Group 4 dimethylsilylenebisamido complexes bearing the 6-[2-(diethylboryl) phenyl]pyrid-2-yl motif: Synthesis and use in tandem ring-opening metathesis/vinyl-insertion copolymerization of cyclic olefins with ethylene

Article abstract of DOI:10.1002/chem.201101829

Two novel Zr^IV- and Hf^IV-based bisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif, that is, [ZrCl ₂{Me₂Si(DbppN)₂}(thf)] (9) and [HfCl ₂{Me₂Si(DbppN)₂

Full text of DOI:10.1002/chem.201101829

DOI: 10.1002/chem.201101829
Group 4 Dimethylsilylenebisamido Complexes Bearing the 6-[2-
(Diethylboryl)phenyl]pyrid-2-yl Motif: Synthesis and Use in Tandem Ring-
Opening Metathesis/Vinyl-Insertion Copolymerization of Cyclic Olefins with
Ethylene
Yuanlin Zou,[a] Dongren Wang,[c] Klaus Wurst,[b] Christa Kꢀhnel,[a] Ingrid Reinhardt,[a]
Ulrich Decker,[a] Venkatanavarana Gurram,[c] Sebnem Camadanli,[a] and
Michael R. Buchmeiser*[c, d]
Abstract: Two novel ZrIV- and HfIV-
based bisamido complexes bearing the
6-[2-(diethylboryl)phenyl]pyrid-2-yl
activity of E, while CPE incorporation
remained close to or at zero. In the
vinyl-insertion copolymerization of
norborn-2-ene (NBE) with E by the
action of 9, statistical cyclic olefin co-
polymers of these two monomers were
obtained. At higher NBE concentra-
tions, however, 9 gave rise to reversible
ring-opening metathesis (ROMP)/
vinyl-insertion polymerization (VIP) of
NBE with E, resulting in the formation
of multi-block copolymers of the gener-
feature of precatalyst 9, that is, the
ability to induce a reversible a-H elimi-
nation/a-H addition reaction, is attrib-
uted to the unique role of the 6-[2-(di-
motif, that is, [ZrCl
(thf)] (9) and [HfCl
(thf)2] (10) (DbppN=6-[2-(diethylbor-
2A
A
E
U
ethylboryl)phenyl]pyrid-2-yl
ligand.
R
Accordingly, a model precatalyst lack-
ing this ligand does not have the ability
to induce a-H elimination/a-H addition
reactions. The different 11B NMR shifts
of various diethylborylphenylpyrid-2-
ylamines and -amides permit a ranking
yl)phenyl]pyridine-2-amido) have been
prepared. Their reactivities have been
compared with that of a model precata-
lyst that does not bear the aminobor-
ane motif. Upon activation with meth-
ylalumoxane, precatalysts 9 and 10 are
active in the homopolymerization of
ethylene (E) yielding high-density
polyethylene (HDPE). In the copoly-
À
of the strengths of the B N bonds in
al formula poly
N
these compounds. This strength of the
À
C
B N bond is correlated with the pro-
pensity of 9/MAO to produce poly-
merization of
E
with cyclopentene
CAHUTGTNRNEG(UN NBE)ROMP-co-polyACHUTGNTREN(NUGN NBE)VIP-co-
poly(E) at different temperatures.
Keywords: metathesis · NMR spec-
troscopy polymers transition
metals · vinyl compounds
(CPE), for example by the action of 9,
the presence of CPE resulted in a dra-
matic increase in the polymerization
·
·
Introduction
Both the vinyl-insertion polymerization (VIP) of olefins[1–7]
and the ring-opening metathesis polymerization (ROMP)[8,9]
of cyclic olefins are based on the insertion of a monomer be-
tween a transition metal (ion) and a growing polymer chain.
They are interrelated, since a cationic, VIP-active catalyst
may be converted into a ROMP-active catalyst by an a-H
elimination process. The reverse process of this a-H elimina-
tion, that is, a-addition of a proton to a metal alkylidene, re-
establishes a cationic, VIP-active species from a metal alk-
[a] Dr. Y. Zou, C. Kꢀhnel, I. Reinhardt, Dr. U. Decker,
Dr. S. Camadanli
Leibniz-Institut fꢀr Oberflꢁchenmodifizierung
Permoserstrasse 15, 04318 Leipzig (Germany)
[b] Dr. K. Wurst
Institut fꢀr Allgemeine, Anorganische und Theoretische Chemie
Universitꢁt Innsbruck, Innrain 52a, 6020 Innsbruck (Austria)
[c] Dr. D. Wang, V. Gurram, Prof. Dr. M. R. Buchmeiser
Institut fꢀr Polymerchemie
AHCTUNGTRENNUNG
Lehrstuhl fꢀr Makromolekulare Stoffe und Faserchemie
Universitꢁt Stuttgart, Pfaffenwaldring 55
70569 Stuttgart (Germany)
ACHTUNGTRENNUNG
(NBE=norborn-2-ene) was first observed some 60 years
ago and aided our understanding of metathesis-based pro-
cesses.[10,11] However, no clear evidence for the presence of
both structures, that is, ROMP- and VIP-derived repeat
units, within one single polymer chain was provided at that
time.[10–14] On the contrary, because of the high crystallinity
of the polymers obtained, two separate types of polymer,
that is, one VIP- and one ROMP-derived, were proposed to
[d] Prof. Dr. M. R. Buchmeiser
Institut fꢀr Textilchemie und Chemiefasern (ITCF)
Kçrschtalstr. 26, 73770 Denkendorf (Germany)
E-mail: michael.buchmeiser@ipoc.uni-stuttgart.de
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101829: Variable-tempera-
1
1
ture H and 11B NMR spectra of compounds 5–7, 9, 10, and 15–18; H
and 13C NMR spectra of compounds 5–7, 9, 10, 12, 13, 15, 19, and 20.
13832
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Chem. Eur. J. 2011, 17, 13832 – 13846

FULL PAPER
tion was governed by tempera-
ture. In complex A (Scheme 1),
the boryl group competes for
the free lone pair of the pyrid-
2-yl moiety, and consequently
the a-H elimination process is
temperature-dependent. Conse-
quently, under specific condi-
tions that disfavor a-H elimina-
tion, precatalyst
A can also
induce the synthesis of highly
linear PE (=HDPE).[32]
In view of these results, we
were interested in ascertaining
the nature of the reactivities
and the a-H elimination pro-
pensities of ZrIV- and HfIV-
Scheme 1. a) VIP-derived poly
(NBE)VIP-co-poly(E), d) structure of [{6-[2-(diethylboryl)phenyl]pyrid-2-ylamido}(dimethylsilyl)(h5-tetrame-
thylcyclopentadienyl)TiCl2] (A).
ACHTNUGTRNENU(NG NBE)VIP, b) ROMP-derived polyACHUTNTRGENG(NUN NBE)ROMP, c) polyACHTGUNTRNEUN(NG NBE)ROMP-co-poly-
ACHTUNGTRENNUNG
based
bis
G
precata-
lysts[33–56] bearing the same ami-
noborane ligand as precatalyst
have formed concomitantly by the action of the chosen ini-
tiators. Hard evidence for the presence of both ROMP- and
VIP-derived structures (Scheme 1c) within one single poly-
A (Scheme 1). Consequently, such systems were prepared
and investigated for their efficacy in the homopolymeriza-
tion of ethylene (E) as well as in the copolymerization of E
with both cyclopentene (CPE) and norborn-2-ene (NBE). In
addition, we have applied 11B NMR as a probe to determine
ACHTUNGTRENNUNG
(NBE) polymer chain was reported by the Farina group.[15,16]
The structure of this particular polymer can only be ex-
plained in terms of a reversible a-H elimination/a-H addi-
tion process, with both VIP and ROMP occurring within the
same polymer chain. Controlled, single switches from
ROMP to VIP and vice versa have been reported by the
groups of Grubbs and Kaminsky, which enabled them to
synthesize AB diblock copolymers.[17–19]
À
the strength of the B N bond as a function of temperature.
Finally, an aminoborane-free precatalyst has also been pre-
pared and its reactivity was compared with that of the corre-
sponding aminoborane-containing system.
We recently reported on a (h5-tetramethylcyclopentadi-
Results and Discussion
ACHTUNGTRENNUNG
enyl)dimethylsilylamido TiIV-based initiator system (A,
Scheme 1d), which, after activation with methylalumoxane
(MAO),[20] proved to be capable of forming both VIP- and
ROMP-derived structures from a cyclic olefin. Moreover,
this system is additionally capable of copolymerizing ethyl-
ene to yield narrowly distributed (1.05<PDI<2.0; PDI=
polydispersity index), high molecular weight copolymers
(Mn ꢀ1500000 gmolÀ1) containing multiple blocks of
ROMP- and VIP-derived structures within one single poly-
mer chain.
Synthesis of ligands and precatalysts: An efficient protocol
has been developed for the synthesis of the aminoborane
ligand 5 (Scheme 2).[57] 2-Bromo-5-aminopyridine (1) was re-
acted with 2-bromophenylboronic acid (2) to yield 2-(2-bro-
mophenyl)-6-aminopyridine (3). Compound 3 was then N-
protected with 1,2-bis[(dimethylamino)dimethylsilyl]ethane
to yield 4. Borylation and deprotection finally yielded com-
pound 5. In this sequence, the use of bis[(dimethylamino)di-
methylsilyl]ethane turned out to be crucial for the high-
yielding synthesis of 5, which was obtained in 51% overall
yield. Deprotonation of 5 with BuLi yielded 6, which was
then reacted with SiMe2Cl2 to yield 7 (Scheme 3).
Compound 7 crystallizes in two different isomorphic
forms. Modification 1 crystallizes in the monoclinic space
group C2/c (no. 15) with a=2430.9(1), b=746.0(1), c=
1730.7(2) pm; a=g=90, b=97.6498; Z=4 (Figure S1 in the
Supporting Information). Modification 2 crystallizes in the
tetragonal space group P43212 (no. 96) with a=1432.98(5),
b=1432.98(5), c=1542.61(6) pm; a=b=g=908; Z=4
(Figure 1). In both isomorphic forms, the diethylboryl group
is coordinated to the pyridine nitrogen, as evidenced by a
B–N distance of 164.3(3) pm (mode 2).
TiIV was chosen as a d0 metal since it allows the genera-
tion of both VIP- and ROMP-active catalysts, that is, both
cationic alkyl and alkylidene complexes.[21–26] Furthermore,
and in contrast to the corresponding group 5 and group 6
complexes,[27] d0 group 4 metal alkylidenes are not suscepti-
ble to a-H elimination to form metal hydride alkylidynes.
Although b-H elimination has long been considered to be
much faster than a-H elimination,[28] Schrock et al. demon-
strated that a- and b-H elimination can in fact occur on the
same time scale, and moreover that a-H elimination can be
faster than b-H elimination in certain complexes.[29–31] There-
fore, for the reversible switching between ROMP and VIP, a
ligand system that can reversibly abstract an a-proton from
the cationic species and re-add a proton to the metal alkyli-
dene was designed. By design, the extent of proton abstrac-
Deprotonation of 7 with two equivalents of BuLi yielded
the dianion 8, reaction of which with ZrCl4·2THF resulted
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13833

