Reactions of (η5-C5Me5)ZrF3, (η5-C5Me4Et)ZrF3, (η5-C5Me5)2ZrF2, (η5-C5Me5)HfF3

Article abstract of DOI:10.1021/om950590n

The reaction of Cp*ZrF₃ (1) (Cp* = η⁵-CsMes) and AlMe₃ resulted in the formation of cis-{[Cp*ZrMe(μ₂-F)][(μ₂-F) ₂AlMe₂]}₂ (6) and [(Cp*Zr)₃Al₆Me₈(μ₃-CH ₂)₂(μ₄-CH)₄(μ₃-CH)] (7), respectively. Analogously, (η⁵-C₅Me₄Et)ZrF₃ (3) reacts with AlMes in a molar ratio of 1:5 with methane elimination to give the Zr₃Al₆C₇ cluster of composition {[(η⁵-C₅Me₄Et)Zr]₃Al ₆Me₈-(μ₃-CH₂) ₂(μ₄-CH)₄(μ₃-CH)} (8), which has been characterized by elemental analysis and ¹H NMR and mass spectrometry. Reaction of 2 equiv of AlMe₃ with Cp*₂ZrF₂ (2) leads quantitatively to Cp*₂ZrMe₂ (12). Reaction of Cp*HfF₃ (4) with AlMe₃ in an equimolar ratio gives {[Cp*HfMe (μ₂-F)][(μ₂-F)₂AlMe₂]} ₂ (9) stereospecifically as its cis isomer in high yield. 9 crystallizes in the space group P2₁/c with four molecules in the elemental cell (Z = 16). From the reaction of 1 equiv of Cp*HfF₃ (4) with 3 equiv of AlMe₃, Cp*HfMe₃ (10) can be obtained in a yield of 85%. As a byproduct of this reaction the Hf₃Al₆C₇ cluster [(Cp*Hf)₃-Al₆Me₈(μ₃-CH ₂)₂(μ₄-CH)₄(μ₃-CH)] (11) can be isolated in a yield of 5%. The characterization of 11 by single-crystal X-ray diffraction and ¹H, ¹³C NMR and mass spectroscopic data will be discussed. Cp*TaF₄ (5) reacts with a 5-fold excess of AlMe₃, leading quantitatively to Cp*TaMe₄ (13) without further decomposition via C-H activation processes.

Full text of DOI:10.1021/om950590n

Organometallics 1996, 15, 909-917
909
Rea ction s of (η5-C5Me5)Zr F 3, (η5-C5Me4Et)Zr F 3,
(η5-C5Me5)2Zr F 2, (η5-C5Me5)HfF 3, a n d (η5-C5Me5)Ta F 4 w ith
AlMe3. Str u ctu r e of th e F ir st
Ha fn iu m -Alu m in u m -Ca r bon Clu ster
Axel Herzog, Herbert W. Roesky,* Felix J a¨ger, Alexander Steiner, and
Mathias Noltemeyer
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received J uly 31, 1995X
The reaction of Cp*ZrF3 (1) (Cp* ) η5-C5Me5) and AlMe3 resulted in the formation of cis-
{[Cp*ZrMe(µ2-F)][(µ2-F)2AlMe2]}2 (6) and [(Cp*Zr)3Al6Me8(µ3-CH2)2(µ4-CH)4(µ3-CH)] (7), re-
spectively. Analogously, (η5-C5Me4Et)ZrF3 (3) reacts with AlMe3 in a molar ratio of 1:5 with
methane elimination to give the Zr3Al6C7 cluster of composition {[(η5-C5Me4Et)Zr]3Al6Me8-
1
(µ3-CH2)2(µ4-CH)4(µ3-CH)} (8), which has been characterized by elemental analysis and H
NMR and mass spectrometry. Reaction of 2 equiv of AlMe3 with Cp*2ZrF2 (2) leads
quantitatively to Cp*2ZrMe2 (12). Reaction of Cp*HfF3 (4) with AlMe3 in an equimolar ratio
gives {[Cp*HfMe (µ2-F)][(µ2-F)2AlMe2]}2 (9) stereospecifically as its cis isomer in high yield.
9 crystallizes in the space group P21/c with four molecules in the elemental cell (Z ) 16).
From the reaction of 1 equiv of Cp*HfF3 (4) with 3 equiv of AlMe3, Cp*HfMe3 (10) can be
obtained in a yield of 85%. As a byproduct of this reaction the Hf3Al6C7 cluster [(Cp*Hf)3-
Al6Me8(µ3-CH2)2(µ4-CH)4(µ3-CH)] (11) can be isolated in a yield of 5%. The characterization
1
of 11 by single-crystal X-ray diffraction and H, 13C NMR and mass spectroscopic data will
be discussed. Cp*TaF4 (5) reacts with a 5-fold excess of AlMe3, leading quantitatively to
Cp*TaMe4 (13) without further decomposition via C-H activation processes.
In tr od u ction
Recently, we found that Me3SnF and nBu3SnF are
suitable fluorinating agents for high-yield syntheses of
cyclopentadienyl-substituted fluorides of group 4 transi-
tion metals.4 The solubility of the fluorides, Cp′MF3 (M
) Zr, Hf), in aromatic solvents is excellent when they
are substituted with bulky ligands such as Cp*. Fur-
thermore, we found that the complexes Cp*ZrF3 (1) and
Cp*2ZrF2 (2) are weakly active homogeneous catalysts
for the polymerization of olefins when a 1000-fold excess
of MAO is used as co-catalyst.5 This activity is the
presupposition for a mechanistic study of these systems,
e.g., via 19F NMR investigations.
Reactions of transition metal(IV) organo halides with
alkyls of group 13 elements, especially those of alumi-
num, are of particular interest with regard to the
mechanisms of homogeneous catalysis for the polymer-
ization of olefins. The methylation of a metallocene-
(IV) chloride is assumed to be the first step of activation
of a polymerization catalyst when AlMe3 containing
methylalumoxane (MAO) is used.1 Nevertheless, only
a few examples of reactions of cyclopentadienyl-substi-
tuted titanium chlorides with AlMe3, leading to well-
defined products, are described in the literature: me-
tathesis reaction with Cp*TiCl3 (Cp* ) η5-C5Me5)
yielding Cp*TiCl2Me2 and the reactions with titanocene
dichlorides from which the Tebbe reagent, Cp2Ti(µ2-
CH2)(µ2-Cl)AlMe2,3 and its analogues can be obtained.
To the best of our knowledge, results of related inves-
tigations using zirconium chlorides have not been
published. Presumably, this is due to the reversible
equilibria in these systems, which prevent the isolation
of defined products. It is striking that up to now
organometallic fluorides were never used as starting
materials for this type of reaction. Due to the strong
Lewis acidity of AlMe3, the equilibria of the reactions
with these complexes should be shifted to the side of
the products, so the study of the stepwise methylation
should be facile.
With regard to this activity, we report herein the
detailed reactions of AlMe3 with the fluorides Cp*ZrF3
(1), (η5-C5Me4Et)ZrF3 (3), Cp*2ZrF2 (2), Cp*HfF3 (4), and
Cp*TaF4 (5), respectively.
Resu lts a n d Discu ssion
P r ep a r a tion of 6 a n d 7. In a recent communica-
tion6 we reported the preliminary results of the meth-
ylation of 1 using AlMe3. The reaction of 1 and AlMe3
in an equimolar ratio in toluene as well as in n-hexane
leads to a Me-F exchange, and the fluorine-bridged
dimer cis-{[Cp*ZrMe(µ2-F)][(µ2-F)2AlMe2]}2 (6) is formed
stereoselectively. The X-ray structure of this complex
has been determined. Four molecules of 6 as depicted
in eq 1 occupy its unit cell. When an excess of AlMe3 is
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) (a) Kaminsky, W.; Steiger, R. Polyhedron 1988, 7, 2375. (b)
Kaminsky, W.; Bark, A.; Steiger, R. J . Mol. Catal. 1992, 74, 109.
(2) Mart´ın, A.; Mena, M.; Pellighelli, M. A.; Royo, P.; Serrano, R.;
Tiripicchio, A. J . Chem. Soc., Dalton Trans. 1993, 2117.
(3) Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J . Am. Chem. Soc.
1978, 100, 3611.
(4) Herzog, A.; Liu, F.-Q.; Roesky, H. W.; Demsar, A.; Keller, K.;
Noltemeyer, M.; Pauer F. Organometallics 1994, 13, 1251.
(5) Roesky, H. W.; Herzog, A., unpublished results.
(6) Herzog, A.; Roesky, H. W.; Zak, Z.; Noltemeyer, M. Angew. Chem.
1994, 106, 1035; Angew. Chem., Int. Ed. Engl. 1994, 33, 967.
