Low-valent pentafulvene titanium dinitrogen complex as a precursor for cationic titanium complexes

Article abstract of DOI:10.1021/om900875e

Treatment of titanium dinitrogen complex [Cp*(η⁶- C₅H₄=C₁₀H₁₄)Ti]₂(μ- N₂) (1) with ferrocenium borate, [Cp₂Fe][BPh₄], in THF results in oxidation of the titanium center, affording the titanium(IV) pentafulvene compound [Cp*(η⁶-C₅H ₄=C₁₀H₁₄)Ti(THF)][BPh₄] (2). Treatment of 1 with anilinium reagent [PhNMe₂H][BPh₄] results in the formation of cationic titanocene(III) complexes. In THF, the titanocene cation is stabilized by two THF solvent molecules, whereas the tetraphenylborate anion is bound to the metal center when the reaction is performed in toluene as a solvent. Treatment of 1 with B(C₆F ₅)₃ affords zwitterionic [Cp*{η⁵- C₅H₃=C₁₁H₁₄)(B{C₆F ₅}₃)}Ti(THF)] (7). Results show the versatility of pentafulvene complex 1 in the preparation of cationic titanium complexes.

Full text of DOI:10.1021/om900875e

Organometallics 2009, 28, 6969–6974 6969
DOI: 10.1021/om900875e
Low-Valent Pentafulvene Titanium Dinitrogen Complex as a Precursor
for Cationic Titanium Complexes
†
†
†
,†
‡
€
Axel Scherer, Detlev Haase, Wolfgang Saak, Rudiger Beckhaus,* Auke Meetsma, and
Marco W. Bouwkamp*,‡
†Institute of Pure and Applied Chemistry, University of Oldenburg, D-26111 Oldenburg, Germany
‡Molecular Inorganic Chemistry Group, Stratingh Institute for Chemistry, University of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
Received October 8, 2009
Treatment of titanium dinitrogen complex [Cp*(η6-C5H4dC10H14)Ti]2( μ-N2) (1) with ferrocenium
borate, [Cp2Fe][BPh4], in THF results in oxidation of the titanium center, affording the titanium(IV)
pentafulvene compound [Cp*(η6-C5H4dC10H14)Ti(THF)][BPh4] (2). Treatment of 1 with anilinium
reagent [PhNMe2H][BPh4] results in the formation of cationic titanocene(III) complexes. In THF, the
titanocene cation is stabilized by two THF solvent molecules, whereas the tetraphenylborate
anion is bound to the metal center when the reaction is performed in toluene as a solvent. Treatment
of 1 with B(C6F5)3 affords zwitterionic [Cp*{η5-C5H3(C11H14)(B{C6F5}3)}Ti(THF)] (7). Results show
the versatility of pentafulvene complex 1 in the preparation of cationic titanium complexes.
Introduction
η5-C5Me5; FvAd=η6-C5H4dC10H14)5 with different borane
and borate reagents, which allowed the isolation and char-
acterization of a variety of new cationic titanium complexes.
Results demonstrate the versatility of the pentafulvene
ligand in titanium chemistry.
Cationic complexes of early transition metals are of great
importance as catalysts for a broad range of chemical
transformations and in particular for olefin polymerization
catalysis.1 The performance of these catalysts is in part
governed by the interaction of the cationic transition metal
complex with its counterion. As these interactions are gene-
rally unfavorable, weakly coordinating anions have been
developed to minimize interference of the counterion.2 Over
the years, many synthetic routes have been developed for the
preparation of transition metal complexes with these weakly
coordinating anions, among which the treatment of transi-
tion metal alkyl complexes with Lewis and Brønsted acidic
borane and borate reagents.2,3 Furthermore, the oxidation
of low-valent metallocene complexes has been reported.4
Here we report the reactivity of the low-valent titanium
dinitrogen complex [Cp*FvAdTi]2( μ-η2:η2-N2) (1, Cp* =
Results and Discussion
Reaction with Ferrocenium Tetraphenylborate. Treatment
of the low-valent dinitrogen-bridged dimer [Cp*FvAdTi]2-
( μ-η2:η2-N2) (1) with [Cp2Fe][BPh4] (1 equiv per titanium) in
THF solution results in a color change from blue-green to
orange. During the reaction gas evolution was observed,
suggesting the release of dinitrogen. The 1H NMR spectrum
of the compound shows the correct number of peaks for the
C1 symmetric titanium cation [Cp*FvAdTi(THF)][BPh4] (2,
Scheme 1), the result of oxidation of both titanium centers by
the ferrocenium reagent. The resonances for the fulvene ring
are found as four multiplets at 3.16, 4.96, 6.08, and 6.68 ppm,
as expected for tucked-in complexes of this type.6 The 13C
NMR shows a resonance at 126.0 ppm for the adamantyl
carbon that is bound to the metal center.
