Synthesis and x-ray crystal structure determination of new zwitterionic complexes of titanocene

Article abstract of DOI:10.1021/om0103052

The reaction of (η⁵-ⁱPrC₅ H₄)₂Ti(Me₃SiC₂SiMe₃) (2) with B(C₆F₅)₃ in toluene at room temperature produces the zwitterionic titanium(III) complex (η⁵-ⁱPrC₅H₄)[η⁵- {1,3-ⁱPrC₅H₃B-(C₆ F₅)₃}]Ti (3) in which the 3-hydrogen atom of one of the C₅ rings is substituted by a B(C₆F₅)₃ group. The complex is analogous in its structure to the previously described titanium(III) zwitterion Cp[η⁵-C₅H₄B(C₆ F₅)₃]Ti (1) formed in the interaction of B(C₆F₅)₃ with Cp₂Ti(Me₃-SiC₂SiMe₃). A characteristic feature of both zwitterionic complexes is the presence of coordinative bonds between the ortho-fluorine atoms of two C₆F₅ substituents and the positively charged titanium center. Complex 1 is also obtained by the reaction of B(C₆F₅)₃ with Cp₂Ti(PhC₂SiMe₃). The oxidation of 1 and 3 by air oxygen affords the zwitterionic titanoxanes {Cp[η⁵-C₅H₄B(C₆ F₅)₃]Ti}₂O (5), respectively, which contain two zwitterionic units in the molecule. In each of these units, only one ortho-fluorine atom of a B(C₆F₅)₃ group is involved in the coordination to the titanium atom. Complex 1 readily reacts also with acetone to give the zwitterionic adduct Cp[η⁵-C₅H₄B(C₆ F₅)₃]Ti(Me₂CO) (6), wherein the molecule of acetone is bonded to the Ti(III) center through the oxygen atom. In this adduct too, only one ortho-fluorine atom of a B(C₆F₅)₃ group is coordinated to the metal.

Full text of DOI:10.1021/om0103052

4072
Organometallics 2001, 20, 4072-4079
Syn th esis a n d X-r a y Cr ysta l Str u ctu r e Deter m in a tion of
New Zw itter ion ic Com p lexes of Tita n ocen e
V. V. Burlakov,† P. Arndt,‡ W. Baumann,‡ A. Spannenberg,‡ U. Rosenthal,*,‡
A. V. Letov,† K. A. Lyssenko,† A. A. Korlyukov,† L. I. Strunkina,†
M. Kh. Minacheva,† and V. B. Shur*,†
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
Vavilov Street 28, 117813 Moscow, Russia, and Institut fu¨r Organische Katalyseforschung an
der Universita¨t Rostock, Buchbinderstrasse 5-6, D-18055 Rostock, Germany
Received April 12, 2001
The reaction of (η5-iPrC5H4)2Ti(Me3SiC2SiMe3) (2) with B(C6F5)3 in toluene at room
temperature produces the zwitterionic titanium(III) complex (η5-iPrC5H4)[η5-{1,3-iPrC5H3B-
(C6F5)3}]Ti (3) in which the 3-hydrogen atom of one of the C5 rings is substituted by a B(C6F5)3
group. The complex is analogous in its structure to the previously described titanium(III)
zwitterion Cp[η5-C5H4B(C6F5)3]Ti (1) formed in the interaction of B(C6F5)3 with Cp2Ti(Me3-
SiC2SiMe3). A characteristic feature of both zwitterionic complexes is the presence of
coordinative bonds between the ortho-fluorine atoms of two C6F5 substituents and the
positively charged titanium center. Complex 1 is also obtained by the reaction of B(C6F5)3
with Cp2Ti(PhC2SiMe3). The oxidation of 1 and 3 by air oxygen affords the zwitterionic
titanoxanes {Cp[η5-C5H4B(C6F5)3]Ti}2O (4) and {(η5-iPrC5H4)[(η5-{1,3-iPrC5H3B(C6F5)3}]Ti}2O
(5), respectively, which contain two zwitterionic units in the molecule. In each of these units,
only one ortho-fluorine atom of a B(C6F5)3 group is involved in the coordination to the titanium
atom. Complex 1 readily reacts also with acetone to give the zwitterionic adduct Cp[η5-
C5H4B(C6F5)3]Ti(Me2CO) (6), wherein the molecule of acetone is bonded to the Ti(III) center
through the oxygen atom. In this adduct too, only one ortho-fluorine atom of a B(C6F5)3 group
is coordinated to the metal.
In tr od u ction
(Me3SiC2SiMe3)8 with B(C6F5)3 in toluene at room
temperature. It turned out that in the course of this
reaction electrophilic substitution of a hydrogen atom
in one of the η5-C5H5 rings by a B(C6F5)3 group takes
place and a zwitterionic complex of trivalent titanium,
Cp[η5-C5H4B(C6F5)3]Ti (1), containing no σ-bonded or-
ganic radicals at the metal atom is produced. Later, in
studying the interaction of B(C6F5)3 with the phenyl-
(trimethylsilyl)acetylene complex of permethyltitanocene
Cp*2Ti(PhC2SiMe3)8b,9 at 20 °C, we observed10 electro-
philic substitution of a hydrogen atom in one of the
methyl groups of the Cp* ring by a B(C6F5)3 moiety. As
a result of this reaction, the zwitterionic Ti(III) complex
Cp*[η5-C5Me4CH2B(C6F5)3]Ti was formed. Under similar
conditions, the reaction of Cp*2Zr(PhC2SiMe3)11 with
B(C6F5)3 afforded a zwitterionic Zr(IV) derivative, Cp*-
[η5-C5Me4CH2B(C6F5)3]ZrC(Ph)dCH(SiMe3), containing
a σ-alkenyl group at the zirconium center.10
Zwitterionic metallocenes of the group IVB metals are
a very promising class of compounds owing to their
ability to catalyze the olefin polymerization in the
absence of Lewis-acidic cocatalysts. The first syntheses
of such metallocenes have been described in 1989 by
Hlatky et al.1 Subsequently, a large number of similar
betaine complexes has been prepared and structurally
characterized (see e.g. ref 2 and refs 3-6). In the
majority of presently known zwitterionic titanocene,
zirconocene, and hafnocene derivatives, a metal atom
is in the +4 oxidation state and contains at least one
σ-bonded organic group.
