Titanium complexes of chelating, dianionic O,S,O-bisphenolato ligands: Syntheses, characterisation, and catalytic activity

Article abstract of DOI:10.1002/ejic.200400713

Titanium complexes based on 2,2′-thiobis[4-(1,1,3,3-tetramethylbutyl) phenolato] (tbop) are prepared by reaction of TiCl₄ or Ti(NMe ₂)₄ with the parent biphenol. Three new complexes are reported: [Ti₂(μ-tbop-κ³O,S,O)(μ-tbop- κ²O,O)-(tbop-K³O,S,O)Cl₂] (1)·2 CH₃CN, [Ti₂(μ-tbop-κ³O,S,O) ₂Cl₄] (2) and [Ti(tbop-K³O,S,O)₂] (3). Substitution of the chlorides in 1 and 2 by 2,6-diisopropylphenolato and imido (NtBu) ligands generates the new compounds [Ti₂(μ-tbop- κ³O,S,O)₂-Cl₂(dipp)₂] (4)·Et₂O and [Ti₂(μ-tbop-κ³O,S, O)₂-(NH₂tBu)₂] (5), respectively. Treatment of 5 with crude Me₃-SiCl, containing Me₃SiOH, produces [Ti(tbop-κ³O,S,O)Cl(O-SiMe₃) (NH₂tBu)] (6). Reaction of 2 with an excess of NHiPr₂ provides a mixture of compounds: ionic [NH₂iPr₂][Ti(tbop-κ³O,S, O)C1₃] (7)·CH₂Cl₂ and molecular [Ti ₂(μ-tbop-κ³O,S,O)₂-Cl ₂(NiPr₂)₂] (8). The structures of 1-8 were confirmed by NMR spectroscopy; complexes 1, 5, 6 and 7 were further investigated by X-ray crystallography. Compounds 1, 2, 4 and 5, when supported on MgCl ₂ and activated with alkylaluminiums, effectively polymerise ethene. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejic.200400713

FULL PAPER
Titanium Complexes of Chelating, Dianionic O,S,O-Bisphenolato Ligands:
Syntheses, Characterisation, and Catalytic Activity
Zofia Janas,*[a] Lucjan B. Jerzykiewicz,[a] Katarzyna Przybylak,[a] Piotr Sobota,[a]
[b]
[a]
´
Krzysztof Szczegot, and Dorota Wisniewska
Keywords: Polymerization / Titanium / O,S ligands
Titanium complexes based on 2,2Ј-thiobis[4-(1,1,3,3-tet-
ramethylbutyl)phenolato] (tbop) are prepared by reaction of
TiCl4 or Ti(NMe2)4 with the parent biphenol. Three new com-
plexes are reported: [Ti2(μ-tbop-κ3O,S,O)(μ-tbop-κ2O,O)-
(tbop-κ3O,S,O)Cl2] (1)·2CH3CN, [Ti2(μ-tbop-κ3O,S,O)2Cl4]
(2) and [Ti(tbop-κ3O,S,O)2] (3). Substitution of the chlorides
in 1 and 2 by 2,6-diisopropylphenolato and imido (NtBu) li-
gands generates the new compounds [Ti2(μ-tbop-κ3O,S,O)2-
Cl2(dipp)2] (4)·Et2O and [Ti2(μ-tbop-κ3O,S,O)2(NtBu)2-
(NH2tBu)2] (5), respectively. Treatment of 5 with crude Me3-
SiCl, containing Me3SiOH, produces [Ti(tbop-κ3O,S,O)Cl(O-
SiMe3)(NH2tBu)] (6). Reaction of 2 with an excess of NHiPr2
provides a mixture of compounds: ionic [NH2iPr2][Ti(tbop-
κ3O,S,O)Cl3] (7)·CH2Cl2 and molecular [Ti2(μ-tbop-κ3O,S,O)2-
Cl2(NiPr2)2] (8). The structures of 1–8 were confirmed by
NMR spectroscopy; complexes 1, 5, 6 and 7 were further in-
vestigated by X-ray crystallography. Compounds 1, 2, 4 and
5, when supported on MgCl2 and activated with alkylalumin-
iums, effectively polymerise ethene.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
well.[9,10] However, there are very few reports of structural
data on S-bridged titanium analogues, especially of their
ligand modifications.[5,11,12] This encouraged us to investi-
gate the titanium compounds with the tridentate O,S,O-
thiobisphenolato ligand 2,2Ј-thiobis[4-(1,1,3,3-tetrameth-
ylbutyl)phenolato] (tbop). In addition to the S bridge, the
tbop ligand seemed to have one more attractive feature: the
long, sterically hindered auxiliary group on the thiobis-
phenolato ligand sufficiently increases solubility of the cata-
lyst in hydrocarbons.
Recently we described the synthesis and structural char-
acterisation of the mixed-ligand complexes [Ti2(μ-OR)2(X)
2-(tbop-κ3O,S,O)2] (R = Me, Et; X = OR or Me).[13] In
these complexes the tbop ligand was found to coordinate to
the titanium in a fac fashion. [Ti2(μ-OR)2(X)2(tbop-
κ3O,S,O)2] complexes supported on MgCl2 and activated
with AlEt2Cl or AlEt2Cl/AlEt3 show very high activity in
ethene polymerisation. The narrow molecular-weight distri-
bution obtained for these systems is indicative of the opera-
tion of typical heterogeneous single-site catalyst behaviour.
We have been exploringthe use of the tbop ligand for the
preparation of new titanium complexes that might serve as
catalysts for the ethene polymerisation process. We report
here their syntheses and structures, along with catalytic be-
haviour in ethene polymerisation.
