Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene dichloride complexes: Applications in ethylene polymerization

Article abstract of DOI:10.1016/j.jorganchem.2019.120890

The alkenyl substituted zirconocene complexes, [Zr(η⁵-C₅H₄{CMeRCH₂CH₂CH = CMe₂})₂Cl₂] (R = Me (1), Ph (2) were prepared from the reaction of the lithium derivative Li(C₅H₄{CMeRCH₂CH₂CH = CMe₂}) (R = Me, Ph) with zirconium tetrachloride. The bulky alkyl substituted cyclopentadienyl ligand precursor was prepared as its fulvene derivative (C₅H₄) = CMeCH₂CHMe₂ (3) via the reaction of cyclopentadiene with 4-methyl-2-pentanone and then converted to Li(C₅H₄{CMe₂CH₂CHMe₂}) (4) via nucleophilic attack of LiMe. The reaction of 4 with [TiCl₄(THF)₂] and ZrCl₄ gave the metallocene complexes [M(η⁵-C₅H₄{CMe₂CH₂CHMe₂})₂Cl₂] (M = Ti (5), Zr (6)), respectively. The ansa-ligand precursor, SiMe₂(C₅HMe₄)(C₅H₄{CMe₂CH₂CHMe₂}) (7), was prepared via the reaction of 4 with SiMe₂(C₅HMe₄)Cl and subsequently converted to its dilithium derivate, Li₂(Me₂Si(C₅Me₄)(C₅H₃{CMe₂CH₂CHMe₂})) (8), using n-butyllithium. The ansa-zirconocene complex, [Zr{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃{CMe₂CH₂CHMe₂})}Cl₂] (9), was synthesized by the reaction of 8 with zirconium tetrachloride. Compounds 1–9 were characterized by ¹H and ¹³C{¹H} NMR spectroscopy. In addition, the molecular structures of 5, 6 and 9 were determined by single crystal X-ray diffraction studies. The metallocene complexes have been tested as catalyst (with co-catalyst MAO) in the polymerization of ethylene where the substituents on the cyclopentadienyl ligand have a direct influence on the catalytic activity.

Full text of DOI:10.1016/j.jorganchem.2019.120890

Journal Pre-proof
Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene
dichloride complexes: Applications in ethylene polymerization
Jesús Ceballos-Torres, Santiago Gómez-Ruiz, Mariano Fajardo, Ana B. Pinar, Sanjiv
Prashar
PII:
S0022-328X(19)30333-X
DOI:
https://doi.org/10.1016/j.jorganchem.2019.120890
JOM 120890
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 15 May 2019
Revised Date: 1 August 2019
Accepted Date: 9 August 2019
Please cite this article as: Jesú. Ceballos-Torres, S. Gómez-Ruiz, M. Fajardo, A.B. Pinar, S. Prashar,
Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene dichloride
complexes: Applications in ethylene polymerization, Journal of Organometallic Chemistry (2019), doi:
https://doi.org/10.1016/j.jorganchem.2019.120890.
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© 2019 Published by Elsevier B.V.

Revised: JORGANCHEM-D-19-00293
Synthesis and characterization of alkenyl and alkyl substituted group 4 metallocene
dichloride complexes: Applications in ethylene polymerization
a
a
b
Jesús Ceballos-Torres , Santiago Gómez-Ruiz a,*, Mariano Fajardo , Ana B. Pinar , Sanjiv
Prashar a,**
a
Departamento de Biología y Geología, Física y Química Inorgánica, E.S.C.E.T., Universidad
Rey Juan Carlos, 28933 Móstoles, Madrid, Spain
b Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
* Corresponding author
** Corresponding author
E-mail addresses: santiago.gomez@urjc.es (S. Gómez-Ruiz), sanjiv.prashar@urjc.es (S.
Prashar).
Dedicated to the memory of Professor Pascual Royo
Abstract
The alkenyl substituted zirconocene complexes, [Zr(η5-C5H4{CMeRCH2CH2CH=CMe2})2Cl2] (R
=
Me (1), Ph (2) were prepared from the reaction of the lithium derivative
Li(C5H4{CMeRCH2CH2CH=CMe2} (R = Me, Ph) with zirconium tetrachloride. The bulky alkyl
substituted cyclopentadienyl ligand precursor was prepared as its fulvene derivative
(C5H4)=CMeCH2CHMe2 (3) via the reaction of cyclopentadiene with 4-methyl-2-pentanone and
then converted to Li(C5H4{CMe2CH2CHMe2}) (4) via nucleophilic attack of LiMe. The reaction of
4
with
[TiCl4(THF)2]
and
ZrCl4
gave
the
metallocene
complexes
[M(η5-
C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)), respectively. The ansa-ligand precursor,
SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7), was prepared via the reaction of 4 with
SiMe2(C5HMe4)Cl
and
subsequently
converted
to
its
dilithium
derivate,
Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8), using n-butyllithium. The ansa-zirconocene
complex, [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9), was synthesized by the
reaction of 8 with zirconium tetrachloride. Compounds 1-9 were characterized by 1H and 13C{1H}
NMR spectroscopy. In addition, the molecular structures of 5, 6 and 9 were determined by
single crystal X-ray diffraction studies. The metallocene complexes have been tested as catalyst
(with co-catalyst MAO) in the polymerization of ethylene where the substituents on the
cyclopentadienyl ligand have a direct influence on the catalytic activity.
Keywords: Titanocene; Zirconocene; ansa-Zirconocene; X-ray Crystal Structures; Catalysis;
Ethylene Polymerization.
1

Revised: JORGANCHEM-D-19-00293
1. Introduction
Metallocene complexes are a very interesting class of compounds with multiple
applications in various fields of research such as structural chemistry [1,2], medicinal chemistry
[3], organic synthesis [4] and catalysis [5].
In particular, group 4 metallocene complexes are well known as olefin polymerization
catalysts [6–8]. They act as single site catalysts producing generally lineal and uniform low
polydispersity polyolefins. The metallocene structure has been shown to be directly related to
the physical properties of the polyethylene produced. Thus, changing the substituents on the
cyclopentadienyl ring and / or the introduction of an ansa-bridging unit has been extensively
studied. Our group has reported a wide number of group 4 metallocene complexes with
interesting applications in olefin polymerization and design of made-to-measure polymers [9–
14].
In spite of current environmental problems associated with the use of polyolefins in daily
life applications [15], the current needs of the polyolefin industry is still high [16,17] so that the
development of novel metallocene catalysts and the research focused on the understanding of
the olefin polymerization mechanism are still ongoing [18–20].
Previous studies of our group have demonstrated promising catalytic properties of
group 4 metallocene complexes containing different bulky groups or long chain alkyl or alkenyl
substituents in the cyclopentadienyl ring [12–14,21,22]. In this context, we present here the
synthesis, characterization and catalytic studies in olefin polymerization of group 4 metallocene
dichloride complexes incorporating bulky alkyl and alkenyl substituted cyclopentadienyl ligands.
2. Experimental
2.1. General manipulations
All reactions were performed using standard Schlenk tube techniques in an atmosphere
of dry nitrogen. Solvents were distilled from the appropriate drying agents and degassed before
use. Cyclopentadiene dimer, pyrrolidine, LiBun (1.6 M in hexane), LiMe (1.6 M in Et2O), 4-
methyl-2-pentanone, ZrCl4 and [TiCl4(THF)2] were purchased from Aldrich and used directly.
Li(C5H4{CMe2CH2CH2CH=CMe2})
[23],
Li(C5H4{CMePhCH2CH2CH=CMe2})
[24]
and
SiMe2(C5HMe4)Cl [25] were synthesized as previously described by us. IR spectra were
recorded on a Thermo Nicolet Avatar 330 FT-IR spectrophotometer. 1H NMR and 13C{1H} NMR
spectra were recorded on a Varian Mercury FT-400 spectrometer. FTIR and NMR spectra of the
compounds can be found in the supplementary data. Microanalyses were carried out with a
Perkin-Elmer 2400 microanalyzer. Polymer molecular weights and distribution were determined
by GPC (Waters 150C Plus or Alliance GPC-2000) in 1,2,4-trichlorobenzene at 150 ºC, using
standard polystyrene calibration.
2.2. Synthesis of compounds
2

