Monocyclopentadienyl and mono(2-methoxyethylcyclopentadienyl) zirconium methyl complexes

Article abstract of DOI:10.1016/S0022-328X(00)00117-0

The reactions of (η⁵-Cp)ZrCl₃(DME) and (η⁵:η¹-Cp°)ZrCl₃ (Cp°=C₅H₄CH₂CH₂OMe) with 1-2 equivalents of MeLi or MeMgI and THF yield the mono- and dimethyl zirconium complexes (η⁵-Cp)ZrCl_3-xMe_x(THF) and (η⁵:η¹-Cp°)ZrCl_3-xMe_x (x=1, 2), respectively. Reaction with three equivalents of MeMgI affords (η⁵-Cp)ZrMe₃(THF) and (η⁵:η¹-Cp°)ZrMe₃. The reaction with three equivalents of MeLi affords (η⁵-Cp)₂ZrMe₂ or (η⁵-Cp°)₂ZrMe₂ and ZrMe₄, as a result of disproportionation. The reaction of (η⁵:η¹-Cp°)ZrMe₃ with B(C₆F₅)₃ in THF affords the cationic zirconium complex [(η⁵:η¹-Cp°)ZrMe₂(THF)][MeB(C ₆F₅)₃]. The chloride-bridged complex [(η⁵:η¹-Cp°)Zr(μ-Cl)Me₂] ₂ was characterized by single-crystal X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(00)00117-0

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 602 (2000) 51–58
Monocyclopentadienyl and mono(2-methoxyethylcyclopentadienyl)
zirconium methyl complexesꢀ
Chris Mattheis a, Adolphus A.H. van der Zeijden a,*, Roland Fro¨hlich b
a Institut fu¨r Anorganische Chemie, Martin-Luther-Uni6ersita¨t Halle-Wittenberg, Geusaer Strasse, D-06217 Merseburg, Germany
b Organisch-Chemisches Institut der Uni6ersita¨t Mu¨nster, Corrensstrasse 40, D-48149 Mu¨nster, Germany
Received 18 November 1999; received in revised form 24 January 2000; accepted 14 February 2000
Dedicated to Professor Dr Karl-Heinz Thiele on the occasion of his 70th birthday
Abstract
The reactions of (h5-Cp)ZrCl3(DME) and (h5:h1-Cp°)ZrCl3 (Cp°=C5H4CH2CH2OMe) with 1–2 equivalents of MeLi or
MeMgI and THF yield the mono- and dimethyl zirconium complexes (h5-Cp)ZrCl3−xMex(THF) and (h5:h1-Cp°)ZrCl3−xMex
(x=1, 2), respectively. Reaction with three equivalents of MeMgI affords (h5-Cp)ZrMe3(THF) and (h5:h1-Cp°)ZrMe3. The
reaction with three equivalents of MeLi affords (h5-Cp)2ZrMe2 or (h5-Cp°)2ZrMe2 and ZrMe4, as a result of disproportionation.
The reaction of (h5:h1-Cp°)ZrMe3 with B(C6F5)3 in THF affords the cationic zirconium complex [(h5:h1-
Cp°)ZrMe2(THF)][MeB(C6F5)3]. The chloride-bridged complex [(h5:h1-Cp°)Zr(m-Cl)Me2]2 was characterized by single-crystal
X-ray crystallography. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Monocyclopentadienyl; Mono zirconium complexes; Dimethyl zirconium complexes
1. Introduction
tuted cyclopentadienyl zirconium precursors. Thus, all
members of the series (h5-C5Me5)ZrCl3−xMex (x=1,
2, 3) were synthesized by Bercaw [3]. More recently,
several trimethyl complexes of the type [h5-C5H3-1,3-
R2]ZrMe3 were prepared (R=tBu [4], SiMe3 [5],
SiMe2CH2PPri2 [6]). Cationic complexes, e.g. [(h5-
C5Me5)ZrMe2L2]+, were first reported by Jordan [7].
Surprisingly, there is almost no information on methyl
zirconium complexes bearing the parent cyclopenta-
dienyl ligand. A recent publication by Negishi claims
the synthesis of (h5-Cp)ZrMe3, but without much detail
[8].
