Synthesis and dynamic features of (chloro)zirconocene cations stabilised by pendant (diarylphosphanyl)alkyl and (dimethylamino)alkyl substituents at their cyclopentadienyl ring systems

Article abstract of DOI:10.1002/ejic.200390210

Treatment of the substituted (diarylphosphanyl)methyl group-4 metallocene complexes [(C₅H₄-CR¹R²- PAr₂)₂ZrCl₂] (2: R¹/ R² = CH₃/CH₃, H/CH₃, H/aryl) with Li[B(C₆F₅)₄] in dichloromethane solution results in chloride ligand abstraction (with LiCl precipitation) to yield the complexes [(C₅H₄-CR¹R²- PAr₂)₂Zr-Cl⁺] (5), with both phosphanyl groups internally coordinated to the metal centre. Three possible diastereoisomers are observed in the case of 5c (R¹ = H; R² = CH₃), while bulkier R² substituents give higher selectivities. The thermally induced (reversible) cleavage of the Zr-phosphane linkage results in dynamic NMR behaviour. Gibbs activation energies of ΔG^≠(298 K) = 14.8 ± 0.5 and 14.5 ± 0.5 kcal/mol were obtained for these intramolecular equilibration processes in the complexes trans-5d (R¹ = H; R² = Ph) and trans-5e (R¹ = H; R² = ferrocenyl), respectively. Treatment of the substituted (dimethylamino)methyl metallocene complexes [(C₅H₄-CR¹R²- NMe₂)₂ZrCl₂] (6a, 6b) with Li[B(C₆F₅)₄] proceeds analogously to yield the cation systems [{C₅H₄-C(CH₃)₂- NMe₂}₂ZrCl⁺] (12a) and [{C₅H₄-CH(CH₃)- NMe₂}₂ZrCl⁺] (12b, three possible diastereoisomers). Both complexes have their pairs of amino groups coordinated to the metal centre. The complexes exhibit dynamic NMR spectra. Selective equilibration of the diastereotopic N(CH₃)^A(CH₃)^B resonances of complex 12a is observed [ΔG^≠(233 K) = 11.5 ± 0.2 kcal/mol], whereas the adjacent C(CH₃)^A(CH₃)^B methyl groups remain diastereotopic. The dynamic equilibration of the latter was observed at a markedly higher temperature [ΔG≠(333 K) = 17.3 ± 0.2 kcal/mol]. Treatment of [{C₅H₄-C(CH₃)₂- NMe₂}CpZrCl₂] (10) with Li[B(C₆F₅)₄] resulted in the formation of complex [{C₅H₄-C(CH₃)₂- NMe₂}CpZr-Cl⁺] (11), which shows the internal -N(CH₃)^A(CH)^B equilibration proceeding with a markedly higher activation barrier [ΔG^≠(333 K) = 17.6 ± 0.2 kcal/ mol] than in 12a, and a stereochemical memory effect indicative of solvent coordination to the metal centre of the resulting highly electrophilic chlorozirconocene cation intermediate. Complex 11 was characterised by an X-ray crystal structure analysis, which shows the internal Zr←amine coordination. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejic.200390210

FULL PAPER
Synthesis and Dynamic Features of (Chloro)zirconocene Cations Stabilised by
Pendant (Diarylphosphanyl)alkyl and (Dimethylamino)alkyl Substituents at
Their Cyclopentadienyl Ring Systems
Steve Döring,[a] Vasily V. Kotov,[a] Gerhard Erker,*[a] Gerald Kehr,[a] Klaus Bergander,[a][‡]
Olga Kataeva,[a][‡] and Roland Fröhlich[a][‡‡]
Keywords: Cations / Metallocenes / N ligands / P ligands / Zirconium
Treatment of the substituted (diarylphosphanyl)methyl
group-4 metallocene complexes [(C5H4−CR1R2−PAr2)2ZrCl2]
(2: R1/R2 = CH3/CH3, H/CH3, H/aryl) with Li[B(C6F5)4] in
dichloromethane solution results in chloride ligand abstrac-
tion (with LiCl precipitation) to yield the complexes
[(C5H4−CR1R2−PAr2)2Zr−Cl+] (5), with both phosphanyl
groups internally coordinated to the metal centre. Three pos-
sible diastereoisomers are observed in the case of 5c (R1 = H;
R2 = CH3), while bulkier R2 substituents give higher selectiv-
ities. The thermally induced (reversible) cleavage of the
Zr−phosphane linkage results in dynamic NMR behaviour.
to the metal centre. The complexes exhibit dynamic NMR
spectra. Selective equilibration of the diastereotopic
N(CH3)A(CH3)B resonances of complex 12a is observed
[∆G϶(233 K) = 11.5
0.2 kcal/mol], whereas the adjacent
C(CH3)A(CH3)B methyl groups remain diastereotopic. The
dynamic equilibration of the latter was observed at a mark-
edly higher temperature [∆G϶(333 K) = 17.3 0.2 kcal/mol].
Treatment of [{C5H4−C(CH3)2−NMe2}CpZrCl2] (10) with
Li[B(C6F5)4] resulted in the formation of complex
[{C5H4−C(CH3)2−NMe2}CpZr−Cl+] (11), which shows the in-
ternal −N(CH3)A(CH)B equilibration proceeding with a mark-
Gibbs activation energies of ∆G϶(298 K) = 14.8 0.5 and 14.5 edly higher activation barrier [∆G϶(333 K) = 17.6 0.2 kcal/
0.5 kcal/mol were obtained for these intramolecular equi-
mol] than in 12a, and a stereochemical memory effect indic-
ative of solvent coordination to the metal centre of the re-
libration processes in the complexes trans-5d (R1 = H; R2
=
Ph) and trans-5e (R1 = H; R2 = ferrocenyl), respectively. Treat- sulting highly electrophilic chlorozirconocene cation inter-
ment of the substituted (dimethylamino)methyl metallocene
complexes [(C5H4−CR1R2−NMe2)2ZrCl2] (6a, 6b) with
Li[B(C6F5)4] proceeds analogously to yield the cation systems
[{C5H4−C(CH3)2−NMe2}2ZrCl+] (12a) and [{C5H4−CH-
(CH3)−NMe2}2ZrCl+] (12b, three possible diastereoisomers).
