Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) complexes: Syntheses, reactions, and catalytic application

Article abstract of DOI:10.1021/om7012293

Reacting tetrabenzo[a,c,g,i]fluorenyllithium {TbfLi(THF)₄ (1)} with TiCl₃(THF)₃ (2) leads to the formation of the η⁵-tetrabenzo[a,c,g,i]fluorenyltitanium(III) derivative TbITiCl₂(THF) (3), which can be conveyed to the titanium(IV)complex TbfTiCl₃ (4) by oxidative chlorination with CCl₄- Subsequent reaction with various lithium phenoxides gives a series of titanium complexes of the type TbITiCl₂(OAr) (Ar = 4-^tBuC ₆H₄ (5), 2,6-Me₂C₆H₃ (6), 2,4,6-Me₃C₆H₂ (7), 2,6-ⁱPrC ₆H₃ (8), 2,6-Ph₂C₆H₃ (9)). Furthermore, 3 was reacted with radicals or radical-generating peroxides to form the complexes TbfTiCl₂TEMPO (10) and TblTiCl₂CBu (11). All compounds were characterized by IR, MS, and NMR measurements and X-ray crystallography. Finally, compounds 6, 8, 9, and 10 were subjected to ethylene polymerization experiments using d-MAO. The activities increase in the following order [kG(PE)mol(Ti)^-1 h^-1 bar^-1]: 6 (320) < 8 (320) < 10 (760) < 9 (1000).

Full text of DOI:10.1021/om7012293

Organometallics 2008, 27, 1859–1868
1859
Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes:
Syntheses, Reactions, and Catalytic Application
Kai Schröder, Detlev Haase, Wolfgang Saak, Ruediger Beckhaus,*
Winfried P. Kretschmer,# and Arne Lützen
Institute for Pure and Applied Chemistry, Carl Von Ossietzky UniVersity, 26111 Oldenburg, Germany,
Stratingh Institute for Chemistry and Chemical Engineering, UniVersity of Groningen,
9747 AG Groningen, The Netherlands, and Kekulé-Institute for Organic Chemistry and Biochemistry,
UniVersity of Bonn, 53121 Bonn, Germany
ReceiVed December 7, 2007
Reacting tetrabenzo[a,c,g,i]fluorenyllithium {TbfLi(THF)4 (1)} with TiCl3(THF)3 (2) leads to the
formation of the η5-tetrabenzo[a,c,g,i]fluorenyltitanium(III) derivative TbfTiCl2(THF) (3), which can be
conveyed to the titanium(IV)complex TbfTiCl3 (4) by oxidative chlorination with CCl4. Subsequent reaction
with various lithium phenoxides gives a series of titanium complexes of the type TbfTiCl2(OAr) (Ar )
4-tBuC6H4 (5), 2,6-Me2C6H3 (6), 2,4,6-Me3C6H2 (7), 2,6-iPrC6H3 (8), 2,6-Ph2C6H3 (9)). Furthermore, 3
was reacted with radicals or radical-generating peroxides to form the complexes TbfTiCl2TEMPO (10)
and TbfTiCl2OtBu (11). All compounds were characterized by IR, MS, and NMR measurements and
X-ray crystallography. Finally, compounds 6, 8, 9, and 10 were subjected to ethylene polymerization
experiments using d-MAO. The activities increase in the following order [kG(PE)mol(Ti)-1 h-1 bar-1]:
6 (320) < 8 (320) < 10 (760) < 9 (1000).
Scheme 1
Introduction
The cyclopentadienide anion and its derivatives are widely
used in organometallic and coordination chemistry, especially
because replacing the hydrogen atoms on the cyclopentadienyl
ring by substituents easily alters the chemical and physical
properties of their corresponding complexes.1 Particularly,
benzo-fused Cp derivatives such as indene and fluorene had a
serious impact in the development of catalyst precursors for
stereospecific olefin polymerization.2 However, fusing aromatic
ring systems to the cyclopentadienyl ring can sometimes cause
problems with regard to the bonding situation between metal
and ligand, due to the tendency of the benzo-fused ring to
preserve its aromatic six-electron system, leading to a hapto-
tropic shift as depicted in Scheme 1.
Ring-slippage can occur on all Cp-type ligand systems, and
this greatly adds to their chemical variety;3 however, for the
above-mentioned reason with (b) indenyl4 and (c) fluorenyl
ligands (Flu)5 this is more likely to take place. Especially the
fluorenyl moiety usually not only refuses to form η5-complexes
even in its ansa-bridged specimen6 but often dimerizes in a
redox reaction with the metal.7 As a natural consequence, only
very few unsubstituted fluorenyl transition metal complexes are
* Corresponding author: Phone: +49 441 798 3656. Fax: +49 441 798
3851. E-mail: ruediger.beckhaus@uni-oldenburg.de.
# Correspondence pertaining to polymerization details: E-mail:
W.P.Kretschmer@rug.nl.
(1) Janiak, C.; Schumann, H. AdV. Organomet. Chem. 1991, 33, 291–
393.
8
known such as FluMn(CO)3 and FluTi(OiPr)2.9
By further adding benzo-fused rings to the fluorenyl moiety
complex stability significantly improves by forming the anionic
five-membered ring; none of the six-electron ring systems are
(2) Kaminsky, W. J. Chem. Soc., Dalton Trans. 1998, 1413–1418.
(3) Review: (a) O’Connor, J. M.; Casey, C. P. Chem. ReV. 1987, 87,
307–318. Selected new examples: (b) Romao, C. C.; Veiros, L. F.
Organometallics 2007, 26, 1777–1781. (c) Jordan, M.; Haase, D.; Saak,
W.; Beckhaus, R. Eur. J. Inorg. Chem. 2007, 5168–5172. (d) Butterick,
R., III; Ramachandran, B. M.; Carroll, P. J.; Sneddon, L. G. J. Am. Chem.
Soc. 2006, 128, 8626–8637.
(6) Dahlmann, M.; Fröhlich, R.; Erker, G. Eur. J. Inorg. Chem. 2000,
1789–1793.
(7) Knjazhanski, S. Y.; Moreno, G.; Cadenas, G.; Belsky, V. K.;
Bulychev, B. M. Tetrahedron 1999, 55, 1639–1646.
(8) (a) King, R. B.; Efraty, A. J. Organomet. Chem. 1970, 23, 527–
533. (b) Decken, A.; MacKay, A. J.; Brown, M. J.; Bottomley, F.
Organometallics 2002, 21, 2006–2009.
(4) (a) Veiros, L. F. Organometallics 2006, 25, 2266–2273. (b) Bradley,
C. A.; Keresztes, I.; Lobkovsky, E.; Chirik, P. J. Organometallics 2006,
25, 2080–2089.
(9) Knjazhanski, S. Y.; Cadenas, G.; Garcia, M.; Perez, C. M.; Nifant’ev,
I. E.; Kashulin, I. A.; Ivchenko, P. V.; Lyssenko, K. A. Organometallics
2002, 21, 3094–3099.
(5) Kirillov, E.; Saillard, J.-Y.; Carpentier, J.-F. Coord. Chem. ReV. 2005,
249, 1221–1248.
10.1021/om7012293 CCC: $40.75
2008 American Chemical Society
Publication on Web 03/26/2008

1860 Organometallics, Vol. 27, No. 8, 2008
Schröder et al.
Scheme 2
Chart 1. Numbering Scheme for Tetrabenzo[a,c,g,i]fluorenyl-
titanium Complexes
Scheme 3
Scheme 4
Figure 1. ORTEP plot of the solid state molecular structure of 3.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0340, Ti(1)-Cl(1) 2.3006(5), Ti(1)-Cl(2)
2.3115(5), Ti(1)-O(1) 2.0536(12), Cl(1)-Ti(1)-Cl(2) 103.19(3),
Cl(1)-Ti(1)-O(1)96.81(4),Cl(2)-Ti(1)-O(1)92.99(4),C17-C3-C4-C19
–18.486(290).
disturbed like in the (d) tetrabenbenzo[a,c,g,i]fluorenyl (Tbf)
ligand,10 which is also depicted in Scheme 1. Originally
developed as a protecting anchor group for the synthesis of
oligonucleotides,11 polypeptides,12 and proteins13 it proved to
be a useful spectator ligand in half-sandwich complexes intended
for syndiospecific styrene polymerization.10 Furthermore, the
sterical repulsion between the benzo-fused rings leads to a slight
helical distortion, which makes the tetrabenzo[a,c,g,i]fluorenyl
moiety intrinsically chiral (see Scheme 2). However due to a
very low racemization barrier in solution, only half the signal
set can be observed in the NMR.14
In this article we wish to report the synthesis of the
tetrabenzo[a,c,g,i]fluorenyltitanium half-sandwich complexes
TbfTiIIICl2(THF) and TbfTiIVCl3 and their subsequent reactions
leading to organometallic complexes of the general formula
TbfTiIVCl2OR.
