Zwitterionic complexes arising from the reaction of tucked-in titanocenes with tris(pentafluorophenyl)borane

Article abstract of DOI:10.1016/j.inoche.2004.12.011

Single tucked-in titanocene [Ti(η⁵-C₅Me ₅)(η⁵:η¹-C₅Me ₄CH₂)] adds to B(C₆F₅)₃ to give the paramagnetic cationic complex [Ti(η⁵

Full text of DOI:10.1016/j.inoche.2004.12.011

Inorganic Chemistry Communications 8 (2005) 222–226
www.elsevier.com/locate/inoche
Zwitterionic complexes arising from the reaction of tucked-in
titanocenes with tris(pentafluorophenyl)borane
a
Vojtech Varga , Pavel Sindel a´ rˇ , Ivana C ´ı sa rˇ ov a´ , Michal Hor a´ cˇ ek ,
b
c
d
ˇ
d
Ji rˇ ´ı Kubi sˇ ta , Karel Mach
d,
*
a
´
Research Institute of Inorganic Chemistry, Revolu cˇ n ı´ 84, 400 01 Ust ı´ nad Labem, Czech Republic
b
Polymer Institute Brno, Tkalcovsk a´ 2, 656 49 Brno, Czech Republic
c
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
d
Organometallic Catalysis, J. Heyrovsk y´ Institute of Physical Chemistry, Academy of Sciences of the Czech Republic,
Dolej sˇ kova 3, 182 23 Prague 8, Czech Republic
Received 18 November 2004; accepted 11 December 2004
Abstract
5
5
1
Single tucked-in titanocene [Ti(g -C
5
Me
5 5 4 2 6 5 3
)(g :g -C Me CH )] adds to B(C F ) to give the paramagnetic cationic complex
5
5
5
3
4
[
Ti(g -C Me ){g -C Me CH B(C F ) }] (1). Doubly tucked-in titanocene [Ti(g -C Me ){g :g -C Me (CH ) }] reacts with
5
5
5
4
2
6
5 3
5
5
5
3
2 2
5
5
1
B(C F ) by one methylene group to give [Ti(g -C Me ){g :g -C Me (CH )CH B(C F ) }] (6). The crystal structure of 6 revealed
6
5 3
5
5
5
3
2
2
6 5 3
that one hydrogen of the methylene group attached to boron agostically interacts with Ti(IV).
2004 Elsevier B.V. All rights reserved.
ꢀ
Keywords: Titanium; Tucked-in titanocene; Borate ligand; Zwitterions; Cationic complexes; X-ray crystallography
Cationic complexes of Group IV transition metals
form one of the most frequently addressed classes of
organometallic compounds in the last decade. Enor-
mous wave of interest arose with the discovery of syn-
thetic routes to well defined titanocene and zirconocene
tive catalysts. The field of cationic catalysts for poly-
merization of olefins has been the subject of a large
number of review articles in recent years [3].
Alkene moieties were used for the formation of cata-
lytic ion pairs in various ways. Erker and co-workers [4]
used zirconocene (Zr(II))–butadiene complex and
[B(C F ) ] to form a ‘‘girdle’’ zwitterion. Analogously,
ꢀ
cationic complexes containing [BMe(C F ) ] [1] or
6
5 3
ꢀ
B(C F ) ] [2] species as counteranions. Using these
6 5 4
[
6 5 3
complexes, the mechanism of polymerizations on single
site metallocene catalysts is now well established and
the results seem to be applicable to single site catalysts
generated by methylalumoxane (MAO), the systems
which are difficult to investigate owing to a large molar
excess of MAO which is necessary to obtain highly ac-
[BH(C F ) ] [5] adds across Zr–C bond of a zircono-
6 5 2
2
cene–alkene complex [Zr(PMePh )(g -RCH = CH )Cp ]
2
2
2
(R = H, Et, C H ) to give a similar ‘‘girdle’’ complex
with an agostic Zr–H–B bond [6]. A girdle type ion pair
complex was also obtained by addition of [B(C F ) ] to
6
5
6
5 3
a zirconocene diacetylide complex [7]. Moreover,
B(C F ) ] attacks the cyclopentadienyl ligand in zircon-
[
6
5 3
*
ocene complexes with disubstituted alkynes to form an
alkenylzirconocene ion pair with the borane directly at-
tached to the Cp ring [8]. In this respect, the titanocene
Corresponding author. Tel.: +420 266 053 735; fax: +420 286 582
3
07.
