(η3-Azaallyl)zirconium chlorides: Synthesis, characterization, and ethylene (Co-)polymerization activity

Article abstract of DOI:10.1021/om100133b

(2,6-Diisopropyl-N-(1-phenylvinyl)benzenamido)magnesium bromide (CH ₂(Ph)C(2,6-ⁱPr₂C₆H ₃)NMgBru2THF, 1b) reacted with 1 equiv of Me₂NMe ₂SiCl to form the N-(2-((dimethylamino)dimethylsilyl)-1-phenylvinyl)- 2,6-diisopropylbenzenamine (1c). The stoichiometric reaction of 1c with lithium diisopropylamide (LDA) formed lithium N-(2-((dimethylamino)dimethylsilyl)-1- phenylvinyl)-2,6-diisopropylbenzenamidate (Me₂NMe₂SiCH(Ph) C(2,6-ⁱPr₂C₆H₃)NLi-3THF, 1d) in high yields. The reaction of zirconium tetrachloride with 2 equiv of 1d produced the bisligated (η³-azaallyl)zirconium dichloride ((η³-(2,6-ⁱPr₂C₆H ₃)N(Ph)CCHSiMe₂NMe₂)₂ZrCl ₂, 2), whereas the stoichiometric reaction of zirconium tetrachloride with 1d formed a monoligated zirconium trichloride complex ((η³: η¹-(2,6-ⁱPr₂C₆H ₃)N(Ph)CCHSiMe₂NMe₂)ZrCl₃, 3), in which the ligand acted as an η³-azaallyl species with N-donation via the dimethylamino group at the silyl bridge. All compounds were fully characterized by elemental and spectroscopic analyses and metal compounds by single-crystal X-ray diffraction. The azaallyl groups of the ligands act in a κ¹-enamido fashion in compounds 1b,d, while the azaallyls appear as an η³-N,C,C mode in compound 2. The η³:η¹ coordination of the azaallyl and dimethylsilyl groups provided a sterically constrained geometry around the zirconium in compound 3. The coordination geometries around each zirconium are pseudo-octahedral in both compounds 2 and 3. The modes of coordination affected their catalytic behaviors toward polymerization: high activity by 3 and good activity by 2.

Full text of DOI:10.1021/om100133b

2132 Organometallics 2010, 29, 2132–2138
DOI: 10.1021/om100133b
(η3-Azaallyl)zirconium Chlorides: Synthesis, Characterization, and
Ethylene (Co-)polymerization Activity
Shifang Yuan,†,‡ Shengdi Bai,† Diansheng Liu,*,† and Wen-Hua Sun*,‡
†Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, People’s Republic of China, and
‡Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
Received February 21, 2010
(2,6-Diisopropyl-N-(1-phenylvinyl)benzenamido)magnesium bromide (CH2(Ph)C(2,6-iPr2C6H3)-
NMgBr 2THF, 1b) reacted with 1 equiv of Me2NMe2SiCl to form the N-(2-((dimethylamino)dime-
3
thylsilyl)-1-phenylvinyl)-2,6-diisopropylbenzenamine (1c). The stoichiometric reaction of 1c with
lithium diisopropylamide (LDA) formed lithium N-(2-((dimethylamino)dimethylsilyl)-1-phenyl-
vinyl)-2,6-diisopropylbenzenamidate (Me2NMe2SiCH(Ph)C(2,6-iPr2C6H3)NLi 3THF, 1d) in high
3
yields. The reaction of zirconium tetrachloride with 2 equiv of 1d produced the bisligated (η3-
azaallyl)zirconium dichloride ((η3-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)2ZrCl2, 2), whereas the
stoichiometric reaction of zirconium tetrachloride with 1d formed a monoligated zirconium
trichloride complex ((η3:η1-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)ZrCl3, 3), in which the ligand
acted as an η3-azaallyl species with N-donation via the dimethylamino group at the silyl bridge. All
compounds were fully characterized by elemental and spectroscopic analyses and metal compounds
by single-crystal X-ray diffraction. The azaallyl groups of the ligands act in a κ1-enamido fashion in
compounds 1b,d, while the azaallyls appear as an η3-N,C,C mode in compound 2. The η3:η1
coordination of the azaallyl and dimethylsilyl groups provided a sterically constrained geometry
around the zirconium in compound 3. The coordination geometries around each zirconium are
pseudo-octahedral in both compounds 2 and 3. The modes of coordination affected their catalytic
behaviors toward polymerization: high activity by 3 and good activity by 2.
1. Introduction
bimetallic η3 fashion (III) (Scheme 1).1 Numerous complexes
of the main-group elements1-3 and transition metals4-7 have
been explored. Our efforts have focused on the (η3-azaal-
lyl)zirconium complexes4 because of the great potential of
zirconium complexes in producing polyolefins with unique
properties.8 The zirconium procatalysts9 are mainly divided
as metallocene derivatives10 and half-metallocene deriva-
tives.11 In fact, the bridged η5:η1-coordinated half-metallo-
cenes, namely constrained geometry compounds (CGC),
have been extensively investigated,11 and an analogous
(Azaallyl)metal complexes have drawn much attention
due to the diverse bonding modes of azaallyl groups such
as the terminal κ1-enamido (I) and a monometallic (II) and
*To whom correspondence should be addressed. Tel: þ86-10-
62557955. Fax: þ86-10-62618239. E-mail: dsliu@sxu.edu.cn (D.-S.L.);
whsun@iccas.ac.cn (W.-H.S.).
(1) (a) Caro, C. F.; Lappert, M. F.; Merle, P. G. Coord. Chem. Rev.
2001, 219-221, 605. (b) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S.
J. Chem. Soc., Chem. Commun. 1994, 2637. (c) Hitchcock, P. B.; Lappert,
M. F.; Layh, M.; Liu, D.-S.; Sablong, R.; Shun, T. Dalton Trans. 2000,
2301.
(2) (a) Hitchcock, P. B.; Lappert, M. F.; Sablong, R. Dalton Trans.
2006, 4146. (b) Merle, L. B.; Hitchcock, P. B.; Lappert, M. F.; Merle, P. G.
Dalton Trans. 2008, 3493. (c) Shaviv, E.; Botoshansky, M.; Eisen, M. S.
J. Organomet. Chem. 2003, 683, 165. (d) Nelkenbaum, E.; Kapon, M.;
Eisen, M. S. J. Organomet. Chem. 2005, 690, 2297. (e) Fernandes, M. A.;
Layh, M.; Omondi, B. Polyhedron 2005, 24, 958.
(3) (a) Hitchcock, P. B.; Lappert, M. F.; Wei, X. H. J. Organomet.
Chem. 2003, 683, 83. (b) Chen, X.; Guan, L.; Eisen, M. S.; Li, H.; Tong, H.;
Zhang, L.; Liu, D.-S. Eur. J. Inorg. Chem. 2009, 3488.
(4) (a) Lappert, M. F.; Liu, D.-S. J. Organomet. Chem. 1995, 500, 203.
(b) Lappert, F. Liu, D.-S. Neth. Pat. Appl. 9500085, 1995. (c) Lappert, M. F.
