Thiophene-NPN ligand supported rare-earth metal bis(alkyl) complexes. synthesis and catalysis toward highly trans-1,4 selective polymerization of butadiene

Article abstract of DOI:10.1021/om800660j

A series of new rare-earth metal bis(alkyl) complexes [L ^1-3Ln(CH₂SiMe₃)₂(THF)_n] (L¹= MeC₄H₂SCH₂NC₆H ₄(Ph)₂P=NC₆H₂Me₃-2,4,6: Ln = Sc, n = 1 (la); Ln = Lu, n = 1 (lb); L² = MeC₄H ₂SCH₂NC₆H₄(Ph)₂P=NC ₆H₃Et₂-2,6: Ln = Sc, n = 1 (2a); Ln = Lu, n = 1 (2b); Ln = Y, n = 1 (2c); L³ = MeC₄H₂SCH ₂NC₆H₄(Ph)₂P=NC₆H ₃ⁱPr₂-2,6: Ln = Sc, n = 0 (3a)) and L ⁴Sc(CH₂SiMe₃)₂(THF) (4a) (L ⁴ = C₆H₅CH₂NC₆H ₄(Ph)₂P=NC₆H₃Et₂-2,6) have been prepared by reaction of rare-earth metal tris(alkyl)s with the corresponding HL^1-4 ligands via alkane elimination. Complexes la, lb, 2a-2c, and 4a are monomeric with a coordinating THF molecule. Each metal ion is coordinated by a NPN ligand, two trans-located alkyl groups, and a THF molecule, forming a distorted trigonal-bipyramidal geometry. Complex 3a is THF-free, adopting a distorted tetrahedron geometry. In combination with A1R₃ and borate, these complexes have shown medium activity and good trans-1,4 selectivity for the polymerization of butadiene. The resultant polymer has moderate molecular weight (M_n = 10 000-18 000) with narrow molecular weight distribution (M_w/M_n < 1.6) and trans-1,4 regularity varying from 49.2% up to 91.3%. The catalyst performances are strongly dependent on the ortho substituent of the N-aryl ring and the presence of the thiophene moiety of the ligands and the type of aluminum alkyls and the lanthanide metal used. The scandium complex 2a displays the highest trans-1,4 selectivity.

Full text of DOI:10.1021/om800660j

Organometallics 2008, 27, 6531–6538
6531
Thiophene-NPN Ligand Supported Rare-Earth Metal Bis(alkyl)
Complexes. Synthesis and Catalysis toward Highly trans-1,4
Selective Polymerization of Butadiene
Dun Wang,†,‡ Shihui Li,†,‡ Xinli Liu,† Wei Gao,†,§ and Dongmei Cui*,†
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, People’s Republic of China, Graduate School of the
Chinese Academy of Sciences, Beijing 100039, People’s Republic of China, and Department of Chemistry,
Jilin UniVersity, Changchun, People’s Republic of China
ReceiVed July 12, 2008
A series of new rare-earth metal bis(alkyl) complexes [L1-3Ln(CH2SiMe3)2(THF)n] (L1
MeC4H2SCH2NC6H4(Ph)2PdNC6H2Me3-2,4,6: Ln ) Sc, n ) 1 (1a); Ln ) Lu, n ) 1 (1b); L2 )
MeC4H2SCH2NC6H4(Ph)2PdNC6H3Et2-2,6: Ln ) Sc, n ) 1 (2a); Ln ) Lu, n ) 1 (2b); Ln ) Y, n )
1 (2c); L3 ) MeC4H2SCH2NC6H4(Ph)2PdNC6H3iPr2-2,6: Ln ) Sc, n ) 0 (3a)) and L4Sc(CH2SiMe3)2(THF)
(4a) (L4 ) C6H5CH2NC6H4(Ph)2PdNC6H3Et2-2,6) have been prepared by reaction of rare-earth metal
tris(alkyl)s with the corresponding HL1-4 ligands via alkane elimination. Complexes 1a, 1b, 2a-2c, and
4a are monomeric with a coordinating THF molecule. Each metal ion is coordinated by a NPN ligand,
two trans-located alkyl groups, and a THF molecule, forming a distorted trigonal-bipyramidal geometry.
Complex 3a is THF-free, adopting a distorted tetrahedron geometry. In combination with AlR3 and borate,
these complexes have shown medium activity and good trans-1,4 selectivity for the polymerization of
butadiene. The resultant polymer has moderate molecular weight (Mn ) 10 000-18 000) with narrow
molecular weight distribution (Mw/Mn < 1.6) and trans-1,4 regularity varying from 49.2% up to 91.3%.
The catalyst performances are strongly dependent on the ortho substituent of the N-aryl ring and the
presence of the thiophene moiety of the ligands and the type of aluminum alkyls and the lanthanide
metal used. The scandium complex 2a displays the highest trans-1,4 selectivity.
)
of catalyst systems have been designed for the trans-1,4-
selective polymerization of isoprene, such as Ziegler-Natta
catalysts based on Ti and V metals,8 Ln(allyl)2Cl(MgCl2)2/AlR3,9
Cp*Nd(BH4)2(THF)2/Mg(nBu)2,10 [(CMe2C5H4)2Sm(C3H5)MgCl2-
(OEt2)2LiCl(OEt2)],11 and Cp*Ln(AlMe4)2/[Ph3C][B(C6F5)4]/Ali-
Bu3.12 trans-1,4-Regulated polybutadiene has been compara-
tively less well explored.13 To date, the catalyst systems that
can initiate the trans-1,4-selective polymerization of butadiene
Introduction
During the past decades, many efforts have been made to
develop new catalyst systems for regio- or stereoselective
polymerization of conjugated dienes, providing an opportunity
to create polymers widely applied in elastomer industry. In
particular, many investigations have been devoted to investigate
cis-1,4-selective catalyst systems because the resulting poly-
dienes are the most important elastomers used for tires and other
elastic materials.1-7 In the meantime, an interest in trans-1,4-
regulated polymer has emerged as a thermoplastic or an
important component of high-performance rubbers. A variety
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* Corresponding author. Fax: (+86) 431 85262773. Tel: +86 431
85262773. E-mail: dmcui@ciac.jl.cn.
† Changchun Institute of Applied Chemistry.
‡ Graduate School of the Chinese Academy of Sciences.
§ Jilin University.
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10.1021/om800660j CCC: $40.75  2008 American Chemical Society
Publication on Web 11/14/2008

6532 Organometallics, Vol. 27, No. 24, 2008
Wang et al.
