Synthesis and protonolysis of neutral aluminum dihydride compounds stabilized by tridentate-substituted pyrrolyl ligands: Synthesis, structural characterization and ring-opening polymerization of ε-caprolactone

Article abstract of DOI:10.1016/j.jorganchem.2011.08.021

A series of aluminum compounds containing tridentate pyrrolyl ligands were obtained from related aluminum dihydride compounds via protonolysis. Treatment of tetranuclear aluminum compound [C₄H₂N{2,5-(CH ₂NMe₂)₂}Al₂H₅] ₂ (1) with two equivalents of [C₄H₃N{2,5- (CH₂NMe₂)₂}] in methylene chloride at 0 °C led to the formation of [C₄H₂N{2,5-(CH₂NMe ₂)₂}]AlH₂ (2). Similarly, when the deuterated aluminum compound 1D was used, the corresponding aluminum compound [C ₄H₂N{2,5-(CH₂NMe₂) ₂}]AlD₂ (2D) could be isolated. The reaction of 2 with one or two equivalents of phenylethyne, triphenylmethanethiol, 2,6- diisopropylaniline, or triphenylsilanol generated mononuclear aluminum compounds [[C₄H₂N{2,5-(CH₂NMe₂) ₂}]AlRR′ (3, R = -CCPh, R′ = H; 4, R = R′ = -CCPh; 5, R = -SCPh₃, R′ = H; 6, R = R′ = -SCPh₃; 7, R = -NH(2,6-ⁱPr₂Ph), R′ = H; 8, R = R′ = -NH(2,6-ⁱPr₂Ph); 9, R = -OSiPh₃, R′ = H; 10, R = R′ = -OSiPh₃). Related Al-D compounds of 3, 5, 7 and 9 were also synthesized and corresponding IR spectroscopic data well matched in comparison of the stretching frequencies of Al-H and Al-D. The molecular structures of 2D, 4, 5, 5D, 7, and 10 have been determined by X-ray crystallography. Compounds 2, 5, and 7 initiated the ring-opening polymerization of ε-caprolactone and produced high-molecular weight of poly-ε-caprolactone.

Full text of DOI:10.1016/j.jorganchem.2011.08.021

Journal of Organometallic Chemistry 696 (2011) 3673e3680
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and protonolysis of neutral aluminum dihydride compounds stabilized
by tridentate-substituted pyrrolyl ligands: Synthesis, structural characterization
and ring-opening polymerization of -caprolactone
3
,
Jr-Chiuan Changa, Ya-Chi Chena, Amitabha Dattaa, Chia-Her Linb, Ching-Sheng Hsiaoa, Jui-Hsien Huanga
*
a Department of Chemistry, National Changhua University of Education, 1 Jing-Der Rd, Changhua 50058, Taiwan
b Department of Chemistry, Chung-Yuan Christian University, Chun-Li 320, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of aluminum compounds containing tridentate pyrrolyl ligands were obtained from related
aluminum dihydride compounds via protonolysis. Treatment of tetranuclear aluminum compound
[C4H2N{2,5-(CH2NMe2)2}Al2H5]2 (1) with two equivalents of [C4H3N{2,5-(CH2NMe2)2}] in methylene
chloride at 0 ꢀC led to the formation of [C4H2N{2,5-(CH2NMe2)2}]AlH2 (2). Similarly, when the deuterated
aluminum compound 1D was used, the corresponding aluminum compound [C4H2N{2,5-(CH2NMe2)2}]
AlD2 (2D) could be isolated. The reaction of 2 with one or two equivalents of phenylethyne, triphe-
nylmethanethiol, 2,6-diisopropylaniline, or triphenylsilanol generated mononuclear aluminum
compounds [[C4H2N{2,5-(CH2NMe2)2}]AlRR0 (3, R ¼ eC^CPh, R0 ¼ H; 4, R ¼ R0 ¼ eC^CPh; 5, R ¼ eSCPh3,
R0 ¼ H; 6, R ¼ R0 ¼ eSCPh3; 7, R ¼ eNH(2,6-iPr2Ph), R0 ¼ H; 8, R ¼ R0 ¼ eNH(2,6-iPr2Ph); 9, R ¼ eOSiPh3,
R0 ¼ H; 10, R ¼ R0 ¼ eOSiPh3). Related AleD compounds of 3, 5, 7 and 9 were also synthesized and cor-
responding IR spectroscopic data well matched in comparison of the stretching frequencies of AleH and
AleD. The molecular structures of 2D, 4, 5, 5D, 7, and 10 have been determined by X-ray crystallography.
Received 25 May 2011
Received in revised form
4 August 2011
Accepted 18 August 2011
Keywords:
Pyrrole
Aluminum
Ring-opening polymerization
Compounds 2, 5, and 7 initiated the ring-opening polymerization of
molecular weight of poly- -caprolactone.
3
3
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
polymeric structures. Structural characterized ligand-stabilized
neutral monomeric aluminum dihydride compounds are rela-
tively few [10e12]. In the past work, we employed bi- or tridentate,
substituted pyrrolyl ligands [C4H3N{2,5-(CH2NMe2)2}] [13,14] as
auxiliary ligands with early transition metals [15e17] or group 13
metals [18,19] to form organometallic compounds, and we assessed
their reactivity toward small organic molecules. Herein, we report
The ever-expanding vistas in metal hydride chemistry prompt
continuing interest in organometallic chemistry. The correspond-
ing derivatives are thought to be responsible for a plethora of
organic transformations, catalytic cycles and olefin polymerization
intermediates, or deactivation products [1e3]. Among the metal
hydrides, aluminum hydrides such as LiAlH4 have been used the
most often in many different reactions because of their inexpensive
cost compared with other metal hydrides. However, the solubility
and control of reactivity are often major issues when using these
aluminum hydrides [4,5]. Increasing the solubility of aluminum
hydrides and controlling their reactivity often can be achieved by
varying their environments.
a
simple method for the synthesis of aluminum dihydride
compounds containing tridentate-substituted pyrrolyl ligands and
further explore their reactions with phenylethyne, triphenylme-
thanethiol, 2,6-diisopropylaniline, and triphenylsilanol. The reac-
tions of aluminum dihydride compounds with phenylethyne
produced novel neutral monomeric aluminum alkynyl compounds.
Monomeric aluminum compounds with terminal alkynyl groups
are relatively rare, and few of these compounds are characterized
structurally [20e24]. In general the alkynyl groups of aluminum
compounds can either coordinate to other metal centers [25e29]
Many aluminum hydrides that contain various organic ligands
have been synthesized, and their reactivity has been studied [6e9].
