Titanium-imido complexes with pendant groups- Synthesis, characterization, and evaluation of their role as precatalysts for ethylene polymerization

Article abstract of DOI:10.1002/ejic.201101005

The synthesis of several anilines (Ar^PGNH₂) substituted in the ortho position with pendant groups (PGs, terminated by potentially coordinative arene, thienyl, furanyl, or pyridyl functionalities) was accomplished by a two- to five-st

Full text of DOI:10.1002/ejic.201101005

FULL PAPER
DOI: 10.1002/ejic.201101005
Titanium–Imido Complexes with Pendant Groups – Synthesis,
Characterization, and Evaluation of Their Role as Precatalysts for Ethylene
Polymerization
Viet-Hoang Nguyen,[a,b] Laure Vendier,[a,b] Michel Etienne,[a,b]
Emmanuelle Despagnet-Ayoub,[a,b] Pierre-Alain R. Breuil,[c] Lionel Magna,[c]
David Proriol,[c] Hélène Olivier-Bourbigou,[c] and Christian Lorber*[a,b]
Keywords: Titanium / Imido ligands / N ligands / Coordination chemistry / Polymerization
The synthesis of several anilines (ArPGNH2) substituted in
the ortho position with pendant groups (PGs, terminated by
potentially coordinative arene, thienyl, furanyl, or pyridyl
functionalities) was accomplished by a two- to five-step syn-
thesis in good yields. The ArPGNH2 proligands were used for
the preparation of titanium complexes starting from
Ti(NMe2)4 in the presence of excess Me3SiCl. Complexes of
the general formula [Ti(NArPG)Cl2(NHMe2)x] (x = 1, 2), which
ligands where PG is arene, thiophene, and furan, ligands
with substituted pyridine sidearms lead to chelating imido–
donor functionalities. The potential hemilabile behavior of
some imido–donor ligands, which results from the reversible
coordination of the side arm, was studied by variable-tem-
perature 1H NMR spectroscopy. These compounds were
evaluated as precatalysts for ethylene polymerization with
various aluminum cocatalysts. Ultrahigh molecular-weight
are supported by a terminal imido functionality, were ob- (UHMW) polyethylenes were obtained. All compounds were
tained in 60–95% yield. The nature of the pendant group
influences the coordination mode of the ligand. Although
only monodentate imido linkages have been observed with
fully characterized by spectroscopic methods (1H and 13C
NMR), and elemental analysis and some were also charac-
terized by single-crystal X-ray diffraction.
Introduction
tion, which is due to the hemilabile coordination of the pen-
dant fragment at some stage in the catalytic cycle.[16,17] In a
somewhat related system, Magna et al. reported aryloxide–
titanium complexes with pendant groups, which exhibit
interesting catalytic activity for the selective dimerization of
ethylene.[18]
Being isolobal with [C5H5]– (Cp),[1] the dianionic, π-do-
nor terminal imido functional group [NR]2– (R = alkyl or
aryl) has emerged as an alternative spectator ligand to Cp
ligands (e.g. in alkene metathesis and olefin polymeriza-
tion).[2–4] Imido complexes have also found application in
materials chemistry (organometallic chemical vapor deposi-
tion[5] and polyoxometalates)[6] and have been implicated in
a number of stoichiometric or catalytic transformations that
involve the M=NR linkage itself, such as ammoxidation of
propene,[7] metathesis reactions,[8] C–H activation,[9] reac-
tions with unsaturated C–C[10] or C–X bonds,[11] alkyne hy-
droamination,[12,13] carboamination reaction,[14] and
strained-heterocycle opening.[9d,15]
Although we[19] and others[4f,20] have shown that early-
transition-metal complexes can incorporate functionalities
at the periphery of the imido functionality, few complexes
are known that incorporate a chelating imido–donor, i.e.
with an imido group attached to the same metal center
through the N atom of the imido functionality and a second
donor atom.[19,20a,20d,20e,20f] To the best of our knowledge,
no hemilabile behavior has been demonstrated in such li-
gand systems (Figure 1).
Several groups have probed the interactions of early-
metal systems with pendant arenes, thienyl, or ether groups
on Cp ligands and reported an enhancement of the catalytic
activities in some examples for olefin oligo- or polymeriza-
[a] CNRS, LCC (Laboratoire de Chimie de Coordination),
205 route de Narbonne, 31077 Toulouse, France
Fax: +33-5-61553003
E-mail: lorber@lcc-toulouse.fr
Figure 1. Titanium–imido systems with hemilabile or coordinated
pendant groups.
[b] Université de Toulouse, UPS, INPT, LCC,
31077 Toulouse, France
[c] IFP Energies Nouvelles, Rond-point de l’Échangeur de Solaize,
69360 Solaize, France
We have previously prepared such imido–titanium com-
plexes with a very short side arm (the distance between the
imido N atom and the donor), which lead to bridging imido
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201101005 or from
the author.
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C. Lorber et al.
FULL PAPER
bimetallic complexes (Figure 2).[19,21] The synthesis of ani- compounds are described in this paper. Preliminary reactiv-
line proligands substituted in the ortho position with pen- ity studies towards ethylene polymerization are also re-
dant groups of longer and varying side-arm lengths and ported.
donor functionalities (with potentially coordinative S, O, N,
and C atoms) was targeted with the goal of fostering chela-
tion. Synthetic methods to obtain these proligands (Fig-
Results and Discussion
ure 3) and the preparation of the resulting titanium–imido
1. Synthesis of the Imido Proligands
Unfortunately, there was no general method for the syn-
thesis of the aniline proligands that were substituted in the
ortho position with pendant groups of varying side-arm
lengths and donor functionalities. Consequently, we devel-
oped three different methods (A, B, and C) that depended
on the length of the linker between the aniline and the pen-
dant group and the nature of the donor atoms of the pen-
dant group. These three methods used are illustrated in
Schemes 1, 2, and 3 and are fully detailed in the Supporting
Figure 2. Previously reported titanium complexes with chelating,
Information. They are based on the use of commercially-
available precursors, afford the desired substituted anilines
bridging imido–donor ligands (from ref.[19]).
in two to five steps in reasonably good overall yields, and
are summarized below.
Starting from 2-cyanoaniline, anilines with one (PG =
thienyl, furanyl) or two carbon atoms (PG = phenyl, 2-pic-
olinyl) in the linker between the aniline ring and the
pendant group were synthesized according to the first route
(Method A, Scheme 1). Importantly, this method afforded
two types of proligand: anilines with an unsaturated meth-
ylidene on the linker were obtained in two steps through a
Figure 3. Targeted ortho-substituted aniline proligands with a pen-
dant group.
Scheme 1. Method A for the synthesis of substituted anilines with one- and two-carbon spacers.
Scheme 2. Method B for the synthesis of substituted anilines with two- and three-carbon spacers.
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Ti Precatalysts for Ethylene Polymerization
Scheme 3. Method C for the synthesis of substituted anilines with three-carbon spacers.
Wittig reaction, and a third reduction step produced ani- linker chain between the ortho position of the aniline and
lines with a saturated linker.
the pendant group, and the nature of the PG (PG = S for
The second route (Method B, Scheme 2) consists of a thienyl, O for furanyl, N for pyridyl, Ph for phenyl).
three-step synthesis starting from 2-nitrobenzyl bromide,
which afforded anilines with two (PG = thienyl, furanyl,
pyridyl) or three carbon atoms (PG = phenyl) in the linker
between the aniline ring and the pendant group.
The last route (Method C, Scheme 3) produced anilines
with a more sterically encumbered three-carbon spacer with
two methyl groups at the α-position in order to force the
2. Synthesis of the Titanium–Imido Complexes
a) Imido Complexes with PG = Thienyl, Furanyl, and
Phenyl
The imido–titanium complexes were prepared according
coordination of the PG to the metal center. This method to our general procedure for easy access to various tita-
was only used for the synthesis of anilines with PG = pyr- nium– and vanadium–imido compounds of the type
idyl.
