Synthesis and catalytic applications of C1 symmetric group 4 ansa-metallocene complexes

Article abstract of DOI:10.1016/j.molcata.2006.09.011

The group 4 ansa-metallocene complexes with chiral substituent bearing cyclopentadienyl ligands, [M{Me₂Si(η⁵-C₅Me₄)(η ⁵-C₅H₃{CHRR′})}Cl₂] (R = Prⁱ, R′ = Me (9); R = Prⁱ, R′ = Ph (10); R = Bu^t, R′ = Me (11); R = Bu^t, R′ = Ph (12); M = Zr (a), Hf (b)), were synthesized by the reaction of the dilithium compounds, Li₂{Me₂Si(C₅Me₄)(C₅ H₃{CHRR′})} (R = Prⁱ, R′ = Me (5); R = Prⁱ, R′ = Ph (6); R = Bu^t, R′ = Me (7); R = Bu^t, R′ = Ph (8)), with the tetrachloride salts of the transition metal. The molecular structures of 11a and 12a have been determined by single-crystal X-ray diffraction studies. The catalytic behaviour of 9-12 in the polymerization of ethylene and propylene has been studied. Isotactic polypropylene with [mmmm] pentads of the order of 60% were obtained with the C₁ symmetric ansa-zirconocene catalysts.

Full text of DOI:10.1016/j.molcata.2006.09.011

Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
Synthesis and catalytic applications of C1 symmetric group
4 ansa-metallocene complexes
a
a,∗
a
a
´
´
´
Santiago Gomez-Ruiz , Sanjiv Prashar , Luis F. Sanchez-Barba , Dorian Polo-Ceron ,
a
b
b,∗∗
˜
Mariano Fajardo , Antonio Antinolo , Antonio Otero ,
c
d
´
Miguel A. Maestro , Cesar J. Pastor
a Departamento de Qu´ımica Inorga´nica y Anal´ıtica, E.S.C.E.T., Universidad Rey Juan Carlos, 28933 Mo´stoles, Madrid, Spain
b Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica, Universidad de Castilla-La Mancha, Facultad de Qu´ımicas,
Campus Universitario, 13071 Ciudad Real, Spain
c Departamento de Qu´ımica Fundamental, Facultade de Ciencias, Campus da Zapateira, Universidade da Corun˜a, 15071 A Corun˜a, Spain
d Servicio Interdepartamental de Investigacio´n, Universidad Auto´noma de Madrid, Cantoblanco, 28049 Madrid, Spain
Received 5 July 2006; received in revised form 5 September 2006; accepted 7 September 2006
Available online 14 September 2006
Abstract
The group
4
ansa-metallocene complexes with chiral substituent bearing cyclopentadienyl ligands, [M{Me2Si(␩5-C5Me4)(␩5-
C5H3{CHRRꢀ})}Cl2] (R = Pri, Rꢀ = Me (9); R = Pri, Rꢀ = Ph (10); R = But, Rꢀ = Me (11); R = But, Rꢀ = Ph (12); M = Zr (a), Hf (b)), were synthesized
by the reaction of the dilithium compounds, Li2{Me2Si(C5Me4)(C5H3{CHRRꢀ})} (R = Pri, Rꢀ = Me (5); R = Pri, Rꢀ = Ph (6); R = But, Rꢀ = Me
(7); R = But, Rꢀ = Ph (8)), with the tetrachloride salts of the transition metal. The molecular structures of 11a and 12a have been determined by
single-crystal X-ray diffraction studies. The catalytic behaviour of 9–12 in the polymerization of ethylene and propylene has been studied. Isotactic
polypropylene with [mmmm] pentads of the order of 60% were obtained with the C1 symmetric ansa-zirconocene catalysts.
© 2006 Elsevier B.V. All rights reserved.
Keywords: ansa-Zirconocene complexes; Homogeneous catalysis; Polymerization; Ethylene; Propylene
1. Introduction
elective (although to a lesser degree than their C2 symmetric
analogues) in the polymerization of propylene [8,9].
As part of our ongoing studies in the design of olefin polymer-
ization catalysts [10–20] we present in this paper the synthesis
and characterization of new ansa-metallocene complexes of
zirconium and hafnium with C1 symmetry and their catalytic
activity and selectivity in the polymerization of ethylene and
propylene.
There is no doubt in the great interest in group 4 metallocene
complexes due to their catalytic applications in the polymeriza-
tion of olefins [1–3]. It is well established that the structural
make-up of the catalyst directly influences the physical proper-
ties of the polymer [4]. Thus small variations in the metallocene
complex should cause notable effects in the polymer produced.
The design of new metallocene catalysts tailored to produce spe-
cific polymers is therefore of upmost importance [5].
2. Experimental
Rigid ansa-metallocene systems have been widely used as
olefin polymerization catalysts and generally offer better cat-
alytic activity and selectivity than their non-ansa counterparts
[6,7]. ansa-Catalysts with C1 symmetry have shown to be isos-
2.1. General procedures
All reactions were performed using standard Schlenk tube
techniques in an atmosphere of dry nitrogen. Solvents were dis-
tilled from the appropriate drying agents and degassed before
use.
∗
∗∗
Corresponding author. Tel.: +34 914887186; fax: +34 914888143.
Corresponding author. Tel.: +34 926295326; fax: +34 926295318.
Me2Si(C5Me4H)Cl, LiBun (1.6 M in hexane), MAO, ZrCl4,
and HfCl4, were purchased from Aldrich and used directly.
E-mail address: sanjiv.prashar@urjc.es (S. Prashar).
1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2006.09.011

S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
261
[M+ − C5H4CHButMe]. Anal. Calc. for C22H36Si: C, 80.41; H,
Li{C5H4(CHRRꢀ)} (R = Pri, But; Rꢀ = Me, Ph) were prepared
11.04. Found C, 80.14; H, 11.04%.
as previously reported [21].
1
1H and 13C{ H} NMR spectra were recorded on a Varian
2.2.4. Me2Si(C5Me4H)(C5H4{CHButPh}) (4)
Mercury FT-400 spectrometer. Microanalyses were carried out
with a Perkin-Elmer 2400 or LECO CHNS-932 microanalyzer.
Mass spectroscopic analyses were preformed on a Hewlett-
Packard 5988A (m/z 50–1000) instrument. Polymer molecular
weights and distribution were determined by GPC (Waters 150C
Plus) in 1,2,4-trichlorobenzene at 145 ◦C. Polymer isotacticity
was calculated from 13C NMR spectra of polymer samples dis-
solved in 1,2,4-trichlorobenzene and C6D6 (1:1).
The synthesis of 4 was carried out in an identical
manner to 1. Me2Si(C5Me4H)Cl (1.97 g, 9.16 mmol) and
Li{C5H4(CHButPh)} (2.00 g, 9.16 mmol). Yield 3.11 g, 87%.
1H NMR (400 MHz, CDCl3; for the predominant isomer):
δ −0.07 (s, 6H, SiMe2), 1.03 (s, 9H, But), 1.90 (6H), 2.01
(6H) (s, C5Me4), 2.97 (1H), 3.25 (1H) (m, HC5), 3.65 (s,
1H, CHButPh), 6.17 (1H), 6.30 (1H), 6.69 (1H) (m, C5H3),
7.19 (2H), 7.28 (2H), 7.43 (1H) (m, Ph). MS electron
impact (m/e (relative intensity)): 390 (10) [M+], 269 (41)
[M+ − C5HMe4], 179 (77) [M+ − C5H4CHButPh], 135 (100)
[M+ − Ph, –Me2Si(C5HMe4)]. Anal. Calc. for C21H34Si: C,
83.01; H, 9.80. Found C, 82.78; H, 9.76%.