M. R. Buchmeiser et al.
tion to Figure 2. As in com-
pound 7, the pyridine nitrogen
is coordinated to the diethyl-
boryl group in the solid state.
In contrast to the Hf compound
10 (see below), which was pre-
pared
analogously
to
9
(Scheme 3) and which accord-
ing to elemental analysis has
two THF molecules coordinat-
ed to the metal, presumably
forming an octahedral ligand
sphere, only one THF coordi-
nates to the ZrIV in 9, most
probably for steric reasons. The
Scheme 2. Synthesis of compounds 3–6.
Figure 1. Single-crystal X-ray structure of compound 7 (modification 2).
À
N(2) B(1) 164.3(3) pm.
Figure 2. X-ray structure of complex 9. Bond lengths (pm) and angles (8):
À
À
À
À
Zr(1) N(1) 208.6(3), Zr(1) N(3) 208.7(3), Zr(1) O(1) 231.1(2), Zr(1)
À
À
À
Cl(2) 245.28(9), Zr(1) Cl(1) 246.62(10), N(2) B(1) 163.5(5), N(4) B(2)
163.0(5); N(1)-Zr(1)-N(3) 74.52(11), N(1)-Zr(1)-O(1) 143.96(10), N(3)-
Zr(1)-O(1) 141.44(10), N(1)-Zr(1)-Cl(2) 104.21(8), N(3)-Zr(1)-Cl(2)
85.68(8), Cl(1)-Zr(1)-Cl(2) 163.12(4).
in the formation of precatalyst 9. Compound 9 crystallizes in
the monoclinic space group C2/c (no. 15), a=2779.24(3), b=
1306.14(3), c=2323.94(6) pm; a=g=90, b=90.6288; Z=8.
Relevant distances and bond angles can be found in the cap-
Scheme 3. Synthesis of compounds 7 and 8 and of the metal complexes 9 and 10.
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Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
oxygen atom of the THF and
the two amide nitrogen atoms
form the base of a distorted
trigonal bipyramid (N(1)-Zr(1)-
Cl(2)=104.21(8) pm,
N(3)-
Zr(1)-Cl(2)=85.68(8) pm). The
Zr–N distances Zr-N(1) and Zr-
N(2) (208.6(3) and 208.7(3) pm,
respectively) are comparable to
those found in other ZrIV-bis-
ACHTUNGTRENNUNG
amide complexes[36,38–40,43,58–62]
and do not seem to be affected
by the small ring size of the
N,N-chelate in 9. The corre-
sponding HfIV-based compound
10 was prepared in an analo-
gous manner (Scheme 3).
The aminoborane-free model
catalyst 15 was prepared as fol-
lows (Scheme 4). 2-Bromo-1-(2-
propyl)benzene was subjected
to halogen–Li exchange fol-
Scheme 4. Synthesis of compound 15.
lowed by borylation with BACTHNUTRGENUG(N O-
2-Pr)3. Hydrolysis yielded 2-(2-
propyl)phenylboronic acid (11),
Pd-catalyzed coupling reaction
of which with 3-bromoaniline
yielded 12. Deprotonation and
reaction with Me2SiCl2 resulted
in the formation of ligand 13,
from which compound 15 was
prepared by double deprotona-
tion
and
reaction
with
ZrCl4·2THF.
For comparative 11B NMR
measurements, four additional
aminoborane-containing ligands
16–18 and 20 were prepared.
Compound 16 was prepared
from 5 by Pd-catalyzed N-aryla-
tion. Deprotonation with BuLi
afforded 17 as its diethyl ether
complex. In a similar manner,
compound 18 was prepared
from 5 and 2-chloro-1-iodoben-
zene (Scheme 5). Finally, com-
pound 19 was accessible from
Scheme 5. Synthesis of compounds 16–18 and 20.
2,6-diACHTUNGTRENNUNG(2-propyl)aniline by de-
protonation/silylation and was
then converted into 20 by reac-
tion with 6 (Scheme 5).
expected, the anionic compounds 6 and 17 displayed 11B
shifts around À1.5 ppm, while the neutral ones, that is, 5, 7,
15, 16, and 18, had 11B shifts in the range 3.5–4.5 ppm. With
increasing temperature, the 11B chemical shifts increased
11B NMR and variable-temperature NMR measurements:
Variable-temperature NMR measurements of compounds 5,
6, 7, 9, 10, and 15–18 carried out in the temperature range
25–808C allowed a distinction between compounds that are
electron-rich and electron-poor at the pyridine nitrogen. As
À
slightly, consistent with the expected increase in B N bond
dissociation at higher temperatures. The corresponding ZrIV
and HfIV complexes 9 and 10 were characterized by 11B
shifts around 6.5 ppm. This relatively high chemical shift
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13835

M. R. Buchmeiser et al.
suggests a reduced electron density at the boron, which is
certainly a result of the coordination of the pyridyl-2-amide
ligand to the highly electrophilic metals, that is, to ZrIV and
HfIV, thereby also reducing the electron density at the pyri-
dine nitrogen and thus at the boron (Figure S2 in the Sup-
porting Information). This effect is somewhat more pro-
nounced with Hf (compound 10) as compared with Zr (com-
pound 9). These findings correlate well with the tetrahedral
character (THC) of boron[63,64] as an empirical parameter
that is used to roughly estimate the barrier to dissociation of
d=7.92 to d=7.70 ppm (Figure S4 in the Supporting Infor-
mation). This upfield shift correlates with the above-de-
À
scribed increase in the B N bond strength with increasing
temperature, with the mesomeric structure with a formal
positive charge at C-7 (Scheme 6a) becoming increasingly
À
intramolecular N B bonds. The larger the THC value, the
À
higher the barrier for dissociation of the B N bond. As can
be deduced from its X-ray structure, the two THC values of
7 are 68.3% (mode 1) and 66.7% (mode 2), respectively
(average 67.5%), according to the equation THC/%=
[120À(q1+q2+q3)/3]/(120À109.5), in which q1–3 represent the
G
three bond angles centered at the boron atom. The THC
values of the two different aminoboranes in 9 were similarly
calculated as 58.8% and 62.9% (average 60.9%). These two
THC values for 7 and 9 suggest that, at least in the solid
À
state, the barriers for dissociation of the N B bonds in these
compounds are both medium-to-high, with a lower barrier
in 9. These data also correlate well with the higher
11B NMR shifts of 9 compared to those of 7. Furthermore,
the lower average THC value of the boron in compound 9
can be attributed to the steric interactions between the two
ethyl groups at the boron and the ZrCl2 moiety of the com-
plex.
A surprising observation was that, in contrast to all of the
other compounds investigated, which showed the expected
increase in the 11B NMR shift with increasing temperature,
Scheme 6. a) Mesomeric structures of the aminoborane ligand in 9 and b)
mesomeric forms of the cationic form of 9.
À
attributable to an increased B N bond dissociation, the
chemical shifts of 9 decreased upon heating, indicative of
À
decreasing B N bond dissociation with increasing tempera-
dominant. A similar, albeit less pronounced shift, is found
for H-9. In compound 9 in its cationic form, as generated by
the addition of MAO, however, the electron lone pair of the
pyrid-2-ylamide is assumed to be involved in the stabiliza-
tion of the cationic metal center (Scheme 6b). Consequently,
this pyrid-2-ylamide nitrogen (bound to the Zr) can no
longer compensate for any positive charge at the pyridine
ture. The only reasonable, albeit purely speculative, explana-
tion that we can offer at the present time is that an increase
in temperature might result in a weaker binding of the aryl-
ACHTUNGTRENNUNGamide ligand to the Zr. This would reduce both the steric in-
teraction and the transfer of electron density from the
ligand to the metal, ultimately resulting in stronger B N
À
À
binding.
nitrogen atom. This leads to a situation where B N dissocia-
Generally, the binding kinetics of aminoboranes can be
followed by variable-temperature NMR spectroscopy.[65]
Such measurements on compound 7 showed coalescence of
the signals at around 608C. At this temperature, the aromat-
ic signals at d=7.75–7.9, 7.4–7.55, 7.2–7.3, and 6.75–
tion increases with increasing temperature, as suggested by
the (co-) polymerization data (see below).
Homopolymerization of ethylene and copolymerization of
ethylene (E) with cyclopentene (CPE): Group 4 bisamido
complexes are known to represent active precatalysts for
olefin homo- and copolymerization.[34,61,66,67] Although non-
1
6.85 ppm in the H NMR spectrum were broadened. Below
and above 608C, the signals sharpened and were fully re-
solved at T=25 and 1008C, respectively (Figure S3 in the
Supporting Information). These measurements suggest that
bridged bisamido complexes display relatively moderate ac-
À1
tivities (<20 kg of polymermolÀ1
h
barÀ1), the bridged
catalyst
À
dissociation of the B N bond in this ligand type occurs in
analogues
350000 kgmol
allow
for
activities
of
up
to
À1
the temperature region around 608C and may be tuned by
choosing polymerization temperatures in the range 50–858C.
For 9, no coalescence of the signals was observed. Instead,
the signal due to H-7, which, by virtue of its phenylenic po-
sition with respect to the pyridine nitrogen, reflects the
charge at this nitrogen, is significantly upfield shifted from
hÀ1 barÀ1, as, for example, in the polymer-
catalyst
ization of 1-hexene.[45,46] However, typical values for PE and
PP
are
in
the
ranges
3.5–5300
and
7–
À1
320 kgmolÀ1
h
barÀ1, respectively.[43,58–60,68–71] In all of
catalyst
these polymerizations, both the polymerization kinetics and
the activity are strongly influenced by the chelate ring size.
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Chem. Eur. J. 2011, 17, 13832 – 13846

Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
Table 1. Results of E polymerization by the action of 9 and 10 activated
Table 2. Results of the copolymerization of E with CPE by 9 and 15, ac-
by MAO.[a]
tivated by MAO.[a]
[d]
[d]
[e]
[e]
[d]
[d]
[e]
[e]
Catalyst
T
[8C]
Activity[b] Branches[c] Mn
Mw/Mn
Tg
Tm
Catalyst
T
[8C]
Activity[b] C[c]
[mol%]
Mn
[ꢃ104]
Mw/Mn
Tg
Tm
A
R
[8C] [8C]
G
G
[8C]
[8C]
1
2
3
4
9[f]
9[g]
50
50
80
50
80
160
120
40
n. d.
1.6
0.9
23
7
10
2.9
3.2
3.6
1.3
n.d. 139
n.d. 137
n.d. 134
3.7 131
1
2
3
4
5
6
7
9[f]
9[f]
25
50
65
50
50
65
50
360
1280
1080
1680
8100
480
<0.1
<0.1
<0.1
0.1
0.1
n.d.
n.d.
86
43
19
29
15
24
24
1.4
1.6
1.5
1.5
1.8
1.7
1.4
–
–
–
–
–
136
138
132
138
129
9[g]
9[f]
10[g]
1.5
470
9[g]
9[h]
[a] 500 mL autoclave, total volume of reaction mixture: 250 mL, t=1 h.
[b] kgmol
data in 1,2,4-trichlorobenzene vs. PS. [e] Measured by DSC; catalyst/
MAO=1:2000. [f] Hexane, 4 bar. [g] Toluene, 4 bar. n.d.=not deter-
mined.
15[f]
15[g]
À25.7 131
hÀ1 barÀ1. [c] Determined by 13C NMR analysis. [d] GPC
À1
catalyst
6400
– 132
[a] 250 mL of toluene (including the volume of monomer), 4 bar of E, t=
1 h, catalyst/MAO=1:2000. [b] kg of polymermol
À1
hÀ1 barÀ1. [c] Co-
catalyst
monomer content in the copolymer [mol%] as estimated by 13C NMR
spectroscopy. [d] GPC in 1,2,4-trichlorobenzene vs. PS. [e] Measured by
DSC. [f] Catalyst/MAO/CPE=1:2000:1000; 10 mmol of catalyst, [cata-
lyst]=0.04ꢃ10À3 molLÀ1, [CPE]=0.04 molLÀ1. [g] Catalyst/MAO/CPE=
1:2000:45000; 5 mmol of catalyst, [catalyst]=0.02ꢃ10À3 molLÀ1, [CPE]=
0.9 molLÀ1. [h] Catalyst/MAO/CPE=1:2000:200000; 2.5 mmol of catalyst,
[catalyst]=0.01ꢃ10À3 molLÀ1, [CPE]=2.0 molLÀ1. n.d.=not determined.
The homopolymerization of E by the action of 9 activated
by MAO produced highly linear PE with melting points in
the range 134<Tm <1398C (Table 1). Moderate activities up
À1
to 240 kgmolÀ1
h
barÀ1 were observed. Molecular
catalyst
weights were in the range 70000<Mn <230000 gmolÀ1.
Figure 3 shows the 13C NMR spectrum of PE prepared by
tion reactions become more
dominant.
Increasing
the
amount of CPE to 45000 and
200000 molar equivalents with
respect to the catalyst resulted
in further increases in activity
up
kgmol
to
1680
and
8100
À1
hÀ1 barÀ1, respective-
catalyst
ly (Table 2, entries 4 and 5).
Concomitantly, the number
average molecular weight fur-
ther decreased.
Figure 4 shows the 13C NMR
spectrum of PE prepared in the
presence of CPE (Table 2,
Figure 3. 13C NMR spectrum of PE prepared by the action of 9/MAO at T=808C. The signal at d=120.2 ppm
stems from C2Cl4 (impurity).
entry 4).
Approximately
0.1 mol% of CPE incorporation
the action of 9/MAO (Table 1, entry 3). One can clearly see
signals due to the C1–C5 short-chain branching[72–82] as well
as the signals of the terminal vinyl group at d=113.7 and
138.9 ppm. The latter may either result from a “standard” b-
H elimination reaction or from an a-H elimination reaction
followed by cross-metathesis with E.
can be detected. Apart from the signal for linear PE at d=
30.5 ppm, the signals at d=32.6 (C4,5), 41.1 and 41.6 (C1,3),
and 43.7 ppm (C2) are typical of 1,3-incorporated CPE units
that are formed by 1,2-insertion of CPE followed by b-H
elimination and subsequent re-insertion.[83] It should be
noted that upon extensive magnification of the 1H NMR
spectra of each of the polymers, the signals due to the termi-
nal vinyl groups become visible at d=5.75, 5.05, and
5.0 ppm (not shown). However, no signals for an exo-meth-
ylidenecyclopentane moiety, mimicked by 2-methyl-exo-
methylidenecyclopentane (d1H =4.8, 4.7 ppm; d13C =158.6,
104.0 ppm), could be observed in either in the 1H or the
13C NMR spectrum. This suggests that termination is gov-
erned by b-H elimination after E insertion (leading to termi-
nal vinyl groups) rather than by a-H elimination after CPE
insertion followed by cross metathesis with E, which would
result in the formation of the above-mentioned terminal
exo-methylidenecyclopentane units. This is also in accord-
ance with the high Mn values found for PE produced in the
presence of CPE.
Remarkably, the HfIV-based catalyst 10 displayed reduced
activity, although it allowed the synthesis of ultra-high mo-
lecular weight PE (UHMWPE) with a number average mo-
lecular weight of up to Mn =4700000 gmolÀ1, PDI=1.3.
Another important effect was observed in the copolymeri-
zation of E with CPE. When the polymerization of E was
conducted in toluene at 508C by the action of 9/MAO in the
presence of CPE, no CPE incorporation was detected by
NMR spectroscopy, although the activity increased from 160
À1
(Table 1, entry 2) to 1280 kgmolÀ1
h
barÀ1 (Table 2,
catalyst
entry 2). In this case, PE with an Mn of 430000 gmolÀ1
(PDI=1.61) and a Tm of 1388C was produced. A further in-
crease in the polymerization temperature to 658C resulted
in decreases in both Mn and activity, suggesting that elimina-
Chem. Eur. J. 2011, 17, 13832 – 13846
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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13837

