Synthesis and structural diversity of group 4 metal complexes with multidentate tethered phenoxy-amidine and phenoxy-amidinate ligands

Article abstract of DOI:10.1021/om300076j

The coordination chemistry of the multidentate tethered amidine-phenol {4,6-tBu₂C₆H₂O(2-C(NR)NR}H₂ ({LON^R}H₂, R = iPr, 2,6-iPr₂C₆H ₃ (Ar)) and new guanidine

Full text of DOI:10.1021/om300076j

Article
pubs.acs.org/Organometallics
Synthesis and Structural Diversity of Group 4 Metal Complexes with
Multidentate Tethered Phenoxy-Amidine and Phenoxy-Amidinate
Ligands
Evgeny Kirillov,* Thierry Roisnel, and Jean-Franco̧ is Carpentier
́ ́
Laboratoire Catalyse et Organometalliques, CNRS, Universite de Rennes 1, Sciences Chimiques de Rennes (UMR 6226), Campus de
Beaulieu, 35042 Rennes Cedex, France
S
* Supporting Information
ABSTRACT: The coordination chemistry of the multidentate tethered amidine-phenol {4,6-tBu2C6H2O(2-C(NR)NR}H2
({LONR}H2, R = iPr, 2,6-iPr2C6H3 (Ar)) and new guanidine-phenol {4,6-tBu2C6H2ON(C6H5)(2-C(NR)NR}H2
({LON(Ph)NiPr}H2) pro-ligands with group 4 metals has been studied. σ-Bond and salt metathesis reactions were explored
to coordinate these (pro)ligands onto zirconium and hafnium. Alkane elimination reactions between {LONR}H2 and
Zr(CH2Ph)4 afforded mixed-ligand monobenzyl {LOHNR}{LONR}Zr(CH2Ph) (R = iPr; 1) and monoligand tribenzyl
{LOHNAr}Zr(CH2Ph)3 (R = Ar; 2) complexes, respectively. Alkane and amine elimination reactions between {LON(Ph)NiPr}H2
and Zr(CH2Ph)4 or Hf(NMe2)4 unexpectedly resulted in cleavage of the ligand backbone and eventual isolation of
{(Ph)NC6H2(tBu)2O}Zr{(iPrN)2CCH2Ph}2 (3) and {(Ph)NC6H2(tBu)2O}Hf{(iPrN)2CNMe2}2 (4), respectively. Salt
metathesis reactions between {LONR}Li2 and ZrCl4(THF)n (n = 0, 2), conducted in 1:1 ratios, led upon crystallization to
diverse chloro complexes: [{LONiPr}ZrCl]3(μ3-O)(μ3-Cl) (5), [{LONAr}2ZrCl(μ2-Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3−OH) (6),
and {LOHNAr}ZrCl3(THF) (7). Similar salt metathesis reactions between the monolithium salts {LHONR}Li and ZrCl4,
conducted in 2:1 ratios, allowed the selective preparation of bis(phenoxy-amidine) complexes with pendant amino groups
{LOHNR}2ZrCl2 (R = iPr, 8; R = Ar, 9). All complexes were authenticated by elemental analysis, X-ray crystallography, and NMR
spectroscopy. Complexes 5, 6, 8, and 9, upon activation with MAO, showed poor to moderate productivities (4−172 (kg of PE)
mol−1 h−1) in the polymerization of ethylene, giving linear polymers with large polydispersities.
Scheme 1. Examples of Group 4 Metal CGC Complexes
Supported by Cp-Amido and Cp-Phenoxide Ligands1−3
INTRODUCTION
■
Group 4 metal “constrained-geometry catalysts” (CGCs)
bearing dianionic bridged cyclopentadienyl-amido ligands (1;
Scheme 1) have received considerable attention because of
their unique ability to produce polyolefin materials of high
commercial interest: e.g., linear low-density polyethylene
(LLDPE) and poly(ethylene-co-styrene) copolymers.1 The
development of new single-site CGCs for the controlled
(co)polymerization of α-olefins has been the focus of extensive
research over the last two decades. In this line, Marks and
others showed that bridged systems of type 2 (Scheme 1) are
highly performing in ethylene and propylene homopolymeriza-
tions and ethylene/norbornene copolymerization.2 Other
heteroleptic complexes incorporating linked cyclopentadienyl-
phenoxide scaffolds (3; Scheme 1) were found to be effective
catalyst precursors for the homo- and copolymerizations of
ethylene and α-olefins, such as 1-hexene.3
Received: February 1, 2012
Published: March 19, 2012
© 2012 American Chemical Society
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On this principle, we have recently prepared the new
amidino-phenol pro-ligands {4,6-tBu2C6H2O(2-C(NR)
NR}H2 ({LONR}H2, R = iPr, cyclohexyl (Cy), 2,6-iPr2C6H3
(Ar)) and studied their corresponding phenoxy-amidinate
complexes of group 3 metals and lanthanides.4 The
coordination chemistry of this ligand system with rare-earth
metals proved quite versatile: two alternative coordination
modes of this dianionic ligand (I and II) and a protonated
monoanionic form (III, Scheme 2) were evidenced.
dianionic ligand was bonded to two different metal centers.
This phenomenon was accounted for by the absence of a spacer
between the phenoxy and amidinate moieties in the ligand
skeleton. In order to decrease the constraint imposed in the
ligand backbone, we have attempted a modification of the
ligand system by introducing an additional heteroatom linker
between the phenoxy and amidinate moieties. The correspond-
ing new guanidine-phenol pro-ligand {LON(Ph)NiPr}H2 was
synthesized by a three-step procedure, starting from 2-anilino-
4,6-di-tert-butylphenol and N,N′-diisopropylcarbodiimide
(Scheme 3). The product was isolated in good yield and
characterized by NMR spectroscopy and elemental analysis.
Crystals of {LONiPr}H2 and {LON(Ph)NiPr}H2 suitable for
structural determination were grown by slow evaporation of the
corresponding CHCl3 solutions in air, the latter compound
being crystallized with an additional water molecule. The
molecular structures of {LONiPr}H2 and {LON(Ph)NiPr}-
H2·H2O are shown in Figures 1 and 2, respectively.
Scheme 2. Coordination Modes of the Dianionic Phenoxy-
Amidinate Ligand (I and II) and a Protonated Monoanionic
Form (III) Observed in Group 3 Metal Complexes4
Amidinates, related aminopyridinates, and guanidinates have
become ubiquitous ligands for supporting early-transition-metal
centers, and many of the resulting complexes have found
valuable catalytic applications.5 For group 4 metal species, this
was in particular evidenced by Kempe,6 Sita,7 Eisen8 and
others9 with the effective polymerization of ethylene, α-olefins,
dienes and styrene.
Accordingly, we describe herein σ-bond (alkane or amine
elimination) and salt metathesis reactions of amidino-phenol
{LONR}H2 and newly synthesized guanidino-phenol {LON-
(Ph)NiPr}H2 pro-ligands with group 4 metal precursors. Factors
governing the reactivity and the coordination chemistry of
these original ligand platforms onto group 4 metal centers have
been investigated. Also, the performance of the prepared
complexes in the polymerization of ethylene and propylene was
briefly explored.
Figure 1. Molecular structure of {LONiPr}H2 (ellipsoids are drawn at
the 50% probability level; H atoms, except those of the NH and OH
groups, are omitted for clarity). Important bond lengths (Å): C(71)−
N(11), 1.2985(19); C(71)−N(12), 1.3957(18); O(1)−H(111),
0.84(3); H(111)−N(11), 1.78(3).
Alkane and Amine Elimination Approaches. To
specifically target “constrained-geometry” group 4 metal
complexes containing phenoxy-amidinate and phenoxy-guani-
dinate ligands, we carried out alkane and amine elimination
reactions between the corresponding bifunctional diprotic pro-
ligands and homoleptic MR4 (R = CH2Ph, M = Zr; R = NMe2,
M = Hf) precursors. Previous investigations have shown that
RESULTS AND DISCUSSION
■
Synthesis of Pro-ligands. The original amidine-phenol
pro-ligands {LONiPr}H2 and {LONAr}H2 were prepared using
our recently published procedure.4 In the latter study, we have
shown that coordination of such phenoxy-amidinate ligands
onto group 3 metals afforded predominantly dimeric bimetallic
complexes featuring “spanned” geometries, in which a single
Scheme 3. Synthesis of the Guanidinate-Phenol Pro-ligand {LON(Ph)NR}H2
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one doublet for the N−H group. Complex 1 appeared to be
very stable in toluene solution and did not undergo further
protolytic reaction of the Zr−benzyl group by the pendant
amino group of the amidine moiety, even upon heating at 100
°C overnight.13
The solid-state molecular structure of 1 was established by X-
ray diffraction (Figure 3) and revealed the zirconium atom in a
Figure 2. Molecular structure of {LON(Ph)NiPr}H2.(H2O) (ellipsoids
are drawn at the 50% probability level; H atoms, except those of the
NH and OH groups, and the H2O molecule are omitted for clarity).
Important bond lengths (Å): C(71)−N(11), 1.3012(19); C(71)−
N(12), 1.3373(19); C(71)−N(12), 1.4177(19); O(1)−H(111),
1.302(2); H(111)−N(11), 1.217(2); O(2)−H(121), 1.01(2);
O(2)−H(122), 0.83(2).
