The synthesis, structure and ethene polymerisation catalysis of mono(salicylaldimmato) titanium and zirconium complexes

Article abstract of DOI:10.1039/b414229b

The siryl ethers 3-Bu^t-2-(OSiMe₃)C₆H ₃CH=NR (2a-e) have been prepared by deprotonation of the known iminophenols (1a-e) and treatment with SiClMe₃ (a, R = C ₆H₅; b, R = 2,6-Pr₂ⁱC ₆H₃; c, R = 2,4,6-Me₃C₆H ₂; d, R = 2-C₆H₅C₆H₄; e, R = C₆F₅). 2a-c react with TiCl₄ in hydrocarbon solvents to give the binuclear complexes [Ti{3-Bu¹-2-(O)C ₆H₃CH=N(R)}Cl(μ-Cl₃)TiCl₃] (3a-c). The pentafluorophenyl species 2e reacts with TiCl₄ to give the known complex Ti{3-Bu^t-2-(O)C₆H₃CH=N(R)} ₂Cl₂. The mononuclear five-coordinate complex, Ti{3-Bu^t-2-(O)C₆H₃CH= N(2,4,6-Me ₃C₆H₂)}Cl₃ (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-Bu^t-2-(O)C₆H₃CH= N(R)}Cl₃(THF) (5a-e). The reaction with ZrCl₄(THF), proceeds similarly to give complexes Zr{3-Bu^t-2-(O)-C₆H₃CH=N(R)}Cl ₃(THF) (6b-e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti{3-Bu^t-2-(O)C ₆H₃CH=O}Cl₃(THF) (7) have been determined. Activation of complexes 5a-e and 6b-e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the inline substituent.

Full text of DOI:10.1039/b414229b

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F U L L P A P E R
The synthesis, structure and ethene polymerisation catalysis of
mono(salicylaldiminato) titanium and zirconium complexes†
Dale A. Pennington,a William Clegg,b Simon J. Coles,c Ross W. Harrington,b
Michael B. Hursthouse,c David L. Hughes,a Mark E. Light,c Mark Schormann,a
Manfred Bochmanna and Simon J. Lancaster*a
a Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy,
University of East Anglia, Norwich, UK NR4 7TJ. E-mail: S.Lancaster@uea.ac.uk;
Fax: 44 1603 592009; Tel: 44 1603 592009
b School of Natural Sciences (Chemistry), University of Newcastle, Newcastle upon Tyne,
UK NE1 7RU
c School of Chemistry, University of Southampton, Highfield, Southampton, UK SO17 1BJ
Received 14th September 2004, Accepted 26th November 2004
First published as an Advance Article on the web 4th January 2005
t
=
The silyl ethers 3-Bu -2-(OSiMe3)C6H3CH NR (2a–e) have been prepared by deprotonation of the known
iminophenols (1a–e) and treatment with SiClMe3 (a, R = C6H5; b, R = 2,6-Pri2C6H3; c, R = 2,4,6-Me3C6H2; d, R =
2-C6H5C6H4; e, R = C6F5). 2a–c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [Ti{3-But-2-
=
(O)C6H3CH N(R)}Cl(l-Cl3)TiCl3] (3a–c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known
t
t
=
=
=
complex Ti{3-Bu -2-(O)C6H3CH N(R)}2Cl2. The mononuclear five-coordinate complex, Ti{3-Bu -2-(O)C6H3CH
N(2,4,6-Me3C6H2)}Cl3 (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation
t
reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-Bu -2-(O)C6H3CH
N(R)}Cl3(THF) (5a–e). The reaction with ZrCl4(THF)2 proceeds similarly to give complexes Zr{3-But-2-(O)-
=
C6H3CH N(R)}Cl3(THF) (6b–e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde
t
=
titanium complex Ti{3-Bu -2-(O)C6H3CH O}Cl3(THF) (7) have been determined. Activation of complexes 5a–e
and 6b–e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending
on the imine substituent.
active,8 and living9 bis(salicylaldiminato) group 4 (V, Chart 2),
Introduction
mono(salicylaldiminato) chromium10 and neutral nickel (VI)11
catalysts for the polymerisation of ethene. We recently reported
mixed salicylaldiminato cyclopentadienyl complexes of titanium
and zirconium (VII).12 The activity of all these pre-catalysts is
highly dependent on the nature of the substituents in the ortho-
position on the phenoxy ring and on the imine nitrogen. We
report here the synthesis, structure and stability of a series of
mono(salicylaldiminato) complexes of titanium and zirconium
intended as precursors to mixed ligand complexes.13 Our prelim-
inary results on titanium complexes have been communicated.14
The use of these new complexes as pre-catalysts for ethene
polymerisation is described.
The ongoing search for new non-metallocene 1-alkene polymeri-
sation catalysts has contributed to intense academic and indus-
trial interest in transition metal coordination chemistry.1 To date
a great many examples of group 4 metal complexes with either
two anionic bidentate ancillary ligands or a single dianionic
tetradentate ligand have been prepared and tested as catalysts.2,3
These essentially octahedral compounds offer significant steric
protection to the metal centre and their catalytic behaviour
is often compared to the metallocenes. However, despite the
well documented differences in catalytic behaviour between
metallocenes and the much more open mono(cyclopentadienyl)
complexes (I, Chart 1)4 there are relatively few examples of
synthetic and catalytic studies of mono(bidentate anionic ligand)
complexes of the group 4 metals. Important examples include
amidinates (II),5 guadinates (III)6 and b-diketiminates (IV).7
Chart 2
Chart 1
Transition metal complexes of the monoanionic bidentate
N,O chelate salicylaldiminato (iminophenolato) ligands have
attracted considerable attention since the discovery of highly
Results and discussion
Syntheses of complexes
Bis(salicylaldiminato) complexes of the group 4 metals are
normally prepared through the reaction of two equivalents of
the deprotonated iminophenol with the appropriate metal tetra-
chloride in tetrahydrofuran solution.9 Our initial investigations
† Electronic supplementary information (ESI) available: Synthetic
procedures and full characterisation data. See http://www.rsc.org/
suppdata/dt/b4/b414229b/
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 6 1
©

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˚
demonstrated that this approach was not suited to the prepara-
Table 1 Molecular dimensions for complex 3b; bond lengths (A),
angles (◦), esds are in parentheses
tion of mono(salicylaldiminato) complexes. Even the reaction
t
=
between our most hindered Li{3-Bu -2-(O)C6H3CH N(2,6-
Pri2C6H3)} reagent and TiCl4 was far from selective and led
only to an intractable mixture of products.
Ti(1)–O(1)
Ti(1)–N(2)
Ti(1)–Cl(3)
1.7843(16) Ti(1)–Cl(5)
2.138(2) Ti(1)–Cl(6)
2.1987(10) Ti(1)–Cl(4)
2.4336(7)
2.4091(7)
2.4907(10)
The requirement for a milder and more selective method to
introduce salicylaldiminato ligands led to an examination of
O(1)–Ti(1)–N(2)
O(1)–Ti(1)–Cl(3)
O(1)–Ti(1)–Cl(5)
O(1)–Ti(1)–Cl(6)
O(1)–Ti(1)–Cl(4)
N(2)–Ti(1)–Cl(3)
N(2)–Ti(1)–Cl(5)
N(2)–Ti(1)–Cl(6)
84.76(7)
102.52(6)
163.22(6)
100.33(5)
84.37(6)
98.44(6)
89.87(5)
166.23(6)
N(2)–Ti(1)–Cl(4)
87.43(6)
93.98(3)
92.97(3)
171.28(3)
81.62(2)
79.51(2)
80.40(3)
the widely employed dehalosilylation route.15 A series of silyl
Cl(3)–Ti(1)–Cl(5)
Cl(3)–Ti(1)–Cl(6)
Cl(3)–Ti(1)–Cl(4)
Cl(6)–Ti(1)–Cl(5)
Cl(5)–Ti(1)–Cl(4)
Cl(6)–Ti(1)–Cl(4)
t
=
ethers, 3-Bu -2-(OSiMe3)C6H3CH NR (2a–e), was prepared by
deprotonation of the known iminophenols (1a–e) and treatment
with SiClMe3 (Scheme 1). It proved necessary to heat the
tetrahydrofuran solution of lithium salt and chlorotrimethyl-
silane under reflux for several hours to ensure good conversion
to the silyl ether.
