Reactivity of functionalised decamethyltitanocenes: Synthesis and structure of chiral monocyclopentadienyl titanium halogenides

Article abstract of DOI:10.1016/j.ica.2013.03.025

The recently described unconventional substituted titanocene complex [Cp^{a -}Ti{η⁵-C₅Me₃(CH ₂-CH(tBu)-η²-C₂-CH(tBu)-CH₂)}] (1) can be derivatised by simple means (Br₂, HX with X = Cl, Br) to generate the titanocene dihalogenides 2-Br, 2-Cl, which give in a subsequent reaction besides Cp^a&-TiX₃ (3-Br: X = Br, 3-Cl: X = Cl) the titanium complexes 4-Cl resp. 4-Br with one functionalised chiral cyclopentadienyl ligand. In the reaction of 1 with Et₃N·3HF an analogous isostructural titanocene dihalogenide 2-F as well as the unusual dimeric anionic heptafluoride 5 are formed. All complexes have been characterised spectroscopically, and X-ray crystal structure determinations were performed for 4-Cl and 2-F.

Full text of DOI:10.1016/j.ica.2013.03.025

Inorganica Chimica Acta 401 (2013) 76–80
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Inorganica Chimica Acta
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Reactivity of functionalised decamethyltitanocenes: Synthesis
and structure of chiral monocyclopentadienyl titanium halogenides
Vladimir V. Burlakov a,b, Konstantin A. Lyssenko b, Anke Spannenberg a, Wolfgang Baumann a,
Perdita Arndt a, Vladimir B. Shur b, , Uwe Rosenthal a,
⇑
⇑
a Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov St. 28, 119991 Moscow, Russia
a r t i c l e i n f o
a b s t r a c t
The recently described unconventional substituted titanocene complex [Cp⁄Ti{ 5-C5Me3(CH2–CH(tBu)–
g
g
Article history:
2-C2–CH(tBu)–CH2)}] (1) can be derivatised by simple means (Br2, HX with X = Cl, Br) to generate the
Received 23 January 2013
Received in revised form 13 March 2013
Accepted 15 March 2013
titanocene dihalogenides 2-Br, 2-Cl, which give in a subsequent reaction besides Cp⁄TiX3 (3-Br: X = Br,
3-Cl: X = Cl) the titanium complexes 4-Cl resp. 4-Br with one functionalised chiral cyclopentadienyl
ligand. In the reaction of 1 with Et3Nꢀ3HF an analogous isostructural titanocene dihalogenide 2-F as well
as the unusual dimeric anionic heptafluoride 5 are formed. All complexes have been characterised spec-
troscopically, and X-ray crystal structure determinations were performed for 4-Cl and 2-F.
Ó 2013 Elsevier B.V. All rights reserved.
Available online 26 March 2013
Keywords:
Mono cyclopentadienyl
Titanocene
Chiral cyclopentadienyl ligand
Halogenides
X-ray crystal structure analysis
1. Introduction
groups of one of the pentamethylcyclopentadienyl ring systems
generates the complex [Cp⁄Ti{ 5-C5Me3(CH2–CHR–g2-C2–CHR0–
g
There is a considerable interest in chiral metallocene complexes
for various stoichiometric reactions and as well as catalysts for ste-
reospecific polymerisations of prochiral olefins [1]. Thus, e.g., the
half-sandwich titanium complexes in the catalytic systems
CH2)}] (R = R0 = tBu) (1) [5] (Scheme 1A).
similar product has been obtained by using tBuC„C–
A
C„CSiMe3 [5]. In these complexes one pentamethylcyclopentadie-
nyl ligand is annellated with an eight-membered ring with a C–C
triple bond, which is coordinated to the titanium centre. Activation
of methyl groups of both pentamethylcyclopentadienyl ligands is
observed for R = R0 = Me, Ph (Scheme 1B), which displays besides
the fulvene also a butadienyl-substituted pentamethylcyclopenta-
dienyl ligand [5]. The reaction with Me3SiC„C–C„CSiMe3 yielded
a titanacyclopropene [4] (Scheme 1C). Earlier we described simple
derivatisation reactions of 1 by acidolysis with HCl or by hydroge-
nation to a titanacyclopropane and the subsequent reaction with
Br2 affording the correspondingly dihalogenated complexes, resp.