As mentioned in a previous article,10 directly reacting
TbfLi(THF)4 (1) with TiCl4(THF)2 ended up in the reduction
of the metal center and coinstantaneous oxidative coupling of
the ligand, leading to the well-crystallizing Tbf-Tbf hydrocar-
bon coupled in the C17 position (Chart 1). As a natural
consequence, the synthesis of tetrabenzo[a,c,g,i]fluorenyltita-
nium trichloride via a silylated tetrabenzo[a,c,g,i]fluorene
derivative was approached, but it did not yield any identifiable
products so far.16 Thus it was tried to use reactants with an
increased electron density on the titanium center such as Ti(III)
complexes.
Synthesis of Tetrabenzo[a,c,g,i]fluorenyltitanium Chlo-
ride Complexes. Reacting TbfLi(THF)4 (1) with TiCl3(THF)3
(2) in toluene formed a green solution, which was left for
crystallization after 1 min of stirring. After 2 days dark green
crystals of TbfTiCl2(THF) (3) were afforded in acceptable yield
(64%), which were suitable for X-ray diffraction (Figure 1).
The compound proved to be extremely air and moisture sensitive
and is hardly soluble in organic solvents with the exception of
THF. In the solid state the compound decomposes without prior
melting at 120 °C.
Results and Discussion
One of the standard procedures for the synthesis of half-
sandwich cyclopentadienyltitanium trichlorides involves the use
of silylated cyclopentadienyl15 derivatives in cases where the
use of lithiated compounds leads to reduction of the metal
center.7
(10) Schröder, K.; Lützen, A.; Haase, D.; Saak, W.; Beckhaus, R.;
Wichmann, S.; Schellenberg, J. Organometallics 2006, 25, 3824–3836.
(11) Ramage, R.; Wahl, F. O. Tetrahedron Lett. 1993, 34, 7133–7136.
(12) Ramage, R.; Raphy, G. Tetrahedron Lett. 1992, 33, 385–388.
(13) Brown, A. R.; Irving, S. L.; Ramage, R.; Raphy, G. Tetrahedron
1995, 51, 11815–11830.
Compound 3 crystallizes in a monoclinic system; the space
group is C2/c with eight molecules per unit. The distance
between Ti(1)-Ct(1) measures 2.0340 Å, which is considerably
longer than the Ti-Ct distance in the analogous cyclopentadi-
enyl titanium complex CpTiCl2(THF) (2.014 Å), which to our
best knowledge is the only other example where a monomeric
(14) (a) Meca, L.;Reha, D.;Havlas, Z. J. Org. Chem. 2003, 68, 5677–
5680. (b) Pammer, F. Sun, Y. May, C. Wolmershäuser, G. Kelm, H. Krüger,
H.-J. Thiel, W. H. Angew. Chem. 2007, 119, 1293–1296; Angew. Chem.,
Int. Ed. 2007, 46, 1270-1273.
(15) Llinas, G. H.; Mena, M.; Palacios, F.; Royo, P.; Serrano, R. J.
Organomet. Chem. 1988, 340, 37–40.
(16) Schröder, K. Ph.D. Thesis, University of Oldenburg, 2007, pp 1–
193.

Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes
Organometallics, Vol. 27, No. 8, 2008 1861
Figure 3. ORTEP plot of the solid state molecular structure of 5.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0665, Ti(1)-Cl(1) 2.274(3), Ti(1)-Cl(2) 2.257(3),
Ti(1)-O(1) 1.782(6), Ti(1)-O(1)-C(30) 161.1(5), O(1)-Ti(1)-Cl(1)
101.6(2), O(1)-Ti(1)-Cl(2) 105.1(2), Cl(1)-Ti(1)-Cl(2) 102.95(10),
C18-C4-C3-C17 –13.722(1594).
Figure 2. ORTEP plot of the solid state molecular structure of 4.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0357, Ti(1)-Cl(1) 2.2303(11), Ti(1)-Cl(2)
2.2173(11), Ti(1)-Cl(3) 2.2512(11), Cl(1)-Ti(1)-Cl(2) 103.07(4),
Cl(2)-Ti(1)-Cl(3) 106.57(4), Cl(1)-Ti(1)-Cl(3) 102.15(5),
C18-C4-C3-C17 15.710(626).
Cp-type titanium(III) chloride compound could be isolated.17,18
Bis THF adducts, as described for CpTiCl2(THF)2, are not found
in the case of 3.17
In order to synthesize a tetrabenzo[a,c,g,i]fluorenyltita-
nium(IV) species from compound 3, oxidative chlorination with
CCl4 promised to be successful.19 Reacting TiCl3(THF)3 with
TbfLi(THF)4 in toluene with subsequent extraction and thus
simultaneous oxidative chlorination using CCl4 afforded TbfTi-
Cl3 (4) in an acceptable overall yield of 66%. The dark purple
compound is quite insensitive to air and moisture. In contrast
to its moderate solubility in dichloromethane and THF, 4 is
poorly soluble in toluene and completely insoluble in diethyl
ether and aliphatic solvents; therefore crystals of 4 suitable for
X-ray diffraction could easily be obtained by layering a solution
in dichloromethane with an equal amount of n-hexane.
The dark violet needle-shaped crystals contain four molecules
of 4 per unit cell along with 2 equiv of solvent. The crystal
system is monoclinic with space group P21/n. As shown in
Figure 2 the titanium atom is coordinated in a pseudotetrahedral
fashion with the tetrabenzo[a,c,g,i]fluorenyl moiety in the apical
position, with a Ct-Ti(1) distance of 2.0357 Å, which is about
the same distance as in TbfTiCl2(THF) within the accuracy of
measurement. The bond lengths between titanium and the three
chloride atoms amount to an average of 2.23 Å.
Table 2 gives a comparative survey of the most important
structural data of compound 4 and similar organometallic com-
plexes like CpTiCl320 and IndTiCl3.21 It can be easily seen that all
Ti-Cl bond lengths and Cl-Ti-Cl angles are almost alike in all
three complexes, thus leaving the Ti-Ct distance in CpTiCl3 at
2.01 Å as the only major difference from 4 and IndTiCl3, in whose
molecular structures the Ti-Ct distances amount to 2.03 Å. These
crystallographic data and its dark violet color suggest that
compound 4 is electronically quite similar to IndTiCl3.
Figure 4. ORTEP plot of the solid state molecular structure of 6.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0701, Ti(1)-Cl(1) 2.2766(16), Ti(1)-Cl(2)
2.2637(17), Ti(1)-O(1) 1.779(3), Ti(1)-O(1)-C(30) 159.7(3),
Cl(1)-Ti(1)-O(1) 105.97(12), Cl(2)-Ti(1)-O(2) 100.72(12),
Cl(1)-Ti(1)-Cl(2) 102.32(7), C29-C5-C1-C6 12.825(946).
Synthesis of Tetrabenzo[a,c,g,i]fluorenyltitanium Monophe-
noxide Complexes. Standard synthetic procedures for the
synthesis of Cp-type titanium monophenoxide complexes from
their trichloride precursors involve the use of either lithiumphe-
noxides22 or phenols in conjunction with an organic base in
order to absorb the HCl released.23
As depicted in Scheme 5 compound 4 was reacted with
lithium phenoxides in a toluene slurry to form an array of
tetrabenzo[a,c,g,i]fluorenyltitanium monophenoxides of the
general formula TbfTiCl2OAr. Generally, working up the
reaction mixtures included evaporation of the solvent with
subsequent extraction of the residue with dichloromethane with
the exception of TbfTiCl2(2,6-Ph2C6H3O) (9), which was filtered
directly in order to remove LiCl. All solutions obtained were
layered with n-hexane to induce crystallization of the product
complexes. This way crystals suitable for X-ray diffraction are
obtained on a regular basis.