Chart 1
are Ziegler-Natta catalysts based mainly on transition metals,
for instance Ti, V,14 and Fe complexes chelated by tridentate
N,N,N-donor ligands,15 a Ti complex bearing an S,S-
bidentate ligand,16 and VCl3{2,6-bis[(2,6-iPr2C6H3)NdC(Me)]2-
(C5H3N)}].17 Rare-earth metal based catalyst systems are limited
to Cp*2Ln[(µ-Me)AlMe2(µ-Me)]2LnCp*2 (Cp* ) η5-C5Me5, Ln
) Ce)5c and lanthanide bis(allyl)s and neodymium alkoxides
or aryl oxides, which need the activation of dialkylmagnesium.18
designed a series of non-Cp-ligated rare-earth metal bis(alkyl)s23
and found that the ligands play distinctive roles in governing
catalytic performance. As shown in Chart 1 the NPN ligand A
reacted with rare-earth metal tris(alkyl)s to induce C-H
activation,23g while B-stabilized bis(alkyl) species were excellent
precursors for highly 3,4-selective polymerization of isoprene.23d
Herein we wish to report the rare-earth metal bis(alkyl)s bearing
ancillary ligands C and D, a new type of precursors for trans-
1,4-selective polymerization of butadiene in the presence of
borate and aluminum alkyls. The influence of the rare-earth
metal, the sterics of ligands, and the polymerization conditions
on the catalytic performance will be presented.
Because rare-earth metal bis(alkyl) complexes supported by
monoanionic ancillary ligands have been demonstrated as highly
active single-component catalysts or excellent precursors for
the polymerizations of conjugated dienes and olefin under the
activation of borates and aluminum alkyls,19-22 our group has
Results and Discussion
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Synthesis and Characterization of NPN-Type Rare-Earth
Metal Bis(alkyl) Complexes 1a-4a. The thiophene-NPN-type
ligands HL1-4 (HL1-3, Chart 1 C, HL1: MeC4H2SCH2NHC6H4-
(Ph)2PdNC6H2Me3-2,4,6; HL2: MeC4H2SCH2NHC6H4(Ph)2Pd
i
NC6H3Et2-2,6; HL3: MeC4H2SCH2NHC6H4(Ph)2PdNC6H3 Pr2-
2,6; HL4: Chart 1 D, C6H5CH2NHC6H4(Ph)2PdNC6H3Et2-2,6)
were prepared by the Staudinger reaction between thiophene-
diphenylphosphinephenylamine MeC4H2SCH2NHC6H4P(Ph)2 or
C6H5CH2NHC6H4P(Ph)2 with 1 equiv of the corresponding
azides. Treatment of these ligands with rare-earth metal tris-
(alkyl)s, Ln(CH2SiMe3)3(THF)2, afforded the bis(alkyl) com-
plexes [L1-3Ln(CH2SiMe3)2(THF)n] (L1, Ln ) Sc, n ) 1 (1a);
Ln ) Lu, n ) 1 (1b); L2, Ln ) Sc, n ) 1 (2a); Ln ) Lu, n )
1 (2b); Ln ) Y, n ) 1 (2c); L3, Ln ) Sc, n ) 0 (3a)) and
L4Sc(CH2SiMe3)2(THF) (L4 ) C6H5CH2NC6H4(Ph)2PdNC6H3Et2-
2,6, 4a) in quantitative yields (Schemes 1 and 2). All complexes
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1
were characterized by H NMR spectroscopy. Complexes 1a,
1b, 2a, 2b, and 2c displayed AB spins at the upfield region (δ
0.11 to -0.79) (JH-H ) 11 Hz) assignable to the diastereotopic
methylene protons of the metal alkyl Ln-CH2SiMe3. In contrast,
the resonances of the methylene protons of Sc-CH2SiMe3 in
complex 3a showed a doublet at δ 0.063, while complex 4a
exhibited a singlet at δ 0.076, suggesting that the two alkyl
groups exchanged quickly in both complexes. The solid state
structures of complexes 1b, 2a, 3a, and 4a were confirmed by
X-ray diffraction analysis (Table 1, Figures 1-4). Complexes
1b, 2a, and 4a are isostructural monomers with one coordinating
THF molecule. The monoanionic thiophene-NPN ligand chelates
to the central metal ion with N, N atoms, adopting meridional
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Rare-Earth Metal Bis(alkyl) Complexes
Organometallics, Vol. 27, No. 24, 2008 6533
Scheme 1. Synthesis of Complexes 1-3
Scheme 2. Synthesis of Complex 4a
Table 1. Crystallographic Data and Refinements for Complexes 1b, 2a, 3a, and 4a
1b · (C7H8)0.5
2a
3a
4a · (C7H8)0.5
formula
fw
C48.50H66LuN2OPSSi2
987.18
C46H64N2OPSScSi2
825.16
C44H60N2PSScSi2
781.11
C50.50H68N2OPScSi2
851.14
cryst syst
space group
a/Å
b/Å
c/Å
triclinic
P1
monoclinic
P2(1)/n
monoclinic
C2/c
41.905(3)
11.7333(8)
20.3477(14)
115.1560(1)
9055.8(11)
8, 1.146
monoclinic
P2(1)/n
j
12.0645(8)
14.3557(9)
15.3451(1)
96.8130(1)
2533.5(3)
2, 1.289
2.102
1010
1.81 to 26.03
-13 e h e 14
-17 e k e 16
-18 e l e 16
14 209
12.2694(9)
26.4988(19)
14.3383(1)
93.1350(1)
4654.8(6)
4, 1.177
0.323
1768
1.62 to 26.07
-15 e h e 10
-28 e k e 32
-16 e l e 17
26 048
13.1455(7)
25.6245(14)
14.6598(8)
91.2780(1)
4936.9(5)
4, 1.124
0.265
1788
1.59 to 26.08
-16 e h e 16
-28 e k e 31
-18 e l e 12
27 624
ꢀ/deg
V/Å3
Z, Dc/g cm-3
µ/mm-1
F(000)
θ range/deg
h,k,l range
0.327
3344
1.82 to 26.06
-51 e h e 51
-14 e k e 9
-23 e l e 25
24 922
no. of reflns measd
no. of unique reflns
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
9741 [R(int) ) 0.0711]
9741/52/579
1.014
R1 ) 0.0470
wR2 ) 0.1179
R1 ) 0.0564
wR2 ) 0.1228
1.705 and -1.513
9177 [R(int) ) 0.0695]
9177/176/634
0.877
R1 ) 0.0560,
wR2 ) 0.0928
R1 ) 0.1159
wR2 ) 0.1102
0.422 and -0.235
8911 [R(int) ) 0.0855]
8911/0/471
0.963
R1 ) 0.0631
wR2 ) 0.1178
R1 ) 0.1321
wR2 ) 0.1453
0.411 and -0.284
9744 [R(int) ) 0.0524]
9744/18/549
1.025
R1 ) 0.0651
wR2 ) 0.1748
R1 ) 0.1007
wR2 ) 0.1997
0.798 and -0.445
R indices (all data)
largest diff peak and hole/e Å-3
configuration, which leads to the thiophene ring (or phenyl) and
N-aryl ring parallel to each other. The two alkyl species are
located in trans positions. The geometry around the central metal
is best described as distorted trigonal bipyramidal. Complex 3a

6534 Organometallics, Vol. 27, No. 24, 2008
Wang et al.