Revised: JORGANCHEM-D-19-00293
[Zr(η5-C5H4{CMe2CH2CH2CH=CMe2})2Cl2] (1): A solution of Li(C5H4{CMe2CH2CH2CH=CMe2})
(0.77 g, 3.96 mmol) in THF (50 mL) was added dropwise during 10 minutes to a solution of
ZrCl4 (0.46 g, 1.98 mmol) in THF (50 mL) at 0 ºC. The reaction mixture was allowed to warm to
room temperature and stirred for 2–3 h. Solvent was then removed in vacuum and a toluene-
hexane 9:1 mixture (50 mL) added to the resulting solid. The suspension was filtered to remove
LiCl and the filtrate concentrated (20 mL) and cooled to -30 ºC to give the title compound as a
pale yellow solid. Yield: 0.56 g, 52 %. FT-IR (KBr): ῡ 1631 (C=C), 2923, 2964 (Cal–H) and 3087,
3101 (Car–H) cm-1. 1H NMR (400 MHz, CDCl3, 25 ºC): δ 1.37 (s, 12 H, CpCMe2), 1.43, 1.65 (m,
4 H each, CH2CH2CH=CMe2), 1.48, 1.62 (s, 6 H each, CH2CH2CH=CMe2), 4.97 (m, 2 H,
CH2CH2CH=CMe2) and 6.31, 6.40 (m, 4 H, C5H4) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 ºC):
δ 17.7, 23.4 (CH2CH2CH=CMe2), 25.9, 27.1 (CH2CH2CH=CMe2), 36.7 (CpCMe2), 47.4
(CpCMe2), 112.7, 116.4, 143.3 (C5H4), 124.5 (CH2CH2CH=CMe2) and 131.6
(CH2CH2CH=CMe2) ppm. Elemental analysis calcd (%) for C28H42Cl2Zr (540.76 g/mol): C 62.19,
H 7.83; found: C 61.77, H 7.82.
[Zr(η5-C5H4{CMePhCH2CH2CH=CMe2})2Cl2] (2): The synthesis of 2 was carried out in an
identical manner to 1: Li(C5H4{CMePhCH2CH2CH=CMe2}) (0.97 g, 3.76 mmol) and ZrCl4 (0.44
g, 1.88 mmol). Yield: 0.18 g, 14 %. FT-IR (KBr): ῡ 1633 (C=C) and 2922 (Cal–H) cm-1. 1H NMR
(400 MHz, CDCl3, 25 ºC, for the two isomers): δ 1.44, 1.45, 1.63, 1.63 (s, 6 H each,
CH2CH2CH=CMe2), 1.81, 1.82 (s, 6 H each, CpCMePh), 1.50‒1.70 (m, 8 H, CH2CH2CH=CMe2),
1.90–2.10 (m, 8 H, CH2CH2CH=CMe2), 5.03 (m, 4 H, CH2CH2CH=CMe2), 5.28, 5.52, 5.96, 5.99,
6.05, 6.14, 6.37, 6.47 (m, 2 H each, C5H4) and 7.10–7.40 (m, 20 H, C6H5) ppm. 13C{1H} NMR
(100 MHz, CDCl3, 25 ºC, for the two isomers): δ 17.8, 23.3, 23.4, 23.6, 24.4, 25.9, 29.9, 32.6,
42.8, 43.6, 43.7, 43.8 (CMePhCH2CH2CH=CMe2) and 109.0, 111.2, 115.4, 116.5, 117.5, 117.6,
119.5, 124.3, 124.4, 126.4, 126.5, 126.5, 127.3, 127.4, 127.5, 128.4, 128.4, 128.5, 131.9,
133.2, 142.5, 142.7, 146.4, 146.5 (CMePhCH2CH2CH=CMe2 and C5H4) ppm. Elemental
analysis calcd (%) for C38H46Cl2Zr (664.90 g/mol): C 68.64, H 6.97; found: C 68.24, H 6.83.
(C5H4)=CMeCH2CHMe2 (3): The synthesis of 3 was carried out in an identical manner to
procedure described by Stone and Little [26] using freshly cracked cyclopentadiene (32.95 g,
500 mol), 4-methyl-2-pentanone (20.00 g, 200 mmol), pyrrolidine (21.60 g, 300 mmol) and
acetic acid (19.20 g, 320 mmol). Finally, the product was purified by column chromatography
using hexane as eluent. Yield: 20.35 g, 69 %. FT-IR (KBr): ῡ 1638 (C=C), 2869, 2957 (Cal–H)
1
and 3069, 3103 (Car–H) cm-1. H NMR (400 MHz, CDCl3, 25 ºC): δ 1.00 (d, 6 H, CHMe2), 2.02
(m, 1 H, CHMe2), 2.25 (s, 3 H, Cp=CMe), 2.48 (d, 2 H, CH2CHMe2) and 6.56 (m, 4 H, C5H4)
ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 ºC): δ 21.4 (Cp=CMe), 23.1 (CHMe2), 28.1 (CHMe2),
46.2 (CH2CHMe2) and 120.9, 121.1, 130.6, 131.0, 143.8, 153.2 (C5H4 and Cp=C) ppm.
Li(C5H4{CMe2CH2CHMe2}) (4): LiMe (23.23 mL, 37.16 mmol, 1.60 M in diethyl ether) was
added dropwise to (C5H4)=CMeCH2CHMe2 (3) (5.00 g, 33.78 mmol) at 0 ºC. The reaction
3

Revised: JORGANCHEM-D-19-00293
mixture was allowed to warm to room temperature and stirred for 4 h. The solvent was removed
in vacuo and the resulting white solid washed with hexane (2 × 50 mL) and dried under vacuum
to yield a free-flowing off white powder. Yield: 4.87 g, 97 %. 1H NMR (400 MHz, d8-THF, 25 ºC):
δ 0.68 (d, 6 H, CHMe2), 1.19 (s, 6 H, CpCMe2), 1.37 (d, 2 H, CH2CHMe2), 1.55 (m, 1 H, CHMe2)
and 5.48 (m, 4 H, C5H4) ppm. 13C{1H} NMR (100 MHz, d8-THF, 25 ºC): δ 26.8 (CHMe2), 27.0
(CHMe2), 32.9 (CpCMe2), 36.9 (CH2CHMe2), 57.5 (CpCMe2) and 102.2, 102.9, 130.6 (C5H4)
ppm.
[Ti(η5-C5H4{CMe2CH2CHMe2})2Cl2] (5): The synthesis of 5 was carried out in an identical
manner to 1: Li(C5H4{CMe2CH2CHMe2}) (2.00 g, 11.77 mmol) and [TiCl4(THF)2] (1.97 g, 5.89
1
mmol). Yield 0.51 g, 26 %. FT-IR (KBr): ῡ 2867, 2922, 2954 (Cal–H) and 3089 (Car–H) cm-1. H
NMR (400 MHz, CDCl3, 25 ºC): δ 0.70 (d, 12 H, CHMe2), 1.37 (s, 12 H, CpCMe2), 1.39 (d, 4 H,
CH2CHMe2), 1.42 (m, 2 H, CH2CHMe2) and 6.46, 6.54 (m, 4 H each, C5H4) ppm. 13C{1H} NMR
(100 MHz, CDCl3, 25 ºC): δ 24.6 (CHMe2), 25.3 (CHMe2), 27.5 (CpCMe2), 38.0 (CH2CHMe2),
56.7 (CpCMe2) and 117.6, 120.5, 149.0 (C5H4) ppm. Elemental analysis calcd (%) for
C24H38Cl2Ti (445.33 g/mol): C 64.73, H 8.60; found: C 65.02, H 8.87.
[Zr(η5-C5H4{CMe2CH2CHMe2})2Cl2] (6): The synthesis of 6 was carried out in an identical
manner to 1: Li(C5H4{CMe2CH2CHMe2}) (4) (1.50 g, 8.83 mmol) and ZrCl4 (1.03 g, 4.41 mmol).
1
Yield: 0.65 g, 63 %. FT-IR (KBr): ῡ 2862, 2925, 2957 (Cal–H) cm-1. H NMR (400 MHz, CDCl3,
25 ºC): δ 0.68 (d, 12 H, CHMe2), 1.37 (s, 12 H, CpCMe2), 1.38 (d, 4 H, CH2CHMe2), 1.40 (m, 2
H, CH2CHMe2) and 6.31, 6.41 (m, 4 H each, C5H4) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 ºC):
δ 24.6 (CHMe2), 25.2 (CHMe2), 27.8 (CpCMe2), 37.0 (CH2CHMe2), 56.5 (CpCMe2) and 112.7,
116.5, 143.8 (C5H4) ppm. Elemental analysis calcd (%) for C24H38Cl2Zr (488.69 g/mol): C 58.99,
H 7.84; found: C 58.90, H 7.97.
SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7): A solution of 4 (2.00 g, 11.77 mmol) in THF (50
mL) was added dropwise to a solution of SiMe2(C5HMe4)Cl (2.53 g, 11.79 mmol) in THF (50 mL)
at -80 ºC. The reaction mixture was allowed to warm to room temperature and stirred for 24
hours. The solvent was then removed in vacuum and hexane (50 mL) was added to the
resulting orange oil. The mixture was filtered and the solvent removed under reduced pressure
to give an orange oil. Yield: 3.77 g, 83 %. 1H NMR (400 MHz, CDCl3, 25 ºC, for the predominant
isomer): δ -0.16 (s, 6 H, SiMe2), 0.82, 0.86 (d, 3 H each, CHMe2), 1.16, 1.17 (s, 3 H each,
CpCMe2), 1.42 (d, 2 H, CH2CHMe2), 1.54 (m, 1 H, CHMe2), 1.86, 2.00 (s, 6 H each, C5Me4),
2.93, 3.19 (s, 1 H each, HC5Me4 and HC5H3) and 5.90, 6.30, 6.57 (m, 1 H each, HC5H3) ppm.
13C{1H} NMR (100 MHz, CDCl3, 25 ºC, for the predominant isomer): δ 1.0 (SiMe2), 24.9, 25.0
(CHMe2), 28.5, 29.5 (CpCMe2) 35.7 (CHMe2), 36.9 (CpCMe2), 40.5, 41.0 (C5Me4), 51.3
(CH2CHMe2), 52.9 (C1─C5Me4) 68.2 (C1─C5H3) and 123.7, 125.0, 130.6, 132.2, 133.2, 133.3,
156.0, 158.8 (C5H3 and C5Me4) ppm.
4