O(1)–C(1)
C(1)–C(2)
C(2)–C(20)
1.352(3)
1.409(3)
1.436(3)
C(20)–N(2)
N(2)–C(21)
1.285(3)
1.466(3)
C(1)–O(1)–Ti(1)
O(1)–C(1)–C(2)
C(1)–C(2)–C(20)
N(2)–C(20)–C(2)
135.86(14) C(20)–N(2)–Ti(1)
120.85(15)
124.29(15)
114.85(19)
116.1(2)
122.1(2)
128.1(2)
C(21)–N(2)–Ti(1)
C(20)–N(2)–C(21)
Ti(1) · · · Ti(2)
Ti(2)–Cl(4)
Ti(2)–Cl(5)
Ti(2)–Cl(6)
3.3578(7)
2.4618(9)
2.5417(7)
2.5381(9)
Ti(2)–Cl(7)
Ti(2)–Cl(8)
Ti(2)–Cl(9)
2.2106(10)
2.1845(9)
2.1971(7)
Cl(4)–Ti(2)–Cl(5)
Cl(4)–Ti(2)–Cl(6)
Cl(7)–Ti(2)–Cl(4)
Cl(8)–Ti(2)–Cl(4)
Cl(9)–Ti(2)–Cl(4)
Cl(6)–Ti(2)–Cl(5)
Cl(7)–Ti(2)–Cl(5)
Cl(8)–Ti(2)–Cl(5)
Ti(2)–Cl(4)–Ti(1)
Ti(1)–Cl(5)–Ti(2)
78.00(3)
78.48(3)
165.61(3)
90.71(3)
89.89(3)
77.08(2)
91.27(3)
89.75(3)
85.38(3)
84.86(2)
Cl(9)–Ti(2)–Cl(5)
Cl(7)–Ti(2)–Cl(6)
Cl(8)–Ti(2)–Cl(6)
Cl(9)–Ti(2)–Cl(6)
Cl(8)–Ti(2)–Cl(7)
Cl(9)–Ti(2)–Cl(7)
Cl(8)–Ti(2)–Cl(9)
164.20(3)
89.87(4)
164.38(3)
90.69(3)
98.90(4)
98.76(3)
100.63(4)
Scheme 1
Treating ZrCl4 with the bulky 2,6-diisopropyl substituted
derivative 2b in dichloromethane solution was not selec-
tive and led to a mixture of products including Zr{3-But-
i
=
2-(O)C6H3CH N(2,6-Pr 2C6H3}2Cl2, which was identified by
Ti(1)–Cl(6)–Ti(2)
85.45(3)
8a
comparison to the reported NMR data. In contrast, reacting
2a–c with TiCl4 in light petroleum solution led to the slow
precipitation of dark red solids (3a–c). Identical products were
obtained in good yield after heating a toluene solution under
reflux overnight (Scheme 2). 3a–c were readily identified by 1H
NMR as the products of a dehalosilylation reaction yielding
salicylaldiminato complexes. However, the elemental analyses
afforded a N : Cl ratio of 1 : 7 and were consistent with the
composition LTi2Cl7, not the expected LTiCl3. The nature of the
association with the second equivalent of TiCl4 was revealed by
determining the crystal structure of 3b (Fig. 1, for selected bond
lengths and angles see Table 1). 3b is a binuclear complex in
which the two titanium centres are bridged by three chloride
ligands. The titanium atoms are both six-coordinate with
distorted octahedral geometries. One metal centre is bonded
to six chloride ligands, the other to four chlorides and the
bidentate salicylaldiminato ligand.14 Complexes 3a and 3c are
formulated as binuclear complexes analogous to 3b on the
basis of NMR and elemental analysis data.16 There are few
precedents for structures such as 3b, in which the titanium
centre is surrounded only by an octahedron of chloride ligands.
The neutral tetranuclear complex {Cl3Ti(l-Cl)3Ti(NPPh3)}2(l-
Cl)2 (VIII, Chart 3) contains titanium with a similar octahedral
chloride ligand coordination environment to 3b; the terminal Ti–
Cl bond lengths are similar (2.189–2.213) but the bridging Ti–Cl
bond lengths cover a greater range (2.399–2.614).17 The structure
Fig. 1 Structure of 3b with displacement ellipsoids at the 50%
probability level; H atoms are omitted for clarity, C atoms are labeled
by number only.
of the [Ti2Cl9]− anion (IX), in which both titanium centres have
an octahedral face-sharing geometry, has been reported and
˚
both the terminal (2.197–2.225 A) and bridging Ti–Cl (2.480–
˚
2.556 A) bond lengths are very similar to those observed for
3b.18
The stability of the binuclear complexes 3 towards further re-
action is remarkable; 3a–c do not react with a second equivalent
of ligand even after heating under reflux for two days in toluene
solution. Despite this, formation of these LTi2Cl7 structures does
appear to be specific to simple aryl-substituted salicylaldiminato
ligands. Lapido has shown that alkyl substituted analogues react
in a 1 : 1 fashion to form monomeric LTiCl3 (for example
X) or dimeric L2Ti2Cl6 complexes (for example XI) with less
14b
bulky substituents. The reaction of the electron-poor ligand
Scheme 2
precursor 2e with TiCl4 proceeded quite differently, leading not
5 6 2
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1

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˚
Table 2 Molecular dimensions for complex 4c; bond lengths (A),
angles (◦), esds are in parentheses
Ti(1)–O(1)
Ti(1)–N(1)
1.8152(13) Ti(1)–Cl(3)
2.1478(14) Ti(1)–Cl(2)
Ti(1)–Cl(1)
2.2327(6)
2.2769(6)
2.2327(6)
O(1)–Ti(1)–N(1)
Cl(3)–Ti(1)–O(1)
Cl(2)–Ti(1)–O(1)
Cl(1)–Ti(1)–O(1)
Cl(3)–Ti(1)–N(1)
81.10(5)
92.79(5)
167.49(4)
92.45(5)
117.07(5)
Cl(2)–Ti(1)–N(1)
86.62(4)
128.80(5)
94.91(2)
113.93(3)
93.42(2)
Cl(1)–Ti(1)–N(1)
Cl(2)–Ti(1)–Cl(3)
Cl(1)–Ti(1)–Cl(3)
Cl(1)–Ti(1)–Cl(2)
O(1)–C(16)
C(11)–C(16)
C(10)–C(11)
1.331(2)
1.406(2)
1.428(2)
N(1)–C(10)
N(1)–C(1)
1.305(2)
1.459(2)
Ti(1)–O(1)–C(16)
O(1)–C(16)–C(11)
C(10)–C(11)–C(16)
N(1)–C(10)–C(11)
147.61(11) Ti(1)–N(1)–C(10)
115.65(15) Ti(1)–N(1)–C(1)
121.33(15) C(1)–N(1)–C(10)
128.27(15)
125.39(12)
121.90(10)
112.60(14)
Chart 3
to a binuclear species but to the bis(salicylaldiminato) complex
have not been able to develop a convenient synthesis of 4c or its
analogues, despite its evident stability and the facile synthesis of
the closely related complex, X.
t
=
Ti{3-Bu -2-(O)C6H3CH N(C6F5}2Cl2, which was identified by
9e
crystallography and comparison to the known structure.