Liu, D.-S. Neth. Pat. Appl. 9400919, 1994. (d) Lappert, M. F.; Raston, C. L.;
Skelton, B. W.; White, A. H. J. Chem. Soc., Chem. Commun. 1982, 14.
(5) (a) Hitchcock, P. B.; Hu, J.; Lappert, M. F. Chem. Commun. 1998,
143. (b) Hitchcock, P. B.; Lappert, M. F.; Layh, M. Z. Anorg. Allg. Chem.
2000, 626, 1081.
(6) (a) Bowen, R. J.; Fernandes, M. A.; Layh, M. J. Organomet.
Chem. 2004, 689, 1230. (b) Bowen, R. J.; Caddy, J.; Fernandes, M. A.;
Layha, M.; Mamo, M. A. Polyhedron 2004, 23, 2273.
(7) (a) Leung, W. P.; So, C. W.; Chong, K. H.; Kan, K. W.; Chan,
H. S.; Mak, T. C. W. Organometallics 2006, 25, 2851. (b) Lorenz, V.;
€
Gorls, H.; Thiele, S. K.-H.; Scholz, J. Organometallics 2005, 24, 797. (c)
Avent, A. G.; Hitchcock, P. B.; Lappert, M. F.; Sablong, R.; Severn, J. R.
Organometallics 2004, 23, 2591.
(8) (a) Braunschweig, H.; Breitling, F. M. Coord. Chem. Rev. 2006,
250, 2691. (b) Chum, P. S.; Kruper, W. J.; Guest, M. J. Adv. Mater. 2000, 12,
1759.
(9) (a) Ziegler, K.; Gellert, H. G.; Zosel, K.; Lehmkuhl, W.; Pfohl, W.
Angew. Chem. 1955, 67, 424. (b) Ziegler, K.; Holzkamp, E.; Breil, H.;
Martin, H. Angew. Chem. 1955, 67, 541. (c) Natta, G. J. Polym. Sci. 1955,
16, 143. (d) Natta, G.; Pino, P.; Corradini, P.; Danusso, F.; Mantica, E.;
Mazzanti, G.; Moraglio, G. J. Am. Chem. Soc. 1955, 77, 1708. (e) Groppo,
E.; Lamberti, C.; Bordiga, S.; Spoto, G.; Zecchina, A. Chem. Rev. 2005, 105,
115.
(10) (a) Sinn, H.; Kaminsky, W.; Vollmer, H.-J.; Woldt, R. Angew.
Chem., Int. Ed. Engl. 1980, 19, 390. (b) Kaminsky, W. Macromol. Chem.
Phys. 1996, 197, 3907. (c) Brintzinger, H. H.; Fischer, D.; M€ulhaupt, R.;
Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
€
(d) Alt, H. G.; Koppl, A. Chem. Rev. 2000, 100, 1205.
r
2010 American Chemical Society
pubs.acs.org/Organometallics
Published on Web 04/05/2010

Article
Organometallics, Vol. 29, No. 9, 2010 2133
Scheme 1. Bonding Modes of Azaallyl Groups
Scheme 2. Syntheses of K1-Enamido Metal Compounds
titanium catalyst has finally been commercialized.12 In terms
of the role of the η5 ligand, the η3-azaallyl species can be
considered as an alternative. In the model of the CGC, the
bridged η5:η1 ligands have two negative charges; however,
our efforts to obtain the bridged dianionic η3:η1 ligand were
unsuccessful. Therefore, we have turned to the monoanionic
bridged η3:η1 ligand in which the ligand contains an anionic
η3 function (η3-azaallyl) group and a neutral donating
(amino) group. The monoanionic bridged η3:η1 coordina-
tion mode has been seen in metal allyls.13
Scheme 3. Synthesis of Zirconium Compounds 2 and 3
In addition to the azaallylzirconium analogues,4 the
1-azaallylmetal complexes of magnesium (CH2(Ph)C(2,6-iPr2-
C6H3)NMgBr 2THF, 1b) and lithium (Me2NMe2SiCH-
3
(Ph)C(2,6-iPr2C6H3)NLi 3THF, 1d) were successfully pre-
3
pared. There is an extra dimethylamine bridge through the
dimethylsilyl group on the azaallyl group in 1d. When the
molar ratio of 1d to zirconium tetrachloride was controlled
in each reaction, the bis(η3-azaallyl)zirconium dichloride
((η3-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)2-ZrCl2, 2) and
the silyl-bridged η3:η1-coordinated zirconium trichloride
((η3:η1-(2,6-iPr2C6H3)N(Ph)-CCHSiMe2NMe2)ZrCl3, 3)
were isolated. The procatalyst 2 revealed considerable cata-
lytic activity toward ethylene polymerization; meanwhile,
procatalyst 3 showed good activity in both ethylene poly-
merization and copolymerization of ethylene with 1-hexene.
Herein the syntheses and characterization of all metal com-
pounds are reported in detail as well as the catalytic behaviors
of zirconium compounds in polymerization.
The reaction of 2 equiv of 1d with ZrCl4 forms the bis(η3-
azaallyl)zirconium dichloride (η3-(2,6-iPr2C6H3)N(Ph)CC-
HSiMe2NMe2)2ZrCl2 (2) in good yields. Compound 2 is a
colorless crystalline solid and is soluble in hydrocarbon
solvents, similar to rac-[Zr{N(SiMe3)C(tBu)C(SiMe3)}2Cl2].4
The stoichiometric reaction of 1d with ZrCl4, however,
produced the monoligated zirconium trichloride complex
(η3:η1-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)ZrCl3 (3), in
high yield (Scheme 3). In compound 3, the ligand acts
as a η3-azaallyl with an N-donor from the dimethylamine
through the silyl bridge. This is the first example of bridged
η3:η1 coordination in a zirconium trichloride. Compound 3 is
soluble in THF and sparingly soluble in Et2O and CH2Cl2.
The microanalysis and NMR spectra of all compounds are in
agreement with their molecular structures, as confirmed by
single-crystal X-ray diffraction.
2. Results and Discussion
2.1. Synthesis and Characterization. The treatment of
Me(Ph)CN(2,6-iPr2C6H3) (1a) with 1 equiv of LDA (lithium
diisopropylamide) and MgBr2 in THF quantitatively produces
the κ1-enamido magnesium complex CH2(Ph)C(2,6-iPr2-
C6H3)NMgBr 2THF (1b). The stoichiometric reaction of 1b
3
with Me2NMe2SiCl in THF forms the compound (2,6-iPr2-
C6H3)NC(Ph)CH2SiMe2NMe2 (1c). Subsequently the com-
pound 1c reacts with 1 equiv of LDA in THF to afford the κ1-
enamido lithium compound Me2NMe2SiCH(Ph)C(2,6-iPr2C6-
H3)NLi 3THF (1d). In addition to elemental and NMR ana-
3
2.2. Crystal Structures. The newly synthesized metal
compounds are highly air and moisture sensitive. The mole-
cular structure of the magnesium compound CH2(Ph)C-
lyses, the structures of 1b,dwere confirmed by single-crystal X-ray
diffraction. The synthetic procedure is illustrated in Scheme 2.
