Carbon-fluorine bond activation of perfluorinated arenes with Cp2*ZrH2

Article abstract of DOI:10.1016/S0022-328X(02)01640-6

Reaction of Cp₂*ZrH₂ (Cp*, pentamethylcyclopentadienyl) with excess hexafluorobenzene produces a mixture of Cp₂*ZrHF, C₆F₅H and Cp₂*Zr(C₆F₅)H in ca. 2:1:1 ratio. Reaction of Cp₂*ZrH₂ with excess C₆F₅H produces a mixture of Cp₂*ZrHF, Cp₂*Zr(C₆F₅)H, Cp₂*Zr(o-C₆F₄H)H, p-C₆F₄H₂, and o-C₆F₄H₂ with preferred ortho aromatic C-F activation. Dual mechanisms are proposed for the formation of Ar^FH and Cp₂*Zr(Ar^F)H species.

Full text of DOI:10.1016/S0022-328X(02)01640-6

Journal of Organometallic Chemistry 658 (2002) 132ꢀ140
/
www.elsevier.com/locate/jorganchem
Carbonꢀ
/
fluorine bond activation of perfluorinated arenes with
ꢁ
Cp2 ZrH2
Bradley M. Kraft, William D. Jones *
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
Received 3 May 2002; received in revised form 10 June 2002; accepted 10 June 2002
Abstract
Reaction of Cp2 ZrH2 (Cp*, pentamethylcyclopentadienyl) with excess hexafluorobenzene produces a mixture of Cp2ZrHF,
ꢁ
ꢁ
ꢁ
C6F5H and Cp2Zr(C6F5)H in ca. 2:1:1 ratio. Reaction of Cp2ZrH2 with excess C6F5H produces a mixture of Cp2ZrHF,
ꢁ
ꢁ
ꢁ
ꢁ
Cp2Zr(C6F5)H, Cp2 Zr(o-C6F4H)H, p-C6F4H2, and o-C6F4H2 with preferred ortho aromatic CÃ
/
F activation. Dual mechanisms are
F
F
ꢁ
proposed for the formation of Ar H and Cp2Zr(Ar )H species. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Bond activation; Perfluorinated arenes; Pentamethylcyclopentadienyl
1. Introduction
The carbonꢀ
unreactive bond found in organic molecules and its use
adjacent double bonds. The effect is prominently
observed by comparison of the reactions of hexafluoro-
benzene and monofluorobenzene. Monofluorobenzene
(without additional activating groups) is virtually inert
toward nucleophiles [1]. Hexafluorobenzene has an
/
fluorine bond is the strongest and most
as an active functional group is a significant chemical
challenge. Some of the major goals in carbonꢀfluorine
/
estimated CÃ
/
F bond dissociation energy of 154 kcal
molꢂ1 [3], the highest of the fluorobenzenes, yet it is
significantly more reactive toward nucleophiles and
electron-rich metal complexes.
bond activation studies include the functionalization of
saturated fluorocarbons and the conversions of chloro-
fluorocarbons (CFCs) into non-ozone-depleting sub-
stances [1]. Transition-metal complexes are one class
In several cases, transition-metal hydride complexes
have been shown to react with C6F6 to form penta-
fluorophenyl hydride complexes. For example,
Cp*Rh(PMe3)H2 reacts to form Cp*Rh(PMe3)(C6F5)H
by a base-catalyzed process involving nucleophilic dis-
placement of fluoride ion by the anion,
[Cp*Rh(PMe3)H]ꢂ [4]. Similarly, Cp*Ir(PMe3)(H)(Li)
reacts with C6F6 to form LiF and Cp*Ir(PMe3)(C6F5)H
[5]. In contrast, an electron transfer mechanism was
proposed in the reaction of Ru(dmpe)2H2 with C6F6 to
give trans-Ru(dmpe)2(C6F5)H [6]. In other cases, metal
complexes react with C6F6 to give pentafluorophenyl
of compounds that have been shown to cleave strong CÃ
F bonds either stoichiometrically or catalytically [1]. In
most examples of CÃF activation reactions by transition
metals, the reactions are thermodynamically driven by
formation of a strong metalꢀfluorine bond, and this
/
/
/
result generally precludes the use of the metal as a
defluorination catalyst. The addition of a second
reductant and/or fluoride acceptor, however, can some-
times regenerate the reactive metal complex, and allow
the facile catalytic cleavage of CÃ/F bonds [2].
Perfluorinated unsaturated compounds are generally
more reactive than their less-fluorinated counterparts.
This is due to the high electronegativity of fluorine,
which imparts an increase in electrophilicity of the
fluoride complexes. For example, Ni(COD)2 (CODꢃ
1,5-cyclooctadiene) reacts with C6F6 in the presence of
PEt3 or Ni(PEt3)4 to give trans-Ni(PEt3)2(C6F5)F [7].
/
[(dtbpm)Pt(neopentyl)H] (dtbpmꢃdi(t-butyl)phosphi-
/
nomethane) reacts thermally with C6F6 to give
(dtbpm)Pt(C6F5)F quantitatively [8]. Low temperature
* Corresponding author. Tel.: ꢄ
6889
E-mail address: jones@chem.chem.rochester.edu (W.D. Jones).
/
1-716-275-5493; fax: ꢄ1-716-473-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 4 0 - 6

B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ
/
140
133
photolysis of Cp*Rh(PMe3)(h2-C6F6) produced
Cp*Rh(PMe3)(C6F5)F in low yield [9].
2. Results and discussion
ꢁ
2.1. Reaction of Cp2 ZrH2 with hexafluorobenzene
ꢁ
We have recently reported the reactions of Cp2ZrH2
with monofluorobenzene and 1-fluoronaphthalene to
ꢁ
Reaction of Cp2 ZrH2 with 20 equivalents of C6F6 in
ꢁ
give Cp2ZrHF and free arene [10]. Fluorobenzene reacts
cyclohexane-d12 over ꢀ6 h at 85 8C affords a clean
/
slowly over 40 days at 85 8C to give a mixture of
ꢁ
ꢁ
ꢁ
Cp2ZrHF, benzene, and Cp2Zr(C6H5)F in 1:1:0.75
ꢁ
mixture of Cp2ZrHF, Cp2Zr(C6F5)H, and C6F5H in
2:1:1 ratio, according to Scheme 1. These species grow in
together, and no intermediates were detected. A small
ꢁ
ratio. Reaction of Cp2 ZrH2 with 1-fluoronaphthalene,
ꢁ
however, gives only Cp2 ZrHF and naphthalene within 4
ꢁ
amount (B5%) of Cp2 ZrF2 is also observed [13]. The
/
days at 85 8C, according to Eq. (1). There was no
evidence for free radicals in these reactions, as the rate
of reaction with fluoronaphthalene was unaffected by
added radical initiators or inhibitors, and otherwise
followed clean bimolecular reaction kinetics. We, there-
fore, proposed a mechanism involving nucleophilic
hydride attack on the ring and fluoride elimination
involving a carbanionic intermediate-transition state.