Figure 1. X-ray structure of 1b with 35% probability thermal
ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Lu(1)-N(1) ) 2.260(4), Lu(1)-N(2)
) 2.349(4), Lu(1)-C(32) ) 2.366(6), Lu(1)-C(42) ) 2.344(6),
N(1)-C(1) ) 1.357(7), P(1)-C(6) ) 1.796(5), C(1)-C(6) ) 1.434(8),
N(1)-C(36) ) 1.470(7), N(2)-P(1) ) 1.610(4), N(1)-Lu(1)-N(2)
) 82.8(2), P(1)-N(2)-Lu(1) ) 117.0(2), C(1)-N(1)-Lu(1) )
137.6(3), C(36)-N(1)-Lu(1) ) 101.4(3), C(42)-Lu(1)-C(32) )
109.2(2), N(2)-P(1)-C(6) ) 115.3(2), N(1)-C(1)-C(6) ) 120.5(5),
C(1)-N(1)-C(36) ) 116.6(4).
Figure 3. X-ray structure of 3a with 35% probability thermal
ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Sc(1)-N(1) ) 2.090(3), Sc(1)-N(2) )
2.147(3), Sc(1)-C(37) ) 2.201(3), Sc(1)-C(38) ) 2.218(4), N(1)-C(1)
) 1.377(4), P(1)-C(6) ) 1.786(4), C(1)-C(6) ) 1.423(5), N(1)-C(31)
) 1.464(4), N(2)-P(1) ) 1.617(3), N(1)-Sc(1)-N(2) ) 90.2(1),
P(1)-N(2) -Sc(1) ) 111.1(1), C(1)-N(1)-Sc(1) ) 137.7(2),
C(31)-N(1)-Sc(1) ) 102.9(2), C(37)-Sc(1)-C(38) ) 103.5(1),
N(2)-P(1)-C(6)
) 114.8(2), N(1)-C(1)-C(6) ) 120.0(3),
C(1)-N(1)-C(31) ) 117.4(3).
Figure 2. X-ray structure of 2a with 35% probability thermal
ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Sc(1)-N(1) ) 2.160(2), Sc(1)-N(2) )
2.198(2), Sc(1)-C(39) ) 2.246(4), Sc(1)-C(43) ) 2.235(4), C(1)-N(1)
) 1.366(3), P(1)-C(6) ) 1.779(3), C(1)-C(6) ) 1.429(4), C(29)-
N(1) ) 1.462(3), N(2)-P(1) ) 1.620(2), N(1)-Sc(1)-N(2) ) 85.4(9),
P(1)-N(2)-Sc(1) ) 116.6(1), C(1)-N(1)-Sc(1) ) 137.8(2), C(29)-
N(1)-Sc(1))101.7(2),C(43)-Sc(1)-C(39))124.0(1),N(2)-P(1)-C(6)
) 113.9(1), N(1)-C(1)-C(6) ) 119.9(3), C(1)-N(1)-C(29) )
115.9(2).
Figure 4. X-ray structure of 4a with 35% probability thermal
ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Sc(1)-N(1) ) 2.153(3), Sc(1)-N(2) )
2.248(3), Sc(1)-C(41) ) 2.242(3), Sc(1)-C(40) ) 2.263(4), C(1)-N(1)
) 1.377(4), P(1)-C(6) ) 1.779(3), C(1)-C(6) ) 1.425(4), N(1)-C(29)
) 1.473(4), N(2)-P(1) ) 1.618(3), N(1)-Sc(1)-N(2) ) 85.2(9),
P(1)-N(2)-Sc(1) ) 116.51(14), C(1)-N(1)-Sc(1) ) 135.5(2),
C(29)-N(1)-Sc(1) ) 105.65(18), C(41)-Sc(1)-C(40) ) 107.0(1),
N(2)-P(1)-C(6)
) 114.1(1), N(1)-C(1)-C(6) ) 119.9(3),
is THF-free, which could be attributed to the more crowded
environment of the ligand. The Sc ion is coordinated by a
monoanionic thiophene-NPN ligand and two alkyl ligands,
adopting a distorted tetrahedral geometry. The average Ln-N
bond length is 2.305(4) Å in 1b, 2.179(2) Å in 2a, 2.119(3) Å
C(1)-N(1)-C(29) ) 115.0(3).
in 3a, and 2.201(3) Å in 4a, while the mean Ln-C bond length
is 2.241(4) Å in 1b, 2.241(4) Å in 2a, 2.210(3) Å in 3a, and
2.253(3) Å in 4a. Both fall within the normal values.22,23c,d The

Rare-Earth Metal Bis(alkyl) Complexes
Organometallics, Vol. 27, No. 24, 2008 6535
Table 2. Polymerization of Butadiene by Using Various Complexesa
microstructuresd(%)
c
entry
cat.
AlR3
activatorb
conv (%)
Mn ( × 10-4
)
Mw/Mn
trans-1,4
cis-1,4
1,2-
Tm1e(°C)
Tm2e(°C)
1
1a
2a
3a
1a
1a
2a
2a
1a
1a
2a
2a
2b
2c
4a
4a
4a
4a
AliBu3
AliBu3
AliBu3
AlEt3
AlMe3
AlEt3
C
C
C
C
C
C
C
A
B
A
B
C
C
B
C
C
C
65
41
23
76
30
73
20
70
65
50
52
46
90
70
73
80
80
1.26
1.34
0.57
1.27
1.62
1.10
1.71
1.56
1.48
0.98
0.93
0.63
2.49
1.13
1.32
0.76
1.31
1.52
1.44
1.28
1.49
1.57
1.49
1.43
1.45
1.44
1.46
1.51
1.79
1.57
1.54
1.51
1.35
1.47
90.9
91.3
81.2
84.1
77.4
89.4
81.5
89.4
83.7
89.8
90.3
59.2
49.2
84.6
88.5
80.1
84.0
1.3
2.6
3.4
5.2
13.7
2.4
8.6
3.3
5.7
2.0
1.1
21.2
43.0
3.4
2.3
4.4
3.7
7.8
6.1
15.4
10.7
8.9
8.2
9.8
7.3
10.6
8.2
8.6
19.6
7.8
12.0
9.2
15.5
12.3
45.9
43.2
43.3
44.7
45.3
43.8
42.1
43.6
43.5
43.4
43.1
89.8
84.5
2
3f
4
89.9
81.9
86.8
80.7
91.2
93.0
82.2
83.5
5
6
7
8
AlMe3
AliBu3
AliBu3
AliBu3
AliBu3
AliBu3
AliBu3
AlMe3
AlMe3
AlEt3
9
10
11
12
13
14
15
16
17
42.7
42.3
40.0
42.0
80.4
83.1
AliBu3
79.9
a Conditions: complex (20 µmol), butadiene (0.54 g, 10.00 mmol) in toluene, [AlR3]:[Ln]:[activator] ) 10/1/1, Tp: 25 °C, 12 h. b Activiator )
[Ph3C][B(C6F5)4] (A), B(C6F5)3 (B), [PhNHMe2][B(C6F5)4] (C). c Determined by GPC against polystyrene standard. d Determined by IR spectroscopy.
f The reaction time is 24 h. g Determined by differential scanning calorimetry.
angle of N-Ln-N is 82.8(2)° in 1b, 85.4(9)° in 2a, 90.2(1)°
in 3a, and 85.2(9)° in 4a. It is noteworthy that the angle of
N-Sc-N in 3a is much larger than those in 1b, 2a, and 4a
owing to the tetrahedral geometry.
