On the quest for new mixed-metal μ-oxo-bridged complexes: Synthesis of compounds containing transition metal-oxygen-main group metal motifs M-O-M 1 (M = Ti, Zr; M1 = Al, Ga) without cyclopentadienyl ligands

Article abstract of DOI:10.1021/ic800567g

The reaction of TiBz₄ (Bz = benzyl) with LAIMe(OH), L = (2,6-iPr₂C₆H₃NC(Me))₂CH, afforded LAIMe(μ-O)TiBz₃ (1) and [LAIMe(μ-O)]₂TiBz ₂ (2), whereas the corresponding reaction with ZrBz₄ resulted only in the formation of the trinuclear species [LAIMe(μ-O)] ₂ZrBz₂ (3). The reaction of (Mes₂Ga(OH)) ₂·THF (Mes = 2,4,6-Me₃C₆H₂) with Ti(NEt₂)₄ yielded the cluster compound TiGa ₆O₇(NEt₂)₂(Mes)₆ (4). All compounds have been characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Additionally, single crystal X-ray structure data of 1, 3, and 4 are reported. Compounds 1-4 show low catalytic activities in the polymerization of ethylene. Revisiting known μ-oxo-bridged complexes containing the M-O-M¹ (M = Ti, Zr, Hf; M¹ = Al, Ga) skeleton revealed that the application of polynuclear group 13 hydroxides and oxo bridged complexes possesses a potential for the preparation of new polyoxometal clusters.

Full text of DOI:10.1021/ic800567g

Inorg. Chem. 2008, 47, 6435-6443
On the Quest for New Mixed-Metal µ-Oxo-bridged Complexes: Synthesis
of Compounds Containing Transition Metal-Oxygen-
Main Group Metal Motifs M-O-M1 (M ) Ti, Zr; M1 ) Al, Ga) without
Cyclopentadienyl Ligands†
Grigory B. Nikiforov, Herbert W. Roesky,* Thomas Schulz, Dietmar Stalke, and M. Witt
Institut fu¨r Anorganische Chemie, Georg-August-UniVersita¨t Go¨ttingen, Tammannstrasse 4,
D-37077, Go¨ttingen, Germany
Received March 31, 2008
The reaction of TiBz4 (Bz ) benzyl) with LAlMe(OH), L ) (2,6-iPr2C6H3NC(Me))2CH, afforded LAlMe(µ-O)TiBz3
(1) and [LAlMe(µ-O)]2TiBz2 (2), whereas the corresponding reaction with ZrBz4 resulted only in the formation of the
trinuclear species [LAlMe(µ-O)]2ZrBz2 (3). The reaction of (Mes2Ga(OH))2 · THF (Mes ) 2,4,6-Me3C6H2) with Ti(NEt2)4
yielded the cluster compound TiGa6O7(NEt2)2(Mes)6 (4). All compounds have been characterized by elemental
analysis, NMR spectroscopy, and mass spectrometry. Additionally, single crystal X-ray structure data of 1, 3, and
4 are reported. Compounds 1-4 show low catalytic activities in the polymerization of ethylene. Revisiting known
µ-oxo-bridged complexes containing the M-O-M1 (M ) Ti, Zr, Hf; M1 ) Al, Ga) skeleton revealed that the
application of polynuclear group 13 hydroxides and oxo bridged complexes possesses a potential for the preparation
of new polyoxometal clusters.
Introduction
The metal atoms of heteropolymetallic clusters arranged
in close proximity to each other may activate substrate
molecules cooperatively or simultaneously; the substrate
is able to switch between the metal atoms, something that
could not be achieved with mononuclear complexes. It is
well-known that µ-oxo bridged aluminum-titanium and
aluminum-zirconium complexes possess high catalytic
activities in olefin polymerization reactions.3
Organometallic polyoxoclusters containing different metals
have recently gained increased interest for application in
technical processes, as well as from theoretical aspects. These
heteropolymetallic compounds may act as suitable model
systems for the immobilization of catalysts at oxide surfaces1
and for the study of their reactivity and properties.2
Consequently increasing research activities are focused on
the synthesis and characterization of mixed metal oxides that
can be employed as multifunctional catalysts or precursors
for the preparation of heterobi- and -polymetallic heteroge-
neous catalysts.4
†
Dedicated to Professor C. N. R. Rao on the occasion of his 75th
birthday.
* To whom correspondence should be addressed. E-mail: hroesky@
gwdg.de.
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10.1021/ic800567g CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 14, 2008 6435
Published on Web 06/25/2008

Nikiforov et al.
Scheme 1. Ar ) 2,6-iPr2C6H3
Examples of heterobimetallic µ-oxo-bridged complexes
exhibiting M-O-M1 motifs (M ) Ti, Zr, M1 ) Al, Ga)
are rare, among them Cp2ZrMe(µ-O)Al6O5(tBu)6(Me),3d
(tBu)2Ga(µ-Neol)2Ti(µ-O)[Ga(tBu)2(HNMe2)] (NeolH2 )
2,2-dimethylpropane-1,3-diol)5 and L*TiCl2(µ-O)AlCl3
(L* ) 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]py-
ridine)6 are known. Recently, we reported a new class of
µ-oxo-bridged heterobimetallic complexes containing the
M(µ-O)Al core (M ) Ti, Zr, Hf).7 The cyclopentadienyl
complexes CpMX2(µ-O)AlMeL (L ) NacNac; X ) Cl,
Me; M ) Ti, Zr) possess high catalytic activity in the
polymerization of ethylene and are considered as model
systems to study the polymerization of olefins. It was
suggested that the bridging oxygen plays an important role
in the active species, forming a kinetically and thermally
stable M(µ-O)Al unit which enhances the Lewis acidity
at the metal atoms.7c However, the noncyclopentadienyl
complexes LAlMe(µ-O)M(NMe2)2(µ-O)AlMeL7f showed
only moderate activity in ethylene polymerization. The
complexes LTiCl2(µ-O)AlMeL and LTiMe2(µ-O)AlMeL
even were unstable at room temperature.8
Scheme 2. Ar ) 2,6-iPr2C6H3
Therefore, we became interested in new µ-oxo-bridged
heterobimetallic systems and quantified the ligand effect on
the stability and polymerization activity of heterobimetallic
µ-oxo-bridged complexes containing the M(µ-O)Al skeleton.
Herein we report on the investigation of the MBz4-LAlMe(OH)
(M ) Ti, Zr) and Ti(NEt2)4-(Mes2Ga(OH))2 ·THF systems.
We describe the synthesis, characterization, and catalytic
activity of new noncyclopentadienyl µ-oxo-bridged bimetallic
and trimetallic compounds with an Al-O-M core and a
polyoxometal cluster with a TiGa6O7 skeleton.