Revised: JORGANCHEM-D-19-00293
Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8): A solution of LiBun (8.82 mL, 22.05 mmol, 2.50
M in hexane) was added dropwise to a solution of 7 (3.77 g, 11.02 mmol) in hexane (50 mL) at -
80 ºC. The reaction mixture was allowed to warm to room temperature and stirred for 24 hours.
The solvent was then removed in vacuum and the resulting solid washed with hexane (2 × 50
mL) and finally dried in vacuum. Yield: 3.45 g, 91 %. 1H NMR (400 MHz, d8-THF, 25 ºC): δ 0.39
(s, 6 H, SiMe2), 0.76, 0.78 (s, 3 H each, CpCMe2), 1.18 (s, 6 H, CHMe2), 1.42 (d, 2 H,
CH2CHMe2), 1.60 (m, 1 H, CHMe2), 1.90, 2.07 (s, 6 H each, C5Me4) and 5.68, 5.77, 5.83 (m, 1
H each, C5H3) ppm. 13C{1H} NMR (100 MHz, d8-THF, 25 ºC): δ 4.8 (SiMe2), 11.6, 14.8 (C5Me4),
25.8 (CHMe2), 26.0 (CHMe2), 31.8 (CH2CHMe2), 36.0 (CpCMe2), 56.1 (CpCMe2) and 103.6,
108.2, 110.4, 111.5, 113.4, 116.4, 129.7, 132.81 (C5H3 and C5Me4) ppm.
[Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9): The synthesis of 9 was carried out in
an identical manner to 1: Li2(Me2Si(C5Me4)(C5H3{CMe2CH2CHMe2})) (8) (3.45 g, 9.75 mmol)
and ZrCl4 (2.27 g, 9.75 mmol). Yield: 0.43 g, 9 %. FT-IR (KBr): ῡ 803 (Si–C stretching), 1259
(Si–CH3 sym bending) and 2873, 2927, 2960 (Cal–H) cm-1. 1H NMR (400 MHz, CDCl3, 25 ºC): δ
0.63 (d, 6 H, CHMe2), 0.81, 0.85 (s, 3 H each, SiMe2), 0.83 (d, 2 H, CH2CHMe2), 1.41, 1.48 (s, 3
H each, CpCMe2), 1.48 (m, 1 H, CH2CHMe2), 1.90, 1.98, 2.00, 2.03 (s, 3 H each, C5Me4) and
5.57, 5.66, 6.85 (m, 1 H each, C5H3) ppm. 13C{1H} NMR (100 MHz, CDCl3, 25 ºC): δ -0.4, 0.4
(SiMe2), 12.2, 12.5 (CpCMe2), 15.2 (CHMe2), 24.3, 25.0, 25.1, 25.6 (C5Me4), 28.3 (CHMe2),
37.0 (CH2CHMe2), 56.2 (CpCMe2), 97.7, 104.2 (C1─Cp), 111.6, 124.0, 127.1, 150.9 (C5H3) and
113.7, 127.6, 135.2, 136.5 (C5Me4) ppm. Elemental analysis calcd (%) for C23H36Cl2SiZr (502.75
g/mol): C 54.95, H 7.22; found: C 54.83, H 7.05.
2.3. Data collection and structural refinement of 5, 6 and 9
Data were collected with an Oxford Gemini CCD system (λ(MoKα) = 0.71073 Å, T = 293(2) K)
using ω and ψ scans. Semi-empirical from equivalents absorption corrections were carried out
with SCALE3 ABSPACK [27]. The structures were solved by direct methods [28]. Structure
refinements were carried out with SHELXL-97 [29]. All non-hydrogen atoms were refined
anisotropically and H atoms were refined using the riding model. Table 1 lists crystallographic
details.
Table 1. Crystallographic data of 5, 6 and 9
Compound
5
6
9
Empirical formula
Molecular weight (g/mol)
Temperature (K)
Wavelength (Å)
C24H38Cl2Ti
445.34
C24H38Cl2Zr
488.66
C23H36Cl2SiZr
502.73
293(2)
293(2)
293(2)
0.71073
Monoclinic
C2/c
0.71073
Monoclinic
C2/c
0.71073
Triclinic
P-1
Crystal system
Space group
5

Revised: JORGANCHEM-D-19-00293
a (pm)
2888.65(18)
665.39(3)
1389.77(7)
90.00
2901.02(4)
670.320(10)
1396.86(2)
90.00
959.80(2)
1020.50(2)
1487.90(2)
72.9040(10)
71.6270(10)
66.508(2)
1244.49(4)
2
b (pm)
c (pm)
α ( )
β ( )
111.149(6)
90.00
111.845(2)
90.00
γ ( )
Volume (Å3)
2.4913(2)
4
2521.30(6)
4
Z
Calculated density (mg/m3)
1.187
1.287
1.342
Absorption
(mm-1)
coefficient
µ
0.564
0.655
0.711
F(000)
952
1024
524
Crystal size (mm)
0.2×0.1×0.05
4.26 a 25.67
-34 ≤ h ≤ 34
-8 ≤ k ≤ 8
-16 ≤ l ≤ 16
64215
0.40×0.20×0.04
4.21 a 29.60
-40 ≤ h ≤ 39
-9 ≤ k ≤ 9
-19 ≤ l ≤ 18
98791
0.30×0.20×0.20
4.17 a 29.53
-11 ≤ h ≤ 11
-12 ≤ k ≤ 12
-18 ≤ l ≤18
70549
θ range ( )
hkl ranges
Collected reflections
2347
[R(int)
=
=
3472
[R(int)
=
5065
[R(int)
=
=
Independent reflections
0.1653]
0.0221]
0.0331]
99.6
99.5
%
(θ
%
(θ
Completeness
97.4 % (θ = 29.60)
25.67 )
29.53 )
and 1.0000
0.97773
Maximum
transition
and
minimum 1.000
0.93502
and 1.0000
0.88308
and
Least squares on Least squares on Least squares on
Refinement method
F2
F2
F2
Data / Restraints / Parameters
Goodness-of-fit on F2
2347 / 0 / 123
1.016
3472 / 0 / 123
1.039
5065 / 0 / 263
1.044
R1 = 0.0671
wR2 = 0.1702
R1 = 0.1347
wR2 = 0.2157
R1 = 0.0270
wR2 = 0.0727
R1 = 0.0296
wR2 = 0.0752
R1 = 0.0395
wR2 = 0.1088
R1 = 0.0452
wR2 = 0.1148
Final R indices [I>2σ(I)]
Final R indices (all data)
Largest diffraction peak and
hole (e·Å3)
0.492 and -0.210
0.670 and -0.308
0.875 and -0.299
2.4 Polymerization
The temperature of a 1 litre glass autoclave was set to 10, 40 or 80 °C. Under an inert N2
atmosphere, the metallocene catalyst (7.5 µmol), MAO (quantity to obtain a Al/M 1000:1 ratio)
and toluene (200 mL) were mixed together for 15 min. The N2 pressure inside the autoclave
6