2.2. Preparation of compounds
2.2.1. Me2Si(C5Me4H)(C5H4{CHPriMe}) (1)
Me2Si(C5Me4H)Cl (3.03 g, 14.07 mmol) in THF (50 mL)
was added to a solution of Li{C5H4(CHPriMe)} (2.00 g,
14.07 mmol) in THF (50 mL) at −78 ◦C. The reaction mixture
was allowed to warm to room temperature and stirred for 15 h.
Solvent was removed in vacuo and hexane (150 mL) was added
to the resulting dark orange oil. The mixture was filtered and sol-
vent removed from the filtrate under reduced pressure to yield
2.2.5. Li2{Me2Si(C5Me4)(C5H3{CHPriMe})} (5)
LiBun (1.6 M in hexane) (11.9 mL, 19.08 mmol) was added
dropwise to a solution of 1 (3.00 g, 9.54 mmol) in Et2O (100 mL)
at −78 ◦C. The mixture was allowed to warm to 25 ◦C and stirred
for 15 h. Solvent was removed in vacuo to give a white solid
which was washed with hexane (2× 50 mL) and dried under
vacuum to yield a white solid of the title complex (2.83 g, 91%).
1H NMR (400 MHz, d8-THF): δ 0.44 (s, 6H, SiMe2), 0.82 (d,
6H, CHMe2), 1.09 (d, 3H, CMe), 1.67 (m, 1H, CHMe2), 1.87
(6H), 2.07 (6H) (s, C5Me4), 2.45 (m, 1H, CHPriMe), 5.59 (1H),
1
the title compound as an orange oil (3.94 g, 89%). H NMR
(400 MHz, CDCl3; for the predominant isomer): δ −0.12 (s,
6H, SiMe2), 0.87 (3H), 0.89 (3H) (d, CHMe2), 1.11 (d, 3H,
CMe), 1.75 (m, 1H, CHPriMe), 1.87 (6H), 2.01 (6H) (s, C5Me4),
2.94 (1H), 3.22 (1H) (m, HC5), 5.93 (1H), 6.16 (1H), 6.50 (1H)
(m, C5H3). MS electron impact (m/e (relative intensity)): 314
(25) [M+], 253 (11) [M+ − Pri, –Me], 193 (80) [M+ − C5HMe4],
179 (100) [M+ − C5H4CHPriMe]. Anal. Calc. for C21H34Si: C,
80.18; H, 10.89. Found C, 79.97; H, 10.85%.
1
5.76 (2H) (m, C5H3). 13C{ H} NMR (100 MHz, d8-THF): δ
3.4, 3.7 (SiMe2), 10.9, 11.1, 13.8, 14.1 (C5Me4), 18.9 (CMe),
19.7, 21.0, 35.4 (Pri), 41.1 (CpC), 100.7, 101.0, 111.6, 113.1,
123.9 (C5Me4), 104.0, 108.9, 111.1, 115.4, 127.1 (C5H4). Anal.
Calc. for C21H32Li2Si: C, 77.26; H, 9.88. Found C, 76.92;
H, 9.90%.
2.2.2. Me2Si(C5Me4H)(C5H4{CHPriPh}) (2)
The synthesis of 2 was carried out in an identical
manner to 1. Me2Si(C5Me4H)Cl (2.11 g, 9.79 mmol) and
Li{C5H4(CHPriPh)}(2.00 g, 9.79 mmol). Yield3.54 g, 96%. 1H
NMR (400 MHz, CDCl3; for the predominant isomer): δ 0.23
(s, 6H, SiMe2), 0.92 (3H), 1.11 (3H) (d, CHMe2), 1.98 (6H),
2.10 (6H) (s, C5Me4), 2.41 (m, 1H, CHMe2), 3.05 (1H), 3.27
(1H) (m, HC5), 3.45 (d, 1H, CHPriMe), 6.17 (1H), 6.40 (1H),
6.63 (1H) (m, C5H3), 7.25 (2H), 7.32 (2H), 7.39 (1H) (m, Ph).
MS electron impact (m/e (relative intensity)): 376 (10) [M+], 253
(41) [M+ − Pri, –Ph], 179 (58) [M+ − C5H4CHPriPh], 135 (100)
[M+ − Me2Si(C5HMe4)(C5H3)]. Anal. Calc. for C26H36Si: C,
82.91; H, 9.63. Found C, 82.67; H, 9.55%.
2.2.6. Li2{Me2Si(C5Me4)(C5H3{CHPriPh})} (6)
The preparation of 6 was carried out in an identical manner to
5. 2 (3.00 g, 7.96 mmol) and LiBun (1.6 M in hexane) (10.0 mL,
15.92 mmol). Yield 2.97 g, 96%. 1H NMR (400 MHz, d8-THF):
δ 0.40 (s, 6H, SiMe2), 0.71 (3H), 0.90 (3H) (d, CHMe2), 2.20
(m, 1H, CHMe2), 1.89 (6H), 2.05 (6H) (s, C5Me4), 3.31 (d,
1H, CHPriPh), 5.74 (1H), 5.80 (1H), 5.83 (1H) (m, C5H3), 6.97
1
(1H), 7.10 (2H), 7.27 (2H) (m, Ph). 13C{ H} NMR (100 MHz,
d8-THF): δ 4.0, 4.3 (SiMe2), 10.9, 11.0, 13.9, 14.2 (C5Me4),
22.0, 22.6, 34.9 (Pri), 56.8 (CpC), 101.4, 102.2, 110.9, 111.6,
122.9 (C5Me4), 104.1, 110.3, 110.6, 115.6, 125.4 (C5H4), 124.4,
127.6, 128.3, 149.9 (Ph). Anal. Calc. for C26H34Li2Si: C, 80.38;
H, 8.82. Found C, 80.05; H, 8.90%.
2.2.3. Me2Si(C5Me4H)(C5H4{CHButMe}) (3)
The synthesis of 3 was carried out in an identical
manner to 1. Me2Si(C5Me4H)Cl (2.76 g, 12.80 mmol) and
Li{C5H4(CHButMe)} (2.00 g, 12.80 mmol). Yield 3.87 g, 93%.
1H NMR (400 MHz, CDCl3; for the predominant isomer): δ
−0.14 (s, 6H, SiMe2), 0.90 (s, 9H, But), 1.13 (d, 3H, CMe), 1.87
(6H), 2.01 (6H) (s, C5Me4), 2.42 (q, 1H, CHButMe), 2.92 (1H),
3.20 (1H) (m, HC5), 5.97 (1H), 6.23 (1H), 6.47 (1H) (m, C5H3).