We therefore set out to investigate the reaction of
(h5-Cp)ZrCl3(DME) [9] with methylating agents. As the
resulting methyl zirconium derivatives appeared to be
thermally sensitive and have some stability only in
ethereal solvents (vide infra), we also studied the stabi-
lizing influence of an internal ether linkage attached to
the cyclopentadienyl ring. Therefore, our recently re-
ported zirconium complex (h5:h1-Cp°)ZrCl3 (Cp°=
C5H4CH2CH2OMe) [10] was also used as a starting
compound. With these two precursors we were able to
isolate and/or characterize all possible combinations of
Dicyclopentadienyl zirconium complexes are well
known pre-catalysts for the Ziegler–Natta polymerisa-
tion of a-olefins. Cationic methyl derivatives are
thought to be the active catalysts after activation of the
metallocene with methylalumoxane and these species
have therefore been thoroughly investigated [1].
Monocyclopentadienyl zirconium compounds were
much less studied with respect to Ziegler–Natta activ-
ity, although the increased unsaturation of the metal
centre may lead to higher reactivity [2]. Studies on
methyl complexes have been confined to ring-substi-
ꢀ Part of this work was presented at the International Workshop
on Organometallic Chemistry and Catalysis, Mu¨nster, Germany,
October 1996, the XIIth FECHEM Conference on Organometallic
Chemistry, Prague, Czech Republic, September 1997 and at the
XVIIIth International Conference on Organometallic Chemistry, Mu-
nich, Germany, August 1998.
* Corresponding author. Present address: Kataleuna GmbH Cata-
lysts, Am Haupttor, D-06237 Leuna, Germany.
E-mail address: zeijden@chemie.uni-halle.de (A.A.H. van der Zeij-
den)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 0 ) 0 0 1 1 7 - 0

52
C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
(h5-Cp)ZrCl3−xMex(THF) and (h5:h1-Cp°)ZrCl3−x
Mex (x=1, 2, 3). In addition, the cationic derivative
[(h5:h1-Cp°)ZrMe2(THF)]+ could be generated and
identified.
-
of the monomethyl derivative, whereas formation of a
trimethyl compound (vide infra) is much slower. The
solubility of the complexes increases considerably the
more chlorides get substituted for by methyl groups.
The compounds were identified by their 1H- and
13C-NMR spectra (Tables 1 and 2); Cp:Me ratios were
obtained by integration of the respective 1H signals.
Because of its short lifetime and low solubility, the
signal for the ZrꢀMe group of 1 could not be observed
in the 13C-NMR spectrum. There are striking similari-
ties between the NMR data of 1 and 3, and between
those of 2 and 4, indicating close structural similarities.
Thus, the data for the methyl groups of 2 in THF-d8
(lH 0.00, lC 41.6 ppm) may be compared with those in
4 (lH 0.03, lC 41.4 ppm). For the Cp° complexes 3 and
4, the low field 13C shifts of the CH2OCH3 nuclei of the
Cp° ligand are indicative of a firm intramolecular coor-
dination of the ether side-arm to zirconium [10]. These
low-field shifts decrease the more chlorides are substi-
tuted for by methyl groups, which is in accord with an
increase of electron density on the zirconium centre and
a weakening of the ZrꢀO bond. In view of the secure
coordination of the ether side-arm in 3 and 4, and the
analogies of the NMR spectra with those of the Cp
derivatives 1 and 2, it was concluded that the latter
exist as mono(THF) adducts in THF-d8.
2. Results and discussion
In the first instance, a suspension of (h5-Cp)-
ZrCl3(DME) or (h5:h1-Cp°)ZrCl3 in THF held at −20
and −30°C was treated with increasing amounts of a
solution of either MeLi or MeMgI in diethyl ether.
Samples were taken regularly, evaporated to dryness,
and the residue was extracted into C6D6 or THF-d8 and
analyzed as quickly as possible by 1H- and 13C-NMR at
room temperature (Tables 1 and 2). However, solutions
measured in C6D6 did not reveal any detectable Cp
compounds, and the NMR spectra had to be run in
THF-d8 in order to detect any methyl zirconium com-
plexes. Apparently, the coordination of THF is essen-
tial for their stability, but even in this solvent all
compounds of the type (h5-Cp)ZrCl3−xMex(THF)
have a lifetime of only a few hours at room tempera-
ture. In contrast, methyl zirconium derivatives contain-
ing the Cp° ligand turned out to be much more stable
in both C6D6 and THF-d8.