The molecular structure of aluminum hydride compounds often
shows a strong tendency to form dimeric, trimeric, or even
through the alkynyl
p-electrons or aggregate to form a metal
cluster [30,31]. In addition, some of the new compounds were
evaluated as initiators of the ring-opening polymerization of
* Corresponding author. Tel.: þ886 7 5919465; fax: þ886 7 5919348.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
3
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.08.021

3674
J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
2. Experimental section
(0.70 g, 2.50 mmol) in 20 mL methylene chloride was added
dropwise at 0 ꢀC. The solution was stirred for 12 h at room
temperature. The volatiles were removed under vacuum and the
resulting solid was recrystallized from methylene chloride to
generate 0.90 g of colorless crystals (78% yield). 1H NMR (C6D6):
7.84e7.07 (m, 15H, phenyl), 6.16 (s, 2H, pyrrolyl), 3.52, 2.87 (dd, 4H,
CH2NMe2), 1.89 (s, 12H, NMe2). 13C NMR (C6D6): 150.4, 131.0, 130.7,
128.3, 126.0, 105.5, 63.6, 59.0, 46.2.
2.1. Materials and physical measurements
Unless otherwise noted, all manipulations were performed under
vacuum line using standard Schlenk techniques under an atmo-
sphere of nitrogen or using glove box techniques. Diethyl ether and
heptane were dried over Na/benzophenone ketyl and distilled before
use. CH2Cl2 was dried over P2O5 and distilled prior use. [C4H3N{2,5-
(CH2NMe2)2}] [13,14], [C4H2N{2,5-(CH2NMe2)2}Al2H5]2 (1) and
[C4H2N{2,5-(CH2NMe2)2}]AlH2 (2) [19] were synthesized according
to published literature. CDCl3 was degassed by using freeze-and-
Complex 5D: Same procedure as described for 5 excepting the
starting material of 2D was used. C29H33DAlN3S (484.65): cacld. C
71.87, H 7.28, N 8.67; found C 69.92, H 7.21, N 8.64.
thaw cycles and dried over 4 A molecular sieves. 1H and 13C NMR
2.2.5. [C4H2N{2,5-(CH2NMe2)2}]Al(SCPh3)2 (6)
ꢀ
spectra were recorded on a Bruker AC200 instrument. Elemental
analysis was performed on PerkineElmer CHN-2400.
A 50 mL Schlenk flask was charged with 2 (0.50 g, 2.40 mmol) in
glove box under nitrogen atmosphere. The compound was dissolved
in 20 mL methylene chloride and triphenylmethanethiol (1.40 g,
2.50 mmol)in20 mL methylenechloridewasaddeddropwise at0 ꢀC.
The solution was stirred for 12 h at room temperature. The volatiles
were removed under vacuum and the resulting solid was recrystal-
lized from methylene chloride to generate 1.30 g of colorless crystals
(72% yield). 1H NMR (CDCl3): 7.50e7.08 (m, 30H, phenyl), 5.82 (s, 2H,
pyrrolyl), 2.86 (s, 4H, CH2NMe2), 2.12 (s,12H, NMe2).13C NMR (CDCl3):
149.7, 133.7, 130.5, 128.0, 126.5, 108.3, 66.1, 59.8, 47.2.
2.2. Synthesis of the complexes
2.2.1. [C4H2N{2,5-(CH2NMe2)2}]AlD2 (2D)
2.2.1.1. Method A. To a stirred diethyl ether solution of 1D (0.50 g,
1.02 mmol), 0.041 g (2.05 mmol) of D2O was added at ꢁ78 ꢀC via
microsyringe. The solution was stirred at room temperature for
another 12 h and filtered. The filtrate was vacuum dried and solid
was recrystallized from diethyl ether to yield 0.23 g (54% yield) of
product. 1H NMR (C6D6): 6.27 (s, 2H, C4H2N), 3.31 (s, 4H, CH2NMe2),
2.17 (s, 12H, NMe2). 13C NMR (C6D6): 131.0 (s, Cipso), 106.0 (d,
JCH ¼ 164 Hz, CH), 60.9 (t, JCH ¼ 137 Hz, CH2), 47.6 (q, JCH ¼ 136 Hz,
2.2.6. [C4H2N{2,5-(CH2NMe2)2}]AlH[NH(2,6-iPr2Ph)] (7)
A 50 mL Schlenk flask was charged with 2 (0.50 g, 2.40 mmol) in
glove box under nitrogen atmosphere. The compound was dis-
solved in 20 mL methylene chloride and 2,6-diisoproylaniline
(0.50 g, 2.50 mmol) in 20 mL methylene chloride was added
dropwise at 0 ꢀC. The solution was stirred for 7 h at room
temperature. The volatiles were removed under vacuum and the
resulting solid was recrystallized from a methylene chloride/diethyl
ether mixed solution to generate 0.90 g of colorless crystals (97%
yield). 1H NMR (C6D6): 7.14e6.89 (m, 3H, phenyl), 6.21 (s, 2H, pyr-
rolyl), 3.39 (m, 2H, CHMe2), 3.52, 3.14 (dd, 4H, CH2NMe2), 2.06 (s,
12H, NMe2), 1.28, 1.25 (d, 12H, CHMe2). 13C NMR (C6D6): 147.8, 135.4,
131.5, 124.1, 117.7, 106.3, 60.2, 47.2, 29.3, 24.4.
CH3). IR (KBr) for AleD: 1261, 1307 cmꢁ1
.
2.2.1.2. Method B. To a 10 mL stirred methylene chloride solution of
1D (1.88 g, 3.85 mmol), 1.40 g (7.73 mmol) of [C4H3N(CH2NMe2)2-
2,5] in 10 mL methylene chloride was added dropwise at 0 ꢀC. The
solution was stirred at room temperature for 12 h. Volatiles were
removed under vacuum to generate 3.10 g of 2D in 95% yield.
2.2.2. [C4H2N{2,5-(CH2NMe2)2}]AlH(C^CPh) (3)
A 50 mL Schlenk flask was charged with 2 (0.30 g, 1.45 mmol) in
glove box under nitrogen atmosphere. The compound was dis-
solved in 20 mL methylene chloride and phenylethyne (0.15 g,
1.45 mmol) was added via syringe. The solution was stirred for 24 h
at room temperature. The volatiles were removed under vacuum
and the residual was washed with heptane. The resulting solid was
recrystallized from methylene chloride to generate 0.138 g of
colorless crystals (31% yield). 1H NMR (C6D6): 7.51 (m, 2H, phenyl),
7.02 (m, 3H, phenyl), 6.24 (s, 2H, pyrrolyl), 3.22, 3.48 (dd, 4H,
CH2NMe2), 2.19 (s, 12H, NMe2). 13C NMR (C6D6): 132.0, 131.6, 130.7,
128.0, 127.3, 124.9, 107.2, 104.2, 60.0, 47.6. IR (KBr) for C^C:
Complex 7D: Same procedure as described for 7 excepting the
starting material of 2D was used.
