C-H bond activation processes in cationic and neutral titanium benzyl compounds with cyclopentadienyl-arene ligands

Article abstract of DOI:10.1021/om0206554

Titanium tribenzyl complexes with cyclopentadienyl-arene ligands, (η⁵-C₅H₄CMe₂Ar)Ti-(CH₂ Ph)₃ (Ar = 3,5-Me₂C₆H₃ (1), Ph (2)), were synthesized. Reaction of 1 with either B(C₆F₅)₃ or [Ph₃C][B(C₆F₅)₄] affords the cation [(η,⁵:η-C₅H₄CMe₂-3,5-Me ₂C₆H₃)Ti(η-CH₂Ph)₂]^- (3), in which the pendant arene group and the benzyl ligands show fluxional behavior. Reaction of 2 with B(C₆F₅)₃ leads to rapid ortho cyclometalation of the pendant arene to give the contact ion pair [(η⁵:η¹-C₅H₄CMe₂C ₆H₄)Ti(η¹-CH₂Ph)][η⁶ -PhCH₂B(C₆F₅)₃] (4) and toluene. Reaction of 2 with [Ph₃C][B(C₆F₅)₄] also leads to ligand ortho metalation, giving [(η⁵:η¹-C₅H₄CMe₂C ₆H₄)-Ti(η²-CH₂Ph)] [B(C₆F₅)₄] (5) with a η²-benzyl group. Thermolysis of compounds 1 and 2 (50 °C, 50 h) results in the ortho-cyclometalated dibenzyl species (η⁵:η¹-C₅H₄CMe₂Ar ′)Ti-(CH₂Ph)₂ (Ar′ = 3,5-Me₂C₆H₂ (6), C₆H₄ (7)) and toluene. The thermolysis of 1 follows first-order kinetics (k ≈ 10^-5 s^-1 at 333 K) with ΔH? = 24 ± 2 kcal mol¹ and ΔS? = -5 ± 5 cal mol^-1 K^-1. For the thermolysis of the related titanium trialkyl (η⁵-C₅H₄CMe₂Ph)Ti-(CH₂ SiMe₃)₃ (9), activation parameters of ΔH? = 21 ±2 kcal mol^-1 and ΔS? = -18 ± 4 cal mol^-1 K¹ were found. Deuterium labeling studies with (η⁵-C₅H₄CMe₂C₆D₅ )Ti(CH₂Ph)₃ (2-d₅) show that thermolysis of the neutral compound involves initial formation of an alkylidene intermediate, followed by o-CH addition to the Ti=C bond. In the corresponding cationic species, ortho cyclometalation proceeds via direct σ-bond metathesis.

Full text of DOI:10.1021/om0206554

5564
Organometallics 2002, 21, 5564-5575
C-H Bon d Activa tion P r ocesses in Ca tion ic a n d Neu tr a l
Tita n iu m Ben zyl Com p ou n d s w ith
Cyclop en ta d ien yl-Ar en e Liga n d s
Patrick J . W. Deckers and Bart Hessen*
Dutch Polymer Institute/ Center for Catalytic Olefin Polymerization,
Stratingh Institute for Chemistry and Chemical Engineering, University of Groningen,
Nijenborgh 4, NL-9747AG, Groningen, The Netherlands
Received August 13, 2002
Titanium tribenzyl complexes with cyclopentadienyl-arene ligands, (η5-C5H4CMe2Ar)Ti-
(CH2Ph)3 (Ar ) 3,5-Me2C6H3 (1), Ph (2)), were synthesized. Reaction of 1 with either B(C6F5)3
or [Ph3C][B(C6F5)4] affords the cation [(η,5η-C5H4CMe2-3,5-Me2C6H3)Ti(η-CH2Ph)2]+ (3), in
which the pendant arene group and the benzyl ligands show fluxional behavior. Reaction of
2 with B(C6F5)3, leads to rapid ortho cyclometalation of the pendant arene to give the contact
ion pair [(η5:η1-C5H4CMe2C6H4)Ti(η1-CH2Ph)][η6-PhCH2B(C6F5)3] (4) and toluene. Reaction
of 2 with [Ph3C][B(C6F5)4] also leads to ligand ortho metalation, giving [(η5:η1-C5H4CMe2C6H4)-
Ti(η2-CH2Ph)][B(C6F5)4] (5) with a η2-benzyl group. Thermolysis of compounds 1 and 2 (50
°C, 50 h) results in the ortho-cyclometalated dibenzyl species (η5:η1-C5H4CMe2Ar′)Ti-
(CH2Ph)2 (Ar′ ) 3,5-Me2C6H2 (6), C6H4 (7)) and toluene. The thermolysis of 1 follows first-
order kinetics (k ≈ 10-5 s-1 at 333 K) with ∆Hq ) 24 ( 2 kcal mol-1 and ∆Sq ) -5 ( 5 cal
mol-1 K-1. For the thermolysis of the related titanium trialkyl (η5-C5H4CMe2Ph)Ti-
(CH2SiMe3)3 (9), activation parameters of ∆Hq ) 21 ( 2 kcal mol-1 and ∆Sq ) -18 ( 4 cal
mol-1 K-1 were found. Deuterium labeling studies with (η5-C5H4CMe2C6D5)Ti(CH2Ph)3 (2-
d 5) show that thermolysis of the neutral compound involves initial formation of an alkylidene
intermediate, followed by o-CH addition to the TidC bond. In the corresponding cationic
species, ortho cyclometalation proceeds via direct σ-bond metathesis.
In tr od u ction
and thermal decomposition of various (η5-C5H4CMe2Ar)-
Ti(CH2Ph)3 complexes and their dialkyl cations. Decom-
position of both the neutral and cationic complexes with
Ar ) Ph leads to ortho metalation of the pendant arene
group, but the pathways to this metalation are differ-
ent: for the cationic systems direct σ-bond metathesis
occurs, whereas in the neutral trialkyls the reaction is
initiated by rate-determining R-H abstraction followed
by the subsequent addition of the arene o-CH bond to
the alkylidene intermediate.
Monocyclopentadienyl (half-sandwich) titanium alkyl
compounds, used in combination with methylalumoxane
or other cocatalysts, are especially known for their
ability to act as (pro)catalysts for the syndiotactic
polymerization of styrene,1 although they also show
interesting behavior in the polymerization of other
olefins.2 For example, Cp*TiMe3 is an effective procata-
lyst for the polymerization of propene to give high-
molecular-weight atactic polypropene with a narrow
polydispersity.2b Remarkably, it was also observed to
produce butyl chain branched polyethene from ethene
homopolymerization.2c
Recently we have been investigating monocyclopen-
tadienyl titanium complexes with a pendant arene
group attached to the cyclopentadienyl ligand. Not only
can this pendant arene coordinate to the metal center
in the cations [(η5:η6-C5H4CMe2Ar)TiMe2]+ (Ar ) Ph,
3,5-Me2C6H3)3 but it also turns these systems into
highly active catalysts for the trimerization of ethene
to 1-hexene.4 In this paper we describe the synthesis
Resu lts a n d Discu ssion
Syn t h esis a n d Ch a r a ct er iza t ion of (η5-C5H 4-
CMe2Ar )Ti(CH2P h )3. The cyclopentadienyl-arene ti-
tanium tribenzyl compounds (η5-C5H4CMe2Ar)Ti(CH2-
Ph)3 (Ar ) 3,5-Me2C6H3 (1), Ph (2)) are readily accessible
by the reaction of the appropriate titanium trichloride3
with 3 equiv of benzylmagnesium bromide in diethyl
ether. Crystallization from pentane afforded 1 and 2 as
air- and moisture-sensitive red crystals in around 70%
yield. They were fully characterized by 1D and 2D NMR
techniques and elemental analysis. The methylene
* To whom correspondence should be addressed. Fax: (+31) 50 363
4315. Tel: (+31) 50 363 4322. E-mail: hessen@chem.rug.nl.
(1) (a) Ishihara, T.; Seimiga, T.; Kuramoto, M.; Uoi, M. Macromol-
ecules 1986, 19, 2464. (b) Ishihara T.; Kuramoto, M.; Uoi, M. Macro-
molecules 1988, 21, 3256.
(2) (a) Wang, B. P.; Chien, J . C. W. J . Polym. Sci. Polym. A: Chem.
1988, 26, 3089. (b) Sassmannshausen, J .; Bochmann, M.; Rosch, J .;
Lilge, D. J . Organomet. Chem. 1998, 548, 23. (c) Pellecchia, C.;
Pappalardo, D.; Gruter, G.-J . Macromolecules 1999, 32, 4491.
(3) (a) Deckers, P. J . W.; Van der Linden, A. J .; Meetsma, A.; Hessen,
B. Eur. J . Inorg. Chem. 2000, 929. (b) Sassmannshausen, J .; Powell,
A. K.; Anson, C. E.; Wocadlo, S.; Bochmann, M. J . Organomet. Chem.
1999, 592, 84. (c) For a related system with a C2 bridge between the
Cp and arene functionalities, see: Flores, J . C.; Wood, J . S.; Chien, J .
C. W.; Rausch, M. D. Organometallics 1996, 15, 4944.
(4) Deckers, P. J . W.; Hessen, B.; Teuben, J . H. Angew. Chem., Int.
Ed. 2001, 40, 2516.
10.1021/om0206554 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 11/02/2002

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5565
Sch em e 1
1
benzyl proton resonance appears as one singlet at δ 2.99
and 2.97 ppm for 1 and 2, respectively. The correspond-
ing methylene 13C NMR resonances are found at δ 93.5
singlet resonance, and the rather large J CH coupling
constant of 148 Hz suggests some η2 character of these
groups.8 For the zirconium species [(η5:η6-C5H4CMe2-4-
MeC6H4)Zr(CH2Ph)2][B(C6F5)4],9 the two resonances of
the diastereotopic benzyl methylene protons are barely
1
ppm for both compounds, with a J CH coupling constant
of 123-124 Hz. These spectroscopic data are similar to
1
those of other monocyclopentadienyl titanium tribenzyl
separated (∆δ ) 0.01 ppm), but the observed J CH
complexes,3b,5 in which the methylene J CH value of
coupling constant of 127 Hz unequivocally indicates η1
coordination.10 The NMR spectroscopic data probably
indicate highly fluxional character of the coordination
mode of the aromatic moieties in 3a (i.e. the hapticity
of the two benzyl groups and the arene functionality;
Scheme 1) on the NMR time scale, yielding an average
NMR spectrum of an ansa complex with η1-benzyl
ligands and an isomer with η2-benzyl groups in which
the π-arene coordination is weakened or lost. Bochmann
and co-workers recently demonstrated similar behavior
for the closely related species [(η5:η-C5H4CHPh2)Ti(η-
CH2Ph)2][B(C6F5)4] in CD2Cl2, for which the two differ-
ent structures could be observed separately by NMR
spectroscopy at -90 °C.3b
1
122-126 Hz is indicative of η1 coordination of the benzyl
ligands.
Cation ic Species fr om (η5-C5H4CMe2-3,5-Me2C6H3)-
Ti(CH2P h )3 (1). The reaction of the tribenzyl com-
pound 1 with the Lewis acid B(C6F5)3 in bromo-
benzene-d5 was studied by NMR spectroscopy. At -30
°C this results in the rapid formation of the ionic
complex [(η5:η-C5H4CMe2-3,5-Me2C6H3)Ti(η-CH2Ph)2]-
[PhCH2B(C6F5)3] (3a ; Scheme 1). 1H and 19F NMR data
are consistent with the abstraction of one benzyl group
to give the free [PhCH2B(C6F5)3]- anion.6 Interaction
of the pendant arene group on the cyclopentadienyl
ligand with the metal center in the cation is indicated
1
by the increase in the separation of the two CH H NMR
Addition of a drop of THF-d8 to a C6D5Br solution of
3a shows a shift of the cyclopentadienyl proton reso-
nances back to the chemical shifts normal for a η5-Cp-
arene ligand (δ 6.11 and 5.90 ppm), indicating release
of the arene moiety in the presence of a hard Lewis base
to give a [(η5-C5H4CMe2-3,5-Me2C6H3)Ti(η1-CH2Ph)2-
(THF-d8)x][PhCH2B(C6F5)3] species (Scheme 1). The Ti-
benzyl methylene proton resonances form an AB system
signals of the monosubstituted cyclopentadienyl ring (∆δ
) 1.62 ppm in 3a , ∆δ ) 0.29 ppm in 1). This increase is
related to the constrained geometry associated with the
simultaneous bonding of both cyclopentadienyl and
arene moieties to the metal. This effect was also
observed for ansa-metallocenes of the type [X(C5H4)2]-
TiCl2 (X ) (CH2)3, GeMe2, SiMe2, CH2), where the
separation of the two sets of Cp protons increases with
decreasing Cp(centroid)-Ti-Cp(centroid) angle.7 In
contrast with this observation, the benzyl CH2 protons
do not show the expected AB pattern but one broad
2
(δ 3.19 and 2.18 ppm), with a J HH value of 9.2 Hz, and
the corresponding methylene carbon resonance is a
triplet at δ 107.0 ppm (1J CH 129 Hz), indicative of η1
(8) (a) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I.
P.; Huffman, J . C. Organometallics 1985, 4, 902. (b) J ordan, R. F.;
LaPointe, R. E.; Bajgur, C. S.; Echols, S. F.; Willett, R. J . Am. Chem.
Soc. 1987, 109, 4111. (c) Bochmann, M.; Lancaster, S. J .; Hursthouse,
M. B.; Abdul Malik, K. M. Organometallics 1994, 13, 2235. (d)
Bochmann, M.; Lancaster, S. J . Organometallics 1993, 12, 633. (e)
J ordan, R. F.; LaPointe, R. E.; Baenzinger, N.; Hinch, G. D. Organo-
metallics 1990, 9, 1539.
(5) (a) Flores, J . C.; Herna´ndez, R.; Royo, P.; Butt, A.; Spaniol, T.
P.; Okuda, J . J . Organomet. Chem. 2000, 593/ 594, 202. (b) Scholz, J .;
Rehbaum, F.; Thiele, K. H.; Goddard, R.; Betz, P.; Kru¨ger, C. J .
Organomet. Chem. 1993, 443, 93. (c) Mena, M.; Royo, P.; Serrano, R.;
Pellinghelli, M. A.; Tiripicchio, A. Organometallics 1989, 8, 476.
(6) (a) Horton, A. D.; De With, J . Chem. Commun. 1996, 1375. (b)
Pellecchia, C.; Immirzi, A.; Pappalardo, D.; Peluso, A. Organometallics
1994, 13, 3773. (c) Amor, J . I.; Cuenca, T.; Galakhov, M.; Royo, P. J .
Organomet. Chem. 1995, 497, 127. (d) Pellecchia, C.; Immirzi, A.;
Zambelli, A. J . Organomet. Chem. 1994, 479, C9. (e) Pellecchia, C.;
Grassi, A.; Immirzi, A. J . Am. Chem. Soc. 1993, 115, 1160. (f)
Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organometallics
1993, 12, 4473.
(9) Sassmannshausen, J . Organometallics 2000, 19, 482.
(10) (a) Ciruelo, G.; Cuenca, T.; Go´mez, R.; Go´mez-Sal, P.; Mart´ın,
A.; Rodr´ıguez, G.; Royo, P. J . Organomet. Chem. 1997, 547, 287. (b)
Horton, A. D.; De With, J . Organometallics 1997, 16, 5424. (c) Thorn,
M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1998, 17, 3636. (d) Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B. J .
Chem. Soc., Dalton Trans. 1995, 25.
(7) Ko¨pf, H.; Klouras, N. Z. Naturforsch., B 1983, 38, 321.