Figure 3. Molecular structure of {LONiPr}{LOHNiPr}Zr(CH2Ph) (1)
(ellipsoids are drawn at the 50% probability level; H atoms, except that
of the N−H group, are omitted for clarity). Important bond lengths
(Å) and angles (deg): Zr(1)−O(1), 2.0516(17); Zr(1)−O(2),
2.0079(16); Zr(1)−N(11), 2.437(2); Zr(1)−N(12), 2.168(2);
Zr(1)−C(71), 2.467(2); Zr(1)−N(21), 2.295(2); Zr(1)−C(11),
2.289(3); C(71)−N(11), 1.322(3); C(71)−N(12), 1.364(3);
C(72)−N(21), 1.318(3); C(72)−N(22), 1.360(3); O(1)−Zr(1)−
N(11), 82.67(7); O(1)−Zr(1)−N(12), 86.15(7); O(2)−Zr(1)−
N(21), 79.25(7); O(1)−Zr(1)−N(21), 171.85(7); O(1)−Zr(1)−
C(11), 96.67(9).
such approaches are efficient one-step routes toward
compounds of the type L2MR2.2a,3,10
Monitoring by 1H NMR spectroscopy of the reaction
between equimolar amounts of Zr(CH2Ph)4 and {LONiPr}H2
in benzene-d6 at room temperature showed rapid and selective
formation of the monobenzyl phenoxy-amidinate phenoxy-
amidine complex 1 (Scheme 4). The latter product resulted
from the alkane elimination reaction of 2 equiv of bifunctional
pro-ligand with 1 equiv of Zr(CH2Ph)4,11 while 1 equiv of the
zirconium precursor remained intact. Further heating of the
reaction mixture at 80 °C over 6−8 h did not lead to significant
changes in the mixture composition. A scaled-up reaction
between {LONiPr}H2 and Zr(CH2Ph)4 (2:1) conducted in
toluene gave analytically pure 1 in 95% yield as a pale yellow
solid.12 In toluene-d8 solution at room temperature, complex 1
featured a dissymmetric structure with two nonequivalent
distorted-pseudo-octahedral coordination environment, pro-
vided by inequivalent dianionic phenoxy-amidinate and
monoanionic phenoxy-amidine ligands and the benzyl group.
Thus, the metal center is six-coordinated with the oxygen atom
of the dianionic ligand and the nitrogen atom of the
monoanionic ligand occupying the axial positions, while the
amidinate group of the dianionic ligand, the oxygen atom of the
monoanionic ligand, and the benzyl group lie in the equatorial
positions. The Zr(1)−O(1) and Zr(1)−O(2) bond lengths in 1
(2.0516(17) and 2.0079(16) Å, respectively) are in the range of
the values of covalent bonds reported for zirconium−
salicylaldimine complexes (1.951−2.064 Å).14 To our knowl-
1
ligands, as revealed by H and 13C NMR spectroscopy. Key
NMR parameters for 1 include four doublets for the phenoxy
hydrogens, two multiplets for the methine hydrogens, four
doublets for the methyl hydrogens of the nonequivalent iPr
groups, two singlets for the tBu groups, two doublets for the
diastereotopic methylene hydrogens of the benzyl group, and
Scheme 4. Formation of Complexes 1 and 2
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edge, the bonding of the amidinate fragment of the dianionic
ligand to the zirconium center in 1 is unprecedented. First,
unlike group 4 metal−amidinate complexes that exhibit a η2-
N,N′ binding, the coordination of the amidinate fragment in 1
is better described as allylic-like of the type η3-N,C,N′. The
Zr(1)−C(71) bond (2.467(2) Å) is significantly shorter than
those observed in regular zirconium−allyl complexes (2.513−
2.565 Å).15 The amidinate fragment in 1 coordinates
nonsymmetrically to the metal center, which is evidenced by
the quite inequivalent Zr(1)−N(11) and Zr(1)−N(12) bonds
(2.437(2) and 2.168(2) Å, respectively), the former being
somewhat longer than those found in zirconium−amidinate
complexes (2.123−2.333 Å).16 Also, the Zr(1)−N(21) distance
(2.295(2) Å) in 1 is somewhat shorter with respect to the usual
range for Zr−N(imino) bond lengths (2.322−2.434 Å)
observed in zirconium−salicylaldimine complexes.14 The sole
benzyl group in 1 is clearly η1 bound to the metal center, as
revealed by a long Zr(1)···Cipso contact (2.995(2) Å) and an
obtuse Zr(1)−C(11)−Cipso angle (103.02(16)°).17,18
Figure 4. Molecular structure of {LOHNAr}Zr(CH2Ph)3 (2·C6H6)
(ellipsoids are drawn at the 50% probability level; H atoms, except
those of the N−H, are omitted for clarity). Important bond lengths
(Å) and angles (deg): Zr(1)−O(1), 2.0353(10); Zr(1)−N(11),
2.3490(12); Zr(1)−C(11), 2.2654(16); Zr(1)−C(11)ipso
,
2.6976(15); Zr(1)−C(12), 2.3404(16); Zr(1)−C(13), 2.2693(15);
C(71)−N(11), 1.3339(14); C(71)−N(12), 1.3553(18); N(11)−
Zr(1)−C(11), 121.65(5); O(1)−Zr(1)−C(13), 95.95(5); Zr(1)−
C(11)−C(11)ipso, 89.69(10); O(1)−Zr(1)−N(11), 76.74(4).
On the other hand, the 1:1 reaction of Zr(CH2Ph)4 with the
more bulky pro-ligand {LONAr}H2, in benzene or in toluene,
afforded selectively {LOHNAr}Zr(CH2Ph)3 (2). Attempts to
obtain a bis(ligand) complex from 2:1 reactions between the
pro-ligand and the metal precursor, in toluene at room
temperature, systematically led to mixtures of 2 and unreacted
pro-ligand.19 Complex 2 was isolated as a pale orange solid and
authenticated by IR and 1H and 13C NMR spectroscopy,
In striking contrast with the amidine-phenol systems, the
guanidine-phenol pro-ligand {LON(Ph)NiPr}H2 unexpectedly
disclosed a very different reactivity trend. Reactions of
equimolar amounts of {LON(Ph)NiPr}H2 and the correspond-
ing group 4 metal precursor under regular σ-bond metathesis
conditions (see the Experimental Section), followed by
crystallization, gave the {anilido-phenoxy}-bis(amidinate) com-
plex 3 and {anilido-phenoxy}-bis(guanidinate) complex 4, in
32% and 24% isolated yields, respectively (Scheme 5). NMR
1
microanalysis, and X-ray crystallography (vide infra). The H
NMR spectrum of 2 was slightly broadened at room
temperature, due to fluxional dynamics possibly arising from
hindered rotation of bulky diisopropylphenyl and benzyl groups
and/or η2/η1 haptotropic rearrangements of the benzyl groups.
Scheme 5. Reactions between the Guanidinate-phenol Pro-
ligand {LON(Ph)NR}H2 and Zr(CH2Ph)4 and Hf(NMe2)4
1
The H and 13C NMR spectra of 2, recorded at 80 °C in
benzene-d6, exhibited a single set of sharp resonances,
consistent with a Cs-symmetric species on the NMR time
scale, in which the amidine part is bound in a monodentate
manner to the metal center. In contrast with the case for 1, no
signal from hydrogen of the pendant amino group was clearly
detected in the 1H NMR spectrum of 2.20 However, the
presence of the NH group in 2 was evidenced from the
observation of a characteristic band at 3315 cm−1 in the FTIR
spectrum (Nujol, KBr).4 Compound 2 is stable in the solid
state and in toluene solution at room temperature. However,
upon heating at 80−100 °C over several days in toluene-d8, it
slowly decomposed to a mixture of unidentified products,
concomitantly releasing toluene; this suggests the possible
formation of {LONAr}Zr(CH2Ph)2, but the latter putative
species could not be unambiguously identified.
The solid-state molecular structure of 2 (crystallized as the
2·C6H6 solvate) revealed a five-coordinate species, in which the
zirconium center lies in a distorted-trigonal-bipyramidal
environment (Figure 4). The phenoxy oxygen atom and the
carbon atom of one benzyl group occupy the axial positions,
while one amidine nitrogen atom and two carbon atoms of two
benzyl groups occupy the equatorial plane. One benzyl group
features noticeable η2 binding with the metal center, suggesting
a tendency toward 6-coordination. This is evidenced by the
monitoring of these two reactions (toluene-d8, −30 to +25 °C),
because of the complexity of the NMR spectra, did not allow us
to establish the nature of possible intermediates involved in the
cleavage of the ligand backbones.
Compounds 3 and 4 were identified by microanalysis and 1H
and 13C NMR spectroscopy and by X-ray crystallography for
complex 4. Both compounds featured a dynamic behavior in
benzene-d6 solution at room temperature, which is tentatively
assigned to hindered rotation of the bulky ligand fragments.
́
short Zr(1)−C(11)ipso distance (2.6976(15) Å) and the
relatively acute Zr(1)−C(11)−C(11)ipso angle (89.69(10)
°).17,21 The Zr(1)−O(1) and Zr(1)−N(11) distances
(2.0353(10) and 2.3490(12) Å, respectively) in 2 fall in the
usual range for the corresponding bond lengths observed in
zirconium complexes of salicylaldimine ligands.14
1
The well-resolved H NMR spectra of 3 and 4, recorded at 60
°C in benzene-d6 (Figures S5 and S6, respectively; see the
Supporting Information), were diagnostic of highly symmetric
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species, in which the amidinate and guanidinate ligands,
respectively, exchange rapidly on the NMR time scale.
The X-ray molecular structure of 4 (Figure 5) revealed a
distorted-octahedral coordination around the hafnium center,
the preparation of the corresponding chloro-yttrium products
by salt metathesis.
In an attempt to obtain chloro-zirconium complexes bearing
the dianionic ligand {LONiPr}2−, the corresponding pro-ligand
was treated with 2 equiv of nBuLi in THF and the resulting salt
was allowed to react with ZrCl4(THF)2 in Et2O (Scheme 6).
Recrystallization of the product from DME yielded small
amounts of colorless crystals of [{LONiPr}ZrCl]3(μ3-O)(μ3-Cl)
(5). The formation of trinuclear oxo complex 5, yet
unexpected, was not completely surprising, though. Similar
Zr3(μ3-O) clusters, supported by cyclopentadienyl, phenoxy, or
alkoxy ligands, have been reported as the major products of
various reactions conducted under moisture- and oxygen-free
conditions: salt metathesis,24 σ-bond metathesis,25 and anodic
oxidation of zirconium metal in anhydrous alcohols.26
However, controlled hydrolysis reactions of Cp*ZrCl3 with
stoichiometric amounts of water are also known to produce
quite selectively diverse species incorporating Zr3(μ3-O)
structural motifs.27
Figure 5. Molecular structure of 4 (ellipsoids are drawn at the 50%
probability level; all H atoms are omitted for clarity). Important bond
lengths (Å) and angles (deg): Hf(1)−O(1), 2.0063(16); Hf(1)−
N(11), 2.136(2); Hf(1)−N(12), 2.111(2); Hf(1)−N(13), 2.194(2);
Hf(1)−N(22), 2.2043(18); Hf(1)−N(23), 2.2325(19); C(71)−
N(12), 1.378(3); C(71)−N(13), 1.378(3); C(71)−N(14), 1.378(3);
C(72)−N(22), 1.335(3); C(72)−N(23), 1.340(3); C(72)−N(24),
1.386(3); O(1)−Hf(1)−N(11), 75.70(7); O(1)−Hf(1)−N(12),
154.59(7); N(12)−Hf(1)−N(22), 100.38(8).
