Thermolysis of titanocene methyl compounds bearing t-butyl- and benzyltetramethylcyclopentadienyl ligands

Article abstract of DOI:10.1016/j.jorganchem.2009.01.039

Elimination of methane during thermolysis of title compounds results in the formation of σ-Ti-C bond to t-butyl or benzyl group. The t-butyl-containing titanocene methyl compound [Ti(III)Me(η⁵-C₅Me₄t-Bu)₂] (5) e

Full text of DOI:10.1016/j.jorganchem.2009.01.039

Journal of Organometallic Chemistry 694 (2009) 1971–1980
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Thermolysis of titanocene methyl compounds bearing t-butyl-
and benzyltetramethylcyclopentadienyl ligands
a
b
c
c
a
a
a,
*
ˇ
ˇ
ˇ
ˇ
Jirí Pinkas , Ivana Císarová , Ana Conde , Rosa Fandos , Michal Horácek , Jirí Kubišta , Karel Mach
a
´
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8, Czech Republic
b Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
c Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avd. Carlos III, s/n, 45071 Toledo, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Elimination of methane during thermolysis of title compounds results in the formation of
r
-Ti–C bond to
5-C5Me4t-Bu)2]
5-C5Me4t-Bu)] (6). The
5-C5Me4CH2Ph)2] was not
isolated because it eliminated methane at ambient temperature to give [Ti(III)(g5 1-C5Me4CH2-o-C6
H4)(
5-C5Me4CH2Ph)] (7) with one phenyl ring linked to titanium atom in ortho-position. The
corresponding titanocene dimethyl compound [TiMe2{
5-C5Me4t-Bu)}2] (9) eliminates two methane
molecules at 110 °C to give the singly tucked-in 1,1-dimethylethane-1,2-diyl-tethered titanocene
[Ti{g5 1-C5Me3(CH2)(CMe2CH2)}( 5-C5Me4t-Bu)] (11). In distinction, the analogous benzyl deriva-
tive [TiMe2(
5-C5Me4CH2Ph)2] (10) eliminates at 110 °C only one methane molecule to afford
[TiMe(g5 1-C5Me4CH2-o-C6H4)( 5-C5Me4CH2Ph)] (12) containing one phenyl group attached to tita-
Received 19 November 2008
Received in revised form 19 January 2009
Accepted 22 January 2009
Available online 30 January 2009
t-butyl or benzyl group. The t-butyl-containing titanocene methyl compound [Ti(III)Me(
(5) eliminates methane at 110 °C to give cleanly [Ti(III)(g5 1-C5Me4CMe2CH2)(
methyl derivative of analogous benzyl-containing titanocene [Ti(III)Me(
g
:
g
g
g
:
g
g
Keywords:
Titanium
g
t-Butyltetramethylcyclopentadienyl
Benzyltetramethylcyclopentadienyl
Thermolysis
Titanocene methyl
Titanocene dimethyl
:
g1
:
g
g
g
:
g
g
nium in o-position and one methyl group persisting on the titanium atom. This compound is stable at
150 °C for at least 3 h. The crystal structures of 5, 6, 7, and 10 were determined.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
boiling of the [TiCl2(
thermolysis of [Ti(
2-Me3SiC„CSiMe3)(
low yields [4b]. The monomethyl compound [TiMe(
g
5-C5HMe4)2]/LiAlH4 mixture [4a] or by
5-C5HMe4)2] albeit in
5-C5HMe4)2]
g
g
Decamethyltitanocene chemistry was thoroughly investigated
very early by Brintzinger and Bercaw [1], and later succeeded by
Teuben and co-workers [2]. Thermal treatment of the dimethyl
g
eliminated methane under the exclusive formation of para-
magnetic dimer (2c) (Scheme 2) [4c].
compound [TiMe2(
tucked-in methyl derivative [TiMe{g5
(1a) [1a,b,d], and at higher temperature the doubly tucked-in perm-
ethyltitanocene [Ti{g4 3-C5Me3(CH2)2}( 5-C5Me5)] (1b) [2a].
The monomethyl compound [Ti(III)Me(
5-C5Me5)2] gave cleanly
the singly tucked-in paramagnetic [Ti(III){g5 1-C5Me4 (CH2)}-
5-C5Me5)] compound (1c) [1a,b,2c,3], another precursor for 1b
[2a] (Scheme 1).
g
5-C5Me5)2] afforded subsequently the singly
Compound [TiMe2(
molecules of methane at only 90 °C to give singly tucked-in and
silylmethylene-tethered compound 3a whereas [Ti(III)Me(g5
g
5-C5Me4SiMe3)2] easily eliminated two
:g g
1-C5Me4(CH2)}( 5-C5 Me5)]
-
:g
g
C5Me4SiMe3)2] gave at the same temperature the silylmethylene-
tethered product 3b (Scheme 3) [5].
g
:g
The phenyl-modified dimethyltitanocene [TiMe2(
Ph)2] afforded a mixture of stereoisomers [TiMe(
5-C5Me4Ph){g5
1-C5Me3Ph(CH2)}] (4a) which at higher temperature gave a mix-
ture of singly tucked-in [Ti(
5-C5Me4Ph){g5 1-C5Me3Ph(CH2)}]
(4c) and among other minor products the doubly tucked-in titano-
g
5-C5Me4
(g
g
:
g
A minimum change in substituents of the cyclopentadienyl ring,
e.g., replacement of one methyl group with hydrogen, trimethyl-
silyl or phenyl group led to mostly surprising thermolytic results.
g
:g
cene [Ti(
[6].
g :g
5-C5Me4Ph){g4 3-C5Me2Ph(CH2)2}] (4b) (Scheme 4)
Thermolysis of [TiMe2(
tucked-in methyl derivative [TiMe{g5
HMe4)] (2a), however, its further thermolysis did not give an isola-
ble yield of doubly tucked-in compound [Ti{g4 3-C5HMe2
(CH2)2}(
5-C5HMe4)] (2b). Compound 2b was obtained from
g
5-C5HMe4)2] afforded cleanly the singly
:g
1-C5HMe3(CH2)}(
g
5-C5
In contrast to the above mentioned substituents, the phenyl
group did not participate in hydrogen abstraction reactions due
to its orientation close to the cyclopentadienyl ring plane, which
precludes the phenyl group to approach the thermally excited
Ti–Me bonds.
:g
g
Here we investigate the thermolytic behavior of permethyltit-
anocene mono- and dimethyl derivatives modified by replacing
one methyl group on each cyclopentadienyl ring with t-butyl or
* Corresponding author. Tel.: +420 2 6605 3735; fax: +420 2 858 2307.
E-mail addresses: mach@jh-inst.cas.cz, karel.mach@jh-inst.cas.cz (K. Mach).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.039

1972
J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
Scheme 4.
Scheme 1.
benzyl substituent with the aim to see their reactivity toward ther-
mally excited titanium-methyl moieties.
2. Results and discussion
The t-butyl-containing titanocene monomethyl compound
[Ti(III)Me(
[7] via its reduction with a half molar equivalent of magnesium fol-
g
5-C5Me4t-Bu)2] (5) was prepared from the dichloride
lowed by salt metathesis of the monochloride [Ti(III)Cl(g
5-C5Me4
t-Bu)2] with methyl lithium (LiMe) (Scheme 5).
The metathesis reaction was carried out using solid LiMe in
hexane, where LiMe was nearly insoluble. Because of heterogeneity
of the reaction system a large molar excess of solid LiMe was used
and the mixture was magnetically stirred and hand shaken until
the blue color of the chloride turned to the dark green color of 5.
Compound 5 is paramagnetic, giving a broad signal (
at g = 1.955 similar to the signals of [Ti(III)Me(
5-C5Me5)2] [2b,8],
[Ti(III)Me(
5-C5Me4SiMe3)2] [4], [Ti(III)Me( 5-C5HMe4)2] [4c] or
[Ti(III)CH2CMe3(
5-C5Me5)2] [2b]. Its electronic absorption spec-
DH = 14 G)
g
g
g
g
trum was characterized by two absorption bands in visible region
close to the band positions for the above mentioned alkyl titanoc-
enes [2c,5,8]. The molecular structure of 5 was determined by
single crystal X-ray diffraction analysis (see below). Heating a tol-
uene solution of 5 to 110 °C resulted in only a slight color change
and evolution of a gas. A greenish brown crystalline product 6
was isolated from hexane in nearly quantitative yield. The EPR
and electronic absorption spectra of 6 were similar to those of 5,
however, the EI-MS spectra for 6 were different from those for 5
showing the base peak m/z 401 to be the molecular ion whereas
the base peak for 5 was the fragment ion [MꢀMe]+ m/z 402. The
Scheme 2.
X-ray diffraction analysis revealed that 6 is [Ti(III)(g5
:g
1-C5Me4C-
5-C5Me4t-Bu)] with one cyclopentadienyl ring linked to
Me2CH2)(
g
the titanium atom via the 1,1-dimethylethane-1,2-diyl tether (see
Scheme 6). Compound 6 can be considered to be thermally extre-
mely stable as it was recovered unchanged after heating to 160 °C.