5566 Organometallics, Vol. 21, No. 25, 2002
Deckers and Hessen
(toluene-d8, -30 °C), due to the η6 coordination of the
[PhCH2B(C6F5)3]- anion to the metal center. This can
be seen by 19F NMR, where the ∆(δm-F-δp-F) shift
difference is 4.2 ppm, indicative of a contact-ion pair,12
Sch em e 2
1
and by H NMR, where separate resonances are seen
for all aromatic and benzylic protons of the anion. The
Ti-benzyl group is η1 bound, as can be seen from the
1
2J HH coupling constant of 10 Hz and the J CH coupling
constant of 126 Hz of the benzyl methylene group, both
of which are characteristic of η1-benzyl coordination.10
From its low-temperature (-30 °C) 1H,1H NOESY
spectrum the structure of 4 in solution can be deter-
mined (see Scheme 2 for the numbering of the H atoms
in 4). The methylene protons of the benzyl of the
[PhCH2B(C6F5)3]- anion (12 and 13) show a correlation
with the two â-protons of the cyclopentadienyl ring (2
and 3). Methylene proton 13 (δ 3.39 ppm) interacts with
both protons 2 and 3, while 12 (δ 2.8 ppm) only
correlates with 3. The methylene proton of the titanium-
benzyl ligand (9, δ 2.80 ppm) displays NOE interactions
with the Ph m-H (8), adjacent to the Ph o-Cipso. Ad-
ditionally, the other methylene proton (10, δ 0.81 ppm)
correlates with the p-H (11) of the benzyl ligand of the
anion. From the NOE interactions it can be concluded
that in solution at low temperature complex 4 adopts a
structure in which the benzyl methylene group of the
coordinated anion is directed toward the cyclopenta-
dienyl ligand and the methylene protons of the metal-
bound benzyl group are pointing away from the cyclo-
pentadienyl moiety. At ambient temperature consider-
able line broadening is observed, suggesting fluxional
behavior of the remaining benzyl ligand and the coor-
dinated anion.
In the closely related cationic cyclopentadienyl-amido
titanium benzyl complexes {[η5:η1-C5H4(CH2)2NR]Ti-
(CH2Ph)}[PhCH2B(C6F5)3] (R ) Me, i-Pr, t-Bu) the anion
is not coordinated to the titanium center.13 In these
cyclopentadienyl-amido systems the nitrogen lone pair
can serve as an additional 2-electron π-donor, thus
affording a 12-electron cationic species, as opposed to
the formally 10-electron cation in 4.14 Possibly, the
additional 2-electron π-donation is sufficient to favor the
solvent-separated ion pair for the Cp-amido systems
(even for small substituents on the amido nitrogen),
whereas for the highly electron-deficient Cp-aryl system
the η6 coordination of the anion (to give a 16-electron
species) is preferred.
coordination of the benzyl ligands in the presence of
THF.10
Compound 3a is reasonably stable at -30 °C in
bromobenzene-d5 but rapidly decomposes at ambient
temperature (t1/2 ≈ 10 min) to give paramagnetic species
and liberation of toluene, as seen by NMR spectroscopy.
After 20 h deep brown-green crystals had formed which,
from a unit cell determination by X-ray diffraction, were
identified as {[(η5:η6-C5H4CMe2-3,5-Me2C6H3]Ti(µ-Br)]2}-
[B(C6F5)4], the same product as formed in the de-
composition of [(η5:η6-C5H4CMe2-3,5-Me2C6H3)TiMe2]-
[MeB(C6F5)3] in C6D5Br solution.3a
Reaction of (η5-C5H4CMe2-3,5-Me2C6H3)Ti(CH2Ph)3
(1) with [Ph3C][B(C6F5)4] in C6D5Br resulted in the
release of 1 equiv of 1,1,1,2-tetraphenylethane and the
formation of the ionic species [(η5:η-C5H4CMe2-3,5-
Me2C6H3)Ti(η-CH2Ph)2][B(C6F5)4]2 (3b). The NMR data
for the cation are identical with those of 3a . This
suggests that the rapid equilibrium between the differ-
ent coordination modes of the aromatic moieties in the
cations is apparently not influenced by the counterion.
Gen er a t ion of ca t ion ic sp ecies fr om (η5-C5H 4-
CMe2P h )Ti(CH2P h )3 (2). The reaction of the tribenzyl
complex 2 with B(C6F5)3 in bromobenzene-d5 at -30 °C
results in the release of 1 equiv of toluene and the
formation of an ionic species that was characterized as
the contact ion pair [(η5:η1-C5H4CMe2C6H4)Ti(η1-CH2Ph)]-
[η6-PhCH2B(C6F5)3] (4; Scheme 2), in which the pen-
dant aromatic group has been ortho-cyclometalated. In
contrast to the ionic dimethyl compounds [(η5:η6-
C5H4CMe2Ar)TiMe2][MeB(C6F5)3]3 and 3a ,b, compound
4 is also soluble in benzene and toluene and was
obtained analytically pure as a green microcrystalline
solid from the reaction of 2 with B(C6F5)3 in pentane.
The Ti-C 13C NMR resonance of the cyclometalated
pendant arene group is found at δ 199.7 ppm, which is
comparable to the chemical shift found for the ipso
carbon of the Ti-Ph group in the neutral metallocenes
[Me2Si(η5-C5Me4)2]TiPh2 (δ 199.6 ppm, CDCl3, 25 °C)
and (η5-C5H4CMe3)2TiPh2 (δ 191.9 ppm, C6D6, 25 °C).11
The complex 4 has an asymmetric structure in solution
Upon reaction of [Ph3C][B(C6F5)4] with the tribenzyl
complex 2 in bromobenzene-d5 at -30 °C, 1 equiv of
1,1,1,2-tetraphenylethane and 1 equiv of toluene are
(12) Horton, A. D.; De With, J .; Van der Linden, A. J .; Van de Weg,
H. Organometallics 1996, 15, 2672.
(13) For R ) Me, an equilibrium between a coordinated and a
noncoordinated state was observed. See: (a) Sinnema, P.-J .; Van der
Veen, L.; Spek, A. L.; Veldman, N.; Teuben, J . H. Organometallics
1997, 16, 4245. (b) Sinnema, P.-J .; Hessen, B.; Teuben, J . H. Macromol.
Rapid Commun. 2000, 21, 562. (c) Sinnema, P.-J .; Lielkelema, K.;
Staal, O. K. B.; Hessen, B.; Teuben, J . H. J . Mol. Catal. 1998, 128,
143. (d) Sinnema, P.-J . Ph.D. Dissertation, University of Groningen,
1999.
(14) In metal-(σ-aryl) complexes, such as 4, π-donation of the aryl
π-system is of relatively little importance. See: (a) Morse, P. M.;
Girolami, G. S. J . Am. Chem. Soc. 1989, 111, 4114. (b) Girolami, G.
S.; Nelsen, M. J . Abstracts of Papers, 213th National Meeting of the
American Chemical Society, San Francisco, April 1997; American
Chemical Society: Washington, DC, 1997; INOR 710. (c) Bouwkamp,
M.; Van Leusen, D.; Meetsma, A.; Hessen, B. Organometallics 1998,
17, 3645.
(11) (a) Erker, G.; Korek, U.; Petrenz, R.; Rheingold, A. L. J .
Organomet. Chem. 1991, 421, 215. (b) Lee, H.; Bonanno, J . B.; Hascall,
T.; Cordaro, J .; Hahn, J . M.; Parkin, G. J . Chem. Soc., Dalton Trans.
1999, 1365.