0276-7333/96/2315-0909$12.00/0 © 1996 American Chemical Society

910 Organometallics, Vol. 15, No. 3, 1996
Herzog et al.
detected at low field when it is dissolved in CDCl3 (for
assignment, see the Experimental Section). Surpris-
ingly, no reaction of 7 with this solvent takes place. The
results lead to the conclusion that the formula of 7
should be written correctly as [(Cp*Zr)3Al6Me8(µ3-CH2)2-
(µ4-CH)4(µ3-CH)].
P r ep a r a tion of 8. A mixture of (η5-C5Me4Et)ZrF3
(3) and an excess of AlMe3 in n-hexane reacts in the
same manner as observed for 1 with 5 equiv AlMe3 in
n-hexane. Related to 1 mol of 3, the evolution of 3.5
mol of methane was found and over a period of 6 days
a yellow microcrystalline solid precipitates. Recrystal-
lization from toluene gives the pure product, which was
identified as {[(η5-C5Me4Et)Zr]3Al6Me8(µ3-CH2)2(µ4-CH)4-
(µ3-CH)} (8).
reacted with 1 in n-hexane, all the fluorines are
displaced from the zirconium and methane evolution can
be observed. The maximum amount of methane (3.5
equiv) can be achieved when 5 equiv of AlMe3 is reacted
with 1. Finally, the Zr3Al6C7 cluster (Cp*Zr)3Al6Me8-
(CH2)2(CH)5 (7) can be isolated in yields of 30 (pure) and
70% (crude) as a yellow crystalline solid. From the
relation of the evolved amount of methane to the
theoretical required (eq 2) a maximum yield for 7 of 88%
can be calculated. Single crystals of 7 could be obtained
only from freshly prepared material by slowly reducing
the volume of a solution of 7 in toluene. Its X-ray
structure analysis has been reported. The hydrogen
atoms on 7 were not set until now (eq 2) due to the
3(η5-C5Me4Et)ZrF3
+ 15AlMe3 f
3
5
+
{[(η -C5Me4Et)Zr]3Al6Me8(µ3-CH2)2(µ4-CH)4(µ3-CH)}
8
9Me2AlF + 12MeH (3)
Unfortunately, no suitable single crystals for X-ray
diffraction measurement were available. Contrary to
expectation, the solubility of 8 in common organic
solvents is even worse than that in the case of 7. In
the EI mass spectrum of 8, the basis peak was found at
m/z ) 1008 with composition of [(C5Me4Et)Zr]3Al6Me2-
(CH2)2(CH)5 where six methyl groups became abstracted
from the molecular ion. The peak with the highest mass
was found to be [M+ - 3Me] (m/z ) 1051). This
indicates a high thermal stability of 8 in the gaseous
state as well as in the solid state which is discernable
from its high decomposition point of 300 °C. In contrast,
8 decomposes to unidentified products already in solu-
tion when warmed to moderate temperatures, but
without further methane elimination. This has also
been observed for 7.
1
1H NMR Sp ectr u m of 8. The H NMR spectrum of
spectroscopic information given herein. The freshly
precipitated material of 7 is sparingly soluble in com-
mon organic solvents.
8 in C6D6 gives the signal pattern of the protons of the
methyl groups at the Al atoms at high field and of the
protons of the methylidine and methylidene moieties at
low field. That is similar to that found for the corre-
sponding protons of 7. The protons of the methyl groups
of the “face to face” bonded C5Me4Et groups in 8 were
found to be magnetically not equivalent. They are split
into three pairs of singlets (δ 1.91, 1.85, and 1.76 ppm)
with integral ratios of 3:3, 3:3, and 6:6, respectively. This
is possibly due to the steric hindrance of rotation of the
C5Me4Et groups.
NMR Sp ectr a of 6 a n d 7. Supplementary to the
published spectroscopical data6 of complex 6, the signals
of the 19F NMR of 6 can be interpreted due to their
coupling pattern. The fluorine atoms bridging the Zr
atoms become chemically different due to the trans
effect of either the Cp* ligands or the methyl groups.
One of them exhibits a doublet from a quintet from a
1
septet signal (δ -32.5 ppm) with 19F-19F and H-19F
2
coupling constants (2J FF ) 33 and 75 Hz, J HF ) 9 Hz).
In order to increase the solubility of the cluster
molecules, we have undertaken preliminary attempts
to substitute the protons of the methylidine and meth-
ylidene moieties or the methyl groups at the Al atoms.
But surprisingly no reaction takes place when, for
The other one gives a doublet of a quintet resonance (δ
2
-69.5 ppm) with J FF coupling constants (20 and 75 Hz).
The fluorine atoms linking the Zr and Al atoms resonate
as a broad singlet (δ -108.2 ppm).
It is significant that bridging F atoms of transition
metal fluoride complexes become electronically strong
deshielded and are found in the high field of the
corresponding 19F NMR spectra. This is in contrast to
the observations that can be made for fluorides of main
group elements.7
The poor solubility of 7 prevents its characterization
by 13C NMR spectroscopy. Therefore, the interpretation
of the 1H NMR signals is difficult. However, the signals
of the methylidene and methylidine protons can be
t
example, 7 was stirred with BuNH2 or (Me3Si)2NH. No
definite product could be isolated from the reaction of 7
with tBuOH. Futhermore, it is impossible to insert
1-butene into the metal-carbon bonds, even under
pressure. Therefore, it is not surprising that ethene
does not polymerize when bubbled through a co-catalyst-
free solution of 7 in toluene. No complex formation of
7 was observed with tertiary phosphines.
However, methylidene transfer reactions of 7 and
carbonyl group-containing organics were successful. The
results, including the reaction conditions, (not opti-
(7) Kra¨uter, T.; Neumu¨ller, B. Z. Anorg. Allg. Chem. 1995, 621, 597.

Hf-Al-C Cluster
Organometallics, Vol. 15, No. 3, 1996 911
Ta ble 1. P r od u cts a n d Yield s in th e Meth ylid en e
Tr a n sfer Rea ction s of 7a
hafnium complexes of 6, 7, and 8. Indeed, when 4 and
AlMe3 were reacted in an equimolar ratio in toluene,
the homologous hafnium complex of 6, cis-{[Cp*HfMe-
(µ2-F)][(µ2-F)2AlMe2]}2 (9), could be isolated in quantita-
tive yield. 9 is generated stereospecifically as its cis
isomer, which is persistent in solution.
starting
material
yield
(%)
product
reaction conditions
CHCl3, room temp,
4 days
25
24
7
H
O
O
toluene, 70 °C, 5 h
CH2
C
C
CHCl3, reflux, 4 h
Cl
O
CHCl3, reflux, 8 h
toluene, reflux, 8 h
11
7
Cl
O
CH2Cl
CH2CH3
a
Yields were determined by GC and are based on 7.
NMR Sp ectr a of 9. The 19F NMR spectrum of 9
reveals three magnetic nonequivalent types of fluorine
atoms as observed for complex 6. Both fluorine atoms
bridging the Hf atoms become chemically different due
to the trans effect of either the Cp* ligands or the methyl
groups. One of them gives a doublet of a quintet
mized) are summarized in Table 1. In all cases a 7-fold
excess of the substrate was taken. Except for the
reaction of (Ph)2CO with 7, which was worked up with
diluted HCl, the products were isolated directly from
the reaction mixture by distillation. After chromato-
graphic separation only the main product was charac-
terized. The reactions in general do not occur when
ether or pentane was used as a solvent. Surprisingly,
esters do not react with 7 using boiling CHCl3. The low
yields of the products originating from chlorine-contain-
ing compounds could result from the additional methyl
transfer reaction, which should be the rate-determining
step of the reaction. Indeed, when benzyl chloride is
reacted with 7, only ethylbenzene can be identified in
low yield.
Besides the Tebbe reagent as the classical represen-
tative of an active “Wittig-type” reagent of group 4
transition metals,1,8 alkylidene transfer reactions using
ketones are also well-known for the related Zr complex
Cp2Zr[µ2-CH(Np)](µ2-Cl)AliBu2 (Np ) neopentyl)9 when
it is treated with HMPTA.9c In comparison, the Ti
species is much more reactive than the Zr one.9c For
both complexes, a free carbene intermediate is discussed
to be necessary for a successful oxo methylidene conver-
sion. A dissociative step cannot be assumed for complex
7. However, Et2AlCH2AlEt2‚Et2O gives (Ph)2CdCH2
from the reaction of (Ph)2CO without using final hy-
drolysis.10
2
resonance (δ -87.3 ppm) with J FF coupling constants
(19 and 86 Hz). The second one exhibits a doublet from
a quintet from a septet signal (δ -56.7 ppm) due to an
1
additional H-19F coupling (2J HF ) 11 Hz). The inten-
sity of these two signals compared to the intensity of a
2
broad doublet (δ -109.8 ppm, J FF ) 10 Hz) is 1:4. It
originates from the four F atoms linking the Hf and Al
atoms.
