'Tucked-in' titanocene alkyls and alkylidenes

Article abstract of DOI:10.1016/S0020-1693(02)01282-3

Titanocene neopentyl complexes with one cyclometallated tert-butylcyclopentadienyl group, (η⁵-C₅H₄R)(η⁵,η ¹-C₅H₄CMe₂CH₂)Ti (CHCMe₃), are readily obtained from the corresponding titanocene dichlorides and bis(neopentyl)magnesium. These compounds lose neopentane by α-H abstraction from the cyclometallated ligand to generate alkylidene species in which the alkylidene moiety is connected to one of the cyclopentadienyl ligands. The alkylidene (C₅H₄Me)(C₅H₄CMe₂CH) Ti(PMe₃) reacts with benzene-d₆ by stereoselective addition of a C-D bond across the Ti=C bond. These 'tucked-in' alkylidene species also exhibit a wide range of reactivity towards unsaturated substrates (alkynes, ethene, benzonitrile), initiated by cycloaddition to the Ti=C bond.

Full text of DOI:10.1016/S0020-1693(02)01282-3

Inorganica Chimica Acta 345 (2003) 27Á36
/
www.elsevier.com/locate/ica
‘Tucked-in’ titanocene alkyls and alkylidenes
Harry van der Heijden a, Bart Hessen b,*
a Shell Research and Technology Centre, Amsterdam, Badhuisweg 3, 1031 CA Amsterdam, The Netherlands
b Stratingh Institute for Chemistry and Chemical Engineering, Centre for Catalytic Olefin Polymerisation, University of Groningen, Nijenborgh 4, 9747
AG Groningen, The Netherlands
Received 19 April 2002; accepted 22 July 2002
Dedicated in honor of Professor Richard R. Schrock
Abstract
Titanocene neopentyl complexes with one cyclometallated tert-butylcyclopentadienyl group, (h5-C5H4R)(h5,h1-
C5H4CMe2CH2)Ti(CHCMe3), are readily obtained from the corresponding titanocene dichlorides and bis(neopentyl)magnesium.
These compounds lose neopentane by a-H abstraction from the cyclometallated ligand to generate alkylidene species in which the
alkylidene moiety is connected to one of the cyclopentadienyl ligands. The alkylidene (C5H4Me)(C5H4CMe2CH)Ti(PMe3) reacts
with benzene-d6 by stereoselective addition of a CÃ
wide range of reactivity towards unsaturated substrates (alkynes, ethene, benzonitrile), initiated by cycloaddition to the TiÄ
# 2002 Elsevier Science B.V. All rights reserved.
/
D bond across the TiÄ
/
C bond. These ‘tucked-in’ alkylidene species also exhibit a
/C bond.
Keywords: Alkylidene; CÃH bond activation; Titanium; Alkyne; Ethene
/
1. Introduction
lecular CÃ
/
H activation reactions for a range of alkyli-
dene species of various metals (e.g. Ti [6], Cr [7], W [8]).
In this contribution we describe the intramolecular
The a-H elimination process in transition-metal
dialkyl species is the classical route for the formation
of metal alkylidenes [1,2]. The principle of microscopic
addition of CÃ
/H bonds of tert-butyl-cyclopentadienyl
ancillary ligands to titanocene alkylidenes. The resulting
alkyl complexes with cyclometallated tert-butyl-cyclo-
pentadienyl ligands provide a route to highly reactive
intramolecularly chelating (‘tucked-in’) alkylidene spe-
cies. For example, the ‘tucked-in’ alkylidene complex
(C5H4Me)(C5H4CMe2CH)Ti(PMe3) is a rare example of
a stable, isolable alkylidene compound that is able to
reversibility requires the reverse reaction, addition of CÃ
H bonds to alkylidenes, to be feasible as well. Several
H bonds to
/
examples of intramolecular addition of CÃ
/
(either proposed or actually observed) metal alkylidene
intermediates were reported from the 1980s onward [3],
but the intermolecular CÃ
denes was only established after reports of the same
NR) [4]. The titanocene
/
H addition to metal alkyli-
effect benzene CÃ
/
H activation. The reactivity of this
and related alkylidenes with reagents such as alkynes,
ethene and benzonitrile has been evaluated using reac-
tions on NMR-tube scale.
reaction for metal nitrenes (MÄ
/
neopentylidene, generated by an a-H elimination pro-
cess from Cp2Ti(CH2CMe3)2, was found to add aro-
matic and benzylic CÃ/H bonds to give mixed aryl/
benzyl-neopentyl titanocenes [5]. This reaction should
be quite general, provided that the alkylidene generated
is electronically unsaturated, does not readily give stable
dimers, and the overall reaction is thermodynamically
favoured. Indeed, subsequent reports revealed intermo-
2. Results and discussion
2.1. Synthesis and thermolysis of
(C5H4R)(C5H4CMe2CH2)Ti(CHCMe3)
* Corresponding author. Tel.: ꢁ
4315
E-mail address: hessen@chem.rug.nl (B. Hessen).
/
31-50-363 4322; fax: ꢁ31-50-363
/
The reaction of the titanocene dichlorides (h5-
C5H4R)(h5-C5H4tBu)TiCl2 (Rꢀ
/
But, 1a; Me, 1b; H,
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 2 8 2 - 3

28
H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á
/36
1c) with (Me3CCH2)2Mg×
/
dioxane in diethyl ether,
followed by extraction with pentane at ambient tem-
perature, yielded the cyclometallated complexes (h5-
C5H4R)(h5,h1-C5H4CMe2CH2)Ti(CH2CMe3) (Rꢀ
/
But,
2a; Me, 2b; H, 2c) as redÁbrown crystalline solids
/
Scheme 2.
(Scheme 1). The NMR spectra of these cyclometallation
products are distinguished by the upfield resonances of
the methylene protons of the C5H4CMe2CH2-group,
resonances for the alkylidene TiÄ
/
CH group at d 11.92
2
133 Hz, JPC
(3JPH 4.3 Hz) and 312.0 ppm (1JCH
25 Hz), respectively. Comparison with the spectral data
of the titanocene neopentylidene Cp2Ti(CHCMe3)PMe3
ꢀ
/
ꢀ
/
ꢀ
/
found e.g. for 2b at d ꢂ
/
2.57 (endo-H) and ꢂ0.02 ppm
/
2
(exo-H) with a JHH of 9.5 Hz. These features are
similar to those observed by Erker et al. in
(C5H4R)(C5H4CMe2CH2)TiPh, obtained by thermolysis
of the related titanocene diphenyl complexes [9]. These
resonances are readily distinguished from the methylene
3
[5] (d 12.32 ppm, JPH
1
7.2 Hz; d 312.9 ppm, JCH
ꢀ
/
ꢀ
/
2
110 Hz, JPC
ꢀ
/
27 Hz) shows that the CÃ
/
H coupling
constant on the alkylidene fragment in 3 is significantly
larger, probably in response to the smaller TiÃCÃ
/
/C
resonances of the neopentyl group (2b: d 0.07 and 1.29
ꢀ
9.9 Hz). The 13C NMR resonances of the
angle enforced by the bridge to the C5H4-moiety. The
31P NMR resonance of the coordinated phosphine in 3,
at d 1.4 ppm, is considerably upfield from that in
Cp2Ti(CHCMe3)PMe3 (d 12.9 ppm), which may suggest
a more weakly bound phosphine ligand in 3.