E-mail address: mach@jh-inst.cas.cz (K. Mach).
1
387-7003/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2004.12.011

V. Varga et al. / Inorganic Chemistry Communications 8 (2005) 222–226
223
-
B(C F )
SiMe3
6
5 3
-
C
B(C F )
-
6
5 2
H
C
SiMe3
+
B(C F )
Ti
6 5 2
F
C
+
Ti
F
+ Zr
F
C
F
F
F
F
Ph
F
F
F
1
3
2
Chart 1.
and zirconocene-alkyne complexes react in various ways
2
that reported by Rosenthal and co-workers [10a]. The
compound was further characterized by IR, EI-MS
and EPR spectra.
depending on the nature of the ancillary ligands. [Ti(g -
5
1
Me SiC„CSiMe )(g -C H ) ] reacts with [B(C F ) ]
3
3
5
5 2
6 5 3
under partial evolution of hydrogen and partial hydro-
genation of the liberated alkyne, whereas one of the ring
ꢀ
carbon atoms of one Cp ligand bears the [B(C F ) ] an-
6
5 3
B(C F )
CH2
6
5 3
ion with ortho-fluorine atoms of its two C F groups
5
Ti
6
1
ð1Þ
coordinated to the titanium atom. The valency of Ti(II)
is increased to Ti(III) [9]. The analogous permethylated
2
5
titanocene complex [Ti(g -Me SiC„CPh)(g -C Me ) ]
3
5
5 2
5
liberated hydrogen and the alkyne to give [Ti(g -
C Me ){g -C Me CH B(C F ) }] (1), whereas the anal-
4
5
5
5
5
4
2
6 5 3
In contrast to synthesis of 1 from the Ti(II) alkyne
complex where elimination of hydrogen was compatible
with a redox mechanism [10], in the present case the
methylene group underwent a clean transmetallation
ogous permethylated zirconocene complex transfers one
hydrogen atom from one cyclopentadienyl methyl group
to the alkyne to give alkenyl compound 2 with an
agostic Zr–H bond and zwitterionic structure [10a].
1
without changing the Ti valency. The presence of d
2
Complex rac-[Ti(g -Me SiC„CSiMe )(ebthi)] (ebthi =
3
3
electron in the initial tucked-in titanocene was proved
by photoelectron spectra showing vertical ionization en-
ergy of this electron to be 5.54 eV and by strongly aniso-
tropic ESR spectra at gav = 1.953, which both are
attributable to a typical alkyltitanocene species with a
r–Ti–C bond [15c]. The non-volatility of compound 1
precluded the measurement of the photoelectron spec-
0
5
1
[
,2-ethylene-1,1 -bis(g -tetrahydroindenyl)) reacts with
B(C F ) ] to give zwitterionic Ti(III) g -(trimethylsi-
6 5 3
2
lyl)ethynylboranate complex 3. The redox reaction of
Ti(II) to Ti(III) is accompanied by elimination of the
trimethylsilyl group [10b] (see Chart 1). The pendant
double bonds attached to cyclopentadienyl rings were
so far explored only sparingly: the allyl group at a cyclo-
pentadienylamidozirconium complex was hydroborated
by [BH(C F ) ] [11], the allyldimethylsilyl group in dib-
1
tra, however, the d state of the metal was demonstrated
by ESR spectrum in toluene solution with g = 1.976,
aTi = 11.2 G, and a = 2.2 G (triplet, ꢁ1:2:1). The small
6
5 2
enzylzirconocene was p-coordinated to a benzylzircono-
cene cation [12], x-alkenylpermethylzirconocene [13],
and x-alkenyloxyzirconocene cations contained the p-
coordinated double bond to the Zr cation [14].
