Synthesis and chemistry of titanacyclopentane and titanacyclopropane rings supported by aryloxide ligation

Article abstract of DOI:10.1021/ja970515z

Treatment of the titanacyclopentadiene compound [Ti(OC₆H₃Ph₂-2,6)₂(C₄Et₄)] (3) (OC₆H₃Ph₂-2,6 = 2,6-diphenylphenoxide) with olefins leads to the formation of a variety of stable titanacyclopentane derivatives along with one equivalent of substituted 1,3-cyclohexadiene. The structural and spectroscopic properties of the ethylene product [Ti(OC₆H₃Ph₂-2,6)₂(CH₂)₄] (4) show a ground state titanacyclopentane structure, but facile fragmentation on the NMR-time scale to form a bis(ethylene) complex has been detected. The substituted products [Ti(OC₆H_-3Ph₂-2,6)₂(C₄H₆R₂)] (R = Me, 5; Et, 6; Ph, 7) formed from α-olefins RCH=CH₂ exist as a mixture of regio- and stereoisomers in hydrocarbon solution. Analysis of a crystal obtained from solutions of 7 showed a trans-2,5-diphenyl-titanacyclopentane ring to be present in the solid state. Alternative routes to the titanacyclopentane compounds involve treatment of the dichlorides [Ti(OC₆H₃Ph₂-2,6)₂Cl₂] (1) or [Ti(OC₆HPh₄-2,3,5,6)₂Cl₂] (2) with either sodium amalgam (2 Na per Ti) or 2 equiv of-Bu(n)Li in the presence of the substrate olefin. Using these conditions the titanabicyclic compounds [(ArO)₂Ti{CH₂CH(C₄H₈)CHCH₂}] (ArO = OC₆H₃Ph₂-2,6,10; OC₆HPh₄-2,3,5,6, 11) can be obtained by intramolecular coupling of 1,7-octadiene. The-spectroscopic properties of 10 and 11 as well as a single-crystal X-ray diffraction analysis of 11 show an exclusive traits stereochemistry is present. Thermolysis of 10 or 11 in the presence of excess 1,7-octadiene leads to the catalytic formation of 2-(methylmethylene)cyclohexane (80%) along with E,Z isomers of 2,6-octadiene (20%). A kinetic study shows the reaction to be zero order in diene with activation parameters, ΔH = +18.7(5) kcal mol^-1 and ΔS = -26(5) eu. The diphenyltitanacyclopentane 7 will catalyze the dimerization of styrene to trans-1,3-diphenylbut-1-ene followed by isomerization to 1,3-diphenylbut-2-ene. This result shows that although a 2,5-diphenyl regiochemistry was observed in the solid state, styrene dimerization occurs via the 2,4-diphenyltitanacyclopentane intermediate. The facile fragmentation of these titanacyclopentane compounds accounts for the products observed in a number of reactions. Addition of phosphine donor ligands (L) leads to a series of titanacyclopropane compounds [Ti(OC₆H₃Ph₂-2,6)₂(η²-CHR=CH₂)(L)] (R H, 14; Me, 15; Et, 16; Ph, 17) along with 1 equiv of olefin. The solid-state structure of the ethylene complex 14 shows the C₂H₄ unit lies approximately coplanar with the Ti-PMe₃ bond. This structure is not only maintained in solution but slow olefin rotation is observed on the NMR time scale. In the case of the a-olefin products, two isomers are detected by ¹H, ¹³C, and ³¹P NMR spectroscopy. Addition of Ph₂C=O or PhCH=NR (R = Ph, CH₂Ph) to the titanacyclopentane and titanacyclopropane compounds leads to different products depending upon the reagent and reaction conditions. These can be classified as 2-oxa(aza)titanacycloheptanes, 2-oxa(aza)titanacyclopentanes, 2,5-dioxa(diaza)titanacyclopentanes, and examples of 2-oxatitanacyclopropane (η²-ketone) and 2,7-dioxatitanacycloheptane compounds. The 2-azatitanacyclopentane compounds [Ti(OC₆H₃Ph₂-2,6)₂{(PhCH₂)NCH(Ph)CH₂CH₂}] (30) and trans-[Ti(OC₆H₃Ph₂-2,6)₂{(Ph)NCH(Ph)CH₂Ph}] (31) react with alkynes to produce the corresponding 2-azatitanacyclopent-4-ene which hydrolyze to produce a stoichiometric equivalent of alkylamine. Reaction of 30 with benzonitrile produces the 2,5-diazatitanacyclopent-2-ene [Ti(OC₆H₃Ph₂-2,6)₂(N=CPhCHPhNR)] (35) along with ethylene.

Full text of DOI:10.1021/ja970515z

8630
J. Am. Chem. Soc. 1997, 119, 8630-8641
Synthesis and Chemistry of Titanacyclopentane and
Titanacyclopropane Rings Supported by Aryloxide Ligation
Matthew G. Thorn, John E. Hill, Steven A. Waratuke, Eric S. Johnson,
Phillip E. Fanwick, and Ian P. Rothwell*
Contribution from the Department of Chemistry, 1393 Brown Building, Purdue UniVersity,
West Lafayette, Indiana 47907-1393
ReceiVed February 18, 1997X
Abstract: Treatment of the titanacyclopentadiene compound [Ti(OC6H3Ph2-2,6)2(C4Et4)] (3) (OC6H3Ph2-2,6 ) 2,6-
diphenylphenoxide) with olefins leads to the formation of a variety of stable titanacyclopentane derivatives along
with one equivalent of substituted 1,3-cyclohexadiene. The structural and spectroscopic properties of the ethylene
product [Ti(OC6H3Ph2-2,6)2(CH2)4] (4) show a ground state titanacyclopentane structure, but facile fragmentation
on the NMR time scale to form a bis(ethylene) complex has been detected. The substituted products [Ti(OC6H3-
Ph2-2,6)2(C4H6R2)] (R ) Me, 5; Et, 6; Ph, 7) formed from R-olefins RCHdCH2 exist as a mixture of regio- and
stereoisomers in hydrocarbon solution. Analysis of a crystal obtained from solutions of 7 showed a trans-2,5-
diphenyl-titanacyclopentane ring to be present in the solid state. Alternative routes to the titanacyclopentane compounds
involve treatment of the dichlorides [Ti(OC6H3Ph2-2,6)2Cl2] (1) or [Ti(OC6HPh4-2,3,5,6)2Cl2] (2) with either sodium
amalgam (2 Na per Ti) or 2 equiv of BunLi in the presence of the substrate olefin. Using these conditions the
titanabicyclic compounds [(ArO)2Ti{CH2CH(C4H8)CHCH2}] (ArO ) OC6H3Ph2-2,6, 10; OC6HPh4-2,3,5,6, 11) can
be obtained by intramolecular coupling of 1,7-octadiene. The spectroscopic properties of 10 and 11 as well as a
single-crystal X-ray diffraction analysis of 11 show an exclusive trans stereochemistry is present. Thermolysis of
10 or 11 in the presence of excess 1,7-octadiene leads to the catalytic formation of 2-(methylmethylene)cyclohexane
(80%) along with E,Z isomers of 2,6-octadiene (20%). A kinetic study shows the reaction to be zero order in diene
with activation parameters, ∆Hq ) +18.7(5) kcal mol-1 and ∆Sq ) -26(5) eu. The diphenyltitanacyclopentane 7
will catalyze the dimerization of styrene to trans-1,3-diphenylbut-1-ene followed by isomerization to 1,3-diphenylbut-
2-ene. This result shows that although a 2,5-diphenyl regiochemistry was observed in the solid state, styrene
dimerization occurs via the 2,4-diphenyltitanacyclopentane intermediate. The facile fragmentation of these
titanacyclopentane compounds accounts for the products observed in a number of reactions. Addition of phosphine
donor ligands (L) leads to a series of titanacyclopropane compounds [Ti(OC6H3Ph2-2,6)2(η2-CHRdCH2)(L)] (R )
H, 14; Me, 15; Et, 16; Ph, 17) along with 1 equiv of olefin. The solid-state structure of the ethylene complex 14
shows the C2H4 unit lies approximately coplanar with the Ti-PMe3 bond. This structure is not only maintained in
solution but slow olefin rotation is observed on the NMR time scale. In the case of the R-olefin products, two
isomers are detected by 1H, 13C, and 31P NMR spectroscopy. Addition of Ph2CdO or PhCHdNR (R ) Ph, CH2Ph)
to the titanacyclopentane and titanacyclopropane compounds leads to different products depending upon the reagent
and reaction conditions. These can be classified as 2-oxa(aza)titanacycloheptanes, 2-oxa(aza)titanacyclopentanes,
2,5-dioxa(diaza)titanacyclopentanes, and examples of 2-oxatitanacyclopropane (η2-ketone) and 2,7-dioxatitanacy-
cloheptane compounds. The 2-azatitanacyclopentane compounds [Ti(OC6H3Ph2-2,6)2{(PhCH2)NCH(Ph)CH2CH2}]
(30) and trans-[Ti(OC6H3Ph2-2,6)2{(Ph)NCH(Ph)CH2CH(Ph)}] (31) react with alkynes to produce the corresponding
2-azatitanacyclopent-4-ene which hydrolyze to produce a stoichiometric equivalent of allylamine. Reaction of 30
with benzonitrile produces the 2,5-diazatitanacyclopent-2-ene [Ti(OC6H3Ph2-2,6)2(NdCPhCHPhNR)] (35) along with
ethylene.
Introduction
the evolution of chiral metallocenes for carrying out asymmetric
synthesis.7 The success of cyclopentadiene-based group 4 metal
chemistry has led a number of research groups to attempt parallel
chemistry utilizing “metallocene equivalents”.8 This approach
hinges on the much analyzed σ2,π4 nature of the interaction of
Cp-based ligation with transition metals.8 The use of isolobal
The organometallic chemistry of the group 4 metals continues
to be dominated by the use of cyclopentadiene ligation.1 The
metallocene dichlorides first discovered by Wilkinson et al.2
represent an important starting material for a range of stoichio-
metric and catalytic transformations. A few significant develop-
ments have been the utilization of bulky cyclopentadiene
ligation,3 the isolation and study of cationic alkyl derivatives,4
the chemistry of group 4 metal-ligand multiple bonds,5,6 and
(4) (a) Jordan, R. F. AdV. Organomet. Chem. 1991, 32, 325. (b)
Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255. (c) Brintzinger, H.
H.; Fischer, D.; Mulhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1143. (d) Marks, T. J. Acc. Chem. Res. 1992, 25,
57. (e) Grubbs, R. H.; Coates, G. W. Acc. Chem. Res. 1996, 29, 85.
(5) Lee, S. Y.; Bergman, R. G. J. Am. Chem. Soc. 1996, 118, 6396 and
references therein.
(6) Howard, W. A.; Parkin, G. J. Am. Chem. Soc. 1994, 116, 606 and
references therein.
(7) (a) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994,
116, 8952. (b) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994,
116, 11703. (c) Verdaguer, X.; Lange, U. E. W.; Reding, M. T.; Buchwald,
S. L. J. Am. Chem. Soc. 1996, 118, 6784. (d) Hicks, F. A.; Buchwald, S.
L. J. Am. Chem. Soc. 1996, 118, 11688.
X Abstract published in AdVance ACS Abstracts, September 1, 1997.
(1) ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone,
F. G. A., Wilkinson, G., Eds.; Pergamon: New York, 1995; Vol. 4.
(2) (a) Wilkinson, G.; Pauson, P. L.; Birmingham, J. L.; Cotton, F. A. J.
Am. Chem. Soc. 1953, 75, 15. (b) Wilkinson, G.; Birmingham, J. L. J. Am.
Chem. Soc. 1954, 76, 4281.
(3) (a) Bercaw, J. E.; Marvich, R. H.; Bell, L. G.; Brintzinger, H. H. J.
Am. Chem. Soc. 1972, 94, 1219. (b) Threlkel, R. S.; Bercaw, J. E. J.
Organomet. Chem. 1977, 136, 1.
S0002-7863(97)00515-5 CCC: $14.00 © 1997 American Chemical Society