Slow diffusion of cyclohexane into a THF solution of
compound 2 resulted in orange crystals that were suitable for
a single-crystal X-ray diffraction study. An ORTEP repre-
sentation of the cation of 2 is depicted in Figure 1 (see Table 1
for selected bond distances and angles). The molecular
structure of 2 is very similar to that of the corresponding
titanium chloride compound, Cp*FvAdTiCl (3), which was
prepared by treatment of Cp*TiCl3 with adamantylfulvene
in the presence of sodium amalgam (vide infra). The structure
*Corresponding authors. E-mail: ruediger.beckhaus@uni-oldenburg.
de; M.W.Bouwkamp@rug.nl.
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2009 American Chemical Society
Published on Web 12/02/2009
pubs.acs.org/Organometallics

6970 Organometallics, Vol. 28, No. 24, 2009
Scherer et al.
Figure 1. ORTEP representation at 30% probability level of compounds 2 and 3. Hydrogen atoms and [BPh4] counterions are omitted
for clarity.
Scheme 1
98.33(4)ꢀ) and Cp*-Ti(1)-FvAd angles (2, 136.04ꢀ; 3,
137.64ꢀ). As a result of the larger THF ligand, the X-Ti-
(1)-Cexofulvene angle is opened up, resulting in a concurrent
decrease of the Cp*-Ti(1)-FvAd angle.
˚
Table 1. Selected Bond Distances (A) and Angles (deg) for
Compounds 2 and 3a
2
3
Ti(1)-Cp*
2.0687
1.9873
Ti(1)-Cp*
2.082
1.988
Although compound 2 can be obtained in reasonable
yields (54%), an alternative route via protonation of an
appropriate methyl precursor was evaluated. As stated
above, compound 3 can be prepared from Cp*TiCl3, ada-
mantylfulvene, and sodium amalgam in THF solution
(Scheme 2). During the reaction a color change from red to
greenish-brown was observed. Compound 3 could be iso-
lated as brown crystals by recrystallization from hexane.
Previously, the synthesis of the comparable titanium chlo-
ride compound, Cp*(η6-C5H4dC(p-Tol)2)TiCl, was reported,
exhibiting a fast rotation of the fulvene ligand around the
Ti-fulvene axis at room temperature in toluene-d8 solu-
tion.6b In the case of 3, such a bond rotation was not obser-
ved at room temperature. Only at temperatures as high as
100 ꢀC could coalescence of the fulvene protons be observed.
At room temperature the four distinct fulvene protons are
found at 3.08, 4.63, 5.56, and 6.68 ppm. The reduced
fluxionality in the system can be ascribed to the increased
steric bulk imparted by the adamantyl group relative to the
two p-Tol groups. Treatment of compound 3 with methyl
lithium in diethyl ether solution results in a green solution
of the corresponding methyl complex, Cp*FvAdTiMe
(4, Scheme 2), which could be isolated as a green solid.
Unfortunately, the reaction of methyl compound 4 with
[PhNMe2H][BPh4] was not conclusive.