[7].
Cp⁄TiCl3/MAO or Cp⁄TiMe3/MAO (Cp⁄ =
g
5-C5Me5) display a high
activity in the production of syndiotactic polystyrene [2]. In spite
of the extensive investigations, less is known about reactive inter-
mediates, and so there is a great interest in the synthesis and char-
acterisation of new complexes of this type and their performance
in catalytic reactions [3]. Recently we reported different C–C
coupling reactions of decamethyltitanocene generated in the
Cp⁄2TiCl2/Mg system with various disubstituted 1,3-butadiynes.
The products of these reactions vary depending on the nature of
the substituents of the diynes [4,5]. For Cp⁄2TiCl2, a reduction by
Mg in the presence of the disubstituted butadiynes RC„C–C„CR0
provides a new method for the generation of functionalised pen-
tamethylcyclopentadienyl derivatives by the formation of different
C–C coupling products of the butadiyne with the pentamethylcy-
clopentadienyl ligand. When using the decamethyltitanocene frag-
ment, [Cp⁄2Ti], the reaction depends strongly on the substituents R
and R0 of the butadiynes and different products were isolated [5–
7]. For R = R0 = tBu, a coupling of the butadiyne with two methyl
Here we report further investigations of reactions of 1 with HX,
e.g. full characterisation of all products and, in particular on the
fluorination with Et3Nꢀ3HF.
2. Experimental
2.1. General
All operations were carried out under argon with standard
Schlenk techniques or in a glovebox. Prior to use nonhalogenated
solvents (including benzene-d6) were freshly distilled from sodium
⇑
Corresponding authors. Tel.: +49 381 1281 176; fax: +49 381 1281 5176.
E-mail address: uwe.rosenthal@catalysis.de (U. Rosenthal).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.03.025

V.V. Burlakov et al. / Inorganica Chimica Acta 401 (2013) 76–80
77
Scheme 1. Reactions of decamethyltitanocene generated in the Cp⁄2TiCl2/Mg system with various disubstituted 1,3-butadiynes.
tetraethylaluminate and stored under argon. Cp⁄2TiCl2 and tBu–C2–
C2–tBu were purchased from MCAT (Metallocene Catalysts and Life
Science Technologies, Konstanz, Germany) and Sigma Aldrich and
used without further purification. The following instruments were
used: NMR spectra: Bruker AV400 and AV300, respectively. The
spectra were assigned with the help of DEPT and correlation exper-
iments. Chemical shifts 1H, 13C: relative to SiMe4, referenced to the
solvent signals: benzene-d6 (dH 7.16, dC 128.0); 19F chemical shifts
are given relative to CFCl3 and 15N chemical shifts relative to nitro-
CH). 13C{1H} NMR (benzene-d6, 100 MHz, 297 K): d = 13.75, 14.01,
14.29 (Me–Cp); 27.31, 27.87 (Me–tBu); 30.38, 32.02 (CH2); 33.03,
35.16 (Cq–tBu); 44.34, 53.04, 129.75, 131.90 (CH); 137.19,
137.81, 138.52, 141.38, 141.84 (Cq–Cp). MS (70 eV, m/z): 452
[M]+ 417 [MꢂCl]+, 382 [Mꢂ2Cl]+, 360 [MꢂClꢂtBu]+.
2.3. Preparation of 3-Br and 4-Br
0.4 mL (2.4 mmol) of a 48% solution of HBr in water were added
to a solution of 1 (0.283 g, 0.59 mmol) in 5 mL of toluene. The color
of the mixture changed quickly from yellow to red-brown. After
2 h at room temperature the complexes 2-Br and 4-Br had formed
in a ratio 6.7:1 (checked by 1H NMR). After heating of the mixture
(80 °C) for 2 days followed by evaporation to dryness in vacuo a
crude mixture of the complexes 2-Br (7%), 3-Br (30%) and 4-Br
(63%) was isolated. Several recrystallisations from n-hexane gave
0.115 g of pure 4-Br.
methane (N = 10.136767 MHz). Detailed NMR data of complexes
4-Cl, 4-Br, 2-F and 5 as well as the assignment of all chemical shifts
could be found in the Supporting Information. – MS: Finnigan MAT
95-XP from Thermo-Electron – Elemental analysis: Leco Tru Spec
elemental analyzer – Melting points: Büchi 535 apparatus. Melting
points are uncorrected and were measured in sealed capillaries un-
der Argon. Compound 1 was prepared according to a published
procedure [5].