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8631
Scheme 1
Scheme 2
ligands such as the formally dianionic alkylimido group9 leads
to analogous chemistry based upon [Cp(RN)M) (M ) group 5)
and [(RN)2M] (M ) group 6) units.8
The alkoxide ligand, whose transition metal chemistry was
originally explored by the Bradley and Chisholm groups is a
formally monoanionic ligand that can also bond to the metal in
a σ2,π4 fashion.10 This analogy was exploited by Wolczanski
et al. in employing ligands such as tritox (But3CO) and silox
(But3SiO) whose cylindrical shape and cone angle mimic that
of the cyclopentadiene ligand.11 Recently Sato et al. have
utilized isopropoxide derivatives of titanium as important
synthons in organic chemistry.12 In our group we have focused
on sterically demanding, ortho-substituted aryloxide ligation to
support organometallic chemistry on early d-block metals.13 In
this paper we report on the chemistry of titanacyclic rings
supported by aryloxide ligation with emphasis on those derived
from olefin substrates. A number of parallels between this
aryloxide chemistry and known metallocene chemistry are
analyzed. Some aspects of this work have been communi-
cated.14
styrene to produce solutions containing titanacyclopentane
derivatives 4-7 along with 1 equiv of 1,3-cyclohexadiene
(Scheme 2). The regio- and stereochemistry as well as the
catalytic formation of the 1,3-cyclohexadiene products is
discussed in detail in a subsequent paper.17 The titanacyclo-
pentane compounds 4-6 can be readily isolated pure from these
reactions mixtures. A superior synthesis of the diphenyl
compound 7 involves sodium amalgam reduction of 1 in
benzene solvent in the presence of styrene (Scheme 3). During
the course of this reaction an intermediate, intense purple color
indicated the formation of the d1-d1 dimer [Ti(OC6H3Ph2-2,6)2-
(µ-Cl)]2 (8) which can be isolated pure by simply adding one
equivalent of Na/Hg to benzene solutions of 1. The solid-state
structure of 8 has been reported and shows terminal phenoxide
ligands and a short Ti-Ti distance of 2.9827(7).18 Attempts to
utilize the 2,3,5,6-tetraphenylphenoxide compound 2 by sodium
amalgam reduction in the presence of alkynes or olefins is
hampered by the formation of the deep blue, sparingly soluble
d1-d1 compound [Ti(OC6HPh4-2,3,5,6)2(µ-Cl)]2 (9) (Scheme
3). The low solubility of 9 hinders further reduction to form
metallacyclic compounds.
Results and Discussion
Synthesis and Characterization of Titanacyclopentane
Compounds. The dichloride compounds [Ti(OC6H3Ph2-2,6)2-
Cl2] (1)15 and [Ti(OC6HPh4-2,3,5,6)2Cl2] (2) can be obtained
in high yield by simple treatment of TiCl4 with two equivalents
of the parent phenol in hydrocarbon solvents (Scheme 1).
Previously we have shown that sodium amalgam reduction of
hydrocarbon solutions of 1 in the presence of 3-hexyne leads
to the titanacyclopentadiene compound [Ti(OC6H3Pr2-2,6)2(C4-
Et4)] (3) in high yield (Scheme 1).16 Solutions of 3 in benzene,
react rapidly with excess ethylene, propene, 1-butene, and
Either by addition of 1,7-octadiene to 3, or reduction of 1 in
the presence of 1,7-octadiene, the titanabicyclic derivative 10
can be isolated. As an alternative to sodium amalgam reduction
methods we have also explored the reaction of BunLi with the
dichlorides 1 and 2. The addition of 2 equiv of BunLi to Cp2-
MCl2 (the Negishi method)19 has been utilized to generate a
“metallocene equivalent” in the presence of suitable organic
substrates. We find that treatment of 1 or 2 with 2 equiv Bun-
(8) Gibson, V. C. Angew. Chem., Int. Ed. Engl. 1994, 33, 1565.
(9) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(10) (a) Bradley, D. C.; Mehrotra, R. C.; Gaur, D. P. Metal Alkoxides;
Academic Press: New York, 1978. (b) Chisholm, M. H. Chemtracts 1992,
4, 273.
(11) Wolczanski, P. T. Polyhedron 1995, 14,3335.
(12) (a) Nakagawa, T.; Kasatkin, A.; Sato, F. Tetrahedron Lett. 1995,
36, 3207. (b) Kasatkin, A.; Nakagawa, T.; Okamoto, S.; Sato, F. J. Am.
Chem. Soc. 1995, 117, 3881. (c) Okamoto, S.; Kasatkin, A.; Zubaidha, P.
K.; Sato, F. J. Am. Chem. Soc. 1996, 118, 2208. (d) Suzuki, K.; Urabe, H.;
Sato, F. J. Am. Chem. Soc. 1996, 118, 8729. (e) Urabe, H.; Sato, F. J. Org.
Chem. 1996, 61, 6756.
(13) (a) Rothwell, I. P. J. Chem. Soc., Chem. Commun., in press. (b)
Rothwell, I. P. Acc. Chem. Res. 1988, 21, 153.
(14) (a) Hill, J. E.; Fanwick, P. E., Rothwell, I. P. Organometallics 1991,
10, 15. (b) Hill, J. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1992,
11, 1771.
(16) Hill, J. E.; Balaich, G. J.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1993, 12, 2911.
(17) (a) Johnson, E. S.; Balaich, G. J.; Rothwell, I. P. J. Am. Chem.
Soc., in press. (b) Balaich, G. J.; Rothwell, I. P. J. Am. Chem. Soc. 1993,
115, 1581.
(18) Hill, J. E.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 1990, 9, 1617.
(19) (a) Negishi, E.; Takahashi, T. Acc. Chem. Res. 1994, 21, 1277. (b)
Negishi, E.; Cederbaum, F. E.; Takahashi, T. Tetrahedron Lett. 1986, 27,
2829. (c) Negishi, E.; Holmes, S. J.; Tour, J. M.; Miller, J. A.; Cederbaum,
F. E.; Swanson, D. R.; Takahashi, T. J. Am. Chem. Soc. 1989, 111, 3336.
(d) Kondakov D.; Negishi, E. J. Chem. Soc., Chem. Commun. 1996, 963.
(15) Dilworth, J. R.; Hanich J.; Krestel M. J. Organomet. Chem. 1986,
315, 9.

8632 J. Am. Chem. Soc., Vol. 119, No. 37, 1997
Thorn et al.
Scheme 3
Figure 1. 1H NMR (200 MHz) spectra of [Ti(OC6H3Ph2-2,6)2(CH2)4]
(4) and ethylene in C6D5CD3 solvent (* indicates protio impurity) over
the temperature range -30 to +60 °C.
Scheme 4
Li in benzene solvent will generate titanacyclopentadiene and
titanacyclopentane compounds directly as detected by 1H NMR
spectroscopy (Scheme 3). In most cases, however, isolated
yields were low due to difficulty in separating the products from
the reaction mixture. One exception is the treatment of
tetraphenylphenoxide 2 with BunLi in the presence of 1,7-
octadiene. Addition of only 1 equiv of BunLi to benzene
solutions of 2 lead to formation of deep blue 9. When 2 equiv
of BunLi are added with rapid agitation, only a small amount
of 9 is produced along with a benzene solution of [Ti(OC6-
HPh4-2,3,5,6)2{CH2CH(C4H8)CHCH2}] (11) (Scheme 3). Fil-
tration, removal of solvent, and addition of toluene was found
to lead to crystallization of 11 in moderate yield as a toluene
solvate.
The solution NMR spectroscopic properties of the titanacy-
clopentane compounds 4-7, 10, and 11 are of interest.20 In
the 13C NMR spectra, signals for the Ti-C(R) and Ti-C(â)
of the solution, broadening of the methylene proton signals
occurs and at +60 °C collapse into the baseline occurs. The
signal due to the free ethylene begins to broaden at +40 °C.
From the coalescence temperature we estimate the activation
energy (∆Gq) for exchange of the R- and â-CH2 methylene
groups within the titanacyclopentane 4 to be 15.9(5) kcal mol-1
at 55 °C. Simulation of the spectra using a program that
accommodates a three-site exchange shows that the rate of
exchange of methylene groups within 4 (160 s-1 at 55 °C)
exceeds the rate of exchange of these groups with free ethylene
(40 s-1 at 55 °C). Accurate simulation of the spectra was not
possible due to the variation of the ethylene intensity with
temperature (probably reflecting changes in solubility) and the
fact that the methylene signals are in reality unresolved
multiplets.22 Furthermore, at temperatures above 60 °C 4 is
converted into a new organometallic compound (Vide infra).
We interpret these gross changes as indicating that not only
fragmentation of 4 in to a “bis(ethylene)” species occurs
(Scheme 4) but that exchange of free and coordinated ethylene
also occurs. The most plausible pathway for the intermolecular
1
carbon atoms display J(13C-1H) coupling constants close to
those expected for sp3-hybridized carbon atoms. Furthermore,
the Ti-C(R) chemical shifts are in the range typical for titanium
alkyl compounds containing aryloxide ligation. This data
supports their proposed structure and is inconsistent with a bis-
(olefin) formulation for the compounds. There is, however,
evidence in the 1H NMR spectrum of titanacyclopentane 4 for
facile, reversible fragmentation into a “bis(ethylene)” species.21
In the presence of 1 atm of ethylene, solutions of 4 in C6D5-
CD3 are stable at temperatures up to 80 °C. At ambient
temperatures the R-CH2 and â-CH2 methylene protons appear
as well resolved signals (Figure 1). The excess ethylene appears
as a sharp singlet at a chemical shift almost identical for C2H4
simply dissolved in C6D5CD3. Upon raising the temperature
(20) For leading references to metallacyclopentane compounds, see: (a)
Knight, K. S.; Wang, D.; Waymouth R. M.; Ziller, J. J. Am. Chem. Soc.
1994, 116, 1845. (b) Nugent W. A.; Taber, D. F. J. Am. Chem. Soc. 1989,
111, 6435. (c) Taber, D. F.; Louey, J. P.; Wang, Y.; Nugent, W. A.; Dixon,
D. A.; Harlow, R. L. J. Am. Chem. Soc. 1994, 116, 9457.
(21) (a) Grubbs, R. H.; Miyashita, A. J. Chem. Soc., Chem. Commun.
1977, 864. (b) Grubbs, R. H.; Miyashita, A. J. Am. Chem. Soc. 1978, 100,
1300.
(22) For a discussion of the problems of interpreting NMR exchange
rates, see: Green, M. L. H.; Wong, L.-L.; Sella, A. Organometallics 1992,
11, 2660.

