(Amidomethyl)pyridine zirconium and hafnium complexes: Synthesis and structural characterization

Article abstract of DOI:10.1016/j.jorganchem.2007.12.004

A series of 2-formyl and 2-acetylpyridines was condensed with 2,6-diisopropylaniline to yield the corresponding imines. Their reaction with sodium borohydride gave the respective N-arylaminomethylpyridines. Treatment of the N-arylformimino- or -acetiminopyridines with trimethylaluminum followed by hydrolysis furnished a series of the respective substituted N-arylaminoethylpyridine derivatives. Their reaction with tetrabenzylzirconium or tetrakis(dimethylamido)zirconium or -hafnium gave the corresponding (chelate ligand)MX₃ systems in a variety of cases. Some of these gave very active ethene polymerization catalysts upon activation with methylalumoxane. Six of the neutral aminoalkylpyridines were characterized by X-ray diffraction, as were eight of the zirconium or hafnium complexes and two aluminum chelate complex systems.

Full text of DOI:10.1016/j.jorganchem.2007.12.004

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1572–1589
www.elsevier.com/locate/jorganchem
(Amidomethyl)pyridine zirconium and hafnium complexes:
Synthesis and structural characterization
Katrin Nienkemper, Gerald Kehr, Seda Kehr, Roland Fro¨hlich, Gerhard Erker *
Organisch-Chemisches Institut der Universita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany
Received 1 October 2007; received in revised form 4 December 2007; accepted 4 December 2007
Available online 14 December 2007
In memoriam Professor F. Albert Cotton
Abstract
A series of 2-formyl and 2-acetylpyridines was condensed with 2,6-diisopropylaniline to yield the corresponding imines. Their reaction
with sodium borohydride gave the respective N-arylaminomethylpyridines. Treatment of the N-arylformimino- or -acetiminopyridines
with trimethylaluminum followed by hydrolysis furnished a series of the respective substituted N-arylaminoethylpyridine derivatives.
Their reaction with tetrabenzylzirconium or tetrakis(dimethylamido)zirconium or -hafnium gave the corresponding (chelate ligand)MX3
systems in a variety of cases. Some of these gave very active ethene polymerization catalysts upon activation with methylalumoxane. Six
of the neutral aminoalkylpyridines were characterized by X-ray diffraction, as were eight of the zirconium or hafnium complexes and two
aluminum chelate complex systems.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Chelate ligands; Pyridine derivatives; Iminopyridines; Amido ligands; Zirconium; Hafnium
1. Introduction
In the recent years a series of patents has appeared
describing the use of the bidentate zirconium complexes 4
and 5 and derivatives thereof, mostly generated in situ,
for use in polymerization catalysis [6,7]. This prompted
us to now disclose and describe our work carried out in
the recent years on the synthesis of a series of closely
related complexes and their detailed spectroscopic and
structural characterization.
Use of the 2,6-bisiminopyridine ligand family has been of
great importance for the development of the ‘‘post-metallo-
cene” homogeneous Ziegler–Natta olefin polymerization
catalysts [1]. Such complexes (1) of the late transition metals,
notably of iron, cobalt or palladium, have been valuable
substrates for the generation of very active catalysts [2,3].
The adoption of such ligand types for applications in
related early metal complex chemistry and catalysis has
resulted in the change and conversion of such systems into
mono- or dianionic derivatives, such as e.g. 2 or 3 (and
many related systems) [4,5]. It turned out that the special
coordination features of the Group 4 metals did not neces-
sarily require the presence of tridentate stabilizing and con-
trolling ligands but that bidentate analogues served their
purpose as well quite efficiently.
2. Results and discussion
2.1. Syntheses of the chelate ligands
The syntheses of three series of 2-aminomethylpyridines
were carried out. They all featured the 2,6-diisopropyl-
phenyl substituent at the nitrogen atom. The synthetic
series started from the respective substituted 2-formyl- or
2-acetylpyridine precursors, which were first converted to
the respective imines by condensation with 2,6-diisopropyl-
aniline followed by either reduction (NaBH4) or reductive
*
Corresponding author. Tel.: +49 251 83 36518; fax: +49 251 83 36503.
E-mail address: erker@uni-muenster.de (G. Erker).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.12.004

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1573
methylation (AlMe3), both followed by hydrolysis. The
carbonylpyridine precursors were prepared by variations
or adaptations of literature procedures (see Scheme 1).
2-Formylpyridine (7a) was prepared by SeO2 oxidation
of commercially available 2-hydroxymethylpyridine (6a).
Similarly, 2-formylquinoline (7b) was obtained by the anal-
ogous oxidation (SeO2) of the 2-hydroxymethylquinoline
precursor (6b) (see Scheme 2). The synthesis of 2-formyl-
4,6-di-tert-butylpyridine (7c) was effected by a pyrylium
route (see Scheme 2) starting from methyl-tert-butylketone
(9) [8,9].
Two 2-acetylpyridines (16b and 16c) were prepared by
means of variants of the Reissert–Henze reaction (see
Scheme 3) [10–12].
The 2-formylpyridines (7a–c) and 2-acetylpyridines
(16a–c) were converted to the respective aldimines (8a–c)
or ketimines (17a–c) by condensation with 2,6-diisopropyl-
aniline (see Schemes 2 and 3) [13–16]. From these precur-
sors (8a–c, 17a–c) we have prepared three series of
substituted (N-arylaminomethyl)pyridines that were then
subsequently used for the synthesis of the respective j2N,
N0-chelate ligand Group 4 metal complexes (see below).
Scheme 1.
Scheme 2.

1574
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
Scheme 3.
The imines 8a and 8c, respectively, were reduced with
Two related examples (20b and 20c, see Scheme 5) were
prepared starting from the respective 6-substituted ketimi-
nopyridine precursors (17b and 17c). Their treatment with
sodium borohydride eventually furnished the corresponding
sodium borohydride to yield the 2-(N-2,6-diisopropyl-
phenyl)aminomethylpyridines 18a [14c] and 18c, respec-
tively (see Scheme 4).
The aldimino pyridines (8a and 8b) were treated with
trimethylaluminum (ca. 2 equiv.) in toluene, to obtain the
chiral (aminoethyl)pyridine products 19a and 19b each
>90% yield after hydrolysis and chromatographic workup
(see Scheme 5).
Scheme 4.
Scheme 5.

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1575
6-alkyl-2-(N-arylaminoethyl)pyridine products in good
yield.
Eventually, the nucleophilic methylation route was also
2.2. Structural characterization of the aminoalkylpyridine
systems
employed for the conversion of the ketimines 17(a–c) to
the respective 1-methylaminoethylpyridine products (22a–
c). Thus, treatment of 17a with a twofold excess of trimeth-
ylaluminum in toluene furnished 22a [17] after hydrolysis
and chromatographic purification. Analogously, the substi-
tuted ketimines 17b and 17c, respectively, were also con-
verted to the corresponding 1-methylaminoethylpyridine
products (22b and 22c) by AlMe3 treatment followed by
hydrolysis.
In all three examples in separate experiments we were
able to actually isolate the corresponding chelate aluminum
compounds (21a–c) when the reactions and workup proce-
dures were carried out under strictly anhydrous conditions.
In these examples the amido(dimethyl)Al complexes were
isolated as yellow solids in 75–85% yield. Two examples
(21b and 21c) were characterized by X-ray diffraction (see
Scheme 6).
Structures of examples of the iminopyridine systems
were recently reported by us [11]. In the course of this pres-
ent study we have now characterized a total of six examples
of the various substituted aminomethyl- and aminoethyl-
pyridines by X-ray diffraction (see Figs. 1–3 and Table 1).
Compound 18a features an undistorted pyridine ring.
The aminomethyl substituent is bonded at the a-position.
The corresponding C2(pyridine)–C7(substituent) bond
length is in the typical C(sp2)–C(sp3) range [18]. The
˚
C7–N8 vector (1.456(2) A) is markedly rotated out of the
pyridine plane (h = ꢀ 74.3(2)°). The C7–N8–C9 angle at
the secondary amine nitrogen amounts to 118.4(1)°. This
general conformational arrangement results in a relatively
large spatial separation of the N–H function from the pyr-
idine H-bridge acceptor (calculated N1–H(N8) distance:
˚
˚
intra 2.849 A; N1#–H(N8): inter 2.327 A). The bulky
2,6-diisopropylphenyl ring is rotated almost normal to
the C7–N8–C9 plane, as expected (see Fig. 1 and Table 1).
In contrast, the aminomethyl substituent in the related
compound 18c, which bears the more bulky 4,6-di-tert-
butylpyridine moiety, is rotated close to in-plane with the
pyridine plane (h = 28.9(2)°). Here we assume the presence
of a marked hydrogen bonding interaction between the
pyridine nitrogen and the amine N–H group (calculated
˚
N1–H(N8) distance: 2.251 A).
The chiral N-arylaminoethylpyridine pair of compounds
(19a and 20c) shows structural and conformational features
that are similar to those of 18a (see Table 1 and Fig. 2),
only that the substituent C7–N9 vector is slightly less
rotated from the plane in 19a (h: 66.4(2)°) and 20c
(h: ꢀ57.6(2)°) than it is observed for the parent compound
18a (h: ꢀ74.3(2)°).
Scheme 6.
Fig. 1. Views of the molecular structures of the N-arylaminomethylpyridine derivatives 18a (left) and 18c (right).

1576
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
Fig. 2. Molecular structures of the compounds 19a (left) and 20c (right).
Fig. 3. Projections of the molecular structures of the compounds 22a (left) and 22c (right).
Table 1
Selected structural parameters of aminoalkylpyridine derivativesa
Compound
C2–C7
C7–N8
N1–H(N8)
N1–C2–C7–N8
C2–C7–N8–C9
C7–N8–C9–C10/C14
18a
1.508(2)
1.456(2)
2.849c
2.327b
2.251c
ꢀ74.3(1)
ꢀ73.8(2)
ꢀ79.7(2)
18c
1.514(2)
C2–C7
1.456(2)
C7–N9
1.462(2)
28.9(2)
ꢀ163.3(1)
C2–C7–N9–C10
ꢀ87.6(2)
C7–N9–C10–C11/C15
Compound
19a
N1–H(N9)
N1–C2–C7–N9
66.4(2)
1.509(2)
2.651c
2.675b
2.509c
78.0(2)
75.0(2)
20c
1.523(3)
C2–C7
1.472(3)
C7–N10
ꢀ57.6(2)
N1–C2–C7–N10
ꢀ84.0(2)
C2–C7–N10–C11
ꢀ73.0(3)
C7–N10–C11–C12/C16
Compound
N1–H(N10)
22a
22c
a
1.533(2)
1.537(3)
1.503(2)
1.498(2)
2.524c
2.294c
ꢀ66.6(1)
ꢀ50.3(2)
ꢀ91.0(1)
ꢀ91.1(1)
ꢀ93.6(2)
ꢀ103.0(2)
˚
Bond lengths in A, dihedral angles in °.
b
c
N1#–H(N8)inter
N1–H(N8)intra
.
.
Compound 22a shows a core geometry that is very similar
to that of 18a (see Table 1 and Fig. 3), only the 2,6-diisopro-
pylphenyl substituents here are oriented almost ideally
normal to the adjacent plane. The rotation of the C7–N vec-
tor is very similar to the observed value in 20c. In the more
bulky system 22c the C7–N10 vector is rotated closer to the

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1577
pyridine plane (h: ꢀ50.3(2)°) which brings the attached N–H
hydrogen into l-H bonding distance to the pyridine nitro-
gen atom (calculated N1–H(N10) distance: 2.294 A).
6-tert-butyl) we could not obtain the respective products
under our typical reaction conditions. With less sterically
encumbered systems these reactions usually went smoothly
and furnished the respective metal complexes in fair yields
(for details see the Section 3).
˚
The chelate amido aluminum complex intermediates
(21b and 21c) used for the preparation of the geminal
dimethyl compounds 22 were also characterized by X-ray
diffraction (see Fig. 4 and Table 2). The tert-butyl-substi-
tuted complex 21c features an almost perfectly planar
five-membered chelate ring. The amide nitrogen to alumi-
Here are two typical examples: the reaction of the
1-methyl-aminoethylpyridine (22a) with Zr(NMe2)4 gave
complex 24e in close to 80% yield. The 1H NMR spectrum
of complex 24e (see Fig. 5 top) features a 6H intensity sin-
glet of the ‘‘bridging” pyridyl–C(CH3)2–[N]– moiety (d
1.39) and a pair of diastereotopic iso-propyl methyl reso-
nances at d 1.22, 1.16, each of 6H intensity, with a single
corresponding –CHMe2 septet at d 3.51 (2H). Complex
˚
num bond is short (1.825(1) A), the pyridine nitrogen
donor to Al acceptor linkage is markedly longer
˚
(2.047(1) A) [19]. The Al center in 21c features a pseudo-
tetrahedral coordination geometry with a small endocyclic
N1–Al–N10 angle (84.83(4)°) and a much larger exocyclic
C27–Al–C28 angle (114.49(7)°). The bulky 2,6-diisopropyl-
phenyl ring is found rotated perpendicular to the mean cen-
tral complex plane (h(C7–N10–C11–C12): 92.5(1)°).
Complex 21b features a very similar structure, but here
the central chelate unit deviates slightly from planarity
(h(N1–C2–C7–N10): ꢀ12.8(2)°).
1
24e features only one broad H NMR resonance of the
[Zr]–N(CH3)2 methyl protons a d 2.63 (18H), indicating
rapid positional equilibration of the NMe2 ligands at Zr
on the NMR time scale. In some of the prepared complexes
this rotational/pseudorotational equilibration process is
sufficiently slowed down or even frozen on the NMR time
scale at room temperature, so that the corresponding sym-
metry related appearance of the NMR spectra can actually
be observed at ambient conditions.
2.3. Formation of the zirconium and hafnium complexes
A typical example is complex 24d. It was isolated from
the reaction of the aminoethylquinoline ligand (19b) with
Zr(NMe2)4 in 78% yield as a yellow solid. In the ambient
We have synthesized a series of zirconium and hafnium
complexes from these substituted aminomethyl- and
aminoethylpyridine chelate ligands by in situ deprotona-
tion [20]. For that purpose the respective neutral ligand sys-
tems were treated with tetrabenzylzirconium [21] or
tetrakis(dimethylamido)zirconium or -hafnium [22]. As
can be seen from the compilation shown in Scheme 7, these
reactions were sensitive to steric hindrance. From the very
hindered substrates (gem. dimethyl plus 6-iso-propyl or
1
temperature H NMR spectrum (see Fig. 5 bottom) it fea-
tures a total of nine separate signals of the Ar–methine
hydrogens at the quinoline nucleus and of the 2,6-diisopro-
pylphenyl substituent. The inherent chirality of the systems
has resulted in the diastereotopic splitting of the non-equiv-
alent pairs of iso-propyl substituents to give a total of four
CH(CH3)2 methyl doublets and two CH(CH3)2 methine
Fig. 4. Views of the molecular structures of the Al–chelate complexes 21b (left) and 21c (right).
Table 2
Selected structural parameters of the chelate aluminum complexes 21(b, c)a
Compound
N1–Al
N10–Al
N1–Al–N10
Me–Al–Me
N1–C2–C7–N10
C2–C7–N10–C11
21b
21c
a
1.996(1)
2.047(1)
1.829(1)
1.825(1)
85.25(5)
84.83(4)
113.71(8)
114.49(7)
ꢀ12.8(2)
ꢀ163.3(1)
0.5(2)
160.7(1)
˚
Bond lengths in A, angles and dihedral angles in °.

