Synthesis, characterization, and activation of zirconium and hafnium dialkyl complexes that contain a C2-symmetric diaminobinaphthyl dipyridine ligand

Article abstract of DOI:10.1021/om058007i

The diamine rac-H₂[MepyN] (rac-N,N′-di(6-methylpyridin-2-yl)-2,2′-diaminobinaphthalene) has been prepared in good yield through reductive amination of rac-2,2′-diaminobinaphthalene with 6-methylpyridinecarboxaldehyde. The [MepyN]² li

Full text of DOI:10.1021/om058007i

Organometallics 2005, 24, 3335-3342
3335
Synthesis, Characterization, and Activation of Zirconium
and Hafnium Dialkyl Complexes that Contain a
C2-Symmetric Diaminobinaphthyl Dipyridine Ligand
Zachary J. Tonzetich, Richard R. Schrock,* Adam S. Hock, and Peter Mu¨ller
Department of Chemistry 6-331, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139
Received February 9, 2005
The diamine rac-H2[MepyN] (rac-N,N′-di(6-methylpyridin-2-yl)-2,2′-diaminobinaphthalene)
has been prepared in good yield through reductive amination of rac-2,2′-diaminobinaph-
thalene with 6-methylpyridinecarboxaldehyde. The [MepyN]2- ligand has been employed to
prepare a variety of zirconium and hafnium complexes, [MepyN]MX2 (M ) Zr, X ) NMe2,
Cl, OSO2CF3, CH2CHMe2, CH2Ph; M ) Hf, X ) NMe2, OSO2CF3, CH2CHMe2). The solid
state structures of [MepyN]Zr(CH2Ph)2, [MepyN]Zr(NMe2)Cl, [MepyN]Hf(CH2CHMe2)2, and
[MepyN]Hf(OSO2CF3)2 have been determined by X-ray diffraction. Activation of [MepyN]-
Zr(CH2Ph)2 and [MepyN]Hf(CH2CHMe2)2 with various Lewis acids leads to observable
cationic alkyls that are not active toward 1-hexene polymerization.
Introduction
most interesting feature of several systems that contain
a diamido/donor ligand is that 1-hexene can be polym-
erized in a living fashion and intermediates in that
process can be observed in NMR spectra. Other types
of non-metallocene polymerization catalysts are also
known that are living to a greater or lesser degree.17
Living characteristics result largely from a reduced
tendency for â-hydride elimination from (in the case of
a terminal olefin) either a 1,2 insertion product or a 2,1
insertion product.
We have been exploring the possibility of preparing
asymmetric catalysts that contain a diamido/donor
ligand, the ultimate goal being to design a living,
stereospecific polymerization process. So far we have not
been successful. Therefore we chose to explore the
chemistry of asymmetric diamido ligands that contain
a relatively rigid and chiral backbone, namely, a C2-
symmetric (rac) binaphthyl backbone. The rigid biaryl
backbone of the binaphthalene provides the desired
stereochemical element that can transmit chiral infor-
mation close to the metal through the amido linkages.
A number of reports of biaryl-based amide ligands exist
in the literature,28-34 including some recent work by
In the past several years interest in “non-metallocene”
early transition metal olefin polymerization catalysts,
as well as late metal catalysts (which often contain
nitrogen donor ligands), has increased markedly.1-4
Our laboratory has been exploring the synthesis and
activation of dialkyl Zr and Hf complexes that contain
diamido/donor ligands, e.g., [(t-BuN-o-C6H4)2O]2- or
[(MesitylNCH2)2C(CH3)(2-C5H4N)]2- 5-9
while a variety
,
of related systems in which the ligand is not a diamido/
donor have been explored in other laboratories.10-27 The
(1) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428.
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(3) Coates, G. W. J. Chem. Soc., Dalton Trans. 2002, 467.
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K.; Matsui, S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.;
Matsugi, T.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 3327.
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Ed. 2002, 41, 2236.
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10.1021/om058007i CCC: $30.25 © 2005 American Chemical Society
Publication on Web 05/25/2005

3336 Organometallics, Vol. 24, No. 13, 2005
Tonzetich et al.
Scheme 1
Brintzinger similar to that reported here.35 In this paper
we report zirconium and hafnium dialkyl complexes that
contain a new binaphthyl-based diamide ligand and
explore activation of the dialkyls.
Results and Discussion
Figure 1. Thermal ellipsoid (50%) plot of [MepyN]Zr-
The diamine rac-H2[MepyN] is prepared from rac-2,2′-
diamino-1,1′-binaphthalene as shown in eq 1. Condensa-
tion of rac-2,2′-diamino-1,1′-binaphthalene with 6-meth-
yl-2-pyridinecarboxaldehyde followed by reduction with
NaBH4 produces the racemic diamine in 80% yield after
recrystallization on a scale of 5-10 g. H2[MepyN] is a
white crystalline solid that is soluble in aromatic and
chlorinated solvents, but is relatively insoluble in al-
kanes or diethyl ether. The proton NMR spectrum is
consistent with it having C2 symmetry; nine aryl
resonances can be observed, while the methylene pro-
tons appear as a complex multiplet at 4.15 ppm and the
methyl group as a singlet at 2.27 ppm in benzene-d6.
(NMe2)Cl. Hydrogen atoms are omitted for clarity.
C2 axis (C2-cis and C2-trans). Structural characterization
of zirconium complexes that contain a related ligand
suggest that both C2-cis and C2-trans coordination are
observable.35 We have no information concerning the
correct structure for the [MepyN]M(NMe2)2 species.
Initial attempts to synthesize [MepyN]Zr(NMe2)2 led
to an unexpected result. Upon addition of H2[MepyN]
to Zr(NMe2)4, a yellow crystalline material was obtained
whose 1H NMR spectrum showed it to be one diastere-
omer that has C1 symmetry. Four doublets arise for each
of the inequivalent methylene protons of the ligand
instead of the AB patterns encountered in C2-symmetric
species, while 18 aryl resonances are observed for each
proton in the binaphthyl and pyridine residues. A broad
peak is also observed that can be assigned to six
dimethylamide protons. A crystal structure of the
complex revealed it to be [MepyN]Zr(NMe2)Cl (Scheme
2). A rational synthesis of [MepyN]Zr(NMe2)Cl consists
of a reaction between [MepyN]Zr(NMe2)2 and lutidinium
chloride in benzene-d6. Recrystallization of H2[MepyN]
from non-chlorinated solvents produced samples that
yielded exclusively the desired bisdimethylamide com-
plex. Therefore we believe that [MepyN]Zr(NMe2)Cl
arises through reaction of [MepyN]Zr(NMe2)2 (generated
in situ) with chloroform that had been retained in the
sample of H2[MepyN] that was first employed in the
reaction.