2.2.7. [C4H2N{2,5-(CH2NMe2)2}]Al[NH(2,6-iPr2Ph)]2 (8)
A 50 mL Schlenk flask was charged with 2 (0.50 g, 2.40 mmol) in
glove box under nitrogen atmosphere. The compound was dissolved
in 20 mL methylene chloride and 2,6-diisopropylaniline (0.90 g,
5.10 mmol) in 20 mL methylene chloride was added dropwise. The
solution was stirred for 7 h at room temperature. The volatiles were
removed under vacuum and the resulting solid was recrystallized
from methylene chloride to generate 1.10 g of colorless crystals (82%
yield). 1H NMR (C6D6): 7.10e6.96 (m, 6H, phenyl), 6.23 (s, 2H, pyr-
rolyl), 3.41 (m, 4H, CHMe2), 3.39 (s, 4H, CH2NMe2), 2.89 (s, 2H, NH),
2.05 (s,12H, NMe2),1.21,1.18 (d, 24H, CHMe2).13C NMR (C6D6): 146.4,
140.1, 133.2, 124.0, 120.9, 108.6, 60.9, 47.3, 29.2, 24.7.
2129 cmꢁ1
.
Complex 3D: Same procedure as described for 3 excepting the
starting material of 2D was used.
2.2.3. [C4H2N{2,5-(CH2NMe2)2}]Al(C^CPh)2 (4)
Similar procedures were used as for 3. 2 (0.87 g, 4.16 mmol) and
phenylethyne (0.85 g, 8.33 mmol) were used for reaction. 1.06 g of
colorless crystals of 4 were obtained (71% yield). 1H NMR (CDCl3):
7.45, 7.28 (10H, phenyl), 5.97 (2H, pyrrolyl), 3.73 (s, 4H, CH2NMe2),
2.73 (s, 12H, NMe2). 13C NMR (CDCl3): 131.6, 130.7, 128.0, 127.3,
124.9, 109.5, 107.2, 104.2, 60.0, 47.6. C26H28AlN3 (409.49): calcd. C
76.26, H 6.89, N 10.26; found C 75.19, H 7.17, N 10.36. IR (KBr) for
2.2.8. [C4H2N{2,5-(CH2NMe2)2}]AlH[OSiPh3] (9)
A 50 mL Schlenk flask was charged with 2 (0.50 g, 2.40 mmol) in
glove box under nitrogen atmosphere. The compound was dis-
solved in 20 mL methylene chloride and triphenylsilanol (0.70 g,
2.50 mmol) in 20 mL methylene chloride was added dropwise at
0 ꢀC. The solution was stirred for 12 h at room temperature. The
volatiles were removed under vacuum and the resulting solid was
recrystallized from a methylene chloride solution to generate 0.60 g
of colorless crystals (51.9% yield). 1H NMR (C6D6): 7.83 (m, 3H,
phenyl), 7.21 (m, 12H, phenyl), 6.25 (s, 2H, pyrrolyl), 3.36, 3.11 (dd,
4H, CH2NMe2), 1.96 (s, 12H, NMe2). 13C NMR (C6D6): 140.1, 136.9,
136.4, 131.3, 130.2, 106.0, 60.4, 47.1.
C^C: 2355, 2322 cmꢁ1
.
2.2.4. [C4H2N{2,5-(CH2NMe2)2}]AlH(SCPh3) (5)
A 50 mL Schlenk flask was charged with 2 (0.50 g, 2.40 mmol) in
glove box under nitrogen atmosphere. The compound was dis-
solved in 20 mL methylene chloride and triphenylmethanethiol

J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
3675
Table 1
Complex 9D: Same procedure as described for 9 excepting the
IR stretching frequency of AleH and AleD for compounds 2, 3, 5, 7 and 9.
starting material of 2D was used.
Compound
nAleH (cmꢁ1
)
nAleD (cmꢁ1
)
2.2.9. [C4H2N{2,5-(CH2NMe2)2}]Al[OSiPh3]2] (10)
Calculation
Observed
A 50 mL Schlenk flask was charged with 2 (1.00 g, 4.80 mmol) in
glove box under nitrogen atmosphere. The compound was dis-
solved in 20 mL methylene chloride and triphenylsilanol (2.70 g,
9.8 mmol) in 20 mL methylene chloride was added dropwise. The
solution was stirred for 12 h at room temperature. The volatiles
were removed under vacuum and the resulting solid was recrys-
tallized from a methylene chloride solution to generate 3.50 g of
colorless crystals (96% yield). 1H NMR (CDCl3): 7.61e7.31 (m, 30H,
phenyl), 5.92 (s, 2H, pyrrolyl), 3.29 (s, 4H, CHNMe2), 1.92 (s, 12H,
NMe2). 13C NMR (CDCl3): 138.3, 135.3, 131.1, 129.2, 127.6, 104.2, 60.3,
47.4. C46H48AlN3O2Si2 (758.05): calcd. C 72.88, H 6.38, N 5.54; found
C 72.44, H 6.81, N 5.26.
2
2D
3
3D
5
5D
7
7D
9
9D
1778/1797
1804
1257/1271
1298
1261/1307
NAa
1446
1022
985
1847
1329
NA
1812
1304
NA
a
NA: IR stretching frequency of AleD is not available due to the overlapping with
other absorption bands.
diethyl ether at ꢁ78 ꢀC generated 2 in 54% yield [19]. However, the
stoichiometric control of H2O is crucial for the reaction. The use of
an excess of H2O resulted in the formation of [C4H3N{2,5-
(CH2NMe2)2}] via hydrolysis. Alternatively, we found a simple
method for the conversion of 1 to 2 by adding two equivalents of
the tridentate ligand [C4H3N{2,5-(CH2NMe2)2}] to 1, with a yield of
85%. The corresponding deuterated aluminum compound, [C4H2N
{2,5-(CH2NMe2)2}]AlD2 (2D) was obtained upon reaction of
deuterated aluminum compound 1D with two equivalents of
[C4H3N{2,5-(CH2NMe2)2}]. Solid-state IR spectra supported the
existence of AleH and AleD. The AleH stretching frequencies of 2
(1778 and 1797 cmꢁ1) disappeared when 2D was used, and new
2.3. Polymerization procedures and polymer characterization
Polymerization of -caprolactone was carried out in a nitrogen
3
filled Schlenk line. In a typical polymerization, monomer and
initiator were dissolved in toluene in separate flasks. In general, the
monomer was added to the initiator/toluene solution and the
polymerizations are carried out at room temperature (28 ꢀC) for
a period of times or until they are solidified. The solutions are
quenched with 0.5 mL of water and collected solids were washed
with methanol. 1H NMR spectroscopy and GPC (gel permeation
chromatography) were used for characterization the conversions of
monomers and molecular weights of PCL, respectively.