(17) Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Am.
Chem. Soc. 1983, 105, 7295–7301.
(18) Cozak, D.; Melnik, M. Coord. Chem. ReV. 1986, 74, 53–99.
(19) Strunkina, L. I.; Minacheva, M. Kh.; Lyssenko, K. A.; Burlakov,
V. V.; Baumann, W.; Arndt, P.; Strunin, B. N.; Shur, V. B. J. Organomet.
Chem. 2006, 691, 557–565.
TbfTiCl2(4-tBuC6H4O) (5) is well soluble in dichloromethane
and THF, of low solubility in toluene, and completely insoluble
(20) Engelhardt, L. M.; Papasergio, R. I.; Raston, C. L.; White, A. H.
Organometallics 1984, 3, 18–20.
(22) (a) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K. Macromolecules
1998, 31, 7588–7597. (b) Thorn, M. G.; Vilardo, J. S.; Fanwick, P. E.;
Rothwell, I. P. Chem. Commun. 1998, 2427–2428.
(21) Ready, T. E.; Day, R. O.; Chien, J. C. W.; Rausch, M. D.
Macromolecules 1993, 26, 5822–5823.
(23) Sturla, S. J.; Buchwald, S. L. Organometallics 2002, 21, 739–748.

1862 Organometallics, Vol. 27, No. 8, 2008
Schröder et al.
Table 1. Comparison of Selected Bond Length and Angles between
Compound 3 and CpTiCl2(THF)17
TbfTiCl2(THF) (3)
CpTiCl2(THF)
Bond Lengths [Å]
2.0340
Ti(1)-Ct
2.014
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)-O(1)
2.3006(5)
2.3115(5)
2.0536(12)
2.310(2)
2.339(3)
2.065(4)
Bond Angles [deg]
103.19(3)
Cl(1)-Ti(1)-Cl(2)
Cl(1)-Ti(1)-O(1)
Cl(2)-Ti(1)-O(1)
105.6(1)
93.7(1)
94.4(1)
96.81(4)
92.99(4)
Table 2. Comparison of Selected Bond Lengths and Angles between
21
Compound 4, CpTiCl3,20 and IndTiCl3
TbfTiCl3 (4)
CpTiCl3
IndTiCl3
Bond Lengths [Å]
2.0357
Ti(1)-Ct
2.01
2.032
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)-Cl(3)
2.2303(11)
2.2173(11)
2.2512(11)
2.201(5)
2.248(5)
2.221(2)
2.2248(8)
2.2319(8)
2.2355(8)
Figure 5. ORTEP plot of the solid state molecular structure of 7.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0589, Ti(1)-Cl(1) 2.2508(6), Ti(1)-Cl(2)
2.2614(7), Ti(1)-O(1) 1.7737(16), Ti(1)-O(1)-C(30) 158.94(13),
Cl(1)-Ti(1)-O(1)102.79(5),Cl(2)-Ti(1)-O(1)103.36(5),Cl(1)-Ti(1)-Cl(2)
103.45(3), C18-C4-C3-C17 12.510(412).
Bond Angles [deg]
Cl(1)-Ti(1)-Cl(2)
Cl(2)-Ti(1)-Cl(3)
Cl(1)-Ti(1)-Cl(3)
103.07(4)
106.57(4)
102.15(5)
102.2(2)
104.1(2)
102.3(3)
102.44(3)
104.09(3)
103.32(3)
Scheme 5
as red crystals with four molecules per unit cell in the monoclinic
crystal system P21/c. As listed in Table 3 the Ti-Ct distance
measures 2.0701 Å and the Ti-Cl bond lengths amount to an
average 2.270 Å (Figure 4). Like in compound 5, in 6 it is
assumed that face-to-face π-stacking interactions take place
between the benzo-fused ring C12-C17 and the phenoxide ring
C30-C35, as the distance between their respective centroids
measures 3.62 Å.
Interestingly, in contrast to complex 6, TbfTiCl2(2,4,6-
Me3C6H2O) (7) does not show any π-π interactions between
the phenoxide and any of the benzo-fused rings, although they
only differ by one methyl group in the para-position of the
phenoxide ligand. It is not known if this is due to a slightly
different electronic structure or a phenomenon of different
packing in the crystal.
Figure 6. ORTEP plot of the solid state molecular structure of 8.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0544, Ti(1)-Cl(1) 2.2467(6), Ti(1)-Cl(2)
2.2545(7), Ti(1)-O(1) 1.7751(14), Ti(1)-O(1)-C(30) 159.17(13),
Cl(1)-Ti(1)-O(1)102.28(5),Cl(2)-Ti(1)-O(1)102.57(5),Cl(1)-Ti(1)-Cl(2)
104.45(2), C18-C4-C3-C17 14.966(406).
With regard to its solubility and its other physical properties,
compound 7 is very similar to complex 6. It crystallizes in the
monoclinic space group P21/n with four molecules per crystal
cell. The Ti-Ct bond length measures 2.0589 Å and is thus
slightly shorter than in 6, whereas the Ti-O bond length and
the Ti-O-C angle are almost identical (Figure 5).
in aliphatic solvents. It could be obtained in 23% yield as deep
red crystals with two molecules per unit cell in the triclinic
Like all other tetrabenzo[a,c,g,i]fluorenyltitanium monophe-
noxide complexes mentioned so far, TbfTiCl2(2,6-iPr2C6H3O)
(8) is well soluble in dichloromethane and THF, to a lesser
extent in aromatic solvents, and completely insoluble in aliphatic
solvents. It can be obtained in 34% yield as red crystals in the
monoclinic space group P21/n with four molecules per unit cell
(Figure 6).
j
crystal system P1. The Ti(1)-Ct distance measures 2.0665 Å,
the Ti(1)-Cl bond lengths amount to an average 2.266 Å
(Figure 3). The distance between centers of the benzo-fused
tetrabenzo[a,c,g,i]fluorene ring C6-C11 and the phenoxide ring
C30-C35 measures 3.841 Å, and therefore it is assumed that
face-to-face π-stacking interactions take place.24
TbfTiCl2(2,6-Me2C6H3O) (6) is well soluble in dichlo-
romethane and THF, of low solubility in toluene, and completely
insoluble in aliphatic solvents. It could be isolated in 21% yield
(24) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885–3896.

Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes
Organometallics, Vol. 27, No. 8, 2008 1863
Table 3. Comparison of Selected Bond Lengths and Angles between Compounds 5, 6, 7, 8, and 9
5
6
7
8
9
Bond Lengths [Å]
Ti(1)-Ct
2.0665
2.0701
2.0589
2.0544
2.0554
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)-O(1)
2.274(3)
2.257(3)
1.782(6)
2.2766(16)
2.2637(17)
1.779(3)
2.2508(6)
2.2614(7)
1.7737(16)
2.2467(6)
2.2545(7)
1.7751(14)
2.2509(6)
2.2570(7)
1.7913(15)
Bond Angles [deg]
Ti(1)-O(1)-C
Cl(1)-Ti(1)-Cl(2)
161.1(5)
102.95(10)
159.7(3)
102.32(7)
158.94(13)
103.45(3)
159.17(13)
104.45(2)
154.61(12)
104.08(3)
Scheme 6
In contrast to the excellent catalyst precursor Cp*TiCl2(2,6-
iPr2C6H3O)25 the Ti-O-C bond angle in compound 8 exhibits
only a relatively small value of 159.17°.
As opposed to the TbfTiCl2(OAr) complexes 5-8, TbfTi-
Cl2(2,6-Ph2C6H3O) (9) is well soluble in aromatic solvents. Its
red crystals can be obtained from a toluene solution in 34%
yield, and the compound crystallizes in the triclinic space group
j
P1 with two molecules of 9 and one molecule of toluene per
unit cell (Figure 7).