Polymerization of Butadiene. The catalytic performance of
all complexes 1a-4a for the polymerization of butadiene (BD)
had been investigated. Although these complexes alone were
inert, on activation by AlR3 and borates they showed medium
activity and varied trans-1,4 selectivity at room temperature.
The polymerization data are summarized in Table 2.
Meanwhile, the trans-1,4 selectivity was also strongly affected
by the bulkiness of the aluminum alkyls, in the sequence
AliBu3(91.3%) > AlEt3(89.4%) > AlMe3(81.5%) (entries 2, 6,
and 7), as observed in other lanthanide metal based systems,
such as [(C5Me5)2Sm(THF)2]/AlR3/[Ph3C][B(C6F5)4]4 and Cp*2Gd-
[(µ-Me)AlMe2(µ-Me)]2GdCp*2/AlR3/[Ph3C][B(C6F5)4].5c In con-
trast, the trans-1,4 selectivity of this catalytic system was slightly
influenced by the type of borate or borane, [PhNHMe2]-
[B(C6F5)4] (91.3%) g [B(C6F5)3] (90.3%) g [Ph3C][B(C6F5)4]
(89.8%) (entries 2, 10, and 11).
The activity of complex 1a, bearing an ortho-methyl sub-
stituent of the N-aryl ring of the ligand, was higher than that of
complex 2a, with an ortho-ethyl substituent, under the same
conditions. When the ortho substituent was replaced by the more
bulky isopropyl group in the case of complex 3a, a much more
obvious decrease in the catalytic activity was observed (entries
1-3). These results indicated that the precursors with ligands
that are too bulky showed low catalytic activity since the steric
environment of the metal center hindered the coordination of
the monomer. Such influence of the bulkiness of ortho substit-
uents on the activity of complexes has been found previously.7a,23d
We also noted that the catalytic activity was strongly affected
by the type of aluminum alkyls, in the sequence AlEt3 g AliBu3
> AlMe3, but less influenced by the type of borate and borane
(entries 1-2, 4-11).
The trans-1,4 selectivity of this system varied with the ortho
substituents of the N-aryl moiety of the ligand, which reached
91.3% for 2a, bearing ortho-ethyl, and dropped slightly for 1a,
bearing ortho-methyl (90.9%). It should be noted that a
significant decrease in trans-1,4 selectivity in the case of 3a
(81.2%), with the much bulkier ortho-isopropyl group, was
observed. This might be attributed to the more crowded metal
center, which influenced the orientation of the incoming
butadiene monomer and the active allyl species, resulting in
the insertion of the incoming butadiene monomer at C3 of the
allyl species with consequent formation of a 1,2 unit (entries
1-3).23a,d This could be proved by the increase of the 1,2-
regularity of polybutadiene obtained (entry 3, 1,2-% ) 15.4).
To investigate the role of the central metal, complexes based
on scandium (2a), lutetium (2b), and yttrium (2c) were
examined. The activity was governed strongly by the central
metal type, Y > Sc > Lu. A trans-1,4 selectivity as high as
91.3% could be obtained with the scandium precursor, 59.2%
with the lutetium analogue, and 49.2% with yttrium (entries 2,
12, and 13). Obviously, the stereoselectivity depends on the size
of the metal ion, Sc > Lu > Y, the inverse of the ionic radii
(Sc (0.89 Å) < Lu (1.00 Å) < Y (1.04 Å)).24
In order to evaluate the influence of thiophenyl group of the
ligand, scandium complex 4a, with a benzyl group of the ligand,
was synthesized. The activity of complex 4a was higher than
the scandium analogues 1a, 2a, and 3a, bearing the thiophenyl
group of the ligand, under the same conditions (entries 14-16).
However, the trans-1,4 selectivity of 4a (84.0%) (entry 17) was
close to that of 3a but lower than those of 1a (90.9%) and 2a
(91.3%). This was attributed to the probable presence of an
interaction between the sulfur of the thiophenyl moiety and the
metal center in the active species in the cases of using complexes
1a, 2a, and 3a as initiators but the absence in the case of 4a,
which increased the spacial crowding of the metal center to some
degree.
(24) Effective ionic radius of Ln3+ for coordination number 6: Shannon,
R. D. Acta Crystallogr., Sect. A 1976, 32, 751-767.

6536 Organometallics, Vol. 27, No. 24, 2008
Wang et al.
for 24 h. After filtration, the solution was cooled to -30 °C to
afford a yellowish-brown solid of MeC4H2SCHdNC6H4P(Ph)2
within 12 h (3.08 g, 80%). 1H NMR (300 MHz, CDCl3, 25 °C): δ
2.31 (s, 3H, CH3-thienyl), alkyl 6.94 (d, J ) 5.0 Hz, 1H,
4H-thienyl), 7.26 (d, J ) 5.0 Hz, 1H, 5H-thienyl), 7.35-7.59 (m,
14H, PPh2 and PC6H4N), 8.15 ppm (s, 1H, CHdN). An ether
solution of MeC4H2SCdNC6H4P(Ph)2 (2.0 g, 5.2 mmol) was treated
with excess LiAlH4 (1.5 ratio) at room temperature for 12 h. When
the color of the mixture changed from yellowish-green to yellowish-
brown, 100 mL of water containing 3 mL of HCl was added slowly.
Then, the aqueous layer was extracted by diethyl ether three times
(50 mL × 3). The combined organic portion was dried over
Conclusion
A series of new rare-earth metal bis(alkyl)s stabilized by
NPN-type ligands was synthesized via alkane elimination, which
in combination with aluminum alkyls and borate established a
new type of catalyst system. This catalytic system provided
medium activity and predominant trans-1,4 selectivity for the
polymerization of butadiene. The central metal, the spacial
crowding of the ortho substituent of the N-aryl ring, and the
presence of the thiophenyl moiety, as well as the type of
aluminum alkyl, played significant roles in controlling the
catalytic activity and selectivity that were, in contrast, influenced
slightly by the type of borate (or borane).
anhydrous
NaSO4.
Removal
of
solvent
afforded
MeC4H2SCH2NHC6H4P(Ph)2 as a white solid (1.80 g, 91%), which
reacted with 1 equiv of mesitylazide in an ether solution at room
temperature overnight. The resultant solution was concentrated to
5 mL, and 5 mL of hexane was added. The solution was stored at
-30 °C overnight to afford HL1 as a brown solid (3.65 g, 70%).