1
1
5
5
Compound 4 [Ti(III){g :g -C
5
Me
4
5
(CH
2
)}(g -C
5 5
Me )] was
obtained by thermolysis of [Ti(III)Me(g -C
5
5 2
Me ) ] [15b,c], purified
by sublimation and finally by crystallization from hexane. The solution
of 4 in toluene (0.317 g in 10 ml, 1.0 mmol) was mixed with a solution
Here, we report the formation of zwitterionic com-
plexes from the most simple ‘‘olefinic’’ precursors,
6 5 3
of [B(C F ) ] (Strem, recrystallized from toluene) (0.1 M, 10 ml), and
5
5
1
after stirring at ambient temperature a brown reaction solution was
concentrated and cooled to ꢀ5 ꢁC overnight. A crop of brown crystals
tucked-in titanocenes [Ti(g -C Me )(g :g -C Me CH )]
(
5
3
5
4
5
4
2
5
4) [15] or [Ti(g -C Me ){g :g -C Me (CH ) }] (5)
5 5 5 3 2 2
of 5 was separated and dried in vacuo. Yield 0.60 g (72%). EI-MS
+Å
[
[
15c,16], and [B(C F ) ]. Compound 4 reacted with
6
5 3
(
direct inlet, 70 eV, 200 ꢁC): m/z (relative abundance, %) 829 (M ; not
+Å
B(C F ) ] in the most simple way: by transmetallation
6
5 3
6 5 3
observed), 513 (20), 512 ([B(C F ) ] ; 100), 511 (24), 444 (13), 413 (6),
+Å
of the methylene group by the Lewis acid boron atom
Eq. (1)). Both valence electrons from previous r–Ti–
CH bond were used in the new covalent B–CH bond
364 (5), 318 (8), 317 (22), 316 ([(C
5
Me
5 2
) Ti–2H] ; 77), 315 (13), 299
(
(
(
(
(
7), 296 (9), 295 (6), 277 (18), 258 (7), 227 (12), 176 (6), 148 (7), 129
(
ꢀ1
10). IR (KBr, cm ): 2950 (m,sh), 2917 (s), 2867 (m), 1643 (s), 1603
m), 1514 (vs), 1456 (vs,b), 1384 (m), 1274 (m), 1083 (s), 1024 (w), 977
s), 801 (vw), 787 (w), 769 (w), 750 (vw), 698 (vw), 572 (vw). EPR
toluene, 22 ꢁC): g = 1.976, aTi = 11.2 G, triplet 1:2:1 a = 2.2 G;
2
2
giving rise to a zwitterionic structure 1 (Eq. (1)). The
structure of the product was determined by X-ray dif-
fraction analysis of single crystals to be identical with
(toluene, ꢀ140 ꢁC): g
1 2 3
= 2.001, g = 1.986, g = 1.944, gav = 1.977.

2
24
V. Varga et al. / Inorganic Chemistry Communications 8 (2005) 222–226
13
1
coupling constant probably arises from interaction of
the unpaired electron with 2 equivalent ortho-fluorine
nuclei. Such an interaction has been observed in the so-
H and C NMR spectra could not be measured (in
C D ) because of low solubility of 6.
6
6
5
5
lid [Ti(g -C H )(g -C H B(C F ) ] [9] and can be antic-
CH2
CH2
-
5
5
5
4
6 5 3
B (C F )
6
5
3
ipated in the solution of 1. In toluene glass, the spectrum
of a rhombic symmetry is much less anisotropic than in
its tucked-in precursor because of a change from trigo-
nal to pseudotetrahedral coordination of the titanium
atom. The solution ESR parameters for 1 (g = 1.980,
aTi = 11.0 G) are comparable with those of 3 which
showed, however, much broader signals (DH = 6.7 G)
B(C F )
H C
2
C
H
6
5 3
+
H
Ti
Ti
5
6
ð2Þ
The molecular structure of one of the two indepen-
[
10b].
