Stereoselective polymerization of styrene with cationic scandium precursors bearing quinolyl aniline ligands

Article abstract of DOI:10.1021/om1000265

The novel N-R-quinolinyl-8-amino ligands HL^1-5 (R = 2,6-Me ₂C₆H₃ (HL¹), 2,4,6-Me ₃C₆H₂ (HL²), 2,6-Et ₂C₆H₃ (HL³), 2,6-ⁱPr ₂C₆H₃ (HL⁴), C₆H ₅ (HL⁵)) reacted with Sc(CH₂SiMe ₃)₃(THF)₂ to afford the well-defined complexes (L^1-5)Sc(CH₂SiMe₃)₂(THF) (1-5), which were fully characterized by NMR spectral and X-ray diffraction analyses. Complexes 1-3 combined with organoborates to establish binary systems that exhibited high activity for the polymerization of styrene, while 4 was less active and 5 was almost inert. The cationic complex [L¹Sc(CH ₂SiMe₃)(DME)₂][B(C₆F ₅)₄] (6) was successfully isolated by treatment of 1 with [PhMe₂NH][B(C₆F₅)₄], and represents probably the structural model of the initiation active species. Remarkably, upon addition of aluminum trialkyls to the binary systems, distinguished improvement in catalytic performances was achieved, among which the ternary system 1/5AlⁱBu₃/[Ph₃C][B(C₆F ₅)₄] displayed the highest activity (1.56 - 10⁶ g mol^-1 h^-1) and syndioselectivity (r = 0.94) via a chain-end control mechanism governed by the concerted steric effect of the ligand and the aluminum alkyls. This represents the first non-cyclopentadienyl stabilized rare-earth metal based catalyst showing both high activity and specific selectivity for the polymerization of styrene, which might shed new light on designing more efficient precursors and further investigation of the mechanism for this polymerization.

Full text of DOI:10.1021/om1000265

1916 Organometallics 2010, 29, 1916–1923
DOI: 10.1021/om1000265
Stereoselective Polymerization of Styrene with Cationic Scandium
Precursors Bearing Quinolyl Aniline Ligands
Dongtao Liu,†,‡ Yunjie Luo,§ 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, §Organometallic Chemistry
Laboratory, Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, People’s Republic of
China, and ^School of Chemistry, Jilin University, Changchun 130012, People’s Republic of China
Received January 7, 2010
The novel N-R-quinolinyl-8-amino ligands HL1-5 (R = 2,6-Me2C6H3 (HL1), 2,4,6-Me3C6H2
(HL2), 2,6-Et2C6H3 (HL3), 2,6-iPr2C6H3 (HL4), C6H5 (HL5)) reacted with Sc(CH2SiMe3)3(THF)2 to
afford the well-defined complexes (L1-5)Sc(CH2SiMe3)2(THF) (1-5), which were fully characterized
by NMR spectral and X-ray diffraction analyses. Complexes 1-3 combined with organoborates to
establish binary systems that exhibited high activity for the polymerization of styrene, while 4 was less
active and 5 was almost inert. The cationic complex [L1Sc(CH2SiMe3)(DME)2][B(C6F5)4] (6) was
successfully isolated by treatment of 1 with [PhMe2NH][B(C6F5)4], and represents probably the
structural model of the initiation active species. Remarkably, upon addition of aluminum trialkyls to
the binary systems, distinguished improvement in catalytic performances was achieved, among which
the ternary system 1/5AliBu3/[Ph3C][B(C6F5)4] displayed the highest activity (1.56 ꢀ 106 g mol-1 h-1
)
and syndioselectivity (r = 0.94) via a chain-end control mechanism governed by the concerted steric
effect of the ligand and the aluminum alkyls. This represents the first non-cyclopentadienyl stabilized
rare-earth metal based catalyst showing both high activity and specific selectivity for the polymer-
ization of styrene, which might shed new light on designing more efficient precursors and further
investigation of the mechanism for this polymerization.
Introduction
bearing such half-sandwich ligands have been investigated.3
Improved catalytic performances can be achieved by replac-
ing a chloride group from Cp*TiCl3 with an anionic moiety
such as aryloxide,4 amide,4c anilide,4c ketimide,5 or bidentate
aniline-ethoxy.6 Introducing more steric and electron-donat-
ing indenyl7a and fluorenyl7b ligands also brings about an
increasing activity, stereoselectivity, and thermal stability to
the attached titanium metal centers,7 whereas a too crowded
environment around a central metal induces a drop in
activity for the related bis(cyclopentadienyl) titanium com-
plexes, which might prohibit bulky monomer styrene (St)
from coordinating to the active sites.3e,8 Regarding the
Ziegler-Natta-type catalytic systems with the general for-
mula TiX4/MAO (X = Cl, Br, OMe, OEt, OiPr, OBu, Bz)3e,9
Polystyrene (PS), one of the most widely used plastics, has
atactic, syndiotactic, and isotactic microstructures that are
determined by the catalysts applied through radical, anionic,
and coordination mechanisms. The stereoregular syndiotac-
tic polystyrene (sPS) has a high melting point, as does the
isotactic polystyrene (iPS), and moreover can crystallize
faster, having potential applications as engineering plastics.1
Thus, since the first sPS prepared via coordination poly-
merization by using the monocyclopentadienyl (Cp) titanium-
based catalyst system Cp*TiCl3/MAO reported by Ishihara
in 1986,2 tremendous amounts of titanium compounds
*Corresponding author. E-mail: dmcui@ciac.jl.cn.
(1) Malanga, M. Adv. Mater. 2000, 12, 1869.
(2) Ishihara, N.; Seimiya, T.; Kuramoto, M.; Uoi, M. Macromole-
(5) Nomura, K.; Fujita, K.; Fujiki, M. Catal. Commun. 2004, 5, 413.
(6) Chen, J.; Li, Y.-S.; Wu, J.-Q.; Hu, N.-H. J. Mol. Catal. A: Chem.
2005, 232, 1.
cules 1986, 19, 2464.
(3) (a) Tomotsu, N.; Ishihara, N.; Newman, T. H.; Malanga, M. T.
J. Mol. Catal. A: Chem. 1998, 128, 167. (b) Rodrigues, A.-S.; Kirillov, E.;
Carpentier, J.-F. Coord. Chem. Rev. 2008, 252, 2115. (c) Po, R.; Cardi, N.
Prog. Polym. Sci. 1996, 21, 47. (d) Schellenberg, J.; Tomotsu, N. Prog.
Polym. Sci. 2002, 27, 1925. (e) Ishihara, N.; Kuramoto, M.; Uoi, M.
Macromolecules 1988, 21, 3356. (f) Pellecchia, C.; Pappalardo, D.; Oliva,
L.; Zambelli, A. J. Am. Chem. Soc. 1995, 117, 6593.
(4) (a) Nomura, K.; Komatsu, T.; Imanishi, Y. Macromolecules 2000,
33, 8122. (b) Nomura, K.; Fudo, A. Catal. Commun. 2003, 4, 269. (c) Byun,
D. J.; Fudo, A.; Tanaka, A.; Fujiki, M.; Nomura, K. Macromolecules 2004,
37, 5520. (d) Nomura, K.; Tanaka, A.; Katao, S. J. Mol. Catal. A: Chem.
2006, 254, 197.
(7) (a) Ready, T. E.; Day, R. O.; Chien, J. C. W.; Rausch, M. D.
Macromolecules 1993, 26, 5822. (b) Knjazhanski, S. Y.; Cadenas, G.; Garca,
M.; Perez, C. M.; Nifantev, I. E.; Kashulin, I. A.; Ivchenko, P. V. Organo-
metallics 2002, 21, 3094. (c) Foster, P.; Chien, J. C. W.; Rausch, M. D.
Organometallics 1996, 15, 2404. (d) Schneider, N.; Prosenc, M.-H.;
Brintzinger, H.-H. J. Organomet. Chem. 1997, 545-546, 291. (e) Xu, G.;
Cheng, D. Macromolecules 2000, 33, 2825.
(8) Ricci, G.; Bosisio, C.; Porri, L. Macromol. Rapid Commun. 1996,
17, 781.