(2,6-iPr2C6H3)NMgBr 2THF (1b) is shown in Figure 1 with
3
selected bond lengths and angles given in the caption. The
magnesium atom of compound 1b is four-coordinate with a
typical terminal κ1-enamido (I, Scheme 1), a bromide, and
two oxo donors of tetrahydrofuran (thf) molecules. This is a
common feature wherein additional “solvent” molecules act
as neutral donors, and this coordination can stabilize the
(11) (a) McKnight, A. L.; Waymouth, R. M. Chem. Rev. 1998, 98,
2587. (b) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem. 1999,
111, 448. (c) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. Engl. 1999, 38, 428. (d) Imanishi, Y.; Naga, N. Prog. Polym. Sci.
2001, 26, 1147. (e) Arndt, S.; Okuda, J. Chem. Rev. 2002, 102, 1953.
(f) Okuda, J. Dalton Trans. 2003, 2367. (g) Gibson, V. C.; Spitzmesser, S. K.
Chem. Rev. 2003, 103, 283. (h) Qian, Y.; Huang, J.; Bala, M. D.; Lian, B.;
Zhang, H. Chem. Rev. 2003, 103, 2633.
(12) (a) Stevens, J. C.; Timmers, F. J.; Wilson, D. R.; Schmidt, G. F.;
Nickias, P. N.; Rosen, R. K.; McKnight, G. W.; Lai, S. Eur. Pat. Appl.
0416815A2, 1991. (b) Shapiro, P. J.; Bunel, E.; Schaefer, W. P.; Bercaw, J. E.
Organometallics 1990, 9, 867. (c) Shapiro, P. J.; Cotter, W. D.; Schaefer, W.
P.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1994, 116, 4623.
(13) (a) Solomon, S. A.; Layfield, R. A. Dalton Trans. 2010, 39, 2469.
(b) Solomon, S. A.; Muryn, C. A.; Layfield, R. A. Chem. Commun. 2008, 3142.
(c) Strohmann, C.; Lehmen, K.; Dilsky, S. J. Am. Chem. Soc. 2006, 128, 8102.
1
˚
complexes. The Mg-N distance (Mg-N=1.995(5) A) is
slightly shorter than the previously reported distance (Mg-
14
˚
˚
N = 2.015(2) A). C(1)-N (1.373(7) A) is slightly shorter
˚
than C(9)-N (1.449(7) A), due to the “charge” delocalization
(14) Fedushkin, I. L.; Makarov, V. M.; Rosenthal, E. C. E.; Fukin, G.
K. Eur. J. Inorg. Chem. 2006, 827.

2134 Organometallics, Vol. 29, No. 9, 2010
Yuan et al.
Figure 2. Molecular structure of compound 1d with all hydro-
gen atoms omitted for clarity. Thermal ellipsoids are shown at
˚
the 30% probability level. Selected bond lengths (A) and bond
Figure 1. Molecular structure of compound 1b with all hydro-
gen atoms omitted for clarity. Thermal ellipsoids are shown at
˚
the 30% probability level. Selected bond lengths (A) and bond
angles (deg): Mg-N = 1.995(5), Mg-O(2) = 2.018(4), Mg-
O(3) = 2.029(5), Mg-Br = 2.457(2), N-C(1) = 1.373(7), N-
C(9)=1.449(7), C(1)-C(8)=1.365(9), C(1)-C(2)=1.502(8);
N-Mg-Br = 127.76(16), C(1)-N-C(9) = 115.0(4), C(8)-C-
(1)-N=126.9(5), C(8)-C(1)-C(2)=117.7(5), N-C(1)-C(2)=
115.4(5), C(9)-N-Mg = 116.6(3), C(1)-N-Mg = 128.3(4),
O(2)-Mg-O(3)=95.55(19).
angles (deg): Li-N(1)=2.011(7), Li-O(1)=1.983(7), Li-O(2)=
2.041(7), Li-O(3) = 2.021(8), N(1)-C(13) = 1.352(4), N(1)-
C(1)=1.408(4), N(2)-C(24)=1.419(7), N(2)-C(23)=1.445(7),
C(13)-C(20) = 1.372(5), N(2)-Si = 1.703(4), C(13)-C(14) =
1.509(5), Si-C(20) = 1.829(4), Si-C(22) = 1.875(5), Si-
C(21) = 1.884(5); N(1)-C(13)-C(20) = 127.8(3), N(2)-Si-
C(20) = 115.1(2), C(13)-N(1)-Li = 132.6(3), C(13)-C(20)-
Si=131.8(3), C(1)-N(1)-Li=111.2(3), C(13)-N(1)-C(1)=
116.0(3), C(20)-C(13)-C(14) = 119.0(3), O(1)-Li-O(2) =
97.5(3), O(2)-Li-O(3)=97.0(3), O(1)-Li-O(3)=101.6(3).
˚
from the double bond C(1)-C(8) (=1.365(9) A). The dihed-
ral angle of C(2)-C(1)-C(8) and C(9)-N-Mg is 7.16°, and
that of the planes C(8)-C(1)-N and C(1)-N-Mg is 9.09°,
which might be partially due to the steric repulsion between
the rotation of two large phenyl groups. The dihedral angles
of two phenyl rings with the plane C(8)-C(1)-N-Mg are
79.03 and 45.45°, respectively.
The molecular structure of the terminal κ1-enamido
lithium compound Me2NMe2SiCH(Ph)C(2,6-iPr2C6H3)-
NLi 3THF (1d) is shown in Figure 2, with selected bond
3
lengths and angles given in the caption. (η3-Azaallyl)lithium
compounds have previously been studied, and some compar-
able compounds are [LiN(Ar)C(R)CHR(thf)2],2e [LiN(R)-
C(Ar)CR2(thf)],15 [LiN(Ar)C(H)CHnPr(thf)3],16 and (with a
neutral coordinating dimethylamide group) [LiN(SiMe2-
NMe2)C(tBu)CHPh(tmeda)].17 As a result of steric crowd-
ing, the lithium compound 1d is uniquely a Z isomer with
wider angles around the sp2-hybridized carbons C(13) and
C(20): N(1)-C(13)-C(20) = 127.8(3)°, C(13)-C(20)-Si =
131.8(3)°, C(20)-Si-N(2) = 115.1(2)°. The five atoms Li,
N(1), C(13), C(20), and Si are almost coplanar, with the
Figure 3. Molecular structure of compound 2, with all hydro-
gen atoms omitted for clarity. Thermal ellipsoids are shown at
˚
the 30% probability level. Selected bond lengths (A) and bond
˚
largest deviation from planarity being 0.018(1) A for C(20),
˚
while the distance between the plane and N(2) is 1.157 A. In
angles (deg): Zr-N(1) = 2.101(4), Zr-N(3) = 2.107(4), Zr-
C(20) = 2.593(5), Zr-C(44) = 2.570(5), Zr-Cl(2) = 2.4242(15),
Zr-Cl(1) = 2.4233(15), N(3)-C(37) = 1.394(6), N(1)-C(13)=
1.392(7), N(3)-C(25) = 1.460(6), N(1)-C(1) =1.462(6), Si(2)-
C(20)=1.854(6), Si(1)-C(44)=1.885(5), N(4)-Si(1)=1.690(6),
N(2)-Si(2) =1.684(6), C(13)-C(14) =1.493(7), C(13)-C(20) =
1.409(8), C(37)-C(44) = 1.355(7), C(37)-C(38) = 1.499(7);
N(1)-Zr-N(3) = 89.84(16), Cl(2)-Zr-Cl(1) =99.31(6), N(1)-
Zr-C(44) =126.33(17), N(3)-Zr-C(44) =58.63(16), N(1)-Zr-
C(20) = 59.52(17), N(3)-Zr-C(20) = 128.43(17), C(13)-N(1)-
C(1) = 120.6(4), C(37)-N(3)-Zr = 92.7(3), C(13)-N(1)-Zr =
93.7(3), N(4)-Si(1)-C(44)=111.1(3), C(1)-N(1)-Zr=141.5(3),
N(2)-Si(2)-C(20)=111.3(3).
