Synthesis of dimetallic ♂-alkylideneamido zirconocene dications by a thermodynamically favorable lithium chloride elimination pathway

Article abstract of DOI:10.1016/S0022-328X(01)01205-0

The reagent chloride abstraction. The resulting in situ formed [Cp₂Zr (N=CHR)]⁺ cations (8) dimerize under the reaction conditions. After removal of a stoichiometric amount of lithium chloride the corresponding μ-alkylideneamido-brid

Full text of DOI:10.1016/S0022-328X(01)01205-0

Journal of Organometallic Chemistry 643–644 (2002) 61–67
www.elsevier.com/locate/jorganchem
Synthesis of dimetallic m-alkylideneamido zirconocene dications by
a thermodynamically favorable lithium chloride elimination
pathway
Steve Do¨ring, Gerhard Erker *, Roland Fro¨hlich 1
Organisch-Chemisches Institut der Uni6ersita¨t Mu¨nster, Corrensstrasse 40, D-48149 Mu¨nster, Germany
Received 1 June 2001; accepted 31 August 2001
Dedicated to Professor Franc¸ois Mathey on the occasion of his 60th birthday
Abstract
The reagent [butyl-B(C6F5)3]−Li+ reacts with the complexes Cp2ZrCl(NꢀCHR) (6) (RꢀCH3 or p-tolyl) at ambient temperature
by chloride abstraction. The resulting in situ formed [Cp2Zr(NꢀCHR)]+ cations (8) dimerize under the reaction conditions. After
removal of
a
stoichiometric amount of lithium chloride the corresponding m-alkylideneamido-bridged dimeric
[Cp2Zr(NꢀCHR)]22+ dications 9a (R=CH3) and 9b (R=p-tolyl) are isolated in yields of ca. 80% (with [butyl-B(C6F5)3]−
counteranion). The complexes 9a and 9b are each obtained as mixtures of cis- and trans-isomers. Crystallization from
dichloromethane gave pure trans-9a and trans-9b samples. Both were characterized by X-ray crystal structure analyses. Treat-
ment of the dications
9
with acetonitrile gave the respective mononuclear monocationic adduct complexes
[Cp2Zr(NꢀCHR1)NꢁCꢂCH3]+[butyl-B(C6F5)3]− (16). © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Zirconocene cation complexes; Metallocenes; Dimerization; Bridging nitrogen-containing ligands
1. Introduction
to trap the bent isomer 3 by adding a suitable second
electrophile to the aldimine nitrogen using the pro-
nounced donor function of the sp2-hybridized nitrogen
center in the bent isomeric situation. This had been
realized in a few instances, e.g. by using strongly elec-
trophilic Group 3 metal centers [7].
We have now generated very electrophilic Group 4
metallocene alkylideneamido cations and found that
they dimerized along the reaction path outlined in
Scheme 1 to yield very stable dimetallic alkylide-
neamido-bridged bis(zirconocene) dications. Their
structures and some of their chemical properties, proba-
bly originating from monomerization reactions, are de-
Bis(alkylidene)ammonium ions [R2CꢀNꢀCR2]+ (1)
exhibit linear heteroallene-type structures around a cen-
tral sp-hybridized nitrogen atom [1]. The corresponding
(alkylideneamido)metal complexes 2 also show near to
linear metallaallene structures in cases where electron-
deficient LnM moieties are employed [2–5]. In such
substances a ligand to metal p-bonding component that
makes use of the Schiff-base nitrogen lone pair often
leads to a considerable stabilization of the linear struc-
ture around the sp-hybridized nitrogen [6]. However, in
many such organometallic systems this p-component is
often weaker than in the purely organic systems 1, and,
therefore, the bent isomers 3 are in an equilibrium
situation with 2, albeit mostly much less favored [2b].
In principle this endothermic equilibrium could be used
scribed. For the preparation of the Group
4
metallocene alkylideneamido cation systems we have
used a favorable LiCl salt elimination route [8].
* Corresponding author. Tel.: +49-251-8333221; fax: +49-251-
8336503.
E-mail address: erker@uni-muenster.de (G. Erker).
1 X-ray crystal structure analyses.
Scheme 1.
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01205-0

62
S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
Scheme 2.