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8633
exchange involves a mono(ethylene) intermediate (dissociative
exchange, Scheme 4). In the case of the titanium complex
[Cp*2Ti(C2H4)], Bercaw et al. have shown that in the presence
of ethylene reversible formation of a titanacyclopentane occurs.23
A much slower rate of rearrangement of a 2,5-dimethylmetal-
lacyclopentane into its 3,4-isomer has been measured by Negishi
et al.24 The exact nature of the intermediate in the rearrange-
ment of 4 is unknown. As shown in Scheme 4 there are a
number of geometries (C2 units coplanar, mutually perpendicu-
lar, and parallel) and resonance pictures possible. Previous work
on a zirconocene system by Buchwald et al. clearly demon-
strated the possibility of a delocalized situation best represented
as intermediate between two zirconacyclopropene-alkyne
complexes (Scheme 4).25
In the case of the disubstituted titanacyclopentanes 5-7
formed by coupling of R-olefins, there are a total of six possible
regio- and stereoisomers. In the case of the dimethyl and diethyl
compounds 5 and 6, 1H and 13C NMR spectra show the presence
of a major and a minor isomer. The major isomer in both cases
is identified as the trans-3,4-disubstituted derivatives. The
coupling of R-olefins at group 4 metallocene centers has been
investigated by numerous groups. With alkyl substituents a
preference for formation of the 3,4-regioisomer has been
reported.26 The presence of a Ti-CH2 function as well as only
one Ti-O-C carbon resonance for the aryloxide ligand (i.e.,
the two aryloxide groups are equivalent) confirms the regio-
and stereochemistry of this major isomer.
Figure 2. Molecular structure of [Ti(OC6H3Ph2-2,6)2(CH2)4] (4).
In the case of the titanabicycles formed by coupling of 1,7-
octadiene, a trans stereochemistry is again confirmed by the
equivalence of the aryloxide ligands in the 13C NMR spectra
as well as by structural and reactivity studies on 11. The
exclusive formation of only the trans isomer contrasts with the
coupling of 1,7-octadiene at metallocene centers where the
kinetically formed cis isomer slowly isomerizes to the trans
form.20b,27
1
The H NMR spectrum of the titanacyclopentane 7 formed
from styrene is broad at ambient temperatures. Furthermore,
addition of excess styrene to C6D5CD3 solutions of 7 as well
as low-temperature NMR studies show that facile metallacycle
fragmentation and exchange of free and coordinated styrene is
taking place. Presumably the lower barriers to fragmentation/
exchange in this case compared to 4 above is a steric
consequence of the phenyl substituents. The complexity of the
1H NMR spectrum of 7 at low temperatures can only be
accounted for by the presence of at least two different
substitutional isomers. Based upon structural and reactivity
studies we assign these major components as the 2,4- and 2,5-
diphenyl derivatives. Studies by Negishi et al. have demon-
strated a distinct preference for phenyl substituents to occupy
R-positions of metallacyclopentane rings.28
Figure 3. Molecular structure of [Ti(OC6H3Ph2-2,6)2{CH(Ph)CH2CH2-
CH(Ph)}] (7).
The titanacyclopentane compounds 4 and 7 and the titanabi-
cycle derivative 11 have been subjected to single-crystal X-ray
diffraction analysis (Figures 2-4 and Tables 1-3). In all cases
the formulation of these compounds was confirmed and in the
case of 11, the trans stereochemistry was also established
(23) Cohen, S. A.; Auburn, P. R.; Bercaw, J. E. . J. Am. Chem. Soc.
1983, 105, 1136.
(24) Takahashi, T.; Fujimori, T.; Seki, T.; Saburi, M.; Uchidi, Y.; Rousset,
C. J.; Negishi, E. J. Chem. Soc., Chem. Commun. 1990, 182.
(25) Warner, B. P.; Davis, W. M.; Buchwald, S. L. J. Am. Chem. Soc.
1994, 116, 5471.
(26) (a) Schock, L. E.; Marks, T. J. J. Am. Chem. Soc. 1988, 110, 7701.
(b) Schmidt, J. R.; Duggan, D. M. Inorg. Chem. 1981, 20, 318.
(27) (a) Gell, K. I.; Schwartz, J. J. J. Am. Chem. Soc. 1981, 103, 2687.
(b) Akita, M.; Yasuda, H.; Yamamoto, H.; Nakamura, A. Polyhedron 1991,
10, 1.
Figure 4. Molecular structure of [Ti(OC6HPh4-2,3,5,6)2{CH2CH-
(C4H8)CHCH2}] (10).
(Figure 4). A number of attempts at determining the crystal
structure of a sample of 7 were unsuccessful. Eventually a data
set was obtained on a crystal which was solved showing the
presence of the trans-2,5-diphenyl-substituted titanacyclopentane
(28) Swanson, D. R.; Rousset, C. J.; Negishi, E.; Takahashi, T.; Seki,
T.; Saburi, M.; Uchida, Y. J. Org. Chem. 1989, 54, 3521.

8634 J. Am. Chem. Soc., Vol. 119, No. 37, 1997
Thorn et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6H3Ph2-2,6)2(C4H8)] (4)
Molecule 1
Ti(1)-O(110)
Ti(1)-O(120)
Ti(1)-C(11)
Ti(1)-C(14)
1.799(1) C(11)-C(12)
1.804(1) C(12)-C(13)
2.087(2) C(13)-C(14)
2.084(2)
1.510(3)
1.511(4)
1.517(4)
O(110)-Ti(1)-O(120) 132.62(6) Ti(1)-C(11)-C(12)
O(110)-Ti(1)-C(11) 104.96(7) Ti(1)-C(14)-C(13)
O(110)-Ti(1)-C(14) 108.12(7) C(11)-C(12)-C(13)
C(11)-Ti-C(14)
Ti(1)-O(110)-C(111) 157.9(1)
106.6(1)
106.3(1)
109.4(2)
109.8(2)
85.59(9) C(12)-C(13)-C(14)
Ti(1)-O(120)-C(121) 155.7(1)
Molecule 2
1.802(1) C(21)-C(22)
1.817(1) C(22)-C(23)
2.084(2) C(23)-C(24)
2.084(2)
Ti(2)-O(210)
Ti(2)-O(220)
Ti(2)-C(21)
Ti(2)-C(24)
1.520(3)
1.512(4)
1.512(4)
O(210)-Ti(2)-O(220) 135.05(6) Ti(2)-C(21)-C(22)
O(210)-Ti(2)-C(21) 107.84(7) Ti(2)-C(24)-C(23)
O(210)-Ti(2)-C(24) 104.23(7) C(21)-C(22)-C(23)
106.1(1)
105.4(1)
109.8(2)
109.6(2)
C(21)-Ti-C(24)
86.22(8) C(22)-C(23)-C(24)
Ti(2)-O(210)-C(211) 159.1(1)
Ti(2)-O(220)-C(221) 151.3(1)
Table 2. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6H3Ph2-2,6)2{CH(Ph)CH2CH2CH(Ph)}] (7)
Figure 5. Molecular structure of [{Ti(OC6H3Ph2-2,6)2(CH2-
CHMeCMe2)}2(µ-O)] (12).
Ti-O(5)
1.801(3) Ti-O(6)
2.103(6) Ti-C(4)
1.537(7) C(2)-C(3)
1.546(8)
1.804(3)
2.115(5)
1.516(8)
Scheme 5
T-C(1)
C(1)-C(2)
C(3)-C(4)
O(5)-Ti-O(6)
Ti-C(1)-C(2)
C(1)-C(2)-C(3) 110.0(5)
Ti-O(5)-C(51) 157.4(3)
126.1(1)
97.7(4)
C(1)-Ti-C(4)
85.6(2)
105.6(4)
Ti-C(4)-C(3)
C(2)-C(3)-C(4) 111.6(5)
Ti-O(6)-C(61) 161.1(3)
Table 3. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6HPh4-2,3,5,6)2{CH2CH(C4H8)CHCH2}] (11)
Ti-O(10)
1.802(3) Ti-C(1)
2.061(5)
1.65(3)
C(1)-C(21)
1.49(2)
135.0(2)
105.2(2)
149.4(3)
C(21)-C(21)
O(10)-Ti-O(10)
O(10)-Ti-C(1)’
Ti-O(10)-C(11)
O(10)-Ti-C(1) 106.6(2)
C(1)-Ti-C(1) 88.5(3)
Ti-C(1)-C(21) 105.0(8)
C(1)-C(21)-C(21) 106.5(8)
ring (Figure 3). In all three titanacyclopentane derivatives the
Ti-O and Ti-C distances are within the ranges typical of
aryloxide and alkyl groups bound to 4-coordinate Ti(IV).29
The titanacyclopentane compounds 4-7 react with excess
H2O to produce a mixture of organic products along with 2
equiv of phenol (Scheme 5). For the unsubstituted derivative
4, butane was detected along with significant amounts of
Table 4. Selected Bond Distances (Å) and Angles (deg) for
[{Ti(OC6H3Ph2-2,6)2(CH2CHMeCHMe2)}2(µ-O)] (12)
Ti-O(1)
1.793(3)
1.801(1)
119.4(1)
100.0(2)
107.2(2)
152.3(1)
167.6(3)
Ti-O(2)
1.795(2)
2.087(5)
110.2(1)
113.46(9)
104.5(2)
160.7(2)
129.7(5)
1
ethylene and ethane (GC analysis and H NMR). In the case
Ti-O(B)
Ti-C(1)
of the diphenyl derivative 7 an almost quantitative conversion
to a 50/50 mixture of styrene and ethylbenzene was observed.
It, therefore, appears that water acts as a simple Lewis donor
ligand as well as a protic source and induces the fragmentation
of the titanacyclopentane prior to protonation of the bound olefin
(Scheme 5). Hydrolysis of titanabicycle 10 and 11 yields trans-
1,2-dimethylcyclohexane.
During an attempt to obtain crystals of the dimethyltitana-
cyclopentane complex 5 by slow cooling of a hexane solution,
the accidental introduction of trace amounts of moisture led to
the formation of crystals of an oxo complex 12 (Scheme 5).
The molecular structure of 12 (Figure 5, Table 4) shows that it
has originated by reactions of 2 equiv of 5 with 1 equiv of water.
A similar type of reaction occurs between metallocene dialkyls
and traces of water.30 The protonation of one of the Ti-C bonds
O(1)-Ti-O(2)
O(1)-Ti-C(1)
O(2)-Ti-C(1)
Ti-O(B)-Ti
Ti-O(2)-C(21)
O(1)-Ti-O(B)
O(2)-Ti-O(B)
O(B)-Ti-C(1)
Ti-O(1)-C(11)
Ti-C(1)-C(2)
in 5 leads to an alkyl group which gives insight into the
regiochemistry of the original titanacyclopentane ring. Clearly
the alkyl group in 12 can only be formed from the 3,4-
dimethyltitanacyclopentane ring, although the same group can
be formed from either the cis or trans stereoisomers.
Thermal Stability of Titanacyclopentanes: Catalytic Cy-
clization of 1,7-Octadiene and Dimerization of Styrene. When
a solution of titanacyclopentane 7 in C6H6 is heated at 100 °C
in the presence of excess styrene, catalytic dimerization occurs
to initially produce trans-1,3-diphenylbut-1-ene (Scheme 6).31
This product presumably arises via a 2,4-diphenyltitanacyclo-
pentane intermediate by abstraction of a hydrogen from the
3-position of the ring. The trans-1,3-diphenylbut-1-ene is
(29) Smith, G. D.; Fanwick, P. E.; Rothwell, I. P. Inorg. Chem. 1990,
29, 3221.
(30) Hunter, W. E.; Nrncir, D. C.; Bynum, R. V.; Penttila, R. A.; Atwood,
J. L. Organometallics 1983, 2, 750.