MS electron impact (m/e (relative intensity)): 328 (24) [M+],
253 (22) [M+ − But, –Me], 207 (90) [M+ − C5HMe4], 179 (79)
2.2.7. Li2{Me2Si(C5Me4)(C5H3{CHButMe})} (7)
The preparation of 7 was carried out in an identical manner to
5. 3 (3.00 g, 9.13 mmol) and LiBun (1.6 M in hexane) (11.4 mL,
18.26 mmol). Yield 3.01 g, 97%. 1H NMR (400 MHz, d8-THF):
δ 0.40 (3H), 0.41 (3H) (s, SiMe2), 0.84 (s, 9H, But), 1.15 (d, 3H,
CMe), 1.87 (6H), 2.05 (6H) (s, C5Me4), 2.42 (q, 1H, CHButMe),
1
5.60 (1H), 5.74 (2H) (m, C5H3). 13C{ H} NMR (100 MHz, d8-
THF): δ 3.7, 4.3 (SiMe2), 10.9, 11.0, 13.8, 14.1 (C5Me4), 18.1

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(CMe), 28.3, 33.9 (But), 45.5 (CpC), 100.3, 102.6, 111.6, 115.6,
122.6 (C5Me4), 105.4, 108.9, 110.9, 116.1, 125.3 (C5H4). Anal.
Calc. for C22H34Li2Si: C, 77.61; H, 10.07. Found C, 77.32; H,
10.15%.
(8) [M+], 519 (18) [M+ − Pri], 483 (100) [M+ − Pri, –Cl]. Anal.
Calc. for C21H32Cl2SiHf: C, 44.48; H, 5.74. Found C, 44.60;
H, 5.70%.
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.84 (3H),
0.87 (3H) (s, SiMe2), 0.98 (3H), 1.05 (3H) (d, CHMe2), 1.24
(d, 3H, CMe), 1.80 (m, 1H, CHMe2), 2.00 (3H), 2.03 (3H),
2.08 (3H), 2.11 (3H) (s, C5Me4), 3.12 (d, 1H, CHPriMe),
2.2.8. Li2{Me2Si(C5Me4)(C5H3{CHButPh})} (8)
The preparation of 8 was carried out in an identical man-
ner to 5. 4 (3.00 g, 7.68 mmol) and LiBun (1.6 M in hexane)
(9.6 mL, 15.36 mmol). Yield 2.87 g, 93%. 1H NMR (400 MHz,
d8-THF): δ 0.38 (3H), 0.40 (3H) (s, SiMe2), 0.91 (s, 9H, But),
1.89 (6H), 2.04 (6H) (s, C5Me4), 3.64 (m, 1H, CHButPh), 5.83
(1H), 5.88 (1H), 5.94 (1H) (m, C5H3), 7.00 (1H), 7.12 (2H),
1
5.34 (1H), 5.67 (1H), 6.60 (1H) (m, C5H3). 13C{ H} NMR
(100 MHz, CDCl3): δ −0.3, 0.2 (SiMe2), 12.0, 12.4, 14.0, 14.6
(C5Me4), 12.6 (CMe), 17.3, 21.1, 33.8 (Pri), 38.7 (CpC), 98.5,
106.2 (C1–Cp), 108.3, 112.7, 121.7, 147.6 (C5H3), 124.1, 125.6,
132.0, 134.9 (C5Me4).
1
1
7.47 (2H) (m, Ph). 13C{ H} NMR (100 MHz, d8-THF): δ 3.9,
Second isomer. H NMR (400 MHz, CDCl3): δ 0.81 (3H),
4.7 (SiMe2), 11.0, 11.1, 13.9, 14.2 (C5Me4), 27.4, 29.2 (But),
35.2 (CpC), 101.2, 104.5, 111.6, 115.8, 124.4 (C5Me4), 106.0,
110.8, 113.7, 123.7, 124.5 (C5H4), 120.4, 126.9, 130.2, 147.9
(Ph). Anal. Calc. for C27H36Li2Si: C, 80.56; H, 9.01. Found C,
81.00; H, 9.04%.
0.88 (3H) (s, SiMe2), 0.75 (3H), 0.89 (3H) (d, CHMe2), 0.70
(d, 3H, CMe), 1.81 (m, 1H, CHMe2), 1.96 (3H), 2.06 (3H),
2.07 (3H), 2.12 (3H) (s, C5Me4), 3.00 (d, 1H, CHPriMe),
1
5.28 (1H), 5.60 (1H), 6.68 (1H) (m, C5H3). 13C{ H} NMR
(100 MHz, CDCl3): δ −0.2, 0.3 (SiMe2), 12.2, 13.9, 14.9, 15.0
(C5Me4), 12.4 (CMe), 20.3, 25.0, 34.7 (Pri), 39.6 (CpC), 98.3,
106.9 (C1–Cp), 108.2, 108.9, 110.5, 143.3 (C5H3), 120.6, 123.1,
132.7, 134.4 (C5Me4).
2.2.9. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHPriMe})}Cl2]
(9a)
THF (50 mL) was added to a solid mixture of ZrCl4 (0.71 g,
3.06 mmol) and Li2{Me2Si(C5Me4)(C5H3{CHPriMe})} (5)
(1.00 g, 3.06 mmol). The resulting solution was stirred for 15 h.
Solvent was removed in vacuo and toluene (75 mL) added to the
resulting solid. The mixture was filtered and the filtrate concen-
trated (10 mL) and cooled to −30 ◦C to yield crystals of the title
complex (0.72 g, 50%). MS electron impact (m/e (relative inten-
sity)): 475 (100) [M+], 407 (19) [M+ − Cl, –2× Me], 389 (55)
[M+ − Me, –2× Cl]. Anal. Calc. for C21H32Cl2SiZr: C, 53.13;
H, 6.79. Found C, 53.45; H, 6.81%.
2.2.11. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHPriPh})}Cl2]
(10a)
The preparation of 10a was carried out in an identi-
cal manner to 9a. ZrCl4 (0.60 g, 2.57 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHPriPh})} (6) (1.00 g, 2.57 mmol). Yield
0.73 g, 53%. MS electron impact (m/e (relative intensity)): 536
(7) [M+], 493 (100) [M+ − Pri], 455 (13) [M+ − Pri, –Cl], 365
(7) [M+ − CHPriPh]. Anal. Calc. for C26H34Cl2SiZr: C, 58.18;
H, 6.38. Found C, 58.01; H, 6.41%.
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.70 (3H),
0.86 (3H) (s, SiMe2), 0.80 (3H), 1.13 (3H) (d, CHMe2), 2.49
(m, 1H, CHMe2), 1.80 (3H), 2.00 (3H), 2.09 (3H), 2.12 (3H)
(s, C5Me4), 4.29 (d, 1H, CHPriPh), 5.04 (1H), 5.72 (1H), 6.99
(1H) (m, C5H3), 7.19 (2H), 7.24 (2H), 7.28 (1H) (m, Ph).
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.82 (3H),
0.89 (3H) (s, SiMe2), 0.99 (3H), 1.06 (3H) (d, CHMe2), 1.28
(d, 3H, CMe), 1.80 (m, 1H, CHMe2), 1.92 (3H), 1.96 (3H),
2.06 (3H), 2.08 (3H) (s, C5Me4), 2.99 (d, 1H, CHPriMe),
1
5.37 (1H), 5.72 (1H), 6.70 (1H) (m, C5H3). 13C{ H} NMR
13C{ H} NMR (100 MHz, CDCl3): δ −0.2, 0.0 (SiMe2), 12.4,
1
(100 MHz, CDCl3): δ −0.4, 0.2 (SiMe2), 12.2, 12.4, 14.9, 15.1
(C5Me4), 12.6 (CMe), 17.1, 21.0, 33.6 (Pri), 39.6 (CpC), 96.9,
104.5 (C1–Cp), 110.8, 115.0, 123.0, 149.0 (C5H3), 126.4, 127.0,
134.0, 136.5 (C5Me4).
