Ethene elimination during thermolysis of Bis(3- butenyltetramethylcyclopentadienyl)dimethyltitanium

Article abstract of DOI:10.1021/om2001487

Thermolysis of [TiMe₂{η⁵-C₅Me ₄(CH₂CH₂CH - CH₂)}₂] (1) in toluene at 120 °C for 4 h resulted in the formation of the cyclopentadiene ring-tethered titanacyclobutane [Ti^IV{η ⁵-C₅Me₄CH₂CH₂CH(κ- CH)}₂CH₂] (2) in virtually quantitative yields. Thermolysis in an NMR tube at 100 °C revealed that initial elimination of methane is followed by addition of one 3-butenyl double bond to a titanocene-methylidene moiety. The formed titanacyclobutane intermediate [Ti{η⁵-C₅Me₄(CH₂CH ₂CH - CH₂)}{η⁵-C₅Me ₄CH₂CH₂CH(κ-CH)CH₂CH ₂(κ-CH₂)}] (4) then underwent a metathesis reaction with the pendant 3-butenyl to give 2 and free ethene. Cleavage of Ti-C bonds of 2 with HCl afforded stable ansa-[TiCl₂{η⁵-C ₅Me₄(CH₂)₇η⁵-C ₅Me₄}] (3). Sunlight photolysis of 1 gave rise to the cyclopentadiene ring-tethered titanacyclopentane [Ti^IV{η ⁵-C₅Me₄(CH₂CH₂CH(κ- CH)CH₂}₂] (5), the known product of cycloaddition reactions following the removal of chlorine atoms from [TiCl₂{η ⁵-C₅Me₄(CH₂CH₂CH - CH₂)}₂] with magnesium (as found by Horacek, M.Chem. Eur. J. 2000, 6, 2397).

Full text of DOI:10.1021/om2001487

ARTICLE
pubs.acs.org/Organometallics
Ethene Elimination during Thermolysis of
Bis(3-butenyltetramethylcyclopentadienyl)dimethyltitanium
Jiꢀrí Pinkas,† Rꢁobert Gyepes,‡ Jiꢀrí Kubiꢀsta,† Michal Horꢁaꢀcek,† and Karel Mach*,†
†J. Heyrovskꢁy Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejꢀskova 3, 182 23 Prague 8,
Czech Republic
‡J. Selye University, Pedagogical Faculty, Bratislavskꢁa cesta 3322, 945 01 Komꢁarno, Slovak Republic
S Supporting Information
b
ABSTRACT: Thermolysis of [TiMe2{η5-C5Me4(CH2CH2CHdCH2)}2] (1) in
toluene at 120 °C for 4 h resulted in the formation of the cyclopentadiene ring-
tethered titanacyclobutane [TiIV{η5-C5Me4CH2CH2CH(κ-CH)}2CH2] (2) in vir-
tually quantitative yields. Thermolysis in an NMR tube at 100 °C revealed that initial
elimination of methane is followed by addition of one 3-butenyl double bond to a
titanoceneꢀmethylidene moiety. The formed titanacyclobutane intermediate
[Ti{η5-C5Me4(CH2CH2CHdCH2)}{η5-C5Me4CH2CH2CH(κ-CH)CH2CH2-
(κ-CH2)}] (4) then underwent a metathesis reaction with the pendant 3-butenyl to
give 2 and free ethene. Cleavage of TiꢀC bonds of 2 with HCl afforded stable ansa-[TiCl2{η5-C5Me4(CH2)7η5-C5Me4}] (3).
Sunlight photolysis of 1 gave rise to the cyclopentadiene ring-tethered titanacyclopentane [TiIV{η5-C5Me4(CH2CH2CH(κ-
CH)CH2}2] (5), the known product of cycloaddition reactions following the removal of chlorine atoms from [TiCl2{η5-
C5Me4(CH2CH2CHdCH2)}2] with magnesium (as found by Horaꢀcek, M. et al. Chem. Eur. J. 2000, 6, 2397).
’ INTRODUCTION
and photolysis of the well-defined bis(3-butenyltetramethylcy-
clopentadienyl)dimethyltitanium, [TiMe2{η5-C5Me4(CH2CH2-
CHdCH2)}2] (1),3 are of interest. This compound melts with-
out decomposition at 72 °C;3 however, its thermolysis might
occur at about 110 °C, the temperature at which the parent
compound of the persubstituted titanocene series [TiMe2Cp*2]
(Cp* = η5-C5Me5) releases the first Me group to give methane
and the singly tucked-in methyltitanocene [TiMe(Cp*){C5Me4-
(CH2)}].4a,b The thorough study of this reaction using the
deuterated compounds [Ti(CD3)2Cp*2] and [TiMe2(Cp*-
d15)2] gave evidence that the methane evolved was formed from
the rupture of one TiꢀMe bond followed by hydrogen transfer
from the other TiꢀMe bond. This led to the formation of the
titanoceneꢀmethylidene intermediate [Ti(dCH2)Cp*2], which
consequently rapidly rearranged to the singly tucked-in com-
pound (Scheme 2). The Cp* ligands were shown not to interfere
with methane elimination.4c Since the analogous methane elim-
It has been shown that reduction of group 4 metallocene
dichlorides bearing pendant ω-alkenyl groups on their cyclopen-
tadienyl ligands induce the formal [2 þ 2 þ 2] cycloaddition
reaction of two d electrons of transient metallocene (MII) and
two pairs of double-bond π electrons.1 Independently of the
metal (Ti, Zr, and Hf), the cycloaddition generates cyclopenta-
dienylringtetheredmetallacyclopentanesaccordingtoScheme1.
For titanocenes, the sterically convenient structure contains
dimethylene tethers as consistent with 3-butenyl pendant groups
yielding compound 5; for longer alkenyl chains, e.g. 4-pentenyl,
the double bonds are shifted into internal positions to give rise to
a 3,4-dimethyl-substituted titanacyclopentane moiety.1a The key
metallocene transient species were obtained from metallocene
dichlorides by reductive chlorine abstraction with magnesium
(for Ti)1a,b or sodium amalgam (for Zr and Hf)1c or by chloride
metathesis with LiBu (for Zr) followed by butyl elimination.1d
With regard to the latter method, the formation of d2 metallo-
cene complexes with olefins arising from alkyl disproportiona-
tion has been exploited in the synthesis of numerous metal-
lacyclopentene and metallacyclopentadiene complexes, where
π-coordinated olefins took part in cycloaddition reactions with
free alkenes or alkynes.2 In contrast with the latter systems, the
above d2 complexes with pendant double bonds neither afford
products with olefins generated from alkyl disproportionation1d
nor do they coordinate bis(trimethylsilyl)acetylene added to the sys-
tem.1a,b Thus, products arising from activation of pendant double
bonds can afford valuable information on the structure of
activating metal species. In this respect, products of thermolysis
t
ination from [TiMe2(η5-C5Me4R)2] (R = Bu, CH2Ph) com-
pounds also proceeds at 110 °C,4d the thermolysis of 1 should
occur at about the same temperature without interference with
the 3-butenyl substituents.