Introduction
Titanium complexes [Ti2(μ-X)2X2(tbmp-κ3O,S,O)2] de-
rived from the sulfide-linked bisphenol tbmpH2 [tbmpH2 =
2,2Ј-thiobis(6-tert-butyl-4-methylphenol); X = Cl, OiPr]
were first reported by Kakugo et al. to be highly active for
the polymerisation of ethene, propene, styrene and dienes,
as well as the copolymerisation of ethene with styrene, upon
activation with methylalumoxane (MAO).[1–3] These tita-
nium complexes were found to be an order of magnitude
more active than the methylene-bridged chelating aryloxide
complexes of the type [TiX2(mbmp)] [mbmp = 2,2Ј-methyl-
enebis(6-tert-butyl-4-methylphenolato)].[4] This is in quali-
tative agreement with theoretical studies that showed the S-
bridged chelating phenolates to have lower insertion barri-
ers than their methylene-bridged or directly bridged ana-
logues.[5–7] Although the Ti–S interaction in [Ti2(μ-X)2-
X2(tbmp-κ3O,S,O)2] is weak, it is likely to be of importance
in stabilizing the active cationic species, facilitating its for-
mation from the former and MAO and making the coordi-
nation of the counterion less tight.[8] Bisphenolato- and bis-
naphtholatotitanium complexes have been well character-
ised both structurally and spectroscopically, and the kin-
etics and thermodynamics of intra- and intermolecular re-
arrangement in bisnaphtholates has been described as
[a] Faculty of Chemistry, University of Wrocław,
14 F. Joliot-Curie Street, 50-383 Wrocław, Poland
Fax: +48-71-3282348
E-mail: zj@wchuwr.chem.uni.wroc.pl
[b] Institute of Chemistry, University of Opole
48 Oleska Street, 45-052 Opole, Poland
Results and Discussion
The reaction between TiCl4 and tbopH2 in n-hexane, de-
pending on the stoichiometry (1:1.5 and 1:1), produces
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DOI: 10.1002/ejic.200400713
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Z. Janas et al.
FULL PAPER
compounds
[Ti2(μ-tbop-κ3O,S,O)(μ-tbop-κ2O,O)(tbop- and two sulfur links [S(1), S(3)] of the tbop ligands occupy
κ3O,S,O)Cl2] (1)·2CH3CN and [Ti2(μ-tbop-κ3O,S,O)2Cl4] the apical sites. The third sulfur atom [S(2)] isnot bonded
(2) with concomitant elimination of three and two equiva- to any Ti atom. The average titanium–sulfur bond length
lents of HCl, respectively (Scheme 1). Surprisingly, reaction of 2.735(2) Å is longer than those found in other complexes,
of TiCl4 with two equivalents of tbopH2 in diethyl ether did for example[Ti2(μ-OiPr)2(OiPr)2(tbmp-κ3O,S,O)2] [tbmp =
not lead to the anticipated [Ti(tbop-κ3O,S,O)2] (3) but to a 2,2Ј-thiobis(6-tert-butyl-4-methylphenolato;
good yield of complex 2. Fortunately, compound 3 is avail- 2.719(1) Å],[Ti(tbmp-κ3O,S,O)(C6H4CH2NMe2-2-κ2C,N)
able by simple addition of tbopH2 to [Ti(NMe2)4]. When Cl] [2.704(1) Å]and [Ti(tbmp-κ3O,S,O)Cl(OiPr)(HOiPr)]
the reaction of tbopH2 with neat TiCl4 is carried out in [2.693(1) Å],[5,11] and shorter than those in [Ti2(μ-OEt)
toluene, a mixture of 1, 2 and 3 is formed, from which only 2(OEt)2(tbop-κ3O,S,O)2] [2.800(1) Å] and [{Ti2(μ-OEt)
compound 1 could be isolated as an analytically pure pro- 2(tbop-κ3O,S,O)2}2-(μ-O)2] [2.762(2) Å].[13] The average Ti–
duct. The IR spectra of 1 and 2 show characteristic modes O distances of 1.832(3) Å and 2.040(3) Å are in the ex-
for terminal coordinated chlorides at 380 and 378 cm–1, pected range for TiIV complexes with non-bridging and
respectively.
bridging aryloxo ligands, respectively.[4] The terminal Ti–Cl
distances of 2.254(2) Å and 2.265(2) Å are slightly shorter
(by less than 0.01 Å) than those in [Ti2(μ-Cl)2Cl2(tbmp-
κ3O,S,O)2].[12]
Figure 1. Molecular structure of 1·2CH3CN. Selected bond lengths
[Å] and angles [°]: Ti(1)–O(11) 1.833(3), Ti(1)–O(21) 1.839(3),
Ti(1)–O(41) 2.024(3), Ti(1)–O(61) 2.048(3), Ti(1)–Cl(1) 2.254(2),
Ti(1)–S(1) 2.752(2), Ti(2)–Cl(2) 2.265(2), Ti(2)–O(31) 1.793(3),
Ti(2)–O(41) 2.041(3), Ti(2)–O(51) 1.863(3), Ti(2)–O(61) 2.048(3),
Ti(2)–S(3) 2.728(2); O(41)–Ti(1)–O(61) 71.88(11), O(21)–Ti(1)–S(1)
75.72(9), O(31)–Ti(2)–O(61) 149.18(12), O(41)–Ti(2)–O(61)
71.54(10), O(61)–Ti(2)–S(3) 74.19(8).
Scheme 1.
The structure of 1 (Figure 1) consists of discrete mole-
cules of dimer [Ti2(μ-tbop-κ3O,S,O)(μ-tbop-κ2O,O)(tbop-
κ3O,S,O)Cl2] together with two MeCN molecules of crystal-
lisation. The coordination environment about the Ti centres
bridged by two oxygen atoms of tbop ligands is best de-
scribed as highly distorted octahedral. The major distor-
1
The H NMR spectra of 1 in C6D6 show more peaks
tions from idealised octahedral geometry are for the O(41)– corresponding to the tbop ligand than would be expected
Ti(1)–O(61), O(21)–Ti(1)–S(1), O(31)–Ti(2)–O(61), O(41)– from the crystal structure. These data suggest that the struc-
Ti(2)–O(61) and O(61)–Ti(2)–S(3) angles, with values of ture of 1 does not stay intact in solution at room tempera-
71.88(11)°, 75.72(9)°, 149.18(12)°, 71.54(10)° and 74.19(8)°, ture. It is most likely that compound 1 undergoes an intra-
respectively. Two tbop ligands in 1 bridge titanium centres molecular rearrangement in solution probably to the chlo-
and the third one is facially coordinated to Ti(1). All the ride- and oxygen-bridged dinuclear derivative A (Scheme 2).