1578
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
2.4. Structural characterization of the zirconium and
hafnium chelate complexes
A series of seven of the j2N, N0-chelate tris(dimethyl-
amido) Group 4 metal complexes were characterized by
X-ray diffraction (four Zr, three Hf complexes), and in
addition the structure of the tribenzyl Zr–chelate complex
23e was determined. All these complexes are of the same
overall structural type. The overall structural characteris-
tics of this general class of compounds shall be illustrated
with the example of the parent hafnium complex 25a (see
Fig. 6 and Table 3).
Complex 25a features a distorted trigonal–bipyramidal
coordination geometry at the central hafnium atom. The
pyridine nitrogen (N1) and one of the –NMe2 ligand nitro-
gen atoms (N24) are found in trans-apical positions (angle
N1–Hf–N24: 170.8(1)°). The remaining pair of –NMe2
ligands and the chelate ligand amide nitrogen center form
the basal arrangement. All three Hf–N(Me) bonds are
˚
short (2.048(4)–2.050(5) A), the Hf–N(chelate) bonds are
˚
˚
markedly longer (Hf–N8: 2.110(3) A, Hf–N1: 2.380(3) A).
The N1–Hf–N8 angle, i.e. the cone angle of the chelate
ligand, amounts to 70.6(1)°, which is markedly smaller
than the adjacent angles (N21–Hf–N27: 113.2(2)°, N21–
Hf–N8: 122.9(1)°, N24–Hf–N8: 101.2(1)°, N21–Hf–N24:
96.9(2)°, N27–Hf–N24: 98.1(1)°, N27–Hf–N8: 117.1(1)°,
N27–Hf–N1: 89.5(1)°, N21–Hf–N1: 84.7(2)°). The plane
Scheme 7.
septets. Most remarkably, we observe three separate
methyl singlets of the three –NMe2 ligands at zirconium,
each of 6H intensity.
Fig. 5. 1H NMR spectra of the complexes 24e (top) and 24d (bottom), 600 MHz, 298K, d8-THF ( ).
*

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1579
Fig. 6. Views of the molecular structures of the complexes 25a (top left), 24c (top right), 25c (bottom left) and 24d (bottom right).
Table 3
Selected structural parameters of the chelate zirconium and hafnium complexes 23–25a
P
Compound
M
N1–M
N8/N9/N10–M
N1–M–N8/N9/N10
Nax–M–N1
Neq–M–Neq
25a
24c
25c
24d
24e
24f
25f
23e
a
Hf
Zr
Hf
Zr
Zr
Zr
Hf
Zr
2.380(3)
2.407(2)
2.380(3)
2.462(2)
2.413(2)
2.479(2)
2.452(3)
2.382(2)
2.110(3)
2.128(2)
2.115(3)
2.107(2)
2.135(1)
2.116(2)
2.091(3)
2.048(3)
70.6(1)
69.0(1)
69.8(1)
70.3(1)
68.9(1)
71.0(1)
71.7(1)
72.2(1)
170.8(1)
172.2(1)
172.2(1)
174.7(1)
173.1(1)
174.5(1)
174.2(1)
172.4(1)b
353.2
351.0
351.8
351.2
349.6
354.8
354.9
348.6
˚
Bond lengths in A, angles in °.
b
C31–M–N1.
˚
of the 2,6-diisopropylphenyl substituent is oriented
almost normal to the Hf-chelate plane (dihedral angle
C7–N8–C9–C10: 75.7(5)°). Complex 24d as well as the pair
of Zr/Hf-complexes 24c and 25c, which all exhibit an
N-aryl-aminoethylpyridine chelate ligand, show very simi-
lar structural features (see Fig. 6 and Table 3).
(Zr–C31: 2.305(3) A) occupy the apical positions (angle
N1–Zr–C31: 172.4(1)°). Again, the Zr–N(amide) bond is
short (Zr–N10: 2.048(3) A). The remaining Zr–C(benzyl)
bond lengths amount to 2.281(4) A (Zr–C41) and
2.302(3) A (Zr–C51), respectively. The corresponding
C41–Zr–C51 angle was found at 118.8(2)°. Again, the
bulky 2,6-diisopropylphenyl substituent at the amide nitro-
gen center is found rotated almost perpendicular to the
mean chelate ligand plane (dihedral angle C7–N10–C11–
C12: 90.9(3)°). The angle between the C–methyl vectors
at C7 amounts to 107.8(3)° (C8–C7–C9). Fig. 7 shows a
˚
˚
˚
The X-ray crystal structure analysis of the tribenzyl zir-
conium chelate complex 23e revealed a closely related
structural framework. The complex geometry is distorted
trigonal–bipyramidal. The pyridine nitrogen atom (N1–
˚
Zr: 2.382(2) A) and one of the benzylic r-carbon ligands

1580
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
Fig. 7. Projections of the molecular structures of the complexes 24e (top left), 23e (top right), 24f (bottom left) and 25f (bottom right).
Table 4
view of complex 23e (top right) along with its correspond-
ing tris(dimethylamido)Zr(chelate ligand) analogues 24e
(top left) and a pair of the 2-isopropyl-substituted com-
plexes 24f and 25f.
Ethene polymerization with the (chelate ligand)ZrX3 (23/24)/MAO
catalystsa
Compound
X
mol[Zr] (ꢁ105) t (min) g PE actb
Tm
23a
23e
24b
24c
24d
24e
24f
a
CH2Ph 2.5
CH2Ph 0.63
17
15
15
15
15
15
17
5.47
6.00
–
0.53
0.96
2.13
0.87
438 122
1905 121
2.5. Polymerization reactions
NMe2
NMe2
NMe2
NMe2
NMe2
2.5
2.5
2.5
2.5
2.5
–
–
42 120
77 122
170 122
70 117
We have carried out a series of preliminary polymerisa-
tion experiments to examine the potential of using the che-
late complexes 23, 24 or 25 as components of active
homogeneous Ziegler–Natta catalysts for olefin polymeri-
zation. The catalysts were generated in situ by treatment
with a large excess of methylalumoxane in toluene
(Al/Zr > 1000) [23]. Ethylene polymerization experiments
were carried out at 25 °C with 2 bar ethene. The results
of selected experiments are listed in Table 4. In all these
cases linear polyethylene was formed with a rather low
molecular weight as judged from the observed melting
Selected examples.
b
g PE/(mmol[Zr] h bar).
bridging C atom inside the chelate is advantageous with
regard to activity. The (chelate ligand)Zr(NMe2)3 systems
(24) were found to give markedly less active ethene poly-
merization catalysts (see Table 4). Again, the series of
examples investigated has revealed that the introduction
of some steric bulk at the a-carbon position inside the che-
late ring markedly and steadily increased the catalyst activ-
ity. However, the presence of a bulky alkyl substituent
1
points and the H NMR spectra.
From the obtained data some trends have become
apparent. Both the (chelate ligand)Zr(benzyl)3 systems
tested (23a and 23e) give very active ethene polymerization
catalysts. The latter is even in the high activity region [2].
Apparently the introduction of some steric bulk in the
i
t
(e.g., Pr, Bu) in the pyridine 6-position diminished the

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1581
catalyst activity or shut if off completely. The correspond-
ing hafnium complexes gave no active ethene polymeriza-
tion reactions under the applied reaction conditions.
General procedure: preparation of aminoalkylpyridines by
imine reduction with NaBH4 (18a, c; 20b, c). At 0 °C NaBH4
was added slowly to a stirred solution of the respective imi-
nes in methanol. The reaction mixture was warmed to
room temperature and then refluxed for 3–4 days. The pro-
gress of the reaction was monitored by TLC. The reaction
mixture was allowed to cool to room temperature and then
quenched with sodium carbonate solution. The organic
phase was separated and the aqueous phase was extracted
with dichloromethane again. The organic solutions were
combined and dried with MgSO4. Then the solvent was
removed and finally the crude product was purified by col-
umn chromatography on silica gel.
2.6. Some conclusions
We have carried out a series of syntheses of substituted 2-
iminopyridine derivatives that were subsequently converted
to the corresponding aminomethyl- or aminoethylpyridines
by either reduction with sodium borohydride or by treat-
ment with trimethylaluminum followed by hydrolysis.
Many of these ligand systems could be converted to the cor-
responding (chelate ligand)M(IV)X3 complexes of the
Group 4 metals zirconium or hafnium employing in situ
NH deprotonation using either tetrabenzylzirconium or tet-
rakis(dimethylamido)Zr or -Hf reagents. Limitations of this
attractive organometallic synthetic route became apparent
when a combination of very bulky substituents at both
a-positions of the pyridine nucleus in the neutral organic
substrates prevented the formation of the respective metal
complexes by this method. The complexes were character-
ized by X-ray diffraction. Especially the (chelate ligand)Zr
(benzyl)3 systems gave very active homogeneous Ziegler–
Natta catalysts upon activation with methylalumoxane.
Preparation of (18a) [13c]. The reaction of 8a (7.16 g,
26.9 mmol) with NaBH4 (15.3 g, 403 mmol) in methanol
(400 ml) yielded after column chromatography (SiO2; pen-
tane/methanol/chloroform/triethylamine, 100:1:1:1) the
product as a white solid (5.92 g, 82%). Crystallization from
methanol gave crystals suitable for X-ray diffraction. M.p.
50 °C (DSC). Anal. Calc. for C18H24N2: C, 80.55; H, 9.01;
N, 10.44; Found: C, 80.24; H, 8.98; N, 10.51%. MS–ESI
(m/z, ES+): 269.2 [M+H]+, 291.2 [M+Na]+.1H NMR
(499.8 MHz, CDCl3, 298 K): d = 8.62 (m, 1H, 6-HPy),
7.68 (td, 3J = 7.7 Hz, 4J = 1.4 Hz, 1H, 4-HPy), 7.33
(d, 3J = 7.7 Hz, 1H, 3-HPy), 7.23 (m, 1H, 5-HPy), 7.11
(m, 2H, 3-HAr), 7.07 (m, 1H, 4-HAr), 4.22 (s, 2H, NCH2),
3.35 (sept, 3J = 6.9 Hz, 2H, CH(CH3)2), 1.22 (d, 3J =
6.9 Hz, 12H, CH(CH3)2). 13C{1H} NMR (125.7 MHz,
CDCl3, 298 K): d = 158.5 (C2Py), 148.8 (C6Py), 142.7
(C2Ar), 142.6 (C1Ar), 137.0 (C4Py), 124.2 (C4Ar), 123.7
(C3Ar), 122.4 (C5Py), 122.2 (C3Py), 56.4 (NCH2), 27.7
(CH(CH3)2), 24.2 (CH(CH3)2). X-ray crystal structure
analysis for 18a: formula C18H24N2, M = 268.39, colorless
crystal 0.40 ꢁ 0.20 ꢁ 0.15 mm, a = 8.373(1), b = 9.703(1),
3. Experimental section
All reactions involving air or moisture sensitive com-
pounds were carried out under inert atmosphere using
Schlenk-type glassware or in a glovebox. Solvents were
dried and distilled prior to use. The following instruments
were used for physical characterization of the compounds:
Melting points, DSC 2010 TA-instruments; elemental anal-
yses, Foss-Heraeus CHNO-Rapid; MS, Micromass Quat-
tro LC-Z electrospray mass spectrometer; NMR, Bruker
AC 200 P (1H: 200 MHz, 13C: 50 MHz), ARX 300
(1H: 300 MHz, 13C: 75 MHz) or Varian UNITY plus
NMR spectrometer (1H: 600 MHz, 13C: 151 MHz). X-ray
crystal structure determinations: Data sets were collected
with Nonius KappaCCD diffractometers, in case of Mo-
radiation a rotating anode generator was used. Programs
used: data collection COLLECT (Nonius B.V., 1998), data
reduction Denzo-SMN (Z. Otwinowski, W. Minor, Meth-
ods in Enzymology, 1997, 276, 307–326), absorption correc-
tion SORTAV (R.H. Blessing, Acta Cryst. 1995, A51, 33–
37; R.H. Blessing, J. Appl. Cryst. 1997, 30, 421–426) and
Denzo (Z. Otwinowski, D. Borek, W. Majewski, W.
Minor, Acta Cryst. 2003, A59, 228-234), structure solution
SHELXS-97 (G.M. Sheldrick, Acta Cryst. 1990, A46, 467–
473), structure refinement SHELXL-97 (G.M. Sheldrick, Uni-
versita¨t Go¨ttingen, 1997), graphics SCHAKAL (E. Keller,
Universita¨t Freiburg, 1997).
˚
c = 10.899(1) A, a = 75.09(1), b = 83.01(1), c = 70.09(3)°,
3
V = 803.95(15) A , qcalc = 1.109 g cmꢀ3, l = 0.493 mmꢀ1
,
˚
empirical absorption correction (0.827 6 T 6 0.930),
˚
ꢀ
Z = 2, triclinic, space group P1 (No. 2), k = 1.54178 A,
T = 223 K, x and / scans, 8489 reflections collected ( h,
k, l), [(sinh)/k] = 0.59 Aꢀ1, 2726 independent (Rint
=
˚
0.029) and 2549 observed reflections [I P 2r(I)], 188
refined parameters, R = 0.047, wR2 = 0.125, max. residual
electron density 0.18 (ꢀ0.14) e Aꢀ3, hydrogen atom at N8
˚
from difference fourier maps and refined free, other calcu-
lated and refined as riding atoms.
Preparation of 18c. A mixture of 4,6-di-tert-butylpyri-
dine-2-carbaldehyde (7c) (1.25 g, 5.69 mmol) and 2,6-diiso-
propylaniline (1.11 g, 6.25 mmol) in methanol (30 ml) was
refluxed for several hours. The progress of the condensa-
tion reaction was followed by NMR spectroscopy. Then
NaBH4 (21.5 g, 0.57 mol) was added and the mixture was
refluxed for another 2 days. After general workup and
purification by column chromatography on silica gel (pen-
tane/ethyl acetate/triethylamine, 80:1:1) the product was
obtained as a white solid (1.30 g, 60%). Crystallization
from methanol gave crystals suitable for X-ray diffraction.
M.p. 56 °C (DSC). Anal. Calc. for C26H40N2: C, 82.05; H,
Tetrakis(dimethylamido)zirconium [22a], tetrakis(dimeth-
ylamido)hafnium [22b], tetrabenzylzirconium [21], 8a [13], 8b
[14c], 12 [8], 6cand 7c([9], Supporting Information), and 17a–
c [11,13–15] were synthesized according to procedures
reported in the literature.

