Synthesis, structure, and catalytic activity of binuclear lanthanide complexes with chiral NOBIN-based NNO ligands

Article abstract of DOI:10.1016/j.jorganchem.2008.11.061

Two new amido binuclear complexes {(1)YN(SiMe₃)₂}₂ · C₇H₈ (3 · C₇H₈) and {(2)SmN(SiMe₃)₂}₂ · C₆H₁₄ (4 · C₆H₁₄) have been readily prepared in good yields by amine elimination reaction between Ln[N(SiMe₃)₂]₃ (Ln = Sm, Y) and chiral NNO ligands, (S)-2-(pyridin-2-ylmethylamino)-2′-hydroxy-1,1′-binaphthyl (1H₂) and (S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(pyrrol-2-ylmethyleneamino)-2′-hydroxy-1,1′-binaphthyl (2H₂), respectively. They both have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. They are active catalysts for asymmetric hydroamination/cyclization of aminoalkenes and ring-opening polymerization of rac-lactide, affording cyclic amines in excellent conversions with moderate ee values and isotactic-rich polylactides, respectively.

Full text of DOI:10.1016/j.jorganchem.2008.11.061

Journal of Organometallic Chemistry 694 (2009) 691–696
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, structure, and catalytic activity of binuclear lanthanide complexes
with chiral NOBIN-based NNO ligands
Qiuwen Wang a, Li Xiang a, Haibin Song b, Guofu Zi a,
*
a Department of Chemistry, Beijing Normal University, Beijing 100875, China
b State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new amido binuclear complexes {(1)YN(SiMe3)2}2 ꢀ C7H8 (3 ꢀ C7H8) and {(2)SmN(SiMe3)2}2 ꢀ C6H14
Received 18 September 2008
Received in revised form 18 November 2008
Accepted 25 November 2008
Available online 7 December 2008
(4 ꢀ C6H14
) have been readily prepared in good yields by amine elimination reaction between
Ln[N(SiMe3)2]3 (Ln = Sm, Y) and chiral NNO ligands, (S)-2-(pyridin-2-ylmethylamino)-20-hydroxy-1,10-
binaphthyl (1H2) and (S)-5,50,6,60,7,70,8,80-octahydro-2-(pyrrol-2-ylmethyleneamino)-20-hydroxy-1,10-
binaphthyl (2H2), respectively. They both have been characterized by various spectroscopic techniques,
elemental analyses, and X-ray diffraction analyses. They are active catalysts for asymmetric hydroamin-
ation/cyclization of aminoalkenes and ring-opening polymerization of rac-lactide, affording cyclic amines
in excellent conversions with moderate ee values and isotactic-rich polylactides, respectively.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
2-Amino-20-hydroxy-1,10-binaphthyl
NNO ligands
Chiral organolanthanide complexes
Asymmetric hydroamination/cyclization
Polymerization of lactide
1. Introduction
tions [32–34], and in some cases, the enantioselectivity is high
up to 96.7% ee [34]. However, to our knowledge, no example of
Chiral organolanthanide complexes based on non-Cp multiden-
tate ligands have received growing attention in the past decades
[1–11]. One of the initial driving forces for this work is the long-
standing interest in the development of catalysts for intramolecu-
lar asymmetric alkene hydroamination [6–11], since the
hydroamination is a highly atom economical process in which an
amine N–H bond is added to an unsaturated carbon–carbon bond
leading to the formation of nitrogen heterocycles that are found
in numerous biologically and pharmacologically active com-
pounds. To date, many non-Cp chiral catalysts based on lanthanide
metals for asymmetric alkene hydroamination have been widely
studied [6–28], however, only a small number of highly enantiose-
lective reactions (>90% ee) have been reported [12]. Thus, the
development of new lanthanide catalysts for asymmetric alkene
hydroamination is a desirable and challenging goal.