2.2. Preparation of 3-Cl and 4-Cl
2.3.1. Analytical data of compound 3-Br
Red crystals. 1H NMR (benzene-d6, 300 MHz, 297 K): d = 1.96 (s,
15H, Me–Cp). 13C{1H} NMR (benzene-d6, 75 MHz, 297 K): d = 15.4
(Me–Cp); 138.1 (Cq–Cp).
Complex 1 (0.666 g, 1.39 mmol), solved in 10–15 mL of toluene,
was treated with 2 mL (8.0 mmol) of a 4 M solution of HCl in 1,4-
dioxane. The color of the mixture rapidly changed from yellow to
red-brown and contained, as checked by NMR, almost pure com-
plex 2-Cl [7]. After heating (80 °C) for 10 days, the solution was
cooled to r.t. and evaporated to dryness in vacuo. 1H NMR spec-
trum of the raw material revealed the formation of 2-Cl (13%), 3-
Cl (42%) and 4-Cl (45%). After several recrystallisations from n-hex-
ane 0.064 g of 3-Cl and 0.055 g of 4-Cl have been isolated.
2.3.2. Analytical data of compound 4-Br
Dark red crystals. Yield: 0.115 g (0.196 mmol, 33 % referred to
Ti). M.p. 193–194 °C. Elemental Anal. Calc. for
C22H35Br3Ti
(587.09): C, 45.01; H, 6.01. Found: C, 44.63; H, 5.59%. 1H NMR (ben-
zene-d6, 400 MHz, 297 K): d = 0.91 (s, 9H, CMe3); 0.92 (s, 9H,
CMe3); 1.89 (dt, 2J ꢁ 14 Hz, 3J ꢁ 5 Hz, 1H, CH); 1.93 (s, 3H, Me–
Cp); 2.12 (s, 3H, Me–Cp); 2.21 (s, 3H, Me–Cp); 2.45 (dd,
2J = 16.8 Hz, 3J = 12.8 Hz, 1H, CH2); 3.12 (dd, 2J = 14.4 Hz,
3J = 5.2 Hz, 1H, CH2); 3.41 (ddd, 3J = 8.6/12.8/4.4 Hz, 1H, CH);
2.2.1. Analytical data of compound 3-Cl
Red crystals. Yield: 0.064 g (0.22 mmol, 16% referred to Ti). M.p.
231–233 °C. Elemental Anal. Calc. for C10H15Cl3Ti (289.45): C,
41.49; H, 5.22. Found: C, 41.19; H, 5.24%. 1H NMR (benzene-d6,
400 MHz, 297 K): d = 1.91 (s, 15 H, Me–Cp) (see also Ref. [8]).
13C{1H} NMR (benzene-d6, 100 MHz, 297 K): d = 14.01 (Me–Cp);
137.36 (Cq–Cp).
3.57, (dd, 2J = 16.8 Hz, 3J = 4.4 Hz, 1H, CH2); 3.77 (t, 2J ꢁ J ꢁ 14 Hz,
3
1H, CH2); 5.26 (m, 1H, CH); 5.29 (m, 1H, CH). 13C{1H} NMR (ben-
zene-d6, 100 MHz, 297 K): d = 15.22, 15.28, 15.87 (Me–Cp,);
27.33, 27.88 (Me–tBu); 31.85, 33.05 (CH2); 33.05, 35.19 (Cq–tBu);
44.26, 53.19, 129.74, 131.89 (CH); 137.63, 138.15, 139.71, 142.38,
143.02 (Cq–Cp).
2.2.2. Analytical data of compound 4-Cl
Dark red crystals. Yield: 0.055 g (0.12 mmol, 8% referred to Ti).