Scheme 7
Like in Figure 6 and Figure 7 it can be seen that one of the
phenoxide’s ortho substituents locks into the cavity in front of
the cyclopentadienyl ring formed by two benzo-fused rings.
With compound 9 it is assumed that this occurs not only in the
solid state but also in solution, as the single proton on the cyclo-
pentadienyl ring is located in the anisotropic cone of the phenyl
ring and thus is shifted upfield in the proton NMR.
Reaction of TbfTiIIICl2(THF) with Radicals. Another pos-
sible synthetic route to introduce ligands into an organometallic
complex is the reaction of one of its low-valent species with
radicals. Thus an O- or N-centered radical is reduced to a
monoanionic ligand while the metal center is oxidized. However,
some applications of the radical-like properties of titanium(III)
species are known in the literature. In that way the free-radical-
like properties of CpTiIIICl2 derivatives are observed in reac-
tions, for example, with quinones26 as well as with azo and
diazo compounds,17 whereas the intermediately generated
Cp2TiIIICl reagent is well introduced in organic reactions.27
A variety of persistent nitroxyl radicals such as TEMPO
(2,2,6,6-tetramethylpiperidine-N-oxyl) or di-tert-butyl nitroxide
have been used to synthesize an array of different metal
complexes, including s-block metalloids,28 early transition
metals,29 and lanthanoids.30
the Ti-Ct distance is slightly elongated to 2.0875 Å, probably
due to a higher electron density donated by the nitroxide moiety,
as the Ti-O-N bond angle of 167.04° implies better dπ-pπ
interactions between the oxygen and the titanium atom.31
Not only persistent radicals can be reacted with low-valent
metal complexes but also those that are generated in situ by
thermal cleavage of peroxides. To our best knowledge, so far
only samarium32 and ytterbium33 compounds were reported into
which a tert-butoxide moiety was introduced by reduction of
di-tert-butylperoxide by the metal center. Here we report the
first Cp-type titanium monoalkoxide complex synthesized by
reacting a titanium(III) species with di-tert-butylperoxide.
As depicted in Scheme 7 the titanium(III) compound 3 was
prepared in situ, and half an equivalent of di-tert-butylperoxide
was added. Heating the reaction mixture fast until reflux affords
a deep red suspension, which was taken to dryness. The residue
was extracted with dichloromethane and filtered. Layering the
solution with n-hexane afforded deep red crystals of TbfTi-
Cl2(OtBu) (11) in only 10% yield. This is strongly associated
with thermal decay of the monomeric titanium(III) species at
those elevated temperatures.
As depicted in Scheme 6 compound 3 was synthesized in
situ and subsequently reacted with TEMPO at ambient temper-
ature to form a burgundy red reaction mixture. Filtration and
cooling of the solution to -10 °C afforded crystals of TbfTi-
Cl2TEMPO (10) in 51% yield.
Compound 10 is well soluble with the exception of aliphatic
j
solvents and crystallizes in the triclinic space group P1 with
two molecules of 10 and one molecule of toluene per unit cell
(Figure 8). In comparison to the TbfTiCl2(OAr) complexes 5–9
In order to obtain higher yields a more conventional synthetic
path was explored: Compound 4 was reacted with potassium
tert-butoxide in a toluene suspension. Workup of the reaction
mixture was identical and afforded crystals of 11 in 27% yield.
Compound 11 is well soluble in chlorinated solvents and THF
and to a lesser extent in aromatic solvents. It crystallizes in the
(25) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai, A. Organo-
metallics 1998, 17, 2152–2154.
(26) Vlcek, A. J. Organomet. Chem. 1985, 297, 43–50.
(27) (a) Gansäuer, A.;Bluhm, H. Chem. ReV. 2000, 100, 2771–2788.
(b) Daasbjerg, K.;Svith, H.;Grimme, S.;Gerenkamp, M.;Mück-Lichtenfeld,
C.;Gansäuer, A.;Barchuk, A.;Keller, F. Angew. Chem. 2006, 118, 2095–
2098; Angew. Chem., Int. Ed. 2006, 45, 2041-2044.
(28) Forbes, G. C.; Kennedy, A. R.; Mulvey, R. E.; Rodger, P. J. A.
Chem. Commun. 2001, 1400–1401.
(31) Nielson, A. J.; Schwerdtfeger, P.; Waters, J. M. J. Chem. Soc.,
Dalton Trans. 2000, 529–537.
(29) (a) Mahanthappa, M. K.; Huang, K.-W.; Cole, A. P.; Waymouth,
R. M. Chem. Commun. 2002, 502–503. (b) Brindley, P. B.; Scotton, M. J.
J. Organomet. Chem. 1981, 222, 89–96.
(32) Barbier-Baudry, D.; Heiner, S.; Kubicki, M. M.; Vigier, E.;
Visseaux, M.; Hafid, A. Organometallics 2001, 20, 4207–4210.
(33) Berg, D. J.; Andersen, R. A.; Zalkin, A. Organometallics 1988, 7,
1858–1863.
(30) Evans, W. J.; Perotti, J. M.; Doedens, R. J.; Ziller, J. W. Chem.
Commun. 2001, 2326–2327.

1864 Organometallics, Vol. 27, No. 8, 2008
Schröder et al.
Figure 7. ORTEP plot of the solid state molecular structure of 9.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0554, Ti(1)-Cl(1) 2.2509(6), Ti(1)-Cl(2)
2.2570(7), Ti(1)-O(1) 1.7913(15), Ti(1)-O(1)-C(30) 154.61(12),
Cl(1)-Ti(1)-O(1)103.98(5),Cl(2)-Ti(1)-O(1)102.78(5),Cl(1)-Ti(1)-Cl(2)
104.08(3), C18-C4-C3-C17 –10.506(390).
Figure 8. ORTEP plot of the solid state molecular structure of 10.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0875, Ti(1)-Cl(1) 2.2940(5), Ti(1)-Cl(2)
2.2789(6), Ti(1)-O(1) 1.7549(14), Ti(1)-O(1)-N(1) 167.04(12),
Cl(1)-Ti(1)-O(1)101.13(4),Cl(2)-Ti(1)-O(1)101.49(5),Cl(1)-Ti(1)-Cl(2)
104.63(3), C18-C4-C3-C17 –21.040(413).
monoclinic space group P21/c with four molecules per unit cell
(Figure 9). The Ti-Ct distance measures 2.0683 Å, and the
Ti-O-C bond angle of 165.38° is very similar to the one in
TbfTiCl2(OiPr) reported previously.10
Common to all compounds discussed above are intermolecu-
lar face-to-face π-stacking interactions24 in the solid state
between the tetrabenzo[a,c,g,i]fluorenyl ligands of the titanium
complexes, resulting in the above-mentioned low solubility of
the compounds. This phenomenon is found in all solid state
structures discussed so far and is most intense in the solid state
structure of compound 4 (see Figure 10), in which the distance
between the centroids of the five-membered ring and one of
the six-membered rings amounts to 3.471 Å, being indicative
of strong face-to-face π-interactions. This correlates with the
compound’s solubility, which is the lowest of all compounds
described here. In the solid state structures of all other
compounds this phenomenon occurs to a lesser extent, which
should be the reason why they are more soluble.
Polymerization Experiments. Cyclopentadienyltitanium
monophenoxide complexes of the general formula CpR5-
TiCl2(OAr) (with R ) H, Me) have been established as
extraordinarily versatile catalysts for the homo- and copoly-
merization of ethylene, propylene, n-hexene, and norbornene
by the works of Nomura. In particular, the compounds Cp-
TiCl2(2,6-iPr2C6H3O) and Cp*TiCl2(2,6-RC6H3O) (R ) Me, iPr)
were proven to be quite potent catalysts for the homopolym-
erizationofethylenewhenactivatedwithdriedMAO(d-MAO).22a,34
In contrast to commercially available methylalumoxane, d-MAO
contains no free trimethylaluminum, which due to its high
oxophilicity would potentially attack the Ti-O bond in the
titanium monophenoxide complexes, resulting in the decom-
position of the ligand framework.35
Figure 9. ORTEP plot of the solid state molecular structure of 11.