12.5, 22.7, 22.8 (C5Me4), 15.1, 19.6, 31.3 (Pri), 51.7 (CpC),
96.7, 105.7 (C1–Cp), 112.0, 113.5, 124.8, 128.1 (C5H3), 135.4,
135.7, 142.7, 144.9 (C5Me4), 125.9, 127.6, 129.8, 140.9 (Ph).
1
1
Second isomer. H NMR (400 MHz, CDCl3): δ 0.88 (3H),
Second isomer. H NMR (400 MHz, CDCl3): δ 0.82 (3H),
0.89 (3H) (s, SiMe2), 0.83 (3H), 0.97 (3H) (d, CHMe2), 2.31
(m, 1H, CHMe2), 1.95 (3H), 1.96 (3H), 2.02 (3H), 2.11 (3H)
(s, C5Me4), 4.25 (d, 1H, CHPriPh), 5.55 (1H), 5.61 (1H), 6.48
(1H) (m, C5H3), 7.00 (2H), 7.22 (2H), 7.26 (1H) (m, Ph).
0.87 (3H) (s, SiMe2), 0.72 (3H), 0.79 (3H) (d, CHMe2), 0.91
(d, 3H, CMe), 1.82 (m, 1H, CHMe2), 1.91 (3H), 1.94 (3H),
2.04 (3H), 2.06 (3H) (s, C5Me4), 3.09 (d, 1H, CHPriMe),
1
5.39 (1H), 5.75 (1H), 6.67 (1H) (m, C5H3). 13C{ H} NMR
1
13C{ H} NMR (100 MHz, CDCl3): δ −0.3, 0.1 (SiMe2), 14.4,
(100 MHz, CDCl3): δ −0.4, 0.1 (SiMe2), 12.0, 12.1, 14.8, 15.0
(C5Me4), 12.3 (CMe), 18.7, 21.0, 34.5 (Pri), 38.7 (CpC), 96.7,
104.4 (C1–Cp), 111.7, 114.9, 123.8, 136.4 (C5H3), 123.0, 126.3,
126.9, 134.0 (C5Me4).
14.5, 19.6, 19.7 (C5Me4), 15.0, 19.7, 32.4 (Pri), 52.0 (CpC),
96.8, 104.6 (C1–Cp), 112.1, 113.4, 124.7, 126.0 (C5H3), 135.1,
135.6, 141.0, 144.2 (C5Me4), 125.8, 127.4, 130.3, 140.9 (Ph).
2.2.10. [Hf{Me2Si(η5-C5Me4)(η5-C5H3{CHPriMe})}Cl2]
(9b)
2.2.12. [Hf{Me2Si(η5-C5Me4)(η5-C5H3{CHPriPh})}Cl2]
(10b)
The synthesis of 9b was carried out in an identical
manner to 9a. HfCl4 (0.98 g, 3.06 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHPriMe})} (5) (1.00 g, 3.06 mmol). Yield
0.68 g, 38%. MS electron impact (m/e (relative intensity)): 562
The preparation of 10b was carried out in an identi-
cal manner to 9a. HfCl4 (0.82 g, 2.57 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHPriPh})} (6) (1.00 g, 2.57 mmol). Yield
0.69 g, 44%. MS electron impact (m/e (relative intensity)):

S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
263
624 (3) [M+], 581 (17) [M+ − Pri], 547 (4) [M+ − Ph],
155 (60) [M+ − Pri, –Me2Si(C5Me4)HfCl2]. Anal. Calc. for
C26H34Cl2SiHf: C, 50.04; H, 5.49. Found C, 49.84; H, 5.45%.
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.70 (3H),
0.86 (3H) (s, SiMe2), 0.80 (3H), 1.12 (3H) (d, CHMe2), 2.47
(m, 1H, CHMe2), 1.87 (3H), 2.08 (3H), 2.12 (3H), 2.15 (3H) (s,
C5Me4), 4.34 (d, 1H, CHPriPh), 5.00 (1H), 5.68 (1H), 7.01 (1H)
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.80 (3H),
0.90 (3H) (s, SiMe2), 0.87 (s, 9H, But), 1.12 (d, 3H, CMe),
2.03 (3H), 2.08 (3H), 2.09 (3H), 2.10 (3H) (s, C5Me4), 2.79
(q, 1H, CHButMe), 5.43 (1H), 5.72 (1H), 6.52 (1H) (m, C5H3).
1
13C{ H} NMR (100 MHz, CDCl3): δ −0.8, −0.6 (SiMe2), 12.2,
14.0, 16.2, 17.4 (C5Me4), 13.3 (CMe), 33.4, 34.5 (But), 39.7
(CpC), 96.4, 102.6 (C1–Cp), 113.9, 120.1, 128.2, 154.7 (C5H3),
133.8, 133.9, 140.3, 144.8 (C5Me4).
1
(m, C5H3), 7.19 (2H), 7.24 (2H), 7.26 (1H) (m, Ph). 13C{ H}
1
NMR (100 MHz, CDCl3): δ −0.3, −0.1 (SiMe2), 12.2, 12.3,
22.0, 22.8 (C5Me4), 14.8, 19.5, 31.3 (Pri), 51.6 (CpC), 98.3,
107.8 (C1–Cp), 109.4, 111.1, 121.8, 122.3 (C5H3), 133.6, 133.7,
142.6, 143.3 (C5Me4), 125.8, 127.5, 129.8, 141.0 (Ph).
Second isomer. H NMR (400 MHz, CDCl3): δ 0.88 (3H),
0.92 (3H) (s, SiMe2), 0.84 (s, 9H, But), 1.20 (d, 3H, CMe),
2.03 (3H), 2.06 (3H), 2.07 (3H), 2.12 (3H) (s, C5Me4), 2.78 (q,
1H, CHButMe), 5.27 (1H), 5.59 (1H), 6.68 (1H) (m, C5H3).
1
1
Second isomer. H NMR (400 MHz, CDCl3): δ 0.89 (3H),
13C{ H} NMR (100 MHz, CDCl3): δ −0.7, 0.2 (SiMe2), 11.5,
0.93 (3H) (s, SiMe2), 0.83 (3H), 0.97 (3H) (d, CHMe2), 2.31
(m, 1H, CHMe2), 2.03 (3H), 2.04 (3H), 2.14 (3H), 2.16 (3H)
(s, C5Me4), 4.32 (d, 1H, CHPriPh), 5.57 (1H), 5.60 (1H), 6.40
(1H) (m, C5H3), 6.99 (2H), 7.23 (2H), 7.28 (1H) (m, Ph).
14.2, 16.4, 17.8 (C5Me4), 13.6 (CMe), 33.3, 34.3 (But), 40.5
(CpC), 99.8, 110.1 (C1–Cp), 115.1, 116.5, 128.4, 149.3 (C5H3),
131.8, 135.8, 141.6, 144.3 (C5Me4).
2.2.15. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHButPh})}Cl2]
(12a)
1
13C{ H} NMR (100 MHz, CDCl3): δ −0.2, 0.0 (SiMe2), 14.6,
14.8, 21.7, 21.9 (C5Me4), 14.7, 19.0, 32.5 (Pri), 52.0 (CpC),
98.5, 106.4 (C1–Cp), 110.0, 111.2, 121.7, 122.7 (C5H3), 128.0,
133.3, 133.8, 142.5 (C5Me4), 126.0, 127.4, 130.3, 141.0 (Ph).