The initial product of the reaction between 2c and TiCl4
was the poorly crystalline binuclear complex 3c. Repeated
recrystallisation of 3c afforded single crystals of a new
complex 4c, which were very small but of sufficient qual-
ity for a structure determination (Fig. 2, for selected bond
lengths and angles see Table 2). The monomeric solid
state structure of 4c contrasts with the chloride-bridged
The pattern of reactivity between the base-free titanium and
zirconium tetrachlorides and the silyl ethers reported here is
reminiscent of that observed for trimethylsilylcyclopentadienes.
For the cyclopentadienyl zirconium system Livinghouse and
Lund demonstrated that the reactivity of the metal centre
15b
could be moderated by the addition of a basic donor.
When the tetrahydrofuran adduct TiCl4(THF)2 was treated
with the silyl ethers 2 in dichloromethane solution the re-
action proceeded slowly and smoothly to yield dark red
six-coordinate mono(salicylaldiminato) complexes Ti{3-But-2-
5b
dimeric structures determined for mono(amidinate) and
mono(guanidinate) titanium trichlorides6 and the benzyl sub-
stituted mono(salicylaldiminato) complex XI. It does however,
resemble the trigonal bipyramidal structure of the tert-butyl
substituted mono(salicylaldiminato) complex X. The most sig-
nificant difference between X and 4c sees the imine nitrogen,
rather than the phenoxide oxygen, in an axial site.19
=
(O)C6H3CH NR}Cl3(THF) (5a–e) (Scheme 3). In each case
satisfactory elemental analyses were obtained with N : Cl
ratios of 1 : 3. The 1H NMR spectra clearly indicated that
a dehalosilylation reaction and complex formation had taken
place. Identical THF adducts could also be obtained through
treating solutions of 3a–c or 4c with excess THF. Three of the
five titanium complexes prepared, 5a (Fig. 3), 5c (Fig. 4) and
5e (Fig. 5) have been crystallographically characterised (selected
bond lengths and angles are collected in Table 3).
The mononuclear complex 4c is the result of the loss of one
equivalent of TiCl4 from the binuclear precursor 3c. 4c is not
accessible through direct reaction of TiCl4 with 2c. As yet we
5a adopts an essentially octahedral geometry. The three
chloride ligands are meridionally arranged. The two O ligating
atoms are mutually trans; in this respect the geometry is
similar to the bis(salicylaldiminato) titanium complex Ti{3-
◦
t
9c
=
Bu -2-(O)C6H3CH NPh}2Cl2 (O–Ti–O = 171.6 ). Complex
5c also adopts a distorted octahedral coordination pattern about
the Ti atom, but now the three Cl atoms are facially arranged
and both the phenoxy and THF ligating O atoms are trans
to chlorides. Complex 5e has a similar distorted octahedral
geometry and relative arrangement of ligands to those in 5c, the
greatest difference being in the orientation of the THF ligand.
For complexes 5a, 5c and 5e the metal–ligand bond lengths to
the salicylaldiminato and chloride ligands are close to those ob-
t
t
9c
=
served in Ti{3-Bu -2-(O)C6H3CH NPh}2Cl2 and TiCp{3-Bu -
Fig. 2 Structure of 4c with displacement ellipsoids at the 50%
probability level.
12
=
2-(O)C6H3CH N(2,4,6-Me3C6H2}Cl2. Not surprisingly, the
Scheme 3
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 6 3

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Fig. 4 Structure of 5c with displacement ellipsoids at the 50%
probability level.
Fig. 3 Structure of 5a with displacement ellipsoids at the 50%
probability level.
terminal Ti–Cl distances are longer than those seen in 4c, which
in turn are longer than those of 3b. This reflects the expected
decrease in Lewis acidity 3 > 4 > 5, moving from the binuclear
complex to the THF adduct. The related mono(amidinate)
titanium complex Ti{PhC(NSiMe3)2}Cl3(THF) has the facial
arrangement of chloride ligands seen for 5c and 5e rather than
resonances for the ortho-substituents on the imine phenyl ring,
indicating a significant steric hindrance to rotation about the
N–C bond. The elemental analyses were consistent with the
expected compositions. Confirmation that we had successfully
prepared the first examples of mono(salicylaldiminato) zirco-
t
=
nium complexes Zr{3-Bu -2-(O)C6H3CH NR}Cl3(THF) (6b–
5b
the meridional pattern of 5a.
e) was provided by the crystal structure determinations of 6b
(Fig. 6), 6d (Fig. 7) and 6e (Fig. 8). Selected bond lengths and
angles for these complexes are collected in Table 4.
In contrast to the non-selective reaction with base-free ZrCl4,
ZrCl4(THF)2 underwent clean dehalosilylation with the silyl
ethers 2b–d in dichloromethane solution to yield the yellow
Structurally the zirconium complexes, exemplified in 6b, 6d,
and 6e, are similar to 5c and 5e, with distorted octahedral
coordination and a fac arrangement of the three Cl ligands.
However, as the steric bulk of the Ar group increases, from 6b
to 6d, the distortion about the metal atom increases – this is
1