Hydrogen atoms are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level. Selected bond lengths [Å] and angles
[deg]: Ti(1)-Ct 2.0683, Ti(1)-Cl(1) 2.2808(5), Ti(1)-Cl(2)
2.2817(5), Ti(1)-O(1) 1.7414(11), Ti(1)-O(1)-C(30) 165.38(12),
Cl(1)-Ti(1)-O(1)103.22(4),Cl(2)-Ti(1)-O(1)100.25(4),Cl(1)-Ti(1)-Cl(2)
103.44(2), C18-C4-C3-C17 19.489(298).
After achieving good results with tetrabenzo[a,c,g,i]fluore-
nyltitanium complexes in the syndiospecific polymerization of
styrene,10 we were eager to test the tetrabenzo[a,c,g,i]fluore-
nyltitanium complexes for their potential to polymerize other
olefin monomers, e.g., ethylene.
In the course of the following studies, the compounds 6, 8,
9, and 10 were subjected to ethylene polymerization experi-
ments. Generally, the catalytic ethylene polymerization reactions
were performed in a stainless steel 1 L autoclave (Medimex) in
semibatch mode (ethylene was added by replenishing flow to
keep the pressure constant). The reactor was temperature and
pressure controlled and equipped with separated toluene,
catalyst, and cocatalyst injection systems and a sample outlet
(34) (a) Nomura, K.; Tanaka, A.; Katao, S. J. Mol. Catal. A: Chem.
2006, 254, 197–205. (b) Nomura, K.; Wang, W.; Fujiki, M.; Liu, J. Chem.
Commun. 2006, 2659–2661. (c) Jamanek, D.; Nicinski, K.; Kazimierczuk,
R.; Wozniewski, T.; Wieczorek, Z.; Skupinski, W. J. Mol. Catal. A: Chem.
2006, 254, 192–196. (d) Nomura, K.; Komatsu, T.; Imanishi, Y. J. Mol.
Catal. A: Chem. 2000, 159, 127–137.
(35) (a) Schellenberg, J.; Leder, H.-J. AdV. Polym. Tech. 2006, 25, 141–
151. (b) Nomura, K.; Fujii, K. Macromolecules 2003, 36, 2633–2641.

Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes
Organometallics, Vol. 27, No. 8, 2008 1865
where the higher temperature of 80 °C leads to a significant
decrease in polymer weight. On run 5 the effect of residual
trimethylaluminum in commercial PMAO is seen, resulting in
a further deterioration of catalyst productivity and polymer
weight.
In contrast to their both aforementioned brethren complexes
9 and 10 deliver a considerably higher productivity in ethylene
polymerization at both 50 and 80 °C when activated with
d-MAO ranging from 640 to 1000 kg(PE) × mol(Ti)-1 h-1
bar-1, which is quite high for cyclopentadienyl-type titanium
monophenoxide complexes and comparable to Nomura’s com-
plexes mentioned above. The weights of the polymers synthe-
sized are higher at 50 °C and are again very similar to those
prepared with CpR5TiCl2(2,6-iPr2C6H3O) (R ) H, Me). With
the exception of complex 10, all TbfTi complexes produced
ethylene polymers with a quite broad molecular weight distribu-
tion, which in the literature is believed to originate from
nonuniform active species.
Figure 10. Intermolecular face-to-face π-stacking interactions
(3.471 Å) in the solid state between the tetrabenzo[a,c,g,i]fluorenyl
ligands in the example of compound 4 (titanium: red; chloride:
green; carbon: gray).
Conclusion
Employing the tetrabenzo[a,c,g,i]fluorenyl ligand as a ben-
zannelated fluorene system, a broad range of Tbf titanium
complexes of high thermal stability becomes available. In order
to obtain TbfTiIVCl3 the primary synthesis of TbfTiIIICl2 is the
best way in order to prevent Wurtz-type C-C coupling
reactions, as observed by direct use of titanium(IV) starting
materials. Radical-type coupling reactions of TbfTiCl2 inter-
mediates with free radicals (TEMPO) as well as radical-
generating substrates (tBu-OO-But) are used as an efficient
preparative tool for the formation of titanium(IV) complexes.
All of the titanium complexes show η5-coordinated Tbf ligands.
Table 4. Ethylene Polymerization Runs Catalyzed by
TbfTiCl2(OAr)/MAOa
run no. catalyst cocat. T [C°] PE [g] productivityb Mw Mw/Mn
1
2
3
4
5
6
7
8
9
10
8
8
8
8
9
d-MAO 30
d-MAO 50
d-MAO 80
0.5
0.8
0.7
0.3
2.5
1.6
1.9
1.8
0.8
0.6
200
320
280
120
1000
640
760
720
320
240
491600 21.1
467000 10.0
122800 13.3
59700 16.0
619600 11.1
PMAO
80
d-MAO 50
d-MAO 80
d-MAO 50
d-MAO 80
d-MAO 50
d-MAO 80
9
484400
590300
342100
8.4
2.9
2.4
10
10
6
478400 37.3
431200 19.5
6
Experimental Section
a 2 µmol of cat., Ti:Al ) 1:500 (m/m), 260 mL of toluene solvent, 5
Reagents and General Techniques. All operations were per-
formed in a nitrogen atmosphere with rigorous exclusion of oxygen
and moisture using glovebox or Schlenk techniques. All chemicals
used were reagent grade or higher and purified according to standard
protocols. Nonchlorinated solvents were distilled over Na/K-alloy
and benzophenone under nitrogen atmosphere. Dichloromethane
was distilled over CaH2 under nitrogen atmosphere.
For polymerization purposes toluene (Aldrich, anhydrous, 99.8%)
was passed over columns of Al2O3 (Fluka), BASF R3-11-supported
Cu oxygen scavenger, and molecular sieves (Aldrich, 4 Å). Ethylene
(AGA polymer grade) was passed over BASF R3-11-supported Cu
oxygen scavenger and molecular sieves (Aldrich, 4 Å). PMAO (4.9
wt % Al in toluene, Akzo Nobel) was used as received. d-MAO
was prepared by removal of all volatiles from PMAO under
vacuum.
bar of ethylene, 15 min run time. b kg(PE) × mol(Ti)-1 h-1 bar-1
.
for continuous reaction monitoring. At 5 bar of ethylene pressure
multiple injection of the catalyst with a pneumatically operated
catalyst injection system was used. During a polymerization run
the pressure, the ethylene flow, the inner and the outer reactor
temperature, and the stirrer speed were monitored continuously.
In a typical semibatch experiment, the autoclave was evacuated
and heated for 1 h at 125 °C prior to use. The reactor was then
brought to the desired temperature, stirred at 600 rpm, and
charged with 230 mL of toluene together with d-MAO (0.058
g, Ti:Al ) 1:500 (m/m)). After pressurizing with ethylene to
reach 5 bar total pressure the autoclave was equilibrated for 5
min. Subsequently 1 mL of a 0.002 M stock solution of the
titanium complex in toluene was injected together with 30 mL
of toluene, to start the reaction. During the run the ethylene
pressure was kept constant to within 0.2 bar of the initial
pressure by replenishing flow. After the desired reaction time
the reactor was vented and the residual PMAO/d-MAO was
destroyed by addition of 20 mL of ethanol. Polymeric product
was collected, stirred for 30 min in acidified ethanol, and rinsed
with ethanol and acetone on a glass frit. The polymer was
initially dried in air and subsequently in vacuum at 80 °C.
The polymerization results are given in Table 4. Compounds
6 and 8 are of only low productivity, ranging between 200 and
320 kg(PE) × mol(Ti)-1 h-1 bar-1 when activated with d-MAO
at all polymerization temperatures applied. The molecular weight
of the polyethylene produced is quite high, with an average
467 000 g mol-1 with the exception of polymerization run 4,
1H and 13C NMR spectra were recorded on a Bruker AVANCE
500 (1H, 500.13 MHz; 13C, 125.75 MHz) spectrometer. Variable-
temperature NMR experiments were conducted on a Bruker
Advance 300.1 MHz spectrometer. 1H chemical shifts are referenced
to residual solvent protons; 13C spectra were referenced to CDCl3
or C6D6, respectively (signal assignment based on NOE measure-
ments). Electron impact (EI) and chemical ionization (CI) mass
spectra were taken on a Finnigan-MAT 95 spectrometer. IR spectra
were recorded on a BIO-RAD FTS-7 spectrometer using KBr
pellets. Elemental analyses were carried out by the Analytische
Laboratorien GmbH, Lindlar (Germany). Melting points were
determined using a Mel-Temp by Laboratory Devices, Cambridge.
