New half-sandwich alkyl, aryl, aryloxide, and propargyloxide titanium(IV) complexes containing a cyclopentadienyl ligand with a pendant ether substituent: Behavior and influence in the hydroamination of alkynes of the ether group

Article abstract of DOI:10.1021/om051031b

The complex Cp^OTiCl₃ (1; Cp^O = C ₅H₄CH₂CH₂OCH₃) reacts with 1.0, 2.0, and 3.0 equiv of MeMgCl to give Cp^OTiMeCl₂ (2), Cp^OTiMe₂Cl (3), and Cp^OTiMe₃ (4). In the solid state, the ether group of the pendant substituent of the cyclopentadienyl ligand is coordinated to the metal center (d(Ti-O) = 2.3373-(18) A in 2 and 2.2818(10) A in 3) disposed transoid to a methyl ligand. In solution the O-donor substituent is involved in a coordination-dissociation equilibrium (ΔH° = 3.0 ± 0.7 kcal mol^-1 and ΔS° = 12 ± 4 cal mol^-1 Kr ^-1 for 2, ΔH° = 4.3 ± 0.1 kcal mol^-1 and ΔS° = 17.2 ± 0.1 cal mol^-1 K^-1 for 3, and ΔH° = 2.3 ± 0.1 kcal mol^-1 and ΔS° = 11.9 ± 0.3 cal mol^-1 K^-1 for 4). The reactions of 1 with 3.0 equiv of PhCH₂MgCl, PhMgCl, and (p-tolyl)MgBr lead to Cp^OTiR₃ (R = PhCH₂ (5), Ph (6), p-tolyl (7)) containing a free pendant ether group. The X-ray structure of 6 shows a β-agostic Ti-H interaction between the metal center and a phenyl group (Ti-C_α-C_β = 139.3(3) and 105.3(2)°). Complex 1 reacts with 1.0 equiv of Li(O-2,6-^tBu₂-4- MeC₆H₂) to give the six-coordinate aryloxide derivative Cp^OTi(O-2,6-^tBu₂-4-MeC₆H ₂)Cl₂ (8), which has been also characterized by X-ray diffraction analysis. The structure suggests a significant multiple bond character for the Ti-aryloxide bond (Ti-O-C = 151.31(14)°). The addition of 1.0 and 2.0 equiv of MeMgCl to 8 affords Cp^OTiMe(O-2,6- ^tBu₂-4-MeC₆H₂)Cl (9) and Cp ^OTiMe₂(O-2,6-^tBu₂-4-MeC ₆H₂) (10). Treatment of 1 with 1.0, 2.0, and 3.0 equiv of Li(O-2,6-^tPr₂C₆H₃) gives rise to Cp^OTi(O-2,6-ⁱPr₂C₆H ₃)Cl₂ (11), Cp^OTi(O-2,6-ⁱPr ₂C₆H₃)₂Cl (12), and Cp ^OTi(O-2,6-ⁱPr₂C₆H₃) ₃ (13). Complex 11 reacts with 1.0 and 2.0 equiv of MeMgCl to afford Cp^OTiMe(O-2,6-ⁱPr₂C₆H ₃)Cl (14) and Cp^OTiMe₂(O-2,6- ⁱPr₂C₆H₃) (15), whereas the reaction of 12 with 1.0 equiv of MeMgCl leads to Cp^OTiMe(O-2,6- ⁱPr₂C₆H₃)₂ (16). Complexes 15 and 16 can be also obtained by addition of 1.0 and 2.0 equiv of 2,6-diisopropylphenol to 4. Treatment of 4 with 1.0 and 2.0 equiv of 1,1-diphenyl-2-propyn1-ol gives the propargyloxide derivatives Cp ^OTiMe₂(OCPh₂C≡CH) (17) and Cp ^OTiMe(OCPh₂C≡CH)₂ (18). Like 5-7, complexes 8-18 contain a free pendant ether group. Complex 4 is a more efficient catalyst precursor than the related CpTiMe₃ (19) for the regioselective anti-Markovnikov hydroamination of phenylacetylene with cyclohexylamine, 2,6-dimethylaniline, tert-butylamine, and 2,6- diisopropylaniline and for the hydroamination of 1-phenylpropyne and diphenylacetylene with cyclohexylamine and 2,6-dimethylaniline.

Full text of DOI:10.1021/om051031b

1448
Organometallics 2006, 25, 1448-1460
New Half-Sandwich Alkyl, Aryl, Aryloxide, and Propargyloxide
Titanium(IV) Complexes Containing a Cyclopentadienyl Ligand
with a Pendant Ether Substituent: Behavior and Influence in the
Hydroamination of Alkynes of the Ether Group
Miguel A. Esteruelas,* Ana M. Lo´pez,* A. Concepcio´n Mateo, and Enrique On˜ate
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
UniVersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
ReceiVed December 2, 2005
The complex CpOTiCl3 (1; CpO ) C5H4CH2CH2OCH3) reacts with 1.0, 2.0, and 3.0 equiv of MeMgCl
to give CpOTiMeCl2 (2), CpOTiMe2Cl (3), and CpOTiMe3 (4). In the solid state, the ether group of the
pendant substituent of the cyclopentadienyl ligand is coordinated to the metal center (d(Ti-O) ) 2.3373-
(18) Å in 2 and 2.2818(10) Å in 3) disposed transoid to a methyl ligand. In solution the O-donor substituent
is involved in a coordination-dissociation equilibrium (∆H° ) 3.0 ( 0.7 kcal mol-1 and ∆S° ) 12 (
4 cal mol-1 K-1 for 2, ∆H° ) 4.3 ( 0.1 kcal mol-1 and ∆S° ) 17.2 ( 0.1 cal mol-1 K-1 for 3, and ∆H°
) 2.3 ( 0.1 kcal mol-1 and ∆S° ) 11.9 ( 0.3 cal mol-1 K-1 for 4). The reactions of 1 with 3.0 equiv
of PhCH2MgCl, PhMgCl, and (p-tolyl)MgBr lead to CpOTiR3 (R ) PhCH2 (5), Ph (6), p-tolyl (7))
containing a free pendant ether group. The X-ray structure of 6 shows a â-agostic Ti-H interaction
between the metal center and a phenyl group (Ti-CR-Câ ) 139.3(3) and 105.3(2)°). Complex 1 reacts
with 1.0 equiv of Li(O-2,6-tBu2-4-MeC6H2) to give the six-coordinate aryloxide derivative CpOTi(O-
2,6-tBu2-4-MeC6H2)Cl2 (8), which has been also characterized by X-ray diffraction analysis. The structure
suggests a significant multiple bond character for the Ti-aryloxide bond (Ti-O-C ) 151.31(14)°).
The addition of 1.0 and 2.0 equiv of MeMgCl to 8 affords CpOTiMe(O-2,6-tBu2-4-MeC6H2)Cl (9) and
CpOTiMe2(O-2,6-tBu2-4-MeC6H2) (10). Treatment of 1 with 1.0, 2.0, and 3.0 equiv of Li(O-2,6-iPr2C6H3)
gives rise to CpOTi(O-2,6-iPr2C6H3)Cl2 (11), CpOTi(O-2,6-iPr2C6H3)2Cl (12), and CpOTi(O-2,6-iPr2C6H3)3
(13). Complex 11 reacts with 1.0 and 2.0 equiv of MeMgCl to afford CpOTiMe(O-2,6-iPr2C6H3)Cl (14)
and CpOTiMe2(O-2,6-iPr2C6H3) (15), whereas the reaction of 12 with 1.0 equiv of MeMgCl leads to
CpOTiMe(O-2,6-iPr2C6H3)2 (16). Complexes 15 and 16 can be also obtained by addition of 1.0 and 2.0
equiv of 2,6-diisopropylphenol to 4. Treatment of 4 with 1.0 and 2.0 equiv of 1,1-diphenyl-2-propyn-
1-ol gives the propargyloxide derivatives CpOTiMe2(OCPh2CtCH) (17) and CpOTiMe(OCPh2CtCH)2
(18). Like 5-7, complexes 8-18 contain a free pendant ether group. Complex 4 is a more efficient
catalyst precursor than the related CpTiMe3 (19) for the regioselective anti-Markovnikov hydroamination
of phenylacetylene with cyclohexylamine, 2,6-dimethylaniline, tert-butylamine, and 2,6-diisopropylaniline
and for the hydroamination of 1-phenylpropyne and diphenylacetylene with cyclohexylamine and 2,6-
dimethylaniline.
geometry have been receiving special attention as a consequence
of their unique polymerization properties.4
Introduction
The subject of titanocenes, their synthesis, structural char-
acterization, and applications to catalysis, has been a very active
research area during the last two decades.1 In recent years,
however, a growing interest in monocyclopentadienyltitanium
complexes has been evident.2 This is in part due to the fact that
the most active transition-metal catalysts are those containing
the lowest number of valence electrons.3 Within the half-
sandwich titanium chemistry, complexes with constrained
A variety of systems based upon alkoxide or aryloxide ligands
have been also examined.5 Reactions that form new carbon-
carbon bonds from organic unsaturated compounds such as
alkynes and olefins have advanced by the application of titanium
alkoxide complexes.6 In addition, half-sandwich O-2,6-iPr2C6H3
species have shown an exceptionally high catalytic activity not
only for ethylene polymerization but also for ethylene-R-olefin
(3) (a) Chaloner, P. A.; Esteruelas, M. A.; Joo´, F.; Oro, L. A.
Homogeneous Hydrogenation; Kluwer Academic: Dordrecht, The Neth-
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A.; Oro, L. A. J. Mol. Catal. A: Chem. 1995, 96, 231. (c) Esteruelas, M.
A.; Oro, L. A. Chem. ReV. 1998, 98, 577. (d) van Leeuwen, P. W. N. M.
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1999, 38, 428. (c) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003,
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* To whom correspondence should be addressed. E-mail: maester@
posta.unizar.es; amlopez@unizar.es.
(1) (a) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255. (b)
Hoveyda, A. H.; Morken, J. P. Angew. Chem., Int. Ed. Engl. 1996, 35,
1262. (c) Petasis, N. A.; Hu, Y.-H. Curr. Org. Chem. 1997, 1, 249. (d)
Gansa¨uer, A. Synlett 1998, 801. (e) Resconi, L.; Cavallo, L.; Fait, A.;
Piemontesi, F. Chem. ReV. 2000, 100, 1253. (f) Kulinkovich, O. G.; de
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Organometallics 2005, 24, 2548.
10.1021/om051031b CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/11/2006