M.p: 196–197 °C. Elemental Anal. Calc. for C22H35Cl3Ti (453.74):
C, 58.24; H, 7.77. Found: C, 58.03; H, 7.47%. 1H NMR (benzene-d6,
400 MHz, 297 K): d = 0.91 (s, 9H, CMe3); 0.92 (s, 9H, CMe3); 1.88
(dt, 3J ꢁ 5/5/14 Hz, 1H, CH); 1.91 (s, 3H, Me–Cp); 2.02 (s, 3H, Me–
Cp); 2.12 (s, 3H, Me–Cp); 2.44 (dd, 2J = 16.8 Hz, 3J = 12.8 Hz, 1H,
CH2); 3.07 (dd, 2J = 14.4 Hz, 3J = 5.3 Hz, 1H, CH2); 3.38 (ddd,
3J ꢁ 4/9/13 Hz, CH); 3.54 (dd, 2J = 16.8 Hz, 3J = 4.4 Hz, 1H, CH2);
3.63 (t, 2J ꢁ 3J ꢁ 14 Hz, 1H, CH2); 5.26 (m, 1H, CH); 5.27 (m, 1H,
2.4. Preparation of 2-F and 5
Complex 1 (0.917 g, 1.91 mmol) was dissolved in 20 mL of THF,
and Et3Nꢀ3HF (0.21 mL, 1.29 mmol) was added to the yellow–green
solution, which immediately became dark and then yellow. This
yellow solution was concentrated in vacuo to 10 mL and allowed
to stand at ꢂ78 °C. After 1 day the cold solution was filtered and
evaporated to dryness under reduced pressure. The crude residue
was a mixture of complexes 2-F (85%) and 5 (15%) (checked by

78
V.V. Burlakov et al. / Inorganica Chimica Acta 401 (2013) 76–80
1H NMR). After extraction with n-hexane (3 ꢃ 15 mL, 50 °C) an un-
solved deposit of almost pure 5 (0.101 g) was obtained, which was
dissolved in 15 mL of warm n-hexane (60 °C). After filtration of the
warm solution and standing 1 day at room temperature light-yel-
low crystals had formed, which were separated from the mother li-
quor, washed with n-hexane and dried in vacuo to give 0.015 g of
analytically pure 5. The collected n-hexane solutions (extraction)
were filtered, concentrated in vacuo (20–25 mL) and cooled to
ꢂ78 °C. After 1 day at this temperature yellow crystals had formed
which were separated from the mother liquor by decanting,
washed with cold n-hexane and dried in vacuo to give yellow crys-
tals of 2-F.
Table 1
Crystallographic data for complexes 2-F and 4-Cl.
2-F
32H50F2Ti
4-Cl
Chemical formula
C
C22H35Cl3Ti
453.75
red
M (g molꢂ1
)
520.62
yellow
orthorhombic
P212121
10.3940(1)
15.2446(2)
18.0777(2)
90.00
90.00
90.00
2864.45(6)
4
1.210
Color
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
ꢀ
P1
9.3969(10)
11.5366(11)
11.951(2)
103.627(5)
97.146(5)
112.576(5)
1128.8(3)
2
1.335
0.739
100(2)
9666
5378
4081
244
0.931
0.0359
0.0921
a
(°)
b (°)
c
(°)
V (Å3)
Z
Density (g cmꢂ3
)
2.4.1. Analytical data of compound 2-F
l
(Mo K
a
) (mmꢂ1
)
0.330
Yellow crystals: Yield: 0.610 g (1.17 mmol, 61% referred to Ti).