1582
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
10.59; N, 7.36; Found: C, 81.75; H, 10.62; N, 7.21%. MS–
Anal. Calc. for C23H34N2: C, 81.60; H, 10.12; N, 8.28;
Found: C, 81.47; H, 10.02; N, 8.28%. MS–ESI (m/z,
ES+): 339.3 [M+H]+, 361.3 [M+Na]+. 1H NMR
1
ESI (m/z, ES+): 381.3 [M+H]+. H NMR (599.8 MHz,
CDCl3, 298 K): d = 7.22 (s, 1H, 5-HPy), 7.13 (m, 2H, 3-
HAr), 7.07 (m, 1H, 4-HAr), 6.97 (s, 1H, 3-HPy), 4.92 (br s,
1H, NH), 4.15 (s, 2H, NCH2), 3.56 (sept, 3J = 6.8 Hz,
2H, CH(CH3)2), 1.42 (s, 9H, 6-C(CH3)3), 1.30 (s, 9H, 4-
C(CH3)3), 1.28 (d, 3J = 6.8 Hz, 12H, CH(CH3)2).
13C{1H} NMR (150.8 MHz, CDCl3, 298 K): d = 168.4
(C6Py), 160.5 (C4Py), 156.2 (C2Py), 144.3 (C1Ar), 142.3
(C2Ar), 123.4 (C3Ar), 123.3 (C4Ar), 116.1 (C3Py), 114.2
(C5Py), 56.5 (NCH2), 37.5 (6-C(CH3)3), 34.8 (4-C(CH3)3),
30.7 (4-C(CH3)3), 30.3 (6-C(CH3)3), 27.7 (CH(CH3)2),
24.3 (CH(CH3)2). X-ray crystal structure analysis for 18c:
formula C26H40N2, M = 380.60, colorless crystal 0.50 ꢁ
3
(599.8 MHz, CDCl3, 298 K): d = 7.48 (t, J = 7.7 Hz, 1H,
3
4-HPy), 7.20 (d, J = 7.7 Hz, 1H, 5-HPy), 7.07 (m, 2H, 3-
3
HAr), 7.02 (m, 1H, 4-HAr), 6.83 (d, J = 7.7 Hz, 1H, 3-
HPy), 4.62 (br s, NH), 4.26 (q, 3J = 6.5 Hz, 1H,
NCH(CH3)), 3.34 (sept, 3J = 6.8 Hz, 2H, CH(CH3)2),
1.41 (s, 9H, C(CH3)3), 1.38 (d, 3J = 6.5 Hz, 3H,
3
NCH(CH3)), 1.25 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ),
1.11 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
3
(150.8 MHz, CDCl3, 298 K): d = 168.8 (C6Py), 161.5
(C2Py), 142.2 (C2Ar), 141.9 (C1Ar), 136.4 (C4Py), 123.3
(C3Ar), 122.9 (C4Ar), 118.5 (C3Py), 117.3 (C5Py), 60.2
(NCH(CH3)), 37.5 (C(CH3)3), 30.1 (C(CH3)3), 27.6
(CH(CH3)2), 24.2 ðCHðCHA3 CH3BÞÞ, 24.0 ðCHðCHA3
0.30 ꢁ 0.30 mm, a = 11.3668(4), b = 21.0615(7), c =
3
˚
˚
10.5678(4) A,
q
b = 109.028(2)°,
V = 2391.71(15) A ,
calc = 1.057 g cmꢀ3, l = 0.453 mmꢀ1, empirical absorp-
CHBÞÞ, 22.1 (NCH(CH3)). X-ray crystal structure analysis
3
tion correction (0.805 6 T 6 0.876), Z = 4, monoclinic,
for 20c: formula C23H34N2, M = 338.52, colorless crystal
˚
˚
space group P21/c (No. 14), k = 1.54178 A, T = 223 K, x
0.30 ꢁ 0.20 ꢁ 0.15 mm, a = 10.0180(5), c = 21.4529(9) A,
3
V = 2153.02(18) A , qcalc = 1.044 g cmꢀ3, l = 0.453 mmꢀ1
,
˚
and / scans, 17355 reflections collected ( h, k, l),
[(sinh)/k] = 0.60 Aꢀ1, 4212 independent (Rint = 0.033) and
empirical absorption correction (0.876 6 T 6 0.935),
Z = 4, tetragonal, space group P41 (No.76), k =
˚
3860 observed reflections [I P 2r(I)], 267 refined parame-
ters, R = 0.048, wR2 = 0.127, max. residual electron den-
1.54178 A, T = 223 K, x and / scans, 9097 reflections col-
˚
sity 0.18 (ꢀ0.19) e Aꢀ3, hydrogen atom at N8 from
lected ( h, k, l), [(sinh)/k] = 0.60 Aꢀ1, 2806 indepen-
˚
˚
difference fourier maps and refined free, other calculated
and refined as riding atoms.
dent (Rint = 0.040) and 2604 observed reflections [I P
2r(I)], 238 refined parameters, R = 0.045, wR2 = 0.117,
Flack parameter ꢀ0.1(7), max. residual electron density
Preparation of 20b. The reaction of 17b (906 mg,
2.81 mmol) with NaBH4 (10.6 g, 0.28 mol) in methanol
(500 ml) yielded after column chromatography (SiO2; pen-
tane/ethylacetate, 40:1) the product as a colourless oil
(560 mg, 62%). Anal. Calc. for C22H32N2: C, 81.43; H,
9.94; N, 8.63; Found: C, 81.13; H, 9.92; N, 8.55%.
MS–ESI (m/z, ES+): 325.3 [M+H]+, 347.3 [M+Na]+.
1H NMR (599.8 MHz, CDCl3, 298 K): d = 7.45
(t, 3J = 7.5 Hz, 1H, 4-HPy), 7.06 (m, 2H, 3-HAr), 7.01
(d, 3J = 7.5 Hz, 1H, 5-HPy), 7.01 (m, 1H, 4-HAr), 6.83
(d, 3J = 7.5 Hz, 1H, 3-HPy), 4.60 (br s, 1H, NH), 4.24
0.15 (ꢀ0.19) e Aꢀ3, hydrogen atom at N9 from difference
˚
fourier maps and refined free, other calculated and refined
as riding atoms.
General procedure: preparation of aminoalkylpyridines by
reaction with (AlMe3)2(19a,b; 22a–c). Trimethylaluminium
was added to a solution of the respective imines in toluene
at 0 °C. The reaction mixture was allowed to warm to room
temperature and stirred overnight. A sodium hydroxide
solution was added carefully to quench the reaction. The
organic phase was separated and the aqueous phase was
extracted with chloroform again. The organic phases were
combined and dried with MgSO4. Then the solvent was
removed and the crude product was purified by column
chromatography on silica gel.
Preparation of 19a. The reaction of 8a (3.11 g,
11.7 mmol) with trimethylaluminium (2.25 ml, 1.69 g,
23.4 mmol) in toluene (80 ml) yielded after column chro-
matography (SiO2; pentane/ethylacetate/triethylamine,
60:1:1) the product as a white solid (3.00 g, 91%). Crystals
suitable for the X-ray diffraction were obtained from a mix-
ture of ethylacetate and triethylamine by evaporation of
the solvent at room temperature. M.p. 51 °C (DSC). Anal.
Calc. for C19H26N2: C, 80.80; H, 9.28; N, 9.92; Found: C,
80.89; H, 9.29; N, 9.83%. MS–ESI (m/z, ES+): 283.2
[M+H]+, 305.2 [M+Na]+, 587.4 [2M+Na]+. 1H NMR
3
3
(q, J = 6.6 Hz, 1H, NCH(CH3)), 3.33 (sept, J = 6.8 Hz,
2H, CH(CH3CH3)Ar), 3.08 (sept, 3J = 6.9 Hz, 1H,
CH(CH3CH3)Py), 1.39 (d, J = 6.6 Hz, 3H, NCH(CH3)),
3
Py
1.35 (d, J = 6.9 Hz, 3H, CHðCHA3 CH3BÞ Þ, 1.34 (d,
3
Py
3J = 6.9 Hz, 3H, CHðCH3ACHB3 Þ Þ, 1.25 (d, J = 6.8 Hz,
3
Ar
6H, CHðCHA3 CHB3 Þ ), 1.11 (d, 3J = 6.8 Hz, 6H,
Ar
CHðCHA3 CH3BÞ ). 13C{1H} NMR (150.8 MHz, CDCl3,
298 K): d = 166.7 (C6Py), 162.2 (C2Py), 142.1 (C2Ar),
142.0 (C1Ar), 136.5 (C4Py), 123.3 (C3Ar), 122.8 (C4Ar),
119.1 (C5Py), 118.8 (C3Py), 60.2 (NCH(CH3)), 36.2
(CH(CH3CH3)Py), 27.6 (CH(CH3CH3)Ar), 24.2 ðCHðCHA
3
Ar
Ar
CHB3 Þ Þ, 24.0 ðCHðCH3ACH3BÞ Þ, 22.5 ðCHðCHA3
Py
Py
CHBÞ Þ, 22.4 ðCHðCHACHBÞ Þ, 22.2 (NCH(CH3)).
3
3
3
Preparation of 20c. The reaction of 17c (2.02 g,
6.00 mmol) with NaBH4 (22.7 g, 0.60 mol) in methanol
(700 ml) yielded after column chromatography (SiO2; pen-
tane/ethylacetate, 40:1) 20c as a white solid (1.75 g, 86%).
Crystals suitable for the X-ray diffraction were obtained
from a mixture of methanol and triethylamine by evapora-
tion of the solvent at room temperature. M.p. 74 °C (DSC).
(599.8 MHz,
CDCl3,
298 K):
d = 8.64
(ddd,
3J = 4.8 Hz, 4J = 1.8 Hz, 5J = 0.9 Hz, 1H, 6-HPy), 7.46
(td, 3J = 7.6 Hz, 2J = 1.8 Hz, 1H, 4-HPy), 7.09 (ddd,
3J = 7.6 Hz, 3J = 4.8 Hz, 4J = 1.1 Hz, 1H, 5-HPy), 7.08
(m, 2H, 3-HAr), 7.02 (m, 1H, 4-HAr), 6.98 (ddd,