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5567
Sch em e 3
Sch em e 4
the formation of titanium dibenzyl species with an
ortho-cyclometalated pendant arene group, (η5:η1-
C5H4CMe2-3,5-Me2C6H2)Ti(CH2Ph)2 (6) and (η5:η1-
C5H4CMe2C6H4)Ti(CH2Ph)2 (7; Scheme 4).16
The 13C NMR spectra show the Ar o-Cipso resonances
of the cyclometalated arene group at δ 201.7 ppm for 6
and δ 200.6 ppm for 7. The observed benzyl methylene
1
2J HH (9.5 Hz for 6 and 10 Hz for 7), and J CH coupling
constants (125 and 122 Hz, respectively) indicate η1
coordination of the benzyl groups.10
Attempts to isolate 6 and 7 from preparative-scale
thermolysis reactions (50 °C) in hexane or benzene
reproducibly afforded viscous oils, which could not be
crystallized. Isolation of the pure titanium dibenzyl
species appears to be thwarted by the occurrence of
further degradation via a secondary decomposition
process, leading to product mixtures. Indeed, prolonged
thermolysis of benzene-d6 solutions of 1 or 2 (>12 h at
80 °C) leads to full decomposition of the initially formed
cyclometalated dibenzyl species 6 and 7. At the final
liberated, and an ionic species with an ortho-cyclo-
metalated pendant arene group and a η2-coordinated
benzyl ligand, [(η5:η1-C5H4CMe2C6H4)Ti(η2-CH2Ph)]-
[B(C6F5)4] (5; Scheme 3), is formed.
The 13C NMR resonance of the Ti-bound aryl carbon
is observed at δ 215.8 ppm and the methylene resonance
of the benzyl ligand at δ 88.1 ppm, the latter with a
1J CH coupling constant of 154 Hz, indicative of η2-benzyl
coordination.8 At -30 °C the benzyl methylene proton
1
stage of the decomposition (no changes of the H NMR
spectrum could be observed for 1 day), 1.3 ((0.1) equiv
of toluene per titanium had been formed, as seen by
comparison with an internal ferrocene standard. In
addition, there is evidence for the formation of para-
magnetic titanium species.17 Oxidation of the product
mixture with excess lead(II) chloride, a method used to
cleanly oxidize Ti(III) to Ti(IV),18 only revealed a
complicated mixture of diamagnetic products that could
not be characterized. This suggests that the secondary
decomposition process leads to a mixture of paramag-
netic species.
Reaction of 7 (prepared in situ in d6-benzene) with 1
equiv of B(C6F5)3 leads to benzyl abstraction, affording
the ionic species 4. Correspondingly, 7 reacts with
[Ph3C][B(C6F5)4] in d5-bromobenzene to give compound
5. Treatment of (η5:η1-C5H4CMe2-3,5-Me2C6H2)Ti-
(CH2Ph)2 (6) with [Ph3C][B(C6F5)4] or B(C6F5)3 in C6D5Br
yields extremely thermally labile species that decompose
within seconds, even at -30 °C, while in benzene-d6, a
brown oil separates from solution. Monitoring the
resonances are observed as two broad signals (W1/2
)
37 Hz), and four broadened resonances (W1/2 ) 33 Hz)
are seen for the cyclopentadienyl protons. This implies
that compound 5 has an asymmetric structure with the
η2-benzyl ligand bound in the cleft between the cyclo-
pentadienyl and arene moieties (Scheme 3). At ambient
temperature the Cp and methylene protons each coal-
esce into broad signals, indicating fluxionality of the
benzyl ligand to give an average Cs symmetry.
Reactions of the analogous titanium trimethyl species
15
(η5-C5H4CMe2Ph)TiMe3 with B(C6F5)3
or [Ph3C]-
[B(C6F5)4]3b cleanly afford the cationic species [(η5:η6-
C5H4CMe2Ph)TiMe2]+. No indications for rapid ortho
cyclometalation of the ancillary ligand have been ob-
served for this compound. Apparently, the benzyl ligands
in 4 help to induce metalation of the cyclopentadienyl-
arene ligand. The benzyl ligands appear to weaken the
coordination of the pendant arene group by binding in
a multihapto fashion (as seen above in the behavior of
3), and consequently facilitate the Cp-arene ligand
ortho cyclometalation. This pathway is not available for
the dimethyl analogues.
(16) For other examples of thermally induced ortho cyclometalation
with comparable ligands, see: (a) Erker, G.; Mu¨hlenbrend, T. J .
Organomet. Chem. 1987, 319, 201. (b) Djakovitch, L.; Herrmann. W.
A. J . Organomet. Chem. 1997, 545/ 546, 399. (c) Licht, E. H.; Alt, H.
G.; Karim, M. M. J . Organomet. Chem. 2000, 599, 261. (d) Bulls, A.
R.; Bercaw, J . E.; Manriquez, J . M.; Thompson, M. E. Polyhedron 1988,
7, 1409. (e) Licht, E. H.; Alt, H. G.; Milius, W.; Abu-Orabi, S. J .
Organomet. Chem. 1998, 560, 69. (f) Djakovitch, L.; Herrmann, W. A.
J . Organomet. Chem. 1998, 562, 71.
Th er m olysis of th e Neu tr a l (η5-C5H4CMe2Ar )Ti-
(CH2P h )3 Com p lexes. Warming benzene-d6 solutions
of the titanium tribenzyl complexes (η5-C5H4CMe2Ar)-
Ti(CH2Ph)3 (Ar ) 3,5-Me2C6H3 (1), Ph (2)) for 50 h at
50 °C and monitoring the reactions by NMR spectros-
copy reveal gradual liberation of 1 equiv of toluene and
(17) The 1H NMR spectrum obtained after complete thermolysis (24
h, 80 °C) only showed the toluene resonances. No precipitation was
observed.
(18) (a) Luinstra, G. A.; Teuben, J . H. J . Chem. Soc., Chem.
Commun. 1990, 1470. (b) Van Leusen, D.; Beetstra, D. J .; Hessen, B.;
Teuben, J . H. Organometallics 2000, 19, 4084.
(15) Deckers, P. J . W. Ph.D. Dissertation, University of Groningen,
2002.

5568 Organometallics, Vol. 21, No. 25, 2002
Deckers and Hessen
F igu r e 2. Eyring plot of the thermolysis of 2 in C6D6 (with
error bars).
F igu r e 1. First-order kinetic plots of the thermolysis of 2
in C6D6 at different temperatures.
compound 7, followed by a secondary decomposition of
7, the overall disappearance of a diamagnetic signal
relative to the internal standard can be used to deter-
mine the rate constant of the secondary degradation
process, since all the organometallic species are com-
pletely soluble at the concentrations used and both
decomposition processes are cleanly first-order and,
thus, independent of concentration. Indeed, monitoring
the disappearance of diamagnetic titanium species in
C6D6 at 72.5 °C affords simple first-order kinetics with
k2 ) 1.5 × 10-5 s-1, equal (within experimental error)
to the rate constant determined for the decomposition
of 7, thus indicating that there is no direct conversion
of 2 to the secondary decomposition product. Similar
analysis of the data from the experiments at other
temperatures (Table 1) allowed the determination of the
kinetic parameters for the secondary degradation proc-
ess as ∆Hq ) 24 ( 2 kcal mol-1 and ∆Sq ) -11 ( 5 cal
Ta ble 1. Ra te Con sta n ts of th e Th er m olysis of
(η5-C5H4CMe2P h )Ti(CH2P h )3 (2)
T (°C)
solvent
[2] (10-2 M)
k1 (10-5 s-1
)
k2 (10-6 s-1
)
72.5
65.0
57.5
50.0
65.0
65.0
65.0
C6D6
C6D6
C6D6
C6D6
C6D6
C6D12
THF-d8
2.6
2.6
2.6
2.6
1.3
2.7
2.5
19.5
7.6
3.2
1.5
7.5
7.2
5.6
14.8
8.0
2.6
1.3
-
7.0
16.7
1
reactions by H NMR shows that additional toluene is
liberated and that unidentified paramagnetic titanium
species are formed. The decomposition pathway of 6
with B(C6F5)3 appears to be different from that of
[(η5:η-C5H4CMe2-3,5-Me2C6H3)Ti(η-CH2Ph)2][PhCH2B-
(C6F5)3] (3a ), since the 19F NMR resonances of the
[B(C6F5)4]- anion, the formation of which accompanies
the decomposition of the latter, are not observed here.
mol-1 K-1
.
Monitoring the thermolysis of 2 in cyclohexane-d12
and in THF-d8 at 65.0 °C showed that the decomposition
processes follow first-order kinetics in these solvents as
well (Table 1). The rate constants in C6D12 of k1 ) 7.2
× 10-5 s-1 and k2 ) 7.0 × 10-6 s-1 are close to those
Kin etic In vestiga tion of th e Th er m olysis of (η5-
C5H4CMe2P h )Ti(CH2P h )3 (2). Despite the occurrence
of secondary decomposition reactions, the kinetics of the
initial thermolysis process could be investigated by
monitoring the disappearance of the titanium tribenzyl
complex (η5-C5H4CMe2Ph)Ti(CH2Ph)3 (2) in benzene-d6
relative to an internal ferrocene standard. The reaction
follows simple first-order kinetics for over 3 half-lives
in the temperature range 50.0-72.5 °C (Figure 1), and
the rate constants k1 are independent of initial concen-
tration (Table 1). The kinetic parameters were deter-
mined from an Eyring plot (of four k1 determinations
over the cited temperature range) as ∆Hq ) 24 ( 2 kcal
mol-1 and ∆Sq ) -5 ( 5 cal mol-1 K-1 (Figure 2)19
The kinetics of the secondary degradation process
were initally investigated in C6D6 at 72.5 °C for starting
compound 2 by monitoring the disappearance of the
initial thermolysis product (η5:η1-C5H4CMe2C6H4)Ti-
(CH2Ph)2 (7) relative to the internal ferrocene standard,
after full conversion of 2. The secondary process also
follows simple first-order kinetics in 7 with a rate
constant k2 of 1.3 × 10-5 s-1, an order of magnitude
smaller than that found for the conversion of 2 to 7 at
this temperature (Table 1). Assuming that the titanium
tribenzyl species 2 is cleanly converted to the dibenzyl
measured at 65 °C in benzene-d6 (k1 ) 7.6 × 10-5 s-1
proceeds at a slightly slower rate of k1 ) 5.8 × 10-5 s-1
,
k2 ) 8.0 × 10-6 s-1). The disappearance of 2 in THF-d8
.
In contrast, the secondary degradation process takes
place significantly more rapidly in THF (k2 ) 1.7 × 10-5
s-1) than in benzene-d6 and cyclohexane-d12. These
observations suggest either participation of THF solvent
in the secondary decomposition process or significant
differences in the polarity of the transition state for the
two independent thermolysis processes, resulting in a
lower rate constant in THF for the conversion of 2 to 7
but a higher rate constant for the degradation of 7.
The first-order kinetics observed in the course of ortho
cyclometalation of the ancillary ligand in the titanium
tribenzyl species 2 to give 7 is consistent with an
intramolecular pathway. The two most likely path-
ways for this transformation are (a) rate-determining
formation of an electronically unsaturated benzylidene
intermediate followed by rapid intramolecular addition
of the aryl o-CH bond to the TidC bond (Scheme 5; top)
and (b) direct σ-bond metathesis (Scheme 5, bottom).
For the cyclometalation of the Cp-arene ligand in (η5-
C5H4CMe2Ph)2Zr(C6H5)2, Erker and co-workers pro-
posed initial formation of an η2-benzyne intermediate
followed by C-H bond addition.16a In contrast, cyclo-
(19) The errors in the kinetic parameters were calculated from the
error propagation formulas derived from the Eyring equation. See:
Morse, P. M.; Spencer, M. D.; Wilson, S. R.; Girolami, G. S. Organo-
metallics 1994, 13, 1646.