[M(=NR)Cl2(NHMe2)2].[19,22–25] In a one-pot synthesis, a
The substituted anilines are named ArnPGNH2 (Figure 4) toluene solution of Ti(NMe2)4 was treated with 1 equiv. of
to take into account the number of carbon atoms (n) in the ArPGNH2 followed by the addition of 6 equiv. of Me3SiCl
(Scheme 4). After suitable workup, the imido complexes
were obtained in yields from 59–95% as orange or red sol-
1
ids (Figure 5). Elemental analysis and H and 13C NMR
spectra are in agreement with compounds of the general
formula [Ti(=NArPG)Cl2(NHMe2)2], i.e. with two dimeth-
ylamino ligands coordinated to the metal center.
Scheme 4. General procedure for the synthesis of the titanium–
imido complexes.
Single crystals of three of these complexes, O1, S1, and
S2, suitable for X-ray diffraction studies were obtained from
room temp. toluene or cold toluene/pentane solutions.
Thermal ellipsoid plots are presented in Figures 6, 7, and
8, and selected metric parameters are given in Table 1. Two
independent molecules are present in the molecular struc-
ture of O1, but as the geometric parameters are not signifi-
cantly different, only one of these molecules (molecule A)
is discussed.
In the solid state, the molecular structures of the three
bisdimethylamino adducts (S1, O1, and S2) are best de-
scribed as a distorted trigonal bipyramid for S1 with axial
dimethylamine ligands (τ = 0.58) or a distorted square pyra-
mid for O1 and S2 [τ = 0.36 (O1), and 0.37 (S2)].[26] The
N
imido–Ti–Cl angles are in the range 107–115°, and the
N
imido–Ti–N angles are in the range 94–100°. The dis-
NHMe2
tances and angles associated with the titanium center and
the ligands are comparable to those found in other
Figure 4. Substituted anilines prepared in this study.
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C. Lorber et al.
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Figure 7. Thermal ellipsoid plot of S1 with partial atom labeling.
Displacement ellipsoids drawn at the 50% level. H atoms bonded
to C omitted. H atoms bonded to N drawn as spheres of arbitrary
radius.
Figure 5. [Ti(=NArPG)Cl2(NHMe2)2] with corresponding yields
and labels.
Figure 8. Thermal ellipsoid plot of S2 with partial atom labeling.
Displacement ellipsoids drawn at the 50% level. H atoms bonded
to C omitted. H atoms bonded to N drawn as spheres of arbitrary
radius.
Table 1. Comparison of average interatomic distances [Å] and
angles [°] in [Ti(=NArPG)Cl2(NHMe2)2].
O1 [a]
S1
S2
Ti–Nimido
Nimido–Cipso
Ti–Cl
1.6979(16)
1.390(2)
2.3387(6)
2.3441(6)
2.184(16)
2.2088(16)
2.403
1.700(2)
1.389(4)
2.3387(10)
2.3251(10)
2.202(3)
2.204(3)
2.482
1.701(3)
1.389(4)
2.3652(9)
2.3375(9)
2.214(3)
2.188(3)
2.529
Figure 6. Thermal ellipsoid plot of O1 (molecule A) with partial
atom labeling. Displacement ellipsoids drawn at the 50% level. H
atoms bonded to C omitted. H atoms bonded to N drawn as
spheres of arbitrary radius.
Ti–NNHMe
2
HNHMe ···Cl
2
Ti–Nimido–Cipso
Cl–Ti–Cl
175.72(14)
138.17(3)
174.6(2)
131.60(4)
170.57(10)
94.45(11)
94.97(11)
159.8
166.9(2)
140.39(4)
162.55(10)
100.64(11)
95.62(11)
148.3
[M(=NR)Cl2(NHMe2)2] complexes (M
=
Ti,[24,25,27]
NNHMe –Ti–NNHMe 160.21(7)
V[22,23]). The complexes exhibit a short Ti–Nimido distance
of 1.6979(16) for O1, 1.700(2) for S1, and 1.701(3) Å for
S2, and the imido linkage is almost linear [Ti–Nimido–Cipso
175.72(14), 174.6(2), and 166.9(2)° in O1, S1, and S2,
respectively]. This is consistent with the lone pair on nitro-
Nimido–2Ti–N
100.20(7)
99.57(7)
158.4
5.453
0.36
2
NHMe2
N–H···Cl
Ti···DPG [b]
τ
[c]
4.511
0.58
7.132
0.37
gen being donated to an acceptor orbital on titanium, and [a] Geometric parameters are given for independent molecule A.
[b] DPG is the donor atom in the PG. [c] A shorter (4.566 Å) inter-
molecular Ti···S distance is found.
the imido Ti–N bond can be considered as a triple bond.
The crystal structure determinations also unambiguously
show noninteracting functional thienyl (S1, S2), and furanyl
(O1) groups, with normal metric parameters, which are sites in the trigonal bipyramid or square pyramid with Cl1–
listed in Table 1. Both chlorine atoms occupy equatorial Ti–Cl2 angles of 138.17(3) (O1), 131.60(16) (S1), and
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Ti Precatalysts for Ethylene Polymerization
140.39(4)° (S2) and mean Ti–Cl bond lengths of 2.34 (O1), tions as described above yields an orange solid in 95%
2.34 (S1), and 2.35 Å (S2). The two trans dimethylamino yield. NMR spectroscopy and an X-ray diffraction study
ligands have mean Ti–NNHMe bond lengths of ca. 2.20 Å clearly show the formation of a bisdimethylamino adduct:
2
for the three compounds. The supramolecular structure is [Ti(=NAr2N)Cl2(NHMe2)2] (N2).
characterized by Me2N–H···Cl intermolecular hydrogen
bonds (NH···Cl 2.403–2.529 Å, N–H···Cl 159.8–148.3°), lected metric parameters are given in Table 2. The structure
which is a feature that is common to many related com- of N2 resembles that of other five-coordinate [Ti(=NArPG
pounds.[22,24,27]
Cl2(NHMe2)2] complexes described here with comparable
Figure 9 shows the molecular structure of N2, and se-
)
Heating solid O1 at 60 °C under dynamic vacuum (ca. metric parameters [Ti–Nimido 1.7129(8) Å, Ti–Nimido–C1
5ϫ10–2 mbar) resulted in no sign of PG donor atom coor- 179.11(8)°, Cl–Ti–Cl 131.857(15)°, mean Ti–Cl 2.351 Å,
dination and left unchanged solids with some degree of de- mean Ti–Namine 2.217 Å]. The main feature in the pentaco-
composition (evidenced by the formation of free aniline li- ordinate titanium center is again the absence of coordina-
gands and NH2Me2Cl). The ammonium salt NH2Me2Cl tion of the PG pyridine nitrogen atom (see below, Ti···NPy
was also detected in substantial amounts after solid O2 had 4.931 Å). The molecular structure is characterized by an in-
been left under dynamic vacuum (ca. 9ϫ10–4 mbar) for tramolecular hydrogen bond between the pyridine nitrogen
12 h at room temp. This suggests that, in the solid state, atom and the hydrogen atom of a NHMe2 ligand (N2)
decomposition of these complexes occurs before the coordi- [NH···NPy 2.408 Å, N–H···NPy 145.8°].
nation of the O or S atom. However, the compounds are
thermally stable in solution: heating a C6D6 solution of O1
to 80 °C resulted in no sign of decomposition, PG donor
atom coordination, or NHMe2 elimination. Furthermore, a
1
variable-temperature H NMR study of O2 in [D8]toluene
showed that the proton in the 2-position from the furanyl
O atom (α from O) is almost unchanged when lowering the
temperature. At low temperature, the only proton that is
notably low-field shifted (from 6.35 ppm at 295 K to
6.85 ppm at 195 K, see Supporting Information) is the H
atom in the 3-position (βЈ from O). This behavior (no line
broadening) suggests the presence of a preferred average
orientation of the furanyl H or C atoms in the 3-position
instead of a dynamic exchange that involves reversible coor-
dination of the oxygen atom.
Figure 9. Thermal ellipsoid plot of N2 with partial atom labeling.
b) Imido Complexes with PG = Pyridyl
Displacement ellipsoids drawn at the 50% level. H atoms bonded
The reaction of the pyridyl-containing PG Ar2NNH2 with
to C omitted. H atoms bonded to N drawn as spheres of arbitrary
Ti(NMe2)4 in the presence of Me3SiCl under similar condi- radius.
Table 2. Comparison of average interatomic distances [Å] and angles [°] in [Ti(=NArnPG)Cl2(NHMe2)x] complexes containing pyridyl
PGs.