The decreased loss in resonance energy in the transition
state was believed to be responsible for the increased
reactivity of fluoronaphthalene in comparison with
ꢁ
ratio of C6F5H to Cp2 Zr(C6F5)H remained unchanged
under conditions employing one equivalent of C6F6 or
neat C6F6 solvent. All products were characterized by
1H and 19F-NMR spectroscopy and GCꢀ
/
MS, and
ꢁ
independent synthesis of Cp2 Zr(C6F5)H [14]. When
ꢁ
the reaction of Cp2 ZrH2 and excess C6F6 was performed
in THF-d8 solvent, many other unidentified CÃ
/
F
ꢁ
activated products along with Cp2 ZrHF, C6F5H, and
ꢁ
Cp2 Zr(C6F5)H were observed. In contrast to the reac-
tion of C6F6 with [Cp2ZrH2]2, the ‘oxidative addition’
ꢁ
product, Cp2 Zr(C6F5)F, was not detected under any
ꢁ
fluorobenzene. In the reaction of Cp2 ZrH2 with
ꢁ
conditions. Cp2Zr(C6F5)F was prepared independently
ꢁ
fluorobenzene, the secondary product, Cp2 Zr(C6H5)F,
was shown to form by an initial ortho aryl CÃ
activation, b-fluoride elimination to give a benzyne
complex, and finally, insertion of benzyne into the ZrÃ
H bond [10].
ꢁ
by reaction of Cp2 Zr(C6F5)H with 70/30 HFꢀ
/pyridine
/
H
in pentane. The X-ray structure of this compound is
shown in Fig. 1. Although required for mass balance, H2
was not observed in the 1H-NMR spectrum in this
reaction.
/
ꢁ
2.2. Reaction of Cp2 ZrH2 with pentafluorobenzene
ð1Þ
ꢁ
Reaction of Cp2 ZrH2 with 20 equivalents of C6F5H in
cyclohexane-d12 over 6 h at 85 8C afforded a clean
Recently reported from our laboratory is the reaction
of [Cp2ZrH2]2 with C6F6 to produce a mixture of
Cp2Zr(C6F5)F, C6F5H, and Cp2ZrF2, according to Eq.
(2) [11]. An oxidative addition to ‘Cp2Zr’ was proposed
to account for Cp2Zr(C6F5)F. The ansa-derivative,
(Me2Si(C5H4)2ZrH2)2, also reacts with C6F6 to give
the apparent oxidative addition product, Me2-
Si(C5H4)2Zr(C6F5)F [12].
mixture of CÃ
/
H and CÃ
/
F activated products consisting
ꢁ
of Cp2ZrHF, Cp2 Zr(C6F5)H, Cp2 Zr(o-C6F4H)H, o-
ꢁ
ꢁ
ꢁ
C6F4H2, p-C6F4H2, and Cp2 ZrF2, according to Scheme
1. Overall, ortho CÃF activation was preferred to give o-
C6F4H2 and p-C6F4H2 in 0.60:0.46 ratio [15]. No
/
ꢁ
Cp2 Zr(p-C6F4H) was observed. The identity of
ꢁ
Cp2 Zr(o-C6F4H)H was confirmed by independent
synthesis [14], and o-C6F4H2 and p-C6F4H2 were
verified by GCꢀ/MS and comparison with authentic
samples.
ð2Þ
ꢁ
2.3. Reaction of Cp2 ZrH2 with perfluorotoluene,
perfluoronaphthalene, and perfluorobiphenyl
Due to the low solubility of these zirconium hydride
complexes, a thorough kinetic and mechanistic study
was not possible, and, therefore, the soluble and
ꢁ
Cp2ZrH2 reacts with perfluorotoluene (one equiva-
lent) in cyclohexane-d12 at room temperature over 3
ꢁ
days to give Cp2ZrHF and p-CF3C6F4H in 1.3:1 ratio.
ꢁ
monomeric Cp2 ZrH2 was chosen as a suitable substrate
to continue this investigation. Surprisingly, reaction of
ꢁ
Cp2ZrH2 with C6F6 did not give the analogous penta-
ꢁ
Only small amounts of Cp2Zr(p-C6F4CF3)H (ꢀ
/4%)
ꢁ
and Cp2 ZrF2 (ꢀ
/
4%) were observed (Scheme 1).
Reaction of perfluoronaphthalene (five equivalents)
ꢁ
fluorophenyl fluoride complex, but rather a penta-
fluorophenyl hydride complex as a major reaction
product. The results of this study are presented in this
paper.
with Cp2 ZrH2 at 85 8C over 1.5 h affords a mixture of
ꢁ
Cp2 Zr(C10F7)H
Cp2 ZrHF, and a small amount (B
Formation of free arene was favored in this case to
[16],
heptafluoronaphthalene,
ꢁ
10%) of Cp2 ZrF2.
ꢁ
/

134
B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ140
/
ꢁ
Scheme 1. Distribution of products in reactions of Cp2 ZrH2 with fluorinated arenes. Percents given in parenthesis are based on total zirconium.
ꢁ
10%) of Cp2 ZrF2 are also formed in these reactions (not shown).
Small amounts (1ꢀ
/
ꢁ
phenyl and Cp2 Zr(p-C6F4-C6F5)H in ꢀ1.8:1 ratio
/
(Scheme 1).
2.4. Reaction profile and kinetic studies
ꢁ
The reaction of Cp2 ZrH2 with C6F6 was monitored
by 19F-NMR spectroscopy over the course of the
reaction at 85 8C [17]. As shown in Fig. 2, C6F5H and
ꢁ
Cp2 Zr(C6F5)H are formed at approximately the same
rate throughout the course of the reaction with con-
ꢁ
comitant formation of two equivalents of Cp2 ZrHF. It,
ꢁ
therefore, appeared that C6F5H and Cp2Zr(C6F5)H
could be formed together from a common intermediate.
ꢁ
The reactions of Cp2ZrH2 with perfluorotoluene, per-
ꢁ
Fig. 1. ORTEP drawing of Cp2Zr(C6F5)F showing the perfluoroaryl
ꢁ
group lying in the wedge of the Cp2Zr moiety (twistꢃ
/
4.58), thermal
˚
ellipsoids are shown at the 30% level; dZr-F(1)
˚
ꢃ/1.95 A; dZrÃC(1)
ꢃ/2.35
˚
A; dZrÃF(2)
ꢃ/
3.47 A; Ú
/
Cp*Ã
/
ZrÃ
/
Cp*ꢃ139.68.
/
ꢁ
produce heptafluoronaphthalene and Cp2 Zr(C10F7)H in
2.3:1 ratio (Scheme 1).