chiral lanthanide catalyst based on 2-amino-20-hydroxy-1,10-
binaphthyl (NOBIN) has been reported yet, in contrast to
binaphthol, biphenol, binaphthylamine and biphenylamine [29–
31,35,36,1,37–40]. More recently, we have reported a new series
of organolanthanides based on chiral NOBIN [41–43]. These
organolanthanides have shown good catalytic activity in the poly-
merization of methyl methacrylate (MMA), the ring-opening poly-
merization of rac-lactide, and the hydroamination/cyclization of
the aminoalkenes [41–43]. We have therefore started exploring
the NOBIN ligand in the lanthanide chemistry. Herein, we report
on some observations concerning the chemistry of ligands (S)-2-
(pyridin-2-ylmethylamino)-20-hydroxy-1,10-binaphthyl (1H2) and
(S)-5,50,6,60,7,70,8,80-octahydro-2-(pyrrol-2-ylmethyleneamino)-20-
hydroxy-1,10-binaphthyl (2H2), which are prepared from (S)-2-
amino-20-hydroxy-1,10-binaphthyl (NOBIN), with lanthanide
amides and the use of the resulting complexes as catalysts in the
asymmetric hydroamination/cyclization of aminoalkenes and the
polymerization of rac-lactide.
In recent years, 2-amino-20-hydroxy-1,10-binaphthyl (NOBIN) as
its (R) or (S) enantiomers has been modified to give variants which
bear appropriate structural and electronic features for intended
specific reactions, and its derivatives have exhibited good to excel-
lent enantioselectivities in a number of asymmetric transforma-
tions [29–31]. For example, the ruthenium complexes with the
ligand 2-(pyridin-2-ylmethylamino)-20-hydroxy-1,10-binaphthyl
(1H2) are useful catalysts for a range of asymmetric transforma-
2. Experimental
2.1. General methods
All experiments were performed under an atmosphere of dry
dinitrogen with rigid exclusion of air and moisture using standard
Schlenk or cannula techniques, or in a glovebox. All organic
* Corresponding author. Tel.: +86 10 5880 2237; fax: +86 10 5880 2075.
E-mail addresses: gzi@bnu.edu.cn, ziguofu@hotmail.com (G. Zi).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.061

692
Q. Wang et al. / Journal of Organometallic Chemistry 694 (2009) 691–696
solvents were freshly distilled from sodium benzophenone ketyl
immediately prior to use. Racemic-lactide was recrystallized
twice from dry toluene and then sublimed under vacuum
prior to use. (S)-2-(pyridin-2-ylmethylamino)-20-hydroxy-1,10-
binaphthyl (1H2) [34], (S)-5,50,6,60,7,70,8,80-octahydro-2-(pyrrol-
Schlenk flask which contained 62 mg (0.32 mmol) of (S)-(+)-O-
acetylmandelic acid. This transfer was quantitated by washing
the NMR tube with a small amount of CDCl3. The resulting mixture
was stirred at room temperature for 2 h and the volatiles were re-
moved in vacuo. The resulting diastereomeric salt was then dis-
solved in CDCl3 and the enantiomeric excesses were determined
by 1H NMR spectroscopy [27].
2-ylmethyleneamino)-20-hydroxy-1,10-binaphthyl
(2H2)
[42],
Ln[N(SiMe3)2]3 [44], 2,2-dimethylpent-4-enylamine [27], 2,20-
dimethylhex-5-enylamine [27], and 1-(aminomethyl)-1-allylcyclo-
hexane [28] were prepared according to literature methods. All
chemicals were purchased from Aldrich Chemical Co. and Beijing
Chemical Co. used as received unless otherwise noted. Infrared
spectra were obtained from KBr pellets on an Avatar 360 Fourier
transform spectrometer. Molecular weights of the polymer were
estimated by gel permeation chromatography (GPC) using a PL-
GPC 50 apparatus. 1H and 13C NMR spectra were recorded on a
Bruker AV 500 spectrometer at 500 and 125 MHz, respectively.
All chemical shifts are reported in d units with reference to the
residual protons of the deuterated solvents for proton and carbon
chemical shifts. Melting points were measured on an X-6 melting
point apparatus and were uncorrected. Elemental analyses were
performed on a Vario EL elemental analyzer.