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1583
4
5
3J = 7.6 Hz, J = 1.1 Hz, J = 0.9 Hz, 1H, 3-HPy), 4.23 (q,
3J = 6.7 Hz, 1H, NCH(CH3)), 4.14 (br s, NH), 3.30 (sept,
3J = 6.9 Hz, 2H, CH(CH3)2), 1.55 (d, 3J = 6.7 Hz, 3H,
Found: C, 80.65; H, 9.56; N, 9.45%. MS–ESI (m/z, ES+):
1
297.2 [M + H]+, 319.2 [M+Na]+. H NMR (599.8 MHz,
CDCl3, 298 K): d = 8.61 (ddd, 3J = 4.8 Hz, 4J = 1.8 Hz,
4J = 0.9 Hz, 1H, 6-HPy), 7.64 (ddd, 3J = 8.0 Hz,
3J = 7.5 Hz, 4J = 1.8 Hz, 1H, 4-HPy), 7.55 (d,
3J = 8.0 Hz, 1H, 3-HPy), 7.15 (ddd, 3J = 7.5 Hz,
3J = 4.8 Hz, 4J = 1.1 Hz, 1H, 5-HPy), 7.05 (m, 3H, 3,4-
NCH(CH3)), 1.27 (d, J = 6.9 Hz, 6H, CHðCHA3 CH3BÞ),
3
1.10 (d, J = 6.9 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
3
(150.8 MHz, CDCl3, 298 K): d = 163.0 (C2Py), 149.3
(C6Py), 141.8 (C2Ar), 141.4 (C1Ar), 135.9 (C4Py), 123.2
(C3Ar), 123.0 (C4Ar), 121.8 (C5Py), 121.5 (C3Py), 60.7
(NCH(CH3)), 27.3 (CH(CH3)2), 24.0 ðCHðCHACHBÞÞ,
3
HAr), 4.14 (br s, 1H, NH), 3.14 (sept, J = 6.9 Hz, 2H,
3
CH(CH3)2), 1.46 (s, 6H, NC(CH3)2), 1.06 (d, J = 6.9 Hz,
3
3
23.9 ðCHðCHACHBÞÞ, 21.5 (NCH(CH3)). X-ray crystal
12H, CH(CH3)2). 13C{1H} NMR (150.8 MHz, CDCl3,
298 K): d = 168.4 (C2Py), 148.4 (C6Py), 146.3 (C2Ar),
140.5 (C1Ar), 136.2 (C4Py), 124.3 (C4Ar), 122.9 (C3Ar),
121.2 (C5Py), 119.3 (C3Py), 59.0 (NC(CH3)2), 29.2
(NC(CH3)2), 28.2 (CH(CH3)2), 23.9 (CH(CH3)2). X-ray
crystal structure analysis for 22a: formula C20H28N2,
M = 296.44, colorless crystal 0.40 ꢁ 0.35 ꢁ 0.25 mm,
3
3
structure analysis for 19a: formula C19H26N2,
M = 282.42, colorless crystal 0.40 ꢁ 0.30 ꢁ 0.15 mm, a =
˚
10.8222(1),
b = 11.1476(1),
c = 14.1578(1) A,
b =
92.171(1)°, V = 1706.79(3) A , qcalc = 1.099 g cmꢀ3, l =
0.485 mmꢀ1, empirical absorption correction (0.811 6 T
6 0.931), Z = 4, monoclinic, space group P21/c (No. 14),
3
˚
˚
˚
k = 1.54178 A, T = 223 K, x and / scans, 15080 reflec-
a = 16.886(1), b = 11.739(1), c = 18.347(1) A, V =
tions collected ( h, k, l), [(sinh)/k] = 0.60 Aꢀ1, 3068
3636.8(4) A , qcalc = 1.083 g cmꢀ3, l = 0.476 mmꢀ1, empir-
3
˚
˚
independent (Rint = 0.050) and 2727 observed reflections
ical absorption correction (0.833 6 T 6 0.890), Z = 8,
˚
[I P 2r(I)],
199
refined
parameters,
R = 0.051,
orthorhombic, space group Pbca (No. 61), k = 1.54178 A,
wR2 = 0.139, max. residual electron density 0.35
T = 223 K, x and / scans, 17996 reflections collected
(ꢀ0.19) e Aꢀ3, hydrogen atom at N9 from difference fou-
( h,
k,
l), [(sinh)/k] = 0.60 Aꢀ1, 3226 independent
˚
˚
rier maps and refined free, other calculated and refined as
riding atoms.
(Rint = 0.034) and 2949 observed reflections [I P 2r(I)],
209 refined parameters, R = 0.054, wR2 = 0.115, max.
residual electron density 0.15 (ꢀ0.15) e Aꢀ3, hydrogen
˚
Preparation of 19b. The reaction of 8b (3.02 g,
9.54 mmol) with trimethylaluminium (1.84 ml, 1.38 g,
19.1 mmol) in toluene (100 ml) yielded after column chro-
matography (SiO2; pentane/ethylacetate/triethylamine,
60:1:1) the product as a colourless oil (2.99 g, 94%). Anal.
Calc. for C23H28N2: C, 83.09; H, 8.49; N, 8.43; Found: C,
82.96; H, 8.47; N, 8.28%. MS–ESI (m/z, ES+): 333.2
atom at N10 from difference fourier maps and refined free,
other calculated and refined as riding atoms.
Preparation of 22b. The reaction of 17b (1.85 g,
5.74 mmol) with trimethylaluminium (1.10 ml, 0.83 g,
11.5 mmol) in toluene (50 ml) yielded after column chro-
matography (SiO2; pentane/methanol/chloroform/triethyl-
amine, 150:1:1:1) the product as a colourless oil (1.30 g,
67%). Anal. Calc. for C23H34N2: C, 81.60; H, 10.12; N,
8.28; Found: C, 81.53; H, 10.30; N, 8.17%. MS–ESI (m/z,
ES+): 339.3 [M+H]+. 1H NMR (599.8 MHz, CDCl3,
298 K): d = 7.55 (t, 3J = 7.7 Hz, 1H, 4-HPy), 7.20 (d,
3J = 7.7 Hz, 1H, 3-HPy), 7.07 (m, 3H, 3,4-HAr), 7.03 (d,
1
[M+H]+. H NMR (599.8 MHz, CDCl3, 298 K): d = 8.10
3
3
(d, J = 8.3 Hz, 1H, 8-HCh), 8.03 (d, J = 8.4 Hz, 1H, 4-
HCh), 7.77 (dd, 3J = 8.1 Hz, 4J = 1.2 Hz, 1H, 5-HCh),
7.70 (ddd, 3J = 8.3 Hz, 3J = 6.9 Hz, 4J = 1.2 Hz, 1H, 7-
HCh), 7.49 (ddd, 3J = 8.1 Hz, 3J = 6.9 Hz, 4J = 1.1 Hz,
1H, 6-HCh), 7.21 (d, 3J = 8.4 Hz, 1H, 3-HCh), 7.04 (m,
2H, 3-HAr), 6.99 (m, 1H, 4-HAr), 4.69 (br s, 1H, NH),
4.50 (q, 3J = 6.7 Hz, 1H, NCH(CH3)), 3.41 (sept,
3J = 6.8 Hz, 2H, CH(CH3)2), 1.48 (d, 3J = 6.7 Hz, 3H,
3J = 7.7 Hz, 1H, 5-HPy), 4.80 (br s, 1H, NH), 3.37 (sept,
Ar
3J = 6.9 Hz, 2H, CHðCH3Þ ), 3.10 (sept, 3J = 6.9 Hz,
2
Py
1H, CHðCH3Þ2 ), 1.42 (s, 6H, NC(CH3)2), 1.34 (d,
Py
2
3
3
NCH(CH3)), 1.24 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ),
3J = 6.9 Hz, 6H, CHðCH3Þ ), 1.07 (d, J = 6.9 Hz, 12H,
Ar
2
3
1.08 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
CHðCH3Þ ). 13C{1H} NMR (150.8 MHz, CDCl3,
(150.8 MHz, CDCl3, 298 K): d = 163.6 (C2Ch), 147.6
(C8aCh), 142.1 (C2Ar), 141.7 (C1Ar), 136.2 (C4Ch), 129.3
(C7Ch), 129.1 (C8Ch), 127.4 (C5Ch), 127.3 (C4aCh), 126.0
(C6Ch), 123.4 (C3Ar), 123.0 (C4Ar), 120.2 (C3Ch), 60.5
(NCH(CH3)), 27.7 (CH(CH3)2), 24.11 ðCHðCHACHBÞÞ,
298 K): d = 166.9 (C2Py), 165.8 (C6Py), 147.0 (C2Ar),
140.7 (C1Ar), 136.7 (C4Py), 124.4 (C4Ar), 122.9 (C3Ar),
118.2 (C5Py), 116.0 (C3Py), 59.1 (NC(CH3)2), 36.3
Py
Ar
ðCHðCH3Þ2 Þ, 29.0 (NC(CH3)2), 28.0 ðCHðCH3Þ2 Þ, 24.2
Ar
Py
ðCHðCH3Þ2 Þ, 22.6 ðCHðCH3Þ2 Þ.
3
3
24.06 ðCHðCHACHBÞÞ, 22.1 (NCH(CH3)).
Preparation of 22c. The reaction of 17c (1.78 g,
5.32 mmol) with trimethylaluminium (1.02 ml, 0.77 g,
10.6 mmol) in toluene (30 ml) yielded after column chro-
matography (SiO2; pentane/methanol/chloroform/ trieth-
ylamine, 150:1:1:1) the product as a white solid (1.43 g,
77%). Crystals suitable for X-ray diffraction were obtained
from a mixture of pentane, methanol, chloroform and tri-
ethylamine by evaporation of the solvent at room temper-
ature. M.p. 77 °C (DSC). Anal. Calc. for C24H36N2: C,
81.76; H, 10.29; N, 7.95; Found: C, 81.62; H, 10.32; N,
3
3
Preparation of 22a [17]. The reaction of 17a (2.00 g,
7.13 mmol) with trimethylaluminium (1.37 ml, 1.03 g,
14.3 mmol) in toluene (50 ml) yielded after column chro-
matography (SiO2; pentane/methanol/chloroform/triethyl-
amine, 100:1:1:1) the product as a white solid (1.65 g, 78%).
Crystals suitable for the X-ray diffraction were obtained
from a mixture of pentane, methanol, chloroform and tri-
ethylamine by evaporation of the solvent at room temper-
ature. Anal. Calc. for C20H28N2: C, 81.03; H, 9.52; N, 9.45;