Scheme 3.
Scheme 5.

J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
1973
stereogenic titanium centre in 8 gives rise to eight signals for the
C5Me4 groups in 1H and 13C NMR spectra, and diastereotopic pro-
tons of both methylene units generate a system of two pairs of
doublets. A close proximity of the stereogenic centre to the teth-
ered CH2-o-C6H4 methylene induced a considerably larger separa-
tion of resonances compared to those of methylene signals of the
untethered benzyl group (CH2-o-C6H4: dH (2JHH) 3.71, 3.85 ppm
(16.2 Hz); CH2Ph: dH (2JHH) 3.35, 3.40 (16.5 Hz)).
The respective titanocene dimethyl compounds [TiMe2(g5
C5Me4t-Bu)2] (9) and [TiMe2(
5-C5Me4CH2Ph)2] (10) were also
obtained by the salt metathesis of the dichlorides [TiCl2(
5-C5
Me4t-Bu)2] [7] and [TiCl2(
5-C5Me4CH2Ph)2] [9] with the solid LiMe.
-
g
g
Scheme 6.
g
In this case, a complete exchange of chlorine ligands for methyl
groups has to be ensured. To accomplish this, a mixture of the di-
methyl and methylchloro derivatives obtained after the first salt
metathesis reaction was treated once more with fresh solid LiMe.
Compound 9 in toluene was heated to 110 °C for 5 h to give a
dark green solution from which a waxy solid extremely well solu-
ble in hexane was obtained. This circumstance prevented its puri-
fication by crystallization, and thus all the bulk product was
investigated by NMR methods. The C6D6 solution of the product
displayed a rather complicated signal pattern in both 1H and 13C
spectra. Nevertheless, the presence of two characteristic doublets
at ꢀ3.28 and ꢀ1.06 ppm (2JHH = 9.9 Hz) and combination of NMR
techniques (APT, gCOSY, gHMBC) allowed us to identify the most
abundant compound. The above mentioned strongly upfield sig-
nals were typical for the methylene group TiCH2CMe2 of a metalla-
cycle formed by the hydrogen atom abstraction from one t-Bu
group residing on cyclopentadienyl ring. The corresponding 13C
signal of the methylene was found at 55.14 ppm. The similar
features are known from 1H and 13C NMR spectra of complexes
Following the procedure for synthesis of 5 an attempt was made
to prepare the analogous benzyl-containing derivative [Ti(III)-
Me(
CH2Ph)2] was obtained by stoichiometric reduction of the dichlo-
ride [TiCl2(
5-C5Me4CH2Ph)2] [9] with a half molar equivalent of
g g
5-C5Me4CH2Ph)2]. The monochloride [Ti(III)Cl( 5-C5Me4
g
magnesium as a non-crystallizing waxy solid, and therefore was
characterized only by spectroscopic methods. Its salt metathesis
with solid LiMe afforded a brown single product 7 crystallizing
as aggregates of thin leaves. A considerable amount of gas evolved
during the reaction and the base peak m/z 469 of the EI-MS spec-
trum of 7, however, indicates that the salt metathesis reaction is
accompanied by methane elimination. Whereas EPR and UV–Vis
spectra could not safely distinguish between [Ti(III)Me(g5
-
C5Me4CH2Ph)2] and the product of its demethanation the X-ray
crystal structure of 7 (see below) revealed that it is the latter,
[Ti(III)(g5 1-C5Me4CH2-o-C6H4)( 5-C5Me4CH2Ph)] (7), containing
:g g
one benzyl substituent linked to the titanium atom by ortho-car-
bon of its phenyl ring. This indicates that [Ti(III)Me(g5
-
[TiPh(g5 1-C5H4CMe2CH2)( 5-C5H4t-Bu)] (TiCH2: dH (2JHH)/dC:
:g g
C5Me4CH2Ph)2] was unstable at ambient temperature, and the
leaving methyl group abstracted selectively one hydrogen atom
from ortho-position of one phenyl ring. Compound 7 was similarly
to 6 thermally stable to 170 °C in m-xylene solution. The structure
of 7 was in agreement with 1H and 13C NMR spectra of the bright
ꢀ1.94, ꢀ0.08 ppm (10.5 Hz)/57.6 ppm) [10] and [Ti(CH2CMe3)(g5
:
g
1-C5H4CMe2CH2)(
g
5-C5H4t-Bu)] (TiCH2: dH (2JHH)/dC: ꢀ2.60,
ꢀ0.02 ppm (9.3 Hz)/46.8 ppm) [12]. The CMe2 group gave rise to
two sets of signals for diastereotopic methyl groups in both 1H
and 13C NMR spectra (CMe2 dH/dC: 1.30, 1.42 ppm/29.28, 32.05
ppm) and a signal at dC 36.38 ppm for its quaternal carbon. The
other t-Bu group remained unactivated as evidenced by only one
signal for its methyl groups in both 1H and 13C NMR spectra
(CMe3 dH/dC: 1.16 ppm/32.65 ppm; CMe3 dC: 35.59 ppm). In addi-
tion, the presence of ring exo-methylene TiCH2 group was estab-
lished on the basis of gCOSY and APT spectra. The data for TiCH2
dH/dC: 0.89, 1.21 ppm/77.00 ppm are close to those for tucked-in
1a, 2a, 3a, and 4a complexes (see Schemes 1–4) and a number of
other singly and doubly tucked-in titanocene complexes [13]. It
follows from the above arguments that the main product of the
thermolysis of 9 is the single tucked-in, 1,1-dimethylethane-1,
orange product of its chlorination with PbCl2, [Ti(IV)Cl(g5 g1
: -
C5Me4CH2-o-C6H4)(g
5-C5Me4CH2Ph)] (8) (Scheme 7).
Compound 8 possesses C1 molecule symmetry, where one
cyclopentadienyl unit is tethered to the titanium atom via a CH2-
o-C6H4 three-carbon atom spacer. The 13C NMR signal of the phe-
nylene carbon atom linked to titanium appears at 199.00 ppm,
close to the resonances for similar compounds. For example, the
r
-Ti–Cipso(phenyl) resonates typically in the dC 190–194 ppm re-
gion [10], and in the cationic complex [Ti(g5 1-C5H4CMe2-o-
C6H4)(
5-C5H5)]+ at 208.0 ppm [11]. Binding of the phenyl group
:g
g
in ortho-position follows from DFT calculations on the latter com-
plex [11] as well as from the crystal structure of 7. The presence of
2-diyl-tethered titanocene [Ti{g5
: :g
g1 1-C5Me3(CH2)(CMe2CH2)}
(g
5-C5Me4t-Bu)] (11) (Scheme 8), a carbon analogue of the known
complex 3a whose crystal structure was determined by X-ray
diffraction analysis [5].
Scheme 7.
Scheme 8.

1974
J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
2.1. Molecular structures of 5 and 6
Compounds 5 and 6 are paramagnetic Ti(III) titanocene carbyl
complexes where the methyl and 1,1-dimethylethane-1,2-diyl,
respectively, are
respectively).
r-bonded to titanium (see Figs. 1 and 2,
The selected geometric data for 5 and 6 (Table 1) demonstrate
differences in the pseudotrigonal coordination of the titanium
atom. Molecule of 5 shows a non-crystallographic symmetry with
respect to the TiꢀC(27) bond and the absence of slippage or tilting
of the cyclopentadienyl rings as it follows from virtually equivalent
Ti–Cg and Ti–Pl distances (Cg – centroid of and Pl – least-square
plane of the cyclopentadienyl ring). The t-butyl groups occupying
opposite side carbon atoms of the cyclopentadienyl rings in bent
titanocene skeleton do not impose additional steric hindrance.
The TiꢀCg distance of 2.0961(6) Å is longer than that for [Ti(III)-
Scheme 9.
Heating of 10 in toluene to 110 °C for 12 h did not result in an
observable change of its yellow color, however, replacement of tol-
uene with hexane followed by attempted crystallization afforded a
yellow non-crystallizing solid apparently different from 10. Its 1H
and 13C NMR spectra revealed that 10 was completely converted
Me(
X(
carbon) [14], and close to that of [Ti(III)CH2CMe3(
2.099(6) Å) [2b]. The Ti–C(27) bond length of 2.1731(15) Å is
slightly shorter than the analogous bond in [Ti(III)Me(
5-C5-
Me4SiMe3)2] (2.213(2) Å) [5] and [Ti(III)CH2CMe3(
5-C5Me5)2]
g
5-C5Me4SiMe3)2] (av. 2.080(1) Å) [5] and other simple [Ti(III)-
to the new compound [TiMe(g5 1-C5Me4CH2-o-C6H4)(g5
:g -
g
5-C5Me5)2] derivatives (X = more electronegative element than
5-C5Me5)2] (av.
C5Me4CH2Ph)] (12) containing one phenyl group attached to tita-
nium in ortho-position and one methyl group preserved on the
titanium atom (Scheme 9).
g
g
The presence of TiMe group (dH/dC: 0.10 ppm/54.63 ppm) was
unambiguously confirmed by gHSQC, and a highly downfield
shifted signal at 196.33 ppm was assigned to Cipso of the TiCH2-o-
C6H4 fragment, close to the analogous resonance for compound 8.