Recently, we have reported7 on the synthesis and
structure of a novel type of zwitterionic metallocene
which was isolated from the interaction of the bis-
(trimethylsilyl)acetylene complex of titanocene Cp2Ti-
* Corresponding authors. E-mail: uwe.rosenthal@ifok.uni-rostock.de
and vbshur@ ineos.ac.ru.
(7) (a) Burlakov, V. V.; Troyanov, S. I.; Letov, A. V.; Mysov, E. I.;
Furin, G. G.; Shur, V. B. Izvest. Akad. Nauk, Ser. Khim. 1999, 1022;
Russ. Chem. Bull. 1999, 48, 1012 (Engl. Transl.). (b) Burlakov, V. V.;
Troyanov, S. I.; Letov, A. V.; Strunkina, L. I.; Minacheva, M. Kh.;
Furin, G. G.; Rosenthal, U.; Shur, V. B. J . Organomet. Chem. 2000,
598, 243.
(8) (a) Burlakov, V. V.; Rosenthal, U.; Petrovsky, P. V.; Shur, V. B.;
Vol’pin, M. E. Metalloorg. Khim. 1988, 1, 953; Organomet. Chem. USSR
1988, 1, 526 (Engl. Transl.). (b) Burlakov, V. V.; Polyakov, A. V.;
Yanovsky, A. I.; Struchkov, Yu. T.; Shur, V. B.; Vol’pin, M. E.;
Rosenthal, U.; Go¨rls, H. J . Organomet. Chem. 1994, 476, 197.
(9) Rosenthal, U.; Go¨rls, H.; Burlakov, V. V.; Shur, V. B.; Vol’pin,
M. E. J . Organomet. Chem. 1992, 426, C53.
† A.N. Nesmeyanov Institute of Organoelement Compounds.
‡ Institut fu¨r Organische Katalyseforschung an der Universita¨t
Rostock.
(1) Hlatky, G. G.; Turner, H. W.; Eckman, R. R. J . Am. Chem. Soc.
1989, 111, 2728.
(2) Piers, W. E. Chem. Eur. J . 1998, 4, 13.
(3) Lee, L. W. M.; Piers, W. E.; Parvez, M.; Rettig, S. J .; Young, V.
G. Organometallics 1999, 18, 3904.
(4) Cowley, A. H.; Hair, G. S.; McBarnett, B. G.; J ones, R. A. Chem.
Commun. 1999, 437.
(5) Lancaster, S. J .; Al-Benna, S.; Thornton-Pett, M.; Bochmann,
M. Organometallics 2000, 19, 1599.
(10) Burlakov, V. V.; Pellny, P.-M.; Arndt, P.; Baumann, W.;
Spannenberg, A.; Shur, V. B.; Rosenthal, U. Chem. Commun. 2000,
241.
(6) Dahlmann, M.; Erker, G.; Fro¨hlich, R.; Meyer, O. Organometal-
lics 2000 19, 2956.
10.1021/om0103052 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/16/2001

New Zwitterionic Complexes of Titanocene
Organometallics, Vol. 20, No. 19, 2001 4073
Sch em e 1
In the present paper, data on the reactivity of the
acetylene complexes Cp2Ti(PhC2Ph),12 Cp2Ti(PhC2-
SiMe3),8b,13 and (η5-iPrC5H4)2Ti(Me3SiC2SiMe3) (2) to-
ward B(C6F5)3 are reported. Also, selected reactions of
the obtained Ti(III) zwitterions with oxygen and acetone
are described. These studies have led to the synthesis
of a series of new zwitterionic complexes of titanocene,
including those containing two zwitterionic units in the
molecule.
1), which revealed the presence of coordinative bonds
between the ortho-fluorine atoms (F(22) and F(34)) of
two C6F5 rings and the positively charged titanium
center (the Ti(1)‚‚‚F(22) and Ti(1)‚‚‚F(34) distances are
2.264(2) and 2.256(2) Å, respectively). As a result of the
coordination of the F(22) and F(34) atoms to titanium,
the C(22)-F(22) and C(34)-F(34) bonds become longer
(1.401(3) and 1.394(3) Å, respectively) as compared with
other C-F bonds in the molecule of 3 (1.341-1.360 Å,
Resu lts a n d Discu ssion
Rea ction s of Acetylen e Com p lexes Cp 2Ti(P h C2-
SiMe3), Cp 2Ti(P h C2P h ), a n d (η5-iP r C5H4)2Ti(Me3Si-
C2SiMe3) (2) w ith B(C6F 5)3. The reactions were carried
out in toluene solution at room temperature and equimo-
lar ratio of the reagents. Under these conditions, the
interaction of Cp2Ti(PhC2SiMe3) with B(C6F5)3 gave the
same zwitterionic titanium(III) complex 1, which was
isolated by us7 from the reaction of B(C6F5)3 with Cp2-
Ti(Me3SiC2SiMe3) (see above). However, the use of Cp2-
Ti(PhC2SiMe3) instead of Cp2Ti(Me3SiC2SiMe3) strongly
diminished the rate of the process. The tolane complex
of titanocene Cp2Ti(PhC2Ph) did not react with B(C6F5)3
at all under the same conditions, not even over a period
of a month. Thus, the replacement of Me3Si groups in
the acetylene ligand by Ph substituents decreases
sharply the reactivity of the corresponding acetylene
complex Cp2Ti(R1C2R2) toward B(C6F5)3.
The reaction of B(C6F5)3 with acetylene complex 2,
which was prepared by the interaction of (η5-iPrC5H4)2-
TiCl2 with Mg in the presence of Me3SiCtCSiMe3 in
THF (see “Experimental Procedure”), proceeds in the
same way as in the case of Cp2Ti(Me3SiC2SiMe3) and
Cp2Ti(PhC2SiMe3). As a result of the reaction, the
zwitterionic Ti(III) complex (η5-iPrC5H4)[η5-{1,3-iPrC5H3B-
(C6F5)3}]Ti (3), containing a B(C6F5)3 group in 3-position
of the Cp ring relative to the iPr substituent, is produced
(see Scheme 1).
