Titanium and zirconium complexes that contain a tridentate bis(phenolato) ligand of the [OOO]-type

Article abstract of DOI:10.1016/S0020-1693(02)01289-6

The oxygen-linked bis(phenol) 2-oxapropanediyl-1,3-bis(2-tert-butyl-4-methylphenol), [OOO]H₂, was prepared in good yield by the condensation of 2-tert-butyl-6-hydroxymethyl-4-methylphenol at 155°C. This bis(phenol) reacted cleanly with titanium tetrachloride to give the orange titanium dichloro complex [OOO]TiCl₂ in virtually quantitative yield. The solubility in pentane indicates a monomeric structure for [OOO]TiCl₂ in solution. The reaction of titanium tetra(isopropoxide) gave the di(isopropoxy) complex [OOO]Ti(OiPr)₂ which also adopts a monomeric structure of C_2v-symmetry in solution. The reaction of the dichloro complex [OOO]TiCl₂ with benzyl Grignard reagent in diethyl ether gave the highly light- and air-sensitive, orange dibenzyl complex [OOO]Ti(CH₂Ph)₂ in good yield. Single crystal X-ray crystallography revealed a penta-coordinate titanium center coordinated to two monohapto benzyl ligands and the tridentate [OOO] ligand in a meridional fashion. The reaction of zirconium tetrabenzyl with [OOO]H₂ gave the bis(ligand) complex [OOO]₂Zr, regardless of the stoichiometry employed. Crystallographic analysis shows an octahedral coordination geometry with cis-configuration of the two ligands. The compound can be transformed into the dichloro complex [OOO]ZrCl₂ by disproportionation with zirconium tetrachloride. Polymerization tests using [OOO]TiCl₂ under methylaluminoxane activation revealed moderate polymerization activity towards ethylene and styrene.

Full text of DOI:10.1016/S0020-1693(02)01289-6

Inorganica Chimica Acta 345 (2003) 221ꢁ227
/
www.elsevier.com/locate/ica
Titanium and zirconium complexes that contain a tridentate
bis(phenolato) ligand of the [OOO]-type
Valentine Reimer a, Thomas P. Spaniol a, Jun Okuda a,*, Henner Ebeling b,
Arno Tuchbreiter b, Rolf Mulhaupt b
¨
a Institut fur Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universitat, Duesbergweg 10-14, D-55099 Mainz, Germany
¨
¨
b Freiburger Materialforschungszentrum und Institut fur Makromolekulare Chemie, Albert-Ludwig-Universitat Freiburg, Stefan-Meier-Strasse 21,
D-79104 Freiburg, Germany
¨
¨
Received 5 June 2002; accepted 6 August 2002
Dedicated in honor of Professor Richard R. Schrock
Abstract
The oxygen-linked bis(phenol) 2-oxapropanediyl-1,3-bis(2-tert-butyl-4-methylphenol), [OOO]H2, was prepared in good yield by
the condensation of 2-tert-butyl-6-hydroxymethyl-4-methylphenol at 155 8C. This bis(phenol) reacted cleanly with titanium
tetrachloride to give the orange titanium dichloro complex [OOO]TiCl2 in virtually quantitative yield. The solubility in pentane
indicates a monomeric structure for [OOO]TiCl2 in solution. The reaction of titanium tetra(isopropoxide) gave the di(isopropoxy)
complex [OOO]Ti(OiPr)2 which also adopts a monomeric structure of C2v-symmetry in solution. The reaction of the dichloro
complex [OOO]TiCl2 with benzyl Grignard reagent in diethyl ether gave the highly light- and air-sensitive, orange dibenzyl complex
[OOO]Ti(CH2Ph)2 in good yield. Single crystal X-ray crystallography revealed a penta-coordinate titanium center coordinated to
two monohapto benzyl ligands and the tridentate [OOO] ligand in a meridional fashion. The reaction of zirconium tetrabenzyl with
[OOO]H2 gave the bis(ligand) complex [OOO]2Zr, regardless of the stoichiometry employed. Crystallographic analysis shows an
octahedral coordination geometry with cis-configuration of the two ligands. The compound can be transformed into the dichloro
complex [OOO]ZrCl2 by disproportionation with zirconium tetrachloride. Polymerization tests using [OOO]TiCl2 under
methylaluminoxane activation revealed moderate polymerization activity towards ethylene and styrene.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Titanium; Zirconium; Phenolato ligands; Alkyl complexes; Polymerization catalysts
1. Introduction
ished. Following the unique polymerization activity of
the titanium complexes containing the sulfur-bridged
bis(phenolato) ligand 2,2?-thiobis(6-tert-butyl-4-methyl-
Oxygen-linked bis(anilido) ligands of the [NON]-type
such as {(tBu-d6Ã
Schrock et al. to be a class of ancillary ligands that
stabilize cationic Group 4 metal alkyl moieties [1ꢁ5].
