Synthesis of chelating, C2-symmetric bis(silylamido) complexes of zirconium, and their activities as olefin polymerization catalysts

Article abstract of DOI:10.1016/S0020-1693(02)01295-1

The zirconium bis(silylamido) complexes {[DADMB]ZrCl₂}₂ (3; DADMB=2,2′-bis(tert-butyldimethylsilylamido)-6,6′- dimethylbiphenyl), and [DMBN]ZrCl₂·THF (4; DMBN=2,2′-bis(tert-butyldimethylsilylamido)-1,1′-binaphthyl) were prepared from the corresponding lithiated silylamines. The structure of 3 was determined by X-ray crystallography. The benzyl and methyl derivatives of 4, [DBMN]Zr(CH₂Ph)₂ (5) and [DMBN]ZrMe₂·THF (6), were prepared by treatment of 4 with PhCH₂K and MeLi, respectively. Reaction of 5 with B(C₆F₅)₃ produces the crystallographically characterized zwitterionic complex [DMBN]Zr(CH₂Ph)[η⁶-PhCH₂B(C ₆F₅)₃] (7), in which the benzyl group of the anion is coordinated in an η⁶-fashion to zirconium. Compounds 3 and 4 are moderately active as ethylene polymerization catalysts when activated with excess MAO. Activation of 5 with 1 equiv. of [Ph₃C][B(C₆F₅)₄] resulted in formation of a catalyst which polymerizes neat 1-hexene to give low molecular weight polyhexene.

Full text of DOI:10.1016/S0020-1693(02)01295-1

Inorganica Chimica Acta 345 (2003) 81ꢁ88
/
www.elsevier.com/locate/ica
Synthesis of chelating, C2-symmetric bis(silylamido) complexes of
zirconium, and their activities as olefin polymerization catalysts
Tomislav I. Gountchev, T. Don Tilley *
Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA
Received 10 May 2002; accepted 24 July 2002
Dedicated to Dick Schrock, in recognition of his many seminal contributions to inorganic chemistry
Abstract
The zirconium bis(silylamido) complexes {[DADMB]ZrCl2}2 (3; DADMBꢀ
methylbiphenyl), and [DMBN]ZrCl2×THF (4; DMBNꢀ2,2?-bis(tert-butyldimethylsilylamido)-1,1?-binaphthyl) were prepared
from the corresponding lithiated silylamines. The structure of 3 was determined by X-ray crystallography. The benzyl and methyl
derivatives of 4, [DBMN]Zr(CH2Ph)2 (5) and [DMBN]ZrMe2×THF (6), were prepared by treatment of 4 with PhCH2K and MeLi,
respectively. Reaction of with B(C6F5)3 produces the crystallographically characterized zwitterionic complex
/
2,2?-bis(tert-butyldimethylsilylamido)-6,6?-di-
/
/
/
5
[DMBN]Zr(CH2Ph)[h6-PhCH2B(C6F5)3] (7), in which the benzyl group of the anion is coordinated in an h6-fashion to zirconium.
Compounds 3 and 4 are moderately active as ethylene polymerization catalysts when activated with excess MAO. Activation of 5
with 1 equiv. of [Ph3C][B(C6F5)4] resulted in formation of a catalyst which polymerizes neat 1-hexene to give low molecular weight
polyhexene.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Olefin polymerization; Zirconium complexes; Silylamido complexes
1. Introduction
We recently reported studies on the structure and
reactivity of silylamido yttrium complexes containing
Chelating and multidentate amido ligands [1ꢁ20]
have recently emerged as a viable alternative to the
/
the [DADMB]2ꢂ ligand (DADMBꢀ
2,2?-bis(tert-butyl-
/
dimethylsilylamido)-6,6?-dimethylbiphenyl) [1], and
their application as olefin hydrosilylation catalysts
[38]. In a continuing effort to explore the properties of
C2-symmetric chelating silylamides as ancillary ligands
for early transition metals, we have investigated a
number of zirconium complexes of these ligands, which
are based on biphenyl or binaphthyl backbones.
traditionally used cyclopentadienide ligands [21ꢁ23] in
/
the chemistry of early transition metals. Complexes of d0
metals can be used as catalysts for olefin polymerization
[3ꢁ
/
23], silane dehydropolymerization [24ꢁ
/
28], olefin
hydrosilylation [29ꢁ
/
38] and related transformations. It
has been recognized that modifying the electronic and
steric environment at the metal center significantly
affects the reactivity of the complex, and coordinative
unsaturation and electrophilicity are believed to con-
tribute to high reactivity in d0 systems.
2. Results and discussion
The lithiated silylamine Li2[DADMB]×
prepared as previously described [1]. The analogous
binaphthyl compound, Li2[DMBN]×2THF (2), was
/
2THF (1) was
/
* Corresponding author. Tel.: ꢃ
8940
E-mail address: tdtilley@socrates.berkeley.edu (T. Don Tilley).
/
1-510-642 8939; fax: ꢃ1-510-642
/
obtained using the same procedure (Eq. (1)), starting
from diaminobinaphthyl.