N2
NЈ2
NЈЈ2
NЈЈЈ2
N3
NЈ3
Ti–Nimido
Nimido–Cipso
Ti–Cl
1.7129(8)
1.3868(12)
2.3607(4),
2.3347(4)
1.694(3)
1.385(5)
2.3437(12),
2.3455(12)
1.708(3)
1.375(4)
2.4029(11),
2.4190(11),
2.4696(10),
2.7771(11)
–
1.7011(15)
1.387(2)
2.3407(5),
2.3334(6)
1.7107(13)
1.391(2)
2.3465(5),
2.3298(5)
1.7006(3)
1.389(2)
2.3660(5),
2.3349(5)
Ti–NNHMe
2.2232(9),
2.2104(9)
–
4.931
2.411
179.11(8)
131.857(15)
2.194(3)
2.2100(15),
2.1991(15)
–
4.387
2.485
174.86(13)
128.12(2)
2.2230(14),
2.1924(13)
–
4.569
–
164.48(12)
135.42(2)
2.1973(14)
2
Ti–NPy
Ti···NPy
2.222(3)
–
–
172.3(3)
142.68(5)
2.314(3)
–
–
172.5(2)
84.83(3), 79.32(3),
2.2400(14)
–
2.444
167.69(12)
138.77(2)
HNHMe ···Cl
2
Ti–Nimido–Cipso
Cl–Ti–Cl
80.76(3)
NNHMe –Ti–NNHMe2
168.74(3)
–
95.31(4),
95.80(4)
–
166.0
0.61
–
–
–
–
173.55(6)
–
94.96(6),
91.35(7)
–
162.9
0.76
164.76(5)
–
99.62(6),
95.32(6)
–
–
0.49
–
N
NHMe2
2–Ti–NPy
159.14(12)
98.15(14)
157.70(6)
99.46(6)
Nimido–Ti–N
NHMe2
Nimido–Ti–NPy
N–H···Cl
τ
102.55(14)
–
0.27
97.19(11)
–
–
102.68(6)
155.5
0.32
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The noncoordination of the strong donor in the pendant Cl4][NH2Me2]2. The chelating imido–pyridine ligand forms
pyridine in N2 is significant, and might be explained by (i) an eight-membered ring. The octahedrally coordinated tita-
the weaker donating properties of the N atom due to ex- nium center is surrounded by four chlorine atoms, the nitro-
tended delocalization through the C=C double bond and/ gen atom of a linear imido linkage [Ti–Nimido 1.708(3) Å,
or (ii) the rigidity of the unsaturated linker.
Ti–Nimido–C1 172.5(2)°], and the N atom of the pendant
In order to test the influence of the length of the side pyridine group in the cis position with respect to the Nimido
arm on the potential coordination of the pendant pyridine atom [Ti–NPy 2.314(3) Å, NImido–Ti–NPy 97.19(11)°]. The
group, we treated the analogous saturated proligand Ti–Cl bond length trans to the Nimido atom is severely elon-
ArЈ2NNH2 with Ti(NMe2)4 in the presence of Me3SiCl gated [2.7771(11) Å] due to the trans influence of the imido
(Scheme 5). Under identical experimental conditions we ob- ligand.
served (by 1H NMR spectroscopy of an aliquot of the solu-
X-ray quality crystals of neutral NЈ2 were also obtained,
tion) the formation of two compounds: a major species NЈ2 which allowed us to determine its molecular structure by
and a minor species NЈЈ2. Integration of the 1H NMR spec- X-ray diffraction (Figure 11). The most prominent feature
trum indicates the presence of only one NHMe2 ligand per of the molecular structure of NЈ2 is the coordination of the
imido in NЈ2, which is in agreement with a compound of nitrogen atom of the pendant pyridine group to the tita-
formula [Ti(=NArЈ2N)Cl2(NHMe2)1], whereas signals as- nium center, which forms an eight-membered ring. The pyr-
signed to dimethylammonium are present in the spectrum idine substituent is located trans to the remaining dimeth-
of NЈЈ2. Complex NЈЈ2 was isolated in a very low yield as ylamino ligand [Ti–NNHMe 2.194(3) Å, Ti–NPy 2.222(3) Å]
2
yellow crystals suitable for an X-ray diffraction study.
within a square pyramidal complex (τ = 0.27). The geomet-
The molecular structure of NЈЈ2 is presented in Figure 10, ric parameters associated with the titanium center and the
and selected metric parameters are given in Table 2. Com- ligands are comparable to those found in related
plex NЈЈ2 is formulated as the ionic complex [Ti(=NArЈ2N
)
[Ti(=NAr)Cl2(NHMe2)2] complexes presented here (see
Table 2). The imido functionality exhibits a short Ti–Nimido
Figure 10. Thermal ellipsoid plot of NЈЈ2 with partial atom label-
ing. Displacement ellipsoids drawn at the 50% level. H atoms
bonded to C omitted. H atoms bonded to N drawn as spheres of
arbitrary radius.
Figure 11. Thermal ellipsoid plot of NЈ2 with partial atom labeling.
Displacement ellipsoids drawn at the 50% level. H atoms bonded
to C and toluene solvate molecule omitted. H atoms bonded to N
drawn as spheres of arbitrary radius.
Scheme 5. Synthesis of chelating imido–pyridine complexes from ArЈ2NNH2.
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Ti Precatalysts for Ethylene Polymerization
distance of 1.694(3) Å and an almost linear imido linkage temp. for 12 h afforded orange N3. The formation of the
[Ti–Nimido–Cipso 172.3(3)°]. The respective trans-located bis-NHMe2 adduct was further confirmed by the 1H NMR
chlorine atoms occupy basal sites in the square pyramid spectrum of N3 and X-ray structure determination. A ther-
with a Cl1–Ti–Cl2 angle of 142.68(5)° and mean Ti–Cl mal ellipsoid plot is presented in Figure 13, and selected
bond lengths of 2.34 Å.
metric parameters are given in Table 2. The structure is sim-
Formation of the ionic NЈЈ2 might result from the reac- ilar to the other five-coordinate bis(dimethylamino) adducts
tion with in situ generated Me2NH2Cl [i.e. from a reaction presented here and is not detailed further.
between liberated NHMe2 and Me3SiCl,[28] Equation (1)].
The factors that govern the formation of such an ammo-
nium salt are still under scrutiny. Nevertheless, in seeking
an alternative synthetic strategy to NЈ2 free of ionic NЈЈ2,
the transimination reaction of [Ti(=NtBu)Cl2(NHMe2)2]
with an equimolar amount of ArЈ2NNH2 was considered
(Scheme 5). This mild exchange reaction afforded a high
yield of pure NЈ2.[29] Interestingly, small amounts of the in-
termediate bis(dimethylamino) adduct (NЈЈЈ2) were crys-
tallized from the pentane washings from this reaction. As
NЈЈЈ2 is very similar to N2, it will not be discussed (Fig-
ure 12 and Table 2), but the isolation of both complexes
with and without coordination of the N atom of the pyr-
idine strongly support the potential hemilabile character of
the pyridine PG in these ligands.
Figure 13. Thermal ellipsoid plot of N3 with partial atom labeling.
Displacement ellipsoids drawn at the 50% level. H atoms bonded
to C omitted. H atoms bonded to N drawn as spheres of arbitrary
radius.
2 Me2NH + Me3SiCl h 2 Me2NH2Cl + Me3SiNMe2
(1)
However, with longer reaction time, we noted a slow
evolution of the NMR spectrum of the above reaction mix-
ture [Ti(NMe2)4, Ar3NNH2, Me3SiCl]. After 10 d of reac-
tion in the presence of Me3SiCl, a new complex, NЈ3, was
obtained as the unique species (Scheme 6). We later found
it more convenient and reproducible to prepare NЈ3 from
isolated N3 and Me3SiCl in toluene. The exact role of the
excess Me3SiCl in this transformation is presently un-
known. Me3SiCl might help the decoordination of the di-
methylamine through silylation of the coordinated NHMe2
(see above). Furthermore, in the absence of Me3SiCl, re-
peated dissolution of N3 in toluene followed by vacuum
treatment (repeated five times) led to dimethylamine elimi-
nation with concomitant formation of NЈ3 (although com-
plete transformation was not achieved, as about 10% of N3
was still present after five repetitions of this treatment).