1H NMR (300 MHz, CDCl3 25 °C): δ 1.93 (s, 6H, o-CH3-N-aryl),
2.05 (s, 3H, p-CH3-N-aryl), 2.15 (s, 3H, CH3-thienyl), 4.32(d, J )
5.0 Hz, 2H, CH2), 6.53 (m, 1H, p-PC6H4N), 6.70 (s, 2H, m-NC6H2),
6.80 (m, 2H, p-PPh2), 6.93 (d, J ) 5.0 Hz, 1H, thienyl), 7.26 (d,
J ) 5.0 Hz, 1H, thienyl), 7.38-7.41(m, 4H, m-PPh2), 7.47-7.60
(m, 6H, o-PPh2, m-PC6H4N), 7.90 ppm (m, 1H, o-PC6H4N).
Experimental Section
General Methods. All reactions were carried out under a dry
and oxygen-free argon atmosphere by using Schlenk techniques or
under a nitrogen atmosphere in an MBraun glovebox. All solvents
were purified from an MBraun SPS system. Organometallic samples
for NMR spectroscopic measurements were prepared in the
1
glovebox by use of NMR tubes sealed with paraffin film. H and
13C NMR spectra were recorded on a Bruker AV400 (FT, 400 MHz
for H; 100 MHz for 13C) spectrometer. NMR assignments were
1
confirmed by 1H-1H COSY and 1H-13C HMQC experiments when
necessary. IR spectra were recorded on a Vertex 70 FT-IR.
Differential scanning calorimetry (DSC) analyses were carried out
on a Q 100 DSC from TA Instruments under a nitrogen atmosphere.
The instrument was calibrated for temperature and enthalpy using
pure indium (mp ) 156.6 °C) and sapphire before experiment.
Measurements during the first heating from 10 to 150 °C and then
the first cooling from 150 to 10 °C as well as the second heating
from 10 to 150 °C at 10 °C/min were performed. Polymer molecular
weight was measured on a Tosoh HLC 8220 GPC with THF as
eluent. Elemental analyses were performed at National Analytical
Research Centre of Changchun Institute of Applied Chemistry
(CIAC). 3-Methylthiophene-2-carboxyaldehyde, etc., were pur-
chased from the National Medicine Company (China) and were
used without further purification. (2-Diphenylphosphino)aniline,
mesityl azide, 2,6-diethylphenyl azide, 2,6-diisopropylphenyl azide,
and Ln(CH2SiMe3)(THF)2 (Ln ) Y, Lu, Sc) were prepared
according to published literature.25
X-ray Crystallographic Studies. Crystals for X-ray analysis
were obtained as described in the preparations. The crystals were
manipulated in a glovebox. Data collections were performed at
-86.5 °C on a Bruker SMART APEX diffractometer with a CCD
area detector, using graphite-monochromated Mo KR radiation (λ
) 0.71073 Å). The determination of crystal class and unit cell
parameters was carried out by the SMART program package. The
raw frame data were processed using SAINT and SADABS to yield
the reflection data file. The structures were solved by using the
SHELXTL program. Refinement was performed on F2 anisotropi-
cally for all non-hydrogen atoms by the full-matrix least-squares
method. The hydrogen atoms were placed at calculated positions
and were included in the structure calculation without further
refinement of the parameters.
Synthesis of MeC4H2SCH2NHC6H4(Ph)2PdNC6H3Et2-2,6
(HL2). Following a similar procedure to that described for the
formation of HL1 but replacing mesitylazide by 2,6-diethylphenyl
1
azide gave HL2 in a 79% yield. H NMR (300 MHz, CDCl3 25
°C): δ 0.83 (t, J ) 7.5 Hz, 6H, o-CH2CH3-N-aryl), 1.96 (s, 3H,
CH3-thienyl), 2.32 (q, J ) 7.5 Hz, 4H, o-CH2CH3-N-aryl), 4.22
(d, J ) 5 Hz, 2H, CH2), 6.45 (m, 1H, p-PC6H4N), 6.57 (m, 1H,
m-PC6H4N), 6.61 (d, J ) 5 Hz, 1H, 4-thienyl), 6.66 (m, 1H,
m-NC6H3), 6.73 (m, 1H, p-NC6H3), 6.80 (m, 2H, p-PPh2), 6.86 (d,
J ) 5.0 Hz, 1H, 5-thienyl), 7.19 (m, 1H, m-NC6H3), 7.30 (m, 4H,
m-PPh2), 7.39 (m, 1H, m-PC6H4N), 7.47 (m, 4H, o-PPh2), 7.64 ppm
(m, 1H, o-PC6H4N).
i
Synthesis of MeC4H2SCH2NHC6H4(Ph)2PdNC6H3 Pr2-2,6
(HL3). Following a similar procedure to that described for the
formation of HL1 but replacing mesitylazide by 2,6-diisopropy-
lphenyl azide gave HL3 in high yield (80%). 1H NMR (300 MHz,
CDCl3, 25 °C): δ 0.74 (d, J ) 6.8 Hz, 12H, o-CHMe2-N-aryl),
1.96 (s, 3H, CH3-thienyl), 3.20 (m, 2H, o-CHMe2-N-aryl), 4.23 (d,
J ) 5.0 Hz, 2H, CH2), 6.46 (m, 1H, p-PC6H4N), 6.56 (m, 1H, m-
PC6H4N), 6.61(d, J ) 5.0 Hz, 1H, 4-thienyl), 6.70 (m, 2H,
m-NC6H3), 6.82 (m, 2H, p-PPh2), 6.86 (d, J ) 5.0 Hz, 1H,
5-thienyl), 7.18(m, 1H, p- NC6H4), 7.32 (m, 4H, m-PPh2), 7.38
(m, 1H, m-PC6H4N), 7.46 (m, 4H, o-PPh2), 7.60 ppm (m, 1H,
o-PC6H4N).
Synthesis of C6H5CH2NHC6H4(Ph)2PdNC6H3Et2-2,6 (HL4).
n
Under a nitrogen atmosphere, BuLi (1.6 M in hexane, 6.6 mL,
10.5 mmol) was added dropwise to a THF solution (25 mL) of the
2-diphenylphosphinoaniline (2.78 g, 10 mmol) at -78 °C. The
reaction mixture remained stirring at -78 °C for 6 h, and then 1
equiv of ClCH2Ph was added slowly. The reaction mixture was
allowed to warm to room temperature slowly and remained stirring
for 6 h. Then 100 mL of water containing 3 mL of HCl was added
to the reaction mixture. The aqueous layer was extracted with ether
three times. The combined organic portion was dried by anhydrous
Na2SO4. Volatiles were removed under reduced pressure to afford
white solids of C6H5CH2NHC6H4(Ph)2P (2.31 g, 63%). To the dry
ether solution of C6H5CH2NHC6H4P(Ph)2 was added 1 equiv of
2,6-diethylphenylazide, and the mixture reacted at room temperature
overnight. The reaction solution was concentrated to 5 mL, 5 mL
of hexane was added, and the mixture then was kept at -30 °C to
Synthesis of MeC4H2SCH2NHC6H4(Ph)2PdNC6H2Me3-2,4,6
(HL1). Under an N2 atmosphere, 3-methylthiophene-2-carboxyal-
dehyde (1.40 g, 10 mmol) and 2-diphenylphosphino aniline (2.78
g, 10 mmol) were dissolved in a hexane/toluene solution (20 mL/
20 mL), and then anhydrous MgSO4 (10 g) and the catalyst p-TsOH
(0.25 g) were added. The reaction mixture was stirred under reflux
(25) (a) Murata, S.; Abe, S.; Tomioka, H. J. Org. Chem. 1997, 62, 3055.