M.p. 202–204 °C. Elemental Anal. Calc. for C32H50F2Ti (520.34): C,
73.83; H, 9.68. Found: C, 73.98; H, 9.85%. 1H NMR (benzene-d6,
300 MHz, 297 K): d = 1.00 (s, 9H, CMe3), 1.00 (s, 9H, CMe3); 1.82
(s, 3H, Me–Cp); 1.89 (s, 15H, Me–Cp); 1.90 (s, 3H, Me–Cp); 1.92
(s, 3H, Me–Cp); 2.02 (dt, 2J = 13.8 Hz, 3J = 5 Hz, 1H, CH); 2.33 (dd,
2J = 16 Hz, 3J = 12.9 Hz, 1H, CH2); 2.82 (dd, 2J = 14.2 Hz, 3J = 5.4 Hz,
1H, CH2); 2.94 (dd, 2J = 16 Hz, 3J = 5.1 Hz, 1H, CH2); 3.23
T (K)
150(2)
27898
6826
6473
330
1.024
0.0315
0.0857
Number of reflections (measured)
Number of reflections (independent)
Number of reflections (observed)
Parameters
Goodness-of-fit (GOF) on F2
R1 (I > 2
wR2 (all data)
r
(I))
3
(t, 2J ꢁ J ꢁ 14 Hz, 1H, CH2); 3.26 (m, 3J = 12.8/5.3 Hz, 1H, CH);
5.33 (m, 1H, CH); 5.35 (m, 1H, CH). 13C{1H} NMR (benzene-d6,
75 MHz, 297 K): d = 10.75, 11.33, 11.33, 11.62 (Me–Cp); 26.90
(CH2); 27.63, 28.20 (Me–tBu); 28.52 (CH2); 33.22, 35.13 (Cq–
tBu); 45.37, 52.75 (CH); 123.98, 124.30, 125.00, 126.82, 128.3,
129.39 (Cq–Cp); 130.33, 131.80 (CH). 19F NMR (benzene-d6,
3. Results and discussion
The reaction of 1 with HX (X = Cl, Br) leads in the first step to the
formation of 2-Cl resp. 2-Br (Scheme 2). Complex 2-Br has been
synthesised earlier starting from 1 but using two synthetic steps
[7].
2
2
284.4 MHz, 297 K): d = 74.8 (d, JF,F = 27 Hz); 73.7 (d, JF,F = 27 Hz).
MS (70 eV, m/z): 501 [MꢂF]+, 385 [MꢂCp⁄]+, 366 [MꢂCp⁄ꢂF]+, 325
[MꢂCp⁄ꢂtBu]+, 309 [MꢂCp⁄ꢂtBuꢂF]+, 271 [MꢂCp⁄ꢂ tBu]+.
Complexes 2-Cl and 2-Br, however, are unstable toward an ex-
cess of HX (X = Cl, Br), implying an acidolysis either of the Cp⁄ or
the modified Cp⁄ ligand, and gives after several days besides
Cp⁄TiX3 (3-Cl, 3-Br) also the complexes 4-Cl and 4-Br with a chiral
cyclopentadienyl ligand (Scheme 2). 4-Br was obtained previously
as a side product in the reaction of 2-Br with an excess of bromine
and was characterised only by X-ray crystallography [11].
In the case of X = Cl after 10 days at 80 °C, a different percentage
of the products in the mixture was detected: 2-Cl (13%), 3-Cl (42%)
and 4-Cl (45%). For X = Br after 2 days at the same temperature a
mixture of 2-Br (7%), 3-Br (30%) and 4-Br (63%) was isolated. The
complexes 3-Cl, 3-Br, 4-Cl and 4-Br were isolated from the reac-
tion mixtures and fully characterised by NMR spectroscopy.
NMR data of 4-Cl and 4-Br verify a titanium complex with one
modified Cp⁄ ligand. The presence of a noncoordinated double
bond was confirmed by signals in both 1H NMR (d: 4-Cl: 5.26,
5.27 ppm; 4-Br: 5.26, 5.29 ppm) and 13C NMR spectra (d: 4-Cl:
129.75, 131.90 ppm; 4-Br: 129.74, 131.89 ppm). It is a characteris-
tic feature of this ligand system (also observed for the complexes 2,
5 and others [5,7]) that the resonances of the two olefinic protons
exhibit a very small chemical shift difference.