On the other hand, the photolysis of dimethyltitanocene,
[TiMe2Cp2], has been studied extensively; however, it is not yet
fully understood. It was assumed that photolytically formed
methyl radicals abstract hydrogen from hydrocarbon solvents
to yield methane, and some thermally stable, insoluble form of
Received: February 16, 2011
Published: April 05, 2011
r
2011 American Chemical Society
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Scheme 1
Scheme 2
Figure 1. Computed molecule of 2 containing a 2-fold axis passing
through titanium and methylene carbon atoms. Hydrogen atoms are not
visualized for clarity. Geometric parameters within the titanacyclobutane
moiety are as follows: TiꢀC = 2.15 Å, CꢀC = 1.57 Å, CꢀTiꢀC =
76.28°, TiꢀCꢀC = 84.31°, CꢀCꢀC = 115.09°.
titanocene was obtained. The presence of a titanocene species in
the latter product was proved by its reaction with tolane,
PhCtCPh, which gave bis(cyclopentadienyl)titanatetrapheny-
lcyclopentadiene, albeit in yields up to 50%.5 This compound was
cleanly obtained from the reaction of tolane with titanocene at
the onset of its formation during the reduction of [TiCl2Cp2]
with magnesium6a or with the well-defined titanoceneꢀbis-
(trimethylsilyl)ethyne complex.6b The titanocene dimethyls
that is common for titanacyclobutane compounds.8a These
chemical shifts were found to be only slightly dependent on
substituents at the CR atoms8b and the cyclopentadienyl ligand
substituents.8c The methine CH groups σ-bonded to titanium
displayed signals at δH 2.70ꢀ2.80 ppm and δC 95.7 ppm, values
close to those found for TiCH in the cyclopentadienyl ring
tethered titanacyclopentanes (78.4ꢀ86.2 ppm).1a Four singlet
signals for nonequivalent methyl groups were resolved for
cyclopentadienyl ligands (δH 1.63, 1.73, 1.75, 1.76 ppm; δC
10.9, 11.2, 12.4, 12.7 ppm). The molecule rigidity gave rise to
diastereotopic protons in the CH2CH2 tether (C5CH2, δH 2.20,
2.33 ppm; C5CH2CH2, δH 2.83, 2.98 ppm).
[TiMe2Cp00 ] (Cp00 = η5-C5Me5, C5Me4SiMe3, C5Me4 Bu) are
t
2
also sensitive to sunlight, however, with a photolytic efficiency
apparently lower than for [TiMe2Cp2].4c,7
Here, we report on thermolytic products of 1, a metathetic
mechanism of the final product formation, and the result of
photolysis of 1 with sunlight.
The structure of 2 was also constructed using the usual bond
lengths and valence angles and optimized by DFT calculations to
’ RESULTS AND DISCUSSION
1
give a slightly asymmetrical molecule. In order to calculate H
and 13C NMR spectra, the molecular structure was symmetrized
by imposing a 2-fold rotation axis, whose presence was derived
from the experimental NMR data. The optimized symmetrical
structure (Figure 1) did not lead to an increase of the total energy
of the molecule, and calculated TiꢀC bond lengths and valence
angles within the titanacyclobutane ring fell into the range
of crystal structure parameters known for three bis(cyclopenta-
dienyl)titanacyclobutane derivatives.8a The chemical shifts com-
puted on this symmetrical molecule were in excellent agreement
with experimental data (see the Supporting Information).
Compound 2 appeared to be inert toward oxidative chlorina-
tion with PbCl2 in THF;9 however, its TiꢀC bonds were cleanly
cleaved with anhydrous HCl1a,b to give the corresponding ansa-
titanocene dichloride containing the heptamethylene bridging
chain, 3 (eq 2).
Heating of 1 in toluene to 120 °C for 4 h afforded cleanly the
red crystalline solid 2 (eq 1), whose EI-MS spectrum showed the
molecular ion at m/z 384 to be the base peak, undergoing only
negligible fragmentation. The molecular ion thus indicated that
one molecule of methane and one molecule of ethene were
liberated during thermolysis to give a thermally robust 2.
Compound 2 did not yield crystals suitable for X-ray diffrac-
tion analysis; however, its structure was unequivocally deter-
mined by 1H and 13C NMR spectroscopy using quantitative 13
C
NMR, gHSQC, gHMBC, and COSY experiments. The spectral
assignment is consistent with the C2 symmetry of the molecule,
the rotation axis passing through the titanium atom and methy-
lene carbon atom of the titanacyclobutane ring. The titanacyclo-
butane ring is characterized by the high-field-shifted 1H and 13
C
resonances of the methylene unit (δH ꢀ0.05 ppm; δC 11.9 ppm)
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Scheme 3
Compound 3 did not give single crystals for X-ray diffraction
δH ꢀ0.68 to ꢀ0.52 and 0.23ꢀ0.38 ppm and δC 1.9 ppm, which
are typical of known titanacyclobutanes.8 The remaining pendant
butenyl group in 4 gave δH and δC chemical shifts almost
identical with those for 1. The absence of molecular symmetry
gave rise to eight singlet signals for cyclopentadienyl methyl
1
analysis; however, its H and 13C NMR spectra allowed a full
assignment using a combination of 1D TOCSY, gHSQC, and
gHMBC experiments. The average C2v symmetry of 3 gave rise
to two signals for methyl groups of cyclopentadienyl ligands (δH
1.98, 2.00 ppm; δC 13.8, 14.7 ppm) and one downfield-shifted
multiplet centered at δH 2.25 ppm and corresponding δC 24.8
ppm attributable to a methylene group (R-CH2) attached to the
cyclopentadienyl ring. The remaining methylene units of the
ansa bridge displayed an unresolved multiplet at δH 1.28ꢀ1.56
ppm in the 1H NMR spectrum and distinct signals in 13C NMR
spectrum for aliphatic CH2 groups (δ-CH2, δC 20.2 ppm;
β-CH2, δC 25.9 ppm; γ-CH2, δC 28.0 ppm).The EI-MS spectra
of 3 displayed a low-abundant molecular ion at m/z 456, whereas
the fragment [M ꢀ Cl]þ was the base peak. The next fragment
ion at m/z 217 ([M ꢀ Cl ꢀ C5Me4(CH2)6]þ) of low-to-
medium abundance is also consistent with the composition of
3. In the infrared spectrum, the absorption band at 750 cmꢀ1 is
indicative of the heptamethylene chain.