Compound 4 could be isolated in 43% yield and, in
addition to the NMR spectra, could be fully character-
ized by microanalysis and X-ray structure determina-
tion (Fig. 1). Selected bond lengths and angles are given
in Table 3. The structure of 4 is very similar to that of
the starting compound (h5:h1-Cp°)ZrCl3 [10a]. Both are
composed of six-coordinate chloride-bridged dimers.
The ZrꢀCl bond lengths in the bridge of 4 are signifi-
cantly longer than in (h5:h1-Cp°)ZrCl3 (trans-Cp:
2.1. Reaction of (p5-Cp)ZrCl3(DME) and (p5:p1-Cp°)-
ZrCl3 with 1–2 equi6alents of MeLi and MeMgI
The reaction of (h5-Cp)ZrCl3(DME) with one equiv-
alent of MeLi or MeMgI yields a mixture of two
air-sensitive compounds: (h5-Cp)ZrCl2Me(THF) (1)
and (h5-Cp)ZrClMe2(THF) (2), leaving behind some of
the starting compound (Scheme 1). Similarly, (h5:h1-
Cp°)ZrCl3 yields a mixture of (h5:h1-Cp°)ZrCl2Me (3)
and (h5:h1-Cp°)ZrClMe2 (4) (Scheme 2). Therefore, the
monomethyl compounds 1 and 3 could not be isolated
as pure compounds. In contrast, the use of exactly two
equivalents of MeLi or MeMgI affords pure (h5-
Cp)ZrClMe2(THF) (2) and (h5:h1-Cp°)ZrClMe2 (4), re-
spectively (Schemes 1 and 2). Apparently, the rate of
formation of the dimethyl derivative is similar to that
,
2.681(2) vs. 2.642(2) A; trans-Me(Cl): 2.663(2) vs.
,
2.562(2) A), illustrating the higher electron density at
the zirconium centre in 4 compared with that in (h5:h1-
Cp°)ZrCl3. Consequently, the ZrꢀO bond length in 4
5
1
,
(2.394(7) A) is also considerably longer than in (h :h -
,
Cp°)ZrCl3 (2.264(4) A), whereas the ZrꢀC(Cp) bond
lengths are similar. The two methyl groups are cis-posi-
tioned (ꢁCꢀZrꢀC 92.9(4)°). The ZrꢀC bond lengths
Table 1
1H- and 13C-NMR data of the CpZr complexes
Compound
Solvent
C5H5
ZrCH3
C5H5
ZrCH3
CpZrCl3(THF)2
CD2Cl2
THF-d8
THF-d8
THF-d8
C6D6
6.6 (5H)
120.3
116.7
114.2
111.3
110.3
CpZrCl2Me(THF) (1)
CpZrClMe2(THF) (2)
CpZrMe3(THF) (5)
Cp2ZrMe2 (7)
6.35 (5H)
6.25 (5H)
6.05 (5H)
5.71 (10H)
6.09 (10H)
0.16 (3H)
0.00 (6H)
−0.34 (9H)
−0.13 (6H)
−0.43 (6H)
n.o. a
41.6
37.8
30.0
THF-d8
a n.o., not observed.