The reaction between H2[MepyN] and M(NMe2)4 (M
) Zr or Hf) proceeds readily to give [MepyN]M(NMe2)2
complexes in good to excellent yields (eq 2). Proton NMR
60 °C
H2[MepyN] + M(NMe2)4
8
toluene
The solid state structure of [MepyN]Zr(NMe2)Cl is
best described as a distorted octahedron, with the ligand
adopting the C1 geometry depicted in Scheme 1 (Figure
1; Tables 1 and 2). In the observed diastereomer, the
dimethylamide ligand is bound trans to one of the
pyridine donors, while the chloride is bound trans to an
amide. The Zr-N(5) bond length of 2.048(1) Å is within
the expected range for a π-donating amide, as are the
Zr-N(2) and Zr-N(3) distances of 2.091(1) and 2.130-
(1) Å, respectively. The pyridine-zirconium lengths
differ to some degree (2.413(1) vs 2.490(1) Å), as might
be expected from the asymmetric binding mode of the
ligand. The angles around Zr are consistent with a
distorted octahedral geometry, with the most acute
angles being N(1)-Zr-N(2) (71.91(5)°) and N(3)-Zr-
N(4) (71.14(5)°). The broadened dimethylamido reso-
nance is probably the consequence of hindered rotation
about the Zr-N(5) bond. The structure of [MepyN]-
[MepyN]M(NMe2)2 + 2 HNMe2 (2)
spectra of the [MepyN]M(NMe2)2 (M ) Zr, Hf) complexes
are consistent with C2-symmetric structures in solution.
Nine aryl resonances can be observed, while the meth-
ylene protons give rise to an AB pattern centered around
5.15 ppm in benzene-d6. The methyl groups of the
dimethylamide ligands and the pyridine moieties appear
as sharp singlets in a 2:1 ratio, as expected. Two of the
three possible modes of coordination of the diamido
ligand in a [MepyN]MX2 complex (Scheme 1) contain a
(32) Westmoreland, I.; Munslow, I. J.; O’Shaughnessy, P. N.; Scott,
P. Organometallics 2003, 22, 2972.
(33) Knight, P. D.; O’Shaughnessy, P. N.; Munslow, I. J.; Kimberley,
B. S.; Scott, P. J. Organomet. Chem. 2003, 683, 103.
(34) Knight, P. D.; Scott, P. Coord. Chem. Rev. 2003, 242, 125.
(35) Kettunen, M.; Vedder, C.; Schaper, F.; Leskela, M.; Mutikainen,
I.; Brintzinger, H. H. Organometallics 2004, 23, 3800.

Zirconium and Hafnium Dialkyl Complexes
Organometallics, Vol. 24, No. 13, 2005 3337
Scheme 2
Table 1. Crystallographic Data, Collection Parameters, and Refinement Parametersa for
[MepyN]Zr(NMe2)Cl, [MepyN]Hf(OSO2CF3)2, [MepyN]Hf(CH2CHMe2)2, and [MepyN]Zr(CH2Ph)2
[MepyN]Zr(NMe2)Cl
[MepyN]Hf(OSO2CF3)2
[MepyN]Hf(CH2CHMe2)2
[MepyN]Zr(CH2Ph)2
empirical formula
fw
C36H34ClN5Zr
663.366
C36H28F6N4O6S2Hf
969.241
C42H46N4Hf
785.331
C48H42N4Zr
766.098
temperature (K)
cryst syst
194(2)
100(2)
100(2)
194(2)
triclinic
P1h
triclinic
P1h
triclinic
P1h
triclinic
P1h
space group
unit cell dimens
a ) 11.2241(8) Å
b ) 11.9467(8) Å
c ) 14.8348(10) Å
R ) 105.336(1)°
â ) 103.617(1)°
γ ) 103.295(1)°
1771.5(2)
a ) 11.7762(4) Å
b ) 12.9221(4) Å
c ) 17.4473(6) Å
R ) 100.366(1)°
â ) 104.987(1)°
γ ) 112.630(1)°
2247.97(13)
2
a ) 11.228(2) Å
b ) 18.140(4) Å
c ) 20.381(4) Å
R )97.18(3)°
â ) 101.92(3)°
γ ) 90.73(3)°
4026.4(14)
4
a ) 12.3177(4) Å
b ) 13.2063(5) Å
c ) 13.8962(5) Å
R ) 98.643(1)°
â ) 91.127(1)°
γ ) 116.507(1)°
1990.28(12)
2
volume (Å3)
Z
2
density (calcd, g/cm3)
1.390
1.734
1.424
1.311
absorp coeff (mm-1
F(000)b
)
0.424
3.550
2.629
0.316
768
1157
1760
817
cryst size (mm)
0.18 × 0.13 × 0.08
0.25 × 0.15 × 0.15
0.25 × 0.20 × 0.20
0.36 × 0.15 × 0.15
θ range for data collection
(deg)
1.50 to 28.25
1.27 to 26.02
1.63 to 26.02
1.49 to 28.33
index ranges
-12 e h e 14
-15 e k e 11
-17 e l e 19
11 351
7908 [Rint ) 0.0146]
empirical
7908/0/446
1.046
R1 ) 0.0313
wR2 ) 0.0796
R1 ) 0.0354
wR2 ) 0.0822
0.434 and -0.295
-14 e h e 13
-15 e ke 15
0 e l e 21
-13 e h e 13
-22 e k e 22
-24 e l e 25
70 696
15 780 [Rint ) 0.0270]
empirical
15 780/0/955
1.017
R1 ) 0.0268
wR2 ) 0.0703
R1 ) 0.0295
wR2 ) 0.0722
2.231 and -0.659
-16 e h e 14
-10 e k e 17
-18 e l e 18
14 821
9789 [Rint ) 0.0145]
empirical
9789/6/502
1.095
R1 ) 0.0527
wR2 ) 0.1595
R1 ) 0.0584
wR2 ) 0.1654
2.178 and -0.474
no. of reflns collected
no. of indep reflns
absorption corr
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
39 931
8866 [Rint ) 0.0280]
empirical
8866/849/743
1.059
R1 ) 0.0370
wR2 ) 0.0986
R1 ) 0.0389
wR2 ) 0.1002
2.143 and -1.553
R indices (all data)
largest diff peak and hole
(e‚Å-3
)
a Wavelength ) 0.71073 Å; refinement was by full-matrix least squares on F2. b The F(000) values include solvents, one bromobenzene
in the hafnium bistriflate species and one benzene in the hafnium diisobutyl species.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for [MepyN]Zr(NMe2)Cl, [MepyN]Hf(OSO2CF3)2,
[MepyN]Hf(CH2CHMe2)2, and [MepyN]Zr(CH2Ph)2
[MepyN]Zr(NMe2)Cl
[MepyN]Hf(OSO2CF3)2
[MepyN]Hf(CH2CHMe2)2
[MepyN]Zr(CH2Ph)2
Zr-N(1)
2.413(1)
2.091(1)
2.130(1)
2.490(1)
2.048(1)
2.517(1)
112.81(5)
159.36(5)
164.09(6)
80.64(5)
150.75(4)
101.48(4)
71.91(5)
71.14(5)
Hf-N(1)
2.389(4)
Hf-N(1B)
2.391(2)
2.111(2)
2.093(2)
2.435(3)
2.308(3)
2.319(3)
138.69(9)
144.26(9)
72.28(9)
78.56(10)
88.47(10)
145.31(12)
125.4(2)
Zr-N(1)
2.518(2)
2.104(2)
2.111(2)
2.540(2)
2.337(3)
2.311(3)
135.12(8)
154.06(8)
70.62(8)
132.07(11)
83.86(9)
78.00(9)
104.97(18)
Zr-N(2)
Hf-N(2)
2.047(4)
Hf-N(2B)
Zr-N(2)
Zr-N(3)
Hf-N(3)
2.048(4)
Hf-N(3B)
Zr-N(3)
Zr-N(4)
Hf-N(4)
2.418(4)
Hf-N(4B)
Zr-N(4)
Zr-N(5)
Hf-0(1)
2.087(3)
Hf-C(1B)
Zr-C(1)
Zr-Cl(1)
Hf-0(4)
2.093(4)
Hf-C(5B)
Zr-C(8)
N(1)-Zr-N(4)
N(2)-Zr-N(4)
N(1)-Zr-N(5)
N(1)-Zr-N(3)
N(3)-Zr-Cl(1)
N(2)-Zr-Cl(1)
N(2)-Zr-N(1)
N(3)-Zr-N(4)
N(1)-Hf-N(4)
N(2)-Hf-N(4)
N(1)-Hf-N(2)
N(1)-Hf-O(1)
Hf-O(1)-S(1)
N(2)-Hf-O(1)
O(1)-Hf-O(2)
139.76(14)
143.76(14)
72.44(14)
89.23(14)
152.4(2)
N(1B)-Hf-N(4B)
N(2B)-Hf-N(4B)
N(1B)-Hf-N(2B)
N(1B)-Hf-C(1B)
N(1B)-Hf-C(5B)
C(1B)-Hf-C(5B)
Hf-C(1B)-C(2B)
N(1)-Zr-N(4)
N(2)-Zr-N(4)
N(1)-Zr-N(2)
C(1)-Zr-C(8)
N(1)-Zr-C(1)
N(1)-Zr-C(8)
Zr-C(1)-C(2)
94.80(14)
132.54(14)
Zr(NMe2)Cl illustrates that the [MepyN]2- ligand can
adopt a geometry that does not contain trans-disposed
pyridyl ligands, one of three possible coordination
geometries (Scheme 1).