Insight into the mechanism of formation of 2 was obtained
from 1H and 13C NMR spectra of the thermolysis of 1 at 100 °C
in C6D6 in a flame-sealed NMR sample tube. The initial over-
whelming reaction was the liberation of methane, resulting in the
formation of an intermediate product (4) which, in a successive
reaction, yielded 2 with evolution of ethene (Scheme 3). The
product mixture 1 (14%), 2 (20%), and 4 (66%) with a maximum
yield of 4 was obtained after 10 h. This composition did not
change upon keeping the NMR sample tube at room tempera-
ture for 1 week, suggesting that 4 is a stable intermediate. Further
heating of the mixture at 100 °C for 35 h afforded virtually pure 2
and roughly equal amounts of evolved ethene and methane (see
the Supporting Information).
1
groups in H (δH 1.50, 1.70, 1.72, 1.73, 1.74, 1.76, 1.78, 1.84
ppm) and seven signals in 13C NMR spectra (δC 10.62, 10.64,
11.52, 11.59, 11.63, 11.79 (2C), 12.02 ppm).
These observations allowed us to formulate the thermally
induced conversion of 1 to 2 as a multistep process (see
Scheme 3). In the first step, the initiating elimination of methane
from 1 is followed by addition of one pendant double bond to the
postulated titanoceneꢀmethylidene species [Ti(dCH2)Cp02]
(Cp0 = η5-C5Me4CH2CH2CHdCH2) to give the cyclopenta-
dienyl ring tethered titanacyclobutane intermediate 4. Com-
pound 4 was shown to be thermally stable at ambient temper-
ature on a time scale of days; however, at 100 °C it was
concurrently eliminating ethene while coordinating the second
pendant double bond. Its cycloaddition to a titaniumꢀpropyli-
dene species afforded the thermally robust product 2.
Most of the reactions of Scheme 3 have their counterparts in the
degenerate metathesis chemistry of the titanoceneꢀmethylidene
species [Ti(dCH2)Cp2]10 stabilized by coordination to dialkyla-
luminum chlorides as the Tebbe reagent [Cp2TiCH2(μ-Cl)-
AlMe2].11 Tebbe reagent stability, however, has been shown to
decrease with increasing electron density on the titanium atom
induced by substitution of the cyclopentadienyl rings with methyl
groups. Tebbe reagents have thus only been prepared for titano-
cenes with a limited number of methyl substituents: e.g., Ti-
(C5H4Me)2 and Ti(1,2,4-C5H2Me3)(C5H5).8c For the [Ti-
(dCH2)Cp*2] species, the thermolysis of [TiMe2Cp*2] is appar-
ently the only source,12 albeit not suitable for its exploitation in
addition reactions. Our experiments performed in an NMR tube
showed that thermolysis of [TiMe2Cp*2] in the presence of excess
tolane at 110 °C did not afford either diphenyltitanacyclobutene or
tolane insertion products into TiꢀMe bond(s), the only product
being the singly tucked-in [TiMe(Cp*){C5Me4(CH2)}]. The
[Ti(dCH2)Cp*2] species was only partially trapped when
[TiMe2Cp*2] was thermolyzed in the presence of organic epoxides
to give decamethyltitanocene enolates.13
The structure of 4 as depicted in Scheme 3 was determined
1
from H and 13C NMR spectra of the reaction mixture above
containing the maximum yield of 4. The molecule possesses a
titanacyclobutane ring tethered at its CR atom with a dimethy-
lene spacer to one cyclopentadienyl ring (TiCH, δH 2.32ꢀ2.40
ppm, δC 96.32 ppm), a feature known for 2. The presence of one
methylene group linked to the titanium atom was deduced from
signals at δH 1.88ꢀ1.97 and 2.08ꢀ2.16 ppm and δC 73.9 ppm,
and the presence of a distant titanacyclobutane methylene group
was indicated by strongly high-field-shifted resonances at
In contrast, the conversion of 1 to 4 implies that the analogous
titanoceneꢀmethylidene intermediate [Ti(dCH2)Cp02] reacts
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easily with the 3-butenyl double bond. The mode of its addition
to the TidCH2 bond results in linking the dimethylene tether
exclusively to CR of titanacyclobutane, the arrangement that was
proved to be sterically convenient for the cyclopentadienyl ring
tethered titanacyclopentanes.1a For nontethered titanacyclobu-
tanes both CR- and Cβ-monosubstituted derivatives are known.
Addition of the bulky monosubstituted alkenes tert-butylethene
and styrene to [Ti(dCH2)Cp2] gave Cβ-substituted titanacyclo-
butanes;8 however, the phenyl group shift to CR was induced
thermally at room temperature only.8b This rearrangement was
suggested to occur for sterically reasons; however, more sterically
congested decamethyltitanocene titanacyclobutanes substituted
at Cβ were not reported to isomerize.14 No sterically induced
rearrangements were observed for the permethyltitanocene
titanacyclobutane with an exo methylene substituent on CR
decomposing only at 170 °C,15a and for its highly thermally
stable analogous titanacyclobutenes bearing even bulky Ph and
SiMe3 substituents on the ring double bond.15b
The following ethene elimination from 4 is a productive
metathesis step which was previously observed only in the
equilibrium reaction of transient [Ti(dCH2)Cp2] with 1,1-
disubstituted allenes.16 Here, the process of ethene replacement
with the second pendant double bond is to be facilitated by a
much higher encounter frequency of the pendant double bond in
the ligand field of titanium compared to that of free ethene. Since
approximate theoretical calculations found a small energy differ-
ence for the model Ti(IV) titanacyclobutane and Ti(II) titano-
ceneꢀmethylidene with π-coordinated ethene,10d,17 the
completion of conversion of 1 to 2 is due to the high stability
of the titanacyclobutane moiety fixed at the open side of the
titanocene shell by two dimethylene tethers (Figure 1).