Gel permeation chromatography (GPC) analysis was carried out
on a Polymer Laboratories Ltd. (PL-GPC210) chromatograph at
150 °C using 1,2,4-trichlorobenzene as the mobile phase. The
samples were prepared by dissolving the polymer (0.1% weight/

1866 Organometallics, Vol. 27, No. 8, 2008
Schröder et al.

Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes
Organometallics, Vol. 27, No. 8, 2008 1867
volume) in the mobile phase solvent in an external oven and were
run without filtration. The molecular weight was referenced to
suspension, which turned dark red upon stirring overnight. The
reaction mixture was evaporated to dryness, and the residue was
extracted with 30 mL of dichloromethane in order to remove LiCl.
The resulting dark red solution was layered with 30 mL of n-hexane
to afford 63 mg (0.11 mmol, 21%) of 6 as dark red crystals suitable
for X-ray diffraction. Mp: 257 °C. 1H NMR (CDCl3, 500.13 MHz,
polyethylene (Mw ) 50 000 g/mol) and polystyrene (Mw
)
100 000–500 000 g/mol) standards. The reported values are the
average of at least two independent determinations.
X-ray Diffraction. Single-crystal experiments were performed
on a Stoe IPDS diffractometer with graphite-monochromated Mo
KR radiation (λ ) 0.71073 Å). The structures were solved by direct
phase determination and refined by full-matrix least-squares
techniques against F2 with the SHELXL-97 program system.36
Synthesis of TbfTi(III)Cl2(THF) (3). To a solution of 330 mg
(0.50 mmol) of TbfLi(THF)4 in 30 mL of toluene was added 185
mg (0.50 mmol) of TiCl3(THF)3 to form a dark green solution,
which after 1 min of stirring was left for crystallization. Dark green,
extremely air-sensitive crystals of 2 (179 mg, 0.32 mmmol, 64%)
were obtained that were also suitable for X-ray diffraction. Mp:
120 °C (dec). MS (CI, isobutane): m/z (relative intensity) 556.6
(5) [MH+], 420.8 (15), 366.8 (100) [TbfH+], 302.8 (15), 264.7
(55), 111.0 (50). Anal. Calcd for C33H25Cl2OTi: C, 71.25; H, 4.53.
Found: C, 71.01; H, 4.46.
3
300 K) [ppm]: δ 9.04 (d, 2 H, JHH ) 7.8 Hz, H-8, H-9), 8.58 (d,
2 H, 3JHH ) 7.8 Hz, H-5, H-12), 8.52 (d, 2 H, 3JHH ) 8.2 Hz, H-4,
3
H-13), 8.10 (d, 2 H, JHH ) 8.0 Hz, H-1, H-16), 7.856 (s, 1 H,
C-17), 7.71 (t, 2 H, 3JHH ) 8.0 Hz, H-7, H-10), 7.66 (t, 4 H, 3JHH
3
) 8.00 Hz, H-3, H-6, H-11, H-14), 7.52 (t, 2 H, JHH ) 7.2 Hz,
H-2, H-15), 6.72-6.67 (m, 3 H, phenyl), 1.638 (s, 6 H, 2-CH3).
13C NMR (CDCl3, 124.75 MHz, 300 K) [ppm]: δ 131.4, 129.2,
128.7, 128.6, 128.2, 128.1, 128.0, 127.8, 127.8, 127.3, 126.7, 126.6,
124.5, 124.4, 123.7, 123.7, 122.9, 120.1, 100.1. IR (KBr) [cm-1]:
ν˜ 3045 (w), 2916 (w), 1454 (m), 1437 (m), 1401 (m), 1262 (m),
1200 (s), 1165 (s), 1098 (m), 1084 (m), 909 (s), 801 (m), 753 (s),
721 (s), 425 (m). MS (EI, 70 eV): m/z (relative intensity) 603.8
(15) [M+], 364.9 (100) [Tbf+], 181.9 (15). Anal. Calcd for
C37H26Cl2OTi C, 73.41; H, 4.33. Found: C, 73.15; H 4.23.
Synthesis of TbfTiCl3 (4). TbfLi(THF)4 (3.932 g, 5.95 mmol)
and 2.205 g (5.95 mmol) of TiCl3(THF)3 were mixed as solids,
and 20 mL of toluene was added to form a green suspension. After
stirring overnight the reaction mixture was evaporated to dryness
and the green residue was continuously extracted from a frit with
30 mL of CCl4. The extract was filtered to give 2.046 g of 4 (3.94
mmol, 66%) as a dark violet microcrystalline solid. Crystals suitable
for X-ray diffraction were prepared by layering a concentrated
solution of 4 in 20 mL of dichloromethane with 40 mL of n-hexane.
Mp: 279 °C. 1H NMR (CDCl3, 500.13 MHz, 300 K) [ppm]: δ 8.91
Synthesis of TbfTiCl2(2,4,6-Me3C6H2O) (7). 4 (260 mg, 0.50
mmol) and 71 mg (0.50 mmol) of 2,4,6-MeC6H2OLi were mixed
as solids, and 30 mL of toluene was added to give a dark violet
suspension, which turned dark red upon stirring overnight. The
reaction mixture was evaporated to dryness and extracted with 30
mL of dichloromethane in order to remove LiCl. The resulting dark
red solution was layered with 30 mL of n-hexane to afford 70 mg
(0.11 mmol, 23%) of 7 as dark red crystals suitable for X-ray
1
diffraction. Mp: 251 °C. H NMR (CDCl3, 500.13 MHz, 300 K)
3
[ppm]: δ 9.03 (d, 2 H, JHH ) 8.0 Hz, H-8, H-9), 8.58 (d, 2 H,
3
3
(d, 2 H, JHH ) 7.9 Hz, H-8, H-9), 8.66 (d, 2 H, JHH ) 8.0 Hz,
H-5, H-12), 8.61 (d, 2 H, 3JHH ) 7.6 Hz, H-4, H-13), 8.47 (d, 2 H,
3JHH ) 6.8 Hz, H-1, H-16), 8.41 (s, 1 H, H-17), 7.76 (m, 6 H, JHH
3JHH ) 8.0 Hz, H-5, H-12), 8.52 (d, 2 H, 3JHH) 8.2 Hz, H-4, H-13),
3
8.09 (d, 2 H, JHH ) 7.5 Hz, H-1, H-16), 7.814 (s, 1 H, H-17),
3
7.71 (dt, 2 H, JHH ), H-7, H-10), 7.67-7.63 (m, 4 H, H-3, H-6,
) 7.4 Hz, H-2, H-3, H-6, H-11, H-14, H-15), 7.66 (t, 2 H, 3JHH
)
3
H-14, H-11), 7.51 (t, 2 H, JHH ) 7.5 Hz, H-2, H-15), 6.477 (s, 2
7.4 Hz, 3JHH ) 7.1 Hz, H-7, H-10). IR (KBr pellet) [cm-1]: ν˜ 3106
(m), 2962 (m), 1603 (m) 1508 (m), 1422 (m), 1397 (m), 1261 (m),
1164 (m), 1020 (m), 801 (m), 756 (s), 721 (s), 425 (s). MS (EI, 70
eV): m/z (relative intensity) 520.0 (10) [M+], 365.1 (100) [Tbf+],
182.1 (35). Anal. Calcd for C29H17Cl3Ti: C, 67.03; H, 3.30. Found:
C, 67.38; H, 3.10.
H, meta-H), 2.913 (s, 3 H, para-CH3), 1.609 (s, 6 H, ortho-CH3).