The 1H NMR spectrum of 9 shows a singlet resonance
(δ 1.83 ppm) for the protons of the Cp* groups. The
protons of the Hf-bonded methyl groups exhibit a
1
doublet of a doublet (δ 0.24 ppm). One of the H-19F
coupling constants can be determined (10 Hz). The
protons of the Al-bonded methyl groups give, depending
upon their syn or anti position in relation to the Cp*
ligands, two multiplets (δ -0.37 and -0.46 ppm).
The resonances of the C atoms of the Cp* rings of 9
appear in the 13C NMR spectrum as singlets (δ 122.4
and 10.6 ppm). However, the C atoms of the methyl
groups at the Al atoms produce two multiplets (δ -11.1
and -12.2 ppm). Finally, for the C atoms of the Hf-
connected methyl groups, a doublet of a doublet (δ 43.5
2
ppm) with J CF coupling constants of 15 and 30 Hz is
found.
P r ep a r a tion of 9. A comparison of the metal-
fluorine bond energies (Zr-F 661 kJ /mol, Hf-F 642 kJ /
mol, Al-F 640 kJ /mol)11 shows that treatment of
Cp*HfF3 (4) with AlMe3 should lead to the analogous
Cr ysta l Str u ctu r e of 9. Single crystals of 9 suitable
for X-ray analysis at 153 K were obtained from a toluene
solution of 9 by slowly reducing the volume under
reduced pressure. Figure 1 shows the structure of 9 in
the crystal. The relevant bond lengths and -angles of 9
are presented in Table 2. Four molecules of 9, as
depicted in Figure 1, occupy the elemental cell (Z ) 16).
9 is isostructural to 6.
(8) (a) Klabunde, U.; Tebbe, F. N.; Parshall, G. W.; Harlow, R. L. J .
Mol. Catal. 1980, 8, 37. (b) Howard, T. R.; Lee, J . B.; Grubbs, R. H. J .
Am. Chem. Soc. 1980, 102, 6876. (c) Pine, S. H.; Zahler, R.; Evans, D.
A.; Grubbs, R. H. J . Am. Chem. Soc. 1980, 102, 3270. (d) Buchwald, S.
L.; Grubbs, R. H. J . Am. Chem. Soc. 1983, 105, 5490. (e) Stille, J . R.;
Grubbs, R. H. J . Am. Chem. Soc. 1983, 105, 1664. (f) Lombardo, L.
Tetrahedron Lett. 1982, 4293. (g) Bruin, J . W.; Schat, G.; Akkerman,
O. S.; Bickelhaupt, F. Tetrahedron Lett. 1983, 3935. (h) Eisch, J . J .;
Piotrowski, A. Tetrahedron Lett. 1983, 2043. (i) Stevenson, J . W. S.;
Bryson, T. A. Tetrahedron Lett. 1982, 3143. (j) Chou, T.-S.; Huang,
S.-B. Tetrahedron Lett. 1983, 2169. (k) Straus, D. A.; Grubbs, R. H.
Organometallics 1982, 1, 1658. (l) Ott, K. C.; de Boer, E. J . M.; Grubbs,
R. H. Organometallics 1984, 3, 223.
(9) (a) Hartner, F. W., J r.; Schwartz, J . J . Am. Chem. Soc. 1981,
103, 4979. (b) Hartner, F. W., J r.; Clift, S. M.; Schwartz, J .; Tulip, T.
H. Organometallics 1987, 6, 1346. (c) Hartner, F. W., J r.; Schwartz,
J .; Clift, S. M. J . Am. Chem. Soc. 1983, 105, 640.
(10) Ashby, E. C.; Scott, R. S. J . Organomet. Chem. 1982, 225, 71.
(11) Sanderson, R. T. Polar Covalence; Academic Press: New York,
1983.
The Hf-C(Me) bond distances amount to 224.4 pm.
This value is in agreement with those found for Cp2-
12
HfMe2 (mean 223.7 pm) or [(Cp2HfMe)2(µ2-O)] (mean
229.5(14) pm).13 However, in another structure deter-
mination of Cp2HfMe2,13 two different and much longer
Hf-C(Me) bond lengths were reported (231.8(8) and
238.2(7) pm), which correspond to the Hf-C(Me) bond
(12) Hunter, W. E.; Hrncir, D. C.; vann Bynum, R.; Penttila, R. A.;
Atwood, J . L. Organometallics 1983, 2, 750.
(13) Fronczek, F. R.; Baker, E. C.; Sharp, P. R.; Raymond, K. N.;
Alt, H. G.; Rausch, M. D. Inorg. Chem. 1976, 15, 2284.

912 Organometallics, Vol. 15, No. 3, 1996
Herzog et al.
F igu r e 2. Crystal structure of [(Cp*Hf)3Al6Me8(µ3-CH2)2-
(µ4-CH)4(µ3-CH)] (11) and anisotropic displacement param-
eters depicting 50% probability. The hydrogen atoms have
been omitted for clarity.
F igu r e 1. Crystal structure of cis-{[Cp*HfMe(µ2-F)][(µ2-
F)2AlMe2]}2 (9), anisotropic displacement parameters de-
picting 50% probability. Only one of the four molecules of
9, which occupy the elemental cell, is shown. The hydrogen
atoms and the uncoordinated lattice toluene molecules have
been omitted for clarity.
cal data found for 10 are in agreement with those given
in literature.15
However, it was generally observed that the crystal-
lization of 10 was accomplished with the formation of a
yellow n-hexane-insoluble solid. Keeping the first fil-
trate of the reaction for several months, the byproduct
of 10 accumulated, forming a yellow microcrystalline
solid as well as yellow single crystals, which were
suitable for an X-ray structure analysis. This revealed
the formation of the Hf3Al6C7 cluster [(Cp*Hf)3Al6Me8-
(µ3-CH2)2(µ4-CH)4(µ3-CH)] (11) as the byproduct of the
metathesis reaction using Cp*HfF3 (4) and excess of
AlMe3. The maximum yield of 11 is 5%, corresponding
to the small amount of methane generated from this
reaction. The yield of 11 cannot be improved by using
more than 3 equiv of AlMe3. Furthermore, the reaction
of Cp*HfMe3 and excess of AlMe3 over a period of 3
weeks gives no significant amount of methane and 11,
respectively.
Figure 2 shows the structure of 11 in the solid state
while the relevant bond lengths and -angles of 11 are
presented in Table 5.
Cr ysta l Str u ctu r e of 11. The solid state structure
of 11 is comparable to that of complex 7 with the
exception that 7 contains 2.5 molecules of toluene/
molecule of 7, localized on special crystallographic
positions.
Ta ble 2. Selected Bon d Len gth s (p m ) a n d An gles
(d eg) of cis-{[Cp *HfMe(µ2-F )][(µ2-F )2AlMe2]}2 (9)
(a) Distances
Hf(1)-C(1)
Hf(1)-F(2)
Hf(1)-F(4)
225.2(13)
213.2(7)
210.0(7)
Hf(1)-F(5)
Hf(2)-F(5)
Al(2)-F(4)
217.2(6)
214.5(6)
177.6(8)
(b) Angles
F(2)-Hf(1)-C(12)
F(4)-Hf(1)-C(12)
Hf(2)-F(2)-Hf(1)
90.9(4)
90.1(4)
112.5(3)
F(4)-Hf(1)-F(2)
F(1)-Hf(1)-F(2)
Al(1)-F(2)-Hf(1)
152.2(3)
96.1(4)
139.9(4)
distances in (η5-C9H7)2HfMe2 (mean 233.2(12) pm).14
The bond distances of Hf and F are in the range of 210-
217 pm and are comparable to the Zr-F bond lengths
in complex 6.6
P r ep a r a t ion of 10 a n d 11. When 1 equiv of
Cp*HfF3 (4) with 3 equiv of AlMe3 were reacted in
n-hexane at room temperature for 16 h, different
products were isolated in comparison to the analogous
reaction using Cp*ZrF3 (1) or (η5-C5Me4Et)ZrF3 (3) and
AlMe3, according to eq 2 and eq 5, respectively. Only a
In 11, three Hf, six Al, and seven C atoms are building
an open core and all the metal atoms are tetragonally
coordinated, but nearly all the C atoms are bond to the
metal atoms hypervalently. The structure exhibits four
µ4 (C1, C2, C3, and C4) and one µ3 (C5) bridging C atoms
of methylidine units as well as two µ3-bridging C atoms
of methylidene groups between the metal centers.
The H atoms have not been localized in the structure
refinement; they are however plausibly placed due to
electronic and geometric reasons. This resulted in an
electronic deficiency at the 12-electron Hf centers, and
therefore, significant metal-metal interactions occur.