N-o-
/
N-o-C6H4)2O}2ꢀ have been shown by
phenolato), {2,2?-S(OC6H2Ã
/
6-tBuÃ
/
4-Me)2}2ꢀ (tbmp)
[6,7], we have been interested in developing Group 4
metal complexes that contain the homologous [OOO]-
/
type ligand {2,2?-O(OC6H2Ã
/
6-tBuÃ
/
4-Me)2}2ꢀ. Theore-
The tetra-coordinate alkyl cation [{(tBu-d6Ã
/
C6H4)2O}ZrMe]ꢂ with a twisted fac coordination of
this diamido/donor ligand acts as an efficient living a-
olefin polymerization initiator [2,5]. When such triden-
tate ligands adopt the mer coordination mode, the
degree of the living polymerization character is dimin-
tical calculations [8] predicted that the barrier for
ethylene insertion is reduced, when the sulfur donor is
exchanged for oxygen in the putative intermediate
{[OXO]TiMe(H2CÄ
/
CH2)}ꢂ (Xꢃ
O, S). However, the
/
difficulty in synthesizing 2,2?-dihydroxydiphenylether
derivatives prompted us to explore the coordination
behavior of the somewhat more flexible ligand with a
CH2OCH2 link between the bulky phenolato functions.
* Corresponding author. Tel.: ꢂ
392 5605
E-mail address: okuda@mail.uni-mainz.de (J. Okuda).
/
49-6131-392 5333; fax: ꢂ49-6131-
/
Group
4
metal complexes with triatomic links
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 2 8 9 - 6

222
V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ227
/
CH2NRCH2 between two phenolato units have recently
been demonstrated by Kol and coworkers to be living 1-
hexene polymerization catalysts, provided the amino
substituent R features an appropriate pendant donor
2.3. [OOO]TiCl2 (2)
Titanium tetrachloride (355 mg, 1.87 mmol) was
stirred in 10 ml of Et2O at 0 8C for 30 min. To the
resulting yellow suspension was added dropwise a
solution of 1 (693 mg, 1.87 mmol) in 10 ml of Et2O.
group [9ꢁ15]. We report here the first examples of
/
titanium and zirconium complexes that contain a
[OOO]-type bis(phenolato) ligand with a central ether
function.
The color of the mixture changed to brownꢁred. The
/
reaction mixture was stirred for 3 h at room temperature
(r.t.) and the solvent was removed under reduced
pressure. The residue was washed with C5H12 and dried
in vacuo to give 893 mg (1.83 mmol, 98%) of pure 2 as
an orange solid. 1H NMR (CDCl3): d 1.45 (s, 18H,
C(CH3)3), 2.30 (s, 6H, 4-CH3), 4.91 (s, 4H, CH2O), 6.85
2. Experimental
4
4
(d, JHH
ꢃ
/
1.6 Hz, 2H, 3-CH), 7.10 (d, JHH
ꢃ1.6 Hz,
/
2H, 5-CH). 13C NMR (CDCl3): d 21.1 (4-CH3), 29.6
(C(CH3)3), 34.7 (C(CH3)3), 74.6 (CH2O), 123.3 (C-2),
126.6 (C-3), 128.2 (C-5), 132.9 (C-4), 136.1 (C-6), 161.3
2.1. General considerations
(C-1). EI MS (70 eV): m/z 441 (19%, [Mꢂꢀ
(17%, [Mꢂꢀ CH3]), 363 (18%, [Mꢂꢀ
C4H9ꢀ
2CH3ꢀ 2C4H9ꢀ2CH3]). Anal.
Cl]), 340 (21%, [Mꢂꢀ
Calc. for C24H32Cl2O3Ti: C, 59.14; H, 6.62. Found: C,
59.21; H, 6.61%.
/
CH3]), 414
C4H9ꢀ
All manipulations were carried out under argon
atmosphere in a glovebox or by using the standard
Schlenk techniques in oven-dried glassware. The sol-
vents Et2O, C6H5CH3, tetrahydrofuran, n-hexane and
n-pentane were dried by refluxing over sodium/benzo-
phenone and CH2Cl2 over CaH2 under an inert gas and
distilled freshly before use. Titanium tetrachloride and
Ti(OiPr)4 were purchased from Acros and used without
further purification. Zr(CH2Ph)4 [16] and 6-tert-butyl-2-
hydroxymethyl-4-methylphenol [17] were synthesized
/
/
/
/
/
/
/
2.4. [OOO]Ti(OiPr)2 (3)
A solution of 1 (91.0 mg, 245 mmol) in 5 ml of Et2O
was added to a stirred solution of titanium tetra(iso-
propoxide) (70.0 mg, 246 mmol) in 5 ml of Et2O at 0 8C.