2.4.2. Analytical data of compound 5
Light yellow crystals. Yield: 0.101 (0.11 mmol, 12% referred to
Ti). M.p. 227–229 °C. Elemental Anal. Calc. for C50H86F7NTi2
(929.9): C, 64.58; H, 9.32; N, 1.51. Found: C, 65.03; H, 9.11; N,
1.47%. 1H NMR (benzene-d6, 300 MHz, 297 K): d = 0.70 (t, 9H,
Me–Et3N); 1.13 (s, 18H, CMe3); 1.15 (s, 18H, CMe3); 1.19 (2H,
CH); 2.17 (s, 6H, Me–Cp); 2.17 (s, 6H, Me–Cp); 2.30 (s, 6H, Me–
Cp); 2.53 (2H, CH2); 2.54 (m, 6H, CH2–Et3N); 3.07 (dd,
2J = 14.1 Hz, 3J = 4.9 Hz, 2H, CH2); 3.49 (2H, CH2); 3.50 (2H, CH);
3.67 (dd, 2J = 16.1 Hz, 3J = 4.8 Hz, 2H, CH2); 5.48 (2H, CH), 5.51
(2H, CH); 8.5 (br, 1H, NH). 13C{1H} NMR (benzene-d6, 100 MHz,
297 K): d = 8.18 (Me–Et3N); 11.37, 11.88, 11.92 (Me–Cp); 27.67
(CH2); 27.92, 28.38 (Me–tBu); 29.22 (CH2); 33.33, 35.23 (Cq–
tBu); 45.07 (CH); 45.20 (CH2–Et3N); 52.80 (CH); 130.30 (CH);
130.78 (Cq–Cp); 131.2 (br, Cq–Cp); 132.64 (CH); 132.9 (br, Cq–
Cp); 134.35 (Cq–Cp). 19F NMR (benzene-d6, 282.4 MHz, 297 K):
d ꢁ ꢂ42 (br, 1F), ꢁꢂ8 (br, 2F), ꢁ82 (br, 2F), 156.2 (2F). 15N NMR
(benzene-d6, 30.4 MHz, 297 K): d = ꢂ326.1. MS (70 eV, m/z): 385
[Cp’TiF2]+, 328 [Cp’TiF2ꢂtBu]+, 308 [Cp’TiFꢂtBuH]+, 299 [Cp0]+,
271 [Cp’TiF2ꢂ2tBu]+, 101 [NEt3]+.
As described for the bromide congener 4-Br [11], in the molec-
ular structure of 4-Cl (Fig. 1) the titanium centre is surrounded by
three halogenide atoms which adopt with the
g
5-coordinated
modified Cp⁄ ligand a piano-stool like coordination geometry.
The cyclooctene unit is oriented away from the metal centre and
there is no hint for any interaction of its double bond (C8–C9
1.333(3) Å) with the metal. Complex 4-Cl crystallises in the centro-
2.5. Crystallographic details
Single crystals of 2-F and 4-Cl were obtained from n-hexane by
fractional crystallisation. Data were collected on Bruker APEX II dif-
ꢀ
symmetric space group P1, therefore the R,R/S,S enantiomers are
fractometers using graphite-monochromated Mo K
structures were solved by direct methods (SHELXS-97) [9] and re-
fined by full-matrix least-squares techniques on F2
a
radiation. The
present in the crystal. As it was already described for other reac-
tions of 1 the chirality (R,R/S,S) once defined for the starting com-
plex 1 [5] is preserved.
(
SHELXL-97) [9].
Diamond was used for graphical representations [10].
Crystal data and details of the data collection and the structure
refinement of complexes 2-F and 4-Cl are given in Table 1.
The reaction of 1 with an excess of Et3Nꢀ3HF resulted in the for-
mation of the difluoride 2-F as well as a dimeric anionic heptaflu-
oride complex 5 (Scheme 3).

V.V. Burlakov et al. / Inorganica Chimica Acta 401 (2013) 76–80
79
Scheme 2. Reactions of 1 with an excess of HCl and HBr.
Fig. 1. Molecular structure of 4-Cl with thermal ellipsoids set at 30% probability.
All hydrogen atoms have been omitted for clarity. Important bond lengths [Å]
and angles [°]: Ti–Cl1 2.2449(6), Ti–Cl2 2.2446(7), Ti–Cl3 2.2382(7), C1–C5
1.428(3), C5–C6 1.503(3), C6–C7 1.549(3), C7–C8 1.514(3), C8–C9 1.333(3), C9–
C10 1.513(3), C10–C11 1.544(3), C1–C11 1.504(3), Cl1–Ti–Cl2 102.72(3), Cl1–Ti–Cl3
102.19(3), C5–C6–C7 116.0(2), C6–C7–C8 112.3(2), C7–C8–C9 129.2(2), C8–C9–C10
132.3(2), C9–C10–C11 113.6(2), C10–C11–C1 110.0 (2) .