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1449
copolymerization in the presence of methylaluminoxane (MAO).7
Furthermore, half-sandwich titanium alkoxide complexes have
been used as models and starting points for the synthesis of
peripheral metal dendrimers.8
Complexes with an ether pendant group are much more scarce
than the related N-functionalized compounds.9d,14 As far as we
know, only a few trichloro derivatives have been reported,15
and alkyl, aryl, and alkoxide complexes are unknown. In the
presence of MAO, some of them exhibit a modest activity for
styrene and ethylene polymerizations.16 The low activity has
been attributed to an oxygen-aluminum coordination, which
could decrease the ability of MAO to abstract an anionic ligand
from titanium, and/or to the increase of steric hindrance around
the catalytic center as a result of the coordination of the ether
pendant group to titanium.
In comparison with the systems with constrained geometry,
complexes containing a cyclopentadienyl ligand with a two-
electron-donor pendant group remain an underrepresented area
within the half-sandwich group 4 metal complexes.9 Due to the
reversible coordination of the pendant group, these types of
ligands stabilize highly reactive electrophilic centers until the
substrates coordinate and replace the pendant group. The
stabilizing effect has a strong influence on the catalytic
properties of the active systems.10 For instance, the complex
CpNTiCl3 (CpN ) C5H4CH2CH2NMe2)11 is an active precursor
in Ziegler-Natta polymerization catalysis.12 The amino group
affects significantly its catalytic reactivity as compared to that
of the parent complex CpTiCl3.13 Thus, the CpNTiCl3-MAO
system shows a considerably lower activity toward styrene and
a significantly higher activity toward ethylene and propylene
than CpTiCl3-MAO.
Although the influence of the pendant groups on the catalytic
activity of these systems is evident, studies on their behavior
in the solid state and in solution are rare in the chemistry of
group 4 metals.15c,e,17 As a part of our work on transition-metal
complexes containing a cyclopentadienyl ligand with a pendant
donor group,18 we have recently reported the preparation of
CpNTiMexCl3-x (x ) 1-3), CpNTiCl(µ-O)2ClTiCpN, and {(2,6-
iPr2C6H3)NH}CpNTi{N(2,6-iPr2C6H3)} (CpN ) C5H4CH2CH2-
NMe2). In the solid state the aminoalkyl substituent of
CpNTiMexCl3-x is weakly bonded to the metal center, disposed
transoid to a methyl ligand. In solution the amine dissociates
and an equilibrium between seven-coordinate and six-coordinate
species is reached. The molar fraction of dissociated amine
increases as the number of methyl ligands at the titanium also
increases. The amino groups of the dimer compound show a
similar behavior.19 Previously, van der Zeijden and co-workers
had proved that the intramolecular coordination of the ether
moiety in (η5-C5H4CH2CH2OR)TiCl3 (R ) Me, menthyl,
fenchyl) is also fluxional. From temperature-dependent NMR
data, they calculated that at room temperature in dichlo-
romethane-d2 about of 30% of the pendant group is coordinated
to titanium for R ) Me, while this figure is significantly lower
for the chiral substituents.15c In contrast to these systems, the
complex {(2,6-iPr2C6H3)NH}CpNTi{N(2,6-iPr2C6H3)} contains
a pendant dimethylamino group strongly coordinated to the
metal center both in the solid state and in solution.19 In this
paper, we report the preparation of the first titanium alkyl, aryl,
aryloxide, and propargyloxide complexes containing a (2-
methoxyethyl)cyclopentadienyl ligand and show the behavior
of their pendant ether group in the solid state and in solution.
Furthermore, as a continuation of our work on the development
of effective methods of C-N bond formation,20 we prove that
the complex CpOTiMe3 is a more efficient catalyst precursor
than the related compound CpTiMe3 (containing an unsubsti-
tuted cyclopentadienyl ligand) for the regioselective anti-
Markovnikov hydroamination of some alkynes.
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1450 Organometallics, Vol. 25, No. 6, 2006
Esteruelas et al.
Scheme 1
ligands around the metal center can be described as a four-
legged piano-stool geometry, with the cyclopentadienyl ring
occupying the three-membered face, while the oxygen atom of
the pendant group lies in the four-membered face disposed
transoid to the methyl ligand (C(1)-Ti-O ) 153.53(9)°). The
Ti-O bond length of 2.3373(18) Å is longer than those found
in the complexes {η5(C5),κ′O-[C5H4CH2CHCH2CH2CH2O]}-
TiCl3 (2.165(4) Å),15a 1 (about 2.214 Å),15b {η5(C5),κ’O-[C5-
Me4CH2CH2OCH3]}TiCl3 (2.295(2) Å),15e and {η5(C5),κ’O-
[C5H4CH(CH3)CH2OCH3]}TiCl3 (2.26(2) and 2.22(3) Å).15d
However, the Ti-C(1) distance (2.141(3) Å) is statistically
identical with the titanium-methyl separations in the complexes
CpNTiMeCl2 (2.144(3) Å) and CpNTiMe2Cl (2.150(5) Å trans
to N, 2.130(5) Å trans to Cl).19 The Ti-Cl bond lengths of
2.3114(18) Å (Ti-Cl(1)) and 2.307(2) Å (Ti-Cl(2)) compare
well with the related parameters in the aforementioned trichloro
derivatives (between 2.29 and 2.32 Å).
In solution, the pendant O-donor substituent of the cyclo-
pentadienyl ligand is involved in a coordination-dissociation
1
process (eq 1). This is strongly supported by the H and 13C-
Results and Discussion
1. Alkyl Derivatives. The addition of 1.0 equiv of MeMgCl
in tetrahydrofuran to a suspension of CpOTiCl3 (1) in diethyl
ether produces the selective substitution of one of the chloride
ligands of 1 by a methyl group and the formation of the
monomethyl derivative CpOTiMeCl2 (2), which is isolated as a
brown solid in 40% yield, according to Scheme 1.
Figure 1 gives a view of the molecular geometry of 2, whereas
selected bond distances and angles are listed in Table 1. The
structure proves the coordination of the ether pendant group to
the titanium atom, in the solid state. Thus, the distribution of
{1H} NMR spectra in toluene-d8, which are temperature
dependent. Figure 2 gives the 1H NMR spectrum as a function
of the temperature. At 333 K, the spectrum contains two
cyclopentadienyl resonances at 6.09 and 6.02 ppm, two triplets
(JH-H ) 6.0 Hz) for the pendant chain protons at 3.11 (CH2O)
and 2.38 ppm (CH2Cp), and singlets at 3.08 (OMe) and 1.75
ppm (TiMe) corresponding to the methyl groups of the molecule.
Lowering the sample temperature produces an increase of the
separation between the cyclopentadienyl resonances, which at
203 K appear at 6.15 and 5.75 ppm, whereas the triplets due to
the pendant chain protons are shifted toward higher field as the
temperature decreases. At 203 K, they are observed at 2.48
(CH2O) and 1.35 ppm (CH2Cp). On the other hand, both methyl
resonances are shifted toward lower field. At 203 K, the OMe
singlet appears at 3.26 ppm, whereas the TiMe resonance is
observed at 1.94 ppm.
Figure 1. Molecular diagram of CpOTiMeCl2 (2).
Table 1. Selected Bond Distances (Å) and Angles (deg) for
the Complex CpOTiMeCl2 (2)
(20) (a) Esteruelas, M. A.; Go´mez, A. V.; Lahoz, F. J.; Lo´pez, A. M.;
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Zeier, B. J. Chem. Soc., Dalton Trans. 1997, 181. (c) Esteruelas, M. A.;
Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E. Organometallics 1998, 17, 3567.
(d) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E.; Ruiz, N.
Organometallics 1999, 18, 1606. (e) Bernad, D. J.; Esteruelas, M. A.; Lo´pez,
A. M.; Modrego, J.; Puerta, M. C.; Valerga, P. Organometallics 1999, 18,
4995. (f) Bernad, D. J.; Esteruelas, M. A.; Lo´pez, A. M.; Oliva´n, M.; On˜ate,
E.; Puerta, M. C.; Valerga, P. Organometallics 2000, 19, 4327. (g) Baya,
M.; Crochet, P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20,
240. (h) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001,
20, 2294. (i) Buil, M. L.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2003, 22, 162. (j) Buil, M. L.; Esteruelas, M. A.; Lo´pez,
A. M.; On˜ate, E. Organometallics 2003, 22, 5274. (k) Asensio, A.; Buil,
M. L.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004, 23, 5787. (l)
Baya, M.; Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2005, 24, 1225. (m) Esteruelas, M. A.; Lo´pez, A. M.
Organometallics 2005, 24, 3584.
Ti-Cl(1)
Ti-Cl(2)
Ti-C(1)
Ti-O
Ti-C(4)
Ti-C(5)
Ti-C(6)
2.3114(18)
2.307(2)
2.141(3)
2.3373(18)
2.351(2)
2.336(6)
2.340(7)
Ti-C(7)
Ti-C(8)
C(2)-C(3)
C(3)-C(4)
O-C(2)
2.391(7)
2.373(6)
1.561(5)
1.501(3)
1.377(5)
1.441(3)
O-C(9)
C(1)-Ti-Cl(1)
C(1)-Ti-Cl(2)
C(1)-Ti-O
88.4(2)
85.2(2)
Cl(2)-Ti-Ma
O-Ti-M
Ti-O-C(2)
Ti-O-C(9)
C(2)-O-C(9)
O-C(2)-C(3)
C(2)-C(3)-C(4)
118.8
99.9
153.53(9)
106.5
120.33(3)
79.30(15)
119.9
116.8(2)
121.53(15)
114.4(3)
106.2(4)
109.0(3)
C(1)-Ti-M
Cl(1)-Ti-Cl(2)
Cl(1)-Ti-O
Cl(1)-Ti-M
Cl(2)-Ti-O
81.13(16)
a M represents the midpoint of the C(4)-C(8) Cp ligand.

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1451
Figure 3. Molecular diagram of CpOTiMe2Cl (3).
Table 2. Selected Bond Distances (Å) and Angles (deg) for
the Complex CpOTiMe2Cl (3)
Ti-Cl
2.3439(5)
Ti-C(8)
Ti-C(9)
O-C(3)
O-C(10)
C(5)-C(4)
C(4)-C(3)
2.3588(16)
2.3374(16)
1.4493(18)
1.4395(18)
1.497(2)
Ti-C(1)
Ti-C(2)
Ti-O
2.1344(17)
2.1345(17)
2.2818(10)
2.3406(15)
2.3659(15)
2.3787(15)
Ti-C(5)
Ti-C(6)
Ti-C(7)
1.506(2)
C(1)-Ti-Cl
C(1)-Ti-C(2)
C(1)-Ti-O
C(1)-Ti-M
Cl-Ti-C(2)
Cl-Ti-O
123.33(5)
82.74(8)
81.94(6)
110.4
87.99(5)
79.65(3)
125.6
C(2)-Ti-Ma
O-Ti-M
107.1
101.8
Ti-O-C(3)
116.78(9)
121.24(9)
111.07(12)
106.58(13)
110.14(13)
Ti-O-C(10)
C(3)-O-C(10)
O-C(3)-C(4)
C(3)-C(4)-C(5)
Cl-Ti-M
C(2)-Ti-O
150.47(6)
a M represents the midpoint of the C(5)-C(9) Cp ligand.
The distribution of ligands around the metal center is similar
to that of 2, with the methyl ligands disposed mutually cisoid
(C(1)-Ti-C(2) ) 82.74(8)°) and the pendant ether group
disposed transoid to C(2) (C(2)-Ti-O ) 150.47(6)°). The Ti-
C(1) (2.1344(17) Å) and Ti-C(2) distances (2.1345(17) Å) are
statistically identical with the related parameter in 2. However,
the Ti-Cl bond length of 2.3439(5) Å is about 0.03 Å longer
than the Ti-Cl separations in the latter. On the other hand, the
Ti-O distance of 2.2818(10) Å is about 0.05 Å shorter than
that in the monomethyl derivative.
Figure 2. Variable-temperature 1H NMR spectra for complex CpO-
TiMeCl2 (2) (toluene-d8). Asterisks denote residual solvent peaks.
For the process shown in eq 1, the equilibrium constants
between 333 and 203 K were determined according to eq 2.21
δ
min(CpCH2) - δ(CpCH2)
[b]
[a]
K )
)
)
δ(CpCH2) - δmax(CpCH2)
min(CH2O) - δ(CH2O)
In solution, the pendant O-donor substituent of the cyclopenta-
dienyl ligand of 3 is also involved in a coordination-dissociation
process like that shown in eq 1. In agreement with this, the
δ
(2)
δ(CH2O) - δmax(CH2O)
1
behavior of the H and 13C{1H} NMR spectra of 3 with the
temperature is similar to that described for 2. In this case, the
temperature dependence of the equilibrium gives the values ∆H°
The temperature dependence of the equilibrium gives the
values ∆H° ) 3.0 ( 0.7 kcal mol-1 and ∆S° ) 12 ( 4 cal
mol-1 K-1. The positive value of ∆S° is in agreement with the
free character of the pendant group in 2b, whereas the low value
of ∆H° indicates a weak Ti-O bond in 2a.
Treatment of 1 with 2.0 equiv of MeMgCl produces the
substitution of two chloride ligands of the starting compound
by methyl groups and the formation of the dimethyl derivative
CpOTiMe2Cl (3), which is isolated as a red solid in 50% yield
(Scheme 1).
Like 2, complex 3 has been characterized in the solid state
by X-ray diffraction analysis. The structure proves that, in this
case, the pendant group also coordinates to the titanium atom.
Figure 3 gives a view of the molecular geometry. Selected bond
distances and angles are collected in Table 2.
) 4.3 ( 0.1 kcal mol-1 and ∆S° ) 17.2 ( 0.1 cal mol-1 K-1
.
The addition of 3.0 equiv of MeMgCl to a diethyl ether
suspension of 1 produces the substitution of the three chloride
ligands of the starting complex by methyl groups. As a result,
the trimethyl derivative CpOTiMe3 (4) is formed, according to
Scheme 1. Complex 4 is isolated as an orange oil in 89% yield.
In solution, the behavior of the pendant O-donor group of 4 is
1
like that of 2 and 3. In accordance with this, the H and 13C-
{1H} NMR spectra of 4 are also temperature dependent and
completely analogous to those of 2 and 3. The values of the
parameters ∆H° and ∆S°, obtained from the temperature
dependence of the equilibrium, are 2.3 ( 0.1 kcal mol-1 and
11.9 ( 0.3 cal mol-1 K-1, respectively.
According to the values of ∆H° and ∆S° calculated for 2-4,
the molar fraction of hexacoordinate form b at 20 °C in toluene-
d8 increases in the sequence 2 (0.71) < 3 (0.78) < 4 (0.88), as
(21) Dalling, D. K.; Zilm, K. W.; Grant, D. M.; Heeschen, W. A.; Horton,
W. J.; Pugmire, R. J. J. Am. Chem. Soc. 1981, 103, 4817.