The average value of the short Hf-Al distances amount
to 285.2(2) pm. From the metal radii a Hf-Al distance
of 302 pm can be derived.16
small amount of methane was collected while an uni-
dentified white solid precipitated, which had to be
filtered off before removing all of the volatiles in vacuo.
After repeated crystallization of the crude product,
Cp*HfMe3 (10) can be obtained at -25 °C from n-hexane
in a yield of 85% as colorless needles. The spectroscopi-
(15) Schock, L. E.; Marks, T. J . J . Am. Chem. Soc. 1988, 110, 7701.
(16) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon
Press: Oxford, England. 1984.
(14) Atwood, J . L.; Hunter, W. E.; Hrncir, D. C.; Samuel, E.; Alt,
H.; Rausch, M. D. Inorg. Chem. 1975, 14, 1757.

Hf-Al-C Cluster
Organometallics, Vol. 15, No. 3, 1996 913
Ta ble 3. Atom ic Coor d in a tes (×104) a n d Equ iva len t Isotr op ic Disp la cem en t P a r a m eter s (p m 2 × 10-1) for 9a
x
y
z
U(eq)
x
y
z
U(eq)
Hf(1)
Hf(2)
Al(1)
Al(2)
F(1)
F(2)
F(3)
F(4)
F(5)
F(6)
C(1)
C(2)
C(3)
C(4)
C(5)
C(1*)
C(2*)
C(3*)
C(4*)
C(5*)
C(6)
C(7)
C(8)
C(9)
C(10)
C(6*)
C(7*)
C(8*)
C(9*)
C(10*)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
Hf(3)
Hf(4)
Al(3)
Al(4)
F(11)
F(12)
F(13)
F(14)
F(15)
F(16)
C(21)
C(22)
C(23)
C(24)
C(25)
C(21*)
C(22*)
C(23*)
C(24*)
C(25*)
C(26)
C(27)
C(28)
C(29)
C(30)
C(26*)
C(27*)
C(28*)
C(29*)
C(30*)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
Hf(5)
Hf(6)
Al(5)
Al(6)
F(21)
F(22)
F(23)
127(1)
658(1)
221(2)
68(2)
585(3)
178(3)
476(3)
79(3)
-13(3)
809(2)
238(5)
-40(5)
265(5)
741(5)
727(5)
2591(1)
2685(1)
3952(2)
1387(2)
3525(3)
3467(3)
1838(2)
1766(3)
2687(3)
2586(3)
2016(6)
2494(6)
2958(6)
2785(5)
2200(6)
1417(7)
2498(7)
3535(7)
3151(6)
1832(6)
3173(6)
2778(5)
2236(7)
2284(7)
2845(6)
3791(6)
2935(8)
1725(7)
1801(7)
3066(8)
2793(8)
2641(6)
4556(7)
4052(7)
701(7)
1446(8)
-344(1)
-346(1)
-264(2)
77(2)
-361(3)
-375(3)
-195(3)
-183(3)
141(3)
-856(3)
-799(6)
-1215(5)
-1231(6)
-814(6)
-541(6)
-659(8)
-1599(7)
-1638(6)
-670(7)
-98(6)
-899(6)
-1268(6)
-1152(6)
-723(6)
-556(6)
-894(9)
-1734(7)
-1461(7)
-463(8)
-138(7)
504(6)
1614(1)
3252(1)
2364(2)
2554(2)
2967(3)
1771(3)
3116(3)
1896(3)
2467(3)
2403(3)
757(6)
479(6)
674(5)
1084(5)
1144(6)
657(7)
24(1)
29(1)
36(1)
51(1)
40(2)
35(2)
48(2)
38(2)
32(2)
24(2)
33(3)
34(4)
28(3)
25(3)
29(3)
55(4)
56(5)
55(4)
42(4)
42(4)
42(4)
31(3)
41(4)
45(4)
36(3)
64(5)
59(5)
70(5)
73(6)
72(6)
58(5)
40(4)
61(5)
54(4)
92(7)
77(6)
22(1)
22(1)
42(1)
30(1)
34(2)
33(2)
30(2)
34(2)
26(2)
27(2)
36(4)
33(3)
35(4)
32(3)
33(3)
73(6)
77(6)
62(5)
56(5)
52(4)
41(4)
39(4)
38(4)
37(4)
38(4)
82(7)
70(6)
64(5)
65(5)
63(5)
43(4)
34(3)
91(7)
79(6)
47(4)
53(4)
22(1)
21(1)
31(1)
33(1)
35(2)
31(2)
30(2)
F(24)
F(25)
F(26)
C(41)
C(42)
C(43)
C(44)
C(45)
C(41*)
C(42*)
C(43*)
C(44*)
C(45*)
C(46)
C(47)
C(48)
C(49)
C(50)
C(46*)
C(47*)
C(48*)
C(49*)
C(50*)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
Hf(7)
Hf(8)
Al(7)
2724(2)
2487(2)
2507(2)
1365(5)
1582(5)
1364(5)
1002(5)
1008(5)
1473(6)
1972(5)
1467(7)
642(6)
-308(3)
148(3)
-2675(3)
-3787(3)
-3800(3)
-4300(6)
-4768(7)
-5234(6)
-5065(6)
-4479(6)
-3734(7)
-4776(8)
-5835(7)
-5455(8)
-4126(8)
-3133(7)
-2550(6)
-2358(6)
-2801(7)
-3300(6)
-3504(8)
-2182(8)
-1738(6)
-2776(8)
-3872(7)
-4518(7)
-3005(6)
-4901(7)
-5500(7)
-2570(9)
-2123(7)
-627(1)
1014(1)
178(2)
147(2)
805(3)
-407(3)
783(3)
-433(3)
160(3)
228(3)
-1664(6)
-1240(6)
-980(6)
-1248(7)
-1660(6)
-2059(7)
-1138(9)
-543(7)
-1136(8)
-2069(8)
1909(5)
26(2)
24(2)
22(2)
31(3)
37(4)
34(4)
39(4)
32(3)
55(5)
58(5)
78(6)
70(6)
57(5)
42(4)
31(3)
33(3)
37(4)
39(4)
71(6)
58(5)
63(5)
60(5)
69(6)
43(4)
33(3)
55(4)
63(5)
66(5)
72(6)
25(1)
20(1)
40(1)
37(1)
33(2)
37(2)
33(2)
34(2)
29(2)
22(2)
41(4)
48(4)
38(4)
46(4)
36(3)
58(5)
71(5)
66(6)
72(6)
63(5)
25(3)
28(3)
29(3)
22(3)
25(3)
50(4)
51(5)
45(4)
42(4)
33(3)
61(5)
31(3)
69(5)
64(5)
66(5)
56(4)
99(9)
62(5)
123(11)
97(7)
104(10)
105(11)
136(11)
88(7)
107(8)
122(10)
83(6)
90(7)
78(6)
164(14)
-853(3)
-1194(6)
-1274(6)
-888(6)
-568(6)
-768(6)
-1547(6)
-1716(6)
-825(9)
-156(7)
-568(7)
-744(7)
-531(5)
-853(6)
-1240(6)
-1174(6)
-548(8)
-122(7)
-788(8)
-1672(6)
-1531(7)
511(6)
685(6)
3992(5)
4018(5)
3679(5)
3442(5)
3640(5)
4310(6)
4386(6)
3600(6)
3057(6)
3507(6)
1533(5)
3438(5)
2827(6)
3072(6)
2144(6)
1930(6)
4347(1)
4885(1)
4875(2)
4834(2)
4901(3)
4488(3)
4867(3)
4459(3)
5024(3)
4199(2)
3786(5)
3535(6)
3402(5)
3563(6)
3802(5)
3966(6)
3401(6)
3106(6)
3467(7)
3999(6)
4751(5)
5047(5)
4761(5)
4273(4)
4270(4)
4895(6)
5557(5)
4926(6)
3863(5)
3836(5)
4956(6)
5724(5)
4481(7)
5532(6)
4434(7)
5492(6)
2525(7)
2442(6)
2387(8)
2399(8)
2521(8)
2570(7)
2587(7)
2474(8)
2673(10)
3135(13)
3389(9)
3205(9)
2749(8)
1997(10)
68(6)
-546(5)
126(6)
-14(7)
455(7)
1182(5)
1131(5)
1411(5)
1584(5)
1486(5)
1249(6)
1203(5)
1473(7)
1860(6)
1629(7)
1070(8)
1034(6)
80(6)
1377(6)
1496(7)
3975(6)
3595(6)
3750(6)
4216(6)
4345(6)
3991(8)
3161(7)
3520(8)
4525(8)
4844(8)
3733(7)
1250(7)
2255(8)
2471(2)
2550(10)
2618(8)
749(1)
520(5)
823(6)
-396(8)
722(7)
-604(9)
2508(1)
2491(1)
3794(2)
1196(2)
3347(3)
3363(3)
1637(3)
1651(3)
2490(3)
2506(3)
2230(7)
2057(7)
2546(6)
3013(7)
2797(6)
1824(7)
1481(7)
2574(8)
3617(7)
3170(7)
2011(5)
2488(6)
2967(5)
2801(5)
2197(5)
1416(6)
2478(7)
3565(6)
3168(6)
1838(6)
2479(7)
2481(5)
4442(6)
3830(8)
563(6)
1145(7)
2233(14)
1968(8)
2296(11)
2810(11)
3098(12)
2830(9)
1982(13)
-2434(11)
-2903(11)
-2905(11)
-2450(10)
-1940(10)
-1917(8)
-2396(12)
-721(5)
639(7)
-433(6)
423(8)
Al(8)
F(31)