addition, the plane of Li, N(1), C(13), C(20), and Si is
approximately perpendicular to the two phenyl rings with
dihedral angles of 89.59 and 72°.
The molecular structure of the crystalline compound
(η3-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)2ZrCl2 (2) is illu-
strated in Figure 3, with selected bond lengths and angles
(15) Lappert, M. F.; Layh, M. Tetrahedron Lett. 1998, 39, 4745.
(16) Bosold, F.; Marsch, M.; Harms, K.; Boche, G. Z. Kristallogr.-
New Cryst. Struct 2001, 216, 427.
(17) Shi, H. P.; Liu, D.-S.; Huang, S.-P. Acta Crystallogr., Sect. E
2003, 59, m339.

Article
Organometallics, Vol. 29, No. 9, 2010 2135
Table 1. Ethylene Polymerization of the Compound 2/MAOa
P
(atm)
T
(°C)
acti-
vityb
Tm
(°C)c
Mw/
Mn
d
d
entry
Al/Zr
Mw
1
2
3
4
5
6
7
8
1
1
1
10
10
10
10
10
10
10
30
50
70
30
30
30
50
60
70
80
1000
1000
1000
500
1000
1500
1000
1000
1000
1000
trace
2.10
trace
3.94
4.64
3.72
6.47
6.89
8.12
6.34
134.4
135.8
134.9
134.1
133.6
133.3
133.1
132.4
8.20
7.90
5.76
5.19
3.05
4.77
2.27
4.2
14
29
8.2
7.7
7.0
4.4
9
10
a Conditions: catalyst, 5 μmol; time, 30 min; total volume, 30 mL of
toluene for 1 atm or 100 mL of toluene for 10 atm. b In units of 104 g (mol
of Zr)-1 h-1 atm-1 c Determined by DSC. d In units of 105 g mol-1
. ;
determined by GPC.
˚
C(13) from C(20)-Zr-N(1) plane is 0.525 A. The dihedral
angle between C(20)-Si-N(2) and C(20)-Zr-N(2) is 13°;
hence, the atom Si is out of the C(20)-Zr-N(2) plane (mean
Figure 4. Molecular structure of compound 3, with all hydro-
gen atoms omitted for clarity. Thermal ellipsoids are shown at
˚
the 30% probability level. Selected bond lengths (A) and bond
˚
deviation 0.259 A). The dihedral angle of C(20)-Zr-N(1)
and C(20)-Zr-N(2) is approximately perpendicular at
82.09°. The dihedral angles of phenyl rings to the η3-azaallyl
N(1)-C(13)-C(20) plane are 64.52 and 35.69°. The η3:η1-
(2,6-iPr2-C6H3)N (Ph)CCHSiMe2NMe2 ligand provides a
constrained geometry around zirconium, which can be con-
sidered as an alternative species for the CGC catalysts.12
2.3. Ethylene Polymerization. Ethylene polymerization
using procatalyst 2 was investigated in the presence of
MAO (Table 1). Good activities were obtained when the
[Al]/[Zr] molar ratio was increased from 500 to 1000; how-
ever, a further increase to 1500 led to a decrease of catalytic
activity (entries 4-6 in Table 1). Probably the active species
was suppressed by an excess of MAO, as suggested in the
literature;18 moreover, the amount of AlMe3 contained in
MAO led to deactivation. At an Al/Zr molar ratio of 1000 at
1 atm of ethylene, the highest activity was obtained, 2.10 ꢀ
104 g (mol of Zr)-1 h-1 atm-1, at a reaction temperature of
50 °C. Increasing the ethylene pressure from 1 to 10 atm led
to a further increase in polymerization activity to 8.12 ꢀ 104 g
(mol of Zr)-1 h-1 atm-1 at 70 °C (entry 9 in Table 1). At low
reaction temperature (30 °C), the polymers show high mo-
lecular weights but broad molecular weight distributions,
which is consistent with the literature.19
Ethylene polymerization using procatalyst 3 was also
investigated (Table 2). Alkylaluminums such as AlEt3 and
Et2AlCl do not activate zirconium compound 3 for ethylene
polymerization over a range of concentrations and reaction
temperatures (entries 1 and 2 in Table 2). However, moderate
activities are observed with both MMAO (entry 3 in Table 2)
and MAO (entry 4 in Table 2). Accordingly, MAO was
selected as a practical activator for further investigations.
Using Al/Zr molar ratios in the range 500-1500 (entries 5-7
in Table 2) at 1 atm ethylene pressure and 50 °C, the
maximum activity was obtained at an Al/Zr molar ratio of
1000 (entry 5 in Table 2). With reaction temperatures in the
range 30-70 °C at 1 atm of ethylene pressure with an Al/Zr
molar ratio of 1000, the catalytic activity showed a maximum
angles (deg): Zr-N(1) = 2.179(3), Zr-N(2) = 2.406(4), Zr-
C(20)=2.467(4), Zr-Cl(1)=2.4172(15), Zr-Cl(2)=2.3983(12),
Zr-Cl(3) = 2.4172(12), N(1)-C(13) = 1.378(5), N(1)-C(1) =
1.418(5), C(20)-C(13) = 1.371(6), C(14)-C(13) = 1.495(6),
Si-C(20) = 1.868(5), Si-N(2) = 1.816(4); N(1)-Zr-N(2) =
87.83(13), N(2)-Zr-C(20) = 72.37(14), N(1)-Zr-C(20) =
59.99(12), N(2)-Si-C(20) = 102.69(18), C(13)-N(1)-C(1) =
121.1(3), C(13)-C(20)-Si=128.0(3), C(13)-N(1)-Zr=89.3(2),
C(13)-C(20)-Zr = 78.1(2), Si-C(20)-Zr = 90.12(16), C(1)-
N(1)-Zr = 143.6(3), Si-N(2)-Zr = 93.34(18), Cl(1)-Zr-
Cl(2)=101.99(5), Cl(2)-Zr-Cl(3)=99.38(5), Cl(1)-Zr-Cl(3)=
87.21(4).
given in the caption. The central zirconium is coordinated
with two chlorides and two anionic η3-azaallyl ligands in a cis
mode. The two zirconacycles Zr-N-C-C are not sym-
metric. The dihedral angle between the planes N(1)-Zr-C-
(20) and N(3)-Zr-C(44) is 59.71°, while the angle between
N(1)-Zr-C(20) and N(1)-C(13)-C(20) is 47.03°, and as a
consequence the atom C(13) is out of the C(20)-Zr-N(1)
˚
plane (mean deviation 0.547 A). The dihedral angle of 28.01°
between N(1)-C(13)-C(20) and C(20)-Si-N(2) is smaller
˚
than that of 45.23° in 1d. The bond distances Zr-N=2.10 A
˚
and Zr-C=2.58 A and bond angles N-Zr-C=58.6° and
N-C-C = 115.5° are similar to the data for Zr({N(R)C-
(tBu)CH}2C6H4-2)Cl2,4 in which a bridged η3-azaallyl ligand
was observed.