(9) (a) Zambelli, A.; Oliva, L.; Pellecchia, C. Macromolecules 1989,
22, 2129. (b) Chien, J. C. W.; Salajka, Z. J. Polym. Sci., Part A: Polym.
Chem. 1991, 29, 1243.
r
pubs.acs.org/Organometallics
Published on Web 03/26/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 8, 2010 1917
and the titanium complexes stabilized by non-Cp ligands
such as amidinate,10 phenoxyimine,11 and bis(phenolate),12
medium to high syndiotacticity can be obtained albeit with
relatively low activity.
tive unsaturation of metal centers and catalytic activity
toward polymerization.
Recently, we have successfully synthesized a series of non-
Cp-ligated rare-earth metal complexes that display versatile
catalytic activities and selectivity toward the polymerizations
of 1,3-conjugated dienes or lactide,17 which is achieved by
swiftly adjusting the sterics and electronics of ligands. These
results compel us to investigate the possibility of designing
new non-Cp-ligated rare-earth metal complexes that could
provide both high activity and specific selectivity for the
polymerization of styrene. To date, the amidinates,18 guani-
dinates,19 β-diketiminates,20 salicylaldiminates,21 etc., non-
Cp ligand supported rare-earth metal complexes have been
extensively examined; however, those bearing quinolinyl
ligands remain scarce and are inert for styrene polymeriza-
tion (vide infra).22 Herein we report the synthesis and char-
acterization of the novel non-Cp quinolinyl aniline ligands
and the corresponding scandium complexes. Under activa-
tion of organoborates and aluminum alkyls these complexes
display high syndioselectivity for the polymerization of
styrene with high activity under mild conditions, which
represents the first example of the non-Cp-ligated rare-earth
metal complexes possessing such distinguished catalytic
performances. In addition, the successful isolation and full
characterization of a cationic ion pair provided a probable
model structure for the true active species in this polymeri-
zation process that may facilitate the further investigation of
the mechanism.
On the other hand, rare-earth metal based systems are
usually superior with respect to the activity and the regios-
electivity for the polymerization of 1,3-conjugated dienes;13
however they generally exhibit low activity for the polymeri-
zation of styrene until the recent landmark neutral lantha-
nocenes [(CpCMe2Flu)Ln(allyl)(thf)]14 and cationic half-
sandwich scandium complex [Cp0Sc(CH2SiMe3)2(THF)2]/
[Ph3C][B(C6F5)4],15 which provide extremely high syndios-
electivity. In contrast, the non-Cp-ligated lanthanide com-
plexes display medium to high activity under high pressure
(>500 MPa) or high temperature (70-100 ꢀC), but give low
stereoregular polystyrenes (r e 0.6).16 Therefore, exploring
non-Cp-ligated complexes attached by lanthanide elements
that can initiate highly active and stereoselective polymeri-
zation of styrene is an attractive and challenging subject, as
the non-Cp metal complexes have garnered an upsurge in
research interest in other fields because of their strong
metal-ligand bonds and exceptional and tunable steric
and electronic features required for compensating coordina-
(10) (a) Flores, J. C.; Chien, J. C. W.; Rausch, M. D. Organometallics
1995, 14, 1827. (b) Flores, J. C.; Chien, J. C. W.; Rausch, M. D. Organo-
metallics 1995, 14, 2106. (c) Liguori, D.; Grisi, F.; Sessa, I.; Zambelli, A.
Macromol. Chem. Phys. 2003, 204, 164. (d) Liguori, D.; Centore, R.; Tuzi,
A.; Grisi, F.; Sessa, I.; Zambelli, A. Macromolecules 2003, 36, 5451.
(e) Averbuj, C.; Tish, E.; Eisen, M. S. J. Am. Chem. Soc. 1998, 120, 8640.
(11) Michiue, K.; Onda, M.; Tanaka, H.; Makio, H.; Mitani, M.;
Fujita, T. Macromolecules 2008, 41, 6289.
(12) (a) Okuda, J.; Masoud, E. Macromol. Chem. Phys. 1998, 199,
543. (b) Capacchione, C.; Proto, A.; Ebeling, H.; Mulhaupt, R.; Moller, K.;
Manivannan, R.; Spaniol, T. P.; Okuda, J. J. Mol. Catal. A: Chem. 2004,
213, 137. (c) Beckerle, K.; Capacchione, C.; Ebeling, H.; Manivannan, R.;
Mulhaupt, R.; Proto, A.; Spaniol, T. P.; Okuda, J. J. Organomet. Chem.
2004, 689, 4636. (d) Capacchione, C.; Manivannan, R.; Barone, M.;
Beckerle, K.; Centore, R.; Oliva, L.; Proto, A.; Tuzi, A.; Spaniol, T. P.;
Okuda, J. Organometallics 2005, 24, 2971.
(13) (a) Zhang, L.; Suzuki, T.; Luo, Y.; Nishiura, M.; Hou, Z. Angew.
Chem., Int. Ed. 2007, 46, 1909. (b) Ajellal, N.; Furlan, L.; Thomas, C. M.;
Casagrande, O. L.Jr; Carpentier, J.-F. Macromol. Rapid Commun. 2006, 27,
338. (c) Zimmermann, M.; Tornroos, K. W.; Anwander, R. Angew. Chem.,
Int. Ed. 2008, 47, 775. (d) Zhang, L.; Luo, Y.; Hou, Z. J. Am. Chem. Soc.
2005, 127, 14562.
(14) (a) Kirillov, E.; Lehmann, C. W.; Razavi, A.; Carpentier, J.-F.
J. Am. Chem. Soc. 2004, 126, 12240. (b) Rodrigues, A.-S.; Kirillov, E.;
Lehmann, C. W.; Roisnel, T.; Vuillemin, B.; Razavi, A.; Carpentier, J.-F.
Chem.;Eur. J. 2007, 13, 5548. (c) Perrin, L.; Sarazin, Y.; Kirillov, E.;
Carpentier, J.-F.; Maron, L. Chem.;Eur. J. 2009, 15, 3773.
(15) (a) Luo, Y.; Baldamus, J.; Hou, Z. J. Am. Chem. Soc. 2004, 126,
13910. (b) Jaroschik, F.; Shima, T.; Li, X.; Mori, K.; Ricard, L.; Le Goff,
X.-F.; Nief, F.; Hou, Z. Organometallics 2007, 26, 5654. (c) Nishiura, M.;
Mashiko, T.; Hou, Z. Chem. Commun. 2008, 2019. (d) Fang, X.; Li, X.; Hou,
Z.; Assoud, J.; Zhao, R. Organometallics 2009, 28, 517.
(16) (a) Yang, M.; Cha, C.; Shen, Z. Polym. J. 1990, 22, 919. (b) Zhang,
Y.; Hou, Z.; Wakatsuki, Y. Macromolecules 1999, 32, 939. (c) Luo, Y.; Yao,
Y.; Shen, Q. Macromolecules 2002, 35, 8670. (d) Luo, Y.; Nishiura, M.; Hou,
Z. J. Organomet. Chem. 2007, 692, 536.
(17) (a) Gao, W.; Cui, D. J. Am. Chem. Soc. 2008, 130, 4984. (b) Liu,
X.; Shang, X.; Tang, T.; Hu, N.; Pei, F.; Cui, D.; Chen, X.; Jing, X.
Organometallics 2007, 26, 2747. (c) Wang, D.; Li, S.; Liu, X.; Gao, W.;
Cui, D. Organometallics 2008, 27, 6531. (d) Li, S.; Miao, W.; Tang, T.;
Dong, W.; Zhang, X.; Cui, D. Organometallics 2008, 27, 718. (e) Li, S.; Cui,
D.; Li, D.; Hou, Z. Organometallics 2009, 28, 481. (f) Yang, Y.; Li, S.; Cui,
D.; Chen, X.; Jing, X. Organometallics 2007, 26, 671. (g) Yang, Y.; Liu, B.;
Lv, K.; Gao, W.; Cui, D.; Chen, X.; Jing, X. Organometallics 2007, 26, 4575.
(h) Yang, Y.; Wang, Q.; Cui, D. J. Polym. Sci., Part A: Polym. Chem. 2008,
46, 5251. (i) Shang, X.; Liu, X.; Cui, D. J. Polym. Sci., Part A: Polym.