1
Complex 5 was characterized by H and 13C NMR and IR
spectroscopy, elemental analysis, and X-ray crystallography.
1
The H and 13C NMR spectra were consistent with a highly
symmetric species in solution, in which all three ligands are
equivalent (see the Supporting Information). The solid-state
molecular structure of complex 5 is depicted in Figure 6. The
central C3-symmetric trimetallic core in 5 is reminiscent of that
of [(RO)2Zr]3(μ-OR)3(μ3-O)(μ3-Cl), where R = neopentyl.24
However, in complex 5, the Zr−μ3-O (2.114(4)−2.125(4) Å)
and Zr···Zr (3.404(4)−3.413(4) Å) distances are longer and
the Zr−μ3-Cl (2.7890(16)−2.8045(16) Å) distances are
shorter than the corresponding distances in the former
compound (2.082(3)−2.090(3), 3.2956(8)−3.3021(7), and
2.847(1)−2.886(1) Å, respectively). The terminal Zr−Cl
bond lengths (2.4262(17)−2.4273(17) Å) in 5 are in the
typical range for the corresponding bond lengths observed in
zirconium complexes with Zr3(μ3-O) cores.25c,26,27b The three
ligands are equivalently coordinated to the three zirconium
centers, bridging them in a “spanned” manner. At the same
time, the coordination of the amidinate fragments to the metal
which is surrounded by four nitrogen atoms of the guanidinate
ligands and one nitrogen and one oxygen atom of the chelating
dianionic anilido-phenoxy ligand. The Hf−O and Hf−N bond
lengths in 4 are quite close to those reported for the amido-
phenoxy22 and bis(guanidinate)23 complexes of hafnium,
respectively.
Salt Metathesis Reactions. In our previous study with
these new ligand systems,4 we have shown that double
deprotonation of the amidine-phenol pro-ligands {LONiPr}H2
and {LONAr}H2 with nBuLi afforded the corresponding
dilithium salts {LONiPr}Li2 and {LONAr}Li2, respectively, in
high yields. The latter compounds were successfully utilized for
Scheme 6. Formation of Complex 5 via Salt Metathesis
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2.310(5), 2.314(5), and 2.314(5) Å, respectively); in addition,
one of the two nitrogen atoms of each amidinate moiety binds a
neighboring Zr center (2.351(5), 2.332(5), and 2.359(5) Å,
respectively). These Zr−N distances are on the longer side of
values reported in zirconium amidinates (2.123−2.333 Å).16
As summarized in Scheme 7, reactions of the in situ
generated {LONAr}Li2 salt with ZrCl4, conducted under similar
conditions in Et2O, led, after recrystallization of the crude
product from hexane, to the isolation of yellow crystals of
[{LONAr}ZrCl(μ2-Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3-OH) (6).
Complex 6 was authenticated on the basis of 1H and 13C NMR
and IR spectroscopy, elemental analysis, and an X-ray
diffraction study.
In contrast to 5, the FTIR spectrum of 6 (Nujol mulls in KBr
plates) displayed two distinct bands at 3323 and 3308 cm−1
assigned to ν(O−H) and ν(N−H) vibrations. This suggests
that, in complex 6, at least one of three ligands is monoanionic
and bears a pendant N(H)Ar moiety, but also an O−H group is
present in the structure (vide infra). Surprisinglt, however, both
the 1H and 13C NMR spectra of 6 in CD2Cl2 at room
temperature were diagnostic of a highly symmetric species in
solution, in which all three ligands are equivalent on the NMR
time scale (see Figures S8 and S9, respectively, in the
Supporting Information). No signals from the N−H or O−H
Figure 6. Molecular structure of [{LONiPr}ZrCl]3(μ3-O)(μ3-Cl) (5)
(ellipsoids are drawn at the 50% probability level; H atoms and iPr
groups are omitted for clarity). Important bond lengths (Å) and angles
(deg): Zr(1)−O(1), 2.016(4); Zr(2)−O(2), 2.003(4); Zr(3)−O(3),
2.009(4); Zr(1)−O(4), 2.115(4); Zr(2)−O(4), 2.125(4); Zr(3)−
O(4), 2.114(4); Zr(1)−N(11), 2.351(5); Zr(1)−N(31), 2.353(5);
Zr(1)−N(32), 2.310(5); Zr(2)−N(21), 2.332(5); Zr(2)−N(11),
2.336(5); Zr(2)−N(12), 2.314(5); Zr(3)−N(31), 2.359(5); Zr(3)−
N(21), 2.341(5); Zr(3)−N(22), 2.314(5); Zr(1)−Cl(1), 2.4262(17);
Zr(2)−Cl(2), 2.4269(16); Zr(3)−Cl(3), 2.4273(17); Zr(1)−Cl(4),
2.8045(16); Zr(2)−Cl(4), 2.7896(16); Zr(3)−Cl(4), 2.7890(16);
C(71)−N(11), 1.400(8); C(71)−N(12), 1.285(8); C(72)−N(21),
1.407(8); C(72)−N(22), 1.308(8); C(73)−N(31), 1.400(8); C(73)−
N(32), 1.283(8); N(11)−Zr(1)−Cl(32), 139.41(19); O(1)−Zr(1)−
Cl(4), 150.94(12); Cl(1)−Zr(1)−O(4), 152.42(11); O(1)−Zr(1)−
N(11), 79.75(16).
1
protons could be detected in the H NMR spectrum of 6,
possibly due to exchange on the NMR time scale between
ligand moieties and extreme broadening.
As revealed by the X-ray diffraction study, complex 6 is a
cluster that contains a triangular core of three Zr atoms nearly
symmetrically capped by a μ3-O(H) group (Figure 7). The
Zr−μ3-O(H) bond lengths in 6 (2.115(6)−2.130(6) Å) are
very similar to those in 5 with the oxo Zr−μ3-O core
(2.114(4)−2.125(4) Å). Comparison of the given distances in
6 with the appropriate ones in [Cp*ZrCl]3(μ-O)3(μ3-OH)(μ2-
OH)3, which has two types of the in-core groups (Zr−μ3-O,
2.092(4)−2.196(4) Å; Zr−μ3-OH, 2.198(4)−2.336(4) Å),27b
did not allow us to unambiguously identify the exact nature of
centers is not that typical: each moiety chelates a Zr center
nonsymmetrically, as indicated by inequivalent Zr−N-
(amidinate) bonds (2.353(5), 2.336(5), and 2.341(5) Å vs
Scheme 7. Formation of Complexes 6 and 7 via Salt Metathesis
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consistent with an average Cs-symmetric structure of this
species on the NMR time scale. Similarly to complex 2, no clear
signal from the proton of the pendant N(H)Ar group was
1
observed in the H NMR spectra of 7. The actual presence of
the amino group in the structure of 7 was evidenced from the
observation of a characteristic band at 3313 cm−1 in the FTIR
spectrum (Nujol, KBr).4
Complex 7 is structurally similar to zirconium salicylaldimi-
nate complexes {LON}ZrCl3(THF),28 with the Zr center lying
in a distorted-octahedral coordination environment (Figure 8).
Figure 7. Molecular structure of [{LONAr}ZrCl(μ2-Cl)]2[{LHONAr}-
ZrCl(μ2-Cl)](μ3-OH) (6) (ellipsoids are drawn at the 50% probability
level; H atoms, except those of the N−H and O−H groups, iPr2C6H2,
and tBu groups are omitted for clarity). Important bond lengths (Å)
and angles (deg): Zr(1)−O(1), 1.974(6); Zr(2)−O(2), 1.980(6);
Zr(3)−O(3), 1.977(6); Zr(1)−O(4), 2.119(5); Zr(2)−O(4),
2.130(6); Zr(3)−O(4), 2.115(6); Zr(1)−N(11), 2.291(7); Zr(2)−
N(21), 2.245(7); Zr(3)−N(21), 2.241(7); Zr(1)−Cl(11), 2.394(3);
Zr(1)−Cl(12), 2.577(2); Zr(2)−Cl(21), 2.389(3); Zr(2)−Cl(22),
2.586(2); Zr(3)−Cl(31), 2.389(3); Zr(3)−Cl(32), 2.584(2); C(71)−
N(11), 1.316(10); C(71)−N(12), 1.362(11); C(72)−N(21),
1.400(11); C(72)−N(22), 1.339(12); C(73)−N(31), 1.384(14);
C(73)−N(32), 1.339(11); Cl(11)−Zr(1)−Cl(12), 164.60(18);
O(1)−Zr(1)−Cl(32), 163.42(9); O(1)−Zr(1)−N(12), 81.50(20);
Cl(12)−Zr(1)−O(4), 76.60(16).
Figure 8. Molecular structure of {LOHNAr}ZrCl3(THF) (7)
(ellipsoids are drawn at the 50% probability level; H atoms, except
that of the N−H group, and iPr groups are omitted for clarity).