During this time the color changed from colorless to
yellow. The reaction mixture was stirred for 4 h, and the
solvent was removed by freeze-drying. The residue was
1
according to the literature. H and 13C NMR spectra
were recorded on a Bruker DRX 400 spectrometer (1H:
400 MHz; 13C: 100 MHz) at 298 K. C6D6, THF-D8,
C6D5Br, and CDCl3 were purchased from Deutero and
purified by conventional methods before use. The
chemical shifts were referenced internally according to
the residual solvent resonances and reported relative to
Me4Si. Mass spectra were obtained on a Finnigan 8230
spectrometer. Elemental analysis was performed by the
Microanalytical Laboratory of this department.
dissolved in C6H14 and cooled at ꢀ70 8C. After several
/
days yellow precipitate of 3 was isolated, yield: 114 mg
(213 mmol, 87%). 1H NMR (C6D6): d 1.31 (d, 12H,
OCH(CH3)2), 1.64 (s, 18H, C(CH3)3), 2.22 (s, 6H, 4-
CH3), 4.48 (s, 4H, CH2O), 4.95 (s, 2H, OCH(CH3)2),
4
4
6.57 (d, JHH
ꢃ
/
1.8 Hz, 2H, 3-CH), 7.18 (d, JHH
ꢃ1.8
/
Hz, 2H, 5-CH). 13C NMR (C6D6): d 21.1 (4-CH3), 26.3
(OCH(CH3)2), 30.1(C(CH3)3), 35.1 (C(CH3)3), 73.5
(CH2O), 80.0 (OCH(CH3)2), 124.6 (C-2), 127.2 (C-3),
128.1 (C-5), 128.6 (C-4), 136.5 (C-6), 160.1 (C-1). EI MS
2.2. [OOO]H2 (1)
Neat 6-tert-butyl-2-hydroxymethyl-4-methylphenol
(24.7 g, 127 mmol) was heated slowly to 155 8C for 5
h. The crude product was dissolved in pentane and
(70 eV): m/z 534 (24%, [M]ꢂ), 475 (6%, [Mꢂꢀ
/
OC3H7]), 358 (100%, [Mꢂꢀ
Anal. Calc. for C30H46O5Ti: C, 67.40; H, 8.67. Found:
/
C4H9ꢀOC3H7ꢀ2CH3]).
/
/
cooled to ꢀ
/
70 8C for several days. During this time a
C, 67.17; H, 8.55%.
colorless solid precipitated which was filtered and dried
in vacuo, yield 16.0 g (43.2 mmol, 68%). 1H NMR
(CDCl3): d 1.41 (s, 18H, C(CH3)3), 2.25 (s, 6H, 4-CH3),
4.68 (s, 4H, CH2O), 6.69 (s, 2H, 3-CH), 6.90 (s, 2H,
OH), 7.08 (s, 2H, 5-CH). 13C NMR (CDCl3): d 20.7 (4-
CH3), 29.6 (C(CH3)3), 34.6 (C(CH3)3), 71.0 (CH2O),
121.4 (C-2), 127.6 (C-5), 128.2 (C-3), 128.5 (C-4), 137.5
(C-6), 152.8 (C-1). EI MS (70 eV): m/z 370 (31%, [M]ꢂ),
194 (82%, [HOC6H2(C4H9)CH3]ꢂ), 177 (100%, 1/
2.5. [OOO]Ti(CH2Ph)2 (4)
To a solution of 2 (320 mg, 657 mmol) in 40 ml of
Et2O, cooled to 0 8C, was added dropwise a 1.21 M
solution of Mg(CH2Ph)Cl in Et2O (0.93 ml, 1.12 mmol).
The reaction mixture was stirred for 12 h at r.t. The
solvent was removed under reduced pressure and the
orange residue was extracted three times with 40 ml of
C6H14. After filtration, hexane was removed to afford
2[Mꢂꢀ
/
OH]ꢂ). Anal. Calc. for C24H34O3: C, 77.79;
1
H, 9.25; Found: C, 77.73; H, 9.27%.