F igu r e 1. Molecular structure of complex 3 in the crystal
at the 30% probability level for thermal ellipsoids.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3
The isolated complex is a dark blue paramagnetic
crystalline solid, which rapidly decomposed on contact
with oxygen. The structure of 3 has been determined
by an X-ray diffraction study (see Figure 1 and Table
Bond Lengths
Ti(1)-C(1)
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-C(4)
Ti(1)-C(5)
Ti(1)-Cp(1)
Ti(1)-C(6)
Ti(1)-C(7)
2.255(3)
2.308(3)
2.360(3)
2.369(3)
2.302(3)
1.980(3)
2.418(3)
2.373(3)
Ti(1)-C(8)
Ti(1)-C(9)
Ti(1)-C(10)
Ti(1)-Cp(2)
Ti(1)-F(22)
Ti(1)-F(34)
C(22)-F(22)
C(34)-F(34)
2.325(3)
2.304(3)
2.333(3)
2.021(3)
2.264(2)
2.256(2)
1.401(3)
1.394(3)
(11) (a) List, A. K.; Koo, K.; Rheingold, A. L.; Hillhouse, G. L. Inorg.
Chim. Acta 1998, 270, 399. (b) Pellny, P.-M., Burlakov, V. V.;
Baumann, W.; Spannenberg, A.; Rosenthal, U. Z. Anorg. Allg. Chem.
1999, 625, 910.
(12) Shur, V. B.; Burlakov, V. V.; Vol’pin, M. E. J . Organomet. Chem.
1988, 347, 77.
(13) Burlakov, V. V.; Rosenthal, U.; Beckhaus, R.; Polyakov, A. V.;
Struchkov, Yu. T.; Oehme, G.; Shur, V. B.; Vol’pin, M. E. Metalloorg.
Khim. 1990, 3, 476; Organomet. Chem. USSR 1990, 3, 237 (Engl.
Transl.).
Bond Angles
Cp(1)-Ti(1)-Cp(2) 139.3(3) Cp(2)-Ti(1)-F(34) 106.1(2)
72.27(8)
Cp(1)-Ti(1)-F(34) 105.7(3) Ti(1)-F(22)-C(22) 141.0(2)
Cp(2)-Ti(1)-F(22) 108.5(3) Ti(1)-F(34)-C(34) 140.8(2)
Cp(1)-Ti(1)-F(22) 108.5(4) F(22)-Ti(1)-F(34)

4074 Organometallics, Vol. 20, No. 19, 2001
Burlakov et al.
Sch em e 2
av 1.354 Å). A similar structure has been established
for the above-mentioned zwitterionic complex 1; how-
ever in this complex the Ti‚‚‚F distances (2.248(2) and
2.223(3) Å) are somewhat shorter than those in 3. This
fact can be explained by a decrease in a partial positive
charge on the titanium atom in 3 due to the electron-
Oxid a tion of Com p lexes 1 a n d 3 by Oxygen . For
the transformation of the above-mentioned Ti(III) zwit-
terionic complexes into the corresponding Ti(IV) deriva-
tives, the oxidation of 1 and 3 by oxygen was carried
out in toluene at room temperature. During the course
of the reactions, a change in color of the reaction
solutions from initial dark blue to brownish-red was
observed, and new complexes {Cp[η5-C5H4B(C6F5)3]-
Ti}2O (4) and {(η5-iPrC5H4)[(η5-{1,3-iPrC5H3B(C6F5)3}]-
Ti}2O (5), respectively, were produced. A study of these
complexes by analytical and spectral means as well as
by an X-ray analysis has shown that they have unusual
structures of zwitterionic titanoxanes (see Scheme 2).
i
donating effect of the Pr groups.
The ESR spectrum of 3 in toluene at 300-350 K
shows a doublet signal (9 G) with g ) 1.966 and a(F) )
8.3 G, thus indicating the retention of only one Ti‚‚‚F
coordinative bond in the complex under such conditions.
On cooling the solution to 230 K, the spectrum becomes
more complicated: it can be tentatively treated now as
superposition of the above-mentioned doublet and a
triplet (∼5 G) with g ) 1.978 and a(2F) ) 7.5 G. The
latter suggests that at 230 K a considerable part of
complex 3 retains both coordinative Ti‚‚‚F bonds in
toluene solution.
Complex 4 is a red crystalline substance practically
insoluble in aromatic and aliphatic hydrocarbons. The
complex is moderately stable in air: its melting point
does not change after keeping 4 in air for 1 h. However,
if the time of the contact of 4 with air is increased to 3
h, its melting point is somewhat decreased. The IR
spectrum of 4 (Nujol mull) contains, in addition to the
bands of η5-C5H5, η5-C5H4, and B(C6F5)3 moieties, a
broad intense absorption band at 731 cm-1 belonging
to vibrations of the Ti-O-Ti group. According to
elemental analysis, the complex contains (after drying
for 5-10 min at 20 °C in a vacuum) half a mole of
toluene per mole of 4. For carrying out the X-ray
diffraction study of 4, the crystals of the complex were
not dried in a vacuum. Under such conditions, the
content of toluene in 4 increased to two moles.
The geometry of the bent sandwich in 3 is not
exceptional. The planes of the C5 rings form a dihedral
angle of 38.4°. The titanium atom and the coordinated
F(22) and F(34) atoms are located approximately in the
bisector plane of this angle. The coordination environ-
ment at titanium can be described as pseudotetrahedral,
with the large Cp(1)-Ti(1)-Cp(2) angle (139.3(3)°) and
small F(22)-Ti(1)-F(34) angle (72.27(8)°) due to the size
difference between the Cp ligand and fluorine atom (Cp-
(1) and Cp(2) are the centroids of Cp rings C(1)-C(5)
and C(6)-C(10), respectively). The Ti(1)-Cp(1) distance
(1.980(3) Å) is somewhat shorter than Ti(1)-Cp(2)
(2.021(3) Å), which can be due to the bonding of the Cp
ring C(1)-C(5) to titanium via the C-B-C-C-F bridges.