2
ppm, JHH
/
methylene carbons in 2b are found at d 45.3 ppm
(1JCH
132 Hz) for the cyclometallated ligand and d
76.6 ppm (1JCH
113 Hz) for the neopentyl group. In
ꢀ
/
ꢀ
/
none of the reactions could the intermediate bis(neo-
pentyl) titanocene compound be observed, indicating
that the a-H abstraction processes in these substituted
titanocene bis(neopentyl) species are fast. It was ob-
The chelating alkylidene moiety, generated by a-H
abstraction in the complexes (C5H4R)(C5H4CMe2-
CH2)Ti(CH2CMe3), can also undergo intramolecular
CÃ
/
H addition. Warming (C5H4But)(C5H4CMe2CH2)-
served
(C5H4R)2Ti(CH2CMe3)2 is significantly faster for Rꢀ
Me than for RꢀH [5]. This a-H abstraction is then
previously
that
a-H
abstraction
in
Ti(CH2CMe3) (2a) in toluene solvent at 80 8C for 2 h
(or prolonged standing of 2a at ambient temperature in
pentane) leads to liberation of neopentane and the
formation of a red compound that, on the basis of its
NMR spectra, was characterised as the doubly cyclo-
metallated compound (h5,h1-C5H4CMe2CH2)2Ti (4,
/
/
followed by a rapid intramolecular addition of a CÃ
/
H
bond of the cyclopentadienyl But substituent to yield the
cyclometallated compounds 2. This reactivity is compar-
able with that observed upon thermolysis of
1
Scheme 3). The H NMR spectrum of 4 simply shows
(C5H4R)(C5H4CMe3)TiPh2, in which case the CÃ
/
H
four multiplets for the non-equivalent protons on the
Cp-ring, two singlets for the diastereotopic methyl
groups and the two doublets characteristic for the
methylene protons of the cyclometallated ligand, in
accordance with the expected C2-symmetry of 4.
activation is performed by an h2-benzyne intermediate
[9].
Warming solutions of (C5H4Me)(C5H4CMe2CH2)-
Ti(CH2CMe3) (2b) to 80 8C in toluene in the presence
of an excess of PMe3 in a closed reaction vessel, followed
by extraction with and crystallisation from pentane,
yielded the unusual ‘tucked-in’ alkylidene complex
(C5H4Me)(C5H4CMe2CH)Ti(PMe3) (3, Scheme 2) as a
2.2. Reactivity of
(C5H4Me)(C5H4CMe2CH)Ti(PMe3) (3)
yellowÁbrown solid. Although crystals of 3 suitable for
/
Warming a solution of the ‘tucked-in’ alkylidene 3 in
C6D6 at 80 8C and monitoring the sample by NMR
spectroscopy shows that under these conditions 3 will
gradually react with C6D6 under liberation of PMe3 to
give the addition product (h5-C5H4Me)(h5,h1-
C5H4CMe2CHD)Ti(C6D5) (d6-5a). This can be distin-
single crystal X-ray diffraction could not be obtained,
the nature of the compound is evident from NMR
1
spectroscopy. It shows characteristic H and 13C NMR
guished by a broadened 1H NMR resonance at d ꢂ
ppm for the exo-proton of the CHD-group in d6-5a,
indicating that the addition across the TiÄC bond in 3
/0.10
/
Scheme 1.
Scheme 3.

H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á
/36
29
(C5H4Me)(C5H4CMe2CHÄ
/
CPhCPh)Ti(PMe3) (7), the
product of ring-opening of 6 upon coordination of
PMe3 (Scheme 5). Characteristic for the titanacyclobu-
tene species 6 are the NMR resonances of the TiÃ
/
C(Ph)Ä
/
(d 217.8 ppm) and TiÃ
/
CH (1H NMR: d 2.19
ppm; 13C NMR d 80.2 ppm) moieties, with the
resonances for the CPh groups very similar to those
reported for Cp2Ti(CH2CPhÄ
lalkylidene compound 7, the TiÄ
at d 305.7 ppm (2JPC
22 Hz), the Ã
163.0 ppm (2JPC
4 Hz), and the ÄCH Ã
113.9 (13C) and 5.22 ppm (1H, JPH
1.8 Hz). The two
/
CPh) [10]. For the viny-
CPh resonance is found
CPhÄ resonance at
resonances at
/
ꢀ
/
/
/
ꢀ
/
/
/
5
ꢀ
/
Scheme 4.
species can be shown to be in equilibrium by evaporat-
ing the volatiles from the above solution, followed by
the redissolution of the brown solid in C6D6. The NMR
spectrum of this solution shows exclusively the titana-
cyclobutene 6, whereas the subsequent addition of a
fourfold excess of PMe3 results in a mixture of 6 and 7 in
a 1:3 ratio, i.e. with the vinylalkylidene as the dominant
species. Although ring-opening of metallacyclobutenes
to give vinylalkylidenes has been studied before (as a
reaction step in the catalysed polymerisation of alkynes
by metal alkylidenes) [11], the observation of both
species in equilibrium is quite rare. Such an equilibrium
was observed in the reaction of the tantalacyclobutene
has taken place in a stereoselective manner (Scheme 4).
In the course of the reaction, two sets of doublet
resonances emerge gradually in the upfield region of
1
the H NMR spectrum, at d ꢂ
/
2.26/ꢂ2.28 ppm (endo-
/
2
0.06 ppm (exo-H) with JHH
H) and ꢂ
/
0.03/ꢂ
/
ꢀ9.8 Hz,
/
and accompanied by a o-Ph resonance at d 6.42 ppm.
These resonances are attributed to the two isomers of
(C5H4Me)[C5H4C(CH3)(CD2H)CH2]Ti(C6D4H) (d6-5b/
c) that are the product of o-metallation of the C6D5-
group, followed by intramolecular addition of a CÃ
/
H
bond of one of the methyl groups in the
C(CH3)2(CD2H) substituent to the benzyne intermediate
generated by the o-metallation (Scheme 4). A continua-
tion of this process eventually leads to extensive H/D-
scrambling between the aryl and metallated tBu groups.
These results indicate that, at 80 8C, the phosphine-
stabilised ‘tucked-in’ alkylidene 3 is able to add arene
(DIPP)3Ta(CRÄ
/
CRCHCMe3) (DIPPꢀ2,6-diisopropyl-
/
phenoxide) with pyridine, but rapid interconversion of
the two species precluded their simultaneous observa-
tion as separate species [11b].
Addition of an excess of 2-butyne to a solution of the
titanacyclobutane 6 in toluene-d8, prepared as described
CÃ
/
H bonds to the TiÄ/C bond. Compound 3 thus
above, and subsequent cooling to ꢂ20 8C, reveals the
/
appears to be much more reactive than the titanocene
neopentylidene Cp2Ti(CHCMe3)PMe3, which under the
same conditions shows no reactivity.
formation of a new product that is tentatively identified
as the cycloaddition product of the intermediate viny-
lalkylidene with 2-butyne (8, Scheme 5). Although the
compound appears to be sterically very crowded, the 1H
and 13C NMR characteristics of the species are con-
The reactivity of the ‘tucked-in’ alkylidene 3 with
unsaturated organic substrates was probed by reactions
on NMR tube scale. With 1 equiv. of diphenylacetylene,
3 reacts at ambient temperature in toluene-d8 to give a
mixture of two compounds in a 3:1 ratio. These are the
titanacyclobutene complex (C5H4Me)(C5H4CMe2-
sistent with the proposed structure, e.g. TiÃ
245.6 ppm, and ÄCH Ã d 5.46 ppm (singlet). At ambient
temperature, 8 rearranges in 1Á2 h to a new compound
/
C(Me)Ä
/
d
/
/
/
that is inert to further added alkyne. Its NMR spectro-
scopic features are consistent with its formulation as the
CHCPhÄ
/
CPh)Ti (6), the product that may be expected
from the [2ꢁ
/
2] cycloaddition of the alkyne to the TiÄ
/C
titanacyclohexadiene (C5H4Me)(C5H4CMe2CHCPhÄ
/
bond in 3, and the vinylalkylidene complex
CPhCMeÄ
/
CMe)Ti (9, Scheme 5). Characteristic NMR
(d 206.2 ppm)
spectral features include the TiÃ
/
C(Me)Ä
/
1
1
135 Hz; H: d
and TiÃ
/
CH (13C: d 75.8 ppm, JCH
ꢀ
/
ꢂ
/
1.28 ppm) resonances. The related tetramethyl-titana-
cyclohexadiene (C5H4Me)(C5H4CMe2CHCMeÄCMe-
CMeÄCMe)Ti (10) is obtained from the reaction of
/
/
the alkylidene 3 with an excess of 2-butyne at ambient
temperature. The formation of 9 from 8 may be
considered to proceed through intramolecular attack
on the Ti-centre by the vinyl Ä
/
CHÃ
/
group in the vinyl-
substituted titanacyclobutene 8. In this way, the link to
the cyclopentadienyl ligand causes the system to deviate
from the metallacyclobutene-vinylalkylidene sequence
Scheme 5.

