Synthesis, structural characterization, and reactivity of the ethyl substituted aluminum hydroxide and catalytic properties of its derivative

Article abstract of DOI:10.1016/j.jorganchem.2007.08.032

The ethyl substituted aluminum hydroxide LAlEt(OH) (2; L = HC[C(Me)N(Ar)]₂; Ar = 2,6-iPr₂C₆H₃) was prepared by the hydrolysis of LAlEt(Cl) (1) in the presence of a N-heterocyclic carbene. The reaction of 2 with Cp₂ZrMe₂ in toluene afforded LAlEt(μ-O)ZrMeCp₂ (3) by evolution of methane, while the reaction of 2 with Cp₃M in THF led to the intermolecular elimination of HCp and formation of LAlEt(μ-O)M(THF)Cp₂ (M = Yb, 4; Er, 5; Dy, 6; Y, 7). Compounds 2 and 3 were characterized by single X-ray structural analysis. Compound 2 crystallizes in the orthorhombic space group P2₁2₁2₁, while compound 3 crystallizes in space group Pnma. In both cases, the displacement of the Al and the γ-C atom out of the NCCN plane is observed in a boat conformation, but with converse direction. Furthermore, compound 3 was used as catalyst for ethylene polymerization.

Full text of DOI:10.1016/j.jorganchem.2007.08.032

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1455–1461
www.elsevier.com/locate/jorganchem
Synthesis, structural characterization, and reactivity
of the ethyl substituted aluminum hydroxide and catalytic
properties of its derivative
b
a
b
Ying Yang a,b, Prabhuodeyara M. Gurubasavaraj , Hongqi Ye , Zhensheng Zhang ,
b,
c
Herbert W. Roesky *, Peter G. Jones
a
School of Chemistry and Chemical Engineering, Central South University, 410083 Changsha, PR China
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstraße 4, 37077 Go¨ttingen, Germany
Institut fu¨r Anorganische Chemie und Analytische Chemie der Technischen Universita¨t Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
b
c
Received 25 June 2007; received in revised form 25 August 2007; accepted 26 August 2007
Available online 4 September 2007
Dedicated in memoriam to Professor F. Albert Cotton
Abstract
The ethyl substituted aluminum hydroxide LAlEt(OH) (2; L = HC[C(Me)N(Ar)]2; Ar = 2,6-iPr2C6H3) was prepared by the hydroly-
sis of LAlEt(Cl) (1) in the presence of a N-heterocyclic carbene. The reaction of 2 with Cp2ZrMe2 in toluene afforded LAlEt(l-
O)ZrMeCp2 (3) by evolution of methane, while the reaction of 2 with Cp3M in THF led to the intermolecular elimination of HCp
and formation of LAlEt(l-O)M(THF)Cp2 (M = Yb, 4; Er, 5; Dy, 6; Y, 7). Compounds 2 and 3 were characterized by single X-ray struc-
tural analysis. Compound 2 crystallizes in the orthorhombic space group P212121, while compound 3 crystallizes in space group Pnma. In
both cases, the displacement of the Al and the c-C atom out of the NCCN plane is observed in a boat conformation, but with converse
direction. Furthermore, compound 3 was used as catalyst for ethylene polymerization.
ꢀ 2007 Published by Elsevier B.V.
Keywords: Aluminum hydroxide; Heterobimetallic oxide; b-Diketiminato ligand; Lanthanide; Polymerization
1. Introduction
tory developed the unprecedented aluminum monohydrox-
ide with a terminal OH group, LAlMe(OH) [4], supported
by the sterically hindered b-diketiminato ligand (L = HC-
[C(Me)N(Ar)]2, Ar = 2,6-iPr2C6H3). LAlMe(OH) turned
out to be a suitable synthon to successfully prepare a series
of new compounds LAlMe(l-O)ZrRCp2 (R = Me, Cl) and
LAlMe(l-O)Ln(THF)Cp2 (Ln = Yb, Er, Dy) with well-
defined structures and noticeable catalytic activity [4,5].
Recent ab initio calculations showed that in the M–O–M0
system the oxygen is responsible for the depletion of the
electron density at the metal centers [2,6]. Furthermore,
our interest was intrigued by varying the group R on the
aluminum site to extend the perspective of LAlR(OH). In
this regard, we report on the preparation and structural
characterization of ethyl substituted aluminum hydroxide
Well-defined heterobimetallic oxides have attracted
extensive attention to acquire structurally unusual materi-
als or potentially good catalysts [1,2]. So far, various
approaches were proposed both in chemistry and material
science [3], among which an elaborate strategy via organo-
metallic hydroxides distinguished itself to be a facile route
to form the M–O–M0 unit in compounds without bridging
OR or OAr arrangements. Especially in the course of
design and synthesis of single-site homogeneous catalysts
containing Al–O–M0 (M0 = Zr, Ti, Ln) moiety, our labora-
*
Corresponding author. Tel.: +49 551 393001; fax: +49 551 393373.
E-mail address: hroesky@gwdg.de (H.W. Roesky).
