Monomeric or Dimeric Aluminum Complexes as Catalysts for Cycloaddition between CO2 and Epoxides

Article abstract of DOI:10.1002/ejic.201500184

A monomeric aluminum complex containing aliphatic tetradentate ligand L1 (HOCMe₂CH₂NMeCH₂CH₂NMeCH₂CMe₂OH) was synthesized and used as a catalyst for cycloaddition between CO₂ and epoxides in the presence of PPNCl as a cocatalyst. To check the effect of ligand L1, coordinated to the aluminum center, on the activity of cycloaddition, the new ligand HOCMe₂CH₂NMe₂, which corresponds to half of L1, was systematically designed to make monomeric or dimeric aluminum complexes. Comparison of the catalytic properties of the aluminum complex containing the tetradentate ligand with those of the two related aluminum complexes containing the bidentate ligand under the same conditions revealed that the first system showed higher activity than the other two for cycloaddition between CO₂ and epoxides in the presence of PPNCl, which was the best cocatalyst out of the six compounds nBu₄PBr, nBu₄NCl, nBu₄NBr, nBu₄NI, DMAP, and PPNCl. The aluminum complexes 1-3 demonstrate catalytic activity for cycloaddition between CO₂ and epoxides in the presence of cocatalysts.

Full text of DOI:10.1002/ejic.201500184

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
FULL PAPER
DOI:10.1002/ejic.201500184
Monomeric or Dimeric Aluminum Complexes as Catalysts
for Cycloaddition between CO and Epoxides
2
[
a]
[a][†]
[b]
Jeong Hee Kim,[a]
So Han Kim, Sang Yeop Han,
[b]
[a]
Yi Young Kang, Junseong Lee,* and Youngjo Kim*
Keywords: Aluminum / Cycloaddition / Carbon dioxide / Epoxides / Oxygen heterocycles
A monomeric aluminum complex containing aliphatic tetra-
the catalytic properties of the aluminum complex containing
the tetradentate ligand with those of the two related alumi-
num complexes containing the bidentate ligand under the
same conditions revealed that the first system showed higher
dentate
ligand
CMe OH) was synthesized and used as a catalyst
and epoxides in the presence
of PPNCl as a cocatalyst. To check the effect of ligand L1,
coordinated to the aluminum center, on the activity of cyclo- and epoxides in the presence of PPNCl, which was the best
addition, the new ligand HOCMe CH NMe , which corre- cocatalyst out of the six compounds nBu PBr, nBu NCl,
L1
2 2 2 2
(HOCMe CH NMeCH CH -
NMeCH
2
2
for cycloaddition between CO
2
activity than the other two for cycloaddition between CO
2
2
2
2
4
4
sponds to half of L1, was systematically designed to make
4 4
nBu NBr, nBu NI, DMAP, and PPNCl.
monomeric or dimeric aluminum complexes. Comparison of
lphyrin-based ligands[27] and salen-type ligands.[7,28] Until
now, much of this research has been focused on the modifi-
Introduction
Cyclic carbonates can easily be synthesized through cation of aromatic chelating ligands coordinated to alumi-
cycloaddition between CO2 and epoxides, and they are num centers. However, examples of aluminum complexes
[1]
widely used as polar aprotic solvents, as electrolytes for containing aliphatic alkoxide-based ligands are very rare.
lithium ion batteries,[ as precursors for polycarbonates
2]
[3]
Recently we reported the synthesis of new dinuclear alu-
and enantiopure amino alcohols,[ as thermosetting minum complexes containing aliphatic aminoethanol-based
coatings, and as pharmaceutical intermediates. Many ligands with pendant –CH CH OMe or –CH CH NMe
4]
[
5]
[6]
2
2
2
2
2
examples of homogeneous catalytic systems for the synthe- groups attached to the nitrogen atom and their application
[
7]
[8]
[9]
[10]
[19]
[29]
sis of cyclic carbonates, including Al, Co, Cr, Cu,
as catalysts for cycloaddition between CO and epoxides.
2
[
11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
Ge, In, Fe, Mg, Ni, Pd, Re, Ru, Sn,
In addition, we recently reported the synthesis and charac-
Ti,[ Zn, and Zr[22] metal centers, have been reported in terization of new titanium complexes containing previously
the literature.
uninvestigated aliphatic tetradentate ligands such as HOC-
Many kinds of aluminum-based complexes have been Me CH NMeCH CH NMeCH CMe OH (L1) and their
20]
[21]
2
2
2
2
2
2
used as catalysts for cycloaddition between CO and epox- controlled ring opening polymerization behavior with l-
2
[
7,23–28]
[30]
ides.
Typical examples of ligands used for these alu- lactide. To the best of our knowledge, monomeric alumi-
minum catalytic systems are benzotriazole-based phenox- num catalysts such as 1 and 2, chelated by aliphatic alk-
[
23]
[24]
ides,
pounds,
pyrazole-based compounds,
quinoline com- oxide ligands, have never been used as catalysts for cycload-
[
25]
[26]
amino-tris(phenolate) compounds,
por- dition between CO and epoxides.