1584
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
7.70%. MS–ESI (m/z, ES+): 353.3 [M+H]+, 375.3
[M+Na]+. 1H NMR (599.8 MHz, CDCl3, 298 K):
d = 7.55 (t, 3J = 7.8 Hz, 1H, 4-HPy), 7.18 (dd,
3J = 7.8 Hz, 4J = 0.7 Hz, 1H, 5-HPy), 7.17 (dd,
3J = 7.8 Hz, 4J = 0.7 Hz, 1H, 3-HPy), 7.05 (m, 3H, 3,4-
HAr), 4.56 (br s, 1H, NH), 3.33 (sept, 3J = 6.9 Hz, 2H,
CH(CH3)2), 1.40 (s, 6H, NC(CH3)2), 1.39 (s, 9H,
C(CH3)3), 1.04 (d, 3J = 6.9 Hz, 12H, CH(CH3)2).
13C{1H} NMR (150.8 MHz, CDCl3, 298 K): d = 167.9
(C6Py), 166.3 (C2Py), 147.1 (C2Ar), 140.4 (C1Ar), 136.5
(C4Py), 124.4 (C4Ar), 122.9 (C3Ar), 116.4 (C5Py), 115.6
(C3Py), 59.4 (NC(CH3)2), 37.6 (C(CH3)3), 30.2 (C(CH3)3),
28.7 (NC(CH3)2), 28.0 (CH(CH3)2), 24.2 (CH(CH3)2). X-
ray crystal structure analysis for 22c: formula C24H36N2,
uminium (0.60 ml, 0.45 g, 6.26 mmol) to yield 21b (950 mg,
77%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 21b in pentane at ꢀ30 °C.
M.p. 170 °C (DSC). Anal. Calc. for C25H39N2Al: C, 76.10;
1
H, 9.96; N, 7.10; Found: C, 76.18; H, 10.22; N: 7.04%. H
NMR (599.8 MHz, [D6]-benzene, 298 K): d = 7.28 (m, 2H,
3
3-HAr), 7.23 (m, 1H, 4-HAr), 6.99 (t, J = 7.9 Hz, 1H, 4-
3
4
HPy), 6.73 (dd, J = 7.9 Hz, J = 1.0 Hz, 1H, 3-HPy), 6.51
(dd, 3J = 7.9 Hz, 4J = 1.0 Hz, 1H, 5-HPy), 3.88 (sept,
Ar
2
3J = 6.8 Hz, 2H, CHðCH3Þ ), 3.55 (sept, 3J = 6.9 Hz,
Py
1H, CHðCH3Þ2 ), 1.34 (s, 6H, NC(CH3)2), 1.32 (d,
Ar
3J = 6.8 Hz, 6H, CHðCH3ACH3BÞ2 ), 1.31 (d, J = 6.8 Hz,
3
Ar
6H, CHðCHA3 CH3BÞ2 ), 1.02 (d, 3J = 6.9 Hz, 6H,
Py
2
CHðCH3Þ ), ꢀ0.21 (s, 6H, Al(CH3)2). 13C{1H}-NMR
M = 352.55, colorless crystal 0.30 ꢁ 0.15 ꢁ 0.10 mm,
(150.8 MHz, [D6]-benzene, 298 K): d = 171.8 (C2Py),
165.5 (C6Py), 151.2 (C2Ar), 142.9 (C1Ar), 140.3 (C4Py),
124.7 (C4Ar), 123.9 (C3Ar), 119.1 (C5Py), 118.9 (C3Py),
˚
a = 10.745(1),
b = 14.093(1),
c = 14.765(1) A,
V = 2235.9(3) A , qcalc = 1.047 g cmꢀ3, l = 0.452 mmꢀ1
,
3
˚
Py
empirical absorption correction (0.876 6 T 6 0.956),
Z = 4, orthorhombic, space group P212121 (No. 19),
63.9 (NC(CH3)2), 35.3 ðCHðCH3Þ2 Þ, 31.0 (NC(CH3)2),
Ar
Ar
28.1 ðCHðCH3Þ Þ, 27.8 ðCHðCHA3 CH3BÞ2 Þ, 24.1
2
Ar
Py
k = 1.54178 A, T = 223 K, x and / scans, 10155 reflec-
ðCHðCHACHBÞ Þ, 23.0 ðCHðCH3Þ Þ, ꢀ6.0 (Al(CH3)2).
˚
3
3
2
2
tions collected ( h, k, l), [(sinh)/k] = 0.60 Aꢀ1, 3904
X-ray crystal structure analysis for 21b: formula
C25H39AlN2, M = 394.56, colorless crystal 0.35 ꢁ 0.30 ꢁ
˚
independent (Rint = 0.041) and 3517 observed reflections
[I P 2r(I)], 248 refined parameters, R = 0.046, wR2 =
0.114, Flack 0.7(6), max. residual electron density 0.12
0.25 mm,
17.6315(1) A,
a = 10.0002(2),
b = 14.3444(3),
c =
3
˚
˚
b = 99.352(1)°,
V = 2495.57(8) A ,
(ꢀ0.14) e Aꢀ3, hydrogen atom at N10 from difference fou-
q
calc = 1.050 g cmꢀ3, l = 0.093 mmꢀ1, empirical absorp-
˚
rier maps and refined free, other calculated and refined as
riding atoms.
tion correction (0.968 6 T 6 0.977), Z = 4, monoclinic,
˚
space group P21/n (No. 14), k = 0.71073 A, T = 198 K, x
General procedure: preparation of amidoalkylpyridine
aluminium complexes (21a–c). Two equivalents of AlMe3
were added carefully to a stirred solution of the respective
imine (1 equiv.) in toluene at 0 °C. Then the reaction mix-
ture was allowed to warm to room temperature over night.
The volatiles were removed in vacuo and the residue was
washed with pentane. The product was obtained as a
yellow powder.
and / scans, 19477 reflections collected ( h, k, l),
[(sinh)/k] = 0.66 Aꢀ1, 5942 independent (Rint = 0.055) and
˚
3986 observed reflections [I P 2r(I)], 263 refined parame-
ters, R = 0.051, wR2 = 0.140, max. residual electron den-
sity 0.22 (ꢀ0.25) e Aꢀ3, hydrogen atoms calculated and
˚
refined as riding atoms.
Preparation of 21c. The iminopyridine 17c (2.04 g,
6.06 mmol) in toluene (40 ml) was reacted with trimethylal-
uminium (1.16 ml, 0.87 g, 12.1 mmol) to yield 21c (2.13 g,
86%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 21c in pentane at ꢀ30 °C.
M.p. 159 °C (DSC). Anal. Calc. for C26H41N2Al: C, 76.43;
H, 10.11; N, 6.86; Found: C, 75.98; H, 9.97; N, 6.97%. 1H-
NMR (599.8 MHz, [D6]-benzene, 298 K): d = 7.26 (m, 2H,
Preparation of 21a. The iminopyridine 17a (2.00 g,
7.13 mmol) in toluene (50 ml) was reacted with trimethylal-
uminium (1.37 ml, 1.03 g, 14.3 mmol) to yield 21a (1.95 g,
78%). M.p. 153 °C (DSC). Anal. Calc. for C22H33N2Al:
C, 74.96; H, 9.44; N, 7.95; Found: C, 74.78; H, 9.39; N,
7.93%. 1H NMR (599.8 MHz, [D6]-benzene, 298 K):
3
4
5
3
d = 7.68 (ddd, J = 5.4 Hz, J = 1.7 Hz, J = 1.0 Hz, 1H,
6-HPy), 7.28 (m, 2H, 3-HAr), 7.24 (m, 1H, 4-HAr), 6.85
(ddd, 3J = 8.2 Hz, 3J = 7.5 Hz, 4J = 1.7 Hz, 1H, 4-HPy),
6.71 (ddd, 3J = 8.2 Hz, 4J = 1.0 Hz, 5J = 1.0 Hz, 1H, 3-
HPy), 6.32 (ddd, 3J = 7.5 Hz, 3J = 5.4 Hz, 4J = 1.0 Hz,
3-HAr), 7.23 (m, 1H, 4-HAr), 6.94 (t, J = 7.9 Hz, 1H, 4-
3
4
HPy), 6.81 (dd, J = 7.9 Hz, J = 1.0 Hz, 1H, 3-HPy), 6.73
(dd, 3J = 7.9 Hz, 4J = 1.0 Hz, 1H, 5-HPy), 3.83 (sept,
3J = 6.8 Hz, 2H, CH(CH3)2), 1.42 (s, 6H, NC(CH3)2),
1.33 (d, 3J = 6.8 Hz, 6H, CHðCH3ACHB3 Þ), 1.31 (d,
3J = 6.8 Hz, 6H, CHðCH3ACH3BÞ), 1.31 (s, 9H, C(CH3)3),
ꢀ0.23 (s, 6H, Al(CH3)2). 13C{1H}-NMR (150.8 MHz,
[D6]-benzene, 298 K): d = 174.2 (C2Py), 166.4 (C6Py),
150.7 (C2Ar), 143.9 (C1Ar), 139.6 (C4Py), 124.6 (C4Ar),
123.8 (C3Ar), 120.1 (C5Py), 119.2 (C3Py), 63.2 (NC(CH3)2),
37.8 (C(CH3)3), 31.2 (NC(CH3)2), 30.6 (C(CH3)3), 28.2
(CH(CH3)2), 26.8 ðCHðCHA3 CH3BÞ2Þ, 24.1 ðCHðCHA3
CHBÞ Þ, ꢀ3.0 (Al(CH3)2). X-ray crystal structure analysis
3
1H, 5-HPy), 3.88 (sept, J = 6.8 Hz, 2H, CH(CH3)2), 1.32
3
3
(d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ), 1.27 (d, J = 6.8 Hz,
6H, CHðCHA3 CH3BÞ), 1.24 (s, 6H, NC(CH3)2), ꢀ0.25
(Al(CH3)2). 13C{1H} NMR (150.8 MHz, [D6]-benzene,
298 K): d = 172.0 (C2Py), 151.4 (C2Ar), 143.3 (C6Py),
142.3 (C1Ar), 139.5 (C4Py), 124.8 (C4Ar), 123.9 (C3Ar),
122.4 (C5Py), 121.5 (C3Py), 64.2 (NC(CH3)2), 30.4
(NC(CH3)2), 28.05 (CH(CH3)2), 28.01 ðCHðCHACHBÞ,
3
3
3
2
Ar), 23.8 ðCHðCHACHBÞÞ, ꢀ6.8 (Al(CH3)2).
for 21c: formula C26H41AlN2, M = 408.59, colorless crystal
3
3
Preparation of 21b. The iminopyridine 17b(1.01 g,
0.40 ꢁ 0.35 ꢁ 0.15 mm, a = 10.528(1), b = 16.085(1), c =
3
˚
˚
3.13 mmol) in toluene (30 ml) was reacted with trimethylal-
15.029(1) A, b = 95.69(1)°, V = 2532.5(3) A , qcalc
=

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1585
1.072 g cmꢀ3, l = 0.094 mmꢀ1, empirical absorption cor-
rection (0.964 6 T 6 0.986), Z = 4, monoclinic, space
C41H48N2Zr, M = 660.03, yellow crystal 0.35 ꢁ 0.15 ꢁ
˚
0.10 mm, a = 10.699(1), b = 15.141(2), c = 22.169(1) A,
3
˚
˚
group P21/n (No. 14), k = 0.71073 A, T = 198 K, x and
b = 103.68(1)°, V = 3489.4(4) A , qcalc = 1.256 g cmꢀ3
,
/ scans, 21016 reflections collected ( h, k, l), [(sinh)/
l = 0.345 mmꢀ1
,
empirical
absorption
correction
k] = 0.67 Aꢀ1, 6137 independent (Rint = 0.050) and 4955
(0.889 6 T 6 0.966), Z = 4, monoclinic, space group P21/
˚
˚
observed reflections [I P 2r(I)], 273 refined parameters,
n (No. 14), k = 0.71073 A, T = 198 K, x and / scans,
R = 0.041, wR2 = 0.111, max. residual electron density
36179 reflections collected ( h,
k,
l), [(sinh)/
0.29 (ꢀ0.25) e Aꢀ3, hydrogen atoms calculated and refined
k] = 0.67 Aꢀ1, 8521 independent (Rint = 0.076) and 6012
observed reflections [I P 2r(I)], 403 refined parameters,
R = 0.056, wR2 = 0.126, max. residual electron density
˚
˚
as riding atoms.
General procedure: preparation of amidoalkylpyridine
Group 4 metal complexes (23a,e; 24b–f; 25a–c,f). The
respective metal complex precursor in toluene was added
to a stirred solution of the respective amine in toluene.
The reaction mixture was heated at 60 °C for 3 h, concen-
trated in vacuo to 1/3 of the volume and the precipitated
product was collected by filtration.
1.36 (ꢀ1.16) e Aꢀ3, hydrogen atoms calculated and refined
˚
as riding atoms.
Preparation of 24b. The reaction of 18c (131 mg,
0.34 mmol) with Zr(NMe2)4 (99 mg, 0.37 mmol) toluene
(7 ml) yielded the product as a white solid (150 mg, 74%).
Anal. Calc. for C32H57N5Zr: C, 63.73; H, 9.53; N, 11.61;
Found: C, 62.46; H, 9.52; N, 11.23%. 1H NMR
Preparation of 23a. The reaction of 18a (105 mg,
0.39 mmol) with tetrabenzylzirconium (178 mg, 0.39 mmol)
in toluene (5 ml) yielded the product as a yellow solid
(185 mg, 74%). Crystals suitable for X-ray diffraction were
obtained from a concentrated solution of 23a in toluene.
1H NMR (599.8 MHz, C6D6, 298 K): d = 7.42 (d,
3J = 5.6 Hz, 1H, 6-HPy), 7.20 (m, 3H, 3,4-HAr), 7.07 (ps t,
4
(599.8 MHz, [D8]-THF, 298 K): d = 7.50 (d, J = 1.9 Hz,
1H, 5-HPy), 7.17 (d, 4J = 1.9 Hz, 1H, 3-HPy), 7.05 (m,
2H, 3-HAr), 6.92 (m, 1H, 4-HAr), 4.65 (s, 2H, NCH2),
3
3.61 (sept, J = 6.8 Hz, 2H, CH(CH3)2), 2.66 (br s, 18H,
N(CH3)2), 1.43 (s, 9H, 6-C(CH3)3), 1.32 (s, 9H, 4-
3
C(CH3)3), 1.27 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ), 1.17
3
3
6H, 3-HBn), 6.86 (t, J = 7.5 Hz, 3H, 4-HBn), 6.75 (ddd,
(d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
3
4
3J = 8.2 Hz, J = 7.6 Hz, J = 1.5 Hz, 1H, 4-HPy), 6.62 (ps
(150.8 MHz, [D8]-THF, 298 K): d = 172.5 (C6Py), 163.6
(C2Py), 162.5 (C4Py), 151.4 (C1Ar), 145.3 (C2Ar), 124.0
(C4Ar), 123.4 (C3Ar), 117.8 (C5Py), 117.2 (C3Py), 66.1
(NCH2), 43.2 (N(CH3)2), 39.0 (6-C(CH3)3), 35.5 (4-
d, 6H, 2-HBn), 6.33 (d, J = 8.2 Hz, 1H, 3-HPy), 6.29 (ddd,
3
3
4
3J = 7.6 Hz, J = 5.6 Hz, J = 0.8 Hz, 1H, 5-HPy), 4.61 (s,
3
2H, NCH2), 3.39 (sept, J = 6.8 Hz, CH(CH3)2), 2.23 (s,
6H, CH2Ph), 1.33 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ),
C(CH3)3),
30.4
(4-C(CH3)3),
30.3
(6-C(CH3)3),
3
1.13 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
28.7 (CH(CH3)2), 26.9 ðCHðCHACHBÞÞ, 24.1 ðCHðCHA
3
3
3
3
(150.8 MHz, C6D6, 298 K): d = 163.1 (C2Py), 149.4
(C1Ar), 148.4 (C6Py), 145.31 (C2Ar), 145.29 (C1Bn), 137.7
(C4Py), 129.5 (C3Bn), 127.2 (C2Bn), 126.2 (C4Ar), 124.6
(C3Ar), 122.1 (C4Bn), 121.0 (C5Py), 120.2 (C3Py), 72.7
(CH2Ph), 67.6 (NCH2), 28.1 (CH(CH3)2), 27.2
ðCHðCHA3 CHB3 ÞÞ, 24.3 ðCHðCH3ACHB3 ÞÞ.
CHB3 ÞÞ.
Preparation of 24c. The reaction of 19a (318 mg,
1.13 mmol) with Zr(NMe2)4 (318 mg, 1.19 mmol) in tolu-
ene (10 ml) yielded the product as a yellow solid (460 mg,
81%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 24c in toluene. M.p.
161 °C (DSC). Anal. Calc. for C25H43N5Zr: C, 59.47; H,
Preparation of 23e [6b–h]. The reaction of 22a (151 mg,
0.51 mmol) with tetrabenzylzirconium (232 mg, 0.51 mmol)
in toluene (4 ml) yielded the product as a yellow solid
(302 mg, 90%). Crystals suitable for X-ray diffraction were
obtained from a concentrated solution of 23e in toluene.
M.p. 104 °C (DSC). 1H NMR (599.8 MHz, C6D6, 298
1
8.58; N, 13.87; Found: C, 59.32; H, 8.74; N, 13.42%. H
NMR (599.8 MHz, [D8]-THF, 298 K): d = 8.34 (ddd,
3J = 5.4 Hz, 4J = 1.7 Hz, 5J = 0.9 Hz, 1H, 6-HPy), 7.92
(ddd, 3J = 8.0 Hz, 3J = 7.5 Hz, 4J = 1.7 Hz, 1H, 4-HPy),
7.59 (d, 3J = 8.0 Hz, 1H, 3-HPy), 7.41 (m, 1H, 5-HPy),
3
4
5
3
4
K): d = 7.34 (ddd, J = 5.5 Hz, J = 1.5 Hz, J = 1.0 Hz,
1H, 6-HPy), 7.20 (m, 3H, 3,4-HAr), 7.08 (ps t, 6H, 3-HBn),
6.85 (m, 4H, 4-HBn, 4-HPy), 6.74 (ps d, 6H, 2-HBn), 6.55
7.09 (dd, J = 7.7 Hz, J = 1.7 Hz, 1H, 30-HAr), 7.06 (dd,
3J = 7.7 Hz, J = 1.7 Hz, 1H, 3-HAr), 6.98 (t, J = 7.7 Hz,
4
3
1H, 4-HAr), 4.81 (q, J = 6.8 Hz, 1H, NCH(CH3)), 3.69
3
(dt, J = 8.1 Hz, J = 5J = 1.0 Hz, 1H, 3-HPy), 6.28 (ddd,
(sept, 3J = 6.9 Hz, 1H, CHðCH3Þ0 Þ, 3.27 (sept,
3
4
2
3J = 7.3 Hz, 3J = 5.5 Hz, 4J = 1.0 Hz, 1H, 5-HPy), 3.43
3J = 6.9 Hz, 1H, CH(CH3)2), 2.67 (br, 18H, N(CH3)2),
1.28 (d, 3J = 6.8 Hz, 3H, NCH(CH3)), 1.22 (d,
3J = 6.9 Hz, 3H, CHðCH3ACH3BÞ), 1.21 (d, 3J = 6.9 Hz,
3
(sept, J = 6.7 Hz, 2H, CH(CH3)2), 2.54 (s, 6H, CH2Ph),
1.35 (d, J = 6.7 Hz, 6H, CHðCHA3 CH3BÞ), 1.15 (d, J =
6.7 Hz, 6H, CHðCH3ACH3BÞ), 1.05 (s, 6H, NC(CH3)2).
13C{1H} NMR (150.8 MHz, C6D6, 298 K): d = 172.4
(C2Py), 149.5 (C2Ar), 148.2 (C6Py), 147.3 (C1Bn), 139.7
(C1Ar), 138.3 (C4Py), 129.0 (C3Bn), 127.3 (C4Ar), 126.6
(C2Bn), 125.5 (C3Ar), 121.5 (C4Bn), 121.1 (C5Py), 120.2
(C3Py), 75.3 (CH2Ph), 72.2 (NC(CH3)2), 30.9 (NC(CH3)2), 28.4
(CH(CH3)2), 27.3 ðCHðCHACHBÞÞ, 25.5 ðCHðCHACHBÞÞ.
3
3
3H, CHðCHA3 CH3BÞ), 1.19 (d, J = 6.9 Hz, 3H, CHðCH3A
3
CHB3 Þ0), 1.17 (d, 3J = 6.9 Hz, 3H, CHðCH3ACHB3 Þ0).
13C{1H} NMR (150.8 MHz, [D8]-THF, 298 K): d = 169.0
(C2Py), 148.5 (C6Py), 147.9 (C20Ar), 147.6 (C1Ar), 146.2
(C2Ar), 138.8 (C4Py), 124.7 (C4Ar), 124.2 (C3Ar), 124.0
(C30Ar), 122.9 (C5Py), 122.5 (C3Py), 69.7 (NCH(CH3)),
43.6 (br, N(CH3)2), 28.7 (CHðCH3Þ20 ), 28.4 (CH(CH3)2),
26.8 ðCHðCHA3 CHB3 ÞÞ, 25.3 ðCHðCH3ACHB3 Þ0Þ, 24.6
3
3
3
3
X-ray crystal structure analysis for 23e: formula