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5569
Sch em e 5
metalation in the half-sandwich niobium compound (η5-
C5H4CMe2Ph)Nb{dN[2,6-(i-Pr)2C6H3]}(NMe2)2 proceeds
via direct σ-bond metathesis.16b
Deu ter iu m La belin g Stu d ies. To establish the
mechanism of the ligand cyclometalation in the de-
composition of 2, isotopic labeling experiments were
carried out. The partially labeled compound (η5-
C5H4CMe2C6D5)Ti(CH2Ph)3 (2-d 5) was prepared via the
same route as its nondeuterated analogue, but using
The kinetic parameters as determined for thermolysis
of 2 of ∆Hq ) 24 ( 2 kcal mol-1 and ∆Sq ) -5 ( 5 cal
mol-1 K-1 can be consistent with a pathway via a
benzylidene intermediate. Bercaw and co-workers showed
conclusively that the conversion of Cp*2Hf(CH2Ph)2 to
Cp*2Hf(CH2-o-C6H4) proceeds through a benzylidene
intermediate.20 The entropy of activation of 1 ( 3 cal
mol-1 K-1 for this reaction is similar to that observed
for the disappearance of 2. Other examples of processes
involving alkylidene intermediates show similarly small
entropy of activation values,21 in contrast to most
examples of direct σ-bond metathesis (∆Sq ) -10 to -25
cal mol-1 K-1).22 However, the kinetic parameters are
not conclusive proof as such for a reaction sequence
involving an alkylidene intermediate. Reactions pro-
ceeding via an alkylidene can in some cases exhibit large
negative entropies of activation,23 and others, for which
the involvement of an alkylidene species is highly
unlikely, show very small ∆Sq values.24 For example,
Berg and co-workers recently found kinetic parameters
similar to ours for the ortho cyclometalation of the
pendant arene group in [(PhCHMe)N(CH2CH2CMe2O)2]-
Zr(CH2Ph)2. Although the entropy of activation suggests
the possibility of a benzylidene intermediate, isotopic
labeling experiments conclusively proved a direct σ-bond
metathesis pathway.25
1
C6D5Li instead of PhLi. The H and 13C NMR data of
2-d 5 are identical with those of 2 except for the signals
of the perdeuteriophenyl group.
Thermolysis of 2-d 5 in benzene-d6 (14 h, 65 °C) was
monitored by 1H and 13C NMR spectroscopy. This
revealed the gradual formation of 1 equiv of toluene,
identified as being exclusively C6H5CH3, and the forma-
tion of the titanium dibenzyl (η5:η1-C5H4CMe2C6D4)Ti-
(CH2Ph)(CHDPh) (7-d 4/1). The methylene proton reso-
nances of the Ti-CH2Ph group in 7-d 4/1 are found at
the same chemical shifts as those in 7. The correspond-
ing methylene 13C NMR resonance consists of two
singlets of equal intensity at δ 90.6 and 90.5 ppm (90.5
ppm for 7), one for each of the two diastereomers (syn-
and anticlinal; Scheme 6).26 The methylene 1H NMR
resonances of the Ti-CHDPh group show a small
upfield isotope shift (∆δ ) -0.06 ppm) and are observed
as two singlets (the H-D coupling is not resolved) of
equal intensity, indicating that the two diastereomers
are formed in a 1:1 ratio (vide infra). The methylene
carbon resonance is observed as a triplet at δ 89.6 ppm
1
(isotope shifted by ∆δ ) -0.9 ppm) with a J CD coupling
1
constant of 19 Hz. Comparable isotope shifts and J CD
coupling constants have been observed for the methyl-
ene group of the neopentyl ligand of (η5-C5H5)2Ti-
(CHDCMe3)(C6D5).23c
(20) Bulls, A. R.; Schaefer, W. P.; Serfas, M.; Bercaw, J . E. Organo-
metallics 1987, 6, 1219.
(21) (a) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J . C. J . Am.
Chem. Soc. 1986, 108, 1502. (b) McDade, C.; Green, J . C.; Bercaw, J .
E. Organometallics 1982, 1, 1629. (c) Li, L.; Hung, M.; Xue, Z. J . Am.
Chem. Soc. 1995, 117, 12746. (d) Vaughan, W. M.; Abboud, K. A.;
Boncella, J . M. J . Am. Chem. Soc. 1995, 117, 11015.
(22) (a) Buchwald, S. L.; Nielsen, R. B. J . Am. Chem. Soc. 1988,
110, 3171. (b) Bruno, J . W.; Smith, G. M.; Marks, T. J .; Fair, C. K.;
Schultz, A. J .; Williams, J . M. J . Am. Chem. Soc. 1986, 108, 40. (c)
Smith, G. M.; Carpenter, J . D.; Marks, T. J . J . Am. Chem. Soc. 1986,
108, 6805. (d) Bruno, J . W.; Marks, T. J .; Day, V. W. J . Am. Chem.
Soc. 1982, 104, 7357. (e) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.;
Knight, L. K.; Parvez, M.; Elsegood, M. J . R.; Clegg, W. Organometallics
2001, 20, 2533.
(23) (a) Amor Nait Ajjou, J .; Rice, G. L.; Scott, S. L. J . Am. Chem.
Soc. 1998, 120, 13436. (b) Cheon, J .; Rogers, D. M.; Girolami, G. S. J .
Am. Chem. Soc. 1997, 119, 6804. (c) Van der Heijden, H.; Hessen, B.
J . Chem. Soc., Chem. Commun. 1995, 145. (d) Legzdins, P.; Veltheer,
J . E.; Young, M. A.; Batchelor, R. J .; Einstein, F. W. B. Organometallics
1995, 14, 407. (e) Schock, L. E.; Brock, C. P.; Marks, T. J . Organo-
metallics 1987, 6, 232.
The observations conclusively rule out a direct σ-bond
metathesis pathway, which would have led to the
formation of (η5-C5H4CMe2C6D4)Ti(CH2Ph)2 and R-d-
toluene. The results confirm the involvement of a
benzylidene intermediate (Scheme 5; top). Phosphines
are known to be able to stabilize electronically unsatu-
rated alkylidene species,27 but attempts to trap the
reactive benzylidene intermediate with PMe3 in our
systems failed, resulting only in the formation of ill-
defined paramagnetic titanium species.
(25) Shao, P.; Gendron, R. A. L.; Berg, D. J .; Bushnell, G. W.
Organometallics 2000, 19, 509.
(26) The synclinal and anticlinal diastereomers of the cyclometalated
species are defined with respect to the orientation of the alkylidene
substituents in the two possible alkylidene rotamers they are formed
from (synclinal, alkylidene substituent pointing towards the Cp ligand;
anticlinal, pointing away).
(24) (a) Fryzuk, M. D.; Haddad, T. S.; Rettig, S. J . Organometallics
1991, 10, 2027. (b) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T.
J . Am. Chem. Soc. 1988, 110, 8731.

5570 Organometallics, Vol. 21, No. 25, 2002
Deckers and Hessen
Sch em e 6
Sch em e 7
Only a very small deuterium isotope effect (kH/kD
)
The formation of R-d-toluene indicates that the ortho
cyclometalation of the pendant arene group in the
cationic species proceeds via σ-bond metathesis, in
contrast to the benzylidene pathway identified for the
ligand cyclometalation in the thermolysis of the neutral
compound (η5-C5H4CMe2Ph)Ti(CH2Ph)3 (2) to 7. Thus
B(C6F5)3 initially abstracts a benzyl group from the
titanium tribenzyl species to form the ansa-cyclo-
pentadienyl-phenyl titanium dibenzyl cation, which
subsequently gives ortho C-H/D bond activation to
afford the cyclometalated cationic species {[η5:η1-
C5H4CMe2C6(H/D)4]Ti(CH2Ph)}+ (Scheme 7) (the same
product is obtained via benzyl abstraction with B(C6F5)3
from the cyclometalated neutral species 7; vide supra).
The reaction is accompanied by a distinctive color
change from brown to green. Although the reaction is
too fast to determine the rate constants for the process,
this color change allows a qualitative assessment of the
isotope effect at ambient temperature. Solutions of 2
turn green within 10 s of the addition of B(C6F5)3,
whereas solutions of 2-d 5/B(C6F5)3 take about 3 min
after mixing for a full color change. These observations
suggest ortho C-H/D bond activation in the rate-
determining step, confirming the proposed σ-bond me-
tathesis pathway.
1.23 ( 0.05 at 65.0 °C) is observed for the thermolysis
of 2-d 5, indicating that the aryl ortho C-H/D bond is
not broken in the transition state of the rate-determin-
ing step. For direct σ-bond metathesis, kinetic isotope
effects of 5.2-6.6 have been reported.22a,b The small
kinetic isotope effect gives additional evidence for the
proposed benzylidene pathway.
In contrast to the observations made above for the
ortho cyclometalation in the neutral complexes, the
reaction of 2-d 5 with B(C6F5)3 in C6D6 results in the
selective formation of R-d-toluene and the contact ion
pair [(η5:η1-C5H4CMe2C6D4)Ti(η1-CH2Ph)][η6-PhCH2B-
(C6F5)3] (4-d 4). The 1H NMR resonance of the CH2D
group in R-d-toluene is observed as a triplet at δ 2.08
2
ppm with a J HD coupling constant of 2.2 Hz, and the
corresponding methyl 13C NMR resonance is a triplet
1
at δ 21.2 ppm with a J CD coupling constant of 19 Hz.
Compound 4-d 4 has the same NMR characteristics as
its nondeuterated analogue, except for the resonances
of the perdeuteriophenyl ring.
(27) (a) Ca´mpora, J .; Buchwald, S. L. Organometallics 1993, 12,
4182. (b) Bennett, M. A.; Schwemlein, H. P. Angew. Chem., Int. Ed.
Engl. 1989, 28, 1296. (c) Buchwald, S. L.; Nielsen, R. B. Chem. Rev.
1988, 88, 1047. (d) Buchwald, S. L.; Watson, B. T.; Huffman, J . C. J .
Am. Chem. Soc. 1986, 108, 7411.

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5571
Th er m olysis of Oth er (η5-C5H4CMe2P h )Ti(CH2R)3
Com p lexes (R ) CMe3, SiMe3). For comparison with
the (η5-C5H4CMe2Ph)Ti(CH2Ph)3 (2) system, the ther-
molysis behavior of two other trialkyl complexes (η5-
C5H4CMe2Ph)Ti(CH2R)3 (R ) CMe3, SiMe3) was studied.
These alkyl groups are known to readily undergo R-H
abstraction processes.21c,28 A reaction of (η5-C5H4CMe2-
Ph)TiCl3 with 3 equiv of LiCH2CMe3 in C6D6, performed
in an NMR tube at ambient temperature, shows rapid
release of 1 equiv of neopentane and formation of the
ortho-cyclometalated titanium dialkyl species (η5:η1-
C5H4CMe2C6H4)Ti(CH2CMe3)2 (8). Diagnostic for the
formation of the ortho-cyclometalated pendant arene
group is the 13C NMR resonance for Ti-Cipso observed
at δ 195.5 ppm. The resonances for the diastereotopic
methylene protons of the neopentyl ligands form an AB
system at δ 2.72 and 2.26 ppm (2J HH ) 10.5 Hz).
Repeated attempts to isolate 8 from reactions on a
preparative scale afforded viscous oils that could not be
crystallized, probably due to secondary degradation
processes similar to those observed for the benzyl
species.29 In contrast with the tribenzyl complex 2, the
corresponding trineopentyl compound, (η5-C5H4CMe2-
Ph)Ti(CH2CMe3)3, could not be isolated, even at -78 °C.
generate the cyclometalated species 7-d 4/1 and 8-d 4/1
with two stereogenic centers, giving rise to diastereo-
mers (Scheme 6). Apparently, the two possible isomers
of the neopentylidene intermediate (syn and anti)26 are
not formed in equal quantities. On the basis of argu-
ments formulated by Gibson for tetrahedral alkylidene
complexes with one dominant π-donor ligand that
possesses two orbitals of π-symmetry, such as Cp, the
substituent on the alkylidene ligand in the electronically
most favorable isomer is expected to point in the
direction of that π-donor (synclinal rotamer).31 For the
monocyclopentadienyl group
4 alkylidene species
[η5:η1-C5H4CH2CH2N(t-Bu)]Ti(dCHR)(PMe3)13a and {η5-
C5H3-1,3-[SiMe2CH2P(i-Pr)2]2}Zr(dCHR)Cl32 (and its Hf
analog),33 NOESY NMR spectroscopy and X-ray analy-
sis, respectively, indeed indicate the formation of the
synclinal rotamer. The orientation is supplemented by
agostic interaction of the R-H with the metal center34
and is generally retained in the solution structure. On
the other hand, ready syn/anti isomerization has been
reported for Mo(CHR)(NAr)(OR′)2 species (∆Gq ) 16-
18 kcal mol-1),35 even at temperatures as low as -70
°C,36 and Re(CR)(CHR′)(OR′′)2 species (∆Gq ) 25-30
kcal mol-1),37 and the molybdenum complexes were
found to display a marked difference in reactivity
between the anti and the syn isomer, e.g. in olefin
metathesis.38
Treatment of (η5-C5H4CMe2Ph)TiCl3 with 3 equiv of
LiCH2SiMe3 in C6D6 at ambient temperature affords the
titanium trialkyl species (η5-C5H4CMe2Ph)Ti(CH2SiMe3)3
(9). The coordination chemical shifts of the ancillary
On the basis of the data available we cannot establish
whether, in the transformation of (η5-C5H4CMe2C6D5)-
Ti(CH2Ph)3 (2-d 5) to 7-d 4/1, the benzylidene intermediate
is immediately formed as a 1:1 syn/anti mixture or if
rapid rotation around the TidC bond,39 combined with
a difference in reactivity between the syn and anti ro-
tamers, leads effectively to the observed 1:1 diastereo-
mer mixture. This lower distereoselectivity may also be
associated with the higher reaction temperatures re-
quired for the decomposition of 2 compared to that of 8.
The instantaneous ortho cyclometalation of the tran-
sient trineopentyl complex (η5-C5H4CMe2Ph)Ti(CH2-
CMe3)3 precludes a kinetic study of this system. An
analysis of the reaction kinetics for the thermolysis of
1
ligand are comparable to those of 2, and the H NMR
resonance of the methylene protons of the neosilyl
ligands is found as a singlet at δ 1.73 ppm. Compound
9 can be obtained on a preparative scale in good yield
from (η5-C5H4CMe2Ph)TiCl3 and 3 equiv of ClMgCH2-
SiMe3 in diethyl ether as a brown oil of >95% purity
(NMR), which could not be crystallized.
Warming benzene-d6 solutions of 9 at 50 °C for 70 h
leads to liberation of 1 equiv of tetramethylsilane and
the formation of the titanium dineosilyl species with an
ortho-cyclometalated arene group, (η5:η1-C5H4CMe2C6H4)-
Ti(CH2SiMe3)2 (10). The Ti-Cipso 13C NMR resonance
is observed at δ 198.6 ppm, and the methylene pro-
ton resonances of the neosilyl ligands appear as two
doublets at δ 2.27 and 2.05 ppm (2J HH ) 10.8 Hz).
The mechanistic aspects of the formation of the
neopentyl and neosilyl ortho-cyclometalated dialkyl
titanium complexes 8 and 10 are similar to those
previously outlined for the dibenzyl species 7. Reaction
of (η5-C5H4CMe2C6D5)TiCl3 with 3 equiv of LiCH2CMe3
on an NMR-tube scale gives release of 1 equiv of
neopentane-d0 and the formation of the titanium dialkyl
species (η5:η1-C5H4CMe2C6D4)Ti(CH2CMe3)(CHDCMe3)
(8-d 4/1), similar to the conversion of the deuterated
tribenzyl compound 2-d 5 to 7-d 4/1, indicating the pres-
ence of a neopentylidene intermediate. In contrast to
the dibenzyl species 7-d 4/1, the two diastereomers of
8-d 4/1 are not formed in a 1:1 ratio. The methylene pro-
ton resonance of the Ti-CHDCMe3 group appears as
two singlets at δ 2.65 and 2.18 ppm in the ratio 15:85.
1
the neosilyl complex 9 was conducted by H NMR, for
reactions at 50.0, 57.5, 65.0, and 72.5 °C, relative to an
internal ferrocene standard. In all instances, the pri-
mary thermolysis of 9 follows first-order kinetics (Table
2) and an overall disappearance of the diamagnetic
(31) (a) Gibson, V. C. Angew. Chem., Int. Ed. Engl. 1994, 33, 1565.
(b) Gibson, V. C. J . Chem. Soc., Dalton Trans. 1994, 1607.
(32) (a) Fryzuk, M. D.; Mao, S. S. H.; Zawarotko, M. J .; MacGillivray,
L. R. J . Am. Chem. Soc. 1993, 115, 5336. (b) Fryzuk, M. D.; Duval, P.
B.; Mao, S. S. S. H.; Zawarotko, M. J .; MacGillivray, L. R. J . Am. Chem.
Soc. 1999, 121, 2478.
(33) Fryzuk, M. D.; Duval, P. B.; Patrick, B. O.; Rettig, S. J .
Organometallics 2001, 20, 1608.
(34) For other metal-alkylidene species with R-H agostic interac-
tions, see: (a) Van Doorn, J . A.; Van der Heijden, H.; Orpen, A. G.
Organometallics 1995, 14, 1278. (b) Hessen, B.; Buijink, J . K.;
Meetsma, A.; Teuben, J . H.; Helgesson, G.; Håkansson, M.; J agner,
S.; Spek, A. L. Organometallics 1993, 12, 2268.
(35) Schrock, R. R.; Crowe, W. E.; Bazan, G. C.; DiMare, M.;
O’Regan, M.; Schofield, M. H. Organometallics 1991, 10, 1832.
(36) Oskam, J . H.; Schrock, R. R. J . Am. Chem. Soc. 1993, 115,
11831.
(37) Toreki, R.; Schrock, R. R.; Davis, W. M. J . Am. Chem. Soc. 1992,
114, 3367.
Addition of the ortho C-D bond to the TidC bond is
expected to proceed selectively in a cis fashion30 to
(38) (a) Oskam, J . H.; Schrock, R. R. J . Am. Chem. Soc. 1992, 114,
7588. (b) Schrock, R. R. Tetrahedron 1999, 55, 8141.
(39) For a recent example of thermally induced syn/anti isomeriza-
tion, see: Adams, C. S.; Legzdins, P.; Tran, E. J . Am. Chem. Soc. 2001,
123, 612.
(28) Schrock, R. R. Acc. Chem. Res. 1979, 12, 98.
(29) The initial product 8 gradually decomposes at room temperature
to paramagnetic species.
(30) Van der Heijden, H.; Hessen, B. Inorg. Chim. Acta, in press.