2
In this context, we report here the synthesis and charac-
terization of aluminum complex 1, containing the tetra-
dentate aliphatic aminoethanol-based ligand L1, and its
[
a] Department of Chemistry and BK21+ Program Research
[
30]
Team, Chungbuk National University,
1
Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 362-763, Re-
use as a catalyst for cycloaddition between CO and epox-
2
public of Korea
ides. As shown in Figure 1, we also investigated the effect
of ligand L1, coordinated to the aluminum center, on the
activity of cycloaddition. To check the degree of influence
of the ligand, we systematically synthesized the new ligand
HOCMe CH NMe (L2), which corresponds to half of L1,
E-mail: ykim@chungbuk.ac.kr
http://omlab2005.chungbuk.ac.kr
b] Department of Chemistry, Chonnam National University,
[
[
7
7 Yongbong-ro, Buk-gu, Gwangju 500-757, Republic of Korea
E-mail: leespy@chonnam.ac.kr
http://chem.chonnam.ac.kr
2
2
2
†] Author deceased
and its aluminum complexes 2 and 3. Their catalytic activi-
ties were then compared with that of 1.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201500184.
Eur. J. Inorg. Chem. 0000, 0–0
1
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
Figure 1. Systematic design of complexes 2 and 3 from 1.
Results and Discussion
As shown in Scheme 1, the tetradentate ligand
[
30]
HOCMe CH NMeCH CH NMeCH CMe OH
(L1)
2
2
2
2
2
2
and the bidentate ligand HOCMe CH NMe (L2) were
2
2
2
synthesized by treatment of isobutylene oxide with N,NЈ-
dimethylethylenediamine and dimethylamine, respectively.
Compounds L1 and L2 were used as ligands for a series of
Scheme 1. Synthetic routes to compounds 1–3.
new aluminum complexes 1–3, which were obtained with membered Al O ring with a center of symmetry. The two
2
2
extremely high yields (96% for 1 and 98% for 2 and 3) in bridging O atoms link the two AlMe moieties, and conse-
2
toluene as illustrated in Scheme 1. In all cases, the synthesis quently the structure of 3 is dinuclear, with two five-coordi-
of 1–3 was achieved under inert atmosphere. Complexes 1 nate aluminum centers joined through two-bridged oxygen
and 3 were prepared simply by adding a solution of 1 equiv. atoms. In addition, there is no direct Al1–Al2 interaction
of AlMe dropwise to a solution of L1 or L2, respectively, in 3. Compounds 1 and 2 each contain an aluminum center
3
in toluene at 0 °C and stirring the reaction mixture at room bonding to two N atoms, two O atoms, and one C atom of
temperature overnight, after which time the solvent and a methyl group, whereas 3 has each of its aluminum centers
CH were removed in vacuo. The other aluminum complex bonding to one N, one O, and two C atoms of methyl
4
2
1
was synthesized in a manner analogous to that used for groups with an inversion center (i) at the centroid of the
and 3 except that half the amount of AlMe was used. Al O ring plane. Even though 1 and 2 have the same bond-
3
2
2
Analytically pure samples were obtained as colorless crys- ing atoms around their aluminum centers, the nitrogen (N1
tals by recrystallization from toluene at –15 °C in a refriger- and N2) and the oxygen atoms (O1 and O2) in 1 and 2 have
ator. Compounds 1–3 were soluble in polar organic solvents different geometries: cis for 1 and trans for 2. All Al–O, Al–
and in toluene. Interestingly, compounds 2 and 3 are N, and Al–C bond lengths in 1–3 are similar to those found
[
29]
slightly soluble even in hexanes. Compound 1–3 were in related pentacoordinate aluminum complexes.
1
13
27
characterized by H, C, and Al NMR spectroscopy and
also by elemental analysis and single-crystal X-ray crystal- determined by the trigonality parameter τ (τ = [α – β]/60,
lography. where α and β are the largest and next-largest interligand
The distortion of the coordination around Al metal was
The molecular structures of 1–3 were determined by bond angles).[31] The largest and next-largest interligand
single-crystal X-ray diffraction analysis. Single crystals bond angles for 1 are ЄO2–Al1–N1 [160.53(7)°] and ЄO1–
suitable for X-ray structural determination were obtained Al1–C21 [125.11(10)°]. For 2 those values are ЄN2–Al1–
by cooling saturated toluene solutions at –15 °C. The crys- N1 [159.14(7)°] and ЄO2–Al1–O1 [129.52(8)°]. In the case
tal structures of 1–3 are shown in Figure 2. They reveal that of 3, the largest interligand bond angles for the two alumi-
complexes 1–3 are pseudo-C -, pseudo-C -, and pseudo-D - num centers are ЄO2–Al1–N1 [150.44(6)°] and ЄO1–Al2–
s
2v
2h
symmetric, respectively. In the solid state, compounds 1 and N2 [150.74(6)°] and the next-largest bond angles are ЄO2–
are monomeric, each possessing just a single Al–Me Al1–C16 [124.89(8)°] and ЄO1–Al2–C7 [126.55(10)°]. The
bond. However, compound 3 contains a dimeric four- trigonality parameter τ for regular trigonal bipyramidal
2
Eur. J. Inorg. Chem. 0000, 0–0
2
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
[
32]
1
00 ppm, and 0 ppm, respectively. Compounds 1–3 each
27
showed two Al NMR peaks at about 100 ppm (δ =
95.1 ppm for 1 in Figure S11 in the Supporting Infor-
mation, 88.6 ppm for 2 in Figure S19, and 111.5 ppm for 3
in Figure S22), as well as at about 70 ppm (aluminosilicate
peak of NMR tube). The 27Al NMR spectroscopic data for
the three complexes vary remarkably little, and 1–3 all have
pentacoordinate tbp or sqp environments around the cen-
tral Al atoms.
