Formation of neutral and cationic methyl derivatives of titanium containing cyclopentadienyl and aryloxide ancillary ligation

Article abstract of DOI:10.1021/om0341404

The formation of dimethyltitanium compounds [CpTi(OAr)Me₂] containing cyclopentadienyl and aryloxide ancillary ligation was analyzed. The polymerization of ethylene and γ-olefins was achieved with mixed [Cp(ArO)TiCl₂] precursors trea

Full text of DOI:10.1021/om0341404

2146
Organometallics 2004, 23, 2146-2156
F or m a tion of Neu tr a l a n d Ca tion ic Meth yl Der iva tives of
Tita n iu m Con ta in in g Cyclop en ta d ien yl a n d Ar yloxid e
An cilla r y Liga tion
Andrew E. Fenwick, Khamphee Phomphrai, Matthew G. Thorn,
J onathan S. Vilardo, Christine A. Trefun, Brigitte Hanna,
Phillip E. Fanwick, and Ian P. Rothwell*
Department of Chemistry, Purdue University, 560 Oval Drive,
West Lafayette, Indiana 47907-2084
Received August 28, 2003
The series of dimethyltitanium compounds [CpTi(OAr)Me2], ligated by one cyclopentadienyl
(Cp) and one 2,6-disubstituted aryloxide (OAr), have been prepared by the reaction of
[CpTi(OAr)Cl2] with 2 equiv of LiMe or by the addition of parent phenol (HOAr) to a cold
ether solution of [CpTiMe3]. The compounds are stable, except for those containing less bulky
o-methyl substituents; the compounds [CpTi(OC6H2Me2-2,6-X-4)Me2] (X ) H (19), Br (20))
undergo ligand exchange to produce [CpTi(OC6H2Me2-2,6-X-4)2Me] (X ) H (22), Br (23))
and [CpTiMe3]. X-ray crystal structures have been obtained for the dimethyl compounds
[CpTi(OC6H2Np-2-But -4,6)Me2] (13), [CpTi(OC6H2{C10H9}-2-But -4,6)Me2] (14), [Cp*Ti-
2
2
(OC6HPh2-2,6-But -3,5)Me2] (15), [CpTi(OC6Ph4-2,3,5,6-Br-4)Me2] (18), [CpTi(OC6H2Me2-2,6-
2
Br-4)Me2] (20), [CpTi(OC6H3Pri -2,6)Me2] (21), and the monomethyl species 23. Reaction of
2
the dimethyl compounds with [B(C6F5)3] generates the corresponding cationic methyl species
[CpTi(OAr)Me][MeB(C6F5)3]. The compound [CpTi(OC6HPh4-2,3,5,6)Me][MeB(C6F5)3] (27) was
studied via solution VT-NMR spectroscopy, and the free energy of activation for methyl
exchange was estimated to be 14.4(5) kcal mol-1 at 10 °C. These thermally unstable cationic
derivatives readily eliminate methane at room temperature, affording compounds of the
type [CpTi(OAr)(C6F5){CH2B(C6F5)2}]. A kinetic study of the conversion of 27 to [CpTi(OC6-
HPh4-2,3,5,6)(C6F5){CH2B(C6F5)2}] (31) was undertaken. Toluene-d8 solutions of 27 were
1
found to cleanly convert to 31 and methane, as monitored by H NMR spectroscopy. A first-
order rate constant of [7.6(2)] × 10-4 s-1 was measured at 25.0(5) °C. The solid-state structure
of [CpTi(OC6HPh2-2,6-Me2-3,5)(C6F5)(CH2B{C6F5}2)] (28) confirms this formulation and
reveals a trigonal-planar boron atom exhibiting no interaction with the adjacent Ti-C6F5
unit.
In tr od u ction
well-defined coordination environment. This allows for
a relationship to exist between the metallocene struc-
ture and the properties of the resulting polyolefin.
Through changes in the coordination environment sur-
rounding the metal center, efficient control over proper-
ties such as molecular weight (Mw), molecular weight
distributions (Mw/Mn), stereochemical microstructure,
crystallization behavior, and comonomer incorporation
has been achieved. These group 4 metallocene catalysts
have greatly enhanced the range and versatility of a
variety of types of polyolefin materials, making their
role in industrial processes an ever-increasing one.
With the great success of group 4 metallocene olefin
polymerization catalysts has come an intense interest
in the development of related homogeneous catalysts
supported by non-Cp ancillary ligation.2-4 Many differ-
ent types of ligand systems have been employed, includ-
ing macrocycles and porphyrins, meeting with varying
degrees of success in terms of their control over polymer
properties. Some ligand systems have attracted more
attention than others, due to their favorable compari-
sons with known metallocene systems in terms of this
control as well as activity. These include the “con-
There has been a great degree of success reported
relating to the use of the group 4 metallocenes as olefin
polymerization catalyst precursors.1 Cationic alkyl com-
plexes of the type [Cp2MR]+ (M ) Ti, Zr, Hf), formed
via activation of dihalides or dialkyl complexes [Cp2MR2]
with MAO or other cocatalysts such as [B(C6F5)3] and
[Ph3C][B(C6F5)4], are now known to be the catalytically
active species in metallocene-based olefin polymeriza-
tion systems. This highly electrophilic 14-electron spe-
cies possesses a very complex reaction chemistry, in
which the formation of temporarily dormant, stabilized
adducts plays a key role. In contrast to heterogeneous
Ziegler-Natta catalysts, the homogeneous metallocene-
based polymerization catalysts allow reactivity to take
place at predominantly a single-metal site that has a
* To whom correspondence should be addressed. E-mail: rothwell@
purdue.edu.
(1) (a) Bochmann, M. J . Chem. Soc., Dalton Trans. 1996, 255. (b)
Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth,
R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (c) Mo¨hring, P. C.;
Coville, N. J . J . Organomet. Chem. 1994, 479, 1. (d) Kaminsky, W.;
Kulper, K.; Brintzinger, H. H. Angew. Chem., Int. Ed. Engl. 1985, 24,
507.
10.1021/om0341404 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/01/2004

Methyl Derivatives of Titanium
Organometallics, Vol. 23, No. 9, 2004 2147
strained geometry” 5 and chelating diamide2a-d,i,j based
catalyst systems.
Sch em e 1
A variety of ligand systems based upon alkoxide or
aryloxide ligands have also been examined. This has
included the use of chelating phenoxide3,4,6 and alkox-
ide7 ligands. For example, Schaverien et al. have shown
that excellent stereocontrol of the resulting polymer can
be achieved using a chelating binaphthoxide catalyst.3a
A number of “constrained geometry” type catalysts
containing oxygen atom linkages to the metal center
have also been designed and studied.5b,8 Finally, a
number of ligand systems consisting of monodentate
aryloxide- or alkoxide-metal linkages have been stud-
ied. This includes results from our group on the isolation
and polymerization chemistry of [(ArO)2MR]+ species.9
In this paper we report upon the formation and struc-
ture of both neutral and cationic methyl compounds of
titanium containing both cyclopentadienyl and aryloxide
ligation.10-12 Studies by Nomura et al. have shown that
(2) (a) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996,
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(3) For the polymerization of olefins by bidentate aryloxides see: (a)
van der Linden, A.; Schaverien, C. J .; Meijboom, N.; Grant, C.; Orpen,
A. G. J . Am. Chem. Soc. 1995, 117, 3008. (b) Fokken, S.; Spaniol, T.
P.; Kang, H.-C.; Massa, W.; Okuda, J . Organometallics 1996, 15, 5069.
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see: Cozzi, P. G.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1995, 14, 4994. (d) Bott, R. K. J .; Hughes, D. L.;
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polymerization of ethylene and R-olefins can be achieved
with mixed [Cp(ArO)TiCl2] precursors treated with a
variety of activators.13 In this study emphasis is placed
upon the fluxionality of the compounds as well as their
thermal stability. Some aspects of this work have been
communicated previously.14
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of Dim eth yl
Com p ou n d s. Treatment of the titanium dichlorides
[Cp(ArO)TiCl2] (1-6) with 2 equiv of [LiMe] in benzene
leads to the corresponding dimethyl compounds 9-14
as yellow solids (Scheme 1). Similar treatment of
[Cp*(ArO)TiCl2] (7, 8) with 2 equiv of [LiMe] afforded
the dimethyl compounds 15 and 16. The 2,3,5,6-tet-
raphenylphenoxide and 2,6-dimethylphenoxide deriva-
tives 17 and 19 and their corresponding 4-bromo
analogues 18 and 20, as well as the 2,6-diisopropyl-
phenoxide species 21,15 were prepared via an alter-
(4) Groysman, S.; Goldberg, I.; Kol, M. Organometallics 2003, 22,
3015 and references therein.