LAlMe(OH) with TiBz4 resulted in a mixture of 2 and
unreacted LAlMe(OH).
The analogous reaction of ZrBz4, stable at ambient
temperature, with 1 to 4 equiv of LAlMe(OH) resulted in
the formation of complex [LAlMe(µ-O)]2ZrBz2 (3) (Scheme
2). Compound 3 was obtained as a powder from the reaction
in toluene followed by crystallization from n-hexane while
crystallization of 3 from DME afforded the 3 · DME0.5
solvate. Surprisingly, the 1:1 complex could not be detected,
the NMR spectrum of the in situ 1:1 mixture of ZrBz4:
LAlMe(OH) exhibits only resonances for ZrBz4 and 3.
The results of the MBz4-LAlMe(OH) (M ) Ti, Zr)
system as well as those of the previously reported
Cp2MMe2-LAlMe(OH)7a,c and M(NMe2)4-LAlMe(OH)7f
showed that only 1:1 and 1:2 complexes could be isolated.
Results and Discussion
For the preparation of µ-oxo-bridged complexes with alkyl
functionalities at the Ti(IV) or Zr(IV) atoms we investigated
the reaction of MMe4 with LAlMe(OH) (M ) Ti, Zr) as
well as that with MBz4 (Bz ) benzyl) and LAlMe(OH). The
reaction of the thermally unstable MMe4 with LAlMe(OH)
resulted in the formation of elemental titanium or zirconium.
The TiBz4 (Bz ) benzyl), stable at room temperature, and
LAlMe(OH) afforded LAlMe(µ-O)TiBz3 (1) and [LAlMe-
(µ-O)]2TiBz2 (2) (Scheme 1). Reactions of 3 to 4 equiv of
(5) van Poppel, L. H.; Bott, S. G.; Barron, A. R. Polyhedron 2003, 22,
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R. B.; Pal, A.; Noltemeyer, M. Inorg. Chem. 2007, 46, 1056–1061.
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H. W. DaltonTrans. 2007, 1360–1370. (f) Mandal, S. K.; Gurubasa-
varaj, P. M.; Roesky, H. W.; Oswald, R. B.; Magull, J.; Ringe, A.
Inorg. Chem. 2007, 46, 4599–4604. (g) Yang, Y.; Schulz, T.; John,
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Jones, P. G., J. Organomet. Chem. 2008, 693, 1455-1461.
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Noltemeyer, M. Dalton Trans. 2007, 4149–4159.
Figure 1. Molecular structure of LAlMe(µ-O)TiBz3, 1, [L ) (2,6-
iPr2C6H3NCMe)2CH)] with selected atoms labeled. Anisotropic displacement
parameters are depicted at the 50% probability level. Only one of the two
crystallographically independent molecules is shown. For clarity reasons
hydrogen atoms are not depicted.
6436 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mixed-Metal µ-Oxo-bridged Complexes
Scheme 3
To prepare a new polyoxometal cluster, we used a gallium
hydroxide with less bulky mesityl groups (Mes2Ga(OH))2 ·THF
and explored its reaction with MR4 (R ) Bz, NEt2). It is
noteworthy that the corresponding aluminum hydroxide
(Mes2Al(OH))2 is unstable at room temperature. Unfortu-
nately, the reaction of the dimeric gallium hydroxide and
MBz4 gives only unidentifiable products. However, the
protocol of 1 and 0.5 equiv of (Mes2Ga(OH))2 · THF with 1
equiv of Ti(NEt2)4 in toluene afforded the polyoxometal
cluster TiGa6O7(NEt2)2(Mes)6 (4) according to the idealized
equation shown in Scheme 3. Compound 4 has been
recrystallized from n-hexane solution to afford crystals
suitable for X-ray structural investigation.
The tendency of (Mes2Ga(OH))2 · THF to form higher
aggregates such as Mes6Ga6O4(OH)4 at room temperature9
and (MesGaO)9 at elevated temperatures10 has been de-
scribed. The reaction of LTiMe3 (L ) NacNac) with
(Mes2Ga(OH))2 ·THF in toluene afforded the di-µ-oxo bridged
complex LTiMe(µ-O)2TiMeL and Mes3Ga8 implying oxygen
transfer from gallium to titanium, whereas in the reaction
depicted in Scheme 3 transfer of the amino substituents from
titanium to gallium occurs.
observed in the EI-MS of 1 and 2 are due to the elimination
of Bz, PhMe, CH4, iPr, and C6H3(iPr)2 from the molecular
ions. The 1H and 13C NMR data of 1 and 2 are in agreement
with the proposed structures (Scheme 1, Figures 1 and 3).
The resonance of the CH2 protons attached to the Ti(IV)
atom appears at 2.00 ppm in 1 and at 2.17 ppm in 2 being
shifted to low frequency relative to TiBz4 (2.79 ppm).11
Compound 1 crystallizes in the monoclinic space group
P21/c and contains two independent molecules in the unit
cell with similar structural features (Figure 1).
As expected, 1 contains the aluminum atom bonded
through an oxygen atom to titanium. The aluminum atom
exhibits a highly distorted tetrahedral coordination site
with two nitrogen atoms of the ꢀ-diketiminato ligand, the
methyl carbon atom, and the (µ-O) atom. The titanium
atom also has a distorted tetrahedral coordination sphere
comprised of the (µ-O) atom and three CH2 groups.
Moreover, Ti(1) and Ti(2) show close contacts with the
carbon atoms of the benzyl group. The shortest contacts
are observed between the Ti atoms and the carbon atoms
C(61) and C(101) in the ꢀ position (2.506 and 2.689 Å,
respectively). The contacts Ti-Cꢀ range from 2.807 to
3.093Å(Figure2).Consequently,theacuteC(61)-C(6)-Ti(1)
and C(101)-C(10)-Ti(2) angles range from 85.8(1)° to
95.3(2)° while the other Ti-CR-Cꢀ angles range from
101.3(2)° to 116.3(2)°. This implies nonequivalent inter-
It is noteworthy that Mes3Ga and unreacted Ti(NEt2)4 (for
a 1:1 ratio of precursors) were detected by NMR spectros-
copy in the in situ mixture, and HNEt2, MesH, and THF
were found in the volatile products.
Characterization of Compounds 1-4. The single crystal
structures of 1, 3, and 4 (Figures 1 to 5) have been
determined by X-ray crystallographic methods. The com-
position and structure of 2 was deduced from elemental
analysis, NMR, and mass spectrometry.
Complexes 1 and 2 are thermally stable (decomp 179 and
187 °C, respectively) and remain unchanged on storage in
sealed ampoules for several months at room temperature.