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 2 9 5 - 1

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T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ88
/
Table 1
˚
Selected bond lengths (A) and angles (8) for compound 3
Bond lengths
Zr(1)ÃCl(1)
Zr(1)ÃCl(2*)
Zr(1)ÃN(2)
2.412(1)
2.733(1)
2.063(3)
Zr(1)ÃCl(2)
Zr(1)ÃN(1)
Zr(1)ÃC(1)
2.575(1)
1.996(3)
2.529(4)
ð1Þ
Reaction of 1 with ZrCl4 in refluxing THF (Eq. (2))
Bond angles
Cl(1)ÃZr(1)ÃCl(2)
Cl(2)ÃZr(1)ÃCl(2*)
Cl(1)ÃZr(1)ÃN(2)
Cl(2)ÃZr(1)ÃN(2)
Zr(1)ÃN(1)ÃC(1)
132.85(4) Cl(1)ÃZr(1)ÃCl(2*)
74.59(3) Cl(1)ÃZr(1)ÃN(1)
96.56(9) Cl(2)ÃZr(1)ÃN(1)
95.14(9) N(1)ÃZr(1)ÃN(2)
93.4(2)
84.17(4)
104.51(9)
119.18(9)
96.8(1)
produced the zirconium complex {[DADMB]ZrCl2}2
(3), isolated in 82% yield from pentane solution. The
solid state structure of 3 (Fig. 1) was determined by X-
ray crystallography. Relevant bond lengths and angles
are listed in Table 1. Compound 3 crystallizes as a
centrosymmetric dimer, with two bridging chloride
ligands and one terminal chloride per zirconium. The
zirconium centers adopt a distorted trigonal bipyrami-
dal geometry. The two m-Cl ligands asymmetrically
in the properties of 3 and 4 is the tendency of 4 to
coordinate 1 equiv. of THF, which could not be fully
removed even after repeated recrystallization.
bridge the zirconium centers, resulting in inequivalent
˚
The reactivity of 3 and 4 as olefin polymerization
catalysts when activated with MAO (500 equiv.) was
investigated. Both complexes were active towards eth-
ZrÃ
/
Clm bond lengths of 2.575(1) and 2.733(1) A. For
comparison, the terminal ZrÃ
/
Clt bond length is 2.412(1)
˚
˚
A. The close ZrÃ
small ZrÃNÃ
of ZrÃcarbon bonding interactions with one of the
biphenyl rings, as is often found in complexes of this
type [3ꢁ39]. Similar dimeric chloride-bridged structures
/
Cipso distance (2.529(4) A) and the
/
/
Cipso angle (93.4(2)8) suggest the presence
ylene polymerization (at 40ꢁ50 psi C2H4, toluene
/
/
solution, room temperature), with activities of 4.59 kg
molꢂ1 hꢂ1 atmꢂ1 for 3 and 4.17 kg molꢂ1 hꢂ1 atmꢂ1
for 4, but no measurable polymer formation was
observed with other olefins (1,3-butadiene, propylene)
under the same conditions. This rather low reactivity is
comparable to that observed for other MAO-activated
amido complexes (cf. 64 kg molꢂ1 hꢂ1 for {Me2Si(NC-
Me3)2}ZrCl2(THF)2 [11], 13 kg molꢂ1 hꢂ1 atmꢂ1 for
{(C6H3)2-2,2?-(NCH2C6H4tBu-4)2-6,6?-Me2}Zr(CH2Ph)2
[8], and 2.9 kg molꢂ1 hꢂ1 atmꢂ1 for [Ti(Me3-
SiNCH2CH2NSiMe3)Cl2] [16]) but is much lower than
those for the best Group 4 metallocene/MAO polymer-
ization catalysts, which often exhibit activities exceeding
/
have often been determined or suggested for zirconium
dichloride derivatives [11,40,41].
ð2Þ
The binaphthyl analogue, [DMBN]ZrCl2×
/
THF (4;
DMBNꢀ2,2?-bis(tert-butyldimethylsilylamido)-1,1?-bi-
naphthyl) was prepared in 95% yield from 1 and ZrCl4
under the same reaction conditions. A notable difference
/
1ꢄ
catalysts with amido or alkoxide ligands (cf.
{Zr[RN(Me2SiCH2CH2SiMe2)NR](NMe2)2} (Rꢀ2,6-
/
105 kg molꢂ1 hꢂ1) [22,23], and lower than many
/
Me2C6H3) 990 kg molꢂ1 hꢂ1 atmꢂ1 [17], 2,2?-S(4-
Me,6-tBuC6H2O)2TiCl2 4740 kg molꢂ1 hꢂ1) [42].
Attempts to isolate alkyl derivatives of 3 by reaction
with MeMgBr, MeLi or PhCH2MgBr resulted in the
formation of yellow oils that were difficult to handle and
characterize due to the very high solubility of these alkyl
derivatives. The analogous complexes of 4, however,
were found to be less soluble and thus easier to isolate
and characterize. The benzyl derivative [DMBN]-
Zr(CH2Ph)2 (5) was obtained as a yellow foamy solid
by reaction of 4 with 2 equiv. of PhCH2K (Eq. (3)).
ð3Þ
Fig. 1. ORTEP diagram of ([DADMB]ZrCl2)2 (3).
The benzyllic protons in 5 give rise to two doublets in

T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ
/
88
83
the 1H NMR spectrum at 2.24 and 2.09 ppm (2JHH
Hz), with the ZrCH2Ph carbon appearing at 72.1 ppm
ꢀ10
/
in the 13C NMR spectrum (1JCH
ꢀ110 Hz). These NMR
/
shifts are consistent with h1-coordination of the benzyl
group and are within the typical ranges reported for Zr
benzyl complexes [11,12,17,19,42ꢁ
The methyl derivative [DMBN]ZrMe2×
/
44].
