A versatile synthetic route for cyclopentadienyl-amido titanium(IV) compounds. NMR spectroscopy study and X-ray molecular structure of [Ti{η5-C5H4SiMe2 NMe(CH2)2-η-NMe}Cl2]

Article abstract of DOI:10.1021/om000950t

The reaction of the chlorosilyl-substituted cyclopentadienyltitanium compound [Ti(η⁵-C₅H₄-SiMe₂Cl) Cl₃] with N,N′-dimethylethylenediamine in the presence of 2 equiv of NEt₃ gave a mixture of two complexes, [Ti{η⁵-C₅H₄SiMe₂ NMe(CH₂)₂-η-NMe}Cl₂] (1) and [Ti{η⁵-C₅H₄SiMe₂-η-N(CH ₂)₂-η-NHMe}Cl₂] (2), in a molar ratio of 3:1. However, a similar reaction with N-methylethylenediamine afforded complex 2 regiospecifically. The dialkyl derivatives [Ti-{η⁵-C₅H₄SiMe₂ NMe(CH₂)₂-η-NMe}R₂] (R = Me (3), CH₂Ph (4)) were prepared by reacting the dichloride complex 1 with 2 equiv of MgClMe or 1 equiv of Mg(CH₂Ph)₂·2THF, respectively. The analogous reaction with LiNMe₂ afforded the diamido derivative [Ti{η⁵-C₅H₄SiMe₂ NMe(CH₂)₂-η-NMe}(NMe₂)₂] (5) in high yield. Complex 1 reacts with dry CO₂ via insertion of a molecule of CO₂ into each of the Ti-N and Si-N bonds to yield the dicarbamate compound [Ti{(η⁵-C₅H₄SiMe₂OC(O) NMe(CH₂)₂NMe (η²-CO₂)} Cl₂] (6), in which the carbamate groups are bound in η²- and η¹-fashion. Thermal decomposition of complex 6 afforded the known oxo derivatives [Ti{μ-(η⁵-C₅H₄SiMe₂-η-O)} Cl₂]₂ and [(TiCl₂)₂(μ-O)-[μ-{(η⁵-C₅ H₄SiMe₂)₂-(μ-O)}] with elimination of CO₂ and 1,3-dimethyl-2-imidazolidinone. The conformational interconversion of 1 and 6 and the reversible coordination of the terminal NHMe group to the metal center in 2 were studied in solution by DNMR spectroscopy. The crystal structure of 1 was determined by X-ray diffraction methods.

Full text of DOI:10.1021/om000950t

Organometallics 2001, 20, 2459-2467
2459
A Ver sa tile Syn th etic Rou te for
Cyclop en ta d ien yl-Am id o Tita n iu m (IV) Com p ou n d s.
NMR Sp ectr oscop y Stu d y a n d X-r a y Molecu la r Str u ctu r e
of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}Cl2]
Gerardo J ime´nez, Esteban Rodr´ıguez, Pilar Go´mez-Sal, Pascual Royo,* and
Toma´s Cuenca*
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´, Campus Universitario,
28871 Alcala´ de Henares, Spain
Mikhail Galakhov
NMR Spectroscopy Center, Universidad de Alcala´, Campus Universitario,
28871 Alcala´ de Henares, Spain
Received November 8, 2000
The reaction of the chlorosilyl-substituted cyclopentadienyltitanium compound [Ti(η5-C5H4-
SiMe2Cl)Cl3] with N,N′-dimethylethylenediamine in the presence of 2 equiv of NEt3 gave a
mixture of two complexes, [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}Cl2] (1) and [Ti{η5-C5H4SiMe2-
η-N(CH2)2-η-NHMe}Cl2] (2), in a molar ratio of 3:1. However, a similar reaction with
N-methylethylenediamine afforded complex 2 regiospecifically. The dialkyl derivatives [Ti-
{η5-C5H4SiMe2NMe(CH2)2-η-NMe}R2] (R ) Me (3), CH2Ph (4)) were prepared by reacting
the dichloride complex 1 with 2 equiv of MgClMe or 1 equiv of Mg(CH2Ph)2·2THF,
respectively. The analogous reaction with LiNMe2 afforded the diamido derivative [Ti{η5-
C5H4SiMe2NMe(CH2)2-η-NMe}(NMe2)2] (5) in high yield. Complex 1 reacts with dry CO2 via
insertion of a molecule of CO2 into each of the Ti-N and Si-N bonds to yield the dicarbamate
compound [Ti{(η5-C5H4SiMe2OC(O)NMe(CH2)2NMe(η2-CO2)}Cl2] (6), in which the carbamate
groups are bound in η2- and η1-fashion. Thermal decomposition of complex 6 afforded the
known oxo derivatives [Ti{µ-(η5-C5H4SiMe2-η-O)}Cl2]2 and [(TiCl2)2(µ-O)-[µ-{(η5-C5H4SiMe2)2-
(µ-O)}] with elimination of CO2 and 1,3-dimethyl-2-imidazolidinone. The conformational
interconversion of 1 and 6 and the reversible coordination of the terminal “NHMe” group to
the metal center in 2 were studied in solution by DNMR spectroscopy. The crystal structure
of 1 was determined by X-ray diffraction methods.
In tr od u ction
the activity to be optimized but also stereochemical
control over polymer composition and structure. Over
the last few years, ligand design has played a key role
in developing new homogeneous Ziegler-Natta cata-
lysts,3 with increasing interest in industrial and aca-
demic laboratories, and new ligand systems for both
early4 and late5 transition metals.
Early-transition-metal complexes have provided im-
portant classes of catalysts for R-olefin polymerization1
and related processes.2 The most extensively investi-
gated compounds are those based on group 4 bent
metallocenes (MCp2X2), which upon activation with
suitable coactivators, typically methylaluminoxane
(MAO), offer highly active catalysts for olefin polymer-
ization. Modification of the ligand environment at the
metal centers (i.e., by linking cyclopentadienyl ligands
with an intraannular bridge or by introducing sterically
bulky substituents onto the Cp rings) allowed not only
(3) For reviews see: (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D.
F. Angew. Chem., Int. Ed. 1999, 38, 428. (b) Kempe, R. Angew. Chem.,
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Deeth, R. J .; Duncalf, D. J .; McCamley, A. J . Chem. Soc., Chem.
Commun. 1996, 2623. (e) J ime´nez, G.; Thorton-Pett, M.; Bochmann,
M. J . Chem. Soc., Dalton Trans. 1998, 393. (f) J ime´nez, G.; Simon, J .
L.; Thorton-Pett, M.; Bochmann, M. J . Am. Chem. Soc. 1998, 120, 6816.
(g) J ime´nez, G.; Thorton-Pett, M.; Bochmann, M. J . Chem. Soc., Dalton
Trans. 1997, 3115. (h) Lee, R. A.; Lachicotte, R. J .; Bazan, G. C. J .
Am. Chem. Soc. 1998, 120, 6037. (i) Yoshida, M.; J ordan, R. F.
Organometallics 1997, 16, 4508. (j) Feng, S.; Klosin, J .; Kruper, W. J .;
McAdon, M. H.; Neithamer, D. R.; Nickias, P. N.; Patton, J . T.; Wilson,
D. R.; Abboud, K. A.; Stern, C. L. Organometallics 1999, 18, 1159. (k)
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1996, 939. (l) Ashe, A. J .; Fang, X.; Kampf, J . W. Organometallics 1999,
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* To whom correspondence should be addressed. Phone:
34918854765 (P.R.), 34918854655 (T.C.). Fax: 34 918854683. E-mail:
pascual.royo@uah.es (P.R.), tomas.cuenca@uah.es (T.C.).