Interaction of the Ti–Cipso(phenyl) with the tether methylene group
(dH/dC: 3.53, 3.64 ppm/33.37 ppm) was corroborated by gHMBC.
The methylene group bearing an unattended phenyl ring appeared
as a singlet (dH/dC: 3.46 ppm/ 34.22 ppm) contrary to the pair of
doublets in 8, presumably due to a lower anisotropic effect of the
Ti–Me moiety with respect to the Ti–Cl effect in 8. Nevertheless,
1H and 13C NMR spectra of 12 are very similar to those of 8 except
for the Ti–Me resonances. The composition of 12 was further cor-
roborated by its EI-MS spectra showing an easy elimination of
methyl group to give the very stable ion [7]+ which further fragm-
enated similarly as in the EI-MS spectra of 7. Surprisingly, com-
pound 12 is thermally very robust being recovered unchanged
after heating in m-xylene to 150 °C for 3 h.
g
(2.231(5) Å [2b]. The Cg(1)ꢀTiꢀCg(2) angle of 146.63(3)° is
one of the largest angles known for permethyltitanocene(Ti(III))
Fig. 2. PLATON drawing of 6 with 30% probability ellipsoids and atom numbering
scheme.
Table 1
Selected bond lengths (Å) and angles (°) for 5 and 6.
Compound
5
6
Bond lengths
Ti–Cg(1)a
Ti–Cg(2)a
Ti–Pl(1)b
Ti–Pl(2)b
Ti–C(X)c
2.0961(6)
2.0962(6)
2.0959(2)
2.0962(6)
2.1731(15)
2.0225(12)
2.0354(13)
2.0158((5)
2.0352(4)
2.210(4)
Angles
Cg(1)–Ti–Cg(2)a
Cg(1)–Ti–C(X)c
Cg(2)–Ti–C(X)c
ud
146.63(3)
106.60(5)
106.77(5)
34.35(5)
152.17(5)
93.94(10)
112.49(10)
23.46(9)
a
Cg(1) denotes the centroid of the C(1–5) cyclopentadienyl ring, and Cg(2) is the
centroid of the C(14–18) cyclopentadienyl ring.
b
Pl(1) denotes the least-squares plane of the C(1–5) cyclopentadienyl ring, and
Pl(2) is the least-squares plane of the C(14–18) cyclopentadienyl ring.
c
C(X) is C(27) for 5, and C(11) for 6.
Dihedral angle between Pl(1) and Pl(2).
Fig. 1. PLATON drawing of 5 with 30% probability ellipsoids and atom numbering
scheme.
d

J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
1975
g
5-C5Me4(SiMe3)}2]
Table 2
compounds, comparable to that of [Ti(III)Me{
(145.94(2)°) [5] and smaller only compared to 152.3° and 152.0°
for the two molecules of [Ti(III)H(
5-C5Me5)2] [15]. Accordingly,
Selected bond lengths (Å) and angles (°) for two independent molecules of 7.
g
Molecule 1
Molecule 2
the pairs of cyclopentadienyl methyl groups residing at hinge posi-
tion of the bent titanocene C(8)/C(9) and C(19)/C(20) and the
methyl groups C(6) and C(22) being close to the methyl C(27) were
deviated from the least-squares planes of the cyclopentadienyl
rings by only 0.221–0.294(2) Å away from titanium. Such values
indicate a very low steric hindrance for bent permethyltitanocene
compounds.
Bond lengths
Ti–Cg(1)a
Ti–Cg(2)a
Ti–Pl(1)b
Ti–Pl(2)b
Ti–C(X)c
2.0577(16)
2.0828(15)
2.0514(15)
2.0818(14)
2.263(3)
2.0494(16)
2.0704(16)
2.0429(14)
2.0701(15)
2.257(3)
Angles
Cg(1)–Ti–Cg(2)a
Cg(1)–Ti–C(X)c
Cg(2)–Ti–C(X)c
ud
141.40(6)
104.09(10)
114.49(10)
35.96(14)
87.87(10)
141.50(7)
104.48(10)
113.78(10)
35.08(12)
88.94(10)
Conversion of one t-Bu group into a tether with the methylene
carbon atom C(11)
r-bonded to titanium in 6 causes shortening of
Ti–Cg distances and a slight elongation of the TiꢀC(11) bond com-
pared to the TiꢀC(27) bond in 5. The tethered cyclopentadienyl
ring is slightly tilted with respect to normal to the TiꢀCg(1) vector,
and this causes yet larger opening of the Cg(1)ꢀTiꢀCg(2) angle (see
Table 1). A relief of steric hindrance between the hinge methyl
groups results in a decrease of their deviations from the least-
squares planes to a maximum of 0.182(5) Å for C(7). On the other
hand, the strain in the tether is revealed by deviation of the quater-
nary carbon atom C(10) from the least-squares plane of the cyclo-
pentadienyl ring toward titanium by as much as 0.467(5) Å, and by
valence angles C(5)ꢀC(10)ꢀC(11) 96.1(3)° and C(10)ꢀC(11)ꢀTi
100.2(2)°, markedly low for sp3 carbon atoms. In this respect, the
unusually long C(10)ꢀC(11) bond length of 1.596(5) Å is appar-
ently also caused by the tether strain. The isopropylidene methyl
carbon atoms C(12) and C(13) sterically hinder with their neigh-
bours on the ring C(6) and C(9) inducing large valence angles
C(5)ꢀC(1)ꢀC(6) and C(5)ꢀC(4)ꢀC(9) equally 129.2(3)°. A similar
effect of the t-butyl group minimizing its steric hindrance by putt-
ing one carbon atom close to the least-squares plane of the cyclo-
pentadienyl ring is observed for the untethered cyclopentadienyl
ligand (C(18)ꢀC(17)ꢀC(22) 130.1(3)°) of 5 and for all the so far
known titanocene compounds with this ligand [7].
we
a
Cg(1) denotes the centroid of the C(11–15) cyclopentadienyl ring for molecule
1, and C(21–25) for molecule 2; Cg(2) is the centroid of the C(117–121) cyclopen-
tadienyl ring for molecule 1 and C(217–221) for molecule 2.
b
Pl(1) denotes the least-squares plane of the C(11–15) cyclopentadienyl ring for
molecule 1, and C(21–25) for molecule 2; Pl(2) is the least-squares plane of the
C(117–121) cyclopentadienyl ring for molecule 1 and C(217–221) for molecule 2.
c
C(X) is C(112) for molecule 1, and C(212) for molecule 2.
Dihedral angle between Pl(1) and Pl(2).
Dihedral angle between the least-squares plane of the phenyl ring C(111–116)
d
e
and Pl(1) for molecule 1, and the least-squares plane of the phenyl ring C(211–216)
and Pl(1) for molecule 2.
to molecule 1 only. The tether phenyl ring, situated nearly perpen-
dicular to the cyclopentadienyl ring planes, brings about a larger
steric congestion to the bent titanocene moiety than the methyl
group in 5. It results in a smaller Cg(1)ꢀTiꢀCg(2) angle and a larger
deviation of methyl groups in hinge position from the least-
squares planes of the cyclopentadienyl rings (max. 0.363(5) Å for
C(125)) Å. Compared with the two-carbon atoms tether of 6 the
three-carbon atom tether of 7 causes a less discernible steric strain.
The benzyl carbon atom C(110) lies almost exactly in the least-
squares plane of the tethered cyclopentadienyl ring, and the angle
C(15)ꢀC(110)ꢀC(111) of 110.8(3)° is close to the theoretical value
for sp3 carbon atom. The valence angles at the ipso-carbon atom
C(110)ꢀC(111)ꢀC(116) and C(110)ꢀC(111)ꢀC(112) as well as the
C(111)ꢀC(112)ꢀTi(1) angle are virtually equal (118.5–118.7(3)°)
and the Ti(1)ꢀC(112) bond length of 2.263(3) Å falls into the range
of TiꢀC@ distances in permethyltitanocenes with one cyclopenta-
dienyl ring tethered to titanium with a 3-membered C@CꢀC chain
[16]. The presence of some strain in the phenyl ring is indicated by
a large Ti(1)ꢀC(112)ꢀC(113) angle of 127.3(2)° and a small
C(111)ꢀC(112)ꢀC(113) angle of 113.8(3)°.
2.2. Molecular structures of 7 and 10
The PLATON drawing of molecule 1 of the two independent
molecules in the unit cell of 7 is shown in Fig. 3.
The main geometric parameters for molecules 1 and 2 (Table 2)
show that differences between them arise from crystal packing de-
mands, and can be neglected in the structure discussion, referring
The PLATON drawing for 10 is shown in Fig. 4 and important
molecular parameters are given in Table 3.
The pseudotetrahedral coordination at the titanium atom fur-
ther decreased the Cg(1)ꢀTiꢀCg(2) angle (138.50(4)°) and the ste-
ric strain at the hinge position of the cyclopentadienyl ligands led
to a yet larger deviation of methyl carbon atoms from the least-
squares planes of the cyclopentadienyl rings (max. 0.412(4) Å for
C(8)). The dimethyltitanium plane C(33)ꢀTiꢀC(34) is close to bi-
sect the Cg(1)ꢀTiꢀCg(2) angle, and is almost perpendicular to it.