1
As shown in Figures 3 and 4, variable-temperature H
NMR experiments in [D ]toluene were carried out with
8
compounds 1 and 2. All dynamic phenomena are reversible
upon lowering/raising the temperature. As shown in Fig-
ures 3 and S6 (in the Supporting Information), the
–
OCMe CH N– methylene protons in 1 were split as two
2 2
broad peaks on the NMR timescale at 298 K. As the tem-
perature is decreased to 263 K (shown in Figures 3 and S4
1
in the Supporting Information), the H NMR spectrum of
1
comes to exhibit two distinct sharp doublets for the CH2
unit adjacent to CMe . At this temperature there are two
2
well-resolved AB spin systems, which implies that inversion
of the configuration at the Al center is definitely slow on
the NMR timescale.
Figure 2. X-ray structures of 1–3 with thermal ellipsoids drawn at
0% probability level. All H atoms are omitted for clarity.
5
(tbp) complexes is 1.0 and τ for square pyramidal (sqp)
complexes is zero, whereas the τ value obtained for 1 is 0.59,
indicating marginal tbp geometry around the Al center in
1. For 2 the τ value is 0.49, which means geometry interme-
diate between tbp and sqp. The two different τ values for 3
are 0.43 and 0.40 for the Al1 center and the Al2 center,
respectively. The two aluminum centers in 3 could thus be
reasonably defined as being closer to marginal sqp geome-
try than 1 and 2.
1
Figure 3. Variable-temperature H NMR spectra of complex 1 in
6 5 3
C D CD (flame-sealed NMR tube).
The H and 13C NMR spectra were in accord with the
1
suggested structures, and all chemical shifts of protons and
Unlike compound 1, compound 2 showed two sharp
carbon atoms were in the expected ranges. For complexes doublets corresponding to the –OCMe CH N– methylene
2
2
1
1
–3, the H NMR spectra showed characteristic shifts, in protons at 298 K (see Figures 4 and S13 in the Supporting
contrast to each ligand. In particular, the –OCMe CH N– Information).
2
2
proton systems in 1 and 2 were each split as two peaks with
Upon heating, the pairs of doublets corresponding to
pairs of diastereotopic AB spin systems [see Figures S3 (for the –OCMe CH N– protons in 1 and 2 each coalesce to a
2
2
1) and S12 (for 2) in the Supporting Information]. The same broad singe resonance, at 308 K and 328 K, respectively
patterns were observed for the –NCH CH N– protons in 1 (see Figures 3, 4, and S7 and S16 in the Supporting Infor-
2
2
and the –NMe protons in 2. These features are very similar mation). The patterns corresponding to the –NCH CH N–
2
2
2
[29,30]
to those reported in our previous paper.
protons in 1 (Figures 3 and S7 in the Supporting Infor-
2
7
Generally, the Al NMR spectra of organoaluminum mation) and to the –NMe protons in 2 (Figure 4 and Fig-
2
compounds can give information about the coordination ure S13 in the Supporting Information) each showed two
geometry and coordination number around aluminum broad peaks at room temperature. As the temperature in-
2
7
atoms, with the Al NMR shifts of tricoordinate, tetraco- creases, the resonances broaden and then coalesce at 308 K
ordinate, pentacoordinate, and hexacoordinate compounds for 1 and at 328 K for 2 (see Figures 3, 4 and S7 and S16
appearing at δ = 250–300 ppm, about 150 ppm, about in the Supporting Information). At higher temperature
Eur. J. Inorg. Chem. 0000, 0–0
3
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
merized products. Out of the three catalysts, 1 showed the
highest catalytic activity (Table 1, Entries 8–10).
Table 1. Cycloaddition between CO
2
and epoxides in the presence
of complexes 1–3.[
a]
Entry
Cat. Cocatal.[k]
TON[l]
Conv.
[
Selectivity
[%]
%][
0
m]
[m]
1[b]
1–3 none
0
–
2[b]
[n]
none nBu
nBu
4
4
4
4
PBr
NCl
NBr
NI
34
47
61
58
79
0
3.4
4.7
6.1
5.8
7.0
0
–
–
–
–
–
–
[
[
[
[
[
b]
b]
b]
b]
b]
[n]
3
4
5
6
7
[n]
nBu
nBu
PPNCl
DMAP
[n]
[n]
[n]
8[
9
1
b]
b]
1
2
3
PPNCl
852
127
104
85.2
12.7
10.4
Ͼ99
Ͼ99
Ͼ99
[
0[b]
1
Figure 4. Variable-temperature H NMR spectra of complex 2 in
b]
C
6
D
5
CD
3
(flame-sealed NMR tube).
11[
1
nBu
nBu
nBu
nBu
4
4
4
4
PBr
NCl
NBr
NI
593
539
627
588
186
59.3
53.9
62.7
58.8
18.6
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
[
b]
b]
b]
b]
12
13
14
15
[
[
[
DMAP
–
323 K for 1 and 338 K for 2 – only one broad averaged
methylene resonance is observed (see Figures 3, 4 and S9 16[
c]
d]
e]
f]
1
PPNCl
913
872
943
525
466
263
676
996
91.3
87.2
94.3
52.5
46.6
26.3
67.6
99.6
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
Ͼ99
[
1
1
1
2
7
8
9
0
and S17 in the Supporting Information).