M. R. Buchmeiser et al.
in the copolymerization of E
with NBE. As found for the
above-mentioned
TiIV-based
system, low NBE concentra-
tions ([NBE]=0.02 molLÀ1) re-
sulted in the formation of vinyl-
insertion copolymerization-de-
rived poly(E)-co-poly
G
.
Only
moderate
activities
À1
(ꢀ80 kgmolÀ1
h
barÀ1) and
catalyst
an NBE incorporation of up to
16.8 mol%
were
observed
(Table 3). A typical 13C NMR
spectrum is shown in Figure 5.
In the 13C NMR spectrum of
poly(E)-co-poly
tained by the action of 9/MAO
(Table 3, entry 3, 1.2 mol% of
(NBE)VIP
ob-
Figure 4. 13C NMR spectrum of mostly linear PE prepared by the action of 9/MAO in the presence of CPE (in
[D2]1,1,2,2-tetrachloroethane).
To shed light on the potential role of the aminoborane
ligand in this process, we also investigated the poly-
Table 3. Results of E-NBE copolymerization by 9/MAO at different
NBE concentrations.[a]
merization activity of the model catalyst 15 in this re-
[d]
[d]
[e]
T
[8C]
Activity[b]
C[c]
[mol%]
Mn
[ꢃ104]
Mw/Mn
Tm
action. In the presence of CPE, polymerization activities
G
N
[8C]
À1
for
E
of 6400 kgmolÀ1
h
barÀ1 (compared to 1680
1[f]
2[f]
25
50
65
50
65
80
50
50
50
80
80
40
40
320
360
320
1020
3040
920
600
1.8
16.8
1.2
18.1
16.7
14.4
10.1
10.4
14.7
9.7
40
39
31
89
44
12
31
21
56
8
2.3
2.2
2.6
1.2
1.2
3.0
1.6
2.1
1.9
2.1
129
128
128
121
catalyst
À1
kgmolÀ1
h
barÀ1 for 9/MAO under the same conditions)
catalyst
3[f]
without any noticeable CPE incorporation were observed
(Table 2, entry 7). The linear PE (HDPE) that formed had
an Mn of 240000 gmolÀ1 (PDI=1.37) and a Tm of 1328C. As
can be deduced from Table 2, the activities of both 9 and 15
in the polymerization of E can be boosted by up to a factor
of 50 in the presence of high concentrations of CPE. Since
CPE is hardly incorporated into the polymer chain (ꢀ
0.1 mol%), it must preferably serve as a stabilizing ligand/
chain-transfer agent, reversibly coordinating to the cationic
Zr center. After b-H elimination, most probably from an E
molecule as the last inserted monomer, the terminal alkene
4[g]
[h]
5[g]
–
6[g]
121
103
97
125
74
7[g,i]
8[g,j]
9[g]
10[g]
[a] 250 mL of toluene (including the volume of monomer); 4 bar of E
À1
unless stated otherwise, t=1 h. [b] kgmol
hÀ1 barÀ1. [c] NBE content
catalyst
[mol%] estimated by 13C NMR. [d] GPC data in 1,2,4-trichlorobenzene
vs. PS. [e] Measured by DSC. [f] 9/MAO/NBE=1:2000:1000 (5 mmol of 9,
[9]=0.02ꢃ10À3 molLÀ1, [NBE]=0.02 molLÀ1), [g] 9 or 15/MAO/NBE=
1:2000:20000 (5 mmol of 9, [9]=0.02ꢃ10À3 molLÀ1, [NBE]=0.4 molLÀ1).
[h] Tg =À858C as measured by DSC. [i] 6 bar E. [j] 8 bar E.
À
is replaced by CPE, which inserts into the Zr H bond and
starts a new polymer chain.
Copolymerization of ethylene
(E) with norborn-2-ene (NBE):
The propensity of group 4 cata-
lysts bearing the aminoborane
motif and activated by MAO to
undergo a-H elimination at
higher concentrations of the
cyclic olefin, resulting in the
formation of poly
ACHTUNGTRENNUNG(NBE)ROMP-
co-poly(NBE)VIP-co-poly(E),
ACHTUNGTRENNUNG
has recently been demonstrated
for a (h5-tetramethylcyclopenta-
dienyl)dimethylsilylamido-TiIV
system.[57] To assess the propen-
sity of ZrIV-bisamido systems
bearing the same aminoborane
motif to promote the formation
Figure 5. 13C NMR spectrum of poly(E)-co-poly
ACHTUNGTRENUNG(NBE)VIP produced by the action of 9/MAO and low NBE con-
of such copolymers, we used 9 centrations (Table 3, entry 3) (in 1,1,2,2-[D2]tetrachloroethane).
13838
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Chem. Eur. J. 2011, 17, 13832 – 13846

Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
NBE in the copolymer), signals characteristic of both alter-
nating (E-NBE) and isolated (E-NBE-E-E) NBE sequences
were observed, which could be assigned as follows: d=47.9,
46.8 (two signals, C2/C3), 41.6, 41.3 (two signals, C1/C4), 32.6
(C7), and 30.5–28.5 ppm (C5/C6, PE, all C2D2Cl4). The co-
polymers contained mainly isolated NBE units with only a
few alternating syndiotactic/isotactic (st/it) E-NBE
diads.[84–89] Signals assignable to NBE-NBE diads and NBE-
NBE-NBE triads were absent. In no case were any signals
No signals for polyACHTUNGTRENNUNG
form if a ROMP-derived polyACTHUNTRGNEUNG(NBE)ROMP underwent cross-
metathesis with E, forming a [H2C=CH-c-(1,2-C5H8)-poly-
mer] macromonomer, followed by its re-insertion into a
growing PE chain. On the basis of these NMR data and the
GPC results, this pathway can therefore also be excluded.
The signals at d=47.5 and 41.3 ppm correspond to alternat-
ing, it VIP-derived E-NBE diads.[84–89] In addition, E-NBE-
E-E sequences become visible. The signals at d=46.8 and
41.1 ppm correspond to alternating, st VIP-derived E-NBE
sequences, whereas that at d=32.6 ppm stems from alternat-
ing E-NBE and isolated NBE sequences. Finally, the signal
at d=29.4 ppm can be attributed to PE sequences. No sig-
attributable to a 1,7-connectivity of poly
observed.[90,91] None of the copolymers showed signals for
ROMP-derived poly(NBE)ROMP. As expected, an increase in
ACHTUGNTRNE(UNNG NBE)VIP sequences
AHCTUNGTRENNUNG
polymerization temperature resulted in a decrease in Mn.
In contrast to these “standard” results, an increase in
NBE concentration (9/MAO/NBE=1:2000:20000; [NBE]=
0.4 molLÀ1) resulted in the desired and expected formation
of polyACHTUNGTRENNUNG(NBE)ROMP-co-polyACHUTNGTRENN(NGU NBE)VIP-co-poly(E) (Figure 6).
The number average molecular weight of the copolymers
decreased with increasing temperature from Mn =
900000 gmolÀ1 (T=508C) to 120000 gmolÀ1 (T=808C,
Table 3, entries 4–6). Notably, monomodal molecular weight
distributions (Figure S5 in the Supporting Information) were
obtained at T=50, 65, and 808C with PDIs of 1.17, 1.24,
and 3.0, respectively.
nals attributable to a 1,7-connectivity of polyACHTNUTRGNEG(UN NBE)VIP se-
quences were observed.[90,91] The most important signals,
however, were found at d=132.99, 132.94, 132.88, and
132.71 and at d=42.91, 41.84, 32.98, and 32.41 ppm (Fig-
ure S9 in the Supporting Information). These signals are
To identify the structure of the polymer, the 13C NMR
absent in the spectrum of pure poly
that of poly
(NBE)VIP-co-poly(E)[57] and can be unambigu-
ously assigned to poly(NBE)ROMP-alt-poly(NBE)VIP sequen-
ces;[57] this confirms the incorporation of poly
(NBE)ROMP
ACHTNUGTNER(UNNG NBE)ROMP as well as in
spectra
polymers were compared with that of poly
well as that of poly(NBE)ROMP-alt-poly(E)3 prepared by al-
of
poly
(NBE)ROMP-co-poly
U
ACHTUNGTRENNUNG
R
E
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ternating ring-opening metathesis copolymerization of NBE
with COE,[92,93] where the latter copolymer mimics one
ROMP-derived polyACHTNUGRTENUNG(NBE) repeat unit followed by three
units into the polymer main chain by reversible a-H elimi-
nation/addition. Further evidence for the formation of one
single copolymer containing multiple blocks of both ROMP-
ethylene units (Figure 6).
and VIP-derived polyACTHNGUTERN(UNG NBE) sequences comes from the
Figure 6. 13C NMR spectra of poly
ACTHNUTRGENNU(G NBE)ROMP-co-polyACHTUNTGRNE(NUGN NBE)VIP-co-poly(E) produced by the action of 9/MAO (Table 3, entry 5), ROMP-type poly-
ACHTUNGTRENNUNG(NBE)ROMP (top), and poly(NBE-alt-COE)n (bottom, all spectra in [D2]1,1,2,2-tetrachloroethane).
Chem. Eur. J. 2011, 17, 13832 – 13846
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13839