Reaction of perfluorobiphenyl (ten equivalents) with
ꢀ
/
ꢁ
Cp2ZrH2 at 85 8C over 20 h affords a mixture of
ꢁ
Cp2ZrHF, Cp2Zr(p-C6F4-C6F5)H, p-C6F5-C6F4H, and
ꢁ
ꢁ
Fig. 2. Reaction profile for reaction of Cp2ZrH2 (0.06 M) and C6F6
ꢁ
10%) of Cp2 ZrF2. For this substrate,
a small amount (B
/
ꢁ
(1.2 M) at 85 8C in C6D12 solvent; "ꢃ
/
Cp2ZrHF; 'ꢃ
/
ꢁ
ꢁ
free fluoroarene was favored to produce nonafluorobi-
Cp2 Zr(C6F5)H; Iꢃ
/
C6F5H; jꢃCp2 ZrF2.
/

B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ
/
140
135
fluoronaphthalene, and perfluorobiphenyl, however,
ꢁ
Table 1
Pseudo-first order rate constants for the reaction of Cp2 ZrH2 (0.055
F
give preferentially free arene and less Cp2 Zr(Ar )H,
ꢁ
M) with excess C6F6 at 85 8C
suggesting that dual mechanisms are involved in the
formation of these two types of products rather than a
mechanism that requires a 1:1 stoichiometry. In the
reaction with C6F6, the identical rates of formation of
these two products could, therefore, be mere coinci-
dence.
[C6F6] (M)
kobs (sꢂ1
)
0.55
1.10
2.20
9.5(4)ꢅ10ꢂ5
1.5(1)ꢅ10ꢂ4
2.4(1)ꢅ10ꢂ4
Errors are shown as standard deviations (S.D.).
The reaction profile with C6F6 also implies that
ꢁ
Cp2Zr(C6F5)H is not formed from a secondary reaction
ꢁ
of Cp2 ZrH2 with C6F5H. Additional support for this
conclusion is seen in the loss of selectivity in the reaction
ꢁ
of Cp2ZrH2 with C6F5H to give several doubly hydro-
defluorinated aromatic products along with
ꢁ
Cp2Zr(C6F5)H (Scheme 1). None of these C6F4H2
products are observed in the reaction with C6F6 (vide
supra).
Kinetic studies were performed to measure the con-
centration dependence and order of the rate of the
reaction on [C6F6]. For a solution containing 0.055 M
Fig. 4. Graph of ln kobs vs. ln[C6F6] for reactions in C6D12 at 85 8C.
ꢁ
Cp2ZrH2 and excess C6F6 (0.55ꢀ
/2.20 M), plots of
ꢁ
ln[Cp2 ZrH2] versus time were linear (Fig. 3) and the
pseudo-first order rate constants (kobs) were obtained
from the slopes (Table 1) [17]. The C6F6 concentration
dependence is not quite first order, as doubling the
concentration of C6F6 did not cause a doubling of the
rate. The order with respect to [C6F6] was determined by
plotting a graph of ln kobs versus ln[C6F6], where kobs
k ×
[C6F6]n (Fig. 4). The slope of the line, n, equals the
kinetic order, and was calculated to be ꢀ0.7, giving the
ꢃ
/
/
/
0.7
ꢁ
k[Cp2 ZrH2][C6F6] .
The apparent first order dependence of the rate on
overall rate equation, rateꢃ
/
ꢁ
Fig. 5. Graph of ln[Cp2ZrH2] vs. time for 1.24 M C6F6 and jꢃ
/
0.031
ꢁ
M; 'ꢃ
/
0.063 M; "ꢃ0.126 M Cp2 ZrH2 in C6D12 at 85 8C.
/
ꢁ
[Cp2ZrH2] was verified. For solutions containing 1.24
M C6F6, three separate reactions were run with different
ꢁ
Cp2ZrH2 concentrations (0.031ꢀ
/
0.126 M). First-order
increases (2.20 Mꢃ25% C6F6 by volume). It is possible
/
ꢁ
plots of ln[Cp2ZrH2] versus time are linear (Fig. 5), and
0.002 minꢂ1 [17].
that the activity of C6F6 does not double as its
concentration is doubled, giving rise to the fractional
order in [C6F6].
give observed rate constants of 0.0119
The results of the kinetic studies are almost but not
exactly consistent with a bimolecular reaction between
/
ꢁ
The reaction of Cp2 ZrH2 with C6F6 was performed in
ꢁ
Cp2ZrH2 and C6F6. It is quite possible that the true
the presence of radical traps, 9,10-dihydroanthracene
and triphenylmethane to test for the possibility of a
radical chain mechanism. In all cases, no decrease in rate
was observed (Fig. 6), no change in the ratios of the
products was observed, and no other products were
detected [17]. Also, no decrease in rate was observed
when the reaction was performed in cumene solvent.
order in [C6F6] is 1.0, and that the apparent deviation
from unity is due to the fact that the nature of the
solvent changes considerably as C6F6 concentration
These observations suggest that free ArF radicals are
+
not involved in this chemistry. When the reaction was
performed in the presence of sodium and naphthalene (a
radical initiator), no increase in rate was observed.
Addition of a small amount of 1-fluorohexane to the
reaction mixture was also ineffective for initiation of the
reaction [10]. Finally, addition of H2 (1.3 atm) to the
reaction mixture had no effect on the rate.
ꢁ
ꢁ
Fig. 3. Graph of ln[Cp2 ZrH2] vs. time for 0.055 M Cp2 ZrH2 and "ꢃ
/
0.55 M C6F6; jꢃ1.10 M C6F6; 'ꢃ2.20 M C6F6 in C6D12 at 85 8C.
/
/

136
B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ140
/
ꢁ
2.6. Mechanism of Cp2 Zr(C6F5)H formation
Several mechanisms for the formation of
ꢁ
Cp2 Zr(C6F5)H can be immediately ruled out. First,
ꢁ
conproportionation of Cp2 Zr(C6F5)F and Cp2 ZrH2 at
ꢁ
ꢁ
85 8C did not produce Cp2Zr(C6F5)H. Second, a
radical mechanism is unlikely as no effect was observed
by the radical inhibitors or initiators. Third, a ‘meta-
ꢁ
thesis’ of Cp2ZrH2 and C6F6 to form ZrÃ
/
ArylF and HÃ
/
ꢁ
Fig. 6. Graph of [Cp2ZrH2] vs. time for 0.037 M Cp2 ZrH2 and 0.73 M
ꢁ
F bonds via a 4-centered transition state is unlikely as
the polarizations of the bonds, dꢄZrÃHdꢂ and dꢄCÃ
Fdꢂ, are incompatible.
One mechanism which could lead to formation of
C6F6 in C6D12 at 85 8C in the presence of radical inhibitors and
/
/
sodium naphthalene. "ꢃ
jꢃ0.19 9,10-dihydroanthracene; mꢃ
naphthalene.