Chem. 2007, 45, 5662. (j) Miao, W.; Li, S.; Cui, D.; Huang, B. J. Organomet.
Chem. 2007, 692, 3823. (k) Miao, W.; Li, S.; Zhang, H.; Cui, D.; Wang, Y.;
Huang, B. J. Organomet. Chem. 2007, 692, 4828. (l) Liu, B.; Cui, D.; Ma, J.;
Chen, X.; Jing, X. Chem.;Eur. J. 2007, 13, 834.
Results and Discussion
Synthesis and Characterization of Quinolinyl Anilido Scan-
dium Complexes. N-R-Quinoline-8-amino ligands HL1-5
(R=2,6-Me2C6H3 (HL1), 2,4,6-Me3C6H2 (HL2), 2,6-Et2C6-
H3 (HL3), 2,6-iPr2C6H3 (HL4), C6H5 (HL5)) were prepared
by amination of 8-bromoquinoline with relevant anilines.23
The acid-base reaction between scandium tris(alkyl) com-
plex Sc(CH2SiMe3)3(THF)2 and one equivalent of HL1-5 in
hexane at room temperature afforded the corresponding
1
complexes 1-5 in quantitative yields (Scheme 1). The H
NMR spectra of complexes 1-4 show a similar topology,
giving an AB spin (JH-H = 11.3-11.6 Hz) around δ
0.15-0.46 assigned to the methylene protons of the metal
alkyl moiety Sc-CH2SiMe3, indicating that the methylene
protons are diastereotopic. In contrast, the methylene pro-
tons of Sc-CH2SiMe3 in 5 are fluxional and exhibit a broad
resonance around δ 0.29. X-ray diffraction analyses show
(18) (a) Bijpost, E. A.; Duchateau, R.; Teuben, J. H. J. Mol. Catal. A:
Chem. 1995, 95, 121. (b) Duchateau, R.; van Wee, C. T.; Teuben, J. H.
Organometallics 1996, 15, 2291. (c) Aubrecht, K. B.; Chang, K.; Hillmyer,
M. A.; Tolman, W. B. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 284.
(19) (a) Duchateau, R.; van Wee, C. T.; Meetsma, A.; Teuben, J. H.
J. Am. Chem. Soc. 1993, 115, 4931. (b) Bailey, P. J.; Pace, S. Coord. Chem.
Rev. 2001, 214, 91. (c) Giesbrecht, G. R.; Whitener, G. D.; Arnold, J.
J. Chem. Soc., Dalton Trans. 2001, 923. (d) Lu, Z.; Yap, G. P. A.; Richeson,
D. S. Organometallics 2001, 20, 706. (e) Ajellal, N.; Lyubov, D. M.;
Sinenkov, M. A.; Fukin, G. K.; Cherkasov, A. V.; Thomas, C. M.; Carpentier,
J.-F.; Trifonov, A. A. Chem.;Eur. J. 2008, 14, 5440–5448.
(20) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L. K.; Parvez,
M.; Elsegood, M. R. J.; Clegg, W. Organometallics 2001, 20, 2533.
(21) (a) Emslie, D. J. H.; Piers, W. E.; McDonald, R. J. Chem. Soc.,
Dalton Trans. 2002, 293. (b) Emslie, D. J. H.; Piers, W. E.; Parvez, M.;
McDonald, R. Organometallics 2002, 21, 4226.
(22) Gao, W.; Cui, D.; Liu, X.; Zhang, Y.; Mu, Y. Organometallics
2008, 27, 5889.
(23) Lee, B. Y.; Kwon, H. Y.; Lee, S. Y.; Na, S. J.; Han, S.; Yun, H.;
Lee, H.; Park, Y.-W. J. Am. Chem. Soc. 2005, 127, 3031.

1918 Organometallics, Vol. 29, No. 8, 2010
Liu et al.
Scheme 1. Synthesis of Complexes 1-5
Figure 1. ORTEP drawing of complex 1 with 35% probability
thermal ellipsoids. Hydrogen atoms are omitted for clarity.
Selected bond lengths (A) and angles (deg): Sc(1)-N(1)
2.284(3), Sc(1)-N(2) 2.145(2), Sc(1)-C(18) 2.211(3), Sc(1)-
C(22) 2.242(3), Sc(1)-O(1) 2.179(2), N(1)-C(9) 1.368(4),
N(2)-C(8) 1.374(4), N(2)-C(10) 1.439(4), N(2)-Sc(1)-N(1)
73.42(9), C(18)-Sc(1)-C(22) 111.18(12), N(2)-Sc(1)-O(1)
91.84(9), O(1)-Sc(1)-N(1) 164.85(9), N(2)-Sc(1)-C(18)
122.46(11), N(2)-Sc(1)-C(22) 124.09(11).
Figure 2. ORTEP drawing of complex 2 with 35% probability
thermal ellipsoids. Hydrogen atoms are omitted for clarity.
Selected bond lengths (A) and angles (deg): Sc(1)-N(1)
2.292(5), Sc(1)-N(2) 2.121(5), Sc(1)-C(19) 2.233(6), Sc(1)-
C(23) 2.236(6), Sc(1)-O(1) 2.184(4), N(1)-C(9) 1.369(7),
N(2)-C(8) 1.378(7), N(2)-C(10) 1.442(7), N(2)-Sc(1)-N(1)
73.67(17), C(19)-Sc(1)-C(23) 116.0(2), O(1)-Sc(1) -N(1)
166.49(17).
˚
˚
where the [L1Sc(CH2SiMe3)(DME)2]þ cation adopts a dis-
torted octahedral geometry different from its neutral pre-
that complexes 1, 2, and 5 are isostructural mononuclear
compounds with a coordinating THF molecule, adopting a
distorted trigonal-bipyramidal geometry (Figures 1-3). The
ligands chelate to the Sc3þ ion in a κ2-N,N bidentate mode,
leading to the N-aryl ring and the quinolinyl ring perpendi-
cular to each other. The nitrogen atom N(1) of the quinolinyl
ring and the oxygen O(1) of the THF molecule are axial,
forming a large angle with Sc(1) (N(1)-Sc(1)-O(1),
165.72ꢀ), while the two alkyl carbon atoms and the aniline
nitrogen atom N(2) occupy equatorial positions. The aver-
age bond lengths of Sc-C and Sc-N(2) fall within the
normal values,17g,22 while the bond angles of C-Sc-C,
varying from 109.50(9)ꢀ (5) to 116.0(2)ꢀ (2), are compar-
able to those found in other scandium bis(alkyl) comp-
lexes.17c,d,g,22
˚
cursor 1 (Figure 4). The Sc-C bond distance in 6 (2.193(4) A)
˚
is shorter than that in 1 (av 2.227 A), and so are the Sc-N
˚
˚
bond lengths (Sc-N(1): 2.263(3) A (6) vs 2.284(3) A (1);
˚
˚
Sc-N(2): 2.105(3) A (6) vs 2.145(2) A (1)). This might be
attributed to the more electron-deficient metal center in 6
that leads to much stronger bond lengths.
Polymerization of Styrene. The catalytic performances of
complexes 1-5 for the polymerization of styrene (St) have
been investigated. The representative polymerization data
are summarized in Table 1 and show that neither the single
components 1-5 nor the binary systems (1-5)/AliBu3 could
initiate the polymerization of styrene. To our delight, upon
activation of [Ph3C][B(C6F5)4] or [PhMe2NH][B(C6F5)4], the
resultant cationic systems based on complexes 1-3 showed
high activity at room temperature to reach a completeness
within half an hour. The resultant polystyrene had a rela-
tively narrow polydispersity (Mw/Mn = 1.59-1.75), indica-
tive of the single-site nature of these systems. Under the same
conditions complex 4, bearing o-isopropyl groups of the
The reaction of 1 with one equivalent of [PhMe2NH]-
[B(C6F5)4] performed in DME at room temperature allowed
the successful isolation of its cationic counterpart [L1Sc-
(CH2SiMe3)(DME)2][B(C6F5)4] (6) (Scheme 2). An X-ray
diffraction study establishes that 6 is a separated ion pair

Article
Organometallics, Vol. 29, No. 8, 2010 1919
Figure 3. ORTEP drawing of complex 5 with 35% probability
thermal ellipsoids. Hydrogen atoms are omitted for clarity.