The largest ion detected in the mass spectrum of 1 corre-
sponds to [M - Bz]+ (m/z 705) whereas in the mass spectrum
of 2 it is [M - PhMe]+ (m/z 1088). Further fragments
Figure 2. Coordination sphere (4.1 Å) around Ti(1) in 1. The values in
brackets are the corresponding bond lengths for the second molecule.
Anisotropic displacement parameters are depicted at the 50% probability
level. Selected distances (Å): Ti(1)-C(51) 2.855 (2.689), Ti(1)-C(52) 3.625
(3.315), Ti(1)-C(56) 3.599 (3.416), Ti(1)-C(61) 2.506 (2.807), Ti(1)-C(62)
3.109 (3.651), Ti(1)-C(66) 3.105 (3.354), Ti(1)-C(71) 3.093 (3.036),
Ti(1)-C(72) 3.698 (3.758), Ti(1)-C(76) 4.051 (3.856).
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1994, 106, 1365–1366; Angew. Chem., Int. Ed. Engl. 1994, 33,
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Inorganic Chemistry, Vol. 47, No. 14, 2008 6437

Nikiforov et al.
distances (2.112(3)-2.143(2) Å) are also similar to those of
the reported Ti(IV) complexes with benzyl ligand (see refs
12–15).
Single crystals of [LAl(Me)(µ-O)]2ZrBz2 ·DME0.5 (3) have
been obtained by recrystallization from DME. Compound 3
j
crystallizes in the triclinic space group P1 (Figure 3).
Both the aluminum and zirconium atoms in 3 exhibit a
distorted tetrahedral coordination with [AlN2(Me)(µ-O)] and
[Zr(µ-O)2(CH2)2] environments (Figure 3). In contrast to the
titanium complex, the zirconium atom shows only weak
contacts to the carbon atoms in the ꢀ position of the Bz
substituent (3.165 and 3.317 Å). Consequently, the C(20)-
C(19)-Zr(1) and C(27)-C(26)-Zr(1) angles are larger
(113.6(2)° and 121.5(2)°) in comparison to those of the
titanium compound 1. Furthermore, the mean angle Zr-C-C
in ZrBz4 is 92° and the average Zr-Cꢀ bond length is 2.74
Å.16 Tetracoordinate zirconium is not common in complexes,
and it is only present when the zirconium atom is encapsu-
lated by bulky ligands, for example, in polymeric
Cs2Ag2ZrTe4 (ZrTe4 polyhedron),17 Zr[CH2(CH2NSiMe-
Figure 3. Molecular structure of 3 with selected atoms labeled. Anisotropic
displacement parameters are depicted at the 50% probability level. Hydrogen
atoms are omitted for clarity reasons.
18
19
Ph2)2]2 and Zr[(NtBu)2SiMe2]2 (ZrN4 polyhedron), and
in ZrCl[N(SiMe3)2]3 (ZrN3Cl polyhedron).20 Therefore, the
tetracoordinate ion in [LAl(Me)(µ-O)]2ZrBz2 (3), as well as
in the related complex [LAl(Me)(µ-O)]2Zr(NMe2)2,7f is the
result of two bulky [LAl(Me)(µ-O)] moieties.
The Zr-(µ-O) bond lengths in 3 (1.9132(14) and 1.9143(14)
Å) and Al-(µ-O) bond lengths (1.7344(15) and 1.7471(15)
Å) are in agreement with those found for [LAl(Me)-
(µ-O)]2Zr(NMe2)2 (1.941(2) and 1.944(2) Å),7f LAlMe(µ-
O)ZrRCp2 (av 1.92 Å) (R ) Me, Cl),7a and LAlMe(µ-
O)TiMeCp2 (1.808(3) Å).7c Two types of Al-(µ-O)-Zr
bond angles are observed in 3 (175.58(9)° and 141.80(9)°)
similar to [LAl(Me)(µ-O)]2Zr(NMe2)2 (166.50(10)° and
173.21(10)°).7f The almost linear Al-(µ-O)-Zr bond angle
is explained by mutual repulsion of the [LAl(Me)] and [Zr(µ-
O)AlMeL] moieties.
Figure 4. Molecular structure of 4 with selected labeled atoms. Anisotropic
displacement parameters are depicted at the 50% probability level. Only
one of the two crystallographically independent molecules is shown.
Hydrogen atoms are omitted for clarity reasons.
actions of the Bz carbon atoms with the titanium atom in
1. The reported Ti-Cꢀ bond lengths in Ti(IV) benzyl
complexes are short (2.464(4)-2.647(4) Å) and result in
small Ti-CR-Cꢀ angles (81.9(2)°-92.5(3)°) (see struc-
tures of TiBz4,12 TiCl3-nBzn(dmpe) (n ) 1,2),13 LTiBz2
(L ) N,N′-bis(trimethylsilyl)aminobenzylamine),14 LTiBz2
(L ) [OSSO]-type ligand)15).
The Al-Me (1.957(2) and 1.959(2) Å), Al-(µ-O)
(1.7468(17) and 1.7391(16) Å) bond lengths as well as
Ti-(µ-O) distances (1.7506(16) and 1.7483(16) Å) and Al(µ-
O)Ti angles (145.4(1)° and 146.5(1)°) compare well with
the recently structurally characterized oxygen bridged het-
erobimetallic compounds of the general formula LAlMe-
(µ-O)M(R)Cp2 (R ) Me, Cl; M ) Ti, Zr, Hf).7 The Ti-CH2
Complex 3 is thermally stable (decomp above 130 °C)
and remains unchanged on storage in sealed ampoules at
room temperature for several months. The ion of highest
mass detected in the mass spectrum of 3 is of weak intensity
and corresponds to [M - C6H3iPr2 - Bz - PhMe]+ (m/z
879). Further ions observed in the EI-MS of 3 are mostly
due to subsequent loss of Bz, PhMe, and C6H3iPr2 from the
molecular ion. The 1H and 13C NMR data of 3 are consistent
1
with the proposed structure (Scheme 2, Figure 3). The H
NMR resonance of the CH2 group attached to the Zr(IV)
atom appears at 1.85 ppm and is shifted to high frequencies
in relation to ZrBz4 (1.44 ppm).
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6438 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mixed-Metal µ-Oxo-bridged Complexes
Ga-O-Ga angles are observed for the Ga(µ-O)(µ-NEt2)Ga
moiety (95.1(1)° to 95.7(1)°) while the largest Ga-O-Ga
angles (135.3(2)° to 136.3(2)°) are found within the Ga(µ3-
O)Ga unit, where one gallium atom belongs to the Ga(µ-
O)(µ-N)Ga moiety. The range of Ga-O-Ga angles, as well
as that of the Ga-O distances, is close to those of
9a
Mes6Ga6O4(OH)4 and (Mes2Ga(OH))2 · THF9b while the
Ti-O-Ga angles in 4 are slightly larger than the Ti-
(µ-O)-Ga angle (106.8(3)°) in (tBu)2Ga(µ-Neol)2Ti(µ-O)-
[Ga(tBu)2(HNMe2)].5
Compound 4 is stable at room temperature under an inert
atmosphere. The biggest ion found in the mass spectrum of
3 corresponds to the [M - Mes - 6 Me]+ cation (m/z 1228).