336 mg (561 mmol, 85%) of 4 as orange crystals. H

V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ
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223
NMR (C6D6): d 1.95 (s, 18H, C(CH3)3), 2.20 (s, 6H, 4-
CH3), 3.33 (s, 4H, CH2O), 3.63 (s, 4H, TiCH2Ph), 6.27
2.7. Reaction of 4 with B(C6F5)3
4
(d, JHH
3
1.6 Hz, 2H, 3-CH), 6.58 (t, JHH
C6D5Br (0.5 ml) was added to an equimolar mixture
of 4 (10 mg, 16.7 mmol) and B(C6F5)3 (8.5 mg, 16.7
ꢃ
/
ꢃ7.6 Hz,
ꢃ7.6 Hz, 4H, meta
/
3
2H, para CH2C6H5), 6.78 (t, JHH
/
mmol) in an NMR tube at ꢀ
/
30 8C. The color turned
CH2C6H5), 7.18 (d, 4H, ortho CH2C6H5), 7.30 (d,
4JHH 1.6 Hz, 2H, 5-CH). 13C NMR (C6D6): d 21.0
1
dark red immediately. H NMR (C6D5Br, ꢀ
/
25 8C): d
ꢃ
/
1.33 (s, 18H, C(CH3)3), 2.21 (s, 6H, 4-CH3), 3.37 (s, 2H,
TiCH2Ph), 3.82 (s, 2H, CH2B(C6F5)3), 4.30 (br, 4H,
(4-CH3), 31.4 (C(CH3)3), 35.4 (C(CH3)3), 78.4 (CH2O),
86.0 (TiCH2Ph), 123.5 (para CH2C6H5), 125.4 (C-2),
126.0 (C-3), 128.4 (meta CH2C6H5), 128.8 (C-5), 128.6
(C-4), 129.7 (ortho CH2C6H5), 136.0 (C-6), 141.3 (ipso
CH2C6H5), 158.8 (C-1). Anal. Calc. for C38H46O3Ti: C,
76.23; H, 7.74. Found: C, 75.98; H, 7.33%.
CH2O), 6.61 (s, 2H, 3-CH), 6.84ꢁ
with solvent signals, 5-CH and CH2C6H5). 19F NMR
(C6D5Br, ꢀ25 8C): d ꢀ129.8 (ortho-F), ꢀ162.6 (para-
F), ꢀ165.5 (meta-F).
/
7.40 (signals overlap.
/
/
/
/
2.8. [OOO]2Zr (5)
2.6. X-ray crystal structure analysis of 4
To a solution of Zr(CH2Ph)4 (49.0 mg, 107 mmol) in 5
ml of Et2O was added an ethereal solution of 1 (80.0 mg,
215 mmol) at 0 8C. The reaction mixture was stirred for
2 h at r.t. All volatiles were removed under reduced
pressure to quantitatively give the zirconium complex 5
Single crystals suitable for X-ray crystal structure
analysis were obtained by cooling a concentrated hexane
solution to ꢀ
methods (SHELXS-86) [18] and refined (SHELXL-97) [19]
against all F2 data, resulting in R1ꢃ
0.1364 and wR2ꢃ
0.1287 for all reflections and R1ꢃ0.0555 as well as
wR2ꢃ0.1041 for all observed reflections with I ꢀ2s(I);
Goodness-of-fitꢃ1.005. The crystal data of compound
/
30 8C. The structure was solved by direct
1
as a colorless solid. H NMR (C6D6): d 1.59 (s, 36H,
C(CH3)3), 2.20 (s, 12H, 4-CH3), 4.46 (s, 8H, CH2O),
/
/
4
4
6.51 (d, JHH
ꢃ
/
1.8 Hz, 4H, 3-CH), 7.22 (d, JHH
ꢃ1.8
/
/
Hz, 4H, 5-CH). 13C NMR (C6D6): d 20.9 (4-CH3), 30.4
(C(CH3)3), 35.1 (C(CH3)3), 75.1 (CH2O), 123.5 (C-2),
127.5 (C-3), 127.8 (C-4), 128.8 (C-5), 137.7 (C-6), 157.8
(C-1). EI MS (70 eV): m/z 826 (65%, [Mꢂ]), 620 (100%,
/
/
/
4 are listed in Table 1.
Mꢂꢀ
/
[OC6H2(C4H9)(CH3)CH2]ꢀ2CH3). Anal. Calc.
/
for C48H64O6Zr: C, 69.61; H, 7.79. Found: C, 70.18;
H, 8.38%.
Table 1
Crystal data and structure refinement parameters for complexes 4 and
5
2.9. X-ray crystal structure analysis of 5
Complex
4
5
Single crystals suitable for X-ray crystal structure
analysis were obtained by cooling a concentrated C5H12
Empirical formula
C
38H46O3Ti
C48H64O6Zr×
/
0.5(C5H12
864.33
193
)
Formula weight
T (K)
598.7
296
monoclinic
solution to ꢀ
methods (SHELXS-86) [18] and refined (SHELXL-97) [19]
against all F2 data, resulting in R1ꢃ
0.0681 and wR2ꢃ
0.1083 for all reflections and R1ꢃ0.0434 as well as
wR2ꢃ0.0962 for all observed reflections with I ꢀ2s(I);
Goodness-of-fitꢃ1.043. The crystal data of compound
/
30 8C. The structure was solved by direct
Crystal system
Diffractometer
triclinic
Bruker AXS
/
/
Enrafꢁ
(CAD4)
/Nonius
/
¯
P1/
/
/
Space group
P21/c
/
Unit cell dimensions
˚
/
a (A)
˚
15.3961(9)
13.980(1)
16.861(1)
13.687(1)
13.846(1)
14.131(1)
82.052(1)
85.799(1)
63.448(1)
2372.3(3)
2
5 are listed in Table 1.