Ti(1)-FvAd
Ti(1)-FvAd
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-C(4)
Ti(1)-C(5)
Ti(1)-C(1)
Ti(1)-C(6)
Ti(1)-Cl(1)
C(1)-C(6)
Ti(1)-C(115)
Ti(1)-C(116)
Ti(1)-C(117)
Ti(1)-C(118)
Ti(1)-C(119)
Ti(1)-C(120)
Ti(1)-O(1)
C(119)-C120
Cp*-Ti1-FvAd
FvAd-C(119)-C(120)
2.306(3)
2.448(2)
2.414(3)
2.264(3)
2.181(3)
2.564(3)
2.138(2)
1.422(4)
136.11
2.283(5)
2.418(2)
2.428(2)
2.314(4)
2.186(4)
2.547(4)
2.364(6)
2.547(4)
137.14
Cp*-Ti1-FvAd
FvAd-C(1)-C(6)
152.4
151.06
a Cp* is defined as the centroid of C(11)-C(15) (compound 2) or
C(16)-C(20) (compound 3); FvAd is defined as the centroid of
C(115)-C(119) (compound 2) or C(1)-C(5) (compound 3).
of compound 3 is included in Figure 1 (see Table 1 for
selected bond distances and angles) and shows a remarkable
resemblance to that of compound 2, with very similar bond
distances and angles. The Ti(1)-Cexofulvene bond distances in
both complexes are relatively long for Ti-C(sp3) bonds (2,
2.564(3) A; 3, 2.547(4) A), compared to fulvene complexes
exhibiting a higher σ-bond content in the Ti-Cexofulvene
bond,7 e.g., Cp*(η6-C5Me4dCH2)Ti, 2.281(14) A,8 or
Cp*(η6-C5H4dC(H)(tBu)TiCl, 2.355(2) A.6a On the other
hand, Ti-Cexofulvene distances comparable to 2 and 3 are
found for Cp*(η6-C5H4dC(Ph)2)TiCl (2.535(5) A)6b or dini-
trogen complex 1 (2.511(5) A)5 as well. The most noticeable
difference between the structures of compounds 2 and 3 are
the X-Ti(1)-C(6) angles (2, X=O, 100.03(5)ꢀ; 3, X=Cl,
Reaction with N,N-Dimethylanilinium Tetraphenylborate.
Compound 1 was treated with Brønsted acidic borate re-
agent, [PhNMe2H][BPh4] (1 equiv per titanium). In THF
solution, immediate gas evolution was observed, similar to
the reaction with ferrocenium tetraphenylborate, resulting in
a green solution of a paramagnetic compound. Slow diffu-
sion of cyclohexane into the THF solution resulted in
€
(7) Koch, R.; Bolter, E.; Stroot, J.; Beckhaus, R. J. Organomet.
Chem. 2006, 691, 4539–4544.
(8) Fischer, J. M.; Piers, W. E.; Young, V. G., Jr. Organometallics
1996, 15, 2410–2412.

Article
Organometallics, Vol. 28, No. 24, 2009 6971
Figure 2. ORTEP representation at 30% probability level of compounds 5 and 6. Hydrogen atoms except for H(215) and H(216) in
compound 6 and the [BPh4] counterion of 5 are omitted for clarity.