/
C6F6 only; 'ꢃ
/
0.19 M triphenylmethane;
/
M
/5
mol% sodium and
ꢁ
Cp2 Zr(C6F5)H involves an initial reversible metal-to-
ring hydride transfer to form the ZrII intermediate,
Cp*(C5Me5H)ZrH (Eq. (3)). This ZrII intermediate
could quickly undergo nucleophilic attack on C6F6 to
2.5. Mechanism of C6F5H formation
A possible mechanism to explain the formation of
C6F5H in the reaction with C6F6 involves nucleophilic
hydridic attack on the arene followed by fluoride
ꢁ
elimination to form Cp2 ZrHF (Fig. 7). This SNAr2
pathway is supported by the known hydridic nature of
displace fluoride ion and form the ZrÃ
/
ArylF bond. The
fluoride ion could then deprotonate the diene ligand to
ꢁ
form Cp2Zr(C6F5)H and HF. HF would quickly react
ꢁ
ꢁ
with Cp2 ZrH2 to give Cp2 ZrHF and H2. This mechan-
ism accounts for the observed products, although it is
ꢁ
Cp2ZrH2 [18] and the reactivity of C6F6 toward
not clear why
ꢁ
a
CÃ
/
F activation reaction with
II
nucleophilic attack [1]. This pathway is also supported
by the observation of increased reactivity with perfluor-
onaphthalene in comparison with C6F6. As in the
[Cp2Zr]2(N2)3 is not observed if a Zr intermediate is
involved (vide supra).
ꢁ
reactions of Cp2 ZrH2 with monofluorobenzene and
monofluoronaphthalene [10], the decreased loss in
resonance energy in the carbanionic intermediate-transi-
tion state may account for the increased reactivity for
the fused-ring system. Similarly, the reaction of
ꢁ
Cp2ZrH2 and C6F5H to give o-C6F4H2 and p-C6F4H2
ð3Þ
It is known that all of the Cp*-methyl protons of
ꢁ
Cp2 ZrH2 are exchanged in the presence of H2 [18]. The
could also occur by the hydridic attack mechanism.
Several other mechanisms for the formation of C6F5H
were discounted. First, a radical chain mechanism is
inconsistent with the observation that there is no effect
on the rate or distribution of products by radical
inhibitors or initiators. Second, the reaction of
proposed mechanism for this exchange involves a metal-
to-ring hydride transfer to form the ZrII intermediate,
Cp*(C5Me5H)ZrH, as proposed in the mechanism
above. It might be expected, however, that HF would
ꢁ
ꢁ
Cp2Zr(C6F5)F or Cp2 Zr(C6F5)H with H2 does not
ꢁ
not react selectively with Cp2 ZrH2 to form Cp2 ZrHF,
ꢁ
occur to give C6F5H under the same reaction conditions.
ꢁ
ꢁ
as formation of some Cp2Zr(C6F5)F might be expected
ꢁ
by reaction of HF with Cp2Zr(C6F5)H. In an indepen-
dent experiment, a limiting amount of 0.12 M HF (70:30
w/w HF:pyridine) in pentane was added to a dilute
II
Third, the possibility of a [Cp2Zr ] intermediate in the
formation of C6F5H is also unlikely as no reaction was
ꢁ
observed with [Cp2 Zr]2(N2)3 and C6F6 at room tem-
perature. Heating this mixture to 85 8C did not give CÃ
/
ꢁ
solution of Cp2ZrH2 (0.002 M) and Cp2Zr(C6F5)H
ꢁ
ꢁ
F activated products, but rather formed Cp2 ZrH2 and
(0.002 M) in pentane in a polyethylene reaction vessel. A
ꢁ
mixture of products including Cp2Zr(C6F5)F,
other unidentified species by an undetermined mechan-
ism.
ꢁ
Cp2 ZrHF, Cp2ZrF2, and small amounts of other
ꢁ
unidentified species were observed, suggesting that HF
ꢁ
does not react selectively with Cp2 ZrH2. This distribu-
tion of products, however, may be due to the fact that
HFꢀ
/
pyridine is different than free HF, and it was found
in an independent experiment that pyridine itself reacts
ꢁ
with Cp2ZrH2 to give unidentified products. High local
concentrations of HF are also undoubtedly present
Fig. 7. Possible intermediate-transition state leading to formation of
ꢁ
C6F5H and Cp2ZrHF.
during the addition of HFꢀpyridine to the indepen-
/

B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ
/
140
137
ꢁ
Cp2 ZrH2
dently
prepared
mixture
of
and
3. Conclusion
Reaction of Cp2 ZrH2 with hexafluorobenzene pro-
ꢁ
Cp2Zr(C6F5)H, and this might also account for the
loss in selectivity that might otherwise be observed.
An alternative mechanism which leads to
ꢁ
ꢁ
ꢁ
mixture of Cp2 ZrHF, C6F5H, and
duces
a
ꢁ
Cp2 Zr(C6F5)H by dual mechanisms. Radical initiators
and inhibitors had no effect on the rate of reaction or
distribution of products. A nucleophilic hydride attack
on C6F6 followed by fluoride elimination is proposed to
explain the formation of C6F5H and one equivalent of
Cp2Zr(C6F5)H is homolytic CÃ
/
F cleavage of C6F6 by
a ‘hydrogen-depleted’ dimer, such as the ZrIII diradical,
ꢁ
ꢁ
[Cp2Zr]2(H)(m-H) or [Cp2 Zr(m-H)]2 (Fig. 8). This
mechanism would also account for the inability to trap
+
free C6F5 radicals. The involvement of a dimeric
ꢁ
Cp2 ZrHF. The formation of Cp2Zr(C6F5)H and the
ꢁ
species has been proposed in the reaction of [Cp2ZrH2]2
with diphenylacetylene, primarily because the dominant
form of the Cp analog is the dimer [19]. The dimeric
ꢁ
second equivalent of Cp2 ZrHF is difficult to explain. A
metal-to-ring hydride transfer followed by attack on the
ArylF ring by the zirconium nucleophile would generate
a zwitterionic intermediate. Elimination of fluoride ion
and subsequent deprotonation of the diene ligand
ꢁ
produces Cp2 Zr(C6F5)H and HF. HF could then react
ꢁ
with an additional equivalent of Cp2 ZrH2 to give
ꢁ
form of Cp2 ZrH2, however, has not been observed. It
might be possible that loss of H2 from the dimer is
induced by C6F6 in a fast termolecular step prior to
homolysis of the CÃ
/
F bond, although the kinetic studies
appear inconsistent with this proposal.
Other zirconocene complexes, (C5Me4H)2ZrH2 [20]
and Me2Si(C5Me4)2ZrH2 [21], which exist as a mono-
ꢁ
Cp2 ZrHF and H2. An alternative mechanism proposed
ꢁ
for formation of Cp2 Zr(C6F5)H involves homolytic
F bond of C6F6 by a hydrogen-depleted
cleavage of a CÃ
/
merꢀdimer equilibrium in solution at room temperature
/
ꢁ
dimer such as (Cp2 ZrH)2.
were examined to broaden the scope of this reaction and
to test the possibility of a reactive dimeric intermediate.