5
The doubly tucked-in compound [Ti(g -C Me )
5
5
3
4
dent molecules of 6 (molecule 1) is shown in Fig. 1
and important molecular parameters for this molecule
are listed in Table 1. The geometric parameters for mol-
ecule 2 differ less than 3-fold esdꢀs. The molecule consists
of a tucked-in titanocene and borate species linked via
one methylene group and these two species do not exert
any contact interaction. The single tucked-in titanocene
moiety possesses a moderately bent structure with the
angle subtended by the two least-squares cyclopentadie-
nyl planes u = 17.2(1)ꢁ. This angle is larger than angles
{
equivalent of [B(C F ) ] to afford yellow diamagnetic
g :g -C Me (CH ) }] (5) reacted cleanly with one
5 3 2 2
6
5 3
5
5
1
[
(
Ti(g -C Me ){g :g -C Me (CH )CH B(C F ) }] (6)
5 5 5 3 2 2 6 5 3
2
Eq. (2)). Its structure was established by X-ray diffrac-
3
tion analysis of single crystals. Compound 6 was fur-
ther characterized by elemental analysis, IR spectra
(KBr pellet) and EI-MS spectra, the latter showing the
molecular and fragment ions of the tucked-in titanocene
and [B(C F ) ] and no molecular ion of 6, however. The
6 5 3
u observed in doubly tucked-in complexes (8.3–12.4ꢁ)
5
[
17] and in single tucked-in complex [Ti{g -C Me (Si-
5
4
2
A solution of [B(C
6
F
5
)
3
] (0.1 M, 10 ml) was mixed with a toluene
5
1
Me CH CH CF )}g :g -C Me (CH )(SiMe CH CH
2
2
2
2
3
5
3
2
2
2
solution (10 ml) made from crystalline 5 [16b] (0.316 g, 1.0 mmol)
under vigorous stirring at room temperature. The reaction solution
was turning through green-brown to yellow-brown. After stirring for 2
h, the solution was concentrated to ca. 5 ml and cooled to ꢀ5 ꢁC. The
first crop of yellow plate crystals of 6 was separated, dried in vacuo,
and used for characterization. Yield of 0.48 g (58%). EI-MS (direct
CF )}] (7) (u = 13.5(1)ꢁ) [18]. The value of the angle at
3
the bridging carbon Ti1–C107–C102 64.8(1)ꢁ falls be-
tween the values found in 4 [15a] and 7 (67.4(3)ꢁ) [18].
Similarly to 4 and 5, the Ti1–Cg1 distance is shorter
˚
by ca. 0.05 A than that of the unperturbed cyclopen-
tadienyl ring (see Table 1). It is of interest that the
+
Å
inlet, 70 eV, 200 ꢁC): m/z (relative abundance, %) 828 (M ; not
+
Å
observed), 513 (20), 512 ([B(C
64 (5), 318 (8), 317 (22), 316 ([(C
7), 296 (9), 295 (6), 277 (18), 258 (7), 227 (12), 176 (6), 148 (7), 129
6 5 3
F ) ] ; 100), 511 (24), 444 (13), 413 (6),
+Å
3
5 5 2
Me ) Ti–2H] ; 77), 315 (13), 299
(
(
(
(
(
ꢀ
1
10). IR (KBr, cm ): 2958 (m), 2918 (s), 2862 (m), 1642 (m), 1604
vw), 1515 (s), 1457 (vs,b), 1384 (m), 1276 (m), 1084 (s), 1021 (w), 978
s), 890 (vw), 819 (vw), 797 (w), 770 (w), 751 (w), 731 (w), 706 (vw), 696
F114
C137
F113
C136
F112
vw), 673 (w), 616 (vw), 574 (vw), 466 (w). Calcd. for C45
H
36BF15Ti: C,
58.72; H, 3.94. Found: C, 58.65; H, 3.89.
3
F104
C138
F115
C133
Structure determination for 6: C38
ꢀ
H
28BF15Ti Æ C (M =
7
H
8
F105
C126
9
a = 10.9240(2) A, b = 17.9780(3) A, c = 22.8620(4) A,
20.45); triclinic, space group P1 (No. 2); T = 150(2) K,
C135
C134
C125
F103
˚
˚
˚
F110
C121
a = 106.1240(9)ꢁ, b = 99.9290(9)ꢁ, c = 107.5030(10)ꢁ; V = 3949.80(12)
˚
3
3
ꢀ1
A , Z = 4, D
from toluene, 0.50 · 0.25 · 0.17 mm , h range for data collection 1.0–
7.5ꢁ, F(000) = 1872; 70 917 collected, 17 977 unique and 12 016
c
= 1.548 Mg/m , l(Mo Ka) = 0.322 mm , yellow plate
C124
F109
F111
H161
C110
C105
3
2
B1
C127
F101
C128
C101
C109
observed (I > 2r(I) diffractions, 1053 parameters, final R = 6.11%,
wR = 15.81% for observed diffractions, R = 9.44% for all data,
C131
C122
F102
C106
C102
C104
˚
ꢀ3
GOF = 1.026, residual electron density +1.078, ꢀ0.656 e A . The
racemic crystal contains two independent molecules of 6 and the molar
equivalent of toluene of crystallization. Diffraction data were collected
on a Nonius KappaCCD diffractometer and analyzed by the HKL
C130
H162
C103
C108
Ti1
C129
C107
F108
F106
C120
program package [21]. The structures were solved by direct methods
C119
2
C115
C111
C112
(
(
SIR-92, [22]) and refined by full-matrix least-squares on F
SHELXL-97 [23]). All non-hydrogen atoms were refined anisotrop-
F107
C116
C114
ically. Hydrogen atoms were fixed and refined in their theoretical
positions except those residing at carbon atoms C107/C207 and C106/
C206. These were identified on difference electron density maps and
refined with isotropic thermal motion parameters. The racemic crystal
contains one molecule of toluene of crystallization per one molecule of
C113
C118
C117
Fig. 1. The PLATON drawing of 6 (30% probability ellipsoids) with
atom labeling scheme. Labels of C(123) and C(132) and hydrogen
atoms except the methylene ones are omitted for clarity.