2.5. General procedure for polymerization of rac-lactide
In a glovebox, a Schlenk flask was charged with a solution of the
complex (typically 0.005 mmol) in toluene (0.2 mL) or THF
(0.2 mL). To this solution was added rapidly a toluene or THF solu-
tion (5.0 mL) of rac-lactide (5.0 mmol), and the reaction mixture
was vigorously stirred for 1 h at room temperature. The polymeri-
zation was quenched by the addition of acidified methanol. The
resulting precipitated polylactide was collected, washed with
methanol several times, and dried in vacuum at 50 °C overnight.
2.6. X-ray crystallography
Single-crystal X-ray diffraction measurements were carried out
on a Rigaku Saturn CCD diffractometer at 113(2) K using graphite
2.2. Preparation of {(1)2YN(SiMe3)2}2 ꢀ C7H8 (3 ꢀ C7H8)
monochromated Mo K
a radiation (k = 0.71070 Å). An empirical
A toluene solution (10 mL) of 1H2 (0.19 g, 0.5 mmol) was slowly
added to a toluene solution (10 mL) of Y[N(SiMe3)2]3 (0.28 g,
0.5 mmol) with stirring at room temperature. The resulting solu-
tion was refluxed overnight to give a yellow solution. The solution
was filtered, and the filtrate was concentrated to about 2 mL.
3 ꢀ C7H8 was isolated as yellow crystals after this solution stood
at room temperature for three days. Yield: 0.25 g (75%). M.p.:
203–205 °C (dec.). 1H NMR (C6D6): d 8.12 (d, J = 9.0 Hz, 2H), 8.07
(d, J = 5.2 Hz, 2H), 7.95 (m, 4H), 7.70 (d, J = 8.0 Hz, 2H), 7.58 (d,
J = 8.0 Hz, 2H), 7.27 (m, 5H), 7.10 (m, 4H), 7.04 (d, J = 8.6 Hz, 2H),
6.80 (m, 2H), 6.75 (m, 2H), 6.64 (m, 2H), 6.33 (m, 2H), 6.20 (m,
4H), 5.98 (d, J = 8.6 Hz, 2H), 4.07 (d, J = 19.3 Hz, 2H), 3.96 (d,
J = 19.3 Hz, 2H), 2.22 (s, 3H), 0.80 (s, 18H), ꢁ0.49 (s, 18H). 13C
NMR (C6D6): d 163.5, 155.1, 153.2, 145.5, 137.5, 137.2, 136.4,
132.6, 131.2, 128.4, 128.3, 127.2, 126.0, 125.6, 124.9, 124.2,
124.1, 122.2, 120.5, 118.9, 116.2, 112.1, 55.8, 22.1, 6.1, 4.0. IR
absorption correction was applied using the SADABS program [45].
All structures were solved by direct methods and refined by full-
matrix least squares on F2 using the SHELXL-97 program package
[46]. All the hydrogen atoms were geometrically fixed using the
riding model. The crystal data and experimental data for 3 and 4
are summarized in Table 1. Selected bond lengths and angles are
listed in Table 2.
3. Results and discussion
3.1. Synthesis and characterization of complexes
Treatment of (S)-2-(pyridin-2-ylmethylamino)-20-hydroxy-1,10-
binaphthyl (1H2) with 1 equiv. of Y[N(SiMe3)2]3 in toluene gives the
dimeric amide complex {(1)YN(SiMe3)2}2 ꢀ C7H8 (3 ꢀ C7H8) in 75%
yield (Scheme 1). Our previous work has shown that interaction be-
tween (S)-5,50,6,60,7,70,8,80-octahydro-2-(pyrrol-2-ylmethylenea-
(KBr, cmꢁ1):
m 3055 (w), 2946 (m), 1606 (m), 1588 (m), 1487 (s),
1419 (s), 1329 (s), 1231 (s), 1149 (m), 1087 (s), 979 (s), 962 (s),
813 (s), 739 (s). Anal. Calc. for C71H80N6O2Si4Y2: C, 63.66; H,
6.02; N, 6.27. Found: C, 63.82; H, 6.36; N, 6.12%.