1452 Organometallics, Vol. 25, No. 6, 2006
Esteruelas et al.
Scheme 2
the chloride ligands at the titanium atom are replaced by methyl
groups. This appears to be a consequence of the steric hindrance
experienced by the ether group and the methyl ligands, when
they are disposed mutually cisoid. In agreement with this, the
treatment of 1 in diethyl ether with 3.0 equiv of PhCH2MgCl
(bulkier than CH3) affords the six-coordinate complex CpOTi-
(CH2Ph)3 (5), containing a free ether pendant group, which was
isolated as a red oil in 80% yield, according to eq 3.
The free character of the ether substituent of the cyclopen-
tadienyl ligand of 5 in solution is strongly supported by the 1H
and 13C{1H} NMR spectra of this compound in toluene-d8,
which, in contrast to those of 2-4, are temperature invariant
aryl ligand, they show a marked difference. While the Ti-C(9)-
C(10) angle is 139.3(3)°, the Ti-C(9)-C(14) angle is 105.3(2)°.
The shortening of the Ti-C(9) bond length, with regard to the
1
between 293 and 193 K. The H NMR spectrum shows the
phenyl resonances between 7.15 and 6.77 ppm, two cyclopen-
tadienyl signals at 5.66 and 5.49 ppm, two triplets (6.0 Hz) for
the pendant chain protons at 3.12 (CH2O) and 2.14 ppm (CH2-
Cp), and singlets at 3.01 and 2.96 ppm corresponding to the
OCH3 and TiCH2 protons, respectively. In the 13C{1H} NMR
spectrum, the most noticeable resonance is a singlet at 92.2 ppm
due to the TiC carbon atoms.
We note that the pentamethylcyclopentadienyl tribenzyl
derivative (η5-C5Me5)Ti(CH2Ph)3 has been previously reported.
Its structure, determined by X-ray diffraction analysis, suggests
that one of the benzyl groups is involved in an R-agostic Ti‚‚
‚H interaction. However, the 1H NMR spectrum of the complex,
as that of 5, shows resonances for only one type of benzyl
ligand, even at -70 °C.22
2. Aryl Derivatives. Complex 1 also reacts with PhMgCl.
Its treatment in diethyl ether at -50 °C with 3.0 equiv of the
organomagnesium reagent leads to the triaryl derivative CpO-
TiPh3 (6), which is isolated at -78 °C as greenish yellow
crystals in 40% yield, according to Scheme 2.
A view of the molecular geometry of 6 is shown in Figure 4.
Selected bond distances and angles are listed in Table 3. The
structure proves that in the solid state the pendant ether
substituent of the cyclopentadienyl ligand is not coordinated to
the titanium atom. Thus, the geometry around the metal center
can be described as a very distorted octahedron, with the
cyclopentadienyl group occupying a face. The distortion is
revealed by the C(9)-Ti-C(15) (104.47(13)°), C(9)-Ti-C(21)
(108.79(14)°) and C(15)-Ti-C(21) (102.23(13)°) angles, which
strongly deviate from the ideal value of 90°.
Without a shadow of a doubt, the most noticeable features
of the structure are the parameters related to the C(9)-aryl ligand.
The Ti-C(9) bond length of 2.079(3) Å is about 0.04 Å shorter
than the Ti-C(21) distance (2.125(3) Å) and about 0.05 Å
shorter than the Ti-C(15) separation (2.131(4) Å). Both Ti-
CR-Câ angles for the C(21)- and C(15)-aryl groups show very
similar values, between 118 and 124°. However, for the C(9)-
Figure 4. Molecular diagram of CpOTiPh3 (6).
Table 3. Selected Bond Distances (Å) and Angles (deg) for
the Complex CpOTiPh3 (6)
Ti-C(9)
2.079(3)
2.131(4)
2.125(3)
2.388(3)
2.372(3)
2.349(4)
2.331(3)
2.356(3)
1.515(4)
C(6)-C(7)
O-C(7)
1.515(4)
1.411(4)
1.408(4)
2.65
3.47
3.14
3.14
3.06
3.21
Ti-C(15)
Ti-C(21)
Ti-C(1)
Ti-C(2)
Ti-C(3)
Ti-C(4)
Ti-C(5)
C(1)-C(6)
O-C(8)
Ti-H(14)
Ti-H(10)
Ti-H(16)
Ti-H(20)
Ti-H(22)
Ti-H(26)
C(9)-Ti-C(15)
C(9)-Ti-C(21)
C(9)-Ti-Ma
C(15)-Ti-C(21)
C(15)-Ti-M
C(21)-Ti-M
C(8)-O-C(7)
O-C(7)-C(6)
104.47(13)
108.79(14)
114.5
102.23(13)
112.4
113.4
110.9(3)
109.3(3)
C(7)-C(6)-C(1)
Ti-C(9)-C(10)
Ti-C(9)-C(14)
Ti-C(15)-C(16)
Ti-C(15)-C(20)
Ti-C(21)-C(22)
Ti-C(21)-C(26)
111.0(3)
139.3(3)
105.3(2)
121.5(3)
122.6(3)
118.6(3)
124.3(3)
(22) Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio,
A. J. Chem. Soc., Chem. Commun. 1986, 1118.
a M represents the midpoint of the C(1)-C(5) Cp ligand.

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1453
Scheme 3
Ti-C(21) and Ti-C(15) distances, and the reduction of the Ti-
C(9)-C(14) angle, with regard to the expected value of about
120°, allows the approach of H(14) to the metal atom to establish
a â-agostic Ti‚‚‚H interaction. The Ti-H(14) separation of 2.65
Å compares well with the values reported for other Ti-H agostic
interactions.22,23
Although the agostic interaction is clearly evident in the
crystal structure, no evidence is observed in solution. Thus, in
dichloromethane at 183 K, the 13C NMR spectrum shows four
aryl resonances at 198.3 (TiC), 132.1 (HCmeta), 129.2 (HCpara),
and 126.1 ppm (HCortho) with H-C coupling constants of 156
Hz in the three cases. In the 1H NMR spectrum, the cyclopen-
tadienyl resonances are consistent with the free character of the
pendant ether substituent and agree well with those of 5. The
C5H4 protons display two signals at 6.76 and 6.58 ppm and the
pendant chain protons give rise to triplets (6.0 Hz) at 3.39
(CH2O) and 2.32 ppm (CH2Cp), whereas the MeO singlet
appears at 3.21 ppm.
Complex 6 is notable, because is a rare example of a half-
sandwich triaryl derivative in the chemistry of the group 4
metals. As far as we know, titanium complexes of this type
have not been previously reported. In addition, it should be
mentioned that its stability is very low, significantly lower than
that of the trialkyl derivatives 4 and 5. In the solid state and in
solution, complex 6 rapidly decomposes to give a complex
mixture of unidentified species.
significant multiple character for the Ti-O bond due to the
π-donor power of the oxygen atom.25 The π-donation from the
The introduction of a methyl substituent in the phenyl groups,
disposed in a para position with regard to the titanium atom,
produces a slight increase in the stability of the system. Thus,
the treatment of 1 in diethyl ether at -50 °C with 3.0 equiv of
(p-tolyl)MgBr leads to CpOTi(p-tolyl)3 (7 in Scheme 2), which
is isolated as a green oil in 37% yield and, in contrast to 6, can
be characterized at room temperature by 1H NMR spectroscopy.
The spectrum is temperature invariant, agrees well with that of
6, and supports the free character of the pendant ether group.
The C5H4 signals appear at 6.74 and 6.59 ppm, the pendant
chain protons give rise to triplets (6.0 Hz) at 3.45 (CH2O) and
2.43 (CH2Cp) ppm, and the MeO singlet is observed at 3.29
ppm. As in 6, the 13C{1H} NMR spectrum of 7 is temperature
invariant and does not show any evidence for a â-agostic Ti-H
interaction in solution. Thus, the aryl groups give rise to four
resonances, which are observed at 197.8 (TiCR), 139.1 (CH3Cδ),
133.5 (Cγ), and 127.5 (Câ) ppm.
3. Aryloxide Derivatives. Treatment of 1 in diethyl ether
with 1.0 equiv of Li(O-2,6-tBu2-4-MeC6H2) produces the
replacement of one of the chloride ligands of 1 by the aryloxide
group to afford CpOTi(O-2,6-tBu2-4-MeC6H2)Cl2 (8), which is
isolated as a red solid in 76% yield, according to Scheme 3.
The use of 2.0 or 3.0 equiv of aryloxide reagent does not give
rise to the substitution of more chloride ligands of the starting
compound.
Figure 5. Molecular diagram of CpOTi(O-2,6-tBu2-4-MeC6H2)-
Cl2 (8).
Table 4. Selected Bond Distances (Å) and Angles (deg) for
the Complex CpOTi(O-2,6-tBu2-4-MeC6H2)Cl2 (8)
Complex 8 has been characterized by X-ray diffraction
analysis. Figure 5 shows a view of its molecular geometry,
whereas Table 4 collects selected bond distances and angles.
In agreement with the request for space of the aryloxide ligand,
the structure shows that in the solid state the pendant ether
substituent of the cyclopentadienyl ligand is not coordinated to
the titanium atom. Thus, the geometry around the metal center
can be described as a distorted octahedron, with the cyclopen-
tadienyl group occupying a face and Cl(1)-Ti-Cl(2), Cl(1)-
Ti-O(1), and Cl(2)-Ti-O(1) angles of 98.09(3), 104.92(5),
and 104.74(5)°, respectively, in the opposite face. The Ti-O(1)
bond length of 1.7946(15) Å compares well with those found
in other alkoxide compounds,5,24 and it is consistent with a
Ti-Cl(1)
Ti-Cl(2)
Ti-O(1)
O(1)-C(9)
Ti-C(1)
Ti-C(2)
Ti-C(3)
2.2546(8)
2.2618(8)
1.7946(15)
1.378(2)
2.354(2)
2.347(2)
2.331(2)
Ti-C(4)
2.330(2)
2.335(2)
1.491(3)
1.516(3)
1.399(3)
1.419(3)
Ti-C(5)
C(1)-C(6)
C(6)-C(7)
O(2)-C(7)
O(2)-C(8)
Cl(1)-Ti-Cl(2)
Cl(1)-Ti-O(1)
Cl(1)-Ti-M
Cl(2)-Ti-O(1)
Cl(2)-Ti-M
98.09(3)
104.92(5)
114.7
104.74(5)
115.1
O(1)-Ti-Ma
117.1
C(9)-O(1)-Ti
C(8)-O(2)-C(7)
O(2)-C(7)-C(6)
C(7)-C(6)-C(1)
151.31(14)
111.7(2)
108.3(2)
111.5(2)
a M represents the midpoint of the C(1)-C(5) Cp ligand.