Whereas the CgꢀTi distances are slightly elongated with respect
to those in 5 the Tiꢀmethyl carbon bond lengths are comparable.
The C(33)ꢀTiꢀC(34) angle of 88.20(10)° is very close to the
ClꢀTiꢀCl in e.g., [TiCl2(
g
5-C5Me4t-Bu)2] (88.9(1)°), where also the
Cg(1)ꢀTiꢀCg(2) angle 138.04(3)° is approaching the value found
for 10 [7].
2.3. Conclusions
Whereas the decamethyltitanocene mono- and dimethyl com-
pounds upon thermolysis eliminate methane under formation of
tucked-in titanocene derivatives (Scheme 1) the hydrogen- or tri-
Fig. 3. PLATON drawing of molecule 1 of 7 with 30% probability ellipsoids and atom
numbering scheme.

1976
J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
Scheme 10.
monotethered [TiCH2CMe3{g5
:g
1-C5H4CMe2CH2)(
g
5-C5H4t-Bu)]
and even the ditethered product [Ti(g5 1-C5H4CMe2CH2)2]
:g
(Scheme 10) [12].
On the other hand, in a recent study on bis(di-t-butylcyclopen-
tadienyl)titanium derivatives the titanocene monomethyl com-
pound [TiMe(g
5-C5H3t-Bu2)2] has been found thermally stable
upon sublimation at 60–70 °C in vacuum [17]. No activation of t-
butyl group was also noticed during synthesis of the most steri-
cally crowded attainable t-butyl titanocene derivatives of [Ti(g5
-
C5H3t-Bu2) (g
5-C5H2t-Bu3)] [18].
Fig. 4. PLATON drawing of 10 with 30% probability ellipsoids and atom numbering
scheme.
In this study, the thermolysis of 5 and 9 revealed the over-
whelming propensity of the t-butyl group to react with thermally
excited Ti-methyl bond, yielding 6 and 11, respectively. In 11,
one of the two leaving methyl groups abstracted hydrogen from
the cyclopentadienyl methyl in vicinal position to the tether, leav-
ing the other t-butyl group intact. Since the methane elimination
from both 5 and 9 occurred at the same temperature of 110 °C
(Schemes 6 and 8) it is probable that the t-butyl group in 9 was
the first reacting with the thermally excited Ti–Me bond. The pri-
mary abstraction of hydrogen from the cyclopentadienyl methyl
group is improbable because the formation of 1a from
methylsilyl-containing analogs showed various thermolytic reac-
tions with activation of both, the cyclopentadienyl methyl groups
and the above mentioned H or SiMe3 moieties (Schemes 2 and
3). In distinction, the phenyl substituent was not activated because
of its remoteness from the leaving methyl groups (Scheme 4). Con-
cerning the reactivity of t-Bu group, it has been previously estab-
lished that leaving phenyl ligand in [TiPh2(
abstracts hydrogen from t-Bu group on otherwise non-substituted
cyclopentadienyl ligand to give [TiPh(
5-C5H4t-Bu)(g5 1-C5H4-
g
5-C5H4t-Bu)2]
[TiMe2(
[1d]. The structures of 6 and 11 are analogous to products 3b
and 3a which arise from thermolysis of [TiMe(
5-C5Me4SiMe3)2]
and [TiMe2(
5-C5Me4SiMe3)2], respectively, at even lower temper-
ature (Scheme 3) [5]. The similar behavior of the t-butyl and tri-
methylsilyl complexes could be expected in view of
surprisingly high thermal stability of monomeric titanocenes
[Ti(II)(
5-C5Me4t-Bu)2] [19a] and [Ti(II)( 5-C5Me4SiMe3)2] [19b],
g
5-C5Me5)2] requires a higher temperature (Scheme 1)
g
:g
CMe2CH2)] [10], and analogous titanocene dineopentyl complex
at the onset of its formation eliminates neopentane yielding the
g
g
a
Table 3
Selected bond lengths (Å) and angles (°) for 10.
g
g
in which a large bulkiness of the CMe3 and SiMe3 groups was
Bond lengths
Ti–Cg(1)a
2.1296(10)
2.1295(4)
2.164(2)
Ti–Cg(2)a
Ti–Pl(2)b
Ti–C(34)
2.1402(10)
2.1402(4)
2.185(2)
apparently the decisive factor. In this respect, a larger size of SiMe3
0
0
Ti–Pl(1)b
Ti–C(33)
compared to t-Bu (Si–C ꢁ 1.86 ÅA versus C–C ꢁ 1.53 AÅ) can rational-
ize the observed lower temperature of the formation of 3b and 3a
(90 °C) against 110 °C for 6 and 11.
Angles
Cg(1)–Ti–Cg(2)a
Cg(1)–Ti–C(33)
Cg(2)–Ti–C(33)
uc
138.50(4)
105.65(8)
104.46(7)
41.80(7)
20.42(8)
C(33)–Ti–C(34)
Cg(1)–Ti–C(34)
Cg(2)–Ti–C(34)
88.20(10)
104.34(7)
104.50(8)
21.38(10)
Of the benzyl-containing complexes, an unprecedented easy
elimination of methane from the transiently formed [TiMe(g5
-
x
(1)d
C5Me4CH2Ph)2] at ambient temperature to give cleanly 7 (Scheme
7) indicates that rotating benzyl substituent on a rotating cyclo-
pentadienyl ligand can approach the methyl group residing on tita-
nium with its phenyl proton in ortho-position causing that the
elimination of methane (or the ortho-phenyl metallation) proceeds
with a low thermal activation. On the other hand, the same
reaction of dimethyltitanocene 10 requires the thermal activation
of 110 °C. This can be accounted for by steric congestion at a
x
(2)e
a
Cg(1) denotes the centroid of the C(1–5) cyclopentadienyl ring, and Cg(2) is the
centroid of the C(17–21) cyclopentadienyl ring.
b
Pl(1) denotes the least-squares plane of the C(1–5) cyclopentadienyl ring, and
Pl(2) is the least-squares plane of the C(17–21) cyclopentadienyl ring.
c
Dihedral angle between Pl(1) and Pl(2).
Dihedral angle between the plane C(33)–Ti–C(34) and Pl(1).
Dihedral angle between the plane C(33)–Ti–C(34) and Pl(2).
d
e

J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
1977
tetrahedrally coordinated titanium resulting in a larger angle of the
cyclopentadienyl ring planes (u) compared to a trigonal monom-
ethyltitanocene (cf. 10: u = 41.87(7)° and e.g., 5: u = 34.35(5)°)
which implies a larger distance of the rotating benzyl group from
either of the two Ti–Me bond. In distinction to 3a and 11 com-
pound 12 does not explore the remaining Ti–Me group for the for-
mation of a tucked-in moiety from the cyclopentadienyl methyl;
surprisingly, the Ti–Me bond in 12 was found to persist 150 °C.
This can be accounted for the rigid and comfortably long three-
carbon tether, as established in 7, which precludes the thermally
excited Ti–Me bond to interact with the vicinal-to-tether cyclo-
pentadienyl methyl substituent.
turnings were purchased from Aldrich. Titanocene dichlorides
[TiCl2(
5-C5Me4t-Bu)2] [7] and [TiCl2{ 5-C5Me4(CH2Ph)}2] [9]
were prepared as reported.
g
g
3.3. Synthesis of [Ti(III)Me(
g
5-C5Me4t-Bu)2] (5)
Titanocene dichloride [TiCl2(
g
5-C5Me4t-Bu)2] (0.944 g, 2.00
mmol) and magnesium (0.0243 g, 1.00 mmol) were weighed into
an ampule and thf (30 ml) was distilled in on a vacuum line with
cooling to liquid nitrogen temperature. The ampule was sealed
off and the content stirred at 60 °C until all magnesium was con-
sumed. Tetrahydrofuran was distilled off in vacuum, and the resi-
due extracted with hexane (50 ml). Crystallization from saturated
hexane solution upon cooling to ꢀ28 °C followed by drying of sep-
arated crystalline solid in vacuum afforded 0.84 g (1.92 mmol) of
The high thermal stability of 12 is also of interest from a view
that thermolysis of [Ti(
at 150 °C afforded a mixture of doubly tucked-in titanocenes
[Ti(
5-C5Me4CH2Ph)(g4 3-C5Me3(CH2)CHPh)] (major) and [Ti
5- C5Me4CH2Ph){g4 3-C5Me2(CH2)2CH2Ph}] (minor) in virtually
g g
2-Me3SiC„CSiMe3){ 5-C5Me4(CH2Ph)}2]
g
:g
blue crystals of [TiCl(g
5-C5Me4t-Bu)2]. These were dissolved in
(g
:g
50 ml of hexane, and the solution poured onto solid LiMe which
was prepared by evaporation of 5 ml of 1.6 M solution in vacuum,
finally at 80 °C. The mixture was shaken until the blue solution
turned brownish green (ca. 30 min). Then, the solution was sepa-
rated from a yellow slurry which was extracted with hexane. The
combined volume of the solution and extracts was reduced to ca.