ð4Þ
/
THF (6), pre-
The solid state structure of 7 was determined by X-ray
diffraction (Fig. 2). Relevant bond lengths and angles
are listed in Table 2. As usually found in such cationic
complexes, the borane anion is closely associated with
the metal cation, the PhCH2B group being coordinated
to the Zr atom in a h6 fashion. The distance between the
pared by reaction of 4 with 2 equiv. of MeLi, was
isolated as a brown foamy solid. Attempts to purify this
compound via recrystallization were prohibited by its
reluctance to crystallize from solution. The sample
presumably contains small amounts of impurities (as
suggested by its color), but these were not detected by
NMR spectroscopy. The methyl groups in 6 give rise to
a singlet at 0.55 ppm in the 1H NMR spectrum, with the
˚
plane of the C6 ring and the Zr atom is 2.325(6) A;
similar to that in other related complexes [44,49]. All
C distances are similar (ranging from 2.675(7) to
ZrÃ
/
carbon atom appearing at 47.0 ppm (1JCH
ꢀ105 Hz) in
/
6
˚
2.773(6) A), which is consistent with an h rather than
the 13C NMR spectrum, consistent with the values
typically reported for ZrMe species [12,17,42,43].
No reaction was observed between 5 or 6 and ethylene
(in benzene-d6) after 3 h at room temperature, and
heating the reaction mixtures at 80 8C resulted in
decomposition with no evidence for polymer formation.
Similarly, no reaction was observed between 5 and
PhSiH3 or H2 (in benzene-d6) after 2 days at room
temperature, and heating at 80 8C resulted in decom-
position of 5 in both systems.
an h4 or lower coordination mode. The remaining h1-
benzyl group (ZrÃ
/
CÃC angle of 132.7(4)8), is not
/
associated with agostic or Zr-aromatic ring interactions.
There are close contacts, however, between the Zr atom
and the ipso carbons of both binaphthyl rings, with an
˚
average ZrÃ
angle of 91.5(3)8.
Reaction of 7 with ethylene (room temperature, 5ꢁ
/
C distance of 2.567(6) A and a ZrÃ
/
NÃ
/
Cipso
/
10
psi) resulted in rapid formation of a new complex within
15 min, presumably an ethylene insertion product, as
observed by 1H NMR (d 0.84, 0.62 (s, 9H each, tBu), ꢂ
/
While the reaction of 6 with B(C6F5)3 gave an
intractable mixture of products, the reaction of 5 with
B(C6F5)3 resulted in clean benzyl abstraction (Eq. (4))
0.24, ꢂ
/
0.26, ꢂ
/
0.54, ꢂ0.76 (s, 3H each, Me2Si), other
peaks obscured). The formation of ethylene oligomers
1
was also detected after 3 h (by H NMR spectroscopy).
/
and
formation
of
the
zirconium
complex
[DMBN]Zr(CH2Ph)[h6-PhCH2B(C6F5)3] (7), isolated
However, unlike compounds 3 and 4, complex 7
produced no measurable amount of polyethylene when
tested under the same conditions (without MAO coca-
talyst). Similar rapid single insertion of a-olefins, but
limited polymerization activity has been reported for the
analogous complex {Me2Si(NCMe3)2}Zr(CH2Ph)[h6-
1
in 71% yield. The H NMR spectrum of 7 reveals the
presence of two inequivalent tBu groups, which suggests
anion coordination leading to a non-C2 symmetric
structure in solution. Such coordination has often been
observed in analogous zwitterionic zirconium species
[11,12,19,42,44ꢁ
/
47]. The ZrCH2Ph group gives rise to
two doublets at 2.14 and 1.58 ppm (2JHH
ꢀ/11 Hz) in the
1H NMR spectrum, and a signal at 73.6 ppm (1JCH
121 Hz) in the 13C NMR spectrum of 7 (cf. 1.95, 52.5
ꢀ
/
1
ppm, JCH
ꢀ122.5 Hz for the ZrCH2Ph group in
/
{Me2Si(NCMe3)2}Zr(CH2Ph)[h6-PhCH2B(C6F5)3]
[11]). The BCH2Ph methylene group appears at 2.8ꢁ
/3.2
ppm (br m) in the 1H NMR spectrum, and the 13C
NMR shift for the BCH2Ph carbon is at 38.5 ppm (cf.
3.36 and 36.2 ppm in {Me2Si(NCMe3)2}Zr(CH2Ph)[h6-
PhCH2B(C6F5)3]). A variable temperature NMR study
of 7 in toluene-d8 showed that coalescence of the signals
from the tBu groups occurs at 300 K, which corresponds
to an activation energy barrier of 63 kJ molꢂ1 (15 kcal
molꢂ1) for anion dissociation. This value is very similar
to that of 13.8 kcal molꢂ1 reported for [(1,2-
Fig. 2. ORTEP diagram of [DMBN]Zr(CH2Ph)[h6-PhCH2B(C6F5)3]×
3.5C6H6 (7). The C6F5 groups of the borane anion have been omitted
/
Me2Cp)2ZrR][CH3B(C6F5)3] (Rꢀ
/
CH2CMe3, CH2Si-
Me3) [48].
for clarity.