2. Results and discussion
rated (ethylideneamido)zirconocene cations 8a (Scheme
2).
Two neutral (alkylideneamido)zirconocene chlorides
were used as the starting materials for our study,
namely the complexes Cp2ZrCl(NꢀCHR) 6a (R=CH3)
and 6b (R=p-tolyl). They were synthesized, as previ-
ously described by us [2a], by means of a hydrozircona-
tion reaction of acetonitrile or 4-methylbenzonitrile,
respectively, employing the oligomeric ‘Schwartz-
reagent’ (Cp2ZrHCl)n (5) [9] suspended in toluene.
These compounds were isolated in ca. 80% yield each.
Complex 6a shows a characteristic ZrꢀNꢀC 13C-NMR
resonance at l 167.5 (1JCH=168 Hz). The related
complex Cp2ZrꢀNꢀCHPh had been characterized by
X-ray diffraction and shown to exhibit an almost linear
ZrꢀNꢀC framework (angle ZrꢂNꢂC: 170.5(5)°) [2a].
The (ethylideneamido)zirconocene chloride complex
6a was treated with lithium[butyltris(pentafluoro-
phenyl)borate] (7) in dichloromethane at room temper-
ature. This results in an effective chloride abstraction
from zirconium. Initially a clear solution of the reagents
is obtained, from which after a short while at ambient
temperature LiCl begins to precipitate. The reaction is
essentially complete after 2 h stirring at room tempera-
ture. The LiCl precipitate is then removed by filtration
and the resulting organometallic product (9) isolated in
70% yield from the solution.
The cis-dimer (cis-9a) exhibits a CH3 signal in the
1H-NMR spectrum in CD2Cl2 at l 1.92, representing
1
six hydrogen atoms and two H-NMR Cp singlets at l
6.84 and 6.81, each representing 10 H atoms. The
corresponding 13C-NMR Cp signals of cis-9 are found
at l 121.0 and 117.8. In contrast, the Ci-symmetric
1
isomer trans-9a exhibits a single H-NMR Cp singlet
(at l 6.83) and a methyl resonance (at l 1.77) in a 20:6
ratio. Both isomers show an identical chemical shift of
the ‘metalloaldimine’-carbon atom at l 194.9 which is
shifted markedly downfield from the neutral reference
6a.
The aryl-substituted complex 6b reacts analogously
upon treatment with an equimolar quantity of the
chloride abstractor [butyl-B(C6F5)3]−Li+ (7). After re-
moval of the LiCl precipitate a 1:1.5 mixture of the cis-
and trans-9b dimers was isolated. They also show the
characteristic symmetry-dependent appearance of the
NMR spectra (1H/13C-NMR pairs of Cp signals of
cis-9b at l 6.70, 6.30/117.3, 114.0 and single Cp reso-
nances of trans-9b at l 6.37/112.6).
The favored formation of the dimeric bis[(alkylide-
neamido)zirconocene] dication complexes was also
confirmed by the results of X-ray crystal structure
analyses. Crystallization of the cis-/trans-9a mixture
from dichloromethane gave single crystals of the pure
trans-9a isomer that were suitable for the X-ray crystal
structure analysis (Fig. 1).
The NMR spectra indicate that a 1:1 mixture of the
dinuclear dication complexes cis- and trans-9a were
formed, that have probably resulted from dimerization
of the in situ generated reactive coordinatively unsatu-

S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
63
In the crystal two [butyl-B(C6F5)3]− anions were
found that show typical tetraorganylborate structural
,
features (averaged BꢂC(aryl): 1.663(4) A, BꢂC(butyl):
,
1.642(4) A). The anions are independent of the dication
in the crystal. The dication shows a rhomboedric Zr2N2
framework. The heavy atoms of the [(CH3CHꢀN)2Zr2]
framework are coplanar. The methyl substituents are
located with Ci-symmetry at the periphery of the
[(CꢀN)2Zr2] frame. The NꢂZrꢂN* angles are rather
small at 77.8(1)°. The corresponding ZrꢂNꢂZr* angles
are markedly larger at 102.2(1)°. The C2ꢂN1 bond
,
length in trans-9a amounts to 1.281(4) A, which is in
the typical range of a Schiff base CꢀN double bond
[10]. Similar bonding features were observed previously
for the typical examples of the neutral or mono-cationic
,
Fig. 2. A view of the trans-9b dication. Selected bond lengths (A) and
angles (°): ZrꢂN1* 2.272(4), ZrꢂN1 2.192(4), N1ꢂC2 1.288(6), C2ꢂC3
1.444(7), BꢂC21 1.658(8), C21ꢂC22 1.509(8), C22ꢂC23a 1.558(8),
C22ꢂC23b 1.555 (8), C23ꢂC24a 1.524(9), C23ꢂC24b 1.535(10), BꢂC31
1.649(8), BꢂC41 1.655(8), BꢂC51 1.648(8); N1*ꢂZrꢂN1 79.0(2),
ZrꢂN1ꢂZr* 101.0(2), ZrꢂN1ꢂC2 119.3(3), N1ꢂC2ꢂC3 129.8(5),
C21ꢂBꢂC31 110.5(5), C21ꢂBꢂC41 115.9(4), C21ꢂBꢂC51 103.8(4),
C31ꢂBꢂC41 102.0(4), C31ꢂBꢂC51 113.6(4), C41ꢂBꢂC51 111.4(4),
BꢂC21ꢂC22 116.1(5), C21ꢂC22ꢂC23a 121.3(7), C21ꢂC22ꢂC23b
97.9(9), C22ꢂC23aꢂC24a 106.6(8), C22ꢂC23bꢂC24b 108.5(9).
,
m-NꢀCR2M2 complexes 10 (CꢂN: 1.25(2) A [7]), 11
,
,
(CꢂN: 1.266(13) A [11]) and 12 (CꢂN: 1.235(19) A [12])
(Scheme 3). In trans-9a the N1ꢂC2ꢂC3 angle is
126.2(3)° and the C3ꢂC2ꢂN1ꢂZr dihedral angle
amounts to −179.0(3)°. The (E)ꢂ(ZrꢂN1) bond
,
(2.255(2) A) is slightly longer than the (Z)ꢂ(Zr*ꢂN1)
5
,
linkage (2.235(2) A). The four h -Cp ligands are ar-
ranged above and below the Zr2N2 plane with a Cp-
(centroid)ꢂZrꢂCp(centroid) angle of 129.6°.
Single crystals of trans-9b were also obtained from
dichloromethane. The molecular structure of the dica-
tion trans-9b in the crystal also shows the typical
distorted Zr2N2 framework (NꢂZrꢂN* angle: 79.0(2)°,
ZrꢂNꢂZr* 101.0(2)°). As expected, the conjugated aryl
group exerts some influence on the coordination fea-
tures of the CꢀN unit. In trans-9b the (Z)ꢂ(ZrꢂN1)
,
bond (2.192(4) A) is shorter than the (E)ꢂ(Zr*ꢂN1)
,
linkage (2.272(4) A). The C2ꢂN1 bond length is
Fig. 1. Molecular structure of trans-9a (only the dication part is
,
1.288(6) A. The aryl substituent at C2 is oriented close
,
depicted). Selected bond lengths (A) and angles (°): ZrꢂN1* 2.235(2),
to coplanar with the central framework of the complex
(dihedral angles ZrꢂN1ꢂC2ꢂC3 −1.3(9)°, N1ꢂC2ꢂC3ꢂ
C4 −11.8(9)°) (Fig. 2).
ZrꢂN1 2.255(2), N1ꢂC2 1.281(4), C2ꢂC3 1.482(4), BꢂC21 1.642(4),
C21ꢂC22 1.532(4), C22ꢂC23 1.537(5), C23ꢂC24 1.475(5), BꢂC31
1.669(4), BꢂC41 1.655(4), BꢂC51 1.666(4); N1*ꢂZrꢂN1 77.8(1),
ZrꢂN1ꢂZr* 102.2(1), ZrꢂN1ꢂC2 124.3(2), N1ꢂC2ꢂC3 126.2(3),
C21ꢂBꢂC31 115.4(2), C21ꢂBꢂC41 105.7(2), C21ꢂBꢂC51 109.7(2),
C31ꢂBꢂC41 111.8(2), C31ꢂBꢂC51 102.1(2), C41ꢂBꢂC51 112.2(2),
BꢂC21ꢂC22 115.9(2), C21ꢂC22ꢂC23 114.1(3), C22ꢂC23ꢂC24 114.8(3).
The remaining solution from the crystallization of
complex trans-9a was enriched in the isomer cis-9a.
Monitoring by H-NMR did not reveal reestablishment
1
of the original 1:1 ratio during several hours at room
temperature. From work reported by Jordan, Boch-
mann and others [13] it is well established that the
formation of nitrile adducts of mononuclear mono-
cations derived from (alkylideneamido)zirconocene sys-
tems are very stable and their formation, e.g. by
treatment of Cp2ZrCH3+ with acetonitrile proceeds
readily (for an example see Chart 1). We, therefore,
investigated whether the formation of such species
could also be achieved starting from our readily avail-
able dimeric dication systems 9.
Scheme 3.

64
S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
the respective metallocene precursors with the suffi-
The dication 9a (cis/trans-mixture) was generated by
treatment of the precursor 6a with [butyl-B(C6F5)3]−
Li+ (7) in dichloromethane (see above and the Section
3). Then one molar equivalent of acetonitrile–Zr was
added. Workup after 1 h reaction time at room temper-
ature revealed that the cis-/trans-9a dication mixture
had been consumed with formation of the mononuclear
zirconocene mono-cation product [Cp2Zr(NꢀCHCH3)·
NꢁCCH3]+ (15a), with [butyl-B(C6F5)3]− counteranion.
The product 15a was isolated in close to 80% yield from
the reaction mixture (Scheme 4). Complex 15a shows a
typical ꢂNꢀCHCH3 13C-NMR resonance at l 173.1.
Analogous treatment of the in situ generated cis-/
trans-9a mixture with tert-butylisonitrile gave the cor-
responding CꢁNꢂCMe3 stabilized [(ethylideneamido)-
zirconocene] mono-cation system 16 (80% isolated),
and the reaction of the cis-/trans-9b dication mixture
with acetonitrile furnished the corresponding system
15b (68% isolated, 13C-NMR ꢂNꢀCHR resonance at l
170.1). In each case a single stereoisomer was obtained.
We assume that this is characterized by coplanar (E)-
arrangement of the R1-substituent with the stabilizing
NꢁCꢂR2 ligand at the linear Cp2Zr(NꢀCHR1) frame-
work as it is depicted in Scheme 4.
ciently soluble reagent 7 provides a simple method for
generating even very reactive metallocene based cations
such as the elusive monomeric [Cp2ZrꢀNꢀCHR]+
cation. This cation is probably formed in situ under the
reaction conditions but rapidly dimerizes to give the
metallacyclic dications 9 in good yield. Whether the
subsequently added nitrile reagents react directly with
the strongly electrophilic dications 9 or trap the
monomers (8) from an endothermic equilibration can-
not be concluded with certainty so far. However, it is
apparent that our halide abstraction method is able to
make reactive metallocene cation systems easily avail-
able. We will investigate whether the system 9 can be
used in organometallic syntheses for reactions that use
the coordinated m−NꢀCHR units as active functional
groups.
3. Experimental
Reactions were carried out under argon using
Schlenk-type glassware or in a glovebox. Solvents were
dried and distilled prior to use. The starting materials
6a and 6b were prepared analogously as described in
the literature [2a]. [Butyl-B(C6F5)3]−Li+ had previously
been mentioned in the literature [14]. The preparation
of the material (7) that was used in this study was
synthesized as described below. For additional general
information including a list of instrumentation used for
the spectroscopic and physical characterization, see
Ref. [15]. B(C6F5)3 was prepared as described in the
literature [16].
We conclude that [butyl-B(C6F5)3]−Li+ (7) is a suit-
able reagent for facile chloride abstraction from Group
4 metallocene units and related systems. Treatment of
3.1. Synthesis of lithium[butyltris(pentafluoro-
phenyl)borate] (7)
Chart 1.
A 1.6 M solution of n-butyllithium in hexane (1.50
ml, 2.40 mmol) was added dropwise with stirring to a
solution of trispentafluorophenylborane (1.00 g, 1.95
mmol) in 50 ml of pentane. The product 7 precipitated
immediately. The mixture was stirred for 2 h to allow
the reaction to go to completion. Then the product 7
was collected by filtration, washed with pentane (2×15
ml) and dried in vacuo [yield: 970 mg (86%)], m.p.
178 °C (dec.). 1H-NMR: ([benzene-d6, THF-d8], 4:1,
200 MHz, 300 K): l=1.67 (br, 2H, BꢂCH2), 1.53 (m,
2H, CH2), 1.28 (br, 2H, CH2), 0.93 (t, 3H, CH3).
11B{1H}-NMR: ([benzene-d6, THF-d8], 4:1, 64.2 MHz,
300 K): l= −12.6 (w1/2=225 Hz). 19F-NMR: ([ben-
zene-d6, THF-d8], 4:1, 282.4 MHz, 300 K): l= −167.9
(m, 6F, m-F), −165.5 (t, 3JFF=21 Hz, 3F, p-F),
−131.7 (m, 6F, o-F). Anal. Calc. for C22H9BF15Li
(576.0): C, 45.87; H, 1.57. Found: C, 45.21; H, 2.52%.
HRMS: Calc. for [C22H9BF15]−: 569.0558, found
569.0562.
Scheme 4.

S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
65
−3
,
max. residual electron density 1.09 (−0.52) e A
3.2. Reaction of (alkylideneamido)zirconocene chlorides
with [butyl-B(C6F5)3]−Li+ (7), preparation of the
[Cp2Zr(N=CHR)]22+2[butyl-B(C6F5)3]− complexes 9,
general procedure
around C23, refinement of split positions for C24 did
not improve the model, hydrogens calculated and
refined as riding atoms.
3.4. Reaction of (p-tolylmethanimido)zirconocene
chloride (6b) with 7: synthesis of cis/trans-9b
The respective Cp2ZrCl(NꢀCHR) complex 6 and the
reagent 7 were suspended in a 1:1 molar ratio in
dichloromethane. The resulting clear yellowish solution
was stirred at ambient temperature until a LiCl precip-
itate appeared (ca. 1 h). The mixture was stirred for
additional 2 h to allow the reaction to go to comple-
tion. The LiCl precipitate was removed by filtration.
Solvent was removed from the clear filtrate in vacuo.
The solid was taken up with pentane and the product 9
collected by filtration. It was washed with pentane
(2×20 ml) and dried in vacuo.
Reaction of 6a (200 mg, 0.53 mmol) with 7 (307 mg,
0.53 mmol) in CH2Cl2 analogously as described above
gave 337 mg (70%) of a 1:1.5 mixture of cis- and
1
trans-9b, m.p. 140 °C. H-NMR (CD2Cl2, 200.1 MHz,
300 K): l=trans-9b: 8.89 (s, 3H, CH), 6.37 (s, 30H,
Cp-H), 2.46 (s, 9H, tolyl-CH3); cis-9b: 9.22 (s, 2H,
CH), 6.77, 6.30 (each s, each 10H, Cp-H), 2.44 (s, 6H,
tolyl-CH3); 7.56–7.07 (m, 20H, tolyl-H), 1.22, 0.81
(each m, S 18H, [butyl-B(C6F5)3]−). 13C{1H}-NMR
1
(CD2Cl2, 50.3 MHz, 300 K): l=148.7 (dm, JCF=242
3.3. Reaction of (ethanimido)zirconocene chloride (6a)
with 7: synthesis of cis/trans-9a
Hz, B(C6F5)3), 138.0 (dm, 1JCF=242 Hz, B(C6F5)3),
1
137.0 (dm, JCF=243 Hz, B(C6F5)3), 132.0 (ipso-tolyl-
C), 129.5, 128.0 (o- and p-tolyl-C), 121.0, 117.8 (Cp-C,
cis-9b), 119.5 (Cp-C, trans-9b), 21.1 (tolyl-CH3), 31.1,
27.3, 23.4 (br), 14.5 ([butyl-B(C6F5)−3 ]), one ipso-C of
tolyl, ipso-C of B(C6F5)3 and NꢀC carbon atoms not
observed. 11B{1H}-NMR (CD2Cl2, 64.2 MHz, 300 K):
l= −13.2 (w1/2=47 Hz). IR (KBr): w˜ =3020 (m),
2964 (m), 2802 (m), 1632 (m), 1510 (vs), 1453 (vs), 1280
The reaction of 6a (200 mg, 0.67 mmol) with 385 mg
(0.67 mmol) of 7 in CH2Cl2 analogously as described
above gave a 1:1 mixture of cis- and trans-9a in a
combined yield of 407 mg (73%), m.p. 153 °C. 1H-
NMR (CD2Cl2, 200.1 MHz, 300 K): trans-9a: l=7.85
3
(q, 2H, JHH=4.7 Hz, CH(CH3)), 6.83 (s, 20H, Cp-H),
3
1.77 (d, 6H, JHH=4.7 Hz, CH(CH3)); cis-9a: 7.66 (q,
(vs), 1120 (s), 1019 (m), 975 (s), 795 (vs), 486 (m) cm−1
;
3
2H, JHH=4.7 Hz, CH(CH3)), 6.84, 6.81 (each s, each
Anal. Calc. for C80H54B2F30N2Zr2 (1817.3): C, 52.87;
H, 3.00; N, 1.54. Found: C, 51.92; H, 3.70; N, 1.64%.
3
10H, Cp-H), 1.92 (d, 6H, JHH=4.7 Hz, CH(CH3));
1.21, 0.80 (each m, S 18H, [butyl-B(C6F5)3−]). 13C{1H}-
NMR (CD2Cl2, 50.3 MHz, 300 K): l=194.9 (NꢀC,
cis- and trans-9a), 148.7 (dm, 1JCF=242 Hz, B(C6F5)3),
3.4.1. X-ray crystal structure analysis of trans-9b
Single crystals were obtained from a solution of the
cis/trans-9b mixture in dichloromethane at −20 °C.
Formula C36H36N2Zr2·2C22H9BF15, M=1817.3, yellow
crystal 0.25×0.20×0.10 mm, a=10.524(1), b=
138.0 (dm, 1JCF=242 Hz, B(C6F5)3), 137.0 (dm, 1JCF
=
243 Hz, B(C6F5)3), 121.0, 117.8 (Cp-C, cis-9a), 119.5
(Cp-C, trans-9a), 67.1 (CH(CH3)), 31.1, 27.3, 23.4 (br),
14.5 ([butyl-B(C6F5)3−]), ipso-C of C6F5 not observed.
11B{1H}-NMR (CD2Cl2, 64.2 MHz, 300 K): l= −13.0
(w1/2=50 Hz). IR (KBr): w˜ =3380 (w), 2964 (s), 2927
(m), 2855 (m), 1645 (m), 1512 (s), 1458 (vs), 1263 (vs),
1100 (s), 1019 (m), 970 (s), 795 (vs) cm−1; m.p. 153 °C.
Anal. Calc. for C68H46B2F30N2Zr2 (1665.1): C, 49.05;
H, 2.78; N, 1.62. Found: C, 49.07; H, 3.49; N, 1.86%.
,
16.288(1), c=20.870(1) A, i=93.86(1)°, V=3569.3(4)
,
3
A , zcalc=1.691 g cm−3, v=4.20 cm−1, empirical
absorption correction via SORTAV (0.9025T50.959),
Z=4, monoclinic, space group P21/c (no. 14), u=
,
0.71073 A, T=198 K, ꢀ and € scans, 11777 reflections
collected (9h, 9k, 9l), [(sin q)/u]=0.62 A−1, 7080
,
independent (Rint=0.056) and 3805 observed reflec-
tions [I]2 |(I)], 543 refined parameters, R=0.064,
wR2=0.119, max. residual electron density 0.39 (−
3.3.1. X-ray crystal structure analysis of trans-9a
Single crystals were obtained from a solution of
cis-/trans-9a in dichloromethane at −20 °C. Formula
C24H28N2Zr2·2C22H9BF15, M=1665.1, yellow crystal
0.36) e A−3, positional disorder of C24 in the n-butyl-
,
group, refined with split positions in the ratio
0.63:0.37(1), thermal displacement parameters of the
Cp-carbon atoms indicate some disorder, not refined,
hydrogens calculated and refined as riding atoms.
Data sets were collected with a Nonius KappaCCD
diffractometer, equipped with a rotating anode genera-
tor Nonius FR591. Programs used: data collection COL-
LECT [17a], data reduction DENZO-SMN [17b],
absorption correction SORTAV [17c,17d], structure solu-
tion SHELXS-97 [17e], structure refinement SHELXL-97
[17f], graphics SCHAKAL [17g].
0.30×0.20×0.20 mm, a=23.978(1), b=11.152(1),
3
,
,
c=23.745(1) A, i=90.90(1)°, V=6348.7(7) A ,
zcalc=1.742 g cm−3, v=4.63 cm−1, empirical absorp-
tion correction via SORTAV (0.8745T50.913), Z=4,
,
monoclinic, space group C2/c (no. 15), u=0.71073 A,
T=198 K, ꢀ and € scans, 19367 reflections collected
(9h, 9k, 9l), [(sin q)/u]=0.65 A−1, 7248 indepen-
,
dent (Rint=0.038) and 5730 observed reflections [I]
2|(I)], 471 refined parameters, R=0.043, wR2=0.099,

66
S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
3.5. Reaction of dications 9 with nitriles: formation of
the [Cp2Zr(NꢀCHR1)NꢁCR2]+[butyl-B(C6F5)3]−
complexes 15, general procedure
(br), 14.5 ([butyl-B(C6F5)−3 ]). The NꢁC carbon atom,
ipso-C of tolyl and ꢂB(C6F5)3 were not observed.
11B{1H}-NMR (CD2Cl2, 64.2 MHz, 300 K): l= −12.6
(w1/2=32 Hz). IR (KBr): w˜ =2957 (m), 2922 (m), 2849
(m), 2304 (NꢁC, m), 1642 (m), 1604 (m), 1512 (s), 1458
(vs), 1265 (m), 1078 (vs), 972 (vs), 806 (vs), 733 (s), 680
(m) cm−1. Anal. Calc. for C43H30BF15N2Zr (961.7): C,
53.70; H, 3.14; N, 2.91. Found: C, 53.08; H, 4.13; N,
2.32%.
The dications 9 were generated by treatment of 0.67
mmol of the respective Cp2ZrCl(NꢁCHR1) complex 6
with 0.65 mmol [butyl-B(C6F5)3]−Li+ (7) in 50 ml of
dichloromethane analogously as described above. Be-
fore workup one molar equivalent of the nitrile
NꢁCꢂR2 was added via syringe. The reaction mixture
was then stirred for 1 h at room temperature (r.t.). The
LiCl precipitate was removed by filtration. Solvent was
removed in vacuo to give the complexes 15 as yellow
solids.
3.8. Reaction of 9a with tert-butylisonitrile, formation
of 16
The reaction of 200 mg (0.67 mmol) of 6a with 385
mg (0.67 mmol) of 7 in CH2Cl2 followed by treatment
with 7.60 ml (0.67 mmol) of NꢁCꢂCMe3 carried out
according to the general procedure gave 490 mg (80%)
of 16, m.p. 123 °C (dec.). 1H-NMR (CD2Cl2, 200.1
3.6. Treatment of 9a with acetonitrile, formation of
15a
The reaction of (ethanimido)zirconocene chloride
(6a, 200 mg, 0.67 mmol) with 385 mg (0.67 mmol) of 7
in dichloromethane followed by treatment with 3.50 ml
(0.65 mmol) of acetonitrile analogously as described
above gave 455 mg (78%) of 15a, m.p. 189 °C (dec.).
1H-NMR (CDCl2, 200.1 MHz, 300 K): l=8.55 (q, 1H,
3JHH=5.1 Hz, CH), 6.19 (s, 10H, Cp-H), 1.88 (d, 3H,
3JHH=5.1 Hz, CH3), 2.22 (bs, 3H, nitrile-CH3), 1.21,
0.80 (each m, S 9H, [butyl-B(C6F5)−3 ]). 13C{1H}-NMR
(CD2Cl2, 50.3 MHz, 300 K): l=173.1 (NꢀC), 148.7
3
MHz, 300 K): l=8.45 (q, 1H, JHH=5.1 Hz, CH),
3
6.14 (s, 10H, Cp-H), 1.87 (d, 3H, JHH=5.1 Hz, CH3),
1.58 (s, 9H, C(CH3)3), 1.21, 0.80 (each m, S 9H,
[butyl-B(C6F5)3−]). 13C{1H}-NMR (CD2Cl2, 50.3 MHz,
300 K): l=173.2 (NꢀC), 148.8 (dm, 1JCF=253 Hz,
1
B(C6F5)3), 137.9 (dm, JCF=257 Hz, B(C6F5)3), 136.7
(dm, 1JCF=227 Hz, B(C6F5)3), 109.1 (Cp-C), 30.0
(C(CH3)3), 27.8 (NꢀCH(CH3)), 22.8 (C(CH3)3), 31.3,
27.4, 22.8 (br), 14.6 ([butyl-B(C6F5)−3 ]), isonitrile CꢁN
carbon and ipso-C of −B(C6F5)3 not observed.
11B{1H}-NMR (CD2Cl2, 64.2 MHz, 300 K): l= −12.8
(w1/2=38 Hz). IR (KBr): w˜ =2961 (m), 2924 (m), 2874
(m), 2219 (CꢁN, m), 1641 (m), 1512 (s), 1457 (vs), 1266
(m), 1080 (s), 972 (s), 806 (s), 677 (w) cm−1. Anal. Calc.
for C39H32BF15N2Zr (915.7): C, 51.15; H, 3.52; N, 3.06.
Found: C, 49.80; H, 3.91; N, 2.83%.
1
1
(dm, JCF=252 Hz, B(C6F5)3), 137.3 (dm, JCF=255
Hz, B(C6F5)3), 137.0 (dm, 1JCF=233 Hz, B(C6F5)3),
110.1 (Cp-C), 27.7 (NꢀCH(CH3)), 22.0 (nitrile-CH3),
31.1, 27.5, 23.2 (br), 14.0 ([butyl-B(C6F5)−3 ]), NꢀC car-
bon atom and ipso-C of ꢂB(C6F5)3 not observed.
11B{1H}-NMR (CD2Cl2, 64.2 MHz, 300 K): l= −13.4
(w1/2=38 Hz). IR (KBr): w˜ =2955 (s), 3015 (s), 2910
(s), 2856 (m), 2310 (NꢁC, s), 1640 (m), 1513 (s), 1456
(vs), 1443 (s), 1375 (m), 1080 (s), 965 (s), 802 (s) cm−1
.
Anal. Calc. for C36H26BF15N2Zr (873.6): C, 49.49; H,
3.00; N, 3.21. Found: C, 49.90; H, 3.57; N, 2.59%.
4. Supplementary material
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with Cambridge Crystallographic Data Cen-
tre as supplementary publications nos. CCDC 162645
and 162646. Copies of this information may be ob-
tained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
3.7. Reaction of 9b with acetonitrile, formation of 15b
The dication 9b was generated by treatment of 250
mg (0.66 mmol) of 6b with 380 mg (0.66 mmol) of 7 in
dichloromethane. Subsequent reaction with 2.80 ml
(0.66 mmol) of acetonitrile as described above gave 432
mg (68%) of 15b as a yellow solid, m.p. 187 °C (dec.).
1H-NMR (CD2Cl2, 200.1 MHz, 300 K): l=9.07 (s,
1H, NꢀCH), 7.34–7.22 (m, 4H, tolyl-H), 6.26 (s, 10H,
Cp-H), 2.42 (s, 3H, tolyl-CH3), 2.29 (bs, 3H, nitrile-
CH3), 1.24, 0.81 (each m, S 9H, [butyl-B(C6F5)−3 ]).
13C{1H}-NMR (CD2Cl2, 50.3 MHz, 300 K): l=170.1
Acknowledgements
1
(NꢀC), 149.7 (dm, JCF=242 Hz, B(C6F5)3), 138.3 (dm,
1JCF=242 Hz, B(C6F5)3), 137.5 (dm, 1JCF=243 Hz,
B(C6F5)3), 131.1, 128.2 (o- and p-tolyl-C), 111.4 (Cp-
C), 22.6 (nitrile-CH3), 21.7 (tolyl-CH3), 31.3, 27.4, 23.4
Financial support from the Fonds der Chemischen
Industrie and the Deutsche Forschungsgemeinschaft is
gratefully acknowledged.

S. Do¨ring et al. / Journal of Organometallic Chemistry 643–644 (2002) 61–67
67
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