[
[
To estimate racemization barriers in 1 and 2, the
‡
equation ΔG
(racemization)
=
4.576T [10.319
+
[g]
h]
c
[
log(T /k )], where T is coalescence temperature and k is 21
c
c
c
c
1/2
[i]
the exchange rate constant at coalescence [k = (π/2 )- 22[
c
j]
2
2 1/2
[33]
23
(
ΔνAB + 6JAB
)
], was applied.
The racemization
barrier determined from the line-shape changes of the [a] Cycloaddition conditions: [epoxide] = 10 mmol, [Al] = 10 μmol,
cocatalyst] = 10 μmol, [epoxide]/[Al] = 1000, CO = 10 bar. [b] Ep-
oxide = propylene oxide, T = 70 °C, time = 24 h. [c] Epoxide =
propylene oxide, T = 50 °C, time = 120 h. [d] Epoxide = propylene
oxide, T = 100 °C, time = 12 h. [e] Epoxide = propylene oxide, Tp
[
2
–
OCMe CH N– and –NCH CH N– methylene protons in
2 2 2 2
1
–1
p
the H NMR spectrum for 1 is 15.3(4) kcalmol (ΔνAB
5
=
p
8.7 Hz, JAB = 16.7 Hz, T = 308 K for –OCMe CH N–;
c
2
2
p
ΔνAB = 51.3 Hz, JAB = 15 Hz, T = 308 K for –NCH - = 130 °C, time = 5 h. [f] Epoxide = 1,2-epoxybutane, T = 70 °C,
c
2
p
CH N–). In addition, the racemization barrier for 2 is time = 24 h. [g] Epoxide = 1,2-epoxyhexane, T
p
= 70 °C, time =
2
–
1
24 h. [h] Epoxide = styrene oxide, T
ide = 1,2-epoxy-3-phenoxypropane, T
oxide = epichlorohydrin, T = 70 °C, time = 13 h. [k] Tetrabut-
ylphosphonium bromide (nBu PBr), tetrabutylammonium chloride
p
= 70 °C, time = 24 h. [i] Epox-
1
3
2
6.1(1) kcalmol (ΔνAB = 59.5 Hz, JAB = 24.7 Hz, T =
c
p
= 70 °C, time = 24 h. [j] Ep-
28 K for –OCMe CH NMe –; Δν
AB
= 94.2 Hz, JAB =
2
2
2
p
7.8 Hz, T = 328 K for –NMe ). These relatively similar
c
2
4
activation energies for the racemization processes indicate (nBu
that 1 and 2 have identical cis geometry in solution.
4
NCl), tetrabutylammonium bromide (nBu
ylammonium iodide (nBu NI), bis(triphenylphosphoranylidene)-
ammonium chloride (PPNCl), 4-(dimethylamino)pyridine
DMAP) entries. [l] Turnover number (TON) = (mol of epoxide
4
NBr), tetrabut-
4
Cycloaddition between CO and epoxides was performed
by using aluminum compounds 1–3 as catalysts. The cyclo-
2
(
1
consumed)/(mol of Al center). [m] Calculated by H NMR spectral
addition results are summarized in Table 1. Under our con- integration. [n] Not determined.
ditions (70 °C for 24 h), 1–3 in the absence of any cocatalyst
did not show any activity (Table 1, Entry 1). In addition,
Further studies to determine the effects of cocatalysts on
salt-type cocatalysts such as tetrabutylphosphonium brom- the catalytic activity were performed with 1 (Table 1, En-
ide (nBu PBr), tetrabutylammonium chloride (nBu NCl), tries 5 and 9–17). Six different kinds of cocatalysts –
4
4
tetrabutylammonium bromide (nBu NBr), tetrabutylam- nBu PBr, nBu NCl, nBu NBr, nBu NI, PPNCl, and
4
4
4
4
4
monium iodide (nBu NI), and bis(triphenylphosphoranyl- DMAP – were used. As shown in Table 1 (Entries 8 and
4
idene)ammonium chloride (PPNCl) in the absence of 1–3 11–15), PPNCl showed superior activity to the other five
showed very low catalytic activities for the synthesis of cocatalysts. Moreover, catalyst 1 showed good activity in
cyclic carbonate (Table 1, Entries 2–6). However, the non- the presence of salt-type cocatalysts nBu PBr, nBu NCl,
4
4
salt-type cocatalyst 4-dimethylaminopyridine (DMAP) did nBu NBr, nBu NI, and PPNCl (Table 1, Entries 8 and 11–
4
4
not show any catalytic activity (Table 1, Entry 7). Under 14). However, catalyst 1 with non-salt-type cocatalyst
our cycloaddition conditions, PPNCl showed the best ac- DMAP showed very low activity (Table 1, Entry 15).
tivity of the six cocatalysts (Table 1, Entry 2–7). Under the
The catalytic activity of 1/PPNCl increases, with shorter
same reaction conditions (70 °C for 24 h), 1–3 in the pres- reaction times being needed to achieve similar activity, as
ence of PPNCl as a cocatalyst produced cyclic carbonates the reaction temperature is increased from 50 °C to 130 °C
efficiently with high selectivities of Ͼ99% without any poly- (Entries 8 and 16–18). Interestingly, 1 did not produce any
Eur. J. Inorg. Chem. 0000, 0–0
4
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
2
Figure 5. A plausible mechanism for cycloaddition between CO and epoxides in the presence of 1 and cocatalyst.