oxygen atoms of the tbop ligands are engaged in the forma- This closely corresponds to the well-documented mecha-
tion of the equatorial planes, while the terminal chlorides nism for intramolecular exchange in [(R2bino)Ti(OiPr)2]2
1064
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Titanium Complexes of Chelating, Dianionic O,S,O-Bisphenolato Ligands
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(R2bino = 3,3Ј-disubstituted-1,1Ј-bi-2-naphtholates)[10] and
[(tartrate)Ti(OiPr)2]2 proposed by Sharpless and Finn.[14]
Scheme 3.
coordination sphere. Unfortunately, the poor-quality X-ray
data for 4 do not allow a discussion of bond lengths and
angles.[15]
Treatment of 2 with one equivalent of Li2NtBu and
NH2tBu per titanium atom in diethyl ether produced [Ti2(μ-
tbop-κ3O,S,O)2(NtBu)2(NH2tBu)2] (5) in high yield. The
coordination of both amine (NH2tBu) and imido (NtBu)
ligands to the titanium centres is implied by the presence of
two inequivalent tBu groups and the broad resonance for
1
the NH2 group in the H NMR spectrum and by ν(NH)
bands in the IR spectra (see Experimental Section). Single-
crystal X-ray diffraction clearly confirms (Figure 2) that 5
contains an approximately linear Ti=NtBu linkage
[166.4(3)°], with a Ti–Nimido distance [1.710(3) Å] consistent
with a formal metal–nitrogen triple bond (σ2π4),[16] and a
Scheme 2.
Fragmentation of A through the interruption of chloride
and oxygen bridges would produce compounds [Ti2(μ-tbop-
κ3O,S,O)2Cl4] (2) and [Ti(tbop-κ3O,S,O)2] (3). All these
compoundscould participate in a facile equilibrium involv-
ing the interconversion of chemically distinct compounds.
Partial confirmation of this hypothesis is the fact that com-
pound 1 gives the same products upon substitution of its
chlorides as 2 (described below). The presence of com-
1
pound 3 was confirmed from the H NMR spectrum.
Attempts to grow crystals of 2 suitable for X-ray diffrac-
tion proved unsuccessful. Therefore, we tried to examine its
structure by indirect methods, by investigating the products
of substitution of the chlorides in 2 (Scheme 3).
We found that the reaction of 2 with Li(dipp) (dipp =
2,4-diisopropylphenolato) in diethyl ether provides orange-
red crystals of [Ti2(μ-tbop-κ3O,S,O)2Cl2(dipp)2] (4)·Et2O in
1
good yield. The H NMR spectrum of 4 contains septet
and doublet resonances for the isopropyl substituents of the
dipp groups and similar resonance sets for the tbop ligand
to those detected for 2, together with resonances corre-
sponding to the free diethyl ether. Single-crystal X-ray dif-
fraction of 4 showed it to be composed of dimeric [Ti2(μ-
tbop-κ3O,S,O)2Cl2(dipp)2] and one Et2O molecule of crys-
tallisation. Two titanium centres are linked by a double
bridge formed from the oxygen atoms of the tbop ligands.
The chloride atoms and dipp ligands are terminally coordi-
Figure 2. Molecular structure of 5. Selected bond lengths [Å] and
angles [°]: Ti–N(1) 1.710(3), Ti–O(11) 2.013(2), Ti–O(21)i 2.010(3),
Ti–N(2) 2.255(3), Ti–O(21) 2.298(2), Ti–S 2.587(2); Ti–N(1)–C(51)
166.4(3), Ti–N(2)–C(61) 126.5(2). Symmetry operation: (i) –x +
nated to each titanium atom to complete the octahedral 1, –y, –z.
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bent Ti–NH2tBu unit with a Ti–N bond length and a Ti– [d(C···O): 3.3033 Å; C–H–O: 136.00°]hydrogen bonds are
N–C angle of 2.255(3) Å and 126.5(2)°, respectively. observed. One may suppose that compound 6 might be an-
The amine and imido groups are terminally coordinated intermediate species in the Ti=NtBu linkage formation.
to the titanium centres. A similar coordination of both
amine and imido groups to the titanium centres is found in
the tetramer [Ti4(μ-Cl)4(μ3-Cl)2Cl2(NtBu)4(NH2tBu)4],
which is obtained from the direct reaction of TiCl4 and four
equivalents of tBuN(H)SiMe3.[17] The octahedral titanium
centres in 5 are bridged by two oxygen atoms [O(21), O(21)
(i)] of the tbop ligands. These two oxygens form the equato-
rial planes together with sulfur and imido nitrogen atoms,
while the remaining oxygens [O(11), O(11)(i)] and amine ni-
trogens [N(2) and N(2)(i)] occupy the apical sites. The Ti–S
bond length of 2.587(2) Å is significantly shorter than that
in 1 and is one of the shortest Ti–S lengths so far reported
in the literature of titanium S-bridged bisaryloxo com-
plexes.[5,11–13] Typically, it is observed that the Ti-μ-OAr dis-
tances are a minimum of 0.1 Å longer than terminal Ti–
OAr bonds, as was found for 1. However, the Ti–O bond
distances in 5 do not reveal this tendency and show a sig-
nificant variation. These variations could be caused by the
trans interactions of bridging O(21) and O(21)(i) atoms with
Figure 3. Molecular structure of 6. Selected bond lengths [Å] and
imido N(1), N(1)(i) atoms and S, S(i) atoms, respectively, as
angles [°]: Ti–Cl 2.385(1), Ti–S(1) 2.757(1), Ti–N 2.232(2), Ti–O(1)
well as terminal O(11) and O(11)(i) atoms situated in axial
1.866(2), Ti–O(2) 1.874(2), Ti–O(3) 1.7758(2); S(1)–Ti–O(3) 174.32,
O(2)–Ti–Cl 159.18(6), N–Ti–O(1) 158.69(9), Ti–N–C(41)
positions with amine N(2) and N(2)(i) atoms, respectively.