(b) Tjaden, E. B.; Swenson, D. C.; Jordan, R. F. Organometallics 1995,
14, 371. (c) Cooper, M. K.; Downes, J. M.; Duckworth, P. A.; Tiekink,
E. R. T. Aust. J. Chem. 1992, 45, 595. (d) Lappert, M. F.; Pearce, R.
J. Chem. Soc., Chem. Commun. 1997, 126.
1
afford brown solids of HL4 within 12 h (3.59 g, 70%). H NMR
(300 MHz, CDCl3, 25 °C): δ 0.83 (t, J ) 7.5 Hz, 6H, o-CH2CH3-
N-aryl), 2.34 (m, 4H, o-CH2CH3-N-aryl), 4.19 (d, J ) 5.0 Hz, 2H,

Rare-Earth Metal Bis(alkyl) Complexes
Organometallics, Vol. 27, No. 24, 2008 6537
CH2), 6.43-6.41 (m, 3H, m,p-NC6H3), 6.82-6.80 (m, 2H, p-PPh2),
7.04-7.03 (m, 3H, PC6H4N), 7.26-7.16 (m, 4H, C6H5), 7.34-7.30
(m, 1H, C6H5), 7.43-7.42 (m, 4H, m-PPh2), 7.51-7.47 (m, 4H,
o-PPh2), 7.51 ppm (m, 1H, o-PC6H4N).
) 8.0 Hz, 6H, CH2CH3), 1.50 (br, 4H, THF), 2.45 (s, 3H, CH3-
thienyl), 2.75 (q, J ) 8.0 Hz, 2H, CH2CH3), 3.01 (q, J ) 8.0 Hz,
2H, CH2CH3), 3.69 (m, 4H, THF), 5.72 (s, 2H, CH2), 6.38 (m, 1H,
m-PC6H4N), 6.77 (d, J ) 5.0 Hz, 1H, 4-thienyl), 6.91 (d, J ) 5.0
Hz, 1H, 5-thienyl), 6.95 (m, 2H, o, m-NC6H4P), 7.04 (m, 3H, m,
p-NC6H3), 7.08 (m, 4H, m-PPh2), 7.16 (m, 1H, o-PC6H4N), 7.24
(m, 2H, p-PPh2), 7.58 ppm (m, 4H, o-PPh2). 13C NMR (100 MHz,
C6D6, 25 °C): δ 4.49 (6C, SiMe3), 14.21(2C, CH2CH3), 14.64 (1C,
CH3-thienyl), 25.93 (1C, CH2CH3), 29.19(1C, CH2CH3), 41.49(1C,
CH2SiMe3), 43.39 (1C, CH2SiMe3), 68.81 (4C, THF), 114.16 (1C,
p-PPh), 114.60 (1C, m-PPh), 122.55 (1C, 4-thienyl), 125.62 (2C, ipso-
thienyl), 126.60 (2C, m-NPh), 126.85 (1C, p-NPh), 127.84 (2C, ipso-
Ph), 128.26 (2C, m-PPh2), 128.95, 129.07 (2C, m-PPh2), 130.26 (1C,
5-thienyl), 133.17 (2C, p-PPh2), 133.40 (1C, ipso-Ph), 133.95 (1C,
o-PPh), 134.01, 134.89 (4C, o-PPh2), 135.33 (1C, m-PPh), 140.24
(1C, ipso-Ph), 142.04, 142.10 (2C, ipso-PPh2), 159.69 ppm (d, J
) 4.0 Hz,1C, ipso-PPh). Anal. Calcd for C46H64N2OPSScSi2 (%):
C, 66.95; H, 7.82; N, 3.39. Found: C, 66.35; H, 7.34; N, 3.23.
Synthesis of L2Lu(CH2SiMe3)2(THF) (2b). Following a similar
procedure, treatment of a solution of HL2 (0.27 g, 0.50 mmol) with
Lu(CH2SiMe3)3(THF)2 (0.29 g, 0.50 mmol) in toluene (2 mL)
afforded complex 2b (0.36 g, 75%). 1H NMR (400 MHz, C6D6, 25
°C): δ -0.75 (AB, J ) 11 Hz, 2H, CH2SiMe3), -0.50 (AB, J )
11 Hz, 2H, CH2SiMe3), 0.45 (s, 18H, CH2SiMe3), 1.05 (t, J ) 7.4
Hz, 6H, CH2CH3), 1.39 (br, 4H, THF), 2.57(s, 3H, CH3-thienyl),
2.79 (q, J ) 7.4 Hz, 2H, CH2CH3), 2.93 (q, J ) 7.4 Hz, 2H,
CH2CH3), 3.66 (br, 4H, THF), 5.53 (s, 2H, CH2), 6.36 (m, 1H,
m-PC6H4N), 6.79 (d, J ) 5.0 Hz, 1H, 4-thienyl), 6.90 (d, J ) 5.0
Hz, 1H, 5-thienyl), 6.98 (m, 4H, o, m-NC6H4P, m-NC6H3), 7.11
(m, 1H, p-NC6H3), 7.11 (m, 4H, m-PPh2), 7.17 (m, 1H, o-PC6H4N),
7.28 (m, 2H, p-PPh2), 7.61 ppm (m, 4H, o-PPh2). 13C NMR (100
MHz, C6D6, 25 °C): δ 5.22 (6C, SiMe3), 14.00 (2C, CH2CH3), 14.83
(1C, CH3-thienyl), 25.64 (1C, CH2CH3), 25.97 (1C, CH2CH3), 26.10
(2C, THF), 41.89 (s, 1C, CH2SiMe3), 42.68 (1C, CH2SiMe3), 69.01
(2C, THF), 112.73 (1C, p-PPh), 115.32 (1C, m-PPh), 122.30 (1C,
4-thienyl), 124.61 (2C, ipso-thienyl), 126.14 (2C, m-NPh), 126.83
(1C, p-NPh), 127.42 (2C, ipso-Ph), 128.26 (2C, m-PPh2), 128.87,
128.99 (2C, m-PPh2), 130.02 (1C, 5-thienyl), 132.86 (2C, p-PPh2),
133.27 (1C, ipso-Ph), 133.77, 133.89 (1C, o-PPh), 134.55, 134.64
(4C, o-PPh2), 135.28 (1C, m-PPh), 140.68 (1C, ipso-Ph), 141.67,
141.72 (2C, ipso-PPh2), 161.30 ppm (d, J ) 4.2 Hz, 1C, ipso-PPh).