The preparation of 12a was carried out in an identi-
cal manner to 9a. ZrCl4 (0.57 g, 2.44 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHButPh})} (8) (1.00 g, 2.44 mmol). Yield
0.52 g, 39%. MS electron impact (m/e (relative intensity)): 550
(4) [M+], 493 (100) [M+ − But], 455 (20) [M+ − But, –Ph]. Anal.
Calc. for C27H36Cl2SiZr: C, 58.88; H, 6.59. Found C, 58.21; H,
6.51%.
2.2.13. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHButMe})}Cl2]
(11a)
The synthesis of 11a was carried out in an identi-
cal manner to 9a. ZrCl4 (0.68 g, 2.94 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHButMe})} (7) (1.00 g, 2.94 mmol). Yield
0.80 g, 55%. MS electron impact (m/e (relative intensity)): 488
(6) [M+], 429 (27) [M+ − But], 393 (100) [M+ − But, –Cl]. Anal.
Calc. for C22H34Cl2SiZr: C, 54.07; H, 7.01. Found C, 54.33; H,
7.06%.
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.67 (3H),
0.84 (3H) (s, SiMe2), 1.12 (s, 9H, But), 1.72 (3H), 1.99 (3H),
2.08 (3H), 2.09 (3H) (s, C5Me4), 4.36 (s, 1H, CHButPh), 4.89
(1H), 5.71 (1H), 7.13 (1H) (m, C5H3), 7.18 (2H), 7.21 (2H), 7.26
1
(1H) (m, Ph). 13C{ H} NMR (100 MHz, CDCl3): δ −0.2, 0.0
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.81 (3H),
0.91 (3H) (s, SiMe2), 0.87 (s, 9H, But), 1.14 (d, 3H, CMe), 1.96
(3H), 2.00 (3H), 2.07 (6H) (s, C5Me4), 2.80 (q, 1H, CHButMe),
(SiMe2), 12.4, 12.5, 14.9, 15.1 (C5Me4), 29.3, 34.6 (But), 56.3
(CpC), 96.4, 104.8 (C1–Cp), 111.8, 115.1, 125.7, 127.2 (C5H3),
135.8, 135.9, 144.3, 144.4 (C5Me4), 124.7, 125.4, 125.6, 137.9
(Ph).
1
5.47 (1H), 5.79 (1H), 6.64 (1H) (m, C5H3). 13C{ H} NMR
1
(100 MHz, CDCl3): δ −0.8, 0.7 (SiMe2), 11.8, 12.7, 14.8,
15.7 (C5Me4), 14.0 (CMe), 28.2, 34.4 (But), 43.5 (CpC), 97.3,
104.6 (C1–Cp), 111.1, 117.0, 121.7, 149.1 (C5H3), 122.7, 130.2,
132.4, 138.0 (C5Me4).
Second isomer. H NMR (400 MHz, CDCl3): δ 0.82 (3H),
0.88 (3H) (s, SiMe2), 0.94 (s, 9H, But), 1.90 (3H), 1.94 (3H),
1.96 (3H), 2.01 (3H) (s, C5Me4), 4.05 (s, 1H, CHButPh), 5.55
(1H), 5.63 (1H), 6.99 (1H) (m, C5H3), 7.22 (2H), 7.28 (2H),
1
1
Second isomer. H NMR (400 MHz, CDCl3): δ 0.82 (3H),
7.46 (1H) (m, Ph). 13C{ H} NMR (100 MHz, CDCl3): δ −0.1,
0.92 (3H) (s, SiMe2), 0.88 (s, 9H, But), 1.33 (d, 3H, CMe), 1.89
(3H), 2.05 (3H), 2.10 (6H) (s, C5Me4), 2.80 (q, 1H, CHButMe),
0.1 (SiMe2), 12.0, 12.7, 15.2, 15.9 (C5Me4), 29.4, 36.0 (But),
57.8 (CpC), 96.7, 104.1 (C1–Cp), 111.0, 115.7, 125.9, 127.8
(C5H3), 129.8, 136.4, 139.9, 140.3 (C5Me4), 122.4, 124.5,
125.7, 134.8 (Ph).
1
5.34 (1H), 5.64 (1H), 6.76 (1H) (m, C5H3). 13C{ H} NMR
(100 MHz, CDCl3): δ −0.4, 0.3 (SiMe2), 12.2, 12.6, 15.0, 15.3
(C5Me4), 13.9 (CMe), 28.0, 33.8 (But), 44.2 (CpC), 103.3,
109.7 (C1–Cp), 115.0, 125.1, 128.0, 143.2 (C5H3), 127.0, 127.9,
128.9, 134.2 (C5Me4).
2.2.16. [Hf{Me2Si(η5-C5Me4)(η5-C5H3{CHButPh})}Cl2]
(12b)
The preparation of 12b was carried out in an identi-
cal manner to 9a. HfCl4 (0.78 g, 2.44 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHButPh})} (8) (1.00 g, 2.44 mmol). Yield
0.48 g, 31%. MS electron impact (m/e (relative intensity)): 638
(2)[M+], 581(28)[M+ − But], 505(2)[M+ − But, –Ph], 461(23)
[M+ − But, –Ph, –Cl], 211 (49) [M+ − Me2Si(C5Me4)HfCl2].
Anal. Calc. for C27H36Cl2SiHf: C, 50.82; H, 5.69. Found C,
50.71; H, 5.64%.
2.2.14. [Hf{Me2Si(η5-C5Me4)(η5-C5H3{CHButMe})}Cl2]
(11b)
The synthesis of 11b was carried out in an identical
manner to 9a. HfCl4 (0.94 g, 2.94 mmol) and Li2{Me2-
Si(C5Me4)(C5H3{CHButMe})} (7) (1.00 g, 2.94 mmol). Yield
0.71 g, 42%. MS electron impact (m/e (relative intensity)): 576
(1) [M+], 519 (13) [M+ − But], 483 (23) [M+ − But, –Cl], 207
(51) [M+ − Hf(C5Me4)Cl2]. Anal. Calc. for C22H34Cl2SiHf: C,
45.88; H, 5.95. Found C, 45.52; H, 5.92%.
Isolated isomer. 1H NMR (400 MHz, CDCl3): δ 0.88 (3H),
0.93 (3H) (s, SiMe2), 1.10 (s, 9H, But), 1.76 (3H), 2.06 (3H),

264
S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
2.09 (3H), 2.10 (3H) (s, C5Me4), 4.38 (s, 1H, CHButPh), 4.86
(1H), 5.66 (1H), 7.03 (1H) (m, C5H3), 7.18 (2H), 7.24 (2H), 7.33
Table 1
Crystal data and structure refinement details for 11a and 12a
1
(1H) (m, Ph). 13C{ H} NMR (100 MHz, CDCl3): δ −0.2, −0.1
11a
12a
(SiMe2), 12.2, 14.3, 14.6, 14.8 (C5Me4), 29.3, 34.7 (But), 56.2
(CpC), 98.0, 103.1 (C1–Cp), 109.5, 112.5, 122.0, 126.1 (C5H3),
133.5, 133.7, 142.0, 144.3 (C5Me4), 125.0, 125.7, 127.1, 135.1
(Ph).
Formula
fw
T (K)
Cryst. syst.