Scheme 2
Scheme 3
˚
Table 2. Selected Bond Distances (A) and Angles (deg) for
turquoise crystals, suitable for a single-crystal X-ray diffrac-
tion study. The structure of the compound, a bis-THF
Compounds 5 and 6a
adduct of a cationic trivalent titanocene complex, [Cp*CpAd
-
5
6
Ti(THF)2][BPh4] (5, CpAd =η5-C5H4C10H15, Scheme 3), is
depicted in Figure 2 (see Table 2 for selected bond distances
and angles). Whereas a mono-THF adduct was obtained in
the case of the decamethyltitanocene cation,9 two molecules
of THF are bound in compound 5, similar to the parent
titanocene cation, [Cp2Ti(THF)2]þ.10 This illustrates the
reduced steric bulk of the adamantylcyclopentadienyl
ligand, compared to the Cp* ligand, which can be explained
by the fact that the adamantyl group can be directed to one
side of the molecule, reducing the effective steric bulk of the
ligand. As expected for a four-coordinate bis-THF adduct,
the Cp*-Ti-CpAd angle in 5 (133.77ꢀ) is smaller than the
corresponding angle in the three-coordinate compound
[Cp*2Ti(THF)][BPh4] (142.11ꢀ).9 This angle is larger compared
Ti(1)-Cp*
2.1049
2.0751
2.2180(16)
2.2409(17)
2.0331
2.0083
Ti(1)-CpAd
Ti(1)-O(11)
Ti(1)-O(12)
Ti(1)-C(215)
Ti(1)-C(216)
Ti(1)-H(215)
Ti(1)-H(216)
Cp*-Ti(1)-CpAd
O(11)-Ti(1)-O(12)
—(TiH2, Ph)
a Cp* is defined as the centroid of C(111)-C(115); CpAd is defined as
the centroid of C(11)-C(15); —(TiH2, Ph) is defined as the angle
between the Ti-H(215)-H(216) plane and the plane of C(213)-C(218).
2.6976(16)
2.6103(19)
2.6961
2.5122
136.10
133.77
77.78
77.26
to the one observed in [Cp2Ti(THF)2][BPh4] (112.47ꢀ).10b Also,
the Ti-O bond distances in 5 (2.180(16) and 2.2409(17) A) are
in the range for the [Cp2Ti(THF)2] cation (2.19-2.24 A).10,11
(9) Bouwkamp, M. W.; De Wolf, J.; Del Hierro Morales, I.; Gercama,
J.; Meetsma, A.; Troyanov, S. I.; Hessen, B.; Teuben, J. H. J. Am. Chem.
Soc. 2002, 124, 12956–12957.
(10) (a) Ohff, A.; Kempe, R.; Baumann, W.; Rosenthal, U.
J. Organomet. Chem. 1996, 520, 241–244. (b) Ahlers, W.; Temme, B.;
(11) (a) Merola, J. S.; Campo, K. S.; Gentile, R. A.; Modrick, M. A.
Inorg. Chim. Acta 1989, 165, 87–90. (b) Plecnik, C. E.; Liu, F.-C.; Liu, S.;
Liu, J.; Meyers, E. A.; Shore, S. G. Organometallics 2001, 20, 3599–3606.
€
Erker, G.; Frohlich, R.; Zippel, F. Organometallics 1997, 16, 1440–1444.

6972 Organometallics, Vol. 28, No. 24, 2009
Scherer et al.
In toluene, the reaction of 1 with [PhNMe2H][BPh4]
results in a base-free trivalent titanocene cation. During the
reaction, gas evolution was observed. Conveniently, the
reaction afforded blue crystals that were suitable for X-ray
analysis. The molecular structure of the ion pair is depicted in
Figure 2 (see Table 2 for selected bond distances and angles).
The compound, a contact ion pair of the type Cp*CpAdTi-
(η2-BPh4) (6), reveals, once again, that the adamantylcyclo-
pentadienyl ligand is smaller compared to the Cp* ligand.
Whereas the coordination sphere of the decamethylmetallo-
cene cation is too small to accommodate the counterion, the
anion in compound 6 is bound to the metal center. In the case
of the base-free [Cp*2Ti] cation, the electron-deficient tita-
nium center binds two C-H bonds of one of the penta-
methylcyclopentadienyl ligands.9 A similar binding of the
anion as observed for compound 6 was also found in the
decamethylscandocene cation, Cp*2Sc(η2-BPh4), in which
the anion can bind to the metal center as a result of the larger
ionic radius of the Sc3þ ion versus the Ti3þ ion.9,12 The inter-
action with the anion is best described as two agostic inter-
actions of the metal center with two C-H bonds of the anion
(Ti-H = 2.696 and 2.512 A; Ti-C = 2.6978(18) and
2.6103(19) A), similar to that in Cp*2Sc(η2-BPh4). The angle
between the planes defined by H-M-H and the coordinated
phenyl group in 6 (77.26(4)ꢀ) is larger compared to that in the
scandium compound (58.0(9)ꢀ).