(5) (a) Devore, D. D.; Timmers, F. J .; Hasha, D. L.; Rosen, R. K.;
Marks, T. J .; Deck, P. A.; Stern, C. L. Organometallics 1995, 14, 3132.
(b) Chen, Y.-X.; Marks, T. J . Organometallics 1997, 16, 3649. (c) Duda,
L.; Erker, G.; Frohlich, R.; Zippel, F. Eur. J . Inorg. Chem. 1998, 1153.
(d) Blais, M. S.; Chien, J . C. W.; Rausch, M. D. Organometallics 1998,
17, 3775.
(6) (a) Thorn, M. G.; Fanwick, P. E.; Chesnut, R. W.; Rothwell, I. P.
Chem. Commun. 1999, 2543. (b) Turner, L. E.; Thorn, M. G.; Fanwick,
P. E.; Rothwell, I. P., Chem. Commun. 2003, 1034. (c) Thorn, M. G.;
Parker, J . R.; Fanwick, P. E.; Rothwell, I. P. Organometallics 2003,
22, 4658. (d) Turner, L. E.; Swartz, R. D.; Thorn, M. G.; Chesnut, R.
W.; Fanwick, P. E.; Rothwell, I. P. J . Chem. Soc., Dalton Trans., 2003,
4580. (e) Turner, L. E.; Thorn, M. G.; Fanwick, P. E.; Rothwell, I. P.
Organometallics, 2004, 23, 1576.
(13) (a) Nomura, K.; Oya, K.; Komatsu, T.; Imanishi, Y. Macromol-
ecules 2000, 33, 3187. (b) Nomura, K.; Oya, K.; Komatsu, T.; Imanishi,
Y. Macromolecules 2000, 33, 8122. (c) Nomura, K.; Okumura, H.;
Komatsu, T.; Naga, N. Macromolecules 2002, 35, 5388. (d) Nomura,
K.; Naga, N.; Miki, M.; Yanagi, K. Macromolecules 1998, 31, 7588. (e)
Nomura, K.; Oya, K.; Imanishi, Y. J . Mol. Catal. A 2001, 174, 127-
140. (f) Nomura, K.; Komatsu, T.; Imanishi, Y. J . Mol. Catal. A 2000,
159, 127-137. (g) Nomura, K.; Komatsu, T.; Imanishi, Y. J . Mol. Catal.
A 2000, 152, 249-252. (h) Nomura, K.; Naga, N.; Miki, M.; Yanagi,
K.; Imai, A. Organometallics 1998, 17, 2152-2154. (i) Imanishi, Y.;
Nomura, K. J . Polym. Sci. A: Polym. Chem. 2000, 38, 4613-4626. (j)
Nomura, K.; Fudo, A. Catal. Commun. 2003, 4, 269-274. (k) Nomura,
K.; Tsubota, M.; Fujiki, M. Macromolecules 2003, 36, 3797-3799. (l)
Nomura, K.; Fudo, A. Inorg. Chim. Acta 2003, 345, 37-43. (m)
Nomura, K.; Okumura, H.; Komatsu, T.; Naga, N.; Imanishi, Y. J . Mol.
Catal. A 2002, 190, 225-234.
(7) Mack, H.; Eisen, M. S. J . Chem. Soc., Dalton Trans. 1998, 917.
(8) Gielens, E. E. C. G.; Tiesnitsch, J . Y.; Hessen, B.; Teuben, J . H.
Organometallics 1998, 17, 1652.
(9) (a) Thorn, M. G., Etheridge, Z. C., Fanwick, P. E., Rothwell, I.
P. Organometallics 1998, 17, 3636. (b) Thorn, M. G.; Etheridge, Z. C.;
Fanwick, P. E.; Rothwell, I. P. J . Organomet. Chem. 1999, 591, 148.
(10) (a) Thorn, M. G.; Vilardo, J . S.; Lee, J . T.; Hanna, B.; Fanwick,
P. E.; Rothwell, I. P. Organometallics 2000, 19, 5636. (b) Vilardo, J .
S.; Thorn, M. G.; Fanwick, P. E.; Rothwell, I. P. Chem. Commun. 1998,
2425. (c) Thorn, M. G.; Vilardo, J . S.; Lee, J .; Hanna, B.; Fanwick, P.
E.; Rothwell, I. P. Organometallics 2000, 19, 5636. (d) Thorn, M. G.;
Lee, J .; Fanwick, P. E.; Rothwell, I. P. Dalton 2002, 3398. (e) Lee, J .;
Fanwick, P. E.; Rothwell, I. P. Organometallics 2003, 22, 1546.
(11) Sturla, S. J .; Buchwald, S. L. Organometallics 2002, 21, 739-
748.
(14) Thorn, M. G., Vilardo, J . S., Fanwick, P. E., Rothwell, I. P.
Chem. Commun. 1998, 2427.
(12) Firth, A. F.; Stewart, J . C.; Hoskin, A. J .; Stephan, D. W. J .
Organomet. Chem. 1999, 591, 185-193.
(15) An alternative procedure for the synthesis of 21 has been
reported.12

2148 Organometallics, Vol. 23, No. 9, 2004
Fenwick et al.
Sch em e 2
F igu r e 2. Molecular structure of [CpTi(OC6H2{C10H9}-2-
But -4,6)Me2] (14).
2
nate procedure (Scheme 2). The in situ synthesis of
[CpTiMe3] (from the addition of 3 equiv of [LiMe] to
[CpTiCl3] in ether at -78 °C) was followed by the
addition of the corresponding phenol. The synthesis
proceeded in high yield. However, in the case of the 2,6-
dimethylphenoxides 19 and 20, slow decomposition was
observed over days to produce (1H NMR) mixtures
containing the bis(aryloxide) monomethyl species [Cp-
Ti(OC6H3Me2-2,6)2Me] (22) and [CpTi(OC6H2Me2-2,6-
Br-4)2Me] (23), respectively (Scheme 2). This latter
reaction presumably occurs via ligand exchange for the
smaller aryloxide ligands. The bis(aryloxide) compounds
were also prepared pure via addition of 2 equiv of 2,6-
dimethylphenols to [CpTiMe3] (Scheme 2).
F igu r e 3. Molecular structure of [Cp*Ti(OC6HPh2-2,6-
But -3,5)Me2] (15).
2
The solid-state structures of dimethyl compounds 13-
15, 18, 20, and 21 have been determined by single-
crystal X-ray diffraction methods. An ORTEP view of
F igu r e 4. Molecular structure of [CpTi(OC6Ph4-2,3,5,6-
Br-4)Me2] (18).
each molecule is shown in Figures 1-6, and selected
bond distances and angles are collected in Tables 1-6.
The solid-state structure of the monomethyl species 23
was also determined (Figure 7, Table 7). Analysis of the
Ti-Me distances and Me-Ti-Me angles for titanium
F igu r e 1. Molecular structure of [CpTi(OC6H2Np-2-But -
4,6)Me2] (13).
2

Methyl Derivatives of Titanium
Organometallics, Vol. 23, No. 9, 2004 2149
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6P h 4-2,3,5,6-Br -4)Me2] (18)
Ti-O(1)
Ti-C(6)
1.828(1)
2.084(2)
Ti-C(7)
Ti-Cp
2.089(3)
2.044(5)
Ti-O(1)-C(11)
O(1)-Ti-C(6)
O(1)-Ti-C(7)
O(1)-Ti-Cp
148.1(1)
C(6)-Ti-C(7)
C(6)-Ti-Cp
C(7)-Ti-Cp
100.8(1)
112.7(1)
112.7(1)
102.8(1)
104.6(1)
121.0(1)
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6H2Me2-2,6-Br -4)Me2] (20)
Ti-O(1)
Ti-C(6)
1.812(1)
2.088(2)
Ti-C(7)
Ti-Cp
2.101(2)
2.046(2)
F igu r e 5. Molecular structure of [CpTi(OC6H2Me2-2,6-Br-
4)Me2] (20).