1. CCDC Reference No. 256174.

V. Varga et al. / Inorganic Chemistry Communications 8 (2005) 222–226
225
Table 1
˚
Selected bond lengths (A) and bond angles (ꢁ) for molecule 1 of 6
a
a
Ti(1)–Cg(1)
Ti(1)–C(101)
Ti(1)–C(103)
Ti(1)–C(105)
Ti(1)–C(106)
1.946(3)
2.104(2)
Ti(2)-Cg(2)
Ti(1)–C(102)
1.997(3)
2.101(3)
2.516(3)
2.267(3)
2.358(3)
2.372(3)
Ti(1)–C(104)
Ti(1)–C(107)
b
2.581(2)
1.454(4)
Ti(1)–CringCp(2)
C(102)–C(103)
C(104)–C(105)
C(102)–C(107)
2.303–2.365(3)
1.451(4)
1.409(4)
C(101)–C(102)
C(103)–C(104)
C(101)–C(105)
C(101)–C(106)
1.415(4)
1.436(4)
1.497(4)
1.421(4)
1.417–1.430(4)
1.695(4)
C
ring–CringCp(2)
C
ring–CMe
1.497–1.505(4)
1.649(4)–1.662(4)
149.5(1)
B(1)–C(106)
C–F(range)
B(1)–Cipso
1.339–1.360(4)
64.8(1)
110.2(2)
Cg(1)–Ti(1)–Cg(2)
B(1)–C(106)–C(101)
C(106)–B(1)–C(127)
C(121)–B(1)–C(127)
C(127)–B(1)–C(133)
a
Ti(1)–C(107)–C(102)
C(106)–B(1)–C(121)
C(106)–B(1)–C(133)
C(121)–B(1)–C(133)
119.6(2)
117.0(2)
101.4(2)
113.1(2)
17.2(1)
102.4(2)
113.2(2)
c
u
Cg(1) and Cg(2) denote the centroids of C(101–105) and C(111–115) cyclopentadienyl rings, respectively.
Nonbonding distance.
The dihedral angle subtended by the least-squares planes of cyclopentadienyl rings.
b
c
C–C bond lengths opposite to the two carbons bearing
the methylene groups are the shortest (1.409(4) and
tronically saturates the Ti(IV) ion so that the Ti–F
interaction known for complex 1 is absent. A more
electropositive zirconium, however, showed agostic
interactions with both the ortho-proton of the phenyl
group and proton(s) of the methylene group in the
thermodynamically stable [ZrPh(C Me ){C Me CH B
˚
.415(4) A) and the Ti1–C104 bond the longest
1
2
˚
.516(3) A as it is common in doubly tucked-in tita-
4
nocenes [17]. It shows that the effect of the bridg-
ing-to-boron methylene group is similar to the effect
of the tucked-in methylene. Indeed, the C106 carbon
atom is declined from the least-squares plane of the
cyclopentadienyl ligand toward titanium by 0.627(4)
5
5
5
4
2
(C F ) )}] complex arising from the reaction of the phe-
6
5 3
nylzirconocene tucked-in complex [ZrPh(C Me )-
5
5
{C Me (CH )}] with [B(C F ) ] [20].