AleD stretching frequencies were observed at 1261 and 1307 cmꢁ1
,
which were calculated at 1257 and 1271 cmꢁ1. Compound 2 is
relatively thermally stable which remains unchanged even at
100 ꢀC for 4 days in C6D6. However, 2 is very moisture sensitive and
releases free pyrrole ligand upon exposure to air.
2.4. Single crystal X-ray structure determination
Colorless crystals of 4, 5, 5D, and 10 suitable for X-ray structure
determination were obtained from a saturated CH2Cl2 solution
at ꢁ20 ꢀC and data were collected at 150 K. Colorless crystals of 7
were obtained from a mixture of diethyl ether and methylene
at ꢁ20 ꢀC and data were collected at 298 K. Crystal data collection
and refinement parameters are listed in Table 2. The crystal of 7 was
sealed in glass capillaries and transferred to a goniostat. The crystals
of 2D, 4, 5, 5D, and 10 were directly mounted on a glass fiber and
transferred to a goniostat. Data were collected on a Bruker SMART
CCD diffractometer with graphite-monochromated Mo-Ka radiation.
3.2. Deprotonation of small organic molecules with aluminum
dihydride compound 2
The reactions of 2 with small organic molecules such as phe-
nylethyne, triphenylmethanethiol, 2,6-diisopropylaniline, and tri-
phenylsilanol are summarized in Scheme 2. The aluminum
dihydride compound 2 acted as a proton-abstracting reagent that
removed the acidic proton from organic molecules to yield dihy-
drogen molecules. The reaction of 2 with one or two equivalents of
phenylethyne in methylene chloride at room temperature
produced compounds [C4H2N{2,5-(CH2NMe2)2}]AlH(C^CPh) (3)
and [C4H2N{2,5-(CH2NMe2)2}]Al(C^CPh)2 (4), respectively, with
Intensity data were collected with a combination of
u and f scans. All
data were corrected for Lorentz and polarization effects, and the
program SADABS [65] was used for the absorption correction. Crys-
tallographic computing was performed using SHELXTL [66,67]
package of programs. On the basis of systematic absences and
statistics of intensity distribution, the space group was determined
for each complex. The structures were solved with Al and S atoms
being disclosed first, followed by the atoms of O, N, and C located on
successive difference Fourier maps. The H atoms were added in
idealized positions and constrained to ride on their parent atoms. All
refinements were carried out by full-matrix least squares using
anisotropic displacement parameters for all non-hydrogen atoms.
All the relevant crystallographic data and structure refinement
parameters for 2D, 4, 5, 7 and 10 are summarized in Table 1.
NMe2
H
Al
H
H
NMe2
H
Al
NMe2
N
N
H
2 H2O
H
N
Al
H
H
H
Al
H
Al
Me2N
NMe2
H
Me2N
H
1
2
3. Results and discussion
2
3.1. Synthesis and characterization of aluminum dihydride
compound 2
N
H
NMe2
Me2N
The synthesis of [C4H2N{2,5-(CH2NMe2)2}]AlH2 (2) is shown in
Scheme 1. The reaction of tetranuclear aluminum compound
[C4H2N{2,5-(CH2NMe2)2}Al2H5]2 (1) with two equivalents of H2O in
Scheme 1.

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J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
N
N
N
Me2N
Ph3C
Al
NMe2
CPh3
Me2N
Al
NMe2
CPh3
Me2N
Al
NMe2
S
S
H
S
HN
H
6
5
NH2
7
2 Ph3CSH
Ph3CSH
N
Al
2
NH2
Me2N
NH
NMe2
N
N
2 HCCPh
Me2N
Al
NMe2
HN
Me2N
Al
NMe2
C
C
H
H
C
C
2
Ph
8
Ph
4
HCCPh
Ph3SiOH
2 Ph3SiOH
N
N
N
Me2N
Ph3Si
Al
O
NMe2
SiPh3
Me2N
Al
NMe2
Me2N
Al
NMe2
SiPh3
O
C
H
O
C
10
H
3
Ph
9
Scheme 2.
the elimination of hydrogen. Compound 3 can also be obtained
from the reaction of 2 and 4 in toluene through ligand redistribu-
tion. Compound 4 was thermally stable and remained intact in
CDCl3 at 70 ꢀC for 2 days. Related AleD compounds of 3, 5, and 7
were synthesized by similar methods.
hydrogen, and the compounds [C4H2N{2,5-(CH2NMe2)2}]AlH
[NH(2,6-iPr2Ph)] (7), [C4H2N{2,5-(CH2NMe2)2}]Al[NH(2,6-iPr2Ph)]2
(8), [C4H2N{2,5-(CH2NMe2)2}]AlH[OSiPh3] (9), and [C4H2N{2,5-
(CH2NMe2)2}]Al[OSiPh3]2 (10) were isolated in good yield.
Compounds 7, 8, 9, and 10 were also characterized by 1H and 13C
NMR spectroscopy, which showed similar resonance patterns as
those described for the previous compounds. Heating 7 in toluene
at 80 ꢀC for 5 days resulted in ligand redistribution, and compounds
2 and 8 were observed. Compound 9 was an air- and moisture-
sensitive solid that decomposed during the recrystallization to
unidentified compounds, along with the formation of hex-
aphenyldisiloxane [32].
The 1H and 13C NMR spectra of 3D are the same as those of 3 in
C6D6. The 1H NMR spectrum of 3 reveals a Cs-symmetric geometry,
as evidenced by an AB pattern (d 3.22 and 3.48) for the methylene
protons of the substituted pyrrolyl ligands. In contrast, the 1H NMR
spectrum of compound 4 indicates a symmetrical coordination of
the substituted pyrrolyl ligand, as evidence by the singlet (d 3.73)
observed for the methylene protons of the ligand. Moreover, the 13C
NMR spectra revealed the existence of the alkynyl groups of 3 and
The hydride resonances of compounds 2, 3, 5, 7, and 9 in C6D6
were not observed with a 200 MHz spectrometer, even at ꢁ40 ꢀC.
However, solid-state IR spectra supported the existence of AleH
(terminal), as evidenced by the absorptions of nAleH at
w1850e1800 cmꢁ1, which were not observed for the correspond-
ing AleD compounds. Table 1 compares the AleH and corre-
sponding AleD stretching frequencies.
4. Two distinct singlets were observed at
resonances of the ethynyl carbons of 4.
d 107.2 and 130.7 for the
The reaction of 2 with one or two equivalents of triphenylme-
thanethiol in methylene chloride at room temperature afforded
compounds [C4H2N{2,5-(CH2NMe2)2}]AlH(SCPh3) (5) and [C4H2N
{2,5-(CH2NMe2)2}]Al(SCPh3)2 (6) in 78% and 72% yield, respectively,
with the elimination of hydrogen. Again, the distinct signals of
methylene protons of CH2NMe2 were used to establish the purity of
compounds 5 and 6. The 1H NMR spectrum of compound 5 revealed
3.3. Molecular structures of compounds 2D, 4, 5, 5D, 7, and 10
an AB pattern with two doublets at
trum of 6 showed one singlet at 2.86 for the methylene protons.