O(1)-Ti-Cp
O(1)-Ti-C(6)
O(1)-Ti-C(7)
Ti-O(1)-C(1)
120.29(9)
103.64(8)
103.72(7)
150.0(1)
C(6)-Ti-C(7)
C(6)-Ti-Cp
C(7)-Ti-Cp
100.80(9)
112.91(9)
113.21(9)
Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6H3P r i2-2,6)Me2] (21)
Ti-O(1)
Ti-C(6)
1.803(2)
2.103(3)
Ti-C(7)
Ti-Cp
2.105(3)
2.045(3)
O(1)-Ti-Cp
O(1)-Ti-C(6)
O(1)-Ti-C(7)
Ti-O(1)-C(1)
120.8(1)
104.0(1)
103.2(1)
157.5(1)
C(6)-Ti-C(7)
C(6)-Ti-Cp
C(7)-Ti-Cp
101.8(1)
112.4(1)
112.6(1)
F igu r e 6. Molecular structure of [CpTi(OC6H3Pri -2,6)-
2
Me2] (21).
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6H2Np -2-Bu t2-4,6)Me2] (13)
F igu r e 7. Molecular structure of [CpTi(OC6H2Me2-2,6-Br-
4)2Me] (23).
Ti-O(10)
Ti-C(6)
1.815(2)
2.076(4)
Ti-C(7)
Ti-Cp
2.091(4)
2.053(5)
Ta ble 7. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6H2Me2-2,6-Br -4)2Me] (23)
Ti-O(10)-C(11)
O(10)-Ti-C(6)
O(10)-Ti-C(7)
O(10)-Ti-Cp
158.9(2)
C(6)-Ti-C(7)
C(6)-Ti-Cp
C(7)-Ti-Cp
97.5(2)
111.0(2)
111.8(2)
105.8(1)
103.8(1)
123.7(2)
Ti-O(1)
Ti-C(6)
1.816(2)
2.108(4)
Ti-Cp
2.043(4)
O(1)-Ti-Cp
O(1)-Ti-C(6)
Ti-O(1)-C(1)
118.1(1)
100.8(1)
152.4(2)
O(1)-Ti-O(1)′
C(6)-Ti-Cp
107.6(1)
108.7(1)
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti{OC6H2{C10H9}-2-Bu t2-4,6}Me2] (14)
Ti-O(10)
Ti-C(7)
1.811(2)
2.103(3)
Ti-C(6)
Ti-Cp
2.097(3)
2.044(3)
Those dimethyl compounds having either only one
cyclopentadienyl ligand (including constrained-geometry
ligand systems) or two anionic donor ligands (e.g. amido
or aryloxo groups) have a larger Me-Ti-Me angle
(>100°) and, on average, slightly shorter Ti-Me dis-
tances (2.02-2.14 Å). The distances and angles for 13,
14, 18, 20, and 21 are very similar and are closer to
this latter subgroup of compounds (Figure 8). In con-
trast, the pentamethylcyclopentadienyl compound [Cp*Ti-
Ti-O(10)-C(11)
O(10)-Ti-C(6)
O(10)-Ti-C(7)
O(10)-Ti-Cp
160.1(2)
C(6)-Ti-C(7)
C(6)-Ti-Cp
C(7)-Ti-Cp
97.7(1)
111.3(1)
111.5(1)
105.6(1)
103.8(1)
123.7(1)
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp *Ti(OC6HP h 2-2,6-Bu t2-3,5)Me2] (15)
Ti(1)-O(110)
Ti(1)-C(117)
1.824(2)
2.088(4)
Ti(1)-C(118)
Ti(1)-Cp*
2.112(4)
2.065(4)
(OC6HPh2-2,6-But -3,5)Me2] (15) has similar Ti-Me
2
Ti(1)-O(110)-C(111) 172.3(2) C(117)-Ti(1)-C(118) 91.6(2)
distances but a smaller Me-Ti-Me angle. The smaller
Me-Ti-Me angle possibly reflects the steric compres-
sion by the bulky Cp* and aryloxide ligands but may
also be a consequence of the more electron releasing Cp*
group. The overall trend in Ti-Me distances can be
accounted for in terms of the ligand-dependent electro-
philicity of the titanium metal center; that is, more
electron-donating cyclopentadienyl ligation leads to
longer Ti-Me distances. The Ti-O distances are com-
parable to those in related Ti(IV) aryloxides, a large
number of which have now been structurally character-
O(110)-Ti(1)-C(117) 103.5(1) C(117)-Ti(1)-Cp*
O(110)-Ti(1)-C(118) 105.4(1) C(118)-Ti(1)-Cp*
110.6(2)
110.7(2)
O(110)-Ti(1)-Cp*
128.6(1)
dimethyl compounds [(X)2TiMe2] has been performed
using data from the Cambridge Crystallographic Data-
base (Figure 8). The data on previously reported com-
pounds clearly show that, as a group, titanocene di-
methyl compounds based upon either cyclopentadienyl
or ansa-metallocene ligands have Me-Ti-Me angles
<95° and Ti-Me distances in the range 2.12-2.22 Å.

2150 Organometallics, Vol. 23, No. 9, 2004
Fenwick et al.
F igu r e 8. Plot of Ti-Me distances versus Me-Ti-Me angles for dimethyl derivatives of titanium. Bis(cyclopentadienyl)
derivatives (b) and other ancillary ligands (2) are differentiated. Parameters for compounds 13-15, 18, 20, and 21 are
indicated by 9.
ized. The very large Ti-O-Ar angles are also as
expected.16
rotation on the NMR time scale at this temperature.
Previous NMR studies of 2,6-bis(1-naphthyl)phenol have
shown the barrier to naphthyl rotation in this molecule
can be estimated as 18.0(5) kcal mol-1 at 67 °C.18
Interestingly, both Ti-Me groups in the previously
In the solution spectra of 9, 10, 12, and 15-21, only
1
one signal is present for the Ti-Me groups in the H
and 13C NMR spectra. The chemical shift of the Ti-
CH3 protons is highly dependent upon the nature of the
ancillary aryloxide ligand. In particular, an upfield
shifting of these protons is observed when o-phenyl
groups are introduced onto the phenoxide nucleus. The
upfield shifting of adjacent ligand protons caused by the
diamagnetic shielding of these o-phenyl aryloxides has
been well documented.17 Furthermore, the increase in
upfield shifting when the o-phenyl ring is buttressed by
meta substituents is also clearly evident: cf. Ti-CH3
chemical shifts of δ 0.91, 0.88, 0.33, 0.26, and 0.10 ppm
in 19, 12, 17, 9, and 10, respectively. The presence of a
single Ti-Me resonance for 12 shows that rapid rotation
about the Ti-OAr bond is occurring on the NMR time
scale.
reported [CpTi(OC6H2{C9H7}-2-But -4,6)Me2] appear as
2
one broad singlet in both the H and 13C NMR spectra
1
at ambient temperatures but appear as two well-
resolved resonances at lower temperatures. This mol-
ecule is identical with 13 and 14, except it contains an
o-inden-3-yl substituent. From the coalescence temper-
ature the barrier to indenyl rotation can be estimated
to be 13.4(5) kcal mol-1 at -5 °C. Hence, it is clear that
the barrier to naphthyl and dihydronaphthyl rotation
is significantly higher than that for indenyl rotation in
these directly related compounds.
In all of the dimethyl compounds [CpTi(OAr)Me2], the
Ti-CH3 carbon atoms resonate in the δ 53-60 ppm
region of the 13C NMR spectrum. Highly characteristic
single resonances for the Ti-O-C ipso carbon (δ 160-
164 ppm) and Cp (δ 113-114 ppm) and Cp* ligands (δ
120-122 ppm) were observed in the 13C NMR spectra.
Syn t h esis a n d Ch a r a ct er iza t ion of Ca t ion ic
Meth yl Com p ou n d s. Addition of [B(C6F5)3] to the
dimethyl compounds [Cp(ArO)TiMe2] (9, 12, 13, and 17)
in benzene or toluene solvent led to the rapid formation
of the thermally unstable (vide infra) cationic methyl
compounds 24-27 (Scheme 3). The Ti-CH3 methyl
carbon resonates in the δ 77-80 ppm region of the 13C
NMR spectra for all four compounds, significantly
downfield of the parent neutral dimethyl compounds.
Variable-temperature NMR spectra of these species are
In contrast, two well-resolved Ti-Me resonances are
observed for the o-(1-naphthyl) and o-(3,4-dihydro-1-
naphthyl) derivatives 11, 13 (Figure 9), and 14. This is
consistent with the presence of the chiral, dl form of
the 2,6-bis(1-naphthyl)-3,5-di-tert-butylphenoxide ligand
in 11. The dramatic upfield shifting of the Ti-CH3
protons by the large diamagnetic anisotropy of o-
naphthyl rings is shown by the chemical shifts of δ
1
-0.35 and -0.81 ppm for the methyl signals in the H
NMR spectrum of 11. Variable-temperature NMR stud-
ies of 13 show that the two methyl signals remain sharp
even at 90 °C (toluene-d8), indicating slow naphthyl
(16) (a) Bradley, D. C.; Mehrotra, R. C.; Rothwell, I. P.; Singh, A.