Space group
C22H34Cl2SiZr
488.70
298(2)
Monoclinic
P2(1)/c
11.4152(4)
9.9214(3)
21.1226(7)
C34H44Cl2SiZr
642.90
100(2)
Triclinic
P-1
9.3673(2)
13.3628(3)
14.2358(3)
116.5720(10)
96.0100(10)
95.6690(10)
1563.58(6)
2
1
Second isomer. H NMR (400 MHz, CDCl3): δ 0.81 (3H),
˚
a (A)
0.88 (3H) (s, SiMe2), 0.93 (s, 9H, But), 1.96 (3H), 1.98 (3H),
2.03 (3H), 2.04 (3H) (s, C5Me4), 4.06 (s, 1H, CHButPh), 5.49
(1H), 5.52 (1H), 6.92 (1H) (m, C5H3), 7.20 (2H), 7.28 (2H), 7.47
˚
b (A)
˚
c (A)
α (◦)
β (◦)
γ (◦)
(1H) (m, Ph). 13C{ H} NMR (100 MHz, CDCl3): δ −0.1, 0.3
1
99.9110(10)
(SiMe2), 12.0, 12.2, 14.7, 15.0 (C5Me4), 29.2, 36.1 (But), 57.6
(CpC), 98.3, 105.1 (C1–Cp), 111.2, 113.3, 117.0, 117.8 (C5H3),
132.9, 134.0, 141.3, 142.3 (C5Me4), 124.8, 125.9, 126.8, 140.9
(Ph).
3
˚
V (A )
2356.53(13)
4
1.377
0.749
1016
Z
Dc (g cm−3
)
1.366
4.968
672
μ (mm−1
F(0 0 0)
)
Cryst. dimens. (mm)
θ range (◦)
h k l ranges
0.40 × 0.38 × 0.29
1.81–26.37
−14 ≤ h ≤ 6,
−11 ≤ k ≤ 12,
−254 ≤ l ≤ 26
4805/235
0.10 × 0.08 × 0.04
3.52–70.57
−11 ≤ h ≤ 10,
−16 ≤ k ≤ 16,
−16 ≤ l ≤ 17
5664/353
2.3. Polymerization reactions
2.3.1. Polymerization of ethylene
The zirconocene catalyst (6 ␮mol), MAO (10% in toluene)
(6000 ␮mol) and toluene (200 mL) were mixed together for
15 min in a 1 L glass autoclave. The N2 pressure inside the
autoclave was reduced by applying vacuum. Ethylene pressure
of 2 bar was then applied and maintained to the autoclave and
stirring of the mixture commenced (1000 rpm). After exactly
15 min, stirring was halted and the ethylene pressure released.
Excess MAO was then destroyed by adding cautiously a mixture
of methanol/HCl (90:10). The polymer was isolated by filtration
and washed with ethanol and dried under vacuum at 90 ◦C for
16 h.
Data/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
1.018
0.993
R1 = 0.0465,
wR2 = 0.1026
R1 = 0.0303,
wR2 = 0.0686
0.334/−0.340
R1 = 0.0386,
wR2 = 0.0914
R1 = 0.0487,
wR2 = 0.0965
1.035/−0.552
R indices (all data)
Largest diff−. p3eak and
˚
hole (e A
)
R1 = ꢀꢁF0| − |Fcꢁ/ꢀ|F0|; wR2 = [ꢀ[w(F02 − Fc2)2]/ꢀ[w(F02)2]]0.5
.
Hydrogen atoms were included in calculated positions, and
refined in the riding mode. Weights were optimized in the final
cycles. Crystallographic data are given in Table 1.
2.3.2. Polymerization of propylene
The zirconocene catalyst (6 ␮mol), MAO (10% in toluene)
(12,000 ␮mol) and toluene (200 mL) were mixed together for
15 min in a 1 L glass autoclave. The N2 pressure inside the auto-
clave was reduced by applying vacuum. Propylene pressure of
2.5 bar was then applied and maintained to the autoclave and
stirring of the mixture commenced (1000 rpm). After exactly
30 min, stirring was halted and the propylene pressure released.
Solvent was then removed under reduced pressure and methanol
(200 mL) added. The mixture was stirred for 16 h and then fil-
tered to isolate the polymer which was washed with ethanol and
dried under vacuum at 25 ◦C for 16 h.
2.4.2. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHButPh})}Cl2]
(12a)
Data were collected on a Bruker SMART CCD-based diffrac-
tometer operating at 50 kV and 100 mA, using ω/2θ scan-
technique. Absorption corrections were applied using the SAD-
ABS program (maximum and minimum transmission coeffi-
cients 0.820 and 0.652) [22]. The structure was solved using
the SHELXTL Structure Determination Package [23] by direct
methods and refined by full-matrix least-squares methods on F2.
All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included in calculated positions, and refined in the
riding mode. Weights were optimized in the final cycles. Crys-
tallographic data are given in Table 1.
2.4. X-ray data collection
2.4.1. [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CHButMe})}Cl2]
(11a)
Data were collected on a Bruker SMART CCD-based diffrac-
tometer operating at 50 kV and 30 mA, using ω/2θ scan-
technique. Absorption corrections were applied using the SAD-
ABS program (maximum and minimum transmission coeffi-
cients 0.8122 and 0.7539) [22]. The structure was solved using
the Bruker SHELXTL Structure Determination Package [23] by
direct methods and refined by full-matrix least-squares methods
on F2. All non-hydrogen atoms were refined anisotropically.
3. Results and discussion
3.1. Synthesis and characterization of ansa-precursors
The preparation of the asymmetrically substituted ansa
ligand precursors, Me2Si(C5Me4H)(C5H4{CHRRꢀ}) (R = Pri,
Rꢀ = Me (1); R = Pri, Rꢀ = Ph (2); R = But, Rꢀ = Me (3); R = But,
Rꢀ = Ph (4)), was achieved by the reaction of Li{C5H4(CHRRꢀ)}

S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
265
with Me2Si(C5Me4H)Cl following previously reported syn-
thetic protocols (Eq. (1)) [10]. 1–4 were isolated as mix-
tures of the double bond position isomers, with one isomer
being predominant as confirmed by 1H NMR spectroscopy.
In addition, 1–4 were characterized by electron impact mass
spectrometry (see Section 2). The ansa-bis(cyclopentadiene)
compounds, 1–4, were lithiated in the traditional man-
ner with n-butyllithium to give the dilithium derivatives,
Li2{Me2Si(C5Me4)(C5H3{CHRRꢀ})} (R = Pri, Rꢀ = Me (5);
R = Pri, Rꢀ = Ph (6); R = But, Rꢀ = Me (7); R = But, Rꢀ = Ph (8))
(Eq. (1)):
5–8, three multiplets between 5.6 and 6.0 ppm. The resolution of
the spectra and the small difference in the chemical shift meant
the expected four signals for the cyclopentadienyl ring methyl
substituents were observed only as two singlets (ca. 1.87 and
2.07 ppm). However, in the 13C{ H} NMR spectra of 5–8, four
1
signals were observed for the methyl carbons (between 10 and
1
14 ppm). An additional singlet was assigned, in the H NMR
spectra, to the ansa bridge methyl groups (ca. 0.4 ppm). The
1
13C{ H} NMR spectra for 5–8 showed the expected signals (see
Section 2).