Important bond lengths (Å) and angles (deg): Zr(1)−O(1), 1.963(6);
Zr(1)−O(2), 2.288(6); Zr(1)−N(11), 2.364(7); Zr(1)−Cl(1),
2.452(3); Zr(1)−Cl(2), 2.434(2); Zr(1)−Cl(3), 2.411(3); C(71)−
N(11), 1.332(10); C(71)−N(12), 1.336(10); N(11)−Zr(1)−Cl(1),
175.38(18); O(1)−Zr(1)−Cl(2), 161.0(2); O(1)−Zr(1)−N(11),
78.8(3).
the central group. Also, the three Zr atoms in 6 are
symmetrically bridged by three μ2-Cl groups, with Zr−Cl
bond distances (2.577(2)−2.586(2) Å) expectedly longer than
the terminal ones (2.389(3)−2.394(3) Å). However, some
structural data suggest that the three ligands in 6 are not of the
same nature. Despite the fact that the Zr−O bonds of the three
phenoxide groups are nearly equivalent (1.974(6), 1.980(6),
and 1.977(6) Å), the Zr−N bonds in the amidinate moieties do
substantially differ: the Zr(1)−N(11) bond (2.291(7) Å) is
somewhat longer as compared with Zr(2)−N(21) and Zr(3)−
N(21) (2.245(7) and 2.241(7) Å, respectively) and is, as
observed in 1, approaching the usual range of the Zr−N(imino)
bond lengths (2.322−2.434 Å) in zirconium salicylaldimine
complexes.14 Also, the C(71)−N(11) bond (1.316(10) Å) in 6
is shorter than that in two other ligands (C(72)−N(21),
1.400(11) Å; C(73)−N(31), 1.384(14) Å), which is in
agreement with its double-bond character. These geometric
data indicate that the ligand bound to the Zr(1) center is
monoanionic, while those coordinated to Zr(2) and Zr(3) are
dianionic. Consistent with this trend, the overall neutrality of
the molecule is ensured by the anionic OH group in the central
trigonal core.
The zirconium−ligand distances in 7 (Zr−O, 1.963(6) Å; Zr−
N, 2.364(7) Å; Zr−Cl, 2.452(3), 2.434(2), and 2.411(3) Å) are
comparable with those in the latter compounds (1.951−1.956,
2.371−2.393, and 2.397−2.442 Å, respectively).28
The remarkable propensity of the phenoxy-amidinate ligands
implemented in this study to systematically afford species with
phenoxy-imine coordinating moieties and pendant N(H)R arms
prompted us to target the synthesis of new species. Given the
great success in olefin polymerization catalysis of group 4 metal
systems incorporating two chelating phenoxy-imino ligands
(often referred to as Fujita’s FI catalysts),29 we set out to
purposely prepare zirconium complexes with two monoanionic
phenoxy-amidine ligands {LHONR}.
As summarized in Scheme 8, the target complexes were
conveniently obtained by salt metathesis reactions using the
corresponding monolithium salts {LHONR}Li and ZrCl4 in a
2:1 stoichiometry. Regular workup and recrystallization of the
products from benzene or hexanes allowed the recovery of
{LOHNiPr}2ZrCl2 (8, isolated as 8·3.5C6H6) and
{LOHNAr}2ZrCl2 (9), respectively.
The solid-state structures of 8 and 9 (Figures 9 and 10,
respectively) both revealed zirconium atoms in distorted-
octahedral coordination environments with global C2-symmet-
ric environments around the metal centers. The relative
arrangement of ligands in the recovered crystals of 8 is trans-
O,O/cis-N,N, whereas it is cis-O,O/trans-N,N in 9. These
molecules exhibit geometrical parameters essentially similar to
those of dichlorozirconium salicylaldiminate complexes.14 For
example, the Zr−O bond lengths in 8 and 9 (2.012(4),
2.007(4) Å and 2.0186(17), 2.0115(18) Å, respectively) are in
In a separate experiment targeted on the synthesis of a chloro
zirconium complex supported by the {LONAr}2− ligand, the
dilithium salt {LONAr}Li2 was treated with ZrCl4(THF)2
(Scheme 7). The product isolated in 50% yield as white
crystals after recrystallization from hexanes was authenticated as
1
{LOHNAr}ZrCl3(THF) (7), on the basis of H and 13C NMR
and IR spectroscopy, elemental analysis, and an X-ray
diffraction study. The 1H and 13C NMR spectra of 7 in
benzene-d6 at 60 °C showed a single set of resonances,
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Scheme 8. Synthesis of Complexes 8 and 9
Figure 9. Molecular structure of {LOHNiPr}2ZrCl2 (8) (ellipsoids are
drawn at the 50% probability level; H atoms, except those of the N−H
groups, are omitted for clarity). Important bond lengths (Å) and
angles (deg): Zr(1)−O(1), 2.012(4); Zr(2)−O(2), 2.007(4); Zr(1)−
N(11), 2.304(5); Zr(1)−N(21), 2.319(5); Zr(1)−Cl(1), 2.4464(16);
Zr(1)−Cl(2), 2.4541(16); C(71)−N(11), 1.322(8); C(71)−N(12),
1.359(8); C(72)−N(21), 1.342(7); C(72)−N(22), 1.354(8);
Cl(11)−Zr(1)−Cl(12), 94.42(6); O(1)−Zr(1)−O(2), 166.17(16);
N(11)−Zr(1)−N(21), 88.49(16).
Figure 10. Molecular structure of {LOHNAr}2ZrCl2 (9) (ellipsoids are
drawn at the 50% probability level; H atoms, except those of the N−H
groups, and iPr2C6H2 moieties are omitted for clarity). Important
bond lengths (Å) and angles (deg): Zr(1)−O(1), 2.0186(17); Zr(2)−
O(2), 2.0115(18); Zr(1)−N(11), 2.355(2); Zr(1)−N(21), 2.370(2);
Zr(1)−Cl(1), 2.4360(7); Zr(1)−Cl(2), 2.4550(7); C(71)−N(11),
1.333(3); C(71)−N(12), 1.348(3); C(72)−N(21), 1.320(7); C(72)−
N(22), 1.347(4); Cl(11)−Zr(1)−Cl(12), 97.65(3); O(1)−Zr(1)−
O(2), 90.92(7); N(11)−Zr(1)−N(21), 175.45(7).
the range of the values of covalent bonds previously reported
for zirconium analogues (1.951−2.064 Å). Similarly, the Zr−N
bond distances in 8 and 9 (2.304(5), 2.319(5) Å and 2.355(2),
2.370(2) Å, respectively) show little variation and are
comparable with those found in bis(salicylaldiminato)-
zirconium complexes (2.322−2.434 Å).14
data, recorded at 253 K in toluene-d8, confirmed these features.
When the temperature is raised above 343 K in toluene-d8,
1
these two series of H NMR signals collapse into one series of
broadened resonances, consistent with a single averaged
symmetric species. It is thus reasonable to assume that the
two species, observed in solution at room temperature,
correspond to O,O/N,N positional isomers of 8, one of
which crystallized preferentially (vide supra).
1
The H and 13C NMR spectra of 8 in toluene-d8 at room
temperature contain two sets of resonances in a ca. 45:55 ratio
that indicate the coexistence of two species in solution, each of
average C2 symmetry on the NMR time scale (see Figure S11 in
the Supporting Information). Key resonances for the first
species include two doublets from phenoxy hydrogens, two
multiplets from methine hydrogens, four doublets from methyls
of the nonequivalent iPr groups, two singlets from tBu groups,
and a doublet from N−H groups. The second species is
presented by a similar series of broadened signals, which do not
become sharper in the range of 213−298 K. The 13C NMR
At the same time, all 1H and 13C NMR data for complex 9 in
toluene-d8 showed the presence of a single highly symmetric
species on the NMR time scale (see Figures S13 and S14 in the
Supporting Information), suggesting that the solid-state
structure observed for 9 is retained in solution.
As noted above for complexes 1, 2, 6, and 7, the presence of
N−H groups in 8 and 9 was corroborated by the observation of
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a
Table 1. Results of Ethylene Polymerizations Mediated by Complexes 2 and 5−9
b
amt of precat.
Tpolym
P
mpolym
productivity
T
m c
d
d
entry precat.
(μmol)
activator (amt (equiv))
(°C)
(bar)
(g)
(kg mol−1 h−1
0
)
(°C)
103Mw
Mw/Mn
1
2
10
[Ph3C][B(C6F5)4] (2)/Al(iBu)3
(50)
50
5
traces
e
2
3
4
5
6
5
6
7
8
9
7
7
MAO (1000)
MAO (1000)
MAO (1000)
MAO (1000)
MAO (1000)
50
50
50
60
60
1
1
5
5
5
0.831
0.086
traces
1.710
0.120
40
4
136.7
130.2
insoluble
115
f
26.9
7
0
f
10
10
172
129.9
136.9
470
580
305
f
12
3.46
a
b
Polymerization conditions: 300 mL high pressure glass reactor; solvent toluene, 150 mL; time 30 min. Apparent productivity calculated over the
c
d
e
whole polymerization time. Determined by DSC (first heating). In g mol −1, determined by GPC in 1,2,4-trichlorobenzene at 150 °C. PE could
not be solubilized in 1,2,4-trichlorobenzene at 160 °C. Multimodal distribution.
f
characteristic bands at 3448 and 3315 cm−1, respectively, in
their FTIR spectra (Nujol, KBr).4
the new guanidine-phenolate pro-ligand {LON(Ph)NiPr}H2 has
been synthesized and used for complexation with group 4
metals. The preparation of dibenzyl Zr(IV) complexes based on
the aforementioned ligands proved to be arduous and resulted
instead in the formation of structurally diverse compounds. Salt
metathesis reactions between ZrCl4(THF)n (n = 0, 2) and
{LONR}Li2 salts unexpectedly afforded Zr3(μ3-O) oxo clusters
with different distributions of monoanionic and dianionic
ligands. On the other hand, treatment of ZrCl4 with
monolithium salts {LHONR}Li provided a facile synthesis of
octahedral bis(phenoxy-amidine) complexes {LHONR}ZrCl2
bearing pendant amino groups. The latter may be used as
suitable precursors for synthesis of multinuclear heterometallic
compounds. Further investigations on the reactivity of these
species and this promising coordination chemistry are under-
way in our laboratories.
Preliminary Olefin Polymerization Tests. The catalytic
potential of complexes 2 and 5−9, in combination with MAO
or [Ph3C][B(C6F5)4]/Al(iBu)3 (2:50) as the activating
system10c,30 (applied for benzyl complex 2), was briefly
evaluated in the homogeneous polymerization of ethylene
(toluene solution, 1−5 bar constant pressure, 50−60 °C).31
The results are summarized in Table 1.