Anal. Calcd for C46H64N2OPSLuSi2 (%): C, 57.84; H, 6.75; N, 2.93.
Found: C, 57.30; H, 6.25; N, 2.37.
Synthesis of L1Sc(CH2SiMe3)2(THF) (1a). A toluene (2 mL)
solution of HL1 (0.26 g, 0.50 mmol) was added dropwise to a
toluene (2 mL) solution of Sc(CH2SiMe3)3(THF)2 (0.29 g, 0.50
mmol) at room temperature, and the mixture was stirred for 30
min. The solution was concentrated to 2 mL under reduced pressure,
2 mL of hexane was added, and the solution was cooled to -30
°C to give 1a as a colorless solid (0.33 g, 80%) within 12 h. Crystals
suitable for X-ray analysis were grown from a mixture of hexane/
1
toluene. H NMR (400 MHz, C6D6): δ 0.20 (AB, J ) 11 Hz, 2H,
CH2SiMe3), 0.23 (AB, J ) 11 Hz, 2H, CH2SiMe3), 0.38 (s, 18H,
CH2SiMe3), 1.47 (br, 4H, THF), 2.13(s, 3H, CH3-thienyl), 2.20 (s,
3H, p-CH3-NPh), 2.38 (s, 3H, o-CH3-NPh), 2.39 (s, 3H, o-CH3-
NPh), 3.74 (br, 4H, THF), 5.70 (s, 2H, CH2), 6.42(m, 1H,
p-PC6H4N), 6.75 (s, 2H, NC6H2), 6.77 (d, J ) 5.0 Hz, 1H,
4-thienyl), 6.87 (d, J ) 5.0 Hz, 1H, 5-thienyl), 6.93 (m, 1H,
m-NC6H4P), 6.95 (m, 1H, m-PC6H4N), 7.02-7.07 (m, 4H, m-PPh2),
7.11-7.13 (m, 2H, p-PPh2), 7.21 (m, 1H, o-PC6H4N), 7.63 ppm
(m, 4H, o-PPh2). 13C NMR (100 MHz, C6D6): δ 4.35 (6C, SiMe3),
14.52 (1C, CH3-thienyl), 21.14 (1C, p-CH3-Ph), 21.85 (2C, o-CH3-
Ph), 25.96 (2C, THF), 41.51, 42.13 (1C, CH2SiMe3), 43.52 (1C,
CH2), 70.03 (2C, THF), 114.28 (d, 1C, p-PPh), 114.70 (d, 1C,
m-PPh), 122.69 (1C, 4-thienyl), 122.81 (1C, 5-thienyl), 126.13 (1C,
ipso-NPh), 126.58 (1C, ipso-thienyl), 127.14, 127.57 (2C, ipso-
Ph), 128.74 (2C, m-PPh2), 129.05, 129.17 (2C, m-PPh2), 129.76
(1C, ipso-thienyl), 130.40, 130.80 (2C, m-NPh), 132.64 (2C, ipso-
Ph), 133.34 (2C, p-PPh2), 133.99 (1C, p-PPh), 134.58-134.68 (4C,
o-PPh2), 135.49 (1C, m-PPh), 136.93 (1C, ipso-PPh2), 139.08 (1C,
ipso-Ph), 139.79 ppm (1C, ipso-Ph), 159.48 ppm (d, J ) 5.0 Hz,1C,
ipso-PPh). Anal. Calcd for C45H62ScN2OPSSi2 (%): C, 66.63;
H, 7.70; N, 3.45. Found: C, 66.27; H, 7.196; N, 3.01.
Synthesis of L1Lu(CH2SiMe3)2(THF) (1b). Following a similar
procedure, treatment of the solution of HL1 (0.26 g, 0.50 mmol)
with Lu(CH2SiMe3)3(THF)2 (0.23 g, 0.50 mmol) in toluene (2 mL)
afforded complex 1b (0.58 g, 70%). The single crystals were
1
obtained from a mixture of hexane/toluene. H NMR (400 MHz,
C6D6): δ -0.70 (AB, J ) 11 Hz, 2H, CH2SiMe3), -0.44 (AB, J )
11 Hz, 2H, CH2SiMe3), 0.46 (s, 18H, CH2SiMe3), 1.26 (br, 4H,
THF), 2.11 (br, 3H, CH3), 2.29 (s, 6H, 2CH3), 2.53 (s, 3H, CH3-
thienyl), 3.66 (br, 4H, THF), 5.49 (s, 2H, CH2), 6.39 (m, 1H,
p-PC6H4N), 6.61 (s, 2H, NC6H2), 6.79 (d, J ) 5.0 Hz, 1H,
4-thienyl), 6.89 (d, J ) 5.0 Hz, 1H, 5-thienyl), 7.01 (m, 1H,
m-NC6H4P), 7.05 (m, 1H, o-NC6H4P), 7.10 (m, 4H, m-PPh2), 7.16
(m, 2H, p-PPh2), 7.23 (m, 1H, o-PC6H4N), 7.62 ppm (m, 4H,
o-PPh2). 13C NMR (100 MHz, C6D6): δ 5.22 (6C, SiMe3), 14.79
(1C, CH3-thienyl), 21.05 (1C, p-CH3-Ph), 21.62 (2C, o-CH3-Ph),
25.56 (2C, THF), 41.77 (2C, CH2SiMe3), 42.62 (1C, CH2), 71.19
(2C, THF), 112.72 (1C, p-PPh), 115.38 (1C, m-PPh), 122.40 (1C,
4-thienyl), 126.13 (1C, ipso-thienyl), 127.06 (1C, ipso-Ph), 127.48
(1C, ipso-Ph), 128.60 (2C, m-PPh2), 128.88, 129.00 (2C, m-PPh2),
129.77 (1C, ipso-thienyl), 130.08 (1C, 5-thienyl), 130.15, 130.29
(2C, m-NPh), 132.85 (2C, p-PPh2), 133.27 (2C, ipso-Ph), 133.51
(1C, p-PPh), 134.37, 134.45, 134.56, 134.65 (4C, o-PPh2), 135.28
(1C, m-PPh), 136.46 (1C, ipso-PPh2), 140.61 (1C, ipso-Ph), 143.21
(1C, ipso-Ph), 161.25 ppm (d, 1C, J ) 4.4 Hz, ipso-PPh). Anal.
Calcd for C45H62LuN2OPSSi2 (%): C, 57.43; H, 6.64; N, 2.98.
Found: C, 56.58; H, 6.07; N, 2.72.