’ EXPERIMENTAL SECTION
General Considerations. Degassed solutions of 1 were handled
on a vacuum line in sealed all-glass devices equipped with breakable
seals. 1H (300 and 500 MHz) and 13C (75 and 125 MHz) NMR spectra
were recorded on a Varian Mercury 300 and Varian INOVA 500
spectrometers in C6D6 solutions at 25 °C. Chemical shifts (δ/ppm)
are given relative to solvent signals (C6D6: δH 7.15 ppm, δC 128.00
ppm). EI-MS spectra were measured on a VG-7070E mass spectrometer
at 70 eV. The crystalline samples in sealed capillaries were opened and
inserted into a direct-inlet probe under argon. IR spectra of samples in
KBr pellets were measured in an air-protecting cuvette on a Nicolet
Avatar FT IR spectrometer in the range 400ꢀ4000 cmꢀ1. KBr pellets
were prepared in a Labmaster 130 glovebox (mBraun) under purified
nitrogen. Photolysis experiments were performed in the summer with
sunlight that passed through two 2.5 mm glass windows and the 2 mm
Pyrex glass of the ampule. Elemental analyses were carried out on a Flash
EA2000 CHN/O automatic elemental analyzer (Thermo Scientific).
Chemicals. The solvents tetrahydrofuran (THF), hexane, toluene,
benzene-d6, and toluene-d8 were dried by refluxing over LiAlH4 and
stored as solutions of the dimeric titanocene [(μ-η5:η5-C5H4C5H4)(μ-
H)2{Ti(η5-C5H5)}2].19 The titanocene dimethyl species [TiMe2{η5-
C5Me4(CH2CH2CHdCH2)}2] (1) was prepared from [TiCl2{η5-
C5Me4(CH2CH2CHdCH2)}2]1a by reaction with LiMe in diethyl
ether under argon and characterized by 1H and 13C NMR, EI-MS, and
IR (KBr) data in full agreement with reported data.3 [TiMe2Cp*2] was
obtained analogously.2b PbCl2 and PhCtCPh (both Aldrich) were
weighed and degassed. Gaseous HCl was made from NaCl by adding
degassed H2SO4 (98%) in an ampule on a vacuum line.
Preparation of [Ti{η5-C5Me4(CH2CH2CH(K-CH)}2CH2] (2).
Compound 1 (0.30 g, 0.70 mmol) was dissolved in toluene (10 mL), and
the solution was heated to 120 °C for 4 h in a sealed ampule. The orange
solution changed to dark red. The ampule was opened on a vacuum line
at ambient temperature, all volatiles were evaporated under vacuum, and
the brownish red residue was dissolved in 2 mL of hexane. The solution
was concentrated to crystallization by a slow distillation of hexane into a
cooler ampule arm in a refrigerator. A few drops of brown mother liquor
were separated from the red crystalline solid of 2. Recrystallization from
hexane at ꢀ28 °C afforded crystalline product not suitable for X-ray
diffraction analysis. Yield: 0.23 g (86%).
Exposure of a toluene solution of 1 to sunlight for 3 weeks
resulted in isolation of a red crystalline product in about 40%
yield. The X-ray diffraction analysis of single crystals as well as
1
successive H and 13C NMR spectra showed that it is the
cyclopentadienyl ring tethered titanacyclopentane 5 (depicted
in Scheme 1). This indicates that the photolysis of 1 generates a
persubstituted titanocene species capable of reacting with the
pendant double bonds in a manner known for the chemical
reduction induced cycloaddition reaction.1a The mother liquor
contained, according to 1H NMR spectra and EI-MS spectra, a
variety of products containing compound 1 as the main compo-
nent. Photolysis of 1 with sunlight was not further investigated
because of the low efficiency and low selectivity of the product
formation.
Data for 2 are as follows. Mp: 170 °C. EI-MS (150 °C): m/z (relative
abundance, %) 386 (15), 385 (39), 384 (M.þ; 100), 383 (16), 382 (17),
1
341 (8), 339 (8), 182 (7), 181 (10), 180 (8), 178 (10). H NMR
(C6D6): ꢀ0.05 (dd, 3JHH = 9.6 Hz, 3JHH = 7.5 Hz, 2H, CHCH2CH);
1.63, 1.73, 1.75, 1.76 (4 ꢁ s, 4 ꢁ 6H, C5Me4); 2.20 (ddd, 2JHH = 13.8 Hz,
3JHH = 9.9 Hz, 3JHH = 7.5 Hz, 2H, C5CH2CH2, Ha); 2.33 (ddd, 2JHH
=
13.8 Hz, 3JHH = 8.4 Hz, 3JHH = 3.0 Hz, 2H, C5CH2CH2, Hb); 2.70ꢀ2.80
(m, 2H, TiCH); 2.79ꢀ2.87 (m, 2H, C5CH2CH2, Ha); 2.91ꢀ3.05 (m,
2H, C5CH2CH2, Hb). 13C{1H} NMR (C6D6): 10.85, 11.18, 12.43,
12.70 (C5Me4); 11.87 (CHCH2CH); 24.11 (C5CH2CH2); 49.07