(1) For recent reviews see: (a) Brintzinger, H. H.; Fischer, D.;
Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed.
Engl. 1995, 34, 1143. (b) Bochmann, M. J . Chem. Soc., Dalton Trans.
1996, 255. (c) Hlatky, G. G. Coord. Chem. Rev. 1999, 181, 243. (d)
J ordan, R. F. Adv. Organomet. Chem. 1991, 32, 325. (e) Marks, T. J .
Acc. Chem. Res. 1992, 25, 57.
(2) For a review see: (a) Hoveyda, A. H.; Morken, J . P. Angew.
Chem., Int. Ed. Engl. 1996, 35, 1262 and references therein. (b)
Millward, D. B.; Cole, A. P.; Waymouth, R. W. Organometallics 2000,
19, 1870.
10.1021/om000950t CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/16/2001

2460 Organometallics, Vol. 20, No. 12, 2001
J ime´nez et al.
In this context, bifunctional cyclopentadienyl ligands
containing an appended donor substituent are attracting
considerable attention due to their ability to modify
steric congestion and Lewis acidity at the electrophilic
metal center.6,7 Several synthetic strategies have been
used to prepare these derivatives. The most usual are
metathesis6e-g reactions of the dilithium salts or Grig-
nard reagents of [(C5R4)LNR′)]2- dianions with the
appropriate metal halide, thermally induced amine6h,8
or alkane6i,9 elimination in the reactions of the neutral
ligand with amido or alkyl precursors, and the HCl
elimination from metal chlorides in the presence of a
base.10 Green11a and Teuben11b employed the desilyla-
tion reaction for the preparation of ansa-monocyclopen-
tadienyl-alkoxo and -imido complexes, respectively. In
all of these examples the N or O functionalities are
incorporated directly into the backbone of the cyclopen-
tadienyl substituent prior to metal coordination. Re-
cently we reported12 an alternative approach which
entails assembling the ligand framework at the metal
coordination sphere.
As part of our current research on such bidentate
ligands, we have investigated the reaction of the chlo-
rodimethylsilyl-substituted monocyclopentadienyltita-
nium [Ti(η5-C5H4SiMe2Cl)Cl3] complex13 with different
diamines to expand this synthetic methodology. It has
allowed us to prepare different types of complexes
bearing chelating cyclopentadienyl-amido ligands. Here,
we report a simple, efficient, and versatile entry into
the chemistry of titanium complexes with cyclopenta-
dienyl-silyl-amido functions bridged by a spacer of
varying length. The derivatization of the dichloride
complex to new dialkyl and diamido derivatives, [Ti-
{η5-C5H4SiMe2NMe(CH2)2-η-NMe}R2], has been studied.
Currently, there is a substantial interest in exploring
the use of carbon dioxide as a renewable source of
carbon for producing chemicals in metal-mediated cata-
lytic processes.14 This moved us to study the reactivity
of 1 with CO2.
Resu lts a n d Discu ssion
The reaction of [Ti(η5-C5H4SiMe2Cl)Cl3]13 with di-
amines provides a useful synthetic route to various
cyclopentadienyl-silyl-amido titanium derivatives. Its
reaction with 1 equiv of the diamine NHMe(CH2)2NHMe
in toluene at -78 °C in the presence of 2 equiv of NEt3
gave a mixture of two different amido derivatives, [Ti-
{η5-C5H4SiMe2NMe(CH2)2-η-NMe}Cl2] (1) and [Ti{η5-
C5H4SiMe2-η-N(CH2)2-η-NHMe}Cl2] (2), in a spectro-
scopic molar ratio of ca. 3:1 with elimination of [NEt3H]Cl
and CH3Cl (Scheme 1). The reaction mixture was
separated by repeated extractions into n-hexane, and
compounds 1 and 2 were obtained as red (53% yield)
and yellow (5% yield) pure solids, respectively. Complex
2 is fairly insoluble in hexane, whereas compound 1 is
slightly soluble.
In an effort to find the working conditions that would
cause the process to be regiospecific, an extensive series
of experiments using various reaction conditions were
carried out, but the attempts were unsuccessful. How-
ever, when the reaction was performed using a second
equivalent of the diamine, instead of NEt3, its lower
basicity made the ratio of final products change to 1:1.
Alternatively, compound 2 could be prepared in good
yield (83%) as an analytically pure product by treatment
of [Ti(η5-C5H4SiMe2Cl)Cl3] with an equimolar amount
of the diamine NH2(CH2)2NHMe in the presence of 2
equiv of NEt3 in toluene at room temperature (Scheme
1).
These results do not distinguish which bond, Ti-Cl
or Si-Cl, reacts preferentially in the aminolysis reac-
tion, which has been reported12a,c to be unselective for
reactions of [Ti(η5-C5H4SiMe2Cl)Cl3] with monoamines
NH2R. Two different pathways may be used to explain
the behavior observed for the reactions with diamines
(Scheme 1). Preferential aminolysis of one of the Ti-Cl
bonds (pathway i) would give an amido compound, A,
which would then be transformed either into compound
2 by aminolysis of the Si-Cl bond with elimination of
X-Cl (X ) H, Me) and coordination of the terminal
amino group to the titanium center or into compound 1
by aminolysis of the Si-Cl bond by reaction with the
terminal amino group. Alternatively, preferential ami-
nolysis of the Si-Cl bond (pathway ii) would give
compound B, which may then be converted either into
2 by aminolysis of the Ti-Cl bond and elimination of
X-Cl and coordination of the terminal amino group or
into 1 by further aminolysis of the Ti-Cl bond by
reaction with the terminal amino group.
(5) (a) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem.
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1993, 12, 1936. (b) Sinnema, P.-J .; Liekelema, K.; Staal, O. K. B.;
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For either of these two pathways, regiospecific double
deprotonation of the NH2 group when N-methylethyl-
enediamine is used is confirmed by the regiospecific
formation of compound 2. Formation of 2 in the reaction
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Gibson, D. H. Chem. Rev. 1996, 96, 2063 and references therein.

Synthesis of Cyclopentadienyltitanium(IV) Compounds
Organometallics, Vol. 20, No. 12, 2001 2461
Sch em e 1
with N,N′-dimethylethylenediamine involves an unex-
pected dehalomethylation with elimination of MeCl,
which is much more unfavorable and leads to a very
low yield of compound 2. The aminolysis of the terminal
amino group is the most favorable process in this case.
However, when X ) H, preferential aminolysis takes
place at the central N, leading to the η5-cyclopentadi-
enylsilyl-η-amidoethylen-η-amino compound 2.
A few examples of CH3Cl elimination have been
reported to give Cp-alkoxo derivatives, always in the
presence of an activator or under thermal conditions.15
However, in our case the elimination of methyl chloride
occurred at room temperature.
the methylene protons of the “N(CH2)2N” fragment,
while that of compound 2 shows an AA′BB′K spin
system, two multiplets (δ 3.29 and 3.62) and a broad
signal (δ 3.94), for the “NCH2CH2NH” moiety, and one
3
doublet (δ 2.92, 3H, J ) 6.1 Hz) for the unique methyl
group, NHMe, coupled with N-H. The chemical shifts
of NHMe protons differ significantly from those found
for the free diamine (δ 2.40 NMe, 1.80-1.90 NH),
indicating some interaction between the titanium atom
and the amino nitrogen.