Trialkyl and trichloro complexes 2 and 7, respectively, both
bearing one and the same type of coordinated ligand, were
found to be inactive in the polymerization of ethylene under
the conditions used (entries 1 and 4). These results are
consistent with those previously obtained with the related
{LON}ZrCl3(THF)/MAO system, where LON is a bulky
diisopropylphenylimino-phenoxide ligand, which also proved
ineffective.28 Complexes 5 and 6, incorporating Zr3(μ3-O)
cores, upon activation with MAO were poorly active toward
ethylene (entries 2 and 3, respectively). In the series of
bis(phenoxy-amidine) zirconium dichlorides, the most effective
ethylene polymerization precatalyst appeared to be the complex
bearing the less bulky ligand 8 (entry 5). However, the
productivity of the latter compound (172 kg mol−1 h−1),
activated with MAO, was inferior by 2−3 orders of magnitude
than those reported for bis(salicylaldiminato) catalysts of group
4 metals.14 Hypothetically, this may be accounted for by the
additional NH functionality in the current systems, which may
react with excess MAO and induce uncontrolled decomposition
pathways.
Another general feature of these polymerizations concerns
the nature of the polymers obtained. The GPC data obtained
for the PE samples showed multimodal traces, resulting in very
large abnormal polydispersity values. This can be directly
related to the existence of multiple catalytically active species
during the course of polymerization reactions. Again, the acidic
pending amino groups present in precatalysts 2 and 7−9 can
potentially be involved in further protolytic reactions with Me−
Al bonds of MAO itself or Me3Al (typical component of
commercial MAO), giving rise to various polymetallic/
aggregated species exhibiting different reactivities. The melting
temperatures of the polyethylene polymers in the range 129−
137 °C are indicative of essentially linear long-chain micro-
structures.10b,32
EXPERIMENTAL SECTION
■
General Conditions. All manipulations requiring an anhydrous
atmosphere were performed under a purified argon atmosphere using
standard Schlenk techniques or in a glovebox. Anhydrous ZrCl4 and
ZrCl4(THF)2 precursors (99.99%) were purchased from Strem
Chemicals and used as received. 2-Anilino-4,6-di-tert-butylphenol33
34
and the metal precursors Zr(CH2Ph)4 and Hf(NMe2)4 were
prepared by the corresponding literature procedures. [Ph3C][B-
(C6F5)4] (Boulder), Al(iBu)3 (Aldrich), and MAO (30 wt % solution
in toluene, Albermale; contains ca. 10 wt % of free AlMe3) were used
as received. Other starting materials were purchased from Acros,
Strem, and Aldrich and used as received. Solvents were freshly distilled
from Na/benzophenone (THF, toluene, Et2O, DME) or Na/K
amalgam (pentane, hexanes) under argon and degassed thoroughly by
freeze−pump−thaw cycles prior to use. Deuterated solvents were
freshly distilled from Na/K amalgam (THF-d8, benzene-d6, toluene-d8)
or CaH2 (CD2Cl2) under argon and degassed prior to use.
Instruments and Measurements. NMR spectra were recorded
on Bruker AC 200, Bruker AC 300, Bruker Avance DRX 400, and
1
Bruker AC 500 spectrometers in Teflon-valved NMR tubes. H and
13C NMR chemical shifts are reported in ppm vs SiMe4 and were
determined by reference to the residual solvent resonances. Assign-
ment of signals was carried out via multinuclear 1D (1H, 13C{1H}) and
2D (1H−13C HMBC and HMQC) NMR experiments. Coupling
constants are reported in Hz.
Elemental analyses (C, H, N) were performed using a Flash EA1112
CHNS Thermo Electron apparatus and are the average of two
independent determinations. IR spectra were recorded as Nujol mulls
on a Bruker-Vertex 70 spectrophotometer.
{(iPrN)2CN(Ph)C6H2(tBu)2O}H2 ({LON(Ph)NiPr}H2). To a solution
of 2-anilino-4,6-di-tert-butylphenol (2.01 g, 6.76 mmol) in diethyl
ether (30 mL) was added n-butyllithium (5.70 mL of a 2.50 M
solution in hexane, 14.25 mmol) at 0 °C. The reaction mixture was
stirred for 0.5 h at room temperature, and a solution of N,N′-
diisopropylcarbodiimide (1.16 mL, 7.45 mmol) in diethyl ether (10
CONCLUSIONS
■
The preparation of discrete group 4 metal complexes based on
multidentate phenoxy-amidinate {LONR}2− and phenoxy-
amidine {LHONR}− ligand platforms has been studied. Also,
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mL) was added dropwise. The reaction mixture was stirred under
reflux overnight and then cooled to room temperature. The white
precipitate that formed was separated by filtration under argon. Water
(50 mL) and Et2O (50 mL) were added stepwise. The organic layer
was separated and dried over NaSO4, and volatiles were removed in
vacuo. The residue was dried in vacuo to give {LON(Ph)NiPr}H2 as a
CH2Ph), 1.64 (s, 9H, C(CH3)), 1.32 (d, J = 10.9, 6H, CH(CH3)), 1.16
(d, J = 10.9, 6H, CH(CH3)), 1.07 (s, 9H, C(CH3)), 0.86 (m, 12H,
CHC(CH3)). 13C{1H} NMR (C6D6, 75 MHz, 80 °C): δ 169.5 (CN2),
159.9 (O-C6H2), 143.5, 138.9, 138.7, 133.5, 128.5, 128.3, 125.8, 125.6,
124.5, 124.4, 122.0, 121.9, 118.7, 74.7 (CH2Ph), 36.4 (C6H2C(CH3)3),
33.8 (C6H2C(CH3)3), 30.9 (C6H2C(CH3)3), 30.8 (C6H2C(CH3)3),
26.2 (CH(CH3)2), 24.8 (CH(CH3)2), 24.3 (CH(CH3)2), 22.05
(CH(CH3)2). IR (Nujol, KBr; ν (cm−1)): 3315 w, 2361 m, 1604 w,
1591 m, 1541s, 1262 m, 1202 m, 980 w, 885 w, 839 w, 791 m, 745 m,
727 m, 698 m, 550 m. Anal. Calcd for C60H75N2OZr: C, 77.37; H,
8.12; N, 3.01. Found: C, 77.56; H, 8.44; N, 3.13.
1
pale pink solid (2.13 g, 5.03 mmol, 74%). H NMR (CDCl3, 500
MHz, 25 °C): δ 7.28 (d, J = 2.5, 1H, C6H2), 7.18 (m, 2H, Ph), 7.07 (d,
J = 2.5, 1H, C6H2), 6.84 (m, 1H, Ph), 6.73 (br m, 2H, Ph), 3.66 (br m,
2H, CH(CH3)), 1.44 (s, 9H, C(CH3)), 1.34 (s, 9H, C(CH3)), 1.18 (d,
J = 6.5, 12H, CH(CH3)). 13C{1H} NMR (CDCl3, 125 MHz, 25 °C): δ
152.4 (CN3), 146.4 (O-C6H2), 140.5, 130.1, 129.4, 128.9, 126.7, 125.8,
119.6, 115.2, 114.4, 45.3 (CH(CH3)2), 35.3 (C6H2C(CH3)3), 34.24
(C6H2C(CH3)3), 31.7 (C6H2C(CH3)3), 29.8 (C6H2C(CH3)3), 23.8
(CH(CH3)2). Anal. Calcd for C27H41N3O: C, 76.55; H, 9.76; N, 9.92.
Found: C, 77.04; H, 10.15; N, 10.01.
Reaction between {LON(Ph)NiPr}H2 and Zr(CH2Ph)4 (1:1
Ratio). Synthesis of {(Ph)NC6H2(tBu)2O}Zr{(iPrN)2CCH2Ph}2 (3).
A Schlenk flask was charged with {LON(Ph)NiPr}H2 (0.204 g, 0.4816
mmol) and Zr(CH2Ph)4 (0.219 g, 0.4816 mmol), and toluene (ca. 5
mL) was vacuum-transferred in. The reaction mixture was stirred
overnight at room temperature. Then, volatiles were evaporated in
vacuo and hexanes (ca. 10 mL) was vacuum-transferred under reduced
pressure. The mixture was filtered, and the solvent was removed from
the filtrate to give 3 as a deep yellow solid (0.126 g, 0.1541 mmol,
32%). 1H NMR (C6D6, 500 MHz, 60 °C): δ 7.56 (d, J = 7.3, 2H, Ph),
7.45 (t, J = 7.3, 2H, Ph), 7.25−7.15 (m, 11H, Ph and CH2Ph), 7.05 (d,
J = 2.2, 1H, C6H2), 6.70 (d, J = 2.2, 1H, C6H2), 3.70 (s, 4H, CH2Ph),
3.69 (m, 4H, CH(CH3)), 1.87 (s, 9H, C(CH3)), 1.41 (s, 9H,
C(CH3)), 1.28 (d, J = 6.2, 12H, CH(CH3)), 1.20 (d, J = 6.2, 12H,
CH(CH3)). 13C{1H} NMR (C6D6, 125 MHz, 60 °C): δ 175.8 (CN2),
151.3 (O-C6H2), 151.2 (NC6H2), 150.0 (ipso, N-Ph), 141.2, 137.6,
135.6, 132.4, 129.0, 128.8, 126.6, 126.5, 123.1, 112.8, 107.7, 48.5
(CH2Ph), 34.6 (C6H2C(CH3)3), 34.5 (C6H2C(CH3)3), 31.9 (C6H2C-
(CH3)3), 31.8 (CH(CH3)2), 30.2 (C6H2C(CH3)3), 25.5 (CH(CH3)2),
25.1 (CH(CH3)2). Anal. Calcd for C48H67N5OZr: C, 70.20; H, 8.22;
N, 8.53. Found: C, 71.00; H, 8.34; N, 8.93.
Reaction between {LONiPr}H2 and Zr(CH2Ph)4 (2:1 Ratio).