1454 Organometallics, Vol. 25, No. 6, 2006
Esteruelas et al.
Scheme 4
oxygen atom into the titanium is also supported by the Ti-
O(1)-C(9) angle of 151.31(14)°, which is certainly greater than
that expected from a pyramidal oxygen atom. The Ti-Cl(1)
and Ti-Cl(2) distances of 2.2546(8) and 2.2618(8) Å, respec-
tively, are similar to those found in other half-sandwich titanium
dichloro aryloxide complexes.5a,7c However, they are between
0.05 and 0.06 Å shorter than those of 2 and 3. The difference
seems to be related to the fact that 8 possesses one ligand less
than 2 and 3.
In solution, the pendant ether group is also free. In agreement
with this, the 1H and 13C{1H} NMR spectra of 8 are temperature
invariant and fully consistent with those of 5-7. The C5H4
protons display two signals at 6.32 and 5.91 ppm, whereas the
pendant chain protons appear at 3.27 and 2.96 ppm and the
MeO singlet is observed at 2.98 ppm.
groups of 8 and 9 do not coordinate to the metal center. In
1
accordance with this, the H and 13C{1H} NMR spectra are
temperature invariant and fully consistent with those of 5-8.
The most noticeable spectroscopic feature of these compounds
is the presence of four C5H4 resonances, at 6.39, 5.90, 5.86,
and 5.57 ppm, in the 1H NMR spectrum of 9. This is a result of
the chirality of the metal center.
In contrast to the case for Li(O-2,6-tBu2-4-MeC6H2), the addi-
tion of 1.0, 2.0, and 3.0 equiv of Li(O-2,6-iPr2C6H3) to 1 in di-
ethyl ether produces the substitution of one, two, and three chlo-
ride ligands of the starting compound to afford the aryloxide der-
ivatives CpOTi(O-2,6-iPr2C6H3)Cl2 (11), CpOTi(O-2,6-iPr2C6H3)2Cl
(12), and CpOTi(O-2,6-iPr2C6H3)3 (13), which are isolated as a
reddish orange solid in 93% yield, a yellow oil in 45% yield,
and an orange oil in 35% yield, respectively, according to
Scheme 4. A comparison of the yields of these substitutions
clearly indicates that the difficulty of the replacement increases
as the number of substituted chloride ligands is augmented: i.e.,
as the steric hindrance around the metal center grows.
Similarly to 8, complex 11 reacts with 1.0 and 2.0 equiv of
MeMgCl to give CpOTiMe(O-2,6-iPr2C6H3)Cl (14) and CpO-
Complex 8 in diethyl ether reacts with 1.0 equiv of MeMgCl
to afford CpOTiMe(O-2,6-tBu2-4-Me-C6H2)Cl (9), as an orange
oil in 69% yield. The reaction of 8 with 2.0 equiv of MeMgCl
gives rise to CpOTiMe2(O-2,6-tBu2-4-MeC6H2) (10), as a yellow
oil in 60% yield. Complex 10 can be also obtained by addition
of 1.0 equiv of MeMgCl to 9 (Scheme 3). The pendant ether

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1455
Scheme 5
Figure 6. Molecular diagram of CpOTiMe(OCPh2CtCH)2 (18).
The alkynol 1,1-diphenyl-2-propyn-1-ol contains two rela-
tively acidic protons, the H-C(sp) and H-OC hydrogen atoms.
Thus, at first glance, the reactions with 4 could afford 17 and
18 or alternatively alkynyl derivatives. Titanium-alkynyl
complexes are known,26 and the formation of alkynyl derivatives
by protonation of Bro¨nsted bases with terminal alkynes,
including alkynols, is a broadly studied process in late-transition-
metal chemistry.27 The obtained products from the reactions of
4 with 1,1-diphenyl-2-propyn-1-ol is a new, very nice illustration
of the differences in behavior between early and late transition
metals. The formation of 17 and 18 instead of alkynyl species
is a consequence of the greater energy of the Ti-O bond with
regard to the Ti-C bond.28
TiMe2(O-2,6-iPr2C6H3) (15), which are isolated as orange and
yellow oils in 84% and 98% yields, respectively. The reaction
of 12 with 1.0 equiv of MeMgCl leads to CpOTiMe(O-2,6-i-
Pr2C6H3)2 (16), as an orange oil in 69% yield. Complexes 15
and 16 can be also obtained by treatment of 4 with 1.0 and 2.0
equiv of 2,6-diisopropylphenol, respectively, in diethyl ether
at room temperature. The yields of these reactions, 94% for the
first of them and 55% for the second one, are consistent with
the yields of the reactions of 1 with Li(O-2,6-iPr2C6H3). The
addition of 3.0 equiv of 2,6-diisopropylphenol to 4 does not
give 13 but 16.
Complexes 11-16 are six-coordinate species with a free
1
pendant ether group. In agreement with this, the H and 13C-
Complexes 17 and 18, like 11-16, are six-coordinate species,
{1H} NMR spectra of these compounds are consistent with those
of 5-10 and are temperature invariant. The most noticeable
spectroscopic features are four C5H4 resonances between 6.24
and 5.68 ppm in the 1H NMR spectrum and between 117.8 and
115.5 ppm in the 13C{1H} NMR spectrum of the chiral complex
14.
1
with a free pendant ether group, and display H and 13C{1H}
1
NMR spectra consistent with those of 5-16. In the H NMR
spectra the most noticeable resonance is a singlet at 2.31 (17)
or 2.36 ppm (18), corresponding to the HC(sp) proton of the
propargyloxide ligands. In the 13C{1H} NMR spectra the
resonances due to the C(sp) atoms appear at about 86 (C) and
75 ppm (CH).
4. Propargyloxide Derivatives. Complex 4 also reacts with
1,1-diphenyl-2-propyn-1-ol (Scheme 5). The addition of 1.0
equiv of this alkynol to a tetrahydrofuran solution of 4 produces
the release of a methane molecule and the formation of CpO-
TiMe2(OCPh2CtCH) (17), which is isolated as a green oil in
94% yield. The reaction of 4 with 2.0 equiv of alkynol leads to
CpOTiMe(OCPh2CtCH)2 (18), as a light yellow solid in 42%
yield. The formation of a tripropargyloxide species by addition
of 3.0 equiv of 1,1-diphenyl-2-propyn-1-ol to 4 is not observed.
Complex 18 was further characterized by an X-ray crystal-
lographic study. Although a discussion of the structural param-
eters is not possible because of low precision of the crystallo-
graphic data (R1 ) 0.23), the structure (Figure 6) proves the
free character of the pendant ether group and the coordination
of the oxygen atom instead of the terminal C(sp) atom of the
monodentate unsaturated ligand.
5. Hydroamination of Alkynes Catalyzed by 4. The direct
addition of a N-H bond across a carbon-carbon triple bond
constitutes an atom-economical method for the synthesis of
nitrogen-containing molecules from inexpensive starting materi-
als.29 In this context, it should be pointed out that complex 4 is
a very efficient catalyst precursor for the regioselective anti-
Markovnikov hydroamination of phenylacetylene and 1-phe-
nylpropyne and the hydroamination of diphenylacetylene with
amines such as cyclohexylamine, 2,6-dimethylaniline, tert-
(23) See for example: (a) Olthof, G. J.; Van Bolhuis, F. J. Organomet.
Chem. 1976, 122, 47. (b) Dawoodi, Z.; Green, M. L. H.; Mtetwa, V. S. B.;
Prout, K. J. Chem. Soc., Chem. Commun. 1982, 802. (c) Cuenca, T.; Flores,
J. C.; Royo, P.; Larsonneur, A.-M.; Choukroun, R.; Dahan, F. Organome-
tallics 1992, 11, 777. (d) Mashima, K.; Nakamura, A. J. Organomet. Chem.
1992, 428, 49. (e) Pupi, R. M.; Coalter, J. N.; Petersen, J. L. J. Organomet.
Chem. 1995, 497, 17. (f) Scherer, W.; Priermeier, T.; Haaland, A.; Volden,
H. V.; McGrady, G. S.; Downs, A. J.; Boese, R.; Bla¨ser, D. Organometallics
1998, 17, 4406. (g) Scherer, W.; Hieringer, W.; Spiegler, M.; Sirsch, P.;
McGrady, G. S.; Downs, A. J.; Haaland, A.; Pedersen, B. Chem. Commun.
1998, 2471. (h) Dias, A. R.; Galva˜o, A. M.; Galva˜o, A. C. J. Organomet.
Chem. 2001, 632, 157. (i) Bouwkamp, M. W.; de Wolf, J.; del Hierro-
Morales, I.; Gercama, J.; Meetsma, A.; Troyanov, S. I.; Hessen, B.; Teuben,
J. H. J. Am. Chem. Soc. 2002, 124, 12956 (j) Basuli, F.; Bailey, B. C.;
Watson, L. A.; Tomaszewski, J.; Huffman, J. C.; Mindiola, D. J. Organo-
metalllics 2005, 24, 1886. (k) Basuli, F.; Bailey, B. C.; Huffman, J. C.;
Mindiola, D. J. Organometallics 2005, 24, 3321.
(26) (a) Krause, N.; Seebach, D. Chem. Ber. 1987, 120, 1845. (b)
Bharathi, P.; Periasamy, M. Organometallics 2000, 19, 5511.
(27) See for example: (a) Esteruelas, M. A.; Lahoz, F. J.; Oliva´n, M.;
On˜ate, E.; Oro, L. A. Organometallics 1995, 14, 3486. (b) Edwards, A. J.;
Esteruelas, M. A.; Lahoz, F. J.; Modrego, J.; Oro, L. A.; Schrickel, J.
Organometallics 1996, 15, 3556. (c) Esteruelas, M. A.; Oro, L. A.; Schrickel,
J. Organometallics 1997, 16, 796. (d) Esteruelas, M. A.; Oro, L. A. Coord.
Chem. ReV. 1999, 193-195, 557.
(24) Willoughby, C. A.; Duff, Jr., R. R.; Davis, W. M.; Buchwald, S. L.
Organometallics 1996, 15, 472.
(25) Huffman, J. C.; Moloy, K. G.; Marsella, J. A.; Caulton, K. G. J.
Am. Chem. Soc. 1980, 102, 3009.
(28) Clemmer, D. E.; Elkind, J. L.; Aristov, N.; Armentrout, P. B. J.
Chem. Phys. 1991, 95, 3387.

