3), 1.28 (s, 18H, C(CH3)3), 0.88 (t, J ) 7.5 Hz, 3H, CH3).
13C NMR (CDCl3): δ 152.4, 141.5, 136.0, 125.0, 123.4, 121.7,
57.2 (ArCH2), 55.5 (CH2), 34.8 (C(CH3)3), 34.2 (C(CH3)3), 31.6
(C(CH3)3), 29.7 (C(CH3)3), 19.4 (CH2), 11.7 (CH3).
3. A solution of 2,4-dimethylphenol (3.66 g, 30.0 mmol), N,N-
dimethylethylenediamine (1.65 mL, 15.0 mmol), and 36%
aqueous formaldehyde (3.5 mL, 42.0 mmol) in methanol (10
mL) was stirred and refluxed for 24 h. The mixture was cooled,
and the product was filtered and washed with ice-cold metha-
nol, to give the colorless product (4.5 g, 84%). Mp: 174 °C (from
methanol). Anal. Calcd for C22H32N2O2: C, 74.12; H, 9.05; N,
C
36H60N2O2: C, 78.21; H, 10.94; N, 5.07. Found: C, 78.33; H,
1
11.07; N, 5.05. H NMR (CDCl3): δ 7.19 (d, J ) 2.0 Hz, 2H),
6.87 (d, J ) 2.0 Hz, 2H), 3.58 (s, 4H, CH2), 2.63 (m, 8H), 1.38
(s, 18H, C(CH3)3),1.26 (s, 18H, C(CH3)3), 1.11 (t, J ) 7.0 Hz,
6H, CH3). 13C NMR (CDCl3): δ 153.2, 140.1, 135.9, 124.7,
123.3, 121.4, 56.6 (ArCH2), 50.0 (CH2), 48.9 (CH2), 45.4 (N(CH2-
CH3)2), 34.9 (C(CH3)3), 34.1 (C(CH3)3), 31.7 (C(CH3)3), 29.6
(C(CH3)3), 9.7 (N(CH2CH3)2).
1
7.86. Found: C, 74.05; H, 9.16; N, 7.83. H NMR (CDCl3): δ
6.84 (s, 2H), 6.67 (s, 2H), 3.58 (s, 4H, CH2), 2.58 (m, 4H, CH2),
2.33 (s, 6H, N(CH3)2), 2.19 (s, 12H, CH3). 13C NMR (CDCl3): δ
152.6, 131.2, 128.3, 127.5, 125.4, 121.6, 56.4, (ArCH2), 56.0
(CH2), 49.0 (CH2), 44.9 (N(CH3)2) 20.4 (CH3), 16.1 (CH3).
4. A solution of 2,4-di-tert-butylphenol (4.12 g, 20.0 mmol),
N,N-dimethyl-1,3-propanediamine (1.26 mL, 10.0 mmol), and
36% aqueous formaldehyde (3.2 mL, 38.4 mmol) in methanol
(5 mL) was stirred and refluxed for 18 h. The mixture was
cooled in the freezer overnight and the supernatant solution
decanted. The solid residue was triturated with ice-cold
methanol, filtered, and washed thoroughly with cold methanol,
to give the bis-adduct as a colorless powder (2.28 g, 42%),
which could be further purified by recrystallization from
methanol. Mp: 144 °C. Anal. Calcd for C35H58N2O2: C, 78.01;
H, 10.85; N, 5.20. Found: C, 77.75; H, 10.83; N, 5.24. 1H NMR
(CDCl3): δ 7.12 (s, 2H), 6.86 (s, 2H), 3.55 (s, 4H, CH2), 2.59
(m, 2H, CH2), 2.47 (m, 2H, CH2), 2.36 (s, 6H, N(CH3)2), 1.78
(m, 2H, CH2), 1.39 (s, 18H, C(CH3)3), 1.26 (s, 18H, C(CH3)3).
13C NMR (CDCl3): δ 153.2, 140.2, 135.9, 125.1, 123.2, 121.2,
58.5 (CH2), 57.5 (CH2), 55.0 (CH2), 45.6 (N(CH3)2), 35.0
(C(CH3)3), 34.0 (C(CH3)3), 31.7 (C(CH3)3), 29.6 (C(CH3)3), 22.8
(CH2).