Selected bond lengths (A) and angles (deg): Sc(1)-N(1)
2.293(2), Sc(1)-N(2) 2.1335(19), Sc(1)-C(16) 2.230(2), Sc(1)-
C(20) 2.230(2), Sc(1)-O(1) 2.1714(17), N(1)-C(9) 1.367(3),
N(2)-C(8) 1.377(3), N(2)-C(10) 1.429(3), N(2)-Sc(1)-N(1)
73.50(7), C(20)-Sc(1)-C(16) 109.50(9), O(1)-Sc(1)-N(1)
165.83(7).
Figure 4. ORTEP drawing of the cationic part of 6 with 35%
probability thermal ellipsoids. Hydrogen atoms are omitted for
clarity. Selected bond lengths (A) and angles (deg): Sc(1)-N(1)
2.263(3), Sc(1)-N(2) 2.105(3), Sc(1)-C(18) 2.193(4), Sc(1)-
O(1) 2.311(3), Sc(1)-O(2) 2.260(3), Sc(1)-O(3) 2.200(3),
N(1)-C(9) 1.368(5), N(2)-C(8) 1.390(4), N(2)-C(10) 1.437(4),
N(2)-Sc(1)-N(1) 75.46(11), C(18)-Sc(1)-O(1) 159.92(14),
C(18)-Sc(1)-O(2) 92.30(14), N(2)-Sc(1)-O(3) 94.60(11),
O(3)-Sc(1)-N(1) 166.70(11), N(2)-Sc(1)-C(18) 104.88(14).
˚
˚
Scheme 2. Synthesis of Cationic Scandium Complex 6 Bearing a
Quinoline Ligand
low activity, consistent with those based on rare-earth
metal25 or titanium26 reported previously, which might be
attributed to the adduct formation between the sterically less
demanding aluminum methyl and the central metal to result
in the less active aluminate species. When switching to AlEt3,
the activity of the corresponding system increased obviously,
and the highest activity was obtained when AliBu3 was used
(entries 9, 13, 14). The catalytic activity was also signifi-
cantly influenced by fluorinated borate/borane in the order
[Ph3C][B(C6F5)4] > [PhMe2NH][B(C6F5)4] > B(C6F5)3
(entries 9, 15, 16). Moreover, with the catalytic system 1/
AliBu3/[Ph3C][B(C6F5)4], the increase of monomer-to-initia-
tor molar ratio from 500 to 3000 caused the molecular weight
of the resultant PS to increase correspondingly from 4.1 ꢀ
104 g/mol to 26.5 ꢀ 104 g/mol but not linearly, indicating that
the polymerization proceeded in a controllable manner
rather than in a living mode (entries 18-21). It was note-
worthy that the ortho-substituent of the N-aryl ring of the
ligand affected the catalytic activity drastically. The highest
activity of 1.56 ꢀ 106 g mol-1 h-1 was achieved for complex
1, bearing ortho-methyl substituent, which halved for com-
plex 3, containing ortho-ethyl, and almost is lost for complex
4, having a bulky ortho-isopropyl, as the spatial steric ligands
might block styrene coordination to the active sites (entries
11, 12). This could be proved further by the catalytic
performance of the tridentate quinolinyl anilido-iminato
scandium bis(alkyl) complex 7 reported recently by our
N-aryl ring of the ligand, was relatively less active, owing
to the more steric environment around the central metal
(entries 1-5). However complex 5 was almost inert (entry 6).
NMR spectrum monitoring revealed that 5 was unstable
even at room temperature, as the signals of the methylene
protons disappeared completely within 4 h and the reso-
nances of unknown products appeared, suggesting that the
ligand in 5 was not bulky enough to stabilize the scandium
bis(alkyl) species and was prone to redistribution.
Remarkably, addition of only one equivalent of AliBu3,
usually as an impurity scavenger,24,25 to 1/[Ph3C][B(C6F5)4]
brought about an obvious improvement in the activity for
the resultant ternary system. The catalytic activity increased
stepwise with the amount of AliBu3, reaching a peak value
when 5 equiv of AliBu3 was loaded (entries 7-9). The type of
aluminum alkyls played a significant role in adjusting the
activity. The system 1/AlMe3/[Ph3C][B(C6F5)4] exhibited
(24) Kucht, H.; Kucht, A.; Rausch, M. D.; Chien, J. C. W. Appl.
Organomet. Chem. 1994, 8, 393.
(25) Hitzbleck, J.; Beckerle, K.; Okuda, J.; Halbach, T.; Mulhaupt,
(26) Kawabe, M.; Murata, M. J. Polym. Sci. A: Polym. Chem. 2001,
39, 3692.
R. Macromol. Symp. 2006, 236, 23.

1920 Organometallics, Vol. 29, No. 8, 2010
Liu et al.
Table 1. Polymerization of Styrene by Complexes 1-7/
Chart 1. Molecular Structure of Complex 7
AlR3/Boratea
[Al]/ time/
entry cat. [Ln] min yield/g activityb Mn ꢀ 10-4 Mn
Mwc/
rd
c
1
2
3
4
5
6
7
8
1/A
1/B
2/A
3/A
4/A
5/A
1/A
1/A
1/A
2/A
3/A
4/A
1/A
1/A
1/B
1/C
6
30
30
30
30
30
180
10
5
2
5
5
30
5
0.52
0.35
0.45
0.40
0.23
trace
0.52
0.52
0.52
0.52
0.52
0.52
0.52
0.37
0.52
0.52
0.21
0.52
1.01
1.89
2.56
0
104
70
90
80
46
3.8
2.9
3.5
3.0
2.3
1.75 0.72
1.70 0.71
1.68 0.70
1.59 0.68
1.61 0.56
1
3
5
5
5
5
5
5
5
5
10
5
5
5
302
624
1560
624
624
104
624
9
624
104
11
52
50
5.1
4.0
2.3
2.0
1.5
2.8
2.0
2.7
2.8
4.0
1.7
4.1
7.4
17.9
26.5
2.20
2.01
activity. This result suggested the presence of the coordina-
tion of aluminum alkyls to the active metal center and the
concerted spatial bulkiness of aluminum alkyls and the
ligands orienting styrene insertion into the active sites in
certain directions, causing an increase in selectivity. Thus
the less steric aluminum tris(methyl)s did not facilitate the
formation of a highly syndioselective ternary system but
provided only low syndiotactic PS (r = 0.66). This could be
proved further by the behavior of the organoborate, which
showed negligent influence on the selectivity because it
existed as a discrete counterion of the cationic active species
without bonding to the active center (see the molecular
structure of complex 6 vide supra; 19F NMR spectra of 6
and 1/[Ph3C][B(C6F5)4]/AliBu3 are almost the same; see
SFigures 9, 17, 18). It should be noted that the too crowded
environment could also bring about a drop in selectivity, as
the case of using precursor 4, bearing much bulkier isopropyl
groups (entry 12). We presumed that the geometry of 4
arising from the bulky ligand did not facilitate the syndio-
tactic configuration resulting from the phenyl-phenyl re-
pulsive interaction.28 These results were consistent with the
microstructure analysis of the obtained sPs samples.
9
1.87 0.94
2.06 0.93
1.96 0.93
1.56 0.61
1.58 0.94
1.63 0.66
1.93 0.93
1.82 0.93
1.96 0.93
1.72 0.94
1.86 0.94
2.29 0.94
2.20 0.94
10
11
12
13e
14f
15
16
17
18g
19h
20i
21 j
22
240
5
30
120
60
120
240
360
60
1/A
1/A
1/A
1/A
7/A
47
43
5
5
a General conditions: 10-5 mol of Sc complex; in chlorobenzene;
monomer/solvent = 5:2 (v/v); [Al] = AliBu3; Tp: 25 ꢀC; [St]/[Ln] = 500;
[Ln]/[activator] = 1:1 (activator = [Ph3C][B(C6F5)4] (A), [PhMe2NH]-
[B(C6F5)4] (B), B(C6F5)3 (C)). b Given in kg of PS/(mol Sc h). c Deter-
3
mined by GPC in THF at 40 ꢀC against polystyrene standard. d Determined
by 13C NMR. e [Al] = AlEt3. f [Al] = AlMe3. g Monomer/solvent = 1:3
(v/v); [St]/[Ln] = 500. h Monomer/solvent = 1:3 (v/v); [St]/[Ln] = 1000.
i Monomer/solvent = 1:3 (v/v); [St]/[Ln] = 2000. j Monomer/solvent =
1:3 (v/v); [St]/[Ln] = 3000.
group (Chart 1),22 which was employed as a precursor
to initiate the polymerization of styrene but is inert. The
space-filling drawings of the molecular structures displayed
clearly a too crowded environment around the Sc3þ ion in 7
as compared with 1 (Figure 5). Noteworthy was that the
cationic complex 6 activated by AliBu3 to extrude the
coordinated DME molecules could catalyze the polymeriza-
tion of styrene with moderate activity, suggesting that 6 to
some degree represented a reaction intermediate in this
process (entry 17).