F(32)
F(33)
F(34)
F(35)
F(36)
C(61)
C(62)
C(63)
C(64)
C(65)
C(61*)
C(62*)
C(63*)
C(64*)
C(65*)
C(66)
C(67)
C(68)
C(69)
C(70)
C(66*)
C(67*)
C(68*)
C(69*)
C(70*)
C(71)
C(72)
C(73)
C(74)
C(75)
C(76)
C(81)
C(82)
C(83)
C(84)
C(85)
C(86)
C(87)
C(91)
C(92)
C(93)
C(94)
C(95)
C(96)
C(97)
-615(7)
1845(1)
3125(1)
2100(2)
2849(1)
2721(3)
1770(3)
3198(2)
2252(3)
2473(2)
2500(2)
1326(5)
1578(5)
1381(5)
1018(5)
983(5)
1750(1)
2421(2)
149(2)
2369(3)
1629(3)
883(3)
141(3)
1289(3)
1204(3)
-244(6)
167(6)
651(6)
564(6)
-2(6)
2166(5)
1924(6)
1521(5)
1520(5)
2066(7)
2654(6)
2094(7)
1206(6)
1184(6)
-1087(7)
1383(6)
246(8)
77(7)
214(8)
39(7)
1387(7)
1977(6)
1531(7)
676(5)
-846(7)
75(9)
1188(7)
946(7)
591(5)
-320(7)
2661(6)
2167(7)
1692(6)
1879(6)
2475(6)
3263(7)
2180(9)
1082(7)
1535(8)
2870(8)
617(7)
2061(6)
2633(10)
2855(8)
187(7)
-460(7)
-4292(1)
-3286(1)
-4903(2)
-2652(2)
-4902(3)
-4167(3)
-3421(3)
3676(5)
3446(5)
3648(6)
3985(5)
4005(5)
3593(7)
3079(6)
3533(6)
4294(6)
4361(6)
1494(5)
3417(5)
2023(7)
1963(7)
2844(6)
3051(6)
1860(1)
3140(1)
2867(2)
2122(2)
2273(3)
3216(2)
1781(2)
1759(11)
1235(9)
710(16)
499(5)
487(8)
-903(9)
883(6)
-327(7)
-348(1)
-335(1)
20(2)
669(13)
1315(15)
1819(17)
2318(12)
-1282(10)
-1006(12)
-523(12)
-329(10)
-574(11)
-1056(10)
-1781(16)
-86(2)
-254(3)
-229(3)
-286(3)
a
U(eq) is defined as one-third of the trace of the orthogonalized Uij tensor.

914 Organometallics, Vol. 15, No. 3, 1996
Herzog et al.
Ta ble 4. Cr ysta l Da ta for 9 a n d 11
9
all shorter than the Hf-C′ (243.2(6) pm) and the Hf-
C′′ (231.0(6) pm) distances in the only known heterobi-
metallic Hf-C-Al complex {Cp2Hf[µ-η1:η2-MeCC′(c-
C6H11)][µ-C′′C(c-C6H11)]AlMe2}.20 In comparison to the
Hf-µ-C bonds, the very long distances Hf2-C3 (225.7-
(6) pm) and Hf3-C2 (227.0(6) pm) deviate significantly
to four proportional short Al2-µ-C bonds (202.2(7), 202.2-
(7), 207.1(8), and 196.2(7) pm). Therefore, an intramo-
lecular polarization in 11 could be postulated. This
finding, likewise observed for complex 7, could serve as
an explanation for their poor solubility in common
organic solvents.
11
formula
fw
C29.50H52Al2F6Hf2
931.65
0.6 × 0.4 × 0.4
P21/c
2804.7(6)
2398.9(6)
2304.0(6)
90
C45H78Al6Hf3
1316.42
0.3 × 0.4 × 0.4
P21/c
1218.1(3)
1991.7(6)
2486.6(9)
90
cryst size (mm)
space group
a (pm)
b (pm)
c (pm)
R (deg)
â (deg)
108.87
90
93.11(4)
90
γ (deg)
V (nm3)
14.669(6)
16
6.024(3)
4
Z
The classification of C5 as methylidenic and C6 as
methylidinic carbon is supported by the structural data
of 11. As expected, all metal-µ-C5 bonds are signifi-
cantly shorter than the related metal-µ-C6 bonds.
Furthermore, the angles between Hf1-C6-Al4 (83.0-
(2)°) and Hf1-C6-Al3 (82.9(2)°) are on average 3.8°
more acute than the angles between Hf2-C5-Al6 (86.8-
(2)°) and Hf3-C5-Al1 (86.7(2)°). This is obviously due
to the requirement of more space for the two H atoms
at C6. Similar observations can also been made for
complex 7.
temp (K)
153(2)
1.687
5.573
153(2)
1.452
5.268
2568
4-25
15 224
10 629
0
Fc (Mg m-3)
µ (mm-1)
F(000)
7248
2θ range (deg)
no. of reflns measd
no. of unique reflns
no. of restraints
refined param
R1 [I > 2σ(I)]
wR2 (all data)
highest diff peak
(10-6 e pm-3)
3.5-22.5
19 355
16 673
1
1489
510
0.0713
0.1468
5.05
0.0439
0.1147
1.72
1H NMR Sp ectr u m of 11. In the 1H NMR spectrum
of 11, measured in toluene-d8, the protons of the Cp*
groups at Hf2 and Hf3 are found to be magnetically
equivalent. They give a singlet (δ 1.98 ppm) which has
a 2:1 ratio compared to the proton signal of the third
Cp* group (δ 1.92 ppm). The resonances for the protons
of the methyl groups at the Al atoms (C40-C47) are
found in the high-field region and can be assigned on
the basis of their integral intensities. The most shielded
protons are those at the methylidene bridge of Al5, Al6,
and Al2. They are diastereotopic and generate a doublet
(δ -1.63 ppm) with a coupling constant of 11 Hz, while
the protons of the second methylidene bridge are as-
signed to a much more low-field-shifted doublet (δ 6.57
ppm, 2J HH ) 11 Hz). The most deshielded proton is that
of the methylidine bridge of Hf2, Hf3, and Al1. It shows
Ta ble 5. Selected Bon d Len gth s (p m ) a n d An gles
(d eg) of [(Cp *Hf)3Al6Me8(µ3-CH2)2(µ4-CH)4(µ3-CH)]
(11)
(a) Distances
Hf1-C3
Hf1-C4
Hf1-C6
Hf2-C1
Hf2-C3
Hf2-C5
Hf3-C2
Hf3-C4
Hf3-C5
Al1-C3
Al1-C4
Al1-C5
Al2-C1
Al2-C2
Al2-C7
218.4(6)
217.9(6)
217.1(7)
222.0(6)
225.7(6)
214.1(6)
221.9(6)
215.8(7)
213.1(6)
212.8(6)
212.6(7)
202.9(6)
202.0(7)
202.2(7)
207.1(8)
Al3-C1
Al3-C3
Al2-Al5
Hf1-Al1
Hf1-Al3
Hf2-Al2
Al3-C6
Al4-C2
Al4-C4
Al4-C6
Al5-C1
Al5-C7
Al6-C2
Al6-C7
200.2(6)
218.2(7)
268.9(3)
283.6(2)
283.8(2)
329.8(2)
212.4(7)
199.3(6)
215.8(7)
211.4(7)
211.0(7)
206.3(8)
212.3(7)
204.7(8)
2
a doublet of a doublet (δ 7.48 ppm, J HH ) 1.7 Hz),
however, the Hf2Al2CH and the HfAl3CH protons give
just singlets (δ 5.16 and 2.82 ppm).
In comparison to 7 or 8, the chemical shift of the latter
indicates a much more deshielding influence of Zr than
Hf on the protons of alkylidene bridges. This has also
been observed for other bimetallic M-Al alkylidene
complexes (M ) Zr, Hf).21
P r ep a r a tion of 12 a n d 13. It can be seen that eq 2
has a certain resemblance to that for the formation of
the Tebbe reagent.3 In this context, we were primarily
interested in whether it is possible to generate a Zr-F
analogous complex. To our knowledge, the reaction of
zirconocene difluorides and AlMe3 has not been studied
before.