Synthesis of {(iPrN)2(H)CC6H2(tBu)2O}{(iPrN)2CC6H2(tBu)2O}Zr-
(CH2Ph) ({LOHNiPr}{LONiPr}Zr(CH2Ph), 1). Protocol A. In the
glovebox, a Teflon-valved NMR tube was charged with
{LONiPr}H2 (0.0358 g, 0.1077 mmol) and Zr(CH2Ph)4
(0.0245 g, 0.0538 mmol). To this mixture, C6D6 (ca. 0.6 mL)
was vacuum-transferred in and the tube was shaken for 2 h at
room temperature. 1H NMR indicated that 1 formed
quantitatively.
Protocol B. A Schlenk flask was charged with {LONiPr}H2 (0.319 g,
0.0959 mmol) and Zr(CH2Ph)4 (0.219 g, 0.0481 mmol), and toluene
(ca. 5 mL) was vacuum-transferred in. The reaction mixture was
stirred overnight at room temperature, filtered, evaporated, and dried
in vacuo to give 1 as a pale yellow microcrystalline material (0.385 g,
0.0457 mmol, 95%). 1H NMR (C6D6, 500 MHz, 25 °C): δ 7.67 (d, J =
2.0, 1H, C6H2), 7.63 (d, J = 2.0, 1H, C6H2), 7.56 (d, J = 2.0, 1H,
C6H2), 7.45 (d, J = 2.0, 1H, C6H2), 7.11 (d, J = 7.3, 2H, CH2Ph), 7.01
(t, J = 7.3, 2H, CH2Ph), 6.76 (t, J = 7.3, 1H, CH2Ph), 5.41 (sept, J =
7.2, 1H, CH(CH3)), 4.49 (d, J = 9.8, 1H, NH), 4.08 (sept, J = 6.2, 1H,
CH(CH3)), 3.86 (m, 1H, CH(CH3)), 3.32 (sept, J = 6.2, 1H,
CH(CH3)), 3.03 (d, J = 10.7, 1H, CHHPh), 2.80 (d, J = 10.7, 1H,
CHHPh), 1.84 (s, 9H, C(CH3)), 1.63 (s, 9H, C(CH3)), 1.61 (d, J =
7.2, 3H, CH(CH3)), 1.55 (s, 9H, C(CH3)), 1.52 (s, 9H, C(CH3)),
1.49 (m, 6H, CH(CH3)), 1.35 (d, J = 7.2, 3H, CH(CH3)), 1.30 (m,
6H, CH(CH3)), 1.09 (d, J = 6.4, 3H, CH(CH3)), 0.69 (d, J = 6.4, 3H,
CH(CH3)). 13C{1H} NMR (C6D6, 125 MHz, 25 °C): δ 171.4 (CN2),
167.6 (CN2), 159.0 (O-C6H2), 158.2 (O-C6H2), 146.3 (ipso-CH2Ph),
139.3 (three signals of the C6H2tBu moieties from both ligands), 136.9
(C6H2-tBu), 128.1 (C6H2 and CH2Ph), 127.3 (C6H2 and CH2Ph),
124.5 (C6H2), 122.3 (C6H2), 120.8 (C6H2 and CH2Ph), 119.8 (C6H2),
58.6 (CH2Ph), 51.3 (CH(CH3)2), 50.1 (CH(CH3)2), 49.1 (CH-
(CH3)2), 47.7 (CH(CH3)2), 35.5 (C6H2C(CH3)3), 35.4
(C6H2C(CH3)3), 34.3 (C6H2C(CH3)3), 34.2 (C6H2C(CH3)3), 31.8
(two signals overlapped from C6H2C(CH3)3 groups), 30.3 (C6H2C-
(CH3)3), 30.2 (C6H2C(CH3)3), 27.7 (CH(CH3)2), 26.5 (CH(CH3)2),
25.0 (CH(CH3)2), 24.2 (CH(CH3)2), 24.1 (CH(CH3)2), 23.2
(CH(CH3)2), 21.5 (CH(CH3)2), 19.3 (CH(CH3)2). IR (Nujol, KBr;
ν (cm−1)): 3444 w, 2361 m, 1604 m, 1576 s, 1302 m, 1290 m, 1256 m,
1240 s, 1201 m, 1170 m, 1113 m, 941 w, 835 m, 795 w, 729 s, 694 w,
598 w, 548 m. Anal. Calcd for C49H76N4O2Zr: C, 69.70; H, 9.07; N,
6.64. Found: C, 70.12; H, 9.33; N, 6.81.
Reaction between {LON(Ph)NiPr}H2 and Hf(NMe2)4 (1:1
Ratio). Synthesis of {(Ph)NC6H2(tBu)2O}Hf{(iPrN)2CNMe2}2 (4).
A Schlenk flask was charged with {LON(Ph)NiPr}H2 (0.430 g, 1.2120
mmol) and Hf(NMe2)4 (0.513 g, 1.2120 mmol), and toluene (10 mL)
was vacuum-transferred in. The reaction mixture was stirred overnight
at room temperature. Then the volatiles were evaporated in vacuo and
hexanes (ca. 15 mL) was vacuum-transferred under reduced pressure.
The mixture was filtered, and the solution was removed from the
filtrate. The resulting solid was recrystallized from hexanes (ca. 3 mL)
at room temperature to give 4 as off-white crystals (0.236 g, 0.2909
1
mmol, 24%). H NMR (C6D6, 500 MHz, 60 °C): δ 7.56 (d, J = 7.6,
2H, Ph), 7.33 (t, J = 7.6, 2H, Ph), 7.01 (t, J = 7.6, 1H, Ph), 6.93 (br d, J
= 1.8, 1H, C6H2), 6.44 (br d, J = 1.8, 1H, C6H2), 3.75 (br m, 2H,
CH(CH3)), 3.51 (sept, J = 6.5, 2H, CH(CH3)), 2.45 (br s, 6H,
NCH3), 1.78 (s, 9H, C(CH3)), 1.31 (s, 9H, C(CH3)), 0.92 (d, J = 6.5,
12H, CH(CH3)). 13C{1H} NMR (C6D6, 100 MHz, 60 °C): δ 170.0
(CN3), 152.4 (O-C6H2), 151.5 (NC6H2), 150.8 (ipso, N-Ph), 140.1,
132.7, 128.0, 122.4, 111.6, 107.7, 48.0 (CH(CH3)2), 46.1 (CH-
(CH3)2), 39.2 (NCH3), 34.5 (C6H2C(CH3)3), 34.4 (C6H2C(CH3)3),
31.9 (C6H2C(CH3)3), 30.1 (C6H2C(CH3)3), 25.1 (CH(CH3)2). Anal.
Calcd for C38H65HfN7O: C, 56.04; H, 8.04; N, 12.04. Found: C,
56.98; H, 8.55; N, 12.54.
[{(iPrN)2CC6H2(tBu)2O}ZrCl]3(μ3-O)(μ3-Cl) ([{LONiPr}ZrCl]3(μ3-
O)(μ3-Cl), 5). A Schlenk flask was charged with {LONiPr}Li2
(generated in situ from {LONiPr}H2 (1.670 g, 5.02 mmol) and n-
butyllithium (3.90 mL of a 2.6 M solution in toluene, 10.14 mmol) in
THF (25 mL) and evaporated to dryness) and ZrCl4(THF)2 (1.900 g,
5.04 mmol), and Et2O (ca. 40 mL) was vacuum-transferred under
reduced pressure. The resulting reaction mixture was stirred at room
temperature overnight. Then, the volatiles were evaporated in vacuo,
and toluene (ca. 40 mL) was vacuum-transferred under reduced
pressure. The mixture was filtered, and the solvent was removed from
the filtrate. The residue was dissolved in DME (ca. 20 mL) and the
resulting solution was kept at room temperature. A first crop of a white
microcrystalline solid, poorly soluble in DME, toluene, and CH2Cl2
solvents, was thus recovered and discarded. The mother liquor, left
after the first crystallization in DME, was concentrated and kept at
room temperature to afford colorless crystals of 5 (0.250 g, 0.1757
Reaction between {LONAr}H2 and Zr(CH2Ph)4 (1:1 Ratio).
Synthesis of {(iPr2C6H3N)2(H)CC6H2(tBu)2O}Zr(CH2Ph)3
({LOHNAr}Zr(CH2Ph)3, 2). Protocol A. Following a protocol
similar to that described above for 1 (protocol A), complex 2
formed quantitatively from {LONAr}H2 (0.0364 g, 0.0639
mmol) and Zr(CH2Ph)4 (0.0292 g, 0.0639 mmol).
Protocol B. A protocol similar to that described above for 1
(protocol B) was used, starting from {LONAr}H2 (0.191 g, 0.3357
mmol) and Zr(CH2Ph)4 (0.153 g, 0.3357 mmol). Workup afforded 2
as a pale yellow microcrystalline material (0.291 g, 0.3124 mmol,
1
93%). H NMR (C6D6, 300 MHz, 80 °C): δ 7.60 (br m, 1H, C6H2),
7.40−7.16 (m, 11H, arom), 7.15−6.80 (m, 11H, arom), 6.76 (br m,
1H, C6H2), 2.96 (sept, J = 10.9, 4H, CH(CH3)), 2.48 (br s, 6H,
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mmol, 11%). 1H NMR (CD2Cl2, 500 MHz, 25 °C): δ 7.60 (d, J = 2.5,
3H, C6H2), 7.24 (d, J = 2.5, 3H, C6H2), 4.02 (sept, J = 7.0, 3H,
CH(CH3)), 3.65 (sept, J = 7.0, 3H, CH(CH3)), 3.53 (s, 6H, CH2O,
DME), 3.37 (s, 9H, OCH3, DME), 1.79 (d, J = 7.0, 9H, CH(CH3)),
1.61 (s, 27H, C(CH3)), 1.41 (d, J = 7.0, 9H, CH(CH3)), 1.36 (s, 27H,
C(CH3)), 1.26 (m, 18H, CH(CH3)). 13C{1H} NMR (C6D6, 125
MHz, 25 °C): δ 187.2 (CN2), 157.2 (O-C6H2), 141.2, 137.1, 128.2,
123.7, 120.9, 71.8 (CH2O, DME), 58.6 (OCH3, DME), 35.5
(C6H2C(CH3)3), 34.2 (C6H2C(CH3)3), 31.5 (C6H2C(CH3)3), 31.1
(C6H2C(CH3)3), 24.7 (CH(CH3)2), 24.2 (CH(CH3)2), 24.0 (CH-
(CH3)2), 23.6 (CH(CH3)2). IR (Nujol, KBr; ν (cm−1)): 1575 s, 1363
m, 1276 s, 1254 s, 1110 s, 922 m, 845 s, 762 m, 735 m, 546 m, 466 s,
451 s. Anal. Calcd for C63H102Cl4N6O4Zr3: C, 53.17; H, 7.22; N, 5.91.