The molecular structure of the compound (η3:η1-
(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2)ZrCl3 (3) is illus-
trated in Figure 4, with selected bond lengths and angles
given in the caption. As shown in the figure, the zirconium is
bonded to three chlorides and one bridged ligand acting as an
anionic η3-azaallyl with the pendant arm coordinated via
N(CH3)2. In the N-C-C-Si-N moiety, the bond angles
N(1)-C(13)-C(20), C(13)-C(20)-Si, and Si-C(20)-N(2)
are 116.4(4), 128.0(13), and 102.69(18)°, respectively.
N(1)-C(13)-C(20) exists in the η3-azaallyl form as a con-
˚
jugated system with N(1)-C(13)=1.378(5) A and C(20)-
˚
C(13) = 1.371(6) A. The Zr-N(1) bond distance in 3 is
(18) Chen, E.-Y.; Marks, T. J. Chem. Rev. 2000, 100, 1391.
(19) (a) Vollmerhaus, R.; Rahim, M.; Tomaszewski, R.; Xin, S.;
Taylor, N. J.; Collins, S. Organometallics 2000, 19, 2161. (b) Xie, G.;
Qian, C. J. Polym. Sci., A: Polym. Chem. 2008, 46, 211. (c) Kim, W. K.;
Fevola, M. J.; Liable-Sands, L. M.; Rheingold, A. L.; Theopold, K. H.
Organometallics 1998, 17, 4541.
slightly longer than that in a similar compound,4 while the
Zr-C bond distances are shorter than those of that similar
compound.4 The dihedral angle between C(20)-C(13)-N(1)
and C(20)-Zr-N(1) is 46.47°, and the distance of the atom

2136 Organometallics, Vol. 29, No. 9, 2010
Yuan et al.
Table 2. Ethylene Polymerization of the Compound 3a
Table 3. Ethylene and 1-Hexene Copolymerization of the
Compound 2/MAOa
P
T
acti-
Tm
Mw/
Mn
d
d
entry
cocat.
(atm) (°C) Al/Zr vityb (°C)c Mw
amt of
1-hexene
(mL)
1
2
3
4
5
6
7
8
Et2AlCl
AlEt3
MMAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
1
1
1
1
1
1
1
1
10
10
10
10
10
10
10
30
30
30
30
50
50
50
70
30
30
30
50
60
70
80
200 trace
200 trace
activityb Tm (°C)c
Mw
Mw/Mn
d
d
entry T (°C)
1000 0.12 135.3
1000 0.54 134.4
500 0.93 133.9
1000 1.35 132.6
1500 1.05 132.2
1000 0.65 132.1
500 0.41 136.4
1000 0.86 136.1
1500 0.46 133.8
1000 2.58 134.0 19.7
1000 2.96 133.9 65.8
1000 3.65 133.6 34.5
1000 1.72 133.5 27.8
1
2
3
4
5
6
7
30
30
30
50
60
70
80
4
6
8
6
6
6
6
4.24
5.68
4.08
6.24
7.76
8.96
6.48
133.1
132.7
131.3
129.1
127.9
127.4
126.8
19.3
23.6
11.5
18
24
36
11
11
8.4
6.3
3.23 41
4.49
3.86
3.03
1.90
9
6.20
4.49 11
3.86 20
6.6
10
11
12
13
14
15
a Conditions: catalyst, 5 μmol; time, 30 min; cocatalyst, MAO; Al/Zr,
1000; total volume, 100 mL of toluene for 10 atm. b In units of 104 g (mol
9.4
6.7
6.0
3.8
-1
of Zr)
determined by GPC.
h-1 atm-1 c Determined by DSC. d In units of 105 g mol-1
. ;
Table 4. Ethylene and 1-Hexene Copolymerization of the
Compound 3/MAOa
a Conditions: catalyst, 5 μmol; time, 30 min; cocatalyst, MAO; total
volume, 30 mL of toluene for 1 atm or 100 mL of toluene for 10 atm. b In
.
units of 105 g (mol of Zr)-1 h-1 atm-1 c Determined by DSC. d In units
amt of
1-hexene acti-
of 105 g mol-1; determined by GPC.
P
T
Tm
Mwd/
Mn
d
entry (atm) (°C) Al/Zr
(mL)
vityb (°C)c Mw
value of 1.35 ꢀ 105 g (mol of Zr)-1 h-1 atm-1 at 50 °C (entry
6 in Table 2), and the resultant polyethylene showed a Mw
value of 3.23 ꢀ 105 g mol-1. As shown by DSC analysis, the
resultant polyethylenes have only one melting point, indicat-
ing the monodisperse nature of the polymers. The melting
points decreased slightly with increasing reaction tempera-
tures (entries 4, 6, and 8 in Table 2) or the Al/Zr molar ratio
(entries 5-7 in Table 2). The PEs obtained at low ethylene
pressure showed broader molecular weight distributions.
With the ethylene pressure increased, the catalytic activity
generally improved and gave higher molecular weights.20,21
In the current system, the activity is greatly affected by the
ethylene pressure (cf. Table 2, entries 6 and 14). The poly-
ethylene obtained possessed melting temperatures in the
range of 132-136 °C, typical for high-density polyethylene
(HDPE). Higher reaction temperatures led to narrower mo-
lecular distributions, whereas increasing the Al/Zr molar ratio
led to broader molecular weight distributions. The broad
MWD indicated the existence of multiple active species; such
phenomena were observed in our previous work.19,22
2.4. Ethylene/1-Hexene Copolymerization. The results of
the copolymerization of ethylene/1-hexene by 2/MAO are
illustrated in Table 3. The ethylene pressure was 10 atm, while
the amount of 1-hexene was varied (entries 1-3 in Table 3).
There is a positive comonomer effect; higher activities were
generally observed in copolymerization (Table 3) than in the
homopolymerization of ethylene (Table 1). As was the case in
ethylene polymerizations, the optimum reaction tempera-
ture was 70 °C, with the highest activity for copolymerization
at ∼9 ꢀ 104 g (mol of Zr)-1 h-1 atm-1 (entry 6 in Table 3).
When the 1-hexene concentration and reaction temperature
were increased, the Tm and Mw values for the obtained
copolymers gradually decreased; however, the MWD values
increased with the concentration of 1-hexene but decreased
with elevating reaction temperature.