Both complexes have their pairs of amino groups coordinated
mediate. Complex 11 was characterised by an X-ray crystal
structure analysis, which shows the internal Zrǟamine coor-
dination.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
theses are often less straightforward and they require stronger
donor ligand stabilisation. A typical example is shown in
Scheme 1. Treatment of the (diarylphosphanyl)alkyl-substi-
tuted [RCp2Zr(CH3)2] derivatives with B(C6F5)3 as a suit-
able methyl anion abstractor[9,10] results in the clean forma-
tion of the corresponding [RCp2ZrCH3ϩ] cation (3).[11]
Treatment of this in turn with a second equivalent of
B(C6F5)3 in the presence of a chloride source then gives rise
to subsequent formation of the doubly internally phos-
phane-stabilised [RCp2ZrClϩ] cation derivative 5 (via 4, see
Scheme 1).[11,12]
It would be interesting to have the corresponding (di-
methylamino)alkyl-substituted Cp systems available in or-
der to study the stabilising influence of the tertiary amine
donor ligands relative to the stabilising phosphanes. How-
ever, their synthesis from 6 by an analogous pathway is pre-
cluded by a preferred internal CϪH activation process that
rapidly takes place at the stage of the intermediate 8 (see
Scheme 2).[13Ϫ16] We therefore had to devise an alternative
pathway to make the (dimethylamino)alkylϪCp-containing
Alkylzirconocene cations are regarded as the active
species
in
homogeneous
ZieglerϪNatta
olefin
polymerisation.[1aϪ1e] Some of such complexes can very eas-
ily be prepared, a typical example being the parent com-
pound [Cp2ZrCH3ϩ] (1), readily available from the neutral
precursor [Cp2Zr(CH3)2] by a variety of methods.[2a,2b,3Ϫ5]
The cation 1 is stabilised by tight ion pair formation with
its anion.[6] Alternatively, it adds a variety of simple neutral
donor ligands such as tetrahydrofuran to form pseudotetra-
hedral adducts (e.g., [Cp2ZrCH3(THF)ϩ] or its respective
‘‘outer-sphere’’ or ‘‘solvent-separated’’ ion pair).[7,8]
[RCp2ZrClϩ] complexes are much less stable. Their syn-
[a]
Organisch-Chemisches Institut der Universität Münster,
Corrensstr. 40, 48149 Münster, Germany
[‡]
NMR spectroscopy
X-ray structure analyses
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
[‡‡]
1599
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/03/0408Ϫ1599 $ 20.00ϩ.50/0

G. Erker et al.
FULL PAPER
Ϫ
[CH3B(C6F5)3Ϫ] anion; 5aЈЈ: Ar ϭ Ph, with [ClB(C6F5)3
]
anion].[11] In one case (5aЈЈ) we succeeded in preparing the
substituted chlorozirconocene cation directly by means of
chloride abstraction by the strong organometallic Lewis
acid B(C6F5)3.[11,12] This result indicated to us that chloride
abstraction by more powerful reagents, such as
Li[B(C6F5)4],[17,18] might provide a suitable direct route to
this general class of internally donor ligand stabilised chlo-
rozirconocene cation systems. Initial tests were therefore
carried out with the substituted [{[(diarylphos-
phanyl)methyl]C5H4}2ZrCl2] systems 2a (Ar ϭ Ph) and 2b
(Ar ϭ p-tolyl), which were each treated with 1 mol-equiv.
of the Li[B(C6F5)4] reagent in dichloromethane solution at
room temperature. After ca. 1 h, the chloride abstraction
was complete. The resulting LiCl precipitate was removed
by filtration and the corresponding chlorometallocene cat-
ion products 5a and 5b were isolated in 55 and 67% yields,
respectively (both with [B(C6F5)4Ϫ] anion, see Scheme 3).
Scheme 1
[RCp2ZrϪClϩ] cation systems synthetically available. Such
a selective preparative route is described in this paper. The
dynamic NMR behaviour of the resulting complexes al-
lowed for an estimate of the internal stabilisation of such
strongly electrophilic group-4 metallocene cations by ter-
tiary amine donor ligands.
Scheme 3
We have also used the previously described complexes
[(C5H4ϪCHRϪPAr2)2ZrCl2] 2c (R ϭ CH3; Ar ϭ Ph), 2d
(R ϭ Ph; Ar ϭ Ph) and 2e (R ϭ ferrocenyl; Ar ϭ p-tol-
yl)[11,12,30] as neutral substrates for the chloride abstraction
reaction with Li[B(C6F5)3] to give the new metallocene cat-
ion complexes 5cϪe (see Scheme 4).
The complexes 2cϪe each contain two stereogenic carbon
centres and were each employed in the ClϪ abstraction reac-
tion as ca. 1:1 meso-/rac-2(cϪe) mixtures of diastereoiso-
mers. The doubly phosphorus-coordinated products 5cϪe
can each form three diastereoisomers: two complexes in
which the substituents at the pair of stereogenic metall-
acyclic ring carbon centres are oriented cis (syn- or anti-
oriented relative to the ZrϪCl vector,[19] thus giving rise to
the formation of compounds syn-cis-5cϪe and anti-cis-
5cϪe, respectively), together with the trans diastereoisomers
(trans-5cϪe) (see Scheme 4).
Scheme 2
In the case of 5c (R ϭ CH3; Ar ϭ Ph) a near to statistical
mixture of the three diastereoisomers was actually obtained
(isolated in 54% yield). This is evident from inspection of
Results and Discussion
Synthesis and Characterisation of [Chlorobis{[(diarylphos-
phanyl)alkyl]cyclopentadienyl}zirconium] Cation Complexes
typical NMR spectra of the organometallic salt 5c. The 31
P
NMR spectrum (at 253 K) shows singlets at δ ϭ Ϫ36.2 and
We had previously prepared
a series of [{(Ar2- Ϫ45.9 ppm corresponding to the pairs of symmetry-equiva-
PCMe2)C5H4}2ZrClϩ] cation systems by a three-step syn- lent phosphorus nuclei of the complexes syn-cis-5c and anti-
thesis via the dication intermediate 4, as outlined in cis-5c (no absolute assignment was achieved) and an AB
2
Scheme 1 [5aЈ: Ar ϭ Ph; 5bЈ: Ar ϭ p-tolyl, with pattern at δ ϭ Ϫ38.1 ppm and δ ϭ Ϫ47.2 ppm with a JP,P
1600
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607

Stabilised (Chloro)zirconocene Cations
FULL PAPER
Treatment of complex [(C5H4ϪCHPhϪPPh2)2ZrCl2] (2d)
with the Li[B(C6F5)4] reagent cleanly resulted in the forma-
tion of the chlorozirconocene cation complex 5d. Again,
diastereomeric complexes are formed, but the 31P NMR
spectrum of 5d shows the presence only of the trans-5d iso-
2
mer (AB system at δ ϭ Ϫ18.4 and Ϫ41.8 ppm, JP,P
ϭ
108 Hz) and of one of the cis-5d isomers, in a ca. 1:1 ratio.
Complex trans-5d shows two 1H NMR CpϪCHR signals
at δ ϭ 5.65 and 5.57 ppm. An increase in the temperature
results in coalescence of the signals of pairwise dia-
stereotopic groups of trans-5d, including these CpϪCHR
resonances with
a
Gibbs activation energy of
∆G϶(298 K) ϭ 14.8 Ϯ 0.5 kcal/mol.[11,20,21] The NMR sig-
nals of the cis-5d isomers remain unaffected by the dynamic
behaviour of trans-5d. We therefore assign a process as de-
picted in Scheme 5 to account for this characteristic behav-
iour, in which a consecutive dissociation of both ZrǟP link-
ages takes place in trans-5d, followed by rotation around
the ZrϪCp vector and reformation of the stabilising intra-
molecular Zrǟphosphane interactions.
Scheme 4
coupling constant of 110 Hz, attributable to the trans-5c
diastereoisomer (see Figure 1).
Scheme 5
Complex 5c shows similar dynamic NMR features at el-
evated temperatures. We have found indications for an in-
tramolecular equilibration process of trans-5c, analogous to
that described above for 5d, and a separate equilibration
between the two cis-5c isomers. Unfortunately, the coales-
cence temperatures could not be reached cleanly in this case
because of a rapid thermal decomposition of the systems.