0022-328X/$ - see front matter ꢀ 2007 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2007.08.032

1456
Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
LAlEt(OH) (2). The reactivity of this OH group was exam-
ined by the reactions with Cp2ZrMe2 and Cp3M (M = Yb,
Er, Dy, Y) to form the desired oxo bridged
heterobimetallic oxides. The catalytic activity of the zirco-
nium derivative LAlEt(l-O)ZrMeCp2 (3) was preliminarily
investigated in ethylene polymerization.
meric composition with m/z (%) 473 (24) [M+ꢀOH] and
461 (100) [M+ꢀEt].
2.2. Synthesis of LAlEt(l-O)ZrMeCp2 (3)
Reaction of 2 with 1 equiv. of Cp2ZrMe2 in toluene at
100 ꢁC afforded the l-O bridged LAlEt(l-O)ZrMeCp2 (3)
(Scheme 2) accompanied by methane evolution.
2. Results and discussion
The mass spectrum of 3 exhibits a peak at m/z (%) 709
(88) representing the fragment [M+ꢀMe]. In the 13C
NMR spectrum of 3 the characteristic Cp resonances
2.1. Synthesis of LAlEt(Cl) (1) and LAlEt(OH) (2)
1
Compound 1 was obtained in high yield by the reaction
of LLi Æ OEt2 with 1 equiv. of EtAlCl2 in toluene (Scheme
1). Subsequent hydrolysis of compound 1 was carried out
with 1 equiv. of H2O in the presence of 1,3-diisopropyl-
4,5-dimethylimidazol-2-ylidene (abbreviated as :C) as a
HCl acceptor [7] in toluene at 0 ꢁC to afford compound 2
as a white solid. Compound [H:C]+Clꢀ is nearly insoluble
in toluene and can be removed by filtration.
appear at d 109.9 ppm. The H NMR spectrum displays
the Cp resonances as singlet (d 5.30 ppm). At high field,
one singlet (d ꢀ0.32 ppm) is assigned to the Me protons
of ZrMe, while one quartet (d ꢀ0.14 ppm) and one triplet
(d 1.14 ppm) are attributed to the methylene and methyl
proton resonances of the AlEt group. No hydroxyl proton
resonance is observed in the expectable range, which is con-
sistent with the absence of any OH absorption in the range
3600–3800 cmꢀ1 in the IR spectrum [4].
The composition of both compounds was confirmed by
1
analytical and spectroscopic methods. The H NMR spec-
trum of 1 shows one quartet (d ꢀ0.04 ppm) and one triplet
(d 0.80 ppm) corresponding to methylene and methyl pro-
ton resonances of the ethyl group on aluminum, while in
the 13C NMR spectrum the resonances of these groups
are assigned to d ꢀ1.0 and 8.5 ppm. In contrast, in the
1H NMR spectrum of 2 the methylene and methyl proton
resonances of the ethyl group on aluminum show upfield
shifts (d ꢀ0.23 and 0.71 ppm) relative to those of 1,
whereas the corresponding 13C NMR resonances are
shifted apart (d ꢀ2.4 and 9.2 ppm). The singlet (d
2.3. Synthesis of LAlEt(l-O)M(THF)Cp2 (M = Yb, 4; Er,
5; Dy, 6; Y, 7)
In contrast to the previous elimination of CH4, the reac-
tion of compound 2 with 1 equiv. of Cp3M in THF at room
temperature resulted in an intermolecular elimination of
HCp to render the yttrium and rare earth metal derivatives
LAlEt(l-O)M(THF)Cp2 (M = Yb, 4; Er, 5; Dy, 6; Y, 7)
(Scheme 3).
The melting points of 4, 6, and 7 are in the range from
208 to 210 ꢁC, and for 5 it is 235 ꢁC. In an average they
are 40 ꢁC lower compared to those of the corresponding
methyl analogues [5], which could be attributed to the dif-
ferent alkyl group on aluminum. IR spectra of 4, 5, 6, and 7
1
0.63 ppm) in the H NMR spectrum of 2 is assigned to
the OH proton resonance, while for LAlMe(OH) this reso-
nance was observed at d 0.53 ppm [4]. This downfield shift
is probably due to the electronic effect of the substituent
changing from methyl to ethyl on aluminum. In the IR
spectrum of 2, the OH stretching frequency is found at
3729 cmꢀ1. The mass spectrum of 2 indicates the mono-
Me
Cp
Zr Me
Cp
Et
N
N
toluene, 100 o
-CH4
C
+
Cp2ZrMe2
2
Al
H
O
Me
Me
Me
Et
Cl
N
N
N
N
toluene, -78 ºC
3
OEt2 + EtAlCl2
Al
Al
Li
H
H
-LiCl
-OEt2
Scheme 2.
Me
Me
1
Me
Me
Et
Et
N
N
N
N
N
Cp
toluene, 0 ºC
THF, rt
-HCp
+
2
Cp3M
Al
+
H2O
+
H
H
1
C:
-
M
-[H:C]+Cl
O
N
OH
Cp
THF
Me
Me
2
M = Yb, 4; Er, 5; Dy, 6; Y, 7
Scheme 3.
Scheme 1.

Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
1457
˚
are free of any OH absorption in the reasonable range. The
mass spectra of 4, 5, and 6 exhibit the most intense peak
[M+ꢀTHFꢀEt] with isotopic pattern, followed by
[M+ꢀTHFꢀEtꢀCp]. In the mass spectrum of 7, the base
peak is assigned to the fragment [M+ꢀEtꢀY(THF)Cp2].
Because of the paramagnetic properties of the three lan-
thanide elements, it is not meaningful to describe the
detailed NMR spectra of 4, 5, and 6 in solution, whereas
the data of the yttrium analogue LAlEt(l-O)Y(THF)Cp2
(7) could be helpful for characterizing these systems. In
the 13C NMR spectrum of 7 the Cp resonances are found
1.711(16) A) [8], and comparable to the terminal ones of
˚
[LAl(OH)]2(l-O) (1.738(3), 1.741(3) A) [9].
Compound 3 crystallizes in the orthorhombic space
group Pnma (Fig. 2). Table 1 shows the crystal data and
structure refinement for compounds 2 Æ (THF)2 and 3.
The ethyl group on Al and the methyl group on Zr are
located in the same Al–O–Zr plane and stay away from
each other in a trans conformation. The Al–O bond length
˚
(1.7285(10) A) falls in between those of LAlMe(l-
O)ZrMeCp2 (1.711(2) A) [4] and of 2 (1.7409(17) A), while
˚
˚
˚
the Al-C distance (1.9688(14) A) is comparable to that of 2
1
˚
˚
at d 110.0 ppm. In the H NMR spectrum, the Cp reso-
(1.965(3) A). The Zr–O bond separation (1.9424(10) A) is
nances appear as singlet (d 5.85 ppm), while one quartet
(d 0.40 ppm) and one triplet (d 1.60 ppm) are assigned to
the methylene and methyl proton resonances of the AlEt
group. Two broad resonances (d 1.34 and 3.08 ppm) corre-
spond to those of the protons of the coordinated THF. The
absence of a hydroxyl proton resonance additionally con-
firms the formation of 7 by intermolecular elimination of
HCp. It is worth mentioning that all 1H and 13C resonances
of the substituents on the metal centers of 7 exhibit a down-
field shift when compared with those of 3, which may be
related to the change of the chemical environment.
slightly longer than that of LAlMe(l-O)ZrMeCp2
(1.929(2) A) [4], because of more steric repulsion by the
˚
ethyl group compared to its methyl counterpart. The Al–
O–Zr angle (144.41(6)ꢁ) is obviously narrower than that
of LAlMe(l-O)ZrMeCp2 (158.2(1)ꢁ) [4]. Selected bond dis-
tances and bond lengths for compounds 2 and 3 are shown
in Table 2.
In both cases, the Al and c-C atoms are arranged out of
the NCCN plane to exhibit a boat conformation as shown
in the simplified side view of 2 and 3 (Fig. 3). Interestingly,
the direction of this arrangement turns upside down when a
more bulky substituent than a proton is attached to the
oxygen atom, while the angles of N(1)–Al–N(2) and N–
Al–C remain almost the same. This property of the ligand
ensures both stability and flexibility in such a system.
2.4. X-ray structural analysis of LAlEt(OH) (2) and
LAlEt(l-O)ZrMeCp2 (3)
Keeping the THF solution of 2 at 4 ꢁC overnight
resulted in colorless X-ray quality crystals. The structure
of 2 is depicted in Fig. 1. Compound 2 crystallizes in the
orthorhombic space group P212121 and shows a mononu-
clear composition with an aluminum center in a distorted
tetrahedral geometry coordinated to the chelating b-dike-
timinato ligand, an ethyl, and an OH group. Selected bond
lengths and angles are listed in Table 2. On the one hand
the N(1)–Al–N(2) angle (95.32(8)ꢁ) is even smaller than
that of LAlMe(OH) (96.3(1)ꢁ) [4], on the other the Al–O
2.5. Ethylene polymerization studies
Table 3 summarizes the polymerization results of cata-
lyst 3. All polymeric materials were isolated as white pow-
ders. Under comparable polymerization conditions, the
methylalumoxane (MAO)/3 catalyst system shows lower
activity compared to that of MAO/LAlMe(l-O)ZrMeCp2
˚
bond length (1.7409(17) A) is slightly longer than those
˚
of LAlMe(OH) (1.731(3) A) and LAl(OH)2 (1.695(15),
Al
C(26)
Zr
O
Fig. 1. Molecular structure of 2. Thermal ellipsoids are drawn at the 50%
level, and the hydrogen atoms of the ligand and the two THF molecules
are omitted for clarity.
Fig. 2. Molecular structure of 3. Hydrogen atoms are omitted for clarity.