Figure 3. ORTEP representation at 30% probability level of
compound 7. Hydrogen atoms are omitted for clarity.
˚
Table 3. Selected Bond Distances (A) and Angles (deg) for
Compound 7a
Ti1-Cp*
2.055
2.033
Ti(1)-O(1)
Ti(1)-F(15)
2.238(2)
2.3036(16)
Ti1-CpAd
Reaction with Tris(pentafluorophenyl)borane. Addition of
THF to a 2:1 mixture of B(C6F5)3 and compound 1 resulted
in gas evolution and the formation of a dark blue solution of
a paramagnetic compound. Slow diffusion of hexane into the
THF solution resulted in dark blue crystals, which were
analyzed using X-ray diffraction (see Figure 3 for an ORTEP
representation and Table 3 for selected bond distances
and angles). Surprisingly, a zwitterionic complex was ob-
tained in which the borane moiety is bound to one of the
carbon atoms of the cyclopentadienyl ring rather than the
adamantyl carbon: [Cp*{η5-C5H3(C10H15)(B{C6F5}3)}Ti-
(THF)] (7, Scheme 4). The expected direct attack of the
Lewis acid B(C6F5)3 on the nucleophilic exocyclic fulvene
carbon, as found in the case of zirconium fulvene complexes,13
is not observed. It is highly unlikely that the formation of
compound 7 is the result of an initial addition of the borane
reagent to the adamantyl carbon, as it is not expected that the
resulting species would rearrange to form compound 7.
Therefore, we would like to suggest that compound 7 is
formed by initial addition of B(C6F5)3 to the 3-carbon of the
cyclopentadienyl ring, affording a transient titanium hydride
cation of the type [Cp{η6-C5H3(C10H14)(B{C6F5}3)}TiH]þ.
This species can rearrange into compound 7 after a reductive
elimination involving the hydride ligand and the adamantyl
carbon (Scheme 4). A similar electrophilic attack of B(C6F5)3
to a cyclopentadienyl ligand was previously observed by
Rosenthal and co-workers.14 The free coordination sites of
the titanocene cation 7 are occupied by one molecule of THF
Cp*-Ti-CpAd
135.99
O(1)-Ti(1)-F(15)
78.09(7)
a Cp* is defined as the centroid of C34-C38; CpAd is defined as the
centroid of C1-C5.
and an o-CF bond, similar to the acetone adduct Cp(η5-
C5H4B{C6F5}3)Ti(OCMe2).14b As a result, the C(33)-F(15)
bond length (1.391(3) A) is slightly elongated and the geo-
metry of the borate anion is deviating from a perfect tetra-
hedron (C(4)-B(1)-C(28) angle is 116.2(2)ꢀ). The Ti-F
bond distance in 7 (2.3063(16) A) is longer compared to that
in the zwitterion Cp(η5-C5H4B{C6F5}3)Ti(OCMe2) (2.252(2) A)
and fluorobenzene adduct [Cp*2Ti(FPh)][BPh4].9
Conclusions
Low-valent titanium dinitrogen complex [Cp*FvAdTi]2-
( μ-N2) (1) is an interesting synthon for a number of cationic
titanium species. Oxidation of the titanium center results in
cationic titanium(IV) complexes, whereas the treatment with
Brønsted acidic borate reagents or Lewis acidic boranes
results in trivalent titanium cations by selective protonation
of the exocyclic fulvene carbon center. The initial step in each
of these reactions is the release of molecular dinitrogen from
the coordination sphere of the titanium center. X-ray analy-
sis of the products shows that the Cp-adamantyl ligand
obtained from a protonation reaction of the adamantylful-
vene ligand is smaller compared to the Cp* ligand, as a result
of the fact that the adamantyl group can be directed to the
side of the molecule, hence reducing the effective steric
shielding of the ligand.