(b) Angles
C1-Al2-C2
C4-Hf1-C3
C6-Hf1-C3
C6-Hf1-C4
C4-Al1-C3
Hf3-C5-Hf2
Al1-C5-Hf3
Al1-C5-Hf2
Al1-C1-Hf2
Al2-C2-Al6
115.5(3)
90.5(2)
94.2(2)
93.9(2)
93.5(3)
124.5(3)
86.7(2)
86.8(2)
102.0(3)
80.5(2)
Al2-C7-Al6
Al3-C6-Al4
Al3-C6-Hf1
Al4-C6-Hf1
Al4-C4-Hf1
Al4-C2-Al6
Al5-C14-Hf3
Al5-C7-Al6
Al6-C2-Hf3
81.1(3)
124.7(3)
82.9(2)
83.0(2)
81.8(2)
104.1(3)
82.2(2)
132.8(4)
166.0(3)
The Al2-Al5 (268.9(3) pm) and Al2-Al6 (267.8(3) pm)
distances are also close to those found in [(Me3-
Si)2CH]2AlAl[CH(SiMe3)2]2 (266.0 pm)17 and [Cp*Al]4
(276.9 pm),18 respectively, and are much shorter than
calculated once from the metal radii (286 pm).16
The Hf-µ-C bond lengths of 11 are in a wide range
(213.1(6)-227.0(6) pm) and are comparable to the Zr-
µ-C bond lengths in 7. This fact is supported by ab initio
studies of the theoretical molecules H2ZrdCH2 (199 pm)
and H2HfdCH2 (198 pm), which reveal no significant
differences in the bond strengths between Zr and Hf
carbenes.19 However, the Hf-µ-C bond lengths in 11 are
During the reaction of 2 equiv of AlMe3 with Cp*2-
ZrF2 (2) in toluene, no gas evolution was observed, and
22
as expected, Cp*2ZrMe2 (12) can be isolated quanti-
tatively. Interestingly, from the analogous reaction of
(19) Cundari, T. R.; Gordon, M. S. J . Am. Chem. Soc. 1992, 114,
539.
(20) Albrecht, M.; Erker, G.; Nolte, M.; Kru¨ger, C. J . Organomet.
Chem. 1992, 427, C42.
(21) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organometallics
1983, 2, 16.
(17) Uhl, W. Z. Naturforsch. B 1988, 43, 1113.
(18) Dohmeier, C.; Robl, C.; Tacke, M.; Schno¨ckel, H. Angew. Chem.
1991, 103, 593; Angew. Chem., Int. Ed. Engl. 1991, 30, 564.
(22) (a) Barger, P. T.; Bercaw, J . E. Organometallics 1984, 3, 278.
(b) Wochner, F.; Brintzinger, H. H. J . Organomet. Chem. 1986, 309,
65.

Hf-Al-C Cluster
Organometallics, Vol. 15, No. 3, 1996 915
4
Cp*ZrF34 (1), (η5-C5Me4Et)ZrF34 (3), Cp*2ZrF24 (2), Cp*HfF3
Cp*2HfF2 with 2 equiv of AlMe3, only ∼50% of Cp*2-
HfMe2 is formed after 6 days stirring the reaction
mixture at ambient temperature. A metathesis reaction
(4), and Cp*TaF423 (5) were synthesized according to literature
methods. AlMe3 solutions (Aldrich) were used as purchased.
23
6. To a suspension of Cp*ZrF3 (2.00 g, 7.1 mmol) in
n-hexane (50 mL) was added an equimolar amount of AlMe3
(3.53 mL of a 2 M solution in n-hexane, 7.1 mmol) via syringe
at once, at room temperature. After a short time (10-15 min),
the reaction suspension abruptly turned into a yellow solution.
The reaction mixture was stirred for an additional 1 h. Then
the volume of the solution was reduced slowly under vacuum
(20 mL), and the product began to crystallize. Precipitation
of colorless crystals of 6 was completed by keeping the reaction
mixture at -25 °C. They were filtered and dried in vacuum.
The reaction yielded 1.92 g (2.7 mmol, 76%) of pure product.
Mp: 208 °C. 1H NMR (250 MHz C6D6): δ 1.76 (s, 30 H, C5-
occurs when Cp*TaF4 (5) is reacted with an excess of
24
AlMe3. Cp*TaMe4 (13) can be obtained in high yield.
Con clu sion
As expected, in contrast to transition metal orga-
no chlorides, reversible reactions of the corresponding
fluorides with an excess of AlMe3 are suppressed due
to the generation of (Me2AlF)4. This is one reason as
well as the elimination of methane from the involved
CH activation processes, which finally result in the
facile formation of Zr-C-Al and Hf-C-Al clusters,
respectively.
2
(CH3)5), 0.54 and 0.50 (2 m, J FF ) 10 Hz, 6 H, ZrCH3), -0.35
(m, 6 H, AlCH3), -0.46 (m, 6 H, AlCH3). 13C NMR (100 MHz,
2
2
C6D6): δ 124.9 (s, C5Me5), 45.2 (dd, J CF ) 11 Hz, J CF ) 30
Hz, ZrCH3), 10.8 (s, C5(CH3)5), -11.1 (m, AlCH3), -12.0 (m,
AlCH3). 19F NMR (235 MHz, C6D6): δ -32.5 (d quint sept, 2J FF
) 33 Hz, 2J FF ) 75 Hz, 2J HF ) 9 Hz, 1 F, ZrFZr), -69.5 (d quint,
2J FF ) 20 Hz, 2J FF ) 75 Hz, 1 F, ZrFZr), -108.2 (s, 4 F, ZrFAl).
IR (Nujol, CsI): ν 1194 s, 1133 s, 1027 s, 804 s, 699 vs, 595 vs,
570 vs, 542 vs, 474 s, 400 vs, 348 vs, 312 vs. MS (70 eV): m/z
(%) 696 (100) (M+ - Me), 620 (50) (M+ - Me - Me2AlF), 544
(50) (M+ - Me - 2Me2AlF). Anal. Calcd (Found): C, 43.92
(43.7); H, 6.80 (6.8); F, 16.03 (16.1).
In summary, from the results and discussion here
presented, one can draw conclusions concerning differ-
ent aspects of the problem in study. First, one can
comment on the ability of the fluoride complexes to
function as single-source Ziegler-Natta catalysts. Then
one can argue the possibility of hypervalent CH units
in complex species involved in catalytic cycles. Such
species are thought to persist in MAO-activated zir-
conocene catalyst solutions from which a permanent
methane evolution can be observed, and it is presumed
that they inhibit the polymerization catalysis.25 This
suggestion corresponds with the result of the catalytical
inactivity of the described Zr clusters, when no co-
catalyst is added.
EPR spectroscopic investigations of the reactions of
monocyclopentadienyl titanium and zirconium trichlo-
rides and MAO have shown that reduction of the
transition metals occurs in this case, forming radical
species.26 Our future studies will be directed at reacting
organometal fluorides using MAO as well as co-catalyst
and investigating such systems by applying the herein
collected 19F NMR spectroscopical data.
7. Cp*ZrF3 (5.00 g, 17.5 mmol) was suspended in n-hexane
(40 mL), and AlMe3 in n-hexane (44.25 mL of an 2 M solution,
88.5 mmol) was added. After the reaction mixture has been
stirred for 18 h, no further gas evolution was observed. The
yellow solution was concentrated to a quarter of the original
volume. 7 precipitated as a yellow microcrystalline solid. The
solution was decanted from the product. The recrystallization
from toluene (50 mL) afforded yellow 7. Yield: 4.00 g (3.79
mmol, 70%). Range of decomposition: 305-333 °C. 1H NMR
4
4
(250 MHz, CDCl3): δ 9.94 (dd, J HH ) 1.7 Hz, J HH ) 0.8 Hz,
2
1 H, Zr2AlCH), 7.07 (s, 2 H, Zr2Al2CH), 4.26 (d, J HH ) 11 Hz,
2 H, ZrAl2CH2), 2.74 (m, 2 H, ZrAl3CH), 2.22 (s, 30 H,
C5(CH3)5), 2.09 (s, 15 H, C5(CH3)5), -0.62 (s, 12 H, Al(CH3)2),
-0.71 (s, 6 H, AlCH3), -0.76 (s, 3 H, AlCH3), -0.97 (s, 3 H,
2
AlCH3), -1.74 (d, J HH ) 11 Hz, 2 H, Al3CH2). IR (Nujol,
KBr): ν 1187 s, 1024 s, 832 s, 787 s, 693 vs, 679 vs, 662 vs,
607 s, 501 s, 365 vs. MS (70 eV): m/z (%) 1040 (4) (M+ - Me),
Exp er im en ta l Section
965 (100) (M+ - 6Me), 951 (20) (M+ - 7Me), 483 (20) (M2+
-
All manipulations were performed under an inert atmo-
sphere of dry nitrogen with Schlenk techniques or in a nitrogen
glovebox. Solvents were dried over Na/K alloy and distilled
prior to use.