The most characteristic feature of the 13C NMR spectra for 5 and 6
d 3.52 and 2.87, and the spec-
Summaries of the crystallographic data and selected bond
lengths and angles are presented in Table 2 and 3, respectively. The
molecular structure of 2D is shown in Fig. 1. The structure of 2D is
an isostructure of that of 2 [19]. Single crystal X-ray structures that
include AleD bond lengths are rare in the literature [19,33,34]. The
d
was the resonance of the tertiary carbon atom of CPh3 at
66.1, respectively.
d 63.6 and
ꢀ
The aluminum amide or aluminum siloxide compounds 7e10
were obtained under similar conditions as for compounds 5 and 6
(Scheme 2). Treatment of 2 with one or two equivalents of 2,6-
diisopropylainiline or triphenylsilanol in a methylene chloride
solution at room temperature led to the rapid evolution of
bond lengths of the Al(1)eD(1) and Al(1)eD(2) are at 1.48(2) A and
ꢀ
1.62(2) A.
The crystal structure of
4 revealed a monomeric, five-
coordinated aluminum center surrounded by a tridentate pyrrolyl
ligand and two phenylethynyl groups where the two

J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
3677
Table 2
The summaries of crystallographic data for compounds 2D, 4, 5, 7, and 10.
2D
4
5
7
10
Empirical formula
Formula weight
Crystal system
Space group
C10H18AlD2N3
211.28
Monoclinic
P21/n
6.3011(8)
24.801(3)
8.5998(11)
107.778(3)
1279.7(3)/4
1.097
C26H28AlN3
409.49
Monoclinic
P21/c
C29H34AlN3S
483.63
Monoclinic
P21/c
9.1023(7)
33.388(3)
9.4926(7)
117.133(1)
2567.4(3)/4
1.251
C22H37AlN4
384.54
Monoclinic
Cc
C46H48AlN3O2Si2
758.03
Monoclinic
C2/c
27.4978(15)
11.7057(7)
25.9438(14)
96.294(1)
8300.5(8)/8
1.213
ꢀ
a, A
9.9646(7)
9.1950(15)
ꢀ
b, A
8.7484(6)
26.7661(18)
91.195(2)
2329.7(3)/4
1.168
30.076(5)
8.6300(14)
98.010(4)
2363.3(7)/4
1.081
ꢀ
c, A
b ꢀ
,
3
ꢀ
Volume, A /Z
Dcalcd, Mg/m3
m
(mmꢁ1
)
0.130
0.104
0.183
0.099
0.148
F(000)
Cryst size (mm)
(min), (max)
456
872
1032
840
3216
0.45 ꢂ 0.42 ꢂ 0.32
1.64e27.56ꢀ
8037
0.30 ꢂ 0.28 ꢂ 0.20
2.05e27.51ꢀ
14,339
0.24 ꢂ 0.22 ꢂ 0.20
2.44e27.53ꢀ
16,289
0.35 ꢂ 0.30 ꢂ 0.28
2.34e26.37ꢀ
6909
0.34 ꢂ 0.28 ꢂ 0.22
1.49e27.52ꢀ
26,003
q
q
Reflns collected
Ind reflns
2909 (Rint ¼ 0.0457)
0.9486 and 0.4553
2909/0/189
0.779
5309 (Rint ¼ 0.0293)
0.9486 and 0.7304
5309/0/275
0.924
5872 (Rint ¼ 0.0506)
0.9486 and 0.8404
5872/0/315
0.711
3291 (Rint ¼ 0.1052)
0.9486 and 0.2440
3291/2/248
0.690
9457 (Rint ¼ 0.0461)
0.9682 and 0.9515
9457/0/491
Max. and min. transmn.
Data/restraints/params
Goodness-of-fit on F2
0.907
R [I > 2
s(I)]
R1 ¼ 0.0389
R1 ¼ 0.0404
R1 ¼ 0.039
R1 ¼ 0.0410
R1 ¼ 0.0403
wR2 ¼ 0.0944
wR2 ¼ 0.10091
wR2 ¼ 0.0759
wR2 ¼ 0.0835
wR2 ¼ 0.0921
R (all data)
R1 ¼ 0.0893
R1 ¼ 0.0639
R1 ¼ 0.0879
R1 ¼ 0.1006
R1 ¼ 0.0772
wR2 ¼ 0.1273
wR2 ¼ 0.1089
wR2 ¼ 0.0885
wR2 ¼ 0.0946
wR2 ¼ 0.1192
3
ꢀ
Largest diff. peak and hole (e A )
0.186 and ꢁ0.123
0.314 and ꢁ0.209
0.275 and ꢁ0.260
0.144 and ꢁ0.175
0.385 and ꢁ0.285
dimethylamino nitrogen atoms occupying the axial positions
(Fig. 2). The bond angle of N(2)eAl(1)eN(3) is 154.35(5)ꢀ. Further,
the coordinated phenylethynyl groups (eC^CPh) exhibited rela-
tively short carbonecarbon triple bond lengths for the C(11)eC(12)
and C(19)eC(20) at 1.201(2) A and 1.181(2) A, respectively. The
AleC^C bond angles of 4 are linear with the bond angles of Al(1)e
C(11)eC(12) and Al(1)eC(19)eC(20) at 175.42(13) and 177.13(14)ꢀ,
respectively. The short C^C triple bond lengths and linearity of
AleC^C angles indicate the terminal alkynyl fragments bind to
aluminum atom in a s bonding mode and no bridging character
was observed. The bonding modes and structures of alkynyl
aluminum compounds have been reviewed by Zheng and Roesky
[35] where the reactive aluminum hydride replaces the CH-acidic
alkynes forming alkynyl aluminum compounds.
Compounds 5 and 5D are isostructural and only the molecular
structure of 5 is shown in Fig. 3. The geometry of 5 can be described
as a distorted trigonal bipyramidal structure with the two dime-
thylamino nitrogen atoms occupying axial positions. The bond
ꢀ
ꢀ
Table 3
ꢀ
ꢀ
Selected bond lengths (A) and angles ( ) of compounds 2D, 4, 5, 7, and 10.