1458
Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
Table 1
Crystal data and structure refinement for compounds 2 Æ (THF)2 and 3
2 Æ (THF)2
3
Formula
fw
C
634.89
39H63AlN2O3
C42H59AlN2OZr
726.11
T (K)
133(2)
100(2)
Crystal system
Orthorhombic
P212121
0.71073
9.4622(9)
Orthorhombic
Pnma
Space group
˚
k (A)
0.71073
18.8469(17)
˚
a (A)
˚
b (A)
15.1590(15)
19.6279(17)
˚
c (A)
26.479(3)
3798.0(6)
10.2628(9)
3796.5(6)
3
˚
V (A )
Z
4
4
qcalc (g/cm3)
1.110
0.090
1.270
0.347
l (mmꢀ1
)
Crystal size (mm)
h Range for data collection (ꢁ)
Index ranges
0.40 · 0.30 · 0.25
0.27 · 0.27 · 0.12
1.54–28.70
2.08–33.73
ꢀ12 6 h 6 12, ꢀ20 6 k 6 20, ꢀ35 6 l 6 35
ꢀ29 6 h 6 29, ꢀ30 6 k 6 30, ꢀ15 6 l 6 16
Reflections collected
44236
128071
Independent reflections [Rint
Data/restr./param.
]
9787 [0.0414]
9787/137/421
1.059
0.0561, 0.1462
0.0817, 0.1656
0.569/ꢀ0.450
7767 [0.0398]
7767/4/240
1.040
0.0286, 0.0734
0.0358, 0.0781
0.772/ꢀ0.461
Goodness-of-fit on F2
R1, wR2 (I > 2r(I))
R1, wR2 (all data)
Largest differences in peak/hole (e A
ꢀ3
˚
)
Table 2
Selected bond distances (A) and angles (ꢁ) for compounds 2 and 3
˚
2
3
Al–O
1.7409(17)
1.9047(18)
1.9147(19)
1.965(3)
1.7285(10)
1.9213(8)
1.9213(8)
1.9688(14)
1.528(2)
Al–N(1)
Al–N(2)
Al–C
C(m)–C(n)a
Zr–O
1.533(4)
1.9424(10)
2.267
Zr–XCp
O–Al–N(1)
O–Al–N(2)
N(1)–Al–N(2)
O–Al–C
N(1)–Al–C
N(2)–Al–C
C(m)–C(n)–Ala
Al–O–Zr
109.42(8)
105.80(9)
95.32(8)
115.70(11)
113.60(10)
114.95(10)
115.04(19)
112.68(3)
112.68(3)
96.59(5)
109.34(5)
112.58(3)
112.58(3)
121.35(10)
144.41(6)
127.73
XCp1–Zr–XCp2
a
C(m) and C(n) stand for the methyl and methylene carbon of AlEt
group.
[4]. However, the MAO activated compound 3 still exhibits
good catalytic activity for the polymerization of ethylene.
Fig. 4 visualizes the MAO/3 ratios dependence activity,
which reveals a gradual increase in the activity with the
MAO/3 till to 400, followed by a slow decrease as the
MAO/3 ratio is raised further.
Fig. 3. Side view of compounds 2 and 3. Only selected atoms are included
for clarity.
2.6. Polymer properties
range of 119–127 ꢁC, somewhat lower than the typical
range for the linear polyethylene. The 13C NMR data exhi-
bit a resonance (d 29.81 ppm) corresponding to the back-
bone carbon of the linear polyethylene.
DSC measurements show that the melting points (Tm) of
the polyethylene produced by MAO activated 3 are in the

Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
1459
Table 3
20 mmol) in toluene (100 mL). The mixture was allowed
to warm to room temperature and stirred for 12 h.
After filtration the filtrate was concentrated (20 mL)
and kept at 4 ꢁC to afford colorless crystals. X-ray qual-
ity crystals were grown from toluene. Yield 8.05 g
(79%).
Ethylene polymerization for compound 3 (12.4 lmol) in 100 mL of
toluene under 1 atm ethylene pressure at 25 ꢁC
Catalyst MAO/
t
PE
Activity (105 g PE/mol
cat h)
Tm
(ꢁC)
3
(min) (g)
3
3
3
3
200
300
400
600
30
30
30
30
0.31
0.50
1.20
1.95
1.61
123
127
121
119
0.75
1.21
1.01
M.p. 153–155 ꢁC. 1H NMR (300.13 MHz, C6D6): d
ꢀ0.04 (q, J = 8.0 Hz, 2H, AlCH2CH3), 0.80 (t,
J = 8.0 Hz, 3H, AlCH2CH3), 1.00 (d, J = 6.8 Hz, 6H,
CH(CH3)2), 1.19 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.30
(d, J = 6.8 Hz, 6H, CH(CH3)2), 1.48 (d, J = 6.6 Hz, 6H,
CH(CH3)2), 1.55 (s, 6H, CMe), 3.21 (sept, J = 6.8 Hz,
2H, CH(CH3)2), 3.76 (sept, J = 6.8 Hz, 2H, CH(CH3)2),
4.96 (s, 1H, c-CH), 7.04–7.15 (m, Ar) ppm. 13C NMR
(75.5 MHz, C6D6): d 170.7 (CN), 146.0, 143.3, 139.7,
127.7, 125.4, 123.9 (i-, o-, m-, p-Ar), 98.7 (c-CH), 29.2,
28.1 (CH(CH3)2), 26.9, 24.9, 24.5, 23.8 (CH(CH3)2),
23.2 (b-CH3), 8.5 (AlCH2CH3), ꢀ1.0 (br, AlCH2CH3)
2.0
1.5
1.0
0.5
0.0
ppm. IR (Nujol mull, cmꢀ1): v = 3062 (s), 1587 (m),
~
200
300
400
500
600
1558 (s), 1534 (s), 1517 (s), 1442 (s), 1344 (s), 1319 (s),
1259 (s), 1177 (m), 1101 (m), 1021 (s), 938 (m), 878
(w), 834 (w), 801 (m), 777 (w), 759 (w), 718 (w), 648
(w), 618 (m), 533 (m). EI-MS: m/z (%): 479 (100)
[M+ꢀEt]. Anal. Calc. for C31H46AlClN2 (509.1): C,
73.13; H, 9.11; N, 5.50. Found: C, 72.45; H, 8.86; N,
5.43%.