M. R. Buchmeiser et al.
above-mentioned unimodal molecular weight distributions
and the low PDIs. As compared to the poly(NBE)ROMP-co-
poly(NBE)VIP-co-poly(E)-type polymer prepared by the
action of (h5-tetramethylcyclopentadienyl)dimethylsilyl
(N-
thesis of the Zr-alkylidene and E, thereby lowering the
number average molecular weight.
AHCTUNGTRENNUNG
N
Indeed, as can be deduced from Table 3, entries 7 and 8,
an increase in E pressure dramatically reduces Mn. Thus, at
pE =8 bar, a copolymer with an Mn of 210000 gmolÀ1 is ob-
tained. At this pressure, the reaction of NBE with the Zr-al-
kylidene (-methylidene) is virtually suppressed and only
non-productive olefin metathesis between the Zr-methyli-
AHCTUNGTRENNUNG
Ar’)amido-TiCl2 (A, Scheme 1),[57] catalyst 9 allows for a
higher NBE incorporation than Ti-1. However, the number
average molecular weights obtained with 9/MAO are lower
than those obtained with Ti-1/MAO (Mn ꢀ1.54ꢃ106 gmolÀ1)
under identical conditions. Both findings can be explained
in terms of the sterically less encumbered nature of 9, which
facilitates access of both NBE and E. Consequently, a
higher NBE content is observed. However, E is more likely
to react with intermediate Zr-alkylidenes, thereby signifi-
cantly lowering the molecular weight.
dene and E occurs. Consequently, only poly
is obtained.
ACHTUGNTNERN(UNG NBE)VIP-co-PE
Active species in the formation of poly
ACHTNUGTNER(UNNG NBE)ROMP-co-poly-
AHCTUNGTREN(GUNN NBE)VIP-co-poly(E): Because of agostic interactions, the
1H NMR chemical shifts of Zr-methylidenes are usually
found in the range dꢁ8–11 ppm.[23,94,95] If the proposed
mechanism is indeed valid, then one should be able to
detect intermediary Zr-alkylidenes, provided that they are
sufficiently stable, are present in appreciable concentration,
and their characteristic signals do not overlap with those of
the monomers or the polymer formed. In fact, most proba-
bly because of a too low concentration, we were not able to
detect any Zr=C species in the 13C NMR spectrum. Howev-
er, upon treatment of 9 with MAO in the presence of NBE,
a signal at d=8.48 ppm (d, J=7.2 Hz) became visible in the
1H NMR spectrum (Figure S6 in the Supporting Informa-
tion). This doublet might either be attributed to the alkyli-
Proposed mechanism: The data presented here allow for
formulation of the mechanism shown in Scheme 7. Thus, re-
action of a cationic VIP-active species with NBE, followed
by a-H elimination, produces a disubstituted Zr-alkylidene,
the formation of which is favored over that of a monosubsti-
tuted alkylidene by a-H elimination after E insertion. High
concentrations of NBE promote both a-H elimination and
ROMP of this monomer. The proton resides, at least for a
certain time, at the pyridine moiety and can be donated
back to the Zr-alkylidene to re-establish the VIP-active spe-
cies. At this point, another NBE molecule can insert, most
probably followed by E insertion. As one might expect, this
process is not the most favorable one and requires, as ob-
dene proton in [Zr]
is coupled to the allylic proton in the five-membered,
NBEROMP-derived ring, or to [Zr](=CH2)·MAO. A similar
[TiCp2A
(=CH2)·MAO] complex has also been reported[96,97] to
have an unsymmetrical structure, resulting in coupled meth-
ACHTUGTNRENNUG(=CH-ACHTUNGTERN(NUGN c-C5H8)-CH=CH-polymer), which
served, high concentrations of NBE to stabilize the Zr-alk
idene. If this interpretation were correct, then an increase in
E pressure should result in an increase in olefin cross-meta-
A
ACHTUNGTRENNUNG
A
CHTUNGTRENNUNG
Scheme 7. Proposed mechanism for the formation of a ROMP-active species from 9 and reformation of the VIP-active species.
13840
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Chem. Eur. J. 2011, 17, 13832 – 13846

Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
and distilled from P2O5. Non-deuterated solvents (i.e., toluene, diethyl
ether, THF, pentane, CH2Cl2) were dried and deoxygenated by sparging
with N2 gas, followed by passage through a triple-column solvent purifica-
tion system (MBraun). Purchased reagents were used without any further
purification. Celite and Al2O3 were dried in vacuo at 1808C for three
days prior to use. Methylalumoxane (MAO, 10 wt.% solution in toluene)
was purchased from Aldrich. The toluene was removed in vacuo and the
remaining white powder was dried in vacuo to remove any free tri-
ylidene protons with similar coupling constants. The same
holds for [TaCp2A(=CH2)
(CH3)].[98] Interestingly, treatment of
9 with MAO results in the appearance of a very similar
signal at d=8.59 ppm (d, J=7.8 Hz), supporting the forma-
G
ACHTUNGTRENNUNG
tion of a complex of the formula [Zr]ACTHNURTGNENUG(=CH2)·MAO.
Confirmation of the role of the aminoborane ligand by the
use of the aminoborane-free model catalyst 15: Finally, to
firmly support the role of the aminoborane ligand in the
above-described polymerizations, the copolymerization of E
with NBE by the action of an aminoborane-free catalyst, 15,
was carried out under identical conditions. In no case were
any ROMP-derived structures observed; instead, all of these
ACHUTNGRENmNUG ethylAHCTUNGTRENNaUGN luminum. Ethylene gas was purchased from Air Products and pu-
rified by passing through columns filled with BASF catalyst R 3–11G
(Ludwigshafen, Germany) and 3 ꢄ molecular sieves (Aldrich). All
homopolyACHTNUTRGENNUGmerHCATUNGTRENiNUGN zation reactions were performed in Schlenk tubes under
an inert atmosphere. All copolymerization reactions of ethylene with
cyclic olefins were performed in a Bꢀchi–Uster pressure reactor (poly-
clave) equipped with a Huber thermostat (Unistat Tango Nuevo). The
feed of the gaseous monomer was kept constant with a Bꢀchi pressflow
bpc 6010 flow controller. The reaction was monitored by means of a
bdsmc Bꢀchi data system.
copolymerizations yielded standard polyACHTNUGTRNE(UNG NBE)VIP-co-PE.
Polymerization activities were considerably higher, reaching
À1
920 kg of polymermolÀ1
h
barÀ1 at T=508C (Table 3,
NMR spectra were recorded on a Bruker Avance 600 spectrometer
(600.25 MHz for 1H and 150.93 MHz for 13C) at 208C unless specified
otherwise. Proton and carbon-13 spectra were referenced to internal sol-
vent resonances and are reported in ppm. IR spectra were recorded on a
Bruker Vector 22 spectrometer using ATR technology. GC-MS investiga-
tions were carried out on a Shimadzu GCMS-QP2010S with an AOC-20i
catalyst
entries 9 and 10). Applying a ratio of 15:MAO/NBE of
1:2000:20000, up to 14.7 mol% of NBE was incorporated
into the copolymer. As expected, a decrease in Mn and an
increase in PDI were observed with increasing temperature,
indicating that b-H elimination becomes more dominant.
autosampler using an SPB fused silica (Rxi-5MS) column (30 m
ꢃ
0.25 mm ꢃ 0.25 mm film thickness). Mass spectra were recorded on a
Bruker Esquire 300 plus or on a Finnigan-MAT 8200 at the Analytical
Chemistry Department of the University of Leipzig, Germany.
Conclusion
Molecular weights and molecular weight distributions were measured by
high-temperature gel chromatography (HT-GPC) on a Polymer Stand-
ards HT-GPC system with triple detection (refractive index, light-scatter-
ing at 15 and 908, viscosimetry) using three consecutive Waters Styragel
HR4 4.6ꢃ300 mm columns in 1,2,4-trichlorobenzene at 1458C. The flow
rate was set at 1 mLminÀ1. Narrow polystyrene standards in the range
162<Mn <6035000 gmolÀ1 (Easi Vial-red, yellow, and green) were pur-
chased from Polymer Labs. DSC data were recorded by heating under a
nitrogen atmosphere on a Perkin–Elmer DSC7 differential scanning calo-
rimeter. The glass transition temperature (Tg) of the polymers was deter-
mined by thermomechanical analysis (TMA) using a UIP-70M thermo-
mechanical analyzer at a heating rate of 2.58CminÀ1. Wide-angle X-ray
diffractograms (WAXDs) were recorded at room temperature using a
Philips diffractometer with a Geiger counter connected to the computer.
Ni-filtered CuKa radiation was used. Traces were collected over a time
period of 20 min in the range 58<2q<558 at a sample rate of 1 Hz.
In summary, ZrIV-dimethylsilylenebisamide complexes bear-
ing the aminoborane motif activated by MAO are capable
of homopolymerizing E and copolymerizing E with NBE to
yield cyclic olefin copolymers with an NBE incorporation of
up to 18 mol%. The corresponding HfIV-based system
allows the synthesis of UHMWPE. The presence of CPE
dramatically increases the activity of the ZrIV-based precata-
lyst 9 activated by MAO by up to a factor of 50. At high
NBE concentrations, this catalytic system is subject to rever-
sible a-H elimination/a-H addition, which allows the copoly-
merization of NBE with E by both ROMP- and VIP-based
mechanisms, yielding copolymers containing both ROMP-
6-(2-Bromophenyl)pyridine-2-amine (3): A solution of 2-amino-6-bromo-
pyridine (1) (17.3 g, 0.10 mol) and PdACHTNUGTRNEUNG(PPh3)4 (0.55 g, 0.50 mmol) in tolu-
and VIP-derived polyACTHNUTRGNEUNG(NBE) structures. Notably, similar pre-
catalysts that lack the aminoborane moiety do not display
such reactivity. We are currently exploring the scope and
limitations of this novel approach in terms of (co-) mono-
mers, catalyst structures, and reaction conditions, with the
final goal being to have at our disposal a set of active cata-
lysts capable of incorporating different cyclic olefins into 1-
olefin polymers with controlled degrees of both VIP- and
ROMP-derived structures.
ene (240 mL) was stirred for 10 min. 2-Bromophenylboronic acid (2, 25 g,
0.13 mol), ethanol (90 mL), sodium carbonate (21.2 g, 0.20 mol), and
water (120 mL) were added successively. The mixture was heated to
reflux for 2 days, then cooled to room temperature, and the aqueous
phase was extracted with ethyl acetate. The extracts were dried over
MgSO4 and concentrated in vacuo to give a solid. This solid was subject-
ed to chromatography on silica gel eluting with EtOAc/CH2Cl2/pentane
(1:1:5, containing 3 drops of triethylamine per 1000 mL of solvents).
Yield: 15.7 g (63.2%). 1H NMR (600.25 MHz, [D6]DMSO): d=5.93 (s,
2H; NH2), 6.46 (d, 1H, 3JHH =7.9 Hz; PyH), 6.64 (d, 1H, 3JHH =6.7 Hz;
PyH), 7.28–7.31 (m, 1H; PyH), 7.42–7.46 (m, 3H; ArH), 7.66 ppm (d,
1H, 3JHH =8.3 Hz; ArH); 13C NMR (150.95 MHz, [D6]DMSO): d=106.8,
112.0, 120.9, 127.3, 129.3, 131.0, 132.6, 136.9, 141.7, 155.9, 159.2 ppm;
FTIR (ATR mode): n˜ =3458 (m), 3296 (w), 3142 (m), 1635 (s), 1463 (s),
1291 (w), 1022 (m), 999 (m), 803 (s), 760 (s), 661 cmÀ1 (w); GC-MS: m/z
calcd for C11H9BrN2: 248.0; found: 248.0 ([M]+, 40%).
Experimental Section
General: Except where noted, all manipulations were conducted in the
absence of O2 and water under an atmosphere of Ar or N2, either by use
of standard Schlenk techniques on double-manifold vacuum lines or
within an MBraun LabMaster 130 glove box (MBraun, Garching, Germa-
ny) utilizing glassware that was oven-dried and evacuated while hot prior
to use. Deuterated NMR solvents were freeze-pump-thaw degassed.
[D6]Benzene, [D8]toluene, and [D8]tetrahydrofuran were dried and dis-
tilled from sodium/benzophenone ketyl; CD2Cl2 and CDCl3 were dried
2-(2-Bromophenyl)-6-(2,2,5,5-tetramethyl-1,2,5-azadisilolidin-1-yl)pyri-
dine (4): A mixture of 3 (2.30 g, 9.30 mmol), 1,2-bis[(dimethylamino)di-
methylsilyl]ethane (2.62 mL, 9.30 mmol), and a catalytic amount of ZnI2
(10 mg) was stirred at 1408C for 1 day. After cooling, dichloromethane
was added, and the mixture was washed with saturated ammonium chlo-
ride solution and brine, and then dried over magnesium sulfate. The sol-
Chem. Eur. J. 2011, 17, 13832 – 13846
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13841