Table 2
1H- and 13C-NMR data of the Cp°Zr complexes a
/
Compound
Solvent
C5H4
CH2
CH2O
OCH3
ZrCH3
C5H4
CH2 CH2O OCH ZrCH3
Cp°ZrCl3
Cp°ZrCl2Me (3)
Cp°ZrClMe2 (4)
C6D6
C6D6
C6D6
THF-d8
(−80°C)
C6D6
THF-d8
C6D6
6.42 (2H), 6.47 (2H)
6.00 (2H), 6.19 (2H)
5.82 (2H), 6.09 (2H)
6.24 (2H), 6.26 (2H)
6.13 (4H)
5.83 (2H), 6.09 (2H)
6.09 (4H)
5.51 (4H), 5.77 (4H)
5.84 (4H), 5.97 (4H)
6.32 (4H), 6.48 (4H)
1.91 (2H)
1.91 (2H)
1.89 (2H)
2.73 (2H)
2.69 (2H)
2.03 (2H)
2.70 (2H)
2.66 (4H)
2.68 (4H)
2.80 (2H)
3.25 (2H)
3.08 (2H)
2.88 (2H)
3.84 (2H)
3.63 (2H)
2.96 (2H)
3.79 (2H)
3.35 (4H)
3.50 (4H)
3.60 (2H)
3.01 (3H)
3.05 (3H)
3.02 (3H)
3.50 (3H)
3.34 (3H)
2.91 (3H)
3.47 (3H)
3.10 (6H)
3.28 (6H)
4.11 (3H)
117.4, 121.7
114.8, 115.8
110.9, 114.3
113.7, 114.1
113.7, 116.1
108.2, 112.6
110.2, 112.2
108.1, 111.6
108.9, 112.4
115.0, 117.5
26.5 81.4
27.2 79.1
27.5 78.0
28.7 78.4
29.2 76.9
27.8 78.2
29.3 78.1
30.8 73.7
29.8 74.3
27.3 82.6
63.5
61.5
60.6
60.9
60.4
59.9
60.1
58.3
58.5
62.5
0.90 (3H)
0.60 (6H)
0.03 (6H)
−0.34 (6H)
0.43 (9H)
−0.17 (9H)
−0.15 (6H)
−0.50 (6H)
0.04 (6H)
58.3
44.2(118)
41.4
36.2
40.2
37.8
30.5
31.3
42.1(115)
THF-d8
Cp°ZrMe3 (6)
Cp2°ZrMe2 (8)
THF-d8
[Cp°ZrMe2(THF)]+[MeB(C6F5)3]− b (13) THF-d8
602
a 1
J
in parentheses; n.o., not observed.
CH
(
b [MeB(C6F5)3]−: lH=0.51 (Me); lC=10.4 (br), 137.1 (d, JCF=245), 138.1 (d, JCF=241), 149.2 (d, JCF=239).
5

54
C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
(or THF in the Cp derivatives). Although this would
yield a highly unsaturated 12e tetrahedral intermediate,
stable monomeric compounds of the type (h5-
C5R5)ZrCl3 are known [12]. Another mechanism in-
volves a Berry type pseudorotation with trigonal
bipyramidal intermediates. Finally, and in view of the
dimeric solid state structure of 4, intermolecular ex-
change can also not be excluded.
Scheme 1. All reactions in THF, −30°C to r.t.; MeLi or MeMgI
added as ether solutions.
,
(2.261(11) and 2.298(9) A) are unexceptional and may
be compared with those in (h5-Cp)2ZrMe2 (2.273(5) and
,
2.280(5) A) [11].
As for dimeric (h5:h1-Cp°)ZrCl3 the chloride bridges
in 4 (and 1–3) will be very weak, and in solution the
compound is largely monomeric. It was noted that
there are two possible structural isomers for the
monomer depending on the relative positions of the
chloride and methyl ligands; one has Cs symmetry
(1b–4b), the other has no element of symmetry (1a–
4a). The NMR spectra of 1–4 appear to be consistent
with symmetric structures. Thus, the presence of only
one signal for the two methyl groups in 4 suggests that
these groups are trans-positioned, which however is in
conflict with the solid state structure of 4. It is therefore
concluded that 4, and 1–3 also, are highly dynamic in
solution with rapid site exchange of chloride and
methyl groups. The NMR spectrum of 4 in THF-d8 at
−80°C shows a gradual shift of the ZrꢀMe signal
(Table 2), however, without decoalescence. The dynam-
ical process obviously has a low barrier of activation.
Several mechanisms are possible. One involves decom-
plexation of the ether side-chain in the Cp° derivatives
Scheme 2. All reactions in THF, −30°C to r.t.; MeLi or MeMgI
added as ether solutions.
Fig. 1. Molecular structure of 4.