b (A)
˚
c (A)
2.10. [OOO]ZrCl2(THF) (6)
a (8)
b (8)
g (8)
108.542(6)
To a solution of ZrCl4(THF)2 (18 mg, 53.3 mmol) in
5.0 ml of Et2O was added a solution of 5 (45 mg, 54.3
3
˚
V (A )
Z
3440.7(4)
4
mmol) in 5 ml of Et2O at ꢀ70 8C. The mixture was
/
Dcalc (g cmꢀ3
)
1.156
0.282
1280
1.210
0.277
922
m(Mo Ka) (mmꢀ1
F(000)
)
warmed to r.t. and stirred further for 14 h to form a
colorless solid precipitate. The solvent was removed in
vacuo and the residue was treated with C5H12. Filtration
and drying afforded the product as colorless crystals in
Crystal dimensions
(mm)
0.40ꢄ
/0.80ꢄ
/0.88
0.23ꢄ/0.31ꢄ0.55
/
u Range (8)
3ꢁ24
0.0555, 0.1041
0.1364, 0.1287
/
3ꢁ28
/
1
81% (51 mg) yield. H NMR (THF-d8): d 1.45 (s, 18H,
C(CH3)3), 2.23 (s, 6H, 4-CH3), 5.04 (s, 4H, CH2O), 6.82
R1, wR2 [I ꢀ/2s(I)]
0.0434, 0.0962
0.0681, 0.1083
1.043
R1, wR2 (all data)
Goodness-of-fit on F2 1.005
4
(d, JHH
4
1.6 Hz, 2H, 3-CH), 7.09 (d, JHH
ꢃ
/
ꢃ
/
1.6 Hz,
2H, 5-CH). 13C NMR (THF-d8): d 20.9 (4-CH3), 30.6

224
V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ227
/
(C(CH3)3), 35.4 (C(CH3)3), 79.2 (CH2O), 125.2 (C-2),
127.5 (C-3), 129.0 (C-4), 129.3 (C-5), 137.2 (C-6), 157.4
(C-1). EI MS (70 eV): m/zꢃ
/
544 (2%, [Mꢂꢀ
/
C4H9]), 528
(2%, [Mꢂꢀ
/
THF]), 493 (5%, [Mꢂꢀ
/
THFꢀCl]), 163
/
(100%, [HOC6H2(C4H9)CH3]ꢂ). Anal. Calc. for
C28H40Cl2O4Zr: C, 55.79; H, 6.69. Found: C, 55.24;
H, 6.65%.
3. Results and discussion
The oxygen-linked bis(phenol) 2-oxapropanediyl-1,3-
bis(2-tert-butyl-4-methylphenol), [OOO]H2 (1), was pre-
pared in 68% yield by the condensation of neat 2-tert-
butyl-6-hydroxymethyl-4-methylphenol at 155 8C. A
variety of other conditions to form the ether linkage
starting from the readily available 2-tert-butyl-6-hydro-
xymethyl-4-methylphenol failed [20].
Scheme 1.
This bis(phenol) 1 cleanly reacted with equimolar
amount of titanium tetrachloride to give the dichloro
titanium complex [OOO]TiCl2 (2) as pentane-soluble,
orange microcrystals in virtually quantitative yield. It is
sensitive to moisture, decomposing within minutes in
1
air. The H and 13C NMR spectra at room temperature
indicate a molecule with C2v-symmetry, since the CH2O
protons appear as a sharp singlet at d 4.91 (d 4.68 in 1).
This signal only broadens below ꢀ80 8C, suggesting a
/
monomeric structure for [OOO]TiCl2 in solution. In
contrast, the [OXO]TiCl2 derivatives containing a 2,2?-
thio- or 2,2?-tellurobis(6-tert-butyl-4-methylphenolato)
ligand are dimeric both in the crystal and solution [21].
Reaction of bis(phenol) 1 with titanium tetra(isoprop-
oxide) gave the yellow di(isopropoxy) complex
[OOO]Ti(OiPr)2 (3). It is extremely soluble in aliphatic
hydrocarbons and very difficult to recover from solu-
Fig. 1. ORTEP drawing of the molecular structure of
[OOO]Ti(CH2Ph)2 (4). Ellipsoids are shown with 50% probability.
Hydrogen atoms are omitted for clarity. Key atoms are labeled.
1
tions. According to the H and 13C NMR spectra, 3
adopts a monomeric structure with C2v-symmetry in
solution. In the absence of molecular weight measure-
ments, we cannot definitely prove the monomeric unit
with a penta-coordinate titanium center. However, it is
notable that the di(isopropoxy) complex [(tbmp)-
Ti(OiPr)2]2 is dimeric and insoluble [22,23].