2D
Al(1)eN(1)
Al(1)eD(1)
N(2)eAl(1)eN(3)
1.844(2)
1.48(2)
155.48(7)
Al(1)eN(2)
Al(1)eD(2)
N(1)eAl(1)eN(2)
2.211(2)
1.62(2)
77.82(7)
Al(1)eN(3)
2.271(2)
77.66(7)
N(1)eAl(1)eN(3)
4
Al(1)eN(1)
Al(1)eC(11)
N(2)eAl(1)eN(3)
Al(1)eC(11)eC(12)
1.836(1)
1.942(2)
154.35(5)
175.42(13)
Al(1)eN(2)
Al(1)eC(19)
N(1)eAl(1)eN(2)
Al(1)eC(19)eC(20)
2.278(1)
1.967(2)
76.25(5)
Al(1)eN(3)
2.201(1)
78.10(5)
N(1)eAl(1)eN(3)
177.13(1)
5
Al(1)eH(1)
Al(1)eN(2)
N(2)eAl(1)eN(3)
Al(1)eS(1)eC(11)
N(1)eAl(1)eH(1)
1.53(2)
2.2596(17)
153.39(6)
119.61(6)
123.6(7)
Al(1)eS(1)
Al(1)eN(3)
N(1)eAl(1)eN(2)
S(1)eAl(1)eH(1)
2.2716(8)
2.2866(17)
76.96(7)
Al(1)eN(1)
1.8371(17)
N(1)eAl(1)eN(3)
N(1)eAl(1)eS(1)
76.87(6)
111.93(6)
124.5(7)
7
Al(1)eH(1)
Al(1)eN(2)
N(2)eAl(1)eN(3)
Al(1)eN(4)eC(11)
N(3)eAl(1)eH(1)
1.55(3)
2.274(3)
77.40(15)
146.0(3)
Al(1)eN(4)
Al(1)eN(3)
N(1)eAl(1)eN(2)
N(4)eAl(1)eH(1)
1.821(3)
1.833(4)
153.81(14)
123.27(99)
Al(1)eN(1)
2.261(4)
N(1)eAl(1)eN(3)
N(3)eAl(1)eN(41)
76.86(16)
113.22(16)
124(1)
10
Al(1)eO(1)
Al(1)eN(2)
1.7231(15)
2.231(2)
Al(1)eO(2)
Al(1)eN(3)
1.7091(16)
2.300(2)
Al(1)eN(1)
O(1)eSi(1)
1.839(2)
1.5994(15)
O(2)eSi(2)
1.6005(16)
N(2)eAl(1)eN(3)
Al(1)eO(1)eSi(1)
N(1)eAl(1)eO(1)
152.73(8)
160.30(11)
120.17(9)
N(1)eAl(1)eN(2)
Al(1)eO(2)eSi(2)
O(1)eAl(1)eO(2)
77.04(8)
169.93(11)
112.22(8)
N(1)eAl(1)eN(3)
N(1)eAl(1)eO(2)
76.14(8)
127.61(9)

3678
J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
Fig. 1. The molecular structure of 2D. Ellipsoids are dawn at the 50% probability level
and hydrogen atoms are omitted for clarity.
Fig. 3. The molecular structure of 5. Ellipsoids are dawn at the 50% probability level.
Excepting the hydride atom, all hydrogen atoms are omitted for clarity.
angle of N(2)eAl(1)eN(3) is 153.39(6)ꢀ. There are numbers of
terminal t-butylthiolate aluminum compounds reported in the
literature [36e38]; however, no terminal bulky triphenylmetha-
nethiolate aluminum compound was seen before. The bond angle
of Al(1)eS(1)eC(11) (119.61(6)ꢀ) is larger than a normal angle of sp3
hybridization and normal Al-thiolate bond angles presumably due
to the steric effect of the large triphenylmethyl group.
bipyramidal. The bond angles of Al(1)eO(1)eSi(1) and Al(1)eO(2)e
Si(2) (160.30(11)ꢀ and 169.93(11)ꢀ) are larger than normal sp3
ꢀ
ꢀ
hybridization. The short AleO (1.7231(15) A and 1.7091(16) A) bond
ꢀ
ꢀ
lengths and doubly bonded OeSi (1.6005(16) A and 1.5994(15) A)
likely explain the large angle of AleOeSi. However, the bond
lengths of AleO and OeSi and related AleOeSi bond angles do not
show any correlation indicating the steric hindrance dominates the
AleOeSi bond angles. A comparison of the bond angles of AleOeSi
and the bond lengths of AleO and SieO for compound 10 with
those of reported structures is shown in Table 4 [46e49].
The structure of 7, which is similar to that of 5, is shown in Fig. 4.
ꢀ
The bond length of AleN(4) (1.821(3) A) and bond angle of Al(1)e
N(4)eC(11) (146.0(3)ꢀ) are in the normal range of aluminum 2,6-
diisopropylphenylanilide [39e45]. Moreover, the bond angle of
Al(1)eN(4)eC(11) is even larger than that of Al(1)eS(1)eC(11) in 5,
probably because of the bulky 2,6-diisopropylphenyl group
pushing the aryl ring away from the aluminum atom.
3.4. Initiation of ring-opening polymerization of
aluminum compounds
3 -caprolactone by
In compound 10 (Fig. 5), the geometry around the aluminum
atom is similar to that of
4 showing a distorted trigonal
Ring-opening polymerizations (ROP) of -caprolactone initiated
3
by metal compounds has been studied [50e52]. ROP initiated by
aluminum alkoxides is well known [53e61]; however, ROP
Fig. 2. The molecular structure of 4. Ellipsoids are dawn at the 50% probability level
Fig. 4. The molecular structure of 7. Ellipsoids are dawn at the 30% probability level.
and hydrogen atoms are omitted for clarity.
Excepting the hydride atom, all hydrogen atoms are omitted for clarity.

J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
3679
Table 4
Table 5
A comparison of the bond angles of AleOeSi and bond lengths of AleO and SieO for
compound 10 with that of reported structures.
Ring-opening polymerization of 3 -caprolactone initiate by aluminum compounds.
Compound
[M]/[I]
Time
Toluene (mL)
Mn
7800
10,700
12,000
8200
11,200
14,700
16,200
7600
12,200
15,000
17,300
PDI
Yield
ꢀ
Compound
Bond angle(s) (ꢀ) Bond length(s) (A)
Ref
2
2
2
5
5
5
5
7
7
7
7
50
100
150
50
100
150
200
50
30a
m
10
20
20
20
20
20
20
20
20
20
20
1.24
1.41
1.33
1.27
1.26
1.28
1.39
1.12
1.37
1.27
1.27
95.1
94.5
89.4
88.9
74.6
76.4
80.3
33.3
91.0
79.9
87.1
30a m
20a m
24 h
AleOeSi
AleO/SieO
10
160.30(11)
169.93(11)
1.7231(15)/1.5994(15) This
1.7091(16)/1.6005(16) work
24 h
3.5a h
2.5a h
24 h
Salen (tBu)AlOSiPh3
Salpen (tBu)AlOSiPh3
Salophen (tBu)AlOSiPh3
157.9(14)
166.3(2)
166.8(6)
1.719(14)/1.608(13)
1.726(2)/1.597(2)
1.702(9)/1.603(9)
16a
16a
16a
100
150
200
24 h
3
a h
AlMe(OSiPh3)2(THF)
149.8(2)
165.5(3)
1.715(4)/1.596(4)
1.699(3)/1.596(4)
16b
16c
16d
2.5a h
Al(OSiPh3)2[C(SiMe3)3](thf) 163.71(18)
170.42(18)
1.726(3)/1.616(3)
1.726(3)/1.616(3)
[M]/[I]: the ratio of monomer to initiator in toluene.
a
Solidified.