This suggests that vacuum treatment also plays an impor-
tant role in displacing the equilibrium of NHMe2 decoordi-
Figure 12. Thermal ellipsoid plot of NЈЈЈ2 with partial atom label-
ing. Displacement ellipsoids drawn at the 50% level. H atoms
bonded to C omitted. H atoms bonded to N drawn as spheres of
arbitrary radius.
Further proof of the intramolecular coordination of such nation. Hence, the chelate complex NЈ3 seems more difficult
pyridine PGs comes from our studies with Ar3NNH2, which to obtain than the parent NЈ2, which we attribute to the
possesses a longer, three-carbon linker (Scheme 6).
length of the donor side arm: the eight-membered metalla-
Treatment of a toluene solution of Ti(NMe2)4 with cycle in NЈ2 is probably more favorable than the nine-
Ar3NNH2 in the presence of 6 equiv. of Me3SiCl at room membered ring in NЈ3.
Scheme 6. Synthesis of monodentate and chelating imido–pyridine complexes from Ar3NNH2.
Eur. J. Inorg. Chem. 2012, 97–111
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103

C. Lorber et al.
FULL PAPER
Scheme 7. From monodentate to chelating imido–pyridine complexes.
A thermal ellipsoid plot of the solid-state structure of correlation between the NH proton (1H δ = 7.37 ppm) of
NЈ3 is presented in Figure 14, and selected metric param- one NHMe2 (15N δ = –339 ppm) with the nitrogen atom of
eters are given in Table 2. The molecular structure of NЈ3 the pyridine (15N δ = –78 ppm) at 183 K. This behavior
clearly indicates the coordination of the nitrogen atom of results from the presence of only one compound at low tem-
the pendant pyridine group to the metal center, which forms perature, which has a hydrogen bond between the N atom
a nine-membered ring. The pyridine substituent is trans to of the pyridine and the NH of one dimethylamine ligand,
the remaining dimethylamino ligand. The geometry of the as observed in the solid-state structure of N3.
metal center is a distorted trigonal bipyramid (τ = 0.77).
The distances and angles associated with the titanium cen-
ter and the ligands are comparable to those found in related
[Ti(=NAr)Cl2(NHMe2)2] complexes presented here
(Table 2). The complex exhibits a short Ti–Nimido distance
of 1.7006(3) Å and an almost linear imido linkage
[Ti–Nimido–Cipso 167.69(12)°]. The chlorine atoms occupy
equatorial sites in the trigonal bipyramid with a Cl1–Ti–
Cl2 angle of 138.77(2)° and mean Ti–Cl bond lengths of
2.35 Å. The trans dimethylamino and pyridine ligands have
The fact that we have not been able to establish hemil-
ability in complexes supported by ligands with a pyridine
PG most probably arises from the stability of pentacoordi-
nate bis(dimethylamine) complexes (possibly enhanced by
H bonding with pyridine N donors), as well as facile and
irreversible NHMe2 displacement in hypothetical octahe-
dral bis(dimethylamine) intermediates through coordina-
tion of the pyridine PG (and elimination of the NHMe2
trans to the imido function), which leads to pentacoordinate
mono-NHMe2 chelate complexes (Scheme 7).
similar Ti–N bond lengths [Ti–NNHMe 2.1973(14) Å, Ti–
2
3. Preliminary Catalytic Ethylene Polymerization Studies
NPy 2.2400(14) Å]. Molecules of NЈ3 are also associated by
Several precatalysts have been evaluated in the polymeri-
zation reaction of ethylene with various cocatalysts [methyl-
aluminoxane (MAO) and triethylaluminum (TEA)] and un-
der different conditions. The results are summarized in
Table 3, with reference to [Ti(=N-2,6-iPr2–C6H3)Cl2-
(NHMe2)2] as a precatalyst.[19]
a network of Me2N–H···Cl hydrogen bonds.
Whatever the precatalyst, low to moderate activities were
observed (Table 3, Entries 1–12). No significant influence
on the activity is observed whether the pendant group is a
thiophenyl, a phenyl, a furanyl, or a pyridyl group. An in-
crease of activity is observed with S1 and PhЈ2 when acti-
vated with MAO compared to TEA. Decreasing the tem-
perature from 60 to 25 °C led to a slight decrease in activity
for NЈ2 (Entries 9 and 10). Optimization of the titanium
concentration led to an increase in activity of up to 24000 g/
(molTi hbar) (Entries 6, 7, and 11). However, no clear bene-
fit to the polymerization activity could be evidenced by the
presence of the PG compared to [Ti(=N-2,6-iPr2–C6H3)-
Cl2(NHMe2)2] (Entry 12). Furthermore, the activities of
these precatalysts remain largely inferior to the some of the
most productive imido–titanium precatalysts.[2c,4g,30] One
explanation for the relatively poor activity of our systems is
the presence of donor ligands in the precatalysts that could
interact with the aluminum cocatalyst.
Figure 14. Thermal ellipsoid plot of NЈ3 with partial atom labeling.
Displacement ellipsoids drawn at the 50% level. H atoms bonded
to C omitted. H atoms bonded to N drawn as spheres of arbitrary
radius.
1
A variable-temperature H NMR study was conducted
on a [D8]toluene solution of N3 (Supporting Information).
At high temperatures (318–358 K), the broadening of sev-
eral signals is observed, in particular those assigned to pyr-
idine and aryl ortho-H. This fluxional behavior indicates a
dynamic equilibrium between two species. At lower tem-
Size exclusion chromatography could not be carried out
peratures, different behavior is evidenced with broadening on the polymer samples as gels were obtained. Accordingly,
and splitting of the signals of NHMe2 (both NH and Me), we conclude that the polymers were UHMW polyethylenes
the methyl groups on the sidearm, and the methylene pro- with Mw above 106 gmol–1. The presence of an additional
tons (attached to the pyridyl substituent) of the sidearm. side arm might therefore favor propagation over termina-
1
The 2D H-15N NMR and NOESY experiments, show a tion.
104
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 97–111

Ti Precatalysts for Ethylene Polymerization
Table 3. Ethylene polymerization with different titanium–imido precatalysts.[a]
Entry
Precatalyst (mmol)
Cocatalyst
Al/Ti
Polymer yield [g]
Activity [g/(molTi hbar)][b]
1
2
3
4
5
6
7
8
9
S1 (0.15)
MAO
TEA
MAO
TEA
MAO
MAO
MAO
MAO
MAO
MAO
MAO
TEA
200
3
200
3
200
500
500
200
200
200
500
3
5.6
0.7
6.3
0.5
8.7
5.6
6.1
9.3
9.5
6.1
6.0
0.26
7.6
1866
233
2100
167
2900
22400
24400
3100
3167
2033
24000
104
S1 (0.15)
PhЈ2 (0.15)
PhЈ2 (0.15)
N2 (0.15)
O2 (0.0125)
Ph3 (0.0125)
N3 (0.15)
NЈ2 (0.15)
[c]
10
NЈ2 (0.15)
11
12
13
NЈ2 (0.0125)
NЈ2 (0.0125)
[Ti(=NAr)Cl2(NHMe2)2][d]
MAO
500
30400
[a] Conditions: toluene (25 mL), 60 °C, ethylene (20 bar), 1 h. [b] Calculated from isolated polymer. [c] T = 25 °C instead of 60 °C. [d]
With Ar = 2,6-C6H3 (synthesis according to ref.[19]).
with 1,2,4-trichlorobenzene with a flow rate of 1 mLmin–1 at
150 °C. Ti(NMe2)4 was purchased from Aldrich. [Ti(=N-2,6-iPr2–
Conclusions
New imido proligands that possess a potentially coordi-
C6H3)Cl2(NHMe2)2] was prepared according to our published pro-
nating functional PG have been synthesized. The corre- cedure.[19] MAO (10 wt.-% toluene solution) and TEA were pur-
chased from Chemtura.
sponding imido complexes were prepared by reaction with
Ti(NMe2)4 in the presence of Me3SiCl or by transamination
from [Ti(NtBu)Cl2(NHMe2)2]. The O-, S-, and Ph-based li-
gands afforded five-coordinate complexes [Ti(NArPG)-
Cl2(NHMe2)2] with no sign of PG coordination, whereas
Crystal Structure Determination: The structures of nine compounds
were determined. Crystal data collection and processing param-
eters are given in Tables 4 and 5. The selected crystals, which were
sensitive to air and moisture, were mounted on a glass fiber using
ligands that bear a pyridyl substituent, which is a better perfluoropolyether oil and cooled rapidly to 180 K in a stream of
cold N2. For all the structures, data were collected at low tempera-
ture (T = 180 K) either with a Stoe Imaging Plate Diffraction Sys-
tem, an Oxford Diffraction Kappa CCD Excalibur diffractometer,
or a Bruker Kappa Apex II diffractometer with graphite-mono-
chromated Mo-Kα radiation (λ = 0.71073 Å) and equipped with
an Oxford Cryosystems Cryostream Cooler Device. Final unit cell
parameters were obtained by means of a least-squares refinement
of a set of 8000 well measured reflections. Crystal decay was moni-
tored during data collection by measuring 200 reflections by image
and no significant fluctuation of the intensities was observed.
coordinating group, associated with a longer and more flex-
ible side arm led to the formation of chelated imido–pyr-
idine complexes [Ti(NArPG)Cl2(NHMe2)1]. However, the
hemilabile behavior of these ligands could not be firmly es-
tablished. When associated with various aluminum acti-
vators, some of these complexes are precatalysts for ethylene
polymerization, which produced UHMW polyethylenes.