1456 Organometallics, Vol. 25, No. 6, 2006
Esteruelas et al.
Table 5. Hydroamination of Alkynes Using 4 and 19 as
Catalystsa
butylamine, and 2,6-diisopropylaniline. Complex 4 is signifi-
cantly more efficient than the related N-functionalized com-
pound CpNTiMe3.19 The reactions were performed in toluene
at 100 °C using 5 mol % of catalyst precursor. Under these
conditions the alkynes react with the amines to afford the
corresponding enamine-imine mixtures, which were trans-
formed in quantitative yield into the secondary amines by
reduction with molecular hydrogen in the presence of PtO2 (eq
4).
The pendant ether group certainly has a marked influence in
the reactivity of 4. This is clearly evident when the results of
the hydroamination in the presence of 4 are compared with those
in the presence of the parent complex CpTiMe3 (19), which
contains an unsubstituted cyclopentadienyl ligand (Table 5).
The hydroamination products from phenylacetylene are
obtained in high yield within a short time (0.16-8 h) and with
extremely high regioselectivity. Thus, pleasingly, the anti-
Markovnikov products are exclusively formed in all the cases.
The difference in efficiency between 4 and 19 is particularly
noteworthy in the reaction with 2,6-dimethylaniline (entries 3
and 4). Using complex 4 as catalyst precursor, 100% conversion
is reached after 2.5 h, while in the presence of 19 only 73% of
the alkyne is converted into hydroamination products after 8 h.
The catalyst precursor has also a marked influence on the
resulting molar ratio of enamine to imine. This is clearly shown
in the reactions with 2,6-diisopropylaniline (entries 7 and 8).
In the presence of 4, the enamine is the main hydroamination
product (73:27). However, the imine is the major derivative
obtained with 19 (15:85).
The replacement of the H-C(sp) hydrogen atom in the alkyne
by a methyl group facilitates the hydroamination of the carbon-
carbon triple bond, without affecting the regioselectivity of the
process. The reactions with 1-phenylpropyne are easier than
those with phenylacetylene, not only in the presence of 4 but
also with 19. Complex 4 is more efficient than 19 in reactions
involving sterically less demanding amines such as cyclohexy-
lamine (entries 9 and 10) and 2,6-dimethylaniline (entries 11
and 12). For the latter, complex 4 is even more efficient than
(29) (a) Mu¨ller, T. E.; Beller, M. Chem. ReV. 1998, 98, 675. (b) Nobis,
M.; Driessen-Ho¨lscher, B. Angew. Chem., Int. Ed. 2001, 40, 3983. (c)
Bytschkov, I.; Doye, S. Eur. J. Org. Chem. 2003, 935. (d) Pohlki, F.; Doye,
S. Chem. Soc. ReV. 2003, 32, 104. (e) Beller, M.; Seayad, J.; Tillack, A.;
Jiao, H. Angew. Chem., Int. Ed. 2004, 43, 3368. (f) Doye, S. Synlett 2004,
10, 1653. (g) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. ReV. 2004, 104,
3079. (h) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 673. (i) Odom,
A. L. Dalton Trans. 2005, 225.
(30) (a) Haak, E.; Bytschkov, I.; Doye, S. Angew. Chem., Int. Ed. 1999,
38, 3389. (b) Haak, E.; Siebeneicher, H.; Doye, S. Org. Lett. 2000, 2, 1935.
(c) Bytschkov, I.; Doye, S. Eur. J. Org. Chem. 2001, 4411. (d) Tillack, A.;
Garcia-Castro, I.; Hartung, C. G.; Beller, M. Angew. Chem., Int. Ed. 2002,
41, 2541. (e) Heutling, A.; Doye, S. J. Org. Chem. 2002, 67, 1961. (f)
Siebeneicher, H. Doye, S. Eur. J. Org. Chem. 2002, 1213. (g) Garcia-Castro,
I.; Tillack, A.; Hartung, C. G.; Beller, M. Tetrahedron Lett. 2003, 44, 3217.
(h) Bytschkov, I.; Siebeneicher, H.; Doye, S. Eur. J. Org. Chem. 2003,
2888. (i) Pohlki, F.; Bytschkov, I.; Siebeneicher, H.; Heutling, A.; Ko¨nig,
W. A.; Doye, S. Eur. J. Org. Chem. 2004, 1967. (j) Heutling, A.; Pohlki,
F.; Doye, S. Chem. Eur. J. 2004, 10, 3059.
a Reaction conditions: alkyne (2.40 mmol), amine (2.64 mmol), n-octane
(2.40 mmol), catalyst (0.12 mmol, 5 mol %), toluene (2.0 mL), 100 °C.
b Determined by GC. c Determined by 1H NMR spectroscopy at the end of
the reaction.
the bis(indenyl) derivative Ind2TiMe2, which has been regarded
a “general catalyst”.30 In the hydroamination with bulky amines,
the pendant ether group of the cyclopentadienyl ligand of 4 and
the substituents at the carbon-carbon triple bond of the internal
alkyne appear to experience a large steric hindrance. In
accordance with this, complex 19 is a more efficient catalyst

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1457
precursor than 4 for the reactions involving tert-butylamine and
2,6-diisopropylaniline.
The ether substituent of the cyclopentadienyl ligand influences
the catalytic properties of CpOTiMe3, which is more efficient
than the related compound CpTiMe3 containing an unsubstituted
cyclopentadienyl ligand for the regioselective anti-Markovnikov
hydroamination of phenylacetylene and internal alkynes with
cyclohexylamine and 2,6-dimethylaniline.
In conclusion, we have reported the preparation and charac-
terization of alkyl, aryl, aryloxide, and propargyloxide titanium
complexes containing the (2-methoxyethyl)cyclopentadienyl
ligand and analyzed the behavior of the pendant ether group of
the new complexes in the solid state and in solution. In addition,
we have shown that the introduction of an ether substituent in
the cyclopentadienyl ligand increases the efficiency of the
titanium cyclopentadienyl catalysts for the hydroamination of
alkynes, in particular for those reactions involving the sterically
less demanding substrates.
Despite the steric hindrance experienced between the pendant
ether group of the cyclopentadienyl ligand and the substituents
of the alkynes, complex 4 is also a very efficient catalyst
precursor for the hydroamination of diphenylacetylene, which
contains a sterically more demanding substituent at the carbon-
carbon triple bond than the methyl group. Thus, in this case
again, the hydroamination products are obtained in high yields
(60-100%) within a short time (1-8 h). As for the hydroami-
nation of 1-phenylpropyne, for the reactions with cyclohexy-
lamine (entries 17 and 18) and 2,6-dimethylaniline (entries 19
and 20) complex 4 is more efficient than 19. However, the latter
is more efficient than 4 for the reactions involving tert-
butylamine (entries 21 and 22) and 2,6-diisopropylaniline
(entries 23 and 24).
On the basis of kinetic studies half-sandwich imido com-
pounds of the type (RHN)CpTidNR have been proposed as
the active species for the hydroamination of alkynes in the
presence of titanium complexes containing η5 ligands.31 Under
the catalysis, two major dangers threaten the active species: the
reversible formation of tris(amide) derivatives, CpTi(NHR)3, and
the irreversible condensation of the catalysts into the dimers
(RHN)CpTi(µ-NR)2TiCp(NHR), which are catalytically inactive.
The higher efficiency of 4 with regard to 19 appears to be
related to the fact that the pendant ether substituent of the
cyclopentadienyl ligand of 4 exercises two protective effects
on the active species. It can prevent the formation of both the
tris(amide) and dimer compounds as a result of the reversible
coordination of the oxygen atom to the metal center and/or as
a consequence of its demand of space.
Experimental Section
General Methods and Instrumentation. All reactions were
carried out under argon with rigorous exclusion of air using
Schlenk-line or drybox techniques. Solvents were dried by the usual
procedures and distilled under argon prior to use. The starting mater-
ials CpOTiCl3 (1)15c and CpTiMe3 (19)32 were prepared by the pub-
lished methods. Diphenylacetylene was dissolved in CH2Cl2, dried
with Na2SO4, and recovered by evaporation of the solvent. Phenyl-
acetylene and 1-phenylpropyne were distilled, and amines were dis-
tilled from CaH2 and stored in the drybox. All other reagents were
purchased from commercial sources and were used without further
purification. The course of the catalytic reactions was followed using
a Hewlett-Packard 5890 series gas chromatograph with a flame
ionization detector, using a 100% cross-linked methylsilicone gum
column (30 m × 0.25 mm, with 0.25 µm film thickness) and
n-octane as the internal standard. The oven conditions used are as
follows: 35 °C (hold 6 min) to 280 °C at 25 °C/min (hold 5 min).
Concluding Remarks
1
This study has revealed that the pendant ether substituent of
the (2-methoxyethyl)cyclopentadienyl ligand (CpO) has a strong
influence on the stoichiometric and catalytic properties of its
derivatives and that its behavior in half-sandwich titanium(IV)
chemistry is determined by the coligands of the particular
compound.
The reaction products were identified by GC-MS and by H and
13C{1H} NMR spectroscopy. GC-MS experiments were run on an
Agilent 5973 mass selective detector interfaced to an Agilent 6890
series gas chromatograph system. Samples were injected into a 30
m × 250 µm HP-5MS 5% phenylmethylsiloxane column with a
film thickness of 0.25 µm (Agilent). The GC oven temperature was
programmed as follows: 35 °C for 6 min to 280 °C at 25 °C/min
for 5 min. The carrier gas was helium at a flow rate of 1 mL/min.
1H and 13C{1H} NMR spectra were recorded on a Varian UNITY
300, a Varian Gemini 2000, a Bruker AXR 300, or a Bruker Avance
400 MHz instrument. Chemical shifts (expressed in parts per
million) are referenced to residual solvent peaks). Coupling
constants, J, are given in hertz. C and H analyses were carried out
in a Perkin-Elmer 2400 CHNS/O analyzer.
Complex CpOTiCl3 reacts with 1.0, 2.0, and 3.0 equiv of
MeMgCl to afford the mono-, di-, and trimethyl derivatives CpO-
TiMeCl2, CpOTiMe2Cl, and CpOTiMe3, respectively. In the solid
state, the pendant ether group of these compounds is bonded to
the titanium atom, disposed transoid to a methyl ligand. In
solution the ether dissociates, and an equilibrium between six-
and seven-coordinate compounds is reached. The molar fraction
of the dissociated ether species increases as the steric hindrance
around the metal center grows. In agreement with this, the
reactions of CpOTiCl3 with 3.0 equiv of PhCH2MgCl, PhMgCl,
and (p-tolyl)MgBr lead to CpOTiR3 (R ) CH2Ph, Ph, p-tolyl),
with a free ether substituent in the solid state and in solution.
The X-ray structure of CpOTiPh3 shows clear evidence for a
â-hydrogen agostic interaction between the metal center and
one of the phenyl groups.
The pendant ether group is also free in the CpOTiX3-n(OAr)n
(X ) Cl, CH3; n ) 1-3) aryloxide and unprecedented
CpOTiMen(OCPh2CtCH)3-n (n ) 1, 2) propargyloxide com-
plexes. The X-ray structure of CpOTi(O-2,6-tBu2-4-MeC6H2)-
Cl2 suggests a significant multiple-bond character for the Ti-O
bond, in agreement with the π-donor power of the oxygen atom
of the aryloxide and propargyloxide ligands.
Preparation of CpOTiMeCl2 (2). To an orange suspension of
1 (500 mg, 1.80 mmol) in 20 mL of diethyl ether at -40 °C was
added dropwise 1.0 equiv of MeMgCl (0.60 mL, 1.80 mmol, 3 M
in tetrahydrofuran). After addition, the mixture was warmed slowly
to room temperature and stirred for 4 h. The volatiles were removed
under reduced pressure, and the residue was extracted with pentane
(3 × 50 mL). The resultant brown solution was concentrated to
ca. 3 mL, and a brown solid appeared, which was separated by
decantation, washed with 2 × 3 mL of pentane, and dried in vacuo.
Yield: 180 mg (40%). Anal. Calcd for C9H14Cl2OTi: C, 42.04;
1
H, 5.50. Found: C, 42.39; H, 5.51. H NMR (300 MHz, C7D8,
3
333 K): δ 6.09, 6.02 (both m, each 2H, C5H4), 3.11 (t, J ) 6.0,
3
2H, CH2O), 3.08 (s, 3H, OMe), 2.38 (t, J ) 6.0, 2H, C5H4CH2),
1
1.75 (s, 3H, TiMe). H NMR (300 MHz, C7D8, 203 K): δ 6.15,
5.75 (both m, each 2H, C5H4), 3.26 (br s, 3H, OMe), 2.48 (m, 2H,
CH2O), 1.94 (br s, 3H, TiMe), 1.35 (m, 2H, C5H4CH2). 13C{1H}
NMR (75.42 MHz, C7D8, 293 K, plus APT and HETCOR): δ 136.1
(31) (a) Johnson, J. S.; Bergman, R. G. J. Am. Chem. Soc. 2001, 123,
2923. (b) Pohlki, F.; Doye, S. Angew. Chem., Int. Ed. 2001, 40, 2305. (c)
Straub, B. F.; Bergman, R. G. Angew. Chem., Int. Ed. 2001, 40, 4632.
(32) Giannini, U.; Cesca, S. Tetrahedron Lett. 1960. 19.