Alkoxo and Aryloxo Derivatives of Metals; Academic Press: London,
2001. (b) Steffey, B. D.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 1990,
9, 963.
(17) Vilardo, J . S.; Lockwood, M. A.; Hanson, L. G.; Clark, J . R.;
Parkin, B. C.; Fanwick, P. E.; Rothwell, I. P. J . Chem. Soc., Dalton
Trans. 1997, 3353.
(18) (a) Vilardo, J . S.; Thorn, M. G.; Fanwick, P. E.; Rothwell, I. P.
Chem. Commun. 1998, 2425. (b) Thorn, M. G.; Vilardo, J . S.; Fanwick,
P. E.; Rothwell, I. P. Chem. Commun. 1998, 2427. (c) Riley, P. N.;
Thorn, M. G.; Vilardo, J . S.; Lockwood, M. A.; Fanwick, P. E.; Rothwell,
I. P. Organometallics 1999, 18, 3016.

Methyl Derivatives of Titanium
Organometallics, Vol. 23, No. 9, 2004 2151
F igu r e 9. 1H NMR (C6D6) spectrum of [CpTi(OC6H2Np-2-But -4,6)Me2] (13).
2
Sch em e 3
at room temperature (Figure 10). On the basis of the
spectra obtained for 27, the free energy of activation for
methyl exchange was estimated to be 14.4(5) kcal mol-1
at 10 °C.
In the case of 26, two broad methyl signals as well as
a single sharp Cp resonance are observed at room
temperature. At -10 °C (toluene-d8) the Ti-Me and Ti-
Me-B signals sharpen, but there is still only a single
Cp resonance. At -30 °C the Cp resonance splits into
two signals in a ratio of 80:20, representing the two
diastereomeric forms of 26 (Scheme 4). The methyl
signals also split into two large equal-intensity signals
and one resolvable smaller peak (presumably a further
methyl signal was obscured by aryloxide But reso-
nances). These changes were interpreted as represent-
ing two distinct dynamic processes (Scheme 4). The
faster process involves exchange between the two dia-
stereomers (80:20 ratio) of 26 (Scheme 4) without
methyl exchange. This process involves cation-anion
dissociation and rearrangement and is presumably also
occurring for 24, 25, and 27 but can only be detected
using the chiral o-(1-naphthyl)phenoxide. An alternative
process for exchange of diastereomers would involve
naphthyl rotation within 26. However, the variable-
temperature NMR studies on 13 and data presented for
another compound below show that this process is too
slow to account for the observed process on the NMR
time scale. The slower process in 26, which is also
detected for 24, 25, and 27, involves Ti-Me/Ti-Me-B
exchange. In the case of 26, this process alone cannot
lead to exchange of methyl signals in the NMR spectra.
However, when coupled with the faster ion-pair dis-
1
highly informative. Low-temperature H and 13C NMR
spectroscopy of 24, 25, and 27 show a single set of Cp
and OAr resonances along with resolved Ti-Me (sharp)
and Ti-Me-B (broad) signals. Spectra obtained for 25
at ambient temperature show broadening of these
methyl signals, but the thermal instability precluded
obtaining limiting high-temperature spectra. This broad-
ening was interpreted as being due to exchange of the
boron between methyl groups (methyl exchange), which
is becoming fast on the NMR time scale. The low-
1
temperature H NMR spectra for 27 clearly show well-
resolved methyl peaks below 0 °C and a broad singlet

2152 Organometallics, Vol. 23, No. 9, 2004
Fenwick et al.
F igu r e 10. 1H NMR (C7D8) spectra of [CpTi(OC6HPh4-2,3,5,6)Me][MeB(C6F5)3] 27 at 25, 10, 0, and -20 °C. The asterisk
(*) indicates the protio impurity of toluene-d8 solvent, and the daggers (†) indicate the buildup of 31.
sociation, it leads to diastereotopic methyl exchange.
Previous work by Marks et al. has shown similar
dynamics are present in [Cp′2Zr(Me){MeB(C6F5)3}] spe-
cies. On the basis of the spectra obtained for 26, the
free energy of activation for ion-pair dissociation was
estimated to be 12.4(5) kcal mol-1 at -25 °C (Cp
coalescence temperature at 300 MHz), while that for the
methyl exchange was estimated to be 15.0(5) kcal mol-1
at -35 °C.
Sch em e 4
Decom p osition P a th w a ys for th e Ca tion ic Meth -
yl Com p ou n d s. As discovered by 1H NMR monitoring,
solutions of 24-27 eliminate methane (determined via
NMR) at a rate which is temperature dependent to
produce the neutral organometallic species 28-31
(Scheme 3). Related reactivity has been observed for the
decomposition of other cationic methyl compounds of the
group 4 metals where [MeB(C6F5)3]- anions are present.
In a particularly important mechanistic study, it was
concluded that the reaction occurs via a σ-bond metath-
esis pathway.19 Cyclometalation (intramolecular CH
bond activation) of aryloxide ligands within cationic
group 4 metal alkyls has also been observed.9 The solid-
state structure of 28 confirms the molecular structure
and shows that the boron atom is trigonal planar with
no interaction present with the adjacent Ti-C6F5 unit
(Figure 11, Table 8).2c The Ti-CH2B distance of 2.115-
(19) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J . Am. Chem. Soc.
2000, 122, 5499.

Methyl Derivatives of Titanium
Organometallics, Vol. 23, No. 9, 2004 2153
of this alternative deactivation step as well as olefin
polymerization studies will be the focus of future
reports.
Exp er im en ta l Section
Gen er a l Deta ils. All operations were carried out under a
dry nitrogen atmosphere using standard Schlenk techniques.
The hydrocarbon solvents were distilled from sodium/ben-
zophenone or purified using an Innovative Technologies
solvent purification system and were stored over sodium
ribbons under nitrogen until use. LiMe was used as received
from Aldrich or evaporated to dryness and used without
further purification. [B(C6F5)3] was purchased from Aldrich,
Lancaster, and Strem and used without further purification.
The preparation of compounds 1-8 has been previously
reported.10 The 1H and 13C NMR spectra were recorded on a
Varian Associates Gemini-200, Inova-300, or General Electric
QE-300 spectrometer and referenced to protio impurities of
commercial benzene-d6 (C6D6) or toluene-d8 (C7D8) as internal
standards. Elemental analyses and molecular structures were
obtained through Purdue in-house facilities.
[Cp Ti(OC6HP h 2-2,6-Me2-3,5)Me2] (9). A sample of 1 (1.5
g, 3.3 mmol) was dissolved in benzene. This solution was
stirred as LiMe (216 mg, 9.8 mmol) was slowly added. The
solution was stirred for approximately 2 h and filtered, and
the filtrate was evacuated to dryness, affording a yellow solid.
Recrystallization from benzene/pentane afforded a yellow
powder (1.36 g, 76%). Anal. Calcd for C27H28OTi: C, 77.88; H,
6.78. Found: C, 77.57; H, 6.73. 1H NMR (C6D6, 30 °C): δ 7.07-
7.29 (aromatics); 6.82 (s, p-H); 5.63 (s, Cp); 2.09 (s, m-Me); 0.26
(s, Ti-Me). Selected 13C NMR (C6D6, 30 °C): δ 161.1 (Ti-O-
C); 113.7 (Cp); 56.1 (Ti-Me); 20.8 (m-Me).
[Cp Ti(OC6HP h 2-2,6-Bu t2-3,5)Me2] (10). To a stirred solu-
tion of 2 (0.41 g, 0.76 mmol) in toluene (25 mL) was added
LiMe (0.035 g, 1.59 mmol). The solution was stirred for 24 h
and filtered, and the solvent was removed under vacuum,
giving 10 as a yellow solid (0.36 g, 95%). 1H NMR (C6D6, 30
°C): δ 7.71 (s, p-H); 7.02-7.31 (aromatics); 5.75 (s, Cp); 1.29
(s, CMe3); 0.10 (s, Ti-Me). Selected 13C NMR (C6D6, 30 °C): δ
163.0 (Ti-O-C); 147.5, 140.8, 132.6, 130.9, 128.3, 126.9, 118.7
(aromatics); 113.5 (Cp); 56.9 (Me); 37.4, (CMe3); 33.1 (CMe3).