5.21 A solution of 2,4-di-tert-butylphenol (5.0 g, 24.2 mmol),
2-(aminomethyl)pyridine (1.5 mL, 14.6 mmol), and 36% aque-
ous formaldehyde (2 mL, 24 mmol) in methanol (8 mL) was
stirred and refluxed for 18 h. The mixture was cooled in the
freezer overnight and the supernatant solution decanted. The
solid residue was triturated with ice-cold methanol, filtered,
and washed thoroughly with cold methanol, to give the bis-
adduct as a colorless powder (3.08 g, 47% yield), which could
be further purified by recrystallization from methanol. Mp:
199 °C. Anal. Calcd for C36H52N2O2: C, 79.36; H, 9.62; N, 5.14.
Found: C, 79.47; H, 9.66; N, 5.13. 1H NMR (CDCl3): δ 8.70
(d, J ) 5.0 Hz, 1H), 7.70 (ddd, J ) 7.5, 8.0, 2.0 Hz, 1H), 7.28
8. A solution of 2,4-dimethylphenol (5.0 g, 41.0 mmol), N,N-
diethylethylenediamine (2.9 mL, 20.6 mmol), and 36% aqueous
formaldehyde (5.0 mL, 60.0 mmol) in methanol (10 mL) was
stirred and refluxed for 24 h. The mixture was cooled and
filtered and the residue washed with ice-cold methanol, to give
the colorless product (6.15 g, 78% yield), which could be
crystallized from ether/methanol. Mp: 143 °C. Anal. Calcd for
C
24H36N2O2: C, 74.96; H, 9.55; N, 7.28. Found: C, 74.93; H,
9.55; N, 7.36. 1H NMR (CDCl3): δ 6.84 (s, 2H), 6.66 (s, 2H),
3.57 (s, 4H, CH2), 2.64 (m, 4H), 2.67 (q, J ) 7.0 Hz, 4H, N(CH2-
CH3)2), 2.19 (s, 12H, CH3), 1.10 (t, J ) 7 Hz, 6H, N(CH2CH3)2).
13C NMR (CDCl3): δ 152.6, 131.1, 128.3, 127.3, 125.4, 121.4,
55.7 (ArCH2), 49.8 (CH2), 48.6 (CH2), 45.7 (N(CH2CH3)2), 20.3
(CH3), 16.0 (CH3), 9.8 (N(CH2CH3)2).
LigZr Bn 2. Gen er a l P r oced u r e. A solution of a ligand
precursor 1-8 (0.40 mmol) in toluene (2 mL) was added
dropwise to a solution of zirconium tetrabenzyl (0.40 mmol)
in toluene (2 mL) at room temperature under a nitrogen
atmosphere. The reaction mixture was then heated to 65 °C
and stirred for 2 h. The toluene was removed under vacuum.
Com p lex 1a . 1a was obtained quantitatively as a yellow
1
solid. Crystal data are presented in Table 8. H NMR (C6D6):
δ 7.74 (d, J ) 7.1 Hz, 2H), 7.62 (d, J ) 2.4 Hz, 2H), 7.39 (t, J
) 8.1 Hz, 2H), 7.05 (t, J ) 7.3 Hz, 1H), 6.95 (d, J ) 2.4 Hz,
2H), 6.90 (d, J ) 7.1 Hz, 2H), 6.73 (t, J ) 8.0 Hz, 2H), 6.55 (t,
J ) 7.3 Hz, 1H), 3.45 (br d, J ) 13.0 Hz, 2H, ArCH2), 2.70 (s,
2H, PhCH2), 2.60 (d, J ) 13.6 Hz, 2H, ArCH2), 2.57 (s, 2H,
PhCH2), 1.88 (s, 18H, C(CH3)3), 1.48 (s, 6H, N(CH3)2), 1.40 (br,
4H, CH2), 1.36 (s, 18H, C(CH3)3). 13C NMR (C6D6): δ 158.2,
149.3, 147.2, 141.3, 136.5, 129.1, 128.4, 128.3, 127.5, 125.2,
124.8, 122.5, 120.4, 68.1 (PhCH2), 66.1 (PhCH2), 65.2 (ArCH2),
60.2 (CH2), 51.2 (CH2), 47.5 (N(CH3)2), 35.7 (C(CH3)3), 34.4
(C(CH3)3), 32.0 (C(CH3)3), 30.8 (C(CH3)3).