1
2
3
4
5
6
7
8
1
10
10
10
10
10
10
10
10
10
50
30
30
30
30
30
50
60
70
80
1000
500
6
6
5
6
7
6
6
6
6
6
0.24 126.6
0.72 132.3
0.65 130.9
0.89 132.0
0.59 132.8
0.54 131.9
1.72 129.2 15.4
2.86 128.5 16.8
3.25 127.4 27.7
3.40
2.87
4.85 11
4.28 13
6.15 36
7.6
5.6
1000
1000
1000
1500
1000
1000
1000
1000
11
10
7.6
6.4
9
10
1.68 126.6
8.82
a Conditions: catalyst, 5.0 μmol; time, 30 min; cocatalyst, MAO; total
volume, 30 mL of toluene for 1 atm or 100 mL of toluene for 10 atm. b In
units of 105 g (mol of Zr) -1 h-1 atm-1
.
c Determined by DSC. d In units
of 105 g mol-1; determined by GPC.
Similar trends of relationship of catalytic activity for the
3/MAO system and the nature of the resultant polymers were
observed on varying the reaction parameters, and the results
are tabulated in Table 4. The important feature of procata-
lyst 3 is its higher catalytic activity and better incorporation
of 1-hexene, which is confirmed by the lower melting points
(126-133 °C) compared with that of linear polyethylene.
High activities were maintained at elevated temperature
(entries 7-10, Table 4), a feature which is relevant to
industrial operation. The resultant polymers, however,
showed broader MWD values; the Mw values for the copo-
lymers indicated suitable for the applicable consideration.
13C NMR analysis of the resultant poly(ethylene-co-1-
hexene) revealed a typical 13C NMR spectrum of linear low-
density polyethylene (LLDPE).23 The 1-hexene incorpora-
tion reached 1.92 mol % using 2/MAO and 3.08 mol % using
3/MAO, and the representative 13C NMR spectra are shown
in the Supporting Information.
Procatalysts 2 and 3 both maintained their activities at
reaction temperature in the range 50-80 °C. A significant
difference in their catalytic performances was observed, with
procatalyst 3 possessing an activity about one order higher
than that observed for procatalyst 2. This behavior is
(20) Yang, X.; Zhang, Y.; Huang, J. J. Mol. Catal., A: Chem. 2006,
250, 145.
(21) Suzuki, N.; Masubuchi, Y.; Yamaguchi, Y.; Kase, T.; Miyamo-
to, T.; Horiuchi, A.; Mise, T. Macromolecules 2000, 33, 754.
(22) (a) Zuo, W. W.; Zhang, M.; Sun, W.-H. J. Polym. Sci., Part A:
Polym. Chem. 2009, 47, 357. (b) Hong, H.; Zhang, Z.; Chung, T. C.; Lee, R.
W. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 639. (c) Smit, M.;
Zheng, X.; Loos, J.; Chadwick, J. C.; Koning, C. E. J. Polym. Sci., Part A:
Polym. Chem. 2006, 44, 6652.
(23) (a) Yano, A.; Gasegawa, S.; Kaneko, T.; Sone, M.; Sato, M.;
Akimoto, A. Macromol. Chem. Phys. 1999, 200, 1542–1553. (b) Quijiada,
R.; Galland, G. B.; Mauler, R. S.; de Menezes, S. C. Macromol. Rapid
Commun. 1996, 17, 607. (c) Chu, K.-J.; Soares, J. B. P.; Penlidis, A.
Macromol. Chem. Phys. 2000, 201, 340. (d) Zhang, Y.; Yang, X.; Yu, Y.;
Qian, Y.; Huang, J. Chin. J. Chem. 2005, 23, 1081. (e) Czaja, K.; Bialek, M.
Polymer 2001, 42, 2289.

Article
Organometallics, Vol. 29, No. 9, 2010 2137
thought to be due to structural differences in the procata-
lysts; procatalyst 3 contains a ligand acting as η3:η1-(2,
6-iPr2C6H3)N(Ph)CCHSiMe2NMe2, reminiscent of con-
strained geometry.
4.2. Preparations of Ligands. 4.2.1. 2,6-Diisopropyl-N-(1-
phenylethylidene)benzenamine (PhMeCdN(2,6-iPr2C6H3), 1a).
According to the literature,24,25 the Schiff base 1a was recrys-
tallized from its ethanol solution and isolated as yellow crystals
(18.2 g, 65% yield). IR (KBr, cm-1): 1645 (νCdN). 1H NMR (300
MHz, CDCl3): δ 0.04 (d, 12H, CH3, 3JHH=6.9 Hz), 1.14-1.30
(s, 3H, CH3), 2.71 (sept, 2H, CH, 3JHH=6.9 Hz), 7.07-7.25 (m,
5H, Ph), 7.49-7.51 (s, 2H, aryl), 8.05-8.06 (s, 1H, aryl). 13C
NMR (75 MHz, CDCl3): δ 18.08 (CH3CPh), 22.96, 23.20
(CH(CH3)2), 28.16 (CH(CH3)2), 127.09, 128.38, 130.37, 136.05
(Ph), 122.90, 123.26, 139.05, 146.68 (aryl), 164.74 (CdN).
4.2.2. (K1-N-(1-Phenylvinyl)-2,6-diisopropylbenzenamido)magne-
3. Conclusion
The κ1-enamido azaallyl magnesium compound 1b and
lithium compound 1d were synthesized, and the two zirco-
nium compounds {η3-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2}2-
ZrCl2 (2) and {η3,η1-(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2}-
ZrCl3 (3) werepreparedbyemployingthesameligand, butacting
in different coordination modes. All metal compounds were stru-
cturally characterized by single-crystal X-ray diffraction. Pro-
catalysts 2 and 3 were both screened for ethylene polymerization
and copolymerization of ethylene with 1-hexene, producing
polymers with high molecular weights and broad molecular
distributions. These resultant polymers showed broader GPC
curves, and only one Tm value for every polymer sample was
observed. The procatalyst 3 showed 1 order higher activity than
did the procatalyst 2, thought to be due to the bridged ligand at
zirconium forming a constrained-geometry type catalyst. Work
on constrained-geometry compounds (CGC) has previously
focused on the bridged dianionic η5:η1 ligands and their IVB
metal complexes,12 whereas the current result has explored the
bridged monoanionic η3:η1-ligands and their IVB metal com-
plexes.
sium Bromide ((CH2)(Ph)C(2,6-iPr2C6H3)NMgBr 2THF, 1b).
3
LDA (0.21 g, 2 mmol) was added to a cold solution of 1a (0.56 g,
2 mmol) in 25 mL of THF, and the mixture was stirred for 3 h at
-78 °C. To the suspension was added MgBr2 (0.37 g, 2 mmol),
and this mixture was then warmed to room temperature for 5 h.
The resultant solution was concentrated in vacuo and washed
with hexane to give colorless crystals of 1b (1.03 g, 98% yield).