MAO / Cat
Fig. 4. Activity against MAO to catalyst ratio of 3.
3. Conclusion
A novel ethyl substituted aluminum hydroxide LAlEt-
(OH) (2) was synthesized by controlled hydrolysis of
LAlEt(Cl) (1) and characterized analytically and spectro-
scopically. In subsequent reactions, the proton of the OH
group exhibited an expected reactivity by intermolecular
elimination of CH4 and HCp, respectively, to afford l-O
bridged heterobimetallic compounds LAlEt(l-O)ZrMeCp2
(3) and LAlEt(l-O)M(THF)Cp2 (M = Yb, 4; Er, 5; Dy, 6;
Y, 7). Compound 3 exhibits good catalytic activity in eth-
ylene polymerization. Currently, we are aiming at the var-
iation of R in LAlR(OH) to explore further M–O–M0
precursor with new properties and applications.
4.3. Synthesis of LAlEt(OH) (2) [13]
To a mixture of 1 (2.04 g, 4 mmol) and [CN(iPr)C2Me2-
N(iPr)] (:C, 0.72 g, 4 mmol) in toluene (60 mL) at 0 ꢁC, dis-
tilled H2O (18 lL, 4 mmol) was added. The suspension was
allowed to warm to room temperature and stirred for 12 h.
The insoluble solid was removed by filtration and from the
filtrate all volatiles were removed in vacuo and the resulting
residue was washed with n-pentane (5 mL) to afford a white
solid. X-ray quality crystals of 2 were grown from THF at
4 ꢁC. Yield 1.43 g (73%).
M.p. 163 ꢁC. 1H NMR (500.13 MHz, C6D6): d ꢀ0.23 (q,
J = 8.2 Hz, 2H, AlCH2CH3), 0.63 (s, 1H, OH), 0.71 (t,
J = 8.2 Hz, 3H, AlCH2CH3), 1.06 (d, J = 6.8 Hz, 6H,
CH(CH3)2), 1.21 (d, J = 7.0 Hz, 6H, CH(CH3)2), 1.32 (d,
J = 7.0 Hz, 6H, CH(CH3)2), 1.34 (d, J = 6.6 Hz, 6H,
CH(CH3)2), 1.58 (s, 6H, CMe), 3.22 (sept, J = 6.8 Hz,
2H, CH(CH3)2), 3.68 (sept, J = 6.8 Hz, 2H, CH(CH3)2),
4.93 (s, 1H, c-CH), 7.07–7.15 (m, Ar) ppm. 13C NMR
(125.8 MHz, C6D6): d 169.3 (CN), 145.4, 143.4, 140.8,
127.3, 124.9, 123,9 (i-, o-, m-, p-Ar), 97.3 (c-CH), 28.9,
27.8 (CH(CH3)2), 26.1, 24.9, 24.4, 24.0 (CH(CH3)2), 23.1
(b-CH3), 9.2 (AlCH2CH3), ꢀ2.4 (br, AlCH2CH3) ppm.
4. Experimental
4.1. General procedures
All manipulations were carried out under an atmosphere
of purified nitrogen using standard Schlenk techniques.
The samples for analytical measurements as well as for
reactions were manipulated in a glove box. The solvents
were purified and dried using conventional procedures,
and were freshly distilled under nitrogen, and degassed
prior to use. Cp2ZrMe2 and EtAlCl2 were purchased from
Aldrich. LLi Æ OEt2 [10], Cp3M [11], and 1,3-diisopropyl-
4,5-dimethylimidazol-2-ylidene [12] were prepared as
described in the literature.
IR (Nujol mull, cmꢀ1): v = 3729 (m, OH), 1654 (w), 1552
~
(w), 1529 (w), 1319 (m), 1261 (w), 1179 (w), 1101 (w),
1059 (w), 1021 (w), 938 (w), 875 (w), 834 (w), 802 (w),
761 (w), 723 (w), 657 (w). EI-MS: m/z (%): 473.3 (24)
[M+ꢀOH], 461.3 (100) [M+ꢀEt]. Anal. Calc. for
C31H47AlN2O (490.7): C, 75.88; H, 9.65; N, 5.71. Found:
C, 75.24; H, 9.44; N, 5.62%.