30
H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á36
/
(leading to alkyne polymerisation) to form a species that
is no longer reactive towards alkynes.
Reaction of the alkylidene complex 3 with 1 equiv. of
ethene proceeds smoothly at ambient temperature with
liberation of PMe3 and formation of the asymmetric
titanacyclobutane cycloaddition product (C5H4Me)-
(C5H4CMe2CHCH2CH2)Ti (11, Scheme 6). A full
1
assignment of the H NMR resonances and couplings
of the 2-substituted titanacyclobutane ring in 11 could
be made from a 1H,1H COSY NMR spectrum and
decoupling experiments. Typical spectral features of this
Scheme 7.
compound are the upfield shift (d ꢂ
H atom trans to the substituent on the ring, and the
upfield 13C NMR chemical shift (d ꢂ
5.3 ppm) of the b-
carbon. At ambient temperature, compound 11 gradu-
ally isomerises to a Cs-symmetric species, the 3-sub-
stituted titanacyclobutane complex (C5H4Me)[C5H4-
CMe2CH(CH2)2]Ti (12). This compound is related to
the (C5Me5)[C5Me4CH2CH(CH2)2]Ti complex reported
by Luinstra et al. from the reaction of (C5Me5)(C5-
/
0.54 ppm) of the b-
carbon of the ring cannot migrate to one of the nitrogen
atoms (leading to 2,6-diaza-titanacyclohexa-2,4-diene
compounds [13,14]), due to the constraint applied by
the anchoring of this carbon atom to the cyclopenta-
dienyl ligand system.
/
2.3. Reactivity of (C5H4CMe2CH2)2Ti (4)
Me4CH2)TiCl with CH2Ä
/
CMeCH2MgBr [12]. The iso-
The doubly cyclometallated complex (C5H4CMe2-
CH2)2Ti (4) is itself a titanocene dialkyl compound
containing a-hydrogen atoms. As it orginated from
merisation from 11 to 12 is likely to occur through a
cleavage of the titanacyclobutane to give a methylidene
intermediate, followed by rotation of the pendant vinylic
substituent and subsequent readdition (Scheme 6).
The alkylidene 3 also reacts readily with nitriles.
Upon reaction with 1 equiv. of benzonitrile, 3 is
converted to the vinylimido complex (C5H4Me)(C5H4-
intramolecular addition of a But CÃ
/
H bond to a
‘tucked-in’ alkylidene, it should in principle be capable
of reactivity characteristic both of that of a dialkyl and
those of an alkylidene. Indeed, the reactivity of 4
towards alkynes and nitriles leads to the same type of
products as those of the reactions of the ‘tucked-in’
alkylidene 3 with these reagents. The main difference is
that, in order to display alkylidene-like reactivity,
CMe2CHÄ
istic spectral features of this species include the reso-
nances of the ÄCH Ã
(1H NMR: d 4.70 ppm, 13C NMR:
2.4 Hz) and C ÄN (d 158.3 ppm,
2.7 Hz) moieties. Titanocene vinylimido species
/CPhN)Ti(PMe3) (13, Scheme 7). Character-
/
/
4
d 110.2 ppm, JCP
3JCP
ꢀ
/
/
compound 4 needs to be warmed to 80Á90 8C or higher
/
ꢀ
/
temperatures to give significant reaction rates. Under
these conditions, 4 reacts with 1 equiv. of diphenylace-
tylene to give the titanacyclobutene (C5H4But)(C5H4-
are typical products from the reaction of titanocene
alkylidenes with nitriles, via an initial cycloaddition
reaction followed by ring-opening and base coordina-
tion [11a,13,14]. Warming solutions of 13 in the
presence of excess benzonitrile leads to phosphine loss
and the formation of a Cs-symmetric product, the 2,6-
diaza-titanacyclohexa-2,5-diene complex (C5H4Me)-
[C5H4CMe2CH(PhCN)2]Ti(PMe3) (14, Scheme 7). This
product formation is similar to that observed for other
titanocene vinylimido complexes with excess nitrile, with
the main difference that in 14 the H-atom on the 4-
CMe2CHCPhÄ
6, can be converted with 2-butyne to the titanacyclohex-
adiene CPhCMeÄ
(C5H4But)(C5H4CMe2CHCPhÄ
/CPh)Ti (15) which, in similar fashion to
/
/
CMe)Ti (16, Scheme 8). With an excess of benzonitrile,
4 is converted to the 2,6-diaza-titanacyclohexa-2.5-diene
complex (C5H4But)[C5H4CMe2(PhCN)2]Ti (17, Scheme
8). Because of the lack of PMe3 in these reactions, and
the higher reaction temperatures required, intermediates
Scheme 6.
Scheme 8.

H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á
/36
31
like the vinylalkylidene and vinylimido species cannot be
observed. To form the products 15 and 17 it is not
required to isolate the compound 4: the same results can
be obtained by the reaction of the cyclometallated
mono(neopentyl) complex (C5H4But)(C5H4CMe2CH2)-
Ti(CH2CMe3) (2a) with the appropriate reagents under
these conditions, with the concomitant formation of 1
equiv. of neopentane.
3. Conclusions
The methylene group of cyclometallated tert-butylcy-
clopentadienyl ligands in titanocene alkyls can itself
undergo a-H abstraction to yield alkylidene species in
which the alkylidene is linked to the cyclopentadienyl
group. This link applies a geometrical constraint to the
1
alkylidene that is expressed e.g. in an increased JCH
coupling constant relative to titanocene neopentylidene
species. It also increases the reactivity of the PMe3-
stabilised titanocene alkylidene, and allowed us to
The dialkyl character of 4 is expressed e.g. in its
reaction towards the Lewis acid B(C6F5)3. In C6D6
solvent, this leads to the rapid formation of the
zwitterionic compound (C5H4CMe2CH2)[C5H4CMe2-
CH2B(C6F5)3]Ti (18, Scheme 9) by electrophilic attack
of the Lewis acid on one of the alkyl a-carbons. We
previously reported such an attack on a cyclometallated
tert-butylcyclopentadienyl ligand in the zirconium com-
pound (C5Me5)(C5H4CMe2CH2)Zr(CH2CMe3), turning
it into a highly selective catalyst for the dimerisation of
1-alkenes [15]. As with this Zr-compound, the low
temperature 19F NMR spectrum of 18 indicates hin-
dered rotation of the borate C6F5 groups (showing 15
establish that the addition of a C6D6 CÃ
/
D bond over
the TiÄ double bond in (C5H4Me)(C5H4C-
/C
Me2CH)Ti(PMe3) (3) proceeds in a stereoselective
manner, initially yielding the addition product (h5-
C5H4Me)(h5,h1-C5H4CMe2CHD)Ti(C6D5) (d6-5a) with
the deuterium on the methylene group exclusively in the
endo position. These ‘tucked-in’ alkylidenes exhibit
normal [2pꢁ2p] cycloaddition chemistry with unsatu-
/
rated substrates and allowed the observation of many
intermediate species, e.g. in the reactivity towards
alkynes. All the reaction steps required for alkyne
polymerisation were observed (titanacyclobutene, viny-
lalkylidene, titanacyclobutene derived from cycloaddi-
tion to vinylalkylidene), but actual polymerisation was
aborted by an intramolecular cyclisation induced by the
link to the cyclopentadienyl ligand. The chemistry of
these intramolecularly chelating alkylidenes thus
provides interesting mechanistic information on the
behaviour of titanocene alkylidenes and derived com-
pounds.