5572 Organometallics, Vol. 21, No. 25, 2002
Deckers and Hessen
of activation is observed. As mentioned above, the ∆Sq
value of -5 cal mol-1 K-1 for the initial decomposition
of the tribenzyl complex 2 is in accord with the small
negative values of -1 to -10 cal mol-1 K-1 typically
observed for the majority of C-H bond abstraction
processes studied.21 The result for the trineosilyl com-
pound 9 (∆Sq ) -18 cal mol-1 K-1) shows considerable
departure from these values but compares well with the
activation parameters found for the thermolysis of {η5-
C5H3-1,3-[SiMe2CH2P(i-Pr)2]2}Zr(CH2Ph)2Cl (∆Hq ) 19
kcal mol-1, ∆Sq ) -22 cal mol-1 K-1).32b The more
negative entropy of activation for 9 suggests a more
ordered transition state for alkylidene formation with
respect to that of 2. Applying Fryzuk’s arguments (vide
supra) for our systems, the pendant arene group may
perform a similar function as the pendant phosphine
arms in those systems in the alkylidene formation.
Interaction of the arene moiety with the metal center
could facilitate R-H elimination and give a more nega-
tive entropy of activation due to the more ordered tran-
sition state. It may be noted that in Cp(O-PR2)Ti-
(CH2CMe3)2 systems (O-PR2 ) phosphino-alkoxide
ligand), the pendant phosphine is not coordinated to the
titanium center in the dineopentyl compound but does
coordinate in the neopentylidene complex Cp(O-PR2)-
Ti(dCHCMe3).41 Similarly, it may be possible that
multihapto (probably η2) coordination of the benzyl
ligands in the tribenzyl species 2 can help to induce R-H
elimination. The availability of three benzyl groups in
2 that can potentially facilitate alkylidene formation (in
addition to the pendant arene on the Cp ligand) could
then lead to a less strongly negative entropy of activa-
tion compared to that for the trialkyl 9. Another system
in which benzyl-assisted R-H elimination may occur is
in the transformation of Cp*W(NO)(CH2CMe3)(CH2R)
(R ) CMe3, Ph) in benzene-d6 to give neopentane and
Cp*W(NO)(CHDR)(C6D5) via rate-limiting alkylidene
formation and subsequent C-D addition of benzene-d6.
The first-order rate constant is higher for the mixed
benzyl/neopentyl species than for the sterically more
demanding dineopentyl species.39
F igu r e 3. Eyring plot of the thermolysis of 9 in C6D6 (with
error bars).
Ta ble 2. Ra te Con sta n ts of th e Th er m olysis of
(η5-C5H4CMe2P h )Ti(CH2SiMe3)3 (9) in C6D6
T (°C)
[9] (10-2 M)
k1 (10-5 s-1
)
72.5
65.0
57.5
50.0
2.6
2.7
2.5
2.6
6.0
3.2
1.4
0.7
signal by a secondary process can be observed, similar
to the decomposition pattern observed for the benzyl
derivative 2. The corresponding Eyring plot is shown
in Figure 3, from which the activation parameters ∆Hq
) 21 ( 2 kcal mol-1 and ∆Sq ) -18 ( 4 cal mol-1 K-1
are obtained for the primary process.
The general trend reported in the literature for the
relative rates of alkylidene formation from metal dialkyl
complexes follows the order neopentyl > neosilyl >
benzyl, which reflects faster rate-determining R-H
abstraction for complexes with alkyl ligands that pro-
vide greater steric congestion at the metal center. For
example, for the first-order decomposition of Ta(CH2R)5
(R ) Ph, SiMe3, CMe3), the rate constants follow the
order Ph (k ) 4.3 × 10-5 s-1, at 313 K)40 < SiMe3 (k )
3.5 × 10-4 s-1, 311 K)21c < CMe3 (too fast to monitor).21c
Our results indicate a deviation from this trend for the
complexes studied here. Whereas the neopentyl species
eliminates neopentane very rapidly, even at low tem-
peratures, comparison of the first-order rate constants
in Tables 1 and 2 for the other trialkyl species reveals
a slower rate of R-H abstraction (expressed in the rate
constant k1) of neosilyl 9 versus benzyl 2 over the
temperature range studied. Similar behavior has been
observed by Fryzuk and co-workers for the {η5-C5H3-
1,3-[SiMe2CH2P(i-Pr)2]2}Zr(CH2R)2Cl (R ) Ph, SiMe3,
CMe3) system, in which a reversal of the trend in rates
is observed (Ph > SiMe3 > CMe3).32b In these compounds
coordination of the two sterically demanding phosphine
groups, attached to sidearms on the Cp ligand, is
required in the transition state for alkylidene formation.
This becomes less favorable with increasing bulk of the
alkyl ligands and helps to explain the otherwise anoma-
lous observation that the more sterically demanding
alkyl ligands are thermally less reactive.
Con clu sion s
The cationic dibenzyl species [(η5:η6-C5H4CMe2Ph)Ti-
(CH2Ph)2]+ decomposes rapidly at ambient temperature
by metalation of the pendant arene group on the
cyclopentadienyl ligand, via a σ-bond metathesis path-
way. The observation that the cationic dimethyl species
[(η5:η6-C5H4CMe2Ph)TiMe2]+ is more stable toward cy-
clometalation than the dibenzyl analogue suggests that
initial displacement of the coordinated arene is required
for cyclometalation. In the [(η5:η6-C5H4CMe2Ph)Ti(CH2-
Ph)2]+ cation this is likely to be compensated for or
assisted by η2 bonding of the benzyl group(s), something
which is not possible for the analogous dimethyl cationic
species.
The neutral (η5-C5H4CMe2Ph)Ti(CH2R)3 (R ) Ph,
CMe3, SiMe3) complexes decompose via rate-determin-
ing R-H elimination to give alkylidene intermediates,
followed by rapid intramolecular addition of the o-CH
bond of the pendant arene group to the TidC bond of
the intermediate. The unusual order of reactivity (R )
While the enthalpies of activation, associated with the
rate-determining R-H abstraction step, are similar for
the benzyl and neosilyl complexes (24 kcal mol-1 for 2
and 21 kcal mol-1 for 9), a large difference in the entropy
(40) Malatesta, V.; Ingold, K. U.; Schrock, R. R. J . Organomet. Chem.
1978, 152, C53.
(41) Van Doorn, J . A.; Van der Heijden, H.; Orpen, A. G. Organo-
metallics 1994, 13, 4271.