The microstructure of the isolated PS was determined by
13C NMR spectroscopic analysis according to the resonance
integrals of the methylene carbon, which was strongly de-
pendent on the catalyst system applied.27 PS obtained by
using the binary systems was moderately stereoregular, with
the r-diad value varying from 0.56 to 0.72. Strikingly, the
ternary systems exhibited high stereoselectivity to afford sPS
with r diad up to 0.94 in high yield. This represented the first
example of rare-earth metal based precursors bearing non-
Cp ligands displaying both high specific selectivity and
The 13C NMR spectrum of the phenyl ipso-carbon region
of polystyrene samples is shown in Figure 6,29 where the
main signal is assigned to the rrrr pentad, while the other four
arise from the probable single-m pentads rmrr and mrrr and
the double-m pentads rmmr and mmrr, respectively. Because
[rmrr] = [mrrr], a chain-end control mechanism arising from
steric control was assumed to operate for the formation of
sPS with this catalyst system; as for a site-control mecha-
nism, the integrals of the pentads should abide by the rule of
2[rmmr] = [mmrr] = [mrrr].30
Conclusion
We have demonstrated that the non-Cp quinolinyl-
anilino-ligated scandium bis(alkyl) complexes activated by
[Ph3C][B(C6F5)4] generated a single-site cationic system pos-
sessing a high activity with moderate selectivity for the
polymerization of styrene, while the ternary system com-
posed of these complexes and AlR3 and organoborates/
borane displayed both high activity and high specific selec-
tivity to afford syndiotactic polystyrene via a chain-end
control mechanism governed by the concerted steric effects
of the ligands and the coactivator aluminum alkyls. The
(27) In the 13C NMR spectra in tetrachloroethane-d2 at 100 ꢀC, the
four distinct signals of the methylene carbon of polystyrene obtained by
1/AliBu3/[Ph3C][B(C6F5)4] correspond best with those reported by
Harder et al (SFigure 13a). Thus they can be assigned to the rrmrr
(45.95 ppm), mrrrr (45.06 ppm), rrrrr (44.44 ppm), and the rmrrr hexads
(43.34 ppm), and the intensity of the rrmrr, mrrrr, and rmrrr hexads
complies with an approximate 1:2:2 ratio. The signal assignments of the
methylene carbon in tetrachloroethane-d2 and chloroform-d are similar
(sFigure 13b), as is the tacticity of our polymers measured by 13C NMR
spectroscopic analysis in chloroform-d. See: (a) Feil, F.; Harder, S.
Macromolecules 2003, 36, 3446. (b) Kawamura, T.; Toshima, N.;
Matsuzaki, K. Macromol. Rapid Commun. 1994, 15, 479. (c) Harder,
S. Angew. Chem., Int. Ed. 2004, 43, 2714. (d) Harder, S.; Feil, F.; Knoll,
K. Angew. Chem., Int. Ed. 2001, 40, 4261.
(28) Longo, P.; Proto, A.; Zambelli, A. Macromol. Chem. Phys. 1995,
196, 3015.
(29) For assignments of major peaks of phenyl ipso-carbon, see:
(a) Michiue, K.; Onda, M.; Tanaka, H.; Makio, H.; Mitani, M.; Fujita,
T. Macromolecules 2008, 41, 6289. (b) Sato, H.; Tanaka, Y. J. Polym. Sci.,
Part B: Polym. Phys. 1983, 21, 1667. (c) Zambelli, A.; Longo, P.;
Pellecchia, C.; Grassi, A. Macromolecules 1987, 20, 2035. (d) Longo, P.;
Proto, A.; Zambelli, A. Macromol. Chem. Phys. 1995, 196, 3015.
(30) Ewen, J. A. J. Am. Chem. Soc. 1984, 106, 6355.

Article
Organometallics, Vol. 29, No. 8, 2010 1921
Figure 5. Space-filling drawings of the molecular structures viewed from above the plane of the quinolinyl ring. Complex 1 (left) and
complex 7 (right).
13C NMR spectra were recorded on a Bruker AV400 (FT,
400 MHz for 1H; 100 MHz for 13C), AV300 (FT, 300 MHz for
1H; 75 MHz for 13C), or AV600 (FT, 600 MHz for 1H; 150 MHz
for 13C). 19F NMR spectra (282 MHz) are referenced to external
C6H5F. The molecular weight (Mn) was measured by TOSOH
HLC-8220 GPC at 40 ꢀC using THF as eluent (the flow rate is
0.35 mL/min) against polystyrene standards. Elemental ana-
lyses were performed at National Analytical Research Centre of
Changchun Institute of Applied Chemistry. X-ray analysis was
performed at -86.5 ꢀC on a Bruker SMART APEX diffracto-
meter with a CCD area detector, using graphite-monochro-
˚
mated Mo KR radiation (λ = 0.71073 A). The determination of
crystal class and unit cell parameters was carried out by the
SMART program package. The structures were solved by using
the SHELXTL program. Refinement was performed on F2
anisotropically for all non-hydrogen atoms by the full-matrix
least-squares method.
Preparation of the Ligands. N-(2,6-Dimethylphenyl)quino-
lin-8-amine (HL1). 2,6-Dimethylaniline (1.45 g, 12 mmol),
Pd(OAc)2 (22 mg, 0.10 mmol), NatOBu (1.44 g,15 mmol),
8-bromoquinoline (2.08 g, 10 mmol), bis[2-(diphenylphos-
phino)phenyl] ether (DPEphos, 80.80 mg, 0.15 mmol), and
anhydrous degassed toluene (20 mL) were added to a flask.
The solution was stirred at 120 ꢀC overnight, and then water
(40 mL) was added. The organic phase was extracted with
toluene (90 mL) and dried over anhydrous MgSO4. Purification
by column chromatography on silica gel eluting with ethyl
acetate and petroleum ether (v/v, 10:1) afforded HL1 (1.15 g,
46%). 1H NMR (300 MHz, CDCl3, 25 ꢀC): δ 2.21 (s, 6H,
o-NC6H3Me2), 6.22 (d, 3JH-H = 7.5 Hz, 1H, quinoline), 7.05-
7.15 (m, 5H, NC6H3Me2, quinoline), 7.21 (t, 3JH-H = 3.9 Hz,
1H, quinoline), 7.39 (q, 3JH-H = 4.2 Hz, 1H, quinoline), 7.52 (br
s, 1H, NH), 8.08 (d, 3JH-H = 8.1 Hz, 1H, quinoline), 8.77 (dd,
3JH-H = 4.2 Hz, 4JH-H = 1.5 Hz, 1H, quinoline). 13C NMR (75
MHz, CDCl3, 25 ꢀC): δ 18.23 (2C, o-NC6H3Me2), 106.01,
114.74, 121.31 (3C, quinoline), 126.10 (1C, NC6H3Me2),
127.58 (1C, quinoline), 128.43 (2C, NC6H3Me2), 128.81,
135.99 (2C, quinoline), 136.60 (2C, NC6H3Me2), 137.96 (1C,
NC6H3Me2), 138.14, 142.73, 147.08 (3C, quinoline).