separate resonances), but no evidence for CÃ
/
FÁ Á ÁTi
interactions. This shows that the anionic alkyl(triar-
yl)borate fragment primarily interacts with the metal
1
through the methylene group, the H NMR resonances
of which are observed as broad signals in the upfield
region of the spectrum at d ꢂ
resonance of the endo proton of the cyclometallated
ButCp ligand is found at very high field, d ꢂ
3.60 ppm,
although not as extreme as that observed for the cationic
niobium species
[(C5H4But)(C5H4CMe2CH2)Nb-
(CH2Ph)]ꢁ (d ꢂ
5.58 ppm) [3e].
/
1.60 and ꢂ
/
1.08 ppm. The
/
/
Upon standing for an hour or more at ambient
temperature, benzene-d6 solutions of 18 deposit a
crystalline solid that is insoluble in weakly coordinating
polar solvents like bromobenzene. This material (which
unfortunately is of insufficient crystal quality to allow
an X-ray structure determination) is probably a kind of
coordination polymer of the zwitterionic compound. It
dissolves in THF-d8 to give a product that is identical to
that formed by addition of a stoichiometric amount of
THF to a C6D6 solution of 18 or dissolution of 18 in
THF-d8, (C5H4CMe2CH2)[C5H4CMe2CH2B(C6F5)3]-
4. Experimental
4.1. General
All experiments were performed under nitrogen atmo-
sphere using standard glove-box and Schlenk techni-
ques. Deuterated solvents (Aldrich, Acros) were flushed
with nitrogen, dried over molecular sieves and stored
and used in a glove-box. Other solvents were distilled
under Ar atmosphere from sodium or sodium benzo-
phenone ketyl. Compounds (C5H4R)(C5H4But)TiCl2
Ti(THF) (18×
/
THF, Scheme 9). In this adduct, the
coordinated THF has displaced the borate methylene
group from the coordination sphere of the metal, as can
be seen from the downfield shift of the BCH2 1H NMR
resonances to d 1.91 and 2.19 ppm.
(Rꢀ
But, 1a; Me, 1b; H, 1c) [16] and Mg(CH2CMe3)2-
/
(dioxane) [17] were prepared following published pro-
cedures. Commercially available diphenylacetylene,
PMe3 and ethene were used as received. Benzonitrile
was stored on molecular sieves under nitrogen. B(C6F5)3
was obtained in hydrocarbon solution (AKZO Nobel)
and recovered as a solid after removal of the solvent in
vacuo. NMR spectra were run on Varian XL-200,
Gemini 300 and Inova 400 spectrometers.
Scheme 9.

32
H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á36
/
4.2. Synthesis of
(C5H4R)(C5H4CMe2CH2)Ti(CH2CMe3)
4.3. Synthesis of (C5H4Me)(C5H4CMe2CH)Ti(PMe3)
(3)
A solution of 2b (0.49 g, 1.54 mmol) and an excess of
PMe3 (0.66 ml, 6.33 mmol) in 15 ml of C6H5CH3 was
stirred at 80 8C for 4 h in a closed thick-walled glass
reaction vessel with a Teflon stopcock. The solvent and
remaining phosphine was subsequently removed in
vacuo, and the residue was recrystallised from a small
4.2.1. (C5H4But)(C5H4CMe2CH2)Ti(CH2CMe3) (2a)
A solution of (C5H4But)2TiCl2 (1a, 0.523 g, 1.45
mmol) in 60 ml of Et2O was cooled to ꢂ
/
10 8C. A
solution of (Me3CCH2)2Mg×dioxane (0.370 g, 1.45
/
mmol) in 20 ml of Et2O was added, after which the
mixture was allowed to warm to room temperature over
15 min. The mixture was centrifuged to remove salts,
and the solvent was removed in vacuo from the super-
natant after decantation. The residue was taken up into
C5H12 and the solution was centrifuged again. Concen-
volume of C5H12 at ꢂ
/
40 8C. This yielded 3 as a
yellowÁbrown solid (0.15 g, 0.46 mmol, 30%). The
/
material appears to be pure by NMR spectroscopy, but
some paramagnetic impurities may still be present. The
material is difficult to purify further by crystallisation.
2
tration of the supernatant and cooling to ꢂ
produced 0.444 g (1.23 mmol, 85%) of redÁbrown solid
2a. 1H NMR (C6D6): d ꢂ
2.60 (d, Jꢀ9.3 Hz, 1H, endo-
CHH), ꢂ0.02 (d, Jꢀ9.3 Hz, 1H, exo-CHH), 0.03 (d,
Jꢀ10.4 Hz, 1H, TiCHHCMe3), 0.98 (12 H, Meꢁ
CMe3), 1.28 (s, 9H, CMe3), 1.49 (s, 3H, Me), 1.55 (d,
Jꢀ10.4 Hz, 1H, TiCHHCMe3), 4.48, 4.82, 5.14, 5.33,
6.07, 6.24 (2ꢃ
), 7.29 (m, 1H each, Cp CH). 13C{1H}
NMR (C6D6): d 29.0, 29.3 (Me), 32.1, 34.9 (CMe3),
CH2CMe3),
/
40 8C
1H NMR (C6D6): d 0.71 (d, JPH
ꢀ5.7 Hz, 9H, PMe3),
/
/
1.32, 1.49 (s, 3H each, Me), 1.92 (s, 3H, Cp Me), 4.84,
4.87, 4.95, 5.15, 5.30, 5.33, 5.50, 5.82 (m, 1H each, Cp
/
/
/
/
H), 11.92 (d, 3JPH
d 16.2 (q, Jꢀ
q, Jꢀ127 Hz, PMe3), 25.4 (d, JCP
Hz, Me), 26.6 (d, JCP
43.9 (s, C), 95.7, 98.4, 98.8, 100.0, 101.4, 102.0, 102.7,
104.6 (d, Jꢀ165Á167 Hz, Cp CH), 114.0, 114.6 (s, Cp
C), 312.0 (d, JCP 25 Hz, d, Jꢀ133 Hz, TiÄCH).
31P{1H} NMR (C6D6): d 1.4.
ꢀ
/
4.3 Hz, TiÄ
/
CH). 13C NMR (C6D6):
1
/
/
/
125 Hz, Cp Me), 20.5 (d, JCP
ꢀ
/
15.3 Hz,
124
125 Hz, Me),
4
/
ꢀ
/
5.9 Hz, q, Jꢀ
/
4
/
ꢀ
/
5.7 Hz, q, Jꢀ
/
/
/
/
2
33.6, 38.7 (C), 46.8 (TiÃ
/
CH2), 75.5 (TiÃ
/
ꢀ
/
/
/
105.8, 106.3, 109.8, 110.8, 113.0, 113.8, 114.5 (Cp CH),
117.4, 139.0 (Cp C).
4.4. Conversion of 2a to (C5H4CMe2CH2)2Ti (4)
4.2.2. (C5H4Me)(C5H4CMe2CH2)Ti(CH2CMe3) (2b)
This compound was prepared following the same
Warming a solution of 2a in C6D6 to 80 8C for 2 h
results in liberation of CMe4 and formation of 4.