The Ti(1)-F(34)-C(34) and Ti(1)-F(22)-C(22) angles
are virtually the same (140.8(2) and 141.0(2) Å). The
mutual orientation of the Cp ligands in 3 is close to
staggered conformation. In complex 1, the Cp ligands
are in eclipsed conformation. The pseudotorsion C(4)-
Cp(1)-Cp(2)-C(6) angle in 3 characterizing the relative
Complex 5 is also a red crystalline solid practically
insoluble in aromatic and aliphatic hydrocarbons. Its
IR spectrum is characterized by a broad intense absorp-
tion band of the Ti-O-Ti group at 730 cm-1. The
crystals of the complex contain one mole of toluene per
mole of 5.
The structures of 4 and 5 are shown in Figures 2 and
3, respectively. The selected bond distances and angles
for 4 and 5 are listed in Tables 2 and 3. The unit cell of
4 contains two crystallographically independent mol-
ecules (4A and 4B) differing from each other only by
the mutual orientation of the noncoordinated C6F5 rings.
i
orientation of the Pr groups is 88°. The Ti-C distances
are in the range 2.30-2.42 Å. The boron atom is located
nearly exactly in the plane of the C5 ring: its displace-
ment from this plane (in the direction away from the
Ti atom) is only 0.06 Å. The C(39) and C(42) atoms of
A remarkable feature of complexes 4 and 5 is the
presence of two zwitterionic units in their molecules.
In each of these units, only one ortho-fluorine atom of a
B(C6F5)3 group is coordinated to the metal. The Ti(1)‚‚
‚F(22) and Ti(2)‚‚‚F(40) distances in 4 and 5 (see Tables
2 and 3) are notably shorter than the analogous
i
the Pr groups are displaced from the plane of the
corresponding C5 ring in the same direction by 0.12 and
0.09 Å, respectively. Coordination at the boron is
essentially tetrahedral.

New Zwitterionic Complexes of Titanocene
Organometallics, Vol. 20, No. 19, 2001 4075
F igu r e 2. Molecular structure of complex 4 in the crystal at the 30% probability level for thermal ellipsoids.
F igu r e 3. Molecular structure of complex 5 in the crystal at the 30% probability level for thermal ellipsoids.
distances in 1 and 3, which can be explained by the
higher oxidation state of titanium in 4 and 5 as
compared to that in 1 and 3. The coordinated C-F bonds
in 4 and 5 are again noticeably longer than other C-F
bonds in these molecules (av 1.351 and 1.351 Å in 4A
and 4B, respectively; 1.350 Å in 5). The Ti(1)-O(1)-
Ti(2) bond angle in both complexes is close to 180°. The
Ti-O bond lengths range from 1.83 to 1.85 Å. The Ti-
(1)-F(22)-C(22) and Ti(2)-F(40)-C(40) angles are
147.1(2)° and 147.9(1)° for 4A, 145.8(2)° and 148.5(2)°
for 4B, and 148.8(2)° and 149.1(2)° for 5.
moieties are 45-46°. The titanium atom as well as the
oxygen and coordinated fluorine atoms in each of the
zwitterionic units of 4 and 5 are disposed practically in
the bisector plane of the corresponding dihedral angle
formed by the pair of C5 rings. The dihedral angle
between these bisector planes in 4A, 4B, and 5 is 81.7°,
79.9°, and 88.9°, respectively; that is, the sandwich
fragments in both complexes are turned almost by 90°
relative to each other.
The titanium atoms in 4 and 5 again have a pseudo-
tetrahedral coordination environment. In each of the
zwitterionic units of 4 and 5, as in 1 and 3, the distance
between the Ti atom and the centroid of the C5 ring
containing a B(C6F5)3 group is somewhat shorter than
The bis(cyclopentadienyl)titanium fragments in 4 and
5 have a typically bent sandwich geometry. The dihedral
angles between the planes of the C5 rings in sandwich

4076 Organometallics, Vol. 20, No. 19, 2001
Burlakov et al.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 4A/4B
Bond Lengths
Ti(1)-C(1)
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-C(4)
Ti(1)-C(5)
Ti(1)-C(6)
Ti(1)-C(7)
Ti(1)-C(8)
Ti(1)-C(9)
Ti(1)-C(10)
Ti(1)-O(1)
Ti(1)-F(22)
Ti(1)-Cp(1)
Ti(1)-Cp(2)
Ti(2)-C(11)
2.434(3)/2.419(3)
2.332(3)/2.334(3)
2.330(4)/2.336(4)
2.315(4)/2.314(4)
2.369(3)/2.354(3)
2.372(3)/2.372(4)
2.368(3)/2.382(4)
2.383(3)/2.352(4)
2.346(3)/2.374(4)
2.381(3)/2.380(4)
1.846(2)/1.851(2)
2.184(2)/2.181(2)
2.044(3)/2.025(3)
2.070(3)/2.053(3)
2.414(3)/2.423(4)
Ti(2)-C(12)
Ti(2)-C(13)
Ti(2)-C(14)
Ti(2)-C(15)
Ti(2)-C(16)
Ti(2)-C(17)
Ti(2)-C(18)
Ti(2)-C(19)
Ti(2)-C(20)
Ti(2)-O(1)
Ti(2)-F(40)
Ti(2)-Cp(3)
Ti(2)-Cp(4)
C(22)-F(22)
C(40)-F(40)
2.376(3)/2.383(4)
2.333(4)/2.332(4)
2.330(4)/2.335(4)
2.338(3)/2.356(4)
2.382(4)/2.394(4)
2.352(4)/2.372(4)
2.362(4)/2.372(4)
2.338(4)/2.336(4)
2.391(4)/2.392(4)
1.831(2)/1.833(2)
2.241(2)/2.185(2)
2.031(3)/2.041(3)
2.055(3)/2.056(3)
1.398(4)/1.394(4)
1.386(3)/1.395(4)
Bond Angles
Cp(1)-Ti(1)-Cp(2)
Cp(1)-Ti(1)-F(22)