Conversion of [MepyN]Zr(NMe2)2 to [MepyN]ZrCl2
was accomplished by heating [MepyN]Zr(NMe2)2 in
toluene or benzene in the presence of 2 equiv of TMSCl
at 80 °C for 16 h. The resulting dichloride species is

3338 Organometallics, Vol. 24, No. 13, 2005
Tonzetich et al.
Figure 3. Thermal ellipsoid (50%) plot of [MepyN]Hf(CH2-
CHMe2)2 (one of two chemically equivalent molecules in
the asymmetric unit). Hydrogen atoms are omitted for
clarity.
Figure 2. Thermal ellipsoid (50%) plot of [MepyN]Hf-
(OSO2CF3)2. Hydrogen atoms are omitted for clarity.
relatively insoluble in common solvents, even dichlo-
romethane. Proton NMR spectra of the dichloride
complex in CD2Cl2 is consistent with the structure being
C2-symmetric in solution and are overall similar to
spectra of [MepyN]Zr(NMe2)2. Insolubility of [MepyN]-
ZrCl2 hampered efforts to convert it to diakyl complexes
by reaction with Grignard reagents. For example, the
reaction between [MepyN]ZrCl2 and Me2CHCH2MgBr
was only successful when conducted in dichloromethane.
However, the yield was poor and not reproducible, most
likely as a consequence of side reactions involving
dichloromethane.
We thought that problems ascribable to insolubility
of [MepyN]ZrCl2 might be circumvented if [MepyN]Zr-
(OSO2CF3)2 was prepared. Treatment of [MepyN]M-
(NMe2)2 (M ) Zr, Hf) with 2 equiv of trimethylsilyl
triflate in benzene proceeded in less than 10 min at
room temperature to yield white crystalline [MepyN]M-
(OSO2CF3)2 species after crystallization (eq 3). The
bistriflate complexes are soluble in benzene and toluene
at elevated temperatures and readily dissolve in THF
and CH2Cl2. Proton NMR spectra of [MepyN]M(OSO2-
CF3)2 species are highly solvent dependent, but in each
case the spectra are consistent with a C2-symmetric
structure in solution. Upon changing from benzene-d6
solution containing approximately 1 equiv of benzene
per hafnium. Due to partial decomposition of [MepyN]-
Hf(OSO2CF3)2 in bromobenzene, ∼5% of the compound
examined contained a bromide in place of one of the
triflates. This disorder was modeled successfully. (The
reader is directed to the Supporting Information for
more details.) The geometry about Hf is a highly
distorted octahedron, with the ligand adopting a binding
mode that is approximately C2-cis (Scheme 1). The
triflates are bound in an η1 fashion, but the O(1)-Hf-
O(2) angle is only 132.54(14)°. The Hf-Namide and Hf-
Npyridyl bond lengths are similar to those in [MepyN]Zr-
(NMe2)Cl. The highly distorted geometry of [MepyN]-
Hf(OSO2CF3)2 likely results from steric restraints im-
posed by the ligand and is similar to distortions found
in structures of C2-symmetric dialkyl species discussed
below. A search of the Cambridge Structural Database
revealed no other example of a structurally character-
ized hafnium complex that contains one or more triflate
ligands.
Attempts to prepare [MepyN]MMe2 by treating either
[MepyN]MCl2 or [MepyN]M(OSO2CF3)2 with a variety
of methylating agents (AlMe3, MeLi, and Me2Mg) under
different conditions in different solvents met with no
success. We suspect that methyl nucleophiles may
deprotonate the benzyl position of the ligand backbone.
In contrast, alkylation was successful with Me2CHCH2-
MgBr to give [MepyN]M(CH2CHMe2)2 (M ) Zr, Hf)
species. These reactions were found to proceed best in
THF. Proton NMR spectra of the zirconium and hafni-
um isobutyl complexes are almost identical, displaying
resonances consistent with C2 symmetry. The isobutyl
methine proton appears as a multiplet, while the methyl
groups appear as doublets and the methylene protons
as doublets of doublets (see Experimental Section). The
[MepyN]M(CH2CHMe2)2 complexes are readily soluble
in aromatic solvents and THF but insoluble in pentane
and diethyl ether.
23 °C
[MepyN]M(NMe2)2 + 2 TMSOSO2CF3 benzene8
[MepyN]M(OSO2CF3)2 + 2 TMSNMe2 (3)
to CD2Cl2 or THF-d8, resonances for the methylene
protons between the amide and pyridine donor broaden
significantly. Since a solid state structure (see below)
reveals that the triflates are monodentate, we speculate
that the fluxional process may involve bidentate coor-
dination of one or more triflates with (possibly) ac-
companying dissociation of a pyridine donor. Solution
IR studies did not support the possibility that a triflate
is lost in polar solvents to yield a cationic species. In
all solvents resonances for the hafnium complex broaden
to a greater degree than those for the zirconium species.
The solid state structure of [MepyN]Hf(OSO2CF3)2
was determined by X-ray diffraction (Figure 2; Tables
1 and 2). Crystals of the triflate complex were grown
by vapor diffusion of pentane into a bromobenzene
The structure of [MepyN]Hf(CH2CHMe2)2 was deter-
mined in an X-ray study (Figure 3, Tables 1 and 2). The
compound crystallizes with both enantiomers in the
asymmetric unit, but only one molecule is shown in
Figure 3 and listed in Table 2. Like [MepyN]Hf(OSO2-

Zirconium and Hafnium Dialkyl Complexes
Organometallics, Vol. 24, No. 13, 2005 3339
{Ph3C}{B(C6F5)4}
[MepyN]M(CH2CHMe2)2 -Ph CH - Me CdCH 8
3
2
2
{[MepyN]M(CH2CHMe2)}{B(C6F5)4} (5)
[MepyN]M(CH2CHMe2)2 {HNMe2Ph}{B(C6F5)4}8
-Me2NPh - Me3CH
{[MepyN]M(CH2CHMe2)}{B(C6F5)4} (6)
The resonances for the isobutyl ligand are shifted
upfield with one of the methylene protons of {[MepyN]-
Hf(CH2CHMe2)}{HB(C6F5)3} appearing at -1.23 ppm
in bromobenzene-d5. An R-agostic interaction is unlikely,
however, as the methylene resonances remain sharp in
bromobenzene-d5 with splitting patterns similar to those
in the neutral dialkyl.