(C5CH2CH2); 95.66 (TiCH); 109.79, 111.69, 114.17, 119.46 (Cq,
C5Me4); 134.18 (Cipso). gCOSY (C6D6): 1H/1H ꢀ0.05/2.70ꢀ2.80
(CHCH2CH/TiCH); 2.20/2.33, 2.79ꢀ2.87, 2.91ꢀ3.05 (C5CH2CH2
(Ha)/C5CH2CH2 (Hb), C5CH2CH2 (Ha), C5CH2CH2 (Hb)); 2.33/
2.20, 2.79ꢀ2.87, 2.91ꢀ3.05 (C5CH2CH2 (Hb)/C5CH2CH2 (Ha),
C5CH2CH2 (Ha), C5CH2CH2 (Hb)); 2.70ꢀ2.80/ꢀ0.05, 2.91ꢀ3.05
(TiCH/CHCH2CH, C5CH2CH2 (Hb)); 2.79ꢀ2.87/2.20, 2.33,
2.91ꢀ3.05 (C5CH2CH2 (Ha)/C5CH2CH2 (Ha), C5CH2CH2 (Hb),
C5CH2CH2 (Hb)); 2.91ꢀ3.05/2.20, 2.33, 2.70ꢀ2.80, 2.79ꢀ2.87
(C5CH2CH2 (Hb)/C5CH2CH2 (Ha), C5CH2CH2 (Hb), CHCH2CH,
’ CONCLUSIONS
Thermolysis of 1 revealed that transiently formed titanoceneꢀ
methylidene reacts with one pendant double bond with unpre-
cedented efficiency to give the cyclopentadienyl ring tethered
titanacyclobutane 4. In contrast to nontethered titanacyclobu-
tanes, which generally undergo nonproductive (degenerate)
metathesis with olefins,18 compound 4 eliminates ethene while
forming doubly cyclopentadienyl ring tethered titanacyclobutane
2 in a productive metathesis step. The reason for the high
selectivity and full conversion of 1 to 2 is to be sought in the
circumstance that the whole process proceeds in the ligand field
of the central titanium atom and in the high stability of 2. The
substantial photolytic conversion of 1 to 5 indicates the forma-
tion of a titanocene species, as previously assumed for simple
titanocene dimethyl photolysis.5
C5CH2CH2 (Ha)). gHSQC (C6D6): H/13C ꢀ0.05/11.87 (CHCH2-
1
CH/CHCH2CH); 1.63/10.85, 1.73/11.18, 1.75/12.70, 1.76/12.43
(C5Me4/C5Me4); 2.20, 2.33/24.11 (C5CH2CH2 (Ha), C5CH2CH2
(Hb)/C5CH2CH2); 2.75/95.66 (TiCH/TiCH); 2.83, 2.98/49.07
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(C5CH2CH2 (Ha), C5CH2CH2 (Hb)/C5CH2CH2). gHMBC (C6D6):
1H/13C (selected signals) ꢀ0.05/49.07, 95.66 (CHCH2CH/C5CH2-
CH2, TiCH); 2.20, 2.33/49.07, 95.66, 111.69, 119.46, 134.18 (C5CH2CH2
(Ha), C5CH2CH2 (Hb)/C5CH2CH2, TiCH, C5Me4, C5Me4, Cipso);
2.91ꢀ3.05/11.87, 24.11, 95.66 (C5CH2CH2 (Hb)/CHCH2CH, C5CH2-
CH2, TiCH). IR (KBr, cmꢀ1): 2966 (s, sh), 2940 (s, sh), 2903 (vs), 2853
(s), 2805 (s), 2719 (w), 1494 (m), 1439 (s), 1375 (s), 1326 (w), 1306
(m), 1220 (w), 1188 (vw), 1143 (vw), 1086 (vw), 1022 (m), 907 (vw),
790 (vw), 672 (vw), 533 (w), 464 (w), 456 (w), 420 (s). Anal. Calcd for
C25H36Ti (384.44): C, 78.11; H, 9.44. Found: C, 78.18; H, 9.47.
Attempted Reaction of 2 with PbCl2. A solution of 2 (0.15 g,
0.4 mmol) in 5 mL of THF was poured onto degassed PbCl2 (0.11 g, 0.4
mmol), and the mixture was stirred at 40 °C, not showing signs of
reaction. The red solution was poured away from the yellowish PbCl2
and evaporated, and the red residue was extracted with hexane, leaving a
trace of yellowish powder of presumably PbCl2. The extract was
identified by 1H and 13C NMR to be pure 2.
Reaction of 2 with HCl To Give 3. A solution of 2 (0.13 g, 0.34
mmol) in 10 mL of hexane was cooled with liquid nitrogen, and about
1 mmol of gaseous HCl was added by condensing on a vacuum line. This
mixture was slowly warmed to room temperature while being stirred. A
fine brown crystalline product separated from an ocher mother liquor.
The mother liquor was decanted into another ampule and cooled with
liquid nitrogen in order to condense all excess HCl. The crystalline solid
was dried under vacuum and then dissolved in toluene to give a brown-
red solution. This was concentrated to saturation and cooled to ꢀ5 °C
for 4 days. A polycrystalline solid was separated, washed with cold
toluene, and dried under vacuum. Yield: 0.13 g (84%).
1.74, 1.76, 1.78, 1.84 (8 ꢁ s, 8 ꢁ 3H, C5Me4); 1.88ꢀ1.97 (m, 1H,
TiCH2); 2.08ꢀ2.16 (m, 3H, C5CH2CH2CHd and TiCH2); 2.20ꢀ2.28
(m, 4H, C5CH2CH2CHTi and C5CH2CH2CHd); 2.32ꢀ2.40 (m, 1H,
C5CH2CH2CHTi); 2.77ꢀ2.86 (m, 1H, C5CH2CH2CHTi); 2.88ꢀ3.00
(m, 1H, C5CH2CH2CHTi); 4.97 (dd, 3JHH = 10.2 Hz, 4JHH = 0.9 Hz,
1H, E-H, dCH2); 5.05 (dd, 3JHH = 17.1 Hz, 4JHH = 1.5 Hz, 1H, Z-H, =
CH2); 5.82 (ddt, 3JHH = 17.1 Hz, 3JHH = 10.2 Hz, 3JHH = 6.5 Hz, 1H,