1458 Organometallics, Vol. 25, No. 6, 2006
Esteruelas et al.
(Cipso C5H4), 119.6, 118.9 (C5H4), 79.5 (TiMe), 72.5 (CH2O), 58.7
(OMe), 30.3 (C5H4CH2). 13C{1H} NMR (75.42 MHz, C7D8, 213
K, plus APT): δ 136.4 (Cipso C5H4), 120.2, 118.5 (C5H4), 80.9
(TiMe), 75.2 (CH2O), 59.9 (OMe), 27.0 (C5H4CH2).
2H, C5H4CH2). 13C NMR (75.42 MHz, CD2Cl2, 183 K): δ 198.3
2
1
(t, JCH ) 6, Cipso Ph), 132.2 (m, Cipso C5H4), 132.1 (dt, JCH
)
156, 2JCH ) 6, m-Ph), 129.2 (dt, 1JCH ) 156, 2JCH ) 6, p-Ph), 126.1
1
2
(dd, JCH ) 156, JCH ) 6, o-Ph), 117.9, 115.6 (both m, C5H4),
1
1
Preparation of CpOTiMe2Cl (3). The same procedure described
for 2 was followed, except that 1 (500 mg, 1.80 mmol) and 2.0
equiv of MeMgCl (1.20 mL, 3.60 mmol, 3 M in tetrahydrofuran)
were used. The product was obtained as a red solid. Yield: 215
mg (50%). Anal. Calcd for C10H17ClOTi: C, 50.75; H, 7.25.
72.5 (t, JCH ) 142, CH2O), 58.2 (q, JCH ) 142, OMe), 30.7 (t,
1JCH ) 142, C5H4CH2).
Preparation of CpOTi(p-tolyl)3 (7). The same procedure
described for 6 was followed, except that 1 (496 mg, 1.79 mmol)
and 3.0 equiv of (p-tolyl)MgBr (5.40 mL, 5.37 mmol, 1 M in
tetrahydrofuran) were used. The product was obtained as a green
oil. Yield: 295 mg (37%). Anal. Calcd for C29H32OTi: C, 78.36;
1
Found: C, 51.05; H, 7.41. H NMR (300 MHz, C7D8, 333 K): δ
5.97, 5.91 (both m, each 2H, C5H4), 3.19 (m, 2H, CH2O), 3.09 (s,
3H, OMe), 2.36 (m, 2H, C5H4CH2), 1.30 (s, 6H, TiMe2). 1H NMR
(300 MHz, C7D8, 193 K): δ 6.07, 5.67 (both m, each 2H, C5H4),
3.20 (br s, 3H, OMe), 2.34 (m, 2H, CH2O), 1.44 (m, 2H, C5H4CH2),
1.29 (br s, 6H, TiMe2). 13C{1H} NMR (75.42 MHz, C7D8, 293 K,
plus APT and HETCOR): δ 132.3 (Cipso C5H4), 116.3, 115.2
(C5H4), 73.3 (CH2O), 68.9 (TiMe2), 58.6 (OMe), 30.0 (C5H4CH2).
13C{1H} NMR (75.42 MHz, C7D8, 213 K, plus APT): δ 133.3
(Cipso C5H4), 117.4, 114.2 (C5H4), 76.8 (CH2O), 68.5 (TiMe2), 60.4
(OMe), 27.4 (C5H4CH2).
1
H, 7.27. Found: C, 78.84; H, 7.79. H NMR (300 MHz, CD2Cl2,
293 K): δ 7.55, 7.00 (both d, 3J ) 7.5, 6H, CH3C6H4), 6.74, 6.59
3
(both m, each 2H, C5H4), 3.45 (t, J ) 6.0, 2H, CH2O), 3.29 (s,
3H, OMe), 2.43 (t, 3J ) 6.0, 2H, C5H4CH2), 2.31 (s, 9H, CH3C6H4).
13C{1H} NMR (75.42 MHz, CD2Cl2, 223 K, plus APT): δ 197.8
(Cipso C6H4), 139.1 (p-CH3C6H4), 133.5 (m-CH3C6H4), 135.0 (Cipso
C5H4), 127.5 (o-CH3C6H4), 117.7, 116.9 (C5H4), 73.5 (CH2O), 59.1
(OMe), 31.8 (C5H4CH2), 22.1 (p-CH3C6H4).
Preparation of CpOTi(O-2,6-tBu2-4-MeC6H2)Cl2 (8). To an
orange suspension of 1 (500 mg, 1.80 mmol) in 15 mL of diethyl
ether at -30 °C was added a precooled (-30 °C) solution of Li-
(O-2,6-tBu2-4-MeC6H2) (408 mg, 1.80 mmol) in 10 mL of diethyl
ether. After addition, the mixture was warmed slowly to room
temperature and stirred overnight. The mixture was filtered, and
the resultant red solution was concentrated to ca. 3 mL and kept at
-78 °C for 15 h. After that, a red solid appeared, which was
separated by decantation and dried in vacuo. Yield: 635 mg (76%).
Anal. Calcd for C23H34Cl2O2Ti: C, 59.88; H, 7.43. Found: C, 59.94;
H, 7.25. 1H NMR (300 MHz, C6D6, 293 K): δ 7.05 (s, 2H, C6H2),
6.32, 5.91 (both m, each 2H, C5H4), 3.27 (t, 3J ) 6.0, 2H, CH2O),
Preparation of CpOTiMe3 (4). The same procedure described
for 2 was followed, except that 1 (493 mg, 1.77 mmol) and 3.0
equiv of MeMgCl (1.78 mL, 5.33 mmol, 3 M in tetrahydrofuran)
were used. The product was obtained as an orange oil. Yield: 343
mg (89%). Anal. Calcd for C11H20OTi: C, 61.06; H, 9.37. Found:
1
C, 61.10; H, 9.34. H NMR (300 MHz, C7D8, 363 K): δ 5.91 (s,
4H, C5H4), 3.35 (t, 3J ) 6.0, 2H, CH2O), 3.12 (s, 3H, OMe), 2.49
3
1
(t, J ) 6.0, 2H, C5H4CH2), 1.14 (s, 9H, TiMe3). H NMR (300
MHz, C7D8, 183 K): δ 6.05, 5.59 (both m, each 2H, C5H4), 2.98
(br s, 3H, OMe), 2.49 (m, 2H, CH2O), 1.71 (m, 2H, C5H4CH2),
1.15 (br s, 9H, TiMe3). 13C{1H} NMR (75.42 MHz, C7D8, 293 K,
plus APT and HETCOR): δ 129.5 (Cipso C5H4), 113.5, 112.7
(C5H4), 73.2 (CH2O), 62.0 (TiMe3), 58.3 (OMe), 30.9 (C5H4CH2).
13C{1H} NMR (75.42 MHz, C7D8, 183 K, plus APT): δ 130.2
(Cipso C5H4), 114.3, 111.8 (C5H4), 75.0 (CH2O), 60.9 (TiMe3), 59.0
(OMe), 29.5 (C5H4CH2).
3
2.98 (s, 3H, OMe), 2.96 (t, J ) 6.0, 2H, C5H4CH2), 2.18 (s, 3H,
CH3C6H2), 1.47 (s, 18H, C(CH3)3). 13C{1H} NMR (75.42 MHz,
C6D6, 293 K, plus APT): δ 169.3 (Ti-O-C), 139.7 (o-C6H2), 138.7
(p-C6H2), 131.8 (Cipso C5H4), 126.3 (m-C6H2), 122.5, 120.6 (C5H4),
71.5 (CH2O), 58.0 (OMe), 35.7 (C(CH3)3), 31.8 (C(CH3)3), 30.2
(C5H4CH2), 21.0 (CH3C6H2).
Preparation of CpOTi(CH2Ph)3 (5). The same procedure
described for 2 was followed, except that 1 (419 mg, 1.51 mmol)
and 3.0 equiv of PhCH2MgCl (2.26 mL, 4.53 mmol, 2 M in
tetrahydrofuran) were used. The product was obtained as a red oil.
Yield: 536 mg (80%). Anal. Calcd for C29H32OTi: C, 78.36; H,
Preparation of CpOTiMe(O-2,6-tBu2-4-MeC6H2)Cl (9). To a
red solution of 8 (274 mg, 0.59 mmol) in 15 mL of diethyl ether
at -40 °C was added dropwise 1.0 equiv of MeMgCl (0.20 mL,
0.59 mmol, 3 M in tetrahydrofuran). After addition, the mixture
was warmed slowly to room temperature and stirred for 10 h. The
volatiles were removed under reduced pressure, and the residue
was extracted with pentane (2 × 25 mL). The resultant orange
solution was removed under vacuum, affording an orange oil.
Yield: 180 mg (69%). Anal. Calcd for C24H37ClO2Ti: C, 65.36;
1
7.27. Found: C, 78.22; H, 7.42. H NMR (300 MHz, C7D8, 293
K): δ 7.15-6.77 (m, 15H, Ph), 5.66, 5.49 (both m, each 2H, C5H4),
3.12 (t, 3J ) 6.0, 2H, CH2O), 3.01 (s, 3H, OMe), 2.96 (s, 6H, CH2-
3
1
Ph), 2.14 (t, J ) 6.0, 2H, C5H4CH2). H NMR (300 MHz, C7D8,
193 K): δ 7.22-6.76 (m, 15H, Ph), 5.57, 5.27 (both m, each 2H,
C5H4), 3.09 (br s, 5H, CH2O, OMe), 2.92 (br s, 6H, CH2Ph), 1.82
(m, 2H, C5H4CH2). 13C{1H} NMR (75.42 MHz, C7D8, 293 K, plus
APT): δ 148.6 (Cipso Ph), 133.1 (Cipso C5H4), 128.8, 126.7, 122.9
(Ph), 118.0, 116.6 (C5H4), 92.2 (CH2Ph), 72.8 (CH2O), 58.2 (OMe),
30.4 (C5H4CH2). 13C{1H} NMR (75.42 MHz, C7D8, 233 K, plus
APT): δ 148.2 (Cipso Ph), 133.4 (Cipso C5H4), 128.8, 126.5, 122.9
(Ph), 118.1, 116.6 (C5H4), 91.9 (CH2Ph), 72.7 (CH2O), 58.2 (OMe),
30.2 (C5H4CH2).
1
H, 8.47. Found: C, 65.82; H, 9.08. H NMR (300 MHz, C6D6,
293 K): δ 7.10 (s, 2H, C6H2), 6.39, 5.90, 5.86, 5.57 (all m, each
1H, C5H4), 3.31 (t, 3J ) 6.3, 2H, CH2O), 3.04 (s, 3H, OMe), 2.85
3
(t, J ) 6.3, 2H, C5H4CH2), 2.22 (s, 3H, CH3C6H2), 1.64 (s, 3H,
TiMe), 1.45 (s, 18H, C(CH3)3). 13C{1H} NMR (75.42 MHz, C6D6,
293 K, plus APT): δ 166.2 (Ti-O-C), 139.5 (o-C6H2), 130.3 (p-
C6H2), 129.2 (Cipso C5H4), 126.1 (m-C6H2), 119.2, 117.5, 115.7,
(C5H4), 72.4 (CH2O), 67.4 (TiMe), 58.2 (OMe), 35.6 (C(CH3)3),
31.9 (C(CH3)3), 31.4 (C5H4CH2), 21.3 (CH3C6H2).
Preparation of CpOTiPh3 (6). An orange suspension of 1 (315
mg, 1.13 mmol) in 18 mL of diethyl ether was treated with 3.0
equiv of PhMgCl (1.70 mL, 3.41 mmol, 2 M in tetrahydrofuran)
added dropwise at -50 °C. After addition, the mixture was stirred
for 4 h at -30 °C. The volatiles were removed under reduced
pressure, and the residue was extracted with pentane (4 × 40 mL).
The resultant yellow solution was concentrated to ca. 3 mL and
kept at -78 °C for 15 h. After that, a greenish yellow solid
appeared, which was separated by decantation and dried in vacuo.
Yield: 182 mg (40%). Anal. Calcd for C26H26OTi: C, 77.60; H,
6.52. Found: C, 77.33; H, 6.55. 1H NMR (300 MHz, CD2Cl2, 183
K): δ 7.61-7.14 (m, 15H, Ph), 6.76, 6.58 (both m, each 2H, C5H4),
3.39 (t, 3J ) 6.0, 2H, CH2O), 3.21 (s, 3H, OMe), 2.32 (t, 3J ) 6.0,
Preparation of CpOTiMe2(O-2,6-tBu2-4-MeC6H2) (10). Method
1. The same procedure described for 9 was followed, except that 8
(267 mg, 0.58 mmol) and 2.0 equiv of MeMgCl (0.38 mL, 1.16
mmol, 3 M in tetrahydrofuran) were used. The product was obtained
as a yellow oil. Yield: 146 mg (60%).
Method 2. The same procedure described for 9 was followed,
except that 9 (70 mg, 0,16 mmol) and 1.0 equiv of MeMgCl (0.05
mL, 0.16 mmol, 3 M in tetrahydrofuran) were used. Yield: 50 mg
(75%). Anal. Calcd for C25H40O2Ti: C, 71.40; H, 9.61. Found: C,
71.33; H, 9.82. 1H NMR (300 MHz, C7D8, 293 K): δ 7.08 (s, 2H,
3
C6H2), 5.99, 5.59 (both m, each 2H, C5H4), 3.36 (t, J ) 6.0, 2H,
CH2O), 3.01 (s, 3H, OMe), 2.70 (t, 3J ) 6.0, 2H, C5H4CH2), 2.24