Figure 6. 13C NMR spectrum (CDCl3, 25 ꢀC) of the phenyl
ipso-carbon region of polystyrene obtained with 1/AliBu3/
[Ph3C][B(C6F5)4] (Table 1, entry 9).
isolation and full characterization of the cationic scandium
complex from a binary system represented to some degree
the true active species in the styrene polymerization process,
which could also explain why orgnoborates in the present
catalyst systems influenced more significantly the activity
than the selectivity, as they exist as a discrete counterion of
the cationic active species without interaction with the active
sites. To our knowledge, this is the first example of rare-earth
metal based precursors attached to the non-Cp ligands
showing high syndioselectivity for polymerization of styrene
with high activity simultaneously, which might provide clues
for designing new efficient catalysts.
Experimental Section
General Considerations. All manipulations were performed
under a dry and oxygen-free argon atmosphere using standard
high-vacuum Schlenk techniques or in a glovebox. All solvents
were purified via a SPS system. Anilines, NaOtBu, bis[2-(di-
phenylphosphino)phenyl] ether, 8-bromoquinoline, Pd(OAc)2,
B(C6F5)3, and aluminum alkyls were purchased from Aldrich
and used without further purification. [Ph3C][B(C6F5)4] and
[PhMe2NH][B(C6F5)4] were prepared according to the pub-
lished procedures.31 Styrene (99%, Acros) was dried over
N-Mesitylquinolin-8-amine (HL2). Following the same proce-
dure described for the formation of HL1, treatment of 2,4,6-
trimethylaniline (1.62 g, 12 mmol), Pd(OAc)2 (22 mg, 0.10
mmol), NatOBu (1.44 g,15 mmol), 8-bromoquinoline (2.08 g,
10 mmol), and bis[2-(diphenylphosphino)phenyl] ether
(DPEphos, 80.8 mg, 0.15 mmol) gave HL2 (1.26 g, 48%).
1HNMR (300 MHz, CDCl3, 25 ꢀC): δ 2.21 (s, 6H, o-NC6H2-
Me2), 2.33 (s, 3H, p-NC6H2Me), 6.26 (d, 3JH-H = 7.5 Hz, 1H,
quinoline), 6.99 (s, 2H, NC6H2Me3), 7.09 (dd, 3JH-H = 8.1 Hz,
4JH-H = 0.9 Hz, 1H, quinoline), 7.26 (t, 3JH-H = 7.8 Hz, 1H,
quinoline), 7.42 (q, 3JH-H = 4.2 Hz, 1H, quinoline), 7.49 (br s,
1
CaH2 under stirring for 48 h and distilled before use. H and
3
1H, NH), 8.12 (d, JH-H = 8.1 Hz, 1H, quinoline), 8.80 (dd,
(31) Chein, J. C. W.; Tsai, W.-M.; Rausch, M. D. J. Am. Chem. Soc.
1991, 113, 8570.
4
3JH-H = 4.2 Hz, JH-H = 1.5 Hz, 1H, quinoline). 13C NMR

1922 Organometallics, Vol. 29, No. 8, 2010
Liu et al.
3
(75 MHz, CDCl3, 25 ꢀC): δ 18.12 (2C, o-NC6H2Me3), 20.92
(1C, p-NC6H2Me3), 105.89, 114.50, 121.28, 127.63, 128.81
(5C, quinoline), 129.13 (2C, NC6H2Me3), 135.44 (1C, quino-
line), 135.62 (1C, NC6H2Me3), 135.97 (1C, quinoline), 136.43
(2C, NC6H2Me3), 137.96 (1C, NC6H2Me3), 143.08, 147.01 (2C,
quinoline).
4H, THF), 6.14 (d, JH-H = 7.8 Hz, 1H, quinoline), 6.79 (d,
3JH-H = 7.8 Hz, 1H, quinoline), 6.95 (q, 3JH-H = 4.8 Hz, 1H,
quinoline), 7.06 (t, 1H, 3JH-H = 7.8 Hz, NC6H3Me2), 7.17 (d,
3JH-H = 7.5 Hz, 2H, NC6H3Me2), 7.24 (t, 1H, 3JH-H = 8.1 Hz,
3
quinoline), 7.71 (d, JH-H = 8.1 Hz, 1H, quinoline), 9.13 (d,
3JH-H = 3.0 Hz, 1H, quinoline). 13C NMR (100 MHz, C6D6, 25
ꢀC): δ 4.27 (6C, SiMe3), 19.43 (2C, o-NC6H3Me2), 25.02 (2C,
THF), 41.65 (br, 2C, CH2SiMe3), 71.81 (2C, THF), 107.18,
111.51, 121.04 (3C, quinoline), 124.54 (1C, NC6H3Me2), 129.27
(2C, NC6H3Me2), 131.06, 131.16 (2C, quinoline), 135.31 (2C,
NC6H3Me2), 140.15 (1C, quinoline), 141.41 (1C, NC6H3Me2),
146.23, 149.12, 153.00 (3C, quinoline). Anal. Calcd for C29H45-
ScN2Si2 (%): C, 64.64; H, 8.42; N, 5.20. Found: C, 63.51; H,
8.19; N, 5.03.
N-(2,6-Diethylphenyl)quinolin-8-amine (HL3). Following the
same procedure described for the formation of HL1, treatment
of 2,6-diethylaniline (1.79 g, 12 mmol), Pd(OAc)2 (22 mg, 0.10
mmol), NatOBu (1.44 g,15 mmol), 8-bromoquinoline (2.08 g, 10
mmol), and bis[2-(diphenylphosphino)phenyl] ether (DPEphos,
1
80.8 mg, 0.15 mmol) gave HL3 (1.36 g, 49%). H NMR (300
MHz, CDCl3, 25 ꢀC): δ 1.15 (t, 3JH-H = 7.5 Hz, 6H, CH2CH3),
2.62 (br s, 4H, CH2CH3), 6.25 (dd, 3JH-H = 7.5 Hz, 4JH-H
=
1.2 Hz, 1H, quinoline), 7.08 (dd, 3JH-H = 8.1 Hz, 4JH-H = 1.2
Hz, 1H, quinoline), 7.21-7.27 (m, 4H, NC6H3Et2, quinoline),
7.42 (q, 3JH-H = 4.2 Hz, 1H, quinoline), 7.58 (br s, 1H, NH),
8.11 (dd, 3JH-H = 8.1 Hz, 4JH-H = 1.5 Hz, 1H, quinoline), 8.81
L2Sc(CH2SiMe3)2(THF) (2). Following a similar procedure
to that described for the preparation of 1, the reaction of
Sc(CH2SiMe3)3(THF)2 (0.18 g, 0.4 mmol in 3 mL of hexane)
with equimolar HL2 (0.12 g, 0.4 mmol in 4 mL of hexane) gave 2
(0.18 g, 82%). 1H NMR (300 MHz, C6D6, 25 ꢀC): δ 0.15, 0.40
(AB, 2JH-H = 11.4 Hz, 4H, CH2SiMe3), 0.26 (s, 18H, SiMe3),
1.13 (br, 4H, THF), 2.31 (s, 6H, o-NC6H2Me3), 2.34 (s, 3H,
p-NC6H2Me3), 3.73 (br, 4H, THF), 6.16 (dd, 3JH-H = 7.8 Hz,
3
4
(dd, JH-H = 4.2 Hz, JH-H = 1.8 Hz, 1H, quinoline). 13C
NMR (75 MHz, CDCl3, 25 ꢀC): δ 14.88 (2C, CH2CH3), 24.73
(2C, CH2CH3), 106.00, 114.51, 121.32 (3C, quinoline), 126.63
(2C, NC6H3Et2), 126.79 (1C, NC6H3Et2), 127.58, 128.75,
135.97, 136.92 (4C, quinoline), 137.81 (1C, NC6H3Et2), 142.88
(2C, NC6H3Et2), 143.79, 147.06 (2C, quinoline).