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8635
Table 5. First-Order Rate Constants for the Cyclization of
1,7-Octadiene Catalyzed by 10
T, C
103k, s-1
equiv of Ti-1 h-1
94
108
118
134
0.102
0.217
0.487
1.28
0.366
0.78
1.75
4.60
Figure 6. Plot showing the appearance with time of 2-(methylmeth-
ylene)cyclohexane within a C6D6 solution containing [Ti(OC6H3Ph2-
2,6)2{CH2CH(C4H8)CHCH2}] (10, 0.0345 mmol) and 1,7-octadiene
(0.977 mmol) heated at 118 °C.
Scheme 6
Figure 7. Plot of ln (k/T) vs 1/T for the cyclization of 1,7-octadiene
into 2-(methylmethylene)cyclohexane (data in Table 5).
Scheme 7
subsequently isomerized within the reaction mixture to produce
1,3-diphenylbut-2-ene. This result shows that although struc-
tural studies demonstrate the presence of the trans-2,5-diphenyl
derivative in the solid state, thermal reactivity in solution
proceeds via the 2,4-diphenyl isomer.
Titanabicycle 10 catalytically converts 1,7-octadiene into a
mixture of 2-methyl-methylenecyclohexane31-34 (80% by GC)
and 2,6-octadiene (predominantly E,E by 13C NMR,35 Scheme
6). Previous work by Nakamura et al. has shown that low valent
titanocene systems are excellent catalysts for the internalization
of terminal olefins and nonconjugated dienes.35 Recent work
by Negishi et al. has shown a zirconocene isomerization of R,ω-
dienes to produce metal bound 1,3-diene structures.36 Attempts
to use 10 as a catalyst for the cyclization of 1,6-heptadiene and
1,8-nonadiene led mainly to olefin isomerization. A kinetic
study of the cyclization of 1,7-octadiene showed the reaction
to be zero order in [diene]. The catalyst 10 was observed
(NMR) to be the predominant Ti species in solution (as long as
there is excess 1,7-octadiene present) and remains active for a
significant number of turnovers (Figure 6, Table 5). Activation
parameters were obtained for the formation of 2-(methylmeth-
ylene)cyclohexane over a 40° temperature range (Figure 7).
A number of distinct mechanistic pathways for these olefin
dimerization/cyclization reactions can be envisaged proceeding
via the titanacyclopentane intermediate. The two most reason-
able differ as to whether the â-hydrogen abstraction occurs
initially by the metal center to generate an intermediate hydride
or in a concerted fashion by the adjacent R-carbon center
(Scheme 7). This latter process corresponds to an intramolecular
σ-bond metathesis reaction, a pathway that is common for ligand
cyclometallation at d0 metal centers.37 These reactions are
directly related to the breakdown of compounds such as [Cp2M-
(31) Dimerization of olefins and cyclization of R,ω-dienes via metalla-
cyclopentanes, see: (a) McLain, S. J.; Wood, C. D.; Schrock, R. R. J. Am.
Chem. Soc. 1978, 101, 4558. (b) Smith, G.; Mclain, S. J.; Schrock, R. R.
J. Organomet. Chem. 1980, 202, 269.
(32) Linear dimerization of dienes, see: Christoffers, J.; Bergman, R.
G. J. Am. Chem. Soc. 1996, 118, 6422 and references therein.
(33) For an alternatiVe selective cyclization of R,ω-dienes catalyzed by
scandium hydrides, see: Piers, W. E.; Shapiro, P. J.; Bunel, E. E.; Bercaw,
J. E. Synlett 1990, 74.
(34) For references to the ring closing metathesis of R,ω-dienes, see:
Zuercher, W. J.; Hashimoto, M.; Grubbs, R. H. J. Am. Chem. Soc. 1996,
118, 6634 and references therein.
(35) Akita, M.; Yasuda, H.; Nagasuna, K.; Nakamura, A. Bull. Chem.
Soc. Jpn. 1983, 56, 554.
(36) Negishi, E.; Maye, J. P.; Choueiry, D. Tetrahedron 1995, 51, 4447.
(37) Rothwell, I. P. In SelectiVe Hydrocarbon ActiVation; Davis, J. A.,
Watson, P. L., Liebman, J. F., Greenberg, A., Eds; VCH Publishers: New
York, 1990; pp 43-75.

8636 J. Am. Chem. Soc., Vol. 119, No. 37, 1997
Thorn et al.
Scheme 8
Scheme 9
(X)(R)] (M ) Zr, Hf) in which the X group contains at least
one â-CH bond. Mechanistic studies by Buchwald et al. on
the formation of thioaldehyde complexes led to the conclusion
that the reactions proceed via a concerted pathway (Scheme
7).38 Particularly informative were a large negative entropy of
activation and a primary deuterium kinetic isotope effect. A
substituent effect study yielded a Hammet plot with F ) +0.39,
indicating positive charge build up on the hydrogen being
transferred in the transition state.38
The kinetic study of the cyclization of 1,7-octadiene yielded
a value of ∆Sq ) -26(5) eu (Figure 7), consistent with the
highly ordered transition state required in the concerted pathway.
However, when an equimolar mixture of C6H5CHdCH2 and
C6D5CDdCD2 was heated with titanacyclopentane 7 at 100 °C
in C6D6, scrambling of both R- and â-olefinic H/D atoms was
observed (1H and 13C NMR) at a rate much faster than
dimerization. The catalyst for this exchange process is presum-
ably a titanium hydride species which undergoes reversible
insertion of styrene monomers to produce both R- and â-phen-
ethyl groups. It is possible that solutions of 7 contain such a
hydride species as a contaminant. An alternative explanation
is that the scrambling is catalyzed by the hydride generated by
â-hydrogen abstraction by the metal center. If this was indeed
the case it would imply that this species was sufficiently long-
lived to carry out multiple insertions with free styrene.
The thermal instability of 4 is also mechanistically significant.
When solutions of 4 and excess ethylene in C6D6 are heated at
80 °C, almost quantitative conversion to the titanacycloheptene
complex 13 occurs (Scheme 8). This complex has been
previously isolated by addition of 1,3-butadiene to 4.39 Small
amounts of 1-butene and ethane were also present in solution
(1H NMR). The thermal decompostion of metallacyclopentanes
of the group 4 metals has been studied by many researchers
dating back to the pioneering studies of Whitesides et al.40 This
reactivity parallels exactly that reported by Erker et al. for the
zirconacyclopentane [Cp2Zr(CH2)4], where ethylene dimerization
was curtailed by formation of a zirconacycloheptene complex.41
The ethylene complex [Cp*2Ti(C2H4)] was demonstrated by
Cohen and Bercaw to be a catalyst for the conversion of ethylene
to 1,3-butadiene and ethane.23 These reactions are believed to
proceed via intermediates formed by â-hydrogen abstraction by
the metal center. The resulting 3-butenyl hydride can then insert
an extra equivalent of ethylene and eliminate ethane with
formation of a 1,3-butadiene complex which in the case of 4
would produce 13 (Scheme 8). An alternative pathway
proposed by Erker et al. proceeds via a titanium dihydride
intermediate.41
The above observations, therefore, imply that the catalytic
dimerization of styrene by 7 and cyclization of 1,7-octadiene
by 10 proceed via metal hydride intermediates and not by way
of a concerted pathway. The zero-order dependence on olefin
is consistent with either rate-determining â-hydrogen abstraction
and relatively fast subsequent steps or alternatively reversible
â-hydrogen with a rate determining elimination step. This latter
scenario could not, however, involve olefin in the rate-
determining step. A pathway which is consistent with these
mechanistic findings and avoids the intermediacy of a highly
unsaturated species [Ti(OAr)2] is shown for ethylene in Scheme
8. Rate-determining â-hydrogen abstraction is followed by
insertion of an equivalent of olefin to generate a dialkyl
intermediate. In the case of ethylene, ethane elimination
eventually leads to 13, whereas in the case of styrene and 1,7-
octadiene elimination of product generates a monoolefin species
which can rapidly regenerate a titanacylopentane (Scheme 8).
Synthesis and Characterization of Titanacyclopropane
Compounds. The titanacyclopentane compounds 4-7 react
rapidly in C6D6 solution with either PMe3 or PMe2Ph to produce
deep-purple solutions containing 1 equiv of olefin and new
organometallic compounds. These new compounds are formu-
lated as titanacyclopropane (monolefin) species containing a
single phosphine ligand (Scheme 9). In the case of the propene-,
butene- and styrene-derived complexes, a mixture of two
isomers is observed in solution by 1H, 13C, and 31P NMR
spectroscopy. The presence of two, nonequivalent Ti-C
resonances in the 13C NMR spectrum of the ethylene complex
(14) indicates a structure for the molecule in which the C-C
unit is coplanar, as opposed to perpendicular, to the Ti-P bond.
This situation was confirmed by a single-crystal X-ray diffrac-
tion analysis of 14a (Figure 8, Table 6). The two isomers
present for 15-17 are due to the olefin substituents being
positioned either proximal or distal to the phosphine ligand. This
reactivity, the structures of compounds 15-17 as well as the
(38) Buchwald, S. L.; Nielsen, R. B. J. Am. Chem. Soc. 1988, 110, 3175.
(39) Balaich, G. J.; Hill, J. E.; Waratuke, S. A.; Fanwick, P. E.; Rothwell,
I. P. Organometallics 1995, 14, 656.
(40) McDermott, J. X.; Wilson, M. E.; Whitesides, G. M. J. Am. Chem.
Soc. 1976, 98, 6529.
(41) Erker, G.; Engel, K.; Dorf, U.; Atwood, J. L.; Hunter, W. E. Angew.
Chem., Int. Ed. Engl. 1982, 21, 914.