Zr Complexes of Amine Bis(phenolate) Ligands
Organometallics, Vol. 20, No. 14, 2001 3027
Ta ble 8. Cr ysta llogr a p h ic Da ta for 1a , 2a , a n d 4a
Ta ble 9. Cr ysta llogr a p h ic Da ta for 5a , 6a , a n d 7a
1a
48H68N2O2Zr‚ C47H65NO2Zr‚ C49H70N2O2Zr
C5H12 C7H14
867.42
2a
4a
5a
6a
7a
formula
C
formula
C50H64N2O2Zr‚ C51H66N2O2Zr C50H72N2O2Zr‚
C5H12
888.40
110
monoclinic
C2/ c
35.5180(8)
13.7990(8)
23.232(1)
119.058(3)
9953.1(8)
8
C7H8
1008.58
110
monoclinic
P21/n
13.2990(4)
15.3160(3)
27.8620(7)
92.780(1)
5668.5(2)
4
fw
868.41
117
810.29
116
fw
830.28
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
116
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
110
orthorhombic
Pbca
18.452(1)
19.131(1)
28.239(1)
90
monoclinic
P21/c
orthorhombic
P212121
11.695(1)
17.167(1)
22.663(1)
90
monoclinic
P21/c
10.4840(1)
19.2970(4)
24.5940(5)
91.048(1)
4974.8(2)
4
11.3160(1)
23.0390(3)
17.7730(2)
90.2480(3)
4633.54(9)
4
â (deg)
V (Å3)
Z
â (deg)
V (Å3)
Z
9968.5(8)
8
4550.0(5)
4
Fcalcd (g cm-3
λ (Å)
)
1.157
1.158
1.183
Fcalcd (g cm-3
λ (Å)
)
1.186
1.190
1.182
0.7107
0.260
0.7107
0.259
0.7107
0.280
0.7107
0.262
0.7107
0.7107
µ (mm-1
)
µ (mm-1
)
0.276
0.237
no. of rflns
measd
9375
12 508
5776
no. of rflns
measd
9032
10 218
13 459
no. of indep
rflns
5867
10 397
3603
no. of indep
rflns
6409
8040
9165
R1(I > 2σ(I))
0.103
0.049
0.129
0.062
0.138
1.030
0.070
0.125
0.145
0.164
1.031
R1(I > 2σ(I))
0.073
0.038
0.092
0.057
0.103
0.982
0.072
0.157
0.117
0.181
1.020
wR2(I > 2σ(I)) 0.264
R1(all data) 0.148
wR2(all data) 0.285
GOF(F2)
1.028
wR2(I > 2σ(I)) 0.192
R1(all data) 0.115
wR2(all data) 0.223
GOF(F2)
1.193
Com p lex 2a . 2a was obtained quantitatively as a colorless
solid. Crystal data are presented in Table 8. H NMR (C6D6):
2.63 (d, J ) 13.6 Hz, 2H, ArCH2), 2.59 (s, 2H, CH2), 1.70 (s,
18H, C(CH3)3), 1.32 (s, 18H, C(CH3)3). 13C NMR (C6D6):
1
δ
δ 7.76 (d, J ) 7.5 Hz, 2H), 7.57 (d, J ) 2.3 Hz, 2H), 7.28 (t, J
) 7.6 Hz, 2H), 7.12 (t, J ) 7.3 Hz, 1H), 6.94 (d, J ) 2.3 Hz,
2H), 6.92 (d, J ) 7.4 Hz, 2H), 6.74 (t, J ) 7.4 Hz, 2H), 6.62 (t,
J ) 7.3 Hz, 1H), 3.30 (d, J ) 13.8 Hz, 2H, ArCH2), 2.99 (s, 2H,
PhCH2), 2.98 (d, J ) 13.6 Hz, 2H, ArCH2), 2.03 (m, 2H, CH2),
1.95 (s, 2H, PhCH2), 1.79 (s, 18H, C(CH3)3), 1.35 (s, 18H,
C(CH3)3), 1.05 (m, 2H, CH2), -0.03 (t, J ) 7.3 Hz, 3H, CH3).