C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
55
Table 3
Although the coordination of THF in 5 will be
weaker than in 1 and 2, it is again essential for its
(limited) stability at room temperature. The related
complexes (h5-C5H4SiMe2R)ZrR3(OEt2) (R=Ph, C6F5)
decompose when the coordinated ether is removed un-
der high vacuum [13]. It was noticed that despite the
formation of methane during the decomposition of 5
(or 1 and 2), we have no indication that it was attended
by the formation of methylene or methylidine deriva-
tives [14].
Although a 2:1 pattern of methyl signals may be
expected for 5 and 6, only one resonance was observed
for all three methyl groups, again suggesting rapid site
exchange of these ligands around zirconium. Our NMR
data for 5 (THF-d8; ZrꢀMe: lH −0.34; lC 37.8 ppm)
are somewhat different from those of Negishi (C6D6/
THF; ZrꢀMe: lH −0.50; lC 32.9 ppm), and we think
that the latter may have been misinterpreted [8]. This is
corroborated by the fact that in our hands 5 cannot be
synthesized by the reaction of (h5-Cp)ZrCl3(DME) with
three equivalents of MeLi, as has been claimed by
Negishi (vide infra). The 13C chemical shifts for the
methyl groups of 5 and 6 may be compared with that in
[h5-C5H3-1,3-(tBu)2]ZrMe3 (l 45.6 ppm in C6D6) [4],
[h5-C5H3-1,3-(SiMe3)2]ZrMe3 (l 45.2 ppm in CD2Cl2)
[5] and [h5-C5H3-1,3-(SiMe2CH2PPr2i )2]ZrMe3 (l 42.7
ppm in C7D8) [6].
5
1
,
Selected bond distances (A) and bond angles (°) for [(h :h -Cp°)Zr(m-
Cl)Me2]2 (4)
Bond distances
ZrꢀC(10)
ZrꢀC(11)
ZrꢀCl (trans-C(11))
ZrꢀCl*(trans-Cp)
ZrꢀO(8)
2.261(11)
2.298(9)
2.663(2)
2.681(2)
2.394(7)
O(8)ꢀC(7)
O(8)ꢀC(9)
C(5)ꢀC(6)
C(6)ꢀC(7)
1.41(2)
1.431(13)
1.45(2)
1.36(2)
Bond angles
ClꢀZrꢀCl*
73.10(8)
80.4(2)
94.4(3)
150.9(3)
78.2(2)
81.8(3)
80.1(2)
160.0(3)
O(8)ꢀZrꢀC(11)
83.2(3)
ClꢀZrꢀO(8)
ClꢀZrꢀC(10)
ClꢀZrꢀC(11)
Cl*ꢀZrꢀO(8)
Cl*ꢀZrꢀC(10)
Cl*ꢀZrꢀC(11)
O(8)ꢀZrꢀC(10)
C(10)ꢀZrꢀC(11) 92.9(4)
ZrꢀClꢀZr*
ZrꢀO(8)ꢀC(7)
ZrꢀO(8)ꢀC(9)
106.90(8)
117.2(9)
126.6(7)
C(5)ꢀC(6)ꢀC(7) 116.7(11)
O(8)ꢀC(7)ꢀC(6) 117.4(13)
C(7)ꢀO(8)ꢀC(9) 112.3(11)
2.3. Reaction of (p5-Cp)ZrCl3(DME) and
(p5:p1-Cp°)ZrCl3 with 2–3 equi6alents of MeLi
Remarkably, the reaction of (h5-Cp)ZrCl3(DME)
and (h5:h1-Cp°)ZrCl3 with 2–3 equivalents of MeLi,
instead of MeMgI, takes a completely different course
(one may also start with the dimethyl complexes 2 and
4 and react them with MeLi). While using MeLi we
never observed the formation of the trimethyl deriva-
tives 5 or 6. Instead, the only product to be detected
was the metallocene derivative (h5-Cp)2ZrMe2 (7) or
(h5-Cp°)2ZrMe2 (8) respectively (Schemes 1 and 2),
obviously a result of a disproportionation reaction. The
identity of the metallocenes was confirmed by an inde-
pendent synthesis from (h5-Cp)2ZrCl2 and (h5-
Cp°)2ZrCl2 with two equivalents of MeLi.