Contrary to that reported occasionally in the literature, the
presence and/or the nature of the PG seems to favor propa-
gation over termination. Another detrimental consequence Structures were solved by direct methods using the program
SIR92[31] and subsequent difference Fourier maps, models were re-
of these PG-functionalized imido compounds could be di-
rect interaction with the cocatalyst. Further studies are nec-
essary to fully understand these catalytic systems and probe
the effects of the various PGs.
fined by least-squares procedures on a F2 with SHELXL-97[32] inte-
grated in WINGX version 1.64,[33] and empirical absorption cor-
rections were applied to the data.[34] For NЈЈ2 and NЈ3, it was not
possible to solve diffuse electron-density residuals (enclosed solvent
molecules). Treatment with the SQUEEZE facility from
PLATON[35] resulted in a smooth refinement. As a few low-order
Experimental Section
reflections were missing from the data set, the electron count is
underestimated. Thus, the values given for D(calc), F(000), and the
molecular weight are only valid for the ordered part of the struc-
ture. Details of the structure solution and refinements are given in
the Supporting Information (CIF files), together with a full list
of atomic coordinates, bond lengths and angles, and displacement
parameters for all structures.
General Methods and Instrumentation: All manipulations were car-
ried out using standard Schlenk or dry box techniques under an
atmosphere of argon. Solvents were dried with appropriate drying
agents under an atmosphere of argon and collected by distillation.
NMR spectra were recorded with Bruker ARX250, DPX300,
Avance300, and Avance500 spectrometers and referenced internally
to residual protiosolvent (1H) resonances and are reported relative
to tetramethylsilane. Elemental analyses were performed at the La-
boratoire de Chimie de Coordination (Toulouse, France). IR spec-
tra were recorded with a Perkin–Elmer Spectrum GX FT-IR spec-
trometer. Samples were prepared under an argon atmosphere in
a glove box as nujol mulls between NaCl plates. Gel permeation
chromatography was conducted with a Waters Alliance GPCV
2000 chromatograph equipped with three columns (two Styragel
HT6E and one Styragel HT2). Samples (1 mgmL–1) were eluted
CCDC-836637 (for O1), -836638 (for S1), -836639 (for NЈЈ2),
-836640(forN2),-836641(forNЈ2),-836642(forNЈ3),-836643(forN3),
-836644 (for S2), and -836645 (for NЈЈЈ3) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Synthesis of Proligands: A full description of the synthesis of the
proligands is given in the Supporting Information.
Eur. J. Inorg. Chem. 2012, 97–111
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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105

C. Lorber et al.
FULL PAPER
Table 4. Crystallographic data, data collection, and refinement parameters for O1, S1, S2, and N2.
O1
S1
S2
N2
Chemical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C16H23Cl2N3OTi
392.14
monoclinic
P21/c
17.7630(6)
14.8830(3)
16.2330(5)
90
C16H23Cl2N3STi
408.21
monoclinic
P21/c
8.5177(18)
27.216(5)
8.943(2)
90
C16H25Cl2N3STi
410.25
monoclinic
P21/c
13.5942(3)
7.2519(2)
20.4286(5)
90
C18H26Cl2N4Ti
417.23
monoclinic
P21/c
17.576(3)
10.2796(15)
12.3180(19)
90
α [°]
β [°]
115.862(4)
90
3861.7(2)
8
1.349
0.726
101.761(6)
90
2029.8(7)
4
1.336
0.789
93.011(2)
90
2011.15(9)
4
1.355
0.797
103.577(9)
90
2163.3(6)
4
1.281
0.65
γ [°]
V [Å3]
Z
Dcalcd. [gcm–3]
μ (Mo-Kα) [mm–1]
F(000)
1632
848
856
872
θ range [°]
3.08 to 26.37
40093
7886/0.0574
435/6
R1 = 0.0312,
wR2 = 0.058
R1 = 0.061,
wR2 = 0.0624
0.876
2.55 to 25.68
18475
3855/0.0316
206/3
R1 = 0.0463,
wR2 = 0.1251
R1 = 0.0585,
wR2 = 0.1346
1.032
3.36 to 26.37
17088
4088/0.0361
212/0
R1 = 0.0459,
wR2 = 0.1300
R1 = 0.0560,
wR2 = 0.1377
1.039
2.61 to 38.69
55082
12212/0.0309
231/0
R1 = 0.0383,
wR2 = 0.0874
R1 = 0.0739,
wR2 = 0.1019
1.004
Measured reflections
Unique reflections/Rint
Parameters/restraints
Final R indices
[I Ͼ σ2(I)]
Final R indices
(all data)
Goodness of fit
Δρmax. – Δρmin.
0.293 and –0.28
1.904 and –0.795
1.057 and –0.802
0.592 and –0.286
Table 5. Crystallographic data, data collection, and refinement parameters for NЈЈ2, NЈЈЈ2, N3, and NЈ3.
NЈ2
NЈЈ2
NЈЈЈ2
N3
NЈ3
Chemical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C16H21Cl2N3Ti, C7H8 C18H30Cl4N4Ti
C18H28Cl2N4Ti
419.24
monoclinic
C2/c
29.7027(18)
16.5297(10)
9.1432(7)
90
106.421(2)
90
4306.0(5)
8
1.293
0.654
1760
C20H32Cl2N4Ti
447.30
orthorhombic
P212121
10.02920(10)
10.81580(10)
21.4911(2)
90
C18H25Cl2N3Ti
402.21
466.29
monoclinic
P21/n
7.5496(7)
10.7460(10)
28.686(3)
90
94.007(6)
90
2321.6(4)
4
492.16
triclinic
triclinic
¯
¯
P1
P1
7.9478(6)
12.1653(11)
16.5930(11)
76.999(7)
81.157(6)
88.214(7)
1544.6(2)
2
8.5768(5)
10.2656(6)
13.8592(7)
81.360(2)
74.808(2)
86.146(2)
1163.74(11)
2
α [°]
β [°]
90
90
γ [°]
V [Å3]
2331.22(4)
4
1.274
0.608
944
Z
Dcalcd. [gcm–3]
μ (Mo-Kα) [mm–1]
F(000)
1.334
0.613
1.058
0.631
1.148
0.601
420
976
512
θ range [°]
Measured reflections
Unique reflections/Rint 4743/R(int) = 0.0483
Parameters/restraints
Final R indices
[I Ͼ σ2(I)]
Final R indices
(all data)
1.42 to 26.37
21076
3.35 to 24.71
17091
5269/0.0605
249/0
R1 = 0.0374,
wR2 = 0.0919
R1 = 0.0729,
wR2 = 0.0961
0.842
2.46 to 27.86
19825
5111/0.0387
231/0
R1 = 0.0339,
wR2 = 0.0772
R1 = 0.0584,
wR2 = 0.0872
1.014
3.36 to 26.37
48330
4767/0.0413
250/0
R1 = 0.0226,
wR2 = 0.0568
R1 = 0.0248,
wR2 = 0.0584
1.065
1.54 to 26.37
20142
4746/0.0243
221/0
R1 = 0.0327,
wR2 = 0.0881
R1 = 0.0425,
wR2 = 0.0923
1.076
266/0
R1 = 0.0603,
wR2 = 0.1356
R1 = 0.1039,
wR2 = 0.1530
1.045
Goodness of fit
Δρmax. – Δρmin.