Synthesis of L3Sc(CH2SiMe3)2(THF) (3a). Following a similar
procedure, treatment of a solution of HL3 (0.28 g, 0.50 mmol) with
Sc(CH2SiMe3)3(THF)2 (0.23 g, 0.50 mmol) in toluene (2 mL)
afforded complex 3a (0.29 g, 75%). The single crystals were
1
obtained from a mixture of hexane/toluene. H NMR (400 MHz,
C6D6, 25 °C): δ 0.061 (s, 2H, CH2SiMe3), 0.066 (s, 2H, CH2SiMe3),
0.30 (s, 18H, CH2SiMe3), 0.82 (d, J ) 6.8 Hz, 6H, CHMe2), 1.51
(d, J ) 6.8 Hz, 6H, CHMe2), 2.38 (s, 3H, CH3-thienyl), 3.85 (m,
2H, CHMe2), 5.71 (s, 2H, CH2), 6.35 (m, 1H, m-PC6H4N), 6.71
(m, 1H, m-PC6H4N), 6.79 (d, J ) 5.0 Hz, 1H, 4-thienyl), 6.92 (m,
1H, p-PC6H4N), 6.97 (d, J ) 5.0 Hz, 1H, 5-thienyl), 7.06 (m, 4H,
m-PPh2), 7.14 (m, 2H, p-PPh2), 7.22 (m, 3H, m, p-NC6H3), 7.24
(m, 1H, o-PPh), 7.55 ppm (m, 4H, o-PPh2). 13C NMR (100 MHz,
C6D6, 25 °C): δ 4.49 (6C, SiMe3), 14.21 (4C, CH2CH3), 14.64 (1C,
CH3-thienyl), 25.93 (1C, CH2CH3), 29.19 (1C, CH2CH3), 41.49(1C,
CH2SiMe3), 43.39 (1C, CH2SiMe3), 68.81 (s, 4C, THF), 114.16
(1C, p-PPh), 114.60 (1C, m-PPh), 122.55 (1C, 4-thienyl), 125.62
(2C, ipso-thienyl), 126.60 (2C, m-NPh), 126.85 (1C, p-NPh), 127.84
(2C, ipso-Ph), 128.26 (2C, m-PPh2), 128.95, 129.07 (2C, m-PPh2),
130.26 (1C, 5-thienyl), 133.17 (2C, p-PPh2), 133.40 (1C, ipso-Ph),
133.95 (1C, o-PPh), 134.01, 134.89 (4C, o-PPh2), 135.33 (1C,
m-PPh), 140.24 (1C, ipso-Ph), 142.04,142.10 (2C, ipso-PPh2),
159.69 ppm (1C, ipso-PPh). Anal. Calcd for C44H60N2PSScSi2 (%):
C, 67.65; H, 7.74; N, 3.59. Found: C, 67.29; H, 7.51; N, 3.11.
Synthesis of L2Sc(CH2SiMe3)2(THF) (2a). Following a similar
procedure, treatment of a solution of HL2 (0.27 g, 0.50 mmol) with
Sc(CH2SiMe3)3(THF)2 (0.23 g, 0.50 mmol, in 2 mL of toluene)
afforded complex 2a (0.29 g, 70%). The single crystals were
1
obtained from a mixture of hexane/toluene. H NMR (400 MHz,
C6D6, 25 °C): δ 0.00 (AB, J ) 10.0 Hz, 2H, CH2SiMe3), 0.16 (AB,
J ) 10.0 Hz, 2H, CH2SiMe3), 0.35 (s, 18H, CH2SiMe3), 1.10 (t, J

6538 Organometallics, Vol. 27, No. 24, 2008
Wang et al.
Synthesis of L4Sc(CH2SiMe3)2(THF) (4a). Following a similar
procedure, treatment of the solution of HL4 (0.26 g, 0.50 mmol)
with Sc(CH2SiMe3)3(THF)2 (0.23 g, 0.50 mmol) in toluene (2 mL)
afforded complex 4a (0.30 g, 75%). The single crystals were
ipso-PPh). Anal. Calcd for C47H64N2OPScSi2 (%): C, 70.11; H, 8.01;
N, 3.48. Found: C, 69.30; H, 8.29; N, 3.01.
A Typical Polymerization Procedure. To a 25 mL flask were
added a toluene solution of butadiene (0.54 g) and 200 µmol of
AliBu3. Then, 20 µmol of 2a and equimolar borate ([Me2-
NHPh][B(C6F5)4]) were added to initiate the polymerization. After
a designated time, the mixture was poured into a large quantity of
ethanol. A white precipitate of polybutadiene was collected and
dried under vacuum at 40 °C for 24 h to a constant weight.
1
obtained from a mixture of hexane/toluene. H NMR (400 MHz,
C6D6, 25 °C): δ 0.076 (s, 4H, CH2SiMe3), 0.32 (s, 18H, CH2SiMe3),
1.15 (t, J ) 7.0 Hz, 6H, CH2CH3), 1.47 (br, 4H, THF), 2.80 (t, 2H,
J ) 7.0 Hz, CH2CH3), 3.10 (t, 2H, J ) 7.0 Hz, CH2CH3), 3.70
(br, 4H, THF), 5.59 (s, 2H, CH2), 6.36 (m, 1H, m-PC6H4N),
6.81-6.91 (m, 2H, C6H5), 7.02-7.06 (m, 2H, m,p-PC6H4N),
7.08-7.11 (m, 7H, C6H5, m,p-NC6H3, o-PC6H4N), 7.13-7.17
(m, 6H, m,p-PPh2), 7.57 ppm (m, 4H, o-PPh2). 13C NMR (100 MHz,
C6D6, 25 °C): δ 4.45 (6C, SiMe3), 14.36 (2C, CH2CH3), 26.05 (1C,
CH2CH3), 26.38 (1C, CH2CH3), 41.37 (1C, CH2SiMe3), 48.08 (1C,
CH2SiMe3),69.39(4C,THF),114.23,114.37(1C,p-PPh),114.96,115.05
(2C, m-PPh), 125.94 (2C, ipso-Ph), 126.66 (1C, ipso-Ph), 126.84
(3C, Ph), 127.03 (2C, Ph), 127.65 (1C, ipso-Ph), 128.27 (2C,
m-PPh2), 128.50, 128.74 (2C, m-PPh2), 128.87, 129.04, 129.16
(3C, Ph), 133.28 (2C, p-PPh2), 133.65, 133.77 (1C, o-PPh), 134.48,
134.57 (4C, o-PPh2), 135.41 (1C, m-PPh), 141.18 (1C, ipso-Ph),
142.06, 142.11 (2C, ipso-PPh2), 159.06 ppm (d, J ) 4.0 Hz, 1C,
Acknowledgment. We are thankful for financial support
from National Natural Science Foundation of China for Project
Nos. 20571072 and 20674081; The Ministry of Science and
Technology of China for Project No. 2005CB623802; and
“Hundred Talent Program” of CAS.
Supporting Information Available: CIF files for complexes 1b,
2a, 3a, and 4a are available free of charge via the Internet at
http://pubs.acs.org.
OM800660J