Table 1
Crystal data and experimental parameters for compounds 3 and 4.
2.3. Preparation of {(2)2SmN(SiMe3)2}2 ꢀ C6H14 (4 ꢀ C6H14
)
Compound
3 ꢀ C7H8
4 ꢀ C6H14
Formula
Formula weight
Crystal system
Space group
a (Å)
C71H80N6O2Si4Y2
1339.59
Orthorhombic
P212121
15.519(2)
18.728(2)
46.425(3)
90
C34H49N3OSi2Sm
722.29
Monoclinic
P21
11.636(2)
15.971(2)
18.997(2)
91.376(6)
3529.4(6)
4
This compound was prepared as yellow crystals from the reac-
tion of 2H2 (0.19 g, 0.5 mmol) with Sm[N(SiMe3)2]3 (0.32 g,
0.5 mmol) in toluene (20 mL) and recrystallization from an n-hex-
ane solution by a similar procedure as in the synthesis of 3 ꢀ C7H8.
b (Å)
c (Å)
Yield: 0.25 g (70%). M.p.: 182–184 °C (dec.). IR (KBr, cmꢁ1):
m 3053
(w), 2930 (m), 1621 (w), 1595 (m), 1567 (s), 1504 (m), 1435 (s),
1391 (s), 1317 (s), 1262 (s), 1179 (s), 1034 (s), 968 (s), 809 (s),
744 (s). Anal. Calc. for C68H98N6O2Si4Sm2: C, 56.54; H, 6.84; N,
5.82. Found: C, 56.32; H, 6.68; N, 5.83%.
b (°)
V (Å3)
13493.0(16)
8
1.319
Z
Dcalc (g/cm3)
1.359
1.760
l(Mo/K
a)
calc
(mmꢁ1
)
1.831
Size (mm)
F(000)
0.24 ꢂ 0.22 ꢂ 0.20
0.22 ꢂ 0.20 ꢂ 0.16
2.4. General procedure for asymmetric hydroamination/cyclization
5584
2612
2h range (°)
2.76–52.00
94332
26426 (0.0778)
20795
0.71, 0.67
0.053
0.091
6.04–50.00
26704
12366 (0.0732)
11338
0.72, 0.68
0.077
0.190
No. of reflections, collected
No. of unique reflections [R(int)
No. of observed reflections
Abscorr (Tmax, Tmin
R
Rw
Rall
GOF
In a nitrogen-filled glove box, pre-catalyst (0.008 mmol), C6D6
(0.7 mL), and aminoalkene (0.32 mmol) were introduced sequen-
tially into a J. Young NMR tube equipped with a Teflon screw
cap. The reaction mixture was subsequently kept at room temper-
ature, or at 120 °C to achieve hydroamination, and the reaction was
monitored periodically by 1H NMR spectroscopy. The cyclic amine
was vacuum transferred from the J. Young NMR tube into a 25 mL
]
)
0.077
1.04
0.082
1.06

Q. Wang et al. / Journal of Organometallic Chemistry 694 (2009) 691–696
693
Table 2
Selected bond distances (Å) and bond angles (deg) for compounds 3 and 4.