1586
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
ðCHðCHACHBÞÞ, 24.1 ðCHðCHACHBÞ0Þ, 23.4 (NCH(CH3)).
density 0.63 (ꢀ0.62) e Aꢀ3, hydrogen atoms calculated
and refined as riding atoms.
˚
3
3
3
3
X-ray crystal structure analysis for 24c: formula
C25H43N5Zr, M = 504.86, light yellow crystal 0.40 ꢁ
0.30 ꢁ 0.25 mm, a = 8.9173(2), b = 9.4329(2), c = 17.2670
Preparation of 24e. The reaction of 22a (212 mg,
0.72 mmol) with Zr(NMe2)4 (203 mg, 0.76 mmol) in tolu-
ene (5 ml) yielded the product as a yellow solid (298 mg,
79%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 24e in toluene. M.p.
186 °C (DSC). Anal. Calc. for C26H45N5Zr: C, 60.18; H,
˚
(3) A, a = 101.540(1), b = 95.897(1), c = 103.228(1)°,
3
V = 1368.41(5) A , qcalc = 1.225 g cmꢀ3, l = 0.421 mmꢀ1
,
˚
empirical absorption correction (0.850 6 T 6 0.902),
ꢀ
˚
Z = 2, triclinic, space group P1 (No. 2), k = 0.71073 A,
1
T = 198 K, x and / scans, 14347 reflections collected
8.74; N, 13.50; Found: C, 60.01; H, 8.81; N, 13.10%. H
˚
( h,
k,
l), [(sinh)/k] = 0.67 Aꢀ1, 6577 independent
NMR (599.8 MHz, [D8]-THF, 298 K): d = 8.41 (ddd,
3J = 5.4 Hz, 4J = 1.8 Hz, 5J = 1.0 Hz, 1H, 6-HPy), 7.92
(ddd, 3J = 8.1 Hz, 3J = 7.4 Hz, 4J = 1.8 Hz, 1H, 4-HPy),
(Rint = 0.036) and 5983 observed reflections [I P 2r(I)],
291 refined parameters, R = 0.032, wR2 = 0.082, max.
residual electron density 0.58 (ꢀ0.53) e Aꢀ3, hydrogen
7.64 (dt, J = 8.1 Hz, J = 5J = 1.0 Hz, 1H, 3-HPy), 7.40
(ddd, 3J = 7.4 Hz, 3J = 5.4 Hz, 4J = 1.0 Hz, 1H, 5-HPy),
7.15 (m, 2H, 3-HAr), 7.04 (m, 1H, 4-HAr), 3.51 (sept,
3J = 6.8 Hz, 2H, CH(CH3)2), 2.63 (br, 18H, N(CH3)2),
1.39 (s, 6H, NC(CH3)2), 1.22 (d, 3J = 6.8 Hz, 6H,
3
4
˚
atoms calculated and refined as riding atoms.
Preparation of 24d. The reaction of 19b (337 mg,
1.13 mmol) with Zr(NMe2)4 (318 mg, 1.19 mmol) in tolu-
ene (10 ml) yielded the product as a yellow solid (490 mg,
78%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 24d in toluene. M.p.
189 °C (DSC). Anal. Calc. for C29H45N5Zr: C, 62.77; H,
CHðCHA3 CHB3 Þ),
1.16
(d,
3J = 6.8 Hz,
6H,
CHðCHA3 CH3BÞ). 13C{1H} NMR (150.8 MHz, [D8]-THF,
298 K): d = 173.3 (C2Py), 149.8 (C2Ar), 148.4 (C6Py),
144.2 (C1Ar), 139.0 (C4Py), 125.4 (C4Ar), 124.6 (C3Ar),
122.6 (C5Py), 121.7 (C3Py), 70.9 (NC(CH3)2), 43.9
(N(CH3)2), 31.6 (NC(CH3)2), 29.1 (CH(CH3)2), 25.4
ðCHðCHA3 CH3BÞÞ, 24.9 ðCHðCH3ACHB3 ÞÞ. X-ray crystal
structure analysis for 24e: formula C26H45N,Zr,
M = 518.89, colorless crystal 0.60 ꢁ 0.50 ꢁ 0.40 mm,
1
8.17; N, 12.62; Found: C, 62.29; H, 8.11; N, 12.15%. H
NMR (599.8 MHz, [D8]-THF, 298 K): d = 8.40 (d,
3J = 8.5 Hz, 1H, 4-HCh), 8.39 (d, 3J = 8.5 Hz, 1H, 8-
HCh), 7.94 (dd, 3J = 8.0 Hz, 4J = 1.4 Hz, 1H, 5-HCh),
7.75 (ddd, 3J = 8.5 Hz, 3J = 6.9 Hz, 4J = 1.4 Hz, 1H, 7-
HCh), 7.66 (d, 3J = 8.5 Hz, 1H, 3-HCh), 7.60 (ddd,
3J = 8.0 Hz, 3J = 6.9 Hz, 3J = 1.0 Hz, 1H, 6-HCh), 7.12
(dd, 3J = 7.7 Hz, 4J = 1.7 Hz, 1H, 3-HAr), 7.09 (dd,
3J = 7.7 Hz, 4J = 1.7 Hz, 1H, 30-HAr), 7.00 (t,
3J = 7.7 Hz, 1H, 4-HAr), 4.98 (q, 3J = 6.9 Hz, 1H,
NCH(CH3)), 3.75 (sept, 3J = 6.8 Hz,0 1H, CH(CH3)2),
˚
a = 9.179(1), b = 9.324(2), c = 17.498(1) A, a = 100.75(1),
3
˚
b = 97.31(1), c = 102.77(2)°, V = 1412.5(2) A , qcalc
=
1.220 g cmꢀ3, l = 0.410 mmꢀ1, empirical absorption cor-
rection (0.791 6 T 6 0.853), Z = 2, triclinic, space group
˚
ꢀ
P1 (No. 2), k = 0.71073 A, T = 223 K, x and / scans,
3
3.31 (sept, J = 6.9 Hz, 1H, CHðCH3Þ2), 2.93 (br s, 6H,
14891 reflections collected ( h,
k,
l), [(sinh)/
A
B
NðCH3Þ2 ), 2.57 (br s, 6H, NðCH3Þ2 Þ, 2.46 (br s, 6H,
k] = 0.67 Aꢀ1, 6829 independent (Rint = 0.035) and 6129
observed reflections [I P 2r(I)], 301 refined parameters,
R = 0.032, wR2 = 0.082, max. residual electron density
˚
C
NðCH3Þ Þ, 1.41 (d, 3J = 6.9 Hz, 3H, NCH(CH3)), 1.25
2
(d, J = 6.8 Hz, CHðCHA3 CH3BÞ), 1.245 (d, 3J = 6.9 Hz,
3
0
0
CHðCHA3 CHB3 Þ ), 1.23 (d, J = 6.9 Hz, CHðCH3ACHB3 Þ Þ,
0.43 (ꢀ0.55) e Aꢀ3, hydrogen atoms calculated and refined
3
˚
1.20 (d, J = 6.8 Hz, CHðCHA3 CH3BÞ). 13C{1H} NMR
as riding atoms.
3
(150.8 MHz, [D8]-THF, 298 K): d = 170.6 (C2Ch), 147.7
(C2Ar), 147.6 (C1Ar), 146.6 (C8aCh), 146.3 ðC20ArÞ, 139.3
(C4Ch), 130.8 (C7Ch), 128.5 (C5Ch), 128.4 (C4aCh), 127.8
Preparation of 24f. The reaction of 20b (313 mg,
0.96 mmol) with Zr(NMe2)4 (268 mg, 1.00 mmol) in tolu-
ene (10 ml) yielded the product as a bright yellow solid
(465 mg, 89%). Crystals suitable for X-ray diffraction were
obtained from a concentrated solution of 24f in toluene.
M.p. 177 °C (DSC). Anal. Calc. for C28H49N5Zr: C,
61.49; H, 9.03; N, 12.80; Found: C, 61.19; H, 9.08; N,
12.53%. 1H NMR (599.8 MHz, [D8]-THF, 298 K):
(C8Ch), 127.3 (C6Ch), 124.8 (C4Ar), 124.2 (C30Ar), 124.1
C
(C3Ar), 120.4 (C3Ch), 70.8 (NCH(CH3)), 44.1 ðNðCH3Þ Þ,
2
B
A
43.6 ðNðCH3Þ2 Þ, 42.6 ðNðCH3Þ2 Þ, 28.6 (CH(CH3)2), 28.5
CHðCH3Þ0 ), 27.0 ðCHðCH3ACH3BÞ0Þ, 25.5 ðCHðCH3A
2
CHB3 ÞÞ, 24.6 ðCHðCH3ACH3BÞ0Þ, 24.5 ðCHðCH3A CHB3 ÞÞ,
23.3 (NCH(CH3)). X-ray crystal structure analysis for
24d: formula C29H45N5Zr, M = 544.92, yellow crystal
3
3
d = 7.85 (t, J = 7.8 Hz, 1H, 4-HPy), 7.40 (d, J = 7.8 Hz,
1H, 5-HPy), 7.34 (d, 3J = 7.8 Hz, 1H, 3-HPy), 7.07 (dd,
3J = 7.6 Hz, 4J = 1.7 Hz, 1H, 30-HAr), 7.05 (dd,
0.35 ꢁ 0.30 ꢁ 0.20 mm, a = 11.7708(1), b = 17.4066(2),
3
4
3
c = 18.4855(1) A, b = 128.624(1)°, V = 2959.01(5) A ,
3J = 7.6 Hz, J = 1.7 Hz, 1H, 3-HAr), 6.95 (t, J = 7.6 Hz,
˚
˚
3
q
calc = 1.246 g cmꢀ3, l = 0.396 mmꢀ1, empirical absorp-
1H, 4-HAr), 4.74 (q, J = 6.7 Hz, 1H, NCH(CH3)), 3.76
tion correction (0.874 6 T 6 0.925), Z = 4, monoclinic,
(sept, 3J = 6.8 Hz, 1H, CHðCH3Þ0ArÞ, 3.46 (sept,
2
Py
space group P21/c (No. 14), k = 0.71073 A, T = 198 K, x
3J = 6.9 Hz, 1H, CHðCH3Þ ), 3.30 (sept, 3J = 6.8 Hz,
˚
2
Ar
A
and / scans, 20000 reflections collected ( h, k, l),
1H, CHðCH3Þ2 ), 3.04 (br, 6H, NðCH3Þ2 ), 2.63 (br, 6H,
B
C
[(sinh)/k] = 0.67 Aꢀ1, 7216 independent (Rint = 0.034) and
NðCH3Þ2 Þ, 2.43 (br, 6H, NðCH3Þ2 Þ, 1.31 (d, J = 6.9 Hz,
3
˚
Py
6114 observed reflections [I P 2r(I)], 338 refined parame-
ters, R = 0.043, wR2 = 0.107, C8 refined with split posi-
tions to a ratio of 0.73(1) to 0.27, max. residual electron
3H, CHðCHA3 CHB3 Þ ), 1.28 (d, 3J = 6.7 Hz, 3H,
NCH(CH3)), 1.26 (d, J = 6.8 Hz, 3H, CHðCHACHBÞ0Ar),
3
3
3
Ar
3
1.24 (d, J = 6.8 Hz, 3H, CHðCHA3 CH3BÞ ), 1.23 (d,