Revised: JORGANCHEM-D-19-00293
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 60 minutes,
stirring was stopped and the ethylene pressure released. Excess MAO was then destroyed by
adding a mixture of MeOH/HCl (9:1). The polymer was isolated by filtration and washed with
ethanol and dried under vacuum at 90 °C for 24 h.
3. Results and discussion
3.1 Synthesis and characterization of alkenyl-substituted zirconocene complexes 1 and 2
The complexes [Zr(η5-C5H4{CMeRCH2CH2CH=CMe2})2Cl2] (R = Me (1), Ph (2)) have
been synthesized by the reaction of two molar equivalents of the corresponding lithium
derivative Li(C5H4{CMeRCH2CH2CH=CMe2}) (R = Me, Ph) with one molar equivalent of ZrCl4 in
THF for 3 hours at room temperature (Scheme 1). 1 and 2 were isolated as pale yellow solids
R
R
2
THF
Cl
Cl
ZrCl4
+
Zr
Li
R = Me, Ph
R
R = Me (1)
R = Ph (2)
Scheme 1. Synthesis of alkenyl-substituted zirconocene complexes 1 and 2
1 and 2 were characterized by IR spectroscopy. For the alkenyl groups, vibration bands
corresponding to the stretching of the C‒H bonds of the alkenyl substituent and in the case of 2
aromatic groups around 2900‒3100 cm-1 were recorded. Furthermore, a band close to
1630 cm-1 was assigned to the stretching vibration of C=C double bonds.
1
Characterization by H NMR spectroscopy showed the expected signals in each case
due to the different groups of protons in the molecule (see Experimental section). In the
spectrum of 1, two multiplets at 6.31 and 6.40 ppm, assigned to the two types of magnetically
equivalent protons of the monosubstituted cyclopentadienyl ligands, were observed. Moreover,
the expected signals for the alkenyl fragment were also present: a singlet at 1.37 ppm
corresponding to the twelve protons of the four equivalent methyl groups, two singlets at 1.48
and 1.62 ppm assigned to the protons of the four terminal methyl groups of the alkenyl
substituent and two multiplets at 1.43 and 1.65 ppm due to the protons of the four methylene
groups. Finally, a multiplet at 4.97 ppm was assigned to the two protons bonded to the sp2
carbon atoms.
7

Revised: JORGANCHEM-D-19-00293
1
The H NMR spectrum of 2 reveals the presence of two diastereomers (meso and rac
isomers) in a ratio of approximately 1:1 as a consequence of the presence of two chiral carbon
atoms in this molecule.
In the 13C{1H} NMR spectrum of 1, the expected signals due to the alkenyl fragment and
the cyclopentadienyl rings were observed (see Experimental section): two signals at 17.7 and
23.4 ppm due to the two carbon atoms of the terminal methyl groups of the alkenyl substituent,
two additional signals corresponding to the two carbon atoms of the methylene groups at 25.9
and 27.1 ppm, another signal assigned to the two equivalent methyl groups at 36.7 ppm. A
signal around 47 ppm due to the quaternary carbon atom bonded directly to the
cyclopentadienyl ring was also observed. The signals corresponding to the sp2 carbon atoms of
the C=C double bond were located at 124.5 and 131.6 ppm, whereas the three carbon atoms of
the cyclopentadienyl ring were recorded at 112.7, 116.4 and 143.3 ppm.
The 13C{1H} NMR spectrum of 2 again confirms the presence of two isomers as a
consequence of two chiral carbon atoms in the molecule (see Experimental section).
3.2 Synthesis and characterization of bulky alkyl-substituted group 4 metallocene complexes 5
and 6
The metallocene complexes, [M(η5-C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)),
were synthesized in a multi-step process (Scheme 2). Initially, the synthesis of 6-isobutyl-6-
methylfulvene (3) was carried out according to the method described by Little and coworkers
[26]. 3 was purified by liquid-liquid extraction with ether and by column chromatography using
hexane as eluent.
N
O
[TiCl4(THF)2]
ZrCl4
H
Cl
Cl
LiMe
M
Li
3
4
M = Ti (5)
M = Zr (6)
Scheme 2. Synthetic route to bulky alkyl-substituted group 4 metallocene complexes 5 and 6
The IR spectrum of 3 showed the band corresponding to the stretching vibration of C=C
double bond at 1638 cm-1, and those assigned to the stretching vibration of C─H bonds at 2869
and 2957 cm-1 (for Cal─H) and 3069 and 3103 cm-1 (for Car─H).
1
In the H NMR spectrum of 3 a set of four signals due to the protons located on the
aliphatic carbon atoms was observed along with a doublet at 1.00 ppm assigned to the two
terminal methyl groups, a multiplet at 2.02 ppm due to the proton located on the tertiary carbon
atom, a singlet at 2.25 ppm corresponding to the methyl group situated on the end of the alkylic
chain and, finally, a doublet at 2.48 ppm assigned to the two protons of the methylene group. In
8

Revised: JORGANCHEM-D-19-00293
addition to these signals, a multiplet at 6.56 ppm corresponding to the protons located on the
sp2 carbon atoms of the cyclopentadiene ring was also observed.
The 13C{1H} NMR spectrum showed the expected signals for the different carbon atoms.
Thus, four signals between 20 and 50 ppm corresponding to the sp3 carbon atoms were
observed, while for the sp2 carbon atoms there were six additional signals between 120 to 160
ppm.
In the subsequent synthetic step, the reaction of 3 with LiMe gave the corresponding
1
lithium derivative Li(C5H4{CMe2CH2CHMe2}) (4) as a highly air-sensitive white powder. The H
and 13C{1H} NMR spectra of 4 are very similar to those obtained for compound 3 (see
Experimental section).
The reaction of 2 molar equivalents of 4 with [TiCl4(THF)2] and ZrCl4 gave the
metallocene complexes [M(η5-C5H4{CMe2CH2CHMe2})2Cl2] (M = Ti (5), Zr (6)), respectively.
The IR spectra of 5 and 6 showed the expected bands due to the different vibration
modes of the molecule, of special importance is the band corresponding to the stretching
vibration of the Cal–H bond of the alkyl fragment and the cyclopentadienyl at ca. 3000 cm-1. (see
Experimental section). In the 1H NMR spectrum of 5, the expected signals of the alkyl fragment
were observed: a doublet at 0.70 ppm assigned to the protons of the two terminal methyl groups
of the alkyl substituents bonded to both cyclopentadienyl rings, a singlet at 1.37 ppm due to the
protons of the two equivalent methyl groups situated on the quaternary carbon atom, another
doublet at 1.39 ppm for the protons of the methylene group and a multiplet at 1.42 ppm
corresponding to the proton bonded to the tertiary carbon atom. In addition to these signals, two
multiplets at 6.46 and 6.54 ppm assigned to the aromatic protons of the cyclopentadienyl rings
were also observed.
In the 13C{1H} NMR spectrum of 5, the five signals assigned to the sp3 carbon atoms of
the alkyl substituent, as well as the corresponding three signals due to the carbon atoms of the
1
aromatic cyclopentadienyl rings were recorded (see Experimental section). The H and 13C{1H}
NMR spectra of 6 are very similar to those obtained for compound 5 (see Experimental section).
3.3. X-ray Crystal Structures of [Ti(η5-C5H4{CMe2CH2CHMe2})2Cl2] (5) and [Zr(η5-
C5H4{CMe2CH2CHMe2})2Cl2] (6)
The molecular structures of the metallocene complexes 5 and 6 were determined by
single-crystal X-ray diffraction studies (Figures 1 and 2). 5 and 6 crystallize in the monoclinic
C2/c space group, with four molecules in unit cell (Z = 4) and only half of the molecule in the
asymmetric unit because of the presence of a symmetry plane. Selected bond angles and
lengths are given in Table 2.
9