products (6b–e) (Scheme 3). The H NMR spectra exhibited
the expected pattern of resonances for a bidentate ligand and
one equivalent of THF. The room-temperature NMR spectra
of 6b, 6e (and their titanium analogues 5b and 5e) gave two
◦
˚
Table 3 Molecular dimensions for complexes 5a, 5c and 5e; bond lengths (A), angles ( ), esds are in parentheses
5a
5c
5e
Ti–O(1)
Ti–N(2)
Ti–Cl(6)
Ti–O(3)
Ti–Cl(4)
Ti–Cl(5)
1.791(5)
2.240(6)
2.327(2)
2.146(5)
2.281(2)
2.342(2)
Ti–O(1)
Ti–N
Ti–O(2)
Ti–Cl(1)
Ti–Cl(2)
Ti–Cl(3)
1.8328(15)
2.2558(17)
2.1669(14)
2.3196(9)
2.2943(9)
2.2914(8)
O(1)–Ti(1)
N(1)–Ti(1)
O(2)–Ti(1)
Cl(1)–Ti(1)
Cl(2)–Ti(1)
Cl(3)–Ti(1)
1.8191(18)
2.248(2)
2.0981(19)
2.3169(8)
2.2587(8)
2.2768(8)
O(1)–Ti–N(2)
O(1)–Ti–Cl(6)
O(1)–Ti–O(3)
O(1)–Ti–Cl(4)
O(1)–Ti–Cl(5)
N(2)–Ti–Cl(6)
O(3)–Ti–N(2)
N(2)–Ti–Cl(4)
N(2)–Ti–Cl(5)
O(3)–Ti–Cl(6)
Cl(4)–Ti–Cl(6)
Cl(6)–Ti–Cl(5)
O(3)–Ti–Cl(4)
O(3)–Ti–Cl(5)
Cl(4)–Ti–Cl(5)
83.1(2)
O(1)–Ti–N
81.27(6)
88.40(6)
168.64(5)
94.97(5)
90.72(5)
84.55(6)
87.99(5)
169.86(4)
91.73(5)
86.89(5)
85.95(5)
176.26(4)
95.00(3)
93.32(4)
97.75(3)
O(1)–Ti(1)–N(1)
O(1)–Ti(1)–O(2)
O(1)–Ti(1)–Cl(1)
O(1)–Ti(1)–Cl(2)
O(1)–Ti(1)–Cl(3)
O(2)–Ti(1)–N(1)
N(1)–Ti(1)–Cl(1)
N(1)–Ti(1)–Cl(2)
N(1)–Ti(1)–Cl(3)
O(2)–Ti(1)–Cl(1)
O(2)–Ti(1)–Cl(2)
O(2)–Ti(1)–Cl(3)
Cl(2)–Ti(1)–Cl(1)
Cl(3)–Ti(1)–Cl(1)
Cl(2)–Ti(1)–Cl(3)
80.41(8)
86.04(8)
165.45(6)
97.06(6)
92.40(6)
86.59(8)
86.28(6)
174.73(6)
88.80(6)
87.36(6)
88.63(5)
175.31(6)
95.73(3)
93.14(3)
95.95(3)
91.85(15)
171.76(19)
98.00(16)
94.36(15)
87.14(16)
88.8(2)
176.72(18)
82.48(16)
86.70(13)
95.91(8)
167.17(9)
90.21(14)
85.55(13)
94.34(8)
O(1)–Ti–O(2)
O(1)–Ti–Cl(1)
O(1)–Ti–Cl(2)
O(1)–Ti–Cl(3)
O(2)–Ti–N
N–Ti–Cl(1)
N–Ti–Cl(2)
N–Ti–Cl(3)
O(2)–Ti–Cl(1)
O(2)–Ti–Cl(2)
O(2)–Ti–Cl(3)
Cl(2)–Ti–Cl(1)
Cl(3)–Ti–Cl(1)
Cl(3)–Ti–Cl(2)
O(1)–C(11)
C(11)–C(12)
C(12)–C(20)
N(2)–C(20)
N(2)–C(21)
1.371(7)
1.403(9)
1.465(9)
1.296(8)
1.448(10)
O(1)–C(1)
C(1)–C(2)
C(2)–C(10)
N–C(10)
1.356(2)
1.408(3)
1.452(3)
1.305(3)
1.463(2)
C(13)–O(1)
C(8)–C(13)
C(7)–C(8)
C(7)–N(1)
C(1)–N(1)
1.340(3)
1.411(4)
1.430(4)
1.297(3)
1.437(3)
N–C(11)
C(11)–O(1)–Ti
146.1(5)
116.4(6)
123.4(6)
127.7(7)
123.0(5)
121.2(4)
115.2(6)
C(1)–O(1)–Ti
O(1)–C(1)–C(2)
C(1)–C(2)–C(10)
N–C(10)–C(2)
C(10)–N–Ti
C(11)–N–Ti
C(10)–N–C(11)
140.64(13)
116.83(17)
122.38(18)
127.82(19)
122.19(13)
124.13(12)
113.68(16)
C(13)–O(1)–Ti(1)
O(1)–C(13)–C(8)
C(13)–C(8)–C(7)
N(1)–C(7)–C(8)
C(7)–N(1)–Ti(1)
C(1)–N(1)–Ti(1)
C(7)–N(1)–C(1)
143.21(17)
116.8(2)
122.5(2)
O(1)–C(11)–C(12)
C(11)–C(12)–C(20)
N(2)–C(20)–C(12)
C(20)–N(2)–Ti
C(21)–N(2)–Ti
C(20)–N(2)–C(21)
127.2(2)
122.87(17)
122.68(16)
113.4(2)
5 6 4
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1

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Fig. 5 Structure of 5e with displacement ellipsoids at the 50%
probability level.
Fig. 6 Structure of 6b displacement ellipsoids at the 50% probability
observed in the dimensions, e.g. the trans O(1)–Zr–Cl angles at
161.72(4), 155.99(8) and 161.50(5)◦ in 6b, 6d and 6e. In 5e and
6e there is a slight shortening of the M–Cl bond trans to the
perfluorophenyl substituted imine donor, relative both to the
cis M–Cl bonds and the trans M–Cl bonds found in the other
derivatives.
level.
to account for the ability of the bis(salicylaldiminato) complexes
9e
to promote living 1-alkene polymerisation.
The zirconium–ligand bond distances in these complexes
Careful inspection of the structure of 6e reveals a close contact
show little variation and are comparable with those found in
t
˚
=
(2.59 A) between a hydrogen atom on the 2-position of the THF
the bis(salicylaldiminato) complexes Zr{3-Bu -2-(O)C6H3CH
t
˚
8a
=
ligand and an ortho-fluorine (the closest contact in 5e is 2.70 A).
NC6H5}Cl2
and Zr{3-Bu -2-(O)C6H3CH N(2,4,6-Me3C6-
This distance is essentially the sum of the van der Waals radii
and this steric interaction along with one to Cl(3) may make a
significant contribution to the resistance to rotation about the
NC6F5 bond. Shorter, stronger interactions between b-H atoms
and the ortho-fluorines of C6F5 substituents have been proposed
H2)}Cl2.12 Structurally they resemble the mono(guanidinato)-
zirconium complex Zr{(PriNH)C(NPri)2}Cl3(THF), which also
has a distorted octahedral coordination sphere completed by
a THF donor and a fac arrangement of the three chloride
ligands.20
◦
˚
Table 4 Molecular dimensions for complexes 6b, 6d and 6e; bond lengths (A), angles ( ), esds are in parentheses
6b
6d
6e
Zr–O(1)
Zr–N
Zr–O(2)
Zr–Cl(2)
Zr–Cl(1)
Zr–Cl(3)
1.9512(17)
2.3934(17)
2.2596(15)
2.4303(8)
2.4223(7)
2.3974(7)
O(1)–Zr(1)
N(1)–Zr(1)
O(2)–Zr(1)
Cl(3)–Zr(1)
Cl(1)–Zr(1)
Cl(2)–Zr(1)
1.953(2)
2.371(3)
2.244(2)
2.4306(9)
2.4350(9)
2.4032(9)
O(1)–Zr(1)
N(1)–Zr(1)
O(2)–Zr(1)
Cl(3)–Zr(1)
Cl(1)–Zr(1)
Cl(2)–Zr(1)
1.9561(14)
2.3857(17)
2.2187(15)
2.4415(5)
2.4049(6)
2.4157(5)
O(1)–Zr–N
77.19(6)
84.73(6)
161.72(4)
96.46(4)
93.34(5)
86.20(5)
86.44(5)
167.99(5)
96.68(4)
86.15(5)
83.05(4)