3.2. Synthesis and characterization of ansa-metallocene
complexes
The reaction of 5–8 with either ZrCl4 or HfCl4, yielded the
corresponding ansa-metallocene(IV) dichloride complexes,
[M{Me2Si(␩5-C5Me4)(␩5-C5H3{CHRRꢀ})}Cl2]
(R = Pri,
Rꢀ = Me (9); R = Pri, Rꢀ = Ph (10); R = But, Rꢀ = Me (11);
R = But, Rꢀ = Ph (12); M = Zr (a), Hf (b)) (Eq. (2)):
(1)
1
5–8 were characterized by 1H and 13C{ H} NMR spec-
(2)
troscopy (see Section 2). In the 1H NMR spectra of 5 and
6, two doublets and a multiplet were observed for the two
diastereotopic methyl groups and proton of the iso-propyl frag-
ment, respectively. For 5, a multiplet at 2.45 ppm and a doublet
at 1.09 ppm, were observed, corresponding to the proton and
methyl group bonded to the chiral carbon atom of cyclopenta-
dienyl substituent, respectively. For 6, the proton bonded to the
chiral carbon atom gave a doublet signal at 3.31 ppm. Three
multiplets (between 6.9 and 7.3 ppm) were recorded for the
phenyl moiety. The tert-butyl signal in 7 and 8 was observed
in the 1H NMR spectra as a singlet at 0.9 ppm. For 7, a quadru-
plet, at 2.42 ppm, and a doublet, at 1.15 ppm, were observed
corresponding to the proton and methyl group bonded to the
chiral carbon atom of cyclopentadienyl substituent, respectively.
For 8, the proton bonded to the chiral carbon atom gave a sin-
glet signal at 3.64 ppm and three multiplets (between 7.0 and
7.5 ppm) were assigned to the phenyl moiety. In addition, the
cyclopentadienyl ring protons gave, in the 1H NMR spectra of
9–12 were isolated as crystalline solids and characterized
spectroscopically. There exists planar chirality about the mono-
substituted cyclopentadienyl ring in 9–12 and this combined
with the presence of a chiral centre in the bulky substituent
gives rise to the possibility of the formation of two diastereoiso-
mers (Fig. 1). NMR spectroscopy confirmed the presence of the
two diastereoisomers in the isolated products. The separation of
one of the isomers from the mixture was achieved by fractional
recrystallization. The 1H NMR spectra for the diastereoisomers
of 9–12 gave three multiplets for the protons of the monosub-
stituted C5 ring (between 4.9 and 7.1 ppm), four singlets for the
methyl groups of the tetramethyl-substituted C5 ring (between
1.8 and 2.2 ppm), and two singlets corresponding to the methyl
groups of the SiMe2 bridging unit (between 0.6 and 0.9 ppm).
Additional signals were observed for the chiral alkyl substituent
with similar chemical shifts and identical spectral patterns to
1
those observed in the lithium precursors 5–8. The 13C{ H}

266
S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
Fig. 1. Stereoisomers for 9–12.
NMR spectra of 9–12 showed the expected signals (see Sec-
tion 2).
The molecular structures, of one of the diastereomers, of
11a and 12a were established by single-crystal X-ray diffrac-
tion studies. The two enantiomers, related by symmetry, were
located in the asymmetric unit. The molecular structures and
atomic numbering schemes of one of the enantiomers are shown
in Figs. 2 and 3. The absolute configuration due to the planar
chirality of the C5 ring is defined by the substituent arrangement
Fig. 3. Molecular structure and atom-labeling scheme for R,Rꢀ(cp)
-
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButPh})}Cl2] (12a), with thermal
ellipsoids at 50% probability.
about the C3 carbon of the cyclopentadienyl moiety. In the case
of 12a, a toluene molecule was also located in the asymmetric
unit. Selected bond lengths and angles for 11a and 12a are given
in Table 2.
Table 2
◦
˚
Selected bond lengths (A) and angles ( ) for 11a and 12a
11a
12a
2.215
Zr–Cent(1)
2.220
Zr–Cent(2)
2.227
2.528
2.532
2.4424(5)
2.4177(6)
2.232
2.522
2.540
2.4420(7)
2.4222(8)
av Zr–C[C(1)–C(5)]a
av Zr–C[C(12)–C(16)]a
Zr–Cl(1)
Zr–Cl(2)
Cent(1)–Zr–Cent(2)
Si(1)–C(1)–Cent(1)
Si(1)–C(12)–Cent(2)
C(1)–Si(1)–C(12)
Cl(1)–Zr–Cent(1)
Cl(1)–Zr–Cent(2)
Cl(2)–Zr–Cent(1)
Cl(2)–Zr–Cent(2)
Cl(1)–Zr–Cl(2)
126.8
163.0
162.7
94.25(8)
106.3
106.5
107.5
109.2
96.03(2)
174.9
127.60
163.39
162.72
94.11(13)
106.9
106.35
105.34
106.48
102.37(3)
170.26
176.92
C(17)–C(14)–Cent(2)
C(17)–C(18)–Cent(3)
Cent(1) and Cent(2) are the centroids of C(1)–C(5) and C(12)–C(16), respec-
Fig. 2. Molecular structure and atom-labeling scheme for R,Sꢀ(cp)-[Zr{Me2
Si(␩5-C5Me4)(␩5-C5H3{CHButMe})}Cl2] (11a), with thermal ellipsoids at
50% probability.
tively. For 12a Cent(3) is the centroid of C(18)–C(23).
a
Average bond distance between Zr(1) and the carbon atoms of the C5 ring
of the corresponding cyclopentadienyl moiety.

S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
267
Table 3
Selected structural data of some ansa-zirconocene complexes
a
Cp–Zr–Cp (◦)
Cl–Zr–Cl (◦)
C(cp)–Si–C(cp) (◦)
Reference
˚
˚
Complex
Zr–Cp (A)
Zr–Cl (A)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H4)}Cl2]
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3Me)}Cl2]
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3Et)}Cl2]
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3Pri)}Cl2]
R-[Zr{Me2Si(␩5-C5Me4)(␩5-
C5H3{menthyl})}Cl2]
2.202 Cp, 2.198 Cp*
2.194 CpR, 2.184 Cp*
2.214 CpR, 2.207 Cp*
2.223 CpR, 2.230 Cp*
2.451(1)
2.414(4)
2.429(4)
2.429
128.10
126.25
126.5
126.9
126.6
104.60(7)
101.1(2)
100.4(2)
98.2(1)
95.2(2)
92.4(8)
93.3(7)
94.2(2)
93.6(4)
[10]
[10]
[11]
[11]
[8,9]
2.419
98.6(2)
R,Sꢀ-[Zr{Me2Si(␩5-C5Me4)(␩5-
C5H3{CHButMe})}Cl2]
2.227 CpR, 2.220 Cp*
2.232 CpR, 2.215 Cp*
2.329
2.4301
126.8
127.60
128.6
96.03(2)
102.37(3)
99.28(3)
94.25(8)
94.11(13)
95.7(1)
This work
This work
[24,25]
(11a)
R,Rꢀ-[Zr{Me2Si(␩5-C5Me4)(␩5-
2.4321
C5H3{CHButPh})}Cl2]
(12a)
[Zr{Me2Si(␩5-C5Me4)2}Cl2]
2.4334(7)
a
Cp* refers to the C5Me4 moiety; CpR refers to the C5H3R moiety.