Reaction of the dichloro complex [OOO]TiCl2 (2)
with 2 equiv. of benzyl Grignard reagent Mg(CH2Ph)Cl
in diethyl ether afforded the highly light- and air-
sensitive, orange dibenzyl complex [OOO]Ti(CH2Ph)2
(4) in good yield (Scheme 1) [24]. The single crystal X-
ray crystallography of 4 revealed a molecule with a
penta-coordinate titanium center coordinated to the
tridentate [OOO] ligand in a meridional fashion. Fig. 1
shows an ORTEP diagram of 4 and Table 2 lists some
pertinent bond parameters. The overall coordination
geometry can be described as a distorted trigonal
bipyramid with C25, C32, O3 defining the equatorial
plane and O1 and O2 occupying the apical positions.
The bond distances between the titanium atom and the
Table 2
˚
Selected bond lengths (A) and bond angles (8) for [OOO]Ti(CH2Ph)2
(4)
Bond lengths
TiÃ
TiÃ
TiÃ
TiÃ
TiÃ
O3Ã
O3Ã
/
O1
1.852(2)
1.863(2)
2.096(3)
2.086(5)
2.109(4)
1.454(5)
1.440(5)
/O2
/O3
/C32
/C25
/C12
/C13
Bond angles
O1ÃTiÃO2
C32ÃTiÃC25
O1ÃTiÃ
O2ÃTiÃ
C1Ã
TiÃO2Ã
C12ÃO3Ã
C26ÃC25Ã
C33ÃC32Ã
/
/
161.2(1)
108.8(2)
79.5(1)
/
/
/
/O3
/
/O3
82.75(1)
142.8(2)
141.1(2)
118.3(3)
103.6(3)
102.8(3)
/
O1Ã
C15
C13
/
Ti
/
/
/
/
/
/
Ti
/
/Ti

V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ
/227
225
˚
phenolic oxygen atoms are 1.852(2) and 1.863(2) A and
are longer than those in related bis(phenolato) dialkyl
titanium complexes ({2,2?-(OC6H2Ã
/
6-tBuÃ
/
4-OMe)2}Ti-
[24]; {2,2?-CH2-
4-Me)2}Ti(CH2SiMe3)2: 1.784(3),
1.786(3) A [25]; {2,2?-CH2(OC6H2Ã6-tBuÃ4-Me)2}Ti-
Me2: 1.799(3) A [26]), but comparable to those found in
{2,2?-N(CH2CH2OMe)(OC6H2Ã4,6-tBu2)2}Ti(CH2Ph)2
TiÃO2 is 161.2(1)8 and
˚
A
(CH2Ph)2: 1.821(8), 1.799(7)
CH2(OC6H2Ã6-tBuÃ
/
/
˚
/
/
˚
/
˚
(1.865(2) A) [11]. The angle O1Ã
/
/
significantly deviates from linearity. The bond length
from the titanium center to the central ether oxygen
˚
atom is 2.096(3) A. This value is significantly smaller
then the other bond distances between ether oxygen
atom coordinated to tetravalent titanium center in
˚
related complexes, e.g. 2.402(4) A in {(tBu-d6Ã
/
N-o-
C6H4)2O}TiMe2 [2,4]. The ether oxygen atom is close to
sp2-hybridization, as can be seen from the angle C12Ã
O3ÃC13 of 118.3(3)8. These geometrical features point
/
/
at a fairly strong interaction between the ether oxygen
and the titanium center.
The two benzyl ligands reside in the equatorial plane
formed by the four atoms Ti, O3, C25 and C32. The sum
Fig. 2. ORTEP drawing of the molecular structure of [OOO]2Zr×
/
0.5(C5H12) (5). Ellipsoids are shown with 50% probability. Hydrogen
atoms and the lattice solvent n-pentane are omitted for clarity. Key
atoms are labeled.
of the angles at titanium C25Ã
/
TiÃ
/
C32, C25Ã
/
TiÃ
/
O3 and
C32ÃTiÃO3 is 3608. They show titanium carbon dis-
/
/
˚
tances of 2.086(5) and 2.109(4) A, comparable to values
found in other dibenzyl titanium complexes such as
˚
4-OMe)2}Ti(CH2Ph)2 (2.08(1) A)
The bis(ligand) complex 5 could be structurally
characterized by single crystal X-ray analysis. Fig. 2
shows an ORTEP diagram of 5 and Table 3 summarizes
some pertinent bond parameters. The two fac ligands
coordinate the zirconium center octahedrally, as can be
{2,2?-(OC6H2Ã
/
6-tBuÃ
/
[24]. The angles at the a-carbon atoms of the benzyl
groups are 103.6(3) and 102.8(3)8, indicating the absence
of any agostic interaction.