(12) Bouwkamp, M. W.; Budzelaar, P. H. M.; Gercama, J.; Del
Hierro Morales, I.; De Wolf, J.; Meetsma, A.; Troyanov, S. I.; Teuben,
J. H.; Hessen, B. J. Am. Chem. Soc. 2005, 127, 14310–14319.
(13) Sun, Y.; Piers, W. E.; Yap, G. P. A. Organometallics 1997, 16,
2509–2513.
Experimental Section
(14) (a) Burlakov, V. V.; Troyanov, S. I.; Letov, A. V.; Strunkina,
L. I.; Minacheva, M. K.; Furin, G. G.; Rosenthal, U.; Shur, V. B.
J. Organomet. Chem. 2000, 598, 243–247. (b) Burlakov, V. V.; Arndt, P.;
Baumann, W.; Spannenberg, A.; Rosenthal, U.; Letov, A. V.; Lyssenko,
K. A.; Korlyukov, A. A.; Strunkina, L. I.; Minacheva, M. K.; Shur, V. B.
Organometallics 2001, 20, 4072–4079.
General Considerations. All manipulations of air- and moist-
ure-sensitive compounds were performed under a nitrogen atmo-
sphere using standard Schlenk line, vacuum line, and glovebox
techniques. Reagents were purchased from commercial suppliers

Article
Organometallics, Vol. 28, No. 24, 2009 6973
Scheme 4
unless stated otherwise. Compounds [Cp*(η6-FvAd)Ti]2( μ-N2),5
C5H4dC10H14,15 Cp*TiCl3,16 [Cp2Fe][BPh4],17 [PhNMe2H]-
displacement parameters for the non-hydrogen atoms were
refined. Final refinement on F2 was carried out by full-matrix
least-squares techniques. For compounds 3 and 7 crystals
were measured using a STOE-IPDS diffractometer. The struc-
tures were solved using direct methods (SHELXS-97).22 Final
refinement on F2 was carried out by full-matrix least-squares
techniques.
19
[BPh4],18 and B(C6F5)3 were prepared according to literature
procedures. Solvents (THF, pentane) were dried by percolation
under a nitrogen atmosphere over columns of alumina, molecular
sieves, and supported copper oxygen scavenger (BASF R3-11)
or by distillation from Na/K alloy (THF, hexane, cyclohexane,
THF-d8, benzene-d6). NMR spectra were recorded on Varian
Inova 500, Varian Gemini VXR 400, Varian VXR 300, Varian
Gemini 200, Bruker 500 AVANCE, and Bruker 300 AVANCE-
NMR instruments. 1H chemical shifts are referenced to residual
protons in deuterated solvents and are reported relative to
tetramethylsilane. Crystals suitable for a single-crystal X-ray
analysis were grown as described in the text. For compounds 2,
5, and 6, a crystal was mounted on a glass fiber inside a drybox
and transferred under an inert atmosphere to the cold nitrogen
stream of a Bruker SMART APEX CCD diffractometer. Inten-
sity data were corrected for Lorentz and polarization effects,
scale variation, decay, and absorption: a multiscan absorption
correction was applied, based on the intensities of symmetry-
related reflections measured at different angular settings
(SADABS),20 and reduced to Fo2.The structures were solved
by Patterson methods, and extension of the model was accom-
plished by direct methods applied to difference structure factors
using the program DIRDIF.21 The positional and anisotropic