13C NMR (CDCl3, 124.75 MHz, 300 K) [ppm]: δ 131.9 (C-17b,
C-16a), 131.4 (C-8a, C-8d), 129.5, 129.1, 128.9 (could not be clearly
assigned), 128.7 (C-4b, C-12a), 128.6, 128.2, 128.1, 127.8 (could
not be clearly assigned), 127.2 (C-16b, C-16b), 126.5, 124.5, 124.4
(could not be clearly assigned), 124.0 (C-8b, C-8c), 123.7 (could
not be clearly assigned), 99.8 (C-17), 20.8 (para-CH3), 16.55 (ortho-
CH3). IR (KBr) [cm-1]: ν˜ 3042 (w), 2945 (w), 1603 (w), 1496
(m), 1438 (m), 1399 (m), 1374 (m), 1212 (s), 1153 (s), 957 (m),
886 (s), 859 (m), 809 (m), 754 (s), 720 (s), 433 (m), 408 (m). MS
(EI, 70 eV): m/z (relative intensity) 617.7 (15) [M+], 364.9 (100)
[Tbf+]. Anal. Calcd for C38H28Cl2OTi: C, 73.69; H, 4.56. Found:
C, 73.44; H, 4.57.
Synthesis of TbfTiCl2(4-tBuC6H4O) (5). 4 (260 mg, 0.50 mmol)
and 50 mg of 4-tBuC6H4OLi were mixed as solids, and 30 mL of
toluene was added to give a dark violet suspension, which turned
dark red upon stirring overnight. The reaction mixture was
evaporated to dryness, and the residue was extracted with 30 mL
of dichloromethane in order to remove LiCl. The resulting dark
red solution was layered with 30 mL of n-hexane to afford 73 mg
(0.11 mmol, 23%) of 5 as dark red crystals suitable for X-ray
Synthesis of TbfTiCl2(2,6-iPr2C6H3O) (8). 4 (260 mg, 0.50
mmol) and 92 mg (0.50 mmol) of 2,6-iPrC6H3OLi were mixed as
solids, and 30 mL of toluene was added to give a dark violet
suspension, which turned dark red upon stirring overnight. The
reaction mixture was evaporated to dryness and extracted with 30
mL of dichloromethane in order to remove LiCl. The resulting dark
red solution was layered with 30 mL of n-hexane to afford 110 mg
(0.17 mmol, 34%) of 8 as dark red crystals suitable for X-ray
1
diffraction. Mp: 261 °C. H NMR (CDCl3, 500.13 MHz, 300 K)
[ppm]: δ 8.85 (d, 2 H, 3JHH ) Hz, H-8, H-9), 8.44-8.41 (m, 4 H,
could not be clearly assigned), 8.37-8.35 (m, 2 H)*, 8.118 (s, 1
H, H-17), 8.69-7.59 (m, 8 H, could not be clearly assigned), 6.67
3
3
(d, 2 H, JHH ) 8.6 Hz, meta-H), 5.61 (d, 2 H, JHH ) 8.6 Hz,
ortho-H), 1.146 (s, 9 H, C(CH3)3). 13C NMR (CDCl3, 124.75 MHz,
300 K) [ppm]: δ 162.9 (ipso-C), 140.1 (para-C), 131.3 (C-8a, C-8d),
130.2 (C-17b, C-16a), 128.7 (C-4a, C-12b), 128.3 (C-4b, C-12a),
128.2 (C-2, C-15), 127.8 (C-7, C-10), 127.3 (C-16b, C-17a), 127.1
(C-8, C-9), 127.0 (C-5, C-12), 125.1 (meta-C), 124.3 (C-4, C-13),
123.6 (C-7, C-10), 123.6, 123.3, 123.2 (could not be clearly
assigned), 118.1 (ortho-C), 34.2 (C(CH3)3), 31.5 (C(CH3)3). MS
(EI, 70 eV): m/z (relative intensity) 661.9 (70) [M+], 526.8 (70),
487.8 (10), 366.0 (100) [Tbf+], 294.8 (65), 258.9 (15).
1
diffraction. Mp: 253 °C. H NMR (CDCl3, 500.13 MHz, 300 K)
3
[ppm]: δ 9.06 (d, 2 H, JHH ) 8.3 Hz, H-8, H-9), 8.60 (d, 2 H,
3
3JHH ) 7.9 Hz, H-5, H-12), 8.55 (d, 2 H, JHH ) 8.2 Hz, H-4,
3
H-13), 7.97 (d, 2 H, JHH ) 7.5 Hz, H-1, H-16), 7.72 (ddd, 2 H,
4
3JHH ) 7.5 Hz, JHH ) 1.0 Hz, H-7, H-10), 7.690 (s, 1 H, H-17),
7.67-7.63 (m, 4 H, 3JHH ) 7.6 Hz, 3JHH ) 7.2 Hz, 4JHH ) 1.0 Hz,
H-3, H-6, H-11, H-14), 7.48 (ddd, 2 H, 3JHH ) 7.6 Hz, 4JHH )1.0
Synthesis of TbfTiCl2(2,6-Me2C6H3O) (6). 4 (260 mg, 0.50
mmol) and 65 mg (0.50 mmol) of 2,6-MeC6H3OLi were mixed as
solids, and 30 mL of toluene was added to give a dark violet
Hz, H-2, H-15), 6.95-6.89 (m, 3 H, phenyl), 2.48 (q, 2 H, 3JHH
)
C
6.8 Hz, CH(CH3)2), 0.94 (d, 12 H, 3JHH ) 6.8 Hz, CH(CH3)2). 13
NMR (CDCl3, 124.75 MHz, 300 K) [ppm]: δ 163.4 (ipso-C), 139.4
(para-C), 131.9 (C-17b, C-16a), 131.4 (C-8a, C-8d), 129.7, 129.2,
128.8 (C-4b, C-8d), 128.7 (C-7, C-10), 128.1 (C-8, C-9), 127.7
(36) Sheldrick, G. M. SHELXL-97. A Program for Refining Crystal
Structures; University of Göttingen: Germany, 1997.

1868 Organometallics, Vol. 27, No. 8, 2008
Schröder et al.
(C-2, C-15), 127.3 (C-16b, C-17a), 126.5 (C-6, C-14), 124.4 (C-5,
C-12), 124.3 (C-1, C-16), 123.8 (C-8b, C-8c), 123.7 (C-4, C-13),
122.6 (meta-C, para-C), 99.2 (C-17), 26.8 (CH(CH3)2), 23.7
(CH(CH3)2). IR (KBr) [cm-1]: ν˜ 2959 (m), 2861 (w), 1509 (w),
1456 (w), 1424 (m), 1382 (m), 1361 (m), 1324 (m), 1247 (m),
1193 (s), 1115 (m), 1092 (m), 914 (s), 811 (m), 793 (s), 723 (s).
MS (EI, 70 eV): m/z (relative intensity) 659.9 (10) [M+], 603.9
(10), 365.0 (100), 182.0 (10). Anal. Calcd for C41H34Cl2OTi: C,
74.44; H, 5.18. Found: C, 73.24; H 5.13.
(C-4, C-13), 123.3 (C-8b, C-8c), 98.0 (C-17), 64.4, 39.7, 26.2 (4
CH3), 16.4 (CH2). IR (KBr) [cm-1]: ν˜ 2964 (w), 2930 (w), 1454
(w), 1434 (w), 1401 (w), 1364 (w), 1260 (m), 1242 (w), 1174 (m),
1091 (m), 1047 (m), 1020 (m), 818 (m), 754 (s), 722 (s), 421 (w).
MS (EI, 70 eV): m/z (relative intensity) 366.1 (100) [Tbf+], 182.0
(16), 126.1 (25), 58.1 (20). Anal. Calcd for C38H35Cl2NOTi ×
0.5C7H8: C, 72.60; H, 5.73. Found: C, 72.44; H, 5.56.
Synthesis of TbfTiCl2OtBu (11). Method a. TiCl3(THF)3 (370
mg, 1.00 mmol) and 661 mg (1.00 mmol) of TbfLi(THF)4 (1) were
mixed as solids, and 20 mL of toluene was added to give a green
suspension. After 2 h a solution of 0.92 mL (0.50 mmol) of
tBuOOtBu in 5 mL of toluene was added, and the reaction mixture
turned dark upon heating until reflux occurred. After cooling to
ambient temperature the reaction mixture was evaporated to dryness
and extracted with 50 mL of dichloromethane in order to remove
LiCl. Layering the dark red solution with 50 mL of n-hexane
afforded 50 mg (0.1 mmol, 10%) of dark red crystals of 11 suitable
for X-ray diffraction.