poly(propylene carbonate) at low temperature of 50 °C. In Experimental Section
addition, out of the six kinds of epoxides – propylene oxide,
General Considerations: All reactions involving air- and moisture-
sensitive materials were performed under dinitrogen with use of
1,2-epoxybutane, 1,2-epoxyhexane, styrene oxide, 1,2-ep-
oxy-3-phenoxypropane, and epichlorohydrin – the last
showed the highest activity in the cycloaddition reaction
standard Schlenk-type glassware and a dual manifold Schlenk
[34]
line.
Dinitrogen was deoxygenated by use of an activated Cu
(
Entries 8 and 19–23). Interestingly, aluminum catalysts
[35]
catalyst and dried with drierite.
All chemicals were purchased
[7,23–28]
with aromatic-based ligands
in the presence of tetra- from Aldrich and were used without further purification. All sol-
butylammonium halides as cocatalyst have previously vents were dried by distillation from sodium diphenylketyl under
shown the best catalytic activities; however, our systems, dinitrogen and were stored over activated molecular sieves (3 Å).
3 6 6
CDCl and C D were dried with activated molecular sieves (4 Å)
and used after vacuum transfer to a Schlenk tube equipped with a
Young valve.
which have aliphatic ligands L1 and L2 with PPNCl cocata-
lyst, gave the highest activities.
As shown in Figure 5, a plausible mechanism for the
cycloaddition between CO and epoxide in the presence of Measurements: H and 13C NMR spectra were recorded at ambient
1
2
temperature with a 400 MHz NMR spectrometer and use of stan-
1
and a cocatalyst would involve attachment of epoxide to
dard parameters. All chemical shifts are reported in δ units with
the Al atom in 1; the resulting complex I would be activated
by the halide anion of the cocatalyst. Thus, DMAP would
show low catalytic activity for our cycloaddition reactions
because DMAP does not have such an anion for nucleo-
philic attack on complex I (Table 1, Entries 7 and 15). The
nucleophilic ring opening of the epoxide would give
carbonato species II, which would be converted by insertion
1
reference to the peaks of residual C
6
D
6
(δ = 7.15 ppm, H NMR;
1
3
δ = 128.0 ppm, C NMR) or C D CD (δ = 7.09, 7.01, 6.97, and
.08 ppm for H NMR). Elemental analyses were performed with
6 5 3
1
2
an EA 1110–FISONS analyzer (CE Instruments).
Synthesis of L1: Ligand L1 was prepared by previously published
procedures.[
30]
HOCMe
2
CH
2
NMe
2
(L2): Isobutylene oxide (4.9 g, 55 mmol) and
O, 50 mmol)
of CO into coordinated Al complex III. Finally, the desired
2
dimethylamine (5.6 mL of 40 wt.-% solution in H
2
product, the cyclic carbonate, would be generated by ring
closure of III. This mechanism is similar to that of cyclo-
were placed in a 25 mL screw-cap vial containing a stirring bar.
The vial was tightly sealed with Teflon tape and paraffin film. The
mixture was maintained at room temperature overnight and was
then heated at 50 °C for 5 d. Removal of volatile compounds at
addition between CO and epoxides in the presence of other
2
[
22,28h,28q,28s]
catalyst systems.
reduced pressure gave the desired product L2 as a colorless oil
1
(
91%, 5.3 g). H NMR (400.13 MHz, C
6
D
6
): δ = 3.10 (br. s, 1 H,
), 2.05 (s, 2 H, -CH -), 1.13 (s, 6 H,
–) ppm. C NMR (100.63 MHz, C ): δ = 70.26
69.87 (HOCMe –), 49.26 (–NMe2), 28.24
aminoethanol-based ligands were prepared, and their cata- (HOCMe –) ppm.
Conclusions
–OH), 2.13 (s, 6 H, –NMe
2
2
1
3
HOCMe
2
6 6
D
Aluminum catalysts containing multidentate aliphatic (-CH -),
2
2
2
lytic behavior in cycloaddition between CO and epoxides
was investigated. Complex 1 in the presence of PPNCl
2
2 2 2 2 2 2
MeAl(OCMe CH NMeCH CH NMeCH CMe O) (1): AlMe3
(
1.0 mL of 2.0 m solution in toluene, 2.0 mmol) was added to a
showed the highest activity of the Al catalysts reported in stirred colorless solution of L1 (0.46 g, 2.0 mmol) in toluene
this paper.
(30 mL) at 0 °C. The mixture was allowed to warm to room tem-
5 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 0000, 0–0

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
perature. After the mixture had been stirred overnight, all volatiles
were removed under vacuum, and then recrystallization from tolu-
ene at –15 °C gave product 1 as colorless crystals (96%, 0.52 g). H
had been cooled and vented, a small sample of the mixture was
taken for analysis by H NMR analysis.