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5573
149.4 (s, Ar Cipso), 149.2 (s, Bz Cipso), 147.3 (s, Cp Cipso), 137.7
CMe3 > Ph > SiMe3), combined with the significantly
negative entropy of activation for the R ) SiMe3 system,
suggest that here interaction of the aromatic moieties
(either the pendant arene group or the metal-bound
benzyl groups in the case of R ) Ph) with the metal
center can assist the R-H elimination process, possibly
through alleviating the electron deficiency of the incipi-
ent 12-electron CpTi-alkyl-alkylidene species.
1
(s, Ar m-Cipso), 128.8 (dm, J CH ) 156, Bz m-CH, overlap with
solvent), 128.3 (dm, 1J CH ) 131, Ar p-CH, overlap with solvent),
1
1
127.0 (dm, J CH ) 153, Bz o-CH), 124.5 (d, J CH ) 155, Ar
1
1
o-CH), 123.0 (d, J CH ) 160, Bz p-CH), 118.4 (dm, J CH ) 171,
1
1
Cp CH), 113.5 (dm, J CH ) 172, Cp CH), 93.5 (t, J CH ) 124,
1
Ti-CH2), 40.4 (s, C(CH3)2), 30.3 (q, J CH ) 122, C(CH3)2), 21.6
(q, 1J CH ) 126, ArCH3). Anal. Calcd for C37H40Ti: C, 83.44; H,
7.57; Ti, 8.99. Found: C, 82.54; H, 7.62; Ti, 8.76.
P r ep a r a tion of (η5-C5H4CMe2P h )Ti(CH2P h )3 (2). To a
stirred solution of 0.52 g of (η5-C5H4CMe2Ph)TiCl3 (1.54 mmol)
in 30 mL of diethyl ether, cooled to -40 °C, was added a
solution of benzylmagnesium bromide (4.62 mmol) in diethyl
ether (1.26 M) dropwise. The mixture was warmed to room
temperature and was stirred for 3 h. The solvent was removed
in vacuo, after which the red solid was extracted with pentane.
Cooling to -40 °C yielded red crystals of 2 (0.56 g, 1.11 mmol,
Exp er im en ta l Section
Gen er a l Com m en ts. All experiments were carried out
under a purified nitrogen atmosphere using standard Schlenk
and glovebox techniques. Deuterated solvents (Aldrich, Acros)
were either degassed and dried over 4 Å molecular sieves
(C6D5Br) or dried over Na/K alloy and vacuum-transferred
before use (C6D6, toluene-d8, THF-d8). Diethyl ether and
pentane (Aldrich) were distilled from Na/K alloy prior to use.
Methylene chloride (Aldrich) was dried on 4 Å molecular sieves
before use.
72%). 1H NMR (500 MHz, C6D6): δ 7.17-7.11 (m, 10H, Ph m-
3
and o-H and Bz m-H), 7.02 (m, 1H, Ph p-H), 6.90 (t, J HH
)
3
7.5, 3H, Bz p-H), 6.81 (d, J HH ) 7.5, 6H, Bz o-H), 5.74 (ps t,
3J HH ) 2.8, 2H, Cp H), 5.50 (ps t, J HH ) 2.8, 2H, Cp H), 2.97
3
The starting materials (η5-C5H4CMe2Ar)TiCl3,3 B(C6F5)3,42
(s, 6H, Ti-CH2), 1.38 (s, 6H, C(CH3)2). 13C NMR (125.7 MHz,
C6D6): δ 149.6 (s, Ph Cipso), 149.1 (s, Bz Cipso), 146.7 (s, Cp Cipso),
[Ph3C][B(C6F5)4],43 LiCH2CMe3,44 and LiCH2SiMe3 were pre-
45
pared according to published procedures. C5H4(SiMe3)CMe2C6D5
was prepared analogously to C5H4(SiMe3)CMe2Ph,3b and PhCH2-
MgBr was prepared from Mg and PhCH2Br (Aldrich, used as
received) in diethyl ether.
1
128.8 (dm, J CH ) 158, Bz m-CH, overlap with solvent), 128.5
1
(d, J CH ) 151, Ph m-CH, overlap with solvent), 127.0 (dm,
1J CH ) 161, Bz o-CH), 126.5 (dm, J CH ) 156, Ph o-CH), 126.4
1
1
1
(dm, J CH ) 156, Ph p-CH), 123.0 (dm, J CH ) 160, Bz p-CH),
NMR spectra were recorded on Varian Gemini 200/300 and
Unity 500 spectrometers in NMR tubes equipped with a Teflon
(Young) valve. The 1H NMR spectra were referenced to
resonances of residual protons in the deuterated solvents (δ
7.15 ppm for C6D6, δ 2.15 ppm for methyl resonance of toluene-
d8, δ 7.28 ppm for downfield signal of C6D5Br, δ 7.24 ppm for
CDCl3). The 13C NMR spectra were referenced to the carbon
resonances of the deuterated solvent (δ 128 ppm for C6D6, δ
137.5 ppm for Cipso for toluene-d8, δ 122.4 ppm for Cipso for
C6D5Br). Chemical shifts (δ) are given relative to tetra-
methylsilane (downfield shifts are positive); J values are given
in hertz. Elemental analyses were performed at the Micro-
analytical Department of the University of Groningen. Given
values are the average of at least two independent determina-
tions. For the compounds 1, 2, and 2-d 5 the found carbon
content is consistently and reproducibly too low, whereas the
values for Ti and H are in reasonable agreement. We have
observed this phenomenon previously for Ti compounds with
all-carbon ligation. It is likely to be associated with the
formation of inert Ti carbides upon combustion.
1
1
118.4 (dm, J CH ) 168, Cp CH), 113.5 (dm, J CH ) 172, Cp
1
CH), 93.5 (t, J CH ) 123, Ti-CH2), 40.5 (s, C(CH3)2), 30.2 (q,
1J CH ) 122, C(CH3)2). Anal. Calcd for C35H36Ti: C, 83.32; H,
7.19; Ti, 9.49. Found: C, 82.63; H, 7.32; Ti, 9.35.
Gen er a t ion
of [(η5:η-C5H 4CMe2-3,5-Me2C6H 3)Ti(η-
CH2P h )2][P h CH2B(C6F 5)3] (3a ). A solution of 37 mg (69
µmol) of (η5-C5H4CMe2-3,5-Me2C6H3)Ti(CH2Ph)3 (1) in 0.25 mL
of C6D5Br (-30 °C) was added to a solution of 36 mg (70 µmol)
of B(C6F5)3 in 0.25 mL of C6D5Br (-30 °C) to obtain a deep
red solution of the cationic complex 3a . 1H NMR (500 MHz,
C6D5Br, -30 °C): δ 7.18 (br, 2H, B-Bz m-H), 7.04 (br, 2H,
B-Bz o-H, partial overlap with solvent), 6.99 (s, 6H, Ti-Bz
m- and p-H), 6.62 (s, 1H, Ar p-H), 6.58 (s, 2H, Ar o-H), 6.46 (s,
2H, Cp H), 6.14 (s, 4H, Ti-Bz o-H), 4.84 (s, 2H, Cp H), 3.36
(br, 2H, B-CH2), 2.88 (s, 4H, Ti-CH2), 2.21 (s, 6H, ArCH3),
1.03 (s, 6H, C(CH3)2). 13C NMR (125.7 MHz, C6D5Br, -30 °C):
1
δ 148.8 (d, J CF ) 240, o-CF), 146.0 (s, Ar Cipso), 144.8 (s, Cp
C
ipso), 142.0 (s, Ar m-Cipso or Ti-Bz Cipso), 140.2 (s, Ar m-Cipso
1
or Ti-Bz Cipso), 138.0 (d, J CF ) 240, p-CF and s, B-Bz Cipso),
P r ep a r a tion of (η5-C5H4CMe2-3,5-Me2C6H3)Ti(CH2P h )3
(1). To a stirred solution of 0.48 g (1.31 mmol) of the
corresponding titanium trichloride in diethyl ether (-40 °C)
was added 3.94 mmol of PhCH2MgBr dropwise as a solution
in diethyl ether (1.26 M). The reaction mixture was warmed
to room temperature and was subsequently stirred for 3 h.
The volatiles were removed in vacuo, and the residue was
stirred with 10 mL of pentane, which was subsequently
pumped off. The red solid was extracted with pentane, and
concentration and cooling to -40 °C gave dark red crystals of
1
1
137.0 (d, J CF ) 240, m-CF), 136.8 (d, J CH ) 164, Ti-Bz
m-CH), 129.6-128.8 (Ti-Bz p-CH, Ar p-CH, B-Bz o-CH,
B-Bz p-CH, B-Bz m-CH, overlap with solvent), 127.0 (d, 1J CH
1
) 161, Ti-Bz o-CH), 123.1 (d, J CH ) 180, Cp CH), 123.0 (d,
1J CH ) 154, Ar o-CH), 119.7 (d, J CH ) 174, Cp CH), 101.5 (t,
1
1J CH ) 148, Ti-CH2), 40.3 (s, C(CH3)2), 32.4 (br, B-CH2), 28.7
(q, 1J CH ) 127, C(CH3)2), 22.1 (q, 1J CH ) 128, ArCH3). 19F NMR
(188.2 MHz, C6D5Br, -30 °C): δ -128.4 (o-F), -160.5 (p-F),
-163.5 (m-F).
Rea ction of 3a w ith THF -d 8. To a deep brown solution of
3a in C6D5Br, prepared as described above, was added a drop
of THF-d8, resulting in a red solution of [(η5-C5H4CMe2-3,5-
Me2C6H3)Ti(CH2Ph)2(THF-d8)x][PhCH2B(C6F5)3]. 1H NMR (500
MHz, C6D5Br/THF-d8, -30 °C): δ 7.25-6.5 (18H, aromatic
protons), 6.11 (s, 2H, Cp H), 5.90 (s, 2H, Cp H), 3.28 (br, 2H,
B-CH2), 3.19 (d, 2J HH ) 9.2, 2H, Ti-CH2), 2.19 (s, 6H, ArCH3),
2.18 (2H, Ti-CH2, overlapped by ArCH3), 1.32 (s, 6H, C(CH3)2).
13C NMR (125.7 MHz, C6D5Br/THF-d8, -30 °C): δ 151.1, 148.7,
146.1, 142.1, 138.3 (s, Ar, Cp, Ti-Bz, and B-Bz Cipso), 148.6
1
1 in 70% yield (0.49 g, 0.92 mmol). H NMR (500 MHz, C6D6):
3
δ 7.15 (t, J HH ) 7.5, 6H, Bz m-H), 6.95 (s, 2H, Ar o-H), 6.90
3
3
(t, J HH ) 7.5, 3H, Bz p-H), 6.82 (d, J HH ) 7.5, 6H, Bz o-H),
6.70 (s, 1H, Ar p-H), 5.80 (ps t, 3J HH ) 2.8, 2H, Cp H), 5.51 (ps
3
t, J HH ) 2.8, 2H, Cp H), 2.99 (s, 6H, Ti-CH2), 2.16 (s, 6H,
ArCH3), 1.45 (s, 6H, C(CH3)2). 13C NMR (125.7 MHz, C6D6): δ
(42) (a) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2,
245. Also see: (b) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1966,
5, 218. (c) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1991,
113, 3623. (d) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc.
1994, 116, 10015.
(43) Chien, J . C. W.; Tsai, W.-M.; Rausch, M. D. J . Am. Chem. Soc.
1991, 113, 8570.
(44) Schrock, R. R.; Fellman, J . D. J . Am. Chem. Soc. 1978, 100,
3359.
(45) Tessier-Youngs, C.; Beachley, O. T. Inorg. Synth. 1986, 24, 95.
1
1
(d, J CF ) 237, o-CF), 137.8 (d, J CF ) 246, p-CF), 136.8 (d,
1J CF ) 249, m-CF), 132-122 (aromatic CH, overlapped by
1
1
solvent), 121.2 (d, J CH ) 174, Cp CH), 117.4 (d, J CH ) 169,
1
Cp CH), 107.0 (t, J CH ) 129, Ti-CH2), 40.4 (s, C(CH3)2), 32.5
(br, B-CH2), 30.2 (q, 1J CH ) 126, C(CH3)2), 22.7 (q, 1J CH ) 127,
ArCH3).