Thermolysis of 2a at this temperature is accompanied
by formation of a small amount of a paramagnetic
impurity. Red crystalline 5 that is free of this impurity
was obtained by allowing a solution of 2a (0.20 g, 0.55
mmol) in C5H12 to stand at ambient temperature for 3
procedure as described for 2a, starting from
(C5H4Me)(C5H4But)TiCl2 (1b). H NMR (C6D6): d ꢂ
1
/
2.57 (d, Jꢀ
Hz, 1H, exo-CHH), 0.07 (d, Jꢀ
TiCHHCMe3), 0.95 (s, 9H, CMe3), 0.98 (s, 3H, Me),
1.29 (d, Jꢀ9.9 Hz, 1H, TiCHHCMe3), 1.47 (s, 3H,
/
9.5 Hz, 1H, endo-CHH), ꢂ
/
0.52 (d, Jꢀ
/
9.5
/9.9 Hz, 1H,
/
weeks, follwed by cooling the solution to ꢂ
yielding 0.10 g (0.35 mmol, 63%) of 4.
1H NMR (C6D6): d ꢂ
3.05 (d, Jꢀ9.3 Hz, 2H, endo-
TiCHH), ꢂ0.38 (d, Jꢀ9.3 Hz, 2H, exo-TiCHH),1.03,
/
20 8C,
Me), 1.99 (s, 3H, Cp Me), 4.36, 4.64, 5.05, 5.10, 5.78,
6.25, 6.51, 7.31 (m, 1H each, Cp H). 13C NMR (C6D6):
/
/
d 15.4 (q, Jꢀ
Me), 33.6 (s, C), 35.2 (q, Jꢀ
45.3 (t, Jꢀ132 Hz, TiÃCH2), 76.6 (t, Jꢀ
CH2CMe3), 106.8, 109.0, 109.4, 112.1, 113.9, 114.1,
117.1 (d, Jꢀ165Á170 Hz, Cp CH), 118.7, 123.2 (s, Cp
/
127 Hz, Cp Me), 29.1, 29.2 (q, Jꢀ
124 Hz, CMe3), 38.8 (s, C),
113 Hz, TiÃ
/
124 Hz,
/
/
/
1.38 (s, 6H each, Me), 4.75, 4.96, 5.93, 6.65 (m, 2H each,
Cp CH). 13C{1H} NMR (C6D6): d 28.9, 29.9 (Me), 34.2
(C), 47.9 (TiCH2), 104.2, 109.0, 113.0, 114.9 (all Cp
CH), 120.2 (Cp C).
/
/
/
/
/
/
C). Anal. Calc. for C20H30Ti (318.34): C, 75.46; H, 9.50;
Ti, 15.04. Found: C, 75.22; H, 9.44; Ti, 15.20%.
4.5. Reaction of 3 with C6D6 and C6H6
A solution of 3 (10.0 mg, 0.03 mmol) in C6D6 was
placed in an NMR-tube equipped with a Teflon valve,
and warmed to 80 8C in the probe of a Varian VXR-
300 spectrometer. The progress of the reaction was
4.2.3. (C5H5)(C5H4CMe2CH2)Ti(CH2CMe3) (2c)
This compound was prepared following the same
procedure as described for 2a, starting from
1
(C5H5)(C5H4But)TiCl2 (1c). 1H NMR (C6D6):
d
monitored by H NMR at regular intervals. After 30
ꢂ
/
2.57 (d, Jꢀ
9.3 Hz, 1H, exo-CHH), 0.15 (d, Jꢀ
TiCHHCMe3), 0.94 (12H, MeꢁCMe3), 1.22 (d, Jꢀ
/
9.3 Hz, 1H, endo-CHH), ꢂ
/
0.30 (d, Jꢀ
/
min a broadened singlet resonance at d ꢂ
observed for the exo-proton in d6-5a. After 1.5 h, two
sets of doublets can be observed in addition, at d ꢂ2.26,
2.28, ꢂ0.06 and ꢂ0.03 (Jꢀ9.8 Hz) for exo- and
endo-TiCHH, respectively of d6-5b/c, together with a
/
0.10 was
/10.0 Hz, 1H,
/
/
/
10.0 Hz, 1H, TiCHHCMe3), 1.45 (s, 3H, Me), 4.37,
4.60, 6.27, 7.24 (m, 1H each, Cp H), 5.81 (s, 5H, Cp).
ꢂ
/
/
/
/

H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á
/36
33
resonance at d 6.42 ppm for the TiÃ
/
C6HD4 o-H. Over
scribed above. After addition the solution was trans-
ferred in an NMR tube to the probe of an NMR
longer periods of time, extensive H/D scrambling occurs
between the phenyl group and the cyclometallated But
group.
spectrometer (ꢂ20 8C) and monitored by NMR spec-
/
troscopy, revealing formation of a new titanacyclobu-
tene species, 8. Upon standing at ambient temperature
in C6H5CH3-d8 solution, 8 rearranges within a few
hours to the green titanacyclohexadiene complex 9.
A sample of non-deuterated 5 was obtained by
warming 3 in C6H6 at 80 8C for 6 h, after which the
solvent was removed in vacuo and the residue was
dissolved in C6D6. 1H NMR (C6D6): d ꢂ
Hz, 1H, endo-TiCHH), ꢂ0.04 (d, Jꢀ
TiCHH), 1.00, 1.35 (s, 3H each, Me), 1.80 (s, 3H Cp
Me), 4.56, 4.96, 5.32, 5.46, 5.48, 5.85 (2ꢃ), 6.79 (m, 1H
each, CH CH), 6.40 (m, 2H, Ph o-H), 6.96 (t, 1H, Ph p-
H), 7.06 (m, 2H, Ph m-H).
/
2.25 (d, Jꢀ
/
9.7
/
/
9.7 Hz, 1H, exo-
4.7.1. (C5H4Me)(C5H4CMe2CHÄ
CMe)Ti (8)
1H NMR (C6H5CH3-d8, ꢂ
1.27,1.60, 1.91 (s, 3H each, Me), 4.69, 4.89 (m, 1H
each, Cp CH), 5.20Á5.25 (m, 3H, Cp CH), 5.30, 5.47 (m,
1H each, Cp CH), 5.64 (s, 1H, ÄCHÃ), 5.79 (m, 1H, Cp
CH), 6.8Á
7.2 (Ph CH). 13C(APT) NMR (C6H5CH3-d8,
20 8C): d 12.0, 14.4, 15.2, 20.6, 22.1 (Me), 35.5 (C),
95.3, 96.9 (TiÃC and b ÄCMeÃ), region between 100
and 130 too complicated for careful analysis, 140.8 (Cp
/
CPhCPhCMeÄ
/
/
/
20 8C): d 1.14, 1.24,
/
/
/
4.6. Reaction of 3 with diphenylacetylene
/
ꢂ
/
Diphenylacetylene (11 mg, 0.06 mmol) and 3 (20 mg,
0.06 mmol) were dissolved in 0.6 ml of C6H5CH3-d8 at
ambient temperature. By NMR, formation of a 3:1
mixture of the titanacyclobutene 6 and the vinylalk-
ylidene 7 was observed. Evaporation of the volatiles and
redissolution of the residue in C6H5CH3-d8 resulted in
exclusive formation of the titanacyclobutene 6. Addition
by microsyringe of a fourfold excess of PMe3 to this
solution resulted in a 1:3 mixture of 6 and 7.
/
/
/
C), 149.7, 150.7, 155.4 (Ph C and Ä
/
CPhÃ
/
), 245.6 (TiÃ
/
CMeÄ).