84
T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ88
/
Table 2
polydispersity of 1.39. This molecular weight is much
lower than those obtained with other recently reported
chelating diamide- and alkoxide-based catalysts. For
˚
Selected bond lengths (A) and angles (8) for compound 7
Bond lengths
comparison,
[Ph3C][B(C6F5)4] and related systems produce molecular
weights up to Mwꢀ o-
239,100 [9,43,51], [(tBu-d6)NÃ
C6H4)2O]ZrMe(PhNMe2)[B(C6F5)4] gives Mnꢀ45,000
[4], and {1,1?-(2,2?,3,3?-OC10H5SiMePh2)}ZrCl2/MAO
results in Mwꢀ674,000 [42]. The activity of the 5/
(MeN(CH2)3NMe)Ti(2,6-iPr2C6H3)2ꢃ
/
Zr(1)ÃN(1)
Zr(1)ÃC(33)
Zr(1)ÃC(4)
2.083(5) Zr(1)ÃN(2)
2.250(6) Zr(1)ÃC(1)
2.558(6)
2.094(5)
2.576(6)
/
/
Bond angles
/
N(1)ÃZr(1)ÃN(2)
Zr(1)ÃN(1)ÃC(1)
B(1)ÃC(40)ÃC(41)
126.1(2) Zr(1)ÃC(33)ÃC(34)
92.0(3) Zr(1)ÃN(2)ÃC(4)
113.5(5)
132.7(4)
91.0(3)
/
[Ph3C][B(C6F5)4] catalyst mixture for ethylene polymer-
ization, 5.10 kg molꢂ1 hꢂ1 atmꢂ1, was not significantly
different from those observed for the MAO-activated
dichlorides 3 and 4.
PhCH2B(C6F5)3] [11]. This may be contrasted to the
high polymerization activity reported for (Me2C5H3)2-
ZrMe[MeB(C6F5)3] 6800 kg molꢂ1 hꢂ1 atmꢂ1 [46,47],
{Me3SiN(CH2C H 2N S iMe3)2}Zr(CH2Ph)[h6-PhCH2B-
(C6F5)3] 330 kg molꢂ1 hꢂ1) [12], Cp*Zr(CH2Ph)2[h6-
PhCH2B(C6F5)3] 88 kg molꢂ1 hꢂ1) [44], and other
catalysts [4,49,50].
3. Conclusions
A series of zirconium chloride and alkyl complexes
with chelating silylamido ligands have been synthesized
and studied. The polymerization activity of the MAO-
activated dichlorides towards ethylene was found to be
moderately low, as compared to both Cp and non-Cp
based catalytic systems. Reaction of the benzyl and
methyl derivatives with Lewis acids results in alkyl
abstraction and formation of zwitterionic species. Anion
coordination has been shown to occur both in the solid
state and in solution for the zwitterionic complex 7. The
activity of non-Cp olefin polymerization catalysts has
already been seen to depend on a number of factors,
including ligand steric bulk and electrophilicity, type of
cocatalyst, coordination affinity of the counter-anion in
case of cationic species, solvent polarity, etc.
Compound 7 was also observed to react rapidly with
1-hexene (by 1H NMR spectroscopy), presumably
t
forming an insertion product (d 0.37, 0.78 (s, Bu, 9H
each), ꢂ
/
0.22, ꢂ
/
0.26, ꢂ
/
0.40, ꢂ0.70 (s, Me2Si, 3H each),
/
other peaks obscured), but only a small amount of
hexene oligomers was observed after 1 day. When the
reaction occurred in neat 1-hexene (in presence of
approximately 10% toluene), at room temperature, no
measurable amount of polymer could be isolated after
standard workup (see Section 4). No reaction occurred
between 7 and PhMeCÄ/CH2 (benzene-d6, room tem-
perature, 24 h).
An attempt to abstract a methyl group from 6 using
[Ph3C][B(C6F5)4] in dichloromethane-d2 solution re-
1
sulted in a new set of H NMR peaks, assigned to a
[13,23,42,44,46ꢁ48]. It has been observed that MAO-
/
cationic zirconium species (d 0.99, 0.96 (s, 9H each,
tBu), 0.25, 0.22, 0.14 (m, 12H total, Me2Si), ꢂ
0.37 (s,
activated catalysts are usually more active than the
borane-activated species, in which anion coordination
can significantly inhibit polymerization activity
[11,20,43,51,52]. While the silylamido complexes pre-
sented in this chapter exhibit reactivity in agreement
with these general trends, they are not among the most
active olefin polymerization catalysts. The wide range of
activities so far observed for chelating diamide catalysts
/
3H, ZrMe); other peaks obscured). This new species,
however, is also inactive as an olefin polymerization
catalyst, as no polymer was formed when an excess of 1-
hexene was added to the reaction mixture (24 h, room
temperature). In addition, no polymer formation oc-
curred on exposure of neat 1-hexene to a mixture of 6
and [Ph3C][B(C6F5)4].
of the type (R?NÃ
MꢀTi or Zr) is quite remarkable, and it would appear
/
LÃ
/
NR?)MRꢃ (Lꢀ
linking group;
/
The reaction of 5 with [Ph3C][B(C6F5)4] in benzene-d6
or dichloromethane-d2 resulted in a mixture of products,
1
as observed by H NMR spectroscopy. Addition of an
/
that much is yet to be learned concerning the major
factors that influence activity in such systems.
excess 1-hexene to this solution did not result in polymer
formation (2 h, room temperature). However, a catalyst
generated in situ from 5 and [Ph3C][B(C6F5)4] (1:1 molar
ratio) was found to polymerize hexene when exposed to
neat olefin (in the presence of approximately 10%
toluene, to improve catalyst solubility). The polymer
formed was shown by gel permeation chromatography
Further studies of the zirconium complexes reported
here will focus on other catalytic reactions. In particular,
our recent discovery that resolved yttrium catalysts of
the type [DADMB]YH(L)n are effective in enantiose-
lective hydrosilations [38] suggests that the zirconium
complexes may be useful as catalysts for a number of
enantioselective transformations.