L[Al(OSiPh3)2
163.13(3)
1.710(3)/1.598(3)
Salen (tBu) ¼ N,N0-ethylenebis(3, 5-di-tert-butylsalicylideneimine).
Salpen (tBu) ¼ N,N0-propylenebis(3, 5-di-tert-butylsalicylideneimine).
Salophen (tBu) ¼ N,N0-phenylenebis(3, 5-di-tert-butylsalicylideneimine).
L ¼ C4H3N(2-CH2NMe2)-H-C4H3N(2-CH2NMe2).
4. Conclusion
A simple method was developed to synthesize the reactive
aluminum dihydride compound 2. Compound 2 is a good starting
material for the preparation of corresponding amide, alkoxide, and
siloxide compounds. The structure of compound 4 represents
a novel neutral monomeric dialkynyl aluminum compound, which
was stabilized by tridentate-substituted pyrrolyl ligands. The
aluminum dialkynyl compound may be useful as an alkynyl transfer
reagent in organic synthesis. Further, the dialkynyl groups of 4 act
initiated by metal hydrides and amides is less studied [62,63]. We
previously reported the ROP of -caprolactone using the aluminum
compounds as initiators [64]. Similarly, here we applied the
3
resulting aluminum compounds as initiators for the ROP of
rolactone. The results are reported in Table 5.
3
as two
p-donating groups, which can react with other transition
Compounds 9 and 10 were inactive in the ROP of
In contrast, compounds 2, 5, and 7 showed activity in the poly-
merization of -caprolactone to form poly- -caprolactone (PCL). The
aluminum hydrides of compound 2 initiated the ROP of -capro-
lactone to yield poly- -caprolactone (PCL); however, the poly-
3
metals to form a heterobimetallic compound [22,23]. Some of the
compounds were catalytically active in the ring-opening poly-
merization of -caprolactone. Steric effect is proposed as the main
3
3
3
variable that affected the rate of the polymerization.
3
dispersity index (PDI, Mw/Mn) values of PCL initiated by 2 were
relatively broad ranging from 1.24 to 1.41, probably because of the
side reactions or multiple reacting sites (AleH or AleN). Similarly,
the PDI values of PCL initiated by 5 and 7 were in the range of
1.12e1.39. Steric effect can be considered as the main reason for the
Acknowledgments
We thank the National Science Council of Taiwan for the
financial support, the National Computing Center for High Perfor-
mance for databank searching, and the National Changhua
University of Education for the X-ray structure analyses.
differing activities of these compounds toward -caprolactone.
3
ꢀ
Short AleO bond lengths (10, 1.7201(13) A) prevents the monomer
from coordinating to the aluminum center and blocks the poly-
merization, whereas the longer AleN and AleS bond lengths (7,
ꢀ
ꢀ
Appendix. Supplementary material
1.821(3) A and 5D, 2.2746(16) A) allow the polymerization to
proceed.
CCDC 813665, 813666, 813667, 813668, 813669 and 813664
contain the supplementary crystallographic 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.
References
[1] G. Wilkinson, F.G.A. Stone, E.W. Abel, Comprehensive Organometallic Chem-
istry, vol. 1, Pergamon, Oxford, U.K., 1982, (Chapter 6).
[2] D.S. Moore, S.D. Robinson, Chem. Soc. Rev. 12 (1983) 415.
[3] J.P. McCue, Coord. Chem. Rev. 10 (1973) 265.
[4] V. Gevorgyan, E. Lukevics, J. Chem. Soc., Chem. Commun. (1985) 1234.
[5] E.C. Ashby, J.R. Sanders, P. Claudy, R.D. Schwartz, Inorg. Chem. 12 (1973) 2860.
[6] R.J. Wehmschulte, P.P. Power, Polyhedron 19 (2000) 1649.
[7] M.G. Gardiner, C.L. Raston, Coord. Chem. Rev. 166 (1997) 1.
[8] M. Ephritikhine, Chem. Rev. 97 (1997) 2193.
[9] C.L. Raston, J. Organomet. Chem. 475 (1994) 15.
[10] L. Contreras, A.H. Cowley, F.P. Gabbaï, R.A. Jones, C.J. Carrano, M.R. Bond,
J. Organomet. Chem. 489 (1995) C1eC3.
[11] S. Bensiek, M. Bangel, B. Neumann, H.-G. Stammler, P. Jutzi, Organometallics
19 (2000) 1292.
[12] C. Jones, G.A. Koutsantonis, C.L. Raston, Polyhedron 12 (1993) 1829.
[13] W. Herz, K. Dittmer, S.J. Cristol, J. Am. Chem. Soc. 69 (1947) 1698.
[14] I.T. Kim, R.L. Elsenbaumer, Tetrahedron Lett. 39 (1998) 1087.
[15] J.-H. Huang, P.-C. Kuo, G.-H. Lee, S.-M. Peng, J. Chin. Chem. Soc. 47 (2000)
1191.
Fig. 5. The molecular structure of 10. Ellipsoids are dawn at the 50% probability level.
All hydrogen atoms are omitted for clarity.

3680
J.-C. Chang et al. / Journal of Organometallic Chemistry 696 (2011) 3673e3680
[16] J.-H. Huang, L.-S. Chi, F.-M. Huang, P.-C. Kuo, C.-C. Zhou, G.-H. Lee, S.-M. Peng,
J. Chin. Chem. Soc. 47 (2000) 895.
[17] J.-H. Huang, L.-S. Chi, R.-C. Yu, G.J. Jiang, W.T. Yang, G.-H. Lee, S.-M. Peng,
Organometallics 20 (2001) 5788.
[18] J.-H. Huang, H.-J. Chen, J.-C. Chang, C.-C. Zhou, G.-H. Lee, S.-M. Peng, Organ-
ometallics 20 (2001) 2647.
[19] J.-C. Chang, C.-H. Hung, J.-H. Huang, Organometallics 20 (2001) 4445.
[20] W. Zheng, N.C. Mösch-Zanetti, H.W. Roesky, M. Hewitt, F. Cimpoesu,
T.R. Schneider, A. Stasch, J. Prust, Angew. Chem. Int. Ed. 39 (2000) 3099.