1
Mp: 182-183 °C dec. H NMR (300 MHz, C6D6): δ 1.11 (d,
3
12H, CH(CH3)2, JHH = 6.9 Hz), 2.62 (sept, 2H, CH(CH3)2,
3JHH=6.6Hz), 4.08-4.10(d, 2H, CH2, 3JHH=6.3 Hz), 7.23-7.30
(m, 5H, Ph), 7.38-7.41 (m, 3H, aryl). 13C NMR (75 MHz, C6D6):
δ 24.44, 26.57 (CH(CH3)2), 31.33 (CH(CH3)2), 96.45 (CH2),
126.12 (p-Ar), 130.29 (m-Ar), 131.45 (o-Ph), 133.76 (p-Ph),
134.05 (m-Ph), 138.66 (ipso-CPh), 139.12 (ipso-CAr), 141.77
(ipso-CAr-N), 168.39 (NdC). Found: C, 63.81; H, 7.68; N, 2.70.
Anal. Calcd for C39H40MgBrNO2: C, 63.83; H, 7.65; N, 2.66.
4.2.3. N-(2-((Dimethylamino)dimethylsilyl)-1-phenylvinyl)-
2,6-diisopropylbenzenamine (Me2NMe2SiCH2(Ph)CN(2,6-iPr2-
C6H3), 1c). To a solution of 1b (1.05 g, 2 mmol) in 25 mL of
THF at 0 °C, was transferred Me2NMe2SiCl (0.30 mL, 2 mmol)
dropwise to form a rose red solution; this color gradually
disappeared and changed to yellow. The mixture was then
warmed to room temperature and stirred for 12 h. The resulting
white residue was extracted with 50 mL of toluene, and removal
of the solvent under reduced pressure gave a yellow oil of 1c
(0.75 g, 97% yield). Attempts to purify the product by extraction
with hexanes were unsuccessful because of the high solubility of
the yellow oil in all these solvents. 1H NMR (300 MHz, CDCl3):
δ 0.01 (d, 6H, Si(CH3)2), 1.08 (s, 2H, CH2), 1.37 (sept, 12H,
4. Experimental Section
4.1. General Procedures. All manipulations were carried out
under an atmosphere of argon using standard Schlenk techni-
ques. Solvents were purchased from commercial sources. The
deuterated solvents C6D6 and CDCl3 were dried over activated
˚
molecular sieves (4 A) and vacuum-transferred before use.
Hexane was dried using sodium potassium alloy. Diethyl ether
was dried and distilled from sodium/benzophenone and stored
over a sodium mirror under argon. Dichloromethane was
˚
distilled from activated molecular sieves (4 A) or CaH2. Toluene
3
CH(CH3)2, JHH=6.9 Hz), 2.33-2.48 (d, 6H, N(CH3)2), 2.98
was refluxed in the presence of sodium/benzophenone and
distilled under nitrogen prior to use. Glassware was oven-dried
at 150 °C overnight. The NMR spectra were recorded on a
Bruker DKX-300 spectrometer with TMS as the internal stan-
dard. Elemental analyses were performed with a Flash EA 1112
microanalyzer. Polymerization grade ethylene was supplied by
Beijing Yansan Petrochemical Co. Et2AlCl (1.90 M in toluene)
and AlEt3 (2 M in hexane) were purchased from Acros Chemi-
cals, while methylaluminoxane (MAO, 1.46 M in toluene) and
modified methylaluminoxane (MMAO, 1.93 M in heptane)
were purchased from Akzo Nobel Corp. 13C NMR spectra of
the copolymers were recorded on a Bruker DMX 300 MHz
instrument at 135 °C in deuterated 1,2-dichlorobenzene with
TMS as an internal standard. The GPC curves were obtained by
plotting detector response versus elution volume using poly-
styrene standards (with an approximate polydispersity index).
Further fractionalization of fractions was not performed. Melt-
ing points of polyolefins were measured on a Perkin-Elmer
DSC-7 differential scanning calorimetry (DSC) analyzer. Under
a nitrogen atmosphere, a sample of about 2.0-6.0 mg was
heated from 50 to 160 °C at a rate of 10 °C/min and kept for
5 min at160 °C toremovethe thermalhistory andthencooled at a
rate of 10 °C/min to 50 °C. The DSC trace and the melting points
of the samples were obtained from the second scanning run.
3
(sept, 2H, CH(CH3)2, JHH=6.9 Hz), 7.22-7.30 (m, 5H, Ph),
7.59 (s, 2H, m-Ar), 8.03 (d, H, p-Ar).
4.2.4. LithiumK1-N-(2-((Dimethylamino)dimethylsilyl)-1-phenyl-
vinyl)-2,6-diisopropylbenzenamidate (Me2NMe2SiCH(Ph)C(2,6-iPr2-
C6H3)NLi 3THF, 1d). To a solution of 1c (0.76 g, 2 mmol) in
3
25 mL of THF at -78 °C was added LDA (0.22 g, 2 mmol) to
form a yellow solution; this color gradually disappeared and
changed to brown. The mixture was stirred for 2 h and then
warmedtoroomtemperatureand stirred for 12 h. A brightyellow
solid was obtained (0.76 g, 98% yield) by concentrating the THF
solution under a nitrogen atmosphere. Crystallization from
hexane and THF (4:1) afforded yellow crystals of 1d (1.17 g,
97% yield). 1H NMR (300 MHz, C6D6): δ -0.10-0.10 (d,
3
6H, Si(CH3)2), 0.67-0.71 (2 sept, 12 H, CH(CH3)2, JHH=5.7
Hz), 0.76-0.83 (q, 12H, 3THF), 2.25 (s, 6H, N(CH3)2), 2.80 (q,
3
12H, 3THF), 3.13 (d, H, CH, JHH =5.1 Hz), 3.33 (sept, 2H,
CH(CH3)2, 3JHH=6.9 Hz), 6.44-6.49 (q, 2H, o-Ph), 6.53-6.61
(m, 3H, m,p-Ph), 6.68 (s, 1H, p-Ar), 7.10-7.13 (m, 2H, m-Ar).
13C NMR (75 MHz, C6D6): δ -3.96 (Si(CH3)2), 23.85-24.58
i
i
(CH3, Pr), 26.03 (CH2, THF), 28.38-29.45 (CH, Pr), 38.86
(N(CH3)2), 68.43 (O-CH2, THF), 73.36 (CH), 121.34 (p-Ar),
123.51 (m-Ar), 126.57 (o-Ph), 127.44 (p-Ph), 129.37 (m-Ph),
143.09 (ipso-CPh), 146.35 (ipso-CAr), 152.14 (ipso-CAr-N),
172.90 (NdC). Found: C, 71.69; H, 9.83; N, 4.64. Anal. Calcd
for C36H59LiN2O3Si: C, 71.72; H, 9.86; N, 4.65.
(24) (a) Coleman, K. S.; Green, M. L. H.; Pascu, S. I.; Rees, N. H.;
Cowley, A. R.; Rees, L. H. Dalton Trans. 2001, 3384. (b) Pascu, S. I.;
Coleman, K. S.; Cowley, A. R.; Green, M. L. H.; Rees, N. H. New J. Chem.
2005, 29, 385.
(25) Okamoto, H.; Shozo, K.; Gasawara, M.; Konnai, M.; Takemat-
su, T. Agric. Biol. Chem. 1991, 55, 2733.

2138 Organometallics, Vol. 29, No. 9, 2010
Yuan et al.