4JH-H = 0.9 Hz, 1H, quinoline), 6.79 (dd, JH-H = 8.1 Hz,
3
4JH-H = 0.9 Hz, 1H, quinoline), 6.95-6.99 (m, 3H, m-NC6H2-
Me3, quinoline), 7.22 (t, 3JH-H = 7.8 Hz, 1H, quinoline), 7.74
(dd, 3JH-H = 8.4 Hz, 4JH-H = 1.5 Hz, 1H, quinoline), 9.12 (dd,
N-(2,6-Diisopropylphenyl)quinolin-8-amine (HL4). Following
the same procedure described for the formation of HL1, treat-
ment of 2,6-diisopropylaniline (2.13 g, 12 mmol), Pd(OAc)2 (22
mg, 0.10 mmol), NatOBu (1.44 g,15 mmol), 8-bromoquinoline
(2.08 g, 10 mmol), and bis[2-(diphenylphosphino)phenyl] ether
3JH-H = 4.8 Hz, JH-H = 1.5 Hz, 1H, quinoline). 13C NMR
4
(100 MHz, C6D6, 25 ꢀC): δ 4.26 (6C, SiMe3), 19.37 (2C,
o-NC6H2Me3), 21.40 (1C, p-NC6H2Me3), 25.10 (2C, THF),
41.44 (br, 2C, CH2SiMe3), 71.82 (2C, THF), 107.20, 111.38,
121.01 (3C, quinoline), 129.98 (2C, NC6H2Me3), 131.07, 131.18
(2C, quinoline), 133.32 (1C, NC6H2Me3), 134.91 (2C, NC6H2-
Me3), 140.12 (1C, quinoline), 141.49 (1C, NC6H2Me3), 146.19,
146.31, 153.33 (3C, quinoline). Anal. Calcd for C30H47ScN2Si2
(%): C, 65.18; H, 8.57; N, 5.07. Found: C, 64.39; H, 8.41;
N, 4.87.
(DPEphos, 80.8 mg, 0.15 mmol) gave HL4 (1.62 g, 53%). H
1
NMR (300 MHz, CDCl3, 25 ꢀC): δ 1.14 (d, 3JH-H = 10.8 Hz,
12H, CH(CH3)2), 3.22 (m, 2H, CH(CH3)2), 6.25 (d, 3JH-H = 7.8
Hz, 1H, quinoline), 7.05 (t, JH-H = 8.1 Hz, 1H, quinoline),
3
i
7.21-7.34 (m, 4H, NC6H3 Pr2, quinoline), 7.43 (q, 3JH-H = 4.2
Hz, 1H, quinoline), 7.53 (br s, 1H, NH), 8.11 (d, 3JH-H = 8.1
3
4
Hz, 1H, quinoline), 8.82 (dd, JH-H = 4.2 Hz, JH-H = 1.2
Hz,1H, quinoline). 13C NMR (75 MHz, CDCl3, 25 ꢀC): δ 23.19
(2C, CH(CH3)2), 24.73 (2C, CH(CH3)2), 28.33 (2C, CH(CH3)2),
L3Sc(CH2SiMe3)2(THF) (3). Following a similar procedure
to that described for the preparation of 1, the reaction of
Sc(CH2SiMe3)3(THF)2 (0.18 g, 0.4 mmol in 3 mL of hexane)
with equimolar HL3 (0.11 g, 0.4 mmol in 4 mL of hexane) gave 3
(0.19 g, 83%). 1H NMR (300 MHz, C6D6, 25 ꢀC): δ 0.20, 0.45
(AB, 2JH-H = 11.6 Hz, 4H, CH2SiMe3), 0.28 (s, 18H, SiMe3),
1.13 (br, 4H, THF), 1.22 (t, 3JH-H = 7.5 Hz, 6H, CH2CH3), 2.72
(m, 2H, CH2CH3), 2.95 (m, 2H,CH2CH3), 3.72 (br, 4H, THF),
6.17 (d, 3JH-H = 7.8 Hz, 1H, quinoline), 6.79 (d, 3JH-H = 7.8
i
106.11, 114.35, 121.36 (3C, quinoline), 123.81 (2C, NC6H3 Pr2),
127.37 (1C, NC6H3 Pr2), 127.60, 128.75, 135.26, 135.98 (4C,
i
i
quinoline), 137.66 (1C, NC6H3 Pr2), 144.67, 147.06 (2C,
i
quinoline), 147.85 (2C, NC6H3 Pr2).
N-Phenylquinolin-8-amine (HL5). Following the same proce-
dure described for the formation of HL1, treatment of aniline
(1.12 g, 12 mmol), Pd(OAc)2 (22 mg, 0.10 mmol), NatOBu
(1.44 g,15 mmol), 8-bromoquinoline (2.08 g, 10 mmol), and
bis[2-(diphenylphosphino)phenyl] ether (DPEphos, 80.8 mg,
0.15 mmol) gave HL5 (1.60 g, 73%). 1H NMR (300 MHz,
3
Hz, 1H, quinoline), 6.97 (q, JH-H = 4.8 Hz, 1H, quinoline),
7.19-7.29 (m, 3H, NC6H3Et2, quinoline), 7.74 (d, 3JH-H = 8.1
Hz, 1H, quinoline), 9.15 (d, 3JH-H = 4.8 Hz, 1H, quinoline). 13
C
3
NMR (100 MHz, C6D6, 25 ꢀC): δ 4.19 (6C, SiMe3), 15.36 (2C,
CH2CH3), 25.32 (2C, CH2CH3), 25.11 (2C, THF), 41.51 (br, 2C,
CH2SiMe3), 71.85 (2C, THF), 108.23, 111.40, 121.03 (3C,
quinoline), 125.00 (1C, NC6H3Et2), 126.75 (2C, NC6H3Et2),
130.75, 131.09, 140.16 (3C, quinoline), 140.72 (2C, NC6H3Et2),
141.30 (1C, NC6H3Et2), 146.21, 148.00, 154.21 (3C, quinoline).
Anal. Calcd for C31H49ScN2Si2 (%): C, 65.68; H, 8.71; N, 4.94.
Found: C, 64.72; H, 8.39; N, 4.71.
CDCl3, 25 ꢀC): δ 7.05 (s, 1H, JH-H = 6.3 Hz, NC6H5), 7.22
(d, 3JH-H = 8.1 Hz, 1H, quinoline), 7.35-7.45 (m, 6H, NC6H5,
3
quinoline), 7.45 (d, JH-H = 7.7 Hz, 1H, quinoline), 8.13 (d,
3JH-H = 8.4 Hz, 1H, quinoline), 8.30 (br s, 1H, NH), 8.79 (d,
3JH-H = 3.6 Hz, 1H, quinoline). 13C NMR (75 MHz, CDCl3,
25 ꢀC): δ 107.76, 116.45 (2C, quinoline), 119.99 (2C, NC6H5),
121.48 (1C, NC6H5), 122.04, 127.23, 128.81 (3C, quinoline),
129.27 (2C, NC6H5), 136.08 (1C, quinoline), 138.50 (1C, NC6-
H5), 140.21, 141.82, 147.20 (3C, quinoline).
L4Sc(CH2SiMe3)2(THF) (4). Following a similar procedure
to that described for the preparation of 1, the reaction of
Sc(CH2SiMe3)3(THF)2 (0.18 g, 0.4 mmol in 3 mL of hexane)
with equimolar HL4 (0.12 g, 0.4 mmol in 4 mL of hexane) gave 4
(0.18 g, 76%). 1H NMR (300 MHz, C6D6, 25 ꢀC): δ 0.16, 0.36
(AB, 2JH-H = 11.6 Hz, 4H, CH2SiMe3), 0.22 (s, 18H, SiMe3),
1.17 (br, 4H, THF), 1.14 (d, 6H, CH(CH3)2), 1.28 (d, 6H,
CH(CH3)2), 3.52 (m, 2H, CH(CH3)2), 3.70 (br, 4H, THF),
6.12 (d, 3JH-H = 7.8 Hz, 1H, quinoline), 6.73 (d, 3JH-H = 7.8
Preparation of the Complexes. L1Sc(CH2SiMe3)2(THF) (1).