Revised: JORGANCHEM-D-19-00293
Figure 1. Molecular structure and atom-labelling scheme for 5 with ellipsoids at 30% probability
(hydrogen atoms are omitted for clarity)
Figure 2. Molecular structure and atom-labelling scheme for 6 with ellipsoids at 30% probability
(hydrogen atoms are omitted for clarity)
10

Revised: JORGANCHEM-D-19-00293
Table 2. Selected Bond Lengths (Å) and Angles (º) for 5 and 6a
5
6
M1–Cent
M1–Cl1
C1–C2
C2–C3
C3–C4
C4–C5
C1–C5
C1–C6
C6–C7
2.083(9)
2.367(2)
1.399(6)
1.412(6)
1.371(6)
1.401(7)
1.408(6)
1.513(8)
1.532(7)
1.564(8)
1.522(8)
1.494(9)
1.515(9)
2.218(8)
2.445(2)
1.416(2)
1.408(2)
1.417(2)
1.396(3)
1.406(2)
1.520(2)
1.529(3)
1.554(3)
1.528(4)
1.514(4)
1.511(4)
C6–C9
C9–C10
C10–C11
C10–C12
Cent–M1–Cent
Cent–M1–Cl1
Cent-M1-Cl1a
Cl1–M1–Cl1a
C2–C1–C6
C2–C3–C4
C1–C6–C7
C1–C6–C8
C1–C6–C9
130.9(3)
106.7(3)
107.3(3)
90.67(7)
125.2(4)
107.2(4)
111.2(4)
111.8(4)
107.6(4)
119.4(5)
109.7(8)
129.3(4)
106.3(3)
107.9(3)
93.26(2)
128.3(1)
109.0(2)
111.4(2)
110.6(2)
108.4(2)
119.3(2)
109.7(3)
C6–C9–C10
C11–C10–C12
a Cent is the centroid of C1–C5 or C1a–C5a.
It should be noted that 5 and 6 are isostructural. Bond distances and angles are similar to those
found in other group 4 metallocene complexes published by our research group [13,30–32]. The
molecular structures of 5 and 6 present the typical conformation of a bent metallocene with the
metal atom situated in a distorted tetrahedral environment (Cent–M1–Cent, Ti 130.9(3)º; Zr
129.3(4)º) with the coordination of the cyclopentadienyl ligands to the metal centre in an η5
mode and M–Cl bonds of 2.367(2) Å, Ti; 2.445(2) Å, Zr. It is interesting to note that the angle
C6–C9–C10 = 119.4(5) , Ti; 119.3(2)º, Zr, is quite different to that which corresponds to an sp3
hybridization (for atom C9), which is a consequence of the presence of the terminal isopropyl
group. Finally, bond lengths and angles involving the carbon atoms of the cyclopentadienyl ring
as well as those of the alkyl substituent confirm their corresponding sp2 and sp3 hybridization.
3.4. Synthesis and characterization of bulky alkyl-substituted ansa-metallocene complex
[Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9)
The preparation of compound 9 was carried out through various synthetic steps
(Scheme 3).
11

Revised: JORGANCHEM-D-19-00293
Scheme 3. Synthetic route for the preparation of 9.
The addition of SiMe2(C5HMe4)Cl to a solution of 4 in THF, in a molar ratio of 1:1, led to
formation of the ansa-bis(cyclopentadiene) derivative
the
SiMe2(C5HMe4)(C5H4{CMe2CH2CHMe2}) (7) as a yellow oil which was isolated as a mixture of
isomers (Figure 3), and characterized by 1H NMR and 13C{1H} NMR spectroscopy.
1
In the H NMR spectrum of 7 the signals corresponding to the different isomers (Figure
2) are observed. The isomers formed are preferably the 1,3-disubstituted cyclopentadiene
derivatives, as a consequence that the nucleophilic attack preferentially occurs in this position
and not in the 2 position of the ring due to steric hindrance exerted by the alkyl substituent.
Furthermore, there is a predominant isomer which corresponds to isomer I (Figure 3) according
to the NMR spectrum. This isomer is observed in the mixture in a proportion of about 66 %.
H
H
H
H
Si
Si
Si
Si
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
IV
I
II
III
Figure 3. Isomers of the ansa-bis(cyclopentadiene) derivative 7.
1
In the H NMR spectrum, the signals corresponding to the predominant isomer were: a
singlet at -0.16 ppm assigned to the protons of the two methyl groups of the ansa-bridge, two
12

Revised: JORGANCHEM-D-19-00293
doublets at 0.82 and 0.86 ppm corresponding to the protons of the two non-equivalent terminal
methyl groups of the alkyl fragment, two singlets which resonated at a very similar chemical
shifts (1.16 and 1.17 ppm) which have been assigned to the protons of the two methyl groups
located at the quaternary carbon of the alkyl substituent, a doublet for the protons of the
methylene group at around 1.42 ppm, a multiplet at 1.54 ppm due to the methine proton of this
substituent and, finally, two singlets due to protons of the four equivalent methyl groups of the
tetramethylcyclopentadiene ring. In addition to these signals, two additional singlets at 2.93 and
3.19 ppm corresponding to the two acidic protons of the two cyclopentadiene rings were
observed, while olefinic protons of the disubstituted cyclopentadiene ring resonated between
5.90 and 6.60 ppm.
With regards to the characterization by 13C{1H} NMR spectroscopy, signals were
assigned to the predominant isomer. The carbon atoms of the ansa-bridge were recorded at 1.0
ppm. In addition, the atoms of the alkyl substituent gave signals from 25 to 53 ppm: the carbon
atoms of terminal methyl groups were observed at very similar chemical shifts (24.9 and 25.0
ppm), the carbons of the two methyl groups on the quaternary carbon atom appeared at 28.5
and 29.5 ppm, the carbon atom belonging to methine group has a chemical shift of 35.7 ppm,
whereas above 50 ppm the signals due the carbon atom of the methylene group and the
quaternary carbon were also observed. The carbon atoms of the four methyl groups of
pentasubstituted cyclopentadiene ring were recorded at 40.5 and 41.0 ppm, and the two sp3
carbon atoms of the cyclopentadiene rings at 52.9 and 68.2 ppm for the di- and penta-
substituted ring, respectively. Finally, the olefinic carbon atoms appeared as eight signals
between 123 and 159 ppm.
Deprotonation of the two cyclopentadiene rings of 7 was carried out using two
equivalents of LiBun to give the corresponding lithium derivative 8 (Scheme 3) which was
isolated as a highly air-sensitive orange solid.
1
8 was characterized using H NMR and 13C{1H} NMR spectroscopy, observing the
1
expected signals due to the protons and carbons of the lithium derivative. The H NMR
spectrum of 8 showed the following signals: a singlet at 0.39 ppm assigned to the six protons of
the two methyl groups of the ansa-bridge, two additional singlets at 0.76 and 0.78 ppm due to
the two methyl groups on the quaternary carbon atom of the alkyl chain, one singlet at 1.18 ppm
corresponding to the two terminals methyl groups of the alkyl substituent, one doublet due to
the methylene group at 1.42 ppm, one multiplet assigned to the methine proton at 1.60 ppm,
two singlets for the four methyl groups of the pentasubstituted cyclopentadienyl ring at 1.90 and
2.07 ppm and, finally, three multiplets between 5.68 and 5.83 assigned to the protons of the
disubstituted cyclopentadienyl ring.
The 13C{1H} NMR spectrum confirmed the proposed structure for this di-lithium
derivative 8 showing a signal at 4.8 ppm corresponding to the carbon atoms of the two methyl
groups of the ansa-bridge, two signals assigned to the four methyl groups of the
pentasubstituted cyclopentadienyl ring at 11.6 and 14.8 ppm, and five signals between 25.8 and
13