Further ions are due to loss of Me, Et, and Mes substituents
and of CH4 from the molecular ion (see Supporting Informa-
tion). The 1H NMR spectrum of 4 contains the expected six
resonances of the aromatic protons of the six Mes groups
(6.81-6.24 ppm) and nine resonances for the Me protons
(1.92 to 2.85 ppm). The relative intensities for aromatic and
Me protons is 1:4.5, as expected for 4. The ethyl groups of
NEt2 give rise to four quintets (3.89, 2.87, 2.76, 2.67 ppm)
and two triplets (0.83, 0.37 ppm) because of the nonequiva-
lence of the Et groups in 4.
Figure 5. TiGa6O7N2 core of 4. Ellipsoids represent 50% probability levels.
Hydrogen atoms are omitted for clarity.
j
Compound 4 crystallizes in the triclinic space group P1.
It contains two crystallographically independent molecules
TiGa6O7(NEt2)2(Mes)6 in the lattice with almost identical
conformation (Figure 4). The core of the molecule consists
of a TiGa6O7N2 cluster, where the titanium is connected to
all gallium atoms via two µ- and two µ3-bridging oxygen
atoms. The two amino nitrogen atoms are bound to two
gallium atoms each, one of them being incorporated in the
cluster by one µ- and one µ3-oxygen atom, the other by two
µ3-oxygen atoms. Additionally, each gallium atom is bound
to one Mes group.
Conclusion
Four oxygen atoms form a highly distorted tetrahedral
environment around the Ti(1) and Ti(2) atoms with two
shorter Ti-(µ-O) bond lengths (1.763(3), 1.767(3) Å and
Ti(2)-O(9) 1.751(3) Å) and two longer Ti-(µ3-O) distances
(1.888(3), 1.893(3) Å and Ti(2)-O(11) 1.901(3), Ti(2)-O(12)
1.909(3) Å) (angles see Tables 1 and 2). The Ti-(µ-O) bond
lengths in cluster 4 are longer than those in (tBu)2Ga(µ-
Neol)2Ti(µ-O)[Ga(tBu)2(HNMe2)] (NeolH2 ) 2,2-dimethyl-
propane-1,3-diol),5 (Ti-O 1.725(9) Å, Ga-O 1.94(1) Å)
which has only one Ti(µ-O)Ga bond, and two Ti(µ-OR)Ga
bonds. Therefore, the latter are different from those of 4.
As a consequence, the Ti-(µ-O) bond in 4 is weaker than
in the above-mentioned complex, while the Ga-(µ-O) bond
strength is similar (Table 1).
The coordination geometry around the gallium atoms is that
of a distorted tetrahedron with Ga-O distances in the range of
1.813(3) to 1.994(3) Å. Longer distances are observed for the
Ga-(µ3-O) bonds and shorter ones for the Ga-(µ-O) bonds.
The Ga-N and Ga-C bond lengths are in a narrower range,
1.989 to 2.021 Å (av 2.009 Å) and 1.944(4) to 1.959(6) Å (av
1.953 Å), respectively. The reported Ga-N and Ga-C distances
are typical for the Ga-(µ-N)21 and Ga-C bonds.9,22 The
O-Ga-O and O-Ga-N angles are smaller than the C-Ga-O
and C-Ga-N ones because of mutual repulsion of the ligands.
The Mes group is sterically more demanding than the oxygen
and nitrogen atoms.
We have investigated the MBz4-LAlMe(OH) system
(M ) Ti, Zr) and prepared the heterobimetallic complexes
LAlMe(µ-O)TiBz3 (1), [LAlMe(µ-O)]2TiBz2 (2), and [LAl-
Me(µ-O)]2ZrBz2 (3) which are stable at room temperature.
Titanium complexes containing more than two LAlMe(µ-
O) moieties are not formed from these precursors, instead
1:1 and 1:2 compounds have been obtained. The polynuclear
complex TiGa6O7(NEt2)2(Mes)6 (4) was isolated from the
reaction of Ti(NEt2)4 with (Mes2Ga(OH))2 · THF.
In general, the activity of complexes for the polymerization
of ethylene is not increased by replacement of the Bz or NEt2
group at the transition metal atom by the bulky [LAl(Me)O]
or (MesGaO) moieties (see Supporting Information). Fur-
thermore, we have compared the stability and polymerization
activities of all literature reported and herein investigated
µ-oxo bridged complexes (Table 3).
Several conclusions can be drawn from the results of Table
3. Compounds B and C, containing the bulky NacNac ligand
attached to the titanium as well as to the aluminum center,
are unstable and decompose in solution. The heterobimetallic
complexes A and D-Y with less bulky ligands, such as Cp,
NMe2, or Bz, on the transition metal are stable. Complex F
contains a bulky ligand on the Ti(IV) center and a small
{OAlCl3} moiety connected to the titanium atom. Further-
more, only 1:1 complexes (A, E, I-K, N, O-Y) have been
obtained from LM1Me(OH) (M1 ) Al, Ga) and cyclopen-
tadienyl complexes Cp2MMe2 (M ) Ti, Zr, Hf) or
Cp2Zr(H)Cl. However, MR4 compounds containing less
bulky R groups (Bz, NMe2) than Cp allowed the preparation
of stable 1:2 complexes (G, H, L, M). Hydrolysis of
cyclopentadienyl complexes LAl(µ-S)2MCp2 (M ) Ti, Zr)
afforded the 1:1 complexes LAl(OH)(µ-O)M(SH)Cp2 (E, I)
while hydrolysis of [(tBu)2Ga(Neol)2]2Ti(NMe2)2 resulted
The deviation of the Ga-O-Ga angles is caused by the
different environment of the oxygen atoms. The smallest
(21) (a) Schmidt, E. S.; Jockisch, A.; Schmidbaur, H. J. Chem. Soc., Dalton
Trans. 2000, 1039–1043. (b) Schmidt, E. S.; Jockisch, A.; Schmidbaur,
H. J. Am. Chem. Soc. 1999, 121, 9758–9759. (c) Atwood, J. L.; Bott,
S. G.; Jones, C.; Raston, C. L. Inorg. Chem. 1991, 30, 4868–4870.
(22) Beachley, O. T.; Churchill, M. R.; Pazik, J. C.; Ziller, J. W.