20 ml, and this was cooled to ꢀ28 °C overnight. A clear green solu-
tion was decanted from white sediment on ampule walls, and con-
centrated to a saturated solution for crystallization at ꢀ28 °C. A
green crystalline material was separated from the mother liquor
and dried in vacuum.
quantitative yield [13a]. Such a high selectivity for the formation of
doubly tucked-in titanocenes was also found for thermolysis of the
[Ti(g g
2-Me3SiC„CSiMe3)( 5-C5Me4R)2] complexes for R = Me [4b]
or SiMe3 [5]. In all cases two hydrogen atoms were transferred
from two vicinal sp3 carbon atoms to the leaving acetylene ligand.
A high selectivity of these thermolyses features this process as a
concerted one whereas thermolyses of titanocene dimethyls are
distinctly stepwise reactions although the particular intermediates
could not be detected in the formation of 3a and 11.
5: Yield 0.52 g (84%); m.p. decomposes at 115 °C with gas evo-
lution. EI-MS (90 °C): m/z (relative abundance) 417 (M+Å; 4), 404
(16), 403 (43), 402 ([MꢀMe]+; 100), 401 (26), 400 (16), 399 (7),
361 (6), 360 ([MꢀMeꢀBu]+; 16), 339 (8), 327 (9), 303 ([MꢀMeꢀ2
Bu]+; 6), 206 (11), 202 (7), 201 (8), 57 ([Bu]+; 17). IR (KBr, cmꢀ1):
2988 (s,sh), 2953 (vs), 2905 (vs), 2866 (s,sh), 1480 (m), 1470 (m),
1462 (m), 1451 (m), 1380 (s), 1359 (s), 1234 (m), 1198 (w), 1123
(vw), 1033 (m), 1021 (m), 927 (vw), 836 (vw), 784 (vw), 744
(vw), 672 (vw), 620 (w), 572 (m), 481 (w), 423 (s). EPR (toluene,
3. Experimental
3.1. Methods
Syntheses of 5-t-butyl-1,2,3,4-tetramethylcyclopenta-1,3-diene
[7] and 5-benzyl-1,2,3,4-tetramethylcyclopenta-1,3-diene [9] and
titanocene dichlorides thereof were carried out under argon. All
titanium(III) compounds were extremely air- and moisture-sensi-
tive, therefore they were handled under vacuum using an all-glass
high vacuum line operated with metal valves and all-sealed glass
devices equipped with breakable seals. Thermolytic reactions with
toluene or m-xylene solutions were carried out in glass ampules
equipped with breakable seals in a thermostatted oven. 1H and
13C NMR spectra were recorded on a Varian Mercury 300 spec-
trometer at 300.0 and 75.4 MHz, respectively, in C6D6 solutions
at 25 °C. Chemical shifts (d/ppm) are given relative to solvent sig-
nals (dH 7.15, dC 128.0). EI-MS spectra were obtained on a VG-
7070E mass spectrometer at 70 eV. Crystalline samples in sealed
capillaries were opened and inserted into the direct inlet under ar-
gon. EPR spectra were recorded on an ERS-220 spectrometer (Cen-
ter for Production of Scientific Instruments, Academy of Sciences of
GDR, Berlin, Germany) operated by a CU-1 unit (Magnettech, Ber-
lin, Germany) in the X-band. g-Values were determined by using
an Mn2+ standard at g = 1.9860 (MI = ꢀ1/2 line). A variable temper-
ature unit STT-3 was used for measurements in the range ꢀ140 to
+25 °C. UV–Vis spectra in the range of 300–800 nm were measured
on a Varian Cary 17D spectrometer in all-sealed quartz cells (Hell-
ma). IR spectra were taken in an air-protecting cuvette on a Nicolet
Avatar FTIR spectrometer in the range 400–4000 cmꢀ1. KBr pellets
were prepared in a glovebox Labmaster 130 (mBraun) under puri-
fied nitrogen.
22 °C): g = 1.955(3),
D
H = 14.0 G; (toluene, ꢀ140 °C): g1 = 1.999,
g2 = 1.981, g3 = 1.889, gav = 1.956. UV–Vis (toluene, nm):
475 > 620. Anal. Calc. for C27H45Ti: C, 77.67; H, 10.86. Found: C,
77.74; H, 10.91%.
3.4. Thermolysis of 5 to [Ti(III)(
(6)
g :g
5-C5Me4t-Bu)(g5 1-C5Me4CMe2CH2)]
A solution of 5 (0.42 g, 1.01 mmol) in 10 ml of toluene was
heated to 110 °C for 3 h. After opening the ampule to a vacuum line
a sample of gas evolved was collected by condensing into liquid
nitrogen-cooled ampule and the toluene was replaced with hex-
ane. Cooling of the saturated solution yielded greenish brown plate
crystals.
6: Yield 0.34 g (85%); m.p. 113 °C. EI-MS (110 °C): m/z (relative
abundance) 403 (15), 402 (37), 401 (M+Å; 100), 400 (43), 399
([Mꢀ2H]+; 78), 398 (40), 397 ([Mꢀ4H]+; 74), 396 (34), 395 (39),
394 (18), 393 (43), 392 (13), 391 (18), 390 (18), 389 (16), 381
(19), 345 (12), 344 ([MꢀBu]+; 33), 342 (11), 341 (10), 340 (10),
339 (14), 328 (11), 327 ([MꢀBuHꢀMeH]+; 25), 326 (10), 325
(16), 206 (19), 205 (13), 204 (12), 203 (11), 202 (24), 201 (30),
200 (18), 191 (14), 187 (14), 167 (14), 57 ([Bu]+; 30). IR (KBr,
cmꢀ1): 2955 (vs), 2909 (vs), 2869 (s,sh), 1480 (m), 1462 (m),
1452 (m), 1381 (s), 1359 (s), 1235 (m), 1198 (w), 1124 (vw),
1034 (m), 1023 (m), 930 (vw), 866 (vw), 784 (vw), 744 (vw), 711
(w), 672 (vw), 664 (vw), 620 (w), 572 (m), 488 (w), 423 (s). EPR
3.2. Chemicals
The solvents tetrahydrofuran (thf), hexane, and toluene were
dried by refluxing over LiAlH4 and stored as solutions of dimeric
titanocene [(
yllithium (LiMe) (1.6 M in diethyl ether), PbCl2, and magnesium
(toluene, 22 °C): g = 1.960,
D
H = 24.4 G; (toluene, ꢀ140 °C):
g1 = 2.000, g2 = 1.983, g3 = 1.898, gav = 1.960. UV–Vis (toluene,
nm): 315 (sh) > 370 (sh) ꢂ 570 (broad). Anal. Calc. for C26H41Ti:
C, 77.78; H, 10.29. Found: C, 77.76; H, 10.28%.
l- :g l-H)(g
g5 5-C5H4C5H4){Ti( 5-C5H5)}2] [20]. Meth-

1978
J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
3.5. Synthesis of [Ti(III)(
(7)
g
5-C5Me4CH2Ph)(g5
:
g
1-C5Me4CH2-o-C6H4)]
126.07 (CH, Ph); 126.47 (Cq, C5Me4); 128.41 (CH, Ph); 128.60 (Cq,
C5Me4); 128.63 (CH, Ph); 134.95, 135.08 (Cq, C5Me4); 137.02 (CH,
C6H4); 141.13 (Cipso, Ph); 155.05 (CH2C, C6H4); 199.00 (TiC, C6H4).
IR (KBr, cmꢀ1): 3100 (vw), 3084 (vw), 3065 (vw), 3040 (s), 3028
(m), 2977 (m), 2952 (m), 2904 (vs), 2883 (s), 2720 (vw), 1602
(m), 1580 (w), 1495 (s), 1483 (w), 1454 (m), 1442 (m), 1429 (m),
1254 (w), 1237 (w), 1099 (vw), 1079 (vw), 1036 (w), 1019 (m),
795 (vw), 742 (s), 728 (m), 697 (w), 461 (w), 438 (m). Anal. Calc.
for C32H37ClTi: C, 76.11; H, 7.39. Found: C, 76.14; H, 7.41%.