Both of these complexes reacted with C6F6 under more
mild conditions to give analogous products. Specifically,
reaction of (C5Me4H)2ZrH2 with C6F6 (20 equivalents)
at room temperature afforded (C5Me4H)2Zr(C6F5)H,
C6F5H, (C5Me4H)2Zr(o-C6F4H)H, (C5Me4H)2ZrHF
and (C5Me4H)2ZrF2 in 1:1.1:0.6:3.1:0.3 ratio. Reaction
of (C5Me4H)2ZrH2 with C6F5H (ten equivalents) pro-
duced (C5Me4H)2ZrHF, (C5Me4H)2Zr(o-C6F4H)H in
4. Experimental
All manipulations were performed inside an N2-filled
Vacuum Atmospheres glovebox or on a high vacuum
line. Cyclohexane and cyclohexane-d12 were dried and
vacuum distilled from purple solutions of benzophenone
ketyl. UHP grade H2 (air products) was purified by
˚
passage over activated 4 A molecular sieves and MnO
on vermiculite. Hexafluorobenzene, pentafluoroben-
zene, perfluorotoluene, perfluoronaphthalene, and per-
fluorobiphenyl were purchased from Aldrich and used
as received. 1H and 19F-NMR spectra were recorded
using a Bruker Avance400 spectrometer. 19F-NMR
spectra were referenced to a,a,a-trifluorotoluene (taken
ꢀ
/
1.4:2.6 ratio and ꢀ10% (C5Me4H)2Zr(C6F5)H.
/
The reaction of Me2Si(C5Me4)2ZrH2 with C6F6 (ten
equivalents) also occurred at room temperature
to afford Me2Si(C5Me4)2ZrHF, Me2Si(C5Me4)2Zr-
(C6F5)H,
and
Me2Si(C5Me4)2Zr(o-C6F4H)H
in
4.5:1.8:1 ratio along with H2 and a small amount (B
/
as d ꢂ
/
63.73 relative to CFCl3 with down-field chemical
10%) of other unidentified species. Only traces of C6F5H
could be detected in this reaction. Although an increase
in the rate of reaction of (C5Me4H)2ZrH2 and Me2-
Si(C5Me4)2ZrH2 with C6F6 might suggest the involve-
ment of a dimeric species, the increased electrophilicity
shifts taken to be positive). GCꢀ/MS analyses were
conducted using a 5890A Series GC equipped with a
Restek RTX-5 column (0.25 mm ID, 0.25 mm, 13 m) and
ꢁ
a HP 5970 series mass selective detector. Cp2ZrH2 [22],
Me2Si(C5Me4)2ZrH2 [21], and (C5Me4H)2ZrH2 [20] were
prepared according to the literature procedures.
ꢁ
of both of these substrates in comparison with Cp2 ZrH2
might also explain the increased reactivity.
ꢁ
4.1. Reaction of hexafluorobenzene with Cp2 ZrH2
A sealable NMR tube was charged with 14 mg (0.038
ꢁ
mmol) of Cp2 ZrH2 and dissolved in cyclohexane-d12.
Hexafluorobenzene (89 ml, 0.77 mmol, dꢃ1.61) was
added via syringe. On the vacuum line, the solution was
freezeꢀpumpꢀthawꢀdegassed three times and sealed
under vacuum. The tube was heated at 85 8C for 8 h
/
/
/
/
ꢁ
upon which all Cp2 ZrH2 had reacted. The reaction
ꢁ
mixture consisted of a 2:1:1 mixture of Cp2 ZrHF,
ꢁ
Cp2 Zr(C6F5)H, and C6F5H. No H2 was observed in
ꢁ
Fig. 8. Possible transition state leading to formation of Cp2 ZrHF and
F
Cp2 Zr(Ar )H.
ꢁ

138
B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ140
/
1
the H-NMR spectrum. For Cp2ZrHF: 1H-NMR
(C6D12): d 1.92 (s, 30H, Cp*), 6.23 (s, 1H, ZrHF).
Cp2 Zr(C10F7)H), 7.59 (dd, Cp2 Zr(C10F7)H?). The Cp*
methyl resonances were overlapping due to the presence
of excess perfluoronaphthalene. 19F-NMR (C6D12): d
ꢁ
ꢁ
ꢁ
19
ꢁ
F-NMR (C6D12): d 77.67 (s, 1F). For Cp2 Zr(C6F5)H:
1H-NMR (C6D12): d 1.88 (s, 30H, Cp*), 7.71 (dd, 1H,
ꢂ
/
100.2 (dm, Zr-o-ArF), ꢂ112.2 (dm, Zr-o-ArF). Other
/
Zr(C6F5)H). 19F-NMR (C6D12): d ꢂ
/
116.3 (m, 1F), ꢂ
160.2 (m, 1F), ꢂ161.9
(m, 1F). For C6F5H: 1H-NMR (C6D12): d 6.74 (m, 1H).
19F-NMR (C6D12): d ꢂ
140.3 (m, 2F), ꢂ155.3 (t, 1F),
163.8 (m, 2F).
/
19F resonances of could not be assigned unambiguously.
1
For 2-H-heptafluoronaphthalene, H-NMR (C6D12): d
117.7 (m, 1F), ꢂ
/
155.2 (t, 1F), ꢂ
/
/
7.01 (m, C10F7H). 19F-NMR: d ꢂ
/
116.2 (dm, 1F),
144.3 (dt, 1F), ꢂ146.1 (dt, 1F),
153.6 (t, 1F), ꢂ156.5 (m, 1F). MS:
/
/
ꢂ
/
134.1 (m, 1F), ꢂ
149.3 (dtd, 1F), ꢂ
/
/
ꢂ
/
ꢂ
/
/
/
254 ([Mꢄ], C10F7H). The chemical shifts for 2-H-
heptafluoronaphthalene match those previously re-
ported [23].