M. R. Buchmeiser et al.
vents were removed in vacuo to give a dark-red solid. This solid was re-
crystallized from ethanol to give light-brown crystals. Yield: 3.18 g
n˜ =3371 (w), 2941 (w), 2859 (w), 2800 (w), 1622 (m), 1570 (s), 1485 (s),
1447 (m), 1373 (m), 1298 (m), 1262 (m), 1170 (m), 1032 (m), 949 (s), 840
(m), 803 (m), 755 cmÀ1 (s); MS (ESI): m/z calcd for C32H42B2N4Si:
532.34; found: 503.30 ([MÀEt]+, 100%).
(87.6%). 1H NMR (600.25 MHz, [D6]DMSO): d=0.29 (s, 12H; CH3),
3
0.80 (s, 4H; CH2), 6.68 (d, 1H, 3JHH =8.3 Hz; PyH), 6.91 (d, 1H, JHH
=
7.4 Hz; PyH), 7.32 (m, 1H; PyH), 7.46 (d, 2H, 3JHH =5.8 Hz; ArH), 7.61
(t, 1H, 3JHH =7.8 Hz; ArH), 7.70 ppm (d, 1H, 3JHH =8.0 Hz; ArH);
13C NMR (150.95 MHz, [D6]DMSO): d=À0.4, 8.0, 110.6, 114.2, 120.6,
127.4, 129.5, 130.8, 132.7, 141.3, 155.8, 159.5 ppm; FTIR (ATR mode):
n˜ =2952 (w), 2904 (w), 1579 (m), 1561 (m), 1476 (m), 1330 (s), 1248 (s),
1028 (m), 990 (m), 903 (s), 803 (m), 783 (m), 745 (m), 670 cmÀ1 (m); GC-
MS: m/z calcd for C17H23BrN2Si2: 390.1; found: 390.0 ([M]+, 40%).
Me2SiACTHNUGTRNE(NUG DbppN)2Li2 (8): n-Butyllithium (2.5m in hexane, 2.0 mL,
5.00 mmol) was added to a solution of 7 (1.04 g, 2.00 mmol) in diethyl
ether/pentane (1:2, v/v) at À378C. The mixture was allowed to warm to
room temperature and stirred for a further 1 h. The precipitate was col-
lected by filtration, washed with cooled diethyl ether/pentane (1:2, v/v),
and dried in vacuo to give a white solid. Yield: 0.98 g (91.2%).
AHCTUNGTREN[GNUN ZrCl2ACHTUNTGRENNUG{Me2SiACHTUNGERTGN(NUN DbppN)2}ACHTNUGERTN(NUGN thf)] (9): A solution of 8 (0.98 g, 1.80 mmol) in
6-[2-(Diethylboryl)phenyl]pyridine-2-amine (5): n-Butyllithium (2.0m in
diethyl ether (15 mL) was added dropwise to a solution of ZrCl4·2THF
(0.68 g, 1.80 mmol) in THF (15 mL) at À378C. The pale-yellow reaction
mixture was warmed to room temperature and stirred for a further 3 h.
After removal of the solvents, benzene was added and the mixture was
stirred for 0.5 h. It was then filtered through a pad of Celite and the fil-
trate was concentrated in vacuo. The obtained oil was crystallized from
CH2Cl2/pentane at À378C to give colorless crystals. Yield: 0.59 g
(35.4%). 1H NMR (600.25 MHz, [D6]benzene): d=0.70 (s, 6H; Si-
cyclohexane, 3 mL, 6.0 mmol) was added to
a solution of 4 (2.0 g,
5.0 mmol) in diethyl ether (20 mL) at À788C and the mixture was stirred
for 1 h at this temperature. Diethylmethoxyborane (1m in THF, 10 mL,
10 mmol) was then added and the resulting mixture was stirred for a fur-
ther 1 h at À788C. The mixture was allowed to warm to room tempera-
ture overnight and then poured into iced water and stirred for 15 min.
The organic phase was isolated and the aqueous phase was extracted
twice with ethyl acetate. The combined organic phases were washed with
brine and dried over MgSO4. After removal of the solvents, the residue
was subjected to chromatography on silica gel (deactivated with 5 wt.%
of water) eluting with EtOAc/pentane (1:10; containing 3 drops of tri-
AHCUTNGERT(GNNUN CH3)2), 0.94–1.67 (m, 28H; THF + BCH2CH3), 3.68 (m, 8H; THF), 4.24
(s, 2H), 7.06 (d, 2H, 3JHH =7.2 Hz; PyH), 7.17 (t, 2H, 3JHH =7.8 Hz;
3
ArH), 7.21 (d, 2H, JHH =7.4 Hz; ArH), 7.38 (t, 2H, 3JHH =7.2 Hz; PyH),
7.60 (d, 2H, 3JHH =8.0 Hz; ArH), 7.62 (d, 2H, 3JHH =7.6 Hz; ArH),
7.92 ppm (d, 2H, 3JHH =7.2 Hz; PyH); 13C NMR (150.93 MHz,
[D6]benzene): d=3.0, 12.4, 15.6, 25.5, 53.7, 75.1, 111.7, 120.6, 121.6, 125.6,
128.3, 128.5, 128.7, 130.2, 130.3, 137.2, 139.9, 158.7, 161.6, 166.2 ppm;
ACHTUNGTRENNUNG
ethylamine per 1000 mL of solvents). Yield: 1.10 g (92.7%). 1H NMR
(600.25 MHz, (CD3)2CO): d=0.34 (t, 6H, 3JHH =7.6 Hz; BCH2CH3),
3
0.80–0.87 (m, 4H; BCH2CH3), 6.34 (s, 2H; NH2), 6.70 (d, 1H, JHH
=
8.8 Hz; PyH), 7.17 (t, 1H, 3JHH =8.1 Hz; PyH), 7.30 (m, 2H; ArH and
1H NMR (600.25 MHz, CD2Cl2): d=0.58 (m, 18H; Si
N
+
3
PyH), 7.45 (d, 1H, JHH =7.2 Hz; ArH), 7.73 (t, 1H, 3JHH =7.9 Hz; ArH),
7.79 ppm (d, 1H, 3JHH =7.9 Hz; PyH); 13C NMR (150.95 MHz,
(CD3)2CO): d=10.9, 14.7, 15.3, 106.0, 109.2, 109.3, 122.2, 126.4, 129.9,
130.5, 139.2, 141.7, 157.3, 157.6 ppm; FTIR (ATR mode): n˜ =3498 (m),
3396 (m), 2931 (w), 2854 (m), 2805 (w), 1174 (m), 1603 (m), 1491 (s),
1299 (m), 1030 (w), 803 (m), 754 (s), 648 cmÀ1 (w); GC-MS: m/z calcd
for C15H19BN2: 238.2; found: 209.0 ([MÀEt]+, 100%).
3
3
THF), 7.26 (t, 2H, JHH =7.2 Hz, 7.5 Hz; ArH), 7.35 (t, 2H, JHH =6.9 Hz,
7.3 Hz; ArH), 7.57 (d, 2H, 3JHH =8.0 Hz; PyH), 7.61 (d, 2H, JHH
=
3
7.2 Hz; PyH), 7.63 (d, 2H, 3JHH =7.4 Hz; ArH), 7.81 (d, 2H, JHH
=
3
7.6 Hz; ArH), 7.89 ppm (d, 2H, 3JHH =7.8 Hz; PyH); 13C NMR
(150.93 MHz, CD2Cl2): d=3.2, 12.1, 15.7, 26.5, 54.9, 75.9, 112.4, 121.0,
121.9, 125.7, 129.9, 130.1, 137.6, 140.7, 158.7, 161.7, 166.2 ppm; MS (ESI):
m/z calcd for C40H56B2Cl2N4O2SiZr: 834.28; found: 857.16 [M+Na]+.
Crystals suitable for single-crystal X-ray analysis were obtained by re-
crystallization from CH2Cl2/pentane.
ACHTUNGTRENNUNG(DbppNH)LiACHTUNGTRENNUNG(Et2O) (6): n-Butyllithium (2.5m in hexane, 4 mL,
10.0 mmol) was added to a solution of 5 (2.38 g, 10.0 mmol) in diethyl
ether/pentane (1:10, v/v) at À378C. The pale-yellow solution was allowed
to warm to room temperature and then stirred for a further 1 h. The pre-
cipitate was collected by filtration, washed with cooled diethyl ether/pen-
A
2ACHTUNGTRNEU{NGN Me2SiACHUTNGTREG(NNUN DbppN)2}ACTHUNGTRENNUNG
a
tane (1:10, v/v), and dried in vacuo to give a yellow solid. Yield: 1.97 g
(0.50 g, 1.10 mmol) in toluene (15 mL) at À378C. The pale-yellow reac-
tion mixture was warmed to room temperature and stirred for a further
3 h. After removal of LiCl by filtration, the organic phase was concen-
trated to a volume of around 2 mL. The obtained oil was crystallized
from toluene/pentane (1:1, v/v) at À378C to give a yellow crystalline
3
(70.2%). 1H NMR (600.25 MHz, [D6]benzene): d=0.83 (t, 12H, JHH
=
7.0 Hz; Et2O), 0.89 (t, 12H, 3JHH =7.5 Hz; BCH2CH3), 1.27 (m, 4H;
BCH2CH3), 1.43 (m, 4H; BCH2CH3), 2.97 (q, 4H, 3JHH =7.0 Hz; Et2O),
3
4.78 (s, 2H; NH), 5.95 (d, 2H, 3JHH =6.7 Hz; PyH), 6.65 (d, 2H, JHH
=
3
3
1
7.4 Hz; ArH), 7.07 (t, 2H, JHH =7.4 Hz; PyH), 7.30 (t, 2H, JHH =7.7 Hz;
product. Yield: 0.71 g (65.8%). H NMR (600.25 MHz, [D6]benzene): d=
3
3
ArH), 7.48 (t, 2H, JHH =7.0 Hz; ArH), 7.71 (d, 2H, JHH =7.6 Hz; ArH),
7.95 ppm (d, 2H, 3JHH =6.9 Hz; PyH); 13C NMR (150.93 MHz,
[D6]benzene): d=11.2, 14.9, 15.2, 66.4, 100.6, 121.3, 125.7, 128.3, 128.5,
128.7, 129.8, 139.0, 139.2 ppm.
0.75 (s, 6H; SiACHTNUGTRNEN(UG CH3)2), 0.94–1.76 (m, 28H; THF + BCH2CH3), 2.11 (s,
3H; toluene), 3.72 (m, 8H; THF), 7.02 (d, 2H, 3JHH =7.6 Hz; o-toluene),
7.04 (t, 1H, 3JHH =7.4 Hz; p-toluene), 7.08 (d, 2H, 3JHH =7.4 Hz; PyH),
7.13 (t, 2H, 3JHH =7.5 Hz; m-toluene), 7.20 (t, 2H, 3JHH =7.8 Hz; ArH),
7.26 (t, 2H, 3JHH =7.8 Hz; ArH), 7.43 (t, 2H, 3JHH =7.2 Hz; PyH), 7.67
Me2SiACHTUNGTRENNUNG(DbppNH)2 (7): Dichlorodimethylsilane (0.34 mL, 2.90 mmol) was
3
3
(dd, 4H, JHH =7.8, 13.8 Hz; ArH), 7.99 ppm (d, 2H, JHH =7.2 Hz; PyH);
13C NMR (150.93 MHz, [D6]benzene): d=3.1, 12.4, 15.2, 21.7, 25.4, 75.3,
111.5, 121.5, 121.8, 125.6, 126.0, 128.0, 128.5, 128.7, 129.7, 130.2, 130.3,
137.2, 138.2, 139.7, 158.8, 161.9, 166.3 ppm; MS (ESI): m/z calcd for
C40H56B2Cl2HfN4O2Si: 924.32; found: 925.29 ([M+H]+, 5%); elemental
analysis calcd (%) for C40H56B2Cl2HfN4O2Si (924.3201): C 51.99, H 6.11,
N 6.06; found: C 51.63, H 6.03, N 5.84.
added to a solution of 6 (1.61 g, 5.80 mmol) in diethyl ether (15 mL) at
À378C. The solution was allowed to warm to room temperature and
stirred for 2 h. It was then cooled to À378C once more, whereupon the
deposited solid was filtered off and washed with pentane. The combined
filtrate and washings were dried in vacuo to give a white solid, which was
recrystallized from diethyl ether/pentane (1:10, v/v) at À378C to yield
colorless crystals. Yield: 1.26 g (83.2%). 1H NMR (600.25 MHz, CDCl3):
d=0.27 (s, 6H; SiACHTUNGTRENNUNG
(CH3)2), 0.74–0.79 (t, 12H, 3JHH =7.6 Hz; BCH2CH3),
2-(2-Propyl)phenylboronic acid (11): nBuLi (66 mL, 1.6m in hexane,
1.10 (m, 2H; BCH2CH3), 1.17 (m, 2H; BCH2CH3), 1.36 (m, 2H;
BCH2CH3), 1.45 (m, 2H; BCH2CH3), 6.01 (s, 1H; NH), 6.14 (s, 1H;
NH), 6.48 (d, 1H, 3JHH =8.9 Hz; PyH), 6.64 (d, 1H, 3JHH =7.7 Hz; PyH),
6.68 (d, 1H, 3JHH =7.2 Hz; ArH), 6.77 (d, 1H, 3JHH =7.7 Hz; ArH), 6.94
(t, 2H, 3JHH =7.7 Hz; PyH), 7.22 (t, 2H, 3JHH =7.5 Hz; ArH), 7.40 (m,
1H; ArH), 7.43 (d, 1H, 3JHH =7.5 Hz; ArH), 7.53 (d, 1H, 3JHH =7.4 Hz;
ArH), 7.56 (d, 1H, JHH =7.4 Hz; ArH), 7.77 (d, 1H, JHH =7.4 Hz; PyH),
7.82 ppm (d, 1H, 3JHH =7.4 Hz; PyH); 13C NMR (150.93 MHz, CDCl3):
d=1.9, 10.6, 10.7, 16.0, 107.9, 108.0, 121.7, 126.2, 128.3, 128.5, 128.7,
129.7, 130.9, 137.9, 141.4, 155.0, 158.3, 163.5 ppm; FTIR (ATR mode):
0.11 mol) was added to
(19.9 g, 0.10 mol) in THF (200 mL) cooled to À788C and the mixture was
stirred for 15 min at the same temperature. A solution of tris(2-propyl)-
borate (62 mL, 0.27 mol) in THF (60 mL) was then added dropwise, and
the resulting mixture was stirred for a further 1 h at À788C and then al-
lowed to warm to room temperature over a further 1 h. The system was
then quenched with aqueous HCl and extracted with EtOAc. After re-
moval of the solvents from the combined extracts, the crude product was
recrystallized from CH2Cl2. Yield: 9.88 g (60.2%). 1H NMR
(600.25 MHz, [D6]DMSO): d=0.45 (d, 6H, 3JHH =6.9 Hz; 2-propyl), 1.35
a solution of 1-bromo-2-(2-propyl)benzene
ACHTUNGTRENNUNG
3
3
13842
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 13832 – 13846

Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
3
(s, 2H; B(OH)2), 2.50 (m, 1H; 2-propyl), 6.37 (t, 1H, JHH =7.0 Hz; H-C5
of phenyl), 6.51 (d, 1H, 3JHH =7.6 Hz; H-C3 of phenyl), 6.54 (t, 1H,
3JHH =7.4 Hz; H-C4 of phenyl), 6.57 ppm (d, 1H, 3JHH =7.2 Hz; H-C6 of
phenyl); 13C NMR (150.93 MHz, [D6]DMSO): d=24.4 (CH3 of 2-propyl),
32.6 (CH of 2-propyl), 124.1 (C3,5 of phenyl), 124.6 (C4 of phenyl), 128.6
(C6 of phenyl), 132.2 (C1 of phenyl), 151.5 ppm (C2 of phenyl).
(m, 10H; ArH); 13C NMR (150.93 MHz, [D6]benzene): d=À1.1, 25.0,
25.4, 30.1, 74.8, 122.7, 123.5, 123.8, 126.2, 126.4, 129.7, 130.4, 141.8, 143.9,
146.8, 151.2 ppm; MS (ESI): m/z calcd for C36H44Cl2N2OSiZr: 708.16;
found: 925.29 [M+3THF+H]+.
6-[2-(Diethylboryl)phenyl]-N-phenylpyridine-2-amine (16): A solution of
PdACHTUNTRGNEUNG(OAc)2 (0.13 g, 0.6 mmol), PtBu3 (0.17 mL, 1.0m in toluene,
2’-(2-Propyl)biphenyl-3-amine (12): A solution of 3-bromoaniline (8.62 g,
0.05 mol) and PdACHTUNGTRENNUNG(PPh3)4 (0.30 g, 0.26 mmol) in toluene (240 mL) was
0.17 mmol), 5 (0.24 g, 1.00 mmol), iodobenzene (0.22 g, 1.10 mmol), and
NaOtBu (0.14 g, 1.50 mmol) in toluene (25 mL) was stirred at 808C over-
night. The toluene was then removed in vacuo to yield a brown oil. The
residue was subjected to flash chromatography on silica gel eluting with
EtOAc/hexane (1:50). Yield: 0.28 g (90.1%). 1H NMR (600.25 MHz,
stirred for 10 min. 2-(2-Propyl)phenylboronic acid (8.20 g, 0.05 mol), eth-
anol (90 mL), sodium carbonate (10.6 g, 0.10 mol), and water (120 mL)
were then added successively. The mixture was degassed for 15 min and
then heated to reflux overnight. After cooling to room temperature, the
aqueous phase was extracted with ethyl acetate. The combined extracts
were dried over MgSO4 and concentrated in vacuo to give a solid. This
solid was subjected to chromatography on silica gel eluting with EtOAc/
CH2Cl2/pentane (1:1:10, containing 2 or 3 drops of triethylamine per
1000 mL of solvent). Yield: 10.37 g (98.1%). 1H NMR (600.25 MHz,
[D6]acetone): d=0.50 (t, 6H, 3JHH =7.6 Hz; B
(CH2CH3)2), 6.88 (d, 1H, 3JHH =8.4 Hz; PyH), 7.28 (t, 1H, JHH
=
ACHTNUGTRNEN(NUG CH2CH3)2), 1.02 (m, 4H;
3
B
G
3
3
7.4 Hz; PyH), 7.37 (d, 1H, JHH =7.7 Hz; PyH), 7.40 (t, 1H, JHH =7.2 Hz;
3
ArH), 7.46–7.49 (m, 3H; ArH), 7.58 (d, 1H, JHH =7.2 Hz; ArH), 7.68 (d,
3
1H; NH), 7.80 (t, 1H, 3JHH =7.9 Hz; ArH), 7.88 ppm (d, 1H, JHH
=
7.6 Hz; ArH); 13C NMR (150.93 MHz, [D6]acetone): d=10.3, 15.0, 106.2,
107.6, 121.8, 124.6, 126.0, 126.6, 129.3, 130.4, 130.7, 138.1, 139.1, 141.8,
154.1, 157.9 ppm; FTIR (ATR mode): n˜ =3404 (m), 2936 (w), 2859 (m),
2807 (w), 1620 (w), 1566 (s), 1516 (m), 1473 (s), 1302 (m), 1163 (s), 1039
(w), 906 (w), 744 (s), 694 cmÀ1 (m); MS (ESI): m/z calcd for C21H23BN2:
314.195; found: 285.2 ([MÀEt]+, 100%).
[D6]benzene): d=1.43 (d, 6H, 3JHH =7.0 Hz; 2-propyl), 3.41 (m, 1H; 2-
3
propyl), 3.87 (s, 2H; NH2), 6.85 (m, 2H; ArH), 6.95 (d, 1H, JHH
=
7.6 Hz; ArH), 7.40–7.44 (m, 3H; ArH), 7.57 (m, 1H; ArH), 7.64 ppm (d,
1H, 3JHH =7.8 Hz; ArH); 13C NMR (150.93 MHz, [D6]benzene): d=24.3,
29.3, 113.5, 116.1, 119.7, 125.2, 125.4, 127.5, 128.3, 129.7, 141.3, 143.2,
146.0, 146.3 ppm; FTIR (ATR mode): n˜ =3369 (w), 2958 (s), 2866 (w),
1612 (s), 1478 (w), 1361 (m), 1316 (m), 871 (s), 704 (w), 633 cmÀ1 (s);
GC-MS: m/z calcd for C15H17N: 211.1; found: 211.0 ([M]+, 100%).
Lithium
{6-[2-(diethylboryl)phenyl]pyridin-2-yl}ACTHUNGTRENNU(G phenyl)amide·ACHTUNGTRENNUNG(Et2O)
(17): n-Butyllithium (1.6m in hexane, 0.92 mL, 1.47 mmol) was added to
a solution of 16 (0.42 g, 1.34 mmol) in diethyl ether/pentane (1:10, v/v) at
À378C. The solution was allowed to warm to room temperature, stirred
for a further 0.5 h, and then concentrated in vacuo to yield a yellow
liquid, which was washed with pentane and dried in vacuo. Yield: 0.50 g
(95.3%). 1H NMR (600.25 MHz, [D8]toluene): d=0.46 (m, 2H; B-
Me2SiACHTUNGTRENNUNG(IpbpNH)2 (13): n-Butyllithium (1.6m in hexane, 6.25 mL,
10.0 mmol) was added to a solution of 12 (2.11 g, 10.0 mmol) in pentane
at À378C. A precipitate formed and the solution was allowed to warm to
room temperature and stirred for a further 5 min. The reaction mixture
was then cooled to À378C once more, whereupon SiMe2Cl2 (0.58 mL,
5.00 mmol) was added. The resulting mixture was allowed to warm to
room temperature and stirred for a further 2 h. The precipitate formed
was filtered off and the filtrate was concentrated in vacuo to give a
AHCTUNGTRENNUNG
B
G
ACHTUNGTRENNUNG
3
3
Et2O), 6.30 (d, 1H, JHH =8.8 Hz; PyH), 6.47 (d, 1H, JHH =6.8 Hz; PyH),
6.93 (m, 3H; ArH-NLi), 7.20 (m, 3H; ArH-NLi, PyH, ArH), 7.33 (t, 1H,
3JHH =7.2 Hz; ArH), 7.58 (d, 1H, 3JHH =7.6 Hz; ArH), 7.63 ppm (d, 1H,
3JHH =7.2 Hz; ArH); 13C NMR (150.93 MHz, [D8]toluene): d=10.2, 11.5,
14.1, 66.1, 98.0, 108.5, 120.4, 121.9, 125.3, 125.4, 128.8, 129.7, 137.4, 137.6,
139.5, 152.7, 156.4, 161.0 ppm.
yellow oil. Yield: 2.25 g (94.2%). 1H NMR (600.25 MHz, [D6]benzene):
3
d=0.12 (s, 6H; Si
N
2H; 2-propyl), 6.32 (dd, 2H, 3JHH =1.4, 8.0 Hz; ArH), 6.78 (s, 2H; NH),
6.80 (d, 2H, 3JHH =7.5 Hz; ArH), 7.10 (q, 4H, 3JHH =7.0, 7.3 Hz; ArH),
7.22 (t, 2H, 3JHH =7.5 Hz; ArH), 7.25 (d, 2H, 3JHH =7.6 Hz; ArH),
7.29 ppm (d, 2H, 3JHH =7.8 Hz; ArH); 13C NMR (150.93 MHz,
[D6]benzene): d=À1.1, 24.8, 30.0, 115.9, 118.3, 120.5, 125.9, 126.1, 129.5,
N-(2-Chlorophenyl)-6-[2-(diethylboryl)phenyl]pyridine-2-amine (18):
A
solution of Pd(OAc)2 (0.11 g, 0.48 mmol), PtBu3 (1.43 mL, 1.0m in tolu-
AHCTUNGTRENNUNG
ene, 1.43 mmol), 1-chloro-2-iodobenzene (2.38 g, 10.0 mmol), 5 (2.38 g,
10.0 mmol), and NaOtBu (1.45 g, 15.0 mmol) in toluene (50 mL) was
stirred under reflux for 3 days. The toluene was then removed in vacuo
and the remaining brown oil was subjected to flash chromatography on
silica G60 eluting with ethyl acetate/hexane (1:50). Yield: 6.30 g (83.8%).
1
130.5, 142.5, 144.1, 146.7, 146.9 ppm; H NMR (600.25 MHz, CDCl3): d=
0.47 (s, 6H; SiACHTUNGTRENNUNG
(CH3)2), 1.24 (d, 12H, 3JHH =6.9 Hz; 2-propyl), 3.11 (m,
2H; 2-propyl), 3.76 (s, 2H; NH), 6.70 (d, 2H, 3JHH =7.5 Hz; ArH), 6.79
(m, 4H; ArH), 7.15–7.22 (m, 6H; ArH), 7.35 (m, 2H; ArH), 7.38 ppm
(d, 2H, 3JHH =7.0 Hz; ArH); 13C NMR (150.93 MHz, CDCl3): d=À0.9,
24.4, 29.4, 115.3, 117.5, 119.8, 125.3, 128.5, 127.6, 128.9, 129.9, 141.6,
143.2, 145.9, 146.5 ppm; FTIR (ATR mode): n˜ =3377 (w), 2959 (m), 1592
(s), 1468 (s), 1359 (s), 1308 (m), 1259 (m), 1091 (w), 1036 (w), 924 (s),
840 (s), 791 (s), 753 (m), 700 (m), 653 cmÀ1 (w); MS (ESI): m/z calcd for
C32H38N2Si: 478.28; found: 479.29 ([M+H]+, 95%).
1H NMR (600.25 MHz, [D6]acetone): d=0.32 (t, 6H, 3JHH =7.7 Hz; B-
3
G
N
7.38 (t, 2H, 3JHH =7.3 Hz; ArH), 7.55 (t, 1H, 3JHH =7.2 Hz; ArH), 7.59
(d, 1H, 3JHH =7.2 Hz; PyH), 7.78 (d, 1H, 3JHH =8.1 Hz; PyH), 8.04 (dd,
2H, 3JHH =7.5 Hz; ArH), 8.26 (d, 1H, 3JHH =3.8 Hz, 7.6 Hz; ArH), 8.85
(d, 1H, 3JHH =8.1 Hz; ArH), 10.97 ppm (s, 1H; NH); 13C NMR
(150.93 MHz, [D6]acetone): d=10.5, 14.5, 109.0, 113.2, 113.3, 117.7,
121.7, 121.8, 122.4, 126.1, 128.4, 129.8, 130.1, 133.0, 139.0, 140.0, 146.7,
155.7, 165.1 ppm; FTIR (ATR mode): n˜ =3455 (w), 3385 (m), 2929 (w),
2857 (m), 2814 (w), 1693 (s), 1645 (s), 1548 (s), 1463 (s), 1426 (s), 1309
(s), 1169 (s), 738 cmÀ1 (s); MS (ESI): m/z calcd for C21H22BClN2: 348.157;
found: 348.1 ([M]+, 85%).
Me2SiACHTUNGTRENNUNG(IpbpN)2Li2 (14): n-Butyllithium (1.6m in hexane, 2.0 mL,
5.97 mmol) was added to a solution of 13 (1.43 g, 2.98 mmol) in pentane
at À378C. After 10 min, a precipitate formed and the mixture was al-
lowed to warm to room temperature and stirred for a further 0.5 h. The
precipitate was collected by filtration, washed with pentane, and dried in
vacuo to give a white solid. Yield: 1.12 g (76.6%).
A
E
E
G
N
ACHTUNGTRENNUNG
a
ACHTUNGTRENNUNG
(0.25 g, 0.65 mmol) in toluene (15 mL) at À378C. The pale-yellow reac-
tion mixture was warmed to room temperature and stirred for a further
3 h. After removal of LiCl by filtration, the organic phase was concen-
trated to a volume of approximately 2 mL. Pentane was then added to
the concentrated solution, whereupon a precipitate formed, which was
collected by filtration and washed with pentane to give a yellow solid.
Yield: 0.31 g (67.3%). 1H NMR (600.25 MHz, [D6]benzene): d=0.51 (s,
(8.86 g, 0.05 mol) in pentane (100 mL) at À378C. The resulting mixture
was slowly warmed to room temperature and stirred for a further 15 min.
The lithium amide was filtered off as an off-white solid and washed with
cold pentane. It was slowly added to Me2SiCl2 (25 mL) in diethyl ether
(50 mL) at À378C. After complete addition of the solid, the reaction mix-
ture was slowly warmed to room temperature and stirred for a further
3 h. It was then filtered and a clear filtrate was collected. The unreacted
dichlorodimethylsilane and solvents were removed in vacuo to leave an
oily liquid, which was distilled under reduced pressure to give the prod-
uct as a colorless liquid. Yield: 7.51 g (55.8%). 1H NMR (600.25 MHz,
6H; Si
propyl), 3.31 (m, 2H; 2-propyl), 3.95 (m, 4H; THF), 6.89 (d, 2H, JHH
7.4 Hz; ArH), 7.10 (td, 4H, 3JHH =1.3, 7.4, 7.4 Hz; ArH), 7.19–7.29 ppm
ACHTUNGTRENNUNG
(CH3)2), 1.00 (m, 4H; THF), 1.17 (d, 12H, 3JHH =6.9 Hz; 2-
3
=
Chem. Eur. J. 2011, 17, 13832 – 13846
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13843