[Cp Ti(OC6HNp 2-2,6-Bu t2-3,5)Me2] (11). To a stirred solu-
tion of 3 (0.54 g, 0.84 mmol) in toluene (25 mL) was added
LiMe (0.055 g, 2.51 mmol). The solution was stirred for 24 h
and filtered, and the solvent was removed under vacuum,
giving 11 as a yellow solid (0.35 g, 69%). 1H NMR (C6D6, 30
°C): δ 7.90 (s, p-H); 7.15-7.62 (aromatics); 5.17 (s, Cp); 1.21
(s, CMe3); -0.35, -0.81, (s, Ti-Me). Selected 13C NMR (C6D6,
30 °C): δ 163.6 (Ti-O-C); 152.0, 148.7, 138.9, 135.1, 134.0,
129.7, 126.0, 125.3, 119.9 (aromatics); 113.3 (Cp); 56.5, 56.1
(Ti-Me); 37.7 (CMe3); 32.0 (CMe3).
F igu r e 11. Molecular structure of [CpTi(OC6HPh2-2,6-
Me2-3,5)(C6F5)(CH2B{C6F5}2)] (28).
Ta ble 8. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Cp Ti(OC6HP h 2-2,6-Me2-3,5)(C6F 5)-
{CH2B(C6F 5)2}] (28)
Ti-O(10)
Ti-C(20)
Ti-C(41)
Ti-Cp
1.770(2)
2.115(2)
2.176(2)
2.044(3)
B(20)-C(20)
B(20)-C(21)
B(20)-C(31)
1.495(3)
1.595(4)
1.594(3)
Ti-O(10)-C(11) 176.2(1)
C(41)-Ti-Cp
109.7(1)
120.0(2)
119.2(2)
122.9(2)
O(10)-Ti-C(20) 102.44(8) Ti-C(20)-B(20)
O(10)-Ti-C(41) 100.25(8) C(20)-B(20)-C(21)
O(10)-Ti-Cp
C(20)-Ti-C(41)
C(20)-Ti-Cp
126.9(1)
C(20)-B(20)-C(31)
98.73(8) C(21)-B(20)-C((31) 117.9(2)
114.61(9)
(2) Å in 28 is identical with corresponding distances
reported in [CpTi(NHC6H3Me2)(C6F5)(CH2B{C6F5}2)]
(2.165 Å),20 [(ArNCH2CH2CH2NAr)Ti(C6F5)(CH2B{C6-
F5}2)] (2.111 Å),21 and [CpTi(NHC6H3Me2)(C6F5)(CH2B-
1
{C6F5}2)] (2.183 Å). In the H NMR spectra of 28, 29,
and 31, a single set of Cp and aryloxide resonances is
present along with well-resolved, diastereotopic Ti-
CH2-B protons. In the case of 30, which contains the
chiral o-(1-naphthyl) ligand, two sets of sharp NMR
signals are present, due to a 70:30 mixture of the two
possible diastereomers (Scheme 4). The fact that ex-
change of these isomers is slow on the NMR time scale
at ambient temperature confirms that naphthyl rotation
cannot account for the observed fluxionality in 26.
A kinetic study of the conversion of 27 to 31 was
undertaken. Toluene-d8 solutions of 27, generated in
situ by addition of [B(C6F5)3] to 17, were found to cleanly
[Cp Ti(OC6H2P h -2-Bu t2-4,6)Me2] (12). A sample of 4 (2.0
g, 4.3 mmol) was dissolved in benzene. This solution was
stirred as LiMe was slowly added (284 mg, 12.9 mmol). The
solution was stirred for approximately 2 h and filtered, and
the filtrate was evacuated to dryness, affording a yellow solid.
Recrystallization attempts from benzene/pentane afforded a
yellow powder (1.04 g, 58%). Anal. Calcd for C27H36OTi: C,
1
convert to 31 and methane, as monitored by H NMR
spectroscopy. Integration of the Cp proton resonances
and a plot of ln{[27]/([27] + [31])} vs time showed a first-
order decomposition of 27 over approximately 4 half-
lives (Figure 12). A first-order rate constant of [7.6(2)]
× 10-4 s-1 was calculated at 25.0(5) °C; t1/2 ≈ 15 min.
The activation of the 2,6-dimethylphenoxide and 2,6-
diisopropylphenoxide precursors 19-21 with [B(C6F5)3]
was also found to lead to cationic methyl compounds.
However, preliminary studies indicated a different
decomposition pathway was present. A detailed study
1
76.40; H, 8.55. Found: C, 76.12; H, 8.67. H NMR (C6D6, 30
°C): δ 6.70-7.60 (aromatics); 5.57 (s, Cp); 1.68 (s), 1.32 (s,
CMe3); 0.85 (s, Ti-Me). Selected 13C NMR (C6D6, 30 °C): δ
160.8 (Ti-O-C); 114.4 (Cp); 58.4 (Ti-Me); 35.8, 34.5 (CMe3);
31.7, 30.5 (CMe3).
[Cp Ti(OC6H2Np -2-Bu t2-4,6)Me2] (13). A sample of 5 (2.0
g, 3.9 mmol) was dissolved in benzene. This solution was
stirred as LiMe was slowly added (0.27 g, 11.6 mmol). The
solution was stirred for approximately 1 h and filtered, and
the filtrate was evacuated to dryness, affording a yellow solid,
which was recrystallized from pentane to give 13 as yellow
(20) Gomez, R.; Gomez-Sal, P.; del Real, A.; Royo, P. J . Organomet.
Chem. 1999, 22, 588.
(21) Scollard, J . D.; McConville, D. H.; Rettig, S. J . Organometallics
1997, 16, 1810.

2154 Organometallics, Vol. 23, No. 9, 2004
Fenwick et al.
F igu r e 12. Plot of ln{[27]/([27] + [31])} vs time (in s) for the disappearance of 27 generated in situ from 17 and [B(C6F5)3].
[17]0 ) 0.106 M.
crystals (1.04 g, 58%). Anal. Calcd for C31H38OTi: C, 78.47;
H, 8.07. Found: C, 78.59; H, 8.64. H NMR (C6D6, 30 °C): δ
[Cp Ti(OC6HP h 4-2,3,5,6)Me2] (17). A diethyl ether solution
of CpTiCl3 (0.50 g, 2.3 mmol) was cooled to -78 °C in a dry
ice/acetone bath. To this solution was added LiMe (4.7 mL,
1.6 M in diethyl ether) via syringe under a flush of nitrogen.
After the mixture was stirred for approximately 4 h, 2,3,5,6-
tetraphenylphenol (0.91 g, 2.3 mmol) was added with stirring.
The mixture was slowly warmed to room temperature and was
stirred overnight. The solvent was removed under vacuum,
and benzene was added to the solid residue. The suspension
was filtered through a plug of Celite over fritted glass to
remove the lithium salts. The filtrate was then evacuated to
dryness, yielding a pale yellow powder (0.91 g, 75%). Anal.
Calcd for C37H32OTi: C, 82.22; H, 5.97. Found: C, 82.06; H,
5.91. 1H NMR (C6D6, 25 °C): δ 6.87-7.34 (aromatics); 5.53 (s,
Cp); 0.33 (s, Ti-Me). Selected 13C NMR (C6D6, 25 °C): δ 161.3
(Ti-O-C); 113.8 (Cp); 57.5 (Ti-Me).
[Cp Ti(OC6P h 4-2,3,5,6-Br -4)Me2] (18). A diethyl ether
solution of CpTiCl3 (1.03 g, 4.70 mmol) was cooled to -78 °C
in a dry ice/acetone bath. To this solution was added LiMe
(9.1 mL, 1.6 M in diethyl ether) via syringe under a flush of
nitrogen. After the mixture was stirred for approximately 4
h, 4-bromo-2,3,5,6-tetraphenylphenol (2.47 g, 5.17 mmol) was
added with stirring. The mixture was slowly warmed to room
temperature and was stirred overnight. The solvent was
removed under vacuum, and benzene was added to the solid
residue. The suspension was filtered through a plug of Celite
over fritted glass to remove the lithium salts. The filtrate was
then evacuated to dryness, yielding a pale yellow powder (2.14
g, 74%). Slow cooling of a saturated benzene solution afforded
X-ray-quality crystals of the title compound as a benzene
solvate. Anal. Calcd for C37H31BrOTi: C, 71.74; H, 5.04; Br,
12.90. Anal. Calcd for C37H31BrOTi‚C6H6: C, 74.04; H, 5.35;
Br, 11.45. Found: C, 72.23; H, 5.33; Br, 12.37. 1H NMR (C6D6,
25 °C): δ 6.72-7.29 (aromatics); 5.61 (s, Cp); 0.31 (s, Ti-Me).