[21] M. Schiefer, N.D. Reddy, H.-J. Ahn, A. Stasch, H.W. Roesky, A.C. Schlicker, H.-
G. Schmidt, M. Noltemeyer, D. Vidovic, Inorg. Chem. 42 (2003) 4970.
[22] H. Zhu, R.B. Oswald, H. Fan, H.W. Roesky, Q. Ma, Z. Yang, H.-G. Schmidt,
M. Noltemeyer, K. Starke, N.S. Hosmane, J. Am. Chem. Soc. 128 (2006) 5100.
[23] J. Zhao, H. Song, C. Cui, Organometallics 26 (2007) 1947.
[24] H. Zhu, J. Chai, H. Fan, H.W. Roesky, C. He, V. Jancik, H.-G. Schmidt,
M. Noltemeyer, W.A. Merrill, P.P. Power, Angew. Chem. Int. Ed. 44 (2005) 5090.
[25] G.D. Stucky, A.M. McPherson, W.E. Rhine, J.J. Eisch, J.L. Considine, J. Am. Chem.
Soc. 96 (1974) 1941.
[40] X.-W. Li, J. Su, G.H. Robinson, Chem. Commun. (1998) 1281.
[41] T. Bauer, S. Schulz, H. Hupfer, M. Nieger, Organometallics 21 (2002) 2931.
[42] D. Rutherford, D.A. Atwood, J. Am. Chem. Soc. 118 (1996) 11535.
[43] M.L. Montero, H. Wessl, H.W. Roesky, M. Teichert, I. Usón, Angew. Chem. Int.
Ed. 36 (1997) 629.
[44] M.A. Beswick, N. Choi, C.N. Harmer, M. McPartlin, M.E.G. Mosquera,
P.R. Raithby, M. Tombul, D.S. Wright, Chem. Commun. (1998) 1383.
[45] H. Zhu, Z. Yang, J. Magull, H.W. Roesky, H.-G. Schmidt, M. Noltemeyer,
Organometallics 24 (2005) 6420.
[46] D.A. Atwood, M.S. Hill, J.A. Jegier, D. Rutherford, Organometallics 16 (1997)
2659.
[47] S.J. Obrey, S.G. Bott, A.R. Barron, Organometallics 20 (2001) 5119.
[48] A.G. Avent, C. Eaborn, I.B. Gorrell, P.B. Hitchcock, J.D. Smith, J. Chem. Soc.,
Dalton Trans. (2002) 3971.
[49] C.-Y. Lin, H.M. Lee, J.H. Huang, J. Organomet. Chem. 692 (2007) 3718.
[50] Ph. Lecomte, F. Stassin, R. Jerome, Macromol. Sym. 215 (2004) 325.
[51] S. Agarwal, C. Mast, K. Dehnicke, A. Greiner, Macromol. Rapid Commun. 21
(2000) 195.
[26] M.J. Albright, W.M. Butler, T.J. Anderson, M.D. Glick, J.P. Oliver, J. Am. Chem.
Soc. 98 (1976) 3995.
[52] W.M. Stevels, P.J. Dijkstra, J. Feijen, Trends Polym. Sci. 5 (1997) 300.
[53] S. Gong, H. Ma, Dalton Trans. (2008) 3345.
[27] M. Albrecht, G. Erker, M. Nolte, C. Krüger, J. Organomet. Chem. 427 (1992) C21.
[28] G. Erker, M. Albrecht, C. Krüeger, M. Nolte, S. Werner, Organometallics 12
(1993) 4979.
[29] M. Schiefer, H. Hatop, H.W. Roesky, H.-G. Schmidt, M. Noltemeyer, Organo-
metallics 21 (2002) 1300.
[54] A. Kowalski, J. Libiszowski, K. Majerska, A. Duda, S. Penczek, Polymer 48
(2007) 3952.
[55] S. Dagorne, F. Le Bideau, R. Welter, S. Bellemin-Laponnaz, A. Maisse-Francois,
Chem. Eur. J. 13 (2007) 3202.
[56] T. Muraki, K. Fujita, A. Oishi, Y. Taguchi, Polym. J. 37 (2005) 847.
[57] J. Lewinski, P. Horeglad, K. Wojcik, I. Justyniak, Organometallics 24 (2005)
4588.
[30] N.D. Reddy, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, Inorg. Chem. 41
(2002) 2374.
[31] W. Uhl, F. Breher, J. Grunenberg, A. Lützen, W. Saak, Organometallics 19
(2000) 4536.
[58] L.M. Alcazar-Roman, B.J. O’Keefe, M.A. Hillmyer, W.B. Tolman, Dalton Trans.
(2003) 3082.
[59] T.-C. Liao, Y.-L. Huang, B.-H. Huang, C.-C. Lin, Macromol. Chem. Phys. 204
(2003) 885.
[32] The hexaphenyldisiloxane is characterized by 1H NMR spectroscopy and
X-ray single crystal diffractometry.
[33] A.V. Khvostov, B.M. Bulychev, V.K. Belsky, A.I. Sizov, J. Organomet. Chem. 568
(1998) 113.
[60] T.-L. Yu, C.-H. Huang, L.-F. Yang, B.-T. Ko, C.-C. Lin, J. Chin. Chem. Soc. 47 (2000)
1185.
[34] Y.K. Gun’ko, B.M. Bulychev, V.K. Belsky, G.L. Soloveichik, J. Organomet. Chem.
440 (1992) 47.
[35] W. Zheng, H.W. Roesky, J. Chem. Soc., Dalton Trans. (2003) 2787.
[36] S. Daniel, D.M. Hoffman, Inorg. Chem. 41 (2002) 3843.
[37] W.-Y. Chen, C. Eaborn, I.B. Gorrell, P.B. Htichcock, J.D. Smith, J. Chem. Soc.,
Dalton Trans. (2000) 2313.
[61] P. Dubois, I. Barakat, R. Jerome, P. Teyssie, Macromolecules 26 (1993) 4407.
[62] K.-C. Hsieh, W.-Y. Lee, L.-F. Hsueh, H.M. Lee, J.-H. Huang, Eur. J. Inorg. Chem.
(2006) 2306.
[63] P.W. Roesky, M.T. Gamer, M. Puchner, A. Greiner, Chem. Eur. J. 8 (2002) 5265.
[64] R.-C. Yu, C.-H. Hung, J.-H. Huang, H.-Y. Lee, J.-T. Chen, Inorg. Chem. 41 (2002)
6450.
[38] J. Knizek, H. Nöth, A. Schlegel, Eur. J. Inorg. Chem. (2001) 181.
[39] K.M. Waggoner, K. Ruhlandt-Senge, R.J. Wehmschulte, X. He, M.M. Olmstead,
P.P. Power, Inorg. Chem. 32 (1993) 2557.
[65] Bruker, SADABS. Bruker AXS Inc., Madison, Wisconsin, USA, 2001.
[66] G.M. Sheldrick, Acta Cryst. A 64 (2008) 112.
[67] Bruker, SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA, 2010.