ꢁ
4.2. Reaction of pentafluorobenzene with Cp2 ZrH2
In a resealable NMR tube, 15 mg (0.041 mmol)
ꢁ
Cp2ZrH2 was dissolved in cyclohexane-d12 followed by
ꢁ
4.5. Reaction of perfluorobiphenyl with Cp2 ZrH2
addition of 90 ml (0.81 mmol, dꢃ1.514) of pentafluor-
/
obenzene. Hydrogen (1.3 atm) was placed over the
reaction mixture and the sample was heated at 85 8C
In a resealable NMR tube, 10 mg (0.027 mmol) of
ꢁ
Cp2 ZrH2 and 92 mg (0.27 mmol) of perfluorobiphenyl
were dissolved in cyclohexane-d12. The tube was heated
in a thermostatted 85 8C oil bath for 20 h forming
ꢁ
for 6 h. A mixture of Cp2 ZrHF, Cp2Zr(o-C6F4H)H,
ꢁ
ꢁ
Cp2Zr(C6F5)H, o-C6F4H2, p-C6F4H2, and Cp2 ZrF2
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
formed in 3:2:1:0.6:0.46:0.2 ratio. For Cp2Zr(o-
Cp2 ZrHF, p-C6F5Ã
/
C6F4H, Cp2Zr(C6F4Ã
/
C6F5)H, and
C6F4H)H, 1H-NMR (C6D12): d 1.847 (s, 30H, Cp*),
Cp2 ZrF2. For Cp2Zr(C6F4Ã
/
C6F5)H: 1H-NMR (C6D12):
ꢁ
C6F4H), 6.83 (br, 1H, ZrH). 19F-NMR
d 7.75 (dd, Cp2 Zr(C12F9)H), 1.91 (s, Cp*). The Cp*
methyl resonances were overlapping due to the presence
of excess perfluorobiphenyl. 19F-NMR (C6D12): d
ꢁ
5.98 (m, 1H, ZrÃ
(C6D12): d ꢂ118.1 (m, 1F), ꢂ
1F), ꢂ
159.0 (m, 1F). For o-C6F4H2, 1H-NMR (C6D12):
d 6.88 (m). 19F-NMR (C6D12): d ꢂ
139.0 (m, 2F),
155.5 (m, 2F). For p-C6F4H2: H-NMR (C6D12): d
/
/
/
139.8 (m, 1F), ꢂ157.4 (m,
/
/
/
ꢂ
/
118.2 (m, 1F, Zr-o-ArF), ꢂ
140.3 (m, 1F), ꢂ142.4 (m, 1F), ꢂ
163.3 (m, 2F), ꢂ161.3 (2F, obscured). For p-C6F5Ã
C6F4H: H-NMR: (C6D12): d 7.09 (m). 19F-NMR: d
137.9 (m, 2F), ꢂ138.7 (m, 2F), ꢂ138.8 (m, 2F),
151.5 (t, 1F), ꢂ
161.6 (m, 2F), MS: 316 [Mꢄ].
/
118.8 (m, 1F, Zr-o-ArF),
1
ꢂ
/
ꢂ
/
/
/154.3 (t, 1F),
6.89 (m). 19F-NMR (C6D12): d ꢂ
/
138.7 (m). The 1H and
19F-NMR resonances of o-C6F4H2, and p-C6F4H2 were
verified by comparison with authentic samples.
ꢂ
/
/
/
1
ꢂ
/
/
/
ꢂ
/
/
ꢁ
4.3. Reaction of perfluorotoluene with Cp2ZrH2
ꢁ
4.6. Kinetics for reaction of Cp2 ZrH2 with C6F6
In a resealable NMR tube, 10 mg (0.027 mmol)
ꢁ
Cp2ZrH2 was dissolved in cyclohexane-d12 followed by
For [C6F6] dependence: In the drybox, 240 ml of a
ꢁ
0.137 M stock cyclohexane-d12 solution of Cp2 ZrH2
addition of 3.90 ml (0.027 mmol, dꢃ
/
1.666) of perfluor-
otoluene. The reaction mixture was allowed to stand at
room temperature (r.t.) for 3 days consuming all
containing 0.023 M a,a,a-trifluorotoluene standard was
syringed into resealable NMR tubes. Hexafluoroben-
zene (38, 76, or 152 ml) was added with a microliter
syringe and the total volume was brought to 0.600 ml.
The tubes were heated side-by-side in a thermostatted
85 8C oil bath and analyzed periodically by 19F-NMR
ꢁ
Cp2ZrH2.
ꢁ
ꢁ
ꢁ
Cp2Zr(p-
C6F4CF3)H, Cp2 ZrF2 were observed in 14:11:1:1 ratio.
Cp2ZrHF,
p-CF3C6F4H,
1
For p-CF3C6F4H, H-NMR (C6D12): d 7.09 (m, 1H).
19F-NMR (C6D12): d ꢂ
/
56.77 (m, 3F), ꢂ
139.6 (m, 2F). GCꢀ
MS (m/z): 218 [Mꢄ]. For
Cp2Zr(p-C6F4CF3)H: 1H-NMR (C6D12): d 1.88 (s,
30H), 7.55 (dd, 1H). 19F-NMR (C6D12): d ꢂ
56.3 (m,
3F), ꢂ118.6 (m, 1F), ꢂ117.4 (m, 1F), ꢂ140.8 (m, 1F),
143.23 (m, 1F).
/
136.3 (m, 2F),
ꢁ
ꢂ
/
/
spectroscopy. For [Cp2 ZrH2] dependence: Into reseal-
able NMR tubes, 150, 300, and 600 ml of a 0.147 M
ꢁ
ꢁ
stock cyclohexane-d12 solution of Cp2 ZrH2 containing
/
/
/
/
0.025 M a,a,a-trifluorotoluene standard was added with
a syringe. Hexafluorobenzene (100 ml, 0.87 mmol) was
added with a microliter syringe and the total volume was
brought to 0.700 ml. The tubes were heated side-by-side
in a thermostatted 85 8C oil bath and analyzed
periodically by 19F-NMR spectroscopy.
ꢂ
/
ꢁ
4.4. Reaction of perfluoronaphthalene with Cp2ZrH2
In a resealable NMR tube, 12 mg (0.033 mmol) of
ꢁ
Cp2ZrH2 and 45 mg (0.16 mmol) of perfluoronaphtha-
ꢁ
ꢁ
lene were dissolved in cyclohexane-d12. The tube was
heated in a thermostatted 85 8C oil bath for 1.5 h
ꢁ
forming Cp2 ZrHF, heptafluoronaphthalene, and
4.7. Reaction of Cp2 ZrH2 and Cp2 Zr(C6F5)H with
HFꢀpyridine
/
ꢁ
ꢁ
ꢁ
Into a polyethylene reaction vessel, 15 mg Cp2 ZrH2
Cp2Zr(C10F7)H [16]. For Cp2Zr(C10F7)H (two roto-
mers or isomers), 1H-NMR (C6D12): d 7.75 (dd,
(0.041 mmol) and 22 mg Cp2 Zr(C6F5)H (0.041 mmol)
ꢁ

B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ
/
140
139
were added and dissolved in 25 ml of pentane. A 0.12 M
solution of HF was prepared by adding 0.085 g of 70:30
1.61) was added via syringe and the tube was stirred at
r.t. for 18 h. The reaction mixture consisted of a mixture
of Me2Si(C5Me4)2ZrHF, Me2Si(C5Me4)2Zr(C6F5)H,
and Me2Si(C5Me4)Zr(o-C6F4H)H in 4.5:1.8:1 ratio. A
small amount of Me2Si(C5Me4)2ZrF2 and other uni-
dentified species were also detected. A total of eight Cp-
methyl resonances were observed in the 1H-NMR
spectrum, but could not be assigned. For Me2Si(C5-
HFꢀ
polyethylene vessel. To the solution of zirconium com-
plexes, 0.33 ml of the dilute HFꢀpyridine solution was
/pyridine solution to 24 ml of pentane in another
/
added at r.t. with stirring. The pentane was removed
under vacuum and the residue was analyzed by NMR
ꢁ
spectroscopy in C6D12. A mixture of Cp2 Zr(C6F5)F,
1
ꢁ
ꢁ
Cp2ZrHF, Cp2 ZrF2, and other species were detected.