Scheme 3.
2.2. Reaction of (p5-Cp)ZrCl3(DME) and
(p5:p1-Cp°)ZrCl3 with 2–3 equi6alents of MeMgI
Two mechanisms can be put forward to explain the
formation of these products (Scheme 3). After forma-
tion of the dimethyl complexes 2 and 4, the reaction of
more MeLi must lead to the formation of the trimethyl
complexes 5 and 6 (Eq. (1) in Scheme 3). The crucial
point now is that the trimethyl complexes quickly react
with additional MeLi resulting in a fast equilibrium
with CpLi (or Cp°Li) and ZrMe4 through the interme-
diacy of the ate complexes [(h5-Cp)ZrMe4][Li(THF)n]
(9) or [(h5-Cp°)ZrMe4][Li(THF)n] (10) (Eqs. (2) and
(3)). In the first mechanism, CpLi (or Cp°Li) subse-
quently reacts with unreacted dimethyl complexes 2 or
The reaction of (h5-Cp)ZrCl3(DME) and (h5:h1-
Cp°)ZrCl3 with 2–3 equivalents of MeMgI yields the
highly air sensitive complexes (h5-Cp)ZrMe3(THF) (5)
and (h5:h1-Cp°)ZrMe3 (6), respectively (Schemes 1 and
2). Again, the Cp derivative 5 slowly decomposes at
room temperature, whereas the Cp° derivative 6 could
be isolated in 58% yield. The isolated trimethyl complex
6 appears to be much more air sensitive than the mono-
and dimethyl precursors 3 and 4, probably because the
former lacks a stabilizing chloride bridge in the solid
state.

56
C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
4 forming 7 or 8 (Eq. (4)). In the second mechanism
CpLi (or Cp°Li) reacts with remaining trimethyl com-
plex 5 or 6 resulting in another fast equilibrium yielding
MeLi and 7 or 8, with the intermediacy of the ate
complex [(h5-Cp)2ZrMe3][Li(THF)n] (11) or [(h5-
Cp°)2ZrMe3][Li(THF)n) (12) (Eqs. (6) and (7)). Accord-
ing to the latter mechanism, only catalytic amounts of
MeLi are needed to decompose the trimethyl complexes
5 and 6.
In either mechanism the formation of 7 and 8 should
be attended by the equimolar formation of ZrMe4. This
compound could not be observed directly; however, it is
known that it is stable only up to ca. −15°C and than
decomposes with blackening [15]. This blackening of
our ether solutions at and above −15°C was indeed
observed by us when using 2–3 equivalents of MeLi.
This observation suggests that ZrMe4 may indeed have
been formed below −15°C, i.e. probably while con-
ducting the reaction at ca. −30°C and moreover that
its formation is not a result of disproportionation of 5
or 6 upon raising the temperature.
(THF)2][BPh4] published by Jordan [7]. The 13C signals
of the CH2OMe moiety of the Cp° ligand shift
downfield compared with those of the starting com-
pound 6, indicating a stronger ZrꢀO bond. Interest-
ingly, complex 13 is fluctional with respect to
site-exchange of the methyl groups, since only one
signal was observed, whereas two signals may have
been expected. The 13C resonance of the methyl group
(l 42.1 ppm with JCH=115 Hz) in 13 is close to the
value of Jordan’s complex (l 50.5 ppm with JCH=117
Hz).
Upon activation with MAO, the complex (h5:h1-
Cp°)ZrCl3 is a poor catalyst for the polymerisation of
ethene [10a]. Complexes like 13 are reminiscent of the
catalytically active species. The strong coordination of
the side-chain in the cation 13 may explain the low
activity, as it probably saturates the zirconium centre
too much preventing facile docking of olefins. Another
explanation may be the aggregation of these open
monoCp systems.
The second mechanism, as depicted in Scheme 3, is
more likely. Thus, equilibria between (h5-Cp)2ZrR2 and
RLi forming (h5-Cp)ZrR3 and CpLi, such as proposed
in Eqs. (2) and (3) of Scheme 3, have already been
demonstrated [8]. There are no reports on stable zir-
conate complexes such as 9/10 and 11/12, but such
species have been suggested as intermediates [8,16].