4.3. Synthesis of Compounds 2 and 3. 4.3.1. Bis{η3-N-(2-
((dimethylamino)dimethylsilyl)-1-phenylvinyl)-2,6-diisopropyla-
nilido}zirconium Dichloride ({η3-(2,6-iPr2C6H3)N(Ph)CCHSi-
Me2NMe2}2ZrCl2, 2). To a solution of 1d (1.21 g, 2 mmol) in
25 mL of THF at -78 °C was added ZrCl4 (0.23 g, 1 mmol) to
form a rose-colored solution, and its color gradually changed to
yellow. The mixture was stirred for short time and then warmed
to room temperature and stirred for 24 h. Volatile compounds
were removed in vacuo, and the resulting residues were solvated
in 30 mL of CH2Cl2. The filtrate was concentrated and recrys-
tallized at -20 °C as colorless crystals of 2 (0.64 g, 69% yield).
the polymerization. The polymerization reaction was quenched
by adding 10% HCl-ethanol solution (60 mL), and then the
mixture was poured into 100 mL of ethanol to precipitate the
polymer, which was further washed with ethanol and water
followed by drying under vacuum at 60 °C to its constant weight.
In the case of ethylene/1-hexene copolymerization, 1-hexene
(dried with calcium hydride) solution in toluene was added prior
to the addition of MAO.
4.4.2. Polymerization under 10 atm of Ethylene. For polym-
erization at higher ethylene pressure, a stainless steel autoclave
(0.5 L capacity) equipped with gas ballast through a solenoid
clave for continuous feeding of ethylene at constant pressure
was used. The autoclave was heated under vacuum to over
80 °C, recharged with ethylene three times, and then cooled to
room temperature. A toluene solution of the catalysts (and
monomer) was transferred to the reactor, which was then
maintained at the desired temperature. MAO solution to give
a final volume of 100 mL was then added to start the polymer-
ization; then the autoclave was immediately pressurized to the
desired pressure. At the end of the reaction time the polymer-
ization reaction was stopped and the autoclave was placed in a
water-ice bath for 1 h when 10% HCl-acidic ethanol was
added. The solid polyolefin was washed with ethanol and water
several times and then dried under vacuum to constant weight.
4.5. X-ray Crystallography. Data collection of 1b,d, 2, and 3
1
Mp 159-161 °C dec. H NMR (300 MHz, CDCl3): δ 0.21 (s,
12H, Si(CH3)2), 0.84, 0.87, 1.03, 1.15 (4 sept, 24H, CH(CH3)2,
3JHH=6.6 Hz), 2.11 (s, 12H, N(CH3)2), 2.56, 2.89 (2 sept, 4H,
3
3
CH(CH3)2, JHH=6.9 Hz), 1.49, 4.09 (d, 2H, CH, JHH=6.9
Hz), 6.91 (q, 4H, o-Ph), 6.99-7.05 (m, 6H, m, p-Ph), 7.14 (m, 4H,
m-Ar), 7.33-7.45 (m, 2H, p-Ar). 13C NMR (75 MHz, CDCl3): δ
i
14.45 (Si(CH3)2), 22.79, 24.89, 28.79, 31.93 (CH3, Pr), 19.19
(CH, iPr), 38.68 (N(CH3)2), 69.27 (CH), 123.55, 125.36, 127.97
(Ar and Ph), 131.64 (ipso-CPh), 137.04, 147.54 (ipso-CAr).
Found: C, 62.60; H, 7.62; N, 6.12. Anal. Calcd for
C49H70Cl2N4Si2Zr: C, 62.57; H, 7.66; N, 6.08.
4.3.2. {η3:η1-N-(2-((Dimethylamino)dimethylsilyl)-1-phenyl-
vinyl)-2,6-diisopropylanilido}zirconium Trichloride [({η3:η1-
(2,6-iPr2C6H3)N(Ph)CCHSiMe2NMe2}ZrCl3, 3). Using the
same procedure as for 2 but with equimolar reactants of lithium
and zirconium, the resultant residue was extracted with dichlor-
omethane and the extract filtered. The filtrate was concentrated
in vacuo and dissolved in a mixture of CH2Cl2 and THF (3:1) at
-20 °C to give compound 3 as yellow crystals (1.01 g, 87%
˚
was performed with Mo KR radiation (λ = 0.710 73 A) on a
Bruker Smart Apex CCD diffractometer at 223(2) K. Crystals
were coated in oil and then directly mounted on the diffract-
ometer under a stream of cold nitrogen gas. A total of N
reflections were collected by using ω scan mode. Intensities were
corrected for Lorentz and polarization effects and empirical
absorption. The structures were solved by direct methods and
refined by full-matrix least-squares on F2. All non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were
placed in calculated positions. Structure solution and refine-
ment were performed by using the SHELXL-97 package.26
Crystal data collection and refinement details for all compounds
are available in the Supporting Information.
1
yield). Mp: 167-169 °C dec. H NMR (300 MHz ,C6D6): δ
-0.02 to þ0.03, 0.31-0.36 (q, 6H, Si(CH3)2), 0.56, 0.93, 1.29,
3
1.70 (4 sept, 12H, CH(CH3)2, JHH = 7.2 Hz), 2.26 (d, 6H,
N(CH3)2, 3JHH=11.1 Hz), 3.79 (sept, 2H, CH(CH3)2, 3JHH=6.9
Hz), 4.54 (s, H, CH), 6.84-6.99 (m, 5H, Ph), 7.34-7.37 (m, 3H,
aryl). 13C NMR (75 MHz, C6D6): δ -1.36, -0.48 (Si(CH3)2),
21.30, 22.54, 24.21, 25.96 (CH(CH3)2), 35.54 (CH(CH3)2),
40.33, 42.95 (N(CH3)2), 80.88 (CH), 93.50, 121.57, 123.02,
124.17, 129.79 (aryl and Ph), 132.50 (ipso-CPh), 134.35, 138.00,
140.90 (ipso-CAryl), 173.84 (NCC). Found: C, 49.91; H, 6.09; N,
4.83. Anal. Calcd for C24H35Cl3N2SiZr: C, 49.94; H, 6.11; N,
4.85.
Acknowledgment. We thank the Natural Science
Foundation of China (Nos. 20772074 and 20702029).
Supporting Information Available: Figures giving 13C NMR
spectra for poly(ethylene-co-1-hexene) and a table and CIF files
giving crystal data and processing parameters and crystallo-
graphic data for compounds 1b,d, 2, and 3. This material is
available free of charge via the Internet at http://pubs.acs.org.
4.4. Procedures for Ethylene Polymerization. 4.4.1. Poly-
merization under 1 atm of Ethylene. The compound (5 μmol)
was added to a Schlenk type flask under nitrogen. This flask was
back-filled three times with nitrogen and twice with ethylene and
then charged with the required amount of freshly distilled
toluene. At the stipulated temperature the reaction solution
was vigorously stirred under 1 atm of ethylene for the desired
period of time, after which the MAO solution was added to start
(26) Sheldrick, G. M. Program for the Solution of Crystal Structures;
€
€
University of Gottingen: Gottingen, Germany, 1997.