1
1
Supporting Information (see footnote on the first page of this arti-
NMR (400.13 MHz, C
.99 (s, H, -NMe- and -OCMe
NCH CH N-), 1.73 (s, 2 H, -NCH CH
2 H, -OCMe CH
N-), –0.41 (s, 3 H, AlMe) ppm. 1 C NMR
): δ = 70.5 (-OCMe CH N-), 67.7 (-OC-
N-), 55.8 (-NCH CH N-), 45.4 (-NMe-), 33.8, 32.5
-), –10.1 (AlMe) ppm. 7Al NMR (104.26 MHz,
CMe
): δ = 95.1 [Δν1/2 = 2500 Hz] ppm. C13 29AlN (272.3631):
calcd. C 57.33, H 10.73, N 10.29; found C 57.12, H 10.98, N 9.87.
6
D
6
): δ = 2.21 (br. s, 2 H, -OCMe
2
CH
2
N-),
1
13
27
cle): H, C, and Al NMR spectra of all of the products.
1
8
2
CH N-), 1.92 (s,
2
2
H,
-
1
2
2
2
2
N-), 1.34 (d, J = 11.8 Hz,
3
2
2
Acknowledgments
(
100.63 MHz, C
Me CH
-NCH
6
D
6
2
2
2
2
2
2
2
This work was financially supported by the Korean Ministry of
Education (MOE) and the National Research Foundation of Korea
(
2
2
C
6
D
6
H
2 2
O
(
NRF) through the Creative Human Resource Training Project for
Regional Innovation (grant number 2014H1C1A1066874).
MeAl(OCMe CH NMe (2): In a manner analogous to that used
2
2
2 2
)
in the procedure for 1, the desired product 2 was prepared from a
toluene solution of AlMe (1.25 mL of a 2.0 m solution in toluene,
.5 mmol) and L2 (0.59 g, 5.0 mmol) in a yield of 98% (0.67 g). H
NMR (400.13 MHz, C ): δ = 2.36 (s, 6 H, –NMe ), 2.28 (d, J =
CH NMe ), 2.18 (d, J = 11.9 Hz, 2 H,
), 2.13 (s, 6 H, –NMe ), 1.28 (d, J = 4.2 Hz,
NMe
), –0.64 (s, 3 H, AlMe) ppm. 13C NMR
): 70.8 (–OCMe CH NMe ), 66.8
), 47.9, 47.5 (–NMe ), 34.4, 33.6 (–OCMe
), –10.9 (AlMe) ppm. Al NMR (104.26 MHz, C
δ = 88.6 [Δν1/2 = 2900 Hz] ppm. C13 31AlN (274.3790): calcd.
C 56.91, H 11.39, N 10.21; found C 57.02, H 11.31, N 10.15.
[
[
1] J. Bayardon, J. Holz, B. Schäffner, V. Andrushko, S. Verekin,
3
A. Preetz, A. Börner, Angew. Chem. Int. Ed. 2007, 46, 5971–
1
2
5974; Angew. Chem. 2007, 119, 6075.
6
D
6
2
2] M. Arakawa, S. Tobishima, T. Hirai, J. Yamaki, J. Electrochem.
Soc. 1986, 133, 1527–1528.
1
–
1
2.6 Hz, 2 H, -OCMe
OCMe CH NMe
2 H, -OCMe CH
2
2
2
2
2
2
2
2
[3] T. Takata, Y. Furusho, K. Murakawa, T. Endo, H. Matsuoka,
T. Hirasa, J. Matsuo, M. Sisido, J. Am. Chem. Soc. 1998, 120,
4530–4531.
2
2
(
(
100.63 MHz,
–OCMe CH
NMe
C
6
D
6
δ
=
2
2
2
[4] K. B. Sharpless, H. T. Chang, Tetrahedron Lett. 1996, 37, 3219–
2
2
NMe
2
2
2
-
27
3222.
CH
2
2
6 6
D ):
[
[
5] D. C. Webster, Prog. Org. Coat. 2003, 47, 77–86.
6] K. Biggadike, R. M. Angell, C. M. Burgess, R. M. Farrell, A. P.
Hancock, A. J. Harker, W. R. Irving, C. Ioannou, P. A. Proco-
piou, R. E. Shaw, Y. E. Solanke, O. M. P. Singh, M. A.
Snowden, R. J. Stubbs, S. Walton, H. E. Weston, J. Med. Chem.
H
2 2
O
[
Me Al(OCMe CH NMe )] (3): In a manner analogous to that
2
2
2
2 2
used in the procedure for 1, the desired product 3 was prepared
from a toluene solution of AlMe (2.5 mL of a 2.0 m solution in
toluene, 5.0 mmol) and L2 (0.59 g, 5.0 mmol) in a yield of 98%
2
000, 43, 19–21.
7] D. Tian, B. Liu, Q. Gan, H. Li, D. J. Darensbourg, ACS Catal.
012, 2, 2029–2035.
8] a) X.-B. Lu, D. J. Darensbourg, Chem. Soc. Rev. 2012, 41,
462–1484; b) J. Wang, J. Wu, N. Tang, Inorg. Chem. Commun.
2007, 10, 1493–1495.
[9] D. J. Darensbourg, Chem. Rev. 2007, 107, 2388–2410.
), [10] M. Ulusoy, O. Sahin, A. Kilic, Catal. Lett. 2011, 141, 717–725.
[11] K. Nakano, K. Kobayashi, K. Nozaki, J. Am. Chem. Soc. 2011,
33, 10720–10723.