3. Conclusions
We could demonstrate for the first time the existence
of all members of the series (h5-Cp)ZrCl3−xMex(THF)
[x=1 (1), 2 (2), 3 (5)]. All compounds have a lifetime
of only a few hours in ethereal solvents. Decomposition
is attended by formation of methane (ethane was not
detected), but we have no evidence for, nor can we
exclude the formation of zirconium methylene or
methylidine species.
In contrast to the Cp derivatives, the analogous Cp°
derivatives (h5-Cp°)ZrCl3−xMex [x=1 (3), 2 (4), 3 (6)]
are all thermally stable solids at room temperature.
This demonstrates the powerful stabilizing effect of the
internal ether side-chain in these compounds.
The trimethyl compounds 5 and 6 can only be syn-
thesized by using the Grignard reagent, the reaction
with MeLi results in disproportionation with formation
of the metallocene complexes 7 and 8. This dispropor-
tionation (Scheme 3) seems to be limited to those
cyclopentadienyl zirconium derivatives that have not
more than one ring substituent. This is concluded from
the fact that the trimethyl zirconium compounds
[h5-C5H3-1,3-(SiMe3)2]ZrMe3 [5] and [h5-C5H3-1,3-
Moreover,
a
stable trihydride complex [(h5-
C5Me5)2ZrH3]Li, reminiscent of 11/12, is known [17].
Fryzuk observed that [P2Cp]ZrMe3 ([P2Cp]={h5-
C5H3-1,3-(SiMe2CH2PPri2)2}) decomposes in the pres-
ence of catalytic amounts of MeLi [6], suggesting the
intermediacy of zirconate complexes similar to 9 and
10. The disproportionation of (h5-Cp)[CPh(NSi-
Me3)2]ZrMe2 to (h5-Cp)2ZrMe2 and (Zr[CPh(NSi-
Me3)2]2Me2) by catalytic amounts of MeLi might pro-
ceed similarly [18].
2.4. Cationic complexes
The reaction of (h5:h1-Cp°)ZrMe3 (6) with B(C6F5)3
affords the cationic complex [(h5:h1-Cp°)ZrMe2-
(THF)][MeB(C6F5)3] (13) (Scheme 4). Its structure is
probably similar to that of [(h5-C5Me5)ZrMe2-
Scheme 4.

C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
57
(SiMe2CH2PPri2)2]ZrMe3 [6] can indeed be synthesized
4.3. X-ray structure determination of
[(p5:p1-Cp°)Zr(v-Cl)Me2]2
by using the lithium methylating reagent. It seems
possible that equilibria of these compounds with ex-
cess MeLi, affording Cp%Li and ZrMe4 (cf. Eqs. (2)
and (3) in Scheme 3), do occur, but that steric hin-
drance prevents the formation of the zirconate com-
Formula C20H34Cl2O2Zr2, M=559.82, 0.25×
0.10×0.10 mm, a=10.685(2), b=7.732(3), c=
3
,
,
14.901(6) A, i=108.52(3)°, V=1167.3(7) A ,
zcalc=1.593 g cm−3, v=11.33 cm−1, empirical ab-
sorption correction via c scan data (0.7655T5
0.895), Z=2, monoclinic, space group P21/c (no. 14),
plexes Cp%ZrMe3Li that would lead to the formation
2
of the metallocenes (cf. Eq. (6) in Scheme 3).
,
u=0.71073 A, T=223 K, ꢀ/2q scans, 2144 reflec-
−1
,
tions collected (9h, −k, −l), [(sin u)/u]=0.59 A
,
4. Experimental
2057 independent (Rint=0.082) and 1175 observed
reflections [I]2|(I)], 121 refined parameters, R=
All manipulations were conducted in Schlenk glass-
ware under an atmosphere of argon. Solvents were
dried and degassed by conventional procedures prior
to use. NMR spectra were obtained from a Varian
0.056, wR2=0.123, max. residual electron density
−3
,
0.79 (−0.97)
refined as riding atoms.
e
A
, hydrogens calculated and
Data set was collected with an Enraf–Nonius
CAD4 diffraktometer, using a sealed tube generator
FR590. Programs used: data collection Express, data
reduction MOLEN, structure solution SHELXS-86, struc-
1
Gemini 300 MHz spectrometer. The H-NMR spectra
were referenced to the residual 1H signals of the
deuterated solvents employed. The starting com-
pounds (h5-Cp)ZrCl3(DME) [9a], (h5:h1-Cp°)ZrCl3
[10a], and (h5-Cp°)2ZrCl2 [19] were synthesized ac-
cording to literature procedures.
ture refinement SHELXL-97, graphics DIAMOND
.