The 13C{1H} NMR spectrum (CD2Cl2) at room tem-
perature of 1 shows two signals at δ 71.0 and 51.3
assigned to the C(1) and C(2) atoms, respectively, for
the “SiMe2NC(1)H2C(2)H2NMeTi” bridged unit. How-
ever, in the 13C{1H} NMR spectrum (CD2Cl2) of 2 the
resonances for the CH3 and the C(1) (δ 39.1 and 56.1)
of the “NC(1)H2C(2)H2NHMe” moiety have values simi-
lar to those found for the free diamine MeNHCH2CH2-
NHMe (δ 36.4 and 52.0).16 The pronounced deshielding
for the “TiNCH2” resonance (∆δ 14.9 ppm) in 1 with
respect to 2 is in agreement with a larger π-donor
character of the Ti-N amido interaction in 1 than in
2.17 This feature is also confirmed by the solid-state
structure studied by X-ray diffraction methods for
complex 1. Other important spectroscopic differences
between 1 and 2 are the cyclopentadienyl ipso-carbon
atom resonance, the methyl silyl carbon atom signals,
and the 29Si resonance, which are significantly shielded
in 2 (δ 111.2, -3.2, and -13.2, respectively) with respect
to 1 (δ 127.4, -1.6, and -4.5, respectively). These data
demonstrate a cyclopentadienyl electron density distri-
bution in complex 1 different from that in 2, resulting
Compounds 1 and 2 are very air sensitive but ther-
mally stable. Both complexes are soluble in aromatic
and chlorinated solvents but poorly soluble in aliphatic
hydrocarbons. Spectroscopic and analytical data (see the
Experimental Section) are in agreement with the pro-
posed structures. The IR spectrum of compound 2 shows
a ν(N-H) sharp absorption band of medium intensity
at 3228 cm-1 8a
The molecular structure of 1 was
.
determined by X-ray diffraction methods.
1
The H NMR spectra (CDCl3) of complexes 1 and 2
at 25 °C are consistent with Cs symmetry, and show
AA′BB′ spin systems for the C5H4 ring protons and one
signal for the SiMe2 resonances. However, the spectrum
of 1 shows two singlets (δ 3.97 and 2.55) for the two
nonequivalent methyl groups attached to the two dif-
ferent nitrogen atoms and one AA′BB′ spin system for
(15) (a) Fandos, R.; Meetsma, A.; Teuben, J . H. Organometallics
1991, 10, 59. (b) Gielens, E. E. C. G.; Tiesnitsch, J . Y.; Hessen, B.;
Teuben, J . H. Organometallics 1998, 17, 1652. (c) Qian, Y.; Huang, J .;
Chen, X.; Li, G.; Chen, W.; Li, B.; J in, X.; Yang, Q. Polyhedron 1994,
13, 1105. (d) Qian, Y.; Huang, J .; Yang, J .; Chan, A. S. C.; Chen, W.;
Chen, X.; Li, G.; J in, X.; Yang, Q. J . Organomet. Chem. 1997, 547,
263.
(16) Levy, G. C.; Nelson, G. L. C-13 NMR for Organic Chemists;
Wiley & Sons: New York, 1972.
(17) Galakhov, M.; Go´mez-Sal, P.; Mart´ın, A.; Mena, M.; Ye´lamos,
C. Eur. J . Inorg. Chem. 1998, 1319.

2462 Organometallics, Vol. 20, No. 12, 2001
J ime´nez et al.
F igu r e 1. Interconversion between the two enantiomeric
conformations observed for compound 1 in solution.
from a different coordination mode of the C5H4 ring to
the metal center and two different pπ-dπ interactions
between nitrogen and titanium. Complex 1 exhibits a
strain-free Cp-amido chelating disposition with η5-C5H4
coordination, whereas a certain contribution from η3:
η2-C5H4 coordination could be proposed for 2.
F igu r e 2. Exchange between the two enantiomeric C1
ground states observed for compound 2 in solution.
The asymmetric solid-state structure of 1 (see the
X-ray study) contrasts with the Cs symmetry observed
in solution at room temperature and suggests that this
compound exhibits dynamic behavior in solution. At 158
K the 1H NMR spectrum of 1 in CD2Cl2 shows two
signals (δ 0.23 and 0.42) for the SiMe2, four resonances
[δ 2.76, 2.87, 3.00, 5.04 (1H each)] for the methylene
groups, and three signals [δ 6.60 (2H), 6.64 (1H), 6.73
(1H)] for the cyclopentadienyl protons. The difference
of the chemical shifts between the two TiNCH2 protons
(∆δ ≈ 2) may be explained by a respective “pseudoaxial”
and “pseudoequatorial” disposition.18 The observed flux-
ional behavior of 1 involves interconversion between the
two enantiomeric conformations shown in Figure 1.
The kinetic parameters of this process [log A ) 13.1
( 0.4, Ea )8.3 ( 0.35 kcal/mol (r ) 0.996, F6.2.4 ) 524.8),
∆Hq ) 7.94 ( 0.35 kcal/mol, ∆Sq ) 0.4 ( 2.0 eu (r )
0.996, F6.2.4 ) 483.9), ∆Gq,298K ) 7.8 kcal/mol], calculated
by full line shape analysis for the mutual exchange of
the SiMe2 resonances, are in agreement with an in-
tramolecular process and indicate the same polarization
in the ground and transition states of 1.
F igu r e 3. ORTEP drawing of the molecular structure of
compound 1 together with the atomic labeling scheme.
the lone electron pair of the amino nitrogen to the
titanium center, which prevents inversion of the lone
electron pair. Similar dispositions have been reported
for half-sandwich zirconium complexes, derived from
X-ray crystallographic and spectroscopic data.6g How-
ever, this is one of the few cases of titanium half-
sandwich complexes for which an intramolecular coor-
dinating amino function is present.20
The 1H NMR spectrum of 2 at 25 °C shows some
broad signals (CH2NH and BB′ part of C5H4), indicating
possible fluxional behavior with the relative rate within
1
the NMR time scale. At 195 K the H NMR spectrum
The kinetic parameters of this process [log A ) 13.6
indicates the loss of the Cs symmetry, as deduced by
the presence of two signals for the SiMe2, one AA′BC
spin system for the cyclopentadienyl protons, and one
ABCD spin system for the methylene protons of the
backbone ligand. The value of the “BC” proton-proton
coupling constant (J ) 3.2 Hz) is consistent with the
“W” disposition of the R-protons in planar fragments and
( 0.3, Ea ) 14.0 ( 0.3 kcal/mol (r ) 0.999, F7.2.5
)
1811.4), ∆Hq ) 13.6 ( 0.3 kcal/mol, ∆Sq ) 2.2 ( 1.3 eu
(r ) 0.999, F7.2.5 ) 1747.9), ∆Gq,298K ) 12.9 kcal/mol,
∆Gq,267K
) 13.0 kcal/mol, ∆Gq,267K
) 12.1 kcal/
calcd
exptl
mol], calculated for the exchange of an AB spin system,
are in accord with an intramolecular process and
nonpolarized transition state. The free Gibbs energy
value (∆Gq,298K ) 12.9 kcal/mol) is in agreement with
the “activation barrier” (∆Gq,280K ) 13.1 kcal/mol) found
for similar zirconium complexes.6g
Cr ystal Str u ctu r e of [Ti{η5-C5H4SiMe2NMe(CH2)2-
η-NMe}Cl2] (1). The structure of complex 1 was con-
firmed by a single-crystal X-ray diffraction study. Figure
3 shows an ORTEP view of the structure along with the
atom-labeling scheme. Selected bond distances and bond
angles with their standard deviations are listed in Table
1. The unit cell contains two independent crystal-
corresponds to 3J HH 19 The observed AA′BC spin system
.
results from very fast exchange, on the NMR time scale,
between AA′ positions and slow exchange of the BC
nucleus.