Treatment of any of these species with excess 1-hex-
ene yielded no detectable poly[1-hexene] at either room
temperature or 60 °C. Solutions were unchanged for
several days at room temperature, although at elevated
temperature decompositions to yield some isobutene and
unidentifiable metal-containing product(s) were ob-
served after several hours.
Figure 4. Thermal ellipsoid (50%) plot of [MepyN]Zr(CH2-
Ph)2. Hydrogen atoms are omitted for clarity.
CF3)2, [MepyN]Hf(CH2CHMe2)2 is a highly distorted
octahedron with the ligand again adopting the C2-cis
orientation shown in Scheme 1. The bond lengths and
angles for the [MepyN]2- ligand are very similar to those
of the triflate species. The isobutyl ligands are ap-
proximately trans to one another (C(1B)-Hf-C(5B) )
145.31(12)°) with relatively long Hf-C bond lengths
(Hf-C(1B) ) 2.308(3) Å; Hf-C(5B) ) 2.319(3) Å), as
expected in a relatively crowded six-coordinate complex.
An alternative approach to dialkyl complexes consists
of ligand addition to tetraalkyls. Reaction of H2[MepyN]
with Zr(CH2CMe3)4 did not lead to any observable
[MepyN]Zr(CH2CMe3)2, even upon heating. At room
temperature, no reaction was observed, and at elevated
temperatures only decomposition of the tetraalkyl was
observed. However, a reaction between H2[MepyN] and
Zr(CH2Ph)4 produced [MepyN]Zr(CH2Ph)2 in good yield
as a yellow-orange crystalline solid. The benzyl complex
is considerably less soluble than [MepyN]Zr(CH2-
CHMe2)2, although it dissolves readily in dichlo-
romethane. The spectral features of [MepyN]Zr(CH2Ph)2
are similar to those for [MepyN]Zr(CH2CHMe2)2, with
the benzyl methylene resonances appearing as a set of
doublets at 2.26 and 1.89 ppm in CD2Cl2. The benzyl
resonances appear at relatively low field, with the ortho
proton resonance appearing at 5.63 ppm. The solid state
structure of [MepyN]Zr(CH2Ph)2 (Figure 4; Tables 1 and
2) shows it to be similar to the isobutyl and bistriflate
structures discussed earlier. The ligand once again
adopts the C2-cis structure shown in Scheme 1. The
Zr-C bond lengths and Zr-C-C angles (Table 2) are
not consistent with any tendency of a benzyl group to
bond in an η2 fashion.
A reaction between [MepyN]Zr(CH2Ph)2 and {HNMe2-
Ph}{B(C6F5)4} in CD2Cl2 at -30 °C or room temperature
occurs quantitatively in seconds. The proton NMR
spectrum of the activated species shows resonances
consistent with formation of a C1-symmetric species,
along with those for dimethylaniline. However, no
toluene is formed, while resonances attributable to two
benzyl ligands are observed. The proton resonances of
the ligand backbone resemble those of the isobutyl
cation except for the resonances due to the methylene
groups between the amido nitrogens and the pyridine
moieties. Unlike the isobutyl cation, only three doublets
are apparent in the range 3-4 ppm, instead of the
expected four. Additionally, a doublet of doublets ap-
pears at 2.79 ppm; this type of resonance is not observed
in any species discussed so far. The gCOSY spectrum
shows a cross-peak between the resonance at 2.79 ppm
and a doublet resonance at 5.63 ppm, with an H-H
coupling constant of 7.5 Hz, consistent with a three-
bond separation. This feature, along with the presence
of two benzyl groups, points toward formulation of the
species as one that results from protonation of an amido
nitrogen, as shown in Scheme 3. As one would expect,
this cationic species is not a catalyst for polymerization
of 1-hexene.
In a similar experiment, [MepyN]Zr(CH2Ph)2 was
treated with {HNMe2Ph}Cl in CD2Cl2; free dimethyla-
niline and toluene were observed, along with a mixture
of [MepyN]Zr(CH2Ph)2, [MepyN]ZrCl2, and [MepyN]-
Zr(CH2Ph)Cl. We cannot rule out prior protonation of
the amide followed by proton transfer to benzyl. How-
ever, the anilinium chloride is not consumed immedi-
ately, and monitoring of the reaction mixture does not
reveal any intermediate species similar to the one
discussed in the preceding paragraph. Solutions of
[MepyN]Zr(CH2Ph)2 activated with {HNMe2Ph}{B-
(C6F5)4} do not yield any monobenzyl cation over a
period of days, even at elevated temperatures. This
result is somewhat surprising considering the observed
tendency for anilinium chloride to protonate the benzyl
ligand, and also the possibility that uncoordinated
dimethylaniline could move a proton between different
Activation of [MepyN]M(CH2CHMe2)2 with B(C6F5)3,
{HNMe2Ph}{B(C6F5)4}, or {Ph3C}{B(C6F5)4} in toluene,
benzene, or bromobenzene gave rise in each case to a
monoisobutyl cation with concomitant formation of the
expected byproducts (eqs 4-6). NMR spectra of the
B(C6F5)3
[MepyN]M(CH2CHMe2)2 -Me CdCH 8
2
2
{[MepyN]M(CH2CHMe2)}{HB(C6F5)3} (4)
cation show the expected asymmetry, with individual
resonances visible for each of the protons of the ligand.

3340 Organometallics, Vol. 24, No. 13, 2005
Tonzetich et al.
Scheme 3
in our laboratory form at least a weak adduct with Me2-
NPh.) Addition of 1-hexene to the benzyl cation failed
to give any detectable poly[1-hexene].
Conclusion
The chemistry of six-coordinate zirconium and hafni-
um complexes of the [MepyN]2- ligand offer an op-
portunity to examine the reactivity of coordinatively
more saturated species with well-defined activators such
as boranes, carbocations, and proton sources. Activation
of dialkyl species, especially [MepyN]M(CH2CHMe2)2,
gives rise to asymmetric, cationic, monoalkyl complexes
that are readily observable by standard NMR tech-
niques. However, these species will not polymerize
1-hexene. The absence of catalytic activity with these
complexes can be ascribed to both their high coordina-
tion number and the presence of a sterically encumber-
ing diamidodipyridine ligand which serves to both
decrease the Lewis acidity at the metal and hinder olefin
approach and binding.
parts of the complex. These observations may be rel-
evant to studies concerning the dibenzyl species re-
ported by Brintzinger, which was inactive toward
propene polymerization when activated with anilinium
borate.35
Treatment of [MepyN]Zr(CH2Ph)2 with strong Lewis
acids does lead to a monobenzyl cation. Reaction of
[MepyN]Zr(CH2Ph)2 with B(C6F5)3 or trityl in CD2Cl2
proceeds to yield the monobenzyl cation cleanly, which
can be observed spectroscopically (eqs 7 and 8).