4.4. Preparation of (p5:p1-Cp°)ZrMe3 (6)
4.1. Reactions of (p5-Cp)ZrCl3(DME),
(p5:p1-Cp°)ZrCl3, (p5-Cp)2ZrCl2 and (p5-Cp°)2ZrCl2
with MeLi or MeMgI (NMR experiments)
To
a
cooled (−80°C) suspension of (h5:h1-
Cp°)ZrCl3 (0.64 g, 2.0 mmol) in 50 ml of THF was
added 3.5 ml of a 1.72 M solution of MeMgI in
diethyl ether (5.8 mmol). The mixture was stirred for
10 min at −80°C, and than stirred another 30 min
at ambient temperature. Solvents were removed in
vacuo and the white residue was extracted with pen-
tane (2×50 ml). Removing the pentane in vacuo af-
forded a yellowish solid of spectroscopically pure
(h5:h1-Cp°)ZrMe3 (0.3 g, 1.2 mmol, 58%). The ob-
tained compound was found to be too reactive to do
a microanalysis.
In a typical procedure, a suspension of (h5:h1-
Cp°)ZrCl3 (0.16 g, 0.5 mmol) in THF (30 ml) was
kept between −20 and −30°C. Addition of 0.5
mmol of MeLi (0.32 ml of a 1.55 M solution in
diethyl ether) resulted in the formation of a clear yel-
low solution. A sample (5 ml) was removed and
evaporated to dryness. The residue was extracted with
1
C6D6 or THF-d8 and analyzed by H- and 13C-NMR
at room temperature (r.t.). Then, another equivalent
of MeLi (corrected for sample loss) was added and
analyzed by the same procedure. The reactions with
(h5-Cp)ZrCl3(DME),
(h5-Cp)2ZrCl2
and
(h5-
4.5. Reaction of 6 with B(C6F5)3; formation of
[(p5:p1-Cp°ZrMe2(THF)][MeB(C6F5)3] (13) (NMR
experiment)
Cp°)2ZrCl2 or with MeMgI (as an 1–2 M solution in
diethyl ether) were investigated similarly.
4.2. Preparation of (p5:p1-Cp°)ZrClMe2 (4)
Approximately 0.15 g of (h5:h1-Cp°)ZrMe3 were
solved in THF-d8 and transferred into an NMR tube.
Then one equivalent of B(C6F5)3 was added and the
To a cooled solution (−80°C) of (h5:h1-Cp°)ZrCl3
(0.8 g, 2.5 mmol) in diethyl ether (50 ml) was added
3 ml of a 1.71 M solution of MeLi (5.13 mmol) in
diethyl ether. The solution was stirred for 15 min and
then allowed to warm to r.t. The solvent was re-
moved in vacuo. The residue was extracted with
toluene (20 ml), filtered, after which 20 ml of pentane
was added. At 0°C colourless crystals of (h5:h1-
Cp°)ZrClMe2 precipitated (0.3 g, 1.1 mmol, 43%).
Anal. Calc. for C10H17ClOZr (M=279.91): C, 42.91;
H, 6.13. Found: C, 42.5; H, 6.1%.
1
solution analyzed by H- and 13C-NMR.
Acknowledgements
Financial support by the Deutsche Forschungs-
gemeinschaft, the Alexander-von-Humboldt-Stiftung
and the Bundesland Sachsen-Anhalt (HSP III pro-
gram) is gratefully acknowledged.

58
C. Mattheis et al. / Journal of Organometallic Chemistry 602 (2000) 51–58
[6] M.D. Fryzuk, S.S.H. Mao, P.B. Duval, S.J. Rettig, Polyhe-
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