Compound 3 ꢀ C7H8
N
Y(1)–O(1)
Y(1)–N(1)
Y(1)–N(5)
Y(2)–O(2)
Y(2)–N(4)
Y(1)–Y(2)
2.360(3)
2.299(3)
2.264(3)
2.330(3)
2.393(4)
3.5951(6)
105.04(11)
Y(1)–O(2)
Y(1)–N(2)
Y(2)–O(1)
Y(2)–N(3)
Y(2)–N(6)
Y(1)–O(1)–Y(2)
Torsion (aryl–aryl)
2.199(3)
2.419(4)
2.195(3)
2.288(3)
2.257(3)
104.18(11)
67.9(2)
HN
OH
2H2
Sm[N(SiMe3)2]3
C7H8
Y(1)–O(2)–Y(2)
78.7(2)
Compound 4 ꢀ C6H14
Sm(1)–O(1)
Sm(1)–N(1)
Sm(1)–N(5)
Sm(2)–O(2)
Sm(2)–N(4)
Sm(1)–Sm(2)
Sm(1)–O(2)–Sm(2)
2.420(10)
2.528(12)
2.297(11)
2.435(9)
2.370(11)
3.7524(9)
106.7(3)
Sm(1)–O(2)
Sm(1)–N(2)
Sm(2)–O(1)
Sm(2)–N(3)
Sm(2)–N(6)
Sm(1)–O(1)–Sm(2)
Torsion (aryl–aryl)
2.241(8)
2.405(9)
2.261(9)
2.555(10)
2.289(9)
106.5(4)
77.4(4)
N
N
N(SiMe3)2
O
Sm
Sm
N
O
(Me3Si)2N
79.8(4)
N
4
Scheme 2. Synthesis of complex 4.
N
H
N
anions 1 or 2 and two amido N(SiMe3)2 groups around two lantha-
nide ions results in the formation of the dimeric complexes
{(1)YN(SiMe3)2}2 and {(2)SmN(SiMe3)2}2 (Figs. 1 and 2). Each Ln3+
OH
1H2
is
r-bound to two nitrogen atoms and two oxygen atoms from
the ligand anions 1 or 2 and one nitrogen atom from the amido
N(SiMe3)2 group in a distorted-trigonal–bipyramidal geometry
Y[N(SiMe3)2]3
C7H8
with the average distance of Ln–N (2.320(4) Å) for
Y and
(2.407(12) Å) for Sm, respectively, and the average distance of
Ln–O (2.271(3) Å) for Y and (2.339(10) Å) for Sm, respectively.
The average Ln–O–Ln angles are 104.6(1)° for Y and 106.6(4)° for
N
N
O
N(SiMe3)2
Y
Y
O
(Me3Si)2N
N
N
3
Scheme 1. Synthesis of complex 3.
mino)-20-hydroxy-1,10-binaphthyl (2H2) with 1 equiv. of Ln[N-
(SiMe3)2]3 (Ln = Y, Yb) gives the trinuclear complexes {(2)2Ln}2LnN-
(SiMe3)2 (Ln = Y, Yb) [42]. However, under similar reaction
conditions, reaction of 2H2 with 1 equiv. of Sm[N(SiMe3)2]3 does
not lead to the expected trinuclear complex {(2)2Sm}2SmN-
(SiMe3)2, instead, a dimeric amide complex {(2)SmN(SiMe3)2}2 ꢀ
C6H14 (4 ꢀ C6H14) has been isolated in 70% yield (Scheme 2).
Both the complexes are stable in a dry nitrogen atmosphere,
while they are very sensitive to moisture. They are soluble in or-
ganic solvents such as THF, DME, pyridine, toluene, and benzene,
and only slightly soluble in n-hexane. They have been character-
ized by various spectroscopic techniques, elemental analyses, and
single-crystal X-ray diffraction analyses. The 1H NMR spectrum of
3 supports the ratio of toluene, amino group N(SiMe3)2, and ligand
1 is 1:2:2, and its 13C NMR spectrum is consistent with the
conclusions.
The single-crystal X-ray diffraction analyses shows that there
are two molecules {(1)YN(SiMe3)2}2 and two solvate toluene mol-
ecules for 3, and one molecule {(2)SmN(SiMe3)2}2 and one solvate
n-hexane molecule for 4 in the lattice. Coordination of two ligand
Fig. 1. Molecular structure of 3 (thermal ellipsoids drawn at the 35% probability
level).

694
Q. Wang et al. / Journal of Organometallic Chemistry 694 (2009) 691–696
3.2. Catalytic activity
To examine the catalytic ability of the complexes 3 and 4, the
asymmetric hydroamination/cyclization of aminoalkenes and
polymerization of rac-lactide have been evaluated under the condi-
tions given in Tables 3 and 4, respectively.