This process may be described as an exchange be-
tween two enantiomeric C1 ground states (Figure 2). The
dissociation of the terminal amino group takes place in
the transition state. The observed C1 symmetry of 2 at
low temperature may be explained by coordination of
(18) Amor, J . I.; Cuenca, T.; Galakhov, M.; Royo, P. J . Organomet.
Chem. 1995, 497, 127.
(19) Bakhmutov, V. I.; Galakhov, M. V.; Nikanorov, V. A.; Gavrilova,
G. B.; Rosenberg, O. A.; Reutov, O. A. Dokl. Akad. Nauk SSSR 1987,
1376.
(20) (a) Yoon, S. C.; Bae, B.-J .; Suh, I.-H.; Park, J . T. Organometallics
1999, 18, 2051. (b) Park, J . T.; Yoon, S. C.; Bae, B.-J .; Seo, W. S.; Suh,
I.-H.; Han, T. K.; Park, J . R. Organometallics 2000, 19, 1269.

Synthesis of Cyclopentadienyltitanium(IV) Compounds
Organometallics, Vol. 20, No. 12, 2001 2463
Ta ble 1. Bon d Len gth s (Å) a n d An gles (d eg) for 1a
molecule 1
molecule 2
Ti(1)-N(2)
1.870(3)
2.2734(12) Ti(2)-Cl(4)
2.3001(13) Ti(2)-Cl(3)
Ti(2)-N(4)
1.864(3)
2.2855(13)
2.2926(13)
2.339(4)
2.350(4)
2.351(4)
2.359(4)
2.367(4)
1.718(3)
1.853(4)
1.873(4)
1.888(4)
1.450(5)
1.462(5)
1.460(5)
1.480(5)
1.415(5)
1.428(5)
1.411(6)
1.382(6)
1.399(5)
1.529(6)
2.026
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)-C(3)
Ti(1)-C(2)
Ti(1)-C(5)
Ti(1)-C(4)
Ti(1)-C(1)
Si(1)-N(1)
Si(1)-C(12)
Si(1)-C(11)
Si(1)-C(1)
N(1)-C(15)
N(1)-C(13)
N(2)-C(14)
N(2)-C(16)
C(1)-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(13)-C(14)
Ti(1)-Cp(1)
2.343(4)
2.347(4)
2.362(4)
2.368(4)
2.369(4)
1.714(3)
1.849(4)
1.859(4)
1.886(4)
1.454(5)
1.456(5)
1.468(5)
1.487(5)
1.421(5)
1.425(5)
1.400(5)
1.394(6)
1.404(5)
1.522(5)
2.030
Ti(2)-C(7)
Ti(2)-C(9)
Ti(2)-C(10)
Ti(2)-C(8)
Ti(2)-C(6)
Si(2)-N(3)
Si(2)-C(22)
Si(2)-C(21)
Si(2)-C(6)
N(3)-C(25)
N(3)-C(23)
N(4)-C(24)
N(4)-C(26)
C(6)-C(7)
C(6)-C(10)
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
C(23)-C(24)
Ti(2)-Cp(2)
F igu r e 4. Effect of spacer length on the dispositions found
for the titanium-silicon backbone.
spacer and the sp2 hybridization of the N(1) atom make
this metallacycle exhibit a conformation different from
those shown for the bidentate Cp-amido complexes
reported to date (Figure 4). In constrained geometry
compounds (one member spacer) the ipso-carbon of the
cyclopentadienyl ligand and the atoms of the metalla-
cycle are in the plane bisecting the Cl-Ti-Cl angle
(Figure 4A). In {Ti[η5-C5H4(CH2)3NPri]Cl2}10 and {Ti-
[η5-C5H4(CH2)3O]Cl2}8a (three member spacers) the
atoms of the side chain displayed a zigzag pattern with
respect to this plane (Figure 4B). In contrast, for 1 the
linkage (four members) between the cyclopentadienyl
and amido functions adopts a helical conformation
around the Cp-Ti bond, locating the SiMe2 moiety
1.946(1) Å [1.946(1) Å] away from the plane defined by
Cp-Ti-N (Figure 4C) to minimize the strain in the
metallacycle.
The C-C distances in the cyclopentadienyl ring
(1.393(6)-1.424(5) Å) and the Cp-Ti distance 2.03 Å
[2.026 Å] are similar to those found for the series of
unconstrained complexes [Ti(C5H4X)(NRR′)Cl2] (X ) H,
R ) R′ ) i-Pr; X ) H, R ) H, R′ ) t-Bu; X ) Me, R ) H,
R′ ) t-Bu).21c,d These features reflect that the length of
the backbone leaves sufficient flexibility in the system
to convey η5-bonding character to the C5H4 ring.
The short Ti-N(2) bond distance 1.870(3) Å [1.864(2)
Å], in the range 1.80-1.90 Å,21c,d,22 suggests the pπ-
dπ bonding between Ti and the amido ligands, and the
planar geometry of the nitrogen atom indicates sp2
hybridization of the N(2) atom with the out-of-plane lone
pair, giving an N(pπ)-Ti(dπ) interaction. The strain-
free chelated ligand allows optimal overlap between the
nitrogen pπ orbital and the vacant titanium dπ orbital,
increasing the Ti-N double-bond character with respect
to the “constrained geometry” systems.
N(2)-Ti(1)-Cl(1) 105.27(10)
N(2)-Ti(1)-Cl(2) 103.66(10)
Cl(1)-Ti(1)-Cl(2) 101.47(5)
N(1)-Si(1)-C(12) 109.7(2)
N(1)-Si(1)-C(11) 110.63(19)
N(4)-Ti(2)-Cl(4) 104.59(10)
N(4)-Ti(2)-Cl(3) 104.48(10)
Cl(4)-Ti(2)-Cl(3) 102.34(5)
N(3)-Si(2)-C(22) 110.97(19)
N(3)-Si(2)-C(21) 110.1(2)
N(1)-Si(1)-C(1)
111.98(16)
N(3)-Si(2)-C(6)
111.62(16)
C(15)-N(1)-C(13) 114.0(3)
C(15)-N(1)-Si(1) 122.9(3)
C(13)-N(1)-Si(1) 120.1(3)
C(14)-N(2)-C(16) 111.7(3)
C(14)-N(2)-Ti(1) 139.4(2)
C(16)-N(2)-Ti(1) 108.6(3)
N(2)-Ti(1)-Cp(1) 114.2
Cl(1)-Ti(1)-Cp(1) 115.4
Cl(2)-Ti(1)-Cp(1) 115.2
C(25)-N(3)-C(23) 115.8(4)
C(25)-N(3)-Si(2) 120.8(3)
C(23)-N(3)-Si(2) 119.4(3)
C(24)-N(4)-C(26) 112.2(3)
C(24)-N(4)-Ti(2) 139.9(3)
C(26)-N(4)-Ti(2) 107.7(2)
Cl(3)-Ti(2)-Cp(2) 113.9
Cl(4)-Ti(2)-Cp(2) 116.2
N(4)-Ti(2)-Cp(2) 113.8
a
Cp(1) is the centroid of C(1),C(2),C(3),C(4),C(5), and Cp(2) is
the centroid of C(6),C(7),C(8),C(9),C(10).
lographic units. Since both molecules show practically
identical structural features, only one is described in
detail (data for the second are given in square brackets).
In the solid state 1 is a chiral compound for which two
independent enantiomers are present.