5574 Organometallics, Vol. 21, No. 25, 2002
Deckers and Hessen
Gen er a t ion
of [(η5:η-C5H 4CMe2-3,5-Me2C6H 3)Ti(η-
1.18 (s, 6H, C(CH3)2). 19F NMR (188.2 MHz, C6D5Br, 25 °C):
δ -132.8 (s, 2F, o-F), -162.9 (t, 3J FF ) 21, 1F, p-F), -168.7 (s,
2F, m-F).
CH2P h )2][B(C6F 5)4] (3b). A solution of 25 mg (47 µmol) of 1
in 0.25 mL of C6D5Br (-30 °C) was added to a solution of 43
mg (48 µmol) of B(C6F5)3 in 0.25 mL of C6D5Br (-30 °C) to
obtain a deep brown solution containing the cationic complex
In Situ P r ep a r a tion of (η5:η1-C5H4CMe2-3,5-Me2C6H2)-
Ti(CH2P h )2 (6). A solution of 1 in C6D6 (4.5 × 10-2 M) was
kept at 50 °C for 50 h. Upon thermolysis the color of the
solution changed from red to dark red. NMR spectroscopy
1
3b and Ph3CCH2Ph. H NMR (500 MHz, C6D5Br, -30 °C): δ
7.2-6.1 (33H, aromatic protons, ill-resolved), 6.33 (s, 2H, Cp
H), 4.85 (s, 2H, Cp H), 3.78 (s, 2H, Ph3CCH2Ph), 2.90 (s, 4H,
Ti-CH2), 2.21 (s, 6H, ArCH3), 1.04 (s, 6H, C(CH3)2). 13C NMR
1
indicates the formation of toluene and compound 6. H NMR
3
(500 MHz, C6D6): δ 7.12 (t, J HH ) 7.5, 4H, Bz m-H), 6.83 (t,
1
(125.7 MHz, C6D5Br, -30 °C): δ 148.6 (d, J CF ) 240, o-CF),
146.7, 146.0, 144.5, 144.0, 143.0, 141.7, 139.9, 138.4, 136.5 (s,
3
3J HH ) 7.5, 2H, Bz p-H), 6.69 (s, 1H, Ar p-H), 6.65 (d, J HH
)
3
7.5, 4H, Bz o-H), 6.58 (s, 1H, Ar o-H), 5.84 (ps t, J HH ) 2.5,
1
Ar, Cp, Ti-Bz, B-Bz, and Ph3CCH2Ph Cipso), 138.5 (d, J CF
)
3
2H, Cp H), 5.71 (ps t, J HH ) 2.5, 2H, Cp H), 3.27 (s, 3H,
1
235, p-CF), 136.6 (d, J CF ) 241, m-CF), 132-122 (aromatic
ArCH3, adjacent to Ti-Cipso), 3.14 (d, 2J HH ) 9.5, 2H, Ti-CH2),
1
CH and Cp CH, overlapped by solvent), 119.4 (d, J CH ) 169,
2
3.03 (d, J HH ) 9.5, 2H, Ti-CH2), 2.10 (s, 3H, ArCH3, overlap
1
Cp CH), 101.2 (t, J CH ) 147, Ti-CH2), 58.6 (s, Ph3CCH2Ph),
with toluene), 1.37 (s, 6H, C(CH3)2). 13C NMR (125.7 MHz,
C6D6): δ 201.7 (Ar o-Cipso), 171.8 (Cp Cipso), 148.4 (Bz Cipso),
148.0 (Ar Cipso), 139.4 (Ar m-Cipso, adjacent to Ti-Cipso), 137.3
(Ar m-Cipso), 128.6 (Bz m-CH), 127.6 (Ar p-CH), 125.3 (Bz
o-CH), 122.5 (Bz p-CH), 121.7 (Ar o-CH), 119.5 (Cp CH), 116.7
(Cp CH), 94.1 (1J CH ) 122, Ti-CH2), 43.3 (C(CH3)2), 29.8
(C(CH3)2), 26.1 (ArCH3), 21.8 (ArCH3, adjacent to Ti-Cipso).
1
45.9 (t, J CH ) 128, Ph3CCH2Ph), 40.1 (s, C(CH3)2), 28.4 (q,
1J CH ) 126, C(CH3)2), 21.8 (q, J CH ) 128, ArCH3).
1
P r ep a r a tion of [(η5:η1-C5H4CMe2C6H4)Ti(CH2P h )][η6-
P h CH2B(C6F 5)3] (4). At -40 °C, a solution of (η5-C5H4CMe2-
Ph)Ti(CH2Ph)3 (2; 430 mg, 0.85 mmol) in 20 mL of pentane
was added to a solution of 440 mg (0.86 mmol) of B(C6F5)3 in
20 mL of pentane. A green precipitate was instantaneously
formed. The supernatant was decanted. The green residue was
brought on a glass frit and was thoroughly rinsed with pentane
to yield 520 mg (0.56 mmol, 66%) of analytically pure 4 (for
labels, see Scheme 2). 1H NMR (500 MHz, toluene-d8, -30
In Situ P r epar ation of (η5:η1-C5H4CMe2C6H4)Ti(CH2P h )2
(7). A solution of 2 in C6D6 (5 × 10-2 M) was kept at 50 °C for
50 h. Upon thermolysis the color of the solution changed from
red to dark red. NMR spectroscopy indicates the formation of
toluene and compound 7. 1H NMR (500 MHz, C6D6): δ 8.00
(d, 3J HH ) 7.5, 1H, Ph m-H, adjacent to Ti-Cipso), 7.12 (t, 3J HH
) 7.5, 4H, Bz m-H), 7.02 (m, Ph m-H, overlap with toluene),
3
°C): δ 6.88 (t, J HH ) 7.7, 2H, Ti-Bz m-H), 6.73 (m, 3H, Ti-
Bz p-H and H6,8), 6.65 (t, 3J HH ) 7.5, 1H, H7), 6.46 (d, 3J HH
)
8.1, 1H, H5), 6.44 (d, 3J HH ) 8.1, 1H, B-Bz o-H), 6.28 (d, 3J HH
3
3
3
6.94 (t, J HH ) 6.8, 1H, Ph p-H), 6.86 (t, J HH ) 7.5, 2H, Bz
) 7.7, 1H, B-Bz o-H′), 6.20 (t, J HH ) 7.3, 1H, B-Bz m-H),
p-H), 6.77 (d, 3J HH ) 7.5, 1H, Ph o-H), 6.71 (d, 3J HH ) 7.5, 4H,
Bz o-H), 5.84 (ps t, J HH ) 2.8, 2H, Cp H), 5.74 (ps t, J HH
2.8, 2H, Cp H), 3.11 (d, J HH ) 10, 2H, Ti-CH2), 2.77 (d, J HH
) 10, 2H, Ti-CH2), 1.32 (s, 6H, C(CH3)2). 13C NMR (125.7
MHz, C6D6): δ 200.6 (Ph o-Cipso), 170.3 (Cp Cipso), 148.8 (Ph
3
5.91 (d, J HH ) 7.3, 2H, Ti-Bz o-H), 5.88 (s, 1H, 1), 5.86 (t,
3
3
3
)
1H, H11, partial overlap), 5.84 (s, 1H, H4), 5.62 (t, J HH ) 7,
2
2
B-Bz m-H′), 5.11 (s, 1H, H3), 4.82 (s, 1H, H2), 3.39 (br, 1H,
2
H13), 2.80 (d, J HH ) 10, 1H, H9), 2.8 (br, 1H, H12, overlap
2
with H9), 1.15 (s, 3H, C(CH3)2), 0.81 (d, J HH ) 10, 1H, H10),
0.73 (s, 3H, C(CH3)2). 13C NMR (125.7 MHz, toluene-d8, -30
°C): δ 199.7 (Ph o-Cipso), 170.9 (Cp Cipso), 160.5, 157.3, 150.4
Cipso), 146.6 (Bz Cipso), 129.7 (Ph m-CH′, adjacent to Ti-Cipso),
129.7 (Ph m-CH), 128.8 (Bz m-CH), 127.2 (Bz o-CH), 123.8 (Ph
p-CH), 123.7 (Ph o-CH), 122.9 (Bz p-CH), 119.3 (Cp CH), 114.5
(Cp CH), 90.5 (1J CH ) 125, Ti-CH2), 43.9 (C(CH3)2), 29.3
(C(CH3)2).
1
(Ph, Ti-Bz, B-Bz Cipso), 148.5 (d, J CF ) 238, o-CF), 139.0 (d,
1J CF ) 238, p-CF), 137.4 (d, J CF ) 238, m-CF), 134.7 (B-Bz
1
m-CH), 132.0 (C6 or C8), 131.2 (B-Bz o-CH), 130.9 (B-Bz
m-CH′), 128.5 (Ti-Bz p-CH, overlap with solvent), 127.7 (Ti-
Bz m-CH, overlap with solvent), 126.5 (Ti-Bz o-CH), 125.5-
124.5 (B-Bz o-CH′, C1, C5, C11, overlap with solvent), 124.0
(C6 or C8), 123.9 (C4), 122.6 (C7), 116.1 (C3), 111.2 (C2), 93.3
P r ep a r a tion of C5H4(SiMe3)CMe2C6D5. To a solution of
3.20 g (19.8 mmol) of bromobenzene-d5 in 50 mL of diethyl
ether was added 7.8 mL of a 2.5 M solution (19.7 mmol) of
n-BuLi in hexanes. The mixture was stirred for 3 h. The
mixture was cooled to -30 °C, and 2.4 mL (2.1 g, 19.8 mmol)
of 6,6-dimethylfulvene was added. The yellowish suspension
was warmed to room temperature and was stirred for an
additional 3 h. The reaction mixture was cooled with an ice
bath, and 1.2 equiv of trimethylsilyl chloride was added. The
ice bath was removed, and the yellow-white suspension was
stirred overnight. The reaction mixture was poured into 100
mL of ice-water. The organic and water layers were separated,
and the water layer was extracted twice with 50 mL of light
petroleum. The combined organic layers were dried over
magnesium sulfate, and the low-boiling volatiles were removed
using a rotary evaporator. The residue was distilled using a
Kugelrohr apparatus. The product distilled at 130 °C at 0.4
Torr. Yield: 3.30 g (12.5 mmol, 64%). 1H NMR (300 MHz,
CDCl3): δ 6.35, 6.28, 6.13 (br, 1H, Cp H), 3.22 (s, 1H, Cp H),
1.53 (s, 6H, C(CH3)2), -0.06 (s, 9H, Si(CH3)3).
1
(Ti-CH2, J CH ) 126), 43.6 (C(CH3)2), 35.3 (br, B-CH2), 29.7,
28.9 (C(CH3)2). 19F NMR (188.2 MHz, C6D6): δ -132.8 (d, 3J FF
3
) 22.8, 2F, o-F), -162.3 (t, J FF ) 21.6, 1F, p-F), -166.5 (m,
2F, m-F). Anal. Calcd for C46H28TiBF15: C, 59.77; H, 3.05; Ti,
5.18. Found: C, 59.61; H, 3.11; Ti, 5.08.
Gen er a t ion of [(η5:η1-C5H 4CMe2C6H 4)Ti(η2-CH 2P h )]-
[B(C6F 5)4] (5). A solution of 10.2 mg (20 µmol) of 5 in 0.6 mL
of bromobenzene-d5 was added to 18.5 mg (20 µmol) of [Ph3C]-
[B(C6F5)4] in an NMR tube equipped with a Teflon (Young)
valve. This resulted in a brown solution containing Ph3-
CCH2Ph, toluene, and the thermally labile species 5. 1H NMR
(500 MHz, C6D5Br, -30 °C): δ 7.8-6.6 (34H, aromatic protons,
ill-resolved), 5.91 (br, W1/2 ) 33, 1H, Cp H), 5.52 (br, W1/2
33, 1H, Cp H), 5.38 (br, W1/2 ) 33, 1H, Cp H), 4.79 (br, W1/2
)
)
33, 1H, Cp H), 3.88 (br, W1/2 ) 37, 1H, Ti-CH2), 3.77 (s, 2H,
Ph3CCH2Ph), 2.16 (s, 4H, C6H5CH3 and Ti-CH2), 1.24 (br, 3H,
C(CH3)2), 1.07 (br, 3H, C(CH3)2). 13C NMR (125.7 MHz, C6D5Br,
-30 °C): δ 215.8 (s, Ph o-Cipso), 169.9, 158.2, 146.7, 142.2, 138.4
P r ep a r a tion of (η5-C5H4CMe2C6D5)TiCl3. The same pro-
cedure was followed as described for the preparation of the
non-isotope-labeled analogue,3b using C5H4(SiMe3)CMe2C6D5
(3.20 g, 12.1 mmol) and TiCl4 (1.3 mL, 2.3 g, 12 mmol). Yield:
1
(s, Cp and aromatic Cipso), 148.6 (d, J CF ) 239, o-CF), 138.6
(d, 1J CF ) 232, p-CF), 136.7 (d, 1J CF ) 248, m-CF), 133.5-120.5
(aromatic CH, overlapped by solvent), 119.9, 118.6, 117.1,
1
1
2.67 g (7.8 mmol, 65%). H NMR (300 MHz, C6D6): δ 6.27 (ps
115.5 (br, Cp CH), 88.0 (t, J CH ) 154, Ti-CH2), 58.6 (s,
3
3
1
t, J HH ) 2.8, 2H, Cp H), 5.99 (ps t, J HH ) 2.8, 2H, Cp H),
1.53 (C(CH3)2). 13C NMR (75.4 MHz, C6D6): δ 154.2 (Cp Cipso),
123.3, 121.7 (Cp CH), 40.8 (C(CH3)2), 28.7 (C(CH3)2). Anal.
Calcd for C14H10D5Cl3Ti: C, 49.09; H + D, 5.88; Ti, 13.98.
Found: C, 49.13; H + D, 5.91; Ti, 13.87.46
Ph3CCH2Ph), 45.9 (t, J CH ) 128, Ph3CCH2Ph), 44.7 (s,
C(CH3)2), 28.2, 27.9 (br, C(CH3)2). 1H NMR (500 MHz, C6D5Br,
25 °C): δ 7.8-6.6 (36H, aromatic protons and Cp H, ill-
resolved), 5.43 (br, W1/2 ) 56, 2H, Cp H), 3.82 (s, 2H, Ph3CCH2-
Ph), 3.76 (br, W1/2 ) 160, 2H, Ti-CH2), 2.16 (s, 3H, C6H5CH3),