[Cp*(η6-C5H4C10H14)Ti(THF)][BPh4] (2). THF (0.5 mL) was
added to a mixture of 1 (56.2 mg, 0.0711 mol) and [Cp2Fe][BPh4]
(71.4 mg, 0.141 mmol). When no more gas evolution was
observed, the color had changed from blue to orange, after
which cyclohexane (3 mL) was layered carefully on top of the
THF solution. After days, orange crystals had precipitated from
the reaction mixture. The supernatant was decanted and the
crystals were washed with pentane (2 ꢀ 1 mL), affording the title
compound (58 mg, 54%). 1H NMR (THF-d8, 300 K): δ 1.86 (s,
15H, Cp*), 0.7-3.5 (overlapping, 14 H, adametnyl), 3.16 (m,
1H, C5H4), 4.96 (m, 1H, C5H4), 6.08 (m, 1H, C5H4), 6.68 (t, 7.1
Hz, 4H, BPh4), 6.68 (m, 1H, C5H4), 6.82 (t, 7.4 Hz, 8H, BPh4),
7.24 (br, Δν1/2=15 Hz, BPh4). 13C{1H} NMR (THF-d8, 300 K):
δ 12.6 (Cp*), 26.3, 28.3, 30.0, 33.7, 37.6, 37.8, 38.1, 46.7, 47.6
(adamantyl), 121.7 (p-BPh4), 121.8 (C5H4), 122.1 (C5H4), 123.9
(C5H4), 125.6 (overlapping C5H4 and m-BPh4), 126.0 (Cexo
adamantyl), 129.0 (Cp*), 137.1 (o-BPh4) 137.8 (Cipso C5H4),
165.1 Cipso BPh4) ppm. Anal. Calcd for C53H61BOTi: C, 82.38;
H, 7.96. Found: C, 82.66; H, 8.28. Melting point: 65 ꢀC.
Cp*(η6-C5H4C10H14)TiCl (3). THF was added to Cp*TiCl3
(1.0 g, 3.45 mmol), adamantylfulvene (0.69 g, 3.45 mmol), and
20% Na/Hg (0.79 g, 6.91 mmol). The resulting suspension was
stirred for 16 h at 200 mbar N2 pressure, resulting in a color
change from red to greenish-brown. The reaction mixture was
filtered over Celite, and the volatiles were removed in vacuo. The
resulting brown residue was recrystallized from hexane (20 mL),
affording 1.2 g (83%) of the title compound. 1H NMR (benzene-
d6, 300 K): δ 1.70 (s, 15H, Cp*), 0.9-3.1 (overlapping, 14H,
adamantyl), 3.08 (m, 1H, C5H4), 4.63 (m, 1H, C5H4), 5.65 (m,
1H, C5H4), 6.68 (m, 1H, C5H4). 13C{1H} NMR (benzene-d6, 300
K): δ 12.7 (Cp*), 28.4, 29.7, 33.4, 37.6, 38.2, 38.3, 45.0, 46.5
(adamantyl), 115.8 (C5H4), 118.5 (C5H4), 119.4 (C5H4), 122.9
(15) Abrams, M. B.; Yoder, J. C.; Loeber, C.; Day, M. W.; Bercaw,
J. E. Organometallics 1999, 18, 1389–1401.
(16) Hidalgo, G.; Mena, M.; Palacios, F.; Royo, P.; Serrano, R.
(Pentamethylcyclopentadienyl)titanium, -zirconium, and -hafnium Trihalides-
M[η5-C5(CH3)5]X3 (M=Ti, X=Cl, Br, I; M=Zr, Hf, X=Cl). Georg Thieme
Verlag: Stuttgart, 1996; Vol. 1, pp 95-97.
(17) Calderazzo, F.; Pampaloni, G.; Rocchi, L.; Englert, U. Organo-
metallics 1994, 13, 2592–2601.
(18) Eshuis, J. J. W.; Tan, Y. Y.; Meetsma, A.; Teuben, J. H.;
Renkema, J.; Evens, G. G. Organometallics 1992, 11, 362–369.
(19) Pohlmann, J. L. W.; Brinckman, F. E. Z. Naturforsch. B 1965,
20b, 5–11.
(20) Sheldrick, G. M. SADABS v2; 2001.
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6974 Organometallics, Vol. 28, No. 24, 2009
Scherer et al.
(Cp*), 123.4 (C5H4), 131.3 (Cipso C5H4) ppm. Anal. Calcd for
C25H33ClTi: C, 72.03; H, 7.98. Found: C, 71.82; H, 7.78.