Me4)2ZrHF: H-NMR (C6D12): d 5.53 (s, 1H, ZrH),
0.72 (s, 6H, Me2Si). 19F-NMR: d 75.6 (s). For Me2-
1
Si(C5Me4)2Zr(C6F5)H: H-NMR (C6D12): d 6.61 (dd,
ꢁ
4.8. Preparation of Cp2Zr(C6F5)F
1H, ZrH), 0.82 (s, 6H, Me2Si). 19F-NMR: d ꢂ
/119.2 (m,
ꢁ
In a polyethylene vial, 60 mg Cp2Zr(C6F5)H was
1F), ꢂ
161.7 (m, 1F). For Me2Si(C5Me4)Zr(o-C6F4H)H: H-
NMR (C6D12): d 6.14 (tm, 1H, ArFH), 6.03 (s, 1H,
ZrH), 0.77 (s, 6H, Me2Si). 19F-NMR: d ꢂ
118.8 (m, 1F),
139.7 (m, 1F), ꢂ156.6 (m, 1F), ꢂ158.2 (m, 1F).
/
121.1 (m, 1F), ꢂ
/
155.1 (t, 1F), ꢂ
/
160.8 (m, 1F),
1
dissolved in 0.5 ml pentane and four drops of 70:30 HFꢀ
/
ꢂ
/
pyridine was added with stirring. Evolution of H2 was
observed and the solution became colorless. The solu-
tion was transferred to a glass vial to neutralize excess
HF and the volatiles were removed in vacuo. Pentane
was added, and the solution was filtered through a glass
/
ꢂ
/
/
/
4.11. Reaction of (Me2Si(C5H4)2ZrH2)2 with C6F6
fiber filter. Concentration and cooling to ꢂ
/
30 8C gave
white crystals (40 mg, 64%). H-NMR (C6D12): d 1.806
(s, Cp*). 19F-NMR (C6D12): d 113.5 (d, Jꢃ
44 Hz, 1F,
ZrÃF), ꢂ111.6 (m, 1F), ꢂ111.1 (m, 1F), ꢂ155.3 (t, 1F),
160.1 (m, 1F), ꢂ162.5 (m, 1F). Anal. Calc. for
1
A resealable NMR tube was charged with 12 mg
(0.043 mmol) of (Me2Si(C5H4)2ZrH2)2 and suspended in
/
/
/
/
/
THF-d8. Hexafluorobenzene (119 ml, 1.03 mmol, dꢃ
/
ꢂ
/
/
1.61) was added via syringe and the tube was heated
at 85 8C for 10 min upon which the solution evolved H2
and became homogeneous. The reaction mixture con-
sisted of Me2Si(C5H4)2Zr(C6F5)F, C6F5H, and Me2-
Si(C5H4)2ZrF2 in 3.5:1:1 ratio by NMR integration. For
Me2Si(C5H4)2Zr(C6F5)F: 1H-NMR (THF-d8): d 0.91 (s,
3H, Me2Si), 0.78 (s, 3H, Me2Si), 5.78 (m, 2H), 6.40 (m,
2H), 6.45 (m, 2H), 6.99 (m, 2H). 19F-NMR (THF-d8): d
C26H30F6Zr: C, 57.01; H, 5.52. Found: C, 56.74; H,
5.39%.
4.9. Reaction of (C5Me4H)2ZrH2 with C6F6
A resealable NMR tube was charged with 10 mg
(0.030 mmol) of (C5Me4H)2ZrH2 and dissolved in
cyclohexane-d12. Hexafluorobenzene (69 ml, 0.60 mmol,
99.3 (brs, 1F), ꢂ
/
114.4 (m, 2F), ꢂ
/
158.8 (t, 1F), ꢂ164.2
/
dꢃ/1.61) was added via syringe and the tube was
(m, 2F). For Me2Si(C5H4)2ZrF2: 1H-NMR (THF-d8): d
0.82 (s, 6H, Me2Si), 6.05 (m, 4H), 6.55 (m, 4H). 19F-
NMR: d 30.4 (brs, 2F).
allowed to stand at r.t. for 2 days. The reaction mixture
consisted of a mixture of (C5Me4H)2Zr(C6F5)H, C6F5H,
(C5Me4H)2Zr(o-C6F4H)H,
(C5Me4H)2ZrHF
and
ꢁ
4.12. X-ray structural determination of Cp2 Zr(C6F5)F
(C5Me4H)2ZrF2 in 1:1.1:0.6:3.1:0.3 ratio. For
(C5Me4H)2ZrHF: 1H-NMR (C6D12): d 6.04 (s, 1H,
ZrHF), 5.17 (s, 2H, C5Me4H), 2.11 (s, 6H), 1.99 (s, 6H),
1.96 (s, 6H), 1.81 (s, 6H). 19F-NMR: d 72.6 (s). For
(C5Me4H)2Zr(C6F5)H: H-NMR (C6D12): d 7.40 (dd,
1H, ZrH(C6F5), 5.25 (s, 2H, C5Me4H), 2.06 (s, 6H),
1.99 (s, 6H), 1.91 (s, 6H), 1.77 (s, 6H). 19F-NMR: d
A Siemens SMART CCD area detector diffract-
ometer equipped with an LT-2 low temperature unit
was used for X-ray crystal structure determination. A
ꢁ
single crystal of Cp2 Zr(C6F5)F was mounted under
Paratone-8277 on a glass fiber and immediately placed
1
ꢂ
/
118.0 (d, 1F), ꢂ
/
120.3 (m, 1F), ꢂ
/
155.9 (t, 1F), ꢂ
/
161.2
in a cold nitrogen stream at ꢂ80 8C on the X-ray
/
(m, 1F),
ꢂ
/
162.4 (m, 1F). For (C5Me4H)2Zr(o-
diffractometer. The X-ray intensity data were collected
on a standard Siemens SMART CCD Area Detector
System equipped with a normal focus molybdenum-
target X-ray tube operated at 2.0 kW (50 kV, 40 mA). A
total of 1321 frames of data (1.3 hemispheres) were
collected using a narrow frame method with scan widths
of 0.38 in v and exposure times of 30 s per frame using a
detector-to-crystal distance of 5.09 cm (maximum 2u
angle of 56.548) for both of the crystals. The unit cell
parameters were based upon the least-squares refine-
C6F4H)H: 1H-NMR (C6D12): d 6.63 (s, 1H, ZrH),
6.04 (m, 1H, ArFH), 5.31 (s, 2H, C5Me4H), 2.00 (s, 6H),
1.97 (s, 6H), 1.91 (s, 6H), 1.65 (s, 6H). 19F-NMR: d
ꢂ
/
118.7 (m, 1F), ꢂ
/
140.4 (t, 1F), ꢂ157.7 (m, 1F),
/
ꢂ
/
159.3 (m, 1F).