176.11(4)
98.13(2)
96.62(3)
93.83(2)
O(1)–Zr(1)–N(1)
O(1)–Zr(1)–O(2)
O(1)–Zr(1)–Cl(3)
O(1)–Zr(1)–Cl(1)
O(1)–Zr(1)–Cl(2)
O(2)–Zr(1)–N(1)
N(1)–Zr(1)–Cl(3)
N(1)–Zr(1)–Cl(1)
N(1)–Zr(1)–Cl(2)
O(2)–Zr(1)–Cl(3)
O(2)–Zr(1)–Cl(1)
O(2)–Zr(1)–Cl(2)
Cl(3)–Zr(1)–Cl(1)
Cl(2)–Zr(1)–Cl(3)
Cl(2)–Zr(1)–Cl(1)
76.39(10)
82.05(10)
155.99(8)
97.77(7)
99.03(8)
93.17(10)
85.86(7)
174.13(8)
89.26(7)
82.94(7)
85.36(7)
177.52(7)
99.58(3)
96.74(4)
92.27(3)
O(1)–Zr(1)–N(1)
O(1)–Zr(1)–O(2)
O(1)–Zr(1)–Cl(3)
O(1)–Zr(1)–Cl(1)
O(1)–Zr(1)–Cl(2)
O(2)–Zr(1)–N(1)
N(1)–Zr(1)–Cl(3)
N(1)–Zr(1)–Cl(1)
N(1)–Zr(1)–Cl(2)
O(2)–Zr(1)–Cl(3)
O(2)–Zr(1)–Cl(1)
O(2)–Zr(1)–Cl(2)
Cl(1)–Zr(1)–Cl(3)
Cl(2)–Zr(1)–Cl(3)
Cl(1)–Zr(1)–Cl(2)
76.68(6)
84.41(6)
161.50(5)
98.04(5)
93.65(4)
85.49(6)
85.92(4)
171.10(5)
92.81(4)
88.06(4)
86.88(4)
177.67(4)
98.40(2)
93.42(2)
94.68(2)
O(1)–Zr–O(2)
O(1)–Zr–Cl(2)
O(1)–Zr–Cl(1)
O(1)–Zr–Cl(3)
O(2)–Zr–N
N–Zr–Cl(2)
N–Zr–Cl(1)
N–Zr–Cl(3)
O(2)–Zr–Cl(2)
O(2)–Zr–Cl(1)
O(2)–Zr–Cl(3)
Cl(1)–Zr–Cl(2)
Cl(3)–Zr–Cl(2)
Cl(3)–Zr–Cl(1)
O(1)–C(1)
C(1)–C(2)
C(2)–C(10)
C(10)–N
1.350(2)
1.408(3)
1.438(3)
1.308(3)
1.470(3)
C(1)–O(1)
1.340(4)
1.406(5)
1.444(5)
1.298(5)
1.459(4)
C(13)–O(1)
C(8)–C(13)
C(7)–C(8)
C(7)–N(1)
C(1)–N(1)
1.343(2)
1.408(3)
1.436(3)
1.309(3)
1.437(3)
C(1)–C(10)
C(10)–C(11)
C(11)–N(1)
C(12)–N(1)
N–C(11)
C(1)–O(1)–Zr
O(1)–C(1)–C(2)
C(1)–C(2)–C(10)
N–C(10)–C(2)
C(10)–N–Zr
C(11)–N–Zr
C(10)–N–C(11)
149.14(14)
116.4(2)
123.40(19)
130.05(19)
123.46(15)
124.33(13)
112.07(17)
C(1)–O(1)–Zr(1)
O(1)–C(1)–C(10)
C(1)–C(10)–C(11)
N(1)–C(11)–C(10)
C(11)–N(1)–Zr(1)
C(12)–N(1)–Zr(1)
C(11)–N(1)–C(12)
148.1(2)
117.5(3)
122.6(3)
127.9(3)
125.9(2)
118.7(2)
114.6(3)
C(13)–O(1)–Zr(1)
O(1)–C(13)–C(8)
C(13)–C(8)–C(7)
N(1)–C(7)–C(8)
C(7)–N(1)–Zr(1)
C(1)–N(1)–Zr(1)
C(7)–N(1)–C(1)
147.31(14)
117.16(18)
123.34(19)
128.6(2)
123.99(14)
123.52(13)
111.98(18)
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 6 5

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˚
Table 5 Molecular dimensions for complex 7; bond lengths (A), angles
(◦), esds are in parentheses
O(2)–Ti(1)
O(1)–Ti(1)
Cl(1)–Ti(1)
1.825(9)
2.094(9)
2.312(4)
O(3)–Ti(1)
Cl(3)–Ti(1)
Cl(2)–Ti(1)
2.100(9)
2.256(4)
2.321(4)
O(2)–Ti(1)–O(1)
O(2)–Ti(1)–Cl(1)
O(2)–Ti(1)–O(3)
O(2)–Ti(1)–Cl(3)
O(2)–Ti(1)–Cl(2)
O(1)–Ti(1)–Cl(1)
O(1)–Ti(1)–O(3)
O(1)–Ti(1)–Cl(3)
83.7(4)
89.3(3)
165.6(4)
98.4(3)
95.9(3)
84.6(3)
82.4(4)
177.7(3)
O(1)–Ti(1)–Cl(2)
O(3)–Ti(1)–Cl(1)
Cl(3)–Ti(1)–Cl(1)
Cl(1)–Ti(1)–Cl(2)
O(3)–Ti(1)–Cl(3)
O(3)–Ti(1)–Cl(2)
Cl(3)–Ti(1)–Cl(2)
85.9(3)
85.7(3)
94.52(15)
168.64(17)
95.4(3)
86.9(3)
94.70(15)
C(7)–O(2)
C(2)–C(7)
1.330(16)
1.431(18)
C(1)–C(2)
C(1)–O(1)
1.431(18)
1.257(15)
Fig. 7 Structure of 6d with displacement ellipsoids at the 50%
probability level.
C(7)–O(2)–Ti(1)
O(2)–C(7)–C(2)
C(1)–C(2)–C(7)
137.4(8)
116.6(12)
122.0(11)
O(1)–C(1)–C(2)
C(1)–O(1)–Ti(1)
126.0(11)
125.7(9)
Fig. 8 Structure of 6e with displacement ellipsoids at the 50%
probability level.
It appears that in octahedral mono(salicylaldiminato) com-
plexes bulkier NAr groups, for example those in 5c, 5e, 6b, 6d
and 6e, enforce a facial arrangement of the chloride ligands and
cis oxygen donors. Where there is less steric encumbrance such
as in 5a, the electronically favourable trans oxygen arrangement
Fig. 9 Structure of 7 with displacement ellipsoids at the 50% probability
level.
partial dissociation, giving rise to resonances for free and
coordinated THF and two sets of ligand signals; presumably
one for the THF adduct and one for the THF-free complex.
Furthermore, when 6b–6e were dissolved in toluene and left
to stand for an extended period the formation of colourless
precipitates was observed. For 6e this process was monitored by
1H NMR in d8-toluene solution over a period of several days.
The resonances for 6e slowly decreased in intensity, with a
concomitant increase in the intensity of new ligand signals,
which by comparison to the literature data were ascribed to
formation of the bis(salicylaldiminato) complex Zr{3-But-2-
8a
reminiscent of the bis(ligand) complexes is found. Further
support for this rationalisation is provided by the salicylaldehyde
t
=
complex Ti{3-Bu -2-(O)C6H3CH O}Cl3(THF) (7), which was
isolated from the reaction between the silyl ether derivative of
the parent aldehyde and TiCl4(THF)2 (Scheme 4). The crystal
structure of 7 (Fig. 9, for selected bond lengths and angles see
Table 5) is similar to that of 5a, with the aldehyde replacing the
phenylimine donor, leading to mutually trans oxygen atoms and
meridional chlorides.
=
(O)C6H3CH N(C6F5)}2Cl2. We interpret these observations as
being consistent with a ligand redistribution pathway that leads
to the decomposition of complexes 6 (Scheme 5), the rate of
which is dependent on the imine-substituent. Clearly, the sta-
bility of these complexes and the identity of any decomposition
products has important implications for their use as catalyst
precursors.