(GPC) to have an Mw value of 2384 (Mnꢀ1720) and a
/

T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ
/
88
85
4. Experimental
reflux for 6 h, which resulted in formation of a white
precipitate, and was then left to cool slowly overnight.
Removal of the volatiles in vacuo yielded brown foamy
oil, which was extracted twice with C5H12 (200 and 50
ml). After filtration, the C5H12 extracts were concen-
trated to about 50 ml, and 40 ml of THF was added.
nBuLi (32 ml, 51 mmol) was added at r.t., resulting in
4.1. General
All reactions with air-sensitive compounds were
performed under dry nitrogen, using standard Schlenk
and glove box techniques. Reagents were obtained from
commercial suppliers and used without further purifica-
tion, unless otherwise noted. Olefin-free C5H12, C6H6,
and C6H5CH3 were prepared by pretreating with concd.
H2SO4, 0.5 N KMnO4 in 3 M H2SO4, NaHCO3 and
finally anhydrous MgSO4. Solvents (C5H12, Et2O, C6H6,
C6H5CH3, THF) were distilled under nitrogen from
sodium benzophenone ketyl. Benzene-d6 was distilled
from Na/K alloy. nBuLi was used as a 1.6 M solution in
hexanes, as supplied by Aldrich, and MeLi as a 1.6 M
solution in Et2O, as supplied by Alpha Aesar.
the formation of a bright yellowꢁ/greenish crystalline
precipitate. The volatile material was removed and the
solid product was washed with C5H12 (2ꢄ50 ml) and
/
dried in vacuo to give 15.0 g (92% yield) of 2. 1H NMR:
d 7.53 (m, 6H), 6.91 (m, 4H), 6.79 (m, 2H, binaphthyl
t
H), 2.86 (m, 8H, THF), 1.11 (s, 18H, BuMe2Si), 1.09
t
(m, 8H, THF), 0.54 (s, 6H, BuMe2Si), 0.13 (s, 6H,
tBuMe2Si). 13C{1H} NMR: d 155.8, 138.7, 128.6, 128.5,
128.1, 127.7, 127.4, 126.5, 122.0, 120.9 (binaphthyl C),
68.5 (THF), 28.7 ((CH3)3C), 25.1 (THF), 21.3
Li2[DADMB]×
/
2THF (1) [1], diaminobinaphthyl
((CH3)3C), 1.1 ((CH3)2Si),
ꢂ0.4 ((CH3)2Si). IR
/
[53,54], B(C6F5)3 [55], and [Ph3C][B(C6F5)4] [56] were
prepared according to published literature procedures.
NMR spectra were recorded at 300 or 500 MHz (1H)
with Bruker AMX-300 and DRX-500 spectrometers, or
at 100 MHz (13C{1H}) with an AMX-400 spectrometer,
at ambient temperature and in C6H6-d6, unless other-
wise noted. Signal multiplicities are reported as follows:
s, singlet; d, doublet; t, triplet; q, quartet; qn, quintet; m,
multiplet. Elemental analyses were performed by the
Microanalytical Laboratory at UC Berkeley or by
Desert Analytics. For Zr complexes containing the
(cmꢂ1): 3056 (w), 2952 (s), 2927 (s), 2857 (s), 1618 (s),
1596 (s), 1510 (m), 1469 (s), 1403 (s), 1343 (s), 1285 (s),
1250 (s), 1148 (w), 990 (m), 941 (w), 830 (s), 775 (m), 746
(m). Anal. Calc. for C40H58Li2N2O2Si2: C, 71.82; H,
8.74; N, 4.19. Found: C, 71.52; H, 8.76; N, 4.03%.
4.3. {[DADMB]ZrCl2}2 (3)
To a mixture of Li2[DADMB]×
/
2THF (1) (3.42 g, 5.72
mmol) and ZrCl4 (1.40 g, 6.01 mmol) was added 200 ml
of THF. The clear, yellow solution was heated at reflux
for 20 h. The solvent was removed in vacuo and the
binaphthyl group (4ꢁ7), we consistently obtained com-
/
bustion analyses which were in agreement with the
proposed elemental compositions, except for the per-
centage of carbon. Since for these complexes the
spectroscopic data supports the presence of pure com-
pounds, we assume that the low carbon analyses result
from the Zr-promoted formation of carbides during the
combustion analysis. IR spectra were recorded with a
Mattson Infinity 60 MI FTIR spectrometer, as KBr
pellets. The molecular weight distributions (vs. poly-
styrene standards) for polyhexene were measured with a
Waters Associates chromatograph equipped with a
refractive index detector and a PLgel 5m mixed-D
column using THF as the mobile phase.
resulting oily solid was extracted with C5H12 (3ꢄ
Concentration of the C5H12 extracts and cooling to ꢂ
78 8C produced a yellow crystalline precipitate, which
was isolated and dried in vacuo to give 3.16 g (82%) of 3,
containing about 1 equiv. of residual THF (by 1H NMR
integration). Recrystallization of 2.88 g of the product
/
80 ml).