Cp(2)-Ti(1)-F(22)
Cp(1)-Ti(1)-O(1)
Cp(2)-Ti(1)-O(1)
O(1)-Ti(1)-F(22)
Ti(1)-F(22)-C(22)
Cp(3)-Ti(2)-Cp(4)
134.4(1)/133.4(1)
102.0(1)/102.1(1)
104.5(1)/105.7(1)
108.6(1)/108.9(1)
108.7(1)/101.4(1)
88.05(8)/86.55(9)
147.1(2)/145.8(2)
133.8(1)/133.9(1)
Cp(3)-Ti(2)-F(40)
Cp(4)-Ti(2)-F(40)
Cp(3)-Ti(2)-O(1)
Cp(4)-Ti(2)-O(1)
O(1)-Ti(2)-F(40)
Ti(2)-F(40)-C(40)
Ti(1)-O(1)-Ti(2)
104.9(1)/104.6(1)
101.8(1)/101.1(1)
109.3(1)/108.9(1)
108.4(1)/108.7(1)
88.66(8)/91.39(9)
147.9(1)/148.5(2)
176.6(1)/178.5(1)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5
were found in the structure of 5. The secondary carbon
atoms of the Pr groups in 5 also deviate considerably
i
stronger (by 0.37 Å for C(57), 0.21 Å for C(60), 0.33 Å
for C(66), 0.19 Å for C(63)) than in 3 from the corre-
sponding C5 ring plane, the strongest deviations being
Bond Lengths
Ti(1)-C(1)
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-C(4)
Ti(1)-C(5)
Ti(1)-C(6)
Ti(1)-C(7)
Ti(1)-C(8)
Ti(1)-C(9)
Ti(1)-C(10)
Ti(1)-O(1)
Ti(1)-F(22)
Ti(1)-Cp(1)
Ti(1)-Cp(2)
Ti(2)-C(11)
2.416(5)
2.325(4)
2.348(4)
2.386(5)
2.383(5)
2.478(4)
2.399(5)
2.341(5)
2.341(5)
2.387(5)
1.847(3)
2.219(3)
2.044(5)
2.070(5)
2.428(5)
Ti(2)-C(12)
Ti(2)-C(13)
Ti(2)-C(14)
Ti(2)-C(15)
Ti(2)-C(16)
Ti(2)-C(17)
Ti(2)-C(18)
Ti(2)-C(19)
Ti(2)-C(20)
Ti(2)-O(1)
Ti(2)-F(40)
Ti(2)-Cp(3)
Ti(2)-Cp(4)
C(22)-F(22)
C(40)-F(40)
2.395(5)
2.375(5)
2.330(4)
2.329(5)
2.428(5)
2.385(5)
2.341(5)
2.354(5)
2.428(5)
1.848(3)
2.226(3)
2.044(5)
2.077(5)
1.404(5)
1.409(5)
i
observed for the Pr groups in the boron-containing
rings. The Ti-C distances range from 2.32 to 2.44 Å in
4A, from 2.31 to 2.42 Å in 4B, and from 2.33 to 2.48 Å
in 5.
Rea ction of Com p lex 1 w ith Aceton e. When the
toluene solution of 1 is treated by an equimolar amount
of dry acetone at room temperature, the color of the
reaction mixture gradually turns from dark blue to
green, and within 48 h green air-sensitive paramagnetic
crystals of the acetone complex Cp[η5-C5H4B(C6F5)3]-
Ti(Me2CO) (6) are precipitated (see Scheme 3). The ESR
spectrum of 6 in toluene solution at 300 K exhibits an
intense broadened (9 G) singlet signal with g ) 1.970.
Cooling of the solution of 6 to 210 K leads to further
broadening of the signal (18 G).
An X-ray diffraction study of the toluene solvate of
the complex, 6‚0.5PhCH3, has shown that in 6 as in 4
and 5 only one ortho-fluorine atom (F(22); see Figure
4) of a B(C6F5)3 group is involved in the bonding to the
positively charged titanium center. The Ti(1)‚‚‚F(22)
distance in 6 is 2.252(2) Å (Table 4), which is noticeably
longer than the similar Ti‚‚‚F distances in 1, 4, and 5.
Correspondingly, the coordinated C(22)-F(22) bond in
6 (1.364(3) Å) is elongated to a considerably lesser extent
than those in 1, 4, and 5 (the average value of the length
of the noncoordinated C-F bonds in 6 is equal to 1.349
Å).
Bond Angles
Cp(1)-Ti(1)-Cp(2) 134.3(2) Ti(1)-O(1)-Ti(2)
Cp(1)-Ti(1)-F(22) 101.7(2) Cp(3)-Ti(2)-F(40) 101.3(2)
Cp(2)-Ti(1)-F(22) 105.3(2) Cp(4)-Ti(2)-F(40) 105.0(2)
176.3(2)
Cp(1)-Ti(1)-O(1)
Cp(2)-Ti(1)-O(1)
O(1)-Ti(1)-F(22)
108.4(2) Cp(3)-Ti(2)-O(1)
108.9(2) Cp(4)-Ti(2)-O(1)
87.3(1) O(1)-Ti(2)-F(40)
108.5(2)
107.8 (2)
89.0(1)
Ti(1)-F(22)-C(22) 148.8(2) Ti(2)-F(40)-C(40) 149.1(2)
Cp(3)-Ti(2)-Cp(4) 135.1(2)
the corresponding distance from the centroid of the
other C5 ring which does not contain a B(C6F5)3 moiety
(see Tables 2 and 3, where Cp(1), Cp(2), Cp(3), and Cp-
(4) are the centroids of the C5 rings C(1)-C(5), C(6)-
C(10), C(11)-C(15), and C(16)-C(20), respectively). The
C5 rings in the Ti(1) sandwich of both titanoxanes are
in eclipsed conformation, while the C5 rings in the Ti-
(2) sandwich are in staggered conformation. The pseudo-
torsion angles C(4)-Cp(1)-Cp(2)-C(6) and C(13)-Cp-
(3)-Cp(4)-C(16) in 5 are 151.5° and 171°, respectively.
An interesting structural peculiarity of complexes 4
and 5 is the considerably stronger deviation of the boron
atoms from the plane of the corresponding C5 ring (in
the direction away from the Ti atom) than those in 1
and 3, which is a consequence of the steric overcrowding
of the molecules of 4 and 5. In the case of 4, these
deviations are 0.27-0.28 Å, and even larger deviations
of the boron atoms (0.40 Å for B(1) and 0.38 Å for B(2))
The acetone ligand in the molecule of 6 is bonded to
titanium through the oxygen atom. The Ti(1)-O(1)
distance in 6 is 2.146(2) Å, while the C(39)-O(1) bond
length is 1.226(3) Å, which is somewhat longer than that
in free aliphatic ketones (av 1.21 Å14). The C(40)-
C(39)-O(1), C(41)-C(39)-O(1), and C(40)-C(39)-C(41)
bond angles are close to 120°.