NMR spectra were obtained with a Bruker AM 250 and were
recorded in benzene-d6, toluene-d8, and CDCl3 with SiMe4 or
CFCl3 as external standard. EI mass spectra were measured
on Finnigan MAT 8230 or Varian MAT CH 5 instruments.
Infrared spectra were acquired on a Bio-Rad FTS-7. Elemen-
tal analyses were obtained from the Mikroanalytisches Labor
Beller, Go¨ttingen, Germany.27
6Me). Anal.27
8. (η5-C5Me4Et)ZrF3 (1.50 g, 5.0 mmol) was suspended in
n-hexane (50 mL), and AlMe3 in n-hexane (12.50 mL of a 2 M
solution, 25.0 mmol) was added. After the reaction mixture
has been stirred for 18 h, no further gas evolution was
observed. The yellow solution was concentrated to a third of
the original volume. 8 precipitated over a period of 6 days as
a grayish yellow microcrystalline solid. The solution was
decanted from the product. The recrystallization from toluene
afforded yellow 8. Yield: 1.29 g (1.2 mmol, 70%). Range of
decomposition: 292-300 °C. 1H NMR (250 MHz, C6D6): δ 9.14
(dd, 4J HH ) 2.4 Hz, 4J HH ) 2.4 Hz, 1 H, Zr2AlCH), 4.01 (s, 1 H,
Zr2Al2CH), 4.00 (s, 1 H, Zr2Al2CH), 2.43 (d, 2J HH ) 11 Hz, 2 H,
(23) Reference NMR data: Roesky, H. W.; Schrumpf, F.; Noltemeyer,
M. J . Chem. Soc., Dalton Trans. 1990, 713.
(24) (a) Schrock, R. R.; Wood, C. D. J . Am. Chem. Soc. 1979, 101,
5421. (b) Mayer, J . M.; Bercaw, J . E. J . Am. Chem. Soc. 1982, 104,
2157. (c) Sanner, R. D.; Carter, S. T.; Burton, W. J . J . Organomet.
Chem. 1982, 240, 157.
(25) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. Angew. Chem. 1995, 107, 1255; Angew. Chem., Int. Ed.
Engl. 1995, 34, 1143.
(26) Bueschges, U.; Chien, J . C. W. J . Polym. Sci. 1989, 27, 1525.
(27) The found C and H values for 7 (C, 47.5; H, 6.6) are systemati-
cally lower than the calculated ones (C, 51.25; H, 7.45). This is caused
by metal carbide formation during the oxidation process even when
V2O5 is added to the sample: (a) Paciorek, K. J . L.; Nakahara, J . H.;
Hoferkamp, L. A.; George, C.; Flippen-Anderson, J . L.; Gilardi, R.;
Schmidt, W. R. Chem. Mater. 1991, 3, 82. (b) Interrante, L. V.; Sigel,
G. A.; Garbauskas, M.; Hajna, C.; Slack, G. A. Inorg. Chem. 1989, 28,
252.
3
ZrAl2CH2), 2.27 (q, J HH ) 7.5 Hz, 6 H, C5Me4CH2CH3), 1.92
(s, 3 H, C5(CH3)4Et), 1.90 (s, 3 H, C5(CH3)4Et), 1.86 (s, 3 H,
C5(CH3)4Et), 1.84 (s, 3 H, C5(CH3)4Et), 1.81 (s, 12 H, C5(CH3)4-
Et), 1.77 (s, 6 H, C5(CH3)4Et), 1.76 (s, 6 H, C5(CH3)4Et), 0.88
(2t, 3J HH ) 7.5 Hz, 9 H, C5Me4CH2CH3), -0.02 (s, 3 H, AlCH3),
-0.08 (s, 3 H, AlCH3), -0.11 (s, 3 H, AlCH3), -0.31 (s, 6 H,
Al(CH3)2), -0.36 (s, 3 H, AlCH3), -0.37 (s, 3 H, AlCH3), -0.67
2
(s, 3 H, AlCH3), -1.68 (dd, J HH ) 5.5 Hz, 2 H, Al3CH2). IR
(Nujol, KBr): ν 1187 s, 1097 s, 1024 s, 832 s, 787 s, 693 vs,
679 vs, 662 vs, 607 s, 501 s, 365 vs. MS (70 eV): m/z (%) 1051
(5) (M+ - 3Me), 1008 (100) (M+ - 6Me), 993 (20) (M+ - 7Me),
504 (20) (M2+ - 6Me). Anal. Calcd (Found): C, 52.57 (51.6);
H, 7.72 (7.8).

916 Organometallics, Vol. 15, No. 3, 1996
Herzog et al.
Ta ble 6. Atom ic Coor d in a tes (×104) a n d Equ iva len t Isotr op ic Disp la cem en t P a r a m eter s (p m 2 × 10-1) for 11
x
y
z
U(eq)
x
y
z
U(eq)
Hf(1)
Hf(2)
Hf(3)
Al(1)
Al(2)
Al(3)
Al(4)
Al(5)
Al(6)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
1839(1)
4204(1)
1599(1)
3062(2)
2183(2)
2959(2)
380(2)
2628(2)
46(2)
3232(5)
880(5)
3497(5)
1349(5)
3336(5)
1259(5)
1406(6)
653(6)
1228(7)
2353(7)
2495(6)
1454(6)
-545(7)
727(12)
3253(10)
3552(7)
1190(9)
6008(5)
3227(1)
3259(1)
2293(1)
2249(1)
3809(1)
4237(1)
3282(1)
5089(1)
4125(1)
4167(3)
3292(3)
3241(3)
2461(3)
2358(3)
4053(3)
4694(4)
3257(5)
2626(5)
2770(4)
3464(4)
3763(4)
3361(8)
1944(6)
2267(5)
3821(5)
4495(5)
2641(4)
4589(1)
3476(1)
3110(1)
4048(1)
2656(1)
4029(1)
3660(1)
2933(1)
2545(1)
3245(3)
2910(3)
4297(3)
3998(3)
3254(2)
4079(3)
2420(3)
5367(3)
5398(3)
5512(3)
5548(3)
5467(3)
5296(4)
5371(4)
5640(4)
5689(3)
5519(4)
3578(3)
18(1)
16(1)
18(1)
20(1)
21(1)
20(1)
21(1)
31(1)
29(1)
20(1)
20(1)
19(1)
21(1)
20(1)
22(1)
34(2)
40(2)
41(2)
36(2)
33(2)
34(2)
85(5)
80(4)
60(3)
50(2)
60(3)
34(2)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
5900(5)
5934(5)
6044(5)
6084(5)
6119(7)
5856(7)
5950(7)
6191(7)
6289(7)
1762(6)
763(6)
66(6)
647(8)
1690(7)
2703(7)
487(9)
-1107(7)
182(11)
2532(11)
3625(7)
2845(6)
3602(6)
-1165(6)
1903(9)
3809(8)
-889(7)
-736(8)
2883(3)
3593(4)
3784(4)
3203(4)
1924(5)
2477(5)
4044(5)
4491(5)
3170(6)
1356(3)
1681(4)
1572(4)
1185(4)
1034(4)
1292(5)
2020(5)
1810(6)
893(5)
3040(3)
3054(3)
3612(3)
3932(3)
3741(5)
2542(3)
2580(3)
3821(4)
4521(4)
2451(3)
2316(3)
2749(3)
3144(3)
2960(3)
2099(4)
1794(3)
2768(5)
3640(4)
3224(5)
4442(3)
2010(3)
4476(3)
3824(3)
3452(4)
2569(4)
3028(3)
1877(3)
25(1)
26(2)
30(2)
35(2)
57(3)
44(2)
46(2)
57(3)
61(3)
30(2)
30(2)
39(2)
42(2)
38(2)
54(3)
54(2)
74(4)
76(4)
79(4)
36(2)
33(2)
36(2)
37(2)
55(2)
57(3)
44(2)
53(2)
599(5)
1470(4)
3461(4)
4957(4)
3184(4)
5676(5)
5527(4)
4627(5)
3825(5)
a
U(eq) is defined as one-third of the trace of the orthogonalized Uij tensor.