The reaction of zirconium tetrabenzyl with [OOO]H2
gave a bis(ligand) complex [OOO]2Zr (5) that formed
regardless of the stoichiometry employed. Other zirco-
nium precursors such as ZrCl4(THF)2, Zr(NMe2)4, and
Zr(NMe2)2Cl2(THF)2 behaved similarly. The bis(ligand)
complex, however, could be straightforwardly trans-
formed into the dichloro complex [OOO]ZrCl2(THF) (6)
by disproportionation with zirconium tetrachloride. The
ready decomposition of 6 in solution precluded the
systematic study of alkylation reactions (Scheme 2).
seen from the three angles at the zirconium center O1Ã
ZrÃO5 (176.19(6)8), O2ÃZrÃO6 (169.89(6)8), and O3Ã
ZrÃO4 (150.14(6)8). The two ligands are arranged in a
cis fashion (O2ÃZrÃO5 96.09(5)8). Remarkably, the
structurally characterized bis(ligand) titanium com-
plexes of the type [ONO]2Ti invariably contain trans
configurated ligands (with fac conformation) [10]. The
zirconium-to-phenolato oxygen distances of 1.965(2) to
/
/
/
/
/
/
/
/
Table 3
˚
Selected bond lengths (A) and bond angles (8) for [OOO]2Zr (5)
Bond lengths
ZrÃ
ZrÃ
ZrÃ
/
O1
O3
O5
1.977(2)
2.013(2)
2.353(2)
ZrÃ
ZrÃ
ZrÃ
/
O2
O4
O6
2.334(2)
2.003(2)
1.965(2)
/
/
/
/
Bond angles
O1Ã
O5Ã
O2Ã
O6Ã
O1Ã
O5Ã
O1Ã
O3Ã
/
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
/
O3
O4
O3
O4
O2
O6
O5
O4
100.68(6)
77.94(6)
76.58(6)
102.80(6)
80.81(6)
79.83(5)
176.19(6)
150.14(6)
O3Ã
O4Ã
O3Ã
O4Ã
O2Ã
O6Ã
O2Ã
/
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
ZrÃ
/
O5
O1
O6
O2
O5
O1
O6
80.65(6)
99.51(6)
93.57(6)
85.23(6)
96.09(5)
103.58(6)
169.89(6)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Scheme 2.

226
V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ227
/
of charge from the Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ (fax: ꢂ44-1223-336-033 or e-mail
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.
/
cam.ac.uk).
Scheme 3.
Acknowledgements
This work was supported by the German Federal
Ministry of Education and Research (BMBF), BASF
AG, and the Fonds der Chemischen Industrie.
˚
2.013(2) A are in the expected range [12], as are the two
zirconium-to-ether oxygen distances of 2.334(2) and
˚
2.353(1) A ([{(tBu-d6Ã
/
N-o-C6H4)2O}ZrCl2]2: 2.336(3)
˚
˚
N-o-C6H4)2O}ZrMe2]: 2.418(3) A [2]).
A; [{(tBu-d6Ã
/
When two tridentate ligands are coordinated in an
octahedral metal complex, three configurational isomers
are conceivable [27]: the trans- and cis-isomer with fac
conformation and an isomer with mer conformation of
the ligand. The temperature independence of the 1H
NMR spectra of 5 in toluene indicates the occurrence of
symmetrization processes, since only one set of ligand
signals is recorded. The C2-symmetric configuration
should render the two ‘halves’ of the [OOO] ligand
inequivalent. We assume that a low-barrier fluxional
process is operating in solution that allows the enantio-
merization of the C2-symmetric solid state structure
(Scheme 3).
References
[1] J.T. Goodman, R.R. Schrock, Organometallics 20 (2001) 5205.
[2] R.R. Schrock, R. Baumann, S.M. Reid, J.T. Goodman, R.
Stumpf, W.M. Davis, Organometallics 18 (1999) 3649.
[3] L.-C. Liang, R.R. Schrock, W.M. Davis, Organometallics 19
(2000) 2526.
[4] R. Baumann, R. Stumpf, W.M. Davis, L.-C. Liang, R.R.
Schrock, J. Am. Chem. Soc. 121 (1999) 7822.
[5] R. Baumann, W.M. Davis, R.R. Schrock, J. Am. Chem. Soc. 119
(1997) 3830.
[6] (a) T. Miyatake, K. Mizunuma, Y. Seki, M. Kakugo, Macromol.
Chem., Rapid Commun. 10 (1989) 349;
(b) T. Miyatake, K. Mizunuma, M. Kakugo, Macromol. Chem.
Macromol. Symp. 66 (1993) 203.
[7] (a) F.G. Sernetz, R. Mulhaupt, S. Fokken, J. Okuda, Macro-
¨
Preliminary polymerization tests for [OOO]TiCl2 (2)
under methylaluminoxane activation (Al:Tiꢃ
1 h, 140 ml of toluene, Tꢃ40 8C, pethylene
revealed moderate ethylene polymerization activity of 67
kg (molTi h)ꢀ1. The polyethylene showed Mnꢃ
66,000
(Mw/Mnꢃ6.5) and Tmꢃ132 8C. Styrene was polymer-
ized under similar conditions (Al:Tiꢃ1000:1; 1 h, 140
ml of toluene, Tꢃ40 8C) with an activity of 138 kg
[molTi]ꢀ1 h. The syndiotactic polystyrene isolated
showed Mnꢃ16,200 (Mw/Mnꢃ6.6) and Tmꢃ259 8C.