6 5 3
5
4
2
˚
˚
A similar to C107 (0.862(4) A), whereas the methyl
carbon atoms are declined farther away from titanium
The pentafluorophenyl groups in 6 are inequivalent
with respect to the methylene group as follows from dif-
ferent valence angles at the boron atom (see Table 1).
This can be caused by various intra- and inter-molecular
interactions in the solid state.
˚
by about 0.1 A. However, the C101–C106 bond length
˚
of 1.497(4) A is within the error of measurement iden-
tical with the C–C bonds between methyl and ring car-
˚
bon atoms (1.500–1.508(4) A). Compared with the
Neither the Ti(III) compound 1 nor the Ti(IV) com-
pound 6 showed polymerization activity toward ethene
in toluene at 1 bar pressure and 20 ꢁC.
structure of 1, this bond is shorter than the bond in
˚
1
of 1.695(4) A is longer with respect to the analogous
(1.514(5) A and correspondingly, the B1–C106 bond
˚
˚
bond in 1 (1.649(6) A) [10a]. The hydrogen atoms of
both methylene groups (C106, C107) were found and
isotropically refined to give C–H bond lengths in the
Acknowledgements
˚
range 0.97(3)–1.02(3) A. The shortest distance be-
tween the titanium atom and hydrogen attached to
˚
C106 (H(162)) was 2.21(3) A, which is the distance
found in decamethyltitanocene cation for agostic
hydrogens of two vicinal methyl groups to titanium
ˇ
V.V. and P.S. were supported by the Ministry of Edu-
cation, Youth and Sports of Czech Republic (Project No.
LN00B142), M.H. by Grant Agency of Academy of Sci-
ences of the Czech Republic (Grant No. KJB4040403),
and J.K. and K.M. by Academy of Sciences of the Czech
Republic (Grant No. K4040111). The Grant Agency of
the Czech Republic sponsored access to Cambridge
Structure Data Base (Grant No. 203/02/0436).
[
19]. Hence, the bonding interaction of this agostic
hydrogen to titanium induces the large bending of
C106 toward titanium and coordinatively and elec-
4
3
4ꢀ
The doubly tucked-in ligand is also called ‘‘allyldiene’’ g :g
References
assigning the presence of trimethylallyl group in the ring and two
double bonds between methylenes and ring carbon atoms [16a].
Indeed, methylene-to-ring bonds are shorter than the bond linking the
corresponding ring carbon atoms [17], and the absence of d electrons
proved by photoelectron spectroscopy shows on a backbonding
interaction of Ti(II) with these double bonds [15c].
[1] X. Yang, C.L. Stern, T.J. Marks, J. Am. Chem. Soc. 113 (1991)
3623.
[2] J.C.W. Chien, W.-M. Tsai, M.D. Rausch, J. Am. Chem. Soc. 113
(1991) 8570.

226
V. Varga et al. / Inorganic Chemistry Communications 8 (2005) 222–226
[
3] (a) H.-H. Brintzinger, D. Fischer, R. M u¨ lhaupt, B. Rieger, R.M.
Waymouth, Angew. Chem., Int. Ed. Engl. 34 (1995) 1143;
[11] (a) W.E. Piers, Chem. Eur. J. 4 (1998) 13;
(b) R.E. von H. Spence, D.J. Parks, W.E. Piers, M. MacDonald,
M.J. Zaworotko, S.J. Rettig, Angew. Chem., Int. Ed. Engl. 34
(1995) 1230.
(
(
(
b) W. Kaminsky, M. Arndt, Adv. Polym. Sci. 127 (1997) 144;
c) M. Bochmann, J. Chem. Soc., Dalton Trans. (1996) 255;
d) T.J. Marks, J.C. Stevens (Eds.), Topics in Catalysis, vol. 7,
[12] M.V. Galakhov, G. Heinz, P. Royo, Chem. Commun. (1998) 17.
[13] C.P. Casey, D.W. Carpenetti II., H. Sakurai, J. Am. Chem. Soc.
121 (1999) 9483.
1
999, p. 1;
e) J.A. Gladysz (Ed.), Chemical Reviews, 2000, p. 100 (special
issue on ‘‘Frontiers in Metal-Catalyzed Polymerization’’);
f) G.W. Coates, J. Chem. Soc., Dalton Trans. (2002) 467.
(
[14] Z. Wu, R.F. Jordan, J.L. Petersen, J. Am. Chem. Soc. 117 (1995)
5867.