Organometallics 1986, 5, 1814–1817.
Inorganic Chemistry, Vol. 47, No. 14, 2008 6439

Nikiforov et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1, 3, and 4a
1
3
4
Ti(1)-O(1) 1.7506(16)
Ti(1)-C(5) 2.112(3)
Zr(1)-O(1) 1.9143(14)
Ti(1)-O(1) 1.763(3)
Zr(1)-O(2) 1.9132(14)
Ti(1)-O(2) 1.767(3)
Ti(1)-C(7) 2.135(2)
Zr(1)-C(19) 2.265(2)
Ti(1)-O(4) 1.888(3)
Ti(1)-C(6) 2.143(2)
Al(1)-O(1) 1.7391(16)
Al(1)-N(2) 1.897(2)
Al(1)-N(1) 1.8998(19)
Al(1)-C(1) 1.957(2)
Zr(1)-C(26) 2.289(2)
Ti(1)-O(5) 1.893(3)
Al(1)-O(2) 1.7344(15)
Ga(1)-O(1) 1.860(3)
Al(1)-N(2) 1.9088(18)
Ga(1)-O(3) 1.921(3)
Al(1)-N(1) 1.9249(18)
Ga(1)-C(1) 1.956(4)
Al(1)-C(18) 1.947(2)
Ga(1)-N(1) 2.021(4)
O(1)-Ti(1)-C(5) 104.3(1)
O(1)-Ti(1)-C(7) 103.4(1)
C(5)-Ti(1)-C(7) 111.0(1)
O(1)-Ti(1)-C(6) 105.6(1)
C(5)-Ti(1)-C(6) 106.9(1)
C(7)-Ti(1)-C(6) 123.9(1)
O(1)-Al(1)-N(1) 110.4(1)
N(2)-Al(1)-N(1) 97.2(1)
O(1)-Al(1)-C(1) 116.2(1)
N(1)-Al(1)-C(1) 110.2(1)
Al(1)-O(1)-Ti(1) 145.4(1)
C(51)-C(5)-Ti(1) 105.7(1)
C(61)-C(6)-Ti(1) 85.8(1)
C(71)-C(7)-Ti(1) 116.3(1)
O(2)-Zr(1)-O(1) 116.5(1)
O(1)-Zr(1)-C(19) 106.7(1)
C(19)-Zr(1)-C(26) 109.8(1)
O(2)-Al(1)-N(2) 111.5(1)
O(2)-Al(1)-N(1) 112.4(1)
N(2)-Al(1)-N(1) 96.5(1)
O(2)-Al(1)-C(18) 111.1(1)
N(2)-Al(1)-C(18) 114.3(1)
Al(2)-O(1)-Zr(1) 175.6(1)
Al(1)-O(2)-Zr(1) 141.8(1)
C(20)-C(19)-Zr(1) 113.6(2)
C(27)-C(26)-Zr(1) 121.5(2)
O(1)-Ti(1)-O(2) 114.8(1)
O(1)-Ti(1)-O(4) 108.0(1)
O(1)-Ga(1)-O(3) 99.2(1)
O(1)-Ga(1)-C(1) 119.9(2)
C(1)-Ga(1)-N(1) 127.0(2)
O(3)-Ga(6)-O(5) 97.0(1)
a Symmetry transformations used to generate equivalent atoms #1 of 3: -x + 1, -y + 2, -z + 1.
Table 2. Range of Angles (deg) in 4
increase of shielding might be responsible for hampering the
interaction between the metal complexes and the activator
(complex G has low activity only by heating) and/or for the
lower activity of the intermediates. Furthermore, introduction
of a second [LAl(Me)O] moiety, four (MesGaO) species,
and replacement of the [LAl(Me)O] on the more bulky
[Al6O5(tBu)6(Me)] also increases the shielding of the transi-
tion metal center resulting in a decrease of the catalytic
activity (compare activities of complexes A, D and G, H,
R; complexes J, K and L, M, P).
angle
min
max
average
O-Ti-O
Ti-O-Ga
O-Ga-O
O-Ga-N
O-Ga-C
C-Ga-N
Ga-O-Ga
Ga-N-Ga
105.8(1)°
107.0(2)°
94.0(1)°
84.5(1)°
110.9(1)°
112.0(2)°
95.1(1)°
88.8(1)°
114.8(1)°
116.1(2)°
104.0(1)°
106.5(1)°
127.9(2)°
127.0(2)°
136.3(2)°
89.7(2)°
109.4°
112.1°
98.1°
94.6°
120.3°
121.2°
113.5°
89.2°
in the 1:2 complex (tBu)2Ga(µ-Neol)2Ti(µ-O)[Ga(tBu)2-
(HNMe2)] (Q) (NeolH2 ) 2,2-dimethylpropane-1,3-diol).
Reaction of the dinuclear gallium hydroxide containing the
Mes group led to the formation of a 1:6 complex (R).
Another 1:6 complex Cp2ZrMe(µ-O)Al6O5(tBu)6(Me) (P)
was obtained by the reaction of Cp2ZrMe2 and [tBuAl(µ-
O)]6. Thus, combination of the aluminum and gallium
compounds bearing substituents of a reasonable size are
opening a route to new polyoxometal clusters.
When the activity of complexes with the LAl(Me)(µ-O)
moiety is compared, it is obvious, that the cyclopentadienyl
titanium and zirconium 1:1 complexes Cp2MR(µ-O)AlMeL
(R ) Me, Cl, M ) Ti, Zr, L ) (2,6-iPr2C6H3NC(Me))2CH)
(A, J, K) exhibit the best activities in the polymerization of
ethylene upon activation with MAO. The catalytic activity
of these complexes was studied in detail in ref 7a,e. As
depicted in Table 3, the catalytic activity depends on the
type of the transition metal (Ti, Zr containing complexes
are more active than Hf complexes), the ligand attached to
this metal, as well as from the subtituents that bind to the
aluminum atom. Namely, replacement of the Cp ligand
(complexes A, J, K) by the Bz (D, G, M), NMe2 (H, L),
and L* ) 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]py-
ridine) (F) decreases the catalytic activity. This could be
explained by the higher stability of active species supported
by the Cp ligand. Replacement of the Me group on the
aluminum atom by the more bulky Et, Ph groups increases
the shielding of the transition metal center and decreases the
activity (compare activities of complexes J and Y, V). The
Experimental Section
All operations were performed under an atmosphere of dry, O2-
free N2 employing both Schlenk line techniques and a MBraun MB-
150B inert atmosphere glovebox. The solvents toluene, n-hexane,
Et2O, THF, and DME were dried over Na/benzophenone and
distilled under nitrogen prior to use. C6D6 was dried over K and
degassed. The compounds LH with the ligand L ) [2,6-
iPr2C6H3NC(Me)]2CH,23,24 LAlMe(OH),7b (Mes2Ga(OH))2 ·THF,9
11
TiBz4, and ZrBz4 were prepared by methods known from the
literature. The purity of all compounds was checked by 1H and 13
C
NMR spectra. TiCl4 (Aldrich 95%) was distilled prior to use in a
dry and O2-free N2 atmosphere. Solutions of BzMgCl (1.0 M in
Et2O), MAO (10 wt %) in toluene, Ti(NEt2)4 (Acros Organics,
1
98%), and AlMe3 (Aldrich, 98%) were used as received. H and
13C NMR spectra were recorded on Bruker Avance DRX 500 and
Varian INOVA-600 spectrometers. Positive chemical shifts are
reported in δ ppm to high frequency of Me4Si with the resonance
of the residual protons of the solvent as the reference signal.