9. To a solution of Cp*HfF3 (2.10 g, 5.0 mmol), dissolved in
toluene (50 mL), was added an equimolar amount of AlMe3
(2.50 mL of a 2 M solution in n-hexane, 5.0 mmol) via syringe
within 30 s, at room temperature. To complete the reaction,
the solution was stirred for 1 h. The volume of the solution
was reduced slowly under vacuum (20 mL), and the product
already began to crystallize. Precipitation of colorless crystals
of 9 was completed by keeping the reaction mixture at -20
°C. They were filtered and dried under vacuum for 3 h. The
reaction yielded 1.95 g (2.2 mmol, 88%) of pure product. Mp:
217 °C. 1H NMR (250 MHz C6D6): δ 1.83 (s, 30 H, C5(CH3)5),
0.26 and 0.22 (2 m, 2J FF ) 10 Hz, 6 H, HfCH3), -0.37 (m, 6 H,
AlCH3), -0.46 (m, 6 H, AlCH3). 13C NMR (100 MHz, C6D6):
was stored for 3 months. During this time, complex 11
precipitates as microcrystalline yellow solid as well as yellow
single crystals, suitable for X-ray structure analysis. Yield:
132 mg (0.1 mmol), 5%. Mp: 310 °C dec. 1H NMR (250 MHz,
4
4
toluene-d8): δ 7.48 (dd, J HH ) 1.7 Hz, J HH ) 0.8 Hz, 1 H,
Hf2AlCH), 6.52 (d, 2J HH ) 11 Hz, 2 H, HfAl2CH2), 5.16 (s, 2 H,
Hf2Al2CH), 2.82 (m, 2 H, HfAl3CH), 1.98 (s, 30 H, C5(CH3)5),
1.92 (s, 15 H, C5(CH3)5), -0.17 (s, 6 H, Al(CH3)2), -0.18 (s, 6
H, Al(CH3)2), -0.51 (s, 6 H, AlCH3), -0.57 (s, 3 H, AlCH3),
2
-0.86 (s, 3 H, AlCH3), -1.63 (d, J HH ) 11 Hz, 2 H, Al3CH2).
13C NMR (100 MHz, toluene-d8): δ 189.0 (s, Hf2CHAl), 121.2
(s, C5Me5), 119.1 (s, C5Me5), 84.9 (s, Hf2Al2CH), 76.3 (s, HfAl3-
CH), 24.9 (s, HfAl2CH2), 12.0 (s, C5(CH3)5), 10.6 (s, C5(CH3)5),
1.1 (s, AlCH3), -2.1 (s, AlCH3), -2.7 (m, AlCH3), -19.6 (s, Al3-
CH2). IR (Nujol, KBr): ν 1187 s, 1097 s, 1024 s, 832 s, 787 s,
693 vs, 679 vs, 662 vs, 607 s, 501 s, 365 vs. MS (70 eV): m/z
2
2
δ 122.4 (s, C5Me5), 43.5 (dd, J CF ) 15 Hz, J CF ) 30 Hz,
HfCH3), 10.6 (s, C5(CH3)5), -11.1 (m, AlCH3), -12.2 (m,
AlCH3). 19F NMR (235 MHz, C6D6): δ -56.7 (d quint sept,
2
2
2J FF ) 19 Hz, J FF ) 86 Hz, J HF ) 11 Hz, 1 F, HfFHf), -87.3
1301 (6) (M+ - Me), 1226 (100) (M+ - 6Me), 1211 (20) (M+
-
2
2
(d quint, J FF ) 19 Hz, J FF ) 86 Hz, 1 F, HfFHf), -109.8 (s,
4 F, HfFAl). IR (Nujol, CsI): ν 1195 s, 1156 s, 1026 s, 804 s,
706 vs, 600 vs, 573 vs, 547 vs, 475 s, 408 vs, 362 vs, 280 vs.
MS (70 eV): m/z (%) 871 (100) (M+ - Me), 795 (40) (M+ - Me
- Me2AlF), 719 (40) (M+ - Me - 2Me2AlF). Anal. Calcd
(Found): C, 35.26 (35.9); H, 5.46 (5.6); F, 12.87 (12.5).
10. A 9.5 mL aliquot of a 2 M solution (19.0 mmol) of AlMe3
in n-hexane was added to a suspension of Cp*HfF3 (2.22 g,
6.0 mmol) in n-hexane (70 mL). After a short time, the
reaction suspension abruptly turned into a yellow solution.
This was stirred for 3 days at ambient temperature. During
this time methane (30 mL) was evolved and an off-white solid
precipitated. After filtration, all volatiles were evaporated
under vacuum and the residue was redissolved in n-hexane
(20 mL). At -40 °C, 10 was obtained as colorless crystals.
Yield: 1.83 g (5.1 mmol, 85%). Spectroscopically pure product
was obtained after repeated recrystallization from n-hexane.
Mp: 83 °C. 1H NMR (250 MHz, C6D6): δ 1.81 (s, 15 H, C5-
(CH3)5), 0.05 (s, 9 H, HfCH3). 13C NMR (63 MHz, C6D6): δ
122.4 (s, C5Me5), 58.0 (s, HfCH3), 10.9 (s, C5(CH3)5). MS (70
eV): m/z (%) 360 (40) (M+), 135 (100) (Cp*+). Anal. Calcd
(Found): C, 43.52 (43.2); H, 6.74 (6.6).
7Me), 613 (20) (M2+ - 6Me). Anal. Calcd (Found): C, 41.05
(39.5); H, 5.97 (6.0).
12. AlMe3 in toluene (3.1 mL of a 2 M solution, 6.2 mmol)
was reacted with Cp*2ZrF2 (1.30 g, 3.0 mmol), dissolved in
toluene (15 mL) for 5 h at room temperature. After evapora-
tion of all volatiles in vacuo, the off-white residue was
redissolved in n-hexane (15 mL). 12 precipitated at -25 °C
as colorless crystals. They were filtered and dried in vacuo.
Yield: 1.10 g (2.8 mmol, 93%). Mp: 168 °C. 1H NMR (250
MHz, C6D6): δ 1.76 (s, 30 H, C5(CH3)5), -0.57 (s, 6 H, ZrCH3).
Anal. Calcd (Found): C, 55.16 (55.1); H, 7.57 (7.4).
13. To a solution of Cp*TaF4 (3.00 g, 7.6 mmol) in toluene
(30 mL) was added 4-fold excess of AlMe3 in toluene (15.3 mL
of a 2 M solution, 30.6 mmol). The reaction mixture was
stirred for 5 h at room temperature. After evaporation of all
volatiles in vacuo, the off-white residue was redissolved in
n-hexane (20 mL). 13 precipitated at -25 °C as colorless
crystals. They were filtered and dried in vacuo. Yield: 2.72
g (7.2 mmol, 95%). Mp: 160 °C dec. 1H NMR (250 MHz,
C6D6): δ 1.67 (s, 15 H, C5(CH3)5), 0.68 (s, 12 H, TaCH3). MS
(70 eV): m/z (%) 361 (100) (M+ - Me), 345 (30) (M+ - 2Me),
329 (60) (M+ - 3Me). Anal. Calcd (Found): C, 44.68 (44.4);
H, 7.23 (7.2).
11. Analogous to the preparation of 10, Cp*HfF3 (2.22 g,
6.0 mmol) and AlMe3 in n-hexane (9.5 mL of a 2 M solution,
19.0 mmol) were reacted in n-hexane (50 mL) for 3 days. The
reaction mixture was filtered, and the resulting yellow solution
X-r a y Mea su r em en ts of 9 a n d 11. Crystal data for the
two structures are presented in Table 4. All data were
collected at low temperatures using an oil-coated shock-cooled

Hf-Al-C Cluster
Organometallics, Vol. 15, No. 3, 1996 917
crystal28 on a Stoe-Siemens AED with Mo KR (λ ) 71.073 pm)
radiation. The structures were solved by direct methods using
SHELXS-9029 and refined with all data on F2 with a weighting
scheme of ω-3 ) σ2(Fo2) + (g1P)2 + g2P with P ) (Fo2 + 2Fc2)/3
using SHELXL-93.30 In 9 and 11, the positions of the hydrogen
atoms were geometrically idealized and refined using a riding
model. Selected bond lengths and angles of 9 and 11 can be
found in Tables 2 and 5, relevant crystallographic data for 9
and 11 are in Table 4, and fractional coordinates of 9 and 11
are presented in Table 3 and Table 6.
Ack n ow led gm en t . We thank the Deutsche For-
schungsgemeinschaft, the Volkswagen Stiftung, and the
BMBF for financial support of this work.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, fractional coordinates, bond lengths and angles, and
coordinates and fully labeled figures of 50% anisotropic
displacement parameters for 9 and 11 (35 pages). Ordering
information is given on any current masthead page.
(28) Kottke, T.; Stalke, D. Appl. Crystallogr. 1993, 26, 615.
(29) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(30) Sheldrick, G. M. SHELXL-93, program for crystal structure
refinement, University of Go¨ttingen, Go¨ttingen, Germany 1993.
OM950590N