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1587
Ar
3
3J = 6.8 Hz, 3H, CHðCH3ACHB3 Þ ), 1.22 (d, J = 6.9 Hz,
wR2 = 0.080, max. residual electron density 2.97
Py
3H, CHðCHA3 CHB3 Þ ), 1.18 (d, 3J = 6.8 Hz, 3H,
(ꢀ1.85) e Aꢀ3, hydrogen atoms calculated and refined as
˚
CHðCHA3 CHB3 Þ0Ar). 13C{1H} NMR (150.8 MHz, [D8]-
THF, 298 K): d = 170.2 (C6Py), 168.7 (C2Py), 148.8
(C1Ar), 147.1 ðC20ArÞ, 145.8 (C2Ar), 139.1 (C4Py), 124.4
riding atoms.
Preparation of 25b. The reaction of 18c (151 mg,
0.40 mmol) with Hf(NMe2)4 (156 mg, 0.44 mmol) in tolu-
ene (7 ml) yielded the product as a white solid (185 mg,
68%). Anal. Calc. for C32H57N5Hf: C, 55.68; H, 8.32; N,
10.15; Found: C, 54.49; H, 8.09; N, 8.91%. 1H NMR
(C4Ar), 124.1 (C3Ar), 123.9 (C30Ar), 120.1 (C3Py), 119.7
C
(C5Py), 70.0 (NCH(CH3)), 44.4 ðNðCH3Þ Þ, 43.7
2
B
A
Py
ðNðCH3Þ2 Þ, 42.4 ðNðCH3Þ2 Þ, 35.8 ðCHðCH3Þ2 Þ, 28.6
ðCHðCH3Þ0ArÞ, 28.3 ðCHðCH3Þ Þ, 27.2 ðCHðCHA3
(599.8 MHz, [D8]-THF, 298 K): d = 7.53 (d, J = 1.9 Hz,
Ar
4
2
2
Ar
Py
CHB3 Þ Þ, 25.8 ðCHðCH3ACH3BÞ Þ, 25.7 ðCHðCHA3
1H, 5-HPy), 7.19 (d, J = 1.9 Hz, 1H, 3-HPy), 7.07 (ps d,
4
CHB3 Þ0ArÞ, 25.3 (NCH(CH3)), 24.8 ðCHðCH3ACHB3 Þ Þ, 24.7
2H, 3-HAr), 6.92 (ps t, 1H, 4-HAr), 4.76 (s, 2H, NCH2),
3.62 (sept, 3J = 6.8 Hz, 2H, CH(CH3)2), 2.67 (br, 18H,
N(CH3)2), 1.46 (s, 9H, 6-C(CH3)3), 1.32 (s, 9H, 4-
Ar
ðCHðCHA3 CHB3 Þ0ArÞ, 23.1 ðCHðCH3ACHB3 Þ Þ. X-ray crystal
Py
structure analysis for 24f: formula C28H49N5Zr, M =
546.94, colorless crystal 0.10 ꢁ 0.10 ꢁ 0.03 mm, a =
C(CH3)3), 1.28 (d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ), 1.17
3
3
9.1486(2), b = 9.2655(2), c = 18.5008(8) A, a = 84.608(1),
(d, J = 6.8 Hz, 6H, CHðCHA3 CH3BÞ). 13C{1H} NMR
˚
3
b = 80.723(1),
q
c = 75.628(1)°,
V = 1496.91(8)
A ,
(150.8 MHz, [D8]-THF, 298 K): d = 172.9 (C6Py), 163.8
(C2Py), 162.5 (C4Py), 151.3 (C1Ar), 145.6 (C2Ar), 124.2
(C4Ar), 123.4 (C3Ar), 118.3 (C5Py), 117.2 (C3Py), 65.9
(NCH2), 43.0 (N(CH3)2), 39.3 (6-C(CH3)3), 35.5 (4-
C(CH3)3), 30.41 (4-C(CH3)3), 30.37 (6-C(CH3)3), 28.6
(CH(CH3)2), 27.0 ðCHðCHACHBÞÞ, 24.1 ðCHðCHACHBÞÞ.
˚
calc = 1.213 g cmꢀ3, l = 0.390 mmꢀ1, empirical absorp-
tion correction (0.962 6 T 6 0.988), Z = 2, triclinic, space
ꢀ
˚
group P1 (No. 2), k = 0.71073 A, T = 198 K, x and /
scans, 14004 reflections collected ( h, k, l), [(sinh)/
k] = 0.60 Aꢀ1, 5369 independent (Rint = 0.044) and 4604
˚
3
3
3
3
observed reflections [I P 2r(I)], 320 refined parameters,
Preparation of 25c. The reaction of 19a (227 mg,
0.80 mmol) with Hf(NMe2)4 (312 mg, 1.19 mmol) in tolu-
ene (10 ml) yielded the product as a white solid (420 mg,
89%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 25c in toluene. M.p.
173 °C (DSC). Anal. Calc. for C25H43N5Hf: C, 50.71; H,
R = 0.041, wR2 = 0.085, max. residual electron density
0.41 (ꢀ0.41) e Aꢀ3, hydrogen atoms calculated and refined
˚
as riding atoms.
Preparation of 25a. The reaction of 18a (182 mg,
0.69 mmol) with Hf(NMe2)4 (255 mg, 0.72 mmol) in tolu-
ene (25 ml) yielded the product as a bright yellow solid
(310 mg, 78%). Crystals suitable for X-ray diffraction were
obtained from a concentrated solution of 25a in toluene.
Anal. Calc. for C24H41N5Hf: C, 49.86; H, 7.15; N, 12.11;
Found: C, 49.19; H, 7.13; N, 11.57%. 1H NMR
1
7.32; N, 11.83; Found: C, 50.35; H, 7.35; N, 11.28%. H
NMR (599.8 MHz, [D8]-THF, 298 K): d = 8.37 (ddd,
3J = 5.4 Hz, 4J = 1.7 Hz, 5J = 0.9 Hz, 1H, 6-HPy), 7.95
(ddd, 3J = 8.0 Hz, 3J = 7.5 Hz, 4J = 1.7 Hz, 1H, 4-HPy),
7.61 (ddd, 3J = 8.0 Hz, 4J = 1.6 Hz, 5J = 0.9 Hz, 1H, 3-
HPy), 7.44 (ddd, 3J = 7.5 Hz, 3J = 5.4 Hz, 4J = 1.6 Hz,
1H, 5-HPy), 7.09 (dd, 3J = 7.6 Hz, 4J = 1.6 Hz, 1H, 3-
(599.8 MHz,
[D8]-THF,
298 K):
d = 8.39
(ddd,
3J = 5.5 Hz, 4J = 1.6 Hz, 5J = 0.9 Hz, 1H, 6-HPy), 7.91
(ddd, 3J = 7.9 Hz, 3J = 7.4 Hz, 4J = 1.6 Hz, 1H, 4-HPy),
4
HAr), 7.06 (dd, 3J = 7.6 Hz, J = 1.6 Hz, 1H, 30-HAr),
7.52 (dd, J = 7.9 Hz, J = 0.9 Hz, 1H, 3-HPy), 7.42 (ddd,
3J = 7.4 Hz, 3J = 5.5 Hz, 4J = 0.9 Hz, 1H, 5-HPy), 7.06
(m, 2H, 3-HAr), 6.95 (m, 1H, 4-HAr), 4.93 (s, 2H, NCH2),
6.97 (t, J = 7.6 Hz, 1H, 4-HAr), 4.94 (q, J = 6.8 Hz, 1H,
3
4
3
3
NCH(CH3)), 3.68 (sept, 3J = 6.9 Hz, 1H, CH(CH3)2),
3.27 (sept, 3J = 6.9 Hz, 1H, CHðCH3Þ0 ), 2.70 (br, 18H,
2
3
3
3.50 (sept, J = 6.9 Hz, 2H, CH(CH3)2), 2.85 (12H), 2.51
N(CH3)2), 1.27 (d, J = 6.8 Hz, 3H, NCH(CH3)), 1.22 (d,
(6H) (each br, N(CH3)2), 1.26 (d, 3J = 6.9 Hz, 6H,
3J = 6.9 Hz, 3H, CHðCH3ACH3BÞ0), 1.215 (d, 3J = 6.9 Hz,
0
CHðCHA3 CHB3 Þ),
1.17
(d,
3J = 6.9 Hz,
6H,
3H, CHðCHA3 CH3BÞ Þ, 1.20 (d, J = 6.9 Hz, 3H, CHðCH3A
CHB3 ÞÞ, 1.16 (d, 3J = 6.9 Hz, 3H, CHðCH3ACHB3 Þ).
13C{1H} NMR (150.8 MHz, [D8]-THF, 298 K): d = 169.2
(C2Py), 148.5 (C6Py), 148.0 (C2Ar), 147.8 (C1Ar), 146.3
ðC20ArÞ, 138.9 (C4Py), 124.6 (C4Ar), 124.1 (C30Ar), 124.0
(C3Ar), 123.2 (C5Py), 122.6 (C3Py), 69.9 (NCH(CH3)),
3
CHðCHA3 CH3BÞ). 13C{1H} NMR (150.8 MHz, [D8]-THF,
298 K): d = 164.8 (C2Py), 150.3 (C1Ar), 148.6 (C6Py),
146.0 (C2Ar), 138.6 (C4Py), 124.3 (C4Ar), 123.5 (C3Ar),
123.0 (C5Py), 122.0 (C3Py), 66.4 (NCH2), 43.9, 43.1 (each
br, N(CH3)2), 28.6 (CH(CH3)2), 27.1 ðCHðCHACHBÞÞ,
3
3
24.2 ðCHðCHA3 CHB3 ÞÞ. X-ray crystal structure analysis for
43.5 (br, N(CH3)2), 28.6 (CH(CH3)2), 28.3 CHðCH3Þ0 ),
2
25a: formula C24H41HfN5, M = 578.11, colorless crystal
27.0 ðCHðCHA3 CHB3 Þ0Þ, 25.3 ðCHðCH3ACHB3 ÞÞ, 24.5
0.40 ꢁ 0.30 ꢁ 0.15 mm,
a = 8.8170(2),
b = 9.5686(2),
ðCHðCHA3 CHB3 Þ0Þ,
24.3
ðCHðCHA3 CHB3 ÞÞ,
23.6
˚
c = 17.1548(5) A, a = 97.262(1), b = 104.504(1), c =
(NCH(CH3)). X-ray crystal structure analysis for 25c:
formula C25H43HfN5, M = 592.13, colorless crystal
0.30 ꢁ 0.15 ꢁ 0.10 mm, a = 8.9470(2), b = 9.4417(2), c =
3
q ,
calc = 1.451 g cmꢀ3
˚
105.248(1)°,
V = 1322.88(6) A ,
l = 3.961 mmꢀ1
,
empirical
absorption
correction
˚
ꢀ
(0.300 6 T 6 0.588), Z = 2, triclinic, space group P1 (No.
17.2841(6) A, a = 101.512(1), b = 95.954(1), c = 103.489
2), k = 0.71073 A, T = 198 K, x and / scans, 13619 reflec-
(2)°, V = 1373.82(6) A , qcalc = 1.431 g cmꢀ3, l = 3.816
3
˚
˚
tions collected ( h, k, l), [(sinh)/k] = 0.67 Aꢀ1, 6416
mmꢀ1, empirical absorption correction (0.394 6 T 6 0.702),
˚
ꢀ
˚
independent (Rint = 0.045) and 5534 observed reflections
Z = 2, triclinic, space group P1 (No. 2), k = 0.71073 A,
T = 198 K, x and / scans, 12583 reflections collected
[I
P
2r(I)], 282 refined parameters, R = 0.034,