Cationic and Neutral Ti Benzyl Compounds
Organometallics, Vol. 21, No. 25, 2002 5575
P r ep a r a t ion of (η5-C5H 4CMe2C6D5)Ti(CH2P h )3 (2-d 5).
The same procedure was followed as described for the prepa-
ration of 2, using (η5-C5H4CMe2C6D5)TiCl3 (1.11 g, 3.2 mmol)
to afford the title compound in 75% yield (1.23 g, 2.4 mmol).
1H NMR (300 MHz, C6D6): δ 7.15 (t, 3J HH ) 7.7, 6H, Bz m-H),
34.1 (C(CH3)3), 33.9 (C(CH3)3), 31.6 (C(CH3)2), 29.8 (C(CH3)4),
29.5 (C(CH3)4).
P r ep a r a tion of (η5-C5H4CMe2P h )Ti(CH2SiMe3)3 (9). To
a solution of 1.03 g (3.05 mmol) of (η5-C5H4CMe2Ph)TiCl3 in
70 mL of diethyl ether cooled to -70 °C was added 9.2 mmol
of ClMgCH2SiMe3 dropwise as a 1.62 M solution in diethyl
ether. The reaction mixture was warmed to room temperature
and was stirred for 3 h. The volatiles were removed in vacuo,
and the residue was extracted with pentane. The pentane was
pumped off to afford 0.93 g (1.88 mmol, 62%) of the title
compound as a brown oil. The purity of 9 is >95%, as seen by
1H NMR. 1H NMR (300 MHz, C6D6): δ 7.2-6.9 (m, 5H, Ph
H), 6.05 (m, 2H, Cp H), 6.01 (m, 2H, Cp H), 1.73 (s, 6H, Ti-
CH2), 1.46 (s, 6H, C(CH3)2), 0.14 (s, 27H, Si(CH3)3). 13C NMR
(75.4 MHz, C6D6): δ 149.8, 144.4 (Ph and Cp Cipso), 128.4,
126.5, 126.3 (Ph CH), 111.9, 109.87 (Cp CH), 85.8 (Ti-CH2),
40.1 (C(CH3)2), 30.2 (C(CH3)2), 2.3 (Si(CH3)3).
3
3
6.91 (t, J HH ) 7.3, 3H, Bz p-H), 6.82 (d, J HH ) 7.3, 6H, Bz
3
3
o-H), 5.75 (ps t, J HH ) 2.7, 2H, Cp H), 5.50 (ps t, J HH ) 2.7,
2H, Cp H), 2.97 (s, 6H, Ti-CH2), 1.38 (s, 6H, C(CH3)2). 13C
NMR (75.4 MHz, C6D6): δ 149.1 (Bz Cipso), 146.7 (Cp Cipso),
128.8, 127.0, 123.0 (Bz CH), 118.4, 113.4 (Cp CH), 93.5
(Ti-CH2), 40.4 (C(CH3)2), 30.1 (C(CH3)2). Anal. Calcd for
C
35H31D5Ti: C, 82.49; H + D, 8.11. Found: C, 82.00; H + D,
8.12.46
In Situ P r epar ation of [η5,η1-C5H4CMe2C6D4]Ti(CH2P h )-
(CHDP h ) (7-d 4/1). A solution of 26.5 mg (52 µmol) of 2-d 5 in
0.6 mL of benzene in an NMR tube with a Teflon valve was
warmed to 50 °C for 50 h. The color of the solution changed
from red to dark red. 1H NMR (300 MHz, C6D6): δ 7.12 (t,
3J HH ) 7.7, 4H, Bz m-H), 6.86 (t, 3J HH ) 7.3, 2H, Bz p-H), 6.71
In Situ P r ep a r a tion of (η5:η1-C5H4CMe2C6H4)Ti-
(CH2SiMe3)2 (10). An NMR tube with a solution of 9 in C6D6
(6 × 10-2 M) was heated to 50 °C for 70 h. NMR spectroscopy
reveals the formation of tetramethylsilane and 10. 1H NMR
(300 MHz, C6D6): δ 8.26 (d, 3J HH ) 7.0, 1H, Ph m-H, adjacent
3
3
(d, J HH ) 7.3, 4H, Bz o-H), 5.85 (ps t, J HH ) 2.6, 2H, Cp H),
3
2
5.74 (ps t, J HH ) 2.6, 2H, Cp H), 3.11 (d, J HH ) 9.9, 1H, Ti-
2
CH2), 3.05 (s, 0.5H, Ti-CDHanti), 2.75 (d, J HH ) 9.9, 1H, Ti-
CH2), 2.71 (s, 0.5H, Ti-CDHsyn), 1.32 (s, 6H, C(CH3)2). 13C
NMR (75.4 MHz, C6D6): δ 200.6 (Ph o-Cipso), 170.2, 148.9 (Cp
and Ph Cipso), 146.6, 146.5 (Bz Cipso), 128.8 (Bz m-CH), 127.2
(Bz o-CH), 122.9 (Bz p-CH), 119.3, 114.5 (Cp CH), 90.6, 90.5
3
to Ti-Cipso), 7.05-6.9 (m, 2H, Ph m-H and p-H), 6.81 (d, J HH
) 7.7, 1H, Ph o-H), 6.43 (m, 2H, Cp H), 6.18 (m, 2H, Cp H),
2
2
2.27 (d, J HH ) 11.0, 2H, Ti-CH2), 2.05 (d, J HH ) 10.6, 2H,
Ti-CH2), 1.47 (s, 6H, C(CH3)2), 0.01 (s, 18H, Si(CH3)3), -0.01
(s, 12H, Si(CH3)4). 13C NMR (75.4 MHz, C6D6): δ 198.6 (Ph
o-Cipso), 170.5, 147.1 (Ph and Cp Cipso), 131.4, 129.2, 124.0, 123.7
(Ph CH), 117.1, 109.9 (Cp CH), 88.0 (Ti-CH2), 43.6 (C(CH3)2),
29.6 (C(CH3)2), 2.5 (Si(CH3)3), 0.0 (Si(CH3)4).
1
(Ti-CH2), 89.6 (t, J CD ) 19, Ti-CDH), 43.9 (C(CH3)2), 29.3
(C(CH3)2).
Gen er a t ion of [(η5,η1-C5H 4CMe2C6D4)Ti(CH 2P h )][η6-
P h CH2B(C6F 5)3] (4-d 4). A solution of 16.5 (32 µmol) of 2-d 5
in 0.6 mL of benzene-d6 was added to 16.7 mg (33 µmol) of
B(C6F5)3. The solution was transferred to an NMR tube
equipped with a Teflon (Young) valve and investigated by
NMR spectroscopy at 6 °C. 1H NMR (500 MHz, C6D6, 6 °C): δ
In Sit u P r ep a r a t ion of (η5:η1-C5H 4CMe2C6D4)Ti-
(CH2CMe3)(CHDCMe3) (8-d 4/1). A solution of 15.5 mg (46
µmol) of (η5-C5H4CMe2C6D5)TiCl3 in 0.5 mL of benzene-d6 was
added to 10.8 mg (138 µmol) of neopentyllithium to form the
title compound, 1 equiv of neopentane, and 3 equiv of lithium
chloride. To remove the LiCl, the benzene solution was filtered
over a small piece of paper (predried at 75 °C) wedged in a
Pasteur pipet. 1H NMR (500 MHz, C6D6): δ 6.56 (s, 2H, Cp
H), 6.22 (s, 2H, Cp H), 2.73 (d, 2J HH ) 10.3, 1H, Ti-CH2), 2.65
(s, 0.15H, Ti-CDHanti), 2.26 (d, 2J HH ) 10.3, 1H, Ti-CH2), 2.18
(s, 0.85H, Ti-CDHsyn), 1.50 (s, 6H, C(CH3)2), 0.94 (s, 18H,
C(CH3)3), 0.90 (s, 12H, C(CH3)4). 13C NMR (125.7 MHz, C6D6):
δ 195.4 (Ph o-Cipso), 170.4, 145.7 (Ph and Cp Cipso), 117.0, 109.0
(Cp CH), 113.2, 113.0, 112.8 (Ti-CH2), 111.8 (t, 1J CD ) 17, Ti-
3
3
6.90 (t, J HH ) 7.7, 2H, Ti-Bz m-H), 6.73 (t, J HH ) 7.3, 1H,
3
3
Ti-Bz p-H), 6.51 (d, J HH ) 7.7, 1H, B-Bz o-H), 6.33 (d, J HH
3
) 7.7, 1H, B-Bz o-H′), 6.23 (t, J HH ) 7.3, 1H, B-Bz m-H),
3
3
6.06 (t, J HH ) 7.1, 1H, B-Bz m-H′), 5.95 (d, J HH ) 7.3, 2H,
Ti-Bz o-H), 5.89 (br, 1H, Cp H), 5.86 (br, 2H, B-Bz p-H and
3
Cp H), 5.13 (d, J HH ) 2.2, 1H, Cp H), 4.83 (m, 1H, Cp H),
2
3.28 (br, 1H, B-CH2), 2.93 (br, 1H, B-CH2), 2.83 (d, J HH
)
9.9, 1H, Ti-CH2), 2.08 (t, 2J HD ) 2.2, 2H, C6H5CH2D), 1.15 (s,
2
3H, C(CH3)2), 0.93 (d, J HH ) 9.9, 1H, Ti-CH2), 0.76 (s, 3H,
C(CH3)2). 13C NMR (125.7 MHz, C6D6, 6 °C): δ 200.0 (Ph
o-Cipso), 171.0, 160.6, 157.8, 150.4 (Cp, Ph, Ti-Bz, and B-Bz
1
CDH), 111.6 (t, J CD ) 17, Ti-CDH), 38.6 (C(CH3)2), 34.1
1
1
C
ipso), 148.5 (d, J CF ) 235, o-CF), 138.9 (d, J CF ) 250, p-CF),
1
(C(CH3)3), 33.9 (C(CH3)3), 31.6 (C(CH3)2), 29.8 (C(CH3)4), 29.5
(C(CH3)4).
137.4 (d, J CF ) 239, m-CF), 133.9 (B-Bz m-CH), 131.2 (B-
Bz o-CH), 130.8 (B-Bz m-CH′), 128.3 (Ti-Bz m-CH), 127.9
(Ti-Bz p-CH, overlap with solvent), 126.5 (Ti-Bz o-CH), 124.7,
124.1 (B-Bz o-CH′, B-Bz p-CH), 124.5, 124.1, 115.9, 111.4
(Cp CH), 94.2 (Ti-CH2), 43.6 (C(CH3)2), 35.6 (br, B-CH2), 29.6,
Kin etic Exp er im en ts. In a typical experiment, the com-
pound of interest (0.0188 mmol) was dissolved in 0.7 mL of
benzene-d6 (2.6 × 10-2 M) at ambient temperature, together
with ferrocene (1.0 mg) used as internal standard. The solution
was transferred to an NMR tube with a Teflon valve, which
was then directly inserted into the (preheated) probe of the
NMR spectrometer. The sample was given 20 min to equili-
brate to the specified temperature. 1H NMR spectra were
recorded at regular intervals (1 h). The progress of thermolysis
1
28.9 (C(CH3)2), 21.2 (t, J CD ) 19, C6H5CH2D).
In Situ P r epar ation of (η5-C5H4CMe2C6H4)Ti(CH2CMe3)2
(8). A solution of 20.7 mg (61.3 µmol) of (η5-C5H4CMe2Ph)TiCl3
in 0.5 mL of benzene-d6 was added to 14.4 mg (184 µmol) of
neopentyllithium to form the title compound, 1 equiv of
neopentane, and 3 equiv of lithium chloride. To remove the
LiCl, the benzene solution was filtered over a small piece of
paper (predried at 75 °C) wedged in a Pasteur pipet. 1H NMR
(300 MHz, C6D6): δ 8.38 (d, 3J HH ) 7.1, 1H, Ph m-H, adjacent
to Ti-Cipso), 7.01-6.82 (m, 3H, Ph o-, m-, p-H), 6.56 (ps t, 3J HH
1
was monitored by integration of the Cp resonances in the H
NMR spectrum relative to the internal ferrocene standard. The
rate constants were calculated via nonlinear-least-squares
analysis of the plot of ln([A]/[A0]) versus time using Microcal
Origin 5.0 software (version 5.0; Microcal Software, Inc., 1991-
1997). The maximum relative error found (2.1%) was used as
the standard error for all determined k1 rate constants. The
temperature of the NMR probe was measured using a metha-
nol temperature standard. At an NMR probe setting of 65 °C
(for different experiments), the temperature was found to
fluctuate between 65 ( 1 °C. The established error in the
temperature of 1 K at this temperature was used for the whole
temperature range.
3
) 2.6, 2H, Cp H), 6.22 (ps t, J HH ) 2.6, 2H, Cp H), 2.72 (d,
2
2J HH ) 10.6, 2H, Ti-CH2), 2.26 (d, J HH ) 10.3, 2H, Ti-CH2),
1.50 (s, 6H, C(CH3)2), 0.94 (s, 18H, C(CH3)3), 0.90 (s, 12H,
C(CH3)4). 13C NMR (75.4 MHz, C6D6): δ 195.5 (Ph o-Cipso),
170.5, 145.7 (Ph and Cp Cipso), 132.4, 128.8, 124.1, 123.5 (Ph
CH), 117.0, 109.0 (Cp CH), 112.8 (Ti-CH2), 38.6 (C(CH3)2),
(46) Since the detection method used in the elemental analysis
cannot distinguish between D2O and H2O, the sample H + D content
was calculated by multiplying the experimentally found H + D content
with (2n + m)/(n + m) for a sample containing n D and m H atoms.
OM0206554