Melting point: 50 ꢀC.
X-ray diffraction. Anal. Calcd for C57H70BO2Ti: C, 80.94; H,
8.34. Found: C, 80.04; H, 8.11.
Cp*(η5-C5H4C10H15)Ti(η2-BPh4) (6). Toluene (5 mL) was
added to a mixture of 1 (100 mg, 126 mmol) and
Cp*(η6-C5H4C10H14)TiMe (4). Compound 1 (4.0 g, 9.6
mmol) was dissolved in ether (280 mL). The resulting solution
was cooled to -80 ꢀC, after which an 1.6 M ether solution of
MeLi (6.0 mL, 9.6 mmol) was added by syringe. After stirring
the reaction mixture for 1 h at -70 ꢀC, the reaction mixture was
slowly warmed to RT. During the reaction a color change from
brown to green was observed. The ether was removed in vacuo,
and the reaction mixture was extracted with pentane (200 mL).
Distilling off the pentane and drying of the compound resulted
in a green oily product (2.6 g, 65%). 1H NMR (benzene-d6, 300
K): δ -1.03 (s, 3H, TiMe), 1.67 (s, 15H, Cp*), 0.8-2.7
(overlapping, 14H, adamantyl), 3.35 (m, 1H, C5H4), 4.63 (m,
1H, C5H4), 5.57 (m, 1H, C5H4), 6.47 (m, 1H, C5H4). 13C{1H}
NMR (benzene-d6, 300 K): δ 12.3 (Cp*), 28.7, 29.9, 32.8, 36.7,
37.5, 38.4, 38.5, 44.3, 45.2 (adamantyl), 44.2 (TiMe), 114.1
(C5H4), 116.8 (C5H4), 117.1 (C5H4), 119.4 (Cexo adamantyl),
119.6 (Cp*), 120.3 (C5H4), 133.1 (Cipso in C5H4). Anal. Calcd for
C26H36Ti: C, 78.77; H, 9.15. Found: C, 78.01; H, 8.97.
[PhNMe2H][BPh4] (112 mg, 253 mmol). Immediate gas evolu-
tion was observed. Over the course of days, blue crystals of the
title compound had formed. The supernatant was decanted, and
the crystals were washed with pentane, yielding 92 mg (52%) of
compound 6. Anal. Calcd for C49H54BTi: C, 83.88; H, 7.76.
Found: C, 83.41; H, 7.59.
[Cp*{η5-C5H3(C10H15)(B{C6F5}3)}Ti(THF)] (7). THF (1
mL) was added to a mixture of 100 mg (126 mmol) of compound
1 and 130 mg (254 mmol) of B(C6F5)3. When no more gas
evolution was observed, hexane (6 mL) was carefully layered on
top of the THF solution. Over the course of days dark blue
crystals had formed, which were isolated by decanting the
supernatant and washing with hexane, affording 136 mg
(56%) of the title compound. Anal. Calcd for C47H41BF15OTi:
C, 58.47; H, 4.28. Found: C, 57.32; H, 3.54.
Acknowledgment. This research was financially sup-
ported by the Fonds der Chemischen Industrie (AS,
University of Oldenburg) and The Netherlands Organi-
zation for Scientific Research (University of Groningen).
[Cp*(η5-C5H4C10H15)Ti(THF)2][BPh4] (5). THF (1 mL) was
added to
a mixture of 1 (100 mg, 126 mmol) and
[PhNMe2H][BPh4] (112 mg, 253 mmol). When no more gas
evolution was observed, cyclohexane (6 mL) was layered on top
of the THF solution. Overnight, turquoise crystals had formed,
which were isolated after decanting of the supernatant and
washing with hexane. This afforded 203 mg (95%) of the title
compound. The paramagnetic compound was characterized by
Supporting Information Available: Crystallographic informa-
tion files of compounds 2, 3, 5, 6, and 7. This material is available
free of charge via the Internet at http://pubs.acs.org.