130.43(17).
On the other hand, an increased axial Ti–O distance is ex-
pected, because axial ligands generally engender more se-
vere steric interactions and experience greater competition
for empty dπ-bonding orbitals than analogous equatorial
ligands.[18] These two effects sufficiently influence the varia-
tion in Ti–O bond distances, although the influence of crys-
tal packingcannot be excluded.
We suggest that the interaction of 5 with crude Me3SiCl
generates a monomeric compound B (Scheme 4), which im-
mediately reacts with Me3SiOH (a product of the hydrolysis
of Me3SiCl that is present in the crude sample) to form 6
On the basis of structures 4 and 5 it seems most likely
that complex 2 is a dimer in which the titanium centres are
doubly bridged by oxygen atoms of the tbop ligands and
the chlorides are coordinated terminally. This is in contrast
to [Ti2(μ-Cl)2Cl2(tbmp-κ3O,S,O)2], reported by Nakamura
and Okuda, which has a chloro-bridged binuclear structure
with tbmp ligands facially coordinated to each titanium
centre,[12] probably because of the bulky tBu substituents in
the tbmp ligands.
Addition of four equivalents of crude Me3SiCl to 5 in
diethyl ether led unexpectedly to yellow crystals of [Ti(tbop-
κ3O,S,O)Cl(OSiMe3)(NH2tBu)] (6) in low yield. The X-ray
structure of 6 (Figure 3) displays a distorted octahedral ge-
ometry around the titanium centre with the tbop ligand co-
ordinated in a fac fashion. The oxygen atom [O(3)] of the
OSiMe3 ligand and the sulfur atom of the tbop group oc-
cupy the apical positions, while oxygens atoms O(1) and
O(2) of the tbop ligand, together with the nitrogen atom of
NH2tBu, occupy the equatorial plane. The Ti–S distance of
2.757(1) Å is similar to those found in 1 and significantly
longer than those detected in 5. The Ti–Oaryloxo [av.
1.87(2) Å], Ti–Oalkoxo [1.7758(2) Å] and Ti–Cl [2.385(1) Å]
distances are in the expected range for TiIV complexes with
non-bridging aryloxo[4] and alkoxo ligands[12] and terminal
chlorides.Interestingly, intramolecular N–H···Cl [d(N···Cl):
3.4179 Å; N–H–Cl: 169.00°] and C(44)–H(44C)···O(2) Scheme 4.
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Titanium Complexes of Chelating, Dianionic O,S,O-Bisphenolato Ligands
FULL PAPER
with elimination of HCl. However, when freshly distilled
Me3SiCl was used, no formation of 6 was observed and a
mixture of B, NH2tBu·HCl, amido and imido products was
1
identified by H NMR and IR spectroscopy.
The reaction of 2 with two equivalents of NHiPr2 in di-
ethyl ether results in the formation of two products: the
ionic complex [NH2iPr2][TiCl3(tbop-κ3O,S,O)] (7) and the
molecular complex [Ti2(μ-tbop-κ3O,S,O)2Cl2(NiPr2)2] (8)
(Scheme 5).
Figure 4. Molecular structure of the [Ti(tbop-κ3O,S,O)Cl3]– anion
in 7·CH2Cl2. Selected bond lengths [Å]: Ti–Cl(1) 2.270(2), Ti–Cl(3)
2.369(2), Ti–Cl(2) 2.380(2), Ti–S 2.652(2), Ti–O(11) 1.863(2), Ti–
O(12) 1.884(2).
Complexes 1, 2, 4 and 5 were tested in ethene polymeri-
sation. Catalysts based on these compounds were prepared
in n-hexane by milling (see Experimental Section) a slurry
of [MgCl2(THF)2] with the titanium compound (10:1) and
AlEt2Cl as cocatalyst. Prior to the polymerisation, ethene
was passed through a suspension of the catalyst. Then, an
additional amount of organoaluminium compound [Al-
(iBu)3 or MAO] was added to the catalyst dispersed in the
prepolymer to form a highly active catalyst. Thus, the pol-
ymerisation of ethene was performed in a two-step process.
The aim of the first step (very low Al:Ti molar ratio, nor-
mal pressure of monomer, very low rate of polymerisation)
was to prepare granules of polymer containing dispersed
catalyst. These granules act as a “microreactor” in the sec-
ond step of the polymerisation with a high rate (Granular
Reactor Technology). This method gave PE yields twice as
high as those obtained with a one-stage activation process.
The ethene polymerisation results and polymer characteri-
sation data are summarised in Table 1.
Scheme 5.
Crystals of 7 consist of [NH2iPr2]+ cations and [Ti(tbop-
κ3O,S,O)Cl3]– anions in a 1:1 ratio and one CH2Cl2 mole-
cule of crystallisation. The molecular structure of the [Ti-
(tbop-κ3O,S,O)Cl3]– anion in 7 is shown in Figure 4. This
anion evidently maintains a mononuclear octahedral envi-
ronment with a facially capped tbop ligand. The oxygen
atom O(12) of the tbop ligand and chloride Cl(2) occupy
an apical coordination sphere, while the remaining donor
atoms form the equatorial plane. The Ti–O distances of
1.863(2) and 1.884(2) Å are relatively short and comparable
to the terminal aryloxide oxygens found in 1 and 5. The Ti–
Cl bond lengths, disposed trans to Ti–O and Ti–S, vary
from 2.270(2) to 2.380(2) Å, presumably due to the trans
influence. The structure of the cation [NH2iPr2]+ is well
known.[19]
1
Table 1.Ethylene polymerisation.[a]
The H NMR spectrum of compound 8 shows similar
sets of resonances for the tbop ligand to 5 and additional
resonances (septet and doublet) for the deprotonated amido
NiPr2 groups. The IR spectrum of 8 also confirms the lack
of the ν(NH) frequencies in the expected region. In com-
pounds 1–7 thetitanium atom prefers to be six-coordinate.