(14) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O., Watson,
D. G.; Taylor, R. In Structure Correlation; Bu¨rgi, H.-B., Dunitz, J . D.,
Eds.; Weinheim-New York, 1994; Vol. 2, p 751.

New Zwitterionic Complexes of Titanocene
Organometallics, Vol. 20, No. 19, 2001 4077
Sch em e 3
The νCO band (1681 cm-1) in the IR spectrum of 6 is
shifted by 38 cm-1 in the low-frequency region relative
to the corresponding νCO band of free acetone. This
indicates the considerable weakening of the CdO bond
of the acetone molecule as a result of its coordination
with the positively charged titanium center of 1.
The titanium atom and the O(1) and F(22) atoms in
complex 6 form a plane which bisects the dihedral angle
(42.1°) between the planes of the C5 rings. Besides the
oxygen atom, all other non-hydrogen atoms of the
acetone ligand are located in this bisector plane as well.
The Ti(1)-O(1)-C(39) and Ti(1)-F(22)-C(22) angles in
6 are 143.2(2)° and 147.3(2)°, respectively.
Coordination at titanium in 6 as in 1 and 3-5 is
pseudotetrahedral with a Cp(1)-Ti(1)-Cp(2) angle of
139.0(2)° and a F(22)-Ti(1)-O(1) angle of 73.48(8)° (Cp-
(1) and Cp(2) are the centroids of the substituted and
unsubstituted C5 rings, respectively). The Ti(1)-Cp(1)
distance (2.022(3) Å) is again somewhat shorter than
Ti(1)-Cp(2) (2.050(3) Å). The Cp ligands are in stag-
gered conformation. The Ti-C distances span the range
2.32-2.41 Å. The displacement of the boron atom from
the plane of the corresponding C5 ring (in the direction
opposite to the Ti atom) is approximately the same (0.26
Å) as in 4 but considerably smaller than in 5.
Con clu sion
In the course of our study, a series of new zwitterionic
complexes of titanocene (3-6) have been prepared and
structurally characterized. Complexes 3 and 6 are the
Ti(III) derivatives, while the Ti atoms in 4 and 5 are in
the +4 oxidation state. In compound 3, two ortho-
fluorine atoms of a B(C6F5)3 unit are coordinated to the
metal, and in such a way the titanium atom in 3
acquires a pseudotetrahedral coordination environment.
In compounds 4-6, one of the coordination sites at
titanium is occupied by oxygen, and as a consequence,
only one ortho-fluorine atom of the B(C6F5)3 moiety is
bonded here to the metal.
Complex 3 is analogous in its structure to the previ-
ously described Ti(III) zwitterion 1.7 However, a study
of 3 by the ESR method allowed us to demonstrate for
the first time that the coordinative bonds between
fluorine atoms of a B(C6F5)3 group and the positively
charged titanium center in Ti(III) zwitterionic metal-
locenes can exist not only in the crystal but also in
solutions. The ESR spectra of 3 also evidence a suf-
ficiently high strength of these coordinative Ti‚‚‚F
bonds: one of them is retained in toluene solution even
at 77 °C, while at -43 °C a considerable part of 3 retains
both Ti‚‚‚F bonds in the solution. In the case of 1 and
6, the ESR spectra do not provide any information on
the state of these compounds in toluene medium.
Complexes 4 and 5 have unusual structures of zwit-
terionic titanoxanes and are the first examples of
metallocenes that contain two zwitterionic units in the
molecule. The complexes are sterically overcrowded. The
presence of two positively charged titanium(IV) centers
in 4 and 5 makes these complexes very promising for
catalysis.
F igu r e 4. Molecular structure of complex 6 in the crystal
at the 30% probability level for thermal ellipsoids.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 6
Bond Lengths
Ti(1)-C(1)
Ti(1)-C(2)
Ti(1)-C(3)
Ti(1)-C(4)
Ti(1)-C(5)
Ti(1)-Cp(1)
Ti(1)-C(6)
Ti(1)-C(7)
Ti(1)-C(8)
2.409(3)
2.323(3)
2.322(3)
2.326(3)
2.372(3)
2.022(3)
2.342(3)
2.359(3)
2.404(3)
Ti(1)-C(9)
2.368(3)
2.341(3)
2.050(3)
2.146(2)
2.252(2)
1.364(3)
1.226(3)
1.472(5)
1.476(5)
Ti(1)-C(10)
Ti(1)-Cp(2)
Ti(1)-O(1)
Ti(1)-F(22)
C(22)-F(22)
C(39)-O(1)
C(39)-C(40)
C(39)-C(41)
Bond Angles
Cp(1)-Ti(1)-Cp(2) 139.0(2)
Ti(1)-F(22)-C(22)
Ti(1)-O(1)-C(39)
O(1)-C(39)-C(40)
O(1)-C(39)-C(41)
147.3(2)
143.2(2)
122.1(3)
120.3(3)
Cp(1)-Ti(1)-F(22) 104.4(8)
Cp(1)-Ti(1)-O(1)
108.7(3)
Cp(2)-Ti(1)-F(22) 104.6(4)
Cp(2)-Ti(1)-O(1)
F(22)-Ti(1)-O(1)
106.9(5)
73.48(8)
C(40)-C(39)-C(41) 117.6(3)

4078 Organometallics, Vol. 20, No. 19, 2001
Burlakov et al.