1.098 and –0.400
0.284 and –0.234
0.281 and –0.220
0.235 and –0.131
0.280 and –0.202
Syntheses of Titanium–Imido Complexes
General Procedure:[19] To
toluene solution (2 mL) of Ti-
(NMe2)4 (300 mg, 1.34 mmol) was slowly added the aniline ArNH2
(1–1.1 equiv.) at room temperature. After slow addition of trimeth-
ylsilyl chloride (TMSCl, 1.1 mL), the solution was stirred overnight
at room temperature. The volatiles were removed under reduced
pressure, the residue was washed with pentane (3ϫ6 mL), and
dried under vacuum to afford the pure material.
a
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Ti Precatalysts for Ethylene Polymerization
Synthesis of S1
(340 mg, 0.82 mmol, 92%) was obtained as an orange solid. 1H
NMR (250 MHz, C6D6): δ = 7.46–7.52 (m, 2 H, H10), 7.36 (dd, J
= 1.1, 8.2 Hz, 1 H, H11), 7.14–7.24 (m, 2 H, H9), 7.04–7.11 (m, 1
H, H3), 6.96–7.04 (m, 2 H, H4 + H5), 6.69 (dt, J = 1.3, 7.5 Hz, 1
H, H6), 5.15–5.25 (m, 2 H, H13), 4.35 (s, 2 H, H7), 2.77 (m, 2 H,
HNH), 2.29 (d, J = 6.1 Hz, 12 H, HMe) ppm. 13C{1H} NMR
(62.5 MHz, C6D6): δ = 158.21 (C1), 150.50 (C12), 140.25 (C8),
134.24 (C2), 129.77 (C9), 129.10 (C5), 128.31 (C10), 128.20 (C3),
127.50 (C11), 126.09 (C4), 122.61 (C13), 115.29 (C6), 43.83 (C7),
40.47 (CMe) ppm. C19H27Cl2N3Ti (416.21): calcd. C 54.83, H 6.54,
N 10.10; found C 54.77, H 6.58, N, 9.97.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (100 mg, 0.45 mmol), toluene (2 mL), Ar1SNH2
(100 mg, 0.5 mmol), and TMSCl (0.35 mL, 2.68 mmol). S1
(175 mg, 0.43 mmol, 95%) was obtained as an orange solid and
Synthesis of SЈ1
1
was recrystallized from toluene/pentane (9:1) at –35 °C. H NMR
(250 MHz, C6D6): δ = 7.05–7.15 (m, 2 H, H3 + H5), 7.02 (dt, J =
1.5, 7.7 Hz, 1 H, H10), 6.81 (dd, J = 0.7, 5.1 Hz, 1 H, H9), 6.70–
6.78 (m, 2 H, H4 + H8), 6.64 (dd, J = 3.7, 5.1 Hz, 1 H, H6), 5.94
(s, 1 H, H12a), 5.31 (s, 1 H, H12b), 2.60 (m, 2 H, HNH), 2.26 (d, J
= 6.1 Hz, 12 H, HMe) ppm. 13C{1H} NMR (62.5 MHz, C6D6): δ =
144.20 (C1), 143.91 (C11), 141.49 (C7), 134.73 (C2), 129.53 (C3),
128.07 (C5), 126.91 (C9), 126.18 (C8), 125.83 (C10), 124.67 (C4),
122.21 (C6), 114.59 (C12), 40.51 (CMe) ppm. C16H23Cl2N3STi
(408.21): calcd. C 47.08, H 5.68, N 10.29; found C 46.81, H 5.61,
N 10.03.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (100 mg, 0.45 mmol), toluene (2 mL), ArЈ1SNH2
(100 mg, 0.5 mmol), and TMSCl (0.35 mL, 2.68 mmol). SЈ1
(140 mg, 0.34 mmol, 77%) was obtained as an orange solid. 1H
NMR (250 MHz, C6D6): δ = 6.70 (dd, J = 1.4, 7.9 Hz, 1 H, H3),
7.13 (dd, J = 1.4, 7.7 Hz, 1 H, H4), 6.92–6.99 (m, 2 H, H5 + H10),
6.81 (dd, J = 1.2, 5.1 Hz, 1 H, H9), 6.76 (dt, J = 1.3, 7.5 Hz, 1 H,
H6), 6.70 (dd, J = 3.4, 5.1 Hz, 1 H, H8), 5.73 (q, J = 7.2 Hz, 1 H,
H11), 2.69 (m, 2 H, HNH), 2.23 (t, J = 6.4 Hz, 12 H, HMe(NH)), 1.68
(d, J = 7.2 Hz, HMe) ppm. 13C{1H} NMR (62.5 MHz, C6D6): δ =
158.84 (C1), 152.86 (C7), 138.57 (C2), 127.65 (C10), 126.71 (C3),
126.30 (C5), 126.22 (C6), 124.08 (C4), 123.27 (C9), 122.99 (C8),
40.64 (CMe(NH)), 40.11 (CMe(NH)), 34.81 (C11), 23.27 (CMe) ppm.
Synthesis of O1
IR: ν = 3239 (νNH) cm–1. C16H25Cl2N3STi (410.23): calcd. C 46.84,
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), Ar1ONH2
(270 mg, 1.46 mmol), and TMSCl (1.0 mL, 7.88 mmol). O1
(470 mg, 1.20 mmol, 90%) was obtained as an orange solid and
˜
H 6.14, N 10.24, found C 46.92, H 6.43, N 10.14.
Synthesis of OЈ1
1
was recrystallized from toluene/pentane (9:1) at –35 °C. H NMR
(250 MHz, C6D6): δ = 6.97–7.15 (m, 4 H, H3 + H4 + H5 + H10),
6.73 (dt, J = 1.0, 7.4 Hz, 1 H, H6), 6.16 (d, J = 1.0 Hz, 1 H, H12a),
6.09 (dd, J = 1.8, 3.1 Hz, 1 H, H9), 5.93 (d, J = 3.1 Hz, 1 H, H8),
5.38 (d, J = 1.0 Hz, 1 H, H12b), 2.80 (m, 2 H, HNH), 2.29 (d, J =
6.1 Hz, 12 H, HNMe ) ppm. 13C{1H} NMR (62.5 MHz, C6D6): δ =
158.30 (C1), 155.542(C7), 142.28 (C10), 137.20 (C11), 132.72 (C2),
129.60 (C3), 128.01 (C5), 125.99 (C4), 122.15 (C6), 113.51 (C12),
110.94 (C9), 108.34 (C8), 40.17 (CMe) ppm. C16H23Cl2N3OTi
(392.15): calcd. C 49.00, H 5.91, N 10.72; found C 48.89, H 5.95,
N 10.58.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (100 mg, 0.45 mmol), toluene (2 mL), Ar1ONH2
(94 mg, 0.5 mmol), and TMSCl (0.35 mL, 2.68 mmol). OЈ1
(160 mg, 0.41 mmol, 91%) was obtained as an orange solid. 1H
NMR (250 MHz, C6D6): δ = 7.24 (dd, J = 1.0, 7.9 Hz, 1 H, H10),
7.09–7.12 (m, 1 H, H3), 7.04 (dd, J = 1.1, 7.7 Hz, 1 H, H5), 6.94
(dt, J = 1.4, 7.7 Hz, 1 H, H4), 6.73 (dt, J = 1.1, 7.6 Hz, 1 H, H6),
6.05–6.15 (m, 2 H, H8 + H9), 5.53 (q, J = 7.1 Hz, 1 H, H11), 2.79
(m, 2 H, HNH), 2.29 (d, J = 6.1 Hz, 12 H, HMe(NH)), 1.77 (d, J =
7.1 Hz, HMe) ppm. 13C{1H} NMR (62.5 MHz, C6D6): δ = 160.32
(C1), 158.84 (C7), 141.05 (C10), 136.91 (C2), 126.80 (C3), 126.63
(C5), 126.51 (C4), 123.08 (C6), 109.90 (C9), 105.14 (C8), 40.48
Synthesis of Ph2
This compound was prepared using the general procedure starting
(CMe(NH)), 40.27 (CMe(NH)), 33.40 (C11), 20.30 (CMe) ppm. IR: ν =
˜
from Ti(NMe2)4 (200 mg, 0.89 mmol), toluene (2 mL), Ar2PhNH2 3280, 3251 (νNH) cm–1. C16H25Cl2N3OTi (394.16): calcd. C 48.75,
(208 mg, 1.00 mmol), and TMSCl (0.7 mL, 5.5 mmol). Ph2 H 6.39, N 10.66; found C 48.63, H 6.62, N 10.83.