Polymerisations
Scheme 4
The mono(salicylaldiminato) titanium complexes 5a–e were
screened as ethene polymerisation pre-catalysts in combination
with MAO (methylaluminoxane). The results are presented in
Table 6. The productivity was found to be fairly insensitive to
the Al : Ti ratio in the range 200 : 5000, therefore a constant
loading of 1000 equivalents was employed for comparison
throughout. The highest and most consistent productivities were
obtained by pre-mixing the pre-catalyst for two minutes with
In the absence of oxygen and moisture all the six-coordinate
mononuclear titanium complexes (5) are indefinitely stable in
aromatic and halocarbon solution. In contrast, the stability
of the zirconium complexes (6) is dependent on the nature
of the imine-substituent. Whereas 6b, 6c and 6e appeared
unchanged when dissolved in deuterated dichloromethane or
chloroform for spectroscopic characterisation, 6d underwent
5 6 6
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1

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Scheme 5
Table 6 Ethene polymerisation results for the titanium mono(salicylaldiminato) complexesa
Run
Complex/lmol
T/◦C
t/min
Polymer yield/g
Productivityb
Mw
235000
271000
171000
513000
1120000
252000
nd
Mn
Polydispersity index
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
5a (6)
5a (6)
5a (6)
5b (6)
5b (6)
5b (6)
5c (6)
5c (6)
5c (6)
5d (6)
5d (6)
5d (6)
5e (6)
5e (6)
5e (6)
0
20
60
0
20
60
0
20
60
0
20
60
0
5
5
5
0.121
0.158
0.233
0.103
0.168
0.074
0.020
0.020
0.010
0.055
0.093
0.013
0.008
0.026
0.024
230
300
440
30
50
20
3
140000
148000
73000
8000
7000
12000
nd
1.7
1.8
2.3
mm
mm
mm
nd
nd
nd
mm
mm
mm
mm
mm
mm
35
35
35
60
60
60
10
10
10
5
3
1
nd
nd
nd
nd
55
93
13
16
52
49
933000
1170000
209000
690000
719000
883000
27000
7000
4000
14000
9000
1800
20
60
5
5
a In 50 cm3, 1 bar ethene pressure, 6 mmol MAO. b × 10−3 g PE {(mol metal) h bar}−1. nd = not determined; mm = multimodal.
half of the MAO before injection into the reactor. In no case
and 10–15, the traces are multimodal and therefore meaningful
−1
did the productivity exceed 106 g PE {(mol metal) h bar}
values for the polydispersity could not be extracted. The
implication is that 5b–e react with MAO to give rise to a
number of catalytically active species. We and Fujita have ob-
served similar behaviour with salicylaldiminato derived catalysts
before.12,21,22
The mono(salicylaldiminato) zirconium complexes 6b–e were
screened as ethene polymerisation pre-catalysts in combination
with MAO and the results for 6b, 6d and 6e are presented in
Table 7. 6c displayed very low activity and gave only a trace
of polymer under the experimental conditions employed. The
catalyst derived from 6e was the only one to exhibit greater than
moderate productivity.
and polymer yields showed an essentially linear dependence on
catalyst loading. Therefore we believe the productivity values are
an accurate measure of the catalyst system and are not affected
by mass transport limitation. For the titanium pre-catalysts
5a–e we did not observe a strong temperature dependence
of productivity. This is possibly the net result of a balance
between the competing effects of the increase in propagation
rate and decrease in monomer concentration with increasing
temperature. The data suggest that the catalyst activation step is
facile and that these catalyst systems have a measure of thermal
stability across the range 0–60 ◦C.
The phenyl-substituted complex 5a was found to give both
It is tempting to assume that the distinctive catalytic be-
haviour of 5a/MAO is indicative of a single-site cationic
mono(salicylaldiminato) titanium dialkyl catalyst. However,
the multimodal traces for 5b–e suggest that the true picture
may be somewhat more complicated. Zambelli’s report of the
apparent generation of bis(amidinate) titanium catalysts by
the in-situ disproportionation of mono(amidinate) complexes,
during propene polymerisation, is a plausible model for the
−1
the highest activity (440 kg PE {(mol metal) h bar} ) at
60 ◦C and the smallest polydispersity index (e.g. 2.3, run 3).
Increasing the steric bulk of the imine substituent causes a
decrease in productivity but a modest increase in Mw (see
runs 6 and 12). The productivity of these bulkier derivatives
is in line with that reported for the tert-butyl substituted pre-
−1
14b
catalyst X (30 kg {(mol metal) h bar} ). While GPC (gel
5b
permeation chromatography) data were obtained for runs 4–6
processes that may be at work in our system. Additional
Table 7 Ethene polymerisation results for zirconium mono(salicylaldiminato) complexesa
Run
Complex/lmol
T/◦C
t/min Polymer Yield/g
Productivityb
Mw
Mn
Polydispersity index
16
17
18
19
20
21
22
23
24
25
6b (6)
6b (6)
6b (6)
6d (6)
6d (6)
6d (6)
6e (6)
6e (6)
6e (6)
6e (6)
0
20
60
0
20
60
−20
0
10
10
10
10
10
10
5
5
5
5
Trace
0.020
0.019
0.059
0.075
0.035
0.293
0.342
0.534
0.155
Very low
17
16
59
75
nd
nd
nd
nd
nd
nd
266000
133000
28000
9300
nd
nd
nd
nd
nd
nd
74000
47000
9500
2000
nd
nd
nd
nd
nd
nd
3.6
2.8
3
35
590
680
1100
52
20
60
4.6
−1
a In 50 cm3, 1 bar ethene pressure, 6 mmol MAO. b × 10−3 g PE {(mol metal) h bar} nd = not determined (insufficient material).
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 6 7

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catalytically active species may also be formed through inter-
or intra-molecular alkylation of the ligand imine function.22
Complex syntheses
t
=
[Ti{3-Bu -2-(O)C6H3CH N(C6H5)}Cl(l-Cl3)TiCl3] (3a).
A
stirred solution of TiCl4 (1.10 cm3, 10 mmol) in toluene (30 cm3)
at −78 ◦C was treated with a solution of 2a (1.27 g, 5 mmol)
in toluene (30 cm3). The resulting solution was then warmed
to room temperature and heated under reflux for 16 h. The
volatiles were removed under reduced pressure and the resulting
red solid was washed with light petroleum (2 × 40 cm3). The
crude product was recrysta◦llised from a dichloromethane–light
petroleum mixture at −30 C, affording a red microcrystalline
Conclusion
Whereas treating ZrCl4 with silylated iminophenols (3-But-
=
2-(OSiMe3)C6H3CH N(Ar)) is not selective, TiCl4 reacts
t
=
cleanly to afford binuclear complexes [Ti{3-Bu -2-(O)C6H3CH
N(Ar)}Cl(l-Cl3)TiCl3]. Treatment of MCl4(THF)2 (M
=
Ti or Zr) with 2a–e provides a facile synthesis of the
octahedral mono(salicylaldiminato) complexes M{3-But-2-
1
solid (2.47 g, 4.15 mmol, 83%). H NMR (300 MHz, 293 K,
=
(O)C6H3CH N(Ar)}Cl3(THF). The zirconium complexes are
=
CDCl3): d 8.54 (CH N), 7.75 (dd, 1H, J = 6.28, 1.5 Hz, Ar–
H), 7.55–7.27 (m, 7H, Ar–H), 1.58 (s, 9H, C(CH3)3). 13C NMR
unstable in toluene solution and slowly undergo a ligand
redistribution reaction, giving rise to bis(salicylaldiminato)
complexes. Mono(salicylaldiminato) complexes of titanium and
zirconium can be activated using MAO to give ethene poly-
merisation catalysts, the productivity of which is sensitive to
the imine substituent. The productivities are modest compared
to bis(salicylaldiminato) derived catalysts. We are currently
exploring the use of these mono(salicylaldiminato) complexes
as precursors to mixed ligand pre-catalysts.