The compound is monomeric with a pseudo-three-
legged piano-stool coordination geometry around the
titanium atom, as expected for complexes of the type
TiCp(X)Cl2.21 The Cp-Ti-N(2) angle, where Cp repre-
sents the centroid of the C5H4 ring, at 114.2° [113.9°] is
significantly larger, ca. 10°, than the corresponding
angle in the constrained ansa-monocyclopentadienyl-
silyl-amido complexes [Ti{(η5-C5R4SiMe2-η-NR′}Cl2].6h
This result suggests that increasing the length of the
spacer leaves a less open metal center as reflected in
the Cl-Ti-Cl angle value 101.4° [102.34(5)°], which is
in the normal range of the values observed for uncon-
strained monocyclopentadienyl-amido derivatives.21c,d
If the centroid of the cyclopentadienyl ring is consid-
ered as a single coordination site, the central core of 1
appears as a seven-membered (Cp-Si-N-C-C-N-Ti)
metallacycle. The length of the “Si-N(1)-CH2-CH2”
The silicon atom is slightly pushed, 0.06 Å [0.10 Å]
out of the Cp ring plane, away from the metal center,
in contrast to the location observed in constrained
geometry compounds in which the chelating ligand
causes the Si atom to be displaced toward the metal
center (0.85-0.95 Å).6g The Si-N distance of 1.714(3)
Å [1.717(3) Å] and the essentially trigonal-planar en-
vironment (sum of the angles about the nitrogen atom
ca. 355°) at the nitrogen atom indicate an important
degree of double-bond character in the Si-N bond. The
distance is comparable to those reported for different
(21) For examples of alkoxy complexes see: (a) Vilardo, J . S.; Thorn,
M. G.; Fanwick, P. E.; Rothwell, I. P. Chem. Commun. 1998, 2425,
2427. (b) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai, A.
Organometallics 1998, 17, 2152. For examples of amido complexes
see: (c) Pupi, R. M.; Coalter, J . N.; Petersen, J . L. J . Organomet. Chem.
1995, 497, 17. (d) Giolando, D. M.; Kirschbaum, K.; Graves, L. J .; Bolle,
U. Inorg. Chem. 1992, 31, 3887.
(22) Lappert, M. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C.
Metal and metalloid Amides; Ellis Horwood, Wiley: New York, 1980.

2464 Organometallics, Vol. 20, No. 12, 2001
J ime´nez et al.
Sch em e 2
Sch em e 3
feature in the 13C NMR spectra of these derivatives is
shielding of the “TiNCH2” resonances with respect to
that observed for 1 [∆δ ) δ(1) - δ(4,5,6) ≈ 10],
depending on the electron properties of the R groups.
Rea ction of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}-
Cl2] (1) w ith CO2. A solution of [Ti{η5-C5H4SiMe2NMe-
(CH2)2-η-NMe}Cl2] in chloroform at -78 °C was satu-
rated with CO2. When the reaction mixture was warmed
to room temperature, the insertion of carbon dioxide into
the Si-N and Ti-N bonds took place to give the
corresponding dicarbamate derivative [Ti{η5-C5H4Si-
Me2OC(O)NMe(CH2)2NMe-η2-OCO}Cl2] (6) (Scheme 3),
which was isolated and analytically and spectroscopi-
cally characterized.
silylamines23 and for the niobium complex [Nb(η5-C5H4-
SiMe2NHtBu)Cl2(NtBu)].12b
All of these structural results lead to the conclusion
that the length and flexibility of the chain provide
considerable “freedom”, more akin to unlinked mono-
cyclopentadienyl complexes than to cyclopentadienyl-
silyl-amido constrained geometry complexes.
Compound 6 is stable at room temperature. However,
when a solution of 6 in benzene-d6 was heated at 70 °C
for 2 days, elimination of 1,3-dimethyl-2-imidazolidinone
and CO2 was observed with formation of a mixture
containing the two well-known dinuclear oxo derivatives
[Ti{µ-(SiMe2O-η5-C5H4)Cl2}]213 and [(TiCl2)2(µ-O){µ-(η5-
C5H4)2-SiMe2O}]24 as the major and minor components,
respectively. Analogous reactions with CO2 have been
reported for amide derivatives of titanium,12a zirco-
nium,25 germanium, and tin compounds.26 However,
although the insertion of CO2 into the M-N bond has
been proposed as the first step in this process, such
carbamate intermediates have not been observed.
Under these conditions the isomerization process of
[Ti{µ-(SiMe2O-η5-C5H4)Cl2}]2 into [(TiCl2)2(µ-O){µ-(η5-
C5H4)2SiMe2O}] has to be ruled out since this transfor-
mation requires heating at temperatures higher than
130 °C. A possible explanation for this process is
proposed in Scheme 4.
Thermolysis of 6 results in the elimination of the
“-C(O)-NMe-CH2-CH2-NMe-C(O)-O-“, which rear-
ranges to give 1,3-dimethyl-2-imidazolidinone, identified
by comparison with a commercial sample, with evolution
of CO2. This elimination may take place by an inter-
molecular reaction, with the possible formation of three
different types of intermediates, A, B, and C, depending
on the relative orientation of the two approaching
molecular units. Similar dinuclear species containing
bridging siloxy groups are known as stable compounds
characterized by X-ray diffraction methods for zirco-
nium.12a,25 Elimination of CO2 and the organic substance
takes place for A by cleavage and formation of two Ti-O
bonds, whereas from B two Si-O bonds are cleaved and
Syn th esis of Alk yl a n d Am id o Com p lexes. The
dichloride derivative 1 was readily converted to the alkyl
compounds [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}R2], R
) Me (3), R ) CH2Ph (4), or the diamido complex [Ti-
{η5-C5H4SiMe2NMe(CH2)2-η-NMe}(NMe2)2] (5) by a salt
metathesis route. Complex 1 reacted with a stoichio-
metric amount of the appropriate Grignard reagent,
MgClMe or Mg(CH2Ph)2·2THF, or the lithium salt
LiNMe2 in toluene at -78 °C to give the corresponding
dialkyl or diamido derivatives, which have been fully
characterized (Scheme 2). Attempts to prepare the
monoalkyl complexes by reaction of 1 with 1 equiv of
the alkylating agent were unsuccessful, always leading
to mixtures of compounds with various degrees of
substitution. Reactions of 2 with the same alkylating
agents were not straightforward and afforded a mixture
of unidentified products.
Compounds 3-5 are air and moisture sensitive and
very soluble in the usual hydrocarbon solvents. How-
ever, 4 and 5 are thermally more stable than 3 and can
be stored for weeks at ambient conditions without
appreciable decomposition. By contrast, the methyl
derivative is light sensitive even in the solid state;
hence, it had to be stored in the dark at low tempera-
ture.
1
The H NMR spectra (C6D6 or CDCl3) at room tem-
perature of 3-5 show one signal for the SiMe2 and one
AA′BB′ spin system for the C5H4 ring protons along with
the expected resonances for the R groups. One AA′BB′
spin system for the methylene and two singlets for the
methyl protons of the “N(Me)CH2CH2N(Me)” moiety are
also observed. The methylene protons of the benzyl
groups in complex 4 exhibit an AB spin system (2J )
11.4 Hz) due to the prochiral character of the metal
center, whereas the observation of four equivalent NMe
groups for the amido ligands in 5 is consistent with fast
rotation around the Ti-N bond. A more important
(24) Noh, S.; Byun, G.; Lee, Ch.; Lee, D.; Yoon, K.; Kang, K. J .
Organomet. Chem. 1996, 518, 1.
(25) Kloppenburg, L.; Petersen, J . L. Organometallics 1996, 15, 7.
(26) (a) Sita, L. R.; Babcock, J . R.; Xi, R. J . Am. Chem. Soc. 1996,
118, 10912. (b) Babcock, J . R.; Liable-Sands, L.; Rheingold, A. L.; Sita,
L. R. Organometallics 1999, 18, 4437. (c) Babcock, J . R.; Incarvito, Ch.;
Rheingold, A. L.; Fettinger, J . C.; Sita, L. R. Organometallics 1999,
18, 5729.