Selected 13C NMR (C6D6, 25 °C): δ 160.3 (Ti-O-C); 114.0 (Cp);
57.9 (Ti-Me).
1
7.10-8.00 (aromatics); 5.41 (s, Cp); 1.64 (s), 1.26 (s, CMe3);
0.58 (s), 0.15 (s, 1J (13C-1H) ) 124.0, 123.1 Hz, Ti-Me).
Selected 13C NMR (C6D6, 30 °C): δ 161.6 (Ti-O-C); 114.1 (Cp);
58.4, 57.8 (Ti-Me); 35.8, 34.6 (CMe3); 31.7, 30.6 (CMe3).
[Cp Ti(OC6H2{C10H9}-2-Bu t2-4,6)Me2] (14). A sample of 6
(1.00 g, 1.93 mmol) was dissolved in benzene. This solution
was stirred as LiMe was slowly added (0.128 g, 5.82 mmol).
The solution was stirred for 24 h and filtered, and the filtrate
was evacuated to dryness, affording a yellow glassy solid,
which was recrystallized from pentane to give 14 as a yellow
solid (0.92 g, 52%). Anal. Calcd for C31H40OTi: C, 78.13; H,
8.46. Found: C, 78.11; H, 8.66. 1H NMR (C6D6, 30 °C): δ 7.56
4
(d), 7.22 (d, J ) 2.4 Hz), 6.90-7.15 (aromatics); 5.92 (t, CH);
5.80 (s, Cp); 2.60 (m), 2.10 (m, CH2CH2); 1.58 (s), 1.26 (s, CMe3);
0.80 (s), 0.54 (s, Ti-Me). Selected 13C NMR (C6D6, 30 °C): δ
161.8 (Ti-O-C); 114.3 (Cp); 58.6, 57.0 (Ti-Me); 35.7, 34.5
(CMe3); 31.7, 30.6 (CMe3); 28.0, 23.6 (CH2CH2).
[Cp *Ti(OC6HP h 2-2,6-Bu t2-3,5)Me2] (15). To a stirred solu-
tion of 7 (0.23 g, 0.38 mmol) in benzene (10 mL) was added
LiMe (0.035 g, 1.59 mmol). The solution was stirred for 24 h
and filtered, and the solvent was removed under vacuum. The
remaining orange powder was recrystallized as X-ray-quality
crystals from a minimum amount of hexane, giving 15 (0.09
g, 41%). Anal. Calcd for C38H50OTi: C, 79.98; H, 8.83. Found:
C, 80.18; H, 8.97. 1H NMR (C6D6, 30 °C): δ 7.75 (s, p-H); 7.10-
7.04 (aromatics); 1.58 (s, C5Me5); 1.26 (s, CMe3); 0.03 (s, Ti-
Me). Selected 13C NMR (C6D6, 30 °C): δ 162.9 (Ti-O-C); 148.2,
141.3, 133.8, 131.9, 128.7, 127.3, 127.2, 122.5 (aromatics); 119.6
(C5Me5); 60.1 (Ti-Me); 38.0 (CMe3); 33.8 (CMe3); 12.3 (C5Me5).
[Cp *Ti(OC6HP h 4-2,3,5,6)Me2] (16). A solvent-sealed flask
was charged with 8 (300 mg, 0.46 mmol), solid LiMe (30 mg,
1.4 mmol), and benzene. This mixture was stirred until the
red solution turned dark yellow (at least 24 h) and filtered,
and the solvent was removed under vacuum, affording a yellow
solid, which could be recrystallized from benzene/pentane to
give yellow crystals (80 mg, 28%). Anal. Calcd for C42H42OTi:
C, 82.61; H, 6.93. Found: C, 82.40; H, 6.93. 1H NMR (C6D6,
30 °C): δ 6.84-7.42 (aromatics); 1.40 (s, C5Me5); 0.27 (s, Ti-
Me). Selected 13C NMR (C6D6, 30 °C): δ 159.9 (Ti-O-C); 122.2
(C5Me5); 59.5 (Ti-Me); 11.1 (C5Me5).
[Cp Ti(OC6H3Me2-2,6)Me2] (19). LiMe (9.0 mL, 1.6 M sol.
in diethyl ether, 14.4 mmol) was added dropwise to a precooled
suspension of CpTiCl3 (1.00 g, 4.56 mmol) in 30 mL of Et2O at
-78°C. After the mixture was stirred for approximately 4 h,
a solution of 2,6-dimethylphenol (0.557 g, 4.60 mmol) in 10
mL of Et2O was added dropwise at -78°C. The mixture was

Methyl Derivatives of Titanium
Organometallics, Vol. 23, No. 9, 2004 2155
slowly warmed to room temperature and was stirred overnight.
The solvent was removed under vacuum, and benzene was
added to the solid residue. The suspension was filtered through
a plug of Celite over fritted glass to remove the lithium salts.
The filtrate was then evacuated to yield a dark yellow liquid
(0.91 g, 76%). The liquid is stored at -30 °C to prevent
of Et2O at -78 °C. After the mixture was stirred for ap-
proximately 4 h, a solution of 4-bromo-2,6-dimethylphenol
(1.83 g, 9.12 mmol) in 15 mL of Et2O was added dropwise at
-78 °C. The mixture was slowly warmed to room temperature
and was stirred overnight. The solvent was removed under
vacuum, and benzene was added to the solid residue. The
suspension was filtered through a plug of Celite over fritted
glass to remove the lithium salts. The filtrate was then
evacuated to dryness, yielding a yellow liquid. Upon standing
at room temperature for a few hours, the liquid solidified,
giving a yellow solid (1.90 g, 79%). X-ray-quality crystals were
picked out from this solid. Anal. Calcd for C22H24Br2O2Ti: C,
50.05; H, 4.55; Br, 30.26. Found: C, 50.16; H, 4.56; Br, 30.19.
1H NMR (C6D6, 25 °C): δ 7.08 (s, 4H, m-H); 5.73 (s, 5H, Cp);
1.94 (s, 12H, o-Me); 1.23 (s, 3H, Ti-Me). Selected 13C NMR
(C6D6, 25 °C): δ 163.1 (Ti-O-C); 115.1 (Cp); 49.9 (Ti-Me).
[Cp Ti(OC6HP h 2-2,6-Me2-3,5)Me][MeB(C6F 5)3] (24). An
NMR tube was charged with 30 mg (0.072 mmol) of 9, 70 mg
(0.14 mmol) of B(C6F5)3, and 0.5 mL of C6D6 or C7D8. The tube
was quickly placed in an ice/acetone bath until just prior to
1H and 13C NMR analysis. 1H NMR (C6D6, 30 °C): δ 6.80-
7.32 (aromatics); 6.74 (s, p-H); 5.44 (s, Cp); 1.90 (s, m-Me); 0.68
(br, Ti-Me); 0.53 (br, B-Me). 1H NMR (C7D8, -20 °C): δ 6.63-
7.14 (aromatics); 5.39 (s, Cp); 1.87 (s, m-Me); 0.67 (s, Ti-Me);
0.46 (br, B-Me). Selected 13C NMR (C6D6, 30 °C): δ 162.5
(Ti-O-C); 119.3 (Cp); 113.0 (br, B-Me); 77.8 (Ti-Me); 19.9
(m-Me).
1
decomposition. H NMR (C6D6, 25 °C): δ 6.98 (d, J ) 7.2 Hz,
2H, m-H); 6.82 (t, J ) 7.2 Hz, 1H, p-H); 5.82 (s, 5H, Cp); 2.17
(s, 6H, o-Me); 0.91 (s, 6H, Ti-Me). Selected 13C NMR (C6D6,
25 °C): δ 163.8 (Ti-O-C); 114.0 (Cp); 54.0 (Ti-Me).