This suggests that complex 8, which is isolated from non-
donor solvents, might be a dimer, as shown in Scheme 5.
By analogy to 5, we propose that the titanium atoms in 8
are joined through the oxygen donors of the tbop ligand
rather than the amido NiPr2 groups. Terminal coordination
of the amido NiPr2 group to the titanium centre has been
observed and crystallographically characterised in
[CpTiCl2(NiPr2)][20] and [Li(tmeda)][TiPh2(NiPr2)2].[21]
Entry
Complex
Cocatalyst Activity[b]
Mw/Mn
1
2
3
4
5
6
7
8
9
1
MAO
Al(iBu)3
MAO
110
345
465
322
357
707
207
402
137
123
3.73
4.23
4.36
4.67
3.05
5.48
3.32
4.74
2.80
3.16
1
2
2
Al(iBu)3
MAO
4
4
Al(iBu)3
MAO
5
5
Al(iBu)3
MAO
[Cp2TiCl2]
[Cp2TiCl2]
10
Al(iBu)3
[a] Polymerisation conditions: for MAO [Ti]0 = 0.05 mmoldm–3,
[Al]/[Ti] = 4000; for Al(iBu)3 [Ti]0 = 0.01 mmoldm–3, [Al]/[Ti] =
2000, time 30 min. [b] kg PE/g Ti/h.
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Z. Janas et al.
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For comparison of catalyst activities, titanocene dichlo-
ride [Cp2TiCl2] was used as a reference under the same con-
ditions (Table 1, entries 9 and 10). It turned out that the
catalyst based on complex 4 (entry 6) exhibits the highest
catalytic activity (707 kg PE/g Ti/h) for ethene polymeris-
ation. This is about two- and sevenfold more than catalysts
basedon[Ti2(μ-OEt)2(Me)2(tbop-κ3O,S,O)2] (344 kg PE/g
Ti/h; 323 K, 0.5 MPa, 0.005 mmol catalyst)[13]and the spe-
cies formulated as [Ti(tbmp)X2] (100 kg PE/g Ti/h; 293 K,
3 MPa, 0.2 mmol catalyst, 25 mmol MAO, toluene),[2b]
respectively, but is comparable with [Ti(tbmp)X2]/MAO
(820 kg PE/g Ti/h for X = Cl and 677 kg PE/g Ti/h for X
= OiPr; 293 K, 3 MPa, 0.001 mmol catalyst, 5.17 mmol
MAO, toluene) originally reported by Kakugo.[1b,1c] The
molecular weights of the polymers produced with com-
plexes 1, 2, 4 and 5 under these conditions range from
924 000 to 1 269 000.The polydispersities, Mw/Mn, for 1, 2,
4 and 5 (see Table 1) are narrower than those reported for
ethylenepolymerisation with catalysts based on [Ti2(μ-OEt)
2(OEt)4-(maltolato-κ2O,O)2] (6.11)[22] and [Ti(tbmp)X2]
(11.9).[2b] It would appear that for polymerisation of ethene,
activation of these systems affords a single, well-defined
active species. This indicates that the cocatalyst does not
abstract the tbop ligand from the titanium centre.
Experimental Section
General Remarks: All operations were carried out under a dry dini-
trogen atmosphere using standard Schlenk techniques. All the sol-
vents were distilled under dinitrogen from the appropriate drying
agents prior to use. The compounds TiCl4, Al(iBu)3, MAO,
NH2tBu, NHiPr2, Me3SiCl and 2,2Ј-thiobis[4-(1,1,3,3-tetrameth-
ylbutyl)phenol] (tbopH2) were obtained from the Aldrich Chemical
Co. and used without further purification, unless stated otherwise.
Infrared spectra were recorded on a Perkin–Elmer 180 spectropho-
tometer in Nujol mulls. NMR spectra were performed on a Bruker
ARX 300 spectrometer. Microanalysis was conducted with a ASA-
1 (GDR, Carl-Zeiss-Jena) instrument (in-house).
[Ti2(μ-tbop-κ3O,S,O)(μ-tbop-κ2O,O)(tbop-κ3O,S,O)Cl2](1)·
2CH3CN: tbopH2 (6.05 g, 13.67 mmol) was addedto a solution of
TiCl4 (1.73 g, 9.11 mmol) in n-hexane (60 mL), and the mixture
was stirred at room temperature until the evolution of HCl had
ceased (48 h). All volatiles were then removed under reduced pres-
sure. The resulting brown solid was washed with n-hexane (60 mL),
and then the brown precipitate was filtered off, washed with n-
hexane (3×5 mL) and dried under vacuum. The resultant solid was
dissolved in warm CH3CN, from which bright-red crystals suitable
for the structure determination were isolated after standing at room
temperature for two days. Yield: 5.83 g (86%). C84H120Cl2O6S3Ti2
(1488.67): calcd. C 67.80, H 8.13, Cl 4.70, S 6.45; found C 68.01,
H 8.26, Cl 5.32, S 6.13. IR (Nujol mull): ν = 380 (s), 412 (w), 438
˜
(s), 454 (w), 488 (w), 546 (m), 580 (s), 628 (s), 682 (m), 734 (w),
766 (m), 828 (s), 890 (m), 1060 (w), 1100 (w), 1144 (w), 1250 (s),
1288 (s), 1592 (w) cm–1. 1H NMR (300 MHz, C6D6, 25 °C): δ =
7.78–5.98 (m, 3 H, C6H3), 1.54–0.71 [multiplet, signals of C(CH3)2-
CH2C(CH3)3] ppm. The crystal structure shows the presence of two
CH3CN molecules in the unit cell. However, the elemental analysis
indicates that these are absent from the powder sample analysed;
they are presumably removed by the vacuum drying to which the
sample was subjected.
The preliminary polymerisation results on our Ziegler–
Natta-like systems are promising on account of the pro-
duction of a polymer with a sufficiently narrow particle-size
distribution.