(23) Anderson, D. G.; Rankin, D. W. H.; Robertson, H. E.; Gunder-
sen, G.; Seip, R. J . Chem. Soc., Dalton Trans. 1990, 161.

Synthesis of Cyclopentadienyltitanium(IV) Compounds
Organometallics, Vol. 20, No. 12, 2001 2465
Sch em e 4
two Si-O bonds are formed to give the same final oxo
compound with two Si-O-Ti bridges [Ti{µ-(SiMe2O-η5-
C5H4)Cl2}]2. However, when the orientation is that
represented by C, elimination occurs by cleavage and
formation of one Si-O and one Ti-O bond, leading in
this case to the final oxo compound, which contains one
Si-O-Si and one Ti-O-Ti bridge [(TiCl2)2(µ-O){µ-(η5-
C5H4)2SiMe2O}]. Formation of [Ti{µ-(SiMe2O-η5-C5H4)-
Cl2}]2 as the major component may result from the
kinetic control based on the steric hindrance of the
bridging system.
0.40 and 0.70) for SiMe2 and two ABCD spin systems
for the C5H4 ring (δ 7.00, 7.02, 7.19, and 7.67) and for
the “NCH2CH2N” protons (δ 2.95, 3.05, 3.87 and 4.53),
indicating the loss of the Cs symmetry observed at room
temperature. We propose that the fluxional behavior of
6 is similar to that observed in 1 and entails enantio-
meric conformational metallacycle interconversion. The
larger values of the activation parameters displayed for
6 in comparison with 1 are related to the increasing size
of the cycle.29
The kinetic parameters calculated for the mutual
exchange of SiMe2 resonances between 233 and 263 K
[log A ) 12.6 ( 0.25, Ea ) 11.5 ( 0.3 kcal/mol (r )
0.9986, N ) 6), ∆Hq ) 11.05 ( 0.3 kcal/mol, ∆Sq ) -2.4
( 1.2 eu (r ) 0.9986, N ) 6), ∆Gq ) 11.7 kcal/mol] are
consistent with the intramolecular nature of the process,
and the ∆Sq value is consistent with the same polariza-
tion in the ground- and transition-state species.
1
The H NMR spectrum of compound 6 (CDCl3) at 25
°C exhibits one singlet for the SiMe2 (δ 0.54), one AA′BB′
spin system for the C5H4 protons (δ 6.98, 7.39), two
narrow singlets for the NMe groups (δ 2.96, 2.98), and
two very broad signals for the methylene protons. The
most notable feature in the 13C{1H} NMR spectrum is
the presence of two resonances at δ 163.9 and 154.6,
corresponding to an η2-carbamate TiO2CN moiety and
a monocoordinated carbamate SiOC(O)N ligand, respec-
tively.27 The pronounced deshielding of the SiMe2-OC-
(O)-NMe (0.14 and 0.43 ppm) and the shielding of Ti-
O2C-NMe (0.99 ppm) resonances with respect to those
found in 1 and the small difference between the chemi-
cal shifts for the two NMe groups in 6 (∆δ ) 0.02)
compared with that observed for 1 (∆δ ) 1.42) are
consistent with our proposal.
Con clu d in g Rem a r k s
The reaction of diamines with the chlorosilyl-substi-
tuted cyclopentadienyl compound [Ti(η5-C5H4SiMe2Cl)-
Cl3] in the presence of a base offers a versatile and
convenient synthetic route for the preparation of dif-
ferent types of linked Cp-amido derivatives of titanium,
the final compound depending on the nature of the
groups on the nitrogen and the length of the carbonated
chain bridging the two nitrogen atoms in the amine
reagents.30 The reaction of [Ti(η5-C5H4SiMe2Cl)Cl3] with
N,N′-dimethylethylenediamine yields a mixture con-
taining mainly [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}-
Cl2] (1) with a substantial amount of [Ti{η5:η-C5H4-
SiMe2N(CH2)2-η-NHMe}Cl2] (2). In contrast, the corre-
sponding reaction of [Ti(η5-C5H4SiMe2Cl)Cl3] with N-
methylethylenediamine specifically affords 2. It is note-
worthy that 1 is the compound with the longest spacer
chelating Cp-amido ligand reported to date for titanium
The infrared spectrum shows two strong absorptions
(1569 and 1668 cm-1) in the 1560-1685 cm-1 region
assigned to the O2CN moiety, which also indicates the
presence of both bidentate and monodentate carbamato
ligands.27,28
Compound 6 shows dynamic behavior in solution. At
213 K the 1H NMR spectrum displays two signals (δ
(27) (a) Chisholm, M. H.; Extine, M. W. J . Am. Chem. Soc. 1977,
99, 782. (b) Chisholm, M. H.; Extine, M. W. J . Am. Chem. Soc. 1977,
99, 792. (c) Go´mez-Sal, P.; Irigoyen, A. M.; Mart´ın, A.; Mena, M.;
Monge, M.; Ye´lamos, C. J . Organomet. Chem. 1995, 494, C19. (d)
Alcalde, M. I. Ph.D. Thesis, University of Alcala, Alcala de Henares,
Spain, 2000.
(29) Eliel, E. L.; Wilen, S. H. Stereohemistry of Organic Compounds;
J ohn Wiley and Sons, Inc.: New York, 1994; p762.
(30) J ime´nez, G.; Cuenca, T.; Royo, P. Unpublished work.
(28) Sanche´z-Nieves, J . Ph.D. Thesis, University of Alcala, Alcala
de Henares, Spain, 2000.

2466 Organometallics, Vol. 20, No. 12, 2001
J ime´nez et al.
yellow solution of Ti(η5-C5H4SiMe2Cl)Cl3 (1.77 g, 5.7 mmol) in
toluene (60 mL) at -78 °C. The cooling bath was removed,
and the reaction mixture was allowed to warm to room
temperature and stirred for 2 h, during which time the mixture
turned red and a white solid precipitated. After filtration and
removal of the solvent, the resultant residue was washed with
hexane (2 × 30 mL) and dried under vacuum to afford 2 as a
yellow solid (1.3 g). Concentration and cooling to -30 °C of
the solution gave a second crop (0.2 g), yielding a total 1.5 g
(4,79 mmol, 84%) of product. Anal. Calcd for C10H18Cl2N2SiTi:
C, 38.35; H, 5.8; N, 8.94. Found: C, 39.20; H, 5.67; N, 8.93.
1H NMR (500 MHz, CDCl3, 25 °C): δ 0.39 (s, 6H, SiMe2), 2.92
derivatives. We report here the first case of the forma-
tion of a titanamidacycle via elimination of CH3Cl in
very mild conditions.
The reaction of 1 with dried CO2 allowed us to isolate
the dicarbamate complex [Ti{η5-C5H4SiMe2OC(O)NMe-
(CH2)2NMe-η2-OCO}Cl2] (6) in a high yield as an
intermediate of the metathesis reaction between CO2
and the nitrogen-group 4 metal bond. This compound
decomposes thermally with elimination of carbon diox-
ide and 1,3-dimethyl-2-imidazolidinone, to give a mix-
ture of two known oxo derivatives. We have been able
to evaluate the kinetic parameters and study the
dynamic behavior in solution for several of these com-
plexes. Examples of such fluxional behavior for chelat-
ing cyclopentadienyl-amido group 4 derivatives have
just been suggested.6g
3
(d, 3H, J H-H ) 6.1 Hz, NHMe), 3.29, 3.62 (m, 2 × 2H, CH2),
3.94 (br s, 1H, NH), 6.38 (m, 2H, C5H4), 7.0 (m, 2H, C5H4).13C-
{1H} NMR (125 MHz, CD2Cl2, 25 °C): δ -3.2 (SiMe2), 39.1
(NMe), 53.4 (NHMeCH2), 56.1 (TiNCH2), 111.2 (C5H4-ipso),
122.2, 129.1 (C5H4). 29Si NMR (99.3 MHz, CDCl3, 25 °C): δ )
-13.2. IR (cm-1): ν (N-H) 3228.