=
(75.5 MHz, 293 K, CDCl3): d 167.9 (C–O), 164.0 (C N), 152.3
(Ar), 138.4, 135.2, 133.6, 129.6, 128.4, 125.7, 124.9, 124.5 (Ar),
35.6 (C(CH3)3), 29.9 (C(CH3)3). Anal. Found: C, 33.57; H, 3.41;
N, 2.22; Cl, 39.01. Calc. For C17H18NOCl2Ti2: C, 34.24; H, 3.04;
N, 2.35; Cl, 41.02%.
t
=
Ti{3-Bu -2-(O)C6H3CH N(C6H5)}Cl3(THF) (5a). A stirred
solution of TiCl4(THF)2 (1.15 g, 3.44 mmol) in dichloromethane
◦
(20 cm3) at −78 C, was treated with a solution of 2a (1.12 g,
3.45 mmol) in dichloromethane (20 cm3). The resulting solution
was allowed to warm slowly to room temperature and stirred
for 16 h. The volatiles were removed under reduced pressure
and the resulting red solid was washed with light petroleum
(2 × 40 cm3). The crude product was recrystallised from a
dichloromethane/light petroleum solvent mixture with a drop of
tetrahydrofuran added at −30 ◦C to give dark red, needle-shaped
crystals (suitable for X-ray diffraction) (1.52 g, 3.17 mmol,
92%).24 1H NMR (293 MHz, 293 K, CDCl3): d 8.17 (s, 1H,
Experimental
General
Syntheses were performed under nitrogen using standard
Schlenk techniques. Solvents were distilled over sodium-benzo-
phenone (diethyl ether, tetrahydrofuran), sodium (toluene),
sodium–potassium alloy (light petroleum, bp 40–60 ◦C), or
CaH2 (dichloromethane). NMR solvents (CDCl3, C6D6, C7D8)
˚
were dried over activated 4 A molecular sieves and degassed by
=
CH N), 7.69–7.15 (m, 8H, Ar–H), 4.24 (m, 4H, THF), 1.72 (m,
several freeze–thaw cycles. NMR spectra were recorded using a
Bruker DPX300 spectrometer. Chemical shifts are reported in
4H, THF), 1.62 (s, 9H, But). 13C NMR (75.5 MHz, 293 K,
=
CDCl3): d 166.4 (C–O), 162.6 (C N), 151.1, 138.8, 134.5,
ppm and referenced to residual solvent resonances (1H, 13C); 19
F
133.9, 129.2, 128.3, 128.0, 125.1, 124.4 (Ar), 76.7 (THF), 35.8
(C(CH3)3), 30.1 (C(CH3)3), 25.7 (THF). Anal. Found: C, 51.49;
H, 5.38; N, 2.77; Cl, 22.60. Calc. for C21H27NO2Cl3Ti: C, 52.69;
H, 5.47; N, 2.93; Cl, 22.22%.
is relative to CFCl3. Nitrogen and ethene (BOC, 99.5%) were
purified by passing through columns of supported P2O5 with
˚
moisture indicator, and activated 4 A molecular sieves. MAO was
purchased from Witco as a 10% solution in toluene and used as
received. GPC analyses were performed in-house on a Polymer
Labs PL-GPC-220 or by RAPRA Technology Ltd. Elemental
analyses were performed by the School analysis service. Mass
spectrometry was provided by the EPSRC National Mass
Spectrometry Service Centre, Swansea.
t
i
=
Zr{3-Bu -2-(O)C6H3CH N(2,6-Pr 2C6H3)}Cl3(THF) (6b).
2b (1.36 g, 3.4 mmol) was treated with ZrCl4(THF)2 (1.29 g,
3.4 mmol) following a similar procedure to that for 5a. The
product was isolated in a similar fashion to 5a giving yellow
needle-shaped crystals (suitable for X-ray diffraction) (1.88 g,
23
ZrCl4(THF)2 and the ligands 1a–e were prepared following
1
8a
3.09 mmol, 91%). H NMR (300 MHz, 293 K, CDCl3): d 8.35
the literature procedures. Example syntheses are presented
=
(s, 1H, CH N), 7.71 (dd, 1H, J = 6.1, 1.6 Hz, Ar–H), 7.28–7.05
below, synthetic procedures and full characterisation data are
available as ESI.†
(m, Ar–H), 4.35 (m, 4H, THF), 2.37 (s 2.02 (m, 4H, THF),
1.56 (s, 9H, C(CH3)3), 1.32 (d, 6H, J = 6.2 Hz, CH(CH3)2),
1.04 (d, 6H, J = 6.8, CH(CH3)2).). 13C NMR (75.5 MHz,
293 K, CDCl3): d 173.5 (C–O), 139.9, 138.3, 135.7, 134.5, 129.5,
128.6, 128.0, 125.7, 124.8, 123.5, 122.1 (Ar), 76.0 (THF), 35.5
(C(CH3)3), 30.1 (C(CH3)3), 28.5 (CH(CH3)2) 26.2 (CH(CH3)2),
25.8 (THF), 21.9 (CH(CH3)2). Anal. Found: C, 50.67; H, 6.19;
N, 1.97; Cl, 20.61. Calc. For C27H38NO2Cl3Zr·0.5CH2Cl2: C,
50.92; H, 6.06; N, 2.16; Cl, 21.86%.
Ligand syntheses
t
=
3-Bu -2-(OSiMe3)C6H3CH N(C6H5) (2a). A stirred solu-
tion of 1a (11.9 g, 30 mmol) in light petroleum (100 cm3) at
◦
−78 C was treated with n-butyllithium (18.8 cm3 of a 1.6 M
hexane solution, 30 mmol). The resulting suspension was stirred
for 2 hours at room temperature and the precipitated lithium salt
isolated by filtration. The salt was dried under reduced pressure
before being dissolved in tetrahydrofuran (100 cm3). Excess
trimethylsilyl chloride (20 cm3) was added and the solution
heated under reflux for 8 h. The volatiles were removed under
reduced pressure. The crude product was extracted with light
petroleum (40 cm3) and crystallised at −30 ◦C to give large
pale yellow plate-like crystals (8.9 g, 27 mmol, 91%). 1H NMR
t
=
Ti{3-Bu -2-(O)C6H3CH O}Cl3(THF) (7). 1f (1.6 g,
5 mmol) was treated with TiCl4(THF)2 (1.62 g, 5 mmol)
following a similar procedure to that for 5a. The volatiles
were removed under reduced pressure and the resulting red
solid was washed with light petroleum. The crude product was
recrystallised from a dichloromethane–light petroleum mixture
with a drop of tetrahydrofuran added and cooled to −30 ◦C to
=
(293 MHz, 293 K, CDCl3): d 8.75 (s, 1H, CH N), 7.90 (dd,
1
1H, J = 5.9, 1.8 Hz, Ar–H), 7.48–7.05 (m, 7H, Ar–H), 1.45
give red, plate-like crystals (suitable for X-ray diffraction). H
(s, 9H, But), 0.25 (s, 9H, Si(CH3)3). 13C NMR (75.5 MHz,
NMR (300 MHz, 293 K, CDCl3): d 9.55 (s, 1H, CH O), 7.86
=
=
293 K, CDCl3): d 159.5 (C–O), 155.9 (C N), 152.7, 141.5, 131.0,
(dd, 1H, J = 7.7, 1.4 Hz, Ar–H), 7.66 (dd, 1H, J = 7.7, 1.4 Hz,
Ar–H), 7.23 (t, 1H, J = 7.7 Hz, Ar–H), 4.63 (m, 4H, THF), 2.13
(m, 4H, THF), 1.55 (s, 9H, But). 13C NMR (75.5 MHz, 293 K,
129.5, 129.2, 126.6, 126.2, 122.1, 121.5 (Ar), 35.3 (C(CH3)3), 20.9
(C(CH3)3), 2.2 (Si(CH3)3). Anal. Found: C, 74.00; H, 8.33; N,
4.49. Calc. for C20H27N: C, 73.79; H, 8.36; N, 4.30%.
=
CDCl3): d 195.4 (C O), 139.6, 135.7, 124.8 (Ar), 77.0 (THF),
5 6 8
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1

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D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 6 9

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35.7 (C(CH3)3), 30.0 (C(CH3)3), 26.1 (THF). Anal. Found: C,
42.65; H, 5.21; Cl, 25.36. Calc. For C15H21O3Cl3Ti: C, 44.64; H,
5.24; Cl, 26.35%.