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8637
Scheme 10
Figure 8. Molecular structure of [Ti(OC6H3Ph2-2,6)2(CH2CH2)(PMe3)]
(14a).
Table 6. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6H3Ph2-2,6)2(η2-CH2CH2)(PMe3)] (14a)
Ti-P(1)
2.5633(5) Ti-O(2)
1.835(1)
2.110(2)
1.425(3)
98.39(4)
83.97(5)
100.76(7)
103.86(7)
39.09(7)
161.3(1)
Ti-O(3)
1.838(1)
2.148(2)
Ti-C(41)
Ti-C(42)
C(41)-C(42)
P(1)-Ti-O(2)
P(1)-Ti-C(41)
O(2)-Ti-O(3)
93.39(4)
P(1)-Ti-O(3)
P(1)-Ti-C(42)
O(2)-Ti-C(41)
O(3)-Ti-C(41)
C(41)-Ti-C(42)
Ti-O(3)-C(31)
122.67(5)
140.73(5)
center in 14a, the lengthening is slightly less than found in
corresponding mononuclear metallocene derivatives of Ti, Zr,
and Hf (Table 7). The bonding of the ethylene moiety in the
species [Cl2Ti(CH2CH2)] has been theoretically analyzed.46
Synthesis and Characterization of Oxa- and Azatitana-
cyclic Compounds. We have probed the reactivity of the
isolated titanacyclopentane and titanacyclopropane species
toward ketones and imine reagents. Initially focusing upon the
reaction with benzophenone, Ph2CdO, by varying the reaction
conditions we have been able to isolate and characterize
oxatitanacyclopropane, -pentane, and -heptane as well as
dioxatitanacyclopentane and -heptane species. The titanacy-
clopentane 4 will react with Ph2CdO in the presence of excess
ethylene to produce the oxatitanacycloheptane complex 18. In
the absence of excess ethylene in solution, 4 produces a mixture
of not only 18 but also oxatitanacyclopentane 19 and dioxati-
tanacycloheptane 20 (Scheme 10). These latter two compounds
are also synthesized by addition of 1 or 2 equiv of Ph2CdO to
[Ti(OC6H3Ph2-2,6)2(η2-CH2dCH2)(PMe3)] 14 (Scheme 10).
Cohen and Bercaw demonstrated the clean coupling of η2-bound
ethylene with acetaldehyde to produce an oxatitanacyclopentane
ring.23 Some related reactions include coupling of η2-cy-
clobutene with acetone44a and the intramolecular coupling of
ene-one substrates.47 In contrast, addition of Ph2CdO to the
titanabicycle 10 was found to produce the oxatitanacycloheptane
21 along with small amounts of the dioxatitanacyclopentane
(benzopinacolate) 22. The addition of Ph2CdO to the diphe-
nyltitanacyclopentane 7 is found, even in the presence of excess
styrene, to yield a mixture of oxatitanacyclopentane 23, diox-
atitanacycloheptane 24, and dioxatitanacyclopentane 22. In
O(2)-Ti-C(42) 100.76(7)
O(3)-Ti-C(42) 107.33(7)
Ti-O(2)-C(21) 160.9(1)
Table 7. Structural Parameters for Selected Group 4
Metalacyclopropane Compounds
compound
M-C, (Å) C-C, (Å) ref
H2CdCH2
1.337(2)
[Cp* Ti(CH2CH2)]
2.160(4) 1.438(5) 22
2
[(ArO)2Ti(CH2CH2)(PMe3)] (14a)
2.110(2) 1.425(3)
2.148(2)
a
[Cp2Zr(CH2CH2)(PMe3)]
2.354(3) 1.449(6) 42
2.332(4)
[Cp2Zr(CH2CHPh)(PMe3)]
[Cp2Hf(CH2CMe2)(PMe3)]
2.35(1)
2.35(2)
2.316(8) 1.46(10 43b
2.368(9)
1.46(2)
42
[{(Et3P)2Cl3Zr}(CH2CH2){(Et3P)2Cl3Zr}] 2.42(2)
1.69(3)
44
2.44(2)
a This work.
lack of facile olefin rotation is similar to that reported for group
4 analogous containing cyclopentadiene ligation.28,42-44
The most interesting feature of the solid-state structure of 14
pertains to the structural parameters of the titanacyclopropane
ring. In Table 7 are collected selected parameters of related
molecules for comparison.
It can be seen that although there is a pronounced elongation
of the ethylene C-C bond upon coordination to the titanium
(42) (a) Takahashi, T.; Murakami, M.; Kunishige, M.; Saburi, M.; Uchida,
Y.; Kozawa, K.; Uchida, T.; Swanson, D. R.; Negishi, E. Chem. Lett. 1989,
761.
(43) Binger, P.; Muller, P.; Benn, R.; Rufinska, A.; Gabor, B.; Kruger,
C.; Betz, P. Chem. Ber. 1989, 122, 1035.
(45) Cotton, F. A.; Kibala, P. A. Polyhedron 1987, 6, 645.
(46) Steigerwald, M. L.; Goddard, W. A. J. Am. Chem. Soc. 1985, 107,
5027.
(44) (a) Fisher, R. A.; Buchwald, S. L. Organometallics 1990, 9, 871.
(b) Buchwald, S. L.; Kreutzer, K. A.; Fisher, R. A. J. Am. Chem. Soc. 1990,
112, 4600.
(47) (a) Kablaoui, N. M.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118,
3182. (b) Hewlett, D. F.; Whitby, R. J. J. Chem. Soc., Chem. Commun.
1990, 1684.

8638 J. Am. Chem. Soc., Vol. 119, No. 37, 1997
Thorn et al.
Scheme 11
Figure 9. Molecular structure of [Ti(OC6H3Ph2-2,6)2(OCPh2)(PMe3)]
(25).
Table 8. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6H3Ph2-2,6)2(η2-OCPh2)(PMe3)] (25)
distance of 1.817(4) is slightly shorter than the distances to the
aryloxide oxygen atoms. These parameters indicate strong
π-back-bonding into the π* (CdO) orbital, and strongly support
the oxatitanacyclopropane resonance picture.
Ti-P(4)
2.592(3)
1.839(5)
2.150(7)
Ti-O(1)
1.849(5)
1.817(4)
1.397(8)
88.6(2)
Ti-O(2)
Ti-O(3)
Ti-C(1)
C(1)-O(3)
P(4)-Ti-O(1)
P(4)-Ti-O(3)
O(1)-Ti-O(2)
O(1)-Ti-C(1)
O(2)-Ti-C(1)
Ti-O(2)-C(21)
127.0(2)
P(4)-Ti-O(2)
P(4)-Ti-C(1)
O(1)-Ti-O(3)
O(2)-Ti-O(3)
O(3)-Ti-C(1)
Ti-O(3)-C(31)
105.5(2)
110.1(2)
40.0(2)
133.0(3)
167.8(5)
90.9(2)
Related reactivity is observed in the reactions involving the
imine reagents PhCHdNR (R ) Ph, CH2Ph). The titanabicycle
10 produces the azatitanacycloheptane 27 (R ) CH2Ph, stere-
ochemistry undetermined), whereas benzylideneaniline was
observed to produce 1,7-octadiene and a new species believed
to be diazatitanacyclopentane 28 (Scheme 11) based upon
spectroscopic data. The diphenyltitanacyclopentane 7 reacts
with PhCHdNPh to produce the azatitanacyclopentane 29 in
high yield. Analysis of the 1H NMR spectrum of 29 as well as
the labeled compound obtained using Ph13CHdNPh, shows a
trans 2,3,5-triphenyl isomer to be present. We justify the single
regio- and stereochemistry for 29 on steric grounds. The trans
stereochemistry allows the phenyl rings at the C-3 and C-5
positions to occupy pseudoaxial and pseudoequatorial positions
respectively (Scheme 11). The axial positioning at C-3 removes
conflict with the N-Ph group while the preference for an
equatorial site for the phenyl group at C-5 will help avoid clashes
with the bulky 2,6-diphenylphenoxide ligands which lie above
and below the plane of the azatitanacyclopentane.
Reaction of the ethylene derivative 14 with PhCHdNCH2-
Ph produces the azatitanacyclopentane 30 and 1 equiv of PMe3
(Scheme 12). In contrast the propene complex forms the
diazatitanacyclopentane 31 along with propene. The 13C NMR
spectrum of 31 shows only one Ti-O-C(aryloxide) resonance
consistent with a trans stereochemistry as shown (Scheme 12).
The azatitanacyclopentanes 29 and 30 react with alkynes to
displace olefin and generate azatitanacyclopent-4-enes (Scheme
12). The regiochemistry of these organometallic products is
readily confirmed by NMR methods and hydrolysis is found to
produce the corresponding allylic amines (Scheme 13). The
regio- and stereochemistry of the coupling of alkynes and imines
at zirconocene metal centers has been extensively investigated
by Buchwald et al.51 The displacement of ethylene from
zirconacyclopentene rings has been shown to be a synthetically
useful reaction.52
109.0(2)
115.8(2)
109.5(2)
159.2(4)
product 23, NMR spectroscopy shows that the ketone has
coupled with the methylene carbon of the styrene ligand, leading
to the 3,3,5-triphenyl-2-oxa-titanacyclopentane regioisomer. This
reaction has also been interrogated utilizing labeled Ph213CdO,
allowing not only confirmation of the 13C NMR chemical shifts
of the carbon, but also to confirm that the reagent benzophenone
is incorporated into only the three products shown (Scheme 10).
The addition of Ph2CdO to the propene complex 15 followed
by vacuum removal of volatile products, allows the isolation
of the oxatitanacyclopropane (η2-ketone) complex 25 (Scheme
11). If the propene is not removed, or if excess propene is added
to a solution of 25, the oxatitanacyclopentane 26 is produced
along with free PMe3. The η2-ketone complex 25 has been
subjected to single crystal X-ray diffraction analysis (Figure 9,
Table 8). Although a large number of aldehyde and ketone
derivatives of the group 4 metals are known, they are typically
bimolecular with bridging ketonic functions.48 There are,
however, mononuclear ketene species which are directly related
to 25.49 The structural parameters for 25 are interesting,
showing a distinct elongation of the C-O bond, 1.397(8),
compared to a value of 1.23 in Ph2CdO.50 The Ti-O(3)
(48) (a) Erker, G. Acc. Chem. Res. 1984, 17, 103. (b) Kropp, K.; Skibbe,
V.; Erker, G.; Kruger, C. J. Am. Chem. Soc. 1983, 105, 3353. (c) Erker,
G.; Hoffmann, U.; Zwetler, R.; Betz, P.; Kruger, C. Angew. Chem., Int.
Ed. Engl. 1989, 28, 630. (d) Erker, G.; Czisch, P.; Schlund, R.; Angermund,
K.; Kruger, C. Angew. Chem., Int. Ed. Engl. 1986, 25, 364. (e) Stella, S.;
Floriani, C. J. Chem. Soc., Chem. Commun. 1986, 1053. (f) Erker, G.; Dorf,
U.; Czisch, P.; Petersen, J. L. Organometallics 1986, 5, 668. (g) Fachinetti,
G.; Biran, C.; Floriani, C.; Villa, A. C.; Guastini, C. Inorg. Chem. 1978,
17, 2995.
(49) (a) Ho, S. C. H.; Straus, D. A.; Armantrout, J.; Schaefer, W. P.;
Grubbs, R. H. J. Am. Chem. Soc. 1984, 106, 2210. (b) Meinhart, J. D.;
Santarsiero, B. D.; Grubbs, R. H. J. Am. Chem. Soc. 1986, 108, 3318.
(50) Fleischer, E. B.; Sung, N.; Hawkinson, S. J. Phys. Chem. 1968, 72,
4311.
(51) (a) Buchwald, S. L.; Watson, B. T.; Wannamaker, M. W.; Dewan,
J. C. J. Am. Chem. Soc. 1989, 111, 4486. (b) Buchwald, S. L.; Wannamaker,
M. W.; Watson, B. T. J. Am. Chem. Soc. 1989, 111, 776.