Revised: JORGANCHEM-D-19-00293
56.1 ppm due to the carbon atoms of the alkyl substituent of the disubstituted cyclopentadienyl
ring. In addition, eight signals for the carbon atoms of the cyclopentadienyl rings were observed.
1
In the H NMR spectrum of 8 the methyl groups of the C5Me4 fragment gave only two
peaks as the chemical shifts are identical in the case of C2 with C5 and C3 with C4. The same
occurs in the 13C{1H} NMR spectrum. For the cyclopentadienyl rings, the ten carbon atoms gave
eight signals, with the pairs C2 with C5 and C3 with C4 giving one signal each. The methyl
groups of the ansa-bridge are also equivalent. All this indicates that the dilithium compound
does not adopt a rigid structure (as in the ansa-zirconocene complex 9) in solution.
Finally, transmetallation reaction using the lithium derivative 8 and ZrCl4 was carried out
in a molar ratio of 1:1, to obtain the ansa-zirconocene complex [Zr{Me2Si(η5-C5Me4)(η5-
C5H3{CMe2CH2CHMe2})}Cl2] (9) (Scheme 3) as a yellow crystalline solid.
1
Complex 9 has been characterized by IR, H NMR and 13C{1H} NMR spectroscopy,
elemental analysis and single-crystal X-ray diffraction studies.
In the characterization by IR spectroscopy, bands corresponding to the stretching
vibration of the Cal-H bonds of the alkyl fragment below 3000 cm-1 were observed.
The 1H NMR spectrum of 9 showed the expected signals. In the case of the alkyl moiety
bound to one of the cyclopentadienyl rings, the spectrum shows the following signals: a doublet
at 0.63 ppm due to the protons of the two terminal methyl groups, another doublet assigned to
the protons of the methylene group at 0.83 ppm, a multiplet at 1.48 ppm corresponding to the
proton located on the tertiary carbon atom and two singlets due to the protons of the two methyl
groups situated on the quaternary carbon atom directly bonded to the cyclopentadienyl ring. In
this case, and in contrast to the compounds 5 and 6, these methyl groups are diastereotopic
because of the presence of planar chirality in the molecule. However, the two terminal methyl
groups of the alkyl substituent, as indicated before, gave only one signal as they are somewhat
distanced from the source of the planar chirality. This was also observed in the dilithium
precursor 8.
In addition to these signals involving the alkyl substituent, four singlets between 1.90
and 2.10 ppm assigned to the protons of the four methyl groups of the other cyclopentadienyl
ring and two singlets about 0.85 ppm, corresponding to the protons of the two methyl groups
forming the ansa-bridge were observed. Finally, the three protons attached to the substituted
cyclopentadienyl ring resonated as three multiplets at 5.57, 5.66 and 6.85 ppm.
Regarding the characterization by 13C{1H}-NMR, the spectrum of 9 shows two signals
around 0 ppm corresponding to the two carbon atoms of the methyl groups attached to the
silicon atoms of the ansa-bridge, two signals at 12 ppm due to the two carbon atoms of the
diastereotopic methyl groups substituting the quaternary carbon atom directly bonded to one of
the cyclopentadienyl rings, only one signal for the two terminal methyl groups of the alkyl
substituent at 15.2 ppm and three more signals due to the remaining sp3 carbon atoms of the
alkyl substituent.
In addition to these signals, the four carbon atoms of the methyl groups bonded to one
of the cyclopentadienyl rings resonated at similar chemical shifts (24.3, 25.0, 25.1 and 25.6
14

Revised: JORGANCHEM-D-19-00293
ppm), while towards lower fields, above 100 ppm, ten signals corresponding to the ten carbon
atoms of the two cyclopentadienyl rings were observed.
3.5. X-ray Crystal Structure of [Zr{Me2Si(η5-C5Me4)(η5-C5H3{CMe2CH2CHMe2})}Cl2] (9)
The molecular structure of the ansa-zirconocene complex 9 was determined by single-
crystal X-ray diffraction studies (Figure 4). Compound 9 crystallizes in the triclinic P-1 space
group with two molecules in the unit cell. Selected bond angles and lengths are given in
Table 3.
Figure 4. Molecular structure and atom-labelling scheme for [Zr{Me2Si(η5-C5Me4)(η5-
C5H3{CMe2CH2CHMe2})}Cl2] (9) with ellipsoids at 30% probability (hydrogen atoms are omitted
for clarity)
The η5 coordination mode of the cyclopentadienyl rings of the zirconium atom and a
distorted tetrahedral environment (bond angle Cent1–Zr1–Cent2 cent1 of 127.3(2)º) were
confirmed by this study. This bond angle, although similar to those found in other ansa-
metallocene complexes [8], is slightly lower than that found for compound 6 directly due to the
presence of the ansa-bridge.
15

Revised: JORGANCHEM-D-19-00293
The angles involving the carbon atoms of the alkyl chain are close to 109.5 again
indicating the sp3 hybridization of these atoms. This fact is confirmed considering the bond
distances values between these carbon atoms that are close to 1.54 Å (C–C single bond).
Finally, and with respect to the ansa-bridge, the distance between the silicon atom and
each of the four carbon atoms, are close to the value of 1.86 Å, in addition, the C1─Si1─C6 and
C11─Si1─C12 angles are of 94.9(1) and 108.3(2), respectively, slightly distorted from the
tetrahedral geometry of the silicon atom. Furthermore, the angles Si1-C1-Cent1 and Si1-C6-
Cent2 are of 163.0(2) and 162.0(2), respectively, and show the slight distortion of the planarity
of the cyclopentadienyl rings.
Table 3. Selected Bond Lengths (Å) and Angles (º) for 9a
Bond Lengths (Å)
Zr1─Cent1
Zr1─Cent2
Zr1─Cl1
Zr1─Cl2
Si1─C1
Si1─C6
Si1─C11
Si1─C12
C1─C2
9
2.235(2)
2.224(2)
2.4291(8)
2.4168(8)
1.872(3)
1.885(3)
1.849(3)
1.857(3)
1.419(4)
1.405(4)
1.437(4)
1.400(4)
1.520(5)
1.524(5)
9
C3─C4
C6─C7
C8─C9
C13─C14
C16─C21
Angles (º)
Cent1─Zr1─Cent2
Cl1─Zr1─Cl2
C1─Si1─C6
C11─Si1─C12
Si1-C1-Cent1
Si1-C6-Cent2
C1─C2─C3
C3─C4─C5
C7─C8─C9
C8─C9─C10
C14─C13─C15
C13─C16─C21
C22─C21─C23
127.3(2)
98.77(4)
94.9(1)
108.3(2)
163.0(2)
162.0(2)
109.9(2)
109.0(2)
108.6(2)
107.8(2)
109.6(3)
118.5(3)
101.7(9)
Cent1 and Cent2 refer to the centroids of C1–C5 and C6–C10, respectively.
3.6. Ethylene polymerization studies
Ethylene polymerization studies have been carried out using the metallocene
complexes 1, 2, 5, 6 and 9 as catalysts. The parent titanocene and zirconocene derivatives
[M(η5-C5H5)2Cl2] (M = Ti, Zr) have been tested as reference catalysts.
The polymerization experiments were carried out using 7.5 µmoles of catalyst and
methylaluminoxane (MAO) in a Al:Ti 1000:1 ratio. The time and temperature of all experiments
were 60 minutes and at temperatures of 10, 40 and 80 C, respectively, using 2.0 bar of
16