Found: C, 53.83; H, 7.69; N, 6.33.
[{(iPr2C6H3N)2CC6H2(tBu)2O}ZrCl(μ2-Cl)]2[{(iPr2C6H3N)-
(iPr2C6H3NH)CC6H2(tBu)2O}ZrCl(μ2-Cl)](μ3-OH) ([{LONAr}ZrCl(μ2-
Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3-OH), 6). To a solution of {LONAr}Li2
(generated in situ from {LONAr}H2 (0.979 g, 1.72 mmol) and n-
butyllithium (1.38 mL of a 2.5 M solution in hexane, 3.45 mmol) in
THF (20 mL) and evaporated to dryness) was added ZrCl4 (0.401 g,
1.72 mmol), and Et2O (20 mL) was vacuum-transferred in under
reduced pressure. The resulting reaction mixture was stirred at room
temperature overnight. Then the volatiles were evaporated in vacuo,
and hexanes (ca. 50 mL) was vacuum-transferred in under reduced
pressure. The mixture was filtered, and the solvent was removed from
the filtrate. The residue was dissolved in a new portion of hexanes (ca.
10 mL), and the resulting solution was kept at room temperature to
give yellow crystals of 6 (0.253 g, 0.3458 mmol, 20%). 1H NMR
(CD2Cl2, 500 MHz, 25 °C): δ 7.47 (d, J = 2.4, 3H, C6H2), 7.43 (d, J =
7.9, 6H, C6H3), 7.27 (t, J = 7.9, 6H, C6H3), 7.12 (d, J = 7.9, 6H, C6H3),
6.62 (d, J = 2.5, 3H, C6H2), 3.46 (br m, 6H, CH(CH3)2), 2.75 (br m,
6H, CH(CH3)2), 1.54 (d, J = 6.4, 18H, CH(CH3)2), 1.37 (s, 27H,
C(CH3)3), 1.20 (d, J = 6.4, 18H, CH(CH3)2), 0.90 (s, 27H, C(CH3)3).
13C{1H} NMR (CD2Cl2, 125 MHz, 25 °C): δ 164.9 (CN2), 156.6 (O-
{(iPrN)2(H)CC6H2(tBu)2O}2ZrCl2 ({LOHNiPr}2ZrCl2, 8). To a
solution of {LONiPr}H2 (1.070 g, 3.22 mmol) in THF (20 mL) was
added n-butyllithium (1.24 mL of a 2.6 M solution in toluene, 3.22
mmol) at room temperature with stirring. After 12 h, anhydrous ZrCl4
(0.380 g, 1.63 mmol) was added, and toluene (ca. 30 mL) was
vacuum-transferred in under reduced pressure. The resulting reaction
mixture was stirred at room temperature overnight. The mixture was
filtered, and the solvent was removed from the filtrate. The residue was
recrystallized from benzene (ca. 5 mL) to give a colorless crystalline
solid, namely 8·3.5C6H6 (0.448 g, 0.408 mmol, 25%). 1H NMR
(toluene-d8, 500 MHz, 25 °C): δ 7.59 (br d, 4H, C6H2), 7.17 (s, 6H,
C6H6), 7.13 (d, J = 1.9, 2H, C6H2), 4.53 (sept, J = 6.9, 2H,
CH(CH3)2), 4.47 (d, J = 9.4, 2H, NH), 3.57 (m, 2H, CH(CH3)2),
1.75 (s, 18H, C(CH3)3), 1.53 (d, J = 6.5, 6H, CH(CH3)2), 1.18 (s,
18H, C(CH3)3), 0.97 (d, J = 6.5, 6H, CH(CH3)2), 0.57 (d, J = 6.5, 6H,
CH(CH3)2), 0.39 (d, J = 6.5, 6H, CH(CH3)2). 13C{1H} NMR
(toluene-d8, 125 MHz, 25 °C): δ 165.3 (CN2), 158.2 (O-C6H2), 139.3,
138.9, 128.2 (C6H6), 127.5, 124.5, 119.8, 49.8 (CH(CH3)2), 48.2
(CH(CH3)2), 35.5 (C6H2CH(CH3)2), 33.9 (C6H2CH(CH3)2), 31.4
(C6H2C(CH3)3), 30.2 (C6H2C(CH3)3), 23.5 (CH(CH3)2), 23.1
(CH(CH3)2), 21.8 (CH(CH3)2), 19.4 (CH(CH3)2). IR (Nujol, KBr;
ν (cm−1)): 3448 w, 2360 w, 1601 m, 1558 s, 1362 m, 1311 m, 1292 w,
1257 s, 1232 w, 1166 m, 1114 s, 1033 w, 916 w, 844 s, 734 m, 682 m,
617 m, 544 s, 472 m. Anal. Calcd for C126H182Cl4N8O4Zr2: C, 68.88;
H, 8.35; N, 5.10. Found: C, 69.22; H, 8.99; N, 5.54.
{(iPr2C6H3N)2CC6H2(tBu)2O}2ZrCl2s ({LOHNAr}2ZrCl2, 9). To a
solution of {LONAr}H2 (1.029 g, 1.809 mmol) in THF (20 mL) was
added n-butyllithium (0.70 mL of a 2.6 M solution in toluene, 1.820
mmol) at room temperature with stirring. After 12 h, anhydrous ZrCl4
(0.211 g, 0.906 mmol) was added, and toluene (ca. 30 mL) was
vacuum-transferred in under reduced pressure. The resulting reaction
mixture was stirred at room temperature overnight. The mixture was
filtered, and the solvent was removed from the filtrate. The residue was
recrystallized from hexanes (ca. 20 mL) to give a colorless crystalline
solid of 9 (0.617 g, 0.475 mmol, 54%). 1H NMR (C6D6, 500 MHz, 25
°C): δ 7.41 (dd, J = 1.9, 7.0, 2H, C6H3), 7.27 (d, J = 2.4, 2H, C6H2),
7.23 (br s, 2H, C6H3), 7.17 (br m, 2H, C6H3), 6.94−6.85 (m, 4H,
C6H3), 6.77 (dd, J = 1.9, 7.0, 2H, C6H3), 6.67 (d, J = 2.4, 2H, C6H2),
4.19 (sept, J = 6.5, 2H, CH(CH3)2), 4.14 (sept, J = 6.5, 2H,
CH(CH3)2), 3.03 (sept, J = 6.5, 2H, CH(CH3)2), 2.96 (sept, J = 6.5,
2H, CH(CH3)2), 1.67 (m, 8H, CH(CH3)2 and NH), 1.58 (d, J = 6.5,
3H, CH(CH3)2), 1.40 (d, J = 6.5, 3H, CH(CH3)2), 1.31 (s, 18H,
C(CH3)3), 1.21 (d, J = 6.5, 3H, CH(CH3)2), 1.07 (d, J = 6.5, 3H,
CH(CH3)2), 0.98 (d, J = 6.5, 3H, CH(CH3)2), 0.92 (s, 18H,
C(CH3)3), 0.51 (d, J = 6.5, 3H, CH(CH3)2), 0.35 (d, J = 6.5, 3H,
CH(CH3)2). 13C{1H} NMR (C6D6, 125 MHz, 25 °C): δ 165.7 (CN2),
159.1 (O-C6H2), 144.4, 144.3, 144.1, 143.9, 142.2, 138.7, 137.4, 134.4,
127.3, 127.2, 127.0, 125.9, 125.6, 125.3, 125.1, 112.9, 119.1, 35.0
(C6H2CH(CH3)2), 33.6 (C6H2CH(CH3)2), 30.9 (C6H2C(CH3)3),
29.9 (C6H2C(CH3)3), 28.8 (C6H2CH(CH3)2), 28.6 (C6H2CH-
(CH3)2), 28.4 (C6H2CH(CH3)2), 28.2 (C6H2CH(CH3)2), 26.9
(CH(CH3)2), 26.2 (CH(CH3)2), 25.8 (CH(CH3)2), 25.4 (CH-
(CH3)2), 23.7 (CH(CH3)2), 23.6 (CH(CH3)2), 22.8 (CH(CH3)2),
21.2 (CH(CH3)2). IR (Nujol, KBr; ν (cm−1)): 3315 w, 2376 w, 1541
s, 1363 m, 1259 m, 1096 w, 1055 w, 855 w, 852 w, 790 w, 773 w, 750
w, 729 w, 542 w. Anal. Calcd for C78H110Cl2N4O2Zr: C, 72.18; H,
8.54; N, 4.32. Found: C, 72.87; H, 8.72; N, 4.94.
Typical Procedure for Ethylene Polymerization. A 300 mL
high-pressure glass reactor was charged with 150 mL of freshly distilled
toluene under argon flash. Mechanical stirring (Pelton turbine, 1000
rpm) was started, and the reactor was then purged with ethylene and
loaded with a solution of MAO or TIBAL at atmospheric pressure and
kept at the desired temperature by circulating thermostated water in
the double wall. A solution of [Ph3C][B(C6F5)4] (when used) in 2 mL
of toluene was injected in by syringe, followed by injection of a
solution of the precatalyst in 2 mL of toluene. The gas pressure in the
reactor was maintained immediately and kept constant with a back
regulator throughout the experiment. The ethylene consumption was
monitored via an Aalborg flowmeter. After a given time period, the
reactor was depressurized and the reaction was quenched by adding ca.