The results (Table 3) clearly show that all substrates are con-
verted to the cyclic product at room temperature or elevated tem-
perature in excellent conversions, and the samarium complex 4 is
noticeably good at room temperature. Not surprisingly, given a
more open coordination sphere the reaction is faster, but the ee va-
lue remains moderate (up to 55%; Table 3, entry 2). On moving to
the smaller Y3+ ion (Table 3, entry 1), both the rate and the ee value
fall slightly. Substrate 6a is the most reactive of the aminoalkenes,
giving the corresponding pyrrolidine within 16 h at room temper-
ature. The data also show that the formation of six-membered
rings can also be performed with our catalysts at 120 °C (Table 3,
entries 5–6), and a moderate enantioselectivity (up to 34%), medi-
ated by the catalyst 4, has been obtained (Table 3, entry 6). The cat-
alytic activities of the binuclear complexes amides 3 and 4 are
more effective than trinuclear complexes {(2)2Ln}2LnN(SiMe3)2
(Ln = Y, Yb) [42], but their enantioselectivities are poorer than
those initiated by {(2)2Ln}2LnN(SiMe3)2 (Ln = Y, Yb) [42] due to
the steric effect. Although the enantiomeric excesses obtained re-
mains moderate, it should be noted that there are only few lantha-
nide catalysts for these reactions that give a significant ee (>90%) at
all [12].
The complexes 3 and 4 are also active catalysts for the ring-
opening polymerization (ROP) of racemic-lactide under mild con-
ditions (Table 4). Yttrium complex 3 allows the complete conver-
sion of 1000 equiv of lactide within 1 h at room temperature in
toluene at [rac-LA]=1.0 mol Lꢁ1 (Table 4, entry 1). Polymerizations
with this yttrium initiator/catalyst proceed much more slowly in
THF (Table 4, entry 3), presumably due to the competitive coordi-
nation between the monomer and this donor solvent, as often ob-
served in this type of ROP reactions promoted by oxophilic meta-
based systems [47]. This difference in activity between toluene
and THF solvent is not observed with complex 4 (Table 4, entries
2 and 4); however, the samarium complex is less active than yt-
trium complex 3 in toluene medium (Table 4, entries 1 and 2).
The resulting polylactides are all isotactic-rich under the condi-
Fig. 2. Molecular structure of 4 (thermal ellipsoids drawn at the 35% probability
level).
Sm complexes, respectively. The average distance of Ln–N(SiMe3)2
is (2.261(3) Å) for Y and (2.293(11) Å) for Sm. The twisting be-
tween the aryl rings of torsion angles are 67.9(2)° and 78.7(2)°
for Y, and 77.4(4)° and 79.8(4)° for Sm. The two Ln3+ centers within
the dications are separated by 3.595(1) Å for Y and 3.752(1) Å for
Sm, respectively. These structural data are close to those found in
{[(S)-2-O-C20H12-20-(NCHC4H3N)]LnN(SiMe3)2}2 [41].
Table 3
Enantioselective hydroamination/cyclization of aminoalkenes.a
Entry
1
Pre-catalyst (M)
Substrate
Product
Temperature (°C)
Time (h)
16
Conversion (%)b
95
ee (%)c
54
3 (Y)
20
NH2
H
N
5a
5b
2
3
4 (Sm)
3 (Y)
20
20
16
16
98
100
55
48
NH2
NH
6b
6a
4
5
4 (Sm)
3 (Y)
20
120
16
16
100
92
54
30
NH2
NH
7a
7b
6
4 (Sm)
120
16
95
34
a
Conditions: C6D6 (0.70 mL), aminoalkene (0.32 mmol), catalyst (0.008 mmol).
Determined by 1H NMR based on p-xylene as the internal standard.
b
c
Determined by 1H NMR of its diastereomeric (S)-(+)-O-acetylmandelic acid salt [27].