Complex 5e was obtained as a similar mixture of a single
cis-5e diastereomer and the trans-5e diastereomer. Complex
trans-5e exhibits a total of eight C5H4 resonances [at δ ϭ
7.18, 6.92, 6.17, 6.06 ppm (ring A), and δ ϭ 6.65, 6.06, 6.00,
Figure 1. 31P{1H} NMR spectrum of the close to statistical mixture
of the syn-cis-5c, anti-cis-5c and trans-5c diastereomers (in
CD2Cl2 solution)
As would be expected, each cis-5c isomer exhibits a set of
four methine 1H/13C NMR signals of the pair of symmetry-
equivalent C5H4 ligand units. In contrast, the
(C5H4ϪCHMeϪ[P]) ligands of the trans-5c isomer are dia-
stereotopic. Consequently, complex trans-5c shows a set of
eight Cp signals of equal intensity (for numerical values see
the Exp. Sect.), a pair of CαϪH multiplets (δ ϭ 4.21 and
1
5.94 ppm (ring B)] and a pair of CpCHR H NMR reson-
ances at δ ϭ 5.06 and 5.12 ppm. From the coalescence of
these last two signals at Tc ϭ 298 K, a Gibbs activation
energy of ∆G϶(Tc) ϭ 14.5 Ϯ 0.5 kcal/mol was obtained.
4.47 ppm), each of 1 H relative intensity, and two methyl Again, the cis-5e isomer is not involved in this dynamic pro-
1H NMR resonances at δ ϭ 1.25 and 1.50 ppm.
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607
cess. It shows a single 31P NMR resonance (δ ϭ Ϫ18.2
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G. Erker et al.
FULL PAPER
1
ppm) and four C5H4ϪR H NMR multiplets at δ ϭ 7.15,
6.42, 6.35, and 6.22 ppm.
Synthesis and Characterisation of [Chlorobis{[(dimethyl-
amino)alkyl]cyclopentadienyl}zirconocene] Cation
Complexes
The starting materials for the preparation of the related
[(dimethylamino)alkylϪC5H4]zirconium complexes (6a,b
and 10) were also prepared by a fulvene route,[22] as de-
scribed previously by us.[14Ϫ16] The synthesis started from 6-
(dimethylamino)-6-methylfulvene.[23] Hydride addition gave
the Li[C5H4ϪCHMeϪNMe2] reagent,[24] which was then
transmetallated with zirconium to yield a meso/rac mixture
of [(C5H4ϪCHMeϪNMe2)2ZrCl2] (6b). Methyllithium ad-
dition to 6-(dimethylamino)-6-methylfulvene[25] gave
Li[C5H4ϪCMe2ϪNMe2]. Transmetallation by treatment
[26]
with [ZrCl4(THF)2]
furnished [(C5H4ϪCMe2Ϫ
[27]
NMe2)2ZrCl2] (6a), whereas treatment with CpZrCl3
gave [(C5H4ϪCMe2ϪNMe2)CpZrCl2] (10).
Scheme 6
Complex 10 was treated with
1
mol-equiv. of
Li[B(C6F5)4] in dichloromethane to yield the cation com-
plex 11 (Ͼ 70% isolated) (see Scheme 6). Single crystals of
11 suitable for an X-ray crystal structure analysis were ob-
tained when liquid pentane was allowed to diffuse slowly
into a CH2Cl2 solution of the organometallic salt. Cations
and anions of 11 are independent in the solid state. The
zirconium atom in 11 is pseudotetrahedrally coordinated by
two η5-cyclopentadienyl rings, the chloride ligand and the
nitrogen atom of the pendant ϪCMe2ϪNMe2 group at-
tached to one of the C5H4 ligands (Figure 2). The resulting
NϪZrϪCl angle is fairly large at 106.0(1)°, whereas the
˚
ZrϪN bond length is short at 2.369(3) A [the respective
ZrϪN(Me2) distance in 9, for example (see Scheme 2),
amounts to 2.469(1) A].[14Ϫ16] The framework of the metal-
˚
lacyclic ring system in complex 11 is reasonably unstrained,
with bond angles C1ϪC6ϪN
ϭ
100.7(3)° and
˚
Figure 2. A view of the molecular geometry of 11 in the crystal
C6ϪNϪZr ϭ 99.6(2) [bond lengths C1ϪC6 1.528(5) A,
˚
(only the cation is depicted); selected bond lengths [A] and angles
˚
C6ϪN 1.541(5) A]. The C1ϪC6 vector at the C1 to C5 Cp
[°]: ZrϪN 2.369(3), ZrϪCl 2.426(1), ZrϪC 2.398(4) to 2.502(4),
ring is oriented slightly out of the C5H4 ring plane toward C1ϪC6 1.528(5), C6ϪN 1.541(5), C6ϪC7 1.527(6), C6ϪC8
1.527(6), NϪC9 1.491(5), NϪC10 1.480(5); NϪZrϪCl 106.0(1),
ZrϪNϪC6 99.6(2), ZrϪNϪC9 101.0(2), ZrϪNϪC10 123.5(2),
C9ϪNϪC6 112.8(3), C10ϪNϪC6 115.1(4), C9ϪNϪC10 104.2(3),
NϪC6ϪC1 100.7(3), NϪC6ϪC7 112.6(3), NϪC6ϪC8 111.0(4),
C7ϪC6ϪC1 112.7(4), C8ϪC6ϪC1 109.8(4), C7ϪC6ϪC8 109.7(4)
the zirconium centre (161.5°).
The internal (dimethylamino)alkyl coordination to the
electron-deficient zirconium centre also shows up in the 15
N
NMR shift of 11.[28] The cation complex 11 exhibits a 15N
NMR resonance at δ ϭ Ϫ359.8 ppm, which is ∆δ Ͼ Ϫ20
as compared to its neutral precursor 10,[14Ϫ16] for which cis-12b, and their diastereoisomer trans-12b. Each of the cis
an open, noncoordinating geometry of the ϪCMe2ϪNMe2 complexes shows four H/13C NMR methine resonances of
1
substituent was found by X-ray diffraction.[14Ϫ16]
their symmetry-equivalent pairs of C5H4 ligands, whereas
The meso-6b/rac-6b mixture also reacts cleanly with the C5H4 ligands of trans-12b are diastereotopic and hence
Li[B(C6F5)4] in dichloromethane at ambient temperature to give rise to the observation of eight respective methine
yield 12b (Scheme 7). The NMR spectra at room tempera- NMR signals. Similarly, we have observed a total of four
ture are quite complicated, due to the dynamics of the sys- ϪCHMeϪ signals in the mixture (one each of syn- and anti-
tem and some signal overlap. At 213 K a clean separation cis-12b and two of trans-12b) as well as four ϪCH(CH3)Ϫ
of most resonances is achieved, and it was shown that a ca. 1H NMR doublets. Both nitrogen centres in the complexes
1:2:1 mixture of three diastereoisomers was obtained. These 12b are coordinated to the zirconium atom. This follows
show the same overall characteristics as seen earlier for the from the observed 1H and 13C NMR patterns, and is clearly
related phosphorus complexes (see above). Consequently, it demonstrated by the observed four 15N NMR resonances[28]
should also be assumed here that two cis-configured cation (again, two for the pair of cis-12b isomers and the remain-
complexes have been obtained, namely syn-cis-12b and anti- ing pair originating from trans-12b), all of which are charac-
1602
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607

Stabilised (Chloro)zirconocene Cations
FULL PAPER
teristically shifted to more negative δ values (by ∆δ ഠ Ϫ30) ing (A and B) methyl groups at the adjacent α-carbon atom.
relative to the open, noncoordinated amino groups of the This indicates that a rapid dynamic process involving cleav-
starting material 6b (15N NMR: 12b: δ ϭ Ϫ369.6, Ϫ369.3, age of the ZrϪN(Me)2 linkage, inversion at the nitrogen
Ϫ364.7, Ϫ367.1 ppm vs. 6b: δ ϭ Ϫ337.6 ppm). Because of atom, rotation around the NϪC(Me2) vector and ring clos-
the complexity of the system, with many overlapping NMR ure by reformation of the ZrϪN bond is taking place in the
resonances at higher temperature, the dynamic NMR fea- complexes 12; this process must take place without con-
tures of the metallocene cation isomers of 12b were not comitant rotation around the ZrϪCp vector, since no
further analysed.