12] I. Shibata, I. Mitani, A. Imakuni, A. Baba, Tetrahedron Lett.
011, 52, 721–723.
3
[
[
2
1
(
–
–
(
(
–
[
1.69 g). H NMR (400.13 MHz, C
6
D
6
): δ = 2.00 (s, 4 H,
), 1.98 (s, 12 H, –NMe ), 1.32 (s, 12 H,
), –0.47 (s, 3 H, AlMe) ppm.
): 69.9 (–OCMe CH NMe
), 46.9 (–NMe ), 31.9 (–OCMe CH
5.60 (AlMe) ppm. 7Al NMR (104.26 MHz, C
): δ = 111.5
Δν1/2 = 2400 Hz] ppm. C16 40Al (346.4641): calcd. C 55.47,
OCMe
OCMe
2
CH
2
NMe
NMe
2
2
1
13
2
CH
2
2
C NMR
), 69.6
NMe
100.63 MHz,
–OCMe CH
C
NMe
6
D
6
δ
=
2
2
2
2
2
2
2
2
2
2
2
6 6
D
1
H
2 2 2
N O
[
[
[
[
[
H 11.64, N 8.09; found C 55.51, H 11.59, N 8.15.
2
13] A. Buchard, M. R. Kember, K. G. Sandeman, C. K. Williams,
Chem. Commun. 2011, 47, 212–214.
14] D. J. Darensbourg, E. B. Frantz, Inorg. Chem. 2007, 46, 5967–
X-ray Structural Determination for 1–3: Crystallographic measure-
ments of complexes 1–3 were performed at 296(2) K with a Bruker
α
APEX II diffractometer and Mo-K (λ = 0.71073 Å) radiation.
5978.
3
Specimens of suitable quality and size (0.1ϫ0.1ϫ0.1 mm ) were
selected, mounted, and centered in the X-ray beam with use of a
video camera. The structure was solved by direct methods and re-
fined by full-matrix least-squares methods by use of the
15] F. Li, C. Xia, L. Xu, W. Sun, G. Chen, Chem. Commun. 2003,
2042–2043.
16] B. M. Trost, S. R. Angle, J. Am. Chem. Soc. 1985, 107, 6123–
6124.
[
36]
SHELXTL
eters for all non-hydrogen atoms. Final refinement based on the
reflections [I Ͼ 2·σ(I)] converged at R = 0.0351, wR = 0.0776,
and GOF = 1.096 for 1, at R = 0.0468, wR = 0.1240, and GOF
1.078 for 2, and at R = 0.0434, wR = 0.1063, and GOF = 1.044
for 3.
program package with anisotropic thermal param-
[17] J.-L. Jiang, F. Gao, R. Hua, X. Qiu, J. Org. Chem. 2005, 70,
381–383.
[
[
[
[
18] Z. Bu, Z. Wang, L. Yang, S. Cao, Appl. Organomet. Chem.
1
2
2010, 24, 813–816.
1
2
19] H. Jing, S. K. Edulji, J. M. Gibbs, C. L. Stern, H. Zhou, S. T.
Nguyen, Inorg. Chem. 2004, 43, 4315–4327.
20] M. J. Go, K. M. Lee, C. H. Oh, Y. Y. Kang, S. H. Kim, H. R.
Park, Y. Kim, J. Lee, Organometallics 2013, 32, 4452–4455.
21] H. S. Kim, J. J. Kim, B. G. Lee, B. G. Jung, H. G. Jang, S. O.
Kang, Angew. Chem. Int. Ed. 2000, 39, 4096–4098; Angew.
Chem. 2000, 112, 4262.
=
1
2
CCDC-911740 (for 1), -1048355 (for 2), and -1048356 (for 3) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[
[
[
22] S. H. Kim, D. Ahn, Y. Y. Kang, M. Kim, K.-S. Lee, J. Lee,
M. H. Park, Y. Kim, Eur. J. Inorg. Chem. 2014, 5107–5112.
23] C.-Y. Li, D.-C. Liu, B.-T. Ko, Dalton Trans. 2013, 42, 11488–
Cycloaddition between CO
2
and Epoxides: Cycloaddition between
CO and epoxides (10 mmol) was performed in a 15 mL stainless-
2
11496.
steel autoclave equipped with a stirring bar, epoxide, aluminum cat-
alyst (10 μmol), and cocatalyst (10 μmol) in a glove box. The auto-
clave was sealed prior to removal from the glove box. The autoclave
24] J. A. Castro-Osma, C. Alonso-Moreno, A. Lara-Sanzhez, J.
Martinez, M. North, A. Otero, Catal. Sci. Technol. 2014, 4,
1674–1684.
was initially operated at a pressure of 10 bar CO
2
and then heated
[25] S. A. Lermontov, T. N. Velikokhat’ko, V. O. Zavel’skii, Russ. J.
Gen. Chem. 2002, 72, 1492–1493.
to the desired temperature for the desired time. After the reactor
Eur. J. Inorg. Chem. 0000, 0–0
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
[
26] a) C. J. Whiteoak, N. Kielland, V. Laserna, F. Castro-Gomez,
North, R. Pasquale, Eur. J. Inorg. Chem. 2007, 3323–3326; p)
M. Alvaro, C. Baleizao, E. Carbonell, M. E. Ghoul, H. Garcia,
B. Gigante, Tetrahedron 2005, 61, 12131–12139; q) X.-B. Lu,
Y.-J. Zhang, K. Jin, L.-M. Luo, H. Wang, J. Catal. 2004, 227,
537–541; r) X.-B. Lu, Y.-J. Zhang, B. Liang, X. Li, H. Wang,
J. Mol. Catal. A 2004, 210, 31–34; s) X.-B. Lu, X.-J. Feng, R.
He, Appl. Catal. A 2002, 234, 25–33.