/
4.7.2. (C5H4Me)(C5H4CMe2CHCPhÄ
CMe)Ti (9)
1H NMR (C6H5CH3-d8): d ꢂ
/
CPhCMeÄ
/
/
1.28 (s, 1H, TiÃ
/CH),
1.00, 1.31, 1.39, 1.46 (s, 3H each, Me), 1.62 (s, 3H, Cp
Me), 4.53, 5.04, 5.32, 5.39, 5.74, 5.96, 6.04, 6.66 (m, 1H
4.6.1. (C5H4Me)(C5H4CMe2CHCPhÄ
1H NMR (C6H5CH3-d8): d 1.20, 1.33, 1.58 (s, 3H
each, Me), 2.19 (s, 1H, TiÃCH), 4.94, 5.17, 5.40, 5.42,
5.64, 6.07, 6.18 (m, 1H each, Cp CH), 6.6Á7.2 (Ph and
1H Cp CH). 13C{1H} NMR (C6H5CH3-d8): d 15.5 (Cp
Me), 26.2, 27.7 (Me), 39.9 (C), 80.2 (TiÃCH), 103.2,
107.2, 107.8, 109.1, 109.8, 110.1, 112.8, 113.5, 116.7 (Cp
CH and ÄCPh), 117.4 (Cp C), 124.6 (MeCp C) 126.2,
126.8, 128.3, 130.4 (Ph CH, others overlapped by
solvent), 139.8, 146.1 (Ph C), 217.8 (TiÃCÄ).
/
CPh)Ti (6)
each, Cp CH), 6.7Á
d8): d 15.7 (Cp Me), 18.8, 21.2, 22.0, 34.7 (Me), 37.8 (C),
75.8 (d, Jꢀ CH), 108.8, 109.2, 110.1, 110.6,
/
7.1 (Ph CH). 13C NMR (C6H5CH3-
/
/
135 Hz, TiÃ
/
/
111.0, 111.8, 112.6, 113.1 (Cp CH), 117.7 (Cp C), 123.1
(MeCp C), 124.8, 125.3, 127.5, 130.7 (Ph CH, others
/
overlapped by solvent), 133.0 (Ä
/
CMeÃ
/
), 142.9, 143.5,
CMeÄ).
145.8, 149.0 (Ph C and ÃCPhÃ), 206.2 (TiÃ
/
/
/
/
/
4.8. Reaction of 3 with excess 2-butyne
/
/
Addition of a threefold excess of 2-butyne (using a
cooled microsyringe) to a solution of 3 (16 mg, 0.05
mmol) in C6D6 and allowing this to stand at ambient
temperature leads to full conversion to the titanahex-
4.6.2. (C5H4Me)(C5H4CMe2CHÄ
/
CPhCPh)Ti(PMe3)
(7)
1H NMR (C6H5CH3-d8): d 0.84 (d, JPH
9H, PMe3), 1.32, 1.55, 1.61 (s, 3H each, Me), 4.45, 4.59,
ꢀ5.7 Hz,
/
2
adiene complex 10 in 24 h. 1H NMR (C6D6): d ꢂ
2.07 (s,
/
4.80 (m, 1H each, Cp CH), 4.9Á
/
5.1 (3H, Cp CH), 5.22
1H, TiCH), 0.84, 1.19, 1.32, 1.63, 1.74, 1.75, 1.83 (s, 3H
each, Me), 4.62, 5.13, 5.36, 5.47, 5.60, 5.81, 6.71 (m, 1H
5
(d, JPH
ꢀ
/
1.5 Hz, 1H, Ä
/
CHÃ
/
), 5.48, 6.53 (m, 1H each,
7.2 (Ph CH). 13C{1H} NMR (C6H5CH3-
Cp CH), 6.8Á
/
each, Cp CH). 13C NMR (C6D6): d 15.83 (q, Jꢀ
/
126
124 Hz, Me), 19.14, 19.25,
125 Hz, Me), 34.23 (q, Jꢀ126 Hz,
Me), 36.81 (s, C), 77.18 (d, Jꢀ131, TiÃCH), 108.36,
108.76, 109.62, 110.06, 110.60, 111.23, 112.54, 112.60 (d,
Jꢀ164Á168, Cp CH), 119.07 (Cp C), 122.65 (MeCp C),
132.48, 133.75, 135.60 (s, ÃCMeÄ), 198.77 (s, TiÃ
CMeÄ).
1
d8): d 16.1 (Cp Me), 19.2 (d, JPC
ꢀ/15.8 Hz, PMe3),
Hz, Cp Me), 15.97 (q, Jꢀ
/
27.9, 34.3 (Me), 35.2 (C), 99.0, 101.6, 102.3, 102.6, 104.0,
21.70, 26.86 (q, Jꢀ
/
/
104.6, 105.1, 107.0, 113.9 (Cp CH and ÄCHÃ), 121.9
/
/
/
/
(Cp C), 124.9 (MeCp C), 126.8 (Ph CH, others over-
lapped by solvent), 147.4, 158.6 (Ph C), 163.0 (d, 3JPC
ꢀ
/
/
/
2
), 305.7 (d, JPC
4.0 Hz, C(Ph)Ä
/
ꢀ
/
22.2 Hz, TiÄ/C).
/
/
/
/
4.7. Reaction of 6 with 2-butyne
4.9. Reaction of 3 with ethene
In a refrigerator inside a drybox, a twofold excess of
2-butyne was added by microsyringe to a solution of
titanacyclobutene 6 in C6H5CH3-d8, prepared as de-
A solution of 3 (20 mg, 62 mmol) in C6D6 was
transferred to a NMR tube which was sealed by a

34
H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á36
/
septum. Ethene (1.4 ml, 63 mmol) was added by gas-tight
syringe at ambient temperature. By NMR, clean libera-
tion of PMe3 and formation of titanacyclobutane 11 was
observed. Upon standing at ambient temperature, 11
gradually isomerises to the 3-substituted titanacyclobu-
tane 12 (after 15 h approximately 75% conversion).
Subsequently warming the solution to 40 8C for 1 h
drives this reaction to completion.
each, Cp CH), 5.4 (m, 2H, Cp CH), 5.66 (m, 1H, Cp
CH), 5.8 (m, 2H, Cp CH), 6.8Á7.2 (m, 5H, Ph).
13C(APT) NMR (C6D6): d 16.1 (MeCp Me), 17.4 (d,
JPC 17.9 Hz, PMe3), 27.2, 43.1 (Me), 35.3 (C), 100.2,
101.4, 102.9, 104.0, 104.6, 106.7, 107.7, 108.4 (all Cp
CH), 110.2 (d, JCP CHÃ), 123.4 (MeCp C),
2.4 Hz, Ä
126.4 (Ph m-CH), 127.9 (Ph o-CH), Ph p-H not
observed, 129.8 (Cp C), 141.2 (d, JCP 2.4 Hz, Ph C),
). 31P NMR (C6D6): d ꢂ
/
ꢀ
/
ꢀ
/
/
/
ꢀ
/
158.3 (d, JCP
ꢀ
/
2.7 Hz, NC Ä
/
/
0.51.
4.9.1. (MeCp)(C5H4CMe2CHCH2CH2)Ti (11)
1H NMR (C6D6): d (for H-atom numbering, see
illustration) ꢂ
0.54 (m, 1H, H1), 0.05 (m, 1H, H2), 1.07,
/
4.10.2. (MeCp)[C5H4CMe2CH(PhCN)2]Ti (14)
1H NMR (C6D6): d 1.20 (s, 6H, CMe2), 2.22 (s, 3H,
Cp Me), 5.45, 5.57 (m, 1H each, Cp CH), 5.68 (s, 1H,
1.16 (s, 3H each, Me), 1.73 (s, 3H, Cp Me), 2.14 (m, 1H,
H3), 2.82 (m, 1H, H4), 3.26 (m, 1H, H5), 4.85, 4.96, 4.99,
5.10, 5.14, 5.22, 5.30, 5.88 (m, 1H each, Cp CH).