Revised: JORGANCHEM-D-19-00293
monomer pressure. The catalytic activities (in kg PE/molM·h), as well as the polymer molecular
weight and distribution values (polydispersity) are given in Table 4.
Table 4. Ethylene polymerization results for 1, 2, 5, 6, and 9 and [M(η5-C5H5)2Cl2] (M = Ti, Zr) a
Temperature
Catalysts
Activity b
Mw
Mw/Mn
( C)
10
40
80
10
40
80
10
40
80
10
40
80
10
40
80
10
40
80
10
40
80
[Ti(η5-C5H5)2Cl2]
Inactive
315
-
-
51000
-
3.2
-
Inactive
Inactive
Inactive
Inactive
1830
[Ti(η5-
-
-
C5H4{CMe2CH2CHMe2})2Cl2]
-
-
(5)
-
-
[Zr(η5-C5H5)2Cl2]
859336
436969
73182
848370
450825
119962
-
3.61
3.65
2.92
3.10
4.43
5.47
-
3704
12716
981
[Zr(η5-
C5H4{CMe2CH2CH2CH=CMe2}
1409
)2Cl2] (1)
661
[Zr(η5-
Inactive
Inactive
Inactive
980
C5H4{CMePhCH2CH2CH=CM
e2})2Cl2] (2)
-
-
-
-
[Zr(η5-
818515
545169
234637
345286
221645
147508
4.88
4.76
5.65
4.16
2.52
3.61
C5H4{CMe2CH2CHMe2})2Cl2]
1001
(6)
841
[Zr{Me2Si(η5-C5Me4)(η5-
56
C5H3{CMe2CH2CHMe2})}Cl2]
311
(9
)
345
a 2 bar monomer pressure, 200 mL toluene, tPol = 60 min.
b In kg polymer / (molM h bar).
In general, at all the studied temperatures, the zirconocene complexes were less active than the
reference catalyst [Zr(η5-C5H5)2Cl2], indicating that the introduction of alkenyl or bulky alkyl
substituents on the cyclopentadienyl rings leads to a significant decrease in the catalytic activity
of these compounds. This fact can be explained principally based on steric hindrance (Scheme
4) which may impede olefin coordination in the catalytic cycle and decrease of catalytic activity
in ethylene polymerization.
17

Revised: JORGANCHEM-D-19-00293
Scheme 4. Steric hindrance consideration in ethylene polymerization
For the alkenyl complexes 1 and 2 an additional factor is the possible intramolecular
interaction of the ligand with the zirconium metal centre that would block the vacant site and
prevent olefin coordination (Scheme 5). This phenomenon has been previously observed
[33,34]. In fact, complex 2 proved to be non-responsive as a catalyst under the tested
experimental conditions.
R
R
Zr
Zr
C=C coordination
Me
Me
R
R
Scheme 5. C=C intramolecular coordination to the metal centre.
The titanocene complex 5, showed no catalytic activity at any of the studied
temperatures under the mild experimental conditions used in the polymerization. In addition, the
reference complex [Ti(η5-C5H5)2Cl2] only presented catalytic activity at 40 ºC, which confirms
that the well-known fact that titanium-based metallocene complexes are far less active than
their zirconium counterparts.
In general increasing temperature gives higher catalytic activities. However, for 1 and 6,
activities at 80 ºC were lower to those recorded at 40 and 10 ºC. Variation in temperature for 1,
6 and 9 is not nearly as influential as that experienced by the reference catalyst [Zr(η5-
C5H5)2Cl2] (see Table 5). The highest catalytic activity was observed for 6 at 40 C (1409 kg
PE/molZr·h bar).
Polyethylene molecular weights obtained with the catalyst 1, 6 and 9 were between
119000 and 850000 g/mol, being similar to the molecular weights of the polymers obtained with
the reference catalyst at each temperature. Molecular weights decreased on increasing the
polymerization temperature.
18

Revised: JORGANCHEM-D-19-00293
Polydispersity values of the polymers obtained are close to 3, being slightly higher than
those for polymers obtained with single-site catalysts. This slight broadening of the molecular
weight distribution (polydispersity) is probably due to the chemical equilibrium between the two
possible rotamers of metallocene complexes, generating the existence of several active sites
(Scheme 6).
Scheme 6. Rotamers in the case of disubstituted zirconocene complex.
The best value of polydispersity (Mw/Mn = 2.52) was recorded for the polyethylene
produced with the ansa-metallocene complex 9 at 40 ºC. The ansa-bridge impedes the rotation
of the cyclopentadienyl ring making a more fixed environment around the zirconium metal
centre.
4. Conclusions
New alkenyl and alkyl substituted group 4 metallocene(IV). dichloride complexes have
been synthesized and characterized. The molecular structures of 5, 6 and 9 have been
determined and reveal the typical bent metallocene conformation. The metallocene complexes
were tested as catalysts in the polymerization of ethylene with only the zirconocene complexes
1, 6 and 9 showing catalytic activity. The alkenyl and alkyl substituents were shown to
negatively influence the catalytic activity probably due to steric hindrance and in the case of the
alkenyl substituted zirconocene 1 and 2 by intermolecular coordination blocking the vacant site
from ethylene monomer coordination.
Acknowledgements
We gratefully acknowledge financial support from the Ministerio de Ciencia, Innovación
y Universidades of Spain (Grant no. RTI2018-094322-B-I00).
Appendix A. Supplementary material
CCDC 1915969-1915971 contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data to this article can be found online at …
References
[1] N.J. Long, Metallocenes: An Introduction to Sandwich Complexes, Wiley, 1998.
19

Revised: JORGANCHEM-D-19-00293
[2] A. Togni, R.L. Halterman, Metallocenes: synthesis, reactivity, applications, Wiley-VCH,
1998.
[3] M.M. Santos, P. Bastos, I. Catela, K. Zalewska, L.C. Branco, Recent Advances of
Metallocenes for Medicinal Chemistry, Mini Rev Med Chem. 17 (2017) 771–784.
doi:10.2174/1389557516666161031141620.
[4] T. Takahashi, ed., Metallocenes in Regio- and Stereoselective Synthesis, Springer-Verlag,
Berlin Heidelberg, 2005. https://www.springer.com/la/book/9783540016069 (accessed
May 14, 2019).
[5] J.B.P. Soares, A.E. Hamielec, Metallocene/Aluminoxane Catalysts for Olefin
Polymerization.
A
Review, Polymer Reaction Engineering.
3
(1995) 131–200.
doi:10.1080/10543414.1995.11671695.
[6] H.G. Alt, A. Köppl, Effect of the Nature of Metallocene Complexes of Group IV Metals on
Their Performance in Catalytic Ethylene and Propylene Polymerization, Chem. Rev. 100
(2000) 1205–1222. doi:10.1021/cr9804700.
[7] G.W. Coates, Precise Control of Polyolefin Stereochemistry Using Single-Site Metal
Catalysts, Chem. Rev. 100 (2000) 1223–1252. doi:10.1021/cr990286u.
[8] S. Prashar, A. Antiñolo, A. Otero, Insights into group 4 and 5 ansa-bis(cyclopentadienyl)
complexes with a single-atom bridge, Coordination Chemistry Reviews. 250 (2006) 133–
154. doi:10.1016/j.ccr.2005.05.017.
[9] A. Antiñolo, M. Fajardo, S. Gómez-Ruiz, I. López-Solera, A. Otero, S. Prashar, A.M.
Rodrıguez, Group 4 metallocene complexes incorporating vinyl or allyl substituted ansa
́
ligands.
X-Ray
crystal
structures
of
[Zr{Me(CH2=CH)Si(η5-C5Me4)2}Cl2],
[Zr{Me(CH2=CHCH2)Si(η5-C5H4)2}Cl2] and [Zr{Me(CH2=CHCH2)Si(η5-C5Me4)(η5-C5H4)}Cl2],
Journal of Organometallic Chemistry. 683 (2003) 11–22. doi:10.1016/S0022-
328X(03)00166-9.
[10] A. Antiñolo, M. Fajardo, S. Gómez-Ruiz, I. López-Solera, A. Otero, S. Prashar,
Hydrosilylation in the Design and Functionalization of ansa-Metallocene Complexes,
Organometallics. 23 (2004) 4062–4069. doi:10.1021/om049791u.
[11] S. Gómez-Ruiz, S. Prashar, M. Fajardo, A. Antiñolo, A. Otero, M.A. Maestro, V. Volkis,
M.S. Eisen, C.J. Pastor, Synthesis, hydrosilylation reactivity and catalytic properties of
group
4
ansa-metallocene complexes, Polyhedron. 24 (2005) 1298–1313.
doi:10.1016/j.poly.2005.03.056.
[12] S. Gómez-Ruiz, S. Prashar, L.F. Sánchez-Barba, D. Polo-Cerón, M. Fajardo, A. Antiñolo,
A. Otero, M.A. Maestro, C.J. Pastor, Synthesis and catalytic applications of C1 symmetric
group 4 ansa-metallocene complexes, Journal of Molecular Catalysis A: Chemical. 264
(2007) 260–269. doi:10.1016/j.molcata.2006.09.011.
[13] D. Polo-Cerón, S. Gómez-Ruiz, S. Prashar, M. Fajardo, A. Antiñolo, A. Otero, I. López-
Solera, M.L. Reyes, Synthesis of chiral unbridged zirconocene complexes: Applications in
the polymerization of ethylene and propylene, Journal of Molecular Catalysis A: Chemical.
268 (2007) 264–276. doi:10.1016/j.molcata.2006.12.040.
[14] D. Polo-Cerón, S. Gómez-Ruiz, J. Ceballos-Torres, S. Prashar, M. Fajardo, M.L. Reyes,
Synthesis and structural characterization of novel three carbon atom bridged ansa-
bis(indenyl)zirconocene complexes: Applications in ethylene polymerization, Polyhedron.
80 (2014) 129–133. doi:10.1016/j.poly.2014.02.033.
[15] U. Romano, F. Garbassi, The environmental issue. A challenge for new generation
polyolefins,
Pure
and
Applied
Chemistry.
72
(2000)
1383–1388.
doi:10.1351/pac200072071383.
[16] D.W. Sauter, M. Taoufik, C. Boisson, Polyolefins, a Success Story, Polymers. 9 (2017)
185. doi:10.3390/polym9060185.
[17] The future of plastic, Nature Communications. 9 (2018) 2157. doi:10.1038/s41467-018-
04565-2.
[18] M.R. Machat, A. Fischer, D. Schmitz, M. Vöst, M. Drees, C. Jandl, A. Pöthig, N.P.M.
Casati, W. Scherer, B. Rieger, Behind the Scenes of Group 4 Metallocene Catalysis:
Examination of the Metal–Carbon Bond, Organometallics. 37 (2018) 2690–2705.
doi:10.1021/acs.organomet.8b00339.
[19] M.E.Z. Velthoen, A. Muñoz-Murillo, A. Bouhmadi, M. Cecius, S. Diefenbach, B.M.
Weckhuysen, The Multifaceted Role of Methylaluminoxane in Metallocene-Based Olefin
Polymerization
Catalysis,
Macromolecules.
51
(2018)
343–355.
doi:10.1021/acs.macromol.7b02169.
20