/
10,000:1,
molecules 30 (1997) 1562;
(b) J. Okuda, E. Masoud, Macromol. Chem. Phys. 199 (1998) 543.
[8] (a) R.D.J. Froese, D.G. Musaev, T. Matsubara, K. Morokuma, J.
Am. Chem. Soc. 119 (1997) 7190;
/
ꢃ
/
2 bar)
/
(b) R.D.J. Froese, D.G. Musaev, K. Morokuma, Organometallics
18 (1999) 373.
/
/
/
[9] E.Y. Tshuva, S. Groysman, I. Goldberg, M. Kol, Organometal-
lics 21 (2002) 662.
/
[10] E.Y. Tshuva, I. Goldberg, M. Kol, Inorg. Chem. 40 (2001) 4263.
[11] E.Y. Tshuva, I. Goldberg, M. Kol, Z. Goldschmidt, Chem.
Commun. (2001) 2120.
/
/
/
NMR experiments directed at observing the benzyl
cation remained inconclusive, as the product of the
dibenzyl complex 4 and B(C6F5)3 partially decomposed
[12] E.Y. Tshuva, I. Goldberg, M. Kol, Organometallics 20 (2001)
3017.
[13] E.Y. Tshuva, I. Goldberg, M. Kol, H. Weitman, Z. Goldschmidt,
Chem. Commun. (2000) 379.
in bromobenzene even at ꢀ30 8C. The observation that
/
[14] (a) E.Y. Tshuva, M. Versano, I. Goldberg, M. Kol, H. Weitman,
Z. Goldschmidt, Inorg. Chem. Commun. 2 (1999) 371;
(b) E.Y. Tshuva, I. Goldberg, M. Kol, Z. Goldschmidt, Inorg.
Chem. Commun. 3 (2000) 611.
the titanium complexes containing the [OOO] ligand are
not so well behaved may be ascribed to the strong
titaniumÃ/ether oxygen bond. Such an interaction prob-
[15] E.Y. Tshuva, I. Goldberg, M. Kol, J. Am. Chem. Soc. 122 (2000)
10706.
ably increases the electron density at the metal center by
p-donation. As a consequence, the bis(phenolato) liga-
tion may not be able to stabilize the alkyl cation through
the preferred twisted fac coordination of the [OOO]
ligand.
[16] U. Zucchini, E. Albizzati, U. Giannini, J. Organomet. Chem. 26
(1971) 357.
[17] J. Pikl, US Pat. Appl., 1957, 2.792.428.
[18] G.M. Sheldrick, SHELXS-86, A Program for Crystal Structure
Solution, University of Gottingen, Gottingen, Germany, 1986.
¨
¨
[19] G.M. Sheldrick, SHELXL-97, A Program for Crystal Structure
Refinement, University of Gottingen, Gottingen, Germany, 1997.
¨
¨
4. Supplementary material
[20] K. Hultzsch, J. Prakt. Chem. 159 (1941) 155.
[21] Y. Nakayama, K. Watanabe, N. Ueyama, A. Nakamura, A.
Harada, J. Okuda, Organometallics 19 (2000) 2498.
[22] L. Porri, A. Ripa, P. Colombo, E. Miano, S. Capelli, S.V. Meille,
J. Organomet. Chem. 514 (1996) 213.
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC, Nos. 190241ꢁ
/
42 for compounds 4
and 5. Copies of this information may be obtained free
[23] (a) S. Fokken, T.P. Spaniol, H.-C. Kang, W. Massa, J. Okuda,
Organometallics 15 (1996) 5069;

V. Reimer et al. / Inorganica Chimica Acta 345 (2003) 221ꢁ
/227
227
(b) S. Fokken, Doctoral Thesis, University of Marburg, Marburg,
1995;
[25] S. Fokken, T.P. Spaniol, J. Okuda, F.G. Sernetz, R. Mulhaupt,
¨
Organometallics 16 (1997) 4240.
(c) J. Okuda, S. Fokken, H.-C. Kang, W. Massa, Polyhedron 17
(1998) 943.
[26] C. Floriani, F. Corazza, W. Lesueur, A. Chiesi-Villa, C. Guastini,
Angew. Chem., Int. Ed. Engl. 28 (1989) 66.
[24] A. van der Linden, C.J. Schaverien, N. Meijboom, C. Ganter,
A.G. Orpen, J. Am. Chem. Soc. 117 (1995) 3008.
[27] A. von Zelewsky, Stereochemistry of Coordination Compounds,
Wiley, Chichester, 1996, p. 101.