/
1
from C5H12 gave 1.35 g of the THF-free complex. H
NMR: d 7.17 (d, 2H), 7.05 (t, 2H), 6.80 (d, 2H, aromatic
H), 1.87 (s, 6H, MeAr), 0.96 (s, 18H, tBuMe2Si), 0.04 (s,
t
t
6H, BuMe2Si), 0.03 (s, 6H, BuMe2Si). 13C{1H} NMR:
d 139.4, 138.2, 137.0, 130.4, 129.6, 128.1 (aromatic C),
27.6 ((CH3)3C), 21.1 ((CH3)3C), ꢂ
/
1.6 ((CH3)2Si), ꢂ3.5
/
((CH3)2Si). IR (cmꢂ1): 3052 (w), 2952 (s), 2927 (s), 2856
(s), 1580 (s), 1465 (s), 1305 (s), 1236 (s), 1036 (m), 960
(m), 830 (s). Anal. Calc. for C26H42Cl2N2Si2Zr: C, 51.97;
H, 7.05; N, 4.66. Found: C, 51.78; H, 7.24; N, 4.43%.
4.2. Li2[DMBN]×
/
2THF (2)
DABN (6.90 g, 24.3 mmol) was dissolved in 250 ml of
THF and the solution was cooled in an ice/water bath.
n
Two equivalents of BuLi (32 ml, 51 mmol) were added
4.4. [DMBN]ZrCl2(THF) (4)
dropwise with a syringe, with vigorous stirring. The
solution turned cloudy and gradually changed from
almost colorless through reddish yellow, to bright
A mixture of 2 (2.51 g, 3.75 mmol) and ZrCl4 (0.92 g,
3.95 mmol) in 80 ml of THF was heated at reflux for 6 h.
The volatiles were removed in vacuo and the yellow
yellowꢁ
/
orange, with formation of an orange precipitate.
solid residue was extracted with Et2O (2ꢄ
filtrate was concentrated to 15 ml and cooled to
78 8C. The resulting crystalline precipitate was
washed with C5H12 and dried in vacuo, to obtain 2.57
/
50 ml). The
After the mixture was stirred at room temperature (r.t.)
overnight, a solution of tBuMe2SiCl (8.31 g, 53.5 mmol)
in 70 ml of C5H12 was added. The solution was heated at
ꢂ
/

86
T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ88
/
g of product in two crops (95% yield). The NMR spectra
contained no evidence for the presence of impurities. 1H
NMR: d 7.62 (m, 2H), 7.51 (m, 2H), 7.43 (m, 2H), 7.08
(m, 2H), 7.01 (m, 2H), 6.91 (m, 2H, binaphthyl H), 3.61
(m, 4H, THF), 1.39 (m, 4H, THF), 0.994 (s, 18H,
crystallinity prevented purification of the product by
1
recrystallization. H NMR: d 7.6 (m, 6H), 7.0 (m, 4H,
binaphthyl H), 3.56 (m, 4H, THF), 1.24 (m, 4H, THF),
t
0.98 (s, 18H, BuMe2Si), 0.55 (s, 6H, ZrMe2), 0.22 (s,
6H, tBuMe2Si), ꢂ0.30 (s, 6H, tBuMe2Si). 13C{1H}
NMR: d 138.6, 134.6, 131.9, 131.1, 129.7, 128.9,
128.7, 128.5, 128.3, 127.9, 127.6, 127.4, 125.6, 124.5
/
tBuMe2Si), 0.15 (s, 6H, tBuMe2Si), ꢂ
/
0.25 (s, 6H,
tBuMe2Si). 13C{1H} NMR: d 138.9, 134.4, 132.8,
131.8, 129.6, 129.0, 128.9, 128.1, 127.6, 126.3 (bi-
naphthyl C), 70.1 (THF), 27.7 ((CH3)3C), 25.8 (THF),
(binaphthyl C), 69.3 (THF), 47.0 (Zr(CH3)2, 1JCH
ꢀ
/
105
Hz), 27.6 ((CH3)3C), 25.6 (THF), 19.6 ((CH3)3C), ꢂ1.4
((CH3)2Si), ꢂ
2.8 ((CH3)2Si). IR (cmꢂ1): 3056 (w), 2951
/
19.9 ((CH3)3C), ꢂ
/
1.6 ((CH3)2Si), ꢂ
/
2.4 ((CH3)2Si). IR
/
(cmꢂ1): 3056 (w), 2953 (s), 2927 (s), 2882 (m), 2855 (s),
1618 (s), 1596 (s), 1509 (m), 1469 (s), 1404 (s), 1391 (s),
1344 (s), 1285 (s), 1250 (s), 1211 (m), 1148 (m), 993 (s),
938 (s), 831 (s), 812 (s), 776 (s), 746 (s), 672 (m). Anal.
Calc. for C36H50Cl2N2OSi2Zr: C, 58.03; H, 6.76; N,
3.76. Found: C, 56.45; H, 6.69; N, 3.50%.
(s), 2928 (s), 2880 (s), 2853 (s), 1616 (w), 1590 (w), 1500
(w), 1470 (m), 1422 (m), 1345 (m), 1261 (s), 1249 (s),
1224 (s), 1148 (m), 1034 (m), 998 (s), 939 (m), 834 (s),
775 (s), 748 (s), 677 (m).