4.10. Reaction of Me2Si(C5Me4)2ZrH2 with C6F6
A resealable NMR tube was charged with 5 mg (0.013
mmol) of Me2Si(C5Me4)2ZrH2 and suspended in cyclo-
hexane-d12. Hexafluorobenzene (14.7 ml, 0.13 mmol, dꢃ
ment of three dimensional centroids of ꢁ
/
5000 reflec-
tions. Data were corrected for absorption using the
/

140
B.M. Kraft, W.D. Jones / Journal of Organometallic Chemistry 658 (2002) 132ꢀ140
/
Acknowledgements
Table 2
Crystal data and structure refinement for Cp2Zr(C6F5)F
ꢁ
We gratefully thank the US Department of Energy
(Grant FG02-86ER13569) for their support of this
work.
Identification code
Empirical formula
Formula weight
Temperature (K)
sad/jonbk17
C26H30F6Zr
547.72
193(2)
0.71073
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
Orthorhombic
Pbca
References
[1] (a) There are several recent reviews on CÃF activation by metal
/
˚
a (A)
15.3752(6)
15.6533(6)
reagents: J.L. Kiplinger, T.G. Richmond, C.E. Osterberg, Chem.
Rev. 94 (1994) 373;
˚
b (A)
˚
c (A)
20.0858(8)
90
(b) J. Burdeiuc, B. Jedlicka, R.H. Crabtree, Chem. Ber./Recl. 130
(1997) 145;
a (8)
b (8)
90
90
(c) T.G. Richmond, In: S. Murai (Ed.) Topics in Organometallic
Chemistry, vol. 3, Springer-Verlag, New York, 1999, p. 243.
[2] (a) J.L. Kiplinger, T.G. Richmond, J. Am. Chem. Soc. 118 (1996)
1805;
g (8)
3
V (A )
˚
4834.1(3)
8
1.505
Z
Dcalc (Mg mꢂ3
)
(b) J. Burdeniuc, R.H. Crabtree, J. Am. Chem. Soc. 118 (1996)
2525;
Absorption coefficient (mmꢂ1
F(000)
Crystal size (mm)
)
0.512
2240
(c) M. Aizenberg, D. Milstein, J. Am. Chem. Soc. 117 (1995)
8674.
0.04ꢅ0.14ꢅ0.26
u Range for data collection (8) 2.03ꢀ
Limiting indices
/23.27
[3] B.E. Smart, Mol. Struc. Energ. 3 (1986) 141.
[4] B.L. Edelbach, W.D. Jones, J. Am. Chem. Soc. 119 (1997) 7734.
[5] T.H. Peterson, J.T. Golden, R.G. Bergman, Organometallics 18
(1999) 2005.
ꢂ175h 513, ꢂ175k 512,
ꢂ215l 522
21 054
Reflections collected
Independent reflections
Absorption correction
Max/min transmission
Refinement method
3470 [Rintꢃ0.0634]
SADABS
[6] M.K. Whittlesey, R.N. Perutz, M.H. Moore, Chem. Commun.
(1996) 787.
0.928000, 0.799125
Full-matrix least-squares on F2
3470/0/298
[7] L. Cronin, C.L. Higgitt, R. Karch, R.N. Perutz, Organometallics
16 (1997) 4920.
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I ꢁ2s(I)]
R indices (all data)
[8] P. Hofmann, G. Unfried, Chem. Ber. 125 (1992) 659.
[9] S.T. Belt, M. Helliwell, W.D. Jones, M.G. Partridge, R.N. Perutz,
J. Am. Chem. Soc. 115 (1993) 1429.
0.810
R1ꢃ0.0469, wR2ꢃ0.1109
R1ꢃ0.0786, wR2ꢃ0.1298
[10] B.M. Kraft, R.J. Lachicotte, W.D. Jones, J. Am. Chem. Soc. 123
(2001) 10973.
Largest difference peak and hole 0.359 and ꢂ0.269
ꢂ3
˚
(e A
)
[11] B.L. Edelbach, A.K.F. Rahman, R.J. Lachicotte, W.D. Jones,
Organometallics 18 (1999) 3170.
[12] See Section 4.
program SADABS. The space group assignment was
made on the basis of systematic absences and intensity
statistics by using the XPREP program (Siemens,
SHELXTL 5.04). The structure was solved by using direct
methods and refined by full-matrix least-squares on F2.
The non-hydrogen atoms were refined with anisotropic
thermal parameters and hydrogens were included in
idealized positions giving data:parameter ratios greater
than 10:1. Table 2 contains crystallographic data.
ꢁ
[13] Cp2ZrF2 may be formed by reaction of Cp2ZrHF with C6F6,
ꢁ
ꢁ
although independent reaction of Cp2 ZrHF with ten equivalents
ꢁ
C6F6 produced Cp2ZrF2 and C6F5H very slowly, reaching only
40% conversion after 9 days at 100 8C.
[14] B.M. Kraft, R.J. Lachicotte, W.D. Jones, Organometallics 21
(2002) 727.
[15] To our knowledge, the preference for ortho over para CÃ
/F
activation of C6F5H is unprecedented.
[16] Two doublet of doublet resonances typical for Cp2Zr(Ar )H
F
ꢁ
1
species were observed in the H-NMR spectrum indicating either
ꢁ
two geometrical isomers or two rotomers of Cp2 Zr(C10F7)H.
ꢁ
[17] The disappearance of Cp2 ZrH2 could be determined only by
ꢁ
monitoring the appearance of Cp2 ZrHF in the 19F-NMR spectra.
Overlap of the Cp* resonances in the 1H-NMR spectrum
prevented direct observation.
5. Supporting information
[18] J.E. Bercaw, Adv. Chem. Ser. 167 (1978) 136.
[19] D.G. Bickley, N. Hao, P. Bougeard, B.G. Sayer, R.C. Burns, M.J.
McGlinchey, J. Organomet. Chem. 246 (1983) 257.
[20] P.J. Chirik, M.W. Day, J.E. Bercaw, Organometallics 18 (1999)
1873.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC no. 184938 for the compound
ꢁ
Cp2Zr(C6F5)F. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
[21] H. Lee, P.J. Desrosiers, I. Guzei, A.L. Rheingold, G. Parkin, J.
Am. Chem. Soc. 120 (1998) 3255.
Union Road, Cambridge, CB2 1EZ, UK (Fax: ꢄ44-
/
[22] L.E. Schock, T.J. Marks, J. Am. Chem. Soc. 110 (1988) 7701.
[23] J. Burdon, H.S. Gill, I.W. Parsons, J. Chem. Soc. Perkin Trans. I
(1980) 2494.
1223-336033; or e-mail: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).