CHd). 13C{1H} NMR (C6D6): 1.90 (TiCH2CH2); 10.62, 10.64, 11.52,
11.59, 11.63, 11.79 (2C), 12.02 (C5Me4); 22.27 (C5CH2CH2CHTi);
26.58 (C5CH2CH2CHd); 34.77 (C5CH2CH2CHd); 48.97 (C5CH2-
CH2CHTi); 73.94 (TiCH2); 96.32 (C5CH2CH2CHTi); 108.20, 109.76,
113.56, 113.90, 114.55 (Cq, C5Me4); 114.63 (dCH2); 114.69, 114.78
(Cq, C5Me4); 118. 33 (Cipso, C5Me4); 120.86 (Cq, C5Me4); 135.59
(Cipso, C5Me4); 138.99 (CHd). gCOSY (C6D6): 1H/1H ꢀ0.68 to ꢀ0.52/
0.23ꢀ0.38, 1.88ꢀ1.97, 2.08ꢀ2.16, 2.32ꢀ2.40 (TiCH2CH2 (Ha)/
TiCH2CH2 (Hb), TiCH2 (Ha), TiCH2 (Hb), C5CH2CH2CHTi);
0.23ꢀ0.38/ꢀ0.68 to ꢀ0.52, 1.88ꢀ1.97, 2.08ꢀ2.16, 2.32ꢀ2.40
(TiCH2CH2 (Hb)/TiCH2CH2 (Ha), TiCH2 (Ha), TiCH2 (Hb),
C5CH2CH2CHTi); 1.88ꢀ1.97/ꢀ0.68 to ꢀ0.52, 0.23ꢀ0.38,
2.08ꢀ2.16 (TiCH2 (Ha)/TiCH2CH2 (Ha), TiCH2CH2 (Hb), TiCH2
(Hb)); 2.08ꢀ2.16/ꢀ0.68 to ꢀ0.52, 0.23ꢀ0.38, 1.88ꢀ1.97 (TiCH2
(Hb)/TiCH2CH2 (Ha), TiCH2CH2 (Hb), TiCH2 (Ha)); 2.09ꢀ2.15/
2.22ꢀ2.28, 4.97, 5.05, 5.82 (C5CH2CH2CHd/C5CH2CH2CHd,
dCH2 (E-H), dCH2 (Z-H), CHd); 2.20ꢀ2.27/2.77ꢀ2.86, 2.88ꢀ
3.00 (C5CH2CH2CHTi/C5CH2CH2CHTi (Ha), C5CH2CH2CHTi
(Hb)); 2.22ꢀ2.28/2.09ꢀ2.15 (C5CH2CH2CHd/C5CH2CH2CHd);
2.32ꢀ2.40/ꢀ0.68 to ꢀ0.52, 0.23ꢀ0.38, 2.77ꢀ2.86, 2.88ꢀ3.00
(C5CH2CH2CHTi/TiCH2CH2 (Ha), TiCH2CH2 (Hb), C5CH2CH2-
CHTi (Ha), C5CH2CH2CHTi (Hb)); 2.77ꢀ2.86/2.20ꢀ2.27, 2.32ꢀ
2.40, 2.88ꢀ3.00 (C5CH2CH2CHTi (Ha)/C5CH2CH2CHTi, C5CH2-
CH2CHTi, C5CH2CH2CHTi (Hb); 2.88ꢀ3.00/2.20ꢀ2.27, 2.32ꢀ2.40,
2.77ꢀ2.86 (C5CH2CH2CHTi (Hb)/C5CH2CH2CHTi, C5CH2CH2-
CHTi, C5CH2CH2CHTi (Ha); 4.97/2.09ꢀ2.15, 5.82 (dCH2 (E-H)/
C5CH2CH2CHd, CHd); 5.05/2.09ꢀ2.15, 5.82 (dCH2 (Z-H)/
C5CH2CH2CHd, CHd); 5.82/2.09ꢀ2.15, 4.97, 5.05 (CHd/
C5CH2CH2CHd, dCH2 (E-H), dCH2 (Z-H)). gHSQC (C6D6):
1H/13C (selected signals) ꢀ0.68-ꢀ0.52, 0.23ꢀ0.38/1.90 (TiCH2-
CH2); 1.88ꢀ1.97, 2.08ꢀ2.16/73.94 (TiCH2); 2.09ꢀ2.15/34.77
(C5CH2CH2CHd); 2.20ꢀ2.27/22.27 (C5CH2CH2CHTi); 2.22ꢀ2.28/
26.58 (C5CH2CH2CHd); 2.32ꢀ2.40/96.32 (C5CH2CH2CHTi);
2.77ꢀ2.86, 2.88ꢀ3.00/48.97 (C5CH2CH2CHTi); 4.97, 5.05/114.63
(dCH2); 5.82/138.99 (CH=).
Data for 3 are as follows. Mp: 172 °C. EI-MS (160 °C): m/z (relative
abundance, %) 456 (Mþ; 4), 424 (17), 423 (55), 422 (49), 421 ([M ꢀ
Cl]þ; 100), 420 (23), 419 (27), 405 ([M ꢀ Cl ꢀ MeH]þ; 8), 229 (8),
227 (16), 219 (15), 218 (17), 217 ([M ꢀ Cl ꢀ C5Me4(CH2)6]þ; 34),
216 (11), 215 (14), 214 (7), 213 (24), 181 ([M ꢀ Cl ꢀ C5Me4(CH2)6 ꢀ
1
HCl]þ; 6), 135 (10), 119 (14), 92 (12), 91 (20). H NMR (C6D6):
1.28ꢀ1.38 (m, 2H, γ-CH2); 1.38ꢀ1.56 (m, 6H, δ-CH2 and β-CH2);
1.98, 2.00 (2 ꢁ s, 2 ꢁ 12H, C5Me4); 2.20ꢀ2.29 (m, 4H, R-CH2).
13C{1H} NMR (C6D6): 13.84, 14.70 (C5Me4); 20.19 (δ-CH2); 24.76
(R-CH2); 25.87 (β-CH2); 27.99 (γ-CH2); 126.00 (Cipso); 130.41,
1
130.70 (Cq, C5Me4). gCOSY (C6D6): H/1H 1.28ꢀ1.38/1.38ꢀ1.56
(γ-CH2/δ-CH2 and β-CH2); 1.38ꢀ1.56/1.28ꢀ1.38, 2.20ꢀ2.29 (δ-
CH2 and β-CH2/γ-CH2, R-CH2); 2.20ꢀ2.29/1.28ꢀ1.38, 1.38ꢀ1.56
(R-CH2/γ-CH2, δ-CH2 and β-CH2). gHSQC (C6D6): 1H/13C
∼1.28ꢀ1.38/27.99 (γ-CH2/γ-CH2); 1.38ꢀ1.46/20.19 (δ-CH2/δ-
CH2); 1.44ꢀ1.56/25.87 (β-CH2/β-CH2); 1.98/13.84 (C5Me4); 2.00/
14.70 (C5Me4); 2.20ꢀ2.29/24.76 (R-CH2/R-CH2). gHMBC (C6D6):
1H/13C (selected) 2.20ꢀ2.29/25.87, 27.99, 126.00, 130.41 (R-CH2/
β-CH2, γ-CH2, Cipso; C5Me4 (Cq)). IR (KBr, cmꢀ1): 2994 (w, sh), 2986
(m), 2958 (m), 2911 (vs), 2863 (m), 2846 (s), 1493 (m), 1484 (m),
1446 (s), 1430 (m), 1384 (m), 1373 (s), 1308 (w), 1198 (vw), 1080
(vw), 1074 (vw), 1021 (m), 813 (w), 794 (vw), 750 (m), 673 (vw), 622
(vw), 410 (s). Anal. Calcd for C25H38Cl2Ti (457.36): C, 65.65; H, 8.37.
Found: C, 65.62; H, 8.40.
Thermolysis of [TiMe2Cp*2] with Tolane. A degassed solution
of [TiMe2Cp*2] (0.05 g, 0.14 mmol) in 1.0 mL of toluene-d8 was added
to tolane (0.05 g, 0.30 mmol), and the solution that formed was
transferred to an NMR tube. This was sealed with a flame and heated
to 110 °C for 19 h. The initially yellow solution turned green. 1H and 13
C
NMR spectra recognized the complete conversion of [TiMe2Cp*2] to
the singly tucked-in [TiMe(Cp*){C5Me4(CH2)}]4c and methane; how-
ever, no products indicating the involvement of tolane were detected.