Conclusions
[Ti2(μ-tbop-κ3O,S,O)2Cl4] (2): tbopH2 (4.05 g, 9.11 mmol) was
added to a solution of TiCl4 (1.73 g, 9.11 mmol) in Et2O or n-
hexane (60 mL) and the mixture was refluxed until the evolution
of HCl had ceased (48 h). The resulting dark-red solid was filtered
off, washed with cold Et2O (3×5 mL), and dried under vacuum.
Yield: 4.07 g (80%). C56H80Cl4O4S2Ti2 (1118.99): calcd. C 60.20,
H 7.22, Cl 12.53, S 5.73; found C 60.86, H 6.96, Cl 12.02, S 5.92.
Reaction of TiCl4 with tbopH2 results in the formation
of dimeric, mixed-ligand complexes 1 and 2 depending on
the stoichiometry. Analytically pure compound 3 can be
only obtained by the protonolysis reaction of tbopH2 with
[Ti(NMe2)4]. The extremely high solubility of 3 makes its
isolation in the solid state difficult. Treatment of 1 and 2
with Li(dipp) or Li2NtBu leads to the partial or complete
substitution of chlorides to form dimeric compounds 4 and
5, respectively. The monomeric complex 6 is a casual pro-
duct of the reaction of 5 with crude Me3SiCl containing
Me3SiOH. The use of the secondary amine NHiPr2 in the
reaction with 2 produces a mixture of the ionic compound
7 and the molecular species 8. The solid-state crystal struc-
IR (Nujol mull): ν = 324 (vw), 340 (vw), 378(vs, sh), 420 (s), 448
˜
(m), 466 (m), 500 (w), 542 (w), 568 (m), 578 (m), 628 (vw), 670
(vw), 720 (m), 748 (w), 780 (m), 824 (s), 840 (vs), 888 (m), 916 (m),
936 (vs), 1048 (w), 1064 (w), 1100 (w), 1150 (w), 1192 (m), 1262
1
(vs), 1324 (m), 1588 (w) cm–1. H NMR (300 MHz, C6D6, 25 °C):
δ = 7.71–6.89 (m, 12 H, C6H3), 1.58 [s, 8 H, C(CH3)2CH2C(CH3)3],
1.19 [s, 24 H, C(CH3)2CH2C(CH3)3], 0.77 [s, 36 H, C(CH3)2-
CH2C(CH3)3] ppm.
[Ti(tbop-κ3O,S,O)2] (3): tbopH2 (2.19 g, 5.44 mmol) was added to
tures of 1, 4 and 5 showthat their dimeric nature is due to a solution of [Ti(NMe2)4] (0.5 g, 2.72 mmol) in hexane (30 mL).
After refluxing the reaction mixture for 6 h, all volatiles were evap-
orated in vacuo and the residue was dissolved in n-hexane (10 mL).
The resulting solution was allowed to stand at room temperature
for several days, upon which orange microcrystals of 3 separated.
Yield: 0.4 g (15.8%). The extremely good solubility of this complex
in organic solvents did not allow us to separate pure 3 with higher
yield. Removal of solvent under vacuum gave a sticky product.
C56H80O4S2Ti (929.30): calcd. C 72.38, H 8.68, S 6.90; found C
oxygen bridges from the tbop ligands. This is in contrast to
the complexes containing a tbmp ligand. It is likely that the
bulky substituents in the ortho positions of the tbmp ligand
are the main reason why chloride bridges are favoured in
[Ti2(μ-Cl)2Cl2(tbmp-κ3O,S,O)2].
The complexes 1, 2, 4 and 5 are highly effective ethene
polymerisation catalysts upon activation with alkylalumin-
ium compounds. The narrow molecular-mass distribution
for these systems suggests the operation of heterogeneous,
well-defined, single-site catalysts.
71.99, H 8.65, S 7.11. IR (Nujol mull): ν = 446 (m), 460 (m), 502
˜
(w), 539 (w), 566 (m), 575 (m), 627 (vw), 669 (vw), 722 (m), 747
(w), 781 (m), 822 (s), 838 (vs), 882 (m), 915 (m), 934 (vs), 1046 (w),
1068
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 1063–1070

Titanium Complexes of Chelating, Dianionic O,S,O-Bisphenolato Ligands
FULL PAPER
1060 (w), 1100 (w), 1151 (w), 1190 (m), 1260 (vs), 1320 (m), 1588
(w) cm–1. 1H NMR (300 MHz, C6D6, 25 °C): δ = 8.35–6.24 (m, 12 κ3O,S,O)2Cl2(NiPr2)2] (8): NHiPr2 (0.16 mL, 1.94 mmol) was
H, C6H3), 1.70 [br, 8 H, C(CH3)2CH2C(CH3)3], 1.40 [br, 24 H, addedto a solution of 2 (1.09 g, 1.94 mmol) in toluene (20 mL) and
C(CH3)2CH2C(CH3)3], 0.95, 0.90, 0.84 [s, 36 H, C(CH3)2CH2C- the mixture was stirred for 12 h. Then, solvent was removed under
[NH2iPr2][Ti(tbop-κ3O,S,O)Cl3] (7)·CH2Cl2 and [Ti2(μ-tbop-
(CH3)3] ppm.
vacuum and the residue extracted with Et2O. CH2Cl2 (5 mL) was
added to the dark-red ether solution, and left at room temperature
for a few days. After that time red crystals of 7 suitable for X-ray
analysis had settled out. They were filtered off and dried under
vacuum. Yield: 0.89 g (66%). C34H56Cl3NO2STi (697.10): calcd. C
58.68, H 8.12, Cl 15.09, N 2.01, S 4.60; found C 58.58, H 8.09, Cl
[Ti2(μ-tbop-κ3O,S,O)2Cl2(dipp)2] (4)·Et2O: A solution of Li(dipp)
(0.50 g, 2.70 mmol) in diethyl ether (20 mL) was added to a solu-
tion of 2 (2.52 g, 2.70 mmol) in diethyl ether (30 mL). The mixture
was stirred over a period of 12 h and then filtered to remove LiCl.