Acknowledgements
The support of the Engineering and Physical Sciences Research
Council and the University of East Anglia, together with
Synchrotron Radiation Source beam-time awarded by CCLRC,
are gratefully acknowledged.
Polymerisation procedure
A solution of MAO in toluene (50 cm3) was saturated with ethene
(1 bar) at the given temperature. Polymerisation was initiated by
addition of a toluene solution of pre-catalyst into the reactor
under vigorous stirring (1000 rpm). Methanol (1 cm3) was added
to terminate the polymerisation. The polymeric product was
precipitated and separated from aluminium residues by addition
of methanol (∼300 cm3) and 2 M HCl (∼5 cm3). The polymer
was collected by filtration, washed with methanol, 2 M HCl,
distilled water and again with methanol before drying until
constant mass at 80 ◦C. Each run is the average of at least two
polymerisations.
References
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Crystal structure analyses
Crystal samples were examined in several laboratories. The
crystal structure and refinement data are collected in Table 8.
Intensity data for complexes 3b, 5a, 5c, and 6b were measured at
UEA on a Rigaku/MSC R-Axis-IIc image-plate diffractometer
equipped with a rotating anode X-ray source (Mo-Karadiation)
and graphite monochromator; complex 4c was analysed at
the Synchrotron Radiation Source at Daresbury (on a Bruker
˚
SMART 1K CCD diffractometer with radiation k = 0.6984 A),
and data for complexes 5e, 6d, 6e and 7 were recorded at the
EPSRC National Crystallography Service at the University of
Southampton on a Nonius KappaCCD diffractometer (with
Mo-Ka radiation and graphite monochromator). The proce-
dures for all were similar, and that for complex 3b is described
below.
From a sample of deep red plate crystals of 3b under oil,
one, ca. 0.4 × 0.27 × 0.23 mm, was mounted on a glass fibre
and fixed in the cold nitrogen stream on the Rigaku R-Axis-
IIc image-plate diffractometer. The total number of reflections
recorded, to hmax = 25.6◦, was 15791 of which 5091 were unique
(Rint = 0.043); 4308 were ‘observed’ with I > 2r(I).
Data were processed using the DENZO/SCALEPACK
programs.25 The structure was determined by the direct methods
routines in the SHELXS program and refined by full-matrix
least-squares methods, on all unique F2, in SHELXL).26 The
non-hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were included in idealised posi-
tions and their Uiso values were set to ride on the Ueq values of
the parent carbon atoms. At the conclusion of the refinement,
wR2 = 0.094 and R1 = 0.042 for all 5091 reflections weighted
w = [r2(Fo2) + (0.0528P)2 + 0.724P]−1 with P = (Fo + 2Fc )/3;
2
2
for the ‘observed’ data only, R1 = 0.034.26
In the final difference map, the highest peaks (to ca. 0.30 e
A ) were close to the titanium atoms.
−3
˚
Scattering factors for neutral atoms were taken from ref.
27. Computer programs used in this analysis have been noted
above, in Table 4 of ref. 28, or in ref. 29, and were run on
a Silicon Graphics Indy at the University of East Anglia, or
a DEC-AlphaStation 200 4/100 in the Biological Chemistry
Department, John Innes Centre.
The diffraction pattern of a crystal of compound 7 suggests
the presence of a second minor crystal, whose orientation matrix
could not be determined, but whose diffraction intensities may
have contributed to those measured for the major crystal. This
would account for the high R factors and large residual density
for this sample. We are confident, however, that the structure
is correct and that the molecular dimensions are reliable within
the limits shown.
12 R. K. J. Bott, D. L. Hughes, M. Schormann, M. Bochmann and S. J.
Lancaster, J. Organomet. Chem., 2003, 665, 135.
13 A. F. Mason and G. W. Coates, J. Am. Chem. Soc., 2004, 126, 10798.
14 (a) D. A. Pennington, D. L. Hughes, M. Bochmann and S. J.
Lancaster, Dalton Trans., 2003, 3480; (b) a complementary study
on mono(salicylaldiminato) complexes of titanium with aliphatic
substituents on the imine nitrogen has recently been reported: D.
Owiny, S. Parkin and F. T. Ladipo, J. Organomet. Chem., 2003, 678,
134.
15 (a) A. M. Cardoso, R. J. H. Clark and S. J. Moorhouse, J. Chem.
Soc., Dalton Trans., 1980, 1156; (b) E. C. Lund and T. Livinghouse,
Organometallics, 1990, 9, 2426; (c) M. J. Sarsfield, M. Said, M.
Thornton-Pett, L. A. Gerrard and M. Bochmann, J. Chem. Soc.,
Dalton Trans., 2001, 822, and references therein.
CCDC reference numbers 214921, 214922 and 250156–
250162.
See http://www.rsc.org/suppdata/dt/b4/b414229b/ for cry-
stallographic data in CIF or other electronic format.
16 The reaction between 2d and TiCl4 gives rise to a mixture of products,
which we have been unable to separate and definitively characterise.
17 F. Weller, F. Schmock and K. Dehnicke, Z. Naturforsch., Teil B, 1996,
51, 1359.
5 7 0
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1

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18 (a) R. Bettenhausen, W. Milius and W. Schnick, Chem. Eur. J., 1997, 3,
1337; (b) See also: E. Solari, C. Floriani, A. Chiesi-Villa, C. Guastini,
J. Chem. Soc., Chem. Commun., 1989, 1747; (c) E. Solari, C. Floriani,
K. Schenk, A. Chiesi-Villa, C. Rizzoli, M. Rosi and A. Sgamellotti,
Inorg. Chem., 1994, 33, 2018; (d) Q. Feng, S. Luo, M. Olmstead,
T. B. Rauchfuss and P. R. Stafford, Chem. Mater., 1997, 9, 641; (e) P.
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J. Organomet. Chem., 2001, 620, 113.
23 L. E. Manzer, Inorg. Synth., 1982, 21, 136.
24 Perhaps due to a tendency towards dissociation in solution, addition
of a small amount of THF was found to aid recrystallisation from
dichloromethane solution.
25 Z. Otwinowski and W. Minor, Methods Enzymol., 1997, 276, 307.
26 G. M. Sheldrick, SHELX-97 – Program for crystal structure de-
termination (SHELXS) and refinement (SHELXL), University of
Go¨ttingen, Germany, 1997.
27 International Tables for X-ray Crystallography, Kluwer Academic
Publishers, Dordrecht, 1992, vol. C, pp. 500, 219 and 193.
28 S. N. Anderson, R. L. Richards and D. L. Hughes, J. Chem. Soc.,
Dalton Trans., 1986, 245.
19 X was reported in ref. 13 without bond lengths and angles because
of technical difficulties.
20 P. Bazinet, D. Wood, G. P. A. Yap and D. S. Richeson, Inorg. Chem.,
2003, 42, 6225.
21 Y. Tohi, H. Makio, S. Matsui, M. Onda and T. Fujita, Macro-
molecules, 2003, 36, 523.
22 For an example see: P. R. Woodman, N. W. Alcock, I. J. Munslow,
C. J. Sanders and P. Scott, J. Chem. Soc., Dalton Trans., 2000, 3340.
29 G. M. Sheldrick, SHELXTL package, including XS (for structure
determination), XL (structure refinement) and XP (molecular graph-
ics), Siemens Analytical Inc., Madison, WI, USA, 1995.
30 H. D. Flack, Acta Crystallogr., Sect. A, 1983, 39, 876.
D a l t o n T r a n s . , 2 0 0 5 , 5 6 1 – 5 7 1
5 7 1