CMeAMeB interconversion is observed under these con-
ditions.
Scheme 8
Scheme 7
This isolated dynamic process of the ZrϪNMe2 moiety
Treatment of [(C5H4ϪCMe2ϪNMe2)2ZrCl2] (6a) with in 12a can be slowed on the 1H NMR timescale and eventu-
Li[B(C6F5)4] cleanly resulted in chloride abstraction with ally frozen (see Figure 3). Below a decoalescence tempera-
formation of the complex 12a (Scheme 6; 78% yield, iso- ture of Tc ϭ 243 K, a 1:1 pair of N(CH3)2 1H NMR reso-
lated). Again, the 15N NMR spectra indicate that both nances is observed, and a Gibbs activation energy of
ϪNMe2 groups were coordinated to the central zirconium ∆G϶(233 K) ϭ 11.5 Ϯ 0.2 kcal/mol was calculated[20,21] for
atom (15N NMR: 12a:
Ϫ337.4 ppm).
δ
ϭ
Ϫ358.6 vs. 6a:
δ
ϭ
this characteristic dynamic process of 12a, which probably
involves a rate-determining (reversible) rupture of the
The dynamic features of complex 12a are slightly differ- zirconiumϪnitrogen linkage (Scheme 9).
ent from those of the phosphorus-containing cations 5. At
298 K the H NMR spectrum of 12a shows a 1:1 pair of eventually also results in a broadening of the pair of
A considerable increase in the monitoring temperature
1
signals for the CpϪC(CH3)2 methyl groups, indicating their CMeAMeB 1H NMR signals and subsequently in their co-
chemical differentiation into syn- and anti-CH3 substituents alescence (see Figure 3). In 1,2-dideuteriotetrachloroethane
relative to the central ZrϪCl vector. At the same time we solvent a Gibbs activation energy of ∆G϶(333 K) ϭ 17.3 Ϯ
observe only a double intensity 1H NMR singlet of the 0.2 kcal/mol was obtained for this second dynamic process
ϪN(CH3)2 groups of 12a at ambient temperature. This indi- of 12a. Unlike the ‘‘low-temperature’’ NMeCMeD exchange
cates that, at room temperature, a rapid equilibration of the in 12a (see above), this ‘‘high-temperature’’ intramolecular
diastereotopic methyl groups of the amino function CMeAMeB equilibration requires rupture of both ZrϪN
(marked C and D in Scheme 8) is taking place in a process linkages to take place at some time. We therefore have to
that does not involve a similar exchange of the correspond- assume the involvement of a chlorozirconocene intermedi-
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607
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G. Erker et al.
FULL PAPER
Scheme 10
2.61, 2.33 ppm), of which only the latter displays coales-
cence with increasing NMR monitoring temperature. This
again indicates that rapid (on the NMR timescale) breaking
of the ZrϪN bond takes place, followed by inversion at the
nitrogen atom without equilibration of the remaining
groups of signals, but that the activation barrier of this pro-
cess is substantially higher [11: ∆G϶(333 K) ϭ 17.6 Ϯ 0.2
kcal/mol] than in 12.
It is remarkable that the internal NMeCMeD equili-
bration of 11 is observed without a concomitant equili-
bration of the adjacent CMeAMeB moiety. We must assume
that the ϪNMe2 group in the respective intermediate (e.g.,
15; see Scheme 10) is not coordinated to the zirconium
atom. Nevertheless,
a
complete rotation of the
C5H4ϪCMe2NMe2 ligand around the ZrϪCp vector can-
not be operative, since this would result in an inversion at
the stereogenic zirconium centre,[19] which would be regis-
tered as a CMeAMeB interconversion on the NMR times-
cale. This is not observed by dynamic NMR spectroscopy
in the experimentally accessible temperature range: the dy-
namic cation system 11 shows a remarkable stereochemical
memory effect. We assume that stereoselective solvent coor-
dination at the reactive intermediate stage (e.g., 15 in
Scheme 10) might account for this observation. A similar
stabilising solvent coordination of the intermediate 14 de-
rived from the ‘‘more symmetrical’’ system 12a would in
principle also be in accord with the observed dynamic fea-
tures of that system.
1
Figure 3. Dynamic H NMR spectra of 12a (600 MHz, C2D2Cl4)
showing the rapid equilibration of the diastereotopic ϪNMe2
methyl resonances (left) followed by a markedly slower dia-
stereotopic signal exchange at the adjacent ϪCMe2Ϫ moieties
(right)
The systems 5a[11] and 12a are suitable for comparison of
the stabilising features of ϪPAr2 and ϪNMe2 groups in a
chlorozirconocene cation system, since these two complexes
exhibit the same type of dynamic CMeAMeB equilibration
process requiring rupture of both ZrϪN/P linkages. Our
experiments show that ϪNMe2 and ϪPAr2 stabilisation in
these [Zr]ϪClϩ systems are about equal, as judged from
the respective enantiomerisation barriers of the two systems
[∆G϶enant(358 K)
ϭ
17.5
Ϯ
0.5 kcal/mol (5a[11]),
∆G϶enant(298 K) ϭ 17.3 Ϯ 0.5 kcal/mol (12a)]. In addition,
comparison of the two nitrogen-stabilised chlorozircono-
cene cation systems 12a and 11 shows a fairly substantial
difference in the ∆G϶ values of their internal ϪNMeCMeD
Scheme 9
ate (such as 14, see Scheme 10) that lacks any favourable equilibration processes. As would be expected, the corre-
internal amine donor stabilisation. sponding activation barrier of 11 is markedly higher be-
Analogous dynamic behaviour is observed for complex cause the chloro zirconocene cation resulting from
11, which at low temperature (223 K) shows two ZrǟNR2Ϫ dissociation now lacks any internal stabilisation
ϪC(CH3)Ϫ 1H NMR singlets (in CD2Cl2, 600 MHz) at δ ϭ (but probably benefits from some solvent or anion interac-
1.60 and 1.55 ppm and a pair of ϪN(CH3)2 singlets (δ ϭ tion). In this case, the observed ∆G϶(12a)/∆G϶(11) differ-
1604
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607

Stabilised (Chloro)zirconocene Cations
FULL PAPER
or [{C5H4(CMe2)NMe2}{Cp}ZrCl]؉[B(C6F5)4]؊: Dichloromethane
(or CD2Cl2 or C2D2Cl4) was added at room temperature to a mix-
ture of equimolar amounts of the cyclopentadienyl complex (2aϪe,
6aϪb, 10) and the chloride anion abstractor Li[B(C6F5)4]. The reac-
tion mixture was stirred for 1 h. The precipitated LiCl was removed
by filtration. The filtrate was concentrated in vacuo or used directly.
The product was washed twice with pentane and dried in vacuo.
ence of ∆∆G϶ ഠ 6 kcal/mol for internal ϪNMeCMeD equi-
libration should probably be regarded as a lower limit of
the stabilisation energy of such an electrophilic zirconocene
cation by an amine donor ligand.