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8639
Scheme 12
Figure 10. Molecular structure of [Ti(OC6H3Ph2-2,6)2{NCPhCHPhN-
(CH2Ph)}] (35).
Scheme 14
Scheme 13
Table 9. Selected Bond Distances (Å) and Angles (deg) for
[Ti(OC6H3Ph2-2,6)2{NCPhCHPhN(CH2Ph)}] (35)
Ti-O(5)
1.816(2)
1.829(2)
1.277(3)
1.466(3)
124.10(8)
108.71(9)
104.27(9)
161.5(2)
Ti-N(4)
Ti-N(1)
C(2)-C(3)
1.886(2)
1.910(2)
1.529(4)
Ti-O(6)
N(1)-C(2)
N(4)-C(3)
O(5)-Ti-O(6)
O(5)-Ti-N(4)
O(6)-Ti-N(4)
Ti-O(5)-C(51)
O(5)-Ti-N(1)
O(6)-Ti-N(1)
N(4)-Ti-N(1)
Ti-O(6)-C(61)
113.61(9)
114.72(9)
81.9(1)
The azatitanacyclopentane compound 30 reacts with one
equivalent of benzonitrile to produce one equivalent of ethylene
and a new titanium compound 35 (Scheme 14). The new
compound is formulated as a 2,5-diazatitanacylopent-2-ene
derivative on the basis of spectroscopic data and a single crystal
diffraction study of 35 (Figure 10, Table 9). The molecular
structure of 35 shows a planar metallacycle ring, in contrast to
the nonplanar situation found for 2,5-diazatitanacylopent-3-ene
species. Solutions of 35 were found to be converted over days
into 2,5-diazatitanacylopent-3-ene (ene-diamide) 36, which was
obtained as an impure liquid, but found to crystallize as its
pyridine adduct 37 (Scheme 14). The isomerization of 2-aza-
metallacyclopentene rings has literature precedence.23,53
151.5(2)
have been developed. The use of sterically demanding aryloxide
groups has been found to generate chemistry which is both
different and complimentary to that developed with cyclopen-
tadiene ligation. The solution spectroscopic properties and
reactivity of the titanacyclopentane rings can only be accounted
for by facile fragmentation into a bis(olefin) intermediate. The
synthetic utility of both types of metallacycles has been probed
with ketones and imines and shown to lead to a wide variety of
new oxa and aza-titanacycles.
Experimental Section
All manipulations were carried out under N2 using a Vacuum
Atmospheres dry box and conventional Schlenk techniques. All
solvents were dried by distillation over sodium/benzophenone under a
nitrogen atmosphere. 1H and 13C NMR spectra were recorded using a
Varian Gemini 200 MHz instrument. Microanalytical, mass spectral,
and X-ray crystallographic data were acquired through Purdue in-house
facilities. The compounds [Ti(OC6H3Ph2-2,6)2Cl2] (1)15 and [Ti(OC6H3-
Ph2-2,6)2(C4Et4)] (3)16 were obtained by published procedures. Syn-
thetic details can be found in the Supporting Information.
Conclusions
Good synthetic routes to a variety of titanacyclopentane and
titanacyclopropane species for use in organometallic synthesis
(52) Takahashi, T.; Kageyama, M.; Denisov, V.; Hara, R.; Negishi, E.
Tetrahedron Lett. 1993, 34, 687.
(53) Strickler, J. R.; Wigley, D. E. Organometallics 1990, 9, 1605 and
references therein.

8640 J. Am. Chem. Soc., Vol. 119, No. 37, 1997
Thorn et al.
[Ti(OC6HPh4-2,3,5,6)2Cl2] (2). Anal. Calcd for TiO2Cl2C66H48,
2‚C6H6: C, 79.92; H, 4.88; Cl, 7.15. Found: C, 79.97; H, 4.70; Cl,
7.21. 1H NMR (C6D6, 30 °C): δ 6.50-7.50 (aromatics).
[Ti(OC6H3Ph2-2,6)2(CH2)4] (4). Anal. Calcd for TiC40H34O2: C,
80.80; H, 5.76. Found: C, 80.69; H, 6.02. 1H NMR (C6D6, 30 °C):
δ 6.90-7.41 (aromatics); 1.98 (broad), 1.60 (broad, CH2). 13C NMR
(C6D6, 30 °C): δ 160.3 (Ti-O-C); 89.7 [1J(13C-1H) ) 127.4 Hz,
TiCH2]; 31.1 [1J(13C-1H) ) 127.7Hz, TiCH2CH2].
[Ti(OC6H3Ph2-2,6)2(CH2CHMeCHMeCH2)] (5). Anal. Calcd for
TiC42H30O2: C, 81.02; H, 6.15. Found: C, 81.31; H, 6.56. 1H NMR
(C6D6, 30 °C): trans isomer δ 6.88-7.48 (aromatic); 2.04 (m, CHMe);
1.88 (t, 10.6 Hz), 1.24 (dd, TiCH2, 10.6 Hz, 4.1 Hz); 0.93 (d, CHMe,
5.4 Hz). 13C NMR (C6D6, 30 °C): trans isomer δ 160.1 (Ti-O-C);
98.0 [1J(13C-1H) ) 129.2 Hz, TiCH2]; 44.8 [1J(13C-1H) ) 126.2 Hz,
CHMe]; 23.3 (CHMe).
[Ti(OC6H3Ph2-2,6)2(CH2CHEtCHEtCH2)] (6). Anal. Calcd for
TiC44H42O2: C, 81.22; H, 6.51. Found: C, 81.54; H, 6.91. 1H NMR
(C6D6, 30 °C): trans isomer δ 6.88-7.8 (aromatics); 2.03 (m, CHEt);
1.85 (t), 1.22 (m, TiCH2); 1.22 (m, CH2CH3); 0.60 (t, CH2CH3). 13C
NMR (C6D6, 30 °C): trans isomer δ 160.2 (Ti-O-C); 95.0 [1J(13C-
1H) ) 126.5 Hz, TiCH2]; 48.7 [1J(13C-1H) ) 126.8 Hz, CHEt]; 28.9
(CH2CH3); 18.1 (CH2CH3)
[Ti(OC6H3Ph2-2,6)2(CH2CH2)(PMe3)] (14a). Anal. Calcd for
TiC41H39O2P: C, 76.63; H, 6.12; P, 4.82. Found: C, 76.99; H, 6.14;
P, 4.58. 1H NMR (C6D6, 30 °C): δ 6.87-7.36 (aromatics); 1.72 [td,
3
3J(1H-31P) ) 6.8 Hz, J(1H-1H) ) 12 Hz CH2 adjacent to PMe3];
3
0.51 [t, J(1H-31P) < 1 Hz, CH2 away from PMe3]; 0.22 (d, PMe3).
1
13C NMR (C6D6, 30 °C): δ 160.0 (Ti-O-C); 78.0 [d, J(13C-1H) )
147.6 Hz, 2J(13C-31P) ) 5.9 Hz, CH2 adjacent to PMe3]; 67.0 [1J(13C-
1H) ) 149.6 Hz, CH2 away from PMe3], 12.5 (d, PMe3). 31P NMR
(C6D6, 30 °C): δ 2.43 (PMe3).
[Ti(OC6H3Ph2-2,6)2(CH2CH2)(PMe2Ph)] (14b). 1H NMR (C6D6,
30 °C): δ 6.80-7.27 (aromatics); 1.70 (m), 0.5 (m, CH2CH2); 0.45
(d, PMe2Ph). 13C NMR (C6D6, 30 °C): δ 160.0 (Ti-O-C); 79.4 [d,
2J(13C-31P) ) 2.8 Hz, CH2 adjacent to PMe2Ph]; 68.8 (CH2 away from
PMe2Ph); 11.0 (d, PMe2Ph).
[Ti(OC6H3Ph2-2,6)2(CH2CHMe)(PMe3)] (15a). Anal. Calcd for
TiC42H41O2P: C, 76.82; H, 6.29; P, 4.72. Found: C, 76.83; H, 6.46;
P, 4.98. 1H NMR (C6D6, 30 °C): major isomer δ 6.8-7.6 (aromatics);
1.61 (m), 1.48 (m, CH2); 1.43 (d, 8.0 Hz, CHMe); 0.53 (m, CHMe);
0.14 (d, PMe3); minor isomer δ 2.32 (m, CHMe); 1.04 (d, 8.0 Hz,
CHMe); 0.90 (m), 0.44 (m, CH2); 0.02 (d, PMe3). 31C NMR (C6D6,
1
2
30 °C) major isomer δ 80.7 [d, J(13C-1H) ) 148.1 Hz, J(13C-31P)
) 5.5 Hz, CH2]; 76.2 [1J(13C-1H ) 148.1 Hz, CHMe]; 22.6 (CHMe);
12.5 (PMe3); minor isomer δ 89.2 [d, 1J(13C-1H) ) 148.3 Hz, 2J(13C-
31P) ) 6.4 Hz, CHMe]; 74.0 [1J(13C-1H) ) 146.5 Hz, CH2]; 20.9
(CHMe); 12.8 (PMe3). 31P NMR (C6D6, 30 °C): major isomer δ 2.19
(PMe3); minor isomer δ 1.40 (PMe3).