Assignment of the resonances was made by 1H 13C correlation and
according to reference 25. Chemical shifts of proton resonances
correlating with carbon resonances are shown in brackets.
Mass spectra were recorded using a Finnigan MAT 8230 mass
spectrometer, and elemental analyses were carried out at the
(23) Krause, E. Ber. Dtsch. Chem. Ges. 1918, 51, 1447–1456.
(24) Stender, M.; Wright, R. J.; Eichler, B. E.; Prust, J.; Olmstead, M. M.;
Roesky, H. W.; Power, P. P. J. Chem. Soc., Dalton Trans. 2001, 3465–
3469.
(25) Basuli, F.; Bailey, B. C.; Watson, L. A.; Tomaszewski, J.; Huffman,
J. C.; Mindiola, D. J. Organometallics 2005, 24, 1886–1906.
6440 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mixed-Metal µ-Oxo-bridged Complexes
Table 3. Heterobimetallic and Polymetallic Complexes Containing
Group 4 (M ) Ti, Zr, Hf) and Group 13 (M1 ) Al, Ga) Elements with
M(µ-O)M1 Motifsa
Analytical Laboratory of the Institute of Inorganic Chemistry at
the University of Go¨ttingen. Melting points were determined in
sealed capillary tubes under nitrogen on a Bu¨chi B540 melting point
apparatus. Melting points of the polymers were measured on a
Netzsch STA 409 PC spectrometer.
Compound [LAlMe(µ-O)]TiBz3 (1). A solution of LAlMe(OH)
(0.45 g, 0.95 mmol) and TiBz4 (0.39 g, 0.95 mmol) in toluene (40
mL) was stirred for 3 d at room temperature. After removal of all
volatiles n-hexane was added (20 mL), the solution filtered,
concentrated, and stored at ambient temperature to yield 1 (0.65 g,
86%) as red crystals which were filtered off, washed with n-hexane
1
(2 × 2 mL), and dried in vacuo. Mp 179 °C (decomp). H NMR
(500.2 MHz, C6D6, rt), δH (ppm) ) 7.18-7.10 (m, aryl-H),
7.06-7.03 (m, aryl-H), 6.89 (m, aryl-H), 6.45-6.43 (m, aryl-H),
4.91 (s, 1H, C(CH3)CHC(CH3)), 3.70 (sept, 2H, J ) 6.80 Hz,
CH(CH3)2), 3.36 (sept, 2H, J ) 6.70 Hz, CH(CH3)2), 2.00 (s, 6H,
TiCH2Ph), 1.56 (s, 6H, C(CH3)CHC(CH3)), 1.51 (d, 6H, J ) 6.80
Hz, CH(CH3)2), 1.35 (d, 6H, J ) 6.80 Hz, CH(CH3)2), 1.17 (d,
6H, J ) 6.70 Hz, CH(CH3)2), 1.12 (d, 12H, J ) 6.80 Hz,
CH(CH3)2), -0.08 (s, 3H, Al-CH3).13C NMR (125.707 MHz,
C6D6, rt), δC (ppm) ) 170.9 (C(CH3)CHC(CH3)), 144.9 (aryl-C),
144.1 (aryl-C), 140.3 (aryl-C), 129.1 (aryl-C 7.06-7.03), 128.7
(aryl-C, 6.45-6.43), 127.7 (aryl-C 7.15), 125.2 (aryl-C 7.11), 124.7
(aryl-C, 7.17), 123.1 (aryl-C, 6.89), 97.6 (C(CH3)CHC(CH3), 4.91),
80.8 (Ti-CH2Ph, 2.00), 29.2 (CH(CH3)2, 3.70), 27.9 (CH(CH3)2,
3.36), 26.3 (CH3, 1.35), 24.91 (CH3, 1.51), 24.89 (CH3, 1.17 or
1.12), 24.84 (CH3, 1.17 or 1.12), 23.5 (C(CH3)CHC(CH3), 1.56),
-8.7 (Al-CH3, -0.08), Elemental analysis for C51H65AlN2OTi:
calcd: C, 76.80; H, 8.16; N, 3.51; found C, 76.87; H, 8.19; N, 3.43.
Compound [LAlMe(µ-O)]2TiBz2 (2). This compound was
synthesized by the procedure described for 1 in a 2:1 molar ratio
from LAlMe(OH) (0.88 g, 1.85 mmol) and TiBz4 (0.38 g, 0.92
mmol). Yield 0.54 g. Mp 187 °C (decomp). 1H NMR (500.2 MHz,
C6D6, rt), δH (ppm) ) 7.17-7.15 (m, aryl-H), 7.10-7.08 (m, aryl-
H), 6.93 (m, aryl-H), 6.80 (m, aryl-H), 6.74 (m, aryl-H), 5.13 (s,
2H, C(CH3)CHC(CH3)), 3.78 (sept, 4H, J ) 6.80 Hz, CH(CH3)2),
3.22 (sept, 4H, J ) 6.80 Hz, CH(CH3)2), 2.17 (s, 4H, TiCH2Ph),
1.60 (s, 12H, C(CH3)CHC(CH3)), 1.28 (d, 12H, J ) 6.80 Hz,
CH(CH3)2), 1.26 (d, 12H, J ) 6.80 Hz, CH(CH3)2), 1.13 (t,
overlapping d + d, 24H, CH(CH3)2) -0.51 (s, 6H, Al-CH3). 13C
NMR (125.707 MHz, C6D6, rt), δC (ppm)
)
170.6
(C(CH3)CHC(CH3)), 147.5 (aryl-C), 144.8 (aryl-C), 144.3 (aryl-
C), 141.4 (aryl-C), 127.3 (aryl-C, 7.17-7.15), 124.8 (,aryl-C,
7.10-7.08), 124.7 (aryl-C, 7.17-7.15), 121.6,(aryl-C 6.80), 99.5
(C(CH3)CHC(CH3), 5.13), 73.6 (Ti-CH2Ph, 2.17), 28.5 (CH(CH3)2,
3.78), 28.2 (CH(CH3)2, 3.22), 26.3 (CH3, 1.28 or 1.26), 26.0 (CH3,
1.28 or 1.26), 24.7 (CH3, 1.13), 24.6 (CH3, 1.13), 24.0
(C(CH3)CHC(CH3), 1.60), -11.3 (Al-CH3, -0.51). Elemental
analysis for C74H102Al2N4O2Ti: calcd: C, 75.25; H, 8.64; N, 4.75;
found: C, 75.31; H, 8.69; N, 4.71.