Eur. J. Inorg. Chem. 2012, 97–111
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107

C. Lorber et al.
FULL PAPER
Synthesis of PhЈ2
1.34 mmol), toluene (2 mL), ArЈ2NNH2 (280 mg, 1.42 mmol), and
TMSCl (1.1 mL, 8.7 mmol). A grey solid was obtained, which was
shown by NMR to contain a mixture of NЈ2 and NЈЈ2 (4:1)
(515 mg). The complexes were separated by selective crystallization
(toluene, –35 °C). Yield for NЈ2: 385 mg (77%).
Method 2: ArЈ2NNH2 (227 mg, 1.07 mmol) was added at room tem-
perature to a toluene solution (6 mL) of [Ti(=NtBu)Cl2(NHMe2)2]
(300 mg, 1.07 mmol). After stirring overnight, the volatiles were
removed under reduced pressure, the residue was washed with pen-
tane/toluene (9:1) (3ϫ2 mL), and concentrated under vacuum to
afford NЈ2 (390 mg, 1.05 mmol, 98%) as a tan solid. 1H NMR
(400 MHz, C6D6): δ = 8.65–8.70 (m, 1 H, H13), 7.01–7.10 (m, 2 H,
H3 + H5), 6.89 (t, J = 7.4 Hz, 1 H, H4), 6.77 (t, J = 7.4 Hz, 1 H,
H11), 6.71 (d, J = 7.6 Hz, 1 H, H6), 6.43 (d, J = 7.6 Hz, 1 H, H10),
6.40 (t, J = 6.4 Hz, 1 H, H12), 4.10 (d, J = 13.3 Hz, 1 H, H8), 3.83–
3.92 (m, 1 H, H7), 3.06–3.18 (m, 1 H, HNH), 2.53 (t, J = 6.0 Hz, 6
H, HMe(NH)), 2.13 (dd, J = 8.2, 13.3 Hz, 1 H, H8), 0.98 (d, J =
6.9 Hz, 3 H, HMe) ppm. 13C{1H} NMR (100 MHz, C6D6): δ =
162.38 (C9), 161.12 (C1), 149.74 (C13), 143.74 (C2), 138.81 (C11),
125.80 (C3), 125.30 (C10), 124.03 (C5), 121.72 (C4), 120.85 (C12),
118.92 (C6), 48.15 (C8), 41.33 (CMe(NH)), 41.05 (CMe(NH)), 37.48
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), ArЈ2PhNH2
(300 mg, 1.42 mmol), and TMSCl (1.1 mL, 8.7 mmol). PhЈ2
(330 mg, 0.79 mmol, 59%) was obtained as an orange solid. 1H
NMR (300 MHz, C6D6): δ = 7.28–7.34 (m, 2 H, H10), 7.18–7.24
(m, 1 H, H11), 7.02–7.15 (m, 3 H, H5 + H9), 6.95–7.00 (m, 1 H,
H3), 6.91 (dt, J = 1.6, 7.5 Hz, 1 H, H4), 6.80 (dt, J = 1.3, 7.5 Hz,
1 H, H6), 4.49 (m, 1 H, H12), 2.87 (m, 2 H, H7), 2.61 (m, 2 H,
HNH), 2.23 (t, J = 5.9 Hz, 12 H, HMe(NH)), 1.29 (d, J = 7.0 Hz, 3
H, HMe) ppm. 13C{1H} NMR (75 MHz, C6D6): δ = 159.16 (C1),
141.57 (C8), 129.20 (C2), 127.86 (C10), 127.06 (C9), 125.90 (C3),
125.85 (C5), 125.58 (C4), 123.06 (C6), 44.90 (C7), 40.72
(CMe(NH)), 39.97 (CMe(NH)), 34.33 (C12), 22.13 (CMe) (C11 signal not
observed; probably obscured by C6D6 signals) ppm.
C19H29Cl2N3Ti (418.23): calcd. C 54.56, H 6.99, N 10.05; found C
54.59, H 6.76, N 9.95.
(C7), 16.15 (CMe) ppm. IR: ν = 3217 (νNH) cm–1. C16H21Cl2N3Ti
˜
(374.13): calcd. C 51.36, H 5.66, N 11.23; found C 51.40, H, 5.91,
N, 11.46.
Synthesis of NЈЈ2: NЈЈ2 was obtained as a minor product in the
synthesis of complex NЈ2 (see Method 1, above). Crystals suitable
for an X-ray diffraction study were obtained from recrystallization
of a mixture of NЈ2 and NЈЈ2 from C6D6/CDCl3 (9:1) at –35 °C.
Synthesis of N2
Synthesis of Complex NЈЈЈ2: NЈЈЈ2 was obtained in low amount as
an intermediate in the synthesis of N2 (see Method 2, above). Crys-
tals suitable for X-ray diffraction were obtained from recrystalli-
zation from a mixture of toluene/pentane (–35 °C).
Synthesis of N3
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), Ar2NNH2
(280 mg, 1.42 mmol), and TMSCl (1.1 mL, 8.7 mmol). N2 (515 mg,
1.28 mmol, 95%) was obtained as an orange solid and was recrys-
tallized from toluene/pentane (9:1) at –35 °C. 1H NMR (300 MHz,
C6D6): δ = 8.36–8.44 (m, 1 H, H13), 7.15–7.22 (m, 2 H, H10 + H12),
6.95–7.10 (m, 3 H, H3 + H4 + H5), 6.90–6.95 (m, 1 H, H8), 6.77
(dt, J = 1.5, 7.4 Hz, 1 H, H6), 6.59–6.67 (m, 1 H, H11), 3.68–3.84
(m, 2 H, HNH), 2.60 (d, J = 1.4 Hz, 3 H, HMe), 2.40 (d, J = 6.1 Hz,
12 H, HMe(NH)) ppm. 13C{1H} NMR (75 MHz, C6D6): δ = 158.12
(C9), 157.60 (C1), 149.24 (C13), 142.69 (C7), 138.74 (C2), 135.78
(C11), 129.34 (C8), 127.46 (C4), 127.16 (C3), 125.62 (C5), 124.02
(C10), 122.10 (C6), 120.85 (C12), 40.44 (CMe(NH)), 20.64 (CMe) ppm.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (6 mL), Ar3NNH2
(320 mg, 1.34 mmol), and TMSCl (1.0 mL, 7.9 mmol). N3 (560 mg,
1.26 mmol, 94%) was obtained as an orange solid and was recrys-
tallized from toluene/pentane (9:1) at –35 °C. 1H NMR (300 MHz,
C6D6): δ = 8.11 (d, J = 4.3 Hz, 1 H, H14), 7.84 (d, J = 7.8 Hz, 1
H, H3), 6.98–7.16 (m, 3 H, H4 + H5 + H13), 6.76 (m, 1 H, H11),
6.69 (d, J = 7.8 Hz, 1 H, H6), 6.57 (dd, J = 5.3, 6.7 Hz, 1 H, H12),
4.66–4.85 (m, 2 H, HNH), 2.88–3.00 (m, 2 H, H9), 2.52 (d, J =
6.0 Hz, HMeNH), 2.40–2.48 (m, 2 H, H8), 1.61 (s, 6 H, HMe) ppm.
13C{1H} NMR (75 MHz, C6D6): δ = 163.49 (C10), 159.85 (C1),
148.82 (C14), 136.98 (C2), 136.27 (C12), 132.99 (C3), 126.75 (C5),
126.26 (C4), 123.11 (C11), 122.63 (C6), 120.54 (C13), 42.25 (C9),
40.36 (CMeNH), 38.46 (C7), 35.03 (C8), 29.09 (CMe) ppm. 15N NMR
(50.71 MHz, C6D5CD3): δ = 298 K –75.5 (NPy), –343.0 (NHMe2);
IR: ν = 3228 (νNH) cm–1. C18H26Cl2N4Ti (417.20): calcd. C 51.82,
˜
H 6.28, N 13.43; found C 51.65, H 6.58, N 13.39.