Synthesis of TbfTiCl2(2,6-Ph2C6H3O) (9). 4 (260 mg, 0.50
mmol) and 252 mg (0.50 mmol) of 2,6-PhC6H3OLi were mixed as
solids, and 30 mL of toluene was added to give a dark violet
suspension, which turned dark red upon stirring overnight. The
reaction mixture was filtered in order to remove LiCl, and the
resulting dark red solution was layered with 30 mL of n-hexane to
afford 119 mg (0.16 mmol, 33%) of 9 as dark red crystals suitable
for X-ray diffraction. Mp: 252 °C. 1H NMR (CDCl3, 500.13 MHz,
3
300 K) [ppm]: δ 8.89 (d, 2 H, JHH ) 8.2 Hz, H-8, H-9), 8.47 (d,
2 H, 3JHH ) 8.3 Hz, H-5, H-12), 8.45 (d, 2 H, 3JHH ) 8.3 Hz, H-4,
H-13), 7.61 (m, 2 H, H-3, H-14), 7.60 (m, 2 H, H-6, H-11), 7.51
(m, 2 H, H-7, H-10), 7.29-7.20 (m, 14 H, H-1, H-2, H-15, H-16,
H-35, H-35′, H-36, H-36′, H-37, H-37′, H-38, H-38′, H-39, H-39′),
Method b. TbfTiCl3(4) (520 mg, 1.00 mmol) and 112 mg (1.00
mmol) KOtBu were mixed as solids, and 50 mL of Toluol were
added to form a violet suspension, which was vigorously stirred
overnight. The reaction mixture was evaporated to dryness and
extracted with 60 mL of dichloromethane in order to remove LiCl.
The dark red solution was layered with 60 mL of n-hexane to afford
135 mg (0.27 mmol, 27%) of dark red crystals of 11. Mp: 254 °C.
1H NMR (CDCl3, 500.13 MHz, 300 K) [ppm]: δ 8.89 (d, 2 H,
3JHH ) 8.2 Hz, H-8, H-9), 8.64 (d, 2 H, 3JHH ) 8.2 Hz, H-5, H-12),
7.18-7.12 (m, 3 H, H-32, H-32′, H-33), 6.450 (s, 1 H, H-17). 13
C
NMR (CDCl3, 124.75 MHz, 300 K) [ppm]: δ 161.8 (C-30), 137.8
(C-31, C-31′), 134.5 (C-34, C-34′), 131.5 (C-4b, C-12a), 131.2 (C-
4a, C-12b), 130.1 (C-32, C-32′), 130.0 (C-16b, C-17a, C-35, C-35′,
C-39, C-39′), 128.8 (C-3, C-14), 128.6 (C-36, C-36′, C-38, C-38′),
128.5 (C-8a, C-8d), 128.4 (C-6, C-11), 128.2 (C-8, C-9), 127.3
(C-37, C-37′), 126.8 (C-2, C-15), 126.7 (C-17b, C-16a), 126.1 (C-
7, C-10), 124.5 (C-1, C-16), 124.2 (C-8b, C-8c), 123.9 (C-5, C-12),
123.8 (C-33), 123.3 (C-4, C-13), 99.8 (C-17). IR (KBr) [cm-1]: ν˜
3023 (m), 1494 (w), 1451 (m), 1439 (m), 1402 (s), 1221 (s), 900
(s), 810 (m), 754 (s), 714 (s), 696 (s). MS (EI, 70 eV): m/z (relative
intensity) 729.8 (15) [M+], 607.8 (15), 364.9 (100) [Tbf+], 182.0.
Anal. Calcd for C47H30Cl2OTi × 0.5 C7H8: C, 77.38; H, 4.14.
Found: 78.05; H 4.48.
3
3
8.61 (dd, 2 H, JHH ) 6.0 Hz, H-4, H-13), 8.43 (dd, 2 H, JHH
)
6.0 Hz, H-1, H-16), 8.079 (s, 1 H, H-17), 7.72-7.67 (m, 6 H, H-2,
H-3, H-6, H-11, H-14, H-15), 7.60 (dd, 2 H, JHH ) 7.2 Hz, H-7,
3
H-10), 1.265 (s, 9 H, OC(CH3)3).). 13C NMR (CDCl3, 124.75 MHz,
300 K) [ppm]: δ 131.7 (C-17b, C-16a), 131.1 (C-8a, C-8d), 128.8
(C-4b, C-12a), 128.7 (could not be clearly assigned), 128.1 (C-8,
C-9), 128.0 (could not be clearly assigned), 127.9 (C-4a, C-12b),
127.8 (could not be clearly assigned), 126.2 (C-7, C-10), 125.2
(C-1, C-16), 124.3 (C-5, C-12), 123.6 (C-4, C-13), 122.6 (C-8b,
C-8c), 101.1 (C-17), 31.2 (OC(CH3)3), 29.3 (OC(CH3)3).). IR (KBr)
[cm-1]: ν˜ 3077 (w), 2970 (m), 2925 (w), 1507 (w), 1454 (m), 1431
(m), 1363 (m), 1262 (w), 1235 (w), 1159 (s), 1109 (m), 999 (s),
819 (m), 754 (s), 722 (s), 666 (w), 479 (w), 426 (m), 406 (m). MS
(EI, 70 eV): m/z (relative intensity) 556.1 (5) [M+], 501.0 (20),
365.1 (100), 182.1 (15), 56.0 (45). Anal. Calcd for C33H26Cl2OTi:
C, 71.12; H, 4.70. Found: 70.93; H, 4.60.
Synthesis of TbfTiCl2TEMPO (10). TiCl3(THF)3 (370 mg, 1.00
mmol) and 661 mg (1.00 mmol) of TbfLi(THF)4 (1) were mixed
as solids, and 20 mL of toluene was added to give a green
suspension, which immediately turned dark red upon adding a
solution of 156 mg (1.00 mmol) of TEMPO in 5 mL of toluene
after 2 h. The reaction mixture was filtered in order to remove LiCl,
and leaving the solution at -10 °C afforded 324 mg (0.51 mmol,
51%) of 10 as dark red crystals suitable for X-ray diffraction. Mp:
1
264 °C (dec). H NMR (CDCl3, 500.13 MHz, 300 K) [ppm]: δ
Supporting Information Available: Additional crystallographic
data for structures 3-11 have been deposited with the Cambridge
Data Centre as supplementary publications nos. CCDC 670166 (3),
CCDC 670167 (4), CCDC 670171 (5), CCDC 670165 (6), CCDC
670170 (7), CCDC 670168 (8), CCDC 670169 (9), CCDC 670172
(10), and CCDC 670173 (11). Copies of the data can be obtained
free of charges on application to CCDC, 12 Union Road, Cambridge
CB21EZ, U.K. (fax(+44)1223-336-033; e-mail deposit@ccdc.cam.
ac.uk), or free of charge via the Internet at http://pubs.acs.org.
9.04 (d, 2 H, 3JHH ) 8 Hz, H-8, H-9), 8.61 (d, 2 H, 3JHH ) 8.0 Hz,
H-5, H-12), 8.59 (dd, 2 H, 3JHH ) 4.5 Hz, H-4, H-13), 8.22 (dd, 2
H, 3JHH ) 4.5 Hz, H-1, H-16), 7.69-7.63 (m, 6 H, H-2, H-3, H-6,
H-11, H-14, H-15), 7.62 (s, 1 H, H-17), 7.62 (dd, 2 H, 3JHH ) 8.0
Hz, H-7, H-10), 1.285 (s, 6 H), 0.872 (s, 12 H, CH3). 13C NMR
(CDCl3, 124.75 MHz, 300 K) [ppm]: δ 131.7 (C-17b, C-16a), 131.5
(C-8a, C-8d), 129.0 (could not be clearly assigned), 128.6 (C-4b,
C-12a), 128.2, 128.1 (could not be clearly assigned), 128.0 (C-8,
C-9), 127.6 (C-16b, C-17a), 127.5 (could not be clearly assigned),
126.2 (C-7, C-10), 125.1 (C-1, C-16), 124.2 (C-5, C-12), 123.7
OM7012293