[Ti(OC6H3Ph2-2,6)2{C4H6(Ph)2}] (7).
Anal.
Calcd for
TiC52H42O2: C, 83.57; H, 5.64. Found: C, 83.63; H, 5.67. 1H NMR
(C6D6, 30 °C): δ 6.20-7.41 (aromatics); 3.30 (m), 2.77 (broad m),
2.00 (broad m), 1.30 (m). 13C NMR (C6D6, 30 °C): δ 160.3 (Ti-O-
C); 107.0 (broad, TiCHPh).
[Ti(OC6H3Ph2-2,6)2(CH2CHMe)(PMe2Ph)] (15b). Anal. Calcd for
TiC47H43O2P: C, 78.54; H, 6.03; P, 4.31. Found: C, 75.23; H, 5.88;
P, 3.02. 1H NMR (C6D6, 30 °C): major isomer δ 6.73-7.59
(aromatics); 1.46 (d, 6.2 Hz, CHMe); 1.63 (m), 1.47 (m, CH2); 0.41
(m, CHMe); 0.64 (d), 0.26 (d, 5.8 Hz, PMe2Ph); minor isomer δ 2.23
(m, CHMe); 1.13 (d, 6.4 Hz, CHMe); 1.00 (m), 0.4 (m, CH2); 0.36 (d,
6.4 Hz, PMe2Ph). 13C NMR (C6D6, 30 °C): major isomer δ 81.8 [d,
1J(13C-1H) ) 146.2 Hz, 2J(13C-31P) ) 2.6 Hz, Hz, CH2]; 77.5 [1J(13C-
1H) ) 148.3 Hz, CHMe]; 22.6 (CHMe); minor isomer δ 90.0 (CH2);
76.2 (CHMe). 31P NMR (C6D6, 30 °C): major isomer δ 14.8 (PMe2-
PH); minor isomer δ 11.4 (PMe2Ph).
Dimerization of Styrene Catalyzed by [Ti(OC6H3Ph2-2,6)2{C4H6-
(Ph)2}] (7). In a typical procedure 0.10 g (0.15 mmol) of [Ti(OC6H3-
Ph2-2,6)2Cl2] (1) was dissolved in 5 mL of benzene. To this solution
was added 2.1 equiv of BunLi (0.12 mL, 0.31 mmol) and 25 equiv of
styrene (0.42 mL, 3.64 mmol). This reacton mixture was then heated
at approximately 100 °C initially producing trans-1,3-diphenylbut-1-
ene. 1H NMR (C6D6, 30 °C): δ 6.80-7.40 (aromatics); 6.33 [AB,
3J(1H-1H) ) 16.0 Hz, trans CHdCH]; 3.42 (m, CHPhCH3); 1.33 (d,
CH3). 13C NMR (C6D6, 30 °C): δ135.1, 128.4 (CHPhdCH); 42.5
(CHPhCH3); 21.2 (CH3). HRMS: calcd for C16H16 208.1252, found
208.1251. Upon further heating this initial product was isomerized to
1,3-diphenylbut-2-ene. 1H NMR (C6D6, 30 °C): 6.80-7.40 (aromatics);
[Ti(OC6H3Ph2-2,6)2(CHPhCH2)(PMe2Ph)] (17). 1H NMR (C6D6,
30 °C): major isomer δ 6.50-7.40 (aromatics); 2.20 (ddd), 1.79 (ddd,
12 Hz, 7Hz, CH2); 1.10 (t, 12 Hz, CHPh); 0.63 (d), 0.03 (d, 7.2 Hz,
PMe2Ph); minor isomer δ 2.70 (dd, 12 Hz, CHPh); 0.98 (dd), 0.22
(dd, 12 Hz, 6 Hz, CH2); 0.46 (d), -0.02 (d, 7.3 Hz, PMe2Ph). 13C
NMR (C6D6, 30 °C): major isomer δ 159.5 (Ti-O-C); 159.3 (Ti-
O-C); 93.1 [d, 2J(13C-31P) ) 2.9 Hz, CH2]; 78.1 (CHPh); minor isomer
3
5.89 [t, J(1H-1H) ) 7.3 Hz, CH]; 3.30 (d, CH2Ph); 1.86 (s, CH3).
[Ti(OC6H3Ph2-2,6)2(µ-Cl)]2 (8). Anal. Calcd for Ti2C72H52O4Cl2:
C, 75.34; H, 4.57; Cl, 6.18. Found: C, 81.54; H, 4.85; Cl, 6.29. The
X-ray crystal structure of 8 has been previously published.
[Ti(OC6HPh4-2,3,5,6)2(µ-Cl)]2 (9). Anal. Calcd for TiO4-
Cl2C120H84: C, 82.05; H, 4.82; Cl, 4.09. Found: C, 81.75; H, 5.05;
Cl, 4.12.
2
δ 160.1 (Ti-O-C); 159.8 (Ti-O-C); 83.3 (CH2); 80.1 [d, J(13C-
31P) ) 5.3 Hz, CHPh]. 31P NMR (C6D6, 30 °C): major isomer δ 15.2
[3J(31P-1H) ) 7.0 Hz, PMe2Ph]; minor isomer δ 13.5 [3J(31P-1H) )
6.0 Hz, PMe2Ph].
[Ti(OC6H3Ph2-2,6)2{CH2CH(C4H8)CHCH2}] (10). Anal. Calcd
for TiC44H40O2: C, 81.47; H, 6.22. Found: C, 81.56; H, 6.41. 1H
NMR (C6D6, 30 °C): δ 6.90-7.42 (aromatics); 0.4-2.0 (aliphatics).
13C NMR (C6D6, 30 °C): δ 160.2 (Ti-O-C); 95.9 [1J(13C-1H) )
128.0 Hz, TiCH2]; 46.8 [1J(13C-1H) ) 129.0 Hz, TiCH2CH]; 37.7
[1J(13C-1H) ) 124.5 Hz, TiCH2CHCH2]; 27.0 [1J(13C-1H) ) 124.5
Hz, TiCH2CHCH2CH2]. The product of hydrolysis of 10 was identified
as trans-1,2-dimethylcyclohexane by comparison of the 1H NMR
spectrum and GC trace to that of an authentic sample.
[Ti(OC6HPh4-2,3,5,6)2{CH2CH(C4H8)CHCH2}] (11). To a stirred
mixture of [Ti(OC6HPh4-2,3,5,6)2Cl2] (2, 3.00 g, 3.03 mmol) and 1,7-
octadiene (0.90 mL, 6.06 mmol, two fold excess) in benzene (10 mL)
was slowly added BunLi (6.06 mmol) in hexane (2.5 M solution). The
resulting brown suspension was filtered and the solvent removed under
vacuum. The oily residue was dissolved in a minimum of toluene and
allowed to stand whereupon orange crystals of the toluene solvate 3b‚-
2C7H8 were deposited. The yield of 3b obtained in this fashion has
been found to vary from 15-75%. Satisfactory microanalytical data
on 3b could not be obtained presumably due to loss of toluene solvate.
[Ti(OC6H3Ph2-2,6)2(OCPh2CH2CH2CH2CH2)] (18). Anal. Calcd
for TiC59H50O3 18‚C6H6: C, 82.90; H, 5.85. Found: C, 82.61; H, 6.14.
1H NMR (C6D6, 30 °C): δ 6.88-7.42 (aromatics); 2.22 (m, CH2CPh2);
1.44 (m, TiCH2CH2); 1.21 (m, CH2CH2CPh2); 1.04 (m, TiCH2). 13C
NMR (C6D6, 30 °C): δ 159.6 (Ti-O-C); 94.1 (OCPh2); 87.5 (TiCH2);
43.4 (TiCH2CH2); 32.4, 26.3 (CH2CH2CPh2).
Preparation of [Ti(OC6H3Ph2-2,6)2(OCPh2CH2CH2)] (19). Anal.
Calcd for TiC51H40O3: C, 81.81; H, 5.38. Found C, 81.62; H, 5.20.
1H NMR (C6D6, 30 °C): δ 6.85-7.38 (aromatics); 3.34 (t), 1.47 (t,
6.6 Hz CH2). Selected 13C NMR (C6D6, 30 °C): δ 160.0 (ipso OAr′′);
148.8 (ipso OCPh2); 92.4 (TiOCPh2); 82.2 [1J(13C-1H) ) 132.2 Hz,
TiCH2]; 53.0 [1J(13C-1H) ) 131.0 Hz, TiCH2CH2].
[Ti(OC6H3Ph2-2,6)2(OCPh2CH2CH2CPh2O)] (20). Anal. Calcd
for TiC64H50O4: C, 82.57; H, 5.41. Found: C, 82.82; H, 5.52. 1H
NMR (C6D6, 30 °C): δ 6.78-7.41 (aromatics); 2.51 (s, CH2). 13C
NMR (C6D6, 30 °C): δ 160.0 (Ti-O-C); 95.1 (TiOCPh2); 38.0 (CH2).
[Ti(OC6H3Ph2-2,6)2{OCPh2CH2CH(C4H8)CHCH2}] (21). Anal.
Calcd for TiC57H50O3: C, 82.39; H, 6.07. Found: C, 82.61; H, 6.16.
1H NMR (C6D6, 30 °C): δ 6.83-7.71 (aromatics): 2.37 (dd, 16 Hz, 8
Hz), 2.18 (d, CH2CPh2); 0.63-1.38 (m, other aliphatic protons); 0.40
(bdd), 0.22 (bdd, TiCH2). 13C NMR (C6D6, 30 °C): δ 160.0, 159.0
(Ti-O-C); 97.5 (OCPh2); 93.1 (TiCH2); 52.5 (OCPh2CH2); 49.3, 39.6
(CH); 37.8, 37.6, 26.8, 26.6 (CHCH2CH2).
[{Ti(OC6H3Ph2-2,6)2(CH2CHMeCMe2)}2(µ-O)] (12). Anal. Calcd
for Ti2C84H66O3: C, 79.99; H, 6.07. Found: C, 80.35; H, 6.58. 1H
NMR (C6D6, 30 °C): δ 6.83-7.39 (aromatics); 0.42-1.48 (aliphatics).
13C NMR (C6D6, 30 °C): δ 160.7 (Ti-O-C); 99.6, 99.2 (TiCH2); 42.4,
41.8 (CHMe); 35.9, 35.7 (CHMe2); 20.6, 20.5 (CHMe); 17.8, 17.5,
17.5, 17.3 (CHMe2).