Photolysis of 1 with Sunlight. A solution of 1 (0.32 g, 0.75
mmol) in toluene (10 mL) in a sealed ampule was exposed to sunlight
for 3 weeks. The initially red solution turned yellow-brown. All volatiles
were evaporated under vacuum, and the residue was dissolved in hexane.
Slow evaporation of hexane to a cooler arm of the ampule yielded well-
developed red crystals of 5 in a brown mother liquor. The mother liquor
was decanted. The crystals were washed with condensing hexane vapor
and dried under vacuum. Yield: 0.12 g (40%).
Formation of 4 during Thermolysis of 1 at 100 °C. An NMR
tube was filled with a solution of 1 (0.04 g) in 1.2 mL of benzene-d6 and
sealed off with a flame. The tube was heated in boiling water, with
interruptions reserved for the measurement of 1H and 13C NMR spectra.
The spectra revealed major conversion of 1 to 4 accompanied by
evolution of methane (δH/δC 0.15/4.3 ppm) and subsequent conver-
sion of 4 to 2 with evolution of ethene (δH/δC 5.25/122.9 ppm).20 After
10 h at 100 °C the maximum yield of intermediate 4 was obtained: 1
(14%), 2 (20%), and 4 (66%). Further heating of the mixture to 100 °C
for 35 h led to conversion of all 1 and 4 into 2.
Data for 5were identical with those reported (EI-MS, IR, 1Hand13CNMR,
and X-ray diffraction unit cell).1a The residue after evaporation of the mother
liquor afforded EI-MS spectra indicating the presence of a variety of products,
including hydrogenated 1 in addition to an overwhelming amount of 1.
Computational Details. DFT calculations have been carried out
at the Fermi cluster at the J. Heyrovskꢁy Institute of Physical Chemistry,
Data for 4 are as follows. 1H NMR (C6D6): ꢀ0.68 to ꢀ0.52 (m, 1H,
TiCH2CH2); 0.23ꢀ0.38 (m, 1H, TiCH2CH2); 1.50, 1.70, 1.72, 1.73,
2585
dx.doi.org/10.1021/om2001487 |Organometallics 2011, 30, 2581–2586

Organometallics
ARTICLE
Academy of Sciences of Czech Republic, vvi, using Gaussian 09, Revision
B.01.21 The geometry optimization of the molecule was done using the
B3LYP functional and the 6-31G(d,p) basis set for all atoms. The
Hessian required for the geometry optimization was computed analy-
tically before the first step of the optimization stage. The NMR shielding
tensor was calculated using the GIAO method22 carried out on the
optimized geometry and using the mPW1PW91 functional along with
the 6-311þG(2d,p) basis set.
(7) Mach, K., Unpublished observation.
(8) (a) Lee, J. B.; Gajda, G. J.; Schaefer, W. P.; Howard, T. R.; Ikariya,
T.; Straus, D. A.; Grubbs, R. H. J. Am. Chem. Soc. 1981, 103, 7358–7361.
(b) Ikariya, T.; Ho, S. C. H.; Grubbs, R. H. Organometallics 1985,
4, 199–200. (c) Finch, W. C.; Anslyn, E. V.; Grubbs, R. H. J. Am. Chem.
Soc. 1988, 110, 2406–2413.
(9) (a) Luinstra, G. A.; Teuben, J. H. J. Chem. Soc., Chem. Commun.
1990, 1470–1471. (b) Luinstra, G. A.; Vogelzang, J.; Teuben, J. H.
Organometallics 1992, 11, 2273–2281. (c) Pinkas, J.; Císaꢀrovꢁa, I.;
ꢀ
Gyepes, R.; Horꢁaꢀcek, M.; Kubiꢀsta, J.; Cejka, J.; Gꢁomez-Ruiz, S.; Hey-
’ ASSOCIATED CONTENT
Hawkins, E.; Mach, K. Organometallics 2008, 27, 5532–5547.
(10) (a) Tebbe, F. N.; Parshall, G. W.; Ovenall, D. W. J. Am. Chem.
Soc. 1979, 101, 5074–5075. (b) Howard, T. R.; Lee, J. B.; Grubbs, R. H.
J. Am. Chem. Soc. 1980, 102, 6876–6878. (c) Lee, J. B.; Ott, K. C.;
Grubbs, R. H. J. Am. Chem. Soc. 1982, 104, 7491–7496. (d) Anslyn, E. V.;
Grubbs, R. H. J. Am. Chem. Soc. 1987, 109, 4880–4890.
(11) (a) Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J. Am. Chem. Soc.
1978, 100, 3611–3613. (b) Klabunde, U.; Tebbe, F. N.; Parshall, G. W.;
Harlow, R. L. J. Mol. Catal. 1980, 8, 37–51. (c) Ott, K. C.; Lee, J. B.;
Grubbs, R. H. J. Am. Chem. Soc. 1982, 104, 2942–2944.
(12) The [TiCl2Cp2]/2LiMe system producing [TiMe2Cp2] has
been found to generate [Ti(dCH2)Cp2] at mild temperatures
(50ꢀ70 °C), being relatively air- and water-stable. As such, it is more
convenient than Tebbe reagent for organic synthesis application: (a)
Petasis, N. A.; Bzowej, E. I. J. Am. Chem. Soc. 1990, 112, 6392–6394. (b)
Petasis, N. A.; Bzowej, E. I. Tetrahedron Lett. 1993, 34, 1721. (c) Petasis,
N. A.; Fu, D.-K. Organometallics 1993, 12, 3776–3780. (d) Berget, P. E.;
Schore, N. E. Organometallics 2006, 25, 552–553.
1
S
Supporting Information. Figures giving the H NMR
b
(500 MHz) spectrum of 2, 13C NMR spectrum (relaxation delay
58 s) of 2, gCOSY, gHSQC, and gHMBC spectra of 2, correla-
tion of observed and calculated δC values for 2, 1H NMR (300
MHz) spectrum of 3, 1DTOCSY, gHSQC, and gHMBC spectra
of 3, 1H NMR spectra of thermolyzed 1 in C6D6 in a sealed NMR
tube at 100 °C, H, 13C{1H}, gCOSY, gHSQC, and gHMBC
1
spectra of a mixture of products (1, 14%; 2, 20%; 4, 66%) after
heating 1 in C6D6 to 100 °C for 10 h, and 1DTOCSY spectra of
4. This material is available free of charge via the Internet at
http://pubs.acs.org.