C6H2), 143.2, 141.2, 138.6, 132.8, 129.4, 129.2, 128.4, 126.1, 124.8,
124.6, 117.5, 35.2 (C6H2C(CH3)3), 33.9 (C6H2C(CH3)3), 30.6
(C6H2C(CH3)3), 30.0 (C6H2C(CH3)3), 28.8 (C6H2CH(CH3)2)
(only one signal of this type was observed), 24.3 (C6H2CH(CH3)2),
21.6 (C6H2CH(CH3)2). IR (Nujol, KBr) ν (cm−1): 3323 w, 3308 w,
2361 m, 1603 m, 1539 s, 1364 m, 1315 w, 1256 m, 1201 w, 1180 w,
1128 w, 1095 w, 1056 w, 970 w, 933 w, 887 w, 873 w, 856 w, 791 w,
771 w, 751 w, 733 w, 677 w, 634 w, 552 w. Anal. Calcd for
C117H164Cl6N6O4Zr3: C, 63.73; H, 7.50; N, 3.81. Found: C, 64.12; H,
8.28; N, 4.05.
{(iPr2C6H3N)2(H)CC6H2(tBu)2O}ZrCl3(THF) ({LOHNAr}ZrCl3(THF),
7). To a solution of {LONAr}Li2 (generated in situ from {LONAr}H2
(0.962 g, 1.69 mmol) and n-butyllithium (1.35 mL of a 2.5 M solution
in hexane, 3.38 mmol) in THF (20 mL) and evaporated to dryness)
was added ZrCl4(THF)2 (0.638 g, 1.6913 mmol), and toluene (ca. 20
mL) was vacuum-transferred in under reduced pressure. The reaction
mixture was stirred overnight and filtered, and the solvent was
evaporated. The residue was recrystallized from hexanes (ca. 5 mL) at
room temperature to afford 7 as a white crystalline solid (0.708 g,
0.8457 mmol, 50%). 1H NMR (C6D6, 500 MHz, 60 °C): δ 7.61 (d, J =
2.4, 1H, C6H2), 7.38 (d, J = 7.5, 2H, C6H3), 7.32 (m, 1H, C6H3), 7.05
(m, 1H, C6H3), 7.00 (d, J = 7.5, 2H, C6H3), 6.96 (d, J = 2.5, 1H,
C6H2), 4.50 (br m, 4H, α-THF), 4.14 (br m, 2H, CH(CH3)2), 3.15
(sept, J = 6.8 2H, CH(CH3)2), 1.77 (br s, 9H, C(CH3)3), 1.76 (br d,
6H, CH(CH3)2), 1.41 (br m, 4H, β-THF), 1.28 (d, J = 6.4, 6H,
CH(CH3)2), 1.00 (s, 9H, C(CH3)3, 0.95 (br m, 6H, CH(CH3)2), 0.91
(br m, 6H, CH(CH3)2). 13C{1H} NMR (C6D6, 125 MHz, 60 °C): δ
168.2 (CN2), 158.6 (O-C6H2), 144.9, 143.3, 142.4, 140.6, 137.8, 134.5,
128.2, 127.2, 125.7, 124.5, 119.7, 75.1 (α-CH2 THF), 35.3
(C6H2C(CH3)3), 33.8 (C6H2C(CH3)3), 30.9 (C6H2C(CH3)3), 30.2
(C6H2C(CH3)3), 28.9 (C6H2CH(CH3)2), 28.3 (C6H2CH(CH3)2),
26.6 (C6H2CH(CH3)2), 25.9 (C6H2CH(CH3)2), 25.2 (β-CH2 THF),
24.9 (C6H2CH(CH3)2), 24.4 (C6H2CH(CH3)2), 21.7 (C6H2CH-
(CH3)2). IR (Nujol, KBr; ν (cm−1)): 3313 w, 1539 s, 1364 m, 1264 m,
854 m, 791 w, 729 w, 559 w. Anal. Calcd for C43H63Cl3N2O2Zr: C,
61.66; H, 7.58; N, 3.34. Found: C, 62.03; H, 7.98; N, 3.65.
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5 mL of a 10% solution of HCl in methanol. The polymer was further
precipitated by adding 500 mL of methanol, washed, and dried in
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Crystal Structure Determination of {LONiPr}H2, {LON(Ph)-
NiPr}H2·H2O, {LOHNiPr}{LONiPr}Zr(CH2Ph) (1), {LOHNAr}Zr(CH2Ph)3
(2), {(Ph)NC6H2(tBu)2O}Hf{(iPrN)2CNMe2}2 (4), [{LONiPr}ZrCl]3(μ3-
O)(μ3-Cl) (5), [{LONAr}2ZrCl(μ2-Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3-OH)
(6), {LOHNAr}ZrCl3(THF) (7), {LOHNiPr}2ZrCl2·(C6H6)3.5 (8), and
{LOHNAr}2ZrCl2 (9). Diffraction data were collected at 100(2) or
150(2) K using a Bruker APEX CCD diffractometer with graphite-
monochromated Mo Kα radiation (λ = 0.710 73 Å). A combination of
ω and ϕ scans was carried out to obtain a unique data set. The crystal
structures were solved by direct methods, and the remaining atoms
were located from difference Fourier synthesis followed by full-matrix
least-squares refinement based on F2 (programs SIR97 and SHELXL-
97).35 For the structures of complexes 5, 6, and 9, the contributions of
the disordered solvents to the calculated structure factors were
estimated following the BYPASS algorithm,36 implemented as the
SQUEEZE option in PLATON.37 New data sets, free of solvent
contribution, were then used in the final refinements. Many hydrogen
atoms could be located from the Fourier difference analysis. Other
hydrogen atoms were placed at calculated positions and forced to ride
on the attached atom. The hydrogen atom positions were calculated
but not refined. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Crystal data and details of data collection
and structure refinement for the different compounds are given in
Tables S1 and S2 (see the Supporting Information). Detailed
crystallographic data (excluding structure factors) are available in the
Supporting Information, as CIF files.
(8) (a) Volkis, V.; Lisovskii, A.; Tumanskii, B.; Shuster, M.; Eisen, M.
S. Organometallics 2006, 25, 2656−2666 and references cited therein..
(b) Volkis, V.; Tumanskii, B.; Eisen, M. S. Organometallics 2006, 25,
2722−2724 and references cited therein..
(9) (a) Flores, J. C.; Chien, J. C. W.; Rausch, M. D. Organometallics
1995, 14, 2106−2108. (b) Liguori, D.; Centore, A.; Tuzi, A.; Grisi, F.;
Sessa, I.; Zambelli, A. Macromolecules 2003, 36, 5451−5458. (c) Coles,
M. P.; Hitchcock, P. B. Organometallics 2003, 22, 5201−5211.
(d) Luconi, L.; Giambastiani, G.; Rossin, A.; Bianchini, C.; Lledos,
A. Inorg. Chem. 2010, 49, 6811−6813.
(10) (a) O’Connor, P. E.; Morrison, D. J.; Steeves, S.; Burrage, K.;
Berg, D. J. Organometallics 2001, 20, 1153−1160. (b) Marquet, N.;
Kirillov, E.; Roisnel, T.; Razavi, A.; Carpentier, J.-F. Organometallics
2009, 28, 606−620. (c) Kirillov, E.; Roisnel, T.; Razavi, A.; Carpentier,
J.-F. Organometallics 2009, 28, 5036−5051.
(11) No intermediate could be detected, suggesting that coordination
of the second ligand proceeds more quickly than the first one.
(12) The analogous reaction between {LONiPr}H2 and Ti(CH2Ph)4
(2:1), carried out in an NMR tube in benzene-d6, was much less
selective, giving the titanium analogue of 1 along with mixtures of
unidentified byproducts. Attempts to obtain pure complex 1-Ti by
scaling up the synthesis, followed up by crystallization workup, were
not successful.
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF files giving crystallographic data for {LONiPr}H2, {LON-
(Ph)NiPr}H2·H2O, {LOHNiPr}{LONiPr}Zr(CH2Ph) (1),
{LOHNAr}Zr(CH2Ph)3 (2), {(Ph)NC6H2(tBu)2O}Hf-
{(iPrN)2CNMe2}2 (4), [{LONiPr}ZrCl]3(μ3-O)(μ3-Cl) (5),
[{LONAr}2ZrCl(μ2-Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3-OH)
(6), {LOHNAr}ZrCl 3(THF) (7), {LOHNiPr}2ZrCl2·3.5C6H6
(8), and {LOHNAr}2ZrCl2 (9), tables giving crystal and
structure refinement data (Tables S1 and S2), and figures
giving representative 1H and 13C NMR spectra for some
complexes. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: evgueni.kirillov@univ-rennes1.fr.
Notes
■
The authors declare no competing financial interest.
(13) Complex 1 showed no fluxional dynamics phenomena (i.e., no
broadening) in toluene-d8 in the temperature range from 0 to 100 °C.
(14) (a) Matsui, S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio, H.;
Matsukawa, N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.;
Tanaka, H.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2001, 123, 6847−
6856. (b) Bott, R. K. J.; Hughes, D. L.; Schormann, M.; Bochmann,
M.; Lancaster, S. J. J. Organomet. Chem. 2003, 665, 135−149.
(c) Pennigton, D. A.; Clegg, W.; Coles, S. J.; Harrington, R. W.;
Hursthouse, M. B.; Hughes, D. L.; Light, M. E.; Schormann, M.;
Bochmann, M.; Lancaster, S. J. Dalton Trans. 2005, 561−571.
(d) Knight, P. D.; Clarkson, G.; Hammond, M. L.; Kimberley, B. S.;
Scott, P. J. Organomet. Chem. 2005, 690, 5125−5144. (e) Bott, R. K. J.;
Schormann, M.; Hughes, D. L.; Lancaster, S. J.; Bochmann, M.
Polyhedron 2006, 25, 387−396.
ACKNOWLEDGMENTS
■
We gratefully thank Nathan Contrella and Prof. Richard F.
Jordan (The University of Chicago) for HT-GPC analyses. Dr.
S. Sinbandhit (CRMPO) is gratefully acknowledged for
technical assistance in NMR spectroscopy experiments for
some complexes. This work was financially supported by the
CNRS, University of Rennes 1, and Institut Universitaire de
France (J.-F.C.).
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