The structural determinations of 11a and 12a reveal, in the
absence of any symmetry planes or axes, the C1 symmetric
nature of the ansa-metallocene complexes. In both structures
the usual bent metallocene conformation was observed with the
geometry around the metal atom being pseudo-tetrahedral as
defined by the two chlorine atoms and the two cyclopentadienyl
moieties. The ansa ligand chelates the zirconium atom and both
C5 rings are bound to the metal in an ␩5 mode. The centroids of
theC5 ringsformananglewiththezirconiumatomof126.8◦ 11a
and 127.60◦ 12a, which are typical values for dichloride group
four ansa-metallocene complexes. The chiral carbon atom (C17)
of the alkyl substituent is located, 5.1◦ for 11a, and 9.74◦ for 12a,
out of the plane defined by the cyclopentadienyl unit. The bulky
chiral substituent is situated more or less above one of the chlo-
rine atoms (dihedral angle θ Cl(2)–Zr· · ·C(14)–C(17) 2.9(2)◦ for
11a and −17.2(2)◦ for 12a) and should therefore be influential in
controlling the coordination mode of the olefin monomer at this
site during polymerization. Selected structural data of 11a and
12a can be compared with similar ansa-zirconocene complexes
using Table 3.
3.3. Polymerization of ethylene
The polymerization of ethylene using the isolated diastere-
omer of the zirconium derivatives as catalyst with a MAO
cocatalyst–metal catalyst ratio of 1000:1 has been carried out.
The polymerization experiments were conducted at 20 ◦C and at
olefin pressure of 2 bar during 15 min. Polymerization was also
carried out with the reference compound [Zr(␩5-C5H5)2Cl2]
under the same experimental conditions. The catalytic activi-
ties and polymer molecular weight and distribution values are
given in Table 4. The hafnium derivatives 9b–12b were also
tested but gave very low catalytic activities.
The catalytic activities for the ansa-zirconocene complexes,
9a–12a, are all slightly lower than the reference compound
[Zr(␩5-C5H5)2Cl2] except for 11a which exhibited an activity
Table 4
Ethylene polymerization results for 9a–12a and [Zr(␩5-C5H5)2Cl2]a,b
Catalyst
Activityb
Mw (g mol−1
)
Mw/Mn
[Zr(␩5-C5H5)2Cl2]
1730
1367
1500
4720
1233
275050
150490
158970
153240
162610
3.0
2.7
3.0
2.9
3.2
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriMe})}Cl2] (9a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriPh})}Cl2] (10a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButMe})}Cl2] (11a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButPh})}Cl2] (12a)
a
At 20 ◦C, 2 bar monomer pressure, 200 mL toluene, [Al] = 3 × 10−2 mol L−1, [Zr] = 3 × 10−5 mol L−1, tPol = 15 min.
b
In kg Pol (mol Zr h)−1
.
Table 5
Propylene polymerization results for 9a–12a and [Zr(␩5-C5H5)2Cl2]a,b
Catalyst
Activityb
Mw (g mol−1
)
Mw/Mn
[mmmm] (%)
[Zr(␩5-C5H5)2Cl2]
565
550
557
613
350
204800
218320
221610
198570
203320
3.2
3.8
3.6
3.3
3.2
3.5
60.5
56.1
65.0
54.9
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriMe})}Cl2] (9a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriPh})}Cl2] (10a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButMe})}Cl2] (11a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButPh})}Cl2] (12a)
a
At 20 ◦C, 2.5 bar monomer pressure, 200 mL toluene, [Al] = 6 × 10−2 mol L−1, [Zr] = 3 × 10−5 mol L−1, tPol = 30 min.
In kg Pol (mol Zr h)−1
.
b

268
S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
Table 6
1
Pentad distribution, calculated from 13C{ H} NMR spectroscopy, for polypropylenes synthesized from 9a to 12a
Catalyst
[mmmm] [mmmr] [rmmr]
[mmrr]
(%)
[mmrm] +
[rmrr] (%)
[mrmr]
(%)
[rrrr]
(%)
[mrrr]
(%)
[mrrm]
(%)
(%)
(%)
(%)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriMe})}Cl2] (9a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHPriPh})}Cl2] (10a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButMe})}Cl2] (11a)
[Zr{Me2Si(␩5-C5Me4)(␩5-C5H3{CHButPh})}Cl2] (12a)
60.5
56.1
65.0
54.9
11.8
12.3
12.5
12.9
2.4
2.9
1.9
3.8
7.8
8.8
8.0
9.1
5.2
7.2
4.5
6.5
3.2
3.5
1.4
3.9
2.2
2.0
1.6
2.4
2.8
2.9
1.1
2.1
4.1
4.3
4.0
4.4
nearly three times greater than the reference compound. The
polymer molecular weights are of the order of 150,000.
3.4. Polymerization of propylene
The polymerization of propylene using the isolated diastere-
omer of the zirconium derivatives with a MAO cocatalyst–metal
catalyst ratio of 2000:1 has been carried out. The polymeriza-
tion experiments were conducted at 20 ◦C and at olefin pres-
sure of 2.5 bar during 30 min. Polymerization was also carried
out with the reference compound [Zr(␩5-C5H5)2Cl2] under the
same experimental conditions. The catalytic activities, polymer
molecular weight and distribution values and tacticity are given
in Table 5. Pentad distribution percentages are given in Table 6.
The hafnium derivatives 9b–12b were also tested but gave very
low catalytic activities.
The catalytic activities for the ansa-zirconocene complexes,
9a–12a, are all of the same order to that recorded for the refer-
ence compound [Zr(␩5-C5H5)2Cl2] except 12a whose activity
is somewhat lower. The polymer molecular weights are of the
order of 200,000.
The isotacticity of the polymers was measured by the pen-
1
tad method using 13C{ H} NMR spectroscopy. The [mmmm]
pentad for the ansa-metallocene catalysts, 9a–12a, were of the
order of 60% and are comparable (if not somewhat lower) than
those reported previously for similar C1 symmetric complexes
[8,9,11].
Fig. 5. Polymer chain back-skip mechanism in the ansa-zirconocene complexes
9a–12a.
Fig. 4. Diastereomeric intermediates in the polymerization of propylene.

S. Go´mez-Ruiz et al. / Journal of Molecular Catalysis A: Chemical 264 (2007) 260–269
269
A Cossee–Arlman site control mechanism can be used to
explain the stereoselectivity of the C1 catalysts, 9a–12a. During
the polymerization of propylene, four possible diastereomeric
intermediates (two at each binding site) are possible. The two
binding sites A and B can be considered as isoselective with
the growing polymer chain being preferentially located in the
less sterically hindered positions, intermediates A1 and B1 (see
Fig. 4). Thus, and in a similar way to that predicted and observed
for C2 ansa-metallocene catalysts [26], isotactic polypropylene
should be produced.
de Madrid (GR/MAT/0929/2004 and S-0505/PPQ-0328) and
the Universidad Rey Juan Carlos (GVC-2004-12). We would
also like to thank Repsol-YPF for their assistance in polymer
analysis.
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polypropylene.
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Crystallographic data for the structural analysis of 11a and
12a have been deposited with the Cambridge Crystallographic
Data Centre, CCDC-611901 & 611902. Copies of this informa-
tion may be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.
cam.ac.uk).
Acknowledgements
We gratefully acknowledge financial support from the Min-
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isterio de Educacion y Ciencia, Spain (Grants no. CTQ2005-
07918-C02-02/BQU and MAT2003-05345), the Comunidad
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