4.7. [DMBN]Zr(CH2Ph)[h6-PhCH2B(C6F5)3]×
3.5C6H6 (7)
/
4.5. [DBMN]Zr(CH2Ph)2 (5)
A mixture of 5 (0.169 g, 0.215 mmol) and B(C6F5)3
(0.11 g, 0.215 mmol) was dissolved in 15 ml of C6H6.
The solution immediately turned bright orange. After
the mixture was stirred for 30 min at r.t., the solvent was
removed in vacuo and the remaining orange powder was
washed with hexanes and dried to obtain 0.24 g of
product (71% yield). 1H NMR: d 8.05 (m, 1H), 7.70 (m,
A mixture of 4 (0.60 g, 0.80 mmol) and KCH2Ph (0.22
g, 1.68 mmol) was dissolved in 25 ml of C6H6 at r.t. The
red insoluble KCH2Ph was consumed within 20 min
resulting in the formation of a cloudy yellow solution.
After 45 min the C6H6 was removed in vacuo and the
solid residue was extracted with hexanes (2ꢄ
The filtrate was concentrated to 10 ml and cooled to
78 8C to give a voluminous oily yellow precipitate.
The product was isolated by filtration at ꢂ78 8C and
/30 ml).
2H), 7.19ꢁ/7.41 (m, 5H), 7.02 (m, 4H), 6.90 (m, 3H), 6.80
ꢂ
/
(m, 2H, aromatic H), 2.8ꢁ
/
3.2 (br m, 2H, BCH2Ph), 2.14
11 Hz, ZrCH2Ph), 1.58 (d, 1H, 2JHH
/
(d, 1H, 2JHH
ꢀ
/
ꢀ11
/
dried in vacuo to give 0.31 g of a yellow foamy solid
(50% yield). The NMR spectra contained no evidence
for the presence of impurities. 1H NMR: d 7.61 (m, 4H),
Hz, ZrCH2Ph), 0.83 (br s, 9H, tBuMe2Si), 0.76 (br s, 9H,
t
tBuMe2Si), ꢂ
/
0.27 (s, 6H, BuMe2Si), ꢂ
/
0.54 (s, 6H,
tBuMe2Si). 13C{1H} NMR: d 150.1, 150.0, 150.0, 148.2,
148.1, 140.4, 138.8, 136.9, 129.3, 128.9, 128.7, 128.6,
128.3, 128.2, 128.1, 128.0, 128.0, 128.0, 127.9, 127.2,
7.32 (m, 2H), 7.22 (m, 3H), 7.06 (m, 4H), 6.99 (m, 2H),
2
6.89 (m, 2H, aromatic H), 2.24 (d, 2H, JHH
ꢀ
/
10 Hz,
2
ZrCH2Ph), 2.09 (d, 2H, JHH
1
124.2 (aromatic C), 73.6 (ZrCH2Ph, JCH
ꢀ
/
10 Hz, ZrCH2Ph), 0.68
t
ꢀ121 Hz),
/
t
(s, 18H, BuMe2Si), ꢂ
/
0.06 (s, 6H, BuMe2Si), ꢂ
/
0.19 (s,
28.0 ((CH3)3C), 27.5 ((CH3)3C), 20.0 ((CH3)3C), 38.5
(BCH2Ph), 0.24 ((CH3)2Si), ꢂ0.72 ((CH3)2Si). IR
6H, BuMe2Si). 13C{1H} NMR: d 144.8, 140.1, 134.7,
131.5, 131.1, 130.2, 130.0, 129.2, 128.7, 128.7, 127.9,
127.0, 125.6, 123.4 (aromatic C), 72.1 (ZrCH2Ph,
/
t
(cmꢂ1): 3050 (w), 2956 (s), 2932 (s), 2898 (m), 2859
(s), 1640 (w), 1598 (s), 1458 (s), 1382 (w), 1263 (s), 1208
(m), 1151 (m), 1084 (s), 981 (s), 935 (m), 835 (s), 814 (s),
776 (m), 750 (m), 677 (m). Anal. Calc. for
C85H77BF15N2Si2Zr: C, 65.04; H, 4.94; N, 1.78. Found:
C, 58.93; H, 4.46; N, 2.16%. For this compound, loss of
solvent of crystallization probably influenced the ob-
served elemental analysis data.
1JCH
ꢀ
/
110 Hz), 27.3 ((CH3)3C), 19.9 ((CH3)3C), ꢂ1.2
2.3 ((CH3)2Si). IR (cmꢂ1): 3055 (w), 3016
/
((CH3)2Si), ꢂ
/
(w), 2951 (s), 2927 (s), 2881 (m), 2854 (s), 1617 (w), 1593
(s), 1470 (m), 1389 (w), 1343 (m), 1249 (s), 1207 (s), 1146
(m), 1030 (m), 991 (s), 938 (m), 865 (m), 834 (s), 810 (s),
744 (s), 697 (m), 670 (m). Anal. Calc. for
C46H56N2Si2Zr: C, 70.44; H, 7.20; N, 3.57. Found: C,
67.70; H, 7.16; N 3.78%.