Experimental Section
General Comments. All manipulations of air- and moisture-
sensitive materials were performed in oven-dried (200 °C)
glassware under an atmosphere of nitrogen on a dual-manifold
Schlenk line or in a Vacuum Atmospheres glovebox. NMR
measurements were carried out in Teflon-valve sealed J.
Young-type NMR tubes. HPLC grade organic solvents were
sparged with nitrogen and dried by passage through activated
alumina (for diethyl ether, toluene, pentane, THF, and meth-
ylene chloride) followed by passage through Q-5 supported
copper catalyst (for benzene) prior to use, then stored over 4
Å Linde-type molecular sieves. Benzene-d6, toluene-d8, and
THF-d8 were dried over sodium/benzophenone ketyl and
vacuum-distilled. Methylene chloride-d2 and bromobenzene-
d5 were dried over CaH2, vacuum distilled, and stored over 4
Å Linde-type molecular sieves. NMR spectra were recorded
on a Varian 500 or Varian 300 spectrometer. Chemical shifts
B(C6F5)3
[MepyN]Zr(CH2Ph)2
8
{[MepyN]Zr(CH2Ph)}{PhCH2B(C6F5)3} (7)
[MepyN]Zr(CH2Ph)2 {Ph3C}{B(C6F5)4}8
-PhCH2CPh
{[MepyN]Zr(CH2Ph)}{B(C6F5)4} (8)
The room-temperature proton NMR spectrum of the
benzyl cation shows a broadened ligand environment
that remains C2-symmetric, as judged from the presence
of a broadened singlet for the pyridine methyl reso-
nances. Resonances for the methylene protons of the
benzyl ligand appear at 1.53 ppm (sharp doublet) and
0.02 ppm (broad doublet). The aryl protons of the benzyl
ligand also remain sharp, as do the peaks corresponding
to the PhCH2B(C6F5)3 anion in the case of activation
with B(C6F5)3. To further elucidate the nature of the
1
1
for H and 13C spectra were referenced to the residual H/13C
resonances of the deuterated solvent (1H: C6D6, δ 7.16; C6D5-
CD3, δ 2.15; CD2Cl2, δ 5.32; C6D5Br, δ 7.29; 13C: C6D6, δ 128.39;
CD2Cl2, δ 54.00) and are reported as parts per million relative
to tetramethylsilane. 19F NMR spectra were referenced exter-
nally to fluorobenzene (δ -113.15 ppm upfield of CFCl3). High-
resolution mass spectrometry measurements were performed
at the MIT Department of Chemistry Instrument Facility, and
elemental analyses were performed by H. Kolbe Microanalytics
Laboratory, Mu¨lheim an der Ruhr, Germany.
1
benzyl cation, the H NMR spectrum was recorded at
temperatures down to -70 °C. Upon decreasing the
temperature, the resonances of the ligand environment
sharpen consistently until at -70 °C they appear in
positions close to those observed in the isobutyl cation.
At this temperature, two singlets of area three are
observed for the pyridine methyl groups, as are four
doublets of area one for each of the methylene protons
of the ligand. The resonances for the methylene protons
of the benzyl group broaden upon decreasing in tem-
perature, then sharpen at -70 °C and appear as a set
2,2′-Diamino-1,1′-binaphthalene,36 Zr(NMe2)4,37 Zr(CH2-
Ph)4,38 Hf(NMe2)4,37 and {HNMe2Ph}{B(C6F5)4}39 were pre-
pared according to published procedures, or slightly modified
versions thereof. 6-Methyl-2-pyridinecarboxaldehyde, TMSCl,
and i-BuMgBr were purchased from Aldrich Chemical Co. and
used as received. Tris(pentafluorophenyl)borane and trimeth-
ylsilyl trifluoromethanesulfonate (TMSOTf) were purchased
from Strem Chemical Co. and used as received. Trityl tetrakis-
(pentafluorophenyl)borate, {Ph3C}{B(C6F5)4}, was obtained as
a gift from the Exxon Mobile Corp. and used as received.
Crystallography. Low-temperature diffraction data were
collected on a Siemens Platform three-circle diffractometer
2
of doublets of area one with a JH-H of 12.5 Hz. One of
the methylene protons is significantly shifted upfield
(-0.54 ppm), while the other shifts slightly to 1.44 ppm
(CD2Cl2).
Addition of dimethylaniline to solutions of the benzyl
cation at room temperature did not reveal any tendency
for the cation to form a dimethylaniline adduct. (Zirco-
nium and hafnium alkyl cations that show activity
toward 1-hexene polymerization that have been studied
(36) Brown, K. J.; Berry, M. S.; Murdoch, J. R. J. Org. Chem. 1985,
50, 4345.
(37) Diamond, G. M.; Jordan, R. F.; Petersen, J. L. Organometallics
1996, 15, 4030.
(38) Zucchini, U.; Albizzati, E.; Giannini, U. J. Organomet. Chem.
1971, 26, 357.
(39) Tjaden, E. B.; Swenson, D. C.; Jordan, R. F. Organometallics
1995, 14, 371.

Zirconium and Hafnium Dialkyl Complexes
Organometallics, Vol. 24, No. 13, 2005 3341
coupled to a Bruker-AXS Smart 1K CCD detector or a Bruker-
AXS Apex CCD detector with graphite-monochromated Mo KR
radiation (λ ) 0.71073 Å), performing æ- and ω-scans. All
structures were solved by direct methods using SHELXS40 and
refined against F2 on all data by full-matrix least squares with
SHELXL-97 (Sheldrick, G. M. SHELXL 97, Universita¨t Go¨t-
tingen, Go¨ttingen, Germany, 1997). All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were included
in the model at geometrically calculated positions and refined
using a riding model. The isotropic displacement parameters
of the hydrogen atoms were fixed to 1.2 times the U value of
the atoms they are linked to (1.5 times for methyl groups).
The disorders in the structures of [MepyN]Hf(OSO2CF3)2 and
[MepyN]Zr(CH2Ph)2 were refined with the help of similarity
restraints on 1-2 and 1-3 distances and displacement pa-
rameters as well as rigid bond restraints for anisotropic
displacement parameters. The occupancies for the disordered
parts in these two structures were refined freely.
1-(2-((6-Methylpyridin-2-yl)methylamino)naphthalen-
1-yl)-N-((6-methylpyridin-2-yl)methyl)naphthalen-2-
amine. H2[MepyN]. A two-neck round-bottom flask was
charged with 5.71 g (20.1 mmol) of 2,2′-diamino-1,1′-binaph-
thalene, a magnetic stirbar, and 50 mL of absolute ethanol.
The flask was fitted with a reflux condenser and a pressure-
equalizing addition funnel. To the addition funnel was added
a solution of 5.61 g (46.3 mmol) of 6-methyl-2-pyridinecarbox-
aldehyde in 20 mL of absolute ethanol. The solution of the
pyridine was added dropwise to the suspension of the diamine
and then heated at reflux under nitrogen for 90 min, during
which time the reaction mixture became a golden yellow
solution. The reaction was allowed to cool, and the volatiles
were removed in vacuo. An additional 150 mL of absolute
ethanol was added, as was 2.28 g (60.3 mmol) of NaBH4. The
reaction was heated again under nitrogen at reflux for 20 h.