1588
K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
l), [(sinh)/k] = 0.67 Aꢀ1, 6617 independent
Appendix A. Supplementary material
˚
( h,
k,
(Rint = 0.036) and 5968 observed reflections [I P 2r(I)],
191 refined parameters, R = 0.027, wR2 = 0.065, max.
CCDC 658274, 658275, 658276, 658277, 658278, 658279,
658280, 658281, 658282, 658283, 658284, 658285, 658286,
658287, 658288 and 658289 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supple-
mentary data associated with this article can be found,
in the online version, at doi:10.1016/j.jorganchem.
2007.12.004.
residual electron density 1.59 (ꢀ1.75) e Aꢀ3, hydrogen
˚
atoms calculated and refined as riding atoms.
Preparation of 25f. The reaction of 20b (186 mg,
0.57 mmol) with Hf(NMe2)4 (224 mg, 0.63 mmol) in tolu-
ene (10 ml) yielded the product as a white solid (260 mg,
72%). Crystals suitable for X-ray diffraction were obtained
from a concentrated solution of 24f in toluene. M.p. 190 °C
(DSC). Anal. Calc. for C28H49N5Hf: C, 53.02; H, 7.79; N,
11.04; Found: C, 52.60; H, 7.81; N, 10.80%. 1H-NMR
3
(599.8 MHz, [D8]-THF, 298 K): d = 7.88 (t, J = 7.8 Hz,
References
1H, 4-HPy), 7.43 (d, 3J = 7.8 Hz, 1H, 5-HPy), 7.36 (d,
3J = 7.8 Hz, 1H, 3-HPy), 7.09 (dd, 3J = 7.6 Hz,
4J = 1.7 Hz, 1H, 3-HAr), 7.06 (dd, 3J = 7.6 Hz,
[1] (a) B.L. Small, M. Brookhart, A.M.A. Bennett, J. Am. Chem. Soc.
120 (1998) 4049–4050;
(b) G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox,
S.J. McTavish, G.A. Solan, A.J.P. White, D.J. Williams, J. Chem.
Soc., Chem. Commun. 7 (1998) 849–850.
3
3J = 1.7 Hz, 1H, 30-HAr), 6.95 (t, J = 7.6 Hz, 1H, 4-HAr),
4.88 (q, 3J = 6.7 Hz, 1H, NCH(CH3)), 3.76 (sept,
Ar
3J = 6.8 Hz, 1H, CHðCH3Þ ), 3.59 (sept, 3J = 6.8 Hz,
[2] G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. 11 (1999)
448–468;
G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int. Ed. 38
(1999) 428–447.
[3] See also: (a) V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003)
283–315;
(b) S. Ittel, L.K. Johnson, M. Brookhart, Chem. Rev. 100 (2000)
1169–1203.
[4] (a) F. Guerin, D.H. McConville, N.C. Payne, Organometallics 15
(1996) 5085–5089;
2
Py
2
1H, CHðCH3Þ ), 3.30 (sept, 3J = 6.8 Hz, 1H,
CHðCH3Þ0ArÞ, 3.03 (s, 6H, NðCH3Þ ), 2.65 (s, 6H,
A
2
2
B
C
3
NðCH3Þ2 Þ, 2.47 (s, 6H, NðCH3Þ2 Þ, 1.32 (d, J = 6.8 Hz,
Py
3H, CHðCHA3 CH3BÞ ), 1.273 (d, 3J = 6.7 Hz, 3H,
NCH(CH3)), 1.269 (d, 3J = 6.8 Hz, 3H, CHðCHA3
Ar
Py
CHB3 Þ ), 1.24 (d, J = 6.8 Hz, 9H, CHðCH3ACHB3 Þ ,
3
0Ar
0Ar
CHðCHA3 CHB3 Þ , CHðCH3ACHB3 Þ ), 1.18 (d, J = 6.8 Hz,
3
Ar
3H, CHðCHA3 CH3BÞ ). 13C{1H}-NMR (150.8 MHz, [D8]-
(b) F. Guerin, D.H. McConville, J.J. Vittal, Organometallics 15
(1996) 5586–5590;
(c) F. Guerin, D.H. McConville, J.J. Vittal, G.A.P. Yap, Organome-
tallics 17 (1998) 5172–5177
(d) See for a comparison: R. Kempe, Eur. J. Inorg. Chem. (2003)
791–803.
THF, 298 K): d = 170.4 (C6Py), 168.7 (C2Py), 148.8
(C1Ar), 147.3 (C2Ar), 146.0 ðC20ArÞ, 139.2 (C4Py), 124.4
(C4Ar), 124.0 (C30Ar), 123.9 (C3Ar), 120.2 (C3Py), 120.1
C
(C5Py), 69.6 (NCH(CH3)), 44.3 ðNðCH3Þ Þ, 43.5
2
Py
B
A
ðNðCH3Þ2 Þ, 42.3 ðNðCH3Þ2 Þ, 35.6 ðCHðCH3Þ2 Þ, 28.5
[5] T.R. Boussie, G.M. Diamond, C. Goh, K.A. Hall, A.M. LaPointe,
M.K. Leclerc, V. Murphy, J.A.W. Shoemaker, H. Turner, R.K.
Rosen, J.C. Stevens, F. Alfano, V. Busico, R. Cipullo, G. Talarico,
Angew. Chem. 118 (2006) 3356–3361;
ðCHðCH3Þ Þ, 28.2 ðCHðCH3Þ0ArÞ, 27.4 ðCHðCH3A
Ar
2
2
Py
CHB3 Þ0ArÞ, 25.9 ðCHðCH3ACH3BÞ Þ, 25.7 ðCHðCHA3
Ar
Ar
CHBÞ Þ, 25.4 (NCH(CH3)), 24.9 ðCHðCHACHBÞ Þ, 24.8
T.R. Boussie, G.M. Diamond, C. Goh, K.A. Hall, A.M. LaPointe,
M.K. Leclerc, V. Murphy, J.A.W. Shoemaker, H. Turner, R.K.
Rosen, J.C. Stevens, F. Alfano, V. Busico, R. Cipullo, G. Talarico,
Angew. Chem. Int. Ed. 45 (2006) 3278–3283.
3
3
3
ðCHðCHA3 CHB3 Þ0ArÞ, 23.3 ðCHðCH3ACHB3 Þ Þ. X-ray crystal
structure analysis for 25f: formula C28H49HfN5,
M = 634.21, colorless crystal 0.20 ꢁ 0.12 ꢁ 0.06 mm, a =
Py
[6] (a) R.E. Murray (Univation Technologies, LLC, USA), US0187362,
2005;
˚
9.1712(2), b = 9.2615(2), c = 18.5057(5) A, a = 84.495(1),
3
˚
b = 80.958(1), c = 75.169(1)°, V = 1498.05(6) A , qcalc
=
(b) D.E. Gindelberger (Univation Technologies, LLC, USA), US
6541412, 2003;
(c) J.A. Cook (Carbide Chemicals & Plastics Technology Corpora-
tion, USA), WO 2002024331, 2002;
(d) J.F. Szul, K.A. Erickson, S. Mawson, D.J. Schreck, M.G. Goode,
P.T. Daniell, M.G. Mckee, C.C. Williams (Univation Technologies,
LLC, USA), WO 2001040330, 2001;
(e) R.E. Murray, S. Mawson, J.F. Szul, K.A. Erickson, T.H. Kwack,
F.J. Karol, D.J. Schreck (Univation Technologies, LLC, USA), WO
2001040325, 2001;
1.406 g cmꢀ3, l = 3.505 mmꢀ1, empirical absorption cor-
rection (0.541 6 T 6 0.817), Z = 2, triclinic, space group
˚
ꢀ
P1 (No. 2), k = 0.71073 A, T = 198 K, x and / scans,
14133 reflections collected ( h,
k,
l), [(sinh)/
k] = 0.66 Aꢀ1, 7080 independent (Rint = 0.058) and 6140
observed reflections [I P 2r(I)], 321 refined parameters,
R = 0.037, wR2 = 0.086, max. residual electron density
˚
1.47 (ꢀ1.60) e Aꢀ3, hydrogen atoms calculated and refined
˚
(f) J.F. Szul, K.A. Erickson, S. Mawson, P.T. Daniell, M.G. Goode,
M.G. Mckee (Univation Technologies, LLC, USA), WO 2001030862,
2001;
as riding atoms.
Acknowledgement
(g) R.E. Murray, S. Mawson, C.C. Williams, D.J. Schreck (Univation
Technologies, LLC, USA), WO 2000037511, 2000;
(h) R.E. Murray (Union Carbide Chemicals & Plastics Technology
Corporation, USA), WO 9901460, 1999;
(i) R.E. Murray, V.M. George, D.L. Nowlin, C.C. Schultz, J.L.
Petersen, Polymer Preprints 43 (2002) 294.
Financial support from the Fonds der Chemischen
Industrie and the Deutsche Forschungsgemeinschaft is
gratefully acknowledged.

K. Nienkemper et al. / Journal of Organometallic Chemistry 693 (2008) 1572–1589
1589
[7] (a) See also for a comparison: T.R. Boussie, G.M. Diamond, C. Goh,
A.M. LaPointe, M.K. Leclerc, C. Lund (Symyx Technologies, Inc.)
US 7157400B2, 2007;
[14] (a) M. Gepraegs, L. Gerrit, P. Brinkmann (BASF, AG), DE
19730867, 1999;
(b) A. Koppl, H.G. Alt, J. Mol. Catal. A: Chem. 154 (2000) 45–53;
(c) G.J.P. Britovsek, S.P.D. Baugh, O. Hoarau, V.C. Gibson, D.F.
Wass, A.J.P. White, W.D.J. Williams, Inorg. Chim. Acta 345 (2003)
279–291;
(b) T.R. Boussie, G.M. Diamond, C. Goh, K.A. Hall, A.M.
LaPointe, M.K. Leclerc, C. Lund, V. Murphy (Symyx Technologies,
Inc.), US 6900321B2, 2005;
(c) T.R. Boussie, G.M. Diamond, C. Goh, K.A. Hall, A.M. LaPointe,
M.K. Leclerc, C. Lund, V. Murphy (Symyx Technologies, Inc.), US
6828397, 2004;
(d) R.E. Murray, A.M. Harrison (Univation Technologies, LLC), US
7199255B2, 2007;
(e) K.A. Frazier, H. Boone, P.C. Vosejpka, J.C. Stevens (Dow Global
Technologies Inc.) US 6953764B2, 2005;
(f) T.H. Peterson (Univation Technologies, LLC), US 6927263B2,
2005;
(g) L.-M. Tau, Y.W. Cheung, C.F. Diehl, L.G. Hazlitt (The Dow
Chemical Company), US 2004/0242784, 2004;
(h) R.E. Murray (Union Carbide Chemicals & Plastics Corporation)
US 6610627B1, 2003.
(d) T. Tagata, M. Nishida, Adv. Synth. Catal. 346 (2004) 1655–1660
(e) See also: K. Yliheikkila¨, K. Axenov, M.T. Ra¨isa¨nen, M. Klinga,
M.P. Lankinen, M. Kettunen, M. Leskela¨, T. Repo, Organometallics
26 (2007) 980–987.
[15] (a) S.P. Meneghetti, P.J. Lutz, J. Kress, Organometallics 18 (1999)
2734–2737;
(b) T.V. Laine, U. Piironen, K. Lappalainen, M. Klinga, E. Aitola,
M. Leskela¨, J. Organomet. Chem. 606 (2000) 112–124;
(c) C. Bianchini, H.M. Lee, G. Mantovani, A. Meli, W. Oberhauser,
New J. Chem. 4 (2002) 387–397.
[16] (a) K. Nienkemper, Doctoral Dissertation, Munster, 2007;
¨
(b) Q. Knijnenburg, J.M.M. Smits, P.H.M. Budzelaar, Organome-
tallics 25 (2006) 1036–1046;
[8] (a) G. Dyker, B. Ho¨lzer, G. Henkel, Tetrahedron: Asymm. 10 (1999)
3297–3307;
(c) V.C. Gibson, D. Nienhuis, C. Redshaw, A.J.P. White, D.J.
Williams, J. Chem. Soc., Dalton Trans. 11 (2004) 1761–1765.
[17] (a) R.C. Job, Union Carbide Chemicals & Plastics Technology
Corporation, USA, WO 2003095508, 2003;
(b) R. Carlson, A. Nordahl, W. Kraus, Acta Chem. Scand. 45 (1991)
46–48.
[9] C. Fontenas, E. Bejan, H. Ait Haddou, G.G.A. Balavoine, Synth.
Commun. 25 (1995) 629–633.
(b) T.H. Peterson, Univation Technologies, LLC, USA, US
2003105254, 2003.
[10] W.K. Fife, J. Org. Chem. 48 (1983) 1375–1377.
[11] K. Nienkemper, V.V. Kotov, G. Kehr, G. Erker, R. Fro¨hlich, Eur. J.
Inorg. Chem. (2006) 366–379.
[12] J.C. Cymermann, K.K. Purushothaman, J. Org. Chem. 35 (1970)
1721–1722.
[18] F.H. Allen, O. Kennard, D.G. Watson, J. Chem. Soc., Perkin Trans.
2 (1987) S 1–S19.
[19] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, J.
Chem. Soc. Dalton Trans. (1989) S1–S83.
[20] C. Wang, G. Erker, G. Kehr, K. Wedeking, R. Fro¨hlich, Organo-
metallics 24 (2005) 4760–4773, and references cited therein.
[21] U. Zucchini, E. Albizzati, U. Giannini, J. Organomet. Chem. 26
(1971) 357–372.
[22] (a) D.C. Bradley, I.M. Thomas, J. Chem. Soc. (1960) 3857–3861;
(b) G. Chandra, M.F. Lappert, J. Chem. Soc. (1968) 1940–1945.
[23] Reviews: (a) H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 18
(1980) 99;
[13] (a) T.V. Laine, M. Klinga, M. Leskela¨, Eur. J. Inorg. Chem. (1999)
959–964;
(b) C. Bianchini, H.M. Lee, G. Mantovani, A. Meli, W. Oberhauser,
New J. Chem. 26 (2002) 387–397;
(c) V.C. Gibson, R.K. O’Reilly, D.F. Wass, A.J.P. White, D.J.
Williams, Dalton Trans. (2003) 2824–2830;
(d) N. Saino, F. Amemiya, E. Tanabe, K. Kase, S. Okamoto, Org.
Lett. 8 (2006) 1439–1442;
(b) H.H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R.
¨
(e) A. Trifonov, E.A. Ferova, I.A. Borovkov, G.K. Fukin, E.V.
Baranov, J. Larionova, N.O. Druzhkov, Organometallics 26 (2007)
2488–2491.
Waymouth, Angew. Chem. 107 (1995) 1255–1283;
(c) H.H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R.
¨
Waymouth, Angew. Chem. Int. Ed. Engl. 34 (1995) 1143–1170.