13C NMR (C6D6): δ 158.3, 148.3, 142.1, 137.4, 136.8, 131.4,
129.5, 125.8, 125.4, 125.2, 125.1, 122.7, 60.9 (CH2), 58.9
(PhCH2), 45.5 (PhCH2), 36.1 (C(CH3)3), 35.0 (C(CH3)3), 32.6
(C(CH3)3), 31.3 (C(CH3)3), 14.0 (CH2), 11.2 (CH3).
Com p lex 3a . 3a was obtained in a very low yield after
crystallization from pentane (0-5%), as a yellow solid. 1H NMR
(C6D6): δ 7.52 (d, J ) 7.5 Hz, 2H), 7.32 (t, J ) 7.6 Hz, 2H),
7.03 (t, J ) 7.3 Hz, 1H), 6.91 (m, 6H), 6.64 (m, 1H), 6.50 (s,
2H), 3.95 (d, J ) 13.5 Hz, 2H, ArCH2), 2.65 (s, 2H, PhCH2),
2.48 (d, J ) 13.6 Hz, 2H, ArCH2), 2.44 (s, 6H, CH3), 2.40 (s,
2H, PhCH2), 2.19 (s, 6H, CH3), 1.86 (m, 2H, CH2), 1.53 (s, 6H,
CH3), 1.25 (m, 2H, CH2). 13C NMR (C6D6): δ 157.1, 150.1,
146.3, 132.2, 129.2, 127.1, 125.4, 124.9, 122.5, 121.9, 120.3,
65.8 (PhCH2), 65.5 (PhCH2), 63.9 (ArCH2), 60.0 (CH2), 51.2
(N(CH3)2), 46.4 (CH2), 20.7 (CH3), 16.7 (CH3).
159.4, 150.6, 150.0, 141.3, 138.0, 137.0, 130.1, 130.0, 129.3,
129.1, 128.2, 125.6, 124.9, 123.7, 122.4, 121.6, 121.1, 68.3
(PhCH2), 67.7 (PhCH2), 64.4 (ArCH2), 59.5 (CH2), 36.1 (C(CH3)3),
34.9 (C(CH3)3), 32.6 (C(CH3)3), 30.0 (C(CH3)3).
Com p lex 6a . 6a was obtained quantitatively as a yellow
1
solid. Crystal data are presented in Table 9. H NMR (C6D6):
δ 8.67 (dd, J ) 1.1, 5.5 Hz, 1H), 7.47 (d, J ) 2.4 Hz, 2H), 7.31
(m, 4H), 7.22 (d, J ) 7.1 Hz, 2H), 6.99 (m, 1H), 6.94 (d, J )
7.8 Hz, 2H), 6.89 (d, J ) 2.6 Hz, 2H), 6.70 (t, J ) 7.3 Hz, 1H),
6.38 (dt, J ) 1.7, 7.6 Hz, 1H), 6.24 (dt, J ) 1.2, 6.3 Hz, 1H),
5.68 (d, J ) 7.4 Hz, 1H), 3.71 (d, J ) 13.4 Hz, 2H, ArCH2),
3.22 (s, 2H, PhCH2), 3.03 (s, 2H, PhCH2), 2.60 (d, J ) 13.5
Hz, 2H, ArCH2), 2.16 (m, 2H, CH2), 1.95 (m, 2H, CH2), 1.62
(s, 18H, C(CH3)3), 1.35 (s, 18H, C(CH3)3). 13C NMR (C6D6): δ
160.85, 159.6, 152.6, 150.6, 150.4, 141.7, 138.7, 137.1, 129.2,
128.0, 127.85, 126.3, 125.6, 125.1, 123.9, 121.9, 121.5, 121.4,
71.7 (PhCH2), 70.3 (PhCH2), 65.8 (ArCH2), 54.5 (CH2), 36.0
(C(CH3)3), 35.0 (C(CH3)3), 32.6 (C(CH3)3), 31.1 (C(CH3)3).