[Cp Ti(OC6H2Me2-2,6-Br -4)Me2] (20). LiMe (9.0 mL, 1.6 M
sol. in diethyl ether, 14.4 mmol) was added dropwise to a
precooled suspension of CpTiCl3 (1.00 g, 4.56 mmol) in 30 mL
of Et2O at -78 °C. After the mixture was stirred for ap-
proximately 4 h, a solution of 4-bromo-2,6-dimethylphenol
(0.916 g, 4.56 mmol) in 10 mL of Et2O was added dropwise at
-78 °C. The mixture was slowly warmed to room temperature
and was stirred overnight. The solvent was removed under
vacuum, and benzene was added to the solid residue. The
suspension was filtered through a plug of Celite over fritted
glass to remove the lithium salts. The filtrate was then
evacuated to dryness, yielding a dark yellow liquid. Upon
standing at room temperature for a few hours, the liquid
solidified, giving a dark yellow solid (0.91 g, 76%). X-ray-
quality crystals were picked out from this solid. The solid was
stored at -30 °C to prevent decomposition. Anal. Calcd for
C
15H19BrOTi: C, 52.53; H, 5.54; Br, 23.29. Found: C, 52.25;
H, 5.41; Br, 22.90. 1H NMR (C6D6, 25 °C): δ 7.09 (s, 2H, m-H);
5.77 (s, 5H, Cp); 1.39 (s, 6H, o-Me); 0.87 (s, 6H, Ti-Me).
Selected 13C NMR (C6D6, 25 °C): δ 162.5 (Ti-O-C); 114.1 (Cp);
54.9 (Ti-Me).
[CpTi(OC6H2P h -2-Bu t -4,6)Me][MeB(C6F5)3] (25). An NMR
2
tube was charged with 30 mg (0.071 mmol) of 12, 72 mg (0.14
mmol) of B(C6F5)3, and 0.5 mL of C6D6 or C7D8. The tube was
quickly placed in an ice/acetone bath until just prior to 1H and
13C NMR analysis. 1H NMR (C6D6, 30 °C): δ 6.87-7.45
(aromatics); 5.44 (s, Cp); 1.43 (br, Ti-Me); 1.34 (s), 1.19 (s,
CMe3); 0.90 (br, B-Me). 1H NMR (C7D8, -10 °C): δ 6.91-7.40
(aromatics); 5.37 (s, Cp); 1.52 (s, Ti-Me); 1.32 (s), 1.16 (s,
CMe3); 0.94 (br, B-Me). Selected 13C NMR (C6D6, 30 °C): δ
163.0 (Ti-O-C); 120.4 (Cp); 113.0 (br, B-Me); 77.7 (br, Ti-
Me); 35.1, 34.4 (CMe3); 30.8, 29.7 (CMe3). Selected 13C NMR
(C7D8, -10 °C): δ 163.2 (Ti-O-C); 120.7 (Cp); 112.9 (br,
B-Me); 77.4 (s, Ti-Me); 35.4, 34.7 (CMe3); 31.1, 30.0 (CMe3).
[Cp Ti(OC6H 2Np -2-Bu t 2-4,6)Me][MeB(C6F 5)3] (26). An
NMR tube was charged with 30 mg (0.063 mmol) of 13, 65 mg
(0.13 mmol) of B(C6F5)3, and 0.5 mL of C6D6 or C7D8. The tube
was quickly placed in an ice/acetone bath until just prior to
1H and 13C NMR analysis. 1H NMR (C6D6, 30 °C): δ 7.05-
7.68 (aromatics); 5.36 (s, Cp); 1.32 (s), 1.19 (s, CMe3); 0.91 (br,
Ti-Me); 0.81 (br, B-Me). 1H NMR (C7D8, -10 °C): δ 6.97-
7.68 (aromatics); 5.27 (s, Cp); 1.31 (s), 1.15 (s, CMe3); 0.96 (br,
Ti-Me); 0.77 (br, B-Me). 1H NMR (C7D8, -30 °C): δ 6.96-
7.67 (aromatics); 5.23 (s, Cp major); 5.14 (s, Cp minor); 1.31
(s), 1.21 (s, CMe3); 0.95 (br, Ti-Me major); 0.76 (br, B-Me
major); 0.54 (br, B-Me minor). Selected 13C NMR (C6D6, 30
°C): δ 163.3 (Ti-O-C); 119.9 (Cp); 113.1 (br, B-Me); 79.4 (br,
Ti-Me); 35.1, 34.4 (CMe3); 30.9, 30.0 (CMe3).
[Cp Ti(OC6HP h 4-2,3,5,6)Me][MeB(C6F 5)3] (27). An NMR
tube was charged with 30 mg (0.056 mmol) of 17, 30 mg (0.059
mmol) of B(C6F5)3, and 0.5 mL of C6D6 or C7D8. The tube was
quickly placed in an ice/acetone bath until just prior to 1H and
13C NMR analysis. 1H NMR (C7D8, 25 °C): δ 6.85-7.29
(aromatics); 5.34 (s, Cp); 0.68 (br, Ti-Me/B-Me). 1H NMR
(C7D8, -20 °C): δ 6.83-7.30 (aromatics); 5.22 (s, Cp); 0.69(br,
Ti-Me); 0.62 (br, B-Me). Selected 13C NMR (C7D8, -20 °C):
δ 162.8 (Ti-O-C); 119.7 (Cp); 113.0 (br, B-Me); 79.2 (s, Ti-
Me).
[Cp Ti(OC6HP h 2-2,6-Me2-3,5)(C6F 5)(CH2B{C6F 5}2)] (28).
A sample of 9 (210 mg, 0.50 mmol) was dissolved in benzene
along with 420 mg (0.82 mmol) of [B(C6F5)3], causing the
formation of a dark solution. The mixture was allowed to react
overnight and evacuated to dryness, giving a dark solid. This
solid was extracted with pentane, and the red extract was
allowed to sit undisturbed overnight, affording red crystals
[Cp Ti(OC6H3P r i2-2,6)Me2] (21). LiMe (9.0 mL, 1.6 M sol.
in diethyl ether, 14.4 mmol) was added dropwise to a precooled
suspension of CpTiCl3 (1.00 g, 4.56 mmol) in 30 mL of Et2O at
-78 °C. After the mixture was stirred for 4 h, a solution of
2,6-diisopropylphenol (0.845 mL, 4.56 mmol) in 10 mL of Et2O
was added dropwise at -78 °C. The mixture was slowly
warmed to room temperature and was stirred overnight. The
solvent was removed under vacuum, and benzene was added
to the solid residue. The suspension was filtered through a
plug of Celite over fritted glass to remove the lithium salts.
The filtrate was then evacuated to dryness, yielding a dark
yellow liquid. The liquid was then frozen with liquid nitrogen
for 1 min. Upon standing at room temperature, the liquid
solidified, giving a clear yellow crystal (1.12 g, 77%). X-ray-
quality crystals were picked out from this solid. Anal. Calcd
for C19H28OTi: C, 71.30; H, 8.75. Found: C, 70.59; H, 8.83.
1H NMR (C6D6, 25 °C): δ 7.11 (d, 2H, m-H); 7.01 (t, 1H, p-H);
5.92 (s, 5H, Cp); 3.35 (sept, 2H, CHMe2); 1.23 (d, 12H, CHMe2);
0.94 (s, 6H, Ti-Me). Selected 13C NMR (C6D6, 25 °C): δ 161.3
(Ti-O-C); 114.0 (Cp); 54.2 (Ti-Me).
[Cp Ti(OC6H3Me2-2,6)2Me] (22). LiMe (9.0 mL, 1.6 M
solution in diethyl ether, 14.4 mmol) was added dropwise to a
precooled suspension of CpTiCl3 (1.00 g, 4.56 mmol) in 30 mL
of Et2O at -78 °C. After the mixture was stirred for ap-
proximately 4 h, a solution of 2,6-dimethylphenol (1.11 g, 9.09
mmol) in 15 mL of Et2O was added dropwise at -78 °C. The
mixture was slowly warmed to room temperature and was
stirred overnight. The solvent was removed under vacuum,
and benzene was added to the solid residue. The suspension
was filtered through a plug of Celite over fritted glass to
remove the lithium salts. The filtrate was then evacuated to
yield a yellow solid (1.45 g, 86%). Anal. Calcd for C22H26O2Ti:
C, 71.39; H, 7.02. Found: C, 71.50; H, 6.92. 1H NMR (C6D6,
25 °C): δ 6.97 (d, J ) 7.2 Hz, 4H, m-H); 6.81 (t, J ) 7.2 Hz,
2H, p-H); 5.85 (s, 5H, Cp); 2.21 (s, 12H, o-Me); 1.34 (s, 3H,
Ti-Me). Selected 13C NMR (C6D6, 25 °C): δ 164.4 (Ti-O-C);
114.8 (Cp); 48.5 (Ti-Me).