Compound [LAl(Me)(µ-O)]2ZrBz2 (3). Toluene (40 mL) was
added to LAlMe(OH) (1.12 g, 2.4 mmol) and ZrBz4 (0.55 g, 1.2
mmol). The resulting solution was stirred for 3 d at room
temperature; after removal of the solvent n-hexane was added (50
mL). Small amounts of insoluble (ca. 0.1 g, 3 according to NMR)
were filtered off, the n-hexane solution concentrated and left at 0
°C for 4 d, during which time a white solid consisting of small
needles deposited. Yield of 3 0.92 g (65%). Compound 3 can be
recrystallized from DME giving X-ray quality needles of 3·DME.
Elemental analysis and further characterization was done for
3 · DME0.5. The compound turns dark above 130 °C, melting at
a Magnitude of activity: low ∼103-104; moderate ∼105; high ∼106 g
(polymer)/mol catalyst ·h·bar, all complexes were activated with MAO. The
activities are compared at room temperature for the best compatibility. n.r.
) not reported. * indicates complex F was obtained from L*TiCl3 and 2
equiv of MAO, activity of L*TiCl3 upon activation with 500 equiv of MAO
is 2.67 × 105 g (polymer)/mol catalyst ·h·bar at 70 °C.
1
197-198 °C with decomp. H NMR (599.74 MHz, C6D6, rt), δH
(ppm) ) 7.16-7.13 (m, aryl-H), 7.10-7.07 (m, aryl-H), 7.03 (m,
Inorganic Chemistry, Vol. 47, No. 14, 2008 6441

Nikiforov et al.
Table 4. Crystallographic Data and Structure Refinement Details for 1, 3, and 4 at 100 K and Mo KR Radiationa
1
3
4
empirical formula
CCDC no
C51H65AlN2OTi
664927
C76H107Al2N4O3Zr
664925
C62H86Ga6N2O7Ti
664926
Mr
796.93
1269.84
1437.55
crystal size/mm
crystal system
space group
0.2 × 0.2 × 0.05
monoclinic
P21/c
0.4 × 0.2 × 0.05
0.1 × 0.05 × 0.02
triclinic
triclinic
j
P1
j
P1
a/Å
b/Å
c/Å
R/°
ꢀ/°
γ/°
V/Å3
Z
18.312(4)
23.545(5)
21.309(4)
90
98.56(3)
90
9090.0(10)
8
1.165
12.2881(9)
17.1318(13)
19.858(2)
111.6850(10)
93.8700(10)
109.3090(10)
3579.3(5)
2
12.9331(12)
14.5324(14)
35.544(3)
81.7410(10)
81.7230(10)
77.0610(10)
6399.9(10)
4
F
calcd./g·cm-3
1.178
0.226
1362
1.492
2.656
2944
µ/mm-1
0.245
3424
F(000)
scan range Θ/°
completeness to Θmax/%
index ranges
1.42 to 26.42
99.3
-22 e h e 22
0 e k e 29
0 e l e 26
77407
1.91 to 25.05
99.5
-14 e h e 14
-20 e k e 18
0 e l e 23
37690
1.45 to 25.41
99.4
-15 e h e 15
-17 e k e 17
0 e l e 42
107136
total reflections
unique reflections
R(int)
18557
0.0521
12607
0.0289
23474
0.0720
data/restrains/parameters
goodness-of-fit on F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
max./min. el. dens. [e ·Å-3
18557/0/1031
1.037
0.0530, 0.1372
0.0821, 0.1499
0.603, -0.416
12607/42/827
1.059
0.0370, 0.0924
0.0459, 0.0962
0.773, -0.412
23474/15/1474
1.012
0.0417, 0.0809
0.0745, 0.0916
0.615, -0.712
]
4
a wR2 ) (∑[w(Fo - Fc )2]/∑[Fo ])1/2, R1 ) ∑||Fo| - |Fc||/∑|Fo|, weight ) 1/[σ2(Fo ) + (AP)2 + (BP)], where P ) (max (Fo , 0) +2Fc )/3; for 1, A )
2
2
2
2
2
0.0903, B ) 0.00; for 3, A ) 0.0468, B ) 2.3106.; for 4, A ) 0.0321, B ) 9.3272.
aryl-H), 6.82 (m, aryl-H), 6.69 (m, aryl-H), 5.03 (s, 2H,
C(CH3)CHC(CH3)), 3.62 (sept, 4H, J ) 6.71 Hz, CH(CH3)2), 3.31
(s, 4H, CH2, DME), 3.17 (sept, 4H, J ) 6.71 Hz, CH(CH3)2), 3.10
(s, 6H, CH3, DME), 1.85 (s, 4H, ZrCH2Ph), 1.55 (s, 12H,
C(CH3)CHC(CH3)), 1.27 and 1.26 (overlapping d + d, J ) 6.71
Hz, J ) 6.71 Hz), 1.15 (d, 12H, J ) 6.71 Hz, CH(CH3)2), 1.10 (d,
12H, J ) 6.80 Hz, CH(CH3)2), -0.56 (s, 6H, Al-CH3). 13C NMR
(125.707 MHz, C6D6, rt), δC (ppm) ) 170.32 (C(CH3)CHC(CH3)),
146.69 (aryl-C), 144.74 (aryl-C), 144.20 (aryl-C), 141.22 (aryl-C),
128.40 (aryl-C, 7.03), 127.49 (aryl-C, 6.69), 127.25 (aryl-C, 7.14),
124.74 (aryl-C, 7.08), 124.70 (aryl-C, 7.13), 121.35 (aryl-C, 6.82),
99.04 (C(CH3)CHC(CH3), 5.03), 72.19 (CH2, DME, 3.31), 59.35
(Zr-CH2Ph, 1.85), 58.71 (CH3, DME, 3.10), 28.54 (CHCH3)2, 3.62),
28.19 (CHCH3)2, 3.17), 26.14 (CH3, 1.27 or 1.26), 26.00 (CH3,
1.27 or 1.26), 24.77 (CH3, 1.15), 24.63 (CH3, 1.10), 23.77
(C(CH3)CHC(CH3), 1.55), -11.36 (Al-Me, - 0.56). Elemental
analysis for 3·DME0.5, C76H107Al2N4O3Zr calcd: C, 71.82; H, 8.43;
N, 4.41; found: C, 72.32; H, 8.59; N, 4.14.