Com p lex 7a . 7a was obtained quantitatively as a yellow
1
solid. Crystal data are presented in Table 9. H NMR (C6D6):
δ 7.74 (d, J ) 7.4 Hz, 2H), 7.60 (d, J ) 2.4 Hz, 2H), 7.38 (t, J
) 7.7 Hz, 2H), 7.04 (t, J ) 7.3 Hz, 1H), 6.93 (d, J ) 2.3 Hz,
2H), 6.90 (d, J ) 7.4 Hz, 2H), 6.73 (t, J ) 7.7 Hz, 2H), 6.55 (t,
J ) 7.3 Hz, 1H), 3.43 (d, J ) 13.5 Hz, 2H, ArCH2), 2.81 (s, 2H,
PhCH2), 2.62 (s, 2H, PhCH2), 2.58 (d, J ) 13.6 Hz, 2H, ArCH2),
2.30 (q, J ) 7.3 Hz, 4H, N(CH2CH3)2), 2.09 (m, 2H, CH2), 1.89
(s, 18H, C(CH3)3), 1.76 (t, J ) 5.0, 2H, CH2), 1.35 (s, 18H,
C(CH3)3), 0.25 (t, J ) 7.2 Hz, 6H, N(CH2CH3)2). 13C NMR
(C6D6): δ 158.8, 147.6, 141.9, 137.1, 129.8, 127.9, 126.5, 125.4,
123.1, 121.1, 69.6 (PhCH2), 68.0 (PhCH2), 65.9 (ArCH2), 52.3
(CH2), 50.2 (CH2), 48.7 (N(CH2CH3)2), 36.4 (C(CH3)3), 35.1
(C(CH3)3), 32.6 (C(CH3)3), 31.6 (C(CH3)3), 9.89 (N(CH2CH3)2).
Com p lex 4a . 4a was obtained quantitatively as a colorless
1
solid. Crystal data are presented in Table 8. H NMR (C6D6):
δ 7.80 (d, J ) 7.4 Hz, 2H), 7.57 (d, J ) 2.4 Hz, 2H), 7.32 (t, J
) 7.5 Hz, 2H), 7.15 (t, J ) 7.2 Hz, 1H), 6.97 (d, J ) 2.4 Hz,
2H), 6.90 (d, J ) 7.1 Hz, 2H), 6.73 (t, J ) 7.3 Hz, 2H), 6.61 (t,
J ) 7.2 Hz, 1H), 3.33 (d, J ) 13.8 Hz, 2H, ArCH2), 3.03 (s, 2H,
PhCH2), 2.97 (d, J ) 14.0 Hz, 2H, ArCH2), 2.28 (m, 2H, CH2),
1.91 (s, 2H, PhCH2), 1.78 (s, 18H, C(CH3)3), 1.59 (s, 6H,
N(CH3)2), 1.41 (m, 2H, CH2), 1.36 (s, 18H, C(CH3)3), 1.30 (m,
2H, CH2). 13C NMR (C6D6): δ 158.4, 148.9, 142.1, 137.1, 131.5,
129.5, 129.4, 126.0, 125.4, 125.2, 125.1, 122.6, 61.3 (ArCH2),
60.8 (PhCH2), 59.0 (PhCH2), 57.0 (CH2), 45.5 (N(CH3)2), 42.5
(CH2), 36.1 (C(CH3)3), 35.0 (C(CH3)3), 32.6 (C(CH3)3), 31.2
(C(CH3)3), 19.3 (CH2).