Experimental Section
[{C5H4(CMe2)PPh2}2ZrCl]؉[B(C6F5)4]؊ (5a): 5a was obtained from
2a (3.72 g, 5.0 mmol) and Li[B(C6F5)4] (3.43 g, 5.0 mmol), and iso-
lated as a yellow-brown solid (3.82 g, 55%). IR (KBr): ν˜ ϭ 3015,
General Remarks: Reactions were carried out under argon in
Schlenk-type glassware or in a glovebox. Solvents (including the
deuterated solvents used for NMR spectroscopy) were dried and
distilled under argon prior to use. The following instruments were
used for characterisation of the synthesised compounds: Bruker AC
200 P NMR spectrometer (1H 200 MHz, 13C 50 MHz) at 298 K or
a Varian Unity Plus NMR spectrometer (1H 600 MHz, 13C
150 MHz) at variable temperature (most NMR assignments were
secured by 2D NMR experiments);[29] a Nicolet 5 DXC FT-IR
spectrometer; a Micromass Quattro LC-Z mass spectrometer; el-
emental analyses were carried out with a FrossϪHeraeus CHN-
rapid elemental analyser or a Vario El III micro elemental analyser.
[{C5H4(CMe2)PPh2}2ZrCl2] (2a),[11] [{C5H4(CMe2)P(tolyl)2}2-
ZrCl2] (2b),[11] [{C5H4(CHMe)PPh2}2ZrCl2] (2c),[12] [{C5H4-
2919, 2856, 1601, 1497, 1443, 1184, 1094, 1018, 802, 514, 492 cmϪ1
.
1H NMR (200.1 MHz, CD2Cl2, 300 K): δ ϭ 1.55Ϫ2.19 (br. s, 12
H, CH3), 6.15Ϫ6.47 (br. m, 8 H, C5H4), 7.32Ϫ7.60 (m, 20 H, Ph)
ppm. 31P{1H} NMR (81.0 MHz, CD2Cl2, 300 K): δ ϭ Ϫ29.1 ppm.
11B{1H } NMR (64.2 MHz, CD2Cl2, 300 K): δ ϭ Ϫ16.6 (w1/2
ϭ
32 Hz) ppm. C64H40BClF20P2Zr (1388.42): calcd. C 55.37, H 2.90;
found C 55.33, 3.36.
[{C5H4(CMe2)P(tolyl)2}2ZrCl]؉[B(C6F5)4]؊ (5b): 5b was obtained
from 2b (4.0 g, 5.0 mmol) and Li[B(C6F5)4] (3.43 g, 5.0 mmol), and
isolated (2.68 g, 67%) as a beige solid. IR (KBr): ν˜ ϭ 3030, 3005,
2939, 1621, 1507, 1451, 1287, 1200, 1105, 802, 534 cmϪ1. 1H NMR
(200.1 MHz, CD2Cl2, 300 K): δ ϭ 1.55, 1.76 (m, each 6 H, CH3),
2.41 (s, 12 H, CH3 of p-tolyl), 6.13, 6.22 (m, each 4 H, C5H4),
7.25Ϫ7.55 (m, 16 H, p-tolyl) ppm. 31P{1H} NMR (81.0 MHz,
CD2Cl2, 300 K): δ ϭ Ϫ31.0 ppm. 11B{1H} NMR (64.2 MHz,
(CHPh)PPh2}2ZrCl2] (2d),[12]
(2e),[30] [{C5H4(CMe2)NMe2}2ZrCl2] (6a),[14Ϫ16] [{C5H4(CHMe)-
[{C5H4(CHFc)P(tolyl)2}2ZrCl2]
NMe2}2ZrCl2]
(6b),[14Ϫ16]
[{C5H4(CMe2)NMe2}{Cp}ZrCl2]
(10),[14Ϫ16] tris(pentafluorophenyl)borane [B(C6F5)3,][9,10] lithium
[tetrakis(pentafluorophenyl)borate] [Li{B(C6F5)4}][17a][17b,18] were
prepared by literature methods.
CD2Cl2, 300 K):
δ
ϭ
Ϫ13.6 (w1/2
ϭ
48 Hz) ppm.
C68H48BClF20P2Zr (1444.53): calcd. C 56.54, H 3.35; found C
56.34, 3.72.
[C5H4(CHFc)P(tolyl)2]Li(THF):[30] This compound was obtained
from (p-tolyl)2PH (2.8 g, 13.0 mmol), nBuLi (8.0 mL, 13.0 mmol)
and 6-ferrocenylfulvene (3.9 g, 14.8 mmol), 5.4 g (75%) isolated. 1H
NMR (200.1 MHz, C6D6/[D8]THF, 298 K): δ ϭ 1.07 (m, 4 H,
THF), 1.94, 2.01 (s, each 3 H, Me of p-tolyl), 2.05 (m, 4 H, THF),
3.60, 3.84, 4.05 (m, 4 H, C5H4 of Fc), 4.09 (s, 5 H, C5H4 of Fc),
[{C5H4(CHMe)PPh2}2ZrCl]؉[B(C6F5)4]؊ (5c): 5c was obtained
from 2c (3.58 g, 5.0 mmol) and Li[B(C6F5)4] (3.43 g, 5.0 mmol),
and isolated (3.67 g, 54%) as a beige solid. IR (KBr): ν˜ ϭ 2965,
2810, 1621, 1479, 1453, 1110, 1088, 1015, 802, 685, 554 cmϪ1. Mix-
ture of three diastereoisomers. syn/anti-cis-5c: 1H NMR
(599.9 MHz, CD2Cl2, 253 K): δ ϭ 1.23, 1.51 (m, each 3 H, Me),
4.10, 4.33 (m, each 1 H, CHMe), 6.20, 6.27, 6.41, 6.88 (br. m,
each 2 H, C5H4), 7.16Ϫ7.65 (m, 20 H, Ph) ppm. 13C{1H} NMR
(150.8 MHz, CD2Cl2, 253 K): δ ϭ 15.1, 19.6 (Me), 26.5, 38.9
(CHMe), 100.6, 102.0, 106.4, 109.0, 112.9, 113.2, 116.2, 120.2
(C5H4), 131.0, 133.0 (ipso-C of C5H4), 129.3Ϫ137.0 (Ph) ppm.
31P{1H} NMR (81.0 MHz, CD2Cl2, 300 K): δ ϭ Ϫ45.9, Ϫ36.2
2
4.62 (d, JPH ϭ 6.1 Hz, 1 H, CHFc), 6.24 (br. s, 2 H of C5H4),
6.30, 6.58 (br. s, each 1 H of C5H4), 6.82, 6.89 (m, each 2 H, p-
tolyl), 7.31 (m, 2 H, p-tolyl), 7.65 (m, 2 H, p-tolyl) ppm. 31P{1H}
NMR (81.0 MHz, C6D6/[D8]THF, 298 K): δ ϭ Ϫ0.9 ppm.
[{C5H4(CHFc)P(tolyl)2}2ZrCl2] (2e):[30] 2e was obtained from
[C5H4(CHFc)P(tolyl)2]Li(THF) (5.0 g, 9.0 mmol) and [ZrCl4-
(THF)2] (1.69 g, 4.5 mmol), and isolated as a yellow solid (4.3 g,
81%) as a 1:1 mixture of diastereoisomers. IR (KBr): ν˜ ϭ 3111,
3091, 2918, 2850, 1595, 1497, 1468, 1456, 1394, 1266, 1185, 1105,
1
ppm. trans-5c: H NMR (599.9 MHz, CD2Cl2, 253 K): δ ϭ 1.25,
1.50 (m, 3 H, Me), 4.21, 4.47 (m, each 1 H, CHMe), 5.99, 6.27,
6.46, 6.94 (br. m, each 2 H, C5H4), 7.16Ϫ7.65 (m, 20 H, Ph) ppm.
13C{1H} NMR (150.8 MHz, CD2Cl2, 253 K): δ ϭ 14.4, 19.3 (Me),
26.7, 28.2 (CHMe), 100.2, 101.0, 108.6, 108.8, 113.2, 115.3, 115.9,
116.5 (C5H4), 132.0, 133.0 (ipso-C of C5H4), 129.3Ϫ137.0 (Ph)
ppm. 31P{1H} NMR (81.0 MHz, CD2Cl2, 300 K): δ ϭ Ϫ47.2 (d,
2JP,P ϭ 110 Hz), Ϫ38.1 (d, 2JP,P ϭ 110 Hz) ppm. [B(C6F5)4]Ϫ anion:
13C{1H} NMR (150.8 MHz, CD2Cl2, 253 K): δ ϭ 124.0 (br. s, ipso-
C of C6F5), 136.2 (dm, JC,F ϭ 242 Hz, m-C6F5), 138.1 (dm, JC,F ϭ
242 Hz, p-C6F5), 148.0 (dm, JC,F ϭ 240 Hz, o-C6F5) ppm. 11B{1H}
NMR (64.2 MHz, CD2Cl2, 300 K): δ ϭ Ϫ16.6 (w1/2 ϭ 33 Hz) ppm.
C62H36BClF20P2Zr (1360.4): calcd. C 54.74, H 2.67; found C
55.34, 3.30.
1090, 1039, 1027, 1018, 998, 813, 734, 512, 503, 500, 486, 423 cmϪ1
.
1H NMR (200.1 MHz, C6D6, 298 K): δ ϭ 2.02, 2.06 (s, each 6 H,
Me of p-tolyl), 3.83 (m, 2 H, Fc), 3.92Ϫ3.93 (m, 4 H, Fc), 4.33 (d,
J
PH ϭ 0.5 Hz, 10 H, Fc), 4.47 (m, 2 H, Fc), 5.04 (d, 2JPH ϭ 1.5 Hz,
2 H, CHFc), 4.65, 4.82, 5.73, 6.32 (m, each 2 H, C5H4), 6.83 (pd,
JH,H ϭ 8 Hz, 4 H, p-tolyl), 6.93 (pd, JH,H ϭ 7 Hz, 4 H, p-tolyl),
7.10 (pt, JH,H ϭ 8 Hz, 4 H, p-tolyl), 7.46 (dd, JH,H ϭ 6, 8 Hz, 4 H,
p-tolyl) ppm. 13C{1H} NMR (50.3 MHz, C6D6, 298 K): δ ϭ 21.1,
21.3 (Me of p-tolyl), 42.2 (d, JP,C ϭ 28.9 Hz, CHFc), 66.3 (d, JP,C ϭ
3
2.2 Hz, Fc), 68.2 (Fc), 69.6 (d, JP,C ϭ 6.1 Hz, Fc), 70.1 (d, JP,C
ϭ
4.4 Hz, Fc), 71.1 (d, JP,C ϭ 5.4 Hz, Fc), 89.9 (d, JP,C ϭ 15.7 Hz,
Fc), 105.8, 110.9, 113.8, 125.7 (C, C5H4), 129.1 (d, JP,C ϭ 8.8 Hz,
p-tolyl), 129.7 (d, JP,C ϭ 4.4 Hz, C, p-tolyl), 131.8 (d, JP,C ϭ 23 Hz,
[{C5H4(CHPh)PPh2}2ZrCl]؉[B(C6F5)4]؊ (5d): 5d was obtained
from 2d (4.20 g, 5.0 mmol) and Li[B(C6F5)4] (3.43 g, 5.0 mmol),
and isolated (2.74 g, 37%) as a light beige solid. Only the signals of
p-tolyl), 131.9 (d, JP,C ϭ 16.6 Hz, C, p-tolyl), 135.7 (d, JP,C
ϭ
17.5 Hz, p-tolyl), 137.3 (d, JP,C ϭ 24.5 Hz, p-tolyl), 137.7 (p-tolyl),
138.0 (d, JP,C ϭ 8.8 Hz, C5H4), 140.0 (p-tolyl) ppm. 31P{1H} NMR
(81.0 MHz, C6D6, 298 K): δ ϭ 12.1, 12.8 ppm.
1
the major cis-5d isomer are listed. H NMR (599.9 MHz, CD2Cl2,
253 K): δ ϭ 5.51 (br. m, 2 H, CHPh), 6.38, 6.48, 6.59, 7.10 (m,
General Procedure for the Preparation of [{C5H4(CR1R2)-
each 2 H, C5H4), 7.2Ϫ7.5 (m, 30 H, Ph) ppm. 13C{1H} NMR
PAr2}2ZrCl]؉[B(C6F5)4]؊, [{C5H4(CR1R2)NMe2}2ZrCl]؉[B(C6F5)4]؊ (150.8 MHz, CD2Cl2, 253 K): δ ϭ 39.1 (CHPh), 102.0, 109.5,
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607
1605

G. Erker et al.
FULL PAPER
112.0, 118.0 (C5H4), 136.0 (dm, JC,F ϭ 240 Hz, m-C6F5), 138.0
X-ray Crystal Structure Analysis of 11: Empirical formula
(ipso-C of Ph at P), 138.1 (dm, JC,F ϭ 247 Hz, p-C6F5), 147.0 (dm, C15H21NClZr·BC24F20, M ϭ 1021.05, colourless crystal 0.35 ϫ
˚
JC,F ϭ 239 Hz, o-C6F5) ppm; ipso-C of C6F5, not observed, Ph 0.35 ϫ 0.15 mm, a ϭ 10.744(1), b ϭ 12.990(1), c ϭ 13.823(1) A,
3
resonances not listed. 31P{1H} NMR (81.0 MHz, CD2Cl2, 300 K):
δ ϭ Ϫ41.8 (d, JP,P ϭ 108 Hz), Ϫ18.4 (d, JP,P ϭ 108 Hz, trans
α ϭ 96.49(1), β ϭ 91.87(1), γ ϭ 101.02(1)°, V ϭ 1878.6(3) A ,
˚
ρ
calcd. ϭ 1.805 g cmϪ3, µ ϭ 4.97 cmϪ1, empirical absorption correc-
2
2
isomer), Ϫ15.0 (cis isomer) ppm. 11B{1H} NMR (64.2 MHz, tion by use of SORTAV (0.845 Յ T Յ 0.929), Z ϭ 2, triclinic, space
˚
¯
CD2Cl2, 300 K):
δ
ϭ
Ϫ16.2 (w1/2
ϭ
37 Hz) ppm.
group P1 (no. 2), λ ϭ 0.71073 A, T ϭ 198 K, ω- and ϕ-scans, 19488
reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] ϭ 0.66 AϪ1, 8895 inde-
˚
C72H40BClF20P2Zr (1484.5): calcd. C 58.25, H 2.72; found C 57.34,
3.48. The coalescence of the CHPh protons of the trans isomer was pendent (Rint ϭ 0.036) and 7149 observed reflections [I Ն 2σ(I)],
observed at 298 K [1H NMR (200 MHz, CD2Cl2, 243 K): δ ϭ 5.57 572 refined parameters, R ϭ 0.050, wR2 ϭ 0.132, max. residual
and 5.65 ppm; ∆ν ϭ 17 Hz]: ∆G϶ ϭ 14.8 Ϯ 0.5 kcal/mol.
electron density 1.06 (Ϫ0.98) eAϪ3, crystals seem to be partly hy-
˚
drolysed, the one high peak in the final difference Fourier calcu-
˚
lation is 1.90 A away from Zr, the typical distance for ZrϪH2O,
[{C5H4(CHFc)P(tolyl)2}2ZrCl]؉[B(C6F5)4]؊ (5e): 5e was obtained
from 2e (5.56 g, 5.0 mmol) and Li[B(C6F5)4] (3.43 g, 5.0 mmol),
and isolated as a beige solid (5.36 g, 61%). IR (KBr): ν˜ ϭ 3019,
hydrogen atoms calculated and refined as riding atoms. Complex
11 seems to add HCl readily. From the mother liquor of a crystal-
lisation
experiment,
the
‘‘open’’
HCl
adduct
2856, 1621, 1491, 1443, 1188, 1088, 1027, 802, 625, 514, 492 cmϪ1
.
[(C5H4ϪCMe2ϪNHMe2)CpZrCl2] (‘‘11ϩHCl’’) was characterised
by single-crystal X-ray diffraction: Empirical formula
C15H22NCl2Zr·BC24F20, M ϭ 1057.51, colourless crystal 0.40 ϫ
Two diastereoisomers. cis-5e: 1H NMR (599.9 MHz, CD2Cl2,
253 K): δ ϭ 2.32 (s, 12 H, CH3 of p-tolyl), 3.96 (s, 10 H, Fc), 3.39,
3.85, 4.07, 4.16 (m, each 2 H, Fc), 6.22, 6.35, 6.42, 7.15 (m, each
2 H, C5H4), 7.24Ϫ7.43 (m, 16 H, p-tolyl) ppm. 13C{1H} NMR
(150.8 MHz, CD2Cl2, 253 K): δ ϭ 35.6 (CHFc), 66.9, 67.8, 68.4,
68.7, 84.4 (Fc), 68.6 (Fc), 101.2, 108.2, 111.4, 116.4, 129.3 (C5H4),
129.5 (p-tolyl) ppm. 31P{1H} NMR (81.0 MHz, CD2Cl2, 300 K):
˚
0.15 ϫ 0.05 mm, a ϭ 10.746(1), b ϭ 13.877(1), c ϭ 14.578(1) A,
3
˚
α ϭ 66.71(1), β ϭ 86.97(1), γ ϭ 85.91(1)°, V ϭ 1991.0(3) A ,
ρ
calcd. ϭ 1.764 g cmϪ3, µ ϭ 5.37 cmϪ1, empirical absorption correc-
tion by SORTAV (0.814 Յ T Յ 0.974), Z ϭ 2, triclinic, space group
˚
¯
P1 (no. 2), λ ϭ 0.71073 A, T ϭ 243 K, ω- and ϕ-scans, 20597
1
δ ϭ Ϫ18.2. trans-5e: H NMR (599.9 MHz, CD2Cl2, 253 K): δ ϭ
reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] ϭ 0.66 AϪ1, 9350 inde-
˚
2.26, 2.35 (s, each 6 H, CH3 of p-tolyl), 3.58, 3.88, 3.96, 3.98, 3.99
(s, each 5 H, Fc), 3.58, 3.88, 3.96, 3.99, 4.12, 4.14, 4.16, 4.21 (br.
s, each 1 H, Fc), 5.06 (d, JPH ϭ 8.7 Hz, 1 H, CHFc), 5.12 (d, JPH ϭ
5 Hz, 1 H, CHFc), 5.94, 6.00 (m, each 1 H, C5H4), 6.06 (m, 2 H,
C5H4), 6.17, 6.65, 6.92, 7.18 (m, each 1 H, C5H4) ppm. 13C{1H}
NMR (150.8 MHz, CD2Cl2, 253 K): δ ϭ 35.9, 36.6 (CHFc), 68.9
(2 ϫ Fc), 67.3, 67.7, 68.0, 68.7, 69.0, 69.1, 69.4, 70.3, 83.4, 84.4
(Fc), 101.0, 103.2, 104.0, 109.4, 113.0, 115.6, 115.7, 116.4, 124.2,
129.5 (C5H4) ppm; tolyl resonances not listed. 31P{1H} NMR
(81.0 MHz, CD2Cl2, 300 K): δ ϭ Ϫ36.1 (d, 2JP,P ϭ 117 Hz), Ϫ24.1
pendent (Rint ϭ 0.031) and 7214 observed reflections [I Ն 2σ(I)],
585 refined parameters, R ϭ 0.044, wR2 ϭ 0.101, max. residual
electron density 0.65 (Ϫ0.59) eAϪ3, hydrogen atoms calculated and
˚
refined as riding atoms. The data set was collected with a Nonius
KappaCCD diffractometer, equipped with a Nonius FR591 rotat-
ing anode generator. Programs used: data collection COLLECT
(Nonius B.V., 1998), data reduction Denzo-SMN[31], absorption
correction SORTAV[32], structure solution SHELXS-97[33], struc-
ture refinement SHELXL-97[34], graphics SCHAKAL[35]. CCDC-
184443 for (11) and -200138 (‘‘11ϩHCl’’) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
[or from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-1223/336-
033; E-mail: deposit@ccdc.cam.ac.uk].
2
(d, JP,P ϭ 117 Hz) ppm. [B(C6F5)4]Ϫ anion: 13C{1H} NMR
(150.8 MHz, CD2Cl2, 253 K): δ ϭ 124.0 (br. s, ipso-C of C6F5),
136.6 (dm, JC,F ϭ 240 Hz, m-C6F5), 138.2 (dm, JC,F ϭ 245 Hz, p-
C6F5), 148.0 (dm, JC,F ϭ 253 Hz, o-C6F5) ppm. 11B{1H} NMR
(64.2 MHz, CD2Cl2, 300 K): δ ϭ Ϫ16.5 (w1/2 ϭ 34 Hz) ppm. ESI-
MS:
m/z
(%)
ϭ
1077
(100)
[C60H56ClFeP2Zr].
C84H56BClF20Fe2P2Zr (1756.46): calcd. C 57.44, H 3.21; found C
56.73, 3.54. The coalescence of the CHFc protons of trans-5e was
observed at 298 K [1H NMR (599.9 MHz, CD2Cl2, 253 K): δ ϭ
5.06 and 5.12 ppm; ∆ν ϭ 36 Hz]: ∆G϶ ϭ 14.5 Ϯ 0.5 kcal/mol.
[{C5H4(CMe2)NMe2}2ZrCl]؉[B(C6F5)4]؊ (12a): 12 was obtained
from 6a (2.31 g, 5 mmol) and Li[B(C6F5)4] (3.43 g, 5 mmol), and
isolated as a light beige solid (3.93 g, 71%). IR (KBr): ν˜ ϭ 3031,
3010, 1613, 1520, 1444, 1260, 1101, 1016, 972, 822, 742, 606, 571
cmϪ1 1H NMR (599.9 MHz, CD2Cl2, 298 K): δ ϭ 1.53 (s, 6 H,
.
[{C5H4(CMe2)NMe2}{Cp}ZrCl]؉[B(C6F5)4]؊ (11): 11 was obtained
from 10 (1.89 g, 5 mmol) and Li[B(C6F5)4] (3.43 g, 5 mmol), and
isolated as a beige solid (3.68 g, 72%). IR (KBr): ν˜ ϭ 3054, 3027,
CMe2), 1.70, 2.40 (s, each 6 H, NMe2), 6.30, 6.33, 6.35, 6.79 (m,
each 1 H, C5H4) ppm. 1H NMR (599.9 MHz, C2D2Cl4, 298 K):
δ ϭ 1.48 (s, 6 H, CMe2), 1.65, 2.34 (s, each 6 H, NMe2), 6.21, 6.26,
6.43, 6.74 (m, each 1 H, C5H4) ppm. 13C{1H} NMR (150.8 MHz,
CD2Cl2, 203 K): δ ϭ 24.0, 24.8 [C(CH3)2], 45.0, 45.5 [N(CH3)2],
59.1 (CMe2), 102.2, 107.7, 116.2, 122.1 (C5H4), 130.3 (ipso-C of
2985, 1684, 1525, 1464, 1273, 1104, 1020, 985, 805, 745, 590 cmϪ1
.
1H NMR (599.9 MHz, CD2Cl2, 298 K): δ ϭ 1.61, 1.68 (br. s, each
3 H, CMe2), 2.52 (br. s, 6 H, NMe2), 6.46, 6.60 (m, each 1 H,
1
C5H4), 6.68 (s, 5 H, Cp), 6.75, 6.81 (m, each 1 H, C5H4) ppm. H
C5H4Cp), 135.7 (dm, JC,F ϭ 245 Hz, m-C6F5), 137.5 (dm, JC,F
ϭ
NMR (599.9 MHz, CD2Cl2, 223 K): δ ϭ 1.55, 1.60 (br. s, each 3
H, CMe2), 2.33, 2.61 (s, each 3 H, NMe2), 6.50, 6.57 (m, each 1 H,
C5H4), 6.64 (s, 5 H, Cp), 6.69, 6.77 (m, each 1 H, C5H4) ppm.
13C{1H} NMR (150.8 MHz, CD2Cl2, 223 K): δ ϭ 23.0, 25.8
[C(CH3)2], 45.3, 47.5, [N(CH3)2], 61.1 (CMe2), 102.5, 108.7, 114.2,
118.3 (C5H4), 120.1 (C5H5), 131.3 (ipso-C of C5H4), 135.7 (dm,
251 Hz, p-C6F5), 143.7 (dm, JC,F ϭ 245 Hz, o-C6F5) ppm, ipso-C
of C6F5 not observed. 11B{1H} NMR (64.2 MHz, CD2Cl2, 298 K):
δ ϭ Ϫ16.5 (w1/2 ϭ 33 Hz) ppm. ESI-MS: m/z (%) ϭ 425 (100)
[C20H32ClN2Zr]. C44H32BClF20N2Zr (1106.2): calcd. C 47.47, H
2.92, N 2.53; found C 47.46, C 3.19, N 2.50.
JC,F ϭ 245 Hz, m-C6F5), 137.5 (dm, JC,F ϭ 251 Hz, p-C6F5), 146.3 [{C5H4(CHMe)NMe2}2ZrCl]؉[B(C6F5)4]؊ (12b): 12b was obtained
(dm, JC,F ϭ 245 Hz, o-C6F5) ppm, ipso-C of C6F5 not observed.
from 6b (2.17 g, 5 mmol) and Li[B(C6F5)4] (3.43 g, 5 mmol), and
isolated as a beige solid (3.50 g, 65%). IR (KBr): ν˜ ϭ 3021, 2856,
1610, 1512, 1454, 1265, 1078, 1016, 972, 806, 740, 610 cmϪ1. 1:2:1
mixture of three diastereoisomers: 1H NMR (599.9 MHz, CD2Cl2,
11B{1H} NMR (64.2 MHz, CD2Cl2, 300 K): δ ϭ Ϫ16.5 (s, w1/2
ϭ
34 Hz) ppm. C39H21BClF20NZr (1021.1): calcd. C 45.88, H 2.07,
N 1.37; found C 45.60, H 2.18, N 1.38.
1606
Eur. J. Inorg. Chem. 2003, 1599Ϫ1607

Stabilised (Chloro)zirconocene Cations
FULL PAPER
[11]
[12]
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B. E. Bosch, G. Erker, R. Fröhlich, O. Meyer, Organometallics
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298 K): δ ϭ 1.43Ϫ1.54 (m, 24 H, CHCH3), 2.39 (m, 48 H, NMe2),
3
3.74 (q, JH,H ϭ 7.2 Hz, 2 H, CHCH3), 3.88 (m, 2 H, CHCH3),
B. E. Bosch, G. Erker, R. Fröhlich, Inorg. Chim. Acta 1998,
3
4.06 (q, JH,H ϭ 7.2 Hz, 2 H, CHCH3), 4.27 (m, 2 H, CHCH3),
270, 446Ϫ458, and references cited therein.
5.88Ϫ6.84 (m, 32 H, Cp) ppm. 1H NMR (599.9 MHz, CD2Cl2,
213 K): δ ϭ 1.37 (m, 18 H, CHCH3), 1.46 (m, 6 H, CHCH3), 2.26,
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2.27, 2.35, 2.36 (s, each 12 H, NMe2), 3.72 (q, JH,H ϭ 7.2 Hz, 2
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[13d]
H, CHCH3), 3.83 (q, JH,H ϭ 7.2 Hz, 2 H, CHCH3), 3.99 (q,
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3JH,H ϭ 7.2 Hz, 2 H, CHCH3), 4.00 (q, JH,H ϭ 7.2 Hz, 2 H,
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CHCH3), 5.95, 6.11, 6.17, 6.19, 6.26, 6.30, 6.31, 6.34, 6.36, 6.45,
6.59, 6.66, 6.70, 6.76, 6.77 (m, each 2 H, C5H4) ppm. 13C{1H}
NMR (150.8 MHz, CD2Cl2, 213 K): δ ϭ 13.5, 13.6, 14.2, 14.4
(CHCH3), 42.3, 44.9, 49.1 (NMe2), 59.6, 59.8, 59.9, 60.0 (CHCH3),
101.1, 101.2, 101.2, 104.8, 106.6, 106.7,108.2, 108.5, 108.5, 111.3,
114.8, 115.8, 120.6, 121.3, 121.3, 122.2, 122.5, 122.5, 125.7, 128.0
(C5H4) ppm. [B(C6F5)4]Ϫ anion: 13C{1H} NMR (150.8 MHz,
CD2Cl2, 213 K): δ ϭ 135.8 (dm, JC,F ϭ 251 Hz, m-C6F5), 137.6
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1
(dm, JC,F ϭ 251 Hz, p-C6F5), 147.4 (dm, JC,F ϭ 239 Hz, o-C6F5)
[18] [18a]
ppm, (ipso-C, C6F5) not observed. 11B{1H} NMR (64.2 MHz,
CD2Cl2, 300 K): δ ϭ Ϫ16.5 (s, w1/2 ϭ 38 Hz) ppm. ESI-MS: m/z
(%) ϭ 397 (100) [C18H28ClN2Zr]. C42H28BClF20N2Zr (1078.15):
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1
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Received August 13, 2002
[I02460]
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