CH), 5.9 (br m, 4H, MeCp CH), 7.1Á
/
7.3 (m, 6H, Ph p-H
7.8 Hz, 4H, Ph o-H). 13C(APT)
and m-H), 7.89 (d, Jꢀ
/
J(1,2)ꢀ
J(1,5)ꢀ
Hz, J(3,4)ꢀ
(C6D6): d ꢂ
(Me), 38.5 (C), 77.6 (TiÃ
/
12 Hz, J(1,3)ꢀ
5 Hz, J(2,3)ꢀ3 Hz, J(2,4)ꢀ
0 Hz, J(4,5)ꢀ
8 Hz. 13C{1H} NMR
5.3 (b-CH2), 15.1 (Cp Me), 24.9, 27.0
CH2), TiÃCH not observed,
/
10 Hz, J(1,4)ꢀ
/
12 Hz,
NMR (C6D6): d 15.8 (MeCp Me), 28.6 (CMe2), 45.4
(C), 78.6 (CH), 104.9, 109.7, 113.4, 117.3 (all Cp CH),
127.4 (Ph m-CH), 128.4 (Ph p-CH), 128.6 (Ph o-CH),
/
/
/
4 Hz, J(2,5)ꢀ
/
13
/
/
/
128.5 (MeCp C), 130.6 (Cp C), 140.9 (Ph C), 159.5 (NÄ
/
/
/
C).
101.1, 105.4, 105.6, 107.5, 108.1, 109.5, 115.7 (Cp CH),
118.5 (Cp C), 112.9 (MeCp C).
4.11. Sequential reaction of 4 with diphenylacetylene and
2-butyne
A solution of 4 (15 mg, 0.05 mmol) and diphenyla-
cetylene (9 mg, 0.05 mmol) in 0.6 ml C6H5CH3-d8 in an
NMR tube sealed with a Teflon stopcock was warmed
at 115 8C for 3 h. This resuled in complete conversion
to the titanacyclobutene complex 15. The same com-
pound can be obtained (with concomitant formation of
neopentane) by warming a solution of equimolar
amounts of 2a and diphenylacetylene in C6D6 at
60 8C overnight. Addition (by cooled microsyringe) of
a threefold excess of 2-butyne to the solution of 15 in
C6H5CH3-d8 described above, and allowing the tube to
stand at ambient temperature overnight, resulted in full
conversion to the titanacyclohexadiene complex 16.
4.9.2. (MeCp)[C5H4CMe2CH(CH2)2]Ti (12)
1H NMR (C6D6): d 1.07 (M, 2H, TiCHH), 1.43 (s,
6H, Me), 1.75 (m, 2H, TiCHH), 1.88 (s, 3H, Cp Me),
2.01 (m, 1H, b-CH), 5.04, 5.49, 5.54, 5.83 (m, 2H each,
Cp CH). 13C NMR (C6D6): d 16.0 (q, Jꢀ
/
127 Hz, Cp
135 Hz, b-CH), 26.1 (q, Jꢀ125 Hz,
Me), 39.0 (s, C), 64.3 (t, Jꢀ138 Hz, TiÃCH2), 104.0,
106.0, 107.3, 111.4 (d, 164Á167 Hz, Cp CH), 123.1,
Me), 25.5 (d, Jꢀ
/
/
/
/
/
124.9 (Cp C).
4.11.1. (ButCp)(C5H4CMe2CHCPhÄ
/
CPh)Ti (15)
1H NMR (C6H5CH3-d8): d 0.77 (s, 9H, But), 1.15,
1.41 (s, 3H each, Me), 2.46 (s, 1H, TiCH), 5.25, 5.34,
5.39, 5.47, 5.57, 5.79, 6.17, 6.43 (m, 1H each, Cp CH),
4.10. Reaction of 3 with PhCN
A solution was made of 3 (16 mg, 0.05 mmol) in 0.6
ml of C6D6. Subsequent addition by microsyringe of 1
equiv. of PhCN to the solution at ambient temperature
led to the formation of the vinylimido complex 13.
Subsequent addition of a twofold excess of PhCN,
followed by warming the solution to 50 8C, led to
phosphine loss and formation of the 2,6-diaza-titanacy-
clohexa-2,5-diene complex 14.
6.8Á
/
7.1 (Ph H), 7.25 (d, Jꢀ7.3 Hz, 2H, Ph o-H).
/
4.11.2. (ButCp)(C5H4CMe2CHÄ
CMe)Ti (16)
/
CPhCPhCMeꢀ
/
1H NMR (C6H5CH3-d8): d ꢂ
/
1.15 (s, 1H, TiCH), 0.73
(s, 9H, But), 1.12, 1.32, 1.37, 1.48 (s, 3H each, Me), 4.66,
5.24, 5.41, 5.69, 5.73, 6.08, 6.28, 6.70 (m, 1H each, Cp
CH), 6.8Á7.2 (Ph H).
/
4.10.1. (MeCp)(C5H4CMe2CHÄ
(13)
1H NMR (C6D6): d 0.68 (d, JPH
1.46, 1.74 (s, 3H each, Me), 2.24 (s, 3H, Cp Me), 4.59
(m, 1H, Cp CH), 4.70 (s, 1H, ÄCHÃ), 4.77, 5.01 (m, 1H
/
CPhN)Ti(PMe3)
4.12. Reaction of 4 with PhCN
ꢀ7.0 Hz, 9H, PMe3),
/
A solution of 4 (12 mg, 0.04 mmol) in 0.6 ml of
C6H5CH3-d8 was placed in an NMR tube equipped with
/
/

H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á
/36
35
a Teflon stopcock, and a fourfold excess of PhCN was
added by microsyringe. The tube was closed and
warmed at 95 8C overnight, after which conversion to
17 was complete. To facilitate the analysis of the 13C
NMR spectra, the volatiles were removed from the
solution, and the orange solid product was redissolved
in C6D6. 1H NMR (C6D6): d 1.14 (s, 6H, CMe2), 1.30 (s,
9H, But), 5.42, 5.62 (m, 2H each, Cp CH), 5.63 (s, 1H,
CH), 6.02, 6.14 (M, 2H each, Cp CH), Ph o-H obscured
1.91, 2.19 (br d, Jꢀ12 Hz, 1H each, BCH2), 2.50, 2.63
/
(m, 2H each, THF a-H), 3.78, 3.83, 4.30, 5.22, 5.72,
5.77, 5.93, 6.30, 6.74 (m, 1H each, Cp CH). 19F NMR
(C6D6): d ꢂ
/
131.1 (o-F), ꢂ
/
164.4 (p-F), ꢂ167.6 (m-F).
/
13C{1H} NMR (THF-d8): d 26.38, 28.03, 29.91, 32.41
(all Me), 35.51, 37.62 (both CMe2), 38 (br, BCH2), 59.48
(TiCH2), 110.33, 111.70, 111.83, 114.56, 116.44 (all Cp
CH), 120.56 (Cp C), 121.13, 122.69, 123.30 (all Cp CH),
1
Ar C), 137.2 (d, JCF
128.1 (br BÃ
/
ꢀ
/
247 Hz, m-CF),
by solvent, 7.25 (t, Jꢀ
Jꢀ
7.6 Hz, 4H, Ph o-H). 13C NMR (C6D6): d 28.61 (q,
Jꢀ126 Hz, CMe2), 31.32 (q, Jꢀ125 Hz, CMe3), 32.91
(s, CMe3), 45.68 (s, CMe2), 78.81 (d, Jꢀ130 Hz, CH),
105.27, 109.33, 111.62, 117.35 (all d, Jꢀ170Á175 Hz,
Cp CH), 127.42, 128.65, 128.77 (all d, Jꢀ165Á170 Hz,
Ph CH), 130.49 (s, Cp C), 140.29 (s, ButCp C), 141.03 (s,
Ph C), 159.55 (s, NÄC).
/
7.6 Hz, 4H, Ph m-H), 7.81 (d,
138.4 (d, 1JCF
o-CF), 151.13 (Cp C).