Fig. 2. Molecular structure of 2-F with thermal ellipsoids set at 30% probability. All
hydrogen atoms have been omitted for clarity. Important bond lengths [Å] and
angles [°]: Ti–F1 1.8596(12), Ti–F2 1.8561(11), C1–C2 1.417(2), C2–C3 1.510(2),
C3–C4 1.540(2), C4–C5 1.516(2), C5–C6 1.329(2), C6–C7 1.511(2), C7–C8 1.537(2),
C1–C8 1.506(2), F1–Ti–F2 96.81(8), C4–C5–C6 131.30(13) C5–C6–C7 130–31(13),
C6–C7–C8 108.80(12).
Yellow crystals of 2-F suitable for an X-ray crystal structure
analysis were isolated in 61% yield from n-hexane (Fig. 2).
The molecular structure of 2-F shows a tetrahedral arrangement
of one pentamethylcyclopentadienyl and one 3,4,5-trimethylcyclo-
From the reaction of 1 with an excess of Et3Nꢀ3HF the second
pentadienyl ligand anellated in 1,2 positions with
a 3,6-di-
product
5 was isolated in 11% yield (Scheme 3). Detailed
tert-butylcyclooct-4-ene ring and two fluorine ligands at the
titanium centre. Altogether it is very similar to that of the congener
2-Cl and 2-Br [7] as shown in the C–C double bond length of the
cyclooctene ring (2-F: 1.329(2) Å, 2-Cl: 1.313(6), 2-Br: 1.318(8) Å)
and the bite angle between the functionalised and nonfunctiona-
lised cyclopentadienyl ligands (2-F: 139°, 2-Cl: 138°, 2-Br: 136°).
Concerning the NMR data of the Cp⁄ and the modified cyclopenta-
dienyl ligand in 2-F in comparison to 2-Br and 2-Cl there were
found also similar 1H and 13C resonances. 19F NMR show two dou-
blets (74.8 and 73.7 with 2JF,F = 27 Hz) close to the value found for
related titanocene fluoride complexes [12–15].
NMR investigations of
5
were performed and revealed the
formation of a dimeric titanium species [Et3NH]+ [({
g
5-C5Me3
(–CH2CH(tBu)CH = CHCH(tBu)CH2–)}Ti)2F7]ꢂ (5) where two Cp’TiF2
units (Cp0 = modified Cp⁄ ligand) are connected by three fluorine
bridges. NMR spectra of 5 shows signals of the cation Et3NH+ (1H
NMR: d 0.70, 2.54, 8.5 ppm; 15N NMR: d ꢂ326.1 ppm rel. to nitro-
methane) and of one functionalised cyclopentadienyl ligand, with
resonances in good accordance with 2-F. Moreover 19F NMR spec-
troscopy gave additional information about fluorine coordination
environment – four different signals were detected: d ꢂ42 (br,
1F), ꢂ8 (br, 2F), 82 (br, 2F), 156.2 (2F) which can be assigned to four
Scheme 3. Reaction of 1 with an excess of Et3Nꢀ3HF.

80
V.V. Burlakov et al. / Inorganica Chimica Acta 401 (2013) 76–80
(2 different) terminal and three bridging fluorine atoms (cis/trans
position). The broadening of the 19F NMR resonances at r.t. can be
explained by dynamic processes, e.g. by exchange of fluoride ions
between bridging and terminal positions or e.g. by assuming a
Fꢀ ꢀ ꢀH–N hydrogen bond flopping process among various fluorine
atoms, which is fast enough to average the multiplet structure of
fluorine resonances. Such fluorine bridges are also obtained for
the anion in [Hdmpy]+ [(Cp⁄Ti)2F7]ꢂ, which was achieved by the
reaction of Cp⁄TiF3 with dmpy 2HF (dmpy = 2,6-dimethylpyridine)
[13]. It was characterised by X-ray structural analysis and 19F NMR
investigations, which were performed at different temperatures
and revealed similar effects [13–15], as for complex 5. Since the
Appendix A. Supplementary material
CCDC 915021 and 915022 contains the supplementary crystal-
lographic data for 2-F and 4-Cl. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.ica.2013.03.025.
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We would like to thank our technical and analytical staff for
assistance. Financial support by Deutsche Forschungsgemeinschaft
(RO 1269/8-1) and the Russian Foundation for Basic Research
(Project code 12-03-00036-a) is gratefully acknowledged.