Ta ble 5. Cr ysta l Da ta , Da ta Collection , a n d Str u ctu r e Refin em en t P a r a m eter s for 3-6
3
4
5
6
1
formula
molecular wt
cryst syst
space group, Z
a, Å
b, Å
C
34H21BF15Ti
C56H18B2F30OTi2 2C7H8
1578.39
monoclinic
P21/c, 8
11.198(3)
45.383(13)
24.336(7)
C68H42B2F30OTi2 C7H8
1654.57
monoclinic
P21/n, 4
15.585(3)
22.012(4)
C31H15BF15OTi /2C7H8
793.21
triclinic
P1h, 2
9.096(2)
13.153(3)
15.561(3)
67.83(3)
77.16(3)
71.89(3)
1627.0(6)
1.619
773.22
monoclinic
P21/c, 4
14.007(3)
11.252(2)
20.389(2)
c, Å
20.934(4)
R, deg
â, deg
100.52(3)
91.40(3)
105.59(3)
γ, deg
V, Å3
3159(1)
1.626
200(2)
STOE-IPDS
1.81-22.51
3.85
7424
3913
2931
464
12364(6)
1.696
110(2)
SMART 1000 CCD
2.18-27.56
3.97
12 1271
28 451
10 509
2008
0.053
0.095
6917(2)
1.589
200(2)
STOE-IPDS
1.64-24.31
3.59
20 200
10 921
4751
969
0.052
0.107
0.678/-0.354
D(calc), g cm-3
temperature, K
diffractometer
θ range (deg)
µ(Mo KR, λ ) 0.71073 Å), cm-1
no. of collected reflns
no. of ind reflns
no. of obsd reflns (I>2σ(I))
no. of params
R1 (on F for obsd reflns)
200(2)
STOE-IPDS
1.84-24.19
3.85
4858
4858
3612
472
0.042
0.112
0.037
0.087
0.278/-0.280
2
wR2 (on F for all reflns)
F
max/Fmin, e Å-3
0.615/ -0.638
0.353/-0.275
at 20 °C. The residue was dissolved in 15 mL of n-hexane, and
the n-hexane solution, after filtration, was evaporated at room
temperature in a vacuum to give a dark yellow oily liquid
representing complex 2.
Finally, acetone adduct 6 is the first example of a
complex of a zwitterionic metallocene with a carbonyl
compound. The acetone ligand in this complex is coor-
dinated to titanium via the oxygen atom, and the CdO
bond in acetone is considerably weakened as a result of
the complexation. The latter suggests that zwitterionic
metallocenes of such a type could be used as catalysts
for reactions of nucleophilic addition to the carbonyl
group of aldehydes and ketones.
The yield of 2 is 1.088 g (89%). Anal. Calcd for C24H40TiSi2:
C, 66.63; H, 9.32. Found: C, 67.22; H, 9.67. 1H NMR (C6D6,
δ): -0.21 (s, 18H, SiMe3); 1.05 (d, 12H, Me); 2.21 (sept, 2H,
CHMe2); 5.82 (m, 4H, Cp); 6.53 (m, 4H, Cp). 13C{1H} NMR
(C6D6, δ): 1.3 (SiMe3); 23.3 (CHMe2); 29.2 (CHMe2); 113.7 (Cp);
114.8 (Cp); 141.4 (Cp); 245.1 (s, CtC). IR (Nujol mull, cm-1):
1636 and 1674 (CtC). MS (70 eV, m/z): 432 ([M])+, 1%), 262
([(iPrC5H4)2Ti]+, 73%), 170 ([Me3SiC2SiMe3]+, 12%), 155 ([Me3-
SiC2SiMe3-Me]+, 100%).
Exp er im en ta l Section
Unless mentioned otherwise, all operations were performed
in an Ar atmosphere with careful exclusion of air and moisture
using standard Schlenk techniques. Solvents were purified in
the usual manner and freshly distilled prior to use over sodium
(toluene, n-hexane) or from sodium/benzophenone (THF) under
Ar. The starting Cp2Ti(PhC2Ph), Cp2Ti(PhC2SiMe3), and 1
were prepared according to published procedures.7b,8b,12 The
compounds (η5-iPrC5H4)2TiCl2 and B(C6F5)3 were purchased
from Strem and used without further purification. The NMR
spectra were recorded on a Bruker ARX 400 spectrometer. The
ESR spectra were registrated on a Varian E12A spectrometer.
The IR spectra were taken on a J FS-25 Bruker instrument.
Syn th esis of Cp [η5-C5H4B(C6F 5)3]Ti (1) by th e Rea ction
of Cp 2Ti(P h C2SiMe3) w ith B(C6F 5)3. An amount of 0.76 g
(1.5 mmol) of B(C6F5)3 was dissolved in 20 mL of toluene under
Ar, and the obtained solution was added to 0.42 g (1.19 mmol)
of solid Cp2Ti(PhC2SiMe3). The resulting red-brown mixture
was then filtered and allowed to stand in an Ar atmosphere
at room temperature. During the course of the reaction, the
solution gradually turned dark blue, and within a month dark
blue crystals of zwitterionic complex 1 were precipitated. The
crystals were separated from the mother liquor by decanting,
washed with a small amount of toluene, and dried at 20 °C in
a vacuum. Yield of 1 is 0.30 g (70%), mp 163-164 °C (dec)
under Ar; lit. mp 161-163 °C (dec) under Ar.7 The decanted
solution was then analyzed by the GLC-MS method, which
revealed the presence of free phenyl(trimethylsilyl)acetylene
in the mixture.
Syn th esis of (η5-iP r C5H4)[(η5-{1,3-iP r C5H3B(C6F 5)3}]Ti
(3). A solution of B(C6F5)3 (1.257 g, 2.46 mmol) in 20 mL of
toluene was added to a solution of 2 (1.064 g, 2.46 mmol) in 3
mL of toluene. After 24 h, the dark blue reaction mixture was
evaporated to dryness in a vacuum, the residue was dissolved
in 20 mL of n-hexane, and the resulting solution was kept after
filtration overnight at room temperature in an Ar atmosphere.
After 1 day, dark blue crystals of zwitterionic complex 3 were
precipitated, which were separated from the mother liquor by
decanting, washed with a small amount of n-hexane, and dried
at 20 °C in a vacuum to give 1.402 g (74.1%) of 3, mp 163-
165 °C (dec) under Ar. Anal. Calcd for C34H21TiBF15: C, 52.81;
H, 2.74. Found: C, 52.22; H, 3.11. MS (70 eV, m/z): 512
[B(C6F5)3]+. The decanted solution was then analyzed by the
GLC-MS method, which revealed the presence of free bis-
(trimethylsilyl)acetylene (96.4%), 1,2-bis(trimethylsilyl)ethane
(2.6%), and cis/ trans-1,2-bis(trimethylsilyl)ethylene (1%) in
the mixture.