Revised: JORGANCHEM-D-19-00293
[20] X. Wang, X. Han, F. Ren, R. Xu, Y. Bai, Porous Organic Polymers-Supported Metallocene
Catalysts for Ethylene/1-Hexene Copolymerization, Catalysts.
doi:10.3390/catal8040146.
8
(2018) 146.
[21] S. Gómez‐Ruiz, D. Polo‐Cerón, S. Prashar, M. Fajardo, A. Antiñolo, A. Otero, Synthesis
and Reactivity of Alkenyl-Substituted Zirconocene Complexes and Their Application as
Olefin Polymerisation Catalysts, European Journal of Inorganic Chemistry. 2007 (2007)
4445–4455. doi:10.1002/ejic.200700394.
[22] S. Gómez-Ruiz, D. Polo-Cerón, S. Prashar, M. Fajardo, V.L. Cruz, J. Ramos, E. Hey-
Hawkins, Synthesis, characterization and catalytic behaviour of ansa-zirconocene
complexes containing tetraphenylcyclopentadienyl rings: X-ray crystal structures of
[Zr{Me2Si(η5-C5Ph4)(η5-C5H3R)}Cl2] (R=H, But), Journal of Organometallic Chemistry. 693
(2008) 601–610. doi:10.1016/j.jorganchem.2007.11.054.
[23] S. Gómez-Ruiz, G.N. Kaluđerović, D. Polo-Cerón, V. Tayurskaya, S. Prashar, M. Fajardo,
R. Paschke, A novel alkenyl-substituted ansa-zirconocene complex with dual application
as olefin polymerization catalyst and anticancer drug, Journal of Organometallic
Chemistry. 694 (2009) 3032–3038. doi:10.1016/j.jorganchem.2009.05.013.
[24] J. Ceballos‐Torres, P. Virag, M. Cenariu, S. Prashar, M. Fajardo, E. Fischer‐Fodor, S.
Gómez‐Ruiz, Anti-cancer Applications of Titanocene-Functionalised Nanostructured
Systems: An Insight into Cell Death Mechanisms, Chemistry – A European Journal. 20
(2014) 10811–10828. doi:10.1002/chem.201400300.
[25] A. Antiñolo, I. López-Solera, I. Orive, A. Otero, S. Prashar, A.M. Rodríguez, E. Villaseñor,
Niobium and Zirconium Complexes Incorporating Asymmetrically Substituted ansa
Ligands. X-ray Crystal Structures of [Me2Si(η5-C5Me4)(η5-C5H3R)]Nb(NtBu)Cl (R = Me, iPr)
and [Me2Si(η5-C5Me4)(η5-C5H3R)]ZrCl2 (R = H, Me), Organometallics. 20 (2001) 71–78.
doi:10.1021/om0006662.
[26] K.J. Stone, R.D. Little, An exceptionally simple and efficient method for the preparation of
a wide variety of fulvenes, J. Org. Chem. 49 (1984) 1849–1853. doi:10.1021/jo00185a001.
[27] SCALE3 ABSPACK - Empirical absoption correction. CrysAlis Software Package, Oxford
Diffraction Ltd., 2006.
[28] G.M. Sheldrick, SHELXS-97; University of Göttingen: Göttingen, Germany, 1997;
Sheldrick, Acta Crystallogr., Sect. A. 46 (1990) 467–473.
[29] G.M. Sheldrick, SHELXL-97, Program for crystal structure refinement; University of
Göttingen: Göttingen, Germany, 1997.
[30] S. Gómez-Ruiz, G.N. Kaluđerović, D. Polo-Cerón, S. Prashar, M. Fajardo, Ž. Žižak, Z.D.
Juranić, T.J. Sabo, Study of the cytotoxic activity of alkenyl-substituted ansa-titanocene
complexes,
doi:10.1016/j.inoche.2007.03.016.
[31] J. Ceballos-Torres, S. Gómez-Ruiz, G.N. Kaluđerović, M. Fajardo, R. Paschke, S.
Prashar, Naphthyl-substituted titanocene dichloride complexes: Synthesis,
Inorganic
Chemistry
Communications.
10
(2007)
748–752.
characterization and in vitro studies, Journal of Organometallic Chemistry. 700 (2012)
188–193. doi:10.1016/j.jorganchem.2011.12.015.
[32] J. Ceballos-Torres, M.J. Caballero-Rodríguez, S. Prashar, R. Paschke, D. Steinborn, G.N.
Kaluđerović, S. Gómez-Ruiz, Synthesis, characterization and in vitro biological studies of
titanocene(IV) derivatives containing different carboxylato ligands, Journal of
Organometallic Chemistry. 716 (2012) 201–207. doi:10.1016/j.jorganchem.2012.06.028.
[33] A.I. Licht, H.G. Alt, Synthesis of novel metallacyclic zirconocene complexes from ω-
alkenyl-functionalized zirconocene dichloride complexes and their use in the α-olefin
polymerization, Journal of Organometallic Chemistry. 648 (2002) 134–148.
doi:10.1016/S0022-328X(01)01454-1.
[34] M. Lamač, M. Horáček, J. Kubišta, J. Pinkas, Intramolecular activation of pendant alkenyl
group as a tool for modification of the zirconocene framework, Inorganica Chimica Acta.
373 (2011) 291–294. doi:10.1016/j.ica.2011.03.061.
21

Highlights
•
•
•
New alkenyl and alkyl substituted group 4 metallocene complexes have been
synthesized and characterized.
Molecular structures of titanocene and zirconocene complexes have been
determined.
Metallocene complexes have been studied as catalysts in ethylene
polymerization.