Syn th esis of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}(CH3)2]
(3). A 2.1 mL sample of a 3 M solution of MgClMe (6.3 mmol)
in THF was added to a solution of Ti[(η5-C5H4)SiMe2NMe-
(CH2)2NMe]Cl2 (1.0 g, 3.0 mmol) in toluene (30 mL) at -78
°C. The reaction mixture was warmed to room temperature
and stirred for 5 h. The toluene was removed under reduced
pressure and the resultant residue extracted with 60 mL of
hexane and reduced to 10 mL. Cooling at -30 °C overnight
gave a yellow solid which was dried under vacuum, recrystal-
lized from cold hexane, and characterized as 3 (0.49 g, 1.71
mmol, 56% yield). Anal. Calcd for C13H26N2SiTi: C, 54.51; H,
Exp er im en ta l Section
All manipulations were performed under argon using Schlenk
and high-vacuum line techniques or a glovebox, model HE-
63. The solvents were purified by distillation under argon
before use by employing the appropriate drying/deoxygenated
agent. Deuterated solvents were stored over activated 4 Å
molecular sieves and degassed by several freeze-thaw cycles.
NEt3 (Aldrich) was distilled before use and stored over 4 Å
molecular sieves. NHMe(CH2)2NHMe (Aldrich), NH2(CH2)2-
NHMe (Aldrich), MgClMe (Aldrich), LiNMe2 (Aldrich), and
CO2 (SEO) were purchased from commercial sources and used
without further purification. [Ti(η5-C5H4SiMe2Cl)Cl3]13 and
Mg(CH2Ph)2·2THF31 were prepared by known procedures. C,
H, and N microanalyses were performed on a Perkin-Elmer
240B and/or Heraeus CHN-O-Rapid microanalyzer. The ana-
lytical values found deviated (>1% (C) due to their air
sensitivity and difficulties in the manipulation of samples. IR
spectra were recorded on a Perkin-Elmer Spectrum 2000
spectrophotometer using CsI pellets; only selected IR data are
reported. NMR spectra, measured at +25 or -60 °C, were
recorded on a Varian Unity 500 Plus spectrometer, and
chemical shifts are referenced to the residual proton and
carbon signals of the solvent. The NMR data were calculated
using gNMR and SPSS 9.0 programs.
1
9.17; N 9.77. Found: C, 53.61; H, 8.21; N, 8.85. H NMR (500
MHz, C6D6, 25 °C): δ 0.14 (s, 6H, SiMe2), 0.70 (s, 6H, TiMe2),
2.30 (s, 3H, SiNMe), 2.51, 3.40 (m, 2 × 2H, CH2), 3.17 (s, 3H,
TiNMe), 5.79, 6.51 (m, 2 × 2H, C5H4). 13C-{1H} NMR (125
MHz, C6D6, 25 °C): δ -1.1 (SiMe2), 37.5 (SiNMe), 45.5
(TiNMe), 50.6 (SiNCH2), 60.3 (TiNCH2), 50.4 (TiMe2), 113.2,
113.8 (C5H4), 116.5 (C5H4-ipso).
Syn th esis of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}(CH2-
P h )2] (4). A solution of Mg(CH2Ph)2·2THF (1.08 g, 3.0 mmol)
in toluene (20 mL) was added to a solution of Ti[(η5-C5H4)SiMe2-
NMe(CH2)2NMe]Cl2 (1.0 g, 3.0 mmol) in toluene (20 mL) at
-78 °C. The reaction mixture was allowed to warm to room
temperature and stirred for 6 h. The solvent was completely
removed and the residue extracted into n-hexane (50 mL). The
resultant solution was concentrated (10 mL) and cooled at -30
°C to give a dark red solid which was dried under reduced
pressure, recrystallized from cold hexane, and characterized
as 4 (0.9 g, 2 mmol, 67% yield). Anal. Calcd for C25H34N2SiTi:
C, 68.46; H, 7.83; N, 6.38. Found: C, 67.23; H, 7.96; N, 6.90.
1H NMR (500 MHz, C6D6, 25 °C): δ 0.05 (s, 6H, SiMe2), 2.28
Syn th esis of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}Cl2]
(1). A solution of NHMe(CH2)2NHMe (0.35 mL, 3.2 mmol) and
NEt3 (0.9 mL, 6.5 mmol) in 20 mL of toluene was added at
ambient temperature to a solution of Ti(η5-C5H4SiMe2Cl)Cl3
(1 g, 3.2 mmol) in 30 mL of the same solvent. The reaction
mixture was stirred for 2 h. The color changed instantaneously
from yellow to dark red, and a large quantity of white solid
precipitated, which was collected by filtration. After toluene
removal, the residue was extracted with hexane (5 × 30 mL)
and cooled overnight at -30 °C to give a small amount (5 ×
10-2, 5%) of yellow crystalline solid characterized as 2.
Concentration and cooling to -30 °C of the resultant solution
affords 1 as a red solid (0.55 g, 53%). Recrystallization from
toluene/hexane gave 1 as a red crystalline substance. Anal.
Calcd for C11H20Cl2N2SiTi: C, 40.38; H, 6.16; N, 8.56. Found:
2
(s, 3H, SiNMe), 2.42, 2.47 (d, 2 × 2H, J HH ) 11.4 Hz, CH2-
Ph), 2.51, 3.18 (m, 2 × 2H, CH2), 3.20 (s, 3H, TiNMe), 5.56,
6.26 (m, 2 × 2H, C5H4), 6.90, 7.22 (m, 6H and 4H, Ph). 13C-
{1H} NMR (125 MHz, C6D6, 25 °C): δ -1.6 (SiMe2), 36.9
(SiNMe), 40.2 (TiNMe), 49.5 (SiNCH2), 60.9 (TiNCH2), 80.1
(CH2Ph), 120.7, 121.7 (C5H4), 121.8 (C5H4-ipso), 125.9, 128.2,
128.9 (Ph), 150.8 (C6H5-ipso).
Syn th esis of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}(N-
Me2)2] (5). A 0.28 g sample of LiNMe2 (6.0 mmol) was added
to a solution of Ti[(η5-C5H4)SiMe2NMe(CH2)2NMe]Cl2 (1.0 g,
3.0 mmol) in hexane (100 mL) at -78 °C. The reaction mixture
was warmed to room temperature and stirred for 6 h. The
solution was filtered, concentrated (10 mL), and cooled at -30
°C to give a brown solid which was dried under reduced
pressure, recrystallized from cold n-hexane, and characterized
as 5 (0.67 g, 1.95 mmol, 64% yield). Anal. Calcd for C15H32N4-
SiTi: C, 52.27; H, 9.38; N 16.26. Found: C, 52.80; H, 9.60; N,
17.01. 1H NMR (500 MHz, CDCl3, 25 °C): δ 0.29 (s, 6H, SiMe2),
2.66 (s, 3H, SiNMe), 2.80, 3.31 (m, 2 × 2H, CH2), 3.00 (s, 12H,
TiNMe2), 3.10 (s, 3H, TiNMe), 6.04, 6.19 (m, 2 × 2H, C5H4).