4.2. Synthesis of LAlEt(Cl) (1)
EtAlCl2 (11.2 mL, 1.8 M in n-hexane, 20 mmol) was
added drop by drop at ꢀ78 ꢁC to LLi Æ OEt2 (9.97 g,

1460
Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
4.4. Synthesis of LAlEt(l-O)ZrMeCp2 (3)
(w), 1100 (w), 1057 (w), 1015 (w), 936 (w), 903 (m),
799 (w), 772 (m), 762 (m), 722 (w). EI-MS: m/z (%):
Toluene (40 mL) was added to the mixture of 2 (0.49 g,
1 mmol) and Cp2ZrMe2 (0.26 g, 1 mmol). The resulting
solution was stirred for 2 h at room temperature, and then
continuously for 24 h at 100 ꢁC. After concentration and
keeping the solution at room temperature for 1 day, color-
less crystals of 3 (0.51 g) were isolated. Yield 0.48 g (66 %).
M.p. 368–369 ꢁC. 1H NMR (500.13 MHz, CDCl3): d
ꢀ0.32 (s, 3H, ZrMe), ꢀ0.14 (q, J = 7.9 Hz, 2H,
AlCH2CH3), 1.04 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.14 (t,
J = 7.9 Hz, 3H, AlCH2CH3), 1.25 (d, J = 6.8 Hz, 6H,
CH(CH3)2), 1.37 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.41 (d,
J = 6.8 Hz, 6H, CH(CH3)2), 1.77 (s, 6H, CMe), 3.15 (sept,
J = 6.8 Hz, 2H, CH(CH3)2), 3.29 (sept, J = 6.8 Hz, 2H,
CH(CH3)2), 5.02 (s, 1H, c-CH), 5.30 (s, 10H, C5H5),
7.24–7.27 (m, Ar) ppm. 13C NMR (125.8 MHz, CDCl3):
d 170.5 (CN), 144.7, 143.9, 141.2, 127.0, 124.7, 124,2 (i-,
o-, m-, p-Ar), 109.9 (C5H5), 97.3 (c-CH), 28.7, 27.1
(CH(CH3)2), 25.3, 25.2, 24.6, 24.6 (CH(CH3)2), 23.8 (b-
CH3), 17.6 (ZrMe), 9.4 (AlCH2CH3), 3.4 (br, AlCH2CH3)
758.3
(100)
[M+ꢀTHFꢀEt],
693.3
(6)
[M+ꢀ
THFꢀEtꢀCp]. Anal. Calc. for C45H64AlErN2O2 (859.2):
C, 62.90; H, 7.51; N, 3.26. Found: C, 61.40; H, 7.36;
N, 3.08%.
4.7. Synthesis of LAlEt(l-O)Dy(THF)Cp2 (6)
The procedure is the same as that described for 4 with
Cp3Dy (0.35 g, 1 mmol) instead of Cp3Yb. Yield 0.24 g
(28%).
M.p. 208–210 ꢁC. IR (Nujol mull, cmꢀ1): v ¼1623 (w),
~
1585 (w), 1528 (w), 1314 (w), 1260 (w), 1175 (w), 1099
(w), 1058 (w), 1018 (w), 936 (w), 898 (w), 799 (w), 772
(w), 761 (w), 722 (w), 664 (w). EI-MS: m/z (%): 754.3
(100) [M+ꢀTHFꢀEt], 688.3 (20) [M+ꢀTHFꢀEtꢀCp].
Anal. Calc. for C45H64AlDyN2O2 (854.5): C, 63.25; H,
7.55; N, 3.28. Found: C, 62.71; H, 7.61; N, 3.26%.
4.8. Synthesis of LAlEt(l-O)Y(THF)Cp2 (7)
ppm. IR (Nujol mull, cmꢀ1): v = 1734 (m), 1653 (w),
~
1624 (w), 1591 (w), 1530 (m), 1396 (s), 1317 (m), 1259
(m), 1177 (m), 1099 (m), 1059 (w), 1019 (m), 940 (w), 872
(w), 839 (m), 795 (s), 759 (w), 724 (w), 643 (w), 599 (w),
587 (w), 568 (w), 530 (w), 442 (w). EI-MS: m/z (%): 709.3
(88) [M+ꢀMe], 695.3 (100) [M+ꢀ2Me+1]. Anal. Calc. for
C42H59AlN2OZr (726.1): C, 69.47; H, 8.19; N, 3.86. Found:
C, 69.40; H, 8.32; N, 3.52%.
The procedure is the same as that described for 4 with
Cp3Y (0.36 g, 1 mmol) instead of Cp3Yb. Yield 0.34 g
(44%).