Synthesis of NЈ2
183 K –77.6 (NPy), –339 (NH···NPy), –342 (NHMe ) ppm. IR: ν =
˜
2
Method 1 (general procedure): This compound was prepared using
3285 (νNH) cm–1. C20H32Cl2N4Ti (447.27): calcd. C 53.71, H 7.21,
the general procedure starting from Ti(NMe2)4 (300 mg,
N 12.53; found C 53.69, H 7.39, N 12.34.
108
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 97–111

Ti Precatalysts for Ethylene Polymerization
Synthesis of NЈ3
1.22 mmol, 91%) was obtained as an orange solid. 1H NMR
(300 MHz, C6D6): δ = 7.28 (dd, J = 0.9, 7.7 Hz, 1 H, H3), 7.16–
7.20 (m, 1 H, H12), 6.96 (dt, J = 1.4, 7.7 Hz, 1 H, H5), 6.89–6.93
(m, 1 H, H4), 6.73 (dt, J = 1.2, 7.5 Hz, 1 H, H6), 6.40 (dd, J = 0.7,
3.1 Hz, 1 H, H10), 6.19 (dd, J = 1.9, 3.0 Hz, 1 H, H11), 3.40–3.47
(m, 2 H, H8), 3.15–3.22 (m, 2 H, H7), 2.69–2.82 (m, 2 H, HNH),
2.24 (d, J = 6.2 Hz, 12 H, HMe) ppm. 13C{1H} NMR (75 MHz,
C6D6): δ = 159.82 (C1), 156.22 (C9), 140.85 (C12), 134.05 (C2),
128.77 (C3), 126.76 (C5), 126.38 (C6), 122.92 (C4), 110.45 (C11),
105.73 (C10), 40.34 (CMe), 30.77 (C7), 29.62 (C8) ppm. IR: ν = 3262,
˜
3227 (νNH) cm–1. C16H25Cl2N3OTi (394.16): calcd. C 48.75, H 6.39,
A of toluene solution (6 mL) of N3 (205 mg, 0.46 mmol) and
TMSCl (0.7 mL, 5.5 mL) was left for 10 d at room temp. Removing
the volatiles under vacuum and washing with pentane afforded NЈ3
(160 mg, 0.40 mmol, 87%) as a yellow solid. Recrystallization from
toluene/pentane at –35 °C gave crystals suitable for X-ray diffrac-
tion. 1H NMR (400 MHz, C6D6): δ = 8.37–8.40 (m, 1 H, H14),
7.17–7.24 (m, 2 H, H3 + H5), 7.01–7.08 (m, 1 H, H4), 6.84–6.89
(m, 1 H, H6), 6.77 (dt, J = 1.6, 7.8 Hz, 1 H, H12), 6.47 (d, J =
7.8 Hz, 1 H, H11), 6.34–6.39 (m, 1 H, H13), 3.18–3.28 (m, 1 H,
N 10.66; found C 48.65, H 6.48, N 10.68.
Synthesis of Ph3
H
NH), 2.54 (d, J = 6.1 Hz, 6 H, HMeNH), 1.37 (s, 6 H, HMe) ppm.
13C{1H} NMR (100 MHz, C6D6): δ = 162.87 (C10), 159.85 (C1),
149.31 (C14), 138.99 (C12), 138.15 (C2), 128.73 (C3), 127.63 (C5),
126.23 (C4), 125.19 (C11), 122.91 (C6), 120.42 (C13), 44.95
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), Ar3PhNH2
(283 mg, 1.34 mmol), and TMSCl (1 mL, 8.0 mmol). Ph3 (470 mg,
1.13 mmol, 84%) was obtained as an orange solid. 1H NMR
(400 MHz, C6D6): δ = 7.30–7.34 (m, 2 H, H12), 7.16–7.28 (m, 3 H,
H3 + H11), 7.04–7.10 (m, 1 H, H4), 6.94–7.00 (m, 2 H, H5 + H13),
6.79 (dt, J = 1.3, 7.5 Hz, 1 H, H6), 3.07–3.13 (m, 2 H, H9), 2.89–
3.96 (m, 2 H, H7), 2.66–2.76 (m, 2 H, HNH), 2.24 (d, J = 6.1 Hz,
12 H, HMe), 2.05–2.15 (m, 2 H, H8) ppm. 13C{1H} NMR
(100 MHz, C6D6): δ = 159.94 (C1), 142.94 (C10), 135.51 (C2), 128.80
(C12), 128.65 (C13), 128.45 (C11), 126.53 (C3), 126.04 (C5), 125.78
(C4), 122.88 (C6), 40.34 (CMe), 36.27 (C9), 33.51 (C7), 30.71 (C8)
(CMe-NH), 40.64 (C7), 39.44 (C8 + C9), 35.95 (CMe) ppm. IR: ν =
˜
3226 (νNH) cm–1. C18H25Cl2N3Ti (402.18): calcd. C 53.75, H 6.27,
N 10.45; found C 53.70, H 6.22, N 10.39.
Synthesis of S2
ppm. IR: ν = 3262 (νNH) cm–1. C19H29Cl2N3Ti (418.23): calcd. C
˜
54.56, H 6.99, N 10.05; found C 54.31, H 7.16, N 10.08.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), Ar2SNH2
(272 mg, 1.34 mmol), and TMSCl (1 mL, 8.03 mmol). S2 (490 mg,
1.20 mmol, 89%) was obtained as an orange solid and was recrys-
tallized from toluene/pentane (9:1) at –35 °C. 1H NMR (300 MHz,
C6D6): δ = 7.28 (dd, J = 1.0, 7.7 Hz, 1 H, H3), 7.10–7.19 (m, 1 H,
H4), 6.96 (dt, J = 1.5, 7.7 Hz, 1 H, H6), 6.87–6.92 (m, 1 H, H12),
6.78–6.86 (m, 2 H, H5 + H11), 6.73 (dt, J = 1.2, 7.5 Hz, 1 H, H10),
3.36–3.45 (m, 2 H, H8), 3.24–3.33 (m, 2 H, H7), 2.66–2.82 (m, 2 H,
HNH), 2.25 (d, J = 6.1 Hz, 12 H, HMe) ppm. 13C{1H} NMR
(75 MHz, C6D6): δ = 159.83 (C1), 144.87 (C9), 133.77 (C2), 129.00
(C12), 126.97 (C3), 126.80 (C5), 126.45 (C6), 125.06 (C4), 123.07
Ethylene Polymerization Studies: All catalytic reactions were car-
ried out in a 110 mL stainless steel autoclave equipped with a me-
chanical stirrer. A toluene solution of the complex was introduced
under an ethylene atmosphere, and the cocatalyst was added. The
reactor was sealed and fed with ethylene up to 10 bar. The reactor
was heated to the desired temperature with stirring and the pressure
adjusted to 20 bar. After 1 h at constant pressure, the reactor was
cooled to room temperature and depressurized. The catalyst and
the cocatalyst were quenched by addition of 10% HCl in MeOH.
The polymer formed was collected by filtration, washed with meth-
anol, and dried in vacuo at 60 °C.
(C11), 122.91 (C10), 40.39 (CMe), 34.09 (C7), 31.49 (C8) ppm. IR: ν
Supporting Information (see footnote on the first page of this arti-
cle): VT NMR experiments and synthetic details for all compounds
prepared in this article.
˜
= 3288, 3253 (νNH) cm–1. C16H25Cl2N3STi (410.23): calcd. C 46.84,
H 6.14, N 10.24; found C 46.63, H 6.25, N 10.21.
Synthesis of O2
Acknowledgments
The research was supported by the Centre National de la Re-
cherche Scientifique (CNRS) and the IFP Energies Nouvelles
(IFPEN). The authors thank Kane Jacob for technical assistance
and Dr. Yannick Coppel for conducting NOESY and VT-NMR
experiments.
This compound was prepared using the general procedure starting
from Ti(NMe2)4 (300 mg, 1.34 mmol), toluene (2 mL), Ar2ONH2
(250 mg, 1.34 mmol), and TMSCl (1 mL, 8.03 mmol). O2 (480 mg,
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109

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Received: September 21, 2011
Published Online: November 24, 2011
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