E. Martin, E. C. Escudero-Adán, C. Bo, A. W. Kleij, Chem.
Eur. J. 2014, 20, 2264–2275; b) C. J. Whiteoak, N. Kielland, V.
Laserna, E. C. Escudero-Adán, E. Martin, A. W. Kleij, J. Am.
Chem. Soc. 2013, 135, 1228–1231.
[
[
27] a) C. Chatterjee, M. H. Chisholm, Inorg. Chem. 2011, 50, 4481–
4
492; b) K. Kasuga, S. Nagao, T. Fukumoto, M. Handa, Poly-
hedron 1996, 15, 69–72.
[29] S. H. Kim, D. Ahn, M. J. Ko, M. H. Park, J. Lee, Y. Kim, Orga-
nometallics 2014, 33, 2770–2775.
[30] S. H. Kim, D. J. Kim, M. J. Go, Y. S. Ko, J. Lee, Y. Kim, Dalton
Trans. 2012, 41, 11619–11626.
[31] D. A. Atwood, M. J. Harvey, Chem. Rev. 2001, 101, 37–52.
[32] R. Benn, A. Rufi n´ ska, Angew. Chem. Int. Ed. Engl. 1986, 25,
861–881; Angew. Chem. 1986, 98, 851.
[33] a) D. Kost, A. Zeichner, Tetrahedron Lett. 1974, 15, 4533–4536;
b) R. J. Kurland, M. B. Rubin, W. B. Wise, J. Chem. Phys. 1964,
40, 2426–2426; c) S. Alexander, J. Chem. Phys. 1962, 37, 967–
974.
28] a) R. Lao, X. Zhou, S. Chen, Y. Li, L. Zhou, H. Ji, Green
Chem. 2014, 16, 1496–1506; b) M. A. Fuchs, C. Altesleben,
T. A. Zevaco, E. Dinjus, Eur. J. Inorg. Chem. 2013, 4541–4545;
c) I. S. Metcalfe, M. North, P. Villuendas, J. CO
2
Util. 2013, 2,
24–28; d) C. Beattie, M. North, P. Villuendas, C. Young, J. Org.
Chem. 2013, 78, 419–426; e) D. Tian, B. Liu, L. Zhang, X.
Wang, W. Zhang, L. Han, D.-W. Park, J. Ind. Eng. Chem. 2012,
1
8, 1332–1338; f) M. North, P. Villuendas, C. Young, Tetrahe-
dron Lett. 2012, 53, 2736–2740; g) M. North, B. Wang, C.
Young, Energy Environ. Sci. 2011, 4, 4163–4170; h) J. Melen-
dez, M. North, P. Villuendas, C. Young, Dalton Trans. 2011, [34] a) D. F. Shriver, M. A. Drezdzon, The Manipulation of Air-Sen-
nd
4
0, 3885–3902; i) M. North, C. Young, Catal. Sci. Technol.
sitive Compounds, 2 ed., Wiley, New York, 1986; b) G. S. Gir-
olami, T. B. Rauchfuss, R. J. Angelici, Synthesis and Technique
in Inorg. Chem. 3rd ed., University Science Books, Sausalito,
CA, USA, 1999.
2
011, 1, 93–99; j) W. Clegg, R. W. Harrington, M. North, R.
Pasquale, Chem. Eur. J. 2010, 16, 6828–6843; k) W. Clegg,
R. W. Harrington, M. North, P. Villuendas, J. Org. Chem.
2
010, 75, 6201–6207; l) M. North, P. Villuendas, C. Young,
[35] W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory
Chemicals, 6th ed., Elsevier, New York, 2009.
Chem. Eur. J. 2009, 15, 11454–11457; m) M. North, R. Pas-
quale, Angew. Chem. Int. Ed. 2009, 48, 2946–2948; Angew. [36] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
Chem. 2009, 121, 2990; n) J. Melendez, M. North, P. Vil-
luendas, Chem. Commun. 2009, 2577–2579; o) J. Melendez, M.
Received: February 22, 2015
Published Online: ᭿
Eur. J. Inorg. Chem. 0000, 0–0
7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I50184
/KAP1
Date: 08-04-15 18:09:16
Pages: 8
www.eurjic.org
FULL PAPER
Aluminum Cycloaddition Catalysts
S. H. Kim, S. Y. Han, J. H. Kim,
The aluminum complexes 1–3 demonstrate
Y. Y. Kang, J. Lee,* Y. Kim* ............ 1–8
catalytic activity for cycloaddition between
2
CO and epoxides in the presence of co-
Monomeric or Dimeric Aluminum Com-
plexes as Catalysts for Cycloaddition be-
catalysts.
2
tween CO and Epoxides
Keywords: Aluminum / Cycloaddition /
Carbon dioxide
heterocycles
/ Epoxides / Oxygen
Eur. J. Inorg. Chem. 0000, 0–0
8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim