Synthesis, APPI Mass-Spectrometric Characterization, and Polymerization Studies of Group 4 Dinuclear Bis(ansa-metallocene) Complexes

Abstract

New ligand platforms of the type p- or m-Ph{-CR(3,6-tBu2Flu)(Cp)}2 (para-, R = Me (2a), H (2b); meta-, R = Me (2c)) were synthesized via nucleophilic addition of the 3,6-tBu2-fluorenyl-anion onto the parent phenylene-bridged difulvenes (1a–c). The corresponding discrete homodinuclear zirconium and hafnium bis(dichloro ansa-metallocene) complexes, Ph[{-CR(3,6-tBu2Flu)(Cp)}MCl2]2 (p-, R = Me (3a-Zr2, 3a-Hf2), R = H (3b-Zr2); m-, R = Me (3c-Zr2), were prepared by salt metathesis reactions. An attempt to generate in situ a heterodinuclear complex 3a-Zr-Hf was also undertaken. For the first time, Atmospheric Pressure PhotoIonization (APPI) mass-spectrometric data were obtained for all dinuclear compounds and found to be in excellent agreement with the simulated ones. Preliminary studies on the catalytic performances of these dinuclear complexes, upon activation with MAO, in ethylene homopolymerization and ethylene/1-hexene copolymerization revealed a few differences as compared to those of the monometallic analogues. In particular, slightly lower molecular weights and a greater formation of short methyl and ethyl branches were obtained with the dinuclear systems.

Full text

catalysts
Article
Synthesis, APPI Mass-Spectrometric Characterization,
and Polymerization Studies of Group 4 Dinuclear
Bis(ansa-metallocene) Complexes
Gilles Schnee 1, Mathilde Farenc 2,3,4 , Leslie Bitard 1, Aurelien Vantomme 5,
Alexandre Welle 5, Jean-Michel Brusson 6, Carlos Afonso 2,4 , Pierre Giusti 3,4,
Jean-François Carpentier 1, * and Evgueni Kirillov 1, *
1
Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35000 Rennes, France;
gilles.schnee@wanadoo.fr (G.S.); leslie.bitard@etudiant.univ-rennes1.fr (L.B.)
2CNRS, COBRA, Univ Rouen, UMR 6014, F-76821 Mont Saint Aignan, France;
mathildefarenc@gmail.com (M.F.); carlos.afonso@univ-rouen.fr (C.A.)
3Total Research and Technologies Gonfreville, BP 27, F-76700 Harfleur, France; pierre.giusti@total.com
4
Total Raffinage Chimie, Joint Laboratory C2MC (Complex Matrices Molecular Characterization), Univ Pau,
Univ Rouen, CNRS, F-64053 Pau, France
5Total Research and Technologies Feluy, Zone Industrielle C, B-7181 Feluy, Belgium;
aurelien.vantomme@total.com (A.V.); alexandre.welle@total.com (A.W.)
6Total SA, Direction scientifique, F-92069 Paris La Défense, France; jean-michel.brusson@total.com
*
Correspondence: jean-francois.carpentier@univ-rennes1.fr (J.-F.C.); evgueni.kirillov@univ-rennes1.fr (E.K.);
Tel.: +33-223-236-118 (E.K.)
Received: 25 October 2018; Accepted: 13 November 2018; Published: 19 November 2018


Abstract:
New ligand platforms of the type p- or m-Ph{-CR(3,6-tBu
2
Flu)(Cp)}
2
(para-, R = Me (
2a
),
H (
2b
); meta-, R = Me (
2c
)) were synthesized via nucleophilic addition of the 3,6-tBu
2
-fluorenyl-anion
onto the parent phenylene-bridged difulvenes (
1a
–
c
). The corresponding discrete homodinuclear
zirconium and hafnium bis(dichloro ansa-metallocene) complexes, Ph[{-CR(3,6-tBu
2
Flu)(Cp)}MCl
2
]
2
(p-, R = Me (
3a-Zr2
,
3a-Hf2
), R = H (
3b-Zr2
); m-, R = Me (
3c-Zr2
), were prepared by salt metathesis
reactions. An attempt to generate in situ a heterodinuclear complex
3a-Zr
-
Hf
was also undertaken.
For the first time, Atmospheric Pressure PhotoIonization (APPI) mass-spectrometric data were
obtained for all dinuclear compounds and found to be in excellent agreement with the simulated ones.
Preliminary studies on the catalytic performances of these dinuclear complexes, upon activation
with MAO, in ethylene homopolymerization and ethylene/1-hexene copolymerization revealed a
few differences as compared to those of the monometallic analogues. In particular, slightly lower
molecular weights and a greater formation of short methyl and ethyl branches were obtained with
the dinuclear systems.
Keywords: metallocene catalysts; mass-spectroscopy; olefin polymerization
1. Introduction
The development and applications of multinuclear group 4 metal
α
-olefin polymerization
catalysts have increased dramatically in the past decade [
1
,
2
]. The interest in this area has primarily
been driven by the potential to exploit intermetallic cooperativity/synergism between the two or
more proximal metal centers to eventually enhance the performance of polymerization systems.
For instance, several studies on dinuclear catalysts suggest that catalyst activity [
3
–
13
] and molecular
weight,
[3,7,10,14]
tacticity, [
13
–
15
], or comonomer incorporation [
8
,
16
–
20
] of/in the resulting polymers
Catalysts 2018,8, 558; doi:10.3390/catal8110558 www.mdpi.com/journal/catalysts

Catalysts 2018,8, 558 2 of 19
can be greater than those of the corresponding mononuclear analogues that have isostructural
catalytic sites.
Group 4 metal catalysts based on one-carbon-bridged ansa-cyclopentadienyl-fluorenyl platforms,
{R
2
C(Cp/Flu)}
2−
, hold a unique position in
α
-olefin polymerization thanks to their high catalytic
activity, excellent control, and remarkable stereospecificity [
21
–
33
]. However, only a few examples of
dinuclear systems of this type have been reported in the literature (Scheme 1) [9,34–37].
Catalysts 2018, 8, x FOR PEER REVIEW 2 of 19
polymers can be greater than those of the corresponding mononuclear analogues that have
isostructural catalytic sites.
Group 4 metal catalysts based on one-carbon-bridged ansa-cyclopentadienyl-fluorenyl
platforms, {R2C(Cp/Flu)}2−, hold a unique position in α-olefin polymerization thanks to their high
catalytic activity, excellent control, and remarkable stereospecificity [21–33]. However, only a few
examples of dinuclear systems of this type have been reported in the literature (Scheme 1) [9,34–37].
Scheme 1. Examples of group 4 dinuclear bis(dichloro ansa-metallocene) complexes that incorporate
{R2C(Cp/Flu)} ligand platforms [8,9].
We herein report on the synthesis of dinuclear group 4 bis(Cp/Flu-metallocene) complexes,
linked at the C1-bridge by a para- or meta-phenylene moiety [3,18–20,38], as well as their
characterization by NMR spectroscopy and advanced Atmospheric Pressure PhotoIonization (APPI)
mass-spectrometric methods. The catalytic performances of the synthesized complexes, after their
activation with MAO, were preliminarily investigated in homogeneous ethylene
homopolymerization and ethylene/1-hexene copolymerization, and compared to those of the
mononuclear ansa-metallocene complexes as a reference.
2. Results and Discussion
2.1. Synthesis of Proligands
An efficient and scalable synthesis via nucleophilic addition of the (3,6-di-tert-butyl)fluorenyl
anion onto fulvenes is regularly utilized to prepare one-carbon-bridged R2C{Cp/Flu}H2 proligands
[21–28]. This methodology was here extended to three different bis(fulvene) platforms (1a–c), which
were prepared from cyclopentadiene and the corresponding aromatic diketones or dialdehydes
(Scheme 2), and isolated in good yields as yellow or orange solids.
Scheme 1.
Examples of group 4 dinuclear bis(dichloro ansa-metallocene) complexes that incorporate
{R2C(Cp/Flu)} ligand platforms [8,9].
We herein report on the synthesis of dinuclear group 4 bis(Cp/Flu-metallocene) complexes,
linked at the C1-bridge by a para- or meta-phenylene moiety [
3
,
18
–
20
,
38
], as well as their
characterization by NMR spectroscopy and advanced Atmospheric Pressure PhotoIonization (APPI)
mass-spectrometric methods. The catalytic performances of the synthesized complexes, after their
activation with MAO, were preliminarily investigated in homogeneous ethylene homopolymerization
and ethylene/1-hexene copolymerization, and compared to those of the mononuclear ansa-metallocene
complexes as a reference.
2. Results and Discussion
2.1. Synthesis of Proligands
An efficient and scalable synthesis via nucleophilic addition of the (3,6-di-tert-butyl)fluorenyl
anion onto fulvenes is regularly utilized to prepare one-carbon-bridged R
2
C{Cp/Flu}H
2
proligands
[21–28]
. This methodology was here extended to three different bis(fulvene)
platforms (
1a
–
c
), which were prepared from cyclopentadiene and the corresponding aromatic diketones
or dialdehydes (Scheme 2), and isolated in good yields as yellow or orange solids.

Catalysts 2018,8, 558 3 of 19
Catalysts 2018, 8, x FOR PEER REVIEW 3 of 19
Scheme 2. Synthesis of the para- and meta-phenylene-bridged bis(fulvenes) 1a–c.
To prepare the targeted p- and m-Ph{-CR(3,6-tBu2FluH)(CpH)}2 proligands 2a–c, bis(fulvenes)
1a–c were subsequently reacted with two equiv. of the {3,6-tBu2Flu}− anion in THF (Scheme 3). After
workup, the corresponding para-bridged proligands 2a,b were isolated in good yields;
synthesis/recovery of the meta-bridged proligand 2c proved somehow to be more difficult (22%
isolated yield). This lower yield may be due to a larger steric hindrance in the final meta-phenylene-
bridged product imposed by the two very bulky {Cp/Flu} moieties as compared to the para analogues.
Scheme 3. Synthesis of the proligands 2a–c.
These proligands are stable at room temperature in solution and in the solid state, and their
structures were authenticated by 1H and 13C NMR spectroscopy (Figures S9, S10, S12, S13, S15, and
S16) and ESI-mass spectrometry (Figures S11, S14, and S17). The NMR data for these compounds
appeared to be complicated by the presence of two stereogenic centers in the molecules, resulting in
Scheme 2. Synthesis of the para- and meta-phenylene-bridged bis(fulvenes) 1a–c.
To prepare the targeted p- and m-Ph{-CR(3,6-tBu
2
FluH)(CpH)}
2
proligands
2a
–
c
, bis(fulvenes)
1a
–
c
were subsequently reacted with two equiv. of the {3,6-tBu
2
Flu}
−
anion in THF (Scheme 3).
After workup, the corresponding para-bridged proligands
2a,b
were isolated in good yields;
synthesis/recovery of the meta-bridged proligand
2c
proved somehow to be more difficult (22% isolated
yield). This lower yield may be due to a larger steric hindrance in the final meta-phenylene-bridged
product imposed by the two very bulky {Cp/Flu} moieties as compared to the para analogues.
Catalysts 2018, 8, x FOR PEER REVIEW 3 of 19
Scheme 2. Synthesis of the para- and meta-phenylene-bridged bis(fulvenes) 1a–c.
To prepare the targeted p- and m-Ph{-CR(3,6-tBu2FluH)(CpH)}2 proligands 2a–c, bis(fulvenes)
1a–c were subsequently reacted with two equiv. of the {3,6-tBu2Flu}− anion in THF (Scheme 3). After
workup, the corresponding para-bridged proligands 2a,b were isolated in good yields;
synthesis/recovery of the meta-bridged proligand 2c proved somehow to be more difficult (22%
isolated yield). This lower yield may be due to a larger steric hindrance in the final meta-phenylene-
bridged product imposed by the two very bulky {Cp/Flu} moieties as compared to the para analogues.
Scheme 3. Synthesis of the proligands 2a–c.
These proligands are stable at room temperature in solution and in the solid state, and their
structures were authenticated by 1H and 13C NMR spectroscopy (Figures S9, S10, S12, S13, S15, and
S16) and ESI-mass spectrometry (Figures S11, S14, and S17). The NMR data for these compounds
appeared to be complicated by the presence of two stereogenic centers in the molecules, resulting in
Scheme 3. Synthesis of the proligands 2a–c.
These proligands are stable at room temperature in solution and in the solid state, and their
structures were authenticated by
1
H and
13
C NMR spectroscopy (Figures S9, S10, S12, S13, S15,

Catalysts 2018,8, 558 4 of 19
and S16) and ESI-mass spectrometry (Figures S11, S14, and S17). The NMR data for these compounds
appeared to be complicated by the presence of two stereogenic centers in the molecules, resulting in the
existence of pairs of diastereoisomers in each case, and also of their different tautomers (i.e., isomers
of C=C bonds within the CpH rings). The ESI-MS measurements data showed clearly the expected
molecular [M + H]+ions at m/z815.55, 787.52 for 2a,b and at 853.51 ([M + K]+) for 2c.
2.2. Synthesis of Group 4 Dinuclear Bis(dichloro ansa-metallocene) Complexes
In order to prepare the corresponding group 4 bis(dichloro ansa-metallocene) complexes,
standard salt-metathesis reactions between the ligand tetraanions, generated in situ in Et
2
O, and MCl
4
salts (2 equiv.), were used (Scheme 4). Thus, the homodinuclear bis(dichloro ansa-zirconocenes)
3a-c-Zr2
and bis(dichloro ansa-hafnocene)
3a-Hf2
were isolated in good yields as red and yellow
solids, respectively.
Catalysts 2018, 8, x FOR PEER REVIEW 4 of 19
the existence of pairs of diastereoisomers in each case, and also of their different tautomers (i.e.,
isomers of C=C bonds within the CpH rings). The ESI-MS measurements data showed clearly the
expected molecular [M + H]+ ions at m/z 815.55, 787.52 for 2a,b and at 853.51 ([M + K]+) for 2c.
2.2. Synthesis of Group 4 Dinuclear Bis(dichloro ansa-metallocene) Complexes.
In order to prepare the corresponding group 4 bis(dichloro ansa-metallocene) complexes,
standard salt-metathesis reactions between the ligand tetraanions, generated in situ in Et2O, and MCl4
salts (2 equiv.), were used (Scheme 4). Thus, the homodinuclear bis(dichloro ansa-zirconocenes) 3a-c-
Zr2 and bis(dichloro ansa-hafnocene) 3a-Hf2 were isolated in good yields as red and yellow solids,
respectively.
Scheme 4. Synthesis of the group 4 homodinuclear bis(dichloro ansa-metallocene) complexes.
As 3a-c-Zr2 and 3a-Hf2 were derived from diastereomeric mixtures of proligands, two
diastereomers for each of these compounds were anticipated, featuring Cs-/Ci-symmetries for the
para-phenylene-bridged complexes 3a,b-M2 and Cs-/C1-symmetries for the meta-phenylene-bridged
complex 3c-Zr2 (Scheme 5). Accordingly, the 1H and 13C NMR spectra of the crude 3a-Zr2 (Figures
S24–S26), 3a-Hf2 (Figures S28 and S29, respectively), and 3c-Zr2 (Figures S35 and S36, respectively)
complexes displayed two sets of resonances corresponding to the two diastereomers. Unexpectedly,
only one set of resonances assigned to a single diastereoisomer of either Cs- or Ci-symmetry was
observed in the 1H NMR spectrum of 3b-Zr2 (Figure S31). As this compound was isolated in a lower
yield than the other ones, one cannot discard that only one diastereoisomer was recovered in the
workup.
Scheme 4. Synthesis of the group 4 homodinuclear bis(dichloro ansa-metallocene) complexes.
As
3a-c-Zr2
and
3a-Hf2
were derived from diastereomeric mixtures of proligands,
two diastereomers for each of these compounds were anticipated, featuring C
s
-/C
i
-symmetries for the
para-phenylene-bridged complexes
3a,b-M2
and C
s
-/C
1
-symmetries for the meta-phenylene-bridged
complex
3c-Zr2
(Scheme 5). Accordingly, the
1
H and
13
C NMR spectra of the crude
3a-Zr2
(
Figures S24–S26
),
3a-Hf2
(Figures S28 and S29, respectively), and
3c-Zr2
(
Figures S35 and S36,
respectively) complexes displayed two sets of resonances corresponding to the two diastereomers.
Unexpectedly, only one set of resonances assigned to a single diastereoisomer of either C
s
- or
C
i
-symmetry was observed in the
1
H NMR spectrum of
3b-Zr2
(Figure S31). As this compound
was isolated in a lower yield than the other ones, one cannot discard that only one diastereoisomer
was recovered in the workup.

Catalysts 2018,8, 558 5 of 19
Catalysts 2018, 8, x FOR PEER REVIEW 5 of 19
Scheme 5. Possible diastereoisomers of the phenylene-bridged bis(dichloro ansa-metallocene)
complexes.
Unfortunately, all attempts to grow single-crystals of these complexes suitable for X-ray
diffraction studies have failed so far. However, the identity of these bis(dichloro ansa-metallocene)
compounds was confirmed unambiguously by mass spectrometry (vide infra).
In order to obtain a better clue about the possible structures of the dinuclear bis(metallocenes),
the corresponding geometries of the two Cs- and Ci-symmetric isomers of 3a-Zr2 (Figure S68; see the
Experimental Section for details) and the two Cs- and C1-symmetric isomers of 3c-Zr2 (Figure S69)
were modeled by DFT computations. It is noteworthy that the optimized geometries of the isomers
belonging to both dinuclear systems 3a-Zr2 and 3c-Zr2 featured relatively long Zr…Zr intermetallic
distances of 10.5–10.8 Å and 9.2–9.8 Å, respectively. Also, the respective orientations of the
metallocenic fragments in these structures resulted in the coordination sites, represented by the
chlorine ligands, pointing in opposite directions. Such an orientation of the metallocenic moieties in
both para- and meta-phenylene-bridged systems may not be favorable to the mutual approach of the
two metal centers in dinuclear active species derived thereof during polymerization (vide infra).
Note, however, that the above observations were made on the most stable neutral isomers as
determined by DFT, and they do not necessarily reflect the proximity that can be reached from
dynamic conformations in those species. Also, the behavior of the active cationic species associated
with counterionic moieties may be quite different.
In an attempt to synthesize a hetero-bis(metallocene) incorporating both zirconium and hafnium
metals, a similar salt-metathesis protocol as that utilized for the synthesis of the homo-bis(dichloro
ansa-metallocenes) 3a-Zr2 and 3a-Hf2 was probed using 1 equiv. of each of the metal precursors ZrCl4
and HfCl4 (Scheme 6). In this case, as anticipated, a statistical 1:1:2 mixture of the homodinuclear 3a-
Zr2 and 3a-Hf2 complexes and the heterodinuclear 3a-Zr/Hf complex was obtained, as revealed by 1H
NMR spectroscopy of the crude sample. No single-crystal suitable for X-ray diffraction studies has
been grown thus far. Due to the complexity of the mixture and the obvious difficulties associated
with regular elemental and spectroscopic analyses, only its mass-spectrometric characterization was
performed (vide infra).
Scheme 6. Attempted synthesis of the heterodinuclear bis(metallocene) 3a-Zr/Hf.
Scheme 5.
Possible diastereoisomers of the phenylene-bridged bis(dichloro ansa-metallocene) complexes.
Unfortunately, all attempts to grow single-crystals of these complexes suitable for X-ray diffraction
studies have failed so far. However, the identity of these bis(dichloro ansa-metallocene) compounds
was confirmed unambiguously by mass spectrometry (vide infra).
In order to obtain a better clue about the possible structures of the dinuclear bis(metallocenes),
the corresponding geometries of the two C
s
- and C
i
-symmetric isomers of
3a-Zr2
(Figure S68; see the
Experimental Section for details) and the two C
s
- and C
1
-symmetric isomers of
3c-Zr2
(Figure S69)
were modeled by DFT computations. It is noteworthy that the optimized geometries of the isomers
belonging to both dinuclear systems
3a-Zr2
and
3c-Zr2
featured relatively long Zr
. . .
Zr intermetallic
distances of 10.5–10.8 Å and 9.2–9.8 Å, respectively. Also, the respective orientations of the metallocenic
fragments in these structures resulted in the coordination sites, represented by the chlorine ligands,
pointing in opposite directions. Such an orientation of the metallocenic moieties in both para- and
meta-phenylene-bridged systems may not be favorable to the mutual approach of the two metal centers
in dinuclear active species derived thereof during polymerization (vide infra). Note, however, that the
above observations were made on the most stable neutral isomers as determined by DFT, and they
do not necessarily reflect the proximity that can be reached from dynamic conformations in those
species. Also, the behavior of the active cationic species associated with counterionic moieties may be
quite different.
In an attempt to synthesize a hetero-bis(metallocene) incorporating both zirconium and hafnium
metals, a similar salt-metathesis protocol as that utilized for the synthesis of the homo-bis(dichloro
ansa-metallocenes)
3a-Zr2
and
3a-Hf2
was probed using 1 equiv. of each of the metal precursors ZrCl
4
and HfCl
4
(Scheme 6). In this case, as anticipated, a statistical 1:1:2 mixture of the homodinuclear
3a-Zr2
and
3a-Hf2
complexes and the heterodinuclear
3a-Zr/Hf
complex was obtained, as revealed by
1
H NMR spectroscopy of the crude sample. No single-crystal suitable for X-ray diffraction studies
has been grown thus far. Due to the complexity of the mixture and the obvious difficulties associated
with regular elemental and spectroscopic analyses, only its mass-spectrometric characterization was
performed (vide infra).
Catalysts 2018, 8, x FOR PEER REVIEW 5 of 19
Scheme 5. Possible diastereoisomers of the phenylene-bridged bis(dichloro ansa-metallocene)
complexes.
Unfortunately, all attempts to grow single-crystals of these complexes suitable for X-ray
diffraction studies have failed so far. However, the identity of these bis(dichloro ansa-metallocene)
compounds was confirmed unambiguously by mass spectrometry (vide infra).
In order to obtain a better clue about the possible structures of the dinuclear bis(metallocenes),
the corresponding geometries of the two Cs- and Ci-symmetric isomers of 3a-Zr2 (Figure S68; see the
Experimental Section for details) and the two Cs- and C1-symmetric isomers of 3c-Zr2 (Figure S69)
were modeled by DFT computations. It is noteworthy that the optimized geometries of the isomers
belonging to both dinuclear systems 3a-Zr2 and 3c-Zr2 featured relatively long Zr…Zr intermetallic
distances of 10.5–10.8 Å and 9.2–9.8 Å, respectively. Also, the respective orientations of the
metallocenic fragments in these structures resulted in the coordination sites, represented by the
chlorine ligands, pointing in opposite directions. Such an orientation of the metallocenic moieties in
both para- and meta-phenylene-bridged systems may not be favorable to the mutual approach of the
two metal centers in dinuclear active species derived thereof during polymerization (vide infra).
Note, however, that the above observations were made on the most stable neutral isomers as
determined by DFT, and they do not necessarily reflect the proximity that can be reached from
dynamic conformations in those species. Also, the behavior of the active cationic species associated
with counterionic moieties may be quite different.
In an attempt to synthesize a hetero-bis(metallocene) incorporating both zirconium and hafnium
metals, a similar salt-metathesis protocol as that utilized for the synthesis of the homo-bis(dichloro
ansa-metallocenes) 3a-Zr2 and 3a-Hf2 was probed using 1 equiv. of each of the metal precursors ZrCl4
and HfCl4 (Scheme 6). In this case, as anticipated, a statistical 1:1:2 mixture of the homodinuclear 3a-
Zr2 and 3a-Hf2 complexes and the heterodinuclear 3a-Zr/Hf complex was obtained, as revealed by 1H
NMR spectroscopy of the crude sample. No single-crystal suitable for X-ray diffraction studies has
been grown thus far. Due to the complexity of the mixture and the obvious difficulties associated
with regular elemental and spectroscopic analyses, only its mass-spectrometric characterization was
performed (vide infra).
Scheme 6. Attempted synthesis of the heterodinuclear bis(metallocene) 3a-Zr/Hf.
Scheme 6. Attempted synthesis of the heterodinuclear bis(metallocene) 3a-Zr/Hf.

Catalysts 2018,8, 558 6 of 19
2.3. Synthesis of Mononuclear Ansa-metallocene Analogues
For comparative studies of mass-spectrometric analyses and of catalytic properties of the
bis(metallocene)s in
α
-olefin polymerization, their mononuclear analogues were also synthesized
(Scheme 7). The complexes
3a’,b’-Zr
and
3b’-Hf
were isolated in good yields and characterized
by
1
H and
13
C NMR spectroscopic studies, X-ray diffraction (for
3a’-Zr
; Figure S67), and APPI
mass-spectrometry (vide infra).
Catalysts 2018, 8, x FOR PEER REVIEW 6 of 19
2.3. Synthesis of Mononuclear Ansa-metallocene Analogues
For comparative studies of mass-spectrometric analyses and of catalytic properties of the
bis(metallocene)s in α-olefin polymerization, their mononuclear analogues were also synthesized
(Scheme 7). The complexes 3a’,b’-Zr and 3b’-Hf were isolated in good yields and characterized by 1H
and 13C NMR spectroscopic studies, X-ray diffraction (for 3a’-Zr; Figure S67), and APPI mass-
spectrometry (vide infra).
Scheme 7. Synthesis of the mononuclear metallocene analogues.
2.4. Mass Spectrometric Studies of Mononuclear and Dinuclear Bis(dichloro ansa-metallocene) Complexes
Atmospheric Pressure PhotoIonization (APPI) was chosen instead of the more common
electrospray (ESI), as APPI is very efficient for the ionization of aromatic molecules that do not
contain polar groups; also, it allows for the use of dry toluene as a solvent to preserve the rather
sensitive metallocene complexes [39,40]. The APPI mass spectra of the mononuclear complexes 3a’-
Zr, 3b’-Zr, and 3b’-Hf are summarized in Figure 1. In each case, the corresponding intact species was
detected as a M+• molecular ion. A free ligand was also observed in the spectra at m/z 444.3 and m/z
430.3, as well as the C21H26 moiety at m/z 278.
Figure 1. The APPI(+) mass spectra of the mononuclear complexes 3a’-Zr (a), 3b’-Zr (b), and 3b’-Hf
(c). The zoomed areas showcase the theoretical and experimental isotopic clusters. For each isotopic
distribution, only the most intense isotope peak is labelled.
By analogy, the M+• molecular ions were identified for the dinuclear bis(zirconocene) 3a-b-Zr2
compound and the dinuclear bis(hafnocene) 3a-Hf2 compound (Figure 2). The accurate masses and
R
*
tBu
tBu
1. nBuLi (2 equiv)
2. MCl4(1 equiv) R
Cl2M
tBu
tBu
R = Me: 3a'-Zr (76%)
R = H: 3b'-Zr (87%)
3b'-Hf (56%)
Et2O
2 LiCl
*
Scheme 7. Synthesis of the mononuclear metallocene analogues.
2.4. Mass Spectrometric Studies of Mononuclear and Dinuclear Bis(dichloro ansa-metallocene) Complexes
Atmospheric Pressure PhotoIonization (APPI) was chosen instead of the more common
electrospray (ESI), as APPI is very efficient for the ionization of aromatic molecules that do not
contain polar groups; also, it allows for the use of dry toluene as a solvent to preserve the rather
sensitive metallocene complexes [
39
,
40
]. The APPI mass spectra of the mononuclear complexes
3a’-Zr
,
3b’-Zr
, and
3b’-Hf
are summarized in Figure 1. In each case, the corresponding intact species was
detected as a M
+•
molecular ion. A free ligand was also observed in the spectra at m/z444.3 and m/z
430.3, as well as the C21H26 moiety at m/z278.
Catalysts 2018, 8, x FOR PEER REVIEW 6 of 19
2.3. Synthesis of Mononuclear Ansa-metallocene Analogues
For comparative studies of mass-spectrometric analyses and of catalytic properties of the
bis(metallocene)s in α-olefin polymerization, their mononuclear analogues were also synthesized
(Scheme 7). The complexes 3a’,b’-Zr and 3b’-Hf were isolated in good yields and characterized by 1H
and 13C NMR spectroscopic studies, X-ray diffraction (for 3a’-Zr; Figure S67), and APPI mass-
spectrometry (vide infra).
Scheme 7. Synthesis of the mononuclear metallocene analogues.
2.4. Mass Spectrometric Studies of Mononuclear and Dinuclear Bis(dichloro ansa-metallocene) Complexes
Atmospheric Pressure PhotoIonization (APPI) was chosen instead of the more common
electrospray (ESI), as APPI is very efficient for the ionization of aromatic molecules that do not
contain polar groups; also, it allows for the use of dry toluene as a solvent to preserve the rather
sensitive metallocene complexes [39,40]. The APPI mass spectra of the mononuclear complexes 3a’-
Zr, 3b’-Zr, and 3b’-Hf are summarized in Figure 1. In each case, the corresponding intact species was
detected as a M+• molecular ion. A free ligand was also observed in the spectra at m/z 444.3 and m/z
430.3, as well as the C21H26 moiety at m/z 278.
Figure 1. The APPI(+) mass spectra of the mononuclear complexes 3a’-Zr (a), 3b’-Zr (b), and 3b’-Hf
(c). The zoomed areas showcase the theoretical and experimental isotopic clusters. For each isotopic
distribution, only the most intense isotope peak is labelled.
By analogy, the M+• molecular ions were identified for the dinuclear bis(zirconocene) 3a-b-Zr2
compound and the dinuclear bis(hafnocene) 3a-Hf2 compound (Figure 2). The accurate masses and
R
*
tBu
tBu
1. nBuLi (2 equiv)
2. MCl4(1 equiv) R
Cl2M
tBu
tBu
R = Me: 3a'-Zr (76%)
R = H: 3b'-Zr (87%)
3b'-Hf (56%)
Et2O
2 LiCl
*
Figure 1.
The APPI(+) mass spectra of the mononuclear complexes
3a’-Zr
(
a
),
3b’-Zr
(
b
), and
3b’-Hf
(
c
).
The zoomed areas showcase the theoretical and experimental isotopic clusters. For each isotopic
distribution, only the most intense isotope peak is labelled.

Catalysts 2018,8, 558 7 of 19
By analogy, the M
+•
molecular ions were identified for the dinuclear bis(zirconocene)
3a-b-Zr2
compound and the dinuclear bis(hafnocene)
3a-Hf2
compound (Figure 2). The accurate masses
and isotopic distributions (m/z1130.2074, 1102.1754, and 1310.2865, respectively) are in very good
agreement (<5 ppm) with those expected theoretically based on the corresponding ions’ molecular
formula (m/z1130.2013, 1102.1700, and 1310.2850, respectively). In addition to the dinuclear species
3a,b-Zr2
and
3a-Hf2
, molecular ions derived from the monometallated fragments, i.e.,
3a,b-Zr
and
3a-Hf
, were detected in each case at m/z972.3776, 944.3398, and 1062.4139, respectively.
These ions were most likely not generated by gas-phase fragmentation, as they were not produced
by collision-induced dissociation of the dinuclear molecular ions. They, however, may have been
produced by partial degradation (e.g., hydrolysis) during the sample handling or in the atmosphere
source that may contain traces of water.
Catalysts 2018, 8, x FOR PEER REVIEW 7 of 19
isotopic distributions (m/z 1130.2074, 1102.1754, and 1310.2865, respectively) are in very good
agreement (<5 ppm) with those expected theoretically based on the corresponding ions’ molecular
formula (m/z 1130.2013, 1102.1700, and 1310.2850, respectively). In addition to the dinuclear species
3a,b-Zr2 and 3a-Hf2, molecular ions derived from the monometallated fragments, i.e., 3a,b-Zr and 3a-
Hf, were detected in each case at m/z 972.3776, 944.3398, and 1062.4139, respectively. These ions were
most likely not generated by gas-phase fragmentation, as they were not produced by collision-
induced dissociation of the dinuclear molecular ions. They, however, may have been produced by
partial degradation (e.g., hydrolysis) during the sample handling or in the atmosphere source that
may contain traces of water.
Figure 2. The APPI(+) mass spectra of the dinuclear bis(metallocene) 3a-Zr2 (a), 3a-Hf2 (b), and 3b-Zr2
(c) complexes. The zoomed areas showcase the theoretical and experimental isotopic clusters. For
each isotopic distribution, only the most intense isotope peak is labelled.
For the mixture containing the heterodinuclear bis(dichloro ansa-metallocene) compound 3a-
Zr/Hf and its homodinuclear counterparts 3a-Zr2 and 3a-Hf2, a set of five isotopic distributions was
observed in the APPI mass-spectrum (Figure 3). Besides the distributions corresponding to the
homodinuclear 3a-Zr2 and 3a-Hf2 and their monometallated versions, i.e., 3a-Zr and 3a-Hf,
respectively, an isotopic distribution at m/z 1222.2463 was identified and unequivocally assigned to
3a-Zr/Hf. APPI should present a low ionization discrimination for these species, so their relative
abundance should be representative of their actual amount in the sample, although the most air-
sensitive molecules may present a lower abundance because of higher degradation. This possibly
accounts for the observed lower intensity of peaks arising from 3a-Hf2.
Figure 2.
The APPI(+) mass spectra of the dinuclear bis(metallocene)
3a-Zr2
(
a
),
3a-Hf2
(
b
), and
3b-Zr2
(
c
) complexes. The zoomed areas showcase the theoretical and experimental isotopic clusters. For each
isotopic distribution, only the most intense isotope peak is labelled.
For the mixture containing the heterodinuclear bis(dichloro ansa-metallocene) compound
3a-Zr/Hf
and its homodinuclear counterparts
3a-Zr2
and
3a-Hf2
, a set of five isotopic distributions was observed
in the APPI mass-spectrum (Figure 3). Besides the distributions corresponding to the homodinuclear
3a-Zr2
and
3a-Hf2
and their monometallated versions, i.e.,
3a-Zr
and
3a-Hf
, respectively, an isotopic
distribution at m/z1222.2463 was identified and unequivocally assigned to
3a-Zr/Hf
. APPI should
present a low ionization discrimination for these species, so their relative abundance should be
representative of their actual amount in the sample, although the most air-sensitive molecules may
present a lower abundance because of higher degradation. This possibly accounts for the observed
lower intensity of peaks arising from 3a-Hf2.

Catalysts 2018,8, 558 8 of 19
Catalysts 2018, 8, x FOR PEER REVIEW 8 of 19
Figure 3. (a) The APPI(+) mass spectrum of the crude reaction mixture resulting from metallation of
the proligand 3a by a 1:1 mixture of ZrCl4 and HfCl4; (b) The enlargement of the m/z 900–1350 area.
The zoomed areas showcase the theoretical and experimental isotopic clusters of the dinuclear
bis(dichloro ansa-metallocene) complexes 3a-Zr-Hf. For each isotopic distribution, only the most
intense isotope peak is labelled.
2.5. Polymerization Catalysis
The dinuclear bis(dichloro ansa-metallocene) complexes 3a-M2, 3b-Zr2, and 3c-Zr2, and their
mononuclear analogues 3a,b’-Zr and 3b’-Hf, in combination with methylalumoxane (MAO), were
evaluated in homogeneous ethylene polymerization (Table 1) and ethylene/1-hexene
copolymerization (Table 2). Each polymerization experiment was repeated independently twice
under the same conditions (toluene, 5.5 bar of ethylene, 60 °C), which revealed good reproducibility
in terms of productivity (polymer yield) and physicochemical properties (Tm, Mw, polydispersity
index (PDI)) of the isolated polymer.
Table 1. Homopolymerization of ethylene a.
Entry Comp. mPE
(g) Prod. (kg·mol−1·h−1) Mw b
(kg·mol−1) Mw/Mn b Tm c
(°C) %Me d (wt%) %Et d (wt%) %nBu d (wt%)
1 3a-Zr2 6.20 24,800 175.1 3.2 132.3 0.0 0.1 0.0
2 3a-Zr2 5.62 22,500 196.6 3.4 132.2 0.0 0.2 0.0
3 3a’-Zr 5.64 22,600 260.4 3.6 132.1 0.0 0.1 0.0
4 3a’-Zr 6.14 24,600 307.9 4.1 131.8 0.0 0.0 0.0
5 3b-Zr2 5.82 23,280 134.6 3.1 127.2 1.5 0.2 0.0
6 3b-Zr2 5.20 20,800 189.2 3.5 129.0 0.9 0.2 0.0
7 3b’-Zr 6.79 27,160 180.9 3.4 132.1 0.0 0.1 0.0
8 3b’-Zr 5.27 21,080 272.6 4.3 133.2 0.0 0.1 0.0
9 3c-Zr2 4.96 19,800 85.0 3.3 nd 0.0 0.2 0.0
10 3a-Hf2 1.53 6100 -
f -
f 132.7 0.0 0.0 0.0
11 e 3a-Hf2 1.63 6500 -
f -
f 133.6 0.0 0.0 0.0
12 3b’-Hf 1.38 5500 1146.3 4,1 nd 0.0 0.0 0.0
a General conditions: toluene (100 mL), Tpol = 60 °C, [Zr]0 = 10.1 µmol·L−1, Pethylene = 5.5 bar, [Al]0/[Zr]0 =
1000, polymerization time = 15 min, nd = not determined; b Determined by SEC at 135 °C in 1,2,4-
trichlorobenzene; c Determined by DSC from a second heating run; d Determined by 13C NMR
spectroscopy; e BHT (300 equiv. versus [Hf] was added to scavenge M3Al of MAO); f Insoluble
polymer was recovered, preventing an SEC analysis.
In general, no significant or limited difference was observed for the experiments involving
dinuclear bis(metallocene) with respect to those using the corresponding mononuclear analogues
(Table 1; compare entries 1–2/3–4, 5–6/7–8, and 10–11/12, respectively). Indeed, all of the systems that
Figure 3.
(
a
) The APPI(+) mass spectrum of the crude reaction mixture resulting from metallation of the
proligand
3a
by a 1:1 mixture of ZrCl
4
and HfCl
4
; (
b
) The enlargement of the m/z900–1350 area.
The zoomed areas showcase the theoretical and experimental isotopic clusters of the dinuclear
bis(dichloro ansa-metallocene) complexes
3a-Zr-Hf
. For each isotopic distribution, only the most
intense isotope peak is labelled.
2.5. Polymerization Catalysis
The dinuclear bis(dichloro ansa-metallocene) complexes
3a-M2
,
3b-Zr2
, and
3c-Zr2
, and their
mononuclear analogues
3a,b’-Zr
and
3b’-Hf
, in combination with methylalumoxane (MAO),
were evaluated in homogeneous ethylene polymerization (Table 1) and ethylene/1-hexene
copolymerization (Table 2). Each polymerization experiment was repeated independently twice
under the same conditions (toluene, 5.5 bar of ethylene, 60
◦
C), which revealed good reproducibility in
terms of productivity (polymer yield) and physicochemical properties (T
m
,M
w
, polydispersity index
(PDI)) of the isolated polymer.
Table 1. Homopolymerization of ethylene a.
Entry Comp. mPE (g) Prod.
(kg·mol−1·h−1)
Mwb
(kg·mol−1)Mw/MnbTmc(◦C) %Me d
(wt%)
%Et d
(wt%)
%nBu d
(wt%)
13a-Zr26.20 24,800 175.1 3.2 132.3 0.0 0.1 0.0
23a-Zr25.62 22,500 196.6 3.4 132.2 0.0 0.2 0.0
33a’-Zr 5.64 22,600 260.4 3.6 132.1 0.0 0.1 0.0
43a’-Zr 6.14 24,600 307.9 4.1 131.8 0.0 0.0 0.0
53b-Zr25.82 23,280 134.6 3.1 127.2 1.5 0.2 0.0
63b-Zr25.20 20,800 189.2 3.5 129.0 0.9 0.2 0.0
73b’-Zr 6.79 27,160 180.9 3.4 132.1 0.0 0.1 0.0
83b’-Zr 5.27 21,080 272.6 4.3 133.2 0.0 0.1 0.0
93c-Zr24.96 19,800 85.0 3.3 nd 0.0 0.2 0.0
10 3a-Hf21.53 6100 -f-f132.7 0.0 0.0 0.0
11 e3a-Hf21.63 6500 -f-f133.6 0.0 0.0 0.0
12 3b’-Hf 1.38 5500 1146.3 4,1 nd 0.0 0.0 0.0
a
General conditions: toluene (100 mL), T
pol
= 60
◦
C, [Zr]
0
= 10.1
µ
mol
·
L
−1
, P
ethylene
= 5.5 bar, [Al]
0
/[Zr]
0
= 1000,
polymerization time = 15 min, nd = not determined;
b
Determined by SEC at 135
◦
C in 1,2,4-trichlorobenzene;
c
Determined by DSC from a second heating run;
d
Determined by
13
C NMR spectroscopy;
e
BHT (300 equiv. versus
[Hf] was added to scavenge M3Al of MAO); fInsoluble polymer was recovered, preventing an SEC analysis.

Catalysts 2018,8, 558 9 of 19
Table 2. Ethylene/1-hexene copolymerization a.
Entry Comp. mPE (g) Prod.
(kg·mol−1·h−1)
Mwb
(kg·mol−1)Mw/MnbTmc(◦C) %Me d
(wt%)
%Et d
(wt%)
%nBu d
(wt%)
13a-Zr26.20 24,800 70.6 2.6 122.5 0.0 0.1 15.7
23a-Zr25.62 22,500 84.3 3.0 123.8 0.0 0.0 23.2
33a’-Zr 7.22 28,900 129.3 3.4 117.7 0.0 0.0 22.6
43a’-Zr 6.77 27,100 132.1 3.3 118.2 0.0 0.0 21.3
53b-Zr27.74 31,000 75.8 2.8 111.4 0.9 0.1 22.5
63b-Zr26.70 26,800 64.0 2.7 112.2 0.4 0.1 19.4
73b’-Zr 7.57 30,300 89.9 2.7 113.9 0.0 0.0 21.1
83b’-Zr 7.30 29,200 96.9 2.9 108.2 0.0 0.0 22.7
93c-Zr27.75 31,000 190.6 3.5 116.0 0.0 0.0 21.3
10 3a-Hf23.78 15,100 447.1 3.1 nd 0.0 0.0 28.1
11 e3a-Hf24.34 17,400 581.5 4.0 nd 0.0 0.0 29.6
12 3b’-Hf 1.66 6600 -f-fnd 0.0 0.0 28.5
a
General conditions: toluene (100 mL), T
pol
= 60
◦
C, [Zr] = 10.1
µ
mol
·
L
−1
, P
ethylene
= 5.5 bar,
[Al]/[Zr] = 1000
,
[1-hexene]
0
= 0.2 M, polymerization time = 15 min, nd = not determined;
b
Determined by size-exclusion
chromatography (SEC) at 135
◦
C in 1,2,4-trichlorobenzene;
c
Determined by DSC from a second run;
d
Determined
by
13
C NMR spectroscopy;
e
BHT (300 equiv. versus Hf) was added to scavenge M
3
Al of MAO;
f
Insoluble polymer
was recovered, preventing an SEC analysis.
In general, no significant or limited difference was observed for the experiments involving
dinuclear bis(metallocene) with respect to those using the corresponding mononuclear analogues
(Table 1; compare entries 1–2/3–4, 5–6/7–8, and 10–11/12, respectively). Indeed, all of the systems
that were produced with similar productivities used polyethylene samples exhibiting quite similar
molecular weight distributions and T
m
values. A slight drop in productivity was observed for the
meta-bridged system
3c-Zr2
(entry 9), also yielding a lower molecular weight polyethylene (PE)
as compared to the para-bridged congeners
3a,b-Zr2
. Interestingly, as established by
13
C NMR
spectroscopy,
3b-Zr2
induced the formation of short branches (methyl and, to a lesser extent, ethyl) to
a significantly greater extent than its mononuclear analogue and any other dinuclear system; the same
observation was made in ethylene/1-hexene copolymerization (vide infra). This may presumably arise
from a chain-walking mechanism.
The Hf-based systems
3a-Hf2
and
3b’-Hf
appeared to be ca. 3-fold less productive (entries 10–12)
than their Zr-based counterparts while affording much higher molecular weight PEs. The addition of
BHT (entry 11) to scavenge the excess “free” AlMe
3
[
41
] present in MAO did not affect the productivity
of this system, and also resulted in an insoluble polymer (likely due to the formation of high molecular
weight polyethylene (HMWPE) because of the absence of transfer to AlMe3).
Also, no strikingly different results were obtained upon using the different mono- and dinuclear
compounds in ethylene/1-hexene copolymerization (Table 2). The Zr-based systems, both di- and
mononuclear, afforded a very narrow range of productivities. It is of note that, in the para-bridged series
3a,b-Zr2
and
3a’b’-Zr
, the dinuclear bis(metallocenes) gave slightly but significantly lower molecular
weight copolymers and narrower dispersities (compare entries 1–2/3–4 and 5–6/7–8, respectively)
than their respective mononuclear analogues. Conversely, the meta-bridged system
3c-Zr2
afforded
a higher molecular weight copolymer than its mononuclear analogue (compare entries 3/4 and 9).
Again, higher molecular weight copolymers were obtained with Hf-based catalysts, but with lower
productivities than their Zr counterparts (entries 10–12). Also, a somewhat higher incorporation of
1-hexene in copolymers was achieved with the Hf-based catalysts.
3. Materials and Methods
3.1. General Considerations
All experiments were performed under a dry argon atmosphere, using a glovebox or standard
Schlenk techniques. THF and Et
2
O were distilled prior to use from sodium benzophenone
ketyl. Hexane and heptane were distilled from CaH
2
and stored over 3
Catalysts 2018, 8, x FOR PEER REVIEW 10 of 19
precursors, (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene and (cyclopenta-2,4-dien-1-
ylidenemethyl)benzene [42], were prepared following protocols published in the literature. ZrCl4 and
HfCl4 were used as received (anhydrous, Strem Chemicals, Bischheim, France). 1-Hexene (Fisher
Chemical, Illkirch, France) was distilled and stored over 3 Ǻ molecular sieves under argon. Ethylene
(N35, Air Liquide, Paris, France) was used without further purification.
3.2. Instruments and Measurements
The NMR spectra of air- and moisture-sensitive compounds were recorded on Bruker AM-400
and AM-500 spectrometers in Teflon-valved NMR tubes at room temperature. 1H and 13C chemical
shifts are reported in ppm versus SiMe4 and were determined using residual solvent signal. Coupling
constants are given in Hertz. Assignments of signals were carried out using 1D (1H, 13C{1H}, JMOD)
and 2D (COSY, HMBC, HMQC) NMR experiments. Elemental analyses were performed on a Carlo
Erba 1108 Elemental Analyzer instrument at the London Metropolitan University by Stephen Boyer
or on a Flash EA1112 CHNS Thermo Electron apparatus at CRMPO, Rennes, and were the average
of a minimum of two independent measurements.
The 13C{1H} NMR and GPC analyses of polymer samples were performed in the research center
of Total Research and Technologies in Feluy (Feluy, Belgium). The 13C{1H} NMR analyses were run
on a 500 MHz Bruker Avance III with a 10 mm cryoprobe HTDUL in trichlorobenzene/C6D6 (2 mL/0.5
mL). The GPC analyses were performed in 1,2,4-trichlorobenzene at 135 °C using PS standards for
calibration. Differential scanning calorimetry (DSC) analyses were performed on a Setaram DSC 131
apparatus under a continuous flow of helium and using aluminum capsules. Glass transition and
melting temperatures were measured during the second heating (10 °C·min−1).
The ESI (ElectroSpray Ionization) mass spectra of organic compounds, including proligands,
were recorded at CRMPO-Scanmat (Rennes, France) on an Orbitrap Thermo Fisher Scientific Q-
Exactive instrument with an ESI source in positive mode by direct introduction at 5–10 µg·mL−1.
Samples were prepared in CH2Cl2 at 10 µg·mL−1.
The ASAP (Atmospheric Solids Analysis Probe) mass spectra of proligands were recorded at the
CRMPO-Scanmat (Rennes, France) on a Q-TOF Bruker Maxis 4G instrument with an APCI source in
positive mode at desorption temperatures of 255 and 300 °C.
3.3. APPI Mass Spectrometric Characterization of Metal Complexes
The mass spectra of metal complexes were recorded on a hybrid quadrupole time-of-flight
instrument (Waters, Synapt G2, Manchester, England) equipped with an APPI source. The
instrument was operated in the positive ion mode. The ionization experimental conditions were set
as follows: desolvation gas flow, 700 L h−1; source temperature, 120 °C; probe temperature, 400 °C;
sampling cone, 20 V; extraction cone, 3 V. The time-of-flight was operated in the ‘resolution mode’
yielding a resolving power of about 20,000. The samples were prepared in a glove box using dried
toluene in 1.5 mL glass vials with a final concentration of 20 µM. For analysis, the sample was taken
with a dry syringe stored in an oven. The solution was directly infused into the source using a syringe
pump at a flow rate of 200 µL h−1. Data were acquired over the m/z 50–2000 range for 2–5 min. Note
that the given accurate masses are given with Water Mass Lynx 4.1 that do not take into account the
mass of the electron removed during ionization. All given masses are monoisotopic values. In the
mass spectra, only the highest abundant isotope is labelled.
3.4. 1,4-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1a)
In a 250 mL round bottom flask equipped with a magnetic stirring bar and an argon inlet, freshly
cracked cyclopentadiene (12.36 mL, 148.0 mmol) and 1,4-diacetylbenzene (4.82 g, 30.0 mmol) were
dissolved in methanol (200 mL). To this solution, pyrrolidine (7.5 mL, 89.0 mmol) was added at 0 °C.
The reaction mixture was stirred at room temperature for 7 days. After neutralization with glacial
acetic acid (7.5 mL) and separation of the organic phase, volatiles were evaporated under vacuum to
give a yellow powder (5.51 g, 21.3 mmol, 72%). 1H NMR (CDCl3, 400 MHz, 25 °C): δ 7.35 (s, 4H, CH-
molecular sieves.
Deuterated solvents (benzene-d
6
, toluene-d
8
> 99.5% D; Euriso-top, Saint-Aubin, France) were

Catalysts 2018,8, 558 10 of 19
distilled from Na/K alloy or CaH
2
(for CD
2
Cl
2
) and stored over 3
Catalysts 2018, 8, x FOR PEER REVIEW 10 of 19
precursors, (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene and (cyclopenta-2,4-dien-1-
ylidenemethyl)benzene [42], were prepared following protocols published in the literature. ZrCl4 and
HfCl4 were used as received (anhydrous, Strem Chemicals, Bischheim, France). 1-Hexene (Fisher
Chemical, Illkirch, France) was distilled and stored over 3 Ǻ molecular sieves under argon. Ethylene
(N35, Air Liquide, Paris, France) was used without further purification.
3.2. Instruments and Measurements
The NMR spectra of air- and moisture-sensitive compounds were recorded on Bruker AM-400
and AM-500 spectrometers in Teflon-valved NMR tubes at room temperature. 1H and 13C chemical
shifts are reported in ppm versus SiMe4 and were determined using residual solvent signal. Coupling
constants are given in Hertz. Assignments of signals were carried out using 1D (1H, 13C{1H}, JMOD)
and 2D (COSY, HMBC, HMQC) NMR experiments. Elemental analyses were performed on a Carlo
Erba 1108 Elemental Analyzer instrument at the London Metropolitan University by Stephen Boyer
or on a Flash EA1112 CHNS Thermo Electron apparatus at CRMPO, Rennes, and were the average
of a minimum of two independent measurements.
The 13C{1H} NMR and GPC analyses of polymer samples were performed in the research center
of Total Research and Technologies in Feluy (Feluy, Belgium). The 13C{1H} NMR analyses were run
on a 500 MHz Bruker Avance III with a 10 mm cryoprobe HTDUL in trichlorobenzene/C6D6 (2 mL/0.5
mL). The GPC analyses were performed in 1,2,4-trichlorobenzene at 135 °C using PS standards for
calibration. Differential scanning calorimetry (DSC) analyses were performed on a Setaram DSC 131
apparatus under a continuous flow of helium and using aluminum capsules. Glass transition and
melting temperatures were measured during the second heating (10 °C·min−1).
The ESI (ElectroSpray Ionization) mass spectra of organic compounds, including proligands,
were recorded at CRMPO-Scanmat (Rennes, France) on an Orbitrap Thermo Fisher Scientific Q-
Exactive instrument with an ESI source in positive mode by direct introduction at 5–10 µg·mL−1.
Samples were prepared in CH2Cl2 at 10 µg·mL−1.
The ASAP (Atmospheric Solids Analysis Probe) mass spectra of proligands were recorded at the
CRMPO-Scanmat (Rennes, France) on a Q-TOF Bruker Maxis 4G instrument with an APCI source in
positive mode at desorption temperatures of 255 and 300 °C.
3.3. APPI Mass Spectrometric Characterization of Metal Complexes
The mass spectra of metal complexes were recorded on a hybrid quadrupole time-of-flight
instrument (Waters, Synapt G2, Manchester, England) equipped with an APPI source. The
instrument was operated in the positive ion mode. The ionization experimental conditions were set
as follows: desolvation gas flow, 700 L h−1; source temperature, 120 °C; probe temperature, 400 °C;
sampling cone, 20 V; extraction cone, 3 V. The time-of-flight was operated in the ‘resolution mode’
yielding a resolving power of about 20,000. The samples were prepared in a glove box using dried
toluene in 1.5 mL glass vials with a final concentration of 20 µM. For analysis, the sample was taken
with a dry syringe stored in an oven. The solution was directly infused into the source using a syringe
pump at a flow rate of 200 µL h−1. Data were acquired over the m/z 50–2000 range for 2–5 min. Note
that the given accurate masses are given with Water Mass Lynx 4.1 that do not take into account the
mass of the electron removed during ionization. All given masses are monoisotopic values. In the
mass spectra, only the highest abundant isotope is labelled.
3.4. 1,4-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1a)
In a 250 mL round bottom flask equipped with a magnetic stirring bar and an argon inlet, freshly
cracked cyclopentadiene (12.36 mL, 148.0 mmol) and 1,4-diacetylbenzene (4.82 g, 30.0 mmol) were
dissolved in methanol (200 mL). To this solution, pyrrolidine (7.5 mL, 89.0 mmol) was added at 0 °C.
The reaction mixture was stirred at room temperature for 7 days. After neutralization with glacial
acetic acid (7.5 mL) and separation of the organic phase, volatiles were evaporated under vacuum to
give a yellow powder (5.51 g, 21.3 mmol, 72%). 1H NMR (CDCl3, 400 MHz, 25 °C): δ 7.35 (s, 4H, CH-
molecular sieves. CDCl
3
(99.8% D, Euriso-top) was used as received. Cyclopentadiene (Acros, Geel, Belgium) was freshly
distilled prior to use. 3,6-Di-tert-butyl-fluorene and MAO were generously provided by Total
Raffinage-Chimie. The fulvene precursors, (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene and
(cyclopenta-2,4-dien-1-ylidenemethyl)benzene [
42
], were prepared following protocols published
in the literature. ZrCl
4
and HfCl
4
were used as received (anhydrous, Strem Chemicals, Bischheim,
France). 1-Hexene (Fisher Chemical, Illkirch, France) was distilled and stored over 3
Catalysts 2018, 8, x FOR PEER REVIEW 10 of 19
precursors, (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene and (cyclopenta-2,4-dien-1-
ylidenemethyl)benzene [42], were prepared following protocols published in the literature. ZrCl4 and
HfCl4 were used as received (anhydrous, Strem Chemicals, Bischheim, France). 1-Hexene (Fisher
Chemical, Illkirch, France) was distilled and stored over 3 Ǻ molecular sieves under argon. Ethylene
(N35, Air Liquide, Paris, France) was used without further purification.
3.2. Instruments and Measurements
The NMR spectra of air- and moisture-sensitive compounds were recorded on Bruker AM-400
and AM-500 spectrometers in Teflon-valved NMR tubes at room temperature. 1H and 13C chemical
shifts are reported in ppm versus SiMe4 and were determined using residual solvent signal. Coupling
constants are given in Hertz. Assignments of signals were carried out using 1D (1H, 13C{1H}, JMOD)
and 2D (COSY, HMBC, HMQC) NMR experiments. Elemental analyses were performed on a Carlo
Erba 1108 Elemental Analyzer instrument at the London Metropolitan University by Stephen Boyer
or on a Flash EA1112 CHNS Thermo Electron apparatus at CRMPO, Rennes, and were the average
of a minimum of two independent measurements.
The 13C{1H} NMR and GPC analyses of polymer samples were performed in the research center
of Total Research and Technologies in Feluy (Feluy, Belgium). The 13C{1H} NMR analyses were run
on a 500 MHz Bruker Avance III with a 10 mm cryoprobe HTDUL in trichlorobenzene/C6D6 (2 mL/0.5
mL). The GPC analyses were performed in 1,2,4-trichlorobenzene at 135 °C using PS standards for
calibration. Differential scanning calorimetry (DSC) analyses were performed on a Setaram DSC 131
apparatus under a continuous flow of helium and using aluminum capsules. Glass transition and
melting temperatures were measured during the second heating (10 °C·min−1).
The ESI (ElectroSpray Ionization) mass spectra of organic compounds, including proligands,
were recorded at CRMPO-Scanmat (Rennes, France) on an Orbitrap Thermo Fisher Scientific Q-
Exactive instrument with an ESI source in positive mode by direct introduction at 5–10 µg·mL−1.
Samples were prepared in CH2Cl2 at 10 µg·mL−1.
The ASAP (Atmospheric Solids Analysis Probe) mass spectra of proligands were recorded at the
CRMPO-Scanmat (Rennes, France) on a Q-TOF Bruker Maxis 4G instrument with an APCI source in
positive mode at desorption temperatures of 255 and 300 °C.
3.3. APPI Mass Spectrometric Characterization of Metal Complexes
The mass spectra of metal complexes were recorded on a hybrid quadrupole time-of-flight
instrument (Waters, Synapt G2, Manchester, England) equipped with an APPI source. The
instrument was operated in the positive ion mode. The ionization experimental conditions were set
as follows: desolvation gas flow, 700 L h−1; source temperature, 120 °C; probe temperature, 400 °C;
sampling cone, 20 V; extraction cone, 3 V. The time-of-flight was operated in the ‘resolution mode’
yielding a resolving power of about 20,000. The samples were prepared in a glove box using dried
toluene in 1.5 mL glass vials with a final concentration of 20 µM. For analysis, the sample was taken
with a dry syringe stored in an oven. The solution was directly infused into the source using a syringe
pump at a flow rate of 200 µL h−1. Data were acquired over the m/z 50–2000 range for 2–5 min. Note
that the given accurate masses are given with Water Mass Lynx 4.1 that do not take into account the
mass of the electron removed during ionization. All given masses are monoisotopic values. In the
mass spectra, only the highest abundant isotope is labelled.
3.4. 1,4-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1a)
In a 250 mL round bottom flask equipped with a magnetic stirring bar and an argon inlet, freshly
cracked cyclopentadiene (12.36 mL, 148.0 mmol) and 1,4-diacetylbenzene (4.82 g, 30.0 mmol) were
dissolved in methanol (200 mL). To this solution, pyrrolidine (7.5 mL, 89.0 mmol) was added at 0 °C.
The reaction mixture was stirred at room temperature for 7 days. After neutralization with glacial
acetic acid (7.5 mL) and separation of the organic phase, volatiles were evaporated under vacuum to
give a yellow powder (5.51 g, 21.3 mmol, 72%). 1H NMR (CDCl3, 400 MHz, 25 °C): δ 7.35 (s, 4H, CH-
molecular
sieves under argon. Ethylene (N35, Air Liquide, Paris, France) was used without further purification.
3.2. Instruments and Measurements
The NMR spectra of air- and moisture-sensitive compounds were recorded on Bruker AM-400
and AM-500 spectrometers in Teflon-valved NMR tubes at room temperature.
1
H and
13
C chemical
shifts are reported in ppm versus SiMe
4
and were determined using residual solvent signal.
Coupling constants are given in Hertz. Assignments of signals were carried out using 1D (
1
H,
13
C{
1
H},
JMOD) and 2D (COSY, HMBC, HMQC) NMR experiments. Elemental analyses were performed on a
Carlo Erba 1108 Elemental Analyzer instrument at the London Metropolitan University by Stephen
Boyer or on a Flash EA1112 CHNS Thermo Electron apparatus at CRMPO, Rennes, and were the
average of a minimum of two independent measurements.
The
13
C{
1
H} NMR and GPC analyses of polymer samples were performed in the research center of
Total Research and Technologies in Feluy (Feluy, Belgium). The
13
C{
1
H} NMR analyses were run on a
500 MHz Bruker Avance III with a 10 mm cryoprobe HTDUL in trichlorobenzene/C
6
D
6
(
2 mL/0.5 mL
).
The GPC analyses were performed in 1,2,4-trichlorobenzene at 135
◦
C using PS standards for calibration.
Differential scanning calorimetry (DSC) analyses were performed on a Setaram DSC 131 apparatus
under a continuous flow of helium and using aluminum capsules. Glass transition and melting
temperatures were measured during the second heating (10 ◦C·min−1).
The ESI (ElectroSpray Ionization) mass spectra of organic compounds, including proligands,
were recorded at CRMPO-Scanmat (Rennes, France) on an Orbitrap Thermo Fisher Scientific Q-Exactive
instrument with an ESI source in positive mode by direct introduction at 5–10
µ
g
·
mL
−1
. Samples were
prepared in CH2Cl2at 10 µg·mL−1.
The ASAP (Atmospheric Solids Analysis Probe) mass spectra of proligands were recorded at the
CRMPO-Scanmat (Rennes, France) on a Q-TOF Bruker Maxis 4G instrument with an APCI source in
positive mode at desorption temperatures of 255 and 300 ◦C.
3.3. APPI Mass Spectrometric Characterization of Metal Complexes
The mass spectra of metal complexes were recorded on a hybrid quadrupole time-of-flight
instrument (Waters, Synapt G2, Manchester, England) equipped with an APPI source. The instrument
was operated in the positive ion mode. The ionization experimental conditions were set as follows:
desolvation gas flow, 700 L h
−1
; source temperature, 120
◦
C; probe temperature, 400
◦
C; sampling cone,
20 V; extraction cone, 3 V. The time-of-flight was operated in the ‘resolution mode’ yielding a resolving
power of about 20,000. The samples were prepared in a glove box using dried toluene in 1.5 mL glass
vials with a final concentration of 20
µ
M. For analysis, the sample was taken with a dry syringe stored
in an oven. The solution was directly infused into the source using a syringe pump at a flow rate of
200
µ
L h
−1
. Data were acquired over the m/z50–2000 range for 2–5 min. Note that the given accurate
masses are given with Water Mass Lynx 4.1 that do not take into account the mass of the electron
removed during ionization. All given masses are monoisotopic values. In the mass spectra, only the
highest abundant isotope is labelled.
3.4. 1,4-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1a)
In a 250 mL round bottom flask equipped with a magnetic stirring bar and an argon inlet,
freshly cracked cyclopentadiene (12.36 mL, 148.0 mmol) and 1,4-diacetylbenzene (4.82 g, 30.0 mmol)

Catalysts 2018,8, 558 11 of 19
were dissolved in methanol (200 mL). To this solution, pyrrolidine (7.5 mL, 89.0 mmol) was added at
0
◦
C. The reaction mixture was stirred at room temperature for 7 days. After neutralization with glacial
acetic acid (7.5 mL) and separation of the organic phase, volatiles were evaporated under vacuum
to give a yellow powder (5.51 g, 21.3 mmol, 72%).
1
H NMR (CDCl
3
, 400 MHz, 25
◦
C):
δ
7.35 (s, 4H,
CH-Ar), 6.59 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp), 6.51 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp), 6.43 (dt,
3J= 5.2
,
4
J= 1.6, 2H, CH-Cp), 6.16 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp), 2.50 (s, 6H, CH
3
).
13
C NMR (CDCl
3
,
125 MHz, 25
◦
C):
δ
149.0, 143.8, 142.0 (Cq), 132.1, 131.9 (CH-Cp), 129.0 (CH-Ar), 123.7, 121.2 (CH-Cp),
22.6 (CH
3
). ESI-MS (m/z): 259.15 ([M + H]
+
), 258.15 ([M]). Anal. calcd. for C
20
H
18
(258.36): C 92.98,
H 7.02; found: C 93.27, H 6.53.
3.5. 1,4-Bis(cyclopenta-2,4-dien-1-ylidenemethyl)benzene (1b)
Using a protocol similar to that described above for
1a
,
1b
was prepared from cyclopentadiene
(30.7 mL, 373.0 mmol), 1,3-terephthalaldehyde (10.0 g, 74.5 mmol), and pyrrolidine (9.3 mL,
112.0 mmol), and isolated as an orange powder (13.03 g, 56.7 mmol, 76%).
1
H NMR (CDCl
3
, 400 MHz,
25
◦
C):
δ
7.63 (s, 4H, CH-Ar), 7.20 (s, 2H, CH-methine), 6.69 (m, 4H, CH-Cp), 6.52 (d,
3
J= 5.0, 2H,
CH-Cp), 6.32 (d,
3
J= 5.0, 2H, CH-Cp).
13
C NMR (CDCl
3
, 125 MHz, 25
◦
C):
δ
146.2, 137.6, (Cq), 137.2,
136.1 (CH-Cp), 131.5 (=CH), 131.1 (CH-Ph), 127.4, 120.3 (CH-Cp). Anal. calcd. for C
18
H
14
(230.30):
C 93.87, H 6.13; found: C 93.98, H 6.56.
3.6. 1,3-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1c)
Using a protocol similar to that described above for
1a
,
1c
was prepared from cyclopentadiene
(30.0 mL, 363.0 mmol), 1,3-diacetylbenzene (11.0 g, 68.0 mmol), and pyrrolidine (17.0 mL, 204.0 mmol),
and isolated as an orange powder (14.9 g, 51.0 mmol, 85%).
1
H NMR (CDCl
3
, 400 MHz, 25
◦
C):
δ
7.41
(broad m, 4H, CH-Ar), 6.66 (dt,
3
J= 5.2,
4
J= 1.8, 2H, CH-Cp), 6.60 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp),
6.51 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp), 6.21 (dt,
3
J= 5.2,
4
J= 1.6, 2H, CH-Cp), 2.58 (s, 6H, CH
3
).
13
C NMR
(CDCl
3
, 125 MHz, 25
◦
C):
δ
149.2, 143.8, 141.9 (Cq), 132.2, 131.9 (CH-Cp), 129.8, 129.2, 127.6 (CH-Ar),
123.6, 121.2 (CH-Cp), 22.7 (CH
3
). ESI-MS (m/z): 259.15 ([M + H]
+
). Anal. calcd. for C
20
H
18
(258.36):
C 92.98, H 7.02; found: C 93.02, H 7.13.
3.7. 1,4-Ph((Me)C-(3,6-tBu2FluH)(CpH))2(2a)
In a Schlenk flask, to a solution of 3,6-di-tert-butyl-fluorene (2.17 g, 7.8 mmol) in THF
(100 mL), was added n-BuLi (3.13 mL of a 2.5 M solution in hexane, 7.8 mmol). This solution was
added dropwise to a solution of
1a
(1.00 g, 3.9 mmol) in THF (100 mL) at
−
10
◦
C over 10 min.
After completion of the addition, the reaction mixture was stirred for 2 days at room temperature.
The mixture was hydrolyzed with 10% aqueous hydrochloric acid (20 mL), the organic phase
was dried over sodium sulfate, and volatiles were evaporated in vacuo. The solid residues was
washed with pentane (200 mL) and dried under reduced in vacuo to afford a white powder (1.96 g,
2.4 mmol, 62%).
1
H NMR (CDCl
3
, 400 MHz, 25
◦
C) (mixtures of tautomers):
δ7.76 (m, 4H, CH-Ph),
7.66 (m, 4H, CH-Flu)
, 7.25–7.08 (m, 4H, CH-Flu), 7.01 (m, 1H, CH-Flu), 6.87 (t,
3
J= 9.0, 1H,
CH-Flu), 6.62
(t, 3J= 9.0, 1H,
CH-Flu),
6.54–6.41 (m, 6H, CH-Flu + CH-Cp),
6.18 (m, 1H, CH-Cp),
4.96 (s, 2H, H-Flu), 3.19–2.99 (m, 4H, CH2-Cp)
, 1.38 (m, 36H, CH
3
-
t
Bu), 1.12–1.07 (m, 6H, CH
3
-bridge).
13
C NMR (CDCl
3
, 125 MHz, 25
◦
C):
δ
156.4, 156.3, 156.2 (Cq-Cbridge), 153.8 (Cq), 150.2, 150.2, 150.1,
150.1 (Cq-C-
t
Bu), 145.5, 145.4 (Cq), 142.8, 142.8, 142.6, 142.5, 142.3, 142.2 (Cq), 134.5, 134.4, 134.3
(CH-Flu), 133.9, 133.8 (CH-Flu), 132.2, 131.9 (CH-Cp), 127.8, 127.8, 127.7, 127.5 (CH-Cp), 126.3 (CH-Cp),
125.7, 125.6, 125.5 (CH-Cp), 123.7, 123.6, 123.5, 123.4 (CH-Flu), 115.9, 115.9 (CH-Ph), 68.1 (Cq), 55.4,
55.4, 55.3 (CH), 54.0, 53.9 (CH), 47.5, 47.4 (Cq), 46.4, 46.3 (Cq), 42.1, 41.0 (CH
2
-Cp), 34.9, 34.8 (Cq),
31.8 (CH
3
-
t
Bu). ESI-MS (m/z): 815.55 ([M + H]
+
), 814.54 ([M]). Anal. calcd. for C
62
H
70
(815.22): C 91.35,
H 8.65; found: C 91.68, H 8.78.

Catalysts 2018,8, 558 12 of 19
3.8. 1,4-Ph((H)C-(3,6-tBu2FluH)(CpH))2(2b)
Using a protocol similar to that described above for
2a
, compound
2b
was prepared from
3,6-di-tert-butyl-fluorene (4.83 g, 17.4 mmol), n-BuLi (7.0 mL of a 2.5 M solution in hexane, 17.4 mmol),
1b
(2.00 g, 8.7 mmol), and isolated as a white powder (4.12 g, 5.2 mmol, 60%).
1
H NMR (CDCl
3
,
400 MHz, 25
◦
C) (mixture of tautomers):
δ
7.72 (m, 4H, CH-Ar), 7.10 (m, 8H, CH-Cp), 7.02 (m, 1H,
CH-Cp), 6.88 (m, 1H, CH-Cp), 6.7 (m, 3H, CH-Cp), 6.45 (m, 2H, CH-Cp), 6.33 (m, 1H, CH-Cp),
6.18 (m, 1H, CH-Cp), 5.96 (m, 1H, CH-Cp), 4.52 (m, 2H, CH-Flu), 4.03 (m, 2H, CH-bridge), 2.96 (m, 3H,
CH
2
-Cp), 1.36 (s, 36H, CH
3
-
t
Bu).
13
C NMR (CDCl
3
, 125 MHz, 25
◦
C):
δ
150.87, 150.69, 150.25, 150.21,
150.19, 150.17, 150.15, 150.13, 150.11, 150.09, 150.05 (Cq-C-
t
Bu), 148.39, 148.34 (Cq), 143.57, 143.55,
143.44, 143.40, 143.37, 143.32 (Cq), 141.69, 141.65, 141.48, 141.45, 141.42, 141.39 (Cq), 140.67 (Cq), 134.50,
134.47, 134.41 (CH-Flu), 133.89, 133.81 (CH-Flu), 132.42, 131.43, 131.40, 131.37 (CH-Cp), 129.25, 129.22,
129.19, 129.16, 128.96 (CH-Cp), 128.90, 128.87, 128.82, 128.80, 128.72, 128.67, 128.62 (CH-Cp), 125.45,
125.33, 125.31, 125.28, 125.23, 125.19, 125.16 (CH-Cp), 123.64, 123.61, 123.57, 123.55, 123.51, 123.46,
123.41 (CH-Flu), 116.12, 116.07 (CH-Ph), 51.50, 51.46, 51.44, 51.22, 51.14, 51.12 (CH-bridge), 50.44, 50.39,
50.30, 50.20, 50.16 (CH), 43.15, 43.12, 41.14, 41.12 (CH
2
-Cp), 34.90, 34.88 (Cq), 31.80 (CH
3
-tBu). Mp:
240
◦
C. ESI-MS (m/z): 787.52 ([M + H]
+
), 786.51 ([M]). Anal. calcd. for C
60
H
66
(787.17): C 91.55, H 8.45;
found: C 91.68, H 8.90.
3.9. 1,3-Ph(MeC-(3,6-tBu2FluH)(CpH))2(2c)
Using a protocol similar to that described above for
2a
, compound
2c
was prepared from
3,6-di-tert-butyl-fluorene (2.17 g, 7.8 mmol), n-BuLi (3.13 mL of a 2.5 M solution in hexane, 7.8 mmol),
and
1c
(1.00 g, 3.9 mmol). The final product
2c
was isolated as a white powder (469 mg, 0.58 mmol,
15%).
1
H NMR (CDCl
3
, 500 MHz, 25
◦
C):
δ
7.80 (m, 1H, CH-Flu), 7.72–7.64 (m, 4H, CH-Ph), 7.53–7.30
(m, 4H, CH-Flu), 7.11 (m, 2H, CH-Flu), 7.04–6.99 (m, 1H, CH-Flu), 6.92–6.70 (m, 4H, CH-Flu), 6.49–6.34
(m, 4H, CH-Cp), 6.26 (m, 1H, CH-Cp), 6.13–6.07 (m, 1H, CH-Cp), 4.84 (m, 2H, CH-Flu), 3.01 (m, 4H,
CH
2
-Cp), 1.36–1.30 (s, 36H, CH
3
-tBu), 1.19–1.06 (m, 6H, CH
3
-bridge).
13
C NMR (CDCl
3
, 125 MHz,
25
◦
C):
δ
156.3, 156.2 (Cq-Cbridge), 153.9 (Cq), 150.2, 150.1, 150.0, 149.9 (Cq-C-
t
Bu), 142.8, 142.4, 142.1,
142.1 (Cq), 134.5, 134.4, 134.3 (CH-Flu), 133.8, 133.6 (CH-Flu), 132.0, 131.9 (CH-Cp), 128.0, 127.9, 127.8
(CH-Cp), 126.4, 126.3 (CH-Cp), 125.9, 125.8, 125.7, 125.6, 125.5 (CH-Cp), 123.6, 123.6, 123.5, 123.4, 123.4
(CH-Flu), 115.9, 115.9, 115.8 (CH-Ph), 66.0 (Cq), 55.5, 55.4 (CH), 54.2, 54.1 (CH), 48.0, 47.9 (Cq), 47.1,
47.0 (Cq), 42.0, 41.9, 41.0 (CH
2
-Cp), 34.9, 34.8 (Cq), 31.7 (CH
3
-tBu). ESI-MS (m/z): 853.51 ([M + K]
+
),
837.54 ([M + Na]
+
), 815.55 ([M + H]
+
). Anal. calcd. for C
62
H
70
(815.22): C 91.35, H 8.65; found: C 91.55,
H 8.69.
3.10. PhMeC-(3,6-tBu2FluH)(CpH) (2a’)
Using a protocol similar to that described above for
2a
, compound
2a’
was prepared from
3,6-di-tert-butyl-fluorene (0.97 g, 3.5 mmol), n-BuLi (1.4 mL of a 2.5 M solution in hexane, 3.5 mmol),
and (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (0.59 g, 3.5 mmol), and isolated as a white powder
(0.65 g, 1.4 mmol, 40%).
1
H NMR (CDCl
3
, 500 MHz, 25
◦
C):
δ
7.75 (dd, J= 7.1, 2.0, 1H, CH-Flu),
7.72 (t,
J= 2.2,
1H, CH-Flu), 7.63 (d, J= 7.8, 2H, CH-Ph), 7.39 (td, J= 7.5, 4.4, 2H, CH-Ph), 7.30 (tt, J= 7.2,
1.4, 1H, CH), 7.14 (ddd, J= 13.8, 8.1, 2.0, 1H, CH-Flu), 7.00–6.88 (m, 2H, CH-Flu),
6.71 (d, J= 8.2, 1H
,
CH-Cp), 6.55 6.48 (m, 2H, CH-Flu), 6.39 (dd, J= 5.3, 1.5, 1H, CH-Cp), 6.24–6.18 (m, 1H, CH-Cp), 6.00 (dd,
J= 13.9, 8.1, 1H, CH-Cp), 4.91 (d, J= 3.5, 1H, CH-Flu), 3.06 (dd, J= 7.1, 1.6, 1H, CH
2
-Cp), 1.45–1.29 (m,
20H, CH
3
-tBu), 1.07 (m, 3H, CH
3
-bridge).
13
C NMR (CDCl
3
, 125 MHz, 25
◦
C):
δ
156.04 (Cq), 153.70 (Cq),
150.20, 150.14, 150.08, 150.06 (Cq), 147.74, 147.17 (Cq), 142.84, 142.79, 142.34, 142.31, 142.20, 142.19,
142.15, 142.08 (Cq), 134.18, 134.01 (CH), 132.07, 131.96 (CH), 128.38 (CH), 127.89, 127.65, 127.57 (CH),
126.47, 126.32, 126.27 (CH), 125.66, 125.47, 125.45, 125.31 (CH), 123.67, 123.61, 123.54, 123.45 (CH),
115.93, 115.87, 115.81, 115.79 (CH), 55.56, 54.30 (CH-Flu), 47.73, 46.59, 42.01, 40.98 (CH
2
-Cp), 34.89,
34.87, 34.81, 31.93, 31.87, 31.77, 31.72, 31.62 (CH
3
-tBu), 18.48, 18.40 (CH
3
). ESI-MS (m/z): 447.30 ([M +

Catalysts 2018,8, 558 13 of 19
H]
+
), 277.19 ([3,6-di-tert-butyl-fluorene]
+
). Anal. calcd. for C
34
H
38
(446.67): C 91.42, H 8.58; found:
C 91.54, H 8.71.
3.11. Ph(H)C-(3,6-tBu2FluH)(CpH) (2b’)
Using a protocol similar to that described above for
2a
, compound
2b’
was prepared from
3,6-di-tert-butyl-fluorene (4.70 g, 16.9 mmol), n-BuLi (6.8 mL of a 2.5 M solution in hexane, 16.9 mmol),
and (cyclopenta-2,4-dien-1-ylidenemethyl)benzene (2.60 g, 16.9 mmol), and isolated as a white powder
(0.70 g, 1.62 mmol, 10%).
1
H NMR (CDCl
3
, 400 MHz, 25
◦
C):
δ
7.71 (m, 2H, CH-Flu), 7.24–7.12 (m, 6H,
CH-Ph + CH-Flu), 7.04 (m, 1H, CH-Flu), 6.89 (d, J= 8.1, 1H, CH-Flu), 6.68–6.01 (m, 4H, CH-Cp),
4.54 (m, 1H, CH-bridge), 4.06 (m, 1H, CH-Flu), 3.12–2.89 (m, 2H, CH
2
-Cp), 1.39–1.32 (m, 18H, CH
3
-tBu).
13
C NMR (CDCl
3
, 125 MHz, 25
◦
C): 150.72, 150.22, 150.15, 150.09 (Cq), 148.38 (Cq), 143.51, 143.22,
142.76 (Cq), 141.45, 141.39 (Cq), 134.34, 134.04 (CH), 132.42, 131.47 (CH), 129.28, 129.09, 129.04, 128.64,
128.54, 128.28, 128.21 (CH), 126.52, 125.34, 125.28, 125.20, 125.13 (CH), 123.68, 123.62, 123.56 (CH),
116.13, 116.09, 116.06 (CH), 51.54, 51.48, 50.61, 50.40 (CH), 43.16, 41.18 (CH
2
-Cp), 34.91, 34.88, 31.88,
31.78, 31.76 (CH
3
-tBu). ESI-MS (m/z): 433.29 ([M + H]
+
). Anal. calcd. for C
33
H
36
(432.64): C 91.61,
H 8.39; found: C 91.92, H 8.84.
3.12. 1,4-Ph{MeC-(3,6-tBu2Flu)(Cp)ZrCl2}2(3a-Zr)
To a solution of
2a
(0.500 g, 0.61 mmol) in diethyl ether (50 mL) was added under stirring
n-BuLi (0.98 mL of a 2.0 M solution in hexane, 2.45 mmol). The solution was kept overnight at
room temperature. ZrCl
4
(0.286 g, 1.23 mmol) was added to the reaction mixture with a bent
finger. The resulting red mixture was stirred at room temperature overnight. Then, the mixture
was evaporated in vacuo and CH
2
Cl
2
(20 mL) was added. The resulting solution was filtered,
and volatiles were evaporated in vacuo to give a red powder (0.528 g, 0.46 mmol, 76%).
1
H NMR
(CD
2
Cl
2
, 500 MHz, 25
◦
C):
δ
8.20–8.10 (m, 3H, CH-Flu), 8.01–7.88 (4H, CH-Flu), 7.87–7.66 (4H,
CH-Flu + CH-Ph), 7.58–7.49 (2H, CH-Ph), 7.40–7.06 (4H, 2H, CH-Flu), 6.63–6.56 (1H, CH-Cp),
6.46–6.28 (4H, CH-Cp), 6.00–5.77 (3H, CH-Cp), 2.68–2.57 (m, 6H, CH
3
), 1.52–1.43 (d, 36H, CH
3
-tBu).
13
C NMR (CD
2
Cl
2
, 125 MHz, 25
◦
C):
δ
158.3 (Cq-tBu), 150.3 (Cq-tBu), 149.7 (Cq-Ph), 145.3 (Cq-Flu),
129.6–128.8 (CH-Ph), 128.1 (Cq-Flu), 127.1 (CH-Flu), 126.8 (CH-Flu), 126.2 (Cq-Flu), 126.4 (CH-Flu),
125.8 (CH-Flu), 123.2 (CH-Cp), 123.1 (CH-Cp), 122.7 (CH-Cp), 120.3 (CH-Cp), 119.8 (CH-Cp),
117.5 (CH-Cp), 112.4 (Cq-Cp), 103.7–103.5 (CH-Cp), 102.5 (CH-Cp), 102.4 (CH-Cp), 77.4 (C-Flu),
53.8–53.4 (CH
3
-bridge), 31.7–30.8 (CH
3
-tBu). APPI-MS (m/z): 1030.20 ([M]
+
), 970.36 ([M–ZrCl
2
]
+
),
810.51 ([M–Zr2Cl4]+). Anal. calcdfor C62H66Cl4Zr2(1135,45): C 65.58, H 5.86; found: C 65.42, H 6.00.
3.13. 1,4-Ph{MeC-(3,6-tBu2Flu)(Cp)HfCl2}2(3a-Hf)
Using a protocol similar to that described above for
3a-Zr
, compound
3a-Hf
was prepared
from 1,4-bis(cyclopenta-2,4-dien-1-yl(3,6-di-tert-butyl-fluoren-9-yl)ethyl)benzene (0.500 g, 0.61 mmol),
n-BuLi (0.98 mL of a 2.5 M solution in hexane, 2.45 mmol), and HfCl
4
(0.380 g, 1.23 mmol).
The compound was recovered as an orange-yellow powder (0.520 g, 0.38 mmol, 62%).
1
H NMR
(toluene-d
8
, 500 MHz, 25
◦
C):
δ
8.33–8.10 (m, 4H, CH-Flu), 8.00 (s, 2H, CH-Flu), 7.77–7.23 (m, 7H,
CH-Flu + CH-Ph), 6.79 (d, J= 9.2, 1H, CH-Flu), 6.34 (d, J= 9.3, 1H, CH-Flu), 6.17–5.85 (m, 4H, CH-Cp),
5.65–5.30 (m, 4H, CH-Cp), 2.30 (s, 6H, CH
3
), 1.70–1.17 (m, 36H, CH
3
-tBu).
13
C NMR (C
6
D
6
, 125 MHz,
25
◦
C):
δ
150.02, 149.75, 149.71, 146.71, 132.18 (Cq), 130.29, 129.93, 129.53, 129.40, 129.22, 128.76, 128.55,
128.45, 128.36, 128.25, 128.16, 128.06, 127.72, 127.43, 127.16, 126.79, 126.43, 125.25, 125.02, 123.49,
123.19, 122.97, 122.61, 122.47, 122.43, 122.34, 121.41, 121.20, 120.39, 120.16, 119.88, 119.74, 119.34, 116.98,
116.79, 115.48, 114.77, 101.70, 101.51, 100.27, 79.57, 78.89 (C-Flu), 49.95, 49.64 (CH
3
), 35.46, 35.42, 35.37,
35.32, 35.27, 35.11, 32.21, 32.18, 32.05, 32.02, 32.00, 31.97, 31.96, 31.47, 29.92, 29.78, 27.45 (CH
3
-tBu).
APPI-MS (m/z): 1310.3046 ([M]
+•
), 1062.4287 ([M–HfCl
2
]
+
). Anal. calcdfor C
62
H
66
Cl
4
Hf
2
(1310.2850):
C 56.85, H 5.08; found: C 56.73, H 5.16.

Catalysts 2018,8, 558 14 of 19
3.14. 1,4-Ph{(H)C-(3,6-tBu2Flu)(Cp)ZrCl2}2(3b-Zr)
Using a protocol similar to that described above for
3a-Zr
, compound
3b-Zr
was prepared from
2b
(0.660 g, 0.84 mmol), n-BuLi (1.37 mL of a 2.0 M solution in hexane, 3.37 mmol), and ZrCl
4
(0.392 g,
1.68 mmol). The compound was isolated as a red powder (0.350 g, 0.32 mmol, 38%).
1
H NMR (CD
2
Cl
2
,
500 MHz, 25
◦
C):
δ
8.16 (d,
3
J= 4.0, 2H, CH-Flu), 7.98 (s, 4H, CH-Ph), 7.67 (m, 4H, CH-Flu), 7.27 (dd,
3J= 9.0, 4
J= 1.6, 2H, CH-Flu), 6.69 (d,
3
J= 9.0, 2H, CH-Flu), 6.64 (s, 2H, CH-ansa), 6.36 (dq,
3
J= 2.5, 4H,
CH-Cp), 5.84 (dq,
3
J= 2.5, 4H, CH-Cp), 1.47 (d, 36H, CH
3
-
t
Bu).
13
C NMR (CD
2
Cl
2
, 125 MHz, 25
◦
C):
δ
150.4 (C-Flu-
t
Bu), 137.6 (Cq), 128.2 (CH-Ph), 127.8 (CH-Ph), 127.5 (CH-Flu), 122.8 (Cq), 121.9 (CH-Flu),
120.3 (Cq), 119.6 (CH-Flu), 119.6 (CH-Cp), 119.5 (CH-Cp), 117.6 (CH-Cp), 106.2 (Cq), 104.9 (CH-Cp),
101.9 (CH-Cp), 73.9 (C-Flu), 41.7 (CH-bridge), 31.2 (CH
3
-tBu). APPI-MS (m/z): 1102.1766 ([M]
+•
),
942.3300 ([M–ZrCl
2
]
+
), 782.8 ([M–Zr
2
Cl
4
]
+
). Anal. calcd. for C
60
H
62
Cl
4
Zr
2
(1102.16997): C 65.08,
H 5.64; found: C 65.75, H 6.01.
3.15. 1,3-Ph{MeC-(3,6-tBu2Flu)(Cp)ZrCl2}2(3c-Zr)
Using a protocol similar to that described above for
3a-Zr
, compound
3c-Zr
was prepared from
2c
(0.520 g, 0.64 mmol), n-BuLi (1.0 mL of a 2.5 M solution in hexane, 2.55 mmol), and ZrCl
4
(0.300 g,
1.27 mmol). The product was isolated as a red powder (0.630 g, 0.56 mmol, 87%).
1
H NMR (C
6
D
6
,
500 MHz, 25
◦
C):
δ
8.43–8.23 (m, 4H, CH-Flu), 8.05 (m, 2H, CH-Flu), 7.70 (dt, J= 7.8, 1.4, 1H, CH-Flu),
7.63–7.25 (m, 6H, CH-Flu + CH-Ph), 7.06–6.90 (m, 2H, CH-Ph), 6.47 (d, J= 9.1, 1H, CH-Ph), 6.28–6.23
(m, 1H, CH-Flu), 6.23–6.15 (m, 1H, CH-Cp), 6.13–6.04 (m, 1H, CH-Cp), 5.90–5.84 (m, 1H, CH-Cp),
5.74 (m, 1H, CH-Cp), 5.67–5.57 (m, 2H, CH-Cp), 5.55–5.36 (m, 1H, CH-Cp), 5.14 (d, J= 2.7, 1H, CH-Cp),
2.55–2.13 (m, 6H, CH
3
), 1.51–1.29 (m, 36H, CH
3
-tBu).
13
C NMR (C
6
D
6
, 125 MHz, 25
◦
C):
δ
150.36,
150.10, 150.00, 149.79, 148.63, 148.55 (Cq), 131.99, 130.20, 129.34, 129.25, 129.19, 127.55, 127.27, 127.05,
126.53, 124.83, 124.53, 124.50, 123.91, 123.86, 123.84, 123.60, 123.52, 123.27, 123.22, 123.19, 123.00, 122.88,
122.85, 122.77, 122.60, 122.56, 120.56, 120.31, 120.21, 120.13, 120.10, 120.05, 119.90, 119.73, 117.86, 117.77,
117.30, 112.98, 112.63, 112.46, 104.92, 103.75, 103.57, 102.37, 101.31, 101.26, 79.19, 78.67, 78.63 (C-Flu),
50.49, 50.18, 50.09 (CH
3
-bridge), 35.22, 35.18, 35.16, 35.08, 32.00, 31.97, 31.95, 31.92, 31.85, 31.78, 31.73,
31.70, 31.36, 30.95, 29.73 (CH
3
-tBu), 18.14. APPI-MS (m/z): 1130.2240. Anal. calcdfor C
62
H
66
Cl
4
Zr
2
(1130.2013): C 65.53, H 5.94; found: C 66.03, H 6.64.
3.16. {Ph(Me)C-(3,6-tBu2Flu)(Cp)}ZrCl2(3a’-Zr)
Using a protocol similar to that described above for
3a-Zr
, compound
3b-Zr
was prepared from
2a’
(0.400 g 0.89 mmol), n-BuLi (0.72 mL of a 2.5 M solution in hexane, 1.79 mmol), and ZrCl
4
(0.209 g,
0.89 mmol). The compound was isolated as a red powder (0.410 g, 0.67 mmol, 76%).
1
H NMR
(toluene-d
8
, 500 MHz, 25
◦
C):
δ
8.07 (ddd, J= 7.0, 1.9, 0.7, 2H, CH-Flu), 7.43 (dt, J= 7.8, 1.7, 1H,
CH-Ph), 7.39 (dd, J= 9.3, 0.8, 1H, CH-Flu), 7.24 (dt, J= 7.8, 1.7, 1H, CH-Ph), 7.22–7.16 (m, 2H, CH-Ph),
7.08–6.96 (m, 3H, CH-Flu), 6.88 (m, 1H, CH-Cp), 6.65 (m, 1H, CH-Cp), 6.12–5.76 (m, 2H, CH-Cp),
5.32 (t, J= 2.7, 2H), 2.01 (s, 3H, CH3-bridge), 1.25 (m, 18H, CH3-tBu). 13C NMR (toluene-d8, 125 MHz,
25
◦
C):
δ
150.05 (C-Flu-tBu), 149.74 (C-Flu-tBu), 147.28 (Cq-Ph), 129.45, 129.19 (CH-Ph), 128.25 (CH-Flu),
127.29 (CH-Ph), 127.23 (CH-Flu), 125.72 (CH-Cp), 125.41 (CH-Cp), 123.65, 123.55, 123.25 (CH-Cp),
122.93, 122.68 (CH-Cp), 120.25 (CH-Cp), 119.94, 119.39, 117.46 (CH-Flu), 112.95 (Cq-Cp), 103.58, 102.30
(CH-Cp), 78.99 (C-Flu), 49.94 (Cq-tBu), 35.15, 35.10 (Cq-tBu), 31.77, 31.07 (CH
3
-tBu). APPI-MS (m/z):
604.1239 ([M]
+•
), 444.2664 ([M–ZrCl
2
]
+
. Anal. calcdfor C
34
H
36
Cl
2
Zr (604.1241): C 67.30, H 5.98; found:
C 67.82, H 6.09.
3.17. {Ph(H)C-(3,6-tBu2Flu)(Cp)}ZrCl2(3b’-Zr)
Using a protocol similar to that described above for
3a-Zr
, compound
3b’-Zr
was prepared from
2b’
(0.430 g, 0.99 mmol), n-BuLi (0.81 mL of a 2.5 M solution in hexane, 1.99 mmol), and ZrCl
4
(0.230 g,
0.99 mmol). The product was isolated as a red powder (0.540 g, 0.86 mmol, 87%).
1
H NMR (C
6
D
6
,