The monochloride [Ti(III)Cl(
from [TiCl2(
5-C5Me4CH2Ph)2] (1.080 g, 2.00 mmol) and magne-
g
5-C5Me4CH2Ph)2] was obtained
g
sium 0.0243 g, 1.00 mmol) in 20 ml of thf. The mixture was stirred
and heated to 60 °C until the red solution turned blue. The thf was
evaporated in vacuum, and the residue was extracted with hexane
(50 ml). The monochloride did not crystallize forming a blue waxy
solid characterized as follows: EI-MS (140 °C): m/z (relative abun-
dance) 508 (12), 507 (32), 506 (31), 505 (M+Å; 68), 297 (10), 296
(40), 295 (33), 294 ([MꢀC5Me4CH2Ph]+; 100), 293 (24), 292 (13),
212 (13), 211 ([C5Me4CH2Ph]+; 13), 135 ([C5Me5]+; 11), 121
([C5HMe4]+; 12), 119 ([C5Me3CH2]+; 13), 92 ([CH3Ph]+; 52), 91
3.7. Synthesis of [TiMe2(
g
5-C5Me4t-Bu)2] (9)
A slurry of [TiCl2(
g
5-C5Me4t-Bu)2] (0.944 g, 2.00 mmol) in 50 ml
of hexane was poured onto solid LiMe which was prepared by evap-
oration of 10 ml of 1.6 M solution in vacuum, finally at 80 °C. The
mixture was shaken until all solid titanocene dichloride dissolved
and the red solution turned orange-yellow (ca. 3 h). Then the solu-
tion was separated from a yellowish slurry, and this was extracted
with hexane. The combined extract was poured over the same
amount of fresh solid LiMe and treated as above in order to convert
the titanocene chloromethyl byproduct (see below for NMR data) to
9. The solution was separated from a white sediment, and concen-
trated to a saturated solution for crystallization at ꢀ28 °C. A lemon
yellow crystalline material was separated from the mother liquor
and dried in vacuum (Warning: During the methylation, crystalliza-
tion, and storing of the solid and the solution avoid their exposure
to sun light as well as strong artificial light).
([CH2Ph]+; 91), 65 (15). EPR (toluene, 22 °C): g = 1.956(7),
DH =
25.0 G; (toluene, ꢀ140 °C): g1 = 1.999(8), g2 = 1.983(8), g3 =
1.889(3), gav = 1.957. UVꢀVis (toluene, nm): 358 (sh) ꢂ 558 > 660
(sh). The monochloride solution was poured onto solid LiMe which
was prepared by evaporation of 5 ml of 1.6 M solution in vacuum,
finally at 80 °C. The mixture was shaken at 60 °C until the blue
solution turned brown (ca. 4 h). Then the solution was separated
from a yellow slurry, and this was repeatedly extracted with hex-
ane. The extract was reduced to ca. 20 ml, and this was cooled to
ꢀ28 °C overnight. A clear brown solution was decanted from a
white sediment on ampule walls, and concentrated to a saturated
solution for crystallization at ꢀ28 °C. Brown needle aggregates
were separated from the mother liquor and dried in vacuum.
7: Yield 0.82 g (87%); m.p. 122 °C. EI-MS (120 °C): m/z (relative
abundance) 471 (16), 470 (42), 469 (M+Å; 100), 468 (19), 467 (15),
453 ([MꢀCH4]+; 7), 363 ([MꢀMeꢀCH2Ph]+; 13), 278 (11), 260 (19),
259 ([MꢀC5Me4CH2C6H4]+; 73), 258 (15), 257 (18), 255 (12), 254
(12), 253 (39), 252 (13), 251 (14), 250 (11), 181 (23), 180 (10),
179 (13), 178 (13), 91 ([CH2Ph]+; 18). IR (KBr, cmꢀ1): 3104 (w),
3081 (w), 3058 (w), 3026m), 2970 (s), 2908 (vs), 2861 (s), 2724
(vw), 1601 (m), 1582 (w), 1493 (vs), 1450 (s), 1427 (s), 1379 (m),
1322 (vw), 1285 (vw), 1233 (w), 1181 (vw), 1155 (vw), 1098 (w),
1074 (w), 1029 (m), 1002 (w), 932 (vw), 825 (vw), 812 (w), 794
(w), 734 (s), 724 (s), 698 (s), 573 (w), 562 (w), 443 (s). EPR (toluene,
9: Yield 0.72 g (83%). 1H NMR (C6D6): ꢀ0.24 (s, 6H, TiMe2); 1.28
(s, 18H, CMe3); 1.63, 2.20 (2 ꢃ s, 2 ꢃ 12H, C5Me4). 13C {1H}(C6D6):
12.20, 16.05 (C5Me4); 32.16 (CMe3); 35.91 (CMe3); 49.98 (TiMe2);
119.88, 120.89 (C5Me4); 136.79 (Cipso). EI-MS (90 °C): m/z (relative
abundance) 432 (M+Å; not found), 417 ([MꢀMe]+; 9), 416
([MꢀCH4]+; 7), 404 (14), 403 (37), 402 ([Mꢀ2 Me]+; 100), 401
(45), 400 (27), 399 (20), 361 (11), 360 ([MꢀMeꢀBu]+; 27), 359
(12), 357 (13), 327 (13), 303 ([MꢀMeꢀ2 Bu]+; 10), 206 (17), 202
(11), 201 (13). IR (KBr, cmꢀ1): 2983 (s), 2959 (vs), 2907 (vs),
1481 (w), 1464 (m), 1450 (w), 1381 (s), 1359 (m), 1233 (w),
1196 (vw), 1123 (vw), 1022 (w), 786 (vw), 667 (vw), 571 (vw),
422 (m). Anal. Calc. for C28H48Ti: C, 77.75; H, 11.19. Found: C,
77.76; H, 11.17%.
22 °C): g = 1.946,
DH = 27.4 G. UV–Vis (toluene, nm): 475
(sh) > 620 (sh). Anal. Calc. for C32H37Ti: C, 81.86; H, 7.94. Found:
C, 81.90; H, 7.98%.
NMR data for [TiClMe(g
5-C5Me4CMe3)2]: 1H NMR (C6D6): 0.55
Compound 7 appeared to be thermally very stable. Heating of
its toluene solution to 150 °C and, after replacement of toluene
with m-xylene, to 170 °C for 4 h did not result in evolution of a
gas, and EI-MS, IR and EPR spectra of such treated 7 remained
the same.
(s, 3H, TiMe); 1.45 (s, 18H, CMe3); 1.56, 1.59, 2.16, 2.23 (4 ꢃ s,
4 ꢃ 6H, C5Me4). 13C {1H}(C6D6): 12.19, 12.39, 16.30, 16.51
(C5Me4); 31.90 (CMe3); 37.41 (CMe3); 54.60 (TiMe); 121.49,
121.66, 123.27, 125.16 (C5Me4); 139.38 (Cipso).
: :g -
3.8. Thermolysis of 9 to [Ti{g5 g1 1-C5Me3(CH2)(CMe2CH2)}(g5
3.6. Chlorination of 7 with PbCl2 to give [Ti(IV)Cl(g5
C5Me4CH2Ph)(g5 1-C5Me4CH2-o-C6H4)] (8)
-
C5Me4t-Bu)] (11)
:g
Heating of 4 (0.17 g, 0.4 mmol) in toluene (10 ml) to 110 °C for
5 h followed by workup with hexane afforded a dark green solution
which in no way afforded crystalline products but viscous oil only.
This circumstance precluded the product purification or identifica-
tion by X-ray diffraction. The structure of the main product 11 was
identified by 1H and 13C NMR spectroscopy using additional gCOSY,
gHMBC experiments.
A solution of 7 (0.30 g, 0.64 mmol) in thf (7.0 ml) was poured on
a degassed powdery PbCl2 (0.10 g, 0.36 mmol), and the mixture
was vigorously stirred for 20 min. A dark orange solution was sep-
arated from black lead sediment, and thf was replaced with hexane
(20 ml). The volume of the solution was reduced to ca. 3 ml of a
brown solution which were separated from a precipitated orange
powder, and discarded. The orange product was crystallized from
hexane to give a microcrystalline orange solid.
2
1H NMR (C6D6, 300 Hz): ꢀ3.29, ꢀ1.06 (2 ꢃ d, 2 ꢃ JHH = 9.9 Hz,
2 ꢃ 1H, TiCH2CMe2); 0.89 (m, 1H, TiCH2); 1.07 (s, 3H, C5Me3);
1.16 (s, 9H, CMe3); 1.21 (m, 1H, TiCH2); 1.26 (s, 3H, C5Me4); 1.30,
1.42 (2 ꢃ s, 2 ꢃ 3H, CMe2); 1.54 (s, 3H, C5Me3); 1.70, 1.83 (2 ꢃ s,
2 ꢃ 3H, C5Me4); 1.91 (s, 3H, C5Me3); 2.15 (s, 3H, C5Me4). 13C
{1H}(C6D6): 11.44, 11.91, 12.31, 12.70, 14.43, 15.09, 15.04 (C5Me3
and C5Me4); 29.28, 32.05 (CMe2); 32.65 (CMe3); 35.59 (CMe3);
36.38 (CMe2); 55.14 (TiCH2CMe2); 77.00 (TiCH2); 117.49, 118.36,
118.67, 120.62, 120.69, 123.80 (Cq, C5Me4 and C5Me3); 125.95
(CCMe2, C5Me3); 129.99 (Cq); 130.65 (CCMe3, C5Me4); 132.52 (Cq).