The reaction was cooled to room temperature and quenched
by pouring onto 5 g of NH4Cl. The ethanol was removed in
vacuo and the resulting residue dissolved in methylene
chloride, washed three times with 100 mL of water, dried over
MgSO4, and filtered through Celite. The methylene chloride
was removed in vacuo and the resulting amber residue
dissolved in a minimal amount of hot toluene. Pentane was
added until the solution became slightly turbid and was then
set aside at -40 °C for 24 h, during which time H2[MepyN]
precipitated as off-white crystals. The compound was further
purified by repeated crystallization from toluene/pentane; yield
8.13 g (82%): 1H NMR (C6D6) δ 7.72 (t, 4 ArH), 7.40 (d, 2 ArH),
7.19 (d, 2 ArH), 7.10 (m, 4 ArH), 6.93 (t, 2 ArH), 6.82 (d, 2
ArH), 6.49 (d, 2 ArH), 4.87 (t, 2 NH), 4.15 (m, 4 CH2), 2.27 (s,
6 pyMe); 13C{1H} NMR (C6D6) δ 159.45, 158.206, 144.95,
136.66, 135.18, 130.38, 128.99, 128.76, 127.53, 124.93, 122.65,
121.33, 118.10, 114.85, 113.10, 49.39 (CH2), 24.67 (pyMe);
HRMS calcd [M + H]+ 495.2543, found [M + H]+ 495.2551.
Anal. Calcd for C34H30N4: C, 82.56; H, 6.11; N, 11.33. Found:
C, 82.65; H, 6.04; N, 11.37.
[MepyN]Zr(NMe2)Cl. This compound was prepared in an
analogous fashion to [MepyN]Zr(NMe2)2 starting with ligand
that contained approximately one-third of an equivalent of
chloroform (65% yield, on ∼1 g scale): 1H NMR (C6D6) δ 7.99
(d, 1 ArH), 7.90 (d, 1 ArH), 7.78 (d, 1 ArH), 7.55 (d, 1 ArH),
7.52 (d, 1 ArH), 7.31 (d, 1 ArH), 7.15 (t, 2 ArH), 7.05 (t, 1 ArH),
7.00 (t, 1 ArH), 6.90 (t, 1 ArH), 6.81 (t, 2 ArH), 6.51 (t, 1 ArH),
6.42 (d, 2 ArH), 6.28 (d, 1 ArH), 5.54 (d, 1 ArH), 5.36 (d, 1
CH2, 2JH-H ) 20.0 Hz), 4.98 (d, 1 CH2, 2JH-H ) 19.0 Hz), 4.49
(d, 1 CH2), 3.88 (d, 1 CH2), 2.95 (s, 3 pyMe), 2.59 (br s, 6 NMe2),
2.35 (s, 3 pyMe). Anal. Calcd for C36H34N5ClZr: C, 65.18; H,
5.17; N, 10.56; Cl, 5.34. Found: C, 65.26; H, 5.24; N, 10.44;
Cl, 5.25.
Crystals suitable for X-ray diffraction were grown by vapor
diffusion of pentane into a saturated benzene solution.
[MepyN]ZrCl2. A solution of 0.900 g (1.36 mmol) of [Me-
pyN]Zr(NMe2)2 in 50 mL of toluene was treated with 0.38 mL
(3.0 mmol) of TMSCl. The solution was heated to 80 °C and
stirred for 24 h, during which time an off-white powder
precipitated from solution. The material was collected by
filtration, washed with pentane, and dried in vacuo; yield 0.759
g (85%): 1H NMR (CD2Cl2) δ 7.83 (m, 4 ArH), 7.68 (t, 2 ArH),
7.51 (d, 2 ArH), 7.34 (t, 2 ArH), 7.21 (m, 6 ArH), 7.04 (d, 2
2
ArH), 5.14 (d, 2 CH2, JH-H ) 20.5 Hz), 4.73 (d, 2 CH2), 2.99
(s, 6 pyMe).
[MepyN]Zr(OSO2CF3)2. A solution of 1.052 g (1.57 mmol)
of [MepyN]Zr(NMe2)2 in 50 mL of benzene was treated with
0.70 mL (3.6 mmol) of TMSOTf. The yellow solution was
stirred at room temperature for 60 min, during which time
the color became lighter. The solution was layered with several
volumes of pentane and allowed to stand for 16 h, over which
time the compound precipitated as white microcrystals. NMR
spectra showed the presence of 1 equiv of benzene, which was
confirmed by analysis; yield 0.968 g (68%): 1H NMR (C6D6) δ
8.15 (d, 2 ArH), 7.78 (d, 2 ArH), 7.63 (d, 2 ArH), 7.55 (d, 2
ArH), 7.15 (t, 2 ArH), 7.04 (t, 2 ArH), 6.52 (t, 2 ArH), 6.24 (d,
2 ArH), 5.75 (d, 2 ArH), 5.10 (d, 2 CH2, 2JH-H ) 20.5 Hz), 4.23
(d, 2 CH2), 2.85 (s, 6 pyMe); 19F NMR (C6D6) δ -77.42 (s,
OSO2CF3). Anal. Calcd for C42H34N4F6O6S2Zr: C, 52.54; H,
3.57; N, 5.84. Found: C, 52.33; H, 3.70; N, 5.62.
[MepyN]Zr(CH2C6H5)2. A reaction vessel was charged with
0.616 g (1.24 mmol) of H2[MepyN] and 0.544 g (1.19 mmol) of
Zr(CH2Ph)4. Benzene (35 mL) was added, and the resulting
orange solution was allowed to stand at room temperature for
20 h. Pentane was added until the solution became turbid. The
product precipitated from solution as orange microcrystals over
several hours at room temperature; yield 0.675 g (74%): 1H
NMR (CD2Cl2) δ 7.83 (app t, 4 ArH), 7.54 (t, 2 ArH), 7.41 (d,
2 ArH), 7.28 (t, 2 ArH), 7.13 (m, 4 ArH), 7.06 (d, 2 ArH), 6.78
(d, 2 ArH), 6.13 (m, m and p Bn), 5.63 (d, 4 o Bn), 4.75 (d, 2
2
CH2, JH-H ) 20.0 Hz), 4.12 (d, 2 CH2), 2.94 (s, 6 pyMe), 2.26
(d, 2 CH2Ph, 2JH-H ) 10.0 Hz), 1.89 (d, 2 CH2Ph); 13C{1H} NMR
(CD2Cl2) δ 163.65, 156.87, 153.67, 148.92, 137.92, 134.51,
130.60, 128.46, 128.17, 127.82, 127.31, 126.80, 126.07, 125.67,
124.86, 123.61, 123.31, 119.27, 119.13, 66.58, 61.68, 26.00
(pyMe). Anal. Calcd for C48H42N4Zr: C, 75.25; H, 5.53; N, 7.31.
Found: C, 75.18; H, 5.46; N, 7.22.