13C-{1H} NMR (125 MHz, CDCl3, 25 °C): δ -1.7 (SiMe2), 36.9
1
C, 39.16; H, 6.50; N, 7.61. H NMR (500 MHz, CDCl3, 25 °C):
δ 0.40 (s, 6H, SiMe2), 2.55 (s, 3H, SiNMe), 2.87, 4.04 (m, 2 ×
2H, CH2), 3.97 (s, 3H, TiNMe), 6.60, 6.65 (m, 2 × 2H, C5H4).
13C-{1H} NMR (125 MHz, CD2Cl2, 25 °C): δ -1.4 (SiMe2), 38.6
(SiNMe), 45.2 (TiNMe), 51.3 (SiNCH2), 71.0 (TiNCH2), 122.2,
126.7 (C5H4), 127.4 (C5H4-ipso). 29Si NMR (99.3 MHz, CDCl3,
25 °C): δ ) -4.5.
Syn th esis of [Ti{η5:η1-C5H4SiMe2N(CH2)2-η-NHMe}Cl2]
(2). A solution of NH2(CH2)2NHMe (0.5 mL, 5.7 mmol) and
NEt3 (1.6 mL, 11.4 mmol) in toluene (30 mL) was added to a
(31) Schrock, R. J . Organomet. Chem. 1976, 122, 209.

Synthesis of Cyclopentadienyltitanium(IV) Compounds
Organometallics, Vol. 20, No. 12, 2001 2467
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
P r oced u r es for Com p ou n d 1
(SiNMe), 45.0 (SiNCH2), 59.3 (TiNCH2), 49.6 (TiNMe), 50.0
(TiNMe2), 113.6, 116.0 (C5H4), 118.5 (C5H4-ipso).
Syn t h esis of [Ti{(η5-C5H 4SiMe2(OCO)NMe(CH2)2N-
Me(η2-OCO)}Cl2] (6). A Schlenk flask containing chloroform
(50 mL) was charged with Ti[(η5-C5H4)SiMe2NMe(CH2)2NMe]-
Cl2 (1.0 g, 3.0 mmol). After the solution had been cooled to
-78 °C the argon atmosphere was replaced by CO2. The
reaction mixture was stirred in the dark for 2 h and then
slowly warmed to room temperature. The color of the solution
changed from red to yellow. The solvent was removed, and 6
was obtained as a yellow microcrystalline solid. Recrystalli-
zation from dichloromethane/n-hexane gave 0.63 g (50%) of 6.
Anal. Calcd for C13H20Cl2N2O4SiTi: C, 37.6; H, 4.86; N, 6.74.
empirical formula
fw
C11H20Cl2N2SiTi
327.18
cryst size (mm)
cryst syst
0.20 × 0.22 × 0.28
monoclinic
P21/n
space group
unit cell dimens
a, b, c (Å)
â (deg)
8.101(1), 14.464(1), 26.601(1)
93.22(1)
3112.0(5)
V (Å3)
Z
8
density(calcd) (g cm-3
F(000)
)
1.397
1360
9.52
1
µ (cm-1
scan mode
no. of reflns collected
)
Found: C, 38.2; H, 5.20; N, 7.56. H NMR (500 MHz, CDCl3,
ω/2θ, 2.08 < θ < 24.97
5870
25 °C): δ 0.54 (s, 6H, SiMe), 2.96, 2.98 (s, 2 × 3H, NMe), 3.4,
3.6 (m, 2 × 2H, -CH2-CH2-), 6.98, 7.39 (m, 2 × 2H, C5H4). 1H
NMR (500 MHz, CDCl3, -60 °C): δ 0.40, 0.70 (s, 2 × 3H,
SiMe), 2.95, 3.05, 3.87, 4.53 (m, 4 × 1H, -CH2-CH2-), 2.98,
3.0 (s, 2 × 3H, NMe), 7.00, 7.02, 7.19, 7.67 (m, 4 × 1H, C5H4).
13C-{1H} NMR (125 MHz, CDCl3, -60 °C): δ -2.8, 1.0 (SiMe),
34.1 (SiOCON), 36.0 (TiO2CN), 45.9 (SiNCH2), 46.8 (TiNCH2),
124.3, 124.9, 128.1, 128.6 (C5H4), 132.2 (C5H4-ipso), 154.6
(SiOCO), 163.9 (TiO2C). IR (KBr, cm-1): ν str(O2CN) 1569 and
1668.
Rea ction of [Ti{η5-C5H4SiMe2NMe(CH2)2-η-NMe}Cl2]
(1) w ith CO2 a t 70 °C. An NMR tube containing chloroform-
d1 (1.5 mL) was charged with 30 × 10-3 g of Ti[(η5-C5H4)SiMe2-
NMe(CH2)2NMe]Cl2 (9 × 10-2 mmol). After the solution had
been cooled to -196 °C the argon atmosphere was replaced
by CO2. The reaction mixture was warmed to -60 °C, and the
formation of 3 was confirmed. After the solution was warmed
at 70 °C for 48 h, it was directly subjected to spectroscopic
measurements, and the formation of the compounds [Ti{µ-(η5-
C5H4SiMe2-η-O)}Cl2]2, (TiCl2)2(µ-O)-[µ-{(η5-C5H4SiMe2)2(µ-O)}],
and 1,3-dimethylimidazolidione was observed.
no. of obsd reflns (I > 2σ(I))
3543
index ranges
0 < h < +9, 0 < k < +17,
-31 < l < +31
no. of std reflns
3 every 200 reflns
full-matrix least-squares on F2
R1 ) 0.0412, wR2 ) 0.0919
wcalcd ) 1/[σ2(Fo2) + (0.0421P)2 +
2.6572P] where
P ) (Fo2 + 2Fc2)/3
+0.570, -0.242
refinement method
final R indices (I > 2σ(I))a
weighting scheme
largest diff peak and
hole (e/Å3)
goodness of fit on F2
1.001
a
R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {[∑w(Fo2 - Fc2)]2/[∑w(Fo2)2]}1/2
.
refined anisotropically, and the hydrogen atoms were intro-
duced from geometrical calculations and refined using a riding
model with fixed thermal parameters (U ) 0.08 Å2). The final
R values and other interesting X-ray structural analysis data
are present in Table 2. Calculations were carried out on an
ALPHA AXP (Digital) workstation.
Cr ystal Str u ctu r e Deter m in ation of [Ti{η5-C5H4SiMe2N-
Me(CH2)2-η-NMe}Cl2] (1). Red crystals of compound 1 were
obtained by crystallization from hexane, and a suitably sized
crystal was sealed, under argon, in a Lindemann tube and
mounted in an Enraf-Nonius CAD 4 automatic four-circle
diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.710 73 Å). Crystallographic and experimental details
are summarized in Table 2. Data were collected at room
temperature. Intensities were corrected for Lorentz and
polarization effects in the usual manner. No absorption or
extinction correction was made. The structure was solved by
direct methods (SHELXL 97)32 and refined by least-squares
against F2 (SHELXL 97).32 All non-hydrogen atoms were
Ack n ow led gm en t. Financial support for this re-
search by DGICYT (Project PB97-0776) is gratefully
acknowledged. G.J . thanks the University of Alcala´ de
Henares for financial support.
Su p p or tin g In for m a tion Ava ila ble: Final crystallo-
graphic atomic coordinates, equivalent isotropic thermal pa-
rameters, hydrogen atom parameters, anisotropic thermal
parameters, a complete list of bond distances and angles, an
ORTEP diagram for 1, and figures giving low-temperature 1H
NMR spectra for complexes 1 and 2. This material is available
free of charge via the Internet at http://pubs.acs.org.
(32) Sheldrick, G. M. SHELX-97: Programs for Crystal Structure
Analysis (Release 97-2), University of Go¨ttingen, Germany, 1998.
OM000950T