8: Yield 0.29 g, (91%); m.p. 171 °C. 1H NMR (C6D6): 1.62, 1.63,
1.64, 1.76, 1.80, 1.84, 1.94, 2.01 (8 ꢃ s, 8 ꢃ 3H, C5Me4); 3.35, 3.40
2
(2 ꢃ d, 2 ꢃ JHH = 16.5 Hz, 2 ꢃ 1H,, CH2Ph); 3.71, 3.85 (2 ꢃ d,
2
2 ꢃ JHH = 16.2 Hz, 2 ꢃ 1H, CH2C6H4); 6.88–7.12 (m, 8H, Ph and
C6H4); 7.21–7.26 (m, 1H, C6H4). 13C {1H}(C6D6): 10.76, 12.12,
12.46, 12.66, 12.96, 13.32, 14.04, 14.37 (C5Me4); 33.73, 33.85
(CH2C6H4 and CH2Ph); 114.34, 123.53, 123.72, (Cq, C5Me4);
123.80, 124.26, 124.83 (CH, C6H4); 125.26, 125.68 (Cq, C5Me4);

J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
1979
3.9. Synthesis of [TiMe2(
g
5-C5Me4CH2Ph)2] (10)
5-C5Me4CH2Ph)2] (1.080 g, 2.0 mmol) in
NMR data for [TiClMe(
g
5-C5Me4CH2Ph)2]: 1H NMR (C6D6): 0.44
(s, 3H, TiMe); 1.83, 1.85, 1.94, 1.95 (4 ꢃ s, 4 ꢃ 6H, C5Me4); 3.91
(CH2); 7.11–7.28 (m, 10H, Ph). 13C {1H}(C6D6): 12.28, 12.33,
12.82, 12.86 (C5Me4); 33.55 (CH2); 54.97 (TiMe); 123.08, 123.13,
123.43, 124.02 (C5Me4); 126.02 (CH, Ph); 126.14 (Cipso, C5Me4);
128.35, 128.58 (CH, Ph); 141.10 (Cipso, Ph).
A suspension of [TiCl2(
g
hexane (50 ml) was poured onto solid LiMe made by evaporation
of 5 ml of 1.6 M solution in vacuum, finally at 80 °C. The mixture
was shaken at 60 °C until all red titanocene dichloride was con-
sumed (ca. 4 h). The solution was separated from a yellowish slur-
ry, and this was repeatedly extracted with hexane. The extract was
reduced to ca. 20 ml, and this was cooled to ꢀ28 °C overnight. A
clear orange solution was decanted from a white sediment on am-
pule walls, and concentrated to a saturated solution for crystalliza-
tion at ꢀ28 °C. A sample of orange crystals was separated,
dissolved in C6D6 and investigated by 1H and 13C NMR spectros-
copy. The spectra revealed the presence of chloromethyl derivative
(30%) (NMR data see below) in addition to 10. The hexane solution
of this product was treated again with the same portion of solid
LiMe for 2 h, and the solution removed and purified as above. Or-
ange crystalline solid was obtained from saturated hexane solution
after cooling to ꢀ5 °C.
3.10. Thermolysis of 10 to [TiMe(g5
:g
1-C5Me4CH2-o-C6H4)
(g
5-C5Me4CH2Ph)] (12)
A solution of 10 (0.50 g, 1.0 mmol) in toluene (20 ml) was
heated to 110 °C for 12 h without observable change in its dark yel-
low color. The ampule was opened at ambient temperature on a
vacuum line showing that a volatile gas was evolved. All volatiles
were evaporated under vacuum, and the residue was dissolved in
hexane (8 ml). A clear yellow solution was concentrated by slow
distillation of hexane to an attached ampule in refrigerator leaving
a brownish-yellow solid on ampule walls. The yellow microcrystal-
line solid was collected, and assigned to 12 on the basis of 1H, 13C
NMR methods (APT, 1DNOESY, gCOSY, gHSQC, gHMBC).
10: Yield 0.81 g (81%); m.p. at 85 °C with gas evolution. 1H NMR
(C6D6): ꢀ0.38 (s, 6H, TiMe2); 1.82 (s, 12H, b-Me, C5Me4); 1.87 (s,
12: Yield 0.46 g (95%). m.p. 124–126 °C. 1H NMR (C6D6): 0.10 (s,
3H, TiMe); 1.47, 1.59, 1.64, 1.69, 1.71, 1.78, 1.85, 1.97 (8 ꢃ s,
8 ꢃ 3H, C5Me4); 3.46 (s, 2H, CH2Ph); 3.53, 3.64 (2 ꢃ d,
12H,
a
-Me, C5Me4); 3.73 (CH2); 7.11–7.28 (m, 10H, Ph). 13C
{1H}(C6D6): 11.96, 12.31 (C5Me4); 33.01 (CH2); 49.93 (TiMe2);
119.95, 120.10 (C5Me4); 122.30 (Cipso, C5Me4); 125.96, 128.38,
128.58 (CH, Ph); 141.55 (Cipso, Ph). EI-MS (130 °C): m/z (relative
abundance) 500 (M+Å; not observed), 486 (7), 485 (19), 484
([MꢀCH4]+; 44), 483 (18), 482 (11), 471 (16), 470 (42), 469
([MꢀCH4ꢀMe]+; 100), 468 (19), 467 (15), 453 ([Mꢀ2 CH4ꢀMe]+;
7), 363 ([MꢀCH4ꢀ2 MeꢀCH2Ph]+; 13), 274 ([MꢀCH4ꢀC5Me4
CHPh]+; 13), 260 (13), 259 ([MꢀC5Me4CHPhꢀCH4ꢀMe]+; 45), 258
(19), 257 (15), 255 (10), 254 (12), 253 (36), 252 (14), 251 (13),
250 (10), 181 (21), 179 (11), 178 (12), 91 ([CH2Ph]+; 14). IR (KBr,
cmꢀ1): 3104 (vw), 3084 (w), 3060 (w), 3027 (m), 2974 (s), 2954
(vs), 2905 (s), 2892 (s), 2725 (vw), 1601 (m), 1583 (w), 1494 (vs),
1452 (s), 1440 (sh), 1379 (m), 1288 (vw), 1074 (w), 1030 (m),
801 (w), 752 (m), 733 (m), 704 (s), 675 (w), 607 (w), 579 (w),
555 (w), 460 (m). UV–Vis (hexane, nm): 430 (sh). Anal. Calc. for
C34H44Ti: C, 81.58; H, 8.86. Found: C, 81.60; H, 8.89%.
2
2 ꢃ JHH = 16.2 Hz, 2 ꢃ 1H, CH2C6H4); 6.98–6.73 (m, 1H, C6H4);
6.87–6.92 (m, 2H, C6H4); 6.98–7.02 (partially overlapped, m, 1H,
C6H4); 7.01–7.06 (m, 3H, Ph); 7.08–7.13 (m, 2H, Ph). 13C
{1H}(C6D6): 10.78, 11.77, 12.22, 12.33, 12.35, 12.52, 12.85, 14.02
(C5Me4); 33.37 (CH2C6H4); 34.22 (CH2Ph); 54.63 (TiMe); 113.13,
120.73, 120.99, 121.77, 121.92, 122.10 (Cq, C5Me4); 123.39,
123.92 (CH, C6H4); 124.06 (Cq, C5Me4); 124.55 (CH, C6H4); 126.01
(CH, Ph); 126.07, 126.90 (Cq, C5Me4); 128.46, 128.62 (CH, Ph);
133.48 (Cq, C5Me4); 135.16 (CH, C6H4); 141.54 (Cipso, Ph); 155.57
CH2C, C6H4); 196.33 (TiC, C6H4). EI-MS (130 °C): m/z (relative abun-
dance) 486 (6), 485 (17), 484 (M.+; 40), 483 (15), 482 (9), 471 (15),
470 (40), 469 ([MꢀMe]+; 100), 468 (19), 467 (15), 453
([MꢀCH4ꢀMe]+; 6), 378 ([MꢀMeꢀCH2Ph]+; 4), 363 ([Mꢀ2
MeꢀCH2Ph]+; 12), 274 ([MꢀC5Me4CHPh]+; 13), 260 (12), 259
([MꢀC5Me4CHPhꢀMe]+; 44), 258 (18), 257 (14), 255 (8), 254
Table 4
Crystallographic data, data collection and structure refinement for 5, 6, 7 and 10.