(
[
4] (a) J. Karl, M. Dahlmann, G. Erker, K. Bergander, J. Am. Chem.
Soc. 120 (1998) 5643;
[15] (a) J.M. Fischer, W.E. Piers, V.G. Young, Organometallics 15
(1996) 2410;
(b) B. Temme, G. Erker, J. Karl, H. Luftmann, R. Fr o¨ hlich, S.
Kotila, Angew. Chem., Int. Ed. Engl. 34 (1995) 1755;
(b) J.E. Bercaw, H.H. Brintzinger, J. Am. Chem. Soc. 93 (1971)
2046;
(
(
c) B. Temme, J. Karl, G. Erker, Chem. Eur. J. 2 (1996) 919;
d) J. Karl, G. Erker, R. Fr o¨ hlich, J. Am. Chem. Soc. 119 (1997)
(c) T. Vondr a´ k, K. Mach, V. Varga, A. Terpstra, J. Organomet.
Chem. 425 (1992) 27.
1
116.
[16] (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) V. Varga, K. Mach, M. Pol a´ sˇ ek, P. Sedmera, J. Hiller, U.
Thewalt, S.I. Troyanov, J. Organomet. Chem. 515 (1996) 57.
[
[
[
5] D.J. Parks, R.E. von H. Spence, W.E. Piers, Angew. Chem., Int.
Ed. Engl. 34 (1995) 809.
6] Y. Sun, W.E. Piers, S.J. Rettig, Organometallics 15 (1996)
ˇ
[17] V. Kupfer, U. Thewalt, I. Ti sˇ lerov a´ , P. St eˇ pni cˇ ka, R. Gyepes, J.
4
110.
7] (a) B. Temme, G. Erker, R. Fr o¨ hlich, M. Grehl, Angew. Chem.,
Int. Ed. Engl. 33 (1994) 1480;
Kubi sˇ ta, M. Hor a´ cˇ ek, K. Mach, J. Organomet. Chem. 620 (2001)
39.
ˇ
[18] L. Luke sˇ ov a´ , M. Hor a´ cˇ ek, R. Gyepes, I. C ´ı sa rˇ ov a´ , P. St eˇ pni cˇ ka, J.
(b) B. Temme, G. Erker, R. Fr o¨ hlich, T. Fox, J. Organomet.
Chem. 527 (1997) 191.
8] J. Ruwwe, G. Erker, R. Fr o¨ hlich, Angew. Chem., Int. Ed. Engl.
Kubi sˇ ta, K. Mach, Collect. Czech. Chem. Commun. 70 (2005), in
press.
[
3
5 (1996) 80.
[19] M.W. Bouwkamp, J. de Wolf, I. del Hierro Morales, J. Gercama,
A. Meetsma, S.I. Troyanov, B. Hessen, J.H. Teuben, J. Am.
Chem. Soc. 124 (2002) 12956.
[
9] (a) V.V. Burlakov, S.I. Troyanov, A.V. Letov, L.I. Strunkina,
M.Kh. Minacheva, G.G. Furin, U. Rosenthal, V.B. Shur, J.
Organomet. Chem. 598 (2000) 243;
[20] Y. Sun, R.E.v.H. Spence, W.E. Piers, M. Pavez, G.P.A. Yap, J.
Am. Chem. Soc. 119 (1997) 5132.
(b) 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, V.B. Shur, Organometallics 20
[21] Z. Otwinowski, W. Minor, HKL Denzo and Scalepack program
package by Nonius. For a reference see Z. OtwinowskiSun, W.
Minor, Method. Enzymol. 276 (1997) 307.
(2001) 4072.
[
10] (a) V.V. Burlakov, P.-M. Pellny, P. Arndt, W. Baumann, A.
Spannenberg, V.B. Shur, U. Rosenthal, Chem. Commun. (2000)
[22] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, C. Giaco-
vazzo, A. Guagliardi, G. Polidori, J. Appl. Cryst. 27 (1994) 435.
[23] G.M. Sheldrick, SHELXL 97 Program for Crystal Structure
Refinement from Diffraction Data, University of G o¨ ttingen,
G o¨ ttingen, 1997.
2
41;
b) P. Arndt, W. Baumann, A. Spannenberg, U. Rosenthal, V.B.
Shur, Angew. Chem., Int. Ed. Engl. 42 (2003) 1414.
(