ꢀ
/
245 Hz, p-CF), 149.2 (d, 1JCF
ꢀ
/
240 Hz,
/
/
/
/
/
/
References
/
/
[1] (a) R.R. Schrock, J. Am. Chem. Soc. 97 (1975) 6577;
(b) R.R. Schrock, J. Am. Chem. Soc. 96 (1974) 6796.
/
[2] For a comprehensive review on the generation of metal alkylidene
species, see: R.R. Schrock, Chem. Rev. 102 (2002) 145.
[3] (a) C. McDade, J.C. Green, J.E. Bercaw, Organometallics 1
(1981) 1629;
4.13. Reaction of 4 with B(C6F5)3
A mixture of solid 4 (22 mg, 0.076 mmol) and
B(C6F5)3 (39 mg, 0.076 mmol) was dissolved in 0.6 ml
of C6D6, resulting in a brown solution. Clean formation
of the zwitterionic compound 18 was observed by NMR
spectroscopy. Allowing this solution to stand at ambient
temperatures for more than 1 h results in the gradual
formation of a brown crystalline solid that does not
dissolve in C6D5Br. Addition of THF redissolved this
material as the THF-adduct of 18 (vide infra). The rate
of precipitation appears to decrease with decreasing
concentation and temperature.
(b) A.R. Bulls, W.P. Schaefer, M. Serfas, J.E. Bercaw, Organo-
metallics 6 (1987) 1219;
(c) L.R. Chamberlain, I.P. Rothwell, J.C. Huffman, J. Am. Chem.
Soc. 108 (1986) 1502;
(d) J.A. van Doorn, H. van der Heijden, A.G. Orpen, Organo-
metallics 13 (1994) 4271;
(e) D.J. Duncalf, R.J. Harrison, A. McCamley, B.W. Royan, J.
Chem. Soc., Chem. Commun. (1995) 2421.
[4] (a) P.J. Walsh, F.J. Hollander, R.G. Bergman, J. Am. Chem. Soc.
110 (1988) 8729;
(b) C.C. Cummins, S.M. Baxter, P.T. Wolczanski, J. Am. Chem.
Soc. 110 (1988) 8731;
(c) C.P. Schaller, P.T. Wolczanski, Inorg. Chem. 32 (1993) 131;
(d) P.J. Walsh, F.J. Hollander, R.G. Bergman, Organometallics
12 (1993) 3705;
4.13.1. (C5H4CMe2CH2)[C5H4CMe2CH2B(C6F5)3]Ti
(18)
(e) C.P. Schaller, C.C. Cummins, P.T. Wolczanski, J. Am. Chem.
Soc. 118 (1996) 591;
1H NMR (C6D6): d ꢂ
/
3.60 (d, Jꢀ
1.08 (br, 1H each, BCH2), 0.26, 0.37,
1.42, 1.58 (s, 3H each, Me), 2.35 (d, Jꢀ10.0 Hz, 1H,
/
10.0 Hz, 1H,
(f) L.J. Bennett, P.T. Wolczanski, J. Am. Chem. Soc 119 (1997)
10696.
TiCHH), ꢂ
/
1.60, ꢂ
/
[5] H. van der Heijden, B. Hessen, J. Chem. Soc., Chem. Commun.
(1995) 145.
/
TiCHH), 3.78, 4.25, 4.93, 5.16, 5.58, 6.12, 6.40, 6.95 (m,
1H each, Cp CH). 19F NMR (C6H5CH3-d8, 25 8C): d
[6] J. Cheon, D.M. Rogers, G.S. Girolami, J. Am. Chem. Soc. 119
(1997) 6804.
ꢂ
/
130.3 (br, o-F), ꢂ
19F NMR (C6H5CH3-d8, ꢂ
129.0, ꢂ132.2, ꢂ132.7, ꢂ
158.8, ꢂ159.2 (m, all p-F), ꢂ
164.0, ꢂ164.4, ꢂ166.3 (m, all m-F).
/
159.6 (br, p-F), ꢂ
60 8C): d ꢂ
133.6 (m, all o-F), ꢂ
160.7, ꢂ162.5, 163.6,
/
164.3 (br, m-F).
[7] M.P. Coles, V.C. Gibson, W. Clegg, M.R.J. Elsegood, P.A.
Porrelli, J. Chem. Soc., Chem. Commun. (1996) 1963.
[8] (a) E. Tran, P. Legzdins, J. Am. Chem. Soc. 119 (1997) 5071;
(b) C.S. Adams, P. Legzdins, E. Tran, J. Am. Chem. Soc. 123
(2001) 612;
/
/
126.8, ꢂ
/
127.8,
ꢂ
/
/
/
/
/157.9,
ꢂ
/
/
/
/
ꢂ
/
/
/
(c) C.S. Adams, P. Legzdins, W.S. McNeil, Organometallics 20
(2001) 4939.
4.14. Reaction of 18 with THF
[9] G. Erker, U. Korek, R. Petrenz, A.L. Rheingold, J. Organomet.
Chem. 421 (1991) 215.
[10] F.N. Tebbe, R.L. Harlow, J. Am. Chem. Soc. 102 (1980) 6149.
[11] (a) C.D. Wood, S.J. McLain, R.R. Schrock, J. Am. Chem. Soc.
101 (1979) 3210;
To a solution of 0.014 mmol of 18 in C6D6, prepared
as described above, THF (2.1 ml, 0.026 mmol) was added
by microsyringe to give a clear yellowÁgreen solution of
/
(b) K.C. Wallace, A.H. Liu, W.M. Davis, R.R. Schrock,
Organometallics 9 (1989) 644.
18.THF. No exchange of free and coordinated THF was
observed on NMR timescale at ambient temperature.
Dissolution of 18 in neat THF-d8 gives the same species.
[12] P.H.P. Brinkmann, M.-H. Prosenc, G.A. Luinstra, Organome-
tallics 14 (1995) 5481.
[13] (a) R.R. Schrock, J.D. Fellman, J. Am. Chem. Soc. 100 (1978)
3359;
1H NMR (C6D6): d ꢂ
0.53 (s, 3H, Me), 0.64 (d, Jꢀ
(m, 4H, THF b-H), 0.98, 1.07, 1.18 (s, 3H each, Me),
/
3.24 (d, Jꢀ/9.0 Hz, 1H, TiCHH),
/9.0 Hz, 1H, TiCHH), 0.95
(b) K.M. Doxsee, J.B. Farahi, J. Chem. Soc., Chem. Commun.
(1990) 1452;

36
H. van der Heijden, B. Hessen / Inorganica Chimica Acta 345 (2003) 27Á36
/
(c) B. Hessen, J.K.F. Buijink, A. Meetsma, J.H. Teuben, G.
Helgesson, M. Ha˚kansson, S. Jagner, A.L. Spek, Organometallics
12 (1993) 2268.
[15] H. van der Heijden, B. Hessen, A.G. Orpen, J. Am. Chem. Soc.
120 (1998) 1112.
[16] (a) S.L. Hart, D.J. Duncalf, J.J. Hastings, A. McCamley, P.C.
Taylor, J. Chem. Soc., Dalton Trans. (1996) 2843;
(b) R.A. Howie, G.P. McQuillan, D.W. Thompson, G.A. Lock, J.
Organomet. Chem. 303 (1986) 213.
[14] (a) K.M. Doxsee, J.B. Farahi, J. Am. Chem. Soc. 110 (1988) 7239;
(b) K.M. Doxsee, J.B. Farahi, H. Hope, J. Am. Chem. Soc. 113
(1991) 8889;
(c) N.A. Petasis, D.-K. Fu, Organometallics 12 (1993) 3776.
[17] R.R. Schrock, J.D. Fellman, J. Am. Chem. Soc. 100 (1978) 3359.