Com p lex 8a . 8a was obtained in 30% yield after crystal-
lization from pentane as a yellow solid. 1H NMR (C6D6): δ 7.52
(d, J ) 7.4 Hz, 2H), 7.33 (t, J ) 7.6 Hz, 2H), 7.00 (t, J ) 7.3
Hz, 1H), 6.96 (s, 2H), 6.92 (m, 4H), 6.64 (m, 1H), 6.53 (s, 2H),
3.58 (d, J ) 13.5 Hz, 2H, ArCH2), 2.80 (s, 2H, PhCH2), 2.55 (s,
2H, PhCH2), 2.51 (m, 8H, ArCH2, CH3), 2.19 (s, 6H, CH3), 2.03
(m, 6H, CH2), 1.48 (m, 2H, CH2), 1.25 (m, 6H, CH3). 13C NMR
(C6D6): δ 157.3, 150.3, 147.6, 132.3, 128.9, 128.6, 128.1, 126.7,
125.4, 124.8, 122.1, 120.4, 68.8 (PhCH2), 68.5 (PhCH2), 64.0
(ArCH2), 54.1 (CH2), 51.1 (N(CH2CH3)2), 46.5 (CH2), 20.7 (CH3),
16.6 (CH3), 8.4 (N(CH2CH3)2).
Com p lex 5a . 5a was obtained quantitatively as a yellow
1
solid. Crystal data are presented in Table 9. H NMR (C6D6):
δ 8.17 (d, J ) 4.9 Hz, 1H), 7.81 (d, J ) 7.5 Hz, 2H), 7.39 (t, J
) 7.6 Hz, 2H), 7.35 (d, J ) 2.4 Hz, 2H), 7.07 (m, 1H), 7.04 (d,
J ) 8.1 Hz, 2H), 6.89 (t, J ) 7.5 Hz, 2H), 6.81 (d, J ) 2.3 Hz,
2H), 6.65 (t, J ) 7.3 Hz, 1H), 6.34 (dt, J ) 1.5, 7.7 Hz, 1H),
6.10 (t, J ) 5.9 Hz, 1H), 5.60 (d, J ) 7.7 Hz, 1H), 3.77 (d, J )
13.1 Hz, 2H, ArCH2), 3.22 (s, 2H, PhCH2), 2.93 (s, 2H, PhCH2),

3028 Organometallics, Vol. 20, No. 14, 2001
Tshuva et al.
P olym er iza tion of Nea t 1-Hexen e. A solution of B(C6F5)3
(ca. 0.015 mmol) in 1-hexene was added dropwise to a solution
of 1a -8a (0.0125 mmol) in 1-hexene at room temperature
under a nitrogen atmosphere. The reaction mixture was stirred
for 2 min to 7 h, during which time heat evolved in several
cases, boiling the 1-hexene. The remaining monomer was
removed under vacuum to yield poly(1-hexene) as a colorless
of heat was moderate. The solvents were removed under
vacuum to yield poly(1-hexene) as a colorless sticky oil.
Ack n ow led gm en t. This research was supported by
the Israel Ministry of Science, Culture and Sports and
was also supported in part by the Israel Science
Foundation founded by the Israel Academy of Sciences
and Humanities. We thank Sima Alfi (BIU) for technical
assistance.
1
sticky oil. H NMR of poly(1-hexene) (CDCl3): δ 1.23 (bs, 8H,
CH2), 1.06 (bs, 1H, CH), 0.89 (t, J ) 5.6 Hz, 3H, CH3). 13C
NMR (CDCl3): δ 40.95 (br, CH2), 35.04 (br, CH2), 32.99 (CH),
29.39 (CH2), 29.03 (CH2), 24.01 (CH2), 14.94 (CH3).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and bond distances and angles for 1a , 2a , 4a -7a .
This material is available free of charge via the Internet at
http://pubs.acs.org.
P olym er iza tion of 1-Hexen e Dilu ted in Hep ta n e. A
solution of B(C6F5)3 (ca. 0.006 mmol) in 1-hexene (2 mL) and
heptane (3 mL) was added dropwise to a solution of 1a (0.006
mmol) in 1-hexene (1 mL) and heptane (4 mL) at room
temperature under
a nitrogen atmosphere. The reaction
mixture was stirred for ca. 10 min, during which time evolution
OM0101285