Reduction of the filtrate volume to 10 mL and storage at 253 K for
1 week provided red crystals of complex 4. Yield: 1.24 g (65%).
C80H114Cl2O6S2Ti2 (1402.65): calcd. C 68.54, H 8.20, Cl 4.99, S
14.89, N 1.96, S 4.48. IR (Nujol mull): ν = 316 (s), 352 (m), 416
˜
(m), 450 (m), 468 (m), 492 (m), 578 (s), 588 (m), 680 (m), 740 (s),
754 (m), 834 (s), 879 (m), 892 (m), 1100 (w), 1140 (w), 1248 (s),
4.57; found C 67.99, H 8.01, Cl 5.05, S 4.68. IR (Nujol mull): ν =
˜
1
1258 (s), 1272 (s), 1290 (s), 1334 (s), 1568 (m), 1579 (m) cm–1. H
350 (m), 386 (s), 416 (m), 428 (m), 456 (m), 488 (m), 544 (w), 572
(m), 588 (m), 616 (w), 628 (w), 640 (w), 684 (m), 724 (s), 736 (s),
748 (s), 796 (m), 830 (s), 890 (m), 922 (s), 976 (w), 1044 (w), 1050
(m), 1100 (m), 1122 (m), 1146 (s), 1194 (s), 1250 (m), 1274(s), 1326
NMR (300 MHz, C6D6, 25 °C): δ = 7.75 (br., 2 H, NH2iPr2), 7.63–
6.50 (m, 6 H, C6H3), 2.88 [m, 2 H, NCH(CH3)2], 1.63 [s, 4 H,
C(CH3)2CH2C(CH3)3], 1.28 [d, 12 H, NCH(CH3)2], 1.25 [s, 12 H,
C(CH3)2CH2C(CH3)3], 0.81 [s, 18 H, C(CH3)2CH2C(CH3)3] ppm.
The crystal structure shows the presence of one CH2Cl2 molecule
in the unit cell. However, the elemental analysis indicates that this
is absent from the powder sample analysed; presumably it is re-
moved by the vacuum drying to which the sample was subjected.
1
(s) cm–1. H NMR (300 MHz, C6D6, 25 °C): δ = 8.5–7.15 (m, 18
H, C6H3), 3.21 [sept, 4 H, C6H3{CH(CH3)2}2], 1.43 [s, 8 H, C(CH3)
2CH2C(CH3)3], 1.35 [d, 24 H, C6H3{CH(CH3)2}2], 0.95 [s, 24 H,
C(CH3)2CH2C(CH3)3], 0.77 [s, 36 H, C(CH3)2CH2C(CH3)3] ppm.
The crystal structure shows the presence of one Et2O molecule in
the unit cell. However, the elemental analysis indicates that this is
absent from the powder sample analysed; presumably it is removed
by the vacuum drying to which the sample was subjected.
The dark-orange, solid residue from the separation of 7 was dis-
solved in toluene (20 mL) and Et2O (20 mL) was added. After
standing for 2 d at room temperature, orange microcrystals of 8
precipitated. These were filtered off, washed with Et2O and dried
under vacuum. Yield: 0.58 g (48%). C68H108Cl2N2O4S2Ti2
(1248.47): calcd. C 65.42, H 8.72, Cl 5.68, N 2.24, S 5.14; found C
[Ti2(μ-tbop-κ3O,S,O)2(NtBu)2(NH2tBu)2] (5): BuLi (2.19 mL,
3.52 mmol) was added to a cooled (233 K) solution of NH2tBu
(0.13 g, 1.76 mmol) in diethyl ether (40 mL). The mixture was al-
lowed to warm to room temperature. After 3 h of stirring, 2 (0.98 g,
0.88 mmol) was added. The orange mixture was stirred for 24 h
and then filtered to remove LiCl. Then, NH2tBu (0.13 g,
1.76 mmol) was added to the filtrate and stirred for 2 h. Concentra-
tion of the reaction mixture to 10 mL gave yellow crystals of 5 after
standing at room temperature for 2 d. These were filtered off and
dried in vacuo. Yield: 0.86 g (76%). C72H120N4O4S2Ti2 (1265.64):
calcd. C 68.33, H 9.56, N. 4.43, S, 5.07; found C 68.98, H 10.16,
65.02, H 8.41, Cl 5.52, N 2.01, S 5.21. IR (Nujol mull): ν = 338
˜
(w), 456 (m), 486 (m), 576 (s), 625 (w), 675 (m), 735 (s), 750 (s),
799 (s), 879 (s), 890 (m), 1105 (w), 1139 (w), 1245 (s), 1251 (s),
1269 (s), 1287 (s), 1330 (s), 1579 (m) cm–1. 1H NMR (300 MHz,
C6D6, 25 °C): δ = 7.63–6.50, (m, 6 H, C6H3), 3.37 [sept, 2 H,
N{CH(CH3)2}2], 1.63 [s, 4 H, C(CH3)2CH2C(CH3)3], 1.28 [s, 12 H,
C(CH3)2CH2C(CH3)3], 1.01 [d, 12 H, N{CH(CH3)2}2], 0.81 [s, 18
H, C(CH3)2CH2C(CH3)3] ppm.
N 4.31, S 5.37. IR (Nujol mull): ν = 346 (vw), 402 (w), 420 (w),
Polymerisation Test: A slurry of [MgCl2(THF)2] (10 mmol) in n-
˜
444 (w), 492 (w), 530 (w), 560 (w), 574 (w), 604 (w), 672 (m), 748 hexane was milled under argon in a glass mill (capacity 250 mL,
(m), 758 (m), 824 (vs), 886 (m), 874 (s), 1018 (s), 1060 (s), 1112 (s), with 20 balls of diameter 5–15 mm) at room temperature for 6 h.