Compound TiGa6O7(NEt2)2(Mes)6 (4). A toluene solution (20
mL) of Ti(NEt2)4 (0.73 g, 2.2 mmol) was added drop by drop to
the toluene suspension of (Mes2Ga(OH))2 ·THF (1.565 g, 2.2 mmol)
at room temperature. The resulting suspension was stirred at room
temperature for 5 d. During this time all solid dissolved. Then, all
volatiles were removed under vacuum, and the residue dissolved
in n-hexane (60 mL). The n-hexane solution was filtered off from
small amounts of solid (ca. 0.05-0.1 g), concentrated to 30 mL,
and left undisturbed at room temperature. Small needles of 4 were
formed from a n-hexane solution during 7 d at room temperature.
The solid was filtered off and washed with n-hexane (3 × 4 mL).
An additional crop of 4 was obtained by further concentrating this
solution. Yield of 4 0.48 g. Mp 295 °C, (decomp). 1H NMR (599.74
MHz, C6D6, rt), δH (ppm) ) 6.81 (s, 2H, aryl-H), 6.76 (s, 2H, aryl-
H), 6.69 (s, 2H, aryl-H), 6.68 (s, 2H, aryl-H), 6.60 (s, 2H, aryl-H)
6.24 (s, 2H, aryl-H), 3.89 (q, 2H, J ) 7.3 Hz, NCH2CH3), 2.87 (q,
2H, J ) 7.2 Hz, NCH2CH3) overlapping with 2.85 (s, 6H, CH3),
2.76 (q, 2H, J ) 6.7 Hz, NCH2CH3), 2.69 (s, 12H, CH3) overlapping
with 2.66 (q, 2H, J ) 7.0 Hz, NCH2CH3), 2.60 (s, 6H, CH3), 2.32
(s, 6H, CH3), 2.16 (s, 6H, CH3), 2.09 (s, 6H, CH3), 2.08 (s, 6H,
CH3), 1.92 (s, 6H, CH3), 0.83 (t, 6H, J ) 7.0 Hz, NCH2CH3), 0.37
(t, 6H, J ) 7.1 Hz, NCH2CH3). 13C NMR (125.707 MHz, C6D6,
rt), δC (ppm) ) 147.17 (aryl), 146.00 (aryl), 145.59 (aryl), 144.81
(aryl), 143.89 (aryl), 139.24 (aryl), 138.54 (aryl), 137.80 (aryl),
137.04 (aryl), 136.77 (aryl), 134.57 (aryl), 128.68 (aryl), 128.53
(CH of aryl, 6.81 ppm), 128.38 (CH of aryl, 6.76 ppm), 127.53
(CH of aryl, 6.68 ppm), 127.47 (CH of aryl, 6.60 ppm), 127.23
(CH of aryl, 6.24 ppm), 126.38 (CH of aryl, 6.69 ppm), 41.38
(NCH2CH3, 2.87 and 2.66 ppm), 40.60 (NCH2CH3, 3.89 and 2.76
ppm), 26.47 (CH3, 2.69 ppm), 25.85 (CH3, 1.92 ppm), 25.48 (CH3,
2.85 ppm), 25.03 (CH3, 2.60 ppm), 25.01 (CH3, 2.69 ppm), 23.95
(CH3, 2.32 ppm), 21.28 (CH3, 2.16 ppm), 21.14 (CH3, 2.09 or 2.08
ppm), 21.11 (CH3, 2.09 or 2.08 ppm), 13.51 (NCH2CH3, 0.83 ppm),
10.86 (NCH2CH3, 0.37 ppm). Elemental analysis of
C62H86Ga6N2O7Ti, calcd: C, 51.76; H, 5.98; N 1.95; found: C, 52.06,
H 5.99, N 1.87.
X-ray Crystallography. The selected bond distances and angles
are presented in Table 1. Crystallographic data and structure
determinations of 1, 3, and 4 are summarized in Table 4. The data
for 1, 3, and 4 were collected from shock-cooled crystals at 100(2)
K.26 The data for 1 and 3 were collected on a Bruker SMART-
APEX II diffractometer with a D8 goniometer, for 4 on a Bruker
TXS-Mo rotating anode with an APEX II detector on a D8
goniometer. The Bruker SMART-APEX II diffractometer employed
graphite-monochromated Mo KR radiation (λ ) 71.073 pm). The
Bruker TXS-Mo rotating anode employed INCOATEC Helios
mirror optics as radiation monochromator. The data of 1, 3, and
(26) (a) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615–619. (b)
Stalke, D. Chem. Soc. ReV. 1998, 27, 171–178.
6442 Inorganic Chemistry, Vol. 47, No. 14, 2008

Mixed-Metal µ-Oxo-bridged Complexes
4 were integrated with SAINT,27 and an empirical absorption
(SADABS) was applied.28 The structures were solved by direct
methods (SHELXS-97)29 and refined by full-matrix least-squares
methods against F2 (SHELXL-97).30 All non-hydrogen-atoms
were refined with anisotropic displacement parameters. The
hydrogen atoms were refined isotropically on calculated positions
using a riding model with their Uiso values constrained as equal
to 1.5 times the Ueq of their pivot atoms for terminal sp3 carbon
atoms and 1.2 times for all other carbon atoms. Disordered
moieties were refined using bond length restraints and isotropic
displacement parameter restraints. In 3, half an uncoordinated
DME solvent molecule per zirconium atom is present in the
lattice.
Acknowledgment. Support of the Deutsche Forschungs-
gemeinschaft, the Go¨ttinger Akademie der Wissenschaften,
and the Volkswagenstiftung is gratefully acknowledged.
G.B.N. thanks the Alexander von Humboldt foundation for
a research fellowship.
Supporting Information Available: X-ray crystallographic data
files in CIF format; EI-MS data for 1, 2, 3, and 4 and notes for the
preparation of 3 and 4; data for polymerization of ethylene with 1,
2, 3, and 4 as catalysts and MAO as cocatalyst (PDF). This material
is available free of charge via the Internet at http://pubs.acs.org.
(27) SAINT-NT; Bruker AXS Inc.: Madison, WI, 2000.
(28) Sheldrick, G. M. SADABS 2.0,; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 2000.
(29) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467–473.
(30) Sheldrick, G. M. SHELX-97: Program for the Solution and Refinement
of Crystal Structures; Universita¨t Go¨ttingen: Go¨ttingen, Germany,
1997.
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