Chemistry of Titanacyclopentane and -propane Rings
J. Am. Chem. Soc., Vol. 119, No. 37, 1997 8641
Reaction of [Ti(OC6H3Ph2-2,6)2{C4H6(Ph)2}] (7) with Ph2CdO.
A sample of [Ti(OC6H3Ph2-2,6)2{C4H6(Ph)2}] (7) was dissolved in
benzene-d6 (1 mL) in a J. Young valve solvent sealed NMR tube. To
[Ti(OC6H3Ph2-2,6)2{N(CH2Ph)CHPhCHPhN(CH2Ph)}] (31). Anal.
Calcd for TiC64H52N2O2: C, 82.74; H, 5.64; N, 3.02. Found: C, 82.83;
H, 5.67; N, 3.02. 1H NMR (C6D6, 30 °C): δ 6.25-7.69 (aromatics);
4.68 (s, CHPh); 3.99 (d), 2.99 (d, 16 Hz, CH2Ph). 13C NMR (C6D6,
30 °C): δ 160.6 (ipso OAr′′); 76.3 (CHPh); 55.7 (CH2Ph).
1
this solution was added solid benzophenone. The H NMR at 30 °C
of the resulting dark red solution was immediately obtained and contains
22, 23 and 24: δ 6.50-7.80 (aromatics); 5.62 (broad d), 5.10 (broad
d, PhCHdCH2); 4.51 (broad, Ti-OCPh2CHPh of 24); 3.71 (t, TiCHPh
of 23); 3.20-3.45 (m, TiCHPhCH2 of 23); 3.38 (dd), 3.01 (broad d,
Ti-OCPh2CH2 of 24). Over the course of one day, or if more
benzophenone was added, the solution became light orange in color.
The 1H NMR of this solution showed that the signals for 23 had
disappeared and the 1H NMR signals for 24 had become more intense.
Reaction of [Ti(OC6H3Ph2-2,6)2{C4H6(Ph)2}](7) with Ph213CdO.
A sample of [Ti(OC6H3Ph2-2,6)2{C4H6(Ph)2}] (7) was placed in a J.
Young valve solvent sealed NMR tube along with benzene-d6 (1 mL).
To this was added one crystal of solid 13C-labeled benzophenone. The
13C NMR, at 30 °C, of the resulting red solution clearly shows the
presence of 22* (δ 112.8), 23* (δ 90.3), and 24* (δ 99.0 and 97.5).
As more benzophenone was added (one crystal at a time) the signal at
δ 90.3 disappeared and the signals at δ 112.8, 99.0, and 97.5 increased
in intensity. This corresponds to the same trend seen in the 1H NMR
above using natural abundance benzophenone.
[Ti(OC6H3Ph2-2,6)2{N(CH2Ph)CHPhCEtCEt}] (32). Anal. Calcd
for TiC56H49NO2: C, 82.44; H, 6.05; N, 1.72. Found C, 82.84; H,
6.27; N, 1.87. 1H NMR (C6D6, 30 °C): δ 6.76-7.61 (aromatics); 4.35
(s, CHPh); 3.14 (d), 2.90 (d, 15.7 Hz, CH2Ph); 1.40 (q, 7.6 Hz), 1.26
(m, CH2CH3); 0.55 (t), 0.40 (t, 7.5 Hz, CH2CH3). 13C NMR (C6D6, 30
°C): δ 218.2 (TiCEt); 160.7, 160.4 (Ti-O-C); 139.8 (TiCEtCEt); 61.7
(CHPh); 55.5 (CH2Ph); 27.2, 23.8 (CH2CH3); 14.8, 13.1 (CH2CH3).
1
Hydrolysis product CHEtdCEtCHPhNHBz H NMR (C6D6, 30 °C):
δ 7.04-7.42 (aromatics); 5.62 (t, 7.3 Hz, CHEt); 4.14 (s, CHPh); 3.63
(dd, 16.9 Hz, 3.5 Hz, CH2Ph); 1.97 (m, CH2CH3); 1.32 (broad, NH);
0.94 (t), 0.80 (t, 7.5 Hz, CH2CH3). 13C NMR (C6D6, 30 °C): δ 68.7
(CHPh); 52.2 (CH2Ph); 21.6, 21.4 (CH2CH3); 14.9, 14.5 (CH2CH3).
HRMS: calcld for 280.2065, found 280.2062.
[Ti(OC6H3Ph2-2,6)2{N(CH2Ph)CHPhCHCPh}] (33). Anal. Calcd
for TiC58H45NO2: C, 83.34; H, 5.43; N, 1.68. Found: C, 83.00; H,
5.54; N, 1.71. 1H NMR (C6D6, 30 °C): δ 6.43-7.61 (aromatics): 6.74
(d, 3.1 Hz, CPhCH); 4.50 (d, 3.1 Hz, CHPh); 3.23 (d); 3.05 (d, 15.8
Hz, CH2Ph). 13C NMR (C6D6, 30 °C): δ 207.5 (TiCPh); 160.9, 160.6
(Ti-O-C); 138.4 (CPhCH); 58.9 (CHPh); 56.6 (CH2Ph). Hydrolysis
[Ti(OC6H3Ph2-2,6)2(OCPh2)(PMe3)] (25). Anal. Calcd for
TiC52H45O3P: C, 78.38; H, 5.69; P, 3.89. Found: C, 79.27; H, 5.90;
P, 3.73. 1H NMR (C6D6, 30 °C): δ 6.79-7.49 (aromatics); -0.23 (d,
PMe3). 13C NMR (C6D6, 30 °C: δ 160.5 (Ti-O-C); 91.4 (CPh2);
12.0 (d, PMe3). Hydrolysis product Ph2CHOH: 1H NMR (C6D6, 30
°C: δ 6.95-7.30 (aromatics) 5.48 (d, OH); 1.69 (d, CH).
1
product trans-CHPhCHCHPhNHBz H NMR (C6D6, 30 °C): δ 7.0-
7.45 (aromatics); 6.51 (d, 15.8 Hz, CdCHPh); 6.25 (dd, 15.8 Hz, 7.0
Hz, CHdC); 4.26 (d, 7.0 Hz, NCHPh); 3.65 (s, NCH2Ph); 1.89 (broad,
NH). 13C NMR (C6D6, 30 °C): δ 65.1 (CHPh); 51.8 (CH2Ph).
HRMS: calcd for 299.1674, found 299.1668.
[Ti(OC6H3Ph2-2,6)2(OCPh2CH2CHMe)] (26). The major isomer
was [Ti(OC6H3Ph2-2,6)2(OCPh2CH2CHMe)] while the minor isomer
was [Ti(OC6H3Ph2-2,6)2(OCPh2CHMeCH2)]. 1H NMR (C6D6, 30
°C): major isomer δ 6.7-7.5 (aromatics); 3.25 (dd, 13 Hz, 12 Hz),
2.94 (dd, 14 Hz, 6 Hz, CH2); 1.88 (m, CHMe); 0.60 (d, 6 Hz, CHMe);
minor isomer δ 3.69 (m, CHMe); 1.12 (dd), 0.99 (dd, CH2); 0.93 (d,
CHMe). 13C NMR (C6D6, 30 °C): major isomer δ 159.7 (Ti-O-C);
149.4, 148.6 (ipso OCPh2); 95.4 (TiCHMe); 89.8 (TiOCPh2); 59.0
(CH2); 21.8 (CHMe).
[Ti(OC6H3Ph2-2,6)2{NPhCHPhCHC(SiMe3)}] (34). Anal. Calcd
for TiC54H47NO2Si: C, 79.29; H, 5.80; N, 1.71. Found: C, 78.90; H,
6.06; N, 1.63. 1H NMR (C6D6, 30 °C): δ 7.57 (d, ortho-Ph2-2,6);
7.39 (d, 4.0 Hz, TiNPhCHPhCH); 6.40-7.30 (aromatics); 5.45 (d,
ortho-NPh); 4.62 (d, 4.0 Hz, TiNPhCHPh); -0.25 [s, Si(CH3)3]. 13C
NMR (C6D6, 30 °C): δ 228.4 (TiNPhCHPhCHCSiMe3); 160.7, 160.5
(Ti-O-C); 137.4 (TiNPhCHPhCH); 54.5 (TiNPhCHPh); -1.0 [Si-
(CH3)3]. Hydrolysis product trans-Me3SiCHdCHCHPhNHPh 1H NMR
(C6D6, 30 °C): δ 6.60-7.30 (aromatics); 6.41 (d, ortho-NPh); 6.10
[dd, 3J(1H-1H) ) 18.5 Hz and 5.0 Hz, Me3SiCHCH]; 5.88 [d, 3J(1H-
1H) ) 18.5 Hz, Me3SiCH); 4.78 (b, Me3SiCHCHCHPh); 3.73 (broad
d, NHPh); -0.02 [s, Si(CH3)3].
[Ti(OC6H3Ph2-2,6)2{NCPhCHPhN(CH2Ph)}] (35). Anal. Calcd
for TiC63H50N2O2 35‚C6H6: C, 82.70; H, 5.51; N, 3.06. Found: C,
83.32; H, 5.78; N, 2.99. 1H NMR (C6D6, 30 °C): δ 6.73-7.62
(aromatics); 5.81 (s, CHPh); 3.72 (d), 2.96 (d, 15.8 Hz, CH2Ph). 13C
NMR (C6D6, 30 °C): δ 186.4 (TiNCPh); 161.4, 160.7 (ipso OAr′′);
90.6 (CHPh); 53.5 (CH2Ph).
[Ti(OC6H3Ph2-2,6)2{N(CH2Ph)CHPhCH2CH(C4H8)CHCH2}] (27).
Anal. Calcd for TiC58H53NO2: C, 82.54; H, 6.33; N, 1.66. Found:
C, 82.58; H, 6.27; N, 1.66. 1H NMR (C6D6, 30 °C): δ 6.69-7.51
(aromatics); 4.30 (d), 3.01 (d, 15 Hz, CH2Ph); 3.67 (d, 12 Hz, CHPh);
2.58 (m, CHPhCH2); 0.31 (m), 0.02 (m, TiCH2); 0.70-1.50 (other
aliphatic protons). 13C NMR (C6D6, 30 °C): δ 160.5, 160.2 (Ti-O-
C); 87.6 (TiCH2); 63.3 (NCHPh); 58.1 (NCH2Ph); 48.1 (CH); 43.4,
39.6, 27.5, 27.1 (CHCH2CH2). Hydrolysis product BzNHCHPhCH2-
CH(C4H8)CH3 1H NMR (C6D6, 30 °C): δ 6.85-7.49 (aromatics); 3.63
(dd, CH2Ph); 3.49 (q, NH); 0.77 (d, CH3); 0.6-2.1 (other aliphatic
protons). Mass spectroscopy: parent M+ at 307 amu.
[Ti(OC6H3Ph2-2,6)2{N(Ph)CHPhCHPhN(Ph)}] (28). 1H NMR
(C6D6, 30 °C): δ 5.84-7.60 (aromatics); 5.73, 5.00 (m’s, olefinic 1,7-
octadiene); 5.41, 4.93 (s,s,cis- and trans-NPhCHPh); 2.00-1.00
(aliphatic 1,7-octadiene). 13C NMR (C6D6, 30 °C): δ73.7, 70.8 (cis-
and trans-NPhCHPh).
[Ti(OC6H3Ph2-2,6){NHCPhCPhN(CH2Ph)}] (36). A sample of
[Ti(OC6H3Ph2-2,6)2{NCPhCHPhN(CH2Ph)}] (30, 0.50 g, 0.62 mmol)
was dissolved in benzene (10 mL). A small amount of PhCN was
added, and the solution was refluxed for 1 h. Excess solvent was
removed under vacuum, and the product 36 was recovered as a dark
red oil. Selected 13C NMR (C6D6, 30 °C): δ 159.2 (Ti-O-C); 117.0,
115.0 (CPhCPh); 58.4 (CH2Ph).
[Ti(OC6H3Ph2-2,6)2{NHCPhCPhN(CH2Ph)}(py)] (37). Anal. Cal-
cd for TiC62H49N3O2: C, 81.30; H, 5.39; N, 4.59. Found: C, 81.67;
H, 5.57; N, 4.49. 1H NMR (C6D6, 30 °C): δ 9.91 (broad, NH); 6.13-
7.60 (aromatics); 4.62 (s, CH2Ph). 13C NMR (C6D6, 30 °C): δ 160.6
(ipso OAr′′); 56.4 (CH2Ph).
[Ti(OC6H3Ph2-2,6)2(NPhCHPhCH2CHPh)] (29). Anal. Calcd for
TiC57H45NO2: C, 83.08; H, 5.51; N, 1.70. Found: C, 82.74; H, 5.63;
N, 1.82. 1H NMR (C6D6, 30 °C): δ 6.50-7.50 (aromatics); 5.91 (d),
5.47 (d, 7.7 Hz, ortho-NPh); 4.37 (d, 3.7 Hz, TiNPhCHPh); 3.32 (ddd,
16.2 Hz, 14.5 Hz, 5.2 Hz), 3.04 (dd, 14.3 Hz, 3.5 Hz, TiCHPhCH2);
2.42 (d, 15.8 Hz, TiCHPh). 13C NMR (C6D6, 30 °C): δ 160.7, 160.1
(Ti-O-C); 107.5 (TiCHPh); 59.0 (TiNPhCHPh); 30.7 (TiCHPhCH2).
[Ti(OC6H3Ph2-2,6)2{N(CH2Ph)CHPhCH2CH2}] (30). Anal. Cal-
cd for TiC58H49NO2 30‚C6H6: C, 82.94; H, 5.88; N, 1.67. Found: C,
82.63; H, 5.95; N, 2.05. 1H NMR (C6D6, 30 °C): δ 6.63-7.43
(aromatics); 3.89 (d), 3.24 (d, 15.1 Hz, CH2Ph); 3.75 (t, 6.9 Hz, CHPh);
2.21 (m, TiCH2CH2); 1.39 (m), 1.15 (m, TiCH2). 13C NMR (C6D6, 30
°C): ∂ 160.4, 160.1 (Ti-O-C); 85.9 (TiCH2); 64.2 (CHPh); 57.1; CH2-
Ph); 33.7 (TiCH2CH2). Hydrolysis product [PhCH2NHCHPhCH2CH3]
1H NMR (C6D6, 30 °C): ∂ 7.08-7.30 (aromatics); 3.66 (d), 3.44 (d,
13.6 Hz, CH2Ph); 3.41 (t, CHPh); 2.7 (broad, NH); 1.63 (dq, CH2);
0.70 (t, 7.4 Hz, CH3). 13C NMR (C6D6, 30 °C): δ 64.6 (CHPh); 51.8
(CH2Ph); 31.4 (CH2); 10.9 (CH3).
Acknowledgment. We thank the National Science Founda-
tion (Grant CHE-9700269) for financial support of this research.
Supporting Information Available: Experimental details
of the synthesis of new compounds; description of the experi-
mental procedures for X-ray diffraction studies; tables of thermal
parameters, bond distances and angles, intensity data, torsion
angles, and mutiplicities for 4, 7, 10, 12, 14a, 25 and 35 (172
pages). See any current masthead page for ordering information
and Internet access instructions.
JA970515Z