[MepyN]Zr(NMe2)2. To 1.012 g (2.05 mmol) of H2[MepyN]
dissolved in 30 mL of toluene was added a solution of 0.547 g
(2.04 mmol) of Zr(NMe2)4 in 10 mL of toluene. The solution
was heated to 50 °C and stirred for 20 h, during which time it
became golden yellow. The toluene was concentrated in vacuo
to ∼10 mL, and several volumes of pentane were added. The
solution was set aside at -25 °C for several hours, during
which time yellow microcrystals precipitated. The crystals
were isolated by filtration, washed with pentane, and dried
in vacuo; yield 1.343 g (98%): 1H NMR (C6D6) δ 7.80 (d, 2 ArH),
7.70 (d, 2 ArH), 7.57 (d, 2 ArH), 7.04 (t, 2 ArH), 6.85 (t, 2 ArH),
6.68 (t, 2 ArH), 6.48 (d, 2 ArH), 6.36 (d, 2 ArH), 5.35 (d, 2 CH2,
2JH-H ) 18.0 Hz), 5.05 (d, 2 CH2), 2.51 (s, 12 NMe2), 2.26 (s, 6
pyMe). Anal. Calcd for C38H40N6Zr: C, 67.92; H, 6.00; N, 12.51.
Found: C, 67.84; H, 6.09; N, 12.38.
Crystals suitable for X-ray diffraction were grown by vapor
diffusion of pentane into a saturated methylene chloride
solution.
[MepyN]Zr(CH2CHMe2)2. A flask was charged with 0.148
g (0.226 mmol) of [MepyN]ZrCl2, and 15 mL of CH2Cl2 was
added. The suspension was cooled to -25 °C. Once cool, 0.24
mL of (0.58 mmol) i-BuMgBr (2.4 M in Et2O) was added
dropwise over the stirring suspension. The reaction was
allowed to stir for 10 min at room temperature, during which
time it became yellow-orange. 1,4-Dioxane (0.15 mL) was
added, at which point a white precipitate formed. The reaction
was filtered through Celite and the volatiles were removed in
vacuo. The resulting orange residue was dissolved in 2 mL of
toluene, and several volumes of pentane were added. The
(40) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467.

3342 Organometallics, Vol. 24, No. 13, 2005
Tonzetich et al.
solution was set aside at -25 °C for several hours, during
which time an orange microcrystalline material precipitated.
The material was collected by filtration, washed with pentane,
and dried in vacuo; yield 70 mg (44%, not optimized): 1H NMR
(C6D6) δ 7.83 (d, 2 ArH), 7.78 (d, 2 ArH), 7.61 (d, 2 ArH), 7.58
(d, 2 ArH), 7.17 (t, 2 ArH), 7.06 (t, 2 ArH), 6.85 (t, 2 ArH),
{[MepyN]Zr(CH2CH(CH3)2)}{HB(C6F5)3}. This species
was observed spectroscopically by mixing equimolar amounts
of [MepyN]Zr(CH2CH(CH3)2)2 and B(C6F5)3 in benzene-d6 at
1
room temperature. H NMR (20 °C): δ 8.05 (d, 1 ArH), 7.75
(d, 1 ArH), 7.55 (d, 1 ArH), 7.46 (d, 1 ArH), 7.26 (d, 1 ArH),
7.22 (d, 1 ArH), 7.18 (app t, 2 ArH), 7.01 (m, 3 ArH), 6.89 (m,
2 ArH), 6.84 (d, 1 ArH), 6.56 (m, 4 ArH), 5.17 (d, 1 CH2), 4.97
(d, 1 CH2), 4.51 (d, 1 CH2), 4.24 (d, 1 CH2), 1.56 (br s, 3 pyMe),
1.40 (s, 3 pyMe), 0.37 (m, 1 CH2CHMe2), 0.129 (d, 3 CH2-
CHMeMe), -0.12 (dd, 1 CHHCHMe2), -0.45 (br d, 3 CH2-
CHMeMe), -1.01 (br m, 1 CHHCHMe2); 19F NMR δ -132.71
(d, o-ArF), -163.97 (t, p-ArF), -166.81 (t, m-ArF).
{[MepyN]Hf(CH2CH(CH3)2)}{A}. This species was ob-
served spectroscopically by mixing equimolar amounts of
[MepyN]Hf(CH2CH(CH3)2)2 and B(C6F5)3, {Ph3C}{B(C6F5)4}, or
{HNMe2Ph}{B(C6F5)4} in bromobenzene-d5 at room temper-
ature. The 1H NMR (20 °C) shifts for the cation formed by
activation with B(C6F5)3 are as follows: δ 8.13 (d, 1 ArH), 7.89
(d, 1 ArH), 7.67 (d, 1 ArH), 7.56 (d, 1 ArH), 7.47 (t, 1 ArH),
7.35 (m, 2 ArH), 7.15 (m, 5 ArH), 7.03 (m, 3 ArH), 6.81 (d, 1
ArH), 6.75 (d, 1 ArH), 6.38 (d, 1 ArH), 5.61 (d, 1 CH2), 5.20 (d,
1 CH2), 4.93 (d, 1 CH2), 4.58 (d, 1 CH2), 1.71 (s, 3 pyMe), 1.57
(s, 3 pyMe), 0.39 (m, 1 CH2CHCMe2), 0.10 (d, 3 CH2CHMeMe),
-0.21 (dd, 1 CHHCHMe2), -0.53 (d, 3 CH2CHMeMe), -1.23
(dd, 1 CHHCHMe2).
2
6.49 (d, 2 ArH), 6.39 (d, 2 ArH), 5.04 (d, CH2, JH-H ) 20.5
Hz), 4.83 (d, CH2), 2.81 (s, 6 pyMe), 1.24 (m, CHHCHMe2), 0.78
(d, CH2CHMeMe), 0.55 (dd, CHHCHMe2), 0.41 (d, CH2-
CHMeMe). Anal. Calcd for C42H46N4Zr: C, 72.26; H, 6.64; N,
8.03. Found: C, 72.14; H, 6.57; N, 7.94.
[MepyN]Hf(NMe2)2. This compound was prepared in a
fashion similar to that for [MepyN]Zr(NMe2)2 starting from
1.001 g (2.02 mmol) of H2[MepyN] and 0.720 g (2.03 mmol) of
Hf(NMe2)4, except that it required heating at 60 °C for 48 h;