Catalysts 2018,8, 558 15 of 19
500 MHz, 25
◦
C):
δ
8.24 (s, 2H, CH-Flu), 7.55 (d, J= 7.4, 2H, CH-Ph), 7.42 (d, J= 9.0, 1H, CH-Ph), 7.24 (m,
3H, CH-Ph), 6.99 (d, J= 8.8, 1H, CH-Flu), 6.92 (d, J= 9.1, 1H, CH-Flu), 6.51 (d, J= 9.0, 1H, CH-Flu),
6.17–6.05 (m, 2H, CH-Flu), 5.80 (s, 1H, CH), 5.48 (t, J= 2.8, 1H, CH-Cp), 5.29 (t, J= 2.8, 1H, CH-Cp),
1.39 (s, 18H, CH
3
-
t
Bu).
13
C NMR (C
6
D
6
, 125 MHz, 25
◦
C):
δ
150.08 (C-Flu-tBu), 149.89 (C-Flu-tBu),
138.64 (C-Flu), 128.78, 128.38 (C-tBu), 127.96, 127.21 (CH-Flu), 122.77, 122.31, 122.24, 121.54 (CH-Cp),
119.95, 119.76, 119.74, 119.51, 117.01 (CH-Flu), 106.86, 105.16, 101.87 (CH-Cp), 73.63 (C-Flu), 41.81 (Cq),
34.98, 34.85 (Cq), 31.57, 31.49 (CH
3
-tBu). APPI-MS (m/z): 590.1115 ([M]
+•
), 430.2659 ([M–ZrCl
2
]
+
.
Anal. calcd for C33H34Cl2Zr (590.1085): C 66.87, H 5.78; found: C 67.11, H 5.97.
3.18. {Ph(H)C-(3,6-tBu2Flu)(Cp)}HfCl2(3b’-Hf)
This compound was prepared as described above for
3a
starting from
2b’
(0.090 g, 0.20 mmol),
n-BuLi (0.16 mL of a 2.5 M solution in hexane, 0.41 mmol), and HfCl
4
(0.060 g, 0.2 mmol). The product
was isolated as an orange powder (0.076 g, 0.86 mmol, 56%).
1
H NMR (C
6
D
6
, 500 MHz, 25
◦
C):
δ
8.22 (dt,
J= 9.0
, 1.9, 2H, CH-Flu), 7.56 (dt, J= 8.0, 1.4, 2H, CH-Flu), 7.40 (dd, J= 9.0, 1.7, 1H, CH-Ph),
7.28–7.20 (m, 3H, CH-Ph), 7.04 (d, J= 9.0, 1H), 6.91 (dd, J= 9.1, 1.8, 1H, CH-Ph), 6.57 (dd, J= 9.1, 1.8,
1H, CH-Ph), 6.09–6.00 (m, 2H, CH-Flu), 5.85 (s, 1H, CH-Cp), 5.44 (q, J= 2.7, 1H, CH-Cp), 5.25 (q, J= 2.8,
1H, CH-Cp), 1.39 (s, 18H, CH
3
-tBu).
13
C NMR (C
6
D
6
, 125 MHz, 25
◦
C):
δ
149.80, 149.60 (Cq), 139.28,
122.45, 121.64, 121.52, 120.32, 119.96, 119.92, 119.42, 118.78, 116.70, 116.43, 110.06, 103.15, 99.85, 74.22
(C-Flu), 42.10, 35.32, 35.18, 34.90, 34.84, 31.94, 31.85, 31.83, 31.79, 31.74, 31.70, 31.64, 31.52 (CH
3
-tBu).
APPI-MS (m/z): 680.1497 ([M]
+•
), 430.2659 ([M–HfCl
2
]
+
), 278.2035 (C
21
H
26
, [3,6-di-tert-butyl-fluorene
+ H]+•). Anal. calcd. for C33H34Cl2Hf (680.1503): C 58.29, H 5.04; found: C 58.55, H 5.26.
3.19. Ethylene Homopolymerization and Ethylene/1-hexene Copolymerization
Polymerization experiments were performed in a 300 mL high-pressure glass reactor equipped
with a mechanical stirrer (Pelton turbine) and externally heated with a double mantle with a circulating
water bath. The reactor was filled with toluene (100 mL), 1-hexene comonomer (when relevant;
typically 2.5 mL), and MAO (0.20 mL of a 30 wt-% solution in toluene) and pressurized at 5.5 bar of
ethylene (Air Liquide, 99.99%). The reactor was thermally equilibrated at the desired temperature
for 30 min, the ethylene pressure was decreased to 1 bar, and a solution of the catalyst precursor
in toluene (ca. 2 mL) was added by syringe. The ethylene pressure was immediately increased
to 5.5 bar (kept constant with a back regulator), and the solution was stirred for the desired time
(typically 15 min). The temperature inside the reactor (typically 60
◦
C) was monitored using a
thermocouple. The polymerization was stopped by venting the vessel and quenching with a 10% HCl
solution in methanol (ca. 2 mL). The polymer was precipitated in methanol (ca. 200 mL), and 35%
aqueous HCl (ca. 1 mL) was added to dissolve possible catalyst residues. The polymer was collected
by filtration, washed with methanol (ca. 200 mL), and dried under vacuum overnight.
3.20. Crystal Structure Determination of 3a’-Zr
Diffraction data were collected at 150 K using a Bruker APEX CCD diffractometer (Bruker, Billerica,
MA, USA) with graphite-monochromated MoK
α
radiation (
λ
= 0.71073
Catalysts 2018, 8, x FOR PEER REVIEW 10 of 19
precursors, (1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene and (cyclopenta-2,4-dien-1-
ylidenemethyl)benzene [42], were prepared following protocols published in the literature. ZrCl4 and
HfCl4 were used as received (anhydrous, Strem Chemicals, Bischheim, France). 1-Hexene (Fisher
Chemical, Illkirch, France) was distilled and stored over 3 Ǻ molecular sieves under argon. Ethylene
(N35, Air Liquide, Paris, France) was used without further purification.
3.2. Instruments and Measurements
The NMR spectra of air- and moisture-sensitive compounds were recorded on Bruker AM-400
and AM-500 spectrometers in Teflon-valved NMR tubes at room temperature. 1H and 13C chemical
shifts are reported in ppm versus SiMe4 and were determined using residual solvent signal. Coupling
constants are given in Hertz. Assignments of signals were carried out using 1D (1H, 13C{1H}, JMOD)
and 2D (COSY, HMBC, HMQC) NMR experiments. Elemental analyses were performed on a Carlo
Erba 1108 Elemental Analyzer instrument at the London Metropolitan University by Stephen Boyer
or on a Flash EA1112 CHNS Thermo Electron apparatus at CRMPO, Rennes, and were the average
of a minimum of two independent measurements.
The 13C{1H} NMR and GPC analyses of polymer samples were performed in the research center
of Total Research and Technologies in Feluy (Feluy, Belgium). The 13C{1H} NMR analyses were run
on a 500 MHz Bruker Avance III with a 10 mm cryoprobe HTDUL in trichlorobenzene/C6D6 (2 mL/0.5
mL). The GPC analyses were performed in 1,2,4-trichlorobenzene at 135 °C using PS standards for
calibration. Differential scanning calorimetry (DSC) analyses were performed on a Setaram DSC 131
apparatus under a continuous flow of helium and using aluminum capsules. Glass transition and
melting temperatures were measured during the second heating (10 °C·min−1).
The ESI (ElectroSpray Ionization) mass spectra of organic compounds, including proligands,
were recorded at CRMPO-Scanmat (Rennes, France) on an Orbitrap Thermo Fisher Scientific Q-
Exactive instrument with an ESI source in positive mode by direct introduction at 5–10 µg·mL−1.
Samples were prepared in CH2Cl2 at 10 µg·mL−1.
The ASAP (Atmospheric Solids Analysis Probe) mass spectra of proligands were recorded at the
CRMPO-Scanmat (Rennes, France) on a Q-TOF Bruker Maxis 4G instrument with an APCI source in
positive mode at desorption temperatures of 255 and 300 °C.
3.3. APPI Mass Spectrometric Characterization of Metal Complexes
The mass spectra of metal complexes were recorded on a hybrid quadrupole time-of-flight
instrument (Waters, Synapt G2, Manchester, England) equipped with an APPI source. The
instrument was operated in the positive ion mode. The ionization experimental conditions were set
as follows: desolvation gas flow, 700 L h−1; source temperature, 120 °C; probe temperature, 400 °C;
sampling cone, 20 V; extraction cone, 3 V. The time-of-flight was operated in the ‘resolution mode’
yielding a resolving power of about 20,000. The samples were prepared in a glove box using dried
toluene in 1.5 mL glass vials with a final concentration of 20 µM. For analysis, the sample was taken
with a dry syringe stored in an oven. The solution was directly infused into the source using a syringe
pump at a flow rate of 200 µL h−1. Data were acquired over the m/z 50–2000 range for 2–5 min. Note
that the given accurate masses are given with Water Mass Lynx 4.1 that do not take into account the
mass of the electron removed during ionization. All given masses are monoisotopic values. In the
mass spectra, only the highest abundant isotope is labelled.
3.4. 1,4-Bis(1-(cyclopenta-2,4-dien-1-ylidene)ethyl)benzene (1a)
In a 250 mL round bottom flask equipped with a magnetic stirring bar and an argon inlet, freshly
cracked cyclopentadiene (12.36 mL, 148.0 mmol) and 1,4-diacetylbenzene (4.82 g, 30.0 mmol) were
dissolved in methanol (200 mL). To this solution, pyrrolidine (7.5 mL, 89.0 mmol) was added at 0 °C.
The reaction mixture was stirred at room temperature for 7 days. After neutralization with glacial
acetic acid (7.5 mL) and separation of the organic phase, volatiles were evaporated under vacuum to
give a yellow powder (5.51 g, 21.3 mmol, 72%). 1H NMR (CDCl3, 400 MHz, 25 °C): δ 7.35 (s, 4H, CH-
). A combination of
ω
- and
ϕ
-scans was carried out to obtain at least a unique data set. The crystal structures were solved by
direct methods, and the remaining atoms were located from a difference Fourier synthesis followed
by full-matrix least-squares refinement based on F2 (programs SIR97 [
43
] and SHELXL-97 [
44
]).
Hydrogen atoms were placed at calculated positions and forced to ride on the attached atom.
All non-hydrogen atoms were refined with anisotropic displacement parameters. The locations
of the largest peaks in the final difference Fourier map calculation as well as the magnitude of the
residual electron densities were of no chemical significance. The main crystal and refinement data
are summarized in Table S1. Crystal data, details of data collection, and structure refinement for
compound
3a’-Zr
(CCDC 1863222) can be obtained from the Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.

Catalysts 2018,8, 558 16 of 19
3.21. Computational Details
All calculations were performed with the TURBOMOLE program package using density
functional theory (DFT) [
45
–
48
]. The gradient-corrected density functional BP86 in combination
with the resolution identity approximation (RI) [
49
,
50
] was applied for the geometry optimizations of
a stationary point. The triple-ζzeta valence quality basis set def-TZVP was used for all atoms [51].
The stationary points were characterized as energy minima (no negative Hessian eigenvalues) by
vibrational frequency calculations at the same level of theory.
4. Conclusions
The synthesis of original bis(Cp/Flu) ligand systems linked at the C1-bridge through a phenylene
group was developed starting from difulvene precursors. These ligand platforms were utilized for the
preparation of homodinuclear zirconium and hafnium bis(dichloro ansa-metallocene) complexes via a
regular salt-metathesis metallation protocol. The synthesis of a heterodinuclear zirconium/hafnium
bis(dichloro ansa-metallocene) was also performed, although the desired product was generated as a
statistical mixture with the corresponding homodinuclear complexes. For the first time, an advanced
APPI mass-spectrometric method was applied to the characterization of dinuclear bis(ansa-metallocene)
complexes and their mononuclear ansa-metallocene analogues, and relevant data were obtained.
Ethylene homopolymerization as well as ethylene/1-hexene copolymerization were conducted
using the homodinuclear dichloro catalyst precursors, as well as with their mononuclear analogues,
in combination with MAO. Limited cooperativity evidence has been observed with dinuclear systems
so far, with, in some cases, slightly different molecular weights or a greater formation of short methyl
and ethyl branches as compared to the mononuclear reference systems. The apparent lack of significant
cooperative behavior observed for the dinuclear systems was substantiated by a computational analysis.
Thus, the computed para- and meta-phenylene-bridged neutral dinuclear structures suggest that the two
metallocenic fragments may orientate their coordination spheres in opposite directions, hence resulting
in distant (>9 Å) isolated metal centers. Further investigations in our laboratories are focused on the
elaboration of other polynuclear precatalysts with improved performances and identification of the
nature of possible intermetallic cooperative effects.
Supplementary Materials:
The following are available online at http://www.mdpi.com/2073-4344/8/11/558/s1,
Figure S1:
1
H NMR spectrum of 1a; Figure S2:
13
C NMR spectrum of 1a; Figure S3: ASAP mass spectrum of 1a;
Figure S4:
1
H NMR spectrum of 1b; Figure S5:
13
C NMR spectrum of 1b; Figure S6:
1
H NMR spectrum of 1c;
Figure S7:
13
C NMR spectrum of 1c; Figure S8: ASAP mass spectrum of 1c; Figure S9:
1
H NMR spectrum of 2a;
Figure S10:
13
C NMR spectrum of 2a; Figure S11: ASAP mass spectrum of 2a; Figure S12:
1
H NMR spectrum of 2b;
Figure S13:
13
C NMR spectrum of 2b; Figure S14: ASAP mass spectrum of 2b; Figure S15:
1
H NMR spectrum of 2c;
Figure S16:
13
C NMR spectrum of 2c; Figure S17: ASAP mass spectrum of 2c; Figure S18:
1
H NMR spectrum of 2a’;
Figure S19:
13
C NMR spectrum of 2a’; Figure S20: ASAP mass spectrum of 2a’; Figure S21:
1
H NMR spectrum of
2b’; Figure S22:
13
C NMR spectrum of 2b’; Figure S23: ASAP mass spectrum of 2b’; Figure S24:
1
H NMR spectrum
of 3a-Zr
2
; Figure S25: HMBC spectrum of 3a-Zr
2
; Figure S26: HSQC spectrum of 3a-Zr
2
; Figure S27: APPI-IMMS of
3a-Zr
2
; Figure S28:
1
H NMR spectrumof 3a-Hf
2
; Figure S29:
13
C NMR spectrum of 3a-Hf
2
; Figure S30: APPI-IMMS
of 3a-Hf
2
; Figure S31:
1
H NMR spectrum of 3b-Zr
2
; Figure S32: HMBC spectrum of 3b-Zr
2
; Figure S33: HSQC
spectrum of 3b-Zr
2
; Figure S34: APPI-IMMS of 3b-Zr
2
; Figure S35:
1
H NMR spectrum of 3c-Zr
2
; Figure S36:
13
C NMR spectrum of 3c-Zr
2
; Figure S37:
1
H NMR spectrum of 3a’-Zr; Figure S38:
13
C NMR spectrum of 3a’-Zr;
Figure S39: APPI-IMMS of 3a’-Zr; Figure S40:
1
H NMR spectrum of 3b’-Zr; Figure S41:
13
C NMR spectrum of
3b’-Zr; Figure S42: APPI-IMMS of 3b’-Zr; Figure S43:
1
H NMR spectrum of 3b’-Hf; Figure S44:
13
C NMR spectrum
of 3b’-Hf; Figure S45: APPI-IMMS of 3b’-Hf; Figure S46:
13
C NMR spectrum of PE (Table 1, run 1); Figure S47:
GPC trace of PE (Table 1, run 1) obtained with 3a-Zr
2
; Figure S48:
13
C NMR spectrum of PE (Table 1, run 3);
Figure S49:
13
C NMR spectrum of PE (Table 1, run 5); Figure S50: GPC trace of PE (Table 1, run 5) obtained
with 3b-Zr
2
; Figure S51: GPC trace of PE (Table 1, run 6) obtained with 3b-Zr
2
; Figure S52: GPC trace of PE
(Table 1, run 7) obtained with 3b’-Zr; Figure S53: GPC trace of PE (Table 1, run 8) obtained with 3b’-Zr; Figure S54.
GPC trace of PE (Table 1, run 9) obtained with 3c-Zr
2
; Figure S55: GPC trace of PE (Table 1, run 12) obtained with
3b’-Hf; Figure S57: GPC trace of PE/PHex (Table 2, run 1) obtained with 3a-Zr2; Figure S58: 13C NMR spectrum
of PE/PHex (Table 2, run 4); Figure S59:
13
C NMR spectrum of PE/PHex (Table 2, run 5); Figure S60: GPC trace
of PE/PHex (Table 2, run 5) obtained with 3b-Zr
2
; Figure S61: GPC trace of PE/PHex (Table 2, run 6) obtained

Catalysts 2018,8, 558 17 of 19
with 3b-Zr
2
; Figure S62. GPC trace of PE/PHex (Table 2, run 7) obtained with 3b’-Zr; Figure S63: GPC trace
of PE/PHex (Table 2, run 8) obtained with 3b’-Zr; Figure S64: GPC trace of PE/PHex (Table 2, run 9) obtained
with 3c-Zr
2
; Figure S65: GPC trace of PE/PHex (Table 2, run 10) obtained with 3a-Hf
2
; Figure S66: GPC trace of
PE/PHex (Table 2, run 11) obtained with 3a-Hf
2
; Figure S67: Molecular structure of 3a’-Zr; Table S1: Summary
of Crystal and Refinement Data for Compound 3a’-Zr; Figure S68: DFT-optimized structures of C
s
-symmetric
and C
i
-symmetric isomers of 3a-Zr
2
; Figure S69: DFT-optimized structures of C
s
-symmetric and C
1
-symmetric
isomers of 3c-Zr2.
Author Contributions:
G.S. (investigation), M.F. (investigation), L.B. (investigation), A.V. (conceptualization,
project administration), A.W. (conceptualization), J.-M.B. (project administration), C.A. (data analysis), P.G.
(data analysis), J.-F.C. (conceptualization, supervision, writing—review and editing), E.K. (conceptualization,
investigation, supervision, writing—original draft preparation, writing—review and editing).
Funding: This research received no external funding.
Acknowledgments:
This work was supported by Total S. A. and Total Research and Technologies Feluy and
Gonfreville (postdoctoral and PhD grants, respectively, to G.S. and M.F.).
Conflicts of Interest: The authors declare no conflict of interest.
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