5
6
7
10
Chemical formula
Molecular weight
Crystal system
Space group
a (Å)
C27H45Ti
417.53
C26H41Ti
ꢀ401.49
Orthorhombic
Pbcn (No. 60)
32.0322 (1)
8.6546 (3)
16.5204 (7)
90.0
90.0
90.0
4579.9 (3)
8
1.165
C32H37Ti
469.52
C34H44Ti
500.59
Triclinic
Triclinic
Triclinic
ꢀ
ꢀ
ꢀ
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
8.4272(2)
8.7685(2)
18.1869 (3)
95.1510 (12)
91.6517 (11)
115.8135 (11)
1201.45 (4)
2
8.5452 (2)
16.5668 (5)
18.9231 (5)
104.0030 (12)
91.2402 (16)
103.1375 (15)
2522.90 (12)
4
9.3007(2)
11.5286 (2)
13.8560 (3)
90.1856 (10)
104.2855 (11)
107.7355 (11)
1366.37 (5)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢀ3
)
1.154
0.366
1.236
0.357
1.217
0.334
l
(mmꢀ1
)
0.382
Crystal description
Crystal size (mm3)
h range (°)
Dark green prism
0.5 ꢃ 0.45 ꢃ 0.35
2.71–27.48
ꢀ10/10; ꢀ11/7; ꢀ23/23
22185
Brown prism
0.6 ꢃ 0.3 ꢃ 0.1
2.44–26.03
ꢀ39/39; ꢀ10/10; ꢀ20/20
42506
Brown prism
0.4 ꢃ 0.3 ꢃ 0.1
1.92–25.04
ꢀ9/10; ꢀ19/19; ꢀ22/22
43043
Orange prism
0.5 ꢃ 0.4 ꢃ 0.22
1.52–27.61
ꢀ12/12; ꢀ14/14; ꢀ18/18
41920
hkl range
Diffractions collected
Unique diffractions
F(000)
5475
458
4508
1752
8879
1004
6296
540
Number of parameters
R(F); wR(F2) (%)
GOF (F2) all data
268
3.89; 9.08
1.069
3.44; 8.73
0.314; ꢀ0.390
257
7.55; 15.30
1.050
5.66; 14.10
0.994; ꢀ0.340
611
8.16; 16.11
1.092
5.67; 14.11
0.621; ꢀ0.596
326
6.07; 14.09
1.023
5.32; 13.56
1.545; ꢀ0.811
R(F); wR(F2) [I > 2
r
(I)]
Dq )
(e Åꢀ3

1980
J. Pinkas et al. / Journal of Organometallic Chemistry 694 (2009) 1971–1980
(c) J.E. Bercaw, J. Am. Chem. Soc. 96 (1974) 5087;
(10), 253 (35), 252 (13), 251 (12), 250 (9), 181 (19), 179 (10), 178
(11), 91 ([CH2Ph]+; 14). IR (KBr, cmꢀ1): 3100 (vw), 3084 (vw), 3059
(vw), 3036 (s), 2986 (s), 2971 (m), 2956 (s), 2908 (vs), 2888 (s),
2720 (vw), 1601 (w), 1583 (vw), 1494 (s), 1451 (s), 1442 (m),
1426 (m), 1377 (m), 1236 (vw), 1097 (vw), 1075 (vw), 1028 (w),
1017 (w), 787 (m), 735 (vs), 701 (s), 580 (vw), 465 (w), 433 (m),
406 (m). Anal. Calc. for C33H40Ti: C, 81.80; H, 8.32. Found: C,
81.78; H, 8.30%.
(d) C. McDade, J.C. Green, J.E. Bercaw, Organometallics 1 (1982) 1629.
[2] (a) J.W. Pattiasina, C.E. Hissink, J.L. de Boer, A. Meetsma, J.H. Teuben, A.L. Spek,
J. Am. Chem. Soc. 107 (1985) 7758;
(b) G.A. Luinstra, L.C. ten Cate, H.J. Heeres, J.W. Pattiasina, A. Meetsma, J.H.
Teuben, Organometallics 10 (1991) 3227;
(c) G.A. Luinstra, J.H. Teuben, J. Am. Chem. Soc. 114 (1992) 3361.
[3] T. Vondrák, K. Mach, V. Varga, A. Terpstra, J. Organomet. Chem. 425 (1992) 27.
[4] (a) K. Mach, V. Varga, V. Hanuš, P. Sedmera, J. Organomet. Chem. 415 (1991)
87;
(b) V. Varga, K. Mach, M. Polášek, P. Sedmera, J. Hiller, U. Thewalt, S.I.
Troyanov, J. Oraganomet. Chem. 506 (1996) 241;
3.11. X-ray crystallography
(c) J.M. de Wolf, R. Blaauw, A. Meetsma, J.H. Teuben, R. Gyepes, V. Varga, K.
Mach, N. Veldman, A.L. Spek, Organometallics 15 (1996) 4977.
ˇ
ˇ
[5] J. Pinkas, L. Lukešová, R. Gyepes, I. Císarová, P. Lönnecke, J. Kubišta, M. Horácek,
K. Mach, Organometallics 26 (2007) 3100.
Single crystals or crystal fragments of compounds 5, 6, 7, and 10
were mounted into Lindemann glass capillaries in a Labmaster 130
glovebox (mBraun) under purified nitrogen, and sealed by a wax.
Diffraction data were collected on a Nonius KappaCCD diffractom-
eter and processed by a HKL program package [21].The phase prob-
lem was solved by direct methods (SIR-92) [22], followed by
consecutive Fourier syntheses and refined by full-matrix least-
ˇ
ˇ
[6] J. Pinkas, I. Císarová, A. Condé, R. Fandos, M. Horácek, J. Kubišta, K. Mach, Inorg.
Chem. Commun. 12 (2009) 11.
[7] L. Lukešová, R. Gyepes, J. Pinkas, M. Horácek, J. Kubišta, J. Cejka, K. Mach,
Collect. Czech., Chem. Commun. 70 (2005) 1589.
[8] W.W. Lukens Jr., M.R. Smith III, R.A. Andersen, J. Am. Chem. Soc. 118 (1996)
1719.
[9] J. Langmaier, Z. Samec, V. Varga, M. Horácek, K. Mach, J. Organomet. Chem. 579
ˇ
ˇ
ˇ
(1999) 348.
squares on F2
(SHELXL-97 [23]). Relevant crystallographic data are
[10] G. Erker, U. Korek, R. Petrenz, A.L. Rheingold, J. Organomet. Chem. 421 (1991)
215.
[11] J. Sassmannshausen, J. Baumgartner, Organometallics 27 (2008) 1996.
[12] H. van der Heijden, B. Hessen, Inorg. Chim. Acta 345 (2003) 27.
given in Table 4. All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were fixed and refined in their theoretical
positions. The final difference Fourier map for 10 displayed a high
positive maximum in close vicinity of Ti atom (Ti-1 0.82 Å),
probably resulting from the imperfection of the measured crystal.
ˇ
[13] (a) V. Kupfer, U. Thewalt, I. Tišlerová, P. Štpnicka, R. Gyepes, J. Kubišta, M.
ˇ
Horácek, K. Mach, J. Organomet. Chem. 620 (2001) 39;
ˇ
ˇ
ˇ
ˇ
(b) M. Horácek, P. Štepnicka, R. Gyepes, I. Císarová, M. Polášek, K. Mach, P.-M.
Pellny, V.V. Burlakov, W. Baumann, A. Spannenberg, U. Rosenthal, J. Am. Chem.
Soc. 121 (1999) 10638;
ˇ
ˇ
ˇ
ˇ
(c) M. Horácek, P. Štepnicka, J. Kubišta, R. Gyepes, I. Císarová, L. Petrusová, K.
4. Supplementary material
Mach, J. Organomet. Chem. 658 (2002) 235;
ˇ
ˇ
ˇ
ˇ
(d) M. Horácek, P. Štepnicka, J. Kubišta, I. Císarová, L. Petrusová, K. Mach, J.
Organomet. Chem. 667 (2003) 154.
CCDC 702259, 702260, 702261 and 702262 contains the sup-
plementary crystallographic data for 5, 6, 7 and 10. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
ˇ
[14] M. Horácek, R. Gyepes, J. Kubišta, K. Mach, Inorg. Chem. Commun. 7 (2004)
155. and references therein.
[15] W.W. Lukens Jr., P.T. Matsunaga, R.A. Andersen, Organometallics 17 (1998)
5240.
[16] J. Pinkas, I. Císarová, R. Gyepes, M. Horácek, J. Kubišta, J. Cejka, S. Gómez-Ruiz,
E. Hey-Hawkins, K. Mach, Organometallics 27 (2008) 5532.
[17] M.D. Walter, C.D. Sofield, R.A. Andersen, Organometallics 27 (2008) 2959.
[18] H. Sitzmann, P. Zhou, G. Wolmershäuser, Chem. Ber. 127 (1994) 3.
[19] (a) T.E. Hanna, E. Lobkovsky, P.J. Chirik, J. Am. Chem. Soc. 126 (2004)
14688;
ˇ
ˇ
ˇ
Acknowledgements
This research was supported by the Grant Agency of the Acad-
emy of Sciences of the Czech Republic (Grant No. IAA400400708)
and the Ministry of Education, Youth and Sports (Project No.
LC06070). I.C. thanks MSM0021620857.
ˇ
ˇ
ˇ
(b) M. Horácek, V. Kupfer, U. Thewalt, P. Štepnicka, M. Polášek, K. Mach,
Organometallics 18 (1999) 3572.
[20] H. Antropiusová, A. Dosedlová, V. Hanuš, K. Mach, Trans. Metal. Chem.
(London) 6 (1981) 90.
[21] HKL DENZO and SCALEPACK program package by Nonius: Z. Otwinowski, W. Minor,
Meth. Enzymol. 276 (1997) 307.
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[23] G.M. Sheldrick, SHELXL-97. Program for Crystal Structure Refinement from
Diffraction Data, University of Göttingen, Göttingen, 1997.
[1] (a) J.E. Bercaw, H.H. Brintzinger, J. Am. Chem. Soc. 93 (1971) 2045;
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