To a hexane solution (3.0 mL) of Sc(CH2SiMe3)3(THF)2 (0.18 g,
0.4 mmol) was dropwise added an equivalent of HL1 (0.10 g, 0.4
mmol in 4 mL of hexane) at room temperature. The resulting red
solution was stirred for 20 min at room temperature and then
was concentrated to about 2 mL and cooled to -30 ꢀC for 12 h to
afford red crystalline solids, which were washed carefully with a
small amount of hexane (0.5 mL) to remove impurities and dried
in vacuo to give red powders of complex 1 (0.17 g, 81%). Red
crystals for X-ray analysis grew from a solution of hexane at
-30 ꢀC within 24 h. 1H NMR (300 MHz, C6D6, 25 ꢀC): δ 0.16,
3
Hz, 1H, quinoline), 6.91 (q, JH-H = 4.8 Hz, 1H, quinoline),
=
i
3
7.11-7.30 (m, 4H, NC6H3 Pr2, quinoline), 7.71 (dd, JH-H
7.4 Hz, 4JH-H = 1.5 Hz, 1H, quinoline), 9.16 (dd, 3JH-H = 4.8
2
4
0.42 (AB, JH-H = 11.3 Hz, 4H, CH2SiMe3), 0.27 (s, 18H,
Hz, JH-H = 1.5 Hz, 1H, quinoline). 13C NMR (100 MHz,
SiMe3), 1.08 (br, 4H, THF), 2.33 (s, 6H, o-NC6H3Me2), 3.69 (br,
C6D6, 25 ꢀC): δ 4.22 (6C, SiMe3), 24.70 (2C, CH(CH3)2), 25.39

Article
Organometallics, Vol. 29, No. 8, 2010 1923
3
1H, quinoline),7.47 (q, JH-H = 4.8 Hz, 1H, quinoline), 8.20
(2C, THF), 26.53 (2C, CH(CH3)2), 28.87 (2C, CH(CH3)2), 41.42
(br, 2C, CH2SiMe3), 72.30 (2C, THF), 110.37, 111.58, 120.99
(3C, quinoline), 124.88 (2C, NC6H3 Pr2), 125.67 (1C, NC6-
(d, 3JH-H = 7.8 Hz, 1H, quinoline), 8.50 (br, 1H, quinoline). 13
C
i
NMR (150 MHz, 25 ꢀC, C6D4Cl2): δ 3.73 (3C, SiMe3), 20.45
(2C, o-NC6H3Me2), 51.59 (br, 2C, CH2SiMe3), 61.54 (br, 4C
CH3OCH2CH2OCH3), 72.29 (4C CH3OCH2CH2OCH3),
110.46, 114.69, 121.81 (3C, quinoline), 126.66 (1C, NC6H3Me2),
130.72 (2C, NC6H3Me2), 132.25, 142.74, 144.29 (3C, quinoline),
149.02 (Ar), 150.62 (Ar), 151.55 (Ar). 19F NMR (282 MHz,
C6D6, 25 ꢀC): δ -18.7 (d, o-F), -49.2 (t, p-F), -53.1 (t, m-F).
Anal. Calcd for C53H46BF20ScN2Si (%): C, 51.39; H, 3.74; N,
2.26. Found: C, 50.82; H, 3.39; N, 2.03.
Polymerization of Styrene. A typical procedure for the po-
lymerization was as follows (Table 1, run 9): A solution of 1
(0.01 mmol, 5.40 mg, in 0.1 mL of C6H5Cl), 0.10 mmol of
AliBu3, and 0.1 mL of C6H5Cl solution of [PhC3][B(C6F5)4]
(0.01 mmol, 9.20 mg) were added into a 10 mL reactor. The
mixture was stirred at room temperature for 10 min, and 0.52 g
(5.0 mmol) of styrene was added under vigorous stirring. After
2 min, methanol was injected into the system to quench the
polymerization, and the reaction mixture was poured into
a large quantity of methanol containing a small amount of
hydrochloric acid to precipitate the white solids. The precipi-
tated polymer was collected by filtration, washed with metha-
nol, and dried under vacuum at 60 ꢀC to a constant weight to
afford 0.52 g (100% yield) of polystyrene.
i
H3 Pr2), 130.30, 131.06, 140.22 (3C, quinoline), 141.16 (1C,
i
i
NC6H3 Pr2), 145.90 (1C, NC6H3 Pr2), 146.45, 146.56, 155.22
(3C, quinoline). Anal. Calcd for C33H53ScN2Si2 (%): C, 66.62;
H, 8.98; N, 4.71. Found: C, 65.81; H, 8.73; N, 4.49.
L5Sc(CH2SiMe3)2(THF) (5). Following a similar procedure
to that described for the preparation of 1, the reaction of
Sc(CH2SiMe3)3(THF)2 (0.18 g, 0.4 mmol in 3 mL of hexane)
with equimolar HL5 (0.09 g, 0.4 mmol in 4 mL of hexane) gave 5
(0.13 g, 61%). 1H NMR (300 MHz, C6D6, 25 ꢀC): δ 0.18 (s, 18H,
SiMe3), 0.32 (br, 4H, CH2SiMe3), 1.06 (br, 4H, THF), 3.73 (br,
3
4H, THF), 6.55 (d, JH-H = 7.8 Hz, 1H, quinoline), 6.80 (d,
3JH-H = 8.1 Hz, 1H, quinoline), 6.96 (q, 3JH-H = 4.8 Hz, 1H,
quinoline), 7.07 (m, 1H, NC6H5), 7.21-7.32 (m, 5H, NC6H5,
quinoline), 7.73 (dd, JH-H = 8.4 Hz, JH-H = 1.5 Hz, 1H,
3
4
3
4
quinoline), 8.99 (dd, JH-H = 4.5 Hz, JH-H = 1.5 Hz,
1H, quinoline). 13C NMR (100 MHz, C6D6, 25 ꢀC): δ 4.23
(6C, SiMe3), 25.08 (2C, THF), 40.10 (br, 2C, CH2SiMe3), 71.52
(2C, THF), 108.62, 111.84, 121.07 (3C, quinoline), 124.14 (1C,
NC6H5), 128.39 (2C, NC6H5), 130.33 (2C, NC6H5), 130.81,
130.91, 140.05 (3C, quinoline), 141.21 (1C, NC6H5), 146.45,
152.43, 155.51 (3C, quinoline). Anal. Calcd for C27H41ScN2Si2
(%): C, 63.49; H, 8.09; N, 5.48. Found: C, 62.83; H, 7.91;
N, 5.29.
L1Sc(CH2SiMe3)(THF)2][B(C6F5)4] (6). A DME solution
(2 mL) of [PhMe2NH][B(C6F5)4] (60 mg, 0.07 mmol) was slowly
added to a DME solution (4 mL) of L1Sc(CH2SiMe3)2(THF)]
(1) (39 mg, 0.07 mmol) in 10 min with vigorous stirring and kept
stirring for 20 min. Removal of the volatiles gave residues, which
were washed with cold hexane and dried under reduced pres-
sure for 2 h to generate 6 (55 mg, 61%). Red single crystals for
X-ray diffraction analysis were obtained by recrystallization
in chlorobenzene/hexane at -30 ꢀC for several days. 1H NMR
(600 MHz, 25 ꢀC, C6D4Cl2): δ -0.39 (s, 9H, CH2SiMe3), 0.20
(s, 2H, CH2SiMe3), 2.12 (s, 6H, o-NC6H3Me2), 3.21 (br,
CH3OCH2CH2OCH3), 3.51 (br, CH3OCH2CH2OCH3), 5.99
(d, 3JH-H = 7.8 Hz, 1H, quinoline), 6.87 (d, 3JH-H = 7.8 Hz,
1H, quinoline),7.04 (t, 3JH-H = 7.8 Hz, 1H, NC6H3Me2), 7.11
(d, 3JH-H = 7.8 Hz, 2H, NC6H3Me2), 7.16 (t, 3JH-H = 7.8 Hz,
Acknowledgment. We thank The National Natural
Science Foundation of China (Project Nos. 20674081
and 20934006) and The Ministry of Science and Tech-
nology of China (Project Nos. 2005CB623802 and
2009AA03Z501) for financial support.
Supporting Information Available: 1H and 13C NMR spectra
of complexes 1, 2, 3, and 5; 19F NMR spectra of 6 and 1/[Ph3C]-
[B(C6F5)4]/AliBu3; crystallographic information files (CIFs)
and a table of the summary of crystallographic data and
refinements for complexes 1, 2, 5, and 6; 1H and 13C NMR
spectra of selected polystyrene samples; and GPC diagrams for
selected polystyrene samples. This material is available free of
charge via the Internet at http://pubs.acs.org.