Syn th esis of {Cp [η5-C5H4B(C6F 5)3]Ti}2O (4). Complex 1
(0.595 g, 0.76 mmol) was dissolved in 25-30 mL of toluene at
60 °C under Ar in a Schlenk tube, and the resulting dark blue
solution was exposed to dry air for 10-15 min after cooling to
room temperature. Then the Schlenk tube was disconnected
from air, and the reaction mixture was kept at 20 °C overnight.
Within 24 h, fine red crystalline aggregates of complex 4 were
formed on the bottom and the walls of the vessel. The crystals
were separated by decanting, carefully washed with toluene,
and dried for 5-10 min at 20 °C in a vacuum. The yield of 4
is 0.283 g (53%), mp 244-246 °C (dec) under Ar. Anal. Calcd
Syn th esis of (η5-iP r C5H4)2Ti(Me3SiC2SiMe3) (2). (η5-i-
PrC5H4)2TiCl2 (0.943 g, 2.83 mmol), 0.069 g (2.84 mmol) of
finely shaved magnesium, and 0.65 mL (2.89 mmol) of bis-
(trimethylsilyl)acetylene in 15 mL of THF were stirred at room
temperature under Ar for 2.5 h, after which the resulting dark
solution was filtered and evaporated in a vacuum to dryness
for
C56H18Ti2B2OF30‚1/2C6H5CH3 (%): C, 49.62; H, 1.54.
Found: C, 50.05; H, 1.36. IR (Nujol mull, cm-1): 3136(w),
3122(w), 1644(m), 1515(vs), 1378(m), 1278(m), 1106(sh), 1092-
(s, br), 973(s, br), 952(m), 852(s), 731(s, br), 695(m). MS (250

New Zwitterionic Complexes of Titanocene
Organometallics, Vol. 20, No. 19, 2001 4079
°C, 70 eV, m/z): 686 ({(C5H5)[C5H4B(C6F5)3]TiO-F}+, 2%), 512
([B(C6F5)3]+, 3%), 474 ([B(C6F5)3-2F]+, 2%), 410 ([C5H5B-
(C6F5)2]+, 2%), 344 ([C5H5TiC5H4(C6F5)]+, 5%), 324 ({[C5H5-
TiC5H4(C6F5)]-HF}+, 9%), 277 ({[C5H5TiC5H4(C6F5)]-TiF}+,
10%), 193 ([(C5H5)(C5H4)TiO]+, 10%), 175 ({[(C5H5)(C5H4)TiO]-
H2O}+, 13%), 168 ([C6F5H]+, 100%), 151 ([C5H5TiF2]+, 17%),
148 ([C6F4]+, 11%), 132 ([C5H5TiF]+, 26%), 131 ([C5H5TiF2-
HF]+, 5%), and 65 ([C5H5]+, 38%).
The crystals of 6 for the X-ray diffraction study were not dried
in a vacuum. Under such conditions, they contained half a mole
of toluene per mole of 6.
X-r a y Cr ysta llogr a p h ic Stu d y. Data for 3, 5, and 6 were
collected with a STOE-IPDS diffractometer (Rostock) and for
4 with SMART 1000 CCD (Moscow) using graphite-monochro-
mated Mo KR radiation. The structures were solved by direct
methods (SHELXS-86)15 and refined by full-matrix least-
squares against F2 (SHELXL-93).16 The hydrogen atoms were
included at calculated positions. All other non-hydrogen atoms
except the atoms of the disordered solvate molecules were
refined anisotropically. Cell constants and other experimental
details are listed in Table 5. XP (SIEMENS Analytical X-ray
Instruments, Inc.) was used for structure representations.
Syn th esis of {(η5-iP r C5H4)[(η5-{1,3-iP r C5H3B(C6F 5)3}]-
Ti}2O (5). Complex 3 (0.454 g, 0.589 mmol) was dissolved in
15 mL of toluene at 60 °C under Ar in a Schlenk tube, and
the resulting dark blue solution was exposed to dry air after
cooling to room temperature and filtration. Within 24 h, dark
red crystalline aggregates of complex 5 were formed on the
bottom and the walls of the vessel. The crystals were separated
by decanting, washed with toluene, and dried at 20 °C in a
vacuum to give 0.130 g (26.8%) of 5, mp 241-242 °C (dec)
under Ar. Anal. Calcd for C68H38Ti2B2OF30‚C6H5CH3: C, 54.58;
H, 2.81. Found: C, 54.21; H, 2.62. IR (Nujol mull, cm-1): 730
(Ti-O-Ti).
Ack n ow led gm en t. The work was supported by the
Deutsche Forschungsgemeinschaft (Project code AR 321/
1-1), the Max-Planck-Gesellschaft, the Fonds der Che-
mischen Industrie, and the Russian Foundation for
Basic Research (Project codes 99-03-33008 and 00-03-
32807). The authors wish to thank Dr. B. L. Tumansky
for recording and discussing the ESR spectra.
Syn th esis of Cp [η5-C5H4B(C6F 5)3]Ti(Me2CO) (6). Com-
plex 1‚C6H5CH3 (0.286 g, 0.366 mmol) was dissolved in 10-
12 mL of toluene at 60 °C under Ar in a Schlenk tube, and
the resulting dark blue solution was treated after filtration
with 0.03 mL (0.41 mmol) of dry acetone. The color of the
mixture rapidly turned from blue to greenish, and within 48
h green crystals of 6 were formed on the bottom and the walls
of the vessel. The crystals were separated by decanting,
carefully washed with toluene, and dried for 1-2 min at 20
°C in a vacuum to give 0.157 g (51%) of complex 6, mp 192-
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement, atomic coordinates, bond
lengths and angles, anisotropic displacement parameters, and
hydrogen coordinates for 3, 4, 5, and 6. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM0103052
193 °C (dec) under Ar. Anal. Calcd for C31H15TiOBF15
: C,
(15) Sheldrick, G. M. Acta Crystallogr. 1990, A 46, 467.
(16) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.
49.84; H, 2.02. Found: C, 50.11; H, 2.27. IR (Nujol mull, cm-1):
1681 (CdO). MS (250 °C, 70 eV, m/z): 689 [M - acetone]+.