M. R. Buchmeiser et al.
CDCl3): d=0.48 (s, 6H; Si
(CH3)2), 2.83 (s, 1H; NH), 3.52 (m, 2H; CH
3H; C6H3); 13C NMR (600.25 MHz, CDCl3): d=2.7 (Si
(CH3)2), 28.6 (CH(CH3)2), 123.5 (o-C(Ph)), 125.8 (iPr-C(Ph)), 136.7 (N-
C(Ph)), 146 ppm (p-C(Ph)H); FTIR (ATR mode): n˜ =3373 (w), 3062 (w),
2962 (s), 1519 (m), 1461 (m), 1443 (m), 1328 (m), 1258 (s), 1048 (w), 924
(s), 816 (s), 744 cmÀ1 (w); GC-MS: m/z calcd for C14H24ClNSi: 269.1;
found: 269.0 ([M]+, 100%).
G
(20 mL), dried over Na2SO4, and concentrated under reduced pressure to
afford a crude mixture of 6-cyclopentylidene-undecane and 6-cyclopen-
tyl-undec-5-ene (550 mg, 60%). 1H NMR (CDCl3, 250 MHz): d=0.77–
0.84 (m, 12H), 1.08–1.32 (m, 28H), 1.48–1.57 (m, 5H), 1.68–1.80 (m,
2H), 1.86–1.91 (m, 4H), 2.02–2.23 (m, 8H), 5.03–5.09 (m, 0.11H), 5.23–
5.25 ppm (t, 0.8H); 13C NMR (CDCl3, 62.5 MHz): d=14.52, 23.07, 23.79,
27.2, 27.56, 28.22, 30.56, 31.30, 32.33, 32.44, 32.52, 33.39, 34.05, 41.56,
124.51, 130.81, 136.67, 148.0 ppm; GC-MS: m/z calcd for C16H30: 222.23;
found: 222.2.
E
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
R
ACHTUNGTRENNUNG
Me2SiACHTUNGTRENNUNG(DbppNH)NHACHTUNGTRENNUNG[2,6-ACTHNUGTREN(NGUN Me2CH)2C6H3] (20): 19 (1.73 g, 6.40 mmol) was
6-Cyclopentylundecane: 10 wt.% Pd/C catalyst (10 wt.% with respect to
the olefin) and ammonium formate (700 mg, 0.011 mol) were added to a
added to a solution of 6 (2.07 g, 6.40 mmol) in diethyl ether (50 mL) at
À378C. The solution was allowed to warm to room temperature and
stirred for a further 2 h. The precipitated solid was filtered off and
washed with pentane. The combined filtrate and washings were concen-
trated in vacuo to give a colorless solid, which was crystallized from pen-
tane at À378C to give the product as colorless crystals. Yield: 2.84 g
solution
of
6-cyclopentylidene-undecane/6-cyclopentyl-undec-5-ene
(250 mg, 0.0011 mol) in methanol (15 mL). The mixture was refluxed for
24 h. After cooling, the mixture was filtered and the filtrate was concen-
trated under reduced pressure. CHCl3 was added to the residue in order
to precipitate the excess ammonium formate. After filtration, the solvent
was evaporated from the filtrate to give 6-cyclopentylundecane (125 mg,
50%) in sufficient purity. 1H NMR (CDCl3, 250 MHz): d=0.86–0.91 (t,
6H), 1.05–1.31 (m, 19H), 1.43–1.71 ppm (m, 7H); 13C NMR (C2D2Cl4,
62.5 MHz): d=14.2, 22.7, 25.4, 26.1, 30.5, 31.5, 32.5, 42.5, 43.6 ppm; IR
(neat, 4000–400 cmÀ1): n˜ =2956, 2849, 2357, 2334, 1453, 1371 cmÀ1; GC-
MS: m/z calcd for C16H32: 224.25; found: 224.3 [M]+.
(94.1%). 1H NMR (600.25 MHz, [D6]benzene): d=0.21 (s, 6H; Si-
3
(CH3)2), 0.87 (t, 6H, JHH =7.7 Hz; BCH2CH3), 1.24 (m, 14H; CH
U
BCH2CH3), 1.46 (m, 2H; BCH2CH3), 2.57 (s, 1H; NH-2,6-di
benzene), 3.48 (m, 2H; CH
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
1H, 3JHH =0.8, 7.2 Hz; ArH), 7.69 (d, 1H, 3JHH =7.7 Hz; ArH), 7.89 ppm
(d, 1H, 3JHH =7.2 Hz; ArH); 13C NMR (150.93 MHz, [D6]benzene): d=
1.8, 10.8, 15.7, 24.2, 29.1, 106.7, 108.4, 121.6, 124.0, 125.7, 126.0, 128.7,
129.8, 130.7, 138.0, 138.1, 140.4, 145.2, 156.3, 158.3 ppm; 1H NMR
6-(1-Methylcyclopent-3-yl)undecane:
1-Bromo-3-methylcyclopentane:
A solution of 3-methylcyclopentanol
(2.0 g, 0.02 mol) in CH2Cl2 (50 mL) was cooled to 08C and PBr3 (6.76 g,
0.025 mol) was added dropwise. The mixture was stirred for 2 h, and then
the reaction mass was quenched with ice and extracted with CH2Cl2 (2ꢃ
25 mL). The combined organic layers were washed with NaHCO3 solu-
tion (50 mL), water (50 mL), and brine (50 mL), dried over anhydrous
Na2SO4, and concentrated under reduced pressure. The residue was dis-
tilled at 1308C to yield 1.5 g (46%) of the desired compound. 1H NMR
(CDCl3, 250 MHz): d=1.02–1.03 (d, 1.5H), 1.10–1.11 (d, 1.5H), 1.16–
1.21 (m, 0.5H), 1.45–1.52 (m, 0.5H), 1.64–1.69 (m, 1H), 1.79–1.85 (m,
0.5H), 1.95–2.0 (m, 0.5H), 2.04–2.16 (m, 2H), 2.2–2.31 (m, 1H), 2.38–
2.48 (m, 1H), 4.26–4.31 (m, 0.5H), 4.48–4.51 ppm (m, 0.5H); 13C NMR
(CDCl3, 62.5 MHz): d=20.6, 21.3, 32.1, 32.6, 32.9, 33.7, 37.9, 38.0, 46.4,
46.6, 50.9, 53.8 ppm; GC-MS: m/z calcd for C6H11Br: 162.0; found: 162.0.
3
(600.25 MHz, CD2Cl2): d=0.37 (t, 6H, JHH =7.6 Hz; BCH2CH3), 0.40 (s,
6H; Si
(d, 12H, 3JHH =6.8 Hz; CH
zene), 3.46 (m, 2H; CH(CH3)2), 5.83 (s, 1H; NH-Py), 6.75 (d, 1H, JHH =
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
3
N
8.3 Hz; PyH), 7.11 (m, 3H; ArH-2,6-diACTHNUGRTNEUNG(2-propyl)benzene), 7.26 (t, 1H,
3
3JHH =7.4 Hz; PyH), 7.29 (d, 1H, 3JHH =7.5 Hz; PyH), 7.37 (t, 1H, JHH
=
3
7.2 Hz; ArH), 7.52 (d, 1H, 3JHH =7.2 Hz; ArH), 7.70 (t, 1H, JHH
=
7.9 Hz; ArH), 7.75 ppm (d, 1H, 3JHH =7.7 Hz; ArH); 13C NMR
(150.93 MHz, CD2Cl2): d=1.5, 10.1, 15.0, 23.9, 29.0, 106.7, 109.0, 121.2,
123.7, 125.0, 129.3, 129.9, 138.0, 138.3, 140.7, 145.0, 156.3, 157.6 ppm;
FTIR (ATR mode): n˜ =3383 (w), 2943 (w), 2859 (w), 2803 (w), 1619 (m),
1567 (s), 1485 (m), 1445 (m), 1299 (w), 1257 (s), 1104 (w), 1033 (w), 907
(s), 754 cmÀ1 (m); MS (ESI): m/z calcd for C29H42BN3Si: 471.32; found:
472.38 ([M+H]+, 85%).
6-(3-Methylcyclopentyl)-undecan-6-ol: A solution of 1-bromo-3-methylcy-
clopentane (2.5 g, 0.015 mol) in THF was slowly added to a suspension of
Mg (0.38 g, 0.015 mol) in THF (50 mL) at 408C to generate the Grignard
reagent. Meanwhile, powdered CeCl3·7H2O (6.0 g, 0.016 mol) was heated
under reduced pressure in a Schlenk flask at 908C for 1 h, and then the
temperature was slowly raised and kept at 1408C for 2 h. After cooling,
the Schlenk flask was filled with nitrogen, THF (30 mL) was added, and
the suspension was ultrasonicated for 1 h. The suspension was then
cooled to À208C, the above solution of 3-methylcyclopentylmagnesium
bromide in THF was added dropwise, and the mixture was stirred for a
further 1.5 h. A solution of 6-undecanone (1.36 g, 0.008 mol) in THF was
then added dropwise to the suspension and the resulting mixture was
stirred for 2 h. Thereafter, the reaction was quenched with 3 vol.%
CH3COOH, the mixture was extracted with ethyl acetate (2ꢃ20 mL),
and the combined organic layers were washed with water (20 mL) and
brine (20 mL), dried over anhydrous Na2SO4, and concentrated under re-
duced pressure. The residual liquid was subjected to column chromatog-
raphy on silica gel to yield 6-(3-methylcyclopentyl)undecan-6-ol (2 g,
50%). 1H NMR (CDCl3, 250 MHz): d=0.79–0.84 (t, 6H), 0.87–0.93 (t,
3H), 0.93–2.11 ppm (m, 24H); 13C NMR (CDCl3, 62.5 MHz): d=14.5,
20.9, 21.6, 23.0, 23.7, 23.8, 25.3, 27.3, 33.1, 33.0, 34.2, 34.3, 35.0, 35.6, 36.2,
37.7, 37.8, 37.9, 37.9, 46.4, 47.9, 75.5, 75.8 ppm; GC-MS: m/z calcd for
C17H34O: 254.2; found: 253.2.
6-Cyclopentylundecane:
6-Cyclopentyl-undecan-6-ol: Cyclopentyl bromide (2.5 g, 0.016 mol) in
THF was slowly added to a 50 mL Schlenk flask containing Mg turnings
(0.41 g, 0.017 mol) in THF at 408C. Meanwhile, powdered CeCl3·7H2O
(6.5 g, 0.017 mol) was heated under reduced pressure at 908C for 1 h, and
then the temperature was slowly raised and kept at 1408C for 2 h. After
cooling, the Schlenk flask was filled with Ar, THF (30 mL) was added,
and the reaction mixture was sonicated for 1 h. The resulting suspension
was then cooled to À208C, cyclopentylmagnesium bromide in THF was
added dropwise, and the mixture was stirred for 1.5 h. A solution of 6-un-
decanone (1.47 g, 0.0086 mol) in THF was then added dropwise to the
suspension and the mixture was stirred for 2 h. The reaction was subse-
quently quenched with 3 vol.% CH3COOH and the mixture was extract-
ed with ethyl acetate (2ꢃ20 mL). The combined organic layers were
washed with water (20 mL) and brine (20 mL), dried over anhydrous
Na2SO4, and concentrated under reduced pressure. The residual liquid
was subjected to column chromatography on silica gel to give 6-cyclopen-
tyl-undecan-6-ol (1.5 g, 40%). 1H NMR (CDCl3, 250 MHz): d=0.86–0.91
(t, 6H), 1.17–1.61 (m, 25H), 1.87–2.01 ppm (m, 1H); 13C NMR (CDCl3,
62.5 MHz): d=14.48, 23.05, 23.74, 26.01, 26.41, 32.96, 38.01, 47.83,
75.57 ppm; GC-MS: m/z calcd for C16H32O: 240.2; found: 239.2.
1-Methyl-3-(1-pentylhexylidene)cyclopentane and 1-methyl-3-(1-pentylhex-
1-enyl)cyclopentane: An aqueous 70 wt.% solution of H2SO4 was slowly
added to 6-(3-methylcyclopentyl)undecan-6-ol (500 mg, 0.002 mol) at
08C. The mixture was stirred for a further 2 h and allowed to reach room
temperature. It was then poured onto ice and neutralized with 5 wt.%
NaOH solution. After extraction with ethyl acetate (2ꢃ15 mL), the com-
bined organic layers were washed with water (20 mL) and brine (20 mL),
dried over Na2SO4, and concentrated under reduced pressure to afford a
6-Cyclopentylidene-undecane and 6-cyclopentyl-undec-5-ene: A solution
of 70 wt.% H2SO4 was slowly added to 6-cyclopentyl-undecan-6-ol (1.0 g,
0.0041 mol) in a 50 mL flask at 08C and the temperature was slowly
raised to rt. Stirring was continued for a further 2 h, and then the mixture
was poured onto ice and neutralized with 5 wt.% NaOH solution. The
resulting mixture was extracted with ethyl acetate (2ꢃ15 mL) and the
combined organic layers were washed with water (20 mL) and brine
13844
www.chemeurj.org
ꢂ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 13832 – 13846