Q. Wang et al. / Journal of Organometallic Chemistry 694 (2009) 691–696
695
Table 4
further efforts will focus on the optimization of the catalyst archi-
tecture to improve the enantiomeric excess for hydroamination/
cyclization, and on the exploration of these catalysts towards other
types of reactions.
Polymerization of rac-lactide catalyzed by chiral organolanthanide amides 3 and 4.a
O
O
O
O
O
O
complex
O
O
O
m
O
+
O n
O
O
O
Acknowledgements
O
O
This work was supported by the National Natural Science Foun-
dation of China (20602003), and Beijing Municipal Commission of
Education.
rac-Lactide
Isotactic Polylactide
b
b
c
Entry Complex Solvent
Conversion (%) Mn (kg/mol) Mw/Mn
Pm (%)
1
2
3
4
3
4
3
4
Toluene 100
72.9
66.2
59.3
54.2
1.21
1.28
1.26
1.23
68
58
59
54
Appendix A. Supplementary material
Toluene
THF
90
88
87
CCDC 692309 and 692310 contain the supplementary crystallo-
graphic data for 3 and 4. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif. Supplementary data associated with
this article can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.11.061.
THF
a
Conditions: 20 °C, precat./LA (mol/mol) = 1/1000; polymerization time, 1 h;
solvent, 5 mL; [LA] = 1.0 mol/L.
b
Measured by GPC (using polystyrene standards in THF).
Pm is the probability of meso linkages between monomer units and is deter-
c
mined from the methine region of the homonuclear decoupling 1H NMR spectrum
in CDCl3 at 25 °C.
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1896.
[3] O. Dechy-Cabaret, B. Martin-Vaca, D. Bourissou, Chem. Rev. 104 (2004) 6147–
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tions examined. Molecular weights and polydispersities of the
polymers produced ranged from 54.2 to 72.9 kg molꢁ1 and 1.21
to 1.28, respectively. The catalytic activities of 3 and 4 resemble
that of [2-(2,6-iPr2C6H3N@CH)C4H3N]2Y(CH2SiMe3)(THF)2 [48],
while the microstructure of the resulting polylactides are similar
to those initiated by [(S)-2-MeO-C20H12-20-(NCHC4H3N)]2LnN-
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In conclusion, two new binuclear lanthanide amides have been
readily prepared from the reactions between Ln[N(SiMe3)2]3 and
chiral NNO ligands, (S)-2-(pyridin-2-ylmethylamino)-20-hydroxy-
1,10-binaphthyl (1H2) and (S)-5,50,6,60,7,70,8,80-octahydro-2-(pyr-
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have significant catalytic activity in the asymmetric hydroamina-
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these catalytic processes are plagued by the poor degree of control
of the polymerization and the moderate enantioselectivity of the
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When changes are made from pyrrol-2-ylmethyleneamino
group to pyridin-2-ylmethylamino group, and from binaphthyl to
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80-octahydro-2-(pyrrol-2-ylmethyleneamino)-20-hydroxy-1,10-
binaphthyl (2H2) exhibit different reactivity patterns. For example,
reaction of (S)-2-(pyrrol-2-ylmethyleneamino)-20-hydroxy-1,10-
binaphthyl or 1H2 with Y[N(SiMe3)2]3 gives the binuclear com-
plex {[(S)-2-O-C20H12-20-(NCHC4H3N)]YN(SiMe3)2}2 [41] or
{(1)YN(SiMe3)2}2 (3), respectively, while reaction of 2H2 with
Ln[N(SiMe3)2]3 (Ln = Sm, Y) affords a binuclear complex {(2)SmN-
(SiMe3)2}2 (4) or a trinuclear complex {(2)2Y}2YN(SiMe3)2 [42],
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and 4 are more effective catalysts for the enantioselective hydro-
amination/cyclization reaction than the pyrrolate binuclear com-
plexes {[(S)-2-O-C20H12-20-(NCHC4H3N)]LnN(SiMe3)2}2 (Ln = Y, Yb)
[42], but less than those initiated by trinuclear complexes
{(2)2Ln}2LnN(SiMe3)2 (Ln = Y, Yb) [42] presumably due to the steric
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