M.p. 208–210 ꢁC. 1H NMR (500.13 MHz, C6D6): d 0.40
(q, J = 8.0 Hz, 2H, AlCH2CH3), 1.15 (d, J = 6.8 Hz, 6H,
CH(CH3)2), 1.31 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.34
(br, 4H, O-(CH2CH2)2), 1.50 (d, J = 6.8 Hz, 6H,
CH(CH3)2), 1.51 (d, J = 6.8 Hz, 6H, CH(CH3)2), 1.52 (s,
6H, CMe), 1.60 (t, J = 8.0 Hz, 3H, AlCH2CH3), 3.08 (br,
4H, O-(CH2CH2)2), 3.45 (sept, J = 6.8 Hz, 2H,
CH(CH3)2), 3.64 (sept, J = 6.8 Hz, 2H, CH(CH3)2), 4.84
(s, 1H, c-CH), 5.85 (s, 10H, C5H5), 7.14–7.19 (m, Ar)
ppm. 13C NMR (125.8 MHz, C6D6): d 170.6 (CN), 145.2,
144.0, 143.0, 126.9, 124.6, 124,5 (i-, o-, m-, p-Ar), 110.0
(C5H5), 99.2 (c-CH), 71.0 (br, O-(CH2CH2)2), 28.8, 27.6
(CH(CH3)2), 26,6, 25.6 (O-(CH2CH2)2), 25.4, 24.9, 24.8
(CH(CH3)2), 23.9 (b-CH3), 12.2 (AlCH2CH3), 6.6 (br,
4.5. Synthesis of LAlEt(l-O)Yb(THF)Cp2 (4)
THF (40 mL) was added to the mixture of 2 (0.84 g,
1.71 mmol) and Cp3Yb (0.63 g, 1.71 mmol) at room tem-
perature. The resulting solution was stirred for 12 h until
the color of the solution turned from dark green to brown.
Finally all volatiles were removed in vacuo, and then the
residual was extracted with THF (30 mL). The resulting
solution was kept at room temperature for 1 day to afford
yellow crystals. Yield 0.62 g (42%).
AlCH2CH3) ppm. IR (Nujol mull, cmꢀ1): v = 3060 (s),
~
M.p. 208–210 ꢁC. IR (Nujol mull, cmꢀ1): v = 3063 (m),
2414 (w), 2069 (w), 1954 (w), 1930 (w), 1754 (w), 1626
(w), 1584 (w), 1524 (s), 1503 (m), 1313 (s), 1255 (s), 1194
(w), 1175 (m), 1100 (m), 1057 (m), 1015 (s), 948 (w), 936
(m), 901 (s), 799 (s), 772 (s), 761 (s), 722 (m), 642 (w),
622 (m), 597 (m), 569 (s). EI-MS: m/z (%): 461.3 [M+–
Et–Y(THF)Cp2] (100). Anal. Calc. for C45H64AlN2O2Y
(780.9): C, 69.21; H, 8.26; N, 3.59. Found: C, 68.76; H,
7.48; N, 3.55%.
~
1624 (w), 1586 (w), 1525 (m), 1504 (m), 1314 (m), 1259 (m),
1195 (w), 1176 (w), 1100 (m), 1057 (m), 1017 (m), 949 (w),
936 (w), 907 (m), 799 (m), 776 (m), 762 (m), 722 (w), 663
(w), 643 (w), 624 (w), 597 (w), 571 (w), 447 (w). EI-MS:
m/z (%): 764.4 (100) [M+ꢀTHFꢀEt], 698.3 (12)
[M+ꢀTHFꢀEtꢀCp]. Anal. Calc. for C45H64AlN2O2Yb
(865.0): C, 62.48; H, 7.46; N, 3.24. Found: C, 61.91; H,
7.30; N, 3.24%.
4.9. X-ray crystal structure determinations for 2 and 3
4.6. Synthesis of LAlEt(l-O)Er(THF)Cp2 (5)
The structures were solved by direct methods (SHELXS-
97) [14] and refined with all data by full-matrix least-
squares on F2 (SHELXL-97). The hydrogen atoms of C–H
bonds were placed in idealized positions. The Flack param-
eter for 2 is ꢀ0.10(18). Other structural details are listed in
Table 1.
The procedure is the same as that described for 4 with
Cp3Er (0.36 g, 1 mmol) instead of Cp3Yb. Yield 0.18 g
(21%).
M.p. 235 ꢁC. IR (Nujol mull, cmꢀ1): v = 3063 (w),
~
1585 (w), 1525 (w), 1313 (w), 1254 (w), 1195 (w), 1175

Y. Yang et al. / Journal of Organometallic Chemistry 693 (2008) 1455–1461
1461
4.10. Polymerization of ethylene
References
On a vacuum line (10ꢀ5 Torr), polymerizations were car-
ried out in a 200 mL autoclave (Buchi). In a typical exper-
¨
[1] (a) H.W. Roesky, I. Haiduc, N.S. Hosmane, Chem. Rev. 103 (2003)
2579–2595;
(b) T. Carofiglio, C. Floriani, M. Rosi, A. Chiesivilla, C. Rizzoli,
Inorg. Chem. 30 (1991) 3245–3246.
[2] S. Singh, H.W. Roesky, Dalton Trans. (2007) 1360–1370.
[3] (a) M.S. Rau, C.M. Kretz, G.L. Geoffroy, A.L. Rheingold, B.S.