Ti(IV) (2-Methoxyethyl)cyclopentadienyl Complexes
Organometallics, Vol. 25, No. 6, 2006 1459
(s, 3H, CH3C6H2), 1.40 (s, 18H, C(CH3)3), 0.95 (s, 6H, TiMe2).
13C{1H} NMR (75.42 MHz, C7D8, 293 K, plus APT): δ 164.7
(Ti-O-C), 139.5 (o-C6H2), 129.2 (p-C6H2), 129.1 (Cipso C5H4),
126.1 (m-C6H2), 116.1, 113.8 (C5H4), 73.5 (CH2O), 60.8 (TiMe2),
58.4 (OMe), 35.6 (C(CH3)3), 31.8 (C(CH3)3), 31.2 (C5H4CH2), 21.5
(CH3C6H2).
Method 2. An orange solution of 4 (250 mg, 1.16 mmol) in 10
mL of diethyl ether was treated with 1.0 equiv of HO(2,6-iPr2C6H3)
(206 mg, 1.16 mmol) at -15 °C. Immediately methane evolution
was observed. The mixture was warmed to room temperature and
stirred for 2 h. Then, the solvent was removed under vacuum.
Yield: 345 mg (79%). Anal. Calcd for C22H34O2Ti: C, 69.82; H,
1
Preparation of CpOTi(O-2,6-iPr2C6H3)Cl2 (11). The same
procedure described for 8 was followed, except that 1 (1090 mg,
3.93 mmol) and a solution of Li(O-2,6-iPr2C6H3) (720 mg, 3.93
mmol) were used. The product was obtained as a reddish orange
solid. Yield: 1.54 g (93%). Anal. Calcd for C20H28Cl2O2Ti: C,
9.07. Found: C, 69.65; H, 9.13. H NMR (300 MHz, C6D6, 293
K): δ 7.12-6.96 (m, 3H, C6H3), 5.96, 5.77 (both m, each 2H,
C5H4), 3.36 (sept, 3J ) 6.9, 2H, CH(CH3)2), 3.27 (t, 3J ) 6.6, 2H,
CH2O), 3.02 (s, 3H, OMe), 2.58 (t, 3J ) 6.6, 2H, C5H4CH2), 1.24
(d, 3J ) 6.9, 12H, CH(CH3)2), 0.94 (s, 6H, TiMe2). 13C{1H} NMR
(75.42 MHz, C6D6, 293 K, plus APT): δ 160.9 (Ti-O-C), 138.1
(o-C6H3), 129.2 (Cipso C5H4), 123.4 (m-C6H3), 122.3 (p-C6H3), 113.4,
112.9 (C5H4), 72.9 (CH2O), 58.3 (OMe), 54.1 (TiMe2), 30.7
(C5H4CH2), 26.8 (CH(CH3)2), 23.7 (CH(CH3)2).
Preparation of CpOTiMe(O-2,6-iPr2C6H3)2 (16). Method 1.
The same procedure described for 9 was followed, except that 12
(202 mg, 0.36 mmol) and 1.0 equiv of MeMgCl (0.12 mL, 0.36
mmol, 3 M in tetrahydrofuran) were used. The product was obtained
as an orange oil. Yield: 134 mg (69%).
1
57.30; H, 6.75. Found: C, 56.95; H, 6.73. H NMR (300 MHz,
C7D8, 293 K): δ 7.00-6.93 (m, 3H, C6H3), 6.23, 5.97 (both m,
each 2H, C5H4), 3.39 (sept, 3J ) 6.9, 2H, CH(CH3)2), 3.22 (t, 3J )
6.0, 2H, CH2O), 2.97 (s, 3H, OMe), 2.84 (t, 3J ) 6.0, 2H,
C5H4CH2), 1.22 (d, 3J ) 6.9, 12H, CH(CH3)2). 13C{1H} NMR
(75.42 MHz, C7D8, 293 K, plus APT): δ 164.5 (Ti-O-C), 138.6
(o-C6H3), 138.4 (Cipso C5H4), 124.8 (p-C6H2), 123.7 (m-C6H2), 121.2,
119.9 (C5H4), 71.6 (CH2O), 58.2 (OMe), 31.5 (C5H4CH2), 27.2 (CH-
(CH3)2), 23.7 (CH(CH3)2).
Preparation of CpOTi(O-2,6-iPr2C6H3)2Cl (12). The same
procedure described for 8 was followed, except that 1 (524 mg,
1.90 mmol) and a solution of Li(O-2,6-iPr2C6H3) (700 mg, 3.80
mmol) were used. The product was obtained as a yellow oil.
Yield: 202 mg (45%). Anal. Calcd for C32H45ClO3Ti: C, 68.48;
Method 2. The same procedure described for 15 was followed,
except that 4 (104 mg, 0.48 mmol) and 2.0 equiv of HO(2,6-i-
Pr2C6H3) (171 mg, 0.96 mmol) were used. Yield: 142 mg (55%).
Anal. Calcd for C33H48O3Ti: C, 73.30; H, 8.97. Found: C, 73.18;
H, 9.04. 1H NMR (300 MHz, C6D6, 293 K): δ 7.12-6.93 (m, 6H,
1
3
H, 8.10. Found: C, 68.72; H, 8.35. H NMR (300 MHz, C6D6,
C6H3), 6.08, 5.96 (both m, each 2H, C5H4), 3.54 (sept, J ) 6.9,
293 K): δ 7.11-6.94 (m, 6H, C6H3), 6.23, 6.10 (both m, each 2H,
C5H4), 3.72 (sept, 3J ) 6.9, 4H, CH(CH3)2), 3.21 (t, 3J ) 6.0, 2H,
CH2O), 2.97 (t, 3J ) 6.0, 2H, C5H4CH2), 2.93 (s, 3H, OMe), 1.28,
1.24 (both d, 3J ) 6.9, each 12H, CH(CH3)2). 13C{1H} NMR (75.42
MHz, C6D6, 293 K, plus APT): δ 163.7 (Ti-O-C), 138.0 (o-
C6H3), 136.6 (Cipso C5H4), 123.7 (m-C6H3), 123.5 (p-C6H3), 119.4,
117.7 (C5H4), 71.9 (CH2O), 58.0 (OMe), 31.1 (C5H4CH2), 26.7 (CH-
(CH3)2), 24.2, 23.6 (CH(CH3)2).
4H, CH(CH3)2), 3.17 (t, 3J ) 6.0, 2H, CH2O), 2.97 (s, 3H, OMe),
3
2.65 (t, J ) 6.0, 2H, C5H4CH2), 1.40 (s, 3H, TiMe), 1.23, 1.21
3
(both d, J ) 6.9, each 12H, CH(CH3)2). 13C{1H} NMR (75.42
MHz, C6D6, 293 K, plus APT): δ 161.4 (Ti-O-C), 137.7 (o-
C6H3), 130.2 (Cipso C5H4), 123.5 (m-C6H3), 122.2 (p-C6H3), 115.4,
113.6 (C5H4), 72.6 (CH2O), 58.1 (OMe), 48.5 (TiMe), 30.2
(C5H4CH2), 26.6 (CH(CH3)2), 23.9, 23.6 (CH(CH3)2).
Preparation of CpOTiMe2(OCPh2CtCH) (17). An orange
solution of 4 (366 mg, 1.70 mmol) in 15 mL of tetrahydrofuran
was treated with 1.0 equiv of HOCPh2CtCH (353 mg, 1.70 mmol)
at -15 °C. Immediately methane evolution was observed. The
mixture was warmed slowly to room temperature and stirred for 2
h. Then, the solvent was removed under vacuum and a green oil
was obtained. The product was washed with pentane (3 × 3 mL),
which was isolated as a green oil. Yield: 650 mg (94%). Anal.
Calcd for C25H28O2Ti: C, 73.51; H, 6.92. Found: C, 73.32; H,
Preparation of CpOTi(O-2,6-iPr2C6H3)3 (13). The same pro-
cedure described for 8 was followed, except that 1 (450 mg, 1.62
mmol) and a solution of Li(O-2,6-iPr2C6H3) (896 mg, 4.87 mmol)
were used. The product was obtained as an orange oil. Yield: 395
mg (35%). Anal. Calcd for C44H62O4Ti: C, 75.17; H, 8.91. Found:
1
C, 75.22; H, 9.06. H NMR (300 MHz, C6D6, 293 K): δ 7.13-
6.82 (m, 9H, C6H3), 6.07, 6.01 (both m, each 2H, C5H4), 3.67 (sept,
3J ) 6.9, 6H, CH(CH3)2), 3.11 (t, 3J ) 6.0, 2H, CH2O), 2.79 (t, 3J
) 6.0, 2H, C5H4CH2), 2.72 (s, 3H, OMe), 1.27 (d, 3J ) 6.9, 36H,
CH(CH3)2). 13C{1H} NMR (75.42 MHz, C6D6, 293 K, plus APT):
δ 163.7 (Ti-O-C), 138.0 (o-C6H3), 134.7 (Cipso C5H4), 123.7 (m-
C6H3), 123.4 (p-C6H3), 119.0, 117.7 (C5H4), 72.0 (CH2O), 57.7
(OMe), 29.8 (C5H4CH2), 26.7 (CH(CH3)2), 24.2 (CH(CH3)2).
1
7.01. H NMR (300 MHz, C6D6, 293 K): δ 7.92-6.99 (m, 10H,
3
Ph), 5.99, 5.73 (both m, each 2H, C5H4), 3.28 (t, J ) 6.0, 2H,
CH2O), 3.04 (s, 3H, OMe), 2.58 (t, 3J ) 6.0, 2H, C5H4CH2), 2.31
(s, 1H, tCH), 0.84 (s, 6H, TiMe2). 13C{1H} NMR (75.42 MHz,
C6D6, 293 K, plus APT): δ 146.8 (Cipso Ph), 129.4 (Cipso C5H4),
128.5 (m-Ph), 127.8 (p-Ph), 126.5 (o-Ph), 113.9, 112.9 (C5H4), 87.4
(CPh2), 85.7 (CtCH), 75.2 (CtCH), 73.0 (CH2O), 58.2 (OMe),
52.5 (TiMe2), 30.7 (C5H4CH2).
Preparation of CpOTiMe(O-2,6-iPr2C6H3)Cl (14). The same
procedure described for 9 was followed, except that 11 (337 mg,
0.80 mmol) and 1.0 equiv of MeMgCl (0.27 mL, 0.80 mmol, 3 M
in tetrahydrofuran) were used. The product was obtained as an
orange oil. Yield: 221 mg (84%). Anal. Calcd for C21H31ClO2Ti:
C, 63.22; H, 7.85. Found: C, 63.68; H, 8.26. 1H NMR (300 MHz,
C6D6, 293 K): δ 7.12-6.94 (m, 3H, C6H3), 6.24, 5.93, 5.91, 5.68
Preparation of CpOTiMe(OCPh2CtCH)2 (18). The same
procedure described for 17 was followed, except that 4 (465 mg,
2.15 mmol) and 2.0 equiv of HOCPh2CtCH (897 mg, 4.31 mmol)
were used. The product was obtained as a light yellow solid.
Yield: 547 mg (42%). Anal. Calcd for C39H36O3Ti: C, 77.98; H,
3
(both m, each 1H, C5H4), 3.33 (sept, J ) 6.9, 2H, CH(CH3)2),
3.22 (t, 3J ) 6.3, 2H, CH2O), 2.99 (s, 3H, OMe), 2.70 (t, 3J ) 6.3,
6.05. Found: C, 77.68; H, 5.93. H NMR (300 MHz, C7D8, 293
1
3
2H, C5H4CH2), 1.52 (s, 3H, TiMe), 1.26, 1.20 (both d, J ) 6.9,
K): δ 7.78-7.00 (m, 20H, Ph), 6.05, 5.89 (both m, each 2H, C5H4),
3.21 (t, 3J ) 6.0, 2H, CH2O), 3.02 (s, 3H, OMe), 2.58 (t, 3J ) 6.0,
2H, C5H4CH2), 2.36 (s, 2H, tCH), 1.13 (s, 3H, TiMe). 13C{1H}
NMR (75.42 MHz, C7D8, 293 K, plus APT and HETCOR): δ
147.2, 147.1 (Cipso Ph), 129.2 (Cipso C5H4), 128.3, 127.6, 126.7,
126.6 (Ph), 114.3, 112.8 (C5H4), 87.5 (CPh2), 85.3 (CtCH), 75.2
(CtCH), 73.0 (CH2O), 58.2 (OMe), 45.9 (TiMe), 30.4 (C5H4CH2).
each 6H, CH(CH3)2). 13C{1H} NMR (75.42 MHz, C6D6, 293 K,
plus APT): δ 162.1 (Ti-O-C), 138.1 (o-C6H3), 132.9 (Cipso C5H4),
123.6 (m-C6H3), 123.4 (p-C6H3), 117.8, 116.7, 116.1, 115.5 (C5H4),
72.3 (CH2O), 61.3 (TiMe), 58.3 (OMe), 31.0 (C5H4CH2), 27.2 (CH-
(CH3)2), 23.8, 23.7 (CH(CH3)2).
Preparation of CpOTiMe2(O-2,6-iPr2C6H3) (15). Method 1.
The same procedure described for 9 was followed, except that 11
(528 mg, 1.26 mmol) and 2.0 equiv of MeMgCl (0.84 mL, 2.52
mmol, 3 M in tetrahydrofuran) were used. The product was obtained
as a yellow oil. Yield: 468 mg (98%).
Determination of Constants and Thermodynamic Parameters
1
for the Equilibriums Shown in Eq 1. Variable-temperature H
NMR spectra of 2 (203-333 K), 3 (193-333 K), and 4 (183-363
K) were recorded in toluene-d8. Equilibrium constants, K, were der-