4.8. Ethylene polymerization
4.6. [DMBN]ZrMe2(THF) (6)
A sample of the Zr complex (approximately 0.03
mmol) and a 500-fold excess of MAO (approximately 15
mmol) were dissolved in 20 ml of C6H5CH3 and the
solution was transferred to a high-pressure glass reac-
tion vessel. The mixture was pressurized with ethylene at
To a solution of 4 (0.60 g, 0.80 mmol) in 30 ml of
Et2O was added 1.1 ml of MeLi (1.7 mmol) at r.t. The
mixture turned dark brown within 30 min. After stirring
for 1 h, the volatiles were removed in vacuo and the
resulting black solid was extracted with a 1:1 hexanes/
C6H6 mixture (75 ml). The filtrate was dried in vacuo to
obtain 0.41 g of dark brown foamy solid. The lack of
40ꢁ50 psi for 1 h at r.t. The reaction was stopped by
/
venting the ethylene gas and pouring the solution into a
mixture of 100 ml CH3OH, 100 ml H2O and 50 ml
concd. HCl. The precipitated polyethylene was sepa-

T.I. Gountchev, T. Don Tilley / Inorganica Chimica Acta 345 (2003) 81ꢁ
/
88
87
rated by filtration, washed several times with CH3OH,
H2O and C3H6O, and dried under vacuum overnight.
Table 3
Crystallographic data for compounds 3 and 7
Compound
3
7
Crystal parameters
Empirical formula
Formula weight
Temperature (8C)
Crystal system
4.9. 1-Hexene polymerization
C
26H42Cl2N2Si2Zr C85H77BF15N2Si2Zr
600.93
ꢂ136
1569.73
ꢂ130
triclinic
A
sample of
5
(7.0 mg, 0.01 mmol) and
monoclinic
C2/c (#15)
30.6339(4)
11.2771(2)
21.7039(3)
90
[Ph3C][B(C6F5)4] (10 mg, 0.01 mmol) was dissolved in
0.2 ml of C6H5CH3. To the resulting bright orange
solution was added 1.0 g of 1-hexene. The mixture
spontaneously heated up. The reaction was stopped
after 90 min by addition of 5 ml of THF containing a
few drops of concd. HCl. The polymer formed was
washed twice with 30 ml of H2O and dried in vacuo for
24 h at r.t. to give 0.78 g of polyhexene (78% isolated
yield) as a viscous colorless oil. 1H NMR (CHCl3-d3): d
1.26 (m), 1.07 (m), 1.01 (m), 0.90 (m), olefinic signals at
5.36, 4.70. 13C{1H} NMR (CHCl3-d3): d 40.46, 34.81,
32.60, 28.93, 23.46, 14.41, olefinic signals at 125.5, 128.4,
129.2.
¯
P1 (#2)
Space group
˚
/
a (A)
˚
15.023(1)
16.254(1)
18.377(1)
73.647(1)
73.426(1)
63.245(1)
3778.4(4)
2
b (A)
˚
c (A)
a (8)
b (8)
g (8)
128.042(1)
90
3
˚
V (A )
5905.0(2)
8
1.352
Z
Dcalc (g cmꢂ3
)
1.380
2.61
1618.00
m(Mo Ka) (cmꢂ1
F(000)
Size (mm)
)
6.51
2512
0.10ꢄ0.04ꢄ0.06 0.17ꢄ0.26ꢄ0.10
Data collection
Unique/total reflection
Rint
4466/12 111
0.045
0.06
12 772/18 308
0.049
0.025
Empirical absorption
correction
4.10. X-ray structure determinations
mR, Tmin
ꢁ/Tmax
0.884ꢁ/0.986
0.732ꢁ0.978
/
Refinement
X-ray diffraction measurements were made on a
Siemens SMART diffractometer with a CCD area
detector, using graphite monochromated Mo Ka radia-
tion. The crystal was mounted on a glass fiber using
Paratone N hydrocarbon oil. A hemisphere of data was
collected using v scans of 0.38. Cell constants and an
orientation matrix for data collection were obtained
from a least-squares refinement using the measured
Observations [I ꢀ3s(I)]
Variables
3330
299
5948
955
Reflection/parameters ratio 11.14
6.23
0.053
0.050
Rꢀa jjFojꢂjFcjj/a jFoj
Rwꢀ[(a v(jFojꢂjFcj)2/
a vFo2)]1/2
0.036
0.046
Goodness-of-fit
1.65
1.49
([a w(jFojꢂjFcj)2/
(NoꢂNv)]1/2
)
Max. and min. peaks in final 0.38/ꢂ0.43
0.54/ꢂ0.75
ꢂ3
positions of reflections in the range 4B
/
2u B458. The
/
˚
difference map (e A
)
frame data were integrated using the program SAINT
(SAX Area-Detector Integration Program; V4.024; Sie-
mens Industrial Automation, Inc., Madison, WI, 1995).
An empirical absorption correction based on measure-
ments of multiply redundant data was performed using
the programs XPREP (part of the SHELXTL Crystal
Structure Determination Package; Siemens Industrial
5. Supplementary material
The material is available from the authors on request.
Automation, Inc., Madison, WI, 1995) or SADABS
.
Acknowledgements
Equivalent reflections were merged. The data were
corrected for Lp effects. A secondary extinction correc-
tion was applied if appropriate. The structures were
Acknowledgment is made to the National Science
Foundation for their generous support of this work. We
thank Dr. Fred Hollander for assistance with the X-ray
structure determinations.
solved using the TEXSAN crystallographic software
package of the Molecular Structure Corporation, using
direct methods, and expanded with Fourier techniques.
All non-hydrogen atoms were refined anisotropically
and the hydrogen atoms were included in calculated
positions but not refined unless otherwise noted. The
function minimized in the full-matrix least-squares
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