yield 1.178 g (77%): 1H NMR (C7D8) δ 7.77 (d, 2 ArH), 7.66 (d,
2 ArH), 7.59 (d, 2 ArH), 7.03 (t, 2 ArH), 6.99 (d, 2 ArH), 6.81
(t, 2 ArH), 6.62 (t, 2 ArH), 6.34 (app d, 4 ArH), 5.32 (d, 2 CH2,
2JH-H ) 17.5 Hz), 5.01 (d, 2 CH2), 2.60 (s, 12 NMe2), 2.28 (s, 6
pyMe); 13C{1H} NMR (CD2Cl2) δ 163.86, 158.18, 152.60, 137.29,
135.69, 129.66, 128.61, 127.82, 127.41, 125,64, 125.54, 122.74,
122.56, 121.97, 119.06, 61.40 (CH2), 41.26 (NMe2), 23.77
(pyMe). Anal. Calcd for C38H40N6Hf: C, 60.11; H, 5.31; N,
11.07. Found: C, 60.15; H, 5.40; N, 10.97.
[MepyN]Hf(OSO2CF3)2. This compound was prepared in
a manner analogous to that used to prepare [MepyN]Zr(OSO2-
CF3)2 starting from 1.128 g (1.49 mmol) of [MepyN]Hf(NMe2)2
and 0.60 mL (3.1 mmol) of TMSOTf. One equivalent of benzene
was present, as judged by NMR/analysis; yield 1.148 g (74%):
1H NMR (C6D6) δ 7.90 (br s, 2 ArH), 7.79 (d, 2 ArH), 7.66 (d,
2 ArH), 7.49 (d, 2 ArH), 7.16 (t, 2 ArH), 7.04 (t, 2 ArH), 6.59
(t, 2 ArH), 6.29 (d, 2 ArH), 5.84 (br d, 2 ArH), 5.32 (d, CH2,
2JH-H ) 19.5 Hz), 4.43 (br d, 2 CH2), 2.77 (br s, 6 pyMe); 13C{H}
NMR (CD2Cl2) δ 164.53, 140.63, 134.04, 131.87, 129.85, 128.84,
127.54, 126.43, 125.51, 125.12, 124.75, 120.21, 199.68 (q,
{[MepyNNH]Zr(CH2C6H5)2}{B(C6F5)4}. This species has
been observed spectroscopically by mixing equimolar amounts
of [MepyN]Zr(CH2C6H5)2 and {HNMe2Ph}{B(C6F5)4} in meth-
ylene chloride-d2 at -25 °C followed by warming to room
temperature. 1H NMR (20 °C): δ 8.30 (d, 1 ArH), 8.11 (t, 1
ArH), 8.07 (d, 1 ArH), 7.72 (d, 1 ArH), 7.68 (d, 1 ArH), 7.60
(app t, 3 ArH), 7.56 (t, 1 ArH), 7.51 (t, 1 ArH), 7.42 (d, 1 ArH),
7.34 (d, 1 ArH), 7.28 (m, 3 ArH), 7.23 (m, 2 ArH), 7.18 (d, 1
ArH), 7.05 (d, 1 ArH), 6.73 (m, 4 ArH), 6.23 (t, 1 CH2Ph), 5.93
3
(t, 2 CH2Ph), 5.63 (d, NH, JH-H ) 7.5 Hz), 5.03 (d, 1 CH2),
1
OSO2CF3, JC-F ) 318 Hz), 62.66 (br, CH2), 23.64 (br, pyMe).
4.74 (d, 2 CH2Ph), 4.21 (d, 1 CH2), 4.14 (d, 1 CH2), 3.44 (s, 3
pyMe), 3.11 (d, 1 CH2Ph), 2.98 (s, 3 pyMe), 2.79 (dd, CH2), 2.71
(d, 1 CH2Ph), 2.51 (d, 1 CH2Ph), 1.41 (d, 1 CH2Ph); 19F NMR
δ -131.36 (d, o-ArF), -161.90 (t, p-ArF), -165.75 (t, m-ArF).
Three of the aromatic carbon peaks could not be unambigu-
ously assigned; however, three very broad peaks appear in the
spectrum between 120 and 160 ppm. 19F NMR (CD2Cl2) δ
-78.09 (s, OSO2CF3). Anal. Calcd for C42H34N4F6O6S2Hf: C,
48.16; H, 3.27; N, 5.35. Found: C, 48.59; H, 3.36; N, 5.10.
Crystals suitable for X-ray diffraction were grown by vapor
diffusion of pentane into a concentrated bromobenzene solu-
tion.
{[MepyN]Zr(CH2C6H5)}{A}. This species was observed
spectroscopically by mixing equimolar amounts of [MepyN]-
Zr(CH2C6H5)2 and {Ph3C}{B(C6F5)4} or B(C6F5)3 in methylene
chloride-d2 at -25 °C followed by warming to room tempera-
1
ture. The H NMR (-70 °C) shifts for the complex formed by
[MepyN]Hf(CH2CHMe2)2. A flask was charged with 0.923
g (0.881 mmol) of [MepyN]Hf(OSO2CF3)2‚(C6H6) and 30 mL of
THF. The solution was chilled to -25 °C, at which point 0.82
mL (1.8 mmol) of Me2CHCH2MgBr was added dropwise. A
precipitate formed immediately upon addition of Grignard. The
mixture was allowed to stir at room temperature for 60 min.
The THF was removed in vacuo and the residue extracted into
toluene and filtered through Celite. The toluene solution was
concentrated to ∼10 mL, layered with several volumes of
pentane, and set aside at -25 °C for several days, during which
time pale yellow crystals formed. The compound could be
further purified by multiple recrystallizations from toluene/
pentane; yield 0.443 g (64%): 1H NMR (C6D6) δ 7.85 (d, 2 ArH),
7.79 (d, 2 ArH), 7.63 (d, 2 ArH), 7.57 (d, 2 ArH), 7.18 (t, 2 ArH),
7.07 (d, 2 ArH), 6.85 (t, ArH), 6.47 (d, 2 ArH), 6.38 (d, 2 ArH),
activation with B(C6F5)3 are as follows: δ 8.44 (d, 1 ArH), 7.95
(m, 3 ArH), 7.70 (m, 6 ArH), 7.41 (d, 1 ArH), 7.24 (m, 6 ArH),
7.12 (t, 1 ArH), 6.89 (t, 2 m-ArH of anion), 6.82 (t, p-ArH of
anion), 6.66 (d, 2 o-ArH of anion), 6.32 (m, m/p-PhCH2), 5.75
(d, 1 CH2), 5.66 (d, 1 CH2), 5.46 (d, o-PhCH2), 5.33 (d, 1 CH2),
5.03 (d, 1 CH2), 2.73 (s, CH2 of anion), 1.81 (s, 3 pyMe), 1.73
2
(s, 3 pyMe), 1.44 (d, CHHPh, JH-H ) 12.5 Hz), -0.56 (d,
CHHPh).
Acknowledgment. R.R.S. thanks the Department
of Energy (DE-FG02-86ER13564) for research support
and Z.J.T. thanks the National Science Foundation for
a predoctoral fellowship.
2
5.16 (d, CH2, JH-H ) 20.5 Hz), 4.86 (d, CH2), 2.79 (s, pyMe),
Supporting Information Available: Experimental de-
tails, labeled thermal ellipsoid drawings, crystal data and
structure refinement, atomic coordinates, bond lengths and
angles, anisotropic displacement parameters, and hydrogen
coordinates and isotropic displacement parameters for [MepyN]-
Zr(CH2Ph)2, [MepyN]Zr(NMe2)Cl, [MepyN]Hf(CH2CHMe2)2,
and [MepyN]Hf(OSO2CF3)2. This material is available free of
charge via the Internet at http://pubs.acs.org.
1.25 (m, 2 CH2CHMe2), 1.01 (dd, 2 CHHCHMe2), 0.84 (d, 6
CH2CHMeMe), 0.39 (d, 6 CH2CHMeMe), 0.37 (dd, CHH-
CHMe2); 13C{H} NMR (CD2Cl2) δ 164.09, 158.03, 153.65,
138.02, 134.26, 130.42, 128.06, 127.90, 127.84, 127.15, 126.95,
125.32, 123.61, 123.35, 119.13, 78.64, 66.81, 31.73, 30.50,
26.44, 25.86. Anal. Calcd for C42H46N4Hf: C, 64.23; H, 5.90;
N, 7.13. Found: C, 64.18; H, 5.86; N, 7.05.
Crystals suitable for X-ray diffraction were grown by vapor
diffusion of pentane into a concentrated benzene solution.
OM058007I