’ ACKNOWLEDGMENT
This research was supported by the Grant Agency of the
Academy of Sciences of the Czech Republic (Grant No.
IAA400400708) and the Ministry of Education, Youth and
Sports (Project No. LC06070). J.K. is grateful to the Grant
Agency of the Czech Republic (Project No. 203/09/P276).
(13) Gibson, C. P.; Dabbagh, G.; Bertz, S. H. J. Chem. Soc., Chem.
Commun. 1988, 603–605.
(14) Synthesis by benzylation of decamethyltitanocene η3-allyl
cation: (a) Tjaden, E. B.; Casty, G. L.; Stryker, J. M. J. Am. Chem. Soc.
1993, 115, 9814–9815. Synthesis by free radical alkylation of η3-allyl
decamethyltitanocene: (b) Casty, G. L.; Stryker, J. M. J. Am. Chem. Soc.
1995, 117, 7814–7815.
’ REFERENCES
ꢀ
(15) Obtained from [TiCl2Cp*2] and 2Li(CHdCH2): (a) Beck-
haus, R.; Thiele, K.-H.; Str€ohl, D. J. Organomet. Chem. 1989, 369, 43–54.
(b) Beckhaus, R.; Sang, J.; Wagner, T.; Ganter, B. Organometallics 1996,
15, 1176–1187.
(16) (a) Hawkins, J. M.; Grubbs, R. H. J. Am. Chem. Soc. 1988,
110, 2821–2823. (b) Buchwald, S. L.; Grubbs, R. H. J. Am. Chem. Soc.
1983, 105, 5490–5491.
(1) For Ti: (a) Horꢁaꢀcek, M; Stꢀepniꢀcka, P.; Gyepes, R.; Císaꢀrovꢁa, I.;
Tiꢀslerovꢁa, I.; Zemꢁanek, J.; Kubiꢀsta, J.; Mach, K. Chem.Eur. J. 2000,
6, 2397–2408. (b) Lukeꢀsovꢁa, L.; Stꢀepniꢀcka, P.; Fejfarovꢁa, K.; Gyepes, R.;
ꢀ
Císaꢀrovꢁa, I.; Horꢁaꢀcek, M.; Kubiꢀsta, J.; Mach, K. Organometallics 2002,
21, 2639–2653. For Zr and Hf: (c) Warren, T. H.; Erker, G.; Fr€ohlich, R.;
Wibbeling, B. Organometallics 2000, 19, 127–134. For Zr: (d) Licht,
A. I.; Alt, H. G. J. Organomet. Chem. 2002, 648, 134–148.
(2) For Ti: (a) Sato, K.; Nishihara, Y.; Huo, S.; Xi, Z.; Takahashi, T.
J. Organomet. Chem. 2001, 633, 18–26. For Zr: (b) Takahashi, T.; Xi, Z.;
Nishihara, Y.; Huo, S.; Kasai, K.; Aoyagi, K.; Denisov, V.; Negishi, E.
Tetrahedron 1997, 53, 9123–9134. (c) Takahashi, T.; Seki, T.; Nitto, Y.;
Saburi, M.; Rousset, C. J.; Negishi, E. J. Am. Chem. Soc. 1991,
113, 6266–6268. For Hf: (d) Negishi, E.; Holms, S. J.; Tour, J. M.;
Miller, J. A.; Cederbaum, F. E.; Swanson, D. R.; Takahashi, T. J. Am.
Chem. Soc. 1989, 111, 3336–3346. (e) Nishihara, Y.; Ishida, T.; Huo, S.;
Takahashi, T. J. Organomet. Chem. 1997, 547, 209–216.
(17) Upton, T. H.; Rappꢁe, A. K. J. Am. Chem. Soc. 1985, 107, 1206–
1218 and references therein.
(18) For reviews see: (a) Takeda, T. In Titanium and Zirconium in
Organic Synthesis; Marek, I., Ed.; Wiley-VCH: Weinheim, Germany,
2002; pp 475ꢀ500. (b) Petasis, N. A. In Transition Metals for Organic
Synthesis; Beller, M., Bolm, C., Eds.; Wiley-VCH: Weinheim, Germany,
2004; pp 427ꢀ447.
(19) Antropiusovꢁa, H.; Dosedlovꢁa, A.; Hanuꢀs, V.; Mach, K. Transi-
tion Met. Chem. (London) 1981, 6, 90–93.
(20) Fulmer, G. R.; Miller, A. J. M.; Sherden, N. H.; Gottlieb, H. E.;
Nudelman, A.; Stoltz, B. M.; Bercaw, J. E.; Goldberg, K. I. Organome-
tallics 2010, 29, 2176–2179.
(21) Frisch, M. J. et al. Gaussian 09, Revision B.01; Gaussian, Inc.,
Wallingford, CT, 2010.
(3) Okuda, J.; du Plooy, K. E.; Toscano, P. J. J. Organomet. Chem.
1995, 495, 195–202.
(4) (a) Bercaw, J. E.; Brintzinger, H. H. J. Am. Chem. Soc. 1971,
93, 2045–2046. (b) Bercaw, J. E.; Marvich, R. H.; Bell, L. G.; Brintzinger,
H. H. J. Am. Chem. Soc. 1972, 94, 1219–1238. (c) McDade, C.; Green,
J. C.; Bercaw, J. E. Organometallics 1982, 1, 1629–1634. (d) Pinkas, J.;
Císaꢀrovꢁa, I.; Conde, A.; Fandos, R.; Horꢁaꢀcek, M.; Kubiꢀsta, J.; Mach, K.
J. Organomet. Chem. 2009, 694, 1971–1980.
(22) Ditchfield, R. Mol. Phys. 1974, 27, 789–807.
(5) (a) Rausch, M. D.; Boon, W. H.; Alt, H. G. J. Organomet. Chem.
1977, 141, 299–312. (b) Samuel, E.; Maillard, P.; Giannotti, C.
J. Organomet. Chem. 1977, 142, 289–298. (c) Alt, H. G.; Rausch,
M. D. J. Am. Chem. Soc. 1974, 96, 5936–5937.
(6) (a) Shur, V. B.; Bernadyuk, S. Z.; Burlakov, V. V.; Andrianov,
V. G.; Yanovsky, A. I.; Struchkov, Yu. T.; Volpin, M. E. J. Organomet.
Chem. 1983, 243, 157–163. (b) Burlakov, V. V.; Polyakov, A. V.;
Yanovsky, A. I.; Struchkov, Yu. T.; Volpin, M. E.; Rosenthal, U.; G€orls,
H. J. Organomet. Chem. 1994, 476, 197–206.
2586
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