[Cp Ti(OC6H2Me2-2,6-Br -4)2Me] (23). LiMe (9.0 mL, 1.6 M
solution in diethyl ether, 14.4 mmol) was added dropwise to a
precooled suspension of CpTiCl3 (1.00 g, 4.56 mmol) in 30 mL

2156 Organometallics, Vol. 23, No. 9, 2004
Ta ble 9. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s
Fenwick et al.
13
14
15
18
20
21
23
28
formula
C
31H38OTi
C31H40OTi
C38H50OTi
C37H31BrOTi‚ C15H19Br- C19H28OTi
C22H24Br2-
O2Ti
C44H24BF15
OTi
-
C6H6
OTi
formula wt
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
474.55
476.56
570.72
697.58
343.13
320.33
528.15
912.37
P21/c (No. 14) I4l/a (No. 88) P21/c (No. 14) P21/c (No. 14) P1h (No. 2) P21/n (No. 14) Pnma (No. 62) P1h (No. 2)
13.1917(8)
11.7251(6)
18.788(1)
90
107.115(2)
90
2777.4(5)
4
1.135
31.586(1)
12.0726(2)
21.8004(6)
26.0711(4)
90
102.123(1)
90
6708.6(4)
8
1.130
10.6104(2)
20.5655(6)
16.5745(5)
90
106.168(2)
90
3473.7(2)
4
1.334
7.646(1)
7.4673(8)
8.2285(3)
20.9915(9)
12.7159(6)
90
90
90
2196.40(16)
4
1.597
150
12.2084(5)
12.3668(2)
13.7876(5)
71.440(2)
84.811(1)
83.982(2)
1958.9(2)
2
9.6760(7) 16.085(1)
11.125(1) 15.237(1)
67.703(4) 90
82.617(5) 93.036(6)
88.058(7) 90
755.10(15) 1827.6(3)
2
1.509
150
10.805(4)
90
90
90
10780.3(1)
16
1.174
193
Z
F
4
calcd, g cm-3
1.164
150
1.547
203
temp, K
296
203
150
radiation (wavelength)
R
Rw
Mo KR (0.710 73 Å)
0.064
0.166
0.049
0.097
0.052
0.130
0.036
0.077
0.028
0.069
0.063
0.157
0.035
0.074
0.052
0.126
(140 mg, 30%). Anal. Calcd for C44H24BF15OTi: C, 57.93; H,
2.65. Found: C, 57.77; H, 2.59. 1H NMR (C6D6, 30 °C): δ 6.85-
7.18 (aromatics); 6.68 (s, p-H); 5.65 (s, Cp); 3.56 (br), 2.67 (br,
Ti-CH2-B); 1.84 (s, m-Me). Selected 13C NMR (C6D6, 30 °C):
δ 162.3 (Ti-O-C); 118.1 (Cp); 114.2 (br, Ti-CH2-B); 20.1
(m-Me).
crystal was mounted on a glass fiber in a random orientation
under a cold stream of dry nitrogen. Preliminary examination
and final data collection were performed with Mo KR radiation
(λ ) 0.710 73 Å.) on a Nonius Kappa CCD. Lorentz and
polarization corrections were applied to the data.22 An empiri-
cal absorption correction using SCALEPACK was applied.23
Intensities of equivalent reflections were averaged. The struc-
ture was solved using the structure solution program PATTY
in DIRDIF92.24 The remaining atoms were located in succeed-
ing difference Fourier syntheses. Hydrogen atoms were
included in the refinement but restrained to ride on the atom
to which they are bonded. The structure was refined in
full-matrix least-squares, where the function minimized
[Cp Ti(OC6H2P h -2-Bu t2-4,6)(C6F 5)(CH2B{C6F 5}2)] (29). A
sample of 12 (200 mg, 0.47 mmol) was dissolved in benzene
along with 362 mg (0.71 mmol) of B(C6F5)3, causing the
formation of a dark solution. The mixture was allowed to react
overnight and evacuated to dryness, giving a dark solid. The
solid was extracted with pentane, and the red extract was
allowed to sit undisturbed overnight, affording red crystals
(245 mg, 57%). Anal. Calcd for C44H32BF15OTi: C, 57.42; H,
3.50. Found: C, 57.48; H, 3.26. 1H NMR (C6D6, 30 °C): δ 7.56
2
2
was ∑w(|Fo| - |Fc| )2 and the weight w is defined as w )
1/[σ2(Fo2) + (0.0585P)2 + 1.4064P], where P ) (Fo + 2Fc2)/3.
2
4
(d), 7.13 (d, J (1H-1H) ) 2.5 Hz, m-H); 6.10 (s, Cp); 4.21 (br),
Scattering factors were taken from ref 25. Refinement was
performed on an AlphaServer 2100 using SHELX-97.26 Crys-
tallographic drawings were carried out using the programs
ORTEP27 and ORTEP-3 for Windows version 1.076.28
3.23 (br, Ti-CH2-B); 1.62 (s), 1.26 (s, CMe3). Selected 13C NMR
(C6D6, 30 °C): δ 163.7 (Ti-O-C); 119.4 (Cp); 107.1 (br, Ti-
CH2-B); 35.8, 34.7 (CMe3); 31.4, 30.6 (CMe3).
[Cp Ti(OC6H2Np -2-Bu t2-4,6)(C6F 5)(CH2B{C6F 5}2)] (30). A
sample of 13 (200 mg, 0.42 mmol) was dissolved in benzene
along with 324 mg (0.63 mmol) of B(C6F5)3, causing the
formation of a dark solution. The mixture was allowed to react
for 4 h and then evacuated to dryness, giving a dark solid.
The solid was extracted with pentane, and the red extract was
allowed to sit undisturbed overnight, affording red crystals
(160 mg, 39%). Anal. Calcd for C48H34BF15OTi: C, 59.40; H,
3.53. Found: C, 59.28; H, 3.97. 1H NMR (C6D6, 30 °C): δ 6.72-
7.86 (aromatics); 6.24 (s), 5.80 (s, Cp); 4.16 (br), 4.14 (br), 3.00
(m, Ti-CH2-B); 1.60 (s), 1.57 (s), 1.19 (s), 1.15 (s, CMe3).
Selected 13C NMR (C6D6, 30 °C): δ 164.4, 164.3 (Ti-O-C);
119.2, 119.0 (Cp); 107.0, 105.5 (br, Ti-CH2-B); 35.9, 35.8, 34.7,
34.7 (CMe3); 31.4, 31.4, 30.7, 30.6 (CMe3).
Ack n ow led gm en t. Support for this research was
provided by the National Science Foundation (Grant No.
CHE-0078405) and by the U.S. Department of Energy,
Office of Basic Energy Sciences, through the Catalysis
Science Grant No. DE-FG02-03ER15466.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data for 13-15, 18, 20, 21, 23, and 28 as CIF files.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM0341404
Cp Ti(OC6HP h 4-2,3,5,6)(C6F 5)(CH2B{C6F 5}2)] (31). The
compound 21 was allowed to sit at room temperature for 2 h,
and NMR analysis was performed. The sample was then
allowed to sit undisturbed overnight, affording large orange
crystals. The crystals were washed several times with benzene
(22) McArdle, P. C. J . Appl. Crystallogr. 1996, 239, 306.
(23) Otwinowski, Z.; Minor, W. Methods Enzymol. 1996, 276.
(24) Beurskens, P. T.; Admirall, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF92 Program System; Technical Report; Crystallography Labo-
ratory, University of Nijmegen, Nijmegen, The Netherlands, 1992.
(25) International Tables for Crystallography; Kluwer Academic:
Dordrecht, The Netherlands, 1992; Vol. C, Tables 4.2.6.8 and 6.1.1.4.
(26) Sheldrick, G. M. SHELXS97: A Program for Crystal Structure
Refinement; University of Gottingen, Gottingen, Germany, 1997.
(27) J ohnson, C. K. ORTEPII; Report ORNL-5138; Oak Ridge
National Laboratory, Oak Ridge, TN, 1976.
and pentane and dried under vacuum. Anal. Calcd for C54H28
-
BF15OTi: C, 62.58; H, 2.72. Found: C, 64.25; H, 3.21. 1H NMR
(C7D8, 25 °C): δ 6.63-7.30 (aromatics); 5.64 (s, Cp); 3.62 (br),
2.75 (br, Ti-CH2-B). Selected 13C NMR (C7D8, 25 °C): δ 162.2
(Ti-O-C), 118.8 (Cp), 115.3 (br, Ti-CH2-B).
X-r a y Da ta Collection a n d Red u ction . Crystal data and
data collection parameters are contained in Table 9. A suitable
(28) Farrugia, L. J . J . Appl. Crystallogr. 1997, 30, 565.