1460 Organometallics, Vol. 25, No. 6, 2006
Table 6. Crystal Data and Data Collection and Refinement Details for 2, 3, 6, and 8
Esteruelas et al.
2
3
6
8
Crystal Data
C10H17ClOTi
236.59
formula
mol wt
C9H14Cl2OTi
257.00
C26H26OTi
402.37
C23H34Cl2O2Ti
461.30
color, habit
size, mm
symmetry, space group
orange, irregular block
0.20 × 0.12 × 0.10
monoclinic, P21
6.8794(6)
9.2704(8)
9.0919(8)
109.0610(10)
548.04(8)
2
red, irregular block
0.40 × 0.38 × 0.30
monoclinic, P21/c
7.4633(6)
11.2428(9)
13.7705(11)
103.666(2)
1122.75(16)
4
yellow, plate
0.14 × 0.10 × 0.04
monoclinic, P21/n
13.071(2)
9.8025(15)
15.986(2)
93.739(3)
2044.0(5)
4
orange, irregular block
0.24 × 0.22 × 0.12
monoclinic, P21/c
20.191(4)
10.3853(17)
11.541(2)
100.225(3)
2381.6(8)
4
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
D
calcd, g cm-3
1.557
1.400
1.308
1.287
Data Collection and Refinement
diffractometer
λ(Mo KR), Å
monochromator
scan type
Bruker Smart APEX
0.71073
graphite oriented
ω scans
µ, mm-1
1.226
0.961
0.432
0.599
2θ range, deg
temp, K
3-57
100.0(2)
no. of data collect
no. of unique data
no. of params/restraints
R1a (F2 > 2σ(F2))
wR2b (all data)
Sc (all data)
6739
13 462
2743 (Rint ) 0.0326)
186/0
0.0266
0.0558
0.984
13 176
4865 (Rint ) 0.1012)
254/0
0.0544
0.0973
0.762
20 777
5770 (Rint ) 0.0640)
261/0
0.0451
0.0892
0.859
2597 (Rint ) 0.0232)
121/31
0.0361
0.0856
1.013
2
2
2
2
2
a R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. b wR2(F2) ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
.
c GOF ) S ) {∑[(Fo - Fc )2]/(n - p)}1/2, where n is the number of
reflections and p is the number of refined parameters.
ived from the temperature-dependent δ(1H) values of the methylene
signals CpCH2 and OCH2 using eq 2. Thermodynamic parameters
were calculated from the equilibrium constants according to eq 5.
of four sets. Each frame exposure time was 10 or 30 s covering
0.3° in ω. Data were corrected for absorption by using a multiscan
method applied with the SADABS program.33 The structures for
all compounds were solved by the Patterson method. Refinements,
by full-matrix least squares on F2 with SHELXL97,34 were similar
for all complexes, including isotropic and subsequently anisotropic
displacement parameters for all non-hydrogen atoms. The hydrogen
atoms were observed or calculated and refined freely or refined
using a restricted riding model, respectively.
For 2, the systematic absences were consistent with space groups
P21 and P21/m, but in the latter group the mirror plane would imply
a nonobserved disorder in the Cp ligand. In the last cycles of
refinement a “rigid bond” [SHELXL-DELU] restraint was used to
the five carbon atoms of the Cp group.
∆S° ∆H°
ln K )
-
(5)
R
RT
Reasonable values for δmin and δmax were obtained by computer-
assisted iteration: δmin and δmax were optimized in such a way that
plotting of ln K versus 1/T gives the straightest line possible.
General Procedure for Hydroamination. A Schlenk tube
equipped with a Teflon stopcock and a magnetic stirring bar was
charged with the alkyne (2.40 mmol), the amine (2.64 mmol),
complex 4 or complex 19 (0.12 mmol, 5.0% mol), toluene (2 mL),
and n-octane (2.40 mmol). The Schlenk was removed from the
glovebox and heated at 100 °C. The reaction was monitored by
periodic GC analysis of samples removed with a syringe. Either
on completion of the reaction or after 8 h, the volatiles were
removed under reduced pressure and the residue was analyzed by
1H and 13C{1H} NMR spectroscopy and by GC-MS. Imines and
enamines were identified by comparison of their NMR spectra with
their literature reported data.19
We have tried unsuccessfully to obtain good-quality data for
complex 18. Unfortunately, the instability of the crystals only allows
us to show the stereochemistry of the complex but not to discuss
the structural parameters. Crystal data for 18: C39H36O3Ti; mol wt
600.58; monoclinic, P21/c; a ) 30.862(5) Å, b ) 11.989(5) Å, c
) 16.960(5) Å, â ) 95.438(5)°; V ) 6247(3) Å3; Z ) 8; Dcalcd
)
1.277 g cm-3; µ ) 0.3 mm-1; 2θ range 3-57°; temperature 100
K; 25 416 data collected; 8152 unique data (Rint ) 0.14); R1(F2 >
2σ(F2)) ) 0.23 (isotropic model).
General Procedure for Hydrogenation. In a Fischer-Porter
bottle, PtO2 (15 mg, 0.07 mmol) was stirred in tetrahydrofuran (3.0
mL) at 25 °C under 1 atm of H2 for 10 min. A solution of the
crude hydroamination product in tetrahydrofuran (3.0 mL) was then
added. The resulting mixture was stirred under 3 atm of H2 at 25
°C for 48 h. Filtration, concentration, and purification by flash
chromatography on silica gel afforded the amines, whose purity
Acknowledgment. Financial support from the MCYT of
Spain (Project CTQ2005-00656 and PPQ2000-0488-P4-02) is
acknowledged. A.C.M. thanks Repsol-YPF for a grant.
1
was checked by H and 13C{1H} NMR spectroscopy and by GC-
Supporting Information Available: CIF files giving crystal
data for compounds 2, 3, 6, and 8. This material is available free
of charge via the Internet at http://pubs.acs.org.
MS. Amines were identified by comparison of their NMR spectra
with their literature reported data.19
Structural Analysis of Complexes 2, 3, 6, 8, and 18. A
summary of crystal data and data collection and refinement details
is reported in Table 6. X-ray data were collected for all complexes
at low temperature on a Bruker Smart APEX CCD diffractometer
at 100.0(2) K equipped with a normal-focus, 2.4 kW sealed-tube
source (Mo radiation, λ ) 0.710 73 Å) operating at 50 kV and 40
mA. Data were collected over the complete sphere by a combination
OM051031B
(33) Blessing, R. H. Acta Crystallogr. 1995, A51, 33-38. SADABS,
Area-Detector Absorption Correction; Bruker-AXS, Madison, WI, 1996.
(34) SHELXTL Package version 6.10; Bruker-AXS, Madison, WI, 2000.
Sheldrick, G. M. SHELXS-86 and SHELXL-97; University of Go¨ttingen,
Go¨ttingen, Germany, 1997.