1146 (s), 1194 (m), 1232 (s), 1260 (vs), 1308 (vs), 1536 (w), 1592 Then, the titanium compound (1 mmol) and n-hexane (50 mL)
1
(m), 3104 (m), 3180 (w) cm–1. H NMR (300 MHz, C6D6, 25 °C): were added, and the mixture was milled for a further 24 h. The
δ = 7.94–6.60 (m, 12 H, C6H3), 4.22 [br. s, 4 H, NH2C(CH3)3], 1.48 sample of precatalyst suspension (containing 0.01 mmol of tita-
[s, 8 H, C(CH3)2CH2C(CH3)3], 1.27 [s, 18 H, NH2C(CH3)3], 1.26
nium) was activated with AlEt2Cl (Al:Ti = 120) for 15 min at 323 K
[s, 24 H, C(CH3)2CH2C(CH3)3], 1.04 [s, 18 H, NC(CH3)3], 0.73 [s, under argon. Prior to polymerisation, ethene was passed through
36 H, C(CH3)2CH2C(CH3)3] ppm.
the suspension of the catalyst (10 mL) in a Schlenk ampoule for
15 min at room temperature and normal pressure to form the pre-
polymer (about 1 g). An additional amount of organoaluminium
compound [Al(iBu)3 or MAO] was then added to the catalyst dis-
persed in the prepolymer (Al:Ti = 2000) to form a highly active
catalyst. The polymerisation of ethylene was carried out in n-hex-
ane at 323 K in a stainless-steel reactor (1 L), equipped with a stir-
rer, at 0.5 MPa pressure. The polymerisation was quenched with a
5% solution of HCl in methanol and dried under vacuum.
[Ti(tbop-κ3O,S,O)Cl(OSiMe3)(NH2tBu)] (6): Crude Me3SiCl
(0.86 g, 7.90 mmol) was added to a solution of 2 (2.5 g, 1.97 mmol)
in diethyl ether (30 mL). The reaction mixture was stirred at room
temperature, upon which the solution changed colour from orange
to dark red. After filtration the solution was concentrated to 10 mL
and allowed to stand at room temperature for 4 d. After that time
red crystals of 6 suitable for X-ray structural analysis separated.
Yield: 1.73 g (72%). C35H60ClNO3SiSTi (686.34): calcd. C 61.28,
H 8.82, Cl 5.10, N 2.04, S 4.67; found C 61.91, H 8.53, Cl 5.28, N
Crystal Data and Refinement Details for 1·2CH3CN, 5, 6, and
2.16, S 5.03%. IR (Nujol mull): ν = 340 (vw), 472 (w), 492 (w),
7·CH2Cl2: Preliminary examination and intensity data collections
˜
584 (m), 622 (w), 680 (m), 736 (m), 762 (s), 836 (s), 892 (s), 928 were carried out on a CCD KUMA KM4 κ-axis diffractometer
(vs), 1028 (m), 1056 (m), 1148 (m), 1248 (s), 1280 (s), 1296 (s), 1568 with graphite-monochromated Mo-Kα. Data were corrected for Lo-
1
(m), 3216 (s), 3280 (s) cm–1. H NMR (300 MHz, C6D6, 25 °C): δ rentz, polarisation and absorption effects. The structures were
= 7.38–6.79 (m, 6 H, C6H3), 4.15 [br. s, 2 H, NH2C(CH3)3], 1.47 solved by direct methods and refined by the full-matrix least-
[s, 4 H, C(CH3)2CH2C(CH3)3], 1.21 [s, 9 H, NH2C(CH3)3], 1.09 [s,
squares method on all F2 data using the SHELXTL-NT v. 5.1 soft-
12 H, C(CH3)2CH2C(CH3)3], 0.65 [s, 18 H, C(CH3)2CH2C(CH3)3], ware package.[23] Carbon-bound hydrogen atoms were included in
0.13 [s, 9 H, Si(CH3)3] ppm.
calculated positions and refined in the riding mode. Other hydrogen
1069
Eur. J. Inorg. Chem. 2005, 1063–1070
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Z. Janas et al.
FULL PAPER
Table 2. Details of data collection and structural refinements for 1·2CH3CN, 5, 6 and 7·CH2Cl2.
1·2CH3CN
5
6
7·CH2Cl2
Empirical formula
M
T [K]
C88H126Cl2N2O6S3Ti2
1570.77
100(1)
C72H120N4O4S2Ti2
1265.64
100(1)
C35H60ClNO3SSiTi
686.34
100(1)
C35H58Cl5NO2STi
782.03
100(2)
λ [Å]
Crystal system
Space group
0.71073
0.71073
monoclinic
C2/c
0.71073
0.71073
monoclinic
P21/c
triclinic
triclinic
¯
¯
P1
P1
a [Å]
b [Å]
c [Å]
α [°]
16.029(2)
17.208(2)
18.016(2)
110.19(1)
103.27(1)
92.05(1)
1.147
17.312(5)
23.068(4)
22.075(6)
90
112.47(5)
90
10.761(2)
11.943(2)
15.433(2)
78.54(1)
88.54(1)
82.00(1)
1.184
17.770(3)
15.272(2)
15.207(3)
90
98.26(1)
90
β [°]
γ [°]
Dc [Mgm–3]
μ [mm–1]
1.029
0.289
1.272
0.618
0.355
0.409
Reflections collected
Independent reflections
31389
19801 (0.0576)
17731
9489 (0.0483)
13320
8476 (0.0323)
26620
9602 (0.0553)
(Rint
)
R1, wR2 [I Ͼ 2σ(I)]
0.0717, 0.1292
0.0752, 0.1665
0.0502, 0.1047
0.0734, 0.1200
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atoms were located in a difference map and refined free. All non-
hydrogen atoms were refined with anisotropic displacement param-
eters. Crystal data are summarised in Table 2.
CCDC-243718 to -243721 (for 1·2CH3CN, 5, 6, and 7·CH2Cl2)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-bridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/
cif.
Acknowledgments
[12] Y. Nakayama, K. Watanabe, N. Ueyama, A. Nakamura, A.
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The authors thank the State Committee for Scientific Research (Po-
land) for financial support of this work (grant no. 4 T09A 137 24).
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¯
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