Haggerty, Organometallics 13 (1994) 1624–1634;
iment, 100 mL of dry toluene (from Na/K) was vacuum-
transferred into the polymerization flask, pre-saturated
with 1.0 atm of rigorously purified ethylene. The catalyst
(0.009 g in toluene; 10 mL, 12.4 lmol) was placed into
the Schlenk flask and appropriate MAO (1.6 M in toluene)
was added. The mixture was stirred for 20 min to activate
the catalyst. The catalyst solution was then quickly injected
into the rapidly stirred flask using a gas-tight syringe. After
a measured time interval, the polymerization was quenched
by the addition of methanol (5 mL) and the reaction mix-
ture was then poured into methanol (800 mL). The poly-
mer was allowed to fully precipitate overnight and then
collected by filtration, washed with fresh methanol, and
dried.
(b) G. Erker, M. Albrecht, S. Werner, C. Kruger, Z. Naturforsch.
¨
45b (1990) 1205–1209;
(c) H.L. Li, M. Eddaoudi, J. Plevert, M. O’Keeffe, O.M. Yaghi, J.
Am. Chem. Soc. 122 (2000) 12409–12410.
[4] G. Bai, S. Singh, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, J.
Am. Chem. Soc. 127 (2005) 3449–3455.
[5] J. Chai, V. Jancik, S. Singh, H. Zhu, C. He, H.W. Roesky, H.-G.
Schmidt, M. Noltemeyer, N.S. Hosmane, J. Am. Chem. Soc. 127
(2005) 7521–7528.
[6] P.M. Gurubasavaraj, H.W. Roesky, P.M.V. Sharma, R.B. Oswald,
V. Dolle, R. Herbst-Irmer, A. Pal, Organometallics 26 (2007) 3346–
3351.
[7] (a) V. Jancik, L.W. Pineda, J. Pinkas, H.W. Roesky, D. Neculai,
A.M. Neculai, R. Herbst-Irmer, Angew. Chem., Int. Ed. 43 (2004)
2142–2145;
4.11. Polymer characterization
(b) L.W. Pineda, V. Jancik, H.W. Roesky, D. Necuali, A.M. Neculai,
Angew. Chem., Int. Ed. 43 (2004) 1419–1421;
(c) H. Zhu, J. Chai, C. He, G. Bai, H.W. Roesky, V. Jancik, H.-G.
Schmidt, M. Noltemeyer, Organometallics 24 (2005) 380–384;
(d) S. Singh, V. Jancik, H.W. Roesky, R. Herbst-Irmer, Inorg. Chem.
45 (2006) 949–951.
13C NMR assay of polymer microstructure was con-
ducted in 1,1,2,2-tetrachloroethane-d2 at 120 ꢁC. Reso-
nances were assigned according to the literature [15] for
polyethylene. Differential Scanning Calorimetric measure-
ments of the polymer melting curves were performed on a
TA instrument 2920 (Modulated Differential Scanning Cal-
orimeter), which was calibrated against indium metal. Typ-
ically ca. 4 mg samples were used (10 ꢁC/min).
[8] G. Bai, Y. Peng, H.W. Roesky, J. Li, H.-G. Schmidt, M. Noltemeyer,
Angew. Chem., Int. Ed. 42 (2003) 1132–1135.
[9] G. Bai, H.W. Roesky, J. Li, M. Noltemeyer, H.-G. Schmidt, Angew.
Chem., Int. Ed. 42 (2003) 5502–5506.
[10] (a) B.X. Qian, D.L. Ward, M.R. Smith, Organometallics 17 (1998)
3070–3076;
Acknowledgements
(b) P.H.M. Budzelaar, A.B. van Oort, A.G. Orpen, Eur. J. Inorg.
Chem. (1998) 1485–1494;
(c) J. Prust, K. Most, I. Muller, A. Stasch, H.W. Roesky, I. Uson,
¨
Eur. J. Inorg. Chem. (2001) 1613–1616.
This work was supported by the Deutsche Forschungs-
gemeinschaft, the Fonds der Chemischen Industrie, and the
Go¨ttinger Akademie der Wissenschaften. Ying Yang
thanks the Chinese Scholarship Council for a fellowship.
[11] J.M. Birmingham, G. Wilkinson, J. Am. Chem. Soc. 78 (1956) 42–
44.
[12] N. Kuhn, T. Kratz, Synthesis (1993) 561–562.
[13] During the revision the preparation of LAlEt(OH) by a different route
´
was reported: K. Leszczynska, I.D. Madura, A.R. Kunicki, J.
Appendix A. Supplementary material
´
Zachara, M. Łos, J. Organomet. Chem. (2007), doi:10.1016/
j.jorganchem.2007.05.045.
CCDC 651788 and 651789 contain the supplementary
crystallographic data for 2 and 3. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
[14] G.M. Sheldrick, SHELX-97 Programs for the Solution and Refinement
of Crystal Structures, Universita¨t Go¨ttingen, Go¨ttingen, Germany,
1997.
[15] (a) G.B. Galland, R.F. de Souza, R.S. Mauler, F.F. Nunes,
Macromolecules 32 (1999) 1620–1625;
(b) W.X. Liu, D.G. Ray, P.L. Rinaldi, Macromolecules 32 (1999)
3817–3819.