Zr and Hf Aminoborane Complexes and their Efficacies in Alkene Polymerization
FULL PAPER
crude mixture of 1-methyl-3-(1-pentylhexylidene)cyclopentane and 1-
methyl-3-(1-pentylhex-1-enyl)cyclopentane (250 mg, 55%).
and refined with isotropic displacement parameters 1.2 or 1.5 times
higher than the values for their carbon atoms. CCDC-852371 (7) and
CCDC-852373 (9) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
6-(1-Methylcyclopent-3-yl)undecane: 10 wt.% Pd/C catalyst (10 wt.%
with respect to the olefin) and ammonium formate (500 mg, 8.5 mmol)
were added to a solution of 1-methyl-3-(1-pentylhexylidene)cyclopentane
and 1-methyl-3-(1-pentylhex-1-enyl)cyclopentane (200 mg, 8.5 mmol) in
methanol (15 mL). The mixture was refluxed for 24 h. After cooling, the
mixture was filtered and the filtrate was concentrated under reduced
pressure. CHCl3 was then added to the residue to precipitate the excess
ammonium formate. After filtration, the solvent was evaporated from
the filtrate to give 6-(1-methylcyclopent-3-yl)undecane (125 mg, 50%).
1H NMR (CDCl3, 250 MHz): d=0.86–0.91 (t, 6H), 0.93–0.98 (dd, 3H),
1.07–1.47 (m, 20H), 1.65–2.0 ppm (m, 5H); 13C NMR (C2D2Cl4,
62.5 MHz): d=14.2, 21.0, 21.7, 22.7, 26.0, 26.0, 26.1, 26.2, 29.6, 31.1, 31.2,
31.3, 31.3, 31.4, 32.5, 32.5, 33.4, 33.6, 34.3, 35.1, 38.1, 40.3, 41.9, 42.7, 42.8,
43.7 ppm; IR (neat): n˜ =2961, 2846, 1462, 1371 cmÀ1; GC-MS: m/z calcd
for C17H34: 238.26; found: 238.3 [M]+.
Acknowledgements
This work was generously supported by the Wissenschaftsgemeinschaft
Wilhelm Gottfried Leibniz (WGL Wettbewerbsprojekt) and by the State
of Baden-Wꢀrttemberg, Germany. We wish to thank B. Autenrieth for
the preparation of exo-methylidene-2-methylcyclopentane.
exo-Methylidene-2-methylcyclopentane: Dry methyltriphenylphosphoni-
um bromide (3.90 g, 10.7 mmol) was placed in a Schlenk flask equipped
with a dropping funnel. THF was added at room temperature and the
suspension was cooled to À508C. At this temperature, a solution of n-bu-
tyllithium in hexane (6.8 mL, 10.7 mmol) was added dropwise. After stir-
ring for 20 min, the orange solution was ready for reaction and 2-methyl-
cyclopentanone (1.00 g, 10.2 mmol) was added. The reaction mixture was
allowed to warm to room temperature and was then gradually heated to
608C. After 5 h, water was added to quench the reaction and the mixture
was repeatedly extracted with pentane. The combined pentane phases
were washed with water and dried over MgSO4. After removal of the sol-
vent, the crude product was purified by column chromatography (alumi-
num oxide, pentane) to afford 1-methyl-2-methylenecyclopentane as a
colorless liquid. Yield: 290 mg (30%). 1H NMR (C2D2Cl4, 250 MHz): d=
4.79, 4.70, 2.28 (m, 3H), 1.83, 1.75–1.4 (m, 4H), 1.02 ppm (d, 3H, J=
6.8 Hz; CH3); 13C NMR (C2D2Cl4, 62.5 MHz): d=158.6, 104.0, 39.1, 35.7,
33.2, 24.3, 19.3 ppm; GC-MS (70 eV): m/z calcd for C7H12 96.1; found:
96.1 ([M]+, 23%).
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Received: June 15, 2011
Published online: November 10, 2011
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